PLASTIC PRESSURE CONTAINER

Description

[0001] The invention relates to a pressure vessel made of plastic according to the preamble of claim 1.

[0002] Containers made of tinplate, colored metal, glass, or ceramic, which were common in the past, are increasingly being replaced by plastic containers. Plastic containers are now the predominant choice, especially for packaging liquids, for example, in households, agriculture, industry, and commerce. Their light weight and lower cost certainly play a significant role in this substitution. The use of recyclable plastic materials and the overall more favorable energy balance during their production also contribute to the increased acceptance of plastic containers among users.

[0003] Plastic containers made of polyethylene terephthalate (PET) and similar materials are usually manufactured using a process called stretch blow molding. In this process, a preform is first produced in an injection mold. More recently, flow molding or extrusion blow molding have also been proposed for the production of preforms. The preform has a generally elongated body and is closed at one end. This end typically also contains a gate point from the injection molding process. A neck section, equipped with a pouring opening, is attached to the other end of the preform. The neck section already has the final shape of the container neck. In many known preforms, the preform body and the neck section are separated by a support ring.The support ring projects radially from the neck wall and serves to transport the preform or the plastic container produced from it and to support the preform on the blow molding tool or the plastic container when closing it.

[0004] US 2001 / 015359 A1 discloses a pressure vessel made of plastic (PET), particularly for an aerosol can, comprising a substantially cylindrical vessel body. The vessel body has an upper valve attachment, a piston in an interior enclosed by the vessel body, and a lower base with a plug for filling with a pressure medium. The vessel body is manufactured by blow molding.

[0005] After production, the preform is demolded and can be processed immediately while still hot in a single-stage stretch blow molding process. In a two-stage stretch blow molding process, the preform is cooled and temporarily stored on a stretch blow molding machine for further processing that is spatially and / or temporally separate. Before further processing in the stretch blow molding machine, the preform is conditioned if necessary, i.e., a temperature profile is applied to it. It is then placed in a blow mold of the stretch blow molding machine. In the blow mold, the preform is finally inflated according to the mold cavity by pressurized gas, usually air, and additionally stretched axially with a mandrel.

[0006] A known injection blow molding process involves stretch blow molding directly after the preform is injected. The preform remains on the injection core, which simultaneously acts as a mandrel. The preform is then inflated by overpressure according to the mold cavity of a blow mold, which is positioned onto the injection core or vice versa, and stretched by the mandrel. The finished plastic container is then demolded. Stretch-blown or injection-blown plastic containers can be identified by the injection point, typically located near the base of the container, which originates from the preform and shows minimal or no stretching of the plastic material.

[0007] Pressure vessels for gases, liquids, pastes, or similar materials are still mostly made of metal. This is primarily because metallic pressure vessels offer high dimensional stability and can withstand higher internal pressures. Since the interior of such pressure vessels is typically divided into two chambers by a piston that is slidably mounted along a longitudinal axis of the vessel, and these chambers must remain pressure-tight, there are high demands on the roundness of the inner wall along which the piston moves. Metal pressure vessels are sufficiently dimensionally stable to guarantee this roundness. However, metal pressure vessels can be deformed in certain areas by external mechanical forces, such as an impact, which can lead to problems with the longitudinal movement of the piston.

[0008] Pressure vessels made of plastic have also been described, which, analogous to metal pressure vessels, are divided into two chambers by a piston that is longitudinally displaceable within the vessel. These pressure vessels are made, for example, of polyethylene terephthalate (PET). The bottom of the pressure vessel is cut off to accommodate the piston. A specially designed bottom section is then inserted into the cut end of the pressure vessel to create a pressure-tight seal. Such plastic pressure vessels are relatively complex to manufacture. The specially designed bottom section is a separate component, which incurs additional costs. Creating a pressure-tight connection between this separate bottom section and the cut end of the pressure vessel is also complex. Furthermore, achieving a pressure-tight separation of the two chambers within the pressure vessel is not straightforward.In many cases, it is necessary to calibrate the inner wall of the pressure vessel, along which the piston can move longitudinally, to ensure the required roundness of the pressure vessel. This additional calibration of the inner wall is a complex process and is likely the reason why such plastic pressure vessels are rarely found on the market.

[0009] The object of the present invention is therefore to overcome the disadvantages of prior art pressure vessels described above. The aim is to create a pressure vessel for gases, liquids, pasty masses, and similar materials that is simple and inexpensive to manufacture. Calibration of the inner wall of the pressure vessel should be unnecessary.

[0010] The solution to these problems consists of a plastic pressure vessel having the features specified in claim 1. Further developments and / or advantageous embodiments of the invention are the subject of the dependent claims.

[0011] The invention provides a plastic pressure vessel, particularly for an aerosol can, comprising a substantially cylindrical body. One longitudinal end of the body has an opening that can be sealed pressure-tight with a valve attachment designed for dispensing a gaseous, liquid, powdery, pasty, or similar substance. The interior of the body is divided by a piston, which is longitudinally displaceable along a longitudinal axis of the body, into a receiving chamber adjacent to the opening for the substance and a pressure-tight reservoir for a pressure medium. The reservoir is sealed pressure-tight by a bottom section. The body is designed as a hollow body produced by a blow molding process.The piston has two circumferential sealing lips spaced axially apart, with an upper sealing lip extending into the receiving chamber and a lower sealing lip extending into the reservoir. The upper and lower sealing lips are pressed against an inner wall that defines the interior of the container body, creating a fluid-tight seal, by the pressure applied in the receiving chamber and the reservoir.

[0012] The piston, located within the pressure vessel body, has an outer contour that essentially corresponds to the inner contour of the vessel body. The piston is essentially cylindrical and is supported by two axially spaced circumferential sealing lips against an inner wall of the vessel body that encloses the interior. It is understood that the vessel body may also have a cross-section that deviates from a circular shape. The essential point is that the piston, which is axially displaceable within the vessel, has an outer contour that essentially corresponds to that of the inner wall of the vessel body. Because the piston is supported against the inner wall not directly via its outer wall but via the two sealing lips, the requirements for the dimensional accuracy of the inner wall can be kept low. The sealing lips ensure a defined position of the piston relative to the vessel axis.This creates the conditions for uniform pressure of the sealing lips against the inner wall of the container body. The sealing lips are sufficiently flexible to compensate for minor dimensional inaccuracies in the inner wall of the container body. The upper and lower sealing lips are pressed against an inner wall that defines the interior of the container body by the pressure applied in the receiving chamber and the reservoir, creating a fluid-tight seal. This ensures a pressure-tight separation between the adjacent receiving chamber for the contents and the reservoir for the pressure medium.

[0013] In one embodiment of the pressure vessel, the piston has an upper boundary surface facing the opening and a lower boundary surface facing the bottom. Each of the two circumferential sealing lips is assigned to one of the upper and one to the lower boundary surfaces. The upper sealing lip extends from the upper boundary surface towards the opening and outwards towards an inner wall of the vessel body, while the lower sealing lip extends from the lower boundary surface towards the bottom and outwards towards the inner wall of the vessel body. Due to the chosen arrangement of the sealing lips, their inner surfaces are subjected to the pressures prevailing in the receiving vessel for the contents or in the reservoir for the pressure medium and are pressed evenly against the inner wall of the vessel body.Due to the elasticity of the sealing lips, this results in a flat contact with the inner wall of the container body, which increases the pressure tightness.

[0014] Another design variant of the pressure vessel provides that, in the unloaded state, the sealing lips form an angle of 45 to 80 degrees with the inner wall of the vessel body. Sealing lips designed in this way ensure a defined and centered bearing of the piston within the vessel body.

[0015] The container body is manufactured using a stretch blow molding process from a preform previously produced using an injection molding or compression molding process, which consists primarily of polyethylene terephthalate (PET). PET plastic containers possess the strengths required for pressure vessels. The stretch blow molding process achieves the necessary stretch strengthening to give the PET the required properties.

[0016] To achieve the pressure resistance of the PET pressure vessel, the vessel body is formed in the stretch blow molding process in such a way that it has an axial stretch ratio in the range of 1:1.5 to 1:15, in particular 1:4 to 1:10, compared to the preform.

[0017] In another embodiment of the pressure vessel, the vessel body is manufactured in a stretch blow molding process from a preform previously produced by an injection molding or compression molding process, such that a region of the vessel body traversed by the piston during operation exhibits a degree of crystallinity equal to or greater than 5%. The degree of crystallinity is determined by density measurements according to ASTM D 1505-10 at an intrinsic viscosity of 0.75 dl / g to 1.25 dl / g, measured according to ASTM D 4603-11. At a degree of crystallinity within the specified range, the vessel body possesses the required mechanical strength and the necessary barrier properties against air and moisture for the contents. In a further embodiment of the pressure vessel, the vessel body exhibits a degree of crystallinity of 5% to 50%, preferably 20% to 30%, in the region traversed by the piston.

[0018] For the definition of the crystallinity grades mentioned above, the density is determined according to the measurement method described in the standard ASTM D 1505-10. This measurement method allows for density determination with an accuracy of 0.001 g and less. The measured density allows conclusions to be drawn about the orientation, crystallinity, and strength of the constrictions. However, amorphous PET can achieve different density values ​​depending on the added copolymers and / or additives. Values ​​between 1.320 g / cm³ and 1.339 g / cm³ are known.

[0019] In order to use the measurement method described in ASTM D 1505-10 despite the copolymers and / or additives added to the amorphous PET, this invention defines an average density of the container body, measured below the longitudinal end of the container body where the valve insert is mounted, as a first reference value. Preferably, the density is determined at at least three different measurement points along the circumference of the container body, and the average density is calculated. Regardless of any actual crystallization that may be present, this invention defines that no crystallization is present at the measurement position(s) where the first reference value was determined, i.e., the degree of crystallinity is 0%.Furthermore, in accordance with this invention, a second reference value is defined which is 0.120 g / cm³ greater than the first determined reference value. By definition, this second reference value corresponds to a degree of crystallinity of 100%. The degrees of crystallinity lying between the two reference values ​​are directly proportional to the determined density values.

[0020] For example, an average density of 1.330 g / cm³ is determined as the first reference value. According to the definition above, this average density corresponds to a degree of crystallinity of 0%. By definition, a degree of crystallinity of 100% is found at a density of 1.450 g / cm³, which represents the second reference value. Due to the direct proportionality between the density values ​​and the degrees of crystallinity, the degree of crystallinity is then 25% at a density of 1.360 g / cm³, 50% at a density of 1.390 g / cm³, and 75% at a density of 1.420 g / cm³.

[0021] In another version of the pressure vessel, the vessel body is made of uncolored plastic. By omitting the addition of a dye, a crystal-clear vessel body is achieved, for example, in the case of PET. This further improves the recyclability of the pressure vessel.

[0022] To increase the shelf life of the filled pressure vessel, the piston features a barrier layer that prevents the passage of the pressure medium from the reservoir to the receiving chamber. When using compressed air as the pressure medium, and when dealing with contents that can degrade upon contact with air, such as ketchup, various condiments and pastes, etc., this barrier layer prevents oxygen from passing through the piston. The barrier layer is composed of a layer from the group consisting of EVOH layers, EVAL layers, polyamide-based layers, lacquer coatings, silicon dioxide coatings, aluminum oxide coatings, silicone coatings, and combinations thereof.

[0023] The barrier layer can be applied to the piston by sputtering. In an alternative design of the pressure vessel, it can have a piston manufactured using an injection molding or compression molding process, with the barrier layer applied during the piston's production, for example, in a two-component injection molding process. Using the so-called co-injection process, the barrier layer can also be simultaneously injected into the core of the flow channel in a single injection process. In this case, the barrier layer is incorporated into or embedded within the plastic material of the piston.

[0024] The recyclability of the pressure vessel can be increased by making the piston primarily (90% or more) the same plastic as the vessel body. In a further embodiment of the invention, the upper and / or lower sealing lip consists of a reversibly elastic material, such as silicone, rubber, EPDM, or FKM. The reversible elasticity of the sealing lip(s) facilitates the compensation of irregularities in the inner wall of the vessel body, eliminating the need for calibration. Due to the elasticity of the sealing lips, their free end areas, which rest against the inner wall, are forced into full contact with the inner wall of the vessel body by the pressure of the pressure medium or the contents, thus increasing the pressure tightness.

[0025] In another embodiment of the pressure vessel, the recyclability of the pressure vessel can be further improved by assembling the valve attachment from components that consist primarily (90% or more) of the same plastic as the vessel body. Moreover, the similarity of the material pairings between the vessel body and the valve attachment facilitates the creation of a pressure-tight connection between the two components.

[0026] In one design variant of the pressure vessel, the bottom section is formed from a previously separated section of the vessel body. This section is inserted into a cut end of the vessel body opposite the opening in such a way that the base of the bottom section is closer to the piston than the cut end of the vessel body. By using the separated bottom section as the bottom section, the need to manufacture a separate bottom section is eliminated. The separated bottom section and the vessel body are made of the same plastic material. Therefore, material-related incompatibilities, such as those arising from the bottom section being made of a different plastic than the vessel body, which could lead to difficulties in creating a pressure-tight connection between the bottom section and the cut end of the vessel body, are also eliminated.The dimensional accuracy of the bottom section is also not a problem, as the cut-off bottom section has the same diameter at the cut edge as the container body. The bottom section is typically cut at a point along the longitudinal axis of the container body where the outer diameter decreases. This allows the bottom section to be easily inserted into the cut end of the container body in reverse orientation, with the bottom facing forward. Correct axial positioning is automatically ensured by the identical outer diameter at the cut edges of the container body and the bottom section.

[0027] The bottom part can also be manufactured as a separate component using an injection molding process. Advantageously, the bottom part is made of a plastic compatible with the plastic material of the container body. One embodiment of the invention provides that the bottom part consists primarily, i.e., 90% or more, of the same plastic as the container body. This facilitates a pressure-tight connection between the container body and the bottom part.

[0028] One variant of the pressure vessel according to the invention provides that the pressure-tight connection between the vessel body and the base is created by a welding process. Various plastic welding processes are known from the prior art. For example, a so-called clear-to-clear laser welding process has been described for PET plastic containers, which can lead to sufficiently strong, material-bonded connections.

[0029] An alternative embodiment of the invention provides that the pressure-tight connection between the bottom part and the cut end of the container body is created using a friction welding process or an ultrasonic welding process. Due to the similar material pairing of the joining partners, local melting of the joining partners in the joining area is sufficient to create a material-bonded connection that exhibits the required pressure resistance.

[0030] Finally, in a further embodiment of the invention, the base part and the container body can also be pressure-tightly connected by gluing.

[0031] To ensure the pressure vessel body possesses the required inherent rigidity and pressure resistance, the wall thickness in the area traversed by the piston during operation is at least 0.35 mm to 0.95 mm. These wall thicknesses guarantee sufficient inherent rigidity even under adverse storage conditions. Furthermore, the amount of plastic material required to achieve these wall thicknesses does not negatively impact the cost-effectiveness of manufacturing the pressure vessel.

[0032] One design variant of the pressure vessel provides that the opening is sealed pressure-tight with the valve attachment, the receiving chamber of the vessel body is filled with a gaseous, liquid, powdery, pasty or similar material, and the reservoir for the pressure medium contains a non-flammable gas or gas mixture, such as in particular air, nitrogen, carbon dioxide or a noble gas, which is kept under a pressure of 1.5 bar to 10 bar.

[0033] Further advantages and features will become apparent from the following description of an embodiment of the invention with reference to the schematic drawings. These show, in a schematic representation not to scale: Fig. 1 an axially sectional view of a first embodiment of a pressure vessel; Fig. 2 an axially sectional view of a piston; Fig. 3 a sequence of axially sectional views a - h to illustrate the manufacture of the embodiment of the pressure vessel according to the invention. Fig. 1 ; and Fig. 4 a second embodiment of the pressure vessel in axial section.

[0034] For the sake of better understanding of the invention, the illustrations Fig. 1 bis Fig. 4 Identical components and parts are each given the same reference numerals.

[0035] A in Fig. 1 The first embodiment of a pressure vessel according to the invention, shown in axial section, bears the reference numeral 1. The pressure vessel has a vessel body 2, the interior of which, enclosed by the vessel body 2, is divided by an inserted, axially displaceable piston 10 into a receiving chamber 4 for a gaseous, liquid, powdery, pasty, or similar filling material and into a pressure-tight reservoir 5 for a pressure medium. The reservoir 5 is pressure-tightly sealed by a bottom part 6. A plug 7 is inserted approximately centrally in the bottom part 6, which can be pierced by a needle or the like for filling the reservoir 5 with the pressure medium. For example, this is a rubber plug with a septum or the like.At the longitudinal end furthest from the bottom section 6, the container body 2 has an opening 8 which can be pressure-tightly sealed with a valve attachment designed for dispensing a gaseous, liquid, powdery, pasty, or similar substance. This occurs after the receiving chamber 4 has been filled with the substance. For the sake of clarity and because it is not essential to the invention, a representation of the valve insert has been omitted.

[0036] The container body 2 is manufactured using a stretch blow molding process. Furthermore, the container body 2 is produced from a previously injection-molded or extruded preform.

[0037] Stretch blow-molded container bodies consist mainly, i.e., 90% or more, of PET plastic.

[0038] The plastic used for the container body can be colored or uncolored. For example, by omitting the addition of a dye, a crystal-clear container body is achieved in the case of PET. This can further improve the recyclability of the pressure vessel.

[0039] In the case of container bodies 2, which are made from a PET preform, the container body is formed in the stretch blow molding process such that it has an axial stretch ratio in the range of 1:1.5 to 1:15, in particular from 1:4 to 1:10, compared to the preform.

[0040] A region of the container body 2 traversed by the axially displaceable piston 10 during operation exhibits a degree of crystallinity equal to or greater than 5%, the degree of crystallinity being determined by density measurements according to ASTM D 1505-10 at an intrinsic viscosity of 0.75 dl / g to 1.25 dl / g, measured according to ASTM D 4603-11. Advantageously, the container body 2 in the region traversed by the piston 10 exhibits a degree of crystallinity of approximately 5% to approximately 50%, preferably approximately 20% to approximately 30%.

[0041] For the definition of the crystallinity grades mentioned above, the density is determined according to the measurement method described in the standard ASTM D 1505-10. This measurement method allows for density determination with an accuracy of 0.001 g and less. The measured density allows conclusions to be drawn about the orientation, crystallinity, and strength. However, amorphous PET can achieve different density values ​​depending on the added copolymers and / or additives. Values ​​between 1.320 g / cm³ and 1.339 g / cm³ are known.

[0042] In order to use the measurement method described in ASTM D 1505-10 despite the copolymers and / or additives added to the amorphous PET, this invention defines an average density of the container body 2, determined below the opening 8 of the container body, as a first reference value. Preferably, the density is determined at at least three different measuring points along a circumference of the container body 2, and the average density is calculated. Regardless of any actual crystallization that may be present, this invention defines that no crystallization is present at the measuring position(s) where the first reference value was determined, i.e., the degree of crystallization is 0%. Furthermore, this invention defines a second reference value that is 0.120 g / cm³ greater than the first determined reference value.This second reference value corresponds, by definition, to a degree of crystallinity of 100%. The degrees of crystallinity lying between the two reference values ​​are directly proportional to the determined density values.

[0043] For example, an average density of 1.330 g / cm³ is determined as the first reference value. According to the definition above, this average density corresponds to a degree of crystallinity of 0%. By definition, a degree of crystallinity of 100% is found at a density of 1.450 g / cm³, which represents the second reference value. Due to the direct proportionality between the density values ​​and the degrees of crystallinity, the degree of crystallinity is then 25% at a density of 1.360 g / cm³, 50% at a density of 1.390 g / cm³, and 75% at a density of 1.420 g / cm³.

[0044] In order for the vessel body 2 of the pressure vessel 1 to have the required inherent rigidity and pressure resistance, the vessel body 2 has a wall thickness of at least 0.35 mm to 0.95 mm in the area traversed by the piston 10 during operation.

[0045] The in Fig. 1 The valve attachment (not shown) or its components are expediently made of the same plastic or plastic mixture as the container body 2.

[0046] The piston 10 is axially displaceable within the interior of the container body 2. It has an upper boundary surface 11 facing the opening 8 of the container body 2 and a lower boundary surface 12 facing the bottom part 6. For pressure-tight separation of the receiving chamber 4 from the reservoir 5, the piston 10 has two axially spaced circumferential sealing lips 13, 14, which bear against an inner wall 3 of the container body 2. One of the two circumferential sealing lips 13, 14 is assigned to the upper boundary surface 11 and the other to the lower boundary surface 12 of the piston 10. The upper sealing lip 13 extends from the upper boundary surface 11 towards the opening 8 of the container body 2 and outwards towards the inner wall 3 of the container body 2. The lower sealing lip 14 extends from the lower boundary surface 12 towards the bottom part 6 and outwards and towards the inner wall 3 of the container body 2.The upper sealing lip 13 extends into the receiving chamber 4, while the lower sealing lip 14 extends into the reservoir 5. When the receiving chamber 4 is filled with the material and the reservoir 5 is filled with the pressure medium, the upper 13 and the lower sealing lip 14 can be pressed against the inner wall 3 of the container body, creating a fluid-tight seal, by the applied pressure.

[0047] The piston 10 consists primarily, i.e., 90% or more, of the same plastic as the container body 2. The upper 13 and / or the lower sealing lip 14 are advantageously made of a reversibly elastic material, such as silicone, rubber, EPDM, or FKM. The reversible elasticity of the sealing lip(s) 13, 14 facilitates the compensation of irregularities in the inner wall 3 of the container body 2, which consequently does not require calibration. Due to the elasticity of the sealing lips 13, 14, their free end areas in contact with the inner wall 3 are forced into full contact with the inner wall 3 of the container body 2 by the pressure of the pressure medium or the contents, thus increasing the pressure tightness.

[0048] Fig. 2 shows an axially cut view of the piston 10. The piston 10 has a bearing in the inserted state in the direction of the opening 8 of the container body 2 ( Fig. 1 The piston 10 has a convex, dome-like outer contour. This convex outer contour improves the even distribution of the pressure medium on the piston 10. As shown, the piston 10 can be equipped with a recess 16 located approximately in the center. When the piston 10 is inserted into the container body 2, this recess serves to receive a projection that typically extends from the valve attachment mounted at the opening 8 of the container body 2. This allows the piston 10 to be positioned closer to the valve attachment in order to empty the contents of the receiving chamber 4 as completely as possible. The convex outer contour of the piston 10 also supports this by conforming to the shape of the container body 2 near the opening 8. The axially spaced sealing lips 13, 14, in the unloaded state, each form an angle α or β of approximately 45 degrees to approximately 80 degrees with the inner wall 3 of the container body 2. The angles α and ββ can be different from each other.

[0049] Piston 10, as shown in Fig. 2 As indicated, a barrier layer 15 is formed, which prevents the passage of the pressure medium from the reservoir to the receiving chamber. When using compressed air as the pressure medium and with filling materials that can degrade upon contact with air, e.g., ketchup, various condiments and pastes, etc., this barrier layer prevents oxygen from passing through the piston 10. The barrier layer 15 is an EVOH layer, an EVAL layer, a polyamide-based layer, a lacquer coating, a silicon oxide coating, an aluminum oxide coating, a silicone coating, or a combination of the aforementioned coatings.

[0050] The barrier layer 15 can be applied to the piston 10 by sputtering. Alternatively, the piston 10 can also be manufactured using an injection molding or flow molding process, and the barrier layer 15 can be applied during the manufacturing of the piston 10, for example in a two-component injection molding process.

[0051] It is understood that the container body 2 can also be provided with an additional barrier layer. This corresponds to the barrier layers mentioned in connection with the piston 10. The barrier layer of the container body 2 can be applied during the production of the preform from which the container body 2 is subsequently blown, or only afterwards to an outer wall or to the inner wall 3 of the container body 2. This can be done, for example, by coating or sputtering. In the case of multi-layered preforms, the barrier layer can also be formed by one of the layers. In the case of a container body 2 produced by extrusion blow molding, the barrier layer can be co-extruded or only applied to its outer wall or inner wall 3 after its production.A coating applied to the inner wall 3 can also have a friction-reducing function with respect to the axially displaceable piston 10.

[0052] Fig. 3 The axially sectioned views a - h show the manufacture of a pressure vessel 1 according to Fig. 1 View a shows the container body 2, which can be stretch-blown, injection-blown, or extrusion-blown. View b indicates that the bottom section 6 is separated from the rest of the container body 2, in particular, cut off. View c shows the piston 10 with its convex outer contour, which, according to view d, is inserted through the cut end 9 of the container body 2 such that the convexly projecting dome of the piston 10 faces the opening 8 of the container body 2. The inserted piston 10 is axially displaceable and separates the interior of the container body into the receiving chamber 4 and the reservoir 5. Views e and f indicate that a plug 7 is inserted approximately centrally into the cut-off bottom section 6, which can be pierced by a needle or the like to fill the reservoir 5 with the pressure medium.View g shows that the previously separated bottom section 6 is inserted into the cut end 9 of the container body 2 such that a container bottom 61 of the bottom section 6 is closer to the piston 10 than the cut end 9 of the container body 2. View h finally shows the container body 2, whose reservoir 5 is pressure-tightly sealed by means of the inserted bottom section 6. The pressure-tight connection between the container body 2 and the bottom section 6 is created, for example, by a welding process. Various plastic welding processes are known from the prior art. For example, a so-called clear-to-clear laser welding process has been described for PET plastic containers, which can lead to sufficiently strong, material-bonded connections. Alternatively, the pressure-tight connection between the bottom section 6 and the cut end of the container body 2 can be created by a friction welding process or an ultrasonic welding process.Due to the similar material pairing of the joining partners, local melting of the joining partners in the joining area is sufficient to create a material-bonded connection that exhibits the required pressure resistance. Finally, the base part 6 and the container body 2 can also be pressure-tightly joined by bonding.

[0053] Fig. 4 Figure 1 shows a second embodiment of a pressure vessel 1 according to the invention in axial section. The pressure vessel 1 essentially corresponds to the embodiment shown in Figure 1. Fig. 1 Therefore, identical or corresponding parts and components are also designated with the same reference numerals. The pressure vessel 1, in turn, has a vessel body 2, the interior of which, enclosed by the vessel body 2, is divided by an inserted, axially displaceable piston 10 into a receiving chamber 4 for a gaseous, liquid, powdery, pasty, or similar material and into a pressure-tight reservoir 5 for a pressure medium, separated from it. The reservoir 5 is pressure-tightly sealed by a bottom part 6. At the longitudinal end opposite the bottom part 6, the vessel body 2 has an opening 8, which can be pressure-tightly sealed with a valve attachment designed for dispensing a gaseous, liquid, powdery, pasty, or similar material. This occurs after the receiving chamber 4 has been filled with the material.For the sake of clarity and because it is not essential to the invention, a representation of the valve insert has been omitted.

[0054] Unlike the in Fig. 1 In the illustrated embodiment, the bottom part 6 is not a section cut off from the stretch-blown, injection-blown, or extrusion-blown container body 2, but rather a separate component manufactured, for example, by an injection molding process. Advantageously, a plastic compatible with the plastic material of the container body 2 is used for the bottom part 6. For example, the bottom part 6 consists primarily, i.e., 90% or more, of the same plastic as the container body 2. This facilitates a pressure-tight connection between the container body 2 and the bottom part 6. For this purpose, a section of the bottom is again cut off from the container body 2, as shown, for example, in view b in Fig. 3As indicated, after the piston 10 is inserted through the cut end into the container body 2, the container body 2 and the separate bottom part 6 are again pressure-tightly connected. The pressure-tight connection between the cut end of the container body 2 and the separate bottom part 6 can be created, for example, by welding. Alternatively, the pressure-tight connection between the bottom part and the cut end of the container body can also be created by friction welding or ultrasonic welding. Finally, the separate bottom part 6 and the cut end of the container body 2 can also be pressure-tightly connected by bonding.

[0055] The invention has been described using specific embodiments as examples. However, the foregoing description serves only to illustrate the invention and is not to be considered limiting. Rather, the invention is defined by the patent claims.

Claims

1. A pressure container of plastic, in particular for an aerosol can, comprising an essentially cylindrical container body (2) whose one longitudinal end comprises an opening (8) which is closable in a pressure-tight manner by a valve attachment which is designed for dispensing a gaseous, liquid, powder-like, pasty or similar filling product, and whose interior which is encompassed by the container body, by way of a plunger (10) which is arranged in a longitudinally displaceable manner along a longitudinal axis of the container body (2), is subdivided into a receiving chamber (4) which is adjacent to the opening (8), for the filling product and into a reservoir (5) which is separated from this in a pressure tight manner and wherein the reservoir (5) is closed in a pressure-tight manner by a base part (6), for a pressure medium, wherein a plug 7 for filling the reservoir 5 with the pressure medium is a roughly centrically inserted in the base part 6 and wherein the container body (2) is a hollow body which is manufactured in a blow moulding method and that the plunger (10) comprises two circumferential sealing lips (14, 14) which are distanced from one another in the axial direction, wherein an upper sealing lip (13) extends into the receiving chamber (4) and a lower sealing lip (14) extends into the reservoir (5), wherein the upper and the lower sealing lip (13, 14) can be pressed or are pressed in a fluid-tight manner onto an inner wall (3) which delimits the interior of the container body (2), by way of a pressure which prevails in the receiving chamber (4) and in the reservoir (5), wherein the container body (2) is manufactured in a stretch blow moulding method from a preform which has been previously manufactured in an injection moulding method or compression moulding method, and which consists essentially of polyethylene terephthalate, wherein the plunger (10) comprises a barrier layer (15) which prevents a passage of the pressure medium, in particular a passage of oxygen, from the reservoir (5) to the receiving chamber (4)and in that the barrier layer (15) is designed as a layer from the group consisting of EVOH layer, EVAL layer, a layer based on polyamide, lacquer coating, silicon oxide coating, aluminium oxide coating, coating from silicones and combinations of the mentioned coatings.

2. A pressure container according to claim 1, characterised in that the plunger (10) comprises an upper delimitation surface (11) which faces the opening (8), and a lower delimitation surface (12) which faces the base part (6) and that one of the two circumferential sealing lips (13, 14) is assigned to the upper (11) and one to the lower delimitation surface (12), wherein the upper sealing lip (13) extends from the upper delimitation surface (11) in the direction of the opening (8) and to the outside in the direction of the inner wall (3) of the container body (2), and the lower sealing lip (14) extends from the lower delimitation surface (12) in the direction of the base part (6) and to the outside and in the direction of the inner wall (3) of the container body (2).

3. A pressure container according to claim 2, characterised in that the sealing lips (13, 14) in the non-loaded state form an angle (α, β) of 45 degrees to 80 degrees with the inner wall (3) of the container body (2).

4. A pressure container according to one of the preceding claims, characterised in that the container body (2) has an axial stretching ratio in the range of 1:1.5 to 1:15, in particular from 1:4 to 1:10 with respect to the preform.

5. A pressure container according to one of the preceding claims, characterised in that the container body (2) in the region over which the plunger (10) travels on use has a degree of crystallisation which is equal to or larger than 5%, wherein the degree of crystallisation is determined via density measurements according to the standard ASTM D 1505-10 given an intrinsic viscosity of 0.75 dl / g to 1.25 dl / g which is measured according to ASTM D 4603-11.

6. A pressure container according to claim 5, characterised in that the container body (2) has a degree of crystallisation of 5% to 50%, preferably 20% to 30% in the region over which the plunger (10) travels.

7. A pressure container according to one of the preceding claims , characterised in that the plastic is present uncoloured.

8. A pressure container according to one of the preceding claims , characterised in that barrier layer (15) is deposited by sputtering.

9. A pressure container according to one of the preceding claims, characterised in that the plunger (10) is manufactured in an injection moulding method or in a compression moulding method, and the barrier layer (15) is deposited or introduced during the manufacture of the plunger (10).

10. A pressure container according to one of the preceding claims, characterised in that the plunger (10) for the most part, thus at 90% or more comprises the same plastic as the container body (2).

11. A pressure container according to one of the preceding claims, characterised in that the upper and / or the lower sealing lip (13, 14) consists of a reversibly elastic material, such as e.g. silicone, rubber, EPDM, FKM.

12. A pressure container according to one of the preceding claims, characterised in that the valve attachment which can be placed upon the opening (8) is composed of components which for the most part, thus at 90% and more comprise the same plastic as the container body (2).

13. A pressure container according to one of the preceding claims, characterised in that the base part (6) is formed by a base section which has previously been separated from the container body (2) and which is inserted into a cut end (9) of the container body (2) which lies opposite the opening (8), in a manner such that a container base (6) of the base section lies closer to the plunger (10) than the cut end (9) of the container body (2).

14. A pressure container according to one of the claims 1 to 12, characterised in that the base part (6) is manufactured in an injection moulding method.

15. A pressure container according to claim 14, characterised in that the base part (6) for the most part, thus at 90% and more consists of the same plastic as the container body (2).

16. A pressure container according to one of the preceding claims, characterised in that the container body (2) has a wall thickness of 0.35 mm to 0.95 mm at least in the region over which the plunger (10) travels on application.

17. A pressure container according to one of the preceding claims, characterised in that the base part (6) and the container body (2) are connected to one another in a pressure-tight manner in a welding method.

18. A pressure container according to claim 17, characterised in that the welding method is a friction welding method or an ultrasonic welding method.

19. A pressure container according to one of the claims 1 to 16, characterised in that the base part (6) and the container body (2) are connected to one another in a pressure-tight manner by way of bonding.

20. A pressure container according to one of the preceding claims, characterised in that the opening (8) is closed in a pressure-tight manner by the valve attachment, and the receiving chamber (4) of the container body (2) is filled with a gaseous, liquid, powder-like, pasty or similar filling material, and the reservoir (5) for the pressure medium contains a non-combustible gas or gas mixture such as in particular air, nitrogen, carbon dioxide or an inert gas which is held at a pressure of 1.5 to 10 bar.