METHOD OF MANUFACTURING A PLASTIC OR SYNTHETIC RESIN LID, MOULD ADAPTED THERETO AND THE LID OBTAINED WITH THAT METHOD

Abstract: Method of manufacturing a plastic lid provided with a coating consisting of a foil material that may comprise a layer of foam plastic material, comprising the following steps: Positioning an injection mould in a moulding cavity, said cavity having a shape adapted to the plastic lid to be manufactured, and applying a layer of foil material (7), injecting into said cavity, after it has been closed, a preheated plastic material that can adhere to the foil material; and opening the mould and removing the lid thus formed from it.

Description: The invention relates to a method of manufacturing a synthetic resin or plastic lid or cap provided with a coating consisting of foil material. Such a plastic lid can e.g. be used as a part of a closure for containers for e.g. foodstuff requiring the use of an oxygen-barrier for which the normal plastics are not adequate. Such a lid can also be provided with a foil serving as a seal for a container, said foil being connected with the container while positioning the lid. When removing the lid the foil has to keep the container closed in the form of a diaphragm and therefore has to be adhered to the lid in a relatively weak fashion. Usually use is made of polyolefins, such as polypropylene, polyethylene etcetera, materials which are permeable to a high degree. There are plastic materials, such as eval (evoh) or pvdc having a low permeability and good barrier properties. Clamped in in barrier-foils, however, they find general application in flexible containers, such as bags, wrappers, etcetera. It is a purpose of the invention to provide a method, by means of which in a very simple and thus cheap manner a plastic lid provided with a coating of foil material can be manufactured. In view thereof the invention proposes a method comprising the following steps: positioning in a moulding cavity of a spraycast-mould, said cavity having a shape adapted to the plastic lid to be manufactured, a layer of foil material; after closing the mould cavity spraying into said cavity a preheated plastic material that can adhere with the foil material; and opening the mould and taking the lid thus formed from it. It is noted that from the article "In-mold decorating upgraded" from the magazine "Modern Plastics International", McGraw Hill, June l986, vol. l6, no. 6, page 66 of Kurz and Battenfeld, a method is known, in which a foil provided with a printing runs through a spraycast mould for printing by means of transfer-printing method, of the mould product. Therefore this article relates to the application of a generally known method of application of printing patterns, texts and the like. The printings are present on a strip of carrier material, that as such does not play a role in the process and is wounded on a winding reel after the printing patterns have been removed from it. The invention on the contrary, relates to the application of a layer of foil material that is not carried by a layer of carrier material. Preferably the method according to the invention is carried out in such a way that the foil material is brought into the mould cavity by removing it, by means of the co-operating edges of two mould halves by closing the mould, from a piece of foil material positioned, in the opened position of the mould, between said two spaced-apart mould halves. Also the invention relates to a method of manufacturing a plastic lid provided with a membrane to be used as a seal for a container to be closed by means of the plastic lid. This method according to the invention is characterized by the use of a foil material having a weak adhesion with the plastic of the lid. This method can be carried out e.g. in such a way that the foil material is adhered to the lid on discrete zones, e.g. points. In this connection it should be noted that a zone-wise adhesion, e.g. on discrete points can have the advantage that between both sides of the foil a pressure equalization can take place due to which the risk is avoided that in case of closing by the lid of a container with sub-atmospheric pressure the foil is torn off the lid as a result of that sub-atmospheric pressure. A further way of carrying out the method according to the invention is characterized in that a strip of foil material is previously provided locally with at least one coating or printing and is, in view of an easy removing of the related parts by the mould, provided with a weakening line extending around every part that is provided with a coating or a printing, said weakening line being in the form of e.g. a line of perforations. In this way an easy removing of the related parts by means of simple means is guaranteed. In a certain embodiment the method can be carried out in such a way that a layer of foil material comprising a layer of foam-plastic is used. The layer of foil material can be designed as a laminate, of which the layer of foam-plastic material forms part, or consist only of the layer of foam plastic material. In case of application of this method a plastic lid is obtained in which the coating of foil material is resiliently compressable. An important application of such a lid is closing containers in which food stuff is present, for which an oxygen barrier is required. Thus far it was usual to use therefore a special filling mass or compound. Such a filling mass requires an additional production step and causes an increase of costs. The method according to the invention herein described above, gives the possibility of refraining from the use of a compound, whilst nevertheless a perfect sealing of the contents of the container is guaranteed, by the barrier properties of the layer of foil material on the one hand and due to the fact that the layer of foam-plastic material has the function of the compound, namely the adaptation to irregularities, if any, at the upper edge of the container, on the other hand. Furthermore the invention relates to a plastic lid provided with a coating and obtained by the application of one of the methods herein mentioned before. Finally the invention relates to a synthetic resin or plastic material sprayscast mould, that is, according to the invention provided with a coating of foil material and obtained by application of the method according to anyone of the preceding claims. The invention will now be explained in more detail with reference to the accompanying drawings. In the drawings: Fig. l shows a schematic perspective view, partially broken away of a spraycast apparatus according to the invention; Figs. 2, 3 and 4 show three successive phases of a spraycasting method according to the invention; Fig. 5 shows a perspective view, partially broken away of a lid according to the invention; Figs. 6 and 7 show two successive phases of a spraycast operation according to the invention; Figs. 8 and 9 show two successive phases of an alternative method; and Fig. l0 shows a special foil strip provided with weakening contours. Fig. l shows a spraycasting apparatus l provided with a mould consisting from several parts. A pressure plate 4 shiftable by means of guidance bars 2 and actuatable by means of a hydraulic cylinder 3 supports a mould part 5 surrounded by a shifting plate 5. A strip 7 of foil material extends between a supply reel 8 and a winding reel 9 between mould parts l0 and ll. Through an injection opening l2 a casting assembly l3 is connected with the mould part ll. The strip 7 of foil material comprises a carrier layer l4, on which with previously determined spacings additional layers l5 are formed, so that locally a coating or printing is present. In this embodiment registration means l6 are present, which are adapted to exactly position the covers or printings l5 successively, in such a way that during the closing of the mould they are brought into the moulding cavity thereof. Fig. 2 shows a cross-section through a mould. A pressure plate l7 carries a mould part l8, the foremost part of which forms part of the boundary of the moulding cavity l9 as is indicated in fig. 4. A stationary mould part 20 is provided with the spraycasting opening 2l. A foil strip 22 extends between a guiding ring 23 and a cutting ring 24 that can punchingly cooperate with a punch 25. A ring 26 forms together with a recess 27 in the stationary mould part 20 and the front part of the mould part l8 the moulding cavity l9 that exhibits a shape adapted to the shape of a lid to be manufactured. Fig. 2 shows the phase in which the mould is ready to be closed. Fig. 3 shows the phase in which by means of a punching operation a laminate part 28 has been punched out by the punch 25 and is ready to be conveyed by the front surface of the mould part l8. The phase according to fig. 4 is the phase in which by supplying preheated synthetic resin material under pressure through the spraycasting opening 2l the moulding cavity l9 is filled for the formation of a lid at the inner surface 28 of which the coating of foil material is present. Fig. 5 shows a ready product, namely a lid 32 made of transparent material. A laminate foil l8 is as a coating present at the inner side of the lid 32. Thus the foil 25 serves as a barrier and also as a non-removable printing element. Fig. 6 shows an alternative embodiment. In this case the moulding cavity is bounded by the front zone of the mould part l8, the front surface of a mould part 29, in which also the spraycast opening 2l is present, the ring 26 and a ring 37. The foil strip l8 is during the closing of the mould clamped in between a ring 30 and a ring 3l. After the explanation relative to figs. 2, 3 and 4 the method according to figs. 6 and 7 will need no further explanation. Figs. 8 and 9 show an alternative embodiment. In this embodiment a coating of foil material is affixed to the outer side surface of a plastic or synthetic resin lid. A foil strip 34 is during the closing of the mould clamped in between the ring 26 and a ring 33. Due to the high pressure and temperature in this embodiment the coating is pressed out of the foil strip 34. In this embodiment, therefore, no longer use is made of a mechanical punching operation. For the ease of the removing of parts 35 provided with local printing patterns (see fig. l0) of the foil strip 34 by the mould around those parts 35 perforated lines 36 having the shapes of circular contours are present. It should be noted that the embodiments shown in the drawings are only exemplary embodiments serving the purpose of explaining the principles of the invention. Many other implementations of the method according to the invention are possible. If desired the foil material can consist of a plurality of layers, each exhibiting a certain desired property, such as the mentioned barrier-properties for oxygen, carbon-dioxyde, water vapour and the like, mechanical resistance, etcetera. Already reference has been made to the possibility of applying even the most complicated types of printing patterns by applying to the inner side surface of a transparent type of plastic, previously printed foil material. Finally it should be noted that a coating can be separated from the foil strip by means of a local heat treatment at the circumference in the mould. For this purpose an electrical heating may be used. Example I Lid provided with a laminate foil WB-40/P-40, commercially available form the firm Envie of Assen, the Netherlands, having a total thickness of about l00 µm. The laminate consists of a foam-plastic foil WB-40 and a barrier foil P-40. The oxygen-permeability thereof amounts to 5,5 g/m²/24h at a pressure of l0⁵ Pa, a temperature of 23°C and a relative humidity of 0-90%. Example II Lid provided with a laminate foil having a total thickness of about 500 µm consisting of a foam-plastic foil of foamed polyethylene, commercially available from the firm Hoechst, and the foil P-40 specified in example I. The resilient properties were sufficient for maintaining a vacuum in a closed container. Example III Lid provided with a laminate foil having the same construction as in example II, but provided with a foam plastic foil made of polypropylene.

Claims: 1. A method of manufacturing a synthetic resin or plastic lid provided with a coating consisting of foil material, characterized by the following steps: positioning in a moulding cavity of a spraycast-mould, said cavity having a shape adapted to the plastic lid to be manufactured, a layer of foil material; after closing the mould cavity spraying into said cavity a preheated plastic material that can adhere with the foil material; and opening the mould and taking the lid thus formed from it. 2. The method according to claim l, characterized in that the foil material is brought into the mould cavity by removing it by means of the co-operating edges of two mould halves by closing the mould from a piece of foil material positioned, in the opened position of the mould, between said two spaced-apart mould halves. 3. The method according to claim l or 2 of manufacturing a plastic lid provided with a membrane to be used as a seal for a container to be closed by means of the plastic lid, characterized by the use of a foil material having a weak adhesion with the plastic of the lid. 4. The method according to claim 3, characterized in that the foil material is adhered to the lid on discrete zones, e.g. points. 5. The method according to claim 2, characterized in that a strip of foil material is previously provided locally with at least one coating or printing and is, in view of an easy removing of the related parts by the mould, provided with a weakening line extending around every part that is provided with a coating or a printing, said weakening line being in the form of e.g. a line of perforations. 6. The method according to anyone of the preceding claims, characterized in that a layer of foil material comprising a layer of foam-plastic is used. 7. A synthetic resin or plastic lid provided with a coating of foil material and obtained by application of the method according to anyone of the preceding claims. 8. A synthetic resin or plastic spraycast mould for application of the method according to claim 2, characterized by means for positioning foil material in the mould cavityby removing it by means of the co-operating edges of two mould halves by closing the mould from a piece of foil material positioned, in the opened position of the mould, between said two spaced-apart mould halves.

Inventors: KORNELIS, WIEBREN DURK HALBE
Applicants: KORNELIS' KUNSTHARS PRODUCTEN INDUSTRIE B.V.
Application year: 1987
Main classification: B29C45
IPC codes: B29C45