ES2956679T3 - Paper material comprising cellulose fibers and leather fibers and process for the production thereof - Google Patents

Abstract

The present invention relates to a composite paper material comprising cellulose fibers and leather fibers. The invention also relates to a process for the production of the aforementioned paper material. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Paper material comprising cellulose fibers and leather fibers and process for the production thereof

Area of application

The present invention relates to a paper material comprising cellulose fibers and leather fibers. The invention further relates to a process for the production of the aforementioned paper material.

Background of the technique

In the field of cellulose materials, in particular in the paper production industry, the problem of preserving the environment and reducing costs remains relevant. For these reasons, considerable attention is paid to recycling techniques for paper materials, thereby attempting to limit the use of virgin cellulose material. Products obtained from recycled cellulose materials, however, have different physical properties than those obtained from virgin cellulose materials.

In the art, paper articles comprising both cellulosic and fiber fibers are known from US 2104996 A, US 2635958 A and GB 2045829 A.

Document No. US1269905A discloses a process for manufacturing roofing felts that consists of the disintegration of residual leather and cellulose fiber to form a pulpy and fibrous mass of the consistency of paper pulp, adding to the pulp a softening agent, cellulose mixture, bichromate of soda or potash, and then forming the pulp into soft absorbent and porous sheets.

Document No. US1211837A discloses a highly absorbent flexible sheet composite material comprising cotton or wool and leather fibers woven together and saturated with a bituminous material.

The present applicant has considered the problem of providing a paper material having a fibrous component comprising alternative fibrous materials to virgin cellulose, preferably derived from recycled materials, without compromising the mechanical properties of the final paper product, such as, for example, stiffness, thickness, burst strength and breaking length. A further objective of the present invention is to provide this type of paper material that also has a high electrical conductivity and a high volume or "volume" values.

The above objectives have been achieved by the applicant by means of a paper material, in which the cellulose fibers of the fibrous component have been partially replaced by leather fibers, in particular leather fibers obtained from waste from the tanning and processing industry. the transformation of leather.

Summary of the invention

According to a first aspect, the present invention relates to a paper material in which the fibrous component comprises leather fibers in a percentage comprised in the range of between 5% and 80% by dry weight and cellulose fibers in a percentage comprised in the range between 95% and 20% by dry weight, in which said dry weight percentages refer to the total dry weight of the fibrous component, and in which said leather fibers and cellulose fibers form a homogeneous mixture by means of of a tanning agent.

The fibrous component of the paper material according to the invention preferably consists of cellulose fibers and leather fibers.

The paper material according to the present invention advantageously has a high electrical conductivity and a high "specific volume".

Another advantage refers to the fact that the use of leather fibers instead of cellulose fibers makes it possible to use a considerably reduced amount of virgin cellulose material, up to 80% less, in the production of the paper material according to the invention.

An additional advantage provided by the present invention is the possibility of effectively recycling waste from the tanning and leather processing industry.

Another advantage lies in the fact that the paper material of the invention is biodegradable or compostable, reducible to pulp and can therefore be recycled in the paper production chain.

Still another advantage is represented by the fact that the paper material according to the present invention can be combined with non-paper materials, in particular biodegradable plastic films, such as PHA. (polyhydroxyalkanoate), Mater-Bi®, PLA (polylactic acid), in order to obtain compostable final products, which can be used in, for example, the packaging industry.

For the purposes of the present invention, a material is considered "biodegradable" if it meets the biodegradability requirements established by standard EN 13432.

For the purposes of the present invention, a material is considered "compostable" if it meets the compostability requirements established by the EN 13432 standard.

For the purposes of this description and appended claims, the term "comprises" and all terms derived therefrom also includes the meaning of the verb "consists" and all terms derived therefrom. The numerical limits and ranges expressed in the present description and attached claims also include the mentioned numerical value or values. Furthermore, all values and subintervals of a numerical limit or interval must be considered as specifically included, as if they had been explicitly mentioned.

Additional features and advantages of the present invention will become apparent from the detailed description provided below.

Detailed description

According to a preferred aspect of the present invention, the leather fibers have a length within the range of between 0.1 and 30 mm, preferably within the range of between 1 and 20 mm, more preferably between 4 and 15 mm.

Preferably, the leather fibers are obtained by defibrating the leather, more preferably leather obtained from waste from the tanning industry and the leather processing industry, such as, for example, waste from the unhairing and splitting stages. from tanning procedures, or trimming waste from the leather processing industry.

For the purposes of the present invention, the aforementioned residual products are reduced to the state of fibers by using procedures and techniques known in the field of leather waste recovery, in particular in the field of the production of so-called "leather". regenerate".

In particular, shredding can be achieved mechanically, by shredding the waste in synchronized hammer and/or knife mills and/or in shredding mills, preferably Pallmann shredding mills. Preferably, the defibration process is continued for a period of time that prevents complete separation of the individual fibers, although for a period that allows leather fibers to be obtained in bundles, which is preferably a maximum of 30 minutes. In fact, it has been observed that shredding times longer than those indicated above damage the collagen fibers that make up the leather and also cause excessive energy consumption.

The leather fibers are preferably partially defibered.

The leather fibers are preferably in the form of fiber bundles, more preferably ball-like.

The fibers obtained from the defiberation procedures described above have a morphology and dimensions similar to those of cellulose fibers. The above causes the leather fibers indicated above to be compatible with cellulose fibers and, therefore, can be used as part of the fibrous component of the paper material.

The use of leather fibers according to the present invention gives the paper material a characteristic appearance, since these fibers are at least partially visible also to the naked eye in the finished product, as shown in Figure 1, attached, which shows a paper material according to the invention.

The presence of leather fibers in bundles can also be observed in Figures 2 and 3, attached, which show electron microscopy images of a sample of leather fibers according to the invention. The presence of bundles of leather fibers offers the advantage of increasing the specific volume value of the obtainable paper material, without substantially deteriorating the other properties.

The leather fibers are preferably obtained from leather tanned by non-chromium type tanning procedures, more preferably vegetable tanning (e.g. using tannin as a tanning agent), or "wet white" tanning (e.g. , using aldehydes as tanning agent). Vegetable tanning and "wet white", in fact, they don't use chrome. The use of fibers derived from said tanned leathers in the production of paper material according to the present invention, therefore, avoids all problems of an environmental nature related to the use of said heavy metal.

The paper material of the present invention is preferably one or more selected from printing paper or cardboard, paper for lining boxes, packaging paper, corrugated paper and cardboard, paper for reusable bags and bags in general, paper for labels and security paper.

The paper material is preferably coated, embossed, die-cut and/or laminated.

The paper material according to the present invention may have various shapes, for example, the shape of a sheet having variable dimensions, the shape of a roll, etc.

According to another preferred aspect, the paper material of the present invention has an electrical conductivity in the range of between 1x10-7 and 10x10-10 S/m, more preferably between 10x10-8 and 1x10-9 S/m. Said conductivity value makes the paper material according to the present invention particularly suitable for use as a support for digital printing, photostatic printing and the like. For this type of application, the fibrous component of the paper material preferably comprises leather fibers in a percentage in the range of 5% to 20%, more preferably 5% to 10% by dry weight, and cellulose fibers. in a percentage in the range of between 95% and 80%, more preferably between 95% and 90% by dry weight, in which said dry weight percentages refer to the total dry weight of the fibrous component.

For comparison purposes, the typical electrical conductivity of paper produced with only cellulose fibers is typically in the range of 1x10-12 to 1x10-14 S/m.

The paper material preferably has an absolute humidity in the range of 4% to 12%, more preferably 5% to 10%. The paper material preferably has a specific volume value (thickness (|jm)/grammage (g/m2) ratio) within the range of 1.2 to 1.8, more preferably within the range of 1.4 and 1.7. These values are on average approximately 25% higher than the specific volume values obtainable with conventional paper materials, that is, without leather fibers.

High specific volume values are desirable for blotting paper, for example. Low specific volume values are desirable for printing paper, for example. With the present invention, a paper material having a desired specific volume value can be obtained using a smaller amount of cellulose fibers than in conventional paper, which does not contain leather fibers.

The paper material preferably has an organic nitrogen content in the range of 1% to 12%, more preferably 3% to 6% (Kjendahl method). This nitrogen content makes the paper material easily compostable.

The paper material preferably has a grammage in the range of between 80 and 1,100 g/m2, more preferably between 100 and 600 g/m2.

The paper material according to the present invention advantageously does not cause skin irritation. Said evaluation can be carried out by carrying out, for example, an occlusive type patch test.

The paper material according to the invention preferably has, on the surface, occlusions that derive from partially defiberated leather fibers. These occlusions provide the material with a characteristic or immediately recognizable appearance.

A second aspect of the present invention relates to a process for the production of a paper material as defined above, and comprises the following steps:

a) preparation of an aqueous type mixture comprising cellulose fibers and leather fibers, in which the leather fibers are present in a percentage within the range of between 5% and 80% by dry weight and the cellulose fibers They are in a percentage between 95% and 20% by dry weight, in which said dry weight percentages are based on the total dry weight of the sum of the cellulose fibers and the cellulose fibers,

a-1) addition of a tanning agent to the aqueous type mixture of said step a),

b) forming a layer of said mixture on a drainage screen and draining the water contained in said mixture, and

c) drying said drained mixture so that said paper material is obtained.

In the present description and attached claims, the term "tanning agent" refers to a compound of the type generally used in tanning procedures for animal hides, which stabilizes collagen.

For the purposes of the present invention, the addition of the tanning agent in step a) favors the formation of a homogeneous mixture of leather fibers and cellulose fibers.

Preferably, the tanning agent is comprised within the group selected from: mineral tanning agents (e.g., zirconium or aluminum salts), tannins, more preferably vegetable tannins, aldehydes (e.g., glutaraldehyde), tanning oils, or combinations thereof.

Preferably, the tanning agent is added in step a) in a percentage by dry weight in the range of between 0.1% and 2.0%, more preferably between 0.2% and 0.8%, in wherein said percentage refers to the total dry weight of the leather fibers.

Preferably, one or more additives of the type commonly used in the paper industry, such as optical brightening agents, dyes, sizing agents, fillers (e.g., carbonate), are added to the aqueous-type mixture of step a). calcium and kaolin), silica, cationic starch, moisture resistance agents, etc., according to the desired characteristics in the final paper material.

Preferably, the dyes are present in an amount in the range of between 0.05% and 10.00% by dry weight, where said percentages refer to the total dry weight of the mixture.

Preferably, stage b) is preceded by a stage of refining the mixture from stage a), more preferably by the use of conical or disc refiners.

The process according to the present invention can be carried out with equipment known to the person skilled in the field of the paper industry. Steps b) and c), in particular, can be carried out with a continuous paper production machine.

The paper material obtained at the end of step c) is preferably subjected to one or more finishing steps selected from the group comprising calendering, embossing, corrugating, coupling and coating.

In particular, the coating can be carried out by using techniques and equipment known to the person skilled in the art, such as air knife coating, curtain coating, rigid knives, curved knives, dosing and press. film roller.

According to a third aspect, the present invention relates to the paper material obtained according to the aforementioned production process.

According to a fourth aspect, the present invention relates to the use of the aforementioned paper material to produce a biodegradable multilayer composite material together with one or more non-paper materials, in particular biodegradable plastic films, that is, films comprising polymers. biodegradable, such as cellulose acetate, PBS (polybutylene succinate), PHA (polyhydroxyalkanoate), Mater-Bi®, PLA (polylactic acid), etc. .

According to a fifth aspect, the present invention relates to a biodegradable multilayer composite material comprising at least one layer of the paper material described above, laminated with at least one biodegradable film.

Said composite material can be advantageously used for the preparation of biodegradable or compostable end products, which can be used, for example, in the packaging and agricultural fields.

Biodegradable films that can be used for the purposes of the present invention are known to those skilled in the art and can be found on the market. Such films comprise biodegradable polymers, such as, for example, polymers and copolymers of hydroxy acids (so-called poly(hydroxy acids), in particular, polymers and copolymers of lactic acid and glycolic acid, cellulose polymers, hydroxyalkanoate polymers (e.g. , polyhydroxybutyrate-covalerate (PHBV), biodegradable copolyesters (e.g., polybutylene succinate adipate (PBSA), polybutylene adipate-co-terephthalate), polycaprolactones (PCL) and starch-based polymers.

Multilayer composite materials according to the present invention can be prepared by procedures known to those skilled in the art.

Brief description of the figures

Figure 1 shows a sample of the paper material according to the invention.

Figure 2 is an electron microscopy image of a sample of leather fibers according to the present invention.

Figure 3 is another electron microscopy image of a sample of leather fibers according to the present invention.

Examples

Below, the present invention is further illustrated by some embodiment examples, as described below herein.

Example 1: Paper material with 60% leather fibers and 40% cellulose fibers (NBSK cellulose softwood).

Composition 1:

- 300 kg of leather shaved and tanned using the "wet white" technique (leather previously defibered in a knife mill and for 10 minutes in a Pallmann defibering mill).

- 300 kg of leather waste tanned using the "wet white" technique (leather previously ground in a knife mill and defibered for 20 minutes in a Pallmann defibering mill).

- 400 kg of ASPA bleached chemical cellulose (NBSK)

- 20 kg of cold soluble cationic starch

- 50 kg of calcium carbonate

- 20 kg of natural tanning agent, 50% dry product (Chimotan OPS, from Chimotan Group).

The materials of composition 1 were introduced into a vat and refined for 10 minutes, using conical refiners, in order to achieve homogenization of the fibrous component. The mixture obtained, 1,090 kg, was added to a continuous Fourdrinier machine for the production of paper, with a production of 1,000 kg/h and a rate of 22 m/min, obtaining a roll of paper material. The final grammage of the paper material obtained was approximately 700 g/m2, while the thickness was 1,100 micrometers. The final absolute humidity of the paper material was equal to 12%.

The paper material is biodegradable, recyclable and reducible to pulp. This last characteristic makes the material suitable for subsequent transformations in the paper process. Table 1, later in this report, item A, shows the characteristics of the paper material obtained.

Example 2: Paper material with 15% leather fibers and optical brightener for printing.

Composition 2:

- 750 kg of paper material from Example 1 cut into sheets

- 2,000 kg of bleached chemical pulp, of which: 500 kg of softwood pulp (NBSK) and 1,500 kg of hardwood pulp (eucalyptus, beech, poplar or poplar)

- 200 kg of calcium carbonate

- 25 kg of optical brightener (Leucophor® ACK from Archroma)

- 5 kg of natural tanning agent, 50% dry product (Chimotan OPS, from Chimotan Group).

The materials of composition 2 were dosed and the following products were added: cationic starch 15 kg dry, polyaluminum chloride 30 kg without modification, colloidal silica 4.5 kg dry and 30 kg of AKS-based sizing agent for the paper gluing. The latter materials are useful for retention.

The mixture was homogenized with a pulping machine; It was stored in a vat and metered into a Fourdrinier continuous paper making machine. The speed of the machine was 120 m/min, with an hourly production of 1,200 kg/h. Final smoothing was carried out to make the paper suitable for printing. The final absolute humidity of the paper material was 7.0%. The production yield was 2,700 kg in the form of rolls that were later cut into sheets. The weight of the paper was 120 g/m2. During production, a starch solution was applied to the surface using a size press to improve the surface characteristics of the paper and make it suitable for printing.

As a resulting product, a paper material was obtained, which is recyclable, reducible to pulp, biodegradable, compostable and gluable. The presence of optical brightening agents makes the paper whiter, favoring its use as printing and writing paper. The presence of bundles of leather fibers gives the paper a characteristic appearance. Table 1, later in this report, item B, shows the characteristics of the paper material obtained.

Example 3: Printing paper roll paper material with 300 leather fibers having a natural color.

Composition 3:

- 2,200 kg of the material obtained according to Example 1 cut into sheets

- 2,000 kg of bleached chemical pulp, of which: 500 kg of softwood pulp (NBSK) and 1,500 kg of hardwood pulp (eucalyptus, beech, poplar or poplar)

- 200 kg of calcium carbonate

- 10 kg of natural tanning agent, 50% dry product (Chimotan OPS, from Chimotan Group).

The following products were added to the materials of composition 3: cationic starch 15 kg dry, polyaluminum chloride 30 kg without modification, colloidal silica 4.5 kg dry and 30 kg of AKS-based sizing agent for sizing the paper. These latter materials are useful for retention.

The mixture was homogenized with a pulping machine, stored in a vat and subsequently dosed to a Fourdrinier continuous paper manufacturing machine. The speed of the machine was 70 m/min, with an hourly production of 1,400 kg/h. The absolute humidity of the final paper material was 7.5%. The production yield was 4,200 kg. The weight of the paper was 250 g/m2. During production a starch solution was applied to the surface using a film press machine to improve the surface characteristics of the paper and thus make it suitable for printing. As a resulting product, a paper material was obtained, which is recyclable, reducible to pulp, biodegradable, compostable and gluable. The presence of bundles of leather fibers gives the paper a characteristic appearance.

Table 1, later in this report, item C, shows the characteristics of the paper material obtained. Due to the presence of animal fibers, a test to evaluate skin irritability (occlusive patch test) was carried out, which gave a negative result.

Example 4: black paper material, with 300 leather fibers, tinted with direct dyes

Composition 4:

- 2,200 kg of the paper material obtained according to Example 1 cut into sheets

- 2,000 kg of bleached chemical pulp, of which: 500 kg of softwood pulp (NBSK) and 1,500 kg of hardwood pulp (eucalyptus, beech, poplar or poplar)

- 200 kg of calcium carbonate

- 40 kg of Cartacrom 2T Black in powder form (CI: Direct Black 80);

- 40 kg of Cartacrom N Black in powder form (CI: Direct Black 168);

- 10 kg of Cartacrom GTN Red 150% in powder form (CI: Direct Red 239).

The following products were added to the materials of composition 4: cationic starch 20 kg dry, polyaluminum chloride 40 kg without modification, colloidal silica 5.5 kg dry and 30 kg of AKS-based sizing agent for sizing the paper. These latter materials are useful for retention.

The mixture was homogenized with a pulping machine, stored in a vat for dyeing and subsequently dosed to a Fourdrinier continuous paper manufacturing machine. The speed of the machine was 120 m/min, with an hourly production of 1,200 kg/h on a roll. Final smoothing was carried out to make the paper suitable for major paper processing, in particular lamination. The final absolute humidity of the paper material was 7.0%. The production yield was 4,250 kg. The weight of the paper was 250 g/m2. During production, a solution of starch and black dye was applied directly to the surface using a size press machine, in order to improve the surface characteristics of the paper and increase the color intensity of the paper.

As a resulting product, a paper material was obtained, which is recyclable, reducible to pulp, biodegradable, compostable and glued, black in color (L=26.5, a=0.7, b=-1.4) and characterized by white inclusions due to the presence of leather fibers that do not absorb direct dyes.

Table 1, item D, shows the characteristics of the material obtained.

Example 5: paper coated with 300 leather fibers.

A roll of paper produced according to Example 3 of 250 g/m2 was coated with an air knife coating machine applying a coating of 10 g/m2. The dry product of the coating was 35% and the pH was adjusted to a value of 8.5 with NaOH.

Composition of the dry coating:

Polymethylurea 100 kg

Precipitated calcium carbonate 200 kg

Kaolin 100 kg

Styrene-butadiene latex 300 kg

Insolubilizing agents 15 kg

Dispersing and wetting agents 5 kg

Thickening agents 6 kg

NaOH 1kg

Optical brightener 4 kg

As a resulting product, a paper material was obtained, which is recyclable, reducible to pulp, biodegradable, compostable, sized and coated, characterized by whitish inclusions due to the presence of collagen, which absorbed the coating in a different way.

Table 1, item E, shows the characteristics of the material obtained.

Example 6: Embossing of the paper material according to the present invention.

A roll of paper produced according to Example 2 (15% leather fibers and optical brightening agents) of 120 g/m2 was embossed with a UNIMATEC embosser at a speed of 100 m/min, at a temperature of 75 °C and at a pressure of 80 bar. The steel marker cylinder was characterized by having a width of 150 cm and a diameter of 25.34 cm. The absolute humidity of the final marked paper was 7.0%.

The resulting product was a paper material with a surface marking similar to canvas fabric. The paper material obtained in this way can be used in, for example, the coating of boxes.

Example 7: biodegradable multilayer composite material

A roll of paper produced according to Example 3 (30% leather fibers and a natural color) of 250 g/m2 was cut using a Jagemberg SYNCHRO cutter in a format of 72x102 cm and coupled on a PAPERPLAST WD coupling machine. with a 32 g/m2 CLARIFOIL ACE ^{B l UE} cellulose acetate film using 4 g/m2 of biodegradable adhesive (aqueous dispersion based on polyester-polyurethane elastomers, EPOTAL P100 Eco from BASF). The absolute humidity of the final laminated paper was 7.0%, while the final grammage was 286 g/m2.

As a resulting product, a biodegradable multilayer composite material was obtained that can be used in, for example, the production of compostable pots for plants.

TABLE 1: physical-mechanical characteristics of the paper materials obtained

Claims (15)

1. Paper material in which the fibrous component comprises leather fibers in a percentage in the range of 5% to 80% by dry weight and cellulose fibers in a percentage in the range of 95% to 20%. by dry weight, wherein said dry weight percentages refer to the total dry weight of the fibrous component, and wherein said leather fibers and cellulose fibers form a homogeneous mixture by means of a tanning agent. 2. Paper material according to claim 1, wherein said leather fibers have a length in the range between 0.1 and 30 mm, preferably between 1 and 20 mm, more preferably between 4 and 15 mm. 3. Paper material according to claim 1 or 2, wherein the leather fibers are obtained by defibrating the leather, preferably leather obtained from waste from the leather tanning and processing industry. 4. Paper material according to any one of the preceding claims, wherein the leather fibers are obtained from leather tanned by tanning procedures of the type that does not use chromium, preferably vegetable tanning or wet white tanning. 5. Paper material according to any one of the preceding claims, wherein said paper material has an electrical conductivity in the range between 1x10-7 and 10x10-10 S/m, more preferably between 10x10-8 and 1x10 -9 S/m. 6. Paper material according to any one of the preceding claims, wherein said material has an absolute humidity in the range of between 4% and 12%, preferably between 5% and 10%. 7. Paper material according to any one of the preceding claims, wherein said material has a specific volume value in the range between 1.2 and 1.8, preferably in the range between 1.4 and 1, 7. 8. Paper material according to any one of the preceding claims, which has an organic nitrogen content in the range of between 1% and 12%, preferably between 3% and 6%. 9. Paper material according to any one of the preceding claims, which has occlusions on the surface that derive from partially defibered fibers. 10. Procedure for the manufacture of a paper material as defined in claims 1 to 9 above, comprising the steps of: a) preparation of an aqueous type mixture comprising cellulose fibers and leather fibers, in which the leather fibers are present in a percentage within the range of between 5% and 80% by dry weight and the fibers of cellulose are present in a percentage between 95% and 20% by dry weight, in which said dry weight percentages refer to the total dry weight of the sum of cellulose fibers and leather fibers, a-1) addition of a tanning agent to the aqueous type mixture of said step a), b) forming a layer of said mixture on a drainage screen and draining the water contained in said mixture, and c) drying said drained mixture so that said paper material is formed. 11. Method according to claim 10, wherein said tanning agent is added to the aqueous-type mixture of step a) in a percentage by dry weight in the range of between 0.1% and 2.0%. preferably between 0.2% and 0.8%, where said percentage refers to the total dry weight of the leather fibers. 12. Method according to any one of claims 10 or 11, wherein said stage b) is preceded by a stage of refining the mixture of stage a), more preferably by the use of conical or disc refiners. 13. Method according to any one of claims 10 to 12, wherein, at the end of step c), said paper material is subjected to one or more refining steps selected from the group comprising calendering, embossing, corrugating , coupling and coating. 14. Use of the paper material according to any one of claims 1 to 9, for the manufacture of a biodegradable multilayer composite material together with one or more non-paper materials, particularly biodegradable plastic films, such as PHA (polyhydroxyalkanates), materBi® and PLA (polylactic acid). 15. Biodegradable multilayer composite material comprising at least one layer of a paper material according to claim 1, laminated with at least one biodegradable film.