WO2012049207A1

WO2012049207A1 - Food coating composition

Info

Publication number: WO2012049207A1
Application number: PCT/EP2011/067800
Authority: WO
Inventors: Martin Jakob; Jürgen PONGRATZ; Karlheinz Rockel; Javier Tortosa
Original assignee: Celanese Emulsions GmbH
Current assignee: Celanese Sales Germany GmbH
Priority date: 2010-10-15
Filing date: 2011-10-12
Publication date: 2012-04-19
Anticipated expiration: 2013-04-15

Abstract

The present invention relates to the use of a composition for coating food wherein said composition comprises a copolymer obtainable by emulsion polymerization of an aqueous radically polymerizable mixture of monomers comprising a) at least one (meth)acrylate monomer (A), b) at least one (meth)acrylate monomer (B) which is different from monomer (A), c) at least one ethylenically unsaturated carboxylic acid monomer (C1) and/or an ethylenically unsaturated electrically charged monomer (C2), and d) optionally at least one monomer (D) which is different from monomer (A) and (B) and which is selected from the group consisting of (meth)acrylate or (meth)acrylamide which may comprise functional groups;wherein the amount of the sum of monomer (A) and monomer (B)is more than 75 wt.-% and wherein the glass transition temperature of the copolymer is 0 to 25°C, determined according to ASTM E 1356 by differential scanning calorimetry and wherein the composition is substantially free of polyvinyl alcohol.

Description

Food Coating Composition

The present invention relates to the use of a composition for coating food wherein the composition comprises a (meth)acrylate based copolymer. Further, the present invention relates to food which is coated with said composition.

The use of plastic dispersions having a very varied polymer base for coating food has long been known. The surface treatment and the subsequent drying on of the dispersions generate an air-permeable water vapor barrier film which prevents not only mold formation on the food, but also excessively rapid drying out of the food during ripening. Especially for climacteric fruits which are fruits that are able to ripen after being picked, a food coating composition can prevent the rapid drying of the fruits as well as avoid a rapid and unpleasant change of the visual characteristics of the fruit.

As a base for such food coating compositions, dispersions especially based on homo- or copolymer poly(vinyl acetate), here in particular based on copolymers with alkyl maleates/fumarates or ethene, have already been described in the prior art.

Other monomers have also been described for food coating compositions. For instance, CH-A419,816, mentions vinyl chloride, vinyl propionate, vinylidene chloride, acrylic esters, styrene, crotonic acid, acrylonitrile, fumaric acid, itaconic acid, vinyl butyrate, vinylpyrrolidone and propylene. In the examples, copolymeric emulsions of vinyl acetate and acrylate monomers are also mentioned which are predominantly made up of vinyl acetate and in addition comprise up to 20 parts by weight of acrylate monomers such as 2-ethylstearyl acrylate, butyl acrylate, polyethoxyethyl methacrylate or methyl methacrylate in the polymer mass of the emulsion.

In example 6 of CH-A-419,816, a 50% strength emulsion of a copolymer consisting of 720 parts of vinyl acetate and 180 parts of methyl methacrylate is described, to which are added 50 parts each of polybutyl acrylate and also a fungicide.

US-A-2003/0055010 describes a method for establishing a high polyene fungicide activity in aqueous solution. These solutions likewise comprise polymer dispersions for coating foods and cheese. Preferred monomers for these dispersions are vinyl acetate, ethylene, vinyl esters of saturated fatty acids of chain lengths C₂-Ci₈, esters of maleic and fumaric acid with monovalent saturated aliphatic alcohols of chain lengths C4-C8 and also acrylic esters of monohydric aliphatic saturated alcohols of chain lengths C₄-C₈, or mixtures of alpha-olefins Ci₄-Ci₆. In the example section of the publication Mowilith^® LDM 5041 is mentioned a 45% strength copolymer dispersion of vinyl acetate and butyl acrylate.

The food coating compositions, especially produced for climacteric fruits must be customized to the individual requirements. The requirements of food coating compositions are set by the mechanical application in applying the coating, the climatic and microbial conditions during room storage and on mechanical loading both in the mechanical handling in the moist storage room and later of the ripened fruit as end product during transport. This is ultimately achieved by suitable selection of appropriate stabilizers for the food coating dispersions and also by the selection of suitable monomer systems.

WO 03/054041 describes a food coating composition based on copolymers of vinyl esters and dialkyl esters of maleic or fumaric acid, which composition is distinguished from conventional products by a significantly improved film glossiness and at the same time an improved shear stability. At the same time, the coatings produced using this dispersion also have low water absorption and good wax adhesion.

US-6, 162,475 discloses a composition comprising a polyvinyl acetate with an average molecular weight in the range of about 2,000 to about 50,000, in amounts effective to provide an edible high-gloss coating for fruits, vegetables, root crops, tree nuts, and prepared foods, wherein said polyvinyl acetate is dissolved in a low molecular weight alcohol .

Food coating compositions are especially known and used in the manufacture and/or ripening of cheese.

EP-Bl-1 537 786 discloses the use of a coating composition which comprises a water-borne polymer dispersion comprising (a) a copolymer comprising a vinylic ester of a saturated hydrocarbon, at least one maleic or fumaric ester, and a stabilizing monomer, (b) a protective colloid, and (c) a nonionic emulsifier, said composition having a water vapor permeability ranging from 1-140 g/m²-24h, in the manufacture and/or ripening of cheese.

EP-A-671,420 describes an aqueous protective-colloid-stabilized polyacrylate dispersion obtainable by emulsion polymerization of olefinically unsaturated monomers in the disperse phase using an oil-soluble free-radical-forming initiator and a water-soluble reducing agent at reaction temperatures between 40 and 90[deg.] C, a mixture of monomers consisting of 40 to 99.9% by weight alkyl (meth)acrylates having 1 to 18 carbon atoms in the alkyl chain and 0.1 to 60% by weight further monomers being polymerized in the presence of a mixture consisting of poly(vinyl alcohol) and hydroxyethylcellulose and, if appropriate, an anionic and/or nonionic emulsifier, without the addition of water-soluble regulators. Embodiments 13 and the comparative example B (stabilization with poly(vinyl alcohol)) lead to films which have a low water absorption at 9% and 8%, respectively.

US-2005/0287257 Al discloses a food coating composition comprising

a) a plastics dispersion or a mixture of plastics dispersions comprising at least one homo- or copolymer poly(meth)acrylate having at least 55% by weight (meth)acrylate monomer units and also 0.1 to 30% by weight of at least one protective colloid, and also

b) aids and/or additives used in food-coating compositions. However, the coating compositions disclosed therein demonstrate a high water vapor permeability, which as a consequence, could lead to a rapid drying out of the coated fruits.

EP-Al-1 541 600 discloses an aqueous copolymer poly(vinyl ester) dispersion comprising

A) 100 parts by weight of a copolymer derived from

Al) from 34.9 to 95% by weight of vinyl esters of aliphatic, saturated carboxylic acids,

A2) from 4.9 to 65% by weight of maleic esters and/or fumaric esters of monohydric aliphatic alcohols having a chain length of C _l-Cis and/or alpha- olefins having from 2 to 8 carbon atoms,

A3) from 0.1 to 10% of at least one comonomer having at least one stabilizing nonionic or ionic group, and also

A4) optionally other comonomers,

the sum of components Al, A2 and A3 and optionally A4 giving 100% by weight,

B) from 0.1 to 4.5 parts by weight, based on the total amount of the monomers used, of at least one protecting colloid,

C) from 0.1 to 10 parts by weight, based on the total amount of the monomers used, of a nonionic emulsifier, and

D) optionally further additives suitable for coating foods.

EP 1 500 689 Al discloses a coating composition comprising a polymer dispersion on basis of methacrylate homopolymers or methacrylate copolymers obtainable by emulsion polymerization in the presence of protective colloids. However, the polymer films disclosed in EP 1 500 689 Al are too brittle for high quality food coatings, in particular for coatings for fruits, such as citrus fruits.

The object underlying the present invention was the provision of an improved food coating composition, in particular a coating composition for climacteric fruits, the films of which have a sufficiently low water vapor transmission rate and provide the coated fruits with an attractive visual appearance. A further object of the present invention was the provision of a coated food which has a sufficiently low water vapor transmission rate and which coating has a decreased surface stickiness compared with conventional vinyl acetate-based coating compositions and which, furthermore, in the moist state, has good mechanical properties so that the coated fruit can be handled without risk of damage.

It has been found that the problems associated with food coating compositions disclosed in the prior art can be solved by a composition which comprises a copolymer obtainable by emulsion polymerization of an aqueous radically polymerizable mixture of monomers, wherein the composition is substantially free of polyvinyl alcohol.

An embodiment of the present invention is the use of a composition for coating food wherein said composition comprises a copolymer obtainable by emulsion polymerization of an aqueous radically polymerizable mixture of monomers comprising

a) at least one (meth)acrylate monomer (A),

b) at least one (meth)acrylate monomer (B) which is different from monomer

(A) ,

c) at least one ethylenically unsaturated carboxylic acid monomer(Cl) and/or an ethylenically unsaturated electrically charged monomer (C2), and

d) optionally at least one monomer (D) which is different from monomer (A) and

(B) and which is selected from the group consisting of (meth)acrylate or (meth)acrylamide which may comprise functional groups; wherein the amount of the sum of monomer (A) and monomer (B) is more than 75 wt.-% and

wherein the glass transition temperature of the copolymer is 0 to 25°C, determined according to ASTM E 1356 by differential scanning calorimetry and wherein the composition is substantially free of polyvinyl alcohol.

The composition used for the coating of food according to the present invention comprises a copolymer obtainable by emulsion polymerization of an aqueous radically polymerizable mixture of monomers which comprise at least one (meth)acrylate monomer (A) hereinafter also referred to as "monomer (A)" as well as at least one (meth)acrylate monomer (B), hereinafter also referred to as "monomer (B)", which is different from monomer (A).

The term "(meth)acrylate" means ester of acrylic acid or methacrylic acid.

Suitable monomers (A) or (B) are the (meth)acrylic alkyl esters having 1 to 18 carbon atoms in the alkyl chain. The acrylates are typically esters of acrylic acid with alcohols, such as, in particular methanol, ethanol, n-butanol, isobutanol or 2-ethylhexanol .

Preferred monomers of this type are acrylic acid methyl, ethyl, n-butyl, isobutyl and 2-ethylhexyl esters.

The methacrylates are typically esters of methacrylic acid with alcohols, such as in particular methanol, ethanol, n-butanol, isobutanol or 2-ethylhexanol .

Preferred monomers of this type are methacrylic acid methyl, ethyl, n-butyl, isobutyl and 2-ethylhexyl esters.

Preference is given to the linear and branched alkyl esters of (meth)acrylic acid having 1 to 8 carbon atoms in the alkyl chain.

For the polymerization, preferably, use is made of one hard monomer and one soft monomer, or a mixture of a plurality of soft monomers and also a mixture of a plurality of hard monomers.

The designation "hard" and "soft" relates to the position of the glass transition temperature of the homopolymer produced from the respective monomer relative to room temperature (25°C). For instance, soft monomers form polymers having a glass transition temperature below room temperature, hard monomers form those having a glass transition temperature above room temperature. The glass transition temperature of the mixed polymer can be set below ambient temperature by the mixing ratio of hard and soft monomers. Preferably, mixing ratios of hard and soft monomers are sought after in which the polymers form a consolidated film at room temperature without the addition of external plasticizers. In particular, the minimum film formation temperature should be below 20°C.

According to a preferred embodiment monomer (A) is selected from monomers which homopolymers have a glass transition temperature (Tg) of 25°C or higher. According to an especially preferred embodiment monomer (A) is selected from the group consisting of methyl methacrylate, ethyl methacrylate, sec-butyl methacrylate, isopropyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl methacrylate and mixtures thereof.

Preferably, monomer (B) is selected from monomers which homopolymers have a glass transition temperature (Tg) of less than 25°C.

Especially preferred is the monomer (B) selected from the group consisting of methyl acrylate, ethylacrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2-propylheptyl acrylate and mixtures thereof.

Good results for the food coating composition can be achieved wherein the amount of the sum of monomer (A) and monomer (B) preferably more than 85 wt.-% and especially preferably more than 95 wt.-%, wherein the weight is based on the total weight of the radically polymerizable mixture of monomers.

Further, the aqueous radically polymerizable mixture of monomers comprises at least one ethylenically unsaturated carbobxylic acid monomer (CI), hereinafter also referred to as "monomer (CI)" and/or an ethylenically unsaturated electrically charged monomer (C2), hereinafter also referred to as "monomer (C2)".

According to a preferred embodiment monomer (CI) is selected from the group consisting of α, β- unsaturated carboxylic or dicarboxylic acids, preferably selected from the group consisting of acrylic acid, methacrylic acid, maleic acid and itaconic acid and/or monomer (C2) is selected from the group consisting of water soluble salts of α,β -unsaturated carboxylic or dicarboxylic acids, preferably selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, itaconic acid and mixtures thereof.

The amount of the sum of monomer (CI) and monomer (C2) is preferably up to 15 weight percent, more preferably 0.5 to 10 weight percent, even more preferably 1 to 4.5 weight percent, based on the total weight of the radically polymerizable monomers.

The radically polymerizable mixture of monomers may optionally comprise at least one monomer (D) which is different from monomer (A) and (B) and which is selected from the group consisting of (meth)acrylate or (meth)acrylamide which may comprise functional groups, preferably -OH and/or -NH₂.

Preferably, monomer (D) is selected from esters of (meth)acrylic acid with C₂-Ci₈ dialcohols, esters of (meth)acrylic acid with dialkylaminoalkanols, N- alkylolamides of (meth)acrylic acid or ethers, preferably selected from hydroxylalkyl(meth)acrylate and aminoalkyl(meth)acrylate, especially hydroxyethyl (meth)acrylate.

Monomer (D) is preferably present in the radically polymerizable monomer composition in an amount of up to 5 weight percent, more preferably ranging from 0.1 to 4.5 weight percent, even more preferably 0.5 to 3 weight percent, based on the total amount of the radically polymerizable monomers.

The composition used according to the present invention is substantially free of polyvinyl alcohol, which is a protective colloid. It has been found that optimum results can be achieved for a composition which is substantially free of any protective colloid. Therefore, according to a preferred embodiment the composition used according to the present invention is substantially free of any protective colloids. Substantially free within the meaning of the present invention means that the polyvinyl alcohol and/or the protective colloid can be present in an amount of less than 0.1 percent by weight, preferably less than 0.05 percent by weight, more preferably less than 0.01 percent by weight, even more preferably less than 0.001 percent by weight and especially completely free, wherein the "percent by weight" is based on the total weight of the composition.

The copolymer which is obtainable by emulsion polymerization of the aqueous radically polymerizable mixture of monomers preferably has a glass transition temperature (Tg) ranging from 2 to 18°C, preferably 3 to 15°C.

According to a preferred embodiment the monomer (A), (B), (C) and optionally (D) are selected in such a manner that the film produced there from has a water vapor transmission rate of less than 40, preferably less than 30, more preferably ranging from 1 to 20, especially ranging from 2 to 15 g/(m²/24h), more especially ranging from 3 to 11 g/(m²/24h) determined on films having 300 μιη layer thickness.

Further, the composition used according to the present invention may comprise further additives such as emulsifiers.

Suitable emulsifiers are sodium salts, potassium salts and ammonium salts of straight-chain aliphatic carboxylic acids of chain length Ci₂-C₂o, sodium hydroxyoctadecanesulfonate, sodium salts, potassium salts and ammonium salts of hydroxy fatty acids of chain length Ci₂-C₂₀ and their sulfination and/or acetylation products, alkyl sulfates, also as triethanolamine salts, alkyl(Ci₀-C₂₀) sulfonates, alkyl(Ci₀-C₂₀) aryl sulfonates, dimethyidialkyl(C₈-Ci₈) ammonium chloride, acyl, alkyl, oleyl and alkylaryloxethylates and their sulfination products, alkali metal salts of sulfosuccinic acid esters with aliphatic saturated monohydric alcohols of chain length C₄-Ci₆, sulfosuccinic acid 4-esters with polyethylene glycol ethers of monohydric aliphatic alcohols of chain length Ci₀-Ci₂ (disodium salt), sulfosuccinic acid 4-esters with polyethylene glycol nonylphenyl ether (disodium salt), sulfosuccinic biscyclohexyl ester (sodium salt), lignosulfonic acid and also its calcium, magnesium, sodium and ammonium salts, polyoxyethylene sorbitan monooleate having 20 ethylene oxide groups, resin acids, hydrogenated and dehydrogenated resin acids and also their alkali metal salts, dodecylinated diphenyl ether disulfonic sodium and also copolymers of ethylene oxide and propylene oxide having a minimum content of 10% by weight ethylene oxide. Those which are preferably used as emulsifiers are: sodium lauryl sulfate, sodium lauryl ether sulfate, if ethoxylated (3 ethylene oxide groups); the polyethylene glycol (4-20) ether of oleyl alcohol and also the polyethene oxide (4-14) ether of nonylphenol.

In particular, anionic and/or nonionic emulsifiers are suitable. These compounds can be used at 0.0 to 5.0% by weight, preferably in an amount of less than 1.7 % by weight, more preferably of less than 1.5 % by weight, e.g. 0.0 to 1.4 % by weight or 0.2 to 1.2 % by weight based on the amount of total monomers.

The solids content of the inventively used composition is 20 to 65% by weight, preferably 30 to 60% by weight, and particularly preferably 40 to 55% by weight.

The compositions (dispersions) to be used inventively are preferably prepared by free-radical emulsion polymerization. The polymerization can be carried out in the batch method, in the feed-stream method, or combined batch/feed-stream methods. Preferably, however, the feed-stream method is employed, customarily a part of the monomers (1 to 15% by weight) being charged at the start of polymerization.

The production of aqueous polymer dispersions has previously been described many times and is therefore known to those skilled in the art [cf. e.g. Encyclopedia of Polymer Science and Engineering, vol. 8, pp. 659 ff (1987)] .

Initiators are used for the free-radical initiation of the emulsion polymerization. As initiators, use is made of, for example : hydrogen peroxide, benzoyl peroxide, cyclohexanone peroxide, isopropyl cumyl hydroperoxide, persulfates of potassium, sodium and ammonium, peroxides of even-numbered saturated monobasic aliphatic carboxylic acids of chain length C₈-Ci₂, tertiary-butyl hydroperoxide, ditertiary-butyl peroxide, diisopropyl percarbonate, azoisobutyrodinitrile, acetylcyclohexanesulfonyl peroxide, tertiary- butyl perbenzoate, tertiary-butyl peroctoate, bis(3,5,5-trimethyl)hexanoyl peroxide, tertiary-butyl perpivalate, hydroperoxypinane, p-methane hydroperoxide. The abovementioned compounds can also be used within a redox system, transition metal salts such as iron(II) sulfate or other reducing agents being used in conjunction . Reducing agents or regulators which can be used in conjunction are alkali metal salts of oxymethanesulfinic acid, mercaptanes of chain length Ci₀- Ci₄, but-(l)-en-(3)-ol, hydroxylamine salts, sodium dialkyldithiocarbamate, sodium bisulfite, ammonium bisulfite, sodium dithionite, diisopropylxanthogen disulfide, ascorbic acid, tartaric acid, isoascorbic acid, boric acid, urea and formic acid.

Preferably, however, water-soluble persulfates, in particular ammonium persulfate or sodium persulfate, are used to start the polymerization.

After completion of the polymerization, for demonomerization, a further post- treatment can follow, preferably using redox catalysts, for example combinations of oxidizing agents with reducing agents such as ascorbic acid or further abovementioned reducing agents.

A physical demonomerization can also follow, for example by stripping with an inert gas or a steam distillation, or a combination of chemical and physical demonomerization can be carried out.

The composition used according to the present invention preferably additionally comprises aids and additives used in food coating compositions. These can be processing aids, dies, biocides, stabilizers or combination of two or more of these additives. It has been found that the composition used according to the present invention is particularly suitable to be mixed with biocides, which are preferably selected from the group consisting of o-phenyl phenol, thiabendazol, imazalil, imazalil sulfate, polyene fungicides like natamycine, sorbic acid and sorbic acid salts.

The additives, in particular the biocides can be present in the composition in an amount up to 10 weight percent, preferably ranging from 0.0001 to 5 percent by weight, more preferably 0.001 to 4 weight percent, even more preferably 0.05 to 3 weight percent, based on the total weight of the composition.

According to a preferred embodiment the composition used according to the present invention has a viscosity of less than 1000 mPas, preferably ranging from 2 to 800 mPas, more preferably ranging from 5 to 600 mPas, especially ranging from 10 to 400 mPas, determined at 23°C; spindle 2; 20 rpm (Brookfield). The viscosity values refer to the viscosity of the composition when applied to the food also called "application viscosity".

The composition used for coating food is especially preferred wherein the food is selected from the group consisting of fruits, vegetables, seeds, meat products, cheese products and sausages products, especially for the coating of apples, bananas, oranges, tangerines, grapefruit, pommelo, lemons, limes, kumquats, pears, mangoes, melons, papayas, nectarines, plums, tomatoes, cherries, avocado, cucumber, squash, root crops, and tree nuts.

Especially preferred is the food selected from fruits and vegetables, especially preferred is the food a climacteric fruit. More especially preferred is the food a citrus fruit.

A further embodiment of the present invention is a food which is coated with the composition as used according to the present invention. Especially preferred is the food selected from fruits and vegetables.

The following Examples serve to illustrate the invention. Data on parts and percentages relate to the weight unless otherwise stated : General Measurement Methods:

Solid content was measured by drying 1 to 2 g of the aqueous dispersion at 105°C for 4 hours, then dividing the weight of dried polymer by the weight of dispersion.

Determination of the glass transition temperature (Tg) was according to ASTM E 1356 by differential scanning calorimetry (DSC), using a Mettler DSC 820 with a fluid N₂ cooling system . The tested range is from -80°C to 130°C with a heating rate of 10°C/min.

Examples:

Example 1 (according to the invention)

In a glass stirred tank reactor with an agitating means, anchor agitator, feed inlets and electronic temperature control, 0.09 active part of Emulsogen^® EPA 073 (commercial product of Clariant GmbH) is dissolved in 36 parts of deionized water. To initiate the reaction, 0.064 part of ammonium peroxodisulfate (APS) in 1.33 parts of deionized water was added at 80 °C.

To this mixture, 2.4% of a monoemulsion consisting of the following components is added to start at 80 °C:

46 parts of methyl methacrylate

54 parts of 2-ethylhexyl acrylate

2 parts of methacrylic acid

1 part of acrylic acid

1 part of hydroxyethyl methacrylate

0.376 part of ammonium peroxodisulfate

0.91 active part of Emulsogen^® EPA 073

44 parts of deionized water The rest of this monoemulsion is metered within 4 hours, and a reaction temperature of 80 °C is maintained. This is followed by postpolymerization at 85 °C for 1 hour and subsequent cooling to room temperature. Then, a pH of 7.2 is adjusted by means of 5% aqueous sodium hydroxide solution.

Solids content: 53.4%;

Brookfield viscosity RVT (23 °C), spindle 3, 20 rpm : 330 mPa-s;

Weight average particle size: d_w = 166 nm, determined by laser aerosol spectrometry;

Glass transition temperature: 6.9 °C (DSC; midpoint);

For spray application, the dispersion was adjusted to a solids content of 45%. The Brookfield viscosity RVT (23 °C), spindle 2, 20 rpm, was 35 mPa-s.

The water vapor transmission rate of the polymer film having a thickness of 300 pm as determined by the method described in EP-A-1 541 600, p. 10, was determined to be 9 g/(m² d).

Dispersion for Comparative Example 2 (according to EP-A-1 541 600)

A dispersion was prepared by analogy with Example 5 of EP-A-1 541 600 with an identical monomer composition, except that 2.25% Celvol^® 840 (commercial product of Sekisui Chem. Co., an 88% partially saponified polyvinyl alcohol with a mean solution viscosity in 4% aqueous solution of 45-55 cP-s) was used as the polyvinyl alcohol instead of 1.5% PVA BP-26. Further, only 1% active Genapol^® O- 109 (commercial product of Clariant GmbH) was used instead of 2% Genapol^® O- 120, the emulsifier being charged completely at the beginning rather than metered.

Solids content: 51.3%;

Brookfield viscosity RVT (23 °C), spindle 6, 20 rpm : 9900 mPa-s;

Weight average particle size: d_w = 1540 nm, determined by Mastersizer;

Glass transition temperature: 9.3 °C (DSC; midpoint); For spray application, the dispersion was adjusted to a solids content of 30%. The Brookfield viscosity RVT (23 °C), spindle 2, 20 rpm, was 30 mPa-s.

The water vapor transmission rate of the polymer film having a thickness of 300 pm as determined by the method described in EP-A-1 541 600, p. 10, was determined to be 46 g/(m² d).

Comparative Example C3

The product used was a typical commercially available product for coating citrus fruits, consisting of modified polyethylene wax and shellac (together 180 g/l), ammonium hydroxide, as well as 0.2% imazalil and 0.5% thiabendazole as biocides. The pH of this emulsion was 10. The product was used without further modification. The Brookfield viscosity RVT (23 °C), spindle 2, 20 rpm, was 10 mPa-s.

Treatment of lemons

Two lemons each without coating agent provided pending in a device were sprayed uniformly with the above described preparations using a hand-held spraying device as commonly used domestically. After completely drying at room temperature, the lemons were stored suspended in a controlled environment chamber at 23 °C/50% relative humidity, and the initial value of the masses, mi, was determined. After 14 days of storage had lapsed, the final value m₂ was determined. The percent water loss is obtained as 100 x (mi-m₂)/mi. The mean values of a double determination are stated in each case. In the case of Comparative Example CI, there was no coating, but the mass loss of untreated lemons was merely determined in a double determination. Table 1

Example 2 (according to the invention¹) and Comparative Example C4

For Example 2, a further coating composition was prepared by further diluting the acrylate dispersion as described under Example 1 to a solid content of 35%. The application viscosity was 12 mPa-s (Brookfield RVT, spindle 2, 20 rpm, 23 °C).

For Comparative Example C4, the commercially available citrus waxing preparation from Comparative Example C3 was used without further modification.

In the device described above, untreated lemons washed with drinking water and dried and having approximately the same masses were fixed in a suspending device connected with analytical balance in the controlled environment and sprayed uniformly. The percent wet application coating amount (related to the mass of uncoated fruit) was determined, and the percent dry application coating amount was calculated by means of the solids content. The drying behavior was followed by repeated measurements in the first 20 minutes. After 5 minutes, the percent change as compared to the previous measurement was < 0.2% in both test series. Subsequently, the coated lemons were subjected to a storage period of 14 days in a controlled environment chamber as described above, and an uncoated washed reference fruit being included for comparison (C5). The results are stated in Table 2.

Table 2

Example 3 (according to the invention¹)

An emulsion was prepared according to Example 1 except that 0.9 active part of Emulsogen^® EPA 073 (commercial product of Clariant GmbH) were dissolved in 35.1 parts of deionized water and no hydroxyethyl methacrylate was used :

46 parts of methyl methacrylate

54 parts of 2-ethylhexyl acrylate

2 parts of methacrylic acid

1 part of acrylic acid

0.376 part of ammonium peroxodisulfate

0.91 active part of Emulsogen^® EPA 073 44 parts of deionized water Solids content: 53.5%;

Brookfield viscosity RVT (23 °C), spindle 3, 20 rpm : 4980 mPa-s;

Weight average particle size: d_w = 170 nm, determined by laser aerosol spectrometry;

Glass transition temperature: 8.2 °C (DSC; midpoint);

The water vapor transmission rate of the polymer film having a thickness of 300 pm as determined by the method described in EP-A-1 541 600, p. 10, was determined to be 6.9 g/(m² d).

Comparative Example C6

The same commercially available citrus fruit coating was used as in Comparative Example C3

Treatment of lemons (using Example 3 and Comparative Example C6)

The same process was applied to coat lemons like described above for the test of Example 1 and comparative examples C1-C3.

Table 3

Comparison of Example 1 and Example 3 of the invention with Example 3 and Example 5 of prior art Reference EP 1 500 689 Al .

Table 4

Claims

1. Use of a composition for coating food wherein said composition comprises a copolymer obtainable by emulsion polymerization of an aqueous radically polymerizable mixture of monomers comprising

a) at least one (meth)acrylate monomer (A),

b) at least one (meth)acrylate monomer (B) which is different from monomer (A),

c) at least one ethylenically unsaturated carboxylic acid monomer (CI) and/or an ethylenically unsaturated electrically charged monomer (C2), and

d) optionally at least one monomer (D) which is different from monomer (A) and (B) and which is selected from the group consisting of (meth)acrylate or (meth)acrylamide which may comprise functional groups; wherein the amount of the sum of monomer (A) and monomer (B) is more than 75 wt.-% and

wherein the glass transition temperature of the copolymer is 0 to 25°C, determined according to ASTM E 1356 by differential scanning calorimetry and

wherein the composition is substantially free of polyvinyl alcohol.

2. Use according to claim 1, wherein the amount of the sum of monomer (A) and monomer (B) is more than 85 wt.-% and especially preferably more than 95 wt.-%, wherein the weight is based on the total weight of the radically polymerizable mixture of monomers.

3. Use according to claim 1 or 2, wherein the glass transition temperature (Tg) of the copolymer is 2 to 18 °C, preferably 3 to 15 °C.

4. Use according to at least one of the preceding claims, wherein monomer (A) is selected from monomers which homopolymers have a glass transition temperature (Tg) of 25 °C or higher.

5. Use according to at least one of the preceding claims, wherein the monomer (A) is selected from the group consisting of methyl methacrylate, ethyl methacrylate, sec-butyl methacrylate, isopropyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl methacrylate and mixtures thereof.

6. Use according to at least one of the preceding claims, wherein monomer (B) is selected from monomers which homopolymers have a glass transition temperature (Tg) of less than 25 °C.

7. Use according to at least one of the preceding claims, wherein the monomer (B) is selected from the group consisting of methyl acrylate, ethylacrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, 2- ethylhexyl acrylate, lauryl acrylate, 2-propylheptyl acrylate and mixtures thereof.

8. Use according to at least one of the preceding claims, wherein the composition is substantially free of protective colloids.

9. Use according to at least one of the preceding claims, wherein monomer (CI) is selected from the group consisting of α,β-unsaturated carboxylic or dicarboxylic acids, preferably selected from the group consisting of acrylic acid, methacrylic acid, maleic acid and itaconic acid and/or monomer (C2) is selected from the group consisting of water soluble salts of α,β - unsaturated carboxylic or dicarboxylic acids, preferably selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, itaconic acid and mixtures thereof.

10. Use according to at least one of the preceding claims, wherein the monomer (A), (B), (C) and optionally (D) are selected in such a manner that the film produced there from has a water vapor transmission rate of less than 40, preferably less than 30, more preferably ranging from 1 to 20, especially ranging from 2 to 15 g(m²/24h), determined on films having 300 pm layer thickness.

11. Use according to at least one of the preceding claims, wherein monomer (D) is selected from esters of (meth)acrylic acid with C₂-Ci₈ dialcohols, esters of (meth)acrylic acid with dialkylaminoalkanols, N-alkylolamides of (meth)acrylic acid or ethers, preferably selected from hydroxylalkyl(meth)acrylate and aminoalkyl(meth)acrylate, especially hydroxyethyl (meth)acrylate.

12. Use according to at least one of the preceding claims, wherein the composition has an application viscosity of less than 1000 mPas, preferably ranging from 2 to 800 mPas, more preferably ranging from 5 to 600 mPas, especially ranging from 10 to 400 mPas, determined at 23°C; spindle 2; 20 rpm (Brookfield).

13. Use according to at least one of the preceding claims, wherein the composition additional comprises at least one biocide, preferably selected from the group consisting of o-phenyl phenol, thiabendazol, imazalil, imazalil sulfate, polyene fungicides like natamycine, sorbic acid and sorbic acid salts.

14. Use according to at least one of the preceding claims, wherein the food is selected from the group consisting of fruits, vegetables, seeds, meat products, cheese products and sausages products, especially for the coating of apples, bananas, oranges, tangerines, grapefruit, pommelo, lemons, limes, kumquats, pears, mangoes, melons, papayas, nectarines, plums, tomatoes, cherries, avocado, cucumber, squash, root crops, and tree nuts.

15. A food coated with a composition as defined in at least one of the preceding claims 1 to 14.