Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J11/00—Recovery or working-up of waste materials
  • C08J11/04—Recovery or working-up of waste materials of polymers
  • C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
  • C08J11/08—Recovery or working-up of waste materials of polymers without chemical reactions using selective solvents for polymer components
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
  • C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
  • C08J2327/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing chlorine atoms
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2355/00—Characterised by the use of homopolymers or copolymers, obtained by polymerisation reactions only involving carbon-to-carbon unsaturated bonds, not provided for in groups C08J2323/00 - C08J2353/00
  • C08J2355/02—Acrylonitrile-Butadiene-Styrene [ABS] polymers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

• the present patent application relates to a process for the treatment of a mixture of ABS and of PS and more particularly to a process for the separation of ABS and of PS by selective dissolution/precipitation.
• Plastics are widely used in the manufacture of varied flexible or rigid articles, such as, for example, tarpaulins, coated fabrics and other components for the interior trim of vehicles, pipes, window frames, electrical cables possessing polymeric insulation, housings and other electrical and electronic equipment parts.
• the Applicant Company has developed a process for the recovery of vinyl polymers, known as the Vinyloop® process, which consists in treating articles comprising PVC with a solvent which is miscible and miscible which forms an azeotrope with water, so as to dissolve the PVC, in removing possible insoluble materials from the solution and in precipitating the PVC in solution by injection of water, at least partly in the form of steam, to carry out an azeotropic distillation of the solvent.
• This process is disclosed in particular in patents EP 945 481 and 1 232 204 and in application EP 1 268 628.
• the present invention relates to a process for the treatment of a mixture of ABS (acrylonitrile-butadiene- styrene terpolymer) and of PS (polystyrene), according to which the said mixture is brought into contact with a liquid medium comprising water and a water-miscible common solvent in proportions and under pressure and temperature conditions such that the ABS is soluble therein and the PS insoluble.
• ABS acrylonitrile-butadiene- styrene terpolymer
• PS polystyrene
• the process according to the invention is applicable to all commercial grades of ABS and of PS.
• the latter can be HIPS (High Impact PS), that is to say a grafted styrene-butadiene copolymer obtained by grafting polystyrene to nodules of partially crosslinked polybutadiene rubber in order to obtain impact strengthening with respect to the PS homopolymer.
• HIPS High Impact PS
• the mixture in which they are present can be composed solely of these polymers. Alternatively, they can comprise other polymers or substances which are preferably insoluble in the solvent chosen.
• the common solvent has to be miscible with water (that is to say, must form a homogeneous phase with water over at least one range of concentration), an essential condition in order for water to be able to interact with the molecules of polymer(s) in solution.
• water is generally present therein as a minor component.
• the liquid medium preferably consists of a single-phase medium given that, with two-phase media (having respectively a water-rich phase and a solvent-rich phase), only the latter will be effective in the process (since the polymers will be dissolved in this phase alone).
• the common solvent (capable of dissolving both the (HI)PS and the ABS) used in the process according to the invention can consist of a pure substance or a mixture of substances.
• Solvents which are highly suitable are polar organic solvents. Examples of such solvents are THF (tetrahydrofuran), MIBK (methyl isobutyl ketone), cyclohexanone and MEK (methyl ethyl ketone). The latter gives good results.
• THF tetrahydrofuran
• MIBK methyl isobutyl ketone
• MEK methyl ethyl ketone
• the proportions of solvent and of water can be variable.
• the water content of the mixture is advantageously in the region of 12 % by weight.
• a 1st possibility consists in bringing the mixture directly into contact with the liquid medium under conditions (in particular temperature, pressure and concentrations) such that the ABS is soluble therein and the PS insoluble, after which the undissolved PS is separated from the ABS solution by any appropriate means.
• an ABS and (HI)PS mixture in the form of granules is introduced into a solvent composed of MEK comprising 12 % of water. The combined mixture is stirred and heated for a few minutes. Stirring is subsequently halted in order to - A -
• a 2 nd way of proceeding consists in dissolving the two polymers of the mixture in solvent comprising little or no water and under conditions such that the two polymers dissolve and in subsequently selectively precipitating the PS by addition of water.
• an ABS and (HI)PS mixture in the form of granules is « dissolved » with stirring in MEK.
• the water is added to saturation and the (HI)PS selectively precipitates.
• Stirring is then halted to promote separation by settling and the supernatant is withdrawn.
• the ABS is collected.
• the polymer separated by settling can be rinsed with a fresh MEK/water mixture in order to extract the maximum amount of ABS.
• a 3rd way of proceeding consists in dissolving the ABS and the PS in a solvent/phase-separation agent mixture optionally comprising water and in subsequently removing the phase-separation agent by distillation and addition of water, if necessary (that is to say, if the liquid medium does not comprise a sufficient amount thereof).
• phase-separation agent is a substance compatible with the solvent and not compatible with the water which renders the solvent more hydrophobic
• a solvent/phase separation agent binary mixture in subsequently removing the phase-separation agent by distillation, water being added to the medium if necessary (optional in the case of a ternary mixture but obligatory in the case of a binary mixture).
• phase-separation agent renders the solvent-rich phase of the mixture richer in water and, by doing this, brings about the precipitation of the PS.
• the latter way of proceeding advantageously involves recourse to the injection of steam or of water/solvent azeotropic vapour.
• a starting solvent having approximately the following composition by weight gives good results : MEK 80 %, isohexane 15 %, water, 5 %.
• an ABS and (HI)PS mixture in the form of granules is dissolved with stirring in an MEK/water/hexane mixture.
• the hexane is distilled off by injection of water/solvent azeotropic vapour.
• the MEK is then found to be saturated with water and the (HI)PS selectively precipitates.
• Stirring is then halted in order to promote separation by settling and the supernatant is withdrawn.
• the ABS is collected.
• the polymer separated by settling can be rinsed with a fresh MEK/water mixture in order to extract the maximum amount of ABS.
• phase-separation agent hexane
• the phase-separation agent can also be removed by injection of steam but, in this case, it is possible for the medium at the end of precipitation to be three- phase (presence of a third denser aqueous phase).
• the presence of this aqueous phase generally does not make possible effective centrifuging of the solid phase, which has a tendency to become located at the interface of the two liquids, which is unfavourable.
• any conventional method can be used to separate it therefrom : separation by settling, centrifuging, and the like.
• the ABS solution is then treated by any appropriate way (separation by settling at a lower temperature and/or pressure; devolatilization under vacuum; azeotropic distillation of the solvent/water mixture (when a solvent is chosen which forms an azeotrope with water, which is the case with the abovementioned solvents, namely : THF, MIBK, cyclohexanone and MEK); atomization; and the like).
• the dissolution/precipitation operations can be repeated and the various solutions collected can be combined for the final treatment for recovery of the ABS.
• the separated polymers collected can be subjected to appropriate treatments (rinsing, drying, and the like) for the purpose of purifying them.
• the process according to the invention exhibits the advantage of being able to be easily made use of on existing plants designed for the abovementioned Vinyloop ® process. This is because the solvents which are used in this process (and in particular MEK) are also common solvents of ABS and of (HI)PS. Consequently, the present invention also relates to a process according to which :
• At least a fraction of the vapours condensed in the preceding stage is used as all or part of the liquid medium in a process for the separation of ABS and of (HI)PS as described above.
• phase-separation agent can be present in the liquid medium and thus in the condensed vapours used. This is the case when dissolution of the polymer takes place in the presence of this agent as disclosed in the abovementioned Application EP 1 268 628 (and the content of which to this effect is introduced by reference into the present patent application).
• Example 1 (illustrative of the 1st method according to the invention) :
• the residue present in the reactor was present in the form of a mass of swollen polymer and of a small amount of supernatant.
• the combined product weighed 1491.9 g.
• the material balance is given in the following table :
• Example 2 (illustrative of the 2 nd method according to the invention) :
• Example 3 (illustrative of the 3rd method according to the invention) :
• the milky mixture was cooled down to 40°C, then introduced into a reactor equipped with a condenser and vigorously stirred.
• the pressure was set at 600 mbar and the azeotrope vapours were injected into the reactor.
• the isohexane was then distilled off, thus making it possible to increase the water content of the MEK, which consequently became a poor solvent of the HIPS.
• the solvent present in the supernatant was evaporated under reduced pressure and the resulting polymer was dried under vacuum at 110°C to constant weight. 399 g of a fraction rich in ABS were thus isolated. The latter comprises 91 % by weight of ABS (versus 3.6 % of ABS for the phase rich in HIPS).

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Processes Of Treating Macromolecular Substances (AREA)

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• 2004
  • 2004-09-17 FR FR0409870A patent/FR2875504B1/fr not_active Expired - Fee Related
• 2005
  • 2005-09-15 EP EP20050784664 patent/EP1791899A1/en not_active Withdrawn
  • 2005-09-15 WO PCT/EP2005/054582 patent/WO2006030020A1/en active Application Filing
  • 2005-09-15 JP JP2007531748A patent/JP2008513559A/ja active Pending

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