Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2003-03-24
2003-11-04
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...
C526S218100, C526S227000, C526S263000
Reexamination Certificate
active
06642333
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a vinylpyrrolidone (co)polymer. More particularly, the present invention relates to a novel vinylpyrrolidone (co)polymer excellent in the color tone and the thermal yellowing resistance despite its low molecular weight.
B. Background Art
Vinylpyrrolidone (co)polymers, such as poly(vinylpyrrolidone) and vinylpyrrolidone copolymers, are widely used in various fields of such as medicines, cosmetics, pressure sensitive adhesives or adhesives, paints, dispersants, inks, and electronic parts, because the vinylpyrrolidone (co)polymers are excellent in such as biocompatibility, safety, and hydrophilicity. In addition, crosslinked products of the vinylpyrrolidone (co)polymers are useful also as water-absorbent resins for various uses requiring water absorption and water retention, for example, disposable diapers.
On the other hand, conventional vinylpyrrolidone (co)polymers relatively easily color, and, especially in the case of subjecting them to thermal hysteresis, the degree of the coloring is high. This tendency is remarkable especially in the case where the vinylpyrrolidone (co)polymers have low molecular weights. Thus, as to the reason why the degree of the coloring is high in the case where the vinylpyrrolidone (co)polymers have low molecular weights, various factors can be considered. For example, there can be cited such that: the lowering of the molecular weights of the vinylpyrrolidone (co)polymers needs to use so relatively large an amount of initiator as to easily cause a side reaction. That is to say, of low-molecular vinylpyrrolidone (co)polymers having a K value of not more than 60, those which are excellent in the color tone, especially, the thermal yellowing resistance, have not been known so far. Thus, there has been a problem that it is difficult to apply the conventional vinylpyrrolidone (co)polymers to uses demanding a vinylpyrrolidone (co)polymer which has a low molecular weight and is excellent in the color tone and the thermal yellowing resistance, such as paints, resin-modifying agents, surface-treating agents, ink-receiving layers, various primers, and various binders.
So far, there have been made several studies to suppress the coloring of the vinylpyrrolidone (co)polymers.
JP-A-062804/1987 (Kokai) discloses a process in which the coloring of a vinylpyrrolidone (co)polymer is suppressed by adjusting pH with a carbonate or hydrogencarbonate when polymerizing N-vinylpyrrolidone by using hydrogen peroxide. However, the effect of suppressing the coloring by this process is insufficient, therefore it is still unsatisfactory for the application to the uses demanding a vinylpyrrolidone (co)polymer which has a low molecular weight and is excellent in the color tone and the thermal yellowing resistance.
U.S. Pat. No. 3,459,720 discloses a process in which the coloring of a vinylpyrrolidone (co)polymer is suppressed by using azoisobutyronitrile and a hydroperoxide together when polymerizing N-vinylpyrrolidone. However, the effect of suppressing the coloring by this process is also insufficient, therefore it is still unsatisfactory for the application to the uses demanding a vinylpyrrolidone (co)polymer which has a low molecular weight and is excellent in the color tone and the thermal yellowing resistance.
JP-A-507097/1993 (Kohyo) discloses a process in which the coloring of a vinylpyrrolidone (co)polymer is suppressed by using t-butyl peroxypivalate and a chelating buffer together when polymerizing N-vinylpyrrolidone. However, this process results in obtaining a vinylpyrrolidone (co)polymer having a high molecular weight, and further, the effect of suppressing the coloring by this process is also insufficient, therefore it is still unsatisfactory for the application to the uses demanding a vinylpyrrolidone (co)polymer which has a low molecular weight and is excellent in the color tone and the thermal yellowing resistance.
SUMMARY OF THE INVENTION
A. Object of the Invention
Accordingly, an object of the present invention is to provide a vinylpyrrolidone (co)polymer excellent in the color tone and the thermal yellowing resistance despite its low molecular weight.
B. Disclosure of the Invention
The present inventors diligently studied to solve the aforementioned problems. As a result, the inventors have found that the aforementioned problems can be solved by using a specific initiator when a polymerizable monomer component including N-vinylpyrrolidone is polymerized to obtain a vinylpyrrolidone (co)polymer.
That is to say, a vinylpyrrolidone (co)polymer, according to the present invention, is a vinylpyrrolidone (co)polymer which has a Hazen value of not more than 30 in the form of 5% aqueous solution and a K value of not more than 60 and is obtained by a process including the step of polymerizing a polymerizable monomer component with an azo compound initiator and/or an organic peroxide initiator, wherein the polymerizable monomer component includes N-vinylpyrrolidone, and wherein the azo compound initiator has a chemical structure as shown by —C(CH
3
)
2
—N═N—C(CH
3
)
2
—, and wherein the organic peroxide initiator is soluble in water or ethyl alcohol of 25° C. in an amount of not smaller than 3 weight %.
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
The vinylpyrrolidone (co)polymer, according to the present invention, is obtained by a process including the step of polymerizing a polymerizable monomer component with a specific initiator, wherein the polymerizable monomer component includes N-vinylpyrrolidone.
As to the N-vinylpyrrolidone as essentially included in the aforementioned polymerizable monomer component, whatever production process it may be a product obtained by, it is useable. Specific examples of the production process include: what is called Reppe process which comprises the steps of causing ammonia to add to butyrolactone, and then dehydrating the resultant product to synthesize 2-pyrrolidone, and then causing acetylene to further add thereto to synthesize the N-vinylpyrrolidone; a process comprising the steps of causing ethanolaamine to add to butyrolactone with dehydration to synthesize N-hydroxyethylpyrrolidone, and then further dehydrating it to synthesize the N-vinylpyrrolidone. In addition, in the case of the latter process, examples thereof include what is called a gas phase dehydration process which uses a gas phase dehydration process in the step of dehydrating the N-hydroxyethylpyrrolidone to synthesize the N-vinylpyrrolidone.
Of the N-vinylpyrrolidone as obtained by the aforementioned various production processes, N-vinylpyrrolidone as produced by the process not using acetylene (more specifically, N-vinylpyrrolidone as obtained by carrying out a gas phase dehydration reaction of N-hydroxyethylpyrrolidone) is preferable for sufficiently displaying the effects of the present invention.
In addition, for sufficiently displaying the effects of the present invention, it is favorable that the aforementioned N-hydroxyethylpyrrolidone, of which the gas phase dehydration reaction is to be carried out, is a product obtained by carrying out a reaction of &ggr;-butyrolactone with monoethanolamine wherein the &ggr;-butyrolactone is a derivative from at least one member selected from the group consisting of maleic anhydride, butadiene and 1,4-butanediol.
The specific process for carrying out the gas phase dehydration reaction of the N-hydroxyethylpyrrolidone is not especially limited, but, for example, processes as reported in JP-A-141402/1996 (Kokai) and Japanese Patent No.2939433 can be adopted.
More specifically, for example, the reaction is carried out with a reactor, such as a fixed-bed flow type reactor, a fluidized-bed type reactor, or a moving-bed type reactor, at such a reaction temperature and under such a reaction pressure that the N-hydroxyethylpyrrolidone which is a raw reaction material can maintain its gas phase state. The reaction
Nippon Shokubai Co. , Ltd.
Pezzuto Helen L.
Roylance Abrams Berdo & Goodman L.L.P.
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