Process for the preparation of ethylene copolymers, and...

Details Process for the preparation of ethylene copolymers, and... Process for the preparation of ethylene copolymers, and...

1998-12-08

2003-01-21

Zitomer, Fred (Department: 1713)

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

Synthetic resins

Polymerizing in tubular or loop reactor

C526S066000, C526S327000, C526S328500, C526S329700, C526S330000, C526S332000, C526S348000, C526S352000

Reexamination Certificate

active

06509424

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the preparation of terpolymers of ethylene, one or more vinyl esters or acrylates, and further olefinically unsaturated compounds, and to the use of the resultant copolymers for improving the cold-flow properties of mineral oils and mineral oil distillates.
DESCRIPTION OF THE RELATED ART
Crude oils and middle distillates obtained by distillation of crude oils, such as gas oil, diesel oil or heating oil, contain, depending on the origin of the crude oils, various amounts of n-paraffins, which, when the temperature is reduced, crystallize out as platelet-shaped crystals and in some cases agglomerate with inclusion of oil. This crystallization and agglomeration causes an impairment of the flow properties of the oils or distillates, which can result in problems during the recovery, transport, storage and/or use of the mineral oils and mineral oil distillates. During transport of mineral oils through pipelines, the crystallization phenomenon can cause deposits on the walls of the pipes, especially in winter, and in individual cases, for example during stoppage in a pipeline, can even cause complete blocking thereof. During storage and further processing of the mineral oils, it may furthermore be necessary in winter to store the mineral oils in heated tanks. In the case of mineral oil distillates, the crystallization may result in blockage of the filters in diesel engines and furnaces, preventing reliable metering of the fuels and in some cases causing complete interruption of the supply of the fuel or heating medium.
In addition to the classical methods of eliminating the crystallized paraffins (thermal, mechanical or using solvents), which merely involve removal of the precipitates which have already formed, recent years have seen the development of chemical additives (so-called flow improvers), which, by interacting physically with the precipitating paraffin crystals, result in their shape, size and adhesion properties being modified. The additives act as additional crystal nuclei and in some cases crystallize with the paraffins, resulting in an increased number of relatively small paraffin crystals having a modified crystal shape. The modified paraffin crystals have a lower tendency toward agglomeration, so that the oils to which these additives have been added can still be pumped and/or processed at temperatures which are frequently more than 20° lower than in the case of oils containing no additives.
Typical flow improvers for mineral oils and mineral oil distillates are copolymers and terpolymers of ethylene with carboxylates of vinyl alcohol, esters of acrylic or methacrylic acid and/or olefins.
EP-A-0 493 796 discloses terpolymers consisting of ethylene, 5-35% by weight of vinyl acetate and 1-25% by weight of vinyl neononanoate or neodecanoate, a process for their preparation, and their use as flow improvers for middle distillates.
DE-A-19 620 118 discloses terpolymers of ethylene, vinyl esters and 4-methylpentene which have improved solubility, a process for their preparation, and additive concentrates having a lowered inherent pour point prepared therefrom.
EP-A-0 203 554 discloses the use of terpolymers comprising, in addition to ethylene, from 0.5 to 20% by weight of diisobutylene and from 20 to 35% by weight of vinyl acetate (based on the terpolymer) and having a mean molecular weight of from 500 to 10,000, as additives for mineral oils and mineral oil distillates.
EP-A-0 099 646 discloses terpolymers having molecular weights of from 1500 to 5500 which comprise ethylene, from 10 to 20% by weight of vinyl acetate and from 3 to 15% by weight of an isoolefin and which contain, per 100 methylene groups, from 6 to 15 methyl groups which do not originate from the vinyl acetate.
EP-A-0 648 257 discloses terpolymers made from ethylene and 2 vinyl esters carrying acid radicals having a maximum of 8 carbon atoms, as constituents of a fuel oil composition.
EP-A-0 649 445 discloses terpolymers made from ethylene and two vinyl esters and/or acrylates in a proportion of up to 10 mol%, where the esters carry side chains having a maximum of 8 carbon atoms, as a constituent of fuel oil compositions.
EP-A-0 271 738 discloses a process for the preparation of copolymers of ethylene and esters of vinyl alcohol, acrylic acid or methacrylic acid by polymerization of monomer streams of different quantitative composition in a tubular reactor, and the use of these copolymers as flow improvers.
However, the terpolymers prepared by the prior-art process (EP 271 738) do not have the properties that would be expected of them on the basis of their monomer composition. For example, the terpolymers prepared in this way frequently impair the filterability of the oils in which they are present or their effectiveness is in many cases unsatisfactory. For example, the terpolymers of EP-A-0 493 796 have very good solubility, but they are ineffective in certain oils. The products prepared by the process of EP-A-0 271 738 have improved effectiveness, but impair the filterability of the oils to which they have been added.
The object was therefore to find a new process for terpolymerization which gives terpolymers whose properties can be controlled better via the specific properties of the various monomers.
SUMMARY OF THE INVENTION
Surprisingly, it has been found that improved terpolymers made from ethylene and at least two further comonomers can be obtained if the terpolymerization is carried out in a tubular reactor with a side branch and the fresh comonomers are fed in separately from one another via different reactor inlets.
The olefinically unsaturated compounds which make up the further comonomers are preferably vinyl esters, acrylates, methacrylates, alkyl vinyl ethers and/or alkenes.
The vinyl esters are preferably those of the formula 1
CH
2
═CH—OCOR
1
  (1)
in which R
1
is C
1
- to C
30
-alkyl, preferably C
1
- to C
16
-alkyl, especially C
1
- to C
12
-alkyl.
In a further preferred embodiment, R
1
is a neoalkyl radical having 7 to 11 carbon atoms, in particular having 8, 9 or 10 carbon atoms. Suitable vinyl esters include vinyl acetate, vinyl propionate, 2-ethylhexanoic acid vinyl ester, vinyl laurate, vinyl neononanoate, vinyl neodecanoate and vinyl neoundecanoate.
The acrylates are preferably those of the formula 2
CH
2
═CR
2
—COOR
3
  (2)
in which R
2
is hydrogen or methyl and R
3
is C
1
- to C
30
-alkyl, preferably C
1
- to C
16
-alkyl, especially C
1
- to C
12
-alkyl. Suitable acrylates include methyl acrylate, methyl methacrylate, ethyl acrylate and 2-ethylhexyl acrylate.
The alkyl vinyl ethers are preferably compounds of the formula 3
CH
2
═CH—OR
4
  (3)
in which R
4
is C
1
- to C
30
-alkyl, preferably C
1
- to C
16
-alkyl, especially C
1
- to C
12
-alkyl.
The alkenes are preferably monounsaturated hydrocarbons having 3 to 30 carbon atoms, in particular 4 to 16 carbon atoms, especially 5 to 12 carbon atoms. Suitable alkenes include isobutylene, diisobutylene, 4-methylpentene, hexene, octene and norbornene.
Particular preference is given to terpolymers in which one of the radicals R
1
, R
3
and R
4
is C
1
- or C
2
-alkyl and the other radical R
1
, R
3
or R
4
is C
4
- to C
16
-alkyl, in particular C
6
- to C
12
-alkyl or an alkene.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a preferred embodiment of the invention, the fresh monomer components are introduced in the main stream and in a secondary stream. In the main stream, ethylene is introduced as a mixture with one of the two further comonomers. In the secondary stream, ethylene is introduced as a mixture with the other comonomer.
In a further preferred embodiment of the invention, the fresh monomer components are introduced in the main stream and in two secondary streams. In this embodiment, there are various preferred variants:
A) In the main stream, ethylene is introduced as a mixture with one of the two further comonomers. In each of the secondary streams, ethylene is introduced as a mixture with the other of the fur

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