RU2574619C1 - Moulding process - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: moulded plastic product comprises outer and inner shells. The claimed process comprises the steps that follow. An injection mould is made to mould the outer shell from the first plastic material on at least two opposite surfaces inside the said injection mould and to mould the inner core from the second plastic material inside the said injection mould. Then, the plastic materials are hardened inside the mould cavity by heating with subsequent cooling plus the compression of the moulding so that one of its sizes is reduced to the required size of the finished product.

EFFECT: higher quality of produced flat or shaped panels.

15 cl, 22 dwg

Description

The present invention relates to a molding method and, in particular, to a molding method for manufacturing a molded product having an outer shell and an inner core.

It was previously proposed to produce rigid plastic structures such as panels for use in construction from recycled plastic material. As will be shown, the ability to use recycled plastic materials has many environmental benefits.

Previously proposed methods for manufacturing panels or other structural elements from recycled plastic material include the so-called injection molding of powder mixtures (PIM), which uses open-type molds consisting of two separate half-forms. Initially, the outer shell is molded on each half-mold by heating the half-molds, followed by the spraying of powdered plastic material on them. When each half-mold is heated, the powdery material melts, which leads to its adhesion to the half-molds in the form of a thin shell. Then, one of the two half-molds is coated with a second powdery plastic material containing a pore-forming agent, after which the two half-molds are combined to form a closed mold cavity, and then the entire mold is placed in the curing oven. During curing in the furnace, the second material expands inside the mold, thereby forming a porous inner core inside the outer shell. When curing is completed, the half-molds are disconnected, and the product is removed from the mold.

The above-described method of molding in an open-type mold has its drawbacks associated with the supporting structures necessary for turning the half-molds and manipulating them. The named structures are often very significant, and it is necessary to place them inside the furnace together with half-forms, which means that most of the thermal energy generated in the furnace is unproductive for heating the supporting structure. In addition, problems arise due to the huge size of the furnace, which is required for this method: in general, large furnaces are less efficient compared to small ones.

In this regard, alternative molding methods have been proposed to eliminate these and other problems associated with injection molding methods of powder mixtures in open molds. One such method involves the use of a mold having an internal cavity. First, an outer shell is formed: for this, the mold is filled with the first granular material and heated until a thin shell of molten granular material forms on the inner surfaces of the mold, while the rest of the granular material remains in the central region of the mold unmelted. Then this unmelted granular material is removed from the cavity of the mold. Then, inside the outer shell, the second inner shell of another granular material is formed by a similar method. However, the material used to form the inner shell contains a pore-forming agent, and therefore, after the unmelted granular material is removed from the central region of the mold cavity, after which the void remains in the central part, the mold is subsequently heated to elevated temperature, after which the remaining inner shell expands, filling the void and, as a result, forming a porous inner core inside the outer shell.

Although the molding method described above, to some extent, solves the aforementioned problems specific to the open-mold molding method, the resulting molded products can often be of poor quality and integrity, making them unsuitable for use in construction. For example, when used in the manufacture of panels from recycled plastic material, this method, known from the prior art, can lead to the creation of panels having unacceptable internal voids, which can significantly reduce the strength and integrity of the panel. In addition, in this way it is not possible to produce panels that are flat or sufficiently flat, which is often necessary in construction.

An object of the present invention is to provide an improved method for manufacturing a molded plastic product having an outer shell and an inner core.

In accordance with the present invention, there is provided a method for manufacturing a molded plastic product having an outer shell and an inner core, the method comprising the steps of: creating a mold having a mold cavity; the formation of the outer shell of the first plastic material, at least two opposite surfaces inside the cavity of the mold; the formation of the inner core of the second plastic material inside the cavity of the mold; and at least partially curing the plastic materials inside the mold cavity by heating, where the aforementioned method also includes the subsequent steps of simultaneously cooling and compressing the casting so that at least one of its dimensions is reduced to the desired size of the finished product .

In a preferred case, the casting is removed from the said cavity of the mold to the simultaneous stages of cooling and compression.

Preferably, said simultaneous cooling and compression steps are performed in a press having a cooling circuit designed to cool the casting in the press. For convenience, the press is a liquid-cooled hydraulic press.

In a preferred case, said press includes a pair of plates, each of which has channels for coolant flow.

Preferably, the cooling step is carried out in such a way that the temperature of the casting is reduced from above 200 ° C to below 40 ° C.

For convenience, the cooling step is carried out so that the temperature of the casting is reduced from a level of about 200 ° C to about 40 ° C.

In a preferred case, said step lasts about 20 minutes.

Preferably, the compression step is carried out so that the aforementioned size is reduced by at least 20%.

For convenience, the compression step involves applying a pressure of at least 150 N / cm ² to the casting, mainly during the entire cooling step. In a preferred case, the pressure force is about 190 N / cm ² .

In a preferred case, the aforementioned step of forming the outer shell includes filling the mold cavity with the aforementioned first plastic material in a granular form, heating the mold to form a shell of molten granular material from the at least two opposed surfaces of the mold and excavating the unmelted granular material from the cavity of the mold after the formation of the required thickness on the named surfaces of the shell.

Preferably, the aforementioned stage of extraction of the unmelted granular material from the mold is carried out by opening the outlet made in the lower part of the mold and ensuring the unmelted granular material to fall out through the outlet under the action of gravity. Alternatively, the mold may be slightly tilted to spill unmelted material. For convenience, the aforementioned outlet is subsequently closed after the extraction of the unmelted granular material, as a result of which the cavity of the mold is ready to accept the second plastic material.

In a preferred case, said step of filling the mold cavity with said first plastic material includes filling the said material in a granular form through an inlet made in the upper part of the mold, and then closing said inlet.

Preferably, said step of forming the inner core includes filling the mold cavity with said second plastic material in a granular form after forming the outer shell on said at least two opposite surfaces and heating the mold to at least partially cure in basically, the entire volume of the named second material inside the cavity of the mold.

For convenience, the said step of filling the mold cavity with said second plastic material includes filling the said material in a granular form through an inlet made in the upper part of the mold, and then closing the said inlet.

In the preferred case, the mold is maintained at an internal temperature of not lower than 200 ° C for at least 5 minutes.

Preferably, the method also includes the step of cooling the mold before the extraction of the casting.

For convenience, at least one of these materials contains recycled high impact polystyrene (OPS).

At least the first material may further comprise a coloring pigment.

The first and second materials may in some cases include a flame retardant.

The first and second materials may in some cases be substantially identical.

In a preferred case, the second material contains recycled polyethylene. For example, the second material may contain about 75% (by weight) of recycled UPS and about 25% of recycled polyethylene. The addition of polyethylene can help reduce the melting point of the material, preferably up to about 140 ° C.

If desired, the second plastic material may contain a pore-forming agent.

It has been found that the molding method according to the type defined above is suitable for the manufacture of very high quality flat or shaped panels from recycled plastic materials. The resulting panels are waterproof and can be made fireproof in the form of products of various thicknesses and different colors for many different conditions of use, for example, for shelving, for use in floodplain conditions, as a cladding in construction, for use in prefabricated buildings and military application.

For a better understanding of the invention, as well as to clarify its additional features, embodiments of the invention will be described below as an example with reference to the accompanying drawings, in which:

FIG. 1 is a front view of a furnace used in accordance with the method of the present invention, where the furnace is shown in an open configuration, in a state of readiness for accepting a mold;

FIG. 2 is a front view of the furnace of FIG. 1, in a closed configuration in which a mold is contained within it;

FIG. 3 is a side view of the furnace of FIG. 1 and 2;

FIG. 4 is a plan view showing a furnace in a closed configuration shown in FIG. 2;

FIG. 5 is a side view of a loading hopper that is used to fill a mold with granular material;

FIG. 6 is a plan view of a loading hopper;

FIG. 7 is a front view of a hopper in a raised position;

FIG. 8 is a view corresponding to FIG. 7, but in which the hopper is shown in the lowered position to fill the mold;

FIG. 9 is a side view of a collection hopper used in the method of the invention for collecting unused granular material from a mold;

FIG. 10 is a plan view of the collecting hopper of FIG. 9;

FIG. 11 is a front view of the collecting hopper of FIG. 9 and 10;

FIG. 12 is a side view of the molding carriage used in the method of the present invention;

FIG. 13 is a front view of the molding carriage, where the molding carriage is shown supporting the mold in an almost vertical position;

FIG. 14 is a view corresponding generally to the view shown in FIG. 13, but where the molding carriage is shown in a different position in which the mold is held in a substantially horizontal position;

FIG. 15 is a plan view of a molding carriage showing a fan unit above a mold;

FIG. 16 is a view corresponding generally to that shown in FIG. 15, but where the fan unit is shown in a different position in which it is carried out a considerable distance from the mold;

FIG. 17 is a front view of a pushing and pressing apparatus used in the method of the present invention;

FIG. 18 is a view corresponding generally to the view shown in FIG. 17, but showing a pushing apparatus in a working position used to push a mold into a pressing apparatus;

FIG. 19 is a plan view of a push and press apparatus in the position shown in FIG. eighteen;

FIG. 20 is a side view of the entire apparatus used in the method of the present invention;

FIG. 21 is a top view of the device shown in FIG. twenty; and

FIG. 22 is a front view of the device shown in FIG. 20 and 21.

Next, the method of the present invention will be described in detail, with particular emphasis on the production of mainly flat panels from recycled plastic material. However, it should be understood that the method of the present invention can be used for the manufacture of molded products of other shapes and configurations.

In FIG. 1-4 show a furnace 1 and a type 2 mold suitable for use in the method of the present invention. In particular, in FIG. 1, furnace 1 includes two half-molds 3, 4, each of which contains a housing mounted on a respective carriage 5, 6 for moving forward and away from each other, as shown by arrow 7. The furnace is shown in FIG. 1 in an open configuration in which two half-molds 3, 4 are separated and retracted from each other so that the casting can be inserted or removed. In FIG. 2 shows a furnace in a closed configuration in which two half-molds 3, 4 are connected in such a way that their respective bodies together form a closed, generally furnace chamber around the mold 2.

The carriages 5, 6, supporting each half-form, are equipped with wheels 8 for rolling rolling over the ground (for example, along the rails provided for this) between their open and closed positions by means of electric motors 9, each of which drives at least one wheel 8.

Each part of the furnace 3, 5 is equipped with a heating source. The heating source may contain one or more burners 10 located inside the furnace chamber. Gas infrared burners may be used, although it should be understood that other types of burners or heaters may also be used.

Each part of the furnace 3, 5 is additionally equipped with, respectively, a lower door 11 and an upper door 12. The lower and upper doors 11, 12 are made in the form of hinged flaps installed so that they rotate around their respective rotation axes 13, 14 between practically horizontal positions shown in FIG. 1, and inclined positions. In FIG. 2, the lower hinged doors 11 are shown in inclined positions, in which it can be seen that the two hinged doors move away from their pivot axes essentially downward towards each other. Although not shown in the figure, it should be understood that the upper hinged doors 12 can move around their pivot axes to upwardly inclined positions in which they move away from their pivot axes substantially upward towards each other. Each hinged door 11, 12 is moved between its horizontal and inclined positions by a corresponding actuator in the form of a hydraulic or pneumatic cylinder 15, 16.

Each hinged door 11, 12 has a locking rod of the mold set so as to move along the hinged door. The locking rods 17 are moved by the corresponding actuators 18, which are attached to the hinged doors and, in the preferred case, are made in the form of hydraulic or pneumatic cylinders.

One of the two half-molds 3 is further provided with upper and lower insulating elements 19, 20. In FIG. 1 and 2, two insulating elements 19, 20 are shown in closed positions, in which they extend outward from the half-mold 3 on which they are provided. As seen in FIG. 2, when two half-molds 3, 4 are located in close proximity to each other around the mold 2, and the insulating elements 19, 20 are in their closed positions, the insulating elements are located in the transverse direction above and below the mold 2, respectively. However, each insulating element can move relative to the housing of the half-mold on which they are provided, and can be moved away from its closed position (shown in the figure) when the furnace is closed, as shown in FIG. 2 to the open position, in which they protrude slightly from the housing and, as a result, are not located above or below the mold.

As shown in FIG. 4, the housing of at least one of the half-molds is provided with an exhaust opening 23 in the upper part, which allows hot gas to escape from the inside of the furnace chamber. The exhaust hole 23 may be connected to the exhaust pipe or exhaust channel (not shown).

Mold 2 is most clearly shown in FIG. 2 and 4. It is understood that a mold of such a shape and design is used that is used for molding almost flat lying in the same plane of the panel. The mold contains a pair of half-molds 24, 25, which can detachably connect to each other, forming a cavity 26 of the mold. The inner surfaces of the cavity 26 of the mold are preferably coated with a high temperature non-stick coating. Although not shown in the figures, it is contemplated that the thickness of the mold 2 can be adjusted to resize the cavity 26, which facilitates the formation of panels of various thicknesses. For example, it is proposed to provide struts of various sizes for their installation between the half-molds 24, 25.

In FIG. 2 and 4, the mold 2 is shown in the molding position in which it is oriented almost vertically inside the furnace chamber at the junction between the two parts of the furnace 3, 4. The mold 2 is designed to open at the top and bottom when it is oriented way, and therefore is equipped with upper and lower shutters 27, 28. The shutters 27, 28 may be in the form of folding doors mounted on the rotary axes. The shutters are arranged to move between open and closed positions using the locking rods 17 and associated actuators 18, which are attached to the hinged doors when the latter are in horizontal positions, without tilting.

In FIG. 5-8 show a block of a hopper 29 that is used to fill a mold with a granular material in a manner that will be described in more detail below. The hopper block comprises a support frame 30 located between a pair of horizontal rails 31. The support frame 30 can be moved along the rails 31 using a plurality of small wheels 32 that engage and roll along the rails.

The support frame 30 comprises a pair of spaced-apart end frames 33, which are interconnected by a pair of transverse beams 34. As shown most clearly in FIG. 7 and 8, the end frames 33 are usually triangular in shape and comprise a horizontal element 35, a middle vertical element 36, and a pair of diagonal tie elements 37. The middle vertical elements 36 have longitudinal channels with a C-shaped cross section; while the channels are located in such a way that their open sides are facing each other and are divided by an aperture between two rails 31.

The loading hopper 38 is held between the two end frames 33. The hopper is designed to hold and dose the granular material, in connection with which it has a traditional shape, tapering downward. The hopper 38 is positioned so as to be able to move vertically between two end frames 33, for which it has a pair of vertically arranged one above the other wheels 39, mounted on each end for rotation. The wheels 39 are designed to fit inside and move along the C-shaped channels bounded by the vertical elements 36 of the two end frames 33. Thus, the wheels 39 together with the vertical elements 36 guide the hopper 38 for vertical movement between the raised position shown in FIG. 7 and the lowered position shown in FIG. 8.

The hopper 38 has a plurality of elongated metering tubes 40 that extend vertically downward from the narrow lower portion of the hopper. Dosing tubes are arranged in a row on the same line along the entire length of the hopper, and each of them has an opening, the size of which is made so as to provide free precipitation of the granular material under the action of gravity. Each tube terminates in an open metering hole 41 at its lower free end.

The movement of the flow of granular material from the hopper chamber downward through the metering tubes 40 is controlled by a drum feeder 42. To minimize the accumulation of granular material in the hopper chamber or discharge tubes, the hopper is equipped with a pair of vibrators 43 at the bottom of the hopper, slightly higher than the metering tubes.

In FIG. 9 to 11 show a collection hopper 44 that is used in the method of the invention to collect unused granular material from the mold 2 in a manner that will be explained in detail below. The collection hopper comprises an elongated rectangular housing 45 open on top, which is mounted on a carriage 46 having wheels 47 for rolling on the ground, for example, on rails provided for this purpose (not shown). In a preferred embodiment, the collection hopper 44 is self-propelled and therefore may comprise an electric motor arranged so as to drive at least one of the wheels 47.

In FIG. 12-16, a carriage block 49 is shown so as to support, transport, and manipulate the mold 2. The carriage block comprises a trolley 50 that is designed so that it can move autonomously with wheels 51 and an engine 52.

The cart 50 includes a support frame 53, which is a support for the shaft 54, rotating in bearings 55 around a horizontal axis 56 located at some distance above the wheels. The support frame 53 is also a support for the motor 57, which is functionally connected through a gearbox 58 to the shaft 54, whereby the motor rotates the shaft 54 in the bearings 55.

A cantilever support frame 59 is mounted on the shaft 54, the cantilever support frame being located on the upper side of the trolley 50. The cantilever frame 59 is designed to support the mold 2, and is shown in FIG. 12 and 13 supporting the mold 2 is almost horizontal. However, by means of the engine 57, the shaft 54 and the cantilever frame 59 can be rotated about an axis 56 so as to maintain the mold 2 in an upright position, as shown above in FIG. 2, 3 and 4. The cantilever frame 59 is shown in this position in FIG. 14. It should be noted that the cantilever nature of the frame 59 means that, regardless of the position of the frame and the mold, there is always free space under the frame and mold. As will be explained in more detail below, this free space is sufficient for the collecting hopper 44 to move under the mold 2 when the latter is in an upright position, as shown in FIG. fourteen.

A vertical post 60 is also located on the trolley 50. The post 60 serves as a support for the yoke 61, which can be rotated around the vertical axis 62 of the post. The yoke 61 comprises a beam 63, such as that shown in this embodiment, an I-beam. On the beam 63, a group of cooling fans 64 are arranged so as to direct the cooling air flow generally in a downward direction. In a preferred case, the cooling fans 64 are provided in the form of devices installed in the air box and can be provided with a source of water or other cooling liquid to create a fine cooling mist. In FIG. 12-15 of the crosshead 61 and cooling fans 64 are shown located above the mold 2, resting on the cantilever frame 59. However, in FIG. 16, the crosshead and cooling fans are shown rotated about an axis 62 by about 90 degrees so that they are at a considerable distance from the mold 2.

In FIG. 17-19, the pressing unit 65 and the pushing unit 66 are shown. The pressing unit comprises a pressing table 67 which is held above the ground by a plurality of legs 68. Table 67 is a support for a hydraulic or pneumatic press 69 including a lower fixed plate 70 and an upper movable plate 71. Two the plates 70, 71 are made of steel and are preferably located in substantially the same plane for use in the manufacture of a substantially flat panel. Each of the plates may have a relief pattern formed in its pressing surface to obtain an imprint of the corresponding pattern on the outer surfaces of the panel, which must be formed between them, as will be described in more detail below.

Each of the plates 70, 71 has internal fluid channels for the flow of water or other coolant, whereby they are cooled; alternatively, they should be cooled with at least a simple supply of coolant.

The upper movable plate 71 is mounted so as to vertically move by means of a hydraulic or pneumatic cylinder 72, which is thus used to press the upper plate 71 down to the lower plate 70. The pressing cylinder is designed to exert very significant pressure on the upper plate 71: in particular, we can talk about pressures in excess of 100 tons.

The pushing unit 66 is generally located close to the pressing unit, but is spaced apart from it, and likewise comprises a table 73, which is supported by a plurality of legs 74. The table serves as a support for horizontal pusher rods 75 that can be moved internally corresponding hydraulic or pneumatic cylinders 76, between the retracted positions shown in FIG. 17 and the extended positions shown in FIG. 18 and 19, in which the push rods 75 are located between the pushing table 73 and the pressing table 67. In FIG. 17, a casting is located between the pusher 66 and the press 65. In FIG. 18 and 19, the casting 77 is shown to be displaced horizontally by the push rods so that it is located between the plates 70, 71 and, in particular, rests on the lower plate 70.

The method of the present invention will now be described with reference to FIG. 20-22, which depicts a substantially complete system of a device comprising the various components described above and shown in FIG. 1-19.

As can be seen from FIG. 20-21, the furnace 1 is located, generally, in the center, under the block of the loading hopper 29. The rails 31 of the block of the hopper are fixed above the furnace 1 and are arranged so that they are practically parallel to the direction in which two parts of the furnace 3 should move on the ground , 4. As most clearly shown in FIG. 21 and 22, the hopper unit 29 actually comprises two separate loading hoppers 38a, 38b with respective associated end frames 33 and the like, both loading hoppers 38a, 38b being positioned so as to move along the same rails 12 .

The first hopper 38a is filled with the first granular material for use in forming the outer shell of the product, which is a panel molded by the method of the present invention. The first granular material contains recycled plastic material and, in the preferred case, consists essentially entirely of recycled plastic material. Recycled plastic material preferably contains high impact polystyrene (OPS) and may in some cases contain an additive to improve shaping and / or a flame retardant. It is believed that the grain size of the first granular material does not matter much for the described method, provided that this material can be filled and passed through the metering tubes 40 of the hopper 38a.

The second feed hopper 38b is filled with a second granular material for use in forming the inner core of the product, which is a panel molded by the method of the present invention. The second granular material also contains recycled plastic material and, in the preferred case, consists essentially entirely of recycled plastic material. Recycled plastic material preferably contains high impact polystyrene (OPS) and may in some cases contain a flame retardant and / or pore-forming agent. It is considered preferable that the second granular material contains both UPS and recycled polyethylene (PE), in the optimal case, in a weight ratio of 75% UPS to 25% PE. Adding PE to OPS serves to reduce the melting point of the material. It has been found that a melting point of about 140 ° C. is preferred. And in this case, the grain size of the second granular material is not considered to be of great importance for the described method, provided that this material can be filled up and passed through the metering tubes 40 of the hopper 38b.

The collection hopper 44 is located so as to move on the ground under the furnace 1 between the wheels 8 located at each end. Thus, the collection hopper can be moved in a direction mainly parallel to the rails 31.

As most clearly shown in FIG. 20 and 21, a press block 65 and a push block 66 are provided on each side of the furnace 1, it being understood that each press block acts in concert with a corresponding push block on the respective sides of the furnace. In addition, a pair of carriage blocks 49 is provided — one on the respective side of the furnace 1. However, it should be understood that the press method 65 and associated pusher 66 and carriage 49 can also be used in the described method.

The panel 78 is functionally connected to all different engines, heaters, coolers and actuators: thus, the entire molding process is controlled by the panel.

The following describes a typical molding cycle suitable for forming a high strength panel.

First, the mold 2 is closed by pressing the two half-molds 24, 25 against each other to limit the cavity of the mold 26 created between them. This is done on one of the blocks of the carriage 49, and it is most convenient to have its cantilever supporting frame 59 located horizontally. After the mold 2 is securely clamped, the cantilever frame 59 is rotated 90 degrees using the carriage engine 57 so that the mold 2 is moved to an almost vertical position. Then, the furnace 1 is opened by moving the two parts of the furnace 3, 4 apart from each other, as shown in FIG. 1. In the position in which the traverse 61 and the group of fans 64 are allotted to a sufficient distance from the mold 2, the carriage 49 is fed to the furnace, moving between the press 65 and the pusher 66 to move the mold 2 into the furnace. As can be seen from FIG. 20, the vertical strut 60, which serves as a support for the beam 61, is high enough so that the beam 61 can, without encountering obstacles, pass over the pressing block 65.

When the mold 2 is placed inside the furnace 1 in the position shown in FIG. 2, the two parts 3, 4 of the furnace move towards each other so that the furnace closes around the mold 2. As can be seen from FIG. 1 and 2, each part 2, 3 of the furnace has a semicircular cutout 79, and these two cuts jointly fit the shaft 54 of the carriage block 49. Thus, the furnace 1 can be closed around the mold 2, but the mold remains held in upright cantilever frame 59 of the carriage.

Then, the lower shutter 28 of the mold 2 is closed with the lower locking rod 17 provided on the furnace. Then the lower and upper hinged doors 11, 12 of the furnace are moved to the horizontal positions in which they are adjacent to the bottom and top of the mold 2. Then, the inside furnace heaters 10 for heating the mold 2. It is preferable that the mold was thus heated to a temperature in the range from 200 ° C to 240 ° C, in the optimal case to 220 ° C.

The feed hopper unit 29 is then used to move the first feed hopper 38a to a vertical position above the furnace 1. When the mold 2 reaches its set heating temperature, the first feed hopper 38a is lowered along its vertical elements 36 so that the metering tubes move into the press cavity -forms and sink to the bottom of the mold. The hopper feeder 42 is then driven to fill the mold with the first granular material. Vibrators 42 are turned on to ensure a stable and continuous flow of material down the metering tubes. The hopper 38a constantly rises along its vertical elements 36, as the mold 2 is filled with the first granular material. As soon as the mold 2 is completely filled with the first granular material, the hopper feeder 42 closes and 38a rises and moves away from the furnace to its original position, as shown in FIG. 21.

Then, the upper shutter 27 on the mold is closed by the upper locking rod 17 located on the furnace, and the heaters 10 continue to be used to heat the mold 2. During this heating phase, the first granular material is melted in areas adjacent to the inner surfaces of the two half molds 24, 25 Thus, on opposite surfaces inside the mold 2, an outer shell of material is formed. During this heating phase, the hinged doors 11, 12 remain in their generally horizontal position and thus are actually pressed against the top and bottom of the mold 2. This prevents significant heating of the upper and lower shutters 27, 28 of the mold , which, in turn, prevents the formation of a shell at the inner surfaces of the gates.

During this heating phase, the mold is usually held at an elevated temperature of about 220 ° C for a period of 8 minutes, as a result of which an outer shell about 3-4 mm thick is formed on the inner surfaces of the mold. However, if it is desired to form shells of greater thickness, longer heating periods may be used.

During the first heating phase described above, the collection hopper 44 is moved to a collection position in which it is located directly below the mold 2.

At the end of the heating phase with the formation of the shell, the lower shutter of the mold 28 opens, and the unmelted granular material remaining between the two layers of the outer shell formed inside the mold is discharged from the mold 2, from where it falls into the collection hopper 44. Then the prefabricated the hopper 44 is taken out from under the furnace, after which the granular material inside can be returned to the first hopper 38a, for example, by means of a worm gear or other similar device (not shown).

After all the unmelted granular material is removed from the mold 2 in the manner described above, the lower shutter 28 of the mold 2 is closed and the upper shutter 27 is opened. Then (or simultaneously) the second feed hopper 38b is moved to the loading position above the mold 2 and is used as described above to fill the mold 2 with a second granular material between two layers of the shell formed on opposite surfaces inside the mold 2. Then the upper the shutter of the mold 27 is closed again.

After that, the furnace folding doors 11, 12 are moved from their horizontal positions to their inclined positions using actuators located on the furnace. As should be understood from the consideration of the inclined lower hinged doors 11 shown in FIG. 2, this is done so that the hot gases inside the furnace move around the ends of the mold 2 and, in particular, to heat the shutters 27, 28 of the mold. The upper and lower insulating elements 19, 20 are closed to prevent leakage of hot gases from the furnace.

Then, the heaters 10 heat the mold 2 and the second granular material contained therein for the second heating phase, intended to cure the second granular material, as a result of which the inner core of the plastic material is formed inside the outer shell. It is proposed that this heating phase lasts for about 20 minutes at a temperature of 220 ° C. It was found that this is sufficient for curing the second plastic material in the manufacture of castings with a thickness of 65 mm. During this heating phase, it may be necessary to rotate the mold 2 inside the furnace by turning the support cantilever frame 59 on the carriage 49 to ensure uniform heating of the mold so as to achieve curing of the entire volume of the second particulate material.

The process steps described above are used to make a casting having a predetermined thickness determined by the dimensions of the mold 2. However, additional steps are required for processing the casting into a finished panel, which are described below.

After completion of the second heating phase described above, the furnace 1 is opened and the mold 2 is removed by moving the carriage block 49 away from the furnace.

The following process steps are performed outside the furnace to free the furnace for making another casting using equipment located on the opposite side of the furnace 1, similar to that described above.

The mold 2, taken out of the furnace, is hot, so before it can be opened, and the casting inside is safely removed for further processing, the mold 2 must be cooled. Therefore, in order to direct the cooling air flow (and possibly fine mist) down onto the mold, the yoke 61 and the group of fans 64 are moved to a position above the mold, and the fans are turned on. During this cooling phase, the mold 2 can be rotated.

Then the mold 2 is opened. In this case, the mold is held in a horizontal position between the pushing unit 66 and the pressing unit 65 below the cantilever frame 59, which is most clearly shown in FIG. 21. Traverse 61 can be used as a crane to remove the upper mold 25 from the lower mold 24.

Then, the pushing unit 66 is actuated so that the casting 77 moves into the space between the two plates 70, 71 of the pressing unit 65. The push rods 75 push the casting 77 onto the lower plate 70, after which they are returned to their original position.

Then, the pressing unit 65 is driven to simultaneously cool and compress the casting 77 between the plates 70, 71. The pressing cylinder 72 is activated to press the upper plate 71 against the casting by a pressing force. Preferably, the pressure exerted by the press is greater than 150 N / cm ² , which typically will require a pressing force of about 60 tons. At the same time, the cooling unit is used to inject coolant through the channels inside the plates 70, 71 in order to cool the casting 77 while the latter is being pressed.

Press 65 is used to compress the mold in order to reduce its thickness to the required thickness of the finished panel while simultaneously finishing the surface of the panel in accordance with any relief pattern formed on the plates.

For example, a rectangular mainly casting (400 mm × 700 mm) 77 formed inside the mold 2, having an initial thickness of 65 mm, can be compressed to a thickness of about 30-50 mm in the press under a pressure of 190 N / cm ² while cooling. Thus, the thickness of the casting, as a rule, decreases as a result of pressing by 20 or more percent; it was considered advisable to use a press as described in the manufacture of such panels, while cooling the casting from an initial temperature of about 200 ° C (after removal from the mold 2) to about 30-40 ° C for about 8 minutes.

Panels made using the technology described above (for example, panels with a total thickness of about 48 mm and a shell thickness of about 3-4 mm) showed extremely good structural properties and integrity. It was found that the manufacture of an intermediate casting 77 of greater thickness and its subsequent compression to the required panel thickness while cooling the casting / panel allows to obtain a much better product in comparison with products obtained using methods known from the prior art. Panels made in accordance with the method of the present invention, as a rule, have significantly better flatness and integrity.

When used in the present description and claims, the terms “includes,” “including,” and variations thereof mean that these features, steps, or systems are included. These concepts should not be interpreted in such a way as to exclude the presence of other features, steps or systems. The features disclosed in the above description or in the claims below or in the accompanying drawings, expressed in their specific forms or in the form of means for performing the disclosed function, or a method or process for achieving the disclosed results, as appropriate, may be or in any combination of such features, used to implement the invention in its various forms.

Although the invention has been described in connection with the exemplary embodiments described above, many equivalent modifications and changes are apparent to those skilled in the art. Accordingly, the embodiments described above should be considered as illustrative and not restrictive. Various changes may be made to the described embodiments without departing from the spirit and content of the invention.

Claims (15)

1. A method of manufacturing a molded plastic product having an outer shell and an inner core, characterized by the content of the following steps: creating a mold having a cavity; the formation of the outer shell of the first plastic material, at least two opposite surfaces inside the cavity of the mold; the formation of the inner core of the second plastic material inside the cavity of the mold; and at least partially curing the plastic materials inside the mold cavity by heating, followed by simultaneous cooling and compression of the casting so that at least one of its dimensions is reduced to the required size of the finished product. 2. The method according to p. 1, characterized in that the casting is removed from the said cavity of the mold to the simultaneously produced stages of its cooling and compression. 3. The method according to p. 2, characterized in that the cooling and compression of the castings performed simultaneously are carried out in a press having a cooling circuit designed in such a way as to cool the casting in the press. 4. The method according to any one of paragraphs. 1-3, characterized in that the cooling of the casting is carried out so that the temperature of the casting is reduced from a level above 200 ° C to a level below 40 ° C. 5. The method according to any one of paragraphs. 1-3, characterized in that the compression of the casting is carried out so that the specified size was reduced by at least 20%. 6. The method according to any one of paragraphs. 1-3, characterized in that the compression includes applying to the casting pressure not lower than 150 N / cm during cooling. 7. The method according to p. 1, characterized in that the said step of forming the outer shell includes filling the mold cavity with the aforementioned first plastic material in a granular form, heating the mold to form a shell of molten granular material in the at least two opposite surfaces of the mold, and the extraction of unmelted granular material from the cavity of the mold after forming the required thickness on the said surfaces of the shell. 8. The method according to p. 7, characterized in that the extraction of the molten granular material from the mold is carried out by opening an outlet made in the lower part of the mold and allowing the molten granular material to fall out through it under the action of gravity or by rotating the mold for rashes of unmelted material. 9. The method according to p. 8, characterized in that the specified outlet is closed after the extraction of the molten granular material, as a result of which the cavity of the mold is ready to accept the second plastic material. 10. The method according to any one of paragraphs. 7-9, characterized in that the said step of filling the mold cavity with said first plastic material includes filling the said material in a granular form through an inlet made in the upper part of the mold, and then closing said inlet. 11. The method according to p. 1, characterized in that the said step of forming the inner core comprises filling the mold cavity with said second plastic material in a granular form after forming the outer shell on said at least two opposite surfaces and heating the mold to at least partially curing substantially all of the volume of said second material within the mold cavity. 12. The method according to p. 11, characterized in that said step of filling the mold cavity with said second plastic material comprises filling the said material in a granular form through an inlet made in the upper part of the mold, and then closing said inlet. 13. The method according to any one of paragraphs. 11 or 12, characterized in that the mold is maintained at an internal temperature of at least 200 ° C for at least 5 minutes. 14. The method according to p. 1, characterized in that at least one of the first and second materials contains recycled high-impact polystyrene (UPS). 15. The method according to any one of paragraphs. 1 or 14, characterized in that the second material contains recycled polyethylene.

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