CS199169B1 - Removing inert porogens from macroporous copolymers - Google Patents

Description

The present invention is a novel process for removing inert porogens from the group of fatty acid esters and polyesters or mixtures thereof from macroporous crosslinked copolymers.

The basic smallcroporous crosslinked copolymers are obtained by suspension copolymerization of a mixture of single double bond monomers and multiple double bond monomers. The copolymerization is carried out in the presence of an inert substance, i.e. fatty acids, esters and polyesters, which is soluble in the basic monomer mixture and does not participate in the actual copolymerization reaction.

Due to its incompatibility with the resulting copolymer, the inert substance separates from the reacting phase during the gelation cycle while remaining closed as an inert phase in the excellence of the macromolecular network. In this way, a spatial network containing an inert porogen is formed during copolymerization. Subsequent removal of this porogen releases the space it occupies and creates the macroporous structure of the copolymers. The pores formed greatly increase the surface of the material and facilitate exchange between the liquid or gaseous medium and the sorbent. With the degree of removal of the inert substance, the porosity increases. pore volume and specific surface area, contributing to better use of the copolymers as a sorbent or to the next step of ion exchange synthesis (Seidl J. et al., Adv. in Polymer Science 1'113-213 1367).

The methods used to remove inert porogens to date have been based on their simple distillation (e.g., using volatile hydrocarbons) or steam-exaggeration thereof (U.S. Pat. No. 3,479,779 to Kuhn K.A.J. Polymer Sci 6 (1968) 2689). The high molecular weight substances are

199 169 were extracted with alcohols (brit, pat. Δ. 1, 126 168) or various solvents (pat. NSR 8.

1, 234 385, cutting edge. U.S. Pat. In the case of the use of unsaturated carboxylic acids as porogens, a method for the removal of these inert porogens by means of extractants having a specific chemical composition has been described (Ss. Certificate 182564).

Alkaline removal of these porogens is further described (French Pat. No. 1,483,946 British, Pat. No. 8,115,019). ''

A disadvantage of the described processes is mainly that the base copolymer in the respective extraction agent is not swellable (alkali) or swellable little and slowly (esters, ethers). In fact, a precondition for a successful extraction is that the base skeleton of the copolymer resulting from the polymerization of monomers having one or more double bonds is first swollen. This greatly accelerates the diffusion of porogen from the skeleton.

The present invention relates to a process for removing porogens from macroporous copolymers prepared by suspension radical copolymerization of styrene with divinylbenzene in the presence of porogens from the group comprising fatty acids, esters and polyesters by extraction. The invention consists in that the crosslinked copolymer at 20 ° C to 140 ^G 0 indicating a period of 10-180 minutes into contact with an extraction agent constituted by aromatic hydrocarbons, optionally substituted on the nucleus with alkyl groups with a total carbon number 6 to 10 and / or aliphatic chlorinated hydrocarbons having a carbon number of 1 to 6. The contacting of the copolymer with the extraction agent is preferably carried out in a stirred particle system or in a fixed bed. It is also advantageous to remove the water from the copolymer by distillation at the boiling point of the mixture of extracting agent and water and to use the extracting agent re-oxygenated for extraction.

The process of the invention is carried out either batchwise in a stirred reactor or continuously in a flow column. Its technical advantage is the fact that liquids are used as the extracting agent, which by their characteristic structure is close to that of the copolymer and thus swells the base skeleton very well and quickly (Table 1). Furthermore, since they are generally good fatty acid solvents, for example the solubility of stearic acid in toluene increases with temperature, it dissolves indefinitely at a temperature close to the boiling point (see Table 2).

Table 1-

Swelling time (min) Volume increase (%) ... 1 15 Dec 2 19 Dec 4 24 8 30 15 Dec 34 20 May 35

Table 2

Tgplota Solubility of stearic acid (% w / w) 20 May 13.25 30 27.48 . 40 45.08 50 65.62 60 87.96 70 unlimited

Furthermore, it is an advantage of this extraction method that aromatic hydrocarbons form azeotropic mixtures during distillation and water, which allows the copolymer to be dehumidified in one operation and at the same time to extract the porogen. After condensation of the azeotrope vapor, the liquid is separated into an organic phase which is returned to the extraction and an aqueous phase which is discharged into the waste water;

According to the invention, the following are used for the removal of the porogen: benzene, toluene, ethylbenzene, xylene, carbon tetrachloride, ethylbenzene, xylene, carbon tetrachloride, ethylene chloride, dichloroethane, trichloroethane, trichlorethylene, diohloropropane, dichlorobutane, dichlorbenzene or mixtures thereof, optionally to 200 ° C.

For the preparation of macroporous copolymers, the porogens used are compounds from the group of fatty acids (caprylic, caproic, capric, pelargic, lauric, myristic, palmitic, stearic, araehic, oleic, etc.) or from the group of esters or polyesters. These are then reaction products derived from alcohols (glycerine, trimethylolpropane, trimethylolmanite, ethylene glycol, propylene glycol, 1,3-butanediol, lower polyethylene glycol, etc.), dicarboxylic acids (phthalic, isophthalic, terephthalic, tetrahydrophthalic, hexahydrophthalic) malic, succinic, glutaric, adipic, pimelic, cork, azelaic, sebacic and monocarboxylic acids (caproic, capric, caprylic, lauric, myristic, palmitic, stearic, arachic and behenic acids), as well as non-drying fatty acids animal oils or hydrogenated fatty acids of oils of vegetable or animal origin, rosin or other natural resins, and linear or branched synthetic fatty acids.

The preparation of the macroporous copolymers is based on mono-vinyl monomers such as styrene, vinyltoluene, vinynaphthalene, acrylic or methacrylic acid esters, vinylpyridine and yy and polyvinyl crosslinkers, e.g. divinylbenzene. trivinylbenzene, glycol dimethacralate, polyvinyl ethane and divinyloxyethane.

The invention is generally carried out by suspending copolymerization of a mixture of monomers with an inert substance (porogen) in an aqueous medium using dispersing agents (e.g. polyvinyl alcohols) and conventional initiators (organic peroxides). It is polymerized in a conventional manner at a temperature depending on the nature of the starting monomers and the initiator used.

After completion of the reaction, the aqueous phase is first removed from the reactor by filtration with a submersible filter, or the aqueous phase is discharged from the reactor. % of the already swollen copolymer in the extractant. The beads of the resulting copolymer are further washed with water while stirring and the irritant (porogen) is removed from the copolymer. Extracting agent is added to the boiler and the mixture is stirred for 10 to 180 minutes. (depending on the nature of the copolymer and the extracting agent) at 20 to 140 ° C (depending on the type of extracting agent). If the extraction is carried out at the boiling point of the mixture, the vapors leaving the reactor are condensed, from the condensate, the aqueous layer is separated and the extract layer is returned to the reactor. At the end of the extraction, the extraction agent is pushed through the filter pad and the extraction is repeated several times, depending on the type of extractant, until the porogen is quantitatively removed. After drying the extracted copolymer, a macroporous bead product of a milky to chalk appearance is obtained.

If the extraction is carried out continuously, the copolymer is started after the copolymerization into a washing and extraction column equipped with two filtration days. The extraction agent is fed to the column at a specific load of 2 to 3 (nP and α, hr ^{3- 3} ) and the extraction is terminated after passing 2 to 4 volumes of the extractant, based on the swollen copolymer volume.

The obtained macroporous copolymer is used directly as a non-polar sorbent for the sorption of various organic substances. Even more important is its application as a carrier skeleton for the synthesis of various types of ion exchangers, both cation exchangers and strongly weakly dissociated anion exchangers.

Porogen removal efficiency can be tested by determining extractable residues by multistage extraction with distilled extender in a Soxhlet apparatus and indirectly by evaluating the macroporous copolymer by mercury porosiaetry. and BET surface determination. '' · ^

The invention is further exemplified by embodiments wherein said parts and percentages are by weight.

Example 1

The copolymer prepared from a mixture of 250 parts of styrene, 50 parts of technical divinylbenzene (active ingredient content 61.5 $) - 7 parts of dibenzoyl peroxide and 100 parts of stearic acid in a stabilizer solution of 0.8 parts of polyvinyl alcohol in 1600 parts of water .

800 parts of benzene are added to the washed copolymer and the mixture is stirred at 40 ° C in the reactor for 60 minutes. The liquid phase is pushed through the immersion filter nucleation into the extraction agent reservoir and a further 800 parts of benzene are fed into the copolymerization vessel and the operation is repeated three more times. After the fourth extraction, the copolymer is overlaid with water in the boiler and azeotropic distillation removes residual extractant from the copolymer. The extractable residues determined by extraction in a Soxhlet apparatus then do not exceed 5% of the original porogen load for the final product. The copolymer has a specific surface area of 27.4 m ² / g, a total pore volume of 0.78 cm 2 / g, a mean pore radius of 54 nm.

Example 2.

Example 1, wherein the copolymer is discharged into the washing and dietary kits, and the water is treated with water at a specific load of > 5 and then at a specific load of > 2.5 and extracted after passing 2000. parts of xylene are discharged into the boiler, overlaid with water and distilled off the azeotroplocs. Extractable porogen residues in the copolymer do not exceed 5% of the initial weight.

Example 3

The copolymer is prepared from a mixture of 250 parts styrene, 50 parts divinylbenzene (active ingredient content 61.5%)> 7 parts dibenzoyl peroxide and 130 parts stearic, palmitic, myristic and oleic acid (70 ': 25: 3: 2) in stabilizing 0.8 parts of polyvinyl alcohol and 114 parts of polyacrylamide (14%) in 1600 parts of water. It is then contacted with 700 parts of toluene, the aqueous phase is separated and the copolymer is washed twice with water in the reactor with stirring. The mixture was heated to 85 ° C, distilling the toluene-water azeotrope (19-20% water). The toluene after condensation is returned to the reactor. After distilling off the water, toluene is forced through a filter pad. To the reactor was added 700 parts of toluene again, the system was heated to 110 ° C and after 20 minutes _the toluene is pressed away. This is repeated once more;

1000 parts of water are added to the copolymer and toluene is distilled off azeotropically at 85 ° C from the system. This completes the extraction. The extractable residues determined as in Example 1 do not exceed 3% of the weight of the porogen.

Example 4

The copolymer prepared in Example 3 was extracted with 750 parts of a 1: 0.5 mixture of toluene and dichloroethane. The extraction mode consists in triple contact of the copolymer with the extender at 60 ° C with stirring. The extraction time is three times 120 minutes. The extractable residues do not exceed 5% of the weight of the porogen.

The subject invented cutting

Claims (4)

The subject invented cutting Process for removing inert porogens from macroporous copolymers prepared by suspension radical copolymerization of styrene with divinylbenzene in the presence of porogens from the group comprising fatty acids, esters and polyesters, by extraction, characterized in that the crosslinked copolymer is brought at 20 to 140 ° C for 10 up to 180 minutes in contact with an extraction agent consisting of aromatic hydrocarbons optionally substituted on the core with alkyl groups having a total carbon number of 6 to 10 and / or aliphatic chlorinated hydrocarbons having a carbon number of 1 to 6. 2. A process according to claim 1, wherein the contact with the extraction agent is preferably carried out in a stirred particle system or in a fixed bed. 3. Process according to claim 1, characterized in that, at the same time as the extraction, water is preferably removed from the copolymer by distillation, at the boiling point of the extraction agent / water mixture. 4. Process according to claim 1, characterized in that extraction is preferably carried out using an extraction agent recycled.