KR100502151B1 - Method of priming polyolefin articles for coating - Google Patents

Abstract

A method is described for providing a waterborne, inorganic blocking coating on a polyolefin substrate. The method comprises applying to the substrate a primer composition containing a vinyl polymer wherein at least 75% of the polymer repeat units comprise a side group having a hydroxyl moiety. This primer coating then facilitates the application and bonding of the barrier coating composition applied to the substrate.

Description

METHODS OF PRIMING POLYOLEFIN ARTICLES FOR COATING}

Cross Reference of Other Applications

This is a partial continuing application of US Patent Application No. 08 / 662,836, filed June 12, 1996 and currently pending.

It is known to coat thermoplastic polymer substrates with a moisture barrier coating composition such that gas and liquids such as oxygen are not permeable. See, for example, US Pat. No. 3,282,729, which describes the application of an aqueous solution of poly vinyl alcohol (PVOH) and trimethylolphenol to a thermoplastic polymer substrate at high temperature. For example, US Pat. No. 5,073,419 describes a film composite comprising a low density straight chain polyethylene film having a PVOH coating of about 0.0003 cm to about 0.0076 cm (about 0.1 to 3 mil) thick. US Pat. No. 5,487,940 describes a metallized polymer film structure comprising an oxygen barrier and a moisture barrier. The oxygen barrier comprises crosslinked PVOH and the moisture barrier is preferably metallized oriented polypropylene or polyethylene.

Similarly, US Pat. No. 4,254,170 relates to this axially oriented polyester hollow body, wherein one wall of the preform consists of at least two incompatible polymers. Coated with the composition, one is water soluble PVOH and the other is polymer latex with low water sensitivity.

US Patent No. 5,384,192 describes a structure comprising an inorganic oxide substrate having an organic polymer layer. In this structure there is an adhesion enhancement layer between the substrate and the organic polymer layer. One component of the adhesive layer is poly vinyl phenol, also known as poly hydroxystyrene.

U. S. Patent No. 5,192, 620 describes a metallized film composition comprising a polymer substrate whose surface is modified by an adhesion enhancer, wherein the modified surface is provided with a PVOH skin layer. The PVOH epidermal layer is applied by a solution coating process. Just above the skin layer is a metal layer.

US Patent No. 5,491,023 describes metallized film compositions comprising a polymer substrate whose surface has been modified with an adhesion enhancer; The modified surface is provided with a PVOH skin layer. The PVOH skin layer is applied by an extrusion process. Just above the skin layer is a metal layer.

Despite the deep academic achievement of barrier coating technology, the polymer films currently in use do not meet the market demand for longer shelf life of packaged foods. In addition, many of these products (eg films coated with aluminum) cannot be used in microwave ovens or are not easily processed {eg films coated with poly (vinylidene chloride)}, environmental Does not satisfy the problem.

For example, there is a need in the art for additional compositions and methods for providing improved barrier coatings to polymeric articles such as films, bottles, and the like.

In one aspect, the present invention provides a method of providing a barrier coating on a polyolefin substrate, preferably a film. This method includes applying a primer composition containing any vinyl copolymer comprising repeating units to the polymer substrate, wherein at least 75% of the copolymer repeating units have a hydroxyl group moiety. It contains a side group. The primer layer is then dried. The third step of the method then includes applying an aqueous barrier coating solution to form a dry inorganic barrier layer on the dried primer layer.

In another aspect, the present invention provides a polyolefin article coated with a barrier.

Other aspects and advantages of the invention are further described in the detailed description of the examples below.

The present invention improves the wetting of the aqueous barrier coating solution on the polyolefin substrate by applying the selected primer composition to the substrate before applying the barrier coating solution, and enhances the adhesion of the inorganic barrier layer thus obtained to the polyolefin substrate. It provides a method to make it. Improved adhesion of the dried inorganic barrier layer is demonstrated in improved vapor barrier performance.

I. Primer composition

The primer composition according to the invention comprises any vinyl polymer comprising repeat units (ie derived from “vinyl” units such as ethylene, propylene, vinyl acetate, vinyl phenol, etc.) and at least 75% of said polymer repeat units Includes a side group having a hydroxyl group moiety. Preferably, the vinyl polymer comprises poly (vinyl alcohol) and poly (para-hydroxystyrene).

In one embodiment, the vinyl polymer useful for the primer is poly (vinyl alcohol) (PVOH). There are various variations of PVOH that are commercially available and / or known in the art. For example, these PVOH variants differ in characteristics such as molecular weight and hydrolysis rate. Poly (vinyl alcohol) is derived from poly (vinyl acetate) by hydrolyzing acetate functional groups. Typically, some of the acetate functional groups are left intact to impart different properties. Hydrolysis rate refers to the portion of the acetate group hydrolyzed to the hydroxyl group portion. Preferably, the average molecular weight distribution of the PVOH polymers useful in the primer composition is between about 50,000 and about 185,000, and the PVOH is hydrolyzed at least about 75%.

PVOH useful in the present invention can be modified by random replacement of some of the vinyl alcohol groups with vinyl butyral groups having the structure:

Where n, p and r represent the mole fraction of polymer repeating units and the sum of n, p and r is one. In order to satisfactorily wet the barrier coating solution on this primer layer, r is preferably at least 0.75. Preferably, the average molecular weight of the modified PVOH is between about 40,000 and 100,000.

Since the PVOH variant can be dissolved in a suitable solvent (eg, water, isopropanol, or a mixture thereof), the primer composition is characterized by a solids content between 0.1% and 10% by weight. If the polymer in the primer composition is PVOH, the solvent useful for the primer composition is preferably water. However, other solvents suitable for PVOH may be readily selected by those skilled in the art.

PVOH solutions are known to help the growth of microorganisms. To prevent this, it is a conventional method to selectively add at least one biocidal agent to the coating solution. Preferred fungicides are 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazoline 3-one (2-methyl-4-isothiazolin-3-one), or 1- (3-chloroaryl) -3,5,7-triaza-1-azoniaadamantane chloride [1- (3- chloroallyl) -3,5,7-triaza-1-azoniaadamantane chloride]. Representative fungicides that do not degrade the performance of the dried primer layer in the coated articles of the present invention are Kathon® LX (Rome and Haas) fungicides.

Another embodiment of a vinyl polymer useful in the primer composition is a straight or branched poly (para-hydroxystyrene; PHS) or variant thereof. There are many variations of PHS that are commercially available and / or known in the art. For example, the above PHS variants differ in properties such as molecular weight, impurity and degree of brancing. The examples below use several variants of poly (para-hydroxystyrene) (branched, straight and partially converted to phenoxide salts), but for example the mole fraction of PHS is at least Other PHS modifications, which are copolymers of 0.75, are expected to function similarly in the primer compositions and methods of the invention.

Preferably, the primer composition containing PHS is characterized by having a solids content between 0.1% and 10% by weight. When the polymer in the primer composition is a PHS variant, the solvent is preferably a dilute aqueous solution of an alkali metal hydroxide. For example, 1 wt% PHS solution can be prepared using 0.1 N concentration of lithium (or sodium or potassium) hydroxide. In this solvent, the PHS is partially converted to alkali metal (eg lithium) phenoxide salts. The linear or branched optional copolymer thus produced has the following structural formula.

Here, M ⁺ is a monovalent cation (for example, Li ⁺ ), and the sum of n and p, which is a mole fraction, is 1. P, the mole fraction of the phenoxide salt, can be adjusted by adjusting the concentration of the alkali metal hydroxide.

Dynamic contact angle experiments show that using a PHS solution of 0.1 N LiOH to form a primer layer on corona treated and biaxially oriented polypropylene (BOPP) films provides a surface that is completely wetted with water. Shows. In addition, metal copolysilicate coatings have been found to wet the primed surface very well, and the barrier layer thus prepared provides excellent vapor barrier performance. For solutions with smaller amounts of base, a co-solvent is needed to completely dissolve the PHS. Such co-solvents can be readily selected by one skilled in the art. One exemplary suitable co-solvent is isopropanol. Alternatively, PHS can simply be dissolved in alcohol (alone or in mixtures) such as ethanol, propanol, butanol, isopropanol (2-propanol) and similar alcohols. Neutral PHS solutions prepared using high purity PHS (eg, Hoechst Celanese Electronic Grade) produce a layer of neutral PHS polymer exhibiting wettability dependent on time and pH. Solutions with a pH greater than 12 completely wet the neutral primer layer. PHS primer solutions prepared using low purity PHS (eg, Hoechst Celanese Polymer Grade) produce primer layers that can be equally wetted at any pH of 7 or more.

Optionally, the primer solution contains one or more surfactants that reduce the surface tension regardless of the type of primer polymer. No surfactant is required when applying the primer by spin coating, but it is known that the wetting conditions are more stringent when the primer is applied by a roll coating method such as reverse gravure coating. Suitable surfactants can be selected by one skilled in the art. The chosen surfactant should have a critical micelle concentration low enough so that the dry primer coating is not damaged by the residual surfactant. Surfactants include acetylenic diols (such as those provided commercially by Air Products) and alkyl ethoxylates (among others provided by Hoechst Celanese). Preferred surfactant in the group of acetylenic diols is Dynol® 604 surfactant and the preferred surfactant in the alkyl ethoxylate group is Genapol. (Registered trademark) UD050 Surfactant The amount of surfactant added to the primer composition depends on the specific surfactant selected, but the polyolefin substrate should be the minimum amount that the primer solution can adequately wet. The amount of active agent may be about 0.1% by weight of acetylenic diol or alkyl ethoxylate. Because the Inol® 604 surfactant is poorly soluble in water, primer solutions containing 0.1% of Dynol® 604 surfactant may be a small amount of undispersed surfactant that floats on the surface of the primer solution. It has been observed to have water droplets, which cause debris to form around the meniscus of the coating solution in containers such as jars, drums, and tanks containing the solution. This is alleviated by the addition of a second surfactant, preferably Genapol UD050 surfactant, to improve the dispersion of the Dinol® 604 surfactant in the primer solution.

II. Aqueous Inorganic Barrier Coating Compositions Useful in the Present Invention

The process of the present invention is useful for various aqueous inorganic barrier coating compositions that act as barriers to gases, vapors, and aromas, as described below.

The term "waterborne" means a coating that is applied from a solution that is primarily water but may contain a smaller amount of auxiliary solvent, such as but not limited to isopropanol.

The term "vapor" means a liquid in partial pressure, such as water vapor. The term "gas" includes oxygen, nitrogen, carbon dioxide, and the like. The term "aroma" includes odorous substances, such as menthol. For simplicity, as used herein, the term "vapor barrier" may be interpreted to mean barriers to gases and aromas as well as steam as defined in the prior art.

Similar to the term used herein, the term "solution" is to be interpreted to include colloidal dispersions and suspensions. By "colloidal dispersion and colloidal suspension" is meant any dispersion or suspension of particles in a liquid, wherein the particles are larger in size than molecules that do not sink. Generally, the particle size of the suspensions or dispersions of the present invention is about 10 to about 50,000 angstroms. As used herein, "coating solution" means a liquid that contains a solid that does not sink or is suspended and that is used to apply the solid to a substrate.

In one embodiment, the aqueous inorganic coating contains alkali metal polysilicates such as sodium polysilicate, potassium polysilicate, lithium polysilicate or mixtures thereof.

In another embodiment, the coating solution contains a copolysilicate, ie a mixture of two different alkali metal polysilicates. In a preferred embodiment, the barrier coating solution is formula (Li ₂ O) _x (K ₂ O) _1-x (SiO ₂ ) _y (y is greater than 4.6 if x is less than 1, or if y is 1-10, x is Copolysilicates of lithium and potassium, expressed as greater than 0.5).

Another preferred barrier coating is a silicate of selected layer structure (e.g., flaky Vermiculite MicroLite® from WR Grace) dispersed in a solid matrix of alkali metal polysilicates (or mixtures thereof). Product}, the weight percent of the layer structure silicate in the dried barrier coating layer is 1% to 99%.

Specific formulations of suitable barrier coatings for use in the compositions and methods of the present invention are described in more detail in the Examples below.

III. Conduct of method

Advantageously, when carrying out the process of the invention, the primer composition enhances the good wetting of the coating solution which is subsequently applied to the substrate and promotes good adhesion of the dried inorganic barrier layer. The above advantages with respect to adhesion are demonstrated in the improved vapor barrier performance of coated articles made according to the process of the invention.

A. Substrate

The process of the present invention is directed to polymers such as polyolefins (particularly polyethylene, polypropylene, copolymers thereof) and cycloolefin copolymers (COC) (such as copolymers of ethylene and norbornene (US Pat. No. 5,087,677)). It is particularly suitable for use in substrates. Typically, polypropylene films are axially oriented according to customer requirements. Articles coated in this manner include, but are not limited to, polymeric films and sheets, rigid and semi-rigid containers, and other surfaces. Particularly preferred articles for coating according to the method of the invention are films, bottles, plastic containers, jars, blisterpacks and lidstocks made of the above polymers. In a particularly preferred embodiment, the article is a film or bottle used for food storage.

The polymeric article to be coated with the primer and coating composition according to the invention may not be pretreated. Often, polymeric articles, such as films or bottles, are first plasma treated to improve the wetting by the primer solution and the adhesion of the dried primer layer. Alternatively, the polymeric article may be corona treated with a corona discharge treatment method widely used in the industry. Suitable other surface treatments that may occur prior to application of the primer layer are flame treatment and chemical oxidation or etching. Optionally, after applying and drying the primer solution and before applying the barrier coating solution, the dried primer layer may be plasma treated, corona treated, flame treated, or chemically oxidized or etched. Alternatively, the article may have a heat seal layer on at least one surface or side. Examples of such thermally adhesive layers are ethylene-propylene copolymers or ethylene-propylene-butylene terpolymers.

Exemplary polyolefin substrates used in the examples below are biaxially oriented polypropylene (BOPP) films of the FND xx and SCM xx grades made by Trespaphan GmbH. The number xx represents the film thickness in micrometers. FND 30 is therefore a 30 μm (or 1.2 mil) thick BOPP film. Such films are covered with metal by thermal or electron-beam deposition of aluminum. BOPP films of FND and SCM grades are three-layer laminates covered with a thin heat-adhesive layer on both sides. One side of the film is corona treated at the factory with a surface energy of 36-39 dynes / cm to improve the adhesion of aluminum. Additional corona treatments, which are performed immediately prior to application of the primer solution, have also been found to be beneficial for such films that have been corona treated at the factory. Similar polypropylene films suitable and commercially useful in the present invention include AQS, MT BASE, and MTV BASE films (AET packaging films). All of these have heat-adhesive layers on only one side and, in the case of AQS, high energy treated surfaces for aqueous coatings. All of them will be coated on the opposite side of the heat tight layer.

B. Application of Primer

In a preferred embodiment, a primer solution is applied over the substrate to provide a dry layer of primer composition having a thickness of about 10 to about 50 nm. Thicker layers provide satisfactory but not good performance and are therefore undesirable in terms of cost. Primers can be applied by any technique known to those skilled in the art. Such techniques include, but are not limited to, roll coating, spray coating, and dip coating techniques. Conventional roll coating techniques employ rod, roll, reverse roll, forward roll, air knife, knife on roll, blade, gravure and slot die coating methods. Including but not limited to. General descriptions of this type of coating method are given in contemporary coating and drying technology (E. Cohen and E. Gutoff, eds; VCH Publishers) published in New York in 1992 and New York in 1984. It can be found in references such as web processing and transformation technologies and devices (D. Satas, ed; Van Nostrand Reinhold). The three-dimensional article can be coated by spray coating or dip coating. The application method does not limit the present invention, but may be selected from the above and other known methods by those skilled in the art.

Preferred primer layers applied according to the process of the invention are practically continuous, ie almost no polyolefin is exposed to the barrier coating solution. Dewetting of the primer solution from the substrate prior to or during drying results in voids in the primer layer and thus in the barrier layer. This results in a finished product with inferior (but in some cases satisfactory) vapor barrier performance. In extreme cases it has been observed that the removal of the primer solution is mostly uncovered but can simply result in a polyolefin substrate decorated with particles of primer material. Atomic force microscopy can be used to confirm that the dried primer layer is indeed continuous. This removal of the primer solution can be minimized by increasing the treatment of the polyolefin substrate or increasing the concentration of the surfactant, or increasing the viscosity of the primer solution before applying the primer solution. Increasing the concentration of the surfactant, or increasing the viscosity of the primer solution, can be easily accomplished by using PVOH grades of high molecular weight and increasing the proportion of PVOH solids in the primer solution.

The primer layer is dried before applying the aqueous inorganic coating layer. The conventional coating thickness of the selected aqueous inorganic oxide coating solution is applied to the primer layer, ie the typical coating thickness used in the absence of a primer such as about 100 to about 500 nm at the substrate surface. Application of the coating solution may be carried out in the manner described above for applying the primer composition.

After coating the article with the barrier coating solution, the product obtained should be dried at room temperature or above a selected temperature. The choice of drying temperature depends on the desired drying time; In other words, the drying time can be reduced by increasing the temperature, but if it takes a long time to dry, there is no need to increase the temperature. However, those skilled in the art can easily adjust the temperature and exposure of the oven as desired. The performance of the dried barrier coating is not affected by drying temperatures over 25-200 ° C. One advantage of the method is that both the primer and barrier coating can be dried at the low temperatures (<100 ° C.) required for roll-coating the polypropylene film.

As an example, the final article (e.g. BOPP film, thickness of 0.0025 cm (1 mil)) coated by the invention of the method is 50 cm ³ / [m ² day atm at 23 ° C. and 50% relative humidity. Has an oxygen transmission rate (OTR) of less than]. If desired, an OTR of about 20 cm ³ / [m ² day atm] can be achieved at 23 ° C. and 50% relative humidity. This performance can be obtained more reproducibly in pilot scale reverse gravure coating than in spin-coating experiments.

If the dried barrier coating is covered with a protective top-coat layer, significantly improved performance can be obtained. The epidermal layer is either a thin (but not necessarily large, 1-10 μm thick) coating or a laminated film. Thin top-coating may be applied by various coating methods such as roll coating, spray coating, dip coating. Laminates may be prepared through melt-extrusion lamination to the barrier coating or through adhesive lamination of the second film. The coating film prepared according to the method (BOPP film) achieved an OTR of about 10 cm ³ / [m ² day atm] at 23 ° C. and 50% relative humidity when a protective skin layer was provided. The epidermal layer further provides improved flex resistance (ie, maintenance of vapor barrier performance after bending) and moisture resistance (ie, maintenance of vapor barrier performance at high relative humidity).

The following examples illustrate the preferred compositions and methods of the present invention. These examples are illustrative only and do not limit the scope of the present invention.

(Example)

Example 1: Preparation of aqueous poly (para-hydroxystyrene) primer

An aqueous base solution of the exemplary poly (para-hydroxystyrene) primer (denoted PHS-Li) was prepared as follows. A 0.1 N (normal) lithium hydroxide solution was prepared by dissolving 4.19 g of lithium hydroxide monohydrate in sufficient distilled water to make 100.0 ml of solution. A 1 wt% PHS-Li solution was prepared by adding finely ground 1.00 g of PHS (Hoechst Celanese, polymer grade) to 99.0 g of 0.1 N lithium hydroxide solution and heating at 50 ° C. until the solids dissolved. The resulting brown-orange solution was filtered through wrinkled manure paper before use. After long standing, the color of the solution changes from orange-brown to green-brown, but does not affect the performance of the solution as a primer for the metal polysilicate barrier coating.

Example 2: Preparation of Poly (para-hydroxystyrene) Primer Solution Based on Solvent

An exemplary alcohol primer solution (PHS-OH) of poly (para-hydroxystyrene) was prepared as follows. A 1 wt% PHS-OH solution was prepared by adding 1.00 g of finely ground PHS (Hoechst Celanese, polymer grade) to a sufficient amount of 2-propanol to make 100.0 ml of solution. The mixture was heated at 50 ° C. until the solids dissolved. The resulting pale orange solution was filtered through wrinkled manure paper before use. Color variations similar to those described in Example 1 occur in these solutions but are lesser and do not affect the performance of the solution as a primer for metal polysilicate barrier coatings.

Example 3: Effect of Lithium Hydroxide on the Composition of a Dried PHS Primer Layer

The dry primer layer prepared using PHS dissolved in aqueous lithium hydroxide is different from the dry primer layer prepared using PHS dissolved in isopropanol. The inventors found that the primer layer attached from the PHS / aqueous base primer was not neutral PHS but part of the weak acid phenol moiety which was converted to phenoxide in the presence of lithium hydroxide. X-ray photoelectron spectroscopy (XPS) measurements can be performed by the lithium hydroxide solution of PHS described in Example 1 above (denoted as PHS-Li, indicating partial conversion to polymer Li phenoxide salts) or Example 2. A BOPP film (Trespaphan® FND 30 grade) primed with a 1 wt% PHS solution (denoted PHS-OH, meaning neutral phenolic polymer) in isopropanol as described above. The basic composition of the surface was determined and averaged at three separate points of each sample. The agreement at these three points is exceptional (standard deviation ≤ 0.7%), demonstrating the high uniformity of the side compositions in the dried primer layer.

As can be seen in Table 1, the carbon / oxygen ratio observed by XPS fits well with the calculated ratio for the PHS polymer chain having the formula (C ₈ H ₈ O) _n . The hydrogen atom cannot be detected by XPS. For PHS-Li coating the carbon / oxygen ratio obtained by XPS is 2.9. As shown in Table 1, this value is lower than the ratio 3.6 that can be expected in a coating consisting entirely of PHS and LiOH as described above. Because of the hydrophilic nature of PHS and LiOH, it is reasonable to assume that some water is retained in the coating. Assuming that one equivalent of water per lithium ion is maintained by the coating, the carbon / oxygen ratio fits better with the experiment.

In the PHS-OH spectrum, one peak by oxygen is observed at 533.8 eV, which may be due to covalently bound oxygen (eg phenol). A second peak in the PHS-Li sample is observed at 532.6 eV, consistent with the ionic oxide species (eg lithium phenoxide or hydroxide). The relative abundance of the two species is 55.5 to 44.5, with more being ionic.

Example 4: Preparation of Poly (vinyl Alcohol) Primer Solution

An exemplary poly (vinyl alcohol) (PVOH) primer solution of the present invention was prepared as follows. 1 g of PVOH {Aldrich, 98-99% hydrolysis, molecular weight M _v = 85,000-146,000} was added to 99.0 g of distilled water in a round bottom flask. The mixture was heated at 80 ° C. and stirred until the polymer completely dissolved. Pure aqueous solution was obtained by filtration of the hot solution through the creased filter paper. The primer solution without surfactants was found to be satisfactory in spin-coating experiments but not roll-coating.

Example 5: Characterization of PVOH Primer Solutions Containing Side Chain Alkyl Ethoxylate Surfactants

This example illustrates the use of branched alkyl ethoxylate surfactants in poly (vinyl alcohol) primer solutions. PVOH primers were prepared using high purity water (Fischer Scientific, Optima® grade) as in Example 4 in a volumetric flask.

The surface tension of the liquid, γ _1v, was measured using an automated Wilhelmy plate surface tension meter (ATI Cahn DCA 315) with an automatic titrator for adding surfactant. Initially the surface tension was measured without surfactants, and Genapol® UD050 branched alkyl ethoxylate surfactant (Hoechst Celanese Corp) was added slowly and then surface tension was measured. Table 2 shows surface tension data.

PVOH has a fairly large intrinsic surface activity that lowers the surface tension of water up to 8 dynes / cm, but the data show that the branched alkyl ethoxylate surfactants perform almost the same in primer solutions as in pure water. Can be. The critical micelle concentration (cmc = 0.11 g / l) and the surface tension convergence value (approximately 27 dynes / cm) are almost the same with or without PVOH, with slight differences in the surface activity of PVOH. Because of the increase. There is no harmful or synergistic reaction between PVOH and Xenapol® UD050 surfactant.

Example 6: Characteristics of PVOH Primer Solutions Containing Straight Alkyl Ethoxylate Surfactants

This experiment demonstrates the use of linear alkyl ethoxylate surfactants in PVOH primer solutions. Three primer solutions (1.0% w / w, 2.0% w / w, 3.0% w / w) were prepared as described in Example 4 for this experiment.

The surface tension, γ _1v of the liquid was measured as described in Example 5 with the slow addition of Xenapol® 26-L-60N linear alkyl ethoxylate surfactant (Hoechst Celanese). Table 3 shows the surface tension data. Above the critical micelle concentration (cmc = 0.01 g / l), it can be seen from Table 3 that it is independent of PVOH and that the convergence value of surface tension (γ _1v up to 31 dynes / cm) is similarly independent of the concentration of PVOH. . There is no evidence of harmful or synergistic reactions between PVOH and Xenapol® 26-L-60N surfactants.

Example 7: Wetability of Primed Substrate Evaluated by Measuring Static Contact Angle with Water

A 4 inch (10.16 cm) circle was cut using a scalpel from this axially oriented polypropylene (BOPP) film (Trespaphan® FND grade). All dust on the film was also removed by the jet of filtered clean air. The film was immediately coated with one of the primer solutions disclosed in Examples 1-6 or coated with one of the primer solutions disclosed in Examples 1-6 after the corona discharge treatment. Additional corona treatment was performed using a Tantec Lab System II corona processor using ceramic electrodes with a 2 mm spacing. The power setting was 90% and the electrode was scanned over the film surface by hand for 20 seconds (about 10 times).

About 10 g of primer solution was dispensed onto the polypropylene film. Immediately following a spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried for up to 30 seconds in an oven kept at 50 ° C. Several coating film samples were prepared using each coating solution.

Static water contact angles were measured using a contact angle meter from Camtec-Tlm®. The static contact angle results measured for polypropylene are shown in Table 4 and compared with the static water contact angle for the uncoated polypropylene film.

The data show that the lithium hydroxide of the PHS primer coating significantly reduces the measured static contact angle of water and, by inference, the measured static contact angle of the metal polysilicate barrier coating aqueous solution, which in particular does not contain a surfactant.

Example 8: Wetness of poly (vinyl alcohol) / poly (vinyl butyral) primer layer

A series of primer solutions were prepared using butyral-modified PVOH polymers represented by the following structural formula.

Where n, p and r represent the mole fraction of polymer repeating units and the sum of n, p and r is one. These polymers, further described in Table 5, were dissolved in water, isopropanol, or a mixture of water / isopropanol. No surfactant was added to the primer solution. Wetness of the primer layer prepared from this solution was measured by dynamic contact angle analysis. Primed samples were prepared by dip-coating a microscope cover slip purified by flame into the primer solution. The increasing and decreasing contact angle of water in this primer layer was measured by a Cahn-ATI DCA 315 dynamic contact angle analyzer. The results are shown in Table 5. Unsatisfactory wetting was observed at n> 0.70.

Example 9: Oxygen Permeability of an PHS Primed Article Prepared by Spin-Coating

This example is the formula _{(Li 2 O) x (K} 2 O) 1-x (SiO 2) Li _y - of that typical for the production of potassium co-polysilicate, wherein the total solids level is 10% by weight, Li ₂ O The mole fraction x is 0.5 and y, the molar ratio of SiO ₂ to the bound alkali metal oxide, is 3.64. The lithium polysilicate used was an Inobond® Li 2043 lithium polysilicate solution (van Baerle) containing 3.0% w / w Li ₂ O and 24.5% w / w SiO ₂ . The potassium polysilicate used was a K-4009 potassium polysilicate solution (van Baerle) containing 13.0% w / w K ₂ O and 26.85% w / w SiO ₂ . 53.1 g of Inobond® Li 2043 solution was diluted with 108.1 g of distilled water with continued stirring, followed by the addition of 38.8 g of K-4009 polysilicate. The dispersion was stirred overnight and filtered through Celite® 545 diatomaceous earth.

A 4 inch (10.16 cm) circle was cut using a scalpel from Trespapan® FND 30 BOPP film. All dust on the film was also removed by the jet of filtered clean air. About 10 g of one of the primer solutions described in Examples 1 and 2 was dispensed onto the BOPP film. Immediately following a spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried for about 30 seconds in an oven kept at 50 ° C.

About 10 g of (Li ₂ O) _x (K ₂ O) _1-x (SiO ₂ ) _y copolysilicate coating solution (x = 0.5, y = 3.64) was distributed to the primed side of the polypropylene film after the priming process. . Immediately following a spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried for about 30 seconds in an oven kept at 50 ° C.

Oxygen transmittance (OTR) was measured using a Mocon® 2/20 instrument. Measurements were made for each sample at 30 ° C. and relative humidity of 0%, 40% and 90%. The results are shown in Table 6.

Example 10 Oxygen Permeability of PVOH Prime Articles Prepared by Spin-Coating

A 4 inch (10.16 cm) circle was cut using a scalpel from this axially oriented polypropylene (BOPP) film (Trespaphan® FND grade). All dust on the film was also removed by the jet of filtered clean air. Corona treatment was performed using a Tantec Lab System II corona processor using ceramic electrodes with a spacing of 2 mm. The power setting was 90% and the electrode was scanned over the film surface using the hand for 20 seconds (about 10 times). About 10 g of the PVOH primer solution described in Example 4 was administered onto a polypropylene film. Immediately following a spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried for about 30 seconds in an oven kept at 50 ° C.

After the prime process, about 10 g of the copolysilicate coating solution described in Example 9 was dispensed on the prime side of the polypropylene film. Immediately following a spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried again for up to 30 seconds in an oven kept at 50 ° C.

Oxygen transmission rate (OTR) was measured at several relative humidity using a Mocon Ox-Tran® 2/20 instrument. The results are shown in Table 7.

Example 11: Comparative Example of Barrier Coating Performance on an Unprimed BOPP Film

This example is a lithium-potassium copolysilicate further comprising an acetylenic diol surfactant, (Li ₂ O) _x (K ₂ O) _1-x (SiO ₂ ) _y (10% total solids, x = 0.5, y = 3.64). Surfactants are necessary to obtain satisfactory wetting of the barrier coating solution on the unprimed BOPP film. A 1 wt% dispersion of Dinol® 604 Acetylene Diol Surfactant (Air Products) was prepared by dispersing 1.00 g of Dinol® 604 surfactant in sufficient distilled water to make 100 ml of total dispersion. . The dispersion was vigorously stirred just before use.

With continued stirring, 53.1 g of Inobond® Li 2043 solution was diluted with 108.1 g of distilled water followed by 38.8 g of K-4009 solution. To this was added 2.0 g of a well stirred surfactant dispersion to make a copolysilicate barrier coating solution having a surfactant concentration of 0.01% by weight.

A 4 inch (10.16 cm) circle was cut using a scalpel from Trespaphan® FND 15 BOPP film. All dust on the film was also removed by the jet of filtered clean air. Corona treatment was performed using a Tantec Lab System II corona processor using ceramic electrodes with a spacing of 2 mm. The power setting was 90% and the electrode was scanned over the film surface using the hand for 20 seconds (about 10 times). About 10 g of copolysilicate blocking solution was dispensed to the corona treated surface of the BOPP film. Immediately following the spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried for up to 30 seconds in an oven kept at 50 ° C.

Oxygen transmittance (OTR) was measured using a Mocon Ox-Tran® 2/20 instrument. An OTR of 429 cm ³ / [m ² day atm] was measured at 30 ° C. and 0% relative humidity for samples prepared in this manner.

Example 12: Comparative example of barrier coating performance on unprimed BOPP film

Barrier coating solutions were prepared as described in Example 11. The film was spin-coated as described in Example 11 except that no corona treatment occurred on this film. Oxygen transmittance (OTR) was measured using a Mocon Ox-Tran® 2/20 instrument. An OTR of 3221 cm ³ / [m ² day atm] was measured at 30 ° C. and 0% relative humidity for samples prepared in this way. This is substantially the same as the OTR of an uncoated Trespaphan® FND 15 BOPP film.

Example 13: Preparation of an article coated with a barrier layer containing delaminated vermiculite (weathered biotite broken into pieces)

Lithium polysilicate and MicroLite® 963 Plus + grade colloidal solution of dispersed vermiculite was first diluted with water using the reagents and contents listed in Table 8, followed by lithium polysilicate. Prepared by adding the silicate solution with stirring. The solution was stirred for 30 minutes immediately before coating and was not filtered.

A 4 inch (10.16 cm) circle was cut using a scalpel from Trespaphan® FND 15 BOPP film. All dust on the film was also removed by the jet of filtered clean air. The film was corona treated to enhance the wetting by the primer solution and to improve the adhesion of the dried primer layer. Corona treatment was performed using a Tantec Lab System II corona processor using a 2 mm ceramic electrode. The power setting was 90% and the electrode was scanned over the film surface using the hand for 20 seconds (about 10 times).

About 10 g of PHS-Li primer solution described in Example 1 was dispensed onto the polypropylene film. Immediately following the spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried for up to 30 seconds in an oven kept at 50 ° C.

After the prime process, about 10 g of one of the copolysilicate / vermiculite dispersions described in Table 8 was dispensed onto the primed side of the polypropylene film. Immediately following a spread cycle of 300 rpm for 1 second followed by a spin cycle of 2000 rpm for 10 seconds. The coated film was dried again for up to 120 seconds in an oven kept at 50 ° C.

Oxygen permeability (OTR) was measured using a Mocon Ox-Tran® 2/20 instrument at 30 ° C. under dry conditions. OTR data is shown in Table 8.

Example 14 Preparation of an article coated with a barrier layer containing flaky vermiculite

An aqueous colloidal suspension containing lithium polysilicate and Microlite® 963 plus + grade of dispersed vermiculite (40 wt.% Of the coating solid is lithium polysilicate) was prepared according to the formulation provided in Example 13. BOPP film samples were prepared for coating, primed with 1 wt% PHS-Li solution, and coated with a polysilicate / vermiculite coating, according to the procedure described in Example 13.

Oxygen transmission was measured for one representative film at several relative humidity. OTR was measured first under dry conditions and then when relative humidity was increased. The film was not taken out of the sample chamber between each measurement. At the end of the test at 90% relative humidity, the sample chamber returned to dry conditions and the OTR was measured again. OTR results are shown in Table 9.

Example 15: Preparation of an article coated with a barrier layer containing flaky vermiculite

An aqueous colloidal suspension containing lithium polysilicate and Microlite® 963 plus + grade dispersed vermiculite (10 wt.% Of the coating solids is lithium polysilicate) was prepared according to the formulation provided in Example 13. BOPP film samples were prepared for coating, primed with 1 wt.% PHS-Li solution, and coated with a polysilicate / vermiculite coating, following the procedure described in Example 13.

OTR was measured for one representative film at different relative humidity. OTR was first measured at dry conditions and then at increased relative humidity. The film was not taken out of the sample chamber between each measurement. At the end of the test at 90% relative humidity, the sample chamber returned to dry conditions and the OTR was measured again. OTR results are shown in Table 10.

Example 16: Application of Primer and Barrier Coating Solutions by Reverse Gravure Coating Process

Lithium polysilicate / dispersed vermiculite solution was prepared using the amounts shown in Table 11 and using the process described in Example 13. The BOPP film is subjected to a multi-stage reverse gravure roll coater with in-line corona treatment to apply a primer layer of either PHS-Li {containing 0.1% Dynol® 604 surfactant} or PVOH. After drying, lithium polysilicate / dispersed vermiculite coating solution was applied and dried when coated using a reverse gravure coating process.

OTR was measured using a Mocon Ox-Tran® 2/20 instrument at 30 ° C. under dry conditions. OTR data is shown in Table 11.

Example 17 Application of PVOH Primer and Barrier Coating Solution by Reverse Gravure Coating Process

PVOH primers with 1% solids were prepared by dissolving 190 g of PVOH (Mv = 31,000-50,000, 98-99% hydrolysis) in 19 kg of water with heating to 75 ° C. The PVOH solution was cooled and transferred to a high density polyethylene (HDPE) reagent bottle (carboy) with 19 g of Dynol® 604 surfactant and 19 g of Xenapol® UD050 surfactant under constant stirring. Added. The surface tension of the primer solution containing 1% PVOH, 0.1% Dinol® 604 surfactant, and 0.1% Xenapol® UD050 surfactant was 26.8 dynes / cm.

A series of lithium-potassium copolysilicate barrier coating solutions of the formula (Li ₂ O) _x (K ₂ O) _1-x (SiO ₂ ) _{y where} x = 0.5, y = 3.64 was solids content by the method disclosed in Example 9. To 3%, 6%, 9%, 12% and 15%.

The primer was applied to the Trespapan® FND 20 BOPP film {0.002 cm (0.8 mil) thick) of cotton corona treated at the factory by reverse gravure coating without additional corona treatment. The primer solution soaks the BOPP film very well. The ceramic coated gravure cylinder had a laser engraved pattern rotated 60 ° about the cylinder axis, 220 lines per inch, and a cell volume of 10 billion cubic microns per square inch. The primer solution was applied at a line speed of 500 feet / minute (152.4 m / min) and dried up to 55 ° C. in a 50 feet air flotation dryer.

Lithium-potassium copolysilicate barrier coating was also applied to the BOPP film primed with PVOH using the same reverse gravure coating parameters above except that the line speed was 200 feet / minute (61.0 m / min).

OTR was measured at 23 ° C. and 50% relative humidity using a Mocon Ox-Tran® 2/20 instrument. OTR data is shown in Table 12.

Example 18 Application of Fungicide-Containing PVOH Primer Solution Through a Reverse Gravure Coating Process

A PVOH primer with 1% solids containing the Katton® LX fungicide (1.5% solution, Rohm and Hass) was 190 g of PVOH (Mv = 31,000-50,000, 98-99% in 18.772 kg of water). Hydrolysis) to dissolve while heating to 70 ° C. The PVOH solution was filtered, cooled and transferred to a high density polyethylene (HDPE) reagent bottle, followed by 19 g of Dynol® 604 surfactant, 19 g of Xenapol® UD050 surfactant and 0.75 with continued stirring. g Carton® LX fungicide was added.

A lithium-potassium copolysilicate barrier coating solution with 12% solids of the formula (Li ₂ O) _x (K ₂ O) _1-x (SiO ₂ ) _y where x = 0.5, y = 3.64 is described in Example 9. Was prepared through.

The primer was applied to Trespapan® FND 20 BOPP film {0.002 cm (0.8 mil) thick) via reverse gravure coating. The side of the film that was corona treated at the factory was primed without further corona treatment. The ceramic coated gravure cylinder had a laser engraved pattern rotated 60 ° from the cylinder axis and 220 lines per inch and a cell volume of 10 billion cubic microns per square inch. The primer solution was applied at a linear speed of 500 feet / minute (152.4 m / min) and dried at up to 55 ° C. with a 50 feet air suspension dryer.

Lithium-potassium copolysilicate barrier coatings are PVOH prime using the same reverse gravure coating parameters except that the cell volume is 15 billion cubic microns per square inch and the line speed is 200 feet / minute (61.0 m / min). To the BOPP film.

OTR was measured using a Mocon Ox-Tran® 2/20 instrument. Four measurements on samples from the film rolls showed an OTR value of 18 ± 2 cm ³ / [m ² day atm] at 23 ° C. and 50% relative humidity.

Example 19: Comparative Example of PVOH Primer Solution Application by Reverse Gravure Coating Process

PVOH primers were prepared by dissolving 80 g of PVOH (Mv = 85,000-146,000, 98-99% hydrolysis) in 4000 g of deionized water while heating to 85 ° C. The PVOH solution was filtered through pleated manure paper while hot. After cooling 4000 g of deionized water was added with constant stirring followed by 1.6 g of Zenapol® UD050 surfactant. The surface tension of the primer solution containing 1% PVOH and 0.02% Xenapol® UD050 surfactant was 28.0 ± 0.2 dynes / cm.

PVOH primers were applied to Trespapan® FND 20 BOPP film {thickness of 0.002 cm (0.8 mil)} by reverse gravure coating. The side of the corona treated film at the factory was primed without further corona treatment. The ceramic coated gravure cylinder had a laser engraved pattern rotated 60 ° about the cylinder axis, and 220 lines per inch and a cell volume of 10 billion cubic microns per square inch. The primer solution was applied at a linear speed of 150 feet / minute (45.7 m / min) and dried at up to 80 ° C. with a 50 feet air suspension dryer.

The primer solution was thoroughly liquid removed from the BOPP film prior to entering the dryer, resulting in a prime film largely uncoated but decorated with PVOH particles.

Example 20: Comparative Example of PVOH Primer Solution Application by Reverse Gravure Coating Process

PVOH primers were prepared by dissolving 80 g of PVOH (Mv = 31,000-50,000, 99% hydrolysis) in 4000 g of deionized water while heating to 70 ° C. After cooling 4000 g of deionized water was added with constant stirring followed by 8 g of Dinol® 604 surfactant. The primer solution containing 1% PVOH and 0.1% Dynol® 604 surfactant had a surface tension of 25.8 ± 0.1 dynes / cm. An undispersed Dinol® 604 surfactant drop accumulated on the surface of the primer in the reagent bottle.

PVOH primers were applied to Trespapan® FND 20 BOPP film {thickness of 0.002 cm (0.8 mil)} by reverse gravure coating. The side of the corona treated film at the factory was primed without further corona treatment. The ceramic coated gravure cylinder had a laser engraved pattern rotated 60 ° about the cylinder axis, and 220 lines per inch and a cell volume of 10 billion cubic microns per square inch. The primer solution was applied at a linear speed of 150 feet / minute (45.7 m / min) and dried at up to 80 ° C. with a 50 feet air suspension dryer.

The PVOH primer solution wets the BOPP film well, but ultimately forms unmarked marks in the gravure cylinder, which appears to be due to undispersed drops of Dinol® 604 surfactant. This prevented subsequent subsequent application of the barrier coating solution.

Many modifications and variations of the present invention are included in the same specification as above and will be apparent to those skilled in the art. Such changes and modifications to the compositions and processes of the invention are considered to be within the scope of the appended claims.

Claims (32)

A polyolefin article coated with a barrier, (a) a polyolefin substrate, (b) a primer layer comprising any vinyl polymer composed of repeat units, wherein at least 75% of the polymer repeat units have a side group having a hydroxyl moiety; Wherein the solids content of the primer layer is from about 1 wt% to about 10 wt%, the primer layer containing at least one surfactant, (c) with an inorganic copolysilicate barrier layer applied from an aqueous coating solution. A barrier coated polyolefin article. The polyolefin article according to claim 1, wherein the polyolefin substrate is selected from polyethylene, polypropylene, cycloolefin copolymers, and copolymers thereof. 3. The polyolefin article coated with the barrier of claim 2, wherein the substrate is a film comprising a heat seal layer on at least one side. The barrier-coated polyolefin article according to claim 3, wherein the thermally adhesive layer is made of ethylene-propylene copolymer or ethylene-propylene-butylene terpolymer. The barrier coated polyolefin article of claim 1, wherein the polyolefin substrate is plasma treated, corona treated, flame treated or chemically etched / oxidized before the primer layer is applied. The polyolefin article according to claim 1, wherein the primer layer is plasma treated, corona treated, flame treated or chemically etched / oxidized before the inorganic barrier layer is applied. The barrier-coated polyolefin article according to claim 1, wherein the vinyl polymer is poly (vinyl alcohol). 8. The barrier-coated polyolefin article according to claim 7, wherein the average molecular weight of the poly (vinyl alcohol) in the primer composition is between 50,000 and 185,000 and the degree of hydrolysis is at least 75%. The method of claim 1, wherein the optional vinyl polymer has the following formula (n, p and r represents the mole fraction of the polymer repeat unit and the sum of n, p and r is 1), A barrier-coated polyolefin article, which is a modified poly (vinyl alcohol) having a. 10. The barrier coated polyolefin article according to claim 9, wherein the average molecular weight of the modified poly (vinyl alcohol) is between 40,000 and 100,000 and r is at least 0.75. The barrier polymer of claim 1, wherein the vinyl polymer is one of linear poly (para-hydroxystyrene) or branched poly (para-hydroxystyrene). Polyolefin articles. The method of claim 11 wherein the poly (para-hydroxystyrene) is partially alkali metal phenoxide (phenoxide), and converted to a salt, this straight-chain or branched random copolymer thus obtained has the formula (M ⁺ of to is one Is a monovalent cation of the above-mentioned alkali metal lithium, sodium, or potassium, and the sum of the mole fractions n and p is 1), A barrier coated polyolefin article having a. The barrier-coated polyolefin article of claim 1, wherein the at least one surfactant is an acetylenic diol and the second surfactant is an alkyl ethoxylate. The barrier-coated polyolefin article of claim 1, wherein the coating solution comprises sodium polysilicate, potassium polysilicate, lithium polysilicate, or mixtures thereof. The method of claim 14, wherein the coating solution comprises a copolysilicate of lithium and potassium of formula (Li ₂ O) _x (K ₂ O) _1-x (SiO ₂ ) _y , wherein (i) x is less than 1 y is greater than 4.6 and (ii) if y is between 1 and 10, x is greater than 0.5. The method of claim 1, wherein the barrier layer comprises a silicate of a layer structure dispersed in a solid matrix of an alkali metal polysilicate, wherein the weight fraction of the silicate of the layer structure of the alkali metal polysilicate is 0.01 to 0.99 Phosphorus, barrier coated polyolefin article. The barrier-coated polyolefin article of claim 1, further comprising a protective topcoat layer. The barrier-coated polyolefin article of claim 1, wherein the substrate is selected from the group consisting of a polymer film, a polymer sheet, and a rigid or semi-rigid polymer container. A method of providing a barrier coating on a polyolefin substrate, (a) applying to the substrate a primer layer comprising any vinyl polymer composed of repeat units, wherein at least 75% of the polymer repeat units comprise a side group having a hydroxy moiety and the solid of the primer layer Applying a primer layer to the substrate, wherein the content is from about 1% to about 10% by weight and comprises at least one surfactant; (b) drying the primer layer, (c) applying an aqueous coating solution that forms a dried inorganic copolysilicate barrier layer on the dried primer layer. Comprising a barrier coating on the polyolefin substrate. 20. The method of claim 19, further comprising plasma treating, corona treating, flame treating or chemical etching or oxidizing the substrate prior to applying the primer. 20. The barrier of claim 19, further comprising plasma treating, corona treating, flame treating or chemical etching or oxidizing the substrate with a dried primer layer of the substrate prior to applying the barrier coating solution. How to provide a coating. The method of claim 19, wherein the vinyl polymer is poly (vinyl alcohol). The method of claim 22, wherein the average molecular weight of the poly (vinyl alcohol) in the primer layer is between 50,000 and 185,000, and the degree of hydrolysis is at least 75%. The method of claim 19, wherein the optional vinyl polymer has the formula (n, p and r represents the mole fraction of the polymer repeat unit and the sum of n, p and r is 1), A modified poly (vinyl alcohol) having a method for providing a barrier coating on a polyolefin substrate. The method of claim 24, wherein the average molecular weight of the modified poly (vinyl alcohol) is between 40,000 and 100,000 and r is at least 0.75. 20. The method of claim 19, wherein the vinyl polymer is one of straight chain poly (para-hydroxystyrene) or branched poly (para-hydroxystyrene). 27. The poly (para-hydroxystyrene) of claim 26, wherein the poly (para-hydroxystyrene) is partially converted to an alkali metal phenoxide salt, and the linear or branched arbitrary copolymers thus obtained are represented by the formula At least one of sodium, sodium, or potassium, and the sum of mole fractions n and p is 1), Providing a barrier coating to a polyolefin substrate. 19. The method of claim 18, wherein the at least one surfactant is acetylenic diol and the second surfactant is alkyl ethoxylate. 19. The method of claim 18, wherein the coating solution comprises sodium polysilicate, potassium polysilicate, lithium polysilicate, or mixtures thereof. The method of claim 29, wherein the coating solution comprises a copolysilicate of lithium and potassium with the formula (Li ₂ O) _x (K ₂ O) _1-x (SiO ₂ ) _y , wherein x is less than 1 And wherein y is greater than 4.6 and less than or equal to 10. 19. The method of claim 18, wherein the barrier layer comprises a layered silicate dispersed in a solid matrix of an alkali metal polysilicate, wherein the weight fraction of the silicate in the layered structure of the alkali metal polysilicate is 0.01 to 0.99. A method of providing a barrier coating on a polyolefin substrate. 19. The method of claim 18, further comprising applying a protective skin layer to the dried barrier layer.