Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a multilayered con-
tainer having a multilayered structure, and more specifi-
cally, to a multilayered container having excellent
delamination resistance, transparency, gas-barrier
property and mechanical strength and a process for
production thereof.
2. Description of the Prior Art
1~ In recent years, hollow containers of thermo-
plastic resins have been widely used to hold cosmetics,
foods and drinks because of their various advantages such
as light weight and safety against bursting. In parti-
cular, the development of hollow containers composed of
1~ polyethylene terephthalate has rapidly advanced as a
result of the improvement of the biaxial stretch-blow
molding technique.
Biaxially oriented containers composed of a
thermoplastic polyester resin, typically polyethylene
2C terephthalate, do not have all the necessary properties.
For example, they have insufficient gas-barrier property
to oxygen and carbon dioxide gas, and will impair the
flavor of foods and drinks requiring a high level of
gas-barrier property.
2~ In an attempt to eliminate this defect, a
multilayered-container was proposed which is produced by
injecting a thermoplastic polyester and a m-xylylene
group-containing polyamide resin (MX nylon~ as a gas-
barrier thermoplastic resin in this sequence into a
30 single mold from separate injection cylinders to form a
three-layered parison composed of an inside and an out-
side layer of the thermoplastic polyester resin and an
inside core layer of M~ nylon, and biaxially blow-molding
~3~L01~9
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the parison ~Japanese Laid-Open Patent Publications Nos.
128516~1982 and 128520/1982; and corresponding U. S.
Patent No. 4,335,901). If in this method, the amount of
MX nylon injected is decreased in an attempt to decrease
the thickness of the inside core layer, the inside core
layer is formed only partly, and the resulting container
has insufficient gas-baerier property.
The present inventors developed an improvement
over this prior method in which three layers of the
thermoplastic polyester resin and two layers of the ~X
nylon are laminated alternately to form a five-layer
structure by injectin~ ~he thermoplastic polyester resin,
MX nylon and again the thermoplastic polyester resin in
this sequence, and consequently, the amount of the MX
nylon injected can be decreased from that in the prior
art although there are two layers of the MX nylon. This
method was applied for a patent tJapanese Laid-Open
Patent Publication No. 240409/1985 and corresponding
U. S. Patent Application Serial No. 731,953 and Japanese
Laid-Open Patent Publication No. 108542/1986 and corres-
ponding U. S. Patent No. 4,728,549?~
A method was also proposed in which the thick-
ness of the inside core layer i8 decreased by first
injecting the resin forming the inside and outside layers
and then simultaneously injecting the resin forming the
inside and outside layers and the resin forming the
inside core layer ~Japanese Patent Publication No.
16326/19~5 corresponding to U. S. Patent No. 4,174,413~.
In the resulting three-layer structure, the inside core
layer is deviated toward either of the inside an~ outside
layers.
Generally, thermoplastic gas-barrier resin
(resin B hereinafter) including MX nylon have poor
affinity for resins (resin A hereinafter) such as thermo-
plastic polyester resins, and the delamination resistanceis weak. If a curved surface having a small radius of
~3~ 9
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curvature exists in the rib portion of the container and
that curved surface is stretched by the gas pressure of
the contents, delamination between resln layers tends to
occur at the stretched part. The delaminated part sep-
arates into two films, and the container looks slightlywhite to present an undesirable appearance. The present
inventors extensively studied this problem, and finally
found that ~hen a curved surface having a radius of
curvature of not more than 5 mm on the rib portion o~ the
container is stretched by the gas pressure of the con-
tents, delamination occurs with a high probability in a
par~ composed of five resin layers, whereas it occurs
with a very low probability in a part composed of three
resin layers; and that the gas-barrier property of the
same amount of the gas-barrier resin is better at the
part composed of five layers containing two layers of the
gas-barrier resin than at the part composed of three
resin layers containing one layer of the gas-barrier
resin. This finding has now led to the present inven-
tion.
SUMMARY OF THE INVENTION
, _
It is an object of this invention to provide ablow-molded container free from delamination between
resin layers.
Another object of this invention is to provide
a blow-molded container having excellent gas-barrier
property and mechanical property and being free from
delamination.
Still another object of this invention is to
provide a blow-molded container having excellent gas-
barrier property and mechanical strength and being free
from occurrence of delamination at a part having a radius
of cur~ature of not more than 5 mm in the rib portion of
the container.
A further object of this invention is to pro-
vide a blow-molded container which does not undergo
~3~
delamination even after it is used for a long period of
time as a container for holding potable watee which
require gas-barrier proper~y to oxygen and/or carbon
dioxide gas.
The objects of this invention are achieved by a
biaxially oriented blow-molded container composed of a
thermoplastic gas-barrier resin (resin B) and a thermo-
plastic resin (resin A) other than resin B; wherein the
mouth portion is composed of resin A and substantially
non-oriented, and the remainder consists of a portion
composed of two layers of resin A and one layer of resin
B which are laminated with the resin A layer and the
resin B layer occurring alternately and a portion com-
posed of three layers of resin A and two layers of resin
B which are laminated with the res.in A layer and the
resin B layer occurring alternately.
BRIEF ~ESCRIPTION OF TEiE ACCOMPANYING DRAWINGS
Figures 1, 2 and 3 are partly broken-away front
views of examples of the blow-molded container of this
inventiOn;
Figure 4 is an enlarged view of a portion
encircled in a broken line in Figure l;
Figure 5 is a sectional view taken on line A-A
of Figure 2;
Figure 6 is a sectional view, corresponding to
Figuee 5, in which the resin B layer is located on the
outside;
Figure 7 is a schematic view of an ex~mple vf
an apparatus used to produce the parison in the present
invention;
Figures 8 to 10 are sectional views of examples
of the parison obtained by the present inYention;
Figures 11 to 14 are sectional views showing
the process of forming the parison shown in Figure 8; and
3s Figures 15 to 18 are sectional views showing
examples of parisons formed under inappropriate condi
tions.
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DETAILED DBSCRIPTION OF PREFERRED EMBODIMENTS
The present invention will be described by
reference to the accompanying drawings.
Figures 1 t 2 and 3 are partly broken-away front
views showing examples of the container of the invention.
Figure 1 shows a self-supporting stretch blow-molded
bottle. Figure 2 shows a base cup-equipped stretch
blow-molded bottle. Figure 3 is a self-supporting
stretch blow-molded bottle having ribs existing at the
lower part of its body portion.
In the example of Figure 1, the bottle includes
a vertical rib 7 as a site having a small radius of
curvature at its shoulder portion 4 and a lateral rib 8
as a site having a small radius of curvature at its
lS bottom portion S. Hence, the shoulder portion 4 and the
bottom portion S are each of a three layer structure
composed of two layers o~ resin A and one layer of resin
B, and the body portion 6 of the bottle is of a five-
layer structure composed of three layers of resin A and
two layers of resin B. Figure 4 is an enlarged view of
the circular part shown by a broken line in Figure 1
presented in order to clearly show the resin B layer
shown by a solid line in Figure 1.
In the example of Yigure 2, the bottle has a
vertical rib 9 and a lateral rib 10 as sites having a
small radius of curvature at its shoulder portion 4.
Thus, the ~houlder portion is of a three-layer structure
composed of two layers of resin A and one layer of resin
B, and the body portion 6 and the bottom portion 5 are
3~ each of a five-layer structure composed of three layers
of resin A and two Iayers o~ resin B. In Figure 5 which
is an enlarged view taken along line A A of Fig~re 2, the
left side is the inside of the bottle and the right side
is the outside of the bottle~
In the example of Figure 3, the bottle has a
lateral rib 7 and a vertical rib 8 as sites having a
l3~1b89
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small radius of curvature at its body portion 6. Hence,
the shoulder portion 4 and the body portion 6 above the
lateral rib 7 are of a five-layer structure composed of
three layers of resin A and two layers of re in B, and
the bottom portion below the lateral rib 7 is of a
three-layer structure composed of two layers of resin A
and one layer of resin B.
As shown in Figures 1 to 3, thle opening end
part 3 of the mouth portion of the bottl~e and its
vicinity are substantially unstretched and composed of
resin A. The reason for this i5 that since this part has
a small surface area and a large thickness~ it does not
so much affect the gas-barrier property of the entire
bottle, and that the gas-barrier resin ~resin B)
generally has high hygroscopicity, and when not oriented,
absorbs water and becomes whitened to present an undesir-
able appearance.
When the radius of curvature of the container
becomes small and the resin layers of the bottle are
stretched under internal pressures during use, an inter-
layer shear strain is generated and delamination of the
eesin layers tends to occur. The stretch blow-molded
container from a parison is for~ed by introducing a
high-pressure gas into a heated parison and inflating it
25 f rom inside and pressing it against the mold. Hence, a
bent part of the container has a sharp shape of a small
radius of curvature faithfully following the shape of the
mold as it is near the outside close to the mold. In
Figure 6 which is an enlarged view taken along line A-A
in Figure 2, the resin B layer is positioned close to the
outside. Since the radius of curvature of the resin B in
the the rib portion of the container is smaller than that
of the resin B layer in Figure 5, delamination tends to
occur in comparison with the case of Figure 6~ Accord-
3~ ingly, it is preferred to position the resin B layer nearthe inside as in Figure 5.
~3~
On the other hand, since the gas-barrier resin
generally decreases abruptly in gas-barrier property as
the humidity approaches 100 %, it is preferred to posi-
tion ~he gas-barrier resin layer (re~in B layer) at a
part near the outside which is remote from the contents.
In the present invention, there are two gas-barrier
layers in that portion of the container which is other
than the sites having a small radius of curvature in the
rib portion, and one of them is located near the outside.
Accordingly, the reduction of the gas-barrier property is
little.
As stated above, th~ blow-molded container of
this invention comprises a substantially non-oriented
portion of resin A including the opening end of the mouth
portion of the container, and the remainder consisting of
a portion composed of two layers o resin A and one layer
of resin B alternately }aminated and a portion composed
of three layers of resin A and two layers of resin B.
The container can be produced by producing a parison
having the corresponding layer structure and then bi-
axially stretching and blow-molding the parison.
The method of producing the parison will be
described.
Figure 7 is a schematic view showlng a device
2S for producing a parison which is a precursor of the
container of the invention. This device is provided with
a cylinder 12 for resin A (reference numeral 11 and a
cylinder 13 for resin B ~refeeence numeral 2) and are
connected to a mold 14 at a nozzle portion lS. The
resins A and B melted in tbe cylinders 12 and 13 re-
spectively are injected simultaneously or alternately
into a cavity 18 of the mold 14 via a hot runner portion
16 and a g2te 17.
The parison as a precursor of the container of
the invention is formed by properly combining simultane-
ous injection and alternate injection of the resins A and
13(~1~8~
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B using the above device. This combination differs
depending upon the positions at which three layers and
fives layers are formed. In the following description,
typical examples shown in Figures 8 to 10 will be taken
up. In the case of Figure 8 in which three layers, five
layers and three layers are formed f rom the opening end
part of the mouth portion toward the bottom portion
~3~/3 layers); in the case of Figure 9, three layees and
five layers are formed from the opening end part of the
mouth portion toward the bottom portion ~3/5 layers); and
in the case of Figure 10, five layers and three layers
are formed from the opening end part of the mouth portion
toward the bottom portion (5/~ layers).
3/5/3 layers
lS A parison of the 3/S/3 layer structure is
formed by the following procedure.
~ 1) The total amount of resin B to be injected
is adjusted to 1 to 2S ~ of the volume of the cavity.
(2) Only resin A is iniected in an amount
corresponding to 20 to 70 % of the volume of the cavity
(step I).
~ 3~ Resin B in an amount 5 to 35 % of the
total amount of resin B to be injected and resin A in an
amount 1.0 to 10 times the amount of resin B to be in-
jected are simultaneously injected (step II ) .
(4) Resin B:in an amount 30 to 90 % of thetotal amount of resin B to be injected is injected either
alone or together with resin A in an amount not more than
two times the amount of resin B injected ~step III).
(S) Resin B in an amount 5 to 35 ~ of the
total amount of resin B to be injected and resin A in an
amount 1.0 to 10 times the amount of resin B injected are
injected simultaneously (step IV).
~6i Finallyr resin A alone is injected in an
amount corresponding to 10 to 70 % of the volume of the
cavity to fill the cavity ~step V).
~L3~
g
By the above procedure, a parison can be formed.
3~5 layers
A parison of the 3/5 layer structure is formed
by the following procedure~
tl) The total amount of resin B to be injected
is adjusted to 1 to 25 % of the volume of the cavity.
(2) Resin A alone i5 injected in an amount
corresponding to 20 to 70 % of the volumle of the cavity
(step I).
t3) Resin B in an amount 10 to 70 ~ of the
total amount of resin B to be injected and resin A in an
amount 1.0 to 10 times the amount of resin B to be in--
jected are simultaneously injected (step II).
~4) Resin B in an amount 30 to 90 ~ of the
total amount of resin B to be injected is injected either
alone or together with resin A in an amount not more than
two times the amount of resin B ~o be injected (step
III).
(5) Finally, resin A alone is injected in an
amount corresponding to 10 to 70 % of the volume of the
cavity to fill the cavity tstep V).
This procedure leads to the formation of a
parison.
5/3 layers
A parison of the 5/3 layer structure is formed
by the following procedure.
(1) The total amount of resin B injected is
adjusted to 1 to 25 % of the volume of the cavity.
(2) Resin A alone is injected in an amount
corresponding to 20 to 70 % of the volume of the cavity
~step I).
(3) Resin B in an amount corresponding to 30
to 90 ~ of the total amount of resin B to be injected is
injected either alone or together with resin A in an
amount not more than 2 times the amount of resin B to be
injected (step III)~
89
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S4) Resin B in an amount corresponding to 10
to 70 % of the total amount of resin B injected and resin
A in an amount 1.0 to 10 times the amount of resin B to
be injected are injected simultaneously (step IVl.
(5) Finally, resin A alone is injected in an
amount corresponding to 10 to 70 % o the volume of the
cavity to fill the cavity (step V).
This procedure can form a parison.
Accordingly, if the amount of resin injected in
step II in the formation of a paeison of the 3/5~3 layer
is increased and step IV is omitted, a parison of the 3~5
layer structure can be obtainedO If step II in the
formation of the parison of the 3~5~3 structure is omitted
and the amount of resin B injected in step IV is in-
creased, a parisQn of the 5/3 layer structure can beobtained.
Various conditions in the above procedures will
be described in detail~
The total amount of resin B described in (1) in
2~ each of the procedures corresponds to 1 to 25 %, prefer-
ably S to 10 %, of the volume of the mold cavity. If it
is less than 1 ~, a layer of resin B is difficult to form
and the re~ulting layer is broken here and thereO The
effe~t of adding the resin B layer cannot be expected.
If, o~ the other hand, it exceeds 25 %, the resin B layer
tends to be distributed deviatingly as shown in ~igure
16. In the deviated part, the boundary line between the
resin A la~er and the eesin B layer becomes conspicuous
and presents an undesirable appearance.
If the amount of resin A injected in step I is
large, the resin B gathers at the bottom portion. If it
is small, the resin B layer tends to stretch in the
direction of the opening end of the mouth portion.
Accordingly, the amount of resin A to be injected in step
I is adjusted to 20 to 70 ~, preferably 40 to 60 ~, of
the volume of the cavi~y.
~3~8~
In step II, resins A and B are injected simul-
taneously. The amount of resin B to be injected is 5 to
35 ~, preferably 10 to 25 ~, for the formation of the
3/5/3 layers, and 10 to 70 %r preferably 20 to 50 %~ for
the formation of the 3/5 layers, both based on the total
amount of the resin B to be injected. rrhe amount of
resin A to be injected is 1.0 to 10 times~ preferably 1.2
to 2 times, the amount of the cesin B to be injected in
step II. If the amount of resin ~ injected is more than
this specified limit, the resin B layer becomes too thin.
If it is less than the specified lower limit, the amount
of resin B becomes too large and three layers cannot be
formed. In such a case, disturbed five layers with
outside thin resin B layers tend to form. In the forma-
tion of the 5/3 layers, step II does not exist.
In step III, resin B in an amount correspondingto 30 to 90 %, preferably 50 to 80 %, of the total amount
of resin B to be injected is injected either alone or
together with resin A in an amount not more than 2 times,
preferably 0.1 to 0.9 time, the amount of resin B to be
injected in step III. If the amount of resin B injected
exceeds 90 ~ it is difficult to form three layers~ If
it is less than 30 %, the five-layer portion becomes
small as shown in Figure 15. When resin B alone is
injectedr two resin B layers in the five-layer portion
have an equal thickness. When resin A and resin B are
simultaneously injected, the resin B layer on the inside
of the parison becomes thicker than the resin B layer
near the outside of the parison as the amount of resin A
injected simultaneously increases.
In step IV, resins A and B are simultaneously
injected. The amount of resin B to be injected is 5 to
35 %, preferably 10 to 25 ~, for the formation of the
3/5/3 layers, and 10 to 70 ~, preferably 20 to 50 %, for
the formation of the 5f3 layers r both based on the total
amount of resin B to be injected. The amount of resin A
~L3~ 8~
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to be 1njected is 1.0 to 10 times, preferably 1.2 to 2
times t the amount of resin B injected in step IV. If the
amount of resin A inject d exceeds the above specified
limit, the resin B layers become too ~hin. If it is less
than the specified limit, the amount of resin B becomes
too large and three layers cannot be formed. Disturbed
five layers with thin outside resin B layers tend to
for~. Step IV does not exist in the case of forming the
3/5 layers.
In step V, only resin A is injected in an
amount corresponding to 10 ko 70 ~, preferably 20 to
S0 %, of the volume of the cavityO If the amount of
resin ~ injected is less than the specified limit, resin
B near ~he gate cannot be completely replaced by resin A,
and in the next injecting cycle, a mixture of resin A and
resin B ~orms. If it is above the specified limit, the
amount of resin A injected previously is so small that as
shown in Figure 18, the resin B layer is pushed out by
resin A injected next and comes out on the surface at the
opening end of the mouth portion. Consequently, troubles
such as cracking and whitening by water absorption occur.
Generally, higher speeds of injecting the
resins are preferred for shortening the cycle time and
preventing whitening ascribed to crystallization. If the
injection speed is too high, heat is generated owing to
shearing and causes decomposition of the resins. This
leads to various troubles such as the formation of vola-
tile components, silver streak a reduction in the mol-
ecular weight which reduces strength. Preferably, the
speed of injecting resin A is 1 to 15 cc/sec in each of
steps I to IV, and 5 to lS cc/sec in step V, and the
speed of injecting resin B is preferably 5 to 70 ccJsec.
The in~ecting speeds of simultaneously injecting resins A
and B are determined by the ratio of the amounts of
3~ injection of resins A ~nd B.
Figures 11 to 14 show the state of flow of the
~L3~ 89
resins in the cavity which chan~es with time in the
production of a parison of the 3/5/3 layer structure.
Each of these figures shows the state at the end of the
series of the steps I to IY. Dotted lines in Figures 12
to 14 indicate resin A simultaneous}y injected with resin
B.
The container of this invention can be produced
by biaxially stretching the parison obtained by the above
method at a temperature of 70 to 130 C at a stretch
ratio of 1 to 4 in the axial direction and 2 to 7 in the
circumferential direction and at an area ratio of 5 to
15. The suitable blowing pressure is lO~to 40 kg/cm2,
prefecably 20 to 35 kg/cm . The suitable thickness of
the container is 200 to 500 microns, preferably 250 to
450 microns.
Examples of resin A used in this invention
include thermoplastic polyester resins, polyolefin
resins, polycarbonates, polyacrylonitrile~ polyvinyl
chloride and polystyrene. The thermoplastic pslyestfer
resins are preferred.
Examples of resin B used in this invention,
i.e~ the thermoplastic gas-barrier resin, include MX
nylon, a saponification product of ethylene/vinyl acetate
copolymer resin, polyacrylonitrile copolymer resin and
polyvinylidene chloride resin. MX nylon is preferred.
A combination of MX nylon with a thermoplastic
polyester resin, especially polyethylene terephthalate,
is especially preferred because it gives excellent
transparency, mechanical st~ength, injection-moldability
and stretch blow-moldability.
The thermoplastic polyester resins denote
polyesters derived from an acid co~ponent at least 80
mole ~, preferably at least 90 mole %, of which consists
of terephthalic acid and a gIycol component at least 80
mole %, preferably at least 90 mole ~, of which consists
of ethylene glycol. The remai~der of the acid component
39
- 14 -
may comprise, for example, isophthalate, diphenyl ether-
4,4-dicarboxylic acid, naphthalene-1,4-(or 2,6)dicarboxy-
lic acid, adipic acidr sebacic acid~ decane-l,10-di-
carboxylic acid or hexahydroterephthalic acid. The
remainder of the glycol component may comprise, ~or
example, propylene glycol, 1,4-butanediol, neopentyl
glycol, diethylene glycol, cyclohexanedimethanol, 2,2-
bis(4-hydroxyphenyl)propane, and 2,2-bist4-hydroxyethoxy-
phenyl~propaneO Polyester resins which also contain a
hydroxycarboxylic acid component such as p-hydroxybenzoic
acid may also be used.
The suitable intrinsic viscosity of the thermo-
plastic polyester resins is at least 0.55, preferably
0.65 to 1.4. If the intrinsic viscosity i5 less than
0.55, it is difficult to obtain a transparent amorphous
mul~ilayered parison, and a container formed from the
resulting parison has insufficient mechanical strength.
MX nylon denotes a polymer of m-xylyl~nediamine
alone or a polymer containing at least 70 mole ~ of
structueal units derived from a mixed xylylenediamine
containing at least 30 % of p-xylylenediamine and an
alpha,omega-aliphatic dicarboxylic acid having 6 to 10
carbon atoms.
Examples of these polymers include homopolymers
such as poly(m-xylylehe adipamide~, poly~m-xylylene
sebacamide) and poly~m-xylylene suberamide); copolymers
such as a m-xylylene~p-xylylene adipamide copolymer, a
m-xylylene/p-xylylene pimeramide copolymer and a m-
xylylene/p-xylylene azelamide copolymer; and copolymers
of the components of the above homopolymers and co-
polymers with aliphatic diamines such as hexamethylene-
diamine, alicyclic diamines such as piperazine, aromatic
diamines such as p-bis(2-aminoethyl)benzene, aromatic
dicarboxylic acids such as terephthalic acid, lactams
such as epsilon-caprolactam, omega-aminocarboxylic acids
such as omega-aminoheptanoic acid, or aromatic amino-
8~
carboxylic acids such as p-aminobenzoic acid.
These polymers may include such polymers as
nylon 6, nylon 66, nylon 610 and nylon llo
These MX nylon resins suitably have a relative
viscosity of at least 1.5, preferably 200 to 4Ø
In the present invention, a coloring agent, an
ultraviolet absorber, an antistatic agent, an anti-
oxidant, a lubricant, a nucleating agent, etc. may be
incorporated into one or both of resins A and B in
a~ounts which do not impair the object of the invention~
The layer structure of the multilayered con-
tainer of this invention conforms to the desired shape of
the container. It is free from delamination between
resin layers and has excellent gas-barier property~ The
process of this invention can easily produce their multi-
layered container having the a~oresaid structure.
The following Examples and Comparative ~xamples
illustrate the present invention in greater detail.
The various properties shown in these examples
were measured by the following methods.
(1) Intrinsic viscosity 1~1 of the polyester
resin
Measured at a temperature of 30 ~C in a 6:4 (by
weight) mixture of phenol and tetrachloroethane.
(2) Relative viscosity [7rel~ of the polyamide
resin
Measured at a temperature of 25 C using a
solution of 1 9 of the resin in 100 ml of 96 % sulfuric
acid.
(3) Oxygen permeability
Measured by using OXTRAN 100 (made by ~odern
Control Inc.) at a temperature of 20 C, an in~ide re-
lative humidity of 100 % and an outside relative humidity
of 65 %.
(4) Carbon dioxide escaping test
Carbonated water ~4 gas volume) was filled in a
~L3~ g
- 16 -
container and stoced at a temperature of 22 C and a
relative humidity of 60 %. The amount of carbon dioxide
gas escaped was meaured by a pressure gauge 12 weeks
later. ~he gas volume were calculated from the pressure
in accordance with the table of carbon dioxide absorption
coefficients.
~5~ Test for delamination due to gas pressure
water at 2 to 4 C was put in a container and
filled to a predetermined depth. The container was
sealed up with a cap having a rubbee septum. The con-
tainer was pressurized with nitrogen gas to a pressure of
7 kg/cm2 for 1 minute, and the occurrence of delamination
between resin layers was examined.
Example 1
Polyethylene terephthalate having an intrinsic
viscosity of 0.75 was used as resin A, and poly(m
xylylene adipamide) having a relative viscosity of 2~1
was used as resin B. By using the device shown in Figure
7, a parison was formed which had an outside diameter of
30 mm, a length of 120 mm, a thickness of 4 mm, a weight
of 50 g and an inner capacity of about 47 cc.
The amounts of resins A and B injected and the
injection speed~ were as indicated in Table 1~ The
temperature conditions were as follows:-
Injection cylinder for resin A: 270 C
Injection cylinder for resin B: 260 C
Resin flow passage within the mold: 270 C
Mold cooling water: 15 ~C
The parison was heated to 95 C by an infrared
heater and biaxially stretched blow-molded under a blow
pressure of 20 kg~cm -G to produce a container having the
shape shown in Figure 1. In the same way, a container
having the shape shown in Figure 2 was produced. Both of
the containers had a capacity of 1,500 ml, an outside
3~ diameter of 90 mm and a height of 300 mm. The bent
portions of the containers were as follows:
13~
F ~ure 1
Vertical rib: depth 1.0 mm, radius of curvature
102 mm
Lateral rib: depth 2.0 mm, radius of curvature
1.8 mm
Fiyure 2
Vertical rib: depth 1.2 mm, raclius of curvature
1.0 mm
Lateral rib: depth 1.75 mm, raclius of curvature
2.0 mm
The two containers were subjected to the mea-
surement of oxygen permeability, the test for carbon
dioxide gas escaping (only the container having the shape
shown in Figure 2) and the test for delamination (only
the container having the shape shown in Figure 2~. The
results were good as shown in Table 2 for Examples 1 1
and 1-2.
Examples 2 to 6 and Comparative Examples l_to 7
In each run, a parison was formed by i~jection
molding in the same way as in Example 1 except that the
amounts of resins A and B injected and the speeds of
injection in steps I to step IV were changed as indicated
in Table 1. The parison had:the layer structure shown in
Table 1.
The parisons obtained in Examples 2 and 3 and
Comparative Examples 1 and 2 were each stretch blow-
molded as in Example 1 to produce containers having the
shapes shown in Figu res 1 and 2.
Eight types of the containers so obtained were
each subjected to the measurement of oxygen permeability,
the test for carbon dioxide gas escaping ~only th~ con-
tainers having the shape shown in Figure 2~ and the test
for delamination tonly the containe rs having the shape
shown in Figure 2).
3~ The results are shown in Table 2 for Examples
2-1, 2-2, 3-1 and 3-2, and Comparative Examples }~ 2,
2-1 and 2-2~
:~L3~
- 18 -
In Comparative Example 1-2, the result of the
carbon dioxide escaping test was good because the con-
tainer had a five-layer structure, but in the delamina~
tion test, delamination occurred at the vertical rib
portion in 48 samples out of 50 samples. On the other
hand, in Comparative Example 2-2, no delamination oc-
curred in the delamination test because the container had
a three-layer structure, but the result of the carbon
dioxide gas escaping test was not satisfactoryO
~3~
- 19 -
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