The present invention relates to a process for the preparation of a gas-barrier film.

Materials suitable for use as a packaging should possess gas-barrier properties, in particular against oxygen, water vapour, carbon dioxide and other gases which could cause the content of the packaging to deteriorate. Polyolefins offer not only good processability but also an excellent water vapor barrier property that is required for many water-sensitive food products such as dried and liquid food products. However, polyolefins have in general poor oxygen (0 ₂ ) barrier properties due to their rather low degree of crystallinity. As a consequence, a polyolefin layer is very often combined with high-oxygen-barrier layers such as ethylene vinyl alcohol (EVOH) for oxygen-sensitive food products, as described in Y. T. Kim et al.; "General characteristics of packaging materials for food system" from Innovations in Food packaging.

It is desirable to provide a gas barrier film having one layer which has both good 0 ₂ barrier properties and water vapor barrier properties.

The invention provides a process for the preparation of a gas barrier film, comprising 1 ) providing an olefin copolymer comprising:

(i) recurring units A derived from an olefin and

(ii) recurring units B derived from a compound according to formula (I), (II) or (III):

wherein

R ¹ is selected from -H or -CH ₃ ;

R ² is selected from -0-, -(CO)-(NH)- or -(CO)-O- R ³ is a moiety comprising 1 -30 carbon atoms;

and n is an integer between 1 and 10,

wherein R ¹ is selected from -H or -CH ₃ and p is an integer between 1 and 10,

wherein R ¹ is selected from -H or -CH ₃ and q is an integer between 1 and 10,

2) grafting a graft compound represented by the formula (IV) or (V) to the olefin copolymer

wherein

R ⁴ is independently -H, C1 -C10 linear, branched or cyclic alkyl;

X is -NH- or -O- and

5 is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester,

wherein

each of R ⁶ , R ⁷ , R ⁸ and R ⁹ is independently -H, C1 -C10 linear, branched or cyclic alkyl; X is -NH- or -O- and

5 is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester and

3) shaping the grafted polymer obtained by step 2) into a film.

The film according to the invention was found to have good oxygen barrier properties. Due to the presence of recurring olefin units, the film also has good water vapor barrier properties. Accordingly, the invention provides one layer having both good oxygen barrier properties and water vapor barrier properties.

It is noted that Polymer 87 (2016) 308-315 describes functionalizing of PP to synthesize supramolecular polypropylenes having self-complementary quadruple hydrogen bonding 2-ureido-4[1 H]-pyrimidinone (UPy) groups (UPy-PP). This document does not disclose an oxygen barrier film.

Preferably, the process according to the invention has the proviso that the following is excluded:

the olefin copolymer comprises

(i) recurring units A derived from propylene and

(ii) recurring units B derived from a comonomer according to formula (III), wherein R ¹ is -H and q is 3 and

the graft compound is represented by formula (IV), wherein R ⁴ is -CH ₃ , X is NH, r is 6 and Y is NCO. Step 1 )

Olefin copolymer

The olefin copolymer comprises (i) recurring units A derived from an olefin and

(ii) recurring units B derived from a comonomer represented by formula (I), (II) or (III).

The recurring units A are derived from an olefin. The recurring units A may all be derived from the same type of olefin. Alternatively, the recurring units A may be derived from different types of olefin. Preferably, the recurring units A are derived from ethylene and/or propylene. Preferably, the recurring units A are derived from ethylene.

The recurring units B are derived from a comonomer represented by formula (I), (II) or (III). The recurring units B are preferably derived from a comonomer represented by formula (I) or (II). This leads to a less brittle film than the film made using the comonomer (III). Most preferably, the recurring units B are derived from a comonomer represented by formula (I).

Preferably, the amount of the recurring unit A is 78.0 to 99.9 mol%, for example 80.0 to 99.9 mol% or 90.0 to 99.5 mol%, with respect to the total of the recurring units A and the recurring units B.

Preferably, the amount of the recurring unit B is 0.10 to 20.0 mol%, for example 0.50 to 10.0 mol% or 1 .00 to 5.0 mol%, with respect to the total of the recurring units A and the recurring units B. Preferably, the amount of the recurring unit B is 1 .0 to 4.0 mol%. Preferably, the total amount of the recurring units A and the recurring units B is 98-100 mol%, for example 100 mol%, with respect to the total recurring units in the ethylene copolymer.

Comonomer (I)

It is preferred that R ³ in formula (I) is a moiety comprising 1 -20 carbon atoms, more preferably comprising 1 -10 carbon atoms.

Preferably, Ft ¹ is -CH ₃ . Preferably, Ft ² is -(CO)-O-.

Preferably, R ³ is a moiety selected from the group consisting of: -[CH2 -CH(CH ₃ )]x -, wherein x is an integer between 1 and 10;

-CH ₂ -CHR ¹⁰ -[O-CH ₂ -CHR ¹⁰ ] _y -, wherein y is an integer between 1 and 9 and each Ft ¹⁰ individually is selected from CH ₃ and H; and

-CH ₂ -CH(OH)-CH ₂ -.

More preferably, R ³ is -CH ₂ -.

Preferably, n is 2, 3, 4 or 5.

More preferably, R ³ is -CH ₂ - and n is 2, 3, 4 or 5. Even more preferably, R ³ is -CH ₂ - and n is 2.

In some preferred embodiments, R ² is ~(CO)-0- and R ³ is a moiety selected from the group consisting of:

-[CH ₂ -CH(CH ₃ )]x -, wherein x is an integer between 1 and 10;

-CH ₂ -CHR ¹⁰ -[O-CH ₂ -CHR ¹⁰ ] _y -, wherein y is an integer between 1 and 9 and each R ¹⁰ individually is selected from CH ₃ and H; and

-CH ₂ -CH(OH)-CH ₂ -.

In some preferred embodiments, R ² is ~(CO)-0- and R ³ is -CH ₂ -.

In some preferred embodiments, R ² is --(CO)-O-, R ³ is -CH ₂ - and n is 2, 3, 4 or 5.

In some preferred embodiments, R ² is --(CO)-O-, R ³ is -CH ₂ -, n is 2, 3, 4 or 5 and R ¹ is -CH ₃ .

Preferably, the recurring units B are derived from a comonomer selected from the list consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2,3-dihydroxypropyl acrylate, 2,3-dihydroxypropyl methacrylate, 4- hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, poly(propylene glycol)

monoacrylate, poly(propyleneglycol) monomethacrylate, poly(ethylene glycol) monoacrylate, poly(ethylene glycol) monomethacrylate, poly(ethylenepropyleneglycol) monomethacrylate, and 2-hydroxyethyl vinyl ether. More preferably, the recurring units B are derived from a comonomer selected from 2- hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3- hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, poly(propylene glycol) monoacrylate, poly(propyleneglycol) monomethacrylate, poly(ethylene glycol) monoacrylate, and poly(ethylene glycol) monomethacrylate.

More preferably, the recurring units B are derived from a comonomer selected from 2- hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, poly(propyleneglycol) monomethacrylate and poly(ethylene glycol) monomethacrylate.

More preferably, the recurring units B are derived from 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate. Alternatively, the recurring units B are derived from poly(propyleneglycol) monomethacrylate or poly(ethylene glycol) monomethacrylate. 2-hydroxyethyl methacrylate (HEMA) has several advantages. It is commercially available at industrial scale, rather cheap, very reactive and can be used in free radical copolymerization. Further it gives the final material great transparency and mechanical properties suited for film application. It also in the positive list for food contact material in Europe.

In a preferred embodiment, the process for the preparation of a gas barrier film, comprises

1 ) providing an ethylene copolymer comprising:

(i) recurring units A, wherein A is ethylene, and

(ii) recurring units B derived from a compound according to formula (I): wherein

R ¹ is -CH ₃ ;

Ft ² is -(CO)-O-;

R ³ is -CH ₂ -;

and n is an integer of 2;

2) grafting a graft compound represented by the formula (IV) or (V) to the ethylene copolymer

wherein

R ⁴ is independently -H, C1 -C10 linear, branched or cyclic alkyl;

X is -NH- or -O- and

5 is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester,

wherein

each of R ⁶ , R ⁷ , R ⁸ and R ⁹ is independently -H, C1 -C10 linear, branched or cyclic alkyl; X is -NH- or -O- and

5 is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester and

3) shaping the grafted polymer obtained by step 2) into a film.

In a preferred embodiment, the process for the preparation of a gas barrier film, comprises

1 ) providing an ethylene copolymer comprising:

(i) recurring units A, wherein A is ethylene, and

(ii) recurring units B derived from a compound according to formula (I):

I)

wherein

R ¹ is -CH ₃ ;

R ² is -(CO)-O-;

R3 is -CH2-;

and n is an integer of 2;

2) grafting a graft compound represented by the formula (IV) or (V) to the ethylene copolymer

wherein

R ⁴ is independently branched or cyclic alkyl, preferably R ⁴ is isopropyl

X is -NH- and

5 is represented by the formula:

where r is 6;

Y is -NCO,

and

3) shaping the grafted polymer obtained by step 2) into a film.

In another preferred embodiment, the process for the preparation of a gas barrier film, comprises

1 ) providing an ethylene copolymer comprising:

(i) recurring units A, wherein A is ethylene, and

(ii) recurring units B derived from a compound according to formula (I):

wherein

R ¹ is -CH ₃ ;

R ² is -(CO)-O-;

R ³ is -CH ₂ -;

and n is an integer of 2;

and wherein the ethylene copolymer was prepared by free radical polymerisation, 2) grafting a graft compound represented by the formula (IV) or (V) to the ethylene copolymer

wherein

R ⁴ is independently -H, C1 -C10 linear, branched or cyclic alkyl;

X is -NH- or -O- and

5 is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester,

(V)

wherein

each of R ⁶ , R ⁷ , R ⁸ and R ⁹ is independently -H, C1 -C10 linear, branched or cyclic alkyl;

X is -NH- or -O- and

5 is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester and

3) shaping the grafted polymer obtained by step 2) into a film.

In another preferred embodiment, the process for the preparation of a gas barrier film, comprises

1 ) providing an ethylene copolymer comprising: (i) recurring units A, wherein A is ethylene, and

(ii) recurring units B derived from a compound according to formula (I): wherein

Ft ¹ is -CH ₃ ;

Ft ² is -(CO)-O-;

R ³ is -CH ₂ -;

and n is an integer of 2

and wherein the ethylene copolymer was prepared by free radical polymerisation; 2) grafting a graft compound represented by the formula (IV) or (V) to the ethylene copolymer

wherein

R ⁴ is independently branched or cyclic alkyl, preferably isopropyl

X is -NH- and

R ⁵ is represented by the formula:

■JrL

where r is 6;

Y is -NCO,

and

3) shaping the grafted polymer obtained by step 2) into a film.

In another preferred embodiment, the process for the preparation of a gas barrier film, comprises

1 ) providing an ethylene copolymer comprising:

(i) recurring units A, wherein A is ethylene and (ii) recurring units B derived from a compound according to formula (I):

wherein

R ¹ is -CH ₃ ;

R ² is -(CO)-O-;

and n is an integer of 2

and wherein the ethylene copolymer was prepared by free radical polymerisation; 2) grafting a graft compound represented by the formula (IV) or (V) to the ethylene copolymer

wherein

R ⁴ is independently branched or cyclic alkyl, preferably R ⁴ is isopropyl

X is -NH- and

5 is represented by the formula:

where r is 6;

Y is -NCO,

and wherein the grafting process is done by reactive extrusion, and

3) shaping the grafted polymer obtained by step 2) into a film.

In a preferred embodiment, the process for the preparation of a gas barrier film, comprises

1 ) providing an ethylene copolymer comprising:

(i) recurring units A, wherein A is ethylene, and

(ii) recurring units B derived from a compound according to formula (I):

wherein

R ¹ is -CH ₃ ;

R ² is -(CO)-O-;

R ³ is -CH ₂ -;

and n is an integer of 2;

2) grafting a graft compound represented by the formula (IV) or (V) to the ethylene copolymer

wherein

R ⁴ is independently -H, C1 -C10 linear, branched or cyclic alkyl;

X is -NH- or -O- and

5 is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester,

(V)

wherein

each of R ⁶ , R ⁷ , R ⁸ and R ⁹ is independently -H, C1 -C10 linear, branched or cyclic alkyl; X is -NH- or -O- and ⁵ is represented by the formula:

where r is an integer between 1 and 20;

Y is -NCO, halogen (I, Br, CI, F), -Si(OMe) ₃ , -N=C=S, -N ₃ , -COOH, an amino acid or an amino ester and

wherein the grafting process is done by reactive extrusion, and

3) shaping the grafted polymer obtained by step 2) into a film.

In a preferred embodiment, the process for the preparation of a gas barrier film, comprises

1 ) providing an ethylene copolymer comprising:

(i) recurring units A, wherein A is ethylene, and

(ii) recurring units B derived from a compound according to formula (I):

I)

wherein

Ft ¹ is -CH ₃ ;

Ft ² is -(CO)-O-;

R3 is -CH2-;

and n is an integer of 2;

2) grafting a graft compound represented by the formula (IV) or (V) to the ethylene copolymer

wherein

R ⁴ is independently branched or cyclic alkyl, preferably R ⁴ is isopropyl

X is -NH- and

R ⁵ is represented by the formula:

where r is 6;

Y is -NCO,

and wherein the grafting process is done by reactive extrusion, and

3) shaping the grafted polymer obtained by step 2) into a film.

comonomer (II)

Preferably, p is 2, 3, 4 or 5. comonomer (III)

Preferably, q is 2, 3, 4 or 5.

Step 1 ) may involve copolymerizing the olefin and the compound (I), (II) or (III).

Alternatively, step 1 ) may involve polymerizing the olefin and functionalizing some of the recurring units such that these recurring units would be represented by (I), (II) or (III). In case the compound is (I) or (II), step 1 ) preferably involves copolymerizing the olefin and the compound (I) or (II). In case the compound is (III), step 1 ) preferably involves polymerizing the olefin, functionalizing the polymer with maleic anhydride and reacting the obtained reaction product with a suitable alcohol amine.

When step 1 ) involves copolymerizing the olefin and the compound (I) or (II), the copolymerization is preferably a high-pressure free-radical polymerisation process. An advantage of polymerisation in such high-pressure free-radical process is that the polymerisation may be performed without the need for a metal-based catalyst being present. This allows for the use of certain comonomers such as polar comonomers which are not suitable as comonomers in the production of ethylene copolymers via catalytic processes such as using Ziegler-Natta or metallocene type catalysts because of the interference with such catalyst.

A further advantage of preparation of the ethylene copolymers according to the invention in a high-pressure free-radical polymerisation process is that such polymerisation results in ethylene copolymers having a certain degree of long-chain branching. In order to qualify for certain applications, including extrusion coating application, ethylene copolymers are required to have a certain degree of such long- chain branching. The presence of such long-chain branching is understood to contribute to the desired melt processing properties. Accordingly, it is preferred that the ethylene copolymers according to the present invention are prepared via a high- pressure free-radical polymerisation process. The pressure in such high-pressure free- radical polymerisation process preferably is in the range of≥ 180 MPa and < 350 MPa, preferably≥ 200 MPa and < 300 MPa. The temperature in such high-pressure free- radical polymerisation process preferably is in the range of≥ 100 and < 350 °C, preferably≥ 150 and < 310 °C.

Such high-pressure free-radical polymerisation process may for example be performed in a tubular reactor. Such tubular reactor may for example be a reactor such as described in Nexant PERP Report 2013-2, 'Low Density Polyethylene', pages 31 -48. Such tubular reactor may for example be operated at pressures ranging from 150 to 300 MPa. The tubular reactor may have a tube length of for example≥ 1000 m and < 5000 m. The tubular reactor may for example have a ratio of length to inner diameter of ≥ 1000:1 , alternatively≥ 10000:1 , alternatively≥ 25000:1 , such as≥ 10000:1 and < 50000:1 , alternatively≥ 25000:1 and < 35000:1. The residence time in the tubular reactor may for example be≥ 30 s and < 300 s, alternatively≥ 60 s and < 200 s. Such tubular reactors may for example have an inner tubular diameter of≥ 0.01 m and < 0.20 m, alternatively≥ 0.05 m and < 0.15 m. The tubular reactor may for example have one or more inlet(s) and one or more outlet(s). The feed composition may for example be fed to the tubular reactor at the inlet of the tubular reactor. The stream that exits the tubular reactor from the outlet may for example comprise the ethylene copolymer. The stream that exits the tubular reactor from the outlet may for example comprise unreacted feed composition. Such unreacted feed compositions may be recycled back into the tubular reactor via one or more inlet.

Step 1 ) may involve polymerizing the olefin, functionalizing the obtained polymer with maleic anhydride and reacting the obtained functionalized product with a suitable alcohol amine. Each of the polymerizing step, the functionalizing step and the reacting step can be performed by known methods.

Step 2)

Typically, step 2) may be performed by a solution process or by a reactive extrusion process. As is known, the solution process is performed in the presence of a catalyst and a solvent. The reactive extrusion process does not require a catalyst or a solvent, and is performed and is performed at temperatures above the melting point of the polymer. Further, the process can be easily scaled-up in comparison to the grafting process in solution. Preferably, step 2) is performed by a reactive extrusion process.

Preferably, step 2) results in 5-100 mol% of the recurring units derived from the comonomer B being grafted with the graft compound. For example, step 2) results in 5- 50 mol%, for example 10-40 mol% or 15-35 mol%, of the recurring units derived from the comonomer B being grafted with the graft compound. For example, step 2) results in 50-100 mol%, for example 50-99 mol%, 55-95 mol%, 60-90 mol% or 70-80 mol%, of the recurring units derived from the comonomer B being grafted with the graft compound.

The amount of the graft compound on the copolymer may be adjusted by both the proportion of the recurring units B in the copolymer and the proportion of the grafted recurring units B among the recurring units B. For example, the copolymer may comprise a smaller proportion of the recurring units B, a higher proportion of which is grafted. The copolymer may also comprise a larger proportion of the recurring units B, a lower proportion of which is grafted. The amount of the remaining OH groups (of units derived from the comonomer B which is not grafted) in the comonomer may be adjusted to control the properties of the final film, such as the stickiness and the oxygen barrier property.

In some embodiments, the amount of the recurring unit B is 0.10-10.0 mol% with respect to the total of the recurring units A and the recurring units B and 50-100 mol% of the recurring unit B is grafted with the graft compound.

In some embodiments, the amount of the recurring unit B is 10.0-20.0 mol% with respect to the total of the recurring units A and the recurring units B and 5-50 mol% of the recurring unit B is grafted with the graft compound. Graft compound (IV)

In formula (IV), preferably,

R ⁴ is -H or -CH ₃ or isopropyl; and/or

X is NH; and/or

r is 2 to 8; and/or

Y is NCO.

More preferably, in formula (IV), R ⁴ is -H or -CH3 or isopropyl;

X is NH;

r is 2 to 8; and

Y is NCO.

More preferably, in formula (IV),

R ⁴ is isopropyl;

X is NH;

r is 6; and

Y is NCO. graft compound (V)

In formula (V), preferably,

each of R ⁶ , R ⁷ , R ⁸ and R ⁹ is independently -H or -CH ₃ ; and/or

X is NH; and/or

r is 2 to 8; and/or

Y is NCO.

More preferably, in formula (V),

each of R ⁶ , R ⁷ , R ⁸ and R ⁹ is independently -H or -CH ₃ ;

X is NH;

r is 2 to 8; and

Y is NCO. More preferably, in formula (V),

each of R ⁶ , R ⁷ , R ⁸ and R ⁹ is -H;

X is NH;

r is 6; and

Y is NCO.

Step 3)

The grafted polymer obtained by step 2) may be shaped into a film by any known method, such as compression molding or injection molding.

The invention further relates to the gas barrier film obtainable by or obtained by the process according to the invention. The invention further relates to a packaging comprising the gas barrier film according to the invention, for example a food packaging, a drink packaging, a healthcare packaging or a cosmetics packaging. It is noted that the invention relates to all possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein.

It is further noted that the term 'comprising' does not exclude the presence of other elements. However, it is also to be understood that a description on a

product/composition comprising certain components also discloses a

product/composition consisting of these components. The product/composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product/composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process.

When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

The invention is now elucidated by way of the following examples, without however being limited thereto. Examples

Synthesis of graft compounds

2-ureido-4[H]-pyrimidione (UPy) synthesis

(formula (IV), R ⁴ = CH ₃ ; X = NH; R ⁵ : r = 6 and Y = NCO)

UPy was obtained by a one-step synthesis from commercially available 6-methyl isocytosine and 7-fold excess of 1 ,6-hexamethylene diisocyanate (Figure 1 ), according to the procedure reported by Meijer et al. {J. Am. C em. Soc, 1998, 120, 6761 ): 1 ,6-hexamethylene diisocyanate (8.7 ml_, 54.3 mmol) was placed in a dry flask under argon atmosphere. After that, 2-amino-4-hydroxy-6-methylpyrimidine (1 .0 g, 8.0 mmol) was added to create a white suspension. The reaction mixture was stirred for 24 h at 100 °C under nitrogen atmosphere. After cooling to room temperature, the obtained product was filtered under vacuum, washed with pentane to remove residual 1 ,6- hexamethylene diisocyanate and dried under vacuum to give UPy as a white powder (2.2 g, 7.5 mmol, 94%).

Figure 1 . UPy synthesis starting from 6-methyl isocytosine and 1 ,6-hexamethylene diisocyanate

1-(6-isocyanatohexyl)-3-(7-oxo-7,8-dihydro-1 ,8-naphthyridin-2-yl)urea (ODIN) synthesis (formula (V), R ⁶ =R ⁷ =R ⁸ =R ⁹ = H; X = NH; R ⁵ : n = 6 and Y = NCO)

ODIN (compound 2, Figure 2) was obtained via two step synthesis starting from commercially available 2,6-diaminopyridine and malic acid in sulfuric according to the method of Zimmermann et. al. (J. Org. Chem., 2010, 75 (14), 4848-4851 ), followed by the addition of a 7-fold excess of 1 ,6-hexamethylene diisocyanate (Figure 2), according to the procedure reported by Meijer et al. (J. Am. Chem. Soc, 1998, 120, 6761 ),

Mw: 109.13 g/Mol Mw: 134.09 g/Mol Mw: 161.16 g/Mol

Mw: 168.20 g/Mol Mw: 329.36 g/Mol Figure 2. ODIN (2) synthesis starting from Diaminopyridine and Malic acid Synthesis of 7-amino-1 ,8-naphthyridin-2(1 H)-one (Compound 1 , Figure 2)

2,6-diaminopyridine (20 g, 183.3 mmol) and malic acid (27 g, 201 .6 mmol) were ground into a fine powder using mortar and pestle and then transferred to a 500 mL three neck round bottom flask equipped with a mechanical stirrer, thermometer and dropping funnel. The mixture was stirred and cooled to 0 °C using an ice water bath. Then, sulfuric acid (94 mL) was added dropwise while maintaining a temperature below 45 °C. Afterwards, the dropping funnel was replaced for a reflux condenser and the mixture was stirred at 120 °C for 2 h. After cooling down to 0 °C, the solution was poured over crushed ice and stirred for 10 min, followed by slow addition of

concentrated ammonia (-30 w%) while stirring vigorously. After a pH of 8 was reached, the formed precipitate was filtered and washed with water. The solid was taken up in a mixture of 1 :9 water:methanol and sonicated for about 30 min, before again filtering and washing with water. The remaining powder was dried to give a yellow solid (25.7 g, 87% yield) that gave characterization consistent with literature values of parent literature.

Synthesis of 1-(6-isocvanatohexyl)-3-(7-oxo-7,8-dihvdro-1 ,8-naphthyridin-2- vDurea (Compound 2 "ODIN", Figure 2)

7-amino-1 ,8-naphthyridin-2(1 H)-one (0.25 g, 1 .55 mmol) was placed in a dry flask under argon atmosphere. After that, 1 ,6-hexamethylene diisocyanate (1 .8 mL, 1 1 mmol) was added to create a yellow suspension. The reaction mixture was stirred for 16 h at 120 °C under nitrogen atmosphere. After cooling to room temperature, the obtained product was filtered under vacuum, washed with acetone and heptane to remove residual 1 ,6-hexamethylene diisocyanate and dried under vacuum to give ODIN as a yellow powder (0.34 g, 67% yield).

Grafting procedure onto functionalized polyolefins

For grafting, a copolymer of ethylene and 2-hydroxyethyl methacrylate (HEMA) was used. The copolymer was prepared by free radical polymerisaiton as described in WO2017/102506.

1 ) In solution

The grafting procedure was performed according to the conditions described by Jangizehi et al. {J. Macro. Sci., Part B: Physics, 2014, 53, 848) A dry copolymer of ethylene and 2-hydroxyethyl methacrylate (HEMA) was dissolved in dry toluene and dibutyltin dilaurate (DBTDL) was added as a catalyst. Subsequently, UPy (formula (IV), Ft ⁴ = CH ₃ ; X = NH; Ft ⁵ : r = 6 and Y = NCO) or ODIN (formula (V), R ⁶ =R ⁷ =R ⁸ =R ⁹ = H; X = NH; R ⁵ : n = 6 and Y = NCO) was added at amounts varying from 0.34 to 12.4 mol%, and the transparent reaction mixture was heated to 80 °C for 4 h using a mechanical stirrer. After the reaction, the obtained polymer was precipitated and filtered, washed with isopropanol and dried under vacuum at 60 °C for 24 h.

2) By reactive Extrusion

The experiments were carried out in a co-rotating twin-screw mini-extruder at 120 °C with a screw rotation speed of 100 rpm. A copolymer of ethylene and HEMA together with IPR-UPy (formula (IV), R4 = Isopropyl; X = NH; R5: r = 6 and Y = NCO) were fed into the extruder at amounts varying from 0.01 to 10 wt% , without the need of any catalyst. The mixture was processed for 10 min and then the extruder chamber was evacuated. Obtained material had no free IPR-UPy which was confirmed by NMR and IR analyses.

Film making by compression molding

The grafted copolymers were converted to films by compression molding at temperatures between 140 °C and 160 °C with an applied force from 20 to 50 kN to a thickness of 100 to 300 μηι.

Results

Oxygen permeability measurements and water vapor permeability measurements were performed on the films made from the copolymers grafted with ODIN in solution. The amount of HEMA and ODIN in the copolymers are shown in Table 1 , as well as the oxygen transmission rate (OTR), determined according to ISO 15105-2, and the water vapor transmission rate (WVTR), determined following ISO 15106-3. The OTR and the WVTR determined taking the thickness of the film into account.

WVTR OTR OTR

(g ^* mm/m2 ^* (cc ^* mm/m2 ^* (cc ^* mm/m2 ^* day ^* bar) day ^* bar) day ^* bar)

HEMA ODIN Thickness 23°C; 23°C; 38°C; (mol%) (mol%) (mm) 85%RH 0%RH 50%RH

CEx 1 6.8 0 0.12 1 .98 126 353

Ex 2 6.8 3.1 0.16 0.9 70 184

CEx 3 7.5 0 0.12 1 .9 1 16 344 Ex 4 7.5 2.3 0.155 1 66 172

CEx 5 12.4 0 0.13 3.6 121 382

Ex 6 12.4 3 0.15 1 .2 46 129 indica tes relative humid ity (%)

Films having favorable WVTR and favorable OTR were obtained from ethylene-HEMA copolymer grafted with ODIN.

Tensile strength and Young's modulus were determined by tensile tests: tensile tests were performed on a Zwick type Z100 tensile tester equipped with a 100 N load cell. Specimens were obtained by cutting strips of 8 cm length and 1 cm width from square films (10 x 10 cm) with an average thickness of 150 microns. Sample strips were clamped and a pre-load of 0.3 MPa was applied before stretching at a speed of 200 mm/min until sample failure occurred

Modulus was measured with DMTA: Rectangular samples suitable for DMTA were cut to dimension of 3 x 5 x 0.5 mm (length x width x thickness). Samples were measured on a TA Instruments Q800 in tensile mode. The storage modulus (E) and loss modulus (E) were monitored while screening the samples during a temperature sweep from 100 to 200 °C at 3 K/min. An oscillation frequency of 1 Hz with an oscillation amplitude of 10 μηι were applied. To assess the influence of cross-linking via ODIN on tensile properties, functionalized polymers were subjected to tensile and DMTA tests and compared to their respective pristine counterparts, as well as the reference PE-sample made in the same reactor. The modulus at 150 °C, measured by DMTA and tensile strength and Young's modulus measured by tensile testing, for the measured polymers are given in the table below.

Heating above Tm of the material did not lead to measurement stop of the DMTA measurement for grafted samples and the elastic character was retained after melting, characteristic for cross-linked polymers. This is attributed to the formation of the cross- linking via multiple hydrogen bonding arrays, that is still effective above Tm.

The functionalization with ODIN tends to increase tensile strength and significantly in- creases stiffness of the soft polymers. The tensile strength of CEx5 was improved more than 3-fold when grafted with ODIN (Ex6), displaying the potential of ODIN motif to improve mechanical properties of polymeric species. Compared to reference PE, tensile properties seem to be on par or slightly increased for the ODIN functionalised samples.

The results show that the grafted functional olefin copolymers show much better barrier properties, a higher melt strength and good mechanical properties compared to the olefin homopolymer and compared to the corresponding copolymers.