EP0914382A1

EP0914382A1 - Fibrous additive for fluxed bitumen, and method for producing same

Info

Publication number: EP0914382A1
Application number: EP97934582A
Authority: EP
Inventors: Bernard Kafka; Jean-Baptiste Rieunier
Original assignee: Saint Gobain Isover SA France
Current assignee: Saint Gobain Isover SA France
Priority date: 1996-07-24
Filing date: 1997-07-17
Publication date: 1999-05-12
Also published as: PL331319A1; BR9710760A; JP2000514860A; TR199900202T2; BG103147A; ZA975105B; AR007881A1; NO990297D0; FR2751639B1; KR20000068001A; CN1233272A; AU3773897A; CA2261844A1; IL128192A0; SK10099A3; WO1998003592A1; FR2751639A1; NO990297L

Abstract

Mineral fibre additives for enhancing the properties of bitumen are disclosed. A mineral fibre additive for fluxed bitumen is provided wherein the fibres are agglomerated into nodules before being added to the bitumen, and the additive comprises a water- and heat-stable binder previously treated with a wetting agent for wetting the fibres with the bitumen. The water- and heat-stable binder preferably consists of phenolic resins of the kind usually used in insulating fibre mats made of either glass wool or rock wool. Similarly, the wetting agent advantageously consists of silicone resins. A method is also provided for producing said additive. According to the method, (a) fibres are taken from a bonded mineral fibre mat such as an insulating mat, (b) a resin acting as a wetting agent for the bitumen is sprayed onto the fibres, and (c) the fibres are treated in a noduliser. Step (b) may be carried out before or after step (c). The use of insulating mineral fibre mats has numerous advantages. Indeed, the problem of recycling industrial products is causing growing concern and finding a use for insulating fibre panels to be recycled is highly important.

Description

LIQUID BITUMEN FIBROUS ADDITIVE AND PROCESS FOR PRODUCING THE SAME

The invention relates to additives based on mineral fibers intended to improve the behavior of bitumen.

Bitumens, whether used to coat surfaces in order to make them waterproof in the case of terraces, to simply allow the rolling of vehicles on roads, or to form a layer permeable to the surface of the road water thanks to the technique of draining mixes, are not generally used in the pure state.

In fact, their performance at low and high temperatures is insufficient.

Alone, they would provide fragile and brittle coatings in freezing weather and which, on the contrary, would become very soft when heated. To improve the behavior of bitumens and especially those intended for making asphalt, and thus widen the range of temperatures where they can be used, various substances are added to the bitumen. They are in particular fibrous materials such as asbestos, rock fibers or glass fibers or cellulose fibers.

With regard to mineral fibers, a technique is known from document EP-A-0 455 553 which consists in adding mineral wool to bitumen in a weight proportion of between 0.5 and 20% relative to bitumen, the fibers having a micronaire before any chemical or mechanical treatment at most equal to 7 per 5 grams and having undergone a subsequent treatment with a nonionic finish.

In this document, a process is described which ends in the formation of nodules by passing through a plate with holes of 3 to 30 mm of average size just before the mixing of the mineral wool and the bitumen, previously, we had subjected the fibers chemical treatment with a non-ionic finish, in particular based on amine oxide.

The technique described in EP-A-0 455 553 had substantial advantages over the prior techniques, in particular the temperature range for which the bitumen does not flow, was very significantly widened upwards. This technique allowed ^the use of bitumen as coating of porous asphalt that provided to these excellent temperature resistance.

In another document, European patent application EP-A-0 509 893, a process and a device for preparing bituminous mixes were described. The process included the following steps: a) drying, heating and mixing of the inert materials, b) formation of nodules by passing the mineral fibers through a plate with holes of 8 to 10 mm of average size so as to obtain at least 75% of the fibers with a length of less than 0.5 mm, c) continuous introduction of fibrous materials at a controlled rate into the stream of liquid bitumen to form a liquid binder before bringing it into contact with the inert materials, d) mixing the inert materials and of the charged liquid binder.

In a variant of the preceding process, a drying-heating and mixing step of the inert materials was provided, followed by the formation of nodules by passing the fibers through a plate with holes of 6 to 10 mm in average size so as to obtain at least 75 % of the fibers with a length of less than 0.5 mm, then a step of mixing bitumen with the inert materials to form a liquid mix and finally the continuous introduction of fibrous materials at a controlled rate into the liquid mix. In the two preceding documents, the best results were obtained when the fibers had undergone, from their preparation, a coating with a non-primer ionic. This primer, which is intended to facilitate the bonding of each individual fiber with the bitumen, is very different from the binders usually used to hold the fibers of an insulating mat of glass wool or rock wool together.

^The invention described here assumes the task of providing an additive to liquid bitumen that is easy to implement with various techniques commonly used on construction sites, that achieves results at least equivalent if n ' is better than those of the previous techniques and which is of a cost price as low as possible.

To achieve this result, the invention provides an additive of liquid bitumen based on mineral fibers, the fibers being before their introduction into the bitumen associated in nodules, the additive comprising a binder stable in water and in heat and having bitumen treated with fiber wetting agent.

The combination of the use of a binder, in particular a binder which is stable to heat, and which remains a binder even in the bitumen in fusion and an agent which promotes the wetting of the fibers by the bitumen allows a setting particularly quick to use and particularly effective bitumen impregnation of fibers and fibrous nodules.

Preferably, the binder which is stable to water and to heat is based on phenolic resins of the type which are usually used to make the insulating fiber blankets, whether glass wool or wool. rock. Likewise, advantageously, the wetting agent is based on silicone resins. These, which are traditionally used to prevent wetting by water, surprisingly have an action which facilitates wetting of the fibers by bitumen.

As regards the nodules, the invention provides that the bitumen additive is preferably constituted at most for 60% by weight by nodules with a dimension greater than 16 mm. Beyond these dimensions, the mixing and impregnation of the nodules with the bitumen becomes difficult and unusable industrially.

The invention also provides a process for preparing the additive of the invention in which the following steps are carried out successively: a) the fibers are taken from a mattress of bonded mineral fibers of the type intended for the insulation, b) a resin is sprayed on the fibers which acts as a wetting agent for bitumen, c) the fibers are treated in a nodulator. Operation b is actually either before or after operation c.

The use of mineral fiber blankets of the type intended for insulation has many advantages. Indeed, the problems of recycling industrial products are becoming more and more worrying and finding a use for insulation fiber panels intended to be recycled is very important. On the other hand, in industrial production lines for insulation wool fibers, we sometimes have results that are unsatisfactory from the point of view of use, either because the density is not what we wanted. , either because the aspect is not correct, or for any other reason. The exploitation of these non-conforming panels is very delicate, their recycling in particular is a complicated operation. Being able to use them as effective additives in bitumen is very important. It is obvious that apart from the operation of removing the fibers, for example by shredding the mattress and the treatment in a nodulator which are entirely conventional, the only new operation, the spraying of a resin which acts as a wetting agent. for bitumen, is extremely simple. In the preferred variant, the wetting agent on the bitumen is based on silicone.

The invention also relates to the application of the bitumen additive to the manufacture of a bitumen-based mixture in which the nodules of mineral fibers are transported and distributed in the bitumen pneumatically. This pneumatic transport technique is very advantageous because it allows a regular distribution of the nodules within the liquid bitumen.

The invention also relates to the application of the additive to the manufacture of a bitumen in which the mineral fiber nodules consist at most of 30% by weight of nodules of dimension greater than 16 mm and where they are first tablets and conditioned for their storage before being introduced in compressed form into the apparatus for preparing the bituminous mixture. Preferably, before their introduction, they have been compressed up to a density included. between 100 and 300 kg / m ³ .

This second technique of introducing nodules into liquid bitumen does not require a complicated device like the previous one, it is much more rustic but because of the compaction of the nodules it cannot be used in as wide a range of particle sizes as the first one.

The figure and the description below will understand the operation of the ^invention and appreciate the advantages.

The figure shows the histograms of four samples of nodules according to the invention. The principle of the invention is as follows:

It is desired to form nodules which are aggregates of mineral fibers of a certain dimension and the fibers of which remain bonded when the nodules are impregnated with bitumen. This characteristic allows bitumen reinforced by fibers to have new properties compared to those which are known from unbound nodules. These result in fact in a final dispersion of the fibers in the bitumen without it being possible to benefit from the mechanical qualities of the nodules themselves.

To obtain the nodules of the invention, it is therefore firstly necessary to combine the fibers with one another using a binder which gives the bond which combines the fibers a character of durability. The first characteristic of this binder will therefore be to remain even when it is subjected to the temperatures of liquid bitumen which can reach

160 ° C.

Another important characteristic so that the binder according to the invention is permanent is its resistance to water. Indeed, it is common on construction sites where bitumen has been prepared to be spread on the roads, that it is necessary to wait, in the event of rain, until dry weather has returned to be able to proceed when spreading the bituminous complex. In this case, the mixture can be subjected for quite long periods to the action of water. Nor is there any question that the binder could be destroyed by it.

Another characteristic to be given to the nodules of the invention is an ability to be completely impregnated with the liquid bitumen as such. They indeed constitute a whole where the bitumen has difficulties to penetrate. This is why the inventors have o studied the agents likely to facilitate the penetration of bitumen inside the fibrous network. After a prolonged study they defined the characteristics which this agent had to respect.

Finally, the preferred variant of the invention is that which uses as binder stable to water and heat phenolic resins of the Bakelite type and as bitumen wetting agent of silicone resins. (We thus observe a certain paradox that the silicone resins which are especially used in practice to avoid wetting by liquid water are precisely an agent which promotes wetting by bitumen. But this is nevertheless what the inventors have observed). From the standpoint of the ^invention, the nature of the mineral fiber matter. Whether it is glass fibers or rock fibers, both are suitable, their diameter and length also matter little.

The fineness of the mineral fibers is determined by specific sizes used by those skilled in the art in these industries; this is how glass fibers have a fineness which is characterized by their "micronaire" while rock fibers have a fineness which is characterized by their "fasonaire". The nodules of the invention use fibers which are most commonly used in the industry for producing insulation panels by the usual centrifugation techniques, that is to say that for glass fibers all fibers are suitable. which have a micronaire of between 2 and 5 under 5 grams and that for rock fibers are suitable fibers which have a fascia equal to or greater than 140.

A particularly advantageous way of obtaining nodules in accordance with the invention is to use as raw material for making them insulation panels fitted with their usual binder and stripped of all their facings or surface equipment so that only remains fibers with their binder. One can, in particular, advantageously, use all the panels which during production of insulation panels do not conform, either because their dimensions are not correct, or because their appearance is not, or again because during their treatment to cover them with a facing, it was damaged or for any other reason that the product obtained cannot be sold. Most common insulation panels are suitable, especially those with a density less than 100 kg / ^m and a proportion of binder (phenolic resin) of between 2 and 8%. We proceed as follows:

Several methods are available for removing the fibers from the mattresses to which they are linked, one of which is to pass them through a shredder. In this case, the insulating mineral wool panels, stripped of their siding, if they had any, are introduced into a shredder. This is a machine that is usually used to condition waste so that it can be compressed without occupying too much space.

This machine produces fragments of bound fibers with a dimension of the order of 2 to 10 cm. The fragments are then introduced into a lump. This device is the same as that described in European patent application EP-A-0 455 553. It has an inlet nozzle and an outlet nozzle, the upstream space is separated from the downstream space by a sheet metal wall pierced with holes. This sheet has the shape of a cylinder which is coaxial with a rotary drum which carries knives whose cutting edge is slightly inclined relative to the common axis. There are also fixed knives which extend the cylinder with holes. The material which enters through a first nozzle on the concave side of the grid is pressed on it by the movable knives and it can thus penetrate through the holes by being calibrated and producing on the other side of the grid enough nodules regular. The machine which has just been described is one of the means which make it possible to obtain nodules, not a single size even with holes of identical diameter in the grid, but a distribution of nodules of different sizes. This distribution does not only depend on the size of the holes in the grid, in fact, the size of the nodules depends on a certain number of other parameters, in particular on the original characteristics of the fibers such as their micronaire or their fasonaire, the pressure exerted at the entrance to the grid, the speed of rotation of the drum. A population of nodules is characterized by the histogram of its dimensions. To obtain such a histogram, a particle size determination technique is used. To do this, conventionally, a sieving system is used with superimposed sieves which have an increasingly reduced mesh size from top to bottom. These sieves are agitated in two movements, a rotary movement in their plane on the one hand, and on the other share a vertical shock at a fairly high frequency since the shocks follow one another at 150 per minute. The sieves are circular, with an internal diameter of 200 mm, their height is 55 mm with the exception of the coarsest sieve which has a height of 85 mm. All the sieves are covered with a cover. All these sieves correspond to the French standard AFNOR NFX 1 1-501. They are installed on an electric sieve shaker of the STEIN and ROUBAIX establishments of the RO-TAP type. The upper sieve has a mesh size of 20 mm, the second of 16 mm, the third of 10 mm, the fourth of 6.3 mm, the fifth of 4 mm. At the bottom of the sieve stack is a bottom that collects what has managed to pass through the 4 mm mesh. There is also a precise centigram balance. The procedure is as follows:

We weigh exactly 25 grams of the most representative sample possible of the whole. These 25 grams are introduced without stripping them into the No. 1 sieve with a 20 mm mesh. We put the cover on. All the successive sieves in the order mentioned above are installed on the sieve shaker which is set in motion for a period of 180 seconds. When the sieving stops, all the sieves are removed and each fraction of the initial sample which is now in each of the sieves or in the bottom is weighed. The results are then presented according to a curve similar to those of the figure. The results are presented in percentage by weight of the whole. For each type of additive in the form of nodules, three successive measurements are made on three samples taken separately. The result presented is the percentage average of the three tests. When the total of the weights recorded on all the sieves exceeds or is less than the original 50 grams of ± 1 g, the test is repeated.

The figure shows the histograms corresponding to four samples of nodules prepared under various conditions, the nodulator was a ROTOPLEX 63/100 knife mill from the company ALPINE. On the abscissa, we see the diameters of the nodules in millimeters. On the left of the abscissa axis, ">20" means that a certain percentage of nodules (noted on the ordinate axis) had a diameter greater than 20, that is to say that the nodules in question do not not pass through the grid, the mesh of which was 20 mm. Thus, for example, the histogram 1 has 70% of its nodules which remain above the 20 mm grid. This same family of nodules had 75% by mass of the nodules which crossed neither the grid of 20, nor the grid of 16 mm and 90% which did not cross either the grid of 20, neither the grid of 16, nor the grid of 10 mm.

Curve 1, the nodules of which have diameters greater than 20 mm for 70% of their mass, corresponds to flows of 6 tonnes per day with a grid with a diameter of 8 mm. Another test made it possible to obtain exactly the same result with a completely different flow rate of 27 tonnes per day but with a diameter of the grid holes of 12 mm.

Curve 2 was obtained with a flow of 12 tonnes per day and a grid with 8 mm holes and curves 3 and 4 with an identical grid 8 mm and a flow of

20 tonnes per day. The histograms 3 and 4 are different, not because of the way the nodules were obtained but because of the origin of the fibers which was not the same.

The four families of nodules in the figure were treated in a traditional bitumen, for example of the 60/70 type, the introduction being carried out by two different methods.

The first method corresponded to that of FIG. 1 of document EP-A-0 509 893. This involves introducing the nodules into a rotating drum using a nozzle which transports them pneumatically, the nodules are introduced directly into the jet of liquid bitumen. This technique is clearly more tolerant than the second which is an earlier technique, that which consisted in introducing in the middle of the rotating drum bags of compressed nodules which disperse in the middle of the aggregates before being themselves, in turn, covered liquid bitumen.

This second method, which does not require the equipment for pneumatic projection of the nodules, does not guarantee the same good dispersion of the nodules in the bitumen. It is therefore more demanding in terms of the quality of the nodules.

Thus, among the four families of nodules in the figure, the histogram 4 and the histogram 3 correspond to nodules which can be implemented by the two techniques. On the other hand, curve 2 corresponds to a family of nodules which can only be implemented by the blowing machine.

As for family 1, it is impossible to obtain good dispersion whatever either the method used.

In summary, it can be said that with the pneumatic method, it is possible to use a family of nodules made up at most for 60% by weight of nodules with a dimension greater than 16 mm. On the other hand, with the traditional method in which the nodules were stored after compression up to densities between 100 and 300 kg / m ^J , it is advisable, in order to obtain a good distribution and a good wetting by bitumen, that the family of nodules is made up of only 30% by weight of nodules larger than 16 mm.

Claims

1. Additive of liquid bitumen, based on mineral fibers, the fibers being, before their introduction into the bitumen, associated in nodules, characterized in that it comprises a binder stable to water and heat and in that it has been treated with a bitumen fiber wetting agent.

2. Bitumen additive according to claim 1, characterized in that the water and heat stable binder is based on phenolic resins.

3. Bitumen additive according to claim 1 or 2, characterized in that the wetting agent is based on silicone resins.

4. Bitumen additive according to one of the preceding claims, characterized in that it is constituted at most for 60% by weight by nodules with a dimension greater than 16 mm.

5. A method to prepare an additive according ^to one of claims 1 to 4, characterized in that it comprises the following steps: a) picks up the fibers of a mineral fiber blanket related the type intended for the insulation, b) a resin is sprayed on the fibers which acts as a wetting agent for bitumen, c) the fibers are treated in a nodulator, operation b) being carried out either before or after operation c).

6. Method according to claim 5, characterized in that the resin which acts as a wetting agent on the bitumen is based on silicones.

7. Application of the additive according to one of claims 1 to 4 to the manufacture of a bitumen in which the mineral fiber nodules are transported and distributed in the bitumen pneumatically.

8. Application of the additive according to one of claims 1 to 3 to the manufacture of a bitumen in which the mineral fiber nodules consist at most of 30% by weight of nodules of dimension greater than 16 mm and where they are first compressed and conditioned for storage before being introduced in compressed form into the apparatus for preparing the bituminous mixture.

9. Application according to claim 8 wherein the nodules have undergone a compression up to a density between 100 and 300 kg / m '.