CA2055131A1 - Process for the preparation of trioxane - Google Patents
Process for the preparation of trioxaneInfo
- Publication number
- CA2055131A1 CA2055131A1 CA002055131A CA2055131A CA2055131A1 CA 2055131 A1 CA2055131 A1 CA 2055131A1 CA 002055131 A CA002055131 A CA 002055131A CA 2055131 A CA2055131 A CA 2055131A CA 2055131 A1 CA2055131 A1 CA 2055131A1
- Authority
- CA
- Canada
- Prior art keywords
- trioxane
- formaldehyde
- acid
- employed
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
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
Landscapes
- 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)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
Abstract of the disclosure:
Process for the preparation of trioxane Trioxane can be obtained with a minimum energy require-ment if acetal polymers are broken down in the presence of water and an acid catalyst. The process represents a contribution to waste disposal and environmental protec-tion.
Process for the preparation of trioxane Trioxane can be obtained with a minimum energy require-ment if acetal polymers are broken down in the presence of water and an acid catalyst. The process represents a contribution to waste disposal and environmental protec-tion.
Description
2`~ L3~
HOECHST AKTIENGESEL~SCHAET HOE 90/F 331 Dr. K/rh Description Process for the preparation of trioxane The invention relates to a process for th~ preparation of S trioxane from homo- and/or copo]L~mers of formaldehyds in the presence o~ acid cataly~ts.
The pxeparation of trioxane from aqueous foxmaldehyde solutions is de6cribed in various in~tances in the literature ~cf. Walker, Formaldehyde, Reinhold Publ. New York, 3rd edition, 1964, pages 198-199).
Trioxane (TO~ formed from aqueous formaldehyde at relatively high temperatures in the presence of acid catalysts and is removed from the reaction mixture by distillation. ~he synthesis vapor is usually worked up in a rectifyiny column mounted on the reactor ~US Paent 2,304,080). The trioxane-rich phase i8 ~ubjected to extraction and/or another separation process. To achieve high space-time yields, the reaction is carried out in a forced eirculation evaporator (Canadian Pa~ent 1,125,774). The copolymers obtained by trio~ane copoly-merization are of a high quality and belong to the field of industrial plastics.
Industrial plastics are processed ~y extrusion Dr in~ec-tion molding, product waste being formed, which must be disposed of. Sprues and burrs are produced during processing by in~ection molding. Extruded goods are mostly machined, up to 50% of the material not infrequently being obtained a8 waste. Material~ which do not always conform to type are al80 sometime~ formed during the production proce~s a~d mu t be dispo~ed of, Incineration and landfill have to date been available as methods of disposal. A recycling process is therefore to be preferred.
: - ' : : . , ,, " ' '' ~ :
:
~ 2 --A process for generating gaseous formaldehyde from polyoxymethylene, such as paraformaldehyde, is known (US-A 3,883,309). In this process, a dispersion of polymeric formaldehyde is decomposed the~ally at lOD - 300C to give formaldehyde, and thi~ eparated off in gaseous form. This process is extremely complicated and requires considerable technical effor~ to prevent blockages due to paraformaldehyde. ~f copolymers are used, contamination of the formaldehyde by comonome:rs cannot be exclud~d.
The object of the present invention waæ to ~ind a process which, inter alia, enables polyacetal to be racycled without displaying the difficulties mentioned, producing a material which can be used again directly for copolymerization.
This has been achieved by a process for the continuous preparation of trioxane from formaldehyde, in which an ace~al polymer is broken down in the presence of w~ter and an acid catalyst and the formaldehyde formed is converted into trioxane in the same process step.
High trioxane concentrations in the synthesis vapor which correspond to those of the maxLmum equilibrium which can be achieved using formaldehyde solutions are obtained by the process according to the invention.
The preparation of trioxane according to the invention is carried out by conversion of homo- and~or copolymers of formaldehyde and if appropriate ~yclic formals, for example in the form of a recycling material, in the presenc~ of w~ter and acid catalys The amount of water added is measured so that a calculated formaldehyde content of 50 - 90, preferably 65 - 85~ by weight is established in the reactor. Addition of foam suppressants may be helpful. Mineral acids, strong organic acids or an amount of another acid catalyst of corresponding cata-lytic activity are used as the catalyst. Acid catalysts, which in general must be less volatile than the reaction .
. ;
:: ; ;
', ' ~
2 ~ ; ~ 6C~3 ~
mixture, which have proved to be usable are, in particu-lar, sulfuric acid, phosphoric acid, p-toluene~ulf4nic acid or ~trongly acid ion exchangers, for example poly-styrene e~changers containing sulfonic acid groups. ~he amount of catalyst is not critic:al and is as a rule 1 to 60, preferably 10 - 50~ by weight, ba~ed on the reaction mixture~
Homo- and copolymers of fQrmaldehyde and/or cyclic formals, preferably copolymers~ in ~omminuted form are employed as ~he recycling material. The recycling mater ials can also contain dyestuffs, pigments, stabilizers and other customary additives. The recycling material i~
metered into the reactor separately, for example via a ~ransfer channel for solids, or together Wit}l wa~er. The additives, for exæmple stabilizers, do not interfexe with the reaction. ~he comonomers are also re-formed in the reactor and are worked up together with the trio~ane.
Separation of the comonomers is prior art. The reaction is carried out according to the invention in a known circulatory reactor with an evaporator. Evaporator6 which are suitable for this are, for example, forced circula-tion e~aporators, alling film e~aporators, ri ing film evaporators or thin film evaporators with forced circula-tion. Such systems are described, for example, in ~5 Ullmann, Volume 1 (1951~, 3rd edition, pages 533 - 537.
Forced circulation e~aporators are particularly suitable.
However, these reactors mu t con~ain baffles to prevent the solid particles being sucked up by the pump vf the forced circulation reactor. Basket-liXe baffles or sieves in front of the pumps are suitable for t~is purpo e.
The residence time of the reaction mixture in the reac-tion system i 5 - 240 minukes, preferably 15 - 60 minutes. ~he temperature of the reaction mixture i9 50 to 150C, preferably 95 to 130C, depending on the pressure.
The reaction mixture, which oonsists of trioxane, orm-aldehyde and water, and if ~ppropriate cyclic formals, is ,~ ~
',;"";. ' ~
:
: : , `
, . :
4 ~'.J'~
removed from the reac~ion system by distillakion with the aid of the evaporator. The reaction hexe can be carried out under normal pressure, under reduced pressure, for examiple under 300 to 1000 mbar, or under increased pressure, for example 1 to 4 bar. It is preferably carried out under l to 2 bar.
The synthesis vapor which leaves the reaction sy~tem i8 enriched in the customary manner, either as the vapor or as the condensate, by means of rectification, as des-cribed in British Patent 1,012,372.
The txioxane-rich fraction obtained, which al80 contain~
cyclic formals if appropriate, can be purified, for example, by extraction with a water-immiscible solvent for trioxane (and if appropriate for the cyclic formals), such as methylene chloride, and subsequent ~eutralization and fractional distillation or crystallization. O~her known iseparation processes can also be used for this purpose (Process Economics Program Stanford Institute Report 23 (1967) 181 or DE-OS 1,570,335). The product stre~ms freed from the trioxane~ which still contain chiefly formaldehyde and water, can be recycled continu-ously into the reaction tank.
The proce~s accordin~ to the invention, which can be carried out continuously or discontinuouisly, makes possible a trioxane synthesis with a minimum energy requirement, since th manufacturing costs for providing highly concentrated formaldehyde are dispensed with. The highly concentrated formaldehyde is replaced here by the recycling material employed. ~he proce s represents a contribution to waste disposal and environmental protection, since waste substances are p~s~ed to the production proces~ and incineration plant~ and landfill sites via which the recycling material previouRly had to be disposed of are tharefore relievad.
. . . ( , ~ :
~,. " .~
::
,r3 ',~', ,?,, ~
. - 5 -~xample~:
250 g of water, 250 g of concentrated sulfuric acid and 500 g of recycling material in granule form (copolymer of trioxane and 3~ by weight of dioxolane) were initially introduced into a ~ 1 four-nec}ced flask with a ~tirrer.
~he mi~ture was heated to the boiling point and ~he distillate was condensed in a quench cooler. i~ ifurther 39 g of granules and 21 g of water (corresponding to a 65% ~trength formaldehyde solution) were introduced separately into ~he flask at interval~ oif in each case 15 minutes. The total reaction tLme was 5 hours. The com-position of the distillate was analyzed hourly. The mean values of the experiments are sho~m in the table. The dioxolane content corresponds to the comonomer content in the granules employed. The trioxane content in the examples according to the inven~ion corresponds to that obtained from aqueous formaldehyde in the conventional ~rioxane process according to the prior art (comparison example).
:, , :: ~
'' :~
:: "~
~' , ' ~ .: ,.
: . . . ~ . ~ . .
, , --Table Conditions: Initially introduced into the flask: 250 ~ of concentrated ~ulfu:ric acid; 250 g of water;
500 g of ~ranules Temperature: 104C, running time S hours ~eed every ~ hour: 39 g of granules, 21 g of water Example Through-TOX CH20 Dioxolane Water putin the in the in the as the g~h dis- dis- dis~illate dif fer-tillate tillate ence~
- % 9~ % %
.. . . _ . ~
201 25.7 39.8 3.1 31.~
1~ 2 223 19 . 7 40 . 1 2 . 4 37 . 8 Comparison~ 250 20 . 6 41. 9 --- 37 . 5 . . ... _ * Formaldehyde feed concentrations 63 . 596 ~ sulfuric acid content in the reactor bottom product 10%
** to make 10 0 ~6 -.
: - , , ~ -~
HOECHST AKTIENGESEL~SCHAET HOE 90/F 331 Dr. K/rh Description Process for the preparation of trioxane The invention relates to a process for th~ preparation of S trioxane from homo- and/or copo]L~mers of formaldehyds in the presence o~ acid cataly~ts.
The pxeparation of trioxane from aqueous foxmaldehyde solutions is de6cribed in various in~tances in the literature ~cf. Walker, Formaldehyde, Reinhold Publ. New York, 3rd edition, 1964, pages 198-199).
Trioxane (TO~ formed from aqueous formaldehyde at relatively high temperatures in the presence of acid catalysts and is removed from the reaction mixture by distillation. ~he synthesis vapor is usually worked up in a rectifyiny column mounted on the reactor ~US Paent 2,304,080). The trioxane-rich phase i8 ~ubjected to extraction and/or another separation process. To achieve high space-time yields, the reaction is carried out in a forced eirculation evaporator (Canadian Pa~ent 1,125,774). The copolymers obtained by trio~ane copoly-merization are of a high quality and belong to the field of industrial plastics.
Industrial plastics are processed ~y extrusion Dr in~ec-tion molding, product waste being formed, which must be disposed of. Sprues and burrs are produced during processing by in~ection molding. Extruded goods are mostly machined, up to 50% of the material not infrequently being obtained a8 waste. Material~ which do not always conform to type are al80 sometime~ formed during the production proce~s a~d mu t be dispo~ed of, Incineration and landfill have to date been available as methods of disposal. A recycling process is therefore to be preferred.
: - ' : : . , ,, " ' '' ~ :
:
~ 2 --A process for generating gaseous formaldehyde from polyoxymethylene, such as paraformaldehyde, is known (US-A 3,883,309). In this process, a dispersion of polymeric formaldehyde is decomposed the~ally at lOD - 300C to give formaldehyde, and thi~ eparated off in gaseous form. This process is extremely complicated and requires considerable technical effor~ to prevent blockages due to paraformaldehyde. ~f copolymers are used, contamination of the formaldehyde by comonome:rs cannot be exclud~d.
The object of the present invention waæ to ~ind a process which, inter alia, enables polyacetal to be racycled without displaying the difficulties mentioned, producing a material which can be used again directly for copolymerization.
This has been achieved by a process for the continuous preparation of trioxane from formaldehyde, in which an ace~al polymer is broken down in the presence of w~ter and an acid catalyst and the formaldehyde formed is converted into trioxane in the same process step.
High trioxane concentrations in the synthesis vapor which correspond to those of the maxLmum equilibrium which can be achieved using formaldehyde solutions are obtained by the process according to the invention.
The preparation of trioxane according to the invention is carried out by conversion of homo- and~or copolymers of formaldehyde and if appropriate ~yclic formals, for example in the form of a recycling material, in the presenc~ of w~ter and acid catalys The amount of water added is measured so that a calculated formaldehyde content of 50 - 90, preferably 65 - 85~ by weight is established in the reactor. Addition of foam suppressants may be helpful. Mineral acids, strong organic acids or an amount of another acid catalyst of corresponding cata-lytic activity are used as the catalyst. Acid catalysts, which in general must be less volatile than the reaction .
. ;
:: ; ;
', ' ~
2 ~ ; ~ 6C~3 ~
mixture, which have proved to be usable are, in particu-lar, sulfuric acid, phosphoric acid, p-toluene~ulf4nic acid or ~trongly acid ion exchangers, for example poly-styrene e~changers containing sulfonic acid groups. ~he amount of catalyst is not critic:al and is as a rule 1 to 60, preferably 10 - 50~ by weight, ba~ed on the reaction mixture~
Homo- and copolymers of fQrmaldehyde and/or cyclic formals, preferably copolymers~ in ~omminuted form are employed as ~he recycling material. The recycling mater ials can also contain dyestuffs, pigments, stabilizers and other customary additives. The recycling material i~
metered into the reactor separately, for example via a ~ransfer channel for solids, or together Wit}l wa~er. The additives, for exæmple stabilizers, do not interfexe with the reaction. ~he comonomers are also re-formed in the reactor and are worked up together with the trio~ane.
Separation of the comonomers is prior art. The reaction is carried out according to the invention in a known circulatory reactor with an evaporator. Evaporator6 which are suitable for this are, for example, forced circula-tion e~aporators, alling film e~aporators, ri ing film evaporators or thin film evaporators with forced circula-tion. Such systems are described, for example, in ~5 Ullmann, Volume 1 (1951~, 3rd edition, pages 533 - 537.
Forced circulation e~aporators are particularly suitable.
However, these reactors mu t con~ain baffles to prevent the solid particles being sucked up by the pump vf the forced circulation reactor. Basket-liXe baffles or sieves in front of the pumps are suitable for t~is purpo e.
The residence time of the reaction mixture in the reac-tion system i 5 - 240 minukes, preferably 15 - 60 minutes. ~he temperature of the reaction mixture i9 50 to 150C, preferably 95 to 130C, depending on the pressure.
The reaction mixture, which oonsists of trioxane, orm-aldehyde and water, and if ~ppropriate cyclic formals, is ,~ ~
',;"";. ' ~
:
: : , `
, . :
4 ~'.J'~
removed from the reac~ion system by distillakion with the aid of the evaporator. The reaction hexe can be carried out under normal pressure, under reduced pressure, for examiple under 300 to 1000 mbar, or under increased pressure, for example 1 to 4 bar. It is preferably carried out under l to 2 bar.
The synthesis vapor which leaves the reaction sy~tem i8 enriched in the customary manner, either as the vapor or as the condensate, by means of rectification, as des-cribed in British Patent 1,012,372.
The txioxane-rich fraction obtained, which al80 contain~
cyclic formals if appropriate, can be purified, for example, by extraction with a water-immiscible solvent for trioxane (and if appropriate for the cyclic formals), such as methylene chloride, and subsequent ~eutralization and fractional distillation or crystallization. O~her known iseparation processes can also be used for this purpose (Process Economics Program Stanford Institute Report 23 (1967) 181 or DE-OS 1,570,335). The product stre~ms freed from the trioxane~ which still contain chiefly formaldehyde and water, can be recycled continu-ously into the reaction tank.
The proce~s accordin~ to the invention, which can be carried out continuously or discontinuouisly, makes possible a trioxane synthesis with a minimum energy requirement, since th manufacturing costs for providing highly concentrated formaldehyde are dispensed with. The highly concentrated formaldehyde is replaced here by the recycling material employed. ~he proce s represents a contribution to waste disposal and environmental protection, since waste substances are p~s~ed to the production proces~ and incineration plant~ and landfill sites via which the recycling material previouRly had to be disposed of are tharefore relievad.
. . . ( , ~ :
~,. " .~
::
,r3 ',~', ,?,, ~
. - 5 -~xample~:
250 g of water, 250 g of concentrated sulfuric acid and 500 g of recycling material in granule form (copolymer of trioxane and 3~ by weight of dioxolane) were initially introduced into a ~ 1 four-nec}ced flask with a ~tirrer.
~he mi~ture was heated to the boiling point and ~he distillate was condensed in a quench cooler. i~ ifurther 39 g of granules and 21 g of water (corresponding to a 65% ~trength formaldehyde solution) were introduced separately into ~he flask at interval~ oif in each case 15 minutes. The total reaction tLme was 5 hours. The com-position of the distillate was analyzed hourly. The mean values of the experiments are sho~m in the table. The dioxolane content corresponds to the comonomer content in the granules employed. The trioxane content in the examples according to the inven~ion corresponds to that obtained from aqueous formaldehyde in the conventional ~rioxane process according to the prior art (comparison example).
:, , :: ~
'' :~
:: "~
~' , ' ~ .: ,.
: . . . ~ . ~ . .
, , --Table Conditions: Initially introduced into the flask: 250 ~ of concentrated ~ulfu:ric acid; 250 g of water;
500 g of ~ranules Temperature: 104C, running time S hours ~eed every ~ hour: 39 g of granules, 21 g of water Example Through-TOX CH20 Dioxolane Water putin the in the in the as the g~h dis- dis- dis~illate dif fer-tillate tillate ence~
- % 9~ % %
.. . . _ . ~
201 25.7 39.8 3.1 31.~
1~ 2 223 19 . 7 40 . 1 2 . 4 37 . 8 Comparison~ 250 20 . 6 41. 9 --- 37 . 5 . . ... _ * Formaldehyde feed concentrations 63 . 596 ~ sulfuric acid content in the reactor bottom product 10%
** to make 10 0 ~6 -.
: - , , ~ -~
Claims (16)
1. A process for the preparation of trioxane from formaldehyde, which comprises breaking down an acetal polymer in the presence of water and an acid catalyst and converting the resulting formaldehyde into trioxane in the same process step.
2. The process as claimed in claim 1, wherein a homo-and/or copolymer of formaldehyde and if appropriate cyclic formals is employed as the acetal polymer.
3. The process as claimed in claim 1, wherein a mixture of trioxane and at least one cyclic formal is obtained.
4. The process as claimed in claim 1 or 2 or 3, wherein a recycling material is employed.
5. The process as claimed in claim 1 or 2 or 3, wherein the acetal polymer is a trioxane copolymer with dioxolane/ethylene oxide or with butanediol formal as comonomer constituents.
6. The process as claimed in claim 1 or 2 or 3, which is carried out continuously.
7. The process as claimed in claim 1 or 2 or 3, wherein the reaction is carried out in a forced circulation reactor.
8. The process as claimed in claim 1 or 2 or 3, wherein the reaction temperature is 50 to 150°C.
9. The process as claimed in claim 1 or 2 or 3, wherein the reaction temperature is 95 to 130°C.
10. The process as claimed in claim 1 or 2 of 3, wherein the amount of water is such that the calculated formaldehyde content in the reactor is 50 - 90% by weight.
11. The process as claimed in claim 1 or 2 or 3, wherein the formaldehyde content is 65 to 85% by weight.
12. The process as claimed in claim 1 or 2 or 3, wherein sulfuric acid, phosphoric acid, p-toluenesulfonic acid or an acid ion exchanger is employed as the acid catalyst in an amount of 1 to 60% by weight, based on the reaction mixture.
13. The process as claimed in claim 1 or 2 or 3, wherein 10 to 50% by weight of an acid catalyst is employed.
14. The process as claimed in claim 1 or 2 or 3, wherein concentrated sulfuric acid is employed as the catalyst.
15. The process as claimed in claim 1 or 2 or 3, wherein the reaction products axe separated off by distilla-tion under a pressure of 1 to 2 bar.
16. The process as claimed in claim 1, and substantially as described herein.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4035495.4 | 1990-11-08 | ||
| DE4035495A DE4035495A1 (en) | 1990-11-08 | 1990-11-08 | METHOD FOR PRODUCING TRIOXANE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2055131A1 true CA2055131A1 (en) | 1992-05-09 |
Family
ID=6417862
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002055131A Abandoned CA2055131A1 (en) | 1990-11-08 | 1991-11-07 | Process for the preparation of trioxane |
Country Status (15)
| Country | Link |
|---|---|
| EP (1) | EP0484786A1 (en) |
| JP (1) | JPH04273869A (en) |
| KR (1) | KR920009819A (en) |
| CN (1) | CN1061412A (en) |
| AU (1) | AU8705491A (en) |
| BR (1) | BR9104850A (en) |
| CA (1) | CA2055131A1 (en) |
| CS (1) | CS338991A3 (en) |
| DE (1) | DE4035495A1 (en) |
| HU (1) | HUT59386A (en) |
| IE (1) | IE913894A1 (en) |
| MX (1) | MX9101959A (en) |
| PL (1) | PL292308A1 (en) |
| PT (1) | PT99451A (en) |
| ZA (1) | ZA918832B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| USH1339H (en) * | 1992-06-03 | 1994-07-05 | Blair Leslie M | Aqueous process for recycling acetal polymer and moldings thereof |
| DE10258663B4 (en) * | 2002-12-13 | 2005-07-28 | Ticona Gmbh | Process for the preparation of trioxane |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2064100A1 (en) * | 1970-12-28 | 1972-07-13 | Badische Anilin- & Soda-Fabrik Ag, 6700 Ludwigshafen | Production of formaldehyde derivatives of aliphatic hydroxy compounds |
-
1990
- 1990-11-08 DE DE4035495A patent/DE4035495A1/en not_active Withdrawn
-
1991
- 1991-10-28 EP EP91118348A patent/EP0484786A1/en not_active Withdrawn
- 1991-11-06 CN CN91108484A patent/CN1061412A/en active Pending
- 1991-11-06 HU HU913480A patent/HUT59386A/en unknown
- 1991-11-06 KR KR1019910019619A patent/KR920009819A/en not_active Application Discontinuation
- 1991-11-06 MX MX9101959A patent/MX9101959A/en unknown
- 1991-11-07 CS CS913389A patent/CS338991A3/en unknown
- 1991-11-07 CA CA002055131A patent/CA2055131A1/en not_active Abandoned
- 1991-11-07 PT PT99451A patent/PT99451A/en not_active Application Discontinuation
- 1991-11-07 ZA ZA918832A patent/ZA918832B/en unknown
- 1991-11-07 PL PL29230891A patent/PL292308A1/en unknown
- 1991-11-07 BR BR919104850A patent/BR9104850A/en unknown
- 1991-11-07 AU AU87054/91A patent/AU8705491A/en not_active Abandoned
- 1991-11-07 IE IE389491A patent/IE913894A1/en not_active Application Discontinuation
- 1991-11-08 JP JP3292637A patent/JPH04273869A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| KR920009819A (en) | 1992-06-25 |
| CS338991A3 (en) | 1992-05-13 |
| CN1061412A (en) | 1992-05-27 |
| PL292308A1 (en) | 1992-06-01 |
| HU913480D0 (en) | 1992-01-28 |
| JPH04273869A (en) | 1992-09-30 |
| AU8705491A (en) | 1992-05-14 |
| ZA918832B (en) | 1992-07-29 |
| EP0484786A1 (en) | 1992-05-13 |
| IE913894A1 (en) | 1992-05-20 |
| HUT59386A (en) | 1992-05-28 |
| BR9104850A (en) | 1992-06-23 |
| DE4035495A1 (en) | 1992-05-14 |
| PT99451A (en) | 1992-09-30 |
| MX9101959A (en) | 1992-06-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |