CA1292443C - Closure cap and a process for making same - Google Patents
Closure cap and a process for making sameInfo
- Publication number
- CA1292443C CA1292443C CA000473777A CA473777A CA1292443C CA 1292443 C CA1292443 C CA 1292443C CA 000473777 A CA000473777 A CA 000473777A CA 473777 A CA473777 A CA 473777A CA 1292443 C CA1292443 C CA 1292443C
- Authority
- CA
- Canada
- Prior art keywords
- closure cap
- gasket
- plastisol
- container
- sealing ring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D53/00—Sealing or packing elements; Sealings formed by liquid or plastics material
- B65D53/06—Sealings formed by liquid or plastic material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D41/00—Caps, e.g. crown caps or crown seals, i.e. members having parts arranged for engagement with the external periphery of a neck or wall defining a pouring opening or discharge aperture; Protective cap-like covers for closure members, e.g. decorative covers of metal foil or paper
- B65D41/02—Caps or cap-like covers without lines of weakness, tearing strips, tags, or like opening or removal devices
- B65D41/04—Threaded or like caps or cap-like covers secured by rotation
- B65D41/0435—Threaded or like caps or cap-like covers secured by rotation with separate sealing elements
- B65D41/0442—Collars or rings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D41/00—Caps, e.g. crown caps or crown seals, i.e. members having parts arranged for engagement with the external periphery of a neck or wall defining a pouring opening or discharge aperture; Protective cap-like covers for closure members, e.g. decorative covers of metal foil or paper
- B65D41/32—Caps or cap-like covers with lines of weakness, tearing-strips, tags, or like opening or removal devices, e.g. to facilitate formation of pouring openings
- B65D41/34—Threaded or like caps or cap-like covers provided with tamper elements formed in, or attached to, the closure skirt
- B65D41/3461—Threaded or like caps or cap-like covers provided with tamper elements formed in, or attached to, the closure skirt the tamper element being retracted by heat or by heat and pressure
- B65D41/3466—Threaded or like caps or cap-like covers provided with tamper elements formed in, or attached to, the closure skirt the tamper element being retracted by heat or by heat and pressure and being integrally connected to the closure by means of bridges
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D53/00—Sealing or packing elements; Sealings formed by liquid or plastics material
- B65D53/02—Collars or rings
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Closures For Containers (AREA)
- Glass Compositions (AREA)
- Sealing Battery Cases Or Jackets (AREA)
Abstract
A CLOSURE CAP AND A PROCESS FOR MAKING SAME
ABSTRACT OF THE DISCLOSURE
A process is disclosed for making a closure cap for a container from a polypropylene material, said closure cap comprising an end wall and a circumferential side wall. The process involves forming gasket in the closure cap via a melting and a cooling operation by applying in the closure cap an amount of plastisol which is shaped therein into a gasket configuration at an elevated temperature adjusted after the plastisol addition, causing the plastisol shaped into the gasket configuration to melt completely by further energy supply and then cooling same to form the gasket. Starting from an integral combination of the closure cap with a sealing ring which is connected with the closure cap by means of a number of frangible bridges capable of being broken on the first opening of the container, the gasket is formed by carrying out the melting operation by heating the closure cap after addition of the plastisol to a temperature of 50-110°C and by subsequently exposing the resulting plastisol shaped into the gasket configuration to microwave energy until the plastisol has become completely molten.
ABSTRACT OF THE DISCLOSURE
A process is disclosed for making a closure cap for a container from a polypropylene material, said closure cap comprising an end wall and a circumferential side wall. The process involves forming gasket in the closure cap via a melting and a cooling operation by applying in the closure cap an amount of plastisol which is shaped therein into a gasket configuration at an elevated temperature adjusted after the plastisol addition, causing the plastisol shaped into the gasket configuration to melt completely by further energy supply and then cooling same to form the gasket. Starting from an integral combination of the closure cap with a sealing ring which is connected with the closure cap by means of a number of frangible bridges capable of being broken on the first opening of the container, the gasket is formed by carrying out the melting operation by heating the closure cap after addition of the plastisol to a temperature of 50-110°C and by subsequently exposing the resulting plastisol shaped into the gasket configuration to microwave energy until the plastisol has become completely molten.
Description
3~43 The invention relates to a closure cap made from a polypropylene material.
Closure caps are known which comprise an end wall and a circumferential side wall, with a gasket being 6 formed in the closure cap via a melting and a cooling operation by applying in the closure cap an amount of plastisol which i5 shaped therein into a gasket configuration at an elevated temperature ad~usted after the plastisol addition, causing the plastisol shaped into the gasket configuration to melt completely by further energy supply and then cooling same to form the gasket.
Such a process is known ~rom Dutch patent applicatibn 80.033~1. In this known process a closure cap often made by injection moulding from an olefin polymer, in particular a high-melting polypropylene having a melting point of approximately 165C, after having been provided with a vinyl chloride resin plastisol, is preheated to a temperature which must be 5-35C below the melting point of the employed olefin polymer, e.g., polypropylene, preferably 5-15C, ~2~ 3 i.e. it must be preheated to a temperature of at least 130 C, preferably 145-160 C, followed by exposure at this temperature in an appropriate oven to microwave energy having a frequency which is not critical from a technical - s point of view indeed, but is effectively 300-300,000 MHz.
Exposure to the microwave energy takes place at the moment when the plastisol shaped into a gaske-t configuration is completely liquid, i.e. completely molten, which means that the resin has been completely solvated by the plasticizer.
Preheating can be appropriately carried out in a hot air oven.
In the known process it is indicated that, in general, a temperature of the closure cap of more than 35 C below the melting temperature thereof is probably not suitable for the conventional plastisols. If there is used a plastisol having a lower melting point, then also a lower temperature of the closure cap can be maintained in the preheating step. However, if there is started from a closure cap made from an olefin polymer melting at a lcwer temperature, then, conversely, the temperature range to be maintained for the closure cap in the preheating step must preferably be only 5-15 C, in particular 5-10 C
below the melting point of the olefin polymer. Therefore, if the closure cap is made from, e.g., polyethylene having a high density, then, accordingly, the temperature range of the closure cap in the preheating step is pre~erably 120-125 C.
In practice, it is assumed in the known process that, e.g., after the plastisol has been added to the closure cap, this closure cap is brought into a hot air oven having an air temperature which is 30 C, preferably 20 C, below the melting point of the olefin polymer material from which the closure cap has been made. For instance, when polypropylene is used as the olefin polymer material, the preheating step is carried out, in practice, at an air temperature of 135-160 C for 1-10 min., e.g., an air temperature of 155 C for approximately 3 minutes, followed by the procedure in a microwave oven in which the ambient temperature is likewise high enough to prevent the preheated closure cap from sustaining heavy losses oE heat, and which is, e.g., at least 140 C. The duration 15 of the microwave procedure depends on the energy supplied and is not less than approximately 1 min.
The step of shaping the plastisol in the closure cap until a gasket configuration has been obtained can be performed in the conventional manner, preferably by 20 injecting the plastisol in liquid or semi-liquid condition into the closure cap which is advantageously arranged upside down, i.e. the end wall is positioned at the bottom side, and distributing same therein by subjecting the closure cap to a rapid rotation. There is preferably used 25 a closure cap the end wall of which is internally provided with an inner edge, the plastisol being injected into the annular space between the inner edge and the side wall of the closure cap.
The known process i~ suitable Eor a varlety oE
types of closure caps and container~, in particular, however, for closure caps of bottles of threaded construction or of the snap-on type, which caps can be provided with an unspecified anti-theft means, however, normally have a limited inner diameter of approximately 25-32 mm.
Various types of anti-theft means applicable in combination with a closure cap are known, a review of which is given in the article "Verschl~s~e f~r Getrankeflaschen", published in Verpackings-Rundschau 10/1983, pages 10~4-1093. Among these, the type comprising a sealing ring produced in one piece with the close cap and connected with the side wall of the closure cap via a number of narrow frangible brldye~ to be broken on the first opening of the container cannot be used within the framework of the known process. Because of the high temperature of the closure cap to be maintained in the preheating step and subsequently upon exposure to the microwave energy of only 5-35C below the melting pOiIlt of the olefin polymer material used for making the closure cap, the narrow frangible bridges and the sealing ring, respectively, will be softened and deformed, which results 2~ in that the whole construction becomes useless.
An object of the invention is to provide a process for making a closure cap provided with a gasket from a polypropylene material, which i9 further provided with a sealing ring of the type that is integrally connected with the closure cap, in particular with its side wall, via a number of narrow bridges which are broken on the first opening of the container.
Another ob~ect of the invention is to provide a closure cap made from an olefin polymer ancl provided with a gasket of a plastisol material, which is suitable for ~.
~g4~3 use on a container having a wide mouth the diameter o~
which may be up to 9o mm and more.
According to one aspect of the invention there is provided a process for making a polypropylene closure cap for a container, said closure cap comprising an end wall and a circumferential side wall, the end wall being thinner by 20-50% at the position where a gasket is to be formed, and being internally provided with an annular space bounded by two undexcuts and within which the gasXet will be contained, the inner undercut being tapered in cross-section and resilient and having a width such that when the container has been closed with the closure cap the inner undercut rests on a paxt of the upper surface of the container edge, in which process the gasket is formed in the closure cap via a melting and a cooling operation by applyiny in the closure cap an amount of plastisol which is shaped therein into a gasket configuration at an elevated temperature adjusted after the plastisol addition, causing the plastisol shaped into the gasket configuration to melt completely by further energy supply and then cooling same to form the gasket, wherein an integral combination of the closure cap with a sealing ring is initially formed, which sealing ring is connected with the closure cap by means of a number of frangible bridges capable of being broken on the first opening of the container, and wherein the melting operation to form the gasket is carried out by heating the closure cap after addition of the plastisol to a temperature of 50-llO~C and by subsequently exposing the resulting plastisol shaped into the gasket configuration to electromagnetic energy having a frequency of from 10 to 200 ; M~lz until the plastisol has become completely molten.
The process according to the invention may start from a closure cap of a standard grade polypropylene: it is therefore not necessary to use a high-melting polypropyl-`` ~Z~2~ ~3 ene material. There can also be used a normal type of plastisol, e.g., that consisting of a microsuspension of a vinyl chloride copolymer resin with 5% vinyl acetate and further comprising conventional constituents, e.g., one or more stabilizers, plasticizers, viscosity-reducing and/or torsion-reducing agents.
It is very advantageous to start from a closure cap the end wall of which is internally provided with an annular space bounded by two undercuts the outer one of which is substantially bounded by the inner periphery of the side wall of the closure cap, and into which annular space a dosed amount of plastisol is injected in the conventional manner.
Preferably, the starting point of the invention is a closure cap the end wall of which is thinner by 20-50%
at the position where the gasket is to be formed, such as at the position of the annular space bounded by the undercuts mentioned before. This promotes the heat transfer to the plastisol in the oven, such as the hot air oven in which the preheating can be performed. Moreover, the higher flexibility of the end wall at the relevant position enhances the self-ventilating action of it when the contents of the container are pasteurized.
According to a further embodiment of the process 25 of the invention the melting operation of the plastisol disposed in situ in the closure cap is carried out by preheating the combination of closure cap and plastisol to 50-110C and then exposing the resulting gasket configuration to microwave energy having a frequency of 10-200 MHz.
According to a preferred embodiment the melting 5 operation is carried out by heating the closure cap to 100C within 15-30 seconds after addition of the plastisol, and completely melting the plastisol shaped into the gasket configuration by 3-15 seconds exposure to microwave energy having a frequency of 27.10-27.15 MHz. This frequency is 10 permitted for industrial uses throughout the whole world.
In the process according to the invention a closure cap is obtained which comprises a homogeneous gasket, and which is further provided with an undamaged, undeformed sealing ring, and which closure cap may have an 15 inner diameter such that it can be applied to a container having a wide mouth. For instance, according to the invention a closure cap can be obtained having an inner diameter which may be up to 90 mm or more.
The invention is particularly suitable for, 20 although not limited to, the preparation of a closure cap with an integrally connected sealing ring, the inner side wall of which is threaded so that this container can be opened or closed by rotation of the closure cap, in conjunction with corresponding provisions made at the neck 25 of the container.
Another aspect of the invention provides a closure cap formed from an olefin polymer, comprising an endwall, a circumferential side wall provided with a gasket formed from a plastisol material, and a sealing ring with 30 which the container can be sealably closed in conjunction with a locking collar disposed around the neck of the container, which sealing ring is integrally connected with the side wall of the closure cap via frangible bridges capable of being broken on the first opening of the 35 container, said end wall having a wall thickness decreased by 20-50% at the gasket and being internally provided with an annular space bounded by two 2~'~3 undercuts and within which the gasket is contained, the inner undercut being tapered in cross-section and resilient and having a width such that when the container has been closed with the closure cap the inner undercut rests on a 5 part of the upper surface of the container edge.
When the closure cap is made from a polypropylene material, it is ensured that the diameter of the sealing ring is large enough to provide that after the container has been closed with the closure cap the sealing ring and 10 the bridges are not in contact with the container. When the sealing ring and the bridges are heated during the sealing procedure, such a contact, as will be elucidated hereinafter, would mean that heat is dissipated via the container so that the polypropylene material becomes 15 insufficiently plastic. On the other hand, when dimensioning the sealing ring and the bridges with a closure cap made from a polypropylene material, it is ensured that in the sealing procedure Z4~3 g the bridges can be overstretched under the locking collar and are malleable.
Finally the invention also relates to a process for closing and sealing a container in which, after the 5 container has been closed, the temperature of the sealing ring is increased and the sealing ring is deformed over and around the locking collar towards the neck of the container. When a closure cap according to the invention is used which has been made from a polypropylene material, 10 the procedure followed is such that after the container has been closed with the closure cap, the sealing ring is subjected to a heat treatment until a sufficient plasticity of the polypropylene material has been obtained, after which the sealing ring is mechanically pressed agalnst 15 the neck of the container over and around the locking collar with simultaneous overstretching and flattening of the bridges over and under the locking collar. The heat treatment may consist in, e.g., exposing the sealing ring and the bridges to air having a temperature of approximate-20 ly 400 C for approximately 2 sec. After mechanicallypinching with e.g. so-called clamps, the ring is positioned around the container under the locking collar and the frangible bridges are stretched and flattened. Thus it is achieved that in spite of per se relatively tough poly-25 propylene material the sealing ring is easily detachedat the frangible bridges on the first openiny of the container.
When the closure cap is loosened for the first time, the -Z~'~3 sealing ring will substantially be detached from the closure cap via -the bridges so that, after the closure cap has been closed again, it will always be visible that the container has been opened.
The closure cap according to the inventlon is the first to incorporate a combination of three properties, namely that (a) the container closed with the closure cap after filling can be closed in compression-proof and vacuum-tight condition substantially without any restriction;
lO (b) the container can be closed again after opening so that it is completely shut off from the atmosphere, and (c) the closure of the container after the first filling is irreversibly sealable.
Because of the fact that the closure cap according 15 to the invention can be made available with an inner diameter which may be up to lO0 mm the possibility has been offered for the first time to seal containers having a wide mouth so that for the first time foodstuffs which, in practice, are packed mainly in containers having a wide mouth, e.g., 20 a neck diameter of 90 mm, whether or not under a partial vacuum, can be offered to consumers in sealed condition with a guarantee of freshness. This ensures that the date indicating until when the product will keep, as it occurs on containers for foodstuffs, is a practically reliable 25 date indeed. In the case of a closure without a sealing capable of being broken irreversibly such a date is actually a fiction.
~2~ ~3 The invention will be further illustrated by means of the drawing which shows an example of embodiment of the closure cap and the method of sealing it. In the drawing Fig. 1 schematically shows an axial cross~section of a container closed with the closure cap;
Fig. 2 schematically shows an axial cross-section of a container closed with the closure cap and provided with a sealing ring, in the pre-sealed state;
Fig. 3 shows a cross-section along the line III-III in Fig. 2;
Fig. 4 shows, in cross-section, the assembly of closure cap and container according to Fig. 2 during sealing with the use of a so-called clamp; and Fig. 5 shows a cross-section along the line V-V in Fig. 4, without the clamp and the container.
In Fig. 1 the wall of the neck oE a container made of glass is indicated by 1, and 2 shows the closure cap of polypropylene. On the inside the closure cap is provided with an annular space formed by the two circumferen-tial undercuts 3 and 4, which annular space comprises the gasket 5. The inner undercut 3 is crescent-shaped and is resilient due to the outwardly decreasing thickness of the material. The crescent-shaped construction permits the inner undercut to rest on a part of the edge of the neck opening of the container. As a result thereof a part of the higher unscrewing torsion of the gasket is absorbed and reduced by the undercut. Moreover, the crescent-shaped undercut 3 ensures that in case of pasteurization of the contents of the container the expanded air generated in that process flows out between the undercut 3, which is thereby resiliently deflicted somewhat, and the edge of the neck whereby the deflected undercut simultaneously causes an additional clamping force to be exerted on the gasket and the gasket is retained in position.
Figs. 2-5 show the closure cap of polypropylene at 10, comprising side wall 11 and sealing ring 13 which is connected with side wall 11 via a frangible bridge 12. The neck portion of the container is shown at 14, which neck portion 14 is provided with locking collar 17.
In the state before sealing (Fig. 2) the side wall 11 with frangible bridges 12 and sealing ring 13 is clear of the container.
Fig. 4 shows the situation in which the frangible bridge 12 with the sealing 13, which where previously exposed to the action of hot air having a temperature of 400 C for 2 sec., has been grasped by the clamp 15 moving towards the container. The frangible bridge 12 is then overskretched over and under the locking collar 17 and flattened, the sealing ring 13 also being flattened simultaneously between the clamp 15 and the neck portion 14 of the container. Fig. 5 shows, in comparison with Fig. 3, the deformation experienced by the frangible bridge '` 3~;2~Z~3 12 and the sealing ring 13, which has resulted in that the sealing ring has a diameter smaller than the largest diameter of the locking collar 17. When the closure cap is unscrewed, an axial shiEt of the closure cap 10 is blocked by abutment of the sealing ring 13 against the locking collar 17. When the unscrewing movement is continued, the increasing force exerted by the locking collar 17 on the combination of sealing ring 13 and frangible bridge 12 will result in that the frangible bridge 12 weakened by overstretching and flattening, which is made of the per se tough polypropylene, is broken along the line of fracture 16 (Fig. 5).
of course, amendments may be made to the invention as described above and shown in the drawing without departing from the scope of the invention.
Closure caps are known which comprise an end wall and a circumferential side wall, with a gasket being 6 formed in the closure cap via a melting and a cooling operation by applying in the closure cap an amount of plastisol which i5 shaped therein into a gasket configuration at an elevated temperature ad~usted after the plastisol addition, causing the plastisol shaped into the gasket configuration to melt completely by further energy supply and then cooling same to form the gasket.
Such a process is known ~rom Dutch patent applicatibn 80.033~1. In this known process a closure cap often made by injection moulding from an olefin polymer, in particular a high-melting polypropylene having a melting point of approximately 165C, after having been provided with a vinyl chloride resin plastisol, is preheated to a temperature which must be 5-35C below the melting point of the employed olefin polymer, e.g., polypropylene, preferably 5-15C, ~2~ 3 i.e. it must be preheated to a temperature of at least 130 C, preferably 145-160 C, followed by exposure at this temperature in an appropriate oven to microwave energy having a frequency which is not critical from a technical - s point of view indeed, but is effectively 300-300,000 MHz.
Exposure to the microwave energy takes place at the moment when the plastisol shaped into a gaske-t configuration is completely liquid, i.e. completely molten, which means that the resin has been completely solvated by the plasticizer.
Preheating can be appropriately carried out in a hot air oven.
In the known process it is indicated that, in general, a temperature of the closure cap of more than 35 C below the melting temperature thereof is probably not suitable for the conventional plastisols. If there is used a plastisol having a lower melting point, then also a lower temperature of the closure cap can be maintained in the preheating step. However, if there is started from a closure cap made from an olefin polymer melting at a lcwer temperature, then, conversely, the temperature range to be maintained for the closure cap in the preheating step must preferably be only 5-15 C, in particular 5-10 C
below the melting point of the olefin polymer. Therefore, if the closure cap is made from, e.g., polyethylene having a high density, then, accordingly, the temperature range of the closure cap in the preheating step is pre~erably 120-125 C.
In practice, it is assumed in the known process that, e.g., after the plastisol has been added to the closure cap, this closure cap is brought into a hot air oven having an air temperature which is 30 C, preferably 20 C, below the melting point of the olefin polymer material from which the closure cap has been made. For instance, when polypropylene is used as the olefin polymer material, the preheating step is carried out, in practice, at an air temperature of 135-160 C for 1-10 min., e.g., an air temperature of 155 C for approximately 3 minutes, followed by the procedure in a microwave oven in which the ambient temperature is likewise high enough to prevent the preheated closure cap from sustaining heavy losses oE heat, and which is, e.g., at least 140 C. The duration 15 of the microwave procedure depends on the energy supplied and is not less than approximately 1 min.
The step of shaping the plastisol in the closure cap until a gasket configuration has been obtained can be performed in the conventional manner, preferably by 20 injecting the plastisol in liquid or semi-liquid condition into the closure cap which is advantageously arranged upside down, i.e. the end wall is positioned at the bottom side, and distributing same therein by subjecting the closure cap to a rapid rotation. There is preferably used 25 a closure cap the end wall of which is internally provided with an inner edge, the plastisol being injected into the annular space between the inner edge and the side wall of the closure cap.
The known process i~ suitable Eor a varlety oE
types of closure caps and container~, in particular, however, for closure caps of bottles of threaded construction or of the snap-on type, which caps can be provided with an unspecified anti-theft means, however, normally have a limited inner diameter of approximately 25-32 mm.
Various types of anti-theft means applicable in combination with a closure cap are known, a review of which is given in the article "Verschl~s~e f~r Getrankeflaschen", published in Verpackings-Rundschau 10/1983, pages 10~4-1093. Among these, the type comprising a sealing ring produced in one piece with the close cap and connected with the side wall of the closure cap via a number of narrow frangible brldye~ to be broken on the first opening of the container cannot be used within the framework of the known process. Because of the high temperature of the closure cap to be maintained in the preheating step and subsequently upon exposure to the microwave energy of only 5-35C below the melting pOiIlt of the olefin polymer material used for making the closure cap, the narrow frangible bridges and the sealing ring, respectively, will be softened and deformed, which results 2~ in that the whole construction becomes useless.
An object of the invention is to provide a process for making a closure cap provided with a gasket from a polypropylene material, which i9 further provided with a sealing ring of the type that is integrally connected with the closure cap, in particular with its side wall, via a number of narrow bridges which are broken on the first opening of the container.
Another ob~ect of the invention is to provide a closure cap made from an olefin polymer ancl provided with a gasket of a plastisol material, which is suitable for ~.
~g4~3 use on a container having a wide mouth the diameter o~
which may be up to 9o mm and more.
According to one aspect of the invention there is provided a process for making a polypropylene closure cap for a container, said closure cap comprising an end wall and a circumferential side wall, the end wall being thinner by 20-50% at the position where a gasket is to be formed, and being internally provided with an annular space bounded by two undexcuts and within which the gasXet will be contained, the inner undercut being tapered in cross-section and resilient and having a width such that when the container has been closed with the closure cap the inner undercut rests on a paxt of the upper surface of the container edge, in which process the gasket is formed in the closure cap via a melting and a cooling operation by applyiny in the closure cap an amount of plastisol which is shaped therein into a gasket configuration at an elevated temperature adjusted after the plastisol addition, causing the plastisol shaped into the gasket configuration to melt completely by further energy supply and then cooling same to form the gasket, wherein an integral combination of the closure cap with a sealing ring is initially formed, which sealing ring is connected with the closure cap by means of a number of frangible bridges capable of being broken on the first opening of the container, and wherein the melting operation to form the gasket is carried out by heating the closure cap after addition of the plastisol to a temperature of 50-llO~C and by subsequently exposing the resulting plastisol shaped into the gasket configuration to electromagnetic energy having a frequency of from 10 to 200 ; M~lz until the plastisol has become completely molten.
The process according to the invention may start from a closure cap of a standard grade polypropylene: it is therefore not necessary to use a high-melting polypropyl-`` ~Z~2~ ~3 ene material. There can also be used a normal type of plastisol, e.g., that consisting of a microsuspension of a vinyl chloride copolymer resin with 5% vinyl acetate and further comprising conventional constituents, e.g., one or more stabilizers, plasticizers, viscosity-reducing and/or torsion-reducing agents.
It is very advantageous to start from a closure cap the end wall of which is internally provided with an annular space bounded by two undercuts the outer one of which is substantially bounded by the inner periphery of the side wall of the closure cap, and into which annular space a dosed amount of plastisol is injected in the conventional manner.
Preferably, the starting point of the invention is a closure cap the end wall of which is thinner by 20-50%
at the position where the gasket is to be formed, such as at the position of the annular space bounded by the undercuts mentioned before. This promotes the heat transfer to the plastisol in the oven, such as the hot air oven in which the preheating can be performed. Moreover, the higher flexibility of the end wall at the relevant position enhances the self-ventilating action of it when the contents of the container are pasteurized.
According to a further embodiment of the process 25 of the invention the melting operation of the plastisol disposed in situ in the closure cap is carried out by preheating the combination of closure cap and plastisol to 50-110C and then exposing the resulting gasket configuration to microwave energy having a frequency of 10-200 MHz.
According to a preferred embodiment the melting 5 operation is carried out by heating the closure cap to 100C within 15-30 seconds after addition of the plastisol, and completely melting the plastisol shaped into the gasket configuration by 3-15 seconds exposure to microwave energy having a frequency of 27.10-27.15 MHz. This frequency is 10 permitted for industrial uses throughout the whole world.
In the process according to the invention a closure cap is obtained which comprises a homogeneous gasket, and which is further provided with an undamaged, undeformed sealing ring, and which closure cap may have an 15 inner diameter such that it can be applied to a container having a wide mouth. For instance, according to the invention a closure cap can be obtained having an inner diameter which may be up to 90 mm or more.
The invention is particularly suitable for, 20 although not limited to, the preparation of a closure cap with an integrally connected sealing ring, the inner side wall of which is threaded so that this container can be opened or closed by rotation of the closure cap, in conjunction with corresponding provisions made at the neck 25 of the container.
Another aspect of the invention provides a closure cap formed from an olefin polymer, comprising an endwall, a circumferential side wall provided with a gasket formed from a plastisol material, and a sealing ring with 30 which the container can be sealably closed in conjunction with a locking collar disposed around the neck of the container, which sealing ring is integrally connected with the side wall of the closure cap via frangible bridges capable of being broken on the first opening of the 35 container, said end wall having a wall thickness decreased by 20-50% at the gasket and being internally provided with an annular space bounded by two 2~'~3 undercuts and within which the gasket is contained, the inner undercut being tapered in cross-section and resilient and having a width such that when the container has been closed with the closure cap the inner undercut rests on a 5 part of the upper surface of the container edge.
When the closure cap is made from a polypropylene material, it is ensured that the diameter of the sealing ring is large enough to provide that after the container has been closed with the closure cap the sealing ring and 10 the bridges are not in contact with the container. When the sealing ring and the bridges are heated during the sealing procedure, such a contact, as will be elucidated hereinafter, would mean that heat is dissipated via the container so that the polypropylene material becomes 15 insufficiently plastic. On the other hand, when dimensioning the sealing ring and the bridges with a closure cap made from a polypropylene material, it is ensured that in the sealing procedure Z4~3 g the bridges can be overstretched under the locking collar and are malleable.
Finally the invention also relates to a process for closing and sealing a container in which, after the 5 container has been closed, the temperature of the sealing ring is increased and the sealing ring is deformed over and around the locking collar towards the neck of the container. When a closure cap according to the invention is used which has been made from a polypropylene material, 10 the procedure followed is such that after the container has been closed with the closure cap, the sealing ring is subjected to a heat treatment until a sufficient plasticity of the polypropylene material has been obtained, after which the sealing ring is mechanically pressed agalnst 15 the neck of the container over and around the locking collar with simultaneous overstretching and flattening of the bridges over and under the locking collar. The heat treatment may consist in, e.g., exposing the sealing ring and the bridges to air having a temperature of approximate-20 ly 400 C for approximately 2 sec. After mechanicallypinching with e.g. so-called clamps, the ring is positioned around the container under the locking collar and the frangible bridges are stretched and flattened. Thus it is achieved that in spite of per se relatively tough poly-25 propylene material the sealing ring is easily detachedat the frangible bridges on the first openiny of the container.
When the closure cap is loosened for the first time, the -Z~'~3 sealing ring will substantially be detached from the closure cap via -the bridges so that, after the closure cap has been closed again, it will always be visible that the container has been opened.
The closure cap according to the inventlon is the first to incorporate a combination of three properties, namely that (a) the container closed with the closure cap after filling can be closed in compression-proof and vacuum-tight condition substantially without any restriction;
lO (b) the container can be closed again after opening so that it is completely shut off from the atmosphere, and (c) the closure of the container after the first filling is irreversibly sealable.
Because of the fact that the closure cap according 15 to the invention can be made available with an inner diameter which may be up to lO0 mm the possibility has been offered for the first time to seal containers having a wide mouth so that for the first time foodstuffs which, in practice, are packed mainly in containers having a wide mouth, e.g., 20 a neck diameter of 90 mm, whether or not under a partial vacuum, can be offered to consumers in sealed condition with a guarantee of freshness. This ensures that the date indicating until when the product will keep, as it occurs on containers for foodstuffs, is a practically reliable 25 date indeed. In the case of a closure without a sealing capable of being broken irreversibly such a date is actually a fiction.
~2~ ~3 The invention will be further illustrated by means of the drawing which shows an example of embodiment of the closure cap and the method of sealing it. In the drawing Fig. 1 schematically shows an axial cross~section of a container closed with the closure cap;
Fig. 2 schematically shows an axial cross-section of a container closed with the closure cap and provided with a sealing ring, in the pre-sealed state;
Fig. 3 shows a cross-section along the line III-III in Fig. 2;
Fig. 4 shows, in cross-section, the assembly of closure cap and container according to Fig. 2 during sealing with the use of a so-called clamp; and Fig. 5 shows a cross-section along the line V-V in Fig. 4, without the clamp and the container.
In Fig. 1 the wall of the neck oE a container made of glass is indicated by 1, and 2 shows the closure cap of polypropylene. On the inside the closure cap is provided with an annular space formed by the two circumferen-tial undercuts 3 and 4, which annular space comprises the gasket 5. The inner undercut 3 is crescent-shaped and is resilient due to the outwardly decreasing thickness of the material. The crescent-shaped construction permits the inner undercut to rest on a part of the edge of the neck opening of the container. As a result thereof a part of the higher unscrewing torsion of the gasket is absorbed and reduced by the undercut. Moreover, the crescent-shaped undercut 3 ensures that in case of pasteurization of the contents of the container the expanded air generated in that process flows out between the undercut 3, which is thereby resiliently deflicted somewhat, and the edge of the neck whereby the deflected undercut simultaneously causes an additional clamping force to be exerted on the gasket and the gasket is retained in position.
Figs. 2-5 show the closure cap of polypropylene at 10, comprising side wall 11 and sealing ring 13 which is connected with side wall 11 via a frangible bridge 12. The neck portion of the container is shown at 14, which neck portion 14 is provided with locking collar 17.
In the state before sealing (Fig. 2) the side wall 11 with frangible bridges 12 and sealing ring 13 is clear of the container.
Fig. 4 shows the situation in which the frangible bridge 12 with the sealing 13, which where previously exposed to the action of hot air having a temperature of 400 C for 2 sec., has been grasped by the clamp 15 moving towards the container. The frangible bridge 12 is then overskretched over and under the locking collar 17 and flattened, the sealing ring 13 also being flattened simultaneously between the clamp 15 and the neck portion 14 of the container. Fig. 5 shows, in comparison with Fig. 3, the deformation experienced by the frangible bridge '` 3~;2~Z~3 12 and the sealing ring 13, which has resulted in that the sealing ring has a diameter smaller than the largest diameter of the locking collar 17. When the closure cap is unscrewed, an axial shiEt of the closure cap 10 is blocked by abutment of the sealing ring 13 against the locking collar 17. When the unscrewing movement is continued, the increasing force exerted by the locking collar 17 on the combination of sealing ring 13 and frangible bridge 12 will result in that the frangible bridge 12 weakened by overstretching and flattening, which is made of the per se tough polypropylene, is broken along the line of fracture 16 (Fig. 5).
of course, amendments may be made to the invention as described above and shown in the drawing without departing from the scope of the invention.
Claims (5)
1. A process for making a polypropylene closure cap for a container, said closure cap comprising an end wall and a circumferential side wall, the end wall being thinner by 20-50% at the position where a gasket is to be formed, and being internally provided with an annular space bounded by two undercuts and within which the gasket will be contained, the inner undercut being tapered in cross-section and resilient and having a width such that when the container has been closed with the closure cap the inner undercut rests on a part of the upper surface of the container edge, in which process the gasket is formed in the closure cap via a melting and a cooling operation by applying in the closure cap an amount of plastisol which is shaped therein into a gasket configuration at an elevated temperature adjusted after the plastisol addition, causing the plastisol shaped into the gasket configuration to melt completely by further energy supply and then cooling same to form the gasket, wherein an integral combination of the closure cap with a sealing ring is initially formed, which sealing ring is connected with the closure cap by means of a number of frangible bridges capable of being broken on the first opening of the container, and wherein the melting operation to form the gasket is carried out by heating the closure cap after addition of the plastisol to a temperature of 50-110°C and by subsequently exposing the resulting plastisol shaped into the gasket configuration to electromagnetic energy having a frequency of from 10 to 200 MHz until the plastisol has become completely molten.
2. A process according to claim 1, wherein the melting operation is carried out by heating the closure cap after addition of the plastisol to 100°C within 15-30 seconds and completely melting the resulting plastisol shaped into the gasket configuration by 3-15 seconds exposure to microwave energy having a frequency of 27.10-27.15 MHz.
3. A closure cap formed from an olefin polymer, comprising an endwall, a circumferential side wall provided with a gasket formed from a plastisol material, and a sealing ring with which the container can be sealably closed in conjunction with a locking collar disposed around the neck of the container, which sealing ring is integrally connected with the side wall of the closure cap via frangible bridges capable of being broken on the first opening of the container, said end wall having a wall thickness decreased by 20-50% at the gasket and being internally provided with an annular space bounded by two undercuts and within which the gasket is contained, the inner undercut being tapered in cross-section and resilient and having a width such that when the container has been closed with the closure cap the inner undercut rests on a part of the upper surface of the container edge.
4. A closure cap according to claim 3, wherein the inner diameter of the closure cap is up to 100 mm.
5. A closure cap according to claim 3, which is made from a polypropylene material, and in which the diameter of the sealing ring is large enough such that, that after the container has been closed with the closure cap, the sealing ring and the bridges are not in contact with the container, but in the sealing procedure the bridges can be overstretched under the locking collar and are malleable.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8400428A NL8400428A (en) | 1984-02-09 | 1984-02-09 | METHOD FOR MANUFACTURING A SEALING CAP WITH A SEALING GASKET FROM A POLYPROPENE MATERIAL FOR A CONTAINER; Sealing cap provided with an olefin polymer, as well as a method for closing and sealing a container with a sealing cap made from polypropylene material. |
| NL8400428 | 1984-02-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1292443C true CA1292443C (en) | 1991-11-26 |
Family
ID=19843469
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000473777A Expired - Lifetime CA1292443C (en) | 1984-02-09 | 1985-02-07 | Closure cap and a process for making same |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0155021B2 (en) |
| JP (1) | JP2545207B2 (en) |
| AT (1) | ATE34148T1 (en) |
| CA (1) | CA1292443C (en) |
| DE (1) | DE3562601D1 (en) |
| DK (1) | DK61285A (en) |
| ES (1) | ES8606173A1 (en) |
| GR (1) | GR850303B (en) |
| IN (1) | IN162719B (en) |
| NL (1) | NL8400428A (en) |
| ZA (1) | ZA85865B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE939052C (en) * | 1948-12-14 | 1956-02-16 | Anton Springer | Borehole inoculation device for wood protection |
| US4675139A (en) * | 1985-10-21 | 1987-06-23 | Continental Can Company, Inc. | Method of forming plastisol gaskets in container closures fabricated from synthetic plastic resins |
| GB2186558A (en) * | 1986-02-17 | 1987-08-19 | Grace W R & Co | Container closure |
| IT1232058B (en) * | 1989-03-29 | 1992-01-23 | Alplast Spa | SCREW CAPS OF THERMOPLASTIC MATERIAL |
| GB2252267A (en) * | 1991-01-31 | 1992-08-05 | Grace W R & Co | Curing of plastisol liner material in thermoplastic closure |
| US6142325A (en) | 1998-10-19 | 2000-11-07 | Playtex Products, Inc. | Container assembly and bottom cap therefor |
| FR2822810B1 (en) * | 2001-03-28 | 2003-08-22 | Rical Sa | CAPPING DEVICE FOR A CONTAINER, PROVIDED WITH HOLDING AND LOCKING MEANS OF A CAST OR MOLD JOINT, AND METHOD FOR PRODUCING THE SAME |
| JP4994172B2 (en) * | 2007-09-26 | 2012-08-08 | 日本クラウンコルク株式会社 | Cap for container |
| MX347689B (en) * | 2010-08-30 | 2017-05-09 | Tetra Laval Holdings & Finance S A * | Sealing cap. |
| CN108910251A (en) * | 2018-08-02 | 2018-11-30 | 宁国市双阳精密制造有限公司 | A kind of wear-resistant material production and sales box for material circulation |
| GB2579839B (en) * | 2018-12-17 | 2021-09-15 | Crown Packaging Tech | Low migration container |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GR66059B (en) * | 1977-01-28 | 1981-01-14 | Continental Group | |
| GR72763B (en) * | 1980-02-14 | 1983-12-02 | Obrist Ag Albert | |
| ZA831232B (en) * | 1982-03-10 | 1983-11-30 | Grace W R & Co | Screw cap |
| GB2116529B (en) * | 1982-03-10 | 1985-07-17 | Grace W R & Co | Screw closure |
| JPS5915059A (en) * | 1982-07-06 | 1984-01-26 | 日本クラウンコルク株式会社 | Vessel cover made of synthetic resin |
| JPS59501203A (en) * | 1982-07-09 | 1984-07-12 | メタル・クロ−ジュア−ズ・グル−プ・ピ−エルシ− | Improvement of lids for containers with screws |
-
1984
- 1984-02-09 NL NL8400428A patent/NL8400428A/en active Search and Examination
-
1985
- 1985-02-02 IN IN75/CAL/85A patent/IN162719B/en unknown
- 1985-02-04 GR GR850303A patent/GR850303B/el unknown
- 1985-02-05 ZA ZA85865A patent/ZA85865B/en unknown
- 1985-02-06 ES ES540171A patent/ES8606173A1/en not_active Expired
- 1985-02-07 EP EP85200149A patent/EP0155021B2/en not_active Expired - Lifetime
- 1985-02-07 CA CA000473777A patent/CA1292443C/en not_active Expired - Lifetime
- 1985-02-07 AT AT85200149T patent/ATE34148T1/en not_active IP Right Cessation
- 1985-02-07 DE DE8585200149T patent/DE3562601D1/en not_active Expired
- 1985-02-08 DK DK61285A patent/DK61285A/en not_active Application Discontinuation
- 1985-02-08 JP JP60022090A patent/JP2545207B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| ES540171A0 (en) | 1986-04-16 |
| AU3856485A (en) | 1985-08-15 |
| ATE34148T1 (en) | 1988-05-15 |
| JPS60204473A (en) | 1985-10-16 |
| AU580751B2 (en) | 1989-02-02 |
| GR850303B (en) | 1985-04-03 |
| IN162719B (en) | 1988-07-02 |
| DE3562601D1 (en) | 1988-06-16 |
| EP0155021A1 (en) | 1985-09-18 |
| ES8606173A1 (en) | 1986-04-16 |
| EP0155021B1 (en) | 1988-05-11 |
| EP0155021B2 (en) | 1994-03-02 |
| JP2545207B2 (en) | 1996-10-16 |
| DK61285A (en) | 1985-08-10 |
| ZA85865B (en) | 1985-10-30 |
| DK61285D0 (en) | 1985-02-08 |
| NL8400428A (en) | 1985-09-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |