DE1203110B - Process for increasing the impermeability of containers and containers treated according to the process - Google Patents

Description

Method of increasing the impermeability of containers and according to Containers treated by the method The invention relates to a method for Increasing the impermeability of containers made up of at least two by means of one thermoplastic adhesive layer interconnected layers of paper, cardboard, Foil or the like. The adhesive layer consists of a risk of damage when producing folding grooves in the container blank or when folding the container underlying material.

When using such a layer material it can happen that that when introducing holes, cuts or the like. Along the fold lines or when Wrinkles themselves damage occurs in the adhesive layer, causing a leak represent and in later use of the container in particular an undesirable Allow water vapor diffusion.

The object of the invention is therefore that in the adhesive layer Damage caused when making creases or when folding the container to fix to increase the impermeability of the sealed container. These The object is achieved according to the invention in that the adhesive layer in the areas the introduced fold lines by applying pressure and / or heat to melt them brought or at least softened. This ensures that the adhesive layer is placed in a plastic state along the endangered points, so that repaired any damage in the adhesive layer caused by the flow of the material will. In particular, a continuous water vapor barrier is achieved.

To make it easier to unfold a container from a blank, holes or cuts are generally made at short intervals along the fold lines or the fold line is created by an embossed fold groove. Even the holes can only be embossed so that they do not penetrate the layers of the material pass through, just reach into it. In all of these cases the adhesive layer can be damaged by the introduction of these folding grooves etc. With the method according to the invention, all possible are produced in this way Damage subsequently repaired. But even if the material is through the Insertion of the folding grooves has not been damaged by the folding process only damage to the adhesive layer occurs along the fold line. Even such injuries would have a permeability of the closed container Episode.

However, this is made perfect by the method according to the invention avoided.

The method of the invention is explained in more detail with reference to the drawing. It shows Fig. 1 a container blank, the fold lines are denoted by A, F i g. 2 shows a cross section along II-II according to FIG. 1, Fig. 3 is a side view of the folded blank in the direction III-III according to FIG. 1, Fig. 4 shows a cross section like the one according to FIG. 2, in which the sections adjacent to the fold line A by one Angles of about 1800 are folded, Fig. 5 is a side view of the unfolded Container in which the sections adjacent to the fold line A form an angle of 90 "together, FIG. 6 shows a cross-section similar to FIG. 2, but with unfolded container according to FIG. 5, FIG. 7 shows a cross section similar to FIG. 6, however, after using the method according to the invention, and FIG. 8 shows a cross section like F i g. 4, but after the method according to the invention has been carried out.

The container blank 10 made of laminated, plate-shaped material consists of front surface 11, rear surface 12 and side surfaces 13 and 14. The fold lines are shown in dashed lines. According to FIG. 2 the fold line is marked by a at A indicated folding groove formed by pressing a recess in the container blank originated. As can be clearly seen from FIG. 4, the cardboard layer is at 43 40 damaged in the area of fold line A. The paper layer 42 also has at 44 damage.

The two damage 43 and 44 can Adhesive layer 41 be injured. At least, however, after the container has been unfolded (Fig. 6) Microscopic cracks can form in the adhesive41 along the fold line A, so that the impermeability to gases and liquids in this area is not more is guaranteed.

After the pressure and / or heat treatment according to the invention the areas change along the fold lines A, as in FIG. 7 shown is. The constrictions of the outer layers at 43 and 44 as well as the one in FIG. 6 shown Rift 50 have disappeared. The area along the fold line is homogenized.

F i g. 8 explains the application of pressure and / or heat before the Unfold in the state indicated in Figure 7. The homogenized state of the endangered Areas is therefore retained even after being unfolded.

Another embodiment of the invention deals with the Fold lines in the folded state of the container surfaces around 1800 by applying from pressure and / or heat. The treatment is preferably carried out during or after the gluing process, at least before the container is erected. In Fig. 7 you can see on the erected container that the inner layer 42 by folding at the Treatment according to the invention is shifted against the fold line. Of the following Examples, Example 4 relates to this embodiment.

The damage to the adhesive layer is particularly serious, if one or more of the container layers are thicker than these thermoplastic ones Adhesive layer. Accordingly, the impermeability naturally deteriorates of the material for gases and liquids.

Mainly the adhesive layer is weakened when the container is folded or damaged, and the subsequent gluing and folding processes do the rest, destroy the protective layer.

With the help of an alcoholic dye solution, which in the smallest If cracks penetrate the thermoplastic adhesive, they can even be examined microscopically Detect invisible imperfections. The water vapor permeability of the test Container material can also be determined by folding one out of it Filling container with anhydrous calcium chloride, sealing it tightly and at normal Pressure and given humidity determines its weight gain. If pinhole-like If there are defects, there is a good correlation between the two aforementioned Test procedure.

The inventive treatment of the container folding lines is preferably carried out, after the main folds have been made; d. That is, in many cases it is sufficient if only those kinks are treated which were first around 1800 and then folded back to 90 ".

The heat treatment of the fold lines works equally well with those that can be glued or heat sealable containers.

The treatment according to the invention is particularly applicable to as Laminating agents comprising waxes or compositions of microcrystalline waxes, preferably if they melt at 55 to 85 "C or if the laminating agent is made of paraffin wax with the addition of polymers. Laminating agents such as asphalt, polyethylene, Polyethylene and cellulose derivatives. Micro- crystalline waxes or paraffin wax with additives such as rubber, vegetable gum and other film-forming agents Elastomers.

The fold lines to be treated can be punched, cut, serrated, pressed in or produced by a combined process.

Suitable container materials are paper, cardboard, films, foils, regenerated cellulose, etc. Under the name "paperboard" is strong, arched Paper to be understood with a weight of more than 164 g per square meter of surface or a thickness greater than 0.175 mm, as is usually the case on the cylinder or the Fourdriner machine will be produced. Thinner or lighter material is referred to here as "paper". As already stated, the treatment according to the invention is particularly indicated when if the container material has a greater layer thickness than the thermoplastic Adhesive.

The treatment is also beneficial for container materials made from consist of more than two layers, especially if the strongest of these layers is thicker is than the entire laminating agent. The process can even be used to advantage Use on layers of laminating agent only 0.025 mm thick. The observation could specially made on a thin layer of microcrystalline wax.

It is usually sufficient to heat treatment on the area of the fold lines focus, preferably up to about 8 mm from the fold lines.

The treatment must be so intense that the thermoplastic adhesive flows. This is the case for most representatives of this class of substances, if that Penetration per ASTM test American Society For Testing Materials) D 5-25 a Exceeds a value of about 60; d. i.e., the heat treatment can be above that Temperature limit take place where the test value 60 is determined.

In some cases the container material does not allow use substantial pressures, one must then heat treatment at a correspondingly higher one Temperature, possibly above the melting point of the adhesive.

Example 1 With a number of container areas, as in Table 1 and F i g. 1 described in more detail, the hems are glued and folded over at two fold lines 1800. A first group of containers is then heat sealed on one side, each loaded with 50 g of anhydrous calcium chloride and then also on the other Hot sealed side. Then the containers become more relative in a room at 50 ° / 0 Humidity is kept until the periodic weight determinations reach a constant Show increase. A second group is treated in the same way, but reheating is carried out closing the sections between two container surfaces along the fold lines under light pressure with a hot iron of two 5 mm wide heating surfaces, which are placed at an angle to 205 "C and compare the transmittance these sections with that of corresponding sections of untreated containers; a third untreated group of containers was subjected to the penetration test alcoholic dye solution and also a fourth group without calcium chloride filling the heating according to the invention under pulled. The test results are in the table II compiled.

Table I Description of the laminated raw material for the production of the cardboard surfaces (1 Rieß -276 m2) Arc- Composition and thickness Be outer layer Inner layer of the thermoplastic laminating adhesive drawing A 0.3 mm thick Dutch sulfite paper: 13.0% attapulgite Coated tallow amide, hydrogenated with 40 g / m2 * {1.5%, as surface-active bleached cardboard. Agent (Armid HT) 1.50 / o TiO2 84.0% microcrystalline wax (Layer thickness: 0.15 mm) B 0.3 mm thick 43 g / m2 vegetable like A coated, parchment bleached cardboard C 0.35 mm thick, 82 g / m² dry 1.66 0 / o Armid HT (as above) solid cardboard waxed 13.34% attapulgite Sulfite paper 85.00 0 / o microcrystalline wax (Layer thickness: 0.15 mm) D as in C as in C 7,0 0 / o alkylammonium montmorillonite (benton) 93.0 ° / 0 microcrystalline wax (Layer thickness: 0.15 mm) E 0.15 mm thick Dutch sulphite paper 10.0% attapulgite lithographic with 40 g / m2 1.5% Armid HT (as above) 120 g / m² paper | | 1.5% TiO2 87.0% microcrystalline wax (Layer thickness: 0.15 mm) F 0.42 mm thick 82 g / m2 dry 3.6% butyl rubber coated, waxed 96.4% microcrystalline wax bleached cardboard sulfite paper (layer thickness: 0.15 mm) G 0.3 mm thick 57 g / m2 0.075 mm composition of microcrystalline wax too bleached cardboard thick coated 33 g / m2 (layer thickness: 0.325 mm) Fourdrinier paper for Rotagravur printing (»Roto paper«) H 0.075 mm thick 0.3 mm thick As G coated bleached cardboard »Roto paper« with 57 g / m² I Like H 0.4 mm thick composition of microcrystalline wax bleached cardboard at 49 g / m2 (layer thickness: 0.05 mm) J 0.4 mm thick painted like I. bleached cardboard | »Roto paper« with 57 g / m2 K 0.3 mm thick As F Composition of microcrystalline wax bleached cardboard layer thickness: 0.15 mm) *) Together they form a thixotropic mixture.

Table II Weight Gain in grams / day / container Bow- with un- edges underneath factor Color test before and after treatment treated minor Group 1 Type of fold line drawing edges pressure heated Group 2 Table I (Group 1) (Group 2) (Group 3) (Group 4) A punched 0.22 0.03 7+ penetration no penetration A cut 0.20 0.03 7- the same. (without injury the adhesive layer) B punched 0.13 0.04 3t the same. C punched 0.15 0.09 2- like. D punched 0.19 0.08 2t the same. E punched 0.07 0.04 2- alternately the same. penetration EXAMPLE 2 Heat-sealable containers made of Fourdrinier cardboard and thus light paper layers laminated together by means of a 0.15 mm thick film of microcrystalline wax are tested by filling them with various foods and placing them in a room of 23 ° C and 50 ° / 0 relative humidity is stored until the periodic weight determinations show a constant increase. The edges are then treated over a width of 3 mm for 2 seconds under low pressure with a hot iron at 2320 ° C. and the increase in weight of the container is determined again. In all cases, heating the fold lines made the containers denser (see Table III).

Example 3 In a number of laminated sheets of material in Fold lines scored on a container tester and then in the fold lines around 1800 folded and folded back to 90 °. Then you treat the inside of the edges For 2 minutes with an alcoholic dye solution. A second series of tests of the same kind The container was then heat-treated as described in Example 1 (for results see Sect. Table IV).

It turns out that the method according to the invention is well suited for the treatment of laminates where the single paper layer is thicker than the adhesive layer.

Table III Weight gain in grams / day / container at 23 ° C and 50% relative humidity Fold lines Packaged material designation factor Table I heated untreated Brown sugar ...................... F -0.014 -0.002 7 Skimmed milk powder .................... F +0.033 +0.005 6+ Sweetened cereals .................... F +0.017 +0.005 3+ Skimmed milk powder .................... A +0.055 +0.005 2+ Sweetened cereals .................... A +0.032 0.000 # (or very large) Dried potato powder ................ A +0.057 +0.008 7+ Table IV Determination of Penetration by Color Tests Arc color test the color test of the loading untreated edges heated edges drawing 93 mm long by 93 mm long Table of 1 mm length by 93 mm length G by penetrating a needle hole stained all over Colored length H complete through- slightly stained, penetration, no penetration seven spots of urgency I normal no penetration penetration J normal penetration Penetration through a small one Job K normal no penetration Penetration and no stains Example 4 Grooves are embossed and pressed into containers made of the following raw material: A. Coated cylinder cardboard, 0.43 mm thick, laminated together with a Holländer-Fourdrinier paper of 61 g / m2 and a thickness of 0.075 mm with the aid of a composition of thermoplastic microcrystalline Wax at 147 g / m2; B. 0.2 mm thick Foudlinier cardboard, which is laminated with the help of 148 g / m2 microcrystalline wax on a Fourdrinier wrapping paper with 66 g / m2.

The containers were glued and folded by 180 ° C. on two edges.

After erecting the container, the inside of the was kinked Edges wetted with alcoholic dye solution, with strong penetration.

If you use the iron to remove the container surfaces, which have been pre-folded on 1,800 heated along the fold line and then straightened up, nothing occurs in the dye test Penetration on.

A number of such containers, some heat-treated, some not, were charged with anhydrous calcium chloride, sealed, and the weight gain is determined during storage at a relative humidity of 50% and 23 ° C. Table V shows the results.

Table V Weight increase in grams / day / container at 50% relative humidity and 23 ° C After heating Only glued, the one around 180a untreated folded arc Material A .......... 0.17 0.10 Material B ........... | 0.20 | 0.13 The numbers make it easy to see the restoration of the gas and liquid impermeability of the containers as a result of the treatment according to the invention.

Claims (9)

Claims: 1. Method for increasing the impermeability of containers consisting of at least two means a thermoplastic Adhesive layer interconnected layers of paper, cardboard, foil or the like. consist, the adhesive layer from one of the risk of damage during manufacture of folding grooves in the container blank or underlying when folding the container Material consists, characterized in that the adhesive layer in the areas of introduced fold lines melted by the application of pressure and / or heat or at least softened. 2. The method according to claim 1, characterized in that the fold lines are pressure and / or heat treated after the intermediate container sections are fully folded are. 3. The method according to claim 1, characterized in that the fold lines are pressure and / or heat treated when the container surfaces are folded flat on top of one another are. 4. The method according to claim 1, characterized in that the adhesive layer is melted after partial erection of the container blank. 5. The method according to claim 1, characterized in that the collapsible container along the fold lines the 180 "C pre-folded sections is treated. 6. By the method according to one or more of claims 1 to 5 treated container, characterized in that the adhesive layer consists of microcrystalline Waxing compound. 7. Container according to one or more of claims 1 to 6, characterized characterized in that at least one of the layers of material laminated together is thicker is than the adhesive layer. 8. Container according to one or more of claims 1 to 7, characterized characterized in that at least two of the material layers are made of paper or cardboard exist. 9. Container according to one of claims 1 to 7, characterized in that that one layer of material consists of paper and a second layer of cardboard. Publications considered: Swiss patent specification No. 248 809; U.S. Patent Nos. 2,288,896, 2,962,405.