Abstract: This invention substantially improves the surface finish on resin filled foamed molded plastic products manufactured by injection molding by pre-heating the skin surface of that part of the mold in contact with the part prior to the injection cycle of the machine and then subsequently chilling the mold via internal tube connections to shorten the time needed in the manufacturing cycle for solidifying the part sufficiently for release from the mold.

Abstract: An apparatus for molding shaped bodies from foamable plastics such as foamable polyurethane resin material comprises a two-piece mold 20, 21 fastened to two clamping plates 17, 18 of a mold holder 11, all of which can revolve around parallel axes 34, 35, 36. The upper plate 18 can move toward the fixed lower plate 17 and back again. The plates are locked and urged together during the molding process by pairs of hydraulic cylinders 28, 29 and 30, 31 mounted on opposite sides of the mold halves 20, 21.

Abstract: The instant invention relates to a method and an apparatus for the production of a foam-forming reaction mixture or homogeneous material-forming reaction mixture from at least two liquid reactants and for the subsequent introduction thereof into a cavity, and in particular into the cavity of a mold. The reactants are introduced into a mixing zone where they are mixed together. The mixture is subsequently fed through an outlet of controlled cross-section and charged into a cavity. In order to carry out the method, an apparatus is provided which comprises a mixing chamber arranged in a housing and having inlet openings for the reactants and an outlet opening for the reaction mixture, wherein an adjustable baffle plate is arranged opposite the outlet opening axially of the outlet opening.

Abstract: A bung for closing a wine bottle in the manner of a cork is formed in a conventional injection-moulding machine from ethylene-vinyl acetate copolymer (EVA) with the addition of sodium metabisulphite and sodium bicarbonate. The sodium metabisulphite, which is in stoichiometric excess in relation to the sodium bicarbonate, decomposes to liberate sulphur dioxide. The sodium bicarbonate decomposes to liberate water and carbon dioxide. The bung as moulded accordingly has a foamed core with a liquid-impervious skin. It contains sulphur dioxide, and water enabling the sulphur dioxide to act as an oxygen scavenger when the bung is in use in a wine bottle. The bung therefore provides the bottle with a long shelf life, with no noticeable tainting of the wine.

Abstract: A process for working up thermoplastic synthetic resin material, in particular unsorted thermoplastic synthetic resin waste material into an article having the working and processing properties of wood, and in which the material is subjected to a mixing operation in a housing including a screw member, and is fluidized, moulded, cooled in the mould, and removed from the mould. According to the invention, the synthetic resin material is supplied to an extruder without a screen member and without an extrusion nozzle, and kept therein until there is obtained a material that is fluid owing to temperature increase, and which material contains a gas when it leaves the extruder. The material is then passed into a mould having open ends, one of which is connected to the outlet of the extruder.

Abstract: Thermoplastic granules mixed with a blowing agent are processed in a barrel unit which encloses a rotating screw which mixes, works and plasticizes the mixture so that at the leading end of the barrel it is in a molten condition suitable for extrusion or injection molding. The screw has two compression stages with an intermediate decompression stage therebetween. At a location corresponding to the decompression stage of the screw the barrel has a vent therein which permits the escape of moisture vapors and other unwanted volatiles in the mixture. At the vent zone the forward faces of the screw flights are undercut to minimize the discharge of mixture through the vent.

Abstract: Shaped synthetic-resin bodies are made in a separable mold by injecting a flowable mass of a synthetic-resin material into the mold cavity. To precool the mass and cause an initial setting at least of the surface thereof, a liquefied gas, i.e. a low-boiling liquid which is in a gaseous state at room temperature and atmospheric pressure, is introduced between the mass and the walls of the cavity. The coolant is discharged from the cavity through at least one controllable cross-section outlet to regulate the contact time between the coolant and the mass. The initially set precooled body is ejected from the mold and is subjected to final cooling and temperature homogenization (tempering), e.g. in a liquid bath.

Abstract: Polystyrene (copolymer) foam is produced by forming a polystyrene (copolymer) solution in an hermetically sealed container using a solvent having a high vapor pressure and a low boiling point, and progressively releasing the thus formed solution under temperature and pressure conditions allowing rapid evaporation of the solvent.

Abstract: A method for the manufacture by foam molding of plastic products by first injecting into a mold non-cellular plastic resin and then injecting a foamed plastic resin of the same basic composition as the non-cellular plastic resin. The process and apparatus consisting of a single extruder and single injection chamber wherein the non-cellular and foamed plastic resin are extruded from the same extruder and stored in an accumulator until shot into the mold by a hydraulic cylinder. Controls are provided for the correct amount of each type of resin to be extruded and stored and the process can be adapted so that the sprue portion of the final product will be solid resin. By a simple addition, coloring of the resin may be accomplished so that the basic resin, method or apparatus will not require changes.

Abstract: Unitary molded plastic hinged article and method of making in which a fluid molten mixture of heat softenable resin and a blowing agent in substantially unfoamed condition is introduced into an expandable mold cavity to fill the cavity and the mold is expanded to allow foaming of the resin to form at least one foam cored article section while the resin adjacent the mold surface is still fluid and in which the hinge structure is formed by a member adapted to form a thin, flex portion and portions transitional from the thickness of the flex portion to the thickness of a cored article section, the shaping member being slidably disposed in an aperture in the mold with portions of the walls of the aperture exposed within the mold cavity at the time the molten mixture is introduced and the exposed portions of the walls being wiped by the shaping member when the mold is expanded.

Abstract: Polyurethane foam is used in a three-piece vehicle wheel as a load bearing and load transmitting structural element. The rim of the wheel, an inner wheel disc, and an outer decorative wheel disc are bonded together by the polyurethane foam. The rim includes an interlock lip to interlock the rim with the inner disc and an interlock lip that interlocks the rim with the outer decorative disc. The wheel can be manufactured by placing the rim, inner disc, and outer disc in a die and injecting the polyurethane foam composition into the interconnected volume enclosed and defined by those wheel components. The foam curing process then occurs in situ. Alternatively, the rim, inner disc, and outer disc can be adhesively bonded to a preformed polyurethane foam member. The resultant vehicle wheel, manufactured by either process, is characterized by high strength, light weight, and a decorative appearance.

Abstract: A process for producing cork lines which comprises holding a leader or lers with a pair of metal molds having at the junctional surfaces thereof one or more cavities for forming a float or floats and one or more furrows formed so as to pass through said cavity or cavities for holding said leader or leaders, injecting a molten synthetic resin mixed witha foaming agent into said cavity or cavities to effect molding and foaming of said resin, cooling said metal molds and taking out a flat or floats integrally fixed to said leader or leaders from said metal molds.

Abstract: Certain polymeric modifiers are surprisingly effective for injection molding and extruding thermoplastic structural foam of lower density, improved appearance, more uniform cell structure, and for lowering injection molding cycle time.

Abstract: Multi-station reaction injection molding apparatus, and method, are disclosed for in-place foaming of polymerizable resins in articles advanced along a production line, as for example in the manufacture of insulated appliance housings such as refrigerator cabinets. The articles are selectively diverted from a feed conveyor, one to each of a plurality of pour stations adjacent the feed conveyor. At the stations, injection of foamable resin mix is accomplished by reaction injection type molding heads which combine at least two liquid resin components. These components are suitably catalyzed to react and form a cellular or foamed polymerized resin. The liquid components are separately but continuously supplied to respective supply manifolds to which all of the heads are connected in parallel by shunting ducts. Excess unmixed liquid components are returned separately from each of the heads through recycle shunting ducts to respective recycle manifolds.

Abstract: A method of forming a ball core is disclosed. A flowable homogeneous mass of a thermoplastic resin and a blowing agent is injected into the spherical cavity of a mold under temperature and pressure conditions sufficient to activate the blowing agent. The mold is cooled to 32.degree. to 65.degree. F. so as to form a skin on the surface of the mass. The mass is held within the mold cavity for a sufficient time so that the skin has adequate strength to prevent its rupture by blowing agent contained within the mass, upon removal of the mass from the mold cavity. The mass is cooled at an exterior temperature of 32.degree. to 65.degree. F. A ball core for baseballs and softballs is also disclosed.

Abstract: A process is provided for producing an imitation wood workpiece by forming a synthetic resin workpiece having a cellular plastic core and a densified covering layer after extruding and solidifying synthetic resin and thereafter imparting an appearance of wood grain to the synthetic resin workpiece by heating the densified covering layer of the workpiece and by relief embossing texture furrows in portions of the densified covering layer.

Abstract: A process for producing moldings comprises the steps of injecting a plastified synthetic resin into a mold cavity, thereafter or simultaneously injecting heated fluid having a viscosity of 0.01 - 100 poise into the same mold cavity to fill it with said fluid in such a manner that said heated fluid is surrounded by said synthetic resin within said mold cavity and releasing said fluid from said mold cavity after at least a portion of said synthetic resin has set. If the injected synthetic resin contains any foaming agent, a foamed article having its outer smooth skin can be obtained according to the present invention. If the injected synthetic resin contains no foaming agent, a hollow, smooth-surfaced article can be obtained.

Abstract: This invention relates to an improved injection foam molding method in which a foamable mixture of molten synthetic polymer resin and a chemical blowing agent in unfoamed condition is injected into a gas-pressurized expandable mold having a mold section movable for expanding the mold cavity to a position in which the surface of that section is in registry to the surface of another mold section, in which process the mold is filled under conditions resisting foaming of the material prior to filling of the mold and a novel controlled time sequence effective to form a fine mold crease line is employed in releasing the gas pressure and expanding the mold to allow foaming of the mixture into conformity with the mold surface.

Abstract: A process is provided for introducing mixed foamable reactants to a mold. The process involves introducing the reactants into a mixing chamber through injection apertures in its side wall portion. The mixing chamber has an outlet aperture communicating with the cavity of the mold. Prior to introducing the reactants into the mixing chamber, a displacement piston having a smaller cross-section than the mixing chamber is inserted into the outlet aperture of the mixing chamber so that the injection apertures communicate with the mold cavity by means of a generally annular passage.

Abstract: Foamable synthetic resin materials are plastified and injected into a mold cavity in an amount less than the volume of mold cavity and a body of gas under pressure is charged in the mold cavity in such manner that it is enclosed by said resin materials. When the injected resin materials sets at least at its outer surface layer, the gas is discharged out of the mold cavity so that the foamable resin materials can be expanded in the hollow portion formed by the pressure of the charged gas. Said foamable resin materials may be surrounded by unfoamable resin materials in the mold cavity.

Abstract: An injection molded polymer having limited surface gloss is provided by preparing an admixture of an injection moldable polymer substrate and an additive chosen from among the group consisting of finely divided textile fibers, finely divided hydrocarbon polymers, and blowing agents and injection molding an article from the admixture. In the embodiment of the invention employing blowing agents the admixing is carried out at a temperature below that at which the blowing agent is activated and the injection molding is carried out at a temperature sufficient to activate the decomposition of the blowing agent.

Abstract: A rigid, dimentionally stable, distortion-free article of foamed polyvinyl aromatic resin, having a solid outer skin, is formed by incorporating in a foamable polyvinyl aromatic resin a finely, divided inert solid that has been surface treated to render the solid hydrophobic and then molding the foamable composition under foaming conditions. Foamed polyvinyl aromatic resin articles molded in accordance with the present invention have physical dimensions capable of meeting tolerances in the order of .+-. 0.002 inches and are suitable for use in the manufacture of precision measuring devices and, particularly, frames for level instruments.

Abstract: Thermoplastic articles with highly porous cores and less porous or nonporous skins are injection-molded with the aid of a nozzle having a flow divider disposed upstream of its aprue for splitting the oncoming plastic mass into a homogeneous outer stream and an inner stream admixed with a foaming agent, the two streams merging inside the gate of a mold cavity. The foaming agent enters through a central channel which may be provided with one or more ducts alternately usable to introduce pressure fluid and coolant into the cavity lined with coalescing layers of nonfoamed and foamed plastic. The flow divider may be axially movable within the nozzle to serve as a control valve and flow regulator.

Abstract: This invention relates to compositions and methods for forming polyether polyurethanes utilizing internal release additives for the purpose of facilitating mold release in the production of molded objects. The invention discloses four classes of internal release additives: (1) mixtures of aliphatic or aryl carboxylic acid and a polar metal compound; (2) carboxyalkylsiloxanes; (3) aliphatic glyoximes; and (4) aralkyl quaternary ammonium salts.

Abstract: A method of producing foamed thermoplastic resin articles having smooth and glossy surfaces free from swirl marks and hair cracks, which comprises melting a thermoplastic resin containing a condensable blowing agent and an organic chemical blowing agent, injecting, in full shot, the molten resin into a mold cavity to which a pressurized gas is being applied during said injection, terminating the application of the pressurized gas to the mold cavity, enlarging the volume in said molded cavity by movement of a mold wall, and thereafter cooling and solidifying the resin to form the foamed articles.

Abstract: A method of injection molding foamed articles wherein, after the mold is closed and while the mold is held closed, a gas counterpressure is generated within the mold cavity against which a portion of the foamable resin is injected under a pressure which prevents foaming. Thereafter, a shape-forming element adapted to be retracted to be flush with a wall of the mold cavity in the final phase thereof, is advanced to force the nonfoamed material, still against the gas counterpressure, into the remainder of the cavity. After a skin has formed, on the mass within the mold cavity the latter element is retracted to permit foaming, preferably after foaming has been initiated by allowing a portion of the foamable mass to recede into the injection cylinder during the inception of the foaming process.

Abstract: Process and apparatus for injection molding plastic to provide a foamed core with an unfoamed outer skin.

Abstract: In a method for the preparation of crosslinked polyolefin foams by charging a polyolefin or its blend with other thermoplastic resins containing a crosslinking agent, foaming agent and if necessary a filler into the heated mold having a changeable cavity and, after decomposition of the crosslinking and foaming agents, retracting the moving-plate of the mold by a definite distance to increase the cavity and at the same time cooling the mold, an improvement for the preparation of the crosslinked polyolefin foams having excellent appearance and dimensional stability, comprising using a mold of which the moving-plate is constructed with a body and a sliding-piece, the body holding the piece slidably whereby the sliding-piece is left behind owing to sliding between the two even on rapid retraction of the body and then retracts at the rate corresponding to the foaming pressure of the resin, in other words, at a self-controllable rate and the mold for the preparation thereof.

Abstract: A method of making nylon (polycarbonamide) foam involving the use of a multi-phase carboxylic acid-containing polymer which reacts with the amine groups of the nylon to produce water which blows the foam during the process.

Abstract: An apparatus for the manufacture by foam molding of plastic products by first injecting into a mold solid plastic resin and then injecting a foamed plastic resin of the same basic composition as the solid plastic resin. The process and apparatus consisting of a single extruder and single injection chamber wherein the solid and foamed plastic resin are extruded and stored until shot into the mold by hydraulic pressure. Controls are provided for the correct amount of each type of resin to be extruded and stored and the process can be adapted so that the sprue portion of the product will be solid resin and by a simple addition, coloring may be added so that the basic resin, method or apparatus will not require changes.

Abstract: Novel dense foam articles having a solid plastic sheet coating on at least a portion of the surface are prepared by injection molding plastic foam into a mold containing a thermoformed solid plastic sheet having the configuration of at least a part of the mold and fitted to a matching mold surface.

Abstract: An injection molding process for forming cross-linked, foamed moldings of an ethylenic polymer by passing a molding composition comprising an ethylenic polymer/cross-linking agent/foaming agent blend through the cylinder of an injection molding machine without substantially decomposing the cross-linking agent and the foaming agent, introducing the molding composition into a molding composition holding chamber provided at the exit end of the cylinder of the injection molding machine to decompose the cross-linking agent and the foaming agent therein, and injecting the molding composition into a mold.The invention also provides apparatus for carrying out the process comprising an injection molding cylinder for conveying and plasticizing the molding composition and a molding composition holding chamber provided at the exit end of the cylinder.

Abstract: Apparatus for making a foamed plastics product. A foamed plastics product is formed by introducing into an at least substantially fully plasticated material a series of discontinuous gaseous bubbles while said plasticating material is under a substantial and often variable pressure, accumulating said material and intermixed bubbles in an injection zone while maintaining said pressure thereon and thereafter injecting said material into a mold whereupon said pressure is sufficiently released to permit expansion of said gas bubbles and the formation of a foam thereby. Said gas is introduced, as aforesaid, by a series of separate injections wherein the pressure on the gas being injected rises from substantially zero to a level potentially in excess of the highest pressure expected to be developed within the plasticating means.

Abstract: Thermoplastic articles with highly porous cores and less porous or nonporous skins are injection-molded with the aid of a nozzle having a flow divider disposed upstream of its sprue for splitting the oncoming plastic mass into a homogeneous outer stream and an inner stream admixed with a foaming agent, the two streams merging inside the gate of a mold cavity. The foaming agent enters through a central channel which may be provided with one or more ducts alternately usable to introduce pressure fluid and coolant into the cavity lined with coalescing layers of nonfoamed and foamed plastic. The flow divider may be axially movable within the nozzle to serve as a control valve and flow regulator.

Abstract: An apparatus for the production of injection-molded synthetic-resin bodies having core portions and skin portions of different densities wherein a blowing agent is introduced into the core material to form macroscopic bubbles or cavities therein within the mold and under the molding conditions so that the expanding body of core material presses the skin material against the walls of the mold. The core material is injected coaxially with the skin material but under conditions such that expansion under the effect of the macropore-producing blowing agent does not occur to any significant extent until the core material is within the mold. This is a division of application Ser. No. 507,465, filed Sept. 19, 1974.

Abstract: A method of injection molding a body of synthetic resin with a smooth surface and a porous core, which comprises the steps of injecting into a mold first outer synthetic resin forming a smooth surface of the body and thereafter synthetic-resin core material containing an expanding or foaming agent. Only part of the outer material is first injected, the remainder being injected simultaneously with the synthetic-resin core material.

Abstract: An apparatus for mixing and molding a chemically foamable reaction mixture is comprised of a mold with a mixing chamber which has its outlet aperture in a wall of the mold and a displacement piston mounted in the opposite wall. An ejector piston is displaceable within the mix chamber and may be so channelled as to serve as a control piston. This ejector piston is displaceable from a position wherein the injection apertures lie between it and the mold cavity to a position wherein its end surface is flush with the mold wall. The displacement piston is so mounted that it may extend across the mold cavity and intrude into the outlet aperture of the mixing chamber. This displacement piston has a diameter smaller than the diameter of those portions of the mixing chamber into which it protrudes so that when this piston is within the mixing chamber an annular cavity is formed between it and the side walls of the mixing chamber. It is withdrawable to a position flush with the mold wall it protrudes through.

Abstract: Encapsulating an insert in plastics by injection moulding with one face of the insert bearing against the mould thus supporting the insert against movement during injection with subsequent relative movement between insert and the supporting mould face to allow the injected material to flow round that face of the insert.

Abstract: A process for molding foam products substantially free from flaws caused by air bubbles in the foamable reaction mixture wherein a foamable reaction mixture having a viscosity .eta. in cP between 100 cP and 2500 cP is introduced into a mold cavity through an opening in the mold wall and against the wall of the cavity opposite the opening of a mold in which the thickness of the cavity and the thickness s of the resulting molded product adjacent to the opening at the time the mixture is introduced into the cavity is maintained at 0.5 mm to 15 mm under conditions whereby the radial distribution rate w.sub.radial in m/sec., .eta.

Abstract: A process is disclosed for producing a structural foam article having a surface that reproducibly and faithfully replicates the surface of the mold within which the article was made. The process is an improvement in the "low pressure" process for producing structural foam, wherein the improvement resides in introducing the molten mixture of foamable thermoplastic material and blowing agent into the mold under such conditions that a no-slip boundary condition is maintained at an interface between the flowing thermoplastic and a predetermined portion of the interior surface of the mold, and by maintaining the temperature at said interface at or above a certain temperature (termed "replication temperature"), while the thermoplastic is flowing in the mold.

Abstract: A settable foam plastic product being formed in a mold cavity is compressed, after a film has formed on the surface of the product, but before final setting of the product. This compression step, which is carried out by reducing the volume of the mold cavity, has the advantage of increasing the accuracy of reproduction of fine surface detail. The compression step also permits stops to be readily removed to enable subsequent full opening of the mold cavity. This use of movable stops in turn facilitates absorption of the forces encountered during the injection step with less massive machine structure than heretofore, resulting in the possibility of economical manufacture of larger products. The machine also includes an improved mold cavity construction in which the parting planes are perpendicular to the main plane of the product, and incorporating laterally movable end and side mold members to facilitate removal of the product and the formation of surface detail on edge surfaces of the product.

Abstract: Apparatus to practice the method of forming foam molded articles without the defects caused by incompletely mixed reactants in the mold cavity is provided. A mixing chamber bounded by a sidewall portion having injection apertures, an outlet aperture which communicates with the mold cavity and a first ejector piston displaceable within the bore of the mixing chamber is provided. Opposite said outlet aperture is a second ejector piston which is retracted at the start of the mold filling operation to provide a receiving chamber in the mold wall. As the mold filling proceeds, this piston is displaced towards the mold cavity until its end surface forms a planar surface with the mold wall. Optionally, this piston may be displaced into the mold cavity to eject the molded article.

Abstract: Plastic molding machine, primarily adapted for generating and molding a closed-cell foam thermoplastic material. The foam is generated by introducing a gas inert to the thermoplastic material into a granular mixture of same so that the gas is thoroughly intermixed among the granular particles. The gas is then held under pressure while the granular particles are reduced to a flowable material, said pressure being sufficient to assure that the gas will not be expelled therefrom during such process. In one preferred embodiment, gas is mixed into the granular thermoplastic in a hopper and held therein under pressure as said granular material is fed into a screw and plasticated thereby.The plastic material is then conducted at a relatively low pressure, such as that generated by the extrusion machine used for plasticating the material, through a branched system past a check valve in each branch of said system, to an injection assembly.

Abstract: A method for producing an improved molded thermoplastic polymeric resinous article comprising: introducing a heat plastified thermoplastic polymeric resinous material into a mold in the presence of a finely divided inorganic material; cooling said heat plastified thermoplastic polymeric resinous material; removing from said mold said cooled mold shaped thermoplastic polymeric resinous material having finely divided inorganic material incorporated therein.

Abstract: A method of and apparatus for the molding of foamed thermoplastic bodies with integral skins wherein, for each mold operation after the first, a portion of previously foamed material produced by expansion in the mold cavity, is temporarily accumulated behind a body of unfoamed thermoplastic and the foamed and unfoamed material are then forced into the mold cavity and permitted to expand therein.

Abstract: Synthetic-resin bodies, preferably composed of hardenable synthetic resins and especially thermosetting resins are formed by introducing a foamable resin into a mold cavity, setting the foamable resin upon permitting the same to expand to fill the mold cavity, and thereafter introducing into the mold cavity, without changing the volume thereof, at least one additional synthetic resin while the foamed body is plastically deformable but possesses sufficient rupture strength to prevent penetration. The resulting body thus has a surface layer of the second material which displaces the foamed first material.

Abstract: The invention relates to structures such as folding (tambour) doors comprising longitudinal juxtaposed slats and comprises a method of making such structures by introducing a molten synthetic resinous mass containing a foaming agent into a mould, permitting foaming of the mass and compressing the mass with a ribbed mould plunger to a predetermined distance above the floor of the mould to constitute the hinges.

Abstract: A mold for forming plastic foam parts in which an injection-molded plastic member forms a molding surface of the foam molding cavity against which foam plastic is adapted to be molded. The plastic member is preferably injection molded in a metal molding die from either polyethylene or polypropylene so that its molding surface is the reverse of the exterior surface of the plastic part to be foam molded therein. Vent passages and sealing beads may be integrally formed with the injection-molded member.

Abstract: Plastic molding machine, primarily adapted for generating and molding a closed-cell foam plastic material. The foam is generated by introducing a gas inert to the plastic material into a granular mixture of same so that the gas is thoroughly intermixed among the granular particles. The gas is then held under pressure while the granular particles are reduced to a flowable material, said pressure being sufficient to assure that the gas will not be expelled therefrom during the plasticization process. In one preferred embodiment, gas is mixed into the granular plastic in a hopper and held therein under pressure as said granular material is fed into a screw and plasticized thereby.The plastic material is then conducted at a relatively low pressure, such as that generated by the extrusion machine used for plasticizing the material, through a branched system past a check valve in each branch of said system, to an injection assembly.

Abstract: a jig-saw puzzle comprises interfitting pieces (1, 2, 3, 4) which when fitted together side-by-side form a three-dimensional upper surface simulating for example hills and valleys. Each piece is formed of a molded open or closed cell thermoplastics foamed core 7 sandwiched between upper and lower thermoplastics skins 8a and 8b. A printed sheet 9 is stuck on to the upper skin 8a. The skins 8a and 9a may be made from any conventional moldable thermoplastics. A preferred thermoplastics is a copolymer of propylene with from 5 to 20% by weight of ethylene made by injecting ethylene into the final stages of an otherwise propylene homopolymerization. The core may be made of the same or different plastics as the skins. Polyurethane is a preferred core material. The printed sheet, which may be paper or fabric, may be stuck on to the upper sheet with adhesive or by penetration or fusing of the skin material into the sheet during molding of the pieces.