Polymerization inhibitors for acrylic acids and esters

Details Polymerization inhibitors for acrylic acids and esters Polymerization inhibitors for acrylic acids and esters

1993-09-02

2001-04-03

O'Sullivan, Peter (Department: 1621)

Distillation: processes, separatory

Addition of material to distilland to inhibit or prevent...

For inhibiting or preventing a polymerization reaction

C203S009000, C203SDIG003, C203SDIG001, C203SDIG002, C544S037000, C544S038000, C564S112000, C564S113000

Reexamination Certificate

active

06210536

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to compounds and compositions useful as polymerization inhibitors for acrylic acids and esters thereof. It also is concerned with a method for inhibiting polymerization of acrylic acids and esters thereof, particularly on a manufacturing scale, by use of these compounds and compositions.
Acrylic acid, methacrylic acid, and esters thereof have wide application as raw materials for fibers and plastics. Since these compounds have reactive unsaturated bonds in their molecules they are prone to polymerize under the conditions encountered during purification, manufacturing or storage. Commercial processes for the manufacture of acrylic and methacrylic acids and esters typically produce products contaminated with various impuruties. These impurities must be removed in order for the monomer product to be suitable for most applications. Such purification is generally accomplished by distillation.
Polymerization is likely to occur during distillation and may occur as a result of the presence of heat, light, oxygen and other conditions. It is therefore most desirable to minimize or eliminate the tendency of acrylic acids or acrylates to polymerize during manufacturing, thus assuring that the vessels and pipes used to transport the material during production remain clean and the reactors free of build up of high viscosity, high molecular weight, polymerized material.
2. Description of Related Art
Japanese patent application 48-35699 is directed to the stabilization of styrene, chloroprene, butadiene, isoprene, or acrylic acid derivatives with various compounds including certain N,N′-dinitroso compounds.
Japanese patent application 48-38399 is directed to stabilization of acrylates or methacrylates with certain N-nitrosoamine compounds.
U.S. Pat. No. 3,816,267 is directed to inhibition of acrylate polymerization during distillation by the use of a quinone and an enol derivative of a quinone. U.S. Pat. No. 4,338,162 is directed to the inhibition of vinyl polymerization of a 2-isocyanatoalkyl ester of unsaturated carboxylic acid with certain nitrogen oxides. U.S. Pat. No. 3,959,358 is directed to polymerization inhibition of acrylate esters by use of an alkyl-substituted phenolic compound.
During distillation of acrylic acids and esters high distillation temperatures are required to achieve a throughput which is efficient and economical. These high temperatures, however, also result in an increased rate of polymerization leading to unacceptable levels of polymer in the distillation apparatus. Accordingly, there exists a strong need for a polymerization inhibitor which will protect the acrylic system from polymerization during distillation at high temperatures.
SUMMARY OF THE INVENTION
This invention is directed to N,N′-dinitroso phenylenediamine compounds useful as polymerization inhibitors, which have the following structure (I):
wherein R is C
1
-C
12
alkyl or C
6
-C
10
aryl; R1 is C
1
-C
12
alkyl, C
6
-C
10
aryl, C
7
-C
11
aralkyl, and C
7
-C
16
alkaryl.
This invention is also directed to polymerization inhibitor compositions comprising:
(a) at least one compound having structure (I) as defined above;
(b) a phenothiazine having the structure
wherein R2 is hydrogen or C
1
-C
12
alkyl; and R3 and R4 are each independently selected from the group consisting of hydrogen, C
6
-C
10
aryl, C
7
-C
11
aralkyl, C
7
-C
16
alkaryl and C
1
-C
12
alkyl; and, optionally
(c) hydroquinone or hydroquinone momomethyl ether, and optionally
(d) a phenylenediamine compound having the following structure
wherein R
6
is C
1
-C
12
alkyl, C
6
-C
10
aryl or C
7
-C
16
alkaryl; and R
7
, R
8
and R
9
are independently selected from the group consisting of hydrogen, C
1
-C
12
alkyl, C
3
-C
12
cycloalkyl, C
7
-C
11
aralkyl and C
7
-C
16
alkaryl. The above components will be hereinafter be referred to as composition I.
In another aspect, this invention is directed to an acrylic or methacrylic acid or ester composition stabilized against polymerization by an effective amount of a compound having structure I or by an effective amount of composition I.
In yet another aspect, this invention is directed to a method for inhibiting polymerization of an acrylic or methacrylic acid or ester composition, said method comprising adding an effective amount of the polymerization inhibitor of structure I or composition I.
DETAILED DESCRIPTION OF THE INVENTION
The subject N,N′-dinitroso phenylenediamine derivatives may be prepared from phenylenediamine, sodium nitrite, and a suitable mineral acid (such as sulfuric or hydrochloric), as more fully set forth below in Examples 1-3.
Preferred N,N′-dinitroso phenylenediamine compounds include those wherein the amine groups are in the para position. Particularly preferred are compounds wherein R is C
3
-C
7
alkyl and R
1
is phenyl or C
3
-C
7
alkyl.
Illustrative preferred N,N′-dinitroso phenylenediamine compounds which may be employed include N-phenyl-N′-isopropyl dinitroso-p-phenylenediame, N-phenyl-N′-(1,3-dimethylbutyl)dinitroso-p-phenylenediamine, N-phenyl-N′-(1,4-dimethylpentyl)-dinitroso-p-phenylenediamine, and N,N′-bis(1,4-dimethylpentyl)-dinitroso-p-phenylenedimine. Moreover, mixtures of N,N′-dinitroso phenylenediamines may be employed.
The phenothiazine compounds are generally known, and their synthesis would be readily apparent to one skilled in the art. Particularly suitable phenothiazine compounds which may be employed in the compositions of the present invention include phenothiazine, 2-methylphenothiazine, 2-octylphenothiazine, 2-nonylphenothiazine, 2,8-dimethylphenothiazine, 3,7-dimethylphenothiazine, 3,7-diethylphenothiazine, 3,7-dibutylphenothiazine, 3,7-dioctylphenothiazine, 2,8-dioctylphenothiazine, 3,7-dinonylphenothiazine, 2,8-dinonylphenothiazine, 2(alpha,alpha-dimethylbenzyl)phenothiazine, 3,7-bis-(alpha,alpha-dimethylbenzyl)phenothiazine, 2,8-bis-(alpha, alpha-dimethylbenzyl)phenothiazine. Moreover, mixtures of two or more phenothiazine and N,N′-dinitroso phenylenediamine comounds may also be employed.
The hydroquinone or hydroquinone monomethyl ether are compounds which are known as antioxidants and, specifically, as monomer stabilizers. They have been used as shelf stabilizers for acrylic monomers.
The phenylenediamine compounds (optional component (d)) are also generally known, and their synthesis would be readily apparent to one skilled in the art. Preferred phenylenediamine compounds include those wherein the amine groups are in the para position. Particularly preferred compounds are the para-phenylenediamines wherein R
7
and R
8
are hydrogen; R
6
is alkyl or phenyl; and R
9
is C
3
-C
8
alkyl or C
3
-C
8
cycloalkyl.
Illustrative of the preferred phenylenediamine compounds which may be employed include N,N′-bis(1,4-dimethylpentyl)-p-phenylenediamine, N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine, N-phenyl-N′-(1,4-dimethylpentyl)-p-phenylenediamine and N-phenyl-N′-cyclohexyl-p-phenylenediamine. Moreover, mixtures of phenylenediamine compounds may also be employed. The phenylenediamine compounds may be of the oxygenated species as described in U.S. Pat. No. 4,774,374 to Abruscato et al.
The N,N′-dinitroso phenylenediamine and phenothiazine/hydroquinone compounds are generally employed in weight ratios of between 10:1 and 1:10. Preferably, weight ratios of between 4:1 and 1:4 are employed. Most preferred ratios include those from 3:1 and 1:3. If a phenylenediamine is employed, it is generally present in weight ratios of between 10:1 and 1:10, based on the weight of N,N′-dinitroso phenylenediamine.
The polymerization inhibitor compositions of this invention may further comprise a solvent such as toluene, MIBK (methyl isobutyl ketone), isobutyl acetate, isopropyl ether, acrylic acid, methacrylic acid, water, and the like.
A primary use of the polymerization inhibitor compounds and compositions of this inventio

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