Method for manufacturing an absorption device and an absorption device

The invention relates to a method for manufacturing an absorption device including support material and absorption material and an absorption device to be implemented by the method. The absorption device according to the invention is especially suitable for absorbing oil and other oil-like chemicals.

Oil spill prevention ways are generally known in which absorption material is spread on surfaces fouled by oil. After absorption has taken place, the absorption material and oil absorbed in it are removed by suitable devices for further treatment. One has tried to facilitate the spreading and removing of absorption material by sealing the absorption material to bags or boxes of different shapes.

Documents FI752374, DE3305223, DE1815592, DE1815592 and GB1251380 presented absorption mats and booms used in preventing oil damages utilising peat as the absorption material. In these solutions, peat is placed in loose form to a bag manufactured of oil-permeating cloth or dense net. Finnish utility model application U920309 describes a cushion-like dryer which includes a bag-like outer layer manufactured of porous paper and an inner part of paper fibre.

A weakness of these solutions is that, when the bag is broken, the absorption material is able to break up from the bag, whereby the whole absorption device becomes unusable. The loose absorption material is also able to move inside the bag, because of which the absorption device has no regular, permanent external appearance. This impedes the transport and storing of the absorption device and complicates the removal of oil from the used absorption device. Because of the uneven distribution of the absorption material included by the bag, the absorbing capacity of the absorption device varies in different parts of the absorption device. The object of the invention is to introduce a method for manufacturing an absorption device and an absorption device, by means of which it is possible to eliminate flaws and disadvantages related to known absorption devices.

The objects according to the invention will be achieved by a method and an absorption device which are characterised by what is presented in the independent claims. Some advantageous embodiments of the invention are described in the dependent claims.

With the method according to the invention, an absorption device including support material and absorption material is manufactured. The main role of the

support material is to function as a cohesive material for the absorption device and the role of the absorption material is to absorb in itself liquid material, such as oil. The basic idea of the invention is that a three-dimensional support material net maintaining the cohesion of the absorption material is formed of the support material by means of the heat treatment of the support material.

In an advantageous embodiment of the method according to the invention, support material and absorption material are mixed in a specified ratio into a mixture of substantially uniform quality. Of this mixture, a blanket is formed on a base which blanket is heated to a temperature in which the support material softens and partially melts adhering to the absorption material. When the support material cools down, it hardens and forms a support material net maintaining the cohesion of the mixture. To the mixture of the support material and the absorption material, it is possible to add in connection with mixing adhesive by means of which the cohesion of the absorption device is further improved. In a second advantageous embodiment of the method according to the invention, a net-like gauze is first formed of the support material on which a layer of absorption material is proportioned. After this, the gauze is folded to a layer-like structure and heated to a temperature in which the support material softens and partially melts adhering to the absorption material. When the support material cools down, it hardens forming a support material net maintaining the cohesion of the layer-like structure. Advantageously, said gauze is formed of support material in fibrous form by a carding technique. Successive gauzes can further be bound together by adhesive to be mixed to the absorption material and/or by needling. On the outer surface of the absorption device, it is possible to fasten a support gauze, if desired, which further improves the cohesion of the absorption device.

In an advantageous embodiment of the invention, the support material includes natural fibre material, textile fibres, polyester and/or polypropylene. The absorption material is advantageously fibrous or fine-grained natural material, such as peat or cellulose fibre. Advantageously, the absorption material and/or the support material are biodegradable materials.

An advantage of the absorption device according to the invention is that it is reliable in operation, because the breaking of a point of the surface layer will not affect the operation of the other part of the absorption device nor lead to the breaking of the whole absorption device.

Furthermore, an advantage of the absorption device according to the invention is that it is an absorption device maintaining its cohesion and shape well, which facilitates the handling, transport and storing of the absorption device and separating oil from the absorption device. A further advantage of the absorption device according to the invention is that it has a uniform absorbing capacity.

The invention will now be described in detail. The description refers to the accompanying drawings in which

Fig. 1 shows by way of an example the steps of a method according to the invention as a diagram.

Fig. 1 shows a simple diagram of the different steps of a method according to the invention. In the method according to the invention, a thin net-like gauze 10 is first manufactured of support material 8 in fibrous form by means of a carding technique. Carding means here a treatment method of fibrous material known as such in which the material is brought to a gauze-like form. Several different textile fibres suitable for the purpose can be utilised as the support material, such as different natural fibres, polyester, polypropylene or their mixtures. On the gauze, a thin layer of absorption material 12 in loose form is proportioned. Advantageously, the absorption material is peat, refined recycled pulp or some other fine-grained material similar to the above. Also a mixture of several materials can be used as the absorption material. The absorption material fills the holes of the net-like gauze and forms a thin layer on the gauze. Among the absorption material, it is possible, if desired, to add also adhesive which binds the absorption material particles to the gauze. Advantageously, the adhesive, the absorption material and the support material are biodegradable materials.

Of the gauze-like support material and the absorption material is formed a thicker structure by folding, whereby individual gauze parts are set on top of each other in layers. Thus is created a layer-like structure 13 in which there are on top of the other several support material gauzes and between them absorption material layers. Of the layer-like material is formed a mat-like absorption device 14 by binding the gauzes on top of each other and the absorption material layers between them together. On the outer surfaces of the layer-like structure, it is possible to arrange a support gauze, if required (not shown in the figure). Advantageously, the support gauze is of textile fibre, such as natural fibre, polyester, polypropylene or a mixture of the above.

In the method according to the invention, the binding of gauzes on top of each other is done by means of heat treatment. In the heat treatment, the temperature of the layer-like structure is increased such that the gauze-like support material softens and partially melts. The temperature of the layer-like structure can be increased to a desired level e.g. by hot air blowers. Melted support material gauzes on top of each other are fastened to each other and form a three- dimensional net-like structure inside the absorption device which structure adheres to the surrounding absorption material. When e.g. polyester is used as the support material, a suitable temperature for the heat treatment is 150-170 ⁰ C. In addition to heat treatment, it is possible to use adhesive binding and/or needling, in which gauzes on top of each other are needled to each other, as a complementary binding method.

After the heat treatment, the absorption device is let to cool back to the normal temperature. When the support material cools down, it hardens forming a three- dimensional support material net maintaining the cohesion of the absorption device, because of which the absorption device maintains its shape.

In an advantageous embodiment of the method according to the invention, the absorption device 14 including support material and absorption material is manufactured by a so-called formatting method in which the fibrous support material 8 and the fine-grained absorption material 12 are mixed to each other in a suitable ratio, whereby a substantially homogeneous mixture of support material and absorption material is obtained. It is also possible to add adhesive to the mixture, if required. Of this mixture, a blanket is shaped on a suitable base for which the above-described heat treatment is performed. In the heat treatment, the temperature of the blanket is increased so high that the support material fibres soften and partially melt. After the support material has cooled down, a support material net maintaining the cohesion of the mixture is produced to the blanket, whereby the blanket becomes the absorption device 14 as described above.

The absorption device according to the above-described method is used in the following way: An absorption mat is spread on a surface fouled by oil, whereby the fibres of the support structure of the absorption device bind oil between them. The oil is further absorbed effectively to the absorption material fibres, because the fibres are evenly distributed in the absorption device. Thus, oil is absorbed to each absorption material fibre to the amount the fibre in question can bind i.e. a maximum amount of oil can be absorbed in relation to the volume of the absorption device. The absorption material will not deliver the material having

been absorbed back so the absorption device can be left in place or intermediately stored for later removal and disposal.

Oil between the fibres can also be removed from the absorption device e.g. by conveying the absorption device between press rolls. After oil removal, it can be immediately retuned back to absorption duties. The absorption device according to the invention is thus especially well-suited to be utilised on oil-combatting vessels, when oil is collected from the surface of water to the vessel by means of absorption devices. The absorption device according to the invention can be used e.g. as a type of a belt conveyor for transferring oil from water to the vessel. It is obvious that only a part of the oil in the absorption device can be removed by pressing it, because in the absorption material a part of the oil is chemically bound inside the absorption material and a part adhered on the surfaces of the particles of the absorption material.

Absorption devices manufactured by the method can be used also in filtering so- called grey waste waters. The absorption device is then formed of a support structure manufactured of an advantageously biodegradable fibre in which absorption material is bound by suitable adhesives. The binding adhesives are most suitably biodegradable.

Above were described advantageous embodiments of a method according to the invention. The invention is not limited to the above-described solutions, but it is possible to apply the inventive idea with several ways within the limitations set by the claims.