WO1998022526A1 - Procede pour secher des polymerisats de styrene contenant de l'eau - Google Patents

Procede pour secher des polymerisats de styrene contenant de l'eau Download PDF

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Publication number
WO1998022526A1
WO1998022526A1 PCT/EP1997/006116 EP9706116W WO9822526A1 WO 1998022526 A1 WO1998022526 A1 WO 1998022526A1 EP 9706116 W EP9706116 W EP 9706116W WO 9822526 A1 WO9822526 A1 WO 9822526A1
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WO
WIPO (PCT)
Prior art keywords
particles
drying
salt solution
polystyrene
blowing agent
Prior art date
Application number
PCT/EP1997/006116
Other languages
German (de)
English (en)
Inventor
Dietrich Scherzer
Klaus Hahn
Karl-Heinz Batscheider
Michael Witt
Bernhard Wagner
Wolfram Husemann
Original Assignee
Basf Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Basf Aktiengesellschaft filed Critical Basf Aktiengesellschaft
Priority to AU53180/98A priority Critical patent/AU5318098A/en
Publication of WO1998022526A1 publication Critical patent/WO1998022526A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments
    • C08F6/008—Treatment of solid polymer wetted by water or organic solvents, e.g. coagulum, filter cakes

Definitions

  • the invention relates to a method for drying water-containing styrene polymer particles, in particular expandable styrene polymer particles.
  • Foams based on styrene polymers have been known for a long time and have been described many times in the literature. Of particular importance here are the so-called polystyrene particle foams, which are produced by foaming polystyrene particles containing blowing agents and then welding these foamed particles into blocks, moldings and other foamed objects.
  • the expandable polystyrene particles containing blowing agents are usually produced by suspension polymerization.
  • the styrene which may also contain other olefinically unsaturated comonomers or polymers which are soluble in styrene, is suspended and polymerized in an aqueous solution.
  • the blowing agent is usually added in the course of the polymerization, but it is also possible to add the blowing agent to the polystyrene particles in a subsequent process step.
  • polystyrene particles produced in this way contain more or less water, which can be both dissolved and in the form of very fine droplets in the polymer.
  • the internal water content is very high, often in excess of 5% by weight.
  • moist particles have a corrosive effect on numerous metals in packaging and machines.
  • the further processing of polystyrene particles containing water, including for example to foam or injection molded parts, is adversely affected by the internal water. For these reasons in particular, it is a technical requirement to dry the particles to such an extent that they no longer contain any significant amounts of water.
  • Plastic particles including expandable polystyrene particles
  • the air temperature during drying must not be higher than 70 ° C. Nevertheless, the expandable polystyrene beads deteriorate even at lower temperatures because the water also removes blowing agents. This reduction in the blowing agent content also has an effect on the foam structure and thus on the processing properties.
  • the pentane usually used as a blowing agent has to be processed by complex processes, e.g. Adsorption on activated carbon, from which the dryer exhaust air is removed.
  • DE-A-16 04 339 describes a process for drying expandable polystyrene particles with air at temperatures of 10 to 35 ° C. At these low temperatures, foaming of the beads is prevented and the loss of blowing agent is minimized, but the drying time required is relatively long. Drying times of more than 12 hours are not uncommon, especially with high internal water contents, such as occur in the manufacture of polystyrene beads containing recycled material. This severely limits the capacity of the production facilities.
  • US Pat. No. 4,303,783 describes a method for producing clear, transparent polystyrene beads for reflector applications.
  • the beads produced by polymerization in aqueous suspension are only dried by evaporating the water (conventionally), but small, air-filled cells form on the surface of the beads, which apparently cause opacity.
  • the polystyrene beads are treated according to the requirements above their glass temperature at 110 to 130 ° C. for 2 to 20 minutes with a salt solution, the air cells disappearing due to the melting of the polystyrene without water being able to diffuse in.
  • the object of the invention was to develop a process for drying styrene polymer particles, in particular expandable styrene polymers, which reduces the internal water content of the particles in a short time, without it in the case of blowing medium-containing polystyrene particles leads to loss of blowing agent or foaming of the particles.
  • the object of the invention was surprisingly achieved in that the styrene polymer particles were treated at from 20 to 105 ° C. with an aqueous salt solution and then separated from the salt solution.
  • Expandable polystyrene particles containing blowing agent which were produced by the suspension polymerization process, can be dried particularly advantageously by the process according to the invention.
  • treatment with the brine is expediently carried out immediately after the suspension polymerization after the particles have been separated from the suspension medium.
  • the concentration of the brine should be between 10% by weight and the saturation concentration and in particular 15 to 30% by weight. If the concentration is below 10% by weight, the time for drying is too long. If the concentration is too high, problems due to salt excretion can occur. With increasing salt concentration and at a higher temperature, the pearls dry faster.
  • temperatures above the glass transition temperature of the polymer with blowing agent-containing polystyrene above about 70 ° C, the particles soften and there is a risk of them converging.
  • suspension stabilizers for example calcium phosphate, polyvinylpyrrolidone, polyvinyl alcohol or methyl cellulose in amounts of 0.05 to 0.5% by weight, based on the polymer.
  • the optimal duration of drying depends on the internal water content of the polystyrene particles, the concentration of brine and the drying temperature. It can easily be determined by preliminary tests.
  • the contact between polystyrene particles and brine should last longer than 1 min.
  • This variant of the drying process according to the invention is therefore expediently carried out discontinuously in stirred tanks. Especially with styrene polymers containing blowing agents and when working at elevated temperatures above 50 ° C, it is necessary to operate at elevated pressure, i.e. to work in closed vessels. The pressure can rise to 20 bar or even higher.
  • the particles are present as a solid bed, for example in a vertical tube, and the salt solution is continuously sprayed on from above. Due to the action of gravity, the salt solution seeps downwards while the particles are wetted. The salt solution can be collected at the bottom and, if necessary after concentration, used again to spray the particles.
  • This method can also be carried out in such a way that only so much salt solution is removed that the air between the particles is completely displaced and the particles are thus completely covered in front of the salt solution.
  • the particles and the salt solution can also be led to one another in cocurrent or countercurrent. This guidance of pearls and salt solution in cocurrent or countercurrent can take place both in vertical and in horizontal drying apparatus, for example pipes, but boiler cascades are also conceivable.
  • salts of inorganic acids in particular chlorides, preferably alkali chlorides, are particularly advantageous. Due to the good availability, sodium chloride solution is expediently used.
  • the plastic particles can be freed of the brine in a known manner, for example by means of screen spinning, and can be worked up normally.
  • the brine can be reused. It is only necessary to concentrate them if necessary.
  • Particular advantages of the present invention Trocknungsver ⁇ drive as set forth in blowing agent-containing expandable styrene polymer usually an internal water content of between 1 and 2 wt - have.%. Expandable polystyrene particles produced in particular using recycled polystyrene, which mostly have very high internal water contents, can be dried gently and advantageously using the process according to the invention.
  • the polystyrene particles dried by the process according to the invention are produced by the known suspension polymerization process.
  • the monomers used mostly styrene, optionally in a mixture with other olefinic comonomers and / or with styrene-soluble polymers, are converted into an aqueous emulsion and thus polymerized.
  • the usual systems for example molecular colloids or so-called Pickering salts, for example magnesium pyrophosphate, can be used as suspension stabilizers .
  • the blowing agent is usually added in the course of the polymerization. However, it is also possible to polymerize without addition of blowing agent and, if necessary, to add the blowing agent in a later process step. Following the polymerization, the polymer particles are separated from the suspension medium in a customary manner, for example by means of a centrifugal screen, and dried without further pretreatment by the process according to the invention.
  • the polystyrene particles are separated from the salt solution, optionally washed with water and, as usual, worked up by surface drying, separation into sieve fraction and surface coating.
  • Styrene polymers containing blowing agents can be processed directly into foams.
  • Blowing agent-free polymers can be processed into moldings, for example in the injection molding process, or converted into expandable styrene polymers by impregnation with blowing agents by customary processes.
  • the expandable polystyrene particles are pre-foamed in the usual way using steam and foamed in non-gas-tight molds and welded into molded parts. Further information on the raw materials used and the manufacturing process can be found, for example, in the "Plastic Handbook", Volume 5 "Polystyrene", edited by R. Vieweg and G. Daumiller, Carl Hanser Verlag, Kunststoff, 1969.
  • the method according to the invention it is possible to reduce the internal water content of particulate, in particular of styrene polymers produced by means of suspension polymerization, in an elegant manner to values below 0.7, preferably below 0.4% by weight.
  • the process according to the invention can be used advantageously, in particular in the case of expandable styrene polymers, since there are no blowing agent losses and no foaming of the particles.
  • the otherwise customary storage of the beads for several days for the purpose of conditioning can be omitted.
  • the container was then cooled to 30 ° C. and the polystyrene beads were separated off by sieving.
  • the saline solution was then restored by adding an appropriate amount of saline brought to the initial concentration and used to dry the next batch of polystyrene beads.
  • Examples 1 to 6 used as polystyrene beads were those with a recycled content of 15%, based on the styrene polymer, and an internal water content of 6.5% by weight.
  • M ++ means magnesium sulfate

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

L'invention concerne un procédé pour sécher des polymérisats de styrène contenant de l'eau, selon lequel les particules subissent un traitement avec une solution saline aqueuse.
PCT/EP1997/006116 1996-11-18 1997-11-05 Procede pour secher des polymerisats de styrene contenant de l'eau WO1998022526A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU53180/98A AU5318098A (en) 1996-11-18 1997-11-05 Method for drying water-containing styrol polymerizates

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE1996147599 DE19647599A1 (de) 1996-11-18 1996-11-18 Verfahren zum Trocknen von wasserhaltigen Styrolpolymerisaten
DE19647599.6 1996-11-18

Publications (1)

Publication Number Publication Date
WO1998022526A1 true WO1998022526A1 (fr) 1998-05-28

Family

ID=7811970

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1997/006116 WO1998022526A1 (fr) 1996-11-18 1997-11-05 Procede pour secher des polymerisats de styrene contenant de l'eau

Country Status (3)

Country Link
AU (1) AU5318098A (fr)
DE (1) DE19647599A1 (fr)
WO (1) WO1998022526A1 (fr)

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB916213A (en) * 1958-12-08 1963-01-23 Koppers Co Inc Improvements in or relating to self-extinguishing foams
DE1604339A1 (de) * 1966-10-07 1970-09-17 Basf Ag Verfahren zum Trocknen von expandierbaren Polystyrolpartikeln
DE2553299A1 (de) * 1975-11-27 1977-06-08 Basf Ag Verfahren zur verringerung des treibmittelgehaltes von expandierbaren styrolpolymerisaten
DE2659403A1 (de) * 1975-12-29 1977-07-07 Arco Polymers Inc Nicht klumpen bildendes verschaeumbares styrolpolymer
US4303783A (en) * 1980-05-05 1981-12-01 Arco Polymers, Inc. Production of reflector beads from precursor beads for expandable polystyrene
EP0612792A1 (fr) * 1993-02-25 1994-08-31 BASF Aktiengesellschaft Perles expansibles de polystyrène à faible teneur en eau, et leur procédé de préparation
DE4308636A1 (de) * 1993-03-18 1994-09-22 Basf Ag Verfahren zur Herstellung von perlförmigen expandierbaren Styrolpolymerisaten mit verbesserter Expandierbarkeit
DE4428200A1 (de) * 1994-08-09 1996-02-15 Thermozell Entwicklungs Und Ve Polystyrolgranulat, Verfahren zu seiner Herstellung, sowie Verwendung des Polystyrolgranulats

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB916213A (en) * 1958-12-08 1963-01-23 Koppers Co Inc Improvements in or relating to self-extinguishing foams
DE1604339A1 (de) * 1966-10-07 1970-09-17 Basf Ag Verfahren zum Trocknen von expandierbaren Polystyrolpartikeln
DE2553299A1 (de) * 1975-11-27 1977-06-08 Basf Ag Verfahren zur verringerung des treibmittelgehaltes von expandierbaren styrolpolymerisaten
DE2659403A1 (de) * 1975-12-29 1977-07-07 Arco Polymers Inc Nicht klumpen bildendes verschaeumbares styrolpolymer
US4303783A (en) * 1980-05-05 1981-12-01 Arco Polymers, Inc. Production of reflector beads from precursor beads for expandable polystyrene
EP0612792A1 (fr) * 1993-02-25 1994-08-31 BASF Aktiengesellschaft Perles expansibles de polystyrène à faible teneur en eau, et leur procédé de préparation
DE4308636A1 (de) * 1993-03-18 1994-09-22 Basf Ag Verfahren zur Herstellung von perlförmigen expandierbaren Styrolpolymerisaten mit verbesserter Expandierbarkeit
DE4428200A1 (de) * 1994-08-09 1996-02-15 Thermozell Entwicklungs Und Ve Polystyrolgranulat, Verfahren zu seiner Herstellung, sowie Verwendung des Polystyrolgranulats

Also Published As

Publication number Publication date
DE19647599A1 (de) 1998-05-20
AU5318098A (en) 1998-06-10

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