WO2008155650A2

WO2008155650A2 - Method and means for moulding by injection or extrusion

Info

Publication number: WO2008155650A2
Application number: PCT/IB2008/001634
Authority: WO
Inventors: Vincenzo Commisso
Original assignee: SINERGETIC Srl
Current assignee: SINERGETIC Srl
Priority date: 2007-06-21
Filing date: 2008-06-20
Publication date: 2008-12-24
Anticipated expiration: 2009-12-21
Also published as: WO2008155650A3; ITTO20070448A1

Abstract

The invention relates to a method for moulding by injection or extrusion, in which between two bodies or media at different temperatures there is a free space or gap. According to the invention, set in said free space or gap is a barrier made of thermally insulating material (C), which comprises at least one insulating material having index of thermal conductivity lower than that of dry air at 0°C and is designed to reduce the thermal dispersion linked both to the convective motions and/ or heat conduction of air and to irradiation, which depends upon the characteristics of the body at a higher temperature.

Description

METHOD AND MEANS FOR MOULDING BY INJECTION OR EXTRUSION

The present invention concerns a method for extrusion of plastic materials, for moulding of plastic materials, thermosetting materials, elastomers, metals and alloys thereof by injection, extrusion or die-casting. The invention moreover concerns the means for implementation of the aforesaid method.

State of the art

All the production of objects made of plastic material is based upon an extremely simple process: the plastic material is heated, injected and pressed, or else, for example, extruded, or else heated and adapted to a particular shape with the heat-forming technique. Then, it is cooled and hence becomes that end product with which we are acquainted in our everyday life for our various needs: for example, bumpers for motor vehicles, simple caps, plastic bags, or packages that preserve foodstuffs in vacuum conditions, or simply blisters, which are hermetic containers for products.

In the particular sector technically defined as "injection moulding of plastic materials", the objects assume their shape because an injection press forcedly introduces into a mould material in the molten state, which fills a cavity. In this cavity, the material cools in a period of time depending upon the characteristics of the shape of the piece that is to be produced, upon the technical, chemical, and physical characteristics of the material injected and pressed in the cavity and upon the characteristics of conditioning outside the cavity.

The same occurs in the sector of extrusion of plastic materials and other materials, where in a continuous cycle the material assumes the shape of a particular profile obtained to meet specific requirements.

The same applies to the sector of processing of materials defined as "thermosetting materials"^'. These materials present characteristics that differ from what has been illustrated with reference to processing of plastic materials. In fact, these materials are injected and pressed in the cold state in a heated cavity. Following manufacturing processes indicated by the producer, they become an object that can be used, for example, the important parts of light assemblies of means of transport.

In the sector of die-casting and injection of the materials that we shall define by way of example as metal materials, such as aluminium and its alloys or, once again as example, magnesium, are treated, i. e. , processed, in hot environment both in the injection or pressing stage and in the cooling stage.

The framework described up to now taking as example a mould for plastic materials presents many parts in common with that of other components, such as plasticizing cylinders for injection or extrusion presses, or other types of machines previously illustrated or considered.

The electrical resistors contribute in a determining way to heating of the systems listed. They present different shapes, i. e. , they may be tubular, cylindrical, spiral-shaped, armoured mounted on ceramic supports, or else in the form of band or simple resistive sheets appropriately insulated, which are enclosed in a container and then housed in the system, and form part of the system. All these production tools produce heat and distribute heat. Drawbacks

The operating temperatures of the machines briefly listed above range from minimum values, such as 150⁰C for thermosetting materials or elastomers, to 650⁰C for magnesium.

The heat produced by the required heating devices does not, however, distribute in a unidirectional way, but follows the natural laws of thermodynamic physics. The efforts made in an endeavour to orient the heat flow are frequently insufficient to achieve the purpose. Consequently, it happens that the heat produced distributes in the environment to be heated following the laws of thermal conductivity of materials, and as regards the surrounding environment - which is considered insulating - the heat follows equally natural laws. In, a known way, in the surrounding environment insulating barriers are arranged, which are in any case insufficient to contain the heat produced in the body, in the cavity, and on the heated surface. This dispersed heat has an economic cost. It must be eliminated for production requirements - the faster the cooling, the higher the productivity that can be achieved - through cooling devices. These require further electrical energy for their operation. But these devices - heat exchangers, refrigerators, air-conditioning systems, etc. - simply transfer into the atmosphere the excess heat that is produced and dispersed into the environment on account of the objective difficulty to contain the heat in the place where it is required. Objects of the invention

An object of the invention is to provide a method for moulding by injection or extrusion that will enable all this energy waste and the consequent adverse effects on the environment to be reduced, contained, and if possible eliminated.

Another object of the invention is to provide means for implementation of the aforesaid method that will be effective, safe, and structurally simple.

Solution according to the invention

The method for moulding by injection or extrusion according to the invention is implemented in a free space or gap between two bodies or media ( of which one, for example, can even be air) at different temperatures. Set in said free space or gap is a barrier made of thermally insulating material, which comprises at least one insulating material, which has an index of thermal conductivity lower than that of dry air at 0⁰C and is designed to reduce the thermal dispersion linked both to the convective motions and/or heat conduction of air and to irradiation, which depends upon the characteristics of the body at a higher temperature. Said barrier made of thermally insulating material is obtained, for example, by means of panels, plates or the like, which contain said at least one insulating material and are arranged in said free space or gap, with or without contact with said body or medium at a higher temperature. According to another embodiment, said barrier made of thermally insulating material is obtained by totally or partially filling said free space or gap using a medium in granules, powder or the like, containing said at least one insulating material. Said insulating material is, for example, chosen in the family of aerogels, derivatives thereof, and/or composites thereof, and/or substances combined therewith. The means for implementation of the method according to the invention are arranged in a free space or gap between two bodies or media at different temperatures.

Said means for implementation of the method according to the invention comprise a barrier made of thermally insulating material, which is set in said free space or gap and includes at least one insulating material, which has an index of thermal conductivity lower than that of dry air at 0° C and is designed to reduce the thermal dispersion linked both to the convective motions and/or heat conduction of air and to irradiation, which depends upon the characteristics of the body at a higher temperature.

Said barrier made of thermally insulating material comprises, for example, panels, plates or the like, which contain said at least one insulating material and are arranged in said free space or gap, with or without contact with said body or medium at a higher temperature.

Said barrier made of thermally insulating material may also consist in a total or partial filling of said free space or gap by means of granules, powder, or the like containing said at least one insulating material. In particular, said insulating material belongs, for example, to the family of aerogels, derivatives thereof, and/or composites thereof, and/or substances combined therewith.

Example of embodiment The attached plate of drawings is provided purely by way of example for a better illustration of the invention, and therein: - Figure 1 is a schematic view, in side elevation, of a known injection press for plastic materials;

- Figure 2 is a view similar to that of Figure 1, but in which the plasticizing cylinder of said press is coated witha highly insulating material, according to the invention;

- Figure 3 is a schematic cross-sectional view from the injection side of a known mould for plastic materials; and

- Figure 4 is a view similar to that of Figure 3, but illustrating insulating panels mounted, according to the invention, in a gap of the mould itself.

With reference to the drawing, Figure 1 is a schematic representation of a conventional injection press; it is very similar to an extruder for plastic materials. The reference A designates the plasticizing cylinder, the reference B one of the heating elements used to bring the cylinder A to the operating temperature.

In Figure 2, the reference C designates, by way of example, a covering shell made of highly insulating material, set on the cylinder A, according to the invention. It can be made in sectors or as single coating or enveloping element. Said shell C forms a barrier made of thermally insulating material set between the cylinder A and the environmental air ( medium outside of the cylinder) , which is at a temperature lower than that of said cylinder. Figure 3 of drawings is a schematic illustration of a known mould for plastic materials, viewed in cross section and from the so-called "injection side". Set within said mould is a system for direct injection of plastic, comprising a distribution plate designated by Al and two injectors designated by Bl, which are the hottest parts of the mould. Figure 4 illustrates the mould according to Figure 3, but in which, according to the invention, insulating modules or panels Cl, viewed in cross section, are provided. Said insulating panels are assembled on the hottest parts of the aforesaid mould, in the air gap between the distribution plate Al and the injectors Bl, on one side, and the outer casing of the mould, on the other. According to the embodiment of the invention illustrated herein by way of example, the panels Cl are cut to the right size and adequately fixed to the parts to be thermally insulated.

The solution according to the invention envisages, by way of example, the use of elements made of the insulating materials made available by nano-technologies and widely tested by the space industry in the last few years. Said elements made of insulating materials are, for example: a) flexible insulating modules which can be easily adapted to pre-existing or newly devised machines and devices; b) parts of machines or apparatuses where these elements made of insulating material are arranged inside and/or outside to contain the thermal interchange between areas at a higher temperature and areas at a lower temperature; and c) heating elements insulated with said elements made of insulating material, which facilitate containment of heat dispersion as fundamental specification and as regards

1 constructional architecture. '

These elements made of insulating material can be easily and at a low cost set between the heated or heating part and the part or medium ( for example, air) that is to remain at a lower temperature. Advantages of the method and corresponding means for moulding by injection or extrusion according to the invention are listed below.

Lower energy consumption. Lower amount of heat introduced into the surrounding environment.

Lower consumption of energy for cooling the surrounding environment.

Lower amount of heat introduced into the atmosphere. Better working conditions for operators forced to remain in those environments.

Higher productivity.

Claims

CLMMS

1. A method for moulding by injection or extrusion, in which between two bodies or media at different temperatures there is a free space or gap, characterized in that set in said free space or gap is a barrier made of thermally insulating material, which comprises at least one insulating material that has index of thermal conductivity lower than that of dry air at O⁰C and is designed to reduce the thermal dispersion linked both to the convective motions and/or heat conduction of air and to irradiation, which depends upon the characteristics of the body at a higher temperature.

2. The method according to Claim 1, characterized in that said barrier made of thermally insulating material is obtained by means of panels, plates or the like, which contain said at least one insulating material and are arranged in said free space or gap, with or without contact with said body or medium at a higher temperature.

3. The method according to Claim 1, characterized in that said barrier made of thermally insulating material is obtained performing total or partial filling of said free space or gap using a medium in granules, powder or the like containing said at least one insulating material.

4. The method according to one or more of the preceding claims, characterized in that said insulating material is chosen in the family of aerogels, derivatives thereof, and/or composites thereof, and/or substances combined therewith.

5. Means for implementation of the method according to one or more of the preceding claims, in which between two bodies or media at different temperatures there is a free space or gap, said means being characterized in that they comprise a

5 thermally insulating barrier (C, Cl), which is set in said free space or gap and includes at least one insulating material that has index of thermal conductivity lower than that of dry air at 0⁰C and is designed to reduce the thermal dispersion linked both to the convective motions and/or heat 10 conduction of air and to irradiation, which depends upon the characteristics of the body at a higher temperature.

6. Means according to Claim 5, characterized in that said thermally insulating barrier comprises panels, plates or the

15 like (C, Cl), which contain said at least one insulating material and are arranged in said free space or gap, with or without contact with said body or medium at a higher temperature.

207. Means according to Claim 5 and/or Claim 6, characterized in that said thermally insulating barrier consists in a total or partial filling of said free space or gap by means of granules, powder or the like containing said at least one insulating material.

25

8. Means according to Claim 5, Claim 6, and/or Claim 7, characterized in that said insulating material belongs to the family of aerogels, derivatives thereof, and/or composites thereof, and/or substances combined therewith.