EP1035931B1 - Fluid composition capable of producing shiny carbon during metal casting and preparation method - Google Patents

Abstract

A fluid composition additive for foundry casting sands enabling formation of lustrous carbon, including a liquid support and particles of at least one substance other than coal capable of forming lustrous carbon during metal casting.

Description

The present invention relates to the field of foundry, and relates more particularly to a new composition of brilliant carbon generator.

Glossy carbon generators are carbonaceous substances that are added to molding sand in foundries to release, at the time of casting, hydrocarbon-type volatiles, whose role is to create a reducing atmosphere in the mold enclosure , and form a carbon deposit of graphitic appearance on the surface of the pieces, thus improving their appearance.

Traditionally, coal powder, finely ground, is the most used substance, with a brilliant carbon generating capacity of the order of 8 to 10% of its weight. Other substances, such as tars, bitumens, certain resins, or polymers such as polystyrene, are often used in admixture with coal dust, to increase the brilliant carbon generating capacity.

Most brilliant carbon generators are used as a finely divided powder, whose grain size is less than 650 microns, with more than 50% less than 150 microns.

But these powders, organic by nature, high in coal powder, are susceptible to self-heating, dust explosion, caking in silos.

In order to avoid these drawbacks, some manufacturers, including the Applicant, have sought to replace the powders with liquids such as bituminous oils. Practice has shown that these oils can not be incorporated into the sand in sufficient quantity to satisfy the need for shiny carbon, because the sand became too plastic, and the smoke release at casting was too great. The use of these oils has therefore remained limited to a few special cases. Other manufacturers have tried to market coal powder suspensions in the water, but this product proved to be too expensive compared to conventional coal powder.

US Pat. No. 3,666,706 solves the problem of the toxicity of coal powder by replacing it with an aromatic hydrocarbon polymer of the polystyrene, polypropylene or polyethylene types.

Some manufacturers have circumvented the problem of storing powdery materials by mixing them with bentonite, which is another common component of foundry casting sand. These mixtures, which have conquered a large part of the European market, have a brilliant carbon / Bentonite ratio between 5 and 0.2.

But the favorable influence of such mixtures on storage safety problems becomes noticeable only for high bentonite contents and these safety problems are not really solved. In addition, these blends are less flexible to use in foundries because the ratio of brilliant carbon generators / Bentonite is predefined, which often forces the foundries to maintain a small stock of brilliant carbon generators separated.

The problems of toxicity of polycyclic aromatic hydrocarbons generated by carbon generators bright as coal, justifies the search for new substitutes or enrichment, the choice of which is however limited because of the strict criteria concerning the storage of pulverulent material.

The present invention aims precisely to offer a solution to the problems mentioned above. This object is achieved by means of an additive for foundry molding sands which makes it possible to generate brilliant carbon consisting of a fluid composition comprising, within a liquid support, particles of at least one substance, other than coal, capable of producing brilliant carbon during casting of the metal according to claim 1.

The content of liquid carrier in the fluid composition of the invention is less than 60% by weight of said composition. The liquid carrier is water mixed with at least one organic liquid, which may also be chosen from organic liquids derived from the distillation of petroleum or coal or from liquid derivatives extracted from plants. Examples that may be mentioned include aromatic solvents, fatty acids, certain naphthenic or terpenic derivatives and their mixture. In the compositions of the invention in which the liquid carrier is a mixture of water and at least one organic liquid, the water advantageously represents at least 30% of the weight of the liquid carrier and / or at least 5% by weight of the fluid composition of the invention.

By fluid composition is meant liquids, suspensions or pastes, substantially homogeneous at least during their use.

Particle content of a substance, other than coal, capable of producing carbon The gloss in the fluid composition of the invention is between about 85 and 5% by weight of the composition. Preferably at least 50% by weight of the particles in the composition of the invention have a size of less than about 500 microns.

All particles of substance known for their ability to produce shiny carbon during the casting of the metal in the mold, used in the prior art in powder form, are used in the context of the present invention. Mention may in particular be made of bitumens, gilsonite, coumarone-indene resins, albores, certain polyolefins or polymers derived therefrom, resinous compounds obtained by the treatment of bis-phenol A production residues, etc. ..

But these particles can also be made of any other potentially interesting material but having disadvantages for application in powder form, in particular because of unfavorable physical characteristics such as, for example, poor grinding ability, high humidity, caking propensity or to granular segregation. These materials are often waste from the production of polymers, which are today most often incinerated. By way of examples of such materials, mention may be made of the residues of the emulsion or suspension manufacture of polyolefins or of their copolymers, residues that often consist of sludge or wet fines, or the residues of the granulometric selection of resins exchange resins. ion.

• La capacité de générer du carbone brillant est d'au moins 15 % en poids de leur poids, mesurée selon la méthode définie par l'industrie Allemande de la fonderie dans Bestimmung von glanzkohlenstoff - V. D. G. p. 85, October 1980.
• La teneur en matières volatiles est d'au moins 50 % mesurée selon la méthode ISO 562-1981 et lesdites matières volatiles se dégagent à 80 % au moins, entre 200°C et 500°C.

The invention therefore generally relates to the use within a liquid carrier of particles of resinous compounds and more particularly of polymer or copolymer particles or their mixture of which the macromolecular chains comprise at least 80% of their weight, carbon and hydrogen atoms. Among these, the invention preferably envisages those of which:

• The ability to generate brilliant carbon is at least 15% by weight of their weight, measured according to the method defined by the German foundry industry in Bestimmung von glanzkohlenstoff - VDG p. 85, October 1980.
• The volatile matter content is at least 50% measured according to the method ISO 562-1981 and said volatiles are at least 80% clear at between 200 ° C and 500 ° C.

Particles of substances capable of producing glossy carbon which are preferred according to the invention have a content of low polycyclic aromatic hydrocarbons (benzo-A-pyrene <50 ppm) and a sulfur content of less than 3%.

The fluid composition according to the invention may further comprise an adequate amount of one or more suspending agents, rheology or surface to prevent settling of the particles or separation of liquid phases. Among these, there may be mentioned clays, bentonites, surfactants and polysaccharides.

The fluid composition of the invention may also comprise one or more additives known for their favorable effects in molding sand, for example to improve fluidity, cohesion or clamping. It may be, for example, saponified oils, fatty acids or their saponified esters or not, glycols, graphite, or additives acting on the activation of bentonite like certain bases.

The fluid composition according to the invention may also comprise one or more additives known for their antifreeze effect such as ethylenes glycols, or their antibacterial effect such as formalin.

Although one of the aims of the present invention is to remove for health reasons at the workplace, the use of coal as a brilliant carbon generator, it may be useful, for technical reasons, As a result of the economics or availability of the raw material, coal powder of the particle size advantageously less than 600 microns can be incorporated in the fluid composition of the invention. In this case, the weight content of the coal powder in said composition will preferably be less than 50%.

• le coke, dont 80 % en poids sera constitué par des particules dont la taille est inférieure à environ 500 microns, et de préférence dont 70 % en poids sera constitué par des particules dont la taille est inférieure à 200 microns,
• un matériau granulaire siliceux ou silico-alumineux poreux dont la taille des particules est inférieure à 600 microns.

According to an advantageous embodiment of the fluid composition of the invention, it comprises up to about 50% and preferably 30% of its weight, of a porous mineral powder such as:

• coke, 80% by weight of which will consist of particles whose size is less than about 500 microns, and preferably 70% by weight of which will consist of particles whose size is less than 200 microns,
• a porous siliceous or silico-aluminous granular material having a particle size of less than 600 microns.

The invention also relates to a process for preparing a fluid composition according to the invention consisting in incorporating into the liquid carrier particles of at least one substance, other than coal, capable of producing shiny carbon, either in the form of fine particles whose size is less than 500 microns at 50% of their weight, dry or wet, or by grinding wet with said liquid carrier. The liquid carrier and the particles used in this process are in accordance with those previously described in the fluid composition of the invention.

The invention also relates to the use of particles of a substance, other than coal, capable of producing glossy carbon during the casting of metal in the mold, for the preparation of a fluid composition constituting an additive for foundry casting sand.

Said particles are of the type defined previously in the fluid composition of the invention.

The invention further relates to the use of an additive previously defined for the preparation of a foundry molding composition, and to a sand-based foundry molding composition comprising such an additive and a process for its preparation. A process for preparing a foundry molding composition comprises mixing with the foundry sand, for example from the after-shake-out, an amount of at least 0.05% by weight of an additive according to any one of the following: Claims 1 to 15, either directly or via a premix with other materials.

Other advantages and characteristics of the invention will appear on reading the following examples concerning the preparation and use of the fluid composition of the invention in a foundry.

The following example relates to the use tests, as a foundry-shining carbon generator, of granulometric selection fines derived as waste from the manufacture of styrene-di-vinyl-benzene copolymer (S-DVB) for ion exchange resins.

These fines were first used in pulverulent form according to the method of the prior art, by mixing them with coal dust, at a rate of 30% of fines of S-DVB for 70% of coal dust. . It is found by emptying this mixture on a plate and tapping the plate slightly that S-DVB fine grains are clearly separated from the coal grains, and therefore the mixture becomes very easily heterogeneous, which prevents its use in foundry.

• a) Fabrication d'un pré-gel par mélange de :
  • 97 g d'eau,
  • 0,14 g de Rhodadol 23 commercialisé par la Société Rhône-Poulenc,
  • 2,29 g de Empilan NP6 commercialisé par la Société ALBRIGHT-WILSON,
  • 0,57 DE Empicol ESB 3M commercialisé par la Société ALBRIGHT-WILSON.
• b) Fabrication de la composition fluide par mélange de :
  • 30 g de poussière de houille,
  • 35 g de fines S-DVB,
  • 35 g de pré-gel de l'étape (a) ci-dessus.

The above mixture was therefore incorporated in a liquid and the resulting fluid composition was used in a foundry mold:

• a) Manufacture of a pre-gel by mixing:
  • 97 g of water,
  • 0.14 g of Rhodadol 23 sold by Rhône-Poulenc,
  • 2.29 g of Empilan NP6 marketed by the ALBRIGHT-WILSON Company,
  • 0.57 Empicol ESB 3M marketed by the ALBRIGHT-WILSON Company.
• b) Production of the fluid composition by mixing:
  • 30 g of coal dust,
  • 35 g of fine S-DVB,
  • 35 g of pre-gel from step (a) above.

• c) Fabrication d'un moule de fonderie de composition suivante en poids :
  • 100 parties de sable siliceux de granulométrie 55 AFS,
  • 7 parties de bentonite calcique activée,
  • 3 partie de la composition fluide de l'étape (b) ci-dessus,
  • 2 parties d'eau.

The mixture obtained is of fluid and homogeneous appearance and remains for more than three weeks, until its use described below.

• c) Manufacture of a foundry mold of the following composition by weight:
  • 100 parts of quartz sand 55 AFS,
  • 7 parts of activated calcium bentonite,
  • 3 part of the fluid composition of step (b) above,
  • 2 parts of water.

The liquid cast iron is then poured into the mold. After cooling, there is a beautiful skin of room without defect and well pickled.

Claims (17)

1. Additive for foundry moulding sands capable of generating lustrous carbon, consisting of a fluid composition comprising:

   a liquid support composed of a mixture of water and at least one organic liquid, in which the water accounts for at least about 30% of the weight of the liquid support and/or at least 5% by weight of the fluid composition,

   particles of at least one substance, other than coal, for forming lustrous carbon during casting of the metal,

   the content of said liquid support being less than 60% by weight of the said composition and the content of the said particles being between 85% and 5% by weight of the said composition.
2. Additive according to claim 1, characterised in that the organic liquid is chosen from among aromatic solvents and fatty acids.
3. Additive according to either claim 1 or 2, characterised in that at least 50% by weight of the particles of the substance other than coal for forming lustrous carbon, are of a size smaller than about 500 microns.
4. Additive according to any one of claims 1 to 3, characterised in that the particles of the substance other than coal for forming lustrous carbon, are particles made from a resinous compound such as polymer or copolymer particles or their mixtures, and having macromolecular chains which comprise carbon and hydrogen atoms to the extent of at least 80% of their weight.
5. Additive according to claim 4, characterised in that the particles of the substance other than coal for forming lustrous carbon, , are made from polyolefins or their copolymers or derived copolymers.
6. Additive according to any one of claims 1 to 5, characterised in that the particles of the substance other than coal for forming lustrous carbon, , have a capacity for generating lustrous carbon, to produce at least 15% by weight of their weight measured according to the method defined by German foundry industry in Bestimmung von Glanzkohlenstoff-V.D.G. p. 85, October 1980.
7. Additive according to any one of claims 1 to 6, characterised in that the particles of the substance other than coal for forming lustrous carbon, , have a content of volatile materials of at least 50% measured according to ISO method 562-1981 and at least 80% of the said volatile materials are released between about 200°C and about 500°C.
8. Additive according to any one of claims 1 to 7, characterised in that the particles of the substance other than coal for forming lustrous carbon, have a low content of polycyclic aromatic hydrocarbons and a sulphur content less than 3%.
9. Additive according to any one of claims 1 to 8, characterised in that the fluid composition also comprises an appropriate quantity of one or more antisettling agents, flow agents or surfactants, to prevent settlement of the particles or separation of liquid phases.
10. Additive according to claim 9, characterised in that the said agents are selected from among clays, bentonites, surfactants and polysaccharides.
11. Additive according to any one of claims 1 to 10, characterised in that the fluid composition also comprises 1 to 50% by weight of coal dust having a particle size smaller than about 600 microns.
12. Additive according to any one of claims 1 to 11, characterised in that the said fluid composition comprises up to about 50% by weight of a coke powder, about 80% by weight of which is constituted by particles of a size smaller than about 600 microns.
13. Additive according to any one of claims 1 to 12, characterised in that the fluid composition comprises up to about 30% by weight of a porous granular siliceous or alumino-siliceous material, the particle size of which is smaller than 600 microns.
14. Process for the preparation of an additive according to any one of claims 1 to 13, characterised in that particles of at least one substance other than coal for forming lustrous carbon, are incorporated into a liquid support, either wet or dry in the form of fine particles with 50% by weight of particles being smaller than about 500 microns, or by grinding in the wet phase with the said liquid support.
15. Use of an additive according to any one of claims 1 to 13 for the preparation of a composition for casting in a foundry.
16. Composition for casting in a foundry, based on sand, comprising an additive according to any one of claims 1 to 13.
17. Process for preparation of a composition for casting in a foundry , characterised in that a quantity of at least 0.05% by weight of an additive according to any one of claims 1 to 13 is mixed with the foundry sand, either directly or through a premix with other materials.