Mercapto-containing block copolymers having polymethacrylic...

Details Mercapto-containing block copolymers having polymethacrylic... Mercapto-containing block copolymers having polymethacrylic...

1998-02-03

2001-06-19

Wilson, Donald R. (Department: 1713)

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

Synthetic resins

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

C525S330100, C525S329800, C525S330300, C525S330400, C560S129000, C560S145000, C560S152000, C560S179000, C560S189000, C526S209000, C526S211000, C526S214000, C526S224000, C562S109000, C562S110000

Reexamination Certificate

active

06248839

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to polymethacrylic acid-polyalkylene oxide block copolymers (hereinafter: polymethacrylic acid-b-polyalkylene oxide copolymers) of the AB and ABA types and their alkali metal or ammonium salts, where A is a polymethacrylic acid block and B is a polyalkylene oxide block.
The invention also relates to poly-t-butyl methacrylate-b-polyalkylene oxide copolymers as novel intermediates for preparing the polymers of the invention.
The invention further relates to a process for preparing such block copolymers and to their use. The products can be used, for example, as emulsifiers and as dispersants for dispersing inorganic materials in aqueous media.
BACKGROUND OF THE INVENTION
Polymethacrylic acid-b-polyalkylene oxide copolymers are known. However, their preparation presents considerable problems. From the prior art, which is not very comprehensive, mention may be made of: J. Polym. Sci. Part A 30, 2251-2261, 1992, describes AB (BA), ABA and BAB block copolymers based on polyethylene oxide and polymethacrylic acid. These products are prepared via a precursor route by first preparing a poly-t-butyl methacrylate-b-polyethylene oxide copolymer or a polyethylene oxide-b-poly-t-butyl methacrylate copolymer by sequential, anionic polymerization of t-butyl methacrylate and ethylene oxide or, conversely, ethylene oxide and t-butyl methacrylate, then subjecting this copolymer to an acid-catalyzed elimination of isobutene from the poly-t-butyl methacrylate segment to give the desired polyethylene oxide-b-polymethacrylic acid copolymers. However, this procedure can hardly be carried out in industry since ionic polymerization requires very pure, water-free solvents (in particular tetrahydrofuran) and reactants. In addition, the reaction has to be carried out at low temperatures of about −78° C. Moreover, the use of specific alkali metal initiators (potassium naphthalide or diphenylmethylpotassium) is necessary.
Similarly, in Eur. Polym. J. 27, 673-680, 1991, Ulbricht et al. describe the preparation of poly-t-butyl methacrylate-b-polyethylene oxide or polyethylene oxide-b-poly-t-butyl methacrylate diblock copolymers by means of anionic polymerization. The authors refer to secondary reactions: inter alia, the use of cumylpotassium as initiator for the polymerization of t-butyl methacrylate at a reaction temperature of 25° C. leads to a series of undesired secondary reactions, recognizable by a broadening of the molecular weight distribution and nonquantitative monomer conversions.
In Macromolecules 15, 223-227, 1982, the synthesis of poly-t-butyl methacrylate-b-polyethylene oxide-b-poly-t-butyl methacrylate copolymers (ABA type) is reported. As initiators, use is made of lithiated diesters of polyethylene oxide. This process too requires extremely high purity of the reagents used and relatively low polymerization temperatures (from −25 to 0° C.). The products obtained have a very broad molecular weight distribution which in this case too points to the occurrence of undesired secondary reactions.
The present invention addresses the industrial problem of preparing block copolymers whose segments are formed from alkylene oxides and methacrylhc acid or its salts. The desired block copolymers should be obtainable in a very simple manner, free of secondary reactions and in high yield in order to make industrial manufacture of these compounds possible.
BRIEF SUMMARY OF THE INVENTION
It has now surprisingly been found that the desired block copolymers can be prepared in a simple manner by first reacting a poly-t-butyl methacrylate segment having a terminal ester or carboxyl group, which is obtained by free-radical polymerization of t-butyl methacrylate in the presence of ester- or carboxyl-functional mercaptans of the R(H)—OC(
0
)—(CH
2
)
p
—SH type, with a monohydroxy- or dihydroxy-functional functional polyalkylene oxide segment of the general structure R
1
—(OC
n
H
2n
)
o
—OH or H—(OC
n
H
2n
)
o
—OH in the necessary stoichiometric ratios in the presence of an esterification or transesterification catalyst and immediately afterwards converting the resulting poly-t-butyl methacrylate-b-polyalkylene oxide copolymer into the corresponding polymethacrylic acid-b-polyalkylene oxide copolymer by elimination of isobutene while retaining the linking ester group.
The invention accordingly provides, firstly, AB and ABA block copolymers of the formulae I or II
where
the radical R
1
is an alkyl, alkylaryl, alkenyl or sulfopropyl radical, preferably containing up to 18 carbon atoms,
m has a mean numerical value of ≧3,
p is a number from 1 to 6,
n is a number from 2 to 18,
o is a number ≧1 and
X is a cation.
DETAILED DESCRIPTION OF THE INVENTION
R
1
is usually derived from an alcohol R
1
OH which functions as initiator alcohol for the polymerization of the oxyalkylene. Examples of radicals R
1
are the methyl, butyl, stearyl, allyl, hexenyl, nonylphenyl or oleyl radical. Preferred radicals R
1
are methyl and butyl radicals.
If n=2, the polyether radical contains only oxyethylene units. If the value of n is >2, the polyether radical comprises oxyethylene units and a proportion of oxyalkylene units having from 3 to 18 carbon atoms. Here, n can be a fraction from 2 to 18. Preferably, the oxyalkylene block comprises oxyethylene units, but if desired, either or both of oxypropylene and oxybutylene units are also permitted to be present in addition to the oxyethylene units. Oxyalkylene units having from 4 to 18 carbon atoms are preferred when it is desired that the product have oleophilic properties.
X is a cation. X is preferably a hydrogen atom, an alkali metal atom or an ammonium group which is unsubstituted or alkyl-substituted. Examples of such substituted ammonium groups are NH(CH
3
)
3
, NH (C
2
H
5
)
3
, and NH (CH
2
—C
6
H
5
) (CH
3
)
2
. Furthermore, it is possible to select the cations known from the prior art for polymethacrylic acid polymers (e.g. those obtained upon neutralization with tetrabutylammonium hydroxide or triethanolamine).
The indices m and o can be identical (if m and o≧3) or different and usually have a mean numerical value of ≧3. Particular preference is given to numerical values of from 4 to 30 for m and from 20 to 100 for o.
Examples of block copolymers according to the invention are:
The invention further provides the t-butyl esters of the polyalkylene oxide-b-polymethacrylic acid copolymers formed as intermediates, which correspond to the formulae
Here, the radicals and indices are as defined above. These intermediates are causal for the structure and properties of the end products. If desired, independent use may be made of them, for example for modifying surface properties of plastic moldings so as to increase the surface polarity.
Examples of these intermediates are:
The Invention further provides a process for preparing the block copolymers of the invention. This process comprises
a) transesterifying polymers of the formula
where the indices m and p are as defined above and the radical R is derived from a chain regulator known per se of the type ROC(O)—(CH
2
)
p
—SH, where R is a hydrogen atom or an alkyl radical having from 1 to 12 carbon atoms, with polymers of the formula
in a molar ratio of from 1.1:1.0 to 1.0:1.1 (for the preparation of AB block copolymers) or from 1.1:0.5 to 1.0:0.55 (for the preparation of ABA block copolymers) with the addition of catalysts known per se, if desired in the presence of an inert solvent, and
b) converting the resulting polymers of the formulae III and IV into the desired block copolymers of the formulae I and II by elimination of isobutene at temperatures above 60° C. in the presence of acid as catalyst and, if desired, a solvent or at above as without catalyst and
c) if desired, converting the product into the alkali metal or ammonium salt in a manner known per se.
Process step a) thus comprises a selective transesterification or esterification of a poly-t-butyl methacrylate which has been prepared by freeradical polymerization using an ester- or carboxyl-funct

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