DK178612B1 - Use of a sealing insert for a metal or plastic container lid - Google Patents

Abstract

The application relates to a metal or plastic container lid for a container for receiving food or beverage in vacuum and at filling and / or storage at room temperature and below, with a sealing insert of a sealing material comprising at least one polymer (with the exception of halogen containing polymers, e.g., PVC) mixed with additional substances, characterized in that the sealing material at 20 ° C has a shore A hardness of maximum 90 and a deformation (DVR) of maximum 40% and at 4 ° C a shore A hardness of maximum 100 and deformation of maximum 50%.

Description

Use of a sealing insert for a metal or plastic container lid 1. Technical area

The present invention relates to the use of a sealing insert for a metal or plastic container lid for food or beverages stored at room temperature (about 20 ° C) or below, especially at about 4 ° C (refrigerator temperature). In particular, the invention relates to the use of a sealing insert of a sealing material comprising compositions suitable for unscrewable (and optionally resealable) container lids or vacuum lids, e.g. twist off lids and Press-on / Twist-off lids.

2. Background of the Invention

Sealing materials for container lids in the packaging industry containing polyvinyl chloride (PVC) have long been used.

However, the use of PVC-containing compositions in packaging materials is generally no longer desired for several reasons. In the incineration of household waste of halogen synthetic substances, e.g. acidic gases which are harmful when released into the atmosphere. In addition, small quantities of PVC are already destroying material recycling of plastic waste. PVC-based sealing elements also require the use of plasticizers that may migrate into the foods contained in the container, which is why they are problematic for health reasons.

Therefore, the present invention makes use of PVC-free sealing materials (hereinafter also referred to as polymer compound) for container lids, especially for food packaging.

Foods (including beverages such as juice and the like) are often packaged in glass or plastic containers, which in many cases have a screw lid. Screw lid stands here for container lids which in full and closed condition are threaded with the container. To open the container, the lid must be screwed relative to the container, thereby removing the seal between the lid and the container edge, and the - often - existing vacuum in the container is also removed. The lid can be removed from the container by such screwing. The known PVC-containing sealing materials have the necessary processing and application properties. Thus, it should be noted that a PVC-free sealant is only a commercially interesting sealing cap for container lids when the PVC-free sealant has very special physicochemical properties that do not substantially retain the properties of the PVC-containing sealants.

Additional requirements for such sealing materials include e.g. the following aspects:

The material composition must be chosen so that undesirable substances are avoided. Therefore, the sealant should not contain substances that are considered to be health problematic, especially plasticizers such as e.g. phthalates; semicarbazide and its sources, in particular ADC and OBSH; 2-ethylhexanoic acid and the sources thereof; tin-organic compounds; primary aromatic amines; bisphenols, nonylphenols; BADGE; photoinitiators; perhalogenated compounds; melamine.

For some applications, the presence of higher content (at room temperature) of liquid substances is undesirable. In that case, the content of such substances (such as, for example, paraffin oil) should be limited to a maximum of 10%, preferably less, and in some cases the sealing material should have no detectable content of such liquid substances. This is especially true for the filling of fatty foods.

The material composition must be selected such that the sealing material, when used, also meets the exacting requirements.

For some applications, the sealing material must have a barrier function, ie. reduce or prevent the entry of unwanted substances into the container.

For special applications, it must be possible to provide the sealing material with absorbent additives (eg oxygen absorbers) or other scavenger substances.

The sealing material must have the necessary processing properties.

Basically, it should be capable of being thermally softened sufficiently (especially by an injection molding method, but also for extrusion with subsequent stamping or molding) to be applicable to conventional processing machines.

However, after insertion into the container lid and cooling to the desired operating temperature (most often room temperature, but possibly also lower temperatures, eg on refrigeration in stores), it must have the necessary sealing properties.

For small container lids, the sealing material must also be able to be introduced on the entire surface.

For PT caps (Prcss-on / Twi st-offK-lid), the sealing material must constitute both the seal and the inner thread of the cap and therefore (as a so-called "contoured ring") must be able to be applied both on the inner surface and on the skirt of the cap and by applying the cap could constitute the mechanical (sufficiently stable) threaded members.

For some applications, the sealing material must "out shell", ie. outside the lid could be formed into a sealing insert which is then used as a finished sealing ring or the like in the container lid.

In particular, the sealing material must be suitable for metal lids and metal-plastic compounds, which may be lacquered internally, but it must also be suitable for plastic lids.

The sealing material must be suitable for standard food packaging.

The sealing insert must also have sufficient vacuum retention in the cold.

The sealing insert must be suitable for standard containers of metal, plastic, glass, etc.

Upon contact with the filler product, especially with fatty foods and other products of (compared to water) lipophilic character, the sealing insert shall not deliver any components or as few as possible to the filler product, nor shall it absorb any lipophilic constituents from the filler product.

The sealing insert must have sufficiently low aperture values to be able to remove the container lid (possibly by cooling) with appropriate force. At the same time, the seal must have a sealing effect for the predetermined life (minimum durability) of the food.

3. Summary of the Invention

In general, according to the invention, polymer compounds (herein also referred to as compositions) are used, with the exception of halogen-containing polymers, such as PVC, as sealing material (or sealant).

More specifically, the invention relates to the use of a sealing insert of a sealing material as defined in claim 1 for a metal or plastic container lid for a container for receiving food or beverage in vacuum and for filling and / or storing at room temperature and below.

Peculiarities arise from foods stored at room temperature (e.g., 20 ° C) or refrigerated (e.g., 4 ° C), and are usually not pasteurized or sterilized. It can be high-fat or low-fat or fat-free foods. Such foods may e.g. are refilled cold and refrigerated until use, but they also include products that are refilled at room temperature or even heat, but then stored at room temperature or cooled. They include products in containers in which a vacuum is generated by means of vacuum or steam which is cooled.

Examples of such foods are: 1. Yogurt and desserts: fatty, must be filled with cold, possibly vacuum, transport and storage in the refrigeration chain; 2. Cheese in oil (eg feta): greasy, must be filled cold or at room temperature, possibly vacuum, transport and storage in the refrigeration chain; 3. Fish in oil (eg salmon substitute): greasy, refilled cold, possibly vacuum, transport and storage in the refrigeration chain; 4. Mustard: fatty according to Regulation (EU) 10/2011, filling up to approx. 50 ° C, optionally vacuum, transport and storage at room temperature; 5. Confit: grease-free, refill hot, vacuum if necessary, transport and storage at room temperature; 6. Mayonnaise: greasy, filling cold, possibly vacuum, transport and storage at room temperature;

Container lids for these applications are mostly screw lids, such as e.g. twist off-lid. Such lids are opened by unscrewing the lid relative to the container where the sealing insert is to slide on the container edge along with which it forms the seal. In this connection, the lid is raised ffa the container edge and any vacuum is lifted. In such applications, in addition to the above requirements, the sealing insert must also withstand temperatures, e.g. when stored in refrigerators, allow easy opening of the container. An important criterion for this is the opening value, which constitutes the maximum torque required to unscrew the lid (ie when opening the container).

The sealing materials disclosed in our previous patent application PCT / EP2011 / 057652 are partially suitable for such applications, however, where the heat sterilizability of the sealing material is emphasized, which is mostly less important in the foods treated here. It makes it possible to adjust the sealing materials within the scope of this invention even more specifically to the requirements (especially with respect to the opening value) arising from foods of the kind mentioned above.

Additional parameters that may serve to characterize suitable sealing materials are their shore A hardness and deformation (DVR), both especially at 20 ° C and at 4 ° C, and the stress loss in a creep test (25% compression at 70 ° C , then free cooling), as will be described below.

If the foodstuffs and beverages considered according to the invention are exceptionally sterilized after filling and closing the container, a sealing insert which can also withstand such measures is particularly desirable. The suitability for sterilization measures can optionally be tested for the sealing material easily by means of Dynamic-Mechanical Thermal Analysis (DMTA), as described in our previously mentioned application PCT / EP2011 / 057652.

The container lids considered herein are used at temperatures (room temperature and below, up to about 0 ° C), where traditional oil and PVC free sealing materials are too hard and inelastic and have too high opening values. The lids utilizing the invention meet the requirements with regard to the hardness (lower) and elasticity (deformation, ANIMAL) of the sealing material as well as their opening value at low temperatures.

The objects of the present invention are met with the PVC-free sealing materials defined in claim 1. Advantageous designs are defined in subclaims.

In this connection, the invention takes into account that different filling products place additional requirements on the sealing material. Admittedly, especially in the case of fat-free filling products, it is possible, and also very convenient, (also) to adjust the properties of the sealing material by means of an oil component. However, it may be undesirable when the filling product is greasy. An in-depth discussion of this problem can be found e.g. In our previous application WO 2011 / 060803.1 such cases, the physical parameters must be set by adding suitable softening materials which are not liquid (at room temperature), especially non-oily. Suitable for this are certain "soft" polymers which are selected to meet the requirements of the invention.

The embodiments of the invention which contain little or no oil are basically suitable for all applications within the scope of the invention. The oily embodiments are preferably not used for fatty filling products.

The PVC-free compositions used according to the invention can be made sufficiently fluid by heating. Only in this way can the sealant be applied to the container lid blank by extrusion or a similar method to the area of the sealing element (also referred to as a seal or sealing insert) to be made.

Subsequently, the PVC-free composition applied to the inside of the container lid can be mechanically formed to the desired sealing member. After cooling, the applied composition may retain its shape and close sealingly against the opening of the container to be closed with the container lid.

In this connection, the PVC-free composition can preferably be used in the production of arbitrary container lids, e.g. for producing seals in twist off lids, screw caps, swivel caps, bottle screw lids and Press-on / Twist-off® lids.

Thus, the PVC-free compositions according to the invention comprise, in particular, a sealing material suitable for container lids, which • can be easily processed, • enable quickly produced quantities in industrial production, • can be used for filling and / or storage at room temperature and cooling, • can be used in a similar recipe even for fatty filling products; • as far as possible or entirely based on non-crosslinked polymers and completely or at least substantially free of health-related substances (such as plasticizers and the like); inexpensive, and / or • enables the manufacture of container lids which exhibit a gas barrier effect, an overpressure valve action and / or a vacuum retention.

4. Definitions In the context of the present invention, the term "PVC-free composition" refers to a composition comprising less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.1% by weight or less than 1% by weight, and most preferably (within the analytical determination limits) no PVC at all (in each case based on the total weight of the PVC-free composition). In the context of the present invention, only those compositions are considered VC-free compositions which can be used as sealant in container lids. Thus, a hot melt adhesive or pure polymer is not a "PVC free composition" in the context of the present invention, even if there is no PVC in it.

In the context of the present invention, the term "plastic" refers to a material comprising at least one synthetic or semi-synthetic polymer.

In the context of the present invention, the term "block copolymer" refers to a copolymer consisting of longer frequencies or blocks of each monomer (e.g., AAAAAAAAABBBBBBBBBBBB ...). In particular, according to the invention, so-called "statistical multi-block resins" are available, which are available from DOW Chemical Co. under the designation "Infuse".

In the context of the present invention, the term "random copolymer" refers to a copolymer with statistical distribution of the monomers, in particular a copolymer of the type obtainable from DOW Chemical Co. under the term "Engage".

In the context of the invention, TPO means an olefin-based thermoplastic elastomer (TPE-O); TPS is a styrene block polymer (TPE-S).

In the context of the invention, room temperature is generally approx. 20 ° C.

5. Physical Parameter Test Procedure According to the present invention, the opening value is the maximum torque required to open the closed container by screwing on the container lid.

The opening value is determined by a torque reader into which the closed container is inserted and then opened manually or (semi) automatically. For example, a suitable device is available from the company Steinfurth under the designation "Torque Measuring System TMS 5000".

For this test, containers of the type for which the lid is designed are selected in such a way that they are representative of the quality of their mouth (evenness of the edge, etc.). The containers are preferably filled with the filling product for which they are intended, alternatively with water or vegetable oil. In this connection, the filling level in the container corresponds to the filling level in the intended use. These containers are then sealed in the intended manner with the container lids to be tested, where the vacuum is adjusted via the amount of steam used, the water content and temperature, and the remaining space above the filling product. Alternatively, the vacuum can also be generated in a chamber by pumps. In this chamber the lid is then put on and closed with a swivel movement. In the case of "mechanically" generated vacuum, values of -0.3 bar are typically obtained, with vapor-sealed containers -0.6 bar.

If in this specification opening values are treated, the always evacuated containers relate to a vacuum of approx. -0.5 bar.

The containers are subsequently stored at 4 ° C.

Since the opening value at constant storage temperature is often increased initially and then reduced again to a stable value, the opening value was determined according to a corresponding storage duration. Usually, a starting value was determined immediately, and then measurements were followed after 1, 2, 5, 7 and 14 days, after 4 weeks and after three months. Within 4 weeks, a constant value usually settled.

The measurements were performed in parallel at several containers (usually at least 10, better up to 40 containers) so that a mean value could be extracted from the measurement data. The opening values given in this specification are averages for at least 10 containers, where the vacuum was set to approx. 0.5 bar vacuum and after storage at 4 ° C for the number of days mentioned in the embodiment.

The diameter of the container doors was 70 mm. The opening value according to the invention is preferably in inches lbs maximum at half the diameter of the lid, at 70 mm diameter ie at maximum approx. 35 inch Ibs. For other diameters, the opening value of the invention results in the same formula.

The permissible oscillation width is preferably a maximum of 20% from the mean, i.e. at an average opening value of 35 inches Ibs, the lids of the invention may be between 28 and 42 inches Ibs (preferably, of course, closer to the mean).

Shore A hardness is determined according to DIN ISO 7619-1.

The deformation DYR is determined by analogy to DIN ISO 815.

With the measurement of the voltage loss in the creep test, an approximation of the compound's behavior must be obtained to real filling conditions.

For this, (usually by injection molding) a sample piece of the polymer compound having a diameter of 20 mm and 6 mm high or thick is prepared. For testing, the specimen is clamped in a universal test machine. Such machines can e.g. available under the designation LR5kN from Lloyd Instruments.

The test piece is conditioned at 70 ° C in the test chamber's heating chamber and compressed by 25% with a force of 1 mm / min. After adjusting the compression, the heating is switched off and the door of the heating chamber is opened. The system is allowed to cool freely. The force acting against the compression is measured and recorded using a force sensor.

6. Detailed description of the invention

Container lids utilizing the invention, as defined by their physical parameters (shore A hardness, deformation, opening value, voltage loss), are basically suitable for all foods and beverages. Differences in the compositions of the corresponding sealing materials are evident from the properties of the filler products, in particular those arising from the presence of fatty or fat-free products. For fat-free products, the necessary physical properties can e.g. (partially) is adjusted by an oil content of the compound higher than that of known sealing materials for use at higher temperatures. For greasy products, relevant oil content is preferably avoided because oil from the compound may end up in the product and / or grease components from the product may end up in the sealing material.

In the following, oily and then oil-free sealing materials are first treated.

6.1 Oily Sealing Materials In preferred embodiments of the invention for use in low-fat or fat-free products, and in particular, if the sealing material is to be sterilized, the compound of the container lid sealing material is based on a TPS, preferably a SEBS mixed with a "hard" polyolefin. (with high shore D hardness, over 65).

The required softness and improved sliding properties at low temperatures (opening value) result in the compound by the addition of a "softer" polyolefin (with lower shore D hardness, below 60) and of oil.

In other preferred embodiments of the invention, especially when sterilizability is not important, the compound is based on a TPS, preferably SEBS, mixed with other polyolefins, e.g. LDPE, LLDPE and other PE copolymers.

SEBS is particularly suitable as TPS components, such as Kraton® G-types with a linear structure at a polystyrene content of approx. 30-35%. The compound generally contains 20 to 50%, preferably 30 to 40% TPS. The preferred SEBS has a high molecular weight and a high absorbency for oil. Shore A hardness may not be determined as the polymer in the pure state is not liquid enough to produce sample bodies. It is located on comparable materials over 70.

As the hard polyolefin, the compound preferably contains a propylene homopolymer with a shore D hardness above 65 and preferably of approx. 70 in content between 5 and 30%, preferably between 8 and 15%.

As the softer polyolefin, the compound preferably contains LLDPE, with a shore D hardness of approx. 50. Relevant LDPE content is preferably avoided. The softer polyolefin content is generally between 10 and 30%, preferably between 8 and 20%.

The compound contains, in particularly preferred variants, significant proportions of oil, especially medical paraffin oil. The content of oil will be higher the lower the operating temperatures of the container lid. In general, the oil content is between 5 and 50%, especially between 30 and 50%.

Embodiment Example 1: SEBS 33%

Gay PP 10.5% LLDPE 15%

Paraffin oil 40%

Pigment 0.3%

Fatty acid amide 1%

Stabilizer 0.2%

Shore A at 20 ° C: 73; at 4 ° C: 80

Deformation at room temperature: 13%; at 4 ° C: 35% Opening values at 4 ° C at 70 mm lid, 5 days: approx. 32 inches-lbs (about 37 cm-kg); 27 days: approx. 30 inch-lbs (about 35 cm-kg)

Voltage loss: 59% Sealing materials of this type are particularly suitable for general use in low-fat or fat-free foods at room temperature and also in the refrigeration chain, down to 0 ° C. They are less suitable for fatty foods because the high oil content can facilitate the migration of fatty components.

6.2 Oil-poor sealing materials In preferred embodiments of the invention, which are also suitable for use in very greasy products, the sealing material's compound is based on a TPS, especially SEBS mixed with an ethylene-octene copolymer, especially a random copolymer.

For such applications, in particular, a SEBS of type Kraton ® G is suitable with a polystyrene content of 11.5 - 13.5% and a shore A hardness of approx. 35. Such SEBS is liquid and has a reduced absorbency for oil.

As additional constituents, TPOs, i.e. polyolefin elastomers, especially PP elastomers, and ethylene-octene block copolymers are preferably used.

Considering higher content of SEBS, the compound can be provided with harder polymers such as e.g. LDPE.

In all of these embodiments, the sealing material contains less than 5% oil and is preferably oil-free.

When using polyolefin elastomers, the content of lubricants (especially fatty acid amide) is generally higher.

The TPS components preferably consist of SEBS, especially of the type Kraton® G. The content of TPS is generally between 5 and 70%, especially between 10 and 30%.

The ethylene-octene copolymer is preferably a random copolymer of the type Engage®. The content is broadly between 10 and 80%, especially between 20 and 60% and preferably between 20 and 35%.

The polyolefin elastomer is preferably a PP elastomer, especially of the Vistamaxx® type. The content of TPO is broadly at 10 to 50%, especially at 30 to 45%.

When the compound contains a TPO, in preferred variants a content of hard polyolefin, especially propylene homopolymer, is obtained. The hard polyolefin content is generally between 0 and 30%, especially between 15 and 25%.

Especially for variants without TPO content, the compound preferably contains significant proportions of ethylene-octene block copolymer, such as the Infuse® type. The content is widely between 10 and 80%, especially between 20 and 60% and preferably between 40 and 50%.

When using higher TPS content (above 25%), a hard polyolefin such as LDPE in particular can be used instead.

For these variants, the content of lubricants may be low and may be at 1% or less.

Embodiment Example 2: SEBS 24% PP Elastomer 40.3%

Homo-PP 18% random copolymer 12.5%

Pigment 0.3%

Lubricant 4%

Stabilizer 0.2%

Shore A hardness at 20 ° C: 78; at 4 ° C: 85 Deformation at room temperature: 32%; at 4 ° C: 47% Opening values at 4 ° C at 70 mm lid, 5 days: approx. 37 inches · Ibs (about 43 cmkg); 27 days: approx. 43 inches · Ibs (approx. 50 cm kg)

Voltage loss: 51%

Embodiment Example 3: SEBS 25% Random Copolymer 28%

Block copolymer 45.5%

Lubricant 1%

Pigment, stabilizer 0.5%

Shore A hardness at 20 ° C: 68; at 4 ° C: 72 Deformation at room temperature: 13%; at 4 ° C: 28% Opening values at 4 ° C at 70 mm lid, 5 days: approx. 35 inches · lbs (about 40 cm-kg); 28 days: approx. 37 inches · lbs (about 43 cm-kg);

Voltage loss: 55%

Claims (21)

Use of a sealing insert of a sealing material comprising at least one polymer with the exception of halogen-containing polymers, e.g. PVC, mixed with additional fabrics, characterized in that the sealing material at 20 ° C has a shore A hardness of maximum 90 and a pressure deformation (DVR) of maximum 40% and at 4 ° C a shore A hardness of maximum 100 and a DVR of a maximum of 50%, wherein the sealing material contains up to 60% by weight of liquid at 20 ° C and between 5 and 30% by weight polyolefin with a shore D hardness at 20 ° C of at least 60 for a container lid of metal or plastic for a container for receiving food or beverages under vacuum and when filling and / or storing at room temperature and below. Use according to claim 1, wherein the sealing material contains between 5 and 50% by weight of paraffin oil. Use according to claim 1 or 2, wherein the sealing material at 20 ° C has a shore A hardness of between 20 and 90, preferably between 50 and 85 and particularly preferably between 60 and 80, and at 4 ° C preferably a shore A. hardness of between 50 and 100, preferably between 70 and 90, and more preferably not more than 85. Use according to claims 1 to 3, wherein at 20 ° C the sealing material has a DVR of maximum 35%, preferably a maximum of 20%, and at 4 ° C preferably a DVR of maximum 50%, especially a maximum of 40% and especially preferably a maximum of 30%. %. Use according to one of claims 1 to 4, wherein in a creep test with compression at 70 ° C with 25% and subsequently free cooling, the sealing material has a loss of voltage of maximum 80%, preferably maximum 60%. Use according to one of claims 1 to 5, wherein the sealing material can be sterilized above 98 ° C and by a dynamic-mechanical thermo-analysis (DMTA) exhibits a heating curve for the phase angle tan (delta), whose turning point is above the required sterilization temperature. Use according to any one of claims 1 to 6, wherein the container lid is to be opened by screwing and the sealing material is composed in such a way that the container lid at approx. 0.5 bar vacuum in the container after 5 days storage of the closed container at 4 ° C and based on the diameter of the 70 mm lid has an average opening value of less than 508 cNm, preferably less than 475 cNm, more preferably less than 452 cNm and particularly preferred at no more than 395 cNm. Use according to any one of claims 1 to 7, wherein the sealing insert in the container lid is arranged in such a way that it seals in a closed state against the part of the container which forms the opening of the container, the container lid preferably consisting of metal. Use according to one of claims 1 to 8, characterized in that the container lid corresponds to a diameter of the container opening of more than 2.5 cm, preferably more than 3 cm, more preferably at least 3.5 cm, more preferably at least 3.8 cm and in particular more than 4 cm, and in particular lies at 58, 63, 66 or 70 mm. Use according to one of claims 1 to 9, characterized in that the container lid is designed as a screw cap for a bottle, a glass or the like. Use according to any one of claims 1 to 10, wherein the container lid is a twist off lid, a Press-on / Twist-off® lid, a metal-plastic composite lid, an assault lid, a crimp-on or disposable lid or a metal roller lid. . Use according to one of the preceding claims, characterized in that the sealing insert is designed as an inner insert on the inner surface and with Press-on / T wist-off® lid also on the skirt of the container lid ("contouring ring"). Use according to claim 11, characterized in that the sealing insert is annular or circularly shaped. Use according to one of the preceding claims, characterized in that the sealing material is designed in such a way that the sealing insert can be used in a heat treatment with or without pressure of the filled container for sterilization above 98 ° C, preferably above 105 ° C, especially preferably above 120 ° C and especially between 121 ° C and 132 ° C. Use according to one of the preceding claims, characterized in that the container lid in the closed state has a gas barrier effect and / or a pressure relief valve effect. Use according to one of the preceding claims, characterized in that the container lid 1 in closed condition exhibits vacuum retention. Use according to one of the preceding claims, wherein the sealing material does not contain plasticizers, especially phthalates. Use according to claim 2, wherein the sealing material contains between 20 wt% and 50 wt% and particularly preferably between 30 wt% and 50 wt% paraffin oil. Use according to claim 1 or 18, wherein the sealing material contains between 20 and 50%, preferably between 30 and 40%, TPS, especially SEBS or SIBS. Use according to claim 1.18 or 19, wherein the sealing material contains between 5 and 30 wt%, preferably between 8 and 15 wt%, homo PP in the form of homo PP with a shore D hardness at 20 ° C of at least 60. Use according to any one of claims 1 or 18 to 20, wherein the sealing material contains between 10 and 30 wt%, preferably between 8 and 20 wt%, polyolefin with a shore D hardness at 20 ° C of less than 60, especially LLDPE.