Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B7/00—Mixing; Kneading
  • B29B7/74—Mixing; Kneading using other mixers or combinations of mixers, e.g. of dissimilar mixers ; Plant
  • B29B7/76—Mixers with stream-impingement mixing head

Definitions

• the present invention relates to a high-pressure mixing head for mixing at least two reactive plastic components, in which the
• Mixing heads are known for two-component plastics, in which the components are injected into a cylindrical mixing chamber under high pressure by opposing injection nozzles, the mixture is transferred from the mixing chamber into a calming chamber arranged at right angles to the mixing chamber and then e.g. is poured freely into open molds (see DE-A 29 07 938).
• Axially displaceable cleaning and ejection pistons are provided both in the mixing chamber and in the settling chamber, which after the filling of a mold, i.e. at the end of the shot. be axially displaced so that they fill the respective chambers.
• Mixing chamber cleaning pistons have opposite longitudinal grooves that cover the injection nozzles when the piston position closes the mixing chamber and establish a connection to return lines for the components.
• Turbulence take place so that the mixture emerges from the calming chamber in a laminar manner.
• the present invention relates to a high-pressure mixing head for mixing at least two reactive plastic components, in particular the components of a polyurethane reactive mixture, the mixing head containing a mixing chamber with metering pistons into which two oppositely arranged injection nozzles for the components open, and the mixing chamber opens into a calming chamber which extends essentially rectangular to the axis of the mixing chamber and has a cleaning slide, which is characterized in that is that the calming chamber and the cleaning slide have a substantially rectangular cross section with an axis ratio of 10 to 100.
• the component mixture therefore emerges from the mixing head in the form of a curtain with a width 10 to 100 times greater than the thickness.
• the calming chamber and the cleaning slide should preferably have an essentially rectangular cross section with an axis ratio of 15 to 80, particularly preferably 25 to 60.
• the calming chamber is thus formed by two parallel boundary surfaces at a short distance, the distance being approximately 1 to 10 mm.
• the mixing chamber preferably opens vertically in the middle through one of the large boundary surfaces of the settling chamber.
• the large transverse dimension of the calming chamber can be 2 to 8 times, particularly preferably at least 3 times, the diameter of the mixing chamber.
• the high-pressure mixing head according to the invention not only ensures excellent calming of the component mixture, but also permits control of the mixture flow rate over a wide range.
• the rate of exit of a reactive polyurethane mixture from the calming chamber can e.g. can be varied without disadvantage in the range between 0.25 to 5 m / sec, in the case of particularly high mixture viscosities even up to 10 m / sec.
• the mixing head is moved back and forth across the mold.
• the high-pressure mixing head according to the invention can particularly preferably be used for the production of two-component plastics filled with solids. Solids are flung sideways against the curtain of the component mixture that flows freely after exiting the calming chamber.
• the invention accordingly also relates to a process for the production of two-component plastics filled with solids, the components being mixed in a high-pressure mixing head with attached calming chamber, which is characterized in that the calming chamber has a substantially rectangular cross section with an axis ratio of 10 to 100 has, so that the mixture emerges in the form of a free-flowing curtain from the calming chamber and the solids are thrown against the curtain.
• a corresponding device for carrying out this preferred method for producing filled two-component plastics has, in addition to the mixing head below the outlet opening of the calming chamber, a device for the directed supply of solids.
• Solids in the form of powder, granules, flakes or fibers can be used as solids as reinforcing or flame retardants; in particular those which have an extent in at least one dimension of at least 0.2 mm, preferably at least 0.5 mm.
• the device according to the invention and the method according to the invention are particularly suitable for solids whose incorporation by other methods causes difficulties due to their mechanical sensitivity.
• expandable graphite can be incorporated as a flame retardant in polyurethanes.
• expanded graphite For example, known intercalation compounds of SO ⁇ , NO x , halogen and / or strong acids in graphite are suitable as expanded graphite. These are also called graphite salts. Expandable graphites are preferred which, at temperatures of, for example, 120 to 350 ° C. with swelling SO 2 , SO 3 , NO and / or
• Expandable graphite can be present, for example, in the form of platelets with a maximum diameter in the range from 0.1 to 5 mm. Preferred this diameter is in the range of 0.5 to 3 mm. Expandable graphites suitable for the present invention are commercially available.
• expanded graphite Based on the ready-to-use fire protection element, for example 1 to 50% by weight expanded graphite can be contained therein.
• This expandable graphite content is preferably 2 to 30% by weight, in particular 2 to 20% by weight.
• expanded graphite as a flame retardant is linked to the size of the graphite particles.
• Expandable graphite particles ground into a binder during the incorporation process only make a very limited contribution to the flame-retardant finish.
• Usual methods for incorporating fillers into reactive polyurethane mixtures lead to a considerable reduction in particle size, which is detrimental to the flame-retardant finish.
• the solid particles are fed to the liquid curtain by a suitable transport organ, in which the necessary kinetic energy is imparted to the particles.
• a transport gas preferably air, can be used for support.
• the invention is furthermore outstandingly suitable for the production of fiber-reinforced polyurethanes, in particular if the fibers have a length that can no longer be controlled by other incorporation processes.
• Natural or synthetic organic or inorganic fibers can be used as reinforcing fibers, the invention being particularly suitable for fiber lengths of 3 to 300 mm.
• Glass fibers are particularly preferably used.
• the glass fibers are preferably fed as a glass fiber strand, conveyed by means of transport and cutting rollers, cut and flung against the free-flowing two-component mixture.
• the glass fibers can have a length of, for example, 10 to 100 mm.
• the solids are preferably thrown against the component mixture curtain at an angle of 40 to 90 °, particularly preferably 40 to 60 °.
• the mixing head according to the invention can be used to fill the reactive polyurethane mixture into open molds, optionally together with solids. Furthermore, the mixing head is suitable for the continuous production of open-pore or closed-pore block foam, the curtain of the reactive mixture being on the lower conveyor belt of the continuous form
• the mixing head is preferably arranged above the conveyor belt in such a way that the curtain points in the direction of the movement of the conveyor belt, the mixing head being moved back and forth transversely to the conveyor belt.
• Combinations of solids can also be used in accordance with the invention, in that the curtain of the reactive mixture e.g. glass fibers are applied on one side and expanded graphite on the other side.
• the curtain of the reactive mixture e.g. glass fibers are applied on one side and expanded graphite on the other side.
• FIG. 1 shows a cross section through a high-pressure mixing head according to the invention
• FIG. 2 shows a section A-A through the mixing head according to FIG. 1
• Fig. 3 shows an inventive device for the production of glass fiber reinforced polyurethane mold parts
• FIG. 4 shows a section B-B through the representation according to FIG. 3
• FIG. 1 and 2 show a high-pressure mixing head 1 according to the invention with a cylindrical mixing chamber 2, into which two opposite injection nozzles 3 for the two mixture components, in the case of polyurethane the components
• the mixing piston 4 In the axis of the mixing chamber is the Dosing piston 4 arranged hydraulically.
• the mixing piston 4 has two opposing grooves 5, which each connect an injection nozzle 3 to the respective return line, not shown, in the closed position.
• the mixing head has a calming chamber 6 with a substantially rectangular cross section transverse to the mixing chamber 2, so that the component mixture in
• a cleaning slide 7 which can be moved hydraulically in the direction of the calming chamber outlet is provided, which in the operating position releases the mixing chamber outlet to the calming chamber 6 and partially covers it in a throttling manner (9).
• Fig. 3 shows a high-pressure mixing head 1 according to the invention, from which the
• Component mixture 8 emerges.
• Glass fibers 15 are flung against the curtain 8 and are conveyed and cut by feeding one or more glass fiber strands 11 between a transport roller 12 and a cutting roller 13, on the lateral surface of which at least one cutting knife 14 is fastened parallel to the axis.
• the surface speed of the transport roller 12 and the cutting roller 13 can be between 1 and 50 m / sec, preferably 3 to 10 m / sec.
• the glass fiber spinner 10 is connected to the high-pressure mixing head 1 in the directions X, Y and adjustable by the angle ⁇ .
• the glass fibers 15 are shot into the curtain 8 due to the speed imparted to them by the transport roller 12 and the cutting roller 13 and wetted by the component mixture.
• the mixture of component mixture and glass fibers is introduced into the open mold half 20, the high-pressure mixing head being moved horizontally over the mold 20.
• the mixing chamber 2 is closed by the metering piston 5 and the remaining component mixture is ejected from the settling chamber 6 by means of a cleaning slide 7.
• the lower mold half 20 is closed by an upper mold half (not shown) by means of a suitable locking device and the component mixture is cured.
• FIG. 4 shows a section B-B through the representation according to FIG. 3.
• FIG. 5 shows a particularly preferred embodiment of the invention, in which the mixture curtain 8 is acted upon by glass fibers 15 from both sides.
• FIG. 6 shows a device analogous to FIG. 5, solid particles 25, for example expanded graphite, being thrown against the liquid curtain 8 by means of centrifugal wheels 20a and 20b.
• the centrifugal wheels can have a peripheral speed of 1 to 50 m / s.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Reinforced Plastic Materials (AREA)

Applications Claiming Priority (5)

Publications (1)

Family

ID=26027195

Family Applications (1)

Country Status (8)

Families Citing this family (19)

Family Cites Families (11)

• 1997
  • 1997-01-24 DE DE29704560U patent/DE29704560U1/de not_active Expired - Lifetime
  • 1997-07-01 WO PCT/EP1997/003442 patent/WO1998001274A1/de not_active Application Discontinuation
  • 1997-07-01 EP EP97930473A patent/EP0912309A1/de not_active Withdrawn
  • 1997-07-01 JP JP10504735A patent/JP2000514008A/ja active Pending
  • 1997-07-01 CN CN97196110A patent/CN1067003C/zh not_active Expired - Fee Related
  • 1997-07-01 KR KR1019980710869A patent/KR20000022436A/ko not_active Application Discontinuation
  • 1997-07-01 US US09/214,188 patent/US6065862A/en not_active Expired - Fee Related
• 2000
  • 2000-01-26 HK HK00100494A patent/HK1021515A1/xx not_active IP Right Cessation

Non-Patent Citations (1)

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