WO2011158024A1 - Procédés concernant des produits de caoutchouc - Google Patents

Procédés concernant des produits de caoutchouc Download PDF

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Publication number
WO2011158024A1
WO2011158024A1 PCT/GB2011/051113 GB2011051113W WO2011158024A1 WO 2011158024 A1 WO2011158024 A1 WO 2011158024A1 GB 2011051113 W GB2011051113 W GB 2011051113W WO 2011158024 A1 WO2011158024 A1 WO 2011158024A1
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WO
WIPO (PCT)
Prior art keywords
rubber
parts
rubber material
carbon dioxide
suitably
Prior art date
Application number
PCT/GB2011/051113
Other languages
English (en)
Inventor
Martin John Forrest
Leslie William Lloyd
Original Assignee
Smithers Rapra Technology Limited
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 Smithers Rapra Technology Limited filed Critical Smithers Rapra Technology Limited
Publication of WO2011158024A1 publication Critical patent/WO2011158024A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L19/00—Compositions of rubbers not provided for in groups C08L7/00 - C08L17/00
    • 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
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C19/00—Chemical modification of rubber
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C19/00—Chemical modification of rubber
    • C08C19/30—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule
    • 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
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/16—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with inorganic material
    • 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
    • C08J2319/00—Characterised by the use of rubbers not provided for in groups C08J2307/00 - C08J2317/00
    • 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
    • C08J2321/00—Characterised by the use of unspecified rubbers
    • 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 relates to a method for treating rubber materials.
  • the invention relates to a method for devulcanisation of rubber materials.
  • Vulcanization of rubber is a very old well known industrial process in which an additive such a sulphur is added to rubber to modify the polymer by forming cross links between the polymer chains. Untreated rubber is sticky, deforms on heating and becomes brittle at low temperatures. Vulcanised rubber has superior mechanical properties and is used to manufacture a wide range of products, especially vehicle tyres.
  • a method for the devulcanisation of a rubber material comprising contacting the rubber material with carbon dioxide and an additive selected from dithiocarbamates, thiazoles, guanidines, thiurams, sulphenamides and mixtures thereof.
  • the present invention relates to a method of treating a rubber material.
  • the rubber material comprises waste rubber masterial, that is vulcanised rubber which has been previously used.
  • the rubber material comprises waste rubber sou reed from used rubber tyres.
  • the rubber material used in the method of the present invention preferably comprises rubber crumb.
  • Rubber crumb is a term well known to those skilled in the art and is used to refer to particulate rubber, typically recovered from vehicle tyres. During the recovery process steel and fluff is removed to leave rubber with a granular consistency. Further processing reduces the size of the particles.
  • the particles are typically sized by passing through a screen with a particular mesh. A 10 mesh screen has 10 holes per inch, a 20 mesh screen has 20 holes per inch, and so on.
  • a 10 mesh screen has 10 holes per inch
  • a 20 mesh screen has 20 holes per inch, and so on.
  • a rubber crumb having a "10 mesh” size will have a particle having a size of less than 0.1 inch
  • a "20 mesh” size will have particles of less than 0.05 for example less than 0.033 inch and so on.
  • the rubber crumb used in the present invention has a size of 30 mesh or less.
  • the method for devulcanisation of the present invention may use rubber crumb having a size of 40 mesh or less, for example 60 mesh or 80 mesh.
  • the rubber material used in the present invention comprises particles having a diameter of less than 2mm, preferably less than 1.5mm, suitably less than 1 mm.
  • the rubber material comprises particles having a diameter of from 0.2 to 0.6mm. It is a particular advantage of the present invention that the method may be used to devulcanise rubber crumb of a variety of sizes including 30 mesh, 40 mesh, 60 mesh and 80 mesh.
  • the rubber material used in the present invention may comprise natural rubber, synthetic rubber or a mixture thereof.
  • the rubber material is contacted with carbon dioxide and an additive selected from dithiocarbamates, thiozoles and mixtures thereof.
  • carbon dioxide is used as liquid carbon dioxide. It may be used as supercritical carbon dioxide.
  • Carbon dioxide may suitably be supplied from a cylinder of the compressed gas. It may be supplied as a liquid but once present in the reaction vessel the temperature and pressure will adapt according to the surroundings.
  • the rate of supply of carbon dioxide is suitably selected to provide a desired ratio of carbon dioxide to rubber material. Control of the flow of carbon dioxide can be easily achieved by the person skilled in the art.
  • carbon dioxide may be used as solid carbon dioxide. In such embodiments said carbon dioxide may be added with other solid ingredients.
  • the method of the present invention involves using an additive selected from dithiocarbamates, thiazoles, guanidines, thiurams, sulphenamindes and mixtures thereof.
  • Suitable dithiocarbamate compounds for use in the method of the present invention include metal salts of alkyl dithiocarbamates especially dialkyl dithiocarbamate salts, diary Ithiocarbamates or di(alkylaryl)thiocarbamates.
  • Preferred are divalent metal salts of dialkyl thiocarbamtes or di(alkylaryl)dithiocarbamates, suitably transition metal salts of dialkyl dithiocarbamates or di(alkylaryl)dithiocarbmates.
  • Preferred dialkyldithiocarbamates include alkyl groups having 1 to 16 carbon atoms, preferably 1 to 12, more preferably 1 to 8 and most preferably 1 to 4 carbon atoms.
  • Preferred di(alkylaryl)dithiocarbamates include dibenzyl dithiocarbamate.
  • Preferred dithiocarbamate compounds for use herein are zinc salts. These include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc dibutyldithiocarbamate and zinc dibenzyldithiocarbamate.
  • An especially preferred dithiocarbamate additive is zinc diethyldithiocarbamate.
  • Any suitable thiazole compound may be used in the method of the present invention.
  • Preferred thiazole compounds include 2-mercaptobenzothiazole or derivatives thereof, for example zinc mercaptobenzathiazole and benzathiazyl disulphide. Other metal salts of mercaptobenzothiazyl could also be used.
  • An especially preferred thiazole is 2- mercaptobenzothiazyl disulfide (MBTS).
  • Suitable guanidine compounds for use herein include ⁇ , ⁇ -diphenyl guanidine and N,N-di- ori 70-tolyl guanidine.
  • Suitable thiuram compounds for use herein include tetramethyl thiurum disulfide, tetraethyl thiuram disulfide, tetrabutyl thiurum disulfide and tetramethyl thiuram monosulfide.
  • Suitable sulphenamide compounds for use herein include N-cyclohexyl-2-benzothiazole sulphenamide, N-ieri-butyl-2-benzothiozole sulphenamide and 2-(4-morpholinothio)- benzothiozole sulphenamide.
  • the additive may comprise a mixture of two or more compounds selected from dithiocarbamates, thiazoles, guanidines, thiorams and sulphenamides.
  • the additive is selected from dithiocarbamates, thiazoles and mixtures thereof.
  • the additive may comprise a mixture of one or more dithiocarbamate compounds and/or one or more thiazole compounds. In some preferred embodiments the additive comprises at least one dithiocarbamate compound and at least one thiazole compound.
  • the additive is suitably present in an amount of at least 0.5 parts by weight for every 100 parts by weight of the rubber material, i.e. for every 100g of rubber material at least 0.5g of additive is used.
  • the additive is used in an amount of at least 1 part by weight per 100 parts of rubber material, suitably at least 1.5 parts, preferably at least 2 parts, more preferably at least 2.5 parts, suitably at least 3 parts, for example at least 3.5 parts.
  • the additive may be present in an amount of up to 15 parts by weight for 100 parts by weight of the rubber material, suitably up to 12 parts, preferably up to 10 parts, more preferably up to 8 parts, preferably up to 7 parts, suitably up to 6 parts for example up to 5 parts.
  • the weight ratio of thiazole compounds to dithiocarbamate compounds is preferably at least 0.5:1 , preferably at least 1 :1 , for example at least 1.5:1 , at least 2: 1 or at least 2.5:1.
  • rubber crumb is contacted with from 0.5 to 2 parts by weight of one or more dithiocarbamate compounds and from 1 to 5 parts by weight of one or more thiozaole compounds for every 100 parts of rubber crumb.
  • a rubber material is contacted with carbon dioxide and one or more additives. The or each additive and the carbon dioxide may be contacted with the rubber material sequentially or simultaneously.
  • the rubber material is further contacted with one or more coagents.
  • One preferred class of coagents comprises metal oxides, preferably transition metal oxides.
  • An especially preferred coagent is zinc oxide.
  • Another preferred class of coagents comprises fatty acids, especially saturated fatty acids having from 12 to 26 carbon atoms.
  • An especially preferred coagent is stearic acid.
  • Another suitable coagent for use in the method of the present invention is zinc stearate.
  • the rubber material is contacted with a metal oxide, for example zinc oxide.
  • a metal oxide for example zinc oxide.
  • This is suitably used in an amount of from 0.05 to 10 parts per 100 parts of rubber material, preferably from 0.1 to 5 parts, more preferably from 0.1 to 3 parts, suitably from 0.1 to 1 parts, preferably from 0.1 to 0.5 parts, for example 0.2 to 0.4 parts.
  • the rubber material is contacted with a fatty acid, for example stearic acid.
  • a fatty acid for example stearic acid.
  • This is suitably used in an amount of from 0.05 to 10 parts by weight per 100 parts of rubber material, preferably from 0.1 to 5 parts, more preferably from 0.1 to 3 parts, suitably from 0.1 to 1 parts, preferably from 0.1 to 0.5 parts, for example 0.2 to 0.4 parts.
  • the rubber material is contacted with zinc oxide and stearic acid.
  • the rubber material is further contacted with a peptiser.
  • Peptisers are common additives used in the rubber industry and the skilled person will know the type of compounds which can be used.
  • Peptisers can be used to scavenge free radicals.
  • Suitable peptisers include aromatic thiols.
  • One preferred peptiser for use herein is bis(2-benzamidophenyl) disulfide which is commercially available under the trade mark Pepton 22.
  • the peptiser is used in an amount of at least 0.5 parts by weight per 100 parts of rubber material, preferably at least one part, for example at least 1 .5 parts. It may be present in an amount of up to 10 parts per weight per 100 parts of rubber material, suitably up to 7 parts, preferably up to 5 parts for example up to 3 parts.
  • the method of the present invention may be carried out in any suitable reaction vessel.
  • the rubber material first is contacted with the additives and when used, the one or more coagents and/or one or more peptisers, and this mixture is subsequently contacted with carbon dioxide.
  • the rubber material, additives, coagents and peptisers may be contacted prior to charging the reaction vessel or they may be contacted in the reaction vessel. In some embodiments these components are thoroughly mixed for example by stirring or other agitation and the mixture then contacted with carbon dioxide.
  • the reaction vessel is suitably charged with a mixture of rubber material, additive, and optionally coagents and/or peptisers. Each of these materials is suitably provided in powdered and/or crumb form.
  • carbon dioxide is then supplied to the vessel in liquid form, for example from a cylinder with a control valve.
  • the reaction vessel may be charged with a mixture of rubber material, additive, carbon dioxide and optionally coagents and/or peptisers all in solid form.
  • carbon dioxide is supplied in an amount of from 0.1 to 20% by weight compared to the total weight of the rubber material, preferably in an amount of from 0.25 to 15%, preferably from 0.5 to 12%, more preferably from 0.6 to 10%, suitably from 0.7 to 8%.
  • the devulcanisation method of the present invention is preferably assisted by the application of heat.
  • the devulcanisation method of the present invention is preferably assisted by application of a shear force to the mixture.
  • a shear force to the mixture.
  • carbon dioxide helps improve contact of the additives and if present cogents with the rubber material by expanding the volume of the reaction mixture. In addition it may increase the shear force.
  • the contents are preferably heated to a temperature of at least 40°C, suitably at least 50°C, preferably at least 60°C, for example at least 70°C, at least 75°C or at least 80°C.
  • the reaction mixture may be heated to a temperature of up to 150°C, for example up to 130°C, suitably up to 120°C, preferably up to 1 10°C, for example up to 100°C, suitably up to 95°C, for example up to 90°C.
  • the reaction mixture is preferably heated in the reaction vessel for a period of at least 0.1 minutes, preferably at least 0.5 minutes, suitably at least 1 minute. It may be heated in the reaction vessel for a period of up to 30 minutes, suitably up to 20 minutes, preferably up to 10 minutes.
  • reaction mixture is subjected to a shear force.
  • the method of the present invention further involves the use of a processing aid.
  • a processing aid This is suitably delivered to the vessel after it has been charged with the rubber material, additive, carbon dioxide and other optional components.
  • the time for which the reaction mixture is heated in the reaction vessel may be regarded as the reaction time.
  • the processing aid is suitably added after at least 10% of the reaction time has elapsed, suitably after at least 20%, for example at least 30%. Preferably it is added during the period when 50 to 70% of the reaction time has elapsed.
  • a preferred processing aid is virgin rubber, that is rubber which has not previously been used and is not vulcanised. This may be obtained from natural and/or synthetic sources. When virgin rubber is used as a processing aid the method of the present invention this is preferably used in finely divided form.
  • Not all methods of the present invention include the use of virgin rubber as a processing aid. Whether such a processing aid is needed and the amount used depends on the process conditions and the intended subsequent use of the devulcanised product.
  • One standard material prepared by the present invention no processing aid is needed.
  • the processing aid suitably virgin natural rubber is added in an amount of from 2 to 15, preferably 5 to 12 parts by weight per 100 parts of rubber material. Rubber produced by this method may be used to form a material which can be readily formed into sheets.
  • processing aid are added per 100 parts of rubber material.
  • the product produced by this method can be later extruded and a good surface finish on the product may be observed.
  • the method of the present invention may be carried out in any suitable vessel.
  • the method is carried out in an extruder, for example of the type typically used in the manufacture of plastics materials.
  • Suitable extruders for use in devulcanisation processes are known to those skilled in the art and include single screw extruders, twin screw extruders, counter rotating screw extruders, co-rotating screw extruders and combinations thereof.
  • the method of the present invention may be carried out in a standard extruder or a specialist extruder can be used.
  • the reaction mixture may be passed once through a single extruder. It may be passed two or more times through the same extruder. Alternatively it may be passed through a series of different extruders.
  • the extruder is suitably designed to deliver an appropriate shear force to the reaction mixture.
  • the method of the present invention suitably involves charging the extruder with 100 parts by weight of vulcanised waste rubber crumb, from 1 to 5 parts, preferably 2.5 to 3.5 parts of 2- mercaptobenzothiozyl disulfide; from 0.5 to 4 parts, preferably 1 to 1.5 parts of zinc diethyldithiocarbamate; from 0.1 to 1 , preferably 0.2 to 0.5 parts of zinc oxide; from 0.1 to 1 , preferably 0.2 to 0.5 parts of stearic acid; and from 0.5 to 4, preferably 1.5 to 2.5 parts of peptiser.
  • These components may be premixed and are suitably delivered to the extruder via a hopper. In preferred embodiments a substantially homogeneous mixture is fed into the hopper.
  • carbon dioxide in solid form this may also be premixed with the other solid ingredients and delivered to the extruder via a hopper. Alternatively the solid carbon dioxide may be added to the hopper separately.
  • the present invention further provides a modified single screw extruder as described in example 2.
  • the design of this screw helps retain carbon dioxide within the extruder and provides good shear.
  • a devulcanised rubber product obtained by the method of the first aspect.
  • the devulcanised rubber product of the present invention offers significant advantages over devulcanised rubber products of the prior art.
  • the product of the present invention can be used directly in a standard vulcanisation process. No further modification of the material is usually necessary and changes to standard vulcanisation processes are not normally needed.
  • the devulcanised rubber product of the second aspect is suitably a non-uniform free-having solid with no regular shape. It may have a sticky consistency and have an appearance resembling cotton wool.
  • the method of the present invention may be a batch process or a continuous process. Preferably it is a continuous process.
  • the devulcanised rubber product of the second aspect may be fed directly into a vulcanisation apparatus and immediately revulcanised. Suitable revulcanisation methods will be known to the person skilled in the art and include compression moulding, transfer moulding and injection moulding.
  • a third aspect of the present invention provides a revulcanised rubber product obtained by the vulcanisation by a standard technique of the devulcanised rubber product of the second aspect. In some embodiments to obtain the revulcanised rubber of the third aspect, the devulcanised product of the second aspect may be mixed with virgin rubber.
  • the weight ratio of virgin rubber to the product of the second aspect may be from 95:5 to 5:95.
  • the products of the second and third aspects have been found to have superior properties compared with similar products of the prior art and in many cases the properties of the product of the second and third aspects compare favourably with those of virgin rubber.
  • the elongation of the product of the second aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • the elongation of the product of the third aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • Elongation may be measured by standard test method ISO 37 (BS9003, Part A2).
  • the tensile strength of the product of the second aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • the tensile strength of the product of the third aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • Tensile strength may be measured by standard test method IS037 (BS9003, Part A2).
  • the abrasion resistance of the product of the second aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • the abrasion resistance of the product of the third aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • Abrasion resistance may be measured by standard test method IS04649 using the DIN abrader.
  • the compression set of the product of the second aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • the compression set of the product of the third aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • Compression set may be measured by standard test method IS0815 (BS903, Part A6).
  • the tear strength/tear resistance of the product of the second aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • the tear strength/tear resistance of the product of the third aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • Tear strength/tear resistance may be measured by the standard test method ISO 34 (BS903, Part A3).
  • the hardness of the product of the second aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • the hardness of the product of the third aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%. Hardness may be measured by the standard IRHD dead-load instrument test described in IS048 (BS903, Part A26).
  • the resilience of the product of the second aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%.
  • the resilience of the product of the third aspect is at least 50% of that of virgin rubber of the same compound, preferably at least 60%, more preferably at least 70%, for example at least 75%. Resilience may be measured by the standard test method IS04662 for Pendulum tests.
  • the products of the second and third aspects may be used in a wide range of applications for general rubber goods manufacture. It can for example be used in the manufacture of vehicle tyres, gaskets, hoses and seals.
  • Useful products that may be manufactured using the rubber products of the second and third aspects include: various types of tyre, for example cycle tyres, air craft tyre treads, agricultural semi-pneumatic tyres and solid tyres for fork-lift trucks; tyre compounds, for example carcass compounds, side wall compounds and cover strip compounds; conveyor belt covers; wiper blades; blow-out preventors; hoses; soft-linings for example for equipment used to handle slurries and sand blasting; footwear soles and toe cap compounds; trawler bobbins; chemically resistant linings for storage tanks; handle grips; pipe gaskets and seals; drive coupling rubbers; puncture proof tyre inserts; ferrules and chair feet; solid balls for valves; instrument boots; off-shore damp pads; and non metallic springs, for example anti-vibration mountings, engine mounts, bridge bearings, earthquake protectors for buildings, dock fenders, rail track pads and suspension bushes.
  • the devulcanised product of the second aspect may be blended with one or more further components prior to revulcanisation and/or the revulcanised product of the third aspect may be blended with one or more further components.
  • Methods of manufacturing products of this type are well known to those skilled in the art.
  • composition was fed via a hopper into a modified single screw extruder:
  • Vulcanised waste rubber crumb (40 mesh) 100 parts by weight
  • the extruder used can be seen in figure 1 and is described in detail in example 2.
  • Liquid carbon dioxide was delivered at a rate of 200g/hour via inlet valves 5 to provide a concentration inside the extruder equivalent to 4% by mass of the mass of rubber.
  • the extruder was heated to 85°C and the screw rotated at a speed of 15 rpm.
  • the resultant product was revulcanised by a standard technique and found to have the following properties, each measured by the standard tests referred to in the description.
  • the present inventors have developed a modified single screw extruder having the structure shown in cross-section in figure 1 .
  • the extruder comprises a barrel 1 having a screw 2 running throught the centre thereof. Rubber crumb and additives are fed into barrel of the extruder via hopper 3 into a feed zone 4. Liquid carbon dioxide may be delivered to the extruder at injection ports 5. When solid carbon dioxide is used this may be fed into the barrel of extruder via hopper 3.
  • the screw is of cylindrical cross section and has a diameter that varies along its length. At the area of the barrel 4 into which the rubber crumb and additives are delivered (the feed zone) the screw diameter 10 is at its narrowest. The diameter then increases slowly along tapered region 6 (a compression zone) to a maximum at 7.
  • Rotation of the screw causes material to be pushed along the barrel of the extruder in the direction indicated by arrow A.
  • the taper at 6 reduces the volume in the barrel of the extruder able to accommodate material thus causing compression of the material.
  • This compression is continued along region 8 (a high shear zone).
  • a sharp decrease in the screw diameter at 9 provides a decompression zone.
  • the screw then returns to its narrowest dimeter at 10.
  • the modified single screw extruder of the present invention provides a number of small compression zones and high shear zones.
  • Figure 2 shows a single screw extruder of the prior art which comprises a single feed zone, a single compression zone and a single metering zone.
  • the modified single screw extruder of the present invention has been found to provide significant advantages over the screw of the prior art. For example carbon dioxide is retained within the extruder more effectively and the product obtained has significantly improved properties.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Abstract

Cette invention concerne un procédé de dévulcanisation d'un matériau de caoutchouc, ledit procédé comprenant la mise en contact du matériau de caoutchouc avec du dioxyde de carbone et un additif choisi parmi les dithiocarbamates, les thiazoles, les guanidines, les thiurames, les sulfénamides et leurs mélanges.
PCT/GB2011/051113 2010-06-14 2011-06-14 Procédés concernant des produits de caoutchouc WO2011158024A1 (fr)

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Application Number Priority Date Filing Date Title
GB1009901.8A GB2481205A (en) 2010-06-14 2010-06-14 Method for the devulcanisation of a rubber material
GB1009901.8 2010-06-14

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WO2011158024A1 true WO2011158024A1 (fr) 2011-12-22

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014042510A1 (fr) * 2012-09-12 2014-03-20 Sekhar Research Innovations Sdn. Bhd. Procédé de production d'un caoutchouc dévulcanisé et appareil associé
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