DD249703A1 - PROCESS FOR THE PREPARATION OF HYDROPHILIC HIGHPOROESIS ADSORBER RESINS - Google Patents

Abstract

The invention relates to a process for the preparation of highly porous adsorber resins, which are well suited for the adsorption of gaseous, liquid or dissolved solids and thus contribute to the solution of water and wastewater problems, separation and cleaning problems in the chemical industry. The adsorber resins are prepared by post-crosslinking of chloromethyl-containing crosslinked polystyrenes in the presence of swelling inert agents and Friedel-Crafts catalysts.

Description

Characteristic of the known technical solutions

Polymers, nonionic adsorbents are generally prepared by suspension polymerization of monomers with a crosslinking agent in the presence of inert species. The inert materials are removed again from the polymer after the polymerization and, together with the crosslinker fraction, are responsible for the degree of porosity. Examples of suitable inerters include: aliphatic and aromatic hydrocarbons, alcohols, esters, ketones and soluble polymers. Porosity can be controlled by this synthesis principle, but porosity values of certain adsorption carbons can not be achieved (J. Seidl, Chem. Prumysl 25 [50] [1975], 416-419).

Further synthetic principles therefore describe other ways of obtaining highly porous adsorbents. US Pat. No. 4,191,813 describes the subsequent crosslinking of low-crosslinked vinylbenzyl chloride copolymers in the presence of swelling inert agent by Friedel-Krafts catalysts. While US Pat. No. 4,263,407 describes the route via postcrosslinking via low crosslinked macroreticular aromatic polymers.

For this purpose, the polymer is swollen in an inert swelling agent which contains the crosslinker in the form of polyfunctional alkylating acylating agents or sulfur halides and postcrosslinked in the presence of Friedel-Krafts catalysts.

Davankov (Angew. Macromolecular Chemistry 91 [1980] 127-142, DD-PS 85,644) describes the synthesis of macrocrosslinked polystyrene backbones by treatment of polystyrene or styrene-divinylbenzene copolymers at a content of the copolymers of divinylbenzene to 1 mol% in the medium of one organic solvent in the presence of Friedel-Kraft catalysts and bifunctional compounds of the general formula ₍

R-

-R

where R is CH ₂ Cl, COCl and η is 1,2,3 or monochlorodimethyl ether. Another solution to this synthesis principle is described in DD-PS 125.824.

EP-PS 0007791 describes the synthesis of polymers by thermal crosslinking of starting polymers containing benzyl alcohol groups. The postcrosslinked products can be used as adsorbers or converted into ion exchangers. DD-PS 150,218 describes the synthesis of polymers which are characterized in that crosslinked styrenic polymers are postcrosslinked in the presence of solvents or swelling agents by treatment with monochlorodimethyl ether and Friedel-Krafts catalysts. On the basis of perl polystyrene, it is also possible to obtain porous polymers (DD-PS149.672). For this purpose Perlpolystyren be suspended in sulfuric acid and treated with a crosslinker of the class Dischwefeldichlorid, trichloroacetaldehyde, Monochiordimethylether, paraformaldehyde, xylylene dichloride in the presence of an inert.

The cited methods have disadvantages which consist in the fact that in the principle of the synthesis of polymer adsorbers by post-crosslinking partially technically difficult to access starting materials, such as the vinylbenzyl chloride used, or polymers containing up to 1 mol% Divinylbenzenvernetzung must be used.

Polymer adsorbers having a surface area of up to only 800 m ² / g can be produced by means of all these known processes.

Object of the invention

The aim of the invention is a very simple process for the production of adsorbents with a larger surface area and improved adsorptive properties.

Explanation of the essence of the invention

The object of the invention was to develop on the basis of technical preliminary and intermediate products, a method which corresponds to the objective of the invention.

It has now been found that it is possible to prepare adsorbents having a surface area of from 800 to 1,600 m ² / g and greater than 300 m ² / ml of water-moist adsorber polymers and improved adsorptive properties if technical-grade chloromethyl-containing crosslinked aromatic polymers, in particular styrene-divinylbenzene copolymers, are used , postcrosslinked in the presence of swelling inert agents and Friedel-Kraft catalysts, wherein the degree of crosslinking of the starting polymer is 2 to 8Ma .-% of divinylbenzene and the degree of substitution of chloromethyl groups at least 0.4 (11.5Ma .-% Cl), preferably greater than 0.7 (17.8 mass% Cl).

The methods of synthesizing the starting polymers and the methods of introducing the chloromethyl groups into the polymers are known. The aromatic polymers which serve as the basis for the adsorbents are products obtained by polymerizing a mixture of one or more monovinyl compounds, one or more polyvinyl compounds, with or without the addition of small amounts of one or more polymerizable polar vinyl compounds and or without the addition of inert substances. Examples of suitable monovinyl compounds which may be mentioned are: styrene, substituted styrenes and vinylnaphthalene. The polyvinyl compounds which can be used as possible crosslinkers are very diverse. Examples of preferred compounds are: divinylbenzene and trivinylbenzene. Mainly cross-linked styrene, for example on the basis of styrene and divinylbenzene, optionally with the addition of further polar monomers, such as, for example, acrylic acid esters or acrylonitrile and / or precipitating or swelling inerting agents, for example aliphatic or aromatic hydrocarbons, have achieved industrial significance. To achieve optimum results, a divinylbenzene content of 2 to 8% by weight, based on the starting polymers, is added according to the invention. The introduction of chloromethyl groups into such polymers is possible in a known manner with chloromethylating agents, such as monochlorodimethyl ether, dichloroether, a mixture of formaldehyde or formaldehyde-supplying substances and hydrogen chloride in the presence of a Friedel-Crafts catalyst. Other chloromethylation processes employ mixtures of paraformaldehyde-methanol or para-formaldehyde-methylal and a chlorine donor such as SOCl ₂ , CISO 3 H, SO ₂ Cl ₂ . Mixtures of methylal and a chlorine donor are also possible. A polymer modified according to such a chloromethylation process can be converted into highly effective adsorbers by the process according to the invention. For this purpose, dry, solvent-free, chloromethyl-containing or up to a maximum methanol content of 5% by weight of starting polymers in a halogenated hydrocarbon, such as dichloroethane or tetrachloroethane, is swollen, a Friedel-Kraft catalyst such as ferric chloride, tin tetrachloride or aluminum trichloride , added and the post-crosslinking with simultaneous formation of porosity at temperatures greater than 75 ⁰ C brought about.

The swelling of the polymer in the inert medium is generally sufficient for 1 to 4 hours at room temperature, the nature of the inert medium and the ratio of polymer to inert agent being of decisive influence on the final product properties. By the process according to the invention, dichloroethane and tetrachloroethane have proved particularly suitable as inert agents. Others are not excluded. The ratio of polymer to inert can be varied from Unterschußquellung, just stirred, up to excess swelling with very good stirrability, the QuelIbarkeit depends on the degree of chloromethylation and the initial crosslinking. The catalyst content can be varied within wide limits and also affects the final product properties, such as. B. incomplete after networking and thus negative influence on the formation of porosity. The proportion of the catalyst should be at least 20% by mass, based on polymer. The degree of chloromethylation of the starting polymers should be greater than 0.4. The reaction temperature and reaction times are also of influence on the final product properties, the boiling temperatures of the inert medium and reaction times of 2 to 20 hours are favorable parameters. A gradual heating of 30 minutes each at 40, 50, 60,70 and 8O ⁰ C has proved to be a particularly advantageous for the pattern formation.

The inert medium can be removed by distillation or by washing with another solvent, for example methanol, which simultaneously serves for the hydrophilization.

A second variant of the process according to the invention consists in firstly chloromethylating an unfunctionalized styrene-divinylbenzene polymer crosslinked with 2 to 8% by weight of divinylbenzene in a one-pot process and then postcrosslinking according to the invention.

An essential advantage of the process according to the invention is that, contrary to the state of the art, starting materials are used which are technically difficult to access, such as, for example, bifunctional crosslinkers and low-crosslinked polymers, which in the postcrosslinking lead to adsorbents having non-optimal adsorption properties per unit volume. technically readily available polymers and chloromethylated polymers are used which provide optimal adsorption properties, based on the volume unit. The adsorption capacities could thereby be increased by 50 to 80% compared to synthesized by crosslinkers and inert agents. The process according to the invention is further distinguished by the fact that only about one third of the Friedel-Crafts catalyst is necessary in comparison with the processes of the prior art. Due to the lower swelling of the starting polymers, a lower inert agent input of about 50 percent is possible.

The products are characterized by good hydrophilicity and are readily wetted by water after drying or washing processes

 The following examples are intended to explain the invention in more detail:

Example 1:

In a sulfonating flask equipped with thermometer, reflux condenser and stirrer, 77 g of a 2% cross-linked chloromethylated styrene-divinylbenzene copolymers (19.5% Cl) are added and added to 280 ml of dichloroethane, mixed and swelled for 2 h at room temperature. Subsequently, 45 ml of tin tetrachloride are added and stirred at 50 ° C for 4h. Then one hour at 60 and 7O ⁰ C and 8h at 83-85 ° C. After the reaction, the reaction solution is separated and washed three times with 300 ml of methanol, then with 50:50 methanol-water mixture and with water until neutral. The product shows the following characteristics: Surface: '1150m ² / g

Water content: 45%

Surface per volume unit wet adsorber: 389m ² / ml

Example 2:

In a flask of the same equipment as in Example 1, 75 g of a chloromethylated, 3.5% crosslinked styrene-divinylbenzene copolymers are presented with a chlorine content of 16.2%, treated with 250 ml of dichloroethane and stirred for 2 h at room temperature. Thereafter, 40 ml of tin tetrachloride are added and stirred for 1 h at 40, 50, 60, 70 ⁰ C and 15h at 83-85 ° C. The work-up of the experiment is carried out analogously to Example 1. The product has the following characteristics: Surface: 1 137m ² / g

Water content: 44%

Surface per unit volume of wet adsorber: 443 m ² / ml

Example 3:

In a sulfonation flask of the same equipment as in Example 1, 102 g of a 3.5% crosslinked styrene-divinylbenzene copolymers are initially charged and mixed with a mixture consisting of 80 ml Monochlordimethylether and 200 ml of dichloroethane and stirred for 3 h at room temperature. Thereafter, 70 ml of tin tetrachloride are added, 4h at 6O ⁰ C, stirred for 1 h at 7O ⁰ C and 10h at 83-85 ⁰ C. After the reaction, the product is separated from the reaction solution and washed as described in Example 1 with methanol, methanol-water mixture and water. A product with the following characteristics was obtained:

Surface: 1058m ² / g

Water content: 38.5%

Surface per unit volume of wet adsorber: 44OmVmI

Example 4:

In a flask of the same equipment, as in the preceding examples, 100 g of a chloromethylated, 3.5% crosslinked styrene-divinylbenzene copolymers are presented with a chlorine content of 19.3%, treated with 200 ml of dichloroethane and swollen for 4 h at room temperature. Subsequently, 9 ml of tin tetrachloride are added and stirred for 1 h at 40.50, 60.7O ⁰ C and 10h at 83-85 ° C. Thereafter, the solution and product are separated on the suction filter and the latter is also washed, as described in Example 1, with methanol, methanol-water mixture and water. It then has the following characteristics:

Surface: 893m ² / g

Water content: - 39.2%

Surface per unit volume of wet adsorber: 409m ² / ml

Example 5:

In a flask of the same equipment as in the preceding examples, 100 g of a chloromethylated, 3.5% crosslinked styrene-divinylbenzene copolymer are mixed with 325 ml of dichloroethane and swelled for 2 h at room temperature. Thereafter, 45 ml of tin tetrachloride are added and stirred at 83-85 ⁰ C for 25h. Solution and products are separated and the latter also, as described in Example 1, washed with methanol, methanol-water mixture and water. The product has the following characteristics:

Surface: 1330m ² / g

Water content: 40.8%

Surface per unit volume of wet adsorber: 57OmVmI

Example 6:

Analogously to Example 5, 100 g of a chloromethylated, 3.5% crosslinked styrene-divinylbenzene copolymer are mixed with 220 ml of dichloroethane, swollen for 2 h at room temperature and then treated with 65 g of aluminum trichloride. Thereafter, for one hour at 40, 50, 60 and 70 ° C and 20 h at 83-85 ⁰ C stirred. The mixture is hydrolyzed with water, washed with methanol and again with water. The product has the following characteristics: Surface: 108OmVg

Water content: 48.5%

Surface per unit volume of adsorber: 312mVml

Example 7:

Analog the other examples are a chloromethylated 100g, 3.5% cross-linked styrene-divinylbenzene copolymers with 200 mI tetrachloroethane mixed, 4 h bei.Raumtemperatur swollen and treated with 15 ml of tin tetrachloride and one hour each at 60, 70, 80, 9O ⁰ C and stirred for a further 10 h at 105 ⁰ C. The cooled product is separated and also, as described in Example 1, washed with methanol, Methanoi-water mixture. The product has the following characteristics: Surface: 1155 m Vg

Water content: 41.2%

Surface per unit volume of wet adsorber: 46OmVmI

Examples:

Analogously to Example 5, in the same equipment, 100 g of a chlorine-containing 3.5% crosslinked styrene-divinylbenzene copolymer are mixed with 240 ml of dichloroethane and swelled at room temperature for 2 h. Thereafter, 30 ml of tin tetrachloride are added. Thereafter, one hour to 40, 50, 60, 70 ° C and 15h at 83-86 ° C stirred. The solution and product are separated and washed, as already described, with methanol, methanol-water mixture and water. The product has the following characteristics:

Surface: 1560m ² / g

Water content: 44%

Surface per volume unit wet adsorber: 560m ² / ml

Claims (1)

Process for the preparation of hydrophilic, highly porous adsorber resins having a specific surface area of 800 to 1,600 m ² / g and greater than 300 m ² / ml of water-moist adsorber, characterized in that chloromethyl-containing, divinylbenzene-crosslinked polystyrenes in the presence of swelling inert agents and Friedel-Krafts Catalysts are postcrosslinked, wherein the crosslinker content, based on divinylbenzene, 2 to 8 wt .-%, the degree of substitution of chloromethyl groups is greater than 0.4 and the inert agent is removed after the reaction from the polymer. Field of application of the invention Polymer adsorbers are adsorbents with good adsorptive and performance properties and those on carbon or inorganic base in numerous cases far superior. They are used for adsorption of gaseous, liquid organic substances or dissolved solids. The adsorption of organic compounds is of particular importance here. The focus here is on the treatment of wastewater, for example the removal of pesticides, butyl acetates and aromatic hydrocarbons. The separation properties of the adsorber resins can also be exploited in analytical chromatography processes.