Valve, and Package

The present invention is in the field of pressure relief valves for food packages.

Certain food products, for example fresh roasted coffee beans or coffee powder, have a tendency of degassing for some time. Therefore, according food packages, for example coffee bags (coffee pouches) have a pressure relief valve. Pressure relief valves allow the gases—for example carbon dioxide—generated in the interior of the package to escape while preventing the surrounding air to enter into the package so that no oxygen will get into the package and freshness is preserved.

Pressure relief valves usually have a cup-shaped main body, wherein of edge the circumferential wall of the main body is welded or glued to an inside of the package material. Both, the bottom of the main body and the package each have an opening. On the bottom of the main body lies a disc as valve membrane, with an oil, for example a silicone oil, between the bottom and the disk. If there is an overpressure within the package, the gas communicating through the opening of the bottom lifts the disc, so that the gas can escape into the interior of the main body and from there through the package opening out of the package. When there is no overpressure within the package, the disc lying against the bottom of the main body ensures a leak-tight sealing.

Pressure relief valves of this kind are beneficial in that they make possible that fresh food is directly packaged to be delivered to the end customer, without any intermediate re-packaging being necessary. This, in addition to ensuring freshness for the customer, has also advantages in terms of ecology. However, the pressure relief valves add to the environmental footprint of the package.

It would be desirable to have further approaches of improving the eco-balance of the packaging of fresh roasted coffee and other roast products that produce gas after the roasting process.

According to an aspect of the present invention, a pressure-relief valve is provided, the valve including a main body equipped to be fastened to a flexible package material, the main body having at least one through hole forming a passage through the main body, a valve membrane lying, on a package side, against the main body in a region around the hole, and a sealing liquid between the main body and the valve membrane. The valve includes a water-soluble polymer, meaning that at least one component of the valve (for example the main body or an additional component such as a fixing part or a permeable membrane as described hereinafter) is made of a polymer composition that includes a water-soluble polymer.

A polymer in the context of the present text is deemed to be water-soluble if it dissolves in water at a temperature at that water is liquid at atmospheric pressure. In embodiments, the water-soluble polymer material is water-soluble at room temperature, but in other embodiments may also be soluble at elevated temperature of for example 60° C. only (thus only hot-water-soluble).

The main body is itself dimensionally stable. It may be equipped to be fastened to the flexible package material by being cup-shaped and having a bottom and a circumferential wall surrounding the bottom, the annular end face of the circumferential wall being attachable to the packaging material. The bottom then includes the at least one through hole forming the passage through the bottom for the gas produced withing the package. The valve membrane is arranged on the package side of the bottom (in the cup constituted by the main body) and covers the at least one through hole. The side of the bottom opposite to the package side is called “product side” in this text.

In embodiments, if the package is to contain a finely grained product such as coffee powder (ground coffee), the valve further includes a permeable membrane, which is attached to the product side of the bottom covering the at least one through hole so as to prevent the product from clogging the through opening while being permeable for gases. The permeable membrane may be a fabric membrane. In this text, “fabric” is used to cover all kinds of flexible materials from fibers or yarns or threads that are interlocked, including nonwovens, woven or knitted textiles or other textile structures.

In embodiments, the valve further includes a fixing part. The fixing part is shaped to be placed on the package side of the valve membrane. It prevents the valve membrane from falling out of the main body even in situations in which the valve is subject to substantial mechanical shock. The valve may especially be subject to such shock, during transportation and assembly processes, if it is provided as a bulk material. In a situation of mechanical shock, the fixing part keeps the valve membrane in place even if adhesion by the sealing liquid might not be sufficient to do so. The fixing part may be held relative to the main body by the circumferential wall of the main body forming an undercut, so that the fixing part is clickable into the main body.

The water-solubility of the polymer has advantages in recycling processes, be it a composting process or even a paper recycling process.

While water-soluble polymers may be bio-degradable, this is not necessarily the case for all water-soluble polymers. The water-soluble polymer of the valve may be bio-degradable in addition to being water-soluble.

In the present text, “bio-degradable” may mean biologically degradable according to the European standard EN 13432 (as of the end of 2021). In addition or as an alternative, it may mean biologically degradable according to the European standard EN 14995 (as of the end of 2021). Thus “bio-degradable” especially refers to “biologically degradable according to EN 13432 and/or according to EN 14995.

As far as in the present text water-soluble polymers are mentioned, such water soluble polymer may optionally be degradable in sewage treatment plants (aerobic biodegradability) in accordance with DIN EN ISO 9888 (as of the end of 2021); determined in accordance with the so-called Zahn-Wellens test.

In embodiments, all components of the valve, i.e., the main body, the valve membrane, and, if present, the permeable membrane and/or the fixing part, respectively, are of bio-degradable materials.

In embodiments, while the valve contains a water-soluble polymer, for example as a material of the main body and/or, if applicable, the fixing part and/or the permeable membrane, the valve membrane is not water-soluble.

In embodiments, at least one of the components is made of a polymer composition belonging to a first category of polymer compositions. Polymer compositions of the first category are water-soluble.

In a group of embodiments, polymer compositions of the first category include a salt in addition to including a water-soluble polymer.

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 a maximum amount being 55% or 40% or 35%. In the present text, all percentages refer to % by weight unless specified otherwise.

The salt may be a hygroscopic salt.

The salt may include a salt of an alkaline metal, an earth alkaline metal, or aluminium salt and/or a mixture thereof. Particular examples include NaCl, Na-citrate, and the respective potassium analogues, magnesium chloride and/or mixtures thereof.

The salt on the one hand may act as lubricant for the polymer in the polymer composition of the first category. The addition of salts to the polymer can enhance the melt flow index (MFI), hence improving hot-melt processability of the polymer composition.

The main body and/or, if applicable, the fixing part may hence be manufactured by injection moulding or other moulding technique if they are made of a polymer composition of the first category that includes a salt. The same may apply if they are made of a different polymer composition, especially a polymer composition of the first category, but without a salt.

In addition, the salt has been found to also improve solubility, disintegration, and bio-degradation speed, for example for composting. The addition of the salt can render a polymer home-compostable, if without the salt it would be capable of being composted industrially only but not per se home-compostable. The salt content, therefore, may be used to tune the properties of the polymer composition depending on the intended use and intended recycling process.

In particular, independent of whether the polymer composition of the first category includes a salt or not, the water-soluble polymer of a polymer composition of the first category may include at least one of poly (vinyl alcohol) (PVOH), cellulose-ether polymer, Butenediol-Vinyl-Alcohol-Copolymer (BVOH), Polyvinyl butyral (PVB) and Ethylene-Vinyl-Alcohol-Copolymers (EVOH).

Polymer compositions of the first category in particular may include a water-soluble polymer that is a vinyl alcohol polymer or -copolymer or a mixture or blend of two or more vinyl-alcohol copolymers. I.e., the water-soluble polymer of may be a polymer that has a plurality of vinyl alcohol [CH2CH(OH)] groups in the polymer chain. These polymers include the mentioned PVOH, BVOH, and EVOH as well as others.

If the water-soluble polymer includes or a mixture or blend of two or more vinyl-alcohol copolymers, the copolymers can differ in molar mass, molecular architecture, e. g. branching, comonomer type and amount, or other variation parameters.

The polymer of polymer compositions of the first category may thus be a vinyl alcohol including, especially a vinyl alcohol rich, copolymer or a vinyl alcohol homopolymer. The polymer can in embodiments include >75%, in particular >90%, monomer units carrying an OH unit.

The water-soluble polymer can include further polar comonomers. Examples include maleic acid and maleic acid anhydride, fumaric acid and itaconic acid.

The water-soluble polymer, in particular the polyvinyl alcohol (PVOH), can have a degree of hydrolysis of 70% to 99.9%. The degree of saponification can relate to the performance to the oxygen barrier. Especially, the degree of hydrolysis may be at least 90% or at least 94% or even at least 96%. A higher saponification can relate to a higher oxygen barrier performance.

The polymer composition of the first category can include at least one of:

Polymer compositions of the first category in embodiments have a maximum water content of 10%. Especially in embodiments containing a salt, the water content may for example be not more than 5%, especially not more than 1% or not more than 0.5%.

Polymer compositions of the first category may further include a plasticizer (liquid or solid) to lower the melt temperature, which is especially beneficial for molding. The plasticizer can in embodiments be hygroscopic. The plasticizer may be selected from the group consisting of polyols (oligo- and polyhydroxy compounds) and low molecular weight amides, especially of trioles, diols, poly-triols, poly-diols, for example glycerine, 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 di-propylene glycol, higher oligomers of ethylene glycol or propylene glycol, butylene glycol, glycerol, pentaerythritol, sorbitol, 1,4-Monoanhydrohexitols, 1,4-3,6-dianhydrohexitols as well as esters of the same. Preferred plasticizers are glycerine, and polypropylene glycol.

The plasticizer may be present in an amount of between 2% and 25%, especially between 5% and 18%, for example between 10% and 15%.

Polymer compositions of embodiments of the first category in embodiments may especially include more salt than plasticizer. More in concrete, the ratio between the salt and the plasticizer may be between 1.5:1 and 6:1.

It is not excluded that polymer compositions of the first category, in addition to including a water-soluble polymer, possibly a salt, and optionally a plasticizer, include further constituents, such as a thermal stabilizer (for example a metallic stearate, such as sodium stearate), for example in a concentration of at most 1%, especially at most 0.5%, and/or a an inorganic filler and/or an organic filler, such as cellulose or a filler as described in WO 2021/224 424 and/or other constituents that influence the properties of the composition, or of ingredients thereof.

Examples of suitable polymer compositions of the first category may for example be found in WO 2014/155059.

As an alternative to compositions as described in WO 2014/155059, the polymer composition of the first category may include, in addition to the polymer (‘resin’, for example the Poly (vinyl alcohol), Ethylene-Vinylalcohol-Copolymers (EVOH), or Butenediol-Vinylalcohol-Copolymer (BVOH) and the plasticizer (but not necessarily the salt) additives, especially saturated fatty acids, a binder, and/or an antioxidant. These additives have proven to be beneficial for the properties of the polymer composition of the first category especially in terms of suitability for the molding process as well as for biodegradation.

Further constituents of the polymer composition of the first category may include water (for example between 1% and 10%, especially between 2% and 6%), and additives including between 0% or 1% and 5% or 3% fatty acids, a binder (for example between 0% or 1% and 5% or 3%), and or an antioxidant (in an amount of for example less than 0.5%, especially between 0.1% and 0.3%).

An other example of a suitable polymer composition of the first category includes between 70% and 85% of polyvinyl alcohol (for example 98% hydrolyzed), between 10% and 15% of glycerol as plasticizer, between 2% and 6% of water, and additives in the form of between 1% and 3% saturated fatty acids, between 1% and 3% of a binder, and between 0.1% and 0.3% of an antioxidant.

In addition—or as an alternative—to including one or more polymer compositions of the first category, the valve may include a component of a polymer composition of a second category. Like the polymer compositions of the first category, also polymer compositions of the second category may be bio-degradable according to the definition used in the present text. The polymer compositions of the second category are not, however, water-soluble, and in embodiments they do not include a salt.

Examples of polymer compositions of the second category have one or more polymers chosen from the group including:

Also embodiments of polymer compositions of the second category may have a plasticizer and/or other constituents, for example an organic filler.

The valve membrane may be of a polymer composition of the second category. Especially, it may be preferred if the valve membrane is not water-soluble.

The polymer compositions of the second category may be vapor resistant.

In contrast thereto, in embodiments, the main body is of a polymer composition of the first category. Alternatively, the main body may be of a polymer composition of the second category.

If present, the fixing part may be of a polymer composition of the first category. For example, the fixing part may be of the same polymer composition as the main body. Also for the fixing part, there exists the alternative that this component may be of a polymer composition of the second category.

If present, the permeable membrane may be of a polymer composition of the first category. It is possible that the permeable membrane is of the same composition as the main body, although in embodiments the composition will be different, for example in that it contains a higher portion of the plasticizer than the main body.

The main body may include a grease groove. Grease grooves are shallow indentations on the surface region of the main body against which the valve membrane lies. Grease grooves act to accommodate excess sealing liquid and act as a reservoir for it. They are beneficial and often necessary to ensure that the space between the valve membrane and the surface against which it lies is always evenly provided with the sealing liquid.

In a group of embodiments, the bottom of the main body has at last one outer grease groove that includes a radial extension. An outer grease groove in this is a groove in the bottom located at a radially outer position, i.e. at a radial distance from the at least one through hole. Especially, the outer grease groove(s) may be closer to the circumferential wall than to the center of the bottom.