WO2010125167A1

WO2010125167A1 - Styrene-butadiene composition

Info

Publication number: WO2010125167A1
Application number: PCT/EP2010/055870
Authority: WO
Inventors: Akira Seo
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2009-05-01
Filing date: 2010-04-29
Publication date: 2010-11-04
Also published as: JP2010260939A; JP5424704B2

Abstract

The present invention provides a styrene-butadiene composition comprising the reaction product of a 20-carbon polycyclic diterpene having a carboxyl group with a block copolymer comprising at least two poly (styrene) blocks and at least one poly (butadiene) block. The present invention further provides a bitumen and an asphalt composition comprising bitumen, respectively asphalt, and the styrene-butadiene composition.

Description

STYRENE-BUTADIENE COMPOSITION

This invention relates to a styrene-butadiene composition to improve the stability and strength of bitumen for applications such as road pavement, waterproof materials, and adhesives. Background to the Invention

Bitumen is conventionally used in a wide range of fields, including road pavement and waterproofing. This bitumen generally utilizes a styrenic block copolymer comprising at least two poly (styrene) and at least one poly (butadiene) block as a reinforcing material. For convenience, in this specification such a block copolymer may be referred to as "SBS". However, SBS loses stability when distributed in the bitumen. Particularly with regard to the storage temperatures associated with industrial applications (150⁰C to 180⁰C), there are problems with the SBS rapidly separating from the bitumen and rising to the surface.

Because of this situation, when SBS is mixed into bitumen as a reinforcing material, stabilizers have been added in order to stabilize the SBS within the bitumen. Conventionally such stabilizers have included substances such as, for example, sulfur, polyoxyethylene nonylphenol, peroxide, carbon black, and aromatic oil.

However, the addition of sulfur as a stabilizer is associated with the risk of generating hydrogen sulfide, polyoxyethylene nonylphenol is an environmental hormone the use of which should be avoided (for example, see Japanese ϋnexamined Patent Publication No. 2000-53865) , and the handling of organic peroxides at high temperatures is associated with the risk of degradation and explosion. Carbon black is expensive in comparison to bitumen, and its use poses a stumbling block in supplying bitumen products for the market (for example, see Japanese Unexamined Patent Publication No. H10-237309) . The addition of aromatic oil can improve stability by dissolving poly (styrene) blocks in SBS, but this means the loss of desirable improvements in elasticity that could come from the presence of those poly (styrene) blocks, and that in turn makes it difficult to obtain the anticipated level of strength in bitumen products.

For some time, there has been increasing demand for technology that would improve both the stability and the strength of bitumen compositions.

The present invention was conceived in response to the problems described above, and its objective is to provide a styrene-butadiene composition needed particularly for manufacturing a bitumen composition that can offer both improved stability and improved strength, and an bitumen composition to which this styrene- butadiene composition is added. Summary of the Invention

Accordingly, the present invention provides a styrene-butadiene composition comprising the reaction product of a 20-carbon polycyclic diterpene having a carboxyl group with a block copolymer comprising at least two poly {styrene) blocks and at least one poly (butadiene) block.

According to one embodiment, preferably the 20- carbon polycyclic diterpene having a carboxyl group has undergone an addition reaction to a double bond in the poly (butadiene) block of the block copolymer comprising at least 2 poly (styrene} blocks and at least one poly (butadiene) block. In particular, the 20-carbon polycyclic diterpene having a carboxyl group is appended to the poly (butadiene) block of a block copolymer comprising at least two poly (styrene) blocks and at least one poly (butadiene) block.

Preferably, the 20-carbon polycyclic diterpene having a carboxyl group is at least appended to the No. 2 carbon position or the No. 3 carbon position in the poly (butadiene) block next to a poly (styrene) block.

The 20-carbon polycyclic diterpene having a carboxyl group is preferably selected from one or more of: abietic acid, dehydroabietic acid, neoabietic acid, pimaric acid, isopinαaric acid, and palustric acid.

The present invention further provides a bitumen composition comprising bitumen and a styrene-butadiene composition as described herein as well as an asphalt composition comprising the bitumen composition and aggregate.

The styrene-butadiene compositions applicable to this invention have double bonds in the poly (butadiene) blocks to which a 20-carbon polycyclic diterpene having a carboxyl group can bond, preferably at least have double bonds in the poly (butadiene) blocks in closest proximity to the poly (styrene) blocks, to which 20-σarbon polycyclic diterpenes having carboxyl groups can bond. These 20-carbon polycyclic diterpenes having carboxyl groups can be two to three times the size of the styrene comprising the poly (styrene) blocks. As a result, the present inventors believe without wishing to be bound to a particular theory, this 20-carbon polycyclic diterpene having a carboxyl group can function to block the free movement (or in some cases the separation from bitumen) of SBS. By positioning bulky 20-carbon polycyclic diterpenes having these carboxyl groups preferably in the vicinity of poly (styrene) blocks, it is possible to prevent mutual aggregation among poly (styrene} blocks in the SBS added to bitumen. By achieving distribution without mutual aggregation among poly (styrene) blocks, it is possible to obtain uniform mixing of SBS within the bitumen, and to improve the stability of the resulting bitumen composition. Brief Description of the Drawings

Fig. 1 This figure shows a schematic perspective view of the measurement portion of the dynamic viscoelasticity tester.

Fig. 2 This figure illustrates the relationship between the modulus of elasticity G* for the wavelength angular frequency ω of a bitumen composition and the loss tangent (tanδ) .

Fig. 3 This figure shows the IR spectrum for abietic acid.

Fig. 4 This figure shows the IR spectrum for a styrene-butadiene composition. Fig. 5 This figure is another illustration of the relationship between the modulus of elasticity G* for the wavelength angular frequency ω of a bitumen composition and the loss tangent (tanδ) .

Fig. 6 This figure shows an example of mutual aggregation among poly (styrene) blocks for SBS added to bitumen. Detailed Description of the Invention

Below, the styrene-butadiene composition will be explained in detail with regard to the best mode for carrying out the invention.

The present inventors experimented to produce a styrene-butadiene composition for addition to an bitumen composition that would resolve the problems described above and provide the desired level of stability and strength. As a result, the inventors discovered that for SBS it was possible to add a bulky molecule in the vicinity of the poly (styrene) block. This was done by applying an addition reaction to a 20-carbon polycyclic diterpene having a carboxyl group (resin acid) . Specifically, by mixing SBS with 20-carbon polycyclic diterpene having a carboxyl group, the 20-carbon polycyclic diterpene having a carboxyl group can be bonded to a double bond comprised in a poly (butadiene) block. As a result, the present inventors believe mutual aggregation among poly (styrene) blocks can be dissolved, and by adding the styrene-butadiene composition of this invention to bitumen, the stability of the final bitumen composition can be improved.

Preferably the block copolymer is selected from the group consisting of those of formulae A (BA) _m or (AB)_nX, wherein A represents a block of predominantly poly (styrene) , wherein B represents a block of predominantly poly (butadiene) , wherein X represents the residue of a multivalent coupling agent and wherein n represents an integer > 1, preferably 1, and m represents an integer ≥ 1, preferably m is 1.

Multivalent coupling agents that may be used include those commonly known in the art. With the term

"predominantly" it is meant that the respective blocks A and B may be mainly derived from styrene monomer and butadiene monomer, which monomers may be mixed with other structurally related or non-related co-monomers, e.g. styrene monomer as main component and small amounts (up to 10%) of other monomers or butadiene mixed with isoprene or with small amounts of styrene. More preferably the copolymers contain pure poly (styrene) and pure poly (butadiene) blocks.

Preferably the A blocks of the block copolymers have an apparent nαol wt. in the range of from 3,000 to 100,000, preferably in the range of from 5,000 to 50,000; whilst the B blocks preferably have an apparent mol wt. in the range of from 10,000 to 300,000, more preferably in the range of from 40,000 to 200,000, and most preferably in the range of from 45,000 to 120,000.

The originally prepared poly (butadiene) blocks usually contain in the range of from 5 to 50 mol% of vinyl groups, originating from 1,2 polymerisation relative to 1,4 polymerisation of the butadiene molecules, and preferably a vinyl content in the range of from 10 to 25%.

The block copolymers to be used according to the present invention preferably contain poly (styrene) in an amount in the range of from 10 to 60% by weight, more preferably in the range of from 15 to 45% by weight, even more preferably 25 to 35% by weight.

The apparent molecular weight of the total block copolymer will preferably be in the range of from 50,000 to 600,000 and more preferably in the range of from 100,000 to 300,000.

More preferably, the block copolymer is a poly (styrene) -poly (butadiene) -poly {styrene) block copolymer.

A preferred styrene-butadiene composition to which this invention applies can be represented by, for example, the following formula.

In the styrene-butadiene composition to which this invention applies, an Ri group is attached to the poly (butadiene) block in the SBS. This Ri group is a 20- carbon polycyclic diterpene having a carboxyl group (hereinafter termed a "resin acid") .

The SBS is added to the bitumen as a thermoplastic elastomer. This SBS shows little loss of physical strength in areas such as kinematic viscosity for degradation of the bitumen composition at manufacturing temperatures, utilization temperatures, and processing temperatures (approximately 150⁰C to 210^σC) , and is an inexpensive elastomer in comparison to hydrogenated thermoplastic elastomers that will be described later. Ordinary SBS has a chemical structure in which the poly (butadiene) block is sandwiched between poly (styrene) blocks, as shown in Chemical Formula 2 below. To the double bond constituting this poly (butadiene) block is added a resin acid, making it possible to stabilize the SBS within the bitumen composition so that the SBS will not tend to separate and rise up from within the bitumen, and also improving the performance of the bitumen composition.

Ordinarily the density of bitumen is higher than that of SBS at the same temperature, so when SBS and bitumen are mixed and then separate, the SBS rises to the surface of the bitumen.

The resin acid may be a substance such as, for example, abietic acid, dehydroabietic acid, neoabietic acid, levopimaric acid, pimaric acid, isopimaric acid, or palustric acid, although it is not limited to these acids, but can also include any resin acid under the definition of a 20-carbon polycyclic diterpene having a carboxyl group. These 20-carbon polycyclic diterpenes having a carboxyl group generally include rosins.

The rosin as used here includes gum rosin, wood rosin, and tall oil rosin. These rosins can be classified into categories such as gum rosin or wood rosin, as described above, according to differences in location of origin, raw materials, and method of harvesting, but all share the common point of being obtained as a residue of the steam distillation of pine resin. These rosins are mixtures containing ingredients including abietic acid, palustric acid, neoabietic acid, dehydroabietic acid, pimaric acid, sandacopimaric acid, and isopimaric acid. These rosins generally soften at approximately 80⁰C, and melt at approximately 90⁰C to 100⁰C. A variety of resin acids can be included within rosins, including abietic acid, dehydroabietic acid, dihydroabietic acid, tetrahydroabietic acid, palustric acid, neoabietic acid, and levopimaric acid, but these resin acids can also be purified and used alone.

These resin acids can be appended through an addition reaction to any of the double bonds in the poly (butadiene) block as shown in Chemical Formula 2. Here, for the styrene-butadiene composition to which the present invention applies, an example will be explained of the addition of a resin acid at double bonds in the poly (butadiene) blocks {block A_x and block A₂) most closely proximate to the poly (styrene) block as shown in Chemical Formula 3

Here, in blocks Ai and A₂ of the poly (butadiene) block, with the carbon atoms proximate to the poly (styrene) blocks designated as Ci, C≥, C₃ and C₄, the resin acid Ri is preferably appended to the carbon atom C_J. However, it is also preferable if this resin acid Ri is appended to the carbon atom C₃ rather than to the carbon atom C₂.

In addition, Chemical Formula 3 below shows an example of the addition of the resin acid R_x to a carbon atom other than in blocks A_x and A₂ of the poly (butadiene) block.

That is to say, this resin acid Ri can be appended to a carbon other than block Ai or A₂ in the poly (butadiene) block.

Chemical Formula 4 below shows a case in which the resin acid Ri is appended to a block other than block Ai of the poly (butadiene) block.

Thus, the resin acid Ri does not necessarily have to be appended to carbon atoms comprising blocks A₁ and A₂ in the poly (butadiene) block, but may also be appended to carbon atoms other than those in blocks Ai and A₂.

This invention may also be an bitumen composition comprising bitumen and the constituents structured as described above.

In this case, these ingredients may be included in the bitumen composition in an amount from 2 wt% to 8 wt% SBS and 0.3 wt% to 3 wt% 20-carbon polycyclic diterpenes having carboxyl groups (resin acid} , based on bitumen composition. Here the term "bitumen" indicates one element of the final product that is the bitumen composition of this invention, and that is first formed into the bitumen composition of this invention through the addition of SBS and resin acid.

Bitumen is comprised of straight bitumen that is obtained as a residual oil from the vacuum distillation of crude oil, depropanated bitumen that is obtained by removing substances such as propane from residual oil following the vacuum distillation of crude oil, and substances such as extracts (solvent extraction) that are obtained from solvent-extracted oil that was in turn obtain by removing substances such as propane from residual oil following the vacuum distillation of crude oil. It can also be comprised of aromatic oils in place of these extracts. These aromatic oils are specified in JIS K6200 as aromatic hydrocarbons containing at least 35 mass% of hydrocarbon processed oil. Bitumen is prepared by the vacuum distillation method described above, by a blowing method (involving the blowing of air) , or by a mixing method (blending method) . This bitumen can contain one or more types of depropanated bitumen, straight bitumen, and/or extracts. Depropanated bitumen is typically obtained from the vacuum-distilled residual oil through a removal process using propane or propane and butane intermixed substances as solvents, yielding a desolvented bitumen. In addition to this depropanated bitumen, it is also acceptable to use any other form of bitumen, for example straight bitumen or blown bitumen.

An example of this depropanated bitumen that may be used would be a product that, under JIS K2207, shows needle penetration of 8 (1/10 mm) at 25°C, softening point of 66.5°C, and density at 15°C of 1028 kg/m³.

For the straight bitumen it is acceptable to use, for example, a product having needle penetration at 25⁰C of 65 (1/10 mm), softening point of 48.5°C, and density at 15°C of 1034 kg/m³. Extracts are extracted oils that are obtained from solvent-extracted oils. Those solvent-extracted oils are typically obtained by removal using substances such as propane from residual oil following the vacuum distillation of crude oil, and the extracts are obtained by further solvent extraction using polar solvents, to yield heavy lube stock as a refined oil. The substance used as an extract may, for example, have a kinematic viscosity of 61.2 mm²/s at 100⁰C, a kinematic viscosity of 3970 mm²/s at 40⁰C, and a density of 976.4 kg/m³ at 15°C. In this regard, it is preferable for this extract to constitute no more than 5 wt% of the bitumen composition of this invention. This is because increasing the content of the added extract beyond 5 wt% does not provide sufficient additional increase in the strength of the resulting bitumen composition from the perspective of bitumen applications.

Preferably, the block copolymer is added to the bitumen composition in an amount of at least 2 wt%. If the bitumen composition of this invention contains less than 2 wt% of SBS, the improvement in temperature sensitivity and physical strength resulting from SBS addition may not be considered sufficient for practical purposes .

Preferably, the block copolymer is added to the bitumen composition in an amount of up to 8 wt%.

If the SBS content exceeds 8 wt%, the viscosity of the final bitumen composition will be high, and as a result it may become more cumbersome to apply this composition to the road. Also, if the SBS content exceeds 8 wt%, the final bitumen composition will show a decrease in thermal stability.

Of the substances comprising this bitumen composition, the 20-carbon polycyclic diterpenes having carboxyl groups (resin acid) described above preferably comprises 0.3 wt% to 3 wt% of the total bitumen composition.

However, if the bitumen composition of this invention contains less than 0.3 wt% of this resin acid, the addition to the SBS poly (butadiene) block of a 20- carbon polycyclic diterpene having a carboxyl group (such as abietic acid, dehydroabietic acid, neoabietic acid, pimaric acid, isopiitiarlc acid, or palustric acid) may not be considered sufficient for practical purposes. If the content of this resin acid exceeds 3 wt%, the stability will not increase significantly, whilst the raw material costs increases. That is to say, the addition of resin acid exceeding 3 wt% is not accompanied by a commensurately large improvement in stability, and is impractical from the perspective of raw material costs.

It is more desirable for this 20-carbon polycyclic diterpene having a carboxyl group (resin acid) to comprise 0.3 wt% to 1 wt% of the bitumen composition.

By placing the upper limit of resin acid content at 1 wt%, it is possible to hold down increases in the cost of raw materials while improving the stability of the bitumen composition of this invention, providing improved cost-effectiveness .

To actually produce an bitumen composition comprising the constituent substances described above, first prepare the bitumen described above. This bitumen is typically a mixture of one or more of the categories of straight bitumen, depropanated bitumen, and extract. The bitumen is held at a temperature of approximately 195°C, and SBS 2 wt% to 8 wt% is added, resin acid 0.3 wt% to 3 wt% as described above is also added, and the ingredients are mixed and stirred in a homogenizer at a temperature of 190⁰C to 210°C at a speed of 1500 to 6000 rpm for 2 to 3 hours.

In this regard, it is acceptable for the mixing time to deviate from the 2 to 3 hour range, but it is considered important to maintain the temperature of the mixture within the range of 190⁰C to 210⁰C as described above . If the mixing temperature is below 190⁰C, it may be more difficult to add the 20-carbon polycyclic diterpene having a carboxyl group (resin acid) at the double bond that constitutes this poly (butadiene) block within the SBS.

If the mixing temperature exceeds 210⁰C, the SBS may tend to degrade and deteriorate. Therefore it was decided to keep the mixing temperature to the temperature range described above.

This makes it possible to apply an addition reaction to the resin acid appending it do the double bond comprising the poly (butadiene) block.

Chemical Formula 5, shown below, is an example of an addition reaction appending the resin acid Ri {isopimaric acid) to the carbon atom C₂ in block Ai of the poly (butadiene) block.

Within the carboxylic acids comprising isopimaric acid, the oxygen atoms carry a negative charge and the hydrogen atoms in that carboxylic acid carry a positive charge. In addition, because the poly (styrene) blocks act as electron donors, there is an increased electron density at the double bonds in the vicinity of the poly (styrene) block, so that the poly (styrene) block itself also has an overall negative charge. As a result, when the isopimaric acid actually attacks the poly (butadiene) block the positively charged hydrogen atoms within the carboxylic acid are attracted to the poly (styrene) blocks, resulting in an attack on the double bonds at the block Ai in closest proximity to the poly (styrene) block. This gives rise to an electrophilic addition reaction between the hydrogen atoms and the corresponding double bond.

This electrophilic addition reaction results in the appending of isopimaric acid to the C₂ carbon atom in block Ai, as shown in Chemical Formula 6 below.

Isopiinaric acid may also be appended to the C₃ carbon rather than the C₂ carbon of block Ai. Isopimaric acid may also be appended to block A₂ by the same mechanism. In addition, isopimaric acid is not limited to blocks Ai and A₂, but can of course also be appended to other double bonds in the poly (butadiene) block. It is also possible to append more than one isopimaric acid group to this poly (butadiene) block. This applies not only to isopimaric acid, but also to any of the resin acids described above comprising 20-carbon polycyclic diterpenes having carboxyl groups, so that the same addition reaction as described above can occur at a double bond in the poly (butadiene) block, resulting in the appending of a resin acid to a carbon atom.

Of these resin acids, it is thought that the electron status and bonding of atoms within the molecules of abietic acid and isopimaric acid cause a rise in electron density at the oxygen atoms within the carboxyl group, making it particularly easy for those substances to react with double bonds within the poly (butadiene) block. Thus, of the resin acids described above, it is particularly desirable to use abietic acid or isopimaric acid. Accordingly the final styrene-butadiene composition shown in Chemical Formula 1 is then obtained.

In this way, the styrene-butadiene composition to which this invention applies, as described above, has at least resin acid Ri appended to double bonds in poly (butadiene) blocks A_x or A₂ in the vicinity of poly (styrene) blocks. That resin acid Ri is 2 to 3 times the size of the styrene comprising the poly (styrene) blocks. As a result, it is thought that this resin acid Ri functions to inhibit the free movement (separation) of the SBS. This bulky resin acid Ri is in the vicinity of the poly (styrene) blocks, so it prevents mutual aggregation among poly (styrene) blocks when SBS is added to bitumen. By achieving distribution without mutual aggregation among poly (styrene) blocks, it is possible to obtain uniform mixing of SBS within the bitumen, and to improve the stability of the bitumen composition.

The present invention further provides an asphalt composition comprising the bitumen composition as herein described and aggregate.

The aggregate in the asphalt composition of the invention comprises filler (aggregate fraction having size smaller than 63μm) , and preferably further comprises sand (size from 63μm up to and including 2mm) and/or stone (size greater than 2mm) . A wide range of aggregate types and size distributions may be employed in the asphalt composition of the present invention, the type and mix of aggregate varying with the application for which the asphalt is to be used. Preferably stones (size greater than 2mm) comprise at least 10%wt of the aggregate, more preferably at least 15%wt and most preferably at least 20%wt. Preferably stones comprise up to 70%wt of the aggregate, more preferably up to 65%wt, most preferably up to 60%wt. Filler and optionally sand preferably constitutes the balance.

The amount of bitumen composition in the asphalt composition of the present invention is preferably in the range of from 1 to 20% wt, more preferably in the range of from 2 to 10% wt, and most preferably in the range from 3 to 7% wt, based on total weight of asphalt composition. Example 1

Below, the styrene-butadiene composition to which this invention applies will be explained in detail, with reference to Experiments. First, we added resin acid to SBS and confirmed reactivity.

For this Experiment according to the invention, we decided on an bitumen composition wherein straight bitumen, depropanated bitumen (PDA) , or bitumen containing at least one of the types of extract described above was held at a temperature of approximately 195°C, 4.5 wt% of SBS was added, and then 0.75 wt% of gum rosin was added as a resin acid.

As a Comparative Experiment, we used a bitumen composition in which the same bitumen as in the

Experiment was held at a temperature of approximately 195°C, and 4.5 wt% of SBS was added, but no resin acid was added such as had been used in the Experiment.

The SBS used was a styrene-butadiene-styrene block copolymer having a bromine value of 220 (g/100 g, JIS

K0070), molecular weight of approximately 150000, styrene content of 32 wt%, and styrene block copolymer content at both ends of the elastomer molecule accounting for 16 wt% each. A substance with an acid value of 160 mg KOH/g was used for the gum rosin.

In experiments, a dynamic viscoelasticity tester was used to investigate the relationship between elasticity and loading time for the Experiment and the Comparative Experiment. Specifically, as shown in Fig. 1, bitumen binder (1) is pressed between two parallel plates (2a and 2b) . A predetermined sine wave distortion is applied to one of these plates (2a) , and the sine stress σ that is transmitted through the bitumen binder (1) to the other plate (2b) is measured. Those conditions of measurement are as follows: diameter of the plates (2a and 2b) 25 mm, thickness of the bitumen binder (1) 1 mm, strain level 10%. Based on those measured results, the modulus of elasticity G* is determined from the following formula (1) . Here, Y in the following formula (1) is the maximum strain applied to the plate.

The loss tangent (tanδ) is an index indicating the magnitude of energy that is lost within the bitumen composition when the sine wave distortion Y is applied to the bitumen composition.

A large loss tangent (tanδ) indicates that a large amount of energy is lost when strain is applied, which is to say that the substance is easily deformed, and that it does not return to its original shape when the applied strain is released. A small loss tangent (tanδ) indicates that a small amount of energy is lost when strain is applied, which is to say that the substance is not easily deformed, and that it is prone to return to its original shape when the applied strain is released.

When the modulus of elasticity G* is measured as described above, the loss tangent (tanδ) is calculated from the phase difference δ between the sine wave distortion γ for the designated angular frequency applied to one plate and the sine stress σ transmitted through the bitumen composition to the other plate.

The modulus of elasticity G* and loss tangent (tanδ) as described above may also be measured on the basis of the method described in "Pavement Review and Test Method Handbook" {edited by the Japan Road Association) under the title "AO62 dynamic shear rheometer test method."

Fig. 2 shows the modulus of elasticity G* and the loss tangent (tanδ) at 60°C for the Experiment of the present invention and the Comparative Experiment. When the Experiment of the present invention and Comparative Experiment were compared, it was clear that when loading time is extended, or in other words when the angular frequency shown on the horizontal axis in Fig. 2 is low, the modulus of elasticity G* is also low. In addition, it became clear that prolonged loading time makes it easy for major deformation to occur in the loss tangent {tanδ) , and after the strain is removed the product may remain deformed, rather than returning to the original shape.

Also, with prolonged loading time the Comparative Experiment showed a modulus of elasticity G* higher than that seen with the present invention. In addition, it became clear that prolonged loading time makes it easy for major deformation to occur in the loss tangent {tanδ) , and after the strain is removed the product may remain deformed, rather than returning to the original shape.

Investigation was also made of the relationship of elasticity to loading time in the bitumen compositions to which this invention applies. This was done by measuring softening point in accordance with the method prescribed by JIS K2207.

Under this JIS K2207 softening point test method, a ball of a specified weight is placed on a specified bitumen plate, which is in turn placed in a water bath, and the water bath is warmed at a rate of 5°C/min to determine the temperature at which a specific amount of flexure is seen in the bitumen plate due to the weight of the ball and the temperature of the water bath. This softening point test thus measures how readily the bitumen flexes and deforms under prolonged load. Results showed the softening point to be 60.0⁰C for the Experiment of the present invention, in comparison to 79.0⁰C for the Comparative Experiment.

In these Experiments of the present invention, the reduction in modulus of elasticity G*, elevation of loss tangent {tanδ) , and reduction in softening point all indicate distribution of SBS without mutual aggregation among poly (styrene) blocks.

In the Comparative Experiment, which was prepared without the addition of resin acid, it appears that mutual aggregation among poly (styrene) blocks did occur, so that within the bitumen composition there were formed poly {styrene) block aggregated structures as shown in Fig. 6, and that particularly during prolonged loading there is generated marked elasticity from the poly (styrene) blocks and rubber-like elasticity from the poly (butadiene) chains, so that elevation of the modulus of elasticity G* and small loss tangent (tanδ) can be observed.

When there is aggregation as shown in Fig. 6 between the poly (styrene) blocks within the bitumen composition, the softening point of the composition rises. This is similar to the effect seen on the glass transition point (Tg) for polystyrene. The Tg is the temperature at which the polystyrene can move freely. Ordinarily this temperature is 90⁰C to 100⁰C, but when there is aggregation between poly (styrene) blocks the glass transition point Tg is elevated.

Based on the results from this measurement of the modulus of elasticity G*, loss tangent (tanδ), and softening point, it is clear that in the bitumen composition to which this invention applies, a resin acid reacts with SBS through an addition reaction, resulting in the appending of a bulky resin acid in the vicinity of the poly (styrene) blocks- This prevents mutual aggregation among the poly (styrene) blocks, so that the SBS will be satisfactorily distributed throughout the bitumen composition. Example 2

Next, infrared (IR) spectroscopy was used to confirm the reaction between the SBS and the resin acid. Two types of samples were prepared: the resin acid abietic acid, and a styrene-butadiene composition in which abietic acid had been added to the SBS. Infrared spectroscopy was performed on both samples. Specifically, abietic acid and SBS were mixed into a prepared oily substance using the Fischer-Tropsch method, with a mixing temperature of 195⁰C, and a homogenizer was used at a speed of 3500 rpm to mix and agitate the mixture for approximately 3 hours. The amount produced was 300 g.

Additionally, for purposes of comparison, similar oily mixtures were prepared with abietic acid, replacing the SBS with SIS and SEBS, and IR was measured.

The SBS used was a styrene-butadiene-styrene copolymer having a bromine value of 220 (g/100 g, JIS

K0070) , molecular weight of approximately 150000, styrene content of 32 wt%, and styrene block copolymer content at both ends of the elastomer molecule accounting for 16 wt% each . The SIS used was a styrene-isoprene-styrene block copolymer having a bromine value of 220, molecular weight of approximately 220000, styrene content of 15 mass%, and styrene block copolymer content at both ends of the elastomer molecule of 7.5 mass% each.

The SEBS used was a styrene-ethylene/butylene- styrene block copolymer having a bromine value of 5 (g/100 g, JIS K0070), molecular weight of approximately 150000, styrene content of 30 mass!, and styrene block copolymer content at both ends of the elastomer molecule of 15 rnass% each.

The oily material that was used had a dynamic viscosity of 5.2 mmVs at 100⁰C.

Fig. 3 shows the IR spectrum for abietic acid alone, and Fig. 4 shows the IR spectrum for the styrene- butadiene composition.

The results in Fig. 3 show a peak in the vicinity of 1690 cm^"1. This peak is due to the C=O bond in the carboxyl group of abietic acid.

The results in Fig. 4 show a peak in the vicinity of 1740 cm^"1 and another peak in the vicinity of 1690 cm^"1. This peak in the vicinity of 1690 cm^""1 is from the C=O bond in the carboxyl group of abietic acid, and the peak in the vicinity of 1740 cm^™1 is from the ester group. In this regard, the formation of an ester represented by COOR (where R is some arbitrary hydrocarbon other than a hydrogen atom) shows a characteristic peak in the vicinity of 1740 cm^""1 even with the same C=O bond.

Because of this, we know that the mixing of SBS and abietic acid results in the formation of an ester represented by COOR (where R is some arbitrary hydrocarbon other than a hydrogen atom) . The group represented here by R appears to correspond to SBS. The theory that abietic acid reacts with SBS to form an ester is substantiated by the results from this IR. From the perspective of high electron density, as described above, this reaction between abietic acid and SBS is most likely to be located at the double bonds in the poly (butadiene) block. This supports the concept of the appending of a resin acid to a double bond in the poly (butadiene) block of the SBS.

When only abietic acid and the oily substance were mixed together in the same way and the IR spectrum was measured, no peak was noted in the vicinity of 1740 cm^"1, such as would be caused by an ester. Additionally, for purposes of comparison, similar mixtures were prepared with abietic acid, replacing the SBS with SIS and SEBS, and IR was measured. No notable peaks were observed in the vicinity of 1740 cm^"1, such as would correspond to the ester described above, Based on the results described above, it is clear that the resin is added to double bonds that are present only in the poly (butadiene) block of SBS.

These results confirm the formation of an ester between the resin acid (for which abietic acid was used as an example in this experiment) and SBS, and that no ester was formed between the resin acid and SIS or SEBS.

The reason that there was no reaction between SEBS and the resin acid is thought to be that, although SEBS has poly (styrene) blocks, it does not contain butadiene, and no double bonds are present. As a result, no electrophilic addition reaction can be elicited between the resin acid and the double bond-deficient SEBS. In contrast, the appending of a resin acid to SBS was presumed for the styrene-butadiene composition to which this invention applies, and because double bonds are present in this poly (butadiene) block, it can naturally be assumed that the resin acid will be appended to this poly (butadiene) block. SIS has double bonds like SBS, but no reaction with the resin acid could be confirmed. Unlike SBS, SIS has methyl groups in the vicinity of the double bonds. When the resin acid attacks a double bond in an isoprene block, the presence of the methyl group results in steric hindrance, making it difficult for bulky molecules such as the resin acid to be added at a double bond in the isoprene block.

From the study results described above, it is clear that in terms of the reaction between the styrene- butadiene composition and the resin acid, it is necessary to select SBS rather than SIS, and also to select SBS rather than SEBS (which is SBS with a hydrogenated poly (butadiene) section) . The resin acid is presumed to undergo an addition reaction and bind to a double bond of the poly (butadiene) block. Example 3

Fig. 5 illustrates the relationship between the modulus of elasticity G* for the wavelength angular frequency ω of this bitumen composition and the loss tangent (tanδ) . Sine wave oscillations are applied as a uniform distortion to the bitumen composition, the angular frequency ω is gradually increased, and the modulus of elasticity G* and the loss tangent (tanδ) are measured in relation to that angular frequency ω.

The modulus of elasticity G* specified for this invention can be measured using a dynamic viscoelasticity tester, as set forth in Example 1.

In this regard, the example in Fig. 5 shows the modulus of elasticity G* and the loss tangent (tanδ) exhibited by an bitumen composition consisting of SBS 4.5 wt%, gum rosin 0.75 wt%, and the remainder bitumen, at 60⁰C with the application of 10% sine wave distortion. The samples of bitumen composition for use were prepared at various mixing temperatures (180⁰C, 185°C, and 190°C} .

Particularly in the case of road pavement in a setting of actual use, the bitumen composition is spread on the road with aggregate {gravel, sand, etc.} . It is then necessary to smooth the paved surface with heavy equipment (such as rollers) and human labor in order to provide an improved ride for traffic on the road, to prevent stumbling by pedestrians, and to prevent water accumulating in puddles. To smooth the pavement surface, a large force is applied slowly to the paved surface in a process much like ironing.

Since at that point the bitumen composition receives vibrations at a low angular frequency ω, the higher the tanδ for the low angular frequency ω, the easier it will be to deform the bitumen composition, and the lower the restoration force will be. Such characteristics are well- suited for providing good onsite workability, that is to say, a substance that can easily be formed into a smooth road surface.

In comparison to the other samples, those prepared at a mixing temperature of 190⁰C tended to have a higher tanδ for low angular frequency ω. In contrast, the samples prepared at a mixing temperature of 185°C or below tended to have a low tanδ for low angular frequency ω. Thus we see that a mixing temperature of 190⁰C or above is desirable from the perspective of workability.

It is also desirable to have a low modulus of elasticity G* for the low angular frequency ω range. In particular, when compacting and smoothing the bitumen composition, a load is placed on that bitumen composition in a low angular frequency ω range, and at this point workability is improved by having the composition be as soft as possible, or in other words having the lowest possible level of elasticity. From the perspective of modulus of elasticity, also, the sample prepared at a mixing temperature of 19O⁰C tended to show a lower modulus of elasticity G* at low angular frequency ω than was the case with other samples. For mixing temperatures of 185°C and below, the modulus of elasticity G* at low angular frequency ω was higher, and the workability of samples tended to be worse. Thus we see that a mixing temperature of 190⁰C or above is desirable from the perspective of workability.

The bitumen composition of this invention, obtained by the manufacturing method described above, can provide stable properties with no separation of SBS from bitumen. The poly (styrene} blocks that comprise SBS characteristically aggregate with other SBS poly {styrene) blocks, but under the present invention a 20-carbon polycyclic diterpene having a carboxyl group (resin acid) can be attached at the double bond comprising the poly (butadiene) block. In particular, by attaching a resin acid in the vicinity of a poly (styrene) block, the bulky resin acid acts on the poly {styrene) block, making it possible to release the aggregation among the poly (styrene) blocks. Because of the release of this aggregation of poly {styrene) blocks, there is no separation between the SBS and the bitumen, and satisfactory stability can be assured.

In this regard, it is possible to determine whether or not this bitumen composition is stable by conducting a storage stability test. This storage stability test was conducted using an aluminum tube having an inner diameter of 5.2 cm and a height of 13 cm, filled to a depth of 12 cm with the bitumen composition of this invention (approximately 250 g) , and heating the sample at 170⁰C for 48 hours. Stability was confirmed by then measuring the softening point in the upper 4 cm and the lower 4 cm for the bitumen composition in the aluminum tube. The measurement of the softening point can be based on the method shown in JIS K2207. Also, the difference absolute value between the upper-level softening point and the lower-level softening point can be used to determine stability. In cases where storage stability is considered satisfactory if the difference absolute value between these softening points is 3.O⁰C or less, the bitumen composition of this invention makes it possible to keep the softening point difference absolute value within 3.0⁰C. It is also possible to increase the strength of the bitumen composition of this invention, produced through the manufacturing method described above. The strength of this bitumen composition can be judged based on DS (Dynamic Stability) values from a wheel tracking test as described in the "Pavement Review and Test Method

Handbook" (edited by the Japan Road Association) . This DS value, which can be determined from Formula 2 below, is the number of tire passes from 45 minutes to 60 minutes after the start of testing in relation to the amount of deformation (mm) occurring in the bitumen composition from 45 to 60 minutes after the start of testing. The higher the DS value, the less deformation there will be in the bitumen composition itself, which means that the composition is strong and resists rutting.

For the bitumen composition of this invention, in particular, the content of extract is preferably kept below 5%, so it is possible to prepare a dense granular mixture (aggregate maximum particle size 13 mm) , for use in ordinary road pavement that will have a DS value as described above of at least 6000 (times/mm) . In this regard, if the DS value is 6000 (times/mm) or above, there will be almost no problems with the surface strength of the bitumen composition, according to the "Pavement Review and Test Method Handbook" (edited by the Japan Road Association) .

Thus, the present invention offers two-pronged improvement; storage stability can be improved by reducing the softening point difference to less than 3.0⁰C , and strength can be improved by increasing the DS value to 6000 (times/mm) or above.

Of course the bitumen composition of this invention is not limited to applications for use in road pavement, but can also be used in applications such as waterproof materials and adhesives. Example 4

Below, Experiments of this invention are explained in detail. As Table 1 shows, bitumen consisting of one or more types of straight bitumen, depropanated bitumen (PDA), or extract was heated to 195°C and held at that temperature while 4.5 wt% SBS was added. The SBS used was a styrene-butadiene-styrene block copolymer having a bromine value of 220 (g/100 g, JIS K0070) , molecular weight of approximately 150000, styrene content of 32 mass%, and styrene block copolymer content at both ends of the elastomer molecule of 16 mass%.

In this regard, bitumen compositions were prepared with admixture of Acid A (straight-chain) , as shown in Comparative Experiments 1 to 6, and bitumen compositions of this invention were prepared with admixture of Rosin B as shown in Experiments 1 to 5, with admixture of Rosin C as shown in Experiment 6, with admixture of abietic acid as shown in Experiment 7, and with admixture of dehydroabietic acid as shown in Experiment 8. For these Experiments and Comparative Experiments, the bitumen compositions were prepared with a mixing ratio of straight bitumen, depropanated bitumen (PDA) , and extract to provide needle penetration of 40 to 50.

Here, Acid A has an acid value of 190 (mg KOH/g, JIS K0070) and an iodine value of 110 (g/100 g, JIS K0070) , being a mixture of 7 wt% straight-chain monomer acid with a carbon number of 18, 76 wt% dimer acid with a carbon number of 36, and 7 wt% trimer acid with a carbon numbec of 54, and has a mean molecular weight of approximately 590. Rosin B is an unhomogenized gum rosin having an acid value of 156 (mg KOH/g, JIS K0070) and a softening point of 77.0ºC (JIS K2207) . Rosin C is a tall oil rosin having an acid value of 170 (mg KOH/g, JIS K0070), saponification value of 178 (mg KOH/g, JXS K0070), and a softening point of 77.0ºC (JIS K2207).

For the ingredients shown in Table 1 all numerical values in the table are wt%.

In Comparative Experiment 1, the extract makes up 12 wt% of the bitumen, in Comparative Experiment 2 the extract makes up 8 wt% of the bitumen, in Comparative

Experiment 3 the extract makes up 6 wt% of the bitumen, and in Comparative Experiments 4 to 6, the extract makes up 4 wt% of the bitumen. In Comparative Experiments 1 to 4, Acid A (straight chain) makes up 0.3 wt%. In Comparative Experiment 5, Acid A {straight chain) makes up 0 wt%, and in Comparative Experiment 6 Acid A (straight chain) makes up 0.5 wt% of the mixture, In Experiments 1 to 5, Rosin B was added instead of the Acid A {straight chain) that was mixed into Comparative Experiments 1 to 6. The content of Rosin B varied among these Experiments 1 to 5. Experiment 6 contained 0.75 wt% of Rosin C, Experiment 7 contained 0.75 wt% of abietic acid, and Experiment 8 contained 0.75 wt% of dehydroabietic acid. The following manufacturing conditions were applied to all compositions. The substances were mixed and agitated at 195°C in a homogenizer at a speed of 3500 rpm for approximately 2 hours. In each case, 1.8 kg of sample was produced. Properties were measured for each manufactured

Comparative Experiment and Experiment. The results of those measurements are shown in Table 1. The following properties were measured: needle penetration (1/10 m), softening point (⁰C), viscosity at 180⁰C (mPa.s), storage stability, DS value. Needle penetration data was for measurements performed at 25°C in accordance with JIS K2207. Softening point was also measured under JIS K2207 conditions. Viscosity was measured under the conditions specified in JPI-5S-54-99 "Viscosity determination of bitumen using rotational viscometer," at a measurement temperature of 180°C, using an SC4-21 spindle at a spindle speed of 20 rpm. Storage stability was tested using an aluminum tube having an inner diameter of 5.2 cm and a height of 13 cm, filled to a depth of 12 cm with the bitumen composition of this invention (approximately 250 g) , and heating the sample at 170⁰C for 48 hours. Next, in accordance with JIS K2207, softening points were measured for the upper 4 cm and the lower 4 cm of the bitumen composition within that aluminum tube. Table 1 shows this upper softening point and the absolute difference between the upper softening point and the lower softening point, that is to say, the softening point difference absolute value.

The DS value was measured based on the wheel tracking test. This DS value was obtained for various combinations of bitumen composition and aggregate composed of dense-graded bitumen mixture (13) , with the bitumen composition making up 5.6 wt%, formed into a sheet-shaped test sample 30 cm long, 30 cm wide, and 5 cm deep, using the method defined in "Pavement Review and Test Method Handbook" {edited by the Japan Road Association) . Japanese roads have been confirmed to reach temperatures of approximately 60⁰C in the summer. When vehicles travel on roads at these temperatures, flow deformation and conditions such as rutting will develop. The wheel tracking test was conceived as a way to experimentally confirm the extent of such rutting. It is conducted in order to evaluate dynamic stability, which is an indicator of fluidity resistance in pavement materials. A tire was used to apply a specific load to a test sample (the provided sample) for 1 hour within a constant-temperature chamber maintained at 60⁰C, and the amount of deformation was measured. Based on the above formula (2) , the DS value was calculated from the amount of deformation detected during the 15-minute period from 45 minutes to 60 minutes after the start of the test. In Table 1 above, the trends seen in Comparative Experiments 1 through 4 indicate that DS values rose as the amount of extract decreased. However, when the amount of extract decreased, the difference absolute value tended to increase between the softening points for the upper and lower sections. For Comparative Experiment 4, in particular, when the extract was decreased to 4 wt% the DS value increase to 7875 {times/mm) , but the softening point difference absolute value worsened to 19.9°C.

As can be seen with Comparative Experiments 5 and 6, when the extract was reduced to 4 wt%, storage stability could not be improved even by increasing the content of Acid A, that is to say, carboxylic acid. In Experiment 1, the extract content was 4 wt% and

Rosin B was 0.3 wt%, but it was still possible to raise the DS value to 7000 (times/mm} or above while making the softening point difference absolute value extremely small. This provided improvements both in strength and in storage stability. In the same way, Experiments 2 through 5 contained Rosin B 0.6 wt%, 0.75 wt%, 1 wt%, and 1.5 wt% respectively, making it possible to maintain DS values of 7000 (times/mm) or above, to hold the softening point difference absolute value to 1.3⁰C or below, and to achieve improvements in both strength and storage stability. However, with regard to this storage stability, it became clear that the softening point difference absolute value was not greatly changed by further increases in the content of Rosin B. It would seem that, even if Rosin A was added to exceed 3 wt%, there would be very little change in this softening point difference absolute value.

In Experiment 6, the extract was reduced to 4 wt% and Rosin C 0.75 wt% was added. This also provided similarly favorable DS value and softening point difference absolute value. In Experiment 7, where abietic acid was added as the only resin acid, and in Experiment 8, where dehydroabietic acid was added as the only resin acid, again similarly favorable DS values and softening point difference absolute values were obtained. The results from Experiments 6 through 8 indicate that even when the type of resin acid is changed, it is possible to maintain a high standard with regard to DS value through the addition of abietic acid and/or dehydroabietic acid, while also obtaining improved storage stability.

In this way, based on the results from Table 1, we see that improvements in both DS value and softening point difference absolute value can be implemented by using no more than 5 wt% extract and adding resin acid in a range of 0.3 wt% to 3 wt%.

The results from Table 1 additionally show that, for identical SBS content, those bitumen compositions having lower softening points after the completion of preparation (after manufacture} also have higher stability. This can be considered to occur because, for systems containing identical compositions of the same thermoplastic elastomer, the lower the softening point after the production of the bitumen composition is completed, the greater the improvement in stability from the addition of a 20-carbon polycyclic diterpene having a carboxyl group (resin acid) to a double bond comprising a poly (butadiene) block within the SBS. Example 5

Table 2 shows the results of a validation experiment, performed by replacing SBS with styrene- ethylene/butylene-styrene (SEBS) or styrene-isoprene- styrene (SIS) and determining whether the expected effects of the present invention were demonstrated. In this validation experiment, the production conditions for the bitumen composition were the same as described above in Table 1. SBS, SEBS, and SIS were all added in quantities of 4.3 wt%, and needle penetration, softening point, and viscosity at 150⁰C and 180⁰C (mPa.s) were measured. Table 2

The samples Rl and R2 in Table 2 were both created using SBS. Sample Rl was prepared without the addition of gum rosin, and is a Comparative Experiment differing in composition from the present invention. In contrast, 0.75 wt% gum rosin was added to Sample R2, making this sample an example of the present invention. In comparing the properties of Samples Rl and R2, the softening point of Sample R2 was much lower than that of Sample Rl, with stability improved by the addition of gum rosin, so that Sample R2 provides the effects expected from this invention.

In Table 2, gum rosin corresponds to Rosin B in Table 1, Experiment 4, and tall rosin corresponds to Rosin C in Table 1, Experiment 4.

In Samples Sl and S2, SEBS was substituted for SBS, so these samples are examples of the use of SEBS. The styrene-ethylene/butylene-styrene block copolymer (SEBS) used here has a hydrogen atom added to the double bond in the SBS poly (butadiene) block, resulting in a single bond, with a bromine value of 5 (g/100 g, JIS K0070), molecular weight of approximately 150000, styrene content of 30 mass%, and styrene block copolymer content at both ends of the elastomer molecule of 15 mass%.

Sample Sl was prepared without the addition of gum rosin, and 1 wt% gum rosin was added to Sample S2. A comparison of the properties of Samples Sl and S2 show almost no change in softening point, and no apparent increase in stabilization effects associated with the addition of gum rosin.

In Samples Pl through P6, SIS has been added in place of SBS.

The SIS used was a styrene-isoprene-styrene block copolymer having a bromine value of 220 {g/100 g, JIS

K0070) , molecular weight of approximately 220000, styrene content of 15 mass%, and styrene block copolymer content at both ends of the elastomer molecule of 7.5 mass%.

Pl through P3 are examples in which gum rosin was added. Almost no change in softening point was observed, regardless of whether or how much gum rosin was added. P4 through P6 are examples in which tall rosin was added. Almost no change in softening point was observed, regardless of whether or how much tall rosin was added. It thus appears that the addition of rosin is not associated with the development of improved stabilizing effects for this SIS.

That is to say, this invention shows improved stabilization effects with the addition of SBS, but these expected results cannot be obtained when SEBS or SIS is substituted for SBS. This improvement in stability can be achieved with SBS, which has a chemical structure with a poly (butadiene) block sandwiched between poly (styrene} blocks and a resin acid attached to the double bond constituting this poly (butadiene) block, but when SEBS or SIS is used, the resin acid cannot be attached and this improvement in stability cannot be obtained.

Claims

C L A I M S

1. A styrene-butadiene composition comprising the reaction product of a 20-carbon polycyclic diterpene having a carboxyl group with a block copolymer comprising at least two poly (styrene) blocks and at least one poly (butadiene) block.

2. A styrene-butadiene composition as claimed in claim 1, wherein the 20-carbon polycyclic diterpene having a carboxyl group has undergone an addition reaction to a double bond in the poly (butadiene) block of the block copolymer comprising at least 2 poly (styrene) blocks and at least one poly (butadiene) block.

3. A styrene-butadiene composition as claimed in claim 1, wherein the 20-carbon polycyclic diterpene having a carboxyl group is appended to the poly (butadiene) block of a block copolymer comprising at least two poly (styrene) blocks and at least one poly (butadiene) block.

4. A styrene-butadiene composition as claimed in Claim 3, wherein the 20-carbon polycyclic diterpene having a carboxyl group is at least appended to the No. 2 carbon position or the No. 3 carbon position in the poly (butadiene) block next to a poly (styrene) block.

5. A styrene-butadiene composition as claimed in any one of the preceding claims, wherein the 20-carbon polycyclic diterpene having a carboxyl group is selected from one or more of: abietic acid, dehydroabietic acid, neoabietic acid, pimaric acid, isopiinaric acid, and palustric acid.

6. A bitumen composition comprising bitumen and a styrene-butadiene composition as claimed in any one of the preceding claims.

7. A bitumen composition as claimed in claim 6, wherein the bitumen composition comprises the reaction product of

2-8 wt% of the block copolymer and

0.3-3 wt% of the polycyclic diterpene based on the bitumen composition.

8. A bitumen composition as claimed in claims 6 or 7, wherein the amount of aromatic extract is no more than 5 wt%, based on the bitumen composition.

9. An asphalt composition comprising the bitumen composition as claimed in any one of claims 6 to 8 and aggregate.

10. An asphalt composition as claimed in claim 9, wherein the bitumen composition comprises from 1 to 20% by weight, based on the asphalt composition.