Note: Descriptions are shown in the official language in which they were submitted.
~ -~ H~1i3 Aktiengesellschaft 21~4~06 o.z. 4719
Patent Department
Multila~er ~lastic ~i~e
The invention relates to a multilayer plastic pipe
comprising an outer layer I. made from a moulding com-
position based on a polyamide, and a further layer II.,
ad~acent to the outer layer, made from a moulding com-
position baised on polyvinylidene fluoride.
Plastic pipes made from polyamide are known and are
employed for a variety of applications. In order to
achieve their ob~ective, the pipes must be, inter alia,
inert to ~the medium flowing in them, and must be resis-
tant to high and low temperatures and mechanical
stresses.
Single-layer pipes are not always capable of satisfying
the neces~ary requirements. In the case of transport of,
for example, aliphatic or aromatic solvents, fueli3 or the
like, they exhibit considerable disadvantages, ~uch as a
poor barrier action to the medium, undesired changes in
dimension or inadequate resistance to mechanical
stresses.
It has been attempted to overcome these disadvantages by
means of multilayer pipes (DE-A 35 10 395, 37 15 251,
38 21 723, 40 01 125 and 40 01 126). However, practical
implementation of these proposals has shown that,
although some disadvantages can be overcome, the overall
property profile i8 still unsatisfactory.
French Patent 2 602 515 describes a two-layer pipe
comprising an outer layer of nylon 11 and an inner layer
of plasticised polyvinylidene fluoride. However, investi-
gations have shown that the barrier action to the flowing
medium is unsatisfactory.
In particular, permeation of methanol-containing fuels
has only been reduced to an inadequate extent by meani3 of
' ji. ' ' - " ' . ' " ' ' .' ~ '
, . .
21~4~06
-2- 23443-504
the abovementioned proposals.
Reduction in permeation by using novel intermediate
layers is therefore of crucial lmportance because, in particular,
the legally permitted emission values are constantly belng
reduced.
The object of the invention was to develop a polyamide
pipe having a good barrier action to the transported medium, in
particular to methanol-containlng fuels, satisfactory dimensional
stability and satisfactory resistance to mechanical stresses. In
partlcular, the improvement~ achieved should also be retained at
elevated temperatures.
Thus the present invention provides a multilayer plastic
pipe comprlslng an outer layer I made from a mouldlng composltion
based on a polyamlde, and a layer II adjacent to the outer layer,
said layer II made from a moulding composition based on
polyvinylidene fluoride, wherein layer II comprises a plasticiser-
free polyvinylldene fluorlde having a melt flow index of less than
about 14 g/10 min ~mea~ured in accordance with DIN 53 735 at 230C
and a load of 5 kg), and whereln the ratio of the thickness of
layer II and the combined thickness of layers I and II. is from
about 1-3 to about 1.20.
Suitable polyamides are primarily aliphatic homo- and
copolycondensates. Examples which may be mentioned are polyamides
~nylons) 4.6, 6.6, 6.12, 8.10 and 10.10. Preference is given to
polyamides 6, 10.12, 11, 12 and 12.12. [The numbering of the
polyamldes correspond6 to the internatlonal standard, the first
~ ':
, . ! ,, , , ' ,: '' ' : '
'' ' ' " ' '''' ~'' ' ' .' ' '' , ' ,, ' , i, i '... ,,,. '
,, . , , , , ' ' : ' ,:,, ,, ,: ` . ., :,
~-",, ` ` . ` : " `: ':
2114~06
-2a- 23443-504 ~ :
number(s) indicating the number of carbon atoms in the starting
diamine and the final number(s) indicating the number of carbon :
atoms in the dicarboxylic acld. If only one number is given, the :
starting materlal was an a1~-aminocarboxylic acid or the lactam .
derived therefrom (H. Domininghaus, Die Kunststoffe und ihre
Eigenschaften [Plastics and their Propertiesl, page 272, VDI- ;~
Verlag ~1976)).] .
,. . . . . .
: ~, , , , , , , :, .
` ' 211~06
- - 3 - O.Z. 4719
If copolyamides are used, these can contain, for example,
adipic acid, sebacic acid, suberic acid, i~ophthalic acid
or terephthalic acid as co-acid or bis(4~-aminocyclo-
hexyl)methane,trimethylhexamethylenediamine,hexamethyl-
enediamine or the like as co-diamine.
The preparation of these polyamides is known (for example
D. B. Jacobs, J. Zimmermann, Polymerization Processe~,
pp. 424-67; Interscienee Publishers, New York (1977);
DE-~ 21 52 194).
Other suitable poly~m~des are mixed aliphatic/aromatic
polyeondensates, a~ described, for example, in US Patents
2,07i,250, 2,071,251, 2,130,523, 2,130,948, 2,241,322,
2,312,966, 2,512,606 and 3,393,210, and in Rirk-Othmer,
Eneyelopedia of Chemieal Teehnology, 3rd Edn., Vol. 18,
pages 328 and 435, Wiley & Sons (1982). Other polyconden-
sates whieh are suitable as polyamides are poly(ether
ester amides) and poly(ether amides). Products of this
type are described, for example, in DE-A 27 12 987,
25 23 991 and 30 06 961.
The moleeular weight (number average) of the polyamides
i8 greater than 5,000, preferably greater than 10,000,
eorresponding to a relative viseosity (~r~) in the range
from 1.9 to 2.4.
The polyamides of the outer layer I. may eontain up to
40 % by weight of other thermoplastie~, 80 long as the
latter do not affeet the propertie~ aeeording to the
invention. Partieular mention may be made here of
polyearbonate ~H. Sehnell, Chemlstry and Physics of
Polycarbon~tes, Interscience Publishers, New York
(1981)1, aerylonitrile-styrene-butadiene eopolymers
(Houben-Weyl, Methoden der organisehen Chemie [Methods of
Organie Chemistry], Vol. 14/1, Georg Thieme Verlag
Stuttgart, pp. 393-406; Ullmanns Encyclop~die der teeh-
nisehen Ch~m~e tUllmann' B Encyclopaedia of Industrial
Chemistry]~ 4th Edition, Vol. 19, Verlag Chemie, Weinheim
; . ......... ., -, . . . . . . . .
, . . .
, .. ., . . , :
~ 4 - 2 ~ O 6 O.Z. 4719
(1981), pp. 279-284), acrylonitrile-styrene-acrylate
copolymers (Ullmann~ Bneyelopadie der teehnisehen Chemie
[ullmann~s Encyclopaedia of Industrial Chemistry], 4th
Edition, Vol. 19, Verlag Chemie, Weinheim (1981), pp.
277-295), acrylonitrile-styrene copolymers (Ullmanns
Eneyclopadie der teehnischen Chemie [Ullmann~s Encyclo-
paedia of Industrial Chemistry], 4th Edition, Vol. 19,
Verlag Chemie, Weinheim (1981) pp. 273 ff.) or poly-
phenylene ethers (DE-A 32 24 691 and 32 24 692, and
US Patents 3,306,874, 3,306,875 and 4,028,341).
If necessary, the polyamides of the outer layer I. can be
impaet-modified. Examples of suitable polymers are
ethylene-propylene or ethylene-propylene-diene copolymers
(EP-A-295 076), polypentenylene, polyoctenylene or random
or block copolymers made from alkenyl-aromatic compounds
with aliphatie olefins or dienes ~EP-A-261 748). N~ntion
may furthermore be made of impaet-modifying rubbers:
eore/~hell rubbers having a tough, resilient core of
(meth)aerylate, butadiene or styrene-butadiene rubber
having glass transition temperatures T~ of ~ -10C, where
the eore may be erosslinked. The shell ean be built up
from ~tyrene and/or methyl methaerylate and/or further
unsaturated monomers (DE-A 21 44 S28 and 37 28 685). The
proportion of impaet-modifying eomponent should be
seleeted 80 that the desired properties are not impaired.
~ayer II. eontains plastieiser-free polyvinylidene
fluoride. The preparation and strueture of the polymer
are known (Hans R. Rrieheldorf, H~ndbook of Polymer
Synthesis, Part A, Publisher Mareel Dekker Ine., New York
- Basle - Hong Xong, pp. 191 ff.; Runststoff Handbuch
~Plasties Handbookl, 1st Edition, Volume XI, Carl Hanser
Verlag, Munieh (1971), pp. 403 ff.).
It is also possible for eopolymer~ based on
polyvinylidene fluoride and containing up to 40~ by
weight of other monomers to be present aceording to the
invention. ~xamples which may be mentioned of sueh
_ 5 _ 2 ~ 0 6 o z 4719
additional monomers are: trifluoroethylene, ethylene,
propene and hexafluoropropene.
The polyvinylidene fluoride employed according to the
invention ha~ a melt flow index of < 14 g/10 min, pre-
S ferably from 5 to 13 g/10 min (DIN 53 735).
The thickness of layer II. is in the range from 0.05 to
0.2 mm, preferably from 0.1 to 0.15 mm. The pipe wall has
an overall thickness in the range from 0.5 to 2 mm,
preferably from 1 to 1.5 mm. The ratio between the thick-
ness of layer II. and the thickness of I. and II. is from1:3 to 1:20, preferably from 1:4 to 1:10. The diameter of
the pipe i8 in the range from 6 to 16 mm.
In addition to layer I. and the ad~acent layer II. in the
multilayer pipes according to the invention, further
layer~ may be applied to the inside of the pipe. An
example which may be mentioned here is a layer of modi-
fied polyvinylidene fluoride having significantly higher
electrical conductivity than the polyvinylidene fluoride
of layer II.
The moulding compo~itions for layers I. and II. may
contain conventional auxiliaries and additives, such as,
for example, flameproofing agents, stabilisers,
proces~ing auxiliaries, visco~ity improvers, fillers, in
particular those for improving the conductivity, pigments
and the like. The moulding compositions of layer I. or of
layers other than layer II. can also contain plasticisers
or impact modifiers.
The multilayer pipes are produced in a known manner, for
example as described above in the prior art. The pipes
are preferably produced by coextrusion.
The multilayer pipes accordin~ to the invention have,
even at elevated temperatures, extremely good resistance
to and a good barrier action to diffusion by
- 6 - 2 ~ 6 0 z 4719
(petro)chemical sub~tances, solvents and fuels. In
addition, it is also possible to produce, in addition to
a two-layer pipe, pipes of other types which comprise,
for example, three or more layer~. Preference is given to
multilayer pipe~ according to the invention in which
layer II. has been rendered electroconductive. It is also
possible to achieve good conductivity by incorporating a
further polyvinylidene layer of high conductivity
ad~acent to layer II. on the inside. Good electro-
conductivity is achieved by adding up to 15% by weightof, for example, conductive black, carbon fibres or the
like.
The plastic pipes accordinq to the invention are pre-
ferably employed for the transport of (petro)chemical
sub~tances or in the motor transport sector for carrying
br~ke, cool$ng and hydraulic fluids and fuel. A further
use of the multllayer pipes is for the production of
hollow articles, such as fuel tanks or filling nozzles,
in particular for the motor vehicle sector.
The results shown in the examples were determined using
the measurement methods below.
The determination of the solution visco~ity (relative
viscosity ~ ) of the polyamides is carried out usinq a
0.5% strength by weight m-cresol solution at 25C in
accordance with DIN 53 727/IS0 307.
The determ~nPtion of the melt flo~ indes of the
polyvinylidene fluorides i3 carried out in accordance
with DIN 53 735 at 230C and under a load of 5 kg.
The determination of the deflection i~ carried out at
23C on a pipe with a length of 15 cm. The pipe is
supported at two points 80 mm apart. The pipe is stressed
from above with a weight of 40 N in the centre between
the two supports. The deflection of the pipe is
determined in mm (DIN 53 452).
7 - 2 ~ 0 6 o z. 4719
The determ;nation of the diffusion of fuel components is
carried out on pipes using a fuel mixture (fuel FAM B:
25.35% by volume of isooctane, 42.25~ by volume of
toluene, 12.675% by volume of diisobutylene, 4.225% by
volume of ethanol, 15% by volume of methanol and 0.5% by
volume of water) at 23C or at 60C and at 50% atmos-
pheric humidity. The samples, having a length of 200 mm,
are filled with the fuel mixture and are connected to a
filled stock tank during the measurement. Diffuisiion is
determined as a 108~ in weight by diffusion over time
(measurement every 24 hours). The unit given is the
weight 1088 recorded per unit area, measured when the
diffusion process has achieved equilibrium, i.e. when the
weight 1088 determined per 24 hours no longer changes
with time.
Examples denoted by letters are not according to the
invention.
~a ples~
A. Co ponent I.
20 PA lsi Hard polyamide 12 (~t.ls 2.1; plasticiser contents ~ ~
O) :',
PA 2: Soft polyamide 12 (~r~S 2.1; plasticisers
N-butylbenzenesulphonamide; plastici3er contents
15 partsi by weight, per 100 parts by weight of
polyamide).
PA 3is Hard polyamide 12 (~r.1s 1.9; plasticiser content:
O)
PA 4s Hard polyamide 6.12 (~r~lS 1.9; pla~ticiBer con-
tent: 0)
0 B. Component II.
8 2~ o.z 4719
Z l: Hard polyvinylidene fluoride [melt flow index:
13 g/lO min; pla~ticiser content: 0; DYFLOR LE
(HULs AG)]
z 2: Soft polyvinylidene fluoride [melt flow index:
13 g/lO min; plasticiser: N-butylbenzene-
sulphonamide; plasticiser content: 15 parts by
weight per 100 parts by weight of polyvinylidene
fluoride; DYFLOR~ LE (HULS AG)]
Z 3: Hard polyvinylidene fluoride [melt flow index:
8.5 g/10 min; plasticiser content: 0; DYFLOR~ EE
(H~LS AG)3
Z 4: Soft polyvinylidene fluoride [melt flow index:
8.5 g/10 min; plasticiser: N-butylbenzene-
sulphonamide; plasticiser content: 15 parts by
weight per 100 parts by weight of polyvinylidene :~
fluoride; DYFLOR~ EE (HULS AG)] ::
C. Production of the multilayer pipe~ .
Two-layer pipes (external diameter 8 mm, overall wall
thickness 1 mm) are produced on a 5-layer pipe coextru-
sion line in which 3 channels remain closed, at a haul-
off speed of 20 m/min and a haul-off ratio of 2:1. The
outer layer i~ produced using a 45 mm/25 D extruder (melt
temperature 230C), and the inner layer is produced using
a 25 mm/25 D extruder (melt tempe.rature 220C).
.
.. . : ~ .
, ~ .. . .. ,.. ;. . : :
.. ,, ,
. :- , . . ' ' . .
-` 211~06
-9- 23443-504
~ __ _ ~ o _ __ ,_ ,_
:
4~ ~1 ~ ~I ~1 ~ ~ ~ ~ ~ l I
8~ _ _ _ _ _ _ __ _ _ ;~ ~
~o~ ~ ~ ~ ~ ~ o LV :
~ D ~ O ~ ~1 ~ ~I r~ ~ ~ O O : ~
~ V '~
_ _ _ _ _ _ _ _ _ _ ~: :
~fi , o~ ~ ~ co ~ ~ o~ ~o co
,~ ~ _ o o o o o o o o o o
.. ~ _ _ _ ':~'
o _ _ _ _ _ _ _ _ _ _
,. ,. ~ ~ ~ ~ ~ ~ ~ ~
~,,,:; :..~.
_ _ _ _ _ _ _ _ _ _
.
~ ~ ,, ~ ,, ~ ,, ~ ,. ~ ~ I
..~ ~ o o o o o o o o o o
,. ~
' . "
~ ,, ~ ,. ~ ,, ~7 ~ ~ ,, I
~ ~ ~ ~ r~ ~ ~ ~ ~ ~ ~ ~
~ - - - - - - - - - -
J~
~¦ L~L --L_; L__ '~
.
U~ o
.
