GB924756A - Recovery of polycarbonates - Google Patents

Recovery of polycarbonates

Info

Publication number
GB924756A
GB924756A GB27797/61A GB2779761A GB924756A GB 924756 A GB924756 A GB 924756A GB 27797/61 A GB27797/61 A GB 27797/61A GB 2779761 A GB2779761 A GB 2779761A GB 924756 A GB924756 A GB 924756A
Authority
GB
United Kingdom
Prior art keywords
polycarbonate
solution
solvent
dihydric
methylene chloride
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
GB27797/61A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PPG Industries Inc
Original Assignee
Pittsburgh Plate Glass Co
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
Priority claimed from US48733A external-priority patent/US3022271A/en
Application filed by Pittsburgh Plate Glass Co filed Critical Pittsburgh Plate Glass Co
Priority claimed from US128465A external-priority patent/US3195178A/en
Publication of GB924756A publication Critical patent/GB924756A/en
Priority claimed from US409914A external-priority patent/US3235640A/en
Expired legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
    • C08G64/40—Post-polymerisation treatment
    • C08G64/403—Recovery of the polymer
    • A—HUMAN NECESSITIES
    • A21—BAKING; EDIBLE DOUGHS
    • A21C—MACHINES OR EQUIPMENT FOR MAKING OR PROCESSING DOUGHS; HANDLING BAKED ARTICLES MADE FROM DOUGH
    • A21C3/00—Machines or apparatus for shaping batches of dough before subdivision
    • 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
    • B29B7/30—Mixing; Kneading continuous, with mechanical mixing or kneading devices
    • B29B7/34—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices
    • B29B7/38—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary
    • B29B7/40—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with single shaft
    • B29B7/42—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with single shaft with screw or helix
    • B29B7/428—Parts or accessories, e.g. casings, feeding or discharging means
    • B29B7/429—Screws
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/268—Throttling of the flow, e.g. for cooperating with plasticising elements or for degassing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/285—Feeding the extrusion material to the extruder
    • B29C48/29—Feeding the extrusion material to the extruder in liquid form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/285—Feeding the extrusion material to the extruder
    • B29C48/297—Feeding the extrusion material to the extruder at several locations, e.g. using several hoppers or using a separate additive feeding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
    • B29C48/397—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using a single screw
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/501—Extruder feed section
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/505—Screws
    • B29C48/63—Screws having sections without mixing elements or threads, i.e. having cylinder shaped sections
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/505—Screws
    • B29C48/67—Screws having incorporated mixing devices not provided for in groups B29C48/52 - B29C48/66
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/68—Barrels or cylinders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/76—Venting, drying means; Degassing means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/76—Venting, drying means; Degassing means
    • B29C48/763—Vent constructions, e.g. venting means avoiding melt escape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/76—Venting, drying means; Degassing means
    • B29C48/765—Venting, drying means; Degassing means in the extruder apparatus
    • B29C48/766—Venting, drying means; Degassing means in the extruder apparatus in screw extruders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/76—Venting, drying means; Degassing means
    • B29C48/765—Venting, drying means; Degassing means in the extruder apparatus
    • B29C48/766—Venting, drying means; Degassing means in the extruder apparatus in screw extruders
    • B29C48/767—Venting, drying means; Degassing means in the extruder apparatus in screw extruders through a degassing opening of a barrel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/0005—Condition, form or state of moulded material or of the material to be shaped containing compounding ingredients

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Food Science & Technology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Manufacturing And Processing Devices For Dough (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Abstract

<PICT:0924756/IV(a)/1> Solid polycarbonate is recovered from its solution in an inert organic solvent by heating the solution to volatilize solvent therefrom and to raise it to a temperature at which the polycarbonate is flowable while maintaining superatmospheric pressure upon the solution so as to retain with the polycarbonate sufficient solvent to keep the polycarbonate-solvent mixture liquid until attaining a temperature at which the polycarbonate is flowable, and thereafter extruding the substantially solvent-free polycarbonate. The solution to be treated is preferably that obtained by phosgenation of an organic dihydric compound in an aqueous alkaline medium containing the organic solvent. The dihydric compound is preferably a bis-phenol but may also be another dihydric phenol, a dihydric alcohol or a mixture of various dihydric compounds. The organic solvent may be chloroform, methyl chloride methylene chloride, ethylene chloride, beta, beta1-dichloroethyl ether, acetylene dichloride, dichloroethylene, a dichlorobutane, benzene, xylene, 1:4-dioxane, acetone, isobutylketone or tetrahydrofurane. In an example, a methylene chloride solution of bisphenol A polycarbonate is fed via an inlet port 3 (where it is preheated to 82 DEG C.) into an extruder comprising a barrel 1 having cylindrical bores 10 and 11 and surrounded by a heating bath 2. In the bores are worm flights 6 and 7 interrupted by pressure blocks 8 and 9 which divide the apparatus into three zones, A (maintained at 215 DEG C.), B (maintained at 283 DEG C. and 140 p.s.i.g.) and C (maintained at 23-34 mm. of Mg. pressure). In zone A the solution is further heated and in zone B most of the methylene chloride is vapourized and is removed through a port 4. In zone C, the remainder of the methylene chloride and other low boiling substances are vapourized and removed through a port 5. Finally, the polycarbonate is extruded through a die 13 at 288 DEG C. into strands which are air-cooled on a perforated surface and then cut up into pellets.
GB27797/61A 1960-08-10 1961-08-01 Recovery of polycarbonates Expired GB924756A (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
FR835527A FR1272132A (en) 1960-08-10 1960-08-10 Plastics processing process and machines
US48733A US3022271A (en) 1960-08-10 1960-08-10 Finishing of solid diphenolic polycarbonates
US12664561A 1961-08-01 1961-08-01
US128465A US3195178A (en) 1960-08-10 1961-08-01 Apparatus for the treatment of plastic materials
US409914A US3235640A (en) 1960-08-10 1964-11-09 Method for the deaeration of plastic materials

Publications (1)

Publication Number Publication Date
GB924756A true GB924756A (en) 1963-05-01

Family

ID=27515032

Family Applications (2)

Application Number Title Priority Date Filing Date
GB27461/61A Expired GB976637A (en) 1960-08-10 1961-07-28 Apparatus for processing plastic materials
GB27797/61A Expired GB924756A (en) 1960-08-10 1961-08-01 Recovery of polycarbonates

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB27461/61A Expired GB976637A (en) 1960-08-10 1961-07-28 Apparatus for processing plastic materials

Country Status (6)

Country Link
BE (1) BE606868A (en)
CH (1) CH382984A (en)
DE (1) DE1529826A1 (en)
FR (3) FR1272132A (en)
GB (2) GB976637A (en)
NL (1) NL267995A (en)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL274253A (en) * 1962-02-01 1900-01-01
US3881708A (en) * 1972-06-15 1975-05-06 Usm Corp Mixing extruders
DE2748717A1 (en) * 1977-10-29 1979-05-10 Bayer Ag DEVICE AND METHOD FOR PROCESSING INHOMOGENIC RUBBER MIXTURES
DE2810089B2 (en) * 1978-03-08 1980-06-19 Kraftwerk Union Ag, 4330 Muelheim Method and device for embedding radioactive, powdery plastic waste
FR2446706A1 (en) * 1979-01-18 1980-08-14 Ems Ind CONTINUOUS MIXER FOR POLYMERS
EP0036024A1 (en) * 1980-02-26 1981-09-23 Detlef Gneuss Screw extruder
US4776784A (en) * 1987-03-06 1988-10-11 The B. F. Goodrich Company Extruder
US6576131B1 (en) * 1997-12-16 2003-06-10 Flint Ink Corporation Process and apparatus for changing the wetting agent of pigments
US6273599B1 (en) 1999-09-17 2001-08-14 Flint Ink Corporation Process for preparing pigment flush
US7947126B2 (en) 2004-08-17 2011-05-24 Flint Group Incorporated Processes for preparing organic pigment dispersions and ink
DE102010039959A1 (en) 2010-08-30 2012-03-01 Aloys Wobben Fluid degassing apparatus and process for degassing fluids
CN110901010A (en) * 2019-12-10 2020-03-24 湖南工业大学 Intermittent type natural exhaust port flash returning device

Also Published As

Publication number Publication date
NL267995A (en) 1900-01-01
FR1272132A (en) 1961-09-22
FR81735E (en) 1963-11-02
FR89139E (en) 1967-05-12
BE606868A (en) 1900-01-01
DE1529826A1 (en) 1970-01-08
CH382984A (en) 1964-10-15
GB976637A (en) 1964-12-02

Similar Documents

Publication Publication Date Title
GB924756A (en) Recovery of polycarbonates
ES277921A1 (en) Procedure and apparatus for incorporating liquid substances in thermoplastic resins (Machine-translation by Google Translate, not legally binding)
US3437638A (en) Method of separating polycarbonates from solution
EP0175118B1 (en) Process for the isolation of aromatic polycarbonates from their solutions
US3156009A (en) Devolatilizing extruder
US3453184A (en) Removal of high and low boiling solvents from polycarbonate solutions
EP0547479B1 (en) Process for cracking polycarbonates
JPH03143921A (en) Method for removal of volatile matter from spiro (bis) indan polycarbonate by extruder
GB1011906A (en) Vertical diffuser
GB1071486A (en) Production of bisphenol-a from resinous by-products
US3022271A (en) Finishing of solid diphenolic polycarbonates
US3317523A (en) 4-substituted-1, 2, 3-benzoxathiazine 2, 2 dioxides
CH388912A (en) Process for extracting organic compounds from their solution
GB1208476A (en) A process and apparatus for the preparation of polyamides
GB902538A (en) Production of polycarbonates
GB1394452A (en) Purification of phenol
ES272104A1 (en) Apparatus for pyrolyzing vapors
DE19608521A1 (en) Process for the production of polycarbonate agglomerate
GB1022980A (en) Production of 1,1,2-trichloroethane
GB987746A (en) Process for producing stable diisocyanate compositions
GB919330A (en) Production of polycarbonates
DE3063907D1 (en) Process for the preparation of cobalt (ii) acetyl acetonate
US2302465A (en) Method of preparing the oxidation products of alkylated benzene and cyclohexane compounds
US2291527A (en) Halomethyl ether esters
GB843881A (en) An improved process for the preparation of macromolecular polycarbonates