MXPA99007168A - Process of roughening thermoplastic films and roughed plastic films - Google Patents

Abstract

The invention relates to process for roughening thermoplastic films and roughed films. The invention further relates to process for preventing thermoplastic packaging films from slipping on each other and a suitable system for such purpose. The essence of the roughening process is that practicles consisting of the same polymer as that of the film and/or other plastic material being able to weld together with that, and having suitable size and/or abrasion resistance are brought to the surface to be roughened of semi-finished product having sufficient reserved heat content to maintain condition appropriate for welding said particles on said thermoplastic film surface to be roughened or on one or on both film surfaces being re-heated to such temperature and are dispersed in suitable closeness and configuration and that condition of the roughened surface is maintained until desired welding process is completed. Process for preventing thermoplastic packaging films from slipping on each other characterised in that a system comprising films to be stacked - at least one of which is roughed - and has protrusions of suitable closeness on its surface;a binding element having a loose fibrous structure and stability is placed on the film or on its specified parts, on the entire surface or on surface part(s);said binding element comprises fibres of such closeness and layer thickness that between the fibres of the binding element and the protrusions of the roughed film a mechanical joint is formed.

Description

PROCESS FOR HARDENING THERMOPLASTIC FILMS AND HARDENED PLASTIC FILMS TECHNICAL FIELD The invention relates to a process for hardening thermoplastic films and hardened films. In this text, the term "film" also includes plastic products of different thicknesses such as plates, sheets, cuticles, which can optionally be supplied with a base or can also be cover layers. The invention also relates to a process for preventing thermoplastic packaging films from sliding between each other and to a system suitable for said purpose. The technical term, "films," also means products similar to a plate of varying thickness varying from completely thin to noticeably thick.

BACKGROUND OF THE INVENTION It is known that the process for the production of thermoplastic films starting from the appropriate mixtures or granules is done in such a way that the unprocessed material is melted or molded through heat and the desired product is formed in a tool through casting by die or compression of the material through the hole of an extrusion die. The gap does not necessarily determine a flat film, for example, in the case of hose-type products, this may also have a round shape. In order to obtain its final shape and for the purpose of its stabilization by leaving the hole in the tool or being taken from the mold, the molded product is frozen by cooling.

Regularly, cooling is done by blowing cold air.

After cooling, unwanted deformation does not occur, so that the cut is presented for sizing, winding, etc. The quality of the surfaces of the films depends mainly on the surface of the tool; In general, be completely flat. Similar to the ways set forth above, the thermoplastic films can be molded through heat transition again and can be subjected to further processing. Together with products prepared from plastic films, difficulties usually arise in that film products, for example, collapsible covers placed on top of one another, slide together, which may cause the falling of documents, in this way the pieces of paper can get dirty and be damaged or stained. In the same way, in the case of plastic bags, instead of the previous conventional bags made of textile material placed one on another, when they are placed on upper piles, in the case of smaller displacement of the center of gravity, the surfaces flat that lie one on the other can slide between them, that is to say nothing of agitation that happens in the boarding course and the transport between plants. Until now the sliding of plastic bags has been tried to avoid in different ways. The most obvious procedure appeared to be to coat the surfaces of the bag, which lie one on top of the other, with adhesive. This solution raised the problem of selecting the adhesive and the quality of the adhesive. For the most part, when an excellent quality adhesive was used, it was difficult to pull the sacks without the consequence of damaging (damaging) the plastic film, while using a poor quality adhesive due to the insufficient adhesion strength, the task either It could be resolved. As another type of solution, they tried to create non-slip surfaces forming a non-uniform appearance from the material of the film. According to a typical solution of that type, the film was embossed from the direction of the inner side of the bags so that protuberances were formed on the outer side of the bags. According to another solution based on a similar principle, grooves were formed in the die casting machine before the gap, which created a rib on the surface of the films in the direction of material movement. Through this, the problem was solved in part only because the slip could only be avoided perpendicular to the line of the ribs mentioned above, the product was able to slide freely in the other direction. An attempt was made to create an anti-slip surface on the sheets of extruded film, forming points and cavities between the tips in the advance cylinders of the film, so that formations were created rising from the surface. Although these formations were theoretically adequate to prevent slippage in any direction, the required effect was not provided either. According to another solution known from the prior art, unprocessed plastic granules were mixed with a foreign substance, which could not be homogenously incorporated into the basic plastic and humps were formed. However, in the course of that type of method, the extruder and cylinders that pass connected were exposed to abrasion, so that the tool deteriorated quickly and it was also impossible to maintain control over the disposal of humps as This was required. A procedure was also applied, where humps were formed on both sides of the film by mixing the starting material with some chemical additive. The disadvantage of this procedure is its high cost, since the additive, having a high price, was demanded in very large quantities, and also that both sides of the product were provided with humps, which limited the scope of use. All the aforementioned procedures are very expensive, not economic and are not as efficient as required. These methods are used because until now there have not been adequate processes, which can solve the problem favorably. An additional disadvantage of all these solutions is that the humps and the formations that arise from the surface are covered by the material of the same film and, although they are subjected to a greater abrasion effect, their resistance to abrasion is equal to that of the other parts of the movie. The common disadvantage of the solutions described above is that, due to their attenuation or to having particles of foreign substance involved in their structure, the tensile strength of the product is reduced. DE 42 07 210 discloses a process according to which the surface of a thermoplastic film material is heated or partially softened in order to form a molten layer for embedding particles therein. The obtained film must be heated, preferably twice and / or compression rollers are applied to ensure a secure adhesion / fixation. The specification teaches to provide a deep immersion of the particles on the surface. The material of these particles can be very different, their geometric aspects are not critical.

DESCRIPTION OF THE INVENTION The object of the invention is to provide a process for forming suitable non-slip films for further use, which eliminates the deficiency and disadvantages of the known methods from the prior art without modifications in well-known technologies and tools. The invention is based on the recognition that if the particles consisting of the substance of the film and / or other plastic material are able to be welded together with those, and that they have a suitable size, they are taken to the molten film, then the temperature of the particles on their sides facing the film surface will be increased and they will also be melted at least partially and will be strongly welded together with the film. The surface to be made straight at least partially, these particles make the surface hard. According to the present invention, the surface of the molded film, like a semi-finished article, which just leaves the hollow of the extruder die during the manufacturing process can also be hardened, by heating it, like that film previously finished. The substantial cavity of the particles used for the creation of hardened surfaces should be selected so that their resistance to abrasion and similarly the particle size are suitable for this purpose. If desired, a homogeneous fraction of particles, such as particles representing a separate fraction passing through screens, is applied to the surface. The film can be heated by any of the methods known in the prior art, for example, by blowing hot air, electric heating, etc. The particles can be applied in an orderly or disordered configuration over the entire surface or specific surface areas such as edges or, if required, in points, repeating the application once or several times depending on the desired pattern. For example, the pattern can be formed using templates or something else. The process according to the present invention is extremely economical, since no special chemical additive and no tool change are needed for the preparation of the film and, similarly, the particular conditions and parameters of the manufacturing process remain the same. Regularly, it is sufficient to harden one side of the product only, however, according to the present invention optionally the film which hardens on both sides or only on one side, can also be prepared.

In this way, the essence of the present invention is that the particles consisting of the substance of the film and / or other plastic material may be capable of being welded together with, and have a suitable side and / or abrasion resistance demanded , be carried: - to the surface to be hardened from the semi-finished product having sufficient reserved heat content to maintain an appropriate condition for the welding of the thermoplastic film surface to be hardened or - to one or both of the reheated film surfaces to said temperature and dispersed in suitable closeness and configuration, and that the condition of the hardened surface is maintained until the desired welding process is completed. The invention also relates to hardened films characterized in that at least one side thereof on the entire surface or in specific areas of the surface, comprise protrusions consisting of particles having a substance of the film and / or other plastic material. being able to be welded together with the substance of the film, which are welded to the surface and at least partially remain straight on the surface. The invention also relates to a process for preventing the plastic packaging films from slipping between them, said process can prevent slippage in the case of external effects even more important than those mentioned above. It is based on the recognition that the connection between two hardened surfaces can be made even firmer if a particular connecting element is placed between them.

BEST MODE FOR CARRYING OUT THE INVENTION The essence of the process is that in a system comprising films that will be fixed, at least one of them is hardened, and a joining element is formed by applying a hardened film with proximity projections and suitable geometric characteristics with respect to the joining element on its surface; a joining element having a loose fibrous structure and a single fiber stability is placed on the film or on its specific parts, on the whole surface or on parts of the surface, said joining element comprises fibers of such closeness and geometry and thickness of the layer between the fibers of the connecting element and the projections of the cured film, a mechanical connection is formed. The welding surface between the film surface and the particles forming the projections is preferably such that the internal section of the particles and the plane of the film do not cover the shape of the projection of the particles seen perpendicular to said film sheet. According to a preferred aspect of the present invention, sheets of hardened film are used on both surfaces of the joining element. According to a further aspect of the present invention, the joining element is fixed to one of the two film sheets (to that which is not hardened); by adhesion, welding or sewing. It is also preferred if the thickness of the bonding element reaches mostly or very preferably is less than the higher value of the projection of the particles on the surfaces, hardened with plastic particles, of the two sheets of films to be connected between yes. Conveniently, a plastic-based bonding element, having a well-ordered or disordered fibrous structure, such as a non-woven fabric, forming a hidden film and having a lattice structure, prepared through thermo-fleece technology, is used. In practical use, a three-part system of 'hardened plastic film with hardened plastic film binding element' is developed, the resulting three-member joint will be strong enough to also withstand superior mechanical stresses without slippage. At the same time, the joint can be simply broken, since although in the direction of the sliding between them the layers are stabilized, in case of elements of need it can easily be elevated among themselves. For the mechanical joining of the surfaces, it is necessary that there are larger protrusions of lower density, or smaller protrusions that are closer together on the surface, so that a certain part of the surface needs to comprise protrusions. The relationship between the size and the proximity of the projections 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. The geometrical shape of the particles is important because in the case of arcuately round, lenticular particles, which lie flat where, for example, the welding line is long, the fibers between the particles obviously can not hold each other as As desired, they slide, they do not stack in cavities between them. As already mentioned above, the joining element has a fibrous structure and, in addition, the fibers must have adequate individual stability to prevent the particles from breaking and the fibers slipping when a tension arises in the sliding direction. In addition, the structure of the joining element must be loose enough to allow the protrusions to penetrate the fibrous structure. As a binding element, a fabric with a disordered, villous, felt structure, etc., can be used, wherein the fibers are joined together using known methods such as adhesive form, sewing, spot welding, etc. Films made suitable for the purpose of packing are usually wound and stored in rolls, until the use and are cut to size and the packaging is made. The place where the joining element will not obtain, is already determined in the process of hardening the film, therefore in the production of the film, when a smooth film is described, which, from the point of view of the invention , it is a semi-finished product, it is in the designated places on its surface that it becomes hard taking the desired position of the joining element into account, but it is also possible to provide the finished film with rigidity in the places where it is necessary. Films may contain a self-adhesive layer on their surface, if required, as well. The system according to the present invention is characterized in that it comprises a hardened film having proximal projections and suitable geometrical aspects with respect to the joining element, and on the cured film or on specified parts of its surface, it has a connecting element having a loose fibrous structure and individual fiber stability, the connecting element contains fibers of such closeness and thickness of film that a mechanical bond is formed between the fibers of the joining element and the protrusions of the cured film.

INDUSTRIAL APPLICABILITY More particularly, the process for curing films according to the present invention is illustrated by the following examples in relation to the manufacture of plastic sacks.

EXAMPLES Example 1 A tubular film used as starting material to manufacture plastic bags was processed through molding and extrusion of the polyethylene starting material, so that the temperature of the substance of the film leaving the hole with round shape of the tool it is 195 ° C. The tubular film, as is usual in extrusion processes of blown hose, is expelled to the cooling tower and, in the usual way, to form a balloon, air is blown inside the hose enclosed by the tool and a pair of lifting press rollers. By setting the parameters, such as the volume of air trapped in the balloon, the rotation speed of the screw of the extrusion machine and the pulling speed, a finished film with a thickness of 0.150 mm and a width of 700 mm is prepared. According to the present invention, the particles consisting of the film substance are brought to the surface with a flow of air concentrically or in separate segments separately before the blowing of cooling air. The film is cooled through the cooling air to the freezing point, so that changes in size can not occur afterwards. After extrusion, the finished film tube is further processed according to the appropriate technology for the manufacture of bags.

The present invention is further illustrated by an anti-slip system as follows: Example 2 Plastic granules were usually packed in plastic bags weighing 25 kg, and these bags were transported in pallets placed on top of each other in stacks in quantities of more than 1000 kg each. To prevent said bags from slipping into each other, sacks were prepared from hardened films. The sacks were prepared from a packed tube in the packing machine. To prevent slippage on both sides of the film tube, except the part that is grounded, they become rigid so that at least 50 protrusions per square centimeter must be on the hardened parts of the surface. In this way, the filled sacks lie one on top of the other with their hardened parts of surfaces. Fleece webs with a width of 10 cm and a length of 30 cm were used as joining elements. When the packaging machine finished filling a sack, it was advanced on a conveyor belt to the stacking machine. A piece of the fleece band was placed on each bag lying on the moving conveyor belt, before reaching the stacking machine, so that it was placed over the entire length at the middle of the bag. The bags were placed one on top of the other through the stacking machine, so that each bag, in a part of its common contact surface, makes contact with the union bags that are one line above with the mediation of the joint element . The fibers of the connecting element are joined to the upper and lower bags and are fastened together with a mechanical connection and prevent them from sliding towards each other.

Claims (18)

1. - A process for hardening thermoplastic films, by placing the particles on the surface of said film, wherein the particles consisting of the substance of the film and / or other plastic material being able to be welded together, and having an adequate size and / or a demanded abrasion resistance are brought to the surface to be hardened from the semi-finished product having a reserved heat content sufficient to maintain an appropriate condition for welding the thermoplastic film surface to be hardened or one or both reheated film surfaces at such temperature and they are dispersed in a suitable closeness and configuration and that condition of the hardened surface is maintained until the welding process is completed.

2. A process according to claim 1, wherein the plastic particles are brought to the film with air flow before cooling.

3. A process according to claim 1 or claim 2, wherein the plastic particles are blown with a flow of air preheated to the external surface of the tubular film just coming from the hollow of the tool.

4. A process according to claim 3, wherein the plastic particles are brought to the external surface of the film before forming or cooling.

5. - A process according to any of claims 1 to 4, wherein the plastic particles are blown towards the film concentrically or over the entire width of the film.

6. A process according to any of claims 1 to 5, wherein the plastic particles are blown to the film and / or each segment separately or each strip separately.

7. A process according to any of claims 1 to 6, wherein the particles are grains.

8. Hardened plastic films characterized in that on at least one side thereof over the entire surface or in specific areas of the surface comprise projections consisting of particles having a substance of the film and / or other plastic material which is capable of welding together with the substance of the film, which are welded strongly to the surface and at least partially remain straight on the surface.

9. A process for preventing the thermoplastic packaging films from sliding together, wherein a system comprising films to be fixed, at least one of them is hardened, and a joining element is formed by applying a hardened film with projections on its surface having closeness and appropriate geometrical aspects with respect to the joining element; A joining element having a loose fibrous structure and a single fiber stability is placed on one of the films, at least on its parts which will be joined with the hardened surface of the other film on the whole surface or a part of the surface, said joining element comprises fibers of such closeness and layer thickness that between the fibers of the joining element and the protrusions of the cured film a mechanical bond can be formed, provided that when a non-hardened film is applied as part of the system , a fixation is formed between the joining element and the surface or surface parts of the film in a manner known per se.

10. A process according to claim 9, wherein the welding surface between the film surface and the particles forming the projections is preferably such that the internal section of the particles and the plane of the film does not cover the shape of projection of the particles viewed perpendicularly to said film sheet.

11. A process according to claim 9 or claim 10, wherein sheets of hardened film are used on both sides of the joining element.

12. A process according to any of claims 9 to 11, wherein the joining element is fixed to one of the two film sheets.

13. A process according to claim 12, wherein the joining element adheres to one of the two film sheets.

14. A process according to claim 12, wherein the joining element is welded to one of the two film sheets.

15. A process according to claim 12, wherein the joining element is sewn to one of the two film sheets.

16. A process according to any of claims 9 to 15, wherein the thickness of the joining element reaches almost up to, and preferably is less than the greater value of the projection of the particles on the surfaces, hardens with particles of plastic, of the two sheets of film that will be connected to each other.

17. A process according to any of claims 9 to 16, wherein the plastic-based binding element is used, having a well ordered or disordered fibrous structure such as a non-woven fabric, forming a hairy film and having a reticular structure prepared from thermo-fleece technology.

18. A system for preventing the hardened thermoplastic packaging films from slipping between them, wherein the system comprises a hardened film with projections that have closeness and geometrical aspects suitable with respect to a joining element, and on the parts of the hardened film that will be joined with another hardened film or in specific parts thereof, have a joining element having a loose fibrous structure and a single fiber stability, the bonding element containing fibers of such closeness and layer thickness as between the fibers a mechanical connection can be formed between the joining element and the protrusions of the cured film. SUMMARY The invention relates to a process for hardening thermoplastic films and hardened films. The invention also relates to a process for preventing thermoplastic packaging films from sliding between each other and a system suitable for said purpose. The essence of the hardening process is that the particles, which consist of the same polymer as that of the film and / or other plastic material that will be able to be welded together with them, and that have an appropriate size and / or a abrasion resistance, are brought to the surface to be hardened from semi-finished product having a reserved heat content sufficient to maintain an appropriate condition for welding said particles on the surface of thermoplastic film to be hardened or on one or both of the film surfaces that are reheated to such temperature, and are dispersed in an appropriate closeness and configuration and that the condition of the hardened surface is maintained until the desired welding process is completed. The process for preventing the thermoplastic packaging films from sliding between each other is characterized in that it has a system comprising films that will be stacked, at least one of which is hardened, and has suitable proximal projections on its surface; a joining element having a loose fibrous structure is formed and stability is placed on the film or its specified parts, over the entire surface or a part of the surface; said joining element comprises fibers of such closeness and layer thickness, that between the fibers of the joining element and the protrusions of the cured film, a mechanical bond is formed.