Hydrolysis-stable and polymerizable acrylphosphonic acids

Details Hydrolysis-stable and polymerizable acrylphosphonic acids Hydrolysis-stable and polymerizable acrylphosphonic acids

1998-10-09

2001-01-09

Merriam, Andrew E. C. (Department: 1714)

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

Synthetic resins

Processes of preparing a desired or intentional composition...

C523S118000, C524S547000, C526S278000, C562S008000, C562S020000, C562S598000

Reexamination Certificate

active

06172131

ABSTRACT:

The present invention relates to polymerizable acrylphosphonic acids which have a high degree of hydrolytic stability and are suitable in particular for the preparation or as components of polymers, adhesives or other materials and in particular of dental materials.
Polymerizable phosphonic acids are of importance in polymer chemistry above all as comonomers, and they allow the preparation of organic polymers in which thermal stability, adhesive properties, flammability and solubility in polar solvents are improved. To this end, numerous monomeric phosphonic acids having polymerizable vinyl, dienyl, allyl or styryl groups were synthesized and polymerized. An overview of phosphonic acids is given by Houben-Weyl, Methoden der Organischen Chemie, Volume E 20, (2nd part), Georg Thieme Verlag, Stuttgart-New York 1987, page 1300 et seq. Examples of such conventional polymerizable phosphonic acids are vinylphosphonic acid, allylbenzenephosphonic acid, &agr;-aminoallylphosphonic acid, phenylethenephosphonic acid, 1,3-butadiene- or isoprenephosphonic acid, 4-vinylbenzenephosphonic acid or 2-(4-vinylphenyl)-ethane phosphonic acid.
However, phosphonic acids in which the double bond is bound to the phosphorus atom directly or via an oxygen atom, such as vinylphosphonic acid or ethylphosphonic acid monovinyl ester, exhibit an only moderate tendency to homopolymerization. Therefore, only homopolymers with a small molecular weight can be obtained from them. In contrast, high-molecular-weight polymerizates can be obtained from (meth)acrylphosphonic acids or esters in which the (meth)acrylic group is not bound directly to the phosphorus. Known (meth)acrylphosphonic acid derivatives are e.g. the phenylphosphonic acid-mono-(methacryloyloxyethyl)-esters of formula (a) or tert-butylphosphonic acid mono[1,3-di(methacryloyloxy)propan-2-yl]-esters of formula (b), described in DE-B-27 11 234.
Moreover, acrylic acid-(2-phosphono-1,1-dimethylethylamine) is known from DE-A-32 10 775 and methacrylic acid-(2-phosphono-1,1-dimethylethylamine) of the formula (c) is known from DE-A-33 13 819 and JP 62-63314 (Chem. Abstr. 107 (1987), 41318f).
Acrylic acid-(2-phosphono-1,1-dimethylethylamine), also called acrylamido-2-methylpropanephosphonic acid, is used in the form of its homo- or copolymers as corrosion inhibitors (cf. EP-B-89 654 and U.S. Pat. No. 4,650,591).
Finally, N-acryl-aminomethanebisphosphonic acid of the formula (d) is also described in DD-A-273 846.
All of these known (meth)acrylphosphonic acid derivatives are, however, not stable in aqueous solution. Rather, a hydrolytic cleavage of the (meth)acrylic group takes place which is even catalysed by dissociated protons of the phosphonic acid group and thereby accelerated.
However, the use of aqueous solutions is advantageous or absolutely necessary in a whole series of applications of polymerizable phosphonic acids. This is e.g. the case in the preparation of low-viscosity adhesives which are free of organic solvents, or in that of dental adhesives which result in an optimum wetting of the moist dentine surface only in aqueous form.
It is therefore the object of the invention to make available polymerizable acrylphosphonic acids which are hydrolysis-stable in aqueous solution and have good adhesion properties, can be polymerized using conventional radical initiators and are therefore suitable as a component of in particular adhesives, shaped bodies, cements or composites and above all of dental materials.
This object is surprisingly achieved by the hydrolysis-stable and polymerizable acrylphosphonic acids according to claims
1
and
2
.
The subject of the present invention is also the process for the preparation of the acrylphosphonic acids according to claim
3
, the use thereof according to claims
4
to
6
, the dental material according to claims
7
and
8
, and polymers and copolymers of the acrylphosphonic acids according to claim
9
.
The acrylphosphonic acids according to the invention are compounds of the following general formula (I), stereoisomers thereof and mixtures of such stereoisomers
where R
1
, R
2
, R
3
, X, Y and n, unless stated otherwise, independently of one another have the following meanings:
R
1
=hydrogen, C
1
to C
10
alkyl or C
6
to C
10
aryl,
R=hydrogen, fluorine, C
1
to C
5
alkyl or phenyl,
R
3
=C
1
to C
8
alkylene, phenylene or is absent,
Y=oxygen, sulphur, C
1
to C
8
alkylene or is absent,
n=1 or 2,
and with the proviso that
(a) for n=1
X=hydrogen, fluorine, C
1
to C
5
alkyl or C
6
to C
12
aryl,
and
(b) for n=2
X=C
1
to C
10
alkylene, C
6
to C
10
arylene, C
7
to C
20
arylenalkylene or is absent.
The individual alkyl and alkylene radicals can be straight-chain, branched or cyclic. Moreover, the individual alkyl, aryl, alkylene, arylene, phenyl, phenylene and arylenalkylene radicals can bear one or more substituents, such as Cl, Br, CH
3
, C
2
H
5
, CH
3
O, OH, COOH, CN or NO
2
.
There also exist for the above-mentioned variables of the formula (I) preferred definitions which, unless otherwise stated, can be chosen independently of one another and are as follows:
R
1
=hydrogen, C
1
to C
5
alkyl or phenyl,
R
2
=hydrogen, fluorine or C
1
to C
3
alkyl,
R
3
=C
1
to C
3
alkylene, phenylene or is absent,
Y=oxygen, C
1
to C
3
alkylene or is absent,
n=1 or 2,
and with the proviso that
(a) for n=1
X=hydrogen, fluorine, C
1
to C
3
alkyl or phenyl,
and
(b) for n=2
X=C
1
to C
6
alkylene, phenylene or is absent.
Preferred compounds are therefore those in which at least one of the variables of the formula (I) has the above-described preferred definition, the formula (I) including all stereoisomers made possible by the mentioned substituents and their mixtures, such as racemates.
The acrylphosphonic acids according to the invention of the formula (I) can be prepared by reaction of &agr;-halomethylacrylic acid esters of the formula (II) with protected mono- or difunctional phosphonic acid esters of the formula (III) and cleavage of the protective groups. In the formulae (II) and (III) U is halogen, SG is protective group and the other variables are as defined above for formula (I). This reaction can be illustrated by the following general reaction equation which is followed by a concrete example.
Concrete example:
The reaction can be conducted by using the methods known from organic chemistry for forming C—C, C—O or C—S bonds (cf. C. Weygand, G. Hilgetag, Organisch-chemische Experimentierkunst, Johann Ambrosius Bart Verlag, Leipzig 1970, pages 963 et seq., 362 et seq. and 657 et seq.).
Used as protective groups (SG) are customary protective groups for phosphoric acid groups, such as ester groups, in particular SG is ethyl. After the reaction has taken place, these are split off according to conventional processes, in order to liberate the acrylphosphonic acids of the formula (I). The hydrolytic cleavage of the protective groups SG is effected in particular by silylation with trialkylsilanes, e.g. trimethylsilyl chloride mixed with sodium iodide or bromide, and subsequent reaction with alcohols or water (cf. S. Freeman, J. Chem. Soc., Perkin Trans, 2 (1991) 263).
The &agr;-halomethylacrylic acid esters (II) used as starting materials can be obtained e.g. by reaction of the corresponding acrylic acid esters with formaldehyde in the presence of 1,4-diazabicyclo[2,2,2]octane (DABCO) and subsequent halogenation with inorganic acid chlorides, such as SOCl
2
, PCl
3
or PBr
3
(cf. L. J. Mathias et al., Macromolecules 20 (1987) 2039, 2326, J. Polym. Sci.: Part A: Polym. Chem. 32 (1994) 2937), and this reaction is illustrated by the following equation and a concrete example:
Concrete example:
Suitable protected mono- or difunctional phosphonic acid esters (III) can be obtained by different methods. A particularly suitable method proceeds via the Michaelis-Arbusow reaction for the preparation of alkylphosphonic acid esters (cf. G. M. Kosolapoff, Org. Reactions 6

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