RU2685292C2 - Paper base, its production method and secured document having said base - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to chemical technology of pulp and paper production and concerns a paper base and a method of producing a security document with such a base. Durable biodegradable paper base for printing a security document, in particular banknotes, comprises cellulose fibers in an amount greater than or equal to 70 % and less than 100 % by dry weight of the total weight of the paper base in a dry state, additives, auxiliary substance, at least one binder, additionally contains: oleophobic and hydrophobic adhesive based on organic compound containing perfluoropolyester groups in amount of more than 0 % and less than or equal to 5 % on dry weight of total weight of paper base in dry state, at least one biodegradable reinforcing substance, selected from substances of vegetable or animal origin, substances synthesized by biotechnological engineering or genetic engineering and then biotechnological engineering, and substances of biological origin, which are then chemically converted.EFFECT: invention provides a paper base for making and printing a security document characterized by high durability, id est having high resistance to dirt and mechanical loads, and biodegradability, which provides natural utilization at the end of life cycle.19 cl, 2 tbl

Description

The technical field to which the invention relates.

The invention relates to a highly durable and biodegradable paper base for printing a security document, in particular, a banknote.

The invention also relates to a method for manufacturing such a paper base and a security document with such a paper base.

The level of technology

Protected documents, in particular, banknotes, are subject to numerous influences in the process of their circulation, which leads to their pollution and increases the risk of their damage or rupture, which may result in premature removal from circulation of the money supply.

To solve this problem in the prior art, various methods are already known for increasing the resistance to contamination and tearing of banknotes.

For example, FR 2 975 408 is known for a sheet of highly durable paper with a protective coating, containing an outer, printable layer based on polyurethane.

Also from the prior art known types of paper with high strength, for which pulp fibers are added materials, such as polyamides, polyesters or polypropylene. For example, reference may be made to the source EP 1 432 576, which discloses, in particular, the use of polyester reinforcing fibers.

Also known are banknotes made of plastic, for example, made of biaxially directed polypropylene (BOPP), characterized as products with a long service life, as well as hybrid products containing both paper sections and polyamide-based plastic materials.

Central banks responsible for the issue, circulation and withdrawal of banknotes from circulation have budget constraints, forcing them to look for ways to lengthen the life of banknotes, which is necessary to reduce the cost of the liquidity cycle of paper, which forces them to consciously turn to the above solutions.

However, the considered methods of increasing the service life have the disadvantage of having to use petrochemical products that are not renewable in nature. Meanwhile, a growing number of states have to take environmental measures and manage waste. And even if banknotes at the end of their life cycle form only an insignificant part of anthropogenic pollution, they have a high symbolic value in nature, therefore it is important to consider their ecological footprint, in particular, from the point of view of their ability to biodegrade.

Some participants who offer plastic banknotes, for example, biaxial-oriented polypropylene (BOPP) banknotes, characterize them as environmentally friendly products, referring to the fact that at the end of the service life banknotes can be reused for the manufacture of other plastic products. However, no serious and independent research on this issue has been proposed so that you can check the accuracy of such a theoretical recycling process chain and method for calculating greenhouse gas emissions.

WO 2013/178986 describes contamination resistant paper, in particular, designed for banknotes and containing microfibrillated cellulose (MFC). However, this document does not suggest the use of an oleophobic and hydrophobic adhesive based on an organic compound containing perfluoropolyether groups, and does not say that such products can be combined without problems to obtain a high-strength and biodegradable base.

In WO 00/19015, only the use of a rubber solution in an organic solvent to impart hydrophobicity to paper is described, and this solution contains less than 1% by weight of polymers containing alkylperfluorinated groups. However, some of these alkyl perfluorinated compounds are considered toxic and differ from the perfluoropolyether groups used in the invention.

DISCLOSURE OF INVENTION

The aim of the invention is to eliminate the above disadvantages inherent in the prior art.

In particular, the aim of the invention is to create a paper base for the manufacture and printing of a security document, in particular, a banknote, which is simultaneously characterized by high durability, i.e. possessing the increased resistance to pollution and mechanical loadings, and biological decomposability, providing natural utilization at the end of the life cycle.

The sign "biodegradable" means mainly, according to the standard EN 13432, concerning the requirements for recyclable packaging by composting and biodegradation, that:

- paper base should contain a small amount of heavy metals and other toxic substances,

- at least 90% by weight of the sample should be converted to carbon dioxide and biomass for not more than 6 months,

- after 12 weeks of aerobic composting, the amount of residues larger than 2 mm should not exceed 10% of the initial dry matter,

- The final compost must pass ecotoxicological tests.

Therefore, the invention relates to a highly durable and biodegradable paper base for printing security documents, in particular, banknotes containing cellulose fibers in an amount greater than or equal to 70% and less than 100% by dry weight of the total weight of the paper base in a dry state, additives, auxiliary substances and at least one binder.

According to the invention, such a base contains:

oleophobic and hydrophobic adhesives based on organic compounds containing perfluoropolyether groups in an amount of more than 0% and less than or equal to 5% by dry weight of the total weight of the paper base in the dry state;

at least one biodegradable substance strengthening structure selected from substances of plant or animal origin, synthetic substances obtained by biotechnological engineering or genetic engineering and subsequent biotechnological engineering, as well as substances of biological origin subjected to chemical transformation.

Due to such features of the invention, the resulting paper meets the above requirements for ensuring high durability and biodegradability.

According to other preferred and non-limiting features of the invention, taken separately or in combination:

- the amount of cellulose fibers is greater than or equal to 85% and less than 100% by dry weight of the total weight of the paper base in the dry state,

- additives, auxiliary substances and a binder are contained in an amount of more than 0% and less or equal to 15% by dry weight of the total weight of the paper base in a dry state,

- biodegradable substance strengthening substance (substances) contains more than 0% and less than or equal to 25%, preferably more than 0% and less than or equal to 20%, more preferably more than 0% and less or equal to 10% by dry weight of the total paper weight basis in a dry state,

- in their chemical formulas, perfluoropolyether groups contain the main fragments - (CF ₂ CF ₂ O) _m - (CF ₂ O) _n -, where m and n are integers.

The invention also relates to a security document, such as, for example, a banknote made using the aforementioned paper base.

Finally, the invention relates to a method of manufacturing the above paper base, comprising the following successive stages:

a) suspension of cellulosic fibers in water,

b) refining said mixture,

c) the introduction of additives, auxiliary substances and binders,

d) cleaning and filtering the fiber suspension,

e) forming a paper base,

f) pressing,

g) pre-drying

h) coating a paper base surface,

i) subsequent drying,

as well as the stages of introducing biodegradable substances strengthening the structure and introducing oleophobic and hydrophobic adhesives, wherein the introduction of biodegradable substances strengthening the structure is carried out between stages a) and b) or at stage h), and the stage of introducing oleophobic and hydrophobic adhesives is carried out between stages ) and d) or at stage h).

The implementation of the invention

The fibers that make up the paper base are mainly cellulosic fibers.

Preferably, the cellulose fibers are selected from hardwood and softwood fibers, seasonal plants, such as cotton, hemp or flax. These different fibers can be used separately or in a mixture.

However, it is preferable that the cellulosic fibers used are cotton fibers. These fibers are used for their positive physical and mechanical properties. In fact, cotton fluff (i.e., fluff of very short fibers bonded to cotton seeds after fiber separation) has a length of 2 to 5 mm and a width of 18 μm, which gives the resulting paper a very high resistance to bending.

The paper base according to the invention also contains non-fibrous additives and auxiliary substances, preferably selected from antifoaming compounds, mineral fillers, substances for imparting wet stability and adhesives used separately or in combination.

Antifoaming agents are, for example, substances such as silicones, silicone emulsions, polyethylene glycols, derivatives of polyethylene glycols, synthetic polyhydric alcohols, derivatives of polyhydric alcohols, antifoaming agents based on amide and ester; surfactants such as oligomers, ethylene oxides (EtO), polypropylene oxides (PPOx); hydrophobic substances such as hydrocarbon waxes, polyethylene waxes, fatty alcohols, fatty acids, fatty esters, ethylenebis (steramide) (EBS), hydrophobic silicas.

Antifoaming agents are added during the preparation of the paper pulp, as well as in the wet compartment of the paper machine, with the goal of preventing the formation of foam, even its destruction, and thus improving sheet formation.

Preferably, the mineral fillers are selected from colloidal silica, sodium silicates, sodium aluminosilicates, natural or precipitated calcium carbonates, talc, natural or calcined kaolin, alumina hydrate, titanium dioxide and barium sulfate, their salts or mixtures.

Such mineral fillers are added to alter the optical properties of the resulting paper, such as whiteness, gloss or opacity, as well as its surface properties. Some of these fillers are cheaper than fibers and are therefore added to reduce costs.

Substances to increase the strength in the wet state are thermoset polymers that are added while the paper is still wet and which form the crosslinked structure of the paper as it passes through the drying chamber. They play the role of a barrier to water after paper making.

Preferably, predominantly polymers are used that bind the fibers together, such as urea formaldehyde resins (UF), melamine formaldehyde resins (MF), polyamideamine-epichlorohydrin-based resins (PAA-E), glyoxal resins, ionic metal complexes, taken separately or in a mixture .

Adhesives slow down the penetration of liquid into the paper. They are used when the paper is either still wet (gluing in paper pulp) or in the area of the gluing press (gluing on the surface).

Preferably, natural products are used, such as modified natural resins (resin-based adhesives), starch or modified starch, or synthetic products, such as alkyl ketene dimer (AKD), alkylene anhydride succinic acid (ASA), and other polymers (for example, copolymers on acrylic and maleic acid esters, acrylonitrile and styrene). Alkyl ketene dimer is a chemical product most widely used for bonding and preferably used when product specifications permit. It is also possible to use paraffin wax and polyethylene waxes. These different products can be used separately or in a mixture.

As will be described later in the section on papermaking, fibers, additives and auxiliaries are mixed and interconnected by using at least one binder.

Such a binder can improve the strength of paper in a dry state.

Preferably, the binder is selected from polyvinyl alcohols, starch, starchy products, latex, hemicelluloses, carboxymethylcellulose (SMS), galactomannans, gelatins, or polyamide-epichlorohydrin resins, taken separately or in a mixture.

According to the invention, the above-mentioned additives, auxiliary substances, binders and at least one biodegradable substance strengthening structure are introduced into the fibers.

Such a biodegradable substance strengthening the structure comes from a natural plant or animal source and can be used either directly or after the purification and / or transformation stage, or it can be synthesized by biotechnological engineering, for example, by bacterial fermentation, or by genetic engineering and then biotechnological engineering. This substance may also be of biological origin, i.e. come from a biological source and then undergo chemical conversion.

Structural reinforcement is understood to mean that at least one of the commonly measured mechanical properties that characterize a base is improved compared to paper that does not have this reinforcing substance; The mechanical properties that are mentioned here, but which are not exhaustive, are: tensile strength, double fold, internal grip, stiffness, tensile strength, elongation and elongation at break, etc.

From biodegradable hardening substances originating from a plant source and intended for the formation of paper sheets, in particular, suitable for target use as banknotes, we can point to the following annual plants, which are known to the average specialist and which do not belong to wood (the main type of raw material for the production of standard paper) or cotton (the main type of raw material for making banknotes): grain crops, in particular, straw of grain crops (rice, wheat, barley, oats, rye, triticale), sa artic reeds (in particular, sugar cane bagasse), bamboo, reeds, grass Algerian feather grass and sabe, flax, kenaf, jute, hemp, abaca and sisal leaves, sugar beet mass, buckwheat shell and wheat bran, in general, are all higher plants containing cellulosic or lignocellulosic fibers.

And although many of them have certain advantages, acting as waste or semi-products of a crop for obtaining grain, seeds, straw, vegetable oils, sugar, sucrose, etc., their main drawback comes from the seasonality of the above crops and from the lack of control in the distribution of morphology cellulose fibers depending on the origin of these resources.

Therefore, according to this invention, it is understood that biodegradable structure-strengthening substances, when based on cellulose, are products of natural origin, for example, one of the above products whose cellulose is either regenerated or finely ground.

In other words, cellulose, which is naturally self-organized macrobiopolymer in the form of fibrils and fibers, is either regenerated after transitional full structural denaturation, or finely ground by mechanical and / or chemical methods, which make it possible to produce particles of nanometric size.

The regenerated cellulose is understood to mean cellulose obtained by the considered methods, which provide little contamination compared to when raw cellulose is dissolved in N-oxide-N-methylmorpholine (slightly toxic and reused in the process) before regeneration. This refers to the fiber, known under the commercial designation Lyocell, produced in such a way as opposed to viscose fibers, the production methods of which require the use of carbon sulphide and copper, which are not environmentally friendly enough.

“Finely divided cellulose” refers to microcrystalline and nanocrystalline cellulose, such as microfibrillated cellulose (MFC) and crystalline nanocellulose or cellulose nanocrystals (NCC).

Cellulose is obtained in this way, the mechanical properties of which are much more controlled and which acts as a structurally reinforcing substance that is more predictable and more reproducible for the paper substrate according to the invention. Since cellulose is used predominantly, the biodegradability of the paper base is also ensured.

From biodegradable structure-strengthening substances derived from a plant source other than a cellulose-based source, one can indicate, for example, sources based on polysaccharides and / or proteins and / or their combinations, either in their native state, i.e. from the raw mixture together with the other components of the examined plant, either purified, i.e. after preliminary passing through the stages of separation, concentration, refining, etc., to achieve a higher degree, providing more stringent control over the desired mechanical properties of the paper base.

In this category, and this is not restrictive, macroscopic algae, such as kelp, and microscopic, such as chlorella or spirulina, can be used, and these algae are preferably crushed. Picocolloids and their derivatives, extracted from these algae, belong to this category of products.

Of the biodegradable structure-strengthening substances derived from an animal source, it is possible to indicate, for example, substances based on polysaccharides and / or proteins and / or their combinations, either in their native state, i.e. originating from the raw mixture with other components of the source, or purified, i.e. after the preliminary stages of separation, concentration, refining, etc., to achieve a higher degree, providing more stringent control over the desired final mechanical properties of the paper base.

Keratin-based products, for example, wool or poultry feathers, can be categorized into this category without limitation.

From biodegradable structure-strengthening substances obtained by biotechnology or by genetic engineering and biotechnology, one can indicate, for example, substances based on polyhydroxyalkanoates (PHA) and / or polysaccharides and / or proteins and / or their combinations, after extraction and / or purification, which allows you to get more stringent control over the desired final mechanical properties of the paper base.

In this category, without limitation, you can use polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHH), polyhydroxybutyrate galerate (PHBV) and any of their derivatives, hyaluronic acid and its derivatives and spider silk. Spider silk can only be obtained by indirect methods of synthesis or biosynthesis, since it is impossible to dilute arachnids and, consequently, collect their silk.

From biodegradable substances that strengthen the structure, one can also indicate, for example, chemical products whose precursors, however, come from a plant or animal source (biological source), for example, substances based on polylactic acid and its derivatives.

Finally, a range of options includes mixtures of substances taken from two or more of the above categories.

In addition, according to the invention, the paper base contains an oleophobic and hydrophobic adhesive substance.

This oleofomic and hydrophobic adhesive is preferably introduced as an aqueous dispersion of perfluoropolyethers containing the main fragments in their chemical formulas - (CF ₂ CF ₂ O) _m - (CF ₂ O) _n -, where n and m are integers.

According to the invention, the above products are introduced in the following amounts:

- cellulose fibers: more than or equal to 70% and less than 100%, preferably more than or equal to 85% and less than 100%, more preferably from 88 to 92%,

- additives, auxiliary substances and binders: more than 0% and less than or equal to 15%, preferably from 8 to 12%,

- biodegradable substance strengthening structure: more than 0% and less or equal to 25%, preferably more than 0% and less or equal to 20%, more preferably more than 0% and less or equal to 10%, preferably from more than 0% to 5%,

- oleophobic and hydrophobic adhesive: more than 0% and less than or equal to 5%, preferably from more than 0 to 2%.

These percentages are given by the dry weight of this product, correlated with the total weight of the corresponding sample of the paper base in a dry state.

The oleophobic and hydrophobic adhesive is used in an amount in which the microbiological processes of decomposition of a rejected valuable document sent to the processing facility for recycling through composting do not slow down or stop. This allows you to comply with the thresholds established by the standard EN 13432 for toxic and hazardous substances and their packages recyclable by biodegradation.

Below is described in more detail an example of the method of manufacturing a paper base.

Cellulose fibers are suspended in water. At this stage, biodegradable structure-strengthening substances can be added to the mixture. The mixture is then refined to form fibrous elements of small size that will simplify the interlacing of the fibers and give the paper sheet excellent mechanical strength.

In the second stage, various additives, auxiliary substances and binders are introduced into the fibrous suspension. Structure-strengthening substances and oleophobic and hydrophobic adhesives containing perfluoropolyether groups can also be added at this stage.

Finally, the fibrous suspension is cleaned by settling to remove impurities and filtered to remove agglomerates of fibers that can break the uniformity of the sheet.

Oleophobic and hydrophobic sizing agents can also be introduced into the paper base by immersion, impregnation, surface treatment, spraying, coating with air flow, curtain making, irrigation coating, using engraved rolls, directly or offset, using a size sizing or film press.

At this stage, the structure-strengthening substances can also be applied on a paper substrate.

The formation of a sheet forming the paper base can be carried out, for example, using a rotating drum with or without applying a preliminary layer under pressure (usually referred to as “short former” in the field of public trust) or using a single-jet or two-jet flat table.

During the manufacture of a paper base, a watermark, security thread, protective fibers, glare, plates or markers can be embedded in it.

The paper base produced therewith is suitable for printing and modifying with any of the known printing or transformation methods, in particular, with the methods used in the field of public trust based papers (offset printing, silk screen printing, metallographic printing, hot printing, flexography, printing). It is also possible to apply varnish before or after printing (flexography, screen printing, offset printing, etc.).

This allows you to make a secure document on the basis of a sheet of such paper base, for example, a banknote.

Work was carried out to determine the high durability of such paper.

Resistance to pollution

Hydrophobicity is characterized as resistance to water penetration and is therefore measured by Cobb test (60 s.). This refers to the amount of water absorbed by the base in g / m ² when using a cylindrical template for soaking for 60 seconds. This is a test that is often used in the papermaking area to characterize the ability of the paper to absorb.

Resistance to contamination was tested using a test, the so-called “dry contamination test” (Fritsche test). This refers to a vibrating device in which small glass beads are located, applying to the paper sample a contaminating coating based on sand, peat, activated carbon, flour and glycerol monoaleate (a fatty substance of sebum). The test lasts 15 minutes. The brightness of the original white zone is measured in several stages before and after exposure to the contaminating composition. The resulting deviation or DL * allows you to determine the adhesion of pollution to a banknote: the smaller it is, the higher the resistance to dry pollution.

Oleophobia was measured by means of a dough in which it was exposed to fatty substances. The method used, called “Kit Test”, uses a mixture of castor oil (a fatty substance), high boiling point solvents, in particular toluene (an aromatic solvent), and n-heptane (an aliphatic solvent).

Depending on the different amounts of the above products, a composition is obtained, the viscosity and surface tension of which vary inversely with its aggressiveness, i.e., its ability to impregnate.

A composition with a high content of castor oil is located at the bottom of the scale, while a composition with a high content of heavy solvents is at the top of the same scale.

There were 12 compositions available, and it can be assumed that a rating greater than or equal to 5 already provides a satisfactory barrier to fats. Evaluation was carried out visually. The results are highly dependent on the state of the base surface.

The results achieved, on the one hand, using a paper base without a coating of oleophobic and hydrophobic substances and, on the other hand, a paper woven basis with 100% cotton coated with an oleophobic and hydrophobic adhesive based on an organic compound containing a perfluoropolyether group ( this refers to the aqueous microdispersion of a fluorinated anionic polymer based on a perfluoropolyether skeleton, known under the trademark Fluorolink * P56 Solvay Solexis), in the amount of 1% in water is given in the following boiling Table 1.

The layer was applied with a threaded rod onto the dry paper already obtained: an aqueous solution was placed along the rod, then it was moved over the sheet to evenly distribute the solution. The threaded rod used applied a layer of oleophobic and hydrophobic adhesive material 12 microns thick. In fact, the obtained material thickness is much less, since the water evaporated during drying. The dry weight applied in this case was about 2 g / m ² .

Roughness
ml / min Permeability,
ml / min Cobb test
g / m ² Kit test Fritsche test,
ΔL Only paper 295 27.0 138.6 0 - 44.23 Paper coated with oleophobic and hydrophobic adhesive in the amount of 1% 823 26.92 62.1 7 - 37.74

Therefore, with respect to the paper according to the invention, the following can be noted:

- the coating increased more than twice the resistance to water. The amount of water absorbed decreased from 138.6 to 62.1 g / m ² ;

- resistance to oil has increased dramatically and was consistent with the test kit test score 7;

- resistance to pollution also increased with less loss of brightness, amounting to less than 10 points after the Friche test.

Therefore, the product according to the invention is characterized by increased resistance to contamination.

The adhesion of colors to the paper base was evaluated by two types of printing characteristic of the production of banknotes: offset and metallographic, after the application of control patterns by these methods and the assessment of durability by means of two laboratory tests.

The first test, called the Pryufbau test, made it possible to quantify abrasion resistance. A sample of white paper was fixed with scotch tape on foam plastic, which in turn was fixed on a load of 625 g. This load was placed on a test banknote made using a paper base according to the invention, and 100 reciprocating movements were performed on the note. The difference between the brightness (DL *) and the color (DE) of white paper before and after friction against a banknote was measured with a spectrophotometer.

The results are shown in the following table 2.

Offset printing Metallographic printing Uncoated paper Paper coated with an adhesive in the amount of 1% Uncoated paper Paper coated with an adhesive in the amount of 1% Average brightness ΔL * 0.80 0.67 - 2.05 - 1.83 Standard deviation 0.16 0.11 0.55 0.23 Average chroma ΔE 1.41 1.34 3.52 3.14 Standard deviation 0.20 0.17 0.71 0.34

The adhesion of the ink to the coated paper was as good as that of the uncoated control paper, while the brightness and chromaticity losses of both types of paper are very close to each other.

In the second test, called the “crushing test,” the crushing strength of the paper substrate was evaluated in the dry and wet conditions. For crumpling in the wet state, the sample was kept in water for 15 minutes before carrying out the collapse. The crumpling was carried out 8 times on a dry sample and 4 times on a wet one with the aid of an instrument launched by IGT Testing Systems, which is widely used in the field of public trust papers.

The result was visible, and the damage was determined with a rating from 0 to 4: the following values were used: 0 = disappearance of elements; 1 - changes exceeded 50%; 2 - changes were less than 50%; 3 = minor change; 4 = no change.

The results are presented in the following table 3.

Offset printing Metallographic printing Uncoated paper (acceptable limit) Paper coated with an adhesive in an amount of 1% (acceptable limit) Uncoated paper (acceptable limit) Paper coated with 1 adhesive in an amount of 1% (acceptable limit) x8, dry condition 3 (3) 3 (3) 3 (2) 3 (2) x4, wet condition 3 (3) 3 (3) 3 (2) 2 (2)

The results were identical for both types of paper after 8 times of collapse in a dry state with both types of printing.

After 4 times of wet wrinkling, the ink separation corresponded to an acceptable limit (numbers in brackets) for paper treated with an oleophobic and hydrophobic adhesive.

Structural Strengthening Properties

Significant preliminary results were obtained by observing the properties of microfibrillated cellulose-treated paper (MFC).

The estimated mechanical property is tensile strength in mN. The coating was applied with a threaded rod to the dry paper already received. Starting from 2.5 g / m ^{2 of} applied MFC, the breaking force for coated paper was increased by approximately 50% with a transition respectively from about 800 mN to 1200 mN in the direction of movement (i.e., the direction of the break perpendicular to the orientation of the fibers) and from about 600 to 900 mN, respectively, in the transverse direction (i.e., the gap is parallel to the average orientation of the fibers). With the increase of successive layers, the tensile strength constantly increased, tending to the plateau. In this way, the MFC layers formed a fiber grid that is fully compatible with the available cellulose grid complex, thus forming a composite that is much more difficult to break than a standard paper.

Other results were obtained using regenerated cellulose, in particular, fibers known under the trade name Lyocell. Thus, regenerated cellulose fibers, having an average length of 2 mm and a unit length of 1.7 decitex (decitex means the weight in grams of a single fiber with a length of 10,000 m), were added to the formed paper stock of 100% cotton. Small forms were made of paper without additives and auxiliary substances under the same conditions and the following mechanical properties were compared:

Mechanical properties Reference paper, 100% cotton Cotton paper with 5% Lyocell fiber content Paper made of cotton with a content of 10% Lyocell fibers Tensile strength, N 58.5 62 66 Breaking length, m, 3732 4478 4529 Formation of a double fold, qty 250 2000 2410

Compared with reference paper containing 100% cotton, i.e. without the content of regenerated cellulose fibers Lyocell, it was noted that the addition of a specific substance in the amount of 5% and 10% has a completely positive effect on the mechanical properties under investigation. Consequently, the tensile strength increases by 6% and by 13% when Lyocell fibers are added in an amount of 5% and 10%, respectively. With respect to breaking elongation, an increase of 20% and 21% was observed when Lyocell fibers were added in the amount of 5% and 10%, respectively. Finally, the number of double folds increased 8 times and almost 10 times when Lyocell fibers were added in an amount of 5% and 10%, respectively.

In both of the above examples, the structure-strengthening substance was retained in the form of cellulose, and only cellulose, which means that it does not interfere with the microbiological decomposition processes that occur at the end of the paper's life when the biodegradation method is chosen.

Properties of biodegradability

Regarding biodegradability, the composting of crumbs from banknotes on a suitable platform made it possible to find out that banknotes made of paper according to the invention did not violate the ongoing microbiological decomposition processes and that the results of the analyzes corresponded to the EN 13432 standard regarding extreme concentrations of heavy metals and other toxic substances.

Claims (31)

1. Highly biodegradable paper basis for printing a security document, in particular a banknote, containing cellulose fibers in an amount greater than or equal to 70% and less than 100% by dry weight of the total weight of the paper base in a dry state, additives, auxiliary substances, at least one binder, characterized in that it contains: - oleophobic and hydrophobic adhesive substance based on organic compounds containing perfluoropolyether groups in an amount of more than 0% and less than or equal to 5% by dry weight of the total weight of the paper base in the dry state, - at least one biodegradable reinforcing structure substance selected from substances of plant or animal origin, substances synthesized by biotechnological engineering or genetic engineering and then biotechnological engineering, and substances of biological origin subjected to chemical transformation. 2. Paper base under item 1, characterized in that the amount of cellulose fibers is greater than or equal to 85% and less than 100% by dry weight of the total mass of paper base in a dry state. 3. Paper base according to claim 1 or 2, characterized in that the additives, auxiliary substances and binders are present in an amount of more than 0% and less or equal to 15% by dry weight of the total weight of the paper base in a dry state. 4. Paper base according to any one of paragraphs. 1-3, characterized in that the biodegradable substance strengthening the structure (substances) is present (are present) in an amount of more than 0% and less or equal to 25%, preferably more than 0% and less or equal to 20%, more preferably more than 0% and less or equal to 10% by dry weight of the total weight of the paper base in a dry state. 5. Paper base according to any one of paragraphs. 1-4, characterized in that the biodegradable substance strengthening the structure comes from a plant source and is obtained on the basis of regenerated cellulose. 6. Paper base according to claim 5, characterized in that the biodegradable substance strengthening the structure is a raw cellulose fiber, which passed the stage of dissolution in N-oxide-N-methylformalin and then regenerated. 7. Paper base according to any one of paragraphs. 1-4, characterized in that the biodegradable substance strengthening the structure comes from a plant source and is obtained on the basis of finely divided cellulose, such as microfibrillated cellulose or nanocrystalline cellulose. 8. Paper base according to any one of paragraphs. 1-4, characterized in that the biodegradable substance strengthening the structure comes from a plant source other than cellulose, and is derived from polysaccharides and / or proteins and / or combinations thereof. 9. Paper base under item 8, characterized in that the biodegradable substance strengthening structure is selected from ground macroscopic algae, such as kelp, and ground microscopic algae, such as chlorella and spirulina. 10. Paper base under item 9, characterized in that the biodegradable substance strengthening structure is selected from phycocolloids and their derivatives. 11. Paper base according to any one of paragraphs. 1-4, characterized in that the biodegradable substance strengthening the structure comes from an animal source and is obtained on the basis of polysaccharides and / or proteins and / or their combinations. 12. The paper substrate according to claim 11, wherein the biodegradable substance strengthening structure is a keratin-based product, such as poultry wool or feathers. 13. Paper base according to any one of paragraphs. 1-4, characterized in that the biodegradable substance strengthening the structure obtained by biotechnology or genetic engineering and then biotechnological engineering based on polyhydroxyalkanoates and / or polysaccharides and / or proteins and / or their combinations. 14. A paper base according to claim 13, characterized in that the biodegradable substance strengthening structure is selected from polyhydroxybutyrates, polyhydroxyvalerate, polyhydroxybutyratevalerates and their derivatives, hyaluronic acid and its derivatives, as well as spider silk. 15. Paper base according to any one of paragraphs. 1-4, characterized in that the biodegradable substance strengthening the structure is obtained on the basis of polylactic acid and its derivatives. 16. Paper base according to any one of paragraphs. 1-15, characterized in that the perfluoropolyether groups in their chemical formulas contain the main fragments - (CF ₂ CF ₂ ) _m - (CF ₂ O) _n -, where m and n are integers. 17. A secure document, characterized in that it contains a paper base according to any one of paragraphs. 1-16. 18. The protected document of clause 17, wherein it is a banknote. 19. A method of manufacturing a paper base according to any one of paragraphs. 1-16, characterized in that it includes the following successive stages: a) suspended cellulose fibers in water b) refined the specified mixture, c) introducing additives, auxiliary substances and binders, d) cleaning and filtering the suspension of fibers; e) form a paper base, f) press, g) carry out pre-drying, h) apply a coating on the surface of the paper base, i) carry out the subsequent drying, and the fact that it also includes the steps of introducing biodegradable substances that reinforce the structure of the structure, as well as the introduction of oleophobic and hydrophobic adhesives; and hydrophobic adhesives are performed between steps c) and d) or in step h).