U.S. patent application number 10/661444 was filed with the patent office on 2004-08-26 for pressurized containers and method for making thereof.
This patent application is currently assigned to General Electric Company. Invention is credited to de Wit, Gerrit.
Application Number | 20040166266 10/661444 |
Document ID | / |
Family ID | 32776294 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040166266 |
Kind Code |
A1 |
de Wit, Gerrit |
August 26, 2004 |
Pressurized containers and method for making thereof
Abstract
A pressurized container for storing gaseous or liquid carbon
dioxide for use in pneumatic power devices, and carbonated
beverages such as beer, soft drinks, and the like, which has
acceptable creep, modulus, and yield strength values, which
container is made from fiber-reinforced polyesters.
Inventors: |
de Wit, Gerrit;
(Ossendrecht, NL) |
Correspondence
Address: |
Robert E. Walter
GE Plastics
One Plastics Avenue
Pittsfield
MA
01201
US
|
Assignee: |
General Electric Company
|
Family ID: |
32776294 |
Appl. No.: |
10/661444 |
Filed: |
September 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60450454 |
Feb 26, 2003 |
|
|
|
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
F17C 2221/011 20130101;
F17C 2270/0563 20130101; F17C 2203/0668 20130101; F17C 2270/0545
20130101; F17C 2270/07 20130101; F17C 2209/2118 20130101; F17C
2221/03 20130101; F17C 2203/0673 20130101; F17C 2203/0697 20130101;
F17C 2203/012 20130101; F17C 2223/033 20130101; F17C 2270/02
20130101; F17C 2270/05 20130101; F17C 1/06 20130101; F17C 2223/035
20130101; F17C 2203/0643 20130101; F17C 2209/2127 20130101; F17C
2203/0617 20130101; F17C 2221/013 20130101; F17C 2203/0636
20130101; Y10T 428/1352 20150115; F17C 2270/0754 20130101; F17C
2201/0104 20130101; F17C 2201/056 20130101; F17C 2209/221 20130101;
F17C 2223/0153 20130101; F17C 2201/058 20130101; F17C 2203/0665
20130101; F17C 2203/0646 20130101; F17C 2223/0123 20130101; F17C
2209/232 20130101; F17C 2260/036 20130101 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
1. A pressurized container made of reinforced polyesters wherein
upon being filled with a liquid having a dissolved carbon dioxide
content of about 0.4-0.6 wt % at an internal pressure of at least 1
bar, said pressurized container maintains a dissolved carbon
dioxide content of at least 0.25 wt % after 0.5 year at a storage
temperature of about 30 to 35.degree. C.
2. The pressurized container of claim 1, wherein the polyesters are
reinforced by reinforcing agents selected from glass fibers, carbon
fibers, metal fibers, aromatic polyamide fibers, and combinations
thereof.
3. The pressurized container of claim 1, obtainable by a
conventional thermoplastic processing method selected from
injection molding, thermoforming, hot-press molding,
injection-compression molding, blow molding, pultrusion, extrusion,
or combinations thereof.
4. The pressurized container of claim 1, further comprising a
plurality of re-enforcing strips attached to and reinforcing said
container with each strip encircling the container in a hoop
direction at least once.
5. The pressurized container of claim 1, wherein the reinforcing
agents are glass fibers having a length of at least 0.5 cm.
6. The pressurized container of claim 1, wherein the polyesters are
reinforced by glass fibers in an amount of at least 20 wt. % based
on the total weight of said reinforced polyesters.
7. The pressurized container of claim 1, wherein the polyesters are
reinforced by glass fibers in an amount of about 1 to about 50
volume % (vol. %).
8. The pressurized container of claim 1, having a wall thickness of
at least 0.2 mm.
9. The pressurized container of claim 1, having a total liquid
volume of at least 15 liters.
10. A pressurized container made of reinforced polyesters having a
wall thickness of at least 0.2 mm and a carbon dioxide permeability
property of less than 0.8 g/100 sq in. in 24 hours per mil.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Serial No. 60/450454 filed on Feb. 26, 2003, which is
incorporated herein by reference in its entirety.
[0002] The present invention relates to pressurized containers or
vessels made from reinforced thermoplastics and methods for making
pressurized containers or vessels from reinforced
thermoplastics.
BACKGROUND OF THE INVENTION
[0003] There has been a growing interest in using plastics for
pressurized containers, primarily for containing beverages, but
increasingly for other utilities such as containers to dispense
either gaseous or liquid carbon dioxide for use in pneumatic power
devices such as garden pressure sprayers, power tools. etc. wherein
the high pressure carbon dioxide provides mechanical power. There
is also an increased interest in the use of plastic containers in
applications such as fire extinguishers, cylinders containing
medical gases for distribution in laboratories and larger (e.g. 5
to 50 liters capacity), and cylinders such as those used in the
distribution of oxygen, nitrogen, carbon dioxide and the like to
industrial users.
[0004] For use in beverage container applications, U.S. Pat. No.
3,712,497 discloses bottles formed of thin walled, flexible
synthetic plastics, in separate parts which are later friction
welded together forming the bottles, capable of withstanding
internal pressures of up to 75 psi.
[0005] Also for beverage containers, U.S. Pat. No. 4,591,066
discloses a unitary molded plastic body for containing pressurized
liquid beverage made out of polystyrene, PET, or polypropylene.
However, in packaging draft beer in containers as disclosed herein,
it is found that these containers are quite permeable to carbon
dioxide. Generally, when used for beer storage and with the
migration of carbon dioxide through the plastic membrane/wall being
temperature related (higher at room temperature than at
30-32.degree. F.), beer stored in the plastic containers of the
prior art will have lost so much of its carbon dioxide content
after a few days that the remaining beer will no longer be
palatable and flat-tasting. EP 0 578 711B1 discloses an improved
container for beer and other beverages in the form of a layered
construction of at least two plastic materials, with the plastic
materials being arranged in adjacent layers fastened together, or
being laminated together. The improved container herein can
withstand pressure of up to approximately 420 kPA or about 65 psi.
In one embodiment of the container, the first plastic material is a
polyethylene terepthalate, and the second plastic material is
nylon.
[0006] Applicants have found that the use of reinforced polyesters
in pressurized containers offers a package with gas and moisture
barrier properties as well as excellent physical properties in
terms of minimal creep or dimensional changes from the effects of
pressure in storage or usage, as well as sufficient impact strength
for safety in storage and handling.
SUMMARY OF THE INVENTION
[0007] The invention relates a pressurized container made of
reinforced polyesters having sufficient creep resistance, impact
strength, CO2 and O2 barrier resistance, wherein upon being filled
with a liquid having a dissolved carbon dioxide content of in the
range of 0.4-0.6 wt % at an internal pressure of at least 1 bar,
said pressurized container maintains a dissolved carbon dioxide
content of at least about 0.25 wt % after 6 months at a storage
temperature of about 30 to 35.degree. C., and an O.sub.2-permeation
of less than 1.0 ppm.
[0008] The invention also relates to the use of long-glass fiber
reinforced polyesters in pressurized containers for excellent creep
resistance, impact strength, water and CO.sub.2/O.sub.2 barrier
properties.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Applicants have found that reinforced plastic materials,
i.e., polyesters reinforced with various materials, e.g.,
long-glass fibers and the like, provide a combination of excellent
barrier and physical properties such as low permeability to gases,
high strength, and low creep at elevated temperatures, thus
excellent for packaging applications such as pressurized containers
for beverages, foodstuff, and the like.
[0010] Reinforced Thermoplastic Materials for the Containers. The
polyester resins utilized in this invention include, in general,
linear saturated condensation products of diols and dicarboxylic
acids, or reactive derivatives thereof. Polyesters are well known
as film and fiber formers, and they are manufactured by methods
known in the art including those disclosed in U.S. Pat. Nos.
2,465,319 and 3,047,539.
[0011] In one embodiment, the polyesters comprise condensation
products of aromatic dicarboxylic acids and aliphatic diols. In
another embodiment, the polyesters are poly(1,4-dimethylol
cyclohexane dicarboxylates, e.g., terephithialates). In addition to
phthalates, small amounts of other aromatic dicarboxylic acids,
such as isophthalic dicarboxylic acid, naphthalene dicarboxylic
acid, or aliphatic dicarboxylic acids, such as adipic acid, can
also be present in the resins. The diol constituent can likewise be
varied, in some embodiments, by adding small amounts of
cycloaliphatic diols.
[0012] In one embodiment, the polyesters comprise a poly(alkylene
terephthalate, isophthalate or mixed isophthalate-terephthalate,
e.g., up to 30 mole percent isophthalate), with the alkylene groups
containing from 2 to 10 carbon atoms, e.g., poly(ethylene
terephthalate) ("PET") or poly(1,4-butylene terephthalate) ("PBT").
In yet another embodiment the polyester resins may comprise
entirely of PET, PBT, or a combination thereof. In one embodiment,
the polyesters comprise a mixture of PBT to PET at a weight ratio
of about 1:1 to about 20:1.
[0013] In one embodiment, the poly(1,4-butylene terephthalate)
resin used is one obtained by polymerizing a glycol component at
least 70 mol %, preferably at least 80 mol %, of which consists of
tetramethylene glycol and an acid or ester component at least 70
mol %, preferably at least 80 mol %, of which consists of
terephthalic acid, and polyester-forming derivatives therefore.
[0014] In another embodiment, the polyester is a poly(1,4-butylene
terephthalate) homopolyester. In yet another embodiment,
copolyesters are used. These comprise at least about 70 mole
percent, based on total monomer content, of butylene and
terephthalate units. The comonomer may be either a dicarboxylic
acid or diol or a combination of the two. Suitable dicarboxylic
acid comonomers include the C.sub.8 to C.sub.16 aromatic
dicarboxylic acids, including the benzene dicarboxylic acids, i.e.
phthalic and isophthalic acids and their alkyl, e.g. methyl,
derivatives and C.sub.4 to C.sub.16 aliphatic and cycloaliphatic
dicarboxylic acids including, for example, sebacic acid; glutaric
acid; azelaeic acid; tetramethyl succinic acid; 1,2-, 1,3- and
1,4-cyclohexane dicarboxylic acids and the like. Suitable diol
comonomers include but are not limited to C.sub.2to C.sub.8
aliphatic and cycloaliphatic diols, e.g. ethylene glycol,
hexanediol, butanediol and 1,2-, 1,3- and
1,4-cyclohexanedimethanol.
[0015] In one embodiment, the polyester resin having a coefficient
of thermal expansion (CTE) higher than that of the intended
reinforcing material used, so that the polyester material shrinks
around the reinforcing material causing compressive stresses which
grip the reinforcing material in place.
[0016] In anther embodiment of the present invention, the
polyesters may be blended with a polycarbonate resin. Polycarbonate
resins useful in preparing the blends of the present invention are
generally aromatic polycarbonate resins.
[0017] Optional Additives to the Polyester Resin Matrix. In one
embodiment of the invention, the polyesters may be modified with
additives such as a high molecular weight polyetherimide base
material (e.g. an polyetherimide ester elastomer) as a warpage
control additive.
[0018] In another embodiment of the invention wherein the polyester
is PBT, additives such as (co-)polyolefins or polyethylenes are
added for improved impact strength. In one example, the impact
strength additive is selected from ethylene vinyl acetate (EVA),
linear low-density polyethylene (LLDPE), and alpha-olefin-glycidyl
methacrylate copolymers and terpolymers.
[0019] In yet another embodiment of the invention wherein the
weight ratio of polyester to the reinforcing agent is equal to or
below about 2.25, a copolymer or interpolymer comprising glycidyl
2-alkenoates and alpha-olefins is added to the polyester for
improved impact strength and improved melt viscosity to facilitate
the construction of the finished pressurized containers.
[0020] In another embodiment, the polyesters may further contain
one or more conventional additives such as, for example,
antioxidants, carbon black, reinforcing agents, plasticizers,
lubricity promoters, color stabilizers, ultraviolet absorbers,
X-ray opacifiers, dyes, pigments, fillers including mineral
fillers, mold release agents such as polyethylene, and the
like.
[0021] In one embodiment, mineral fillers include alumina,
amorphous silica, anhydrous aluminum silicates, feldspar, talc,
milled glass, phenolic resins, glass microspheres, metal oxides
such as titanium dioxide, zinc sulfide, ground quartz, clays such
as hydrated aluminum silicate, and the like are used in the
polyester matrix.
[0022] In yet another embodiment, thermal, oxidative and/or
ultraviolet stabilizers comprise phenols and their derivatives,
amines and their derivatives, compounds containing both hydroxyl
and amine groups, hydroxyazines, oximes, polymeric phenolic esters
and salts of multivalent metals may be optionally added to the
polyester resins.
[0023] Reinforcing Agents for the Polyester Resin Matrix. In one
embodiment, the reinforcing agents are fibers in the form of
fiberglass, carbon or aramid fibers in roving, woven fabric form,
or in combination of fiberglass and carbon or aramid fibers. In
another embodiment, the reinforcing agents are metals drawn into
wire or filaments, or polyamide polymers characterized by the
presence of the amide group --CONH. In yet another embodiment, the
reinforcing agents are solely glass fibers available in roving,
continuous strand mat, and stitched rovings (0.degree., 90.degree.,
and .+-.45.degree. orientations).
[0024] In one embodiment, the fibers are precoated with a binder to
enhance compatibility with the polyester resin matrix. The coating
can comprise normal fiberglass coating materials: polyurethane
resin, polyacrylate resin, polyester resin, polyepoxide resin, and
functional silanes, especially epoxy or amine functional alkoxy
silanes. The amount of the coating agent employed is generally that
amount which is sufficient to bind the filaments into a continuous
strand. Generally, this may be about 1.0 weight percent based on
the weight of the glass filament.
[0025] The fiber diameters typically range from about 3 to 50
microns. In another embodiment, the filaments in the form of glass
fibers have a diameter of about 5 to 30 microns. In yet another
embodiment, the fiber has a diameter of about 10 to 20 microns.
[0026] In embodiment of fibers as reinforcing agents, the fibers in
the form of chopped fiberglass strands have a length of about 1/8"
to about 1". In another embodiment, long-fibers with lengths of
more than 1" are used, for increased strength and moldability of
the containers. In yet another embodiment, the fiberglass fibers
are comprised of lime-aluminum borosilicate glass that is
relatively soda free. This is known as "E" glass. In other
embodiments, other glasses are used as well e.g., the low soda
glass known as "C." In another embodiment, glass filaments known as
G filaments are used.
[0027] The glass filaments are made by standard processes, e.g., by
steam or air blowing, flame blowing and mechanical pulling. In one
embodiment, the filaments are made by mechanical pulling. In one
embodiment, the filaments are in the form of being bundled into
fibers and the fibers bundled in turn to yarns, ropes or rovings,
for final use in reinforcing the polyesters for use in the
pressurized containers of the invention.
[0028] In one embodiment of the invention, the reinforcing agents
comprise a range of materials other than glass fibers and in the
form other than filaments, e.g., microspheres. These include but
are not limited to glass, ceramic materials such as graphite,
wollastonite, carbons, metals, e.g., aluminum, iron, nickel,
stainless steel and the like, titanates, e.g., titanate whiskers,
quartz, clay, mica, talc, mixtures of the foregoing and the like.
The metal and metal glass fiber materials that can be used include
those disclosed in the U.S. Pat. No. 4,525,314, the entire
disclosure of which is incorporated herein by reference. The
ceramic materials from which the reinforcing fibers can be made
include silicon carbide, silicon nitride, carbon, graphite and
aluminum oxide. The metal, ceramic, and glass microspheres than can
be used as reinforcing agents include those disclosed in U.S. Pat.
No. 4,671,994, the entire disclosure of which is incorporated
herein by reference.
[0029] In one embodiment, reinforcing agents are used in an amount
ranging from about 5 to about 60 weight percent based on the total
weight of the thermoplastic blend composition. In another
embodiment, the concentration of the reinforcing agents is
expressed as volume %, and ranging from about 1 to about 50 volume
% (vol. %). The volume percent can be calculated by comparing the
total area of the cross section of a finished part with the cross
sectional area of the fibers. In another embodiment, this amount is
less than about 40 vol. %. In a third embodiment, it is less than
30 vol. %. In a fourth embodiment, it is about 5 to 20 vol. %.
[0030] Processing of the Reinforced Polyesters/Forming the
Pressurized Containers. In one embodiment of the invention, wherein
the reinforcing agents used are long fibers, a pultrusion process
known in the art is used to form the components into shape. In a
pultrusion process, the long glass fiber material is drawn through
a bath containing the polyester resins plus any additives. In one
embodiment of the pultrusion process, the long glass fiber material
is first impregnated with the polyester resin of the invention
(plus any optional additives). Laminate formed is pulled through a
heated die controlled to precise tolerances depending on the final
container application specifications. The finished product is cut
and tooled into various parts of the container, e.g., sidewall, top
or bottom part and the like. The parts are subsequently welded
forming the finished containers.
[0031] In yet another embodiment, a process as generally described
in EP 0 820848B1 is used for a lineal structure particularly useful
for a tall pressurized container, which reference is expressedly
incorporated herein. This process comprises feeding the melted
polyester materials of the invention into a die having an inlet for
receiving the melted material, and an outlet having a geometry
corresponding to the desired part of the container of the
invention. The outlet is positioned downstream from the inlet
wherein the melted polyester resin flows from the inlet to the
outlet. A plurality of fiber bundles are introduced to the stream
at predetermined spaced apart radial positions for providing the
fiber reinforcement to the lineal profile. The fiber bundles extend
in the longitudinal direction at predetermined locations in the
profile. The finished product is cut and tooled into various parts
of the container, e.g., sidewall, top or bottom part and the
like.
[0032] Subsequent to the pultrusion or extrusion process forming
the parts, and the assembling of the parts via welding or other
processes known to the art to form the finished containers, the
containers can be further reinforced with additional bands of
materials at generally taught in EP0852695B1 for "Blast Resistant
And Blast Directing Containers." In one embodiment, the pressurized
container further comprises a plurality of spaced, substantially
parallel composite strips attached to and reinforcing the container
with each strip being a tape of unidirectional high strength fibers
or oriented film encircling the container in a hoop direction at
least once.
[0033] In another embodiment of the invention, chopped glass
strands are used as reinforcing agents. The chopped glass strands
may be first blended with the polyester resin and then fed to an
extruder and the extrudate cut into pellets. In another example,
they may be separately fed to the feed hopper of an extruder to
preparing reinforced polyester pellets. The pellets so prepared
when cutting the extrudate may be on fourth inch long or less. The
dispersed glass fibers are reduced in length as a result of the
shearing action on the chopped glass strands in the extruder
barrel.
[0034] The reinforced polyester resins are subsequently shaped into
pressurized containers or parts thereof, via common processes known
in the art, such as extrusion blow molding, injection blow molding,
profile extrusion, pipe extrusion, co-extrusion, extrusion coating,
foam molding, foam extrusion, thermoforming, and the like. The
parts can be subsequently welded to form the finished pressurized
containers.
[0035] Properties of the Pressurized Containers. In one embodiment
of the invention, wherein the reinforced polyester pressurized
containers of 2-4 mm thickness are used as beer containers, i.e.,
beer kegs, it is found that the reinforced polyester pressurized
containers of the invention have inherently low CO2 and oxygen
permeation properties, wherein upon being filled with a liquid
having a dissolved carbon dioxide content of 0.4-0.6 wt % at an
internal pressure of at least 1 bar, said pressurized container
maintains a dissolved carbon dioxide content of at least 0.25 wt %
after 0.5 year at a storage temperature of about 30 to 35.degree.
C. and an O2-permeation of less than 1.0 ppm.
[0036] With respect to creep properties, in one embodiment of the
invention, the pressurized containers, made out of reinforced
polyesters, used at an initial internal pressure of 1-5 bar have a
creep <3% after 0.5 year at room temperature.
[0037] With respect to impact break resistance properties, in
embodiments wherein long-glass-fibers are used as reinforcing
agents and pultrusion technology is used to fabricate the
pressurized containers of the present invention, tests on a number
of differently designed and produced 15 liter vessels of 2-4 mm
thickness show that pressurized containers (50% filled and 80%
filled) are break-resistant upon being dropped from heights ranging
from 0.45-1 m.
[0038] In food applications, e.g., as beer kegs or pressurized
containers for soft drinks and a variety of foodstuffs, it is found
that the reinforced polyesters containers of the present invention
do not import unacceptable levels flavoring changes to the
products.
EXAMPLE
[0039] The examples below are merely representative of the work
that contributes to the teaching of the present application.
Examples 1-4
[0040] In this example, reinforced polyester compositions
comprising of PBT (poly(butyleneterephthalate) with molecular
weight of appr. 80,000 (as expressed as PS molecular weight),
0.15%, Irganox 1010 as a stabilizer, approximately 1% of a
polyethylene as release agent, and from 30 to 50 wt. % of glass
fiber.
[0041] The compositions are referred to as 30%, SGF, 50% LGF, 30%
LGF, and 50% LGF, depending on whether short glass or long glass
fiber is used. The short glass fiber is in the form of E-glass
chopped strands commercially available from NEG as T-120. The long
glass fiber (e.g. E-glass based) can be treated with a finishing
agent such as a silane-based coupling agent, greige goods such
urethane-based resins or epoxy-based resins, a thermal stabilizer
such as typically phosphite-based resins, or any other adequate
surface-treating agents depending upon aimed uses, if required.
[0042] The LGF compositions are made according to the pultrusion
process as generally disclosed in U.S. Pat. No. 4,559,262, the
entire disclosure of which is incorporated herein by reference. In
the examples, PBT polymer melts are prepared in a bath of about
260.degree. C. Fiber glass filaments (in the form of a glass
roving) are pulled through the molten polymer over one spreader bar
situated in the bath at a rate of 30 cm/minute, giving a dwell time
in the bath of 30 seconds. The impregnated roving is pulled through
a 3 mm diameter die in the wall of the bath and then cooled, for a
completely wetted material. The amount of PBT in the finished
product (for 30 or 50 wt. % concentration of fiber) is controlled
by the length of the path over which the fiber band contacts the
heated spreader surface.
[0043] The products obtained by the continuous pultrusion are
subsequently chopped to form pellets having a length in the range
of at least 5-10 mm. The used LGF products are supplied by LNP
under the name of Verton AF 7006 (30% LGF) and WF 700 10 (50%
LGF).
[0044] The SGF blends are made by dry blending of ingredients with
exception of the glass fiber. The blends are subsequently
compounded on a WP25 mm co-rotating extruder, where the glass is
separately fed down-stream the extruder. The melt temperature was
approx. 250-260.degree. C. and at RPM of 300. The products obtained
are extrudated to form pellets.
[0045] The SGF and LGF products are molded into samples using an
Engel 75 tons machine with a temperature setting of 240-260 C.
(from throat to nozzle) and a mold temperature of 60 C. Prior to
molding the pellets were predried at 120 C. for 2 hours.
[0046] The properties of the short-glass fiber (SGF) and long-glass
fiber (LGF) samples in Examples 1-4 are measured according to the
following procedures:
[0047] Notched Izod (NI) and Unnotched Izod (UNI): This test
procedure is based on the ISO180 method, with the notched (INI) and
the unnotched (UNI) impact strengths being obtained by testing a
notched or unnotched specimen. The results of the test is reported
in terms of energy absorbed per unit of specimen width, and
expressed in kilojoules per square meter (kJ/m2). Typically, the
final test result is calculated as the average of test results of
five test bars.
[0048] The Flexed Plate Impact Test: This test procedure is used to
determine maximum force, energy at max, and energy at break and
deflection at break, based on the ISO6603 method and used at
different speeds.
1 Energy @ Energy @ Defl. @ INI INI UNI Max. Force Max. Force Max
(J) Break (J) Brk (mm) (kJ/m2) (kJ/m2) (kJ/m2) Type (N) @ 4 m/s (N)
@ 0.1 m/s @ 4 m/s @ 4 m/s @ 4 m/s acc. LNP acc. GEP acc GEP 50% SGF
2526 2780 8.1 13.8 10.4 13.4 14.1 45.9 50% LGF 2834 2741 8 17.9
15.1 40 42.1 59.2 30% LGF 2656 2519 9.5 15.9 11.9 30 32.5 56.2 30%
SGF 2292 2365 9.3 12.1 12.8 9.9 48.9
Example 2
[0049] In this example, the 50% LGF composition in Example 2 is
used in a fiber-reinforced polyester pressurized vessel. i.e., beer
kegs, with a pultrusion process is used to form the components of
the beer kegs.
[0050] The beer kegs are filled from beer tanks at suitable
internal pressure of about 2 bars and at temperature of about 20 to
35.degree. C., and with the beer having a dissolved carbon dioxide
content of about 0.5 wt %.
[0051] After a shelf life of approx. six months and at a
temperature of 20 to 35.degree. C., it is found that the beer in
the fiber-reinforced polyester beer kegs of the present invention
has a dissolved carbon dioxide content of at least 0.25 wt. %. It
is also found that the beer is not flat when dispensed and
consumed. It is also found that after the beer is partially
consumed and in storage in the keg at about 20 to 35.degree. C. for
two to three days, the remaining beer still contains a dissolved
carbon dioxide volume of about 0.25 wt %. Additionally, the beer
also retains a palatable taste and is not flat, all without the
need for any external pressure source.
[0052] It should be understood that the foregoing description is
only illustrative of the invention. Various alternative
modifications can be employed by those skilled in the art without
departing from the scope of the invention. Accordingly, the present
invention is intended to embrace all such alternative,
modifications and variances, which fall within the scope of the
appended claims.
* * * * *