JP2004256176A - Pressure container and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic-made pressure container which is excellent in gas and humidity shielding property, creep resistance and shock resistance, and is particularly suitable for beverage. <P>SOLUTION: The pressure container for storing a gas used for an air pressure device or carbonated drinks such as liquid carbon dioxide, beer and soft drinks is formed of fiber reinforced polyester and has excellent creep resistance, elastic modulus and yield strength. The pressure container comprising the reinforced polyester maintains dissolved carbon dioxide of 0.25wt% or more at a storage temperature of 30 to 35°C in a six month if a liquid containing the dissolved carbon dioxide of about 0.4 to 0.6wt% is filled in the container at an internal pressure of 1 bar or more. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a pressurized container made of reinforced thermoplastics and a method for producing a pressurized container from reinforced thermoplastics.

  There is increasing interest in the use of plastics in pressurized containers, mainly pressurized containers for beverages, but also for pressurized sprays for horticulture, gas or pneumatics for mechanically powering with high pressure carbon dioxide, such as power tools. There is also increasing interest in using plastics for other applications, such as liquid carbon dioxide supply vessels. In addition, plastics can be used for various purposes, such as fire extinguishers, medical gas cylinders for laboratory delivery, large (eg, about 5 to 50 L) cylinders, and cylinders used for delivery of oxygen, nitrogen, carbon dioxide, etc. to industrial users. There is also increasing interest in using containers.

  For use in beverage containers, U.S. Pat. No. 3,712,497 discloses that a bottle made of a plurality of separate pieces of thin, flexible synthetic plastic that is subsequently friction welded together can withstand an internal pressure of up to 75 psi. A possible bottle is disclosed.

Regarding beverage containers, U.S. Pat. No. 4,591,066 also discloses an integrally molded plastic body for pressurized liquid beverages made of polystyrene, PET or polypropylene. However, when draft beer is placed in the container disclosed in this US patent, it can be seen that the container is permeable to carbon dioxide. In general, prior art plastic containers are used for beer storage because the movement of carbon dioxide through the plastic membrane / wall is temperature related (room temperature is more mobile than 30-32 ° F). Beer stored in a few days loses most of its carbon dioxide content after a few days, and is no longer palatable, but rather depressed. EP 0 578 711 discloses an improved container for beer and other beverages having a layered structure of two or more plastic materials, wherein these plastic materials are clamped and / or laminated adjacent layers. An improved container is disclosed. The improved container withstands pressures up to about 420 kPa or about 65 psi. In one embodiment of the container, the first plastic material is polyethylene terephthalate and the second plastic material is nylon.
U.S. Pat.No. 3,712,497 U.S. Pat. No. 4,510,066 European Patent Specification No. 0578711

  The present inventors have found that the use of reinforced polyester in a pressurized container not only has gas and moisture shielding properties, but also has excellent physical properties in that creep or dimensional change due to the influence of pressure during storage or use is extremely small. It has been found that a package having both sufficient impact strength for safe storage and handling can be obtained.

The present invention has excellent creep resistance, impact strength, a CO ₂ and O ₂ enhanced polyester pressure vessel having a shielding property, about dissolved carbon dioxide content in the inner pressure 1 bar or more from 0.4 to 0. The invention relates to a pressurized container which, when filled with 6% by weight of liquid, maintains a dissolved carbon dioxide content of 0.25% by weight or more and a O ₂ permeability of less than 1.0 ppm after 6 months at a storage temperature of about 30 to 35 ° C.

The present invention has excellent creep resistance, impact strength, relates to the use of long glass fiber reinforced polyester in pressurized for imparting water and CO ₂ / O ₂ barrier properties.

  The present inventors have reinforced plastic materials, i.e. polyesters reinforced with various materials such as long glass fibers, provide a combination of excellent shielding properties and properties, such as low gas permeability, high strength and low creep at high temperatures, It has been found to be optimal for packaging applications such as pressurized containers used in beverages, foods and the like.

Reinforced Thermoplastic Materials for Containers The polyester resins used in the present invention generally include linear saturated condensates of diols with dicarboxylic acids or reactive derivatives thereof. Polyester is well known as a film and fiber forming material and is made by methods known in the art, including those disclosed in U.S. Patent Nos. 2,465,319 and 3,047,539.

  In one embodiment, the polyester comprises a condensate of an aromatic dicarboxylic acid and an aliphatic diol. In another embodiment, the polyester is poly (1,4-dimethylolcyclohexanedicarboxylate), for example, poly (1,4-dimethylolcyclohexaneterephthalate). In addition to phthalate, small amounts of other aromatic dicarboxylic acids (eg, isophthaldicarboxylic acid, naphthalenedicarboxylic acid) or aliphatic dicarboxylic acids (eg, adipic acid) may be present in the resin. Similarly, in some embodiments, the diol component can be modified by the addition of small amounts of alicyclic diols.

  In one embodiment, the polyester is a poly (alkylene terephthalate), poly (alkylene isophthalate) or poly (alkylene hybrid isophthalate-terephthalate) having 2 to 10 carbon atoms in the alkylene group (e.g., having an isophthalate content of 30 mole% or less). For example, poly (ethylene terephthalate) (abbreviated PET) or poly (1,4-butylene terephthalate) (abbreviated PBT). In still other embodiments, the polyester resin may consist solely of PET, PBT or a combination thereof. In one embodiment, the polyester comprises a PBT / PET mixture in a weight ratio of about 1: 1 to about 20: 1.

  In one embodiment, the poly (1,4-butylene terephthalate) resin used comprises a glycol component comprising at least 70 mol%, preferably at least 80 mol%, of tetramethylene glycol, and at least 70 mol%, preferably at least 80 mol%. The above is obtained by polymerization with an acid or ester component comprising terephthalic acid and its polyester-forming derivative.

In another embodiment, the polyester is a poly (1,4-butylene terephthalate) homopolyester. In yet another embodiment, a copolyester is used. The copolyester contains about 70 mol% or more of butylene and terephthalate units, based on the total amount of monomers. The comonomer may be a dicarboxylic acid, a diol, or a combination thereof. Suitable dicarboxylic acid comonomers include C ₈ -C ₁₆ aromatic dicarboxylic acids, specifically benzenedicarboxylic acids, ie, phthalic acid and isophthalic acid and their alkyl (eg, methyl) derivatives, and C ₄ -C ₁₆ aliphatic. And alicyclic dicarboxylic acids, specifically, sebacic acid, glutaric acid, azelaic acid, tetramethylsuccinic acid, 1,2-, 1,3- and 1,4-cyclohexanedicarboxylic acid. Suitable diol comonomers, C ₂ -C ₈ aliphatic and cycloaliphatic diols, such as ethylene glycol, hexanediol, butanediol and 1,2, and the like 1,3- and 1,4-cyclohexane dimethanol However, it is not limited to these.

  In one embodiment, the polyester resin has a CTE that is higher than the coefficient of thermal expansion (CTE) of the reinforcement used, such that the polyester material shrinks around the reinforcement, creating compressive stress and causing the reinforcement to shrink. Hold in place.

  In another embodiment of the present invention, the polyester may be blended with a polycarbonate resin. Polycarbonate resins useful in forming such blends are generally aromatic polycarbonate resins.

Optional Additives to the Polyester Resin Matrix In one embodiment of the present invention, the polyester may be modified with various additives, such as high molecular weight polyetherimide-based materials as warpage inhibitors (eg, polyetherimide ester elastomers). Good.

  In another embodiment of the invention where the polyester is PBT, additives such as (co) polyolefins or polyethylene are added for the purpose of improving impact strength. For example, the impact modifier is selected from ethylene-vinyl acetate (EVA), linear low density polyethylene (LLDPE) and α-olefin-glycidyl methacrylate copolymers and terpolymers.

  In another embodiment of the present invention, wherein the weight ratio of polyester / reinforcement is about 2.25 or less, glycidyl 2-alkenoate and glycidyl 2-alkenoate to improve impact strength and melt viscosity to facilitate manufacture of the finished pressurized container. A copolymer or interpolymer consisting of an α-olefin is added to the polyester.

  In another embodiment, the polyester further comprises one or more conventional additives, such as antioxidants, carbon black, reinforcing agents, plasticizers, lubricants, color stabilizers, UV absorbers, X-ray opaque agents, dyes, pigments. , A filler such as an inorganic filler, and a release agent such as polyethylene.

  In one embodiment, alumina, amorphous silica, anhydrous aluminum silicate, feldspar, talc, glass powder, phenolic resin, glass microspheres, metal oxides such as titanium dioxide, zinc sulfide, quartz powder, hydrated aluminum silicate, etc. Inorganic fillers, including clays, are added to the polyester matrix.

  In another embodiment, heat, including phenols and derivatives thereof, amines and derivatives thereof, compounds containing both hydroxyl and amine groups, hydroxyazines, oximes, high molecular weight phenol esters, salts of polyvalent metals, etc. Oxidation and / or UV stabilizers may be optionally added to the polyester resin.

Reinforcement for Polyester Resin Matrix In one embodiment, the reinforcement is fiberglass-like fiber, roving or woven carbon or aramid fiber, or a combination of glass fiber and carbon or aramid fiber. In another embodiment, the reinforcement is a metal drawn into a wire or filament, or a polyamide polymer having an amide group -CONH. In another embodiment, the reinforcement is only glass fibers available as rovings, continuous strand mats or stitched rovings (0 °, 90 ° and ± 45 ° orientation).

  In one embodiment, the fibers are pre-coated with a binder to increase compatibility with the polyester resin matrix. Coatings include common glass fiber coating materials such as polyurethane resins, polyacrylate resins, polyester resins, polyepoxide resins and functional silanes, especially epoxy or amine functional alkoxysilanes. The amount of coating material used is generally sufficient to bind the filaments into a continuous strand. Generally, this amount may be about 1.0% by weight, based on the weight of the glass filament.

  The fiber diameter is typically about 3 to 50 μm. In another embodiment, the filaments in the form of glass fibers have a diameter of about 5-30 μm. In yet another embodiment, the fiber diameter is about 10-20 μm.

In embodiments where fibers are used as reinforcement, the fibers in the form of chopped glass fiber strands have a length of about 1/8 to 1 inch. In another embodiment, long fibers longer than 1 inch are used to increase the strength and moldability of the container. In yet another embodiment, the glass fibers comprise a lime-aluminum borosilicate glass having a relatively low soda content. This is known as "E-glass". In another embodiment, other glasses are used, for example, low soda glass known as "C glass". In another embodiment, a glass filament known as a G filament is used.

  Glass filaments are produced by conventional methods such as steam or air blowing, flame blowing or mechanical drawing. In one embodiment, the filament is manufactured by a mechanical drawing method. In one embodiment, the filament may be bundled as a fiber bundle, or the fiber bundle may be further bundled into yarn, rope, or roving, for final use in reinforcing the polyester used in the pressurized container of the present invention. Good.

  In one embodiment of the present invention, the reinforcement includes a wide range of materials besides glass fibers, and also includes forms other than filaments, such as microspheres. By way of example, not only glass, but also ceramic materials, such as graphite, wollastonite, carbon, metals, such as aluminum, iron, nickel, stainless steel, etc., titanates such as titanate whiskers, quartz, clay, mica, talc, These include mixtures. As the metal and metallic glass fiber material, those disclosed in U.S. Pat. No. 4,525,314 (the disclosure of which is incorporated herein by reference) can be used. Ceramic materials that can be the source of reinforcing fibers include silicon carbide, silicon nitride, carbon, graphite, and aluminum oxide. Metal, ceramic, and glass microspheres that can be used as reinforcement include those disclosed in U.S. Patent No. 4,674,1994, the disclosure of which is incorporated herein by reference.

  In one embodiment, the reinforcement is used in an amount of about 5-60% by weight, based on the total weight of the thermoplastic blend composition. In another embodiment, the concentration of the reinforcement, expressed as a percentage by volume, is in the range of about 1 to 50% by volume. Volume% can be calculated by comparing the total cross-sectional area of the finished part to the cross-sectional area of the fiber. In another embodiment, the amount of reinforcement is less than about 40% by volume. In a third embodiment, less than 30% by volume, and in a fourth embodiment, about 5-20% by volume.

Processing Reinforced Polyester and Forming Pressurized Containers In one embodiment of the present invention using long fibers as reinforcement, the components are shaped into a predetermined shape using a pultrusion process known in the art. In the pultrusion method, a long glass fiber material is drawn through a bath containing a polyester resin and optional additives. In one example of the pultrusion method, a long glass fiber material is first impregnated with the polyester resin of the present invention (plus any optional additives). The formed laminate is drawn through a heating die controlled to precise tolerances according to the final container application specification. The resulting product is cut and processed into various parts of the container, such as side walls, tops, bottoms and the like. These parts are later welded to form the finished container.

  In yet another embodiment, a straight structure particularly useful for tall pressurized containers is described in EP-A-0 820 848, the disclosure of which is incorporated herein by reference. Use the method that you have. In this method, the molten polyester material of the present invention is supplied to a die. The die has an inlet for receiving the molten material and an outlet having a shape corresponding to a desired portion of the container of the present invention. The outlet is located downstream of the inlet and the molten polyester resin flows from the inlet to the outlet. A plurality of fiber bundles are introduced into the flow at predetermined radially separated positions to impart fiber reinforcement to the linear profile. The fiber bundle extends lengthwise at a predetermined position in the profile. The resulting product is cut and processed into various parts of the container, such as side walls, tops, bottoms, and the like.

  After forming these parts by pultrusion or extrusion and assembling the parts by welding or other methods known in the art into a finished container, the European patent specification entitled "Blast Resistant And Blast Directing Containers". The container can be further reinforced with a band of material as taught in US Pat. In one embodiment, the pressurized container includes a plurality of substantially parallel spaced apart composite strips attached to the container and reinforcing the container. Each strip is a tape or stretched film of unidirectional high strength fibers, surrounding the container one or more turns in the hoop direction.

  In another embodiment of the invention, chopped glass strands are used as reinforcement. The chopped glass strands are first compounded with a polyester resin, fed to an extruder, and the extrudate is cut into pellets. In another example, chopped glass strands and polyester resin are separately fed to a feed hopper of an extruder to produce reinforced polyester pellets. Pellets obtained by cutting the extrudate may be 1/4 inch or less in length. The dispersed glass fibers are reduced in length as a result of the shearing action on the chopped glass strands in the extruder barrel.

  The reinforced polyester resin is then pressed using conventional methods known in the art, such as extrusion blow molding, injection blow molding, profile extrusion, pipe extrusion, coextrusion, extrusion coating, foam molding, foam extrusion, thermoforming, and the like. Form into containers or parts thereof. The parts can then be welded to form a finished pressurized container.

Reinforced polyester pressurized vessel beer container pressure vessel characteristics thickness 2-4 mm, i.e. in one embodiment of the present invention for use as a beer keg, reinforced polyester pressurized container of the present invention is low CO ₂ as inherent property When filled with a liquid having an internal pressure of 1 bar or more and a dissolved carbon dioxide content of about 0.4 to 0.6% by weight, the storage temperature is about 30 to 35 ° C., and after 0.5 year the dissolved carbon dioxide It was found that the carbon content was maintained at 0.25% by weight or more and the O ₂ permeability was less than 1.0 ppm.

  With respect to creep properties, in one embodiment of the present invention, a pressurized container made from reinforced polyester has a creep <3% after 0.5 years at room temperature using an initial internal pressure of 1-5 bar.

  Regarding the impact fracture resistance, in the embodiment in which the glass long fiber is used as a reinforcing material and the pressurized container of the present invention is manufactured using a pultrusion molding technique, a large number of different designs having a thickness of 2 to 4 mm and a capacity of 15 L are used. As a result of manufacturing and testing the container, it is confirmed that the pressurized container (50% filling and 80% filling) is resistant to breakage even when dropped from a height of 0.45 to 1 m.

  For food applications, such as beer barrels or soft drinks and pressurized containers for various foods, it can be seen that the reinforced polyester containers of the present invention do not impart unacceptable levels of flavor change to the contents.

  The following examples are merely representative of the work that has contributed to the teachings of the present application.

Examples 1-4
In this example, the reinforced polyester composition comprises PBT (polybutylene terephthalate) having a molecular weight of about 80000 (expressed as PS molecular weight), 0.15% Irganox 1010 as a stabilizer, about 1% polyethylene as a mold release agent and Consists of 50% by weight of glass fibers.

  Depending on the use of either short glass fibers (SGF) or long glass fibers (LGF), these compositions are referred to as 30% SGF, 50% SGF, 30% LGF and 50% LGF. Short glass fiber is E glass chopped strand commercially available as T-120 from NEG. The glass long fiber (for example, E glass type) may include a finishing agent such as a silane-based coupling agent, a sizing agent such as a urethane-based resin or an epoxy-based resin, and a phosphite-based resin if necessary according to the intended use. It may be treated with a typical example of a heat stabilizer or other suitable surface treatment agent.

  The LGF composition is manufactured by a pultrusion process as disclosed in US Pat. No. 4,559,262, the disclosure of which is incorporated herein by reference. In the examples, a PBT polymer melt is prepared in a bath at about 260 ° C. Glass fiber filaments (in the form of glass rovings) are drawn from the molten polymer at 30 cm / min along one spreader bar placed in the bath, giving a residence time in the bath of 30 seconds. The impregnated roving is withdrawn through a 3 mm diameter die located on the bath wall and then cooled to a completely wet material. The amount of PBT in the resulting product (fiber concentration 30 or 50% by weight) is controlled by the length of the passage where the fiber bundle contacts the heated spreader surface.

  The product from continuous pultrusion is then cut to form pellets 5-10 mm in length. The LGF products used were supplied by LNP as Verton AF7006 (30% LGF) and WF70010 (50% LGF).

  In the production of an SGF blend, components other than glass fibers are first dry-blended. The blend is then kneaded in a WP 25 mm co-rotating extruder, with the glass being fed separately from downstream of the extruder. The melting temperature was about 250-260 ° C. and the number of revolutions was 300 rpm. The resulting product is extruded to form pellets.

  The SGF and LGF products are molded using an Engel 75 ton molding machine at a temperature setting (from throat to nozzle) of 240-260 ° C and a mold temperature of 60 ° C to obtain samples. Prior to molding, the pellets were dried at 120 ° C. for 2 hours.

  The properties of the short glass fiber (SGF) and long glass fiber (LGF) samples of Examples 1 to 4 are measured by the following methods.

Notched Izod (INI) and Notched Izod (UNI)
In this test method, notched or unnotched specimens were tested according to the ISO 180 method to obtain notched (INI) and unnotched (UNI) impact strength. The test results are described as absorbed energy per unit width of the test piece, and are expressed in kilojoules / square meter (kJ / m ² ). Typically, the final test result is calculated as the average of the test results of five test specimens.

Bending plate impact test In this test method, the maximum force, the maximum energy, the energy at break, and the deflection at break are measured at various speeds based on the ISO6603 method.

Example 2
In this example, the 50% LGF composition of Example 2 is used in a fiber reinforced polyester pressurized container, i.e., a beer keg, to form parts of a beer keg using a pultrusion process.

  The beer keg is filled with beer from a beer tank at a suitable internal pressure of about 2 bar and a temperature of about 20-35 ° C. The dissolved carbon dioxide content of the beer is about 0.5% by weight.

  After a storage period of about 6 months at a temperature of 20-35 ° C., the dissolved carbon dioxide content of the beer in the fiber reinforced polyester beer keg of the present invention is determined to be about 0.25% by weight or more. Also, when the beer is poured and drunk, it is also confirmed that the beer is not unreliable. Also, after consuming a portion of the beer and storing it in a beer barrel at about 20-35 ° C. for a few days, the remaining beer still contains about 0.25% by weight of dissolved carbon dioxide Is confirmed. In addition, the beer retains good taste, is not wily, and does not require any external pressure source.

  The above description is only illustrative of the present invention. Those skilled in the art will be able to use various changes and substitutions without departing from the technical scope of the invention. Therefore, the present invention covers all such substitutions, changes and modifications that fall within the scope of the appended claims.

Claims (10)

A reinforced polyester pressurized container filled with a liquid having an internal pressure of 1 bar or more and a dissolved carbon dioxide content of about 0.4 to 0.6% by weight. A pressurized container that maintains a dissolved carbon dioxide content of 0.25% by weight or more after 5 years. The pressurized container of claim 1, wherein the polyester is reinforced with a reinforcement selected from the group consisting of glass fibers, carbon fibers, metal fibers, aromatic polyamide fibers, and combinations thereof. 2. The pressurized container according to claim 1, obtained by a conventional thermoplastic processing method selected from the group consisting of injection molding, thermoforming, hot press molding, injection compression molding, blow molding, pultrusion molding, extrusion and combinations thereof. . The pressurized container of claim 1, further comprising a plurality of reinforcing strips attached to the container for reinforcing the container, each strip surrounding the container one or more times in a hoop direction. The pressurized container according to claim 1, wherein the reinforcing material is glass fiber having a length of 0.5 cm or more. The pressurized container according to claim 1, wherein the polyester is reinforced with glass fibers in an amount of at least 20% by weight based on the total weight of the reinforced polyester. The pressurized container of claim 1 wherein the polyester is reinforced with glass fibers in an amount of about 1 to 50% by volume. The pressurized container according to claim 1, wherein the wall thickness is 0.2 mm or more. The pressurized container according to claim 1, wherein the total liquid volume is 15L or more. Thickness 0.2mm or more, the carbon dioxide permeability 0.8 g / 100in ^2/24 hours / reinforced polyester pressure vessel is less than mils.