JPH09511182A - Metal-plastic structure can by drawing and ironing, and its manufacturing method - Google Patents

Abstract

(57) [Summary] The present invention includes a can made by squeezing and ironing and a foil of a plastic material to which two outer metal foils are bonded, and the ratio of the thickness of the plastic material to the total thickness of the metal is 0. It relates to the fabrication process starting from more than 5 layered or laminated metal-plastic structures (1). Forming this laminate on the can body (5) involves first drawing in one or several steps and then ironing, preferably in four consecutive passes. The can is specifically intended to contain a beverage. The benefit of this process is that the cost of the raw materials remains low while still providing as good use properties as a metal can.

Description

Detailed Description of the Invention         A metal-plastic can made by drawing and ironing,         The manufacturing methodBACKGROUND OF THE INVENTION   The present invention generally relates to cans used for beverage or food packaging. And making aerosol containers by squeezing and ironing It is. To be more precise, the invention is of the metal-polymer-metal containing type, namely , A new type of polymer with a polymer layer placed between two metal sheets and glued to it. It relates to an improved metal-plastic laminate structure.   In the following, special identification will be made to identify this new and improved laminated material of the present invention. Without metal-plastic-metal, metal-polymer-metal, or more simply H The abbreviation PH is used.   There are numerous documents describing layered metal-plastic structures. these Of the metal-polymer or poly-metal-polymer structure, Mar-metal structures are rare.   All of these documents that refer to MPM structures are subject to throttling and ironing. Materials and thicknesses that are particularly suitable for making industrial beverage or food cans. I don't tell you the appropriate range.   WO 82/00020, published on January 7, 1982, is For the sake of clarity, take the metal foil or plate in its simplest form. Describe a metal-plastic structure including an attached polyethylene (PE) film doing. Another example is a single metal preform that forms a complex PE-metal-PE. It contains two PE films attached to both sides of the sheet. Finally, the third embodiment , Composed of two metal plates or foils attached to both sides of PE film . The PE used, obtained by copolymerization under low pressure ethylene and butene-1, is , A linear low density type (LLDPE) with a density of 0.91 to 0.94 is there. The LLDPE described in this application can be used directly without the use of adhesives. It has the interesting property of adhering to metals. Applying heat and pressure at the same time By (heat sealing), just attach it to the metal and you'll be in time.   The metal substrates described in this application include steel, tin or chrome or chrome / Steel with oxide or zinc coating, nickel treated or Contains no aluminum, copper, or zinc. It has undergone a chemical conversion process May be.   Regarding the intended absolute or relative example of a simple metal-plastic structure Although there is no clear instruction, this announcement document states that 210-micron-thick steel, tin-plated steel Of various metals, such as chrome, chrome-chromium oxide, or aluminum 100 micron thick polyethylene film heat sealed to Explaining Rum. The specimens thus obtained are pleated, punched and drawn. It is formed into a hollow article by reworking and wall ironing. Adhesion of coating Properties are compared to show the superiority of linear low density polyethylene (LLDPE) .   French Patent No. FR2 665 887 (Petini Embassy Ali) Maintainer) is a two-layer adhesive bonded together by an adhesive layer with a Shore hardness of less than 80. Drawing, drawing and ironing, characterized by being composed of luminium , Or explaining a capsule attached to a cork made by Flow Turn I have. Adhesive layer should be ethylene acrylic acid or polyethylene or acid functional Can consist of polypropylene modified by. The total thickness of the composite is 120 ~ At 400 microns, it has the following total thickness composition ratios:     Aluminum outer layer 20-50%     Adhesive layer 3-30%     Aluminum inner layer 40-60%     European specialties transferred to Schwezerische Aluminum AG Permitted application EP-A-0 046 444 describes a plastic layer with two It describes an MPM composite laminate that can be as thick as the combined metal layers. One of the expressive requirements for achieving deep drawability is that when the composite is stretched, The load generated by the plastic core is generated by each metal strip. Choosing a plastic core layer and a metal surface layer that are larger than the same It is. This condition is due to the use of oriented or stretched plastic layers. Is achieved. Thin strips of soft or semi-hard aluminum are particularly suitable It is also stated. Squeezing and ironing is not taught as a suitable process. Deep drawing by stretching, which is not, but a convenient process for such semi-rigid containers There is teaching of machining as well as deep drawing.   A similar MPM configuration method is based on BASF Aktiengesellschaft. Described in European Patent Application EP-A-0 034 781 assigned to ing. The inventors of this application give plastic ductile properties close to the metal of choice. For this purpose, the plastic film is rolled before being bonded to the metal foil.   Laminates of metal-plastic-metal structures that can be formed into a variety of useful articles include Do European Patent Application No. EP-A-assigned to the Chemical Company No. 0134958. This invention is a standard laboratory test Given the ability of the laminate to withstand at least a predetermined level of tensile formability measured, The ability to bend into a sharp radius without metal damage and a certain level of thermal stability. And is defined in detail.   This patent specification is the standard for drawing or drawing / ironing Are also formed by drawing or drawing / ironing. The ability of the build is also not listed. The laboratory tests described have made the material thinner Biaxial tension that stretches the material uniformly while maintaining the fixed outer edge This is a form of testing. Such a stretch forming process has traditionally been used for automobile panels. It is used in forming shallow parts like It is not used to The early stages of making food cans and beverage cans. Conventional drawing processes, such as those used for tape, flow material from the outer edge. With little or no thickness reduction.   United States Patent No. 3, assigned to Continental Can Company 298559 is cold drawn in a conventional mold, such as a cake pan. A laminated metal-plastic container is described. Metals Described-Plastic There are several MPM types in the container. Wide range of metals and pluses Tick thicknesses are claimed, but taught about the importance of these thickness percentages There is no. Ratio of plastic to total metal thickness for these examples dealing with MPM structures In the case of 5-9. The metal layer in this MPM example is extremely soft or zero temper It is explained. In forming such a container by the drawing and ironing process To be made, or to be able to create a squeezed container suitable for food cans Is none.Presentation task   The problem presented to the inventors was to improve cans for gas-filled beverages. . Generally, this can has a cylindrical shape with a capacity of about 33 cm. It is coated with an approved varnish for the outside, and the outside shows the nature and manufacturer name of the product 1 With an easy-open lid, which is coated with one or more decorative layers To be sealed. The most frequently used molding process for these cans is squeezing and ironing. It is a process of processing. This process allows for very fast production cycles This made this type of can exceptionally popular worldwide.   Known to those skilled in the art, this process is, as the name implies, one or several refinements. First series consisting of work and second series consisting of one or several ironing operations Contains. Flat round steel or aluminum alloy with a thickness of about 300 microns Start with the disc. This disc was first obtained with the help of the device shown in Figure 1a. , Drawn to form the initial shallow cup. The initially flat disc (1 ) Is illustrated here in a variant. It is a fixed modified die play A pressure is applied between the pressure plate (2) and the pressure plate (3). Power operated by piston The lowering of the punch (4) allows for the formation of cups which are virtually free of thickness reduction. Next, the designated aperture number (of FIG. 1b) corresponds to the same component of FIG. 1a. The cup forms a cup.   Later, the sides of this cup are generally designated by the numeral 3 with a gradually decreasing inner diameter. It is ironed with the help of a series of ironing rings. This is shown in Figure 2. One of the ironing rings is shown and its function is explained. Cup (5) Is fitted to the punch (6) with slight play, and the punch (6) fits the cup (5), It is passed inside a ring (7) whose inner diameter is smaller than the outer diameter of the cup. This makes the wall Is thinned and stretched correspondingly. Of this stretching or ironing The size is controlled by the difference between the outer diameter of the cup and the inner diameter of the ring. One ironing Regarding the deformation capacity of the cup-shaped body that could not reach the final height of the can in the processing pass, As shown in the figure, three phosphoruss are passed in succession one after another with the same punch stroke. It is useful to provide a group.   Among the cost elements of beverage cans made by the process discussed above, being lightweight Nevertheless, the cost of metal constitutes the overwhelming part. Therefore, with economical material Researchers have come up with the idea of replacing a piece of plastic with a piece of metal.   The elastic modules and limits of elasticity of most plastic materials are Substituting plastic for metal is much smaller than Face some structural problems. In addition to these structural problems, metal in general Cans are made under conditions that are significantly different from those used to mold plastics There was a process problem related to the fact. For example, metal containers are usually fast While it is produced at room temperature or medium temperature, the behavior of plastic is It seemed that the containers were usually made at low speed and high temperature.   The researchers mentioned above, as described in detail in WO 82/02020, The plastic layer adhered to the foil simplifies the conventional metal forming process. It can be formed by This means that metal-plus during molding The behavior of the tic structure is controlled by a metal that is stronger and thicker than plastic In fact, as well as the stresses produced in the thin plastic layer, are a result of its good adhesion. It can be explained by the fact that it is easily transferred to metal foil.   This limitation on relatively thin plastic layers is due to the general role of plastic in Protects metals from corrosion, and a relatively thin plastic layer fulfills this protection So, it wasn't a problem in the above study.   In WO 82/00020, lamination is made of polyethylene film if desired. It even says that it may be made of sheet metal or foil bonded on both sides, but more That thick plastic layers are desired or possible with such MPM structures Not shown. The 100 micron plastic described in this patent specification. Produces MPM structure pair using black film and two 210 micron metal foils In this case, the thickness ratio of the plastic core to the total metal thickness will be less than 0.24. This As we show, this low ratio is below what is needed to achieve the desired cost savings. .   In addition to using a plastic layer that is thin enough that the metal dominates during molding Well, the researchers mentioned above use two methods. French patent FR141 The first described in US Pat. No. 4475 and U.S. Pat. No. 4,390,489. Things come from the heating materials utilized in conventional plastic processes such as thermoforming The first step is to carry out molding.   The second method is that the plastic core dominates the molding and the aluminum deformation is Metal-plus with each material selected to be followed by deformation of the stick It is processing using a tic structure. The aforementioned EP-A-O 0464 4. At 44, this condition is greater than the load produced by each metal strip. It specifies the load generated by the stick core. This is soft or semi The use of hard aluminum strips and the benefits of stretched or stretched plastic layers Achieved by.   In EP-A-P 034 781, the inventors have given a given metal foil. In order to make the plastic film more dominant compared to Cold roll the rum. This allows them to use somewhat strong metal foils. You. The inventors have stated their conclusions regarding the proportion of load caused by metal. No, but the final metal stress is equal to that of the metal foil when tested on its own Based on assumptions, the percentages for each of the illustrated layer structures are easily Can be calculated. From this calculation, it is only 46. 4% tensile load, no cold rolling, same layer plastic thicker It can be seen that it is 20.8% in the comparative sample using the glass. Again, the aperture ・ For containers that are ironed as well, in order to receive the wall ironing process without failure No mention is made of the layered capabilities of.   In U.S. Pat. No. 3,298,559, the inventors of the present invention applied a drawing method such as cold rolling. Rust is not applied to each of the given MPM examples It is also characterized as extremely soft or zero temper. Plastic for total metal thickness The stick thickness ratio is at least 5-1 in each MPM example. Departure The authors do not mention the percentage of load that a metal occupies and calculate it. Although it does not provide mechanical data for The combination of high thickness ratios shows that the plastic layer dominates the molding process .   As shown below, the plast is very thin compared to the soft alloy or layer metal thickness. The use of a backing layer cannot withstand significant mechanical loads such as internal pressure until some time. The purpose of the present inventors is to significantly reduce the raw material cost of the inevitable container. I don't.   The present inventors can withstand deep drawing, more specifically, draw and iron. In terms of the ability to withstand the subsequent ironing steps required for beverage and food cans Is the unstretched plastic core layer rather than the stretched plastic core Was also found to be suitable.   The object of the present invention is to reduce the thickness and hence the cost of the metal used. To achieve this, the inventors should put the plastic layer between two metal layers. Also, the plastic layer is a container made of a metal-plastic structure. It has been discovered that it must be thicker than the thickness achieved. Stronger and more rigid Low cost as a central layer placed between two outer layers made of different materials or Other types of mechanical structures that utilize low density materials are well known. Such "Sun The "ditch" structure is made up of a single layer of stiffer material with the same thickness as the total thickness of the sandwich. Known for achieving near bending stiffness.   The less resistant central material contributes to the bending stiffness of the structure, which is It barely contributes to the tensile resistance of the switch. This is two outer metal layers This limits the possibility of reducing the total thickness of Equipped with a relatively thin metal wall like a container The tensile resistance of the obtained structure is called the film strength.   The inventors of the present invention have found that the bottom of a rigid container such as a space for a gas-filled beverage has a concave shape when viewed from the outside. The pressure at which a shape begins to become convex depends on a complex function of bending stiffness and membrane strength. I discovered that. This pressure is commonly referred to as the bottom buckling pressure. this The two forms of resistance function are the exact shape of the concave dome and the shape of the recess on the bottom of the container wall. It depends on the shape of the bottom part connecting the chamber.   The bottom buckling pressure (F) is as follows as a function of thickness for single layer metal: The formula can be expressed:       P = keⁿ Where k = proportional constant depending on the material, e = material thickness, n = 1 depending on the shape of the bottom It is an index that varies between 2 and 2. This is the buckling pressure if the index n is close to 1. The force means that it is sensitive to the membrane strength, and if the index is close to 2, the buckling pressure will bend. It means being sensitive to stiffness. Index for the bottom of most beverage cans Lies between 1.2 and 1.9. The closer the index is to 2, the arbitrary thickness of the outer metal layer In addition, the thickness of plastic required is small.   Figure 3 shows that the same buckling pressure as the 330 micron thick overall metal structure is achieved. For the total thickness e of the two metal layers_mPlastic thickness required in case of_pOf Show. The index at which the film strength is at its most critical state, as observed for different curves When the bending stiffness is at the most critical state than when n = 1.2, the index is n = 1.7. By far, it does not require the thickness of plastic.   Also, in this FIG. 3, in the case of an arbitrary bottom surface configuration, and therefore an arbitrary value n, Series of plastic thickness e_pAnd the total thickness e of the two corresponding metal layers_mExists, It can also be seen that they provide the required bottom buckling strength. For example, index 1.5 For all configurations, all allowable combinations are the horizontal axis of each point of the curve indicated by 1.5. Corresponds to the ordinate.   In general, the point to the left of each curve is low in high metal and high in cheap plastic. The points to the left of each curve represent the most economical structure as they are included.   The ratio of the plastic thickness to the total metal thickness at these points was achieved in the prior art. Also note that it is more expensive than   From the MPM structure using conventional metal forming processes such as drawing and ironing The container production that started is not a structure composed of few metals and many plastics. It was thought to be difficult. One of the reasons for this expectation is the same as ironing It means that the MPM structure is subjected to tensile stress when drawing a large amount of leprosy. With existing technology, it is possible to stretch the MPM structure until it breaks the entire metal structure. It was supposed to be the same. In this stretch, the low module results As a result, plastic materials have a small amount of tensile stress induced by drawing and ironing. Will support the department. Widely accepted for stretching to failure In order to test the predictions, the inventors Each layer of the aluminum alloy has a constant thickness of 100 microns and the thickness of the plastic is varied. A uniaxial tensile test was performed while moving.   As shown in FIG. 4, the inventors of the present invention have shown that the plastic thickness can be increased by stretching until the damage. Surprised to observe that the increase in plastics up to nearly 300 microns has been achieved Was. This is 1.5 P / (M_i+ M_e) Is equivalent to.   The explanation for this astonishing increase in elongation to failure is entirely clear. However, examination of the specimens after damage revealed that the necking of either of the outer metal layers had not been opened. It relates to the ability of plastics to disperse stress concentrations due to I found out. The plastic disperses the stress on the surface of the opposing outer layer, This prevents the necking of the first outer layer from breaking. The plastic layer is the If thicker than a reasonable value, the plastic will transfer little concentrated stress to the opposing outer layers. It seems that the necking does not work, and the necking progresses continuously with the two metal layers.   The improved toughness of the MPM structure, which is characterized by stretching to failure, MPM structures with much higher relative plastic thickness than previously achieved You can now successfully squeeze and iron. As mentioned above, any bottom bag The economic balance of cling pressure is even more favorable for such thick plastics. It will be good.   Each metal foil has a thickness of 100 microns, and is made of aluminum alloy 3003. Tensile breaking strength is 239MP, the same tension used to make FIG. Using the sample data, the inventors calculated the portion of the total load caused by the metal foil. did. Percentages vary from 99% for 55 micron thick cores to 420 It varied up to 82% of the case of Ron's core.Summary of the invention   For these and other purposes, the present invention is useful in forming can bodies as well as cans. It also provides an unprecedented excellent metal-polymer-metal laminate and structure. Of. The nature and thickness of the layers of the laminate are determined by the required mechanical properties of the desired metal can, Uto, gas-filled beverage or food packaging, and squeezing and ironing Specially configured to provide up to the means to form.   The present invention is based on drawing and ironing of MPM type metal-plastic structure. , Including the production of metal cans for packaging food or drinking water, for the same purpose. I'm out.Brief description of the drawings   1a and 1b schematically show a prior art two-pass drawing of a circular disc. Do;   Fig. 2 Ironing the drawn cup wall to form the cup into a can Shows;   In FIG. 3, the isobaric line of the bottom buckling thickness P, the metal e as the horizontal axis_mThe total thickness of Intermediate polymer layer e on each ordinate_pIndicates the thickness of;   FIG. 4 shows an MPM structure in which each outer metal foil is 100 microns thick, Shows the variation of the stretch to failure as a function of the thickness of the central polymer layer,   Figures 5a and 5b show two preferred configurations of the punch base according to the invention,   FIG. 6 shows a second pass molded part for drawing according to the present invention.Description of the preferred embodiment   The can body has a bottom surface and a metal-polycarbonate of the type specifically intended to contain a beverage. A metal-metal-plastic structure with a wall whose busbar is perpendicular to the bottom of the structure. It is an object of the invention that the metal-plastic structure is Thickness is M_iAnd M_eThermoplastic with thickness P coated on the inside and outside with metal foil which is It has a central layer, and the ratio P / (M_i+ M_e) Is greater than 0.5 and the body is squeezed -It is made by ironing so that the can body is made thinner by the bottom surface. It is characterized by becoming.   After the same explanation of the problem developed above, this ratio P / (M_i+ M_e) Is 0.7 It is preferably between 1 and 2.5, more preferably between 1 and 2.   In an advantageous method for realizing a metal-plastic structure, before ironing The thickness of the central polymer layer is 100-500 microns and each metal before ironing The thickness of the foil is 25-150 microns. These thicknesses were obviously reduced It is thinner than the rear body wall. In a further advantageous way, this plastic layer is In addition to the additional stretching that normally occurs during stick film casting and blow molding. Are essentially unstretched.   The polymer forming the central layer is selected from one of the following thermoplastic materials:   Polypropylene, high and low density polyethylene, polyester, polyamide, The polymer did not contact the food or beverage contained in the container and was recovered Note that it is possible and recommended to use polymers. Times I tried with the collected polyester and polypropylene and got completely satisfactory results Was done.   Metals are steel, tin plated or unplated, chrome or zinc Or nickel coated, chrome-chrome oxide, aluminum Either aluminum or aluminum alloy, or aluminum alloy is suitable It is. The breaking strength of the metal foil in the single test and in the tension should not exceed 185 MPa. And are more preferable.   The selection of specific materials and layer thicknesses is done by pulling the starting sheet under uniaxial tension. When loading, it is preferable to select such that most of the load is generated by the bonded metal layer. Good. It is even better if the percentage of load generated by the bonding metal layer is 70% or more. Good.   The metal foils can be of different thicknesses or of different metals. it can. For the reasons explained later, the metal foil corresponding to the outer surface of the can is used for the inner surface of the can. Alloy with high corrosion resistance as the foil for the inner surface of the can. You can select an alloy with high mechanical strength as the foil that corresponds to the outer surface of the can. Wear.   A suitable adhesive layer with a thickness of 1 to 20 microns between the polymer central layer and the foil or metal foil The thickness of the adhesive layer is included in the total thickness of the polymer P.   The adhesive interposed between the polymer and metal is, for example, polyethylene or epoxy. Or, it is changed in the conventional manner by ethylene acid (maleic acid, crotonic acid, etc.). Polyolefin, ethylene acrylate (EAA), polyester or Either a thermosetting polymer, such as a monomeric copolymer corresponding to the above polymer is there.   Adhesion of the metal foil to the central polymer layer obviously leads to the metal-plastic structure and Is an important characteristic of the can body made from these structures. Adhesiveness depends on peel strength It is measured by peeling a strip of metal foil of a given width from its polymer support. It is the force required to move and therefore the force per unit length. Aperture / ladder The structure for manufacturing the main body of the metal working can exceeds 0.4 Newton / mm. It should have a peel strength.   The metal-plastic structure may be of its own without departing from the scope of the invention. The varnish or polymer film can be coated on one or both sides.   Another object of the invention is to start with a body or shape whose characteristics are described above. It is about finished and finished cans. To make a can from the can body, first Trim the body to the desired height by shearing the top of the wall, then , Neck the top. The top edge allows you to seam the lid after filling the can As such, it should be wound on a curve with a small radius. Because according to this small radius Away from the center of the curve when bending the metal-plastic structure That is, the expanded metal foil breaks at the minimum radius point, but the other metal foil is damaged. This is because it was found that they were not damaged. However, this phenomenon is explained here. A uniform metal of the same thickness without a polymer layer, because it would be too long to reveal. Does not occur in. Faced with this problem, the inventors first conducted research to solve the problem, Then, the failure of the metal foil in the expanded state is caused by filling and seaming the machine of the can. The hypothesis was immediately established that it had no effect on mechanical strength. As a matter of fact Worrying, one of the two metal foils had a broken flange The can can't withstand the tensile stresses created by the internal pressure trying to separate the lid That is the point. However, the axis of the cylinder under pressure The internal stress in the direction is about half that in the direction perpendicular to the axis. Therefore, perpendicular to the axis In order to withstand pressure on the surface, with its two layers of metal, the finished metal-plastic structure Withstand enough axial stress on the rest of the pristine layer, if enough metal is present It means that it contains enough metal. This hypothesis was calculated. Also , The total thickness of the rim is generally thicker than the thinnest part of the wall, which makes it safer You can afford. Make the outer foil thicker and stronger than the inner foil to make the can stronger It is also possible to select the alloy. Finally, the damaged part of the metal foil is The lid is covered with a fold-back lid that the user does not even notice, so the appearance of the can is shaded. There is no sound. The metal foil farther from the center of the curve, and thus in the expanded state, is half Metal-plastic, metal-poly, with upper winding edge breaking at minimum diameter The finished metal-metal can constitutes a second object of the invention.   In addition to seaming technology, other known technologies such as heat sealing and gluing It is equally possible to attach the cover to a metal-plastic can.   The present invention is for packaging beverages, characterized in that it comprises the following steps: Equally involved in the process of making squeezed and ironed cans:   a) A metal layer, a thermoplastic polymer layer, and a second metal layer are sequentially included, and each metal layer and poly A strip of metal-plastic structure with an adhesive polymer layer between the polymer layers. To prepare the table.   b) Cutting a circular disc from the strip.   c) Each of the two passes has a base with a radius of curvature of 5-10 mm. Preferably using a cylindrical punch with a circular base bonded to the In addition, the second pass is performed when the incident angle of the fixed platen with respect to the horizontal is 10 ° to 70 °. It is preferable to squeeze the disc into two cups in two consecutive passes. To work.   d) The first one called calibration, with wall thickness up to 2-25% Cups, preferably obtained by a series of four ironing rings that reduce Ironing the walls of.   The metal-plastic structure target of step a of the present invention can be achieved by various known methods. Is prepared. The most widely used are direct coextrusion, heat sealing, And high frequency bonding. The last two methods are plastic film and metal strip. It is preferred to practice on a line where the cups are fed continuously.   Direct coextrusion is seamlessly spread out between the two metal layers that make up the outer layer. Is to extrude a central polymer layer on which two thin layers of adhesive are applied. This The composite product obtained in this way is passed between rollers and different layers are attached. You. Obviously, this technique only applies in the case of thermoplastic adhesives.   The thermal bond is coated on both sides with an adhesive layer, here also a thermoplastic. Starting with a composite strip of polymer containing a central layer or polymer, It is to introduce the flap between two sheets of metal foil. Thermal bonding is the Fused product melts the adhesive layer enough to ensure adhesion between the polymer core and the metal foil Or at least to pass between two pieces heated to a temperature sufficient to soften Therefore, it is guaranteed.   Finally, high-frequency bonding is a well-known method in which thermosetting is performed on the inner surfaces of the two metal foils. This is coated from one side and the other with the aid of a roller, with the help of rollers. The thin layer is attached to the central polymer layer.   Molding of cans is generally performed in one continuous run using a device such as that shown in FIG. Alternatively, it involves step c consisting of a plurality of drawing passes. MPM in a specific case In order to match the operating conditions to the type of metal-plastic structure, the inventors have This is the same as when reliably drawing a structure without causing cracks, wrinkles or peeling. Priority is given to a specific punch base shape that affects the I decided to let it.   The punch, which is generally in the shape of a rotating cylinder, is prepared by any of the preferred methods of the invention. , The axial direction where the bus bar is connected to the base of the punch by an arc of radius 5-10 mm Present the cross section. This connection is the part of the second arc whose center is on the axis of rotation of the punch. From the point of view, it is applied to the base of the punch either directly or by means of an intermediate. 5a and 5 b shows the above-mentioned two types of modification.   FIG. 5a is an example of the simplest shape. Punch 9 is shown with a cross-section through the axis And is in the form of a cylinder that rotates about axis 10. Bus bar 11 Within the range of 5 to 10 mm (for example, 8 mm for a punch with a diameter of 85 mm) It is joined to the base by an arc of diameter R1. This arc is the circle of the torus. Caused by a roll.   Figure 5b shows a slightly more complicated evolution shape. The center of the busbar matches the axis of the punch The first circular arc 14 having a radius R1 of 5 to 10 mm which is tangent to the second circular arc It is connected to the source. The arc cormorant (15) creates a spherical dome, and the arc (14) It forms part of the torus. As an example, R1 is about 6 mm and R2 is about 250 mm. Can be   Another preferred method of the present invention, which cooperates with the particular shape of the punch described above, is described in detail. , The shape of the entrance of the die plate used in the second aperture pass. Usually for diaphragm The die plate has a first squeeze pass starting from the flat circular disc as described above. It has a shape as schematically illustrated in Figure 1a. In Figure 6, the starting material is According to the present invention, which is not a disc but a shape which has already been stretched during the first pass. The following squeezing pass is shown. The cup (24) is in the middle of the drawing process, Its initial diameter, which corresponds to (25), during the process is such that the punch (27) and the die Decreasing towards the final diameter (26) defined by the space between the doors (28) You. Along with this, the height of the wall can be ironed in the general sense of the word. In other words, the thickness is increased without being significantly reduced. Internal pressurization inside the starting cup A plate (29) is arranged.   The inventors have formed a busbar of the insert cone with a horizontal plane perpendicular to the axis of the punch. The angle is critical for drawing MPM type metal-plastic structures I found it to be an angle. This angle is between 10 ° and 70 °, preferably about 60 ° Should be   Molding of cans is an ironing process in which the wall is stretched by thinning the wall accordingly. It is. This process is shown schematically in FIG.   Applicants can use MPM discs without defects such as cracks and peeling. The wall of the cups drawn from a slab, preferably in particular in European patent application EP 0 040 20 Four consecutive ironing operations instead of the three passes commonly practiced in No. 06 It was discovered that ironing can be performed by processing in a pass. More suitable The first of these consecutive passes is a symptom that reduces the thickness percentage to 2-25%. Make a proper calibration pass.   An example after the description of a particular case, which is various steps of the invention.Example 1   A strip of polypropylene with a thickness of 300 microns should be A 10 micron thick adhesive consisting of acid modified polypropylene film is coated. Has been The two adhesive films are made by passing between two rolls Attached to the film at room temperature. The composite strips thus obtained are It is unwound from the bobbin and ovend at a temperature of 200 ° C so that the adhesive melts. Alloy 3003 with a thickness of 100 microns, preheated through Continuously guides between two foils of manganese alloy according to the "Aluminum Association" standard. Be entered. The MPM structure thus obtained is then subjected to a pressure of about 4000 Kpa. It is passed between adding rollers. Starting from this structure, a circle with a diameter of 140 mm The disc is cut off. These discs are then the ones shown in Figure 5a. Squeezed in two consecutive passes with the help of a similar R1 = 8mm punch ing. A die plate with an angle α of 60 ° is used in the second drawing pass. You. By the first pass, a cup-shaped body having an outer diameter of 86 mm and a height of 35 mm is obtained. Second party The cup forms a cup-shaped body having an outer diameter of 67 mm and a height of 56 mm. Move by punch Finally, the cylindrical cup is made up of a series of four rings of decreasing diameter. Through a tool containing a to obtain a cup of beverage can with a diameter of 66 mm and a height of 130 mm. Can be Expressing each wall thickness reduction as a percentage of the initial thickness, it is 20%, 50% , 52% and 57%. These cups were carefully inspected for metal or No signs of lasting cracks were observed. Stripping between metal and plastic No separation was observed.Example 2   The composite MPM strip is the same 3003 alloy as in Example 1 and has a thickness of 80 microns. Between two foils, 250 micron thick polypropylene and 10 on each side Coextruding a core consisting of an adhesive layer of micron maleic acid modified polypropylene Created by Adhesion is 200 while applying a pressure of 4000 Kpa. This is accomplished by passing between two rollers heated to ° C. Example 1 already Soft drink bottles were produced under the same conditions as. Inspect these cups However, no crack of metal or plastic was observed. Also gold No delamination between the genus and the plastic was also observed.Example 3   The MPM composite strip was coextruded using the same ingredients as in Example 2 under the same conditions. However, the core was made of poly recovered from a can made from the same MPM structure. Made using propylene. By collecting polypropylene from used cans Could not separate the adhesive from the polymer, but the resulting structure was of excellent quality, Neither cracking nor peeling was observed. Production of beverage cans under the same conditions as in Example 1 did. We inspected these cups and found no cracks in the metal or plastic. It did not fit. No delamination between metal and plastic was also observed.Example 4   Under the same process conditions as in FIG. 2, 80 micron thick 3003 alloy foil, thickness 1 0 micron amorphous polyethylene terephthalate adhesive layer, thickness 2 00 micron polyethylene terephthalate layer, another 10 micron thick ammo Rufus polyethylene terephthalate layer, finally another 3 with 80 micron thickness An MPM structure composed of 003 alloy foil was manufactured. Inspected these cups However, no crack of metal or plastic was observed. Also with metal No delamination between the plastics was observed.Example 5   Example 5 is a plastic bottle containing the polyethylene terephthalate used. Production of the same cup-shaped body as in Example 4, with the difference being that it was recovered from the tor It is about. After washing and drying, these bottles are pulverized and extruded. It was put into the feed hopper of the machine. Even structures can be obtained by drawing and ironing. No quality problems were observed with the cups formed.

Claims (1)

[Claims]   1. M_i-PM_eWith bottom and upright sides with type of laminated structure A squeezing and ironing can,_iAnd M_eAre the inner and outer metal foil layers respectively , P is essentially a non-oriented polymer monolayer, and the thickness ratio P / (M_i+ M_e) Is 0.5 The thickness of the side surface is smaller than that of the bottom surface, and the thickness of the polymer layer P is The thickness is 100 to 500 microns, and each metal layer M_iAnd M_eThickness is 25 to 15 The can body is 0 micron.   2. Ratio P / (M_i+ M_e) Is 0.7 to 2.5, and is a contract The can main body according to claim 1.   3. Ratio P / (M_i+ M_e) Is 1.0 to 2.0, and The can main body described in Scope 2 of the application.   4. Can body according to claim 1, intended for containing beverages.   5. The peel strength of the metal layer on the plastic layer of the laminated structure is 0.4 N / Can body according to claim 1, characterized in that it is greater than mm.   6. M_iAnd M_eAre steel, tinned steel, chrome or zinc or nickel, respectively Steel coated with aluminum, aluminum coated with chrome-chromium oxide It is a metal foil that is separately selected from the aluminum and aluminum alloys. The can main body according to claim 1.   7. Metal foil M_iAnd M_eIs characterized by being made of aluminum alloy The can body according to claim 5.   8. The polymer layer P is made of polypropylene, high density polyethylene or low density polyethylene. Thermoplastic selected from the group consisting of ren, polyester, and nylon Can body according to claim 1, characterized in that it comprises a polymer.   9. The polymer layer P according to claim 1, characterized in that the polymer layer P contains a recovered polymer. The body of the can.   10. Thermosetting polymer adhesive based on polyurethane and epoxy adhesive The central polymer layer P and the metal foil layers M each having a thickness of 1 to 20 μm._iAnd M_e And an adhesive layer, the thickness of which is included in the total thickness of the polymer P. The can main body according to claim 1, wherein   11. Polymers derived from ethylenically unsaturated carboxylic acids, olefins and ethylene Consist of polyester and polyester derived from unsaturated carboxylic acid polyurethane A thickness of between 1 and 20 microns, Central polymer layer P and each metal foil layer M_iAnd M_eSandwiched between the two, and its thickness is the total thickness of polymer P The can book according to claim 1, further comprising an adhesive layer contained in body.   12. Metal foil layer M_iAnd M_eIs M_iIs a metal foil with excellent corrosion resistance. Side foil layer M_eAre separate materials that have good mechanical strength. The can main body according to claim 1, which is a characteristic.   13. The side surface is a metal foil layer M_iSpreads and breaks where the radius of curvature is minimal Can body according to claim 1, characterized in that it comprises an upper winding region.   14． Metal foil M forming the outer surface of the can body_eForms the inside of the can body Foil layer M_iCan body according to claim 1, characterized in that it is thicker.   15. A method for reducing the metal content of a can body, comprising:   M_iAnd M_eAre the inner and outer metal foil layers, P is the central polymer layer, and Ratio P / (M_i+ M_e) Exceeds 0.5 M_i-PM_eSteps to provide laminated sheets And   Cutting the disc from the sheet,   Squeeze the disc in at least one pass to form a cup. Tep,   At least one ironing pass, the cup-shaped body after drawing is Forming a can body including an upright side surface having an upright side surface portion having a total thickness smaller than that of the surface portion The method comprising:   16. Ratio P / (M_i+ M_e) Is 0.7 to 2.5, The method according to claim 15.   17． Ratio P / (M_i+ M_e) Is 1.0 to 2.0, The method according to claim 15.   18. The drawing step is characterized by including a plurality of drawing passes. 16. The method according to claim 15.   19. In the laminated sheet, the thickness of the polymer layer P is 100 to 500 microns And each metal layer M_iAnd M_eCharacterized by a thickness of 25 to 150 microns 16. The method according to claim 15, wherein   20. Laminated sheet M_i-PM_eIs a central polymer layer with a thickness of 1 to 20 microns P and each metal foil layer M_iAnd M_eSandwiched between the two, and the thickness of which is included in the total thickness of the polymer P. 16. The method according to claim 15, further comprising a binder layer.   21. In the lamination, the polymer layer P is polypropylene, high density polyethylene. From the group consisting of low density polyethylene, polyester, and polyamide 16. The method according to claim 15, characterized in that it is a selected thermoplastic polymer. Law.   22. Adhesive is a thermoplastic made from polyurethane epoxy based adhesive 16. Method according to claim 15, characterized in that it is a polymer.   23. Adhesives are ethylenically unsaturated carboxylic acids, polyethylene and polypropylene Acid anhydrides, olefin and acrylic acid copolymers, polyesters and Characterized by being a thermoplastic polymer selected from polyester copolymers 21. The method according to claim 20.   24. Metal foil M_iAnd M_eAre steel, chrome or tin-plated steel, aluminum It is a metal foil selected separately from aluminum and aluminum alloy foil. 16. The method according to claim 15, wherein   25. Metal foil M on the outer side of the body_eIs a foil layer M on the inner side of the can body._iThan 16. The method according to claim 15, characterized in that it is thin.   26. In the drawing step, the busbar has a radius of curvature of 5 to 10 mm. At least two times using a cylindrical punch with a circular bottom mixed with the bottom. A drawing pass is performed, and the second pass has a horizontal entry angle of 10 ° to 7 with the die plate. The method according to claim 15, characterized in that it is performed at 0 °.   27. In the body of the drawn and ironed can, the arc is the Characterized by connecting to the base merge of the second arc aligned with the axis of the punch 16. The method according to claim 15.   28. In the ironing step, ironing the cup-shaped body that has been drawn The work is accomplished with the help of four consecutive ironing rings, the first of which is Only calibrate the cup, ie the wall thickness of the cup is only 2 to 25 16. A method according to claim 15, characterized in that it only reduces by%.   29. Metal foil M_iAnd M_eAt least one of them has a tensile strength of 185 MPa Can body according to claim 1, characterized in that it is a foil of a larger material.   30. Most of the load is due to the composite metal layer when the sides are stretched in a single axial direction. M_iAnd M_eThe can body according to claim 1, which is produced by   31. Metal foil M_iAnd M_eAt least one of them has a tensile strength of 210 MPa Can body according to claim 1, characterized in that it is a foil of a larger material.   32. A polymer layer P, characterized in that it is essentially non-oriented. The can body described in 1.