DE2159345A1 - Process for the manufacture of laminate articles - Google Patents

Description

PATENT OFFICE THOMSEN - TiEDTKE -

TEL. (0 * 11) 53 0211. TELEX: 5-24 303 topat

»0812

PATENTA NW Ä L'T E Munich: Frankfurt / M .:

Dlpl.-Chem. Dr. D. Thomaen Dipl.-Ing. W. Welnkiuff Dipl.-Ing. H. Tledtke (Fuchthohl 71)

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

80 00 Munich 2

Kaleer-kudwIg-Platie3o. 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 surrounding the bricks.

It has been proposed to manufacture such articles from plastic materials by injection molding, 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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One such procedure is in the UK

U.S. Patent 1,156,217 in which the plastic materials Are thermoplastics and the core-forming material is foamable.

If the plastic materials are in the flowing state, d. H. as melt, are injected through a runner into a mold cavity with constant cross-section, they flow from the Runner to the outside until the melt front is stopped locally by hitting 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.

A second material is injected into the first material after a predetermined amount of the latter material has been injected, the second material expands the surrounding skin of the first material until the mold cavity is filled. In view of the different flow paths, the enveloping skin must be stronger in some directions than in others are expanded so that more skin remains in some places on the surface of the molded article than in 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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a thin section of the sole with a thick skin and a thick heel 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 does can be used to modify the gate position and / or the article thickness to give the molding expert a further degree of freedom admit.

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 are passed through the same Runners have been injected, it should be considered that separate runners may be used provided that that the two channels are sufficiently close to one another so that the core material penetrates into the interior of the skin material can be injected. This means that the two sprues must be so close or close to each other that after the injection of the skin material this has filled the mold cavity so far that the runner for the core material through the Skin material is covered. 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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According to the invention, this is achieved in that both skin and core materials are injected through a sprue channel and a further amount of skin and / or core material is injected through a further sprue channel.

Accordingly, the invention provides a method for the manufacture of articles having a skin of plastic material, which encloses a core made of dissimilar plastic material, in which skin and core materials are consecutively imprinted Flow state is injected through a first runner into a mold cavity, the core material being injected into the skin material is, while the skin material is still flowing, so that the core material expands the enveloping skin material, wherein the method is characterized in that to achieve a desired distribution of skin and core material in the molding injects a further amount of skin and / or core material in the flow state through a second sprue channel into the mold cavity, which is offset from the first runner, with the further amount of skin material or skin material followed is of core material and is injected at such a time that it is the skin material injected through the first runner touches while the latter is still flowing, so that the skin material injected through the second runner in the skin material injected through the first runner passes over or penetrates into this, while if the further amount of material is core material, it is injected after the skin material injected through the first or another runner expands to below the second runner has and is still in the flowing state, so that the further amount of

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- 5 core material is injected into the interior of the skin material.

As can be seen, there are three possible alternatives. In the first case, that is injected through the second runner Material only skin material. In the second case it is core material, while in the third case it is skin material with the following Core material is. To ensure that the core material is enclosed by the skin, sufficient skin material must be injected are to ensure that when the enveloping skin expands through the core material, the mold cavity is filled and the enveloping skin does not tear. This amount can be determined without difficulty by using a few simple test runs using different Quantities of skin material are determined.

In the first case that the material injected through the second runner is skin material, this can be done before, during or after the injection of the skin material can be injected through the first runner so that it is together with the skin material injected through the first runner forms the skin material obtained by injecting the core material is expanded. Preferably, the skin material is injected through the second runner after that through the first Sprue channel injected skin material to below the second Sprue has been expanded. It is also possible to feed the skin material through the second runner into the mold cavity after the core material has started to be injected through the first runner. In this embodiment it is preferred that the skin material through the second sprue

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channel is injected before the core material injected through the first sprue channel extends to below the second sprue channel has expanded so that the skin material injected through the second runner does not inject into the core material will. To make the core material penetrate the skin material further in one direction than in another, In some cases it may be desirable to pass the skin material through the second runner during or after the injection of the Core material through the first runner and after expansion of the core material injected through the first runner to to be injected below the second runner so that the skin material injected through the second runner into the core penetrates and thus displaces it.

In the second case, where that through the second runner First injected material is core material, it is for encapsulating the core through the skin (with the exception of the Sprue area of the briquettes according to the following description) necessary that the core material through the second sprue channel is injected after the skin material injected through the first runner or through a further runner has expanded to below the second runner so that the core material injected through the second runner in the skin material is injected. Although this is made possible by the The core material injected into the second runner is preferably injected after that injected through the first runner Core material extends below the second sprue can so that the core injected through the second runner

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material into the core material injected through the first runner penetrates and integrally connects with this, in those cases in which it is desired, on the object To have areas with areas of skin material which encloses a core, which is defined by areas consisting only of skin material is segregated, the core material will be injected through the second runner before that through the first runner injected material has expanded to below the second runner '. In this case, the core material can be injected through the second runner before the core material is injected through the first runner.

From the above description it is clear that the core material injected through the second runner is different from the core material the first sprue injected material can be different if necessary, so that moldings with different physical properties can be produced in different areas. So this procedure can be used are used in the manufacture of shoe soles, in which a flexible core material in the sole section and a rigid core material can be used in the heel section.

In the third alternative, in which skin material followed by core material is injected through the second runner is, the skin material can before, during or after the injection of the skin material through the first runner or

are injected during or after the injection of the core material through the first runner, but preferably before the core material injected through the first runner becomes

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has expanded to below the second runner . In the same way, the core material can be injected through the second runner before, during or after the injection of the skin or core material through the first runner. However, the core material is preferably injected through the second runner after the core material injected through the first runner has expanded to below the second runner, so that the core material injected through the second runner penetrates into the core material injected through the first runner and becomes attached to it united; Of course, as described above with reference to the first embodiment, in which core material is only injected through the second runner, there may be cases in which it is desirable to inject the core material through the second runner before the core material injected through the first runner reaches below the second runner has spread.

In the embodiment in which both skin and Core materials are injected through the second runner, it does not matter which runner is used as the first runner and which is considered to be the second runner.

The above description related to the use of two runners; of course, more than two runners can be used are provided. What is only essential for the purposes of the invention is that skin and core materials are sequential be injected through one of the sprue channels and that skin and / or core materials through the other sprue

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be injected. For example, skin and Core materials injected sequentially through a runner skin material through a second runner and core material through a third runner. In such a case it is not necessary for the second runner to be covered by the skin material injected through the first runner, before the core material is injected through the second runner, since the second runner is covered by skin material which is injected through the third runner.

To further modify the distribution of skin and core materials within the mold, more can be added to the mold cavity Skin material is injected as desired, the excess skin material being pushed back through the sprue, through which it has been injected by injecting core material.

It should be emphasized that the material injected through the outer runner must be injected into a w Point of time at which it touches the skin material injected through the first runner, and the latter is in a state of flow is located so that the material injected through the second runner coincides with that injected through the first runner Skin material united or in the latter

Of course, the dimensions of the individual runners can differ from one another, which also applies to the individual sprue runners to be injected, material quantities apply. Provided

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If the plastic materials are thermoplastics, they must be cooled in order for them to solidify from the molded state in which they were injected into the mold cavity. The mold is cooled to aid solidification, although the choice of mold temperature depends on the materials being processed. In general, mold temperatures in the range from ⁰ ° C. to 100 ° C. are suitable. However, if the runners are somewhat spaced from one another, it may be necessary to heat the mold a portion of the mold around the runners to ensure that the skin material injected through one runner is in the flow state when passing through another runner injected material comes into contact with this material so that it merges into the skin material injected through a runner or penetrates the skin material. The mold area surrounding the runners can be heated during the molding cycle and then cooled so that the plastic materials solidify (if they are thermoplastics). In the event that the material injected through one sprue can penetrate or penetrate the skin material injected through another sprue, the sprues can alternatively be heated with the aid of a movable probe that pushes the material injected through the other sprue after the other Sprue channel has been covered by the skin material in order to enable the injection of the material injected through a sprue channel in this way.

Plastic materials used in the invention of ^ ©! « are those that can be injected into a mold cavity

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- li -

if they are in a viscous liquid state and which can then harden in the mold cavity. For example, thermoplastic resin materials can be used which can be injected in the form of viscous melts and which can be hardened by cooling in the mold cavity. Alternatively, thermosetting resin materials can be used which are injected into the mold cavity in the state of a viscous liquid and which are allowed to harden by causing crosslinking in the mold cavity. Generally, the thermosetting resin materials are those which are crosslinked by heating.

Examples of such injection moldable thermoplastic resins which are useful are polymers and Copolymers of © (olefins, such as high and low density polyethylene, Polypropylene, polybutene, poly-M-methylpentene-1, propylene / Ethylene copolymers, copolymers of ^ -Methylpentene-l with linear c <-01efinen, 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 0 (-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 ethers, and N-aryl maleimides such as N-o-chlorophenyl maleimide; Polyvinyl acetate, polyvinyl butyral; Polystyrene, styrene / acrylonitrile copolymers, polyacrylonitrile, copolymers of butadiene with methyl methacrylate and / or styrene and optionally acrylonitrile, poly

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methyl methacrylate, copolymers of methyl methacrylate with smaller ones 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 copolymers, melt-processable copolymers of tetrafluoroethylene and hexafluoro p.jipylen.

Halogenated polymers or copolymers are usable ι example halogenierteo (olefin polymers such as chlorinated polyethylene, or halogenated vinyl chloride polymers, such as chlorinated polyvinyl chloride.

Other spritzgußformbare thermoplastic polymers which are useful are condensation polymers such as spritzgußverarbeitbare linear polyesters such as polyethylene terephthalate, polyamides such as polycaprolactam, Polyhexamethylenadipamxde and copolyamides such as copolymers of hexamethylenediamine adipate and Hexamethylendiaminisophthalat, particularly those containing 5 to 15 wt -. Contain% Hexamethylendiaminisophthalat, polysulphones and Copolysulphone, 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, for example cellulose acetate butyrate.

If a copolymer is used, the amounts of comonomers used in the copolymer depend, among other things, on. of the

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- 13 desired properties of the bricks.

Thermosetting resins include plastic materials that are either intrinsically or crosslinked obtained in the presence of a hardener or a catalyst when heated to a sufficiently high temperature. The designation thus includes materials that fall under what is commonly understood as "thermosetting" and plastic material, which is normally thermoplastic but contains a crosslinking agent such as a peroxide that causes 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 be a curing agent or a catalyst contain »where this is necessary for the hardening of the harses is.

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 _c

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The choice of materials that make up the subject is to be produced depends on the intended use to which the object is to be subject. The inventive method provides a particularly useful way of making articles with a core of relatively inexpensive material a good outer skin. For example, the core can consist of a thermoplastic material that contains fillers, while the outer skin consists of a material that contains a desired surface quality guaranteed. Unless the method is applied to parts of motor vehicle bodies A stiff outer skin is required to produce it, with filled polypropylene being a particularly good resin for formation the outer skin is. If a flexible molding is desired, for example for the interior lining of a motor vehicle, then a plasticized vinyl chloride polymer would be extremely suitable as the outer skin of the molded article.

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 merge 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 that modify the properties of the skin material. For example, differing "before skin materials plasticized polyvinyl chloride üer one side and plasticized polyvinyl chloride," nth & lzonü

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Nitrile rubber on the other hand is nitrile rubber provides additional wear resistance to the composition.

The core material can be the same as the skin material with the exception of additives in one or the other of the materials are included or in both, but in different proportions. Alternatively, the plastics be very different and contain different additives.

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, the material being injected at a temperature above the activation temperature of the blowing agent. It is preferred that the plastic material to the foaming temperature, d. H. beyond the activation temperature with the injection in the runner is heated by relying on the dynamic heating applied as the material passes through the Injection nozzle of the injection molding machine occurs.

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,

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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 pore cavity, allowing the core material to foam and at the same time the surrounding material to foam 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 manufacture Foamed moldings as described above can increase the size of the mold cavity in one of two ways be effected. One or more molded parts delimiting the mold cavity can be withdrawn by any external force which instantly expands the cavity to the desired extent or which gradually enlarges the cavity. at Using a squeeze mold, the clamping pressure holding the mold halves together 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

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Locking pressure can be 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 can be provided in the mold to allow the trapped air to be forced out,

The size and shape of the mold cavities depend on that

• *

object to be produced, with shapes with a maximum cavity thickness of less than 25 mm and preferably between 2 mm and 10 mm in thickness are particularly useful.

The method of the invention is expediently carried out using a machine that works for each runner 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 taps be provided to control the flow of material from the injection cylinders into the To control the mold cavity, especially the Matriaistrom

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through the first runner, so that through the first runner injected material on a return flow into the injection cylinder as a result of injecting material through the second 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 Pormhohlraum is enlarged, so that the batch from 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 Gate areas of the article.

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.

The core material is injected into the mold cavity through a runner to allow it to enter the interior of the skin material

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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 using a further, smaller one Amount of skin material injected through the same runner through which the core material was injected after the core material was injected, so that after removing the sprue from the molding, only a small ring of core material remains freely visible. This small or tight ring is a result of core material that has not been injected from the runner 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 is cash.

It is therefore preferred to pass a further amount of skin material through the first runner and / or through the second Injection runner, provided that core material has been injected through this runner, this injection takes place 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, plug toys, 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 illustrated in the following with the aid of a schematic Drawings explained in more detail.

Fig. 1 to 16 are cross-sections through a mold cavity which is provided with two runners, different mold filling stages are shown;

Figures 17 and 18 are corresponding to Figures 1 to 16

Views showing a mold cavity provided with three runners.

In the drawings, each runner is for simplicity with only a simple multi-way valve with a single

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Hole provided shown. Preferably, however, each valve or faucet has a separate bore for each through material to be conveyed through the sprue. Such valves are described in British Patent 1,219,097. Where in the Drawings the valve is shown in the closed position, the bore shown is filled with the material that was before closing of the valve has been injected through it. For the sake of simplicity, it also has a cavity in the illustration constant cross-section and the same cross-section for every filling sequence. In practice, however, certain sequences are more useful for cavities of non-uniform or irregular cross-section.

Fig. 1 shows a known method in which only one of the runners I ₅ 2 is used. 3. Here, a conveyor channel and sprue is injected skin material 1 through a valve ¹ I in the mold cavity. If a predetermined amount of skin material has been injected, the valve M is switched over in order to enable the injection of core material from the conveying channel 5. The core material expands the enveloping skin material to the ends of the mold cavity, so that the situation of Fig. 1 is obtained. In the process of expanding the skin material to the ends of the cavity, the skin is thinned, which can result in portions of the molding at the sprue 1 remote locations which have a thinner skin than those closer to the sprue 1, so that the molding has uneven skin thickness .

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In the known embodiment of FIG the runner 1 and valve 4 not used, with skin and core materials closer to one end of the cavity through runner 2 via the valve 6 with feeding through the channels 3 (for the skin material) and 7 (for the core material) to the cavity are fed. While such a procedure can be used to make a significant change in skin thickness in the However, it is not very versatile in bringing about a molding.

3 to 6 show a sequence according to the invention during the filling process of the mold cavity. Here are both sprues and used both valves. According to FIG. 3, skin material is injected through both sprue channels while being fed from conveyor channel 3.

Injection through the two channels does not have to take place simultaneously. The valve ¹ J is then switched to the blocking position, while the valve 6 is switched to bring about a connection with the conveying channel 7 for core material. There is then injected, the core material, as shown in Fig. K, through the sprue 2, wherein the core material expands, the surrounding skin material, so that the latter passes into the skin material which has been injected through the runner 1 and wherein the skin material is pushed towards the ends of the mold cavity. The valve 6 is then switched to the blocking position, as shown in FIG. 5. If the core material is foamable, it can be made to foam by enlarging the mold cavity as shown in FIG. With

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Consider injecting skin material through the runner 1, a greater amount of skin material was supplied in the area where the skin is stretched the most, so that the resulting molding has a more uniform skin thickness.

. In Fig. 7 a modification of the method is shown, which is designed so that the molding has a non-uniform distribution of the skin material with respect to the core material. Here, skin material according to FIG. 3 is injected from the conveying channel 3 through both sprue channels 1 and 2. Then the Sprue channel 1 is injected from the feed channel 5 core material. In this way, the molded article has a substantial Section which consists only of skin material and a remaining section in the layer structure with a section surrounded by the skin material Having core.

FIG. 8 shows a preferred variation of the system according to FIG. 7. After the core material has been injected through the runner 1, the valve h is switched to inject a further smaller amount of skin material through the runner 1, so that when the sprue formed in the runner 1 and 2 is removed from the molding, an object is produced in which the exposed area when the sprue formed in the runner 1 is removed shows only a small ring of core material instead of the solid area of the core material, as would be seen if the runner formed in the runner 1 is removed from a molding which is followed by the system

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Fig. 7 has been generated.

9 is a further variant of the system 7 shown, in which after the injection of the skin material through the conveying channel 2, the valve 6 is not in the blocking position is switched but remains in connection with the conveying channel 3 and the sprue channel 2. When injecting the core material from the feed channel 5 through the sprue 1 some skin material is returned through the sprue 2 into the feed channel 3 printed.

In FIGS. 10 and 11, another sequence of steps is shown in which first skin material through the runner 2 at least is injected until it has filled the runner 1 (as shown in Fig. 10), then core material is injected from the conveying channels 5 and 7 via the runners 1 and 2 (as shown in FIG. 11), so that a Object is created, the areas of laminar structure from the has skin material surrounding the core, which are separated from an area which consists only of the skin material.

A further sequence of steps is shown in FIGS. 12 and 13, which is a variant of that according to FIGS. 10 and 11 represents. In this case, skin material is injected through the sprue channel 1 from the delivery channel 3 and then the valve 4 switched to skin material from the conveying channel 5 through the

Inject runner 1. Has the core material got down to below of the runner 2 expanded, the valve is out of his

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Locking position switched to inject the core material from the conveying passage 7 through the runner 2, wherein the valve can be switched into the locking position ¹ I (SHE. Pig. 13).

In the system of Fig. I ¹ I, of that a variant according to FIGS. 12 and 13, 2 skin material is used instead of the core material is injected through the runner after the injected through the sprue 1 core material is extended to below the sprue '2 Has.

In the sequence of steps according to FIGS. 15 and 16, skin material is injected through both runners 1 and 2 and then Core material injected through both runners (see Fig. 15). Injecting the core material stretches the surrounding skin material so that the two sections of skin material merge into one another and result in an article comprising two sections with a laminar structure separated by a portion composed solely of skin material.

In Figs. 17 and 18 there is shown a system which three sprue channels 1, 2, 8 are used, the additional sprue channel 8 being provided with a valve 9. It becomes skin material injected through runners 2 and 8 (see Fig. 17); the skin material injected through the runner 8 has the runner 1 is filled, valves Ί and 6 are switched over to inject core material through sprues 1 and 2. That Injection of the core material expands the enveloping skin material so that the two sections of skin material into one another

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pass over and the excess skin material through the runner 8 is pushed back.

The following is an example of how the procedure can be carried out:

A mold cavity in the shape of a disk cm with a diameter of 20, a thickness of ¹ I mm, an elongation of 10 cm with a width of 3 cm, the board from the periphery of the disc, is enclosed by the mold parts a vertical Abquetschform.

A first runner is provided in the center of the disc, while a second is provided at the junction of the Disc is arranged with the extension. The total volume of the mold cavity under the influence of the runners was 150 cm Through the first runner an amount of about 40 cm ^ injected on polypropylene as skin material; another 15 cm ^ of polypropylene skin material was fed through the second runner at the same time as that through the first runner injected. The skin materials are injected at a temperature of 210 ° C and a pressure of about 135 MNm. Immediately after completion of the injection of the skin material, polypropylene with a content of 0.1% by weight is used as the core material. Azodicarbonamide as a blowing agent at a temperature of 210 ° C and a

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A pressure of about 135 MNm is injected through the first runner.

The amount of injected unfoamed core material is about 95 cm, so that the mold cavity is filled by expanding the wrapping skin material that is inserted into the through the second

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Sprue channel injected material passes over when it comes to this comes into contact before significant foaming of the core material occurs. The molded parts of the vertical squeeze mold then allowed to move apart by releasing the pressure holding the mold halves together until the mold cavity has a thickness of 10 mm so that the core material can foam. The molding is then cooled and removed from the mold cavity taken.

The invention thus provides a method in which a skin material is inserted into a mold cavity through a runner is injected, whereupon a core material follows, wherein a further amount of skin and / or core material into the mold cavity through a second runner is injected spaced from the first.

209823/0636

Claims (8)

Claims j 1.) Process for the manufacture of items with a skin made of plastic material surrounding a core made of dissimilar plastic material, the skin and core materials are injected in succession in the poured state through a first runner into a mold cavity and the core material is injected into the skin material while it is in the plied state, so that the core material is the enclosing Skin material expands, characterized in that to achieve a desired distribution of skin and core material in the molding a further amount of skin and / or core material in the flowing state into the mold cavity through a second sprue channel injected, which is from the first runner at a distance, then if the further amount of material skin material or skin material followed by core material, this material is injected at such a time that it passes through the first Sprue channel injected skin material touches while the latter is in the flow state, so that through the second Sprue channel injected skin material merges into the skin material injected through the first sprue channel or into the latter penetrates, while if the further amount of material is core material, this is injected after through the first or skin material injected into a further runner has expanded to below the second runner and has become is still in the flow state, so that the further amount of core material is injected into the skin material. 209823/0836 2. The method according to claim 1, characterized in that that the core material is injected through the second runner after core material is injected through the first runner has been and has expanded below the second runner so that the injected through the second runner Core material penetrates into the core material injected through the first sprue channel and merges into it. 3. The method according to claim 2, characterized in that the material injected through the second runner Skin material is followed by core material and the skin material is injected through the second runner before going through The core material injected into the first runner has expanded to below the second runner, so that the through skin material injected through the second runner does not penetrate into the core material injected through the first runner. 4. The method according to claim 1, characterized in that that the skin material is injected through the second runner before the core material injected through the first runner expands to below the second runner so that the skin material injected through the second runner does not inject into that through the first runner Core material penetrates. 5. The method according to claim 3 or 4, characterized characterized in that the skin material is injected through the second runner after the switch by the first runner 209Ö23 / 0836 Injected skin material has been expanded to below the second runner. 6. The method according to any one of the preceding claims 1 to 5, characterized in that a further amount of Skin material is injected through one or more of the runners, through which core material is injected after the skin material will. 7. The method according to any one of the preceding claims 1 to 6, characterized in that the core material is a is foamable composition which contains a polymeric material and a blowing agent and which is at a temperature above that Activation temperature of the blowing agent is injected. 8. The method according to claim 7, characterized in that the injected foamable composition in such Amount is injected so that the mold cavity is filled before the foaming takes place and that the mold cavity is then enlarged, to enable foaming. 209823/0836