DE10159606A1 - Packaging material containing a polyurethane dispersion - Google Patents

Abstract

Packaging material, consisting of a support layer (I) and a layer (II) made of a polyurethane dispersion applied thereto. A thermoplastic polymer or paper, cardboard or paperboard can be used as a support layer. The polymer dispersion thus used can be made inter alia from aliphatic diisocyanates and polyester diols. The packaging material is particularly suitable for packaging goods containing fat, e.g. food products for humans and animals.

Description

The present invention relates to a packaging material, consisting of a carrier layer I and an applied thereon Layer II made of a polyurethane dispersion.

Furthermore, the present invention relates to a method for Production of the packaging material according to the invention, and its use for packaging fatty goods.

Packaging is often made with a thin metal foil coated to make them mechanically more stable and their resistance to improve against environmental influences. It is also known Cardboard to be provided with a plastic film in this way increase its stability and insensitive to water close. However, packaging coated in this way shows that Disadvantage that they are very expensive to manufacture and that moreover, the actual packaging process an increased Effort required. As packaging materials continue to be Polyvinylidene chloride coated cartons are used that are simple and are inexpensive to manufacture, but especially thermal Release recycling toxic substances. Quality Packaging materials should also be as sealable, blockproof and be fat-resistant and high water vapor permeability exhibit.

Aqueous polyurethane dispersions (also briefly as PUR dispersions ) and processes for their preparation are general known. PUR dispersions have long been used to coat Substrates such as B. leather, textiles, wood, metal or Plastic used (DE-A 26 45 779, EP-A 787751). Because of your excellent mechanical properties are preferred PUR dispersions based on polyesterols are used.

In EP-B 595 149 the use is more aqueous PUR dispersions for the production of pore-free, water vapor permeable Coatings described.

EP-A 1 002 001 relates to PUR dispersions which are as very hydrolysis-resistant coatings for materials Metal, plastic, paper, textile, leather or wood are suitable. Out However, this document does not show that such PUR Dispersions are also suitable as special packaging materials.

In the two older applications DE-A 101 27 208.1 and DE-A 101 33 789.2 are also aqueous polyurethane dispersions discloses which u. a. are very resistant to hydrolysis and become Manufacture of coatings, adhesives, impregnations and Sealants are suitable. But from both registrations is not known, such polyurethane dispersions as part of Use packaging material.

The present invention was therefore based on the object remedied disadvantages and an improved To develop packaging material which u. a. sealable, blockproof and is fat-resistant, low water swelling and high Has water vapor permeability and is also ecological is harmless.

Accordingly, an improved packaging material has been found consisting of a carrier layer I and one thereon applied layer II from a polyurethane dispersion. Farther The present invention also extends to a method for the production of the packaging material according to the invention and on its use for the packaging of fatty goods.

The carrier layer I consists u. a. made of thermoplastic polymers or from paper, cardboard or corrugated cardboard.

As thermoplastic polymers that form the backing layer, come u. a. Polyolefins such as polyethylene, Polypropylene, polybut-1-ene or polyisobutylene. Further suitable thermoplastic polymers are, for example Polyvinyl chloride, polyester, polycarbonate, polyacrylate, Polymethacrylate, polyamide, polyacetal, polybutylene terephthalate or Polystyrene. These thermoplastic polymers can be used both in Form of homopolymers as well as copolymers are used, the latter in addition to the respective Main monomers are still suitable comonomers to a lesser extent having. The carrier layer A can also be recycled from these contain thermoplastic polymers.

As the carrier layer I can be used for the invention Packaging material but also commercially available paper, cardboard or Use corrugated cardboard.

• a) Diisocyanaten,
• b) Diolen, von denen
  • 1. 10 bis 100 mol-%, bezogen auf die Gesamtmenge der Diole (b), ein Molekulargewicht von 500 bis 5000 aufweisen, und
  • 2. 0 bis 90 mol-%, bezogen auf die Gesamtmenge der Diole (b), ein Molekulargewicht von 60 bis 500 g/mol aufweisen,
• c) von den Monomeren (a) und (b) verschiedene Monomere mit wenigstens einer Isocyanatgruppe oder wenigstens einer gegenüber Isocyanatgruppen reaktiven Gruppe, die darüber hinaus wenigstens eine hydrophile Gruppe oder eine potentiell hydrophile Gruppe tragen, wodurch die Wasserdispergierbarkeit der Polyurethane bewirkt wird,
• d) gegebenenfalls weiteren von den Monomeren (a) bis (c) verschiedenen mehrwertigen Verbindungen mit reaktiven Gruppen, bei denen es sich um alkoholische Hydroxylgruppen, primäre oder sekundäre Aminogruppen oder Isocyanatgruppen handelt und
• e) gegebenenfalls von den Monomeren (a) bis (d) verschiedenen einwertigen Verbindungen mit einer reaktiven Gruppe, bei der es sich um eine alkoholische Hydroxylgruppe, eine primäre oder sekundäre Aminogruppe oder eine Isocyanatgruppe handelt.

Furthermore, the packaging material according to the invention also consists of a layer II of a polyurethane dispersion applied to the surface of the carrier layer I. The polyurethane dispersion preferably consists of

• a) diisocyanates,
• b) diols, of which
  • 1. 10 to 100 mol%, based on the total amount of diols (b), have a molecular weight of 500 to 5000, and
  • 2. 0 to 90 mol%, based on the total amount of diols (b), have a molecular weight of 60 to 500 g / mol,
• c) monomers different from the monomers (a) and (b) with at least one isocyanate group or at least one group which is reactive toward isocyanate groups and which additionally carry at least one hydrophilic group or a potentially hydrophilic group, thereby causing the water-dispersibility of the polyurethanes,
• d) optionally further polyvalent compounds with reactive groups which differ from the monomers (a) to (c) and which are alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups and
• e) if appropriate, monomers different from the monomers (a) to (d) having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group.

Particularly worth mentioning as monomers (a) are diisocyanates X (NCO) ₂ , where X represents an aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic or aromatic hydrocarbon radical having 6 to 15 carbon atoms or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms. Examples of such diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), 2,2-bis (4-isocyanatocyclohexyl) propane, trimethylhexane diisocyanate , 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanato-diphenylmethane, 2,4'-diisocyanato-diphenylmethane, p-xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI), the isomers of the bis - (4-isocyanatocyclohexyl) methane (HMDI) such as the trans / trans, the cis / cis and the cis / trans isomer and mixtures consisting of these compounds.

Such diisocyanates are commercially available.

As mixtures of these isocyanates, the mixtures of respective structural isomers of diisocyanatotoluene and Diisocyanato-diphenylmethane is important, especially the mixture from 80 mol% 2,4-diisocyanatotoluene and 20 mol% 2,6-diisocyanatotoluene suitable. Furthermore, the mixtures of aromatic isocyanates such as 2,4-diisocyanatotoluene and / or 2,6-diisocyanatotoluene with aliphatic or cycloaliphatic Isocyanates such as hexamethylene diisocyanate or IPDI in particular advantageous, the preferred mixing ratio of aliphatic to aromatic isocyanates 4: 1 to 1: 4.

The structure of the polyurethanes can be used as compounds other than the aforementioned also use isocyanates which, in addition to the free Isocyanate groups further blocked isocyanate groups, e.g. B. Wear uretdione groups.

With regard to good film formation and elasticity come as diols (b) primarily higher molecular weight diols (b1) into consideration, the one Molecular weight from about 500 to 5000, preferably from about Have 1000 to 3000 g / mol.

The diols (b1) are in particular polyester polyols which, for. B. from Ullmann's Encyclopedia of Industrial Chemistry, 4th Edition, Volume 19, pp 62 to 65 are known. Polyester polyols are preferably used which are obtained by reacting dihydric alcohols with dihydric carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols or their mixtures can also be used to prepare the polyester polyols. The polycarboxylic acids can be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic and optionally, e.g. B. by halogen atoms, substituted and / or unsaturated. Examples include: suberic acid, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, fatty acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, fatty acid, maleic acid, maleic acid, maleic acid, fatty acid, maleic acid, in, in Dicarboxylic acids of the general formula HOOC- (CH ₂ ) _y - COOH are preferred, where y is a number from 1 to 20, preferably an even number from 2 to 20, e.g. B. succinic acid, adipic acid, sebacic acid and dodecanedicarboxylic acid.

As polyhydric alcohols such. B. ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,3-diol, butene-1,4-diol, butyne-1,4-diol, pentane-1,5- diol, neopentyl glycol, bis (hydroxymethyl) cyclohexanes such as 1,4-bis (hydroxymethyl) cyclohexane, 2-methylpropane-1,3-diol, methylpentanediols, also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, Dibutylene glycol and polybutylene glycols are considered. Alcohols of the general formula HO- (CH ₂ ) _x -OH are preferred, where x is a number from 1 to 20, preferably an even number from 2 to 20. Examples include ethylene glycol, butane-1,4-diol, hexane-1,6-diol, octane-1,8-diol and dodecane-1,12-diol. Neopentyl glycol is also preferred.

Also come polycarbonate diols, such as z. B. by Implementation of phosgene with an excess of the Build-up components for the low molecular weight polyester polyols Alcohols can be obtained.

Lactone-based polyester diols are also suitable, these being homopolymers or copolymers of lactones, preferably addition products of lactones with terminal hydroxyl groups onto suitable difunctional starter molecules. Suitable lactones are preferably those which are derived from compounds of the general formula HO- (CH ₂ ) _z -COOH, where z is a number from 1 to 20 and an H atom of a methylene unit also by a C ₁ - to C ₄ -alkyl radical may be substituted. Examples are ε-caprolactone, β-propiolactone, γ-butyrolactone and / or methyl-ε-caprolactone and mixtures thereof. Suitable starter components are e.g. B. the above-mentioned as a structural component for the polyester polyols low molecular weight dihydric alcohols. The corresponding polymers of ε-caprolactone are particularly preferred. Lower polyester diols or polyether diols can also be used as starters for the preparation of the lactone polymers. Instead of the polymers of lactones, the corresponding, chemically equivalent polycondensates of the hydroxycarboxylic acids corresponding to the lactones can also be used.

In addition, polyether diols are suitable as monomers (b1). They are in particular by polymerization of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with themselves, for. B. in the presence of BF ₃ or by addition of these compounds, optionally in a mixture or in succession, to starting components with reactive hydrogen atoms, such as alcohols or amines, for. B. water, ethylene glycol, propane-1,2-diol, propane-1,3-diol, 1,2-bis (4-hydroxydiphenyl) propane or aniline available. Polytetrahydrofuran with a molecular weight of 240 to 5000, and especially 500 to 4500, is particularly preferred.

Polyhydroxyolefins are also suitable, preferably those with 2 terminal hydroxyl groups, e.g. B. α, -ω-dihydroxypolybutadiene, α, -ω-Dihydroxypolymethacrylester or α, -ω-Dihydroxypolyacrylester as monomers (c1). Such connections are, for example known from EP-A 0622378. Other suitable polyols are Polyacetals, polysiloxanes and alkyd resins.

The polyols can also be used as mixtures in a ratio of 0.1: 1 to 1: 9 can be used.

Polyester polyols are preferably used, particularly preferably those used as the acid component ortho-, iso- or terephthalic acid in proportions of at least 10 mol%, based on the total number the acid used.

The hardness and elastic modulus of the polyurethanes can be increase if as diols (b) in addition to the diols (b1) low molecular weight diols (b2) with a molecular weight of about 60 to 500, preferably from 62 to 200 g / mol, are used.

Above all, the structural components of the for monomers (b2) the production of short-chain polyester polyols Alkanediols used, the unbranched diols having 2 to 12 C atoms and an even number of C atoms as well Pentane-1,5-diol and neopentyl glycol are preferred.

The proportion of diols (b1) is preferably based on the Total amount of diols (b) 10 to 100 mol% and the proportion of Monomers (b2), based on the total amount of diols (b) 0 to 90 mol%. The ratio of the diols is particularly preferably (b1) to the monomers (b2) 0.1: 1 to 5: 1, particularly preferred 0.2: 1 to 2: 1.

To achieve the water dispersibility of the polyurethanes, are the polyurethanes in addition to components (a), (b) and optionally (d) from components (a), (b) and (d) various monomers (c) which have at least one isocyanate group or at least one group reactive towards isocyanate groups and moreover at least one hydrophilic group or a group, which can be converted into a hydrophilic group, built up. In the following text the term "hydrophilic groups or potentially hydrophilic groups "with" (potentially) hydrophilic Groups ". The (potentially) hydrophilic groups react with isocyanates much more slowly than the functional ones Groups of monomers used to build the polymer backbone serve.

The proportion of components with (potentially) hydrophilic groups on the total amount of components (a), (b), (c), (d) and (e) is generally dimensioned so that the molar amount of (Potentially) hydrophilic groups, based on the amount by weight of all Monomers (a) to (e), 30 to 1000, preferably 50 to 500 and is particularly preferably 80 to 300 mmol / kg.

The (potentially) hydrophilic groups can be non-ionic or preferably around (potentially) ionic hydrophilic Trade groups.

In particular come as nonionic hydrophilic groups Polyethylene glycol ether from preferably 5 to 100, preferably 10 to 80 repeat ethylene oxide units. The content of Polyethylene oxide units is generally 0 to 10, preferably 0 to 6% by weight, based on the amount by weight of all monomers (a) to (e).

Preferred monomers with nonionic hydrophilic groups are Polyethylene oxide diols, polyethylene oxide monools and the Reaction products from a polyethylene glycol and a diisocyanate, the carry a terminally etherified polyethylene glycol residue. Such diisocyanates and processes for their preparation are in the patents US-A 3 905 929 and US-A 3 920 598.

Ionic hydrophilic groups are primarily anionic groups such as the sulfonate, carboxylate and phosphate groups in the form their alkali metal or ammonium salts and cationic groups such as ammonium groups, especially protonated tertiary Amino groups or quaternary ammonium groups.

Potentially ionic hydrophilic groups are primarily those that by simple neutralization, hydrolysis or Quaternization reactions in the above ionic hydrophilic Have groups transferred, e.g. B. carboxylic acid groups or tertiary amino groups.

(Potentially) ionic monomers (c) are e.g. B. in Ullmanns Encyclopedia of Technical Chemistry, 4th Edition, Volume 19, Pp. 311-313 and for example in DE-A 14 95 745 in detail described.

As (potentially) cationic monomers (c) are primarily monomers with tertiary amino groups of particular practical importance, for example: tris (hydroxyalkyl) amines, N, N'-bis (hydroxyalkyl) alkylamines, N-hydroxyalkyl dialkylamines, Tris (aminoalkyl) amines, N, N'-bis (aminoalkyl) alkylamines, N-aminoalkyl-dialkylamines, the alkyl radicals and alkanediyl units of these tertiary amines independently of one another from 1 to 6 Carbon atoms exist. There are also tertiary nitrogen atoms comprising polyethers with preferably two terminal ends Hydroxyl groups, such as. B. by alkoxylation of two Amines containing amine nitrogen-bonded hydrogen atoms, e.g. B. Methylamine, aniline or N, N'-dimethylhydrazine, in itself more usual Are accessible. Such polyethers have generally a molecular weight between 500 and 6000 g / mol on.

These tertiary amines are either with acids, preferably strong mineral acids such as phosphoric acid, sulfuric acid, hydrohalic acids or strong organic acids or by reaction with suitable quaternizing agents such as C ₁ - to C ₆ -alkyl halides or benzyl halides, e.g. As bromides or chlorides, converted into the ammonium salts.

Suitable monomers with (potentially) anionic groups are usually aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acids and sulfonic acids which carry at least one alcoholic hydroxyl group or at least one primary or secondary amino group. Dihydroxyalkylcarboxylic acids are preferred, especially those with 3 to 10 carbon atoms, as are also described in US Pat. No. 3,412,054. In particular, compounds of the general formula (c ₁ )


in which R ¹ and R ^{2 represent} a C ₁ to C ₄ alkanediyl unit and R ^{3 represents} a C ₁ to C ₄ alkyl unit and especially dimethylolpropionic acid (DMPA) is preferred.

Corresponding dihydroxysulfonic acids and Dihydroxyphosphonic acids such as 2,3-dihydroxypropanephosphonic acid.

Otherwise, dihydroxyl compounds with a Molecular weight over 500 to 10,000 g / mol with at least 2 Carboxylate groups, which are known from DE-A 39 11 827. you are through Implementation of dihydroxyl compounds with Tetracarboxylic acid dianhydrides such as pyromellitic dianhydride or Cyclopentanetetracarboxylic dianhydride in a molar ratio of 2: 1 to 1.05: 1 in a polyaddition reaction available. As Dihydroxyl compounds are especially those as chain extenders listed monomers (b2) and the diols (b1) are suitable.

As monomers (c) with amino groups reactive towards isocyanates come aminocarboxylic acids such as lysine, β-alanine or those in the DE-A 20 34 479 adducts of aliphatic diprimaries Diamines on α, β-unsaturated carboxylic or sulfonic acids into consideration.

• - R⁴ und R⁵ unabhängig voneinander für eine C₁- bis C₆ -Alkandiyl-Einheit, bevorzugt Ethylen
  und X für COOH oder SO₃H stehen.

Such compounds obey, for example, the formula (c ₂ )

H ₂ NR ⁴ -NH-R ⁵ -X (c ₂ )

in the

• - R ⁴ and R ⁵ independently of one another for a C ₁ to C ₆ alkanediyl unit, preferably ethylene
  and X represents COOH or SO ₃ H.

Particularly preferred compounds of the formula (c ₂ ) are the N- (2-aminoethyl) -2-aminoethane carboxylic acid and the N- (2-aminoethyl) -2-aminoethanesulfonic acid or the corresponding alkali metal salts, Na being particularly preferred as the counter ion.

The adducts of the abovementioned are also particularly preferred aliphatic diprimary diamines 2-Acrylamido-2-methylpropanesulfonic acid, as z. B. are described in DE-B 19 54 090.

If monomers with potentially ionic groups are used can be converted into the ionic form before, during, however, preferably after the isocyanate polyaddition, because the ionic monomers in the reaction mixture often only difficult to solve. The sulfonate or Carboxylate groups in the form of their salts with an alkali ion or an ammonium ion as a counter ion.

The monomers (d) differ from the monomers (a) to (c) are and which may also be components of the polyurethane are generally used for networking or Chain extension. They are generally more than two-valued non-phenolic alcohols, amines with 2 or more primary and / or secondary amino groups as well as compounds in addition to one or several alcoholic hydroxyl groups one or more primary and / or wear secondary amino groups.

Alcohols with a higher valence than 2, for adjustment a certain degree of branching or networking can, for. B. trimethylolpropane, glycerin or sugar.

Also suitable are monoalcohols which, in addition to the hydroxyl Group carry a further group reactive towards isocyanates such as mono alcohols with one or more primary and / or secondary amino groups, e.g. B. Monoethanolamine.

Polyamines with 2 or more primary and / or secondary Amino groups are mainly used when the chain extension or crosslinking should take place in the presence of water, since Amines are generally faster than using alcohols or water Isocyanates react. This is often necessary when aqueous dispersions of cross-linked polyurethanes or polyurethanes with a high molecular weight. In such cases you go so that you prepare prepolymers with isocyanate groups, these quickly dispersed in water and then by adding Compounds with several isocyanate-reactive Amino groups chain-extended or cross-linked.

Suitable amines are generally polyfunctional amines of the molecular weight range from 32 to 500 g / mol, preferably from 60 to 300 g / mol, which at least two amino groups, selected from the group of primary and secondary amino groups, contain. Examples include diamines such as diaminoethane, Diaminopropanes, diaminobutanes, diaminohexanes, piperazine, 2,5-dimethylpiperazine, amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane (Isophoronediamine, IPDA), 4,4'-diaminodicyclohexylmethane, 1, 4-diaminocyclohexane, aminoethylethanolamine, hydrazine, hydrazine hydrate or Triamines such as diethylenetriamine or 1,8-Diamino-4-aminomethyloctane.

The amines can also be in blocked form, e.g. B. in the form of corresponding ketimines (see e.g. CA-A 1 129 128), ketazines (cf. z. B. US-A 4 269 748) or amine salts (see US-A 4 292 226) be used. Also oxazolidines, such as those in the US Pat. No. 4,192,937 are capped polyamines, for the production of the polyurethanes according to the invention Chain extension of the prepolymers can be used. at the use of such capped polyamines in generally with the prepolymers in the absence of water mixed and then this mixture with the dispersion water or part of the dispersion water mixed so that the corresponding polyamines are released hydrolytically.

Mixtures of di- and triamines are preferably used, mixtures of isophoronediamine (IPDA) and Diethylenetriamine (DETA).

The polyurethanes preferably contain 1 to 30, especially preferably 4 to 25 mol%, based on the total amount of the components (b) and (d) a polyamine with at least 2 opposite Isocyanate-reactive amino groups as monomers (d).

For the same purpose, monomers (d) can also be higher than divalent isocyanates are used. commercial Compounds are, for example, the isocyanurate or the biuret of hexamethylene diisocyanate.

Monomers (e), which may also be used, are Monoisocyanates, monoalcohols and monoprimary and secondary amines. in the in general, their proportion is at most 10 mol%, based on the total molar amount of monomers. These monofunctional Compounds usually carry further functional groups such as olefinic groups or carbonyl groups and are used for Introduction of functional groups in the polyurethane that the Dispersion or crosslinking or other polymer-analog Enable implementation of the polyurethane. Consider this Monomers such as isopropenyl-α, α-dimethylbenzyl isocyanate (TMI) and Esters of acrylic or methacrylic acid such as hydroxyethyl acrylate or Hydroxyethyl methacrylate.

Coatings with a particularly good property profile are obtained especially when essentially only as monomers (a) aliphatic diisocyanates, cycloaliphatic diisocyanates or araliphatic diisocyanates and essentially as monomer (b1) only a polyester diol, built up from the aliphatic mentioned Diols and diacids can be used.

This combination of monomers is excellently supplemented as Component (c) by diaminosulfonic acid alkali salts; all especially through the N- (2-aminoethyl) -2-aminoethanesulfonic acid or their corresponding alkali salts, with the Na salt being the best is suitable, and a mixture of DETA / IPDA as component (d).

In the field of polyurethane chemistry, it is well known how the molecular weight of the polyurethanes by choosing the proportions of the mutually reactive monomers and the arithmetic mean the number of reactive functional groups per molecule can be adjusted.

• A) der Molmenge an Isocyanatgruppen und
• B) der Summe aus der Molmenge der Hydroxylgruppen und der Molmenge der funktionellen Gruppen, die mit Isocyanaten in einer Additionsreaktion reagieren können

0,5 : 1 bis 2 : 1, bevorzugt 0,8 : 1 bis 1,5, besonders bevorzugt 0,9 : 1 bis 1,2 : 1 beträgt. Ganz besonders bevorzugt liegt das Verhältnis A : B möglichst nahe an 1 : 1. Components (a) to (e) and their respective molar amounts are normally chosen so that the ratio A: B with

• A) the molar amount of isocyanate groups and
• B) the sum of the molar amount of the hydroxyl groups and the molar amount of the functional groups which can react with isocyanates in an addition reaction

0.5: 1 to 2: 1, preferably 0.8: 1 to 1.5, particularly preferably 0.9: 1 to 1.2: 1. The ratio A: B is very particularly preferably as close as possible to 1: 1.

The monomers (a) to (e) used bear on average usually 1.5 to 2.5, preferably 1.9 to 2.1, particularly preferably 2.0 Isocyanate groups or functional groups with isocyanates can react in an addition reaction.

The polyaddition of components (a) to (e) to produce the present in the packaging material according to the invention Polyurethane is preferably carried out at reaction temperatures of up to 180 ° C, preferably up to 150 ° C under normal pressure or under autogenous pressure.

The required response times are in the range from 1 to 20 hours, especially in the range of 1.5 to 10 hours. It is known in the field of polyurethane chemistry, such as the Response time through a variety of parameters such as temperature, Concentration of the monomers, reactivity of the monomers affected becomes. It can also be recommended to neutralize the excess acid after polyaddition of ammonia should enforce.

The polyaddition of the monomers a) to e) to produce the PUR Dispersion can be in the absence or in the presence of organometallic catalysts. Under the label organometallic catalysts should be understood Connections of elements from the following groups of the Periodic table: Ia (with the exception of hydrogen), IIa, IIIa with the exception of boron, IVa with the exception of carbon, Va with the exception of Nitrogen and phosphorus, VIa with the exception of oxygen and Sulfur, IIIb, IVb, Vb, VIb, VIIb, VIIIb, Ib, IIb as well as the Lanthanides and actinides that form a covalent bond Have element carbon. These include u. a. also the frequently used ones organic tin compounds, such as Dibutyltindilaurate.

Stirred kettles come into consideration as polymerization apparatus, especially if by using solvents for low viscosity and good heat dissipation is ensured.

Preferred solvents are infinitely miscible with water, have a boiling point at normal pressure of 40 to 100 ° C and do not react or react slowly with the monomers.

Most often the dispersions are made according to one of the following Process made:

After the "acetone process" is in a miscible with water and at normal pressure below 100 ° C boiling solvent from the Components (a) to (c) made an ionic polyurethane. It as much water is added until a dispersion forms, in the water is the coherent phase.

The "prepolymer mixing process" differs from Acetone process in that not a fully reacted (potentially) ionic Polyurethane but first a prepolymer is made which carries isocyanate groups. The components are like this chosen that the definition A: B ratio greater than 1.0 to 3, preferably 1.05 to 1.5. The prepolymer is first in Dispersed water and then optionally by reaction of the isocyanate groups with amines that are more than 2 opposite Carry isocyanate-reactive amino groups, crosslinked or with amines, which carry 2 amino groups reactive towards isocyanates, chain extended. A chain extension also takes place if no amine is added. In this case, isocyanate groups hydrolyzed to amino groups with those still remaining Isocyanate groups of the prepolymers with chain extension react.

Usually, if in the manufacture of the polyurethane a solvent was used, most of the Solvent removed from the dispersion, for example by Distillation under reduced pressure. Preferably, the Dispersions have a solvent content of less than 10% by weight and are particularly preferably free of solvents.

The dispersions generally have a solids content of 10 to 75, preferably 20 to 65% by weight and a viscosity of 10 to 500 m Pas (measured at a temperature of 20 ° C. and a shear rate of 250 s ^-1 ).

Particularly preferred packaging materials contain one Polyurethane dispersion that is available by first off Macrools, ionic and potentially ionic polyols and excess polyisocyanates an NCO-terminated prepolymer is produced, this prepolymer with compounds that have at least 2 isocyanate-reactive amino groups, in a ratio of NCO groups / NH groups of ≤ 1: 1, neutralized and then dispersed with water.

Compounds used in particular as macrools are: which have a molecular weight of 500 to 5000, preferably of 800 have up to 4500, particularly preferably from 800 to 3000. All the use of macrodiols is particularly preferred.

The macrodiols are, in particular, polyesterols which, for. B. from Ullmann's Encyclopedia of Industrial Chemistry, 4th edition, volume 19, page 62-65 are known. In this regard, we also refer to our above explanations regarding the diols (b ₁ ), the polycarbonate diols, the lactone-based polyesterols, the polyetherols and the polyhydroxyolefins.

As far as the polyisocyanates used are concerned apply the same diisocyanates as already above described.

The described macrools, ionic or potentially ionic Polyols and isocyanates and possibly short-chain polyols can also an NCO-terminated prepolymer. in this connection are preferably polyols containing difunctional building blocks used. The ratio of NCO groups to NCO reactive Groups should be between 1.1: 1 to 2: 1, preferably 1.15: 1 to 1.9: 1, particularly preferably 1.2: 1 to 1.5: 1.

This prepolymer can then be reacted further in step b become. All aliphatic and / or cycloaliphatic compounds are used which carry at least two amino groups reactive towards isocyanates. The use of diamine is preferred. To do this in particular ethylene diamine, propylene diamine, hexamethylene diamine, Isophoronediamine (IPDA), p-xylylenediamine, 4,4-diamino-dicyclohexylmethane and 4,4-diamino-3,3-dimethyldicyclohexylmethane.

The prepolymer is preferred with the compounds mentioned in an NCO group / NH group ratio of 0.9: 1 to 1: 1 implemented. A ratio of 0.95: 1 to is particularly preferred 1: 1, very particularly 1: 1. It follows that the NCO content after Step b) is 0, at most 0.2% by weight, based on the prepolymer.

Following the implementation of the prepolymer Neutralization. For this, z. B. ammonia, N-methylmorpholine, Dimethylisopropanolamine, triethylamine, dimethylethanolamine, Methyldiethanolamine, triethanolamine, morpholine, tripropylamine, Ethanolamine, diethanolamine, triisopropanolamine, N-ethyl-diisopropylamine and mixtures thereof.

The use of ammonia is particularly preferred. The content of COO ^- NH ₄ ⁺ after neutralization should be between 100 and 600 mmol / kg, preferably 200 to 500, particularly preferably 250 to 500.

After neutralization, disperse with water and, if necessary, Distilled off solvent. By adding water and that then removing the solvent by distillation the desired solid concentration in particular to adjust. In this way one can contain a macroole Produce polyurethane dispersion, which is preferred for coating the packaging material according to the invention is suitable.

It is also possible to combine the polyurethane dispersions with other dispersions, for example based on Polyolefins, which are acrylates, styrene, butadiene or acrylonitrile included. Furthermore, the Polyurethane dispersions also together with dispersions based on Vinyl chloride or vinylidene chloride can be used. In such Dispersion mixtures is the proportion of Polyurethane dispersions but always at least 20% by weight, preferably 50% by weight, based on the total dispersion mixture.

Hydrophobic aids that may be difficult to homogenize to be distributed in the finished dispersion, such as Phenolic condensation resins from aldehydes and phenol or Phenol derivatives or epoxy resins and other z. B. in DE-A 39 03 538, 43 09 079 and 40 24 567 polymers mentioned in Polyurethane dispersions serve, for example, as adhesion promoters, can according to the scriptures mentioned in the two above described methods before the polyurethane or the prepolymer be added to the dispersion.

The polyurethane dispersions can be commercially available auxiliaries and Additives such as blowing agents, defoamers, emulsifiers, Thickeners and thixotropic agents, colorants such as dyes and Pigments included.

The packaging material according to the invention preferably has a thickness of 0.01 mm to approximately 20 mm, in particular 0.1 to 10 mm and particularly preferably 0.5 to 2 mm. A base weight of usually 10 to 250 g / m ² , in particular 20 to 100 g / m ^2, and an application weight of usually 2 to 50 g / m ² , in particular 10 to 20, apply to the carrier layer I. g / m ² .

The production of the packaging material according to the invention is preferably done in that the polyurethane dispersion with Using a squeegee, roller, stick or brush evenly applied to the surface of the carrier layer I. becomes. Preferred coating apparatus contain u. a. Air brushes or reverse gravure rollers or other commercially available blade or roller application systems, as well as size presses or Curtain coaters. Following the application of the Polyurethane dispersion usually follows a drying process to Example in heated channels.

The packaging material according to the invention is particularly suitable for packaging fatty goods, such as Food for humans (nuts, chips, pastries) or for animals (canine or dry cat food).

The packaging is particularly suitable for fresh, hot Food such as B. French fries, or baked goods, such as pizza or cake. This particular suitability is based on the fact that Although coatings are extremely impervious to grease and water vapor but let through. As a result, none is formed in the pack Condensed water so that the food is not unwanted or soft get mushy.

The packaging materials according to the invention are characterized u. a. due to good sealability and block resistance as well Fat resistance. They show only a slight tendency to Water swelling, have a high water vapor permeability and are ecologically harmless.

example 1. Preparation of the polyurethane dispersion

The following are placed in a stirred flask:
600 g (0.40 mol) of a polyesterol composed of adipic acid, isophthalic acid (molar ratio 1/1) and 1,6-hexanediol with OH number 56,
80.4 g (0.60 mol) DMPA and
36.0 g (0.40 mol) 1,4-butanediol

Add at 105 ° C
400 g (1.80 mol) IPDI and
160 g acetone.

After four hours of stirring at 105 ° C with 1600 g of acetone diluted.

The NCO content of this solution is 1.11% (calculated: 1.09%). The solution is cooled to 45 ° C and with 68.0 g (0.40 mol) of isophoronediamine are added.

After 90 min, 50.0 g (0.73 mol) of 25% aqueous Neutralized ammonia, dispersed with 3000 g of water and that Acetone distilled off in vacuo.

An almost transparent PUR dispersion is obtained with a Fixed salary of approx. 30%. A cast film of this dispersion shows a tensile strength of 29 MPa with an elongation at break of 415% on (tensile test according to DIN 53 504).

2. Production of the packaging material by coating Paper with the polyurethane dispersion

In the simplest case, the production of a paper coating with a polymer dispersion can be carried out using a glass rod or spiral doctor. However, since the tests described later are strongly influenced by the quality of the coating (e.g. application quantity, uniform layer thickness), machine application is preferable. The coating devices known from other fields (adhesive sector) do not meet the requirements in the protective paper sector. Coating machines are therefore used which correspond in a reduced form to the machines used in practice. The work technique in practice (e.g. defined application using an air brush or reverse gravure roller, pre-drying and drying in heated channels, variation of the coating speed) can thus be largely adhered to. In order for the tests to be carried out on the coated paper to give as realistic a statement as possible about the quality of the product or the coating, other influencing variables, such as, for. B. fluctuations in the quality of the paper used with regard to surface quality and raw weight can be kept as low as possible. Therefore, a standard paper is used as a carrier material for testing certain dispersions, which should have the following properties, for. B. Special paper for coating, satin, wood-free, white, bleached, fully sized, gross weight 70-80 g / m ² .

This paper is available from various paper mills. For the type control, the carrier material mentioned is provided with 2 coatings. Approx. 12 g / m ² (solid) should be applied for the first coat and approx. 10 g / m ² for the second coat.

The application is carried out with a suitable coating machine carried out.

3. Examination of the packaging material received a) Determination of the seal seam strength and the Sealing temperature of the coated papers Testers

tensile testing machine
Thermosealer with defined pressure, time and temperature settings

execution

The coated paper is stored for approx. 24 hours at 23 ° C and 50% relative humidity, then sealed. Sealing conditions sealing pressure: 0.25 N / mm ²
Sealing time: 0.25 s
smooth sealing jaws (optimal closing of the sealing jaws must be guaranteed)

You start with a product-specific temperature (e.g. from 100 ° C) and increases the temperature in each case 10 ° C.

The sealing samples are taken in a further step 15 mm wide strips with a free leg length of cut approx. 50 mm and another 24 h at 23 ° C and 50% air-conditioned.

These strips are separated using a Tensile testing machine at a take-off speed of 150 mm / min.

Extreme test values are deleted and from the remaining values formed the mean.

The seal seam strength is given in N per 15 mm strip width. In addition, the seal is assessed:
partial seal
full protection

The sealing behavior becomes the optimal one Sealing temperature determined.

b) determination of the pore density (oil density) of the coated papers test equipment

Test oil consisting of:
900 g of turpentine
100 g petrol (boiling range 100-140 ° C)
2.5 g Sudan blue

Quick test on the sheet side

A sheet of coated paper (format 21 × 30 cm) is made brush with the test oil. Here should leave an edge of approx. 1 cm all around.

Now count the ones on the uncoated side as blue Points recognizable pores.

The assessment is immediate
after 10 minutes
and after 60 minutes.

The color dots are counted, whereby after 30 Strikes the counting is canceled.

c) Determination of the water vapor permeability of the coated papers

The determination of the water vapor permeability WDD from the coated paper is carried out according to DIN 53 122. The exams are both based on that described there Climate B (38 ± 1 ° C, 90 ± 2% relative humidity) as even with climate D (23 ± 1 ° C, 85 ± 2% relative Humidity).

5 test pieces are taken from each coating to be tested of 90 mm diameter punched out using a template. The Test specimens are placed on the with silica gel (Blaugel) filled metal bowl so that the coated Side out. Then - as in DIN 53 122 described - the edges of the bowl with sealed with a wax mixture. The bowls are in the desiccators or in a climate cabinet with climate B or D set and conditioned overnight.

Each time after 24 hours of storage (or in other fixed equal intervals) are the samples weighed and the weight gain plotted in a table.

Is the weight gain at least 3 successive measuring points constant, the test is completed.

The water vapor permeability WDD is determined according to the calculation scheme listed in DIN 53 122 and is given in g / m ² .24 hours.

4. Results of the tests

The packaging material obtained according to paragraph 2, consisting of paper and the polyurethane dispersion applied to it, was compared with two other packaging materials with regard to its sealing properties, its blocking ability, its water absorption (according to Cobb), its water vapor permeability and its fat resistance (pore tightness). The two comparative packaging materials also consisted of paper as the backing and were coated with a polyacrylate dispersion (comparison acrylate) and with a dispersion based on a styrene-butadiene copolymer (comparison copolymer SB). The results of each test are shown below.

The packaging material according to the invention, which with a Polyurethane dispersion is coated, stands out from the Comparative packaging materials, which with a Acrylate dispersion or with a dispersion of a copolymer Styrene and butadiene are coated, in particular by a high fat resistance, good sealing and blocking properties as well due to improved water resistance.

Claims (12)

1. Packaging material, consisting of a carrier layer I and a layer II made of a polyurethane Dispersion. 2. Packaging material according to claim 1, wherein as Backing layer I uses a thermoplastic polymer. 3. Packaging material according to claim 1, wherein as Backing layer I used paper, cardboard or corrugated cardboard. 4. Packaging material according to one of claims 1 to 3, wherein one uses a polyurethane dispersion which is composed of a) diisocyanates, b) diols, of which 1. b1) 10 to 100 mol%, based on the total amount of diols (b), have a molecular weight of 500 to 5000, and 2. b2) 0 to 90 mol%, based on the total amount of diols (b), have a molecular weight of 60 to 500 g / mol, c) monomers different from the monomers (a) and (b) with at least one isocyanate group or at least one group which is reactive toward isocyanate groups and which additionally carry at least one hydrophilic group or a potentially hydrophilic group, thereby causing the water-dispersibility of the polyurethanes, d) optionally further polyvalent compounds with reactive groups which differ from the monomers (a) to (c) and which are alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups and e) if appropriate, monomers different from the monomers (a) to (d) having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group. 5. Packaging material according to claim 4, wherein the polyurethane dispersion is composed of aliphatic diisocyanates X (NCO) ₂ , where X represents an aliphatic hydrocarbon radical having 4 to 15 carbon atoms. 6. Packaging material according to claim 4, wherein the polyurethane Dispersion of polyester diols as diols (b1) is built up. 7. Packaging material according to claim 6, wherein the polyurethane Dispersion composed of polyester diols as diols (b1), which by reacting dihydric alcohols with divalent aromatic polycarboxylic acids have arisen. 8. Packaging material according to one of claims 4 to 7, wherein the polyurethane dispersion can be obtained by implementing the Monomers a), b), c) and optionally d) and e) in Temperatures of up to 180 ° C and average reaction times of 1 up to 20 hours. 9. Packaging material according to one of claims 1 to 8, wherein such a polyurethane dispersion is used, the is obtainable by first consisting of macrools, ionic and potentially ionic polyols and excess Polyisocyanates an NCO-terminated prepolymer, this Prepolymer with compounds that are at least 2 opposite Have isocyanate reactive amino groups in a ratio NCO groups / NH groups of ≤ 1: 1 converted, neutralized and then dispersed with water. 10. Packaging material according to claim 9, wherein with ammonia is neutralized. 11. Method for producing a packaging material according to one of claims 1 to 10, characterized in that the Polyurethane dispersion using a doctor blade, roller, a stick or brush evenly on the surface the carrier layer I is applied. 12. Use of the packaging material according to one of the claims 1 to 10, for the packaging of fatty products.