Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/162—Selection of materials

Definitions

• the invention relates to a sound-absorbing molded foam body with a degree of sound absorption in the frequency range of 0.5 to 4 kHz from 50 to 95%.
• Open cell foam plastics based on polyurethane and Melamine / formaldehyde condensation resins are ideal as sound absorption materials, they are increasing used in many technical applications. However, are natural these foams also have some disadvantages, for example in damp rooms, in the hygiene area and in dust-sensitive areas Investments. There was therefore a need for another Foam plastic with sound absorbing properties.
• the crystallite melting point (DSC maximum) of the under a. to e. listed Polyolefins are generally between 90 and 170 ° C.
• Their heat of fusion, determined by the DSC method, is preferably between 20 and 300 J / g, the melt index MFI (230 ° C, 2.16 kp for propylene polymers and 190 ° C, 2.16 kp for ethylene polymers) according to DIN 53 735 between 0.1 and 100 g / 10 min.
• a preferred method for producing the EPO particles is based on polyolefin granules, which preferably have average diameters of 0.5 to 5 mm. 100 parts by weight of these granules are dispersed in 100 to 500 parts by weight of water in a stirred reactor with the aid of a suspension aid. A blowing agent is then injected in amounts of preferably 2 to 50 parts by weight, based on 100 parts by weight of polymer, and the reactor contents are heated. Suitable blowing agents are hydrocarbons, such as butane, halogenated hydrocarbons, alcohols and CO 2 , N 2 and NH 3 . The blowing agent can be added before or during the heating (this also includes holding times) of the reactor contents to the expansion temperature.
• the preferred propylene polymers are used at 110 ° C to 180 ° C.
• a pressure is established in the reactor which is generally higher than 2 bar and does not exceed 100 bar.
• the bulk density of the resulting EPO particles can be controlled by the choice of the impregnation temperature and the blowing agent.
• the reactor is expanded, the expansion advantageously being carried out in an intermediate container in which a pressure of preferably 0.5 to 5 bar prevails.
• the polyolefin granulate containing blowing agent expands and EPO particles with an average diameter of 1 to 20 mm are formed.
• the bulk density of the EPO particles can be set between 10 and 200 g / l. EPO particles with relatively low bulk densities between 15 and 40 g / l are particularly suitable.
• the EPO particles are predominantly closed-cell and have a cell number of 1 to 5000 cells / mm 2 , in particular 10 to 1500 cells / mm 2 .
• foam particles are now in conventional molding machines with the help of water vapor in perforated tools welded. It is essential that, in contrast to the usual Molding production no or at most a low counter pressure prevails during the filling process. In this way the Incomplete welding according to the invention achieved.
• the amount at cavities, i.e. the gusset volume is between 10 and 40%, preferably between 20 and 38%. A small one, at least spot welding is necessary, however, so that a coherent Shaped body is created.
• Polystyrene foam particles are produced by another, also known and conventional method.
• the monomeric styrene optionally in a mixture with other olefinically unsaturated comonomers, initiators, auxiliaries and additives, is suspended in water and polymerized in the presence of suspension stabilizers.
• the resulting polystyrene beads are separated, washed and dried.
• the blowing agent can be added during the polymerization, but it is also possible to introduce the blowing agent into the polystyrene beads in a subsequent process step.
• Suitable blowing agents are C 4 -C 8 hydrocarbons, preferably pentane.
• the foaming of the polystyrene particles containing blowing agents usually also takes place according to those known in the prior art Procedure by first using water vapor in open or closed pre-expanders in several stages be foamed.
• the pre-expanded polystyrene particles show generally an average particle size of 1 to 10 mm, in particular from 2 to 8 mm.
• the preferred bulk density is 10 to 20 g / l.
• the production of molded bodies takes place in block presses, beforehand in a mixer on the foam particle surface an adhesion promoter (e.g. bitumen) is applied. In the block press, the foam particles become light Back pressure welded into a loose bond.
• an adhesion promoter e.g. bitumen
• a great advantage of the sound-absorbing foam molded body based on polyolefins and polystyrene is that these thermoplastic materials meltable and therefore recyclable are.
• PP foam particles with an average bulk density of 28 g / l were pneumatically compressed from a container under 0.5 bar using a conventional automatic molding machine transported a perforated mold cavity that was under atmospheric pressure.
• the foam particles in bulk in the mold cavity were cross-steamed with 2.8 bar superheated steam from both sides for 3 seconds each, the shut-off valves in the condensate line being open, and being welded in a punctiform manner.
• Example 2 The procedure was analogous to Example 1, but with the differences that for filling the mold cavity under atmospheric pressure a differential pressure between the filling container and the mold cavity is applied was and the transverse steaming with 3.2 bar and a steaming time of 4 sec.
• the resulting cuboid shaped part had a gusset portion from 25% to.
• the degree of sound absorption in the frequency domain 1.25-2 kHz was between 55 and 70%.
• Acoustic panels with the dimensions 300 x 200 x 60 mm were produced from PP foam particles with an average bulk density of 17 g / l (Neopolen 2 9220) on a conventional molding machine.
• the foam particles were transported pneumatically into a perforated mold cavity under atmospheric pressure.
• the foam particles in bulk in the mold cavity were cross-steamed with hot steam of 2.4 bar from both sides for 3 seconds each (with the shut-off valves in the condensate line of the machine open).
• the foam particles were spot welded.
• a cuboid molding with a density of 24 kg / m 3 could be removed.
• the gusset percentage inside the molded part was 30%.
• the degree of sound absorption was 80% in the frequency range between 1.25 and 2 kHz.
• PE foam particles (Neopolen E 1710 from BASF AG) with a bulk density of 13 g / l, which had previously been physically cross-linked by electron radiation, were poured onto an air-permeable, rotating conveyor belt (belt width 1100 mm) approx. 200 mm high and through a Hot air duct transport. The transport speed was 1.6 m / min. and the circulating air in the heating duct 160 ° C. After leaving the 6 m long channel, a point-welded coherent foam particle composite was obtained, which had about 40% voids. The degree of sound absorption in the frequency range 1.25 to 2 kHz of this molded part (density: 14 kg / m 3 ) was 85 to 90%.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Applications Claiming Priority (2)

Publications (3)

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ID=7865953

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• 1998
  • 1998-04-27 DE DE19818811A patent/DE19818811A1/de not_active Withdrawn
• 1999
  • 1999-04-22 US US09/296,329 patent/US6060529A/en not_active Expired - Lifetime
  • 1999-04-26 DE DE59912478T patent/DE59912478D1/de not_active Expired - Lifetime
  • 1999-04-26 EP EP99108136A patent/EP0953964B1/fr not_active Expired - Lifetime
  • 1999-04-26 ES ES99108136T patent/ES2246552T3/es not_active Expired - Lifetime
  • 1999-04-27 BR BRPI9901288-0A patent/BR9901288B1/pt not_active IP Right Cessation

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