This invention relates to a polymer modified bitumen (petroleum-asphalt) composi¬ tion and a process for the preparation of this composition.

The modification of mineral oil bitu¬ mens is carried out for improving certain substance-speci ic properties (characteristics) and is above all aimed to extend the tempera¬ ture range of applicability. The use of mineral oil bitumens in road construction and insulation is limited thereby that the bitumen becomes brittle (rigid), fragile at lower temperatures, whereas it is softened and looses its solidity and bonding strength at elevated temperatures. The extending of the range of the plastic behaviour of petroleum bitumens can be achieved by the addition of various native and synthetic polymers having a high molecular weight such as the native and synthetic rubber, polyolefines , ethylene/viny1 acetate copoly- mers and the styrene/butadiene, i.e. so- called "SBS" type copolym.ers.

The addition of SBS type block polymers has not only economical limits but, in additim to the improvement of some properties of application techniques of the bitumen, other technical characteristics are iπfavourably influenced by this modification, e.g. , together with an increase in the cold flexibility, the strength and similarly the resistance

to penetration are decreased, particularly at higher temperature. Although the addition of SBS copolymers in a higher proportion seems preferable for the behaviour of the substance at both low and elevated tempera¬ tures, the high-grade increase in the viscosity of the composition is unfavourable since it deteriorates the workability and treatment. For the modification of bitumen the quality of starting bitumen has also to be considered} thus, on modification several viewpoints should be made valid. On incorporat¬ ing the SBS copolymer, a propensity to separa¬ tion appears in the bitumen, i.e. it is desirable to increase the stability of the modified bitumen composition and it is also important to have the possibility to improve the adhesion properties together with keeping other parameters and favourable workability features constant.

According to the Hungarian patent application published under No. T/52135, in order to ensure the so-called colloid stability of bitumen, synthetic resins are incorporated to the systems, i.e. to the starting bitumens, which increase the solubility of the polymeric additives in the bitumen, decrease the interfacial tension of bitumen and improve the cohesion and adhesion proper¬ ties. According to the above-cited Hungarian document aromatic oil or extract of lubricat¬ ing oil, SBS copolymer, hydrocarbon resins, atactic polypropylene and rubber grist are

added to the bitumen. Thus, some properties of the bitumens used for road construction can be improved.

The aim of the present invention is to develop and prepare a bitumen composi¬ tion, by the use of which the properties of the bitumen/polymer mixtures can be modified to a great extent simultaneously keeping the favourable parameters constant by using a cheap additive and, in addition, the bitumen (obtained) can be utilized for both road construction and insulation purposes as well .

The modified composition according to the present invention comprises 75-95 parts by weight of mineral oil bitumen, 2-15 parts by weight of styrene/butadiene block polymer, 1-15 parts by weight of vegetable oil, a mixture thereof or regenerated vegetable oil, 0-30 parts by weight of paraffinic, naphthenic or aromatic mineral oil derivatives and 0-25 parts by weight of mineral flour.

The process of the invention for the preparation of a modified bitumen composi¬ tion comprises adding 0-30 parts by weight of paraffinic, naphthenic or aromatic mineral oil, 2-15 parts by weight of styrene/butadiene block polymer, 1-15 parts by weight of vegetable oil, a mixture thereof or regenerated vegetable oil to 75-95 parts by weight of mineral oil bitumen at a temperature between 170 C and 190 C under vigorous stirring, stirring the mixture at the defined temperature for

at least 30 minutes and optionally mixing at most 25 parts by weight of mineral flour with a particle size below 0.1 mm thereto. The bitumen (petroleu -aspbal ) used had a ring-and-ball softening point of 40-60 °C, a penetration of 40-200x10 mm at 25 C, a breaking point (Traass) between -5 C and -15 C and an asphaltene content of 8-15 % by weight. The SBS copolymers suitable for the purposes of this invention had a styrene content of 20-40 % by weight and a molecular weight between 100,000 and 300,000. The mineral oil derivative used had a flash point above 150 C, and a viscosity between 10 and 100 mm /s measured at 40 C. Such types are e.g. the so-called white products, insulating oil, spindle oil, extract oil and the like. According to the invention, the vegetable oil means both drying and semi-drying oils, however, animal fats may also be used. Among the oils pressed from oily seeds linseed oil, as well as the oil of sunflower, soybean, rape, pumpkin seed, sesam, olive, fish, maize, linseed oil and regenerated oils with a solidification point between -10 C and -20 C and an iodine number of 90-190 may be mentioned. Hog's fat, beef tallow and wool fat are useful animal fats.

According to our recognition, the vegetable oils or animal fats improve the behaviour of the modified bitumen system at a low temperature without unfavourably

influencing its properties at elevated temperatures j they significantly improve the stability of bitumen composition, decrease its propensity to the separation otherwise observed, which occures in the case of co- polymer-modified bitumens. The presence of vegetable oils improves the adhesion of bitumen compositions to the breakstone used in the road construction and, on the other hand, the adhesion of the bitumen compositions to the carrier textile (web) of roofing felt. Through an interaction, the mineral oil additives also influence the properties of modified bitumens to a great extent, i.e. the mineral oil additives are effective not only as diluting agents or solvents but, depending on their composi¬ tion, they influence the micro- and macro- structure of the composition as well.

By modifying the content of the com¬ position according to the invention self- adhesive masses can be prepared which are particularly favourable for the preparation of roofing felts. The roofing felts coated with the self-adhesive mass adhere to the metal, concrete or plaster base surface under the influence of a simple pression without using any adhesive or without melting the active ingredient (agent) of the roofing felt. The adhesion is sufficient to fasten the felt on a horizontal or vertical surface and ensures the impermeability required of the overlapping of the felts.

The invention is illustrated in more detail by the following Examples. Example 1

90 parts by weight of bitumen used for road construction (with a softening point of 48 C, breaking point of -14 C, penetra¬ tion of 7.8 mm and an asphaltene content of 14.5 ._ by weight) are heated at 180 °C and 2 parts by weight of aromatic oil fraction (containing 60-70 % aromatic hydrocarbons, 15-20 % of saturated ingredients with a flash point above 180 C, and viscosity of 20-50 mm ² /s at 100 °C) are added under slow stirring. Subsequently 4 parts by weight of SBS copolymer are added under vigorous stirring and the mixture is stirred at 180-190 °C for 1 hour. Finally, 1 part by weight of naphthenic oil fraction and 3 parts by weight of sunflower oil are added. The modified bitumen thus obtained may be used as asphalt binder and has a softening point at 75-80 C, breaking point at -20 C and does not show any separation during a storage of 72 hours at 180 C. When examined at -20 C, the retention of particles (grains) which is characteristic of the adhesiveness, is about 95 % . The strength of the asphalt prepared by using the modified bitumen accord¬ ing to the composition of the Hungarian standard No. MSZ 07-3210 is better than that of the asphalts prepared with known modified bitumen; and it shows particularly

excellent features in the course of investiga¬ tion of repeated loading at a higher temperature or adhesiveness at a low temperature.

Comparative Example:

A modified bitumen was prepared by using the bitumen and polymer of the above-mentioned quantity and quality without naphthenic oil fraction adn sunflower oil. The product had a softening pointz of 80-85 C and break¬ ing point of -14 C. After a storage of 72 hours at 180 C a sample was taken and the SBS polymer was significantly enriched in the upper part of the sample, a phenomenon indicating that the compatibility of the bitumen and polymer was not adequate. The strength of asphalt prepared by using this modified bitumen possessed poorer properties at normal temperature than the bitumen according to the invention. The grain-retain¬ ing ability of the binder was found to be about 50 % at -20 °C.

Example 2

90 parts by weight of distillation bitu¬ men (with a softening point of 41 C, breaking point of -16 C, penetration of 17 mm and asphaltene content of 11 % ) are heated 18 180 °C and 20 parts by weight of aromatic oil fraction are added while slowly stirring. Subsequently, 5 parts by weight of SBS copo¬ lymer are added under vigorous stirring, then the mixture is stirred at the above- defined temperature for 1 hour. Finally, 3 parts by weight of rapeseed oil are added.

The product obtained has a softening point at 80-85 C, breaking point at -21 C and a grain-retaining ability of at least 80 % at -20 °C. The asphalt prepared by using this modified bitumen as binder possesses at law temperature excellent, even better properties than the binder of Example 1. For comparison, the above mixture was prepared without adding any mineral or vegetable oil. The product obtained had a softening point of 85-90 C but a breaking point of only -17 C, with a grain-retaining ability of 50-60 % at -20 °C. In connection with this, the features of asphalts prepared by using this comparative binder were both at a high or a low temperature poorer than those of the asphalts prepared with the binder of the invention. Example 3

85 parts by weight of bitumen with a quality according to Example 1 are molten at 180 °C and 2 parts by weight of aromatic mineral oil fraction are added. Subsequently, 10 parts by weight of SBS polymer are added while vigorous stirring and the mixture is stirred at 180-190 °C for 1 hour. Finally, 3 parts by weight of sunflower oil are added. The modified bitumen obtained has a softening point at 115-120 C and a breaking point below -30 C. From this product a roofing felt can be prepared in the usual way which has a flow point of 90-100 C and is resistant in the bending test at -20 C.

A requirement against a roofing felt prepared with a modified bitumen of good quality consists therein that their material be not . flowable vertically at 90 °C, be flexible without breakage or crack, respectively at -15 C as well as be capable to reliably bridge over the statical and dynamical fissures of the base surface (e.g. concrete). These requirements cannot be satisfied by the standard distillation or blown bitumens.

For comparison, the above mixture was also prepared without adding the aromatic oil fraction and sunflower oil. The product obtained had a breaking point at -24 C and the felt was broken in the course of bending at -15 C. In addition, the mixture had high viscosity and it could not be processed b using the traditional roofing plate manufacturing equipment. Examp1e 4

78 parts by weight of bitumen used for road construction (with a softening point of 46 °C) are molten at 180 °C and 2 parts by weight of naphthenic oil fraction (containing 5-10 ?o of C _ft , 40-45 % of C _N and 50-55 % of C _p , with a flash point above 150 C and a solidification point below -20 C) are added. Subsequently, 10 parts by weight of SBS polymer with a styrene content of 30 % and an average molecular weight of 250,000 are added. After vigorous stirring for 90 minutes, 10 parts by weight of sunflower oil and 25 parts by weight of talc having

a particle size below 0.1 mm are added. The composition obtained has a softening point at 100-105 C, breaking point belo -30 C, a penetration of 9-10 mm and is useful as a base material for self-adhesi e roofing felts. A roofing felt of about 2 mm in thickness prepared from the usual glass or plastic fibre web carrier shows a heat resistance of at least 90 C and can be bent without fissure at -20 C. On the one side of the felt a polyethylene foil of 0.1 mm in thickness and on the other side a siliconized paper are applied. On using the felt the latter one can easily be removed and when pressed onto the surface of the concrete or plaster the self-adhesive side of the felt, adheres on it without separa¬ te bonding or mechanical fixation. The adhe¬ sion is accomplished under effect of a smooth pressure at a temperature above +5 C. The overlapped parts of the felt adhere to each other strongly, which makes possible simple preparation of water-impermeable junctions .

Example 5

80 parts by weight of bitumen (with a softening point of 40 C) are molten and heated to 180 °C. After adding 2 parts by weight of naphthenic oil fraction and vigorous stirring, 8 parts by weight of SBS having a quality of Example 4 are added and the mixture is stirred for 90 minutes. Subsequent¬ ly, 8 parts by weight of soybean oil and

10 parts by weight of talc having a particle size below 0.1 mm are incorporated into the mixture. The mixture obtained has a softening point at 95 C and a breaking point at -30 C. This composition may be used as self-adhesive sticking composition (layer) when it is applied in a thickness of 0.1-1.0 mm onto felts or foils which are then covered with a siliconized protective paper until use. When the protective paper is removed and the felt or foil is pressed onto a metal, concrete or plaster base treated with a suitable priming material, the self- adhesive layer ensures a satisfactory bonding and a suitable adhesion in the overlapping parts of the product.