JPS60150887A - Removing method of endotoxin - Google Patents

Abstract

PURPOSE:To remove efficiently the endotoxin in water or in an aq. soln. by using a polyolefinic porous membrane having a specified micro laminated structure, keeping the temp. of a liquid to be treated at 35-70 deg.C, and treating said liquid. CONSTITUTION:A polyolefinic porous membrane having a micro laminated structure wherein vertically arranged microfibrils are connected by a jointing part 2 which is almost vertical to the microfibrils and many short shelf-shaped fine pores 3 formed by the joining part 2 are connected to each other in the thicknesswise direction, and having 20-90vol% porosity measured by a mercury porosimeter, is prepared. The water or the aq. soln. is brought into contact with said porous membrane and treated while keeping the temp. at 35-70 deg.C to remove the endotoxin in the water or in the aq. soln. The pore diameter of the hollow opening part of said porous membrane is preferably regulated to 200-300mum.

Description

Detailed Description of the Invention (a) Technical field The present invention relates to a method for removing endotoxin using a polyolefin porous membrane, in particular, a method for preventing clogging of the membrane,
In addition, it increases the ability to remove endotoxins and can be easily mixed with water or water.
/4 This invention relates to an improved method for removing endotoxin from a liquid.

(b) Prior Art Pyrogen present in water is said to be endotoxin mainly derived from bacterial cell membranes. This substance is stable against heating, and is said to not decompose at 100°C, but to decompose at temperatures above 250'C.

Since endotoxin causes fever when it enters the body, the removal of endotoxin has become an extremely important issue in the pharmaceutical industry, hospital water, and medical-related industries. Distillation is the traditional method for removing it.

Although reverse osmosis membrane methods are being used, they are not fully satisfactory in terms of energy costs, equipment costs, and ti production efficiency.

The present inventors previously developed a method for removing pyrodiene using a polyolefin porous membrane, and proposed this method in Japanese Patent Application No. 57-45983. These methods have the advantage of being able to remove endotoxins easily and with extremely low energy consumption compared to conventional methods, but when filtering water with a low purity level such as tap water, the pressure increases due to clogging. It was also found that filtering a large amount of water tends to reduce the ability to remove endotoxins. Therefore, there has been a need for a method that can treat a larger amount of water and effectively remove endotoxins.

(c) Purpose of the Invention The purpose of the present invention is to provide a method for removing endotoxins from water or an aqueous solution that does not easily cause clogging and does not reduce the endotoxin removal ability even when a large amount of water is filtered. be.

(d) Structure of the Invention The method for removing endotoxin in water or an aqueous solution according to the present invention is a method for removing endotoxins from water or an aqueous solution. Processes water or aqueous solutions using a polyolefin porous membrane that has a micro-laminated structure in which micropores are interconnected in the thickness direction of the membrane and has a porosity of 20 to 90% by volume as measured by a mercury porosimeter. In doing so,
It is characterized by maintaining the salinity of the liquid to be treated between 35°C and 70°C.

(e) Embodiment The polyolefin porous membrane used in the method of the present invention may be in any form such as a flat membrane or a tube membrane, but a porous hollow fiber membrane is particularly preferred since it can provide a large membrane area per unit volume. .

In addition, porous hollow fibers having a special microstructure as described above can be produced by, for example, highly oriented crystalline fibers obtained by melt-spinning polymers such as polypropylene or polyethylene using a special nozzle for manufacturing hollow fibers. It is produced by appropriately controlling each process condition in the main process of cold stretching and then heating stretching the drawn hollow fibers.

Next, the special microstructure of the separation membrane used in the present invention will be explained in more detail with reference to the drawings.

Figure 1 is a schematic diagram of one plane of the f1 layer structure of strip-shaped micropores, in which (1) is a microfibril, (2) is a node connected almost at right angles to the microfibril (11), and (3
) are rectangular micropores, and the rectangular micropores (3) constituted by microfibrils and nodes have a laminated structure with each node interposed therebetween.

Furthermore, the 111-layer structure of the micropores means that the fibers are laminated in the length direction of the fibers in one plane via the knots, and at the same time, the planes having such a structure are stacked in the thickness direction of the wall membrane of the hollow fibers.

Next, in the present invention, the appropriate range for the porosity measured with a mercury porosimeter is 20 to 90% by volume; if it is less than 20% by volume, water permeation rate is low, and if it exceeds 90% by volume, the mechanical strength of the membrane itself is low. weak. Among these, those with a content of 40 to 80% by volume are particularly preferred.

Since the micropores of the porous membrane of the present invention have a rectangular shape, the pore diameter cannot be defined by normal methods. So AS
If this is expressed as a bubble point measured in accordance with TMF-316-80, for the purpose of the present invention, 2.0
kg/crA to 15 kg/c- is appropriate.

If the bubble point is less than 1 to 2.0 kg/ct, endotoxin removal will be insufficient, and 15 kg/cff
If it exceeds l, water permeability will be insufficient.

Further, the thickness of the wall membrane layer of the porous hollow fiber is 10 to 1.00.
It is preferable that the diameter is μm because industrially stable production can be achieved. If the thickness is less than 10 μm, the mechanical strength of the wall film itself is weak (<17°C). However, it does not have to be smaller than 100 μm, and is particularly preferably 20 to 80 μm.

Although the diameter of the hollow opening in the porous hollow fiber of the present invention is not particularly limited, a diameter of about 200 to 300 μm is usually used.

The gist of the present invention is to maintain the temperature of the liquid to be treated between 35° C. and 70° C. when filtering water or an aqueous solution to remove endotoxin using the polyolefin porous membrane described above. Figure 2 shows a porosity of 63%.

A module with a filtration area Q of 3% was manufactured by bundling polyethylene hollow fiber membranes with a hollow fiber inner diameter of 270 μm, a membrane thickness of 55 μm, and a bubble point of 4.8 kir/cIIl into a loop shape and bonding the ends with polyethylene resin. This shows the pressure increase when city tap water is filtered. When the water temperature is 35°C or higher, the pressure rise is small and clogging is small, but when the water temperature is around room temperature, the pressure rise is large.

FIG. 3 shows the results of measuring the endotoxin concentration of the filtrate in the same experiment as FIG. 2. Here, the endotoxin concentration of the raw water before filtration was 4.7 ng/ml.

When the water temperature is 35°C or higher, the rate of increase in the endotoxin concentration in the filtrate is small even if the integrated filtration flow rate increases; however, when the water temperature is around room temperature, the endotoxin concentration in the filtrate increases.
The toxin concentration shows a rapid rise, indicating that endotoxin cannot be removed above a certain cumulative flow rate.

In this way, it was completely unexpected that the temperature of the water to be filtered would have a specific effect on clogging and endotoxin removal ability, and as a result, an extremely advantageous endotoxin removal method was developed. It is.

(f) Example The present invention will now be described in more detail with reference to Examples.

■ Stellaboar (manufactured by Mitsubishi Rayon Co., Ltd.) used in the examples is a membrane with many strip-shaped micropores formed by nodes in which microfibrils arranged in the vertical direction are connected at almost right angles to the microfibrils. This is a water filtration module incorporating a polyethylene porous hollow fiber membrane with a microlayer structure interconnected in the thickness direction.

Example 1 Tap water was passed through a preheater and heated to the temperature shown in Table 1, and 7. -i-'y bore ■, crotch area, 3 m + porosity of porous hollow fiber membrane 63% by volume, bubble point 4,
9 kg/cnl) (flow rate 11/min)
), Stellaboar■ pressure -1=! (clogging) and the endotoxin concentration of the filtrate were measured using a synthetic substrate method.

The data is for 22 water passes.

Table 1 Temperature Pressure rise difference Endotoxin concentration (kg/c
nt) (ng/m1) 37°C0,60,O8 50°c 0.4 0.20 60°c 0.23 0.17 (Membrane area 4 m', porosity of porous hollow fiber membrane 63 volume H1 %
, the bubble point was 4.7 kg/ct) (flow rate 3.5±0.51/·i·). Stella Boar (
l! The endotoxin concentration of the filtrated water was measured. 500 ml of 99% ethanol was added to the used module and filtered, and the concentration of organic matter in the filtrate was measured gravimetrically.

The data is for 30M water flow.

Table 2 45~50°CO, 10, 150, 41

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram in one plane of a laminated structure of strip-shaped micropores of a porous hollow fiber membrane used in the present invention. FIG. 2 is a diagram showing the relationship between the integrated flow rate and the crotch differential pressure at various temperatures of the liquid to be treated. FIG. 3 is a diagram showing the integrated flow rate of the liquid to be treated at various temperatures and the endotoxin concentration in the filtrate. I: microfibril, 2: node, 3: strip-like fine structure. Figure 1 Figure 2 Figure 3 - O* 3't R@ (m3)

Claims (1)

[Scope of Claims] 1. A large number of strip-shaped micropores formed by nodes in which microfibrils arranged in the longitudinal direction are connected at approximately right angles to the microfibrils are interconnected in the thickness direction of the membrane. When treating water or an aqueous solution using a polyolefin porous membrane that has a micro-laminated structure and a porosity of 20 to 90% by volume as measured by a mercury porosimeter, the temperature of the liquid to be treated is kept between 35°C and 70°C. A method for removing endotoxin in water or an aqueous solution, which comprises maintaining the endotoxin at ℃. 2. Bubble point of porous membrane is 2.0kg10J~1
5 kg/c+J. The method for removing endotoxin according to claim 1. 3. The endotoxin removal method according to claim 1 or 2, wherein the porous membrane is a hollow fiber membrane.