SU268408A1 - The method of purification of pyromellitic dianhydride - Google Patents

Description

(54) METHOD FOR CLEANING OF PYROMELLITE DIANHYDRIDE

From the purity of pyromellitic dianhydride (PDA) to a large extent depends on the possibility of obtaining a high quality measure, such as the presence of impurities negatively affect such properties of polymers as molecular weight, heat resistance, dielectric loss factor, etc.

A known method of purification with dioxane, which consists in the fact that PDA-. raw is treated three times by stirring in an excess of solvent, followed by Hepaciv. the crystalline mass boiled with an even greater excess of dioxane; precipitated after hot filtration and crystallisin, the precipitate is dried at 12 ~ 140 ° C and pressure. SRI 12O mm Hg Art. This method allows extracting up to 98% of PDA from potential with purity up to 99%.

The disadvantage of this method is the lack of growth of the solvent and the complexity of its regeneration process.

: To simplify and reduce the cost of the process, a method has been proposed for purifying the U1A-fume, for example, alkaline acetic acid ester,

for example, > tilatatatu and its mixture with acetone.

According to this method, the first stage of ochispsy is two-hour mixing of raw Sch1A with ethyl acetate in a ratio up to 1: in at 26.-° C or with a mixture of ethyl acetate and acetone (from 3: 1 to 5: 1) in a ratio from 1: 4 to 1; 6 g at a temperature from -JLO to + 10 ° C with the Subsequent separation of the precipitate from | filtrate by filtration, curing or other known precipitation. If the raw material does not contain amethanic amount of mechanical impurities, then after carrying out the second purification stage, which is similar to the first one, the precipitate is dried on air for 1–12 hours at 80 ° C for 3 hours. For purification from mechanical impurities, the third stage of purification is carried out - a hot cross -; Steelization from acetone lacetate mixture (from 3: 1 to 4: 1) with the ratio of PDA: solvent from 1: 4 to 1: 6. methylene salt, chloroform or another low-boiling solvent and dried for 3 hours at a temperature of 90 ° C °. The proposed method allows to extract 95% of PDA from the testosseous with a purity higher than 99%. In addition, the staging is reduced: the four-stage treatment is replaced by a two-stage process, and the five-stage treatment is replaced by a three-stage Edium treatment. The proposed method allows drying after hot recrystallization at a lower temperature, which reduces energy costs, and attains an atmospheric pressure, which allows refusing the use of such complex and expensive iuuero equipment as a vacuum dryer. Purification with ethyl acetate 1i and stage) ./A.Crushed raw PDA with an acid number of 937 and a content of 84% of the main product in an amount of 5 g is mixed with 25 g of ethyl acetate for 2 hours at a temperature of 40 with a reverse cooler. Then the crystal mass is filtered and again treated the same time. The crystalline precipitate obtained after two treatments was dried at 1 for 2 hours, after which the weight of the white crystals was 4.15 g, kr. lot number (k. h.) 1D.26, and so pl. , 5 ° C. The yield of PDA from the theoretical 99.3% .. B. 5- g of crushed raw PDA described above is mixed with 30 g of ethyl acetate at 2b-C for 2 hours followed by separation of the precipitate and filtrate, as. described above. This treatment is repeated a second time. The resulting precipitate is dried in air at room temperature at 18 h, after which its weight reaches 4.12 g, q. Including 1024, so pl. 285 286 ° C. The yield of PDA is 98% of the theoretical, B.5 g of the crushed raw material is mixed with 20 g of ethyl acetate at about reflux temperature. After. separating the filtrate and the precipitate, the latter is again treated in the same way. The precipitate is dried for 3 hours at VO ° C, after which its weight is 3.9 g, q, h 1026, and t, pl. , 50C. The output of the PDA 93% of theoretical. The regeneration of pacTSOpHTejMi in this case, as in the other points of the example, is carried out by distilling off the solvent from the obtained filter. re mixed for 2 us. The crystal portion of the & 1 filter and the oSrabachadvaugugg a second time under the same conditions as the & first time. Then: the white crystalline mass is separated from the filtrate as described, and air dried for 12 hours. Draft weight 3.64 g, q.h, 1022} m. Pl. 2a5 "286 ° C. The yield of substance is 87% of the theoretical. B. 3 g of minced raw, described by Bbimej, is introduced into 18 g of a mixture consisting of 5 wt. h, ethyl acetate and 1 wt. including acetone. The reaction mass is cooled to + 10 ° C and stirred at this temperature for 2 hours, then the precipitate is from 4 to 1 ml and the entire operation is repeated a second time. The precipitate obtained is dried for 3 hours at 8 ° C, which means that its weight is 3.56 g, q, h. 1025, t, pl. 285 286 ° C. The output of the PDA is 85% of the theorem. In this case, as in the other points of the example, the regeneration of the solvent is carried out by distillation from the filtrate. PRI me R 3, Recrystallization from 9-Acetate Acetone (Stage). A.5 g of precipitate obtained directly after purification twice with ethyl acetate (for the conditions of preparation, see Example 1, A), but not dried, are placed in a flask with a reflux condenser. 40 g of a mixture of 3 wt. including ethyl acetate and 1 weight; including acetone; and heated to dissolve. Then the reaction mass is left overnight. The precipitate formed is sucked off, crushed in a mortar, washed with a small amount of ether and dried for 1 hour on air / air at KONS. natal temperature, then dried for 3 hours at 9 ° C. Weight; 1) Chevd-South sediment 4.63 g, so pl. ,, to, h. 1O26. The yield of PDA is 93.2% of theoratite, in ns-based on PDA-; rip; immediately after filtration (without drying), placed in 6O g of solvent. The solvent is obtained by mixing 4 weight, h, ethyl acetate and 1 weight. including acetone. The reaction mass is heated to dissolve in a flask under reflux, then vysrydivayut several hours at room temperature. The precipitate is filtered off, crushed and; washed with a small amount of chloroform, then 3 hours, dried at 100 ° C. The finished product has a weight of 3.44 g, q, h. 1026, t. Pl.

In the case, as in other points of experience, solvent regeneration is carried out from the filtrate & oA from the filtrate.

PRI me R 4. I will add 2 g of PDA from each other, obtained by the method of vapor-phase windowsling, 5

 from r. 937, on a6atyv1ot from three times by rubbing in a mortar, lie to the slashes of & tempera ture. With 5O s neobutilovogo ufsuonoy acid After a single promyakn

; four carbon (2 ml) white 10 crystalline mass is dried for 3 hours at

(The temperature and the normal pressure of the scientific research institute. About the PDA thus sought, it has a mp of 285 ° C, as h. 1O26. Specific in e "

I bone O, solution of polyamic acid, 5

obtained from it on the basis of diaminodiphenyl n-dimethylformamide at

dry matter content of 13%, corales l et 1.2.

Formula invented

The method (scrubber of meteorite bottom I hydride, obtained by 1 phi vapor-phase oxidant alkylobenzenes, the stepped-crn str of the suv from organic), is dissolved with tiocT fKiaQ & washing iq BcrannoB in drying, from the outside to the soup with what, with the simplification of the process, as a quality. All of the solvent used is alkyl acetic acid and acetone, washing the crystals of the solvent with a solvent, not a solvent product, and drying it with a lead.