Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Reexamination Certificate
1999-03-23
2002-04-30
Warden, Jill (Department: 1743)
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
C252S182290, C252S182120, C252S403000, C252S404000, C252S397000, C585S003000, C585S004000, C585S005000
Reexamination Certificate
active
06379588
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to monomer compositions containing
A) vinyl-containing monomers in which a heteroatom selected from the group consisting of the halogens, nitrogen, oxygen, sulfur and silicon is present on the vinyl group, and
B) at least one N-oxyl compound of a secondary amine which carries no hydrogen atoms on the &agr;-carbon atoms, in an amount effective as stabilizer for preventing premature polymerization.
2. Description of the Background
The present invention furthermore relates to processes for inhibiting the premature polymerization of vinyl-containing monomers and to the use of N-oxyl compounds of secondary amines which carry no hydrogen atoms on the &agr;-carbon atoms as stabilizers for preventing premature polyemrization.
It is necessary to add stabilizers to the monomers in order to prevent premature polymerization. Sterically hindered amines, such as 2,2,6,6-tetraalkylpiperidine and derivatives thereof, including the N-oxyl derivatives, have proven particularly suitable for preventing free radical polymerizations.
U.S. Pat. No. 5,254,760 describes the stabilization of vinylaromatic compounds, such as styrene, during distillation and purification by a combination of at least one nitroxyl compound and at least one aromatic nitro compound. There is a danger here that traces of nitroxyl compounds will enter the purified monomers. However, even traces of nitroxyl compounds interfere with the subsequent polymerization; they cause delayed polymerization and uncontrolled chain terminations, leading to polymers having poor reproducibility and short chain lengths. These disadvantageous effects are described by Mardare et al. in Polym. Prep. (Am. Chem. Soc., Div. Polym. Sci.) 35 (1), (1994) 778.
For example, derivatives of phenylenediamine (U.S. Pat. No. 5,396,005), fullerenes (DE-A 44 14 773) or 2,6-di-tert-butyl-p-cresol (DE-A 43 28 950) have been used to date for stabilizing hetero-substituted vinyl compounds, such as N-vinylformamide or N-vinylpyrrolidone, during distillation and purification. However, these stabilizers are unsatisfactory with regard to their effectiveness.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide monomer compositions which contain hetero-substituted vinyl compounds and suitable stabilizers, exhibit improved stabilization to premature polymerization and scarcely have any adverse effect on the subsequent specific polymerization of the monomers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
We have found that this object is achieved by the monomer compositions stated at the outset.
The hetero-substituted vinyl monomers preferably carry a halogen, oxygen, nitrogen or sulfur as the heteroatom on the vinyl group.
Examples of suitable hetero-substituted vinylmonomers are vinyl halides, such as vinyl chloride, vinyl carboxylates, such as vinyl acetate, vinyl propionate or vinyl butyrate, vinyl ethers, such as methyl vinyl ether, ethyl vinyl ether or butyl vinyl ether, vinyl thioethers, vinylcarbazoles, vinylpyrrolidones, vinylphthalimides, vinyl isocyanates, vinylcaprolactams, vinylimidozoles, vinylformamide, vinylsulfonic acid and vinylsilanes, such as vinyltriacetoxysilane, vinyltrichlorosilane or vinyltrimethoxysilane.
Preferred monomer compositions contain
A) monomers of the general formula I
CH
2
═CH—X—R
1
I,
where
X is oxygen or —NR
2
—,
R
1
is
or —R
3
,
R
2
is hydrogen or C
1
-C
4
-alkyl or, together with R
3
, is a saturated or unsaturated C
3
-, C
4
- or C
5
-alkylene bridge in which one or two CH
2
groups may be replaced by NH, N(C
1
-C
4
-alkyl), N(C
6
-C
10
-aryl) or oxygen and one or two CH groups may be replaced by N, and
R
3
is hydrogen, C
1
-C
4
-alkyl or a radical which, together with R
2
, is a saturated or unsaturated C
3
-, C
4
- or C
5
-alkylene bridge in which one or two CH
2
groups may be replaced by NH, N(C
1
-C
4
-alkyl), N(C
6
-C
10
-aryl) or oxygen and one or two CH groups may be replaced by N, and
B) at least one N-oxyl compound of a secondary amine which carries no hydrogen atoms on the &agr;-carbon atoms, in an amount effective as a stabilizer for preventing premature polymerization.
In the monomers (A) of the general formula I which are contained in the novel mixtures, X may be oxygen. Among these monomers, the vinyl ethers in which R
1
is C
1
-C
4
-alkyl, i.e. methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl or tert-butyl, are particularly suitable as a component of the novel monomer compositions.
If X is —NR
2
—, R
1
is preferably —CO—R
3
.
Other suitable radicals R
3
in addition to hydrogen and the stated C
1
-C
4
-alkyl groups are those radicals which, together with —NR
2
—, form a saturated or unsaturated 5- to 7-membered ring. Examples of such ring systems are:
in particular the N-pyrrolidinonyl and the N-caprolactamyl radical.
Preferred monomers in the novel compositions are N-vinylformamide, N-vinyl-2-pyrrolidone, N-vinyl-&egr;-caprolactam and the abovementioned C
1
-C
4
-alkyl vinyl ethers.
Particularly preferred among these monomers is N-vinylformamide.
The novel monomer compositions contain, as stabilizers (B), at least one N-oxyl compound of a secondary amine which carries no hydrogen atoms on the &agr;-carbon atoms. These compounds may be present as free compounds or in the form of their salts.
Suitable N-oxyls of amines are, for example, the following structures
where R are identical or different alkyl, cycloalkyl, aralkyl or aryl radicals which may also be bonded in pairs to form a ring system, and Y is a group which is required to complete a 5- or 6-membered ring. For example, R is C
1
-C
20
-alkyl, in particular C
1
-C
8
-alkyl, C
5
- or C
6
-cycloalkyl, benzyl or phenyl. Y is, for example, alkylene -(CH
2
)
2
— or —(CH
2
)
3
—.
N-Oxyl compounds such as the following structures
where the aromatic rings may each furthermore carry from 1 to 3 inert substituents, for example C
1
-C
4
-alkyl, C
1
-C
4
-alkoxy or cyano, are also suitable.
Sterically hindered derivatives of cyclic amines, for example of piperidine or pyrrolidine compounds, which may contain a further heteroatom, such as nitrogen, oxygen or sulfur, in the ring, are preferably used, this heteroatom not being adjacent to the hindered amine nitrogen. The steric hindrance is achieved by substituents in two positions adjacent to the amine nitrogen, suitable substituents being hydrocarbon radicals which replace all four hydrogen atoms of the &agr;-CH
2
groups. Examples of such substituents are phenyl, C
3
-C
6
-cycloalkyl, benzyl and in particular C
1
-C
6
-alkyl, where the alkyl radicals bonded to the same &agr;-carbon atom may furthermore be bonded to one another to form a 5- or 6-membered ring. The radicals mentioned specifically under R
4
and R
5
are particularly preferred. Preferably used N-oxyls of sterically hindered amines are derivatives of 2,2,6,6-tetraalkylpiperidine.
Preferred N-oxyl compounds in the novel monomer compositions are those of the general formula II
where
R
4
and R
5
are each C
1
-C
4
-alkyl or phenyl or, together with the carbon atom to which they are bonded, are a 5- or 6-membered saturated hydrocarbon ring,
R
6
is hydrogen, hydroxyl, amino or an m-valent organic radical bonded via oxygen or nitrogen or, together with R
7
is oxygen or a ring structure defined under R
7
,
R
7
is hydrogen or C
1
-C
12
-alkyl or, together with R
6
is oxygen or, together with R
6
and the carbon atom to which they are bonded, is one of the following ring structures
where, when R
6
forms a common radical with R
7
; m is 1,
R
8
is hydrogen, C
1
-C
12
-alkyl or —(CH
2
)
z
—COOR
9
,
R
9
are identical or different C
1
-C
18
-alkyl radicals,
k is 0 or 1,
z and p are each from 1 to 12 and
m is from 1 to 100.
R
4
and R
5
may be, for example, the C
1
-C
4
-alkyl groups stated for R
1
or together they may form a tetra- or pentamethylene group. R
4
and R
5
are each preferably methyl.
Examples of suitable radicals R
7
are hydrogen, the abovementioned C
1
-C
4
-alkyl groups a
Aumüller Alexander
Dupuis Jacques
Koch Andreas
Niessner Manfred
Sutoris Heinz Friedrich
BASF - Aktiengesellschaft
Cole Monique T.
Warden Jill
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