Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-01-31
2002-05-21
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S258000, C526S263000
Reexamination Certificate
active
06391994
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a production process for a vinylpyrrolidone polymer.
B. Background Art
Vinylpyrrolidone polymers, such as poly(vinylpyrrolidone) and vinylpyrrolidone copolymers, are widely used in various fields such as medicines, cosmetics, pressure sensitive adhesives or adhesives, paints, dispersants, inks, and electronic parts, because the vinylpyrrolidone polymers have merits and advantages of biocompatibility, safety, hydrophilicity, and so on. In addition, crosslinked products of the vinylpyrrolidone polymers are useful as water-absorbent resins for various uses requiring water absorption and/or water retention, for example, disposable diapers.
Up to now, N-vinylpyrrolidone as used for producing the vinylpyrrolidone polymers is, for example, industrially produced by a process comprising the step of carrying out a reaction between 2-pyrrolidone and acetylene (Reppe process) or by a process comprising the step of carrying out a dehydration reaction of N-hydroxyethylpyrrolidone. In addition, both 2-pyrrolidone and N-hydroxyethylpyrrolidone, which are precursors of the N-vinylpyrrolidone in these production processes, are usually derived from &ggr;-butyrolactone, and this &ggr;-butyrolactone is known to be produced by, for example, (1) a process comprising the step of obtaining &ggr;-butyrolactone by way of 1,4-butanediol from acetylene and formaldehyde, (2) a process comprising the step of obtaining &ggr;-butyrolactone by way of 1,4-butanediol from butadiene and acetic acid, or (3) a process comprising the step of carrying out a hydrogenation reaction of maleic anhydride.
However, in many cases where N-vinylpyrrolidone as obtained by these processes is polymerized, the molecular weight of the resultant polymer is hard to raise, or a large amount of monomers remain. Such disadvantages do not only reduce the purity or yield of the resultant vinylpyrrolidone polymer, but also bring about problems of such as use limitation or productivity deterioration. Furthermore, for example, in the case where the resultant polymer is crosslinked to convert it into a water-absorbent resin, the above disadvantages are causes of the deterioration of resin properties such as water absorption capacity and gel strength.
SUMMARY OF THE INVENTION
A. Object of the Invention
An object of the present invention is to provide a production process for a vinylpyrrolidone polymer which process enables to obtain a vinylpyrrolidone polymer that has a desired molecular weight and involves only a small amount of residual monomers, wherein the vinylpyrrolidone polymer can display excellent properties even if the vinylpyrrolidone polymer is, for example, crosslinked to convert it into a water-absorbent resin.
B. Disclosure of the Invention
The present inventors diligently studied to solve the above-mentioned problems. As a result, the inventors directed their attention to a fact that 2-pyrrolidone or N-hydroxyethylpyrrolidone, which is a raw material for synthesizing N-vinylpyrrolidone, is usually derived from &ggr;-butyrolactone, and then they have found that the polymerization of N-vinylpyrrolidone is easily hindered when the &ggr;-butyrolactone content in N-vinylpyrrolidone is more than a certain amount. Furthermore, they have found that in the case where acetylene is used as a raw material when obtaining N-vinylpyrrolidone, for example, in the case where acetylene is used when producing the &ggr;-butyrolactone which is an intermediate raw material for N-vinylpyrrolidone or where N-vinylpyrrolidone is produced by the reaction between 2-pyrrolidone and acetylene, by-products by nucleomethylation of N-vinylpyrrolidone are formed and hinder the polymerization of N-vinylpyrrolidone. The present invention has been completed on the basis of these findings.
That is to say, a production process for a vinylpyrrolidone polymer, according to the present invention, comprises the step of polymerizing a polymerizable monomer component or components which include N-vinylpyrrolidone, wherein:
(1) the N-vinylpyrrolidone as used is N-vinylpyrrolidone having a &ggr;-butyrolactone content of not more than 500 ppm; and/or
(2) the N-vinylpyrrolidone as used is N-vinylpyrrolidone obtained without using acetylene as a raw material.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a detailed description is given about a mode for carrying out the present invention.
In the present invention, firstly, it is important to use N-vinylpyrrolidone having a &ggr;-butyrolactone content of not more than 500 ppm. When synthesizing N-vinylpyrrolidone, there is a case where &ggr;-butyrolactone remains in the resultant N-vinylpyrrolidone because N-vinylpyrrolidone is usually produced by way of &ggr;-butyrolactone. In the case where the &ggr;-butyrolactone content in N-vinylpyrrolidone exceeds 500 ppm, the polymerization of N-vinylpyrrolidone is hindered. The method for decreasing the &ggr;-butyrolactone content to not more than 500 ppm is not especially limited. However, for example, in the production process for N-vinylpyrrolidone, the &ggr;-butyrolactone content in N-vinylpyrrolidone can be decreased by promoting the conversion of &ggr;-butyrolactone using an excess of ammonia relative to &ggr;-butyrolactone in the case of producing N-vinylpyrrolidone by way of 2-pyrrolidone as a precursor, or using an excess of ethanolamine relative to &ggr;-butyrolactone in the case of producing N-vinylpyrrolidone by way of N-hydroxyethylpyrrolidone as a precursor. In addition, the &ggr;-butyrolactone content in N-vinylpyrrolidone or in 2-pyrrolidone and N-hydroxyethylpyrrolidone, which are precursors, may be decreased by conventional purification methods such as distillation and crystallization.
In the present invention, secondly, it is important to use N-vinylpyrrolidone obtained without using acetylene as a raw material, whereby not only can the formation of by-products by nucleomethylation of N-vinylpyrrolidone, namely, N-vinyl-3-methyl-2-pyrrolidone, N-vinyl-4-methyl-2-pyrrolidone, and N-vinyl-5-methyl-2-pyrrolidone, be inhibited, but also the bad influence that the polymerization of N-vinylpyrrolidone is hindered, which bad influence is caused by the above by-products, can be prevented. In more detail, there is a possibility that acetylene is used in steps, such as (1) and (2) below, in the production process for N-vinylpyrrolidone. However, it is important to avoid using acetylene in both of:
(1) a step of a vinylation reaction of 2-pyrrolidone with acetylene, and
(2) a step of synthesizing 1,4-butanediol from formaldehyde and acetylene in order to obtain &ggr;-butyrolactone which is used as a precursor of 2-pyrrolidone or N-hydroxyethylpyrrolidone which is a raw material for synthesizing N-vinylpyrrolidone.
In the present invention, it is the most preferable to use N-vinylpyrrolidone which has a &ggr;-butyrolactone content of not more than 500 ppm and is obtained without using acetylene as a raw material.
There is no especial limitation in the production process for N-vinylpyrrolidone as used in the present invention if this process is the above process without using acetylene. However, the process preferably involves a gas phase dehydration reaction of N-hydroxyethylpyrrolidone. Furthermore, it is preferable that a product derived from maleic anhydride is used as &ggr;-butyrolactone which is a precursor of N-hydroxyethylpyrrolidone. The specific method for carrying out the gas phase dehydration reaction of N-hydroxyethylpyrrolidone is not especially limited and, for example, methods as reported in JP-A-141402/1996 and Japanese Patent No. 2939433 can be adopted.
The purity of the aforementioned N-vinylpyrrolidone, as used in the present invention, is preferably not less than 99.7 weight %. In the case where N-vinylpyrrolidone having a purity of less than 99.7 weight % is polymerized, there are disadvantages in that the polymerization of the N-vinylpyrro
Harada Nobuyuki
Kuriyama Toshiaki
Naka Akio
Nishibayashi Hideyuki
Shimasaki Yuuji
Nippon Shokubai Co. , Ltd.
Pezzuto Helen L.
Roylance Abrams Berdo & Goodman L.L.P.
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