DE1595399B2 - Process for the production of high molecular weight O-hemiacetals of formaldehyde. Elimination from: 1230007 - Google Patents

Description

Solvent so enters into a liquid hydroxyl-containing polymer, wherein the reaction temperature is at least 2O ⁰ C and preferably 50 to HO is, ⁰ C to the boiling point of pure formaldehyde and the concentration of free formaldehyde during the reaction, 8%, preferably 5%. does not exceed.

A suitable pure formaldehyde should contain no more than 0.002% water and must be so far from Impurities such as B. formic acid, so that it does not polymerize.

The formaldehyde, which can be diluted with an inert gas such as nitrogen if desired, is always above the boiling point of monomeric formaldehyde (-21 ° C) in gaseous form in the high-molecular Alcohol registered.

■ It is still possible to use low-value semi-formals of polymers with several hydroxyl groups by introducing only as much formaldehyde as the conversion only one (with Diols) or second hydroxyl groups (in the case of triplets). As polymers containing hydroxyl groups come into question: polyols such. B. polyvinyl alcohol, polyester, preferably condensates from diacids with trimethylolpropane or glycerine, polyether, polythioether, polycarbonate, saponified Copolymers of vinyl acetate with vinyl chloride, styrene, butadiene, vinylidene chloride, acrylic esters, methacrylic esters and acrylonitrile or maleic anhydride. But also hydrogenated ketone-formaldehyde resins are outstandingly suitable, as well as copolymers which, for example, glycide, endomethylenetetrahydrobenzyl alcohol or contain allyl alcohol as alcoholic components. The hydroxyl group content can vary within wide limits, between 0.001 and 30%, preferably between 0.05 to 50%, without there is crosslinking or cyclic full acetal structures.

The high molecular weight should either be liquid at the reaction temperature or in inert solvents such as benzene, toluene, chloroform, carbon tetrachloride, cyclohexane, dimethyl sulfoxide or cyclic Acetals such as 1,3-dioxolane or its homologues can be soluble.

The high molecular weight alcohol is expediently presented in pure form. This is how you get the shark acetals in pure form, free of diluents, which is especially valuable when you have the shark acetals needed directly for further implementations. However, an inert solvent can also be used. Ethers such as diethyl ether, diisopropyl ether, di-n-butyl ether, methyl ethyl ether and hydrocarbons are suitable as such such as propane, η-propane, n-pentane, η-hexane, n-decane and mixtures such as petroleum ether, Ligroin and gasoline, aromatics such as benzene, xylene, anisole or their mixtures and chlorinated hydrocarbons such as carbon tetrachloride, chloroform, tetrachloroethane, trichlorethylene and methylene chloride.

It has proved to be expedient to carry out the reaction at 0 to 140 ⁰ C, preferably 30 to 130 ⁰ C, in particular 40 to 100 ⁰ C. Under normal conditions, it is expedient to process solid hydroxyl-containing polymers in the melt, provided their melting point is not higher than about 110 ^° C. and the viscosity of the melt allows very intensive stirring and introduction of the monomeric formaldehyde. Higher-melting compounds are expediently dissolved in one of the solvents mentioned, which absorbs the hydroxyl-containing polymer in high concentration, and the formaldehyde is allowed to act at a lower temperature.

The formation of the O-half-formals generally proceeds only at a moderate rate, but particularly slowly at temperatures below O ⁰ C, which then leads to high local formaldehyde concentrations, which lead to undesirable side reactions, such as the addition of a formaldehyde molecule to an already existing half-formal molecule so that one then comes to the known polyhalbformal mixtures mixed with free alcohol. At low temperatures, considerable proportions of paraformaldehyde are often formed, which are then precipitated. Even if the monomeric formaldehyde is introduced too quickly, formaldehyde concentrations that are too high can arise locally. For this reason, the formaldehyde is only added slowly to the extent that it is converted and, by stirring as vigorously as possible, ensures that the aldehyde that has been introduced is properly and immediately distributed. It is best to work in such a way that a negative pressure is created in the entire system, which ensures a local formaldehyde concentration below 1%. The same function is exercised by increasing the reaction temperature. By raising the partial pressure of the steam Fomaldehyds with the temperature (at 4O ⁰ C for about 5 atm) at the same time reduces the solubility of the free formaldehyde in the corresponding high molecular weight alcohol, and leaving only the bound and half Formal formaldehyde.

In some cases the reaction with formaldehyde only takes place at temperatures above 80 ° C, namely when the individual hydroxyl groups are too shielded by hydrogen bonds are. The introduction of the monomeric formaldehyde takes place at such a rate that in each If a quantitative implementation is achieved.

In the semi-formal formation, considerable heat is released, which is dissipated by good cooling.

The O-half-formals are permanent compounds, which are mostly miscible or soluble with alcohols such as methanol, ethanol, propanol, etc., with aromatics such as benzene and toluene, with ethers such as diethyl ether and with halogenated hydrocarbons such as chloroform, carbon tetrachloride, trichlorethylene and methylene chloride. If the diol component is miscible with water, then so are the corresponding ones O-semi-formals soluble in water.

Give the O-half-formals, kept in open vessels, formaldehyde gradually decreases. These properties make them ideally suited as disinfectants and as insecticides. In addition, represent the O-half formals as reactive compounds valuable intermediates for organic syntheses.

As mentioned above, the poly semi-formals are also suitable as valuable components for Structure of plastics, paints and adhesives.

Example 1 to 4

600 g of commercial paraformaldehyde are thermally decomposed with 270 g of phosphorus pentoxide and 750 ml paraffin oil with stirring and the exclusion of oxygen within 3 hours at 85-130 ⁰ C. the

resulting pyrolysis gases pass through a perpendicular Dimroth condenser in a cooling system, which consists of 3 cold traps, be the temperatures of -30 ⁰ C, -30 C ^{0 0} C and -6O. In the first and second cold trap, the monomeric formaldehyde is largely purified by prepolymerization; in the third cold trap, monomeric formaldehyde is obtained as a water-clear liquid. The purity of the formaldehyde is 99.9%.

In one equipped with a stirrer, inlet pipe (except for the bottom of the vessel), thermometer and exhaust gas nozzle, the amount of the respective high molecular weight alcohol adapted 3-neck flask is, as from the Table showing the formaldehyde introduced into the alcohol presented. The exhaust port is over a wash bottle with a mercury immersion, so that any volumetric change in the System can be easily viewed. The formaldehyde sets up immediately, generating a lot of heat to the hemiacetal. The stirring speed is 500 rpm. The respective temperature is Maintained by cooling according to column 4. The turnover is quantitative. They arise in everyone Cases clear products with their elemental analytical values determined by combustion analysis match the calculated ones. The IR spectra give no 'clues' for the presence of

ίο acetal structures.

Insofar as they are solid under normal conditions, the polymers are presented in a dissolved state. The semi-formals are formed without full acetal formation or precipitation due to crosslinking, even if the solvents are removed ^{in vacuo at temperatures of 10 to 30 ° C.} The semi-formals of the polymers can be crosslinked with suitable reagents, very hard or elastic materials being obtained depending on the crosslinking density.

Production of semi-formals by reacting formaldehyde with polymers containing hydroxyl groups

example polymer Parts by weight Solution
middle
Parts shape
aldehyde
Parts by weight Monotony
temperature
⁰ C management
duration
Minutes 1 Polyester made from glycerine and adipine
acid in a ratio of 1: 1 1004 - 120 50 75 2 hydrogenated condensation resin
Acetophenone and formaldehyde,
Hydroxyl number 300 to 320, Er
softening point 105 to 115 ° 700 793 acetone 175 20th 70 3 Copolymer, consisting of 87%
Vinyl chloride, 9% vinyl acetate and
4% propylene glycol monoacrylate 500 1112 butyl
acetate 6th 20th 5 4th Polyethylene glycol MW 400 800 - 120 30th 60

Claims (1)

1 ■■■■ · ■■ · .._ 2 containing aqueous distillate extremely cumbersome and Claim: is costly. Furthermore, the applicability made even more difficult by the fact that many semi-formals in the Process for establishing high molecular equilibrium with alcohols giving azeotropes.
O-half-acetals of formaldehyde, characterized 5 Another difficulty which characterizes the production that one opposes pure form pure half-formals in this way, aldehyde slowly to the extent of the conversion under consists in the necessary constant increase of the cooling, possibly in the presence of a bottom temperature for complete distillative de-inert solvent, in a liquid hydroxyl removal of the water, which in the presence of the still group-containing polymer enters in such a way that the water present, experience has shown, condensation reaction temperature of at least 2O ⁰ C is favored by ionic reactions,
It is also known that instead of form and the concentration of free formaldehyde solutions, paraformaldehyde in the presence of during the reaction does not exceed 8% aldehyde solutions. Catalysts with monohydric and polyhydric alcohols 15 to implement. This gives in the presence of acids such as p-toluenesulfonic acid or Lewis acids - like BF ₃ from simple alcohols with water leakage always only the corresponding full acetals, from simple Diols such as glycol, 1,3-propanediol, and 1,4-butanediol O-hemiacetals of aldehydes always apply to a few 20 the corresponding cyclic acetals, while Exceptions generally as very unstable compounds - the higher homologous diols such as 1,5-pentadiol, fertilize, so that one is often forced to submerge their existence 1,7-heptanediol and 1,10-decanediol to ensure physically. In particular, it exits to the corresponding straight-chain polyist so far it has not been possible to react to O-hemiacetals of the formal formal. In contrast, counteraldehyde is obtained in to represent in pure form. This has to do with the maintenance of alkalis such as sodium and potassium hydroxide led that reactions with pure semi-formal semi-formal mixtures without resulting in a water are practically unknown. cleavage with formation of full acetals, cyclic From J. Am. Chem. Soc. 50, p. 503 (1928) it is true that acetals or polyformals come,
known that in some cases - the lowest possible aldehyde is acetaldehyde - when mixing alkali, however, only at higher temperatures of equimolar amounts of aldehyde and alcohol does a ^{significant (50 to 80 0} C) with Speed takes place before setting to the hemiacetal, but pulls H ο u, which then, however, to a very violent be nW eyl, Vol. VII, Part 1, p. 416 (1954), which this exothermic reaction occurs, which is particularly important Publication cited, from the whole of science - larger conversions technically very difficult to expose - the conclusion that aldehydes are predominant. So per unit of time, apart from chloral, controllable amounts of formaldehyde are released in alcoholic solvent, which solution is only up to 50% as a hemiacetal, with a partial polyaddition of the formaldehyde to the equilibrium in the higher homologous aides - an already formed semi-formal lead and thus to hyden more and more on the part of the free component mixtures. Another very significant disadvantage lies. 40 is the constant presence of water in the Um-For the formaldehyde, which as the initial element of settlement products, due to the aldehyde constitution-related water content of behavior in the paraform of a homologous series anyway, has recently been assumed (JF about 5%, originating from the Hydroxyl end groups.Walker, Formaldehyde, Reinhold Publishing Corp., However, this water can only be removed by distillation to a limited extent, as above New York, 1964, p. 264, lines 9 and 10) that explains 45.
Equilibrium between formaldehyde and alcohol Even pure formaldehyde has occasionally been brought into implementation with alcohol to a far greater extent on the half-formal side. This creates lies, as is the case with other aldehydes. by JF W a 1 ker (J. Am. Chem. Soc. 55, 2821, we have variously described, by transesterification 2825 [1933]) at -8O ⁰ C during the combining of setting of aqueous formaldehyde solutions with Aiko- 5 ° Get liquid formaldehyde with the same volume and then dehydrate semi-formals. However, according to the German patent specifications 1057 086 and 1090191, at higher temperatures under intense heat, there is always only a temporarily solidified semi-formal-semi-formal mixture consisting of semi-formal and aluminum mixture. According to the German patent kohol, some water, formaldehyde and Polyhälb- 55 1 090191 ^: the reaction is formed in gaseous formals. Apart from the fact that you are always forced to use formaldehyde with liquid or gaseous alcohol, formaldehyde in excess, because get a mixture in which even in the molar ratio of this to a considerable extent when removing the water-formaldehyde to alcohol such as 50:50 the largest part in vacuum is volatile and, in addition, the formaldehyde is bound to the hemiacetal in the form of short polyaddition chains, long distillation times because of the temperature.
sensitivity of the semi-formals and especially of the process for the production of pure O-hemiacetals in the presence of poly-half-formals from formaldehyde and alcohols have so far had to accept water, this process is just not known. very narrowly applicable. It has now been found that it is very easy to use Alcohols must not be below 100 ° C, the boiling point 65 way, high-molecular O-hemiacetals of the form- boil of the water to be removed, and also not obtain aldehyde by using pure form be volatile in steam (cyclohexanol about to aldehyde slowly to the extent of the conversion under 4 ° / o)> since their removal from the formaldehyde cooling, optionally in the presence of an inert