KR20000011130A - Bitumen compositions and a process for their preparation - Google Patents

Abstract

PURPOSE: A bitumen composition is prepared which has a good low temperature performance and a good high temperature rutting resistance, and has improved resistance to solvency of petroleum products. CONSTITUTION: A bitumen composition comprising a bitumen component, a thermoplastic rubber in an amount of less than 8 wt.% and an ethylene-vinyl acetate copolymer in an amount of less than 5 wt.%, both based on total bitumen composition, wherein the ethylene-vinyl acetate copolymer has a vinyl content in the range of from 20 to 35 wt.%, based on copolymer; a process for preparing such bitumen composition; and the use of such bitumen compositions in asphalt mixtures for road applications

Description

Bitumen composition and preparation method thereof

The present invention relates to bitumen compositions, methods for their preparation and their use in asphalt mixtures for road construction.

Bitumen is used as a binder in road asphalt mixtures and has been continually evolving to meet increasing performance demands from road builders. In general, bitumen performs well on road asphalt, but due to the increasing traffic volume, many roads are prematurely worn due to surface cracks and blemishes. The cracks cause water to reach the lower layers of the road surface, causing rapid deterioration, which is a serious defect in road asphalt and promotes the need for early repair. Increasing the bitumen content of the asphalt or using more flexible grade bitumen increases the crack resistance of the asphalt at low temperatures but increases the risk of excessive lubrication at high temperatures because the mixture is actually more flexible. Conversely, the rubbing resistance can be improved by reducing the bitumen amount in the asphalt mixture or by using a firm grade bitumen, but the crack resistance is reduced because the mixture is less flexible.

Accordingly, much effort has recently been made to develop hard bitumen compositions that meet current cracking requirements, ie bitumen compositions having both good low temperature performance and good high temperature rubbing resistance.

Another requirement that is frequently encountered in recent bitumen compositions is the solubility of petroleum products such as fuels (eg gasoline and kerosene) and oils such as lubricating oils. This resolution is important in areas where asphalt mixtures are regularly exposed to fuel and oil spills. Such areas include, for example, airfields, waste disposal plants, gas stations and tankers. When the asphalt mixture is exposed to fuel or oil effluent, bitumen eventually leaches out of the asphalt mixture, resulting in the loss of coarse aggregate from the road surface, the so-called wear of the road surface.

In view of the above, it is clear that it is advantageous to develop hard bitumen compositions that meet current cracking requirements and exhibit improved solvent resistance to petroleum products.

Surprisingly, it has now been found that such bitumen compositions can be prepared by adding thermoplastic rubber and additionally certain ethylene-vinylacetate copolymers to the bitumen component.

Therefore, the present invention comprises a bitumen component, less than 8% by weight thermoplastic rubber and less than 5% by weight ethylene-vinylacetate copolymer based on the total bitumen composition, wherein the ethylene-vinylacetate copolymer is 20 to It provides a bitumen composition having a vinylacetate content in the range of 35% by weight.

The use of ethylene-vinylacetate copolymers in thermoplastic rubber-containing bitumen compositions is known in general terms (see eg EP-B1-0337282 and EP-B1-0340210), but certain vinylacetates as currently claimed. Advanced uses of ethylene-vinylacetate copolymers having a content have not been disclosed previously.

Preferably, the ethylene-vinylacetate copolymers used according to the invention have a vinylacetate content in the range of 25 to 35% by weight, more preferably in the range of 30 to 35% by weight, based on the copolymer.

Preferably, the ethylene-vinylacetate copolymers used according to the invention are present in less than 3% by weight based on the total bitumen composition. More preferably, the ethylene-vinylacetate copolymer is present in the range of 0.5 to 3 weight percent based on the total bitumen composition.

Preferably, the thermoplastic rubber is present at less than 6 weight percent based on the total bitumen composition.

The bitumen composition comprises thermoplastic rubber. Suitably, the bitumen composition may comprise one or more different types of thermoplastic rubber.

A wide range of thermoplastic rubbers may be suitably used in accordance with the present invention, but preferred thermoplastic rubbers consist of two or more terminal poly (monovinylaromatic hydrocarbon) blocks and one or more central poly (conjugated diene) blocks, optionally hydrogenated to form a continuous network. Block copolymers.

Preferably the block copolymer component is selected from the group consisting of the formula A (BA) _m or (AB) _n X, wherein A is a predominantly block copolymer of poly (monovinylaromatic hydrocarbon), and B is mainly A poly (conjugated diene) block, X represents a residue of a polyvalent coupling agent, n represents an integer of 1 or more, preferably an integer of 2 or more, and m represents an integer of 1 or more, preferably 1.

More preferably, block A mainly represents a poly (styrene) block and B block mainly represents a poly (butadiene) block or a predominantly poly (isoprene) block. Multivalent coupling agents used include conventional ones known in the art.

The term “predominantly” means that blocks A and B are monovinyl aromatic hydrocarbon monomers and conjugated diene monomers, respectively, which monomers may be mixed with other structurally related or unassociated comonomers, such as monovinyl aromatic as main component. Mostly derived from hydrocarbon monomers and small amounts (up to 10%) of other monomers or butadiene mixed with isoprene or small amounts of styrene.

More preferably, the block copolymer comprises pure poly (styrene), pure poly (isoprene) or pure poly (butadiene) blocks, wherein the poly (isoprene) or poly (butadiene) blocks are selectively hydrogenated to Residual ethylenic unsaturations of up to 20%, more preferably less than 5%, of the original unsaturated content. However, preferably the block copolymer is not selectively hydrogenated. Most preferably, the applied block copolymer has the structure ABA, where A has a molecular weight of 3000 to 100,000, preferably 5000 to 25,000, and diblock AB has a molecular weight in the range of 50,000 to 170,000. Has Preferably, diblock AB has an apparent molecular weight in the range of 70,000 to 120,000.

As used herein, the term "apparent molecular weight" refers to the molecular weight of a polymer measured by gel permeation chromatography (GPC) using the poly (styrene) assay (according to ASTM 3536),

The initially prepared poly (conjugated diene) blocks usually contain 5 to 65% by weight of vinyl groups derived from 1,2-polymerization with respect to conjugated diene molecules, and preferably 10 to 55% by weight of vinyl.

The complete block copolymers used according to the invention usually comprise 10 to 60% by weight and preferably 15 to 45% by weight of polymerized vinyl aromatic monomers.

The apparent molecular weight of the total block copolymer is usually in the range of 100,000 to 500,000 and preferably in the range of 150,000 to 200,000.

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 registered trademark).

The bitumen used may be distillation residues, cracking residues, crude oil extracts, bitumen derived from: propane bitumen, butane bitumen, pentane bitumen or mixtures thereof. Other suitable bitumens include mixtures of the bitumen with extenders (flushs) such as petroleum extracts, such as aromatic extracts, distillates or residues. Suitably, the bitumen component which has not been oxidized is used. Suitably, the bitumen has a permeability in the range from 50 to 400 dmm, preferably from 60 to 200 dmm (measured by ASTM D 5 at 25 ° C.) and in the range from 30 to 60 ° C., preferably from 35 to 50 ° C. It has a softening point (measured by ASTM D 36).

Fillers such as carbon black, silica and calcium carbonate, stabilizers, antioxidants, pigments, and solvents are known to be useful in bitumen compositions and can be incorporated into bitumen compositions of the present invention at concentrations familiar to the art.

The present invention also provides a process for preparing a bitumen-based composition of the present invention comprising mixing bitumen at an elevated temperature with less than 8% by weight of thermoplastic rubber and less than 5% by weight of ethylene-vinylacetate copolymer based on the total bitumen composition It is about.

Suitably, the process is carried out at a temperature in the range from 160 to 220 ° C.

Preferably, the process according to the invention is carried out at a temperature in the range from 170 to 190 ° C.

The method can be carried out at ambient or elevated pressure. Usually, however, it is carried out at ambient pressure.

Suitably, the method is carried out for a time of less than 6 hours, preferably less than 2 hours.

The present invention also provides the use of the bitumen composition of the above in an asphalt mixture for road construction.

The invention is illustrated by the following examples.

Example 1

The bitumen composition according to the present invention is prepared as follows.

Bitumen with a penetration of 88 dmm (measured by ASTM D 5 at 25 ° C.) and a softening point of 47.5 ° C. (measured by ASTM D 36) was determined by weight of 4 wt% straight-chain non-hydrogenated polystyrene-polybutadiene-polystyrene block copolymer and Mix with 2 wt% ethylene-vinylacetate copolymer. The ethylene-vinylacetate copolymer has a 33 wt% vinylacetate content based on the copolymer. The block copolymer has a styrene content of 31% by weight, an apparent molecular weight of 170,000 and contains a polystyrene-polybutadiene diblock having an apparent molecular weight of 90,000. The bitumen composition thus obtained is then mixed with the aggregate to prepare an asphalt mixture. Subsequently, an asphalt test piece is manufactured according to the Marshall method RAW 57. The asphalt specimens are then stored for 24 hours under jet fuel A1. The solution is then decanted and the mass of the asphalt specimen is measured. The kerosene resistance, expressed as a percentage of the original asphalt specimen mass, is 0.8%.

Example 2

The bitumen composition according to the present invention is prepared in a similar manner as described in Example 1 except that 5% by weight block copolymer based on total bitumen composition is used. An asphalt test piece was then prepared from the bitumen composition thus obtained in a similar manner to that described in Example 1. Asphalt test pieces exhibit kerosene resistance of 0.6%.

Example 3

For comparison purposes, similar to that described in Example 1, except that 5.5 weight% ethylene-vinylacetate copolymers based on the total bitumen composition, having 18 weight% vinyl acetate content on the basis of the copolymer, without the use of block copolymers, were used. The bitumen composition is prepared by the method. An asphalt test piece was then prepared from the bitumen composition thus obtained in a similar manner to that described in Example 1. Asphalt test pieces exhibit 2.3% kerosene resistance.

Example 4

For comparison purposes, the bitumen composition is prepared in a similar manner as described in Example 1 except for using an ethylene-vinylacetate copolymer having an 18% by weight vinylacetate content based on the copolymer. An asphalt test piece was then prepared from the bitumen composition thus obtained in a similar manner to that described in Example 1. Asphalt test pieces exhibit kerosene resistance of 3.1%.

Example 5

For comparison purposes, the bitumen composition is prepared in a similar manner as described in Example 2 except for using an ethylene-vinylacetate copolymer having a 40 wt% vinylacetate content based on the copolymer. An asphalt test piece was then prepared from the bitumen composition thus obtained in a similar manner to that described in Example 1. Asphalt test pieces exhibit 3.0% kerosene resistance.

From the above, it is clear that the present invention provides a hard bitumen composition with improved kerosene resistance (Examples 1 and 2) as compared to bitumen (Examples 3-5) which lies just outside the scope of the present invention.

Claims (12)

A bitumen component, less than 8% by weight thermoplastic rubber and less than 5% by weight ethylene-vinylacetate copolymer, based on the total bitumen composition, wherein the ethylene-vinylacetate copolymer ranges from 20 to 35% by weight based on the copolymer Bitumen composition having a vinyl acetate content of. The composition of claim 1 wherein the vinylacetate content is in the range of 25 to 35% by weight, based on the copolymer. The composition of claim 2 wherein the vinylacetate content is in the range of 30 to 35% by weight, based on the copolymer. The composition of claim 1, wherein the ethylene-vinylacetate copolymer is present in less than 3% by weight, based on the total bitumen composition. 5. The composition of claim 1, wherein the thermoplastic rubber is present at less than 6% by weight based on the total bitumen composition. 6. The bitumen according to any one of claims 1 to 5, wherein the bitumen has a penetration in the range of 50 to 400 dmm (measured by ASTM D 5 at 25 ° C.) and a softening point in the range of 30 to 60 ° C. (measured by ASTM D 36). Having a composition. The composition according to claim 1, wherein the thermoplastic rubber comprises an optionally hydrogenated block copolymer consisting of at least two terminal poly (monovinylaromatic hydrocarbon) blocks and at least one central poly (conjugated diene) block. . 8. The block copolymer according to claim 7, wherein the block copolymer has the structure A (BA) _m or (AB) _n X, wherein A mainly represents a poly (monovinylaromatic hydrocarbon) block and B mainly represents a poly (conjugated diene) block. , X represents a polyvalent coupling agent moiety and n is an integer of 1 or more and m is an integer of 1 or more. 9. The composition of claim 8, wherein the A blocks are mainly poly (styrene) blocks and the B blocks are mainly poly (butadiene) blocks or mainly poly (isoprene) blocks. The method according to claim 8 or 9, wherein the diblocks prepared from A and B have an apparent molecular weight in the range of 50,000 to 170,000. Mixing bitumen with less than 8% by weight of thermoplastic rubber and less than 5% by weight of ethylene-vinylacetate copolymer based on the total bitumen composition, wherein the ethylene-vinylacetate copolymer is based on the copolymer A process for preparing bitumen compositions as defined in any of claims 1 to 10 having a vinylacetate content in the range of 20 to 35% by weight. Use of bitumen compositions as defined in any of claims 1 to 10 in asphalt mixtures for road construction.