WO2013174870A1

WO2013174870A1 - Multilayer material comprising fabric

Info

Publication number: WO2013174870A1
Application number: PCT/EP2013/060518
Authority: WO
Inventors: Massimo DE RIGO; Roberto Pippa; Stefano ZUIN
Original assignee: CONSORZIO VENEZIA RICERCHE; De Rigo SpA
Current assignee: CONSORZIO VENEZIA RICERCHE; De Rigo SpA
Priority date: 2012-05-23
Filing date: 2013-05-22
Publication date: 2013-11-28
Anticipated expiration: 2014-11-23
Also published as: ITMI20120895A1

Description

Multilayer material comprising fabric

DESCRIPTION

The present invention relates to a multilayer material comprising a fabric of natural fibres and plasticized cellulose acetate, a method for its production and an article, in particular a spectacle frame, comprising the multilayer material.

Cellulose acetate is a thermoplastic polymer directly obtainable from cotton or wood pulp (cellulose) by treatment with acetic anhydride.

However, for use as industrial material, cellulose acetate is normally plasticized to decrease its softening and processing temperatures and to transform it into sheets or plates, for example by extrusion. Without plasticizing additives, in fact, the softening temperature of ethyl acetate is very close to its decomposition temperature, which occurs with the formation of volatile substances and with irreversible changes of its characteristics.

Plasticized cellulose acetate (normally by addition of diethyl phthalate in amount 20- 40% w/w ) is one of most widely used polymers in the manufacture of spectacle frames(i.e. eyeglasses, eyewear ). It shows peculiar characteristics and well-known behaviour during processing, which make it virtually irreplaceable in the production of objects with shapes and designs that vary annually according to the market needs of the fashion industry. In fact, the possibility of operating on sheets of variable thickness and colour using highly automated mechanical technologies (cutting, milling etc.) allows to manufacture objects in different forms (patterns) also for the production of small-scale series of eyeglasses. This is an essential economical requirement for the productive sector of the spectacle frames.

The currently used multilayers of cellulose acetate essentially consist of sheets of the same polymer, optionally with different colours. Various designs are obtained by different techniques, including screen printing and pad printing.

For technological applications other than the production of eyeglasses frames, technologies are available for the production of multilayer fabric by impregnating the fabric with intermediate liquids such as for example polyols and isocyanates, which react to form thermosetting polymer type polyurethanes. However, these materials are not bio-degradable and they are difficult to process via the standard machining techniques. Other fabric -polymer multilayers are used in the clothing industry and consist of a limited number of layers, usually resulting in materials less than 2 mm thick, for applications in the sports industry.

For example, EP947313 discloses a multilayer laminate for waterproof and breathable garments comprising a fabric bonded to a coating of polypropylene via an adhesive layer made of olefin polymers. EP922567 discloses a multilayer structure comprising a layer based on unsaturated polymer of acrylonitrile and a layer of an organic polymer. EP2199728 discloses a material for applications in bulletproof fabrics, obtained by pasting a polymeric material of high strength of a base fabric by an adhesive based on polyurethane, polyethylene, polyamide and/or polyester.

US2010330333 describes a composite material comprising a fabric in the form of a sheet and a layer of polyurethane, provided with capillary holes that pass through it, which is joined to the fabric directly or via an additional adhesive layer.

W093/11927 discloses a multilayer material for use in motor vehicles with foams made of polyolefin particles and a decorative layer comprising a fabric with a mesh based on olefin polymers. In EP2177351 a multilayer textile material is described comprising an essentially transparent outer casing of polymer material, such as polyamide, polyurethane, teflon or acrylic polymer, and an inner filling consisting of textile fibres, natural and non-natural, in the form of tops and/or a web.

WO2011/091878 describes a composition comprising a multilayer fabric, at least one layer of foam made from polyvinyl chloride and an outer layer stabilizer comprising a compound of calcium and/or zinc.

WO2011/022031 describes a multilayer material that includes, in addition to a fabric, a layer comprising high modulus fibres, in a non-vowen form, that are not oriented in a thermoplastic matrix consisting of polyolefins, polyesters or polyamides.

WO2010049743 relates to a multilayer material comprising a fabric and a metallic layer joined together using an adhesive layer of plastic material.

US 2,036,424 relates to the impregnation of cellulose materials such as cloth, thread, paper etc. with an organic solvent solution of a cellulose ester or ether to obtain a material suited for electrical insulation or a moisture-resistant thread.

US 4,061,823 discloses a highly machinable, shapeable decorative laminate made from a non-abrasive base core consisting of a plurality of sheets, each sheet consisting essentially of cotton linter fibres in paper form containing a curd phenolic resin, the core having superimposed thereon a print sheet impregnated with a cured thermoset resin.

GB 2322099 provides wear-resistant laminated articles, in particular composite rotor blades of natural fibre or regenerated natural fibre -reinforced thermoset resin with an aramid fibre-fabric working surface to reduce erosion in use.

The plastic materials used for the preparation of the multilayer according to the prior art are, partially or totally, petroleum derivatives, i.e. deriving from a non-renewable source, and hardly recyclable and/or biodegradable. Moreover, the materials comprising multilayer fabrics according to the prior art are hardly treatable by the techniques normally used for the machining of spectacle frames, as they are subject to delamination of the layers or general deterioration during such treatments as cutting, milling, hot bending etc.

An object of the present invention is to provide a multilayer material that is more eco-friendly and bio-degradable than the prior art materials.

An aim of the present invention is to provide a multilayer material, comprising a fabric, which is readily-machinable by the techniques normally used in manufacturing, particularly in the production of frames for glasses.

Another aim of the present invention is to provide a material, preferably in the form of sheet or semi-finished plate, which can be used in the production of a manufactured product having the outer surface with a tactile sensation similar to a fabric and with designs and textures derived from those usually found on clothes.

This object, and others that will be better apparent hereinafter, are achieved by a multilayer material comprising at least one layer a) and at least one layer b), alternating and permanently adhering to each other, wherein:

- layer a) comprises a fabric of natural fibres impregnated with a substance selected from a plasticized cellulose acetate polymer, a polymer or copolymer of at least one alkyl acrylate, a polyester or a functionalized polyether urethane, or mixtures thereof, and

- layer b) comprises a polymer of cellulose acetate comprising at least one plasticizer.

This goal was also achieved by a sheet or a finished or semi-finished item, selected from an eyeglasses frame, an household good, a piece of furniture, an eyeglasses case, an automotive or vehicle component comprising said multilayer material. This aim is also achieved by a process for the preparation of said multilayer material comprising the steps of:

a) impregnating a fabric of natural fibre with a solution comprising a plasticized cellulose acetate polymer and at least one organic solvent, or with an emulsion or with an aqueous suspension of an alkyl polyacrylate, a polyester or a functionalized polyether urethane, or mixtures thereof ;

b) drying the impregnated fabric obtained in step a) completely or almost completely by removing the organic solvent or water;

c) overlaying, in an alternating sequence, one layer of the impregnated and dried fabric obtained in step b) and a layer of cellulose acetate comprising at least a plasticizer, to obtain a semi-finished multilayer material;

d) joining the layers of the semi-finished material of step c) forming a multilayer material by thermo compression at 120 to 190°C and with a closure force from 1 to 10 tons for 1 to 20 min, wherein temperature, pressure and time of the treatment may vary according to the number of layers and the thickness of the material to be obtained, and

e) cooling multilayer material of step d) to 20-30°C under a closure force from 10 to 25 tons in 1 to 15 min.

Figures 1-4 and tables 1-6 disclose experimental data to provide a better understanding of the invention, without intending to limit the purpose:

- Table 1 : "Peeling test" according to ASTM D9033 of different samples of the material according to the invention and of a comparison material (Sample iii).

- Table 2: Comparison of the mechanical properties (according to ASTM UNI EN ISO 13934-1) on plates of a sample according to the invention and of a sample of the prior art (CAp "as is").

- Table 3: Comparison of the mechanical flexural properties (ASTM D790) of plates according to the invention and of the prior art (CAp "as is") at various temperatures and thermal HDT (ASTM D648), thickness 4 mm.

- Table 4: Comparison of data on plates according to the invention and a prior art (CAp as is) for notched Izod impact strength (ASTM D256) on 4 mm-thick sheets.

- Table 5: Tensile mechanical properties of a non-impregnated fabric (T) and a CA- impregnated fabric at +23 ⁰ C (UNI EN ISO 13934-1).

- Table 6: test of eyeglasses frames according to the UNI EN ISO 12870. Figure 1 : Photograph of multi-layer according to the invention with CA-impregnated Denim Silverstone - CAp Sheet (Optiroid™ by Mazzucchelli 1849 S.p.A.), total thickness 6 mm.

Figure 2: Production Scheme for the multilayer material (e.g. with cellulose acetate as impregnation polymer) according to the invention.

Figure 3: Stress strain curve (UNI EN ISO 13934- 1) Jacky Royal8™ fabric as is (sample T) and Jacky Royal8™ impregnated with 77% w / w CA for treatment with a solution of CA 8% in acetone ( sample T-CA1, CA-T curve).

Figure 4: Photograph of Sample n. 120476 subjected to tests for eyeglasses frames according to ISO 12870.

In the context of the present invention, it is understood that an element or composition "comprising" a certain substance may consist of said substance or of a mixture including said substance, in addition to other substances.

In the context of the present invention, it is intended that a solvent (or water) is totally removed or almost completely from a composition when the content of free solvent after drying is reduced to less than 90% of the initial content, preferably to less than 95% or less than 99%.

In the context of the present invention, "alternating layers" of two different materials having contact faces are layers in any sequence, wherein each layer can be adjacent, on each contact face, to a layer of the same material or of different material (e.g., naming the two materials A and B, the sequence of layers can be ABABAB, ABBA, BAABABABAABB etc.).

In the present invention, the term "natural fibres" includes fibres of vegetable origin such as, but not limited to, cotton, hemp and flax, and of animal origin such as, but not exclusively, wool and silk, and mixtures thereof.

The terms "fabrics" and "cloth" indicate a product obtained by weaving (traditional fabric, denim cotton type) or through different methods (type "non- woven", for example, obtained by pressing of stacked layers).

In the context of the present invention, the term "alkyl acrylate" means an acrylic (or polyacrylic) acid ester with methyl alcohol, ethyl and/or butyl.

In the context of the present invention, the term "cellulose acetate" indicates a cellulose ester, normally diacetate or triacetate, obtained by acetylation of cellulose, which can have an acetylation degree between 50-62% by weight of acetic acid liberated by basic hydrolysis of cellulose acetate.

In the context of the present invention, the term "plasticized polymer" means a mixture comprising a polymer and at least one plasticizer.

In the context of the present invention, the term "plasticizer" means a substance, miscible with the polymer, which can reduce the glass transition temperature (Tg) of the polymer, so as to lower its softening temperature and the viscosity of the melt, and to allow the machining of the material at temperatures below the decomposition temperature, avoiding the loss of functional, visual and tactile properties. Non- limiting examples of plasticizers in the present invention are esters of alkylphthalates (dialkylphtlalate as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-2- methoxyethyl phthalate), trimellitates (trimethyl trimellitate, triethyl trimellitate and tributyl trimellitate), esters of orthophosphoric acid (triphenyl phosphate, triethyl phosphate, tricresyl phosphate, ethylhexyl diphenyl phosphate, isodecyl diphenyl phosphate), citrates and biodegradable plasticizer (triethyl citrate, acetyl triethyl citrate, acetyl tributyl citrate), benzoates (ethyl-or benzoyl benzoate), tartrate (dibutyl tartrate), etilftaliletilglioclato (EPEG) methyl-phthaltlethyl glycoate (MPEG), N- ethyltoluensulfonamide, O-cresyl p-toluene sulfonate, and mixtures thereof, also "bio-plasticizers" made from renewable resources, for example by fermentation of biomass from succinic acid, or fully hydrogenated castor oil ( castor oil), acetylated monoester of glycerol, glycerine triacetate (triacetin), glycerine diacetate ( diacetin ) and 1,2-hydroxystearic acid.

The term "a solution of plasticized cellulose acetate" means a composition wherein a polymer is dissolved in an organic solvent to obtain a solution with a concentration by weight less than 30% and with suitable viscosity to penetrate and impregnate a fabric. Non-limiting examples of solvents for cellulose acetate are: acetone (also in mixtures with 5- 10% water), methyl-ethyl ketone, cyclohexanone, diacetone alcohol, methyl acetate, ethyl acetate, ethyl lactate, methyl glycol, methyl glycol acetate, dimethylformamide, tetrachlorofurane and methylene chloride (also in mixture with 10% methanol).

Unless otherwise specified, in the context of the present invention, percentages of the components of a mixture refer to weight of the component with respect to the total weight of the mixture (w/w).

Unless otherwise specified, in the context of the present invention, the beginning and ending values of a range are included in the numerical values of the ranges (relating to width, thickness, etc.).

In one embodiment, the present invention provides a multilayer material comprising at least one layer a) and at least one layer b), alternating and permanently adhering to each other, wherein:

- layer a) comprises a fabric of natural fibres impregnated with a substance selected from a plasticized cellulose acetate polymer, a polymer or copolymer of at least one alkyl acrylate, a polyester or a functionalized polyethereurethane, or mixtures thereof, and

It has been surprisingly found that the material according to the present invention, when subjected to the machining typically used in the manufacture of eyeglasses frames, has characteristics of higher resistance compared to products comprising multilayer material of the prior art.

In fact, preliminary laboratory tests were performed preparing 4 mm thick, 80 mm wide and 105 mm long specimens.

The comparison specimen, obtained by thermo-compression (130- 160°C) of alternating layers of fabric and sheets of CA by 0.5 mm in thickness, shows a good surface appearance but an insufficient adhesion between the layers, such as to show detachments of layers for 90° bending of specimens, with evident de-laminations between the layers.

The delaminated layers show a low penetration of CA within the texture of the fabric and wires. A cutting test using a rotary cutter results in a high formation of "unraveling" (with damaged/breaking yarns) of the fabric and detachment of the layers, which cannot be improved by changing the cutting parameters (type of mills, speed, etc.).

Therefore, it is evident that the adhesion of the layers of the material obtained by simple thermo-compression is insufficient and that the limited thermal stability (degradation) of the polymer (CA) does not allow operating at higher temperatures in order to decrease the viscosity of the "free-flowing" polymer and to improve penetration within the fabric.

Test multilayer materials were obtained by thermo-compression of interposed layers of natural fibres fabrics and layers of plasticized cellulose acetate approximately 0.5 mm thick, wherein the latter layers are on one or on both sides of the fabric. Even these multilayer materials show a layer adhesion that is insufficient to ensure a good workability, for example by milling or cutting.

It has been found that a surprising improvement of adhesion between the layers is obtainable by pre-treating the fabrics of natural fibres with a solution of plasticized cellulose acetate, or with an emulsion or aqueous suspension of polyacrylate alkyl or a polyester or polyether urethane or mixtures thereof, so that the fabric and its yarn are impregnated, preferably in depth, with the solution or emulsion or aqueous suspension, to a suitable concentration and method of application, and that, after evaporation of the solvent or water, the polymer covers and impregnates the whole weft, warp and yarn, where present, of the fabric.

Optionally, with repeated sequences of impregnation and drying, ratios of polymer / fabric can be achieved as high as needed, also, as a non-limiting example, in 1 : 1 polymer / fabric weight ratio.

For the preparation of the multilayer material, said treated fabric (TP) is the layer which is alternated to the sheets of plasticized cellulose acetate (CAp) obtaining, for example, a sequence (TP / CAp / TP / CAp) n where n is a number equal to or greater than 1, up to the desired thickness of the sheet.

It was found that the adhesion between the layers containing the treated fabric TP and the sheets of plasticized cellulose acetate CAp is very high.

Furthermore, the natural fibre cloths that are evenly coated/impregnated by the polymer, after evaporation of the solvent, are more rigid than the un-impregnated/un- coated fibre.

As a result, the multilayer material according to the invention can be mechanically processed, for example cut or milled, causing substantially no ravellings, obtaining surfaces, either smooth or with the texture of the fabric, that are resistant and aesthetically pleasing and do not produce sharp edges or surfaces in case of breakage.

Preferably, in the multilayer material according to the invention, the plasticizer content of the layer a) and/or b) is from 20 to 40% by weight on the total weight of the layer. Preferably, in the multilayer material according to the invention, the plasticizer of the layer and/or b) is diethyl phthalate. Preferably, in the material according to the invention layer a) is from 0.1 to 2.0 mm thick, preferably 0.5 mm, and layer b) is from 0.1 to 4, 0 mm thick.

It has been found that it is particularly advantageous to use natural fibre fabrics, since, in this way, an optimum adhesion is obtained with the adjacent layers of cellulose acetate. In this way, moreover, compared to plasticized cellulose acetate multilayer materials of the prior art, the required amount of plasticizer (usually greater than 20% in weight), which is produced mainly from petroleum derivatives, is decreased. Thus, the multilayer material according to the invention is a material with a greater quantity of components obtained from renewable resources (bio-based materials), therefore more environmentally friendly and, advantageously, also more bio-degradable.

Preferably, in the multilayer material according to the invention the natural fibre consists of or comprises cotton.

Preferably, the plasticizer used in the layers a) and/or b) of the multilayer material of the invention is obtained from completely or partially renewable resources (bio- plasticizer).

Preferably, the plasticizer used in the layers a) and/or b) of the multilayer material of the invention is biodegradable or compostable.

Preferably, the natural fibre is cotton, in particular in the form of denim fabric, and the fabric is up to 100% cotton, impregnated with the polymer of cellulose acetate plastic.

The multilayer material of the present invention may consist of alternating layers of: - Fabric of natural fibres, preferably cotton, with different texture and weight, preferably denim, which can be treated with products and processes normally used in the textile and clothing industry, such as natural dyes, for example indigo which can enable the effect "washed", "aged" in the typical style of "jeans", and with dyes or synthetic colours that are stable to washing. The choice of fabric is independent of the weft, warp, yarn weight. Said fabric is modified by impregnation with a polymer such as plasticized cellulose acetate, or polar thermoplastic polymers "compatible" (i.e., able to adhere permanently after a process such as thermo-compression) with plasticized cellulose acetate, such as for example polyalkylacrilates or modified polyesters (sulfonates) or polyether urethanes.

Preferably, in the multilayer material according to the invention the polymer impregnating/coating the natural fibre is at least one of cellulose acetate or methyl ethyl or butyl acrylate, and/or their copolymers, terpolymers, also bio-polymers, compatible, miscible or partially miscible with the cellulose acetate.

The plasticized cellulose acetate used as a layer adjacent to the layer of impregnated fabric may comprise a type and a quantity of plasticizer normally available from manufacturers of semi-finished materials in sheet (thickness 0.2-0.5 mm) or plate (thickness 1 - 10 mm). Examples of these materials may be Mazzucchelli 1849 SpA: type Optiroid™, LA / ES SpA: Type Optistyle™ 2000 (98-8688), or Mazzucchelli 1849 SpA M49™-type bioplastic (For example, as the materials described in WO2012004727). Preferably the amount of plasticizer is from 20 to 40%, more preferably from 30 to 40%, in weight / weight of the layer of plasticized cellulose acetate.

The thickness of the layer of plasticized cellulose acetate can be chosen in function of the mechanical properties and of the aesthetic requirements of the final multilayer material, for example, the thickness can be from 0.1 mm to 4 mm, preferably 0.5 mm.

To obtain the multilayer material of the invention, different technologies can be used. For example, the multilayer material of the invention can be obtained using thermo- compression and/or coupling, which provide the possibility of forming the alternating layers comprising, generally, a small number of high thickness layers for applications in the automotive sector or a small number of thin layers for the sector of textiles and clothing (waterproof, windproof, breathable technical fabrics etc.). The multilayer material according to the invention obtained by thermo-compression, for example in press plates, can be of variable thickness, depending on the needs of subsequent machining, for example as high as 10 mm, comprising 13 layers of an impregnated denim fabric and 15 layers of cellulose acetate plastic (CAp).

More variations are possible on the sequence of the layers, for example:

- Two outer impregnated fabric (TP);

- One external (TP) and the second external (CAp);

- Inner layers of different thickness to CAp;

- Impregnated fabric (TP) of different texture and colour;

- Fabrics dyed with natural or synthetic colours.

In another embodiment of the invention, the fabric may be impregnated with polymers other than cellulose acetate, for example with an emulsion or suspension polymers of the alkyl polyacrylates type, insoluble in water, or with a functionalized polyester (e.g., sulfonate) or with a polyether eurethane, or mixtures thereof.

In the material according to the present invention, the fabric may be impregnated with functionalized polyester in mixture with other substances, for example polyester sulfonate can be used in mixture with polyacrylic acid.

The fabric can be treated with a series of repeated impregnations and drying, preferably by impregnating it with a polymer of alkyl acrylate (Acr-T). These polymers are normally used in the technologies of finishing yarn and show good adhesion and compatibility with the fabric, in particular with cotton. Also in this embodiment, the amount of acrylic polymer that coats the fabric can be up to about 100% of the weight of the fabric. The subsequent stages of the preparation of the multilayer material are equal to those for the fabric impregnated with cellulose acetate.

The multilayer material according to the present invention is workable with all the mechanical cutting technologies, also automated, known to the person skilled in the art and normally used for the manufacture of spectacle frames from sheets of plasticized cellulose acetate alone.

In particular, without changing substantially the procedures and equipment currently in use, or making minimal changes, the following steps can be performed on the material of the invention:

• bonding with acetone;

• cutting, milling and drilling various profiles;

• die-cutting the piece;

· inserting hinges and metal rods;

• carrying out operations such as contouring, encapsulation, tumbling, lacquering, bending, or

• proceeding with the lens mounting under pressure.

Furthermore, the multilayer material according to the present invention shows an improved impact behaviour even at low temperatures with respect to the materials comprising only cellulose acetate normally used in eyeglasses frames of the prior art, particularly with a significant increase of notched IZOD resilience of ca. 500% both at +23°C and at -30/-20°C with typical morphology of the fracture surfaces of a tough material with incomplete rupture, without formation of sharp edges or surfaces.

The multilayer material of the invention can be prepared in various forms, including plates or sheets of different thicknesses.

In one embodiment, the present invention relates to a plate comprising said multilayer material, which comprises at least one layer a) and at least one layer b), alternating and permanently adhering to each other, wherein a) and b) comprise: a) a fabric of natural fibres impregnated with a substance selected from a plasticized cellulose acetate polymer, a polymer or copolymer of at least one alkyl acrylate, a polyester or a functionalized polyethereurethane, or mixtures thereof, and

b) a polymer of cellulose acetate comprising at least one plasticizer.

Besides the application in the production of spectacle frames, the multilayer material of the invention and the sheets/plates that comprise it can be used in eco-friendly manufacturing in various fields, e.g., as a non-limiting example, for furniture, household goods, cases for glasses, plates, thermoformed sheets to produce components for aesthetic finishing of internal and/or external surfaces in the automotive industry such as dashboards, inserts, etc.

In one embodiment, the present invention relates to an artefact selected from a piece of furniture, a case for glasses, a component for automobiles or a vehicle comprising said multilayer material.

In one embodiment, the present invention relates to an eyeglasses frame comprising said multilayer material.

In another embodiment, the present invention relates to a process for the preparation of said multilayer material comprising the steps of:

a) impregnating a fabric of natural fibre of a solution comprising a plasticized cellulose acetate polymer and at least one organic solvent, or of an emulsion or of an aqueous suspension of an alkyl polyacrylate, a polyester or a functionalized polyether uretane, or mixtures thereof ;

c) overlaying, in an alternating sequence, one layer of the impregnated and dried fabric obtained in step b) and a layer of cellulose acetate comprising at least a plasticizer, to obtain a semi-finished multilayer material; d) joining the layers of the semi-finished material of step c) to form a multilayer material by thermo-compression at 120 to 190°C, with a closure force from 1 to 10 tons for 1 to 20 min, wherein the temperature, pressure and time of treatment may vary according to the number of layers and the thickness of the material to be obtained, and

e) cooling to 20-30°C under a force of 10-25 tons in 1 to 15 min.

Preferably, in step a) of the method according to the invention a solution in acetone is used, if the polymer comprises cellulose acetate plasticized or a suspension, or an aqueous emulsion is used, if the polymer comprises an alkyl acrylate and/or a functionalized polyester and/or a polyether urethane.

Preferably, the solution of cellulose acetate that is used to impregnate the fabric is obtained by dissolving plasticized cellulose acetate in the solvents normally used in the prior art, for example acetone, with concentrations varying according to the technique of impregnation, such as immersion and absorption, coating with or without pressure, brushing, spraying, etc. also using solutions containing plasticized cellulose acetate in 30% by weight / total weight of the solution, preferably in a concentration from 8 to 10% by weight / total weight of the solution, having a viscosity that suitable for the impregnation technique and penetration into the fabric and in the yarn.

The following examples are provided to better illustrate the invention, without intent to limit it.

Selection of the fabric and of the Cellulose Acetate plastic (CAp) sheet or plate. The fabric is made of natural vegetable or animal fibres, in particular cotton, with various wefts and warps, in particular "denim", also with drawings, paintings etc. and with variable weight, for example from 150 to 1000 g / sqm.

For example, the following fabrics were used in cotton "denim":

- ROYAL DENIM JAKY 8™ Berto Textile Industries with the following characteristics:

- Finished fabric with a weight of 275 g / m² and thickness approx. 0.4 mm;

- Washed at 90°C to remove all impurities (sizings, textile oiling, dirt, etc.).

- Finished by de- sizing to eliminate the sizing of warp yarns, making the fabric absorbent and homogeneous for the subsequent processing steps, compacting and shrinking of the plots; - dyed with an indigo dye (i.e., treated with a dispersion of indigo dye, with the addition of various substances, such as alkali, acid and other auxiliaries, the indigo dye was deliberately chosen because extractable with water washing).

- DENIM SILVERSTONE80™ (hereafter "Silverstone") of Berto Textile Industries: - Finished fabric with a weight of 400 g / sq m, and 0.7 mm thick

- Washed at 90°C to remove all the impurities;

- Subjected to a final finishing of dye carriers (bath with starch to improve the appearance and to render the fabric more wear resistant) and shrinking for compacting the plots;

- dyed with coloured indigo dye (i.e. treated with a dispersion of indigo dye by addition of various substances, such as alkali, acid and other additives), deliberately chosen because extractable with water washing.

Unless otherwise specified, the plasticized cellulose acetate used in the examples contains diethyl phthalate as a plasticizer in amount of 20 to 38% by weight / total weight of the acetate and of the plasticizer.

Plasticized cellulose acetate used in the examples comprises (hereinafter: CAp) with standard synthetic diethyl phthalate plasticizers such as those available from Mazzucchelli 1849 SpA, or with plasticizers made from renewable resources and/or with biodegradable plasticizers, in the form of sheets or plates of the desired thickness, for example 0.2 - 4.0 mm, preferably 0.5 mm.

Treatment of the fabric.

The fabric, in continuous or discontinuous systems on sheets of the same size of the plate, is impregnated with a solution of CAp, preferably of the same type used for plasticized sheets or plates, in a solvent thereof, preferably acetone. The concentration of the solution of CAp may vary from 2% to 30% by weight / total weight of the solution, preferably 10% by weight in terms of its viscosity sufficient to penetrate into the fabric texture and impregnate the yarn. The operation can be performed with various methods and equipment, such as for example: immersion and absorption, coating with or without pressure, brushing, spraying, etc.

In alternative to the CAp, the fabric may be impregnated with emulsion and/or aqueous suspensions of thermoplastic polymers compatible with CA, for example acrylic polymers or copolymers (alkyl acrylates), polyesters etc.

Drying The drying can be performed with a variety of technologies known to those skilled in the art in controlled thermal environment, aspirated and suitable, according to the environmental regulations and safety, for the recovery and recycling of the organic solvent, for example acetone. As known to the person skilled in the art, the amount of CAp (% by weight on the weight of the fabric) optimal for good adhesion in the multilayer may vary according to the type of fabric, for example from 1 to 200% by weight, preferably 50% by weight, if the amount of CA is not achieved with a cycle as described above, the above steps are repeated for the procedure cycles until it reaches the desired impregnation. The impregnated fabric is more rigid than the non- impregnated one but it can be rolled without delamination of the polymer from the fabric. After drying, the impregnated fabric may contain a residual organic solvent in an amount less than the limits prescribed by the relevant regulations.

For aqueous suspensions or emulsions of polymers compatible with CAp, the procedure is similar to that already described for the CAp, with drying of the water up to a residual value of less than 0.1% by weight for example by drying at 60-70°C for 5-6 hours.

Composition of the layers

A variety of multilayer materials of fabric and CAp alternating sequence can be obtained with different possibilities of having both the outer layers of CAp, both of impregnated fabric or alternating. Sheets of fabric treated and CAp equal to the measures of length and width of a flange-mold with variable thicknesses are cut out, for example, from 3 mm to 15 mm, preferably 6 mm. The number of sheets is determined by the thickness of the sheets of the treated fabric and of those of CAp, so that the sum of the thicknesses of all sheets exceed 20-70% of the thickness of the flange-mold, preferably 40%, achieving a good ratio of compression in the next step. Molding by thermo-compression

This is performed in a temperature range of 120- 190°C, preferably 150°C and a closure force of plates between 1- 10 tons preferably 2 tons and for 1-20 minutes depending on the thickness of the plate. Subsequently, the plate thus obtained is cooled, or allowed to cool, to room temperature under a force of 10-25 tons, preferably 20 tons, for 1- 15 minutes.

Finally the plate is detached from the mold and can be used as semi-finished product, in particular for the processing normally used for the manufacture of spectacle frames from plates of plasticized cellulose acetate polymer or for the production of objects, cases for glasses, aesthetic components for furniture or automotive also obtained for thermoforming. EXAMPLE 1

A denim cotton fabric of Silverstone™80 type, average thickness 0,72 mm, weight 400 g/m² and a denim cotton fabric, thickness 0.4 mm, Jacky Royal™ 8 type, weight 275 g / sq m, are cut into pieces (width 8 cm and length 18 cm). These pieces are impregnated with various polymers as described for the preparation of the following samples:

- Sample A: Fabric Silverstone impregnated with a solution of plasticized cellulose acetate (8% by weight / total weight of the solution in acetone), for 4 successive stages of immersion impregnation / brush and drying by evaporation of the solvent in an oven at 40°C, with an increase in final average weight of 43% referred to the initial weight of the fabric;

- Sample B - Fabric Silverstone with aqueous micro-emulsion of alkyl acrylate polymer (Atom™ Colorificio S. Marco) to 30% by weight / total weight of the micro-emulsion, for an impregnation and drying by evaporation of water in oven at 70 ⁰ C, with a increase in weight of 29% in relation to the initial weight of the fabric; - Sample C - Fabric Silverstone with no treatment of impregnation with polymers.

- Sample D - Fabric Jacky Royal 8, impregnated as sample A, with a solution of cellulose acetate but with a concentration equal to 25% by weight / total weight of the solution in acetone;

- Sample E - Fabric Silverstone with aqueous solution of polar polymer, polyester sulfonate, coating for textile (Dicrylan 7836 of Huntsman) for impregnation and drying by evaporation of water in oven at 70°C, an increase in weight of 10% reported to the initial weight of the fabric;

- Camp. F - fabric Jacky Royal 8, impregnated as sample A, with a solution in acetone to 8% by weight of cellulose acetate plasticized (Optiroid - Mazzucchelli 1849 SpA) but with increase in weight of 77% referred to the initial weight of the fabric. With the same measures were cut sheets 0.5 mm thick polymer cellulose acetate plastic (CAp) produced by Mazzucchelli 1849 Spa - type Optiroid.

These were placed inside a stainless steel 8 X 18 cm frame and a thickness of 4 mm or 6 mm, placed between two stainless steel plates, according to an order of alternating sequence, according to the following criterion for the various samples :

- i. With 6 layers of impregnated fabric Silverstone (sample A) alternating with 5 sheets of polymer CAp, with outer fabric impregnated final thickness of the sheet 4mm;

- ii. with 7 layers of fabric impregnated Silverstone (sample B) alternating with 6 sheets of polymer CAp for final thickness of the sheet 6 mm;

- iii. as previous sample L, but with fabric Silverstone not impregnated, final thickness of the slab 4 mm;

- iv. with 6 layers of impregnated fabric Jacky Royal 8, (sample D) alternating with 5 sheets of CAp for final slab thickness 4 mm;

- v. as sample, ii., 7 layers of impregnated fabric Silverstone (sample E) alternating with 6 sheets of CA for the final plate thickness 6 mm;

- vi. with 4 layers of fabric Jacky Royal 8, impregnated with cellulose acetate (referred to as TCA, sample D) and 2 sheets of CAp 0.5 mm thick and a central 2.00 mm CAp with the following sequence:

TCA TCA-2mm-CAp-CAp-CAp-TCA-TCA

(The central sheet with a thickness of 2 mm is produced by LA-ES SpA type Optistyle 2000).

The sample is placed between the plates of an electrically heated hydraulic press, model P7 34E (Campana Sri; CVB Campana Ing Benedict) with dishes electrically heated to a temperature of 150-160°C and a maximum closure force of 2 tons is applied for 10 minutes, then the press plates are opened and the multilayer material are placed between air-cooled plates and under maximum closure force of 25 tons for 5 minutes. After cooling, multilayer plates are obtained with the following thicknesses:

camp. i. thickness 4.4 mm;

camp. ii. thickness 6.3;

camp. iii. thickness 4.0 mm;

camp. iv. thickness 4.4 mm;

camp. v.. thickness 6.2 mm;

camp. vi. thickness 4.5 mm

From the multilayer plates obtained by the above procedure, the specimens are obtained by cutting in the shape and dimensions provided in the following physico- mechanical characterization.

Adhesion between the layer of impregnated or not-impregnated outer fabric and the sheet of CAp is evaluated by determining the force required for the separation according to the method ASTM D903 "Peeling Test" at 180°C, by dynamometer with the following criteria: from the apex is detached, with the use of any tool if needed, the fabric layer that adheres to the CA layer, the two flaps are locked in the terminals and the dynamometer crosshead is moved at a speed of 250 mm / min, recording the applied load, with cells from 10 KN. This determines the average load (N), which, divided by the width of the test, shows the peeling strength in N / mm.

The results, shown in Table 1, demonstrate that sample iii., obtained with untreated fabric, has the lowest level of adhesion, while samples L, ii., iv., v. and vi., all variants with impregnation treatment of the fabric, show significant increases in adhesion.

The increase of adhesion strength (Fad) for the various samples can be expressed as the ratio between (Fad) sample / (Fad) of sample iii, which is taken as reference. This represents a remarkable advantage of the multilayer material of the invention, which shows a significant increase of adhesion strength between the layers compared to untreated materials.

EXAMPLE 2

The following example shows the physical-mechanical characteristics of the fabric / CAp multilayer plates compared to the slab of CAp such (4 mm thick) normally used (commercial material Optiroid - Mazzucchelli 1849 SpA).

The specimens were cut with a 4 mm slab cutter and prepared in the manner described in Example 1, and relative to samples i. and vi. After conditioning in the laboratory at 23°C and 50% relative humidity, tests were carried out for:

- RESISTANCE TO TRACTION (UNI EN ISO 13934- 1) on 127 x 13 x 4 mm bars, crossbar speed 50 mm/min on CAp sample "as is" and on sample i. (Table 2);

- FLEXURAL PROPERTIES (ASTM D790) on 127x13x4 mm bars support distance 80 mm, cross speed 2mm/min on sample CAp "as is", Sample L, Sample vi. at +23°C, +40°C, -20°C (Table 3)

- NOTCHED IZOD IMPACT STRENGTH (ASTM D256) at +23°C, -20°C on samples of CAp as is and on Sample L, and +23°C, -30°C on Sample vi. (Table 4) - THERMAL PROPERTY - deflection temperature under flexural load (HDT) (ASTM D648) on samples: CA as is, Sample A (Table 3).

The results of these characterizations are shown in Tables 2 to 4.

In reference to the plate of CAp "as is", an improvement of the module is observed at the different temperatures for sample vi., whereas sample L, with less rigidity, shows an important increase in the impact resistance, also detected by observations at the optical microscope of the fracture surfaces. Sample i. does not show a complete rupture of the specimen, "hinge" effect, and no detachment is observed between the layers even at low temperatures (-20 °C). Sample vi. shows a very high level of notched impact strength at low temperatures (-30°C), which allows to obtain manufactured articles, for example spectacle frames, which are not subject to brittle fracture with sharp, hence dangerous, edges. The thermal properties (HDT) are substantially unchanged.

Therefore also the improvement of the mechanical properties of multi-layer plates of the invention is a significant and unexpected advantage.

EXAMPLE 3

The mechanical properties are determined for a sample ( named T) of denim fabric (Jacky Royal 8) and for a sample of the same material impregnated with 77% w/w of CA by treatment with 8% w/w CA solution in acetone and drying (sample named T- CA1), a process repeated four times. The results are reported in tab. 5 and in fig. 3, where the stress-strain curve to traction is shown (UNI EN ISO 13934- 1).

In the initial portion of fig. 3 the typical contribution of the polymer in the fabric deformation is observed, indicative of a strong interaction between the polymer and the fibres, which form the warp of the fabric.

The impregnated fabric shows behaviour to tensile deformation more similar to a sheet of thermoplastic polymer. EXAMPLE 4

Description of the aesthetic and processing results of the glasses.

Multi-layer plates (size 80-180 mm. Thickness 6.5 mm) is prepared by thermo- compression in the manner described in Example 1) for sample F with: - Denim fabric, Jacky Royal™ 8, impregnated (TCA) with 70% of its initial weight of plasticized cellulose acetate by application and drying of four coats of acetone solution with 8% w/w of plasticized cellulose acetate (Optiroid™-Mazzucchelli 1849 SpA), 9 layers applied (TCA);

- Sheets of cellulose acetate plastic (CAp), 0.5 mm thick (Optiroid™-Mazzucchelli SpA), 8 layers (applied CAp);

- multi-layer plates consist of the following sequence: TCA-CAp-CAp-TCA-TCA- TCA-CAp-CAp-CAp-TCA-TCA-TCA-CAp-CAp-CAp-TCA-TCA (TCA outer layers).

The plates were mechanically processed (cut, milled, etc.). according to the usual mode of production of a spectacle frame, without ravellings or separation of the layers and with a very good and original surface appearance.

The frames thus obtained, sample n. 120476 (fig. 4), are subjected to the following tests according to ISO 12870:2004 - Spectacle frames:

Test A6 - Contact area -

4.6 - Dimensional stability at high temperature (+55°C +5)

4.7 - Resistance to perspiration

4.9 - Resistance to ignition

4.10 - Resistance to Xenon Radiation.

The frame is found to comply with the above tests, as reported in Table 6.

Therefore the multilayer sheets (semi-finished) obtained according to the present invention are suitable to produce eyeglasses frames or other items that are produced using similar technologies such as machining, thermoforming, gluing, etc.

Tab.1 - "Peeling Test" (ASTM D903)

Tab.2 -Tensile properties (UNI EN ISO 13934-1) on plate sam

Samples

CAp (as is),

Property

comparative

Tensile strength [N] 15.8 ± 0.1 22.1 ±0.2

Yield strength [MPa] 29.4 ±0.1 22.0 ±0.7

Elongation at yield point [%] 6.4 ± 1.1 4.4 ±0.1

Ultimate tensile strength [MPa] 25.6 ±0.4 44.6 ± 0.6

Ultimate elongation [%] 14.0 ±1.4 33.7 ±0.5 Tab. 3 - Flexural properties (ASTM D790) on plates at different temperatures, and deflection temperature (HDT according to ASTM D648) under flexural load.

Thickness 4 mm.

Tab. 4 - Izod impact strength (Notched Izod; ASTM D256) on plates. Thickness 4 mm.

Samples

CAp as is

Property Temperature i vi

(comparative)

Izod [kJ/m²] 53 ± 2 25.33 11

+23 °C

Izod [J/m] 530 ± 20 257.34 112 ± 1

Izod [kJ/m²] 32 ± 6 - 1

- 20 ^<€

Izod [J/m] 330 ± 60 - 11

Izod [kJ/m²] - 13.16 -

- 30 ^<€

Izod [J/m] - 133.73 - Tab. 5 - Tensile mechanical properties of a non-impregnated fabric (T) and of impregnated fabric at +23 C (UNI EN ISO 13934-1).

Tab. 6 - Tests on eyeglass frames according to UNI EN ISO 12870.

Claims

I . A multilayer material comprising at least one layer a) and at least one layer b), alternating and permanently adhering to each other, wherein:

2. The multilayer material according to claim 1 wherein the content of plasticizer in layer a) and/or b) is from 20 to 40% by weight on the total weight of the layer.

3. The multilayer material according to claims 1 - 2 wherein the plasticizer of a) and/or b) is diethyl phthalate.

4. The multilayer material according to claim 1 and 2 wherein the plasticizer of a) and/or b) is obtained from completely or partially renewable resources (bio-based plasticizer).

5. The multilayer material according to claims 1 - 2 wherein the plasticizer of a) and/or b) is biodegradable or compostable.

6. The multilayer material according to one of the preceding claims wherein layer a) is from 0.1 to 2.0 mm thick and layer b) is from 0.1 to 4.0 mm thick.

7. The multilayer material according to one of the preceding claims wherein the natural fibre is constituted by or comprises cotton.

8. The multilayer material according to claim 7 in which in which the fabric is denim.

9. The multilayer material according to one of the preceding claims wherein the polymer which impregnates the natural fibre in layer a) is cellulose acetate or methyl ethyl or butyl acrylate, and/or their copolymers, terpolymers, and bio-polymers, that are compatible, miscible or partially miscible with the cellulose acetate.

10. A finished or semi-finished sheet or plate comprising the multilayer material according to the preceding claims.

I I . A spectacle frame comprising the multilayer material according to the preceding claims.

12. A finished or semi-finished item, selected from an decoration object, a piece of furniture, an eyeglasses case, a component for a car or a vehicle, wherein the item comprises the multilayer material according to the claims 1-9.

13. A process for the preparation of a multilayer material according to claims 1-9 comprising the steps of

a) impregnating a fabric of natural fibre with a solution comprising a plasticized cellulose acetate polymer and at least one organic solvent, or with an aqueous emulsion or suspension of an alkyl polyacrylate, a polyester or a functionalized polyether urethane, or mixtures thereof ;

d) joining the layers of the semi-finished material of step c) forming a multilayer material by thermo-compression at a temperature from 120 to 190°C and with a closure force from 1 to 10 tons for 1 to 20 min, wherein temperature, force and time are variable according to the number of layers and the thickness of the material to be obtained, and

e) cooling the multilayer material of step d) to 20-30°C with a closure force from 10 to 25 tons.

14. A process according to claim 13 wherein in step a) a solution in acetone is used, if the polymer comprises cellulose acetate, or a aqueous suspension/emulsion is used, if the polymer comprises an alkyl acrylate and/or a functionalized polyester and/or a polyether urethane.