CA1236473A - Process for the preparation of pure trioxane - Google Patents
Process for the preparation of pure trioxaneInfo
- Publication number
- CA1236473A CA1236473A CA000478923A CA478923A CA1236473A CA 1236473 A CA1236473 A CA 1236473A CA 000478923 A CA000478923 A CA 000478923A CA 478923 A CA478923 A CA 478923A CA 1236473 A CA1236473 A CA 1236473A
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- Prior art keywords
- trioxane
- crystallization
- weight
- mixture
- carried out
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D323/00—Heterocyclic compounds containing more than two oxygen atoms as the only ring hetero atoms
- C07D323/04—Six-membered rings
- C07D323/06—Trioxane
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Heterocyclic Compounds That Contain Two Or More Ring Oxygen Atoms (AREA)
- Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)
Abstract
Abstract of the disclosure:
The present invention relates to an effective and energy-saving process for the work-up of a trioxane mixture, in which the trioxane mixture is subjected to a crystalli-zation in a closed system, preferably in several steps and with exclusion of moisture and the presence of an inert gas, the crystallization being carried out at least partially as melt crystallization. The trioxane thus puri-fied provides polyoxymethlenes of high molecular weight.
The present invention relates to an effective and energy-saving process for the work-up of a trioxane mixture, in which the trioxane mixture is subjected to a crystalli-zation in a closed system, preferably in several steps and with exclusion of moisture and the presence of an inert gas, the crystallization being carried out at least partially as melt crystallization. The trioxane thus puri-fied provides polyoxymethlenes of high molecular weight.
Description
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~3~'~ 73
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In the present state of the art, trioxane is usually pre-pared by heating 30 - 70 % strength a~ueous formaldehyde solutions in the presence of acid cataly~;ts, for example 2 - 25 % mineral acid (German Patent 1,543,390), or in the the presence of acid ion exchangers tGerman Patent 1,135,491) .
5 ~he trioxane is removed from the reaction mixture by distil-lation. ~his is carried out either in a column placed on the reactor, in accordance with U.S. Patent 2,304,080, or in a separate column, as described in British Patent 1,012,372. ~he water-containing distillate rich in tri-oxane is extracted, for example, with methylene chloride,ethylene chloride, benzene, or toluene, as described in German Auslegeschrift 1,668,687, for example. '~he extract is neutralized and purified by distillation as described in German Patent 1,543,815, for example.
~he extractlon men-tioned is necessary in order to reach a ~eparation of the trioxane from water, while the purification by distillation mentioned is necessary in order to remove the by-products obtained in the trioxane syn-thesis, such as formaldehyde, methanol, formic acid, methyl 20 formate, methylal, dioxymethylene dimethyl ether and others, and thus to obtain a polymerizable trioxane. Higher boiling impurities which are contained in the trioxane which has not reacted in the polymeriæation and is to be worked up again are also removed in thes~e distillation steps.
Combined purification processes have also been pro-posed for the final purification mentioned. ~hus, German ~ Patent 1,237,583 discloses the treatment of the molten trioxane with weakly acid ion exchangers prior to the fractional distillation, with the intention of essentially 30 removing the impurities having a basic action. Special ion exchan~ers for the purification of trioxane are the sub-ject-matter of German Offenlegungsschrift 2,156,112.
~ he removal of impurities in trioxane by extractive distillation in the presence of water or of ethylene gly-cols is disclosed in U.S. Patent 3,281,336. ~
In the present state of the art, trioxane is usually pre-pared by heating 30 - 70 % strength a~ueous formaldehyde solutions in the presence of acid cataly~;ts, for example 2 - 25 % mineral acid (German Patent 1,543,390), or in the the presence of acid ion exchangers tGerman Patent 1,135,491) .
5 ~he trioxane is removed from the reaction mixture by distil-lation. ~his is carried out either in a column placed on the reactor, in accordance with U.S. Patent 2,304,080, or in a separate column, as described in British Patent 1,012,372. ~he water-containing distillate rich in tri-oxane is extracted, for example, with methylene chloride,ethylene chloride, benzene, or toluene, as described in German Auslegeschrift 1,668,687, for example. '~he extract is neutralized and purified by distillation as described in German Patent 1,543,815, for example.
~he extractlon men-tioned is necessary in order to reach a ~eparation of the trioxane from water, while the purification by distillation mentioned is necessary in order to remove the by-products obtained in the trioxane syn-thesis, such as formaldehyde, methanol, formic acid, methyl 20 formate, methylal, dioxymethylene dimethyl ether and others, and thus to obtain a polymerizable trioxane. Higher boiling impurities which are contained in the trioxane which has not reacted in the polymeriæation and is to be worked up again are also removed in thes~e distillation steps.
Combined purification processes have also been pro-posed for the final purification mentioned. ~hus, German ~ Patent 1,237,583 discloses the treatment of the molten trioxane with weakly acid ion exchangers prior to the fractional distillation, with the intention of essentially 30 removing the impurities having a basic action. Special ion exchan~ers for the purification of trioxane are the sub-ject-matter of German Offenlegungsschrift 2,156,112.
~ he removal of impurities in trioxane by extractive distillation in the presence of water or of ethylene gly-cols is disclosed in U.S. Patent 3,281,336. ~
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Besides a number of further processes for the puri-fication of trioxane previously proposed, such as the use of activated aluminum oxide or a molecular sieve, German Offenlegungsschrift 2,855,710 discloses for the removal of the impurities by crystallizing liquid trioxane in an open system, while passing air or an inert gas over it, optionally under pressure. However, for example, by passing air over trioxane, new impurities can be formed therein. Moreover, it is predominantly only the low boiling impurities which are removed in this procedure. High boilers, which may likewise interfere with the polymerization, still remain in the product in significant amounts. Moreover, the high sublimation pressure of trioxane is a disadvantage in the process described, the result being losses of material.
In general, it is possible to say of the known pro-cesses for the work-up of trloxane mixtures that t~ey are energy-intensive and costly in apparatus, tha-t unpredictable side reactions may take place due to the use of additional auxiliaries, and that some of them do not lead to trioxane having the requisite purity.
Thus, the object of the present invention was to make available a process for the work-up at trioxane mixtures which does not have the disadvantages of the state of the art and which leads to a highly pure trioxane, in particular, by applying a less energy-intensive procedure with simple apparatus.
This object is achieved according to the invention by subjecting the trioxane mixture to a, preferably multistep, frac-tional crystallization in a closed system until a tri-oxane of the requisite purity is produced.
~ hus the invention relates to a process for the pre-paration of highly pure trioxane by crystallization of a trioxane mixture, which comprises subjecting the trioxane ~5 mixture to a, preferably multistep, crystallization in a closed system, the crystalization being carried out at least partially as melt crystallization.
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Besides a number of further processes for the puri-fication of trioxane previously proposed, such as the use of activated aluminum oxide or a molecular sieve, German Offenlegungsschrift 2,855,710 discloses for the removal of the impurities by crystallizing liquid trioxane in an open system, while passing air or an inert gas over it, optionally under pressure. However, for example, by passing air over trioxane, new impurities can be formed therein. Moreover, it is predominantly only the low boiling impurities which are removed in this procedure. High boilers, which may likewise interfere with the polymerization, still remain in the product in significant amounts. Moreover, the high sublimation pressure of trioxane is a disadvantage in the process described, the result being losses of material.
In general, it is possible to say of the known pro-cesses for the work-up of trloxane mixtures that t~ey are energy-intensive and costly in apparatus, tha-t unpredictable side reactions may take place due to the use of additional auxiliaries, and that some of them do not lead to trioxane having the requisite purity.
Thus, the object of the present invention was to make available a process for the work-up at trioxane mixtures which does not have the disadvantages of the state of the art and which leads to a highly pure trioxane, in particular, by applying a less energy-intensive procedure with simple apparatus.
This object is achieved according to the invention by subjecting the trioxane mixture to a, preferably multistep, frac-tional crystallization in a closed system until a tri-oxane of the requisite purity is produced.
~ hus the invention relates to a process for the pre-paration of highly pure trioxane by crystallization of a trioxane mixture, which comprises subjecting the trioxane ~5 mixture to a, preferably multistep, crystallization in a closed system, the crystalization being carried out at least partially as melt crystallization.
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The process according to the invention is preferably carried out under an inert gas atmosphere and with moisture essentially excluded at least during the last steps, pre-ferably during in all steps of the melt crystalli~ation.
A particularly suitable inert gas for this is nitrogen.
It is also possible to use carbon dioxide or argon for this purpose.
In this context, "trioxane mixture" is to be under-stood to include not only the aqueous system produced in the known trioxane synthesis but also the already prepuri-fied, and as a consequence of this, substantially anhydrous mixture containing in general less than 20 % by weight, preferably less than 10 % by weight and particularly less than 1 % by weight of water. ~his term further includes the trioxane which is not reacted in the polymerization to give polyoxymethylene and which, a-~ter appropria-te work-up, is to be used again in t,he polymerization proces~.
Since the trioxane -~orms a eutectic system with any im-purities present, in principle all trioxane mixtures whose trioxane contents are above the eutectic composition are suitable for the fractional melt crystallization. The con-comitants contained in these trioxane mixtures are com-pounds such as, for example, water, formic acid, form-aldehyde, methanol, methylal, dioxymethylene dimethyl ether, dioxolane, dioxane, trioxepane~ trioxymethylene dimethyl ether, tetroxane and the like. As a rule, the trioxane content of the trioxane mixture used as the starting mix--ture for the ~elt crystallization at the start of purifi-cation makes up at least 50 % by weight, in particular at least 90 % by weight, and particularly preferably at least 95 % by weight. In principle, the trioxane content can als~
be less than 50 % by weight, and thus come even closer to the eutectic. However, in this case, it is possible to separate only little pure trioxane.
If a water-containing trioxane mixture is used for the work-up according to the invention, the trioxane con-tent of this, as a rule, should be at least 20 % by weight, ~3~ 3
The process according to the invention is preferably carried out under an inert gas atmosphere and with moisture essentially excluded at least during the last steps, pre-ferably during in all steps of the melt crystalli~ation.
A particularly suitable inert gas for this is nitrogen.
It is also possible to use carbon dioxide or argon for this purpose.
In this context, "trioxane mixture" is to be under-stood to include not only the aqueous system produced in the known trioxane synthesis but also the already prepuri-fied, and as a consequence of this, substantially anhydrous mixture containing in general less than 20 % by weight, preferably less than 10 % by weight and particularly less than 1 % by weight of water. ~his term further includes the trioxane which is not reacted in the polymerization to give polyoxymethylene and which, a-~ter appropria-te work-up, is to be used again in t,he polymerization proces~.
Since the trioxane -~orms a eutectic system with any im-purities present, in principle all trioxane mixtures whose trioxane contents are above the eutectic composition are suitable for the fractional melt crystallization. The con-comitants contained in these trioxane mixtures are com-pounds such as, for example, water, formic acid, form-aldehyde, methanol, methylal, dioxymethylene dimethyl ether, dioxolane, dioxane, trioxepane~ trioxymethylene dimethyl ether, tetroxane and the like. As a rule, the trioxane content of the trioxane mixture used as the starting mix--ture for the ~elt crystallization at the start of purifi-cation makes up at least 50 % by weight, in particular at least 90 % by weight, and particularly preferably at least 95 % by weight. In principle, the trioxane content can als~
be less than 50 % by weight, and thus come even closer to the eutectic. However, in this case, it is possible to separate only little pure trioxane.
If a water-containing trioxane mixture is used for the work-up according to the invention, the trioxane con-tent of this, as a rule, should be at least 20 % by weight, ~3~ 3
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preferably at least 50 % by weight otherwise the quanti-ties of water introduced into the crystallization apparatus would be rather large, the quantity of trioxane separated rather small and the requisite crystallization temperature would be rather lowO In dependence of the quan-tity of water and on the temperature of the water-containing tri-oxane mixture, the first step of the crystallization is a predominantly melt crystallization or solution crystalli-zation (i.e. a crystalline precipitation from the solution) procedure, in the latter case this solution crystallization and the subsequent melt crystallization taking also place in the same apparatus according to the inven-tion. A solu-tion crystallization takes place in the first step, for example, in cases where the quantity of water of the -tri-oxane mixture is at least abou-t 20 % by weight at a tem-perature of form about 60 to about 70C. The trioxane mix-ture produced in the solution crystallization step and to be subjected to the melt crystallization step is in gene-ral substantially anhydrous after the first step and con-tains at least 50 ~ by weight of trioxane.
~ he crystallization temperatures used in the processaccording to the invention can vary within wide limits, and are generally in the range -10 to +63C, preferably between -~5 and +63C. The use of seeding crystals is ad-visible to initiate crystalliz~ation more rapidly. ~he mostfavorable temperatures for the initiation of crystalliza-tion and the most favorable crystallization times can readily be determined by experiments. The type of crystals formed in the process according to the invention is not ~0 critical. After crystallization of the fused crude trioxane, the remaining liquid fraction is rapidly removed, and the re-sulting trioxane, which is already more pure, is subjected, preferably once or several time more, to melt crystalli-zation after fusion in an analogous manner, until the re-quisite degree of purity is reached. This is mostly thecase after only two or three steps~ The non-crystallized .
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preferably at least 50 % by weight otherwise the quanti-ties of water introduced into the crystallization apparatus would be rather large, the quantity of trioxane separated rather small and the requisite crystallization temperature would be rather lowO In dependence of the quan-tity of water and on the temperature of the water-containing tri-oxane mixture, the first step of the crystallization is a predominantly melt crystallization or solution crystalli-zation (i.e. a crystalline precipitation from the solution) procedure, in the latter case this solution crystallization and the subsequent melt crystallization taking also place in the same apparatus according to the inven-tion. A solu-tion crystallization takes place in the first step, for example, in cases where the quantity of water of the -tri-oxane mixture is at least abou-t 20 % by weight at a tem-perature of form about 60 to about 70C. The trioxane mix-ture produced in the solution crystallization step and to be subjected to the melt crystallization step is in gene-ral substantially anhydrous after the first step and con-tains at least 50 ~ by weight of trioxane.
~ he crystallization temperatures used in the processaccording to the invention can vary within wide limits, and are generally in the range -10 to +63C, preferably between -~5 and +63C. The use of seeding crystals is ad-visible to initiate crystalliz~ation more rapidly. ~he mostfavorable temperatures for the initiation of crystalliza-tion and the most favorable crystallization times can readily be determined by experiments. The type of crystals formed in the process according to the invention is not ~0 critical. After crystallization of the fused crude trioxane, the remaining liquid fraction is rapidly removed, and the re-sulting trioxane, which is already more pure, is subjected, preferably once or several time more, to melt crystalli-zation after fusion in an analogous manner, until the re-quisite degree of purity is reached. This is mostly thecase after only two or three steps~ The non-crystallized .
i~
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liquid fraction which is produced in the crystallization steps and still contains trioxane can be repeatedly re-turned and subjected to renewed crystallization. In theory, this i3 possible until the eutectic composition i~ reached in the liquid fraction. ~or practical purposes, a stop will be made a few percent above this eutectic composition. In an analogous manner, the aqueous mother-liquor produced in the solution crystallization and which still contains trioxane can be returned and be subjected to renewed crystallization at a lower temperature. ~or economic reasons, this proce-dure will be repeated only until a determined re~idual tri-oxane content in the solution is reachedO
In principle, the process according to -the invention can be carried out in any closed crystallizer which a:Llows mel-t crystallization which is preferably multistep and takes place in rapid sequence, preferably under inert ~as and with exclusion of moisture. Suitable for this purpose is, for example, a tube crystallizer (called a drip appar-tus) as is described in Winnacker-Kuchler, Chemische ~echnologie (Chemical Technology), 4th edition, vo. 6 (1982), page 148, and which is operated discontinuously. A crystallizer as described in U.S. Patent 3,621,664, which allows the pro-cess to be carried out semicontinuously, is preferably used according to the invention. In principle, this crystallizer is composed of a, preferably r~elatively large, number of crystallization elements (tubes) which are arranged in pa-rallel and usually vertically, and through which the liquid mixture which is to be frac-tionated flows down as a film.
The crystallization then takes place on the cooled walls.
After a determined thickness of the crystal layer has been reached, the supply of liquid mixture is interrupted, -the liquid fraction adhering to the crystal layer is removed, and then the crystal layer is melted off.
The trioxane purified in the process according to the invention generally has a purity of 99.99 %, preferably 99.995 ~, and, on homo- or copolymerization provides poly-~.~3~73
liquid fraction which is produced in the crystallization steps and still contains trioxane can be repeatedly re-turned and subjected to renewed crystallization. In theory, this i3 possible until the eutectic composition i~ reached in the liquid fraction. ~or practical purposes, a stop will be made a few percent above this eutectic composition. In an analogous manner, the aqueous mother-liquor produced in the solution crystallization and which still contains trioxane can be returned and be subjected to renewed crystallization at a lower temperature. ~or economic reasons, this proce-dure will be repeated only until a determined re~idual tri-oxane content in the solution is reachedO
In principle, the process according to -the invention can be carried out in any closed crystallizer which a:Llows mel-t crystallization which is preferably multistep and takes place in rapid sequence, preferably under inert ~as and with exclusion of moisture. Suitable for this purpose is, for example, a tube crystallizer (called a drip appar-tus) as is described in Winnacker-Kuchler, Chemische ~echnologie (Chemical Technology), 4th edition, vo. 6 (1982), page 148, and which is operated discontinuously. A crystallizer as described in U.S. Patent 3,621,664, which allows the pro-cess to be carried out semicontinuously, is preferably used according to the invention. In principle, this crystallizer is composed of a, preferably r~elatively large, number of crystallization elements (tubes) which are arranged in pa-rallel and usually vertically, and through which the liquid mixture which is to be frac-tionated flows down as a film.
The crystallization then takes place on the cooled walls.
After a determined thickness of the crystal layer has been reached, the supply of liquid mixture is interrupted, -the liquid fraction adhering to the crystal layer is removed, and then the crystal layer is melted off.
The trioxane purified in the process according to the invention generally has a purity of 99.99 %, preferably 99.995 ~, and, on homo- or copolymerization provides poly-~.~3~73
7 - HOE 85/~ 039 J
mers having high molecular weights and excellent heat-resistance.
Apart form the preferred use as a monomer for polymers and copolymers, it is also possible to use the trioxane obtained according to the invention as a synthon, for ex-ample for pharmaceuticals, plant-protection agents, textile auxiliaries and preservatives, where appropriate in the presence of a s-tabilizer.
The advantages of the process according to the inven-tion are not only the very high puri-ty of the resulting trioxane and the fact that the procedure is non-injurious to the product and environmentally acceptable, but also the considerable saving in energy which is provided by the process compared with multistep fractional distillation.
It was not to be expected, and it has to be regarded as surprisin~" that the trioxane, even in a pure and very pure state, withstands several fusion and sol:Ldification operations without ~spontaneous polymerization starting.
~urthermore, it wa.s not to be expected that the solution crystallization and the melt crystalliza-tion step in the case of water-containing trioxane mixture can be carried ou-t in the same apparatus.
The process according to the invention is illustrated by the examples which follow, but it is not restricted to these examples. The percentage~s are percent by weight in each case.
Exam~le 1 A -trioxane which had been concentrated by distillation (from the synthesis of trioxane from aqueGus formadehyde solutions in the presence of acid catalysts; trioxane con-tent: about 9~.5 %) and which had a solidification point of +58.5~C and the following composition:
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~ ~36'~
mers having high molecular weights and excellent heat-resistance.
Apart form the preferred use as a monomer for polymers and copolymers, it is also possible to use the trioxane obtained according to the invention as a synthon, for ex-ample for pharmaceuticals, plant-protection agents, textile auxiliaries and preservatives, where appropriate in the presence of a s-tabilizer.
The advantages of the process according to the inven-tion are not only the very high puri-ty of the resulting trioxane and the fact that the procedure is non-injurious to the product and environmentally acceptable, but also the considerable saving in energy which is provided by the process compared with multistep fractional distillation.
It was not to be expected, and it has to be regarded as surprisin~" that the trioxane, even in a pure and very pure state, withstands several fusion and sol:Ldification operations without ~spontaneous polymerization starting.
~urthermore, it wa.s not to be expected that the solution crystallization and the melt crystalliza-tion step in the case of water-containing trioxane mixture can be carried ou-t in the same apparatus.
The process according to the invention is illustrated by the examples which follow, but it is not restricted to these examples. The percentage~s are percent by weight in each case.
Exam~le 1 A -trioxane which had been concentrated by distillation (from the synthesis of trioxane from aqueGus formadehyde solutions in the presence of acid catalysts; trioxane con-tent: about 9~.5 %) and which had a solidification point of +58.5~C and the following composition:
:: `
~ ~36'~
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M~y~ ~.ol Di~- Di ~ ~ri~ ~i~y-¦~methyl- M~hyl- ~cy~ ~r~ie ether p~e et~ bic~o- bicy~k~ tet~E
t~r~ e t~x~.e 2.7~m 4-3% 0.15% 0.5% 0.71% ~ P~ 6~0p~ 10-~3~ ~ p~m * Dioxy ether= dioxymethylene dimethyl ether was introduced into a moisture-free tube crystallizer (as described in Winnacker-KUchler, Chemische Technologie, 4th edition, vol. 6 (1982), page 148), which was rendered thoroughly inert with nitrogen and whose jacket was con-nected to a thermostat with a temperature/time programmer.
~he crude trioxane was cooled to 58C under nitrogen, and inoculated with a few seed crystals. After about 30 minutes, the contents of the crystallizer were cooled to 50C within one hour, and the liquid reaction remaining in the apparatus was rapidly drained off. The well-formed crystals remaining in the apparatus were then fused under nitrogen, and the melt, which now had a solidification point of 60C, was inoculated with seed crystals at this temperature and sub-jected to renewed melt crystallization taking place undersimilar temperature and time conditions. After removal of the liquid fraction from the second 9tep, the crystals re-maining in the appratus were again fused, and the melt was isolated with exclusion of oxygen and moisture. 130 parts by weight of crude trioxane were used for each 100 parts by weight of trioxane crystallized in two steps. ~he iso-lated trioxane had the following residual impurities:
M~U~ ~h~ Di~w- ~ne ~i~Tri~ ul-¦M~yl- ~ic~o- ~x~.e¦
ether p~.e ether bicy~k~ ¦bic~o- tetr~
tetr~ne,tetr~.e ~ I
_ _ 35 ~m_ _ _ I _ _ xample 2 An aqueous solution containing 55 % by weight of tri-oxane was initially introduced into a crystallizer as des cribed in U.S. Patent 37621,664~ at a -temperature of 70C.
,.:, ~L~3~
M~y~ ~.ol Di~- Di ~ ~ri~ ~i~y-¦~methyl- M~hyl- ~cy~ ~r~ie ether p~e et~ bic~o- bicy~k~ tet~E
t~r~ e t~x~.e 2.7~m 4-3% 0.15% 0.5% 0.71% ~ P~ 6~0p~ 10-~3~ ~ p~m * Dioxy ether= dioxymethylene dimethyl ether was introduced into a moisture-free tube crystallizer (as described in Winnacker-KUchler, Chemische Technologie, 4th edition, vol. 6 (1982), page 148), which was rendered thoroughly inert with nitrogen and whose jacket was con-nected to a thermostat with a temperature/time programmer.
~he crude trioxane was cooled to 58C under nitrogen, and inoculated with a few seed crystals. After about 30 minutes, the contents of the crystallizer were cooled to 50C within one hour, and the liquid reaction remaining in the apparatus was rapidly drained off. The well-formed crystals remaining in the apparatus were then fused under nitrogen, and the melt, which now had a solidification point of 60C, was inoculated with seed crystals at this temperature and sub-jected to renewed melt crystallization taking place undersimilar temperature and time conditions. After removal of the liquid fraction from the second 9tep, the crystals re-maining in the appratus were again fused, and the melt was isolated with exclusion of oxygen and moisture. 130 parts by weight of crude trioxane were used for each 100 parts by weight of trioxane crystallized in two steps. ~he iso-lated trioxane had the following residual impurities:
M~U~ ~h~ Di~w- ~ne ~i~Tri~ ul-¦M~yl- ~ic~o- ~x~.e¦
ether p~.e ether bicy~k~ ¦bic~o- tetr~
tetr~ne,tetr~.e ~ I
_ _ 35 ~m_ _ _ I _ _ xample 2 An aqueous solution containing 55 % by weight of tri-oxane was initially introduced into a crystallizer as des cribed in U.S. Patent 37621,664~ at a -temperature of 70C.
,.:, ~L~3~
- 9 - HOE 85/~ 039 J
Trioxane was crystallized by gradually lowering the tem-perature to +10C within a period of 35 minutes. The re-sidue still containing 12 % by weight of trioxane, was re-moved from the system. A trioxane having a purity of 95 per-5 cent was obtained after partially fusing twice a 800 gportion of the crystallized trioxane by gradually raising the temperature to 55C. For the further purification, the trioxane was subjected to a multistep melt crystallization in accordance with ~xample 3.
Exam~l e 3 A trioxane which had been concentra-ted by distillation (from the synthesis of trioxane from aqueous formaldehyde solutions in the presence of acid catalysts, trioxane con-15 tent: about 97.5 %) of the following composition:
~y~ ~ ~ y- C~la~ne Triax~ ~i~ l*m~yl~ ~ ~Iqy~ qbt~
ether p3ne ether bicycl~ bicycl~ ~03ne tfftr~e tetrc~e _ _ _ _ _ . ..
Clo ppm 96 p~m 1.7 % g70 pp~ 0.18 % 0.17 % 40 ppm 5C0 p~m 0.21 % ZX) p~m was initially introduced into a crystallizer as described in U.S. Patent 3,621 ,664 for the purpose of melt crystalli-zation under an atmosphere free of moisture and rendered 25 thoroughly inert with nitrogen. Crystallization was carried out in three steps in a temperàture range from +10C to ~63C, and after 140 minutes of total crystallization and fusion time, the fused crystals from the third step were used directly for polymeriza-tion. 106 parts by weight of 30 trioxane which had been prepurified by destillation were necessary for each 100 parts by weight of trioxane purified in three steps. None of the impurities contained in the starting material were any longer detectable by gas chro-matography in the trioxane which had been purified in three 35 steps.
~36~3
Trioxane was crystallized by gradually lowering the tem-perature to +10C within a period of 35 minutes. The re-sidue still containing 12 % by weight of trioxane, was re-moved from the system. A trioxane having a purity of 95 per-5 cent was obtained after partially fusing twice a 800 gportion of the crystallized trioxane by gradually raising the temperature to 55C. For the further purification, the trioxane was subjected to a multistep melt crystallization in accordance with ~xample 3.
Exam~l e 3 A trioxane which had been concentra-ted by distillation (from the synthesis of trioxane from aqueous formaldehyde solutions in the presence of acid catalysts, trioxane con-15 tent: about 97.5 %) of the following composition:
~y~ ~ ~ y- C~la~ne Triax~ ~i~ l*m~yl~ ~ ~Iqy~ qbt~
ether p3ne ether bicycl~ bicycl~ ~03ne tfftr~e tetrc~e _ _ _ _ _ . ..
Clo ppm 96 p~m 1.7 % g70 pp~ 0.18 % 0.17 % 40 ppm 5C0 p~m 0.21 % ZX) p~m was initially introduced into a crystallizer as described in U.S. Patent 3,621 ,664 for the purpose of melt crystalli-zation under an atmosphere free of moisture and rendered 25 thoroughly inert with nitrogen. Crystallization was carried out in three steps in a temperàture range from +10C to ~63C, and after 140 minutes of total crystallization and fusion time, the fused crystals from the third step were used directly for polymeriza-tion. 106 parts by weight of 30 trioxane which had been prepurified by destillation were necessary for each 100 parts by weight of trioxane purified in three steps. None of the impurities contained in the starting material were any longer detectable by gas chro-matography in the trioxane which had been purified in three 35 steps.
~36~3
- 10 - HOE 85/~ 039 J
Ex ~m~
A trioxane which had been concentrated by distillation (trioxane content: about 97 %) of the following composition:
y~l ~anol ~i axy- ~ ~3ne Cri~ ~ri~y- l~yl- I~thyl- ~i~ l~ne ether p~e ether bicyclo- bicyclo tet~e _ ~ tet~xane t~ 10 PEm 1~7 ppn 2.4 % 0.12 % 0.22 % 0.22 % 20 ~pn 4X) p~m 0.17 % lO~ p~m 10 was initially introduced into the same crystallizer and under the same conditions as described in Example 3 for the purpose of melt crystallization. Crystallization was carried out in four steps in a temperature range from ~5C
to +63C, and after 160 minutes of total crystallization 15 and fusion time, the fused crystals from the Eour th step were directly used Eor polymerization. 108 parts by weight o f trioxane which had been prepuri~ied by dis tillation were necessary for each 100 parts by weight of trioxane puri-fied in four s-teps. Not only after the fourth, but already 20 after the third crystallization step, none of the impuri-ties contained in the starting material were any longer detectable by gas chromatography.
Ex ~m~
A trioxane which had been concentrated by distillation (trioxane content: about 97 %) of the following composition:
y~l ~anol ~i axy- ~ ~3ne Cri~ ~ri~y- l~yl- I~thyl- ~i~ l~ne ether p~e ether bicyclo- bicyclo tet~e _ ~ tet~xane t~ 10 PEm 1~7 ppn 2.4 % 0.12 % 0.22 % 0.22 % 20 ~pn 4X) p~m 0.17 % lO~ p~m 10 was initially introduced into the same crystallizer and under the same conditions as described in Example 3 for the purpose of melt crystallization. Crystallization was carried out in four steps in a temperature range from ~5C
to +63C, and after 160 minutes of total crystallization 15 and fusion time, the fused crystals from the Eour th step were directly used Eor polymerization. 108 parts by weight o f trioxane which had been prepuri~ied by dis tillation were necessary for each 100 parts by weight of trioxane puri-fied in four s-teps. Not only after the fourth, but already 20 after the third crystallization step, none of the impuri-ties contained in the starting material were any longer detectable by gas chromatography.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the preparation of highly pure tri-oxane by crystallization of a trioxane mixture, which com-prises subjecting the trioxane mixture to a crystallization in a closed system, the crystallization being carried out at least partially as melt crystallization.
2. The process as claimed in claim 1, wherein the cry-stallization is carried out in several steps, in the pre-sence of an inert gas and with exclusion of moisture at least in the last steps.
3. The process as claimed in claim 1, wherein the trioxane mixture contains at least 50 % by weight of trioxane.
4. The process as claimed in claim 2, wherein the trioxane mixture contains at least 50% by weight of trioxane.
5. The process as claimed in claim 1, 2 or 3, wherein the trioxane mixture is substantially an-hydrous and wherein the crystallization is carried out only as melt crystallization.
6. The process as claimed in claim 1 or 2, wherein the trioxane mixture contains from 30%
to 50 % by weight of water and wherein the first step of the crystallization is carried out as solution crystalli-zation.
to 50 % by weight of water and wherein the first step of the crystallization is carried out as solution crystalli-zation.
7. The process as claimed in claim 1, 2 or 3, wherein the trioxane obtained has a degree of purity of 99.99%.
8. The process as claimed in claim 1, 2 or 3, wherein the crystallization temperature is between +5°C. and +63°C.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3413903.6 | 1984-04-13 | ||
| DE3413903 | 1984-04-13 | ||
| DE19853508668 DE3508668A1 (en) | 1984-04-13 | 1985-03-12 | METHOD FOR PRODUCING PURE TRIOXANE |
| DEP3508668.8 | 1985-03-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1236473A true CA1236473A (en) | 1988-05-10 |
Family
ID=25820354
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000478923A Expired CA1236473A (en) | 1984-04-13 | 1985-04-11 | Process for the preparation of pure trioxane |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0162252B1 (en) |
| JP (1) | JPH0678333B2 (en) |
| CA (1) | CA1236473A (en) |
| DE (2) | DE3508668A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5872263A (en) * | 1994-05-02 | 1999-02-16 | Hoechst Aktiengesellschaft | Process for separating formaldehyde and trioxane |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19833620A1 (en) * | 1998-07-25 | 2000-01-27 | Ticona Gmbh | Separation of trioxane from gaseous mixtures with formaldehyde |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1515032A (en) * | 1966-10-19 | 1968-03-01 | Houilleres Bassin Du Nord | Process for the preparation of homogeneous bands of solid trioxane and apparatus for its implementation |
| JPS5487792A (en) * | 1977-12-24 | 1979-07-12 | Mitsubishi Gas Chem Co Inc | Polymerization of trioxane |
-
1985
- 1985-03-12 DE DE19853508668 patent/DE3508668A1/en not_active Withdrawn
- 1985-04-04 EP EP85104100A patent/EP0162252B1/en not_active Expired
- 1985-04-04 DE DE8585104100T patent/DE3567653D1/en not_active Expired
- 1985-04-08 JP JP60072851A patent/JPH0678333B2/en not_active Expired - Fee Related
- 1985-04-11 CA CA000478923A patent/CA1236473A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5872263A (en) * | 1994-05-02 | 1999-02-16 | Hoechst Aktiengesellschaft | Process for separating formaldehyde and trioxane |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3508668A1 (en) | 1985-10-24 |
| EP0162252A1 (en) | 1985-11-27 |
| JPH0678333B2 (en) | 1994-10-05 |
| DE3567653D1 (en) | 1989-02-23 |
| JPS60228476A (en) | 1985-11-13 |
| EP0162252B1 (en) | 1989-01-18 |
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