WO1988009298A1 - Moulded plastics articles - Google Patents

Moulded plastics articles Download PDF

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Publication number
WO1988009298A1
WO1988009298A1 PCT/GB1988/000401 GB8800401W WO8809298A1 WO 1988009298 A1 WO1988009298 A1 WO 1988009298A1 GB 8800401 W GB8800401 W GB 8800401W WO 8809298 A1 WO8809298 A1 WO 8809298A1
Authority
WO
WIPO (PCT)
Prior art keywords
container
parts
crystallisation
dish
mould
Prior art date
Application number
PCT/GB1988/000401
Other languages
French (fr)
Inventor
Peter Reginald Clarke
Original Assignee
R. Clarke & Co. (Moulds) Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to GB8712161 priority Critical
Priority to GB08712161A priority patent/GB2205063A/en
Application filed by R. Clarke & Co. (Moulds) Limited filed Critical R. Clarke & Co. (Moulds) Limited
Publication of WO1988009298A1 publication Critical patent/WO1988009298A1/en

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B65CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65DCONTAINERS 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
    • B65D81/00Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
    • B65D81/34Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents for packaging foodstuffs or other articles intended to be cooked or heated within the package
    • AHUMAN NECESSITIES
    • A47FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47JKITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
    • A47J36/00Parts, details or accessories of cooking-vessels
    • A47J36/02Selection of specific materials, e.g. heavy bottoms with copper inlay or with insulating inlay
    • A47J36/022Cooking- or baking-vessels or supports thereof for using only once
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C51/00Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
    • B29C51/26Component parts, details or accessories; Auxiliary operations
    • B29C51/42Heating or cooling
    • B29C51/426Producing specific thermal regimes during thermoforming to obtain particular properties
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2067/00Use of polyesters or derivatives thereof, as moulding material

Abstract

The invention relates to a food container in the form of a dish made of partly crystalline P.E.T., in which the P.E.T. has different degrees of crystallisation in different regions, so that parts of the containers are selectively hardened while others remain relatively flexible and less frangible upon impact. The mould (30) for moulding the article includes heaters (38) and thermal barriers (36) or cooling passages (40) so that the article is heated to different temperatures and the degree of crystallinity is varied from one region in the container to the other so that some parts remain amorphous and flexible while other parts are hardened by crystallisation.

Description

MOULDED PLASTICS ARTICLES
The invention relates to a food container made of partly crystalline poly(ethylen terephthalate) , herein referred to as P.E.T. and in particular to a container in the form of a dish.
The conventional manner of constructing such a food container is to form it from a blank, usually cut from an extruded flat sheet. The term "forming" is used here to include any process by which the sheet is stretched or deformed into the shape of a mould, for example by air pressure, vacuum or mechanical pressure.
P.E.T. has been used in the packaging of food because of its strength and its chemically inert character. It also has the property that it changes in crystal structure when heated above a predetermined temperature and upon partial crystallisation its physical properties are changed significantly. In particular, the strength is improved and this change is accompanied by a change in the appearance of the material and more importantly by an increase in brittlenesε. The increase in strength is naturally desirable but the brittleneεε can cause problems by making the finished article more frangible upon impact.
According to the present invention, there is provided a food container in the form of a dish made of partly crystalline P.E.T, in which the P.E.T. has different degrees of crystallisation in different regions, whereby parts of the containers are selectively hardened while others remain relatively flexible and less frangible upon impact.
Conventionally, an article is heated uniformly after it has been formed or during its formation and undergoes crystallisation uniformly. The present invention, by contrast, recognises that in oven dishes the physical properties suited to some regions are not desirable for others. In particular, strength is required in the side walls of the dish and in its base, but the corners are easily damaged by impact and therefore it is desirable to retain in the corner regions the flexibility, resilience and impact resistance of the amorphous material.
Also in the case of an oven dish where a foil is used to seal food in the container, it has been found that the foil can be made to adhere well to the amorphous plastics material but tends to form a poorer bond with the partly crystallised material.
If the container includes a carrying handle bent out of the plane of the blank after the dish is moulded, the hinge section between the handle and the rim of the container is another region which should preferably remain amorphous in order not to break during use.
Because the properties of the P.E.T. are controlled by the degree of crystallisation and this is in turn temperature dependent, the invention permits all parts of an article to have the physical properties best suited to their function by controlling the temperature to which the various regions of the article are heated during the manufacturing process.
The mould for forming such an article from a blank may include means for locally heating different regions of the mould so as to maintain a temperature gradient within the mould and heat the moulded article unevenly, only selected parts of the article which are to be hardened by partial crystallisation being heated above the temperature necessary to initiate crystallisation. The mould may conveniently include so-called cartridge heaters which consist of electrically heated rod like elements which are inserted in suitably positioned bores in the mould.
The temperature difference required to vary the physical properties of P.E.T. significantly is only small, typically some 20°C. A temperature of 135°C is required to initiate crystallisation while a temperature of 115°C is sufficient to permit the article to be moulded and to remain amorphous. Maintaining such a temperature gradient can readily be effected by including thermal barriers in the mould and carefully positioning the heating elements, without resorting to forced cooling of any regio'n. It is however also possible to circulate a coolant through the mould so that both heat sources and heat sinks should be present to create the required temperature gradient.
The invention will now be described further, by way of example, with reference to the accompanying drawings, in which :
Figure 1 is a perspective view of a food container, and
Figure 2 is a section through a mould for forming the container in Figure 1.
The container 10 shown in Figure 1 has a single dished compartment 12 and two carrying handles 14. The container is made by vacuum moulding a blank which may be a flat blank cut from an extruded sheet or is preferably an injection moulded blank in which the thickness is not uniform to permit local strengthening of the container without increasing the entire thickness of the blank. The handles 14 initially lie in the plane of the blank and are bent up during use of the container. Clearly therefore, the hinge of the handles needs to remain flexible if it is not to snap during use. For this to be the case, the hinge region 18 should remain amorphous.
The corners 20 are a further region where flexibility is an advantage as brittle containers tend to be damaged there when dropped.
When food is placed in the container, it is sealed by means of a foil adhered to its rim 22. It has been found that the foil adheres better to amorphous P.E.T. than it does to the crystallised material, for which reason it is preferable not to harden the rim 22.
As for the remainder of the container, it is preferred that these parts should be hardened by crystallising the P.E.T. as this adds to the strength of the container and to its rigidity.
From the above description, it will be clear that the hardness requirements of the container differ from one region to the other and conventionally the container was hardened uniformly. A compromise had to be reached to strengthen the container sufficiently without making it too frangible in the corners.
The P.E.T. material of a container of the invention is hardened during the forming process by using a mould cavity 30 in which steps are taken to maintain a temperature gradient.
The mould cavity 30 of Figure 2 is for vacuum moulding of an injection moulded blank. The blank is injection moulded as this makes more efficient use of the plastics material and can permit the thickness in each region to be varied to provide reinforcement where necessary. The blank, which is initially flat, is placed in a recess 32 in the mould cavity 30 and clamped against the recess by means of a movable collar 34. The mould cavity 30 includes passages (not shown) for evacuating the space beneath the blank to cause the heating blank to be formed against the inner surface of the mould cavity.
The mould cavity 30 has cartridge heaters 38 which are fitted within long receiving bores in the mould. In the mould cavity, the formed container is heated above the temperature where crystallisation takes place and once hardened, the container is ejected from the mould cavity.
As so far described, the mould cavity is generally conventional. To maintain parts of the container in the amorphous state, the mould cavity 30 additionally contains means for creating a temperature gradient either by forced cooling or by careful use of thermal insulators.
It has been mentioned previously that the corners 20 should remain amorphous. This is achieved using the mould of Figure 2 by a thermal barrier 36. The barrier
36 is disposed between the corners and the adjacent cartridge heaters to impede heat flow to the corners.
The barrier 36 may be an air gap or a thermal insulator.
Because the heat flow is impeded, during use the corners reach a lower temperature that the rest of the container and remain amorphous while other parts are crystallised.
To keep the rim 20 in an amorphous state, the collar 34 is shown including passages 40 for circulation of a coolant, such as water or cold air. This active cooling can of course also be used in place of a thermal barrier to achieve the desired cooling of the corners 20.

Claims

1. A food container in the form of a dish made of partly crystalline P . E . T , characterised in that the P. E . T . has different degrees of crystallisation in different regions, whereby parts of the containers are selectively hardened while others remain relatively flexible and less frangible upon impact.
2. A food container as claimed in claim 1, wherein the corners of the dish are less crystalline than the walls and the base of the dish.
3. A food container as claimed in claim 2, having a rim to which a foil is to be adhered after the container has been filled with food, wherein the rim is less crystalline that the walls of the dished compartment.
4. A food container as claimed in claim 3, having handles bent out of the plane of the rim and wherein the hinge region between the handles and the rim is less crystalline than the walls of the dish.
PCT/GB1988/000401 1987-05-22 1988-05-20 Moulded plastics articles WO1988009298A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB8712161 1987-05-22
GB08712161A GB2205063A (en) 1987-05-22 1987-05-22 Moulded plastics articles

Publications (1)

Publication Number Publication Date
WO1988009298A1 true WO1988009298A1 (en) 1988-12-01

Family

ID=10617785

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1988/000401 WO1988009298A1 (en) 1987-05-22 1988-05-20 Moulded plastics articles

Country Status (3)

Country Link
AU (1) AU1784188A (en)
GB (1) GB2205063A (en)
WO (1) WO1988009298A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5154939A (en) * 1989-04-19 1992-10-13 Wm. Wrigley Jr. Company Use of salt to improve extrusion encapsulation of chewing gum ingredients

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6814905B1 (en) 1999-12-02 2004-11-09 Associated Packaging Enterprises, Inc. Continuous process and apparatus for making thermoformed articles
DE60116724D1 (en) * 2000-11-28 2006-04-06 Associated Packaging Entpr Inc Thermoforming process and apparatus for the continuous production of articles
US6394783B1 (en) * 2000-03-27 2002-05-28 Apex Research Ltd., Inc. Continuous rotary melt thermoformer
US7044057B2 (en) * 2003-01-08 2006-05-16 Mary Louise Parker Fabrication of printed dining plates
WO2012123391A1 (en) 2011-03-15 2012-09-20 Cryovac, Inc. Partially crystallized polyester containers
DE102013016453A1 (en) * 2013-10-02 2015-04-02 Isk Iserlohner Kunststofftechnologie Gmbh Method and device for producing a component in a molding process and component

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4374800A (en) * 1981-03-18 1983-02-22 The Goodyear Tire & Rubber Company Method for making an article of partially crystalline organic resin
EP0124305A1 (en) * 1983-04-22 1984-11-07 Imperial Chemical Industries Plc Nestable container suitable for containing structured paint

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
LU57593A1 (en) * 1967-12-20 1969-04-08
CH507802A (en) * 1970-02-25 1971-05-31 Synthexa Establishment Process and injection mold for the production of hollow bodies from thermoplastics
GB2024087B (en) * 1978-06-29 1982-08-25 Yoshino Kogyosho Co Ltd Blow moulding polyester container
GB2074932B (en) * 1978-06-29 1983-01-19 Yoshino Kogyosho Co Ltd Blow moulded polyester bottle
GB2050919B (en) * 1979-06-11 1983-05-18 Owens Illinois Inc Method and apparatus for forming heat treated blown thermoplastic articles

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4374800A (en) * 1981-03-18 1983-02-22 The Goodyear Tire & Rubber Company Method for making an article of partially crystalline organic resin
EP0124305A1 (en) * 1983-04-22 1984-11-07 Imperial Chemical Industries Plc Nestable container suitable for containing structured paint

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5154939A (en) * 1989-04-19 1992-10-13 Wm. Wrigley Jr. Company Use of salt to improve extrusion encapsulation of chewing gum ingredients

Also Published As

Publication number Publication date
AU1784188A (en) 1988-12-21
GB2205063A (en) 1988-11-30
GB8712161D0 (en) 1987-06-24

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