AND A PROCESS FOR ITS PREPARATION

Field of the invention

The present invention concerns the field of coconut fiber-based products, and more specifically its subject is a new process for preparing a sheet material based on coconut fiber and coir pith, without the addition of any additive or glue, and the absorbent material obtainable with this process.

State of the art

Coconut palm, or Cocos nucifera, is one of the most exploited plants for a wide variety of applications, and not only for the food consumption of its fruits, commonly called "coconuts". Indeed, even the fruit, as well as being consumed fresh or used in the food and drink industry to prepare drinks, oils and other products intended for food, is widely used in cosmetics, soaps, and to make carpets and ropes.

This fruit has a composite structure, with a smooth and thin exocarps, brown in colour, a fibrous and light mesocarp and an endocarp, or shell, that is extremely hard and woody. Among the materials most used obtained from coconuts are coconut fiber, obtained in particular from the mesocarp, and coir pith, obtained from the shell. Coconut fiber obtained from mature fruits consists of fibres having ligno-cellulosic structure that can be woven, or in any case processed, to make ropes, doormats, rugs, brushes, and similar, whereas coir pith is a particulate material, of various granulometry, widely used as moisture absorber, or as material for plant nursery and horticulture.

Such materials, present in very large quantities at very low prices being substantially by-products of the food industry, are also compounds of natural origin, completely biodegradable and biocompatible and at the same time biologically pure: indeed, they have exceptional resistance to decomposition since they do not contain fungi, insects, and similar. Moreover, they are extremely porous materials, with high draining capability, and they have great sound and heat-insulation capabilities. Due to these properties, coconut fibre and coir pith have been used for decades, in particular to make absorbent products, for example to produce litter for animals; more recently they have been used as rehydrater for potted plants; in this case the blocks of compacted coconut fiber and coir pith, once rehydrated with water and chopped on the ground surrounding the plants, indeed ensure the water needs of the plant are satisfied for a long time.

Such materials are generally prepared using additives, in particular glues, which have the function of holding together the fibres or the particulate creating a material that is not fragile, long-lasting, of acceptable strength for wide-ranging applications. Such applications, precisely due to the use of glues and chemical adhesives during production, cannot however be applied to certain sectors, like the food industry or farming. In cases in which, on the other hand, glues are not added during processing, the end product is made in the form of briquettes, blocks or similar shapes that help the product per se to be more compact and strong, but these are still low quality products, which tend to break apart, and consequently are not suitable for certain applications where compactness of the material and cleanliness of the environment are required.

Let us consider in particular intensive animal farming, where the litters are usually changed for every life cycle of the animals and for the entire duration of a life cycle (for example on average about 40 days for chickens) these litters must be able to perform their absorbing function effectively and homogeneously over large surfaces, to then be easily replaced before the start of the next cycle. Currently, also in the farming sector, coconut fiber already has been applied instead of sawdust and wood shavings, but in the form of blocks that are suitably broken up at the moment of use and distributed, thus creating a non-homogeneous surface, which must moreover be wetted to avoid the material turning to dust. This, obviously, as well as making the preparation of the litter harder work, contributes to lowering the absorbent capability of the material, since it is already wet from the outset. A product based on coconut fiber sheets, totally devoid of glues and adhesives would therefore be extremely useful in particular in this field of intensive animal farming.

As far as the Applicant is aware, there are currently no processes for the preparation of materials based on coconut fiber in the form of sheets, which do not use glues. The use of glues and similar additives, if on the one hand give strength to the material, on the other hand is undesirable, especially if the finished product must be used in domestic settings or in animal farms, or if in any case it is to come into contact with food products; moreover, the processing, if glues were not used, would obviously be more cost-effective, and have less impact on the environment and on the health of the workforce.

Therefore there is a need in the field to provide new processes for processing coconut fiber that make it possible, in particular, to obtain a finished product in sheets, of high compactness and solidity whilst not containing glues or binding additives of any kind, at the same time highly absorbent, useful for example as moisture absorber for industrial uses, in particular in the food industry and in intensive animal farming.

Summary of the Invention

The Applicant has now surprisingly found a new process for processing coconut fiber that allows the technical problems highlighted above for the known processes to be overcome, and allows a highly absorbent, compact and strong sheet material to be produced without using any kind of additive, glue or adhesive.

The material obtained, besides being completely biodegradable and biocompatible, has demonstrated high absorbent capability, and great compactness and solidity even when processed in the form of thin sheets, therefore offering an extremely vast spectrum of applications. Thanks to its compactness, the material of the invention does not turn into dust, and also has an extraordinary ability to absorb liquids, for example in quantities of over six times its own weight.

Subject of the present invention is therefore a process for the preparation of an absorbent sheet material consisting essentially of coconut fiber and coir pith, completely devoid of additives, glues, and similar products, comprising the following steps:

(i) dry preparation of a mixture starting from coconut fiber in an amount ranging from 10 to 40% by weight with respect to the total weight of the mixture, and from coir pith in an amount ranging from 60 to 90% by weight with respect to the total weight of the mixture, in which coconut fiber and coir pith have a substantially identical moisture degree, which is comprised between 5 and 15% by weight with respect to their respective weight;

(ii) processing of the mixture obtained from step i) by calendering to obtain the desired absorbent sheet material.

A further subject of the invention is an absorbent sheet material consisting essentially of coconut fiber and coir pith, completely devoid of additives, glues, adhesives, and similar, in which the amount of coconut fiber is comprised between 10 and 40% by weight with respect to the total weight of the mixture, and the amount of coir pith is comprised between 60 and 90% by weight with respect to the total weight of the mixture.

Yet a further subject of the invention is a composite absorbent material, comprising at least one sheet of the aforementioned absorbent material and at least one film of plastic material or a sheet of Kraft paper; and the process for making such a composite material.

Yet a further subject of the invention is an absorbent sheet material, consisting essentially of coconut fiber and coir pith, completely devoid of additives, glues, adhesives, and similar, possibly coupled with one or more films or sheets of different material, for instance plastic films or sheets of Kraft paper, obtainable with the aforementioned process.

Yet a further subject of the invention is the use of the aforementioned materials as moisture absorber and/or soundproofing.

Further characteristics and advantages of the invention will become clearer from the following detailed description.

Brief description of the figures

Figure 1 schematically shows the apparatus used for making the present absorbent material, and the flow chart that indicates the steps of the process.

Figure 2 schematically shows the apparatus used to make a coupled material according to the invention comprising Kraft paper coupled with the present absorbent material, and the flow chart that indicates the steps of the process.

Detailed description of the invention

From the processing of the coconut residues, in particular from the food industry, coconut fiber and coir pith are obtained both having a moisture degree typically comprised between 5 and 15% by weight with respect to the total weight. Such materials, as stated above, already have wide-ranging applications in various fields both of agriculture and industry, and they are also the starting materials of the present process for preparing new absorbent materials.

In the present invention by "moisture degree" of the coconut fiber or of the coir pith their water content is meant, expressed as percentage weight with respect to the total weight of the coconut fiber or coir pith, respectively; on the other hand by "substantially identical moisture degree between coconut fiber and coir pith" a moisture degree is meant that differs at most by 1-2% by weight between coconut fiber and coir pith.

In the case in which fiber and coir pith are available as starting materials with moisture degrees differing by more than 2% by weight or in any case if they have a moisture degree outside of the range 5-15% by weight, the present process is preceded by an operation to adjust the moisture degree - which will generally be a drying operation - to take it to the values comprised in the range 5-15%; such an operation is preferably carried out on the mixture of coconut fiber and coir pith rather than on the two separate materials, so as to ensure greater uniformity of the moisture degree of the resulting material. Preferably, the moisture degree of the starting materials is comprised between 10 and 13%.

According to a preferred embodiment of the invention, the solid mixture of the starting materials contains an amount of coconut fiber comprised between 10 and 30% by weight, whereas the amount of coir pith is comprised between 70 and 90% by weight, proportions that are clearly maintained also in the final absorbent material. The particularly preferred process of the invention and the absorbent material obtained are those in which the amount of coconut fiber is equal to 20% by weight, whereas the amount of coir pith is equal to 80% by weight.

Therefore, the starting materials, coconut fiber and coir pith possibly subjected to adjustment of the moisture degree, are mixed uniformly in a dry mixer, for example with a slow auger agitator, then the solid mixture thus obtained is subjected to calendering in a suitable apparatus, shown schematically, together with a flow chart with the steps of the process according to an embodiment of the invention, in Figure 1 attached here.

The starting materials, as well as the end product, consist of coconut fiber and coir pith in the indicated proportions, apart from an amount of water indicated by the moisture degree defined as stated above.

With reference to Figure 1 , which represents an example, but not limiting, embodiment of the invention, the transfer of the solid mixture from the mixer 1 to the calender 2 can be carried out through a conveyor belt 3 that carries the mixture to be introduced in a dosing hopper 4. From the hopper 4 the mixture is distributed on a belt 5 that continuously feed a pre-compression area 6 that precedes the calender 2. In this pre-compression area 6 there is a first reduction of the thickness of the layer of material, before the introduction into the calender 2, where the material is subjected to a certain pressure through slow passage through the rollers with parallel axes of the calender, so as to obtain a compact sheet material of the desired thickness.

Calenders normally used in the production of paper, for example apparatuses with just two rollers, can be used to carry out the process of the invention, preferably using a few provisions: for example, the lower roller of the calendar is preferably bound by a layer of felt so as to deposit the sheet material thereupon, which is progressively forming; moreover, in order to uniformly feed the dry mixture to the rollers of the calendar, suitable feeding augers can be applied such as to eliminate possible links to the mixture still contained in the dosing hopper. The rollers of the calendar are also regulated, through springs and spacers, to be a distance apart by a height equal to the thickness of the material that is wished to be obtained.

The material thus obtained can then be subjected to cutting and packaging operations in suitable cutting section 7 and packaging section 8, in a process that is preferably continuous from the initial mixing to the packaging and is also automated and controlled through suitable electronic means and control unit. The present process is also preferably carried out at room temperature. The cutting section 7 can for example comprise a cutter consisting of a rotary drum and a blade that, at each turn of the drum, hits the drum itself, cutting the absorbent material that is on top of it in sheets of the desired dimensions.

On the other hand with reference to Figure 2, a process for preparing a coupled material is described in which at least one sheet of the absorbent material of the invention is coupled with at least one sheet or film of other material, for example with a sheet of Kraft paper or with a film of plastic material, if necessary using adhesives and glues, which however are totally absent in the uncoupled absorbent material. Such coupled materials can be useful for certain industrial applications in which it is for example necessary to have a greatly absorbent material on one side, but coated with plastic material on the opposite side, for example with a film of polyethylene that is fixed at points with a vinyl glue or similar adhesives, or a material having a greatly absorbent surface, with an internal thickness, light and flexible, created by a central sheet of Kraft paper, typically having a maximum granulometry of about 150 g/m ² . With reference to Figure 2, the apparatus for carrying out the preparation process of the present absorbent material is illustrated, coupled with Kraft paper, together with a flow chart carrying out the steps of such a process according to a particular embodiment of the invention; also in this case, like in the process illustrated in Figure 1 , coconut fiber and coir pith are mixed in a dry mixer 1 , transferred into a doser 4 through a conveyor belt 3, then distributed by this on a belt 5 that conveys the dry mixture into a pre- compression area 6 and from here to the calender 2, where the absorbent sheet material is formed. The coupling is carried out on the absorbent material at the outlet from the calender 2, and upstream of the subsequent cutting step 7 and packaging step 8, through relay rollers 9 on which vinyl glue or similar is possibly sprayed, through suitable injectors, if necessary to fix together the layers of different material.

In the present invention the term "sheet material" means a material of negligible thickness with respect to width and length of the sheet, which can in some cases be even so large that the sheet must be stored in rolls. According to the invention, the present sheet material can for example have a thickness equal to or less than 10 mm, and preferably comprised between 0.5 and 10 mm, for a length of the sheets that can reach 50 m and a width comprised for example between 50 cm and 200 cm. According to a particularly preferred embodiment of the present invention, the material has a thickness comprised between 1.5 mm and 5 mm, for a length of the sheets that can reach 150 cm and a width comprised between 50 cm and 100 cm.

The material according to the present invention, consisting solely of biodegradable materials, i.e. coconut fiber and coir pith, is also a completely biodegradable material, which also conserves the other advantageous properties of the starting materials, such as biocompatibility, resistance to decomposition, lightness, and above all moisture absorbing capability.

In particular, the experiments carried out on the sheet material obtained with the present process have highlighted how it has conserved the same absorbency as the starting products, with an ability to absorb many different liquids at the same time, not only on the surface but also inside the sheet, in its entire thickness. The absorbing capability of the present sheet material is a function of its thickness, and it has been found in particular that, for the preferred thicknesses comprised between 1.5 mm and 5 mm, the absorption capability is about six times the weight of the material, or more. Thanks to its characteristics, the material of the invention is useful as moisture absorber in all situations in which there is a need for a vast, but thin, absorbing surface, with high absorption capability, for example in industry, for the storage, transportation and movement of goods that can release liquids. The present absorbent material is particularly useful for use as material for farm litter, in particular for intensive poultry farms. The advantages in use of the present sheet material are clear in this case, also in comparison with similar loose materials made from coconut fiber or coir pith, not compacted in sheets: the application of the sheets is simpler and faster with respect to the same amount of loose material, as well as the moisture absorbing capability being higher for the same amount of material and it being uniform over the entire surface covered. The cost of the product is very low, thus being able to coat large surfaces at low cost, and the biodegradability and biocompatibility of the material is ensured by its composition based on coconut fiber and coir pith without the addition of any other product, additive or glue.

The following examples are provided in order to illustrate the present invention without however constituting a limitation thereof.

EXPERIMENTAL PART

Example 1 : Preparation of the absorbent sheet material of the invention

The coir pith and the coconut fibres were dry-mixed in an auger agitator so as to make the material to be processed uniform. The proportion between coir pith and coconut fiber was 80% by weight of coir pith for 20% by weight of coconut fiber with respect to the total weight of the mixture, and the measured moisture degree of the two materials was 12% by weight. The dry mixture thus obtained was introduced into a dosing hopper through a suitable conveyor belt in an amount suitable for the dimensions of the sheet of absorbent material that is wished to be obtained: in particular, wishing to obtain a sheet of thickness of about 2.5 mm, through the dosing hopper, about 2 Kg of dry mixture were evenly distributed on a second conveyor belt, creating a layer of thickness of about 50 mm, said conveyor belt taking it to a pre- compression area. Here, thanks to the regulation of the rollers, a material of thickness of about 25 mm was obtained, which was then introduced into a calender, i.e. a calender with two rollers commonly used in paper production, and subjected to a force of 500 Kg/cm, obtaining at the outlet of the calendar a material of thickness 2.5 mm. The sheet obtained was of excellent consistency and it was possible to cut it to the desired dimensions, in particular dimensions of 60 cm x 40 cm.

Sheets of the same dimensions but of thickness 3.5 mm were obtained following the same procedure described above, simply distributing a proportionally higher layer of the dry mixture from the dosing hopper.

The preparation described above was also repeated using a different composition of the starting dry mixture, i.e. 90% by weight of coir pith and 10% by weight of coconut fiber, to end up with a material of thickness 2.5 mm, which was then also cut to the aforementioned dimensions.

Other preparations were made of materials of similar thickness and composition that, before cutting, were coupled through relay rollers with a single sheet of Kraft paper and, respectively, with a polyethylene film, and fixed to them by spraying vinyl glue thereupon with suitable injectors.

The materials thus prepared were all equipped with excellent consistency, and it was possible to subject them to a cutting step with a cutter similar to those used in the production of paper, obtaining sheets of the aforementioned dimensions and perfectly intact. Such materials were also very compact, not releasing dust either during movement and application or during cutting, also demonstrating good tensile strength and ultimate strength for various stresses. Given the absence of any kind of glue, adhesive or additive, the characteristics of strength and compactness of the present material were all unexpected, given the nature of the starting materials.

Example 2: Test on materials prepared in Example 1

The following water absorbency tests were carried out on 3 samples of uncoupled absorbent sheet material, all having dimensions of about 60 cm x 40 cm, but of different thickness and composition, prepared as described above in Example 1.

The following Table 1 shows the results of the tests carried out, from which it can be seen how the amount of water absorbed by the sheet material of the invention is roughly six times the weight of the material itself, therefore extremely high and comparable to the amount of water absorbed by a comparable amount of the same mixture of coconut fiber and coir pith not processed according to the process of the invention. The material of the invention, moreover, once the water has been absorbed, does not break up and breaks only after great stress, thus being suitable for example for use as litter, to be replaced periodically; the strength of the material even after absorbing large amounts of liquids ensures, indeed, that the sheets of material already used as litter in one farming cycle can easily be replaced before the start of the next cycle without leaving residues, thus facilitating the cleaning operations.

Table 1

The present invention has been described with reference to a preferred embodiment. It should be understood that there can be other embodiments that derive from the same inventive core, as defined by the scope of the claims given hereafter.