Plastic containers

The present invention relates to the manufacture of containers of composite elements, of plastic material, with improved physical properties, and, in particular, to containers made of composite elements 5 used in the food industry.

It is known that in the canned food industry, such as meat products: ham, minced beef, frozen and minced meat, ¹⁰the casings are usually made of sheet metal, which are filled with the respective foodstuffs, covered with a lid and sealed, eontainers which, however, have the disadvantage that, in the presence of the food product 15 within them, it can corrode what may have a consequence contamination and deterioration of food.

It is also known that in order to ²⁰This disadvantage was eliminated by substituting metal in the preservation of foodstuffs with certain inert synthetic resins such as polyethylene and polypropylene, materials which, however, present ₂the disadvantage is that they are excessively permeable to gases such as oxygen and it is known that they once penetrate cause unwanted take-off and an impairment in taste ³⁰ and the quality of canned foods. Consequently, the gas permeability of synthetic resins such as polyethylene has resulted in their rejection, but due to the chemical inertia of these resins they can be used much more advantageously.

Eontainers are also known for storage, as is the case with engine oil products, where their walls are made of resins, thermoplastics, such as polyethylene and polypropylene, but in general they have not proven acceptable in terms of rigidity and the purpose of superimposed storage due to the efforts of the surrounding containers.

Also known are solutions to reduce gas permeability and to increase the rigidity of thermoplastic resins, polyethylene and others which, by making a container from a plurality of layers of thermoplastic material, one of the layers being formed from a thermoplastic resin having very high gas-tightness properties, such as polyvinyl chloride and acrylonitrile polymers, '

There are also known solutions according to which in thermoplastic resin. a filling material such as sawdust (wood flour) is incorporated, mine82089 '/ -' H ·:? - ί · / ·. . -. ..... PRICE T.E1 27.77

Β2089 inorganic dyes such as clay or small or with a second resin such as nylon which has a high gas permeability, methods that are effective in reducing gas permeability, however, have the disadvantage that they do not increase stiffness and improve other physical properties, but even more important problems are encountered when it comes to achieving sealing.

It is known that in sealing containers with metal caps made of steel, tiles or aluminum plates, these caps are fixed by the upper edge of the body of the container through a double seam, operation in which, the cap provided with the peripheral portions is applied in the open area. of the head of the container, also provided with a peripheral flange. The peripheral flange of the container is specially constructed and dimensioned so as to allow and intercalate with the flange of the lid in a double joint for fixing the head to the body of the container, during the double joint operation the flanges of the body and the lid are rolled together. so as to make a double interlock. During this operation, these flanges are compressed or pressed together under pressure to achieve a hermetic joint. Moreover, the metal lids can be easily double-bonded with the plastic containers formed from any unmodified thermoplastic resin, and when these resins are modified by laminating or adding other resins or by incorporating in them other filling materials, the containers formed from such thermoplastic resins are modified. flexibility and strength in the case of vertical stresses during the double jointing, which leads to the fact that the upper portions of the container are broken or broken during the joining operation.

The plastic container of elements composed of material with improved properties and process for obtaining, according to the present invention, eliminates the disadvantages shown by the fact that in order to obtain increased rigidity and resistance it enters the gases, the process consists of the preparation phase of a composite element consisting of a peripheral outer part, from an unchanged thermoplastic resin from an inner central heart composed of a modified thermoplastic resin with a second material that prints improved physical properties and then followed by the molding phase of this element in the form of an empty container inside whose body is closed at the lower part with a bottom and ends at the upper part with an opening provided with a peripheral flange which forms an integral part of the body and is formed by a resin unmodified plastic in the body made of modified thermoplastic resin, container used for food packaging obtained by the process shown being composed of a hollow body inside closed at one end and open at the other Ia which ends with a peripheral flange that is an integral part from the body and adapted to receive a lid, the flange formed from an unchanged thermoplastic resin and the body formed from a modified thermoplastic resin with a second material that has improved physical properties, the flange being made from polyethylene, polypropylene or polystyrene, and the body from a thermoplastic mixture with a high gas permeability and a second low gas permeability resin, selected from a group containing vinyl chloride polymers, nylon and acrylonitrile copolymers of at least 60% by weight; the body of the container being formed also of a laminate composed of a first layer of thermoplastic resin with a high gas permeability and another second layer formed of a second resin with a low coefficient of gas permeability selected from a eonstand group from polymers and vinylin, nylon chlorides and acrylonitrile copolymers having an acrylonitrile content of at least 60% by weight; and the core of element A may be made of a mixture of thermoplastic resin and a filler such as wood sawdust, a mineral material such as mica, asbestos, fibers, calcium carbonate (CaCCh) and titanium dioxide (TiOa).

By implementing the present invention, a thermoplastic resin container with improved physical properties can be obtained which can be double-bonded without breaking the peripheral flange of the container subjected to the joint, without reducing its flexibility and making it suitable for sealing under the conditions. double. When the peripheral flange of the container made of unmodified thermoplastic resins is interspersed with the flange portion of the metal lid during the double joint operation, this portion of the container does not allow gas to pass into the container and is not subjected to external forces.

The following is an example of embodiment of the invention in connection with FIGS. 1 ... 8, which represents:

FIG. 1 is a plan view of a container element made of a thermoplastic resin, the central section of which is modified with a material that improves the physical properties of the resin;

FIG. 2, a sectional view along the line A-A of the element in fig. 1;

FIG. 3, a sectional view of the thin wall of the container obtained from the element shown in fig. 1 and 2;

FIG. 4 is a vertical section view of a container fragment showing a metal lid applied to an element such as that in FIG. 2 before starting the double jointing operation;

FIG. 5 is a view similar to that of FIG. 4, illustrating the eontainer of FIG. 4 after the metal lid has been subjected to the double joint operation with the container element;

- Fig. 6, series detail views showing a molding method of the composite element shown in fig. 1 in the form of a container with that of FIG. 3, the element being positioned in the mold in a molding chamber prior to the commencement of this operation;

FIG. 7 is a side view of the mold elements inserted completely into the molding chamber to form a container in the respective block;

FIG. 8, illustrates the operation of separating the mold elements after the manufacture of the container and immediately before injecting the container into the molding chamber.

The compound element A shown in FIG. 1 and 2 is made of a central core or a heart 1 formed of a thermoplastic resin modified with a material that improves its physical properties, and from an outer peripheral edge 2 made of an unchanged thermoplastic resin.

A container 3 is made from the element Qompus A shown in FIG. 3, 4 and 5 as having a wall a and a portion 'bottom b which makes common body with it made of modified thermoplastic resin derived from the heart 1 of the element A and an outer peripheral flange c formed from unmodified thermoplastic resin derived from the peripheral part outer part 2 of element A.

A metal cover 4 having a peripheral flange d is applied to the open side of the container 3. The peripheral flange given to the metal cover is joined with the peripheral flange as the container 3 to form a double ring through which the cover 4 is sealed and joined to the body of the container 3 The resulting container is composed,_sfrom the metal cover. 4. Stamped by the body 3 in the container, body made of a modified thermoplastic resin 'to reduce the gas permeability or to improve the rigidity. When the peripheral flange c of unmodified thermoplastic resin of the body of the container 3 is bent together with the waterproof metal flange provided by the metal cover 4, the watertight container has no portion of the unmodified plastic resin - exposed inwards.

Plastic containers can be made from composite elements of the present invention by any conventional molding process such as compression and impact molding.

The process for making containers from composite blocks is to take the composite element to its outer peripheral portion and to the gradual formation of the central portion while it is in a heated state so soft, by forcing the piston to pass over it resulting in pressing. heart 1 of modified thermoplastic material that forms the side walls of the container 3.

In FIG. 6, .8 illustrates the very advantageous process of molding the composite elements in the form of containers 3, a process which is described more briefly in the following and a more detailed description of this molding process is given in Patent, USA, no. . 437 453,

Referring to FIG. 6, 8, it can be seen that a compound element A in convenient form formed from an outer peripheral portion 5 of a flexible unmodified thermoplastic resin having a relatively high gas permeability or low stiffness and a heart 6 from a thermoplastic resin modified to have low gas permeability or increased rigidity, the element A being placed between a lower assembly B of a mold and an upper assembly C thereof, the pair of mold assemblies being constructed in such a way that it is difficult to advance through a molding chamber 7. The lower mold assembly is arranged to move in a go-and-come race, by means of a non-training means. presented telescopically with respect to the interior percents f of the molding chamber 7.

The upper assembly C of the mold is formed by a support plate 8 having fixed by it a cylinder 9 and a head 10 thereof from which it is mounted.

The interior of the molding chamber 7 has a predetermined cross-sectional dimension that exceeds that of the upper cylinder 9, in order to allow it to penetrate between the interior walls of the forming chamber 7 which are at some distance from each other during the molding cycle. To achieve the desired space, the molding chamber 7 is provided with an annular cover 11, mounted

02089 ρε ο top edge of it. The annular cover 11 has an orifice with a diameter large enough to allow the sliding contact with an outer peripheral surface ha of the cylinder 9. The circular space made between the cylindrical surface h and the inner wall of the molding chamber f defines a cavity i which has the shape and dimensions desired for the walls. sides of container 3 to be molded.

Molding chamber 7 is also provided with a jig formed in the inner portion of the edge! its superior. The nut j is adapted so as to receive the plastic material displaced during the molding operation from the outer peripheral portion 5 of the unmodified thermoplastic resin of the composite element A to form the socket flange e of the molded container 3.

As shown in FIG. 6, the compound element A is placed on the surface of the lower portion of the mold B raised at the edge level! higher than the molding chamber 7. If desired, the composite element A can be heated to a uniform temperature xle forming by means of a convenient heating means (not shown in the drawing) before being molded onto the assembly B,

As shown in FIG. 7, the element A is compressed between the mold assemblies B and C in order to cause the outer portion 5 to flow radially outwardly between these elements and to be extruded into the groove j to form the peripheral flange 5 of the container 3. After assigning the portion corresponding to the groove j, the assembly of the mold elements B and C through the molding chamber 7 makes a continuous layer of the thermoplastic heart material which is extruded into the cavity i to form the side wall of the container 3.

As shown in FIG. 8 after the extrusion of the central material of the block has been completed by forwarding the mold assemblies B and C through the molding chamber 7, a container 3 has been formed which has a peripheral flange c at the top of unmodified thermoplastic material and the side walls of as well as a portion of bottom d formed of a modified thermoplastic resin to have improved physical properties. After the formation of the container 3, the mold C is withdrawn from the molding chamber 7, in a completely open position. The lower die B is raised upwards through the molding chamber to remove container 3 from it. After removal of container 3, the lower mold remains in the initial position to retrieve another compound A and to repeat immediately the molding cycle.

Containers. 3 obtained from the molding chamber are ready for immediate packing and for the execution of the operation they double joint, without requiring any other time or other treatment after the formation.

The element composed of them are made containers, according to the present invention, can be made of any thermoplastic material which until now has not been convenient to make the containers in the areas required for the packages where high rigidity or low gas permeability is required such as oxygen, carbon dioxide and vapors. Examples of such thermoplasmic resins can be given as examples: polyvinyl chloride, acrylonitrilebutadiene-styrene (ABS) copolymers, olefin polymers and polystyrene such as polyethylene, poly-1-butene, poly-4-methyl - pentena-1 , and other homopolymers and copolymers of olefins 1 - mono similar having more than eight carbon atoms per molecule. These thermoplastic resins in unmodified form are located in the peripheral portions of the composite block from which the flange for joining the container is formed. The inner core portion 1 from which the bottom and side walls of the container are formed consists of thermoplastic resins to have low gas permeability and increased rigidity. Among the means by which thermoplastic resins can be modified to increase their rigidity or to reduce gas permeability, by incorporating into them a filler such as natural fibrous organic materials in a divided form, especially wood sawdust, mineral fillers such as titanium dioxide (TiO?), calcium carbonate (CaCO.) asbestos fibers, clays of flat or flattened structure, such as small, vermiculites, talc as well as silicon fillers such as silica, calcium silicate, aluminum silicate ^; in a proportion of 1% up to 30½ BCⁿ weight, additions that will determine the desired improvement of the physical properties of the resin, which will however allow the containers to be achieved by molding using the compression method or the impact method. In addition to the filler materials, the thermoplastic resin can be incorporated as a binder, a second resin that has low gas permeability, such as resins in the group or include nylon, acrylonitrile / alkyl acrylate copolymers or acrylonitrile copolymers. have acrylonitrile content! at least 60% by weight and polymers of vinyl chloride (saran), such as polyvinyl chloride, vinyl chloride / vinyl chloride and vinyl copolymers / acrylonitrile!

In addition to low gas permeability resins or fillers, a thermoplastic resin consisting of one or more layers may be used and a low gas permeability resin may be used as core material. Thus the core of the element A may consist of a laminated structure composed of two or more sheets of thermoplastic resin such as polyethylene or polypropylene which has interposed an inner layer that is serous or 33arrax.

The coinposed element used in accordance with the present invention may be of any shape, circular, square or polygonal and may be prepared by extruding unmodified and modified resins in a given bar-type profiled structure and then cut into composite bars or other profiled structures. to the desired dimensions. The actual size of the composite block will be determined experimentally depending on the respective molding chamber, the mold configuration and the total volume of the element, which will have to be large enough to achieve the desired size container.

The process and containers made according to the invention have the advantage of having improved physical properties, and the lid can be fixed by a double joint without causing it to break or break.

Also, the containers have a high resistance to gas penetration and a rigidity large enough to be stored in shelves upright.