PROCESS FOR PREVENTING PACKAGING FILMS FROM SLIPPING ON EACH OTHER

Description

Technical Field

[0001] The invention relates to a process for preventing thermoplastic packaging films from slipping on each other and a suitable system for such purpose. In the present context the term of "film" also includes plastic products of different thicknesses such as plates, sheets, pellicles, which may optionally be supplied with a base or may be covering layers as well. The technical term "films" also means plate-like products of different thickness varying from entirely thin to markedly thick products.

Background Art

[0002] It is known that the process for production of thermoplastic films starting from the appropriate mixtures or granules is made so that the unprocessed material is melted or moulded by heating and the desired product is formed in a tool by die-casting or pressing the material through the gap of an extruding die.

[0003] The gap does not necessarily determine a flat film, for example in case of hose-like products it can be round shaped as well.

[0004] In order to gain its final shape and for the purpose of its stabilisation at leaving the gap of the tool or being taken out of the mould the moulded product is congealed by cooling. Most often the cooling is made by blowing cold air on. After cooling undesired deformation does not occur any more, so cutting to size, winding etc. can take place.

[0005] The quality of films' surfaces is depending mostly on the surface of the tool; in general that is completely plain.

[0006] Similarly to the manners as stated above thermoplastic films can be moulded by heat transmission again and may be subjected to further processing.

[0007] In connection with the products prepared from plastic films it often creates difficulties that film products, for example folders put on top of each other, are slipping on each other, which can cause falling out of documents, thus the pieces of paper can get dirty and damaged or spoiled. In the same way, in case of plastic sacks instead of the earlier conventional sacks made of textile put on top of each other, when setting up upper sacks, in case of the smallest displacement of the centre of gravity plain surfaces lying on each other can slip on each other to say nothing of shake which takes place in the course of shipment and interplant transport.

[0008] Until now various attempts have been made to prevent plastic sacks from slipping on each other. The most obvious procedure seemed to be to coat sack surfaces lying on each other with adhesive. This solution has raised the problem of choosing the adhesive and the quality of the adhesive. Mostly, when adhesive of an excellent quality was used, it was difficult to pull the sacks apart without the consequence of damaging (deterioration) of the plastic film, while using an adhesive of poor quality due to the insufficient adhesion strength, the task could not be deemed to be solved either.

[0009] As an other type of solution it was tried to create antislip surfaces by forming unevenness from the material of the film. According to a typical solution of that kind the film was embossed from the direction of the internal side of the sacks so that humps were formed on the external side of the sacks. According to an other solution based on a similar principle grooves were formed in the die casting machine before the gap which created ribs on the films' surface in the direction of the material's movement. By this means the problem was solved in part only because the slipping could only be prevented perpendicularly to the line of the aforementioned ribs, the product was able to slip freely in the other direction. Antislip surface on extruded film sheets was tried to create also by forming tips and cavities between the tips on the cylinders forwarding the film by which formations rising from the surface were created. Although these formations were theoretically suitable to prevent slipping in any direction, the required effect could not be achieved.

[0010] According to an other solution also known from the prior art unprocessed plastic granules were mixed with extraneous substance which could not be incorporated homogeneously into the basic plastic and humps were formed. However in the course of that kind of method the extruder and the connected passing cylinders were exposed to abrasion, so the tool was getting deteriorated early and besides it was impossible to keep control over the' disposal of humps as it would have been required.

[0011] A procedure was also applied, where humps were formed on both sides of the film by mixing the raw material with some chemical additive. The drawback of that procedure is its high cost, because the additive, having a high price, was demanded in quite large quantities, and also that both sides of the product were provided with humps, which limited the scope of utilisation.

[0012] All of the aforementioned procedures are costly, uneconomical and are not as efficient as it would be required. These methods are used because until now there have been no adequate processes which would solve the problem favourably. A further disadvantage of all these solutions is that humps and formations rising from the surface are covered by the material of the film itself and, although they are subjected to greater abrasion effect, their resistance to abrasion is equal to that of the other parts of the film.

[0013] The common disadvantage of the solutions described above is that, due to its extenuation or its having extraneous substance particles implied in its structure, the tensile strength of the product is reduced.

[0014] From DE 42 07 210 a process has been known according to which the surface of a thermoplastic film material is warmed or partially softened in order to form a molten layer for embedding particles into the same. The film obtained should be warmed, preferably two times and/or pressing rolls are applied to ensure a safe adhesion/fixing. The specification teaches to provide a deep embedding of the particles into the surface. The material of the said particles may be very different, their geometric features are not critical.

[0015] DE 34 37 414 discloses films with roughened areas with protrusions for preventing thermoplastic films from slipping. FR 13 34 410 teaches to prevent slipping of stacked plastic sacks by providing a binding element on the sacks, and GB 21 65 203 refers to the packaging of infusion bags containing e.g. tea.

Disclosure of Invention

[0016] The object of the invention is to provide a process for preventing packaging films from slipping on each other which eliminates the deficiency and drawbacks of the methods known from the state of the prior art. This is achieved by the process on the system as defined in attached claims 1, 11. Preferred embodiments are disclosed in the subclaims.

[0017] The films are roughened if particles consisting of the substance of the film and/or other plastic material being able to weld together with that, and having suitable size are brought to the melted film, are used. The temperature of the particles at their sides looking on the film surface will increase and also themselves will be melted at least partly and will be strongly welded together with the film. Standing out of the surface at least partly, these particles make the surface rough.

[0018] The surface of the moulded film, as a semi-finished article, just leaving the gap of the extruder die during the manufacturing process can as well be roughened as, by reheating it, that of previously finished film.

[0019] The substantial quality of the particles used for the creation of roughened surfaces should be selected so that their abrasion resistance and similarly the particle size are suitable for this purpose. If desired, a homogeneous fraction of particles such as particles representing a fraction separated by passing through sieves, are applied to the surface.

[0020] The film can be heated with any of the methods known from the state of the prior art, for example with blowing on hot air, electrical heating etc.

[0021] The particles may be applied in well ordered or disordered configuration to the entire surface or to specified surface areas such as edges or, if demanded, in spots, repeating the application once or several times depending on the desired pattern. For example the pattern may be formed by using templates or otherwise.

[0022] The process according to the present invention is extremely economical, because no special chemical additives and no change of the tool for preparation of the film are needed and similarly, the particular conditions and parameters of the manufacturing procedure are remaining the same. Quite often it is sufficient to use films roughened on one side only, however, in accordance with the present invention optionally film made rough either both sides, or only one side may be used as well.

[0023] At least on one side of on the entire surface or on specified areas of the surface of the films are provided with protrusions consisting of particles having substance of the film and/or other plastic material being able to weld together with the substance of the film, which are welded into the surface and at least partly standing out of the surface.

Best Mode for Carrying Out the Invention

[0024] The essence of the process is that a system comprising films to be fixed - at least one of them is roughened - and a binding element is formed applying a roughened film with protrusions of suitable closeness and geometric features with respect to the binding element on its surface; a binding element having a loose fibrous structure and individual fibre-stability is placed on the film or on its specified parts, on the entire surface or on surface part(s) which binding element comprises fibres of such closeness, geometry and layer thickness that between the fibres of binding element and the protrusions of the roughened film a mechanical joint is formed.

[0025] The welding surface between the film surface and the particles forming the protrusions is preferably such that the inter-section of the particles and the plane of the film does not cover the shape of projection of particles viewed perpendicularly to said film sheet.

[0026] According to one preferable embodiment of the present invention roughened film sheets are used on both surfaces of the binding element.

[0027] According to a further preferable embodiment of the present invention the binding element is fixed to one of the two film sheets (to that one which is not roughed); by sticking, welding or sewing.

[0028] It is also preferable if the thickness of the binding element reaches at most up to or more preferably is less than the greatest value of the projection of the particles in the surfaces, roughened with plastic particles, of the two film sheets to be connected with each other.

[0029] Suitably a binding element based on plastic, having well ordered or disordered fibrous structure, such as non-woven fabric, forming veily film and having reticular structure, prepared by thermo-fleece technology is used.

[0030] When in practical use, roughened plastic film-binding element-roughened plastic film' tripartite system is built, the resulted three-member joint will be strong enough to withstand also greater mechanical stress without slipping. At the same time the joint can be broken off simply, because though in the direction of the slipping on each other the layers are stabilised, in case of necessity elements can easily be lifted off each other.

[0031] For the mechanical joint of the surfaces it is needed that there are bigger protrusions of lower density or smaller protrusions being closer to each other in the surface, so a certain part of the surface needs to comprise protrusions. The relation between size and closeness of protrusions is determined by several factors such as the thickness of the film and its resistance to mechanical stress or that can be decided depending on the field of application.

[0032] Geometric shape of particles is important because in case of plainly lying, lenticular, archedly rounded particles, where for example the welding line is long, the fibres being between the particles obviously can not keep on holding them as it would be desired, they slide off, they do not get stuck in cavities between them.

[0033] As it was mentioned above, the binding element has a fibrous structure and, in addition, fibres must have suitable individual stability to prevent the particles from tearing it apart and the fibres from slipping off it when stress in the direction of slipping arises. In addition the structure of the binding element must be loose enough to let the protrusions penetrate into the fibrous structure. As binding element may be used a fabric with disordered structure, fleece, felt, etc., where fibres are bound together by using known procedures such as adhesive way, sewing, spot-welding etc.

[0034] Films made suitable for the purpose of packaging are usually wound and stored in rolls, at the utilisation they are cut to size and the packaging is carried out.

[0035] The place where the binding element will get into is already determined at the roughening process of the film, accordingly at production of the film, when smooth film, which, from the invention point of view, is described as a semi-finished product, is in the appointed places of its surface made rough with taking the desired position of the binding element into account but it is also possible to provide the smooth finished film with roughness in the places where necessary. Films may contain a self adhesive layer on their surface, if required, too.

[0036] The system according to the present invention is characterised in that it comprises roughened film having protrusions of suitable closeness and geometric features with respect to the binding element, and on the roughened film or on specified parts of its surface it has a binding element having a loose fibrous structure and individual fibre-stability, the binding element contains fibres of such closeness and layer thickness that between the fibres of the binding element and the protrusions of the roughened film a mechanical joint is formed.

EXAMPLES

[0037] The present invention is illustrated by an antislip system as follows:

Example 1

[0038] Plastic granules are usually packaged in plastic sacks of 25 kg of weight and these sacks are transported on pallets put on top of each other in stacks in quantities of more than 1000 kgs each. To prevent such sacks from slipping up on each other, sacks are prepared from roughened films. The sacks are prepared from gusseted tube on a packaging machine. To prevent slipping both sides of the film tube, except the part which is gusseted, are made rough so that at least 50 protrusions pro square centimetre should be in the roughened parts of the surface. Thus the filled sacks lie on each other with their roughed parts of surfaces. Fleece bands of 10 cm of width and 30 cm of length are used as binding elements. When the packaging machine finished filling up a sack, that is forwarded on a conveyer to the stacking machine. A piece of fleece band is placed on each sack lying on the moving conveyer before reaching the stacking machine so that it is placed lengthwise in the middle of the sack. The sacks are put on each other by the stacking machine so that each sack, in a part of their common contact surface, contacts the adjoining sacks being one line above with the mediation of the binding element. The fibres of the binding element are clinging to the upper and lower sacks and fasten them to each other with a mechanical joint and prevent them from slipping on each other.

Claims

1. Process for preventing thermoplastic packaging films from slipping on each other wherein a system comprising films to be fixed - at least one of which is roughened - and a binding element is formed by applying the roughened film with protrusions on its surface having suitable closeness and geometric features with respect to the binding element; the binding element having a loose fibrous structure and individual fibre-stability is placed on one of the films at least on its part(s) to be bound with the roughened surface of the other film on the entire surface or on surface part(s), which binding element comprises fibres of such closeness and layer thickness that between the fibres of binding element and the protrusions of the roughened film a mechanical joint can be formed, wherein in case a non-roughened film is applied as a part of the system, a fixing is formed between the binding element and the surface or surface part(s) of the non-roughened film.

2. The process as claimed in claim 1 wherein the protrusions are formed by particles.

3. A process as claimed in claim 2 wherein the inter-section of the particles and the plane of the film does not cover the shape of projection of particles viewed perpendicularly to said film.

4. A process as claimed in any of claim 1 to claim 3 wherein roughened film sheets are used on both surfaces of the binding element.

5. Process as claimed in any of claims 1 to 4 wherein the binding element is fixed to one of the two film sheets.

6. A process as claimed in claim 5 wherein the binding element is stuck to one of the two film sheets.

7. A process as claimed in claim 5 wherein the binding element is welded to one of the two film sheets.

8. A process as claimed in claim 5 wherein the binding element is sewn to one of the two film sheets.

9. A process as claimed in any of claims 2 to 8 wherein the thickness of the binding element reaches at most up to, preferably is less than the greatest value of the projection of the particles in the surfaces, roughened with plastic particles, of the two film sheets to be connected with each other.

10. A process as claimed in any claims of 1 to 9 wherein the binding element based on plastic having well ordered or disordered fibrous structure such as a non-woven fabric, forming veily film and having reticular structure prepared by thermo-fleece technology is used.

11. System for preventing thermoplastic packaging films from slipping on each other wherein said system comprises

a) films to be prevented from slipping on each other,

b) at least one of the films being roughened in the whole or in parts of its surface with protrusions in its surface, the protrusions having suitable closeness and geometric features,

c) a binding element placed between the films to be prevented from slipping on each other,

d) the binding element having a loose fibrous structure and individual fibre-stability and further comprising fibres of such closeness and layer thickness that a mechanical joint is formed between the fibres of the binding element and the protrusion of the roughened film(s),

e) and in case one of the films is non-roughened, the non-roughened film is fixed to the binding element.

12. The system as claimed in claim 11 wherein in case one of the films is non-roughened, it is fixed to the binding element with sticking, welding and/or sewing.

13. A system as claimed in any of claims 11 to 12 wherein the protrusions are formed by particles.

14. A system as claimed in claim 13 wherein the inter-section of the particles and the plane of the film does not cover the shape of projection of particles viewed perpendicularly to said film.

15. A system as claimed in any of claims 13 to 14 wherein the thickness of the binding element reaches at most up to, preferably is less han the greatest value of the projection of the particles in the surfaces, roughened with plastic particles, of the film(s).

16. A system as claimed in any of claims 13 to 15 wherein the binding element is based on plastic having well ordered or disordered fibrous structure such as a non-woven fabric, forming veily film and having reticular structure prepared by thermo-fleece technology.

Ansprüche

1. Verfahren zum Verhindern des Aufeinanderrutschens von thermoplastischen Verpackungsfolien, wobei ein System, das zu fixierende Folien - wobei mindestens eine davon aufgeraut ist - und ein Bindungselement umfasst, durch Aufbringen der aufgerauten Folie mit Vorsprüngen auf ihrer Oberfläche mit geeigneter Dichte und geeigneten geometrischen Merkmalen in Bezug auf des Bindungselement gebildet wird, wobei das Bindungselement mit einer lockeren Faserstruktur und Stabilität der einzelnen Fasern auf den Folien zumindest an (einem) Teil(en), der mit der (die) aufgerauten Oberfläche der anderen Folie auf der gesamten Oberfläche oder auf einem Oberflächenteil(en) zu verbinden ist (sind), positioniert wird, wobei das Bindungselement Fasern mit einer derartigen Dichte und Schichtdicke umfasst, das zwischen den Fasern des Bindungselements und den Vorsprüngen der aufgerauten Folie eine mechanische Verbindungsstelle gebildet werden kann, wobei im Falle des Aufbringens einer nicht aufgerauten Folie als Teil des Systems, eine Fixierung zwischen dem Bindungselement und der Oberfläche oder (dem) Oberflächenteil(en) der nicht aufgerauten Folie gebildet wird.

2. Verfahren nach Anspruch 1, wobei die Vorsprünge durch Teilchen gebildet werden.

3. Verfahren nach Anspruch 2, wobei der Schnittpunkt zwischen den Teilchen und der Folienebene die senkrecht zu der Folie betrachtete Form der Teilchenprojektion nicht bedeckt.

4. Verfahren nach einem der Ansprüche 1 bis 3, wobei aufgeraute Folienlagen auf beiden Oberflächen des Bindungselements verwendet werden.

5. Verfahren nach einem der Ansprüche 1 bis 4, wobei das Bindungselement auf einer der beiden Folienlagen fixiert wird.

6. Verfahren nach Anspruch 5, wobei das Bindungselement auf eine der beiden Folienlagen geklebt wird.

7. Verfahren nach Anspruch 5, wobei das Bindungselement auf eine der beiden Folienlagen geschweißt wird.

8. Verfahren nach Anspruch 5, wobei das Bindungselement auf eine der beiden Folienlagen genäht wird.

9. Verfahren nach einem der Ansprüche 2 bis 8, wobei die Dicke des Bindungselements höchstens den größten Wert der Teilchenprojektion in den mit Kunststoffteilchen aufgerauten Oberflächen der beiden miteinander zu verbindenden Folienlagen erreicht, vorzugsweise weniger beträgt.

10. Verfahren nach einem der Ansprüche 1 bis 9, wobei das Bindungselement auf der Basis eines Kunststoffs mit gut geordneter oder ungeordneter Faserstruktur wie eines durch Thermofleece-Technologie hergestellten Vlieses, das eine verhüllte Folie bildet und netzförmige Struktur aufweist, verwendet wird.

11. System zum Verhindern des Aufeinanderrutschens von Verpackungsfolien, wobei das System Folgendes umfasst:

a) Folien, deren Aufeinanderrutschen zu verhindern ist,

b) wobei mindestens eine der Folien in der gesamten oder in Teilen ihrer Oberfläche mit Vorsprüngen auf ihrer Oberfläche aufgeraut sind, wobei die Vorsprünge eine geeignete Dichte und geeignete geometrische Merkmale aufweisen,

c) eine Bindungselement, das zwischen den Folien, deren Aufeinanderrutschen zu verhindern ist, positioniert ist,

d) wobei das Bindungselement eine lockere Faserstruktur und Stabilität der einzelnen Fasern aufweist und des Weiteren Fasern mit einer derartigen Dichte und Schichtdicke umfasst, dass eine mechanische Verbindungsstelle zwischen den Fasern des Bindungselements und den hervorstehenden Teilen der aufgerauten Folie(n) gebildet wird.

e) und in dem Falle, in welchem eine der Folien nicht aufgeraut ist, die nicht aufgeraute Folie auf dem Bindungselement fixiert ist.

12. System nach Anspruch 11, wobei in dem Falle in welchem eine der Folien nicht aufgeraut ist, sie durch Kleben, Schweißen und/oder Nähen an das Bindungselement fixiert ist.

13. System nach einem der Ansprüche 11 bis 12, wobei die Vorsprünge durch Teilchen gebildet sind.

14. System nach Anspruch 13, wobei der Schnittpunkt zwischen den Teilchen und der Folienebene die senkrecht zu der Folie betrachtete Form der Teilchenprojektion nicht bedeckt.

15. System nach einem der Ansprüche 13 bis 14, wobei die Dicke des Bindungselements höchstens den größten Wert der Teilchenprojektion in den mit Kunststoffteilchen aufgerauten Oberflächen der Folie(n) erreicht, vorzugsweise weniger beträgt.

16. System nach einem der Ansprüche 13 bis 15, wobei das Bindungselement auf einem Kunststoff mit gut geordneter oder ungeordneter Faserstruktur wie einem durch Thermofleece-Technologie hergestellten Vlies basiert, das eine verhüllte Folie bildet und netzförmige Struktur aufweist.

Revendications

1. Procédé pour empêcher des films d'emballage en thermoplastique de glisser l'un sur l'autre, dans lequel l'on forme un système comprenant des films à fixer - dont l'un au moins est rugueux ― et un élément de maintien par application au film rugueux, à sa surface, de reliefs présentant une proximité et des caractéristiques géométriques appropriées par rapport à l'élément de maintien ; on place l'élément de maintien présentant une structure fibreuse lâche et une stabilité de fibre individuelle sur l'un des films au moins sur une (des) partie(s) à maintenir avec la surface rugueuse de l'autre film sur toute la surface ou sur une (des) partie(s) de la surface, que l'élément de maintien comprend des fibres dont la proximité et l'épaisseur de couche sont telles qu'entre les fibres de l'élément de maintien et les saillies du film rugueux une jonction mécanique peut être formée, dans lequel dans le cas où l'on applique comme partie du système un film non rugueux, on forme une fixation entre l'élément de maintien et la surface ou la (les) partie(s) de surface du film non rugueux.

2. Procédé selon la revendication 1, dans lequel les reliefs sont formés par des particules.

3. Procédé selon la revendication 2, dans lequel l'intersection des particules avec le plan du film ne couvre pas la forme de projection des particules vues perpendiculairement audit film.

4. Procédé selon l'une des revendications 1 à 3, dans lequel des feuilles de film rugueux sont utilisées sur les deux surfaces de l'élément de maintien.

5. Procédé selon l'une des revendications 1 à 4, dans lequel l'élément de maintien est fixé à l'une de deux feuilles de film.

6. Procédé selon la revendication 5, dans lequel l'élément de maintien est appliqué contre l'une de deux feuilles de film.

7. Procédé selon la revendication 5, dans lequel l'élément de maintien est soudé à l'une de deux fouilles de film.

8. Procédé selon la revendication 5, dans lequel l'élément de maintien est cousu à l'une de deux feuilles de film.

9. Procédé selon l'une des revendications 2 à 8, dans lequel l'épaisseur de l'élément de maintien atteint au plus, de préférence est inférieure à, la plus grande valeur de la projection des particules dans les surfaces, rendues rugueuses avec des particules de plastique, des deux feuilles de film à relier l'une à l'autre.

10. Procédé selon l'une des revendications 1 à 9, dans lequel on utilise l'élément de maintien à base de plastique présentant une structure fibreuse bien ordonnée ou désordonnée telle qu'une étoffe non-tissée, formant un film en voile et présentant une structure réticulaire préparée par technologie de nappage thermique.

11. Système pour empêcher des films d'emballage en thermoplastique de glisser l'un sur l'autre, dans lequel ledit système comprend

a) des films que l'on doit empêcher de glisser l'un sur l'autre,

b) au moins l'un des films étant rugueux sur tout ou partie de sa surface avec des reliefs à sa surface, les reliefs présentant une proximité et des caractéristiques géométriques appropriées,

c) un élément de maintien placé entre les films que l'on doit empêcher de glisser fun sur l'autre,

d) l'élément de maintien présentant une structure fibreuse lâche et une stabilité de fibre individuelle comprenant des fibres dont la proximité et l'épaisseur de couche sont telles qu'une jonction mécanique est formée entre les fibres de l'élément de maintien et les saillies du (des) film(s) rugueux,

e) et dans le cas où l'un des films n'est pas rugueux, le film non rugueux est fixé à l'élément de liaison.

12. Système selon la revendication 11, dans lequel, dans le cas où l'un des films n'est pas rugueux, il est fixé à l'élément de liaison par collage, soudage et/ou couture.

13. Système selon l'une des revendications 11 à 12, dans lequel les reliefs sont formés par des particules.

14. Système selon la revendication 13, dans lequel l'intersection des particules avec le plan du film ne couvre pas la forme de projection des particules vues perpendiculairement audit film.

15. Système selon l'une des revendications 13 à 14, dans lequel l'épaisseur de l'élément de maintien atteint au plus, de préférence est inférieure à, la plus grande valeur de la projection des particules dans les surfaces, rendues rugueuses avec des particules de plastique, du (des) films.

16. Système selon l'une des revendications 13 à 15, dans lequel l'élément de maintien est à base de plastique présentant une structure fibreuse bien ordonnée ou désordonnée telle qu'une étoffe non-tissée, formant un film en voile et présentant une structure réticulaire préparée par technologie de nappage thermique.