Polyurethane dispersion

Abstract

A polyurethane dispersion comprising a polyurethane polymer (PU) which is the reaction product of an isocyanate group-terminated prepolymer (PR) and a chain-extension agent (CE), wherein the isocyanate group-terminated prepolymer (PR) is produced by the reaction of: a) at least one polyisocyanate compound (PI); b) at least one polyol compound (PO) having an equivalent weight no greater than 200 g / mol; c) at least one polyamine compound (PA) having an equivalent weight no greater than 100 g / mol; and d) at least one hydrophilic compound (HC) containing at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in an aqueous medium either directly or after the reaction with a neutralizing agent.

Description

POLYURETHANE DISPERSIONTechnical Field

[0001] The present invention relates to polyurethane dispersions which are particularly suitable for imparting gas barrier properties to a substrate.Background

[0002] Gas barrier films have been widely used for the production of packaging material, in particular for food packaging. Known solutions typically take the form of a laminated film, whereby a base film is coated with a polymeric material having gas barrier properties. The most commonly used gas barrier polymeric films include polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA) or ethylene-vinyl alcohol copolymer (EVOH). These known polymeric materials despite having excellent gas barrier properties suffer from various limitations. The PVDC polymeric material contains a relatively high amount of chlorine, which upon incineration does not only generate a toxic and hazardous gas, but can also produce organic chlorine-containing compounds having high carcinogenicity. For these reasons and due its poor recyclability, PVDC is regarded as having poor sustainability characteristics. As for the PVA / EVOH types, these materials suffer from severe gas barrier performance limitations under highly humid environment, due to their water sensitivity and high hydrophilicity. They also exhibit sub-optimal performance on several aspects, including insufficient resistance to chemical exposure, limited pot-life, cost inefficiency, as well as inadequate sustainability features.

[0003] In the field of packaging materials, polyurethane resin compositions and dispersions have recently emerged as an alternative solution to PVA and EVOH, as these are provided with good gas barrier properties. Such polyurethane dispersions are described e.g. in US 2012 / 0016075-Al (Uchida). Without contesting the technical advantages associated with the solutions known in the art, there is still a need for polymeric materials which overcome at least partially the above-mentioned deficiencies.Summary

[0004] According to one aspect, the present disclosure relates to a polyurethane dispersion comprising a polyurethane polymer (PU) which is the reaction product of an isocyanate group-terminated prepolymer (PR) and a chain-extension agent (CE), wherein the isocyanate group- terminated prepolymer (PR) is produced by the reaction of: a) at least one polyisocyanate compound (PI); b) at least one polyol compound (PO) having an equivalent weight no greater than 200 g / mol; c) at least one polyamine compound (PA) having an equivalent weight no greater than 100 g / mol; and d) at least one hydrophilic compound (HC) containing at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in an aqueous medium either directly or after the reaction with a neutralizing agent.

[0005] According to another aspect, the present disclosure is directed to a process of manufacturing a polyurethane dispersion as described above, wherein the method comprises the steps of: a) preparing an isocyanate group-terminated prepolymer (PR) by reacting: i. at least one polyisocyanate compound (PI); ii. at least one polyol compound (PO) having an equivalent weight no greater than 200 g / mol; iii. at least one polyamine compound (PA) having an equivalent weight no greater than 100 g / mol; and iv. at least one hydrophilic compound (HC) containing at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in aqueous medium either directly or after the reaction with a neutralizing agent; b) dispersing the isocyanate group-terminated prepolymer (PR) into an aqueous medium; and c) reacting the isocyanate group-terminated prepolymer (PR) dispersed into the aqueous medium with a chain-extension agent (CE) thereby forming a polyurethane dispersion.

[0006] According to still another aspect, the present disclosure relates to a coating material comprising a polyurethane dispersion as described above.

[0007] In yet another aspect, the present disclosure is directed to the use of a polyurethane dispersion as described above for the manufacturing of a gas barrier coating material, in particular for use in a packaging laminate material.Detailed description

[0008] According to first aspect, the present disclosure relates to a polyurethane dispersion comprising a polyurethane polymer (PU) which is the reaction product of an isocyanate group- terminated prepolymer (PR) and a chain-extension agent (CE), wherein the isocyanate group- terminated prepolymer (PR) is produced by the reaction of: a) at least one polyisocyanate compound (PI); b) at least one polyol compound (PO) having an equivalent weight no greater than 200 g / mol; c) at least one polyamine compound (PA) having an equivalent weight no greater than 100 g / mol; and d) at least one hydrophilic compound (HC) containing at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in an aqueous medium either directly or after the reaction with a neutralizing agent.

[0009] In the context of the present disclosure, it has been surprisingly found that a polyurethane dispersion comprising a polyurethane polymer (PU) as described above provides superior gas (oxygen and water vapor) barrier performance, as well as improved coating performance and properties. More specifically, the polyurethane dispersion of the present disclosure was found to provide excellent film forming capabilities and results into defect-free coatings provided with excellent clarity. These properties were found to advantageously impact the overall gas barrier performance. It has no less surprisingly been found that the polyurethane dispersion of the present disclosure results into coatings provided with excellent water and solvent resistance.

[0010] In particular, the polyurethane dispersion as described above was surprisingly found to provide a reduced minimum film formation temperature (MFFT). This specific property advantageously affects the formation of defect-free coatings at a moderate temperature and without requiring the use of additional co-solvents. A reduced MFFT can be of particular significance for coatings having a relatively low thickness as these are more prone to high waterevaporation rate due to the high surface to volume ratio. These properties directly result into reduced energy consumption and lower emission of volatile organic compounds. Advantageously still, the polyurethane dispersion as described above provides well controlled particle size and excellent colloidal stability, which directly results into extended pot-life and more robust formulations.

[0011] These are particularly surprising and counterintuitive findings considering that obtaining in particular superior gas barrier properties, water resistance, colloidal stability, coating performance and reduced minimum film formation temperature are somewhat technically self-contradicting or at least technically challenging to achieve in combination.

[0012] In the context of the present disclosure, the Applicant successfully managed to formulate a polymeric dispersion combining all the above-detailed excellent characteristics and performance attributes while preserving excellent performance of the crosslinked (or cured) material, such as hardness, flexibility, blocking resistance, solvent resistance and adhesion towards polymeric material or vacuum metalized polymeric substrates.

[0013] Without wishing to be bound by theory, it is believed that these excellent characteristics and attributes are due in particular to the use of a polyurethane polymer (PU) as described above and which is the reaction product of an isocyanate group-terminated prepolymer (PR) and a chain-extension agent (CE), wherein the isocyanate group-terminated prepolymer (PR) is produced by using in particular at least one polyamine compound (PA). Accordingly, the isocyanate group-terminated prepolymer (PR) used as an intermediate to produce the polyurethane polymer (PU), actually comprises urea functional groups within its structure and could therefore formally qualify as a urethane-urea (co)polymer. Still without wishing to be bound by theory, it is further believed that the presence of urea functional groups within the isocyanate group-terminated prepolymer (PR) introduces additional hard segments within its structure. Facilitated by strong hydrogen bonding, these hard segments are believed to aggregate and form hard micro-domains which in turn are believed to promote linear chain entanglement and reduce interstitial movement within the isocyanate group-terminated prepolymer (PR). The presence of urea functional groups in addition to the urethane groups is believed to reduce the overall gas solubility characteristics of the isocyanate group-terminated prepolymer (PR). All these structural characteristics are believed to advantageously impact at least the overall gas (oxygen and water vapor) barrier performance of the coatings resulting from the polyurethane dispersion of the present disclosure. Still without wishing to be bound by theory, it is further anticipated that the polyamine compound (PA) may in somecircumstances form a cyclic adduct according to a cyclo-condensation reaction, and which is believed to further advantageously impact at least the overall gas (oxygen and water vapor) barrier performance as described above.

[0014] This technical approach for achieving superior gas (oxygen and water vapor) barrier performance while maintaining excellent coating performance and properties, is seen as particularly counterintuitive and disruptive considering that the person skilled in the art of gas barrier polymeric films would not consider introducing urea functional groups within the structure of the isocyanate group-terminated prepolymer (PR), but rather through a chain extension agent as it is generally practiced in the art. Moreover, the skilled person would have assumed that the incorporation of additional urea functional groups in a polymeric material would unfavorably increase its glass transition temperature characteristics and thereby detrimentally affect various performance attributes, in particular the film forming capabilities, the flexibility characteristics and the adhesion properties. The incorporation of additional urea functional groups in a polymeric material would also be expected to unfavorably decrease the polymer solubility and / or increase its viscosity during the manufacturing process.

[0015] As such, the polyurethane dispersion according to the present disclosure is outstandingly suitable for forming gas barrier coating material, in particular for use in a (food) packaging laminate material It has indeed further been found that a polyurethane dispersion as described above, may be used to form simplified laminate constructions which may therefore be more easily recycled and advantageously contribute to the circular economy.

[0016] In an advantageous aspect, the polyurethane polymer (PU) for use herein has an overall content of urea functional groups of at least 10 wt.%, at least 11 wt.%, at least 12 wt.%, at least 13 wt.%, or even at least 14 wt.%, based on the overall weight of the aqueously dispersible polyurethane polymer (PU).

[0017] In one exemplary aspect, the polyurethane polymer (PU) has an overall content of urea functional groups no greater than 20 wt.%, no greater than 19 wt.%, no greater than 18 wt.%, no greater than 17 wt.%, no greater than 16 wt.%, or even no greater than 15 wt.%, based on the overall weight of the polyurethane polymer (PU).

[0018] In still another advantageous aspect, the polyurethane polymer (PU) for use herein has an overall content of urea functional groups in a range from 10 to 20 wt.%, from 10 to 18 wt.%, from 10 to 16 wt.%, from 12 to 16 wt.%, from 12 to 15 wt.%, from 13 to 15 wt.%, or even from 13 to 14 wt.%, based on the overall weight of the polyurethane polymer (PU).

[0019] In the context of the present disclosure, the overall content of urea functional groups in the polyurethane polymer (PU) is determined by calculations well known to those skilled in the art, and based on the stoichiometry of the corresponding reactants used to prepare the polyurethane polymer (PU). Typically, the overall content of urea functional groups in the polyurethane polymer (PU) is calculated by multiplying the total number of equivalents of urea functional groups present in the polyurethane polymer (PU) by the molecular weight of a urea functional group (58 g / mol), which is then divided by the overall weight of the polyurethane polymer (PU).

[0020] According to another exemplary aspect, the polyurethane polymer (PU) has an overall content of urethane functional groups no greater than 45 wt.%, no greater than 42 wt.%, no greater than 40 wt.%, no greater than 38 wt.%, no greater than 36 wt.%, no greater than 34 wt.%, or even no greater than 32 wt.%, based on the overall weight of the aqueously dispersible polyurethane polymer (PU).

[0021] According to another advantageous aspect of the disclosure, the polyurethane polymer (PU) for use herein has an overall content of urethane functional groups of at least 25 wt.%, at least 26 wt.%, at least 27 wt.%, at least 28 wt.%, at least 29 wt.%, or even at least 30 wt.%, based on the overall weight of the aqueously dispersible polyurethane polymer (PU).

[0022] According to yet another advantageous aspect, the polyurethane polymer (PU) for use in the present disclosure has an overall content of urethane functional groups in a range from 25 to 45 wt.%, from 25 to 42 wt.%, from 26 to 40 wt.%, from 25 to 38 wt.%, from 26 to 36 wt.%, from 28 to 36 wt.%, from 28 to 34 wt.%, or even from 30 to 32 wt.%, based on the overall weight of the polyurethane polymer (PU).

[0023] In the context of the present disclosure, the overall content of urethane functional groups in the polyurethane polymer (PU) is determined by calculations well known to those skilled in the art, and based on the stoichiometry of the corresponding reactants used to prepare the polyurethane polymer (PU). Typically, the overall content of urethane functional groups in the polyurethane polymer (PU) is calculated by multiplying the total number of equivalents of urethane functional groups present in the polyurethane polymer (PU) by the molecular weight of a urethane functional group (59 g / mol), which is then divided by the overall weight of the polyurethane polymer (PU).

[0024] In another advantageous aspect of the disclosure, the polyurethane polymer (PU) for use herein has a weight ratio of urea functional groups to urethane functional groups greaterthan 0.38, greater than 0.40, greater than 0.42, greater than 0.44, greater than 0.45, greater than 0.46, greater than 0.48, or even greater than 0.50.

[0025] In the context of the present disclosure, the expression “weight ratio of urea functional groups to urethane functional groups” is meant to designate the ratio of the total weight of urea functional groups to the total weight of urethane functional groups present in the polyurethane polymer (PU). This ratio is determined by calculations well known to those skilled in the art. Typically, the weight ratio of urea functional groups to urethane functional groups is calculated from the values described hereinbefore.

[0026] In an exemplary aspect, the polyurethane polymer (PU) has a weight ratio of urea functional groups to urethane functional groups no greater than 1.0, no greater than 0.80, or even no greater than 0.60.

[0027] In yet another advantageous aspect, the polyurethane polymer (PU) as described herein has a weight ratio of urea functional groups to urethane functional groups in a range from 0.38 to 1.0, from 0.38 to 0.80, from 0.38 to 0.60, from 0.40 to 0.50, or even from 0.40 to 0.45.

[0028] According to advantageous aspect of the disclosure, the isocyanate group-terminated prepolymer (PR) for use herein has an equivalent ratio of the polyamine compound (PA) to the polyol compound (PO) no greater than 25:75, no greater than 20:80, no greater than 15:85, no greater than 10:90, or even no greater than 5:95.

[0029] In the context of the present disclosure, the expression “equivalent ratio of the polyamine compound (PA) to the polyol compound (PO)” is meant to designate the ratio of amine equivalents to hydroxyl equivalents present in the isocyanate group-terminated prepolymer (PR). This ratio is determined calculations well known to those skilled in the art, and based on the weight of the corresponding reactants used to prepare the isocyanate group- terminated prepolymer (PR). Typically, the amine equivalents are calculated by dividing the weight of all the polyamines by their equivalent weights, and then summed up. The hydroxyl equivalents are typically calculated by dividing the weight of all the polyols by their equivalent weights, and then summed up.

[0030] According to another advantageous aspect, the isocyanate group-terminated prepolymer (PR) for use herein has an equivalent ratio of the polyamine compound (PA) to the polyol compound (PO) of at least 1 :99, at least 2:98, at least 5:95, at least 8:92, or even at least 10:90.

[0031] According to still another advantageous aspect, the isocyanate group-terminated prepolymer (PR) has an equivalent ratio of the polyamine compound (PA) to the polyol compound (PO) in a range from 5:95 to 15:85, or even in a range from 5:95 to 10:90.

[0032] In the context of the present disclosure, it has been surprisingly found that controlling the equivalent ratio of the polyamine compound (PA) to the polyol compound (PO) as described above advantageously impacts not only the synthesis of the isocyanate group-terminated prepolymer (PR), but also the overall synthesis of the polyurethane dispersion comprising the polyurethane polymer (PU). More specifically, a careful control of the equivalent ratio of the polyamine compound (PA) to the polyol compound (PO) enables favorable process-related steps, which ultimately results into superior gas barrier performance, as well as improved coating performance and properties.

[0033] Polyisocyanate compounds (PI) for use herein are not particularly limited. Any polyisocyanate compounds commonly known in the art may be used in the context of the present disclosure. Suitable polyisocyanate compounds (PI) for use herein will be easily identified by those skilled in the art in the light of the present disclosure.

[0034] In an advantageous aspect, the polyisocyanate compound (PI) for use herein has an equivalent weight no greater than 150 g / mol, no greater than 140 g / mol, no greater than 120 g / mol, no greater than 100 g / mol, no greater than 90 g / mol, no greater than 80 g / mol, or even no greater than 70 g / mol.

[0035] In the context of the present disclosure, the term “equivalent weight of the polyisocyanate compound (PI)” is meant to designate the molecular weight of the polyisocyanate compound (PI) divided by the number of equivalents of isocyanate functional groups present per molecule of the polyisocyanate compound (PI).

[0036] In still another advantageous aspect, the polyisocyanate compound (PI) for use herein has an equivalent weight in a range from 60 to 140 g / mol, from 60 to 120 g / mol, from 80 to 100 g / mol, from 85 to 100 g / mol, or even from 90 to 100 g / mol.

[0037] In the context of the present disclosure, it has been surprisingly found that using short chain polyisocyanate compounds (PI), in particular polyisocyanate compounds (PI) having an equivalent weight as specified above, enables increasing the density of urea and urethane functional groups within the isocyanate group-terminated prepolymer (PR), while minimizing the chain length between these functional groups. These characteristics result into a more compact and (functionally) dense isocyanate group-terminated prepolymer (PR) which isbelieved to advantageously impact at least the overall gas barrier performance of the polyurethane dispersion.

[0038] In another advantageous aspect, the polyisocyanate compound (PI) for use herein is selected from the group of aliphatic polyisocyanates, cycloaliphatic polyisocyanates, aromatic polyisocyanates, and any combinations of mixtures thereof.

[0039] In a more advantageous aspect, the polyisocyanate compound (PI) is selected from the group of linear aliphatic polyisocyanates, cycloaliphatic polyisocyanates, aromatic polyisocyanates wherein the isocyanate functional groups are not directly linked to the aromatic ring, and any combinations or mixtures thereof.

[0040] More advantageously, the polyisocyanate compound (PI) for use herein is selected from the group of tri-isocyanates, di-isocyanates, and any mixtures thereof. Even more advantageously, the polyisocyanate compound (PI) is selected from the group of di-isocyanates, and any mixtures thereof. In the context of the present disclosure, it has been surprisingly found that using di-isocyanates as the polyisocyanate compound (PI) enables obtaining isocyanate group-terminated prepolymers provided with improved linearity characteristics, which is believed to advantageously impact at least the overall gas barrier performance of the polyurethane dispersion.

[0041] According to an even more advantageous aspect of the disclosure, the polyisocyanate compound (PI) for use herein is selected from the group consisting of ethane diisocyanate, propane diisocyanate, butane diisocyanate (BDI), pentane diisocyanate (PDI), hexane diisocyanate (HDI), cyclohexane diisocyanate (CHDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), toluene diisocyanate (TDI), phenylene diisocyanate, naphthalene diisocyanate (NDI), isophorone diisocyanate (IPDI), tetramethyl xylylene diisocyanate (TMXDI), methylene diphenyl diisocyanate (MDI), hydrogenated methylene diphenyl diisocyanate (H12MDI), and any mixtures thereof.

[0042] According to a particularly advantageous aspect of the disclosure, the polyisocyanate compound (PI) is selected from the group consisting of butane diisocyanate (BDI), pentane diisocyanate (PDI), hexane diisocyanate (HDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), hydrogenated methylene diphenyl diisocyanate (H12MDI) and any mixtures thereof.

[0043] According to a preferred aspect, the polyisocyanate compound (PI) is selected from the group consisting of xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), and any mixtures thereof.

[0044] In the context of the present disclosure, it has been surprisingly found that using aromatic polyisocyanates wherein the isocyanate functional groups are not directly linked to the aromatic ring enables increasing the structural rigidity of the isocyanate group-terminated prepolymer (PR), which is believed to advantageously impact the overall gas barrier performance of the polyurethane dispersion.

[0045] Polyol compounds (PO) for use herein are not particularly limited as long as they have an equivalent weight no greater than 200 g / mol. Suitable polyols compounds (PO) for use herein will be easily identified by those skilled in the art in the light of the present disclosure.

[0046] In an advantageous aspect, the polyol compound (PO) for use herein has an equivalent weight no greater than 180 g / mol, no greater than 160 g / mol, no greater than 140 g / mol, no greater than 120 g / mol, no greater than 100 g / mol, no greater than 80 g / mol, no greater than 60 g / mol, no greater than 50 g / mol, no greater than 40 g / mol, or even no greater than 35 g / mol.

[0047] In the context of the present disclosure, the term “equivalent weight of the polyol compound (PO)” is meant to designate the molecular weight of the polyol compound (PO) divided by the number of equivalents of hydroxyl functional groups present per molecule of the polyol compound (PO).

[0048] In another advantageous aspect, the polyol compound (PO) has an equivalent weight in a range from 30 to 200 g / mol, from 30 to 180 g / mol, from 30 to 160 g / mol, from 30 to 140 g / mol, from 30 to 120 g / mol, from 30 to 100 g / mol, from 30 to 90 g / mol, from 30 to 80 g / mol, from 30 to 60 g / mol, from 30 to 50 g / mol, from 30 to 45 g / mol, from 30 to 40 g / mol, or even from 30 to 35 g / mol.

[0049] In the context of the present disclosure, it has been surprisingly found that using short chain polyol compounds (PO), in particular polyol compounds (PO) having an equivalent weight as specified above, enables increasing the density of urethane functional groups within the isocyanate group-terminated prepolymer (PR), while minimizing the chain length between these functional groups. These characteristics result into a more compact and (functionally) dense isocyanate group-terminated prepolymer (PR) which is believed to advantageously impact at least the overall gas barrier performance of the polyurethane dispersion.

[0050] In still another advantageous aspect, the polyol compound (PO) is selected from the group of linear or branched aliphatic polyols, cycloaliphatic polyols, aromatic polyols, and any combinations of mixtures thereof. More advantageously, the polyol compound (PO) for use herein is selected from the group of linear aliphatic polyols, and any mixtures thereof.

[0051] In a more advantageous aspect, the polyol compound (PO) is selected from the group of triols, diols, and any mixtures thereof. Even more advantageously, the polyol compound (PO) is selected from the group of diols, and any mixtures thereof. In the context of the present disclosure, it has been surprisingly found that using diols as the polyol compound (PO) enables obtaining isocyanate group-terminated prepolymers provided with improved linearity characteristics, which is believed to advantageously impact at least the overall gas barrier performance of the polyurethane dispersion.

[0052] Advantageously still, the polyol compound (PO) is selected from the group of non- polymeric polyols. In the context of the present disclosure, it has been surprisingly found that using non-polymeric polyols advantageously impacts the overall gas barrier performance of the polyurethane dispersion due to their shorter chain length and lower equivalent weight. Typical polymeric polyols include polyester polyols, polyether polyols, polycarbonate polyols, polyacrylic polyols, and poly siloxane polyols, which generally have a degree of polymerization greater than 3 repeating monomeric units and an equivalent weight way greater than 200 g / mol.

[0053] In another advantageous aspect, the polyol compound (PO) for use herein is a polyol with a crystalline character. This particular type of polyol compound (PO) is believed to provide additional hard and compact micro-domains within the structure of the isocyanate group- terminated prepolymer (PR) and which have the ability to hinder gas diffusion thereby advantageously impacting the overall gas barrier performance of the polyurethane dispersion.

[0054] According to an even more advantageous aspect of the disclosure, the polyol compound (PO) for use herein is selected from the group consisting of ethylene glycol, propylene glycol, 1,3 -propanediol, 1,3 -butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- hexanediol, cyclohexane dimethylol (also known as cyclohexane dimethanol), neopentyl glycol, 2-ethyl-2-butyl-l,3-propanediol, 1,7-heptanediol, 1,8-octanediol, 2-ethyl-l,6- hexanediol, trimethylolethane, trimethylolpropane, glycerol, di-trimethylolethane, pentaerythritol, di-trimethylolpropane, erythritol, pentaerythritol, sorbitol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, dibutylene glycol, 2-methyl-l,3-pentanediol, 2 -butyne- 1,4-diol, 2, 2, 4-trimethyl- 1,3 -pentanediol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, isosorbide, isomannide, isoidide, and any mixtures thereof.

[0055] According to an even more advantageous aspect of the disclosure, the polyol compound (PO) is selected from the group consisting of ethylene glycol, propylene glycol, cyclohexane dimethylol, and any mixtures thereof.

[0056] According to a particularly advantageous aspect of the disclosure, the polyol compound (PO) for use herein is selected from the group consisting of ethylene glycol, cyclohexane dimethylol, and any mixtures thereof.

[0057] According to a preferred aspect, the polyol compound (PO) for use herein is selected to be (or comprise) ethylene glycol.

[0058] According to an alternatively advantageous aspect of the disclosure, the polyol compound (PO) is selected from the group consisting of polyols comprising at least one urethane functional group, polyols comprising at least one urea functional group, and any combinations or mixtures thereof.

[0059] In the context of the present disclosure, it has been surprisingly found that using polyols comprising at least one urethane functional group (also referred to as urethane-in- polyols) or polyols comprising at least one urea functional group (also referred to as urea-in- polyols), enables increasing the density of urea and urethane functional groups within the isocyanate group-terminated prepolymer (PR), which is believed to advantageously impact at least the overall gas barrier performance of the resulting polyurethane dispersion.

[0060] Exemplary urethane-in-poly ols for use herein include urethane-in-diols which are typically obtained by the reaction between 1 mole of an alkylene diamine (such as ethylene diamine) with 2 moles of a cyclic carbonate (such as ethylene carbonate). Exemplary urea-in- polyols for use herein include urea-in-diols which are typically obtained by the reaction between 1 mole of a diisocyanate (such as xylylene diisocyanate) and 2 moles of an alkanolamine (such as ethanolamine).

[0061] Polyamine compounds (PA) for use herein are not particularly limited as long as they have an equivalent weight no greater than 100 g / mol. Suitable polyamine compounds (PA) for use herein will be easily identified by those skilled in the art in the light of the present disclosure.

[0062] In an advantageous aspect, the polyamine compound (PA) for use herein has an equivalent weight no greater than 80 g / mol, no greater than 60 g / mol, no greater than 50 g / mol,no greater than 40 g / mol, no greater than 35 g / mol, no greater than 30 g / mol, no greater than 25 g / mol, or even no greater than 20 g / mol.

[0063] In the context of the present disclosure, the term “equivalent weight of the polyamine compound (PA)” is meant to designate the molecular weight of the polyamine compound (PA) divided by the number of equivalents of amino functional groups present per molecule of the polyamine compound (PA).

[0064] In another advantageous aspect, the polyamine compound (PA) has an equivalent weight in a range from 10 to 100 g / mol, from 10 to 90 g / mol, from 15 to 80 g / mol, from 20 to 60 g / mol, from 25 to 50 g / mol, from 25 to 45 g / mol, or even from 25 to 40 g / mol.

[0065] In the context of the present disclosure, it has been surprisingly found that using short chain polyamine compounds (PA), in particular polyamine compounds (PA) having an equivalent weight as specified above, enables increasing the density of urea functional groups within the isocyanate group-terminated prepolymer (PR), while minimizing the chain length between these functional groups. These characteristics result into a more compact and (functionally) dense isocyanate group-terminated prepolymer (PR) which is believed to advantageously impact at least the overall gas barrier performance of the polyurethane dispersion.

[0066] In still another advantageous aspect, the polyamine compound (PA) for use herein is selected from the group of linear or branched aliphatic polyamines, cycloaliphatic polyamines, aromatic polyamines, and any combinations of mixtures thereof. More advantageously, the polyamine compound (PA) for use herein is selected from the group of linear aliphatic polyamines, and any mixtures thereof.

[0067] In a more advantageous aspect, the poly amine compound (PA) is selected from the group of triamines, diamines, and any mixtures thereof. Even more advantageously, the polyamine compound (PA) is selected from the group of diamines, and any mixtures thereof. In the context of the present disclosure, it has been surprisingly found that using diamines as the polyamine compound (PA) enables obtaining isocyanate group-terminated prepolymers provided with improved linearity characteristics, which is believed to advantageously impact at least the overall gas barrier performance of the polyurethane dispersion.

[0068] Advantageously still, the polyamine compound (PA) is selected from the group of non- polymeric polyamines. In the context of the present disclosure, it has been surprisingly found that using non-polymeric polyamines advantageously impacts the overall gas barrierperformance of the polyurethane dispersion due to their shorter chain length and lower equivalent weight. Typical polymeric polyamines include polyethyleneimines, and polyamides, which generally have a degree of polymerization greater than 3 repeating monomeric units and an equivalent weight way greater than 100 g / mol.

[0069] According to an even more advantageous aspect of the disclosure, the polyamine compound (PA) for use herein is selected from the group consisting of hydrazine, urea, 1,2- ethylenediamine, 1,2-propanediamine, 1,3 -propanediamine, 1,4-butanediamine, 1,5- pentanediamine, 1,6-hexanediamine, 1,2-cyclohexanediamine, 2- methylpentamethylenediamine, m-xylylenediamine, and any mixtures thereof.

[0070] According to a particularly advantageous aspect of the disclosure, the polyamine compound (PA) is selected from the group consisting of 1,2-ethylenediamine, 1,2- propanediamine, 1,3 -propanediamine, m-xylylenediamine, and any mixtures thereof.

[0071] According to a preferred aspect, the polyamine compound (PA) is selected to be (or comprise) 1,2-ethylenediamine.

[0072] Hydrophilic compounds (HC) for use herein are not particularly limited as long as they contain at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in an aqueous medium either directly or after the reaction with a neutralizing agent. Any hydrophilic compounds (HC) commonly known in the art may be used in the context of the present disclosure. Suitable hydrophilic compounds (HC) for use herein will be easily identified by those skilled in the art in the light of the present disclosure.

[0073] In an advantageous aspect, the hydrophilic compound (HC) for use herein contains at least two reactive groups capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in an aqueous medium either directly or after the reaction with a neutralizing agent.

[0074] In another advantageous aspect, the hydrophilic compound (HC) is selected from the group of polyols and polyamines containing an ionic or non-ionic functional group.

[0075] In a more advantageous aspect, the hydrophilic compound (HC) for use in the present disclosure is selected from the group of polyols and polyamines containing one or more anionic salt groups or acid groups which may be converted to an anionic salt group.

[0076] In an even more advantageous aspect, the hydrophilic compound (HC) is selected from the group of polyols containing one or more anionic salt groups containing carboxylate, sulfonate or phosphonate salt groups, or acid groups containing carboxylic acid, sulfonic acid or phosphonic acid groups.

[0077] In an even more advantageous aspect, the hydrophilic compound (HC) is selected from the group of carboxyl group-containing polyols, in particular polyhydroxy alkanoic acids, and any mixtures thereof.

[0078] According to a particularly advantageous aspect of the disclosure, the hydrophilic compound (HC) is selected from the group consisting of 2,2-dimethylol ethanoic acid, 2,2- dimethylol propionic acid, 2,2-dimethylol butanoic acid, 2,2-dimethylol pentanoic acid, 2,2- dimethylol hexanoic acid, and any mixtures thereof.

[0079] According to a preferred aspect, the hydrophilic compound (HC) is selected from the group consisting of 2,2-dimethylol propionic acid, 2,2-dimethylol butanoic acid, and any mixtures thereof. More preferably, the hydrophilic compound (HC) is selected to be (or comprise) 2,2-dimethylol propionic acid.

[0080] According to an alternatively advantageous aspect, the hydrophilic compound (HC) for use herein is selected from the group consisting of nonionic polyols. A particular example of nonionic polyol includes polyethyleneglycol monomethylether-based trimethylolpropane (commercially available under the trade designation Ymer® N120 from Perstorp). This diol can be used alone (nonionic stabilization) or associated with the acid molecules described above mixed anionic / nonionic stabilization).

[0081] In an alternative aspect of the polyurethane dispersion according to the disclosure, the isocyanate group-terminated prepolymer (PR) for use herein is produced by further reaction with at least one ethylenically unsaturated compound (EU) comprising at least one ethylenically unsaturated group and at least one further reactive group which is capable of reacting with isocyanate groups.

[0082] The incorporation of ethylenically unsaturated groups within the isocyanate group- terminated prepolymer (PR) allows improving the curing profile of the resulting polyurethane polymer (PU) by enabling and promoting radiation curing induced by actinic radiations (electron beam or ultraviolet light typically in the presence of a photoinitiator) or thermal curing (typically in the presence of a thermal initiator).

[0083] In an exemplary aspect, the ethylenically unsaturated compound (EU) for use herein comprises at least one (meth)acrylate group and at least one further reactive groups which are capable of reacting with isocyanate groups.

[0084] In an advantageous aspect, the ethylenically unsaturated compound (EU) is selected from the group of hydroxyl group-containing ethylenically unsaturated compounds, in particular of hydroxyl group-containing (meth)acrylates.

[0085] In a more advantageous aspect, the ethylenically unsaturated compound (EU) is selected from the group consisting of hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, glycerol mono-methacrylate, and any mixtures thereof.

[0086] In a preferred aspect, the ethylenically unsaturated compound (EU) is selected from the group consisting of hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, and any mixtures thereof.

[0087] In another advantageous aspect, the ethylenically unsaturated compound (EU) for use herein is selected from the group consisting of pentaerythritol triacrylate, dipentaerythritol pentaacrylate, trimethylolpropane diacrylate, ditrimethylolpropane triacrylate, glycerol diacrylate, as well as their polyoxyethylated or polyoxypropylated variants. This category is usually referred to as polyester acrylates.

[0088] In still another advantageous aspect, the ethylenically unsaturated compound (EU) for use herein is selected from the group consisting of acrylated mono- or diepoxy molecules capable of generating respectively 1 or 2 hydroxyl groups. Examples of these epoxidized molecules include, but are not limited to, glycidyl methacrylate, bisphenol A diglycidyl ether, mono-epoxy glycerol and epoxidized soybean oil. Other examples are commercially available for example under the trade designation Cardura® E10 from Hexion or UltraLite® 513 by Cardolite. This category is generally referred to as epoxy acrylates.

[0089] Chain-extension agents (CE) for use herein are not particularly limited. Any chainextension agents commonly known in the art may be used in the context of the present disclosure. Suitable chain-extension agents (CE) for use herein will be easily identified by those skilled in the art in the light of the present disclosure.

[0090] In an advantageous aspect, the chain-extension agent (CE) for use in the present disclosure is selected from the group of water-soluble aliphatic, alicyclic, aromatic or heterocyclic primary or secondary polyamines. As will be easily apparent to those skilled in the art, the polyamines for use herein as chain-extension agent (CE) may advantageously containadditional functional groups, in particular hydroxyl functional groups which may beneficially impact the curing performance of the polyurethane polymer (PU) present in the polyurethane dispersion.

[0091] In another advantageous aspect, the chain-extension agent (CE) is selected from the group of polyamines having an equivalent weight no greater than 100 g / mol, no greater than 80 g / mol, no greater than 60 g / mol, no greater than 50 g / mol, no greater than 40 g / mol, no greater than 30 g / mol, no greater than 25 g / mol, or even no greater than 20 g / mol.

[0092] In still another advantageous aspect, the chain-extension agent (CE) is selected from the group of polyamines having an equivalent weight in a range from 15 to 100 g / mol, from 20 to 90 g / mol, from 25 to 80 g / mol, from 30 to 70 g / mol, from 30 to 60 g / mol, from 30 to 50 g / mol, or even from 30 to 40 g / mol.

[0093] In the context of the present disclosure, it has been surprisingly found that using short chain-extension agents (CE), in particular polyamine compounds (PA) having an equivalent weight as specified above, enables increasing the density of urea functional groups within the polyurethane polymer (PU), while minimizing the chain length between these functional groups. These characteristics result into a more compact and (functionally) dense polyurethane polymer (PU) which is believed to advantageously impact at least the overall gas barrier performance of the polyurethane dispersion.

[0094] In yet another advantageous aspect, the chain-extension agent (CE) for use herein is selected from the group of polyamines having an average amine-functionality in a range from 2 to 4, from 2 to 3, or even exactly 2.

[0095] In a more advantageous aspect, the chain-extension agent (CE) is selected from the group consisting of 2-(2-aminoethylamino)ethanol, hydrazine, urea, ethylene diamine, piperazine, 1,2-propanediamine, 1,3 -propanediamine, 1,4-butanediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,10-decanediamine, l,12-dodecane_,diamine, 2- methylpentamethylenediamine, triethylene triamine, isophorone diamine, m-xylylene diamine, hydrogenated m-xylylene diamine, bi s(4-aminocyclohexyl)m ethane, bis(4-amino-3- methylcyclohexyl)methane, polyethylene imines, polyoxyethylene amines, polyoxypropylene amines, polyetheramines, and any mixtures thereof.

[0096] In a particularly advantageous aspect, the chain-extension agent (CE) is selected from the group consisting of 2-(2-aminoethylamino)ethanol, ethylene diamine, m-xylylene diamine, urea, and any mixtures thereof.

[0097] In a preferred aspect, the chain-extension agent (CE) for use herein is selected to be (or comprise) 2-(2-aminoethylamino)ethanol.

[0098] In a typical aspect of the disclosure, the chain-extension agent (CE) is different from the at least one polyamine compound (PA) and different from the at least one polyol compound (PO).

[0099] According to an alternative aspect of the disclosure, the polyurethane polymer (PU) is produced by reaction of the isocyanate group-terminated prepolymer (PR) with a chain-capping agent (CP) in addition to (or in lieu of) the chain-extension agent (CE) as described above.

[0100] Chain-capping agents (CP) for use herein are not particularly limited. Any chaincapping agents commonly known in the art may be used in the context of the present disclosure. Suitable chain-capping agents (CP) for use herein will be easily identified by those skilled in the art in the light of the present disclosure.

[0101] In an advantageous aspect, the chain-capping agent for use herein selected from the group consisting of monoalkylamines (such as N-butylamine), dialkylamines (such as N,N- dibutylamine), monoalkanolamines (such as ethanolamine), dialkanolamines (such as diethanolamine), and any combinations or mixtures thereof. More advantageously, the chaincapping agent is selected to be (or comprise) diethanolamine.

[0102] In a typical aspect, the polyurethane polymer (PU) for use herein has a number average molecular weight (Mn) in the range from 1,000 to 100,000 g / mol, from 5,000 to 50,000 g / mol, or even from 10,000 to 30,000 g / mol.

[0103] In another typical aspect, the isocyanate group-terminated prepolymer (PR) for use herein has a number average molecular weight (Mn) in the range from 250 to 10,000 g / mol, from 250 to 5,000 g / mol, or even from 250 to 2,500 g / mol.

[0104] In a typical aspect, the polyurethane dispersion of the present disclosure is a fully reacted polyurethane dispersion.

[0105] In a particular aspect, additional functionalities may be introduced into the polyurethane polymer (PU) through any of its constituents or reactants depending on the targeted properties. According to a beneficial aspect, polysiloxane functionalities may be advantageously introduced to impart adhesion properties in laminate constructions. In that respect, the use of gamma-aminopropyltrimethoxysilane as a chain capping agent is particularly advantageous.

[0106] According to an advantageous aspect, the polyurethane dispersion of the present disclosure further comprises water dispersible crosslinking agents, in particular polyisocyanates, polycarbodiimides and polysiloxanes.

[0107] According to another advantageous aspect, the polyurethane dispersion has a particle size no greater than 400 nm, no greater than 350 nm, no greater than 300 nm, no greater than 250 nm, no greater than 200 nm, no greater than 150 nm, no greater than 100 nm, no greater than 90 nm, no greater than 80 nm, or even no greater than 70 nm, when determined by DLS measurements according to the test method described in the experimental section.

[0108] According to still another advantageous aspect, the polyurethane dispersion has a particle size in a range from 50 to 300 nm, from 50 to 250 nm, from 50 to 200 nm, from 50 to 150 nm, from 50 to 100 nm, from 60 to 90 nm, or even from 70 to 80 nm, when determined by DLS measurements according to the test method described in the experimental section.

[0109] According to yet another advantageous aspect, the polyurethane dispersion has a solid content in a range from 15 to 50 wt.%, from 20 to 45 wt.%, from 20 to 40 wt.%, from 20 to 35 wt.%, or even from 20 to 30 wt.%, when determined by gravimetric method according to the test method described in the experimental section.

[0110] According to yet another advantageous aspect, the polyurethane dispersion has a viscosity no greater than 500 mPa.s, no greater than 200 mPa.s, no greater than 100 mPa.s, no greater than 50 mPa.s, no greater than 20 mPa.s, or even no greater than 10 mPa.s, when determined according to the test method described in the experimental section.

[0111] According to yet another advantageous aspect, the polyurethane dispersion of the disclosure has a colloidal stability greater than 5 or even greater than 10 days, when determined at 60°C according to the test method described in the experimental section.

[0112] In still another advantageous aspect, the polyurethane dispersion according to the present disclosure has a minimum film formation temperature (MFFT) no greater than 40°C, no greater than 30°C, no greater than 20°C, no greater than 15°C, or even no greater than 10°C, when determined according to the test method described in the experimental section.

[0113] In yet another advantageous aspect, the polyurethane dispersion has a pH in a range from 7 to 12, from 8 to 11 or even from 9 to 10, when determined according to the test method described in the experimental section.

[0114] According to another aspect, the present disclosure is directed to a process of manufacturing a polyurethane dispersion as described above, wherein the method comprises the steps of: a) preparing an isocyanate group-terminated prepolymer (PR) by reacting: i. at least one polyisocyanate compound (PI); ii. at least one polyol compound (PO) having an equivalent weight no greater than 200 g / mol; iii. at least one polyamine compound (PA) having an equivalent weight no greater than 100 g / mol; and iv. at least one hydrophilic compound (HC) containing at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in aqueous medium either directly or after the reaction with a neutralizing agent; b) dispersing the isocyanate group-terminated prepolymer (PR) into an aqueous medium; and c) reacting the isocyanate group-terminated prepolymer (PR) dispersed into the aqueous medium with a chain-extension agent (CE) thereby forming a polyurethane dispersion.

[0115] According to still another aspect, it is provided a process of manufacturing a polyurethane dispersion as described above, wherein the method comprises the steps of: a) providing an isocyanate group-terminated prepolymer (PR) as described above; b) dispersing the isocyanate group-terminated prepolymer (PR) into an aqueous medium; and c) reacting the isocyanate group-terminated prepolymer (PR) dispersed into the aqueous medium with a chain-extension agent (CE) thereby forming a polyurethane dispersion.

[0116] Methods of forming polyurethane dispersions into an aqueous medium are well known to those skilled in art. A typical procedure involves: a) forming an isocyanate group-terminated pre-polymer (PR) by reacting a polyisocyanate with a polyol containing an acid group and a polyol not comprising any further functional groups; b) neutralizing the prepolymer by neutralizing the acid groups with a suitable base; and c) dispersing the neutralized pre-polymer in water, often followed by a reaction with a chain extension agent (CE) to increase molecularweight. An exemplary general procedure is described for example in US 2012 / 0016075-Al (Uchida).

[0117] In an advantageous aspect, the processes as described above further comprise the step of reacting the isocyanate group-terminated prepolymer (PR) dispersed into the aqueous medium with a chain capping agent (CP) in addition to (or in lieu of) the chain-extension agent (CE).

[0118] In another advantageous aspect, the aqueous medium comprises a miscible co-solvent, which can advantageously be acetone.

[0119] According to still another aspect, the present disclosure relates to a (gas barrier) coating material comprising a polyurethane dispersion as described above.

[0120] As will be easily apparent to those skilled in the art, the coating material of the disclosure or its liquid polymer dispersion precursor may comprise conventional additives, including but not limited to, plasticizers, antifoamers, leveling agents, dispersion stabilizers, fillers, colloidal silica, antifungal agents, anticorrosive agents, delustering agents, fire retardants, tackifiers, thickening agents, lubricants, antistatic agents, surfactants, reaction retardants, antioxidants, ultraviolet absorbers, hindered amine light stabilizers (HALS), antiblocking agents, waxes, weathering stabilizers, heat stabilizers, dyes, inorganic pigments, organic pigments, extender pigments, curing agents, anti-tack agents, inorganic particles, crystal nucleating agents, water swellable inorganic layered compounds such as montmorillonite, synthetic mica, or organic particles.

[0121] In an advantageous aspect, the coating material of the disclosure further comprises silicate particulate material, in particular clay particles. Suitable additives will be chosen in accordance with the purpose and targeted application.

[0122] The coating material may be formed according to techniques well known to those skilled in the art.

[0123] In an advantageous aspect, the coating material according to the disclosure has an oxygen barrier performance (PO2) no greater than 100 cm3 / m2.day, no greater than 95 cm3 / m2.day, no greater than 90 cm3 / m2.day, no greater than 85 cm3 / m2.day, no greater than 80 cm3 / m2.day, no greater than 75 cm3 / m2.day, no greater than 70 cm3 / m2.day, or even no greater than 65 cm3 / m2.day, when determined according to the test method described in the experimental section.

[0124] According to still another aspect, the present disclosure is directed to a (gas barrier) laminate comprising a substrate and a polyurethane layer formed on at least part of the surface of the substrate, wherein the polyurethane layer is produced by applying (and drying) a liquid coating composition comprising a polyurethane dispersion as described above.

[0125] In an advantageous aspect, the laminate according to the disclosure is a gas (oxygen and water vapor) barrier laminate.

[0126] The laminate may be formed according to techniques well known to those skilled in the art of laminates, in particular packaging laminate materials. The laminate typically comprises a substrate on top of which is provided the polyurethane layer, wherein an additional metal deposition layer or an oxide layer is formed on the polyurethane layer. Alternatively, the laminate may comprise a substrate on top of which an additional metal deposition layer or an oxide layer is formed, and wherein the polyurethane layer is formed on the metal deposition layer or the oxide layer.

[0127] The polyurethane layer is produced according to techniques well known to those skilled in the art, whereby a liquid coating composition comprising the polyurethane dispersion is typically applied on the substrate by any known coating technique such as, for example, gravure coating, reverse coating, roll coating, bar coating, spray coating, air knife coating or dipping method. The coated liquid layer is then typically dried at a temperature in a range from 40 to 160°C for a drying time in a range from 0.1 to 5 minutes and with an air flow velocity typically comprised in a range from 0.1 to 5 meters per second.

[0128] In an advantageous aspect, the laminate according to the disclosure further comprises metal oxide layers formed on the polyurethane layer and obtained by chemical vapor deposition.

[0129] In another advantageous aspect, the laminate further comprises a metal deposition layer formed on the polyurethane layer. Exemplary metals include, but are not limited to, aluminum, titanium, zirconium, magnesium, calcium, barium, silicon, germanium, and their oxides. Preferably an aluminum layer is used as the metal deposition layer.

[0130] The substrate for use herein is not particularly limited. Any substrate commonly known in the art of laminate forming may be used in the context of the present disclosure. Suitable substrates for use herein will be easily identified by those skilled in the art in the light of the present disclosure. Exemplary substrates for use herein include thermoplastic films, heat- sealable plastic films

[0131] In an advantageous aspect, the substrate for use herein comprises a (heat-sealable) plastic film, in particular a cast or (bi)oriented polyolefin film. More advantageously, the polyolefin material used for making the plastic films for use herein are selected from the group of polyethylene, polypropylene, polyethylene-co-propylene random or block co-polymers, polyethylene terephthalate (PET), polystyrene (PS), polylactic acid, polyvinyl chloride (PVC), and any combinations, mixtures or copolymers thereof.

[0132] According to yet another aspect of the present disclosure, it is provided a food packaging material comprising a laminate as described above.

[0133] According to yet another aspect, the present disclosure provides a process of manufacturing a laminate, wherein the method comprises the steps of: a) providing a polyurethane dispersion as described above; and b) applying (and drying) the polyurethane dispersion onto at least part of the surface of a substrate.

[0134] In yet another aspect, the present disclosure is directed to the use of a polyurethane dispersion as described above for the manufacturing of a gas barrier coating material, in particular for use in a packaging laminate material.

[0135] In an advantageous aspect, the use of a polyurethane dispersion as described above is for the manufacturing of an oxygen and / or water vapor barrier coating material.EXAMPLES

[0136] The present disclosure is further illustrated by the following examples. These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims.

[0137] Throughout the present disclosure and example section, the following test and measurement methods are used to characterize the exemplary polyurethane dispersions and the coating material obtained therefrom.Test Methods:A) Particle size

[0138] Dynamic light scattering (DLS) measurements are used to characterize the hydrodynamic size of particles in the various polyurethane dispersions. DLS measurements are performed at 23 °C using a Delsa Nano-c particle analyzer of Beckman-Coulter. Incident monochromatic light used in the DLS measurement has a wavelength of 1 = 658 nm. Scattered light is detected in near-backscattering geometry at an angle of 165°. The z-average particle size along with the poly dispersity index is determined from a second-order cumulant analysis of the electric-field auto-correlation function.B) Viscosity

[0139] The viscosity of the various polyurethane dispersions is measured at 23°C with a cone and plate type rheometer MCR092 (Paar-Physica) according to test method DIN EN ISO 3219. A fixed shear rate of 25 s-1 is used.C) Colloidal stability

[0140] The colloidal stability of the various polyurethane dispersions is assessed at 60°C by visually observing the decantation and / or phase separation (expressed in percent of the total height) on samples weighing 20g and placed in an oven at 60°C. The colloidal stability is herein reported as the number of days before a sedimentation exceeding 2% of the total height of the sample. In the context of the present disclosure, a good colloidal stability is achieved when no product deterioration is observed during at least 10 days at 60°C.D) Solid content

[0141] The solid content (SC) of the various polyurethane dispersions is determined by gravimetric method, which comprises a drying step for 2 hours at 120°C.E) Molecular weight

[0142] The number-average molecular weight (Mn) of the polyurethane polymer (PU) and the isocyanate group-terminated prepolymer (PR) are determined by conventional sizeexclusion chromatography (SEC). The samples are delivered as dispersions in water. They are freeze-dried and immediately dissolved in a 0.1M solution of LiBr in N,N-dimethylacetamide (LiBr / DMAc), which is used as the mobile phase for further SEC analyses. The pump used for the measurements is 1260 Infinity II and the autosampler is 1200 Infinity II, both available from Agilent Technologies. The RI detector is Optilab, at wavelength 1 = 658 nm, available from Wyatt Technology. The columns with guard column are successively coupled Polar gel M (7.5 x 300 mm, particle size: 8 micrometers) and Polar gel L (7.5 x 300 mm, particle size: 8 micrometers), both available from Agilent Technologies. The flow rate of the mobile phase is 0.8 mL / min. The sample concentration is 1 mg / mL and the injection volume is 100 microliters. The number-average molecular weight (Mn) is calculated based on column calibration with polystyrene standards with narrow molecular weight distribution.F) Minimum film formation temperature (MFFT)

[0143] The minimum film formation temperature (MFFT) of the various polyurethane dispersions is measured on a gradient-heated metal plate according to standard test method ASTM D2354 using Minimum Film Forming Temperature Instrument model MFFT 90 available from Rhopoint Instruments.G) Oxygen barrier performance (PO2)

[0144] The oxygen barrier performance of (PO2) the various coating material is determined by first measuring (at 0% relative humidity and 23°C) the oxygen transmission rate (OTR)of a laminate comprising the polyurethane material coated onto a corona treated PET film having a 12 micrometer thickness according to test method ASTM D3985 and using permeation analyser OX-TRAN® Model 2 / 21 available from Mocon. The coated polyurethane material is obtainedby coating a 25% polyurethane dispersion onto the PET film using a drawdown bar so as to obtain a 3 gsm coating. The wet coating is evaporated to dryness at 80°C in an oven for 5 minutes.Raw materials and startins products:

[0145] In the examples, the following raw materials and starting products are used:Xylylene diisocyanate is commercially available from Mitsui. Referred to hereinafter as XDI.Dicyclohexylmethane-4,4'-diisocyanate is commercially available from Covestro. Referred to hereinafter as H12MDI.Ethylene glycol is commercially available from Sigma-Aldrich. Referred to hereinafter as EG.Trimethylol propane is commercially available from Sigma-Aldrich. Referred to hereinafter as TMP.Ethylene diamine is commercially available from Sigma-Aldrich. Referred to hereinafter as EDA.Meta-xylene diamine is commercially available from Sigma-Aldrich. Referred to hereinafter as MXDA.Dimethylol propionic acid is commercially available from Geo Specialty Chemicals, Inc. Referred to hereinafter as DMPA.Triethylamine is commercially available from Sigma- Aldrich. Referred to hereinafter as TEA.2-(2-aminoethylamino)ethanol is commercially available from Sigma-Aldrich. Referred to hereinafter as 2(2AEAE).Daotan® TW-7000 / 40WA is a water-borne polyurethane dispersion suitable for packaging lamination and coatings and having reasonably good oxygen barrier property, commercially available from Allnex. Referred to hereinafter as D-TW7000.Takelac™ WPB-341 is a waterborne polyurethane dispersion offering reasonably good oxygen-barrier property and recommended for packaging and industrial films, commercially available from Mitsui. Referred to hereinafter as T- WPB341.Examples:Example 1 : General procedure for the preparation of exemplary polyurethane dispersions (Ex, 1 and Ex, 2) and comparative polyurethane dispersions (Ex, Cl to Ex,C3),

[0146] The diol(s), the diamine and the hydrophilic compound DMPA are mixed with acetone in a double-layered glass reactor fitted with a U-shape mechanical stirrer, a condenser, a thermometer and a dropping funnel. The reactants are mixed under an agitation of 130 rpm at ambient temperature and then a first portion of the diisocyanate(s) is added. The mixing is followed by an exotherm and continued for 15 minutes until the temperature stabilizes. This operation is repeated with a second and a third portion of the diisocyanate(s). The reactor jacket is then heated to a temperature of 50°C and the urethanization reaction is monitored until the target isocyanate content (INCO) value is reached. Then, TEA is added in the reactor and the mixing is continued for 15 minutes until complete homogenization is achieved. In a separate mixing vessel, demineralized water and a cowless blade turning at 400 rpm are incorporated. The dispersion is performed by transferring the warm neutralized pre-polymer slowly into the demineralized water. Immediately after complete polymer dispersion, a mixture of 2(2AEAE) diluted in demineralized water at a 33 wt.% concentration is slowly added into the mixing vessel and the polymer dispersion is hold under agitation at 150 rpm for 1 hour. The product is transferred back in the reactor with the U-shape mechanical stirrer turning at 130 rpm and the reactor jacket is heated to 60°C. The vacuum is increased progressively to 100 kPa using a vacuum pump and the solvent is stripped for 3 hours while preventing foam formation.

[0147] The comparative polyurethane dispersions (Ex. Cl to Ex.C3) are prepared in a manner similar as described above at the exception that no diamine is used during the preparation of the pre-polymer.Example 2: Formulation of exemplary polyurethane dispersions (Ex.l and Ex, 2) and comparative polyurethane dispersions (Ex, Cl to Ex,C3),

[0148] The exemplary polyurethane dispersions (Ex. l and Ex.2) and comparative polyurethane dispersions (Ex. Cl to Ex.C3) are prepared according to the procedure described hereinbefore. Comparative polyurethane dispersions (Ex. Cl to Ex.C3) do not use a diamine for the preparation of the pre-polymer. The corresponding formulations are presented in Table 1 below.Table 1 : Formulation of exemplary polyurethane dispersions (Ex.l and Ex.2) and comparative polyurethane dispersions (Ex. Cl to Ex.C3).Example 3: Performance and characteristics of exemplary polyurethane dispersions (Ex.l and Ex, 2) and comparative polyurethane dispersions (Ex, Cl to Ex,C3),

[0149] The performance and characteristics of exemplary polyurethane dispersions (Ex. land Ex.2) and comparative polyurethane dispersions (Ex. Cl to Ex.C3) have been determined according to the corresponding test methods described hereinbefore. The results are presented in Table 2 below.Table 2: Performance and characteristics of exemplary polyurethane dispersions (Ex. l and Ex.2) and comparative polyurethane dispersions (Ex. Cl to Ex.C3)N / A(<!): not measurable due to excessive instability of the dispersion and inability to form a film.

[0150] As can be seen from the results shown in Table 2, the polyurethane dispersions according to the present disclosure (Ex.l and Ex.2) are provided with excellent balance of properties, in particular oxygen barrier property, MFFT and colloidal stability. In contrast, the polyurethane dispersions of comparative examples Ex. Cl to Ex.C3 are less advantageous. In particular, none of these the comparative polyurethane dispersions can beneficially combine these three performance attributes. Ex. Cl is deficient in terms of oxygen barrier property. Ex.C2 is deficient in terms of oxygen barrier property and colloidal stability. As for Ex.C3, the polyurethane dispersion is so instable and the particle size so unacceptably large that no coating film can be formed out of the dispersion.Example 4: Performance of exemplary polyurethane dispersions (Ex.l and Ex, 2) and comparative commercial polyurethane dispersions (Ex,C4 and Ex,C5),

[0151] The performance of exemplary polyurethane dispersions (Ex. l and Ex.2) and comparative commercial dispersions (Ex.C4 and Ex.C5) has been determined according to the corresponding test methods described hereinbefore. Comparative example Ex.C4 uses commercial polyurethane dispersion D-TW7000 and Ex.C5 uses commercial polyurethane dispersion T- WPB341. The results are presented in Table 3 below.Table 3: Performance of exemplary polyurethane dispersion (Ex. l and Ex.2) and comparative commercial polyurethane dispersions (Ex.C4 and Ex.C5)

[0152] As can be seen from the results shown in Table 3, the polyurethane dispersions according to the present disclosure (Ex.l and Ex.2) are provided with excellent balance of properties, in particular oxygen barrier property and MFFT. In contrast, the polyurethane dispersions of comparative examples Ex.C4 and Ex.C5 are less advantageous. In particular, the comparative polyurethane dispersions are deficient in terms of oxygen barrier property and MFFT property.

Claims

CLAIMS1. A polyurethane dispersion comprising a polyurethane polymer (PU) which is the reaction product of an isocyanate group-terminated prepolymer (PR) and a chainextension agent (CE), wherein the isocyanate group-terminated prepolymer (PR) is produced by the reaction of: a) at least one polyisocyanate compound (PI); b) at least one polyol compound (PO) having an equivalent weight no greater than 200 g / mol; c) at least one polyamine compound (PA) having an equivalent weight no greater than 100 g / mol; and d) at least one hydrophilic compound (HC) containing at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in an aqueous medium either directly or after the reaction with a neutralizing agent.

2. A polyurethane dispersion according to claim 1 , wherein the polyurethane polymer (PU) has a weight ratio of urea functional groups content to urethane functional groups content greater than 0.38, greater than 0.40, greater than 0.42, greater than 0.44, greater than 0.45, greater than 0.46, greater than 0.48, or even greater than 0.50.

3. A polyurethane dispersion according to any one of claim 1 or 2, wherein the isocyanate group-terminated prepolymer (PR) has an equivalent ratio of the polyamine compound (PA) to the polyol compound (PO) no greater than 25:75, no greater than 20:80, no greater than 15:85, no greater than 10:90, or even no greater than 5:95.

4. A polyurethane dispersion according to any one of the preceding claims, wherein the at least one polyisocyanate compound (PI) has an equivalent weight no greater than 150 g / mol, no greater than 120 g / mol, no greater than 100 g / mol, no greater than 90 g / mol, no greater than 80 g / mol, or even no greater than 70 g / mol.

5. A polyurethane dispersion according to any one of the preceding claims, wherein the at least one polyisocyanate compound (PI) is selected from the group consisting of butane diisocyanate (BDI), pentane diisocyanate (PDI), hexane diisocyanate (HDI), xylylenediisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), hydrogenated methylene diphenyl diisocyanate (H12MDI) and any mixtures thereof .

6. A polyurethane dispersion according to any one of the preceding claims, wherein the at least one polyol compound (PO) has an equivalent weight no greater than 180 g / mol, no greater than 160 g / mol, no greater than 140 g / mol, no greater than 120 g / mol, no greater than 100 g / mol, no greater than 80 g / mol, no greater than 60 g / mol, no greater than 50 g / mol, no greater than 40 g / mol, or even no greater than 35 g / mol.

7. A polyurethane dispersion according to any one of the preceding claims, wherein the at least one polyol compound (PO) is selected from the group consisting of ethylene glycol, propylene glycol, cyclohexane dimethylol, and any mixtures thereof.

8. A polyurethane dispersion according to any one of the preceding claims, wherein the at least one polyamine compound (PA) has an equivalent weight no greater than 80 g / mol, no greater than 60 g / mol, no greater than 50 g / mol, no greater than 40 g / mol, no greater than 35 g / mol, no greater than 30 g / mol, no greater than 25 g / mol, or even no greater than 20 g / mol.

9. A polyurethane dispersion according to any one of the preceding claims, wherein the at least one polyamine compound (PA) is selected from the group consisting of 1,2- ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, m-xylylenediamine, and any mixtures thereof.

10. A polyurethane dispersion according to any one of the preceding claims, wherein the hydrophilic compound (HC) is selected from the group of polyols and polyamines containing an ionic or non-ionic functional group.

11. A polyurethane dispersion according to any one of the preceding claims, wherein the chain-extension agent (CE) is selected from the group of water-soluble aliphatic, alicyclic, aromatic or heterocyclic primary or secondary polyamines.

12. A polyurethane dispersion according to any one of the preceding claims, wherein the polyurethane polymer (PU) is produced by further reaction with a chain capping agent (CP) in addition to the chain-extension agent (CE).

13. A process of manufacturing a polyurethane dispersion according to any one of the preceding claims, wherein the method comprises the steps of: a) preparing an isocyanate group-terminated prepolymer (PR) by reacting: i. at least one polyisocyanate compound (PI); ii. at least one polyol compound (PO) having an equivalent weight no greater than 200 g / mol; iii. at least one polyamine compound (PA) having an equivalent weight no greater than 100 g / mol; and iv. at least one hydrophilic compound (HC) containing at least one reactive group capable of reacting with isocyanate groups and at least one hydrophilic group capable of rendering the polyurethane polymer (PU) dispersible in aqueous medium either directly or after the reaction with a neutralizing agent; b) dispersing the isocyanate group-terminated prepolymer (PR) into an aqueous medium; and c) reacting the isocyanate group-terminated prepolymer (PR) dispersed into the aqueous medium with a chain-extension agent (CE) thereby forming a polyurethane dispersion.

14. A coating material comprising a polyurethane dispersion according to any one of claims 1 to 12.

15. Use of a polyurethane dispersion according to any one of the claims 1 to 12 for the manufacturing of a gas barrier coating material, in particular for use in a packaging laminate material.

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