Semipermeable membrane supporting body and manufacturing method thereof

Abstract

A task of the invention is to provide a semipermeable membrane supporting body which has excellent smoothness on a semipermeable membrane coating surface and can not be permeated by the semipermeable membrane solution. The semipermeable membrane supporting body is characterized in that the semipermeable membrane supporting body is composed of non-woven fabric which comprises more than two main synthetic fiber and adhesive synthetic fiber with different fiber diameters and is provided with the semipermeable membrane coating surface and a semipermeable membrane non-coating surface. In a thickness direction when observed from a cross section SEM of the non-woven fabric, a cross section aspect ratio (long diameter / short diameter of the cross section of the fiber) of the main synthetic fiber in a range between a surface and 1 / 3 part of the semipermeable membrane coating surface and / or a cross section aspect ratio (long diameter / short diameter of the cross section of the fiber) of the main synthetic fiber in a range between a surface and 1 / 3 part of the semipermeable membrane non-coating surface are 1.2-3.0.

Description

Technical field [0001] The present invention relates to a semipermeable membrane support and a manufacturing method of the semipermeable membrane support. Background technique [0002] Semi-permeable membranes are widely used in the fields of desalination of seawater, water purification, food concentration, wastewater treatment, blood filtration, and ultrapure water production for medical use and semiconductor cleaning. The semipermeable membrane is composed of synthetic resins such as cellulose resin, polysulfone resin, polyacrylonitrile resin, fluorine resin, polyester resin, polyamide resin, and polyimide resin. However, the semipermeable membrane monomer has poor mechanical strength, so it is used on one side of the semipermeable membrane support (hereinafter referred to as "semipermeable membrane coating surface") composed of a fibrous substrate such as non-woven fabric or woven fabric. A semi-permeable membrane is used. [0003] The method of providing a semipermeable membr...

AI Technical Summary

Problems solved by technology

However, there is a problem that since thick fibers are used on the surface of the semipermeable membrane, although the adhesiveness between the semipermeable membrane and the semipermeable membrane support is improved, the smoothness is low.

In addition, there is the following problem: due to the use of thick fibers, the semipermeable membrane solution enters the inside of the semipermeable membrane support, and in order to obtain the desired thickness of the semipermeable membrane, a large amount of semipermeable membrane solution is required

In addition, there is the following problem: the former uses thin fibers on the non-coating surface, so the adhesiveness between the non-coating surfaces is not good

However, there is a problem that the semipermeable membrane is set so as to reach the concave portion of the semipermeable membrane support having a concave portion on the non-coating surface or the semipermeable membrane reaches the semipermeable membrane through a hole formed on the semipermeable membrane coating surface. The semipermeable membrane is installed so as to reach the non-coated surface, so the thickness of the semipermeable membrane is not uniform

However, this method has the following problem: the semipermeable membrane support having the characteristics of low absolute value of the average density in the region from the semipermeable membrane application side to 50% of the total thickness cannot prevent the penetration of the semipermeable membrane solution

In addition, in order to increase the breaking length, it is necessary to increase the heat or pressure applied to the non-woven fabric in the hot-pressing process, although there is a possibility of improving the non-uniformity of the non-woven fabric caused by the tensile stress or the partial expansion and contraction of the fiber caused by heat. However, the following problems remain: Excessive application of heat and pressure in the entire thickness direction of the nonwoven fabric, excessive melting of the binder synthetic fibers contained in the nonwoven fabric, and excessive reduction of voids; wrinkle

Especially in Patent Document 8, there is also the following problem: since the smoothness of the semipermeable membrane coating surface and the non-coating surface are equalized, the smoothness of the semipermeable membrane coating surface and the semipermeable membrane Compatibility with the adhesiveness of the semi-permeable membrane support is difficult, and further, there are still problems with the adhesiveness between the non-coated surfaces

[0012] In order to improve the adhesion between the semipermeable membrane and the semipermeable membrane support, a semipermeable membrane support containing special-shaped cross-section fibers in the semi-permeable membrane coating surface layer has also been proposed, but there is the following problem: the special-shaped cross-section fibers are matched to the semi-permeable membrane. In the case of a semi-permeable membrane support, when the fibers are dispersed in water in the wet papermaking process, the fibers are caught and entangled in the convex or concave portions formed on the fibers with a different cross-section, and cannot be dispersed uniformly (for example, refer to Patent Document 9).

However, when using a binder synthetic fiber composed of a core-sheath type polyester conjugate fiber, the binder component is only the sheath portion, so the binder component is about 1 compared to the unstretched binder synthetic fiber. / 2, therefore, sometimes sufficient adhesive strength cannot be obtained

[0017] As mentioned above, the smoothness of the coated surface of the semipermeable membrane, the adhesiveness between the semipermeable membrane and the semipermeable membrane support, the adhesiveness between the non-coated surfaces, the prevention of penetration, and the prevention of semipermeable membrane cannot be fully balanced. A semi-permeable membrane support with properties such as lateral bending and wrinkle prevention when forming a permeable membrane

In particular, there is no consideration in Patent Documents 1 to 13 regarding the adhesiveness between non-coated surfaces.

Images