U.S. patent application number 10/395559 was filed with the patent office on 2003-11-13 for plastic containers with uniform wall thickness.
Invention is credited to Dijkstra, Dirk-Jacques, Hepperle, Jens, Horn, Klaus, Hufen, Ralf, Krieter, Markus, Munstedt, Helmut.
Application Number | 20030209553 10/395559 |
Document ID | / |
Family ID | 28042861 |
Filed Date | 2003-11-13 |
United States Patent
Application |
20030209553 |
Kind Code |
A1 |
Horn, Klaus ; et
al. |
November 13, 2003 |
Plastic containers with uniform wall thickness
Abstract
A container having uniform wall thickness, molded of a
thermoplastic composition is disclosed. The wall of the container
at its thickest being at most three times as thick as at its
thinnest. Also disclosed is a process for the preparation of the
container. The process entails extrusion blow molding or injection
stretch blow molding of a thermoplastic material characterized in
that at a temperature of 200.degree. C., its S value is greater
than 1.1 at a Hencky elongation .epsilon. of 2.0 and an elongation
rate range {dot over (.epsilon.)} of between 0.1 and 0.01, and its
S value is greater than 1.1 at a Hencky elongation .epsilon. of 2.5
and an elongation rate range {dot over (.epsilon.)} of between 0.1
and 0.01, wherein S is .eta..sub.E divided by 3.eta..
Inventors: |
Horn, Klaus; (Dormagen,
DE) ; Hufen, Ralf; (Duisburg, DE) ; Krieter,
Markus; (Langenfeld, DE) ; Dijkstra,
Dirk-Jacques; (Levekusen, DE) ; Hepperle, Jens;
(Koln, DE) ; Munstedt, Helmut; (Buckenhof,
DE) |
Correspondence
Address: |
BAYER POLYMERS LLC
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
28042861 |
Appl. No.: |
10/395559 |
Filed: |
March 24, 2003 |
Current U.S.
Class: |
220/669 |
Current CPC
Class: |
B29C 49/0005 20130101;
B29K 2069/00 20130101; B29C 49/04 20130101; B29L 2031/7126
20130101; C08G 64/06 20130101; B29L 2031/7158 20130101; B65D 1/0207
20130101; B29C 49/06 20130101; B29C 49/20 20130101 |
Class at
Publication: |
220/669 |
International
Class: |
B65D 006/08; B65D
006/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 2002 |
DE |
10229594.8 |
Mar 25, 2002 |
DE |
10213230.5 |
Claims
What is claimed is:
1. A container having uniform wall thickness, molded of a
thermoplastic composition the wall at its thickest being at most
three times as thick as at its thinnest.
2. The container according to claim 1, wherein at its thickest the
wall is at most 2.6 times as thick as at its thinnest.
3. The container according to claim 1, wherein at its thickest the
wall is at most 2.2 times as thick as at its thinnest.
4. The container according to claim 1, wherein the container is a
bottle.
5. The container according to claim 1, wherein the container is a
water bottle.
6. The container according to claim 1 wherein the thermoplastic
composition comprise polycarbonate.
7. A process for producing the container according to claim 1
comprising molding by a process selected from the group consisting
of extrusion blow molding and injection stretch blow molding
thermoplastic material characterized in that at a temperature of
200.degree. C., S is greater than 1.1 at a Hencky elongation
.epsilon. of 2.0 and an elongation rate range {dot over
(.epsilon.)} of between 0.1 and 0.01, and S is greater than 1.1 at
a Hencky elongation .epsilon. of 2.5 and an elongation rate range
{dot over (.epsilon.)} of between 0.1 and 0.01, wherein S is
.eta..sub.E divided by 3.eta..
8. A process for producing the container according to claim 1
comprising molding by a process selected from the group consisting
of extrusion blow molding and injection stretch blow molding a
thermoplastic material characterized in that at a temperature of
200.degree. C., S is greater than 1.3 at a Hencky elongation
.epsilon. of 2.0 and an elongation rate range {dot over
(.epsilon.)} of between 0.1 and 0.01, and S is greater than 1.5 at
a Hencky elongation .epsilon. of 2.5 and an elongation rate range
{dot over (.epsilon.)} of between 0.1 and 0.01, wherein S is
.eta..sub.E divided by 3.eta..
Description
FIELD OF THE INVENTION
[0001] The present invention relates to plastic containers and more
particularly to containers with uniform wall thickness
SUMMARY OF THE INVENTION
[0002] A container having uniform wall thickness, molded of a
thermoplastic composition is disclosed. The wall of the container
at its thickest being at most three times as thick as at its
thinnest. Also disclosed is a process for the preparation of the
container. The process entails extrusion blow molding or injection
stretch blow molding of a thermoplastic material characterized in
that at a temperature of 200.degree. C., its S value is greater
than 1.1 at a Hencky elongation .epsilon. of 2.0 and an elongation
rate range {dot over (.epsilon.)} of between 0.1 and 0.01, and its
S value is greater than 1.1 at a Hencky elongation .epsilon. of 2.5
and an elongation rate range {dot over (.epsilon.)} of between 0.1
and 0.01, wherein S is .eta..sub.E divided by 3.eta..
BACKGROUND OF THE INVENTION
[0003] Containers made of plastics material, in particular of
polycarbonate, are basically known. These containers are produced,
for example, from compositions (also called compounds) which
contain a polymer, in particular polycarbonate, and conventional
additives. These compositions that include the polymer (for
instance polycarbonate) and the additives are also called plastics
material. The additives may include stabilizers, processing aids,
etc. In addition, the plastic containers may also comprise further
components, such as seals made of rubber or grips made of metal or
other materials. Therefore, it is more correct to speak of
"containers made of plastics material" than of "plastic
containers". In addition to the plastics material, the containers
may, for example, comprise the aforementioned components and/or
other components. Hereinafter "plastic containers" mean "containers
made of plastics material".
[0004] Plastic containers have numerous advantageous properties,
such as high transparency, good mechanical properties, great
resistance to environmental influences and a long life, as well as
low weight and easy, inexpensive producibility.
[0005] Plastic containers may be produced, for example by extrusion
blow molding or injection stretch blow molding.
[0006] In extrusion blow molding the plastics material is usually
melted using a single-screw extruder and molded by a die into a
free standing parison. The parison generally hangs downwards from
the die. The parison is then surrounded by a blow mold which
squashes the parison together at the lower end. The parison is then
inflated within the mold so the parison obtains the desired
shaping. After a cooling period the mold is opened and the blow
molded container may be removed.
[0007] Extrusion blow molding is disclosed, for example, in
Brinkschroder, F. J.: "Polycarbonate" in Becker, Braun,
Kunststoff-Handbuch, Vol. 3/1, Polycarbonate, Polyacetale,
Polyester, Cellulose ester, Carl Hanser Verlag Munich, Vienna 1996,
pages 248 to 255).
[0008] Injection stretch blow molding is a combination of injection
molding and blow molding.
[0009] Injection stretch blow molding proceeds in three stages:
[0010] 1. Injection molding the parison in the plastic temperature
range of the plastics material
[0011] 2. Inflating the parison in the thermoplastic range of the
plastics material (the core of the injection mold is simultaneously
the blowing mandrel)
[0012] 3. Stripping the blow molding and optionally cooling the
blowing mandrel with air
[0013] Injection stretch blow molding is disclosed, for example, in
Anders, S., Kaminski, A., Kappenstein, R., "Polycarbonate" in
Becker,/Braun, Kunststoff-Handbuch, Vol. 3/1, Polycarbonate,
Polyacetale, Polyester, Cellulose ester, Carl Hanser Verlag Munich,
Vienna 1996, pages 213 to 216.
[0014] The plastic containers known from the prior art have the
drawback that they do not meet certain requirements which are
important for practical use of the containers.
[0015] Therefore, great mechanical stress in the known plastic
containers may lead to bursting thereof. This may occur, for
example, if a container filled with liquid falls to the floor from
a great height, for example from the loading area of a lorry on
which the container is being transported.
[0016] Of course the mechanical strength of the containers might be
increased by using a great deal more plastics material per
container so the wall is much thicker. However, this has the
drawback that the material consumption increases and this inter
alia causes high costs.
[0017] The object of the present invention is therefore to provide
plastic containers having high mechanical strengths with the lowest
possible expenditure on material.
[0018] It has accordingly been found that the cause of the
aforementioned mechanical failure is an irregular container wall
thickness.
[0019] Known containers produced by extrusion blow molding or by
injection stretch blow molding have non-uniform wall thickness.
DESCRIPTION OF THE FIGURES
[0020] FIG. 1 shows the uniaxial stretching viscosity and the
three-fold shear viscosity as function of time for polycarbonate
suitable for the purpose of the present invention.
[0021] FIG. 2 shows the uniaxial stretching viscosity and the
three-fold shear viscosity as function of time for polycarbonate
unsuitable for the purpose of the present invention.
[0022] FIG. 3 shows an exemplified bottle.
[0023] FIG. 4 shows the locals of the measurements of the wall
thickness.
[0024] FIG. 5 is a graphic representation of the measured wall
thickness.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The object of the present invention is a container made of
plastics material, wherein at its thickest point the wall of the
container is at most three times as thick as at its thinnest
point.
[0026] At its thickest point the regular container wall is
preferably at most 2.6 times as thick as at its thinnest point.
[0027] At its thickest point the regular container wall is
particularly preferably at most 2.2 times as thick as at its
thinnest point.
[0028] The container is preferably a bottle.
[0029] The container is particularly preferably a water bottle.
[0030] The container is preferably made of polycarbonate molding
composition.
[0031] The object of the present invention is achieved by injection
blow molding or by injection stretch blow molding.
[0032] Rotationally symmetrical containers are preferred.
Containers with only one aperture are preferred.
[0033] Uniformity of wall thickness of the container is taken to
mean the container wall at all the points at which thicker or
thinner points are not intentionally provided. Such intentionally
provided thicker points might be seen in FIG. 4 in the region of
the bottleneck. Under ideal conditions of producing containers the
regular container wall would be uniformly thick all around.
[0034] The containers according to the invention have been
produced, for example, from a polycarbonate with certain
rheological properties. Therefore, the uniaxial stretching test
with which these theological properties may be measured is to be
described hereinafter.
[0035] The uniaxial stretching test of polymer melts and its
implementation are known to the person skilled in the art. The
uniaxial stretching test may be carried out with apparatuses of the
Munstedt type. These are described in H. Munstedt, J. Rheol., Vol.
23, pages 421 to 436 (1979). These are also described in current
text books such as in Ch. W. Macosko: Rheology, Verlag Wiley/VCH,
1994, in particular pages 288 to 297 and in M. Phal, W.
Glei.beta.le, H. -M. Laun: Praktische Rheologie der Kunststoffe und
Elastomere, VDI-Verlag, 1995, in particular pages 349 to 357.
[0036] The methods for determining the shear viscosity as a
function of time are known to the person skilled in the art.
[0037] Determination of the shear viscosity as a function of time
is preferably carried out in a rotary rheometer at low shear
speeds. Determination of the shear viscosity may be carried out in
the rotary rheometer also with oscillating deformation and may be
converted into a time-dependent viscosity by means of common
methods.
[0038] The construction and mode of use of rotary rheometers are
described in current text books. For example in M. Pahl, W.
Glei.beta.le, H -M. Laun: Praktische Rheologie der Kunststoffe und
Elastomere, VDI-Verlag, 1995.
[0039] The stretching viscosity as a function of time is preferably
determined by means of a Munstedt-type stretching rheometer. The
uniaxial stretching test may also be carried out with a range of
other rheometers, for example with the commercially available
Meissner-type stretching rheometer. This is described in J.
Meissner, Rheologica Acta 8, Vol. 78 (1969) and in J. S,. Schulze
et al., Rheol. Acta Vol. 40 (2001) pages 457 to 466.
[0040] The Hencky elongation .epsilon. is a non-dimensional
variable. The stretching viscosity .eta..sub.E has the unit Pascal
multiplied by seconds. The shear viscosity .eta. also has the unit
Pascal multiplied by seconds.
[0041] The quotient S serves as a measure of the relevant increase
in the stretching viscosity .eta..sub.E. The quotient S is
non-dimensional. S is the quotient from the quotient from the
stretching viscosity .eta..sub.E and three-fold shear viscosity
3.eta.. S depends on the measuring temperature T, the Hencky
elongation rate {dot over (.epsilon.)} (unit: 1 divided by seconds)
and the Hencky elongation .epsilon. and the time.
[0042] The following formula applies:
S=.eta..sub.E(t, {dot over (.epsilon.)}) divided by 3.eta.(t)
[0043] The total stretching .epsilon. (unit: non-dimensional)
depends on the sample starting length L.sub.0 (unit: meters) and
its length L (unit: meters) as function of stretching and the
elongation rate of {dot over (.epsilon.)} (unit: 1 divided by
seconds) and the time t (unit: seconds) by:
.epsilon.=natural logarithm of (L divided by L.sub.0)={dot over
(.epsilon.)} multiplied by t.
[0044] A plastics material, in particular polycarbonate, is
preferred in which, at a temperature of 200.degree. C., the ratio S
is greater than 1.1 at a Hencky elongation .epsilon. of 2.0 and an
elongation rate range {dot over (.epsilon.)} of between 0.1 and
0.01, and is greater than 1.1 at a Hencky elongation .epsilon. of
2.5 and an elongation rate range {dot over (.epsilon.)} of between
0.1 and 0.01, wherein S is defined as S=.eta..sub.E divided by
3.eta..
[0045] A plastics material, in particular polycarbonate, is
particularly preferred in which, at a temperature of 200.degree.
C., the ratio S is greater than 1.3 at a Hencky elongation
.epsilon. of 2.0 and an elongation rate range {dot over
(.epsilon.)} of between 0.1 and 0.01, and is greater than 1.5 at a
Hencky elongation .epsilon. of 2.5 and an elongation rate range
{dot over (.epsilon.)} of between 0.1 and 0.01.
[0046] The present invention relates to a container containing
plastics material. This means a container made of plastics
material, for example as wall material. It does not mean a
container made of completely different materials and which only
contains the plastics material as filler.
[0047] The present invention also relates to a method for producing
this container by extrusion blow molding or by the injection
stretch blow molding.
[0048] To obtain plastics materials, in particular polycarbonates,
with the aforementioned rheological stretching properties the
person skilled in the art may adjust various parameters of the
plastics materials, in particular polycarbonates. For example, he
may influence the molecular weight and the degree of branching. The
choice of the monomers and comonomers or the terminal groups also
has an effect on the rheological stretching properties. The person
skilled in the art may also use suitable additives to obtain the
desired theological stretching properties according to the
invention.
[0049] The advantage of the aforementioned plastics material, in
particular polycarbonate, is that it enables production of the
containers according to the invention with their advantageous
properties. The known and advantageous processes (extrusion blow
molding and/or injection stretch blow molding) may be used.
[0050] Of course the present invention is not limited to containers
containing plastics material in which the plastics material has the
aforementioned rheological properties. These are only preferred as
they allow the containers to be produced by simple and known
processes (extrusion blow molding or injection stretch blow
molding). In general it is only important for the uniformity of
wall thickness to be achieved. This may also be attained by using
other methods and other plastics material (for example injection
molding or compression).
[0051] The containers according to the invention have the advantage
that they have high mechanical strength with a predetermined
quantity of plastics material per container.
[0052] The containers according to the invention have numerous
further advantages. They are more resistant to mechanical stresses,
i.e. resistant to breaking, and also have an advantageous range of
other additional mechanical properties. They have good optical
properties, in particular a high degree of transparency. They have
a high heat distortion temperature. Owing to the high heat
distortion temperature the containers according to the invention
may be cleaned with hot water or sterilized with hot steam. They
have high resistance to the conventional detergents which, for
example, are used to clean reusable water bottles, a field of
application of the containers according to the invention. They may
be produced easily and inexpensively by known processes. The good
processing properties of the plastics material, in particular
polycarbonate, are thus advantageously manifested here. Their
material ages slowly during use and therefore they have a long
service life. For possible repeated use this means many use
cycles.
[0053] Containers in the sense of the present invention may be used
for packaging, storing or transporting liquids, solids or gases.
Containers for packaging, storing transporting liquids (liquid
containers) are preferred, containers for packaging, storing or
transporting water (water bottles) are particularly preferred.
[0054] Containers in accordance with the invention are preferably
blow moldings with a volume of 0.1 l to 50 l, preferably 0.5 l to
50 l, with volumes of 1 l, 5 l, 12 l and 20 l being particularly
preferred.
[0055] 3 and 5 gallon water bottles are most particularly
preferred.
[0056] The containers preferably have an empty weight of preferably
0.1 g to 3,000 g, more preferably 50 g to 2,000 g and particularly
preferably of 650 g to 900 g.
[0057] The wall thicknesses of the containers are preferably 0.5 mm
to 5 mm, more preferably 0.8 mm to 4 mm.
[0058] Containers in the sense of the invention preferably have a
length of preferably 5 mm to 2,000 mm, particularly preferably 100
mm to 1,000 mm.
[0059] The containers preferably have a maximum circumference of
preferably 10 mm to 250 mm, more preferably of 50 mm to 150 mm and
most particularly preferably of 70 to 90 mm.
[0060] Containers in the sense of the invention preferably have a
bottleneck of a length of preferably 1 mm to 500 mm, more
preferably of 10 mm to 250 mm, particularly preferably of 50 mm to
100 mm and most particularly preferably of 70 to 80 mm.
[0061] The wall thickness of the bottleneck of the containers is
preferably between 0.5 mm and 10 mm, particularly preferably of 1
mm to 10 mm and most particularly preferably of 1 mm to 3 mm.
[0062] The diameter of the bottleneck is preferably between 5 mm
and 200 mm. 10 mm to 100 mm are particularly preferred and 45 mm to
75 mm most particularly preferred.
[0063] The bottle base of the containers according to the invention
has a diameter of preferably 10 mm to 250 mm, more preferably 50 mm
to 150 mm and most particularly preferably 70 to 90 mm.
[0064] Containers in the sense of the present invention may have
any geometric shape, for example they may be round, oval or
polygonal with, for example, 3 to 12 sides. Round, oval and
hexagonal shapes are preferred.
[0065] The design of the containers may be based on any surface
structure. The surface structures are preferably smooth or ribbed.
The containers according to the invention may also have a plurality
of different surface structures. Ribs or beads may round the
periphery of the containers. They may have any spacing or a
plurality of spacing which are different from one another. The
surface structures of the containers according to the invention may
be roughened or integrated structures, symbols, ornaments, coats of
arms, manufacturer's emblems, trademarks, signatures, producer's
details, material characteristics and/or information on volume.
[0066] The containers according to the invention may have any
number of handles which may be located on the sides, at the top or
at the bottom. The handles might be on the outside or integrated
into the contour of the container. The handles may be foldable or
fixed. The handles may have any contour, for example oval, round or
polygonal. The handles preferably have a length of 0.1 mm to 180
mm, preferably 20 mm to 120 mm.
[0067] In addition to the plastics material according to the
invention the containers according to the invention may also
contain small amounts of other substances, for example seals made
of rubber or handles made of other materials.
[0068] The containers according to the invention are preferably
produced by extrusion blow molding or by injection stretch blow
molding.
[0069] In a preferred embodiment for producing the containers
according to the invention, the plastics materials according to the
invention are processed on extruders with a smooth or grooved,
preferably a smooth, feed zone.
[0070] The drive power of the extruder is selected in accordance
with the screw diameter. By way of example it is mentioned that,
with a screw diameter of 60 mm, the drive power of the extruder is
approximately 30 to 40 kW, and with a screw diameter of 90 mm,
approximately 60 to 70 kW.
[0071] The universal three zone screws conventional in the
processing of industrial thermoplastics are suitable.
[0072] To produce containers having a volume of 1 l a screw
diameter of 50 to 60 mm is preferred. To produce containers having
a volume of 20 l a screw diameter of 70 to 100 mm is preferred. The
length of the screws is preferably 20 to 25 times the diameter of
the screw.
[0073] In the case of blow molding the temperature of the blow mold
is preferably adjusted to 50 to 90.degree. C. to obtain a sparkling
and high quality container surface.
[0074] To ensure uniform and effective temperature adjustment of
the blow mold the base region and the other regions of the die may
be adjusted in temperature separately.
[0075] The blow mold is preferably closed with a compressive force
of 1,000 to 1,500 N per centimeter of pinch-off weld length.
[0076] The plastics material is preferably dried before processing
so the quality of the containers is not impaired by visible streaks
or bubbles and is not hydrolytically degraded during processing.
The residual moisture content after drying is preferably less than
0.01% by weight. A drying temperature of 120.degree. C. is
preferred. Lower temperatures do not ensure sufficient drying, and
at higher temperatures there is the risk of plastics material
granules sticking together and then no longer being capable of
being processed. Dry air driers are preferred.
[0077] The preferred melt temperature for processing plastics
materials based on polycarbonate is 230.degree. to 300.degree.
C.
[0078] The containers according to the invention may be used for
packaging, storing or transporting liquids, solids or gases. The
embodiment which, for example, is used for packaging, storing or
transporting liquids, is preferred. The embodiment as a water
bottle which, for example, may be used for packaging, storing or
transporting water, is particularly preferred.
[0079] Polycarbonates in the sense of the present invention are
preferably thermoplastically processable aromatic polycarbonates.
Both homopolycarbonates and copolycarbonates may be used.
[0080] Particularly preferred polycarbonates are the
homopolycarbonate based on bisphenol A, the homopolycarbonate based
on 1,1 bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and the
copolycarbonates based on the two monomers bisphenol A and
1,1-bis-(4-hydroxyphenyl)-3,3,5- -trimethylcyclohexane.
[0081] The polycarbonates according to the invention also include
polycarbonates in which up to 80 mol %, in particular from 20 mol %
to 50 mol %, of the carbonate groups are replaced by aromatic
dicarboxylic acid ester groups. Polycarbonates of this type which
include both acid residues of carbon dioxide and acid residues of
aromatic dicarboxylic acids incorporated in the molecule chain, are
also called aromatic polyester carbonates.
[0082] The polycarbonates may be produced in a known manner from
diphenols, carbon dioxide derivatives, optionally chain terminators
and optionally branching agents. A portion of the carbon dioxide
derivatives is replaced by aromatic diocarboxylic acids or
derivatives of dicarboxylic acids to produce the polyester
carbonates. This proceeds according to the carbonate structural
units to be replaced in the aromatic polycarbonates by aromatic
dicarboxylic acid ester structural units.
[0083] Details of the production of polycarbonates are known.
Reference is made by way of example to:
[0084] 1. Schnell, "Chemistry and Physics of Polycarbonates",
Polymer Reviews, Volume 9, Interscience Publishers, New York,
London, Sydney 1964;
[0085] 2. D. C. Prevorsek, B. T. Debona und Y. Kesten, Corporate
Research Center, Allied Chemical Corporation, Morristown, N.J.
07960: "Synthesis of Poly(ester Carbonate) Copolymers" in Journal
of Polymer Science, Polymer Chemistry Edition, Vol. 19, 75-90
(1980);
[0086] 3. D. Freitag, U. Grigo, P. R. Muller, N. Nouvertne', BAYER
AG, "Polycarbonates" in Encyclopedia of Polymer Science and
Engineering, Vol. 11, Second Edition, 1988, pages 648-718;
[0087] 4. U. Grigo, K. Kircher und P. R- Muller "Polycarbonate" in
Becker/Braun, Kunststoff-Handbuch, Vol. 3/1, Polycarbonate,
Polyacetale, Polyester, Cellulose ester, Carl Hanser Verlag Munich,
Vienna 1992, pages 117-299.
[0088] The polycarbonates, including the polyester carbonates,
preferably have mean molecular weights Mw of 12,000 to 120,000
g/mol (determined by measuring the relative viscosity at 25.degree.
C. in methylene chloride at a concentration of 0.5 g polycarbonate
per 100 ml methylene chloride). 15,000 to 80,000 g/mol are
preferred, 15,000 to 60,000 g/mol are particularly preferred.
[0089] Dihydroxy compounds suitable for producing polycarbonates
are, for example, hydroquinone, resorcinol, dihydroxydiphenyl,
bis-(hydroxyphenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes,
bis-(hydroxyphenyl)-sulphides, bis-(hydroxyphenyl)-ether,
bis-(hydroxyphenyl)-ketones, bis-(hydroxyphenyl)-sulphones,
bis-(hydroxyphenyl)-sulphoxides,
(.alpha.,.alpha.'-bis-(hydroxyphenyl)-di- isopropylbenzenes, and
their compounds alkylated on the nucleus and halogenated on the
nucleus.
[0090] Preferred diphenols are 4,4'-dihydroxydiphenyl,
2,2-bis-(4-hydroxyphenyl)-1-phenyl-propane,
1,1-bis-(4-hydroxyphenyl)-phe- nyl-ethane,
2,2-bis-(4-hydroxy-phenyl)propane, 2,4-bis-(4-hydroxyphenyl)-2-
-methylbutane, 1,1-bis-(4-hydroxy-phenyl)-m/p diisopropylbenzene,
2,2-bis-(3-methyl-4-hydroxyphenyl)-propane,
bis-(3,5-dimethyl-4-hydroxyph- enyl)-methane,
2,2-bis-(3,5-dimethyl-4-hydroxy-phenyl)-propane,
bis-(3,5-dimethyl-4-hydroxyphenyl)-sulphone,
2,4-bis-(3,5-dimethyl-4-hydr- oxyphenyl)-2-methylbutane,
1,1-bis-(3,5-dimethyl-4-hydroxy-phenyl)-m/p-dii- sopropyl-benzene,
2,2 and 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohe- xane.
[0091] Particularly preferred diphenols are 4,4'-dihydroxydiphenyl,
1,1-bis-(4-hydroxy-phenyl)-phenyl-ethane,
2,2-bis-(4-hydroxyphenyl)-propa- ne,
2,2-bis(3,5-dimethyl-4-hydroxyphenyl)-propane,
1,1-bis-(4-hydroxypheny- l)-cyclohexane,
1,1-bis-(4-hydroxyphenyl)-m/p diisopropylbenzene und
1,1-bis-(4-hydroxy-phenyl)-3,3,5-trimethylcyclohexane.
[0092] These and other suitable dihydroxy compounds and their
production are disclosed, for example, in U.S. Pat. Nos. 3,028,635,
2,999,835, 3,148,172, 2,991,273, 3,271,367, 4,982,014 and
2,999,846, in DE-A 1,570,703, 2,063,050, 2,036,052, 2,211,956 and
3,832,396, in FR-A 1 561 518, in the monograph "H. Schnell,
Chemistry and Physics of Polycarbonates, Interscience Publishers,
New York 1964" and in JP-A 62039/1986, 62040/1986 and
105550/1986.
[0093] In the case of the homopolycarbonates, only one dihydroxy
compound is used, in the case of the copolycarbonates a plurality
of such compounds are used, wherein of course the diphenols used
(also called bisphenols) may be contaminated with the impurities
originating from their own synthesis, like all other chemicals and
auxiliary agents added to the synthesis, although it is desirable
to work with raw materials which are as clean as possible.
[0094] Suitable chain terminators which may be used in the
production of polycarbonates are monophenols and monocarboxylic
acids.
[0095] Suitable monophenols are, for example, phenol, alkyl phenols
such as cresols, p-tert.butylphenol, p-n-octylphenol,
p-iso-octylphenol, p-n-nonylphenol and p-iso-nonylphenol, halogen
phenols such as p-chlorophenol, 2,4-dichlorophenol, p-bromophenol
and 2,4,6-tribromophenol and mixtures thereof.
[0096] Suitable monocarboxylic acids are, for example, benzoic
acid, alkyl benzoic acids and halogen benzoic acids.
[0097] Preferred chain terminators are the phenols of formula
(I)
R.sup.6-Ph=OH (I)
[0098] wherein R.sup.6 represents H or a branched or unbranched
C.sub.1-C.sub.18 alkyl radical.
[0099] The quantity of chain terminator to be used is preferably
0.5 mol % to 10 mol %, based on mol of the respectively used
diphenols. The chain terminators may be added before, during or
after phosgenation.
[0100] The polycarbonates may be branched. Suitable branching
agents which may be used to branch the polycarbonates are the tri-
or more than trifunctional compounds known in polycarbonate
chemistry, in particular those with three or more than three
phenolic OH groups.
[0101] Suitable branching agents are, for example phloroglucin,
4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene-2,
4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane,
1,3,5-tri-(4-hydroxyphe- nyl)-benzene,
1,1,1-tri-(4-hydroxyphenyl)-ethane, tri-(4-hydroxyphenyl)-ph-
enylmethane,
2,2-bis-[4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-propane,
2,4-bis-(4-hydroxyphenyl-isopropyl)-phenol,
2,6-bis-(2-hydroxy-5'-methyl-- benzyl)-4-methylphenol,
2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propan- e,
hexa-(4-(4-hydroxyphenyl-isopropyl)phenyl)-orthoterephthalic acid
ester, tetra-(4-hydroxyphenyl)-methane,
tetra-(4-(4-hydroxy-phenyl-isopro- pyl)-phenoxy)-methane und
1,4-bis(4',4"-dihydroxy-triphenyl)-methyl)-benze- ne and
2,4-dihydroxybenzoic acid, trimesic acid, cyanurchloride and
3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindol.
[0102] The quantity of branching agent to optionally be used is
preferably 0.05 mol % to 2.5 mol %, based on mol of respectively
used diphenols.
[0103] The branching agents may either be introduced with the
diphenols and the chain terminators in the aqueous alkaline phase
or be added prior to phosgenation dissolved in an organic
solvent.
[0104] All of these measures for producing the polycarbonates are
familiar to the person skilled in the art.
[0105] Aromatic dicarboxylic acids suitable for producing the
polyester carbonates are, for example, phthalic acid, terephthalic
acid, isophthalic acid, ter.-buty-lisophthalic acid,
3,3'-diphenyldicarboxylic acid, 4,4'-diphenyldicarboxylic acid,
4,4-benzophenonedicarboxylic acid, 3,4'-benzophenonedicarboxylic
acid, 4,4'-diphenyletherdicarboxylic acid,
4,4'-diphenylsulphonicdicarboxylic acid,
2,2-bis-(4-carboxyphenyl)-propan- e,
trimethyl-3-phenylindane-4,5'-dicarboxylic acid.
[0106] Of the aromatic dicarboxylic acids, terephthalic acid and/or
isophthalic acid are particularly preferably used.
[0107] Derivatives of the dicarboxylic acids are, for example, the
dicarboxylic acid dihalides and the dicarboxylic dialkylesthers, in
particular the dicarboxylic acid dichlorides and the dicarboxylic
acid dimethylesters.
[0108] The carbonate groups may be replaced substantially
stoichiometrically and also quantitatively by the aromatic
dicarboxylic acid ester groups, so the molar ratio of the reaction
partners is again found in the resulting polyester carbonates. The
aromatic dicarboxylic acid ester groups may be incorporated
randomly and also block by block.
[0109] The polycarbonates are preferably produced by the
interfacial process or the known melt transesterification process.
In the first case phosgene preferably serves as carbon dioxide
derivative, in the latter case preferably diphenylcarbonate.
[0110] Catalysts, solvents, working up, reaction conditions, etc.
for the production of polycarbonate are known in both cases.
[0111] The melt transesterification process is described, in
particular, in H. Schnell, "Chemistry and Physics of
Polycarbonates", Polymer Reviews, Vol. 9, pages 44 to 51,
Interscience Publishers, New York, London, Sidney, 1964 and in DE-A
1 031 512, in U.S. Pat. No. 3,022,272, in U.S. Pat. No. 5,340,905
and in U.S. Pat. No. 5,399,659.
[0112] The polycarbonates may also contain the conventional
additives, for example pigments, UV stabilizers, heat stabilizers,
antioxidants and mold-release agents in the quantities conventional
for polycarbonates.
[0113] For the case where the polycarbonates contain additives, the
compositions that include polycarbonate and additives are also
called polycarbonate molding compounds.
[0114] These conventional additives may be added to the
polycarbonates in a known manner.
[0115] When producing polycarbonate, raw materials and auxiliary
agents with a low degree of contaminants are preferably used. The
bisphenols used and the carbon dioxide derivatives used should be
as free from alkali ions and alkaline earth ions as possible, in
particular when produced by the melt transesterification process.
Pure raw materials of this type may be obtained, for example, by
recrystallizing, washing or distilling the carbon dioxide
derivatives, for example carbon dioxide esters.
[0116] When producing polycarbonates by the melt
transesterification process, the reaction of the bisphenol and of
the carbon dioxide diester may be carried out continuously or
discontinuously, for example in agitated tanks, film evaporators,
falling-film evaporators, series of stirred-tank reactors,
extruders, kneaders, simple disc reactors and high viscosity disc
reactors.
[0117] Carbon dioxide diesters which may be used to produce
polycarbonates, are, for example, diarylesters of carbon dioxide,
the two aryl radicals preferably each having 6 to 14 carbon atoms.
The diesters of the carbon dioxide are preferably used on the basis
of phenol or alkyl-substituted phenols, in other words, for example
diphenylcarbonate or dicresylcarbonate. Based on 1 mol bisphenol
the carbon dioxide diesters are preferably used in a quantity of
1.01 to 1.30 mol, particularly preferably in a quantity of 1.02 to
1.15 mol.
[0118] If phenols, alkylphenols and/or arylphenols are used in the
production of polycarbonates they have the effect of chain
terminators. This means they limit the maximum achievable mean
molecular weight. They may be added either together with the
monomers required to produce the polycarbonate, or in a later phase
of polycarbonate synthesis. They act as monofunctional compounds in
the sense of the polycarbonate synthesis and therefore act as chain
terminators.
[0119] The phenol, alkylphenols and/or arylphenols optionally used
in production of the polycarbonates are preferably used in a
quantity of 0.25 to 10 mol %, based on the sum of the respectively
used bisphenols.
[0120] Mixtures of phenol and/or one or more alkylphenols and/or
arylphenols may also be used.
[0121] The alkylphenols and/or arylphenols optionally used in the
production of polycarbonates lead to terminal alkylphenol groups
and to terminal arylphenol groups. In addition, other terminal
groups may occur in the resulting polycarbonate, depending on the
production process, such as phenolic terminal OH groups or terminal
chloroformic acid ester groups.
[0122] Phenol, alkylphenols and/or arylphenols without the addition
of further substances which may act as chain terminators, are
preferably exclusively used as chain terminators.
[0123] Suitable further substances which may act as chain
terminators are monophenols and monocarboxylic acids. Suitable
monophenols are, for example, phenol, p-chlorophenol or
2,4,6-tribromophenol. Suitable monocarboxylic acids are benzoic
acid, alkylbenzoic acids and halogenbenzoic acids.
[0124] The preferred further substances which may act as chain
terminators are phenol, p-tert.butylphenol, cumylphenol and
isooctylphenol.
[0125] The quantity of further substances which may act as chain
terminators is preferably between 0.25 and 10 mol %, based on the
sum of respectively used dihydroxy compounds.
[0126] The measuring of the uniaxial stretching viscosity is
described hereinafter.
[0127] To measure the uniaxial stretching viscosity a cylindrical
plastic sample (effective dimensions: diameter substantially
between 4 and 5 mm, length substantially between 20 and 25 mm) is
fixed at the ends by means of clamping jaws and fixed in a
stretching rheometer.
[0128] The temperature of the sample is controlled by means of an
oil bath which, at the measuring temperature of 200.degree. C., has
approximately the same density as the plastics material. After
reaching constant temperature, the deformation is predetermined via
the take-off rod connected to the clamping jaws at one end of the
sample. A constant Hencky elongation rate {dot over (.epsilon.)} is
given. This means that the take-off rate u increases exponentially
with time.
[0129] At the other end of the sample the tensile force is measured
as a function of time or total elongation. The uniaxial stretching
viscosity may be ascertained by referring the tensile stress
ascertained to the time-dependent cross-sectional area.
[0130] In the stretching rheometer used for the measurements in the
examples of the present document, the maximum take-off length is at
approximately 500 mm and this corresponds to a maximum deformation
of approximately L/L.sub.0=25 or a maximum Hencky elongation of
approximately In (L/L.sub.O)=3.2. However, the total elongation is
not always achieved in the polycarbonates investigated as the
samples may tear off or fail beforehand.
[0131] The evaluation of the uniaxial stretching test is as
follows. The logarithm of the single stretching viscosity value and
of the three-fold shear viscosity value are shown together in a
graph as a function of time. It has been found that, in particular
the plastics materials suitable for producing containers are those
in which the stretching viscosities increase greatly (in terms of
the ratio 5 as defined above) in comparison with the three-fold
shear viscosity (see FIG. 1). The plastics materials in which the
stretching viscosities do not increase greatly in comparison with
the three-fold shear viscosity (see FIG. 2) are less suitable or
unsuitable for producing water bottles in accordance with the
invention.
[0132] The melts of the polycarbonates which are not advantageous
for producing water bottles, may to an extent not deform at high
total elongations (.epsilon.>2.5) as the samples constrict
and/or fail.
[0133] The measured results of the uniaxial stretching viscosity
depend heavily on the correct test procedure. With an incorrect
test procedure, greatly increased stretching viscosities may be
measured which are not real. To ascertain correct measuring values
an adequate test procedure and evaluation is to be observed (cf.
Th. Schweizer, Rheol. Acta 39 (2000) 5, pages 428 to 443; J. S.
Schulze et al., Rheol. Acta 40 (2001) pages 457 to 466; and V. C.
Barroso, J. A. Covas, J. M. Maia Rheol. Acta 41 (2002) pages 154 to
161).
[0134] FIGS. 1 and 2 will be described hereinafter.
[0135] FIG. 1 shows the uniaxial stretching viscosity
.eta..sub.E(t, {dot over (.epsilon.)}) and the three-fold shear
viscosity 3.eta.(t) for a polycarbonate which is advantageous for
producing water bottles by extrusion blow molding (produced in
accordance with the example according to the invention). The
three-fold shear viscosity 3.eta.(t) is shown as a solid line. The
uniaxial stretching viscosities .eta..sub.E(t, {dot over
(.epsilon.)}) for three different elongation rates {dot over
(.epsilon.)} of 0.1 and 0.03 and 0.01 (unit: 1 divided by seconds)
are shown as lines with symbols. It may be seen that for all
elongation rates the stretching viscosities increase greatly with
increasing time and come to lie above the three-fold shear
viscosity.
[0136] FIG. 2 shows the uniaxial stretching viscosity
.eta..sub.E(t, {dot over (.epsilon.)}) and the three-fold shear
viscosity 3.eta.(t) for a polycarbonate which is not advantageous
for producing water bottles by extrusion blow molding (produced in
accordance with the comparison example). The three-fold shear
viscosity 3.eta.(t) is shown as a solid line. The uniaxial
stretching viscosities .eta..sub.E(t, {dot over (.epsilon.)}) for
three different elongation rates {dot over (.epsilon.)} of 0.2 and
0.1 and 0.05 (unit: 1 divided by seconds) are shown as lines with
symbols. It may be seen that for all elongation rates the
stretching viscosities do not increase greatly with increasing time
and come to lie in the region of the three-fold shear
viscosity.
[0137] In FIGS. 1 and 2, the time axis t for a curve with a
specific Hencky elongation rate {dot over (.epsilon.)} may be
converted into the Hencky elongation .epsilon. as:
Hencky elongation .epsilon.=Hencky elongation rate {dot over
(.epsilon.)} multiplied by time t applies.
[0138] FIG. 3 shows the bottles produced in the examples. The
dimensions thereof are given in millimetres (mm).
[0139] FIG. 4 shows the position of the measuring points on the
bottles at which the wall thickness was measured in the examples.
The numerals 1-46 indicate the locals of thickness
measurements.
[0140] FIG. 5 is a graphic representation of the locations of the
measurements of the wall thickness reported in Table 2. The wall
thickness in mm is plotted against the corresponding points 1 to
46. The bottle made of polycarbonate in accordance with the example
shows a regular course (square symbols). The bottle made of
polycarbonate in accordance with the comparison example shows an
irregular course (triangular symbols).
[0141] The invention is further illustrated but is not intended to
be limited by the following examples in which all parts and
percentages are by weight unless otherwise specified.
EXAMPLES
[0142] A polycarbonate was produced with the Theological stretching
properties in accordance with the example. Water bottles with a
volume of 5 gallons were subsequently produced from the plastic
granules and the wall thickness distribution measured. The same
process was carried out with a comparison product which had the
rheological stretching properties in accordance with comparison
example.
[0143] Water bottles with a homogeneous wall thickness distribution
were obtained from the polycarbonate according to the example but
not from the polycarbonate according to the comparison example.
[0144] 1. Producing the Polycarbonates
Example
[0145] 5515.7 g (24.16 mol) bisphenol A and 31.10 g isatinbiscresol
were dissolved in 33.40 kg 6.5% sodium hydroxide solution in a
nitrogen atmosphere while stirring. A mixture of 70.6 g phenol and
36.03 kg methylene chloride was added to this solution. 2967.6 g
phosgene were then introduced within 30 minutes at 20 to 25.degree.
C. and a pH of 13, maintained by adding further sodium hydroxide
solution, while stirring intensively. After this introduction, 28.3
g N-ethylpiperidine were added and the solution stirred for 45
minutes at a pH of 13.
[0146] The alkali phase was separated from the organic phase. The
organic phase was adjusted with diluted phosphoric acid or
hydrochloric acid to a pH of 1. The phase was then washed free of
electrolytes with deionised water. After exchanging the methylene
chloride for chlorobenzene the polycarbonate was isolated in a
known manner via a stripping extruder.
[0147] The polycarbonate thus obtained had a relative solution
viscosity, measured at a concentration of 0.5 g polycarbonate in
100 ml methylene chloride at 25.degree. C., of 1.325.
Comparison Example
[0148] 6.91 g isatinbiscresol and 78.4 g phenol were used as in the
above example. A polycarbonate with a relative solution viscosity
of 1.305 was obtained. Isatinbiscresol is commercially obtainable
and has the correct name
3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindol.
[0149] 2. Description of the Production of 5 Gallon Water Bottles
Made of Polycarbonate by Extrusion Blow Molding
[0150] The bottles were produced using an extrusion blow molding
machine KBS 2-20 from SIG Blowtec with the following machine
requirements. An extruder with a screw 100 mm in diameter and a
length of 25 D was used, which introduced little frictional heat
into the material at relatively low screw speeds. The plasticizing
capacity was between about 145 and 190 kg/h at a bottle weight of
about 750 g net and a piece number of 130 to 144 bottles/hour. The
plasticizing cylinder was equipped with regulated heating zones and
fans guaranteeing exact and constant temperature control. The drive
was provided by a thyristor-controlled d.c. unit which provided for
uniform conveying of material and a constant torque. The parison
die consisted of a fifo accumulator head (fifo=first in-first out)
with 3.5 litre storage volume and overlapping heart-shaped grooves.
The double heart-shaped grooves offset by 180.degree. produced an
inner and an outer parison and convey the flow of melt into the
accumulator chamber. Mandrel and die in the parison die were
conical in design. The mandrel was displaced axially with respect
to the conical die via a wall thickness control programme.
Consequently, it was possible to optimise the weight of the bottle
and adapt the wall thicknesses in the corresponding wall regions,
for example in the base region.
[0151] The extruder temperatures were 110.degree. C. in the feed
zone and between 245.degree. C. and 265.degree. C. in the
individual heating zones. The die head temperatures were
245.degree. C. to 250.degree. C. and the die temperature
275.degree. C. The melt temperature was 267.degree. C. The mean
cycle time was .+-.0.2 s at 25.8 s, with an ejection time of the
parison of 5.3 s, corresponding to a piece number of 138 to 140
bottles per hour. A conventional vertical wall thickness profile
for 5 gallon polycarbonate bottles was used to control the wall
thickness. The bottles produced had a net weight of 750 g to 850 g
and were immediately adjusted in temperature by means of infrared
radiation. The temperature control served to rapidly relax the
material and to relax the process-induced internal stress
associated therewith. A Protherm 850-3 model, Serial No.: KRK 7110,
infrared radiation oven from Process Dynamics Inc., USA was used.
The adjustable temperatures of the seven heating zones present were
selected such that a surface temperature of the bottles of
130.degree. C..+-.2.degree. C. was ensured.
1TABLE 1 Bottle geometry and weight of the water bottle
example/comparison example: Average wall Calculated thickness Area
Volume weight Example [mm] [cm.sup.2 [cm.sup.3 [g] Neck 2.35 129.53
30.440 36.53 Shoulder 2.01 642.44 129.130 154.96 Bod 1.30 2747.82
357.217 428.66 Base 2.14 547.11 117.082 140.50 Total 4066.90 633.87
760.65 Com- Average wall Calculated parison thickness Area Volume
weight Example [mm] [cm.sup.2 [cm.sup.3 [g] Neck 2.75 129.53 35.588
42.71 Shoulder 2.30 642.44 147.681 177.22 Bod 1.35 2747.82 369.696
443.64 Base 2.23 547.11 122.224 146.67 Total 4066.90 675.19
810.23
[0152] 3. Description of the Wall Thickness Measurement of the
Water Bottles:
[0153] The wall thicknesses were ascertained using an ultrasonic
wall thickness measuring apparatus from Krautkramer GmbH & Co,
Hurth, Germany of the CL3 DL type. This apparatus operates by the
impulse-echo principle. Measurement of the time covered by the
pulse in the material starts with the entry echo produced when a
portion of the ultrasonic pulse is reflected from the boundary face
between advance section and the surface of the material to be
measured. Depending on the thickness of the material the CL3 DL
automatically decides on a measurement from the entry echo to the
first slap-back (interface-to-first modes) or on a measurement
between successive slap-back echoes (multi-echo-modes). An
ultrasonic advance probe specifically for plastics materials called
ALPHA DFR-P and with a nominal frequency of 22 MHz and a connecting
face of 6.4 mm was used for a measuring range of 0.125 mm to 3.8
mm. The wall thickness measurements were made at 46 measuring
points (see FIG. 4) directly on the bottle using an ultrasonic
coupling means.
2TABLE 2 Wall thickness of the measuring point Wall Wall thickness
thickness [mm] Measuring Measuring [mm] Comparison point region
Example example 1 Neck 2.47 2.57 2 Neck 2.42 2.92 3 Shoulder 2.28
2.78 4 Shoulder 2.14 2.66 5 Shoulder 1.88 2.39 6 Shoulder 1.72 1.92
7 Body 1.53 1.63 8 Body 1.36 1.36 9 Body 1.22 1.14 10 Body 1.16
1.45 11 Body 1.14 1.08 12 Body 1.16 1.32 13 Body 1.19 1.17 14 Body
1.24 1.78 15 Body 1.3 1.86 16 Body 1.38 1.96 17 Body 1.45 1.76 18
Body 1.57 1.89 19 Base 1.72 1.78 20 Base 1.94 2.28 21 Base 2.16
2.56 22 Base 2.33 2.73 23 Base 2.46 2.53 24 Base 2.45 2.39 25 Base
2.35 2.48 26 Base 2.19 2.29 27 Base 2.02 1.94 28 Base 1.76 1.36 29
Body 1.58 1.21 30 Body 1.45 1.09 31 Body 1.35 1.37 32 Body 1.29
1.43 33 Body 1.25 1.34 34 Body 1.19 0.94 35 Body 1.16 1.18 36 Body
1.15 0.96 37 Body 1.14 1.27 38 Body 1.22 0.94 39 Body 1.33 1.03 40
Body 1.48 1.13 41 Shoulder 1.68 1.35 42 Shoulder 1.92 2.09 43
Shoulder 2.12 2.51 44 Shoulder 2.3 2.69 45 Neck 2.45 2.86 46 Neck
2.25 2.64
[0154] Although the invention has been described in detail in the
foregoing for the purpose of illusion, it is to be understood that
such detail is solely for that purpose and that variations may be
made therein by those skilled in the art without departing from the
spirit and scope of the invention except as it may be limited by
the claims.
* * * * *