Use of expanded and hydrophobic popcorn to produce three-dimensional shaped parts

Abstract

The invention relates to shaped parts produced from popcorn which has previously been hydrophobised with a polymer. This allows very light and flexible shaped parts to be produced.

Claims

1. A molded article made from a molding compound, the molding compound consisting of popcorn particles, a hydrophobic polymer, and a binder, wherein ?95% by weight of the individual popcorn particles are surrounded by a hydrophobic polymer, and a binder, wherein the summed proportion of the hydrophobic polymer and binder is ?20% (w/w) based on the total weight of the molded article.

2. The molded article according to claim 1, wherein the summed proportion of hydrophobic polymer and binder is ?15% (w/w) based on the molded article.

3. The molded article according to claim 1, wherein the popcorn has a particle size distribution in which the fat content of the popcorn before processing is ?10 wt %.

4. The molded article according to claim 1, wherein the proportion of hydrophobic polymer in the molded article in wt % based on the weight of the molded article is ?5%.

5. The molded article according to claim 1, wherein the proportion of binder in the molded article (in % by weight based on the weight of the molded article) is ?10%.

6. The molded article according to claim 1, wherein the hydrophobic polymer is selected from the group comprising polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyacrylate, condensed aminoplast resins, polylactic acids (PLA), polyhydroxy acids, cellulose derivatives or mixtures thereof.

7. The molded article according to claim 1, wherein the binder is selected from urea-formaldehyde resin, melamine-formaldehyde resin, melamine-reinforced urea-formaldehyde resin, tannin-formaldehyde resin, phenol-formaldehyde resin, polymeric diphenyl-methane di-isocyanate, or mixtures thereof.

8. The molded article according to claim 1, wherein the ratio of binder to hydrophobic polymer (w/w) is from ?1:1 to ?4:1.

Description

(1) Further details, features and advantages of the subject matter of the invention result from the subclaims as well as from the following description of the associated drawings, in whichby way of exampleseveral embodiments of the process according to the invention are shown. The drawings show:

(2) FIG. 1 to FIG. 3 a schematic of the sequence of a manufacturing process of a molded article according to the invention according to a first embodiment; and

(3) FIG. 4 schematically shows the sequence of a manufacturing process of a molded article according to the invention in accordance with a second embodiment.

(4) FIGS. 1 to 3 schematically show the sequence of a manufacturing process of a molded article according to the invention in accordance with a first embodiment. In this, in step 1, shown in FIG. 1, a molding compound 10 consisting of popcorn surrounded by polymer with possibly further binder is introduced into a cavity which is formed by two corresponding mold bodies 20 and 21. In step 2, shown in FIG. 2, heating is performed so that under the influence of temperature (and pressure formed under the influence of temperature) the molded article 30 is formed, which is then removed in step 3, shown in FIG. 3.

(5) FIG. 4 schematically shows the sequence of a manufacturing process of a molded article according to the invention according to a second embodiment by means of an automatic molding machine. Here, the cavity formed by the two mold bodies 40 and 41 is first closed (step A), then the molding compound 10 is filled in under pressure (step B).

(6) After heating under pressure (step C) and cooling (step D), the resulting molded article 30 can then be removed.

(7) The invention is also explained by means of examples which are purely illustrative and are to be regarded as non-limiting.

(8) The molded articles with different densities produced in the manner described above were examined with regard to their strength properties. The results are summarized in Table 1.

(9) TABLE-US-00001 TABLE 1 Mechanical-technological properties of popcorn molded articles surrounded by a polymer layer of polypropylene (PP) or polyethylene (PE) as a function of bulk density Bending Compressive Thermal Density force QZ stress conductivity Polymer [Kg/m.sup.3] [N/mm.sup.2] [kPa] [kPa] [W/(m * K] PP 100 2.2 140 280-310 0.040 PE 1.8 180 295-320 PP 120 2.8 170 335 0.041 PE 2.3 210 355 PP 140 3.8 160 350 0.042 PE 2.5 230 372 PP 160 4.4 175 380 0.044 PE 2.7 255 388 PP 180 4.9 230 410 0.045 PE 2.9 290 400 PP 200 5.6 295 480 0.048 PE 3.1 330 420

(10) A polypropylene-based polymer and a melamine-urea-formaldehyde (MUF) resin were used to produce flexible molded articles front popcorn granules. In the first stage, the polypropylene was sprayed 2% atro (based on the popcorn) onto the popcorn in a mixer. Then the material was dried at about 105? C. In the second process step, the material was conveyed in a mixing unit and glued with polymer using a MUF (66% solids) at a dosage of 5% atro on popcorn, and the material was introduced as a molding compound into the cavity, which is heated under pressure and conductive heat transfer. The cavity is then closed using a pressure piston. The pressure causes the molding compound to acquire the shape specified by the mold. In the final process step, the finished, flexible molded article is removed from the mold. Table 2 lists the mechanical and technological properties of these flexible molded articles.

(11) TABLE-US-00002 TABLE 2 Mechanical-technological properties of popcorn molded articles surrounded by a polymer layer a polypropylene (PP) or polyethylene (PE) and glued with MUF as a function of hulk density Polymer Bending atro Density force QZ Compressive popcorn [Kg/m.sup.3] [N/mm.sup.2] [kPa] stress [kPa] PP 2% 140 4.3 300 130-180 MUP 5% PE: 2% 160 4.9 380 170-220 MUF 5% PP 2% 140 6.0 350 150-170 MUF 5% PP 2% 160 6.8 420 180-230 MUF 5%

(12) For the production of molded articles from popcorn granules by dry steam, the popcorn granules were pretreated with a polymer (polyethylene) and urea-formaldehyde resin (UF, BASF Kaurit 350).

(13) First, 1.5% polyethylene was applied to the popcorn granules. Then, the 66% urea-formaldehyde resin was applied to the popcorn granules treated in this way in the gluing unit. In the second step, the glued material was conveyed into the cavity by a negative pressure (vacuum) of 2.5 bar and cured by means of dry steam.

(14) To generate the dry steam, wet steam was passed through a separator that eliminated about 98% of the original wet steam and converted it to about 99% dry steam. The temperature of the dry steam used here was >100? C.

(15) Depending on the thickness and bulk density of the molded article, different amounts of dry steam were passed through the molded article for up to 90 seconds. The finished molded article was then removed from the cavity. Table 3 shows the mechanical properties of the molded articles produced by dry steam.

(16) TABLE-US-00003 TABLE 3 Mechanical-technological properties of UF resin-bonded molded articles with different densities and thicknesses after crosslinking by means of hot dry steam of approx. 150? C. Polymer atro Density Thickness QZ popcorn [Kg/m.sup.3] [mm] [kPa] PE 1.5% 150 20 310 UF 7% 50 295 PE 1.5% 120 20 275 UF 7% 50 255 PE 1.5% 80 20 243 UF 7% 50 217

(17) The individual combinations of the components and features from the embodiments already mentioned are exemplary; the interchange and substitution of these teachings with other teachings contained in this publication with the cited publications are also expressly contemplated. The skilled person will recognize that variations, modifications and other embodiments described herein may also occur without departing from the spirit and scope of the invention.

(18) Accordingly, the above description is exemplary and is not to be considered limiting. The word comprise as used in the claims does not exclude other components or steps. The indefinite article a docs not exclude the meaning of a plural. The mere fact that certain dimensions are recited in mutually different claims does not make it clear that a combination of those dimensions cannot be used to advantage. The scope of the invention is defined in the following claims and their equivalents.