USE OF ELECTROMAGNETIC RADIATION IN THE PRODUCTION OF POPCORN-CONTAINING SHAPED PARTS

Abstract

The present invention relates to two-dimensional and three-dimensional shaped parts and composite materials made of popcorn and synthetic and/or natural binding agents which are cured in automatic moulding machines or similar pressing installations by means of radio wave technology or microwaves. By means of these technologies, light-weight, two-dimensional and three-dimensional shaped parts and composite materials can be produced for packaging, as interior and exterior parts (for example in automobile and mobile-home construction), shock absorbers, space-dividing elements, furniture, consumer goods, for the building trade of for heat insulation.

Claims

1. A method for producing popcorn-containing shaped parts, wherein during the production of the shaped parts, the shaped parts are temporarily exposed in a targeted manner to electromagnetic radiation in a frequency range from ≥30 kHz to ≤300 GHz.

2. The method according to claim 1, wherein radio and/or microwaves are used.

3. The method according to claim 1, comprising a pressing step wherein, during compressing of the shaped parts, the shaped parts are temporarily exposed in a targeted manner to electromagnetic radiation in a frequency range of ≥30 kHz to ≤300 GHz.

4. The method according to claim 1, wherein, when the electromagnetic radiation is used, at least partial bonding and/or melting takes place at the surface of the shaped part.

5. The method according to claim 1, wherein a temperature of ≥70° C. is achieved at least at a region on the surface of the shaped part when the electromagnetic radiation is used.

6. The method according to claim 1, wherein the electromagnetic radiation has a power of ≥20 W to ≤5000 W.

7. The method according to claim 1, wherein the power density (measured with respect to the surface of the shaped part) is from ≥1 W/cm.sup.2 to ≤250 W/cm.sup.2.

8. The method according to claim 1, comprising the steps of, a) production of popcorn; b) optional hydrophobization of the popcorn produced in step a) by means of a polymer; c) optional post-treatment; d) optional addition of a binder; e) production of the shaped part; f) optional coating of the shaped part surface; and g) optional lamination.

9. The method according to claim 8, wherein step d) is not optional and as binders thermoplastics, thermosets, aminoplastics, phenoplastics, isocyanates, proteins, tannins, starch, synthetic binders or natural binders, or mixtures of binders are used, such as 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.

10. The method according to claim 8, wherein step e) is carried out by means of compression molding and/or use of automatic moulding machines.

11. The method according to claim 10, wherein in step e) a compression time of ≥0.5 s/mm shaped part and ≤24 s/mm shaped part is used.

12. The method according to claim 10, wherein in step e) an overpressure of ≥0.1 bar and ≤10 bar is used.

13. The method according to claim 10, wherein in step e) a negative pressure of ≥0.1 bar and ≤3 bar is used.

14. A shaped part, obtained by the method according to claim 1, wherein the shaped part consists substantially of popcorn.

15. Use of shaped parts produced according to the method of claim 1 for use as: composite acoustic moldings; packaging materials; cooling boxes; protective packaging for electrical appliances; spice boxes; automotive parts; motor home parts; headrests; sun visors; child seat shells; insulation mats; insulation materials (e.g. for electrical appliances); tableware; sporting goods; yoga rolls; bolsters; toys; picture frames; gift hampers.

Description

[0100] FIG. 1 to FIG. 3 schematically show the sequence of a method for producing a shaped part according to the invention in accordance with a first embodiment;

[0101] FIG. 4 shows schematically the sequence of a method for producing a shaped part according to the invention in accordance with a second embodiment; and

[0102] FIG. 5 shows a diagram showing the sound absorption properties of shaped parts according to the invention and of comparative materials.

[0103] FIGS. 1 to 3 schematically show the sequence of a method for producing a shaped part according to the invention in accordance with a first embodiment. In this embodiment in step 1, shown in FIG. 1, a molding compound 10 consisting of popcorn surrounded by polymer optionally with a further binder is introduced into a cavity formed by two corresponding molding bodies 20 and 21. In step 2, shown in FIG. 2, the shaped part is targetedly exposed to electromagnetic radiation in a frequency range of ≥30 kHz to 300 GHz, so that the shaped part 30 is formed under irradiation (and possibly pressure), and is then removed in step 3, shown in FIG. 3.

[0104] FIG. 4 schematically shows the sequence of a method for producing a shaped part according to the invention in accordance with a second embodiment by means of an automatic moulding machine. Here, first the cavity formed by the two molding bodies 40 and 41 is closed (step A), and then the molding compound 10 is filled in under pressure (step B). After irradiation with electromagnetic radiation in a frequency range from ≥30 kHz to ≤300 GHz, optionally under pressure (step C) and cooling (step D), the resulting shaped part 30 can then be removed.

[0105] The invention is further explained by means of examples which are purely illustrative and are to be considered as non-limiting. [0106] 1) Production of Two- and Three-Dimensional Shaped Parts by Use of Radio Waves.

[0107] For the production of shaped parts from popcorn granules by means of radio wave technology, the popcorn granules were provided with various binders.

[0108] In the 1st variant (see Table 1), a polymer based on polypropylene and a urea-formaldehyde resin (UF, BASF Kaurit 350) were used. In the first stage, the polypropylene was applied 1% atro (based on the popcorn granules) and then the UF was sprayed onto the popcorn in a gluing unit. In the second process step, the glued material was injected by means of injection nozzles into the cavity of the automatic moulding machine, in which an optional overpressure (e.g. 0.1 to 6 bar) and approx. 5 to 7 kV radio waves are generated. Depending on the thickness and bulk density of the shaped part, dwell times of 15 to 50 seconds were used. In the final process step, the finished shaped part was removed from the cavity. Table 1 lists the mechanical-technological properties of the shaped parts produced in this way. Instead of the polymer and the UF resin, only UF resin (see Table 2) and natural binders based on albumin and rapeseed protein were used in further tests (see Table 3).

TABLE-US-00001 TABLE 1 Mechanical-technological properties and formaldehyde emission values of PP and UF resin-bonded shaped parts with different densities and thicknesses after crosslinking by use of radio waves Formaldehyde emission Polymer atro Density Thickness QZ in [mg/h .Math. m.sup.2] Popcorn [kg/m.sup.3] [mm] [kPa] DIN EN 717-2 PP 1% 150 20 260 0.60 UF 7% 50 210 0.65 PP 1% 120 20 190 0.51 UF 7% 50 182 0.55 PP 1% 90 20 179 0.40 UF 7% 50 140 0.43 PP 1% 60 20 100 0.30 UF 7% 50 85 0.36

TABLE-US-00002 TABLE 2 Mechanical-technological properties and formaldehyde emission values of UF resin-bonded shaped parts with different densities and thicknesses after crosslinking by radio waves Formaldehyde emission Binder atro Density Thickness QZ in [mg/h .Math. m.sup.2] Popcorn [kg/m.sup.3] [mm] [kPa] DIN EN 717-2 UF 8% 150 20 300 0.66 50 275 0.69 UF 8% 120 20 258 0.56 50 240 0.59 UF 8% 90 20 220 0.43 50 205 0.46 UF 8% 60 20 140 0.33 50 128 0.39

TABLE-US-00003 TABLE 3 Mechanical-technological properties and formaldehyde emission values of albumin or rape protein-bonded shaped parts with different densities after crosslinking by means of radio waves Binder Density Thickness QZ atro Popcorn [kg/m.sup.3] [mm] [kPa] Albumin 10% 160 30 220 Rape protein 9% 205 Albumin 10% 120 30 175 Rape protein 9% 155 Albumin 10% 80 30 135 Rape protein 9% 105

[0109] Moreover, for the production of 20 mm thick flexible shaped parts made of popcorn granules, a double gluing process was carried out, in which the popcorn granules were first coated with liquid gelatine (approx. 50% solids content, Fritz Häcker GmbH) in a dosage % based on atro popcorn. After drying at 70° C. in a flash drier, the material was glued with MUF (66% solids content, BASF Kauramin 620), UF (BASF Kaurit 350) and PUR (Hexion) in various dosages atro on popcorn with gelatin and introduced into the cavity as a molding compound, which was then crosslinked with use of overpressure (e.g. 0.1 to 6 bar) and radio waves. After a total of 30 seconds (1.5 s/mm plate thickness), the finished, flexible shaped part is removed from the cavity and conditioned. Table 4 lists the mechanical-technological properties of these flexible shaped parts.

TABLE-US-00004 TABLE 4 Mechanical-technical properties and formaldehyde emission values of gelatin, UF resin, MUF resin and PUR-bonded shaped parts after crosslinking by means of radio waves Bending Formaldehyde Polymer atro Density strength QZ emission in [mg/h .Math. m.sup.2] Popcorn [kg/m.sup.3] [N/mm.sup.2] [kPa] DIN EN 717-2 Gelatine 4% 150 5.3 230 0.65 UF 6% Gelatine 4% 150 5.9 280 0.43 MUF 6% Gelatine 5% 150 10.0 350 not detectable PUR 3% [0110] 2) Production of Two- and Three-Dimensional Shaped Parts by Means of Radio Waves without Binders

[0111] Popcorn granules were produced according to example 1) by the Bichsel process and then compressed without any wetting of synthetic and/or natural binders and additives in an automatic moulding machine by means of radio waves at 6 kV and an overpressure of 0.5 bar. Surprisingly, it has been found that even without the use of any binder and additives, a certain crosslinking between the individual popcorn granules takes place due to the caramelization and simultaneous Maillard reaction on the surface of the starch granules. Accordingly, the following mechanical-technological properties have been determined (Table 5).

TABLE-US-00005 TABLE 5 Mechanical-technological properties of binder-free shaped parts after crosslinking by means of radio waves Bending Gluing atro Density strength QZ Popcorn [kg/m.sup.3] [N/mm.sup.2] [kPa] 0% 120 1.1 15 0% 80 0.9 11 0% 60 0.25 8 [0112] 3) Production of Two- and Three-Dimensional Shaped Parts by Use of Radio Waves Using PLA (Polylactic Acid).

[0113] For the production of shaped parts from popcorn granules by use of radio wave technology and PLA, the popcorn granules were treated as follows: The powdered PLA was mixed with the popcorn granules at a dosage of 8% atro (based on the popcorn granules) in a gluing unit by use of hot air at 140° C. The heating process made the PLA flowable and evenly distributed on the popcorn surface. Then, the PLA-coated granules were conveyed into the automatic moulding machine and cured by use of radio waves at 8.3 kV and a negative pressure of 2.8 bar for 4 s/mm of shaped part thickness (wall thickness 20 mm).

[0114] In the final process step, the finished shaped part was removed from the cavity. The following Table 6 shows the mechanical-technological properties:

TABLE-US-00006 TABLE 6 Mechanical-technological properties of PLA-bonded shaped parts after crosslinking by use of radio waves Bending Gluing atro Density strength QZ Popcorn [kg/m.sup.3] [N/mm.sup.2] [kPa] PLA 8% 120 4.9 140 PLA 8% 80 2.7 105 PLA 8% 40 1.8 65 [0115] 4) Production of Two- and Three-Dimensional Shaped Parts Using Microwaves.

[0116] For the production of shaped parts from popcorn granules by use of microwave technology, the popcorn granules were provided with melamine-reinforced urea-formaldehyde resin (MUF, BASF 5 Kauramin 620).

[0117] First, the MUF was applied at 8% atro (based on the popcorn granules) in a gluing unit to the popcorn. Subsequently, the glued material was conveyed by a pneumatic filling system into the cavity of the automatic moulding machine, in which the dielectric heating of the popcorn granules took place at a microwave power of approx. 1.2 to 3 kW. Depending on the thickness and bulk density of the shaped part, dwell times of up to 90 seconds were used. Finally, the finished shaped part was removed from the cavity. Table 7 lists the mechanical-technical properties of the shaped parts produced by use of microwave technology.

TABLE-US-00007 TABLE 7 Mechanical-technological properties and formaldehyde emission values of MUF resin-bonded shaped parts with different densities and thicknesses after crosslinking by use of microwaves Formaldehyde emission in Binder atro Thickness QZ [mg/h .Math. m.sup.2] Popcorn Density [mm] [kPa] DIN EN 717-2 MUF 8% 150 20 300 0.45 50 275 0.48 MUF 8% 120 20 258 0.38 50 240 0.43 MUF 8% 90 20 220 0.29 50 205 0.36 MUF 8% 60 20 140 0.22 50 128 0.25 [0118] 5) Production of Two- and Three-Dimensional Shaped Parts with Different Popcorn Granule Sizes by Use of Radio Waves Using PLA (Polylactic Acid) and Urea Formal-Dehyde Resin (UF).

[0119] For the production of shaped parts from popcorn granules by use of radio wave technology and PLA and UF, the popcorn granules were treated as follows.

[0120] The popcorn granules were separated into different granule sizes (fraction 1: 1 mm-2.5 mm and fraction 2: 2.6 mm-4.5 mm) directly after the expansion process and treated separately.

[0121] The liquid PLA solution was applied at a dosage of 5-8% atro (based on the popcorn granules) separately to both fractions in a gluing unit. Both fractions were dried at approx. 60-80° C. Subsequently, the PLA-coated fractions were glued with 5-8% UF resin in a gluing unit and, depending on the above-mentioned fraction size 1 and 2, altemately pneumatically conveyed into the automatic moulding machine. Thus, multilayer shaped parts were produced in which the different fractions were layered on top of each other. There is also the possibility that, depending on the properties of the shaped parts, the popcorn granule sizes are mixed in a targeted manner, whereby adhesion forces on the individual granule surfaces are reinforced. The shaped parts were cured by use of radio waves at 7 kV and a negative pressure of 0.6 bar for 4 s/mm of shaped part thickness.

[0122] In the final process step, the finished shaped part was removed from the cavity. In the following Table 8 the mechanical-technological properties are shown:

TABLE-US-00008 TABLE 8 Mechanical-technological properties of PLA und UF-bonded shaped parts after crosslinking by use of radio waves Bending Heat Density strength conductivity λ Gluing atro Popcorn [kg/m.sup.3] [N/mm.sup.2] [N/mm.sup.2] [W/m .Math. K)] PLA 5% + UF 8% 120 5.1 0.23 0.040 PLA 8% + UF 5% 120 5.3 0.25 0.041 PLA 5% + UF 8% 80 3.8 0.22 0.0385 PLA 8% + UF 5% 80 3.6 0.21 0.0380 PLA 5% + UF 8% 60 1.8 0.18 0.0372 PLA 8% + UF 5% 60 1.6 0.15 0.0375

[0123] It should be noted that the production method according to the invention can be further varied, whereby additional preferred embodiments of the invention are provided.

[0124] For example, in a further variant, fractions land 2 are first coated together, glued and then separated.

[0125] Furthermore, it should be noted that it is possible to achieve positive effects, such as, among others, better surface adhesion, better sound absorption properties, lower thermal conductivity properties, by varying the different granule sizes, and thus to further noticeably improve the physical-technological properties.

[0126] In particular, the sound absorption properties were investigated in more detail. FIG. 5 shows the sound absorption properties of flat popcorn shaped parts produced according to the invention (upper curve in the range 1500-2000 Hz) compared with those of Ba-sotec L materials available on the market (lower curve in the range 1500-2000 Hz). DIN 11654, which is also registered as a reference, describes the recommended sound absorption limit in the frequency range 0 to 4000 Hz. It can be seen that the popcorn shaped parts are very suitable for sound absorption purposes and even outperform some commercially available materials.

[0127] The individual combinations of the components and the features of the already mentioned embodiments are exemplary; the interchange and substitution of these teachings with other teachings included in this publication with the cited printed matter are also expressly contemplated. Those skilled in the art will recognize that variations, modifica-tions and other embodiments described herein may also occur without departing from the spirit and scope of the invention. Accordingly, the above description is exemplary and is not to be considered as limiting. The word “comprise” used in the claims does not exclude other components or steps. The indefinite article “a” does not exclude the meaning of a plural. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used advantageously. The scope of the invention is defined in the following claims and the associated equivalents.