DK143449B - MODIFIED ASPHALTIC BITUMEN MASS - Google Patents

Description

U3449

The present invention relates to a modified asphaltic bitumen mass, i.e. a material containing asphaltic bitumen modified with certain block copolymers of styrene and conjugated dienes.

5 Asphaltic bitumen is characterized by different physical properties and their mode of manufacture. The bitumen produced by direct distillation usually contains the residuals obtained by fractional distillation of petroleum oils and petroleum fractions. Starter is often obtained either by the same method or as precipitate when extracting 10 of certain oil fractions by means of a solvent. Cracked bitumens are obtained as residuals by a cracking treatment, while blown bitumens are those obtained by blowing bitumen produced by direct distillation or by blowing a precipitation bitumen or cracking bitumen.

15 As a rule, the brittleness and softening point of bitumen are not independent of each other. A bitumen with a high softening point is brittle at low temperatures, while a bitumen which is still sufficiently flexible at low temperature has a low softening point. In particular, it would be desirable to provide a low brittleness and high softening bitumen material when these bitumen e.g. must be used for road paving purposes or for roofing. From Dutch Patent Application No. 6404385, corresponding to Belgian Patent No. 646835, it is known that by the addition of block copolymers with configuration ABA, where each A, independently of the other A, denotes a polystyrene block having a molecular weight of 2000 to 100,000 and B represents a polymer block of a conjugated diene having a molecular weight of 5000 to 200,000, mixtures with improved viscosity at elevated temperature and improved extensibility and flexibility at low temperature are obtained. In these mixtures, the 30 block copolymer content is from 0.01 to 75% by weight. In United States Patent No. 3,265,765, it is mentioned that block copolymers of type A-B-A, where blocks A are non-elastomeric polymer blocks of molecular weight 2000 - 100,000, and block B is an elastomeric polymer block of molecular weight between approx. 25,000 and 1,000,000, can be dispersed in asphalt to improve high temperature viscosity and to improve extensibility and low temperature viscosity, but no detailed information on the amount and properties of the asphalt is provided.

U3449 2

It has now been found that not every bitumen is miscible with this type of block copolymer. According to the invention, to obtain a homogeneous mixture, it is necessary to use a bitumen whose softening point is at most 63 ° C. Furthermore, it has been found that the softening point 5 of the bitumen is essential for the properties of the bitumen / block copolymer mixture.

The invention therefore relates to a modified asphaltic bitumen mass containing a block copolymer of the general formula ABA, wherein each 10 A, independently of the other A, is a polystyrene block having a molecular weight of 2,000 - 100,000 and B represents a polymer block having a molecular weight of 5,000 - 200,000 of a conjugated diene, the modified asphaltic bitumen mass being characterized in that the asphaltic bitumen has a softening point of not more than 63 ° C and contains 15 0.1 to 24.9% by weight of the mass copolymer of each block A has an average molecular weight between 10,000 and 30,000, and that block B has an average molecular weight between 30,000 and 125,000.

The present bitumen comprises, by direct distillation, prepared, cracked and blown asphalt bitumen, provided that the softening point is not higher than 63 ° C. Usually, the softening points are in the range of 21 to 63 ° C, preferably between 29 and 56 ° C. Preferably, the bitumen in question has a penetration, measured by ASTM method 25 D5-61, between 150-300. Softer bitumens are usually described by their viscosity and are those having a viscosity of 100-1000 S SF (see Furol) at 99 ° C. Mixtures of bitumens, e.g. those obtained by admixing a very soft asphaltic oil or a soft asphaltic bitumen with a 30 bitumen having a relatively high softening point to obtain a product having a softening point not exceeding 63 ° C.

The block copolymers are known per se, e.g. from Dutch Patent Application No. 6404385 (Belgian Patent No. 646835) and U.S. Patent No. 353,665,765, A particularly suitable block copolymer has the composition polys tyrene-polyisoprene - polys tyrene.

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The block copolymers containing up to 50% by weight of blocks A, based on the weight of the copolymer, are most suitable for improving the flexibility of the bitumen mass.

5 The average molecular weights given here are the molecular weights calculated on the basis of predetermined relations between intrinsic viscosity and molecular weight, which relationships are established by, supported by and supplemented by tritium counting methods. These molecular weight determination methods have been found to be closely matched.

10

The block copolymers in question have the special feature that they behave like vulcanized rubber jugs, without being subjected to vulcanization treatment.

Furthermore, it has been found that using copolymers of the present invention it is unnecessary to employ apparatus which give great shear forces when the materials in question are produced by mixing their constituents. Furthermore, it is unnecessary to use the block copolymers in solution or in the form of emulsions or latexes, since none of these precautions are necessary to obtain a satisfactory dispersion of the block copolymers in the bitumen with a softening point in the specified range. The modified asphaltic bitumen mass of the present invention is therefore most conveniently prepared by mixing its constituents by conventional dry mixing, i.e. without the use of solvents or emulsifiers.

In the presence of the smaller amounts of block copolymers in the bitumen materials, preferably from 0.2 to 10% by weight, the physical properties of their intended applications, e.g. in pavements and 30 in roofing, improved. Thus, e.g. By the improvement in the properties of relatively high temperatures, bulging and spore formation in asphalt pavement are prevented at hot summer temperatures. The improvements in cold-weather properties result in a sharp reduction in cracking due to brittleness. By adding 35 of the block copolymers to bituminous roofing materials, their physical properties with respect to tensile strength and flexibility are improved and they are less likely to "collapse". The good physical properties of the materials prepared in this way enable their use as specialized products, e.g. roofing, paving, bitumen-based drilling mud, joint sealants and other applications. The materials can be modified using filler materials. The modulus of the materials is greatly increased by the presence of thermoplastic substances which are compatible with the system. The presence of polystyrene also improves the workability of the resulting materials.

A particularly interesting area of application for the materials in question is for the production of fertilizers or slow release fertilizers 10 of the fertilizer. Here, such bullets or pills are envisaged where the fertilizer is mixed with the materials concerned in such an amount that the fertilizer is bound in suitable molds and sizes for fertilization. The presence of the block copolymer together with the asphaltic bitumen not only increases the strength of the bitumen, but also causes an elastomeric action by preventing the pellets or bullets from breaking due to sharp temperature and size changes that can occur. occur under changing freezing and molding conditions.

The pellets in question may be coated with a surface film of the material which does not contain the fertilizer so that they can be easily handled without the fertilizer being exposed to the atmosphere before being placed in the soil.

Another use is the pelletization of low-concentration mineral mines.

These materials not only fulfill the function of binding the powdered ores to any desired pellet size, but they can also simultaneously act as reducing agents and as fuels in the purification process.

30

Example 1.

The bitumen used for the comparative experiments described below has the following properties: Penetration: 85 dmm at 25 ° C, annular and ball softening point: 47.5 ° C. The block copolymers used in the experiments (referred to in the tables as "SIS") have the general composition of polystyrene-polyisoprene-polystyrene, with the block molecular weights being 10,000 - 75,000 - 143449. For comparison, similar coatings are prepared in which the same asphalt is used, but in which the typical copolymer rubber known as "SBR", which is a random copolymer of styrene, is used instead of the block copolymer. and butadiene. The material used is a typical SBR with a styrene content of 23.5% and a Mooney viscosity, ML-4, of 52.

The viscosity of the bitumen without admixture and of the mixtures with the two types of elastomers is ascertained by a sliding plate microviscosimeter. Table I shows the results obtained.

Table I

Block copolymer / bitumen mixtures: viscosity-temperature data, measured with a sliding plate microviscosimeter.

15 -

Polymer Viscosity Ratio, Poise at 0.1 See. 1

between polymer and bitumen 20 ° C 30 C 45 ° C 60 ° C

20 η I c T ~ 1: 500 Bitumen control 0.54x10 0.62x10 0.72x10 0.84x10 SIS 0.52 0.63 0.81 1.09 SBR 0.49 0.62 0.58 0.73 1 : 200 Bitumen control 0.54x107 0.62x10® 0.72x10® 0.87xl01 SIS 0.56 0.79 0.9 1.42 25 SBR 0.36 0.66 0.54 0.63 1: 100 Bitumen control 0.54x107 0.62x10® 0.62x10® 0.87xl01 SIS 1.00 0.85 0.95 2.4 SBR 0.3 0.77 0.67 0.77 1:20 Bitumen Control 0.54x107 0, 62x10® 0.72x10® 0.85xl01 SIS 2.7 3.7 3.8 9.1 SBR 0.19 0.80 0.95 0.82 1:10 Bitumen Control 0.54x107 0.62x10® 0, 72x10® 0.87xl01 SIS 4.6 6.7 14.7 25 SBR 0.49 2.0 3.0 4.1 35

The relative changes in the viscosity of the mixtures do not vary much -3 with the shear rate in the area tested (4 x 10 and x 10 4 reciprocal seconds). The viscosities of Table I are determined at 6 143449 a constant shear rate of 1 x 10 10 reciprocal seconds.

It is clear from Table I that as little as 0.2% by weight of the block copolymer significantly increases the viscosity of the bitumen at 20 ° C. The relative effect on viscosity still increases when going from 20 ° C 5 to 60 ° C and from a chewing gum concentration of 0.2% by weight to the maximum tested in this series, namely 10% by weight. Due to the thermoplastic nature of the block copolymers in question, the fluidity of the blends above 100 ° C is sufficient at the processing temperatures. It is clear that at a given concentration, the block copolymer is significantly better than a typical SBR rubber for modifying asphalt viscosity. Thus, approx. 5% by weight of unvulcanized SBR before viscosity is significantly affected.

Measurements of the dynamic stiffness (ie the dynamic shear modulus) are made in a microelastometer at 0, 15 and 30 ° C. The results at frequencies of 10 and 40 cycles per per second is shown in Table II for mixtures containing 1% by weight of the block copolymer.

Table II

20

1: 100 block copolymer and bitumen mixtures: Dynamic stiffness temperature data, measured on microelastometer.

2

Dynamic stiffness (dyn / cm)

Temperature Polymer 10 cycles / sec. 40 cycles / sec.

25 ___ 0 ° C Bitumen control 1.50 x 1010 1.75 x 1010 SIS 0.24 0.32 SBR 0.20 0.23 15 ° C Bitumen control 0.85 x 10 ^ 1.50 x 108 30 SBR 1 , 08 1.90 30 ° C Bitumen control 0.23 x 108 0.92 x 108 SIS 0.81 1.90 SBR 0.48 1.60

The relative increase of the bitumen dynamic stiffness induced by the SBR in the mixture containing 1% SBR is clearly greater than the viscosity of the same mixture.

35 7 U3U9

Table III shows softening points determined by ASTM test method 36-26 and penetrations at 25 ° C (ASTM test method D5-61). It will be seen that in most of the tested products, the block copolymer decreases the bitumen penetration, while the normal SBR actually induces an increase in penetration.

Table III

Block copolymer / bitumen blends, softening point and penetration data.

10

Ratio Polymer Softening Point, Penetration, between ° C mm Polymer and Bitumen 1: 500 Bitumen Control 48 72 15 SIS 48 66 SBR 48.5 72 1: 200 Bitumen Control 48 72 SIS 48.5 68 1: 100 Bitumen Control 48 72 20 SIS 50 67 SBR 50 79 1:20 Bitumen control 48 72 SIS - 67 SBR 57 96 1:10 Bitumen control 48 72 25 SIS 71 67 SBR 67 84 30 Example 2.

The block copolymer used in this example has the general structure of polystyrene-polybutadiene-polystyrene, and the molecular weights of the blocks are 14,000 - 65,000 - 14,000. This block copolymer is mixed with asphaltic bitumens with different softening points, respectively 39, 65 and 86 ° C (ring and ball method). In each mixture, the amount of the block copolymer is 10% by weight. Table 1A3Å49 8 below shows the penetration (25 ° C, dmm), the softening point (° C) and the Fraass break point (° C) for these bitumens and for the mixtures of bitumen block copolymers.

5 Table

Bitumen or Mixture Penetration Softening Point Fraass fracture. hence dmm ° C point, ° C

10 1) bitumen 180/200 190 39 - 24 2) do + block copolymer 73 110 25 3) bitumen 20/30 22 65 -8 4) do + block copolymer 18 105 + 1 15 5) bitumen R 85/25 22 86 - 14 6) do + block copolymer 22 123 cannot be determined

From the contents of the table it appears that with bitumen 180/200, 20 is obtained a mixture with much less penetration and a softening point which is 71 ° C higher than for the bitumen itself, whereas the Fraass breaking point has even slightly decreased. With bitumen 20/30, the decrease in penetration is relatively small and the increase in the softening point of the mixture is only 45 ° C; the breaking point has risen to + 1 ° C. With bitumen R 85/25, a mixture with unchanged penetration is obtained and the increase in the softening point is only 37 ° C. Determination of Fraass break point is not possible (see below).

When mixing the asphaltic bitumen and the block copolymer carried out at elevated temperature, observe the following: mixture (2) is a homogeneous and low viscous liquid after stirring at 160 ° C for 3 hours. Mixture (4) is homogeneous at 180 ° C after 3 hours of stirring, but the mixture has high viscosity and stirring is difficult. Mixture (6) is not homogeneous even after 6 hours of mixing at 200 ° C; the mixture is very stiff after cooling and very inhomogeneous, and the block copolymer forms such a coarse dispersion in the asphaltic bitumen that a reliable Fraass determination cannot be performed.