Abstract:
Filler-containing molded parts or articles are produced from a free-flowing reaction mixture, e.g. of polyol and isocyanate, in a manner which permits the changeover to a different filler content to be carried out more rapidly and, possibly, without material loss. This is achieved by dividing at least one of the reaction components into at least two portions, at least one of which is charged with filler, by adjusting the mixing ratio of these portions and hence the filler content of the finished molded part. At least two storage vessels are provided for at least one of the reaction components. Adjustable metering devices are arranged between these two storage vessels and the mixing device.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a process and to an apparatus for the production of filler-containing molded parts or articles from a free-flowing reaction mixture. In the process of the present invention, at least two free-flowing chemical reaction components of which at least one contains filler are caused to react by mixing. The free-flowing reaction mixture is introduced into a mold where it finishes reacting. The molded article or part is then removed from the mold.  
           [0002]    It is generally known to manufacture filler-containing molded polyurethane parts by mixing and reacting a polyol and an isocyanate, at least one of which contains filler and introducing the resulting reaction mixture into a mold, allowing it to cure and subsequently removing it from the mold.  
           [0003]    Examples of chemical reaction components used in such processes include isocyanates and polyols. Preferred fillers include fibers such as glass fibers, carbon fibers and natural fibers, e.g., jute and hemp fibers. Substances in the form of granules and powders such as recycled products, melamine and chalk may also be used, however.  
           [0004]    Currently, such molded parts are usually manufactured in relatively large plants. Lines from storage vessels with agitators lead via metering devices to mixing devices which are assigned to one mold in each case, e.g., in a so-called multi-point metering system. One or two of such molds may be arranged on one stationary mold support.  
           [0005]    It is often necessary to manufacture, in the same plant, molded parts or articles of identical or different shape but which have a different filler content. To this end, a batch of one reaction component and filler in the corresponding amount is prepared in a storage vessel.  
           [0006]    Changing over from one series of molded parts to another one with a different filler content then requires the preparation of a new batch of reaction component(s) and cleaning of the plant to remove the previous filler-containing reaction component. This means lost production time due to the time required for the changeover, as well as a loss of material.  
         SUMMARY OF THE INVENTION  
         [0007]    The object of the present invention is to provide the ability to changeover to a reaction mixture with a different filler content during the production of filler-containing molded parts more rapidly and, if possible, without loss of material.  
           [0008]    This and other objects which will be readily apparent to those skilled in the art are achieved by dividing at least one of the reaction components into at least two parts and charging at least one of those parts with filler. Adjusting the mixing ratio of the reaction component parts also adjusts the filler content of the finished molded part. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 illustrates an apparatus suitable for carrying out the process of the present invention in which only one of the chemical reaction components is divided into two portions—one portion containing filler and the other containing no filler.  
         [0010]    [0010]FIG. 2 illustrates an apparatus suitable for carrying out the process of the present invention in which both chemical reaction components are divided into two portions with one portion of each. component containing filler and the other portion containing no filler.  
         [0011]    [0011]FIG. 3 is a schematic representation of the streams flowing into a mixing device in the apparatus illustrated in FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    In the process of the present invention, at least one of the reaction components is divided into two portions. One of those portions includes a filler. The other portion does not. Adjustment of the mixing ratio of these portions makes it possible to change the filler content of the finished molded part without significant disruption to the production process.  
         [0013]    As a result, a changeover to a reaction mixture having a different filler content can take place more or less by means of a simple switchover, while retaining the polyol-polyisocyanate formulation ratio, by altering the proportion of the filler-free portion fed to the filler-containing portion, or, alternatively, the proportion of the first filler-containing portion fed to the second filler-containing portion.  
         [0014]    The chemical formulation, i.e. the quantity ratio of the reaction components to one another, remains constant during a change in filler content in the process of the process of the present invention. If only one filler-containing component part is made available, this should correspond at least to the maximum expected filler content in the finished molded part in order that all the filler contents may be adjusted to the possible maximum content. If component parts are charged with filler, the charge with filler must be different. One part should have a high filler content and the other a low filler content in order that the desired filler content may be adjusted in the molded part.  
         [0015]    In one embodiment of the process of the present invention, at least two portions of the same type of reaction component charged with filler in different amounts are made available for processing or processed.  
         [0016]    It is also possible to make available for processing or to process one filler-free portion and one filler-containing portion of each of the two reaction components.  
         [0017]    It goes without saying that at least one of the reaction components may also be divided into more than two portions, at least two portions being charged with filler. This is not necessary as a rule, however, and far too much equipment is required.  
         [0018]    Fibers are preferably used as fillers. Examples of suitable fiber materials include: mineral fibers such as glass fibers; synthetic fibers such as polyamide fibers; and natural fibers such as jute or hemp fibers.  
         [0019]    Suitable fillers also include the conventional fillers in the form of granules such as recycled products or in the form of powders such as melamine or chalk.  
         [0020]    The apparatus for the production of filler-containing molded parts from a free-flowing reaction mixture in accordance with the present invention is based on at least two storage vessels for free-flowing chemical reaction components, at least one of which is charged with filler. The storage vessels are generally connected by metering devices to at least one mixing device which opens into a mold.  
         [0021]    At least two storage vessels are provided for at least one of the reaction components. At least one of the two portions of this reaction component is charged with filler. Adjustable metering devices are arranged between these two storage vessels and the mixing device.  
         [0022]    [0022]FIGS. 1 and 2 show purely schematic views of apparatus suitable for the production of filler-containing molded parts of polyurethane from isocyanate and polyol reaction components in accordance with the present invention. FIG. 1 shows a first embodiment of a suitable device, FIG. 2 shows a second embodiment of the device, and FIG. 3 shows a top view onto the mixing device and onto the lines leading into it for the reaction components optionally charged with filler.  
         [0023]    In FIG. 1, line  4  leads from storage vessel  2  provided with an agitator  1  for filler-free-isocyanate to piston-type metering device  3  and ends in mixing device  5 . Line  8  leads from storage vessel  7  provided with an agitator  6  for polyol charged with a high filler content via a piston-type metering device  9  to mixing device  5 . Line  12  leads from storage vessel  11  provided with an agitator  10  for polyol charged with a lower filler content via a piston-type metering device  13  into mixing device  5 . The mixing device  5  ends in a mold  14  in which a molded part  15  is indicated. Without any substantial alteration to the device described, the storage vessel  11  may alternatively be filled with pure polyol, and the polyol contained in storage vessel  7  is charged at least with the highest expected filler content for the molded part  15  to be produced.  
         [0024]    In FIG. 2, line  24  leads from storage vessel  22  provided with an agitator  21  for filler-free isocyanate via a piston-type metering device  23  and ends in mixing device  25 . Line  28  leads from storage vessel  27  provided with an agitator  26  for isocyanate charged with a low filler content via piston-type metering device  29  into mixing device  25 . Line  32  leads from storage vessel  31  provided with an agitator  30  for filler-free polyol leads via piston-type metering device  33  to mixing device  25 . Finally, Line  36  leads from storage vessel  35  provided with an agitator  34  for polyol charged with a high filler content via piston-type metering device  37  into mixing device  25 . The mixing device  25  ends in a mold  38  in which a molded part  39  is indicated. In this embodiment too, the storage vessels  22 ,  27 ,  31  and  34  can be filled in different ways, depending on the process to be carried out, without any substantial alteration to the structure of the device.  
         [0025]    In FIG. 3, two feed lines  41 ,  42  for filler-containing parts of a reaction component composed of polyol lead into mixing device  43 . These feed lines  41 ,  42  are fed from the branching line  44  and end exactly, diametrically opposite in mixing device  43 . At 90° to these, a feed line  45  for filler-free polyol and a feed line  46  for filler-free isocyanate end opposite one another. It goes without saying that mixing device  43  may be fed in a different way via feed lines  41 ,  42 ,  45 ,  46 , according to the mode of operation selected. In order to illustrate only one variant, for example, only two filler-containing parts of the same reaction component can be introduced opposite one another via feed lines  41  and  42 , while the two other feed lines  45  and  46  are being fed with the other, filler-free reaction component. In order to obtain particularly good mixing, it is advantageous if the energy of the flows in opposite feed lines are of the same order of magnitude.  
         [0026]    During the manufacture of molded parts, the isocyanate-polyol-filler mixture produced at any one time in the mixing device must comply with the required ratios. That is, not only must the quantity ratios of the individual components in the mold be absolutely correct but also the ratios of the individual volumetric flows to one another must likewise be complied with at any one time.  
         [0027]    The following modes of operation may be carried out with the apparatus of the present invention.  
       EXAMPLES  
     Example 1  
       [0028]    The apparatus illustrated in FIG. 1 was used to manufacture a polyurethane molded part containing glass in the form of fibers as filler. The reaction components were isocyanate and polyol and glass. The total volume was 3,000 cm 3 . The glass content in the finished molded part was 14 wt. %. The two reaction components were fed in a mass ratio of 100:170.9. The polyol component was divided into a filler-free part and a filler-containing part. The mass ratio of polyol to glass in the filler-containing reaction component was 100:80. The densities of the reaction components were 1.02 kg/l for the polyol, 1.12 kg/l for the isocyanate and 2.56 kg/l for the glass. The density of the filler-containing polyol can be calculated from this at 1.392 kg/l. If a metering or filling time of 0.8 sec is selected, the following volumetric flows are obtained:  
                                                           Isocyanate:   2,136.5   cm 3 /sec           Filler-containing polyol:   997.8   cm 3 /sec           Filler-free polyol:   615.7   cm 3 /sec.                      
 
         [0029]    The production was then changed over to increase the glass fiber content in the molded part to 22 wt. % while maintaining the same molded part volume. Here, too, the reaction components must be fed in a mass ratio of 100:170.9. The mass ratio of polyol to glass in the filler-containing component likewise remained constant at 100:80. With the same metering or filling time of 0.8 sec and a glass content of 22 wt. % in the finished molded part, the following volumetric flows are calculated:  
                                                           Isocyanate:   2,040.3   cm 3 /sec           Filler-containing polyol:   1,651.0   cm 3 /sec           Filler-free polyol:   58.7   cm 3 /sec.                      
 
       Example 2  
       [0030]    The apparatus illustrated in FIG. 1 was used to manufacture a polyurethane molded part containing glass in the form of fibers as filler. The reaction components were isocyanate and polyol and glass. The total volume was 3,000 cm 3 . The glass content in the finished molded part was 14 wt. %. The two reaction components were fed in a mass ratio of 100:170.9. The polyol component was divided into a filler-poor part, the mass proportions of polyol to glass being 100:40, and into a filler-rich part, the mass proportions of polyol to glass being 100:80. The densities of the pure reaction components were 1.02 kg/l for the polyol, 1.12 kg/l for the isocyanate and 2.56 kg/l for the glass. The resulting densities of the filler-poor polyol and the filler-rich polyol were 1.232 kg/l and 1.392 kg/l respectively. If a metering or filling time of 0.8 sec is selected, the following volumetric flows are calculated:  
                                                           Isocyanate:   2,136.5   cm 3 /sec           Filler-rich polyol:   185.8   cm 3 /sec           Filler-poor polyol:   1,427.7   cm 3 /sec.                      
 
         [0031]    If the glass proportion of the molded part is to be increased to 22 wt. %, the marginal conditions otherwise remaining the same, the following volumetric flows are calculated.  
                                                           Isocyanate:   2,040.3   cm 3 /sec           Filler-rich polyol:   1,573.6   cm 3 /sec           Filler-poor polyol:   136.0   cm 3 /sec.                      
 
       Example 3  
       [0032]    The apparatus illustrated in FIG. 1 was used to produce a polyurethane molded part containing glass in the form of fibers as filler. The reaction components were isocyanate and polyol and glass. The total volume was 3,000 cm 3 . The glass content in the finished molded part was 30 wt. %. The two reaction components were fed in a mass ratio of 100:170.9. The polyol component was divided into a filler-free part and a filler-containing part. The mass ratio of polyol to glass in the filler-containing reaction component was 100:80. The isocyanate also contained filler. The mass ratio of isocyanate to glass was 100:60. The densities of the pure reaction components were 1.02 kg/l for the polyol, 1.12 kg/l for the isocyanate and 2.56 kg/l for the glass. The density of the filler-containing polyol can be calculated from this at 1.392 kg/l. The density of the filler-containing isocyanate can be calculated at 1.419 kg/l. If a metering or filling time of 0.8 sec is selected, the following volumetric flows are obtained:  
                                                           Filler-containing isocyanate:   2,441.0   cm 3 /sec           Filler-containing polyol:   277.5   cm 3 /sec           Filler-free polyol:   1,031.6   cm 3 /sec.                      
 
         [0033]    If the glass proportion of the finished molded part is to be increased to 38 wt. %, the conditions otherwise remaining the same, the following volumetric flows must be set:  
                                                           Filler-containing isocyanate:   2,290.1   cm 3 /sec           Filler-containing polyol:   1,219.6   cm 3 /sec           Filler-free polyol:   240.4   cm 3 /sec.                      
 
       Example 4  
       [0034]    The apparatus illustrated in FIG. 2 was used to produce a polyurethane molded part containing glass in the form of fibers as filler. The reaction components were isocyanate and polyol and glass. The total volume was 3,000 cm 3 . The glass content in the finished molded part was 30 wt. %. The two reaction components were fed in a mass ratio of 100:170.9. The polyol component was divided into a filler-free part and a filler-containing part. The mass ratio of polyol to glass in the filler-containing reaction component was 100:80. The isocyanate component was likewise divided into a filler-free and a filler-containing part. The mass ratio of isocyanate and glass in the filler-containing part was 100:60. The densities of the pure reaction components were 1.02 kg/l for the polyol, 1.12 kg/l for the isocyanate and 2.56 kg/l for the glass. The density of the filler-containing polyol can be calculated from this at 1.392 kg/l. The density of the filler-containing isocyanate can be calculated at 1.493 kg/l. If a metering or filling time of 0.8 sec is selected, the following volumetric flows are obtained:  
                                                           Filler-containing isocyanate:   1,958.0   cm 3 /sec           Filler-free isocyanate:   483.4   cm 3 /sec           Filler-containing polyol:   277.5   cm 3 /sec           Filler-free polyol:   1,031.6   cm 3 /sec.                      
 
         [0035]    If the glass content of the finished molded part is to be increased to 38 wt. %, the conditions otherwise remaining the same, the following volumetric flows must be set:  
                                                           Filler-containing isocyanate:   1,837.0   cm 3 /sec           Filler-free isocyanate:   453.5   cm 3 /sec           Filler-containing polyol:   1,219.6   cm 3 /sec           Filler-free polyol:   240.4   cm 3 /sec.                      
 
         [0036]    Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.