Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L95/00—Compositions of bituminous materials, e.g. asphalt, tar, pitch
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/01—Hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
  • C08L25/02—Homopolymers or copolymers of hydrocarbons
  • C08L25/04—Homopolymers or copolymers of styrene
  • C08L25/08—Copolymers of styrene
  • C08L25/10—Copolymers of styrene with conjugated dienes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2555/00—Characteristics of bituminous mixtures
  • C08L2555/40—Mixtures based upon bitumen or asphalt containing functional additives
  • C08L2555/80—Macromolecular constituents
  • C08L2555/84—Polymers comprising styrene, e.g., polystyrene, styrene-diene copolymers or styrene-butadiene-styrene copolymers

Definitions

• This invention relates to a polymer-modified asphalt composition which is primarily useful in road paving.
• the composition allows for development of the desired strength without carrying out curing.
• polymer- modified asphalt uses a thermoplastic elastomer, e.g. styrene-butadiene-styrene block copolymer (SBS), as a strengthening agent and is generally used in heavy traffic road surfaces.
• SBS styrene-butadiene-styrene block copolymer
• the maturing process has been a limitation in the production of polymer-modified asphalt. As this maturing process must be maintained for 1 to 3 days at 160-180°C in a large maturing tank, large-scale capital investment is required and the burden on the environment has become a problem as it is energy intensive. In addition, if the demand for polymer-modified asphalt for road surfaces is high and there is rapid, large-scale demand for polymer- modified asphalt, the supply would be delayed since a period of 1 to 3 days is required for the maturing process and there is the problem that road surface construction would be delayed.
• the present inventors have sought to provide a polymer-modified asphalt composition in which the softening point can be lowered whilst maintaining a high rut resistance (DS value) without post-production curing in order to shorten the lead time from asphalt production to delivery on site.
• the inventors have conducted intensive studies and focused on lowering the softening point whilst maintaining a high rut resistance (DS value) without post-production curing by optimising the styrene- based thermoplastic elastomer that is added to the polymer-modified asphalt.
• the present invention provides a polymer-modified asphalt composition characterised by containing base asphalt, from 3 to 6wt% of a
• thermoplastic elastomer which is a mixture of a first styrene-based thermoplastic elastomer having a 25% toluene solution viscosity in the range of from 3,000 to
• thermoplastic elastomer having a 25% toluene solution viscosity in the range of from 500 to 2,500mPa «s at 25°C, and from 0.3 to 2wt% of a polycyclic diterpene of carbon number 20 and having a carboxyl group, wherein the content by percentage of the first styrene thermoplastic elastomer in the thermoplastic elastomer is 60-80wt%.
• the inventors have shown that, by mixing a first styrene-based thermoplastic elastomer having a 25% toluene solution viscosity in the range of 3,000- 6,000mPa «s at 25°C and a second styrene-based
• thermoplastic elastomer having a 25% toluene solution viscosity in the range of 500-2, 500mPa «s at 25°C at a predetermined ratio, superior properties could be demonstrated experimentally not only for the softening point but also for the DS value without curing.
• the base asphalt of the invention may be straight asphalt (refer to JIS K 2207), blown asphalt (refer to JIS K 2207), semi-blown asphalt (refer to 'Asphalt
• solvent-deasphalted asphalt (refer to 'New Petroleum Dictionary', the Petroleum Society, 1982, p308) or mixtures thereof, and each type of asphalt to which aromatic heavy mineral oil has been added may be used.
• base asphalt used in the invention asphalt to which aromatic heavy mineral oil has been added to straight asphalt and solvent- deasphalted asphalt are preferred.
• penetration grades of asphalt of the invention are investigated and suitably up to the equivalent of straight asphalt 60/80-100/120 may be used.
• propane-deasphalted asphalt using propane or propane and butane is preferred.
• the mixing ratio of straight asphalt and solvent- deasphalted asphalt is, for example, 60-80 and is adjusted according to the desired penetration.
• Aromatic heavy mineral oil as stipulated in
• Petroleum Based Solvent Extracted Oil and JIS K6200 is a solvent extracted oil when brightstock (heavy lubricating oil) is obtained, that is, an extract obtained by solvent extraction using a polar solvent such as furfural of aromatic hydrocarbon process oil containing at least 35wt% hydrocarbons and the like and, further, solvent de- asphalted oil obtained by de-asphalting using propane and the like vacuum distilled residual oil from crude oil.
• extract it is preferable to add extract as an aromatic heavy mineral oil .
• the role of the extract in the invention is to increase the solubility of thermoplastic elastomer in asphalt. To avoid separation in storage, a lot of thermoplastic elastomer is added and the amount of extract which needs to be added increases. Moreover, if more extract than needed is added to the thermoplastic elastomer, the strength decreases.
• the amount of extract added to the overall asphalt composition is determined in consideration of a complex modulus indicating penetration, softening point, storage stability, strength and dynamic stability (DS value) in the wheel tracking test, as well as the Cantabor loss rate indicating low temperature properties but, in the range investigated in the invention, the amount of extract present in the overall asphalt composition is preferably 4-12wt%.
• the styrene-based thermoplastic elastomer used in the polymer-modified asphalt composition of the invention contains a mixture of a first styrene-based thermoplastic elastomer and a second styrene-based thermoplastic elastomer .
• the first styrene-based thermoplastic elastomer has a 25% toluene solution viscosity at 25°C in the range of from 3000 to 6000mPa «s.
• Examples of the first styrene- based thermoplastic elastomer are not particularly limited as long as they satisfy the viscosity criterion, and mention can be made of a styrene-butadiene-styrene block copolymer (SBS), a styrene-butadiene-styrene block copolymer in which the SBS butadiene block double-bonded part is completely hydrogenated (SEBS), and a
• SBS styrene-butadiene-styrene block copolymer
• SEBS styrene-butadiene-styrene block copolymer in which the SBS butadiene block double-bonded part is completely hydrogenated
• SBBS selectively partially hydrogenated
• SIS styrene-isoprene-styrene block copolymer
• SEPS styrene-ethylene/propylene-styrene block copolymer in which the SIS butadiene block double bonded part has been completely hydrogenated
• the first styrene-based thermoplastic elastomer has a 25% toluene solution viscosity at 25°C in the range of from 3000 to 6000mPa «s and it is of a higher molecular weight than the second styrene-based thermoplastic elastomer. If the 25% toluene solution viscosity of the first styrene-based thermoplastic elastomer is less than 3000mPa «s, the difference in molecular weight between it and the lower molecular weight second styrene-based thermoplastic elastomer becomes small if the molecular weight is too low.
• the first styrene-based thermoplastic elastomer and the second styrene-based thermoplastic elastomer show an interaction and this is not preferred as the desired modification effect is not obtained.
• the 25% toluene solution viscosity at 25°C of the first styrene-based thermoplastic elastomer shows an interaction and this is not preferred as the desired modification effect is not obtained.
• the viscosity of the polymer-modified asphalt composition markedly increases if the molecular weight is too high and is not preferred as compacting becomes difficult when mixing aggregate at low temperature .
• the first styrene-based thermoplastic elastomer can more suitably exhibit the effects mentioned above in the preferred 25% toluene solution viscosity in the range of from 4000 to 5000mPa «s at 25°C.
• the second styrene-based thermoplastic elastomer has a 25% toluene solution viscosity at 25°C in the range of from 500 to 2500mPa «s.
• Examples of the second styrene-based thermoplastic elastomer are not particularly limited as long as they satisfy the viscosity criterion, and mention can be made of a styrene-butadiene-styrene block copolymer (SBS), a styrene-butadiene-styrene block copolymer in which the SBS butadiene block double-bonded part is completely hydrogenated (SEBS), and a
• SBS styrene-butadiene-styrene block copolymer
• SEBS styrene-butadiene-styrene block copolymer in which the SBS butadiene block double-bonded part is completely hydrogenated
• SBBS selectively partially hydrogenated
• SIS styrene-isoprene-styrene block copolymer
• SEPS styrene-ethylene/propylene-styrene block copolymer in which the SIS butadiene block double bonded part has been completely hydrogenated
• the second styrene-based thermoplastic elastomer has a 25% toluene solution viscosity at 25°C in the range of from 500 to 2500mPa «s, it is of a higher molecular weight than the first styrene-based thermoplastic elastomer. If the 25% toluene solution viscosity of this second styrene-based thermoplastic elastomer is less than 500mPa «s at 25°C, it is not preferred as the desired modification effect is not obtained as the molecular weight becomes too low. However, if the 25% toluene solution viscosity of this second styrene-based
• thermoplastic elastomer is more than 2500mPa «s at 25°C, the difference in molecular weight between it and the higher molecular weight first styrene-based thermoplastic elastomer becomes small.
• first styrene- based thermoplastic elastomer and the second styrene- based thermoplastic elastomer show an interaction and this is not preferred as the desired modification effect is not obtained.
• the second styrene-based thermoplastic elastomer can more suitably exhibit the effects mentioned above in the preferred 25% toluene solution viscosity in the range of from 1000 to 2000mPa «s at 25°C.
• thermoplastic elastomer As described above, by combining two types of styrene-based thermoplastic elastomer in the invention comprising a first styrene-based thermoplastic elastomer having a high 25% toluene solution viscosity at 25°C and a second styrene-based thermoplastic elastomer having a low 25% toluene solution viscosity at 25°C, it is possible to lower the softening point compared to conventional polymer-modified asphalt.
• rut resistance is high and can be maintained.
• thermoplastic elastomer When the total amount of thermoplastic elastomer is shown by the sum of the amounts of a first styrene-based thermoplastic elastomer and a second styrene-based thermoplastic elastomer, the content by percentage of a first styrene-based thermoplastic elastomer in the overall thermoplastic elastomer needs to be from 60 to 80wt% and preferably from 73 to 80wt%.
• thermoplastic elastomer in a polymer-modified asphalt composition is less than 3wt%, the performance mentioned above cannot be sufficiently exhibited. Further, if the total amount of thermoplastic elastomer in a polymer- modified asphalt composition exceeds 6wt% overall, the above effects are saturated and, by increasing the amount of expensive thermoplastic elastomer added, the raw material cost markedly increases and this presents problems. That is, even if the amount of thermoplastic elastomer added exceeds 6wt%, the mechanical properties of the asphalt composition will not be improved
• the amount of thermoplastic elastomer needs to be from 3 to 6wt% compared to the total amount of polymer-modified asphalt composition. To suitably exhibit the above effects further, the amount of
• thermoplastic elastomer is preferably from 4 to 5wt%.
• a polycyclic diterpene (resin acid) of carbon number 20 and having a carboxyl group may include abietic acid, dehydroabietic acid, neoabietic acid, pimaric acid, isopimaric acid and palustric acid although not limited to these, and includes any resin acid falling under the definition of a polycyclic diterpene of carbon number 20 and having a carboxyl group.
• This polycyclic diterpene of carbon number 20 and having a carboxyl group generally includes rosin.
• gum rosin, wood rosin and tall oil rosin may be used as rosins.
• these rosins can be classified as gum rosins or wood rosins and they may be obtained as the residual component of steam distillation of pine resin.
• Rosin is typically a mixture containing abietic acid, palustric acid, neoabietic acid, dehydroabietic acid, pimaric acid, sandaracopimaric acid, isopimaric acid and so on. Rosin normally softens at about 80°C and melts at
• tetrahydroabietic acid palustric acid, neoabietic acid and laevopimaric acid are contained within the rosin, but these resin acids may also be refined and used
• gum rosin as an example of the polycyclic diterpene (resin acid) of carbon number 20 and having a carboxyl group. Impurities are removed from this gum rosin by filtering raw tapped pine resin, after which the rosin is obtained by distillation, and separating out the terpene oil in the low boiling point component.
• this gum rosin contains 20-40wt% abietic acid, 15-25wt% of neoabietic acid, 20-30wt% palustric acid, 3-8wt% pimaric acid, 10-20wt% isopimaric acid and 3-8wt% dehydroabietic acid .
• rosin instead of using the rosin as is, it is also possible to use one or more acids selected from among abietic acid, dehydroabietic acid, neoabietic acid, pimaric acid, isopimaric acid and palustric acid.
• the polycyclic diterpene (resin acid) of carbon number 20 and having a carboxyl group is present at from
• the polycyclic diterpene (resin acid) of carbon number 20 and having a carboxyl group is present within the range of from 0.3 to lwt% relative to the total weight of polymer-modified asphalt composition.
• test methods, examples and comparative examples mentioned in the invention will be described in more detail below but the invention is not limited to these examples .
• the following examples give units in % only, it is assumed to indicate wt%.
• tests of properties comprising parameters of penetration (25°C), softening point and viscosity (180°C) were carried out as tests to confirm binder properties in samples obtained for an experimental study as shown in Tables 1A and IB.
• the DS value was measured as a test to confirm the mechanical strength indicated by rut resistance of mixtures
• Viscosity was measured under the conditions of JPI- 5S-54-99 'Asphalt - Method for Testing Viscosity using a Rotating Viscometer' with a measurement temperature of 180°C and measurements were undertaken at 20 spindle rotations/minute using an SC4-21 spindle.
• each polymer- modified asphalt composition and a combination with aggregate shown in Table 2 was used, the asphalt content of the mixture was 5.0wt%, test pieces in sheet form measuring 30cm vertically, 30cm horizontally and with a depth of 5cm were used and tests were carried according to the 'Wheel Tracking Test Method' in the 'Handbook of Methods of Evaluating and Testing Pavement' (Japan Road Association) . Japanese roads have been experimentally verified to reach a temperature of 60°C in summer. Under these conditions, when cars pass over them, flow
• a wheel tracking test is a test designed to confirm experimentally the degree to which this rutting occurs and is a test carried out in order to evaluate the dynamic stability which is an indicator of flow resistance properties in paving materials. Specifically, a tyre upon which a specified load has been applied is run backwards and forwards over the experimental sample (test piece) for 1 hour in a constant temperature tank maintained at 60°C, and the amount of deformation is measured. The DS value (times/mm) was determined using the amount of deformation (mm) in 15 minutes from 45-60 minutes after the start of the test and the number of tyre passes in 15 minutes from 45-60 minutes after the start of the test using the following equation:
• DS value (times/mm) (number of tyre passes in the period from 45 min to 60 min (times)/ (amount of
• the DS value becomes 6000 times/mm or more it is reported as an DS value of 6000 times/mm or more but, to obtain a higher road surface strength, actually obtained DS values are used in this invention.
• the DS value is 6000 times/mm or more and preferably 6300 times/mm or more.
• examples, comparative example and reference examples using SBS as a styrene-based thermoplastic elastomer were prepared.
• Samples comprising straight asphalt, extract, propane-deasphalted asphalt, SBS, and antistripping agent (dimeric acid, rosin) at the blending ratios shown in Tables 1A and IB (Examples 1-6, comparative examples 1-6 and reference examples 1-2) were prepared.
• the properties of straight asphalt used in these examples and comparative examples are typical properties and are a penetration of 67 (1/lOmm), a softening point of 48.0°C and a 15°C density of 1036kg/m 3 .
• the properties of propane-deasphalted asphalt are typical properties and are a penetration of 12 (1/lOmm), a softening point of 63.5°C and a 15°C density of 1062kg/m .
• typical properties of the extract used are a kinematic viscosity of 556mm 2 /s at 60°C and a 15°C density of
• SBS in the first row is a first styrene-based thermoplastic elastomer having a styrene content of 31wt% and a 25% toluene solution viscosity of 4500mPa «s at 25°C.
• the second to fourth rows from the top show SBS2- SBS4 and are second styrene-based thermoplastic
• SBS2 has a styrene content of 30wt% and a 25% toluene solution viscosity of 1700mPa «s at 25°C
• SBS3 has a styrene content of 31wt% and a 25% toluene solution viscosity of 1150mPa «s at 25°C
• SBS4 has a styrene content of 45wt% and a 25% toluene solution viscosity of 170mPa «s at 25°C.
• the 25% toluene solution viscosity at 25°C can be, for example, measured using a Brookfield (BL) viscometer as noted in Japanese unexamined patent JP2008-31267.
• this gum rosin contains 20-40wt% abietic acid, 15-25wt% neoabietic acid, 20-30wt% palustric acid, 3-8wt% pimaric acid, 10-20wt% isopimaric acid and 3-8wt% dehydroabietic acid.
• this gum rosin if this gum rosin is added, the amount is 0.5wt% to total amount of composition.
• dimeric acid is used in reference examples 1-2 and in comparative example 1.
• Reference examples 1 and 2 both showed experimental results of conventional asphalt compositions.
• the thermoplastic elastomer is composed of one type SBS1 only and it is present at 4.3wt%.
• a dimeric acid is used as an antistripping agent.
• reference example 1 shows the properties before curing and the properties when curing is carried out over a period of 1-2 days are shown in reference example 2.
• the softening point exceeds 70°C prior to curing as shown in reference example 1, and although the DS value falls below 6000 times/mm, in reference example 2 the softening point is 70°C or more and the DS value becomes 6000 or more after curing.
• Comparative example 1 is a thermoplastic elastomer composed of a mixture of SBS 1 and SBS2 and the ratio of SBSl to the overall thermoplastic elastomer is 75wt%.
• a dimeric acid is used as an antistripping agent. The softening point exceeds 70°C in this
• comparative example 2 is composed a thermoplastic elastomer comprising SBS 2 only, the ratio of SBSl to the overall thermoplastic elastomer is 0wt%.
• rosin is used as an antistripping agent.
• the softening point in comparative example 2 was 57.0°C, it has been shown that it can be adjusted to 70°C or lower and, as a result, it has been shown that the viscosity can be lowered.
• the DS value was 3706 (times/mm), it fell below 6000 (times/mm).
• Comparative example 3 is a thermoplastic elastomer composed of a mixture of SBS 1 and SBS2 and the ratio of SBSl to the overall thermoplastic elastomer is 50wt%.
• rosin is used as an antistripping agent.
• As the softening point in comparative example 3 was 56.0°C, it has been shown that it can be adjusted to 70°C or lower and, as a result, it has also been shown that the viscosity can be lowered.
• the DS value was 4846 (times/mm), it fell below 6000 (times/mm).
• Comparative example 4 is a thermoplastic elastomer composed of a mixture of SBS 1 and SBS2 and the ratio of SBSl to the overall thermoplastic elastomer is 84wt%. In addition, rosin is used as an antistripping agent. The softening point in comparative example 4 was 75.5°C and exceeded 70°C. As the DS value was 5727 (times/mm), it fell below 6000 (times/mm).
• Comparative example 5 is a thermoplastic elastomer composed of a mixture of SBS 1 and SBS2 and the ratio of SBSl to the overall thermoplastic elastomer is 95wt%. In addition, rosin is used as an antistripping agent. The softening point in comparative example 5 was 79.5°C and exceeded 70°C. In addition, as the DS value was 4846 (times/mm), it fell below 6000 (times/mm).
• Comparative example 6 is a thermoplastic elastomer composed of a mixture of SBSl only and the ratio of SBSl to the overall thermoplastic elastomer is 100wt%.
• rosin is used as an antistripping agent.
• the softening point in comparative example 6 was 80.5°C and exceeded 70°C. As the DS value was 4345 (times/mm), it fell below 6000 (times/mm).
• thermoplastic elastomer the amount of thermoplastic elastomer, the content by percentage of first styrene- based thermoplastic elastomer in the above thermoplastic elastomer, and the type of antistripping agent are combined in any range specified in the present invention.
• thermoplastic elastomer is composed of a mixture of SBSl and SBS2.
• the ratio of SBSl to thermoplastic elastomer overall from example 1 over the next 3 samples was 63wt%, 70wt%, 75wt% and 77wt% and gradually increased.
• rosin is used as an antistripping agent.
• the DS value in examples 1-4 was 6000 (times/mm) or more. That is, a notable difference in effect between comparative example 3 having a ratio of SBSl to thermoplastic elastomer overall of 50wt% and example 1 having a ratio of SBSl to thermoplastic elastomer overall of 63wt%, in particular, is shown in the DS value.
• thermoplastic elastomer 1st styrene-based thermoplastic elastomer
• thermoplastic elastomer overall of 60wt% or more
• thermoplastic elastomer in thermoplastic elastomer overall at 77wt%, 84wt%, 95wt% and 100wt% was newly found, and among them it is said that a rate of 80wt% was experimentally found to be the threshold at which the predetermined DS value could be obtained.
• example 5 is a
• thermoplastic elastomer composed of a mixture of SBSl and SBS3 and the ratio of SBSl to the overall thermoplastic elastomer is 77wt%.
• rosin is used as an antistripping agent.
• the softening point is 63.0°C, it is possible to suppress this to 70°C or below and the DS value becomes 6000 (times/mm) or more. Therefore, it has been shown that superior properties for both the DS value and softening point could be
• SBS3 having a 25% toluene solution viscosity at 25°C of 1150mPa «s as a 2nd styrene-based thermoplastic elastomer is used in example 5 and, although it has a lower molecular weight than SBS2, it has been shown that identical superior properties could be demonstrated experimentally.
• Example 6 is a thermoplastic elastomer composed of a mixture of SBS1 and SBS4 and the ratio of SBS1 to the overall thermoplastic elastomer is 77wt%.
• rosin is used as an antistripping agent.
• the softening point is 61.5°C, it is possible to suppress this to 70°C or below and the DS value becomes 6000 (times/mm) or more. Therefore, it has been shown that superior properties for both the DS value and softening point could be demonstrated experimentally.
• SBS4 having a 25% toluene solution viscosity at 25°C of 170mPa «s as a second styrene-based
• thermoplastic elastomer is used in example 6 and, although it has a lower molecular weight than SBS2, it has been shown that identical superior properties could be demonstrated experimentally.

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