Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-12-05
2001-10-09
Dentz, Bernard (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C562S598000, C546S184000
Reexamination Certificate
active
06300513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of stabilizing N-oxyl compounds in vinyl compounds.
2. Description of the Related Art
It is well known that vinyl compounds such as (meth)acrylic acid and esters thereof are liable to polymerize by light and heat. In order to prevent polymerization of vinyl compounds, various kinds of polymerization inhibitors are added therein.
JP-B-4-14121 describes to use N-oxyl compounds such as bis-(2,2,6,6-tetramethyl-4-piperidinoxyl)-sebacate as a polymerization inhibitor for vinyl compounds.
SUMMARY OF THE INVENTION
We have researched stability of the vinyl compounds in which N-oxyl compounds have been added as a polymerization inhibitor during storage or transportation thereof, and then found the following: Such N-oxyl compounds were lost with time in the vinyl compounds, so that the vinyl compounds could not be stably stored or transported.
With a view to the above circumstance, it is an object of the present invention to provide a method of stabilizing N-oxyl compounds in vinyl compounds.
We have found that by allowing an N-oxyl compound in vinyl compounds to co-exist with an N-hydroxy-2,2,6,6-tetramethylpiperidine compound and a 2,2,6,6-tetramethylpiperidine compound, a disappearance of the N-oxyl compound with time can be reduced, and then the present invention has been achieved.
According to the present invention, there is provided a method of stabilizing an N-oxyl compound in vinyl compounds by allowing the N-oxyl compound in the vinyl compounds to co-exist with an N-hydroxy-2,2,6,6-tetramethylpiperidine compound and a 2,2,6,6-tetramethylpiperidine compound.
In accordance with the present invention, the reduction in concentration of the N-oxyl compound that has been added in the vinyl compounds for a stabilizer is controlled, and then the vinyl compound is maintained stably. More specifically, in accordance with the present invention, the concentration reduction of N-oxyl compounds in the vinyl compound can be controlled and then the vinyl compound can be stably maintained in the case of handling the vinyl compound, such as storing in a tank, transportation by a tank truck and piping.
The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiments.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The viny compound to be used in the present invention is a compound having a vinyl bond and polymerizable during the production or handling thereof, and may include for example (meth)acrylic acid, esters thereof and acrylonitrile. Among them, (meth)acrylic acid and esters thereof are more preferable.
As the representative of acrylic esters, it may cite methyl acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate, etc. As the representative of methacrylic esters, it may cite methyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, etc.
The amount of N-oxyl compounds to be used is not particularly restricted as long as polymerization of vinyl compounds can be prevented, but may be in the range of 0.0005 to 0.1 part by weight, based on 100 parts by weight of the vinyl compound.
The N-oxyl compound to be used in the present invention is not particularly restricted, but may include N-oxyl compounds, which are generally used for preventing polymerization of the vinyl compounds. Among them, 2,2,6,6-tetramethylpiperidinoxyl compounds represented by the formula (1):
wherein R
1
stands for CHOH, CHCH
2
OH, CHCH
2
CH
2
OH, CHOCH
2
OH, CHOCH
2
CH
2
OH, CHCOOH or C═O, and R
2
stands for a hydrogen atom or CH
2
OH, are preferable.
As the representative of 2,2,6,6-tetramethylpiperidinoxyl compounds, 4-hydroxy-2,2,6,6-tetramethylpiperidinoxyl, 4-oxo-2,2,6,6-tetramethylpiperidinoxyl, and 4-carboxy-2,2,6,6-tetramethylpiperidinoxyl, etc may be cited. The N-oxyl compound may be used singly or in a combination of two or more thereof. Among them, 4-hydroxy-2,2,6,6-tetramethylpiperidinoxyl and 4-oxo-2,2,6,6-tetramethylpiperidinoxyl are preferable, and 4-hydroxy-2,2,6,6-tetramethylpiperidinoxyl is most preferable.
As the representative of N-hydroxy-2,2,6,6-tetramethylpiperadine compounds, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, and 1-hydroxy-2,2,6,6-tetramethylpiperidine, etc may be cited. The N-hydroxy-2,2,6,6-tetramethylpiperidine compounds may be used singly or in a combination of two or more thereof.
The amount of the N-hydroxy-2,2,6,6-tetramethylpiperidine compound is not particularly restricted as long as reduction in the amount of the N-oxyl compound with time can be controlled, but may be in the range of 0.01 to 500 parts by weight, preferably 0.1 to 150 parts by weight, based on 100 parts by weight of the N-oxyl compound.
As the representative of 2,2,6, 6-tetramethylpiperidine compounds, 2,2,6,6-tetramethylpiperidine, and 4-hydroxy-2,2,6,6-tetramethylpiperidine, etc may be cited. The 2,2,6,6-tetramethylpiperidine compounds may be used singly or in a combination of two or more thereof.
The amount of the 2,2,6,6-tetramethylpiperidine compound is not particularly restricted as long as reduction in the amount of the N-oxyl compound with time can be controlled, but may be in the range of 0.01 to 500 parts by weight, preferably 0.1 to 150 parts by weight, based on 100 parts by weight of the N-oxyl compound.
A method of adding to the vinyl compounds, the N-oxyl compound, the N-hydroxy-2,2,6,6-tetramethylpiperidine compound and the 2,2,6,6-tetramethylpiperidine compound is not particularly restricted, and they may be added separately or simultaneously.
The vinyl compound to be used in the present invention may include impurities which were by-produced in the production thereof, or derived from the raw materials therefor. When acrylic acid is used for the vinyl compound, an advantageous stabilizing effect of the present invention can be expected even if water, organic acids such as acetic acid, aldehydes such as acrolein and the like are contained.
In the present invention, conventional polymerization inhibitors such as phenothiazine, methoquinone, copper dialkyldithiocarbamate, manganese acetate, p-phenylenediamine or the like may be additionally incorporated in the vinyl compounds. The amount of the conventional polymerization inhibitors is not particularly restricted as long as it may be usually used, but may be in the range of 0.0005 to 0.1 part by weight, based on 100 parts by weight of the vinyl compound.
In accordance with the present invention, the quantity reduction of the N-oxyl compounds in the vinyl compound can be effectively controlled or suppressed in the case of handling the vinyl compounds, such as storing in a tank, transportation by a tank track, and piping. As a result, polymerization of the vinyl compounds can be also prevented.
REFERENCES:
patent: 5322960 (1994-06-01), Sakamoto et al.
patent: 5504243 (1996-04-01), Sakamoto et al.
patent: 40-14121 (1992-03-01), None
Nakahara Sei
Sakamoto Kazuhiko
Serata Naoki
Ueno Kouji
Ueoka Masatoshi
Dentz Bernard
Mathews, Collins Shepherd & Gould P.A.
Nippon Shokubai Co. , Ltd.
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