Compositions and articles comprising blends including branched polyamide

Abstract

To provide compositions for realizing articles with desirable properties such as a high puncture resistance, tensile strength and oxygen transmission rate, as well as a low water vapor transmission rate.SOLUTION: A composition comprises a blend of: polyamide-6 or low-density polyethylene; and a branched polyamide including a lactam, a dimer acid and a diamine.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 068,254, filed August 20, 2020, the entire contents of which are incorporated herein by reference.

[0002] This disclosure relates to articles made with polyamides, and more particularly, to articles made with blends including branched polyamides to achieve desirable properties such as high puncture resistance, tensile strength, and oxygen permeability, as well as low water vapor permeability. [Background technology]

[0003] Typically, polyamides are formed from precursors such as caprolactam through the reactions of hydrolysis, addition polymerization, and polycondensation. In the case of polyamide-6 materials formed from caprolactam, hydrolysis opens the caprolactam monomers to form two end groups, one amine end group and one carboxyl end group, addition polymerization combines the caprolactam monomers into intermediate molecular weight oligomers, and polycondensation combines the oligomers into higher molecular weight polymers.

[0004] The polycondensation reaction involves a reversible chemical reaction in which polyamide-6 oligomers or prepolymers form higher molecular weight polyamide chains with the additional product water, as shown below in Reaction 1. Polycondensation occurs simultaneously with hydrolysis and addition polymerization, and the total number of end groups present decreases as the reaction progresses to form higher molecular weight polyamide chains.

[0005] [ka]

[0006] The water content affects the molecular weight and total number of end groups of the resulting polyamide chains. By removing water, the reaction proceeds toward producing higher molecular weight polymer chains in order to maintain reaction equilibrium. In one method, when a significantly higher molecular weight polyamide is desired, water is removed from the reaction product by applying an increasing vacuum. However, applying increasing vacuum for extended periods of time is not practical because the mixture becomes increasingly water-poor, making water extraction more difficult over time.

[0007] Articles formed from polyamides can include, for example, films, fibers, and wires. Increasing the molecular weight of the polyamide can significantly improve the strength of the article. However, due to the difficulty of removing water as the molecular weight increases, commercially available high molecular weight polyamides are in the range of about 27 to 30 kilodaltons (kDa). It may be limited to the average molecular weight (Mn).

[0008] Furthermore, as the molecular weight of the polyamide polymer increases during the polycondensation reaction, the viscosity of the polymer also increases. As the viscosity increases, the pressure required to extrude the article can exceed the limitations of extrusion systems, such as high-speed spinning systems for fiber, extruders for wire, and blow molding systems for film, as are known in the art. Thus, a balance exists between achieving higher molecular weights to produce higher strength polyamide articles and the ability to efficiently manufacture such polyamide articles given the increased melt viscosity associated with higher molecular weight polyamides. Summary of the Invention

[0009] The present disclosure provides compositions and articles comprising polyamide-6 or low density polyethylene and branched polyamides.

[0010] In one form thereof, the present disclosure provides a composition comprising a blend of polyamide-6 and a branched polyamide.

[0011] The branched polyamide of the composition may have the formula:

[0012] [ka]

[0013] wherein a=6-10, b=6-10, c=4-10, d=4-10, x=80-400, and m=1-400. The branched polyamide may be present in an amount of 5% to 50% by weight based on the total weight of the blend of polyamide-6 and branched polyamide. The branched polyamide may be present in an amount of 15% to 25% by weight based on the total weight of the blend of polyamide-6 and branched polyamide. The branched polyamide may include one or more monofunctional or difunctional end-capping agent residues. The one or more end-capping agent residues may include monofunctional acid residues, difunctional acid residues, monofunctional amine residues, and difunctional amine residues. The concentration of amine end groups may be less than 25 mmol / kg, and the concentration of carboxyl end groups may be less than 18 mmol / kg.

[0014] The branched polyamide of the composition may have a viscosity of 20 to 80 FAV. The polyamide-6 may have a viscosity of 80 to 140 FAV. The blend may consist essentially of polyamide-6 and branched polyamide. The blend may consist of polyamide-6 and branched polyamide.

[0015] In another of its forms, the present disclosure provides a composition comprising a blend of low density polyethylene and a branched polyamide.

[0016] The branched polyamide of the composition may have the formula:

[0017] [ka]

[0018] wherein a=6-10, b=6-10, c=4-10, d=4-10, x=80-400, and m=1-400. The branched polyamide may be present in an amount of 5% to 30% by weight of the total weight of the blend of polyethylene and branched polyamide. The branched polyamide may contain one or more monofunctional or difunctional end-capping agent residues. The blend may consist essentially of polyethylene and branched polyamide. The blend may consist of polyethylene and branched polyamide.

[0019] In another of its aspects, the present disclosure provides articles formed from the compositions disclosed herein.

[0020] The article may be a film. The article may be a fiber. The article may be a wire.

[0021] The article can be a film having a lower haze than a film comprising a composition comprising a blend of low-density polyethylene and polyamide-6. The article can be a film having a tensile strength greater than a film comprised of polyamide-6 and a film comprised of a branched polyamide. The film can have a tensile strength in the machine direction greater than a film comprised of polyamide-6 and a film comprised of a branched polyamide. The article can be a film having a penetration to break greater than a film comprised of polyamide-6 and a film comprised of a branched polyamide. The article can be a film having a puncture force greater than a film comprised of polyamide-6. The article can be a film having a greater elongation to break than a film comprised of polyamide-6. The article can be a film having an oxygen transmission rate greater than a film comprised of polyamide-6. The article can be a film having a water vapor transmission rate greater than a film comprised of polyamide-6. The article can be used as a packaging film for cut flowers or produce.

[0022] While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative and not restrictive. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a graph showing the enthalpy of melting for blends of branched or unbranched polyamides with LDPE in accordance with the present disclosure. [Figure 2] FIG. 2 is a graph showing the tensile strength of polyamide films comprising blends of polyamide-6 and branched polyamides in accordance with the present disclosure. [Figure 3] FIG. 3 is a graph showing the elongation of polyamide films comprising blends of polyamide-6 and branched polyamides in accordance with the present disclosure. [Figure 4] FIG. 4 is a graph showing the tensile strength of polyamide films comprising blends of polyamide-6 and branched polyamides in accordance with the present disclosure. [Figure 5] FIG. 5 is a graph showing penetration to break of polyamide films comprising blends of polyamide-6 and branched polyamides in accordance with the present disclosure. [Figure 6] FIG. 6 is a graph showing the puncture force of polyamide films comprising blends of polyamide-6 and branched polyamides in accordance with the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0024] While the present invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and will be described in detail below. It is not, however, intended to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives included within the scope of the present invention as defined by the appended claims.

[0025] The present disclosure provides compositions and articles comprising a blend of a branched polyamide with another polymer, such as polyamide-6 or low-density polyethylene. Surprisingly, it has been discovered that articles such as films, fibers, and wires formed from blends of branched polyamides with polyamide-6 can have improved properties compared to either the branched polyamide or polyamide-6 alone. Importantly, because the branched polyamide can have a lower molecular weight, such as 15-25 kDa, the pressures at which the polyamide can be extruded to form articles are significantly lower.

[0026] The present disclosure provides compositions and articles comprising blends of branched polyamides and polyamide-6. The branched polyamides contain dimer acid residues. The dimer acid residues provide the polyamide with a branched chain structure. Branched polyamides exhibit properties similar to higher molecular weight linear polyamides. Without being bound by any theory, it is believed that branch-chain interactions contribute to the increased strength of the polyamides. It is also believed that branched polyamides are relatively hydrophobic, and articles comprising branched polyamides may absorb less water and therefore exhibit a relatively low water vapor transmission rate (WVTR). In addition, it is believed that branch-chain interactions in branched polyamides contribute to an increase in free volume between polyamide monomers, thereby allowing for a relatively high molecular diffusion rate through articles comprising branched polyamides.

[0027] As known in the art, a polymer blend is a composition in which at least two polymers are blended or mixed together to create a new material with different physical properties.

[0028] The present disclosure provides compositions comprising blends of polyamide-6 and branched polyamides. In compositions comprising blends of polyamide-6 and any of the branched polyamides described herein, the branched polyamide can be present in an amount of at least 5 weight percent (wt%), 10 wt%, 15 wt%, 20 wt%, or 25 wt%, or as much as 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%, or any range defined between any two of the above values, such as 5 wt% to 50 wt%, 10 wt% to 45 wt%, 15 wt% to 40 wt%, 20 wt% to 35 wt%, 25 wt% to 30 wt%, 20 wt% to 40 wt%, 25 wt% to 35 wt%, 15 wt% to 25 wt%, or 10 wt% to 30 wt%. All weight percentages are based on the total weight of the blend of polyamide-6 and branched polyamide.

[0029] The blend may consist essentially of polyamide-6 and branched polyamide. The blend may consist of polyamide-6 and branched polyamide. Polyamide-6, also known as nylon-6 or polycaprolactam, is commercially available. For example, Aegis® H100ZP nylon 6 extrusion grade homopolymer is available from AdvanSix Inc., Parsippany, NJ. Aegis® H100ZP (H100ZP) is a medium viscosity polymer for cast or blown films and has a formic acid viscosity (FAV) of about 100. Another example is Aegis® H135ZP nylon 6 extrusion grade homopolymer, also available from AdvanSix Inc., Parsippany, NJ. Aegis® H135ZP (H135ZP) is a high viscosity polymer for cast or blown films and has a formic acid viscosity (FAV) of about 135. Yet another example is Aegis® H35ZP nylon 6 extrusion grade homopolymer, also available from AdvanSix Inc., Parsippany, NJ. Aegis® H35ZP (H35ZP) is a low molecular weight, relatively low viscosity nylon 6 homopolymer for cast or blown films, with a formic acid viscosity (FAV) of about 40. A further example is Aegis® H95ZP nylon 6 extrusion grade homopolymer, also available from AdvanSix Inc., Parsippany, NJ. Aegis® H95ZP (H95ZP) is a medium molecular weight, medium viscosity nylon 6 homopolymer for cast or blown films, with a formic acid viscosity (FAV) of about 90.

[0030] The polyamide-6 may have a formic acid viscosity as low as 80 FAV, 85 FAV, 90 FAV, 95 FAV, 100 FAV, 105 FAV, or 110 FAV, or as high as 115 FAV, 120 FAV, 125 FAV, 130 FAV, 135 FAV, or 140 FAV, or within any range defined between any two of the above values, such as, for example, 80 FAV to 140 FAV, 85 FAV to 135 FAV, 90 FAV to 130 FAV, 95 FAV to 125 FAV, 100 FAV to 120 FAV, 105 FAV to 115 FAV, 100 FAV to 135 FAV, 95 FAV to 140 FAV, 80 FAV to 110 FAV, or 115 FAV to 135 FAV.

[0031] The branched polyamide conforms to the formula:

[0032] [ka]

[0033] In the formula, a = 6 to 10, b = 6 to 10, c = 6 to 10, d = 6 to 10, m = 1 to 400, and x = 80 to 400. The polyamide represented by formula I is a random copolymer. It is understood that.

[0034] The branched polyamide may be formed from caprolactam and one or more diamines. Additionally, one or more dimer acids may be included to provide a branched structure, and optionally, one or more end-capping agents may also be included, as described below. The resulting branched polyamide contains residues of caprolactam, diamine, dimer acid, and, optionally, one or more end-capping agents.

[0035] Caprolactam (also known as hexano-6-lactam, azepan-2-one, and ε-caprolactam) is shown below.

[0036] [ka]

[0037] The diamine can be, for example, a C4-C6 linear or branched diamine. The diamine can include, for example, hexamethylenediamine, available from Sigma-Aldrich Corp, St. Louis, MO.

[0038] The branched polyamide composition may contain residues of diamines in an amount of at least 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, or 3 wt%, or as much as 3.2 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, or 5 wt%, or for example 1 wt% to 5 wt%, 1. It may be present in an amount within any range defined between any two of the above values, such as 2% to 4.8% by weight, 1.5% to 4.5% by weight, 1.8% to 4.2% by weight, 2% to 4% by weight, 2.2% to 3.8% by weight, 2.5% to 3.5% by weight, 2.8% to 3.2% by weight, 1% to 3% by weight, 2% to 4.5% by weight, or 3.2% to 5% by weight, etc. All weight percentages are based on the total weight of the branched polyamide.

[0039] The dimer acid may be as shown below:

[0040] [ka]

[0041] wherein a and b may each independently be in the range of 6 to 10, and c and d may each independently be in the range of 4 to 10. The dimer acid may be saturated or may contain one or more unsaturated bonds. As shown in Formula I, two carbon chains, identified by carbon atom numbers c and d in Formula III, branch off from the main polymer chain, making the polymer composition of Formula I a branched polyamide composition. The two branched carbon chains may each have 6 to 10 carbon atoms. It has been discovered that branched polyamide compositions having short chain (10 carbons or less) branches blended with polyamide-6 can exhibit increased tensile strength compared to polyamide-6 alone. It is believed that the branching causes the branched polyamide to behave like a polyamide with a much higher molecular weight, resulting in higher tensile strength, higher penetration to break, and greater puncture strength.

[0042] In addition, the branching of branched polyamides is believed to also contribute to increasing the free volume between polyamide monomers in blends of branched polyamides and polyamide-6. In this case, the additional free volume is believed to allow some molecules to pass more easily through the blends compared to polyamide-6 alone. Oxygen transmission rate (OTR) is defined as the steady-state rate at which oxygen gas permeates through a film at specified temperature and relative humidity conditions. In the case of articles (e.g., films) containing blends of branched polyamides and polyamide-6, higher oxygen transmission rates are observed through the films compared to polyamide-6 alone, which is believed to be due to the increased free volume between polyamide monomers. Therefore, articles (e.g., films) containing such blends of branched polyamides and polyamide-6 may exhibit a higher OTR than films containing polyamide-6 alone.

[0043] Furthermore, branched polyamides are believed to be more hydrophobic than polyamide-6. In this case, a blend of branched polyamides and polyamide-6 may exhibit lower moisture absorption than a composition containing polyamide-6 alone. Water vapor transmission rate (WVTR) is defined as the steady-state rate at which water vapor permeates through a film at specified temperature and relative humidity conditions. For articles (e.g., films) containing a blend of branched polyamides and polyamide-6, lower moisture transmission rates are observed through the film compared to polyamide-6 alone, which is believed to be due to the hydrophobicity of the branched polyamide. Therefore, an article (e.g., film) containing such a blend of branched polyamides and polyamide-6 may exhibit a lower WVTR than a film containing polyamide-6 alone. This is surprising because the hydrophobicity of the branched polyamides outweighs the expected increase in free volume between the polyamide monomers in the blend.

[0044] Films made from such blend compositions of branched polyamides and polyamide-6 can be advantageous in the context of packaging, particularly in the context of flower and produce packaging, more specifically in the context of fruit packaging and / or fresh cut flower packaging. Desirable packaging materials for fruit and / or fresh cut flowers exhibit high strength, high oxygen permeability, and high moisture retention. As previously mentioned, blend compositions of branched polyamides and polyamide-6 exhibit higher tensile strength, high penetration to break, high puncture strength, high oxygen permeability, and low water vapor permeability than polyamide-6 alone. Thus, films comprising blend compositions of branched polyamides and polyamide-6 can be particularly useful in the context of produce packaging, particularly fruit packaging, and also in the context of flower packaging, particularly fresh cut flower packaging, among other applications, because the blend films are stronger, more oxygen permeable, and retain more water vapor than nylon-6 alone.

[0045] Dimer acids, also known as dimerized fatty acids, are dicarboxylic acids produced by dimerizing unsaturated fatty acids. Additional information on dimer acids can be found in Kirk-Othmer Encyclopedia of Chemical Technology, Volume 2, pp. 1-13. Dimer acids can include, for example, Pripol™ 1013, available from Croda International Plc, Edison, NJ, or C36 dimer acid, available from The Chemical Company, Jamestown, RI.

[0046] The branched polyamide may contain residues of dimer acid in an amount as low as 1%, 2%, 5%, 8%, 12%, or 15% by weight, or as high as 18%, 20%, 22%, 25%, 28%, or 30% by weight, or within any range defined between any two of the above values, such as 1% to 30%, 2% to 28%, 5% to 25%, 8% to 22%, 10% to 20%, 12% to 18%, 15% to 20%, 10% to 15%, or 18% to 30% by weight. All weight percentages are based on the total weight of the branched polyamide.

[0047] The branched polyamide may have a formic acid viscosity as low as 20 FAV, 25 FAV, 30 FAV, 35 FAV, 40 FAV, 45 FAV, or 50 FAV, or as high as 55 FAV, 60 FAV, 65 FAV, 70 FAV, 75 FAV, or 80 FAV, or within any range defined between any two of the above values, such as, for example, 20 FAV to 80 FAV, 25 FAV to 75 FAV, 30 FAV to 70 FAV, 35 FAV to 65 FAV, 40 FAV to 60 FAV, 45 FAV to 55 FAV, 40 FAV to 75 FAV, 35 FAV to 80 FAV, 20 FAV to 500 FAV, or 55 FAV to 75 FAV.

[0048] Branched polyamides may be singly or doubly end-capped with mono- or difunctional end-capping agents, as desired. Increasing the level of end-capping agent reduces the concentration of reactive amine and / or carboxyl end groups. The use of an end-capping agent results in the end-capping of carboxyl or amine end groups, respectively, through a chemical reaction. That is, one equivalent of end-capping agent reduces the corresponding end group by one equivalent. End-capping also affects the water content of the final polyamide polymer compared to a polymer with the same molecular weight. End-capped polymers also have lower water contents than unend-capped polymers, consistent with the equilibrium kinetics of the reaction. Furthermore, the end groups of end-capped polymers cannot undergo further addition polymerization or polycondensation reactions, thus maintaining their molecular weight and exhibiting stable melt viscosity, which is important for the consistency of the extrusion process.

[0049] The singly end-capped branched polyamide may be formed by the residue of a carboxyl end-capping agent or an amine end-capping agent. The end-capping agent may contain residues of a capping agent. Amine end-capping agents may include, for example, monofunctional acids such as acetic acid, propionic acid, benzoic acid, and / or stearic acid, and / or difunctional acids such as terephthalic acid and / or adipic acid. Carboxyl end-capping agents may include, for example, monofunctional amines such as cyclohexylamine, benzylamine, and / or polyetheramines, and / or difunctional amines such as hexamethylenediamine and / or ethylenediamine. Increasing the level of end-capping agent decreases the concentration of reactive amine and / or carboxyl end groups.

[0050] The singly end-capped branched polyamide may contain residues of a carboxyl end-capping agent in an amount as low as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%, or as high as 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, or within any range defined between any two of the above values, such as, for example, 0.1 wt% to 1 wt%, 0.2 wt% to 0.8 wt%, 0.3 wt% to 0.7 wt%, 0.4 wt% to 0.6 wt%, 0.1 wt% to 0.5 wt%, or 0.6 wt% to 0.9 wt%. All weight percentages are based on the total weight of the branched end-capped polyamide, excluding additional additives.

[0051] The single-endcapped polyamide may contain residues of an amine end-capping agent in an amount as low as 0.1%, 0.2%, 0.3%, 0.4%, or 0.5% by weight, or as high as 0.6%, 0.7%, 0.8%, 0.9%, or 1% by weight, or within any range defined between any two of the above values, such as, for example, 0.1% to 1%, 0.2% to 0.8%, 0.3% to 0.7%, 0.4% to 0.6%, 0.1% to 0.5%, or 0.6% to 0.9% by weight. All weight percentages are based on the total weight of the branched end-capped polyamide, excluding additional additives.

[0052] The double end-capped polyamide may comprise residues of a carboxyl end-capping agent and residues of an amine end-capping agent, the amine end-capping agent and the carboxyl end-capping agent being as described above.

[0053] The double end-capped polyamide may contain residues of a carboxyl end-capping agent in an amount as low as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%, or as high as 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, or within any range defined between any two of the above values, such as, for example, 0.1 wt% to 1 wt%, 0.2 wt% to 0.8 wt%, 0.3 wt% to 0.7 wt%, 0.4 wt% to 0.6 wt%, 0.1 wt% to 0.5 wt%, or 0.6 wt% to 0.9 wt%. All weight percentages are based on the total weight of the branched end-capped polyamide, excluding additional additives.

[0054] The double end-capped polyamide may contain residues of an amine end-capping agent in an amount as low as 0.20%, 0.25%, 0.30%, or 0.40% by weight, or as high as 0.50%, 0.60%, 0.65%, 0.70%, or 1% by weight, or within any range defined between any two of the above values, e.g., 0.20% to 1%, 0.25% to 0.70%, 0.30% to 0.65%, 0.40% to 0.60%, 0.50% to 1%, or 0.40% to 0.70% by weight. All weight percentages are based on the total weight of the branched end-capped polyamide, excluding additional additives.

[0055] The branched end-capped polyamide may have a low moisture level as measured by ASTM D-6869-17. The moisture level may be less than about 2000 ppm, about 1500 ppm, or less than about 2000 ppm. The moisture content may be less than about 1200 ppm, less than about 1000 ppm, less than about 800 ppm, less than about 600 ppm, less than about 500 ppm, or less than about 400 ppm, or any range defined between any two of the foregoing values. All weight percentages are based on the total weight of the branched end-capped polyamide and do not include additional additives.

[0056] Branched polyamides can be synthesized by feeding caprolactam, dimer acid, diamine, and water to a reactor, mixing the reactants together in the reactor, and reacting the reactants in the reactor at a reaction temperature. The reactor can be under reaction pressure during at least a portion of the reaction process. A vacuum can be applied to the reactor to remove water generated during the reaction process. Mixing can be continuous during at least a portion of the reaction process.

[0057] The reaction temperature may be as low as about 225°C, about 230°C, about 235°C, about 240°C, or about 245°C, or as high as about 250°C, about 255°C, about 260°C, about 270°C, about 280°C, or about 290°C, or within any range defined between any two of the above values, such as about 225°C to about 290°C, about 230°C to about 280°C, about 235°C to about 270°C, about 230°C to about 260°C, about 260°C to about 280°C, about 230°C to about 240°C, or about 260°C to about 270°C.

[0058] In the supplying step, a condensation catalyst may be supplied. Suitable condensation catalysts include, for example, hypophosphites or sodium hypophosphite. The condensation catalyst may be supplied at a concentration as low as about 25 ppm, about 50 ppm, about 100 ppm, or about 150 ppm, or as high as about 200 ppm, about 250 ppm, or about 300 ppm, or within any range defined between any two of the above values, such as about 25 ppm to about 300 ppm, about 50 ppm to about 300 ppm, about 100 ppm to about 250 ppm, about 150 ppm to about 200 ppm, about 50 ppm to about 150 ppm, or about 150 ppm to about 250 ppm. All weight percentages are based on the total weight of the branched, end-capped polyamide, excluding additional additives.

[0059] An amine end-capping agent and / or a carboxyl end-capping agent may optionally be added to the reactor along with the caprolactam, dimer acid, diamine, and water to produce the branched end-capped polyamide described above.

[0060] The branched end-capped polyamide also contains some residual amine and carboxyl end groups that are not end-capped with an end-capping agent. The degree of end-capping can be determined by measuring the concentration of the residual amine and carboxyl end groups, as described below.

[0061] The amine end group concentration (AEG) can be determined by the amount of hydrochloric acid (0.1 N standard HCl) required to titrate a polyamide composition sample in a solvent of 70% phenol and 30% methanol according to Equation 1 below.

[0062]

number

[0063] For example, the branched end-capped polyamide may have a molecular weight of at least 20 mmol / kg, 22 mmol / kg, 24 mmol / kg, 26 mmol / kg, 28 mmol / kg, or 30 mmol / kg. mol / kg, or as high as 32 mmol / kg, 34 mmol / kg, 36 mmol / kg, 38 mmol / kg, or 40 mmol / kg, or any range defined between any two of the above values, such as, for example, 20 mmol / kg to 40 mmol / kg, 22 mmol / kg to 38 mmol / kg, 24 mmol / kg to 36 mmol / kg, 26 mmol / kg to 34 mmol / kg, 28 mmol / kg to 32 mmol / kg, 20 mmol / kg to 30 mmol / kg, or 20 mmol / kg to 24 mmol / kg. Alternatively, the branched end-capped polyamide may be "highly end-capped" and may have an amine end group concentration of less than 20 mmol / kg, less than 18 mmol / kg, less than 10 mmol / kg, less than 8 mmol / kg, less than 7 mmol / kg, or less than 5 mmol / kg, or may have an amine end group concentration within any range defined between any two of the above values, e.g., from 5 mmol / kg to 20 mmol / kg, from 7 mmol / kg to 18 mmol / kg, or from 8 mmol / kg to 10 mmol / kg.

[0064] The carboxyl end group (CEG) concentration can be determined by the amount of potassium hydroxide (KOH) required to titrate a sample of polyamide in benzyl alcohol according to Equation 2 below.

[0065]

number

[0066] For example, the branched end-capped polyamide may have a carboxyl end group concentration as low as 20 mmol / kg, 22 mmol / kg, 24 mmol / kg, 26 mmol / kg, 28 mmol / kg, or 30 mmol / kg, or as high as 32 mmol / kg, 34 mmol / kg, 36 mmol / kg, 38 mmol / kg, or 40 mmol / kg, or within any range defined between any two of the above values, such as 20 mmol / kg to 40 mmol / kg, 22 mmol / kg to 38 mmol / kg, 24 mmol / kg to 36 mmol / kg, 26 mmol / kg to 34 mmol / kg, 28 mmol / kg to 32 mmol / kg, 20 mmol / kg to 30 mmol / kg, or 20 mmol / kg to 24 mmol / kg. Alternatively, the branched end-capped polyamide may be "highly end-capped" and may have a carboxyl end group concentration of less than 20 mmol / kg, less than 18 mmol / kg, less than 16 mmol / kg, less than 14 mmol / kg, less than 10 mmol / kg, less than 8 mmol / kg, less than 7 mmol / kg, or less than 5 mmol / kg, or may have a carboxyl end group concentration within any range defined between any two of the above values, e.g., from 5 mmol / kg to 20 mmol / kg, from 7 mmol / kg to 18 mmol / kg, or from 8 mmol / kg to 16 mmol / kg.

[0067] Another method for measuring the level of endcapping is by the degree of endcapping. The degree of endcapping of branched endcapped polyamides can be determined using the following formula:

[0068]

number

[0069] The branched end-capped polyamide may have a total end-capping percentage as low as 20%, 25%, 30%, 35%, 40%, 45%, or 50%, or as high as 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 95%, or any range defined between any two of the above values, such as, for example, 20% to 90%, 25% to 85%, 30% to 80%, 35% to 75%, 40% to 70%, 45% to 65%, 50% to 60%, 55% to 60%, or 20% to 60%.

[0070] The present disclosure also provides compositions and articles comprising blends of branched polyamides and low density polyethylene (LDPE). Low density polyethylene is a widely available polymer and is commonly used in flexible packaging, for example as a sealant material. LDPE generally has a viscosity of 0.917 g / cm. 3 ~0.930g / cm 3 It is thought to have a density of

[0071] The present disclosure also provides compositions comprising blends of low-density polyethylene (LDPE) and branched polyamides. In compositions comprising blends of low-density polyethylene (LDPE) and any of the branched polyamides described herein, the branched polyamide can be present in an amount of at least 5 weight percent (wt%), 10 wt%, 15 wt%, 20 wt%, or 25 wt%, or as much as 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%, or any range defined between any two of the above values, such as 5 wt% to 50 wt%, 10 wt% to 45 wt%, 15 wt% to 40 wt%, 20 wt% to 35 wt%, 25 wt% to 30 wt%, 20 wt% to 40 wt%, 25 wt% to 35 wt%, 15 wt% to 25 wt%, or 10 wt% to 30 wt%. All weight percentages are based on the total weight of the blend of low-density polyethylene and branched polyamide.

[0072] Similar to blends of branched polyamides with polyamide-6, branched polyamide compositions having short chain (10 carbons or less) branches blended with LDPE can exhibit increased tensile strength compared to LDPE alone. It is believed that the branching of the polyamide causes the branched polyamide to behave like a polyamide with a much higher molecular weight, resulting in higher tensile strength, higher penetration to break, and greater puncture strength.

[0073] In addition, the branching of the branched polyamide is also believed to contribute to increasing the free volume between the polyamide monomers in the blend composition of branched polyamide and LDPE. This additional free volume allows some molecules to be more easily integrated into the blend than LDPE alone. It is believed that oxygen can pass more easily through the composition. In the case of articles (e.g., films) containing blend compositions of branched polyamides and LDPE, higher oxygen transmission rates can be observed through the films compared to LDPE alone, which is believed to be due to the increased free volume between the polyamide monomers. Therefore, articles (e.g., films) containing such blend compositions of branched polyamides and LDPE can exhibit a higher OTR than films containing LDPE alone.

[0074] It is also believed that branched polyamides may be more hydrophobic than LDPE, and that blends of branched polyamides and LDPE may exhibit lower moisture absorption than LDPE alone. For articles (e.g., films) containing blends of branched polyamides and LDPE, lower moisture permeability through the film may be observed compared to LDPE alone, which may be due to the hydrophobicity of the branched polyamide. Therefore, articles (e.g., films) containing such blends of branched polyamides and LDPE may exhibit lower WVTR than films containing LDPE alone.

[0075] Films made from blend compositions of branched polyamides and LDPE can be advantageous in the context of packaging, particularly in the context of packaging flowers and produce, more specifically in the context of packaging fruit and / or fresh cut flowers. Desirable packaging materials for fruit and / or fresh cut flowers exhibit high strength, high oxygen permeability, and high moisture retention. As previously mentioned, blend compositions of branched polyamides and LDPE can exhibit higher tensile strength, high penetration to break, high puncture strength, high oxygen permeability, and low water vapor permeability than LDPE alone.

[0076] Articles comprising blends of branched polyamides and polyamide-6 or low density polyethylene described herein can include films, fibers, and wires. Films can be formed, for example, by extrusion blow molding. Fibers can be formed, for example, by extrusion spinning. Wires can be formed, for example, by extrusion molding.

[0077] As used herein, the phrase "within any range defined between any two of the above values" literally means that any range from any two of the values ​​listed before the phrase may be selected, regardless of whether the values ​​are toward the lower end of the list or toward the upper end of the list. For example, a pair of values ​​may be selected from the two lower values, the two upper values, or a lower value and an upper value.

[0078] Example Example 1 - Preparation of branched polyamide (BPA) This example demonstrates the production of a branched polyamide. A reactor was prepared by fitting a helical stirrer to a 12-liter stainless steel vessel. The reactants fed to the reactor included 4,800 grams of caprolactam (AdvanSix Resins and Chemicals LLC, Parsippany, NJ), 672 grams of Pripol™ 1013 dimer acid (Croda Incorporated, Wilmington, DE), and 195 grams of a solution consisting essentially of 70% by weight hexamethylenediamine and 30% by weight water (Sigma-Aldrich Corp., St. Louis, MO). A condensation catalyst in the form of hypophosphite at a concentration of approximately 50 ppm was also fed to the reactor, along with 100 grams of deionized water.

[0079] The reactants, catalyst, and water were mixed together in a reactor. The reactor was heated to a reaction temperature of about 230°C, and the reactants were mixed for 1 hour. A reactor pressure of about 6 bar was observed. After 1 hour, the reactor was vented to release the pressure. The reaction temperature was maintained at 230°C for 1 hour while nitrogen was passed through the reactor (2 L / min) and the contents were mixed with a helical agitator to promote the polyamide dispersion. The molecular weight increased. After 4 hours, the polyamide was extruded from the reactor into a water bath and cooled. The cooled polyamide was pelletized in a pelletizer to form polyamide chips. The chips were subjected to three 1-hour leaching procedures in deionized water at 120°C under a pressure of approximately 15 psi for a total of 3 hours to remove unreacted caprolactam. The rinsed polyamide was dried in a vacuum oven at 80°C and 28 inches of mercury to produce a polyamide composition with a moisture content of approximately 800 ppm.

[0080] Example 2 - Preparation of end-capped branched polyamide This example demonstrates the production of end-capped branched polyamides. A reactor was prepared by fitting a helical stirrer to a 12-liter stainless steel vessel. The reactants fed to the reactor included 4,800 grams of caprolactam (AdvanSix Resins and Chemicals LLC, Parsippany, NJ), 672 grams of Pripol™ 1013 dimer acid (Croda Incorporated, Wilmington, DE), 40 grams of stearic acid (Sigma-Aldrich Corp., St. Louis, MO), and 195 grams of a solution consisting essentially of 70% by weight hexamethylenediamine and 30% by weight water (Sigma-Aldrich Corp., St. Louis, MO). A condensation catalyst in the form of hypophosphite at a concentration of approximately 50 ppm was also fed to the reactor, along with 100 grams of deionized water.

[0081] The reactants, catalyst, and water were mixed together in a reactor. The reactor was heated to a reaction temperature of approximately 230°C, and the reactants were mixed for 1 hour. A reactor pressure of approximately 6 bar was observed. After 1 hour, the reactor was vented to release the pressure. The reaction temperature was maintained at 230°C for 1 hour while nitrogen was passed through the reactor (2 L / min) and the contents were mixed with a helical stirrer to increase the molecular weight of the polyamide. After 4 hours, the polyamide was extruded from the reactor into a water bath and cooled. The cooled polyamide was pelletized in a pelletizer to form polyamide chips. The chips were subjected to three leaching procedures in deionized water at 120°C under a pressure of approximately 15 psi for 1 hour each, for a total of 3 hours, to remove unreacted caprolactam. The rinsed polyamide was dried in a vacuum oven at 80° C. and 28 inches of mercury vacuum to produce a polyamide composition with a moisture content of about 800 ppm.

[0082] Example 3 - Comparing the compatibility of branched and unbranched polyamides with polyolefins This example compares the relative compatibility of branched and unbranched polyamides with low molecular weight polyethylene. The branched polyamide of Example 1 is compared to an unbranched, unend-capped polyamide-6 (Aegis® H85ZP, available from AdvanSix Incorporated).

[0083] Strands of low-density polyethylene (LDPE) were produced using an 18 mm twin-screw extruder and subsequently pelletized. The LDPE was of a type commonly used as a sealant material in flexible packaging. The LDPE was blended with pellets of the branched polyamide (BPA) or unbranched polyamide (PA) of Example 1, extruded, and pelletized to produce pellets containing 10 wt% BPA, 15 wt% BPA, 30 wt% BPA, 10 wt% PA, and 30 wt% PA, balance LDPE.

[0084] Monolayer films were made from blends of 50% virgin LDPE with 50% of each of the LDPE, BPA, and PA pellet groups to produce films consisting of 50% LDPE, 5% BPA, 7.5% BPA, 15% BPA, 5% PA, and 15% PA with the balance being virgin LDPE. Films were also made from 100% virgin LDPE (LDPE that had not been processed through the extruder as described above). The films were measured for haze. The results are shown in Table 1 below.

[0085] [Table 1]

[0086] Surprisingly, across the entire range of concentrations evaluated, films made with branched polyamide (BPA) were found to exhibit less haze than films made with unbranched polyamide (BPA) at the same concentration. These results suggest that at this level, branched polyamides are more compatible with LDPE. Without being bound by any theory, it is believed that the branched side chains (olefinic side groups) may enhance the compatibility of branched polyamides with polyolefin materials (LDPE).

[0087] The effect of BPA compatibility with LDPE was further evaluated by comparing the enthalpy of fusion of a blend of 15 wt% BPA and 85 wt% LDPE, as measured using differential scanning calorimetry (DSC), with a blend of 15 wt% PA and 85 wt% LDPE. LDPE and PA alone were also measured by DSC. The results are shown in Figure 1. Figure 1 shows the heat flow for LDPE 10, PA 12, 85 wt% LDPE / 15 wt% BPA 14, and 85 wt% LDPE / 15 wt% PA 16. The observed heat flow for PA was 60 J / g (220 °C). Therefore, the melting enthalpy of the 15% blend was estimated to be approximately 9 J / g (15% of 60 J / g). However, the measured melting enthalpy for the 15% BPA blend was 4 J / g. The 5 J / g difference from the estimated value may be explained by missing polymer sections that became miscible with LDPE. Without being bound by any theory, it is believed that the less polar dimer acid sections that make up the branches of BPA may be responsible for its improved compatibility with LDPE.

[0088] Example 4 - Property Comparison of Blends of Branched Polyamide with Medium Viscosity Unbranched Polyamide This example compares the relative tensile strength and elongation at break of blends of the branched polyamide of Example 1 (referred to herein as B-PA6) with Aegis® H100ZP. As noted above, H100ZP is a medium-viscosity unbranched polyamide-6. Monolayer films were prepared from blends of 20 wt%, 30 wt%, and 50 wt% BPA, with the balance being H100ZP. Films were also prepared from 100% H100ZP and 100% BPA. Tensile strength and elongation at break were measured using an Instron testing machine according to ASTM D-822. Measurements in the machine and transverse directions were averaged. Tensile strength results are shown in Figure 2, and elongation at break results are shown in Figure 3.

[0089] As shown in Figure 2, surprisingly, the blend of branched polyamide (B-PA6) with unbranched polyamide (H100ZP) produced less polymer than H100ZP or B-PA6 alone. Films with higher tensile strengths were produced than either of the two blends. In particular, the 20 wt. % B-PA6 blend exhibited the highest tensile strength. As shown in Figure 3, the elongation at break appears to be almost completely controlled by the softness of the B-PA6, resulting in improved elongation at break.

[0090] Example 5 - Comparison of properties of blends of end-capped and non-end-capped branched polyamides with high viscosity non-branched polyamides This example compares the tensile strength, break penetration, and puncture force of blends of the branched polyamide of Example 1 or the end-capped branched polyamide of Example 2 with Aegis® H135ZP. As noted above, H135ZP is a high-viscosity unbranched polyamide-6. The non-end-capped BPA of Example 1 was produced in both low and high relative viscosity (RV) versions. The end-capped BPA of Example 2 was a low RV polyamide. Monolayer films of blends of 10 wt%, 20 wt%, and 30 wt% BPA with the balance H135ZP were produced for low RV end-capped BPA, low RV non-end-capped BPA, and high RV non-end-capped BPA, respectively. Films of 100% H135ZP and 100% BPA (end-capped low RV, non-end-capped low RV, and non-end-capped high RV) were also produced. The tensile strength results are shown in FIG. 4, the penetration at break results are shown in FIG. 5, and the puncture force results are shown in FIG.

[0091] As shown in Figure 4, surprisingly, the end-capped and non-end-capped low-RV BPA blends showed increased tensile strength in the machine direction at a concentration of 10 wt% compared to H135ZP or either BPA alone. At higher concentrations, the tensile strength in the machine direction and cross direction was between that of H135ZP and BPA. The non-end-capped high-RV BPA blends showed tensile strength between that of H135ZP and BPA in all cases, but surprisingly improved at 20 wt% compared to the 10 and 30 wt% concentrations.

[0092] As shown in Figure 5, the end-capped low RV BPA blends at 30 wt% showed a greater increase in intrusion to break than either H135ZP or BPA alone. The non-end-capped low RV BPA blends at 20 wt% showed a surprising improvement compared to the 10 wt% and 30 wt% concentrations. Surprisingly, the non-end-capped high RV BPA blends consistently showed greater intrusion to break than either H135ZP or BPA alone at all concentrations.

[0093] As shown in Figure 6, the end-capped low RV BPA blends exhibited increased puncture forces at 20 wt% and 30 wt% concentrations compared to H135ZP alone, which was between H135ZP and BPA alone. The non-end-capped low RV BPA blend exhibited a surprising improvement at 20 wt% compared to the 10 wt% and 30 wt% concentrations. The non-end-capped high RV BPA blends consistently exhibited greater puncture forces than H135ZP alone at all concentrations. In all cases, the blends exhibited greater puncture forces than H135ZP alone, but not as great as BPA alone.

[0094] Taken together, Figures 4-6 show that blends of branched polyamide with unbranched polyamide-6 provide surprising improvements in tensile strength and penetration to break, while also increasing the puncture force of the film compared to unbranched polyamide-6 alone.

[0095] Example 6 - Property comparison of branched / unbranched polyamide blends and unbranched polyamides In this example, the oxygen transmission rate (OTR) and water vapor transmission rate (WVTP) were compared for blended polyamide formulations versus pure polyamide-6 formulations. In each of these cases, the blend composition included the branched polyamide of Example 1 and Aegis® H95ZP, while the pure polyamide-6 formulation The unbranched polyamide included Aegis® H95ZP. As noted above, H95ZP is an unbranched polyamide-6 with a typical measured FAV of approximately 90. Six monolayer cast films were produced for testing: three containing 100% H95ZP and three containing 15% by weight BPA and 85% by weight H95ZP.

[0096] Two sets of monolayers were subjected to two OTR tests, the first at 23°C and 0% relative humidity (RH) and the second at 23°C and 80% RH. OTR results are reported in cm 3 -mils / 100 inches 2 -Reported in days and shown in Table 2 below.

[0097] [Table 2]

[0098] As shown in Table 2, the free volume of the 15%-BPA / 85-Aegis H95ZP blend composition exhibited a higher OTR compared to the 100% Aegis H95ZP film in both the first test at 0% RH and the second test at 80% RH. As previously mentioned, the higher OTR observed in the blend composition is likely due to the increased free volume between each polyamide monomer in the blend compared to pure H95ZP.

[0099] WVTR testing was performed on one set of monolayers at 37.8°C and 100% RH. WVTR is expressed in g-mils / 100 inches. 2 -Reported in days and shown in Table 3 below.

[0100] [Table 3]

[0101] As shown in Table 3, the hydrophobic nature of BPA likely contributed to the observed lower WVTR for the 15% BPA / 85% H95ZP blend film compared to the 100% H95ZP film. This was somewhat surprising, as it could be theorized that the increased free volume of the blend composition would result in a higher WVTR. However, the lower WVTR for the blend composition suggests that the water solubility in the branched material is the dominant factor, and thus the lower water solubility of the branched polyamide reduces the moisture permeability of the blend composition. be.

[0102] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above relate to particular features, the scope of the present invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the claims, together with all equivalents thereof.

Claims

[Claim 1] Polyamide-6 or low density polyethylene, a branched polyamide comprising a lactam, a dimer acid, and a diamine; A composition comprising a blend of:

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