Abstract:
A method for forming a molded article of a vehicle that includes providing a mold including a molding surface, the molding surface having a shape that corresponds to that of the molded article; heating the mold to a temperature in the range of 300 degrees F. to 450 degrees F.; conducting a first slush molding step to attach a first thermoplastic material to the molding surface; conducting a second slush molding step to attach a second thermoplastic material to the molding surface, the second thermoplastic material including a blowing agent; and laminating a substrate to the second thermoplastic material while the second thermoplastic material is in a molten state and the blowing agent is releasing a gas to foam the second thermoplastic material. The first thermoplastic material forms an exterior surface of the molded article, and the second thermoplastic material forms an interior foam of the molded article.

Description:
FIELD 
       [0001]    The present disclosure relates to slush molding. 
       BACKGROUND 
       [0002]    Slush molding is a molding process that enables thermoplastic products to be manufactured with very detailed and often complex shapes. A prime application for this process is the manufacture of vehicle dashboard “skins” that are ultimately back-filled with a foam system, providing the finished product with the necessary rigidity. The technique allows parts to be made with a single “cosmetic” side. It can also be used to make hollow parts, if necessary. 
         [0003]    A variety of materials can be processed using this technique, but most often polyvinyl chloride (PVC), thermoplastic polyurethane (TPU) and thermoplastic polyolefins (TPO) are employed, depending upon the final performance specification. The actual molding material may be a plastisol or a powder. If a rotational technique is used, the material is charged into the mold and then the mold is tumbled while, at the same time, its temperature is elevated. Alternatively, the material are to be sprayed into the mold. Either process encourages the molding material to form a skin on the mold surface, which then becomes the molded part. Once the part is fully formed, the mold is cooled and the part can be peeled from the surface of the mold. 
       SUMMARY 
       [0004]    The present disclosure provides a method for forming a molded article of a vehicle that includes providing a mold including a molding surface, the molding surface having a shape that corresponds to that of the molded article; heating the mold to a temperature in the range of 300 degrees F. to 450 degrees F.; conducting a first slush molding step to attach a first thermoplastic material to the molding surface; conducting a second slush molding step to attach a second thermoplastic material to the molding surface, the second thermoplastic material including a blowing agent; and laminating a substrate to the second thermoplastic material while the second thermoplastic material is in a molten state and the blowing agent is releasing a gas to foam the second thermoplastic material, The first thermoplastic material forms an exterior surface of the molded article, and the second thermoplastic material forms an interior foam of the molded article. 
         [0005]    Further areas of applicability of the teachings of the present disclosure will become apparent from the detailed description, claims and the drawings provided hereinafter, wherein like reference numerals refer to like features throughout the several views of the drawings. It should be understood that the detailed description, including disclosed embodiments and drawings referenced therein, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application or uses. Thus, variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIGS. 1A to 1G  illustrate a slush molding system and method according to a principle of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0007]    The present disclosure is directed to slush molding.  FIGS. 1A-1G  illustrates a slush molding system  100  according to a principle of the present disclosure. Slush molding system  100  includes a molding shell or member  10  ( FIG. 1A ) that is preferably formed from a metal material such as nickel (Ni), and defines a molding surface  12  that is shaped to correspond to the dimensions of the final molded part. Molding surface  12  is attached to a box-like frame  14  that defines a hollow interior  16 . Molding surface  12  can be textured, which will dictate both the texture and the appearance of the exterior surface of the final molded article. Accordingly, molding surface  12  is formed to have any shape and contour as desired by one skilled in the art. Frame  14  includes a plurality of an opening  17  that allow for communication with a fluid such as air or water that can be used to heat and/or cool molding surface  12  during the slush molding process. Frame  14  includes a hook  18  that allows molding member  10  to be moved through a plurality of stations and rotated during the slush molding process. 
         [0008]    In this regard, slush molding system  100  includes plurality of stations including a first station  20  (heating station  20 — FIG. 1B ), a second station  22  (first slush molding station  22 — FIG. 1C ), a third station  24  (second slush molding station  24 — FIG. 1D ), a fourth station  26  (lamination station  26 — FIG. 1E ), a fifth station  28  (cooling station  28 — FIG. 1F ), and sixth station  30  (article removing station  30 — FIG. 1G ). Firstly, molding member  10  is transferred via a robot, crane, or other type of conveying device (not shown) that grasps hook  18  and locates molding member  10  at heating station  20  ( FIG. 1B ). At heating station  20 , molding member  10  is heated to a temperature that ranges between 300 degrees F. to 450 degrees F. Molding member  10  is heated by feeding a heated fluid such as air into opening  17  with a heating device  19 , or molding member  10  is heated by induction heating. Once molding member  10  is heated, molding member  10  is grasped by conveying device and transferred to a first slush molding station  22 . 
         [0009]    At first slush molding station  22  ( FIG. 1C ), molding member  10  is coupled to a first slush feeding device  32   a.  First slush feeding device  32   a  includes a tank  34   a  that contains materials  36   a  in powder form therein. Extending outward from tank  34   a  is a connection surface  35  that couples to frame  14  via various coupling mechanisms (not illustrated) that are well known to one skilled in the art. A seal (not shown) ensures that materials  36   a  do not escape from slush feeding device  32   a  and molding member  10  when molding member  10  and slush feeding device  32   a  are rotated, as will be described in more detail later. Materials  36   a  held within tank  34   a  include thermoplastic materials such as thermoplastic elastomers (TPE), thermoplastic olefins (TPO), and thermoplastic urethanes (TPU). It should be understood, however, that other materials such as plasticizers and surfactants may also be added to tank  34   a  without departing from the scope of the present disclosure. Regardless, the materials  36   a  held within tank  34   a  are selected to form an exterior surface of the molded article. 
         [0010]    Once molding member  10  is coupled to slush feeding device  32   a,  the molding member  10  and slush feeding device  32   a  are rotated to invert the molding member  10  and slush feeding device  32   a,  as is known in the art. Inversion of molding member  10  and slush feeding device  32   a  allow the materials  36   a  to come into contact with the heated molding member  10 . As the powdered materials  36   a  contact the heated molding surface  12 , the powdered materials  36   a  will liquefy and distribute over the heated molding surface  12 . To assist in ensuring that the molding surface  12  is properly covered by the molten materials  36   a,  molding member  10  and slush feeding device  32   a  may be agitated (vibrated) during inversion thereof. In addition, the time that molding member  10  and slush feeding device  32   a  are inverted is monitored, and the number of inversions can be controlled to ensure that materials  36   a  have satisfactorily covered molding surface  12  to form the exterior surface of the molded article. The exterior surface, preferably, has a thickness that ranges between 0.1 mm to 0.5 mm. Other thicknesses, however, are contemplated. 
         [0011]    As an alternative to the rotational technique described above, it should be understood that materials  36   a  may be sprayed into molding member  10 . Regardless, once it is determined that the materials  36   a  have satisfactorily covered molding surface  12 , molding member  10  and slush feeding device  32   a  are rotated to a non-inverted orientation, which allows non-melted materials  36   a  to return to tank  34   a.  Molding member  10  is then decoupled from slush feeding device  32   a,  and moved by conveying device to second slush molding station  24  ( FIG. 1D ). Alternatively, before molding member  10  is moved to second slush molding station  24 , molding member  10  can be moved back to heating station  20  to re-heat molding member  10  to ensure that molding member  10  remains at the desired temperature. 
         [0012]    At second slush molding station  24 , molding member  10  is coupled to a second slush feeding device  32   b.  Second slush feeding device  32   b  is substantially similar to first slush feeding device  32   a  and includes a second tank  34   b.  Materials  36   b  held within tank  34   b,  however, include thermoplastic materials such as thermoplastic elastomers (TPE), thermoplastic olefins (TPO), and thermoplastic urethanes (TPU), as well as a chemical blowing agent such as azodicarbonamide. Materials  36   b,  in particular, are selected for their suitability in forming foams. 
         [0013]    Once molding member  10  is coupled to slush feeding device  32   b,  the molding member  10  and slush feeding device  32   b  are rotated to invert the molding member  10  and slush feeding device  32   b.  Inversion of molding member  10  and slush feeding device  32   b  allow the materials  36   b  to come into contact with the heated molding member  10 . As the powdered materials  36   b  contact the heated molding surface  12 , the powdered thermoplastic of materials  36   b  will melt and distribute over the heated molding surface  12  including the previously-applied materials  36   a.  In addition, because the mold member  10  is pre-heated to a temperature that ranges between 300 degrees F. and 450 degrees F., the blowing agent will begin to reach the temperature at which gas will be released to foam the liquefied thermoplastic material. The time that molding member  10  and slush feeding device  32   b  are inverted can be monitored, and the number of inversions can be controlled to ensure that materials  36   b  have satisfactorily covered the materials  36   a.  Preferably, the second materials  36   b  are deposited such that the resultant foam will have a thickness that ranges between 2 mm and 5 mm. 
         [0014]    As an alternative to the rotational technique described above, it should be understood that materials  36   b  may be sprayed into molding member  10 . Regardless, once it is determined that the materials  36   b  have satisfactorily covered the materials  36   a,  molding member  10  and slush feeding device  32   b  are rotated to a non-inverted orientation, which allows non-melted materials  36   b  to return to tank  34   b.  Molding member  10  is then decoupled from slush feeding device  32   b,  and moved by conveying device to lamination station  26  ( FIG. 1E ). Alternatively, before molding member  10  is moved to lamination station  26 , molding member  10  can be moved back to heating station  20  to heat molding member  10  to ensure that molding member  10  remains at the re-desired temperature. 
         [0015]    Once reaching lamination station  26 , a substrate  38  is mated with the materials  36   b.  Substrate  38  is shaped to correspond to molding surface  12 , and is formed from thermoplastic materials such as PVC, polyethylene, polypropylene, polystyrene, and the like. Once substrate  38  is mated with materials  36   b,  a molded article is formed including an exterior surface, a foam, and the substrate  38 . The molded article can be used for, for example, an interior panel for a vehicle, with the exterior surface being the surface that is exposed in the vehicle. 
         [0016]    It should be understood that substrate  38  is mated with the materials  36   b  while the thermoplastic of materials  36   b  are in a molten state, or at least substantially in a molten state, and the chemical blowing agent is releasing gas to foam the thermoplastic. It is important that materials  36   b  remain in a substantially molten state during mating of substrate  38  and materials  36   b  to ensure sufficient adhesion between substrate  38  and materials  36   b.  A “molten state” includes a liquid state and states that are gel-like in nature such that substrate  38  will adhere to materials  36   b.  Once substrate  38  is laminated to materials  36   b,  the blowing agent will continue to release gas and complete the foaming of materials  36   b  between substrate  38  and materials  36   a.  To ensure that any excess gas that is produced is allowed to escape, substrate  38  can include small apertures formed therein (not shown). Regardless, the mating of substrate  38  to materials  36   b  while molten ensures adhesion of the materials  36   b  to the substrate  38 , which increases productivity in comparison to previous methods that required additional steps of applying adhesives between the exterior surface and foam, and between the foam and substrate  38 . 
         [0017]    Once it is determined that the substrate  38  and materials  36   b  have satisfactorily adhered to each other, molding member  10  is then moved by conveying device from lamination station  26  to cooling station  28  ( FIG. 1F ). At cooling station  28 , a fluid such as water or cooled air is fed into opening  17  using cooling device  39  to cool molding member  10 . The cooling of molding member  10  allows for materials  36   a  and  36   b  to fully harden or cure, and causes any foaming that is still occurring to stop. Once it is determined that the molded article is satisfactorily cooled, molding member  10  is then moved to article removing station  30  ( FIG. 1G ) where the molded article  40  is removed from molding member  10 . Molding member  10  is then returned to heating station  20  where the slush molding process can be repeated. 
         [0018]    According to the above method, a molded article  40  including an exterior surface or skin  36   a,  a foam  36   b,  and a substrate  38  can be formed in one process in contrast to previous methods where a skin is molded, and then a foam and substrate are backfilled onto the skin using adhesives and the like. By omitting the backfilling steps and adhesives, the process for forming the molded article is simplified and production costs are lowered. 
         [0019]    It should be understood that various steps and stations of the slush molding system  100  and method according to the present disclosure can be eliminated without departing from the scope of the present disclosure. For example, molded articles  40  that include only layer  36   a  and substrate  38  are contemplated by the present disclosure such that second slush station  24  and its associated steps can be omitted. Alternatively, molded articles  40  that include only layer  36   b  and substrate  38  are contemplated such that first slush station  22  can be omitted. In addition, it should be understood that a separate cooling station  28  may be omitted from the system and method in favor of a lamination station  26  that is configured to provide cooling after lamination of substrate  38 . 
         [0020]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.