Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant
Patent
1981-07-30
1982-07-20
Phynes, Lucille M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From aldehyde or derivative thereof as reactant
C08G 208
Patent
active
043407200
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to processes for producing high-molecular polyacetals.
BACKGROUND OF THE INVENTION
At present high-molecular polyacetals are produced in the form of homopolymers and copolymers. Homopolymer-structure polyacetals are formed by polymerization of formaldehyde or cyclic oligomers thereof. Copolymers are obtained by copolymerization of formaldehyde with various comonomers taken in an amount of from 2 to 3% by weight, i.e. the starting feedstock for the production of high-molecular polyacetals is monomeric formaldehyde or cyclic oligomers of formaldehyde such as trioxane or tetraoxane (cf. N. S. Enikolopyan, S. A. Volfson "Chemistry and Processing of Polyformaldehyde," "Khimiya" Publishers, Moscow, 1968, in Russian).
One of the ways for improving the process for the production of high-molecular polyacetals is to reduce the number of the process stages. More promising in this respect is the way, when as the starting feedstock for the production of high-molecular polyacetals, use is made of monomeric formaldehyde, since this enables the elimination of the stages of synthesis of intermediate products.
Commercial production of formaldehyde is based on catalytic oxidative dehydrogenation of methanol in the presence of air oxygen on metallic or oxide-type catalysts. The resulting formaldehyde is in the form of a mixture with different components: H.sub.2 O, CH.sub.3 OH, HCOOH, N.sub.2, CO.sub.2, CO, H.sub.2, CH.sub.4, O.sub.2, and the like. The proportion of formaldehyde in the mixture depends on the catalysts employed and can vary from 2 to 19%. Recovery of formaldehyde from this mixture is effected, as a rule, by absorption thereof with water or alcohols. The resulting solutions can be used as a source for the production of concentrated monomeric formaldehyde or low-molecular polymers. Low-molecular polymers, in turn, can be used as a source for the production of monomeric formaldehyde through pyrolysis. To obtain concentrated monomeric formaldehyde, said solutions of formaldehyde are subjected to evaporation at a temperature within the range of from 110.degree. to 130.degree. C., followed by fractional condensation of vapours of water or an alcohol and separation thereof. Formaldehyde is thus produced in its monomeric form with the content of the main product ranging from 95 to 99%. The thus-recovered formaldehyde is subjected to further purification to the content of the main product of about 99.9%. For purification use is made of various physico-chemical methods based on profound condensation of impurities or chemical conversion thereof into different modifications, followed by separation.
Recovery and purification of monomeric concentrated formaldehyde constitute a multi-staged and complicated process due to an exclusively high chemical activity of formaldehyde and impossibility of storing it in its pure form (cf. J. Walker "Formaldehyde," Chemical Literature Publishing House, Moscow, 1957).
Therefore, difficulties associated with the recovery and purification of monomeric formaldehyde, impossibility of its storage in the pure form are serious obstacles in the way towards simplification of the process and reducing the production costs of the production of high-molecular polyacetals.
This is the basic factor hindering the extension of the manufacture of polyacetals on the basis of monomeric formaldehyde.
Known in the art are a number of processes for the production of high-molecular polyacetals by way of polymerization (copolymerization) of monomeric formaldehyde. Thus, known is a process comprising polymerization (copolymerization) of monomeric gaseous formaldehyde. To this end, the recovered and purified gaseous formaldehyde is fed into a reactor containing an inert hydrocarbon solvent and an ionic-type catalyst. In the case of copolymerization a comonomer such as cyclic formals, cyclic oxides is additionally introduced into the reactor. The polymerization (copolymerization) is carried out at a temperature within the range of from -50.degree. to +120.degr
REFERENCES:
patent: 3413270 (1968-11-01), Heinz et al.
patent: 3657189 (1972-04-01), Ishida et al.
patent: 3687899 (1972-08-01), Ackermann et al.
Bychkov Nikolai M.
Grishin Boris P.
Gruznov Alexandr G.
Lipets Konstantin V.
Romanov Leonid M.
LandOfFree
Process for producing high-molecular polyacetals does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing high-molecular polyacetals, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing high-molecular polyacetals will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-250923