JPS60141733A - Manufacture of fine porous sheet - Google Patents

Abstract

PURPOSE:To obtain titled sheet of high thermal stability (in particular, to high- pressure vapor) free from drop in its filtration rate due to heat, by crystallization treatment, in a specific manner, of fine porous sheet consisting mainly of cellulose acetate. CONSTITUTION:A cellulose acetate solution is prepared by dissolving a cellulose acetate (cellulose diacetate, cellulose triacetate or a mixture thereof) in a combination of its good, poor and/or non-solvents; said solution being coated or cast on a substrate to form a film followed by drying to make a fine porous sheet with an average pore size 0.01-10mu, porosity 60-90% and film thickness 50- 250mu. This sheet can be crystallized at significantly lower temperatures then those taken in conventional such processes, by performing heat treatment using >=120 deg.C water or non-aqueous solvent insoluble for cellulose acetate (e.g. ethylene glycol, diethylene glycol dimethyl ether) or saturated vapor therefrom, thus obtaining the objective sheet.

Description

[Detailed description of the invention] (Field of application of the invention) The present invention relates to a method of making microporous sheets.

In particular, the present invention relates to a method for producing a microporous sheet in which the p-overrate does not decrease even under high temperatures.

(Prior Art) Microporous sheets have been known for a long time (for example, l.
by Kesting [synthetlcPolymer
(Published by Membrane JMcGraw-14i11) It is widely used in filtration filters, etc. Microporous sheets are described, for example, in US Pat. I/No. 3
, /33, /32 issue, 2,917μ, O/7 issue, Tokuko Sho≠3-11491, Tokko Sho IA! -333/3 issue,
Same lIL! -32! ? As described in No. 6 and No. 4Lt-≠0030, it is produced using cellulose acetate as a raw material.

However, microporous sheets made from cellulose acetate are extremely unstable at high temperatures, so their use has been limited. For example, microporous sheets that are mainly composed of cellulose acetate and are used to filter pharmaceuticals are usually sterilized before use, but if a heat sterilization method such as high-pressure steam is used, the filtration rate of the sheet can be reduced. had the disadvantage that it decreased significantly. For this reason, only special and limited methods (such as gas sterilization) can be used to sterilize microporous sheets containing cellulose acetate as the main component, and therefore, only special and limited methods (such as gas sterilization) can be used. Its use was severely restricted.

As a method for improving this, Japanese Patent Application Laid-open No. 145-145 discloses containing cellulose ether in addition to cellulose ester.

However, there was a desire for a microporous sheet that would not reduce the amount of excess F even under high temperatures.

The present invention was developed to solve these drawbacks.

(Object of the invention) The object of the present invention is to provide a microporous sheet with excellent thermal stability, a special
An object of the present invention is to provide a method for producing a microporous sheet having excellent thermal stability against high-pressure steam.

(Structure of the Invention) As a result of various researches, the present inventors have created a microporous sheet whose main component is cellulose acetate, and by crystallizing the microporous sheet. It has been discovered that a microporous sheet with excellent thermal stability can be obtained, and the microporous sheet containing cellulose acetate as a main component can be obtained by using water with a temperature of 100 C or higher or a non-aqueous liquid that does not dissolve cellulose acetate. The object of the present invention has been achieved by a method for producing a microporous sheet in which cellulose acetate is crystallized in water or in the saturated vapor of water or a non-aqueous liquid that does not dissolve cellulose acetate.

In general, the heat resistance temperature of cellulose acetate is 160℃? ．． It is known that the temperature is 200°C. However? 1.7m lower temperature than 7nm. Simply exposing a microporous sheet of cellulose acetate to saturated steam at 210C deforms the pores and makes them unusable for filtration. This phenomenon κ was previously thought to be due to deterioration of cellulose acetate due to hydrothermal decomposition K, or to softening of cellulose acetate due to the plasticizing action of water. However, as a result of research by the present inventors, this phenomenon is due to the molecular movement that causes the molecular chains to rearrange, as cellulose acetate softens due to the plasticizing effect of water and simultaneously crystallizes. I thought I was deaf. In other words, it is thought that the microporous sheet contracts in a three-dimensional direction during the process of rearrangement of the molecular chains, and as a result, the pores inside the sheet shrink and disappear. Therefore, a microporous sheet in which the crystallization of cellulose acetate has sufficiently progressed will no longer undergo changes accompanied by pore deformation even when exposed to saturated steam K at t-2oDc or higher.

The microporous sheet in the present invention uses cellulome acetate as a main component. Cellulose acetate in the present invention includes both cellulose diacetate and cellulose triacetate, and either one may be used. However, since cellulose triacetate is easier to form microcrystals, it is desirable to use a mixture of the two. When cellulose diacetate and cellulose triacetate are used as a mixture, they are used in a weight ratio of λ to 7 to 3. Also, the average degree of acetylation of mixed cellulose acetate is jj
%from! It is desirable that it be 2%. Here, the degree of acetylation refers to a value expressed by the following formula.

Degree of acetylation of acetic acid obtained by saponifying cellulose acetate - = X/00 Weight of cellulose acetate In the present invention, the degree of acetylation of cellulose acetate is an important factor in generating microcrystals. However, this is not the essence of the present invention.

In addition to cellulose acetate, plasticizers such as organic phosphoric acid esters, phthalic acid esters, glycerin derivatives and ethylene glycol derivatives can be added to the microporous sheet K of the present invention. Examples of plasticizers that can be added include glycerin derivatives such as monoacedene, diacetin, triacetin, tributyrin, etc., compounds with the general formula HO-{-CH2-
At cH2-0"o', H = / to 14L polyethylene glycol, ethylene glycol cyclopionate to ethylene glycol butyrate, ethylene glycol diacetate, dielene glycol succinic acid and polyester, diethylene glycol, diethylene glycol, polyester with leicic acid, tri-thi V7 guryoya and ajivi, acid. 3 polyesters, 1 polyester, 1 to 1, and 1 monobasic acid or di-salt. workman,. f-2 class, To1no,, =
〇、． ．． Organic phosphoric acid esters such as 7Eight, B7E=Yaji, E=YaoO, EIGHT, TrikV di'phosphite,
Di f4″'7) L/-}, Geo f#7) L/-In)
There are fukuic acid esters such as

AK. Yo, Yu7-1e water. Contains good properties such as moisture absorption and surfactants. Ejikui - Nyusai],
Fly IJ-51J7 and IJ41J Doka 5,. ,
? 9] Yo. ? . Ka25, 1a, 3-2 sulfuric acid*: r-1fkfX, gIJxfV7gly'12, 1ka2 sulfuric acid. 3 pieces, 2 salts, A, fJ & Prime F, 77″- ,,,7...,・゛'""@(DfJ': J%"="'
゛“,,$1,...″゛′゛″”゜′゜゛”,,＊z$
n″′”″”゜′”“′゛′,,,sg)po・2゜2
゜“III゛′゛′”−′,. 7..., 71Jl"1"
) v゛'/kep7%/",5,...~・'゛'"゛'"""'゛",7,...゛'""'''''゛''"~
”′゛′,8,...″′”−゛,dIJfoeV7
″゛″′,． ．． ，・・・１′”″′゛”″′”″−“１
、． ,・chi・1″“゜”−,71J:7−/”O*oe
"", 7 system 1 activity"""゛1゛ra゜゛゜#?6 methods for producing t-resistance 1 limited"''-゛0,1
t〈General 1 Method゛4゛Ra゛8 Normal acetic acid, 2.-
3A, such a method is also used in the present invention; preferably (1 M'l is used for acetic acid, O-XO&F8, and 1. 0 Solvent k-ef!e-tv., 2. Make a solution f-, apply this solution to the support, iH spread L7', then 2
A microporous sheet is obtained by drying 1 and ELH with 11 ml of acetic acid, and finally removing the film from the support. Here, a good solvent refers to a solvent that dissolves cellulose acetate and has lower volatility or a lower boiling point than a poor solvent and a non-solvent.

General good solvents for cellulose acetate are difficult to define depending on the ester residue used, but examples include methylene chloride, chloroform, ethylene chloride, ethythelene chloride, trichloroethane, tetrachloroethane, and ethyl bromide. - Logenated hydrocarbons, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethers such as dioxane, tetrahydrofuran, methyl cellosolve, etelselon rub, methyl formate, ethyl formate, probyl formate, pter formate, methyl acetate, acetic acid One or more types are selected from esters such as ethyl and butyl acetate, fatty acids such as formic acid and acetic acid, and nitrogen-containing compounds such as niometa, nitroethane, nitropropane, dimethylformamide, and morpholine. A good solvent having a boiling point of about 20 to 200 m or less is particularly preferred. The poor solvent is cellulose acetate. It is a solvent that does not substantially dissolve but causes swelling.
It is desirable that it be miscible with 11 agents. As a specific example of a poor bath medium, one ester residue iK to be used (although it is difficult to define, for example, ethylene chloride, trichloroethane,
Tetrachloroethane. chloroethylene, carbon tetrachloride, amyl chloride, butyl chloride, chlorobenzene, fats [i7 alcohols and alicyclic alcohols such as methanol, ethanol, isopro, e/+7tz, -ipsol, cyclohexanol] , isopyupyl ether, cyphthyl ether, ethyl cellosol, ethyl selonlube, tetrahydrofuran, etc., and more than one kind is required. Particularly preferred are those having lower volatility or higher boiling point than the good solvent.

The nonsolvent is a solvent that does not substantially dissolve or swell cellulose acetate and is miscible with a poor solvent.

The dissolvent is often water, and sometimes aliphatic hydrocarbons such as hexane, heptane, decane, cycloaliphatic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as toluene, benzene, tetralin, ethylene glycol, diethylene glycol, glycerin. Polyhydric alcohols such as are used.

It goes without saying that two or more of the above three types of solvents can be used in combination.

In the present invention, the terms "good solvent", "poor solvent" and "non-solvent" are defined relative to each other, mainly determined by the dissolving action and swelling action on cellulose acetate. Therefore, such definitions and specific examples of the solvent will uniquely correspond to each other. It is not possible. That is, depending on the type of ester residue of cellulose acetate used, the types of good solvent, poor solvent, and non-solvent may differ, or they may be replaced. However, these relationships are based on the chemical and physical properties of cellulose acetate, and anyone skilled in the art can freely select between cellulose acetate and the three types of solvents based on common knowledge. Therefore, in the method of the present invention, there is no need to particularly consider these relationships.

The method of dissolving and mixing cellulose acetate, a good solvent, a poor solvent and a non-solvent is not particularly limited. For example, a method of dissolving cellulose acetate in a good solvent and then adding a poor solvent and a non-solvent; There are several methods, such as adding and dissolving a portion of the mixture and adding the remaining poor solvent and nonsolvent to this solution, and any of these methods can be used. In addition, there are no special restrictions on conditions such as the mixing ratio of each solvent and the temperature at the time of mixing (there is a condition that the temperature is preferably below the boiling point of the solvent). Additionally, in some cases, one of the antisolvent and nonsolvent may not be used. In other words, by using inorganic salts, etc., a good solvent and
A combination of poor or non-boiling medium may also be used.

However, since the prepared cellulose acetate solution is stable and subsequent operations are simple, it is preferable to carry out dissolution and mixing to obtain a stable solution. A stable solution is one in which cellulose acetate does not undergo gelation or phase separation in the solution.To achieve this, the amount of a good solvent in the solvent must be greater than the amount of each of the other solvents, or the amount of acetic acid Any method may be used to add and dissolve cellulose in a mixture of all of the good solvent and part of the poor solvent.

The cellulose acetate solution thus prepared is cast onto a support such as glass, film, or cloth. Simultaneously with or after coating or casting, the coating on the support is dried. Drying is carried out in order to cause phase separation of cellulose acetate in the skin abdomen. Usually, drying is carried out at a temperature below the boiling point of a good solvent, preferably at a temperature at which cellulose acetate tends to gel (below 3°C, above 1/!0°C). This is desirable. In this case, if the drying time is increased (i.e., if it dries gradually), the pore size will become uniform; if the drying time is shortened (i.e., if it dries rapidly, the pore size will become non-uniform). Cobcervation occurs in the film due to drying,
Convert to cellulose acetate brush. After forming the micropores, heat is applied (J1 is below the softening point of cellulose acetate) to allow sufficient drying. 7 for producing microporous sheets?
-kboVarious operations are already well known%
Nine points are based on the aforementioned prior patents and U.S. Patent J,/2F. Ij
It is described in No. Y, No. J, 1121, No. jIlLt, etc. Recently, a method has been developed in which a microporous sort is formed by coating or casting onto a support and then immersing the material in a non-solvent. Also in the present invention,
It goes without saying that microporous sorts created by non-solvent immersion can be used.

The microporous sheet made in this way has an average pore diameter/Oμ
It has micropores of 0.0/μ or more. Here, the average pore size is
It can be measured by the bubble point method specified in ASTM-F-J/t-qo. Moreover, the porosity of the microporous sheet thus obtained is 20% from to, and in particular, the porosity is t! It is desirable that the content is 3%. Here, the porosity is calculated from the ratio of the apparent volume of 1 microporous 7-t to the volume of mercury injected by mercury intrusion method (AsTM-D-.2I7J-7o).

The thickness of the microporous sheet is about 60 to λjoμ,
Preferably it is 10 to itoμ.

The microporous sheet of vinegar obtained as described above is further crystallized.
The crystallization sass 60 and 1 to 6 are produced by the dry air above ``cl'l'IO''C generated at the above temperature. Yes, single piece. 1. In that case, it's 1, good 1, . ? ，? ．． 7-,
Ayu? 8f, - When κ changes and disappears - C, P passes.
year. The effect of the effect disappears.

and. Uh, one shot. Mr. The fine IL-/-k7k" is acetic acid,...-8,. It is difficult to dissolve it in a di-L aqueous solution. σ'.

Saturated steam heat treatment. . Toyu, Te Kazuya? If you do this, the micropores will deform and disappear. . 2,. 〈, Guchi P over,. ．． , low e saiayu. Gaku crystal'<evki b・a6.1,,4 normal.

Crystallization occurs at degrees 1, 3, and 9.

This is the original. . m&iBKM'xhi'F"water liquid 2,・ha'
,. -8. Eh M5IBM. 3ゎyu,,ke4-・'pi-
ghyz. ,7,. . il,'xfpykyo2,・μ・
'atevc+. fxEm9) A*wbv-c+ma・
..."766...5.-asAa#WthL"""
te"2'"i゛, ゜hede・',"""kyr7, mesitylene, naphtha 1
Non, t'fp:/- ,,,...'''IJ7゛'/l'１＊7゛゛7"'l
@ ,2. ..."1"'"/L/j-)>゛:7,,
7,・1・・'1”′′′”′゜−′ru, thiethylene glycol κ series t#*1″ r−,.1−…”=7−y(Diala”1′”゛″., 4, Ri-ri-monoacid ゜′゜゛High-grade fatty acid ゛1-acid'
2, to 7, ~, 1ㅅ”・7゜ゞ″′acid”′゛,,,y
) gl..."""゛'1'"゛-)'<"Ff"-7
, 7 nights... Ueda oil゛0゜2゜"゛6'゜,,.,v
,t? oy+)-hIJ7""""1"゜"""1, ρ
...,yJ)-1A/"""゛'゛'2,2oi8
Among the high boiling point non-aqueous liquids, it is more preferable. 6・゛'EtSf'nguri・1'
・Pu゜ゞ″gno゜１′・,１Methi・・Guri゜−“・′゛ノゞ゛ノ′. Cheap polyvalent a4: ff-2, thiethylene glycol dimethyl ether,
Dimethylene ether, diethylene glycol,
These include polyhydric alcohol derivative ethers such as polyethylene glycol and polypropylene glycol.

Many of these polyhydric alcohols and their derivative ethers not only have high boiling points and are easily soluble in water, but also have a plasticizing effect on cellulose acetate. When used, the @ degree of crystallization decreases, l306
It is even more preferable because crystallization occurs sufficiently at about C.

Similar to polyhydric alcohols and their derivative ethers, plasticizers for spinning cellulose acetate, such as vinyl diphenyl phosphate, diethylene glycol diacetate, and dibutyl 7-thale, also form microporous sheets at relatively low temperatures. It is a preferred non-aqueous liquid because it can crystallize.

The non-aqueous liquids used for crystallization can be used alone or in other ways. It goes without saying that two or more types may be used in combination. It can also be used by mixing a water-soluble non-aqueous liquid with water.

The temperature for crystallization must be determined by taking into consideration the liquid used, the use of saturated steam, the time required for crystallization, and the temperature for crystallization. Is it possible to have a warm face with a low temperature? To do/. It is possible if it is 20"C or higher.b.For example, in the case of diethylene glycol liquid, /,,・C
Crystallization can be performed by heat treatment at about f/0 minutes.

When using water to crystallize la, is it a pressure cooker? It is used to pressurize (increase the pressure to above atmospheric pressure).
Raise the liquid @ above o'c and heat treat it. , g1KtoL, Teii/. It is possible to crystallize at 20'C~/jO'coitxo, and particularly preferred is l2j''C,t 弘0・C(7)Chapterncircle.For example, K which crystallizes at about 130aC is possible in about ! minutes.

When using water or non-aqueous liquid gold, the microporous sheet can be crystallized by either immersing it in a tank containing the liquid or by floating it on the surface of the liquid in Japanese cypress and subjecting it to heat treatment.

In the case of heat treatment using saturated steam of water or non-aqueous liquid, it is sufficient to simply expose the microporous sheet to saturated steam, but preferably the microporous sheet is exposed to water or non-aqueous liquid. After soaking in
It is best to immerse them in saturated steam.

Is heat treatment performed in liquid or steam? The sheet may be passed through continuously, or the sheet may be left for a certain period of time.

In heat treatment, the sheet is placed in a frame and tension is applied to cause heat shrinkage during the process. By preventing this, deformation of the micropores can be prevented. After heat treatment, use water or non-aqueous liquid.
It can be removed by drying, but if it is a non-aqueous liquid, wash it with water.
It is preferable to dry it after c.

The present invention will be explained in more detail with reference to examples, but is not limited to the examples alone.

example l Prepare a solution with the following composition.

Cellulose triacetate V. ．． Double t cellulose thidiacetate λ, fz metele/chloride S<t methanol 3j water! The above solution is cast onto a polyester sheet to a thickness of about 1 m. After drying without air at 25 to 306°C for the first 30 minutes until the film becomes pure white, it is further dried for about 1 hour at a temperature of to-to-°C. The cut-out microporous sheet is peeled off from the polyester sheet and fixed by sandwiching the microporous sheet Th with a set of metal frames and screws. This was crystallized by immersing it in diethylene glycol of /3j''C for ! minutes, and after washing with water and drying, the film thickness and P overrate were measured.

On the other hand, the microporous sheet subjected to the crystallization treatment was set in a filter, and the crystallization treatment was carried out at lλA'C/. High-pressure steam sterilization was performed for 10 minutes in 4 LKg/cm2 saturated steam, and the P overrate and membrane thickness of the microporous sheet were then measured. In addition, when measuring the F overspeed, the water of tt"c is
P per unit area (an2) and within unit time (minutes)
Ilr of the water that is passed (me1 is a trap. These results 1!
/fi.

Example 2 (Comparative Example) The microporous sheet prepared in Example 1 before crystallization was treated with TaO in place of the l35″C diethylene glycol in Example 1.
Crystallization treatment was carried out in the same manner as in Example 1 except that 0C diethylene glycol was used. The physical properties of the microporous sheet were measured in the same manner as in Example 1, and the results are shown in Figure 1.

Example 3 Water was impregnated into the micropores of the crystallized microporous sheet prepared in Example 1, and after 7C, the sheet was fixed on a metal plate in the same manner as in Example 1, and the sheet was saturated with /cor0C. Crystallization treatment in steam for 60 minutes? went. The physical properties of the microporous sheet thus produced were measured in the same manner as in Example 1, and the results are shown in Table 1.

Examples 4 to 7 (including comparative examples) The microporous sheet of the crystallized fiber produced in Example 1 was crystallized for each IO minute in the same manner as in Example 3. went. However, the temperature of water vapor is lλa”c, /200CSllO°
C, l'00c: and both were treated in an atmosphere with saturated steam stirring. Physical properties of the microporous sheet thus produced Example 1
The results are shown in Table 1.

Implementation Full 8 In Example 3K, the crystallization treatment was performed in the same manner as in Example 3, except that water was not contained in the micropores of the microporous sheet. went.

The results are shown in Table K.

Example 9 (Comparative Example) Example! In /3. ! A microporous 7-t was prepared in the same manner as in Example 1, except that instead of the crystallization treatment with diethylene glycol of r''c, the crystallization treatment was performed in air at .2 lO'C for j minutes. The physical properties were measured in the same manner.

The results are shown in Table I.

Example 1o (Comparative Example) The microporous sheet prepared in Example 1 before crystallization treatment was used as it was, and its physical properties were measured in the same manner as in Example 1, and the results are shown in Table 1.

The crystallinity was measured using X-ray generators D, C, y7fv-s.
z y z counter sc-J-, counting t iia I) c”-T
``S'' (both manufactured by Rigaku Denki ■)
The line circuit pattern is shown in Fig. 8. The degree of quality cannot be obtained absolutely directly.The illumination angle. #1 Shidoka, et al. . . a. , ep-7. Comparison can be made by calculating the cumulative metal ratio C.

8, Figure (a) IreM crystal fhi place oga. ? Example...0
6L porous sheet, Figure 7 (b) and (c) V'i crystallization treatment *L, :.i,,ypHp4+.2
0) ii, Y@: {'t'! ”'4AJ, (a) VCM
< (b) kU (c) 75, a < lm &('c degree is inferior κ
I understand that.

[Brief explanation of drawings]

@Figure 7 shows the X-height diffraction pattern? show. (ilfd lol m Example 10, (b) t: + Example 5, (c)
FIG. 3 is an illustration of the X-ray diffraction pattern of Tri-photograph Example 3. Tokuken Applicant: Fuji Photo Film Co., Ltd. Procedural Amendment Document, Showa Ao, January ♂・,9・,゜1＼, Commissioner of the Japan Patent Office 1. Incident display Showa! ! 2017 Patent Application No. 241r4tt No. 2
．． Name of the invention Method for manufacturing microporous sheet 3. Person making an amendment Relationship to the case Patent applicant Address 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name (520) Fuji Photo Film Co., Ltd. Representative Minoru Onishi Contact Address: Fuji 2-26-30 Nishi-Azabu, Minato-ku, Tokyo 06 Photo Film Co., Ltd. Tokyo Head Office Telephone: (406) 2537 4. Column 5 of “Details of the Invention 1” of the specification to be amended. Contents of the Amendment In the "Detailed Description of the Invention" section of the description, the following amendments are made. No. Replace page 23 with a separate sheet. -237-

Claims (1)

[Claims] Acetic acid. In addition to the sea bream dish of microporous sheet containing +e yellow rose as a main component, l. 2000 or more water or acetic acid
- A method for producing a tossled microporous sheet, comprising crystallizing cellulose acetate in a non-aqueous liquid that does not dissolve cellulose acetate, or in water or saturated steam of a non-aqueous liquid that does not dissolve cellulose acetate.