WO2011003864A1

WO2011003864A1 - Cold-sealable polymer dispersion produced by emulsion polymerization in the presence of an ethylene/(meth)acrylic acid copolymer

Info

Publication number: WO2011003864A1
Application number: PCT/EP2010/059561
Authority: WO
Inventors: Michael Gross; Oral Aydin; Heiko Diehl; Georg Langhauser
Original assignee: Basf Se
Priority date: 2009-07-09
Filing date: 2010-07-05
Publication date: 2011-01-13

Abstract

The invention relates to a cold-sealable composition in the form of an aqueous polymer dispersion, wherein the aqueous polymer dispersion can be produced by emulsion polymerization of radical polymerizable monomers in the presence of at least one ethylene/(meth)acrylic acid copolymer having an acid number between 160 and 230 mg KOH/g as a protective colloid. The invention further relates to the use of the aqueous polymer dispersion for cold sealing, in particular of polymer films, and to corresponding coated polymer films and the use thereof for producing packages.

Description

Cold sealable polymer dispersion prepared by emulsion polymerization in the presence of ethylene / (meth) acrylic acid copolymer

The invention relates to a cold-sealable composition in the form of an aqueous polymer dispersion, wherein the aqueous polymer dispersion can be prepared by emulsion polymerization of free-radically polymerizable monomers in the presence of at least one ethylene / (meth) acrylic acid copolymer as protective colloid, the use of the aqueous polymer dispersion for cold sealing, in particular of polymer films , as well as corresponding coated polymer films and their use for the production of packaging.

Cold-sealable compositions are adhesives that do not feel sticky on a substrate after application and drying, but which adhere to each other when pressed together at room temperature with pressure. They differ from pressure-sensitive adhesives by their absence at room temperature or at most very low tackiness. They differ from heat-sealable compositions in that they can be pressure bonded together without heat activation. Cold-sealable compositions are known, for example, for sealing bagged packaging, in particular for food or other heat-sensitive goods, in the packaging of which the application of heat is undesirable, e.g. Ice cream or chocolate or when fast packaging speeds and high cycle times are required. Because of their non-tacky properties, substrates coated therewith can be rolled on rolls and stored until use, with no adhesion to the opposite other side of the support substrate, preferably provided with a release coating. Typically, for cold seal adhesives, polymer dispersions based on natural rubber latex are used. The disadvantage here is a comparatively high price volatility, natural quality fluctuations of the natural raw material and, above all, the allergenic potential that these natural products contain.

Cold-sealable compositions which are as free as possible of organic solvents, ie aqueous dispersions of polymers which form a cold-sealable coating after drying, are desired. Polymer dispersions which can be prepared by emulsion polymerization generally contain, as a result of the preparation, non-polymeric emulsifiers for stabilizing the dispersions. For some applications, however, emulsifiers are disruptive and undesirable, and emulsifier-free or low-emulsifier systems are desired. It is known that it is also possible to use polymeric protective colloids to stabilize polymer dispersions which can be prepared by emulsion polymerization. For example, WO 2007/085588 describes autoadhesive adhesives which can be prepared by emulsion polymerization, and it is mentioned that protective emulsions can also be used as surface-active compounds in emulsion polymerization, including hydrophilically modified polyolefins, for example acrylic acid. re / ethylene copolymers can act. However, these polymeric additives may adversely affect the application properties of the dispersions for cold seal applications. For example, it has been found that when ethylene / acrylic acid copolymers are used as protective colloids during emulsion polymerization, the rheological properties may be compromised such that the resulting polymer dispersions have such high viscosity that they are unsuitable for common application techniques such as brushing or spraying. Although application of the ethylene / acrylic acid copolymers is possible only after the polymerization has taken place, the adhesive forces which can be achieved by cold sealing can be impaired to such an extent that the specified requirements are not met. In addition, such polymer dispersions are generally not emulsifier-free. In EP 798 357, for another technical field (heat sealing), a process is described using an aqueous polymer dispersion which contains an ethylene copolymer of at least 20% by weight of ethylene and at least 5% by weight of an ethylenically unsaturated acid.

It is an object of the present invention to provide aqueous polymer dispersions which are as low in emulsifier or emulsifier as possible, free of allergenic potential, can be applied well by conventional application techniques (such as printing) (in particular on film substrates) and can be sealed with cold-sealable coatings can form high adhesion forces to themselves, but at the same time are block resistant to release coatings.

The object is achieved according to the invention by a cold-sealable composition in the form of an aqueous polymer dispersion, wherein the aqueous polymer dispersion can be prepared by emulsion polymerization of radically polymerizable monomers in the presence of at least one ethylene / (meth) acrylic acid copolymer having an acid number of 160 to 230 mg KOH / g as a protective colloid. Cold-sealable means that when two coated with a composition according to the invention and dried surfaces when at temperatures below 40 ⁰ C, in particular less than 30 ⁰ C or less 25 ⁰ C, in particular at room temperature (20 ⁰ C) in contact with exerting pressure be brought together, adhere to each other. The adhesion (autoadhesive adhesion) after sealing with 1, 4 bar at 20 ° C is preferably at least 2 N / 15 mm, measured by the method described in the examples for determining the seal strength after storage for one day at room temperature after coating and before sealing and Storage one day after sealing and before measurement (SNF 1 d / 1 d). In practical application, the cold sealing is expediently carried out at ambient temperature, ie generally at temperatures of 10 to 30 ⁰ C, in particular 15 to 25 ⁰ C and at pressures of a few millibar to several bar above normal pressure (1 bar), eg at 0, 01 to 5 bar, in particular from 0.1 to 3 bar above normal pressure. The sealing time, ie the time during which the pressure is maintained is, for example, 0.1 to 20 seconds, in particular 0.1 to 3 seconds, in particular 0.5 seconds are usual.

When "polymer" or "emulsion polymer" is mentioned below, unless expressly stated otherwise, what is meant is the polymerization product formed by emulsion polymerization of the radically polymerizable monomers in the presence of the ethylene / (meth) acrylic acid copolymer.

After application to a substrate and after drying, the polymer dispersions according to the invention form a coating which is preferably auto-adhesive and block-resistant to polyamide surfaces. Autoadhesive means that two coated surfaces are cold sealable against each other. Blocking means that the adhesion of a surface coated and dried with a composition according to the invention to a polyamide surface after loading a circular surface with a diameter of 10 cm at 10 tons for one day at 20 ^° C. is at most 0.1 N / 25 mm, measured according to the method described in the examples.

The polymer dispersions according to the invention are dispersions of polymers in an aqueous medium. This may be e.g. to act completely desalinated water or mixtures of water and a miscible solvent such as methanol, ethanol or tetrahydrofuran. Preferably, no organic solvents are used. The solids contents of the dispersions are preferably from 15 to 75% by weight, preferably from 40 to 60% by weight, in particular greater than 50% by weight. The solids content may e.g. by appropriate adjustment of the amount of water used in the emulsion polymerization and / or the amount of monomers. The average particle size of the polymer particles dispersed in the aqueous dispersion is preferably less than 400 nm, in particular less than 300 nm. More preferably the average particle size is between 140 and 250 nm. By average particle size is meant here the dso value of the particle size distribution, i. 50 wt .-% of the total mass of all particles have a smaller particle diameter than the dso value. The particle size distribution can be determined in a known manner with the analytical ultracentrifuge (W. Mächtle, Makromolekulare Chemie 185 (1984), page 1025-1039). The pH of the polymer dispersion is preferably adjusted to pH greater than 4, in particular to a pH of between 5 and 9.

The composition may consist solely of the water-dispersed polymer and the ethylene / (meth) acrylic acid copolymer for use in the present invention. However, it can also contain other additives, for example fillers, anti-blocking agents, dyes, leveling agents or thickeners. The polymer dispersions according to the invention are preferably emulsifier-poor, ie they contain emulsifiers (non-polymeric, amphiphilic, surface-active substances) in an amount of preferably less than 3 or less than 1% by weight. Particularly preferred are emulsifier-free systems. In one embodiment of the invention, therefore, carried out in the presence of the protective colloid emulsion polymerization emulsifier-free.

In the following, the term "(meth) acrylic ..." and similar terms will be used as a shorthand notation for "acrylic ... or methacrylic ...".

The ethylene / (meth) acrylic acid copolymer is formed from ethylene as the first monomer and from a second monomer type selected from acrylic acid, methacrylic acid or a mixture thereof. In addition, the copolymer may optionally be formed from further, preferably nonionic monomers.

The amount of acid monomer is preferably such that the acid value of the copolymer is from 160 to 230 mg KOH / g. The acid number can be determined by acid / base titration. For an ethylene / methacrylic acid copolymer, this corresponds approximately to a content of methacrylic acid of 25-35% by weight. For an ethylene / acrylic acid copolymer, this corresponds approximately to a content of acrylic acid of 20.5-29.5% by weight.

The ethylene / (meth) acrylic acid copolymer preferably has a melt viscosity at 120 ^° C. in the range of 400-2000 mPa s, for example 800 +/- 100 mPa s. The melt viscosity can be determined with a cone-plate viscometer (ICI Cone & Plate Viscosimeter, Epprecht Instruments + Control AG, measuring body C, 1 1, 72 rpm, stage 2).

The ethylene / (meth) acrylic acid copolymer may optionally be formed from further comonomers, apart from ethylene and (meth) acrylic acid. Preferably, no further comonomers are contained. Most preferably, the copolymer consists only of ethylene and methacrylic acid. If comonomers are included, their amount is preferably at most 15% by weight or at most 10% by weight, e.g. 1-10 wt.%, In each case based on the total amount of monomers. Comonomers are, for example, C1-20 alkyl acrylates, C1-20 alkyl methacrylates, vinyl silanes or vinyl phosphonic acid esters.

In one embodiment, the ethylene / (meth) acrylic acid copolymer is formed from

(a) ethylene,

(b) methacrylic acid in an amount such that the acid number of the copolymer is from 160 to 230 mg KOH / g, and

(c) optionally further nonionic comonomers other than (a) and (b), for example C1-20 alkyl acrylates, C1-20 alkyl methacrylates, vinyl silanes or nylphosphonsäureester in a total amount of 0 to 15 wt.% or a total of 0.1 to 10 wt.%, Based on the sum of the monomers (a) to (c), wherein the ethylene / (meth) acrylic acid copolymer has a melt viscosity of 400 - 2000 mPa s at 120 ⁰ C.

The ethylene / (meth) acrylic acid copolymer is preferably used in amounts of from 0.5 to 60 parts by weight or from 1 to 30 parts by weight, more preferably from 5 to 20 parts by weight (especially when the total solids content of the inventive composition more than 50% by weight), based on 100 parts by weight of the monomers to be polymerized.

The active ingredient of the cold-sealable composition acting as a binder is the polymer which can be prepared by emulsion polymerization of free-radically polymerizable monomers. The polymer is preferably at least 60% by weight, preferably at least 80% by weight, e.g. from 80 to 100% by weight, more preferably at least 90% by weight or to 100% by weight of one or more of the main monomers described below. The main monomers are selected from the group consisting of C 1 -C 20 -alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of 1 alcohols containing up to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers.

To name a few are z. B. (meth) acrylic acid alkyl ester having a Ci-Cio-alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate. In particular, mixtures of (meth) acrylic acid alkyl esters are also suitable. Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are, for. As vinyl laurate, stearate, vinyl propionate, vinyl versatate and vinyl acetate. Suitable vinylaromatic compounds are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile. The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride. To name as vinyl ethers are, for. As vinyl methyl ether or vinyl isobutyl ether. Vinyl ether is preferably from 1 to 4 C-containing alcohols. As hydrocarbons having 4 to 8 carbon atoms and two olefinic double bonds may be mentioned butadiene, isoprene and chloroprene.

Preferred main monomers are the C 1 to C 10 -alkyl acrylates and methacrylates, in particular C 1 to C 8 -alkyl acrylates and methacrylates, and vinylaromatics, in particular styrene and mixtures thereof. Very particular preference is given to methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-hexyl acrylate, octyl acrylate, Acrylate and 2-ethylhexyl acrylate, 2-propylheptyl acrylate, styrene and mixtures of these monomers.

In addition to the major monomers, the polymer may contain other monomers, e.g. Monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called z. For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid. Other monomers are z. As well as hydroxyl-containing monomers, in particular Ci-Cio-hydroxyalkyl (meth) acrylates and (meth) acrylamide. Phenyloxyethylglycol mono- (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, amino (meth) acrylates such as 2-aminoethyl (meth) acrylate may also be mentioned as further monomers. Other monomers which may also be mentioned are crosslinking monomers.

In one embodiment, the polymer may contain hydrophilic groups selected from carboxyl groups, hydroxyl groups, amino groups and carboxamide groups. The content of these hydrophilic groups is in particular 0.001 to 0.5 mol per 100 g of polymer. The content is preferably at least 0.005 mol, particularly preferably at least 0.008 mol and not more than 0.2 mol, in particular not more than 0.1 mol, very particularly preferably not more than 0.05 or 0.03 mol per 100 g / polymer. Particularly preferred are the hydrophilic groups selected from carboxyl groups, hydroxyl groups and carboxamide groups. More preferably, at least 20 mole percent of the total moles of these groups are carboxyl groups. Carboxyl groups are understood as meaning both carboxylic acid groups and their salts. In the case of the salts, these are preferably salts with volatile bases, eg. B. ammonia. The hydrophilic groups can be bound to the polymer by copolymerization of the corresponding monomers. Preferred monomers having hydrophilic groups are the abovementioned monomers having carboxyl groups and hydroxyl groups, in particular z. For example, acrylic acid. In particular, the polymer is at least 60% by weight, more preferably at least 80% by weight, e.g. of from 80 to 100% by weight, and very particularly preferably at least 95% by weight or to 100% by weight, of C 1 to C 20 alkyl (meth) acrylates. In one embodiment, the binder is the homopolymer of ethyl acrylate

The polymer preferably has a glass transition temperature calculated from Fox of the monomer composition from -50 to + 20 ⁰ C, more preferably from -30 to +10 ⁰ C. The glass transition temperature is according to the Fox equation from the glass transition temperature, the homopolymers of the present in the copolymer Calculated monomers and their weight fraction:

1 / Tg = xA / TgA + xB / TgB + xC / TgC +

Tg: calculated glass transition temperature of the copolymer TgA: glass transition temperature of the homopolymer of monomer A TgB, TgC: Tg corresponding to monomers B, C, etc.

xA: mass of monomer A / total mass of copolymer,

xB, xC corresponding to monomers B, C etc.

The Fox equation is given in standard textbooks, eg. See also Handbook of Polymer Science and Technology, New York, 1989 by Marcel Dekker, Inc.

The preparation of the polymers can be carried out by emulsion polymerization, it is then an emulsion polymer. In emulsion polymerization, ionic and / or nonionic emulsifiers and / or protective colloids or stabilizers are generally used as surface-active compounds in order to promote the dispersion of the monomers in the aqueous medium. According to the invention, the ethylene / (meth) acrylic acid copolymers having an acid number of 160 to 230 mg KOH / g can be used as the sole protective colloid or as the sole dispersant, i. without additional emulsifiers and without other protective colloids of other types. If desired, however, small amounts of emulsifiers or of other protective colloids can also be used. If emulsifiers and / or additional protective colloids are used as aids for dispersing the monomers, the total amounts used thereof are, for example, from 0.1 to 5% by weight, based on the monomers. Of course, in the case of the use of mixtures of surfactants, the individual components must be compatible with each other, which can be checked in case of doubt by hand on fewer preliminary tests. A detailed description of suitable protective colloids can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, macromolecular materials, Georg-Thieme-Verlag, Stuttgart, 1961, pages 41 1 to 420. Suitable as protective colloids z. B. amphiphilic polymers, ie polymers with hydrophobic and hydrophilic groups. They may be natural polymers such as starch or synthetic polymers. Suitable emulsifiers are both anionic, cationic and nonionic emulsifiers. Emulsifiers whose molecular weight, in contrast to the protective colloids, are usually below 2000 g / mol, preferably below 1500 g / mol, are preferred as accompanying surface-active substances, while the number average molecular weight of the protective colloids is above 2000 g / mol, for example 2000 to 100000 g / mol, in particular from 5000 to 50,000 g / mol.

If emulsifiers are used as additional surface-active substances, they are preferably anionic or nonionic emulsifiers. Suitable emulsifiers are, for example, ethoxylated Cs to C36 or C12 to ds fatty alcohols having a degree of ethoxylation of from 3 to 50 or from 4 to 30, ethoxylated mono-, di- and tri-C ₄ - to C 12 or C ₄ - C 1 -C 4 -alkylphenols having a degree of ethoxylation of from 3 to 50, alkali metal salts of dialkyl esters of sulfosuccinic acid, alkali metal and ammonium salts of C 2 -C 12 -alkyl sulfates, alkali metal and ammonium salts. salts of C12 to Cis-alkylsulfonic acids and alkali metal and ammonium salts of Cg to Cis-alkylarylsulfonic acids. Cationic emulsifiers are, for example, compounds having at least one amino or ammonium group and at least one C 8 -C 22 -alkyl group. Further suitable emulsifiers are compounds of the general formula

wherein R ⁵ and R ^{6 are} hydrogen or C ₄ - to Cu-alkyl and are not hydrogen at the same time, and X and Y may be alkali metal ions and / or ammonium ions. Preferably R ⁵ , R ^{6 are} linear or branched alkyl radicals having 6 to 18 C atoms or hydrogen and in particular having 6, 12 and 16 C atoms, wherein R ⁵ and R ^{6 are} not both simultaneously hydrogen. X and Y are preferably sodium, potassium or ammonium ions, with sodium being particularly preferred. Particularly advantageous are compounds II in which X and Y are sodium, R ^{5 is} a branched Al kylrest with 12 C atoms and R ^{6 is} hydrogen or R ⁵ . Industrial mixtures are used which have a share of 50 to 90 wt .-% of the monoalkylated product, for example Dowfax ^® 2A1 (trademark of Dow Chemical Company). Suitable emulsifiers can also be found in Houben-Weyl, Methods of Organic Chemistry, Volume 14/1, Macromolecular substances, Georg Thieme Verlag, Stuttgart, 1961, pages 192 to 208. Tradenames of emulsifiers are z. B. Dowfax ^® 2 A1, Emulan ^® NP 50, Dextrol ^® OC 50, 825 emulsifier, emulsifier 825 S, Emulan ^® OG, Texapon ^® NSO, Ne kanil ^® 904 S, Lumiten ^® I-RA, Lumiten ^® E 3065, Disponil ^® FES 77, Lutensol ^® AT 18

Steinapol ^® VSL and Emulphor NPS 25. ^® are also suitable copolymerizable emulsifiers containing a radically polymerizable ethylenically unsaturated double bond, for example, reactive anionic emulsifiers such as ADEKA® Resoap SR-tenth The emulsion polymerization is generally carried out at 30 to 130, preferably 50 to 90 ⁰ C. The polymerization medium may consist of water only, as well as mixtures of water and thus miscible liquids such as methanol. Preferably, only water is used. The emulsion polymerization can be carried out both as a batch process and in the form of a feed process, including a stepwise or gradient procedure. Preferably, the feed process in which one submits a portion of the polymerization, heated to the polymerization, polymerized and then the rest of the polymerization, usually over several spatially separate feeds, one or more of which monomers in pure or in emulsified form, continuously or gradually supplied.

The emulsion polymerization is carried out in the presence of the ethylene / (meth) acrylic acid copolymers as protective colloid. This means that the ethylene / (meth) acrylic acid Copolymers and optionally further protective colloids are introduced or fed together with monomers to the polymerization vessel. They are preferably initially introduced in the emulsion polymerization, while optionally additionally used emulsifiers together with the monomers can also be supplied in the course of the polymerization.

In the emulsion polymerization, the usual and known adjuvants, e.g. water-soluble initiators and regulators are used. Water-soluble initiators for emulsion polymerization are e.g. Ammonium and alkali metal salts of peroxodisulfuric acid, e.g. For example, sodium peroxodisulfate, hydrogen peroxide or organic peroxides, z. B. tert-butyl hydroperoxide. Also suitable are so-called reduction-oxidation (red-ox) initiator systems. The redox initiator systems consist of at least one mostly inorganic reducing agent and one inorganic or organic oxidizing agent. The oxidation component is z. B. to the above-mentioned initiators for emulsion polymerization. The reduction components are, for. B. to alkali metal salts of sulfurous acid, such as. As sodium sulfite, sodium bisulfite, alkali metal salts of the desulfurous acid such as sodium, bisulfite addition compounds aliphatic aldehydes and ketones, such as acetone bisulfite or reducing agents such as hydroxymethanesulfinic acid and salts thereof, or ascorbic acid. The red-ox initiator systems can be used with the concomitant use of soluble metal compounds whose metallic component can occur in multiple valence states. Usual Red Ox initiator systems are z. As ascorbic acid / iron (II) sulfate / sodium peroxydisulfate, tert-butyl hydroperoxide / sodium disulfite, tert-butyl hydroperoxide / Na-hydroxymethanesulfinic acid or tert-butyl hydroperoxide / ascorbic acid. The individual components, eg. As the reduction component, mixtures may also be z. B. a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium disulfite. The compounds mentioned are usually used in the form of aqueous solutions, the lower concentration being determined by the amount of water acceptable in the dispersion and the upper concentration by the solubility of the compound in question in water. In general, the concentration is 0.1 to 30 wt .-%, preferably 0.5 to 20 wt .-%, particularly preferably 1, 0 to 10 wt .-%, based on the solution. The amount of initiators is generally 0.1 to 10 wt .-%, preferably 0.5 to 5 wt .-%, based on the monomers to be polymerized. It is also possible to use a plurality of different initiators in the emulsion polymerization. To remove the residual monomers, initiator is usually also added after the end of the actual emulsion polymerization.

In the polymerization regulators can be used, for. B. in amounts of 0 to 0.8 parts by weight, based on 100 parts by weight of the monomers to be polymerized, whereby the molecular weight is reduced. Suitable z. B. Compounds with a thiol group such as tert-butylmercaptan, thioglycolic acid ethylacrylic ester, mercaptoethanol, Mercaptopropyltrimethoxysilane or tert-dodecylmercaptan. Furthermore, regulators without thiol group can be used, such as terpinolene.

In one embodiment of the invention, it is a composition wherein the emulsion polymer prepared by emulsion polymerization is a pure acrylate, i. consists exclusively of alkyl (meth) acrylate monomers, wherein the alkyl group preferably has 1 to 8 C atoms and wherein preferably at least one monomer is ethyl acrylate or which is n-butyl acrylate / methyl methacrylate copolymer which is ethylene / (meth ) acrylic acid copolymer of 65 to 75 wt.% Ethylene and 25 to 35 wt.% Methacrylic acid and the ethylene / methacrylic acid copolymer in an amount of 5 to 20 parts by weight, based on 100 parts by weight of the polymerized Monomers is used.

The invention also relates to the use of the above-described aqueous polymer dispersions for cold-sealing, wherein the polymer dispersion after application to a substrate and after drying forms an autoadhesive coating which is block-resistant at room temperature

The composition according to the invention is suitable for cold sealing of any two substrates, wherein

- The two substrates at the sites to be bonded, each coated with the composition of the invention or are coated and

- The two substrates are optionally brought under pressure and the temperature in the coated composition is less than 40 ⁰ C (cold sealing, see above).

Suitable substrates to be bonded are any, for. As substrates of wood, metal, paper or plastic, which can be glued together in any combination, wherein preferably at least one substrate is a polymer film. The substrates are coated with the composition according to the invention. The coating can be carried out in a customary manner, for example by printing, in particular by flexographic printing or by gravure printing (gravure printing). Typical layer thicknesses (after drying) are, for example, 1 to 30 g / m ² , preferably 1 to 10 g / m ² or 1 to 5 g / m ² . In particular, the composition according to the invention is suitable for the production of packaging. In this case come packaging from any materials, eg. B. of paper or preferably made of plastic. Called z. As packaging of polymer films, optionally also metallized polymer films, for. Example of polyethylene, polypropylene, PVC, polyester, polyacetate.

A carrier coated on both sides is particularly suitable for the production of packaging, the carrier being provided on one side (hereinafter referred to as front side). characterized) has an outer layer of the composition of the invention and on the other side (hereinafter referred to as the back) having an outer release coating. The carrier may, for. B. from one of the above-mentioned polymer films or metallized polymer films may be mentioned, in particular films of oriented polypropylene, polyethylene, preferably high density polyethylene or polyethylene terephthalate. The polymer films may also be pretreated with corona. The composition according to the invention may be coated directly on the front side of the carrier, but other layers may also be present between the carrier and the composition according to the invention, e.g. B. primer layers or colored or black and white ink layers, but ink layers are preferably located on the back of the carrier. It is essential that the layer of the composition according to the invention is located on the outside. The release coating may be of any material, it may be a polymeric film, eg, an oriented polypropylene film which is laminated or coextruded, or a liquid paint, e.g. B. a polyamide paint, which is applied and filmed act; It is essential that the adhesive layer applied on the front side of the carrier (in the present case, the composition according to the invention) does not adhere to the release coating (blocking resistance). The carrier is generally rolled up and later processed by the roll. When rolled up, the front and back of the wearer come into direct contact. Sticking the front on the backside would render the carrier unusable. There may be additional layers between the release coating and the carrier; In turn, layers of a primer that improves adhesion and ink layers can be considered. The outer release coating also has the task of protecting the lower layers, in particular the ink layer against external influences. Preferred supports are constructed as follows, the order of the layers corresponding to the spatial arrangement:

Adhesive layer (composition according to the invention)

carrier

Optionally, primer layer

Optionally ink layer

Release coating.

The carrier coated on both sides is used in particular for the production of packaging, preferably it is adhesively bonded to itself by cold sealing, wherein in each case the front sides coated with the outer composition according to the invention are brought into contact. It is essential that both to be bonded carrier to be bonded, forming the subsequent seal Sites are coated with the composition of the invention. The package is sealed by cold sealing the adhesive layer together once the product to be packaged is filled. The packaging is particularly suitable for food.

The invention also relates to a coated polymer film, wherein a polymer support film at least partially, i. at least at the areas forming the subsequent seal seam is coated with a composition according to the invention. The polymer film according to the invention preferably has a first and a second side, wherein the first side as an outer layer is at least partially coated with a composition according to the invention and the second side has a release coating as the outer layer. In one embodiment, the polymer support film of the coated polymer film of the invention is polyethylene or oriented polypropylene, and the release coating is formed on the basis of polyamide.

The invention also provides the use of the coated polymer film according to the invention for the production of packaging, in particular film packaging for food.

Examples

Unless otherwise stated in the context, the percentages always indicate percent by weight. The indication of a content refers to the content in aqueous solution or dispersion.

The following starting materials were used:

Acronal® S 790: aqueous dispersion of a polymer based on acrylate ester

Styrene from BASF SE: solids content 50%; pH 7.5-9.0

Joncryl® 74: acrylate dispersion from BASF SE: solids content 48%;

pH 8.1

Joncryl® DFC 3025: a polymer resin solution (Styrene Acrylic Resin Solution)

Company BASF SE: solids content 34.2%; pH 8.5

Binzil® CC 30: transparent liquid of colloidal silicate from Eka / Akzo Nobel: solids content 29%; pH 8.0

Slip dispersion 8645: aqueous, anionic dispersion of montan ester wax of

Company BASF SE: solids content 19-21%; pH 3-5

Dynol® 604 and EnviroGem® are wetting agents from Air Products

Emulan® EL40: a castor oil ethoxylate from BASF SE

Disponil® FES77: sulfated fatty acid ethoxylate from Cognis

Poligen® WE3: aqueous dispersion of a polymer based on ethylene-acrylic acid

(80/20) from BASF SE: solids content 24-26%; pH 8.5-9 Dissolvine® E-Fe 13: Ethylenediaminetetraacetic acid, ferric sodium complex

Oppalyte® 33MW247: film recommended for cold seal applications made of surface treated, biaxially oriented polypropylene from Exxon Mobil Corp.

Treofan® SHD40: Oriented polypropylene film recommended by Treofan GmbH & Co. KG for cold-seal applications

Gecko® Coldseal Release Lacquer 70 GL 282547: Solvent-based polyamide release lacquer from Huber Group

Viscosity measurement:

The melt viscosity was measured with a cone and plate viscometer (ICI

Cone & Plate Viscosimeter, Epprecht Instruments + Control AG, serial no. 6623), measuring body C, angle 0.5 °, cone diameter 19.5 mm, diameter of the lower plate 25.4 mm at 1 1, 72 rpm, level 2. Cold seal test

Coating with polyamide release varnish

Apply Gecko® Coldseal Release Lacquer 70 GL 282547 to the pre-treated side of the SHP40 OPP film and dry with hot air for 10 seconds with a 0.07 mm wire bar. Order quantity of release varnish approx. 1, 0g / m ² .

Coating the OPP film

With the bar blade, the adhesive is applied to the pretreated side of the OPP film Oppalyte® ® 33MW247 and 1 min. At 70 ⁰ C dried. The coated film is covered with a release varnish-coated OPP film.

Sealed seam strength (SST) without load

15mm wide strips are cut from the coated film and sealed on the sealer for 0.5 sec. With 200N (1, 4bar). After sealing, the peel strengths are determined in N / 15 mm at a pull-off speed of 50 mm / min.

"SNF 7d / 7d" is the seal seam strength of a coated film which, after coating, was stored for 7 days at room temperature, then sealed against a same, coated film and, after sealing, was stored again for 7 days at room temperature before measuring the seal strength.

"SNF 1d / 1d" is the seal seam strength of a coated film which, after coating, was stored for one day at room temperature, then sealed against a same, coated film and, after sealing, was stored again for one day at room temperature before measurement of the seal seam strength. SNSF) with load

Immediately after the coating, the coated foils are placed against the release varnish-coated side of an OPP foil SHD40 and a circular With a diameter of 10 cm, 1 d is loaded with 10 tons. Then 15mm wide strips are cut from the loaded section and sealed on the sealing device for 0.5 sec. With 200N (1, 4bar). After sealing, the peel strengths are determined in N / 15mm with a take-off speed of 50mm / min. "SNF 1d (10 to) / 7d" is the seal strength of a coated film which, after coating, was stored for 1 day at room temperature under a pressure of 10 tons, then sealed against a same coated film, and after sealing before measurement of seal strength Stored for 7 days at room temperature.

block test

The coated film is placed against the release varnish-coated side of an OPP-FoNe SHD40, and a 10 cm diameter circular cutout is loaded with 10 tons for 1d. Thereafter, the peel strengths of 25 mm wide strips are determined at a take-off speed of 800 mm / min in N / 25mm.

Example D1

In an open 4L reactor equipped with an anchor stirrer (% methacrylic acid content, 800 mPa 31, 5 wt. S melt viscosity at 120 ⁰ C) at 95 ° C 100 g of an ethylene / methacrylic acid copolymer containing 25 wt-melted and by the addition of 12.5 g of % ammonia and 125g of distilled water dissolved within 30 minutes. % Ammonia and 320.75g of distilled water were 5g 25 wt then at 70 ⁰ C. Was added.

Feed 1: 800 g of n-butyl acrylate, 200 g of methyl methacrylate, 2 g of tert-dodecylmercaptan. Feed 2: 150 g of a 3.33% strength by weight solution of tert-butyl hydroperoxide in distilled water.

Feed 3: 100 g of distilled water, 30 g of 10% strength by weight ascorbic acid solution, 10 g of 1% by weight of Dissolvine® E-Fe 13 solution and 1.5 g of 25% strength by weight ammonia.

Subsequently, feeds 1, 2, 3 were started in parallel and metered in as indicated. Feed 1 was added within 3 hours. 10% of feed 2 was added in 20 minutes, the remainder of feed 2 in 4 hours. 10% of feed 3 was added in 20 minutes, another 40% in 140 minutes, the remaining 50% were added in 20 minutes. The mixture was stirred for 30 minutes, cooled to room temperature and then filtered through a 125 .mu.m sieve.

Solids content: 60%

SNF 1d (10 to) / 7d: 2.5 N / 15mm

SNF 1d / 1d: 2.7 N / 15mm Example D2

As Example 1, but feed 1 contained 1000 g of ethyl acrylate and 2 g of tert-dodecylmercaptan. Solids content: 59.3%

SNF 1d (10 to) / 7d: 3.6 N / 15mm

SNF 1d / 1d: 3.8 N / 15mm Example D3

As in Example 1, but 200g of ethylene / methacrylic acid copolymer were used and the amount of ammonia doubled accordingly. Feed 1 contained 1000 g of ethyl acrylate. Solids content: 59.5%

SNF 1d (10 to) / 7d: 2.8 N / 15mm

SNF 1d / 1d: 4.3 N / 15mm

Example D4

In an open 4L reactor equipped with an anchor stirrer were at 95 ° C

100 g of an ethylene / methacrylic acid copolymer (30.4 wt.% MAS content, 790 mPa s melt viscosity at 120 ⁰ C) melted and by addition of 12.5 g 25-

% By weight of ammonia and 125 g of distilled water dissolved within 30 minutes. Subsequently, the following feeds were metered in at 50 ^° C.

Feed 1 contained 1000 g of ethyl acrylate, 2 g of tert-dodecyl mercaptan and 10 g Dynol ^® 604. Feed 2 comprised 150 g of a 3.33 wt.% Solution of tertiary butyl hydroperoxide in distilled water.

Feed 3 contained 426 g of distilled water, 30 g of 10% strength by weight ascorbic acid solution, 10 g of 1% by weight Dissolvine® E-Fe 13 solution and 1 l of 25% strength by weight ammonia.

Feeds 1, 2, 3 were started in parallel and metered in as indicated. Feed 1 was added within 3 hours. 10% of feed 2 was added in 20 minutes, the remainder of feed 2 in 4 hours. Feed 3 was added within 3 hours. The mixture was stirred for 30 minutes, cooled to room temperature and then filtered through a 125 .mu.m sieve.

Solids content: 58.9%

SNF 1d (10 to) / 7d: 3.5 N / 15mm

SNF 1d / 1d: 3.2 N / 15mm

Example D5

As Example 4, but feed 1 contained 1000 g of ethyl acrylate, 2 g of tert-dodecylmercaptan and 10 g of Envirogem® AD01.

Solids content: 58.6%

SNF 1d (10 to) / 7d: 4.0 N / 15mm

SNF 1d / 1d: 4.4 N / 15mm

Example D6

Like example 4, but feed 1 contained 1000 g of ethyl acrylate, 2 g of tert-dodecylmercaptan and 10 g of Emulan® EL40.

Solids content: 57.8% SNF 1d (10 to) / 7d: 4.1 N / 15mm

SNF 1 d / 1d: 4.3 N / 15mm

Example D7

100 g of an ethylene-n-butyl acrylate-methacrylic acid terpolymer (29.5% by weight of methacrylic acid content, 5.7% by weight of n-butyl acrylate content, 820 mPa s melt viscosity at 120 ° C.) were used in an open 4 L reactor equipped with an anchor stirrer ⁰ C) and dissolved by addition of 12.5 g of 25 wt.% Ammonia and 125 g of distilled water within 30 minutes. Feeds were then added at 50 ⁰ C fol- constricting.

Feed 1 contained 1000 g of ethyl acrylate and 2 g of tert-dodecylmercaptan.

Feed 2 contained 150 g of a 3.33% by weight solution of tert-butyl hydroperoxide in distilled water.

Feed 3 contained 419.5 g of distilled water, 30 g of 10% strength by weight ascorbic acid solution, 10 g of 1% by weight of dissolvine E-Fe 13 solution and 1 1 g of 25% strength by weight ammonia.

Feeds 1, 2, 3 were started in parallel and metered in as indicated. Feed 1 was added within 3 hours. 10% of feed 2 was added in 20 minutes, the remainder of feed 2 in 4 hours. Feed 3 was added within 3 hours. It was stirred for 30 minutes, cooled to room temperature and then filtered through a 125 .mu.m sieve.

Solids content: 59.5%

SNF 1d (10 to) / 7d: 3.6 N / 15mm

SNF 1d / 1d: 5.3 N / 15mm Example D8

As Example 7, but an ethylene-2-ethylhexyl acrylate-methacrylic acid terpolymer (30.0 wt.% MAS content, 4.1 wt.% 2-EHA content, 820 mPa s melt viscosity at 120 ° C) was used.

Solids content: 58.9%

SNF 1d (10 to) / 7d: 3.5 N / 15mm

SNF 1d / 1d: 5.5 N / 15mm

Example D9

As Example 7, but an ethylene-2-propylheptyl acrylate-methacrylic terpolymer (30.0 wt.% MAS content, 4.4 wt.% 2-PHA content, 820 mPa s melt viscosity at 120 ⁰ C) was used ,

Solids content: 59%

SNF 1d (10 to) / 7d: 4.5 N / 15mm

SNF 1d / 1d: 4.3 N / 15mm

formulation Examples Formulation Example F1

100 parts by weight (based on solids content) of the dispersion from Example D1 are mixed with 5 parts by weight (based on solids content) of Joncryl® DFC 3025 (34% pure).

SNF 1d (10 to) / 7d: 4.6 N / 15mm

SNF 1d / 1d: 5.0 N / 15mm

Formulation example F2

80 parts by weight (telquel) of the dispersion from Example D3 are mixed with 20 parts by weight (telquel) Binzil® CC 30 (15% strength).

SNF 1d (10 to) / 7d: 2.9 N / 15mm

SNF 1d / 1d: 3.0 N / 15mm

Formulation Example F3

80 parts by weight (telquel) of the dispersion from Example D3 are mixed with 20 parts by weight (telquel) lubricant dispersion 8645 (20% strength).

SNF 1d (10 to) / 7d: 3,1 N / 15mm

SNF 1d / 1d: 3.9 N / 15mm Formulation Example F4

80 parts by weight (telquel) of the dispersion from Example D3 are mixed with 20 parts by weight (telquel) Acronal ® S790 (50%).

SNF 1d (10 to) / 7d: 1, 8 N / 15mm

SNF 1d / 1d: 2.4 N / 15mm

Formulation Example F5

90 parts by weight (based on solids content) of the dispersion from Example D2 are with

10 parts by weight (based on solids content) of Joncryl® 74 (48% pure).

SNF 1d (10 to) / 7d: 3.2 N / 15mm

SNF 1d / 1d: 2.8 N / 15mm

Comparative Example VO (with emulsifiers, without protective colloid)

In a conventional emulsion polymerization in the presence of low molecular weight

Emulsifiers were prepared a polymer dispersion for mixing experiments with nachträgli- sher addition of ethylene / (meth) acrylic acid copolymers. In an open 4L reactor equipped with an anchor stirrer, 400 g of distilled water were introduced at 70 ⁰ C and the apparatus for 30 minutes, purged with nitrogen. Subsequently, the following feeds were metered in at 70 ^° C.

Feed 1 contained an emulsion of 1000 g ethyl acrylate, 2 g of tert-dodecyl mercaptan, 30 wt 66,67g a.% Strength Disponil ^® FES77 solution, 11, 11 g of a 45 wt.% Solution of Dowfax ^® 2A1 solution and 520g distilled water. Feed 2 contained 160 g of a 5% strength by weight solution of tert-butyl hydroperoxide in distilled water.

Feed 3 contained 158 g of a 5.06% strength by weight solution of sodium formaldehyde sulfoxylate (Rongalit®) in distilled water.

Feeds 2, 3 were started in parallel and metered in as indicated. In each case 20% of feed 2 and 3 was added in 20 minutes, the remainder in 5 hours. Feed 1 was started 5 minutes after the start of feeds 2 and 3 and metered in within 3 hours. The mixture was stirred for 30 minutes, cooled to room temperature and then filtered through a 125 .mu.m sieve.

Example wt V1 (E / MAA copolymer having acid number of 198 as a protective colloid, emulsifier) (in an open 4L reactor equipped with an anchor stirrer was at 70 ⁰ C 668g of a solution of an ethylene-methacrylic acid copolymer 30.4.% MAS content 790 mPa s melt viscosity at 120 ⁰ C) and the apparatus rinsed for 30 minutes with nitrogen. The solution contained 25% by weight of ethylene-methacrylic acid copolymer, the calculated degree of partial neutralization of the carboxyl groups with ammonia was 75%. The preparation of the copolymer solution was carried out analogously to Example D4.

The following feeds were metered in at 70 ° C.

Feed 1 contained 333 g of ethyl acrylate and 0.67 g of tert-dodecylmercaptan.

Feed 2 contained 53.28 g of a 5 wt .-% solution of tert-butyl hydroperoxide in distilled water.

Feed 3 contained 312.6 g of an O, 85% strength by weight solution of sodium formaldehyde sulfoxylate (Rongalit®) in distilled water.

In each case 90% of feeds 2 and 3 were added within 3 minutes. Subsequently, feed 1 and the residual feeds of 2 and 3 were metered in over the course of 1.5 hours. The mixture was stirred for 1 hour at 70 ⁰ C, then cooled to room temperature and filtered through a 125 .mu.m sieve.

Solids content: 34.9% Comparative Example C2 (E / MAS copolymer with acid number 198 added subsequently) A solution of an ethylene-methacrylic acid copolymer (30.4% by weight MAS content, 790 mPa s melt viscosity at 120 ° C.) was prepared analogously to Example D4 produced. The solution contained 25% by weight of ethylene-methacrylic acid copolymer, the calculated degree of partial neutralization of the carboxyl groups with ammonia was 75%. An appropriate amount of this solution was mixed at room temperature with an appropriate amount of the acrylate polymer dispersion of Comparative Example VO and the solids content was adjusted to 35% with distilled water. The content of the ethylene-methacrylic acid copolymer in the solid content was 33%. Comparative Example C3 (E / AS copolymer with acid number 156 as protective colloid, emulsifier-free) Equipped with an anchor stirrer, in an open 4L reactor a solution of an ethylene-acrylic acid copolymer (20% AS content wt.) Was added at 70 ⁰ C 334g presented and the apparatus for 30 minutes, purged with nitrogen. The solution contained 25% by weight of ethylene-acrylic acid copolymer, trade name Poligen WE3. The following feeds were metered in at 70 ^° C.

Feed 1 contained 165.5 g of ethyl acrylate and 0.33 g of tert-dodecylmercaptan.

Feed 2 contained 26.64 g of a 5% strength by weight solution of tert-butyl hydroperoxide in distilled water.

Feed 3 contained 157.97 g of an O, 85% by weight solution of Rongalit C in distilled water.

5% of feed 1 were presented at 70 ⁰ C. Subsequently, in each case 30% of the feeds 2 were metered in within 3 minutes. Subsequently, feed 1 and the residual feeds of 2 and 3 were metered in over the course of 1.5 hours. The mixture was stirred for 1 hour at 70 ⁰ C, then cooled to room temperature and filtered through a 125μm sieve.

Solids content: 37.3%

The dispersion was pasty and unsuitable for further testing. Comparative Example C4 (E / AS copolymer added subsequently with acid number 156) As Comparative Example C2, but a dispersion of an ethylene-acrylic acid copolymer (20 wt.% AS content, trade name Poligen WE3) was mixed with the acrylate polymer dispersion of Comparative Example C0. An appropriate amount of terminal WE3 was mixed at room temperature with an appropriate amount of the acrylate polymer dispersion of Comparative Example VO and the solids content was adjusted to 35% with distilled water. The content of the ethylene-acrylic acid copolymer in the solid content was 33%.

Comparative Example V5

Commercially available natural rubber latex, NK latex from Eukalin,

pH 9.9, solids content 55%

SNF 1d / 1d: 1, 8 N / 15mm The results of the cold seal tests are shown in Table 1.

Table 1: Results of the cold seal tests

¹ > The dispersion was too pasty and unsuitable for coating applications

Compared with the comparison compositions, composition V1 according to the invention is distinguished by an unexpected combination of advantageous intrinsic properties in terms of good rheological properties and good applicability despite the freedom of emulsifiers, high seal strength even after prolonged storage, good blocking resistance and freedom from emulsifiers.

Claims

claims

1. Cold-sealable composition in the form of an aqueous polymer dispersion, wherein the aqueous polymer dispersion can be prepared by emulsion polymerization of radically polymerizable monomers in the presence of at least one ethylene / (meth) acrylic acid copolymer having an acid number of 160 to 230 mg KOH / g as a protective colloid ,

2. Composition according to the preceding claim, characterized marked, that the polymer dispersion forms after application to a substrate and after drying an autoadhesive at room temperature and against polyamide surfaces block-resistant coating.

3. Composition according to the preceding claim, characterized marked, that the autoadhesive adhesion after sealing with 1, 4 bar at 20 ⁰ C is at least 2 N / 15 mm and the adhesion to a polyamide surface after loading a circular surface with a diameter of 10 cm with 10 tonnes for one day at 20 ^° C is not more than 0,1 N / 25 mm.

4. Composition according to one of the preceding claims, characterized in that the ethylene / (meth) acrylic acid copolymer is formed from

(a) ethylene,

(c) optionally further nonionic comonomers other than (a) and (b) in an amount of 0 to 15% by weight,

wherein the ethylene / (meth) acrylic acid copolymer has a melt viscosity of 400 - 2000 mPa s at 120 ° C.

5. The composition according to any one of the preceding claims, characterized in that the emulsion polymer prepared by emulsion polymerization is composed of at least 60 wt .-% of main monomers which are selected from the group consisting of C1 to C20 alkyl (meth) acrylates, Vi - Nylestern of carboxylic acids containing up to 20 carbon atoms, vinyl aromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds and mixtures of these monomers.

6. Composition according to one of the preceding claims, characterized in that the emulsion polymer produced by emulsion polymerization risat free of acid groups and to 60 to 100 wt.% From C1 to C20 alkyl (meth) acrylates is constructed.

7. Composition according to one of the preceding claims, characterized in that the emulsion polymer prepared by emulsion polymerization is a pure acrylate, the ethylene / (meth) acrylic acid copolymer of 65 to 75 wt.% Ethylene and 25 to 35 wt.% Methacrylic acid and the ethylene / methacrylic acid copolymer is used in an amount of 5 to 20 parts by weight based on 100 parts by weight of the monomers to be polymerized, and the ethylene / (meth) acrylic acid copolymer has a melt viscosity of 400 - 2,000 mPa · s at 120 ⁰ C.

8. Composition according to the preceding claim, characterized in that the composition has a solids content of greater than 50 wt.% Has up.

9. Composition according to one of the preceding claims, characterized in that in the ethylene / (meth) acrylic acid copolymer nonionic comonomers (c) in an amount of 0.1 to 10 wt.% Based on the sum of the monomers ( a) to (c) are selected from C1-20 alkyl acrylates,

C1-20 alkyl methacrylates, vinyl silanes, vinyl phosphonic acid esters or mixtures of these monomers.

10. The composition according to any one of the preceding claims, characterized in that the emulsion polymerization taking place in the presence of the protective colloid takes place emulsifier-free.

1 1. Use of an aqueous polymer dispersion according to any one of the preceding claims for cold sealing, wherein the polymer dispersion after application to a substrate and after drying a blockable at room temperature, autoadhesive

Coating forms.

12. Use according to the preceding claim, characterized in that it is the substrate is a polymer film.

13. Coated polymer film, characterized in that a polymer carrier film is at least partially coated with a composition according to any one of claims 1 to 9.

14. A coated polymer film according to the preceding claim, characterized in that the polymer film has a first and a second side, wherein the first side as an outer layer at least partially with a composition according to any one of claims 1 to 10 and the second side has a release coating as the outer layer.

15. Coated polymer film according to one of the two preceding claims, characterized in that the polymer carrier film consists of polyethylene or oriented polypropylene and the release coating is formed on the basis of polyamide.

16. Use of the coated polymer film according to any one of claims 13 to 15 for the production of packaging.