EP2912223B1

EP2912223B1 - Composition and process for weigthing silk

Info

Publication number: EP2912223B1
Application number: EP13820917.6A
Authority: EP
Inventors: Riccardo ALBONICO
Original assignee: Tinteco Srl
Current assignee: Tinteco Srl
Priority date: 2012-10-26
Filing date: 2013-10-28
Publication date: 2017-12-27
Anticipated expiration: 2033-10-28
Also published as: WO2014064662A2; JP2016500768A; WO2014064662A3; EP2912223A2; US20150299939A1

Description

Technical field of the invention

The present invention relates to a composition, a process using said composition for silk treatment and the silk thus treated.
In particular, the present invention relates to the process known as loading or weighting silk carried out using the present aqueous composition comprising metal salts and organic monomers.
Silk loading is an industrial process that consists in incorporating metal salts, vegetable materials or synthetic substances derived from organic monomers into fibroin to compensate for the loss of weight that occurs during the degumming step.
Degumming is a treatment carried out on raw silk and consists in partial or complete removal of sericin, a sheath covering the silk fibres. This sheath has an unattractive look, being opaque and yellowish, typical of raw silk. Only after degumming does silk acquire brilliance and softness but at the same time it undergoes a considerable loss in weight, generally up to 30%.
The loading process primarily serves to increase the volume, density and restore at least the original weight of the silk, at the same time maintaining the mechanical properties and especially giving softness, beyond improving some properties such as colour, shininess and dyeability.
In the industrial sector of silk, it is normal to return to at least the original weight and, preferably, increase it by at least 25%, in some cases getting weight gain up to 1000% with respect to the weight of the original silk after degumming.

Prior Art.

Loading silk with organic monomers is considered a very effective process and for this reason has attracted the interest of many scientists and chemists in the last thirty years. The grafting of vinyl monomers onto silk was introduced as a valid alternative to mineral loading. The grafting reaction generally requires a chemical or energetic (radiations) initiator.
At present silk loading on an industrial scale is carried out using a monomer called methacrylamide (MAA) in the presence of suitable activators; the silk obtained in this way not only exhibits a considerable increase in weight but also exhibits many advantages; for example it is shiny, soft and pleasant to touch.
Unfortunately however MAA is possibly carcinogenic, possibly mutagenic and is damaging for the nervous system. Further, it causes a yellowing of the silk fibres which limits their resistance to sunlight and can lead to results that are not entirely satisfactory on dying.
The experiments and research carried out to date, known to the Applicant and using monomers different from MAA, such as methyl methacrylate (MMA) or 2-hydroxy ethyl methacrylate (HEMA), alone or in a mixture, have generally led to only poor results.
In fact the other vinyl monomers studied to date have not been seen to be suitable in traditional process conditions, especially at an industrial scale, in giving all the properties required for a silk of very high quality which is also soft, strong, shiny, not yellowing, loaded homogeneously, dyeable, and so on.
These monomers, in traditional conditions, through increasing weight, result in a silk which can exhibit one or more of the above drawbacks, such as insufficient loading (practice is to add at least 25% over and above the recovery/recuperation of the weight lost in the degumming), a non-homogeneous loading, a touch that is not soft as the thread stiffens, loss of resistance to traction with consequent problems of ultimate tensile strength, non-homogeneity of colour (bad joins) during the dyeing step which causes lines of colour that are different in the finished fabric, generally white lines, or stains on the thread and, in particular in the case of HEMA, attachment of the silk threads, forming homopolymer bridges between a thread and another, with consequent difficulty in or impossibility of unwinding the thread from the reel.
All of these problems or even only one of them make it impossible to use silk loaded in this way for high-quality industrial productions, which require very high-quality final properties.
In document WO2008/145413 (Evonik Rohm) the prior art is commented on and various works are cited in which alternative processes and monomers for silk loading have been studied. The loading process is carried out with mixtures of vinyl monomers, in the presence of ammonium persulphate in large quantities and with a pH of around 3. During the process combinations of activators are not used.
On the basis of the considerations recited in WO2008/145413 and also on the direct experience of the Applicant, it can be deduced that to date there are no industrial processes for silk loading that can be satisfactory.
In fact silk, treated with the compositions and processes described in the prior art comprising monomers, such as for example MMA (methyl methacrylate), HEMA (hydroxy ethyl methacrylate) and MAA alone or in a mixture, exhibits some defects and characteristics that are not optimal such as for example a reduction of up to 60% of the tenacity and resistance to breakage of the fibre (page 4 Evonik), which creates problems in the weaving step; a reduction in softness, a characteristic typical of silk, and an increase in the rigidity even only at loading levels of 20%, which creates problems during the step of unwinding from the reel; an increase in yellowing; problems of homogeneity during the dyeing step, encountered especially with the use of hydrophobic monomers such as MMA.
The known silk loading processes generally lead to a grafting performance expressing the quantity of monomer loaded onto the silk with respect to the quantity of monomer introduced into the treatment bath, not quantitative, generally of about 80% in weight or less.
In consideration of the defects of conventional processes, the Applicant has focused on the research for a new loading process and, advantageously, to the use preferably of HEMA which exhibits the best prospects in terms of eco-sustainability because of its lower toxicity and better biodegradability, while at the same time it gives the silk a set of properties that are superior to the average for high-range applications (designer luxury articles such as for example ties).
In this regard the Applicant has repeated the experiments following the teachings of WO2008/145413 but, specifically, increasing the quantity of HEMA in the monomer mixture to above 30%, the results were very unsatisfactory. In fact, in both the laboratory tests and even more on an industrial scale, the main defects encountered were the following:

1. before drying the silk was limp and sticky;
2. once dried the silk was stiff;
3. a significant reduction in tenacity and ultimate tensile strength was observed;
4. impossibility of treating the silk thread in the following dying and weaving steps;
5. significant yellowing of the silk.

In the articles Journal of Applied Polymer Science, Vol. 81, 1401-1409 (2001) Tsukada et al. and the Journal of Applied Polymer Science, Vol. 67, 1393-1403 (1998) Tsukada et al. studies are cited relating to silk loading processes with MAA, MMA and HEMA with various initiators used alone and never in mixtures; these studies decidedly discourage the use of HEMA alone or in high percentages.
In particular it is mentioned, for example that in relation to the systems comprising HEMA/AIBN (2,2'-azobisisobutyronitrile) and HEMA/ADC (2,2'-azobis-2-methylpropionamide dichlorhydrate) the greater the weight increase of the fibres the more the degree of yellowing is observed. Further, the wet fibres thus-loaded are still very sticky, making it difficult to perform work operations on them.
In the cited article Journal of Applied Polymer Science, Vol. 67, 1393-1403 (1998) Tsukada et al., the authors conclude that only MAA can be used with success while the use of HEMA is discouraged.
In the article Journal of Applied Polymer Science, Vol. 103, 4039-4046 (2007) Ferrero et al., an in-depth study is made of the process of loading the silk with monomers such as MAA, HEMA, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (EHMA), triethylene glycol - monoethylether - methacrylate(TEGEEMA) and ethylene glycol dimethacrylate (EGDMA) initiated by ammonium persulphate (APS), so as to optimize the operative conditions. In this study too and in the preceding documents cited in the article, the use of HEMA is discouraged as it gives excessive rigidity to the samples when dried.
The Applicant has repeated the loading processes cited in the above-cited articles, and in the conditions described therein, with a single initiator in high quantities and pH around 3, and especially using monomer mixtures comprising from 30 to 100% in weight of HEMA - the loaded silk was sticky when wet and stiff when dry, even in the laboratory tests. On an industrial scale, using spools of 600 g, the reels were hard and it was impossible to unwind the thread from them. The silk loaded in this way, while exhibiting an increased weight, was entirely unusable.
Even when repeating the tests with MMA, the results were not satisfactory: in fact, the silk loaded with MMA according to traditional processes was off-white and powdery; and on industrial scale too the result was 600 g silk spools covered with white powder (precipitation from the loading). The silk obtained had gained weight but had no commercial value and was unusable.
In the Journal of American Science, 2010;6(12), 1515 - 20 (Gawish, Ramadan), some silk loading processes are reported, carried out in laboratory tests and on fabrics, which use compositions comprising HEMA. The fabric is pre-treated with APS and, separately, with a solution comprising the monomer. No specific indications are given regarding the pH, times or temperature of the process.
The problems encountered in these experiments, on laboratory scale, are certainly not comparable to those presented on industrial scale where they are considerably amplified.
In fact, by using reels of silk thread with a weight generally comprised between 300 and 600 g there are difficulties of loading due to the non-homogeneity and compactness of the reel, which do not occur in laboratory experiments carried out at a lower scale and/or on pieces of fabric of about 1 gr. The stickiness of the fibres, which can be manifested in the case of industrially-treated threads on reels, does not constitute a problem in the case of small reels and/or fabrics. Further, the laboratory experiments described in the above-cited articles, beyond using very low weight samples, often carry out a series of successive washings with solvents that are not allowable on an industrial scale, such as for example acetone, methanol etc. In other words, the laboratory samples repeated on an industrial scale generally lead to an unusable silk.
To increase the loading on the silk, as well as to improve its characteristics, some researchers have added a second initiator to the loading process. For example, in patent application CN 102677468 the silk-loading process is studied with mixtures of acrylamide and methacrylates, this process is initiated by potassium persulphate and calcium chloride.
In he Journal of Applied Polymer Science, 2004; 93, 1743-47, (Ramadan et al.) a study is made of the silk-loading process with monomers such as acryl amide (AM) and glycidyl methacrylate (GM) alone or in a mixture, initiated by ammonium persulphate (APS) and copper sulphate.
The silk thus-obtained is however of poor quality because the polymer chains tend to bond together.
In conclusion, to date, as far as the Applicant knows, there exists no alternative process to the traditional one with methacrylamide which is industrially valid to load the silk.
The Applicant has surprisingly found new compositions and a new process for silk loading, applicable industrially, that are particularly advantageous.
This process includes the combined use of at least two different initiators in very much smaller quantities with respect to those used in the traditional loading processes and, preferably at a higher pH. This specific combination significantly reduces the duration of the process and the washings and therefore overall the energy consumption and costs, and improves the quality of the silk in terms of softness and touch, ease of dying and resistance during weaving.
In the present process the yield has also been improved, expressed in terms of the quantity of monomer loaded on the silk with respect to the quantity of monomer introduced in the treatment bath (grafting). In particular, minimizing the formation of sub-products of homopolymerisation of the vinyl monomers has been achieved, with a smaller formation of homopolymers which, once precipitated as powders, would damage/ruin the softness and the look of the final silk. Further the significant reduction of the overall quantity of initiators and acid, with respect to the traditional processes, leads to a significant reduction and simplification of the successive work operations (elimination of bleaching treatments with sodium hydrosulphate, which is toxic, elimination or substantial reduction of washings with surfactants) and a smaller polluting load in the effluent. The silk treated in the more soft/bland conditions (pH, additive quantities, times and temperatures) of the present process is not sticky when wet and is very soft at the end of the work operations; it maintains its mechanical resistance and exhibits a smaller degree of yellowing with respect to the loaded silk according to known processes.
Further, the present silk loading process enables significantly reducing or avoiding use of monomers that are not very eco-sustainable and are toxic, including at the industrial scale, with considerable advantages for the environment, and for the safeguarding of the personnel directly involved in the industrial process or as final users. The present silk loading process advantageously enables reducing the quantity of water used, not only in the bath but also during the following work operations on the silk (washings).
Lastly, with the use of copper sulphate the present process enables obtaining a silk provided with anti-bacterial properties due to the presence of copper ions on the thread.

Summary of the Invention

Therefore a first object of the present invention is constituted by an aqueous composition for silk loading, comprising at least:

a) from 0.1 to 200 g/l of one or more vinyl monomers preferably selected from (meth)acrylamides, (meth)acrylonitriles, alkyl(meth)acrylates, hydroxy alkyl (meth)acrylates and (poly)ethylene glycol (meth)acrylates;
b) from 0.01 a 20 g/l of a radical initiator,
c) from 0.015 to 36 g/l of a second redox initiator selected from metal salts

A second object of the present invention is constituted by a process for silk loading comprising:

supplying the silk,
supplying an aqueors composition according to the present invention,
immersing the silk in the composition,
heating the composition in which the silk is immersed to a temperature comprised between 60 and 90°C for a time preferably comprised between 5 and 120 minutes, more preferably between 15 and 45 minutes, still more preferably between 20 and 35 minutes,
removing, washing and drying the silk.

A third object of the present invention is constituted by a process for silk loading comprising:

supplying the silk,
supplying an aqueous composition comprising the component a) according to the present invention,
immersing the silk in the composition,
adding the components b) and c) according to the present invention and bringing the pH of the aqueous composition to a value comprised between 3.3 and 6.8
heating the composition in which the silk is immersed to a temperature comprised between 60 and 85°C for a time preferably comprised between 5 and 120 minutes, more preferably between 15 and 45 minutes, still more preferably between 20 and 35 minutes,
removing, washing and drying the silk.

Also disclosed is a silk loaded according to the present processes of the invention.
A fourth object of the present invention - is constituted by a silk loaded with products of polymerization of vinyl monomers wherein said vinyl monomers comprise from 31% to 100% in weight, with respect to the overall weight of vinyl monomers, of hydroxy alkyl (meth) acrylate, preferably HEMA characterised by a titre of greater than 8.5 tex, preferably greater than 12 tex, more preferably greater than 19 tex and by one or more of the following characteristics:

an ultimate tensile strength of greater than 250cN, preferably greater than 300 cN;
an average ultimate elongation of greater than 12.5%, preferably greater than 16%;
a degree of whiteness of greater than 60%, preferably greater than 65%.

Detailed description of the invention

A first object of the present invention is an aqueous composition for silk loading, comprising at least:

a) from 0.1 to 200 g/l of one or more vinyl monomers preferably selected from (meth)acrylamides, (meth)acrylonitriles, alkyl(meth)acrylates, hydroxy alkyl (meth)acrylates and (poly)ethylene glycol (meth)acrylates;
b) from 0.01 to 20 g/l of a radical initiator, preferably selected from ammonium persulphate, potassium persulphate, AIBN (2,2'-azobisisobutyronitrile), ADC (2,2'-azobis(2-methyl-propionamidine) dichlorhydrate;
c) from 0.015 to 36 g/l of a second redox initiator selected from metal salts

In the present invention, component a) is a vinyl monomer, preferably a derivative of acrylic or methacrylic acid, preferably selected from (meth)acrylamides, alkyl(meth)acrylates and hydroxy alkyl(meth)acrylates.
Among the meth(acrylamides) the preferred ones are methacrylamide (MAA) or its N-alkylated derivatives, such as for example N-(n-butoxymethyl) methacrylamide.
Among the alkyl(meth)acrylates are preferred those in which the alkyl is methyl-, ethyl-, isopropyl-, n-butyl-, benzyl-, ethoxyethyl or glicidyl-, in particular methyl methacrylate (MMA), n-butylmethacrylate (BMA), 2-ethylhexyl methacrylate (EHMA), triethylene glycol-monoethylether-methacrylate (TEGEEMA), ethylene glycol dimethacrylate (EGDMA), more in particular MMA.
Among the hydroxy alkyl (meth)acrylates the preferred are 2-hydroxyethyl methacrylate (HEMA) and hydoxy propylene methacrylate, in particular 2-hydroxyethyl methacrylate.
Advantageously in the present composition said one or more vinyl monomers comprise from 31% to 100% in weight, preferably from 51% to 100%, from 61% to 100% in weight of a hydroxy alkyl (meth)acrylate, preferably HEMA, with respect to the overall weight of vinyl monomers present in the composition.
In the present invention the component b) is preferably selected from ammonium persulphate and potassium persulphate, and preferably is ammonium persulphate.
In the present invention the component c) is preferably selected from metal salts which can perform the function of initiators of oxidation-reduction reactions, such as iron sulphate, aluminium sulphate, copper sulphate etc., preferably copper sulphate.
The aqueous composition of the present invention preferably comprises at least:

a) from 10 to 100 g/l, from 15 to 50 g/l, from 10 to 40 g/l, from 19 to 40 g/l, from 30 to 40 g/l, from 30 to 37 g/l, from 20 to 30 g/l of one or more vinyl monomers or mixtures thereof selected from (meth)acrylamides, (meth)acrylonitriles, alkyl (meth)acrylates, hydroxyalkyl (meth)acrylate and (poly)ethylene glycol(meth)acrylates;
b) from 0,1 to 5 g/l, preferably from 0.1 to 1 g/l of a radical initiator, preferably selected from ammonium persulphate, potassium persulphate, AIBN (2,2'-azobisisobutyronitrile), ADC 2,2'-azobis(2-methyl-propionamidine) dichlorhydrate;
c) from 0.1 g/l to 7 g/l, preferably from 0.15 to 2 g/l of a second redox initiator selected from metal salts in which said one or more vinyl monomers comprise, preferably from 51% to 100% in weight, from 61% to 100% in weight of - a hydroxyl alkyl(meth)acrylate with respect to the overall weight of vinyl monomers present in the composition.

The aqueous composition of the present invention preferably comprises at least

a) from 0.1 to 200 g/l of one or more vinyl monomers or mixtures thereof selected from (meth)acrylamides, alkyl(meth)acrylates, and hydroxy alkyl (meth)acrylates
b) from 0.01 a 20 g/l of ammonium persulphate,
c) from 0.015 to 36 g/l of copper sulphate

The aqueous composition of the present invention preferably comprises at least:

a) from 0.1 to 200 g/l of one or more vinyl monomers or mixtures thereof selected from MAA, MMA and HEMA,
b) from 0.01 to 20 g/l of a radical initiator preferably selected from ammonium persulphate, potassium persulphate, AIBN (2,2'-azobisisobutyronitrile), ADC 2,2'-azobis(2-methyl-propionamidine) dichlorhydrate,
c) from 0.015 to 36 g/l of a second redox initiator selected from metal salts

The aqueous composition of the present invention preferably comprises at least

a) from 0.1 to 200 g/l of one or more vinyl monomers or mixtures thereof selected from among MAA, MMA and HEMA,
b) from 0.01 to 20 g/l of ammonium persulphate,
c) from 0.015 to 36 g/l of copper sulphate

In a preferred embodiment the aqueous composition of the present invention comprises at least

a) from 10 to 100 g/l, from 15 to 50 g/l, preferably from 30 to 40 g/l, of one or more vinyl monomers or mixtures thereof selected from MAA, MMA and HEMA,
b) from 0.1 to 1 g/l of ammonium persulphate,
c) from 0,15 to 2 g/l of copper sulphate

In a more preferred embodiment the aqueous composition of the present invention comprises at least

a) from 30 to 40 g/l of HEMA,
b) from 0.1 to 1 g/l of APS,
c) from 0.15 to 2 g/l of copper sulphate

The component a) comprises one or more vinyl monomers and mixtures thereof.
In an embodiment of the present invention, the component a) comprises one or more vinyl monomers or mixtures thereof of which at least 51%, 61%, 70%, 80%, 90%, 95%, 99% in weight is represented by a hydroxy alkyl (meth)acrylate.
In an embodiment of the present invention, the component a) comprises 100% in weight of one or more hydroxy alkyl (meth)acrylates, preferably 100% in weight of one/a sole hydroxy alkyl (meth)acrylate, more preferably of HEMA.
In a preferred embodiment the component a) of the aqueous composition of the present invention comprises from 0% to 39%, preferably between 1 and 20% in weight of MMA, from 0% to 60%, preferably from 10% to 50%, more preferably between 30% and 50%, between 30% and 40% in weight of MAA and, preferably from 51% to 100%, from 61% to 100% in weight of HEMA with respect to the total weight of the mixture of monomers.
The percentage in overall weight of said one or more vinyl monomers with respect to the weight of the silk to be treated can vary between 0.1% and 200%, between 10% and 140%, between 30% and 90%, between 40 and 80%, between 50% and 60% in weight.
In a preferred embodiment, at least 51%, 61%, 70%, 80%, 90%, 95%, 99% or 100% is represented by a hydroxy alkyl (meth)acrylate, preferably HEMA.
In the present composition the component b) is preferably present in a quantity of at least 0.4%, and the component c) in a quantity of at least 0.9% in weight with respect to the overall quantity of said one or more vinyl monomers a).
The component b) is preferably present in a quantity of less than 3%, 2%, 1% in weight and component c) in a quantity of less than 5%, 4%, 3%, 2%, 1.5% in weight with respect to the overall quantity of said one or more vinyl monomers a).
The aqueous composition of the present invention generally has a pH comprised between 3.3 and 6.8, more preferably between 3.5 and 6, still more preferably between 4 and 5. Acids commonly used to bring the pH of the bath to desired values are formic acid, citric acid, acetic acid etc., though the type of acid is not limiting.
The present composition preferably uses water as a solvent, though it could be mixed with appropriate water-soluble or water-dispersant solvents.
The present invention can possibly incorporate one or more additives commonly used in the field such as for example a reticulating additive for metal redox systems for improving the homogeneity of the loading (for example Temed, CAS RN 110-18-9).
A second object of the invention is constituted by a process for silk loading, comprising:

supplying the silk,
supplying an aqueous composition according to the present invention,
immersing the silk in the composition,
heating the composition in which the silk is immersed to a temperature comprised between 60°C and 90°C for a time preferably comprised between 5 and 120 minutes, more preferably between 15 and 45 minutes, still more preferably between 20 and 35 minutes,
removing, washing and drying the silk.

Alternatively the process of the present invention comprises: supplying the silk,
supplying an aqueous composition comprising component a) of the present invention,
immersing the silk in the composition,
adding components b) and c) according to the present invention and bringing the pH of the aqueous solution to a value comprised between 3.3 and 6.8, more preferably between 3.5 and 6, still more preferably between 4 and 5,
heating the composition in which the silk is immersed to a temperature comprised between 60°C and 90°C for a time preferably comprised between 5 and 120 minutes, more preferably between 15 and 45 minutes, still more preferably between 20 and 35 minutes,
removing, washing and drying the silk.
In the above-described processes one or more of the vinyl monomers preferably comprise from 51% to 100% in weight, more preferably between 61% to 100% in weight of a hydroxy alkyl(meth)acrylate, preferably HEMA, with respect to the overall weight of vinyl monomers.
Still more preferably, in the above-described processes the vinyl monomer is HEMA, said component b) is ammonium persulphate and said component c) is copper sulphate.
Still more preferably, in the above-described processes the percentage of loading is greater than > 50%, preferably greater than> 70%, more preferably greater than> 90%.
Still more preferably in the above-described processes the percentage of grafting is greater than 80%, preferably greater than 90%, more preferably greater than 95%.
Still more preferably, in the above-described processes said component a) is HEMA in a quantity comprised between 0.1 and 200 g/l; said component b) is ammonium persulphate in a quantity comprised between 0.1 and 1 g/l; said component c) is copper sulphate in a quantity comprised between 0.15 and 3 g/l; said pH is comprised between 4 and 5; said temperature is comprised between 65°C and 75°C and said time is comprised between 20 and 45 minutes.
Still more preferably, in the above-described processes the bath ratio is less than 100 1/Kg, preferably less than 50 1/Kg, more preferably less than 30 1/Kg, still more preferably less than 20 1/Kg.
The silk to which the present process is applied is a silk of any origin, which has been subjected to a preparatory process of degumming. The silk can be treated in the form of a thread, preferably wound in hanks or on reels, of fabric or other.
Also disclosed is a silk loaded according to one of the above-described processes.
The silk is preferably characterised by a titre of greater than 8.5 tex, preferably greater than 12 tex, more preferably greater than 19 tex.
The silk is preferably characterised by an ultimate tensile strength of greater than 250cN, preferably greater than 300 cN.
Still more preferably the silk is characterised by an average elongation at break of greater than 12.5%, preferably greater than 16%.
A further object of the present invention is a silk loaded with the products of polymerization of vinyl monomers wherein said vinyl monomers comprise from 31% to 100% in weight, with respect to the overall weight of vinyl monomers, of a hydroxy alkyl (meth) acrylate, preferably HEMA characterised by a titre of greater than 8.5 tex, preferably greater than 12 tex, more preferably greater than 19 tex and by one or more of following characteristics:

an average ultimate tensile strength of greater than 250 cN, preferably greater than a 300 cN
an average elongation at break of greater than 12.5%, preferably greater than 16%
a degree of whiteness of greater than 60%, preferably greater than 65%.

Said silk preferably contains the products of polymerisation of one or more vinyl monomers which comprise from 61% to 100% in weight with respect to the overall weight of vinyl monomers, of a hydroxyl alkyl (meth)acrylate, preferably HEMA. The ratio between the volume of the aqueous composition in which the treatment occurs and the weight of the silk to be treated (known as the bath ratio) is in general lower than 100 1/Kg, preferably less than 50 1/Kg, more preferably less than 30 1/Kg, still more preferably less than 20 1/Kg, and in preferred industrial embodiments about 15 1/Kg.
The absolute quantity of monomer a) to be used, in the limits defined in the present description, will vary according to the bath ratio: the Applicant has found that by working in more diluted conditions, such as for example happens at laboratory scale with bath ratios of greater than 40 1/Kg, it is necessary to increase the quantity of monomer in the bath so as to maintain a high loading, while on an industrial scale with bath ratios of less than 40 1/Kg, preferably less than 30 1/Kg, more preferably less than 20 1/Kg, it is possible to reduce the quantity of monomer, reaching an optimal grafting of about 100% and a significant weight increase in the silk. In the present process the aqueous composition can be prepared in one-pot, adding all the ingredients in water and, lastly, immersing the silk or preferably, for successive steps, which include the initial addition of the vinyl monomers (component a)) to the water, followed by immersion of the silk and lastly by addition of the components b) and c), with corrections of the pH up to the desired value.
Component a) is present in the aqueous composition from 0.1 a 200 g/l, preferably from 10 to 100 g/l, from 15 to 70 g/l, from 15 to 50 g/l, from 30 to 50 g/l, from 10 to 40 g/l, from 20 to 40 g/l, from 30 to 40 g/l, from 30 to 37 g/l, from 20 to 30 g/l.
The quantity of component a) will mainly depend on the bath ratio and on the desired increase of the final weight. The overall weight percentage of said one or more vinyl monomers with respect to the weight of the silk to be treated can vary between 0.1% and 200%, between 10% and 140%, between 30% and 90%, between 40 and 80%, between 50% and 60% in weight. Component a) comprises one or more vinyl monomers or their mixtures selected from (meth)acrylamides, ((meth)acrylonitriles, alkyl(meth)acrylates, hydroxy alkyl (meth) acrylates and (poly)ethylene glycol (meth)acrylates, preferably selected from (meth)acrylamides, alkyl(meth)acrylates and hydroxy alkyl (meth)acrylates, more preferably among MAA, MMA and HEMA.
Component a) comprises one or more vinyl monomers or their mixtures comprising from 31% to 100% in weight, preferably from 51% to 100% in weight, from 61% to 100% in weight of a hydroxy alkyl (meth) acrylate with respect to the overall weight of vinyl monomers present in the composition.
Preferably the component a) comprises one or more vinyl monomers or their mixtures comprising from 51% to 100% in weight, from 61% to 100% in weight of HEMA with respect to the overall weight of vinyl monomers present in the composition.
The component a) of the aqueous composition of the present invention comprises preferably from 0% to 39% in weight of MAA, from 0% to 60% in weight of MMA and from 31% to 100% in weight of HEMA with respect to the total weight of the mixture of monomers.
In the present process, the component a) is dissolved or suspended in the deionized water of the bath, by shaking, at temperatures preferably comprised between 25° and 40°C, possibly in the presence of appropriate additives able to facilitate the solubilisation thereof.
The component b) of the present aqueous composition is preferably selected from ammonium persulphate and potassium persulphate, and is preferably ammonium persulphate.
In the present process, the component b) is preferably dissolved in water and the solution thus obtained, is added to the bath, before or after the introduction of the silk.
The quantity of the component b) is preferably calculated on the basis of the volume of the bath and does not correspond necessarily, as in the traditional process, to 3% of the monomer a) used for the loading process.
The component c) of the present composition is preferably selected from redox systems (metal salts) such as iron sulphate, aluminium sulphate, copper sulphate etc., and is preferably copper sulphate.
Component c) is also preferably dissolved in water and the solution thus-obtained is added to the bath, before or after the introduction of the silk.
In the present process attempts to cause the grafting reaction at less drastic pH levels have been successful, with evident advantages in terms of softness and, more in general, in terms of the properties of the final silk.
In particular the pH of the bath is corrected by addition of acids to a value comprised between 3.3 and 6.8, more preferably between 3.5 and 6, still more preferably between 4 and 5. Acids commonly used to bring the pH of the bath to the desired values are formic acid, acetic acid, citric acid etc., though the type of acid is not limiting.
In the present process preferably water is used as a solvent, though it can possibly be in a mixture with suitable water-soluble or water-dispersible solvents.
In the present process one or more additives commonly used in the field can possibly be incorporated, such as for example reticulating additives compatible with metallic redox systems for improving the loading homogeneity.
The temperature of the loading process can vary between 60°C and 90°C, preferably between 65°C and 75°C, more preferably between 67°C and 72°C.
During the step of preparation of the present aqueous composition, the water is preferably pre-heated to temperatures generally around 30 - 35°C, so as to facilitate the incorporation of the components of the composition.
The loading time can vary in general between 5 minutes and 120 minutes, preferably between 10 and 80 minutes and more preferably between 20 and 60 minutes. The duration of the present process is generally much less than that of the known processes and is therefore advantageous as it enables overall reducing process costs and increasing productivity.
The present silk loading process is preferably done while shaking the bath to maintain homogeneity of temperatures and composition and facilitating impregnation of the fibres.
The process of the present invention exhibits numerous advantages with respect to known processes. In fact, beyond loading the silk successfully, homogeneously even on threads wound on a reel, significantly increasing the weight thereof, for example up to 90%, the thread loaded in this way maintains the typical softness of silk to the touch, dyes uniformly like silk loaded with MAA while maintaining excellent properties of tenacity and resistance to breakage. The present process enables greatly increasing the weight of the silk without altering the essential properties thereof of softness, shininess and resistance.
Further, the thread is very much less yellow, thus solving also the typical problem of yellowing with silk loaded with this monomer. Also as regards weaving, the results have been satisfactory and indeed better.
The present process is very much more rapid than traditional processes, enabling even high loadings in short times, with ensuing important industrial advantages.
The present process is also successful in maintaining or improving the monomer yield (grafting), expressed as a quantity of monomer loaded on the silk with respect to the quantity of monomer added to the treatment bath, in comparison with traditional processes with undoubted advantages in economic terms. In the present process the grafting can reach 100% in weight, and generally varies between 80% and 100% in weight.
An important aspect of the present process is its real industrial applicability with excellent results in terms of silk quality, differently to many processes in the prior art studied only at laboratory scale which enable lower loadings and produce final properties of thread that are insufficient. The present process enables loading the silk, increasing its weight significantly and at the same time giving softness, shininess and high mechanical resistance.
The weight gain of the silk (loading) is generally calculated with respect to the weight of the raw silk, i.e. before the degumming treatment (removal of sericin), with the following formula: $loading % = (W - Wo / Wo) \times 100$
wherein W is the weight of the silk after loading and Wo is the weight of the raw silk after degumming.
The silk loading process of the present invention enables incorporating greater quantities of monomer with respect to traditional processes, reducing waste in real terms. This determines higher reaction yield and therefore lower costs, and further enables reducing the pollutant load in the effluent water.
The incorporation of the monomer into the silk, known as grafting, is expressed in percentage terms and can be calculated using the following formula: $grafting % = (W - Wo / Wm) \times 100$
wherein W represents the weight of the silk after loading, Wo the weight of the raw silk after degumming and Wm the weight of the monomer introduced into the bath.
The present loading process, as well as enabling a higher incorporation of the monomer, advantageously uses smaller quantities of additives in combination, in particular of radical initiators, redox salts and acids, with respect to traditional processes. This leads to significant reductions in costs, reaction times and working times.
In fact silk treated in this way, as well as exhibiting an excellent softness even with high loadings of 110%, on the one hand does not become yellow like the silk obtained with traditional loadings and therefore does not require successive whitening treatments such as for example those using hydrosulphites, and on the other hand as there are far fewer reaction sub-products and/or unreacted additives present, the silk does not remain sticky when wet and requires fewer washings with water and fewer final treatments with chemical substances such as for example surfactants.
Further, the present process does not use toxic metal salts such as mercury, chrome, etc.
In the following experimental part, a description is made of the process and composition according to the present invention, by way of non-limiting example.
In the following examples degummed silk has been used having the following characteristics: Tram Silk 20/22, four articles; Tram Silk 20/22, three articles, Organzino 20/22, two articles.
The apparatus used for loading, on semi-industrial scale, was UGOLINI SP 110/1^a and on industrial scale Loris Bellini MOD BBNV 760/1090 or MOD BBNV 1040/1090 or MOD BBNV 1040/2180 - vertical axis.
For drying the silk, microwave ovens were used for laboratory samples and TDS RF System radio-frequency dryers for semi-industrial or industrial samples.

Example 1 (industrial scale)

Place 416 litres of deionized water in a reaction recipient and bring the temperature to 35 degrees (heating velocity of 1 degree/minute). Contemporaneously start up the centrifuge pump to maintain the liquid in the recipient thermally and chemically homogeneous.
Place 8 Kg of HEMA (19.2 g/1) and maintain the temperature at 35°C for 10 minutes. Transfer the resulting mixture into the recipient, where there are 10 kg of degummed silk.
Add 96 g of ammonium persulphate (0.23 g/l), 224 g of copper sulphate (0.54 g/l) and formic acid up to bringing the pH to 4.5.
Bring the temperature to 68°C (velocity heating 1 degree/minute) and maintain the temperature for 30 minutes. Extract the loaded silk and wash it with cold water for 10 minutes and then with water at 70°C for 10 minutes with a non-ionic surfactant.
Rinse the silk with water at 40°C for 5 minutes.
Dry the silk in an oven. Weigh the silk to check the percentage of loading. The silk thus-loaded weighs 17 Kg.
The silk is soft and pleasant to the touch, homogeneous and much less yellowed with respect to silk loaded using the tradition process with MAA and also with respect to the silk loaded with HEMA according to the processes described in the prior art.
The loaded thread of the present process has been subjected to tests for determining the ultimate tensile strength on breaking of the single threads according to standard UNI EN ISO 2062 : 2010.
In particular test 1 refers to the loaded silk thread according to the present process and dyed, test 2 is performed on the silk thread after degumming and before the loading process, test 3 is a comparative test with a silk thread loaded according to known processes and dyed.
In particular, the thread of test 3 was prepared according to the experimental conditions reported in example 6A, which is alike the process described in WO2008/ 145413.
The conditions used in the ultimate tensile strength tests were:

Types of pack/conditions of the thread : hank/dye
Test method used: A
Initial length 250 mm
Velocity 250 mm/min
Pre-tension 0.,066 N
Identification of apparatus used: Dynamometer C.R.E. - Hounsfield
Type of clamps: Bollard
Number of tests: total/disregarded 10/0

Test performed in conditioned environment on material at 20°C ± 2°C and 65% ± 4% U.R.
The table reports the values obtained with the three threads:

TEST 1 TEST 2 TEST 3

average elongation at break (cN) 294 292 301
Differently to what is reported in the prior art, for example in Tsukada (2001), where the loading process with HEMA determines a deterioration of 60% in the thread mechanics, in the present process (Test 1) the ultimate tensile strength is much greater and is comparable to the results obtained with MAA (Test 3).

Example 2 (industrial scale)

Place 416 litres of deionized water in a reaction recipient and add 6.6 Kg of HEMA. Bring the temperature to 35 degrees and maintain for 10 minutes.
Transfer the mixture obtained into the bath containing 10 kg of degummed silk. Bring the temperature to 45°C and maintain for 5 minutes. Add 83.2 g of ammonium persulphate previously dissolved in water at room temperature in about 5 minutes.
Wait for 5 minutes and add 191.4 g of copper sulphate previously dissolved in water at T=90°C and cooled to 40°C, in about 7 min. Wait about 5 min and bring the pH to between 4 and 5, adding formic acid in water at room temperature in about 5 minutes. Heat up to about 70°C with a gradient of about 1°C/min and maintain at this temperature for 25 minutes. Drain the mixture, wash the silk in cold water for 10 minutes and dry in the oven.
The loaded silk exhibits a weight of about 16.4 Kg which corresponds to a percentage weight increase of about 65% (with respect to the weight of the silk after degumming).
The silk thus treated is soft, shiny and not yellow.

Example 3 (industrial scale)

Place 1135 litres of deionized water in a reaction recipient and add 37 Kg of HEMA (32.6 g/1). Bring the temperature to 35 degrees and maintain for 10 minutes.
Transfer the mixture obtained into the bath containing 56 kg of degummed silk (corresponding to 75 Kg of raw silk). Bring the temperature to 45°C and maintain for 5 minutes. Add 227 g of ammonium persulphate (0.20 g/l) previously dissolved in water at room temperature in about 5 minutes.
Wait for 5 minutes and add 522.1 g of copper sulphate (0.46 g/l)previously dissolved in water at T=90°C and cooled to 40°C, in about 7 min. Wait about 5 min and bring the pH to between 4 and 5, adding formic acid in water at room temperature in about 5 minutes. Heat up to about 70°C with a gradient of about 1°C/min and maintain at this temperature for 25 minutes.
Drain the mixture, wash the silk in cold water for 10 minutes and dry in the oven.
The loaded silk exhibits a weight of about 92 Kg which corresponds to a percentage weight increase of about 64% (with respect to the weight of the silk after degumming).
The incorporation of the monomer (grafting) is 97%.
The silk thus treated is soft, shiny and mechanically improved.

Example 4 (semi-industrial scale)

Place 15 litres of deionized water in a reaction recipient and add 6.6 Kg of HEMA (49.3 g/l). Bring the temperature to 35 degrees and maintain for 10 minutes.
Transfer the mixture obtained into the bath containing two 315 g reels, each of degummed silk. Bring the temperature to 45°C and maintain for 5 minutes. Add 3 g of ammonium persulphate (0.20 g/1) previously dissolved in water at room temperature in about 5 minutes.
Wait for 5 minutes and add 6.9 g of copper sulphate (0.46 g/l) previously dissolved in water at T=90°C and cooled to 40°C, in about 7 min. Wait about 5 min and bring the pH to between 4 and 5, adding formic acid in water at room temperature in about 5 minutes. Heat up to about 70°C with a gradient of about 1°C/min and maintain at this temperature for 25 minutes.
Drain the mixture, wash the silk in cold water for 10 minutes and dry in the oven.
The loaded silk exhibits a weight of about 690 g for each reel which corresponds to a percentage weight increase of about 60% with respect to the initial weight of the silk before degumming, and at a loading of 119% with respect to the weight of the degummed silk. The incorporation of the monomer (grafting) is about 100%.
The silk thus treated is very soft and shiny.

Example 5 (industrial scale)

Place 1135 litres of deionized water in a reaction recipient and add 22 Kg of HEMA (38.76 g/l). Bring the temperature to 35 degrees and maintain for 10 minutes.
Transfer the mixture obtained into the bath containing 56 Kg of degummed silk (about 73 Kg of raw silk).
Bring the temperature to 45°C and maintain for 5 minutes. Add 227 g of ammonium persulphate (0.20 g/l) previously dissolved in water at room temperature in about 5 minutes. Wait for 5 minutes and add 522.1 g of copper sulphate (0.46 g/l) previously dissolved in water at 90°C and cooled to 40°C, in about 7 min. Wait about 5 min and bring the pH to between 4 and 5, adding formic acid in water at room temperature in about 5 minutes. Heat up to about 70°C with a gradient of about 1°C/min and maintain at this temperature for 40 minutes. Drain the mixture, wash the silk in cold water for 10 minutes, wash at 70°C with a non-ionic surfactant for 10 minutes, rinse for ten minutes, unload and dry in the oven.
The loaded silk exhibits a weight of about 93 Kg which corresponds to a percentage weight increase of about 28% with respect to the weight of the silk before degumming.
The silk thus treated is very soft, shiny and resistant.

Example 6

The following table compares the experimental conditions and the results of the silk loading according to the traditional process (Example 6A comparative, for example according to WO2008/145413 ) with the process according to the present invention (Example 6B with only HEMA and Example 6C with HEMA/MAA 1:1)

	Ex. 6A traditional process (comparative)	Es. 6B	Es. 6c
Weight of raw silk	75 Kg	75 Kg	75 Kg
Weight of degummed silk	56 Kg	56 Kg	56 Kg
Litres in bath	1200	1200	1200
Bath ratio (litres in bath	16 l/Kg	16 l/Kg	16 l/Kg
vs weight of raw silk)
Monomer	MAA	HEMA	MAA/HEMA (1:1)
Quantity of monomer	45 Kg	37 Kg	20Kg/20Kg
Duration of complete process	5.30 h	2 h	3 h
Duration of loading process	120 min	25 min	35 min
Quantity initiator APS	1540 g	240 g	240 g
Quantity of redox initiator (copper sulphate)	---	396 g	396 g
Quantity of acid	6 Kg	1.55 Kg	1.8 Kg
Conditions	70°C 120', then 80°C 20',then 50°C 15'	70°C for 25'	70°C for 35'
Quantity of surfactant	3.12 Kg	---	1.2 Kg
Quantity of hydrosulphite	600 gr	---	---
Final weight of silk	90 Kg	95 Kg	95 Kg
Incorporation of monomer	75%	105%	97%

As evidenced by the data in the table, the process of the present invention enables obtaining a higher loading, in shorter times and with significantly smaller quantities of reactants.
In test 6b(where it has probably remained incorporated in the water) the grafting is practically quantitative and equal to 97% in test 6c. The silk obtained is soft and resistant.

Example 7 (industrial scale)

Place 2240 litres of deionized water in a reaction recipient and add 75 Kg of HEMA (33.4 g/1). Bring the temperature to 35 degrees and maintain for 10 minutes.
Transfer the mixture obtained into the bath containing 110 Kg of degummed silk (about 143 Kg of raw silk).
Bring the temperature to 45°C and maintain for 5 minutes. Add 440 g of ammonium persulphate (0.2 g/l) previously dissolved in water at room temperature in about 5 minutes. Wait for 5 minutes and add 1000 g of copper sulphate (0.45 g/l) previously dissolved in water at T=90°C and cooled to 40°C, in about 7 min.
Wait about 5 min and bring the pH to between 4 and 5 at room temperature in about 5 minutes. Heat up to about 70°C with a gradient of about 1°C/min and maintain at this temperature for 25 minutes.
Drain the mixture, wash the silk in cold water for 10 minutes and dry in the oven.
The loaded silk exhibits a weight of about 185 Kg which corresponds to a percentage weight increase of about 30% (with respect to the weight of the silk before degumming), equal to 68% if referred to the silk after degumming.

Example 8 (comparative)

225Kg of degummed silk was loaded in 4300 litres of bath, using 180 Kg of HEMA in standard procedure conditions (according to Journal of Applied Polymer Science, Vol. 81, 1401-1409 (2001) Tsukada et al. and Journal of Applied Polymer Science, Vol. 67, 1393-1403 (1998) Tsukada et al.), adding about 5.4 kg of initiator (ammonium persulphate), correcting the pH to 3 (about 5 gr/l of formic acid) and heating for 60 minutes at 80°C. After working and drying, a silk was produced that when wet was very sticky and when dry, while exhibiting a significant improvement in weight, though with a grafting of lower than 80%, was so stiff as to be unusable.

Example 9 (comparative)

The following table reports the results obtained when operating according to the experimental conditions described in the present invention (samples 9A and 9B) in comparison to the results obtained when operating according to the known conditions (samples 9C-9F).
Sample 9C uses 100% glycidyl methacrylate (GM) with respect to the total of vinyl monomers; sample 9E uses 77% methacrylamide (MAA) and 23% hydroxy ethyl methacrylate (HEMA); all the other samples use 100% HEMA.
In particular, samples 9A and 9B were obtained by operating according to the experimental conditions described in the present invention respectively on a semi-industrial scale and an industrial scale. All the other samples were obtained by operating according to the teachings of the prior art, as indicated.
The percentage of loading and the percentage of grafting were determined as described in the present application.
The titre of the thread was calculated on the basis of the UNI 9275:1988 standard (Textiles. Determination of the mass per unit of length (titre) of a thread extracted from a fabric). The traction and elongation of the thread were calculated on the basis of UNI EN ISO 2062:2010 standard (Textiles - Packing threads - Determination of the elongation at break and ultimate tensile strength of the single threads by means of a dynamometer with a constant rate of extension (CRE).
The degree of whitening was calculated on the basis of the UNI 7623:1986 standard (Paper and board. Measurement Of Diffuse Blue Reflectance Factor (ISO degree of whiteness) and UNI EN ISO 105 J02:2001 (Textiles - Proof of colour fastness - instrumental evaluation of relative degree of whiteness.)

The softness was evaluated qualitatively to the touch by a group of three experts in the sector on the basis of the following scale: soft and suitable for successive work operations (+++), stiff/rollable (++) and stiff/unrollable (+).

Sample	9A	9B	9C	9D	9E	9F
Monomer used	HEMA	HEMA	GM	HEMA	MAA/HEMA	HEMA
Process	INV	INV	Ramadan, 2004	Ramadan, 2004	Evonik Rohm, 2008	TSUKADA,2001
Litres in bath	15	2100	0.1	0.1	9	15
Quantity of monomer	400 g (26.6 g/l)	77 Kg (36.6 g/l)	2 g (20 g/l)	2 g (20 g/l)	260 g (29 g/l)	260 g (17.4 g/l)
Quantity of first initiator	3 g (0.2g/l)	440 g 0.2 g/l	0.04 g (0.4 g/l)	0.04 g (0.4 g/l)	5.2 g/l (0.6 g/l)	6.2 g (0.4 g/l)
Quantity of second initiator	5 g 0.33 g/l	650 g (0.31 g/l	2.5 g (25 g/l)	5 g (50 g/l)	-	-
Time of reaction	25 min	25 min	60 min	60 min	120 min	60 min
Final temperature	70°C	70°C	80°C	80°C	70°C	80°C
Sample	9A	9B	9C	9D	9E	9F
Bath ratio (litres in bath vs weight of raw silk)	50 l/Kg	18 l/Kg	50 l/Kg	50 l/kg	30 l/Kg	50 l/Kg
PH composition	4.2	4.2	3	3	3	2.5
Form of silk	Perforat	Perforated	hank	hank	Perforate	Perforated
	ed reel	reel		d	d reel	reel
Weight of degummed silk	310 g	110 Kg	2.18 g	2.21 g	310 g	310 g

Sample	9A	9B	9C	9D	9E	9F
Final weight of silk	710 g	195.36	2.21	2.30	527 g	550 g
% of loading	129%	77%	1.4%	4%	70%	77%
% of grafting	100%	110%	1.5%	4.5%	83%	92%
Titre of degummed silk	7.1 tex	7.1 tex	7.1 tex	7.1 tex	7.1 tex	7.1 tex
Titre of final thread	19.4 tex (174.6 den)	12.3 tex (110.7 den)	8 tex (72 den)	8.4 tex (75.6 den)	Not able to unreel	Not able to unreel
degummed thread - averageo ultimate tensile strength	294 cN	294 cN	294 cN	294 cN	294 cN	294 cN
Final thread ultimate tensile strength	-	304 cN	243 cN	250 cN	NOT CALCULABL E (thread does not unreel)	NOT CALCULABLE (thread does not unreel)
Average elongation at break		16.7%	12.5%	13.2%
Average breaking tenacity (cN/TEX)		24.7	30.4	29.8
Sample	9A	9B	9C	9D	9E	9F
Degree of whiteness	70% (firs t side) 78%(seco nd side)
Softness	+++	+++	++	++	+	+
Qualitative characteristics of the silk	dyable	dyable	No increase in weight	No increase in weight	Not dyable	Not dyable

As can be understood from the examples reported, the silk of the present invention has both a high percentage of loading, specifically above 50%, and excellent mechanical characteristics with respect to the prior art, such as or example titre, resistance to elongation to break point and to elongation of the thread. The grafting is practically quantitative (in test 9B the value exceeds 100% probably due to incorporation of water).
Further, the silk of the present invention, having this high percentage of loading, also exhibits qualitative characteristics that are better than those of the prior art, such as softness and dyeability.

EXAMPLE 10

The present process is also particularly advantageous in terms of reduction of the volumes of water used for the washings, as can be seen from the data reported in the following table:

	INVENTION	Traditional method (Evonik, 2008) (Es. 6A)
Monomer used	HEMA	MAA
Consumption of litres of water per Kg of silk	29 litres	73 litres
Water saving	60%
Energy consumption saving	60%
Use of monomer in the process	100 %	80 % (20 % unloaded in the waste water)
Time of process	2 hours	5 hours

As can be seen from the above-cited example, the process of loading the silk of the present invention enables reducing the quantity of water used, as well as enabling an energy saving and reducing the pollutant discharges.

Claims

An aqueous composition for silk loading comprising at least:
a) from 0.1 to 200 g/l of one or more vinyl monomers preferably selected from (meth)acrylamides, (meth)acrylonitriles, alkyl(meth)acrylates, hydroxy alkyl (meth) acrylates and (poly)ethylene glycol (meth)acrylates;

b) from 0.01 a 20 g/l of a radical initiator,

c) from 0.015 to 36 g/l of a second redox initiator selected from metal salts
wherein said one or more vinyl monomers comprise from 31% to 100% in weight, with respect to the overall weight of vinyl monomers, of a hydroxy alkyl (meth) acrylate and/or
wherein the aqueous composition has a pH comprised between 3.3 and 6.8.
The aqueous composition of claim 1 having a pH comprised between 3.5 and 6, preferably between 4 and 5.
The aqueous composition of claim 1 or 2 wherein the one or more vinyl monomers of the component a) are selected from MMA, MAA and HEMA, the component b) is selected from ammonium persulphate (APS), potassium persulphate (PPS), 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methyl-propionamidine) dichlorhydrate (ADC), preferably between ammonium persulphate and potassium persulphate, and the component c) is selected from iron sulphate, aluminium sulphate and copper sulphate.
The aqueous composition of any one of claims from 1 to 3 comprising at least:
from 10 to 100 g/l, from 15 to 50 g/l, preferably from 30 to 40 g/l, of component a), from 0.1 to 5 g/l, preferably from 0.1 to 1 g/l of component b), and from 0.1 g/l to 7 g/l, preferably from 0.15 to 2 g/l of component c).
The aqueous composition of any one of claims from 1 to 4 wherein said one or more vinyl monomers comprise from 61% to 100% in weight of a hydroxy alkyl (meth)acrylate, preferably HEMA, with respect to the overall weight of vinyl monomers.
The aqueous composition of any one of claims from 1 to 5 comprising at least:
a) from 30 to 40 g/l of HEMA;

b) from 0.1 to 1 g/l of APS,

c) from 0.15 to 2 g/l of copper sulphate
wherein said aqueous composition has a pH comprised between 4 and 5.
A process for silk loading comprising:
supplying the silk,

supplying an aqueous composition of any one of claims from 1 to 6,

immersing the silk in the composition,

heating the composition in which the silk is immersed to a temperature comprised between 60°C and 90°C for a time preferably comprised between 5 and 120 minutes, more preferably between 15 and 45 minutes, still more preferably between 20 and 35 minutes,

removing, washing and drying the silk.
A process for silk loading, comprising:
supplying the silk,

supplying an aqueous composition comprising one or more vinyl monomers a) as defined in claims from 1 to 6,

immersing the silk in the composition,

adding components b) and c) to the composition and bringing the pH to a value comprised between 3.3 and 6.8 , to give a composition of any one of claims from 1 to 6,

heating the composition in which the silk is immersed to a temperature comprised between 60°C and 90°C for a time preferably comprised between 5 and 120 minutes, more preferably between 15 and 45 minutes, still more preferably between 20 and 35 minutes,

removing, washing and drying the silk.
The process of claims 7 or 8, wherein the pH is comprised between 3.5 and 6, still more preferably between 4 and 5.
The process of claims from 7 to 9, wherein the temperature is comprised between 65°C and 75°C, more preferably between 67°C and 72°C.
The process of any one of claims from 7 to 10 wherein said one or more vinyl monomers comprise from 61% to 100% in weight of a hydroxy alkyl(meth)acrylate, preferably HEMA, with respect to the overall weight of vinyl monomers.
The process of any one of claims from 7 to 11 wherein said vinyl monomer is HEMA, said component b) is ammonium persulphate and aid component c) is copper sulphate.
The process of any one of claims from 7 to 12 wherein the percentage of loading is greater than 50%, preferably greater than 70%, more preferably greater than 90%.
The process of any one of claims from 7 to 13 wherein the percentage of grafting is greater than 80%, preferably greater than 90%, more preferably greater than 95%.
The process of any one of claims from 7 to 14 wherein said component a) is HEMA in a quantity comprised between 0.1 and 200 g/l; said component b) is ammonium persulphate in a quantity comprised between 0.1 and 1 g/l; said component c) is copper sulphate in a quantity comprised between 0.15 and 3 g/l; said pH is comprised between 4 and 5; said temperature is comprised between 65 and 75°C and said time is comprised between 20 and 45 minutes.
The process of any one of claims from 7 to 15 wherein the bath ratio is less than 100 l/Kg, preferably less than 50 l/Kg, more preferably less than 30 l/Kg, still more preferably less than 20 l/Kg.
A silk loaded with products of polymerisation of vinyl monomers wherein said vinyl monomers comprise from 31% to 100% in weight, with respect to the overall weight of vinyl monomers, of a hydroxy alkyl (meth) acrylate, preferably HEMA characterised by a titre of greater than 8.5 tex, preferably greater than 12 tex, more preferably greater than 19 tex and by one or more of the following characteristics:
- an average ultimate tensile strength of greater than 250 cN, preferably greater than a 300 cN

- an average elongation at break of greater than 12.5%, preferably greater than 16%

- a degree of whiteness of greater than 60%, preferably greater than 65%.
The silk of claim 17, containing the products of polymerisation of one or more vinyl monomers which comprise from 61% to 100% in weight with respect to the overall weight of vinyl monomers, of a hydroxy alkyl (meth)acrylate, preferably HEMA.