Crumb rubber modified bitumen process

Abstract

Described herein is a continuous process for producing a crumb rubber modified bitumen. The resulting crumb rubber modified bitumen (CRMB) product comprises bitumen, crumb rubber and oil. The CRMB product may be used for a variety of applications including chip sealing, cold asphalt mix binder, hot asphalt mix binder and emulsions.

Description

[0001] CRUMB RUBBER MODIFIED BITUMEN PROCESS

[0002] RELATED APPLICATIONS

[0003] This application derives priority from New Zealand patent application number 808187 filed on 13 February 2024 with WIPO DAS code 54ED incorporated herein by reference.

[0004] TECHNICAL FIELD

[0005] Described herein is a crumb rubber modified bitumen process. More specifically, a continuous process is described for producing a crumb rubber modified bitumen. The resulting crumb rubber modified bitumen (CRMB) product from the process comprises bitumen, crumb rubber and oil. The CRMB product may be used for chip sealing and for manufacture of hot or cold asphalt mix binders.

[0006] BACKGROUND ART

[0007] Addressing rubber waste especially from used tyres is a global problem. New Zealand generates about 8 million End of Life (EoL) tyres (passenger car tyre equivalent) annually. In New Zealand, approximately 3.1 million of EoL tyres are consumed in cement kilns as a supplementary fuel for cement production while the majority of the remaining volume of EoL tyres end up in landfill or in stockpiles. Dumped EoL tyres in landfills or stockpiles pose threats to the environment. One of the major threats of tyre stockpiles is the fire risk. Tyre flammability and special characteristics of tyre piles mean that tyre pile fires are extremely difficult to deal with and they can burn for months, cause considerable air pollution and run-off which may contaminate groundwater and soil. Tyre stockpiles are also an ideal habitat for the breeding of insects and rodents carrying diseases. Landfill buried tyres decompose extremely slowly and can leech undesirable toxics compounds.

[0008] This problem is not limited to New Zealand and is a global issue.

[0009] European waste hierarchy identifies reducing, reusing, and recycling as the most effective ways of dealing with wastes with a high impact on reducing the CO2 footprint. Recycling of discarded materials provides industry with an alternative source of raw material and is a means to reduce the demand for virgin materials and their extraction, transport and processing. Re-use of waste endeavours to reduce overall emissions. With respect to EoL tyres, the recovery of used tyres happens in two different ways: energy recovery and material recovery (e.g. granulate recovery). The energy recovery (for example as a cement kiln fuel noted above) happens through combustion and thermochemical processes such as pyrolysis and gasification (economic viability has not yet been proven). For the energy recovery process, the EoL tyres are normally required to be chipped.

[0010] In a granulate recovery process, after EoL tyres are chipped, the chips are further ground and their steel and fabric are separated. This product is milled and the final product is then called Crumb Tyre Rubber (CTR). The CTR is used in a variety of civil engineering applications such as a rubber modified bitumen as a mixture for pavements, flooring for playgrounds and sports stadiums, shock absorbing mats, paving blocks and roofing materials.

[0011] The use of alternative fuels for cement production has both supporters and opponents. The supporters claim that these fuels firstly reduce net CO2 footprint from the cement production and secondly are diverted from landfills, because, they are carbon neutral (in case of biomass) or have higher calorific values compared to fossil fuels (in case of waste tyres). Opponents argue that incineration of alternative fuels generates CO2 and toxic emissions. The toxic emissions are hard to remove by the conventional methods used in the industry. For example, waste tyre incineration generates dioxins and furans, Polycyclic Aromatic Hydrocarbons (PAHs), and 1-3 butadiene which are major air pollutants.

[0012] EoL tyres are a valuable source of rubber which are already used to a limited extent in road surfacing applications. That said, the use of crumb rubber in road surfacing applications in New Zealand is very low despite its popularity in other countries like Australia and South Africa.

[0013] From 2017 to 2022, the crumb rubber use in road surfacing applications in Australia has increased from 11,000 tonne to 23,000 tonnes per annum. This increase is still small in proportion to the extent of EoL tyres produced annually.

[0014] Adding a small percentage of a polymer (typically up to 5wt% but more usually 3-4wt%)to a bituminous binder will significantly improve the properties of the bitumen. The changes are commonly greater elastic recovery, higher softening point, greater viscosity and greater cohesive strength.

[0015] There are two main types of polymers currently used in roading applications being plastomers and elastomers. Elastomers are much more common. Elastomers are either thermoplastic or thermoset. Thermoplastic elastomers melt at lower temperatures so their recovery and reuse are much easier. Styrene-butadiene-styrene (SBS) is a thermoplastic elastomer that is commonly used for production of polymer. However, most road owners cannot afford the use of polymer modified bitumen due to the high cost of the polymers. Crumb rubber from EoL tyres are thermoset elastomers and much lower in cost than virgin polymers such as SBS.

[0016] Chipsealing is applied to around 80-85% of the road surfacing in New Zealand each year. The following issues are reported for crumb rubber use in chipsealing applications in New Zealand via prior art crumb rubber containing products and methods:

[0017] Prior art crumb rubber bitumen processes require additional construction requirements such as pre-coating and use of liquid additives (e.g. compatible cutback agents) to improve crumb rubber bitumen mixture compatibility, aggregate adhesion, and workability. Without these additional inputs, the products are unworkable or not commercially viable and even with these additional inputs the commercial viability of the art products and methods may be marginal;

[0018] Spray application of crumb rubber bitumen prior art products for chipsealing is unpleasant / low safety due to emission of odorous fumes and high temperatures (>200°C) needed;

[0019] Prior art crumb rubber bitumen products may lack stability during storage and transport;

[0020] Prior art crumb rubber bitumen may only comprise very small amounts of crumb rubber (<5% by weight);

[0021] Prior art crumb rubber bitumen products may struggle to reach desired construction grades / standards e.g. struggle to reach an enhanced penetration grade bitumen or performance grade, e.g. PG-64 (Very Heavy Traffic "V") bitumen or PG 64 Extreme "E" Prior art crumb rubber bitumen products may struggle to be cost effective.

[0022] Further aspects and advantages of the crumb rubber modified bitumen process will become apparent from the ensuing description that is given by way of example only.

[0023] SUMMARY

[0024] Described herein is a continuous process for producing a crumb rubber modified bitumen. The resulting crumb rubber modified bitumen (CRMB) product from the process comprises bitumen, crumb rubber and oil. The CRMB product may be used for a variety of applications including chip sealing, cold asphalt mix binder and hot asphalt mix binder.

[0025] In a first aspect, there is provided a process configured for continuous production of a crumb rubber modified bitumen (CRMB) product by: selecting crumb rubber and oil; mixing the crumb rubber and oil at a temperature of at least 80°C to form a premix slurry; adding the pre-mix slurry and bitumen to a reactor to produce a crumb rubber modified bitumen product, the pre-mix slurry and bitumen undergoing reaction at a temperature of at least 200°C and a pressure greater than 1 bar; removing a portion of the crumb rubber modified bitumen product from the reactor on a continuous basis.

[0026] In a second aspect, there is provided a process configured for continuous production of a crumb rubber modified bitumen (CRMB) product by: selecting bitumen, crumb rubber and oil; mixing the bitumen, crumb rubber and oil at a temperature of at least 80°C to form a pre-mix slurry; adding the pre-mix slurry to a reactor to produce a crumb rubber modified bitumen product, the pre-mix slurry undergoing reaction at a temperature of at least 200°C and a pressure greater than 1 bar; removing a portion of the crumb rubber modified bitumen product from the reactor on a continuous basis.

[0027] In a third aspect, there is provided a crumb rubber modified bitumen (CRMB) product produced by the process substantially as described above comprising: bitumen, crumb rubber and oil.

[0028] In a fourth aspect, there is provided a chip sealing mix comprising: crumb rubber modified bitumen product produced by the process substantially as described above; and, at least one cutback agent.

[0029] In a fifth aspect, there is provided a hot asphalt mix binder comprising: crumb rubber modified bitumen product produced by the process substantially as described above; and at least one adhesion agent.

[0030] In a sixth aspect, there is provided a cold asphalt mix binder comprising: crumb rubber modified bitumen product produced by the process substantially as described above; at least one adhesion agent; and at least one cutback agent.

[0031] In a seventh aspect, there is provided a bitumen emulsion comprising: bitumen; water; surfactant; pH modifier agents; and crumb rubber modified bitumen product produced by the process substantially as described above; at least one adhesion agent; and at least one cutback agent.

[0032] The process and CRMB product from the process described herein may provide a number of advantages over the prior art. Examples may be use of a waste material (EoL tyres) and the related outcomes associated with this. The CRMB product may also be versatile in that it may be used for a number of different applications. Further, when used with the cutback agent of WO2022 / 191718, spraying application may be completed at lower temperatures than prior art products (with or without crumb rubber present) reducing energy needed and increasing safety. Further advantages are described below.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further aspects of the crumb rubber modified bitumen process will become apparent from the following description that is given by way of example only and with reference to the accompanying drawings in which:

[0035] Figure 1 illustrates a photograph of the results of a test to check for chip adhesion using a crumb rubber modified bitumen product from the process mixed with adhesion agent and cutter; illustrates a photograph of the results of a test to check for chip adhesion using a crumb rubber modified bitumen product the process mixed with cutter alone; and llustrates a schematic process flow diagram of one example of the crumb rubber modified bitumen process. DETAILED DESCRIPTION

[0036] As noted above, described herein is a continuous process for producing a crumb rubber modified bitumen. The resulting crumb rubber modified bitumen (CRMB) product comprises bitumen, crumb rubber and oil. The CRMB product may be used for a variety of applications including chip sealing, cold asphalt mix binder and hot asphalt mix binder.

[0037] For the purposes of this specification, the term 'about' or 'approximately' or 'substantially' and grammatical variations thereof mean a quantity, level, degree, value, number, frequency, percentage, dimension, size, amount, weight or length that varies by as much as 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% to a reference quantity, level, degree, value, number, frequency, percentage, dimension, size, amount, weight or length.

[0038] The term 'comprise1and grammatical variations thereof shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements.

[0039] Process

[0040] In a first aspect, there is provided a process configured for continuous production of a crumb rubber modified bitumen (CRMB) product by: selecting crumb rubber and oil; mixing the crumb rubber and oil at a temperature of at least 80°C to form a premix slurry; adding the pre-mix slurry and bitumen to a reactor to produce a crumb rubber modified bitumen product, the pre-mix slurry and bitumen undergoing reaction at a temperature of at least 200°C and a pressure greater than 1 bar; removing a portion of the crumb rubber modified bitumen product from the reactor on a continuous basis.

[0041] In the above first aspect process, bitumen need not be added to the pre-mix slurry. Bitumen may instead be added to the pre-mix slurry of crumb rubber and oil in the reactor.

[0042] In a second aspect, there is provided a process configured for continuous production of a crumb rubber modified bitumen (CRMB) product by: selecting bitumen, crumb rubber and oil; mixing the bitumen, crumb rubber and oil at a temperature of at least 80°C to form a pre-mix slurry; adding the pre-mix slurry to a reactor to produce a crumb rubber modified bitumen product, the pre-mix slurry undergoing reaction at a temperature of at least 200°C and a pressure greater than 1 bar; removing a portion of the crumb rubber modified bitumen product from the reactor on a continuous basis.

[0043] In the above second aspect process, bitumen may be added, at least to some extent, to the pre-mix slurry. Bitumen in this process need not be added to the reactor with the pre-mix slurry although, may be added if bitumen concentration needs to be increased beyond that present in the pre-mix slurry.

[0044] Raw Materials

[0045] The bitumen added to the pre-mix slurry may be in liquid or semi-liquid form.

[0046] The crumb rubber may be added to the pre-mix slurry as a powder or granular composition.

[0047] The oil may be added to the pre-mix slurry as a liquid or semi-liquid form.

[0048] Pre-mix Slurry Composition:

[0049] The pre-mix slurry may comprise:

[0050] 0-60% by weight bitumen;

[0051] 30-50% by weight crumb rubber; and,

[0052] 10-70% by weight oil.

[0053] As noted above, the amount of bitumen may in fact be zero or, at an amount lower than the bitumen amount in the final CRMB product. Adding bitumen to the pre-mix slurry may be optional and may be completed to facilitate pumping and movement of the pre-mix slurry to the reactor post mixing. The amount of bitumen added may also depend on the amount and type of oil used.

[0054] In the inventor's experience it may be useful to add bitumen to the pre-mix slurry when the oil to crumb rubber ratio is less than 1. Bitumen, in this example, may be added to the pre-mix slurry to ease pumping of the pre-mix slurry post mixing. If bitumen is added to the pre-mix slurry, it may be heated prior to mixing to at least 140°C prior to, or during, pre-mix slurry mixing. The bitumen added to the pre-mix slurry may in one example, be heated to 160-170°C.

[0055] Oil

[0056] The oil may be a high flash point petroleum oil with at least 14 carbon atoms.

[0057] The oil may be a vegetable derived oil. The vegetable derived oil may be a recycled cooking oil.

[0058] The oil may be recovered lubrication oil.

[0059] Recycled oil such as recovered lubrication oil or a recycled cooking oil may be advantageous as they are comparably cost effective and sustainable raw materials, essentially being waste or low value materials.

[0060] The quantity and type of oil used may depend on the grade of bitumen to be produced. The inventor's understanding of the mechanisms behind oil, crumb rubber and bitumen interaction are discussed further below.

[0061] Pre-mixing

[0062] Pre-mixing of the pre-mix slurry may occur in a mixer. The mixer may be a ribbon mixer.

[0063] Slurry

[0064] As noted elsewhere, the pre-mix may be a pre-mix slurry. The term 'slurry' as used herein refers to a semi-liquid mixture of liquid or semi-liquid bitumen (if used), liquid or semi-liquid oil and particles of crumb rubber mixed into the bitumen and oil.

[0065] Reactor

[0066] The reactor may be a reactor that comprises internal mixers to create a high shear turbulent environment that the pre-mix slurry passes through while in the reactor.

[0067] The reactor may be that described in US 7,871,509 or as published in WO2014 / 035262. These types of reactors may be characterised by several factors including the temperature of the reactor contents, the pressure of the reactor contents and the presence of turbulence and mixing within the reactor.

[0068] The temperature of the pre-mix slurry in the reactor may be from 200°C to 250°C.

[0069] The pressure in the reactor may be greater than 1 bar. The pressure in the reactor may be greater than 1, or 2, or 3, or 4, or 5 bar. The pressure in the reactor may be 6-7 bar.

[0070] The pre-mix slurry, whilst in the reactor, may circulate through the reactor via pumps that subject the premix to high shear mixing.

[0071] The process may operate on a continuous basis with pre-mix slurry fed to the reactor and CRMB product being removed from the reactor both at a continuous pace or flow rate.

[0072] A residence time of pre-mix slurry in the reactor may be at least 1 minute. The residence time of pre-mix slurry in the reactor may be from 5 to 10 minutes. The term 'residence time' as used herein, refers to the time that a particle of pre-mix slurry spends in the reactor from entry to exit. It should be noted that this residence time may be an average residence time. Some pre-mix slurry and extra bitumen if added separately, may spend longer in the reactor whilst some pre-mix slurry and extra bitumen may travel quicker through the reactor. As noted above, the flow through the reactor may be turbulent and hence different particles of pre-mix slurry and added bitumen if used, may travel through the reactor at different speeds. The residence time may also be a function of reactor size, layout and volume hence, the residence time described may vary beyond (faster or slower) the example residence times noted.

[0073] Additional Bitumen

[0074] Additional bitumen may be added to the pre-mix slurry while the pre-mix slurry is in the reactor. Additional bitumen may be added at a rate sufficient to achieve a total bitumen content in the crumb rubber modified bitumen product of 70-90% by weight.

[0075] The addition of bitumen may depend on the amount of bitumen used to form the pre-mix slurry.

[0076] Degassing

[0077] During the main process, some fumes including condensable and non-condensable gases will be generated which may be separated from the reactor, for example using a degassing tank. Gas Addition

[0078] Air or an oxygen rich gas may be added to the pre-mix slurry during reacting of the pre-mix slurry in the reactor

[0079] Addition of air or oxygen rich gas may act to accelerate the chemical reaction between oil, bitumen and the crumb rubber particles. Oxygen may act as a cross linking agent between the reactants and therefore facilitates chemical interactions between the crumb rubber particles and the bitumen.

[0080] Air or other oxygen rich gas may be added to the reactor at a rate of 0.5-4 litres per minute, or at a rate of around 0.5-1.5 litres per minute.

[0081] Additional Reagents

[0082] Post collecting of the resulting CRMB product from the reactor, additional reagents may be added to the CRMB product. The additional reagents may comprise at least one cutback agent, at least one adhesion agent, or both at least one cutback agent and at least one adhesion agent.

[0083] Cutback Agent Addition

[0084] Cutback agent may be added. The cutback agent may be one of many art cutback agents although the cutback agent as published in WO2022 / 191718 may be particularly useful to mix with the above described CRMB product. The contents of WO2022 / 191718 are therefore incorporated herein by reference.

[0085] Specifically, the cutback agent of WO2022 / 191718 may comprise a mixture of: an alkyl ester of a fatty acid compound, and a phenyl alkyl ester benzoic acid compound, and an ether alcohol compound and their esters.

[0086] In the inventor's experience, the cutback agent described in WO2022 / 191718 has excellent / complete miscibility in the above described CRMB product. In addition, through use of the above cutback agent, the spray temperature needed to apply the CRMB product may be less than that common with art cutback agent (>200°C). In the inventor's experience, temperatures of 150-170°C may be sufficient to spray the above CRMB product when the above cutback agent is added to the CRMB product. Where added, the concentration of cutback agent in the CRMB product may be less than 10 parts per hundred (PPH) cutback agent by weight. A further advantage of using the cutback agent of WO2022 / 191718 is that any unpleasant odours may be avoided or masked by the more pleasant odour of the cutback agent.

[0087] Adhesion Agent

[0088] Adhesion agent may be added. Adhesion agents suitable for hot asphalt mix, warm asphalt mix and cold asphalt mix may be added. The adhesion agents may be selected from: amine based adhesion agents, silane based adhesion agents, organo phosphor based adhesion agents, oil amino esters adhesion agents, and combinations thereof

[0089] CRMB Product

[0090] In a third aspect, there is provided a crumb rubber modified bitumen (CRMB) product produced by the process substantially as described above comprising: bitumen, crumb rubber and oil.

[0091] The CRMB product may comprise 70-90% by weight bitumen; 5-20% crumb rubber; and 3-20% oil. For example, the CRMB product may substantially comprise 75% by weight bitumen, 9% by weight crumb rubber and 16% by weight oil. In another example, the CRMB product may substantially comprise 85% by weight bitumen, 12% by weight crumb rubber and 3% by weight oil.

[0092] The CRMB product may be a polymer modified bitumen.

[0093] The bitumen grade of the final CRMB product may depend on the oil and crumb rubber ratio along with the type of oil used. For example, by using recovered lubricant oil, a PG-64 (Heavy Traffic "H") grade CRMB product can be produced by using an oil to crumb rubber ratio of 1 parts oil to 4 parts crumb rubber by weight.

[0094] The reason why the ratio of oil to crumb rubber influences CRMB product grade is understood by the inventors to be related to the structure of bitumen. Bitumen is mainly composed of asphaltenes and maltenes. Asphaltenes are the solid part of bitumen and maltenes are the oil part of bitumen. Crumb rubber particles at sizes less than 1 mm may be fluffy solid particles with a density of about 350-450 kg / m3. The density of oil may vary from 800 to 1000 kg / m3while the density of bitumen may vary from 950 to 1100 kg / m3. As crumb rubber has a sponge like texture, it absorbs oil or the bitumen maltenes significantly. To compensate for maltene absorption by crumb rubber particles, sufficient amount of oil must be added to still provide a final CRMB product with the desired attributes.

[0095] Further, crumb rubber particles may become denser due to oil absorption and may disperse better in bitumen as a result of the oil absorption.

[0096] The type of additional oil added may also impact the properties of the final CRMB product. For example, vegetable oils may increase the elasticity of the final CRMB product to a greater extent than observed for petroleum based oils.

[0097] Chip Sealing Mix

[0098] In a fourth aspect, there is provided a chip sealing mix comprising: crumb rubber modified bitumen product produced by the process substantially as described above; and, at least one cutback agent.

[0099] The at least one cutback agent may comprise a mixture of: an alkyl ester of a fatty acid compound; and a phenyl alkyl ester benzoic acid compound; and an ether alcohol compound and their esters.

[0100] As noted above, the CRMB product may be used in chip sealing applications using compatible cutback agents such as the cutback agent described in WO2022 / 191718. The amount of cutback agent used may vary depending on when the chip sealing product is to be used and / or the ambient temperature and also the viscosity of the bitumen. For example, in New Zealand, approximately 3 parts per hundred (PPH) cutback agent may be needed to form the chip sealing binder with 130 / 150 penetration grade of bitumen at ambient temperature of 25°C for resealing. . Alternatively, in winter with cooler temperatures, approximately 8 PPH cutback agent may be used to form the chip sealing binder with polymer modified bitumen PG-64H at ambient temperature of 15°C for resealing.

[0101] Hot Asphalt Mix

[0102] In a fifth aspect, there is provided a hot asphalt mix binder comprising: crumb rubber modified bitumen product produced by the process substantially as described above; and at least one adhesion agent. The at least one adhesion agent may be selected from: an amine based adhesion agent, a silane based adhesion agent; an organo phosphor based adhesion agent, a tall oil amino esters adhesion agent, and combinations thereof.

[0103] As noted above, the CRMB product may be used for hot asphalt mix binder. In this case, the hot asphalt mix binder may comprise approximately 95-99.9% by weight CRMB product and approximately 0.1-5% by weight adhesion agent.

[0104] A hot asphalt mix may be produced by mixing together 5-7% by weight of the hot asphalt mix binder noted above with aggregates and fines comprising 93-95% by weight.

[0105] Cold Asphalt Mix

[0106] In a sixth aspect, there is provided a cold asphalt mix binder comprising: crumb rubber modified bitumen product produced by the process substantially as described above; at least one adhesion agent; and at least one cutback agent.

[0107] The at least one adhesion agent may be selected from: an amine based adhesion agent, a silane based adhesion agent, an organo phosphor based adhesion agent, a tall oil amino ester adhesion agent, and combinations thereof; and the at least one cutback agent may comprise a mixture of: an alkyl ester of a fatty acid compound, and a phenyl alkyl ester benzoic acid compound, and an ether alcohol compound and their esters.

[0108] The CRMB product may further be used as noted for production of cold asphalt mix binder. In this case the cold asphalt mix binder may comprise for example, 75% bitumen, 5% adhesion agent and 20% cutback agent.

[0109] A cold asphalt mix may be produced by mixing together 5-7% by weight of the cold asphalt mix binder noted above with aggregates and fines comprising 93-95% by weight.

[0110] Bitumen Emulsions

[0111] In a seventh aspect, there is provided a bitumen emulsion comprising: bitumen; water; surfactant; pH modifier agents; and crumb rubber modified bitumen product produced by the process substantially as described above; at least one adhesion agent; and at least one cutback agent.

[0112] The described crumb rubber modified bitumen product is similar to a polymer modified bitumen without any crumb left in the bitumen. This makes it a consistent product. The crumb rubber modified bitumen product can as a result, be used for manufacture of polymer modified bitumen emulsion using the same approach as polymer modified bitumen products manufactured from virgin polymers.

[0113] Advantages

[0114] Selected examples of advantages of the above described crumb rubber modified bitumen process and resulting CRMB product may include one or more of the following:

[0115] Uses a waste material (EoL tyres)

[0116] Use in this manner is more environmentally friendly than as a fuel Avoids / minimises landfill dumping and stockpiles of tyres and the associated problems of dumping and stockpiling

[0117] Simple and economic process of manufacture

[0118] Resulting product has desired grade and capability for wide use

[0119] May be used for the production of hot asphalt mix, warm asphalt mix and cold asphalt mix applications

[0120] May be used for the production of bitumen emulsions

[0121] May be used for the production of hot asphalt mix, warm asphalt mix and cold asphalt mix.

[0122] Uses a higher amount of crumb rubber than other art CRMB products which can be used with the same spraying systems as conventional bitumen

[0123] Uses optionally recycled oils as well therefore increasing the environmental friendliness of the method and product

[0124] Product is stable in storage and transport When used with the cutback agent of WO2022 / 191718, spraying can be completed at lower temperatures than art bitumen products (with or without crumb rubber present) and the unpleasant odour of art spraying is avoided or masked by the cutback agent.

[0125] The embodiments described above may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features.

[0126] Further, where specific integers are mentioned herein which have known equivalents in the art to which the embodiments relate, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0127] WORKING EXAMPLES

[0128] The above described crumb rubber modified bitumen process and CRMB product are now described by reference to specific examples.

[0129] EXAMPLE 1

[0130] In this example a specially designed standard grade bitumen (similar to 130 / 150 penetration grade or PG 58 (Standard Traffic "S") performance grade) using crumb rubber modified bitumen is described conforming to NZTA M01-A Specification for Performance Graded Asphalt Binder.

[0131] The product is manufactured using a reactor as described in WO2014 / 035262.

[0132] The CRMB product described in this example: comprises 10 to 30% of recycled materials; is highly stable during transportation and storage; is highly compatible with cutters / cutback agents including that described in WO2022 / 191718; can be sprayed using regular spraying systems; can be sprayed at regular spraying temperatures (150°C-170°C) if the cutback agent of WO2022 / 191718 is used; and the nuisance smell during spraying will be masked if the cutback agent of WO2022 / 191718 is used.

[0133] The resulting technical properties of this CRMB product are described further in Table 1 below. Table 1 - Technical Properties of Example 1 CRMB:

[0134] EXAMPLE 2 In this example a specially designed performance grade bitumen (PG 64(H)) using crumb rubber modified bitumen product is described conforming to AASHTO M332.

[0135] The CRMB product is manufactured using a reactor as described in WO2014 / 035262.

[0136] The CRMB product described in this example: contains 15 to 20% of recycled materials; - is highly stable during transportation and storage; is highly compatible with cutters / cutback agents including that described in WO2022 / 191718; can be sprayed using regular spraying systems; can be sprayed at regular spraying temperatures (such as 165°C to 180°C) if the cutback agent of WO2022 / 191718 is used; and the nuisance smell during spraying will be masked if the cutback agent of WO2022 / 191718 is used.

[0137] The resulting technical properties of this CRMB product are described further in Table 2 below. Table 2 - Technical Properties of Example 2 CRMB:

[0138] EXAMPLE 3 In this example, a method of producing a PG64 (heavy (H)) CRMB product is described. Test data is shown for the final product along with an example of addition of a cutback agent and the results of an adhesion test. For the example, a lab scale batch type reactor based on the commercial reactor described in WO2014 / 035262 is used. The processing time in the lab scale batch reactor varies from 1 hour to 3 hours whilst the residence time of the commercial continuous reactor is in the order of minutes (5-10 min).

[0139] 511.80g of 60 / 70 grade bitumen was melted (to 160°C-170°C) and mixed with 72.16g of crumb rubber and 18.04g of recovered lubricant oil to form a pre-mix slurry. The pre-mix slurry was mixed well at this small scale using a pre-heated metal rod. The pre-mix slurry was then transferred into a high shear bitumen reactor. The pre-mix slurry was heated to 200°C and under 6-7 bar pressure in the reactor. The pre-mix slurry circulates in the reactor initially with low speed mixing at 500 RPM. Once the pre-mix slurry attained a temperature of approximately 200°C, air was added to the circulating mixture at a rate of 2 litre / min air and the stirring speed increased to 1000 RPM. These parameters were then kept constant for approximately 3 hours. The resulting CRMB product was collected from the reactor.

[0140] Samples were taken from the CRMB product to test for the viscosity, penetration, rheological analysis (using Dynamic Shear Rheometer (DSR)), segregation test, and rutting properties after short term and long term aging using Rolling Thin Film Oven (RTFO) and Pressurised Aging Vessel (PAV).

[0141] For Performance Grade (PG) bitumen specification, the American Association of Highway and Transportation Officials (AASHTO) M 332 (Performance-Graded Asphalt Binder Using Multiple Stress Creep Recovery (MSCR) Test) have been followed. This specification is the basis for NZTA M01-A (Notes to the Specification Performance-Graded Asphalt Binders). The tested properties are summarised in Table 3 below.

[0142] Table 3 - The tested properties for the CRMB Product of Example 3

[0143] A sample of the CRMB product above was mixed with 8 parts per hundred (PPH) of the cutback agent of WO2022 / 191718 using a hand mixer for approximately 2 minutes. The viscosities at different temperatures were tested using a rotational viscometer and the results shown in

[0144] Table 4 below.

[0145] Table 4 - Viscosity of CRMB Product, PG 64(Heavy), with 8 PPH Cutback Agent

[0146] A Vialit Adhesion test was completed to test the impact of cutback agent and adhesion use on adhesion of the above CRMB product to chipseal.

[0147] As shown in Figure 1 and Figure 2, adhesion agent made a significant difference to adhesion. Figure 1 shows the resulting adhesion of aggregate or chip 10 to a CRMB product sample mixed with 0.5 PPH amine-based adhesion agent and 8 PPH cutback agent shown generally using arrow 20. In this case, 95% of chips 10 were retained / adhered. By contrast, as shown in Figure 2, the resulting adhesion for a CRMB product sample mixed with 8 PPH cutback agent compound only and no adhesion agent only achieved 11% chip 10 retention / adherence.

[0148] EXAMPLE 4

[0149] In this example, a method of producing a PG58 (Standard Traffic "S") CRMB product is described. Test data is shown for the final CRMB product. For the example, a lab scale batch type reactor based on the commercial reactor described in WO2014 / 035262 is used. The processing time in the lab scale batch reactor varies from 1 hour to 3 hours whilst the residence time of the commercial continuous reactor is in the order of 5-10 minutes.

[0150] 504.53 g of 60 / 70 grade bitumen was melted (to 160-170°C) and mixed with 55.5g of crumb rubber and 129.4 g of recycled lubrication oil to form a pre-mix slurry. The pre-mix slurry was mixed well at this small scale using a pre-heated metal rod. The pre-mix slurry was then transferred into a high shear bitumen reactor. The pre-mix slurry was heated to 200°C and under 6-7 bar pressure in the reactor. The pre-mix slurry circulates in the reactor initially with low speed mixing at 500 RPM. Once the pre-mix slurry attained a temperature of approximately 200°C, air was added to the circulating mixture at a rate of 0.5 litre / min air and the stirring speed increased to 1000 RPM. These parameters were then kept constant for approximately 2 hours.

[0151] The resulting CRMB product was collected from the reactor.

[0152] Samples were taken from the CRMB product to test for viscosity, penetration, DSR, segregation, and RTFO. For performance grade bitumen (PG ) specification, the AASHTO M 332-20 guidelines were followed which is the basis for NZTA M01-A.

[0153] The tested properties are summarised in Table 5 below.

[0154] Table 5 - The tested properties for the CRMB Product of Example 4

[0155] EXAMPLE 5

[0156] In this example, the manufacturing process is described in more detail with reference to Figure 3.

[0157] The process for manufacture of the CRMB product comprises of two main steps:

[0158] [A] The crumb rubber / polymer pre-mix slurry step 400 - In the pre-mix slurry step 400, crumb rubber and / or virgin polymer (natural or synthesised) 300 is fed to a mixer 400 (e.g. a ribbon mixer) and is blended with appropriate proportions of recovered lubrication oil (RLO) 200 and bitumen 100 to make a pre-mix slurry 600. The pre-mix slurry 600 can be 30-50% of crumb rubber 300 with or without other types of polymer, 10%-70% of recycled lubricant oil 200 and 0%-60% of bitumen 100. In one example, the pre-mix slurry comprises 0% bitumen, 35% crumb rubber and 65% oil all by weight. In another example, the pre-mix slurry comprises 50% bitumen, 40% crumb rubber and 10% oil all by weight. Additional bitumen 700 may be added to the reactor 800 once the pre-mix slurry 600 is mixed together and in the reactor 800.

[0159] [B] The main reacting step - the pre-mix slurry 600 is directed through a pump 500 (an appropriate slurry pump such as a Progressive Cavity Pump) to the reactor 800. The reactor 800 as noted elsewhere may be a reactor with high shear such as that described in the art. The pre-mix slurry is optionally mixed with further bitumen 700 in the reactor 800 and is processed under high temperature (>200°C) and high pressure (>6 bar). Air or an oxygen source (not shown) can be injected to the reactor 800 to adjust reacting of the pre-mix slurry.

[0160] The process flow is summarised in Table 6 below and in the process flow diagram of Figure 3.

[0161] Table 6 - Process flow table CRMB process - For a PG64 H CRMB product (termed 64H PMB

[0162] Product below)

[0163] Aspects of the crumb rubber modified bitumen process have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the claims herein.

Claims

WHAT IS CLAIMED IS:

1. A process configured for continuous production of a crumb rubber modified bitumen (CRMB) product by: selecting bitumen, crumb rubber and oil; mixing the bitumen, crumb rubber and oil at a temperature of at least 80°C to form a pre-mix slurry; adding the pre-mix slurry to a reactor to produce a crumb rubber modified bitumen product, the pre-mix slurry undergoing reaction at a temperature of at least 200°C and a pressure greater than 1 bar; and removing a portion of the crumb rubber modified bitumen product from the reactor on a continuous basis.

2. A process configured for continuous production of a crumb rubber modified bitumen (CRMB) product by: selecting bitumen, crumb rubber and oil; mixing the bitumen, crumb rubber and oil at a temperature of at least 80°C to form a pre-mix slurry; adding the pre-mix slurry to a reactor to produce a crumb rubber modified bitumen product, the pre-mix slurry undergoing reaction at a temperature of at least 200°C and a pressure greater than 1 bar; and removing a portion of the crumb rubber modified bitumen product from the reactor on a continuous basis.

3. The process as claimed in claim 1 or claim 2 wherein the pre-mix slurry comprises:0-60% by weight bitumen;30-50% by weight crumb rubber; and10-70% by weight oil.

4. The process as claimed in any one of the above claims wherein the oil is a high flash point petroleum oil with at least 14 carbon atoms.

5. The process as claimed in any one of claims 1 to 3 wherein the oil is a vegetable derived oil.

6. The process as claimed in any one of claims 1 to 3 wherein the oil is recovered lubrication oil.

7. The process as claimed in any one of the above claims wherein the reactor comprises internal mixers to create a high shear turbulent environment that the pre-mix slurry passes through while in the reactor.

8. The process as claimed in any one of the above claims wherein the temperature of the pre-mix slurry in the reactor is from 200°C to 250°C.

9. The process as claimed in any one of the above claims wherein the pressure in the reactor is greater than 1 bar.

10. The process as claimed in any one of the above claims wherein a residence time of premix slurry in the reactor is at least 1 minute.

11. The process as claimed in any one of the above claims wherein additional bitumen is added to the pre-mix slurry while the pre-mix slurry is in the reactor at a rate sufficient to achieve a total bitumen content in the crumb rubber modified bitumen product of 70- 90% by weight.

12. The process as claimed in any one of the above claims wherein air or an oxygen rich gas is added to the reactor contents during reacting of the pre-mix slurry in the reactor.

13. A crumb rubber modified bitumen (CRMB) product produced by the process as claimed in any one of the above claims comprising:70-90% by weight bitumen;5-20% crumb rubber; and3-20% oil.

14. A chip sealing mix comprising: crumb rubber modified bitumen product produced by the process as claimed in any one of claim 1-12; and at least one cutback agent.

15. The chip sealing mix as claimed in claim 14 wherein the at least one cutback agent comprises a mixture of: an alkyl ester of a fatty acid compound, and a phenyl alkyl ester benzoic acid compound, and an ether alcohol compound and their esters.

16. A hot asphalt mix binder comprising: crumb rubber modified bitumen product produced by the process as claimed in any one of claims 1-12; and at least one adhesion agent.

17. The hot asphalt mix binder as claimed in claim 16 wherein the at least one adhesion agent is selected from: an amine based adhesion agent, a silane based adhesion agent;an organo phosphor based adhesion agent, a tall oil amino ester adhesion agent, and combinations thereof.

18. A cold asphalt mix binder comprising: crumb rubber modified bitumen product produced by the process as claimed in any one of claims 1-12; at least one adhesion agent; and at least one cutback agent.

19. The cold asphalt mix binder as claimed in claim 18 wherein: the at least one adhesion agent is selected from: an amine based adhesion agent, a silane based adhesion agent, an organo phosphor based adhesion agent, a tall oil amino ester adhesion agent, and combinations thereof; and the at least one cutback agent comprises a mixture of: an alkyl ester of a fatty acid compound, and a phenyl alkyl ester benzoic acid compound, and an ether alcohol compound and their esters.

20. A bitumen emulsion comprising: bitumen; water; a surfactant; pH modification agents; and crumb rubber modified bitumen product produced by the process as claimed in any one of claims 1-12; at least one adhesion agent; and at least one cutback agent.

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