JPS60238335A - Method for treating porous film - Google Patents

Abstract

PURPOSE:To improve the sanitary property of a porous sulfonated polyethylene film without deteriorating the performance of the film, by treating the film with an aqueous solution of a hypohalite. CONSTITUTION:A porous sulfonated polyethyene film is treated with an aqueous solution containing a hypohalite. The above-mentioned film preferably has 0.05- 2 milliequivalents/g, expressed in terms of exchange equivalent, sulfone groups present on the outside of the film and pore surface and further 0.05-1mum average pore diameter and 30-85% porosity. Sodium hypochlorite is preferred for the hypohalite, and used as an aqueous solution adjusted to 5-9pH and 0.5- 3wt% concentration. The treatment is preferably carried out at 50-80 deg.C for 10-120min, preferably 30-60min.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for treating a hydrophilic membrane, and more specifically, the present invention relates to a method for treating a hydrophilic membrane, in particular a method for treating a hydrophilic porous membrane obtained by sulfonating a polyethylene porous membrane with an aqueous solution containing a hypohalite. This invention relates to a method for improving membrane hygiene without reducing membrane performance.

(Prior art and its problems) In recent years, precision filtration membranes have been widely used in various fields including industrial wastewater treatment, separation and concentration in food and pharmaceutical manufacturing processes, and the like. Such precision filtration membranes made of materials such as cellulose acetate, polyamide, polyvinyl alcohol, and ethylene-vinyl alcohol copolymers have been developed and put into practical use. However, porous membranes made from these hydrophilic polymer compounds have an affinity for water and aqueous liquids, so they are suitable for filtering water and aqueous liquids, but on the other hand, they have an affinity for water. This causes swelling and softening in water and aqueous liquids, resulting in a compaction phenomenon in which the form of the porous membrane physically changes during filtration of water and aqueous liquids, leading to problems such as a decrease in water permeability over time. An attempt has been made to solve the above-mentioned drawbacks by subjecting only the pore surface and outer surface of a polyethylene porous membrane, which is a hydrophobic polymer, to hydrophilic treatment (Japanese Unexamined Patent Publication No. 57-14143).
Publication No. 2). This membrane has properties such as high permeability, excellent chemical resistance, excellent mechanical strength, and sharp pore size distribution, making it suitable for filtration of aqueous liquids. However, with this membrane, if the object to be filtered is a high-temperature aqueous liquid of 70 to 100°C, there is a risk that the eluate from the membrane will mix with the F solution, so it is not suitable for food or pharmaceutical applications where eluate from the membrane is extremely disliked. The problem was that it wasn't suitable.

As a result of intensive research to solve the above-mentioned drawbacks, the present inventors have found that by treating a sulfonated polyethylene porous membrane with an aqueous solution containing a hypohalite, the membrane becomes more hydrophilic.
The present invention was achieved by discovering a highly permeable membrane that reduces eluates from the membrane without deteriorating its performance.

(Structure of the Invention) The present invention is a method for treating a porous membrane, which is characterized by treating a porous sulfonated polyethylene membrane with an aqueous solution containing a hypohalite.

As a sulfonated polyethylene porous membrane, sulfone groups of 0.05 to 2 milliequivalents/gram in terms of exchange equivalent are mainly present on the outer surface and pore surface of the membrane, and the average pore size is 0.
．． A porous membrane having a porosity of 0.05 to 1 μm and a porosity of 30 to 85% is preferred. An average pore diameter of 005 to 1 μm is suitable for removing fine particles, bacteria, etc. in water and aqueous liquids, or blood cell components in blood. A porosity of 30 to 85% is appropriate for achieving a good balance between permeability and mechanical strength. , Car A with a porosity of 30% has excellent mechanical strength and elongation, but has low permeation performance and cannot be effectively used as a porous membrane. Further, when the porosity is 85% and the porosity is 14%, it has high permeability, but the mechanical strength and elongation are too small to be used for practical use. An exchange equivalent of 0.05 to 2 milliequivalents/gram is suitable for achieving a good balance between hydrophilicity and mechanical strength and elongation. If the exchange equivalent is o, o s mi+) equivalent/gram ice drop, it is good in terms of mechanical strength and elongation, but it does not have hydrophilic properties. If the exchange equivalent is less than 2 milliequivalents/gram, hydrophilicity is imparted, but the mechanical strength and elongation are too low to be of practical use.

The tetragenate hypochlorite in the present invention includes sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, sodium hypobromite, etc. is preferred.

In the method of treating an aqueous solution containing a hypohalite in the present invention, a sulfonated polyethylene porous membrane is treated with an aqueous solution containing a hypohalite.
It is preferable to immerse in a hypohalite aqueous solution having a H of 5 to 9, a temperature of 50 to 80°C, and a concentration of 05 to 3N%. If the concentration, temperature, and pH of the hypohalite aqueous solution are lower than the above range, there will be little effect in reducing eluates from the membrane, while if it is higher than the above range, the strength and elongation of the membrane will tend to decrease. The treatment time for hypohalite aqueous solution, which shows
-120 minutes, preferably 30-60 minutes.

In the present invention, by treating a sulfonated polyethylene porous membrane with an aqueous solution containing a hypohalite, the contradictory performance requirements of substantially eliminating eluates from the membrane and not reducing the hydrophilicity of the membrane can be met. It is amazing how satisfied the scales are.

The reason for this is not clear, but FT-IR (Fourier transform infrared absorption spectrum), XPS (X-ray photoelectron spectrum)
Analysis of sulfonated polyethylene porous membranes shows that sulfone groups give hydrophilicity, but membranes treated with an aqueous solution containing hypohalite have both sulfone groups and carboxylic acid groups, and these It is presumed that this is because the two types of functional groups impart hydrophilicity.

Note that the various physical properties shown in this specification were determined by the following measurement method.

The amount of eluate from the membrane is determined by the amount of potassium permanganate consumed (KMnO4 consumption) of the eluate test solution, that is, the amount of potassium permanganate consumed (KMnO4 consumption) of the eluate test solution, that is, the amount of potassium permanganate consumed (KMnO4 consumption) of the eluate test solution. The amount consumed is measured by the difference from the blank test solution.

The breaking strength (strength ψ) and elongation at break (%) were measured using an Instron tensile tester according to ASTM D-882 (strain rate l).
A;, 1. )ic.

The average pore diameter (μ) is measured as a pore diameter that indicates a pore volume of 2 of the total pore volume on a pore diameter-pore volume integral curve determined by a mercury porosimeter.

The exchange equivalent (milliequiv./gram) is the sulfonic acid (-8o
A porous membrane of type 3H) is placed in an aqueous calcium chloride (IN) solution to achieve equilibrium, and the hydrogen chloride generated in the solution is reduced to 0.
The value of X (C
Dry permeability R(e/nt” of C) in calcium salt state
, hr, atm) at 25°C and a differential pressure of 1 k! ? /d.

The porosity (%) is calculated by the formula: wall pore volume/porous membrane volume×100.

Water permeability pressure (kg/i) is measured as the pressure at which water begins to permeate when water pressure is applied to a dry membrane. Here, 0 means instantaneous wetness.

(Effects) As described above, according to the present invention, eluates from the membrane can be eliminated without deteriorating membrane performance such as hydrophilicity and permeability of the membrane.

Porous membranes will now be used for pharmaceutical-related applications.

(Example) Next, the present invention will be explained in detail with reference to Examples.

Comparative Example 1 Fine powder silicic acid [Nila0sil VN3LP (trade name); specific surface area 2som/1. average pore diameter 16ty+μ) 100 parts by weight,
After thoroughly mixing 228 parts by weight of dioctyl phthalate (DOP) with a Henschel mixer, high-density polyethylene resin powder [Santic 3360P (trade name)] 9
97% by weight was added and mixed again to form a homogeneous composition.

The mixture was extruded into a film using a 30% twin-screw extruder equipped with a T-die having a width of 400 mm.

The formed membrane was immersed in 1,1.1-)lychloroethane (Chlorocene VG (trade name)) for 5 minutes, the DOP was extruded, and then dried.

The porous membrane was then treated in fuming sulfuric acid containing 80.25% of free sulfuric acid at 40° C. for 5 minutes. This membrane was thoroughly washed with water and immersed in a 40% aqueous solution of caustic soda at a temperature of 60° C. for 5 minutes to extract fine powder silicic acid, followed by washing with water and drying to obtain a sulfonated polyethylene porous membrane.

The obtained porous membrane was a porous membrane forming a network structure with a porosity of 70% and an average pore diameter of 0.15 μm, and the exchange equivalent of this membrane was 0.17 meequivalent/gram.

Is the tensile strength of the membrane 35 kg/crt? The tensile elongation at break was 150%, indicating excellent mechanical properties. The water permeability of this membrane is 1800 A/m? ,hr,atm
There was f.

The permeability pressure, ρ~InO, and consumption of this membrane are shown in Table J.

Example 1 The membrane obtained in Comparative Example 1 was heated to 70°C with sodium hypochlorite 05.
It was immersed in a wt% aqueous solution (liquid pH 5) for 1 hour. The water permeability pressure, KMnO, and consumption of this membrane are shown in Table 1.

Example 2 The sulfonated polyethylene porous membrane obtained in Comparative Example 1 was heated to 50°C.
It was immersed in a 2% by weight aqueous solution of sodium hypochlorite (liquid pH 5) for 1 hour.

The water permeability pressure and Ikon 04 consumption of this membrane are shown in Table 1.

Example 3 The sulfonated polyethylene porous membrane obtained in Comparative Example 1 was heated to 70°C.
l) 1% by weight aqueous solution of rum (liquid pH 9)
) for 1 hour. The permeability pressure of this membrane and KMnO
, consumption amount is shown in Table 1.

Example 4 The sulfonated polyethylene porous membrane obtained in Comparative Example j was heated to 30°C.
Hypochlorous acid) 11um 0.3% by weight aqueous solution (liquid p
Hro) for 1 hour. The permeability pressure of this membrane and K
The consumption amount of tVnO is shown in Table 1.

Example 5 The sulfonated polyethylene porous membrane obtained in Comparative Example 1 was heated to 90°C.
Sodium hypochlorite 5M aqueous solution '(liquid pH 3
) for 1 hour.3, the permeability pressure and KMn of this membrane
o.The consumption amount is shown in Table 1.

spear 1 table

Claims (1)

[Claims] 1. A method for treating a porous membrane, which comprises treating a sulfonated polyethylene porous membrane with an aqueous solution containing hypohalite.