Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
"091/09732 PCT/US90/07~05
- 1 - 2~7~ ~13
SULFONATED ,~lULTILAYER CO~ITAINEn~_AND A METHOD
FOR PRODUCIN~ THE SAME
Prior art
For the weight reduction of automobiles, many
attempts are being made to make the fuel tank from plas-
tics and a variety of plastics are being offered to this
end. The fuel tank is.required to have gasoline barrier
5 properties as well as qood mechanical strength and impact
resistance. None of the plastics avai~able meet this .
requirement.
In general, polyamides are ~uperior in gasoline
barrier properties but poor in impact resistance. By con-
trast, polyolefins are inferior in gasoline barrier prop-
erties but superior in impact resistance. For this
reason, many attempts ~ave been made to produce a con-
tainer superior in both impact resistance and gasoline
barrier properties from a polyamide and polyolefin i~
combination.
For example, Japanese Patent Publlcation No.
14695~19B5 discloses a molded article of composite mate-
rial composed of polyolefin, polyamide, and alkylcarboxyl-
substituted polyolefin, with the polyolefin forming a co~-
ti~uous matrix phase, t~e po~yamide existing in layer formin the cont~nuous matrix phase,~ and the alkylcarboxyl-
su~stituted polyolefi~ ex$stlng between the polyamid~
layer~. ~ container for~ed ~rom this compo~ite mater~al
is poor i~ low-temperature.impact resistance despite the
modified polyolefin incorporated therein a~d the polyamlde
SUIE~5TITUTE SHET
~ . ~
: :
~ ; . .. ...
WO91/09732 ~ PCT/US90/0~0
- 2 -
e\~
dispersed therein in layer for~, because the polyamide
layer is poor in adhesion to the continuous matrix phase
of polyolefin. Another disadvantage is that t~e composite
material of multilayer structure makes it difficult to
recycle flash.
on the other hand, there has been proposed a means to
improve the gasoline barrier properties by substituting
sulfonated or fluorinated polyolefin for polyamide having
a poor affinity (adhesion) for polyolefin. For example,
Japanesc Patent Pu~lication No. Z3914/1971 discloses a
polyolefin container having a sulfonated surface which is
substantially impermeable to fuels and organic solvents.
Problems to be solved by the invention
The above-mentioned impe~eable container, howe~er,
has a disadvanta~e that the sulfonation for surface treat-
ment costs much time and expenses. Moreover, it has been
found t~at the sulfonation itself is not satisfactory.
Accordingly, it is an object of the present invention
to provide a sulfonated multilayer container which exhib
its good gasoline barrier properties owing to the high
degree of s~lfonation. It is anothex object of the
present invention to prov~de a method for produc~ng the
- sulfonated multilayer contalner efficiently.
~e~ns to solve the problems
-25 ~ In order to`achieve the ibo~e-mentioned objects, the
- presene inventors carried out a serieS of researches ~hich
led to the finding that the gcGd gasoline ~arrier proper-
(
.
- S1113STlTUoll~E SHET
. ..... ,.. ,... ..... , . . ~ . . , , , ... ~,
; . . ,
:..
. . , ~ . ,:` . ' .. . . .. ~; . , , ~ . .,
'
~ 91/09732 2 ~ ~ ~ 8 ~ ~ PCT~USgo/07s05
- 3 -
tles and impact resistance are obtained by multilayer blow
molding from sulfonated high-density polyethylene in
combination with untreated hig~-density polyethylene
instead of sulfonating the molded container, the former
S component being prepared by sulfonating high-density poly-
ethylene in the form of powder ha~ing a large surface
area. This finding led to the present invention.
The sulfonated multilayer container pertaining to
the present invention co~prises an interlayer formed
from sulfon~ted high-density polyethylene powder and
inner and outer layers of high-density polyethylene.
According to the present invention, the sulfonated
multilayer container may have, if necessary, an additional
layer of modified high-density polyethylene between the
interlayer and each of the inner and outer layers, said
first layer having good adheslon to the other layers.
Also, the method for pros~ucing the sulfonated multi-
layer container according to the present invention com-
~prises the steps of sulfonating high-density polyethylene
~ powder having a particle dia~eter of 100-3000 ~m with a
~as ~ontaining 12-25 vol~ of S03 at 45-60 C, and subjecting
the sulfonated high-den~ity polyethylene tog~ther with
untreated high-density polyethylene to ~ultilayer blow
.. ~ . . . . . . . ... .. . . .~, .
mold ~ process, so that the sulfonated hig~-density poly-
~, 25 ethylene forms the interlayer and the untreated high-
density polyethylene forms t~e inner and outer Iayers.
51JBSTITUl'E. S~E1'
, ~ . ................ ~
.
c~
~r_,J
W091/~9732 r~l PCT/US90io750
C~2
- 4 -
In what follows, the present invention will be
described in more detail.
The in~erlayer in the sulfonated multilayer container
of the present invention is made of high-density polyeth-
S ylene having a density higher than 0.93 g/cm3~ preferably0.94-0.97 g/cm~, a weight-average molecular weight higher
than 100,000, prefera~ly higher than 150,000, a melt index
~ML: l90 C, 2.16 kg load) lower than 1.0 g/lO min, prefer-
ably 0.2-0.01 g/10 min (which translates into a high-load
melt index (HLMI: l90'C. 21.6 kg load) lower than 70 g/10
min, preferably 20-1 g/10 min).
The greater the weight-average m~lecular weight, the
better the molded product in barrier properties and impact
resistanca. Therefore, it is necessary that the high-
density polye~hylene have a wei~ht average molecularwei~ht higher than 100,000, preferably higher than l50,000
~say 200,000~.
With a melt i~dex higher than 1.0 g/lO min, the high-
density polyethylene is liable to dra~down during multi-
layer blow moldlng. The one.having a melt. index of
0.2-0.01 gllO min is desirable in vie~ of moldability and
....
impact resis~ance. Incidentally, the MI of small values
may be replaced by the HLMI (high-load melt index) in
` ` order to avold errors in measurements. With an HL~I higher
:
5llE~5TlTUTE SI~EE~T~
,, ` ` ,~
` .' ;:' : ~ ,~ .
:, .. ... . ~ `
~7~
PCI/US90/07505
`"O 91/09732
. ..
than 70 g/10 min, the high-density polyethylene is liable
to excess drawdown. The preferred HLMI ranges ~rom 20 to
1 g~10 min.
Incidentally, the high-density polyethylene is not
limited to homopolymers. It may also include copolymers
of ethylene with an ~-olefin such as propylene, butene-l,
and hexene-1.
According to the present invention, the h1gh-density
polyethylene is sulfonated in the form of powder. Having
a large surface area, powder is capable of rapid and effi-
cient sulfonation. For the object of the present inven-
tion to be achieved, the hiqh-density polyethylene powder
should have a particle diameter smaller than 5,000 ~m,
preferably from 100 to 3,000 ~m. With a particle diameter
larger than 5,000 ~m, the high-density polyethylene powder
undergoes sulfon~tion so inef~iciently that it is a non-
~ sense to use powder. Reducing the particle diameter belo~
;~ 100 ~m produces no effect commensurate with iS.
The sulfonàtion of high-density polyethylene powder
is acco~plished by exposing the powder to an SO~-containing
gas. The treatlng gas usually contains SO~ ln an amounE of
12-25 vol%, with the remainder being an inert gas such as
, . . ..
~ nitrogen. For effici`ent sulfonation, the SO~-containinq
....
gas should be passed through the high-density polyethylene
;` powder held in a breathable container such as a wire net.
5UB5TITU~E: S~EI~.
., - - - ............... ... .
- : ;
WO91/09732 ~_ PCT/US9~io750
An alternative method for sulfonation consists of fluidiz-
ing the ~igh-density polyethylene powder with the SO~-
containing gas in a fluidized bed. In either cases, t~e
sulfonation should be performed at 40-70 C, preferably
45-60'C, for 3-lO minutes.
After the completion of sulfonation, the S03-
containing gas should be purged with nitrogen gas, and
residual S03 should be removed by absorption into sulfuric
acid in a vent scrubber.
In this way, there is obtained a sulfonated high-
density polyethylene powder having a degree of sulfonation
of 1-5 wt%. With a degree of sulfonation lower than 1
w~.~, the sulfonated high-density polyethylene powder does
not provide.satisfactory gasoline barrier properties.
Reducing the degree of sulfonation below S wt% produces
not effect commensurate with it.
The sulfonated high-density polyethylene powder sub-
sequen~ly undergoes ~he step oE neu~cralizi-~g s~llfonic
groups contalned therein~ Neutralization ~ay he accom-
plished ~ith a neutralizing agene such as sodium hydrox-
- ide, potassium hydroxide, lithium hydroxide, sodium car-
bonate, sodium bicarbonate, potassium carbonate, potassium
.
carbonate, lithium bicarbonate, and ammonia.~ ~mmonia is
preferable because of i~s.ability to be used for gas phase r
- `---25 reactiOn.
. ~ .
.
513E~STITUI~E S~EET;
.
:
. . ;
~091/09732 2 ~ 7 ~ ~13 PCT/~S90/07~05
The neutralization is accomplished ~ith a neutraliz-
ing agent in an amount of 2 mol for l mol of sulfonic
groups. Therefore, the volume of ammonia yas should be
twice that of SO~ gas that has bonded to the high-density
S polyet~ylene. Neutralization with ammonia gas should be
perfonmed at 45-60 C for 4-9 minutes. After the neutral-
ization is complete, the residual ammonia gas should be
purged with nitrogen gas.
In the meantime, basically the high-density polyeth-
10 ylene for the inner and outer layers may be the same as
that used for the interlayer. It should preferably be a
high-~olecular weight high-density polyethylene having a
weig~t-average molecular weight higher than 150,000
from the standpoint of impact resistance.
According to the first embodiment of the present
~` invention, the multilayer comtainer is composed of three
layers, that is, an interlayler 1 of sulfo~ated higb-
1 density polyethylene and an inner layer 2 and an outer
layer 2' of untraated high-density polyethylene, as shown
20 in Fig. l. The interlayer 1 should have a thickness of
10-500 ~. With a t~ickness less than lO ~m, the inter-
layer l does not pro~ide th~ multilayer container ~it~
.' . .~ .. - - .
satisfactory gasoline barrier properties. With a
thickness in excess of 500 ~, the i~terlayer 1 does
?.5 not produce any effect commensurate with the increased
~ ... .,, . . , . : . . , - ..
thicXness. The
511BSTITIIT. S~ T
''
.. . . . .
', ' , ~,
:, ,.
c~
WO 91/09732 -~C~ PCr/US90~0750C~.
c~ - 8 -
preferred thickness of the interlayer 1 is 100-200 ~m. On
t~e other hand, the inner layer 2 and the outer layer 2'
both should have a thickness of 1.5-5 mm. With a thick-
ness less than 1.5 mm, they do not provide the multilayer
container with sufficient ~echanical strength and impact
resistance. With a thickness in excess of 5 mm, they do
not produc~ any effect commensurate with ~he increased
thickness.
According to the second embodiment of the present
10 invention, the multilayer container is composed of an
interlayer 1 of sulfonated high-density polyethylene, an
inner layer 2 and an outer layer 2' of untreated high-
density polyethylene, and additional layers 3 and 3' of
modified high-density polyethylene each interposed between
15 the interlayer 1 and the inner layer 2 and between the
interlayer 1 and the outer layer 2', as shown in Fig. 2.
The modified high-density polyethylene is one which
is ohtained by modifying t~e same high-density polyethyl-
ene as mentioned above wlth an unsaturated carboxylic acid
20 or anhydride t~ereof; Examples o~ t~e unsaturated carbox-
- ylic acid or anhydxide thereof include monocarboxylic acid
lsuch as acrylic acld and methacryIic acid), dicarboxylic
acid (such as Maleic acid, fumaric acid, and itaconic
acid), and dicarboxylic acid anhydride lsuch as.maleic
.
~ 25 an~ydride and itaconic anhydride). Preferable among them ~ I
519@~ ITIJl E:~ S~IEET
- - .
; `. ............... .
"' ` ~; ` ' '' '
'~91/09732 ~ æ~ 3 PCT/~S90/07~05
are dicarboxylic acids and anhydrides thereof.
The modified high-density polyethylene should contain
the unsaturated carboxylic acid or anhydride thereof in an
amount of 0.2-0.6 mol%. With an amount less than 0.2
mol%, it does not permit the modified high-density poly-
ethylene to firmly bond to the high-density polyethylene.
With an amount in excess of 0.6 mol%, it does not produce
any effact commensurate with the increased amoun~.
In the second embodiment, the additional layers 3 and
3~ of the modified high-density polyethylene, each inter-
posed between the interlayer l and each of the inner and
outer layers 2 and 2', should have a thickness of 10-500
~m. With a thickness smaller t~an lO ~m, the additional
layers 3 and 3' of the modified high-density polyethylene
do not exhibit good adhesion to the interlayer 1 and the
inner and outer layers 2 and ~', and hence contribute
little to the improvement in impact resistance. With a
thickness in excess of $00 ~m, they do not produce any
effect commensurate wit~ the increased thickness. Inci-
dentally, the interlayer l and the inner and outer layers2 and 2' may have the same thicknesses as mentioned above.
; ~ ~ In either cases of the first and second embodiments,
the multilayer container may be produced by multilayer
- blow molding process, which is carri~d out as follows:
5UB5TITUT S~IEE~:T
.. , . . .. ... .. . .. . . .... .,, ... ~ . .. ,, .. . ~ .. ~. .. ... . . .. ........ .
; . ,
. .
. .: .
WO 91/09732 ~ PC~/US90/075~-
~ - .
6~
- 10 _
The sulfonated ~igh density polyethylene for the inter-
layer and the untreated high-density polyethylene for the
inner and outer layers are melted and mixed separately at
180-220-C. The melts are fed simultaneously to the multi-
layer blow molding die and then extruded from it into a
parison. The parison is blown up in a mold by hot com-
pressed air to be made into a molded article of desired
shape and size. ID the case where ~he additional layers
of the modified high-density polyethylene are to be
formed, the melt of the modified high-density polyethylene
should be fed to the multilayer blow molding die simulta-
neously with other melts.
. Exampl es
The invention will be explaine~ in more detail with
reference to the following examples.
J, ~xample 1
High-density p~lyethylene ~B-5742~ (a product of
Tonen SeklyukagakU XOK~ having an HLMI of 4 g/10
. , .
min and a density of 0.945 gtcm~ in the fon~ of powder
- 20 ~ha~ing a partiele diameter of 150-2gO0 ~) was sulfonated
ln the following manner. The powder, held in a wire net
container, was exposed at 53'C or 4 minutes to nitrogen
--- gas containing 18 vol% of 503 which waa flow'ng at a flow
ra~e of 5 L/min. ~he remaining gas was purged with nitro-
gen gas and the residual S03 was absorbed into H2SO4 by
:
,'
SUBSTITUTE S~EET ;; ~`
.
'`':
,
.
~ 91~09732 2~7 ~ ~3 PCT/US90/07505
.'
- 11 -
means of a vent s~rubber.
The high-density polyethylene powder was subsequently
exposed to an ammonia gas stream at 53 C for 6 minutes for
the n~utralization of sulfonic groups. The remaining
S ammonia gas was purged with nitrogen gas. Thus there was
obtained a sulfonated high-density polyethylene powder
having an ~LMI of 5 g/lO min and a density of O.9S0 g/cm3 .
- She degree of sulfonation was measured by fluores-
cence X-ray analysis. In actual pr~ctice, a working curve
was prepared for a sulfonated hi~h-density polyethylene
plate, and a table showing the relationship between the
degree of sulfonation and the number of counts was pre-
pared from the working curve, so that measurements ~ere
made by comparing the number of counts of sulfonated high-
lS density polyethylene powder with that of reference in the
table. The results of the analysis showed that the degree
of sulfonation was about 2 wt%. In the meantime, it is
considered that the sulfonated lligh-density polyethylene
has a structure as s~lown below. ,
~ ~1 H 1 H
- C --C - C ---C -
3 H ~1. n ! SO; ,
~NH4. (NH~j~ )
A 40-liter mult~layer container of the following
struCture was produced by multilayer blo~ molding process
SUB5TITIJTE~SS~EE~T
.. . .. ... ~ . .. ., . ~ , ~ .. ... . . . . . . . .... .. .. . ...
,
. ~ ' ' ,
,
c~
WO91/09732 ~ PCT/US90/075~;
C~
C~
- 12 -
from ~he sulfonated high-density polyethylene powder (for
the interlayer~, maleic anhydride-modified high-density - j
polyethylene containing 0.4% of maleic anhydride ~made by
Tonen Sekiyukagaku K.~ or the adhesion layers),
and untreated high-density polyet~ylene ~-S742) ~for the
inner and outer layers). Blow molding was accomplished by
using a large-sized multilayer blow molding machine with
an accumulator head (made ~y The Japan Steel Works, Ltd.).
Inner layer: HDPE (B-5742), 1.5-5 mm thick
Adhesion layer: maleic anhydride-modified high-density
polyethylene, 150 ~m thick
Interlayer: sulfonated %DPE ~B-5742), l00 ~m thick
Adhesion layer: maleic anhydride-modified high-density
- polyethylene, 150 ~m thick
15 ~ Outer layer: HDP~ ~B-5742), l.5-5 mm thick
This multilayer cc.~tainer was tested for impact
resistance and gasoline barrier properties in the follow-
ing manner. - ~
~l) Low-temperature drop impact test
This ~est was perr'ormed on the multilayer container,
co~pletely filled with water, under the following condi-
tion. ' .
Temperature: -40 C ~~
I Drop heigh~: 6 m, 9 m, and-12 m
.. I
.
SU13~TlTl)TE: 591EET . I
. , .. ,... ~ . ......... ...
.
',' ' . ' , ,
~'~91/09732 2 0 7 ~ 3 1 3 PCT/US90/07505
Drop direction: with the pinch-off part parallel to
the ver~ical direction
Minimum wall thickness of the container: 3.0 mm
Total weight: 46 kg (completely filled with water)
(2) Gasoline permeability
The multilayer container (90 liters) was filled with
20 liters of gasoline, and tAe half-filled container was
allowed to stand at 40 C for 8 weeks. The amount of gaso-
line lost during this period was recorded to calculate the
permeability to gasoline. This test conforms to the stan-
dards of the Ministry of ~ransport (No. 1327~ ~echnical
Standards for Plastics Fuel Tank for Passenger Cars). The
results are shown in Table 1.
Example 2
A 40-liter multilayer container of the following
three-layer structure was produced from t~e sulfonated
high-density polyethylene prepared in.Example 1 and
- untreated high-density polyethylene ~B-5742).
Inner layer: H~PE (B-5742j, 1.5-5 mm thi~k
~ Interlayer sulfonated HDPF, ~B-5742), 100 ~m thick
- Outer layer: HDPE (~-5742~, 1.5-5 mm thick
` This~multilayer container was tested ln the same
... . - .. ~
- manner as in Example 1. The results are shown in Table 1.
; ~ ~ '
51JlB~;TlTU~F 5~EET
... ` ` ., ` ` .: .,.... . ~, . , .: ,. . .... .
WO 91/09732 ~-.' PCT/US90/075
~ .
~- 14 _
Example ~
The same procedure as in Example l was repeated for
sulfonation, except that B-5742 (powder of high-density
polye~hylene for sulfonation) was replaced by a powder
S t200-2~00 ~m in particle diameter~ o~ ~-6012 having an MI
of 0.15 g/l0 min and a density o~.O.q52. g/cm~ ~a product of
Tonen Sekiyukagaku K.K.). There was obtained a
powder of sulfonated HDPE having an MI of 0.l5 ~l0 min
and a density of 0.957 g/rm~.
A 40~ er mul~ilayer container of the following
three-~ayer structure was produced by mult.ilayer blow
molding process from the sulfonated high-density polyeth-
ylene (for the interlayer) and untreated high-density
polyethylene ~B-57421.
Inner layes: HDPE (B-5742), 1.5-5 mm thick
Interlayer: sulfonated HDPE ~B-6012), 100 ~m thick
Ou~er layer: HDPE (B-5742), 1.5-5 mm thic~
This multilayer container ~as tes~ed i~ the same
; manner as in Example l. The results are shcwn in Table lo
Comparative Example 1
~, ,
A 40-liter container of single-layer
structure having the same shape and size as that in
Exampl~ 1 was produced by blow ~olding process from a-s742
. high-density polyethylene. This single-layer container
was tested in the same manner as in ~xample l. The
.
SUl~STlTiJTE 5~E:FT. .~
...... . .. ~ . . ..... . . . . . . . . . .
. ~ , . .
: - , ,
.. ~. ; :
- ,
O91/09732 2 ~ 7 ~ ~ ~ 3 PCT/VS90io7505
results are shown in Table 1.
Comparati~e Exampl a 2
A 40-iiter five-layer container of the following
structure having the same shape and size as that in
Example 1 was produced by multilayer blow molding process .
rom high-density polyethylene lB-5742), nylon 6 (CM-1046,-
made by Toray Industries, Inc.), and maleic anhydride-
modified high-dens~ty polyethylene containing 0.9~ sf
maleic anhydride (made by Tonen Sekiyukagaku K.K.).
~ Inner layer: HDPE ~-5742), l.S-5 mm thick
Adhesion layer: maleic anhydride-modified high-density
. polyethylene, 200 ~m thick
:~ Interlayer: nylon S, 100-200 ~m thick
: Adhesion layer: maleic anhydride-modified ~igh-density
polyethylene, 200 ~m thick
Outer layer: ~DPE ~B-5742), 1.5-5 mm thic~
This multilayer con~ainer was tested i~ the same
manner as in Example 1. T~e resules are shown in Table 1
Tabl~l
.___ _ _
- ~ampleNo. Dr~ ~ _
C~n~t~e 6m 9m 12m Penneab~-~ d
~ampleNo.~ . ~asoline~day)
. . . ... _
` 1 _ not broken nol broken not broken .
- -~ - 2 not broken not broken nol broken 0.7
,.~ , 3 - ~ n~t blokënnot broken~ ~` r~ot broken . _
. . - - !~ . nbt br~k-n not broken- nol broken . '
(2) r ot b~oken ~ ken broken 0.5
_ .. _ .
SIIB5TIlUT@: S13E~T~
,, .. , ...... .. ,.. ........ , ., .. " . ., ... .... , ,. ..... , . .,.. , . ; , ~ . . .... ....... ...
WO 91/09732 C~o P~r/lJS90iO750
~ - 16 -
For any fuel tank to meet the requirement for gaso-
line barrier properties set up by the SHED regulation in
the U.S., it must have a gasoline permeability lower than
2 g/day. It is noted from Table l that the multilayer
containers in Example 1 to 3 all meet this requirement.
By contract, the single-layer container in Comparative
Example l has a gasoline permeability as high as 8.0
g/day.
on the other hand, there are no regulations for
impact xesi~tanoe; however, it is necessary that the fuel
tank, an important component, should not be broken at the
worst. The ~ultilayer container having a nylon interlayer
does not have sufficient impact resistance.
Effect of the invention
As mentioned above, the present invention provides a
sulfonated multilayer container which is composed o an
interlayer of highly sulfonated high-density polye~hylene
and inner and outer-layers of high-density polyethylene.
- Because of this structure, the multilayer container exhib~
~: .
` 20 its good gasoline barrier properties as well as high
- impact resistance. The interlayer of sulfonated high-
density polyethylene is not affected by gasoline because
.. _ ~ . . . . .. . ..
-- - it--is isolated f~om gasoline.by~ the inner layer. There- r
fore, the multilayer container of the presënt invention is
- 25 suitable for use as the automotive fuel tank and other
. .
. . .
,.~ .
51Jg35TlTlJTE S~3EET .
: , ,, `
, ~ .,
. .. ..
.. .
. .
,~ . . : . , , ;" . , ~ .
. , ~ . . . .
~ ~ 7 ~ pC~/US9~t075~
~vo 91/09732
containers which need gasoline barrier properties.
4. arief Description of the Drawings:
Fig 1 is a partial sectional view showing the struc-
ture of the multilayer container in one embodiment of the
present invention.
Fig. 2 is a partial sectional view showing the struc-
ture of the multilayer container in another embodiment of
the present invention.
1 ... Interlayer
2, 2' ... Inner and outer layers
3, 3' ... Modified high-density polyethylene layers
.` ; .
" ' .
S IJ~;TlTlJTE. 5~EES
:
:, . . .
,
