DE1180128B - Process for the recycling of organic auxiliary fluids that are wasted in the production of polyoxymethylenes or their esters or ethers - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 08 g

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German class: 39 c - 18

F 37052 IVd / 39 c
June 13, 1962
October 22, 1964

When formaldehyde is polymerized in inert organic solvents, impurities, such as water, methanol, formic acid, methyl formate, methyl formate, formaldehyde dimethyl acetal and other by-products of formaldehyde vapor production, not quantitatively over Chain start, chain termination and transfer reactions are used to form the end groups. The impurities mentioned are also not quantitatively removed from the insoluble polyoxymethylenes bound by adsorption, i.e. physically. With increasing polymerization time and increasing Suspension concentrations of the polyoxymethylenes in the inert reaction medium therefore increase the above-mentioned impurities and lead to a reduction in the uniformity in the Average molecular weights, to a slowdown in the rate of polymerization, to a coupled with this, reduced polymerization yield and often also to a deterioration in the color properties of the end-group stabilized subsequently by acetylation or etherification high molecular weight polyoxymethylene.

In the production of high molecular weight polyoxymethylenes from formaldehyde vapors increased Water content with the help of Sn (II) compounds as polymerization catalysts according to an older one In addition to the impurities mentioned, soluble impurities accumulate in the polymerization media low molecular weight “vo'-dihydroxy-polyoxymethylene which, at higher concentrations, adversely affect the polymerization process. Also enriched amounts of methanol and unknown decomposition products of paraformaldehyde pyrolysis lead to deactivation of the Sn (II) catalyst, so that the average molecular weights fall steadily. To avoid the difficulties mentioned, it is particularly important to a continuously designed process is required, to keep the contamination level in the solvents constant below the critical limit, an optimum in uniformity, yield, polymerization rate and color To maintain properties of the products.

The invention relates to a process for the recycling of organic auxiliary liquids which fall off during the production of polyoxymethylenes or their esters or ethers. The process is characterized in that such auxiliary liquids are used in this production process, which in a known manner by treatment with ion exchangers, optionally in combination processes for recycling organic
Auxiliary liquids used in the manufacture of
Polyoxymethylenes or their esters or
Ethers fall off

Applicant:

Paint factories Bayer Aktiengesellschaft,

Leverkusen

Named as inventor:

Dr. Kuno Wagner, Leverkusen,

Kurt Klinkmann, Monheim,

Dr. Adolf Richter,

Dr. Ernst-Ulrich Köcher, Leverkusen

nation with activated carbon and aluminum oxide.

The possibility of purifying these auxiliary liquids via ion exchangers is surprising, they namely contain, inter alia, decomposition products of paraformaldehyde pyrolysis, z. B. Aldol condensates. It is therefore to be expected that when these contaminated auxiliary liquids are treated with acidic or basic compounds, the aldol condensates are subject to further chemical reactions, creating new ones unwanted impurities arise. It is very surprising that when using ion exchangers, which contain acidic or basic groups, these difficulties do not occur, but rather simple cleaning is easily possible.

To carry out the process according to the invention, acidic, basic or neutral ion exchangers are required usable. In a preferred embodiment, combinations of acidic and basic and neutral ion exchangers are used, in which case, too, it is often advantageous to use the To combine ion exchanger combinations with zones of activated carbon and / or aluminum oxide.

The ion exchangers used to carry out the process according to the invention can belong to a wide variety of chemical compound classes. In a preferred embodiment are in the cleaning process ion exchangers based on crosslinked polystyrene sulfonic acids or crosslinked ones Polystyrenes with basic groups used; but it can also be crosslinked ion exchangers

409 708/440

3 4

Phenol-formaldehyde resins or crosslinked urine- In an advantageous manner, the inventive

Substance-formaldehyde, melamine-formaldehyde or ani processes are carried out continuously by

lin formaldehyde resins are used. with continuously running formaldehyde polymer

Among the strongly acidic cation, polyoxymethylene acetylation or -veräthe cation exchangers to be used with preference cross-linked polystyrene sulfonation are the contaminated auxiliary liquids for the individual

to name acids that are only taken from their processing reactors and to the extent of their

degree of wetting, their swelling capacity in organic

see liquids, their porosity and their condition being fed back into the reactors.
Water absorption differ more or less.

From the series of weakly acidic ion exchangers io Example 1
are suitable for carrying out the method according to the invention, for. B. Granular condensation Relatively water-containing formaldehyde vapors (such as products based on phenol and polyacrylic acid. 1% ^ zO) are in methylene chloride, cyclohexane, ion exchangers, petroleum ether (Sp. 70 to 90 ° C), petroleum ether (Sp 110 which have both weakly acidic and strongly acidic (15 to 180 ° C), a mixture of active paraffin-hydrocarbon exchange groups. substances with 14 to 18 carbon atoms (Sp. 200 to

Among the preferred used practically new- 300 ° C), benzene, toluene, carbon tetrachloride, ethyltralen Ion exchangers are the alkali salts of acetate, di-n-butyl ether and anisole with the help of cross-linked polystyrene sulfonic acids, especially tin (II) compounds as polymerization catalysts Potassium salt. 20 gates polymerized, being about 140 parts by weight

Among the ba-formaldehyde vapors to be used according to the invention per liter of organic liquid sic anion exchangers are said to be crosslinked poly- are introduced. The ones made from high molecular weight polystyrene called, which contain primary, secondary or tertiary oxymethylene filtered, clear solutions Amino groups, in particular quaternary amino groups, 0.6 to 0.2% of soluble in the solvents contain. 25 low molecular weight «, cu'-dihydroxy-polyoxymethylenes,

In combination with the acidic ones mentioned, the new ones have water with a proportion via their end groups

neutral or basic ion exchangers can also bind from 10 to 25%. When using the

So-called adsorber resins, also so-called carbon-filtered mother liquors, act to polymerize

Exchanger with advantage for cleaning the auxiliary in particular mother liquors with 0.8 to 0.6% to the

liquids are used. 30 named oligomers as too intense chain

The implementation of the criminals and carriers according to the invention in the polymerization, driving is explained in more detail in the examples. After their extensive removal by combination of the various ion exchangers, shake with water or distillation of the organic Adsorber resins, optionally in the presence of a solvent made from water (1: 1), contain the geZones Aluminum oxide and activated carbon or carbon-35 called organic solvents water in one exchange, the various auxiliary liquid content from 0.3 to 0.1%. 1 1 each of the pre-cleaned potencies according to their throughput through separation columns in the case of organic solvents is under the same Residence times from 1 to 10 minutes in colorless and conditions (room temperature) over a column for the individual process steps in a sufficient degree of purity from 100 parts by weight of a crosslinked polystyrene can be obtained. 40 sulfonic acids and potassium salt led to the acid

^{Approximately 38 cm 3} per minute taken from the term “organic auxiliary liquids”. With a middle fall the following exemplified organic leren residence time of 2 to 3 minutes of the organic solvent: aliphatic hydrocarbons, such as liquids in the ion exchange system, the z. B. hexane, petroleum ether, a mixture of paraffin- achieved cleaning sufficient. The solutions have hydrocarbons with 14 to 18 carbon atoms, 45 a water content of 0.02 to 0.03% and derivatives substituted therewith, such as methylene chloride, tetra, the solvents are sufficiently pure for chlorinated carbon, 1,2-dichloropropane; cycloaliphatic reuse in the above-mentioned hydrocarbons, such as. B. Cyclohexane, Decahydro-Polymerization,
naphthalene; aromatic hydrocarbons, such as. B. B eisdie 1 2
Benzene, toluene, xylene, diisopropylbenzene, and sub-50

substituted derivatives such as anisole, chlorobenzene; ali- During example 1 only the water removal

phatic esters such as B. butyl acetate, ethyl acetate, from the auxiliary liquids is described in Example 2

Ethyl orthoformate, low molecular weight poly- the efficiency of the removal process

Ethylene oxide, propylene oxide, phthalic acid - from catalyst poisons in CH ₂ O polymerization

dibutyl ester; Ether, such as B. diethyl ether, dibutyl 55 and removal of strongly chain-breaking impurities

ether, diisopropyl ether; Acetals such as B. Methylal, shown:

Formaldehyde dibutyl acetal; Anhydrides such as B. Vinegar- The mother liquors of technical polymerization acid anhydride, Propionic anhydride. approaches, z. B. consisting of methylene chloride, di-

The cleaning effect of the invention ver isopropylbenzene, decahydronaphthalene or a

applied ion exchanger and adsorber resin is based on a mixture of paraffinic hydrocarbons with 14 to

due to their relatively high water absorption, the fixation 18 carbon atoms, contain in addition to the two

of metal ions, the fixation of Η ions, the soluble ω, ω'-dihydroxy-polyoxy-

Ability of strongly acidic ion exchangers to methylene to a small extent impurities,

Acetalization of methanol in the presence of which is extremely troublesome with the tin (II) -

Formaldehyde and, last but not least, formaldehyde polymerization catalyzed by adsorption 65 noticeable

of catalyst poisons that make formaldehyde; their accumulation in the mother liquors of the

Steam generation in the polymerization medium a auxiliary liquids is a consequence of the technically less

be towed. formaldehyde vapor generation that can be carried out gently,

ζ. B. by pyrolysis of paraformaldehyde in substance, in the heat exchanger in self-cleaning screws, in a fluidized bed, by methanol hydrogenation, pressure distillation of aqueous CH ₂ O, etc.

In general, these impurities consist of small amounts of formic acid, methanol, methyl formate, formaldehyde dimethyl acetal and small amounts of yellowish, volatile impurities, which are the most intensive contact poisons in formaldehyde polymerization. Although these small amounts of impurities are less than 0.2% based on CH ₂ O, they have a very adverse effect on the course of the polymerization. They are removed in the following ways:

41 each of methylene chloride, diisopropylbenzene, decalin and a mixture of paraffin hydrocarbons with 14 to 18 carbon atoms are separated by columns that have a cross section of 3 cm and are filled with the following exchanger zones (from bottom to top):

100 parts by weight of crosslinked polystyrene sulfonic acid, 10 parts by weight of activated carbon,
100 parts by weight of a basic ion exchanger,

10 parts by weight of aluminum oxide, ^ ⁰

50 parts by weight of crosslinked, neutral polystyrene

potassium sulfonate,
10 parts by weight of Α coal and
100 parts by weight of polystyrene sulfonic acid.

With a residence time of the respective solvents of 4 to 6 minutes, the purified solvents are completely colorless, have no significant methanol and formic acid content and can be _{reused as polymerization liquids in CH 2} O polymerization.

Example 3

The cleaning procedure is as in Example 2 (2nd paragraph), but one hundred times enlarged ion exchange columns connected to the following reactors continuously running formaldehyde polymerization plant:

Pyrolysis reactor:

4001 of a mixture of paraffinic hydrocarbons with 14 to 18 carbon atoms,

Polymerization reactor:

4001 CH ₂ Cl ₂ ,

Washing tower:

1001 of a mixture of paraffinic hydrocarbons having 14 to 18 carbon atoms.

The amount of auxiliary liquids circulating in the reactors is reduced within half an hour led through the ion exchange columns for cleaning. By this measure, one obtains in the polymerization reactor polyoxymethylenes that differ in their uniformity, color and yield Products that are manufactured without the cleaning effect of the separation columns are significantly superior.

Example 4

During the acetylation or alkylation of high molecular weight polyoxymethylenes, color is formed strongly disruptive by-products. Especially with acetylation in the presence of tertiary, organic Bases or sodium acetate as acetylation catalysts and depending on traces of iron or Acetylation liquors often turn dark brown after only 10 hours of use colored to black.

1000 parts by volume of brown-black colored acetic anhydride and 1000 parts by volume of ethyl orthoformate (brownish yellow) are given individually over separation columns that have the following zone fillings :

50 parts by weight of a basic ion exchanger,

50 parts by weight of activated carbon and
50 parts by weight of a basic ion exchanger.

At the lower end of the columns, 20 to 30 cm ^{3 of} auxiliary liquid are withdrawn per minute. The defined auxiliary liquid is also valid here, since these liquids are used in an extremely large excess over the amount used for the end group reaction. The solvents obtained are colorless and can be used again for the acetylation or alkylation of polyoxymethylenes.

Claims (1)

Claim: Process for the recycling of organic auxiliary liquids used in the production of Polyoxymethylenes or their esters or ethers fall off, characterized in that that one uses such auxiliary liquids in this production process, which are known per se Way by treatment with ion exchangers, optionally in combination with activated carbon and aluminum oxide are. Considered publications:
German Auslegeschrift No. 1 037 705;
Chimia, June 9, 1955, p. 132. 409 708/440 10.64 © Bundesdruckerei Berlin