FR2674454A1 - PROCESS FOR IMPREGNATING POROUS RIGID MATERIALS AND NEW DISPERSIONS. - Google Patents

Abstract

Process for impregnating porous rigid materials, in which an already formed copolymer, in particular a copolymer based on (meth) acrylic acids in aqueous dispersion, is made to penetrate into the body of said material, new dispersions and process in which the a reduced pressure is created at the part to be treated and the copolymer dispersion is made to flow over the site to be treated.

Description

The present invention relates to a method for impregnating materials

  rigid porous and new dispersions. The need to impregnate porous materials is well known, particularly with regard to

  relates to porous metallic parts.

  Indeed, after molding the metal parts can have leaks, easily detectable for example, by putting the part under water and injecting compressed air The presence of bubbles is evidence of

the existence of faults.

  Among the defects, mention may be made in particular of micro-shrinkage, shrinkage, blowing, cracks or interdentritic segregation. 15 A number of techniques are already known for remedying some of these defects. Mention may be made, for example, of English patents No 1,297,103 and 1,308,947 which

  describe monomeric systems with or without catalyst

  We have more recently described in French Patent No. 2,362,167, filed in 1977, a process using a liquid monomer system which is practically completely acrylic or methacrylic, containing at least a certain proportion of polyfunctional monomers, a free radical catalyst and an inhibitor of catalyst in certain proportions, the hardening being carried out by immersion in a water bath at 90 C. We are always looking for a simple, non-polluting process, which moreover would not require heating to be economical in energy, and therefore usable at

low temperature.

  This is why, the subject of the present invention is a method of impregnating rigid porous materials, characterized in that it is penetrated into the

  body of said material a copolymer already formed.

  By rigid material is meant plastics, wood, mineral or synthetic stones, but preferably metals. By metals is meant both the metals and their alloys, in particular light alloys. The treatment according to the invention is particularly intended for parts which must undergo a certain pressure. Such parts are found in the

  foundry, in valves, both industrial (petro-

  chemical, nuclear, food) than general (sanitary, building), in the mechanical, electrical industry, the heating industry (radiators, water heaters, fuel pumps), in the navy, aeronautics and more particularly the automotive (in particular cylinder heads, cylinder blocks, gearboxes, water or oil pumps, carburetors, tubeless rims) By "copolymers already formed" is meant that the copolymer is already polymerized during its application, unlike prior art methods using a mixture of monomers to be polymerized

by heating after treatment.

  The copolymers according to the invention are advantageously used in the form of an aqueous dispersion. A wide variety of copolymers suitable for use can be used, which can be easily selected using a test consisting of treat according

  the invention of porous control tubes, and detect the eff-

  effectiveness of the treatment by immersing the treated tubes in

  water and injecting them with pressurized air.

  However, advantageously, the copolymer is based on (meth) acrylic acids, that is to say esters and / or acrylic and / or methacrylic acids. These esters, as well as the acids, are well known. for example, the copolymers whose base monomers are chosen from acrylic acid, methacrylic acid and their water-soluble salts, such as their ammonium and

  alkali metals, the quaternary salts of dimethylamino-

  (di) ethyl (meth) acrylate, methyl acrylate, methyl methacrylate, butyl acrylate and butyl methacrylate When the copolymer is said to be based on (meth) acrylic acids, l 'It is also understood that the major part, namely more than 80% and preferably more than 90% of the monomers are chosen from those above. A single copolymer or a mixture of copolymers can be used. Among the copolymers in the form of an aqueous dispersion which can be used according to the invention, the copolymers are particularly chosen in the form of a dispersion of fine particles and of medium viscosity. means that their average diameter is of the order of 0.1 Mm, that is to say, for example, from 0.01 to 1 Mm. By average viscosity, it is meant that the viscosity at 20 ° C. of the dispersion aqueous can range, for example, from

  at 2,500 m Pa s, and particularly from 500 to 1,000 m Pa s.

  The amount of dry extract that can contain the above dispersions can range from 10 to 70%, but

  will preferably be around 45%.

  Aqueous dispersions suitable for the implementation of the invention exist on the market. Mention may in particular be made of the aqueous dispersions of resins sold by the French Company Hoechst, under the

  SYNTHACRYL VSW references 6857, 6866 or 6899.

  The above aqueous dispersions can be

  see additives to improve their performance

  these in the implementation according to the invention.

  We can especially add an anti-foam.

  The defoamers used in particular are the defoamers intended for aqueous emulsions and water-dilutable systems, particularly the oil-in-water emulsions of hydrophobic copolymers, for example, of the polysiloxane-polyether type. Such products are commonly found in commerce and may especially mention those sold by the company TEGO Chemie under the reference FOAMEX 1488 or 7447 The antifoam can be, for example, used at a dose of approximately 0.2% by weight, that is to say for example 0, 05 to 1%. Relative to the weight of the single copolymer, these additives can represent, for example, of the order of

0.7%.

  We can also add to the devices below

  above fillers capable of improving the thermal properties of the copolymer Among such fillers, mention may be made in particular of graphite. This may be incorporated into the ready-to-use dispersion in proportions which can

range from 0.1 to 3% by weight.

  It is of course possible to incorporate again

  other additives such as for example a colorant.

  To seal significant defects, it is also possible to introduce into the preparation of fillers, based on bentonite for example, in proportions

by weight from 1 to 2%.

  The present invention also relates to aqueous dispersions of (meth) acrylic copolymers as defined above, characterized in that they contain an antifoam, in particular those for which

  the antifoam is a hydrophobic polysiloxane copolymer-

polyether.

  We particularly remember the disper-

  above, characterized in that they also contain a filler capable of improving the thermal properties

  copolymer such as graphite.

  The above process can be carried out according to several methods, thus allowing the recovery of discarded parts for porosities, micro-soiling,

  internal pitting or blowing for inserts.

  These methods can be classified as follows general method for various parts by vacuum-pressure, simplified method for various parts by immersion practiced under reduced pressure exclusively, local method by pressure for large series or large parts,

spray method.

  The examples which follow illustrate the present invention, without however limiting it.

EXAMPLE 1

  The vacuum pressure method is used in the case of large or medium series The parts are

  introduced either directly into an autoclave, or using the baskets delivered with the apparatus.

  The locked autoclave is pressurized.

  The abrupt opening of the drain valve removes all traces of humidity, then the parts are maintained under a reduced pressure of less than 15 mbar for approximately 5 minutes. At the end of this time, under the action of the vacuum. , the impregnating liquid is drawn into the autoclave. Two different dispersions were used: Dispersion A: Synthacryl R VSW 6866: 800 g of propane-diol emulsion 1.2: 50 g (5% by weight) Water: 150 g Foamex 1488: 3 g Dispersion B: Synthacryl R VSW 6857: 800 g Foamex 1488: 3 g Graphite: 2 g When the autoclave is full, it is put under a pressure of 6 Bars. Under the effect of the pressure, the liquid is then discharged into the storage tank. pre-rinsing in the autoclave The parts are then extracted and washed with ordinary water in the rinsing tank The impregnation operation properly

talking is over.

  If dispersion B is used, no other additional operation is necessary (provided that the ambient temperature is higher than C). The parts are then operational after approximately 2 hours of drying. In the case of the use of dispersion A, the temperature of the parts is raised to around 70 C for

minutes.

  This temperature rise in the rooms can be carried out in several ways: immersion in hot water or in any other liquid such as oil, a glycol placed in an oven (in this case, the duration of 10 min must be increased by the rise time in temperature of

rooms).

  Parts are ready for testing after

  cooling them to room temperature.

  The average duration of an impregnation is generally less than 15 minutes With more viscous impregnation products (for example if 1.2 propane diol is removed from dispersion A), it is possible to

  add a pressurization phase.

EXAMPLE 2

  The simplified vacuum immersion method exclusively consists of immersing the parts in the impregnation liquid contained in a vacuum enclosure

  and to create a reduced pressure of less than 15 mbar.

  The rinsing operations in cold water and

  crosslinking are identical to the previous method.

EXAMPLE 3

  The localized treatment method applies to mass production parts (engine blocks, cylinder heads, pumps). All the openings of the water circuit of the engine block are closed to produce a volume which can be assimilated to the autoclave above, according to an assembly diagrammed as follows in FIG. 1: The part to be treated 1 is connected by an orifice 2 in the lower part of said part and by a pipe 3 to a tank 4 for storing the impregnation liquid 5 This tank is also connected to a collector 6, itself connected by a pipe 7 to a second orifice 8 disposed at the part upper part of part 1 The impregnation liquid can circulate in the porous lines of part 1 between orifices 2 and 8 The manifold also includes a line 9 for pressure injection, a line 10 connected to a vacuum pump and a rinse aid (water) inlet pipe The above assembly includes

  in addition the appropriate valves (not shown).

  First, the manifold, the vacuum pump, the storage tank and the

  piece 1 to obtain a pressure of less than 15 mbar.

  Under the action of the reduced pressure, the impregnation product enters the volume to be treated through the orifice 2, and leaves in the collector located above the block. The impregnation liquid contained in the volume to be treated and in the collector is then subjected to

  a pressure of approximately 2 to 3 Bars for one minute.

  The impregnation product is then relaxed and returned to its storage tank by air injection.

  compressed to a pressure of around 200 mbar.

  Through the collector, the volume

  treated is washed off from the impregnation product by a circulation

  tion of cold water, as above but under the pressure of 2-3 bars In the case of dispersion A, the setting of the

  resin is made by the methods described above

  is lying. We can also practice for example: the impregnation of the water circuit and the oil circuit on a cylinder block, the impregnation of cylinder heads

the impregnation of radiators.

EXAMPLE 4

  The spray method is used to treat a porous area well located on the part. The principle consists in subjecting the area to be treated to a reduced pressure and causing a flow

  of impregnation liquid on the porous area The diff

  pressure ference between that of the porosities and that of the external medium then promotes the penetration of the dispersion. The higher the vacuum level, the more effective the penetration This method can be applied

  to pieces of all sizes, and in large series.

  In the case of a large room, the reduced pressure is produced inside a bell fixed on the porous area (see figure 2) and the liquid

  of impregnation is projected on the defects.

  In FIG. 2, a distinction is made between the part 1 to be treated comprising porosities 12.

  bell 13 against the piece 1 The whole is made airtight

  that thanks to a seal 14 The bell is provided with a nozzle 15 for spraying impregnating liquid 5 connected on a pipe 3 to a storage tank 4 The bell is also provided, at its lower part, with 'an evacuation of the impregnation liquid connected to said storage tank It finally comprises a pipe 10 connected to a vacuum pump The reduction in pressure presses the bell against the part and causes the circulation of the impregnation liquid; this can be combined with

  the use of circulation pumps.

  In the case of small parts, the part is entirely placed under a vacuum bell and the impregnation liquid is directed by a nozzle onto the area to be treated, the rest of the device being similar to the above. In both cases, the liquid is collected at the bottom of the empty bell, then reinjected under the action of the vacuum. This process is economical because the part is only partially in contact with the resin, it follows

low product consumption.

  The impregnation cycle by this process can be short, 1 to 3 minutes for parts with weak defects. It is nevertheless limited to parts whose porous zones are easily accessible to the flow.

impregnation liquid.

  Rinsing with cold water and setting the

  resin are carried out as described previously.

  The present application finally relates to a method of impregnating rigid porous materials as defined above, in which a copolymer already formed in aqueous dispersion is used, characterized in that a reduced pressure is created at the level of the part to be treated

  and causes the copolymer dispersion to flow over the location-

ment to treat.

f

Claims (5)

  1 Method for impregnating rigid porous materials, characterized in that it penetrates into the   body of said material a copolymer already formed. 5 2 The method of claim 1, charac-   terized in that the copolymer is used in aqueous dispersion. 3 Method according to claim 1 or 2,   characterized in that the copolymer is based on (meth) - acrylates   4 Method according to claim 3, charac-   terized in that the copolymer is in the form of a dispersion   fine particles and medium viscosities.   Method according to any one of claims 1 to 4, characterized in that the impregnation is followed by rinsing.   6 Method according to any one of the res-   dications 1 to 5, characterized in that said material is subjected to drying at a temperature below 80 ° C. 7 Dispersions of copolymers specially designed for carrying out the process according to one   any one of claims 1 to 6, characterized in that   that they are aqueous dispersions of copolymers   (meth) acrylics containing an antifoam.   8 Dispersions according to claim 7, characterized in that the defoamer is a copolymer hydrophobic polysiloxane-polyether.   9 Dispersions according to claim 7, characterized in that they contain a filler capable of   improve the thermal properties of the copolymer.   Method for impregnating rigid porous materials according to any one of Claims 2 to 6,   characterized in that a reduced pressure is created at the part to be treated and the copolymer dispersion35 flows over the location to be treated.