KR100480220B1 - Polyester composition and its extrusion coating - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to solid extrusion coating compositions for use in metal substrates, extrusion coating methods for metal substrates, and metal articles. The extrusion coating composition is a thermoplastic material which contains (a) a polyester having a weight average molecular weight of 10,000 to 50,000 and optionally (b) an epoxy resin, an acrylic resin or a polyolefin resin having an epoxy equivalent of 500 to 15,000. do. This extrusion coating composition is coated on a metal substrate during the extraction process to form a film of the composition having a thickness of about 1 to about 40 microns.

Description

Polyester Compositions and Extrusion Coatings thereof

The present invention provides an extrusion coating composition for a metal substrate that provides excellent adhesion, weather resistance, barrier properties and flexibility after use, a method for extrusion coating a metal substrate, and a metal can or container or at least one side as an adhesive layer of the extrusion coating composition. Metal articles such as structures such as coated aluminum side plates. The extrusion coating composition contains (a) a polyester having a weight average molecular weight of about 10,000 to 50,000 and optionally (b) a modifying resin such as an epoxy or phenoxy resin having an epoxy equivalent of 500 to 15,000. This extrusion coating composition is coated on a metal substrate with a film having a thickness of about 1 to about 40 microns.

It is well known that untreated metal substrates corrode untreated metal substrates when in contact with aqueous solutions. Thus, metal articles, such as metal containers containing aqueous products such as foods or beverages, are treated to be corrosion resistant to inhibit or eliminate interactions between the aqueous products and the metal articles. Generally, corrosion resistance is provided to a metal article or generally a metal substrate by immobilizing the metal substrate or by coating the metal substrate with a corrosion inhibiting coating.

Researchers in the art continue to work on improved coating compositions that reduce or eliminate corrosion of metal articles and do not adversely affect aqueous products packaged in metal articles. For example, research has been conducted to improve the impermeability of coatings such that corrosion causing ions, oxygen molecules and water molecules cannot contact and interact with the metal substrate. Impermeability can be improved by providing a thicker, more flexible, and more adhesive coating, but often one improvement of one desirable property will lower the other.

In addition, the thickness, adhesion and flexibility of coatings coated on metallic substrates are limited properties due to practical problems. For example, thick coatings are expensive, have longer curing times, are not aesthetically pleasing, and can adversely affect the process of stamping and molding coated metal substrates into useful metal articles. Likewise, the coating should be sufficiently flexible so as not to break during stamping and molding the metal substrate into a metal article of the desired shape.

In addition, studies have been made on coatings with chemical resistance in addition to corrosion inhibition. Useful coatings inside the metal container must be resistant to the solvation of the product packaged in the metal container. If the coating does not have sufficient chemical resistance, the coating components can be extracted into the packaged product and adversely affect the product. Even small amounts of extracted coatings can give sensitization to sensitive products such as beer.

Conventionally, organic solvent-based coating compositions have been used to obtain cured coatings with good chemical resistance. Such solvent-based compositions include components that are inherently insoluble in water, and thus can exhibit effective resistance to the solvation properties of aqueous products packaged in metal containers. However, the number of waterborne coating compositions is on the rise because of environmental and toxic issues and increasingly stringent government regulations. The waterborne coating composition comprises a water soluble or water dispersible component, so that the cured coating obtained from the waterborne coating composition is more susceptible to the solvability of water.

In addition, aqueous coating compositions generally contain more than two pounds of organic solvent per gallon of coating composition and thus do not completely address the environmental and toxicological problems associated with organic solvents. Organic solvents are essential ingredients for dissolving and dispersing the components of the composition and improving the flow rate and viscosity of the composition. Thus, solid coating compositions that can be coated on metallic substrates have been studied to completely solve environmental and toxicological problems associated with organic solvents. However, up to now, it has been difficult to obtain a solid coating composition comparable to the liquid coating composition in terms of film uniformity, film appearance and film performance.

Among the previous studies to obtain useful solid coating compositions, powder coating, laminated film coating, radiation cured coating and extrusion coating have been tested. In addition, considerable research has been conducted using free membrane stacks of polymers such as polyethylene terephthalate (PET), polypropylene (PP) and polyethylene (PE). The method used in this study is to coat a metal substrate with a preformed polymer film having a thickness of about 10 to about 25 microns. Such a film lamination method is a rapid method of coating metal substrates, but expensive and coated metal substrates do not meet all the properties required or required by can, pipe and stopper manufacturers.

Solid powder coatings have also been used to coat metal substrates with coating compositions. However, with this powder coating method, it was difficult to coat a thin and uniform coating on the metal substrate, that is, a coating of less than 40 microns. Often, when a thin film is coated on a metal substrate using a powder coating method, the coating is incomplete and a damaged film is formed. Such damage is unacceptable in the food and beverage container industry which requires a thin film that can withstand even the formation of flat coated metal substrates into cans, tubes or stoppers.

In addition, the solid coating composition was extrusion coated onto a metal substrate as disclosed in European Patent 0 067 060, PCT Publication WO 94/01224 and US Pat. No. 5,407,702 (Smith et al.). Extrusion coating of such a solid composition onto a metal substrate has the problem that the solid composition must be heated sufficiently to flow through the extrusion device. This heating step results in premature curing of the coating composition, specifically the thermosetting composition, making it difficult to crosslink in the extruder and extrude onto the metal substrate, as well as adversely affect the performance of the composition coated on the metal substrate.

In order to overcome this problem of premature curing, a study has been attempted for extrusion coating a thermoplastic coating composition on a metal substrate. However, this study also addresses the serious problem of too high molecular weight or too low molecular weight for easy and economical extrusion of the composition to provide an extruded membrane that is too soft for many practical applications, such as the interior or exterior of food or beverage containers. Had. Accordingly, many patents and publications reported in the art describe an extrusion apparatus and an extrusion method for coating a solid coating composition on a metal substrate.

Therefore, the researchers found that the properties of tackiness, flexibility, chemical resistance and corrosion resistance are desirable, and the economical exterior of food and beverage containers without adversely affecting the flavor and other aesthetic properties of the sensitive food and beverage packaged in the container. And extrudable solid coating compositions for use in intestines. In particular, we have studied extrusion coating compositions useful for reducing environmental and toxicological problems associated with organic solvents. Specifically, (1) satisfying increasingly stringent environmental regulations, (2) exhibit corrosion resistance at least equivalent to existing organic solvent-based coating compositions, and (3) easily extrusion coated as a uniform thin film on a metal substrate, Solid extrusion coating compositions for food and beverage containers were studied. Such extrusion coating compositions meet long-standing needs in the art.

1 is a plot of viscosity versus time of an extrusion coating composition according to the invention showing that the viscosity change over time at the melting point of the inventive extrusion coating composition is within acceptable range.

Detailed Description of the Preferred Embodiments

The extrusion coating composition of the present invention provides an extruded coating composition that effectively inhibits corrosion of metal substrates such as, but not limited to, aluminum, iron, steel and copper after being coated on the metal substrate. In addition, the extruded coating composition exhibits good adhesion to metal substrates, good chemical and scratch resistance and good flexibility. The extruded coating composition does not already provide food or beverages in contact with the composition.

In general, the extrusion coating composition of the present invention comprises (a) a polyester having a M _w of about 10,000 to about 50,000, or a mixture of these polyesters. The extrusion coating composition is a solid and contains no organic solvent. The extrusion coating composition may optionally include (b) a modifying resin such as an epoxy or phenoxy resin having an EEW of about 500 to about 15,000, and / or (c) fillers and / or (d) flow control agents. In addition, the extrusion coating composition of the present invention may contain any component that improves the aesthetics of the composition, facilitates the preparation and / or extrusion of the composition, or improves the functionality of the composition. Each composition component will be described in more detail below.

(a) polyester

According to a principal feature of the invention, the extrusion coating composition contains at least one thermoplastic polyester in a total amount of from about 50% to about 100% of the total weight of the composition. Preferably, the extrusion composition contains about 55% to about 90% polyester of the total weight of the composition. In order to fully take advantage of the present invention, the extrusion coating composition contains about 60% to about 85% of the total weight of the composition. The term "polyester" as used herein means either a single polyester or a mixture of two or more polyesters.

Polyesters are prepared from dicarboxylic acids, preferably aromatic dicarboxylic acids and aliphatic diols. These components interact to provide polyesters having an M _w of about 10,000 to about 50,000, preferably about 15,000 to about 40,000, and from about 20,000 to about 35,000 in order to fully benefit from the present invention. In other words, the polyester exhibits a number average molecular weight (M _n ) of about 5,000 to about 30,000. Accordingly, the polyesters of the present invention are considered to be high molecular weight polyesters. The polyester has an acid value of about 0 to about 150 mg KOH / g, preferably about 5 to about 100 mg KOH / g. This polyester has a hydroxyl value of 0 to about 150 mg KOH / g, preferably about 5 to about 100 mg KOH / g.

Useful polyesters also have properties that can be blended with optional modifying resins and other composition components, such that certain polyesters that can be extruded onto the metal substrate and coated on the metal substrate prior to forming the metal substrate into a metal article It is possible to provide an extruded coating composition having adhesiveness and flexibility. In addition, the polyester should be sufficiently unreactive so that the polyester does not crosslink with the optional modifying resin or other composition components when the extrusion composition is melted before and during the extrusion process.

Polyesters suitable for use in the extrusion coating compositions of the present invention provide extruded coating compositions that exhibit good film tensile strength, good water permeability, retortability and good barrier properties. Accordingly, the polyester and extrusion coating compositions appear to have a softening point of at least 140 ° C. as measured using the procedure described in DIN 52011. The polyester and the extrusion coating composition preferably have a softening point of 120 ° C to about 200 ° C. Above about 200 ° C., the polyester and extrusion coating compositions lose flexibility, and molding the coated metal substrate into a metal article can damage the membrane. Below 120 ° C., the polyester and extrusion coating compositions are too soft to withstand the processing and pasteurization temperatures of the food packaging machine when the food is filled into metal containers.

Similarly, the Tg of the polyester is about −30 ° C. to about 120 ° C., preferably about 15 ° C. to about 100 ° C. In order to fully take advantage of the present invention, it is preferred that the Tg of the polyester is from about 20 ° C to about 80 ° C. In this Tg range, the polyester is flexible enough to deform the extruded coating composition without forming cracks and hard enough to exhibit chemical and damage resistance. When the Tg of the polyester is below about -30 ° C, the extruded coating composition is too soft to provide effective chemical and damage resistance. If the Tg of the polyester exceeds about 120 ° C., the extruded coating composition will not have sufficient flexibility.

The polyester has a melt viscosity of about 10 to about 100 Pa · s (Pascal second), preferably about 20 to about 100 Pa · s at 200 ° C., or about 25 to about 200 Pa · s, preferably at 240 ° C. Is usefully about 40 to about 175 Pa · s. The melt flow index (MFI) of useful polyesters measured using DIN 53735 is from about 20 to about 800 g / 10 minutes, preferably from about 25 to about 600 g / 10 minutes at 200 ° C.

Polyesters are generally prepared by condensation of dicarboxylic acids with aliphatic diols. In order to provide a polyester having suitable properties for the extrusion coating composition of a food or beverage container, the dicarboxylic acid is preferably an aromatic dicarboxylic acid. In order to fully take advantage of the present invention, dicarboxylic acids include, for example, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and mixtures thereof. It is also apparent that esterified derivatives of dicarboxylic acids such as dimethyl esters or anhydrides of dicarboxylic acids can also be used.

Specifically, examples of the dicarboxylic acids used to prepare the polyester include aliphatic dicarboxylic acids and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, adipic acid, malonic acid, 2,6-naphthalene Dicarboxylic acid, 1,5-naphthalenedicarboxylic acid, hexahydroterephthalic acid, cyclohexanedicarboxylic acid, sebacic acid, azelleic acid, succinic acid, glutaric acid and mixtures thereof and esterifiable derivatives thereof It is not limited. Also useful are substituted aliphatic dicarboxylic acids and substituted aromatic dicarboxylic acids such as halogen or alkyl substituted dicarboxylic acids. Preferably at least 60 mol% of aromatic dicarboxylic acids are used for the preparation of the polyester.

Non-limiting examples of diols used in polyester production include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, butylene glycol, neopentyl glycol, trimethylpropane diol, cyclohexane di Methanol, polyethylene glycol or polypropylene glycol having a molecular weight of about 500 or less and mixtures thereof. Triols or polyols may also be used in small amounts, i.e. in amounts of 0 to 3 mol% of diols, to provide a non-linear, partially branched polyester.

Interaction of diols with dicarboxylic acids in the correct proportions according to standard esterification methods yields polyesters having the desired M _w , molecular weight distribution, branching, crystallinity and functionality useful in the extrusion coating compositions of the present invention. . Examples of useful polyesters can be prepared as described in US Pat. No. 4,012,363 (Brunig et al) and Canadian Patent 2,091,875, which is incorporated herein by reference.

Further useful polyesters are commercially available under the trade name DYNAPOL, a Hughes AG product in Berlin, Germany. Examples of specific polyesters are DYNAPOL P1500, DYNAPOL P1510, and DYNAPOL P1550 available from Hums AG, all of which are based on terephthalic acid and / or isophthalic acid. Another useful polyester is GRILESTA V 79/20 available from EMS. Other useful commercially available polyesters include SHELL CARIPAK P76, available from Shell Chemicals, Switzerland, and SELAR PT 6129 and SELAR PT 8307, available from Dupont Packaging and Industrial Polymers, Wilmington, Germany. It includes, but is not limited to. In a preferred embodiment, the extrusion coating composition of the present invention contains polyester mixtures of various molecular weights that optimize the performance and aesthetics of the membrane.

In addition, polyester can be manufactured by condensing the above-mentioned dicarboxylic acid, the derivative of dicarboxylic acid, and a low molecular weight epoxy compound. Low molecular weight epoxy compounds contain an average of about 1.5 to about 2.5 epoxy groups per molecule and have an EEW of about 150 to about 500. An example of a low molecular weight epoxy compound is EPON 828, a shell chemical company based in Houston, Texas.

Particularly useful polyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and polybutylene naphthalate (PBN) and mixtures thereof.

(b) optional modification resin

The extrusion coating composition contains the optional modifying resin in an amount of 0% to about 25% of the total weight of the composition. Preferably, the extrusion coating composition preferably contains an optional modifying resin in an amount of about 2% to about 20% of the total weight of the composition. In order to fully benefit from the present invention, the extrusion coating composition preferably contains an optional modifying resin in an amount of about 8% to about 15% of the total weight of the composition.

The optional modifying resin does not substantially react with the polyester during the manufacture of the extrusion coating composition or the extrusion process. Therefore, the extrusion coating composition does not need to be cured after coating on the metal substrate. However, the modifying resin improves the barrier of the extruded coating and the adhesion of the extruded coating composition to the metal substrate.

One of the useful modifying resins is an epoxy or phenoxy resin having an EEW of about 500 to about 15,000, preferably about 1000 to about 10,000. In order to fully take advantage of the present invention, epoxy or phenoxy resins preferably have an EEW of about 2000 to about 8000. Within this EEW range, the epoxy resin or phenoxy resin provides an extruded coating composition that is flexible enough to deform without crack formation and sufficiently rigid to exhibit good chemical and damage resistance.

Preferably, the epoxy resin or phenoxy resin is a solid material capable of providing the extrusion coating composition of the present invention when melt mixed with the molten polyester. Preferred epoxy and phenoxy resins contain epoxy novolac resins, ie, from about 2.5 epoxy groups to about 6 epoxy groups, containing on average about 1.5 to about 2.5 epoxy groups per molecule of epoxy resin, but containing more than about 2.5 epoxy groups per molecule. Resin containing can be used.

The epoxy resin or phenoxy resin can be an aliphatic resin or an aromatic resin. Preferred epoxy resins and phenoxy resins are preferably aromatics such as epoxy and phenoxy resins based on diglycidyl ethers of bisphenol A or bisphenol F. Epoxy resins can be prepared using commercially available forms or using low molecular weight epoxy compounds through standard methods known in the art.

Examples of epoxy resins include EPON 1004, EPON 1007 and EPON 1009, shell chemical companies in Houston, Texas, or ARALDITE® 6099, a Ciba Gauge Corporation product in Adslay, NY.

In general, suitable epoxy resins and phenoxy resins are aliphatic epoxy resins, for example, cycloaliphatic epoxy resins or aromatic epoxy resins such as the epoxy resins represented by the formulas (I) and (II).

Wherein each A is independently a divalent hydrocarbyl group having from 1 to about 12 carbon atoms, preferably from 1 to about 6 carbon atoms, most preferably from 1 to about 4 carbon atoms, and each R is independently hydrogen or Alkyl groups having from 1 to about 3 carbon atoms, each X is independently hydrogen or hydrocarbyl having from 1 to about 12 carbon atoms, preferably from 1 to about 6 carbon atoms, most preferably from 1 to about 4 carbon atoms, or Hydrocarbyloxy group, or halogen atom, preferably chlorine or bromine, n is 0 or 1, n 'is an average value of about 2 to about 30, preferably 10 to about 30.

Specifically, preferred epoxy and phenoxy resins are (diglycidyl ether / bisphenol A) resins prepared by polymer addition reaction of diglycidyl ether of bisphenol A represented by formula (III) and bisphenol A represented by formula (IV), That is, polyether diepoxides.

In this case, the epoxy resin is a mixture comprising polymer species corresponding to various n 'values in the following ideal formula (V).

Wherein n 'is a number from about 2 to about 30.

In addition to bisphenol A, it can be prepared using the diglycidyl ether of bisphenol illustrated as follows, but is not limited to this example.

Currently, government officials are discussing regulations on the amount of free epoxy groups contained in coatings used in food and beverage containers and closures. Thus, epoxy resins are not suitable as reforming resins for some applications. In these applications, acrylic resins or polyolefin resins may be used as the selective modification resin. In addition, a mixture of an epoxy resin, an acrylic resin and a polyolefin resin may be used. Acrylic resins have a M _w of about 15,000 to about 100,000, preferably about 20,000 to about 80,000. The polyolefin resin preferably has a M _w of about 15,000 to about 1,000,000, preferably about 25,000 to about 750,000.

Examples of acrylic resins include, but are not limited to, acrylic acid, methacrylic acid, esters of acrylic acid, esters of methacrylic acid, homopolymers and copolymers of acrylamide and methacrylamide. Examples of polyolefin resins include, but are not limited to, ethylene, propylene, ethylene-propylene blends, homopolymers and copolymers of 1-butene and 1-pentene. In addition, the polyolefin may include an olefin having a functional group such as an olefin having a hydroxyl group or a carboxy group as a functional group.

(c) optional inorganic fillers

In order to fully benefit from the present invention, the extrusion coating composition contains from 0% to about 50%, preferably 0% to about 20%, of an inorganic filler of the total weight of the composition. Inorganic fillers can improve the physical properties of the extruded coating composition.

Examples of the inorganic filler used in the coating composition of the present invention include clay, mica, aluminum silicate, fumed silica, magnesium oxide, zinc oxide, barium oxide, calcium sulfate, calcium oxide, aluminum oxide, aluminum magnesium oxide, zinc aluminum oxide, and oxide Magnesium titanium, iron oxide, titanium oxide, and mixtures thereof, including but not limited to. Inorganic fillers are substantially non-reactive and are generally added to the extrusion coating composition in the form of a powder having a diameter of about 10 to 200 microns, especially about 50 to about 125 microns.

(d) optional flow regulators

The extrusion coating composition of the present invention may contain a flow regulator which serves to form a uniform film of the coating composition extruded on the metal substrate. The flow regulator is added in an amount of 0% to about 6%, preferably 0% to about 5% of the total weight of the composition.

Examples of flow regulators include, but are not limited to, polyacrylates available from Henkel Corporation, such as PERENOL F 30 P. Another useful polyacrylate flow regulator is ACRYLON MFP. In addition, many other compounds and other acrylic resins known as flow regulators in the art may also be used.

(e) other optional ingredients

The extrusion coating composition of the present invention may contain an extrusion coating composition or other optional ingredients that do not adversely affect the resulting extruded coating composition. Such optional components are well known in the art, which enhance the aesthetics of the composition, facilitate the manufacture and use of the extrusion coating composition, and enhance the specific functional properties of the extrusion coating composition or the extruded coating composition obtained therefrom. To the extrusion coating composition.

Such optional components include, for example, dyes, pigments, preservatives, antioxidants, adhesion promoters, light stabilizers and mixtures thereof. Each optional component is added in an amount sufficient to provide the desired use, but in an amount that does not adversely affect the properties of the extrusion coating composition or the extruded coating composition formed therefrom.

For example, pigments, which are generally optional ingredients, are added in an amount of 0 to about 50 weight percent of the composition. Common pigments include titanium dioxide, barium sulfate, carbon black or iron oxides. In addition, organic dyes or pigments may be added to the extrusion coating composition.

In addition, an additional polymer, ie a second modifying polymer, may be added to the extrusion coating composition to improve the properties of the extruded coating composition. It is preferred that the second modifying polymer is compatible with the other composition components and does not adversely affect the extruded coating composition. In order to obtain a coated metallic substrate having a non-gloss finish, a second modifying polymer is used that is substantially incompatible with the polyester and the optional modifying polymer. Such second modifying polymer may be a thermoplastic polymer or a thermoset polymer and is added in the extrusion coating composition in an amount of 0% to about 50%, preferably 0% to about 20% of the total weight of the composition.

Examples of optional second modifying polymers that may be added to the extrusion coating composition of the invention include carboxylated polyesters, carboxylated polyolefins, polyamides, fluorocarbon resins, polycarbonates, styrene resins , ABS (acrylonitrile-butadiene-styrene) resins, chlorinated polyethers, urethane resins and similar resins, but are not limited thereto. Polyamide resins include, for example, nylon 66, nylon 6, nylon 610 and nylon 11. Useful polyolefins include, for example, polyvinyl chloride and homopolymers thereof and copolymers such as ethylene or vinyl acetate. Fluorocarbon resins include tetrafluorinated polyethylene, trifluorinated monochlorinated polyethylene, hexafluorinated ethylene propylene resin, polyvinyl fluoride and polyvinylidene fluoride. As such, an optional second modifying polymer may be added to the extrusion coating composition of the present invention, but no crosslinking agent is added and is not extruded onto the metal substrate and then subjected to a curing step.

The extrusion coating composition of the present invention is heated to a temperature sufficient to melt a method known in the art, such as polyester and optional modifying resin, respectively, and the melted polyester and the optional modifying resin are for example extruded or It can be prepared in a manner to mix in a twin screw extruder to provide a uniform extrusion coating composition. Optional components may be added to one melt component and bottled into the extrusion coating composition prior to mixing the melt components or may be added to the melt extrusion coating composition after mixing the melt components. When an optional second modifying polymer is added to the composition, the second modifying polymer is melt added to the melt extrusion coating composition at any convenient step in the manufacturing process. Alternatively, all of the composition components may be mixed in a solid state, and then the resulting mixture may be melted and extruded to obtain a uniform molten composition.

After preparing a uniform melt composition, the extrusion coating composition is cooled and solidified. The resulting extrusion coating composition is then prepared into pellets having a particle diameter of about 1 to about 10 mm. The pellets are collected and stored in a dry state until use in the extrusion process. The pellets are preferably heated prior to extrusion to remove all moisture absorbed in the extrusion coating composition during storage.

To demonstrate the usefulness of the waterborne coating composition of the present invention, the following examples were prepared and extruded onto a metal substrate to obtain a coated metal substrate. The coated metal substrates were then tested using as food or beverage containers. Extruded coatings were tested for corrosion resistance to metal substrates, adhesion to metal substrates, chemical resistance, flexibility and scratch resistance and damage resistance.

The extrusion coating composition of the present invention contains (a) a polyester or a blend of polyesters and optionally (b) a resin for modification. This extrusion coating composition can be extruded onto a metal substrate as a thermoplastic. Thus, there is no need for a crosslinking step such as an additional heating step after the composition is extruded onto the metal substrate or the use of a crosslinking agent. Although the extrusion coating composition of the present invention does not contain an organic solvent, the extruded membrane has proved to be excellent in coating properties such as adhesion, hardness and flexibility.

The solid extrusion coating composition of the present invention does not contain an organic solvent and is free of environmental and toxic problems with the liquid coating composition. In addition, the thermoplastic extrusion coating composition of the present invention provides an extruded coating that is sufficiently flexible so that the coated metal substrate can be deformed without breaking film continuity. In contrast, thermosetting compositions often provide a hard cured film, which makes it impossible to coat the metal substrate before it is transformed, ie, molded, into a metal article such as a metal stopper, can or tube. However, it is standard practice in the industry to coat a metal substrate prior to forming the metal substrate.

As another advantage, the extrusion coating composition of the present invention can be used on the base, tube and stopper, so that the container manufacturer does not need to use multiple coating compositions in the manufacture of the container. In addition, the extrusion coating compositions of the present invention exhibit sufficient transparency, hardness and damage resistance after being used as exterior coatings for metal containers. Accordingly, the extrusion coating composition of the present invention is more widely used, for example, for the interior of metal containers of food or beverage products or for the exterior of structures such as metal containers or aluminum side plates, and the environmental and toxic properties of liquid coating compositions. It overcomes the problems and solves the shortcomings presented in other methods of coating a solid coating composition on a metal substrate.

Summary of the Invention

The present invention effectively inhibits the corrosiveness of the metal substrate after being used in the metal substrate, does not adversely affect the product packaged in the container coated with the composition, the flexibility, barrier properties, weather resistance, chemical resistance and adhesion An extrusion coating composition exhibiting excellent results. The extrusion coating compositions of the present invention can be used in closures, pipes, tubes, container interiors and exteriors, as well as structures such as aluminum side plates and troughs. The extrusion coating composition effectively inhibits the corrosiveness of the ferrous metal and the nonferrous metal substrate when extruded onto the surface of the metal substrate.

The extrusion coating composition of the present invention comprises (a) a thermoplastic polyester having a weight average molecular weight (M _w ) of about 10,000 to about 50,000 or a combination of these polyesters and optionally (b) an epoxy equivalent weight (EEW) of about 500 to about Modifying resins such as epoxy or phenoxy resins that are 15,000. This composition does not contain an organic solvent.

Specifically, the extrusion coating composition of the present invention comprises (a) a polyester having a M _w of about 10,000 to about 50,000, preferably about 15,000 to about 40,000, or a mixture of such polyesters at about 50% of the total weight of the composition. To about 100% and optionally (b) a modification resin, such as an epoxy or phenoxy resin with an EEW of about 500 to about 15,000, preferably about 1000 to about 10,000, M _w of about 15,000 to about 100,000 Acrylic resins, polyolefins having a M _w of about 15,000 to about 1,000,000 or mixtures thereof, contain from 0% to about 25% of the total weight of the composition. The extrusion coating composition of the present invention may optionally contain (c) from 0% to about 50% of the total weight of the composition and (d) from 0% to about 4% of the total weight of the composition.

In particular, the polyesters included in the extrusion coating composition are thermoplastic polyesters prepared from acids, preferably terephthalic acid, isophthalic acid or mixtures thereof and aliphatic diols. It is most preferable that this polyester is a copolyester containing terephthalic acid and isophthalic acid. The polyester has an acid value of 0 to about 150 mg KOH (potassium hydroxide) / g, a hydroxyl value of 0 to about 150 mg KOH / g, a softening point of 140 ° C. or higher and a glass transition temperature (Tg) of about −30 ° C. to About 120 ° C. In addition, the polyester has a melt viscosity of about 10 to about 100 Pa · s (Pascal second) at 200 ° C. or about 25 to about 200 Pa · s (Pascal second) at 240 ° C., and a melt flow index (MFI) of 200 ° C. From about 20 to about 800 g / 10 min (minutes). Blends or mixtures of polyesters are also useful in the compositions and methods of the present invention.

Component (a) and, if contained, components (b), (c), (d) and other optional components are heated and mixed sufficiently to obtain a homogeneous extrusion coating composition. After cooling this extrusion coating composition, it is ground into pellets having a particle diameter of about 1 to about 10 mm, preferably about 4 to about 8 mm.

The term "extrusion coating composition" as used herein refers to a solid coating composition containing polyester, optional modifying resin, optional filler, optional flow control agent and other optional ingredients. The term "extruded coating composition" means an adhesive polymer coating obtained by extruding an extrusion coating composition onto a metal substrate.

Accordingly, an important first aspect of the present invention is to provide an extrusion coating composition that effectively inhibits corrosion of ferrous metal substrates and nonferrous metal substrates. The extruded coating composition extrudes onto a metal substrate and then effectively suppresses corrosion, exhibits good flexibility and tack on the metal substrate, and does not adversely affect products such as foods or beverages that the extruded coating composition contacts. It provides an adhesive barrier layer. Because of this desirable property, the extruded coating composition can be used to coat the interior of food and beverage containers and to overcome the drawbacks of conventional liquid compositions and the drawbacks of solid compositions that are coated by methods such as powder coating and lamination. The extruded coating composition contains polyester, optionally a modifying resin, a filler and a flow control agent, which components make up the majority of the extrusion coating composition.

In a second aspect of the invention, the extruded coating composition exhibits excellent flexibility and adhesion to the metal substrate. The good adhesion of the coating composition extruded to the metal substrate improves the barrier properties and corrosion inhibition of the coating composition. Due to the excellent flexibility of the extruded coating composition, it is possible to easily process the coated metal substrate into the coated metal article as in a mold or stamping process step, i.e. the cured coating composition is continuous and adhered to the metal substrate. Keep it. The extruded coating composition exhibits good chemical resistance and does not adversely affect food or beverage packaged in a container coated with a coating composition whose internal surface is cured. The extruded coating composition is hard enough to exhibit scratch resistance.

In a third aspect of the invention, the extrusion coating composition of the invention is extruded onto a metal substrate to form a uniform film of the extruded coating composition having a film thickness of about 1 to about 40 microns, preferably 2 to about 30 microns. do. Such thin uniform films are not obtainable using powder coating compositions and methods. In addition, the extrusion coating composition of the present invention can be used for the interior and exterior of the tube body and the tube bar, container manufacturers do not need to use a plurality of coating compositions.

These and other aspects and advantages of the present invention are apparent from the following detailed description of the preferred embodiments.

Examples 1-9 illustrate the method of extruding the coating composition of the present invention, illustrating the main features and embodiments of the extrusion coating composition of the present invention.

Example 1

The extrusion coating composition of Example 1 was prepared by melting the polyester and adding the molten polyester with barium sulfate and a flow regulator under stirring. The resulting mixture was heated to keep the polyester in a molten state. The pre-melted epoxy resin was then mixed with the melted polyester through a twin blade extruder. The resulting composition of Example 1 was cooled to room temperature and solidified. This solid composition was made of pellets composed mostly of particles having a particle diameter of about 1 to about 10 mm. The extrusion coating composition of Example 1 had a melt flow index (MFI) of 62.2 g / 10 min at 200 ° C. and the highest melting point was 172.2 ° C. (measured by differential scanning calorimetry (DSC)).

Example 2

The composition of Example 2 was prepared substantially in the same manner as the composition of Example 1 except that barium sulfate was not added. The solid composition of this Example 2 was also prepared from pellets containing mostly particles having a particle diameter of about 1 to about 10 mm. The extrusion coating composition of Example 2 had a melt flow index (MFI) of 66.2 g / 10 min at 200 ° C and a peak melting point of 170.7 ° C (measured by DSC).

Example 3

The composition of Example 3 was prepared in substantially the same manner as the composition of Example 1, except that additional fillers and pigments were added in this composition. The solid composition of Example 3 was then prepared into pellets consisting mostly of particles having a particle diameter of about 1 to 10 mm. The extrusion coating composition of Example 3 had a melt flow index (MFI) of 86.9 g / 10 min at 200 ° C. and a highest melting point of 171.9 ° C. (measured by DSC).

Example 4

The composition of Example 4 was prepared in the same manner as the composition of Example 2. The solid composition of this Example 4 was also prepared from pellets containing mostly particles having a particle diameter of about 1 to about 10 mm.

Example 5

The composition of Example 5 was prepared in the same manner as the composition of Example 3. The solid composition of Example 5 was then prepared into pellets consisting mostly of particles having a particle diameter of about 1 to about 10 mm. The extrusion coating composition of Example 5 had a melt flow index (MFI) of 80.3 g / 10 min at 200 ° C. and a highest melting point of 158.2 ° C. (measured by DSC).

Example 6

The composition of Example 6 was prepared in the same manner as the composition of Example 3. This solid composition was then prepared into pellets consisting mostly of particles having a particle diameter of about 1 to 10 mm. The extrusion coating composition of Example 6 had a melt flow index (MFI) of 92.2 g / 10 min at 200 ° C. and a highest melting point of 159.9 ° C. (measured by DSC).

Example 7

The composition of Example 7 was prepared in the same manner as the composition of Example 3. This solid composition was then prepared into pellets consisting mostly of particles having a particle diameter of about 1 to about 10 mm. The extrusion coating composition of Example 7 had a melt flow index (MFI) of 96.8 g / 10 min at 200 ° C. and a highest melting point of 157.3 ° C. (measured by DSC).

Example 8

The composition of Example 8 was prepared in the same manner as the composition of Example 3. This solid composition was then prepared into pellets consisting mostly of particles having a particle diameter of about 1 to about 10 mm. The extrusion coating composition of Example 8 had a melt flow index (MFI) of 66.5 g / 10 min at 200 ° C. and a highest melting point of 157.8 ° C. (measured by DSC).

Example 9

The composition of Example 9 was prepared in the same manner as the composition of Example 3. This solid composition was then prepared into pellets consisting mostly of particles having a particle diameter of about 1 to about 10 mm. The extrusion coating composition of Example 9 had a melt flow index (MFI) at 200 ° C. of 86.3 g / 10 min and a highest melting point of 159.3 ° C. (measured by DSC).

The extrusion coating composition of the present invention is extruded onto a metal substrate to provide a coated metal substrate having a tacky barrier layer of the extruded composition. Generally, the composition is coated on a sheet or coil of metal substrate moving in a relative direction with an extruder that applies the composition to the metal substrate. The extruder includes a screw for moving the molten composition and a die for coating the composition to a metal substrate to a predetermined thickness. The extruder coats the extrusion coating composition onto the metal substrate with a layer of about 1 to about 40 microns, preferably about 2 to about 30 microns. In order to fully take advantage of the present invention, the thickness of the extruded coating composition is preferably from about 1 to about 10 microns.

The coated metal substrates were then tested for use as interior surfaces of food or beverage containers. As explained in more detail below, the extruded coating composition obtained by extruding the extrusion coating composition of the present invention is suitable as an interior material of a metal container for food or beverage. The extrusion coating composition of the present invention provided a good extruded coating without the curing step.

Specifically, the extrusion coating composition of the present invention can be applied to virtually any metal substrate. Examples of metal substrates include aluminum, tin free steel, tin plate, steel, galvanized steel, zinc alloy plated steel, lead plated steel, lead alloy plated steel, aluminum plated steel, aluminum alloy plated steel, and stainless steel. It is not limited to this.

In the extrusion coating method, the extrusion coating composition is first slowly heated to carefully melt the composition by about 100 to about 120 ° C., and then slowly increases to a temperature of about 180 ° C. to about 240 ° C. to completely melt the extrusion coating composition. Let's do it. There is no particular upper limit to the temperature, but it is sufficient that it is high enough to melt the composition. The composition should not be heated to a temperature well above the melting point (ie, above about 100 ° C. above the melting point) in order to avoid undesirable reactions between the polyester and the optional modifying resin or to degrade the polyester.

The main feature exhibited by the extrusion coating composition of the present invention is the stability of the composition at the melting point. 1 illustrates that the viscosity increases to less than 100 Pa · s when the extrusion coating composition of the present invention is kept above the melting point or melting point for 20 minutes. This slight increase shows that the polyester and epoxy do not react, i.e. do not cure at the melting point to form a crosslinked resin, and the polyester does not decompose. If crosslinking occurred, the viscosity would increase rapidly and would be so difficult that it would be impossible to extrude the extrusion coating composition onto the metal substrate. The decrease in viscosity indicates that the polyester decomposes at the melting point.

In addition, the metal is heated to a temperature of about 120 ° C. to about 250 ° C. prior to extrusion. Preheating of the metal substrate is important for sufficiently flowing the extrusion coating composition onto the metal substrate and sticking the extruded composition to the metal substrate.

The extrusion coating composition does not cure or crosslink to any substantial extent during or after extrusion onto the heated substrate. Thus, no curing step at elevated temperature of the extruded composition is necessary. However, to optimize the properties of the extruded composition, the coated metal substrate is cooled to about 250 ° C. to about 550 ° C. for about 5 to about 30 seconds, preferably from about 300 ° C. to about 500 for about 10 to about 20 seconds. It is preferable to treat it by a heating step after extrusion at a temperature of ℃.

The resulting extruded coating composition exhibits a soft glossy appearance and is free of defects. Extruded coatings exhibit good adhesion and good barrier and corrosion resistance.

In particular, the extrusion coating composition of the present invention provides a highly barrier self-lubricating layer when extruded onto a metal substrate. The composition can be extruded at high speed onto a metal coil or sheet to provide an extruded composition layer having a thickness of about 1 to about 40 microns, preferably about 2 to about 30 microns. In many embodiments, the extruded composition is about 1 to about 10 microns in thickness. Generally, the extruder has a length to diameter ratio (L / D) of about 10: 1 to about 30: 1, preferably about 15: 1 to about 25: 1. The extruder may comprise single screw or twin screw that is corotating or counterrotating. Extruded compositions perform better than liquid and powder coating compositions and cost less to coat barrier thin films on metal substrates.

Collectively, the extrusion coating composition of the present invention eliminates the chemical pretreatment step of the metal substrate, uses a small induction oven for preheating and postheating the metal substrate instead of a large convection oven for drying the liquid composition, and Instead of the containing liquid composition, a solid composition containing no organic compound is used, and no lubrication zone and solvent incinerator are required.

Various tests were performed on the extrusion coating composition. As one test, the extrusion coating composition was subjected to a batch mixer test. The batch mixer uses a pair of roller-shaped blades for mixing the composition in a 50 cc (cm 2) chamber. Batch mixers measure torque against time and working temperature. The “torque versus time” curve is a measure of the processability of the composition, and the torque change can be interpreted as a rate such as, for example, the rate of decomposition or crosslinking.

In this test, the mixer is first preheated to the experimental temperature. The device is set to zero torque at experimental rotational speed and temperature. A test composition sample (70% of the mixer volume) was added and torque (meter grams) measured over time and temperature. Specifically, the compositions of Examples 1 and 3 were compared to commercially available low density polyethylene (ie CHEVRON 1017) controls. In a batch mixer test, as in the control, the compositions of Examples 1 and 3 were stable for at least 10 minutes at 200 ° C. The compositions of Examples 1 and 3 were less viscous than the control (ie lower torque).

In addition, the composition of Example 3 was extruded onto an aluminum substrate. The test results showed that excellent membrane properties were obtained. In particular, the membrane was flexible and had good adhesion to the substrate and low enamel rating as observed in the water pasteurization test, the boiling DOWFAX test and the reverse impact test.

The composition of Example 3 was extruded onto other metal panels and the panel was subjected to a retort test to determine whether the extruded coating composition was able to withstand the high temperatures processed during food processing. Specifically, the coated metal substrates were treated for 90 minutes at 250 ° F. and 15 psi for dog food, cat food or tomato products. The composition of Example 3 extruded onto tin-free steel or aluminum and withstand the retort test could be used for food packaging. The postheating step (ie after extrusion) was observed to show better adhesion, fouling resistance and peeling resistance than the unheated coated substrate. In addition, co-extrusion of the polymer layer and the composition of Example 3 in order to improve the adhesion to the metal was able to obtain a coated substrate having excellent adhesion between the mutual coating.

As another test, the composition of Example 3 was applied onto a sheet of tin free steel (0.19 mm thick). Six sheets made an extrusion coating thickness of 25 microns (sheet A) and the other six sheets made a coating thickness of 20 microns (sheet B). Sheets A and B were post-heated at 500 ° F. for about 12 seconds.

Sheets A and B were tested and found to have excellent membrane flexibility and tack and low membrane porosity. The coated sheet could be retorted for 1 hour at 121 ° C. in deionized water. Thus, the composition of Example 3 is suitable for the exterior of metal food cans. The sheet was also observed to be suitable for the exterior and interior of metal cans containing acidic products such as applesauce (ie, passed a 30 minute retort test at 100 ° C). Sheets A and B were shown to have insufficient retort for 1 hour at 121 ° C. in the presence of polyphosphate. The test results are shown in Table 1 below.

Collectively, sheets A and B exhibit better overall performance than metal substrates coated with liquid coating compositions.

As another test, the composition of Example 3 was coated onto an aluminum substrate and a tin-free steel substrate at a process rate of 400 fpm (feet per minute). The substrate temperature at 3.5 fpm was 190 ° C., so the substrate temperature at 400 fpm was estimated at 170 ° C. The thickness of the coating extruded on aluminum (sheet C) was 5 to 8 microns. The thickness of the coating extruded on the tin-free steel (sheet D) was 7-11 microns. Sheet C and sheet D were post-heated to improve adhesion. These sheets were not quenched after postheating.

Sheets C and D were tensioned to create metal containers and pipes. About two thirds of the rooms were reheated. One half of the reheated tube was cooled slowly and one half was quenched.

The integrity of the composition extruded on the flat part and the molded part of the tube bottom was evaluated by enamel evaluation and copper chloride pinhole test on the five molded tube parts. The results are shown in Table 2.

Moreover, the adhesive test was done. Tack test results are summarized in Table 3. The extruded composition of Example 3 exhibited good tack and was hard enough to withstand the effects of food and beverages stored in metal containers.

The pipes coated with Example 3 and not reheated showed particularly good performance. It is a common idea that reheating a molded tube can disrupt the coating and reduce its performance. The shaped tube with the extruded coating of Example 3 was not whitened and also successfully passed the wet tape test.

Tables 4 and 5 summarize the test results for cans made of aluminum sheets coated with the extrusion coating composition of Example 3. Various kinds of cans were prepared by various combinations of the film thickness and the cooling mechanism (ie, without quenching or quenching). Tack, pinhole formation and heat resistance were tested for each can.

Cans coated with the extrusion coating composition of Example 3 exhibited very good performance, in particular over other solid compositions. It was also observed that reheating the can significantly improved the performance exhibited by the extruded composition of Example 3.

The extrusion coating composition of the present invention, i.e., the compositions of Examples 3 and 7, is extruded onto an aluminum substrate, and the resulting extruded coating is coated as a liquid on the film and the aluminum substrate of Example 3 coated on an aluminum substrate by powder coating Compared with a commercially available solvent-based thermosetting polyester composition. The test results are shown in Table 6.

The comparative data in Table 6 show that the extruded coating outperforms the powder coating of the same composition, and the extruded coating is thinner than the powder coating, ie about two to three times thinner. Thus, the extruded coating significantly improves the economics of the coating process as it provides better barrier properties through thinner coatings. In addition, the extruded thermosetting composition of Example 3 showed superior performance compared to the liquid thermosetting composition.

The extrusion coating composition of the present invention exhibited at least equivalent coating properties as currently available compositions when used in similar practical applications. The above data demonstrate that the extrusion coating compositions of the present invention provide useful extrusion coating compositions for interior or exterior coating of food or beverage containers.

In particular, the coating composition for a metal container must have good adhesion and flexibility because it first coats a flat sheet of metal substrate and then molds the coated sheet into the desired formation to produce the metal container. Poor tack coatings can be separated from the metal substrate during the molding process. Thus, the lack of tack can adversely affect the ability of the cured coating composition to inhibit corrosion of the metal substrate. The extrusion coating composition of the present invention exhibits good adhesion to the metal substrate, whereby the coating can be extruded onto the metal substrate, which can then be deformed without adversely affecting the continuity of the coating film.

The extruded coating composition exhibits good flexibility. Flexibility is an important property of the polymer coating because the metal substrate is coated before it is stamped or otherwise molded into the desired metal article, ie the metal container. The coated metal substrate is subject to various deformations during the molding process, and the coating will crack or break if the coating's flexibility is insufficient. Such cracks can corrode the metal substrate because the aqueous component contained in the vessel allows more access to the metal substrate. The metal substrate coated with the extrusion coating composition of the present invention did not show any cracks or breaks even when deformed in the form of a metal can. In addition, as described above, the extruded coating coated with the extrusion coating composition of the present invention has sufficient adhesion to the metal substrate and maintains sufficient adhesion even during processing into the metal substrate to further improve corrosion resistance.

The tests described in Tables 1 to 6 demonstrate that the extruded coating compositions of the present invention maintain adhesion to metal substrates, are flexible, and exhibit sufficient rigidity and are scratch, damage, whitening and chemical resistant. do. The combination of these advantages is an essential factor or at least a desirable factor for coatings to be coated for the interior of food and beverage containers.

The above-described advantages have been obtained through the extrusion coating compositions of the present invention useful for coating the intestines of various metal articles or extruded surfaces such as the intestines of food and beverage metal containers. The extrusion coating composition of the present invention is particularly useful as a coating material for metal containers containing flavor-sensitive foods or beverages, such as beer, since substantially no ingredients affect the flavor of the food or beverage.

The above tests conducted on the metal substrate coated with the extrusion coating composition of the present invention are outlined as well known in the art.

DOWFAX Test Method

The coated sample was immersed in boiling 1.67% aqueous solution of DOWFAX 2A1 surfactant for 15 minutes, then washed with hot water and dried. Then, after cross-hatching the sample, the tape was attached to evaluate the degree of adhesion by the following grades.

0-complete

1-the edges of the rectangle are drawn very slightly

2-low withdrawal rate (1 to 2%)

3-Withdrawal rate (2-50%)

4-High withdrawal rate (> 50%)

5-Withdrawal rate very serious. Coating removed during crosshatch.

In addition, the sample was evaluated for the degree of whitening as follows.

0-complete

1-Weak haze on the surface

2-slightly cloudy appearance

3-usually cloudy appearance

4-Very cloudy and faint appearance that may show discoloration.

Whitening resistance tests were demonstrated through the resistance of the extruded coatings after treatment with hot detergent solutions. Adhesion was done with a crosshatch tack test, which produced a vertical crosshatch pattern in the cured coating using a laser blade. An adhesive tape was coated on this crosshatch pattern, and the adhesive tape was quickly removed at an angle of 90 degrees. The amount of extruded coating remaining as metal substrate was then measured.

Wet tape test

The coated sample was immersed in water in a pressure cooker at 15 psi for 1 hour. This sample was graded as in the DOWFAX test.

Hot water test

The coated sample was immersed in water at 65 ° C. for 30 minutes. The grade was then evaluated as in the DOWFAX test.

Pinhole test

Circular pore clay (usually about 50 cm 2) was placed on the coated sample with respect to the flat sheet. 2% (wt / v) of copper chloride was injected into the inner region of the circle and left for several hours. The samples were then examined for red deposits indicating the presence of pinholes formed during coating. The tube was inverted and a copper chloride solution was injected into the cavity made of awl.

Feathering test

The coupon (usually about 50 cm 2) was left in water at 65 ° C. for 15 minutes. Two 45 ° grooves were made to face each other at a distance of about 3 cm from one corner and a fastener was installed in the metal outside the grooves. The free metal between the two grooves was twisted at an angle using pliers to form triangular metal pieces from the coupon. The metal edges on the coupon were then examined for coating protrusions. In the absence of a protruding coating, the complete rating is 0.

Diet Sprites and Gatorade Exam

Four coated metal substrate samples were each placed in a beaker containing lemon lime ghatorade (a beverage containing a large amount of salt for athletes) or a diet sprite (citrus carbonated beverage). The beaker was covered and the beaker containing each beverage was stored at 65 ° C. and 82 ° C. for 7 days. The samples were then evaluated for sticking and whitening as in the DOWFAX test. This sample was examined for peeling formation and pencil hardness.

The grade of peeling formation was evaluated as follows.

0-complete, no peeling off

1-presence of delamination (<1/6 cm 2) or rough surface

2-forming few peels

3-not completely covering the surface but forming many peelings

4-The coating peels off completely.

Pencil hardness

Pencil hardness of various hardness was used to check the pencil hardness of the sample. The strongest pencil hardness that does not penetrate the surface is the grade of the coating. The pencil consists of 4H, the strongest hardness, and 2B, the softest, and 3H, 2H, H, F, HB, B in between.

Water pasteurization

After soaking in 180 ° F. water for 30 minutes, the coated panels were tested for back shock, whitening and pencil hardness under 25 lbs.

Retort test

The retort test was evaluated for the resistance and tack of the coating under food processing conditions (90 minutes at 250 ° F. and 15 psi).

Enamel grade (ER)

Enamel grade is a test for the continuity of a coating film coated on a can part such as a pipe bottom or a tube body. An enamel grade test is measured by passing an electric current from an electrode to an molded can part through an electrolyte. This coating acts as an insulating material, so that if the film's continuity is complete no current will flow. The lower the milliamp (mA) reading, the greater the continuity of the coating present on the metal substrate.

4-Kant Dose

This is an approximately rectangular thin elongated tube. 4 Bend each edge and vary the bend diameter of each edge. 4-Kant Dose is made of a metal substrate coated with a coating prior to forming the tube.

Mi (lactic acid), Cy (cysteine) and NaCl / HAC (sodium chloride / acetic acid) tests

The coated substrate was molded into a 4-Kant Dose container, and test solution was added to this 4-Kant Dose and maintained at 120 ° C. for 1 hour. As the lactic acid solution, an aqueous 1% lactic acid solution was used. The cysteine solution contains 0.45 g of cysteine and about 10 g of phosphate per liter of aqueous solution. NaCl / HAC solution contains 2% sodium chloride and 3% acetic acid in water.

Civo Exam

The 4-Kant Dose vessel was placed in a larger large vessel and filled with 3% aqueous acetic acid solution. This large vessel was heated to 70 ° C. and left for 2 hours. The vessel was cooled and stored at 40 ° C. for 10 days. The 4-Kant Dose container was then examined for defects.

In addition, the following extrusion coating compositions of Examples 10 to 41 were prepared and extruded onto a metal substrate by the method described above. This example shows that an excellent extrusion coating composition is obtained when excluding the modifying resin from the composition or when using a mixture of polyesters in the composition.

Examples 9-41

Examples 9 and 10 illustrate extrusion coating compositions with and without a single polyester and optionally modifying polymers (Example 9). Examples 11 to 30 illustrate extrusion coating compositions containing PET or PBT polyester alone and extruded coating compositions containing a blend of PET or PBT polyester with copolyester with and without modifying resin, respectively. will be. Examples 31-39 illustrate extrusion coating compositions containing a blend of PET and PBT polyester, and a blend of copolyester and PET and PBT polyester, respectively, with and without modifying resins. Examples 40 and 41 illustrate a colored extrusion coating composition.

The properties of the extruded coating compositions formed from the extrusion coating compositions of Examples 10-41 are described in Table 7 below. In general, the results listed in Table 7 show that PET and PBT polyesters improve the cohesiveness of the copolyesters to metal substrates (Examples 11-30). Thus, modifying resins that improve tack can be excluded from the extrusion coating composition. Examples 31 to 40 show that the polyester blends provide excellent film properties and that small amounts of copolyester result in improved performance, i.e. less browning is observed. The use of polyesters, such as PET or PBT, provides the property of lowering the cost of the composition without compromising the performance of the extruded coating composition and providing the ability to produce an extrusion coating composition of suitable viscosity for a particular application of devices and methods. You have an advantage.

As described above, the present invention may be variously modified and modified without departing from the scope and spirit of the present invention, and the present invention should be limited only through the appended claims.

Claims (43)

(a) heating the metal substrate to a temperature of 120 ° C. to 250 ° C. to obtain a preheated metal substrate, (b) (i) Melt viscosity at 10,000 to 35,000 in weight average molecular weight, glass transition temperature at -30 ° C to 120 ° C and 240 ° C at 75 to 150 Pa · s, 200 ° C and melt flow index at 20 to 200 g / 10 min, polyester having a softening point of 120 ° C. to 200 ° C., 50% to 100% of the total weight of the composition, and (ii) a reforming resin selected from the group consisting of epoxy resins or phenoxy resins having an epoxy equivalent of 500 to 3,000, acrylic resins having a weight average molecular weight of 15,000 to 100,000, polyolefin resins having a weight average molecular weight of 15,000 to 1,000,000, and mixtures thereof Heating a solid thermoplastic coating composition comprising 0% to 15% of the total weight of the composition to 180 ° C to 240 ° C to melt the composition to provide a melted coating composition, (c) extruding the molten coating composition onto the surface of the preheated metal substrate to provide a layer of molten coating composition having a thickness of 1 to 40 microns on the preheated metal substrate, resulting in a coated metal substrate. , (d) cooling the coated metal substrate and (e) heating the coated metal substrate cooled in step (d) at a temperature of 300 ° C. to 550 ° C. for 5 to 30 seconds. The method of claim 3 wherein the thermoplastic coating composition is (iii) from 0 to 50% of the total weight of the composition; (iv) further comprising a flow regulator that is 0-4% of the total weight of the composition. The method of claim 2 wherein the coating composition comprises from 0% to 20% of an inorganic filler of the total weight of the composition. The inorganic filler according to claim 2, wherein the inorganic filler is clay, mica, aluminum silicate, fumed silica, magnesium oxide, zinc oxide, barium oxide, calcium sulfate, calcium oxide, aluminum oxide, aluminum aluminum oxide, aluminum zinc oxide, titanium oxide, magnesium oxide Iron titanium, calcium titanium oxide and mixtures thereof. The method of claim 2, wherein the flow regulator comprises acrylic resin. The method of claim 1, wherein the thermoplastic coating composition further comprises 0% to 50% of the second modifying polymer of the total weight of the composition. The polymer of claim 6 wherein the second modifying polymer is a carboxylated polyester, carboxylated polyolefin, polyamide, fluorocarbon resin, polycarbonate, styrene resin, ABS (acrylonitrile-butadiene-styrene ) Resins, chlorinated polyethers, urethane resins and mixtures thereof. The method of claim 6, wherein the second modifying polymer can provide a coated metal substrate having a matt appearance. The method of claim 6 wherein the second modifying polymer is a thermoplastic polymer. The method of claim 6, wherein the second modifying polymer is a thermosetting polymer. The metal substrate of claim 1, wherein the metal substrate is composed of aluminum, tin-free steel, tin plate, steel, galvanized steel, zinc alloy plated steel, lead plated steel, lead alloy plated steel, aluminum plated steel, aluminum alloy plated steel, and stainless steel. Selected from the group. The method of claim 1 wherein the coating composition is heated to a temperature up to 100 ° C. above the melting point of the coating composition. The method of claim 1 wherein the coating composition is free of organic solvents. The method of claim 1 wherein the coating composition comprises a polyester that is 60% to 85% of the total weight of the composition. The method of claim 1 wherein the weight average molecular weight of the polyester is 15,000 to 35,000. The process of claim 1 wherein the polyester has an acid value of 0 to 150 mg KOH / g and a hydroxyl value of 0 to 150 mg KOH / g. The method according to claim 1, wherein the glass transition temperature of the polyester is 15 ° C to 100 ° C. The method of claim 1 wherein the coating composition comprises at least two polyesters. The process of claim 1 wherein the melt viscosity of the polyester is from 90 to 125 Pa · s at 240 ° C. The process of claim 1 wherein the melt flow index of the polyester is 25 to 150 g / 10 min at 200 ° C. 3. The polyester of claim 1 wherein the polyester comprises a condensation product of (i) an esterifiable derivative of dicarboxylic acid or dicarboxylic acid with (ii) an aliphatic diol, At least 60 mol% is an aromatic dicarboxylic acid. The method of claim 21, wherein the aromatic dicarboxylic acid is selected from phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid and mixtures thereof. The process of claim 1, wherein the polyester comprises a reaction product of (i) a dicarboxylic acid or an esterifiable derivative of dicarboxylic acid and (ii) a low molecular weight epoxy resin having an EEW of from 150 to 500. The group of claim 1 wherein the polyester is comprised of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthanate (PEN) and polybutylene naphtanate (PBN), copolyesters and mixtures thereof Selected from. The method of claim 1 wherein the coating composition contains a modifying resin at 2% to 20% of the total weight of the composition. The method according to claim 1, wherein the modifying resin comprises an epoxy resin having an epoxy equivalent of 2000 to 8000. The method of claim 1 wherein the epoxy resin is a solid material comprising an average of 1.5 to 2.5 epoxy groups per molecule of epoxy resin. The method of claim 1 wherein the epoxy resin is a solid material comprising an average of 2.5 to 6 epoxy groups per epoxy resin molecule. The method of claim 1, wherein the epoxy resin comprises a mixture of an epoxy resin comprising an average of 1.5 to 2.5 epoxy groups per epoxy resin molecule and an epoxy resin comprising an average of 2.5 to 6 epoxy groups per epoxy resin molecule. The method of claim 1 wherein the epoxy resin is an aromatic epoxy resin. 31. The method of claim 30, wherein the aromatic epoxy resin is based on bisphenol A or bisphenol F. The method of claim 1 wherein the modifying resin is an acrylic resin having a weight average molecular weight of 20,000 to 80,000. The method of claim 1 wherein the acrylic resin is acrylic acid, methacrylic acid, esters of acrylic acid, esters of methacrylic acid, homopolymers of acrylamide and methacrylamide, or copolymers and copolymers of homopolymers. The method of claim 1 wherein the modifying resin is a polyolefin resin having a weight average molecular weight of 25,000 to 750,000. The method of claim 1 wherein the polyolefin resin is a homopolymer or copolymer of ethylene, propylene, ethylene propylene blend, 1-butene and 1-pentene. The method of claim 1 wherein the polyolefin comprises an olefin having a functional group. The method of claim 1 wherein the molten coating composition is extruded onto opposite surfaces of the preheated metal substrate. The method of claim 1 wherein the molten coating composition layer has a thickness of 2 to 30 microns. The method of claim 1, wherein the molten coating composition layer has a thickness of 1 to 10 microns. 40. The method of claim 39 wherein the extruder screw is a single screw screw, a co-rotating twin screw or a counter-rotating twin screw. The method of claim 1, wherein the molten coating composition is extruded onto the preheated metal substrate through an extruder having a screw and a die, wherein the preheated metal substrate moves relative to the die. The method of claim 1 wherein the heating step (e) is carried out at 300 ° C. to 500 ° C. for 15 seconds to 20 seconds. The method of claim 1 wherein the thermoplastic coating composition further comprises a pigment, an organic dye or a mixture thereof.