Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant
Patent
1997-03-07
1998-03-17
Krass, Frederick
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From aldehyde or derivative thereof as reactant
528234, 528235, 528237, 528241, 528242, 528245, 528249, 528250, 528270, 528392, C08G 210
Patent
active
057287988
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a polyacetal copolymer. In particular, it relates to an improved, novel process for copolymerizing trioxane as the principal monomer with a cyclic ether or a cyclic acetal as the comonomer to produce a polyacetal copolymer.
2. Description of the Related Art
Processes for producing polyacetal copolymers have so far been known. In particular, copolymerization of trioxane as the principal monomer with a cyclic ether or cyclic formal having two or more vicinal carbon atoms as the comonomer is known. In general, cationic catalysts are used as catalysts for these copolymerizations, and specific examples thereof include Lewis acids such as halides of boron, tin, titanium, phosphorus, arsenic and antimony, e.g., boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride, arsenic pentafluoride and antimony pentafluoride, and compounds such as complexes or salts of them; protonic acids such as perchloric acid; protonic acid esters such as esters of perchloric acid with lower aliphatic alcohols, e.g., tert-butyl perchlorate; protonic acid anhydrides such as mixed acid anhydrides of perchloric acid and lower aliphatic carboxylic acids, e.g., acetyl perchlorate; and trimethyloxonium hexafluorophosphate, triphenylmethyl hexafluoroarsenate, acetyl tetrafluoroborate, acetyl hexafluorophosphate and acetyl hexafluoroarsenate. Among them, boron fluoride and coordinate compounds of boron fluoride with organic compounds such as ethers are the most conventional as catalysts for copolymerizing trioxane as the principal monomer with a comonomer and widely used industrially.
However, there have been problematic that conventionally used polymerization catalysts such as boron fluoride series compounds are required in relatively large quantities (for example, 40 ppm or more based on the whole monomers), that the polymerization degrees of the resulting polymers are limited, and that the resulting polymers contain unstable terminal moieties in considerable amounts which requires a complicated step for stabilization thereof.
The present inventors have found that it is very effective to use a heteropoly-acid or an acidic salt thereof as a polymerization catalyst for solving such the problems as described above. By using the heteropoly-acid or the acidic salt thereof in a very small amount, the copolymerization can be further easily conducted to give, at a high yield, a copolymer having a high degree of polymerization and unstable ends in a small amount (see Japanese Patent Publication-A No. 1-170610 and Japanese Patent Publication-B No. 7-35704).
However, since heteropoly-acid series polymerization catalysts are solid in themselves, it has to be added in the form of a liquid prepared by dissolving or dispersing it in a diluent in order to conduct the polymerization uniformly. Ethers such as n-butyl ether are used as the diluent, since they are inert to the copolymerization and therefore exert no adverse effects on the copolymerization, and can dissolve the heteropoly-acid or the acidic salt thereof. However, there have been problematic as yet that ethers can dissolve the heteropoly-acid or the acidic salt thereof unsufficiently to be required considerable amounts and that the diluents contaminate the copolymer.
DISCLOSURE OF THE INVENTION
3. Summary of the Invention
An object of the present invention is to provide a process for producing a polyacetal copolymer in which the preceding problems involved in the conventional copolymerization of trioxane with a comonomer in the presence of the heteropoly-acid series catalyst are solved, and further by which a polymerization yield, and a degree of polymerization (molecular weight) and stability of the resulting copolymer are improved.
Thus, the present invention is a process for preparing a polyacetal copolymer through copolymerization of trioxane as the principal monomer with a cyclic ether or cyclic formal having at least one
REFERENCES:
patent: 4956445 (1990-09-01), Yamamoto et al.
Nakai Akira
Yamamoto Kaoru
Krass Frederick
Polyplastics Co. Ltd.
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