Writing material in the form of sheets based on regenerated leather and production process thereof

Abstract

Writing material in sheet form made from a composition which comprises : ( a) from 40% to 90% by weight o f regenerated leather fibres; (b ) from 5% to 30% by weight of a natural rubber; ( c ) from 5% to 30% by weight of a fatty substance; the composition having a residual moisture from 5% to 20% by weight, preferably from 10% to 15% by weight; the percentages by weight being expressed with respect to the overall weight of the dry composition. Sheets made from said composition have numerous advantages when used as a writing material : they are flexible and tear-resistant; they have high dimensional stability; they can be recycled; they do not show any "ghost effect" typical of writing on paper, i. e. the writing does not appear on the opposite side o f the sheet even when observed against the light; they do not cause smudging during ink application; they can be easily used for writing with any type of pen; they are printable with conventional office printers; they can be easily cut and glued.

Description

[0001] WRITING MATERIAL IN THE FORM OF SHEETS BASED ON

[0002] REGENERATED LEATHER AND PRODUCTION PROCESS THEREOF

[0003] The present invention relates to a writing material in the form of sheets based on regenerated leather, and a production process thereof .

[0004] As is well known, paper used as writing material (handwriting or printing) is an industrial product based on cellulose in fibrous form that is suitably mixed with additives to obtain a wet pulp that can be processed to obtain thin and flexible sheets . The fibrous material generally consists of the so called "wood pulp" , which is obtained by wood processing . The timber used to produce wood pulp is generally obtained from coni fers ( e . g . fir, pine , larch) or deciduous trees ( e . g . eucalyptus , poplar, birch) .

[0005] The production of wood pulp, which can be carried out with mechanical , semi-chemical or completely chemical methods (Kraft and sulphite processes ) , involves a considerable consumption of energy, water and chemicals , with consequent problems in terms of environmental impact , such as the management of material and energy resources and the treatment of processing ef fluents to ensure their non-toxicity . Additionally there is the need to properly manage the production of the raw material , i . e . the wood, through intensive cultivation and modern deforestation practices , in order to provide a reliable and renewable source of raw material for paper mills .

[0006] The Applicant therefore has faced the technical problem of providing a writing material that is free o f cellulose components , that results from regenerated materials in accordance with the principles of the Circular Economy, and that has properties suitable for writing, either by manual means or with automatic printing devices (e.g. office printers) .

[0007] The Applicant has found that this technical problem, and others which are better explained hereinafter, can be solved by using, as writing material, a composition comprising regenerated leather fibres bound together by means of a natural rubber and a fatty substance, as reported in this description and in the attached claims.

[0008] According to a first aspect, the present invention thus relates to a writing material in sheet form made from a composition which comprises:

[0009] (a) from 40% to 90% by weight of regenerated leather fibres;

[0010] (b) from 5% to 30% by weight of a natural rubber;

[0011] (c) from 5% to 30% by weight of a fatty substance ; the composition having a residual moisture from 5% to 20% by weight, preferably from 10% to 15% by weight; the weight percentages being expressed with respect to the overall weight of the dry composition.

[0012] In a second aspect, the present invention relates to the use as writing material of a composition in sheet form, which comprises:

[0013] (a) from 40% to 90% by weight of regenerated leather fibres;

[0014] (b) from 5% to 30% by weight of a natural rubber;

[0015] (c) from 5% to 30% by weight of a fatty substance ; the composition having a residual moisture from 5% to 20% by weight, preferably from 10% to 15% by weight; the weight percentages being expressed with respect to the overall weight of the dry composition.

[0016] Preferably, the composition comprises:

[0017] (a) from 60% to 75% by weight of regenerated leather fibres;

[0018] (b) from 10% to 25% by weight of a natural rubber;

[0019] (c) from 5% to 15% by weight of a fatty substance ; the composition having a residual moisture from 5% to 20% by weight, preferably from 10% to 15% by weight; the weight percentages being expressed with respect to the overall weight of the dry composition.

[0020] Preferably, the writing material in sheet form according to the present invention has a thickness from 0.05 mm to 2.0 mm, more preferably from 0.1 mm to 0.4 mm.

[0021] For the purposes of the present invention, in the following description and claims, the definitions of numerical ranges comprise the individual values within the range and its extremes, unless otherwise specified.

[0022] For the purposes of the present description and the following claims, the term "comprising" also includes the terms "which essentially consists of" or "which consists of" .

[0023] The sheets obtained from said composition have numerous advantages when used as writing material:

[0024] - are flexible and tear-resistant;

[0025] - have high dimensional stability;

[0026] - can be recycled;

[0027] - do not show any "ghost effect" typical of writing on paper, i.e. the writing does not appear on the opposite side of the sheet even when observed against the light;

[0028] - do not cause smudging during ink application;

[0029] - can be easily used for writing with any type of pen;

[0030] - are printable with conventional office printers;

[0031] - can be easily cut and glued.

[0032] Preferably, the composition in accordance with the present invention is free of cellulose or derivatives thereof .

[0033] Regarding regenerated leather fibres, they are obtained from leather processing wastes (e.g. cuttings and tanned shavings) and / or leather resulting from end- of-life articles. The recycled material is generally subjected to milling with hammer or knife synchrony mills, in order to reduce the leather into fibres having sizes compatible with further processing. For this purpose, after milling, the fibres are sieved, so as to obtain fibres having an average size preferably not higher than 8.0 mm, more preferably not higher than 5.0 mm.

[0034] Natural rubber (NR) is a well-known and widely available product on the market in latex form. It is a natural rubber dispersion in water, obtained by extraction from the bark of rubber trees, such as Hevea Brasiliensis . It is a milky, viscous, environmentally friendly and recyclable liquid provided with natural elasticity, durability and hygienic characteristics that make it suitable for various uses, e.g. for the production of mattresses and pillows. Natural rubber latex generally comprises about 40% by weight of natural rubber (polyisoprene) , the remainder being water in addition to low percentages (around 2% by weight) of proteins, resins, secondary metabolites (ammonia, alkaloids) and mineral salts.

[0035] The fatty substance included in the composition according to the present invention is generally an oil obtained from vegetable or animal sources, used for example in tanneries after leather tanning operations (so-called " f atliquoring" ) . Preferably, the fatty substance is a fish oil, which is rich in polyunsaturated fats, especially eicosapentaenoic acid (EPA) , docosahexaenoic acid (DHA) and other monounsaturated fats, with a significant portion of oleic acid and palmitoleic acid.

[0036] The composition according to the present invention may possibly comprise further ingredients, such as: dyes, pigments, pH neutralising agents, tannins.

[0037] Regarding tannins, these are polyphenolic substances that are synthesised by the bark of plants, and are able to bind to the leather proteins, so that they remain stably bound to the fibres and give them absorbent and breathable properties. The amount of tannins that may be present is generally from 1% by weight to 10% by weight, preferably from 2% by weight to 6% by weight, with respect to the overall weight of the dry composition.

[0038] In a further aspect, the present invention relates to a process for producing the above composition in sheet form, wherein said process comprises: grinding the regenerated leather to obtain leather fibres preferably having an average size preferably not higher than 8.0 mm, more preferably not higher than 5.0 mm; adding water to the leather fibres to obtain a mixture with a dry content from 2 % to 20% by weight , preferably from 5% to 10% by weight ; adding a fatty substance to the mixture ; mixing the mixture thus added, and possibly further diluted with water until obtaining a dry content from 0 . 5% to 5% by weight, preferably from 1 % to 3% by weight , with a natural rubber latex ; adding a coagulation agent , pre ferably aluminum sulphate , to the mixture , mixed with natural rubber latex and possibly diluted, so as to coagulate the natural rubber on the leather fibres ; depositing the mixture thus obtained on a canvas , so as to form a thin layer from which the water is drained to obtain a sheet ; partially removing the remaining water until a residual moisture from 5% to 20% by weight , preferably from 10% to 15% by weight , is obtained .

[0039] The aforesaid process can be carried out in a machine commonly used for producing paper, in particular a continuous machine .

[0040] The canvas on which the mixture is deposited i s provided with holes through which the water is drained, so that the maj ority of the same is removed . Subsequently, the water content i s further reduced until a residual moisture from 5% to 20% by weight , preferably from 10% to 15% by weight , is obtained . This reduction can be achieved, for example , by applying a pneumatic vacuum and sucking water vapour, or through cylindrical presses surmounted by felts , which perform a mechanical squeezing without causing cracks in the material . To complete the partial removal of residual moisture, hotair ovens can be further employed.

[0041] The following embodiment example is provided merely to illustrate the present invention and should not be construed so as to limit the scope of protection defined by the appended claims.

[0042] EXAMPLE .

[0043] A sheet (in roll form) having a thickness of 0.2 mm (± 1 / 10 mm) and a height of 150 cm was produced by the process according to the present invention from a composition made up of:

[0044] 70% by weight of leather fibres obtained from leather cuttings and tanned shaving, having an average length of approximately 1.2 mm;

[0045] 20% by weight of natural rubber;

[0046] 6% by weight of fish oil;

[0047] 4% by weight of tannins; the percentages being expressed with respect to the dry weight.

[0048] The residual water content was 12% by weight, with respect to the dry weight.

[0049] The material had the following mechanical properties : average elongation: > 20% (UNI EN 3376:2006) ; tensile strength: 8 N / mm2(UNI EN ISO 3377:2006) ; dimensional stability: 1% (UNI 8481:2010) .

[0050] The sheet was subjected to a writing test, both by a ballpoint and a fountain pen. In both cases, the writing was easy and fluent, without smudgings and without showing any "ghost effect", i.e. the writing was not visible from the opposite side of the sheet even when observed against the light. The sheet further showed high resistance to the pressure exerted by the writing instrument .

[0051] The same sheet, cut to A4 si ze, was fed into an of fice laser printer, which provided a clear and neat print .

Claims

CLAIMS1. Writing material in sheet form made from a composition which comprises:(a) from 40% to 90% by weight of regenerated leather fibres;(b) from 5% to 30% by weight of a natural rubber;(c) from 5% to 30% by weight of a fatty substance ; the composition having a residual moisture from 5% to 20% by weight, preferably from 10% to 15% by weight; the weight percentages being expressed with respect to the overall weight of the dry composition.

2. Writing material in sheet form according to claim 1, wherein the composition comprises:(a) from 60% to 75% by weight of regenerated leather fibres;(b) from 10% to 25% by weight of a natural rubber;(c) from 5% to 15% by weight of a fatty substance ; the composition having a residual moisture from 5% to 20% by weight, preferably from 10% to 15% by weight; the weight percentages being expressed with respect to the overall weight of the dry composition.

3. Writing material in sheet form according to any one of the preceding claims, having a thickness from 0.05 mm to 2.0 mm, preferably from 0.1 mm to 0.4 mm.

4. Writing material in sheet form according to any one of the preceding claims, wherein the composition is free of cellulose or derivatives thereof.

5. Writing material in sheet form according toany one of the preceding claims, wherein the leather fibers have an average size not higher than 8.0 mm, preferably not higher than 5.0 mm.

6. Writing material in sheet form according to any one of the preceding claims, wherein the fatty substance is an oil obtained from vegetable or animal sources .

7. Writing material in sheet form according to claim 6, wherein the fatty substance is a fish oil.

8. Writing material in sheet form according to any one of the preceding claims, wherein the composition further comprises tannins.

9. Writing material in sheet form according to claim 8, wherein the tannins are present in an amount from 1% by weight to 10% by weight, preferably from 2% by weight to 6% by weight, based on the total weight of the dry composition.

10. Process for producing a composition in sheet form according to any one of the preceding claims, wherein said process comprises: grinding the regenerated leather to obtain leather fibres, preferably having an average size preferably not exceeding 8.0 mm, more preferably not exceeding 5.0 mm; adding water to the leather fibres so as to obtain a mixture having a dry content of from 2% to 20% by weight, preferably from 5% to 10% by weight; adding a fatty substance to the mixture; mixing the mixture thus added, and possibly further diluted with water until obtaining a dry content from 0.5% to 5% by weight, preferably from 1% to 3% by weight, with a natural rubber latex; adding a coagulation agent, preferably aluminumsulphate, to the mixture, mixed with natural rubber latex and possibly diluted, so as to coagulate the natural rubber on the leather fibres; depositing the mixture thus obtained on a canvas, so as to form a thin layer from which the water is drained to obtain a sheet; partially removing the remaining water until a residual moisture from 5% to 20% by weight, preferably from 10% to 15% by weight, is obtained.

11. Use as material for writing a composition in the form of a sheet, which comprises:(a) from 40% to 90% by weight of regenerated leather fibres;(b) from 5% to 30% by weight of a natural rubber;(c) from 5% to 30% by weight of a fatty substance; the composition having a residual moisture of 5% to 20% by weight, preferably 10% to 15% by weight; the weight percentages being expressed with respect to the overall weight of the dry composition.

12. Use according to claim 11, wherein the composition is defined according to any one of claims 2 to 9.