Polypropylene wax

Details Polypropylene wax Polypropylene wax

2000-05-25

2001-12-18

Wu, David W. (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...

C526S351000, C523S160000, C523S161000, C430S056000, C430S135000, C430S965000, C106S031130, C106S031620, C106S270000, C106S272000

Reexamination Certificate

active

06331590

ABSTRACT:

The present invention relates to a low-viscosity, hard polypropylene wax, to a process for its preparation and to its use.
The thermal degradation of isotactic polypropylene gives hard PP waxes, but is energy-intensive and leads to sometimes discolored products which contain double bonds.
The polymerization of propene using Ziegler-Natta catalysts (EP-A-584 586, DE-A-23 29 641) requires large amounts of hydrogen and is therefore likewise restricted to relatively high-viscosity waxes.
The preparation of 1-olefin polymer waxes which have a narrow molecular weight distribution and a high isotacticity by means of metallocenes is known. However, the resulting products continue to have a melt viscosity of 100 mPas even when regulation is carried out by means of a high hydrogen level (EP-A-321 852).
EP-A-321 853 describes the use of metallocene catalysts for preparing low molecular weight PP waxes. However, the resulting products have a low isotacticity of less than 70%.
Furthermore, there are metallocenes (EP-A-416 566) which have been used for preparing polypropylene of different molecular weight depending on the polymerization temperature. The mean molecular weight decreases as the polymerization temperature increases. The products prepared by this method have unsaturated chain ends and therefore have little thermal stability in use. it is therefore an object of the invention to prepare very low-viscosity polypropylene waxes having a high hardness and good thermal stability.
It has been found that polymerization of propene together with comonomers using metallocenes and, in addition, hydrogen enables novel low molecular weight PP waxes to be prepared. These have a melt viscosity of less than 100 mPas at 170° C. and have no unsaturated or polar groups in the chain, which groups could promote discoloration and crosslinking reactions. The polypropylene homopolymer waxes preferably have an isotacticity of greater than 70% and a heat of fusion of greater than or equal to 80 J/g in order to ensure a high hardness.
The invention accordingly provides hard PP homopolymer and PP copolymer waxes prepared using metallocenes and having saturated chain ends, where the wax has no unsaturated end groups or less than 10% of unsaturated end groups, a melt viscosity of less than 100 mPas measured at 170° C. and an isotactic index of greater than or equal to 70%. The invention also provides for the use of these waxes.
It has also been found that these novel waxes can be advantageously employed in many fields of application. As a component of toners, they allow good miscibility in toner production owing to their low viscosity. Low-viscosity PP waxes are therefore employed, in particular, as a component in black and color toners in photocopiers and laser printers.
In the same way, these waxes can be advantageously used for producing printing inks, in surface coatings and as a component in melt adhesives.
If pulverulent mixtures are to be prepared, the high crystallinity of the waxes allows them to be readily milled during mixing and avoids conglutination of the powders, as is regularly observed when using low-isotacticity waxes.
In all applications, discoloration or crosslinking of the melt is avoided, as a result of which the user experiences no alteration of the wax melt even at high temperatures and long waiting times in processing machines.
For this reason, the use of the waxes prepared in this way as auxiliaries in plastics processing, for example as lubricant, is very advantageous. Their use in the preparation of masterbatches, for example of pigments or dyes for coloring polymers, is particularly advantageous. The low viscosity of the wax melt allows improved wetting and dispersion of the colorants and thereby increases the color yield and intensity.
Preference is given to polyolefin waxes prepared using sandwich chelate compounds, in particular those prepared using metallocene compounds, wherein the metallocene is a compound of the formula I:
This formula also encompasses compounds of the formula Ia
and the formula Ib
In the formulae I, Ia and Ib, M
1
is a metal of group IVb, Vb or VIb of the Periodic Table, for example titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, preferably titanium, zirconium and hafnium.
R
1
and R
2
are identical or different and are each a hydrogen atom, a C
1
-C
10
-, preferably C
1
-C
3
-alkyl group, in particular methyl, a C
1
-C
10
-, preferably C
1
-C
3
-alkoxy group, a C
6
-C
10
-, preferably C
6
-C
8
-aryl group, a C
6
-C
8
-, preferably C
6
-C
8
-aryloxy group, a C
2
-C
10
-, preferably C
2
-C
4
-alkenyl group, a C
7
-C
40
-, preferably C
7
-C
10
-arylalkyl group, a C
7
-C
40
-, preferably C
7
-C
12
-alkylaryl group, a C
8
-C
40
-, preferably C
8
-C
12
-arylalkenyl group or a halogen atom, preferably chlorine.
R
3
and R
4
are identical or different and are each a monocyclic or polycyclic hydrocarbon radical which can form a sandwich structure with the central atom M
1
. R
3
and R
4
are preferably cyclopentadienyl, indenyl, benzindenyl or fluorenyl, where the base structures can also bear additional substituents or be bridged to one another. In addition, one of the radicals R
3
and R
4
can be a substituted nitrogen atom, where R
24
is as defined for R
17
and is preferably methyl, t-butyl or cyclohexyl.
R
5
, R
6
, R
7
, R
8
, R
9
and R
10
are identical or different and are each a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C
1
-C
10
-, preferably C
1
-C
4
-alkyl group, a C
6
-C
10
-, preferably C
6
-C
8
-aryl group, a C
1
-C
1
-, preferably C
1
-C
3
-alkoxy group, an —NR
16
2
—, —SR
16
—, —OSiR
16
3
—, —SiR
16
3
— or —PR
16
2
radical, where R
16
is a C
1
-C
10
-, preferably C
1
-C
3
-alkyl group or C
6
-C
10
-, preferably C
6
-C
8
-alkyl group, or in the case of Si- or P-containing radicals is also a halogen atom, preferably a chlorine atom, or two adjacent radicals R
5
, R
6
, R
7
, R
8
, R
9
or R
10
together with the carbon atoms connecting them form a ring. Particularly preferred ligands are the substituted compounds of the base structures indenyl, benzindenyl, fluorenyl and cyclopentadienyl.
═BR
17
, ═AIR
17
, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO
2
, ═NR
15
, ═CO, ═PR
15
or ═P(O)R
15
, where R
17
, R
18
and R
19
are identical or different and are each a hydrogen atom, a halogen atom, a C
1
-C
30
-, preferably C
1
-C
4
-alkyl group, in particular a methyl group, a C
1
-C
10
-fluoroalkyl group, preferably a CF
3
group, a C
6
-C
10
-fluoroaryl group, preferably a pentafluorophenyl group, a C
6
-C
10
-, preferably C
6
-C
8
-aryl group, a C
1
-C
10
-, preferably C
1
-C
4
-alkoxy group, in particular a methoxy group, a C
2
-C
10
-, preferably C
2
-C
4
-alkenyl group, a C
7
-C
40
-, preferably C
7
-C
10
-arylalkyl group, a C
8
-C
40
-, preferably C
8
-C
12
-arylalkenyl group or a C
7
-C
40
-, preferably C
7
-C
12
-alkylaryl group, or R
17
and R
18
or R
17
and R
19
, in each case together with the atoms connecting them, form a ring.
M
2
is silicon, germanium or tin, preferably silicon or germanium.
R
13
is preferably ═CR
17
R
18
, ═SiR
17
R
18
, ═GeR
17
R
18
, —O—, —S—, ═SO, ═PR
17
or ═P(O)R
17
.
R
11
and R
12
are identical or different and are as defined for R
17
m and n are identical or different and are zero, 1 or 2, preferably zero or 1, where m plus n is zero, 1 or 2, preferably zero or 1.
R
14
and R
15
are as defined for R
17
and R
18
.
Examples of suitable metallocenes are the rac isomers of:
ethylenebis-1-(2-methyltetrahydroindenyl)zirconium dichloride,
ethylenebis-1-(4,7-dimethylindenyl)zirconium dichloride,
ethylenebis-1-(2-methyl-4-phenylindenyl)zirconium dichloride,
ethylenebis-1-(2-methyl-4,5-benzindenyl)zirconium dichloride,
ethylenebis-1-(2-methyl-4,5-benzo-6,7-dihydroindenyl)zirconium dichloride,
ethylenebis-1-(2-methylindenyl)zirconium dichloride,
ethylenebis-1-tetrahydroindenylzirconium dichloride,
and also the alkyl or aryl derivatives of each of these metallocene dichl

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