PROCEDURE FOR THE STRENGTHENING OF THE BLOCKS OF SINTERED MATERIAL OR COMPACTED FRIABLE, IN ORDER TO FACILITATE TRANSPORT AND STORAGE, THROUGH THE APPLICATION OF LAYERS OF POLYURETHANE OR FIBER REINFORCED POLYCARBAMIDE RESIN. DESCRIPTION

The present invention relates to a procedure for strengthening and/or sealing blocks or bails of sintered or compacted friable material, or of incoherent pressed materials bound into bails, in order to simplify the operations involved in their transport and storage, by the application of layers of fibre-reinforced polyurethane or polyurea (pblycarbamide) resins. Various loose or powdery materials are compacted or sintered into blocks to facilitate their handling, transport and storage; other materials would be able to be thus manipulated if the fragility of the masses obtained did not compromise their stability. Still others are compacted and bound with cords or metal straps, but tend to lose material fragments or are susceptible to moisture, and hence cannot be stored in places which are not suitably sheltered. The procedure proposed herein enables the material to be perfectly contained and the strength of the block increased, while at the same time protecting it from contact with air and moisture.

The block or bale, after its formation by normal methods (simple compression, possibly with binding), is surrounded on its six faces by

layers of a suitable resin, such as polyurethane or polyurea or other suitable resins. These layers can be reinforced, or not, by a mesh elements of suitable fibre or by cloth elements. The polyurethane or polyurea resin layers, reinforced by natural or artificial mineral or organic fibres either in the form of single fibres, or woven or mesh elements, are applied to the lateral surfaces of the block. Once this reinforcement has acquired consistency, the block can be handled, transported and stored. Analogous processes or techniques are not known to the writer, except the surrounding of blocks and bales with polymer film, which is not able to reinforce them but only able to protect them from the external environment.

The procedure proposed herein also enables considerable strengthening of the block of variously bound or sintered friable material (for example, dried and compressed mud, compressed sawdust, sulphur etc.) to be easily achieved by forming about it an adhering binding which prevents it from yielding during handling or storage. If instead the procedure is applied to a bale (for example, of mashed paper), the material is protected from the external environment, fragments cannot be dispersed, and the danger of ignition is considerably reduced. The proposed procedure

A first resin layer is applied to the lateral surfaces of the block or of the bale (in this case the vertical surfaces), after these surfaces have been left to dry or have been dried by hot air or other suitable means, if necessary.

The resin in which the fibres have been incorporated is then applied to the surfaces prepared in this manner. Several successive layers can be applied until an adequate material thickness has been obtained, such as to attain the required degree of strengthening or protection. As an alternative to fibre-filled resin, cloth elements or mesh elements can be applied, and then cemented by the resin.

The fibres, or the constituent material of the cloth elements or mesh elements can be of natural or artificial mineral or organic origin. For example, these fibres, cloth elements or mesh elements can be of glass, polyamide, cotton or jute fibre.

The resins used in the procedure can be polyurethane, polyurea, epoxy or other resins.

Polyurethane resins have the advantage of being able to harden within a few minutes. Compared with polyurethane resins, polyurea resins are easier to apply in a humid environment or when the block or bale surface tends to impregnate with moisture (although in such cases a worsened adhesion is achieved), and can also be applied at temperatures close to O ⁰ C. Epoxy resins have considerable mechanical characteristics, although their curing time is greater.

These materials can be applied manually, by spraying, or by robot.

The resin or polymer used can cure naturally by chemical reactions taking place within the mass or by reaction with atmospheric moisture (as is

usual in the case of said resins), or the curing process can be accelerated or induced by heat, hot air, steam, infrared or ultraviolet radiation, or by any other type of radiant energy. At the end of the procedure the block or bale will be clad by an outer reinforcement of greater or lesser firmness depending on the materials used and the thickness applied, this reinforcement preventing its breakage, particle dispersion, moisture absorption, etc., during its handling, transport or storage. It should be noted that this reinforcement also tends, to a certain extent, to compress the block and so reduce fragility, or to prevent the bale from flaking under any situation, should the binding yield.