Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1999-05-27
2001-04-03
Hardee, John (Department: 1751)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C562S125000
Reexamination Certificate
active
06211400
ABSTRACT:
The invention relates to sulfinic acid derivatives and their preparation and use in various application areas.
As is known, sulfinic acid, H
2
SO
2
, is one of the strongest known reducing agents. The free sulfinic acid is unstable. Accordingly, it is only available commercially in the form of its stable and correspondingly manageable derivatives.
The following sulfinic acid derivatives have to date achieved economic importance:
1. Sodium dithionite (fiber bleaching in papermaking, vat dyeing and textile bleaching, mineral bleaching, heavy metal reduction in industrial wastewaters)
2. Sodium formaldehyde sulfoxylate dihydrate (textile discharge printing, textile bleaching, redox cocatalyst in emulsion polymerization, heavy-metal reduction, pharmaceuticals)
3. Formamidinesulfinic acid (fiber bleaching in papermaking, textile bleaching)
4. Zinc formaldehyde sulfoxylate (textile printing and textile bleaching)
All of the abovementioned sulfinic acid derivatives are used in the form of aqueous solutions or dispersions. In aqueous media, sodium dithionite and alkali metal formamidinesulfinate—the free formamidinesulfinic acid is virtually insoluble in water and, in its acid form, has only a very slight reducing action—are only stable for a short time. As a result, even at room temperature they exhibit an excellent reductive capacity and an excellent bleaching effect on fibers. Aqueous preparations of sodium formaldehyde sulfoxylate and of zinc formaldehyde sulfoxylate are stable at room temperature for months. As a result, both formaldehyde sulfoxylates only exhibit their true reducing action at temperatures above 90° Celsius. In strongly alkaline or acidic media or in the presence of suitably strong oxidizing agents, both formaldehyde sulfoxylates do of course also have a reducing effect at temperatures lower than 90° C. This particular property of the formaldehyde sulfoxylates, namely to exhibit a very uniform and easily controlled reducing effect at temperatures between 5° C. and 90° C., is made use of in free-radical-initiated emulsion polymerization. Here, the formaldehyde sulfoxylates are used in various emulsion polymerization systems. In the case of the cold preparation of SBR (styrene butadiene rubber), the polymerization is initiated using organic peroxides. At the low polymerization temperature of about 5° C., the organic peroxides do not, however, decompose into the required free radicals. The peroxide cleavage must be initiated by catalytic amounts of iron(II) salts. The iron in oxidation stage two is converted into oxidation stage three making it no longer suitable for the peroxide cleavage. With the help of the formaldehyde sulfoxylate, the iron(III) ions are again reduced to iron(II) ions—the peroxide cleavage and the free-radical initiation continues. In other emulsion polymerization systems, peroxide compounds, such as hydrogen peroxide or peroxodisulfate, are used as free-radical formers. In order to increase the rate of free-radical formation, reducing agents are again used. Examples which may be mentioned are formaldehyde sulfoxylates, bisulfites, ascorbic acid, isoascorbic acid and sodium erythrobate. Formaldehyde sulfoxylates, in particular sodium formaldehyde sulfoxylate, have proven to be particularly effective and good value reducing agents. During the reduction process, however, the formaldehyde sulfoxylates eliminate formaldehyde. Plastics or polymer dispersions which must not contain formaldehyde are polymerized either using bisulfites, ascorbic acid, isoascorbic acid or sodium erythrobate. Since the formaldehyde-free reducing agents are weaker reducing agents, the disadvantage of less complete polymerization compared with formaldehyde sulfoxylates must be accepted. Furthermore, the use of ascorbic acid, isoascorbic acid and of sodium erythrobate leads to an undesired yellowing of the polymer.
The object of the present invention is to provide novel sulfinic acid derivatives whose chemical properties are as similar as possible to those of formaldehyde sulfoxylate, but which do not eliminate formaldehyde during or after use.
Surprisingly, it has now been found that this object is achieved by sulfinic acid derivatives of the type described in more detail below.
The present invention thus provides sulfinic acid compounds of the formula (I):
where
M is a hydrogen atom, an ammonium ion, a monovalent metal ion or an equivalent of a divalent metal ion of the groups Ia, IIa, IIb, IVa or VIIIb of the Periodic Table of the Elements;
R
1
is OH or NR
4
R
5
, where R
4
and R
5
independently of one another are H or C
1
-C
6
-alkyl;
R
2
is H or an alkyl, alkenyl, cycloalkyl or aryl group, it being possible for these groups to have 1, 2 or 3 substituents which are chosen independently of one another from C
1
-C
6
-alkyl, OH, O-C
1
-C
6
-alkyl, halogen and CF
3
; and
R3 is COOM, SO
3
M, COR
4
, CONR
4
R
5
or COOR
4
, where M, R
4
and R
5
are as defined above, or, if R
2
is aryl, which may be unsubstituted or substituted as defined above, R
3
is also H,
and the salts thereof.
For the purposes of the present invention, the expressions listed below have the following meanings:
Alkyl represents straight-chain or branched alkyl groups which preferably have 1-6, in particular 1-4, carbon atoms. Examples of alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-hexyl, etc.
The same applies to the alkyl groups in O-alkyl.
Alkenyl represents straight-chain or branched alkenyl groups which preferably have 3-8 carbon atoms, in particular 3-6 carbon atoms. A preferred alkenyl group is the allyl group.
Cycloalkyl is, in particular, C
3
-C
6
-cycloalkyl, cyclopentyl and cyclohexyl being particularly preferred.
Aryl (also in aralkyl) is preferably phenyl or naphthyl. If the aryl radical is a phenyl group and is substituted, it preferably has two substituents. These are, in particular, in the 2- and/or 4-position.
Halogen represents F, Cl, Br and I, preferably Cl and Br.
M is preferably an ammonium ion, alkali metal ion or an equivalent of an alkaline earth metal ion or zinc ion. Suitable alkali metal ions are, in particular, sodium and potassium ions. Suitable alkaline earth metal ions are in particular magnesium and calcium ions.
R
1
is preferably a hydroxyl or amino group.
R
2
is preferably a hydrogen atom or an alkyl or aryl group which may be substituted as above. It preferably has one or two hydroxyl and/or alkoxy substituents.
R
3
is preferably either COOM or COOR
4
(M and R
4
are as defined above) or, if R
2
is aryl, which may be substituted as stated above, may also be a hydrogen atom.
A preferred embodiment covers compounds of the formula (I) in which
M is an alkali metal ion or an equivalent of an alkaline earth metal ion or zinc ion;
R
1
is a hydroxyl or amino group; R
2
is H or alkyl; and
R
3
is COOM or COOR
4
, where M is H, an alkali metal ion or an equivalent of an alkaline earth metal ion, and R
4
is C
1
-C
6
-alkyl.
A further preferred embodiment covers compounds of the formula (I), in which
M is an alkali metal ion or an equivalent of an alkaline earth metal ion or zinc ion;
R
1
is a hydroxyl or amino group;
R
2
is an unsubstituted aryl or aryl substituted as stated above, in particular hydroxyphenyl or C
1
-C
4
-alkoxyphenyl; and
R
3
is a hydrogen atom.
The novel compounds are prepared from dithionite salts. Advantageously, a salt having a cation which is also desired in the sulfinic acid compounds is used. The dithionite salts are reacted by preparing those compounds in which R
2
is an unsubstituted or substituted aryl radical and R
3
is a hydrogen atom, with the corresponding aromatic aldehyde. This reaction can be illustrated using sodium dithionite and 2-hydroxybenzaldehyde as an example by the following reaction equation:
All other compounds of the formula M are prepared by reacting the dithionite salts with the corresponding 1,2-dicarbonyl compound or a sulfonic acid equivalent thereof. The 1,2-dicarbonyl compound used is, in particular, glyoxylic acid or the corresponding keto compounds and their esters. The reactio
Berghofer Josef
Rothmann Harry
Hardee John
L. Bruggemann KG
McDonnell & Boehnen Hulbert & Berghoff
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