U.S. patent application number 10/628246 was filed with the patent office on 2004-07-22 for heat-resistant resin container and method of producing the same.
This patent application is currently assigned to TOYO SEIKAN KAISHA, LTD.. Invention is credited to Iwasaki, Tsutomu, Kogure, Masahito, Oda, Yasuhiro, Otsuki, Masahiko.
Application Number | 20040140593 10/628246 |
Document ID | / |
Family ID | 26587214 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040140593 |
Kind Code |
A1 |
Oda, Yasuhiro ; et
al. |
July 22, 2004 |
Heat-resistant resin container and method of producing the same
Abstract
A container with a flange having excellent heat resistance and
impact resistance in the lower part of the barrel portion and
having excellent transparency in the wall despite the container is
formed by molding an amorphous polyester sheet, and a method of
producing the same.
Inventors: |
Oda, Yasuhiro;
(Yokohama-shi, JP) ; Otsuki, Masahiko;
(Yokohama-shi, JP) ; Iwasaki, Tsutomu;
(Sagamihara-shi, JP) ; Kogure, Masahito;
(Yokohama-shi, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037
US
|
Assignee: |
TOYO SEIKAN KAISHA, LTD.
|
Family ID: |
26587214 |
Appl. No.: |
10/628246 |
Filed: |
July 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10628246 |
Jul 29, 2003 |
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09959955 |
Nov 13, 2001 |
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6716500 |
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09959955 |
Nov 13, 2001 |
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PCT/JP01/01918 |
Mar 12, 2001 |
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Current U.S.
Class: |
264/550 |
Current CPC
Class: |
B65D 1/26 20130101; B29C
51/428 20130101; B29C 51/421 20130101; B29L 2031/712 20130101; Y10T
428/1352 20150115; B29C 51/426 20130101; B29C 2791/006 20130101;
B29K 2995/0041 20130101; B29C 51/002 20130101; B29C 61/02 20130101;
B29C 43/003 20130101; B29C 51/06 20130101; B29C 2791/007 20130101;
B29K 2067/00 20130101; B29C 51/04 20130101 |
Class at
Publication: |
264/550 |
International
Class: |
B29C 051/04; B29C
051/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2000 |
JP |
67078/00 |
Oct 3, 2000 |
JP |
303773/00 |
Claims
1. An heat-resistant and impact resistant container obtained by
heat-molding a sheet provided with a thermoplastic polyester layer
comprising chiefly an ethylene terephthalate unit, and having a
flange portion, a barrel portion and a closed bottom portion, the
wall of the barrel portion being oriented and crystallized so as to
possess a crystallinity of not smaller than 15% as measured by the
density method, and the wall of the barrel portion being oriented
to satisfy the following formulas (1), (2) and (3),
Iu(-110)/Iu(010).ltoreq.1.02 (1) IL(-110)/IL(010).ltoreq.0.89 (2)
and (Iu(-110)/Iu(010))-(IL(-110)/IL(010- )).gtoreq.0.13 (3) wherein
Iu(-110) is a diffraction intensity of the surface having an index
of a plane of (-110) in the upper part of the wall of the barrel
portion of when an X-ray is incident on the wall surface of the
container perpendicularly thereto and when the axial direction of
the container is regarded to be a perpendicular of the optical
coordinate, Iu(010) is a diffraction intensity of the surface
having an index of a plane of (010) in the upper part of the wall
of the barrel portion of when an X-ray is incident on the wall
surface of the container perpendicularly thereto and when the axial
direction of the container is regarded to be a perpendicular of the
optical coordinate, IL(-110) is a diffraction intensity of the
surface having an index of a plane of (-110) in the lower part of
the wall of the barrel portion of when an X-ray is incident on the
wall surface of the container perpendicularly thereto and when the
axial direction of the container is regarded to be a perpendicular
of the optical coordinate, and IL(010) is a diffraction intensity
of the surface having an index of a plane of (010) in the lower
part of the wall of the barrel portion of when an X-ray is incident
on the wall surface of the container perpendicularly thereto and
when the axial direction of the container is regarded to be a
perpendicular of the optical coordinate, as measured by the X-ray
diffraction by using a curved PSPC microdiffractometer.
2. An impact resistant container according to claim 1, wherein the
ratio (H/R) of the height (H) of the barrel portion to the inner
diameter (R) at the top of the barrel portion is not smaller than
0.8.
3. An impact resistant container according to claim 1 or 2, wherein
the flange portion has a crystallinity of smaller than 10% as
measured by the density method.
4. An impact resistant container according to claim 1 or 2, wherein
the flange portion has a crystallinity of not smaller than 20% as
measured by the density method.
5. A method of producing an impact resistant container by heating a
sheet provided with an amorphous thermoplastic polyester layer
comprising chiefly an ethylene terephthalate unit at a sheet
temperature (Ts) that satisfies the following formula (4),
Tg<Ts<Tg+50.degree. C. (4) wherein Tg is a glass transition
point of the thermoplastic polyester, and molding and heat-setting
the sheet by using a plug having a bottom area of not smaller than
70% of the bottom area of the container and a plug temperature (Tp)
that satisfies the following formula (5), Tg-30.degree.
C.<Tp.ltoreq.Tg+30 C (5) wherein Tg is the glass transition
point of the thermoplastic polyester, in one step or in two steps
in a metal mold with a plug-assisted compressed air or vacuum.
6. A production method according to claim 5, wherein the metal mold
has a temperature (Tm) that satisfies the following formula (6),
Tg<Tm (6) wherein Tg is a glass transition point of the
thermoplastic polyester.
7. A production method according to claim 5 or 6, wherein said plug
has a stepped shoulder for forming a flange.
8. A method of producing a heat resistant resin container by
molding a thermoplastic resin sheet by using the compressed air
into the shape of a female mold that is heated at a temperature not
lower than the crystallization temperature of said resin, and
reducing the pressure in the molded article so as to shrink into
the shape of a plug having the shape of a final container to impart
the shape thereto, followed by cooling.
9. A method of producing a heat resistant resin container according
to claim 8, wherein a primary molded article obtained by stretching
a thermoplastic resin sheet by using a plug, is molded with the
compressed air.
10. A method of producing a heat resistant resin container
according to claim 8 or 9, wherein the thermoplastic resin sheet is
an amorphous sheet of a thermoplastic polyester.
11. A method of producing a heat resistant resin container
according to any one of claims 8 to 10, wherein the surface area of
the plug is not smaller than 3 times as great as the to-be-molded
area of the thermoplastic resin sheet.
12. A method of producing a heat resistant resin container
according to any one of claims 8 to 11, wherein the temperature of
the plug is not lower than a glass transition point of the
thermoplastic resin but is not higher than the temperature of the
female mold.
13. A method of producing a heat resistant resin container
according to any one of claims 8 to 12, wherein an intermediate
article obtained by stretch-molding the thermoplastic resin sheet
by using a plug for stretch-molding prior to effecting the molding
with the compressed air, is molded with the compressed air and is
shrunk in a separate step by being supported by a plug for
imparting the shape.
14. A method of producing a heat resistant resin container
according to claim 13, wherein the temperature of the plug for
imparting the shape is lower than a glass transition point of the
thermoplastic resin.
15. A heat-resistant resin container obtained by molding a
thermoplastic polyester sheet, at least the side wall of the
container being oriented and crystallized due to stretching, and
the crystallinity being larger on the outer surface than the
crystallinity on the inner surface in every portion of the
container.
16. A container according to claim 15, wherein said container has a
flange portion, a side wall portion and a bottom portion, and the
ratio (H/D) of the height (H) of the container to the diameter (D)
of the container is not smaller than 0.5.
17. A container according to claim 16, wherein the flange portion
of the container is cloudy and the side wall is transparent when it
contains no pigment.
18. A container according to any one of claims 15 to 17, wherein a
change in the volume of the container is not larger than 1.0% after
it is heat-treated in an oven at such a temperature that the side
wall portion thereof is maintained at 90.degree. C. for 3
minutes.
19. A method of producing a heat-resistant container by preparing
an intermediate article by heat-shrinking a pre-molded article
obtained by solid-phase-molding the sheet provided with an
amorphous thermoplastic polyester layer, molding the intermediate
product with the compressed air in a female metal mold for final
molding heated at a temperature not lower than the crystallization
start temperature of said polyester, heat-setting the molded
article, reducing the pressure inside the molded article so that
the molded article shrinks along the outer surface of the plug
having the shape of the final container to impart the shape
thereto, followed by cooling.
20. A method according to claim 19, wherein the sheet is
solid-phase-molded by pressing the sheet by using a plug for
pre-molding, the sheet being clamped by a clamping metal mold and a
female mold for pre-molding, and by supplying the pressurized gas
to between the sheet and the plug.
21. A method according to claim 20, wherein in molding the sheet,
the sheet temperature is maintained to lie between the glass
transition point (Tg) of the thermoplastic polyester+15.degree. C.
and the glass transition point+40.degree. C.
22. A method according to claim 21, wherein the plug is maintained
at a temperature between the glass transition point of the
thermoplastic polyester-30.degree. C. and the glass transition
point+20.degree. C.
23. A method according to claim 21 or 22, wherein the female mold
for pre-molding is maintained at a temperature between the glass
transition point of the thermoplastic polyester+10.degree. C. and
the glass transition point+50.degree. C.
24. A method according to any one of claims 19 to 23, wherein the
pre-molded article is supported by the plug for intermediate
molding and is inserted in the female mold for intermediate
molding, and the molded article is caused to shrink along the outer
surface of the plug to impart the shape thereto followed by
cooling.
25. A method according to claim 24, wherein the female mold for
intermediate molding is maintained at a temperature in a range of
not lower than the crystallization start temperature.
26. A method according to claim 24 or 25, wherein the plug for
intermediate molding is maintained at a temperature lower than the
temperature of the female mold for intermediate molding and in a
range of from 80 to 110.degree. C.
27. A method according to any one of claims 19 to 26, wherein the
surface area of the pre-molded article is from 1.1 to 1.5 times as
large as the surface area of the intermediate article.
28. A method according to any one of claims 19 to 27, wherein the
female mold for final molding is maintained at a temperature of not
lower than the crystallization start temperature of the
thermoplastic polyester.
29. A method according to any one of claims 19 to 28, wherein the
plug for the final container is maintained at a temperature in a
range of from the glass transition point of the thermoplastic
polyester-20.degree. C. to the glass transition point+20.degree.
C.
30. A container having excellent heat resistance and impact
resistance obtained by stretching and molding a thermoplastic
polyester, the thermoplastic polyester in the bottom portion of the
container having a crystallinity of not smaller than 15%, and the
center in the bottom portion of the container being substantially
transparent and having a distinguished diffraction peak in the
surface of an index of a plane (010) in the X-ray diffraction.
31. A container according to claim 30, wherein the oriented
crystallization tendency (U) as defined by the following formula
(I), U=H(010)/H(-110) (I) wherein H(010) is a diffraction intensity
of the surface having an index of a plane (010) in the X-ray
diffraction, and H(-110) is a diffraction intensity of the surface
having an index of a plane (-110) in the X-ray diffraction, is not
smaller than 1.3 at the center in the bottom portion.
32. A container according to claim 30 or 31, wherein the sheet
having the thermoplastic polyester layer is stretched and molded in
the solid phase.
33. A container according to any one of claims 30 to 32, wherein
the crystallinity of the thermoplastic polyester in the side wall
of the container is not smaller than 15%.
Description
TECHNICAL FIELD
[0001] The present invention relates to a container with a flange
obtained by heat-molding a sheet provided with a thermoplastic
polyester layer, and to a method of producing the same. More
specifically, the invention relates to a polyester container with a
flange having improved impact resistance and heat resistance in the
lower part of the barrel thereof and having superior
transparency.
BACKGROUND ART
[0002] Thermoplastic polyesters such as polyethylene terephthalate
and the like have excellent impact resistance, heat resistance and
transparency as well as a certain degree of gas barrier property,
and have been widely used for producing a variety of kinds of
packaging containers.
[0003] Such packaging containers can be represented by a container
with a flange obtained by molding a stretched or unstretched
thermoplastic polyester sheet.
[0004] Japanese Unexamined Patent Publication (Kokai) No.
53852/1984 discloses a method of producing a transparent container
by monoaxially stretching a thermoplastic resin sheet while
maintaining the reduction ratio of the width of the sheet to be not
larger than 10% and heat-molding the thus obtained monoaxially
oriented sheet (prior art 1).
[0005] Japanese Examined Patent Publication (Kokoku) No. 27850/1989
discloses a method of heat-molding a polyester sheet by molding a
biaxially stretched polyester sheet having a crystallinity of not
larger than 30% and an index of surface orientation of from 0.02 to
0.15 by utilizing the compressed air along a mold heated at a
temperature which is not higher than the crystallizing temperature
(Tc.degree. C.) of the polyester but is not lower than
(Tc-70).degree. C., heat-treating the obtained molded article by
bringing it into contact with the heated mold, fitting a cooling
mold to the heating mold, the cooling mold having a shape nearly
corresponding to the heating mold, forcibly transferring the molded
article toward the cooling mold side from the heated mold side by
blowing the compressed air, and cooling the molded article upon
contact with the cooling mold (prior art 2).
[0006] Japanese Examined Patent Publication (Kokoku) No. 36534/1992
discloses a polyester container having a heat-adhering portion that
can be thermally adhered to the closure member, the container being
obtained by molding a polyester sheet containing a polyethylene
terephthalate as a chief constituent component, the heat-adhering
portion having a crystallinity of smaller than 20%, and the bottom
portion and(or) the side portion of the container having the
crystallinity of not smaller than 20%, the container being useful
as an ovenable tray (prior art 3).
[0007] Japanese Patent No. 2947486 discloses a method of producing
a biaxially stretched thermoplastic product by forming a biaxially
stretched intermediate product by blow-molding a sheet-like
thermoplastic material in a tube at a stretching temperature while
preventing the material from adhering to the top of the side walls,
placing the intermediate product on a male mold of a preset size
and a texture, heating the intermediate product and the mold at a
temperature higher than the temperature for stretching the
thermoplastic material so that the intermediate product is
thermally shrunk on the surface of the mold, cooling the
intermediate product that is thermally shrunk, and taking the
thermally shrunk intermediate product out of the mold (prior art
4).
[0008] The prior art 1 uses a monoaxially stretched sheet as the
sheet for molding. This molding method may be capable of improving
the transparency of the container but still leaves room for
improvement concerning the heat resistance of the container.
[0009] The prior art 2 uses a biaxially stretched sheet as the
sheet for molding. This molding method may be capable of improving
the heat resistance of the container but is not still satisfactory
concerning the impact resistance of the container.
[0010] These prior arts 1 and 2 use a sheet that has been stretched
in advance as the sheet to be molded and, hence, require a
particular stretching step and, hence, an additional cost. It is
therefore desired to use an unstretched sheet and to impart, in a
step of forming the container, the molecular orientation that is
desired from the standpoint of imparting the container properties.
It is further desired that the properties such as heat resistance,
impact resistance and transparency are imparted in the steps of
molding the container without requiring any particular step.
[0011] According to the prior art 3, an amorphous polyester sheet
that is heated and plasticized is formed into a tray by using a
metal mold maintained at a crystallizing temperature in order to
heat-crystallize the bottom portion and/or the side portion.
However, there is no disclosure concerning molecularly orienting
the side portion by stretching, and it is considered that the
container that is obtained is still insufficient with respect to
impact resistance and transparency.
[0012] The prior art 4 is to produce a final container by preparing
a biaxially stretched intermediate product by the blow-molding and
by heat-shrinking the intermediate product on the male mold. This
method, however, requires both heating for heat-shrinking the
intermediate product on the male mold and cooling for shaping the
heat-shrunk intermediate product and for taking it out. Therefore,
this method is not still satisfactory from the standpoint of
thermal economy, extended periods of time occupying the molds and
low productivity.
DISCLOSURE OF THE INVENTION
[0013] It is therefore an object of the present invention to
provide a container with a flange exhibiting excellent heat
resistance and impact resistance in the lower part of the barrel
portion and excellent transparency in the container wall despite it
is obtained by molding an amorphous polyester sheet, and a method
of producing the same.
[0014] Another object of the present invention is to provide a
heat-resistant thermoplastic resin container having a novel profile
of crystallinities in that the side wall portion of the container
comprises oriented crystals, and the outer surface of the side wall
has a crystallinity larger than that of the inner surface of the
side wall, and a method of producing the same.
[0015] A further object of the present invention is to provide a
method of producing a thermoplastic resin container, having split
functions of effecting the heat-set by a female mold and effecting
the cooling by a plug, shortening the time for occupying the mold
and enhancing the productivity.
[0016] A still further object of the present invention is to
provide a sheet-molded container having excellent heat resistance,
impact resistance and transparency not only in the side wall of the
container but also in the central portion on the bottom of the
container despite the container is obtained by molding an
unoriented or amorphous thermoplastic polyester sheet, and a method
of producing the same.
[0017] According to the present invention, there is provided an
impact resistant container obtained by heat-molding a sheet
provided with a thermoplastic polyester layer comprising chiefly an
ethylene terephthalate unit, and having a flange portion, a barrel
portion and a closed bottom portion, the wall of the lower part of
the barrel portion being oriented and crystallized so as to possess
a crystallinity of not smaller than 15% as measured by the density
method, and the wall of the barrel portion being oriented to
satisfy the following formulas (1), (2) and (3),
[0018] Iu(-110)/Iu(010).ltoreq.1.02 (1)
IL(-110)/IL(010).ltoreq.0.89 (2)
[0019] and
(Iu(-110)/Iu(010))-(IL(-110)/IL(010)).ltoreq.0.13 (3)
[0020] wherein Iu(-110) is a diffraction intensity of the surface
having an index of a plane of (-110) in the upper part of the wall
of the barrel portion of when an X-ray is incident on the wall
surface of the container perpendicularly thereto and when the axial
direction of the container is regarded to be a perpendicular of the
optical coordinate, Iu(010) is a diffraction intensity of the
surface having an index of a plane of (010) in the upper part of
the wall of the barrel portion of when an X-ray is incident on the
wall surface of the container perpendicularly thereto and when the
axial direction of the container is regarded to be a perpendicular
of the optical coordinate, IL(-110) is a diffraction intensity of
the surface having an index of a plane of (-110) in the lower part
of the wall of the barrel portion of when an X-ray is incident on
the wall surface of the container perpendicularly thereto and when
the axial direction of the container is regarded to be a
perpendicular of the optical coordinate, and IL(010) is a
diffraction intensity of the surface having an index of a plane of
(010) in the upper part of the wall of the barrel portion of when
an X-ray is incident on the wall surface of the container
perpendicularly thereto and when the axial direction of the
container is regarded to be a perpendicular of the optical
coordinate,
[0021] as measured by the X-ray diffraction by using a curved PSPC
microdiffractometer.
[0022] In the container of the present invention, the ratio (H/R)
of the height (H) of the barrel portion to the inner diameter (R)
at the top of the barrel portion is desirably in a range of from
0.8 to 2.0 for fulfilling the object of the invention. Further, the
flange portion may have a crystallinity of smaller than 10% as
measured by the density method, or the flange portion may have a
crystallinity of not smaller than 20% as measured by the density
method.
[0023] According to the present invention, there is further
provided a method of producing an impact resistant container by
heating a sheet provided with an amorphous thermoplastic polyester
layer comprising chiefly an ethylene terephthalate unit at a sheet
temperature (Ts) that satisfies the following formula (4),
Tg<Ts<Tg+50.degree. C. (4)
[0024] wherein Tg is a glass transition point of the thermoplastic
polyester,
[0025] and molding and heat-setting the sheet by using a plug
having a bottom area of not smaller than 70% of the bottom area of
the container and a plug temperature (Tp) that satisfies the
following formula (5),
Tg-30.degree. C.<Tp.ltoreq.Tg+30.degree. C. (5)
[0026] wherein Tg is the glass transition point of the
thermoplastic polyester,
[0027] in one step or in two steps in a metal mold with a
plug-assisted compressed air or vacuum.
[0028] In the production method of the present invention, it is
desired that the metal mold has a temperature (Tm) that satisfies
the following formula (6),
Tg.ltoreq.Tm (6)
[0029] wherein Tg is a glass transition point of the thermoplastic
polyester.
[0030] Further, the plug may be an ordinary plug or a plug having a
stepped shoulder for forming a flange.
[0031] According to the present invention, further, there is
provided a heat-resistant resin container obtained by molding a
thermoplastic polyester sheet, at least the side wall of the
container being oriented and crystallized due to stretching, and
the side wall of the container having a crystallinity which is
larger in the outer surface thereof than in the inner surface
thereof.
[0032] In the heat-resistant resin container of the present
invention, it is desired that:
[0033] 1. The container has a flange portion, a side wall portion
and a bottom portion, and the ratio (H/D) of the height (H) of the
container to the diameter (D) of the container is not smaller than
0.5;
[0034] 2. The flange portion of the container is cloudy and the
side wall is transparent when it contains no pigment; and
[0035] 3. A change in the volume of the container is not larger
than 1.0% after it is heat-treated in an oven at such a temperature
that the side wall portion thereof is maintained at 90.degree. C.
for 3 minutes.
[0036] According to the present invention, further, there is
provided a method of producing a heat-resistant resin container by
molding a thermoplastic resin sheet into the shape of a female mold
heated at a temperature higher than the crystallization temperature
of the resin by the compressed air, followed by heat-setting and,
then, reducing the pressure in the molded article so that the
molded article shrinks into the shape of a plug having the shape of
a final container to impart the shape thereto, followed by
cooling.
[0037] In the method of producing the heat-resistant resin
container of the present invention, it is desired that:
[0038] 1. A primary molded article obtained by stretching the
thermoplastic resin sheet by using a plug is molded with the
compressed air;
[0039] 2. The thermoplastic resin sheet is an amorphous sheet of a
thermoplastic polyester;
[0040] 3. The plug has a surface area wider by more than three
times than the area to be molded of the thermoplastic resin sheet;
and
[0041] 4. The temperature of the plug is not lower than the glass
transition point of the thermoplastic resin but is lower than the
temperature of the female mold.
[0042] The method of producing the heat-resistant resin container
of the present invention can be put into practice even by a
one-step molding method or by a two-step molding method.
[0043] In the two-step molding method, it is desired that the
thermoplastic resin sheet is stretched and molded by using a plug
for stretch-molding prior to applying the compressed air, and the
obtained primary molded article is supported by a shape-imparting
plug in a separate step to effect the molding with the compressed
air and the shrinking. In this case, further, it is desired that
the temperature of the shape-imparting plug is not higher than the
glass transition point of the thermoplastic resin.
[0044] According to the present invention, further, there is
provided a method of producing a heat-resistant container by
preparing an intermediate article by heat-shrinking a pre-molded
article obtained by solid-phase-molding the sheet provided with an
amorphous thermoplastic polyester layer, molding the intermediate
product with the compressed air in a female metal mold for final
molding heated at a temperature higher than the crystallization
start temperature of said polyester, heat-setting the molded
article, reducing the pressure inside the molded article so that
the molded article shrinks along the outer surface of the plug
having the shape of the final container to impart the shape
thereto, followed by cooling.
[0045] In the embodiment of the present invention, it is desired
that the sheet is solid-phase-molded by pressing the sheet by using
a plug for pre-molding, the sheet being clamped by a clamping metal
mold and a female mold for pre-molding, and by supplying the
pressurized gas to between the sheet and the plug. In molding the
sheet in this case, it is desired that the sheet temperature is
maintained to lie between the glass transition point (Tg) of the
thermoplastic polyester+15.degree. C. and the glass transition
point+40.degree. C., that the plug is maintained at a temperature
between the glass transition point-30.degree. C. and the glass
transition point+20.degree. C., and that the female mold for
pre-molding is maintained at a temperature between the glass
transition point of the thermoplastic polyester+10.degree. C. and
the glass transition point+50.degree. C.
[0046] In the present invention, further, it is desired that the
pre-molded article is supported by a plug for intermediate molding
and is inserted in the female mold for intermediate molding, and
the molded article is caused to shrink along the outer surface of
the plug to impart the shape thereto followed by cooling. In this
case, it is desired that the female mold for intermediate molding
is maintained at a temperature in a range of not lower than the
crystallization start temperature, that the plug for intermediate
molding is maintained at a temperature lower than the temperature
of the female mold for intermediate molding and in a range of from
80 to 110.degree. C., and that the surface area of the pre-molded
article is from 1.1 to 1.5 times as large as the surface area of
the intermediate article.
[0047] According to the present invention, further, it is desired
that the female mold for final molding is maintained at a
temperature of not lower than the crystallization start temperature
of the thermoplastic polyester, and that the plug for the final
container is maintained at a temperature in a range of from the
glass transition point of the thermoplastic polyester-20.degree. C.
to the glass transition point+20.degree. C.
[0048] According to the present invention, there is further
provided a container having excellent heat resistance and impact
resistance obtained by stretching and molding a thermoplastic
polyester, the thermoplastic polyester in the bottom portion of the
container having a crystallinity of not smaller than 15%, and the
center in the bottom portion of the container being substantially
transparent and having a distinguished diffraction peak in the
surface of an index of a plane (010) in the X-ray diffraction.
[0049] In the container of the present invention, it is desired
that:
[0050] 1. The oriented crystallization tendency (U) as defined by
the following formula (I),
U=H(010)/H(-110) (I)
[0051] wherein H(010) is a diffraction intensity of the surface
having an index of a plane (010) in the X-ray diffraction, and
H(-110) is a diffraction intensity of the surface having an index
of a plane (-110) in the X-ray diffraction,
[0052] is not smaller than 1.3 at the center in the bottom
portion;
[0053] 2. The sheet having the thermoplastic polyester layer is
stretched and molded in the solid phase; and
[0054] 3. The crystallinity of the thermoplastic polyester in the
side wall of the container is not smaller than 15%.
BRIEF DESCRIPTION OF DRAWINGS
[0055] FIG. 1 is a diagram illustrating the principle of X-ray
diffraction by using a curved PSPC microdifractometer;
[0056] FIG. 2 is a diagram of X-ray diffraction of a barrel portion
of a container according to the present invention;
[0057] FIG. 3 is a diagram illustrating the crystal lattice of a
polyethylene terephthalate;
[0058] FIG. 4 is a diagram of X-ray diffraction of a crystalline
polyethylene terephthalate;
[0059] FIG. 5 is a graph illustrating a relationship between the
temperature of a metal mold and the ratio of peak intensities;
[0060] FIG. 6 is a sectional view illustrating a container of the
present invention together with a plug and a metal mold that are
used;
[0061] FIG. 7 is a sectional view of a laminated sheet used in the
present invention;
[0062] FIG. 8 is a side sectional view illustrating a step of
supplying a thermoplastic resin sheet in a one-step molding
method;
[0063] FIG. 9 is a side sectional view illustrating a step of
clamping and pre-stretching the thermoplastic resin sheet in the
one-step molding method;
[0064] FIG. 10 is a side sectional view illustrating a step of
stretching the thermoplastic resin sheet in the one-step molding
method;
[0065] FIG. 11 is a side sectional view illustrating a step of
compressed air-molding and heat-setting into a secondary mold in
the one-step molding method;
[0066] FIG. 12 is a side sectional view illustrating a step of
shrinking, shaping and cooling a tertiary molded article in the
one-step molding method;
[0067] FIG. 13 is a side sectional view illustrating a step of
parting the tertiary molded article in the one-step molding
method;
[0068] FIG. 14 is a side sectional view illustrating a step of
supplying the thermoplastic resin sheet in a first step in a
two-step molding method;
[0069] FIG. 15 is a side sectional view illustrating a step of
compressed air-molding the primary molded article into the
secondary molded article in the first step in the two-step molding
method;
[0070] FIG. 16 is a side sectional view illustrating a step of
parting the secondary molded article in the first step in the
two-step molding method;
[0071] FIG. 17 is a side sectional view illustrating a step of
inserting the secondary molded article in the metal mold in the
second step in the two-step molding method;
[0072] FIG. 18 is a side sectional view illustrating a step of
compressed air-molding and heat-setting the secondary molded
article in the second step in the two-step molding method;
[0073] FIG. 19 is a side sectional view illustrating portions of
measurement of the containers of Examples 6 to 8 and Comparative
Example 7 that will be described later;
[0074] FIG. 20 is a side sectional view illustrating a step of
clamping the sheet in the first-step molding (into a pre-molded
article);
[0075] FIG. 21 is a side sectional view illustrating a step of
stretching and shaping the sheet in the first molding step;
[0076] FIG. 22 is a side sectional view illustrating the pre-molded
article molded in the first molding step;
[0077] FIG. 23 is a side sectional view illustrating a step of
inserting the article in the metal mold in the second molding step
(for molding an intermediate article);
[0078] FIG. 24 is a side sectional view illustrating a step of
heat-shrinking in the second molding step;
[0079] FIG. 25 is a side sectional view illustrating a step of
cooling and shaping in the second molding step;
[0080] FIG. 26 is a side sectional view illustrating an
intermediate article molded in the second molding step;
[0081] FIG. 27 is a side sectional view illustrating a step of
inserting the article in the metal mold in a third molding step
(into a finally molded article);
[0082] FIG. 28 is a side sectional view illustrating a step of
heat-setting in the third molding step;
[0083] FIG. 29 is a side sectional view illustrating a step of
shrinking and shaping in the third molding step;
[0084] FIG. 30 is a side sectional view illustrating a step of
parting the finally molded article formed in the third molding
step; and
[0085] FIG. 31 is a view illustrating an X-ray diffraction image at
the center of bottom of the container according to another
embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0086] [First Embodiment]
[0087] A container according to a first embodiment of the present
invention is obtained by heat-molding a sheet provided with a
thermoplastic polyester layer comprising chiefly an ethylene
terephthalate unit, and having a flange portion, a barrel portion
and a closed bottom portion, the wall of the lower part of the
barrel portion being oriented and crystallized so as to possess a
crystallinity of not smaller than 15% as measured by the density
method, and the wall of the barrel portion being oriented to
satisfy the above-mentioned formulas (1), (2) and (3) as measured
by X-ray diffraction based upon the transmission method.
[0088] Referring to FIG. 1 illustrating the X-ray diffraction
method used in this invention, the samples to be measured are cut
out from the lower part (sample is cut about a center which is 10
mm above the bottom) and from the upper part (sample is cut about a
center which is 15 mm below the flange) of the barrel portion of
the heat-molded container, and are mounted in a sample holder of a
curved PSPC (position sensitive proportional counter)
microdiffractometer (PSPC-MDG) in a manner that the X-ray is
perpendicularly incident on the container wall surface and that the
axial direction of the container is in agreement with the optically
vertical direction of the device. The X-ray is converged by a
collimator into a fine beam, caused to be incident on the surface
of the sample perpendicularly thereto, and the position (2.theta.)
of the diffracted line and the intensity thereof are recorded on
the PSPC.
[0089] FIG. 2 shows an X-ray diffraction image of the upper part
and the lower part of the barrel portion of the container of the
present invention measured as described above.
[0090] In general, it has been known that the crystalline structure
of the polyethylene terephthalate is of the triclinic system having
the following lattice constants; i.e.,
[0091] a=4.56 angstroms
[0092] b=5.94 angstroms
[0093] c=10.75 angstroms
[0094] .alpha.=98.5.degree.
[0095] .beta.=118.degree.
[0096] .lambda.=112.degree.
[0097] Referring to FIG. 3 illustrating the atomic arrangement of
crystal unit lattice of a polyethylene terephthalate, the molecular
chains of the polyethylene terephthalate are extending in the
direction of c-axis and are positioned at the ridgelines in the
direction of c-axis, and a plane including a benzene ring is nearly
along the surface of an index of a plane (100).
[0098] In the measurement of the above-mentioned PSPC-MDG in
connection with the crystalline polyethylene terephthalate (PET),
diffraction peaks appear conspicuously on the surfaces having,
generally, indexes of planes (010), (-110), (100) and (105).
Relationships between the planes (hkl) of the crystal unit lattices
and the diffraction angle 2.theta. are as tabulated below,
1 (h, k, l) 2 .theta. (010) 16.degree. to 18.degree. (-110)
22.degree. to 24.degree. (100) 26.degree. to 27.degree. (105)
42.degree. to 45.degree.
[0099] FIG. 4 is a diagram of X-ray diffraction image of a barrel
portion of a crystalline polyethylene terephthalate container by
using the PSPC-MDG, and in which are clearly appearing diffraction
peaks of the surfaces having the above-mentioned indexes of planes
(010), (-110), (100) and (105).
[0100] When the X-ray diffraction image of the barrel portion of
the PET container of the present invention shown in FIG. 2 is
compared with the X-ray diffraction image of the crystalline PET
shown in FIG. 4, diffraction peaks are conspicuously appearing on
the surfaces having indexes of planes (010) and (-110) in the case
of the barrel portion of the container of the present invention,
whereas diffraction peaks are disappearing on the surface having
the index of a plane (100).
[0101] Further, when the X-ray diffraction image of the upper part
of the barrel portion of the container in FIG. 2 is compared with
the X-ray diffraction image of the lower part of the barrel portion
of the container, it is obvious that the diffraction peak intensity
of the surface having the index of a plane (-110) is decreasing in
the lower part of the barrel portion compared to the upper part of
the barrel portion while the diffraction peak intensity of the
index of a plane (010) is increasing.
[0102] In the PET crystals, it was pointed out already that the
plane including the benzene ring is nearly in line with the surface
having the index of a plane (100). Here, however, the surface
having the index of a plane (010) is at right angles with the
benzene plane, X-axis and Y-axis.
[0103] In the barrel portion of the container of the present
invention, the X-ray diffraction image shown in FIG. 2 is
conspicuous, i.e., the diffraction peaks are conspicuous on the
surfaces of the indexes of planes (010) and (-110), whereas the
diffraction peaks are extinguishing in the X-ray diffraction image
of the surface of the index of a plane (100), from which it is
reasonable to consider that, in the barrel portion of the
container, the benzene plane is arranged in parallel with the wall
surface of the barrel portion of the container.
[0104] That is, in the X-ray diffraction method, if the benzene
plane is nearly in parallel with the surface of the sample sheet,
the diffraction on the plane (100) is not measured but the
diffraction is measured on the plane (010) which is nearly
perpendicular thereto. A large diffraction peak intensity on the
plane (010) means that the benzene plane of a unit of ethylene
terephthalate is in parallel with the surface of the sheet.
Conversely, a large diffraction peak intensity on the plane (100)
means that the benzene plane of a unit of ethylene terephthalate is
inclined with respect to the film surface and is not in parallel
therewith.
[0105] The ratio Iu(-110)/Iu(010) and the ratio IL(-110)/IL(010) in
the above-mentioned formulas (1), (2) and (3) represent, in a
standardized manner, the degrees of parallelism between the benzene
plane of PET and the wall surface of the barrel portion at the
upper and lower parts of the barrel portion of the container. The
ratios become small when the degree of parallelism is large and
becomes large when the degree of parallelism is small.
[0106] In biaxially stretching the polyethylene terephthalate
containing a plane a phenylene group in the molecular chains
thereof, however, it has been known that the plane of the phenylene
group is arranged in parallel with the film surface (see, for
example, Journal of the Academy of Fibers, Vol. 33, No. 10,
1977).
[0107] The container of the present invention, therefore, is
biaxially oriented despite it is formed by heat-molding the
polyethylene terephthalate sheet, and the degree of the biaxial
orientation is increasing in the lower part of the barrel portion,
which is quite an unexpected fact.
[0108] In the present invention it is important that the ratio
Iu(-110)/Iu(010) and the ratio IL(-110)/IL(010) lie in the ranges
satisfying the above-mentioned formulas (1), (2) and (3) from the
standpoint of accomplishing the impact resistance, heat resistance
and transparency. If all of them are not satisfied, both the impact
resistance and the heat resistance become inferior as demonstrated
in Comparative Examples 1 to 5 appearing later.
[0109] In the present invention, it is desired that the ratio
Iu(-110)/Iu(010) is not larger than 1.02 and, most desirably, not
larger than 1.0. It is further desired that the ratio
IL(-110)/IL(010) is not larger than 0.89 and, most desirably, not
larger than 0.7.
[0110] It is further desired that the difference between the ratio
Iu(-110)/Iu(010) and the ratio IL(-110)/IL(010) is not smaller than
0.13 and, particularly, not smaller than 0.20.
[0111] In the container of the present invention, it is desired
that the wall at the lower part of the barrel portion has a
crystallinity of not smaller than 15% and, particularly, not
smaller than 17% as measured by the density method.
[0112] In this specification, the crystallinity stands for the
density method crystallinity (Xcv) expressed by the following
formula, 1 Xc = c .times. ( - a ) .times. ( c - a ) .times. 100
[0113] wherein .rho. is a density (g/cm.sup.3, 25.degree. C.) of
the sample measured by using a density-gradient tube, .rho.a is a
density of a perfectly amorphous substance and is, generally, 1.335
g/cm.sup.3 in the case of the PET, .rho.c is a density of a perfect
crystal and is, generally, 1.455 g/cm.sup.3 in the case of the PET,
and Xcv is a crystallinity (%).
[0114] When the crystallinity is not larger than 15%, the container
exhibits a decreased heat resistance and cannot be used for
hot-packaging the content.
[0115] In the container with a flange of the present invention, the
flange portion may have any crystallinity. In one embodiment, the
flange portion may have a crystallinity of smaller than 10% as
measured by the density method. The flange portion having such a
low crystallinity exhibits excellent heat-adhesiveness to the
closure member. In another embodiment, the flange portion is so
oriented and crystallized as to possess a crystallinity of not
smaller than 20% as measured by the density method. The flange
portion having such a high degree of crystallinity exhibits
excellent mechanical properties and thermal stability.
[0116] A container according to the first embodiment of the present
invention is obtained by heating a sheet provided with an amorphous
thermoplastic polyester layer comprising chiefly an ethylene
terephthalate unit at a sheet temperature (Ts) that satisfies the
following formula (4),
Tg<Ts<Tg+50.degree. C. (4)
[0117] wherein Tg is a glass transition point of the thermoplastic
polyester,
[0118] and molding the sheet by using a plug having a bottom area
of not smaller than 70% of the bottom area of the container and a
plug temperature (Tp) that satisfies the following formula (5),
Tg-30.degree. C.<Tp.ltoreq.Tg+30.degree. C. (5)
[0119] wherein Tg is the glass transition point of the
thermoplastic polyester,
[0120] in one step or two steps in a metal mold with a
plug-assisted compressed air or vacuum, followed by
heat-setting.
[0121] In the container of the present invention, the lower part of
the barrel portion has preferentially been oriented biaxially as
pointed out already. To form the container having such a profile of
orientation, it was learned that the sheet temperature (Ts) and the
plug temperature (Tp) must be maintained in suitable ranges in
executing the molding with the plug-assisted compressed air or
vacuum and, besides, the plug must have a proper shape.
[0122] That is, in effecting the molding with the plug-assisted
compressed air or vacuum, the sheet is stretched onto the plug in
the axial direction of the container and, hence, the wall of the
barrel portion is chiefly monoaxially oriented. It is, however,
important that the lower part of the barrel portion of the
container of the present invention is biaxially oriented. This can
be effectively done by pulling the sheet that is molded while
supporting it on the plug and, particularly, by pulling the
polyester of a portion of a small diameter on the bottom of the
plug up to a barrel portion of the plug having a large
diameter.
[0123] For this purpose, the sheet must be heated at a sheet
temperature (Ts) that satisfies the above-mentioned formula (4),
and the plug temperature (Tp), too, must satisfy the
above-mentioned formula (5).
[0124] When the sheet temperature (Ts) exceeds the range of the
formula (4)(see Comparative Example 1 appearing later), it becomes
difficult to accomplish the orientation profile structure defined
by the invention, and the container exhibits inferior impact
resistance and inferior heat resistance.
[0125] When the sheet temperature (Ts) becomes lower than the range
of the formula (4), the polyester is not plasticized to a
sufficient degree and cannot be stretch-molded into a
container.
[0126] Further, when the plug temperature (Tp) exceeds the range of
the formula (5)(see Comparative Example 2 appearing later), it
becomes difficult to accomplish the orientation profile structure
defined by the invention, and the container exhibits inferior
impact resistance and inferior heat resistance.
[0127] When the plug temperature (Tp) becomes lower than the range
of the formula (5), the polyester sheet remains cold and cannot be
stretch-molded into the container.
[0128] In the present invention, it is important to use the plug
having a bottom area which is not smaller than 70% and, preferably,
not smaller than 80% of the bottom area of the container in molding
the sheet with the plug-assisted compressed air or vacuum, from the
standpoint of imparting the orientation profile to the barrel
portion.
[0129] When the bottom area of the plug becomes smaller than 70%,
it becomes difficult to accomplish the orientation profile
structure defined by the present invention, either, and the
container exhibits inferior impact resistance and inferior heat
resistance as demonstrated in Comparative Example 3 appearing
later.
[0130] This is presumably due to that when the plug has a large
bottom area, the polyester that is stretched up to the barrel
portion of the plug remains in a sufficiently large amount in the
bottom of the plug contributing to increasing the biaxial
orientation due to the stretching in the axial direction and in the
circumferential direction.
[0131] In the present invention, the molding with the plug-assisted
compressed air or in vacuum and the heat-setting can be conducted
in one step or in two steps.
[0132] In the one-step method, a metal mold is heated at a
heat-setting temperature, the plug is advanced in the metal mold to
draw the sheet, and the sheet that is drawn with the compressed air
or in vacuum is inflated and is brought into contact with the metal
mold to heat-set the barrel portion.
[0133] A two-step method, on the other hand, uses a metal mold that
is cooled and a metal mold that is heated at a heat-setting
temperature, wherein the plug is advanced in the metal mold that is
cooled to draw the sheet, the sheet that is drawn with the
compressed air or in vacuum is inflated to prepare a pre-molded
article which is then put into the metal mold that is heated and is
further inflated with the compressed air or in vacuum, and is
brought into contact with the metal mold to heat-set the barrel
portion.
[0134] In the present invention, it is desired that the metal mold
used for the heat-setting has a metal mold temperature (Tm) that
satisfies the above-mentioned formula (6).
[0135] FIG. 5 illustrates a relationship between the metal mold
temperature (Tm) and the ratio of peak intensities
(I(-110)/I(010)), from which it is learned that confining the metal
mold temperature (Tm) in the range of the formula (6) is still
effective in placing the profile of orientation within the range of
the invention.
[0136] In the present invention, the container with a flange which
is amorphous or lowly crystalline can be produced by the
plug-assisted molding by holding a portion that becomes a flange by
a clamp. On the other hand, the container with a flange which is
oriented and crystallized can be produced by using a plug having a
shoulder portion for forming flange, stretching even a portion that
becomes a flange in a majority portion of the step of advancing the
plug, and tightening the portion that becomes the flange between
the shoulder portion and the metal mold in the last period of the
step of advancing the plug.
[0137] Referring to FIG. 6 which illustrates the container of the
present invention together with the plug and the metal mold, the
container 1 is produced by drawing the polyester sheet 2 by using
the plug 3, inflating the polyester sheet 2 by the compressed air
or vacuum in the metal mold, and bringing the wall of the container
into contact with the metal mold so as to be heat-set.
[0138] The container 1 includes a flange portion 11, a barrel
portion 12 and a closed bottom portion 13, the barrel portion 12
having crystallinity and oriention properties as described
above.
[0139] It is desired that the container has a ratio (H/R) of the
height (H) of the barrel portion 12 to the diameter (R) thereof of,
generally, not smaller than 0.8 and, particularly, in a range of
from 1.0 to 2.0.
[0140] In molding the sheet, the plastic sheet is heated at the
above-mentioned sheet temperature (Ts). The plastic sheet is heated
by using infrared rays or far infrared rays, by using a hot air
furnace or by the conduction of heat.
[0141] The plug and the metal mold are maintained at the
above-mentioned plug temperature (Tp) and at the metal mold
temperature (Tm). These temperatures are controlled by turning
on/off the heaters incorporated in the plug and in the metal mold,
or by passing a heat medium through the plug and the metal mold to
control the temperature.
[0142] It was pointed out already that the plug used for the
present invention should have a bottom area of not smaller than 70%
of the bottom area of the container. It is, however, desired that
the end of the barrel portion of the plug, i.e., a portion that is
continuous to the bottom portion is forming a tapered portion 31 of
which the diameter gradually increases toward the upper side as
shown in FIG. 6. That is, upon forming such a tapered portion 31,
it is allowed to easily draw the polyester on the bottom portion of
the plug onto the barrel portion, to produce the container 1 having
a good orientation profile.
[0143] It is desired that the tapered angle (.alpha.) of the
tapered portion 31 is from 0.5 to 10.degree. and, particularly,
from 2 to 6.degree. and that the tapered portion 31 is formed at a
ratio of from 0.3 to 0.9 times of the height of the plug.
[0144] In the embodiment shown in FIG. 6, further, the plug 3 has a
flange-molding portion 32 so as to form a flange portion 11 that is
oriented and crystallized.
[0145] The pressure applied to the sheet that is being molded may
be the compressed air from the plug side or may be the vacuum from
the metal mold side, or may be a combination thereof. In general,
the pressure having a magnitude of from 2 to 10 kg/cm.sup.2 is
applied from the side of the inner surface of the sheet.
[0146] [Second Embodiment]
[0147] According to the method of producing a heat-resistant resin
container of the present invention, a thermoplastic resin sheet is
molded, by the compressed air, into the shape of a female mold that
is heated to be higher than the crystallization temperature of the
resin and is heat-set and, then, the pressure in the metal mold is
decreased permitting the molded article to shrink to the shape of
the plug which is of the shape of a final container, thereby to
impart the shape and cool.
[0148] The plug used in the present invention has the shape and
size in agreement with the shape and size of inner surfaces of the
final container, whereas the female mold has the shape and size
larger than the shape and size of outer surfaces of the final
container. The plug and the female mold are arranged in concentric
in such a manner that they bite each other and separate away from
each other. Further, a clearance (in the radial direction and in
the axial direction) is formed between the outer surface of the
plug and the inner surface of the female mold to permit the
inflation of the thermoplastic resin being molded by the compressed
air from the inner side and to permit the shrinkage thereof due to
a decrease in the pressure from the inner side.
[0149] The plug used in the present invention works to stretch-mold
the resin sheet into a molded article (primary molded article)
which is in agreement with the outer surface of the plug and to
shrink-mold the resin sheet into a final molded article (tertiary
molded article). In the one-step molding method, the primary molded
article and the tertiary molded article have nearly the same shapes
and sizes. In the two-step molding method, the primary molded
article and the tertiary molded article may have the same or
different shapes and sizes. On the other hand, the female mold used
in the invention is to mold the primary molded article into a
secondary molded article of a size larger than the primary molded
article.
[0150] In the present invention, a feature resides in that the
female mold is heated to heat-set the secondary molded article that
is molded by the compressed air, the plug is cooled to impart the
shape to the tertiary molded article that has shrunk due to a
reduction in the pressure and to remove it out, and the functions
are separately effected, i.e., the female mold effects the heating
and the plug effects the cooling.
[0151] According to the production method of the present invention,
therefore, the female mold is only heated while the plug is only
cooled, and the molded article needs stay in the metal mold for a
very shortened period of time contributing to improving the
productivity as compared to when the plug and the metal mold are
heated and cooled alternately.
[0152] The primary molded article obtained by the stretch-molding
being assisted by the plug is further smoothly molded into the
secondary molded article by using the compressed air from the
inside of the primary molded article (i.e., from the inside of the
plug). Moreover, the secondary molded article that is heat-set, is
smoothly shrink-molded into a final container (tertiary molded
article) by reducing the pressure from inside the secondary molded
article (i.e., from inside the plug). Thus, the molding operation
by using the female mold and the molding operation by using the
plug are very smoothly carried out in cooperation without at all
wasting the time.
[0153] According to the present invention, the molding operation
can be put into practice by either the one-step method or the
two-step method without departing from the above-mentioned spirit
and scope of the invention. The one-step molding method is
conducted through the following steps by using a pair of plugs in
combination with the female mold; i.e.,
[0154] {circle over (1)} stretch-molding into a primary molded
article by using the plug;
[0155] {circle over (2)} molding the primary molded article into a
secondary molded article using the compressed air;
[0156] {circle over (3)} heat-setting the secondary molded article
by using the female mold;
[0157] {circle over (4)} shrink-molding the heat-set secondary
molded article into a tertiary molded article by reducing the
pressure; and
[0158] {circle over (5)} (cooling the tertiary molded article by
using the plug.
[0159] The two-step molding method is the same as the one-step
molding method with respect to that the above-mentioned basic steps
{circle over (1)} to {circle over (5)} are executed in the order as
described above. The two-step molding method, however, is different
using plural pairs of plugs and plural female molds in combination,
executing the steps {circle over (1)} and {circle over (2)} by
using one pair of plugs and one female mold, and executing the
steps {circle over (3)}, {circle over (4)} and {circle over (5)} by
using another pair of plugs and another female mold. In other
respects, these methods are in common.
[0160] In molding the container, the thermoplastic resin sheet must
have been heated at a temperature at which the stretch-molding can
be effected. The sheet temperature (Ts) differs depending upon the
kind of the resin but is, usually, not lower than a glass
transition temperature (Tg) of the resin but is not higher than the
crystallization temperature of the resin. In the case of the sheet
provided with an amorphous thermoplastic polyester layer, it is
desired that the sheet temperature (Ts) satisfies the following
formula (7),
Tg<Ts<Tg+50.degree. C. (7)
[0161] (particularly, Tg+20.degree. C.<Ts<Tg+30.degree. C.)
wherein Tg is a glass transition point of the thermoplastic
polyester.
[0162] When the temperature is not higher than Tg, the stretching
becomes locally excessive in executing the primary molding, and
favorable thickness profile is not obtained. When the temperature
is not lower than Tg+50.degree. C., on the other hand, the sheet is
not oriented to a sufficient degree, and the container lacks the
strength and is whitened, too.
[0163] In the present invention, the plug is for stretch-molding
the resin sheet and, hence, must have a surface area over at least
a predetermined range. It is usually desired that the plug has a
surface area which is not smaller than 3 times and, particularly,
from 5 to 10 times as great as the to-be-molded area of the
thermoplastic resin sheet.
[0164] The to-be-molded area of the thermoplastic resin sheet
stands for the area of the sheet on the inside of a portion that is
held as a flange in molding the sheet.
[0165] When the surface area of the plug is smaller than the
above-mentioned range, it becomes difficult to impart molecular
orientation to the molded container to a sufficient degree. Namely,
the container exhibits insufficient mechanical strength, decreased
heat resistance and, besides, the walls thereof are whitened during
the heat-setting.
[0166] The surface temperature Tp of the plug differs depending
upon the plug of the first step and the plug of the second step in
the one-step method and the two-step method.
[0167] (One-Step Molding Method)
Tg<Tp<Th (8)
[0168] wherein Tg is a glass transition point of the thermoplastic
polyester, and Th is a heat-setting temperature by using the female
mold described later.
[0169] When the plug temperature is lower than the above range, the
stretching becomes locally excessive in executing the primary
molding, and it is not allowed to obtain the primary molded article
having a good thickness profile.
[0170] When the plug temperature exceeds the above range, on the
other hand, the plug exhibits a decreased effect for cooling and
imparting the shape.
[0171] (Second Step in the Two-Step Molding Method).
Tg<Tp<Tc (9)
[0172] wherein Tg is a glass transition point of the thermoplastic
polyester, and Tc is a crystallization start temperature of the
thermoplastic polyester.
[0173] When the plug temperature is lower than the above range, the
stretching becomes locally excessive in executing the primary
molding, and it is not allowed to obtain the primary molded article
having a good thickness profile.
[0174] When the plug temperature exceeds the above range, on the
other hand, the sheet is partly whitened in the initial stage of
the stretch-molding and it is not allowed to obtain the primary
molded article having a transparent and favorable surface.
[0175] (First Step in the Two-Step Molding Method).
Tg-30.degree. C.<Tp<Th (10)
[0176] wherein Tg is a glass transition point of the thermoplastic
polyester, and Th is a heat-setting temperature by using the female
mold described later.
[0177] When the plug temperature is lower than the above range, the
female mold exhibits a decreased effect for heat-setting, and an
extended period of molding time is required for accomplishing a
predetermined heat-setting.
[0178] When the plug temperature exceeds the above range, on the
other hand, the plug exhibits a decreased effect for cooling and
imparting the shape.
[0179] The female mold has a cavity of a size larger than the plug
in either the radial direction or the axial direction. Due to the
difference in the size (clearance), the secondary molded article is
biaxially oriented as it is being molded with the compressed air.
The clearance gives an important meaning in the lower part of the
barrel portion of the container, in preventing the bottom portion
from being whitened, in the rate of molding and in imparting
resistance against deformation by heating.
[0180] It is desired that the clearance CL between the plug and the
female mold is 0.3 mm.ltoreq.CL.ltoreq.1.0 mm and, particularly,
0.5 mm.ltoreq.CL.ltoreq.0.75 mm. The CL which is not larger than
0.3 mm lowers the cooling efficiency, rate of molding, heating
efficiency and resistance against deformation by heating. On the
other hand, the CL which is not smaller than 1.0 mm deteriorates
the shape-imparting performance.
[0181] The heat-setting temperature (Th) by the female mold is
higher than the resin sheet temperature (Ts) as a matter of course
and is, generally, from 120 to 220.degree. C. and, particularly,
from 150 to 200.degree. C. When the heat-setting temperature is
lower than the above range, the heat resistance is not imparted to
a sufficient degree. When the heat-setting temperature exceeds the
above range, on the other hand, the resin of the flange portion is
thermally deteriorated resulting in a drop in the mechanical
strength of the resin.
[0182] The heat-resistant resin container of the second embodiment
of the present invention is obtained by molding the thermoplastic
polyester sheet, at least the side wall of the container being
oriented and crystallized by stretching, and the crystallinity in
the outer surface of the side wall being greater than the
crystallinity in the inner surface thereof.
[0183] The heat-resistant resin container of the present invention
has a feature in that the crystallinity (Co) in the outer surface
of the side wall of the container is greater than the crystallinity
(Ci) in the inner surface thereof due to that the outer surface of
the secondary molded article is heat-set upon coming in contact
with the inner surface of the female mold.
[0184] The container of the present invention, therefore, includes
the outer surface layer having excellent heat resistance and
rigidity, and the inner surface layer having flexibility and impact
resistance, which are being distributed in the direction of
thickness, creating a structure having excellent heat resistance
and impact resistance in combination. In the flange portion,
further, the surface to be heat-sealed has a low crystallinity
offering an advantage of excellent heat-sealability.
[0185] It is desired that the crystallinity (Co) in the outer
surface is not smaller than 20% and, particularly, from 25 to 50%,
and that the difference (Co--Ci) between the crystallinity (Co) in
the outer surface and the crystallinity (Ci) in the inner surface
is not smaller than 10% in the flange portion, and is not smaller
than 1% in other portions, from the standpoint of attaining the
above-mentioned effect.
[0186] The heat-resistant resin container of the present invention
has the flange portion, the side wall portion and the bottom
portion. Here, it is desired that the ratio (H/D) of the height (H)
of the container to the diameter (D) of the container is not
smaller than 0.5 and, particularly, in a range of from 1.2 to 2.3,
from the standpoint of moldability, imparting molecular orientation
and appearance.
[0187] In the present invention, the female mold that is used is
heated at the heat-setting temperature, and the wall of the flange
portion is less subject to be molecularly oriented. In general,
therefore, the container is obtained having a flange portion that
is cloudy. On the other hand, the side wall of the container is
effectively and molecularly oriented suppressing lamella
crystallization and is, hence, transparent when there is contained
no pigment exhibiting excellent appearance.
[0188] The container of the present invention has excellent heat
resistance suppressing a change in the volume to be not larger than
1.0% even after the container is heat-treated in an oven at such a
temperature that the side wall of the container is heated at
90.degree. C. for 3 minutes.
[0189] The molding operation according to the second embodiment of
the present invention will now be described with reference to FIGS.
8 to 18 of the accompanying drawings.
[0190] (Constitution of the Device)
[0191] The device used for the production method of the invention
roughly comprises, as shown in FIG. 8, a plug 1, a female mold 2
and a clamping metal mold 3.
[0192] The plug 1 works to stretch-mold the resin sheet 4 into an
article (primary molded article) that comes in agreement with the
outer surface of the plug, and to shrink-mold it to a final article
(tertiary molded article). Here, the primary molded article and the
tertiary molded article are nearly in agreement in shape and in
size.
[0193] If described in further detail, the plug 1 includes a short
cylindrical portion 11 that serves as a stack portion of the
container in an upper part on the outer surface thereof, and a
tapered portion 12 connected to the lower side of the cylindrical
portion and having a diameter contracting downward. An annular rim
13 is formed along the periphery in the bottom of the plug 1, the
annular rim 13 protruding downward in an arcuate shape by a small
distance in cross section. A bottom panel 14 is positioned in the
annular rim 13 and is protruding upward by a small distance from
the lower end of the rim. A gas passage 15 is formed in the axial
direction of the plug 1 for introducing the compressed air and for
reducing the pressure.
[0194] The female mold 2 used in the present invention works to
mold the primary molded article formed by using the plug 1 into a
secondary molded article of a size larger than the primary molded
article by using the compressed air, and to heat-set the secondary
molded article that is formed.
[0195] If described in further detail, the female mold 2 has in the
upper part thereof a holding surface 25 for holding the peripheral
edge of the resin sheet in cooperation with the clamping metal mold
3. Further, a gas passage 26 is formed in the central portion of
the female mold for discharging or supplying the gas.
[0196] The clamping metal mold 3 is to clamp the peripheral edge of
the resin sheet in cooperation with the holding surface of the
female mold 2, and comprises a short hollow cylinder. That is, the
clamping metal mold 3 has an inner surface 31 of a diameter nearly
the same as the cylindrical inner surface of the female mold, and
has a holding surface 32 at the lower end thereof for holding the
peripheral edge of the disk-like resin sheet.
[0197] The plug 1, the female mold 2 and the clamping metal mold 3
are arranged in concentric, the plug 1 and the female mold 2 being
allowed to move relative to each other in the axial direction (up
and down in the drawing) so as to be in mesh with each other and to
separate away from each other, and the clamping metal mold 3 being
similarly allowed to move in the axial direction.
[0198] (Step of Supplying the Thermoplastic Resin Sheet)
[0199] In FIG. 8, either the plug 1 or the female mold 2 is at an
ascended position and the other one is at a descended position, and
the resin sheet 4 heated at a stretching temperature is supplied
into between the female mold 2 and the clamping metal mold 3.
[0200] (Step of Clamping/Pre-Stretching the Thermoplastic Resin
Sheet)
[0201] Then, the clamping metal mold 3 is lowered to hold the
peripheral edge of the resin sheet 4 between the holding surface 25
of the female mold 2 and the holding surface 32 of the clamping
metal mold 3 as shown in FIG. 9.
[0202] The resin sheet 4 that is clamped is, then,
inflation-deformed in a direction opposite to the direction in
which the plug 1 is pushed by using the compressed air, in order to
stretch and orient the stacking portion at the upper part of the
side wall of the container. In this embodiment, therefore, the
compressed air is supplied through the gas passage 26 of the female
mold 2 to inflation-deform the resin sheet 4 upward like a dome.
Therefore, a slightly inner portion of the resin sheet that is
clamped is effectively and molecularly oriented to establish a
structure which is thermally and mechanically strong.
[0203] (Step of Stretch-Molding Into the Primary Molded
Article)
[0204] The plug 1 is pushed into the resin sheet 4 that is clamped.
Referring to FIG. 10, the resin sheet is stretched in a shape in
line with the outer surface of the plug 1 except a bottom wall
portion 44, and is molded into a primary molded article 40a. That
is, a flange portion 41 is formed between the holding surface 25 of
the female mold 2 and the holding surface 32 of the clamping metal
mold 3, a stacking portion 42 is formed on the outer surface side
of the cylindrical portion 11 of the plug 1, and a tapered portion
43 is formed on the outer surface side of the tapered portion 12 of
the plug 1. Further, a bottom portion 44 is formed so as to be
supported by an annular rim portion 13 of the plug 1.
[0205] (Step of Molding Into the Secondary Molded Article with the
Compressed Air and of Heat-Setting)
[0206] The compressed air is supplied into the interior of the
primary molded article 40a in FIG. 10 through the gas passage 15 in
the plug 1 and/or a gap between the plug 1 and the inside of the
flange portion of the secondary molded article 40b. Referring to
FIG. 11, the primary molded article is formed into a secondary
molded article 40b comprising a side wall portion 42b along the
cylindrical inner surface 22 of the female mold 2 and a bottom wall
portion 44b along the inner bottom surface 23 of the female mold
2.
[0207] The inner surface of the female mold 2 has been heated at a
temperature for heat-setting the resin and, besides, the secondary
molded article 40b is pressed onto the inner surface of the female
mold 2 due to the compressed air from the interior. As shown in
FIG. 11, therefore, the secondary molded article 40b is heat-set
due to heat H conducted from the female mold 2, whereby the resin
is crystallized and distortion in the mold is relaxed.
[0208] (Step of Shrinking Into the Tertiary Mold, Imparting the
Shape and Cooling)
[0209] As the secondary molded article 40b is progressively
heat-set and as the compressed air is no longer supplied from the
interior, the secondary molded article 40b starts shrinking as
shown in FIG. 12.
[0210] Then, the pressure is reduced through the gas passage 15 of
the plug 1 and/or through the above-mentioned gap. As required, the
compressed air is supplied through the gas passage 26 of the female
mold 2, whereby the secondary molded article 40b that is heat-set
is correctly shaped following the outer surface of the plug 1 as
shown in FIG. 12, and is cooled down into a state in which it can
be taken out.
[0211] The thus obtained finally molded article (tertiary molded
article) 40 includes a flange portion 41, a cylindrical stacking
portion 42 continuous to the inner periphery of the flange portion,
a tapered portion 43 contracting downward to be continuous to the
lower end of the stacking portion, a rim portion (grounding
portion) 46 protruding downward to be continuous to the lower end
of the tapered portion, and a panel-like bottom portion 45
positioned over the rim portion maintaining a small distance.
[0212] (Step of Parting the Tertiary Molded Article)
[0213] Finally, referring to FIG. 13, the plug 1 and the clamping
metal mold 3 ascend, and the tertiary molded article 40 is taken
out from the female mold 2. To accomplish good parting, the air can
be blown onto the molded article 40 through the gas passages 15 and
26.
[0214] (Two-Step Molding Method)
[0215] The two-step molding method is carried out by using a first
pair of plugs 1a, a female mold 2a, a clamping metal mold 3a, a
second pair of plugs 1b, a female mold 2b and a clamping metal mold
3b. These devices, however, are basically constituted in the same
manner as those used in the one-step molding method. The
temperature of the female mold 2a in the first step is adjusted to
be not higher than the glass transition point Tg of the resin, and
the female mold 2b in the second step is heated at the heat-setting
temperature.
[0216] The step of supplying the thermoplastic resin sheet in FIG.
14 is the same as that of FIG. 8, the step of clamping and
pre-stretching the thermoplastic resin sheet is the same as that of
FIG. 9, the step of stretching the thermoplastic resin sheet is the
same as that of FIG. 10, and the step of molding the primary molded
article into the secondary molded article by using the compressed
air in FIG. 15 is the same as that of FIG. 11. Here, however, the
temperature on inner surface of the female mold 2a is adjusted to
be not higher than the glass transition point Tg, and the primary
molded article 40a is shaped to acquire the shape of the inner
surface of the female mold 2a to obtain the secondary molded
article 40b. The plug may have the shape the same as the finally
molded article or different therefrom.
[0217] In the step of parting the secondary molded article in FIG.
16, the female mold 2a descends, the plug 1a and the clamping metal
mold 3a ascend, and the secondary molded article 40b that has not
been heat-set is taken out from the female mold 2a.
[0218] In the step of inserting the secondary molded article into
the metal mold in FIG. 17, the secondary molded article 40b is held
by the plug 1b and the clamping metal mold 3b, and is inserted in
the cavity 21 of the female mold 2b. The flange portion 41 of the
secondary molded article 40b inserted in the cavity 21 of the
female mold 2b is held by the holding surface 25 of the female mold
2b and by the holding surface 32 of the clamping metal mold 3b.
[0219] In the step of molding the secondary molded article with the
compressed air and heat-setting the secondary molded article in
FIG. 18, the wall of the secondary molded article 40b is pressed
onto the inner surface of the female mold 2b that has been heated
at a heat-setting temperature by utilizing the compressed air
introduced through the gas passage 15 of the plug 1b and/or the gap
between the plug 1 and the inner side of the flange portion of the
secondary molded article 40b.
[0220] The step of heat-setting the secondary molded article is the
same as the one shown in FIG. 11, the step of shrinking the
secondary molded article into the tertiary molded article,
imparting the shape to it and cooling it is the same as the one
shown in FIG. 12, and the step of parting the tertiary molded
article is the same as the one shown in FIG. 13. Therefore, these
steps with reference to these drawings are not described here.
[0221] [Third Embodiment]
[0222] In this embodiment of the invention, the heat-resistant
container is produced in three steps; i.e., forming a pre-molded
article, forming an intermediate article and forming a final
container. Here, a distinguished feature resides in that the
intermediate article is formed and the final container is formed
both by heating (heat-setting) the solid-phase-molded article,
heat-shrinking the molded article, and cooling and shaping the
heat-shrunk article.
[0223] That is, by conducting the solid-phase molding in one step,
the wall of the final container is molecularly oriented (surface
oriented) to a conspicuous degree not only in the barrel portion
but also in the center of the bottom portion. Upon conducting the
heat-setting in the second step following the solid-phase molding,
further, the orientation and crystallization are promoted.
Moreover, by effecting the heat-shrinking following the
heat-setting, the distortion is effectively relaxed.
[0224] In the heat-resistant container of the present invention,
therefore, deformation due to heat is effectively prevented at the
time of heat-sterilization such as sterilization by boiling even in
the bottom portion which is an important portion for imparting the
self-standing performance to the container or for imparting
self-standing stability. Besides, the barrel portion of the
container exhibits excellent impact resistance withstanding the
impacts of when it falls down. Even in the bottom portion which can
be least oriented, no spherulite is formed, exhibiting not only
excellent impact resistance but also very good appearance such as
transparency.
[0225] Upon effecting the heat-shrinking between the heat-setting
and the cooling/shaping, further, good heat efficiency is
accomplished since the functions are separated between the heating
portion and the cooling portion as compared to when the heating and
cooling are effected in the same portion and, besides, the time for
occupying the mold can be shortened. Therefore, the method of the
present invention accomplishes such advantages as decreasing the
energy cost and improving the productivity.
[0226] (1) Molding into the Pre-Molded Article.
[0227] In the present invention, the pre-molded article is
desirably obtained by molding the sheet in solid phase, i.e., by
pressing the sheet using the plug for pre-molding, the sheet being
clamped by the clamping metal mold and by the female mold for
pre-molding, and by supplying the compressed gas into between the
sheet and the plug.
[0228] In molding the sheet in this case, it is desired that the
sheet is maintained at a temperature of from the glass transition
point (Tg) of the thermoplastic polyester+15.degree. C. to the
glass transition point+40.degree. C. The range of from the glass
transition point+15.degree. C. to the glass transition
point+40.degree. C. is the one where the PET resin is most
efficiently oriented and crystallized. When the sheet temperature
is lower than the above range, the resin is over-stretched at the
time of molding and is whitened. When the sheet temperature is
higher than the above range, on the other hand, the resin is not
oriented or crystallized to a sufficient degree and tends to become
whitened in a subsequent step of heat-setting due to heat
crystallization.
[0229] In forming the pre-molded article, further, it is desired to
maintain the plug at a temperature of from the glass transition
point of the thermoplastic polyester-30.degree. C. to the glass
transition point+20.degree. C. When the plug temperature lies
outside this temperature range, the resin temperature at the
contact portion undergoes a change due to the contact with the plug
during the stretch-molding, and the stretching is not evenly
effected.
[0230] It is further desired to maintain the female mold for
pre-molding at a temperature of from the glass transition point of
the thermoplastic polyester+10.degree. C. to the glass transition
point+50.degree. C. In order to efficiently promote the orientation
and crystallization in the bottom portion of the pre-molded
article, the female metal mold must be maintained at a temperature
of from the glass transition point+10.degree. C. of the
thermoplastic polyester to the glass transition point+50.degree.
C.
[0231] The plug used for stretch-molding the resin sheet into the
pre-molded article must have a surface area which lies at least
within a predetermined range. It is, generally, desired that the
plug has a surface area which is not smaller than 3 times and,
particularly, from 5 to 10 times as large as the area to be molded
of the thermoplastic resin sheet.
[0232] The area to be molded of the thermoplastic resin sheet
stands for the area of the sheet on the inside of a portion that is
held as a flange in molding the sheet.
[0233] When the surface area of the plug is smaller than the above
range, it becomes difficult to molecularly orient the molded
container to a sufficient degree; i.e., the container exhibits
insufficient mechanical strength, decreased heat resistance, and is
whitened on the walls during the heat-setting.
[0234] (2) Molding into an Intermediate Article.
[0235] It is desired that an intermediate article is molded from
the pre-molded article by inserting the pre-molded article in the
female mold for intermediate molding of which the temperature is
adjusted while supporting the pre-molded article by the plug for
intermediate molding, by shrinking the molded article along the
outer surface of the plug, and shaping and cooling the molded
article.
[0236] It is desired that the female mold for intermediate forming
is maintained at a temperature of not lower than the
crystallization start temperature of the thermoplastic polyester.
The molded article efficiently heat-shrinks when the temperature of
the female mold is high. When the temperature is set to be lower
than this range, however, the molded article cannot be shrunk along
the outer surface of the plug.
[0237] It is desired that the temperature of the plug for
intermediate molding is not higher than the temperature of the
female mold for intermediate molding and is maintained in a range
of from 80 to 110.degree. C. The temperature of the plug must be
set in a region lower than the temperature of the female mold. When
the temperature is lower than the above range, the molded article
is not efficiently heated by the conduction of heat, and the time
for heat-shrinking becomes long. When the temperature is higher
than this range, on the other hand, the molded article is not
cooled to a sufficient degree and undergoes deformation due to
shrinkage after the step of parting.
[0238] In the present invention, it is desired that the surface
area of the pre-molded article is from 1.1 times to 1.5 times as
large as the surface area of the intermediate product from the
standpoint of removing distortion and moldability. That is, when
the surface area is smaller than the above range, the distortion is
not removed to a sufficient degree due to heat shrinking. When the
area is larger than the above range, on the other hand, wrinkles
develop on the surface of the intermediate product due to the lack
of shrinking, and the intermediate article is not favorably
shaped.
[0239] (3) Molding into a Final Container.
[0240] In the method of the present invention, it is desired that
the female mold for final molding is maintained at a temperature of
not lower than the crystallization start temperature of the
thermoplastic polyester. The female mold must be maintained at a
temperature not lower than the crystallization start temperature
from the standpoint of promoting the crystallization. Due to the
heat-setting at this temperature, the orientation and
crystallization proceed to a sufficient degree, and the final
container exhibits improved heat resistance.
[0241] It is further desired that the plug for the final container
is maintained at a temperature in a range of from the glass
transition point of the thermoplastic polyester-20.degree. C. to
the glass transition point+20.degree. C. When the temperature is
lower than this range, the step of heat-setting is not efficiently
effected by the conduction of heat. When the temperature is higher
than this range, the cooling is not effected to a sufficient
degree, and the molded article undergoes deformation due to
shrinkage after the step of parting.
[0242] In the present invention, it is desired that the surface
area of the female mold for final molding is from 1.01 times to
1.10 times as large as the surface area of the plug for the final
container from the standpoint of removing distortion and
moldability. That is, when the ratio of the surface areas is
smaller than the above range, the distortion is not removed to a
sufficient degree due to heat shrinking. When the ratio of the
surface areas is larger than the above range, on the other hand,
wrinkles develop on the surface of the final container, and the
final container is not favorably shaped.
[0243] The molding operation according to a third embodiment of the
present invention will now be described with reference to FIGS. 20
to 30 of the accompanying drawings.
[0244] (Constitution of the Devices)
[0245] The devices used in the production method of the present
invention are the same as shown in FIGS. 8 to 19. The device used
in the one-step molding roughly includes a plug 11, a female mold
12 and a clamping metal mold 13 as shown in FIG. 20.
[0246] Further, the device used in the two-step molding includes a
plug 21, a female mold 22 and a clamping metal mold 23 as shown in
FIG. 23.
[0247] Further, the device used in the three-step molding includes
a plug 31, a female mold 32 and a clamping metal mold 33 as shown
in FIG. 27.
[0248] The plug 11 for the one-step molding assists the
stretch-molding of the polyester sheet 4 into the pre-molded
article 5, the plug 21 for the two-step molding has an outer shape
for shrinking and shaping the pre-molded article 6 into an
intermediate particle 6, and the plug 31 for the three-step molding
has an outer shape for shrinking and shaping the intermediate
article 6 into a finally molded article 7.
[0249] More specifically, the plug 11, plug 21 and plug 31, in
common, have a short cylindrical portion 14 that serves as a
stacking portion of the container at an upper part of the outer
surface, and a tapered portion 15 connected to the lower side of
the cylindrical portion and having a diameter that is contracting
downward. An annular rim 16 is formed along the periphery on the
bottom of the plugs 11, 21, 31, protruding downward in a nearly
arcuate shape by a small distance in cross section. A bottom panel
portion 17 is positioned inside the annular rim 16 protruding
upward by a small distance from the lower end of the rim. A gas
passage 18 is formed in the axial direction of the plugs 11, 21, 31
for introducing the compressed air and for reducing the
pressure.
[0250] The female mold 12 for the one-step molding used in the
present invention is for defining the shape of the pre-molded
article 5 molded by using the compressed air, the female mold 22
for the two-step molding is for heating the pre-molded article 5
and for shrinking it into the intermediate article 6, and the
female mold 32 for the three-step molding is for heat-setting the
intermediate article 6 by heating it and for shrinking it into the
final molded article 7.
[0251] If described in further detail, the female mold 12, female
mold 22 and female mold 32, in common, have, at their upper parts
thereof, a holding surface 25 for holding the peripheral edge of
the resin sheet, of the pre-molded article or of the intermediate
article in corporation with pairs of clamping molds 13, clamping
molds 23 and clamping molds 33. Further, a gas passage 26 is formed
in the central portions of the female molds for discharging and
supplying the gas.
[0252] The clamping metal molds 13, 23 and 33 work to clamp the
peripheral edge of the resin sheet, of the pre-molded article or of
the intermediate article in cooperation with the holding surfaces
of the female molds, and comprise short hollow cylinders. That is,
the clamp metal molds 13, 23 and 33 have an inner surface 34 of a
diameter nearly the same as that of the cylindrical inner surface
of the female mold, and have, at the lower ends thereof, a holding
surface 35 for holding the peripheral edge of the disk-like resin
sheet.
[0253] The plug 11 (21, 31), female mold 12 (22, 32) and the
clamping metal mold 13 (23, 33) are arranged in concentric, the
plug 11 (21, 31) and the female mold 12 (22, 32) being provided to
move relative to each other in the axial direction (up and down in
the drawing) so as to come in mesh with each other and to separate
away from each other, and the clamping metal mold 13 (23, 33) being
similarly provided to move in the axial direction.
[0254] (First Molding Step)
[0255] Step of Clamping the Sheet.
[0256] In FIG. 20, either the plug 11 or the female mold 12 is at
the ascended position and the other one is at the descended
position, and the resin sheet 4 heated at a stretching temperature
is supplied to between the female mold 12 and the clamping metal
mold 13.
[0257] The polyethylene terephthalate sheet 4 heated at a molding
temperature of 105.degree. C. is clamped by the clamping metal mold
13 and by the female mold 12, and is molded.
[0258] The polyethylene terephthalate used in this embodiment has
an inherent viscosity (IV) of 0.8, a glass transition point (Tg) of
70.degree. C. and a sheet thickness of 1.2 mm.
[0259] Step of Stretching/Shaping.
[0260] Referring to FIG. 21, the sheet 4 is stretched, oriented and
crystallized as the plug 11 of which the temperature is adjusted
descends. Immediately thereafter, the compressed air (0.6 MPa) is
introduced through the gas passage 18 in the plug and through a gap
between the plug and the molded article and, as required, vacuum is
introduced through the gas passage 26 of the female mold, whereby
the molded article is pressed onto the female mold 12 adjusted at
100.degree. C. and is shaped to be in conformity with the shape of
the inner walls of the female mold.
[0261] Pre-Molded Article.
[0262] The plug 11 is ascended, and the clamping metal mold 13 and
the female mold 12 are opened to take out the pre-molded article 5
that has been oriented and crystallized.
[0263] Referring to FIG. 22, the pre-molded article 5 includes a
cylindrical barrel portion 51, a closed bottom portion 52
continuous to the lower end of the barrel portion and a flange
portion 53 continuous to the upper end of the barrel portion.
[0264] (Second Molding Step)
[0265] An intermediate article 6 is formed from the pre-molded
article 5 formed in the first molding step.
[0266] Step of Insertion in the Metal Mold.
[0267] In FIG. 23, the pre-molded article 5 is supported by the
plug 21 and is inserted in the female mold 22.
[0268] Step of Heat-Shrinking.
[0269] In FIG. 24, the pre-molded article 5 heat-shrinks due to the
conduction of heat from the inner wall of the female mold 22 heatd
at 180.degree. C.
[0270] Step of Cooling/Shaping.
[0271] Referring to FIG. 25, the pre-molded article 5, then,
shrinks up to the outer surface of the plug 21 and, nearly at the
same time, cooled and shaped by the outer surface of the plug 21
heated at 110.degree. C. due to vacuum through the gas passage 18
of the plug and through the gap between the plug and the molded
article and, further as required, due to the compressed air through
the gas passage 26 of the female mold 22.
[0272] Intermediate Article.
[0273] The clamping metal mold 23 and the female mold 22 are opened
and the plug 21 is ascended to take out the intermediate product 6
that is shrunk. Here, as required, the air is blown from the outer
side to cool the intermediate article so that it is quickly
parted.
[0274] As shown in FIG. 26, the intermediate product 6 that is
formed includes a short cylindrical stacking portion 61 and a
tapered portion 62 having a diameter contracting downward. The
lower end of the tapered portion is closed by a bottom panel
portion 64 through an annular rim 63 that protrudes downward.
Further, a flange portion 65 is formed at the upper end of the
stacking portion 61.
[0275] (Third Molding Step)
[0276] A finally molded article 7 is formed from the intermediate
article 6 formed in the second molding step.
[0277] Step of Insertion in the Metal Mold.
[0278] In FIG. 27, the intermediate article 6 is supported by the
plug 31 and is inserted in the female mold 32.
[0279] Step of Heat-Setting.
[0280] In FIG. 28, the compressed air (0.6 MPa) is introduced
through the air vent 18 of the plug and through the gap between the
plug and the molded article and, as required, vacuum is introduced
through the vent 26 of the female mold in order to heat-set the
molded article 6a while pressing it onto the surface of the female
mold 32 heated at 200.degree. C.
[0281] Step of Shrinking/Shaping.
[0282] Referring next to FIG. 29, the molded article starts
heat-shrinking due to the transfer of heat from the female mold 32.
Further, vacuum is introduced through the gas passage 18 of the
plug 31 and through the gap between the plug and the molded article
and further, as required, the compressed air is introduced through
the gas passage 26 of the female mold 32, so that the molded
article shrinks up to the outer surface of the plug 31 and that the
molded article is cooled and shaped into the finally molded article
7 due to the contact with the plug 31 heated at 90.degree. C.
[0283] Step of Parting.
[0284] Finally, the female mold 32 and the clamping metal mold 33
are opened as shown in FIG. 30, and the plug 31 is ascended to take
out the finally molded article 7.
[0285] [Fourth Embodiment]
[0286] A preferred container of the present invention is obtained
by heat-molding a sheet having a thermoplastic polyester layer
comprising chiefly an ethylene terephthalate unit, and includes a
flange portion, a barrel portion and closed bottom portion, and has
a feature in that the thermoplastic polyester in the bottom portion
of the container has a crystallinity of not smaller than 15% and
the bottom portion of the container is substantially transparent
and exhibits a distinguished diffraction peak on the surface of an
index of a plane (010) in the X-ray diffraction.
[0287] Though the container of this type of the invention is
obtained by heat-molding the thermoplastic polyester sheet, the
thermoplastic polyester in the bottom portion of the container
exhibits a crystallinity of not smaller than 15% and, hence,
excellent heat resistance. Besides, the bottom portion of the
container exhibits astonishing properties in combination, i.e., a
distinguished diffraction peak on the surface of an index of a
plane (010) in the X-ray diffraction, and substantial
transparency.
[0288] In obtaining the container by molding the sheet, it is
relatively easy to molecularly orient the barrel portion by
stretching. It is, however, relatively difficult to molecularly
orient the bottom portion by stretching. It is, however, important
to impart the required properties to the bottom portion of the
container even though it is the one obtained by molding the sheet
from the practical point of view. For example, the bottom portion
of the container that has not been molecularly oriented to a
sufficient degree is liable to be cracked due to impacts such as of
when it is caused to fall down. Further, the bottom portion of the
container having insufficient heat resistance is deformed during
the sterilization by heating depriving the container of the
self-standing performance and standing stability.
[0289] When the sheet-molded container is heat-treated such as
heat-set in order to impart heat resistance thereto, the bottom
portion is whitened to a conspicuous degree arousing such a problem
that a purchaser may doubt the content has been degenerated (e.g.,
dregs have been precipitated).
[0290] According to the embodiment of the present invention, the
surface is oriented even at the center of the bottom portion of the
container so as to exhibit a distinguished diffraction peak on the
surface having an index of a plane (010) by the X-ray diffraction
and, besides, the bottom portion is crystallized to possess a
crystallinity of not smaller than 15%. Thus, there are obtained
excellent impact resistance and heat resistance effectively
preventing the center of the bottom portion from being whitened and
maintaining transparency even at the center of the bottom
portion.
[0291] FIG. 31 shows an X-ray diffraction image at the center of
the bottom portion of the container of the present invention
measured as described above.
[0292] From a comparison of the X-ray diffraction image of the
bottom portion of the PET container of the invention shown in FIG.
31 with the X-ray diffraction image of the crystalline PET shown in
FIG. 4, it is obvious that the diffraction peak is conspicuously
exhibited on the surface of an index of a plane (010) in the bottom
portion of the container of the invention while the diffraction
peak is disappearing from the surface of an index of a plane (100).
In the bottom portion of the container of the present invention,
the X-ray diffraction image is distinctly exhibited as shown in
FIG. 31, i.e., the diffraction peak is ditinctly exhibited on the
surface of the index of a plane (010) while the diffraction peak is
disappearing from the surface of the index of a plane (100), from
which it is reasonable to consider that a benzene plane has been
arranged in parallel with the wall surface in the bottom portion of
the container.
[0293] That is, in the X-ray diffraction method, if the benzene
plane is nearly in parallel with the surface of the sample sheet,
the diffraction is not measured on the plane (100) but the
diffraction is measured on the plane (010) nearly at right angles
thereto. Thus, a large diffraction peak intensity on the plane
(010) means that the benzene plane of a unit of ethylene
terephthalate is in parallel with the surface of the sheet.
Conversely, a large diffraction peak intensity on the plane (100)
means that the benzene plane of a unit of ethylene terephthalate is
inclined relative to the film surface and is not in parallel
therewith.
[0294] It is thus obvious that the surface has been oriented to a
conspicuous degree on the wall even at the center of the bottom
portion of the container of the present invention.
[0295] The wall has a crystallinity of not smaller than 15% at the
center in the bottom portion of the container of the present
invention.
[0296] In the container of the present invention, even the center
of the bottom portion has been crystallized. However, the crystals
are not those (spherulite) of the type but are the crystals that
are oriented offering such advantages as excellent heat resistance
and impact resistance as well as excellent transparency.
[0297] The wall at the center of the bottom portion of the
container of the present invention exhibits a haze value of,
generally, not larger than 20% and, particularly, not larger than
10% as measured by using a hazeometer manufactured by Suga Shikenki
Co.
[0298] In the container of the present invention, the wall at the
center of the bottom portion has been crystallized due to the
surface orientation as described already. The crystallinity due to
the orientation can be evaluated in terms of the oriented
crystallization tendency (U) represented by the above-mentioned
formula (I).
[0299] That is, as described already, the diffraction peak
intensity on the surface of an index of a plane (010) by PSPC-MDG
is related to the degree of orientation of the surface of the wall.
The oriented crystallization tendency (U) represented by the
above-mentioned formula (I) is to represent the diffraction peak
intensity H (010) which is standardized with the diffraction peak
intensity on the surface of an index of a plane (-110). The larger
this value, the larger the degree of crystallization due to
orientation.
[0300] In the present invention, it is desired that the oriented
crystallization tendency (U) is not smaller than 1.3 at the center
of the bottom portion from the standpoint of impact resistance,
heat resistance and transparency.
[0301] It is desired that the container of the present invention is
obtained by solid-phase-molding the sheet which contains a
thermoplastic polyester and, more particularly, by
solid-phase-molding the sheet through at least two steps of
stretching and a step of heat-shrinking.
[0302] More concretely, the container of the invention is
preferably produced by the method shown in FIGS. 20 to 30 and
described by way of the third embodiment.
[0303] [Polyester]
[0304] The polyester sheet may be the one of a single polyester
layer or a multi-layer sheet comprising a polyester layer and other
resin layers.
[0305] In the present invention, the polyester constituting a sheet
of at least one layer is a polyester of which the thermoplastic
polyester is derived from a carboxylic acid component comprising
chiefly an aromatic dicarboxylic acid and from an alcohol component
comprising chiefly an aliphatic diol and, particularly, is a
polyester in which not less than 50 mol % of the carboxylic acid
component comprises a terephthalic acid component and of which not
less than 50 mol % of the alcohol component comprises an ethylene
glycol component.
[0306] The polyester may be a homopolyester, a copolymerized
polyester, or a blend of two or more kinds thereof provided the
above-mentioned conditions are satisfied.
[0307] Examples of the carboxylic acid component other than the
terephthalic acid component, include isophthalic acid,
naphthalenedicarboxylic acid, P-.beta.-oxyethoxybenzoic acid,
biphenyl-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic
acid, 5-sodiumsulfoisophthalic acid, hexahydoterephthalic acid,
adipic acid, sebacic acid, trimellitic acid and pyromellitic
acid.
[0308] As the alcohol component other than ethylene glycol, on the
other hand, there can be exemplified 1,4-butanediol, propylene
glycol, neopentyl-glycol, 1,6-hexylene glycol, diethylene glycol,
triethylene glycol, cyclohexane dimethanol, ethylene oxide adduct
of bisphenol A, glycerol, trimethylolpropane, pentaerythritol,
dipentaerythritol and sorbitan.
[0309] Though not necessarily limited thereto only, preferred
examples of the thermoplastic polyester include polyethylene
terephthalate which is most desirable, as well as
polyethylene/butylene terephthalate, polyethylene
terephthalate/2,6-naphthalate, polyethylene
terephthalate/isophthalate, and the above compounds and
polybutylene terephthalate, polybutylene
terephthalate/isophthalate, polyethylene-2,6-naphthalate,
polybutylene terephthalate/adipate,
polyethylene-2,6-naphthalate/isophthalate, polybutylene
terephthalate/adipate, and a blend of two or more kinds
thereof.
[0310] The polyester should have a molecular weight in a range of
forming a film, and should have an inherent viscosity [IV] of not
smaller than 0.5 and, particularly, in a range of from 0.6 to 1.5
as measured by using a phenol/tetrachloroethane mixed solvent as a
solvent, from the standpoint of moldability, mechanical properties
and heat resistance.
[0311] The polyester may contain at least one kind of reforming
resin component such as ethylene polymer, thermoplastic elastomer,
polyarylate or polycarbonate. It is desired that the reforming
resin component is used in an amount of up to 50 parts by weight
and, particularly preferably, in an amount of from 5 to 35 parts by
weight per 100 parts by weight of the polyester.
[0312] As the ethylene polymer, there can be exemplified low-,
medium- or high-density polyethylene, linear low-density
polyethylene, linear ultra-low-density polyethylene,
ethylene-propylene copolymer, ethylene-butene-1 copolymer,
ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate
copolymer, ionically crosslinked olefin copolymer (ionomer) and
ethylene-acrylic acid ester copolymer.
[0313] Among them, ionomer is preferred. As the base polymer of the
ionomer, there can be used an ethylene-(meth)acrylic acid copolymer
or an ethylene-(meth)acrylic acid ester-(meth)acrylic acid
copolymer. As the kind of ions, there can be used Na, K or Zn.
[0314] As the thermoplastic elastomer, there can be used
styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene
block copolymer, hydrogenated styrene-butadiene-styrene block
copolymer and hydrogenated styrene-isoprene-styrene block
copolymer.
[0315] The polyarylate can be defined as a polyester derived from a
dihydric phenol and a dibasic acid. As the dihydric phenol, there
can be used bisphenols, such as 2,2'-bis(4-hydroxyphenyl)propane
(bisphenol A), 2,2'-bis(4-hydroxyphenyl)butane (bisphenol B),
1,1'-bis(4-hydroxyphenyl)e- thane, bis(4-hydroxyphenyl)methane
(bisphenol F), 4-hydroxyphenyl ether and p-(4-hydroxy)phenol. Among
them, bisphenol A and bisphenol B are preferred. As the dibasic
acid, there can be used terephthalic acid, isophthanol acid,
2,2-(4-carboxyphenyl)propane, 4,4'-dicarboxydiphenyl ether, and
4,4'-dicarboxybenzophenone-.
[0316] The polyarylate may be a homopolymer derived from the above
monomeric component or may be a copolymer. Or, the polyarylate may
be a copolymer of an aliphatic glycol with an ester unit derived
from a dibasic acid within a range of not spoiling the essentials
thereof. These polyacrylates are available as U-series or AX-series
of U-polymers of Unitika Co., as Ardel D-100 of UCC Co., as APE of
Bayer. Co., as Durel of Hoechst Co., as Arylon of Du Pont Co. and
as NAP resin of Kanegafuchi Kagaku Co.
[0317] The polycarbonate is a carbonic acid ester resin derived
from bicyclic dihydric phenols and phosgene, and features a high
glass transition point and heat resistance.
[0318] As the polycarbonate, there can be used those derived from
bisphenols such as 2,2'-bis(4-hydroxyphenyl)propane (bisphenol A),
2,2'-bis(4-hydroxyphenyl)butane (bisphenol B),
1,1'-bis(4-hydroxyphenyl)e- thane, bis(4-hydroxyphenyl)methane
(bisphenol F), 1,1-bis(4-hydroxyphenyl)- cyclohexane,
1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl-
)-1-phenylmethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane and
1,2-bis(4-hydroxyphenyl)ethane.
[0319] The sheet used in the present invention may be blended with
known blending agents used for the plastics, such as antioxidant,
heat stabilizer, ultraviolet-ray absorbing agent, antistatic agent,
filler, coloring agent, etc. To make the molded container opaque,
the sheet may be blended with fillers such as calcium carbonate,
calcium silicate, alumina, silica, various clays, calcined gypsum,
talk or magnesia, inorganic pigments such as titanium white, yellow
iron oxide, red iron oxide, ultramarine or chromium oxide, or
organic pigments.
[0320] From the standpoint of strength and moldability of the
container, it is desired that the plastic sheet used in the present
invention has a thickness of, usually, from 0.5 to 5 mm and,
particularly, from 1 to 3 mm though it may vary depending upon the
size of the container and the like.
[0321] The container of the present invention may comprise the
above single polyester layer or may comprise a laminated layer
thereof with layers of other resins such as gas-barrier resin,
recycled polyester resin, oxygen-absorbing resin, etc.
[0322] The layers of other resins may be to form a two-layer
constitution serving as an inner layer or an outer layer, or to
form a three-layer constitution serving as an intermediate
layer.
[0323] As the gas-barrier resin, there can be used any one that has
been known, such as ethylene-vinyl alcohol copolymer (EVOH), nylon
resin (Ny), gas-barrier polyester resin (BPR) or cyclic olefin
copolymer.
[0324] As the gas-barrier resin layer, there can be used an
ethylene-vinyl alcohol copolymer containing a vinyl alcohol in an
amount of from 40 to 85 mol % and, particularly, from 50 to 80 mol
%.
[0325] There is no particular limitation on the molecular weight of
the ethylene-vinyl alcohol copolymer provided it is large enough
for forming a film. Generally, however, it is desired that the
ethylene-vinyl alcohol copolymer has an inherent viscosity (I.V.)
in a range of from 0.07 to 0.17 dl/g as measured in a mixed solvent
of 85% by weight of phenol and 15% by weight of water at a
temperature of 30.degree. C.
[0326] Other examples of the gas-barrier resin include nylon resin
such as nylon 6, nylon 6,6, nylon 6/nylon 6,6 copolymer and
polyamide containing a xylylene group.
[0327] As the .omega.-aminocarboxylic acid component constituting
the nylon resin, there can be exemplified .epsilon.-caprolactam,
aminoheptanoic acid and aminooctanoic acid. As the diamine
component, there can be exemplified aliphatic diamines such as
hexamethylene diamine, alicyclic diamine such as piperazine, as
well as m-xylylene diamine and/or p-xylylenediamine. As the dibasic
acid component, there can be exemplified aliphatic dicarboxylic
acids such as adipic acid, sebacic acid and suberic acid. As the
aromatic dicarboxylic acid, there can be exemplified terephthalic
acid and isophthalic acid.
[0328] In particular, there can be exemplified a polyamide having
excellent barrier property, in which not less than 35 mol % and,
particularly, not less than 50 mol % of the diamine component is an
m-xylylene and/or a p-xylylenediamine, and in which the dibasic
component is an aliphatic dicarboxylic acid and/or an aromatic
dicarboxylic acid and, as required, containing not more than 25 mol
% and, particularly, not more than 20 mol % of an
.omega.-aminocarboxylic acid unit per the whole amide recurring
units.
[0329] It is desired that the polyamide that is used has a relative
viscosity (.eta.rel) of from 0.4 to 4.5 as measured by using a
sulfuric acid of 96% by weight at a concentration of 1 g/100 ml and
at a temperature of 25.degree. C.
[0330] As the gas-barrier resin, there can be used a gas-barrier
polyester. A gas-barrier polyester (hereinafter often written as
BPR) contains, in a polymer chain thereof, a terephthalic acid
component (T) and an isophthalic acid component (I) at a molar
ratio T:I of from 95:5 to 5:95 and, particularly, from 75:25 to
25:75, and contains an ethylene glycol component (E) and a
bis(2-hydroxyethoxy)benzene component (BHEB) at a ratio E:BHEB of
from 99.999:0.001 to 2.0:98.0 and, particularly, from 99.95:0.05 to
40:60.
[0331] As the BHEB, there is preferably used a
1,3-bis(2-hydroxyethoxy)ben- zene.
[0332] It is desired that the polyester (BPR) has a molecular
weight which is at least large enough for forming a film and,
generally, has an inherent viscosity [.eta.] of from 0.3 to 2.8
dl/g and, particularly, from 0.4 to 1.8 dl/g as measured in a mixed
solvent of phenol and tetrachloroethane at a weight ratio of 60:40
at a temperature of 30.degree. C.
[0333] As the recycled polyester (PCR), there can be used a
granular or a powdery polyester obtained by recovering the used
polyester containers, removing foreign matters therefrom, and
washing and drying the polyester. It is desired that the recycled
polyester has an inherent viscosity (IV) in a range of from 0.60 to
0.75 as measured by the above-mentioned method.
[0334] The recycled polyester can be used by itself or being
blended with a virgin polyester. When the recycled polyester has a
decreased inherent viscosity, it is desired to use the recycled
polyester being blended with the virgin polyester. In this case, it
is desired that the blending ratio of recycled polyester:virgin
polyester is from 9:1 to 2:8.
[0335] It is desired that the recycled polyester (PCR) layer is
used in a multi-layer structure having three or more layers being
sandwiched by the virgin polyesters.
[0336] As other resin layers, there can be used a layer of an
oxygen-absorbing resin. As the layer of the oxygen-absorbing resin,
there can be used the one containing a metallic oxidizing catalyst
and an oxidizing organic component.
[0337] The oxidizing organic component is a resin which is oxidized
with oxygen in the air due to the catalytic action of a transition
metal catalyst, i.e., (i) a resin containing a carbon side chain
(a), and containing, in the main chain or in the side chain
thereof, at least one functional group (b) selected from the group
consisting of carboxylic acid ester group, carboxylic acid amide
group and carbonyl group, (ii) a polyamide resin, or (iii) an
ethylene-type polymer containing an unsaturated group.
[0338] As the metallic oxidizing catalyst, there can be exemplified
metal components of the Group VIII of periodic table, such as iron,
cobalt and nickel, as well as metals of the Group I, such as copper
and silver, metals of the Group IV, such as tin, titanium and
zirconium, vanadium which is of the Group V, chromium which is of
the Group VI, and manganese which is of the Group VII. Among these
metal components, cobalt is particularly preferred because of its
large oxygen-absorbing rate.
[0339] The transition metal catalysts are usually used in the form
of inorganic acid salts or organic acid salts of the above
transition metals having low valencies. It is desired that these
catalysts are used in amounts of from 100 to 1000 ppm in the
resin.
[0340] The container of the present invention may include layers of
any other resins in addition to the above-mentioned polyester resin
layer and the gas-barrier resin layer.
[0341] For example, when there is no heat adhesiveness between the
polyester layer and the gas barrier resin layer, an adhesive resin
layer may be interposed between the above two resin layers.
[0342] Though there is no particular limitation, there can be used,
as the adhesive resin, an acid-modified olefin resin such as maleic
anhydride-grafted polyethylene, maleic anhydride-grafted
polypropylene and the like.
[0343] Referring to FIG. 7 illustrating, in cross section, the
structure of a multi-layer plastic sheet, the sheet 2 has a
laminated-layer structure including an inner layer 21 and an outer
layer 22 of a thermoplastic polyester resin, an intermediate layer
23 of a gas-barrier resin, and adhesive layers 24 and 25 which are,
as required, provided for strongly adhering the inner layer, the
outer layer and the intermediate layer.
[0344] The laminated-layer sheet is preferably obtained by
co-extruding the above-mentioned thermoplastic polyester resin, the
gas-barrier resin and, as required, the adhesive resin into the
above-mentioned multi-layer structure through a multi-layer
multiple die. The laminated-layer sheet, however, can also be
produced by any other layer lamination technology, such as sandwich
lamination, extrusion coating method or the like method.
EXAMPLES
[0345] The invention will now be described by way of working
examples in which measurement was taken in a manner as described
below.
[0346] Measurement of Crystallinity.
[0347] As for the wall of the lower part of the barrel portion, a
sample measuring 3 mm.times.3 mm was cut out from the thermoplastic
polyester layer 10 mm above the bottom surface of the container in
the axial direction of the container. A sample measuring 3
mm.times.3 mm was also cut out from the flange portion. The
densities of the samples were measured by using an n-heptane and a
carbon tetrachloride density-gradient tube (Ikeda Rika Co.) at a
temperature of 20.degree. C.
[0348] The crystallinity Xc was calculated in compliance with the
following formula,
Xc=(.rho.c/.rho.).times.(.rho.-.rho.am)/(.rho.c-.rho.am).times.100
[0349] .rho.: density of the sample (g/cm.sup.3)
[0350] .rho.am: amorphous density (1.335 g/cm.sup.3)
[0351] .rho.c: crystalline density (1.455 g/cm.sup.3)
[0352] X-ray Measurement.
[0353] As for the upper part of the wall of the barrel portion, a
sample was cut out from the thermoplastic polyester layer 15 mm
below the flange surface in the axial direction of the container.
As for the lower part of the wall of the barrel portion, the sample
was cut out from the thermoplastic polyester layer 10 mm above the
bottom surface of the container in the axial direction of the
container. The sample was so set that the axial direction of the
container was on the vertical axis of the optical coordinate, and
the diffraction peak was measured by the transmission method
relying upon the micro X-ray diffraction (PSPC-150C)(manufactured
by Rigaku Denki Co.).
[0354] The measurement was taken under the conditions of a tube
voltage of 30 KV, a tube current of 150 mA, a collimator of 100
.mu.m and a measuring time of 1000 seconds.
[0355] After the measurement, the background was removed (base line
was corrected) over a range of 2.theta. of from 10.degree. to
35.degree., and a ratio of diffraction intensities was found on the
planes (010) and (-110).
[0356] Drop Impact Strength.
[0357] The container was filled with 220 cc of water, and a closure
member having a polyester layer on the innermost surface thereof
and the flange portion of the container were heat-sealed by using a
heat sealer (manufactured by Shinwa Kikai Co.) at a seal bar
temperature of 230.degree. C. for a sealing time of 2 seconds.
After sealing, the container was dropped on the concrete floor
surface from a height of 90 cm with the bottom portion of the
container being directed downward a maximum of 10 times. The number
n of the samples was 10, and average numbers until the samples were
broken were evaluated as follow:
2 Average number of times until broken Evaluation 8 to 10 times
excellent 6 to 7 times good 4 to 5 times acceptable 1 to 3 times
bad
[0358] Heat Resistance.
[0359] The container was measured for its full volume, fully filled
with the hot water of 70.degree. C. and was left to stand until the
temperature dropped down to 30.degree. C. The container was
measured again for its full volume to find a change in the volume
before and after it was filled with the hot water. The number n of
the samples was 3, and the containers were evaluated depending upon
their changes in the volumes.
[0360] Change in volume (%)=(full volume before fully filled-full
volume after fully filled)/(full volume before fully
[0361] filled.times.100
3 Change in the volume (%) Evaluation smaller than 0.5% excellent
not smaller than 0.5% but smaller than 1% good not smaller than 1%
but smaller than 2% acceptable not smaller than 2% bad
Example 1
[0362] A polyester was obtained by melt-kneading a thermoplastic
polyester, RT-580CA (HOMO PET manufactured by Unipet Co.) by using
a 65-mm extruder (manufactured by Nihon Seikosho Co.), and was
extruded from a T-due of a width of 400 mm and was quickly quenched
to prepare a substantially amorphous sheet having a thickness of
1.2 mm. The sheet was cut into a square of 30 cm, heated at
100.degree. C. by a heater by using a plug-assisted compressed
air/vacuum molding machine (FK-0431 manufactured by Asano Kenkyujo
Co.), and was held by an aluminum plug heated at 65.degree. C. by a
heater embedded therein and having a bottom area 84% of the bottom
area of the container and by a metal mold (female mold) heated at
110.degree. C. by a heater mounted surrounding the metal mold.
Thereafter, the compressed air was blown from the side of the plug
for 10 seconds while evacuating the air from the side of the metal
mold, in order to mold a transparent container having a container
diameter of 65 mm, a container height of 100 mm and a volume of 235
cc.
[0363] Very good results were obtained concerning the crystallinity
of the wall of the lower part of the barrel portion of the molded
container, crystallinity of the flange portion, X-ray measurement
of the upper and lower parts of the container, drop impact testing
and heat resistance as shown in Table 1. Good heat resistance was
further obtained even in the evaluation with the container being
filled with the hot water of 90.degree. C.
Example 2
[0364] A sheet was molded in the same manner as in Example 1 but
using EFS-7H (HOMO PET manufactured by Kanebo Gosen Co.) as the
thermoplastic polyester to obtain a transparent container of the
same shape. Very good results were obtained concerning the
crystallinity of the wall of the lower part of the barrel portion
of the molded container, crystallinity of the flange portion, X-ray
measurement of the upper and lower parts of the container, drop
impact testing and heat resistance as shown in Table 1. Good heat
resistance was further obtained even in the evaluation with the
container being filled with the hot water of 90.degree. C.
Example 3
[0365] A sheet having a thickness of 1.2 mm was molded by using the
RT-580CA as the thermoplastic polyester in the same manner as in
Example 1. Thereafter, a transparent container of the same shape
was molded in the same manner as in Example 1 but setting the metal
mold temperature at 80.degree. C. in molding the container. Good
results were obtained concerning the crystallinity of the wall of
the lower part of the barrel portion of the molded container,
crystallinity of the flange portion, X-ray measurement of the upper
and lower parts of the container, drop impact testing and heat
resistance as shown in Table 1.
Example 4
[0366] A sheet having a thickness of 1.2 mm was molded by using the
RT-580CA as the thermoplastic polyester in the same manner as in
Example 1. Thereafter, a transparent container of the same shape
was molded in the same manner as in Example 1 but using an aluminum
plug heated at 65.degree. C. by a heater embedded therein and
having a bottom area 84% of the bottom area of the container and
having a shoulder portion for molding the flange and by using a
metal mold heated at 110.degree. C. by a heater mounted surrounding
the metal mold and having a flange-molding portion in a cavity
thereof in molding the container. Very good results were obtained
concerning the crystallinity of the wall of the lower part of the
barrel portion of the molded container, crystallinity of the flange
portion, X-ray measurement of the upper and lower parts of the
container, drop impact testing and heat resistance as shown in
Table 1. Good heat resistance was further obtained even in the
evaluation with the container being filled with the hot water of
90.degree. C.
Example 5
[0367] A three-kind-five-layer sheet having a thickness of 1.2 mm
was molded by using J125T (manufactured by Mitsui Kagaku Co.) as a
thermoplastic polyester of inner and outer layers, Evar EP-F101B
(manufactured by Kuraray Co.) as an intermediate layer and Modec
F512 (manufactured by Mitsubishi Kagaku Co.) as an adhesive among
the intermediate layer and the polyester layers, through the use of
a multi-layer sheet-molding machine. Then, the sheet was molded in
the same manner as in Example 1 to obtain a container of the same
shape. Very good results were obtained concerning the crystallinity
of the wall of the lower part of the barrel portion of the molded
container, crystallinity of the flange portion, X-ray measurement
of the upper and lower parts of the container, drop impact testing
and heat resistance as shown in Table 1. Good heat resistance was
further obtained even in the evaluation with the container being
filled with the hot water of 90.degree. C.
Comparative Example 1
[0368] A sheet having a thickness of 1.2 mm was molded by using
RT-580CA (manufactured by Unipet Co.) as a thermoplastic polyester
through the use of a sheet-molding machine in the same manner as in
Example 1. Then, a container of the same shape was molded in the
same manner as in Example 1 but heating the sheet again at
130.degree. C. in molding the container. The crystallinity of the
wall of the lower part of the barrel portion of the molded
container, crystallinity of the flange portion, X-ray measurement
of the upper and lower parts of the container, drop impact testing
and heat resistance were as shown in Table 1, from which it was
learned that the impact resistance and heat resistance were
inferior.
Comparative Example 2
[0369] A sheet having a thickness of 1.2 mm was molded by using
RT-580CA (manufactured by Unipet Co.) as a thermoplastic polyester
through the use of a sheet-molding machine in the same manner as in
Example 1. Then, a container of the same shape was molded in the
same manner as in Example 1 but using an aluminum plug heated at
110.degree. C. by a heater embedded therein and having a bottom
area 84% of the bottom area of the container in molding the
container. The crystallinity of the wall of the lower part of the
barrel portion of the molded container, crystallinity of the flange
portion., X-ray measurement of the upper and lower parts of the
container, drop impact testing and heat resistance were as shown in
Table 1, from which it was learned that the impact resistance was
inferior.
Comparative Example 3
[0370] A sheet having a thickness of 1.2 mm was molded by using
RT-580CA (manufactured by Unipet Co.) as a thermoplastic polyester
through the use of a sheet-molding machine in the same manner as in
Example 1. Then, a container of the same shape was molded in the
same manner as in Example 1 but using an aluminum plug heated at
65.degree. C. by a heater embedded therein and having a bottom area
65% of the bottom area of the container in molding the container.
The crystallinity of the wall of the lower part of the barrel
portion of the molded container, crystallinity of the flange
portion, X-ray measurement of the upper and lower parts of the
container, drop impact testing and heat resistance were as shown in
Table 1, from which it was learned that the impact resistance was
inferior.
Comparative Example 4
[0371] A sheet having a thickness of 1.2 mm was molded by using
RT-580CA (manufactured by Unipet Co.) as a thermoplastic polyester
through the use of a sheet-molding machine in the same manner as in
Example 1. Then, a container of the same shape was molded in the
same manner as in Example 1 but setting the metal mold temperature
at 20.degree. C. in molding the container. The crystallinity of the
wall of the lower part of the barrel portion of the molded
container, crystallinity of the flange portion, X-ray measurement
of the upper and lower parts of the container, drop impact testing
and heat resistance were as shown in Table 1, from which it was
learned that the impact resistance and heat resistance were very
inferior.
Comparative Example 5
[0372] A sheet having a thickness of 1.2 mm was molded by using
RT-580CA (manufactured by Unipet Co.) as a thermoplastic polyester
through the use of a sheet-molding machine in the same manner as in
Example 1. Then, a container of the same shape was molded in the
same manner as in Example 1 but setting the metal mold temperature
at 60.degree. C. in molding the container. The crystallinity of the
wall of the lower part of the barrel portion of the molded
container, crystallinity of the flange portion, X-ray measurement
of the upper and lower parts of the container, drop impact testing
and heat resistance were as shown in Table 1, from which it was
learned that the impact resistance and heat resistance were
inferior.
Comparative Example 6
[0373] A container having the same shape was molded in the same
manner as in Example 1 but using (Eastapak polyester 15041,
(manufactured by Eastman Co.) which is used for a C-PET tray) as a
thermoplastic polyester. The crystallinity of the wall of the lower
part of the barrel portion of the molded container, crystallinity
of the flange portion, X-ray measurement of the upper and lower
parts of the container, drop impact testing and heat resistance
were as shown in Table 1, from which it was learned that the heat
resistance was excellent but the impact resistance was very
inferior.
4 TABLE 1 Barrel wall Flange X-ray measurement Drop crystallinity
crystallinity Formula Formula Formula impact Heat (%) (%) (1) (2)
(3) strength resistance Ex. 1 29 2.8 0.87 0.45 0.42 excellent
excellent Ex. 2 30 3.1 0.72 0.33 0.29 excellent excellent Ex. 3 18
2.6 1.01 0.75 0.26 good acceptable Ex. 4 29 24.3 0.85 0.42 0.43
excellent excellent Ex. 5 30 2.7 0.79 0.37 0.42 excellent excellent
Comp. Ex. 1 12 2.6 1.04 1.09 -0.05 bad bad Comp. Ex. 2 15 2.7 1.06
0.99 0.07 bad acceptable Comp. Ex. 3 13 2.6 0.85 1.01 -0.16 bad
acceptable Comp. Ex. 4 12 2.6 1.2 1.08 0.12 bad bad Comp. Ex. 5 13
2.6 1.07 1 0.07 bad bad Comp. Ex. 6 30 25 1.02 0.95 0.07 bad
excellent wherein: Formula (1): Iu (-110)/Iu (010) Formula (2): IL
(-110)/IL (010) Formula (3): Iu (-110)/Iu (010) - IL(-110)/IL
(010)
Example 6
[0374] A polyethylene terephthalate having an inherent viscosity of
0.80 and a glass transition point of 70.degree. C. was
melt-extrusion-molded to obtain a substantially amorphous sheet
having a thickness of 1.2 mm. The sheet was heated at a sheet
temperature of 95.degree. C. and was supplied to the molding device
shown in FIG. 8. The sheet was held by the holding surfaces of the
female mold and of the clamping mold, and was stretched in the
axial direction by a plug heated at 75.degree. C., having an
effective diameter of 69 mm, having an effective height of 86 mm,
and having a surface area which was 6.2 times as wide as the
to-be-molded area of the sheet, thereby to obtain a primary molded
article.
[0375] The compressed air of 0.6 MPa was blown into the interior of
the primary molded article through the gas passage of the plug to
form and heat-set a secondary molded article in the female mold
heated at 150.degree. C. by the compressed air.
[0376] Next, the pressure in the interior of the secondary molded
article was reduced by a vacuum pump through the gas passage of the
plug to shape it into a tertiary molded article which was, then,
cooled and taken out to obtain a final molded article. The finally
molded article was evaluated in a manner as described below.
[0377] {circle over (1)} Samples for measurement, each measuring 4
mm.times.4 mm, were cut out from the bottom portion (A) of the
molded article shown in FIG. 19, from a measuring center (B) 30 mm
above the bottom, from a measuring center (C) 55 mm above the
bottom, from a measuring center of the stacking portion (D) and
from a measuring center of the flange portion (E). Each sample was
sliced into the inner surface side and into the outer surface side
of the container along a neutral plane. Crystallinities on the
inner surface side and on the outer surface side at each of the
measuring points were measured relying upon the density method.
[0378] {circle over (2)} The molded article was left to stand in a
temperature-controlled oven so that the temperature of the side
wall of the molded article became 90.degree. C. for 3 minutes. The
full volume of the molded article was measured before it was put
into the oven and after it was taken out from the oven. A change in
the volume was calculated in compliance with the following formula
to evaluate the heat resistance of the molded article,
[0379] Change in the volume (%)=[(full volume before put into the
oven)-(full volume after taken out from the oven)]/(full volume
before put into the oven).times.100
[0380] {circle over (3)} The molded article was filled with 200 ml
of water, and the mouth was heat-sealed with a closure member to
obtain a sample for evaluation. The sample was dropped on the
concrete surface from a height of 90 cm in such a manner that the
axis of the container was in parallel with the concrete surface.
The sample was repetitively dropped until it was broken, and the
impact resistance was evaluated based on the number of times until
it was broken.
[0381] {circle over (4)} The transparency of the whole container
was evaluated by naked eyes.
[0382] The results of evaluation were as shown in Table 2 from
which it was learned that the container obtained by the molding
method of the present invention exhibited both excellent heat
resistance and excellent impact resistance, and was transparent
over the whole container except the flange.
Example 7
[0383] A polyethylene terephthalate having an inherent viscosity of
0.80 and a glass transition point of 70.degree. C. was used as an
inner layer and an outer layer, a polymethaxyleneadipamide (MXD6)
was used as an intermediate layer, and a maleic acid-modified
ethylene-.alpha.-olefin copolymer was interposed as adhesive layers
among the inner layer, the outer layer and the intermediate layer.
The laminate of these layers was melt-extrusion-molded to obtain a
substantially amorphous 5-layer sheet having a thickness of 1.2 mm.
The sheet was molded under the same conditions as in Example 6 to
obtain a finally molded article which was, then, evaluated in the
same manner as in Example 6.
[0384] The results of evaluation were as shown in Table 2 from
which it was learned that the container obtained by molding the
multi-layer sheet by the molding method of the present invention,
too, exhibited both excellent heat resistance and excellent impact
resistance, and was transparent over the whole container except the
flange.
Example 8
[0385] A polyethylene terephthalate having an inherent viscosity of
0.80 and a glass transition point of 70.degree. C. was
melt-extrusion-molded to obtain a substantially amorphous sheet
having a thickness of 1.2 mm. The sheet was heated at a sheet
temperature of 95.degree. C. and was supplied to the molding device
shown in FIG. 8. The sheet was held by the holding surfaces of the
female mold and of the clamping mold, and was stretched in the
axial direction by a plug heated at 80.degree. C., having an
effective diameter of 69 mm, having an effective height of 86 mm,
and having a surface area which was 6.2 times as wide as the
to-be-molded area of the sheet, thereby to obtain a primary molded
article.
[0386] The compressed air of 0.6 MPa was blown into the interior of
the primary molded article through the gas passage of the plug to
form a secondary molded article in the female mold heated at
50.degree. C. by the compressed air, followed by shaping, cooling
and parting to obtain an intermediate article (first step in the
two-step molding method).
[0387] Then, the intermediate article was supplied into the molding
device shown in FIG. 14 to effect the second step in the two-step
molding method.
[0388] The plug used in the second step was heated at 50.degree. C.
and the female mold was heated at 150.degree. C. The plug possessed
an outer shape which was such that the effective diameter was 64
mm, the effective height was 51 mm and the surface area was 4.2
times as wide as the to-be-molded area of the sheet. The
intermediate article supported by the plug was inserted in the
female mold, the compressed air of 0.6 MPa was blown through the
gas passage of the plug to form a secondary molded article in the
heated female mold and to heat-set the secondary molded
article.
[0389] Next, the pressure in the interior of the secondary molded
article was reduced by a vacuum pump through the gas passage of the
plug to shape it into a tertiary molded article which was, then,
cooled and taken out to obtain a final molded article. The finally
molded article was evaluated in the same manner as in Example
6.
[0390] The results of evaluation were as shown in Table 2 from
which it was learned that the container obtained by the two-step
molding method of the present invention, too, exhibited both
excellent heat resistance and excellent impact resistance, and was
transparent over the whole container except the flange.
Comparative Example 7
[0391] A polyethylene terephthalate having an inherent viscosity of
0.80 and a glass transition point of 70.degree. C. was
melt-extrusion-molded to obtain a substantially amorphous sheet
having a thickness of 1.2 mm. The sheet was heated at a sheet
temperature of 95.degree. C. and was supplied to a widely-known
compressed-air molding device (prior art 2). The plug (cooling
type) used in the known compressed-air molding was heated at
120.degree. C. as described in the known literature, and the female
mold (heating type) was heated at 220.degree. C. The plug and the
female mold possessed such outer shapes that the effective diameter
was 69 mm, the effective height was 86 mm, and the surface area was
6.2 times as wide as the to-be-molded area of the sheet. The
conditions were the same as those of Example 6 except the heating
temperature.
[0392] The sheet was sandwiched by the plug and the female mold
that fitted to each other, molded by the compressed air and was
heat-set. Immediately thereafter, the compressed air was blown
through the gas passage of the female mold to shape the molded
article along the plug. The molded article was then parted. The
thus obtained finally molded article was evaluated in the same
manner as in Example 6.
[0393] The results of evaluation were as shown in Table 2, from
which it was learned that the container obtained by the above
molding method exhibited excellent heat resistance but very poor
impact resistance and transparency.
5TABLE 2 Item evaluated Example 6 Example 7 Example 8 Comp. Example
7 {circle over (1)} Crystallinity % outer inner outer inner outer
inner outer inner Measuring point surface surface surface surface
surface surface surface surface A 28.0 18.5 28.1 18.3 25.2 16.7
42.0 37.8 B 31.2 27.9 31.3 28.0 28.1 25.1 46.8 41.8 C 36.0 29.9
35.6 31.2 32.4 26.9 44.5 44.9 D 33.4 30.5 33.2 30.7 30.1 27.5 44.4
45.8 E 27.1 4.0 26.3 4.0 24.4 3.6 40.7 42.4 {circle over (2)}
Change 0.5 0.6 0.7 0.9 in volume (%) {circle over (3)} Note.sup.1)
Drop .largecircle. .largecircle. .largecircle. X testing {circle
over (4)} Note.sup.2) .largecircle. .largecircle. .largecircle. X
Transparency Note.sup.1) X represents the containers that were
broken in the drop testing of 1 to 4 times, and .largecircle.
represents the containers that were not broken. Note.sup.2)
.largecircle. represents the containers that were judged by three
monitors to be transparent, .DELTA. represents the containers that
were judged to contain opaque portions, and X represents the
containers that were judged to be opaque.
Example 9
[0394] By using a sheet-molding machine, a polyethylene
terephthalate resin (SA135 manufactured by Mitsui Kagaku Co.) was
melt-extrusion molded to prepare a substantially amorphous sheet
having a thickness of 1.2 mm and a width of 320 mm. The sheet was
cut into a square of 300 mm and was heated at 95.degree. C. by
using a compressed air/vacuum molding machine (FK-0431 manufactured
by Asano Kenkyujo Co.). Then, the metal mold was tightened, and the
plug heated at 50.degree. C. was driven by an air cylinder in a
state where the sheet was held by the holding surfaces of the
female mold for pre-molding heated by a heater at 100.degree. C.
and of the clamping method, in order to mold the sheet in the solid
phase. At the same time, the compressed air of 0.6 MPa was blown
from the side of the plug to prepare a pre-molded article having a
diameter of 66 mm and a surface area of 159 cm.sup.2.
[0395] At a next step, the pre-molded article was held by the
female mold for pre-molding heated at 180.degree. C. and by the
clamping mold, and the pressure on the side of the plug was reduced
in a state where the plug was inserted in the pre-molded article,
the plug being heated at 110.degree. C. and having the shape nearly
the same as the shape of the inner surface of the container. The
pre-molded article was heated and shrunk by heat radiated from the
female mold so as to come into intimate contact with the surface of
the plug, thereby to form an intermediate article having the shape
nearly the same as the shape of the container and having a diameter
of 66 mm and a surface area of 130 cm.sup.2. Table 3 shows the
ratio of the surface areas of the pre-molded article and of the
intermediate article.
[0396] At a next step, the intermediate article was held by the
clamping mold and by the female mold for final molding heated at
180.degree. C. higher than the crystallization start temperature of
the polyethylene terephthalate resin. Then, the compressed air of
0.6 MPa was blown from the side of the plug to heat-set the
intermediate article while it was being intimately adhered to the
female mold. Thereafter, the pressure on the side of the plug was
reduced in a state where the plug heated at 90.degree. C. and
having a shape nearly the same as the shape of the inner surface of
the container was inserted in the intermediate article, so that the
intermediate article was intimately adhered onto the surface of the
plug to thereby shape the container. At the same time, the
container was cooled down to the plug temperature and was, then,
taken out. Thereafter, the periphery of the flange was trimmed to
obtain a substantially transparent container having a container
diameter of 66 mm, a container height of 53 mm and a volume of 158
cc.
[0397] The container was evaluated in a manner as described
below.
[0398] 1. Heat Resistance.
[0399] An empty container after its full volume was measured, was
heat-treated in the hot water of 90.degree. C. for 30 minutes,
taken out from the hot water, left to cool down to room
temperature, and was measured again for its full volume. A change
in the volume before and after the heat treatment was found from
the following formula, and the heat resistance was evaluated as
described below.
[0400] Change in the volume (%)=(full volume before the heat
treatment-full volume after the heat treatment)/(full volume before
the heat treatment).times.100
6 Change in the volume (%) Evaluation smaller than 1.0% excellent
not smaller than 1% but smaller than 2% good not smaller than 2%
but smaller than 4% acceptable not smaller than 4% bad
[0401] 2. Impact Strength.
[0402] The container was fully filled with water, and a closure
member having a polyester layer on the innermost surface thereof
and the flange portion of the container were heat-sealed by using a
heat sealer (manufactured by Shinwa Kikai Co.) at a seal bar
temperature of 230.degree. C. After sealing, the container was
dropped on the concrete floor surface from a height of 90 cm with
the bottom portion of the container being directed downward a
maximum of 10 times. The number n of the samples was 10, and
average numbers until the samples were broken were evaluated as
follows:
7 Average number of times until broken Evaluation 8 to 10 times
excellent 6 to 7 times good 4 to 5 times acceptable 1 to 3 times
bad
[0403] 3. Transparency.
[0404] The transparency of the whole container was evaluated by
naked eyes.
[0405] The container was evaluated for its transparency, heat
resistance and impact resistance to be all excellent as shown in
Table 3.
Example 10
[0406] A pre-molded article and an intermediate article of the same
shape were prepared from the polyethylene terephthalate resin
(SA135 manufactured by Mitsui Kagaku Co.) in the same manner as in
Example 9.
[0407] At a next step, the intermediate article has held by the
clamping mold and the female mold for final molding heated at
130.degree. C. higher than the crystallization start temperature of
the polethylene terephthalate resin, and a substantially
transparent container having the same shape was prepared in the
same manner as in Example 9.
[0408] The container was evaluated for its transparency, heat
resistance and impact resistance to be all excellent as shown in
Table 3.
Example 11
[0409] A substantially transparent container having the same shape
was obtained in the same manner as in Example 9 with the exception
of forming, by using a multi-layer sheet-molding machine, a
three-kind-five-layer sheet comprising inner and outer layers of a
polyethylene terephthalate resin (J125T manufactured by Mitsui
Kagaku Co.), an intermediate layer of a polymethaxyleneadipamide
(MXD6,6007 manufactured by Mitsubishi Gas Kagaku Co.), and adhesive
layers of an acid-modified ethylene-butene copolymer (Modic F512
manufactured by Mitsubishi Kagaku Co.) among the intermediate layer
and the inner and outer layers, having a thickness of 1.2 and a
width of 320 mm, the polyethylene terephthalate layers being
substantially amorphous.
[0410] The container was evaluated for its transparency, heat
resistance and impact resistance to be all excellent as shown in
Table 3. The barrier property was favorable, too.
Example 12
[0411] By using a multi-layer sheet-molding machine, there was
prepared a two-kind-three-layer sheet comprising inner and outer
layers of a polyethylene terephthalate resin (SA135 manufactured by
Mitsui Kagaku Co.), and an intermediate layer of a recycled
polyethylene terephthalate (Clear-Flake manufactured by Yono PET
Bottle Recycle Co.), having a thickness of 1.2 and a width of 320
mm. An intermediate article and a substantially transparent
container of the same shape were prepared in the same manner as in
Example 9 except that the pre-molded article prepared from the
above sheet possessed such a shape as a diameter of 66 mm and a
surface area of 185 cm.sup.2.
[0412] The container was evaluated for its transparency, heat
resistance and impact resistance to be all excellent as shown in
Table 3.
Example 13
[0413] A pre-molded article of the same shape was prepared from the
polyethylene terephthalate resin (SA135 manufactured by Mitsui
Kagaku Co.) in the same manner as in Example 9.
[0414] At a next step, the pre-molded article has held by the
clamping mold and the female mold for intermediate molding heated
at 180.degree. C., and the pre-molded article was heated and shrunk
by heat radiated from the female mold without inserting the plug
thereby to obtain an intermediate article having a diameter of 66
mm and a surface area of 120 cm.sup.2. The ratio of surface areas
of the pre-molded article and of the intermediate article was as
shown in Table 3.
[0415] Next, a substantially transparent container having a
container diameter of 66 mm, a container height of 53 mm and a
volume of 158 cc was obtained from the above intermediate article
in the same manner as in Example 9.
[0416] The container was evaluated for its transparency, heat
resistance and impact resistance to be all excellent as shown in
Table 3.
Comparative Example 8
[0417] A sheet was prepared from the polyethylene terephthalate
resin (SA135 manufactured by Mitsui Kagaku Co.) in the same manner
as in Example 9. A pre-molded article was prepared in the same
manner as in Example 9 except that the pre-molded article prepared
from the sheet possessed a diameter of 66 mm and a surface area of
199 cm.sup.2.
[0418] At a next step, the pre-molded article has heat-shrunk in
the same manner as in Example 9. However, the pre-molded article
did not shrink to a sufficient degree, i.e., did not shrink to the
shape of the plug, and there was obtained no intermediate
article.
Comparative Example 9
[0419] A sheet was prepared from the polyethylene terephthalate
resin (SA135 manufactured by Mitsui Kagaku Co.) in the same manner
as in Example 9. An intermediate article and a container were
prepared in the same manner as in Example 9 except that the
pre-molded article prepared from the sheet possessed a diameter of
66 mm and a surface area of 135 cm.sup.2.
[0420] The container was evaluated for its transparency, heat
resistance and impact resistance as shown in Table 3, from which it
was learned that the bottom portion of the container had been
whitened deteriorating the transparency and the impact resistance
was inferior, either.
Comparative Example 10
[0421] A pre-molded article and an intermediate article of the same
shape were prepared from the polyethylene terephthalate resin
(SA135 manufactured by Mitsui Kagaku Co.) in the same manner as in
Example 9.
[0422] At a next step, the intermediate article was held by the
clamping mold and the female mold for final molding heated at
90.degree. C. lower than the crystallization start temperature of
the polyethylene terephthalate resin, and a substantially
transparent container having the same shape was prepared in the
same manner as in Example 9.
[0423] The container was evaluated for its transparency, heat
resistance and impact resistance as shown in Table 3, from which it
was learned that the heat resistance was inferior.
8TABLE 3 Surface area of pre-molded article/ surface area of
intermediate Heat Impact article Transparency resistance resistance
Example 9 1.22 transparent excellent excellent Example 10 1.22
transparent good excellent Example 11 1.22 transparent excellent
excellent Example 12 1.42 transparent excellent good Example 13
1.33 transparent excellent excellent Comp. Ex. 8 1.53 container
could not be formed Comp. Ex. 9 1.04 bottom excellent bad whitened
Comp. Ex. 10 1.22 transparent bad excellent
Example 14
[0424] A polyethylene terephthalate resin (SA135, I.V.=0.8,
manufactured by Mitsui Kagaku Co.) was melt-extrusion molded to
prepare a substantially amorphous sheet having a thickness of 1.2
mm and a width of 320 mm. The sheet was cut into a square of 300 mm
and was heated at 95.degree. C. by using a compressed air/vacuum
molding machine (FK-0431 manufactured by Asano Kenkyujo Co.). Then,
the metal mold was tightened, and the plug heated at 75.degree. C.
and having the shape of the inner surface of the container was
driven by an air cylinder in a state where the sheet was held by
the holding surfaces of the female mold heated by a heater at
80.degree. C. and of the clamping mold, in order to stretch-mold
the sheet. At the same time, the compressed air of 0.6 MPa was
blown from the side of the plug so that the stretch-molded article
was intimately adhered to the female mold and was heat-set. Next,
the pressure on the side of the plug was reduced so that the
stretch-molded article was intimately adhered onto the surface of
the plug and was shaped. The stretch-molded article was then cooled
down to the plug temperature and, then, the metal mold was opened.
Thereafter, the periphery of the flange was trimmed to obtain a
substantially transparent container having a container diameter of
66 mm, a container height of 100 mm and a volume of 256 cc.
[0425] The container was evaluated in a manner as described
below.
[0426] 1. Heat Resistance.
[0427] An empty container after its full volume was measured, was
put into a dry-heating oven heated at 150.degree. C. and was
heat-treated therein in a state where the container wall was heated
at 100.degree. C. for 10 seconds and was, then, taken out, and was
cooled down to room temperature. The container was measured again
for its full volume. A change in the volume before and after the
heat treatment was found from the following formula, and the heat
resistance was evaluated as described below.
[0428] Change in the volume (%)=(full volume before the heat
treatment-full volume after the heat treatment)/(full volume before
the heat treatment).times.100
9 Change in the volume (%) Evaluation smaller than 1.0% excellent
not smaller than 1% but smaller than 2% goog not smaller than 2%
but smaller than 4% acceptable not smaller than 4% bad
[0429] 2. Impact Strength.
[0430] The container was fully filled with water, and a closure
member having a polyester layer on the innermost surface thereof
and the flange portion of the container were heat-sealed by using a
heat sealer (manufactured by Shinwa Kikai Co.) at a sealing
temperature of 230.degree. C. After sealing, the container was
dropped on the concrete floor surface from a height of 90 cm with
the bottom portion of the container being directed downward a
maximum of 10 times. The number n of the samples was 10, and
average numbers until the samples were broken were evaluated as
follows:
10 Average number of times until broken Evaluation 8 to 10 times
excellent 6 to 7 times good 4 to 5 times acceptable 1 to 3 times
bad
[0431] The container was evaluated for its crystallinity at the
center in the bottom portion and on the side wall thereof, X-ray
diffraction measurement thereof, transparency, strength in the drop
impact testing and heat resistance as shown in Table 4, from which
it was learned that excellent heat resistance and impact resistance
were exhibited.
Example 15
[0432] By using a multi-layer sheet-molding machine, there was
prepared a three-kind-five-layer sheet comprising inner and outer
layers of a polyethylene terephthalate resin (J125T manufactured by
Mitsui Kagaku Co.), an intermediate layer of an ethylene-vinyl
alcohol copolymer (Evar EP-F101B manufactured by Kuraray Co.), and
adhesive layers of an acid-modified ethylene-butene copolymer
(Modic F512 manufactured by Mitsubishi Kagaku Co.) among the
intermediate layer and the inner and outer layers, having a
thickness of 1.2 and a width of 320 mm, the polyethylene
terephthalate layers being substantially amorphous. Thereafter, a
container was molded in the same manner as in Example 14 to obtain
a container of the same shape having a substantially transparent
bottom portion.
[0433] The container was evaluated for its crystallinity at the
center in the bottom portion and on the side wall thereof, X-ray
diffraction measurement thereof, transparency, strength in the drop
impact testing and heat resistance as shown in Table 4, from which
it was learned that excellent heat resistance and impact resistance
were exhibited. The gas-barrier property of the container was also
evaluated to be excellent.
Example 16
[0434] By using a multi-layer sheet-molding machine, there was
prepared a two-kind-three-layer sheet comprising inner and outer
layers of a polyethylene terephthalate resin (SA135 manufactured by
Mitsui Kagaku Co.), and an intermediate layer of a recycled
polyethylene terephthalate (Clear-Flake, manufactured by Yono PET
Bottle Recycle Co.), having a thickness of 1.2 and a width of 320
mm. Thereafter, a container was molded in the same manner as in
Example 14 to obtain a container of the same shape having a
substantially transparent bottom portion.
[0435] The container was evaluated for its crystallinity at the
center in the bottom portion and on the side wall thereof, X-ray
diffraction measurement thereof, transparency, strength in the drop
impact testing and heat resistance as shown in Table 4, from which
it was learned that excellent heat resistance and impact resistance
were exhibited.
Example 17
[0436] By using a multi-layer sheet-molding machine, there was
prepared a three-kind-five-layer sheet comprising inner and outer
layers of a polyethylene terephthalate resin (J125T manufactured by
Mitsui Kagaku Co.), an intermediate layer of a
polymethaxyleneadipamde (MXD6,6007 manufactured by Mitsubishi Gas
Kagaku Co.), adhesive layers of an acid-modified ethylene-butene
copolymer (Modic F512 manufactured by Mitsubishi Kagaku Co.) among
the intermediate layer and the inner and outer layers, having a
thickness of 1.2 and a width of 320 mm, the polyethylene
terephthalate layers being substantially amorphous. The sheet was
cut into a square of 300 mm and was heated at 95.degree. C. by
using a compressed air/vacuum molding machine (FK-0431 manufactured
by Asano Kenkyujo Co.). Then, the metal mold was tightened, and the
plug heated at 50.degree. C. was driven by an air cylinder in a
state where the sheet was held by the holding surfaces of the
female mold for pre-molding heated by a heater at 100.degree. C.
and of the clamping mold, in order to stretch-mold the sheet. At
the same time, the compressed air of 0.6 MPa was blown from the
side of the plug to prepare a pre-molded article having a diameter
of 66 mm and a surface area of 159 cm.sup.2.
[0437] At a next step, the pre-molded article was held by the
female mold for intermediate molding heated at 180.degree. C. and
by the clamping mold, and the pressure on the side of the plug was
reduced in a state where the plug was inserted in the pre-molded
article, the plug being heated at 110.degree. C. and having the
shape nearly the same as the shape of the inner surface of the
container. The pre-molded article was heated and shrunk by heat so
as to come into intimate contact with the surface of the plug,
thereby to form an intermediate article having the shape nearly the
same as the shape of the container and having a diameter of 66 mm
and a surface area of 130 cm.sup.2. The ratio of the surface areas
of the pre-molded article and of the intermediate article was
1.22.
[0438] At a next step, the intermediate article was held by the
clamping mold and by the female mold for final molding heated at
180.degree. C. Then, the compressed air of 0.6 MPa was blown from
the side of the plug to heat-set the intermediate article while it
was being intimately adhered to the female mold. Thereafter, the
pressure on the side of the plug was reduced in a state where the
plug heated at 90.degree. C. and having a shape nearly the same as
the shape of the inner surface of the container was inserted in the
intermediate article, so that the intermediate article was
intimately adhered onto the surface of the plug to thereby shape
the container. At the same time, the container was cooled down to
the plug temperature and was, then, taken out. Thereafter, the
periphery of the flange was trimmed to obtain a container having a
container diameter of 66 mm, a container height of 53 mm and a
volume of 158 cc with its bottom portion being substantially
transparent.
[0439] The container was evaluated for its crystallinity at the
center in the bottom portion and on the side wall thereof, X-ray
diffraction measurement thereof, transparency, strength in the drop
impact testing and heat resistance as shown in Table 4, from which
it was learned that excellent heat resistance and impact resistance
were exhibited. The container further exhibited favorable heat
resistance even after it was heat-treated in the hot water of
90.degree. C. for 30 minutes. The container further exhibited
excellent gas-barrier property.
Comparative Example 11
[0440] A sheet was prepared in the same manner as in Example 14,
and a container of the same shape having a substantially
transparent bottom portion was obtained under the same conditions
as in Example 14 but heating the female mold at 60.degree. C.
[0441] The container was evaluated for its crystallinity at the
center in the bottom portion and on the side wall thereof, X-ray
diffraction measurement thereof, transparency, strength in the drop
impact testing and heat resistance as shown in Table 4, from which
it was learned that excellent impact resistance was exhibited but
the heat resistance was inferior.
Comparative Example 12
[0442] A sheet was prepared in the same manner as in Example 14,
and a container of the same shape was obtained under the same
conditions as in Example 14 but heating the sheet at 120.degree.
C.
[0443] The center in the bottom portion of the container was
substantially transparent but was slightly cloudy.
[0444] The container was evaluated for its crystallinity at the
center in the bottom portion and on the side wall thereof, X-ray
diffraction measurement thereof, transparency, strength in the drop
impact testing and heat resistance as shown in Table 4, from which
it was learned that excellent heat resistance was exhibited but the
impact resistance was inferior.
11TABLE 4 Crystallinity Crystallinity at bottom of barrel
Orientation Heat Impact center (%) portion (%) tendency
Transparency resistance resistance Example 14 31 39 1.5 transparent
excellent excellent Example 15 29 38 1.3 transparent excellent
excellent Example 16 31 38 1.4 transparent excellent good Example
17 35 37 2 transparent excellent excellent Comparative 11 19 1
transparent bad excellent Example 11 Comparative 30 35 1.2 bottom
is excellent bad Example 12 slightly cloudy
INDUSTRIAL APPLICABILITY
[0445] According to the present invention, a sheet provided with at
least a layer of an ethylene terephthalate polyester is subjected
to the plug-assisted compressed-air or vacuum molding at a
particular sheet temperature, at a particular plug temperature or
at a particular metal mold temperature by using a plug having a
particular shape, making it possible to produce a heat-molded
container having particular orientation profile properties, i.e.,
in which the biaxial orientation is preferentially taking place in
the lower part of the barrel portion. This container exhibits
excellent heat resistance and excellent impact strength in
combination, and is useful for containing a content while it is
hot.
[0446] According to the present invention, further, there is
produced a thermoplastic resin container having excellent
resistance against deformation caused by heat and excellent
strength by molding a thermoplastic resin sheet into the shape of a
female mold heated at a temperature higher than the crystallization
temperature of the resin by utilizing the compressed air,
heat-setting the molded article and, then, reducing the pressure in
the molded article to shrink the molded article into the shape of a
plug which has the shape of a final container to impart the shape
thereto, followed by cooling.
[0447] According to the preparation method of the present
invention, the functions are separated into heat-setting by the
female mold and cooling by the plug, contributing to shorten the
time for occupying the metal mold and, hence, offering an advantage
of enhancing the productivity. The container molded from the
thermoplastic polyester sheet has a novel crystallinity profile in
that the side wall of the container is oriented and crystallized,
and the side wall has a crystallinity which is higher on the side
of the outer surface than on the side of the inner surface,
exhibiting excellent heat resistance, impact resistance and
appearance.
[0448] According to the present invention, further, pre-molded
article obtained by solid-phase-molding a sheet provided with an
amorphous thermoplastic polyester layer is heat-shrunk to obtain an
intermediate article which is, then, molded with the compressed air
in a female mold for final molding heated at a temperature higher
than the crystallization start temperature of the polyester and is
heat-set, and the pressure in the interior of the molded article is
reduced, so that the molded article shrinks along the outer surface
of the plug having the shape of a final container, to impart the
shape thereto, followed by cooling. Therefore, there is obtained a
sheet-molded container having excellent heat resistance, impact
resistance and transparency not only in the side wall of the
container but also at the center in the bottom portion of the
container, despite the container is formed by molding an unoriented
or amorphous thermoplastic polyester sheet. According to the
preparation method of the present invention, the functions are
separated into heat-setting by the female mold and cooling by the
plug, contributing to shorten the time for occupying the metal mold
and, hence, offering an advantage of enhancing the
productivity.
[0449] The present invention further makes it possible to obtain,
in an astonishing combination, an excellent heat resistance
stemming from the crystallinity of the thermoplastic polyester of
not smaller than 15% in the bottom portion of the container, to
obtain excellent impact resistance stemming from a distinguished
diffraction peak on the surface of an index of a plane (010) in the
X-ray diffraction, and to obtain a substantial transparency in the
bottom portion of the container, despite the container is formed by
heat-molding a thermoplastic polyester sheet.
* * * * *