Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-05-13
2003-05-13
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S307500, C526S307700, C526S320000, C526S307300, C524S829000, C524S831000, C524S832000
Reexamination Certificate
active
06562926
ABSTRACT:
The present invention relates to a process for preparing water-soluble homopolymers and copolymers having oligoalkyleneimine side chains of the general formula I,
where
is a linear or branched oligoalkyleneimine chain comprising m alkyleneimine units, where
m is an integer from 1 to 20, and the number average of m in the oligoalkyleneimine side chains is at least 1.5,
Y is the anion equivalent of a mineral acid, and
x is 0≦x≦m,
and to the copolymers obtained by this process and their use as auxiliaries in papermaking.
In papermaking, in particular in papermaking under neutral conditions, polymers having basic amino groups, the acid addition salts thereof or amino-containing, amphoteric polymers are often employed. They are often used as fixing agents and as drainage aids, flocculents and retention aids.
U.S. Pat. No. 3,280,218 describes graft polymers having polyalkyleneimine side chains. These polymers are prepared by reacting polyacrylic acid as grafting base with a large excess of ethyleneimine. A disadvantage of this process is the high ethyleneimine requirement. Polymers free from acid groups cannot be prepared by this route, since some of the carboxylate groups do not react owing to steric effects. Furthermore, other functional groups cannot be introduced into the polymer in this manner.
EP-A 387 567 describes polymers which are obtainable by reacting a carboxyl-containing, water-soluble polymer with ethyleneimine. This process provides polymers having oligomeric alkyleneimine side chains and molecular weights of up to 1,000,000. As a consequence of their method of preparation, such polymers likewise necessarily contain carboxylic acid groups. The amphoteric polymers described in this reference are used as flocculents and drainage aids in papermaking.
Likewise, EP-A 411 654 describes amphoteric polymers having aminoalkylene side groups. Similar to EP-A 387 567, they are preferably prepared by reacting a carboxyl-containing, water-soluble polymer with ethyleneimine. The polymer likewise necessarily contains acid groups.
One disadvantage of the preparation methods described in the prior art is that acid-free polymers having oligoalkyleneimine side chains cannot be prepared in this manner. Furthermore, the molecular weight of the polymers obtainable in this manner depends on the molecular weight of the grafting base used. There is an upper limit for the latter molecular weight, since otherwise this causes viscosity problems that inhibit or even prevent the reaction with the ethyleneimine. Furthermore, it has been observed that relatively high molecular weights of the grafting base lead to gel formation, even at low ethyleneimine conversions, thus also limiting the maximum achievable molecular weight. This method does not permit controlled adjustment of chain lengths with the oligomeric alkyleneimine side chains either.
We have found, surprisingly, that water-soluble polymers having oligoalkyleneimine side chains of the general formula I defined at the beginning can be prepared by polymerizing at least one ester of the formula II which can also be used in the form of an oligomer mixture,
and where
m and Y are as defined above, the number average of m in the oligomer mixtures of II being at least 1.5,
R is hydrogen or C
1
-C
4
-alkyl, and
n is 1≦n≦m,
alone or together with other monomers in water using free-radical polymerization initiators, and that this process yields polymers which meet the requirements made on paper auxiliaries to a particular extent. If polymerized on its own, monomers A yield homopolymers which have oligoalkyleneimine side chains of the formula I, are acid-free and have a particularly high cationic charge density.
The present invention therefore provides a process for preparing water-soluble homopolymers or copolymers having oligoalkyleneimine side chains of the general formula I defined at the beginning, which comprises polymerizing ethylenically unsaturated monomers M, comprising:
at least one monomer A of the above-defined general formula II or an oligomer mixture of monomers of this type and
optionally one or more water-soluble monomers B which are different from said monomers A and/or monomers C which are different from said monomers A and B,
in an aqueous polymerization medium in the presence of an initiator which triggers the free-radical polymerization of the monomers M.
Linear oligoalkyleneimine structural units
are best described by the following structural formula Ia
where m is as defined above and R′ and R″ are monovalent organic radicals, such as C
1
-C
4
-alkyl or phenyl, or hydrogen. R′ and R″ are preferably hydrogen.
Branched oligoalkyleneimine structural units
can be described, for example, by the following structural formula Ib
where p is 0 or an integer 1, 2, 3 . . . which is different from 0, q and r are each, independently of one another, integers which are different from 0, and the sum p+q+r+1=m. Ib represents a singly branched oligoalkyleneimine unit
It will be appreciated that the present invention also covers the preparation of polymers in which the oligoalkyleneimine unit
is branched more than once.
The monomers A of the general formula II are usually oligomer mixtures of such compounds. In this case, m represents the number of ethyleneimine repeating units in the respective molecules of the general formula II; according to the invention, m in these molecules is from 1 to 20 and preferably from 1 to 10. According to the invention, the composition of the oligomer mixtures of compounds of the general formula II is selected such that the number average of m in these mixtures is at least 1.5, preferably at least 2.1, and is, for example, in the range from 1.5 to 15, preferably in the range from 2.1 to 8 and in particular in the range from 2.5 to 4.5. According to the invention, preference is given to those oligomer mixtures which comprise less than 25% by weight of compounds of the general formula II where m=1. If monomers A in the form of chemically uniform compounds of the general formula II are used, m is naturally at least 2, so as to ensure a number average of m in the range of at least 1.5.
In the monomers of the general formula II, at least one of the nitrogen atoms contained therein, preferably more than one or all of the nitrogen atoms contained therein, are present in protonated form. The monomers A are thus formally acid addition compounds. The anion equivalents required for charge neutrality are usually derived from low molecular weight acids, in particular from mineral acids such as hydrochloric acid, sulfuric acid or nitric acid. This means that Y— is preferably Cl—, HSO
4
—, ½ SO
4
2
—, NO
3
—, H
2
PO
4
—, ½ HPO
4
2
— or ⅓ PO
4
3
—. Particularly preferably, Y— is Cl—, ½ SO
4
2
— and NO
3
— and in particular Cl—.
Provided that the number average of m≧2.1, the number average of n is preferably at least 2.
In the formula II, R is preferably hydrogen or in particular methyl. R and R′ in the formulae Ia and Ib are preferably hydrogen.
Preference is given to using the monomers A in the form of oligomer mixtures of the formula II. In this case, preference is given to those oligomer mixtures which comprise less than 25% by weight of compounds of the formula II where m=1. This is usually the case when the average value of {overscore (m)}≧2.1.
According to the invention, at least one further water-soluble monomer B, which is different from the monomers A, can be copolymerized together with the monomer A. The solubility of the monomer B in water is typically at least 50 g/l at 25° C. and in particular at least 100 g/l at 25° C. and 1 bar. The monomers B comprise neutral monomers (monomers B1), acidic monomers (monomers B2) and/or cationic monomers (monomers B3).
Examples of neutral monomers B1 are amides of monoethylenically unsaturated carboxylic acids, e.g. acrylamide and methacrylamide, hydroxyalkyl esters of ethylenically unsaturated carboxylic acids, e.g. hydroxyethyl acrylate, hydroxyethyl
Decker Jürgen
Frenzel Stefan
Meixner Hubert
Rübenacker Martin
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