Sealing c npositictns useful for ensuring tightness of joins of concrete highways have already been recommended. This is particularly the case of French Patent 1539392 in which the compositions described cαrprises:

- from 10 to 75% by weight of a non-cxiriized asphalt having a viscosity of between 107 and 484 cSt at 135'C (preferably straight distillation asphalt having a viscosity of between 140 and 375 cSt at 135*C) and a softening point (ball and ring) included between 30 and 60*C,

- from 10 to 35% by weight of a block copolymer having the general configuration A-B-A and more particularly a copylymer,

- from 15 to 55% by weight of a petroleum oil having a content of aromatic components of at least 50% by weight (preferably 69 to 75% by weight) and a viscosity included between 15.5 and 24 cSt at 99*C.

The present invention concerns the preparation of sealing membranes; these sealing membranes are in the farm of films or sheets which ccπprise a sealing product, a filler and a reinfααpqβneπt (generally a screen or a grid) on which the sealing element containing the filler is deposited. After manufacture, these films or sheets are wound on themselves and positioned on site by known processes, such as for example heat sealing and/or gluing.

Production of these sealing membranes involves the suitable choice of the constituents of the "sealing product". It has been found that this sealing product was advantageously to be

SUBSTITUTE SHEET

obtained by mixing a "specific bitumen", an SBS copolymer and a particular petroleum oil.

The present invention therefore firstly relates to the specific bitumens adapted to be used for the preparation of the sealing product intended for manufacturing the sealing membranes defined hereinabove.

The usable specific bitumens according to the invention are hard bitumens, of Newtonian character, derived from the treatment of the residues in vacuo by propane deasphalting and characterized by:

. a viscosity of 560 to 850 s Saybol furol at 135'C (or 1200 to 1800 cSt),

. a "ball and ring" softening point of between 65 and 74*C,

. a needle penetration of 25'C of 10 to 20 tenths of millimeter,

. a content of asphaltprips of 20 to 35% mass.

These bitumens are obtained, in refinery, by semi-blowing and they present properties which differ greatly from those of the bitumens obtained by straight distillation of the same crudes. Table I gives the physical characteristics of three bitumens (obtained from different crudes) that may be used a xrrding to the invention and of the three corresponding bitumens obtained, from these same crudes, by straight distillation.

A block copolymer and a particular petroleum oil are therefon.added to these specific bitumens.

The block cσpolymers that may be used are block copolymers constituted by an alternate succession of a thermoplastic homopolymer of styrene and of an elastomer obtained by polymerization of conjugated diene. The preferred block copolymer is polys1.vrene-polybutadiene^»lystyrene for which the polystyrene represents from 20 to 40% mass of the block copolymer. The typical copolymer is characterized by a styrene/butadiene mass ratio of 30/70, a molecular weight of between 250,000 and 300,000 or a viscosity in solution of 20 Pa.s

(if the viscosity of the dissolutions of 25% in mass of the SBS copolymer in toluene is expressed) .

To this mixture of bitumen and of block copolymers there is added a particular petroleum oil. This is an aromatic oil which is prepared as follows: during the refining operations in the production of mineral oils, the di ti lation in vacuo of the reduced crude given petroleum cuts which are known as vacuum distillates. Said distillates are mixtures of mineral oils, aromatic oils, paraffins and waxes. At this stage, the refiner must, by solvent treatment methods, separate successively from the distillates, the aromatic oils (for example by a furfurol treatment) , then the liquid paraffins and the waxes- (for example by a treatment with methyl ethyl ketone) in order to confer to the mineral oils the required lubricant qualities.

From the aromatic oils obtained on the various vacuum distillates, those proving to be capable of giving the compatibility and physical properties desired for the sealing binder have been selected. These oils are characterized by a viscosity at 100'C of 43 to 64 cSt, a flash point included between 280*C and 320'C. Table 2 summarizes the 'typical physical characteristics of these specific oils rendering the mixture of the special bitumen and the SBS copolymer compatible.

Given that the bitumens selected may have different compositions, on account of their origin, like the aromatic oils, the proportions of these constituents for a given content of SBS copolymermust be adjusted in order to render the bitumens and copolyπars perfectly compatible. The proportion of aromatic oils to be used is high, since it is necessary to have in the mixture just enough aromatic oils to peptize the polymer and asphaltenes present in the mixture by physical adsorption, and to obtain a colloidal suspension of bitumen in the continuous polymer medium.

The solution to this problem therefore consists in carrying out a simple compatibility test which will enable any man skilled in the art, having a certain bitumen, a certain polymer and aromatic oil at his disposal, to adjust the relative.

proportions of the mixture of bitumen and oil. This test consists in intimately mixing the bitumen and the desired quantity of polymer, then adding to this mixture increasing quantities (5, 10, 20, 30 and 40% for example) of aromatic oils. The homogeneous mixtures obtained are maintained at 165*C without stirring and, after 5 days of storage, the softening points of samples taken in the lower part and in the upper part of the mixtures are determined. In the absence of aromatic oils, the appearance of noteworthy differences are more or less rapidly observed between the softening points of the upper and lower samples and, for a restricted range of concentrations of aromatic oils in the mixtures, these differences disappear. -

Compatibility is also translated by performances unegualed from the standpoint of the physical and mechanical properties of the membranes. As shown by the results of Table 3, the "ball and ring" softening points measured before and after storage for 5 days at 165'C, as a function of the addition of aromatic oil, converge towards a point which coincides precisely with the optimal proportions of aromatic oil for which compatibility is attained and translated by the similarity of the softening points measured in the upper 35 and lower parts of the test pieces.

It will be in the interest of the man skilled in the art having determined the adequate proportions in which the aromatic oil should-be added to the bitumen in order to obtain optimal inpat-lbility with the SBS copolymer, to measure the density of the bitumen-oil mixture at a reference temperature of 15 or 25*c or, if necessary, the surface tension of this mixture. In fact, it is established that the density and surface tension of the mixture evolve in parallel with the content of aromatics in the mixture. The separate deliveries of aromatic oil and of bitumen will be the object of a measurement of density and, knowing the density of the compatible product to be produced, he may easily determine the proportions of the bitumenoil mixture that should

be made in order to obtain a sealing membrane of satisfactory quality.

In practice, the relative proportions of bitumen, of block copolymer and of the petroleum oil referenced hereinabove are as follows:

Bitumen 55 - 75% by weight SBS copolymer 8 - 15% by weight Oil 15 - 35% by weight

Table 4 recalls the obligations defined by the specification of the UEATC (union Europeeπne pour l'Agrement Technique dans la Const-ruction) concerning the binding agents based an bitumen and SBS elastomer rubbers. The results shown in this Table were obtained from mixtures (having no fillers), non-aged (new) or aged, such ageing being effected at 70*C for 6 months in a ventilated stove, this test being carried out on a plate 2 mm thick far the binding agent and an the membrane itself for the finished product.

Table 5 mentions the typical characteristics of the products (binding agent having no filler and sheet) seen in the present invention so as to be certain that, after ageing, all these products surely satisfy the specification of the UEATC.

Two examples of products acε-ording to the invention will now be described.

In these two examples, the following are used:

69% by weight of the bitumen A of Table 1

11% by weight of star SBS copolymer

20% by weight of the oil of specification A ('binding agent A") of Table 2 or the oil of specification B ("binding agent B") of said Table 2.

The properties of these binding agents (not filled) are mentioned in Table 6.

Table 7 mentions a certain number of properties of the binding agent A which has received a suitable filler (calcium carbonate).

TO ffP! 1

BHUMENS THAT MAY BE USED ACCORDING TO TOE INVENTION (PHYSICAL CHARACTERISTICS)

EESIGNATIO A *1 B C

*L

SOFTENING POINT *C 70 40 66 39 72

NEEDLE PENETRATION AT

25*C (1/10 mm) 12 200 16 200 11

RELATIVE DENSITY AT 15*C 1.051 1.028 1.038 1.011 1.054 AT 25*C 1.045 1.022 1.032 1.005 1.048

FLASH POINT (OPEN CUP) ^* C 354 342 337 330 352

CHEMICAL COMPOSITION IN % MASS

Asphaltenes 31.6 16.3 25.0 9.5 34.9

Oils 7.7 27.6 13.5 20.5 16.9

Resins 60.7 56.1 61.5 70 48.2

KINEMATIC VISCOSITY cSt AT 135*C 1750 260 1170 180 2500

Indications A, B and C concern bitumens obtained from oils of various origins; indications A., B. concern bitumens obtained from oils of the same origin as A, B, C, but prepared by straight distillation.

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ABTR 2

PHYSICAL CHARACTERISTICS OF THE SPECIFIC OILS THAT MAY BE USED ACCORDING TO THE INVENTION

DESIGNATION A B C D E

VISCOSITY cSt at 100'C 66.2 63.8 82.0 81.3 64.2 cSt at 120°C 32.6 31.1 36.7 36.1 30.4

DENSITY AT 15°C 0.984 0.963 0.989 0.982 0.953

FLASH POINT

°C COC 324 302 252 298 300

FLOW POINT "C 21 32 26 30 37

ANILINE POINT °C 70.2 79.0 64.8 66.0 78.0

INDEX OF REFRACTION

AT lO'C 1.5340 1.5220 1.5344 1.5335 1.5199

SULFUR CONTENT

% MASS 3.62 1.29 4.2 1.26 1.12

The different oils A, B, C, D, E came from various crude oils already mentioned in Table 1.

TAWTK 3

EVOIDΓION OF THE BALL-PNG TEMPERATURES AS A FUNCTION OF THE RECIPROCAL CONTENT OF BITUMEN A

AND OIL A

% Bitumen/Oil 85/15 80/20 75/25 70/30 65/

BALL-PJNG EMPERATURE

*C UPPER 138 132 128 110 108

LOWER 83 82 78 110 108

SPECIFICATION OF UEATC

Non-aged St-ilt'j Aged sta ^f φ THE fiTN ¹ !**? ^Αtzp Wl'

BALL AND RING, ^* C >110±5 >100±15

COLD FOLDING, *C <-20 <-5

ELASTIC RETURN, % >100 >25

^rw TπTTSHEET

COLD FCtEDING, "C <-15 <0

RESISTANCE TO HEAT, ^* C >100 >90

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AKTK 5

CHAr CTERISTTCS REQUIRED FOR THE PRODUCTS ACCORDING TO THE TJ^VENTTON

ON THE BINDING AGENT (WITHOUT FILLER)

BALL AND RING, °C >120

COLD FOLDING, °C <-25

EIASnC RETURN, % >150

EENETRATTON AT 25°C 1/10 mm <45

NEEDLE PENETRATION AT 50°C 1/10 mm <120

INDEX OF F N T ATION <0.4

BALL AND RING GRADIENT, °C (1) <10

ON THE SHEET

COLD FOLDING, °C <-20

RESISTANCE TO HEAT, °C >100

(1) The "ball and ring" gradient is measured on samples taken from the top and bottom of a sample of binding agent stored for 5 days at 165°C; this gradient enables the cxj patibility of he various constituents of the product to be assessed.

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TATjLE_6

PROPERTIES OF THE BINDING AGENTS ACCORDING TO THE ΓNVENTION

BINDING AGENT A BINDING AGENT B

BALL AND RING °C 129 130

NEEDLE PENETRATION at 25°C 1/lOmm 41 38

NEEDLE PENETRATION at 50°C 1/10 mm 100 95

INDEX OF PENETRATION 0.4 0.4

COLD DRAWING °C -30 -30

RESISTANCE TO HEAT GOOD GOOD

ELASTIC RETURN % 150 150

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AB E_7

PROPERTIES OF FILLED BINDING AGENT A

COLD ELASTIC n in UNFOIDING Rh'l KN

°c

1. NEW STATE 129 40 98 < -30 31 to 150%

2. AGEING, VENTIIATED. STOVE. 70 ^β C

. 7 DAYS 128 34 90 < -28 -

. 14 DAYS 125 32 86 < -25 -

. 28 DAYS 124 27 80 < -22 31.5 TO 100-'

. 2 MONTHS 120 24 70 < -18 31.5 TO 60%

. 4 MONTHS 112 20 65 < -17 31.5 TO 40%

. 6 MONTHS 104 18 51 < -15 31.5 TO 25%

3. RESISTANCE TO HEAT

(6 MONTHS AT 90°C) NO CREEPING

I BALL AND RING °C

II PENETRATION AT 25°C (l/10mm)

III PENETRATION AT 50"C (1/lOmm)