U.S. patent application number 10/902050 was filed with the patent office on 2005-02-24 for plastic container.
This patent application is currently assigned to SUMITOMO CHEMICAL COMPANY, LIMITED. Invention is credited to Nozawa, Hiroshi, Shiromoto, Seiji.
Application Number | 20050042401 10/902050 |
Document ID | / |
Family ID | 34190048 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050042401 |
Kind Code |
A1 |
Shiromoto, Seiji ; et
al. |
February 24, 2005 |
Plastic container
Abstract
Disclosed is a plastic container having a wall comprising a
layer made of a composition comprising a major amount of
crystalline propylene-ethylene-butene-1 copolymer which has
specific structural unit proportions and a specific melt flow rate
and a minor amount of ethylene-.alpha.-olefin copolymer which has
specific structural unit proportions, a specific melt flow rate and
a specific density, the container being superior in flexibility,
impact strength at low temperatures anddurability.
Inventors: |
Shiromoto, Seiji;
(Chiba-shi, JP) ; Nozawa, Hiroshi; (Ichihara-shi,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
SUMITOMO CHEMICAL COMPANY,
LIMITED
|
Family ID: |
34190048 |
Appl. No.: |
10/902050 |
Filed: |
July 30, 2004 |
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
B65D 1/0207 20130101;
B65D 23/003 20130101; Y10T 428/1352 20150115 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2003 |
JP |
2003-206727 |
Claims
What is claimed is:
1. A plastic container having a wall comprising a layer made of a
composition comprising from 70 to 99 parts by weight of a
crystalline propylene-ethylene-butene-1 copolymer having features
[1] and [2] defined below and from 1 to 30 parts by weight of an
ethylene-.alpha.-olefin copolymer having features [3], [4]and [5],
where the combined amount of both copolymers is 100 parts by
weight: [1] to have a content of propylene-derived structural units
of from 70 to 97% by weight, a content of ethylene-derived
structural units of from 1 to 10% by weight and a content of
butene-1-derived structural units of from 2 to 20% by weight, [2]
to have a melt flow rate, measured at a temperature of 230.degree.
C. and a load of 2.16 kgf, of from 1 to 10 g/10 min, [3] to be a
copolymer of ethylene and an .alpha.-olefin having from 4 to 12
carbon atoms, the copolymer having a content of ethylene-derived
structural units of 50% by weight or more, [4] to have a melt flow
rate, measured at a temperature of 190.degree. C. and a load of
2.16 kgf, of from 0.1 to 50 g/10 min, and [5] to have a density of
from 865 to 898 kg/m.sup.3.
2. The container according to claim 1, wherein the
propylene-ethylene-bute- ne-1 copolymer satisfies formula (1)
defined below:x+1<y (1)wherein x denotes a content (% by weight)
of ethylene-derived structural units and y denotes a content (% by
weight) of butene-1-derived structural units.
3. The container according to claim 1 or 2, wherein the wall is
composed of a single layer made of the composition.
4. The container according to claim 1 or 2, wherein the wall is
composed of two or more layers including at least one layer made of
the composition.
5. The container according to claim 1 or 2, wherein the container
is obtained by extrusion blow molding.
6. The container according to claim 1 or 2, wherein the container
is a container for medical use.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to plastic containers.
[0003] 2. Description of the Related Art
[0004] Containers made of polypropylene resin are superior in many
characteristics such as heat resistance, rigidity, chemical
resistance and water vapor barrier property and therefore are used
in awide variety of applications. However, the containers have a
problem of being poor in transparency and many proposals for
improving their transparency have been made.
[0005] For example, a container obtained by use of a resin
composition containing a composition comprising from 98 to 70% by
weight of propylene-ethylene random copolymer resin and from 2 to
30% by weight of ethylene-hexene-1 copolymer resin polymerized
using a metallocene catalyst and from 0.02 to 1.0 part by weight,
based on 100 parts by weight of the composition,
ofahigherfattyacidderivative is known (see JP-A-2001-181455). The
container has an improved transparency. However, when it is
subjected to heat treatment, the higher fatty acid derivative
contained in the container migrates to the surface of the
container, reducing the transparency or making the surface sticky.
Therefore, still some room for improvement is left.
[0006] On the other hand, known is a container made of resin
comprising a crystalline propylene copolymer having a melt flow
rate measured at 230.degree. C of from 0.3 to 8 g/10 min, a
propylene content of from 82 to 96.5% by weight, an ethylene
content of from 3 to 8% by weight and a content of .alpha.-olefin
having 4 or more carbon atoms of from 0.5 to 10% by weight and a
crystalline ethylene copolymer having a melt flow rate measured at
190.degree. C. of from 0.3 to 50 g/10 min and a density of from 900
to 935 kg/m.sup.3, wherein the crystalline ethylene copolymer is
blended in an amount of from 4 to 0.05% by weight based on the
crystalline propylene copolymer (see JP-A-8-47980). However, it is
not sufficient in transparency.
SUMMARY OF THE INVENTION
[0007] The object of the present invention is to provide a plastic
container which is flexible and is superior in impact strength at
low temperatures and which causes a small decrease in transparency
and do not get very sticky even when it is subjected to heat
treatment.
[0008] The present invention provides a plastic container having a
wall comprising a layer made of a composition comprising from 70 to
99 parts by weight of a crystalline propylene-ethylene-butene-1
copolymer having features [1] and [2] defined below and from 1 to
30 parts by weight of an ethylene-.alpha.-olefin copolymer having
features [3, [4] and [5], where the combined amount of both
copolymers is 100 parts by weight:
[0009] [1] to have a content of propylene-derived structural units
of from 70 to 97% by weight, a content of ethylene-derived
structural units of from 1 to 10% by weight and a content of
butene-1-derived structural units of from 2 to 20% by weight,
[0010] [2] to have a melt flow rate, measured at a temperature of
230.degree. C. and a load of 2.16 kgf, of from 1 to 10 g/10
min,
[0011] [3] to be a copolymer of ethylene and an .alpha.-olefin
having from 4 to 12 carbon atoms, the copolymer having a content of
ethylene-derived structural units of 50% by weight or more,
[0012] [4] to have a melt flow rate, measured at a temperature of
190.degree. C. and a load of 2.16 kgf, of from 0.1 to 50 g/10 min,
and
[0013] [5] to have a density of from 865 to 898 kg/m.sup.3.
[0014] A first embodiment of the present invention is directed to a
plastic container having a wall composed of a single layer made of
the composition comprising from 70 to 99 parts by weight of the
crystalline propylene-ethylene-butene-1 copolymer having the
features [1] and [2] defined above and from 1 to 30 parts by weight
of the ethylene-.alpha.-olefin copolymer having the features [3],
[4] and [5] defined above, wherein the combined amount of both
copolymers is 100 parts by weight.
[0015] A second embodiment of the present invention is directed to
a plastic container having a wall composed of two or more layers
including at least one layer made of the composition comprising
from 70 to 99 parts by weight of the crystalline
propylene-ethylene-butene-1 copolymer having the features [1] and
[2] defined above and from 1 to 30 parts by weight of the
ethylene-.alpha.-olefin copolymer having the features [3], [4] and
[5] defined above, wherein the combined amount of both copolymers
is 100 parts by weight.
BRIEF DESCRIPTION OF THE DRAWING
[0016] FIG. 1 shows a container produced in Example 1 using the
third-angle projection.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The essential composition used in the plastic containers of
the present invention contains, as constituents, acrystalline
propylene-ethylene-butene-1 copolymer having the features [1] and
[2] defined below and an ethylene-.alpha.-olefin copolymer having
the features [3], [4] and [5] defined below.
[0018] The propylene-ethylene-butene-1 copolymer used in the
present invention is acrystalline copolymermade up of propylene,
ethylene and butene-1, the copolymer containing from 70 to 97% by
weight of propylene-derived structural units, from 1 to 10% by
weight of ethylene-derived structural units and from 2 to 20% by
weight of butene-1-derived structural units. In the present
invention, a crystalline polymer refers to a polymer whose heat of
fusion measured by a differential scanning calorimeter is 20 J/g or
more. The heat of fusion of the ethylene-propylene-butene-1
copolymer used in the present invention is preferably from 20 to
100 J/g, more preferably from 25 to 90 J/g, and particularly
preferably from 30 to 80 J/g. In the present invention, the heat of
fusion of a polymer is determined according to the following
procedure. First, a crystal fusion curve is produced according to
the following procedure using a differential scanning calorimeter
DSC-VII manufactured by PerkinElmer, Inc. or a measuring instrument
equivalent to this. The heat of fusion (J/g) is calculated from the
area of a portion surrounded by the resulting crystal fusion curve
and its baseline.
[0019] (1) A sheet 65 mm in diameter and 100 .mu.m in thickness is
prepared by compression molding at a temperature of 230.degree.
C.
[0020] (2) A test piece is prepared by punching the sheet produced
in step (1) into a diameter of 5 mm by means of a punching
machine.
[0021] The test piece is weighed on an electronic balance.
[0022] (3) The test piece prepared in step (2) is put into a sample
pan.
[0023] (4) The test piece in the sample pan is applied with the
thermal hysteresis shown below under a nitrogen atmosphere:
[0024] (i) the test piece is heated from 24.degree. C. to
220.degree. C. at a rate of 300.degree. C./min,
[0025] (ii) after the heating (i), the test piece is held at
220.degree. C. for five minutes,
[0026] (iii) after the step (ii), the test piece is cooled to
150.degree. C. at a rate of 300.degree. C./min,
[0027] (iv) after the cooling (iii), the test piece is held at
150.degree. C. for one minute,
[0028] (v) after the step (iv), the test piece is cooled to
50.degree. C. at a rate of 5.degree. C./min,
[0029] (vi) after the cooling (v), the test piece is held at
50.degree. C. for one minute, and (vii) after the step (vi), the
test piece is heated to 180.degree. C. at a rate of 5.degree.
C./min.
[0030] In the present invention, a single kind of or two or more
kinds of propylene-ethylene-butene-1 copolymers are used. For
example, two or more kinds of copolymers differing in molecular
weight may be employed. Alternatively, two or more kinds of
copolymers differing in contents of the three kinds of structural
units may be used.
[0031] For the propylene-ethylene-butene-1 copolymer having the
features [1] and [2], it is desirable to have a content of
ethylene-derived structural unit of from 1.3 to 8% by weight and a
content of butene-1-derived structural units of from 2.5 to 15% by
weight. It is more desirable for the copolymer to have a content of
ethylene-derived structural unit of from 1.5 to 5% by weight and a
content of butene-l-derived structural units of from 3 to 12% by
weight. It is particularly desirable for the copolymer to have a
content of ethylene-derived structural unit of from 2 to 3% by
weight and a content of butene-1-derived structural units of from 4
to 10% by weight. If the content of ethylene-derived structural
units is less than 1% byweight or the content of butene-1-derived
structural units is less than 2% by weight, containers will be poor
in flexibility. If the content of ethylene-derived structural units
is more than 10% byweight or the content of butene-1-derived
structural units is more than 20% by weight, the container will be
poor in heat resistance.
[0032] The combined content of the ethylene-derived structural
units and the butene-1-derived structural units in the
propylene-ethylene-butene-lc- opolymerisfrom3 to30%byweight,
preferably from 3.8 to 23% by weight, and more preferably from 4.5
to 17% by weight. If the combined content is less than 3% by
weight, the container tends to be poor in flexibility, whereas if
more than 30% by weight, containers tend to be poor in heat
resistance.
[0033] The propylene-ethylene-butene-1 copolymer preferably is a
copolymer satisfying formula (1) below. If formula (1) is
satisfied, containers tend to have particularly favorable heat
resistance. Thepropylene-ethylene-butene-lcopolymerismore
preferably a copolymer satisfying formula (2) below, and even more
preferably is a copolymer satisfying formula (3) below:
x+1<y (1)
x+2<y (2)
x+3<y (3)
[0034] wherein x denotes a content (% by weight) of
ethylene-derived structural units and y denotes a content (% by
weight) of butene-1-derived structural units.
[0035] Thepropylene-ethylene-butene-1-copolymerhasameltflow rate
measured at a temperature of 230.degree. C. and a load of 2.16 kgf
(henceforth referred to as MFR(230.degree. C., 2.16 kgf)) is from 1
to 10 g/lO min, preferably from 1.5 to 8 g/lomin, and more
preferably from 2 to 6 g/10 min. If MFR(230.degree. C., 2.16 kgf)
is less than 1 g/10 min, the surface of containers is roughened
during their molding, leading to decrease in transparency. If
MFR(230.degree. C., 2.16 kgf) is over 10 g/10 min, the impact
strength at low temperatures of containers becomes poor and the
flexibility of containers is affected.
[0036] The content of the propylene-ethylene-butene-1 copolymer in
the composition is from 70 to 99 parts by weight, preferably from
75 to 97 parts by weight, more preferably from 80 to 96 parts by
weight, and particularly preferably from 82 to 95 parts by weight,
wherein the combined amount of the propylene-ethylene-butene-1
copolymer and the ethylene-.alpha.-olefin copolymer mentioned later
is 100 parts by weight. If the amount of the
propylene-ethylene-butene-1 copolymer is less than 70 parts by
weight, the heat resistance of containers becomes poor. If the
amount of the propylene-ethylene-butene-1 copolymer is more than 99
parts by weight, the impact strength at low temperatures of
containers becomes insufficient.
[0037] The method for producing the propylene-ethylene-butene-1
copolymer may be a method in which propylene, ethylene and butene-1
are polymerized in the presence of a polymerization catalyst
comprising a transition metal compound, which method is disclosed
in JP-A-11-228629. The polymerization of the monomers may be, for
example, solution polymerization, bulk polymerization and gas phase
polymerization. The monomers may be polymerized by a single
polymerization technique or alternatively by a multistage
polymerization composed of these polymerization methods in
combination. From the viewpoint of production cost, use of gas
phase polymerization is preferred.
[0038] The ethylene-.alpha.-olefin copolymer refers to a copolymer
of ethylene and an .alpha.-olefin having from 4 to 12 carbon atoms,
which copolymer contains at least 50% by weight of ethylene-derived
structural units. The content of ethylene-derived structural units
is preferably up to 55% by weight, more preferably up to 60% by
weight, and even more preferably up to 65% by weight. Examples of
the .alpha.-olefin include butene-1, 4-methylpentene-1, hexene-1,
octene-1 and decene-1. Preferable .alpha.-olefin includes
butene-1and hexene-1. The ethylene-.alpha.-olefin copolymer (B) may
be a mixture of two or more ethylene-.alpha.-olefin copolymers
differing in molecular weight or in kind and content of
.alpha.-olefin.
[0039] The amount of the .alpha.-olefin having from 4 to 12 carbon
atoms is ordinarily 5% by weight or more, preferably 8% by weight
or more, and more preferably 10% by weight or more.
[0040] The ethylene-.alpha.-olefin copolymer has a melt flow rate
measured at a temperature of 190.degree. C. and a load of 2.16 kgf
(henceforth, referred to as MFR(190.degree. C., 2.16 kgf)) of from
0.1 to 50g/lomin, preferably from0.5 to 40 g/lomin, morepreferably
from 1 to 30 g/10 min, and even more preferably from 2 to 20 g/10
min.
[0041] If MFR (190.degree. C., 2.16 kgf) is less than 0.1 g/10 min,
dispersed particles of the ethylene-.alpha.-olefin copolymer in
containers become coarse, resulting in poor transparency of
containers. If MFR(190.degree. C., 2.16 kgf) is over 50 g/10 min,
the impact strength at low temperatures of containers becomes
insufficient.
[0042] The density of the ethylene-.alpha.-olefin copolymer is from
865 to 898 kg/m.sup.3, preferably from 868 to 897 kg/m.sup.3, and
more preferably from 870 to 896 kg/m.sup.3.
[0043] If the density is less than 865 kg m.sup.3, the density
difference between the ethylene-.alpha.-olefin copolymer and the
propylene-ethylene-butene-1 copolymer becomes large and the
transparency of containers becomes poor. Also if the density is
over 898 kg/m.sup.3, the density difference between the
ethylene-.alpha.-olefin copolymer and the
propylene-ethylene-butene-1 copolymer becomes large and the
transparency of containers becomes poor.
[0044] The method for producing the ethylene-.alpha.-olefin
copolymer may be a method in which ethylene and .alpha.-olefin are
polymerized in the presence of a catalyst (metallocene catalyst)
containing a transition metal compound comprising a group having a
cyclopentadiene-type anion skeleton, which method is disclosed in
JP-A-3-234717. The polymerization of the monomers may be known
polymerization methods, for example, solution polymerization,
slurry polymerization, gas phase polymerization and high-pressure
ion polymerization.
[0045] The essential composition used in the plastic containers of
the present invention may contain a crystalline propylene-ethylene
copolymer containing at least 90% by weight of propylene-derived
structural units and a crystalline propylene-butene-1 copolymer
containing at least 65% by weight of propylene-derived structural
units, unless the effect of the present invention is affected.
[0046] The addition of a propylene-ethylene copolymer or
propylene-butene-1 copolymer having a low MFR improves the impact
strength at low temperatures of containers. Addition of a
propylene-ethylene copolymer or propylene-butene-1 copolymer having
a high MFR improves the transparency of containers.
[0047] The combined content of the propylene-ethylene copolymer
andthepropylene-butene-1 copolymerbasedon 100 parts byweight of the
propylene-ethylene-butene-1 copolymer and the
ethylene-.alpha.-olefin in total is up to 30 parts byweight,
preferably up to 25 parts by weight, and more preferably up to 20
parts by weight.
[0048] The content of ethylene-derived structural units in the
propylene-ethylene copolymer is preferably from 3 to 10% by weight,
more preferably from 3.5 to 8% by weight, and even more preferably
from 4 to 7% by weight. If the content of ethylene-derived
structural units is less than 3% by weight, containers tend to be
poor in flexibility. If over 10% byweight, containers tend to be
poor in heat resistance.
[0049] The content of butene-1-derived structural units in the
propylene-butene-1 copolymer is preferably from 3 to 35% by weight,
more preferably from 4 to 30% by weight, and even more preferably
from 5 to 25% by weight. If the content of butene-1-derived
structural units is less than 3% by weight, containers tend to be
poor in flexibility. If over 35% byweight, containers tend to be
poor in heat resistance.
[0050] The propylene-ethylene copolymer and the propylene-butene-1
copolymer has an MFR(230.degree. C., 2.16 kgf) of from 0.1 to 100
g/10 min, preferably from 0.3 to 50 g/10 min, and more preferably
from 0.5 to 30 g/10 min. If MFR(230.degree. C., 2.16 kgf) is less
than 0.1 g/10 min, the surface of a container is roughened during
its molding, leading to decrease in transparency. MFR(230.degree.
C., 2.16 kgf) over 100 g/10 min results in a poor workability for
molding a container and containers will have a poor impact strength
at low temperatures.
[0051] The methods for producing the propylene-ethylene copolymer
and the propylene-butene-1 may be, for example, a method in which
monomers are polymerized in the presence of a polymerization
catalyst comprising a transition metal compound, which method is
disclosed in JP-A-11-228629. The polymerization of the monomers may
be, for example, solution polymerization, bulk polymerization and
gas phase polymerization. The monomers may be polymerized by a
single polymerization technique or alternatively by a multistage
polymerization composed of these polymerization methods in
combination. From the viewpoint of production cost, use of gas
phase polymerization is preferred.
[0052] The composition containing the propylene-ethylene-butene-1
copolymer and the ethylene-.alpha.-olefin copolymer may contain, in
addition to the propylene-ethylene-butene-1 copolymer and the
ethylene-.alpha.-olefin copolymer, additives such as talc, calcium
carbonate, mica, glass fiber, carbonfiber, neutralizingagents,
antioxidants, thermal stabilizers, weathering agents, lubricants,
UV absorbers, antistatic agents, antiblocking agents, anticlouding
agents, antifoaming agents, dispersing agents, antifungus agents,
fluorescent whitening agents, dyestuff and pigment, unless the
effect of the present invention is affected.
[0053] The combined amount of the additives is from 0.001 to 5
parts by weight based on total 100 parts by weight of the combined
amount of the propylene-ethylene-butene-1 copolymer and the
ethylene-.alpha.-olefin copolymer.
[0054] In one embodiment of the present invention, a plastic
container has a wall composed of a single layer made of the
composition comprising from 70 to 99 parts by weight of the
crystalline propylene-ethylene-butene-1 copolymer having the
features [1] and [2] defined above and from 1 to 30 parts by weight
of the ethylene-.alpha.-olefin copolymer having the features [3],
[4] and [5] defined above, wherein the combined amount of both
copolymers is 100 parts by weight. In this case, the thickness of
the layer of the composition may be determined appropriately
depending on the application of the container and is not
particularly limited.
[0055] Another embodiment of the present invention is directed to a
multilayer plastic container having a wall composed of two or more
layers including at least one layer made of the composition.
Examples of the material which constitutes the layer or layers
other than the layer of the composition include ethylene-vinyl
alcohol copolymer, polyamide resin and polyethylene terephthalate
resin. Moreover, a composition prepared by recycling flashes
generated during the molding of plastic containers of the present
invention may be used. In the multilayer plastic container, the
thickness of the wall may be determined appropriately depending on
the application of the container and is not particularly limited.
The thickness of the layer made of the essential composition is
preferably 30% or more, more preferably 40% or more, and
particularly preferably 50% or more of the whole thickness of the
wall.
[0056] The method for producing the containers of the present
invention will be explained below. It should be noted that although
the method for producing containers having a wall composed of a
single layer made of the essential composition will mainly be
described, multilayer containers can also be produced by
application of the following teachings to multilayer molding
techniques using multilayer molding machines.
[0057] The container of the present invention can be obtained by
mixing a propylene-ethylene-butene-1 copolymer, an
ethylene-.alpha.-olefin copolymer and, if desired, other components
to yield a mixture, kneading the mixture to yield a composition,
and molding the composition.
[0058] The method for mixing a propylene-ethylene-butene-1
copolymer, anethylene-.alpha.-olefin copolymer and, if desired,
other components is not particularly restricted. For example, a
method comprising mixing the components by means of a conventional
mixing machine may be used.
[0059] Examples of the mixing machine include a Henschel mixer
(trade name), a Super mixer (trade name), a ribbon blender and a
tumbler.
[0060] The method for kneading the mixture resulting from the
mixing of a propylene-ethylene-butene-1 copolymer, an
ethylene-.alpha.-olefin copolymer and, if desired, other components
is not particularly restricted. For example, a method comprising
kneading the components by means of a conventional kneading
machine. Examples of the kneading machine include a single screw
extruder, amultiple screw extruder, a Banbury mixer, a kneader and
a roll mill. The mixing machine and the kneading machine may be
connected to a machine for molding containers.
[0061] The conditions for the kneading are not particularly
restricted unless the molten resin is significantly degraded from
shear stress, externally-applied heat and shear heat generation
during the kneading and a long residence of the resin in the
kneading machine or an insufficient and uneven dispersion state is
formed.
[0062] Examples of the method for molding containers of the present
invention include injection molding, compression molding, injection
compression molding, pressure molding, vacuum molding, extrusion
blow molding, injection blow molding and injection stretch blow
molding.
[0063] Of these techniques, extrusion blow molding, injection blow
molding and injection stretch blow molding are preferable, and
extrusion blow molding is especially preferable. Containers
produced by extrusion blow molding are particularly desirable
because they are superior in flexibility, transparency, impact
strength at low temperatures, and heat resistance.
[0064] For the production of plastic containers of the present
invention, conventional blow molding machines may be used. Ablow
molding machine has, for example, a section where aparison is
formed by continuously or intermittently extruding, through a die,
a plasticated composition kneaded in an extruder, a mold having a
cavity with a product shape and a device for blowing compressed gas
into the mold cavity. Available are a reciprocating type extrusion
blow molding machine in which a mold reciprocates between the
extruder and the blowing machine and a rotary type extrusion blow
molding machine in which two or more molds are arranged on a
vertical or horizontal circular orbital and the molds are rotated
continuously.
[0065] The outline of the method for producing a plastic container
of the present invention using an extrusion blow molding machine is
described below.
[0066] The raw material charged into an extruder is melted and
kneaded in the cylinder of the extruder, and then extruded through
a gap between a die and a core mounted at one end of the extruder,
forming a tubular parison. The extruded parison is trapped between
mold halves which are combined to define acavity together. Then,
compressed gas is blown into the parison. The parison is formed
into the shape of the mold cavity by the action of the compressed
gas, and then cooled. Subsequently, the mold halves are opened and
a resulting container is ejected.
[0067] One preferred method of extrusion blow molding is described
below.
[0068] For melt kneading the raw materials, a single screw,
combined screws, a gear pump, or the like may be employed. Parisons
may be extruded either continuously or intermittently. The shape
and material of a die and a core for forming parisons and the gap
between the die and the core are not particularly restricted. For
preventing an extruded parison from draw-down or making the parison
have a thickness distribution suitable for an intended blow-up
ratio, the thickness of the parison may be controlled by means of a
parison controller. One may blow compressed gas into a parison
during the extrusion of the parison. One may pinch-off a bottom of
an extruded parison and then blow compression air into the
parison.
[0069] There are no particular limitations on resin temperature,
mold temperature, kind of compressed gas, blowing pressure and
blowing time unless the effect of the present invention is
affected.
[0070] The plastic containers of the present invention include the
composition containing the specific propylene-ethylene-butene-1
copolymer and the specific ethylene-.alpha.-olefin copolymer as
described above. Therefore, the containers are superior in impact
strength, flexibility and transparency and release less odor. In
addition, they exhibit less reduction in transparency and their
surfaces do not get very sticky when they are subjected to heat
treatment. Consequently, they are available for a wide variety of
applications, e.g. liquid packaging containers, food packaging
containers, medical containers, automotive appliances, home
electrical appliances, industrial products and sundries.
Especially, they can be employed suitably as medical containers,
such as containers for containing and transporting drug solutions
such as solutions of blood components, physiological saline
solution, electrolyte, dextran preparations, mannitol preparation,
saccharide preparations, amino acid preparations and lipid
microspheres.
EXAMPLES
[0071] The present invention will be further described by referring
to examples below. However, the invention is not restricted to the
examples.
[0072] Evaluation methods used in the examples and comparative
examples are as follows.
[0073] 1. Melt Flow Rate (MFR)
[0074] MFRs (g/10 min) of propylene-ethylene-butene-1 copolymers
and propylene-ethylene copolymers were measured at 230.degree. C.
according to JIS K 7210, Condition 14. MFR (g/10 min) of resin
compositions was measured under the same conditions as above. MFR
(g/10 min) of ethylene-.alpha.-olefin copolymers was measured at
190.degree. C. according to JIS K 6760.
[0075] 2. Density (d)
[0076] Density (kg/m.sup.3) of polymers was measured according to
JIS K 6760-1981.
[0077] 3. Flexural Modulus (FM)
[0078] Flexural modulus (MPa) of compression molded sheets was
measured according to JIS K 7106.
[0079] 4. IZOD Impact Strength (Izod)
[0080] A test piece with a V notch was prepared according to JIS K
7110. After being allowed to stand in a thermostat at 0.degree. C.
for 24 hours or longer, the test piece was measured for IZOD impact
strength (kJ/m.sup.2).
[0081] 5. Haze and Transmittance
[0082] Haze (%) and transmittance (%) of a 1 mm thick compression
molded sheet prepared according to JIS K 6758 were measured
according to JIS K 7105.
[0083] 6. Drop Strength of Container
[0084] A container was filled with 500 g of water and a
polypropylene cap was fitted thereto. After being allowed to stand
in a thermostat at 5.degree. C. for 24 hours or longer, the
container was dropped freely from a height of 1.2 m onto a concrete
floor ten times repeatedly with the body of the container down.
After the ten drops, the condition of the container was observed.
Ten test bottles of the same structure were subjected to the same
test. The ratio (%) of the number of unbroken bottles to the number
of the whole bottles tested was used as the drop strength of
bottles of that structure.
[0085] 7. Haze and Transmittance of Container
[0086] A test piece was prepared by cutting out a central portion
of a container. Haze (%) and transmittance (%) of the test piece
were measured according to JIS K 7105.
[0087] 8. Heat Resistance of Container
[0088] A container was hung using a hanger formed on the bottom of
the container and was allowed to stand in a thermostatic chamber at
121.degree. C. for 20 minutes. Thereafter, it was cooled to room
temperature and a central portion of the sidewall of the container
was cut out. Thus, a test piece was prepared. Haze (%) and
transmittance (%) of the test piece were measured according to JIS
K 7105.
[0089] 9. Stickiness of Container
[0090] A container was hung using a hanger formed on the bottom of
the container and was allowed to stand in a thermostatic chamber at
121.degree. C. for 20 minutes. Thereafter, it was cooled at ambient
temperature for 24 hours and then two test pieces were prepared by
cutting a central portion of the body of the container into
rectangles each sized 225 mm in a longitudinal direction and 50 mm
in a transverse direction. The two pieces were laminated together
on their outer surfaces and was allowed to stand in a thermostat at
60.degree. C. for three hours with a 9.5-kg weight having a bottom
sized 225 mm by 50 mm thereon. The lower test piece was fixed and
the upper test piece was held with a chuck at its one end. The
upper test piece was pulled up while the tensile load was increased
at a rate of 20 gf/min. A tensile load (gf/100 cm.sup.2) at the
time the test pieces peeled off was recorded. The larger the
tensile load, the more the stickiness.
[0091] 10. Heat of Fusion
[0092] Using a differential scanning calorimeter DSC-VII
manufactured by Perkin Elmer, Inc., a crystal melting curve of a
polymer was produced in the procedure described previously and then
a heat of fusion (J/g) was calculated.
[0093] The polymers used in examples and comparative examples are
as follows.
[0094] 1. Propylene-Ethylene-Butene-1 Copolymer
[0095] Propylene-Ethylene-Butene-1 Copolymer (1):
[0096] MFR(230.degree. C., 2.16 kgf) was 3.8 g/10 min. The content
of ethylene-derived structural units and that of butene-1-derived
structural units were 2.4% by weight and 6.8% by weight,
respectively. The heat of fusion measured by a differential
scanning calorimeter was 70.9 J/g.
[0097] 2. Propylene-Ethylene Copolymer
[0098] Propylene-Ethylene copolymer (1):
[0099] MFR(230.degree. C., 2.16 kgf) was 1.5 g/10 min. The content
of ethylene-derived structural units was 5.6% by weight.
Propylene-ethylene copolymer (2):
[0100] 3. Ethylene-.alpha.-Olefin Copolymer
[0101] Ethylene-.alpha.-Olefin Copolymer (1):
[0102] An ethylene-hexene-1 copolymer named Excellen FX CX2001
manufactured by Sumitomo Chemical Co., Ltd. This is a copolymer
produced in the presence of a metallocene catalyst. It has an
MFR(19OdegC., 2.16 kgf) of 2.0 g/10 min and a density of 896
kg/m.sup.3.
[0103] Ethylene-.alpha.-Olefin Copolymer (2):
[0104] An ethylene-hexene-1 copolymer named Excellen FX CX4002
manufactured by Sumitomo Chemical Co., Ltd. This is a copolymer
produced in the presence of a metallocene catalyst. It has an
MFR(190.degree. C., 2.16 kgf) of 8.0 g/10 min and a density of 883
kg/m.sup.3.
[0105] Ethylene-.alpha.-Olefin Copolymer (3):
[0106] An ethylene-hexene-1 copolymer named Excellen FX CX5007
manufactured by Sumitomo Chemical Co., Ltd. This is a copolymer
produced in the presence of a metallocene catalyst. It has an
MFR(190.degree. C., 2.16 kgf) of 17.7 g/10 min and a density of 875
kg/m.sup.3.
[0107] Ethylene-.alpha.-Olefin Copolymer (4):
[0108] An ethylene-butene-1 copolymer named Excellen VL VL100
manufactured by Sumitomo Chemical Co., Ltd. This is a copolymer
produced in the presence of a Ti-Mg catalyst. It has an MFR
(190.degree. C., 2.16 kgf) of 0.8 g/10 min and a density of 900
kg/m.sup.3.
[0109] Ethylene-.alpha.-Olefin Copolymer (5):
[0110] An ethylene-butene-1 copolymer named Sumikathene-L FS250A
manufactured by Sumitomo Chemical Co., Ltd. This is a copolymer
produced in the presence of a Ti-Mg catalyst. It has an
MFR(190.degree. C., 2.16 kgf) of 1.8 g/10 min and a density of 922
kg/m.sup.3.
Example 1
[0111] Ninety-four parts by weight of
propylene-ethylene-butene-1copolymer (1) and 6 parts by weight of
ethylene-.alpha.-olefin copolymer (1) were blended and then 0.01
part by weight of hydrotalcite DHT-4C (manufactured by Kyowa
Chemical Industry Co., Ltd.) and 0.1 part by weight of Irganox B220
(manufactured by Ciba Specialty Chemicals) were added and mixed in
a Henschel mixer. The resulting mixture was melt-kneaded in a
single screw extruder having a full flight type screw 40 mm in
diameter, at a temperature of 230.degree. C. and a screw rotation
speed of 100 rpm. Thus, a resin composition was obtained. The resin
composition had an MFR of 3.9 g/10 min. The blend proportions of
the copolymers and the MFR of the composition are shown in Table 1.
Moreover, a compression molded sheet made of the resin composition
had a flexural modulus of 760 MPa, an Izod impact strength of 3.5
kJ/m.sup.2, a transmittance of 89.1% and a haze of 33.6%. The sheet
was superior in flexibility, impact strength at low temperatures
and transparency. The physical properties of the compression molded
sheet are summarized in Table 3.
[0112] The resin composition was extruded to form a hot parison at
an extrusion rate of 5 kg/h at a die and core temperatures of
210.degree. C. using a blow molding machine NB3B manufactured by
The Japan Steel Works, Ltd. having a full flight type screw 50 mm
in diameter. The hot parison was trapped between molds controlled
to 14.degree. C. and compressed air having a pressure of 0.3 MPa
was blow into the parison for 20 seconds. Thus, a container with a
hanger on its bottom, the container having a weight of 28 g, a side
wall thickness of about 0.4 mm, a capacity of 600 ml and a shape
shown in FIG. 1 was produced. The container had a transmittance of
91.8%, a haze of 3.5%, a transmittance and haze after heat
treatment of 90.4% and 8.4%, and a peel load of 25.6 g/100 cm2. The
container was superior in flexibility, transparency, heat
resistance and sanitariness. Physical properties of hollow
container is shown for table 4.
Examples 2 to 6
[0113] In the same manner as Example 1, resin compositions were
obtained by melt-kneading copolymers selected from
propylene-ethylene-butene-1 copolymers and ethylene-.alpha.-olefin
copolymers in a blend proportions given in Table 1. Moreover,
containers were also produced in the same manner as Example 1. The
physical properties of the resin compositions and those of the
containers made from the compositions are summarized in Table 3 and
Table 4, respectively. These containers were superior in
flexibility, transparency and heat resistance and exhibited less
stickiness.
Comparative Examples 1 to 7
[0114] In the same manner as Example 1, resin compositions were
obtained by melt-kneading copolymers selected from
propylene-ethylene-butene-1 copolymers and ethylene-.alpha.-olefin
copolymers in a blend proportions given in Table 2. Moreover, a
container was also produced in the same manner as Example 1. The
physical properties of the resin compositions and those of the
containers made from the compositions are summarized in table 3 and
Table 4, respectively. These containers were superior in
flexibility, but were poor in impact strength, transparency and
degree of stickiness.
1 TABLE 1 Example 1 2 3 4 5 6 Propylene-ethylene-butene-1 block
copolymer Propylene-ethylene-butene-1 94 94 90 80 94 84 block
copolymer (1) Propylene-ethylene copolymer Propylene-ethylene
copolymer (1) -- -- -- -- -- 10 Ethylene-.alpha.-olefin copolymer
Ethylene-.alpha.-olefin copolymer (1) 6 -- -- -- -- --
Ethylene-.alpha.-olefin copolymer (2) -- 6 10 20 -- 6
Ethylene-.alpha.-olefin copolymer (3) -- -- -- -- 6 --
Ethylene-.alpha.-olefin copolymer (4) -- -- -- -- -- --
Ethylene-.alpha.-olefin copolymer (5) -- -- -- -- -- -- MFR (g/10)
of composition 3.9 4.2 4.4 5.1 4.4 3.7
[0115]
2 TABLE 2 Comparative Example 1 2 3 4 5 6
Propylene-ethylene-butene-1 block copolymer
Propylene-ethylene-butene-1 100 50 90 90 -- -- block copolymer (1)
Propylene-ethylene copolymer Propylene-ethylene copolymer (1) -- --
-- -- 100 94 Propylene-ethylene copolymer (2) -- -- -- -- -- --
Ethylene-.alpha.-olefin copolymer Ethylene-.alpha.-olefin copolymer
(1) -- -- -- -- -- -- Ethylene-.alpha.-olefin copolymer (2) -- 50
-- -- -- 6 Ethylene-.alpha.-olefin copolymer (3) -- -- -- -- -- --
Ethylene-.alpha.-olefin copolymer (4) -- -- 10 -- -- --
Ethylene-.alpha.-olefin copolymer (5) -- -- -- 10 -- -- MFR (g/10)
of composition 3.8 8.8 3.4 3.7 1.5 1.8
[0116]
3 TABLE 3 Physical properties of compression molded sheet Izod
Transmittance FM (MPa) (kJ/m.sup.2) (%) Haze (%) Example 1 760 3.5
89.1 33.6 Example 2 630 3.4 89.7 31.3 Example 3 760 4.1 91.2 32.0
Example 4 470 7.6 93.3 31.5 Example 5 750 3.0 88.8 31.5 Example 6
640 3.4 88.5 33.7 Comparative 790 1.8 86.2 38.1 Example 1
Comparative 200 27.4 88.8 55.0 Example 2 Comparative 690 3.3 87.2
42.3 Example 3 Comparative 710 2.5 85.1 40.6 Example 4 Comparative
630 3.0 88.0 35.3 Example 5 Comparative 620 3.3 88.9 34.2 Example
6
[0117]
4 TABLE 4 Physical properties of container Non-heat treatment After
heat treatment Fall Trans- Trans- Peel load strength mittance Haze
mittance Haze (g/100 (%) (%) (%) (%) (%) cm.sup.2) Example 1 80
91.8 3.5 90.4 8.4 25.6 Example 2 80 92.2 2.2 91.2 6.6 30.6 Example
3 90 91.7 4.3 90.9 8.2 29.6 Example 4 100 90.1 6.4 89.9 12.2 41.2
Example 5 70 91.3 7.0 91.1 9.8 34.1 Example 6 80 90.9 4.8 90.1 7.5
34.6 Comparative 0 90.6 13.8 90.4 16.8 26.4 Example 1 Comparative
100 89.4 25.3 86.4 34.7 56.1 Example 2 Comparative 70 89.1 29.2
86.8 37.9 41.5 Example 3 Comparative 70 88.8 28.4 86.9 39.8 38.7
Example 4 Comparative 60 90.1 14.7 89.9 24.0 62.8 Example 5
Comparative 70 90.6 13.5 90.1 20.8 63.7 Example 6
[0118] According to the present invention, a plastic container can
be obtained which is flexible and is superior in impact strength at
low temperatures and which causes a small decrease in transparency
and do not get very sticky even when it is subjected to heat
treatment.
* * * * *