The present invention relates to a functionalized PET with antioxidant activity and the relative synthesis method.

In today's society, plastic is a particularly important material that guarantees a series of benefits for human health and the environment. By way of example, it should be remembered that

• plastic packaging protects food and goods from waste and/or contamination, thus saving resources;

• the lightness of the plastic packaging saves fuel and reduces emissions during transportation with respect to the use of other materials;

• plastic water supply systems and storage containers/tanks can provide clean water;

• low-density plastics, used for replacing metals or ceramics in cars and airplanes, save fuel and reduce emissions;

• protective plastic clothing and safety devices (e.g. fireproof materials, helmets, airbags) prevent injuries;

• plastic products for medical applications contribute to improved health (e.g. blood bags, tubes, disposable syringes, prostheses).

Such diverse plastic consumption, however, leads to a diverse waste stream and, mainly due to the short lifespan of many plastic products (around 40% of these products are estimated as having a useful life of less than 1 month), large volumes of plastic waste are generated which create serious environmental and management problems.

Since ancient times there has been a need for storing and transporting food. With the advent of polymeric materials, there has been an enormous increase in materials in contact with a consequent increase in the need for highly specialized methods and techniques capable of ensuring a high degree of preservation of food products without affecting the quality (food safety).

In recent years, food packaging has therefore required continuous and greater efforts for finding solutions aimed at ensuring an optimal product shelf-life. There are, in fact, numerous functions that a food packaging must exert as the interactions between food and packaging have the same importance as the interactions between packaging and environment.

For this reason, it is important for consumers to be increasingly aware of the quality and potential of polymer-based packaging: it has been demonstrated that fresh food products such as vegetables, dairy products or meat last an average of ten to twenty-five days longer if properly packaged and that CO2 emissions deriving from packaging production are less than 10% than those caused by food production. Safe and hygienic packaging prevents food from spoiling prematurely and is extremely important as today over a third of all food produced in the world is wasted. According to the FAO, this food waste is responsible for up to 8% of global greenhouse gas emissions.

Factors that determine the deterioration of food are mainly oxygen and bacteria; both contribute to microbial growth, odour development and nutrient loss.

Food oxidation is a major concern of the food industry in the processing of fatty and oxygen-sensitive foods. It is responsible for the unpleasant rancid tastes and smells of food and thus negatively affects the acceptance of the product by consumers. The oxidation of food occurs through different pathways. The main cause is in fact self-oxidation which occurs in mild environmental conditions due to the presence of oxygen and light. Self-oxidation causes the formation of hydroperoxides which further degrade to produce aldehydes and ketones responsible for the sensory deterioration of food. Oxidation prevention is achieved by adding antioxidants to the food or packaging material.

For this reason, important characteristics of a material for packaging and preserving food are the oxygen transmission rate (OTR) and the water vapour permeability (WVP).

In order to counteract the action of oxygen and bacteria, what is known as smart packagings have been developed, which in turn are divided into active or intelligent packagings. Active packaging allows the lifetime of the food to be extended, improving its quality by controlling the temperature, oxygen and light. Packaging with active feasibility makes it possible to monitor, record and transmit information about product changes.

The most widely studied active packagings are those that involve the addition of an antioxidant and an antibacterial agent. The former act through a radical mechanism and can neutralize oxygen, the most widely used are phenols and polyphenols. They can be of a synthetic origin such as hydroxytoluene butylate (BHT, 2,6-di-/er/-butyl-4-methylphenol) with its derivatives or bio-based such as extracts of plants, fruit and essential oils.

The most widely used material for containing food is certainly plastic. This is light, flexible, long-lasting and has a low cost and for these reasons about one-third of the demand for plastic materials comes from the packaging industry, in particular for food packaging. Thanks to these characteristics, over the years, polymeric plastic materials have become essential for everyday and non-everyday life. Thermoplastics make up 90% of the world's polymer production. The thermoplastic polymer chains do not have strong interactions and they have the characteristic of being able to be melted and remodelled several times without undergoing alterations to the chemical structure of the polymer itself, thus allowing its recycling also mechanically.

Among thermoplastic polymers, PE (polyethylene), PP (polypropylene), PVC (polyvinyl chloride), PS (polystyrene) and PET (polyethylene terephthalate) can be mentioned. These are particularly used for food packaging. In particular, PET, prepared for the first time in 1946 by Whinfield and Dickson, is widely used for the containment of liquids and also for food purposes; furthermore it has excellent barrier characteristics (a good OTR and WVP). It is light, transparent, and safe, in addition, it is unbreakable. It has excellent tensile strength, impact resistance, good resistance to chemical agents and a reasonable thermal resistance. It can be easily processed by injection or extrusion. PET can be synthesized according to two methodologies. The first involves a direct reaction between terephthalic acid and ethylene glycol. This is a classic Fisher esterification reaction in which an acid reacts with an alcohol. The second technique involves a transesterification reaction in which dimethyl terephthalate reacts with ethylene glycol.

An example of active packaging was made (Ozogul Y. et al., Int. J. Food Sci. Tech. 2010, 45, 1717-1723) by producing antioxidant films by depositing a coating of an antioxidant agent (extracts of rosemary and cloves) on the internal surface of a polyethylene terephthalate (PET) film, previously treated, and evaluating its antioxidant activity in contact with the tissues of mackerel fish. Rosemary and cloves are known to be powerful antioxidants and antimicrobial agents concerning other natural herbs and are widely used in food and medicinal applications. The coating of the film with these extracts is obtained by means of a first surface treatment of the film. Surface treatment techniques include: corona, chemical modification and plasma treatment. The film used was PET, known for its good barrier and mechanical properties. This work shows that surface-treated films contribute to the preservation of food against oxidation, but the main problem is that, once used, the film must be processed and, in the recycling, and heating process there is no longer a surface coating. A new deposition of the antioxidant coating on the surface is therefore necessary in order to be able to use the film again.

The objective of the present invention is to overcome the drawbacks of the state of the art previously described, identifying a functionalized polyethylene terephthalate (PET) with antioxidant activity, recyclable, and particularly suitable for use in food packaging.

These and other objectives are achieved by employing the functionalized polyethylene terephthalate (PET) with an antioxidant activity according to the present invention.

The present invention, therefore, relates to a functionalized polyethylene terephthalate (PET) with an antioxidant activity, having the following formula (1)

wherein n and m, the same as or different from each other, are such that n + m ranges from 125 to 130 and wherein Y is selected from -OCH2CF2O(CF2CF2O)p(CF2O) _q CF2CH ₂ O- having a molecular weight ranging from 1,300 to 1,700, with p ranging from 5 to 7 and q ranging from 10 to 13, or a POSS (Polyhedral Oligomeric Sesquioxane) having the following formula wherein the substituents R, the same or different, are selected from alkyl and cycloalkyl groups; the substituents X, suitable for binding with PET, are selected from -OH, -NH2or -SH groups, preferably -OH groups; said POSS derivatives having a molecular weight ranging from 50 to 500.

The functionalized PET with an antioxidant activity having formula (1) in the various embodiments of the present invention is characterized by the following formulas (!') and (1”):

The substituents R are preferably linear- or branched-chain alkyl groups having a number of carbon atoms ranging from 1 to 8 or cycloalkyl groups having a number of carbon atoms ranging from 4 to 7, the R groups are even more preferably the same as each other and are linear- or branched-chain alkyl groups having a number of carbon atoms ranging from 1 to 8.

The selection of the R group can also modify the physical nature of the POSS which can therefore be solid or liquid depending on the density of the particular R group selected, i.e. depending for example on the linear- or branched-chain alkyl group having from 1 to 8 atoms of carbon.

The X groups of POSS are chemical functionalities suitable for binding with PET and can vary in their position in the POSS structure based on their chemical synthesis/modification. The X groups are preferably -OH groups.

The present invention further relates to a synthesis process of a functionalized polyethylene terephthalate (PET) with antioxidant activity, having formula (1)

wherein n and m, the same as or different from each other, are such that n + m ranges from 125 to 130 and Y is selected from -OCH ₂ CF ₂ O(CF ₂ CF ₂ O) _P (CF ₂ O) _q CF ₂ CH ₂ O- having a molecular weight ranging from 1,300 to 1,700, with p ranging from 5 to 7 and q ranging from 10 to 13, or a POSS (Polyhedral Oligomeric Sesquioxane) having the following formula wherein the substituents R, the same or different, are selected from alkyl and cycloalkyl groups; they are preferably selected from linear- or branched - chain alkyl groups having a number of carbon atoms ranging from 1 to 8 or cycloalkyl groups having a number of carbon atoms ranging from 4 to 7, they are more preferably the same as each other and are linear- or branched- chain alkyl groups having a number of carbon atoms ranging from 1 to 8; the substituents X, suitable for binding with PET, are selected from -OH, -NH ₂ or -SH groups, preferably -OH groups; said POSS derivatives having a molecular weight ranging from 50 to 500, said process comprising the following steps: i) etherification reaction of a perfluoro alkyl derivative having formula (2’) HOCH2CF2O(CF2CF2O)p(CF2O) _q CF2CH ₂ OH

(2’) having a molecular weight ranging from 1,300 to 1,700, with p ranging from 5 to 7 and q ranging from 10 to 13 or a POSS (Polyhedral Oligomeric Sesquioxane) having formula (2”) wherein R and X have the meanings indicated above, with an epoxide having formula (3) ii) subsequent reaction of a compound having formula (4 'or 4”) obtained at the end of step i) with a polyethylene terephthalate (PET) having formula (5) wherein 1 ranges from 125 to 130 according to the following schemes 1 and 2

to give the functionalized PET with an antioxidant activity having formula (1’, 1”).

The present invention further relates to the use of a functionalized PET with antioxidant activity having formula (1) as a material for food packaging.

A first advantage of the functionalized PET according to the present invention is linked to the formation of a covalent bond between PET and antioxidant molecule, through the bond with the fluorinated agent. This allows the antioxidant action to be exerted directly on the surface of the functionalized PET, as the fluorinated compound or POSS, by its very nature, will tend to rise to the surface. In addition, the functionalized PET, i.e. the polymenc system, will maintain the same structure even after recycling: it will therefore be possible to exploit the same mechanism and retain the antioxidant activity of the functionalized PET in the subsequent reuse.

The synthesis process of functionalized PET according to the present invention is particularly advantageous as it surprisingly allows the oxidizing agent to be fixed on the surface of the polymer. Furthermore, it can also use PET recycled from bottles of water as a raw material for the formation reaction of the covalent bond, as it is a process that does not require special processing conditions.

A further advantage of the functionalized PET according to the present invention is that a material is obtained that can be used for food packaging, capable of slowing down the oxidative process without altering the health and safety parameters of the food contained therein, thanks to the formation of a covalent bond, between PET and additives, a bond that does not break thus preventing the antioxidant agent from being absorbed by the food.

In order to achieve this objective, it was necessary to identify and synthesize an antioxidant molecule belonging to the polyphenol family not only capable of binding to the polymer matrix of PET, but capable of migrating towards the surface of the same to be in contact with food and in this way exert its antioxidant function.

Antioxidants however are not capable of spontaneously migrating towards the surface of the polymeric matrix and for this reason it was necessary to bind the antioxidant to PET using a fluorinated compound, more specifically by means of perfluoroalkyl substances (abbreviated as PFAS) or by POSS molecules (Polyhedral Oligomeric Sesquioxane).

It is known in literature that fluoroalkyl derivatives have the capacity to spontaneously migrate to the surface of a polymeric matrix to which they are chemically bound (Rolland, J. P. et al., Angew. Chem. Int. Ed. 2004, 43, 5796- 5799; Rolland, J. P. et al., J. Am. Chem. Soc. 2004, 126, 2322-2323).

The addition of a fluorinated compound or a POSS is essential as it allows the antioxidant to arrange itself on the surface of the polymer and to come into contact with food, without however being released for exerting its action.

The fact that the antioxidant encounters the food, but remains bound to the polymer matrix, limits the possible contamination of food, thus increasing the safety of the material.

It should be pointed out that perfluoroalkyl substances (abbreviated as PFAS) are widely used in various sectors as they provide resistance, resilience and durability to the materials they are associated with. The use of PFAS in applications involving food contact has recently attracted the attention of public opinion, concerned about the possible health consequences resulting from excessive exposure to these substances. The Food and Drug Administration (FDA) has established that fluoroalkyl polymers currently used in food packaging and other applications in contact with food are safe. PFAS producers have, in fact, collaborated with the Environmental Protection Agency (EPA) and today the phaseout of long-chain PFAS is complete. In order to ensure the safety and benefits of using PFAS, innovative chemical alternatives have in fact been developed based on polymeric products based on short-chain fluoroalkyl polymers. Furthermore, the potential dangerousness of PFAS products was linked to the presence of perfluorooctanoic acid (PFOA), used years ago in some processes for the preparation of long-chain perfluoroalkyl polymer, but which is now very rarely found in modern products. PFAS are therefore not dangerous to health when used properly. Finally, from the point of view of Circular Economy, treatment with PFAS does not affect the capacity of recycling the food packaging material, i.e. the functionalized PET with an antioxidant activity, unlike many other alternatives that can prevent the recycling of the packaging or its compostability. The PFAS used in functionalized PET with an antioxidant activity according to the present invention satisfies all these characteristics, has a molecular weight that is sufficient for not being bioavailable and is extremely stable, not presenting a significant risk to human health or the environment.

Perfluoroalkyl substances (PFAS) are therefore widely used in many industrial and commercial applications, above all thanks to their capacity of rising to the surface once introduced en masse into the composite matrices, and thus modifying their impermeability characteristics. In recent years, however, in consideration of the widespread use of the same, a greater sensitivity has been found in relation to the impact that PFAS seem to have on the environment. These substances, in fact, tend to accumulate in the environment and in living organisms specifically as a result of their high thermal and chemical stability. Recent studies have shown that the negative effect on the environment and on human beings can be attributed however to only a few perfluoro alkyl substances, whereas most PFAS are still under observation for the necessary toxicological assessments. These possible problems relating to the use of PFAS has therefore led to the identification of alternative solutions to PFAS and, in particular, POSS (Polyhedral Oligomeric Silsesquioxane) has been identified as an alternative molecule capable of exerting the same action as the fluorinated compound, eliminating, however, any problems relating to the alleged toxicity of the same. Specifically, this molecule exploits the same reactivity, following the same chemical methodology, with the aim of covalently binding to both PET and to the antioxidant molecule and is capable of spontaneously migrating to the surface.

POSS (Polyhedral Oligomeric Silsesquioxanes) are chemicals that have a nano-structure capable of improving the performance of the final product. The POSS molecule can contain various chemical functionalities, such as for example hydroxyl and/or amino groups, capable of forming covalent bonds with both polymeric matrices and with small organic molecules suitable for chemical transformation. Through these features, the POSS molecule is capable of binding the molecule with antioxidant properties to PET and spontaneously migrating to the surface, thus making exploiting its activity to the full and remaining at very low concentration levels.

More specifically, the perfluoroalkyl derivative used in the functionalized PET according to the present invention is a commercial product of Solvay S.p.A. called FOMBLIN D2, having the following formula (2') and used for functionalizing the polymer matrix with the antioxidant molecule: HOCH2CF2O(CF2CF2O)p(CF2O) _q CF2CH ₂ OH

(2’) having a molecular weight ranging from 1,300 to 1,700, with p ranging from 5 to 7 and q ranging from 10 to 13.

In step i) of the synthesis process of functionalized PET with an antioxidant activity according to the present invention, the perfluoroalkyl derivative having formula (2') reacts with an epoxide having formula (3)

The epoxide having formula (3) is synthesized as shown in the following scheme 1 wherein the synthesis reaction involves three different steps, respectively an oxidation reaction, a Friedel Craft acylation reaction, followed by the one-pot reduction of the resulting ketone and finally an epoxidation, according to scheme 3 below:

Scheme 3

Scheme 1

As specified above, the synthesis process of functionalized PET with an antioxidant activity having formula (!') wherein n and m, the same as or different from each other, are such that n + m ranges from 125 to 130, comprises the following steps: i) etherification reaction of a perfluoroalkyl derivative having formula (2') p(CF ₂ O) _q CF ₂ CH ₂ OH having an equal molecular weight ranging from 1,300 to 1,700, with p ranging from 5 to 7 and q ranging from 10 to 13, with an epoxide having formula (3) ii) subsequent reaction of a compound having formula (4') obtained at the end of step i) with a polyethylene terephthalate (PET) having formula (5) wherein 1 ranges from 125 to 130

(4') ( F) to give the functionalized PET with an antioxidant activity having formula (1 ).

Scheme 2

As specified above, the synthesis process of functionalized PET with an antioxidant activity having formula (1") wherein n and m, the same as or different from each other, are such that n + m ranges from 125 to 130;

R and X have the meanings indicated above, comprises the following steps: i) etherification reaction of a POSS (Polyhedral Oligomeric Sesquioxane) wherein R and X have the meanings indicated above, with an epoxide having formula (3) ii) subsequent reaction of a compound having formula (4") obtained at the end of step i) with a polyethylene terephthalate (PET) having formula (5) wherein 1 ranges from 125 to 130

to give the functionalized PET with an antioxidant activity having formula (1").

The etherification step i) is preferably carried out in the presence of an acid catalyst, in an aprotic polar solvent, at room temperature and for a time ranging from 1 to 24 hours, preferably for a time equal to about 24 hours.

The acid catalyst of step i) is selected from FeCh.btEO and a strongly acidic cationic resin, the acid catalyst is preferably a strongly acidic cationic resin such as, for example, the resin Amberlyst® 15, marketed by Merck Serono S.p.A.

The aprotic polar solvent is selected from tetrahydrofuran, dimethylformamide, acetone, ethyl acetate, acetonitrile, dimethyl sulfoxide and cyclopentylmethylether. The preferred aprotic polar solvent is tetrahydrofuran.

In the etherification step i), the acid catalyst is present in a quantity ranging from 0.1 to 0.5 equivalents, preferably equal to 0.25 equivalents, with respect to the epoxide having formula (3).

In the etherification step i), the perfluoroalkyl derivative having formula (2') or POSS having formula (2”) and the epoxide having formula (3) are present in a weight ratio ranging from 1 to 2 and is preferably equal to 2.

In step ii) of the synthesis process of functionalized PET with an antioxidant activity according to the present invention, the compound having formula (4') or (4”) obtained at the end of step i) is reacted with polyethylene terephthalate (PET) having formula (5) wherein 1 ranges from 125 to 130 according to schemes 1 and 2 previously indicated.

Step ii) of the process according to the present invention is preferably carried out in the presence of an acid catalyst, in air, at a temperature ranging from 100 to 270°C, preferably equal to about 100°C, and for a time ranging from 2 to 24 hours, preferably equal to about 24 hours.

The acid catalyst used in step ii) of the process is selected from Ce(OAc)3, Zn(OAc)2, Na(OAc)2, Mn(0Ac)2, Cu(OAc)2, Mg(OAc)2 or Pd(OAc)2. The acid catalyst used in step ii) is preferably Ce(OAc)3.

In step ii), the acid catalyst is present in a quantity ranging from 0.1 to 1% w/w with respect to the PET, and is preferably equal to 0.5% w/w.

In step ii) of the synthesis, the compound having formula (4') or (4”) obtained at the end of step i) is reacted with PET and the derivative having formula (4') or (4") and the PET are present in a weight ratio ranging from 0.015 to 0.5, preferably equal to 0.3.

As previously indicated, the present invention also relates to the use of a functionalized PET with an antioxidant activity having formula (1) as a material for food packaging, for example in the form of a film or tray or absorbent sheet in combination with cellulosic materials, or as a micro-perforated film for food to increase transpiration and maintain its antioxidant nature.

In the case of products in PET, whether they be films or trays in functionalized PET, this can have a thickness ranging from 0.10 to 4.5 mm.

Some examples according to the present invention are provided hereunder by way of non-limiting example of the present invention.

Example 1

Synthesis of the epoxide having formula (3)

1.7 g (20 mmoles) of pent-4-en-l-ol were subjected to an oxidation reaction by placing 60 ml of anhydrous dimethylformamide (DMF) and 4 equivalents of pyridinium dichromate (PDC) inside a flask. The reaction was left under stirring for 24 hours at room temperature under a nitrogen flow. Once the reaction was complete, a solvent extraction was effected by mixing diethyl ether (Et2O) and water in a 1:1 ratio. The purified product appears as a yellow oil. The Friedel Craft reaction was subsequently carried out. The oxidized derivative was cooled to 0°C in the presence of trifluoroacetic acid (TFA, 1.16 equivalents) and left under stirring for 8 hours at the same temperature. At this point 0.5 equivalents of 2,6-di-tert- butylphenol (phenol derivative) were added to the reaction mixture which was stirred at room temperature until the 2,6-di-tert-butylphenol had disappeared. After 3 hours, ethanol (EtOH, 4ml/mmole), glacial acetic acid (CH3COOH, 2ml/mmole), hydrochloric acid (HC1, 0.65ml) and zinc (Zn( _s ), 15 equivalents) previously activated, were added in succession to reduce the carbonyl oxygen. and the reaction was stirred at 90°C for the whole night until the disappearance of the intermediate. The solid was filtered using a Gouch filter and the subsequent work-up made use of a saturated solution of NaHCCh, added slowly (NaHCO3(sat), 30ml) until a neutral pH had been reached. The mixture was subsequently processed by extraction with solvent in hexane, completely anhydrified with anhydrous Na2SO4 (added in such a quantity as to remain powdery during stirring) and concentrated under vacuum. The reaction raw material was purified to obtain the pure alkenylphenol derivative in the form of a transparent oil with a yield of 71%. The alkenylphenol derivative was then used for producing the epoxide having formula (3), by dissolving it in dichloromethane (20 ml/mmole) and adding m-chloroperbenzoic acid (m-CPBA, 2 equivalents) directly into the mixture at 0°C, and left under stirring until room temperature had been reached. The reaction was left under stirring for 24 hours. At the end of the process the solvent was evaporated under vacuum and the product (4) was obtained pure with a yield of 65% after purification by chromatography.

Scheme 3 Example 2

Synthesis of the derivative having formula (4’1

2.9 g (10 mmoles) of the epoxide having formula (3) obtained as described in Example 1 were subjected to an etherification reaction with the perfluoroalkyl derivative having formula (2') (5.8 g), adding the tetrahydrofuran (THF, 14 ml/mmole) as solvent and an acid FeChrithO (0.25 equivalents). The reaction was left under stirring for 20 hours at room temperature. Once the reaction was complete, the catalyst was removed by filtration and the pure product was obtained in the form of a yellow oil, removing the solvent under vacuum. Example 3

Synthesis of functionalized PET having formula (!’)

0.015 g of the derivative having formula (4') obtained as described in Example 2 were mixed with 1 g of a PET powder (w/w ratio PET:derivative having formula (4') equal to 1:0.015): 15 mg of compound (4') were reacted with 1 g of PET, the mixture derivative having formula (4')/PET therefore seems to be 1.5% by weight, in reality in the derivative having formula (4') the compound (2') is in a 2:1 weight ratio with compound (3) and the final polymeric matrix obtained therefore contains 0.5% by weight of antioxidant compound having formula (3), the same applies to all the other final polymer matrices in functionalized PET at 1%, 5% and 10% by weight of antioxidant compound having formula (3) (PET-0.5, PET-1.0, PET-5.0, PET-10).

The above-mentioned PET powder was obtained using a vibromill MM 400, Retzsch, by means of a 35ml steel jar and a single steel ball with a diameter of 20 mm. The quantity of PET powder (1 g) was poured into a round-bottom flask and the compound having formula (4') (0.015 g) was added together with 0.05 g of acid catalyst, namely Ce(OAc)3 (0.5% by weight with respect to the PET). The reaction temperature was stabilized at 100°C, using a heating plate under continuous stirring. After about 24 hours, at the end of the reaction, the reaction mixture was allowed to cool to 50°C and a minimal quantity of trifluoroacetic acid (TFA) (0.5-1 ml) was added directly to the reaction flask. The viscous solution was then transferred to a Petn dish and dried in a ventilated oven at 60 C for 1 hour to form a disc and the residual TFA was then removed by the action of a vacuum pump for about 4 hours.

A white-coloured solid polymer matrix in functionalized PET having formula (T) was thus obtained, which was characterized as indicated hereunder.

An FTIR-ATR characterization (Infrared Spectroscopy) was performed and the attached figures show the spectra relating to the virgin PET (figure 1), the compound having formula (T) (figure 2 - indicated as PET1) and an overlapping of the two (figure 3) wherein the characteristic peaks of the functional groups relating to the compound having formula (T) are highlighted in the boxes.

The same samples were subsequently analyzed in thermogravimetry (TGA) (figures 4-6) to establish that there is a weight loss of about 20%, between 150- 250°C (STEP1), which shows a slight decrease in the degradation-onset temperature (Tonset), generally associated with a reaction which in the present invention relates to a transesterification and formation of the covalent bond between the recycled PET and the derivative having formula (4'). When there is a transesterification reaction, this can occur randomly between the various chains present and in different parts of the same chain, bringing a small percentage of the PET used to have shorter chains that have a slightly lower degradation temperature. It is essential to note that the recycled PET used as starting material (STEP2, Figure 6) in both cases has a superimposable degradation temperature (Tonset 404-405°C), which leads to the conclusion that its properties are maintained, for subsequent processing.

In particular, Example 3 was repeated identically, using different PET:derivative having formula (4') weight/weight ratios as indicated in the following table 1

Table 1

As previously explained, the PET-derivative having formula (4') ratio of 1:0.3 indicated in table 1, corresponds to a derivative having formula (1') containing a quantity of antioxidant, i.e. of compound having formula (3) equal to 10% by weight with respect to the weight of PET (PET- 10.0): 300mg of compound having formula (4) were in fact reacted with 1,000 mg of PET. In the compound having formula (4') there are 2 parts of compound having formula (2') and one part of the antioxidant compound having formula (3), therefore 100 mg of antioxidant in 1,000 mg of PET.

Similarly, the PET derivative having formula (4') ratio of 1:0.15 indicated in table 1, corresponds to a derivative having formula (T) containing a quantity of antioxidant, i.e. of compound having formula (3) equal to 5% by weight with respect to the weight of PET (PET-5.0), the PET derivative having formula (4') ratio of 1:0.03 indicated in table 1, corresponds to a derivative having formula (T) containing a quantity of antioxidant, i.e. of compound having formula (3) equal to 1% by weight with respect to the weight of PET (PET- 1.0) and PETderivative having formula (4') the ratio of 1:0.015 indicated in table 1, corresponds to a derivative having formula (T) containing a quantity of antioxidant, i.e. of compound having formula (3) equal to 0.5% by weight with respect to the weight of PET (PET-0.5).

Example 4

Antioxidant activity of functionalized PET having formula (1 ’)

Tests for the antioxidant activity were carried out on the four samples obtained in Example 3 (Examples 3, 3a, 3b, 3c) at the Biochemistry Laboratory of the School of Pharmaceutical Sciences and Health Products of the University of Camenno.

Two different types of spectrophotometric assays were performed, the first known as ABTS + and the second as DPPH. ABTS+ is a cationic radical, whereas DPPH is a neutral radical.

That is, two colorimetric assays were conducted to evaluate the antioxidant activity of both the samples of functionalized PET according to the invention and the antioxidant compound linked to PET.

The first essay exploits the reduction of the radical 2,2-DiPhenyl-l- PycrilHydrazyl (DPPH) [Valencia E., et al., Planta Med. 1994, 60, 395-399] whereas the second essay exploits the reduction of the radical formed from the cationic form of 2,2'-Azino-bis (3-ethylBenzoThiazoline-6-Sulfonic acid) (ABTS +) [Re R., et al., Free Radic. Biol. Med. 1999, 26, 1231-1237], radicals that react with the antioxidant bound to the functionalized or free PET in solution.

Aliquots of the various samples of functionalized PET according to the present invention were collected, weighed and added in a test-tube to a methanol solution to allow the assay to be carried out, exactly as indicated in the literature cited above. The calibration curve for evaluating the quantity of antioxidant [compound having formula (3)] incorporated in the functionalized PET was produced using a methanol solution of the pure compound having formula (3). The DPPH and ABTS assays were effected as described in literature.

In these assays, the absorbance of the different samples is measured from which the antioxidant activity is then obtained by interpolation with a calibration curve built based on the antioxidant activity of the epoxide having formula (3) alone. All the samples, even those of the calibration line, were incubated for 30 minutes in the dark.

The results of the antioxidant activities of the functionalized PETs of Examples 3, 3a, 3b and 3c are shown in Table 2, whereas Table 3 indicates the values relating to the antioxidant activity of the epoxide having formula (3).

Table 2

As explained previously, PET-0.5 refers to a sample wherein the percentage of compound having formula (3), i.e., of antioxidant, is equal to 0.5% by weight with respect to the weight of PET.

Table 3

The IC50 value for the epoxide having formula (3) is lower in the ABTS+ assay than that obtained in the DPPH test; this means that the ABTS+ assay is more sensitive than the DPPH test for evaluating the antioxidant activity of the epoxide alone.

When evaluating the antioxidant activity of the functionalised PET samples, the activities with the ABTS+ assay are lower than the activities obtained with the DPPH assay. This can be explained by the fact that the ABTS+ test is based on using a cationic radical which can interact with the polymer matrix and be less sensitive in determining the antioxidant activity of said samples.

Both assays, however, show a proportionality between the quantity of antioxidant [compound having formula (3)] added to the PET and the antioxidant activity expressed. In particular, the activity is expressed above all in samples 3b and 3c in which a percentage an antioxidant compound having formula (3) of 5 and 10% by weight respectively, concerning the weight of PET has been added.