JPS61200815A - Membrane having organic acid permselective capacity - Google Patents

Abstract

PURPOSE:To concentrate an org. acid from a low concn. org. acid aqueous solution in high selectivity and high flow flux, by using a membrane wherein the void parts of a porous polymer membrane are impregnated with trioctylphoshine oxide and paraffin. CONSTITUTION:A polymer porous membrane is impregnated with a mixture consisting of trioctylphosphine oxide (TOPO) forming colloid along with an org. acid and paraffin diffusing said colloid. TOPO pref. occupies 30-85% of a total liquid wt. The polymer membrane has a max. pore size of 1mum or less, a void ratio of 20% or more, a membrane thickness of 200mum or less and also has piercing pores in the front and back surfaces thereof and pref. has a property not chemically reacting with a liquid impregnant or an org. acid. The base material of the membrane is pref. a hydrophobic one.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquid-impregnated membrane that is the next most effective for concentrating organic acids from low concentration organic acid aqueous solutions.

(Prior art) The membrane can be applied to the separation of liquid mixtures of M substances, azeotropic mixtures and near-boiling mixtures that are difficult to separate using distillation methods, or mixtures that require a large amount of energy to separate. I'm sure.

Furthermore, the following three methods are considered to be effective for concentrating organic matter from an organic matter aqueous solution using a membrane.

(1) A reverse osmosis method in which the organic water bath solution is supplied under pressure to the primary side of a membrane to selectively allow water to pass through it.

(2) By supplying the organic aqueous solution to the primary side of the membrane and reducing the pressure or flowing an inert gas through the secondary side of the membrane, the substance that selectively permeates to the secondary side can be converted into a gas or However, in the reverse osmosis separation method, when an organic aqueous solution is concentrated, the osmotic pressure increases, making it practically impossible to concentrate to a high concentration. In addition, the membranes used in pervaporation separation methods or vapor permeation methods that have been previously reported are made of hydrophilic materials such as cellulose, PVA, and PAN, or are made of hydrophilic materials such as pyrrolidone, sulfonic acid, and carboxylic acid. Most of them are made of materials that selectively allow water to permeate.For organic acid aqueous solutions, there is a report on the selective permeation of acetic acid using silicone membranes (H, Eu5tache and Q).
.

) (isti J, Membr Sci,, Dan 10
5-114 (1981)).

When separating organic acids from a low-concentration organic acid aqueous solution, it is better to selectively allow organic acids with a low content to permeate through the membrane for better separation efficiency. Specific examples of such low-concentration organic acid aqueous solutions include, for example, Kraft valve waste liquid, organic acid-manufactured water by the method, and polyvinyl alcohol and cellulose acetate M'll membranes, which do not have very good selective separation. Also, flux (unit membrane area, membrane permeation t of υ per unit time)
It's also 1 metre.

The present inventors have developed a separation membrane for pervaporation that has organic acid permselectivity under such circumstances, has a large flux of organic acids, and has heat resistance that can be used at high temperatures; As a result of intensive study to develop a separation membrane for vapor permeation, we arrived at the present invention.

Note that the low concentration organic acid aqueous solution referred to in the present invention is one having an organic acid concentration of less than 50%.

(Means for Solving the Problem) The present invention provides a pre-impregnated membrane in which a liquid is retained in the pores of a porous polymer membrane, and the liquid to be impregnated contains trioctylphosphine oxide (hereinafter referred to as TOPO) and paraffin. This is a membrane having an organic acid selective permeation ability characterized by comprising:

First, the porous polymer membrane in the present invention serves as a support for an impregnated membrane that performs separation, and the impregnated liquid has a differential pressure between the front and back of the membrane (preferably less than 3.0 to 9/cr/1). U1k
g/crl or less), the pore diameter is reduced by -1 to the extent that it does not flow out. That is, the maximum pore diameter of the porous polymer membrane measured by the bubble point method is 1.0 μm, preferably 0.1 μm.
m or less, porosity by gravimetric method i1. , 20 or more, preferably 35 or more, is suitable. Further, a porous polymer membrane having a high permeation flux of membrane-permeable components and having pores penetrating both the front and back sides of the membrane is suitable. Furthermore, it is necessary that the membrane does not chemically react with the impregnating liquid or organic acid.
Further, it is desired that the material be a hydrophobic material that does not selectively permeate water through the support layer, and that it be a polymer having a softening point that does not change the membrane structure even at temperatures of 80° C. or higher. Suitable examples of such a porous polymer membrane include those made of polypropyne, polytetrafluoroethylene, polyvinylidene heptaide, polycarbonate, polyvinyl chloride, polyvinylidene chloride polysulfone, polyether sulfone, and the like.

The shapes of porous polymer membranes include tubular, flat membrane,
Any form, such as hollow fiber form, can be selected.

Next, in the present invention, each of the porous polymer membranes has an impregnation slit. In the pervaporation method and vapor permeation method,
Since the partial pressure of the permeate is lowered by reducing the pressure or flowing an inert gas through the permeate side of the membrane, the impregnating liquid used must have a low vapor pressure. It is preferable that the vapor pressure of paraffin at 150°C is less than l Q mm) (, p. Also, the impregnating medium must be liquid at the temperature used as a separation membrane, and the aggregate of TOPO and organic acid must be present in the membrane. In order to facilitate the diffusion of paraffin, it is desirable that the chemical structure of paraffin is mainly linear and the melting point is below 65°C.Even if it is a mixture of paraffin and paraffin, if the above conditions are met, it will greatly improve membrane performance. It has no impact.

The composition ratio of TOPO and paraffin in f9-containing fibers significantly affects the separation coefficient and flux of organic acids.

As mentioned above, TOPO captures organic acids.
The larger the ratio of 11 to paraffin, the more it becomes impossible to use it as a separation membrane, and the membrane performance as a selectively permeable organic acid membrane and the impregnated liquid are desirable.

Any method may be used to impregnate a porous body with a liquid, but for example, it can be easily created by heating the liquid to be impregnated to about 80°C, immersing the porous body therein, and keeping the porous body under reduced pressure. I can do it. In addition, using the membrane having selective permeability of the present invention, organic acids that can be condensed for minutes and mature organic acids at room temperature (20°C), such as @acid, acetic acid, propionic acid, and caprylic acid. etc., and a # degree of less than 50% is practical.

According to the impregnated membrane of the present invention, it is possible to produce a collapsed effect for the purpose of collapsing organic acids from an organic acid aqueous bath solution.

(Example) The present invention will be explained in more detail with reference to Examples below, but the present invention was maintained at a certain temperature without any limitations as per the Examples below.

The membrane-permeable substance was collected by condensation at low temperature, and the flux was determined from the weight measurement in units of g/rrl·1.

In addition, the composition of the collected liquid was determined by neutralization titration with sodium hydroxide, and the separation coefficient α of the membrane was calculated.

Note that the separation coefficient α is defined by the following equation.

ACOH YA(:01(/Y H, OH* O
) (Ac OH/X Ht O where x and yi indicate the concentration of each component in the feed liquid and permeate liquid, respectively.

Example 1 As a porous polymer membrane, a membrane made of polypropylene, having an average pore diameter of 0.2 μm in major axis x 0.02 μm in short axis, and a porosity of 38 mm (Polyplastic Duraguard 240P) was used. Here, TOPO and melting point 48α gummy acid = (1.4
Q. =449/ze・At 70℃, acetic acid “o=°”3 Q=”°”i/m”°”′(
It was 1.

Comparative Example 1 An impregnated membrane was obtained in the same manner as in Example 1 using paraffin having a melting point of 68 to 70°C. When a pervaporation experiment was conducted using this membrane, the results shown in Table 1 were obtained.

When paraffin with such a high melting point is used, the separation coefficient,
Both permeation flux becomes low.

Examples 2 to 6 Containing TOPO and varying the melting point of paraffin,
An impregnated membrane was prepared in the same manner as in Example 1.

Using this impregnated membrane, we conducted a pervaporation experiment. Results first
Shown in the table.

Example 7 Using the membrane used in Example 1, a mixture of acetic acid and water with an acetic acid concentration of 20% by weight was heated with steam water.

Examples 8 to 10 Using TOPO and various paraffins with different melting points,
An impregnated membrane was obtained in the same manner as in Example 1.

Using this impregnated membrane, vapor permeation separation was performed at a vapor temperature of 110°C, and the results shown in Table 1 were obtained.

Comparative Example 2 Vapor permeation separation was performed, but it was not successful. As described above, the membrane not containing TOPO significantly lowers both the separation coefficient and the flux.

Comparative Example 3 An impregnated membrane was obtained using paraffin with a melting point of 68 to 70°C in the same manner as in Example 1, and vapor permeation separation was performed using this membrane under the same conditions as in Example 2. The results shown in the table were obtained. Although the separation coefficient does not decrease significantly with paraffin having a high melting point, a decrease in permeation flux is observed compared to vapor permeation separation using a membrane using paraffin having a low melting point.

(Effect of the invention) According to such an impregnated membrane, an amendment to the procedure for concentrating an organic acid with high selectivity and high flux, especially from a low concentration organic acid aqueous solution (spontaneous), published in P., 1985, by the Japan Patent Office. Director Uga Michibe 1, Indication of the case Patent Application No. 40320 of 1985 2, Name of the invention Membrane with organic acid selective permeability 3, Person making the amendment Relationship to the case Patent applicant address Tokyo 4A Mountain doctor M4: 3-1, Nam-chome Name: IM site Ibara can selection mW^IL number Restaurant cover telephone (501) 1511 extension 4601-5 Thickness, preferably corrected to ``.

(2) Bottom line of page 5 of the specification [Nylidene polysulfone,”
"Nyriden, polysulfone,"; this is corrected.

Claims (3)

[Claims] (1) An impregnated membrane in which a liquid is retained in the pores of a porous polymer membrane, which has an organic acid selective permeability, characterized in that the impregnated liquid consists of trioctylphosphine oxide and paraffin. (2) The vapor pressure of paraffin is 10mm at 150℃
The membrane having the ability to selectively permeate an organic acid according to claim (1), which has a melting point of Hg or less and a melting point of 65° C. or less. (3) The membrane having organic acid selective permeation ability according to claim (1), wherein trioctylphosphine oxide accounts for 30% or more and 85% or less of the weight of the impregnated liquid.