Valves and Packages

Abstract

According to one aspect of the present invention, a pressure relief valve is provided, the valve comprising a body (1) adapted to be fastened to a flexible packaging material. The body has at least one through hole (14) forming a passageway through the body. A valve membrane (2) contacts the body on the packaging side in an area around the hole (14) and has a sealing liquid between the body (1) and the valve membrane (2). The valve comprises a water-soluble polymer, meaning that at least one component of the valve, e.g. the body (1), is made from a polymer composition comprising a water-soluble polymer.

Description

[Technical field]

[0001] The present invention is in the field of pressure relief valves for food packages. Certain foods, such as freshly roasted coffee beans or coffee powder, tend to degas for a while. Therefore, some food packages, such as coffee pouches, have a pressure relief valve. The pressure relief valve allows gases generated inside the package, such as carbon dioxide, to escape while preventing ambient air from entering the package, so that oxygen does not enter the package and freshness is maintained.

[0002] The pressure relief valve usually has a cup-shaped body, and the peripheral wall of the body among the edges is welded or glued to the inside of the packaging material. The bottom of the body and the package each have an opening. At the bottom of the body there is a disk as a valve membrane, and between the bottom and the disk there is oil, for example silicone oil. When there is overpressure in the package, the gas communicating through the opening of the bottom lifts the disk, so that the gas can escape to the inside of the body and from there to the outside of the package through the opening of the package. When there is no overpressure in the package, the disk abutting the bottom of the body ensures a leak-proof seal.

[0003] This type of pressure relief valve is beneficial in that it allows fresh food products to be directly packaged and delivered to the end customer without the need for intermediate repackaging. In addition to ensuring freshness for the customer, this also has benefits from an ecological perspective. However, pressure relief valves increase the environmental footprint of the package.

[0004] It would be desirable to have further approaches to improve the eco-balance of packaging of fresh roasted coffee and other roasted products that generate gases after the roasting process.

[0005] According to one aspect of the present invention, a pressure relief valve is provided, the valve comprising a body equipped to be fastened to a flexible packaging material, the body having at least one through hole forming a passage through the body, a valve membrane contacting the body on the packaging side in the area around the hole, and a sealing liquid between the body and the valve membrane. The valve comprises a water-soluble polymer, which means that at least one component of the valve (e.g., the body or an additional component such as a fixing part or a permeable membrane as described below) is made from a polymer composition comprising a water-soluble polymer.

[0006] A polymer in the context of this specification is considered to be water-soluble if it dissolves in water at a temperature where water is liquid at atmospheric pressure. In embodiments, the water-soluble polymeric material is water-soluble at room temperature, but in other embodiments may be soluble only at elevated temperatures (and thus only hot water-soluble), for example at 60°C.

[0007] The body itself is dimensionally stable. It is equipped to be fastened to a flexible packaging material by being cup-shaped and having a bottom and a peripheral wall surrounding the bottom, the annular end face of the peripheral wall being attachable to the packaging material. The bottom then comprises at least one through hole forming a passage through the bottom for gas generated in the package. The valve membrane is arranged on the package side of the bottom (in the cup constituted by the body) and covers the at least one through hole. The side of the bottom opposite the package side is referred to herein as the "product side".

[0008] In an embodiment, when the package contains a particulate product such as coffee powder (ground coffee), the valve further comprises a permeable membrane attached to the bottom product side, which is permeable to gas while covering at least one through hole so that the product does not clog the through opening. The permeable membrane may be a fabric membrane. In this specification, "fabric" is used to cover all kinds of flexible materials from interlocked fibers or yarns or threads, including nonwovens, woven or knitted fabrics or other textile structures.

[0009] In an embodiment, the valve further comprises a fixing part. The fixing part is shaped to rest on the package side of the valve membrane. This prevents the valve membrane from falling off from the body even in situations where the valve is subjected to significant mechanical shock. If the valve is provided as a bulk material, it may be subjected to such shock especially during the transportation and assembly process. In situations of mechanical shock, the fixing part holds the valve membrane in place even if the adhesion by the sealing liquid is not sufficient. The fixing part may be held against the body by a peripheral wall of the body forming an undercut, so that the fixing part can click into the body.

[0010] The water solubility of the polymer has advantages in recycling processes, whether that be composting processes or even paper recycling processes.

[0011] The water-soluble polymer may be biodegradable, although this is not necessarily true for all water-soluble polymers. In addition to being water-soluble, the water-soluble polymer of the valve may be biodegradable.

[0012] In this specification, "biodegradable" may mean biologically degradable according to European standard EN 13432 (as of the end of 2021). Additionally or alternatively, it may mean biologically degradable according to European standard EN 14995 (as of the end of 2021). Thus, "biodegradable" refers in particular to "biodegradable according to EN 13432 and / or EN 14995".

[0013] Insofar as water-soluble polymers are mentioned in this specification, such water-soluble polymers may optionally be degradable in sewage treatment plants (aerobic biodegradable) as determined according to the so-called Zahn-Wellens test in accordance with DIN EN ISO9888 (as of the end of 2021).

[0014] In an embodiment, all components of the valve, ie the body, the valve membrane, and, if present, the permeable membrane and / or the anchoring portion, respectively, are biodegradable materials.

[0015] In an embodiment, the valve contains a water-soluble polymer, for example as material of the body and / or of the fastener and / or permeable membrane, if applicable, but the valve membrane is not water-soluble.

[0016] In an embodiment, at least one of the components is made from a polymer composition that belongs to a first category of polymer compositions. The first category of polymer compositions are water soluble.

[0017] In one group of embodiments, the first category of polymer compositions includes a salt in addition to including a water-soluble polymer.

[0018] The salt may be present in an amount of at least 1%, or at least 2%, or at least 3%, or at least 10%, or at least 15%, or even at least 20%, or at least 25%, with maximum amounts being 55% or 40% or 35%. In this specification, all percentages refer to weight % unless otherwise stated.

[0019] The salt may be a hygroscopic salt. Salts may include alkali metal salts, alkaline earth metal salts, or aluminum salts and / or mixtures thereof. Specific examples include NaCl, Na citrate and their respective potassium analogs, magnesium chloride and / or mixtures thereof.

[0020] On the other hand, salts may act as lubricants for the polymers in the first category of polymer compositions. The addition of salts to the polymers can increase the melt flow index (MFI), thus improving the hot melt processability of the polymer composition.

[0021] Thus, the body and / or, if applicable, the fastening part, if made from a polymer composition of the first category containing salt, may be manufactured by injection molding or other molding techniques, the same may also apply if they are made from a different polymer composition, in particular a polymer composition of the first category but not containing salt.

[0022] Moreover, salt has been found to improve solubility, disintegration, and biodegradation rate, for example for composting. The addition of salt can make the polymer home compostable, whereas without salt it can only be industrially compostable, but not home compostable per se. Thus, the salt content can be used to adjust the properties of the polymer composition depending on the intended use and the intended recycling process.

[0023] In particular, regardless of whether the first category of polymer compositions includes a salt, the water-soluble polymer of the first category of polymer compositions may include at least one of poly(vinyl alcohol) (PVOH), a cellulose ether polymer, a butenediol-vinyl-alcohol-copolymer (BVOH), a polyvinyl butyral (PVB), and an ethylene-vinyl-alcohol-copolymer (EVOH).

[0024] The first category of polymer compositions may include water-soluble polymers that are, inter alia, vinyl alcohol polymers or copolymers, or mixtures or blends of two or more vinyl alcohol copolymers. That is, the water-soluble polymers may be polymers that have multiple vinyl alcohol [CH2CH(OH)] groups in the polymer chain. These polymers include the mentioned PVOH, BVOH, and EVOH, as well as others.

[0025] When the water-soluble polymer comprises a mixture or blend of two or more vinyl alcohol copolymers, the copolymers can differ in molar mass, molecular structure, such as branching, type and amount of comonomer, or other variable parameters.

[0026] Thus, the polymer of the first category of polymer compositions may be vinyl alcohol, particularly including vinyl alcohol-rich copolymers or vinyl alcohol homopolymers. The polymer may, in embodiments, comprise more than 75%, particularly more than 90%, of the monomer units having OH units.

[0027] The water-soluble polymers may contain additional polar comonomers, examples of which include maleic acid and maleic anhydride, fumaric acid and itaconic acid.

[0028] The water-soluble polymer, especially polyvinyl alcohol (PVOH), can have a degree of hydrolysis of 70% to 99.9%. The degree of saponification can be related to the performance for oxygen barrier. In particular, the degree of hydrolysis can be at least 90%, or at least 94%, or even at least 96%. Higher saponification can be related to higher oxygen barrier performance.

[0029] The first category of polymer compositions can include at least one of the following: poly(vinyl alcohols), obtained, for example, by saponification of poly(vinyl ester) homopolymers or copolymers, -ethylene-vinyl alcohol-copolymer (EVOH), -Butenediol-vinyl alcohol-copolymer (BVOH).

[0030] The first category of polymer compositions in embodiments have a maximum water content of 10%. In particular salt-containing embodiments, the water content may be, for example, 5% or less, particularly 1% or less or 0.5% or less.

[0031] The polymer composition of the first category may further include a plasticizer (liquid or solid) to reduce the melting temperature, which is particularly beneficial for molding. The plasticizer may be hygroscopic in embodiments. The plasticizer may be selected from the group consisting of polyols (oligo- and polyhydroxy compounds) and low molecular weight amides, particularly triols, diols, polytriols, polydiols, such as glycerin, ethylene glycol, propylene glycol, triethylene glycol, low molecular weight polyethylene glycols, and low molecular weight amides. In embodiments, the plasticizer may be selected from the group consisting of dipropylene glycol, higher oligomers of ethylene glycol or propylene glycol, butylene glycol, glycerol, pentaerythritol, sorbitol, 1,4-monoanhydrohexitol, 1,4-3,6-dianhydrohexitol, and esters thereof. The preferred plasticizers are glycerin and polypropylene glycol.

[0032] The plasticizer may be present in an amount of from 2% to 25%, in particular from 5% to 18%, for example from 10% to 15%.

[0033] The polymer composition of the first category of embodiments may particularly include more salt than plasticizer, more particularly, the ratio of salt to plasticizer may be from 1.5:1 to 6:1.

[0034] It is not excluded that the polymer compositions of the first category, in addition to comprising a water-soluble polymer, optionally a salt and optionally a plasticizer, comprise further components, such as heat stabilizers (e.g. metal stearates such as sodium stearate) at a concentration of, for example, up to 1%, in particular up to 0.5%, and / or inorganic and / or organic fillers, for example celluloses or fillers as described in WO 2021 / 224424, and / or other components that affect the properties of the composition or its components.

[0035] Examples of suitable polymer compositions of the first category can be found, for example, in WO 2014 / 155059.

[0036] As an alternative to compositions such as those described in WO 2014 / 155059, the polymer compositions of the first category may comprise, in addition to the polymer ("resin", e.g. poly(vinyl alcohol), ethylene-vinyl alcohol-copolymer (EVOH) or butenediol-vinyl alcohol-copolymer (BVOH) and the plasticizer (not necessarily a salt), additives, in particular saturated fatty acids, binders and / or antioxidants. These additives have proven beneficial in terms of the properties of the polymer compositions of the first category, in particular their suitability for molding processes and biodegradation.

[0037] Further components of the first category of polymer compositions may include water (e.g. 1% to 10%, in particular 2% to 6%, and additives including fatty acids between 0% or 1% and 5% or 3%, binders (e.g. between 0% or 1% and 5% or 3%), and or antioxidants (e.g. in an amount of less than 0.5%, in particular 0.1% to 0.3%).

[0038] Another example of a suitable polymer composition in the first category comprises 70% to 85% polyvinyl alcohol (e.g., 98% hydrolyzed), 10% to 15% glycerol as a plasticizer, 2% to 6% water, and 1% to 3% additive in the form of saturated fatty acids, 1% to 3% binder, and 0.1% to 0.3% antioxidant.

[0039] In addition to or as an alternative to comprising one or more polymer compositions of the first category, the valve may comprise a component of a polymer composition of the second category. As with the polymer compositions of the first category, the polymer compositions of the second category may also be biodegradable according to the definition used herein. However, the polymer compositions of the second category are not water-soluble, and in embodiments, they do not comprise salts.

[0040] Examples of polymer compositions in the second category have one or more polymers selected from the group including: -Polyhydroxybutyrate (PHB), -Poly(hydroxyalkanoates) (PHAs) and other polyesters -Polyester, (PHB is polyester) Aliphatic polyesters, -Poly-4-hydroxybutyrate (P4HB), -Polyhydroxyvalerate (PHV), -polyhydroxyhexanoate (PHH), and -Polyhydroxyoctanoate (PHO) Embodiments of the second category of polymer compositions may also have plasticizers and / or other components, such as organic fillers.

[0041] The valve membrane may be a polymer composition of the second category. In particular, it may be preferred that the valve membrane is not water soluble.

[0042] The second category of polymer compositions may be steam resistant. In contrast, in embodiments, the body is a polymer composition of the first category. Alternatively, the body may be a polymer composition of the second category.

[0043] If present, the anchoring portion may be of a first category of polymer composition. For example, the anchoring portion may be of the same polymer composition as the body. For the anchoring portion, there is also the alternative that this component may be of a second category of polymer composition.

[0044] If present, the permeable membrane may be a polymeric composition of the first category. The permeable membrane can be of the same composition as the body, but in embodiments the composition differs in that it contains, for example, a higher proportion of plasticizer than the body.

[0045] The body may be provided with grease grooves, which are shallow depressions in the surface area of ​​the body that the valve membrane contacts. The grease grooves act to contain and act as a reservoir for excess sealing liquid. They are beneficial, and often necessary, to ensure that the space between the valve membrane and the surface it contacts is always provided with a uniform amount of sealing liquid.

[0046] In one group of embodiments, the base of the body has an outer grease groove with a radial extension at the end, the outer grease groove being a groove in the base located at a radially outer position, i.e. at a radial distance from the at least one through hole. In particular, the outer grease groove may be closer to the peripheral wall than to the center of the base.

[0047] The external grease groove or system of external grease grooves, except for the radial extension, generally extends along the circumferential direction, for example with the main part being parallel to the circumferential wall (parallel meaning that the vertical distance is constant).

[0048] The radial extension is the portion of the grease groove that extends radially away from the main portion of the grease groove.

[0049] The radial extensions have the advantage that they reduce membrane adhesion depending on their size, thereby allowing control of membrane adhesion.

[0050] The background is as follows: for a particular size of a pressure relief valve and its valve membrane, the adhesion force between the body and the valve membrane may be too high for a particular application. For example, in some cases, the pressure required to lift the valve membrane may be too high, and returning the valve to the closed state may be more unpredictable, for example in the case of relatively large packages, if a large amount of gas escapes after the valve membrane is lifted. However, in other packages, a relatively high adhesion is required to ensure sufficient airtightness. This can in principle be addressed by making the valves different sizes. However, if different valve sizes need to be provided for different types of packages, manufacturing becomes more complicated. Another prior art approach is to use sealing liquids of different compositions depending on the desired adhesion force. However, it is a challenge to fine-tune the adhesion force by changing the chemical composition without compromising with respect to other properties, especially when the materials of the valve membrane and the body are selected taking into account other properties and there is no freedom to adapt them.

[0051] The radial extension approach allows for a standard size body and valve membrane and a sealing liquid with a relatively high tendency to adhere to all packages. This expansion reduces the effective length of the path through which the valve membrane adheres to the body surface. This also reduces the adhesive force that the pressure buildup in the package must overcome before the valve is actuated, and the reduction in adhesive force that must be overcome increases with the size of the radial extension. Thus, only one parameter, the size (radial dimension) of the radial extension, needs to be changed to adapt the valve to different applications requiring different actuation / trigger pressures.

[0052] The radial extension may in particular be an inward extension. In one group of embodiments, the body comprises a plurality of external grease grooves, for example the external grease groove may comprise a circular array of at least two external grease grooves that together form an (interrupted) ring.

[0053] In particular, the outer grease grooves may comprise a circular array of first outer grease grooves and a circular array of second outer grease grooves, the first outer grease grooves being arranged around the second outer grease grooves. In such a configuration, the second outer grease grooves may be staggered with respect to the first outer grease grooves, such that the second outer grease grooves cover the gaps between the first outer grease grooves, such that there is no radial line from the center of the base to its periphery that is not blocked by the outer grease grooves.

[0054] In embodiments where the outer grease grooves are provided in at least one circular array, there may be one inward extension per grease groove. If there are several circular arrays, one inward extension per grease groove in one of the arrays may be sufficient.

[0055] In an embodiment having two circular arrays of grease grooves, the radially inward extensions may be inward extensions of a first outer grease groove, and may optionally extend through a gap between the second outer grease grooves to a location radially inward of the location of the second outer grease groove.

[0056] Thereby, in addition to the function of adjusting the adhesive force mentioned above, the radial extension balances the distribution of sealing liquid between the first grease groove and the second grease groove.

[0057] The body inside the peripheral wall in the plane defined by the valve membrane may comprise an extended accommodation groove, which provides a space in which the valve membrane can expand so as not to bulge when inflated, for example when absorbing moisture.

[0058] The surface portion of the body that the valve membrane contacts may be flat, as opposed to the curved (arched) surface portion of prior art valves. Such a flat structure may be beneficial, particularly when the valve membrane and / or body are made of biodegradable materials, since the adhesive forces do not change when properties such as material elasticity change slightly due to moisture uptake or aging. A flat structure is particularly beneficial in conjunction with an extended containment groove, since this combination allows for precise seating of the valve membrane by adapting its diameter to the inner diameter of the cup-shaped body, without the risk of the membrane arching or otherwise deforming upon expansion.

[0059] In one group of embodiments, especially when the valve has a permeable membrane, the body has at least one recess on the product side, thus forming a recessed portion. At least one through hole, or at least one of the through holes, has its product-side mouth in the recessed portion. This means that the mouth of the through hole on the product side is offset with respect to the outermost product side surface. This means that the mouth of the through hole is offset with respect to the plane of the permeable membrane, if a permeable membrane is present. This is particularly beneficial when both the permeable membrane and the body contain a water-soluble polymer, for example by being made from a polymer composition of the first category. That is, packaged foods often contain residual moisture, even when dry. This is the case for example with roasted coffee (ground or bean). This residual moisture can cause the water-soluble polymer to absorb some water and thereby become sticky. This tendency is potentially increased in the polymer composition of the first category due to the salt content. However, when the permeable membrane sticks to the body, airflow in the "horizontal" direction (parallel to the plane defined by the bottom of the body) between the permeable membrane and the body is prevented. Thus, gas can only diffuse through a small area of ​​the permeable membrane having the diameter of the through-hole. This can be insufficient in that such a small area is susceptible to clogging etc. The approach of arranging the through-holes in recessed areas solves this problem. The recessed areas can effectively constitute a system of vent channels with spacers between them.

[0060] In an embodiment, the spacers have rounded edges, so there is less risk of damaging the permeable membrane when the package is subjected to mechanical stress.

[0061] In addition to relating to a pressure relief valve, the present invention also relates to a package, in particular a coffee pouch for coffee beans or ground coffee. The package comprises a flexible, pliable packaging material as described herein, and a pressure relief valve. The body of the pressure relief valve is attached to the packaging material. In particular, the annular end face of the pressure relief valve may be attached to the packaging material with the valve membrane (and the fixing part, if present) located in the hollow space between the bottom of the body and the packaging material. The packaging material is generally airtight, but has an opening or other permeable structure at a position surrounded by the peripheral wall of the body.

[0062] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, in which like numbers indicate like or corresponding elements. [Brief description of the drawings]

[0063] [Figure 1] FIG. 2 is an exploded view of the components of the pressure relief valve. [Diagram 2] This is the main body in the figure. [Diagram 3] FIG. 1 shows a cut and assembled valve. [Figure 4] This is the main body from a different perspective. [Diagram 5] FIG. [Figure 6] FIG. 13 is a further view of the cut and assembled valve. [Figure 7] FIG. 2 is a schematic diagram of a valve in a package. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064] The pressure relief valve shown in Figures 1, 3 and 6 comprises a body 1, also shown in Figures 2, 4 and 5. The body 1 has the overall shape of a flat cup having a bottom 11 and a peripheral wall 12. The bottom 11 has a sealing surface and a product surface opposite the sealing surface.

[0065] The peripheral wall 12 surrounds the sealing surface of the bottom 11 and has at its end opposite the bottom 11 a flange 13, i.e. an outwardly projecting collar, which results in a wider annular end surface 16 carrying the package-side energy-guiding rib 18. The bottom as at least one through hole 14 (in the embodiment shown there are three through holes 14) is covered by the valve membrane 2 which contacts the bottom 11 on its sealing surface. Between the bottom 11 and the valve membrane 2 there is a thin layer of sealing liquid, in particular an oil, for example silicone oil. Silicone oil is known for this purpose. The sealing liquid will therefore not be described in further detail here.

[0066] The pressure relief valve for use is placed inside an airtight flexible package in that the annular end surface of the peripheral wall 11 is joined to the package inner surface, for example by welding. The package material has at least one gas passageway (for example at least one small through hole or permeable section) at the location surrounded by the annular end surface. When there is overpressure in the package, the gas lifts the valve membrane 2 from the bottom 12, forming a gas passageway. The excess gas can then escape through the through hole 14, between the valve membrane and the bottom, and through the gas passageway of the package. When there is no overpressure in the package, the membrane closes the package by contacting the bottom, and capillary forces cause the sealing liquid to adhere to the bottom and the valve membrane to form a seal.

[0067] The body 1, defined by the valve membrane 2 inside the peripheral wall 12 in a plane, is provided with an extending receiving groove 41. Such a groove 41 has been found to be beneficial for the following reasons: the valve membrane 2 may be of a biodegradable polymer composition. In contrast to prior art valve membrane materials, it has been found that these materials may be prone to undergo dimensional changes depending on the environmental conditions. For example, they may expand slightly when exposed to moisture.

[0068] In an embodiment, the pressure relief valve has a permeable membrane 3 in addition to the body 1 and the valve membrane 2. In contrast to the valve membrane 2, the permeable membrane 3 is gas permeable. It may be, for example, a fabric, such as a nonwoven fabric. The permeable membrane is attached to the bottom product-side surface and covers at least the through opening 14. The permeable membrane is useful when the package contains particulate products, especially ground coffee, in that it prevents the product from clogging the opening and coming into contact with the sealing liquid and the valve membrane 2. It is not essential that the package contains, for example, coffee beans or other crude products.

[0069] The permeable membrane 3 may be of polymeric material, for example by being a fabric of thermoplastic fibers. In an embodiment, it may be welded to the body. For this purpose, the body has product-side energy-guiding ribs 38 on the side facing the packaged product.

[0070] On the sealing face side, the body has a plurality of grease grooves. More specifically, the body has an inner grease groove 21 surrounding the opening, and further has a ring of three first outer grease grooves 22 and a ring of three second outer grease grooves 23, the first outer grease grooves 23 being arranged around the second outer grease groove 22. The outer grease grooves 22, 23 generally extend in a circumferential direction, each having a main portion 27 extending in a circumferential direction parallel to the circumferential wall. Each of the second outer grease grooves 23 has an outward extension 24 extending radially outward from the main portion 27 into the gaps between the first outer grease grooves 22. Each of the first outer grease grooves 22 has an inward extension 25 extending radially inward from the main portion 27 into the gaps between the second outer grease grooves 23 and further extending radially inward.

[0071] As used herein, "radial" as well as "outer" or "inner" or "circumferential" are meant to refer to the axis 10 of the body; the existence of a central axis does not necessarily imply axial symmetry, although such symmetry is an option.

[0072] The outer grease grooves have the function as reservoirs for sealing liquid. For this purpose, they are located in a radial position so that they are covered by the valve membrane (see, for example, FIG. 3 or FIG. 6). For example, if the valve is subjected to temporary mechanical loads, for example during transportation of the valve before bonding to the package or during transportation of the package with the valve, it may happen that the sealing liquid is pushed out from between the bottom 11 and the valve membrane 2. The grease groove ensures that capillary forces can then draw the sealing liquid out again from the grease groove under the valve membrane. Similar considerations apply to the manufacturing process. For the grease groove, it is sufficient that a drop of sealing liquid is dispensed on the bottom or on the membrane, the grease groove ensures that the sealing liquid is well distributed and that the sealing membrane adheres uniformly to the bottom over the entire circumference of the through hole 14.

[0073] In addition to having this well-known function, the special structure of the outer grease grooves 22, 23 allows for better control of the adhesive forces: the distance between the inner grease groove 21 and the outer grease grooves 22, 23 determines the minimum length p of the path along which the adhesive forces must be overcome in order to trigger the valve by lifting the valve membrane 2 off the bottom 11. l If no internal grease groove is present, the quantity of interest is the distance between the through hole 14 and the inward extension 25.

[0074] As shown in FIG. 5, this path length p l may be controlled by selecting the length of the inward extension 25.

[0075] Both the outward extension 24 and the inward extension 25 have the further function of distributing sealing liquid between the grease grooves. For example, the outward extension 24 and the inward extension 25 may provide communication of sealing liquid between a first outer grease groove and a second outer grease groove, and between different first grease grooves and different second grease grooves.

[0076] Nevertheless, a system comprising a circular array of at least two (three in the illustrated embodiment) first external grease grooves 22 and / or a circular array of at least two (three in the illustrated embodiment) second external grease grooves 23 features the advantage that the sealing liquid is better distributed along the periphery of the bottom 11 than an arrangement in which the grease grooves are an uninterrupted ring, even in situations in which the valve is maintained in an unchanging vertical orientation for long periods of time.

[0077] In an embodiment, the pressure relief valve has a fixed part 4 in addition to the body 1 and the valve membrane 2, possibly in addition to the permeable membrane 2. The fixed part 4 is optional and may function as a spacer between the flexible packaging material and the valve membrane 2, ensuring that the valve membrane 2 cannot be displaced even in the event of severe mechanical violent vibration. In the illustrated embodiment, the fixed part 4 is star-shaped with three rays. It has a first distance-keeping rib 51 and a second distance-keeping rib 52. The entire star shape and the distance-keeping ribs 51, 52 constitute a material-saving shape and still have a stable orientation. The star shape also ensures a certain degree of elasticity of the fixed part 4.

[0078] As can be seen for example in figure 6, the shape of the peripheral wall 12 forms a slight undercut 42 on the inside, and the inner surface of the body is slightly conical. This undercut shape allows the fastener 4 to be clicked into the body and remain there due to its elasticity.

[0079] On the side facing the product, the body 1 is constructed with a system of ventilation grooves 31 and spacers 33. The system is such that the through holes 14 are at the bottom of the ventilation grooves, i.e. in a position where the product-side surface is recessed. The radial channels 32 belonging to the system of ventilation grooves 31 ensure that the gas diffusing through the permeable membrane into the ventilation channel can reach the through holes 14. Thereby, the gas can diffuse through a relatively large surface area, in that it encounters less resistance and the membrane is not pressed against a flat surface by the overpressure inside the package. Rather, the spacers 33 move the membrane away from the plane in which the through holes 14 have their mouths.

[0080] A further advantage of the system of ventilation grooves is that it prevents the permeable membrane 3 from sticking to the body in the area around the through holes 14. Such sticking can occur during the process of joining the permeable membrane 3 to the body, for example by ultrasonic welding.

[0081] For example, as shown in FIG. 5, the spacers 33 have rounded edges 35 so that there is less risk of damaging the permeable membrane when the package is subjected to mechanical stress.

[0082] The overall shape of the body with the flange 13 and the wide end face 16 (joined to the packaging material) provides further improvements with regard to the process of joining the valve to the packaging material and the stability of the joint: the shoulder defined by the flange, which is an outwardly protruding collar, provides a joint surface 17 on which the tool for joining the valve to the packaging material can directly act. Thereby, the energy coupled by the tool into the body 1 for the joining process (usually ultrasonic energy) does not have to be coupled through the entire height (axial extension) of the body, but only through the thickness of the flange 13. This makes the joining process more efficient compared to the situation where the tool presses against the product-side end face of the body.

[0083] The tool may for example be a tube-shaped sonotrode with a tube diameter that corresponds approximately to the diameter of the flange 13 .

[0084] However, the flange 13 and the wide end face 16 are merely optional. In alternative embodiments, the body 1 does not have this structure. Also in these alternative embodiments, the body 1 can be welded to the packaging material in that the sonotrode impinges on the product side end face of the body. Also in these embodiments, the sonotrode used can optionally be tubular in shape, the tube diameter being larger than the outside diameter of the area with the system of ventilation grooves and spacers. However, alternatively, the sonotrode can have a flat outcoupling face.

[0085] In the illustrated embodiment, the body 1, the fixing part 4 and the permeable membrane 3 are all made from a polymer composition comprising a water-soluble polymer and further comprising, for example, a salt: - the body 1 and the fastening part 4 are injection moulded from a polymer composition comprising, for example, PVOH obtained by saponification of poly(vinyl ester), salt (in particular sodium chloride) and glycerin. In an alternative embodiment, the body 1 and the fastening part 4 are injection moulded from a polymer composition comprising, for example, PVOH obtained by saponification of, for example, 98% hydrolysed poly(vinyl ester), 10% to 15% glycerol as plasticiser, 2% to 6% water and additives in the form of 1% to 3% saturated fatty acids, 1% to 3% binders and 0.1% to 0.3% antioxidants. The polymer composition of the body and the fastening part may be the same.

[0086] The permeable membrane is, for example, a woven fabric of fibers of a polymer composition that also contains PVOH, obtained by saponification of poly(vinyl ester), salt (especially sodium chloride), and glycerin.

[0087] The valve membrane 2 is made from PHB. Therefore, all components are biodegradable.

[0088] Figure 7 shows a schematic representation of a package with a valve. The body 1 is welded to a packaging material 60. The packaging material has a through hole 61 for the gas to be released.

Claims

1. A pressure relief valve comprising a body (1) equipped to be fastened to a flexible packaging material, the body (1) having at least one through hole (14) forming a passage through the body, a valve membrane (2) contacting the body on the package side in the area around the at least one through hole (14), and a sealing liquid between the body (1) and the valve membrane (2), characterized in that at least one component of the valve is made from a polymer composition comprising a water-soluble polymer.

2. The valve of claim 1 , wherein the polymer composition of the at least one component comprises a salt.

3. The valve of claim 1 or 2, wherein at least the body is made from a polymer composition comprising a water-soluble polymer and a salt.

4. 2. The valve of claim 1, wherein the water-soluble polymer comprises a polymer chain having a plurality of vinyl alcohol groups, the water-soluble polymer being, for example, poly(vinyl alcohol) (PVOH).

5. 10. A valve according to any one of the preceding claims, wherein the valve membrane (2) is made from a water-insoluble material.

6. 10. A valve according to any one of the preceding claims, made from a biologically degradable material.

7. 10. The valve according to any one of the preceding claims, further comprising a permeable membrane (3) secured to the body (1) so as to cover the at least one through hole (14) on a product side opposite the packaging side.

8. 10. The valve according to any one of the preceding claims, wherein the permeable membrane (3) is a fabric made from a polymer composition comprising a water-soluble polymer.

9. 10. A valve as claimed in any one of the preceding claims, wherein the through hole (14), or the product side mouth of at least one of the through holes (14), is offset relative to an outermost surface defined by the product side surface of the body.

10. 10. The valve of claim 9, wherein the body has a system of ventilation grooves with spacers between them, and the through hole (14) or the mouth of the at least one of the through holes (14) is in the ventilation grooves.

11. 10. A valve according to any one of the preceding claims, wherein the body (1) is cup-shaped with a bottom (11) and a peripheral wall (12), and the valve further comprises a fixing part (4) fixed relative to the peripheral wall, such that the valve membrane (2) is sandwiched between the bottom part (11) and the fixing part (4).

12. 10. A valve according to any one of the preceding claims, wherein the body (1) is cup-shaped with a bottom (11) and a peripheral wall (12), the bottom (11) having, on the package side, a system of grease grooves for accommodating a portion of the sealing liquid, the system of grease grooves comprising at least one external grease groove (22, 23) having a circumferentially extending main portion (27) and having radially inwardly extending portions (24, 25) extending radially inwardly from the main portion (27).

13. 13. The valve of claim 12, wherein the grease groove system comprises at least one circular array of at least two first external grease grooves (22) and at least one circular array of at least two second external grease grooves (23), the first external grease grooves (22) being arranged around the second external grease grooves (23) and the second external grease grooves being staggered with respect to the first external grease grooves.

14. 14. A valve according to claim 12 or 13, wherein the grease groove system further comprises an inner grease groove (21) extending around the at least one through hole (14).

15. 10. A package for packaging food products, comprising a flexible, pliable packaging material (60) and a pressure relief valve according to any one of the preceding claims, said body (1) being attached to said packaging material (60).

Images