Metal coated with functional polyolefin film

Abstract

The present invention relates to articles including paper coated with an aqueous dispersion of polyolefin particles, as well as to paper coated with a polyolefin film resulting from this dispersion. More particularly, the polyolefin particles of the present invention are primarily polypropylene particles.

Description

[Technical Field]

[0001] The present invention relates to articles containing metals coated with an aqueous dispersion of polyolefin particles, and to metals coated with a polyolefin film resulting from this dispersion. More specifically, the polyolefin particles in the aqueous dispersion of the present invention are mainly polypropylene particles.

[0002] The application of various treatment and pretreatment solutions to metals to slow down or suppress corrosion is well established. This is particularly true in the field of metal food and beverage cans, buckets, and drums, as well as non-food metal containers. Coatings are used on the inside of such containers to prevent the contents (e.g., food or beverage) from coming into contact with the metal of the container. Contact between metal and food or beverage, and non-food substances, can cause corrosion of the metal container, which can then contaminate the food or beverage, or non-food contents, of such metal containers. Corrosion is particularly problematic when food and beverage products are highly acidic and / or have a high salt content. Also, strongly alkaline contents of non-food substances, such as hair dyes, can react with metals such as aluminum. For example, coatings applied to the inside of food and beverage cans also help prevent corrosion in the headspace of the can, which is the area between the filling line of the food product and the lid of the can. Coatings may also be applied to the outside of metal containers to provide protection from the external environment and / or to provide a decorative layer containing fillers and / or pigments. In addition to corrosion prevention, coatings on food and beverage cans must be non-toxic and inert, and when applied to the inner surface, must not adversely affect the taste or appearance (e.g., the color of the food or beverage inside the can) or contribute to contamination of the can's contents. Resistance to "popping," "blistering," and / or "blistering" is also desirable, especially during high-temperature processing conditions, such as retorting. Retorting is a process in which packaged food or beverages are sterilized and cooked as necessary to achieve safety and quality. During retorting, sealed food or beverage cans containing their contents are sterilized at temperatures of approximately 121°C or higher. However, many coatings cannot withstand such temperatures and provide subsequent coating performance. Coatings on metal substrates for achieving superior retorting performance are still needed.

[0003] U.S. Patent Application Publication No. 2020 / 0123393(A1) discloses an aqueous dispersion and its use in coating metal substrates, particularly in coating metal cans for food and beverage packaging, wherein the aqueous dispersion contains 15% by weight (wt) to 60% by weight of solids based on the total weight of the aqueous dispersion. The solids content is 155 0 15-60% by weight of acid-functionalized polypropylene-based polymer with a melting point of ~170°C, 0.88 g / cm³ (g / cm³) 3 The melt blend product comprises 16-50% by weight of a polypropylene copolymer having a density of less than 1 / 2, 5-20% by weight of an acid-functionalized polypropylene wax, and 15-30% by weight of an acid-functionalized polyolefin, where the weight percentage is based on the total weight of the melt blend product, and the components of the melt blend product sum up to 100% by weight. U.S. Patent Publication 2020 / 0123393(A1) does not disclose the use of fatty acid dispersants and the effect of such dispersants on the formulation of coatings on metal substrates.

[0004] U.S. Patent No. 6,166,118 discloses an emulsion of a functionalized polyolefin for use in coatings, including temporary metal coatings and paper coatings, wherein the functionalized polyolefin has a weight-average molecular weight greater than 10,000, fatty acids, and a sufficient amount of base to neutralize the functionalized polyolefin and fatty acids. U.S. Patent No. 6,166,118 does not disclose (a) the use of a combination of high melting point and functionalized base resins, (b) the use of a blend of functionalized and non-functionalized base resins, or (c) the formation of retort-resistant coated metal articles.

[0005] U.S. Patent No. 9701824 discloses a polyolefin dispersion blend for paper coating applications, wherein the polyolefin comprises polyethylene or polypropylene resin and may contain up to about 20% by weight of any modified polyolefin having a melting point of 105°C or higher. U.S. Patent No. 9701824 does not disclose metal coatings or methods for meeting the requirements for metal coatings.

[0006] The present invention provides a method for manufacturing a coated metal substrate, comprising the following steps.

[0007] a) A step of applying a coating formulation derived from an aqueous dispersion composition onto a metal substrate, wherein the aqueous dispersion composition is i) A fatty acid dispersant with 14 to 60 carbon atoms having an acid value in the range of 60 to 250, in an amount of 1 to 15 weight percent based on the weight of the polymer solids in the dispersion, ii) An acid-functionalized propylene copolymer having an acid value in the range of 0.5 to 20, based on the weight of polymer solids in the dispersion, with an acid value of more than 25% to less than 70% by weight, and a melting point of 130°C or higher as determined by DSC, iii) 15 to 60 weight percent of an unfunctionalized propylene-co-alkene-based copolymer based on the weight of polymer solids in the dispersion, iv) A functionalized polyolefin wax having an acid value in the range of 25 to less than 60, with an amount of 2 to 15 weight percent based on the weight of polymer solids in the dispersion, v) A step comprising a neutralizing agent which is an organic base or volatile base having a boiling point of less than 250°C, and b) A step of curing the composition by heating or solidifying it to produce a cured film having a thickness in the range of 1 μm to 20 μm.

[0008] The present invention further provides articles produced by the process of the present invention.

[0009] The composition, which is an aqueous dispersion containing a dispersant, a base polymer, a functionalized polyolefin wax, and a neutralizing agent, can be prepared by a continuous process or a batch process. An example of a preferred continuous process is twin-screw extrusion, as described in Comparative Example E of U.S. Patent No. 8,722,787. A batch process uses, for example, a 2CV Helicone mixer, which is a conical batch mixer using double-meshing conical blades for mixing high-viscosity materials. The concentration of the polymer in the aqueous dispersion is preferably in the range of 20, more preferably 25, most preferably 30 by weight percent, preferably 60, and even more preferably 55 by weight percent, based on the weight of the mixed water and polymer.

[0010] Dispersant The dispersant contains a fatty acid with 14 to 60 carbon atoms having an acid value in the range of 60 to 250. The term “acid value” or “acid value number” refers to the mass of milligrams of potassium hydroxide (KOH) required to neutralize 1 gram of copolymer, as determined by ASTM (D974). All individual values ​​and subranges from 60 to 250 are incorporated into and disclosed herein. For example, the acid value may range from the lower limit of 60, 75, 80, 100, 120, or 150 to the upper limit of 250, 225, 200, or 175. For example, the acid value may be 75 to 250, or in another alternative example, 80 to 250, or in another alternative example, 75 to 200, or in another alternative example, 100 to 250. “Fatty acid” is a carboxylic acid having a long fatty chain that is either saturated or unsaturated. The fatty acid dispersant may contain linear, branched, cyclic, or aromatic structural segments, or combinations thereof. Suitable fatty acids include, but are not limited to, myristic acid, stearic acid, palmitic acid, behenic acid, oleic acid, tall oil, tall oil fatty acids, alkenyl succinic anhydride, monoesterified alkenyl succinic anhydride, and combinations thereof. The concentration of the fatty acid dispersant is preferably in the range of 1 to 15% by weight, based on the weight of the polymer solids in the dispersion, and more preferably in the range of 2 to 10% by weight, based on the weight of the polymer solids in the dispersion.

[0011] The dispersant may further comprise a high molecular weight acid-functionalized polyolefin copolymer, where “high molecular weight” means a weight-average molecular weight of at least 10,000 as determined by GPC. The acid-functionalized polyolefin copolymer dispersant typically comprises structural units of ethylene and carboxylic acid monomers, such as acrylic acid, methacrylic acid, or itaconic acid, thereby the dispersant being a copolymer comprising structural units of ethylene and acrylic acid (EAA) or ethylene and methacrylic acid (EMAA). As used herein, “structural units” of a specified monomer refer to the monomer residue after polymerization. For example, the structural units of methacrylic acid are as follows:

[0012] [ka] [In the formula, the dotted lines represent the bonding points of structural units to the polymer backbone.]

[0013] The acid-functionalized polyolefin copolymer dispersant has a melt flow index in the range of 50 to 2000 g / 10 min at 190°C / 2.16 kg (according to ASTM D1238), and the weight-to-weight ratio of ethylene structural units to carboxylic acid monomer structural units is in the range of 95:5 wt percent, preferably 90:10 wt percent, more preferably 85:15 wt percent, 70:30 wt percent, and preferably 75:25 wt percent, based on the weight of the dispersant copolymer. The polymer dispersant has an acid value of 60 to 250. Preferably, additional acid-functionalized polyolefin copolymer dispersants are not used to prepare aqueous dispersions of polyolefin particles. However, if added, the concentration of the acid-functionalized polyolefin copolymer dispersant is in the range of 5 to 30 wt percent, more preferably up to 15 wt percent, based on the weight of polymer solids in the dispersion. However, the concentration of the dispersant in the composition is sufficient to obtain a cured film on a metal substrate having a post-retort adhesion of 4B, more preferably 5B (measured at 135°C / 60 min with 2% lactic acid). Suitable commercially available acid-functionalized polyolefin copolymer dispersants include NUCREL® 960 (EMAA copolymer with an acid value of about 98) or Primacor 5980i (EAA copolymer with an acid value of about 155).

[0014] Base polymer The base polymer or base copolymer includes both unfunctionalized polypropylene copolymers and high-melting-point acid-functionalized propylene-based polyolefin copolymers. The terms “polypropylene copolymer” and “propylene-based polyolefin copolymer” mean, respectively, that the repeating polymer chain contains structural units derived from at least 60 wt percent (wt%) of propylene and structural units derived from one or more α-olefin comonomers in amounts from 0.1 to 40 wt%. Examples of comonomers that can be used in the production of polypropylene copolymers or propylene-based polyolefin copolymers are C2 and C4-C10 alpha-olefins. All individual values ​​and subranges of 0.1 to 40 wt% are included and disclosed herein. For example, the wt% of structural units derived from one or more alpha-olefin comonomers may range from the lower limit of 0.1, 1, 3, 4, 5, 7, or 9 wt% to the upper limit of 40, 35, 30, 27, 20, 15, 12, or 9 wt%. For example, a polypropylene copolymer may contain 0.1 to 35% by weight of structural units derived from one or more alpha-olefin comonomers. A polypropylene copolymer may contain 1 to 30% by weight of structural units derived from one or more alpha-olefin comonomers. A polypropylene copolymer may contain 1 to 27% by weight of structural units derived from three or more alpha-olefin comonomers. A polypropylene copolymer may contain 1 to 20% by weight of structural units derived from three or more alpha-olefin comonomers. A polypropylene copolymer may contain 1 to 15% by weight of structural units derived from three or more alpha-olefin comonomers. Embodiments of this disclosure provide a non-functionalized polypropylene copolymer with a concentration of 0.900 g / cm³ according to ASTM D792. 3 It provides having a density of less than 0.858 g / cm³. For example, polypropylene copolymer has a density of 0.858 g / cm³. 3 ~0.891 g / cm³ 3 It can have a density in the range of 0.858 g / cm³. 3 ~0.891 g / cm³ 3All individual values and sub-ranges thereof are included and disclosed herein. For example, non-functionalized polypropylene copolymers can have a density from 0.858, 0.860, or 0.862 g / cm 3 to 0.891, 0.878, or 0.876 g / cm 3 at the upper limit. Embodiments of the present disclosure provide that the high melting point acid-functionalized propylene-based polyolefin copolymer has a density of at least 0.900 g / cm 3 by ASTM D792. For example, the high melting point acid-functionalized propylene-based polyolefin copolymer can have a density in the range of 0.900 - 0.910 g / cm 3 and all individual values and sub-ranges are included and disclosed herein.

[0015] The non-functionalized polypropylene copolymer includes a non-functionalized propylene-co-alkene copolymer, and the weight-to-weight ratio of propylene structural units to alkene structural units ranges from 99.8:0.2, preferably from 99.7:0.3, more preferably from 99.6:0.4, to 50:50, more preferably to 60:40, and more preferably to 65:35. Preferred non-functionalized propylene-co-alkene copolymers include propylene-co-ethylene, propylene-co-octene, propylene-co-butene, propylene-co-hexene copolymer, or mixtures thereof. Commercially available examples of non-functionalized polypropylene copolymer-based polymers include VERSIFY™ 4200 (propylene-ethylene copolymer having a melt index of 25 g / 10 min (230 °C / 2.16 Kg) by ASTM D792, a density of 0.876 g / cm 3 by ASTM D1238, and a melting point of 84 °C), and VERSIFY™ 3000 (melt index of 8 g / 10 min (230 °C / 2.16 Kg) by ASTM D792, a density of 0.891 g / cm 3Examples include propylene-ethylene copolymers having a density and a melting point of 108°C, all of which are available from Dow, Inc. or its affiliates. The concentration of the unfunctionalized polypropylene copolymer is sufficient to obtain a cured film on a metal substrate having a post-retort adhesion of 4B, more preferably 5B (measured at 135°C / 60 min, 2% lactic acid), and is preferably 60% by weight or less, more preferably 50% by weight or less, preferably at least 15% by weight, and more preferably at least 30% by weight, based on the weight of polymer solids in the dispersion. Preferably, the concentration of the unfunctionalized polypropylene copolymer is in the range of 15% by weight, more preferably 30% by weight, and more preferably 60% by weight, based on the weight of polymer solids in the dispersion.

[0016] The high-melting-point acid-functionalized propylene polyolefin-based polymer is an acid or anhydride-functionalized propylene homopolymer or copolymer having an acid value in the range of 0.5 to 20 and a melting point of 130°C or higher, as determined by DSC as described in the Experiments and Examples section. The concentration of the high-melting-point acid-functionalized propylene polyolefin-based polymer is sufficient to obtain a cured film on a metal substrate having a post-retort adhesion of 4B, more preferably 5B (measured at 135°C / 60 min with 2% lactic acid), and is preferably less than 70% by weight, more preferably less than 65% by weight, preferably more than 25% by weight, and more preferably more than 30% by weight, based on the weight of polymer solids in the dispersion. Preferably, the concentration of the high-melting-point acid-functionalized propylene polyolefin-based polymer is in the range of more than 25% by weight and less than 70% by weight, based on the weight of polymer solids in the dispersion. A commercially available example of a high-melting-point acid-functionalized propylene polyolefin-based polymer is Fusabond P613 (melt index of 49 g / 10 min according to ASTM D1238 (190°C / 1.0 kg), 0.903 g / cm³ according to ASTM D792). 3Anhydrous modified polypropylene (with density and melting point of 162°C according to ASTM D3418), and Fusabond P353 (melt index of 22 g / 10 min according to ASTM D1238 (160°C / 325 g), 0.904 g / cm³ according to ASTM D792) 3 Examples include anhydrous modified polypropylene (with density and melting point of 135°C according to ASTM D3418), all of which are available from Dow, Inc. or its affiliates.

[0017] wax The functionalized polyolefin waxes have an acid value in the range of 20 to less than 60, more preferably 25 to less than 60. All individual values ​​and subranges of 20 to 60 are included herein and disclosed herein. The functionalized polyolefin waxes of this disclosure have a desired acid value (AN) and a desired melt index of 500 to 5,000,000, preferably 1,000 or more, which is the amount of polymer melt that passes through a heated syringe or cylinder at 190°C with a 2.16 kg loaded plunger in 10 minutes, or may include any material having a viscosity of 75 to 10,000 Pa.s, preferably 150 Pa.s or more, obtained for the polymer via DIN 53019 method (2010) at 170°C, wherein more than 50% by weight of the polymer contains propylene in a polymerized form that can improve the compatibility between the acid-functionalized polypropylene-based polymer and any of the acid-functionalized polyolefin copolymer dispersants of this disclosure. The melt index of acid-functionalized polypropylene waxes is significantly higher than the corresponding measurements for both polypropylene copolymers and acid-functionalized polypropylene-based polymers, and the viscosity may be so high that it can become a more practical measure for defining acid-functionalized polyolefin waxes. Suitable acid-functionalized polyolefin waxes may include acid-functionalized modified polypropylene, preferably maleic anhydride polypropylene copolymer, maleic anhydride grafted polypropylene, or maleic anhydride modified polypropylene wax.

[0018] The concentration of the functionalized polyolefin wax is sufficient to obtain a cured film on a metal substrate having a retort post - adhesion of 4B, more preferably 5B (measured at 135 °C / 60 minutes with 2% lactic acid), and is preferably at least 2% by weight, preferably 15% by weight or less, based on the weight of the polymer solids in the dispersion. Preferably, the concentration of the functionalized polyolefin wax ranges from 2 to 15 weight percent, based on the weight of the polymer solids in the dispersion. Commercially available functionalized polyolefin waxes include LICOCENE (trademark) PP MS 641, which is available from Clariant Corporation or its affiliates, a maleic anhydride grafted polypropylene wax (sometimes called MA - g - PP), having an acid value of 41 according to QM - AA - 634, a density of 0.93 g / cm3 according to ISO1183, and a viscosity of 1100 MPa.s according to QM - AA - 158 at 170 °C. For direct comparison, the melt flow index of Licocene PP MS 641 is estimated to be greater than 700 g / 10 min (190 °C / 2.16 kg) by the method described in the reference (Dutta A. On viscosity - melt flow index relationship, Rheol Acta 23:565 - 569, 1984).

[0019] The dispersion solids can further optionally contain 0.1 - 5% by weight of a non - functionalized wax, such as POLYWAX (trademark) 655 polyethylene, available from Baker Hughes, Inc. or its affiliates.

[0020] Neutralizing agent The neutralizing agent can be an organic base or a volatile base having a boiling point below 250°C. Suitable organic bases or volatile bases include ammonia or amines. Examples of suitable amines include N,N-dimethylethanolamine (DMEA), diethylamine, and morpholine. Preferably, the neutralizing agent is ammonia or dimethylethanolamine (DMEA). The concentration of the neutralizing agent is high enough to neutralize at least half of the carboxylic acid groups present in the dispersion composition. For example, if the dispersion composition contains 0.05 moles of carboxylic acid groups in a given amount, at least 0.025 moles of a base such as DMEA would be required. Thus, the molar ratio of the basic functional groups in the neutralizing agent to the carboxylic acid groups in the dispersion composition is at least 0.5:1. Preferably, this ratio ranges from 0.7:1, more preferably from 0.9:1, up to 2.5:1, preferably up to 2:1, more preferably up to 1.7:1.

[0021] Other components The composition may optionally be mixed or formulated with one or more additional components or additives that can be understood by those skilled in the art. Examples of additives include, but are not limited to, crosslinking agents, other aqueous dispersions, resin binders (including, but not limited to, epoxy, urethane, polyester, polyvinyl chloride containing organosol / vinyl, phenol, alkyd, oleoresin, acrylic resin, etc.), pigments, fillers, wetting agents, defoamers, solvents, rheology modifiers, surfactants, antioxidants, catalysts, flow agents, release agents, slip agents, lubricants, antiblocking agents, additives for masking sulfur contamination, antisettling agents, UV stabilizers, adhesion promoters, corrosion inhibitors, preservatives, and other additives for improving the aesthetic and performance attributes of coated metals. Different amounts of various additives may be used for different coating applications.

[0022] As described above, the coating compositions disclosed herein can be applied to metal substrates. Examples of metal substrates include, but are not limited to, metal sheets or coils, beverage cans, food cans; non-food aerosol containers such as those for hairspray, hair dye, or color spray lacquer; drums; barrels; pails; decorative tinplate; open trays; tubes; bottles; monoblocks; caps, lids such as thin aluminum foil-based lids for yogurt and butter containers, or crown caps; closures for glass jars and bottles such as roll-on closures, vacuum closures, and anti-theft closures; easy-release lids for can closures; and easy-open ends or conventional ends for cans. Cans to which the coating compositions disclosed herein can be applied may be two-piece or three-piece cans. Examples of beverage cans include, but are not limited to, beer cans, carbonated soft drink cans, energy drink cans, isotonic beverage cans, water cans, juice cans, tea cans, coffee cans, and milk cans. Examples of food cans include, but are not limited to, vegetable cans, fruit cans, meat cans, soup cans, cooked food cans, fish cans, cooking oil cans, and sauce cans. Such cans can have a variety of shapes. For example, such cans may be cylindrical, cubic, spherical, hemispherical, bottle-shaped, elongated cubic, shallow or tall, circular or rectangular or other suitable shapes, or combinations thereof. Examples of metals include, but are not limited to, aluminum and aluminum alloys, steel, electrolytic tinplate cold-rolled low-carbon mild steel, electrolytic chromium / chromium oxide coated cold-rolled low-carbon mild steel, and other pre-treated steels. Pre-treatments include, but are not limited to, treatment with phosphoric acid, zirconium phosphate, chromium phosphate, Cr(III) and Cr(VI) compounds, and silanes for reasons such as primary corrosion protection and improved adhesion. The metal substrate may include sheets, strips, or coils. The substrate may be pre-coated with one or more pre-coating compositions. Examples of such pre-coating compositions include, but are not limited to, one or more resin binders, one or more resin crosslinking agents, one or more solvents, one or more additives, and one or more pigments.Examples of resin binders include, but are not limited to, epoxy, polyurethane, polyester, polyvinyl chloride containing organosol / vinyl, phenol, alkyd, oleoresin, acrylic resin, and coatings derived from polyolefin dispersions. Examples of crosslinking agents include, but are not limited to, hydroxyalkylamides and phenol-formaldehyde resins; amino-formaldehyde resins including, but not limited to, urea-formaldehyde, melamine-formaldehyde, and benzoguanamine-formaldehyde; and anhydride resins, blocked isocyanate resins, and epoxy-group-containing resins, but are not limited to, epoxy resins, epoxy-group-containing polyesters, acrylic resins, vinyl resins, etc. Examples of solvents and thinners include, but are not limited to, glycol ethers, alcohols, aromatics such as aromatic hydrocarbons, white spirits, branched ketones, and esters. Examples of additives include, but are not limited to, catalysts, lubricants, wetting agents, defoamers, fluidizers, release agents, slip agents, anti-blocking agents, additives to mask sulfur contamination, pigment wetting / dispersing agents, anti-settling agents, UV stabilizers, and adhesion promoters. Examples of pigments include, but are not limited to, titanium dioxide, carbon black, zinc oxide, aluminum oxide, zinc, and aluminum. The substrate may be pre-coated with one or more pre-coated laminate compositions. Such compositions may include, for example, polyethylene, polypropylene, or polyester compositions and may be applied as a film on a metal substrate via a film lamination process or a melt extrusion coating process.

[0023] Metal substrates can be formed by stamping, drawing, redrawing, wall ironing, bending, beading, embossing, debossing, flanging, necking, stretching, blow stretching, and / or other suitable conventional methods. Such methods are known to those skilled in the art. According to many embodiments, a coating composition can be applied, for example, to a metal substrate, such as a metal sheet or metal foil, and the coated substrate can then be formed into a coated article, such as a container device, such as a metal can or a coated closure device. According to many embodiments, the substrate can be formed into a container, such as a container device or closure device, and the container device or closure device can then be coated with the coating composition to form a coated article. The coating composition can be applied by various methods, such as roller coating, spray coating, powder coating, dip coating, electrodeposition coating, printing, wash coating, flow coating, drawdown coating, and / or curtain coating. The coating, i.e., the coating composition applied to the metal substrate, can have a thickness ranging from 0.01 micrometers (μm) to 2 millimeters (mm). All individual values ​​and subranges from 0.01 μm to 2 mm are included in and disclosed herein. For example, a coating may have a thickness from a lower limit of 0.01 μm, 0.05 μm, or 1 μm to an upper limit of 2 mm, 1.5 mm, or 1 mm. For example, a coating may have a thickness of 0.01 μm to 2 mm, 0.05 μm to 1.5 mm, or 0.1 μm to 1 mm. According to some embodiments, a coating may have a thickness in the range of 5 μm to 50 μm, preferably 1 μm to 20 μm, and more preferably 7 μm to 10 μm. Coatings may also be arranged on top of each other as a multilayer coating.

[0024] A coating composition applied to a substrate can be cured, for example, to form a cured coating. The curing process may include drying, such as air drying, convection oven drying, hot air drying, and / or infrared oven drying. According to many embodiments, curing may include radiation curing, such as electron beam curing. A coating composition applied to a substrate can be cured at a metal temperature in the range of 140°C to 375°C for a period of less than 60 minutes, for example, less than 40 minutes, less than 30 minutes, less than 20 minutes, less than 10 minutes, less than 5 minutes, less than 2 minutes, less than 1 minute, or less than 20 seconds. All individual values ​​and subranges of 140°C to 375°C are included and disclosed herein. For example, a coating composition applied to a substrate may be cured at a metal temperature in the range of 160°C to 260°C for less than 60 minutes, for example, less than 40 minutes, less than 20 minutes, less than 10 minutes, less than 5 minutes, less than 2 minutes, or less than 1 minute. Alternatively, a coating composition applied to a substrate may be cured at a metal temperature in the range of 180°C to 235°C for less than 60 minutes, for example, less than 40 minutes, less than 10 minutes, less than 5 minutes, less than 2 minutes, or less than 1 minute.

[0025] As mentioned above, in some coating applications, it is desirable that the coated article simultaneously provide performance characteristics such as specific mechanical and chemical resistance properties and specific appearance properties. Specific mechanical properties desirable in some coating applications include the König hardness value, for example, a König hardness value greater than 70 seconds. Specific chemical resistance properties desirable in some coating applications include the methyl ethyl ketone (MEK) double friction value, for example, a MEK double friction value of 200 or higher is desirable in some coating applications, and that the coating passes post-retort appearance evaluation, for example, 2% lactic acid solution, 3% acetic acid solution, and 3% citric acid solution.

[0026] Experimental preparation and testing methods Preparation of dispersions The aqueous polyolefin dispersion (POD) is prepared according to the procedure of the examples. The degree of neutralization (DoN) of the polyolefin dispersion, expressed as a percentage, is determined according to the following formula.

[0027]

number

[0028] In the formula, W is the weight in grams of the added base, and E B This is the equivalent weight of the base, and A i This is the acid value of the i-th component in mgKOH / g units, and ω i This is the weight fraction of the i-th component in the solid content of the POD dispersion.

[0029] Coating formulations and preparations When preparing POD-based can coating formulations, aqueous and / or water-soluble components are added to the POD dispersion, followed by the addition of solvent systems and / or water-insoluble components. The pH of the aqueous components is generally adjusted to a similar level to the pH of the POD dispersion, typically 9-10, by using basic water (e.g., 0.3% dimethylethanolamine (DMEA) dissolved in DI water). Primid® QM-1260, available from EMS-Chemie AG, is a hydroxyalkylamide compound derived from adipic acid and diisopropanolamine and is used as a crosslinking agent for acidic functional groups in POD resin blends. The level of Primid® QM-1260 is calculated according to the desired equivalence of the acidic functional group using the following formula.

[0030]

number

[0031] 0.25 equivalents of Primid® QM-1260 relative to the total acidic functional groups are added to the exemplary POD coating formulations included in this application. The viscosity of the formulations is adjusted by adding Acrysol® ASE75, an acid-containing acrylic emulsion copolymer available from Dow, Inc., at a ratio of 1% of the total formulation weight. All formulations further contain a 1 / 1 mixture of butanol and butyl CELLOSOLVE® (a fast-evaporating glycol ether available from Dow, Inc.) at a ratio of 0.4 relative to the POD solids. All formulations in the examples have a formulation solids content of 26% by weight.

[0032] Preparation of metal-coated samples The coating formulation is typically aged at room temperature for at least one night before the coated substrate is fabricated. A drawdown coating is fabricated on a tinplate substrate (measured 0.009 x 4” x 12”) supplied by Lakeside Metal using a wound drawdown bar (typically #16). Unless otherwise specified, the coated panels are cured for 4 minutes in a Despatch brand oven (serial #183952) at 205°C. The dry coating thickness is typically in the range of 7–10 μm (0.3–0.4 mil).

[0033] DSC standard methods The results of differential scanning calorimetry are determined using a TA instrument model Q1000 DSC equipped with an RCS cooling accessory and autosampler. A nitrogen purge gas flow rate of 50 ml / min is used. The sample is pressed into a thin film, melted in the press at approximately 175°C, and then air-cooled to room temperature (25°C). Next, 3-10 mg of the material is cut into 6 mm diameter discs, accurately weighed, placed in a lightweight aluminum pan (approximately 50 mg), and then crimped closed. The thermal behavior of the sample is investigated using the following temperature profile. To remove previous thermal history, the sample is rapidly heated to 180°C and held isothermally for 3 minutes. Next, the sample is cooled to -90°C at a cooling rate of 10°C / min and held at -90°C for 3 minutes. Next, the sample is heated to 180°C at a heating rate of 10°C / min. The cooling curve and the second heating curve are recorded.

[0034] The DSC melting peak temperature is measured as the maximum value of the heat flow rate (W / g) relative to a linear baseline drawn between -30°C and the end of melting. The heat of fusion is measured as the area under the melting curve between -30°C and the end of melting, using a linear baseline. For ethylene-based materials, the total crystallinity percentage is equal to 100 × enthalpy of the sample / enthalpy of the PE crystal, and the enthalpy of a perfect polyethylene crystal is equal to 292 J / g, as reported in Macromolecular Physics, Vol. 1, Academic Press, New York, 1973, p. 154. For propylene-based materials, the total crystallinity percentage is equal to 100 × enthalpy of the sample / enthalpy of the PP crystal, and the enthalpy of a perfect polypropylene crystal is equal to 165 J / g, as reported in P. Edward, JR Moore, Polypropylene Handbook, Hanser Publisher, Cincinnati 1996.

[0035] Retort testing A Tuttnauer® EZ10 autoclave or a similar autoclave was used for the retort test. A 2" x 3" (2 inches x 3 inches) strip cut from a coated panel was placed in a glass beaker half-filled with food imitation. The beaker was covered with aluminum foil and then treated in the autoclave at 135°C for 60 minutes. After the autoclave cooled to 60°C, it was opened and the test panel was removed. The test panel was rinsed, tapped dry, and then subjected to a cross-cut adhesion test in the area immersed in the imitation within 30 minutes of removal from the autoclave. A 2% lactic acid solution in deionized water was used as the imitation for the disclosed examples.

[0036] Crosshatch adhesion test Cross-hatch adhesion was measured according to ASTM D3359-09. Since the coating thickness was less than 5 mils, method "B" was used. In this test, a square grid pattern was created with 10 cuts in each direction, spaced 1 mm apart from two adjacent cuts. Pressure-sensitive tape was applied to the grid and then removed. Adhesion was evaluated according to the following scale: 5B: The edges of the breaks are perfectly smooth. None of the squares in the grid are separated. 4B: Small pieces of the coating are peeling off at the intersections. Less than 5% of the area is affected. Small pieces of the 3B coating are peeling off along the edges and at the intersections of the cuts. The affected area is 5-15% of the grid. The 2B coating is thinned along the edges and parts of the square. The affected area is 15–35% of the grid. The 1B coating is peeling off in thin flakes along the edges of the large ribbon breaks, and the entire square is delaminating. The affected area is 35–65% of the grid. 0B - Worse peeling and delamination than Grade 1.

[0037] Materials used Table 1 shows the materials used in preparing the polyolefin dispersion.

[0038] [Table 1] [Examples]

[0039] Example 1 - Preparation of an aqueous dispersion of polypropylene - P613-based polymer, V4200-based polymer, wax, and dispersants P613 at 24.2 g / min, V4200 at 38.6 g / min, Lico641 at 7.6 g / min, and U350 at 5.3 g / min were added to a 25 mm diameter twin-screw extruder using a controlled-speed feeder, and the components were advanced to melt-blend. The extruder temperature profile was raised to a maximum of approximately 170°C. Water and a base (dimethylethanolamine / DMEA) were supplied to the extruder as neutralizing agents at 5.9 g / min and 3 g / min, respectively. Dilution water was supplied to the extruder's dilution zone at a rate of 90 g / min via a single pump. The extruder temperature profile was cooled to below 100°C near the end of the extruder. The extruder speed was approximately 450 rpm. At the extruder outlet, a back pressure regulator was used to adjust the pressure inside the extruder barrel to a suitable pressure for reducing vapor formation. The aqueous dispersion was filtered through a 100-micron filter. The remaining dispersion examples and comparative examples shown in Table 2 were prepared according to the procedure of dispersion example 1, but utilizing the components listed in Table 2. The solid content of the aqueous dispersions of the examples and comparative examples listed in Table 2 was measured using an infrared solids analyzer, and the particle size of the solid particles of the aqueous dispersions of the examples and comparative examples in Table 2 was measured using a COULTER® LS-230 particle size analyzer (Beckman Coulter Corporation, Fullerton, California). The solid content ranged from 30 to 50% by weight, and the average particle size (PS) of the solid particles of the dispersion ranged from 10 nanometers to 10 micrometers. Table 2 also shows the post-retort adhesion test results for each metal coating sample, as described in the experimental preparation and test methods. PP represents polypropylene, PE represents polyethylene, and HDPE represents high-density polyethylene.

[0040] Table 2

Claims

1. A process for manufacturing a coated metal substrate, a) A step of applying a coating formulation derived from an aqueous dispersion composition onto a metal substrate, The aqueous dispersion composition is i) A fatty acid dispersant having 14 to 60 carbon atoms and an acid value in the range of 60 to 250, in an amount of 1 to 15 weight percent based on the weight of the polymer solids in the aqueous dispersion composition, ii) An acid-functionalized propylene copolymer having an acid value in the range of 0.5 to 20, based on the weight of the polymer solids in the aqueous dispersion composition, which is greater than 25% by weight but less than 70% by weight, and a melting point of 130°C or higher as determined by DSC, iii) 15 to 60 weight percent of a non-functionalized propylene-co-alkene-based copolymer based on the weight of the polymer solids in the aqueous dispersion composition, iv) A functionalized polyolefin wax having an acid value in the range of 25 to less than 60, in an amount of 2 to 15 weight percent based on the weight of the polymer solids in the aqueous dispersion composition, v) A neutralizing agent which is an organic base or volatile base having a boiling point of less than 250°C, The acid-functionalized polyolefin copolymer dispersant is not used in the steps for preparing the aqueous dispersion composition. b) A process comprising the step of curing the aqueous dispersion composition by heating, drying, or radiation curing the aqueous dispersion composition to produce a cured film having a thickness in the range of 1 μm to 20 μm.

2. The process according to claim 1, wherein the cured film has a thickness in the range of 2 μm to 10 μm.

3. The process according to claim 1, further comprising the step of mixing the aqueous dispersion composition with one or more additives before curing the aqueous dispersion composition, wherein the one or more additives are selected from crosslinking agents, other aqueous dispersions, pigments, resin binders, wetting agents, defoaming agents, solvents, rheology modifiers, surfactants, antioxidants, fillers, catalysts, flow agents, release agents, slip agents, lubricants, antiblocking agents, additives for masking sulfur contamination, anti-settling agents, UV stabilizers, adhesion promoters, corrosion inhibitors, preservatives, and combinations thereof.

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