Technical Field

The present invention relates to a process for obtaining plastic material from flours and similar products.

Background Art

Biodegradable polymers play an increasingly important role in plastics engineering.

Research is increasingly focusing its efforts on replacing oil-based polymers, which are non-biodegradable and from non-renewable sources, with polymers derived from vegetable substances, which are biodegradable and have less impact on the environment.

Among all natural polymers, starch is the one most used today as it provides good results in obtaining plastic material. In particular, the most widely used starch is the one extracted from the grains of corn, after grinding them to obtain flour.

The use of purified corn starch, however, is inconvenient because its extraction from flour requires laborious and expensive processes as well as a harmful impact on the environment. Corn is also a macro-thermal species, the cultivation of which, in many warm-temperate areas of the planet, can only be done in the spring- summer cycle with the aid of irrigation, with high economic and environmental costs.

In view of the above, it is clear that there is a need to devise plasticizing processes for obtaining plastic material that can be applied to flours“as they are” rather than to purified starch and to flours other than corn flours.

For this reason, plasticization processes have been developed that allow plastic material to be obtained directly from flour-based mixtures, in which starch is naturally present.

Flour, in fact, if subjected to certain conditions of effort and temperature, can plasticize.

In particular, it is known how to obtain plastic material from wheat flour ( Benincasa et al, 2017 - Industrial Crop and Products). Some known processes provide for the insertion of an initial mixture comprising refined flour in an extruder which is adapted to heat and subject the mixture to mechanical stresses in order to obtain the plasticization thereof.

There are documents that encourage the use of refined flour, commonly called “00 grade flour” or“0 grade flour”.

For example, in the publication“ Terri , C., Constantinescu, V., Leblanc, N, Salter, J.-M., 2010. Influence of proteins on the mechanical properties of agro- based materials. Macromol. Symp. 296, 617-62”, the authors encourage the use of refined flour, pointing out that the presence of proteins and fibers influences the production of plastic material, both in terms of quality and in terms of the mechanical characteristics of the material obtained.

The known processes do have some drawbacks related to the use of refined flours.

A first drawback is related to the fact that the use of refined flours involves numerous and laborious treatments aimed at separating the bran parts from the rest of the farinaceous mixture.

These treatments increase the times and costs of making the initial mixture and have a significant environmental impact.

A second drawback is that the bran parts are a by-product to be disposed of, of low economical value, which is not always used advantageously in other production chains.

For example, in Italy, the crisis in animal husbandry has reduced the use of these bran parts in animal feeding.

A third drawback is related to the fact that the known processes necessarily provide for the use of synthetic additive substances aimed at plasticizing and/or improving the mechanical performance of the mixture.

The use of these substances, not only increases the costs of the process, but also has a high environmental impact due to the manufacturing processes of the synthetic substances.

Alternatively, the bran parts mixed with the refined flours can act as a reinforcement in obtaining plastic material thus affecting the mechanical properties of the plastic material obtained, also depending on the proportion of bran and the degree of grinding of the same.

Description of the Invention

The main aim of the present invention is to devise a process for obtaining plastic material from flours and similar products that allows the use of any grade of flour.

One object of the present invention is to devise a process for obtaining plastic material from flours and similar products that allows a reduction in the environmental impact and the production costs.

Another object of the present invention is to devise a process for obtaining plastic material from flours and similar products that allows overcoming the mentioned drawbacks of the prior art in the context of a simple, rational, easy, effective to use and low cost solution.

The aforementioned objects are achieved by the present process for obtaining plastic material from flours and similar products having the characteristics of claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will be more evident from the description of a preferred, but not exclusive, embodiment of a process for obtaining plastic material from flours and similar products, illustrated by way of an indicative, but non-limiting example, in the attached tables of drawings in which Figure 1 is a schematic view of the process according to the invention.

Embodiments of the Invention

With particular reference to this figure, reference numeral 1 globally indicates a process for obtaining plastic material from flours and similar products.

In a first embodiment, the process comprises an extrusion phase E of a starting mixture 1.

According to the invention, the starting mixture 1 comprises flour, in the present discussion indicated with reference numeral 2, comprising bran 3 present in a concentration by weight, evaluated with respect to the total weight of the flour, ranging from 15% to 65%.

Advantageously, the starting mixture 1 comprises flour F comprising bran 3 present in a concentration by weight, evaluated with respect to the total weight of the flour F, ranging from 20% to 50%.

The flour F is of the wheat flour type.

The flour F usefully comprises flours which are commercially known as “wholemeal flours”,“2 grade flours” or“1 grade flours”.

The use of“reconstituted flours” cannot be ruled out, i.e. wholemeal, 2 grade or 1 grade flours obtained by mixing 0 grade or 00 grade flours with bran parts in quantities such as to produce reconstituted flours with bran present in a concentration by weight, evaluated with respect to the total weight of flour F, ranging from 15% to 65%.

The use of flours deriving from other micro-thermal cereals, such as e.g. barley, rye, triticale, oats, spelt, or macro-thermal cereals, e.g. corn, sorghum, different species of millet, cannot be ruled out.

It should be noticed, however, that wheat flours are more available and advantageous with respect to other flours and it may possible that they become available for uses other than food: unsold stocks, poor batches, presence of mycotoxins, etc..

Advantageously, the starting mixture 1 comprises flour F present in a concentration by weight, evaluated with respect to the total weight of the starting mixture 1, above 30%.

According to a first embodiment, the flour F is equal to 68%.

Still according to the invention, the starting mixture 1 comprises at least one solvent substance 4.

The solvent substance 4 is preferably of the water type, but the use of water- based mixtures or other solvent substances, such as e.g. glycerol, cannot be ruled out.

A starting mixture 1 in which the solvent substance 4 is absent cannot be ruled out.

The starting mixture 1 usefully comprises facilitating additives, for simplicity not shown in the figures, adapted to facilitate the plasticization process of the plasticizable fraction of flour F.

In the present embodiment, the facilitating additives comprise at least one of the following substances: glycerol, sorbitol, magnesium stearate, polyvinyl alcohol. It should be noticed that glycerol can also be used as a plasticizer, alternative or complementary to water.

The facilitating additives usefully comprise at least one of the following: glycerol, ethylene glycol, formamide, urea, polyols and other substances comprising“OH” hydroxyl groups suitable for plasticization.

In the present embodiment the facilitating additives comprise:

glycerol present in a concentration, evaluated with respect to the weight of the starting mixture 1, ranging from 10% to 35%;

sorbitol present in a concentration, evaluated with respect to the weight of the starting mixture 1, ranging from 1.5% to 5.2%.

The process comprises a preliminary preparation phase A of the starting mixture

1.

Subsequently, the starting mixture 1 is subjected to the extrusion phase E.

The extrusion phase E has a work temperature ranging from 60 °C to 180 °C. Usefully, the extrusion phase E has a work temperature ranging from 90 °C to 150 °C.

Preferably, the extrusion phase E has a work time ranging from 2 minutes to 15 minutes.

Usefully, the extrusion phase E has a work time ranging from 4 minutes to 8 minutes.

Preferably, the extrusion phase E is carried out in a co-rotating and counter rotating two- screw extruding device 5, in which the action of the counter rotating screws is used to crush the structure of starch present in the flour F.

The shear forces and other mechanical forces applied to the starting mixture 1 are proportionate to the number of revolutions of the co-rotating screws and the geometry of the extruding device 5.

In the present discussion, the reference extruding device is of a“DSM Explorer 5&15 CC Micro Compounder” type.

Usefully, the number of revolutions of the co-rotating screws of the extruding device 5 ranges from 1 rpm to 400 rpm.

Advantageously, the number of revolutions of the co-rotating screws of the extruding device 5 ranges from 25 rpm to 130 rpm.

In this first embodiment, the extrusion phase E:

has a work temperature ranging from 125 °C to 145 °C;

has a work time ranging from 3 minutes to 9 minutes;

is carried out in an extruding device 5 the number of revolutions of which ranges from 1 rpm to 250 rpm.

As an example, the extrusion phase E takes place at a work temperature ranging from 130 °C to 140 °C, for a work time of 6 minutes and at a number of revolutions of the extruding device 5 equal to about 30 rpm.

It should be noticed that the values indicated depend on the rheological characteristics of the system, as well as the time required for plasticization to take place depend on the parameters and ingredients used.

In this first embodiment, the plastic material obtained is substantially rigid, particularly adapted to be used as a structural supporting element, such as e.g. as a base 6 on which to place heavy material, or to make films for rigid packaging or to make separation elements for pallets or other applications such as flat sheets, protective sheets and the like.

A second embodiment of the process is entirely similar to the first embodiment described above and differs in the fact that the extrusion phase E:

has a work temperature ranging from 130 °C to 150 °C.

has a work time ranging from 3 minutes to 9 minutes;

is carried out in an extruding device 5 the number of revolutions of which is equal to 120 rpm.

As an example, the extrusion phase E takes place at a temperature ranging from 135 °C to 145 °C, for a work time of 6 minutes and at a number of revolutions of the extruding device 5 substantially equal to 120 rpm.

Advantageously, the starting mixture 1 comprises a farinaceous mixture comprising flour F and polycaprolactone.

By farinaceous mixture, therefore, we mean the mixture obtained by mixing flour F and polycaprolactone.

Polycaprolactone is present in a concentration by weight, evaluated with respect to the total weight of the farinaceous mixture, ranging from 15% to 40%. Preferably, polycaprolactone is present in a concentration by weight, evaluated with respect to the total weight of the farinaceous mixture, ranging from 20% to 30%, e.g. equal to 25%.

Alternative solutions in which polycaprolactone is comprised in a concentration by weight, evaluated with respect to the total weight of the farinaceous mixture, greater than 40%, cannot be ruled out.

The use of polymers other than polycaprolactone cannot be ruled out.

It should however be noticed that of all possible polymers that can be used, polycaprolactone is the only one that has a work temperature inside the extruding device 5 compatible with the plasticization temperature of flour F.

This characteristic makes it particularly suitable for the process to which this patent relates.

The farinaceous mixture usefully comprises at least one plasticizing agent present in a concentration by weight, evaluated with respect to the total weight of the farinaceous mixture, ranging from 0.3 to 1.5%.

The plasticizing agent is preferably citric acid and is present in a concentration by weight, evaluated with respect to the total weight of the farinaceous mixture, ranging from 0.6 to 1.5%, for example equal to 0.8%.

In this second embodiment, the plastic material obtained is a film 7 resistant to stress and breakage.

The aforementioned film 7 may be adapted to be used in mulching cloths as it has useful characteristics for this type of use.

In fact, the plastic material obtained is compostable and is able to retain the moisture present in the soil.

The cloth can be deformed when it is applied to the ground, thus adapting to the shape of the surface, for the benefit of the functionality of use.

It has in practice been ascertained that the described invention achieves the intended objects and, in particular, it is stressed the fact that the process for obtaining plastic material from flours and similar products allows the use of any type of flour.

Thanks to this process, in fact, it is possible to use wholemeal flour directly, thus eliminating any preliminary refining phases, which are costly and have a strong environmental impact.

In particular, the devised process allows using wheat flours as an alternative to corn starch, with economic and environmental benefits.

Wheat, in fact, is less expensive and has less environmental impact than corn and wheat flour that exceeds market demand or that cannot be used for food purposes (waste, portions contaminated with fungi or bacteria, etc..) can be reused to produce plastic material.

The devised process, moreover, can be applied to different types of mixture and different types of flour, as it can be adapted according to the type of plastic material to be obtained.

Starting from a certain type of initial mixture, the process allows obtaining plastic materials with different characteristics of rigidity and resistance to breakage.

This way it is possible to obtain different types of plastic material by simply varying the parameters according to the type of farinaceous mixture used.

The process also allows eliminating or reducing the use of synthetic oil-based polymers, to the benefit of the environmental impact and resulting in reduced costs.