DESCRIPTION

FIELD OF THE INVENTION

The present invention is part of the sector of recycling materials and the production of paper, poster board or cardboard, preferably packaging paper, poster board or cardboard, starting from a composition comprising a pulp and a solid material ( hydrochar ) obtained from a hydrothermal treatment (thermal hydrolysis or hydrothermal carbonisation) of organic waste.

PRIOR ART

In recent years, with the increase in society’s awareness of and interest in the environment and the sustainable exploitation of resources, increasing effort is being concentrated on developing technologies for recycling waste that instead of disposing of waste in landfill sites or incinerating it, can enable the waste to be effectively recovered and reused in productive processes. In the sector of the paper industry, processes are known that, starting with waste paper, enable the cellulose contained therein to be recovered for use as a “second raw material”, namely as a raw material of recycled origin, which is ready to enter again the production cycle of the paper mill. In addition to the traditional processes of recycling cellulose for the production of paper material, in recent years, processes have been developed that involve adding organic materials of different origins to the cellulose fibres used to make the pulp normally used in the manufacture of paper or cardboard. Examples of such organic materials are vegetable residues of various type (i.e. nutshells, olive or date stones, coffee beans, etc.) as disclosed for example in ES2314011T3 or alga material as disclosed in CA2093154C. Document WO 2016/201414 on the other hand describes the use of biocarbon deriving from the pyrolysis of organic waste (b/ocbar) within a pulp. Despite the efforts to try to devise increasingly sustainable processes, however, one of the main principles that remains in the current prior art relates to being able to provide a method for the production of paper, poster board or cardboard starting from recycled materials that is actually sustainable from an ecological point of view but is at the same time also economically advantageous for the paper industry. Further, there remains a need in the sector for providing a method for producing paper or cardboard that enables not only the use of cellulose to be reduced as much as possible, in particular the use of virgin cellulose coming from trees, so as to limit deforestation and the use of precious resources for the ecosystem and the environment, but also in order to be able to use at the same time waste materials that would otherwise be destined for disposal in landfill sites or for incineration.

The present invention solves the problems listed above by providing an alternative method for producing a second raw material starting from waste materials (biomass); the second raw material can be effectively used to make paper or cardboard, preferably packaging paper, poster board or cardboard, having the desired final mechanical properties as an alternative to the methods traditionally used in the sector.

The composition of the present invention involves adding a solid material ( hydrochar ) arising from the transformation of organic waste with hydrothermal treatments (thermal hydrolysis or hydrothermal carbonisation) to a pulp (the pulp having a virgin cellulose fibre base and/or deriving from recycled cellulose fibres).

Hydrothermal treatments, namely thermal hydrolysis or hydrothermal carbonization are thermochemical processes used for the conversion of biomass at relatively low temperature and pressure conditions, in the presence of water into liquid state under subcritical conditions, and allow organic material to be decomposed by converting it into a carbonaceous solid called hydrochar - HC and into a liquid component. Unlike biochar, which is obtained by pyrolysis or gasification of biomass with a generally low moisture content (lower than 30% w/w), the hydrochar is on the other hand a material obtained by the aforesaid hydrothermal processes, namely processes that treat wet biomass (preferably with a moisture content > 50% w/w), at lower temperatures, generally comprised between 120 and 280 °C and at pressure comprised between 2 and 60 bar, resulting in fact in a different material from biochar both from the point of view of chemical-physical properties and from the point of view of the composition, of the morphological features and of the surface functions (Kambo & Dutta, “A comparative review of biochar and hydrochar in terms of production, physico-chemical properties and applications”, Renewable and Sustainable Energy Reviews, 2015, vol. 45, issue C, 359-378). With respect to hydrothermal processes, pyrolysis is in fact a dry process that is conducted in total absence of oxygen and at temperatures comprised between 350 and 600 °C, generally for 5 minutes-12 hours, whereas gasification is a process that is conducted in the presence of small quantities of oxygen at higher temperatures (generally 600-900 °C) and for shorter periods (10-20 seconds). The present invention accordingly provides an alternative method for producing pulp comprising cellulose fibres (virgin and/or recycled) and a solid product ( hydrochar ) coming from the thermal hydrolysis or hydrothermal carbonisation of organic waste/biomass. The composition provided by the present invention thus enables not only the quantity of cellulose to be reduced that is necessary for the production of paper, poster board or cardboard whilst maintaining the mechanical features thereof unvaried but also enables the aforesaid organic waste/biomass to be reused and recycled effectively, avoiding in this manner the disposal thereof in landfill sites, cement plant or incinerators.

SUMMARY OF THE INVENTION

The object of the present invention is a composition comprising:

- a pulp comprising cellulose fibres and water; and

- a solid material ( hydrochar ) obtained by hydrothermal treatment (thermal hydrolysis or hydrothermal carbonisation) of biomass. The biomass is preferably a waste material. The cellulose fibres are preferably fibres of recycled cellulose.

The invention further relates also to a process for producing said composition that comprises a step of subjecting said biomass to the aforesaid hydrothermal treatment until a solid material ( hydrochar ) is obtained having a moisture content comprised between 30 and 90% w/w, to be dispersed within a pulp comprising cellulose fibres and water. A further object of the present invention is use of the composition as described previously, possibly obtainable with said process, for the production of paper, poster board or cardboard, preferably packaging paper, poster board or cardboard. The present invention further relates to a method for producing said paper, poster board or cardboard, preferably packaging paper, poster board or cardboard, using the composition as disclosed above in the typical processing of the paper industry. An object of the present invention is further a paper, poster board or cardboard, preferably packaging paper, poster board or cardboard, characterised in that it comprises a solid material ( hydrochar ) obtained by a hydrothermal treatment (thermal hydrolysis or hydrothermal carbonisation) of a biomass, preferably said paper, poster board or cardboard being obtainable with the method as disclosed previously.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a graph showing the trend of the SCT index ( Short (Span) Compression Test index that measures the intrinsic compressive strength) in function of different quantities of hydrochar (HC) dispersed within the pulp (BASE) of the composition according to the present invention, as disclosed in Example 1.

Figure 2 shows a graph showing the trend of the tensile index in function of different quantities of hydrochar (HC) dispersed within the pulp (BASE) of the composition according to the present invention, as disclosed in Example 1. Figure 3 shows a graph showing the trend of the burst index in function of different quantities of hydrochar (HC) dispersed within the pulp (BASE) of the composition according to the present invention, as disclosed in Example 1.

Figure 4 shows a graph showing the trend of the stiffness index in function of different quantities of hydrochar (FIC) dispersed within the pulp (BASE) of the composition according to the present invention, as disclosed in Example 1.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, the terms “pulp” or “cellulose paste” are used as perfectly interchangeable synonyms.

For the purposes of the present invention, the term “hydrothermal treatment” generally refers to the thermal hydrolysis process or to the hydrothermal carbonisation process.

For the purposes of the present invention, the phrases “moisture content” or “water concentration” are used as synonyms to indicate a given quantity of water contained within a certain composition or a certain material. By way of example, “a biomass having a moisture content of at least 50% w/w” is a “biomass comprising water in a quantity of at least 50% w/w”.

The object of the present invention is a composition comprising: a pulp comprising cellulose fibres and water; and a solid material ( hydrochar ) obtained from a process of thermal hydrolysis or hydrothermal carbonisation of a biomass, wherein said solid material is dispersed within said pulp.

According to one embodiment, the composition of the invention essentially consists of:

- said pulp comprising cellulose fibres and water; and

- said solid material ( hydrochar ) obtained by a process of thermal hydrolysis or hydrothermal carbonisation of a biomass, wherein said solid material is dispersed within said pulp. According to another embodiment, the composition of the invention consists of:

- said pulp comprising cellulose fibres and water; and

- said solid material ( hydrochar ) obtained by a process of thermal hydrolysis or hydrothermal carbonisation of a biomass, wherein said solid material is dispersed within said pulp.

Preferably, said solid material is dispersed uniformly within said pulp, or said solid material is a material dispersed uniformly within said pulp. According to one preferred embodiment of the invention, said solid material ( hydrochar ) is dispersed within said pulp in a quantity comprised between 5 and 40% w/w, preferably between 10 and 30% w/w, more preferably between 10 and 20% w/w. Without wishing to be bound by a specific theory, the Applicant found that using the aforesaid quantities of said solid material dispersed within the pulp does not detract from the desired performance and mechanical features of the paper, poster board or cardboard produced with the composition according to present invention. The Applicant also found that by adjusting the quantity of hydrochar within the aforesaid preferred ranges it is possible to modulate the mechanical properties and in particular, the vertical compressive strength and/or the stiffness of the paper, poster board or cardboard obtainable from said composition, making them in fact particularly advantageous for applications like packaging material. According to one preferred embodiment, said biomass is a waste material selected from the group consisting of: vegetation water, digestate, agro-industrial waste, sewage, the organic fraction of urban solid waste, sewage sludge, preferably civil, agro-industrial, paper mill sludge, and a combination thereof. According to one embodiment of the invention, the solid material ( hydrochar ) obtained from a process of thermal hydrolysis or hydrothermal carbonisation of said biomass is a shovelable, non-powder, sterilised and odourless material that can be easily dispersed, preferably in a uniform manner, within said pulp. Without wishing to be bound by a specific theory, the Applicant found that according to the origin of the biomass from which said hydrochar derives, the composition of the invention can be characterised by different properties and that these properties are modulable. Preferably, if the hydrochar is obtained from a hydrothermal treatment of a digestate or of a sludge, it is in general a hardly fibrous material, but which advantageously acts as a filler, conferring on the composition and, consequently, on the finished product (paper, poster board or cardboard), the desired technological features of colour/characteristic appearance and mechanical resistance. If, on the other hand, the hydrochar derives from a biomass comprising cellulose rejects (for example arising from the paper industry, wine industry) or from wood processing, said hydrochar can contain a greater fibrous component (mainly comprising cellulose and lignin) being in a composition (and relative subsequent finished product) with mechanical properties of compressive strength, tensile strength and/or stiffness further increased to the quantity of hydrochar dispersed in the pulp. According to one embodiment, the composition according to the present invention does not comprise biochar. According to one particularly preferred embodiment of the invention, said cellulose fibres are fibres of recycled cellulose. Preferably, said fibres of recycled cellulose are fibres deriving from waste paper, paper, poster board or cardboard trimmings or a combination thereof. According to one preferred embodiment, said pulp comprises from 70 to 98% w/w waste paper. According to another preferred embodiment, said pulp comprises from 70 to 98% w/w paper, poster board and/or cardboard trimmings. More preferably, said waste paper is pulp conforming to standard UNI EN 643-1-02-00; said trimmings are trimmings conforming to UNI EN 643-4-01-00.

The object of the present invention is also a process for producing the composition as described previously.

Said process comprises the steps of:

(i) subjecting a biomass to a process of thermal hydrolysis or hydrothermal carbonisation, obtaining an aqueous mixture or suspension;

(ii) subjecting said aqueous mixture or suspension to a dehydration process, optionally adding a chemical agent selected from sulphuric acid, hydrochloric acid and citric acid, and/or an adjuvant chosen from a polyelectrolyte, an aluminium silicate, cellulose and recycled cellulose until a solid material { gάGqq Bή having a moisture content comprised between 30 and 90% w/w, preferably between 60 and 80% w/w, is obtained;

(iii) dispersing said solid material ( hydrochar ) obtained in step (ii) within a pulp comprising cellulose fibres and water.

According to a preferred embodiment of the present invention, the step (i) is carried out at a temperature comprised between 120 and 280 °C, preferably between 150 and 250 °C, and at a pressure comprised between 2 and 60 bar, preferably between 2 and 50 bar. In other words, said step (1) involves subjecting said biomass to thermal hydrolysis or hydrothermal carbonisation treatment, said treatment comprising the step of heating said biomass to a process temperature comprised between 120 and 280 °C, preferably between 150 and 250 °C, until registering an increase in the steam pressure within said reactor comprised between 2 and 60 bar, preferably between 2 and 50 bar, as a function of said process temperature; Preferably, said step (i) is carried out for a period of time comprised between 0.5 and 8 hours. Preferably, said step (i) is conducted in a closed reactor. Optionally, said step (i) involves adding to said biomass at least one chemical agent selected from the group consisting of: sulphuric acid, hydrochloric acid or citric acid. Preferably, said biomass is as described previously. Advantageously, according to the present invention, the solid material ( hydrochar ) obtained downstream of step (ii) is a shovelable, non-powder, sterilized and odourless material that can be easily dispersed within a pulp (as disclosed in step (iii) of the process according to the present invention) for producing paper, poster board or cardboard. Preferably said pulp of step (iii) is as described previously. According to one embodiment of the present invention, in step (iii), said solid material ( hydrochar ) obtained in the step (ii) is dispersed within a pulp comprising cellulose fibres and water in a quantity as disclosed previously. Preferably, said solid material ( hydrochar ) obtained in the step (ii) is dispersed within said pulp uniformly. According to one embodiment, said biomass, before being subjected to step (i) of the process according to the present invention, is subjected to a step of:

(ia) separating extraneous materials from said biomass, preferably by screening and/or filtration, more preferably said filtration being performed by filters chosen from screw-filters, basket filters, or the like; and/or

(ib) grinding said biomass until a paste is obtained.

Preferably, if the biomass to be subjected to the process of thermal hydrolysis or hydrothermal carbonisation according to step (i) contains a quantity of water below 50% w/w, the process according to the present invention comprises a step of:

(ic) diluting the biomass, possibly obtained downstream of the step (ia) and/or (ib), with water until water content of at least 70% w/w is obtained. Without wishing to be bound by a specific theory, the Applicant found that the composition as described previously can be advantageously obtained with the process according to the present invention as disclosed here.

An object of the present invention is also a use of the composition as described previously for the production of paper, poster board or cardboard. Preferably, said paper, poster board or cardboard being packaging paper, packaging poster board or packaging cardboard, more preferably chosen from: Test Liner 1 , 2, 3, 4 paper, GD/GT liner, Medium paper, Wellenstoff, Floutting, grey poster board and a combination thereof. The object of the present invention is also a method for the production of paper, poster board or cardboard, preferably packaging paper, poster board or cardboard, comprising the steps of:

(a) providing the composition as described previously;

(b) subjecting the composition obtained in the step (a) to at least one further process for the production of paper, poster board or cardboard. Preferably, said at least one further processing of the step (b) comprising the refining and mixing of said composition followed by the formation of the sheet of paper, poster board or cardboard and subsequent formation of a roll. According to one embodiment of the invention, said method also comprises an optional step of adding at least one chemical additive commonly used in the paper industry. Preferably said additive is added to the composition of the step (a) (in this case we speak of internal or wet end addition) or on the finished sheet of paper, poster board or cardboard after complete or partial drying (in this case we speak of surface or dry end addition).

An object of the present invention is also a paper, poster board or cardboard, preferably packaging paper, packaging poster board or packaging cardboard, characterised in that it comprises a solid material ( hydrochar ) obtained from a process of thermal hydrolysis or hydrothermal carbonisation of a biomass. Without wishing to be bound by a specific theory, it is nevertheless possible to assert that said solid material ( hydrochar ) is dispersed within said paper, poster board or cardboard, preferably uniformly with the cellulose fibres that make up said paper, poster board or cardboard. Preferably, said solid material { gάGqq bή is present in a quantity comprised between 5 and 40% w/w, more preferably between 10 and 30% w/w, still more preferably between 10 and 20% w/w. Without wishing to be bound by a specific theory, the Applicant found that the presence of said solid material {IigάGqqΐΊ3ή within the paper, poster board or cardboard according to the present invention not only bestows the desired mechanical properties, as moreover demonstrated in the section of the examples, but according to the concentrations, enables paper, poster board or cardboard to be obtained with a dotted appearance that facilitates the recognition thereof. Further, as said solid material ( hydrochsr ) is obtained from hydrothermal processes, it is a sterilized material that although it derives from a biomass, preferably from waste materials like those described above, does not have any odour. Preferably, said paper, poster board or cardboard is obtainable with the method as disclosed above. Without wishing to be bound by a specific theory, the Applicant found that using the composition according to the present invention (comprising, essentially consisting of, or consisting of: a pulp comprising cellulose fibres and water; and a solid material ( hydrochar ) obtained from a process of thermal hydrolysis or hydrothermal carbonisation of a biomass, wherein said solid material is dispersed within said pulp), provided in the step (a) of the method according to the present invention, means that said solid material is effectively dispersed also within said paper, poster board or cardboard obtainable from the subsequent processing of said composition according to the step (b) of the method of the present invention. According to one embodiment, said paper, poster board or cardboard, preferably packaging paper, packaging poster board or packaging cardboard according to the present invention, does not comprise biochar.

EXAMPLES

Example 1 - Measurement of mechanical properties Compositions have been produced according to the present invention containing variable quantities of hydrochar (HC), dispersed within a pulp (called base mixture - “BASE”) obtained from traditional waste paper. More specifically, this base mixture is 80% w/w corrugated cardboard trimmings (UNI EN 643-4-01-00) and 20% w/w waste paper (UNI EN 643-1-02-00). In the following table (Table 1), the different compositions are shown that were produced and used in the production of the tested samples of poster board. The compositions produced according to the present invention (compositions 2-4) were used in the production of paper samples (in the form of sheets) on which the mechanical properties were measured. The results were compared with the samples obtained from a composition comprising only the base mixture (composition 1).

Table 1

In general terms, the mechanical features of paper are influenced by the quantity of fibres contained and by the quality thereof, length and width above all. Adding non fibrous materials to the paper mill mixtures generally occurs for aesthetic reasons and/or to save on cellulose fibres. The laboratory tests have the purpose of verifying whether the reduction of fibres in the mixture through the addition of a filling material like hydrocharas in the compositions according to the present invention, enables paper to be made that is suitable from the mechanical point of view for the production of packaging. As can be seen from the graphic display in figures 1-4, the decline in performance is in line with the reduction of fibres in the mixture but is not homogeneous in the various tests and in particular it is possible to note how stiffness is affected only marginally. Overall, it is seen that with 10% hydrochar, the maintenance of the mechanical features is such as to enable use for corrugated cardboard packaging, also for poster board where rather high strength is required. By increasing the percentage of hydrochar, the mechanical features are suitable for corrugated paper or for stiff poster board of great thickness (see Table 2).

Table 2