GB2077724A

GB2077724A - Production of Formats of Pentaerythritol and Dipentaerythritol

Info

Publication number: GB2077724A
Application number: GB8116685A
Authority: GB
Original assignee: Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 1980-06-12
Filing date: 1981-06-01
Publication date: 1981-12-23
Also published as: SE8103681L; DE3021983A1; BE889183A

Abstract

The monoformals and diformals of pentaerythritol and dipentaerythritol are produced by reacting these alcohols with paraformaldehyde at a temperature of from about 90 to 150 DEG C in the present of an acid substance as catalyst. The pentaerythritol and the dipentaerythritol as well the paraformaldehyde are used in the form of solid substances and the reaction is carried out in the absence of a solvent.

Description

SPECIFICATION A Process for the Production of Formals This invention relates to a process for the production of the formals of pentaerythritol and dipentaerythritol by reacting these alcohols with paraformaldehyde at elevated temperature in the presence of an acid substance as catalyst.

It is known that the monoformal of pentaerythritol is formed when pentaerythritol is reacted with trioxymethylene in the presence of aqueous hydrochloric acid at the boiling temperature of the mixture (Ber. 61(1927), 55 to 57). The yield is low. The diformal of pentaerythritol is produced by reacting pentaerythritol with aqueous formaldehyde solution at 850C on an acid ion exchanger (CA 60 (1964), 5338 e). Although good yields are obtained in this process, long reaction times are required.

Finally, it is known that formals of pentaerythritol can be produced by reacting pentaerythritol with aqueous formaldehyde or paraformaldehyde, optionally in solution or suspension, at temperatures in the range from 120 to 2200C. The reaction is carried out in the presence of an acid, such as sulphuric acid or ptoluene sulphonic acid, as catalyst. In addition, a solvent, such as glycerol, has to be added to reduce the melting point (DE-AS No. 1 ,1 35,878).

The yields obtained in this process are unsatisfactory.

The present invention provides a process for the production of formals of pentaerythritol and dipentaerythritol by reacting the alcohol with paraformaldehyde in the presence of an acid substance as catalyst the reaction being carried out at a temperature of from about 90 to 1 500C in the absence of a solvent. In this process, very favourable yields are obtained for short reaction times. The formation of secondary products is negligible so that pure formals are directly obtained.

According to the invention, pentaerythritol and dipentaerythritol, i.e. alcohols corresponding to the following formula

in which n=O or 1, are reacted with paraformaldehyde to form the corresponding monoformals or diformals.

To carry out the process, the alcohols and the paraformaldehyde are used in the form of solids.

No solvents are used either for diluting the reaction mixture or for reducing the melting point.

Although the quantitative ratio of alcohol to paraformaldehyde may be selected largely as required (sub-stoichiometric to overstoichiometric), it is generally best to use at least substantially stoichiometric quantities and, with advantage, over-stoichiometric quantities of paraformaldehyde. It is preferred to use from 1.10 to 1.25 moles and, more particularly, 1.20 mole of paraformaldehyde per mole of alcohol for producing the monoformals and from 2.10 to 2.25 moles of paraformaldehyde per mole of alcohol for producing the diformals.

The catalysts used are the acid substances normally employed for this reaction, for example sulphuric acid, p-toluene sulphonic acid and acid ion exchangers. The catalysts are generally used in a quantity of from 0.01 to 1.0% by weight, based on the alcohol.

According to the invention, the reaction is carried out at a temperature of from about 80 to 1 500C and preferably at a temperature of from 90 to 1 300C. The pressure may be selected as required, although it is generally advisable to carry out the reaction under normal pressure or at most moderately reduced or elevated pressure.

The formals are generally present in the reaction mixture in such highly pure form that the reaction mixture may be directly used as such, for example in cases where the formals are used as reactive diluents in stoving lacquers. If necessary, the formals are separated off from the reaction mixture, for example by neutralising the reaction mixture with alkaline substances and then subjecting it to fractional distillation.

The invention is illustrated by the following Examples.

Example 1 A mixture of 136 g (1.0 mole) of pentaerythritol, 38 g of 95% paraformaldehyde (corresponding to 1.2 moles of formaldehyde) and 0.14 g of p-toluene sulphonic acid was heated to 1300 C. The mixture turned liquid at around 11 00C. It was then kept for 60 minutes at 130 to 1 400C. Thereafter no more free formaldehyde could be detected. Analysis by gas chromatography showed that the reaction mixture contained 80% of pentaerythritol monoformal, 10% of pentaerythritol diformal and 10% of unreacted pentaerythritol. Distillation of the reaction mixture gave pentaerythritol monoformal in a purity of more than 98%. It was colourless. The melting point was 61 to 620C.

The yield amounted to 75%, based on the pentaerythritol used.

Example 2 A mixture of 136 g of pentaerythritol, 70 g of 95% paraformaldehyde (corresponding to 2.2 moles of formaldehyde) and 0.14 g of p-toluene sulphonic acid was first melted at 1000C and then kept for 60 minutes at 1 400C. The reaction mixture was pale yellow in colour. 98% of the reaction mixture consisted of pentaerythritol diformal. Distillation gave pentaerythritol diformal in a purity of 99.9%. It was colourless. The melting point was 51 OC. The yield amounted to 90%, based on the pentaerythritol used.

Example 3 A mixture of 254 g of diperitaerythritol, 70 g of 95% paraformaldehyde (corresponding to 2.2 moles of formaldehyde) and 0.14 g of sulphuric acid was first melted at 1000C and then kept for 60 minutes at 1400 C. The reaction mixture was pale yellow in colour. 95% of the reaction mixture consisted of dipentaerythritol diformal. Distillation gave dipentaerythritol diformal in a purity of more than 98%. It was colourless. The melting point was 104%C. The yield amounted to 87%, based on the dipentaerythritol used.

Claims

1. A process for the production of the formals of pentaerythritol and dipentaerythritol which comprises reacting the alcohol with paraformaldehyde in the presence of an acid substance as catalyst, the reaction being carried: out at a temperature of from about 90 to 1 500C in the absence of a solvent.

2. A process for the production of the formals of pentaerythritol and dipentaerythritol substantially as described with particular reference to any of the Examples.

3. A formal of pentaerythritol or dipentaerythritol when produced by a process as claimed in either of claims 1 or 2.