The results of mechanical reclamation of waste moulding sands with furfuryl resin and activators of new generation are presented.

The aim of the research described in this study was to determine what effect the addition of reclaim obtained in the process of dry mechanical reclamation could have on the properties of furan sands.

The sand supplied by one of the domestic foundries was after the initial reclamation subjected to a two-step proper reclamation

process. The following tests were carried out on the obtained reclaim: pH, S and N content, loss on ignition and comprehensive

sieve analysis. The obtained reclaim was next used as a component of moulding sands with furfuryl resin, wherein it formed 50%

and 80% of the base moulding material, respectively. The strength properties of the ready sand mixtures (bending strength Rg u and tensile strength Rm u ) were determined after the hardening time of 0.5, 1, 2, 4 and 24 hours.

Growing emission requirements are forcing the foundry industry to seek new, more environmentally friendly solutions. One of the

solutions may be the technologies of preparing moulding and core sands using organic biodegradable materials

as binders. However, not only environmental requirements grow but also those related to the technological properties

of moulding sand. Advancing automation and mechanization of the foundry industry brings new challenges related to the moulding sands.

Low elasticity may cause defects during assembly of cores or moulds by the manipulators.

The paper presents the study of flexibility in the room temperature according to new method and resistance to thermal deformation of selfhardening

moulding sands with furfuryl resin, containing biodegradable material PCL. The task of the new additive is to reduce the

moulding sands harmfulness to the environment and increase its flexibility in the room temperature. The impact of the additive and the

effect of the amount of binder on the properties of mentioned moulding sands were analysed. Studies have shown that the use of 5% of

PCL does not change the nature of the thermal deformation curve, improves the bending strength of tested moulding mixtures and

increases their flexibility at room temperature.

Increasing demands are imposed on foundries to enforce the manufacture of castings characterized by tight dimensional tolerances, high surface finish and total absence of casting defects. To face these challenges, castings are increasingly made in loose self-hardening sands with furfuryl resin, commonly known as furan sands. In the group of self-hardening sands with synthetic resins, loose self-hardening sands with furfuryl resin enjoy the greatest popularity. The sand mixtures based on furan resins are usually subjected to mechanical reclamation. The consumption of binder and hardener and thus the cost of the sand depend on the quality of reclaim, and mainly on the dust removal degree.

The planned tightening of the environmental protection regulations in the EU countries, including limiting the content of free furfuryl alcohol in resins and reducing the emission of furfuryl alcohol, formaldehyde and BTEX compounds at workplaces, necessitated the development of a new generation of eco-friendly furfuryl resins that have recently appeared on the market.

The main aim of this article was to determine the effect of reclaim content on the sand parameters, such as bending strength, tensile strength, bench life, gas-forming tendency and loss on ignition. Tests were carried out with reclaim content in the sand mixture varying from 50 to 90%. The reclaim obtained by dry mechanical reclamation was supplied by one of the domestic foundries.

The results showed that the highest mechanical properties were obtained in sands containing 60% of the reclaim.

Recently, some major changes have occurred in the structure of the European foundry industry, such as a rapid development in the production of castings from compacted graphite iron and light alloys at the expense of limiting the production of steel castings. This created a significant gap in the production of heavy steel castings (exceeding the weight of 30 Mg) for the metallurgical, cement and energy industries. The problem is proper moulding technology for such heavy castings, whose solidification and cooling time may take even several days, exposing the moulding material to a long-term thermal and mechanical load. Owing to their technological properties, sands with organic binders (synthetic resins) are the compositions used most often in industrial practice. Their main advantages include high strength, good collapsibility and knocking out properties, as well as easy mechanical reclamation. The main disadvantage of these sands is their harmful effect on the environment, manifesting itself at various stages of the casting process, especially during mould pouring. This is why new solutions are sought for sands based on organic binders to ensure their high technological properties but at the same time less harmfulness for the environment. This paper discusses the possibility of reducing the harmful effect of sands with furfuryl binders owing to the use of resins with reduced content of free furfuryl alcohol and hardeners with reduced sulphur content. The use of alkyd binder as an alternative to furfuryl binder has also been proposed and possible application of phenol-formaldehyde resins was considered.