EP1676941A1

EP1676941A1 - Process for the preparation of polyurethane nanocomposite fibers or films having an enhanced dyeability and UV-ray resistance

Info

Publication number: EP1676941A1
Application number: EP05027322A
Authority: EP
Inventors: Giuseppe Serravezza; Walter Cardinali; Marinella Levi; Stefano Turri
Original assignee: Alcantara SpA; Politecnico di Milano
Current assignee: Alcantara SpA; Politecnico di Milano
Priority date: 2004-12-29
Filing date: 2005-12-14
Publication date: 2006-07-05
Anticipated expiration: 2025-12-14
Also published as: ATE403767T1; DE602005008697D1; PT1676941E; ITMI20042548A1; EP1676941B1; ES2311922T3

Abstract

Process for the preparation of fibres or films comprising polyurethanes and organophilic delaminated functionalized clays, said organophilic delaminated functionalized clays being dispersed in said polyurethane, said process including the following steps:

(a) functionalization of one or more lamellar organophilic clays with one or more compounds selected from those having general formula (I) (X-R)_nSi(-OR')_p(R")_m (I) wherein n is from 1 to 3, m is from 0 to 2 and p = 4-n-m with the condition that p ≥ 1;
(b) treatment of the functionalized organophilic clay obtained at the end of step (a) with a polyurethane solution in an aprotic polar solvent, thus obtaining a dispersion of said functionalized organophilic clay and the polyurethane added thereto, said treatment being continued until the total, or at least partial, delamination of said functionalized organophilic clay, thus obtaining a dispersion of said functionalized organophilic delaminated clays in polyurethane;
(c) spinning or filming of the dispersion of said functionalized organophilic delaminated clays obtained at the end of step (b).

Description

The present invention relates to polyurethane fibres and films. More specifically, the present invention relates to a process for the preparation of polyurethane fibres or films, both obtained by drying or by coagulation, having an enhanced dyeability, by incorporating a modified lamellar clay into said polyurethane. This process also allows the stability of polyurethane to UV exposure to be improved, by fixing an additive, capable of absorbing the harmful UV component, to the polymer.
Elastomeric fibres, such as those deriving from polyurethane, are suitable for films and fabrics, due to their exceptional stretching and recovery properties.
Certain polyurethane filaments however are not easily dyeable with respect to conventional filaments for fabrics, such as those spun in the molten state starting from polyester or nylon. Furthermore, the polyurethane filaments subjected to dyeing have a poor stability of the dyes to water washing.
Patent application WO 97/49847 solves the above-mentioned problem by using organophilic clays, in particular montmorillonite modified with quaternary ammonium salts, such as N-((tallow-alkyl)-bishydroxyethyl) methyl ammonium or N-((tallow hydrogenated alkyl)-2-ethylhexyl) methyl ammonium. The solution suggested by WO 97/49847, however, is limited to dyes capable of inserting themselves in the interlayer spaces, in place of the modifying ammonium group, i.e. basic (or cationic) dyes. Dyeing with acidic (or anionic) dyes, which bind themselves to said ammonium salts present in the layers of electrostatically modified clay, usually give a lower stability of the colours, particularly to washing, due to the weakness of these bonds in an aqueous environment.
An improved process with respect to WO 97/49847 has now been found, as it allows the stable dyeing of polyurethane fibres not only with acidic or basic dyes, but also with dyes belonging to different groups.
Furthermore, the process of the present invention allows the more stable biding not only of dyes, but also of other types of additives, as, for example, UV stabilizers.
In accordance with this, the present invention relates to a process for the preparation of fibres or films comprising polyurethanes and organophilic delaminated functionalized clays, said organophilic delaminated functionalized clays being dispersed in said polyurethane, said process including the following steps:

(a) functionalization of one or more lamellar organophilic clays with one or more compounds selected from those having general formula (I)

(X-R)_nSi(-O-R')_p(R")_m (I)

wherein n is from 1 to 3, m is from 0 to 2 and p = 4-n-m with the condition that p ≥ 1;
R is selected from alkyl, alkylaryl, arylalkyl, alcoxyalkyl, alkoxyaryl, aminoalkyl, aminoaryl radicals and corresponding halogenated products, having from 2 to 30 carbon atoms, preferably from 2 to 6 carbon atoms, in which at least one hydrogen atom is substituted by X; or RX is a residue deriving from a UV stabilizing molecule linked to the silicon atom present in the compound of general formula (I), preferably through a ureic (-NHCONH-) or urethane (-OCONH-) bond;
R' is an alkyl radical having from 1 to 6, preferably from 1 to 3 carbon atoms;
R" is selected from -H and an alkyl, alcoxyalkyl, alkylamino-alkyl group having from 1 to 6 carbon atoms;
X is selected from -OH, -SH, -S-M⁺, -O^-M⁺, -NHR¹, epoxy products, -N=C=O, - COOR¹, halogens, unsaturated hydrocarbons, M⁺ being a metal cation selected from Li⁺, Na⁺, K⁺ and R¹ a hydrogen atom, or an alkyl radical having from 1 to 6 carbon atoms; X is preferably selected from -NH₂, epoxies and alcohols;
thus obtaining one or more organophilic functionalized clays carrying one or more polar groups X;
(b) treatment of the organophilic functionalized clay obtained at the end of step (a) with a polyurethane solution in an aprotic polar solvent, thus obtaining a dispersion of said functionalized organophilic clay and the polyurethane added thereto, said treatment being continued until the total, or at least partial, delamination of said functionalized organophilic clay, thus obtaining a dispersion of said functionalized organophilic delaminated clays in polyurethane;
(c) spinning or filming of the dispersion of said functionalized organophilic delaminated clays obtained at the end of step (b).

The dispersion of said functionalized organophilic delaminated clays in said polyurethane is called nano-composite organophilic functionalized clay/polyurethane.
The present invention also relates to a process for dyeing fibres or films including polyurethanes and functionalized organophilic delaminated clays, said functionalized organophilic delaminated clays being dispersed in said polyurethane, said process comprising steps (a) to (c) as in claim 1 and a subsequent step (d) which includes the dyeing of film or fibre obtained at the end of step (c) by means of contact of said film or fibre with a solution or dispersion of dye, preferably reactive dye.
The polyurethanes used in the present invention include elastomeric polyurethane, segmented polyurethane, polyurethane-urea, spandex®. Spandex represents a long-chain synthetic fibre including at least 85% by weight of a segmented polyurethane. Said segmented polyurethane is made up of "soft segments" and "hard segments". The soft segments can be polymeric portions based on polyethers, for example deriving from poly(tetramethylene ether) glycol (PTMG), polyesters, such as, for example, adipic acid esters such as polyhexamethylene adipate (PHA), poly-3-methyl pentamethylene adipate (PMPA) or polyneopentyl adipate (PNA) or carbonic acid such, as for example, polyhexamethylene carbonate (PHC) or polypentamethylene carbonate (PPMC). The hard segments refer to portions of polymeric chains deriving from the reaction of an organic diisocyanate, such as, for example, methylene-bis-(4-phenylisocianate) (MDI) or toluene-diisocyanate (TDI) with a diamine or glycolic chain.
For illustrative purposes, polyethers which can be used for the preparation of the soft segment based on glycol, include polyethers deriving from ethylene glycol (PEG), propylene glycol (PPG) tetramethylene glycol or tetrahydrofuran (PTMG), 3-methyl-1,5-pentadiole, 3-methyl tetrahydrofuran and related copolymers.
Typical examples of glycol-terminated polyesters (or co-polyesters) which can also be used as the soft portion of polyurethane, are the reaction products of glycols (for example ethylene glycol, tetramethylene glycol, 2,2-dimethyl-1,3-propandiole and relative blends) with dicarboxylic acids (for example adipic acid, succinic acid, dodecandioic acid and relative blends); others can be produced through the opening of cyclic molecules such as caprolactone (polycaprolactone, in short PCL).
Polyesters can also be used as soft segments, formed by co-polymerization of the above-mentioned polyethers and polyesters, as well as diol-terminated polycarbonates, such as poly(pentamethylene-carbonate) diol (PHC). Polyols used for the synthesis of polyurethane-ureas of the experimental examples, normally have a number average molecular weight of between 1,000 and 3,000, preferably between 1750 and 2250.
The prior art is well aware that the completion of the synthesis of polyurethane can be effected by means of diamines (which act as chain-extenders), with the consequent formation of polyurethane-ureas. The aliphatic diamines which can be used are ethylene diamine (EDA), 1,3-cyclohexanediamine (1,3-CHDA), 1,4-cyclohexanediamine (1,4-CHDA), isophorondiamine (IPDA), 1,3-propylenediamine (1,3-PDA), 2-methylpentamethylenediamine (MPDM), 1,2-propylenediamine (1,2-PDA), and relative blends. Typical examples of aromatic diamines are 3,3'-dichloro-4,4'-diaminodiphenylmethane, methylene-bis(4-phenylamine) (MPA), 2,4-diamino-3,5-diethyltoluene, 2,4-diamino-3,5-di(methylthio)toluene. Said diamines, aliphatic and/or aromatic can be added as such or developed in situ by the reaction between the corresponding isocyanate and water. The chain extension can also be obtained by means of diols such as ethylene glycol, tetramethylene glycol and blends thereof (thus obtaining polyurethanes). Finally, the chain extension can also be obtained by means of dicarboxylic acids such as malonic, succinic, adipic acid.
The chemical names of polyurethanes can be abbreviated according to their composition. For example, a polyurethane-urea prepared starting from polycaprolactone (PCL), methylene-bis-(4-phenylisocyanate) (MDI) and ethylenediamine (EDA) is abbreviated as PCL(2000):MDI:MPA. The numbers in brackets which follow the acronym of the polymeric diol, refer to the weight average molecular weight of the diol. A polyurethane-urea which can be used in the present invention can be abbreviated as PTMG(2000)/PCL(2000):MDI:MPA. A preferred polyurethane-urea is PHC(2000)/PNA(2000):MDI:MPA.
The reactions used for preparing polyurethanes and polyurethane-ureas are normally effected in aprotic inert solvents, such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpirrolidone (NMP). The above-mentioned preparations are well known to experts in the field.
The term "lamellar organophilic clays" stands for lamellar clays in which the original inorganic cation situated between the clay lamellae has been substituted with organic "onium" ions (which will be defined hereunder) in order to increase the inter-layer distance and the compatibility with the polymer which is to be intercalated inside the clay.
As far as the lamellar clays used for preparing the organophilic clays are concerned, these are stratified clays (phyllo-silicates) carrying negative charges on the layers and exchangeable cations in the space between the layers. In addition to their ion exchange capacity, the lamellar clays show the capacity of incorporating water, alcohol or other polar substances between their layers, thus swelling.
These clays can have a triple-layer structure, wherein each layer consists of an octahedral layer based on magnesium or aluminum situated between two tetrahedral layers of silica. Example of lamellar clays are smectic clays, for example montmorillonite, saponite, beidelite, nontronite, ectorite, stevensite, bentonite, vermiculite, sauconite, magadite, kenianite, or substitutions or derivatives of the above clays and relative blends. Said clays can be natural or synthetic. Preferred lamellar clays are selected from montmorillonite, bentonite and relative blends.
The swollen mica is also a useful lamellar clay. Examples of swollen mica are chemically synthesized micas, such as that called "SOMASIF®" of CO-OP Chemical Co Ltd. Tokyo, Japan and tetra-silica mica.
With respect to the "onium" ions present in the lamellar organophilic clays, these can be primary, secondary, tertiary or quaternary ammonium compounds, pyridinium compounds, imidazolinium compounds, phosphonium compounds, sulphonium compounds. Preferred examples of "onium" compounds are the tallow-alkyl-bis(hydroxyethyl) methyl ammonium ion, the tallow-alkyl-bis(hydroxymethyl) methyl ammonium ion, the (tallow hydrogenated alkyl) 2-ethylhexyl dimethyl ammonium ion, the bis(tallow hydrogenated alkyl) dimethyl ammonium ion, the bis(tallow hydrogenated alkyl) methyl ammonium ion, the (tallow hydrogenated alkyl) benzyl dimethyl ammonium ion.
The term "tallow" indicates the fat product deriving from the fat tissues of cattle and/or sheep. Tallow contains, in the form of glycerides, oleic, palmitic, stearic, myristic and linoleic acid. It also contains, in lower amounts, cholesterol, arachidonic acid, elaidic and vaccenic acid. The most known characteristics of tallow is its solidification point, which is between 40 and 46°C. Furthermore, the terms tallow-alkyl or hydrogenated tallow-alkyl are commercial terms which normally refer to blends of C₁₆-C₁₈ alkyl groups deriving from tallow.
Typical examples of lamellar organophilic clays (therefore containing organic "onium" ions) which are commercially available are organophilic montmorillonite containing the tallow-benzyldimethylammonium cation or the (tallow hydrogenated)benzyldimethylammonium cation. The preparation of said organophilic clays is well known to experts in the field. It is mainly based on the exchange of inorganic cations with onium-organic ions.
Said lamellar organophilic clays have a distance between the layers of at least 17 Å. Said distance can be efficaciously measured through X-ray diffraction. As far as the compounds having general formula (I) are concerned, typical examples of said compounds are γ-propyl amino triethoxysilane, γ-propyl amino trimethoxysilane, γmercaptopropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl triethoxyysilane, N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane, γ-glycidopropyl triethoxysilane, γ-glycidopropyl methyldiethoxysilane, γ-isocyanatepropyl triethoxysilane, γ-isocyanatopropyl trimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ-metacryloxypropyl trimethoxysilane.
In the preferred embodiment, the compound having general formula (I) is selected from γ-aminopropyl-trimethoxysilane and γ-glycidoxypropyl-trimethoxysilane.

Step (a) of the process of the present invention consists of the functionalisation of the lamellar organophilic clay described above, by means of the reaction of said clay with the compound having general formula (I). Said step can be carried out in an aprotic polar solvent, for example DMF, at a temperature of 60-90°C for 4-12 hours, preferably 8-10 hours.

In step (a) the O-R' groups allow the-R-X groups to become fixed to the layers of the silicate through reaction between the alkoxy-silane groups of (I) and the-OH surfaces of the layers, forming siloxane bonds (X-R-Si-O-Si-layer), which are covalent, thus particularly stable.
The functionalised organophilic clays obtained at the end of step (a), has a functionalisation degree which is in relation to the type of lamellar clays used (content of Si-OH groups present on the surface or, in any case, accessible) and of the type and quantity of functionalising compound (I) used. Said functionalisation degree can be determined by making use of one of the known analytical techniques for any type of functional X group introduced.
-RX can also be selected from residues deriving from additives such as antioxidants, radical absorbers, UV stabilizers, flame retardants. For the preparation of compounds having general formula (I), in which -RX has the above meaning, it is sufficient to react one of the above-mentioned additives, in particular UV stabilizers, with a compound having general formula (I) in which a functional group is present in place of the -RX group, capable of reacting with functional groups present in the additives. For example, if an -OH, -NH₂. -COOH or -SH group is present in said additives, it is possible to react said additive with a compound having general formula (I) having a radical which carries a -N=C=O group in place of - RX. Typical examples of UV stabilizers are 2-(2'-hydroxy-3',5'-dialkylphenyl)benzotriazoles, 2-hydroxybenzophenones, esters of benzoic acid such as salicylates and benzoyl-resorcinol, HALS (sterically-hindered amines) and 2-(2'hydroxyphenyl)-1,3,5-triazine.

Step (b) of the process of the present invention consists of the treatment of the functionalised organophilic clay obtained at the end of step (a) with a solution of polyurethane in an aprotic polar solvent (for example N,N-dimethyl formamide and N,N-dimethyl acetamide), preferably at a temperature ranging from 15 to 40°C, over a time ranging from a few hours to 12-14 hours, according to the distance between the layers of clay and the compatibility between the functionalised organophilic clay and the polymer. Quantities of functionalised organophilic clay ranging from 0.5 to 12% by weight are normally used, with respect to the polymer, preferably from 1% to 6%. Step (b) is carried out until the total, or at least partial, delamination of said functionalised organophilic clay, thus obtaining a polyurethane nanocomposite /functionalised organophilic clay.
The term "delamination" means the total or partial destruction of the lamellar aggregate of the clay, with the formation of the nano-compound having an intercalated or exfoliated structure.
Step (c) of the process of the present invention consists of the spinning or filming of the nano-compound obtained at the end of step (b). Said spinning or filming process is carried out according to techniques well-known to experts in the field.
Should the process proceed with the dyeing (step d) of the polyurethane film or yarn obtained at the end of step (c), the nano-structured polyurethane film or yam is put in contact with a solution or dispersion of a dye, preferably a solution of reactive dye, which (according to a non- binding hypothesis of ours) is capable of chemically binding itself to the X group present on the pending chain of the functionalised clay, thus forming a covalent chemical bond. The dyeing cycle can be effected by heating the nano-compound (fibre or film) to a temperature ranging from 20 to 120°C and pH values from 4 to 10, depending on the nature of the reactive group present on the clay and on the dye used. The duration of the dyeing process also depends on the type of dye and the functional group present on the clay, in addition to the characteristics of the substrate (dried or coagulated polyurethane), and from its morphology (in the case of coagulated films), in addition to the dyeing temperature. It can normally vary from 20 minutes to 1-2 hours. After the dyeing step, a cleaning step is usually carried out using surface-active agents, reducing agents or other chemical compounds, well-known to experts in the field, for removing the non-fixed excess of dye from the nano-structured polyurethane.

Typical examples of reactive dyes are those commercialized under the following trade-names: Procion®, Drimarene®, Cibacron® and Levafix®, Remazol® and
Lanasol®. They contain reactive groups such as substituted triazine or pyrimidine rings, β-sulphate-ethylsulphones and α,β-di-halogen ketones.
The polyurethanes obtained according to the process of the present invention have the following properties:

optimum dyeability;
high stability to washing of the dyed fibres;
enhanced stability to light (when bound to UV stabilizers).
Moreover, contrary to what is described in the field of scientific literature relating to the use of organophilic non-functionalized clays (for example S.S.Ray M.Okamoto, "Polymer/layered silicate nanocomposite: a review from preparation to processing", Prog. Polym. Sci. - 2003, 28, 1539-1641), the variation in the physico-mechanical properties (in particular tensile modulus) of the polyurethane nanocomposites/functionalized organophilic clay with respect to the polyurethane as such, is very moderate. This represents a great advantage and is an extremely important requisite for keeping the sensorial properties of the final product unaltered. A further confirmation of this was obtained by effecting dynamical-mechanical analyses (DMA) of films of polyurethane nanocomposite /functionalized organophilic clay: the shear modulus, measured under a linear visco-elastic regime (deformation lower than 0.5%), shows a small decrease in value with respect to that of the polyurethane as such, whereas a high increase (30%) is observed for the polyurethane nanocomposite/organophilic clay, consistent with the literature data.
The following examples are provided for a better understanding of the present invention.

Examples

Description of the materials

The following examples comprise the use of polyurethane as an elastomeric matrix and organophilic clays as such (comparative example) and functionalized (present invention). The polyurethane used in the examples are aromatic polyurethanes prepared starting from 4,4'methylene-bis-(phenyl isocyanate), hereinafter called MDI, through synthesis in N,N dimethylformamide (hereinafter DMF), whose pre-polymer, obtained by the reaction of MDI and diol polymers (hereinafter polyols) of various natures, is extended by the addition of water as already described in previous patents (EP-A-0584511, EP-A-1323859). The polyols used for the polyurethane defined PU1 are polytetramethyleneglycol (with MW 2000) and polycaprolactone (with MW 2000); for the polyurethane defined PU2, they are polyhexamethylenecarbonate (with MW 2000) and polyneopentyladipate (with MW 2000).
The lamellar organophilic clays used are montmorillonites modified by substituting the interlayer metal cation with quaternary ammonium salts. In particular commercial montmorillonite Dellite® 43B, produced by Laviosa Chimica Mineraria SpA, was used. Dellite® 43B is an organophilic montmorillonite containing the tallow-benzyl dimethylammonium ion.
The alkyl alkoxy xylanes used for the functionalisation of the clays are produced by GE Advande Materials and sold under the trade-mark of Silquest®.
The reactive dyes used for dyeing the polyurethane film composite /functionalized clays, are produced by Ciba and sold under the trade-name of Lanasol® and Cibacron®.
The reactive stabilizer used in the example is Tinuvin® 213 produced by Ciba: it consists of a blend of 3-(3-(2H-benzotriazol-2-yl)-5-tributyl-4-hydroxyphenyl) propionate) of polyethylene glycol (di-ester of polyethylene glycol, 35% by weight of the mix) and polyethylene glycol with a molecular weight of 300 (the remaining 13% by weight of the mix). Said UV stabilizer must be purified from polyethyleneglycol before use.

EXAMPLE Comparative 1 ― preparation of the PU nanocomposite/ clay with the method of intercalation in solution and filming.

1.016 g of Dellite® 43Bare are weighed in a 250 ml beuta equipped with an emery plug and mechanical stirrer and 17 g of DMF are added. The dispersion is left under stirring for 2-3 hours, 127 g of a polyurethane PU2 solution in DMF at 16% by weight of polymer, are then added. The solution is left under stirring for a further 12-14 hours before its use. The solution thus formed contains 14% by weight of polymer and 5% by weight of clay, with respect to the polymer.
The dried PU nanocomposite film is prepared by pouring 64 g of the solution formed on a polyethylene sheet having dimensions of 26 x 26 cm, equipped with edges and the whole matter is placed in a vacuum oven, maintaining the system at 60°C and atmospheric pressure for 4 hours, then at 60°C and 300 mmHg until the complete removal of the solvent. The film thus produced, with a thickness of about 0.9-1.0 mm, shows with X-rays an increase in the interlayer distance of the clay planes, from 17.9 Å of the commercial clay, to 31.6 Å of the composite, thus revealing the formation of a nanocomposite of the intercalated type. IR analysis of the film shows the presence of a very intense band between 1020 and 1040 cm^-1 due to the bending movements of the Si-O-Si bonds.
The physico-mechanical characterization of the dried films was effected following the ISO37 regulation and the results are shown in the annexed Table 1. The addition of Dellite® 43B clay to the polyurethane PU2 causes a significant increase in the tensile modulus at 100% of strain with respect to the polyurethane with no addition (33%), and limited decreases in the ultimate tensile stress and elongation to break (15% and 10% respectively). The shear modulus of the dried film of nano-composite organophilic clay/polyurethane obtained, measured by means of DMA, shows a significant increase in value (30% with respect to the PU2 polyurethane film as such (see enclosed table 2).
The coagulated film of nanocomposite PU is prepared, on the contrary, by pouring again 64 g of the solution formed on a polyethylene sheet of 26 x 26 cm equipped with edges and placing the sheet, this time, in a tank containing softened water at room temperature. The polymer is left to coagulate in water for 3-4 hours, the film is then removed from the sheet and is left in water for a further 5-6 hours, in order to allow the removal of the solvent from the film. The film is then removed from the tank and is left to dry in the air or between blotting paper.

EXAMPLE 2 - clay functionalisation with γ-aminopropyl-trimethoxysilane.

50 g of Dellite® 43B are dispersed in a beuta with 800 g of DMF, maintaining the system under a nitrogen flow at room temperature. After 1 hour, 75 g of Silquest® A 1110 (γ-aminopropyl-trimethoxysilane) are slowly added under stirring and the dispersion is left under stirring for a further hour. The dispersion is then heated to a temperature of 85°C for 10 hours and, after cooling to room temperature, it is filtered on a buchner and is washed with various aliquots of DMF and subsequently with acetone, to remove traces of non-reacted silane. The clay is dried in an oven at 80°C, care being taken to stir it, from time to time, to avoid the formation of large-dimensional granules.
The clay thus obtained can be titrated with HCl by using a mixture of water/isopropanol 2:3 as solvent; the titre found is equal to 0.4 milli-equivalents of HCl/g of functionalized organophilic clay.
X-ray analysis of the powder thus produced shows an enlargement of the interlayer space from 17.9 Å of the commercial clay to 34 Å.

EXAMPLE 3 - preparation of polyurethane nanocomposite/ functionalised clay with an amino-group and filming thereof.

1.016 g of functionalised Dellite® 43 B, prepared as described in example 2, are weighed in a 250 ml beuta equipped with an emery plug and magnetic stirrer and 17g of DMF are added. The dispersion is left under stirring for 2-3 hours, 127 g of a polyurethane PU2 solution in DMF at 16% by weight of polymer, are then added. The solution is left under stirring for a further 12-14 hours before its use. The solution thus formed contains 14% by weight of polymer and 5% by weight of clay, with respect to the polymer.
The preparation of the dried film and of the film coagulated in water is effected as described in example 1.
The X-ray analysis of the dried film shows the disappearance of the peak relating to the interlayer distance between the layers of the modified clay (distance over 40 A), this being an index of the formation of a nanocomposite with a delaminated (or exfoliated) structure. This is confirmed by TEM analysis of the film produced, wherein clay layers are revealed, dispersed in the polymeric matrix, without lamellar structures grouped into aggregates containing on average more than 5 lamellas. IR analysis of the film shows the presence of a very intense band between 1020 and 1040 cm^-1, due to the bending motions of the Si-O-Si bonds.
The physico-mechanical characterization of film (shown in enclosed Table 1) does not reveal any significant differences in the tensile modulus with respect to the polyurethane without additives; the decrease in the elongation to break is moderate (10%), whereas the ultimate tensile stress has decreased by 25%. The shear modulus of the dried film of nanocomposite obtained, measured by means of DMA, shows a modest value decrease (8%) with respect to the polyurethane PU2 film as such (see enclosed table 2).

EXAMPLE 4 - functionalisation of clay with γ-glycidoxypropyltrimethoxysilane.

50 g of Dellite® 43B are dispersed in a beuta with 800 g of DMF, maintaining the system under nitrogen flow at room temperature. After 1 hour 98.8 g of Silquest® A 187 (γ-glycidoxypropyl-trimethoxysilane) are slowly added under stirring and the dispersion is left under stirring for a further hour. The dispersion is then heated to 85°C for 10 hours and, after cooling to room temperature, it is filtered on a buchner and is washed with various aliquots of DMF and subsequently with acetone, to remove traces of non- reacted silane. The clay is dried in an oven at 80°C, care being taken to stir it from time to time, to avoid the formation of large-dimensional granules.
X-ray analysis of the powder thus produced shows an enlargement of the interlayer space of part of the clay from 17.9 Å (value of the commercial clay) to 29.8 Å; a second peak appears, corresponding to an interlayer distance of 15.5 Å (slightly smaller than the commercial clay).

EXAMPLE 5 - preparation of the polyurethane nanocomposite/clay functionalized with an epoxy group and filming thereof.

1.016 g of functionalised Dellite® 43B, prepared as described in example 4, are weighed in a 250 ml beuta equipped with an emery plug and mechanical stirrer and 17 g of DMF are added. The dispersion is left under stirring for 2-3 hours, 127 g of a polyurethane PU2 solution in DMF at 16% by weight of polymer, are then added. The solution is left under stirring for a further 12-14 hours before its use. The solution thus formed contains 14% by weight of polymer and 5% by weight of clay, with respect to the polymer. The preparation of the dried film and of the film coagulated in water is carried out as described in example 1.
X-ray analysis of the dried film shows the disappearance of the peak relating to the interlayer distance of the lamellas equal to 15.5 Å and a small peak appears at a distance of 17.9 Å of the commercial clay and that corresponding to a distance of 29.8 Å is strongly reduced; the formation of a nanocomposite having an intermediate structure between an intercalated and exfoliated structure, can therefore be deduced. IR analysis of the film shows the presence of a very strong band between 1020 and 1040 cm^-1 due to the bending motions of the Si-O-Si bonds. The physico-mechanical characterization of the film (shown in enclosed Table 1) shows a slight increase in the tensile moduli (16% and 18%, respectively), whereas the ultimate tensile stress decreases by 35%. The shear modulus of the dried film measured by means of DMA (see Table 2), shows a slight decrease (10%) in the value with respect to the polyurethane PU2 film as such (see enclosed table 2).

EXAMPLE 6 - dyeing of the dried and coagulated film of polyurethane nanocomposite/clay functionalised with amino-groups, using reactive dyes.

2 g samples of dried or coagulated film of polyurethane PU2 (prepared as specified in example 1), nanocomposite PU2/Dellite® 43B (example 1), nanocomposite PU2/clay functionalised with an amino-group (example 3), were dyed in polymat using the active dye for wool Lanasol® Blue 3R (Reactive Blue 50) or the active dye for cotton Cibacron® Navy FN-B Reactive Blue 238).
The dyeing cycle used is outlined as follows:
Dyeing with Lanasol® dye

Dye concentration in the bath 3% with respect to polyurethane;
Solution pH 8.5;
Dyeing temperature 80°C;
Dyeing duration 60 minutes;

Dyeing with Cibacron® dye

Ascent of dye on the film
- Saline dyeing solution containing 3% of dye with respect to polyurethane and sodium chloride at a concentration of 60 g/l;
- Treatment temperature 80°C;
- Duration of the treatment 30 minutes.
Film dyeing
- A solution of sodium carbonate 18 g/l is added to the dye solution;
- Dyeing temperature 60°C;
- Duration of the dyeing 60 minutes:

Washing to eliminate the non-fixed dye

Surface-active agent Univadina Top®
Surface-active agent concentration 2 g/l
Washing temperature 80°C
Dyeing duration 20 minutes.

Even if the two dyes used have different reaction mechanisms with the NH₂ functional groups present on the functionalised organophilic clay, they show the same behaviour, described below, on the dyed films of polyurethane nanocomposite /functionalised organophilic clay.
The dried films produced starting from polyurethane PU2 do not show colouring and those with nanocomposite PU2/Dellite® 43B have weak patches of residual dye; the films of nanocomposite PU2/clay functionalised with amino-groups on the contrary, appear to be coloured and the dye is not even lost by leaving the film dipped in cold water for two weeks, or in perchloro ethylene for two days.
The films of PU2 and of nanocomposite PU2/clay obtained by coagulation, have a colouring, after dyeing, which is slightly more intense than that of the corresponding dried films; nevertheless, the difference in shade found in the coagulated films of the nanocomposite PU2/functionalised clay remains particularly relevant. Also in this case, the dye is not lost by leaving the film dipped in cold water for two weeks or in perchloro ethylene for two days.
The dyed films of nanocomposite PU2/clay functionalized with amino-groups were subjected to tests for the evaluation of the dye resistance to wet rubbing (AATCC 8-2001), to washing with soap (AATCC 61-2001) and dry washing. The evaluation shown in the following table, relating to the films of nanocomposite PU2/functionalised clay, dyed by means of the dye Cibacron®, were effected as follows:

a) for the discharge of the dye on the test sample (multi-fibre felt for washings and cloth for rubbings) the dirtying is evaluated by means of comparison with the ISO 105A02 grey scale;
b) for the shade change of the sample, before and after the test, the ISO105A02 grey scale is used;
c) the evaluation is effected by comparing the shade change or dirtying level with the standard contrasts by means of the appropriate grey scale; an evaluation equal to 5 corresponds to no change in colour shade or transfer, whereas an evaluation of 1 corresponds to the maximum contrast appearing in the grey scale used.

Test	Film type	Evaluation
WET RUBBING	Dried	4
	Coagulated	4
DRY RUBBING	Dried	5
	Coagulated	5
WASHING WITH SOAP (shade change)	Dried	5
	Coagulated	5
WASHING WITH SOAP (colour discharge on multi-fibres)	Dried	5
	Coagulated	5
DRY WASHING (shade change)	Dried	5
	Coagulated	5
DRY WASHING (colour discharge on multi-fibres)	Dried	5
	Coagulated	5

EXAMPLE 7 ― dyeing of the dried and coagulated film of polyurethane nanocomposite/clay functionalised with the epoxy group using reactive dyes.

Samples of about 2 g of dried or coagulated films of polyurethane PU2 (prepared as described in example 1), nanocomposite PU2/Dellite® 43B (example 1), nano-composite PU2/clay functionalised with the epoxy group (example 5), were dyed in polymat using the reactive dye for wool Lanasol® Blue 3R (Reactive Blue 50) or the reactive dye for cotton Cibacron® Navy FN-B (Reactive Blue 238).
The dyeing cycle used is outlined as follows:

Pre-treatment for the opening of the epoxy ring to be carried out in water at acidic or alkaline pH.

Dyeing with dye Lanasol®

Dye concentration in the bath 3% with respect to polyurethane;
pH solution 8.5;
Dyeing temperature 80°C;
dyeing duration 60 minutes;

Dyeing with dye Cibacron®

Ascent of dye on the film
- Saline dyeing solution containing 3% of dye with respect to polyurethane and sodium chloride at a concentration of 60 g/l;
- Treatment temperature 80°C;
- Duration of the treatment 30 minutes.
Film dyeing
- A solution of sodium carbonate 5 g/l is added to the dye solution over 10 minutes and, subsequently, a NaOH 36°Bé 2 ml/l over 15 minutes;
- Dyeing temperature 60°C;
- Duration of the dyeing 60 minutes:

Washing to eliminate the non-fixed dye

Even if the two dyes used have different reaction mechanisms with the alcoholic functional groups present on the functionalised organophilic clay (obtained by the opening of the epoxide following the pre-treatment), they show the same behaviour, described below, on the dyed films of polyurethane nanocomposite/functionalised organophilic clay.
The dried films produced starting from polyurethane PU2 do not show colouring and those with nanocomposite PU2/Dellite® 43B have weak patches of residual dye; the films of nanocomposite PU2/clay functionalised with amino-groups on the contrary, appear to be coloured and the dye is not even lost by leaving the film dipped in cold water for two weeks, or in perchloro ethylene for two days.
The films of PU2 and nanocomposite PU2/clay obtained by coagulation, have a colouring, after dyeing, which is more intense than that of the corresponding dried films; the shade difference found in the coagulated films of the nanocomposite PU2/functionalised clay, however, remains particularly relevant. Also in this case, the dye is not lost by leaving the film dipped in cold water for two weeks or in perchloro ethylene for two days.

The dyed films of nanocomposite PU2/clay functionalized with amino-groups were subjected to tests for the evaluation of the dye resistance to wet rubbing (AATCC 8-2001), to washing with soap (AATCC 61-2001) and dry washing. The evaluation shown in the following table, relating to the films of nanocomposite PU2/functionalised clay, dyed by means of the dye Cibacron®, were effected as follows:
a) for the discharge of the dye on the test sample (multi-fibre felt for washings and cloth for rubbings) the dirtying is evaluated by means of comparison with the ISO 105A03 grey scale;
b) for the shade change of the sample, before and after the test, the ISO105A02 grey scale is used;
c) the evaluation is effected by comparing the change in shade or the dirtying level with the standard contrasts by means of the suitable grey scale; an evaluation equal to 5 corresponds to no change in shade or colour transfer, whereas an evaluation of 1 corresponds to the maximum contrast appearing in the grey scale used.

EXAMPLE 8 - purification and functionalisation of the UV stabilizer

5 g of Tinuvin® 213 are purified from the polyethylene glycol present by means of liquid/liquid separation with a separating funnel, with the use of demineralized water and carbon tetrachloride as solvents: an organic fraction is collected containing the molecules with a UV stabilizing function and a water fraction containing the glycol not bound to the stabilizer.
After evaporation of the solvent from the organic phase, 4.61 g of an oil, formed by the esters containing the UV stabilizers, are collected. The IR spectrum of the oil thus obtained differs from that of the starting mix by the presence and/or the form of some peaks which can be attributed to the polyethylene glycol (3427 cm^-1, 1644 cm^-1, 1090 cm^-1, 838 cm^-1). Moreover, the IR spectrum of the extract from the water phase coincides with the IR spectrum of polyethylene glycol.
The oil containing the UV stabilizer is then diluted with 18.4 g of DMF and heated, under a nitrogen flow, to 70°C. 1.15 ml of Silquest® A-Link 35 (y-isocyanatopropyl trimetoxysilane) and a drop of tin dibutyl-dilaurate are added. The reaction is followed by means of titration of the free isocyanate content over a period of time.
After 8 hours, the amount of free isocyanate is null. This is also confirmed by the IR spectrum of the solution which shows the complete disappearance of the absorbing peak of NCO (2270 cm^-1) and of the OH groups (3486 cm^-1), the appearance of the absorbance of the NH groups (3359 cm^-1) and the formation of the urethane bonds (band at 1500-1550 cm^-1 and 1700 cm^-1).

EXAMPLE 9 - clay functionalisation with the silane bound to the UV stabilizer.

5 g of Dellite® 43B are dispersed in a beuta with 80 g of DMF, maintaining the system under a nitrogen flow at room temperature. After 1 hour, the solution of the silane bound to the UV stabilizer prepared in the previous example 8, is slowly added, under stirring and the whole system is left under stirring for a further hour. The dispersion is then heated to a temperature of 85°C for 10 hours and, after leaving it to cool to room temperature, it is filtered on a buchner and washed with aliquots of DMF and subsequently with acetone to remove traces of non-reacted silane. The clay is dried in an oven at 80°C, care being taken to stir it from time to time to avoid the formation of large-dimensional granules.
X-ray analysis of the powder thus produced does not show any clear shifting of the peak relating to the interlayer space; a considerable raising of the base line to interlayer space values lower than that of the clay as such, can be observed however, which can perhaps be attributed to a distribution of interlayer distances due to the polyethylene glycol bound to the UV stabilizer which, as it is polydispersed, causes a distribution of the lengths of the pending chain bound to the clay and therefore of interlayer distances.

EXAMPLE 10 - preparation of the polyurethane nanocomposite/clay functionalized with the UV stabilizer and its filming.

1.016 g of Dellite® 43B functionalised as described in example 9, are weighed in a 250 ml beuta equipped with an emery plug and magnetic stirrer and 17 g of DMF are added. The dispersion is left under stirring for 2-3 hours, 127 g of a solution of polyurethane PU1 in DMF at 16% by weight of polymer, are then added. The solution is left under stirring for a further 12-14 hours before its use. The solution thus formed contains 14% by weight of polymer and 5% by weight of clay, with respect to the polymer.
The preparation of the dried film and of the film coagulated in water are effected as described in example 1.
X-ray analysis of the dry film shows the shifting of the peak relating to the interlayer distance between the lamellas, from a distance of 17.9 Å of the commercial clay, to 32 Å, and this value presumes the formation of a nanocomposite of the intercalated type. The TEM analysis of the film produced confirmed this, revealing the presence of clay layers dispersed in the polymeric matrix, having lamellar-type structures grouped into aggregates containing, on an average, more than 5 lamellas.
Furthermore, the UV spectrum of the film produced, measured in diffused reflectance, shows an enlargement of the UV absorbing band, which, in the polyurethane as such and in that with non-functionalised clay ranges from 200 to 330 nm, up to about 400 nm (380 nm), including, in this way, also the characteristic absorption band of the UV stabilizer (250-400 nm with peaks at 303 and 344 nm).
The physico-mechanical characterization of the film (shown in enclosed table 1) shows a sharp-increase in the tensile moduli to 100% and 300% of elongation (50% and 30%, respectively), whereas the decrease in the ultimate tensile strength and elongation to break values is extremely contained (5% and 15%, respectively).

EXAMPLE 11 ― UV accelerated aging test of the polyurethane nanocomposite film/clay functionalised with UV stabilizer.

A film of dried nanocomposite film PU1/clay functionalised with UV stabilizer, was subjected to an accelerated aging test to UV rays, using as comparison a PU1 film as such, in order to evaluate the efficacy of the stabilizer introduced. The exposure conditions adopted are those prescribed by the DIN 75202 (PV 1303) regulation; in particular:

chamber relative humidity = 20 ± 10°C;
Irradiation = 60 W/m² (cumulative in the region 300-400 nm);
temperature of the black panel = 100 ± 3°C;
chamber temperature = 65 ± 3°C;
exposure duration = 1 Fakra (corresponding to 10 MJ/m²)

The film containing the stabilizer bound to clay proves to have resisted much better to the test, as it has a much more contained yellowing degree and better elastomeric characteristics, which means a more contained degradation of the polyurethane.

TABLE 1 PHYSICO-MECHANICAL ANALYSIS OF THE DRIED FILMS PRODUCED (ISO 37 REGULATION)

Film	Ex.	Elastic modulus 100%(kg/cm²)	Elastic modulus 300%(kg/cm²)	Ultimate tensile strength(kg/cm²)	Elongation to break (%)
PU1	1	40	70	400	780
PU1/43B-UV	10	60	90	370	650
PU2	1	60	160	540	500
PU2/43B	1	80	180	450	450
PU2/43B-NH₂	3	60	150	400	450
PU2/43B-Epox	5	70	190	350	480

TABLE 2 CONSERVATIVE COMPONENT OF THE SHEAR MODULUS OF THE FILMS PRODUCED (DMA)

FILM	Example	Shear modulus G' (MPa)
PU2	1	3.8
PU2/43B	1	4.9
PU2/43B-NH₂	3	3.5
PU2/43B-Epox	5	3.4

Claims

A process for the preparation of fibres or films comprising polyurethanes and organophilic delaminated functionalised clays, said organophilic delaminated functionalised clays being dispersed in said polyurethane, said process comprising the following steps:
(a) functionalisation of one or more lamellar organophilic clays with one or more compounds selected from those having general formula (I)

(X-R)_nSi(-O-R')_p(R")_m (I)

wherein n is from 1 to 3, m is from 0 to 2 and p = 4-n-m with the condition that p ≥ 1;
R is selected from alkyl, alkylaryl, arylalkyl, alkoxyalkyl, alkoxyaryl, aminoalkyl, aminoaryl radicals and corresponding halogenated products, having from 2 to 30 carbon atoms in which at least one hydrogen atom is substituted by X;
R' is an alkyl radical having a number of carbon atoms from 1 to 6;
R" is selected from -H and an alkyl, alkoxyalkyl, alkylamino-alkyl group having from 1 to 6 carbon atoms;
X is selected from -OH, -SH, -S-M⁺, -O^-M⁺, -NHR¹, epoxy products, -N=C=O, - COOR', halogens, unsaturated hydrocarbons, M⁺ being a metal cation selected from Li⁺, Na⁺, K⁺ and R¹ a hydrogen atom, or an alkyl group having from 1 to 6 carbon atoms; thus obtaining one or more organophilic functionalized clays carrying one or more polar groups X;

(b) treatment of the organophilic functionalized clay obtained at the end of step (a) with a polyurethane solution in an aprotic polar solvent, thus obtaining a dispersion of said functionalized organophilic clay and the polyurethane added thereto, said treatment being continued until the total, or at least partial, delamination of said functionalized organophilic clay, thus obtaining a dispersion of said functionalized organophilic delaminated clays in polyurethane;

(c) spinning or filming of the dispersion of said functionalized organophilic delaminated clays obtained at the end of step (b).
The process according to claim 1, wherein X is selected from -NH₂, -SH, epoxies and alcohols, preferably from -NH₂, epoxies and alcohols.
The process according to claim 1, wherein in the compound having general formula (I), R is a C₂-C₆ radical.
The process according to claim 1, wherein RX is a residue deriving from a molecule of a UV stabilizer, bound to the silicon atom present in the compound having general formula (I) by means of a ureic (-NHCONH-) or urethane (-OCONH-) bond.
The process according to claim 1, wherein R' is an alkyl group having from 1 to 3 carbon atoms.
The process according to claim 1, characterized in that step (a) is effected in an aprotic polar solvent.
The process according to claim 6, wherein the aprotic polar solvent is N,N-dimethylformamide.
The process according to claim 1, wherein the organophilic lamellar clays contain "onium" ions selected from ammonium compounds, pyridinium compounds, imidazolinium compounds or from phosphonium compounds.
The process according to claim 1, wherein the lamellar clays are selected from smectic clays and swollen micas, preferably montmorillonites.
The process according to claim 1, wherein the organophilic lamellar clays are selected from organophilic montmorillonites containing the tallowbenzyldimethylammonium cation or the (hydrogenated tallow)benzyldimethylammonium cation.
The process according to claim 1, characterized in that step (a) is effected at a temperature ranging from 60 to 90°C.
The process according to claim 1, characterized in that step (b) is effected at a temperature ranging from 15°C to 40°C.
The process according to claim 1, wherein in step (b), quantities of functionalised organophilic clay of 0.5% to 12% by weight with respect to the polymer, are used.
The process according to claim 1, wherein in step (b), quantities of functionalised organophilic clay of 1% to 6% by weight with respect to the polymer, are used.
The process according to claim 1, wherein the polyurethane is selected from polyurethane-ureas.
The process according to claim 1, wherein the polyurethane-ureas are selected from polyurethane-ureas obtained by reacting 4,4'methylene-bis-(phenylisocyanate) with polymeric diols and/or lactones, subsequently extended by the addition of water.
The process according to claim 16, wherein the polymeric diols and/or lactones are selected from polytetramethyleneglycol and polycaprolactone.
The process according to claim 15, wherein the polyurethane-ureas are selected from polyurethane-ureas obtained by reacting 4,4'methylene-bis-(phenylisocyanate) with polymeric esters of adipic acid and carbonic acid, subsequently extended by the addition of water.
The process according to claim 18, wherein the polymeric esters are selected from polyhexamethylene carbonate and polyneopentyl adipate.
A process for dyeing fibres or films comprising polyurethanes and functionalized organophilic delaminated clays, said functionalized organophilic delaminated clays being dispersed in said polyurethane, said process comprising steps from (a) to (c) as in claim 1, and a subsequent step (d) comprising the dyeing of the film or fibre obtained at the end of step (c) by contact of said film or fibre with a dye solution or dispersion.
The process according to claim 20, wherein the dye is selected from reactive dyes.