EP4388895A1

EP4388895A1 - Paper for producing dispersible cigarette filters and method for producing same

Info

Publication number: EP4388895A1
Application number: EP21954103.4A
Authority: EP
Inventors: Paula AMUNARRIZ ALBERDI; Senen AMUNARRIZ ALBERDI
Original assignee: Papel Aralar SA
Current assignee: Papel Aralar SA
Priority date: 2021-08-19
Filing date: 2021-08-19
Publication date: 2024-06-26
Also published as: WO2023021227A1

Abstract

The present invention relates to paper for producing dispersible cigarette filters and a method for producing same. The paper consists of at least ninety-three percent (93%) by weight cellulose fibres and between zero and seven percent (0 to 7%) by weight optionally applicable natural additives. The cellulose fibres consist of between seventy and ninety percent by weight (70% to 90%) natural, virgin or recycled pulp fibres, and consist of ten to thirty percent by weight (10 to 30%) short regenerated cellulose fibres. The natural pulp fibres have a length comprised between half and four millimetres (0.5 to 4 mm) and the short regenerated cellulose fibres, have a length comprised between eight and twelve millimetres (8 to 12mm). The density of the natural pulp fibres is comprised between one and two decitex (1 to 2 dtex); while the density of the regenerated cellulose fibre is comprised between zero point nine and two point four decitex (0.9 to 2.4 dtex) and the density of the final product is comprised between 10 and 99 Kg/m<sup>3</sup>, achieving strengths ranging from 20N/5cm to 60N/5cm. The paper thus obtained does not contain any non-natural polymers, or chemical products in general, and the degree of water absorption measured under the UNE-EN ISO 9073-6 test gives absorption values comprised between 600% and 1200% according to the ISO standard and preferably between 700% and 900%, thus ensuring dispersions (according to Slosh box test) greater than 80% in less than 5 minutes. The method for producing this paper consists in: mixing with water all the cellulose fibres formed by natural pulp fibres, in addition to the short regenerated cellulose fibres, subsequently passing the fibres to a headbox (1.6) of the high-dilution paper machine (1); subjecting the fibres, in a subsequent step, to hydroentanglement (1.8); and then passing them to a step of drying the paper, which is carried out using a through-air dryer (TAD) (1.9).

Description

Technical field

The present invention relates to the industry dedicated to the production of cigarettes, proposing a paper intended for producing a cigarette filter and, preferably, for producing its core, as well as the method for producing that paper; such that it provides the filter with the ability to disperse in water, added to being biodegradable.

Prior art

Currently there are biodegradable alternatives for producing of cigarette filters, according to which the cellulose acetate in the core of the filter is replaced by cellulose compounds (basically paper) that are biodegradable.
The filters are made with normal machine paper of greater or lesser weight. In this already known solution, the paper used is normally long fibre cellulose-based, to which chemical products are added that give flavour to the filter, that affect its proper functioning as such a filter and that, above all, although they provide the condition of biodegradability, the filter is not dispersible.
In other words, these biodegradable filters behave like an apple that, being biodegradable, is not dispersible and if it is flushed down the toilet it gets stuck. The lack of dispersibility in cigarette filters also translates into serious environmental problems, in places such as beaches, the banks of rivers and reservoirs, etc.
The subject matter of European Patent EP2985375, held by Glatfelter , is a dispersible non-woven fabric but expressly applicable for producing what are known as wipes and not for use in the production of cigarette filters.
PCT WO95/35044 held by Philip Morris et al. , discloses a cigarette filter made by a mixture of Lyocell filaments with one or more other types of fibres, such as cellulose acetate filaments or wood pulp fibres, subjecting all of them to a hydroentanglement process, by using pressurised waterjets. This Patent also discloses the use of chemical solvents because its aim is to obtain a biodegradable filter, such chemical solvents being incompatible with the concept of dispersibility that is sought by the present invention, in which the cigarette filter should be, in addition to being biodegradable, dispersible and dispersibility is the main aim; such that for this purpose, the material that constitutes it cannot incorporate any amount of chemical product, because this would go directly against its dispersibility.
As a solution that is applicable to the production of dispersible cigarette filters, there is the European Patent held by Daicel Chemical that discloses a cigarette filter that disintegrates or disperses easily in water. This Patent mentions other prior Patents that, for the same purpose, used conventional plasticisers for the cellulose ester fibre that is used to manufacture the filters and provides as a novelty the use of a water-soluble polymer, instead of such plasticisers. That being said, the use of plasticisers or even water-soluble polymers is not suitable for use in a cigarette filter.
European Patent EP2761085 held by Delfortgroup discloses a paper that can be used for making cigarette filters, the aim of which is to achieve the dispersion or disintegration of the filter in water to improve the biological degradability of a cigarette filter made from that paper.
This Patent proposes a filter made in at least 95% by weight pulp fibres. Of these pulp fibres, 0 to 90% is mercerised pulp and the rest is long fibre pulp.
Mercerised pulp is made by treating cotton fibre with caustic soda and then washing it. With this treatment it undergoes certain changes in its process, which can affect the biodegradability of the final fibre. Furthermore, cotton fibres, even though they are cellulose, are already less biodegradable than long-fibre natural pulp fibres and more difficult to produce for the paper industry, in "shortcut" fibre version.
There is also PCT application number WO2021115619A1 held by Delfortgroup , the subject matter of which is a filtering material and a filter of a smoking article made therefrom, which is easily biodegradable. In this Patent it states that cigarette filters made from cellulose acetate and polylactide fibres were already known, indicating that they biodegrade very slowly in the environment and that the aim of the invention is to propose materials that are more biodegradable. In this invention it states that the production of cigarette filters from paper and non-woven fabrics is known in the state of the art, indicating that one of the main reasons why paper filter segments have not yet found widespread use is its visual appearance.
To achieve this greater biodegradability, it proposes a material for a cigarette filter made up of a hydroentangled non-woven fabric, made up of wood pulp fibres, fibres made from regenerated cellulose and non-natural polymers, indicating that, to ensure good biodegradability, it must contain less than 30% non-natural polymers.
Compared to this solution proposed by PCT number WO2021115619A1 , the aim of which is to seek the greatest possible biodegradability for filters for cigarettes, the subject matter of the present invention is that the filter of the cigarette is, in addition to being biodegradable, dispersible and dispersibility is the main aim; such that for this purpose, the material that constitutes it, cannot incorporate any amount of non-natural polymers (synthetic polymers). The incorporation of a non-natural polymer or chemical products in general, as binding additives or chemical glues would go directly against its dispersibility, so this solution proposed by PCT number WO2021115619A1 , although it contains less than 30% non-natural polymers, even if the amount were minimal, being non-natural would prevent the filter from being dispersible.
In view of the described drawbacks or limitations of solutions existing today, a solution is necessary that allows a paper to be obtained to produce cigarette filters that the dispersible condition is added to the biodegradable condition, this paper offering sufficient resistance without adding any binder or chemical glue at all, all made from cellulose fibres and physically linked through mechanical means.

Object of the invention

For the purpose of fulfilling this objective and solving the technical problems discussed up until now, in addition to providing additional advantages that may be seen later, the present invention provides a paper for producing a filter of a cigarette and the method for producing this paper that can be made entirely with cellulose fibres, of which between 70 and 90% by weight are natural, virgin or recycled pulp fibres, with a length comprised between 0.5 and 4 mm; while between 10 and 30% weight are short regenerated cellulose fibres, with the particular feature that this regenerated cellulose fibre, which is normally a fibre of the order of 38 mm, is now cut into even smaller pieces, in a measurement comprised between 8 and 12 mm.
The density or linear mass of these cellulose fibres measured in decitex (dtex) is as follows: In long-fibre natural pulp fibres, the density thereof will be comprised between 1 and 2 dtex; while in the regenerated cellulose fibre the density thereof will be comprised between 0.9 and 2.4 dtex. Regarding the density of the final product, this value varies according to two parameters: the grammage (g/m²) and the thickness in microns (µm = 10^-6m). According to the present invention, the grammage and thickness values are adjusted so that the density is comprised between 10 and 99 Kg/m³.
To achieve good dispersibility it is very important that the product obtained has a high degree of liquid absorption, specifically water. In this case this is achieved because the product obtained according to the present invention does not contain any non-natural polymer, that is, no synthetic polymer and it does not contain chemical products in general, such as binding additives or chemical glues. This, together with the specific fibre length ranges, the method for producing the product itself and other technical features that will be seen in detail later, makes the absorption very high, reaching levels over 900%. Thanks to this property, the thus hydroentangled and bonded high-strength fibres, lose their bonds based on hydrogen bonds (which are destroyed in water) and therefore this network of fibres dissolves, providing the product with the important property of instant dispersibility in water.
The paper which is subject matter of the present invention can be produced in a composition in which 100% of its weight is cellulose fibres made up of a mixture of natural pulp fibres and short regenerated cellulose fibres, but, optionally and as reinforcement of the bonds between fibres, additives can also be added, as long as these are natural.
These natural additives can be added in mass and/or on the surface. If the natural additive is added in mass to the dissolution of fibres in water, its percentage by weight is comprised between 1 and 5% of the total weight of the product; whereas if it is added on the surface, as a surface reinforcement, its percentage by weight is comprised between 0.5 and 2% by weight.
The method for producing this product is developed according to the following steps:
All cellulose fibres formed by natural pulp fibres and short regenerated cellulose fibres are mixed with water in blenders, which are part of the paper machine.
In the paper machine, the cellulose fibres are subjected to hydroentanglement, spraying high-pressure water jets thereon, which allows the fibres to be joined with knots, that will reinforce the bond between natural pulp fibres and short regenerated cellulose fibres, creating a solid paper structure, for handling same, but retaining the dispersibility properties.
An important particular feature of the present invention is that the paper drying phase is carried out through a through air drying system, also called TAD or Through-Air Dryer. This drying system gives the paper a much greater thickness than any other conventionally dried paper.
Being able to achieve sufficient strength in the bonds between the fibres, without adding any chemical binder or glue at all, achieving it based on physically bonded cellulose fibres, thanks to pressurised water jets, is important, since due to the fact that the application of this product is the production of cigarette filters, chemical binders or adhesives, in addition to affecting the taste of tobacco smoke, when it passes through the filter, may not be suitable, from a public health point of view and, above all, go directly against the concept of the dispersibility condition, which is the main aim of this invention.
Optionally, natural pulp fibres may be subjected to refining to increase their fibrillation, creating greater bonds between them to achieve greater consistency of the product.
In accordance with ISO 5267, the natural pulp fibres refined according to the present invention, would have a refinement level of between twelve and forty Shopper degrees (12°S to 40°S).
The paper obtained according to the present invention can reach a dispersion level of 90% according to the "Slosh box" Test, set forth in the INDA/EDANA guidelines under the FG502 trial; as well as in the Spanish standard UNE 149002, under the disintegration test with stricter conditions of time and acceptability criteria.
The "Slosh box" test has been carried out under the following parameters; 5 minutes /26 rpm/2L/ sieve 12.5mm.
Thanks to technology, first for refining the natural pulp fibre and second for the hydroentanglement of the fibre mixture, it has been possible to strengthen the bond between the cellulose fibres, achieving very high final product strengths without compromising dispersibility. The strengths achieved in different compositions can range from 20N/5cm to 60N/5cm, always maintaining dispersions in "Slosh box", in 5-minute tests, above 80%.
Furthermore, adding natural reinforcing additives, if it is necessary to continue increasing strength, strength values of up to 80N/5cm can be achieved with dispersions always above 60%.
This solution, subject matter of the present invention, achieves high porosity and thickness values, with the advantages that this entails.
Thanks to the combination of hydroentanglement technology and the "TAD" through air drying system, the thickness of the product increases considerably (10 times greater than conventional paper for the same grammage), providing the material with an open and very breathable structure. This property is key for the proper functioning of the material as the core of the cigarette filter, where the air has to pass through the material without causing much pressure difference and avoid having to apply a great aspiration when smoking a cigarette.
Given the natural concept of the components of this paper, it is dispersible in water, in addition to being biodegradable and compostable in all environments, in accordance with the standard EN 13432.
Moreover, since it does not contain any component defined as plastic in its composition, it falls completely outside the scope of the new European regulation for the reduction of single-use plastic (SUP).
It is worth noting that since all the mechanical strengths achieved are done so through hydrogen bonds between cellulose fibres, the water dispersibility of the product is guaranteed, since these bonds are greatly weakened when wet (disposal of the product), preserving the dispersibility properties, even with high dry mechanical properties.

Description of the figures

Figure 1 shows, in a block diagram, how the method for producing the paper is performed for the production of dispersible cigarette filters that are the subject matter of the present invention.

Detailed description of the invention

The present invention relates to a paper preferably intended for forming the core of the filter of a cigarette to give it a dispersible nature and the method of producing this paper that could also be used to obtain the wrapping paper for that core of the filter or even both components, that is, the core and the surrounding paper.
The composition of this paper consists of, at least ninety-three percent (93%) by weight cellulose fibres and between zero and seven percent (0 to 7%) by weight optionally applicable natural additives; such that the composition of this paper can be one hundred percent by weight cellulose fibres, without any additive, or have a weight of, at least ninety-three percent by weight cellulose fibres and the rest of the weight will be made up of natural additives.
Regarding the cellulose fibres, between seventy and ninety percent by weight (70% to 90%) will consist of virgin or recycled natural pulp fibres and between ten and thirty percent by weight (10 to 30%) will consist of short regenerated cellulose fibres. Natural pulp fibres can be, as a non-limiting example, of the NBSK variant which is a sulphate bleached long fibre cellulose pulp.
Short regenerated cellulose fibres are known in the market as "Shortcut" and are specially developed short fibres that can be used as additives for wet non-wovens in the paper industry, for filters and in components for the automotive and construction sectors.
As a preferred option, the short regenerated cellulose fibres could be rayon, also known in Europe as viscose, which is a manufactured and regenerated artificial cellulose fibre and/or Lyocell.
Lyocell is a biodegradable synthetic fibre, which may be referred to as a form of rayon. It consists of cellulose fibre, made from dissolving the pulp and then reconstituted by dry jet-wet spinning. It is commonly known as "Tencel", as this is the Brand that developed it.
Indeed, both rayon and Lyocell are 100% cellulose that is brought to a liquid or semi-liquid phase and subsequently extruded, pulling out threads that finally solidify, having specific diameter and length measurements.
The natural pulp fibres will have a length comprised between half and four millimetres (0.5 to 4 mm) and the short regenerated cellulose fibres will have lengths comprised between eight and twelve millimetres (8 to 12mm).
To achieve good dispersibility it is very important that the product obtained has a high degree of liquid absorption, specifically water. In this case this is achieved because the product obtained according to the present invention does not contain any non-natural polymer, that is, no synthetic polymer and it does not contain chemical products in general, such as binding additives or chemical glues. This, together with specific fibre length ranges, the method for producing the product itself and other technical features that will be seen below, makes the absorption very high, reaching levels over 900%. Thanks to this property, the thus hydroentangled and bonded high-strength fibres, lose their bonds based on hydrogen bonds (which are destroyed in water) and therefore this network of fibres dissolves, giving the product the important property of instant dispersibility in water.
The degree of water absorption measured under the UNE-EN ISO 9073-6 test gives absorption values between 600% and 1200% absorption according to the ISO standard. Preferably the absorption values are between 700% and 900%, thus ensuring dispersions (according to Slosh box test) greater than 80% in less than 5 minutes.
To carry out this absorption test, the following means are used: a shears; a circular stainless steel mesh; clips; a container for water and a stopwatch.
The operating method starts with the preparation of the sample, cutting five 10x10cm samples that are identified as test tubes.
In a next step, the weight of the sample to be tested is taken, which is identified as (Ms) and the test tubes are hooked with the clips to the stainless steel mesh.
Next, the inside of the container is filled until the water reaches a height of approximately 20mm and the test is verified, which consists of introducing the sample into the water without leaving air bubbles. The sample is left submerged for one minute. After that, the sample is drained vertically for two minutes, with the least possible contact with the sample and without crushing it at any time. The sample is weighed again, identifying this weight as (M_H).
To calculate the liquid absorption capacity that is identified as (CAL), the following formula is applied: $CAL = (M_{H} - M_{S}) / M_{S} \times 100$
The density or linear mass of these cellulose fibres measured in decitex (dtex), which is the mass in grams per ten thousand metres of fibre, is as follows:
Regarding the long-fibre natural pulp fibres, their density or linear mass will be comprised between one and two decitex (1 to 2 dtex).
Regarding the regenerated cellulose fibre, its density or linear mass will be comprised between zero point nine and two point four decitex (0.9 to 2.4 dtex).
Regarding the density of the final product, this value varies according to two parameters: the grammage (g/m²) and the thickness in microns (µm = 10^-6m). According to the present invention, the grammage and thickness values are adjusted so that the density is comprised between 10 and 99 Kg/m³.
Natural additives such as Carboxymethyl cellulose (CMC), different types of micro and nano cellulose, such as micro fibrillated cellulose (MFC) or starch can be optionally added in order to reinforce the bonds between fibres.
These natural additives can be added by one or both of the following methods:

Mass.
Surface.

In surface methods, the natural additive that is in liquid state is sprayed through nozzles, being sprayed on the surface of the paper web, already semi-formed in the machine and before final winding.
If the natural additive is added in mass to the dissolution of fibres in water, its percentage by weight is comprised between one and five percent (1 a 5 %).
If the natural additive is added on the surface, as a surface reinforcement, its percentage by weight is comprised between zero point five and two percent (0.5 to 2 %).
The method for producing this product is developed according to the following main steps:
All cellulose fibres formed by natural pulp fibres and short regenerated cellulose fibres are mixed with water in the corresponding blenders, to later reach the headbox of the paper machine.
The headbox of the paper machine is high dilution which allows the use of regenerated cellulose fibres. The fibres suspended in water have a concentration of 0.05% by weight, compared to conventional headboxes which are at 4%. Thanks to this very high dilution, it is possible to work with long regenerated cellulose fibres comprised between 8 and 12 mm, which would not be possible in a normal dilution headbox.
They are subjected to hydroentanglement in the paper machine. Hydroentanglement is a well-known technique that consists of bonding the fibres with knots, spraying high-pressure water jets on them that will reinforce the bond between the natural pulp fibres and the short regenerated cellulose fibres, creating a solid paper structure, for handling same, but retaining the dispersibility properties, since the bonds created, which are based on hydrogen bonds, weaken in water, which will maintain the dispersibility property in the final product that are the filters of cigarettes once discarded and when these filters come into contact with the water in sewers, WC, the sea, rivers, etc.
Being able to achieve sufficient strength in the joints between the fibres, without adding any chemical binder or glue at all, achieving it only using physically bonded natural cellulose fibres, thanks to pressurised water jets, is important, since due to the fact that the application of this product is the production of cigarette filters, chemical binders or adhesives, in addition to affecting the taste of tobacco smoke, when it passes through the filter, may not be suitable from a public health point of view.
In order to achieve dispersibility, it is essential that the product does not incorporate any amount of non-natural polymers (synthetic polymers); in addition to not incorporating chemical binders or glues.
The hydro entanglement technology was officially introduced by the DuPont company, from Wilmington, Del., in 1973 and consists of subjecting the fibres to multiple rows of fine high-pressure water jets generated in nozzles called jet strips.
According to the present invention, to achieve this hydroentanglement, the paper machine has a series of high-pressure water jets (jet strips) to physically hydroentangle the paper, specifically, there is a row of continuous jets, preferably in a number comprised between five and ten jets, of which some are in the working phase and others in reserve function.
The water passes through perforated sheets called strips, with different hole configurations. Specifically and in relation to those holes, the following are defined: the number of rows of holes, the diameter of the holes, and the number of holes per unit area.
The paper drying step is carried out by a through air drying system, also called TAD or Through-Air Dryer.
The traditional method of drying paper is to first press it, before drying it using drying cylinders. However, this TAD drying system, using transverse air, dries the paper through a method without physical contact with the paper, using hot air that passes through the paper, after the sheet of paper has gone through the dewatering process in the fabric section. The distribution of the fibres of the sheet of paper that has not been pressed is three-dimensional, so it has good air permeability. As a result, the utilisation rate of the fibre can be improved by about 20%, and the water absorption capacity of the paper sheets processed using this method are much better than those treated with traditional methods. The dust containment values of the paper sheets processed with this method are also improved and are much better than those treated with traditional methods.
This TAD drying system confers the paper a much greater thickness than any other paper dried in a more conventional way. The specific application of the through air drying (TAD) system is carried out as follows:
Hot air penetrates through the paper and that hot air is recovered, once it has gone through the paper, to be reinserted inside a drying cylinder. The drying cylinders are perforated cylinders through which hot air exits and passes through the paper. This TAD drying technology gives the paper a very high thickness, with the values previously outlined. This thickness parameter is key, taking into account the final use of the paper that is intended for forming filters, in addition to having a low density and higher absorption levels, thanks to the three-dimensionality of the material.
According to the present invention, there are preferably four TAD drying cylinders, arranged one after another in correlation, thereby achieving a high drying capacity, which allows the machine to be provided with greater speed. That being said, this number of cylinders may vary, for example a smaller number when using larger cylinders, without thereby altering the essence of the invention in any way.
Herein, a "quire" of paper, which is its volume, related to thickness and weight according to the formula: Volume = Thickness / Weight (cm3/g). With equal grams, thicker paper will logically have a greater volume.
It is usually said that a paper has a "smaller quire" or "larger hand" than another, to indicate that when touched it gives a greater or lesser sensation of volume.
Well, this TAD drying system, compared to a conventional drying system, achieves a "quire" of the paper that is multiplied by ten. This aspect is very beneficial for a paper that is to be used in the production of filters, since it enables a filter to be made with much less product (fewer grams of paper per filter for equal square meters).
Natural pulp fibres, may optionally be subjected to refining, to increase its fibrillation, creating greater bonds therebetween for product consistency. Refining is carried out using conical and/or disc refiners where the fibres flow parallel to the blade intersections. The first effect is the partial elimination of the primary wall of the fibres, leaving the secondary wall exposed, thus allowing hydration and flexibility of the fibre.
According to ISO 5267, natural pulp fibres, refined according to the present invention, would have a refinement level of between twelve and forty Shopper degrees (12°S and 40°S).
Figure 1 shows a flowchart formed by a block diagram that represents a work line with the different most important parts that allow the development of the method that is the subject matter of the present invention.
The numerical reference (1) identifies the paper machine itself with its different components included within the box represented by dashed lines.
Outside the paper machine (1) and within the work line, are the following means/equipment: a storage warehouse (2); packaging equipment (3); a rewinder (4); a natural pulp fibre tank (5); a regenerated cellulose fibre tank (6) and a general water tank (7).
The pulp is supplied from the natural pulp fibre tank (5) to a mixer (1.3), to which water is also supplied from the general tank (7). Likewise, the fibres are supplied from the regenerated cellulose fibre tank (6) to a mixer (1.1) to which water is also supplied from the general tank (7).
The mixers (1.1) and (1.3), referred to as pulper, break the fibre bales and mix them with the water until they form a semi-pasty fluid like a purée.
The mixture goes from the mixers (1.1) and (1.3) respectively to storage tanks (1.2) and (1.4), from which and through pumping means (1.5) the product is supplied to the headbox (1.6) of the paper machine (1) which has the particular feature of being a high-dilution input box.
The product passes from the high-dilution headbox (1.6) to the hydroentangler (1.8) where pressurised water jets perform the hydroentanglement of the fibres.
Once the hydroentanglement has been performed, the drying phase take place which, as a particular feature of the present invention, is carried out using one or more through-air dryers (TAD), identified by the block with the number reference (1.9).
Once drying has been performed, using the TAD dryer or dryers (1.9), the sheet of paper thus formed passes to a winder (1.10) in which the winding of the sheet of paper is carried out, to form a large reel referred to as the "parent" reel.
The "parent" reel is taken to a rewinder (4), located outside the paper machine (1), where the "parent" reel is cut into smaller width sheets that are rewound into smaller diameter reels in order to be supplied to the final producer of the filters of the cigarettes; such that the "parent" reels are transformed into reels of smaller size and weight, with the required width and length measurements. In this way, the material is supplied to the end customer in the form of a paper web arranged according to a reel that allows its transport, storage and handling, both in its transportation to the production lines, and once arranged on the production lines of the filters.
The smaller reels thus formed pass from the rewinder (4) to packaging equipment (3), where these smaller reels are duly wrapped, then going to a storage warehouse (2) where they will remain until they are sent to the final customer.
In relation to the high-dilution headbox (1.6) and with the hydroentangler (1.8), there is a vacuum plant (1.7); while in relation to the hydroentangler (1.8) there is a water treatment and cleaning plant identified with the number reference (1.11).
As can be seen in the diagram in Figure 1, both the high-dilution headbox (1.6), and the hydroentangler (1.8) are connected to a tank for the excess water identified with the number reference (1.13). This tank (1.13) for the excess water is connected to the general water tank (7).
Moreover, the pump (1.5), in addition to sending product to the high-dilution headbox (1.6), also sends it to a storage silo referred to a "PIT" and identified with the number reference (1.12). As such, the product exiting the pump (1.5) can be sent from this silo (1.12) to the high-dilution headbox (1.6) if necessary during the process. The storage silo (1.6) can receive water from the tank (1.13) when necessary.
If a natural additive or additives is/are to be added, if the additives are added in mass, they would preferably be incorporated into the tanks (1.2) and (1.4) respectively; while if they are added on the surface, they would be incorporated at the outlet of the hydroentangler (1.8) between same and the TAD drying step (1.9). These additives can be incorporated at other points according to the arrangement of the work line without altering the essence of the invention.
Moreover, and in the event a refining of the natural pulp fibres is to be carried out, this refining would be carried out, preferably, at the outlet of the storage tank (1.4) of the mixture formed by natural pulp fibres and water, before this mixture accesses the pumping means (1.5).
A possible practical exemplary embodiment is detailed below.
It relates to the production of a paper, to make the core of the filter of a cigarette. This paper, according to the invention, is obtained from 85% long-fibre natural pulp fibre and 15% short regenerated cellulose fibre.
For this purpose, long-fibre natural pulp fibre is used, which is marketed under the Brand "Celeste 90" (SCA), the average fibre length of which is between 2.30 and 2.55 mm.
The Lyocell type was used as the short regenerated cellulose fibre, specifically the Lyocell from the "Tencel" Brand (Lenzing) with a length of 10 mm.
The natural pulp fibre was refined to reach the value of 25°S and mixed with the regenerated cellulose fibre, to subsequently introduce it into the paper machine.
A hydroentanglement was applied to this mixture of fibres already in the paper machine, which consists of 6 rows of water jet nozzles with pressures in bars from the first to the last row of: 35 bar / 35 bar / 40 barf 35 bar / 35 bar / 35 bar.
The paper obtained had a weight, expressed in grams per square metre, of 55 g/m² and a breaking strength expressed in Newton per centimetre of 30 N/5cm, reaching a dispersion level of 90% according to the "Slosh box" Test.
The dispersibility of the material was established under the "Slosh box" test, set forth in the INDA/EDANA guidelines under the FG502 trial; as well as in the Spanish standard UNE 149002, under the disintegration test with stricter conditions of time and acceptability criteria.
The "Slosh box" test was carried out under the following parameters; 5 minutes /26 rpm/2L/ sieve 12.5 mm).
Thanks to technology, first for refining the natural pulp fibre and second for the hydroentanglement of the fibre mixture, it has been possible to strengthen the bond between the cellulose fibres, achieving very high final product strengths without compromising dispersibility, since these bonds (hydrogen bonds) are greatly weakened in an aqueous state. The strengths achieved in different compositions can range from 20N/5cm to 60N/5cm, always maintaining dispersions in "Slosh box", in 5-minute tests, above 80%.
Furthermore, adding natural reinforcing additives such as 1% CMC added in mass, if it is necessary to continue increasing strength, strength values of up to 80N/5cm can be achieved with dispersions always above 60%.
This solution, subject matter of the present invention, achieves high porosity and thickness values, with the advantages that this entails.
Thanks to the combination of hydroentanglement technology and the "TAD" through air drying system, the thickness of the product increases considerably (10 times greater than conventional paper for the same grammage), providing the material with an open and very breathable structure (high porosity between the "loose" structure of the fibres). This property is key for the proper functioning of the material, as a core of the cigarette filter, where the air has to pass through the material without causing much pressure difference and avoid having to apply a great aspiration when smoking a cigarette.
Given the natural concept of the components of the material, this paper, in addition to being dispersible, is perfectly biodegradable and compostable in all environments, in accordance with the standard EN13432, passing all relevant tests.
Moreover, and since it does not contain any component defined as a plastic, this paper falls completely outside the scope of the new European regulation for the reduction of single-use plastic (SUP), since it does not contain any component defined as a plastic in said regulation.
Since all the mechanical strengths achieved are done so through hydrogen bonds between cellulose fibres, the water dispersibility of the product is guaranteed, since these bonds are greatly weakened when wet (disposal of the product), preserving the dispersibility properties, even with high dry mechanical properties (transformation and use of the cigarette core).

Claims

A paper for producing dispersible cigarette filters, characterised in that it comprises, at least 93% by weight cellulose fibres and 0 to 7% by weight natural additives; the cellulose fibres being 70% to 90% by weight virgin or recycled natural pulp fibres, and 10 to 30% by weight short length regenerated cellulose fibres; wherein the natural pulp fibres have a length comprised between 0.5 and 4mm and the short regenerated cellulose fibres have a length comprised between 8 and 12 mm; wherein the paper does not contain any non-natural polymer, or chemical products in general, as binding additives or glues, and wherein the degree of water absorption measured under the UNE-EN ISO 9073-6 test gives absorption values comprised between 600% and 1200% according to the ISO standard and preferably between 700% and 900%, thus ensuring dispersions (according to Slosh box test) greater than 80% in less than 5 minutes.
The paper for producing dispersible cigarette filters, in full accordance with the preceding claim, wherein the density of the natural pulp fibres is comprised between 1 and 2 decitex; while the density of the regenerated cellulose fibre is comprised between 0.9 and 2.4 decitex; and wherein the strengths achieved range from 20 N/5cm to 60 N/5cm, always preserving dispersions greater than 80%.
The paper for producing dispersible cigarette filters, in full accordance with claim 1, wherein the density of the final product is comprised between 10 and 99 Kg/m³.
A paper for producing dispersible cigarette filters, in full accordance with claim 1, wherein according to the "Slosh box" test carried out under the following parameters: 5 minutes /26 rpm/2L/ sieve 12.5 mm, a dispersion level is reached for the core of a cigarette filter made with this paper, which can reach 90%.
The paper for producing dispersible cigarette filters, in full accordance with claim 1, wherein the short regenerated cellulose fibres are, preferably, rayon or viscose and/or Lyocell.
The paper for producing dispersible cigarette filters, in full accordance with claim 1, wherein natural pulp fibres may optionally be subjected to refining, to increase its fibrillation and, in this case, they will have a refinement level of between twelve and forty Shopper degrees (12°S and 40°S) in accordance with the ISO 5267 standard.
A paper for producing dispersible cigarette filters, in full accordance with claim 1, wherein when the composition of the paper incorporates additives, these additives are natural; and wherein, if the natural additive is added in mass, to the dissolution of fibres in water, its percentage by weight is comprised between 1 and 5%; while if the natural additive is added on the surface, as a surface reinforcement, its percentage by weight is comprised between 0.5 and 2%.
The paper for producing dispersible cigarette filters, in full accordance with claims 1 and 7, wherein the natural additives that can be optionally added as reinforcement of the bonds between fibres are, preferably, Carboxymethyl cellulose (CMC), different types of micro and nano cellulose, such as micro fibrillated cellulose (MFC) or starch.
A method for producing a paper for producing dispersible cigarette filters, a paper that is made up of, at least 93% by weight cellulose fibres and/or 0 to 7% by weight natural additives, which comprises a first phase in which all the cellulose fibres formed by the short regenerated cellulose fibres and the virgin or recycled natural pulp fibres, are mixed with water separately in mixers (1.1-1.3) respectively, to subsequently pass to storage tanks (1.2-1.4) and from there, through pumping means (1.5), pass to the headbox (1.6) of the paper machine (1), to subsequently and from the headbox (1.6), pass to a hydroentangler (1.8), where they are subjected to a hydroentanglement, and then passing them to a step of drying the paper, which is carried out using a through-air dryer (TAD) (1.9).
A method for producing a paper for producing dispersible cigarette filters, in full accordance with the preceding claim, wherein the headbox (1.6) of the paper machine (1), is high dilution; such that the fibres suspended in water have a concentration of no more than 0.05% by weight.
A method for producing a paper for producing dispersible cigarette filters, in full accordance with claim 9, wherein natural additives can be added in mass and/or on the surface; such that if it is added in mass, the natural additive is incorporated into the dissolution of fibres in water; while if it is added to the surface, the natural additive is sprayed through nozzles, being sprayed on the surface of the sheet of paper, already semi-formed in the machine and before final winding and wherein if the natural additive is added in mass, its percentage by weight is comprised between 1 and 5%; while if it is added to the surface, its percentage by weight is comprised between 0.5 and 2%.
A method for producing a paper for producing dispersible cigarette filters, in full accordance with claim 9, wherein natural pulp fibres, before bonding to the short regenerated cellulose fibres, can be subjected to refining, to increase its fibrillation; such that, according to ISO 5267 the refined long-fibre natural pulp fibres have a refinement level of between twenty and forty Shopper degrees (20°S and 40°S).