COPOLYMERES DE TETRAFLUOROETHYLENE, D'HEXAFLUOROPROPYLENE ET D'ETHYLENE

COPOLYMERS OF TETRAFLUOROETHYLENE, HEXAFLUOROPROPYLENE AND ETHYLENE

Abrégé anglais

Copolymers, containing from 45 to 55 mol % of units of
tetrafluoroethylene, from 10 to 20 mol % of units of
hexafluoropropylene and from 25 to 40 mol % of units of
ethylene and having a melting point of from about 140 to
about 170°C can be processed from the melt. They are
suitable as coatings for temperature-sensitive
substrates.

Revendications

- 5 -
Patent Claims
l. A copolymer containing from 45 to 55 mol % of units
of tetrafluoroethylene, from 10 to 20 mol % of units
of hexafluoropropylene and from 25 to 40 mol % of
units of ethylene and having a melting point in the
range from about 140 to about 170°C.
2. A copolymer as claimed in claim 1, containing from
48 to 55 mol % of units of tetrafluoroethylene, from
11 to 18 mol % of units of hexafluoropropylene and
from 27 to 39 mol % of units of ethylene.
3. A copolymer as claimed in claim 2, containing from
29 to 38 mol % of units of ethylene.
4. A substrate coated with a copolymer as claimed in
claim 1.
5. A substrate coated with a copolymer as claimed in
claim 2.
6. A substrate coated with a copolymer as claimed in
claim 3.
7. A process for coating a temperature-sensitive
substrate, which comprises contacting the said
substrate with a melt of a copolymer as claimed in
claim 1.
8. A process for coating a temperature-sensitive
substrate, which comprises contacting the said
substrate with a melt of a copolymer as claimed in
claim 2.
9. A process for coating a temperature-sensitive
substrate, which comprises contacting the said
substrate with a melt of a copolymer as claimed in
claim 3.

- 6 -
10. A film consisting essentially of a copolymer as
claimed in claim 1.
11. A film consisting essentially of a copolymer as
claimed in claim 2.
12. A film consisting essentially of a copolymer as
claimed in claim 3.

Description

70~5
HOECHST AKTIENGESELLSCHAFT HOE 94/F 910 Dr.KL-nu
Werk Gendorf
Copolymers of tetrafluoroethylene, hexafluoropropylene
and ethylene
Description
The invention relates to copolymers containing from 45 to
55 mol % of units of tetrafluoroethylene (TFE), from 10
to 20 mol % of units of hexafluoropropylene (HFP) and
from 25 to 40 mol % of units of ethylene (ET) and having
a melting point in the range from about 140 to about
170C. The presence of subordinate amounts of further
comonomers compatible with the specified monomers is not
excluded.
Preferred copolymers contain from 48 to 55 mol % of TFE,
from 11 to 18 mol % of HFP and from 27 to 39 mol %, in
particular from 29 to 38 mol %, of ET.
On a weight basis, the copolymers of the invention
contain from about 53 to 6g % of TFE, from about 18 to
36 % of HFP and from about 7 to 15 % of ET.
The polymers of the invention are distinguished by their
relatively low melting point. They are therefore suitable
for processing from the melt together with substrates
which cannot withstand relatively high temperatures, such
as fiber material or temperature-sensitive plastics.
Terpolymers of TFE, HFP and ET have been known for a long
time: US-A 3 817 951 describes terpolymers composed of,
(in mol percent) from 40 to 60 % of ET, from 20 to 30 %
of TFE and from 10 to 30 % of HFP. Reference is expressly
made to the fact that the advantageous properties of
these terpolymers are achieved only within this critical
narrow range of the specified proportions. Corresponding
to the low TFE content, the terpolymers mentioned in the
examples contain 46 or 50 mol % of ET.

2147045
US-A 4 338 237 relates to a process for preparing stable
aqueous colloidal dispersions of copolymers, including
terpolymers of TFE, HFP and ET. The TFE content is from
30 to 60 mol %, the HFP content is from 0 to 15 mol % and
the ET content is from 40 to 60 mol %. The terpolymers of
these monomers mentioned in the examples contain 4.5 or
4.7 mol % of HFP and correspondingly 46.5 or 46.8 mol %
of ET. The concentrated dispersions are suitable for
impregnating or coating fiber materials and surfaces and
the coagulated dispersions can be worked up to give melt
granules. In this form, the copolymers can then be
processed from the melt.
EP-B 92 675 discloses sheathing materials for optical
fibers, with a copolymer containing from 30 to 60 mol %
of ethylene, from 20 to 69 mol % of TFE or chlorotri-
fluoroethylene and from 1 to 30 % of a further olefin,
which can be HFP, being used. The Example 1 relates to a
terpolymer containing 55 mol % of ET, 25 mol % of TFE and
20 mol % of HFP; the Comparative Example 3 relates to a
terpolymer containing 70 mol % of ET, 23 mol % of TFE and
7 mol % of HFP.
The preparation of the copolymers of the invention can be
carried out in a manner known per se, as is also
described in the abovementioned documents. The
copolymerization is preferably carried out in aqueous
medium, if desired using a low-molecular-weight hydrocar-
bon as chain transfer agent, and a redox system as
initiator.
The copolymers of the invention have a high resistance to
aggressive media. In conjunction with the relatively low
melting point they are therefore suitable for coating or
lining shaped articles which cannot withstand high
temperatures. For this purpose, for example, the
copolymers can be first processed into a film which is
then welded to the substrate, if desired with the aid of
a suitable binder.

2t4704S
The invention is illustrated in the following examples.
Percentages are by weight, unless otherwise indicated.
Example 1
An internally enamelled polymerization reactor having a
total volume of 195 l, provided with an impeller stirrer,
is charged with 120 1 of deionized water, and 500 g of
ammonium perfluorooctanoate (in the form of 1667 g of a
30 % strength solution in water, commercial product of
the 3M company), 242 g of diammonium oxalate monohydrate
and 69 g of oxalic acid monohydrate are dissolved there-
in. After sealing the reactor, it is first flushed five
times with nitrogen and subsequently once with 1 bar of
TFE.
After depressurization and heating to 43C, 10 g of n-
pentane and 9 kg of HFP are pumped in via a line under
moderate stirring. The stirring is then increased to
210 rpm and 2.05 kg of TFE and 133 g of ET are fed into
the reactor via the gas phase, so that a total pressure
of 17 bar is achieved.
The polymerization is then initiated by pumping in a
solution of 5 g of potassium permanganate in 250 ml of
water and maintained by continuously feeding in 14 g of
potassium permanganate, dissolved in 0.7 l of water, per
hour. The total monomer pressure of 17 bar is automati-
cally maintained by continuous feeding in of a mixturehaving a molar ratio of TFE : ET : HFP = 2.3 : 1.7 : 1.
The reaction is stopped at a copolymer solids content,
based on aqueous reaction medium used, of about 21 % by
venting of the monomer mixture.
The dispersion is then coagulated by means of the rapidly
running stirrer. The precipitated copolymer solid is
separated off from the liquor, washed a number of times
with water, dried in a nitrogen atmosphere for 15 hours

~ 21~7045
-- 4
at 110C and subsequently melt granulated.
The polymer composition and further characteristic data
are summarized in the table below.
Examples 2 to 5
The Exampleæ 2 to 5 are carried out using a similar
method to Example 1. Alterations, for example to the
metering in of como~omer, are given together with the
polymer propertieæ in the table below.
Table
1 0 Example No. 1 2 3 4 5
Polymerization temperature [C] 43.041.0 45.0 49.0 42.0
TFE: Total amount [kg] 20.3515.68 15.33 13.40 20.40
of this, initially charged[kg] 2.05 2.18 1.831.27 2.10
of this, subsequently metered in [kg]18.3013.5013.50 12.13 18.30
HFP: Total amount [kg]20.8816.3318.20 19.07 20.88
of this, initially charged [kg]9.0o 8.61 9.50 10.50 9.00
of this, subsequently metered in [kg]11.887.728.70 8.57 11.88
ET: Total amount [kg] 3.82 2.85 2.24 1.843.79
of this, initially charged[kg] 0.13 0.1490.0870.070 0.133
of this, subsequently metered in [kg] 3.69 2.70 2.16 1.77 3 66
n-pentane [g] 10.00 15.00 --- --- 20.00
KMnO4 [g] 66.00 50.00 51.00 75.00 66.00
Polymerization time [h] 5.00 3.30 2.80 4.20 5.00
Polymer solids content [~] 20.50 15.10 15.30 15.40 20.10
MFI 5 kg/297C [g/10 min] 7 21 0.6 17.8 57.0
Mp by DSC [C] 155 169 152 140 159
Fluorine content [~] 65.9 65.9 68.2 68.8 65.9
Product composition : TFE [mol-~] 48.7350.5754.05 52.49 49.44
(NMR) HFP [mol-~] 13.5111.9414.8017.8712.91
8T [mol-~] 37.7637.4931.1529.6437.66
MFI: Melt flow index at 297C and 5 kg load, in accord-
ance with D~N 53 735/ASTM D 3159.