HK1117552B

HK1117552B - Aqueous polyurethane compositions

Info

Publication number: HK1117552B
Application number: HK08108191.2A
Authority: HK
Inventors: 巴布罗．斯帝温克尔; 安德里亚斯．雅格布斯．约斯恩．谷斯; 保卢斯．约翰内斯．玛丽亚．霍内; 格拉尔杜斯．柯纳里斯．欧文比克
Original assignee: 帝斯曼知识产权资产管理有限公司
Priority date: 2005-03-17
Filing date: 2006-03-13
Publication date: 2012-10-26

Description

Aqueous polyurethane composition

The present invention relates to aqueous polyurethane compositions, to a process for preparing such compositions and to the use of such compositions for coating substrates.

Polyurethane compositions have long been used to produce coatings having desirable coating characteristics. For example, such coatings include primers for plastic substrates, particularly substrates used in the film packaging industry (including food packaging), as well as primers for film, label, and art applications. Such base coats are typically used with heat sealable top coats. The topcoat includes anionic and cationic polyvinylidene chloride (PVDC), acrylic, polyurethane, and mixtures thereof.

US 5656701 describes a polyurethane resin composition prepared by chain extending a polyurethane prepolymer with a mixture of chain extenders and chain terminators. These polyurethanes are characterized by having at least one group selected from the group consisting of hydrazine groups, hydrazide groups and semicarbazide groups in the molecule. The polyurethane resin may be prepared using a chain extender and/or a chain terminator having at least one hydrazine group or hydrazide group. The use of a chain terminator can lead to the formation of low molecular weight species, which are detrimental to the adhesion of the polyurethane.

EP 646609 describes terminal hydrazide-functional polyurethane dispersions obtained by, for example, over-extension of chain extenders comprising hydrazine or hydrazide (e.g. adipic dihydrazide, ADH) or mixtures thereof.

EP 350157 describes the use of a hyperbranched aqueous polyurethane resin with an acrylic polymer dispersion containing amide or ketone groups. Here, the polyurethane is described as having-NHNH by extension with more than one stoichiometric equivalent of a hydrazine derivative₂And (4) performing functional treatment.

A disadvantage of using more than one equivalent of one or more hydrazine-containing chain extenders is that free hydrazine is often detectable in the product dispersion, and is generally considered toxic and therefore undesirable.

Surprisingly, the aqueous polyurethane composition of the present invention uses ammonia as at least a portion of the neutralizing agent and hydrazine or a hydrazine derivative as the chain extender, which provides good adhesion to plastic substrates (when used as a primer) and gives high initial seal strength and moisture seal strength (when top coated with a heat seal layer), and since less than or equal to one stoichiometric equivalent of chain extender is used, no free hydrazine is present.

The present invention provides an aqueous polyurethane composition comprising a polyurethane having an acid value of from 4 to 150mgKOH/g and comprising the reaction product of: (A) an isocyanate-terminated prepolymer obtained by reacting components comprising:

(i) at least one organic polyisocyanate;

(ii) at least one isocyanate-reactive compound having anionic or potentially anionic water-dispersing groups;

(iii) (iii) at least one isocyanate-reactive compound not comprised by (ii),

wherein the isocyanate-terminated prepolymer component is reacted at a ratio of isocyanate to isocyanate-reactive groups of from 1.1: 1 to 6: 1; and

(B) at least one active hydrogen chain extending compound comprising at least one isocyanate terminated prepolymer

(A) An isocyanate content of at least 0.2 stoichiometric equivalents of an active hydrogen chain extending compound selected from hydrazine, hydrazine derivatives and mixtures thereof,

wherein (A) and (B) are reacted in a ratio of isocyanate to isocyanate-reactive groups of from 1: 0.5 to 1: 1, and

wherein at least 0.2 stoichiometric equivalents of the anionic or potentially anionic water-dispersing groups are neutralized with ammonia.

The term "polyurethane" as used herein includes one polyurethane as well as more than one polyurethane.

The term "isocyanate-terminated prepolymer" as used herein includes one isocyanate-terminated prepolymer as well as more than one isocyanate-terminated prepolymer.

Methods for preparing polyurethanes are well known in the art and are described, for example, in Polyurethane Handbook 2 of g.oertel^ndEdition, a Carl Hander Publication, 1994, or Szycher's Handbook of Polyurethanes, CRC Press, 1999, of Michael Szycher, which methods are incorporated herein by reference. The polyurethanes may be prepared in a conventional manner by reacting at least one organic polyisocyanate with at least one isocyanate-reactive compound by methods well known in the art. The isocyanate-reactive group comprises-CHR¹-COOH (wherein R¹May be H), alkyl (more preferably C)₁-C₈Alkyl), -OH, -SH, -NH-and-NH₂wherein-OH, -NH-and-NH₂Is preferred.

Component (i) comprises any suitable organic polyisocyanate, including aliphatic, cycloaliphatic, araliphatic (araliphatic) and/or aromatic polyisocyanates. Examples of suitable polyisocyanates include ethylene diisocyanate, 1, 6-Hexamethylene Diisocyanate (HDI) and its oligomers, isophorone diisocyanate (IPDI), cyclohexane-1, 4-diisocyanate, 4 '-dicyclohexylmethane diisocyanate (4, 4' -H12MDI), p-xylylene diisocyanate, p-tetramethylxylene diisocyanate (p-TMXDI) (and its meta isomer m-TMXDI), 1, 4-phenylene diisocyanate, hydrogenated 2, 4-toluene diisocyanate, hydrogenated 2, 6-toluene diisocyanate, 4 '-diphenylmethane diisocyanate (4, 4' -MDI), polymethylene polyphenylene polyisocyanate, 2, 4 '-diphenylmethane diisocyanate, 4' -MDI, IPDI, 3(4) -isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI) and 1, 5-naphthylene diisocyanate. Mixtures of polyisocyanates may be used, as may polyisocyanates that have been modified by the introduction of urethane, allophanate, urea, biuret, carbodiimide, uretonimine, uretdione or isocyanurate residues. Preferably, the polyisocyanate is an araliphatic diisocyanate. More preferably, the polyisocyanate is selected from the group consisting of isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, 2, 4-toluene diisocyanate, and mixtures thereof. Most preferably, the polyisocyanate is isophorone diisocyanate.

Preferably, the isocyanate-terminated prepolymer comprises 10 to 90 wt%, more preferably 15 to 60 wt%, most preferably 20 to 40 wt% of component (i) (i.e. relative to the weight of (i) + (ii) + (iii)).

Component (ii) comprises any suitable polyol, preferably a diol, containing anionic or potentially anionic water-dispersing groups.

Preferred anionic water-dispersing groups are carboxyl, phosphoric or sulfonic acid groups. Preferred examples of such compounds include carboxyl group-containing diols and triols, such as dihydroxyalkanoic acids of 2, 2-dimethylolpropionic acid (DMPA) or 2, 2-dimethylolbutanoic acid (DMBA), especially DMPA. Other useful compounds include aminocarboxylic acids such as lysine, cysteine and 3, 5-diaminobenzoic acid, and sulfonic acid derivatives such as 4, 6-diaminobenzene-1, 3-disulfonic acid, 5-sodiosulfoisophthalic acid (SSIPA) and aminoethanesulfonic acid.

Examples of higher molecular weight anionic water-dispersing group-containing compounds include carboxylic acid group-containing polyether, polyester and polycarbonate polyols, such as polyether glycol fumarate, as described in US 4460738, or such as caprolactone-modified dibasic alkanoic acids.

Alternatively, anionic or potentially anionic water-dispersing groups may be introduced as follows: the OH functional polyol or polyurethane is reacted with the cyclic anhydride before, during or after incorporation of this moiety into the final polyurethane.

Preferred compounds containing anionic or potentially anionic water-dispersing groups are DMBA, DMPA and mixtures thereof.

In the polyurethane dispersion, the anionic water-dispersing groups are preferably in the form of salts in whole or in part. The conversion into the salt form is optionally effected by neutralization of the polyurethane with a base, which is preferably carried out during the preparation of the polyurethane and/or during the preparation of the aqueous coating composition of the invention.

When neutralizing anionic or potentially anionic water-dispersing groups, preferably at least 0.25, more preferably from 0.25 to 3, even more preferably from 0.5 to 2, most preferably from 0.7 to 2, stoichiometric equivalents of anionic or potentially anionic water-dispersing groups are neutralized by ammonia.

Alternatively, more than 3 stoichiometric equivalents of ammonia may be added, for example, in one or more portions during and after polyurethane preparation, to provide better dispersion stability (but only with the addition of excess ammonia after dispersion). Neutralizing the remaining anionic or potentially anionic water-dispersing groups with an amine or an inorganic base. Furthermore, additional amines up to 2 SA may be used. Suitable amines include tertiary amines such as triethylamine dimethylbutylamine or N, N-dimethylethanolamine. Triethylamine is known to have adverse toxicity. Suitable inorganic bases include alkali metal hydroxides and carbonates, for example lithium hydroxide, sodium hydroxide or potassium hydroxide. Quaternary ammonium hydroxides, such as N, may also be used⁺(CH₃)₄(OH). Typically, a base is used that provides a counter ion that may be desirable for the composition. For example, preferred counterions include Li⁺、Na⁺、K⁺、NH₄ ⁺And substituted ammonium salts.

Preferably, the isocyanate-terminated prepolymer comprises from 0.1 to 80 wt%, more preferably from 0.1 to 40 wt%, most preferably from 1 to 15 wt%, especially from 2 to 10 wt%, most especially from 2 to 8 wt% of component (ii).

Preferably, the weight average molecular weight (Mw) of component (ii) is 100-10000g/mol, more preferably 100-5000g/mol, most preferably 120-1000g/mol, especially 125-155 g/mol.

Component (iii) may comprise cationic water-dispersing groups and/or may also comprise non-ionic water-dispersing groups. Examples of cationic water-dispersing groups include pyridyl, imidazolyl and/or tertiary amine groups which can be neutralized with an acid or permanently ionized, for example with dimethyl sulfate.

Preferred nonionic water-dispersing groups are polyalkylene oxide groups, more preferably polyethylene oxide groups. A short segment of the polyethylene oxide group may be replaced by a propylene segment and/or a butylene oxide segment, but the polyethylene oxide group should still contain ethylene oxide as a major component. When the water-dispersible group is polyethylene oxide, the polyethylene oxide group preferably has a molecular weight of 175-5000g/mol, more preferably 350-2200g/mol, most preferably 660-2200 g/mol.

Examples of such compounds containing nonionic water-dispersing groups include methoxypolyethylene glycols (MPEG) having molecular weights of, for example, 550, 750, 1000 and 2000 g/mol.

The resulting polyurethane preferably contains ionic and/or nonionic water-dispersing groups in sufficient concentration due to components (ii) and (iii) to render the polyurethane self-water-dispersible (i.e., dispersible in water without the use of additional dispersing agents), but the concentration of such groups is preferably not so great as to render the polyurethane unacceptably highly water-soluble so as not to compromise the water-sensitivity of the final coating.

Furthermore, the strength of the ionic and/or nonionic water-dispersing groups or their efficiency as dispersing and/or stabilizing groups may also influence the optimum amount required.

Component (iii) may also contain crosslinkable groups. The crosslinkable groups can provide a self-crosslinkable polyurethane that can crosslink at room temperature by a variety of mechanisms including, but not limited to, Schiff base crosslinking and silane condensation.

Schiff base crosslinking means that crosslinking occurs by reaction of a carbonyl functional group, where carbonyl functional group refers to an aldehyde or ketone group, including an enolic carbonyl group such as that found in an acetoacetyl group, with a carbonyl-reactive amine and/or hydrazine (or blocked amine and/or blocked hydrazine) functional group.

Silane condensation refers to the reaction of alkoxysilane or-SiOH groups in the presence of water to provide siloxane bonds by removing water and/or an alkyl alcohol (e.g., methanol) during drying of the aqueous coating composition.

Other crosslinking mechanisms known in the art include those provided by the following reactions: the reaction of masked epoxy groups with amino or mercapto groups, reaction of isothiocyanates with amines, alcohols or hydrazines, reaction of amines (e.g. ethylenediamine or polyfunctional amine-terminated polyalkylene oxides) with β -diketone (e.g. acetoacetoxy or acetoacetamide) groups to form enamines, by reaction of epoxy groups with amino, carboxylic acid or mercapto groups, reaction of mercapto groups with ethylenically unsaturated groups such as fumarates and acryloyl groups. It may be advantageous to use blocked crosslinking groups, for example blocked isocyanate groups. In those cases where crosslinking is desired, the most preferred mode of crosslinking is Schiff base crosslinking or alkoxysilane crosslinking.

Polyols having a molecular weight of 500-6000g/mol include in particular diols and triols and mixtures thereof, but polyols having higher functionality may also be used, for example as secondary components in mixtures with diols. The polyol may be any chemical type of polyol used or suggested for use in polyurethane formulations. In particular, the polyol may be a polyester, polyesteramide, polyether, polythioether, polycarbonate, polyacetal, polyolefin, or polysiloxane. The weight average molecular weight (Mw) of the polyol is preferably 600-4000g/mol, more preferably 700-3000 g/mol.

Polyester polyols which may be used include the hydroxyl-terminated reaction products of polyhydric alcohols, such as ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, 1, 4-butanediol, furan dimethanol, cyclohexane dimethanol, glycerol, trimethylolpropane or pentaerythritol or mixtures thereof, with polycarboxylic acids, in particular dicarboxylic acids or their ester-forming derivatives, such as for example phthalic acid, succinic acid, glutaric acid, adipic acid, malonic acid, maleic acid and dimeric fatty acids, anhydrides or short-chain alkyl esters thereof (e.g. dimethyl terephthalate). Polyesters obtained by polymerizing lactones (e.g., caprolactone) with polyols may also be used. Polyesteramides may be obtained by incorporating aminoalcohols (e.g. ethanolamine) or polyamines in polyesterification mixtures.

Polyether polyols which may be used include the products obtained as follows: polymerization of cyclic oxides such as ethylene oxide, propylene oxide or tetrahydrofuran; or one or more such oxides may be added to a multifunctional initiator such as water, ethylene glycol, propylene glycol, diethylene glycol, cyclohexanedimethanol, glycerol, trimethylolpropane, pentaerythritol or bisphenol a. Particularly useful polyesters include polyoxypropylene diols and triols obtained by the simultaneous or sequential addition of ethylene oxide and propylene oxide to suitable initiators, poly (oxyethylene-oxypropylene) diols and triols and polytetramethylene ether glycols obtained by the polymerisation of tetrahydrofuran.

Polythioether polyols which may be used include products obtained by condensing thiodiethylene glycol alone or with other glycols, dicarboxylic acids, formaldehyde, amino alcohols or aminocarboxylic acids.

Polycarbonate polyols which may be used include products obtained by reacting diols such as 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, diethylene glycol or tetraethylene glycol with diaryl carbonates such as diphenyl carbonate or with phosgene.

Polyacetal polyols which may be used include those prepared by reacting a diol such as diethylene glycol, triethylene glycol or hexanediol with formaldehyde. Suitable polyacetals can also be prepared by polymerizing cyclic acetals.

Suitable polyolefin polyols include hydroxy-terminated butadiene or terpene homopolymers and copolymers.

The polyol is preferably a polyether polyol, more preferably polytetrahydrofuran (also known as polytetramethylene glycol, polybutylene oxide and polytetrahydrofuran).

Most preferably, component (iii) is selected from the group consisting of poly THF, polypropylene glycol, polyester, amino-terminated polyalkylene oxide (e.g. Jeffamine available from Huntsman) or derivatives thereof (e.g. those described in EP 317258B 1) and mixtures thereof. Preferably, the Mw of the thus selected component (iii) is 300-3000 g/mol.

For component (iii) it is also possible to use low molecular weight organic compounds which contain at least one, preferably at least two, isocyanate-reactive groups and have a weight average molecular weight of less than 500g/mol, preferably from 40 to 250 g/mol. Examples thereof include: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and similar polyglycols made from propylene glycol and 1, 3-or 1, 4-butanediol (molecular weight up to 499g/mol), neopentyl glycol; 1-propanol, di (hydroxyethyl) terephthalate, furandimethanol, glycerol, 1, 4-cyclohexyldimethanol and reaction products of these examples with propylene glycol and/or ethylene glycol (molecular weight up to 499 g/mol). Component (iii) preferably contains less than 15 wt.%, more preferably less than 10 wt.% of these low molecular weight organic compounds.

The isocyanate-terminated prepolymer preferably comprises from 5 to 90% by weight, more preferably from 10 to 80% by weight, most preferably from 20 to 75% by weight, especially from 45 to 70% by weight, most especially from 50 to 70% by weight of component (iii).

The particle size of the resulting polyurethane in the composition is preferably 20-5000nm, more preferably 25-1000nm, most preferably 30-250 nm.

The acid value of the polyurethane is preferably from 4 to 100mgKOH/g, more preferably from 8 to 65mgKOH/g, most preferably from 10 to 42mgKOH/g, in particular from 15 to 30 mgKOH/g.

The number average molecular weight (Mn) of the polyurethane is preferably 2000-1000000g/mol, more preferably 3000-200000g/mol, even more preferably 4000-100000g/mol, most preferably 8000-40000g/mol, especially 10000-20000 g/mol. Molecular weight can be measured by Gel Permeation Chromatography (GPC) using a suitable eluent (e.g., tetrahydrofuran or N, N-dimethylacetamide) and with reference to polystyrene standards.

Isocyanate-terminated prepolymers are conventionally formed by the following process: reacting a stoichiometric excess of an organic polyisocyanate with an isocyanate-reactive compound under substantially anhydrous conditions at a temperature of about 30-130 ℃ until the reaction between the isocyanate groups and the isocyanate-reactive groups is substantially complete; the components of the isocyanate-terminated prepolymer are preferably used in a ratio corresponding to a preferred ratio of isocyanate groups to isocyanate-reactive groups of about 1.1: 1 to 4: 1, more preferably 1.3: 1 to 3: 1, especially 1.4: 1 to 2: 1.

If desired, catalysts such as dibutyltin dilaurate and stannous octoate, zirconium or titanium-based or tertiary amine-based catalysts may be used to assist in the formation of the isocyanate-terminated prepolymer and/or polyurethane.

Organic solvents may optionally be added to control viscosity before, during or after isocyanate-terminated prepolymer formation or final polyurethane formation. Examples of solvents include water-miscible solvents such as N-methylpyrrolidone, N-ethylpyrrolidone, dimethylacetamide, glycols and glycol ethers such as butyldiglycol, acetone, methyl ethyl ketone and alkyl ethers of glycol acetate or mixtures thereof. If a solvent is used, it is preferred to use the minimum amount of solvent. Preferably less than 5 wt%, more preferably less than 1 wt% of organic solvent is used based on the weight of the aqueous composition of the present invention. Most preferably, no organic solvent is added during the preparation of the aqueous composition of the present invention.

The aqueous polyurethane composition may be prepared as follows: the isocyanate-terminated prepolymer (a) (optionally in an organic solvent medium) is dispersed in an aqueous medium and then chain-extended in the aqueous phase with at least one active hydrogen-containing chain extender (B).

The active hydrogen-containing chain extender (B) preferably comprises at least 0.4, more preferably at least 0.5, especially 0.8 stoichiometric equivalent of an active hydrogen-containing chain extending compound selected from hydrazine, hydrazine derivatives and mixtures thereof, relative to the isocyanate content of the isocyanate-terminated prepolymer (a).

Examples of suitable hydrazine derivatives include: azines, such as acetone azine; substituted hydrazines, such as dimethylhydrazine, 1, 6-hexamethylene-bis-hydrazine, carbodihydrazine; hydrazides of polycarboxylic and sulfonic acids, for example mono-or dihydrazides of adipic acid, succinic dihydrazide, oxalic dihydrazide, isophthalic dihydrazide, tartaric dihydrazide, 1, 3-phenylene-disulfonic dihydrazide, omega-amino-adipic dihydrazide, citric trihydrazide, 1, 2, 4-butanetricarboxylic acid trihydrazide; hydrazides obtained by reacting lactones with hydrazides, such as gamma-hydroxybutyric hydrazide, bis-semicarbazide and bis-hydrazinocarbo-carbonate of diol; and semicarbazide obtained from the reaction of a polyisocyanate with excess hydrazine (and then optionally reacted with a ketone such as acetone to form the corresponding semicarbazone).

More preferred hydrazine derivatives are selected from the group consisting of acetone azine, dimethylhydrazine, 1, 6-hexamethylene-bis-hydrazine, carbodihydrazide, adipic acid mono-hydrazide, adipic acid dihydrazide, succinic acid dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, tartaric acid dihydrazide, 1, 3-phenylene-bis-sulfonic acid dihydrazide, citric acid trihydrazide, 1, 2, 4-butane tricarboxylic acid trihydrazide, gamma-hydroxybutyric hydrazine and mixtures thereof.

The remaining isocyanate groups in the isocyanate-terminated prepolymer (a) may be chain extended using an active hydrogen-containing chain extender (used with hydrazine and/or hydrazine derivatives) including amino alcohols, primary or secondary aliphatic, cycloaliphatic, aromatic, araliphatic or heterocyclic polyamines, especially diamines. Water soluble chain extenders are preferred. Examples of suitable chain extenders which may be used herein include ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, butylenediamine, hexamethylenediamine, cyclohexanediamine, piperazine, 2-methylpiperazine, phenylenediamine, tolylenediamine, xylylenediamine, tris (2-aminoethyl) amine, 3 ' -dinitrobenzidine, 4 ' -methylenebis (2-chloroaniline), 3 ' -dichloro-4, 4 ' -diphenyldiamine, 2, 6-diaminopyridine, 4 ' -diaminodiphenylmethane, methanediamine, xylylenediamine, isophoronediamine, and adducts of diethylenetriamine and acrylic acid ester or hydrolysis products thereof.

Where the chain extender is, for example, a polyamine and/or hydrazine derivative, it may be added to the aqueous dispersion of the isocyanate-terminated prepolymer or it may already be present in the aqueous medium when the isocyanate-terminated prepolymer is dispersed in the aqueous medium. The isocyanate-terminated prepolymer may also be dissolved in an organic solvent (typically acetone) and then chain extended to form polyurethane by adding water to the solution until the water is a continuous phase, followed by removal of the solvent by distillation to form an aqueous dispersion.

Chain extension can be carried out at high, low and ambient temperatures. Suitable temperatures are from about 5 to 95 deg.C, more preferably from about 10 to 50 deg.C.

The total amount of active hydrogen chain extending compound used should be such that the ratio of isocyanate groups in the isocyanate-terminated prepolymer (a) to active hydrogen in the chain extender (B) is about (but preferably just above) 1: 1, preferably 1: 0.6 to 1: 1, more preferably 1: 0.7 to 1: 1, most preferably 1: 0.8 to 1: 0.99, especially 1: 0.8 to 1: 0.97.

One embodiment of the present invention provides an aqueous polyurethane composition comprising a polyurethane having an acid value of from 10 to 42mgKOH/g and comprising the reaction product of:

(A) an isocyanate-terminated prepolymer obtained by reacting:

(i)10-90 wt%, more preferably 20-40 wt% of at least one organic polyisocyanate;

(ii)0.1-80 wt%, more preferably 2-8 wt% of at least one isocyanate reactive compound having anionic or potentially anionic water-dispersing groups;

(iii)5-90 wt.%, more preferably 50-70 wt.% of at least one isocyanate-reactive compound not comprised by (ii),

wherein (i) + (ii) + (iii) is 100%,

(B) at least one active hydrogen chain extending compound comprising at least 0.4 stoichiometric equivalent of an active hydrogen chain extending compound selected from hydrazine, hydrazine derivatives and mixtures thereof relative to the isocyanate content of the isocyanate-terminated prepolymer (A),

wherein (A) and (B) are reacted in a ratio of isocyanate to isocyanate-reactive groups of from 1: 0.8 to 1: 0.99, and

wherein from 0.25 to 3 stoichiometric equivalents of said anionic or potentially anionic water-dispersing groups are neutralized with ammonia.

Another embodiment of the present invention provides an aqueous polyurethane composition comprising a polyurethane having an acid value of 10 to 42mgKOH/g and comprising the reaction product of:

(A) an isocyanate-terminated prepolymer obtained by reacting:

(i)20 to 40 weight percent of at least one organic polyisocyanate selected from the group consisting of isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, 2, 4-toluene diisocyanate, and mixtures thereof;

(ii)2-8 wt% of at least one isocyanate reactive compound having anionic or potentially anionic water dispersing groups selected from 2, 2-dimethylolpropionic acid (DMPA), 2-dimethylolbutanoic acid (DMBA) and mixtures thereof;

(iii)50-70 wt% of at least one isocyanate reactive compound not comprised by (ii), said isocyanate reactive compound having a Mw of 300-3000g/mol, more preferably 600-2000g/mol, most preferably 800-1200g/mol, selected from the group consisting of poly THF, polypropylene glycol, polyester, amino terminated polyalkylene oxide or derivatives thereof, and mixtures thereof, wherein (i) + (ii) + (iii) is 100%,

The isocyanate-terminated prepolymer (or polyurethane) can be dispersed in an aqueous medium (e.g., water) using techniques well known in the art. Preferably, the isocyanate-terminated prepolymer (or polyurethane) is added to the water with stirring, or the water is added to the isocyanate-terminated prepolymer (or polyurethane) with stirring.

The surfactant and/or high shear may be used in any order to aid in the dispersion of the isocyanate-terminated prepolymer (or polyurethane) in water (even if it is self-dispersible). Suitable surfactants include, but are not limited to, conventional anionic, cationic and/or nonionic surfactants, such as Na, K and NH of dialkyl sulfosuccinates₄Salts, sulfuric acid esterified oils Na, K and NH₄Salts, Na, K and NH of alkylsulfonic acids₄Salts, alkyl esters of sulfuric acid, Na, K and NH₄Salts, alkali metal salts of sulfonic acids; fatty alcohols, ethoxylated fatty acids and/or fatty amines, and Na, K and NH of fatty acids such as sodium stearate and sodium oleate₄And (3) salt. Other anionic surfactants include alkyl or (alk) aryl groups linked to sulfonic acid groups, sulfuric acid half-ester groups (in turn linked to polyglycol ether groups), phosphonic acid groups, phosphoric acid analogs, and phosphate or carboxylic acid groups. The cationic surfactant comprises an alkyl or (alk) aryl group linked to a quaternary ammonium salt group. The nonionic surfactant includes polyglycol ether compounds and polyethylene oxide compounds. The amount of surfactant used is preferably from 0 to 15% by weight, more preferably from 0 to 8% by weight, more preferably from 0 to 5% by weight, especially from 0.1 to 3% by weight, most especially from 0.3 to 2% by weight, based on the weight of the polyurethane.

One embodiment of the present invention provides a method of preparing the aqueous composition of the present invention, comprising the steps of:

a) reacting components (i) - (iii) to form an isocyanate-terminated prepolymer (a);

b) forming an aqueous dispersion of the isocyanate-terminated prepolymer (a);

c) optionally neutralizing the isocyanate-terminated prepolymer (a);

d) chain extending the isocyanate terminated prepolymer (a) by reaction with an active hydrogen chain extending compound (B).

Steps b), c) and d) may occur in any order, for example these three steps may occur simultaneously or step d) may occur after steps b) and c). Step c) may take place after and/or during step a) and/or before and/or during step b). Preferably, steps b), c) and d) occur simultaneously.

The process may further comprise step e) (addition of a reactive diluent) and step f) (subsequent polymerization of said reactive diluent added in step e). The addition of the reactive diluent (step e)) can be carried out at any stage, for example before the start of the prepolymer reaction, or at any stage during and/or after the formation of the prepolymer, or it can be added to the aqueous phase before, during and/or after the dispersing step b).

Preferably, step f) is carried out after step b). Preferably, when the isocyanate-terminated prepolymer (or polyurethane) is dispersed in an aqueous medium, some or all of the ammonia is already present in the aqueous medium.

The polyurethane dispersions of the present invention may be combined with one or more other polymers known in the art, such as vinyl polymers (including (meth) acrylate polymers), alkyds, polyesters, polyethers, polycarbonates, and amino resins.

In another embodiment of the present invention, if a reactive diluent is used, particularly when the reactive diluent comprises an olefinically unsaturated monomer (also referred to as a vinyl monomer), it may be polymerized in situ to produce a vinyl polymer.

Useful as reactive diluents and subsequently polymerised in situ to form vinyl polymersExamples of vinyl monomers include, but are not limited to, 1, 3-butadiene, isoprene; trifluoroethyl (meth) acrylate (TFEMA); dimethylaminoethyl (meth) acrylate (DMAEMA); polyalkylene glycol di (meth) acrylates such as 1, 3-butylene glycol diacrylate, ethylene glycol diacrylate; divinylbenzene, styrene, alpha-methylstyrene, (meth) acrylamide and (meth) acrylonitrile; vinyl halides such as vinyl chloride; vinylidene halides, such as vinylidene chloride; a vinyl ether; vinyl esters, such as vinyl acetate, vinyl propionate, vinyl laurate; vinyl esters of versatic acids, such as VeoVa 9 and VeoVa 10(VeoVa is a trademark of Resolution); a heterocyclic vinyl compound; alkyl esters of monoethylenically unsaturated dicarboxylic acids, such as di-n-butyl maleate and di-n-butyl fumarate; and in particular of the formula CH₂＝CR¹-COOR²Acrylate and methacrylate esters of (A) wherein R is¹Is H or methyl, R²And optionally substituted alkyl or cycloalkyl of 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, and examples thereof are methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate (all isomers), octyl (meth) acrylate (all isomers), 2-ethylhexyl (meth) acrylate, isopropyl (meth) acrylate, and n-propyl (meth) acrylate. Formula CH₂＝CR¹-COOR²Preferred monomers of (a) include butyl (meth) acrylate (all isomers), methyl (meth) acrylate, octyl (meth) acrylate (all isomers), and ethyl (meth) acrylate. Particularly preferred vinyl monomers include (meth) acrylate monomers and styrene monomers. Most preferred monomers are methyl methacrylate, butyl (meth) acrylate, 2-ethylhexyl acrylate, styrene and acrylonitrile.

By containing at least 40 wt% of one or more of the formulae CH as defined above₂＝CR¹-COOR²The vinyl polymer produced from the monomer system of (a) is defined herein as a (meth) acrylate polymer. More preferably, the monomer system comprises at least 50 wt.%, in particular at least 60 wt.% of such monomers. Thus (first)Group) the other monomers in the acrylate polymer (if used) may include one or more of the other vinyl monomers mentioned herein, and/or may include different vinyl monomers. Preferably, the vinyl polymer is a (meth) acrylate polymer.

It is also preferred to use vinyl monomers that do not contain isocyanate or isocyanate-reactive groups. Thus, suitable vinyl monomers include ethylenically unsaturated hydrocarbons, esters and ethers (particularly esters) of (meth) acrylic acid, esters and ethers of vinyl alcohol, and styrene. Specific examples include butadiene, isoprene, styrene, substituted styrenes, lower alkyl (C1-C6) esters of (meth) acrylic and maleic acids, vinyl acetates and butyrates, (meth) acrylates, acrylonitrile, allyl methacrylate, vinyl methyl, propyl and butyl ethers, divinyl ether, divinyl sulfide, vinyl chloride, dichloroethylene, hexanediol diacrylate, trimethylolpropane triacrylate, and the like.

The vinyl monomer may include a vinyl monomer having a functional group such as a crosslinking group and/or a water-dispersing group. Such functionality may be introduced directly into the polymer by free radical polymerization, or the functional group may be introduced by reaction of a reactive vinyl monomer which is subsequently reacted with a reactive compound bearing the desired functional group. Some functional groups may perform more than one function, for example (meth) acrylic acid is commonly used as a water-dispersing monomer, but it may also act as a crosslinking monomer. These variations are known to those skilled in the art.

Preferred vinyl monomers which provide crosslinking groups for crosslinking processes such as autoxidation, Schiff base crosslinking and silane condensation include acrylic and methacrylic monomers having at least one free carboxyl, hydroxyl, epoxy, acetoacetoxy, allyl, fatty acid or amino group, such as (meth) acrylic acid, glycidyl acrylate, glycidyl methacrylate, acetoacetoxyethyl methacrylate, allyl methacrylate, tetraethylene glycol methacrylate, divinylbenzene, t-butylaminoethyl methacrylate and dimethylaminoethyl methacrylate. The amino functionality may be introduced by methods known to those skilled in the art, for example by preparing a vinyl polymer comprising a vinyl monomer such as acrylic or methacrylic acid, followed by conversion of at least a portion of the carboxylic acid groups to amino groups (as part of the amino ester groups), for example by an imidization reaction using an alkylenimine (such as an ethylenimine or propyleneimine).

Such crosslinking functionality can be used to render the composition potentially crosslinkable (so that crosslinking occurs, for example, after the aqueous composition is subsequently dried) when combined with externally added crosslinkers and/or reacted with each other and/or with the polyurethane polymer.

Vinyl monomers having ionic or potentially ionic water-dispersing groups include, but are not limited to, (meth) acrylic acid, itaconic acid, maleic acid, beta-carboxyethyl acrylate, monoalkyl maleates (e.g., monomethyl maleate and monoethyl maleate), citraconic acid, styrene sulfonic acid, vinylbenzyl sulfonic acid, vinyl sulfonic acid, acryloxyalkyl sulfonic acids (e.g., acryloxymethyl sulfonic acid), 2-acrylamido-2-alkyl alkane sulfonic acids (e.g., 2-acrylamido-2-methyl ethane sulfonic acid), 2-methacrylamido-2-alkyl alkane sulfonic acids (e.g., 2-methacrylamido-2-methyl ethane sulfonic acid), mono (acryloxyalkyl) phosphates (e.g., mono (acryloxyethyl) phosphate), and mono (methacryloxyalkyl) phosphates (e.g., mono (methacryloxyethyl) phosphate) ) Esters).

Preferably, however, vinyl monomers having ionic or potentially ionic water-dispersing groups are not used for the vinyl polymers prepared in situ, since they would destabilize the polyurethane dispersion.

The nonionic water-dispersing groups can be in the chain, pendant or terminal. Preferred vinyl monomers having nonionic water-dispersing groups include alkoxypolypropylene glycol (meth) acrylates, preferably having an Mn of 350-3000 g/mol. Examples of such monomers that are commercially available include omega-methoxypolyethylene glycol (meth) acrylate. Examples of vinyl monomers having nonionic water-dispersing groups with Mn of less than 350g/mol include diethylene glycol monovinyl ether.

Most preferably, the vinyl monomer used to prepare the vinyl polymer is selected from the group consisting of methyl methacrylate, butyl (meth) acrylate, ethyl acrylate, styrene, (meth) acrylic acid, and mixtures thereof.

Preferably, the acid value of the vinyl polymer is from 0 to 100mgKOH/g, more preferably from 0 to 70mgKOH/g, especially from 0 to 50 mgKOH/g.

It is known in the art that if the vinyl polymer is prepared in the presence of polyurethane (in situ), preferably the vinyl monomer used to prepare the vinyl polymer contains only a small amount, preferably essentially no (meth) acrylic acid.

For vinyl polymers prepared in situ, the preferred vinyl monomers are liquid under the temperature conditions at which the isocyanate prepolymer is formed, although the possibility of using solid vinyl monomers (optionally together with an organic solvent) is not excluded.

For the vinyl polymer prepared in situ, all of the vinyl monomer may be present at the beginning of the preparation of the isocyanate-terminated prepolymer, or some or all of the vinyl monomer may be added during the preparation. Preferably, the vinyl monomer is not polymerized until after chain extension is complete.

The proportion of vinyl monomers used as reactive diluent for the preparation of the isocyanate-terminated prepolymer is preferably from 0 to 95% by weight, more preferably from 0 to 80% by weight, most preferably from 5 to 50% by weight, in particular from 10 to 40% by weight, based on the total weight of polyurethane and vinyl polymer prepared in situ.

The acid value of the vinyl polymer prepared in situ is preferably from 0 to 20mgKOH/g, more preferably from 0 to 10mgKOH/g, and especially substantially 0 mgKOH/g.

The polyurethane of the composition of the present invention may also be combined with a separately prepared polymer, such as a separately prepared vinyl polymer. Suitable vinyl monomers for forming the separately prepared vinyl polymer include all vinyl monomers suitable for forming the vinyl polymer prepared in situ.

The acid value of the independently prepared vinyl monomer is preferably from 0 to 100mgKOH/g, more preferably from 0 to 70mgKOH/g, still more preferably from 0 to 50mgKOH/g, and particularly preferably from 0 to 40 mgKOH/g.

The weight average molecular weight (Mw) of the vinyl polymer (prepared in situ or separately) is preferably 1000-.

Preferably, the Tg of the vinyl polymer (prepared in situ or separately) is preferably from-80 to 150 deg.C, more preferably from-60 to 120 deg.C, most preferably from-40 to 106 deg.C, especially from-20 to 80 deg.C, more especially from 0 to 80 deg.C, most especially from 10 to 80 deg.C, calculated (by the well-known Fox equation).

The vinyl polymer (prepared in situ or separately) may be a sequential vinyl polymer. If the vinyl polymer is a sequential vinyl polymer, there are at least two Tg values, the difference between the two Tg values preferably being at least 40 ℃ and more preferably at least 55 ℃. If the vinyl polymer is a sequential vinyl polymer, at least 40 weight percent of the vinyl polymer preferably has a Tg of-40 to 30 deg.C, more preferably-20 to 15 deg.C. If the vinyl polymer is a mixture of different vinyl polymers, it is preferred that 30 to 90 wt.% of the vinyl polymer have a Tg of 25 ℃ or less and 10 to 70 wt.% of the vinyl polymer have a Tg of 45 ℃ or more, more preferably 55 ℃ or more.

The weight ratio of the total amount of polyurethane to the solids of the vinyl polymer (prepared in situ or separately) is preferably from 10: 90 to 99: 1, more preferably from 30: 70 to 95: 5, most preferably from 40: 60 to 90: 10, especially from 50: 50 to 80: 20, most especially from 60: 40 to 80: 20.

In one embodiment of the present invention, the aqueous polyurethane composition of the present invention comprises an in situ prepared vinyl polymer having a polyurethane to vinyl solid ratio of 60: 40 to 80: 20, wherein the vinyl polymer has a Tg of 10 to 80 ℃ and is prepared from a vinyl monomer selected from the group consisting of methyl methacrylate, ethyl (meth) acrylate, butyl (meth) acrylate, styrene, and combinations thereof.

In another embodiment of the present invention, the aqueous polyurethane composition of the present invention comprises a separately prepared vinyl polymer having a polyurethane to vinyl solids ratio of 60: 40 to 80: 20, wherein the vinyl polymer has a Tg of 0 to 50 ℃ and is prepared from a vinyl monomer selected from the group consisting of methyl methacrylate, ethyl (meth) acrylate, butyl (meth) acrylate, acrylic acid, and combinations thereof.

The vinyl polymers (prepared in situ or separately) are preferably prepared by free radical polymerization, but in some cases anionic polymerization is also employed. Free radical polymerization may be accomplished by techniques well known in the art, such as emulsion polymerization, solution polymerization, suspension polymerization, or bulk polymerization. Preferably, for the vinyl polymer prepared in situ, an emulsion polymerization process is used.

Bulk polymerization of vinyl monomers is described in detail in EP 0156170, WO 82/02387 and US 4414370. Typically, during bulk polymerization, a mixture of two or more vinyl monomers is continuously fed into a reaction zone containing a molten vinyl oligomer having the same proportion of vinyl monomers as the vinyl monomer mixture.

Free radical polymerization can be carried out using batch, step, gradient (also known as dynamic feed) or semi-continuous polymerization processes to produce single or multistage vinyl polymers.

Free radical polymerization of vinyl monomers requires the use of a free radical generating initiator to initiate vinyl polymerization. Suitable free radical generating initiators include potassium, sodium or ammonium persulfates; hydrogen peroxide; a percarbonate ester; organic peroxides, such as acyl peroxides including benzoyl peroxide; alkyl hydroperoxides such as tert-butyl hydroperoxide and cumene hydroperoxide; dialkyl peroxides, such as di-tert-butyl peroxide; peroxy esters such as t-butyl perbenzoate and the like; mixtures may also be used. The peroxy compounds are in some cases advantageously used in combination with suitable reducing agents, for example sodium or potassium pyrosulfite or sodium or potassium bisulfite and erythorbic acid (redox systems). Metal compounds such as fe.edta (EDTA is ethylenediaminetetraacetic acid) may also be usefully employed as part of the redox initiator system, for example, a combination of tert-butyl hydroperoxide, erythorbic acid and fe.edta may partition between the aqueous and organic phases. Azo-functional initiators may also be used. Preferred azo initiators include azobis (isobutyronitrile) and 4, 4' -azobis (4-cyanovaleric acid). The amount of initiator or initiator system used is conventional, for example from 0.05 to 6% by weight, based on the total weight of the vinyl monomers used. Preferred initiators include ammonium persulfate, sodium persulfate, potassium persulfate, azobis (isobutyronitrile), and/or 4, 4' -azobis (4-cyanovaleric acid).

Chain transfer agents such as mercaptans, e.g., n-dodecyl mercaptan, n-octyl mercaptan, t-dodecyl mercaptan, mercaptoethanol, isooctyl thioglycolate, C, and halogenated hydrocarbons may be used to control molecular weight₂-C₈Mercaptocarboxylic acids and esters thereof (e.g., 3-mercaptopropionic acid and 2-mercaptopropionic acid), and halogenated hydrocarbons such as carbon tetrabromide and bromotrichloromethane. Molecular weight control may also be achieved with catalytic chain transfer agents such as transition metal complexes, in particular selected cobalt chelates disclosed in US 4526945, US4680354, EP 0196783, EP 0199436, EP 0788518 and WO 87/03605.

After polymerization, the content of free vinyl monomers in the aqueous polyurethane composition of the present invention is preferably less than 500ppm, more preferably less than 150ppm, most preferably less than 70 ppm.

The solid content of the aqueous polyurethane composition of the present invention is 1 to 60% by weight, more preferably 2 to 55% by weight.

The aqueous polyurethane compositions of the present invention have a free hydrazine content of 20ppm or less, more preferably 10ppm or less, most preferably 4ppm or less, especially 2ppm or less (undetectable free hydrazine).

The aqueous polyurethane composition of the present invention may contain other conventional ingredients including coagulating organic solvents, pigments, dyes, emulsifiers, surfactants, thickeners, heat stabilizers, leveling agents, anti-cratering agents, fillers, precipitation inhibitors, rheology modifiers, UV absorbers, antioxidants, drying salts and the like, which are introduced at any stage in the manufacturing process or subsequently. For example, antimony oxide may be included in the dispersion in an amount to improve flame retardancy. To improve chemical resistance to, for example, water, detergents and alcohols, the aqueous compositions of the present invention may comprise external crosslinkers such as CX-100, CX-300 (available from DSM Neoresins BV) or water-dispersible polyisocyanates, which are introduced at any stage in the preparation process, but preferably subsequently.

The aqueous polyurethane composition prepared by the process of the present invention is a dispersion that can be stored stably without the need for additional solvents or surfactants, but may also contain small amounts of emulsifiers and/or solvents if desired.

The aqueous polyurethane compositions of the present invention may be used as coating compositions, or to provide the main component of coating compositions (e.g., protective or decorative coating compositions), for which purpose they may be further diluted with water and/or organic solvents, or they may be provided in a more concentrated form by evaporating the water and/or organic components of the liquid medium.

The aqueous polyurethane composition of the present invention can be applied to various substrates including wood, board, metal, stone, cement, glass, cloth, leather, paper, plastic, foam, and the like by conventional methods such as brushing, dipping, flow coating, and spraying. The aqueous medium, which typically includes water and any co-solvent, is removed by drying, either naturally or with acceleration (heating), to form a coating.

In the oriented polypropylene (OPP) -based food packaging film industry, several structures (flat, coextruded, voided, tinted, coated, laminated) have been developed to form suitable films.

When conventional structures cannot be used due to extreme requirements, this can be solved by using special coatings. The coating can be used not only to improve the printing properties, gloss and barrier properties (such as oxygen, moisture and odor) of the printing ink, but also to improve the heat sealability, metallization and appearance of the packaging material. If barrier properties are desired, polyvinylidene chloride (PVDC) or ethylene vinyl alcohol copolymer (EVOH) coatings are the most suitable products, and PVDC has the additional advantage of being heat sealable. Acrylic coatings are widely used because of their excellent printability, heat sealability and transparency.

It has been found that the adhesion of the coating to the substrate is an important property. In particular, when a polypropylene (OPP) film for food packaging is sealed on a packaging line, excellent adhesion is required in order to obtain optimum seal strength. Coatings may be used to achieve heat sealability. The seal is typically formed at the lowest possible temperature, lowest possible pressure and shortest time, and preferably the seal should retain its strength under harsh conditions for an extended period of time. One such condition is seal strength moisture resistance. At this point, the seal should maintain its strength for an extended period of time under tropical conditions (i.e., high temperature and high humidity). The heat seal strength of the coating is preferably 200g/inch (78.74g/cm) or more, more preferably 400g/inch (157.48g/cm) or more. The heat seal strength is a heat seal strength measured initially (initial seal strength) and a heat seal strength measured after undergoing wet and warm conditions (wet seal strength).

In general, the coated OPP film can have a layered structure comprising the following layers: top coat, base coat, OPP, base coat, top coat.

In particular, the aqueous polyurethane compositions of the present invention are suitable as primer coatings for plastic substrates, more particularly for polyethylene and (oriented) polypropylene substrates. The aqueous polyurethane compositions of the invention are particularly suitable as primer coatings for (oriented) polypropylene substrates which are subsequently coated with the polymer dispersion. Suitable polymer dispersions for coating are vinyl polymers (including (meth) acrylate polymers) and vinyl polymers whose main component is the vinyl monomer dichloroethylene (containing more than 50 wt%, more preferably more than 88 wt% of dichloroethylene). The advantage of containing dichloroethylene is that the resulting coating can be heat sealed.

Typically, the plastic substrate is preheated to increase the surface polarity. Techniques known in the art to increase the polarity of a surface include flame treatment, corona treatment, and treatment with chromic acid (or salts thereof).

The aqueous polyurethane composition of the present invention is also suitable for use as a label coating in which a label is coated with the aqueous polyurethane composition to have adhesion to a substrate. The substrate may be a plastic substrate as described above. Alternatively, the aqueous polyurethane composition of the present invention is suitable for use as a primer for film labels.

An embodiment of the present invention provides a substrate having a coating layer comprising the aqueous polyurethane composition of the present invention, and also provides a method of coating a substrate using the aqueous polyurethane composition of the present invention, the method comprising applying the aqueous polyurethane composition to a substrate and removing the aqueous medium.

One embodiment of the present invention provides a primer, preferably for coating plastic substrates, comprising the aqueous polyurethane composition of the present invention.

The invention also provides a label coating obtained from the aqueous polyurethane composition.

The invention will now be illustrated with reference to the following examples. All parts, percentages and proportions are by weight unless otherwise indicated.

Examples

Abbreviations used

SA-stoichiometric amount

DMPA ═ 2, 2-dimethylolpropionic acid

pTHF-1000 ═ polytetrahydrofuran, Mw1000

IPDI ═ isophorone diisocyanate

TDI-2, 4-toluene diisocyanate

DES W-methylene-dicyclohexyl diisocyanate 4, 4' -dicyclohexylmethane diisocyanate

PPG-1000 ═ polypropylene glycol, Mw1000

EDA ═ ethylenediamine

NMP ═ N-methylpyrrolidone

MMA ═ methyl methacrylate

BMA-butyl methacrylate

Biaxially oriented BOPP

PVDC ═ polyvinylidene chloride

Diofan A-050 ═ anionic polyvinylidene chloride available from Solvin

TEA ═ triethylamine

NH₃Ammonia used as a 25% aqueous solution

N₂H₄Hydrazine used as a 15.2% aqueous solution

Neocryl BT-36 ═ acrylic emulsion available from DSM Neoresins BV

Water softening Water

Dynomin UM-15 ═ Cymel UM-15 ═ methylated urea-formaldehyde resins available from Cytec

NeoCryl XK-90 (a sequential acrylic emulsion available from DSM Neoresins BV, Mw 2000000

ML-160. Michem Lube ML-160, an anionic carnauba wax emulsion obtainable from Michelmann

FP-348 ═ formalpol FP-348, a dispersion of synthetic amorphous silica in water available from Formulated Polymer Products

Jeffamine ═ amino-terminated polyalkylene oxide available from Huntsman, Mw1000

Example 1

Step 1: pTHF-1000(1520.4 g; OH number 110 mgKOH/g; premelted at 50 ℃) and DMPA (168.0g) were charged to the reactor. The mixture was homogenized to a fine suspension and IPDI (1111.7g) was then added. The reactor was purged with nitrogen and its contents were heated to 50 ℃. A catalytic amount of tin octoate (0.25g) was added at 50 ℃. The mixture is brought to a reaction temperature of 90 ℃ by means of the heat evolved and additional external heating. The course of the reaction was monitored by determining the amount of residual isocyanate groups by back-titration of the excess dibutylamine added to a sample solution of the prepolymer in toluene. The reaction temperature was maintained until the NCO content of the resulting polyurethane prepolymer had fallen below the theoretical value of 6.7% NCO, and then cooled to 75 ℃.

Step 2: water (1629.5g), ammonia (neutralizer, 26.1g, 25% aqueous solution; 1.0SA for DMPA acid groups of the polyurethane prepolymer) and hydrazine (chain extender, 129.9g, 15.2% aqueous solution; 0.95SA for residual isocyanate groups of the polyurethane prepolymer) were charged to the second reactor and the temperature of the resulting aqueous phase was set to 30 ℃.

And step 3: the polyurethane prepolymer (850.0g) prepared in step 1 was added to the aqueous phase prepared in step 2 over a period of 1 hour using a heated 1L dropping funnel while maintaining the temperature of the polyurethane prepolymer at 75 ℃. In this dispersion step, the temperature of the aqueous phase was raised to 39 ℃. In step 3, neutralization, chain extension and dispersion in water are carried out simultaneously.

The resulting translucent polyurethane dispersion had a solids content of 33.0%, a pH of 7.6 and a Brookfield viscosity of 50 mPas at room temperature (23. + -. 2 ℃ C.). The concentration of free hydrazine as determined by HPLC is about 1ppm, which is the limit of detection of the equipment used.

The relative amounts of the components used in all examples are given in table 1 below.

Example 2

A polyurethane dispersion was prepared according to the method of example 1, except that: chain extension was performed with EDA at 0.35SA followed by hydrazine at 0.60 SA.

Example 3

A polyurethane dispersion was prepared according to the method of example 1, except that: the prepolymer was prepared from PPG-1000, DMPA and DES W at an NCO/OH ratio of 1.5, with 5% NMP as co-solvent, neutralized with 1.3SA ammonia, and chain extended with 0.98SA hydrazine.

Example 4

A polyurethane dispersion was prepared according to the method of example 3, except that: the prepolymer was neutralized with 1.3SA of ammonia in the aqueous phase before dispersion and 1.7SA of ammonia was added to the water after dispersion to raise the pH.

Example 5

A polyurethane dispersion was prepared according to the method of example 1, except that: the prepolymer was prepared from a polyester polyol having an OH value of 110mgKOH/g (prepared from the fatty acid dimer Pripol 1009(99.4 parts, available from Uniqema), adipic acid (24.8 parts), and cyclohexanedimethanol (75.8 parts)), DMPA, IPDI, and Jeffamine (1/1 mole adduct of Jeffamine M1000 with hydroxyethyl acrylate, which can be prepared separately by mixing the two ingredients and heating to 70 ℃ for 2 hours as described in EP 317258B 1) at an NCO/OH ratio of 1.5, followed by simultaneously: dispersed in water, neutralized with 1.1SA of ammonia and chain extended with 0.95SA of hydrazine.

Example 6

A polyurethane dispersion was prepared according to the method of example 1, except that: the prepolymer was prepared from pTHF-1000, DMPA and TDI at an NCO/OH ratio of 1.5 (at 80% solids in a mixture of BMA and MMA monomers in a 4: 1 ratio) and then simultaneously: dispersed in water, neutralized with 1.3SA of ammonia and chain extended with 0.98SA of hydrazine. Finally, the monomers were converted to acrylic polymer using fe.edta (2.0g, 1% aqueous solution) and redox-initiated p-tert-butyl hydroperoxide (0.7g, 70% aqueous solution), isoascorbic acid (4 × 10.2g, 1% aqueous solution) (both 0.1% based on monomer). The Tg of the BMA/MMA polymer, calculated according to the Fox equation, was 34 ℃. The ratio of polyurethane to vinyl polymer was 80: 20.

Example 7

The polyurethane dispersion of example 1 (527.1g) was mixed with the formaldehyde urea resin Dynomin UM-15(2.6 g).

Example 8

The polyurethane dispersion of example 1 (527.1g) was mixed with sequential acrylic emulsion polymer (165.7g) (NeoCryl XK-90, available from DSM Neoresins BV, having two Tg values (calculated using the Fox equation, 0 ℃ and 80 ℃).

Comparative example C1

A polyurethane dispersion was prepared according to the method of example 1, except that: the prepolymer was neutralized with TEA (1.0SA) instead of ammonia and the polyurethane dispersion (500g) was mixed with the formaldehyde urea resin Dynomin UM-15(5.1 g).

Comparative example C2

A polyurethane dispersion was prepared according to the method of example 1, except that: chain extension was performed with EDA (0.95SA) instead of hydrazine.

Comparative example C3

A polyurethane dispersion was prepared according to the method of example 1, except that: chain extension was performed with a stoichiometric excess (1.20SA) instead of a sub-stoichiometric amount of hydrazine. The amount of free hydrazine present in the dispersion is greater than 200ppm, so that toxicologically, the dispersion cannot be used as a primer.

The particle size of examples 1-8 was less than 200 nm. The polyurethanes prepared in these examples had Mn of less than 40000 g/mol. The details of the examples are given in table 1 below.

TABLE 1

Examples	1	2	3	4	5	6	C1	C2	C3
										Polyurethane prepolymers
DMPA％	6.0	6.0	5.5	5.5	5.2	9.0	5.2	6.0	6.0

Polyol 1	pTHF1000	pTHF1000	PPG1000	PPG1000	Polyester	pTHF1000	pTHF1000	pTHF1000	pTHF1000
										1% of polyhydric alcohol	54.3	54.3	56.5	56.5	52.6	58.2	56.6	54.3	54.3
Polyol 2					Jeffamine
										2 percent of polyol					5.0
Diisocyanate	IPDI	IPDI	DES W	DES W	IPDI	TDI	IPDI	IPDI	IPDI
										Diisocyanate%	39.7	39.7	38.0	38.0	37.2	37.2	38.2	39.7	39.7
Cosolvent%			NMP(12.0)	NMP(12.0)	NMP(10.0)	BMA/MMA(20)
										Tin octylate%	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
Additive g						IonolCP(0.2)
										NCO/OH	1.80	1.80	1.50	1.50	1.80	1.50	1.80	1.80	1.80
NCO％	6.42	6.42	3.01	3.01	5.34	4.12	6.41	6.42	6.42
										Dispersion product
Prepolymer g	850.0	320.0	500.0	500.0	611.1	500.0	500.0	320.0	320.0
										Neutralizer g	NH₃(26.1)	NH₃(9.8)	NH₃(16.9)	NH₃(38.9)	NH₃(14.5)	NH₃(25.1)	TEA(19.8)	NH₃(9.8)	NH₃(9.8)
Neutralizing agent SA	1.0	1.0	1.3	3.0(1.3/1.7)	1.1	1.3	1.0	1.0	1.0
										Chain extender	N₂H₄	EDA/N₂H₄	N₂H₄	N₂H₄	N₂H₄	N₂H₄	N₂H₄	EDA	N₂H₄
Chain extender g	129.9	4.9/33.5	37.0	37.0	79.0	50.6	70.3	16.0	61.8

Chain extender SA	0.95	0.30/0.65	0.98	0.98	0.95	0.98	0.95	0.98	1.20
										Water g	1629.5	614.8	931.6	931.6	1100.0	693.6	1190.8	667.5	606.5
Properties of
										Solids%	33.0	32.5	30.5	30.1	30.3	38.5	27.7	32.5	32.5
Viscosity of the oil^*	50	30	184	120	51	72	40	40	40
										pH	7.6	8.0	8.5	9.9	7.7	6.9	8.1	9.9	8.2
Acid number #	25	25	23	23	22	30	22	25	25
										N₂H₄ppm	1	1	BDL	BDL	BDL	BDL	5	BDL	205
^*mPa · s # mgKOH/g BDL: below the detection limit of the equipment used

The polyurethane and polyurethane/acrylic dispersions described in examples 1-8 were tested as a primer on corona treated BOPP foil with PVDC heat sealable top coat (diovan a-050) and referred to as examples 1(a) -8 (a).

In example 1(b), the polyurethane dispersion of example 1 was tested as a primer on corona treated BOPP foil with an acrylic heat sealable top coat (NeoCryl BT-36).

In example 3(b), the polyurethane dispersion of example 3 was tested as a primer on corona treated BOPP foil with an acrylic heat sealable top coat (NeoCryl BT-36).

In example 6(b), the polyurethane dispersion of example 6 was tested as a primer on corona treated BOPP foil with an acrylic heat sealable top coat (NeoCryl BT-36).

The polyurethane dispersions of comparative examples C1 and C2 were tested as a base coat on corona treated BOPP foil with a PVDC heat sealable top coat (diovan a-050).

Priming and coating experiments for heat-sealable packaging applications

A water-based primer comprising the polyurethane dispersions prepared in examples 1 to 8 and comparative examples C1 and C2, respectively, diluted with demineralized water to a solids content of 5%, was applied to a corona-treated OPP-based film (23 DR-360 of Derprosa, the surface tension of which after corona treatment was 40 to 42dynes/cm) on an experimental film coater (RK coater from RK Print-Coat Instruments) by means of a reverse gravure coating system and then dried with hot air at 80 ℃ to give a dry coating weight of 0.15g/m²The primed plastic substrate of (1).

The primed plastic substrate was then coated with either a water-based anionic PVDC dispersion (a) or a water-based acrylic emulsion (b) formulated as in table 2 below by reverse gravure coating and then dried with hot air at 90 ℃. The dry coat weight of the PVDC topcoat was 1.5g/m²And the dry coat weight of the acrylic topcoat was 1g/m²。

TABLE 2

	Diofan A-050	NeoCryl BT-36	ML-160	FP-348	Water (W)
						PVDC	83.7	3.7	0.9	11.7
Acrylic acid		70.6	3.4	0.2	25.8

The coated film was left at room temperature (23. + -. 2 ℃) for 1 week to complete the crystallization of the PVDC topcoat.

Wet seal strength

The coated film prepared as above was folded in half (top coat to top coat) and then heat sealed on a Brugger heat sealer (model HSG-C) equipped with a heated flat metal upper caliper (2cm width) and an unheated flat rubber lower caliper. At 130 ℃ at 2.8kg/cm²The sealing was performed for 1 second at a pressure of (40 psi).

The initial heat seal strength (g/inch) was measured on an Instron Tensile tester.

The sealed film was stored in a humidified chamber (38 ℃ C., 90% relative air humidity) for 4 weeks. The residual seal strength measured after 1 day, 1 week, 2 weeks, 3 weeks and 4 weeks, respectively, should be maintained at similar levels.

Table 3 shows the initial adhesion of the sealing foil and the adhesion (in g/inch and g/cm) after storage under warm and humid conditions (38 ℃ C., 90% relative air humidity).

TABLE 3

Examples	1(a)	1(b)	2(a)	3(a)	3(b)	4(a)	5(a)
								Top coat	PVDC	Acrylic acid	PVDC	PVDC	Acrylic acid	PVDC	PVDC
Adhesion (Wet seal Strength) g/inch (g/cm)
								Initial	489(193)	638(251)	725(285)	778(306)	565(222)	724(285)	298(117)
1 day	357(141)	524(206)	356(140)	487(192)	524(206)	387(152)	449(177)
								1 week	476(187)	621(244)	416(164)	562(221)	621(244)	535(211)	580(228)
2 weeks	517(205)	595(234)	407(160)	601(237)	636(250)	564(220)	631(248)
								3 weeks	431(170)	637(251)	353(139)	616(243)	692(272)	618(243)	672(265)
4 weeks	419(165)	634(250)	300(118)	603(237)	621(244)	584(230)	628(247)

Table 3 (continuation)

Examples	6(a)	6(b)	7(a)	8(a)	C1(a)	C2(a)
							Top coat	PVDC	Acrylic acid	PVDC	PVDC	PVDC	PVDC
Adhesion (Wet seal Strength) g/inch (g/cm)
							Initial	756(298)	412(162)	275(108)	417(164)	84(33)	115(45)
1 day	472(186)	287(113)	268(106)	273(107)	46(18)	60(24)
							1 week	634(250)	206(81)	272(107)	258(102)	44(17)	62(24)
2 weeks	669(263)	240(94)	419(165)	309(122)	46(18)	40(16)
							3 weeks	577(227)	266(105)	373(147)	214(84)	112(44)	40(16)
4 weeks	624(246)	237(93)	439(173)	302(119)	78(31)	40(16)

Claims

1. An aqueous polyurethane composition comprising a polyurethane having an acid value of from 4 to 150mgKOH/g and comprising the reaction product of:

(A) an isocyanate-terminated prepolymer obtained by reacting components comprising:

(i) at least one organic polyisocyanate;

(iii) (iii) at least one isocyanate-reactive compound not comprised by (ii),

(B) at least one active hydrogen chain extending compound comprising at least 0.2 stoichiometric equivalent of an active hydrogen chain extending compound selected from hydrazine, hydrazine derivatives and mixtures thereof relative to the isocyanate content of the isocyanate-terminated prepolymer (A),

wherein at least 0.2 stoichiometric equivalents of the anionic or potentially anionic water-dispersing groups are neutralized with ammonia;

the hydrazine derivative is selected from the group consisting of acetone azine, dimethylhydrazine, 1, 6-hexamethylene-bis-hydrazine, carbodihydrazide, adipic acid mono-hydrazine, adipic acid bis-hydrazine, succinic dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, tartaric acid dihydrazide, 1, 3-phenylene-bis-sulfonic acid dihydrazide, omega-amino-adipic acid dihydrazide, citric acid trihydrazide, 1, 2, 4-butane tricarboxylic acid trihydrazide, gamma-hydroxybutyric acid hydrazide, bis-hemi-carbazide and hemi-carbazide.

2. An aqueous polyurethane composition according to claim 1, having a free hydrazine content of 20ppm or less.

3. The aqueous polyurethane composition according to claim 1, wherein the acid value of the polyurethane is from 4 to 100 mgKOH/g.

4. An aqueous polyurethane composition according to claim 1, wherein the active hydrogen-containing chain extender (B) comprises at least 0.4 stoichiometric equivalent, relative to the isocyanate content of the isocyanate-terminated prepolymer (a), of an active hydrogen chain extending compound selected from the group consisting of hydrazine, hydrazine derivatives selected from the group consisting of acetone azine, dimethylhydrazine, 1, 6-hexamethylene-bis-hydrazine, carbodihydrazine, adipic acid mono-hydrazine, adipic acid bis-hydrazine, succinic acid dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, tartaric acid dihydrazide, 1, 3-phenylene-dicarboxylic acid dihydrazide, omega-amino-adipic acid dihydrazide, citric acid trihydrazide, 1, 2, 4-butanetricarboxylic acid trihydrazide, gamma-hydroxybutyric hydrazide, bis-semicarbazide and semicarbazide, and mixtures thereof.

5. An aqueous polyurethane composition according to claim 1, wherein the ratio of the isocyanate groups in the isocyanate terminated prepolymer (a) to the active hydrogens in the chain extender (B) is from 1: 0.6 to 1: 1.

6. An aqueous polyurethane composition according to claim 1 wherein at least 0.25 stoichiometric equivalents of the anionic or potentially anionic water-dispersing groups are neutralized by ammonia.

7. An aqueous polyurethane composition according to claim 1, comprising a polyurethane having an acid number of from 10 to 42mgKOH/g and comprising the reaction product of:

(A) an isocyanate-terminated prepolymer obtained by reacting:

(i)10 to 90 wt% of at least one organic polyisocyanate;

(ii)0.1 to 80 wt% of at least one isocyanate reactive compound having anionic or potentially anionic water-dispersing groups;

(iii) (iii)5 to 90% by weight of at least one isocyanate-reactive compound not comprised by (ii),

wherein (i) + (ii) + (iii) is 100%,

wherein 0.25 to 3 stoichiometric equivalents of the anionic or potentially anionic water-dispersing groups are neutralized with ammonia and the hydrazine derivative is selected from the group consisting of acetone azine, dimethylhydrazine, 1, 6-hexamethylene-bis-hydrazine, carbodihydrazide, adipic acid mono-hydrazine, adipic acid bis-hydrazine, succinic acid dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, tartaric acid dihydrazide, 1, 3-phenylene-bis-sulfonic acid dihydrazide, omega-amino-adipic acid dihydrazide, citric acid trihydrazide, 1, 2, 4-butane tricarboxylic acid trihydrazide, gamma-hydroxybutyrylhydrazine, bis-semicarbazide and semicarbazide.

8. An aqueous polyurethane composition according to claim 7 wherein component (i) is selected from the group consisting of isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, 2, 4-toluene diisocyanate, and mixtures thereof.

9. The aqueous polyurethane composition of claim 7 wherein component (ii) is selected from the group consisting of 2, 2-dimethylolpropionic acid (DMPA), 2-dimethylolbutanoic acid (DMBA), and mixtures thereof.

10. An aqueous polyurethane composition according to claim 7 wherein component (iii) is selected from the group consisting of poly-THF, polypropylene glycol, polyester, amino terminated polyalkylene oxide, and mixtures thereof.

11. The aqueous polyurethane composition as claimed in claim 10, wherein the Mw of component (iii) is 300-3000 g/mol.

12. An aqueous polyurethane composition as claimed in claim 10 wherein component (iii) comprises less than 15% by weight of organic compounds having an Mw of less than 500 g/mol.

13. The aqueous polyurethane composition of claim 1 further comprising a vinyl polymer, wherein the weight ratio of polyurethane to vinyl polymer is from 10: 90 to 99: 1.

14. The aqueous polyurethane composition of claim 13, wherein the vinyl polymer is a (meth) acrylate polymer.

15. An aqueous polyurethane composition as claimed in claim 13, wherein the vinyl polymer has a Tg of-80 to 150 ℃.

16. An aqueous polyurethane composition according to claim 13, wherein the acid value of the vinyl polymer is from 0 to 100 mgKOH/g.

17. An aqueous polyurethane composition according to claim 13 comprising a separately prepared vinyl polymer having a polyurethane to vinyl solids ratio of from 60: 40 to 80: 20, wherein the vinyl polymer has a Tg of from 0 to 50 ℃ and is prepared from a vinyl monomer selected from the group consisting of methyl methacrylate, ethyl (meth) acrylate, butyl (meth) acrylate, styrene, (meth) acrylic acid, and mixtures thereof.

18. A process for preparing the aqueous composition of claim 1 comprising the steps of:

(i)10 to 90 wt% of at least one organic polyisocyanate;

wherein (i) + (ii) + (iii) is 100%,

wherein the isocyanate-terminated prepolymer component is reacted at a ratio of isocyanate to isocyanate-reactive groups of from 1.1: 1 to 6: 1;

b) forming an aqueous dispersion of the isocyanate-terminated prepolymer (a);

c) optionally neutralizing the isocyanate-terminated prepolymer (a);

d) chain extending said isocyanate-terminated prepolymer (a) by reaction with said active hydrogen chain extending compound (B).

19. The method of claim 18, further comprising the step of:

e) adding a reactive diluent;

f) subsequent polymerization of the reactive diluent.

20. Use of the aqueous polyurethane composition of claim 1 for coating a substrate.

21. A method of coating a substrate with an aqueous polyurethane composition comprising applying the aqueous polyurethane composition of claim 1 to a substrate and removing the aqueous medium.

22. A primer comprising the aqueous polyurethane composition of claim 1.

23. A label coating comprising the aqueous polyurethane composition of claim 1.

24. A coating obtained from the aqueous polyurethane composition of claim 1, which has a heat seal strength of 200g/inch or more at the time of heat sealing.