Polymer oxidates and their use

Details Polymer oxidates and their use Polymer oxidates and their use

1999-12-21

2002-05-07

Lipman, Bernard (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...

C525S388000, C524S585000

Reexamination Certificate

active

06384148

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to polymer oxidates with improved dispersability in aqueous media, their preparation by oxidative degradation of polyethylene plastic, and their use.
DESCRIPTION OF THE RELATED ART
Ethylene homo- and copolymers which have the nature of plastics may be reacted to give polar products via controlled oxidative degradation. Polymer oxidates of this type have oxygen-containing functional groups, e.g. carboxyl, ester and ketone groups, and, due to the polarity which these give, are suitable for preparing aqueous dispersions for applications in polishes or the industrial sector for example. Polyethylene oxidates also serve as auxiliaries for processing and shaping plastics (cf. Ullmann's Encyclopaedia of Industrial Chemistry, 5th Edn, Vol. A28, pp.155-156, Weinheim 1996).
Processes for the oxidative degradation of polyethylene plastic are known. For example, this may be done by treating the finely divided raw material at below its softening point with oxygen or with oxygen-containing gases (DE-A-1 520 008). A variant of this procedure is to carry out the reaction in the presence of an inert dispersion medium, e.g. water (DE-A-3 238 652). The oxidative degradation of ethylene homo- and copolymers at temperatures above the softening point in the presence of an inert dispersion medium has also been described (DE-A-2 035 706, EP-A-28 384). The polyethylene used for the oxidation is prepared by ethylene polymerization with the aid of titanium and/or chromium transition metal catalysts by the low-pressure process or by the free-radical high-pressure process. It is also known that low-molar-mass polyethylene waxes can be oxidized to give wax oxidates. These are obtained by bringing oxygen-containing gases into contact with the melts of the raw materials. The starting material here has low viscosity and it is therefore unnecessary to add a dispersion medium. The oxidation of polyethylene waxes whose weight-average molar Mass is below 40,000 g/mol, generally below 10,000 g/mol, gives products whose type differs from those obtained from high-molar-mass polyethylene which has the nature of plastic. Wax oxidates have relatively low molar mass and are softer than polymer oxidates, and if used in floor covering polish formulations, for example, they are inferior to polymer oxidates in terms of hardness and resistance to foot traffic. Wax oxidates are disclosed, for example, in DE-A-1 227 654.
Aqueous dispersions prepared using the abovementioned polymer oxidates frequently have disadvantages in practical use, for example insufficient transparency, excessive viscosity, reduced gloss after film application or unsatisfactory storage stability.
The object was therefore to provide polymer oxidates with improved dispersion and usage properties and not having the disadvantages of previously known polymer oxidates.
Surprisingly, it has now been found that polymer oxidates with improved properties are obtained if the high-molar-mass polymer used as starting material has been prepared with the aid of metallocene catalysts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention therefore provides polymer oxidates wherein a starting polymer, which is a polyethylene obtained using metallocene catalysts and having a weight-average molar mass above 40,000 g/mol, is oxidized by reaction with oxygen or oxygen-containing gas mixtures.
Starting Polymer
Polymerization processes for preparing polyethylene with the aid of metallocene catalyst systems are known. A suspension process is described in EP-A-578 838, there are details for the gas-phase process in EP-A-323 716, for example, and the high-pressure process in EP-A-361 866, for example.
Suitable starting polymers are polyethylenes prepared using metallocene catalysts, and for the purposes of the present invention these are ethylene homo-, co- or terpolymers with weight-average molar masses Mw above 40,000 g/mol, preferably from 50,000 to 4,000,000 g/mol. The melt viscosities of polymers of this type, measured at 140° C., are above 50,000 mPa.s, usually above 100 Pa.s. The melt flow rate MFR 190/5, which is the variable usually used for polymer viscosities, is below 100 g/10 min, usually less than or equal to 50 g/10 min.
Besides ethylene, this starting polymer may also comprise amounts of from 0.1 to 20% by weight, based on total polymer, of (&agr;-olefins with chain lengths from 3 to 30, preferably from 3 to 8, e.g. propene, 1-butene, 1-hexene or 1-octene. Particular preference is given to ethylene copolymers with up to 10% by weight of propene or 1 -butene.
Preferred starting polymers have narrow molar mass distribution M
w
/M
n
of below 5, preferably below 4, in particular less than or equal to 3.5.
Preparation of the Starting Polymer
Catalyst systems for preparing the starting polymer are composed of one or more metallocene compounds (I) together with a cocatalyst (II), and also, if desired, another catalyst component (III) and a scavenger (IV). The catalyst system is frequently used after fixing on a support, in which case the species active for polymerization is produced either prior to, during or after application to the support, depending on variations in the order in which components (I) to (IV) and the support are used.
The metallocene compound (I) typically has the formula I
and includes, for example, structures of the formulae (Ia):
of the formula Ib:
or of the formula Ic:
M
1
in the formulae is a metal of group IVb, Vb, VIb or VIIIb of the Periodic Table, for example titanium, zirconium, iron, chromium, cobalt or nickel.
R
1
and R
2
are identical or different and are a hydrogen atom, a C
1
-C
10
-alkyl group, a C
1
-C
10
-alkoxy group, a C
6
-C
10
-aryl group, a C
6
-C
10
-aryloxy group, a C
2
-C
10
-alkenyl group, a C
7
-C
40
-arylalkyl group, a C
7
-C
40
-alkylaryl group, a C
8
-C
40
-arylalkenyl group or a halogen atom.
R
3
and R
4
are identical or different and in the embodiments of the formulae (Ia) to (Ic) are alkyl, pyridyl, arylalkyl, alkylaryl, or mono- or bisalkylpyridyl-substituted imido radicals, which may have bridging to one another via alkyl, bisalkylaryl or bisalkylpyridyl groups. One of the radicals R
3
and R
4
may moreover be a substituted nitrogen atom, in which case R
28
is defined as for R
21
and is preferably methyl, tert-butyl or cyclohexyl.
R
5
to R
14
are identical or different and, independently of one another, are a hydrogen atom, a halogen atom, a C
1
-C
18
-aryl group, a C
1
-C
10
-alkoxy group, or an —NR
20
2
—, —SR
20
—, —OSiR
20
3
—, —SiR
20
3
—, or —PR
20
2
— radical, where R
20
is a C
1
-C
10
-alkyl group or a C
6
-C
10
-aryl group, or, in the case of radicals containing Si or P, also a halogen atom, or two adjacent radicals R
5
, R
6
, R
7
, R
8
, R
9
, R
10
, R
11
, R
12
, R
13
or R
14
, together with the carbon atoms connecting them, may form a ring system. This gives, for example, 2-methyl-4-naphthylindenyl or substituted benzoindenyl or fluorenyl. Preferred substituents for these ligands have been given in the description of R
1
.
R
17
is:
═BR
21
, ═AIR
21
, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO
2
, ═NR
19
, ═CO, ═PR
19
or ═P(O)R
19
, where R
21
, R
22
and R
23
are identical or different and are a hydrogen atom, a halogen atom, a C
1
-C
30
-alkyl group, a C
1
-C
10
-fluoroalkyl group, a C
6
-C
10
-fluoroaryl group, a C
6
-C
10
-aryl group, a C
1
-C
10
-alkoxy group, a C
2
-C
10
-alkenyl group, a C
7
-C
40
-arylalkyl group, a C
8
-C
40
-arylalkenyl group or a C
7
-C
40
-alkylaryl group, or R
21
and R
22
or R
21
and R
23
, in each case together with the atoms connecting them, may form a ring having from 2 to 8 ring-carbon atoms.
M
2
is silicon, germanium or tin, preferably silicon. R
17
is preferably ═CR
21
R
22
, ═SiR
21
R
22
, ═GeR
21
R
22
, —O—, —S—, ═SO, ═PR
21
or ═P(O)R
21
.
R
15
and R
16
are identical or different and are as defined for R
21
.
m and n are identical or different and are 0, 1 or 2.
R
18
and R
19
are as defined for R
21
and R
22
.
Illustrative exampl

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