HRP960561A2 - Bitumen compositions and a process for their preparation - Google Patents

Description

The present invention relates to bitumen mixtures, a process for their preparation and their use in bitumen for industrial applications, especially roof applications.

Bitumen has been continuously developed to meet the ever-increasing demands from, for example, builders. The progress of construction techniques requires the development of very good performances in the roof covering system. Such roofing systems should be sufficiently flexible, elastic and resistant to permanent deformation at all necessary temperatures in order to adapt to work without losing their waterproof properties.

A well-known technique for improving the properties of bitumen involves modifying the bitumen by incorporating a high level of thermoplastic rubber into it. In this way, a higher degree of elasticity and improved duration can be established.

Another known technique involves subjecting the bitumen to a so-called blowing process, optionally in the presence of a bitumen blowing catalyst, a method that reduces the temperature sensitivity of the bitumen. A combination of the above-mentioned techniques is, for example, contemplated in US 5,342,866, where blowing is carried out under mild conditions.

In application, the bitumen is oxidized with an oxygen-containing gas, optionally in the presence of a blowing catalyst, over a period of time until the bitumen reaches a pre-selected softening point or penetration.

Given that the blowing process should be constantly monitored in order to protect the bituminous product and prevent temperature rise, self-ignition, explosion and fire, it would be very useful to develop an oxidation process that would be carried out for a short time until reaching the pre-selected point of softening or penetration.

Surprisingly, it has now been found that the blowing process of relatively soft bitumens can be carried out with, or for a shorter period of time or at a lower temperature, when compared to conventional blowing processes, and when the bitumen to be oxidized contains an additional small amount of thermoplastic rubber, and optionally a small amount of bitumen blowing catalyst.

Ycontaining oxygen and which mixture comprises bitumen having a penetration (penetration) of at least 300 dmm (as measured by ASTM D 5 at 25°C) and a thermoplastic rubber present in an amount of less than 1% by weight, based on the total mixture .

Preferably, the thermoplastic rubber is present in an amount ranging from 0.1 to 0.5% by weight, based on the total composition.

Effect on the reaction kinetics of the blowing process, while the amount is insufficient to modify the bitumen as described hereinbefore.

Preferably, the process is carried out in the presence of a bitumen blowing catalyst.

An additional surprising effect is the finding that the use of a small amount of thermoplastic rubber allows the use of a very small amount of bitumen blowing catalyst. Conveniently, bitumen blowing catalyst is used in an amount of less than 1% by weight, based on the total mixture.

More preferably, bitumen blowing catalyst is used in an amount of less than 0.7% by weight, most preferably in an amount in the range of 0.3 to 0.5% by weight, based on the total mixture.

Suitable bitumen blowing catalysts, all of which are well known in the art, include ferric chloride, phosphorus pentoxide, aluminum chloride, boric acid and phosphoric acid. The use of phosphoric acid is preferred.

Blowing is carried out with a gas containing oxygen, such as air or pure oxygen. Air is preferably used.

Conveniently, the process of the present invention is carried out at a temperature in the range of 190 to 310°C.

The process according to the present invention can be carried out at ambient pressure or elevated pressure. However, it will normally be carried out at ambient pressure. Conveniently, the present procedure is carried out over a period of time longer than 1 hour, preferably longer than 2 hours. The procedure is normally carried out over a period of time that does not exceed 6 hours.

The compound includes thermoplastic rubber. The mixture may include one or more different types of thermoplastic rubber.

Although a wide variety of thermoplastic rubbers may be conveniently used in accordance with the present invention, preferred thermoplastic rubbers include optionally hydrogenated block copolymers comprising at least two terminal poly(monovinylaromatic hydrocarbon) blocks and at least one central poly(conjugated diene) block.

Preferably, the components of the block copolymer are selected from the group consisting of those of the formula A(BA)m or (AB)nX, where A represents a predominantly poly(monovinylaromatic hydrocarbon) block, where B represents a predominantly poly(conjugated diene) block, where X represents the residue of a multivalent binding agent and where n represents an integer ≥1, preferably ≥2, and m represents an integer ≥1, preferably m is 1.

Preferable A blocks are predominantly poly(styrene) blocks and B blocks are predominantly poly(butadiene) or poly(isoprene). Multivalent binders used include those commonly known in the art.

With the term "predominantly" it was meant that blocks A and B, respectively, can mainly originate from monovinyl aromatic hydrocarbon monomers and conjugated diene monomers, which monomers can be mixed with other structurally appropriate or inappropriate comonomers, for example, monovinyl aromatic hydrocarbon monomer as the main ingredient and a small amount (up to 10%) of other monomers or butadiene mixed with isoprene or with a small amount of styrene.

More preferably, the copolymers contain pure poly(styrene), pure poly(isoprene) or pure poly(butadiene) blocks, of which the poly(isoprene) or poly(butadiene) blocks can be selectively hydrogenated to a maximum residual ethylenic unsaturation of 20% and preferably less of 5%. The most preferably used block copolymer has the structure ABA, where A has an apparent molecular weight of 3,000 to 100,000, and preferably of 5,000 to 40,000, and B has an apparent molecular weight of 10,000 to 250,000 and preferably of 40,000 to 200,000. Originally prepared poly(conjugated diene) blocks usually contain from 5 to 50 mole % of vinyl groups, resulting from 1,2 polymerization relative to the conjugated diene molecules, and preferably a vinyl content of 10 to 25%.

The complete block copolymer to be used according to the present invention normally contains polymerized monovinyl aromatic hydrocarbon monomer in an amount of from 10 to 60% by weight and preferably from 15 to 45% by weight.

The apparent molecular weight of the total block copolymer will normally be in the range of 15,000 to 350,000 and preferably in the range of 40,000 to 250,000.

Examples of suitable pure block copolymers include KRATON G-1651, KRATON G-1654, KRATON G-1657, KRATON G-1650, KRATON G-1701, KRATON D-1101, KRATON d-1102, KRATON D-1107, KRATON D-1111, KRATON D-1116, KRATON D-1117, KRATON D-1118, KRATON D-1122, KRATON D-1135X, KRATON D-1184, KRATON D-1144X, KRATON D-1300X, KRATON D-4141 and KRATON D-4158 (KRATON is a trade name).

Bitumen can be crude oil distillation residue, cracked residue, crude oil blowing residue or crude oil distillation residue or crude oil extracts, bitumen obtained from propane bitumen, butane bitumen, pentane bitumen or mixtures thereof. Suitably, the bitumens include mixtures of the above bitumens with fillers (diluents) such as petroleum extracts, for example, aromatic extracts, distillates or residues. Suitably, the bitumen contains no more than 50% by weight of filler, preferably no more than 45% by weight, based on the total bitumen.

The bitumen applied to the current process has a penetration (penetration) of at least 300 dmm (as measured by ASTM D 5 at 25°C). One skilled in the art, however, typically characterizes such bitumens not by their penetration value, but by their viscosity at 100°C (as measured by ASTM D 2171). A penetration (penetration) of 300 dmm (at 25°C) corresponds to a viscosity (at 100°C) of about 1.5 Pa s. Preferably the bitumen has a viscosity as defined above of at least 0.05 Pa s., especially 0.1 to 1 Pa s.

The resulting bitumen mixture preferably has a penetration (penetration) of less than 100 dmm, preferably less than 50 dmm (as measured by ASTM D 5 at 25°C) and a softening point in the range of 60 to 140°C, preferably in the range of 80 to 120°C (as measured by ASTM D 36), and contains less than 1% by weight, preferably 0.1 to 0.5% by weight of any of the aforementioned thermoplastic rubbers, based on the total bitumen mixture.

Fillers such as carbon black, silicon or calcium carbonate, stabilizers, antioxidants, pigments and solvents are known to be useful in bituminous mixtures and can be incorporated into the mixtures of this invention at concentrations designed in the art.

As the skilled person will understand, the mixture of bitumen and thermoplastic rubber is preheated before being subjected to the blowing process. The mixture of bitumen and thermoplastic rubber is normally preheated to establish the initial temperature of the mixture in the range of 160 to 220°C. The preheated mixture is then normally oxidized at a temperature ranging from 240 to 290°C.

The present invention further provides a bituminous mixture obtainable by any of the processes described hereinbefore. Such a bituminous mixture has attractive oxidizing properties.

The present invention still further relates to the use of bituminous compound as previously described herein in industry, for example in roofing applications.

The present invention will now be illustrated in terms of the following Examples.

Examples

Example 1

Bitumen is prepared from a mixture of 65% by weight of non-naphthenic short residue and 35% by weight of paraffinic distillate. The bitumen had a viscosity of 0.17 Pa s (as determined by ASTM D 2171 at 100°C). To that bitumen was added 0.3% by weight of block copolymer and 0.7% by weight of phosphoric acid, based on the total mixture. The block copolymer used was a hydrogenated polystyrene-polybutadiene-polystyrene block copolymer with 30% by weight styrene content and a number average molecular weight of 103,000 as measured by GPC with a polystyrene standard. The ethylene unsaturation of the polymer was reduced to less than 1% of the original unsaturation with hydrogenation.

First, bitumen and block copolymer were mixed at a temperature of 180°C. After that, the preheated mixture thus obtained was blown with air in a blowing vessel at a temperature of 200°C for 2 hours. Phosphoric acid was introduced into the preheated mixture at the beginning of the blowing process. The main properties of the blown bituminous mixture are shown in Table 1.

Example 2

The blowing process was carried out in a similar way as described in Example 1, except that the preheated mixture contained 0.5% by weight of phosphoric acid. The main properties of the blown bituminous mixture are shown in Table 1.

Example 3

The blowing process was carried out in a similar manner as described in Example 1, except that the preheated mixture did not contain phosphoric acid. The main properties of the blown bituminous mixture are shown in Table 1.

Example 4

The comparative blowing procedure was carried out in a similar manner as described in Example 1, except that the preheated bituminous mixture contained neither block copolymer nor phosphoric acid. The main properties of the blown bituminous mixture are shown in Table 1.

Example 5

The blowing procedure was carried out in a similar way as described in Example 2, except that the bitumen was prepared from a mixture of 58% by weight of non-naphthenic short residue and 42% by weight of paraffinic distillate and that a temperature of 255°C was applied for 4 hours and 20 minutes. The bitumen had a viscosity of 0.14 Pa s (as determined by ASTM D 2171 at 100°C).

Example 6

The comparative blowing procedure was carried out in a similar manner as described in Example 4, except that the bitumen was prepared from a mixture of 48% by weight of non-naphthenic short residue and 52% by weight of paraffinic distillate and that a temperature of 265°C was applied for 4 hours and 20 minutes . The bitumen had a viscosity of 0.08 Pa s (as determined by ASTM D 2171 at 100°C).

From the results shown in Table 1, it will be clear that with the process according to the present invention (Examples 1, 2 and 3) it is possible to prepare a bituminous mixture that has a penetration index in the range of 3 to 8 in a much shorter time when compared to the usual blowing procedures (Example 4). In the examples, the time savings for a penetration index of 4 varies from 25% to 45%, depending on the amount of blowdown catalyst used.

From the results in Table 2, it will be clear that with the process according to the present invention (Example 5) it is possible to prepare a bituminous mixture that has a penetration index in the range of 3 to 8 at a reduced temperature when compared to the usual blowing process (Example 4) .

Table 1

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Table 2

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Claims (12)

1. A process for preparing a bituminous mixture, characterized in that it comprises blowing the mixture with some gas containing oxygen and which mixture includes bitumen having a penetration (penetration) of at least 300 dmm (as measured by ASTM D 5 at 25°C) and a thermoplastic gum that is present in an amount of less than 1% by weight, based on the total mixture. 2. The method according to claim 1, characterized in that the thermoplastic rubber is present in an amount of 0.1 to 0.5% by weight, based on the total mixture. 3. Process according to claims 1 or 2, characterized in that the mixture is blown with air. 4. The method according to any one of claims 1-3, characterized in that the thermoplastic rubber comprises an optionally hydrogenated block copolymer comprising at least two terminal poly(monovinylaromatic hydrocarbon) blocks and at least one central poly(conjugated diene) block. 5. The method according to claim 4, indicated by the fact that the block copolymer has the formula A(BA)m or (AB)nX, where A represents a predominantly poly(monovinylaromatic hydrocarbon) block and where B represents a predominantly poly(conjugated diene) block, where X represents the residue of a multivalent binding agent and where n is an integer ≥ 1 and m is some integer ≥ 1. 6. The method according to claim 5, characterized in that the A blocks are predominantly poly(styrene) blocks and the B blocks are predominantly poly(butadiene) blocks or poly(isoprene) blocks. 7. The process according to any one of claims 1-6, characterized in that the bitumen has a viscosity at 100°C of 0.1 to 1 Pa s. (as determined by ASTM D 2171). 8. The process according to any one of claims 1-7, characterized in that it is carried out in the presence of a bitumen blowing catalyst. 9. The method according to claim 8, indicated by the fact that bitumen blowing catalyst is used in an amount of less than 1% by weight, based on the total mixture. 10. The method according to any one of claims 1-9, characterized in that the bitumen blowing catalyst includes phosphoric acid. 11. Bituminous mixture, characterized by the fact that it can be obtained by the process defined in any of claims 1-10. 12. Bituminous mixture as defined in claim 11, characterized in that it is used in bitumen for industrial applications.