Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
  • C10G1/10—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal from rubber or rubber waste
• • 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
  • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
  • B29B17/02—Separating plastics from other materials
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
  • C03C25/002—Thermal treatment
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B47/00—Destructive distillation of solid carbonaceous materials with indirect heating, e.g. by external combustion
  • C10B47/28—Other processes
  • C10B47/30—Other processes in rotary ovens or retorts
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B53/00—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form
  • C10B53/07—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form of solid raw materials consisting of synthetic polymeric materials, e.g. tyres
• • 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
  • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
  • B29B17/0026—Recovery of plastics or other constituents of waste material containing plastics by agglomeration or compacting
  • B29B17/0042—Recovery of plastics or other constituents of waste material containing plastics by agglomeration or compacting for shaping parts, e.g. multilayered parts with at least one layer containing regenerated plastic
• • 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
  • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
  • B29B17/04—Disintegrating plastics, e.g. by milling
  • B29B2017/0424—Specific disintegrating techniques; devices therefor
  • B29B2017/0496—Pyrolysing the materials
• • 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
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
  • B29C70/46—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
  • B29C70/48—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM], e.g. by vacuum
• • 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
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
• • 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
  • B29K2707/00—Use of elements other than metals for preformed parts, e.g. for inserts
  • B29K2707/04—Carbon
• • 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
  • B29K2709/00—Use of inorganic materials not provided for in groups B29K2703/00 - B29K2707/00, for preformed parts, e.g. for inserts
  • B29K2709/08—Glass
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/141—Feedstock
  • Y02P20/143—Feedstock the feedstock being recycled material, e.g. plastics
• • 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 invention substantially relates to a method aimed at recovering carbon and/or glass fibers from composite materials in polymeric matrix (also known as FRP: Fiber Reinforced Plastics), coming from different industrial processing stages and/or from manufacts at end of life, by means of a pyrolysis thermal treatment and of a subsequent cleaning treatment from residues, the latter being called "upgrading" .
• the involved commodity field is that of the production of second raw materials derived from industrial waste with particular attention to the mechanical die.
• Carbon, glass, etc. fibers are the material which is wanted to be recovered from the scraps and from the industrial production waste, with a combined process of pyrolysis and subsequent upgrading of the fibers.
• CFRP scraps and waste are sent to dump and they represent a cost both for the firms producing the waste and for the community.
• carbon fibers, or CF are not recovered from CFRP.
• this process does not allow recovering carbon fibers from the composite materials which have already undergone the whole processing, that is the reticulation process and resin cure up to the end product .
• CF physical-mechanical features are considerably better than the ones of the materials used nowadays (nylon, glass fibers, etc.) to produce fabrics and tapes of unidirectional fibers .
• carbon fibers have a tensile strength ten times greater than high-resistant steels and also the other mechanical features such as compressive strength, flexural strength, torsional strength, ' etc. are considerably higher than the other materials for mechanical constructions.
• the rolled sections produced with CF are among the most advanced manufacts used in modern technologies.
• the density of these new materials is less than a half of light alloys and it is about five times smaller than steels, even if at the same time it provides a much higher resistance. It is then evident that practically all construction materials can be replaced by composite materials, when hardness superficial features and/or a particular resistance to high temperatures are not required, to great advantage to the considerable decrease in weight, the mechanical features of the manufact being the same.
• the main obj ect of the present invention to provide a method for recovering carbon fibers from composite materials reinforced with resins , also called CFRP, aimed at reutilizing the same in the production of manufacts having mechanical features very similar to the manufacts produced with "virgin” carbon fibers .
• the treatment steps are a pyrolysis of the material to decompose the resinous matrix and an "upgrading" step of the recovered fibers , wherein the recycled fibers are cleaned from the carbon residues of the first step in order to allow the reutilization thereof to produce new composite materials.
• Figures 1, 2 and 3 show the starting materials • utilized to feed the plant performing the treatment thereof according to the method sofar described;
• figures 4 and 5 respectively show stereomicroscope and optical microscope photos of fibers impregnated with epoxy resin;
• figures 7 and 8 respectively show optical microscope photo and SEM image of the solid residue after the pyrolysis treatment ,-
• 9 shows the microanalysis performed on the fibers of figures 7 and 8;
• figures 10 and 11 show the SEM image of the reinforcing fibers recovered after the upgrading step;
• figure 12 is a block diagram underlining the main steps of the developed process, either in continuous (or flow) and in batch;
• figure 13 is a block diagram of the implemented plant .
• the process according to the invention substantially comprises two subsequent steps, pirolysis and upgrading, which take place preferably in consecutive way inside a reactor: the material pyrolysis to decompose the resinous matrix by setting free the fibers and the upgrading to clean the recycled fibers from carbon residues of the preceding step.
• the upgrading is performed by supplying a reactive gas flow to the reactor: the main upgrading gases are C0 2 , air, oxygen, vapour; they can be used on their own or mixed, even with other gases.
• pyrolysis and upgrading are purely formal , since the same can take place without interruption: for example, by utilizing air as process gas, it is obtained that, during heating of the composite material, the fibers undergo the upgrading while the process advances.
• pyrolysis and upgrading take place at the same time, since whereas some fibers undergo pyrolysis, some others are subjected to upgrading and this without interrupting the process nor adding reaction gas.
• the method can be extended to any other kind of composite material formed by fibers in polymeric matrixes .
• process temperature, gas flow, residence time, upgrading gas vary with the starting material .
• the recovered fibers can be used for preparing manufacts, by utilizing them as such (sheets or fiber fragments) or after trimming the same.
• sheets or fiber fragments sheets or fiber fragments
• the pyrolysis process which itself has been a well known process for many years, has never been applied in significant way to scraps and CFRP waste for the recovery of carbon fibers.
• the invention to make possible this application it has been necessary to set up the geometrical parameters and the management mode of the plant as well as the parameters conditioning the kinetics of the process itself.
• the pyrolysis which as already said is the first step of the method which is described (figure 12) , consists in the thermal degradation process performed in absence of oxygen, by means of indirect heating.
• the material supplied to the reactor undergoes a thermal cracking, by resolving into one solid and one volatile component.
• the volatile fraction can undergo cooling and partial condensation by producing one liquid fraction and one incondensable gaseous faction.
• gaseous fraction mainly constituted by hydrogen, methane, ethylene, ethane and carbon oxydes
• Percentages and compositions of the above- mentioned fractions depend upon conditions thereunder the process is performed and mainly upon: — temperature of the material in the pyrolysis reactor; - working pressure ;
• Table 2 shows the commodity composition typical for CFRPs; tables 3 and 4 respectively show the immediate and average elementary analysis for CFRPs, whereas figure 6 shows the qualitative microanalysis of the resin present on starting fibers: it is to be noted the presence of O, S and Cl in the resin. The presence of Au is determined by the metalization of the sample.
• the organic O percentage is calculated by difference and therefore it comprises possible existing halogens.
• the material supplied to the plant is treated then at temperatures ranging from 250 to 700°C and with a residence time of a few hours .
• the residence time depends upon the reactor geometry, upon the 0 2 percentage and upon the temperature. It is important to underline that, from the implementation point of view, the pyrolysis reactor and the upgrading reactor can coincide, that is they can be constituted by the same reactor wherein both steps occur.
• the process environment is guaranteed either by pyrolysis gases developing in the reactor or by a nitrogen flow, utilized as conveying gas of the produced vapours .
• the weight percentages of the products obtained by pyrolysis of CFRP composite materials at a process temperature of 550°C are the following, on the average:
• Gas mainly constituted by light hydrocarbons, has a lower calorific power equal (or net heat value) to about 8,000 kcal/Nm 3 . It can be utilized as fuel and it helps heating the pyrolysis reactor so as to amortize process costs.
• the oily residue which has a calorific power around 10 , 000 Kcal/kg, is constituted by aromatic , aliphatic components and by olefines ; even such fraction can be utilized to supply energy to the process .
• the preferred solution consists in utilizing the pyrolysis vapours as such, without condensation, to supply energy to the process .
• the solid residue is constituted by recovered carbon fibers and by charcoal which will be removed during the upgrading procedure of . fibers .
• the content in ashes is almost exclusively constituted by inert feedstocks and by metals, added as catalysts utilized during the manufacturing processes of the composite materials.
• the weight percentage of the solid fraction differs by about 10% from the quantity of fibers existing in the original composite material, as shown by data of the commodity analysis: this 10% represents the carbon residue generated by the thermal cracking of the resin (the decomposition of the polyethylene film does not produce appreciable quantities of solid residue) .
• Figures 7 and 8 show the solid residue after the pyrolysis treatment: the fibers are coated with a layer of material. The performed microanalysis, shown in figure 9, has pointed out that this material is very- rich in carbon and it has appreciable quantities of O, S and Cl.
• the material is surely a char due to cracking of the resin, wherein O, S and Cl were previously present. T ⁇ ite presence of carbon residue on fibers causes a great change in their properties, by making them hard, stiff and fragile and then it prevents the reuse thereolE .
• Impregnation tests of fibers with epoxy resins to obtain again the starting manufacts have demonstrated that apart from influencing the processability of fibers:,,, the carbon residue strongly limits the adhesion of fiber with the resin, causing to obtain inferior manufacts .
• the second part of the process performs indeed the "improvement” (upgrading) of recovered fibers, by •implemen-ting the removal of the carbon residue.
• the upgrading step is consecutive to the pyrolysis step and it preferably takes place without any operation of cooling, opening and discharging of the reactor.
• the upgrading process could also be made either in parallel to the pyrolysis analysis or subsequently . , otherwise with a . combined pyrolysds/upgrading process in a single step.
• the upgrading is carried out by supplying to the reactor a flow of reactive gas (such as for example
• the process temperature, the gas flow and the residence time (which shows contact time of fibers with gas at the process temperature) vary according to the utilised process gas.
• Focr example by using air in mixture with nitrogen in 30:70 proportion (0 2 percentage in the gaseous flow equal to 6%) at a temperature of 500 ⁇ 700°C with a residence time of gas in the reactor equal to about ten minutes, the residence time for the upgrading on the average results. to be 2 ⁇ 3 hours.
• Figures 10 and 11 show the SEM image of recovered CF: as it can be seen, fibers are clean and well distinct one from the other.
• Table 5 shows the results of the elementary analysis performed on recovered CF.
• Tables 6 and 7 respectively show the results of traction tests performed on virgin carbon fibers and on the ones recovered under different process conditions and the properties percentage loss.
• the recovered fibers can be used for preparing manufacts, by using them as such (sheets or fiber fragments) or after trimming the same.
• fibers are used in the original form of fabric, by re-impregnating them with resin and by processing them, or by crumbling them and producing a casual scattering of the same on a resin layer, the MAT (non-woven fabric) , which can be then processed.
• the procedure and preparation conditions vary according to the type of resin, or plastic material, used for preparing composite materials.
• the manufacts have been prepared starting from sheets or fragments of carbon fibers, as obtained after recovery and cleaning treatment; samples have been obtained by means of impregnation in epoxy resin and subsequent polymerization and cure.
• a relative composition of fibers and resin of about 3/2 has been used (60% of weight by fibers, 40% of weight by resin) : such composition has been calculated starting from the densities of components and it allows obtaining an end manufact with a density in fiber volume equal to about 50%.
• the preparation can be schematized as follows :
• the matrix has been prepared by making epoxy resin to react in stoichiometric quantities with the cross- linking agent (72% resin, 18% cross-linking agent) , at room temperature and until obtaining a homogeneous product .
• the so-obtained preimpregnated material has .been kept into refrigerator to prevent resin reticulation.
• the sample, set free from the antiadherent film, has been placed between two steel mirror plates and subjected to the cure thermal treatment, carried out under press, at the temperature of 70°C for 2 hours, at the pressure of 6 ⁇ 8 atm.
• the preparation has ended with the post-cure treatment, performed in stove at the temperature of 140 °C for 2 hours.
• the implemented plant provides the following main sections: 1) reaction section, wherein the pyrolysis and upgrading steps take place in sequence ; 2) fume-treating section, optional for the process, wherein the pyrolysis and upgrading vapours are treated in order to allow the discharge into atmosphere of cleaned gases, as well as the cogeneration .
• the fume-treating section may comprise:
• Figure 14 is a simplified process diagram of the implemented plant.
• the main procedures of the processing are : 1) Reactor loading; 2) material pyrolysis; 3) upgrading,- 4) cooling and discharge.
• the flow process can be implemented by simply following the diagram of figure 12 and by utilizing for the pyrolysis and upgrading steps two rotating-drum reactors, in series one to the other, or any other technology usually utilized to carry out thermotreating processes.
• the used oxygen is that of the air, enriched during some tests (as it will be seen later) with technical oxygen.
• carbon fibers are referred to, the same considerations can be extended to glass, kevlar, etc. fibers.
• Table Al shows the dependence of cleaning time upon process temperature by utilizing air as upgrading gas.
• Table A2 relates to the dependance of cleaning time upon process temperature by utilizing air enriched with oxygen (0 2 end content 45%) as upgrading gas.
• Table A3 shows the dependance of cleaning time upon the 0 2 percentage present in the gaseous flow at the temperature of 500°C.
• the recovered fibers can be reutilized as such in the manufacturing process of new composite materials or they can be trimmed and reutilized to produce MAT (unwoven fabric) , by utilizing fibers distributed randomly on a layer or to produce felts .
• MAT unwoven fabric

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Physics & Mathematics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Mechanical Engineering (AREA)
• Combustion & Propulsion (AREA)
• Thermal Sciences (AREA)
• Wood Science & Technology (AREA)
• Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)

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• 2002
  • 2002-04-19 IT IT2002RM000217 patent/ITRM20020217A1/it unknown
• 2003
  • 2003-04-17 AU AU2003236029A patent/AU2003236029A1/en not_active Abandoned
  • 2003-04-17 EP EP03723071A patent/EP1526956A1/de not_active Withdrawn
  • 2003-04-17 WO PCT/IT2003/000247 patent/WO2003089212A1/en not_active Application Discontinuation

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