JP2012130890A - Separation membrane support, the method for manufacturing the same, separation membrane sheet, and membrane separation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation membrane support comprising nonwoven fabric, having excellent film-forming property and high mechanical strength when supporting a separation membrane such as a precise filter membrane, an ultrafilter membrane, a nano-filter membrane, and a reverse osmosis membrane, and further contributing to enhancing the performance of the separation membrane; and to provide a method for manufacturing the same.SOLUTION: The separation membrane support is constituted by forming a membrane having a separation function on the surface of the same and is characterized by comprising the nonwoven fabric having hydrophilicity.

Description

  The present invention relates to a separation membrane support for supporting a separation membrane such as a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane, a method for producing the same, a separation membrane sheet, and a membrane separation element. Is.

  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, and flat membranes formed mainly from synthetic polymers are generally poor in mechanical strength with membranes having a separation function. It is often used by being fixed and integrated with a support such as a woven fabric. Among them, a nonwoven fabric is excellent in cost because a nonwoven fabric can be obtained without going through a weaving process.

  In many cases, the separation membrane and the support are integrated by a method in which a polymer solution as a raw material for the separation membrane is cast and fixed on the support, but the polymer solution sufficiently penetrates into the support. While the separation membrane and the support can be firmly bonded to each other, if the polymer solution permeates excessively and reaches the back of the support, the membrane formation apparatus is soiled and causes the defects of the separation membrane that is manufactured later. The separation membrane support has excellent film-forming properties, such as when it is attached to a support plate during manufacture of the membrane separation element, the adhesive strength with the support plate is insufficient and the durability of the membrane separation element is poor. It was important to have

  In the case of a semipermeable membrane such as a reverse osmosis membrane, which is often used under high pressure, the support is required to have high mechanical strength in order to improve the durability of the separation membrane. Even in separation membranes for sewage treatment applied to the separated activated sludge method, inorganic substances such as sand, sludge, and other solids collide violently during use, and supply of oxygen to activated sludge and clogging are prevented. Therefore, it is important that the support has a high mechanical strength that can sufficiently withstand such an impact because bubbles caused by the aeration operation performed for this purpose collide violently with the film surface.

  Conventionally, as such a separation membrane support, a double structure of a surface layer having a large opening and a large surface roughness using a thick fiber and a back layer having a small structure and a small opening using a thin fiber Separation membrane support characterized by comprising a non-woven fabric of a multilayer structure based on the above (see Patent Document 1), and at least a modified cross section having a fiber specific surface area larger than that of a circular cross-section surface layer on the membrane production side A separation membrane support comprising a fiber mainly composed of fibers is known (see Patent Document 2). However, these separation membrane supports have no problem with respect to strength, and there is a problem that sufficient strength cannot be obtained.

  Further, the separation membrane support having such a high mechanical strength is composed of a long-fiber nonwoven fabric composed of thermoplastic continuous filaments, and the tensile strength in the transverse direction of the long-fiber nonwoven fabric is 50 to 900 N / 5 cm. In addition, a separation membrane support is known in which the nonwoven fabric nonwoven fabric has a tensile strength aspect ratio of 1.0 to 2.7 (see Patent Document 3).

  However, these conventional separation membrane supports have not only excellent membrane-forming properties and high mechanical strength, but also functions to improve the performance of the separation membrane, such as the rejection rate and water permeability of the substance to be separated. It wasn't.

Japanese Patent Publication No. 4-21526 JP 11-347383 A JP 2009-131840 A

  The present invention comprises a nonwoven fabric and has excellent membrane-forming properties and high mechanical strength when supporting separation membranes such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes, and further separation It aims at providing the separation membrane support which contributes to the performance improvement of a membrane, and its manufacturing method.

  That is, the present invention is a separation membrane support for forming a membrane having a separation function on the surface thereof, and is a separation membrane support characterized by comprising a hydrophilic nonwoven fabric.

  Further, the present invention is a method for producing the separation membrane support of the present invention, comprising a step of thermocompression bonding the nonwoven fabric and a step of applying a hydrophilic agent, wherein the hydrophilic agent is applied after the nonwoven fabric is thermocompression bonded. This is a method for producing a separation membrane support.

  The present invention also provides a separation membrane sheet comprising a membrane having a separation function formed on the surface of the separation membrane support of the present invention.

  The present invention also provides a membrane separation element comprising the separation membrane sheet of the present invention.

  According to the present invention, it is made of non-woven fabric and has excellent film forming properties and high mechanical strength when supporting separation membranes such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes, and further separation It becomes possible to obtain a separation membrane support capable of enhancing the performance of the membrane.

  The separation membrane support of the present invention comprises a nonwoven fabric. Examples of the polymer of fibers constituting the nonwoven fabric in the present invention include polyester polymers, polyamide polymers, polyolefin polymers, and mixtures and copolymers thereof. Among these, a polyester polymer is preferable because a separation membrane support having excellent mechanical strength, durability such as heat resistance, water resistance, and chemical resistance can be obtained.

  The polyester polymer is a polyester composed of an acid component and an alcohol component. Examples of the acid component include aromatic carboxylic acids such as terephthalic acid, isophthalic acid and phthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexanecarboxylic acid. Further, as the alcohol component, ethylene glycol, diethylene glycol, polyethylene glycol, or the like can be used.

  Examples of the polyester polymer include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid and polybutylene succinate, and copolymers thereof.

  A biodegradable polymer is also preferable as a fiber polymer constituting the nonwoven fabric because it can be easily discarded after use and has a low environmental load. Examples of the biodegradable resin include polylactic acid, polybutylene succinate, polycaprolactone, polyethylene succinate, polyglycolic acid, and polyhydroxybutyrate. Of these, polylactic acid is a plant-derived resin that does not deplete petroleum resources, is relatively high in mechanical properties and heat resistance, and is preferably a biodegradable resin with low production costs. The polylactic acid 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 fibers constituting the nonwoven fabric constituting the separation membrane support of the present invention may be a single component fiber, a composite fiber composed of a plurality of components, or a so-called mixed fiber type in which a plurality of types of fibers are mixed. 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 the melting point of the high melting point polymer is arranged around the high melting point polymer is preferable. By using such a composite fiber, the fibers in the nonwoven fabric are firmly bonded to each other by thermocompression bonding. Therefore, when the nonwoven fabric is used as a separation membrane support, nonuniformity at the time of casting a polymer solution due to fluffing and membrane defects are caused. Can be suppressed. In addition, since the number of adhesion points increases compared to a mixed fiber type in which fibers consisting only of a high melting point polymer and fibers consisting only of a low melting point polymer are mixed, the mechanical strength when used as a separation membrane support is increased. It leads to improvement. The difference in melting point between the high melting point polymer and the low melting point polymer is preferably 10 to 140 ° C. By setting the difference in melting point to 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, by setting the difference in melting point to 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 roll at the time of thermocompression bonding using a hot roll, and productivity is increased. Can be suppressed.

  The melting point of the high-melting polymer is 160 to 320 ° C., because the membrane-forming property when forming the separation membrane on the separation membrane support of the present invention is good and a separation membrane with excellent durability can be obtained. Is preferred. By setting the melting point of the high-melting polymer to 160 ° C. or higher, more preferably 170 ° C. or higher, and more preferably 180 ° C. or higher, the morphological stability can be improved even when passing through the process of applying heat during the production of the separation membrane or membrane separation element. Excellent. On the other hand, by setting the temperature to 320 ° C. or lower, more preferably 300 ° C. or lower, and more preferably 280 ° C. or lower, it is possible to suppress a great decrease in productivity due to the great consumption of heat energy for melting during the production of the nonwoven fabric. .

  Moreover, as melting | fusing point of a low melting-point polymer, 120 degreeC or more is preferable, More preferably, it is 140 degreeC or more.

  Examples of the combination of the high melting point polymer and the low melting point polymer (high melting point polymer / low melting point polymer) include polyethylene terephthalate / polybutylene terephthalate, polyethylene terephthalate / polytrimethylene terephthalate, polyethylene terephthalate / polylactic acid, and Examples include polyethylene terephthalate / copolymerized polyethylene terephthalate. Moreover, as a copolymerization component of copolymer polyethylene terephthalate, isophthalic acid etc. are preferable here.

  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. By setting the proportion of the low melting point polymer to 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more, thermal adhesiveness that can be used as a separation membrane support can be obtained. . On the other hand, 70 mass% or less, More preferably, it is 60 mass% or less, More preferably, it is 50 mass% or less, and a low melting-point polymer component fuse | melts to the said roll at the time of the thermocompression bonding with a hot roll, and productivity falls. This can be suppressed.

  Additives such as crystal nucleating agents, matting agents, lubricants, pigments, antifungal agents, antibacterial agents and flame retardants may be added to the nonwoven fabric as long as the effects of the present invention are not impaired. Among these, metal oxides such as titanium oxide are preferable because they have the effect of improving the adhesiveness of the nonwoven fabric by increasing the thermal conductivity during thermocompression molding of the nonwoven fabric with a hot roll. Aromatic bisamides and / or alkyl-substituted aliphatic monoamides are preferred because they have the effect of improving the adhesion stability by increasing the releasability between the thermal roll and the web.

  Examples of the composite form of the composite fiber include a concentric core-sheath type, an eccentric core-sheath type, and a sea-island type from the viewpoint of efficiently obtaining a thermal bonding point between fibers.

  Examples of the cross-sectional shape of the fibers constituting the nonwoven fabric include a circular cross section, a flat cross section, a polygonal cross section, a multileaf cross section, and a hollow cross section.

  Among them, a concentric core-sheath type as a composite form and a circular cross section or a flat cross section as a fiber cross-sectional shape can firmly bond fibers to each other by thermocompression bonding. This is preferable because the thickness can be reduced and space can be saved when a membrane separation element is obtained.

  As an average fiber diameter of the fiber which comprises a nonwoven fabric, it is preferable that it is 3-30 micrometers. By setting the average fiber diameter of the fibers to 3 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more, spinnability is unlikely to deteriorate during the production of the nonwoven fabric, and excessive densification of the nonwoven fabric can be suppressed. it can. On the other hand, by setting the average fiber diameter of the fibers to 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. Densification can be suppressed.

  As the nonwoven fabric constituting the separation membrane support of the present invention, a spunbond nonwoven fabric produced by a spunbond method is preferred. This is because a 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 separation membrane support of the present invention can be a laminate composed of a plurality of nonwoven fabric layers, so that it is possible to obtain a separation membrane support with better uniformity, and further the density distribution in the thickness direction of the support. This is preferable because it can be easily adjusted. Examples of the laminated body include a laminated body of two layers of spunbonded nonwoven fabric and a laminated body of a three-layer structure in which a meltblown nonwoven fabric is arranged between two layers of spunbonded nonwoven fabric, and at least one layer is It is preferably a spunbond nonwoven fabric, and more preferably composed of only a spunbond nonwoven fabric.

As a fabric weight of the nonwoven fabric which comprises the separation membrane support body of this invention, 20-300 g / m < ² > is preferable. By setting the basis weight to 20 g / m ² or more, more preferably 30 g / m ² or more, and even more preferably 40 g / m ² or more, it is possible to obtain a good film-forming property with less permeation and the like during casting of the polymer solution. In addition, a separation membrane sheet having high mechanical strength and excellent durability can be obtained. On the other hand, when the basis weight is 300 g / m ² or less, more preferably 240 g / m ² or less, and even more preferably 180 g / m ² or less, the thickness of the separation membrane sheet can be reduced and the membrane separation element can be saved. Space can be achieved.

  It is preferable that the nonwoven fabric which comprises the separation membrane support of this invention contains the high-density part by partial thermocompression bonding, and the low-density part which is not partially thermocompression-bonded. By including the high-density part by partial thermocompression bonding, the mechanical strength of the nonwoven fabric is improved, and a separation membrane support having excellent durability can be obtained. Here, the partial thermocompression bonding is a thermocompression bonding using a roll having a pair of irregularities, or a roll having an irregularity and a flat roll, and a portion not partially thermocompression is a roll having a pair of irregularities. In the case of partial thermocompression bonding, it is a part that does not touch any convex part, that is, a part where the concave part and the concave part overlap. In the case of partial thermocompression bonding with a roll having unevenness and a flat roll, the convexity of the roll having unevenness. The part that doesn't touch the part. In addition, even when the entire surface of the nonwoven fabric is thermocompression bonded with a flat roll before and after partial thermocompression bonding, the portion that does not touch the convex portion during partial thermocompression bonding with a rugged roll is partially thermocompression bonded. There is no part.

  Further, the fiber density of the high-density portion by partial thermocompression bonding is preferably 0.6 to 1.0. Separation membrane support excellent in durability by improving the mechanical strength of the nonwoven fabric by setting the fiber density of the high density portion to 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more. Can be obtained.

  On the other hand, by including a low-density part that is not partially thermocompression bonded, there are voids in the nonwoven fabric, and when used as a separation membrane support, the polymer solution that is the raw material of the membrane during the film formation is inside the separation membrane support By permeating into the substrate, the separation membrane and the separation membrane support can be firmly bonded, and the water permeability inside the support can also be secured. Furthermore, in the process of manufacturing the membrane separation element from the separation membrane sheet, the separation membrane support and the support plate are bonded so that the liquid before and after separation does not enter and exit at the part other than the separation membrane when used as the membrane separation element. In many cases, the end portions of the separation membrane support are bonded to each other, but in this case, the adhesive substance penetrates into the low density portion of the separation membrane support so that it can be firmly bonded. it can. The fiber density of the low density portion is preferably 0.1 to 0.5. By setting the fiber density of the low density portion to 0.1 or more, more preferably 0.2 or more, it is possible to prevent the occurrence of fuzzy membrane defects when contacting with the process member or the like during membrane formation of the separation membrane. Further, by setting the fiber density of the low density portion to 0.5 or less, more preferably 0.4 or less, the polymer solution as a raw material of the membrane at the time of forming the separation membrane sufficiently penetrates into the inside of the support, and the membrane and the support. The body can be firmly bonded, and the water permeability inside the support can also be secured.

  As an area ratio with respect to the nonwoven fabric of the high-density part formed by partial thermocompression bonding, 10 to 50% is preferable. By making the area ratio of the high density portion 10% or more, more preferably 12% or more, and further preferably 14% or more, the mechanical strength of the nonwoven fabric is improved, and a separation membrane support having excellent durability is obtained. Can do. On the other hand, by setting the area ratio to 50% or less, more preferably 40% or less, and even more preferably 30% or less, the polymer solution that is a raw material of the membrane at the time of forming the separation membrane sufficiently permeates the inside of the support, and the separation The membrane and the separation membrane support can be firmly bonded, and the water permeability inside the support can be secured.

  The major axis / minor axis ratio of the high-density portion formed by partial thermocompression bonding is preferably 1.0 to 3.0. By setting the major axis / minor axis ratio to 3.0 or less, more preferably 2.0 or less, and even more preferably 1.5 or less, even if a force is applied in any direction of the nonwoven fabric, the deformation is small. A separation membrane support having excellent strength can be obtained. As the shape of the high density portion, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, and the like are preferable.

  The high-density portions formed by partial thermocompression bonding are preferably present at regular intervals in both the length direction and the width direction of the nonwoven fabric. By uniformly interspersing the high density portions, it is possible to reduce variation in strength within the nonwoven fabric.

The size of the high-density portion formed by partial thermocompression bonding is preferably 0.2 to 5.0 mm ² . By setting the size of the high-density portion to 0.2 mm ² or more, more preferably 0.3 mm ² or more, and further preferably 0.4 mm ² or more, the mechanical strength of the nonwoven fabric is improved and the separation is excellent in durability. A membrane support can be obtained. On the other hand, by setting the size of the high density portion to 5.0 mm ² or less, more preferably 4.0 mm ² or less, and even more preferably 3.0 mm ² or less, a polymer solution that becomes a raw material of the membrane at the time of forming the separation membrane However, there is little difference between the portion that penetrates into the support and the portion that does not penetrate sufficiently, and the separation membrane and the separation membrane support can be firmly bonded.

The number density of the high-density portion formed by partial thermocompression bonding is preferably 5 to 50 / cm ² . By setting the number density of the high-density portion to 5 pieces / cm ² or more, more preferably 10 pieces / cm ² or more, and even more preferably 15 pieces / cm ² or more, the mechanical strength of the nonwoven fabric is improved and durability is improved. An excellent separation membrane support can be obtained. On the other hand, by setting the number density of the high density portion to 50 pieces / cm ² or less, more preferably 45 pieces / cm ² or less, and further preferably 40 pieces / cm ² or less, it becomes a raw material of the membrane at the time of forming the separation membrane. The polymer solution sufficiently permeates the inside of the support, the separation membrane and the separation membrane support can be firmly bonded, and water permeability can be ensured.

  The thickness of the nonwoven fabric constituting the separation membrane support of the present invention is preferably 0.05 to 0.50 mm. By setting the thickness of the non-woven fabric to 0.05 mm or more, more preferably 0.10 mm or more, and still more preferably 0.15 mm or more, it is possible to obtain a good film forming property with less over-penetration and the like during casting of the polymer solution. In addition, a separation membrane sheet having high mechanical strength and excellent durability can be obtained. On the other hand, the thickness of the non-woven fabric is 0.50 mm or less, more preferably 0.45 mm or less, and even more preferably 0.40 mm or less, thereby reducing the thickness of the separation membrane sheet and saving the membrane separation element. Space can be achieved.

  The tensile strength of the nonwoven fabric constituting the separation membrane support of the present invention is preferably 250 to 800 N / 5 cm, more preferably 300 to 750 N / 5 cm, still more preferably 350 to 700 N / 5 cm. Moreover, as a tensile elongation of the nonwoven fabric which comprises the separation membrane support body of this invention, 15 to 50% is preferable, More preferably, it is 18 to 45%, More preferably, it is 20 to 40%.

Moreover, as a strong elongation product of the nonwoven fabric which comprises the separation membrane support body of this invention, 400-1000 N / 5cm is preferable. Here, the high elongation product is a value calculated by the following equation.
Strong elongation product [N / 5 cm] = tensile strength [N / 5 cm] × (1 + tensile elongation [%] / 100)
When the membrane separation element is formed by setting the high elongation product of the nonwoven fabric to 400 N / 5 cm or more, more preferably 450 N / 5 cm or more, and even more preferably 500 N / 5 cm or more, aeration operation or pressure fluctuation during operation of the filtration device Therefore, it is possible to suppress damage due to instantaneous force. On the other hand, the strength elongation product of the nonwoven fabric is 1000 N / 5 cm or less, more preferably 950 N / 5 cm or less, and even more preferably 900 N / 5 cm or less. Liquid leakage and deformation of the separation membrane can be suppressed.

  The stress at 5% elongation of the nonwoven fabric constituting the separation membrane support of the present invention is preferably 100 to 500 N / 5 cm. By setting the stress at 5% elongation of the nonwoven fabric to 100 N / 5 cm or more, more preferably 150 N / 5 cm or more, and even more preferably 200 N / 5 cm or more, when the membrane separation element is used, Deformation due to vertical pressure can be suppressed. On the other hand, when the stress at 5% elongation of the nonwoven fabric is 500 N / 5 cm or less, more preferably 450 N / 5 cm or less, and even more preferably 400 N / 5 cm or less, the bonded portion with the support plate is caused by the texture of the nonwoven fabric becoming harder. Leakage of liquid from the can be suppressed.

  The separation membrane support of the present invention is a separation membrane support that forms a membrane having a separation function on the surface thereof.

  In the separation membrane support of the present invention, it is important that the nonwoven fabric to be formed has hydrophilicity. By using a hydrophilic nonwoven fabric as the separation membrane support, a separation membrane having high water permeability can be obtained. The mechanism is presumed as follows. That is, the separation membrane and the support are often integrated by a method of casting and fixing a polymer solution as a raw material of the separation membrane on the support, but in fixing the polymer solution, A widely used method is to immerse and fix the stretched polymer solution together with the support in a coagulation liquid containing water as a main component. At this time, by using the aspect of the present invention as a separation membrane support, that is, a hydrophilic nonwoven fabric, the coagulation liquid efficiently penetrates into the support from the opposite surface on which the polymer solution is cast, From the support side, the solidification of the polymer solution, that is, the formation of the separation membrane proceeds rapidly. Thus, it is considered that the micropore diameter in the film can be formed with an appropriate size without becoming too small. In addition, since the amount of the polymer solution penetrating into the inside of the support can be suppressed, it has high water permeability by suppressing the amount of the membrane substance inside the support that becomes the resistance of water to permeate when used as a separation membrane. It is considered that a separation membrane can be obtained.

  The water absorption time of the nonwoven fabric constituting the separation membrane support of the present invention is preferably 0 to 10 seconds. By setting the water absorption time of the nonwoven fabric to 10 seconds or less, more preferably 7 seconds or less, and even more preferably 5 seconds or less, the coagulating liquid containing water as a main component quickly penetrates into the separation membrane support during the production of the separation membrane. The polymer solution cast on the support can be coagulated to improve the water permeability of the formed separation membrane.

  The separation membrane formed on the separation membrane support of the present invention is a separation membrane formed by forming a membrane having a separation function, such as a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane. And the like. In particular, since the separation membrane support of the present invention is considered to contribute to the formation of micropores with an appropriate pore size by the mechanism presumed as described above, a microfiltration membrane or an ultrafiltration membrane consisting only of a membrane having a separation function. It can be preferably used for a film.

  Next, a method for producing the separation membrane support of the present invention will be described.

  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, sucked and drawn by a high-speed suction gas, spun, and then collected on a moving conveyor to collect the web. Furthermore, it is possible to produce a long-fiber non-woven fabric by integration by continuous thermocompression bonding. At this time, in order to cause the constituent fibers to be highly oriented and crystallized, 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 the case of the melt-blowing method, a high-speed gas fluid is sprayed on the melted thermoplastic polymer to stretch the thermoplastic polymer into ultrafine fibers and collect them to produce a long fiber nonwoven fabric.

  Moreover, if it is a short fiber nonwoven fabric, the method of cut | disconnecting a long fiber to make 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 laminated body mentioned above, for example, as a manufacturing method of the laminated body which consists of a nonwoven fabric of two layers, after superimposing two layers of the nonwoven fabric of the temporarily bonded state obtained with one pair of rolls, it is partial thermocompression bonding. The method of integrating with each other can be preferably used. In addition, as a method for producing a laminate having a three-layer structure in which a meltblown nonwoven fabric is disposed between two layers of spunbond nonwoven fabric, a separate line is provided between two layers of temporarily bonded spunbond nonwoven fabric obtained by a pair of rolls. After stacking the melt blown nonwoven fabric manufactured in step 1, the method of integration by partial thermocompression bonding, the spunbond nozzle, the meltblown nozzle, the spunbond nozzle arranged on the top of the collection conveyor A method of collecting, laminating and thermocompression-bonding the extruded and fiberized webs in order can be preferably used.

  The partial thermocompression bonding of the nonwoven fabric can be performed using a roll having a pair of irregularities or a combination of a roll having irregularities and a flat roll.

  The temperature of the roll during partial thermocompression bonding is preferably 20 to 90 ° C., more preferably 30 to 70 ° C. lower than the melting point of the fibers constituting the nonwoven fabric. In the case of a composite fiber in which a low melting point polymer is arranged around a high melting point polymer, the roll temperature is preferably 20 to 90 ° C lower than the melting point of the low melting point polymer, and 30 to 70 ° C lower. Is more preferable. The linear pressure of the roll is preferably 196 to 784 N / cm, and more preferably 294 to 686 N / cm.

  In addition, as a method of partial thermocompression bonding, a so-called ultrasonic bonding method using an uneven roll and an ultrasonic vibrator can be used.

Further, in order to control the fiber density of the low density portion of the nonwoven fabric that has not been partially thermocompressed, a pair of flat rolls are wound continuously or once after the nonwoven fabric integrated by partial thermocompression is wound. A two-stage thermocompression bonding method in which the whole is thermocompression bonded can be preferably used. In this case, it is preferable that the difference between the temperature T ₁ of the melting point and the flat roll of the polymer constituting the surface of the fibers constituting the nonwoven fabric 70 to 150 ° C., more preferably 80 to 140 ° C., more preferably 90 130 ° C. The linear pressure of the flat roll is preferably 196 to 1960 N / cm, more preferably 294 to 1568 N / cm, and still more preferably 392 to 1176 N / cm.

  When the polymer is not hydrophilic, hydrophilicity can be imparted to the nonwoven fabric constituting the separation membrane support of the present invention by imparting a hydrophilic agent. Examples of hydrophilic agents include fatty acid salts, polyoxyethylene alkyl ether carboxylates, monoalkyl sulfates, alkyl polyoxyethylene sulfates, higher alcohol sulfates, polyoxyethylene alkyl ether sulfates, alkylbenzene sulfonates, and oleic acid. Anionic surfactants such as amide sulfonate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, dialkyl sulfosuccinate, aliphatic amine salt, aliphatic quaternary ammonium salt, alkyltrimethylammonium salt, dialkyl Cationic surfactants such as dimethylammonium salt, alkylbenzyldimethylammonium salt, alkylpyridium salt, alkylisoquinolium salt, benzethonium salt, polyoxyethylene alkyl ether, sorbitan fatty acid Steal, polyether polyester block copolymer, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene polyhydric alcohol fatty acid ester, polyhydric alcohol fatty acid ester, Nonionic surfactants such as sugar fatty acid esters and zwitterionic surfactants such as alkyldiethylenetriamineacetic acid, alkylcarboxybetaine, alkyldimethylbetaine, and alkylmethylaminocarboxylate can be used.

  As a method of imparting a hydrophilic agent to the nonwoven fabric constituting the separation membrane support of the present invention, a method of adding a hydrophilic agent to a resin that is a raw material for fibers, a method of imparting a hydrophilic agent to fibers, and a hydrophilic agent to a nonwoven fabric web A method of granting can be employed. Among them, the method of applying a hydrophilic agent after thermocompression bonding of the nonwoven fabric is preferable because the fibers can be bonded more strongly at the time of thermocompression bonding than when the hydrophilic agent is applied to the nonwoven fabric or fibers before thermocompression bonding. .

  As a method for applying the hydrophilic agent after thermocompression bonding of the nonwoven fabric, a spray coating method, a roll coating method using a gravure roll or a kiss roll, an impregnation method, or the like can be used. Among these, the impregnation method is preferable because it easily imparts a hydrophilic agent to the inside of the nonwoven fabric.

When applying the hydrophilic agent, a method of applying the hydrophilic agent in a state of an aqueous solution diluted with water is preferable because it can be applied more uniformly. In this case, if moisture remains in the nonwoven fabric, the polymer solution that becomes the raw material of the membrane coagulates in the portion where moisture is present during film formation, and the film formation becomes uneven. Need to be removed. At this time, preferably 5 to 40 ° C. As the difference _T 1 -T ₂ of temperatures _{T 1} and the drying temperature _{T 2} of the flat roll in case of thermocompression bonding at a pair of flat rolls. By setting T ₁ -T ₂ to 5 ° C. or higher, more preferably 10 ° C. or higher, and further preferably 15 ° C. or higher, the fiber density controlled by thermocompression using a flat roll is rarely changed. On the other hand, when T ₁ -T _{2 is set} to 40 ° C. or lower, more preferably 35 ° C. or lower, and further preferably 30 ° C. or lower, moisture can be sufficiently removed in a short drying time.

  The separation membrane sheet of the present invention is a separation membrane sheet formed by forming a membrane having a separation function on the surface of the separation membrane support of the present invention, and the separation membrane is formed on the separation membrane support of the present invention. As a method for producing a separation membrane sheet, a method of forming a separation membrane by casting a polymer solution on at least one surface of a separation membrane support to form a separation membrane is preferably used. The polymer solution cast on the separation membrane support has a separation function when it becomes a membrane, such as polyarylethersulfone such as polysulfone and polyethersulfone, polyimide, polyvinylidene fluoride, and cellulose acetate. The solution of is preferably used. Of these, a solution of polysulfone, polyarylethersulfone and polyvinylidene fluoride is more preferably used in terms of chemical, mechanical and thermal stability. The solvent can be appropriately selected according to the film-forming substance. In addition, 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 cross-linked polyamide membrane obtained by polycondensation of a polyfunctional acid halide and a polyfunctional amine is preferably used. it can.

  The membrane separation element of the present invention is a membrane separation element in which the above-mentioned separation membrane sheet is integrated with a flow path material or the like for easy handling. Examples of the form of the membrane separation element include a flat membrane plate frame type and pleats. Examples include molds and spiral molds. Among them, a flat membrane plate frame type in which the flow path material is sandwiched and integrated by two separation membrane sheets with the surface on which the separation membrane is formed outside is preferably used. A plurality of membrane 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, 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 the 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 first decimal place.

(4) Fabric weight of nonwoven fabric (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.

(5) Thickness (mm) of the high density portion and low density portion of the nonwoven fabric
Ten small sample samples were taken at random from the nonwoven fabric, taken with a scanning electron microscope at a cross section of 50 to 300 times, and the thickness of each of the high density portion and the low density portion was measured for each sample, and the average of them was measured. The values were rounded off to the second decimal place, and the thicknesses of the high density part and low density part were obtained. Here, the thickness of the high-density part is the smallest part in the thermocompression-bonded part, and the thickness of the low-density part is the thickest part in the part that is not thermocompression-bonded. Was measured respectively.

(6) Non-woven fiber density (-)
The weight was calculated from the basis weight (g / m ² ), thickness (mm), and polymer density obtained in the above (4) and (5), respectively, using the following formula and rounded off to the second decimal place.
Fiber density = basis weight (g / m ² ) ÷ thickness (mm) ÷ 10 ³ ÷ polymer density (g / cm ³ ).
The polymer densities of the polyethylene terephthalate resin and the copolyester resin were both calculated as 1.38 g / cm ³ .

(7) Tensile strength (N / 5cm) and tensile elongation (%) of nonwoven fabric
Based on 6.3.1 of JIS L 1913 (2010 edition), 5cm × 30cm non-woven fabric sample is strong at 5 points each in the machine direction and the transverse direction at a gripping distance of 20cm and a tensile speed of 10cm / min. Measure the elongation and elongation, read the strength and elongation at break, round the first decimal place to the longitudinal and transverse tensile strength and elongation, average longitudinal and transverse Values obtained by rounding off the first decimal place of the value were taken as the tensile strength and tensile elongation of the nonwoven fabric, respectively.

(8) Strong elongation product of nonwoven fabric (N / 5cm)
From the tensile strength and tensile elongation of the nonwoven fabric measured in the above (7), the strong elongation product was calculated by the following formula, and the value obtained by rounding off the first decimal place was taken as the strong elongation product of the nonwoven fabric.
Strong elongation product [N / 5 cm] = tensile strength [N / 5 cm] × (1 + tensile elongation [%] / 100).

(9) Stress at 5% elongation of nonwoven fabric (N / 5cm)
Measured based on 6.3.1 of JIS L 1913 (2010 edition). For the nonwoven fabric sample of 5 cm × 30 cm, measurement was performed at five 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 strength at 5% elongation is read from the obtained strength-elongation curve, and the value rounded to the first decimal place is the 5% elongation stress in the longitudinal and transverse directions, and the average value in the longitudinal and transverse directions The value obtained by rounding off the first decimal place was taken as the 5% elongation stress of the nonwoven fabric.

(10) Nonwoven fabric water absorption time (seconds)
Five nonwoven fabrics of 20 cm × 20 cm were collected, and the collected samples were fixed to a holding frame having a diameter of 15 cm and a height of 1 cm. The tip of the buret was placed above the fixed sample so that the distance from the sample surface was 1 cm, and one drop of water was dropped from the buret. The time from when the water droplet reached the sample surface until the specular reflection disappeared and only the wet state remained as the sample absorbed the water droplet was measured in units of 1 second using a stopwatch. The time of each of the five samples was measured, and the value obtained by rounding off the second decimal place of the average value of the obtained values was taken as the water absorption time of the nonwoven fabric.

(11) Membrane permeability coefficient of separation membrane (× 10 ⁻⁹ (m / s) / Pa)
Using the produced separation membrane, it was cut into a circle with a diameter of 5 cm, set in a cylindrical filter holder, and preliminarily permeated for 5 minutes while maintaining distilled water at 25 ° C. and a head height of 1 m (equivalent to a water pressure of 9800 Pa). After that, the permeated water was sampled for 3 minutes with the water head height kept at 1 m, and the permeation amount per unit time / unit area was obtained, and divided by the water pressure applied to the permeation surface. The water permeability coefficient was determined.

(12) Polystyrene latex fine particle rejection rate of separation membrane (%)
The produced separation membrane was set in a stirring cell (VHP-43K manufactured by Advantech Co., Ltd.) and filtered through a reverse osmosis membrane (SUL-G10 manufactured by Toray Industries, Inc.) at an evaluation pressure of 9.8 kPa and a stirring speed of 600 rpm. An evaluation stock solution is obtained by filtering an evaluation stock solution in which polystyrene latex fine particles (nominal pore size 0.083 μm manufactured by Celadin Co., Ltd.) are dispersed in water to a concentration of 20 ppm as fine particles having an average particle size of 0.09 μm or less. With respect to the filtered permeate, the absorbance of ultraviolet light having a wavelength of 250 nm was measured with a spectrophotometer (U-3200, manufactured by Hitachi, Ltd.), and the fine particle blocking rate was determined by the following equation.
Fine particle blocking rate = [(absorbance of raw water−absorbance of permeate) / absorbance of stock solution] × 100.

[Example 1]
(Core component)
A core component obtained by drying a polyethylene terephthalate resin having an intrinsic viscosity of IV 0.65, a melting point of 260 ° C., and a titanium oxide content of 0.3 mass% to a moisture content of 50 ppm or less was used.

(Sheath component)
What dried the copolymer polyethylene terephthalate resin of intrinsic viscosity IV0.66, isophthalic acid copolymerization rate 11 mol%, melting | fusing point 230 degreeC, and the content of titanium oxide 0.2 mass% to 50 ppm or less of moisture content was used as a sheath component. .

(Spinning and fiber web collection)
The core component and the sheath component are melted at temperatures of 295 ° C. and 270 ° C., respectively, and are combined into a concentric core-sheath type (circular cross section) at a base temperature of 300 ° C. and a core / sheath weight ratio of 80/20. After spinning, it was spun by an ejector at a spinning speed of 4400 m / min and collected as a fiber web on a moving net conveyor.

(Thermo-compression bonding)
The collected fiber web is passed between a metal concavo-convex roll in which true circular convex portions are uniformly arranged in a staggered pattern as an upper roll and a flat roll as a lower roll, and the upper and lower roll surface temperatures are 170. Partial thermocompression bonding was performed at 0 ° C. and a linear pressure of 588 N / cm. Further, the partially thermocompression-bonded sheet is continuously passed between a pair of flat rolls, and the entire surface is thermocompression bonded at the upper and lower roll surface temperatures of 120 ° C. and the linear pressure of 686 N / cm, and the fiber diameter is 13 μm and the basis weight is 110 g / m ² . A spunbonded nonwoven fabric having circular recesses with a diameter of 0.8 mm and a number density of 32 / cm ² was obtained.

(Hydrophilic treatment)
The obtained spunbonded nonwoven fabric was impregnated with a hydrophilic agent aqueous solution containing 0.2% by mass of polyoxyethylene sorbitan monostearate, dehydrated under pressure with a mangle roll, and then dried with a hot air dryer at a temperature of 110 ° C. for 72 seconds. A separation membrane support made of nonwoven fabric was obtained.

(Separation membrane formation)
Mixing 17% by mass of polyvinylidene fluoride (KF # 850 manufactured by Kureha Chemical Co., Ltd.), 8% by mass of polyoxyethylene sorbitan monostearate, 72% by mass of N, N-dimethylformamide, and 3% by mass of water, The mixture was sufficiently stirred at a temperature to obtain a film-forming stock solution. After cooling the obtained membrane-forming stock solution to a temperature of 30 ° C., 250 g / m ² was applied to the separation membrane support, and after application, immediately immersed in pure water at a temperature of 20 ° C. for 5 minutes, and further 90 ° C. Was immersed in hot water at a temperature of 2 ° C. for 2 minutes to wash away N, N-dimethylformamide as a solvent and polyoxyethylene sorbitan monostearate as a pore opening agent to form a separation membrane to obtain a separation membrane sheet.

[Example 2]
In the hydrophilization treatment, a separation membrane support was obtained in the same manner as in Example 1 except that the concentration of polyoxyethylene sorbitan monostearate in the hydrophilic aqueous solution was 0.02% by mass. A separation membrane was formed in the same manner as in Example 1 to obtain a separation membrane sheet.

[Example 3]
In the hydrophilization treatment, a separation membrane support was obtained in the same manner as in Example 1 except that the temperature of the hot air dryer was 130 ° C. and the drying time was 54 seconds. Thus, a separation membrane was formed to obtain a separation membrane sheet.

[Example 4]
(Core component)
The same polyethylene terephthalate resin as used in Example 1 was used as the core component.

(Sheath component)
The same copolymerized polyethylene terephthalate resin as used in Example 1 was used as the sheath component.

(Spinning and fiber web collection)
Using the above core component and sheath component, spinning and fiber web collection were performed in the same manner as in Example 1.

(Hydrophilic treatment)
The collected fiber web was spray-coated from above the web with a hydrophilic agent aqueous solution containing 5.0% by mass of polyoxyethylene sorbitan monostearate.

(Thermo-compression bonding)
After the hydrophilization treatment, the fiber web was subjected to partial thermocompression bonding and entire surface thermocompression bonding in the same manner as in Example 1 to provide 32 circular recesses having a fiber diameter of 13 μm, a basis weight of 110 g / m ² , and a diameter of 0.8 mm. A spunbonded nonwoven fabric having a number density of 1 piece / cm ² was obtained, and this was used as a separation membrane support.

(Separation membrane formation)
A separation membrane was formed on the separation membrane support in the same manner as in Example 1 to obtain a separation membrane sheet.

[Example 5]
(Mixed fiber web)
Each is made of polyethylene terephthalate, and polyoxyethylene sorbitan monostearate is attached to the fiber in advance at an adhesion rate of 0.2% by mass, the fiber diameter is 10 μm, the drawn fiber is 20% by mass with a fiber length of 38 mm, and the fiber diameter is 17 μm. Then, 30% by mass of drawn fiber having a fiber length of 64 mm and 50% by mass of undrawn fiber having a fiber diameter of 22 μm and a fiber length of 38 mm were mixed, and a mixed fiber web was produced using a card machine.

(Short fiber nonwoven fabric)
The mixed fiber web is continuously passed between a pair of flat rolls, and the whole surface is thermocompression bonded at a roll surface temperature of 180 ° C. and a linear pressure of 1176 N / cm to obtain a short fiber nonwoven fabric having a basis weight of 110 g / m ² and separated. A membrane support was obtained.

(Separation membrane formation)
A separation membrane was formed on the separation membrane support in the same manner as in Example 1 to obtain a separation membrane sheet.

In each of Examples 1 to 5, the film-forming property was good, and the membrane water permeability was 50 × 10 ⁻⁹ (m / s) / Pa or more.

[Comparative Example 1]
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that the hydrophilic treatment was not performed, and this was used as a separation membrane support, and a separation membrane was formed on the separation membrane support in the same manner as in Example 1. A separation membrane sheet was obtained.

In Comparative Example 1, the membrane permeability coefficient was less than 50 × 10 ⁻⁹ (m / s) / Pa.

Claims (7)

  A separation membrane support for forming a membrane having a separation function on the surface thereof, comprising a nonwoven fabric having hydrophilicity.   The separation membrane support according to claim 1, wherein the nonwoven fabric has a water absorption time of 0 to 10 seconds.   The separation membrane support according to claim 1 or 2, wherein the nonwoven fabric is a spunbonded nonwoven fabric composed of thermoplastic continuous filaments.   The separation membrane support according to any one of claims 1 to 3, which is a support for a microfiltration membrane or an ultrafiltration membrane.   A method for producing the separation membrane support according to any one of claims 1 to 4, comprising a step of thermocompression bonding the nonwoven fabric and a step of applying a hydrophilic agent, and applying the hydrophilic agent after thermocompression bonding the nonwoven fabric. A method for producing a separation membrane support.   A separation membrane sheet, wherein a membrane having a separation function is formed on the surface of the separation membrane support according to any one of claims 1 to 4.   A membrane separation element comprising the separation membrane sheet according to claim 6.