DE3520103A1 - Process for the treatment of catalysts and/or residues of initiator-containing polymers or solutions thereof - Google Patents

Abstract

The invention relates to a process for the treatment of a) solutions of polymers in organic solvents or b) low to moderate viscosity melts of polymers with the aid of pressure filtration in the presence of a solid (adsorbent) containing the catalysts present in a) or b) and/or residues of initiator-adsorbing oxides, at pressures of from 1 to 100 bar and in the temperature range from 0 to 200 DEG C, where polymers a) or b) are used which have been prepared by anionic polymerisation and in which, furthermore, boric acid and/or boron trioxide are used as adsorbent.

Description

Process for the treatment of catalysts and / or residues of

Polymers containing initiators or their solutions. The invention relates to a process for the treatment of a) solutions of polymers in organic Solvents or b) low to moderately viscous melts of polymers with With the aid of pressure filtration in the presence of one of the catalysts contained in a) or b) and / or residues of solid absorbing initiators (adsorbent) at pressures from 1 to 100 bar and in the temperature range from 0 to 2000C.

Regarding the state of the art, we mention: (1) DE-PS 22 44 682 and (2) DE-OS 33 36 355 Catalysts or residues of initiators in products or product streams can lead to undesirable side reactions during further processing (e.g. cross-linking, Degradation or discoloration) or prevent applications (e.g. refusal of food law approval); for these reasons it is necessary in many cases To remove catalysts or initiator residues from the products.

So far, this task has been performed on polymers that are prepared anionically were solved in that the product stream possibly after previous oxidation or reduction is brought into contact with a liquid extractant; the extractant is a nonsolvent for the product stream. The extractant usually consists of a main component, which is one or more effectiveness-enhancing components Additives can be added.

For example, in (1) a polymer solution is used to remove a hydrogenation catalyst with an oxidizing agent and at the same time or subsequently with an aqueous citric acid solution treated as an extraction agent.

In (2) there is pressure filtration for cationically produced polyisobutenes described on a solid adsorbent of various oxides.

The method known from (1) has the disadvantage that in addition to the product streams large amounts of extractant handled, processed or disposed of Need to become; In addition, the extraction process is particularly expensive if only small amounts of residue are to be extracted; therefore both became out Reasons of energy and cost savings as well as process simplification looking for new ways to separate catalyst and initiator residues.

There was therefore the task of polymers by anionic Polymerization, e.g. produced with the help of Li-organic initiators and, if necessary have been hydrogenated to suggest a useful method. The solution to the task succeeds with a method according to claim 1.

The invention thus relates to a method for treating a) solutions of polymers in organic solvents or b) low to moderately viscous Melting of polymers with the aid of pressure filtration in the presence of a die absorbing catalysts and / or initiator residues contained in a) or b) Oxide-containing solid (adsorbent) at pressures of 1 to 100 bar and im Temperature range from 0 to 2000C. This procedure is characterized by that one uses polymers a) or b) which are prepared by anionic polymerization and that boric acid and / or boron trioxide are also used as an adsorbent.

Surprisingly, it was found that the catalyst and initiator residues largely from the product tears by adsorptive filtration over boric acid or boron trioxide or solutions thereof in inert solvents can be removed; depending on Oxidation stage of the catalysts or initiator residues to be removed (this are mostly metals, originating from organometallic compounds or residues of Adsorptive filtration may be hydrogenation catalysts, e.g. of the transition metals upstream an oxidation. By a simple pressure filtration known per se of the product tears via boric acid and / or boron trioxide can be e.g. the metal ion content the product streams originating from the polymerisation, e.g. Li, or the hydrogenation, e.g. the well-known complex catalyst systems Ni / Al, Co / Al etc., from 200 - 500 ppm down to values of a few ppm.

In principle, product streams can be used according to the claimed process are freed from catalyst and initiator residues * those for boric acid or do not act as a solvent for boron trioxide; the product streams require after Adsorptive filtration no further aftertreatment.

Adsorptive filtration is particularly suitable for the treatment of Polymer solutions (in organic solvents) or low-viscosity melts of oligomers. As organic solvents in which the (co) polymers are dissolved are, or in which they are generated by anionic polymerization, may be mentioned: Toluene, xylene, benzene, cyclohexane, methylcyclohexane and aliphatic hydrocarbons and ether.

The following polymers in the context of the present invention are: homo- or copolymers of conjugated ones produced by anionic polymerization Serves and / or vinyl aromatics, e.g. polybutadienes, styrene-butadiene copolymers or the copolymers of styrene with isoprene.

These (co) polymers are used in a manner known per se of Li-organic compounds, e.g. n-butyl-Li, generated anionically. It can linear or branched (co) polymers are involved (cf.

DE P 25 50 227 or 25 50 226 and those mentioned in these documents State of the art). The arrangement of the monomers in the copolymers can be statistical or blocky. Optionally, the anionically generated (Co) polymers hydrogenated or partially hydrogenated in a known manner after the polymerization (see DE-OS 31 06 959) before being subjected to the process according to the invention will.

General Description of the Process The boric acid was made from water recrystallized to obtain coarser crystals (needles: 2-4 mm long); the Coarser crystals have the same effectiveness in adsorptive filtration as microcrystalline material, but show a significantly lower pressure build-up. After recrystallization, the coarsely crystalline boric acid was left overnight in a vacuum drying cabinet dried at 60 "C.

A pressure-resistant tube 35 cm long was used for the filtration tests used with an inner diameter of 5 cm; the tube could be thermostated via a double jacket will; The tube was closed at the bottom by a pressure-resistant sieve bottom. 50-60 g of the recrystallized boric acid were poured into the tube so that a dump height of approx. 15 cm was achieved. The different Products or product solutions were at temperatures of 20-200 "C and at pressures filtered from 1 - 50 bar through the boric acid. The metal content of the various (co) polymers and their solutions were each before and after the Filtrat ion in a known manner determined by atomic absorption to prove the effectiveness of the treatment (gt Tabel).

On the basis of the residue determination, the person skilled in the art can determine the for certain Requirements for the final metal content, associated residence times or

Determine the service life of the adsorbents through a few experiments.

The solutions of the (co) polymers obtained in the process according to the invention are worked up in a known manner and the intended uses known per se supplied, which by the structure and the composition of the (co) polymers to the Is known to those skilled in the art. For example, linear Bu-Styro} block copolymers are used as rubbers used; linear ABA block copolymers are used in the production of packaging materials and other linear or branched copolymers can after the hydrogenation as VI improvers are used in lubricating oils.

The method according to the invention is described below with the aid of a few examples explained in more detail (all data in% by weight).

Example 1 Hydrogenated Styrene-Butadiene Random Copolymer 500 g of a randomly built up styrene-butadiene copolymer produced by anionic polymerization (MW: 120,000) were as a 20% solution in cyclohexane with a soluble hydrogenation catalyst based on Ni / aluminum under normal conditions (120 ° C, 25 bar H2) in a stirred autoclave hydrogenated. The hydrogenation catalyst was then treated with peracetic acid (8 ml hydrogen peroxide (30zig), 5 ml of acetic acid, dissolved in 100 ml of water) destroyed by oxidation (1 hour on 80 "C). To remove the catalyst residues (nickel and aluminum) as well as the initiator residues (lithium) still contained in the product from the polymerization the 2OX polymer solution (solvent: cyclohexane) was used at 60 ° C. over 50 g of boric acid filtered (pressure build-up: 15 bar; filtration capacity: 955 g polymer solution (20Zig) per 100 g boric acid and per hour). Before and after the filtration, the metal content was determined in the polymer by means of atomic absorption.

Metal content (based on polymer) Li Ni Al before filtration 90 25 60 cpm] after filtration 1 1 2 [ppm) Example 2 Hydrogenated styrene-butadiene block copolymer 750 g of a hydrogenated styrene-butadiene block copolymer (30% styrene; MW: 130,000) were filtered as in Example 1 as a 15% solution in ethylbenzene through 50 g of boric acid (Temp. 100 "C; filtration pressure: 11 bar; filtration capacity: 1,370 g of polymer solution (15 dough) per 100 g boric acid per hour).

Metal content (based on polymer) Li Ni Al before filtration 80 40 90 cppml after filtration 1 1 1 eppm] Example 3 Hydrogenated styrene-isoprene block copolymer 600 g of a hydrogenated styrene-isoprene block copolymer (15% styrene; MW 90,000) the solution in cyclohexane was filtered through 50 g of boric acid as in Example 1 (Temp. 80 "C; filtration pressure: 17 bar; filtration performance: 1,430 g of polymer solution (18%) per 100 g boric acid and per hour).

Metal content (based on polymer) Li Ni Al before filtration 95 35 85 [ppm] after filtration 1 2 2 [PPm] Example 4 Hydrogenated polybutadiene analog ztl Example 1 were 800 g of a hydrogenated polybutadiene (NW: 200,000) as 10% Solution in toluene at 80 ° C. filtered through 50 g of boric acid (filtration pressure: 14 bar; Filtration performance: 1,380 g polymer solution (10%) per 100 g boric acid and per hour).

Metal content (based on polymer) Li Ni Al before filtration 55 30 70 [ppm] after the filtration 1 [3 [ppm] Example 5 Oligomeric polybutadiene (MW 3,000) 1,200 g of polybutadiene oil were under a nitrogen atmosphere at 1400C over 50 g boric acid filtered (filtration pressure; 25 bar; filtration capacity: 620 g filtrate per 100 g of boric acid and per hour;) to remove the initiator residues.

Metal content Li before filtration 720 [ppm] after filtration 5 [ppm]

Claims (2)

Claims 1. Process for the treatment of a) solutions of polymers in organic solvents or b) low to moderately viscous melts of polymers with the aid of pressure filtration in the presence of one of those contained in a) or b) Oxides containing catalysts and / or residues of initiators Solid (adsorbent) at pressures from 1 to 100 bar and in the temperature range of 0 to 200 "C, characterized in that polymers a) or b) are used, which have been produced by anionic polymerization and that boric acid is also used and / or boron trioxide is used as an adsorbent. 2. The method according to claim 1, characterized in that the by anionic polymerization produced polymers a) or b) catalytically before the treatment have been hydrogenated.