DE2159383A1 - Process for the manufacture of laminate articles - Google Patents

Description

PATENT AGENCY OFFICE "HOMSEN - TlEDTKE - BüHLING

TEL. (0811) 53 0211 TELEX: S-24 303 topat 2159383

53 0212

PATENTANWÄLTE Munich: Frankfurt / M .:

Dipl.-Chem. Dr. D. Thomsen Dlpl.-Ing. W. Welnkauff

Dipl.-Ing. H. Tledtke (Fuchthohl 71)

Dipl.-Chem. G. Bühling Dipl.-Ing. R. Kinne Dipl.-Chem. Dr. U. Eggers

80 0 0 Munich 2

Kalaer-Ludwig-Platee3o. November 1971

Imperial Chemical Industries Limited London, UK

Process for the manufacture of laminate articles

The invention relates to the manufacture of laminated articles, i. H. Objects with a sandwich structure made of a skin made of a plastic material, which has a core made of dissimilar plastic material with the exception of the gate area of the Pormling surrounds.

It has been proposed to manufacture such articles from plastic materials by injection molding, wherein the plastic materials are sequentially injected into a mold cavity so that the second and any subsequent injected material penetrates into the first material and causes the enveloping first material to expand.

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MOndllch · agreements, intbetonder · by telephone, require written approval Potttchedc (Munich) account 11W 74 Dresdner Btnk (Manchen) account 6960700

One such method is described in British Patent 1,156,217, in which the plastic materials Are thermoplastics and the core-forming material is foamable.

When the plastic materials are in the flowing state, i. H. as melt, through a runner into a mold cavity are injected with a constant cross-section, they flow from the sprue to the outside until the melt front hits locally is held up on the walls of the mold cavity. Usually the melt front contacts the walls of the mold cavity in some places before others, d. H. the lengths of the flow paths from the runner to the mold cavity boundaries are of one part different in shape to the other. This also applies if, as often happens, the cavity does not have a constant cross-section.

If a second material is injected into the first material, after a predetermined amount of the latter material has been injected, the second material expands that surrounding it Skin from the first material until the mold cavity is filled. With regard to the different flow paths the enveloping skin must be expanded more in some directions than in others, so that in some places on the On the surface of the bricks, more skin remains than on others.

In other cases it may be desirable to have a more uneven distribution of skin thickness in the molded article bring about than one would otherwise receive. For example, it may be desirable to produce a shoe sole that

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has a thin sole section with a thick skin and a thicker Persen section with a thinner skin. While it is often possible to change the distribution of the skin material with respect to the core material by changing the gate position and / or to modify the thickness of the desired article, it is desirable to provide an alternative method that additionally can be used to modify the gate position and / or the article thickness to give the molding expert further freedom grade to give.

The invention is based on the principle of injecting the material through more than one runner.

While in the aforementioned patent specification 1,156,217 it is preferred that skin and core materials have been injected through the same runner, should be considered that separate runners can be used provided that the two channels are sufficiently close to one another that the core material can be injected while penetrating into the interior of the skin material. This means that the two runners must be so close or close to each other that after the injection of the skin material this the mold cavity so far has filled that the runner for the core material is covered by the skin material. Admittedly, this technique gives the mold specialist some latitude in modifying the distribution of the skin and core materials in the mold cavity, but it is desirable to get another degree of leeway.

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In the invention, this is achieved by using three or more runners reached.

According to the invention a method for the production proposed of objects with a skin made of plastic material, which surrounds a core made of dissimilar plastic material, which is made of skin material in the pleated or liquid state or skin material followed by core material is injected into a porous cavity through a first runner and in the flow state Skin material and / or core material is injected into the Pormhohlraum through at least two runners, which from the first runner are offset, with core material or skin material followed by core material through at least one of the runners injected and the materials injected through the runners unite or penetrate one another, while they are still liquid and where the core material is injected into the skin material that was previously in the porous cavity was injected.

To ensure that the core material is away from the skin is encased, sufficient skin material must be injected to ensure that the encasing skin through the core material is expanded to fill the mold cavity and does not tear the surrounding skin. This amount can be done without difficulty by using a few test moldings different amounts can be determined in skin material.

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In order for the core material to be injected into the interior of the skin material, it is necessary that there is sufficient skin material is injected into the mold cavity prior to injecting the core material to ensure that the skin material settles has expanded to below the runner or runners through which core material is to be injected and that the core material is injected as long as the skin material is flowable or is fluid. Where the skin material is injected through more than one sprue, it is necessary to ensure that the advancing skin materials are in a state of flow when they come into contact with one another, so that they merge into one another or, however, penetrate each other.

It is preferred that more than three runners be used, however for simplicity the invention is further developed in FIG Explained with reference to three runners.

It will be seen that there are several possible alternative modes of operation.

One can assume that it is unimportant which runner is used is considered to be the first runner, which is the second and which is the third, eight alternative options can be found, as given in the table below.

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alternative Injected through runner followed
core Runner
2 material A. Runner
1 followed
core skin Runner
3 B. skin followed
core core core C. skin followed
core skin core D. skin
from followed
core skin skin E. skin
from followed
core core core P. skin
from Skin followed
from core core Q skin
from Skin followed
from core skin H skin
from Skin followed
from core core skin
from Skin followed
from core

Processes that use two or more runners, where skin material followed by core material is injected through one or more runners is common in the UK Patent application 56695 is described, although such methods using three or more runners, i. H. Alternatives C to H are intended to fall within the scope of the invention, only one alternative C will be described in detail, reference being made to said patent application for a more complete description of the other alternatives.

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In the first embodiment - alternative A - skin material is injected through two sprues and core material is injected through a third sprue. The skin material can be injected through the two runners simultaneously or sequentially: all that is essential is that when the advancing portions of the skin material injected through the two runners touch each other, they are still flowing and merge. Core material is then injected through the third runner after the previously injected skin material has expanded to below the third runner and is still in the flow state, so that the core material enters the interior of the skin material. It is not necessary that the skin material injected through the two first and second runners be injected prior to injecting the core material through the third runner. Skin material can thus be injected through the first runner, core material through the third runner and then skin material through the second runner.

In the second embodiment, alternative B, skin material is injected through one sprue and core material is injected through two sprues. It is necessary that the skin material be injected first so that it expands below the runner to be injected through the core material and that it is still flowable when the core material is injected so that the latter penetrates into the interior of the skin material. However , it is not necessary to inject core material through both sprue channels at the same time and it is also not necessary to

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that the skin material has expanded under both runners when the core material is injected through one of them will. Thus, the injection of the core material, which can be done while still the injection of the skin material takes place, expand the skin material to a position where it is below the other runner, is to be injected through the core material.

In alternative B, if the core materials are injected at the same time, the resulting article has generally separate sandwich structure areas (made of core material enclosed by skin material), ctie are connected by areas, which only consist of skin material. This build-up also occurs when the core materials are successively passed through the first and second runner are injected and the core material injected through the first runner is not up has expanded below the location of the second runner, prior to injection, of the core material through the second runner he follows.

In the third embodiment - alternative C - is skin material is injected through one runner, followed by core material, and skin material is injected through the other runner. It it is not necessary that the skin material followed by the core material be injected before the other batches of skin material. However, as with alternative A, it is necessary that when the injected batches of skin material touch one another, they are in a state of fluidity so that they merge into one another.

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It is not necessary that the skin material be injected through the other runners before the core material is injected although it is preferred that the skin material be injected through the other runners before the core material that following the skin material through the first runner is injected, has expanded to under the other runners, since in the case of injection it is through the other Sprues injected skin material would penetrate into the core material.

To continue the distribution of skin and core materials To modify within the mold, more skin material can be injected into the mold cavity than is necessary, the Excess skin material is pushed back by injecting the core material through the sprue through which it is injected became. This procedure is described in British patent application 48712/71.

Of course, the dimensions of the various runners can be different and the amount of material injected through the various runners can also differ. Where the plastic materials are thermoplastics, they must be cooled in order for them to harden from the flow state in which they were injected into the mold cavity. In order to support such setting or solidification, the mold is cooled, although the choice of mold temperature depends on the materials being processed. Generally in the range of O Formtemperaturren suitable ⁰ C to 100 ⁰ C. However, if the sprue channels are spaced apart, it may be necessary

2 0 9 8 2 ^ / 097? -

be to heat the mold or part of the mold around the runners to ensure that this passes through a runner Injected skin material is injected in the flow state when the material is injected through a different runner comes into contact with this material so that it merges into the skin material injected through this one runner or penetrates into this.

The area of the mold surrounding the runners can be heated during the molding cycle and then cooled therewith. the plastic materials can solidify, provided they are thermoplastics. In the event that through a runner injected material is intended to penetrate into the interior of the skin material that has been injected through another sprue channel, Alternatively, the runners can be heated by a movable probe which is pushed in so that it passes through the another sprue channel injected skin material pierces after this has covered the one sprue channel, thereby injecting of the material to be injected through this one runner.

Plastic materials that can be used in the invention are those that are injected into a mold cavity if they are in a viscous liquid state and which can then harden in the mold cavity. Thus, thermoplastic resin materials can be used which

can be injected in the form of viscous melts and which can harden by cooling in the mold cavity. Alternatively you can

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thermosetting resin materials are used in the state a viscous one. Liquid can be injected into the mold cavity and which can be obtained by causing crosslinking in the mold cavity let harden. Generally, the thermosetting resin materials are those which are crosslinked by heating.

Examples of such formable by injection molding of thermoplastic resins which can be used are polymers and copolymers of o (-01efinen such as high- and low-density poly ethylene φ, polypropylene, polybutene, poly - ^ - methyl-pentene-l, propylene / ethylene Copolymers, copolymers of 4-methylpentene-1 with linear <X-olefins, containing 4 to 18 carbon atoms, and ethylene / vinyl acetate copolymers, polymers and copolymers of vinyl chloride, vinyl acetate, vinyl butyral, styrene, substituted styrenes such as CX-methylstyrene, acrylonitrile, Butadiene, methyl methacrylate, vinylidene chloride, specific examples of such polymers are vinyl chloride homopolymers and copolymers of vinyl chloride with vinyl acetate, propylene, ethylene, vinylidene chloride, alkyl acrylates such as 2-ethylhexyl acrylate, alkyl fumarates, alkyl vinyl ethers such as cetyl vinyl ether, and N-aryl-chloro-enyl acetate, polyvinyl acetate, such as no-maleic-chloro-phenyl , Polyvinyl butyral; polystyrene, styrene / acrylonitrile copolymers, polyacrylonitrile, copolymers of butadiene with M ethyl methacrylate and / or styrene and optionally acrylonitrile, polymethyl methacrylate, copolymers of methyl methacrylate with smaller amounts of alkyl acrylate, such as methyl acrylate, ethyl acrylate and butyacrylate, copolymers of methyl methacrylate, N-aryl maleimides and, optionally, styrene, and vinylidene chloride / acrylonitrile-workable copolymers, and vinylidene chloride / acrylonitrile-workable copolymers . 209824/0977

Halogenated polymers or copolymers are for example halogenated c * -01efin polymers, such as chlorinated polyethylene, or halogenated vinyl chloride polymers such as chlorinated polyvinyl chloride.

Other injection moldable thermoplastic polymers that are useful are condensation polymers such as injection processable linear polyesters such as polyethylene terephthalate, polyamides such as polycaprolactam, polyhexamethylene adipamides and Copolyamides such as copolymers of hexamethylene diamine adipate and hexamethylene diamine isophthalate, especially those which contain 5 to 15% by weight of hexamethylene diamine isophthalate, polysulphones and copolysulphones, polyphenyloxides, polycarbonates, thermoplastic polymers and copolymers of formaldehyde, thermoplastic linear polyurethanes and the thermoplastic derivatives of cellulose such as cellulose acetate, cellulose nitrate and cellulose butyrate and mixed cellulose esters such as cellulose acetate butyrate.

If a copolymer is used, the amounts of comonomers used in the copolymer will vary, among other things. of the desired properties of the moldings.

Thermosetting resins include plastic materials that a cross-linking either on its own or in the present a hardener or a catalyst obtained by heating to a sufficiently high temperature. The designation thus closes Materials that are commonly referred to as "thermosetting"

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understood scope fall as well as plastic material that normally is thermoplastic, but contains crosslinking agents such as a peroxide that brings about crosslinking, when the plastic material is heated to a sufficiently high temperature.

Examples of such usable thermosetting resins are phenol-aldehyde resins, amine-formaldehyde resins, epoxy resins, Polyester resins, thermosetting polyurethanes and vulcanizable rubbers.

The resins can contain curing agents or a catalyst where necessary for the resin to cure.

Injection moldable crosslinkable thermoplastics include copolymers of methyl methacrylate and glycol dimethacrylate and Ethylene / vinyl acetate copolymers containing a crosslinking agent.

Mixtures of plastic materials can be used.

The choice of materials _a from which the object is to be made depends on the _{intended use 8 to} which the object is to be subject. The inventive method provides a particularly useful way for creating objects mn with a core of relatively cheap material with good skin, For example, the "core of

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- 1 * 1 -

consist of a thermoplastic material that contains fillers, whereas the outer skin consists of a material that guarantees a desired surface finish. Provided the process used to manufacture parts of motor vehicle bodies requires a stiff outer skin, whereby Filled polypropylene is a particularly good resin for forming the outer skin. If a flexible molding is required, for the interior lining of an automobile, for example, a plasticized vinyl chloride polymer would be exceptional suitable as the outer skin of the molding.

Where skin material is injected through more than one runner, the skin materials can be different from one another provided that they are compatible so that they blend into one another and form a close bond with one another. In general, such different skin materials will only differ in the additives they contain, e.g. B. Pigments, so that two or more colored objects can be created, or in the additives which the properties of the skin material modify. For example, different skin materials can be plasticized polyvinyl chloride on the one side and plasticized polyvinyl chloride containing nitrile rubber on the other side; Nitrile rubber provides additional abrasion resistance to the composition.

The core material can be the same as the suture material, with the exception of additives that are contained in one or two other materials , or in both, but in

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different proportions. Alternatively, the plastics can be very different and contain different additives.

Where the core material is injected through more than one runner, that may be injected through one runner If necessary, core material can be different from that which is injected through a further runner, so that Moldings with different mechanical and physical properties are produced in different areas can. This technique can be used, for example, in the manufacture of shoe soles, where a flexible core is in the Sole section and rigid core material in the heel is needed.

In a preferred embodiment, the core material is foamable. Preferably, it consists of a polymeric material with a blowing agent, which when heated above a certain Temperature (referred to as activation temperature) a gas develops, e.g. B. by volatilization (when the pressure on the composition is reduced) or by decomposition, whereby the material is at a temperature above the activation temperature of the blowing agent is injected. It is preferred that the plastic material be adjusted to the foaming temperature, i.e. H. is heated beyond the activation temperature with the injection into the runner by relying on the dynamic Heating leaves the passage of the material through the dei

Injection nozzle of the injection molding machine occurs.

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Will the core material with the usual injection speeds and pressure injected as used in injection molding, there will be essentially no foaming occur until the desired amount of core material has been injected. If a foamable core material is used, two alternative modes of operation can be used. The first is the amount of skin material injected and foamable, but not yet foamed core material is insufficient, to fill the mold cavity, allowing the core material to foam and at the same time the surrounding material Allow skin material to stretch to the extreme limits of the mold cavity. In the second way of working, the amount of injected skin material and foamable, but still unfoamed core material selected so that the cavity is filled, before substantial foaming occurs, then increasing the cavity for foaming.

It is preferred to use the second of these alternative modes of operation, as it is more regular in cell structure at the core of the molded article and ensures articles with a better surface finish.

In this preferred embodiment for the production of foamed moldings as described above, the enlargement of the mold cavity can be effected in one of two ways. One or more of the molded parts bordering the mold cavity can be sucked back by any external force which instantly expands the cavity to the desired extent or which gradually enlarges the cavity. With a vertical squeeze mold, the mold halves can be

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holding clamping pressure can be reduced, so that the pressure of the through the decomposition or volatilization of the blowing agent evolved gases enlarges the mold cavity; here again the locking pressure gradually decreased to achieve gradual expansion of the mold cavity; also is instantaneous Possible to reduce the clamping pressure in order to achieve sudden expansion.

The mold should be designed so that there is minimal loss of material from the mold during the molding cycle, especially when the materials are under high pressure. It was found that the forms of construction as they are general known as vertical squeeze molds, are particularly useful when it is desired to enlarge the mold cavity. Where there is a possibility of air being trapped between the advancing fronts of skin material in the mold cavity vents may be provided in the mold to allow the trapped air to be forced out.

The dimensions and shape of the mold cavities depend on the object to be produced, with molds having a maximum Void thicknesses of less than 25 mm and preferably between 2 mm and 10 'mm in thickness are particularly useful.

The method according to the invention is expediently carried out using a machine which, for each Angulkana1 has an injection molding cylinder, the use of these cylinders being synchronized to achieve the desired injection cycle obtain. It is preferred that valves or cocks be provided

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in order to control the flow of material from the injection cylinders into the mold cavity, so that that through a runner injected material on one return flow into the injection cylinder as a result of injecting material through another Runner can be stopped unless reflux is particularly desired. If the method according to the invention is used to produce moldings with a foamed core, whereby the mold cavity is enlarged to allow the batch to run out Foamable material can foam, this enlargement of the shape must in the same way when programming the machine must be taken into account.

As described above, the method according to the invention is used to produce objects that have a skin made of plastic material have that surrounds and touches a core of dissimilar plastic material, with the possible exception of the Sprue areas of the object.

In general, injection molded articles are removed from the mold cavity along with the adhering material solidified in the runners. These sprues are usually not part of the desired item and are thus removed from the molding after it has been removed from the mold cavity. The area of the subject from which the gate has been removed is referred to as the gate area.

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The core material is injected into the mold cavity through a runner to allow it to enter the interior of the skin material occurs, a small amount of core material will appear on the surface of the sprue area of the article appear when the sprue is removed from the molding.

The amount of core material exposed in the gate area can be reduced by injecting another, smaller amount of skin material through the same runner that the core material has been injected after the core material has been injected, so that after the sprue has been removed only a small ring of core material remains freely visible from the molding. This small or tight ring arises made of core material that did not come out of the runner due to the injection this small additional amount of skin material has been squeezed out as it adheres to the walls of the runner. at Using high injection speeds and heated runners, however, only a small amount of core material remains as an adhesive layer adhere to the sprue walls so that the narrow ring of core material that remains in the sprue area of the molded article remains can be made so narrow that it is practically indistinguishable.

It is therefore preferred, as described above, to inject a further amount of skin material through each runner, has been injected through the core material after injecting the core material.

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The method according to the invention can be used for the manufacture of articles for a wide range of applications. As described above, the method is particularly useful in the production of moldings from a thin Section and a thick section exist, e.g. B. in the manufacture of shoe soles. Items with a rigid or with a flexible skin can be made by this process. Examples of such items with a rigid skin are Pieces of furniture and wainscoting which can be structural panels or panels for making the bodies of automobiles or trains. In addition to shoe soles, examples of such articles with flexible skin are parts of the interior lining of motor vehicles, railroad cars, Caravans, airplanes, and a wide variety of other uses. In one embodiment of the invention can at least parts of one or more walls of the mold cavity prior to injecting the materials into the mold cavity with a removable liner made of a material that retains its shape at temperatures at which the plastic materials be injected into the mold cavity. The plastic materials then stick to the liner when they are in injected into the mold cavity, in which case an object with a sandwich structure with a permanently connected lining on the object can be removed from the mold cavity after solidification of the plastic material. This way of working can can be used to obtain a rigid support for example for cellular articles with an unfoamed core. This is particularly useful in making flexible moldings for automotive interior linings where there is

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It is desirable to have a resilient liner with a pleasing surface that is rigid in the motor vehicle is mounted. In such a case, one of the walls of the mold can be lined to provide support for the mold To obtain lining, while the other mold wall is not coated so that it provides the attractive surface. Examples of such linings are wooden panels such as plywood or hardboard, metal panels or panels thermoplastic materials that retain their shape, d. H. are dimensionally stable at the injection temperature. Alternatively, the lining if necessary, consist of flexible material, for example as the upper material of a shoe or boot, to the the sole is molded by the method according to the invention.

The invention is explained in more detail below with reference to schematic drawings.

1 to 9 are cross-sections through a mold cavity with three runners, with different ones Mold cavity filling stages are shown.

In FIGS. 1 to 3 the above-described alternative A is selected, in FIGS. ¹ I to 6 the aforementioned alternative B and in FIGS. 7 to 9 the alternative C.

For the sake of simplicity, in the drawings each runner is provided with a simple valve with a single bore. However, where more than one material is to be injected through a runner, it is preferred that each valve be separate

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Holes for each material to be conveyed through the runner having. Such valves are described in British Patent 1,219. Is the valve in the closed position in the drawings? As shown, the bore is shown filled with the material that was injected through this valve before it was closed. Furthermore, for the sake of simplicity, the cavity is shown with a constant cross-section and the same shape at each filling stage. Of course In practice, certain sequences are more useful for cavities with non-uniform or irregular cross-sections.

1 to 3 show a filling sequence of the mold cavity according to alternative A according to the invention.

First, the skin material ¹ and 5 I injected into the mold cavity through runners 1 and 2 consists of a conveyor channel 3 via valves.

Injection through the two channels does not have to take place simultaneously. As shown in FIG. 1, the valve ¹ I then switched in the blocking position while forge drive with the injection through the runner. 2

The skin material injected through the runner 2 and still in the flowing state touches the through the Sprue channel 1 injected material and passes into this, as shown in FIG. Injecting skin material through the runner 2 is continued until the skin material

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has expanded to such an extent that it fills the runner 6 (as can be seen from FIG. 2); then the valve 5 is in the blocking position switched. A valve 7 is then switched in such a way that a core material feed channel 8 connects to the sprue channel 6 comes into contact, the core material then through the runner 6 into the still liquid skin material below the runner 6 is injected. The injected core material pushes the skin material towards the ends of the mold cavity. In this way an article is obtained which has an area with a sandwich construction from a core enclosed by a skin material (with the exception of of the sprue area which is exposed when the sprue formed in the sprue channel 6 is removed) and an area which consists only of skin material.

Alternative B is shown in FIGS. First, skin material is removed from the conveying channel 9 via the valve

5 is injected into the mold cavity through the runner 2. Has the skin material expands to the extent that it is the sprue

6 fills, the valve 5 is switched to the blocking position and the valve 7 switched so that the injection of core material from the conveying channel 8 through the sprue channel 6 is possible, with the core material in the interior of the still liquid skin material penetrates (see Fig. 5).

Through the sprue channel 1, core material, which may differ from the core material injected through the sprue channel β, is injected from the delivery channel ^{10 via the valve 2, after the skin material has filled the sprue channel 1, so that}

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the core material injected through the conveying channel 1 penetrates into the interior of the skin material which is still liquid. The injection of the core materials expands the enveloping skin material to the ends of the porous cavity, as shown in FIG is.

In the third embodiment - alternative C according to FIG 7 to 9, skin material is first injected through all three runners 1, 2, 6 (see Fig. 7). Valves

4 and 7 are then switched to the blocking position and valve

5 is brought into connection with the conveying channel 3, so that core material is injected into the runner 2 and penetrates into the interior of the still liquid skin material.

By injecting the core material, the enveloping skin material is expanded, wherein the skin material with the liquid skin material injected through the sprues 1 and 6 comes into contact and merges into this (see. Fig. 8). Injection of the core material continues until the mold cavity is substantially filled; then is preferred Valve 5 switched to establish a connection with the conveying channel 9, so that a further, small amount of skin material is injected (see Fig. 9). In this way, after removing the sprues formed in the runners, the exposed gate areas skin material with the exception of a narrow ring of exposed core material in the gate area corresponding to the sprue formed in the sprue channel 2.

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If the core material is foamable, it can be foamed by moving the two mold halves apart, which limit the mold cavity.

An example is now given of how the method can be carried out.

A mold cavity in the form of a square plate with a dimension of 50 cm is created by the mold parts of a vertical one Squeeze shape delimited. The cavity thickness was 0.4 cm.

A main runner communicates with the center of the cavity, while an additional runner communicates with the mold cavity at one point on each diagonal of the square 22 cm from the center of the square. The total volume of the mold cavity was 1008 cm, with each of the additional runners having a volume of about 1.5 cm .

About ¹ cm IOO slightly plasticised vinyl chloride polymer composition was injected as a skin material through the central Hauptangußkanal with a temperature of 185 ° C; at the same time, 29 cnr of the same mass was injected through each of the four additional runners.

As the skin material injected through the five runners neared the end, the advancing front of the skin material injected through the main runners contacted the skin material injected through the additional runners

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and passed into this. The skin materials are made with a

"Ο
Injected pressure of about 135 MNm.

Upon completion of the injection of the skin material, a plasticized vinyl chloride polymer composition became a blowing agent With a content of 0.7 wt. £ azodicarbonamide as a blowing agent with a temperature of 180 ° C and a pressure of about 135 MNm " injected through the main runner. Injecting the core material stretches the enveloping skin material until it is filled of the mold cavity. It will be adequate (about 492 cm ') injected non-foamed, but foamable core material, so that the mold cavity is filled without a foaming process. It the mold cavity is then enlarged by reducing the clamping pressure holding the mold parts together, so that the thickness of the mold cavity was enlarged to 0.7 cm, thereby enabling the foamable or foamable core to be foamed became. The molding is then cooled and removed from the mold cavity. The molding has a more uniform skin thickness in particular in the areas of the corners of the square than would otherwise be obtained if both materials were only through one central runner would be injected,

• The invention thus provides a method in which Skin and core materials sequentially into a mold cavity are injected, the skin material through a first runner and skin and / or core material through two or more runners are injected spaced apart from the first.

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Claims (9)

Claims 1. Process for the manufacture of objects with a skin made of plastic material, which has a core of dissimilar Enclosing plastic material, skin and core materials being sequentially injected into a mold cavity in the flow state and the core material is injected into the interior of the skin material so that the latter is expanded through the core material is, characterized in that to achieve a desired distribution of skin and core material in the molding Skin material or skin material followed by core material injected into the mold cavity through a first runner, and skin material and / or core material into the mold cavity through at least two sprue channels located at a distance from the first sprue channel injecting that core material or skin material followed by core material is injected through at least one of the runners wherein the materials injected through the runners merge or penetrate one another while they are still in the Flow conditions are where the core material is injected into the interior of the skin material that is first injected into the mold cavity became. 2. The method according to claim 1, characterized in that skin material through at least one of the at least two sprues is injected. 209324/09 7 7 3. The method according to claim 2, characterized in that skin material through a runner after the start of injection of the core material through another runner, but before the core material is expanded to below the runner is injected through which the skin material is to be injected. Ii. Method according to claim 1, characterized in that that the core material is injected through at least two sprues. 5. The method according to claim ¹ I, characterized in that the core material is injected through a runner before core material is injected through a second runner, and core material is injected through the second runner after the core material injected through the one runner is below the second runner has expanded so that the core material injected through the second runner penetrates into the core material and merges into the core material that was injected through the one runner. 6. The method according to claim 2 or 3, characterized in that skin material followed by core material one sprue is injected and skin material is injected through the other runners. 7. The method according to any one of the preceding claims 1 to 6, characterized in that after the injection of the core material, a quantity of skin material is injected, through at least one of the sprue channels ₉ through the core material. ¹ ^ η QQO / i C: Q 1 * ϊ material was injected. 8. The method according to any one of the preceding claims 1 to 7 »characterized in that the core material is a Foamable mass is a polymeric material and a blowing agent and is injected at a temperature above the activation temperature of the blowing agent. 9. The method according to claim 8, characterized in that the amount of injected foamable mass is selected
that the porous cavity is filled before the foaming
takes place and that the Pormhohlraum is then enlarged for foaming. 209824/0977 Blank page