Maleic anhydride copolymers containing amine oxide groups...

Details Maleic anhydride copolymers containing amine oxide groups... Maleic anhydride copolymers containing amine oxide groups...

2000-02-03

2002-07-23

Michl, Paul R. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C524S447000

Reexamination Certificate

active

06423785

ABSTRACT:

RELATED APPLICATIONS
This application claims priority to German application DE 199 04 603.4, filed Feb. 5, 1999, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to maleic anhydride copolymers containing amine oxide groups and to their use as dispersants for pigments or fillers.
2. Description of the Related Art
In accordance with the prior art it is common to use, as dispersants, polyacrylic esters having acidic and/or basic groups, which may also be in salt form, which can be prepared by polymerizing corresponding monomeric acrylic esters, such as butyl acrylate, acrylic acid, 2-hydroxyethyl acrylate and its alkoxylation products, and other monomers having vinylic double bonds, such as styrene or vinylimidazole, for example (see for example EP-B-0 311 157). There are also descriptions, however, of how it is possible by transesterification reactions on alkyl polyacrylates, by replacing the alkyl group in the manner of a polymer-analogous reaction by alcohols or amines, to produce dispersants of this kind (see for example EP-B-0 595 129, DE-C-39 06 702, EP-A-0 879 860). Advantages of the polymer-analogous reaction regime are said to lie in the narrower molecular weight distribution and absence of disruptive or toxic monomer fractions. In this way it is also said to be possible to produce polymers which are not available by direct polymerization owing to the lack of industrial availability of corresponding polymerizable monomers. Such alcoholyses or aminolyses often require the use of, in general, strongly acidic catalysts such as, for example, sulfuric acid or para-toluenesulfonic acid, or metal salts such as, for example, titanates, which at the reported reaction temperatures of up to 200°°C. result not only in unwanted side reactions, which cause an increase in molecular weight, but also in often strongly colored products, whose coloring means that they are poorly suited or even totally unsuitable for demanding dispersion tasks.
In a very similar way, use is also made of polymers containing diesters of free-radically polymerizable dicarboxylic acids, such as dialkyl maleates, for example, as a basis for preparing dispersants, as set out, for example, in WO 96/14347. That document describes first of all a transesterification of the alkyl dicarboxylate with a hydroxy-functional polyoxyalkylene followed by a subsequent copolymerization with a further vinylically unsaturated monomer. A disadvantage here again is that the transesterification step, in the presence of preferably acidic catalysts, requires reaction temperatures of approximately 160°°C., which again entail the abovementioned disadvantages in respect of the possible use of the dispersants obtained in this way. The subsequent copolymerization is dependent on the addition of large amounts of costly organic peroxides as initiator in order to obtain sufficient conversions and reproducible copolymers. Despite this, and especially when using monomers having weight-average molecular weights of more than 500 g/mol, there still remain considerable fractions of unpolymerized monomer in the reaction mixture in unreacted form, which can also no longer be removed economically. In addition to the economic disadvantages, this is particularly undesirable owing to the potential toxic properties inherent in the majority of free-radically polymerizable vinyl compounds. Furthermore, the products have generally undergone further severe darkening after the copolymerization. This again places great restrictions on possible applications.
With the prior art dispersants described above it is, moreover, impossible to meet (fully) the diverse performance requirements made in particular in the sector of high-quality industrial coatings, such as, for example, the OEM finishing of automobiles. For instance, time and again, disadvantages which are in some cases mutually contradictory—for example, absence of compatibility with various binders, adequate activity only at very high levels of added dispersant, excessive dispersion times, levels of achievable pigmentation which are too low, insufficient development of color strength, constancy of viscosity and shade (especially after storage), or flocculation and aggregation (including that observed after a time delay) owing to excessively weak stabilization of the pigments by the dispersant—prevent their broad use.
OBJECT OF THE INVENTION
An object of the present invention is therefore to overcome a large number of the above disadvantages and to provide novel dispersants which are easy to prepare and which in particular feature extraordinarily good performance properties.
It has surprisingly been found that it is possible to obtain novel dispersant which are superior to the prior art and do not have the above mentioned disadvantages.
SUMMARY OF THE INVENTION
These are maleic anhydride copolymers containing amine oxide groups, which are obtainable by reacting at least about 1 mol % of the anhydride groups of maleic anhydride copolymers with diamines from the group consisting of
a) HR
1
N—R
2
—NR
3
R
4
 where
R
1
is hydrogen or a monovalent hydrocarbon radical having 1 to 24 carbon atoms,
R
2
is a divalent alkylene radical having 2 to 24 carbon atoms, and
R
3
and R
4
are aliphatic and/or alicyclic alkyl radicals having 1 to 12, preferably 1 to 6, carbon atoms, which can be identical or different
and subsequently carrying out oxidation with the formation of amine oxide groups which are attached by way of monoamide groups and/or imide groups and are of the following general formula (as the skilled worker is well aware, the wavy lines are intended to indicate that, hereinbelow, this representation relates merely to a section of a polymer compound)
Preference is given to maleic anhydride copolymers containing amine oxide groups, in which a further portion of the anhydride groups has been reacted with alcohols and/or amines from the group consisting of
b) saturated or unsaturated, alicyclic or cyclic monohydroxy and/or monoamine compounds of the general formula
HO—R
1
or HR
2
N—R
1
, respectively,
 where
R
1
is a hydrocarbon radical having 2 to 24 carbon atoms, and
R
2
is hydrogen or a monovalent hydrocarbon radical having 1 to 24 carbon atoms,
with the formation of corresponding monoester, monoamide or imide structures, respectively.
Preference is likewise given to maleic anhydride copolymers containing amine oxide groups, in which a further portion of the anhydride groups has been reacted with
c) polyoxyalkylene compounds of the general formula
H—(O—C
2
H
4−a
R
3
a
)
b
(O—C
c
H
2
c
)
d
O—R
4
,
 where
R
3
are identical or different alkyl radicals or alkylene radicals having 1 to 24 carbon atoms or are substituted or unsubstituted phenyl radicals having up to 24 carbon atoms, and
R
4
is hydrogen or a saturated or unsaturated, optionally branched or cyclic or aromatic hydrocarbon radical having up to 24 carbon atoms, which can, if desired, also include heteroatoms from the group consisting of O, S, N, P, Si, F, Cl, Br, and I,
a=0 to 3,
b=0 to 100,
c=2 to 12,
d=0 to 100,
and the sum (b+d)=2 to 200,
the sequence of the polyoxyalkylene segments (O—C
2
H
4−a
R
3
a
)
b
and (O—C
c
H
2c
)
d
being arbitrary
with the formation of corresponding monoester structures.
Preference is likewise given to maleic anhydride copolymers containing amine oxide groups, in which a further portion of the anhydride groups has been reacted with
d) polyoxyalkylene compounds of the general formula
H
2
N—R
5
—(O—C
2
H
4−a
R
3
a
)
b
(O—C
c
H
2c
)
d
O—R
6
,
 where
R
3
are identical or different alkyl radicals or alkylene radicals having 1 to 24 carbon atoms or are substituted or unsubstituted phenyl radicals having up to 24 carbon atoms,
R
5
is a divalent alkylene radical having 2 to 6 carbon atoms, and
R
6
is hydrogen or a saturated or unsaturated, optionally branched or cyclic or aromatic hydrocarbon radical having up to 24 carbon atoms, which can, if desired, also include heteroat

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