DE2645779A1 - PROCESS FOR PRODUCING EMULSIFIER-FREE, ANIONIC POLYURETHANE DISPERSIONS - Google Patents

Description

BASF Aktiengesellscha. ^T 't

Our sign; O ₀ Z ₀ 32 2] 35 BR / DK

6700 Ludwigshafen, O8.IO.I976

A process for the preparation of emulsifier-free, disperse polyurethane anionic ion ___

The invention relates to a method for producing emulsifier-free, anionic polyurethane dispersions from which coatings with improved properties can be achieved »

The preparation of _emulsifier-a aqueous polyurethane dispersions of ionic by incorporation centers in the polymer molecule, dissolving in a water-containing organic solvent and removing the organic solvent, for example, DT-AS lh 95 745 and from the magazine "Angewandte Chemie", 82/2 ( I97O), Verlag Chemie GmbH, Weinheim, pages 53 - 90 known ο

The DT-OS 20 34 479 also teaches that this is the starting product Polyhydroxy compounds with a molecular weight of 35Ο to 10 000 and to introduce the ionic centers equimolar Addition products from the alkali salts of, ^, - olefinic Carboxylic acids to aliphatic diprimary diamines are particularly suitable. The dispersion can take place in any way, It is preferred to work in such a way that the higher molecular weight polyhydroxyl compound is initially mixed with excess diisocyanate in the melt reacted to a prepolymer with isocyanate end groups, this in a water-miscible, below 100 C boiling organic Solvent taken up and with an aqueous solution of the salt group-containing diamine and then with V / water is added »The organic solvent is then distilled off O

However, coatings produced from the dispersions obtainable in this way still have certain deficiencies, those of their technical properties Oppose use, especially as leather coatings, Fine, stable dispersions are obtained with aliphatic or cycloaliphatic diisocyanates, but they are

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coatings obtainable therefrom are very soft and have a rubber-like appearance Griff »Aromatic diisocyanates, on the other hand, result in relatively coarse dispersions which tend to sediment easily and which Coatings made from it have poor strength and strength Wear behavior on »

The present invention was based on the object of providing polyurethane dispersions without developing the disadvantages mentioned »

It has now been found that the disadvantages described are eliminated leave when looking to build polyurethane ionomers a combination of aliphatic or cycloaliphatic with aromatic diisocyanates, either first the aromatic, then the (cycloi-aliphatic or both at the same time, sets in » Polyurethane ionomers from these isocyanate combinations are not suggested by the prior art, especially as the components known to react very differently quickly, and are the known from purely aliphatic or purely aromatic diisocyanates Surprisingly superior »They form finely divided, stable dispersions, from which hard and at the same time produce tough coatings with excellent strength and wear properties, =

The combination of (cycloialiphatic with aromatic diisocyanates to build the polyurethane ionomers according to the invention has the purpose of incorporating longer polar segments of aromatic diisocyanate and chain extenders into the polymer molecule. The finished polyurethane then contains longer chains of, for example _, polyesters or polyethers from one another separate segments of aromatic diisocyanate and chain extenders without salt groups as well as segments of aliphatic or cyeloaliphatic diisocyanate and chain extenders which contain ionic groups. This is essential to the invention is not suggested by the state of the art »It leads to a favorable combination of properties

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nation: stable, finely divided dispersions with excellent mechanical Properties of the impregnations, coatings and films made from them. The disadvantages of the corresponding known products are thereby overcome.

The present invention thus provides a process for the production of emulsifier-free, aqueous polyurethane dispersions the end

A) Dihydroxy compounds with a molecular weight of 500 to 5,000;

B) diisocyanates ^

C) water-soluble salts of aliphatic amino (preferably Diamino) carboxylic or sulfonic acids with at least one, preferably two, bonded to different nitrogen atoms Hydrogen atoms and

D) Compounds without salt groups with at least 2 opposite isocyanate groups reactive hydrogen atoms and one Molecular weight below 300 as chain extenders,

by dissolving or dispersing the polyurethanes in aqueous-organic Solvents and removal of the organic solvent components, characterized in that a combination is used as the diisocyanate of aromatic and aliphatic or cycloaliphatic diisocyanates with 10 to 50 mol $ (cyclo) aliphatic content used is, and that either the aromatic, then the (cyclo) -aliphatic diisocyanates or both are used at the same time will"

Suitable dihydroxy compounds (A) are the known polyesters, Polyethers, polythioethers, polylactones, polyacetals, polycarbonates and polyester amides with 2 terminal hydroxyl groups. The molecular weights of these dihydroxy compounds should be in the range between 500 and 5,000, the range between 750 and 3,000 being particularly advantageous. Of course you can too

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Mixtures of these higher molecular weight dihydroxyl compounds with one another can be used. If appropriate, minor amounts of hydroxyl compounds with an average of more than two Hydroxyl groups per molecule are also used. These more functional Polyhydroxyl compounds should then only be used in such proportions are used that the functionality does not exceed a total of 2.2. Normally however, difunctional polyhydroxy compounds are preferred. They must not have fewer than 2 hydroxyl groups on average.

Suitable diisocyanates (B) are the customary aliphatic and cycloaliphatic ones and aromatic diisocyanates such as 1,4-butane diisocyanate, 1,6-hexane diisocyanate, 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanate, Cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, xylylene diisocyanate, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanato-dicyclohexylmethane, 2,4- and 2,6-toluene diisocyanate, as well as their technical isomer mixtures. Mixed aliphatic-aromatic diisocyanates are also used in the process according to the invention instead of the purely aliphatic suitable. The molar ratio of the (cyclo) aliphatic to the aromatic diisocyanates is expediently in the range of 1: 1 to 1: 9, preferably from 1: 2 to 1: 6.

Suitable water-soluble salts of aliphatic aminocarbon or -sulfonic acids (C) are e.g. in DOS 20 34 479 or DOS 19 54 OQO described. These are preferably the alkali salts, especially the sodium and potassium salts, the addition products of lower aliphatic diprimary diamines, e.g. ethylenediamine, to unsaturated Carboxylic acids such as (meth) acrylic acid, crotonic acid or maleic acid and alkali salts of lysine. Compounds are generally preferred with two hydrogen atoms bound to different nitrogen atoms and with only one salt group in the molecule, i.e. compounds which make the product dispersible but not too hydrophilic and which are also suitable for chain lengthening. The alkali salts of the addition products of propane sultone with aliphatic diprimary diamines are also very suitable. You will be in

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such amounts applied, that the total polyurethane composition contains 0.02 to 1 wt.% salt-like groups "

Suitable low molecular weight chain extenders (D) without salt groups and with molecular weights below 300 are customary Glycols, such as ethylene glycol, propylene glycol, butanediol-1,3 and -1,4, Hexanediol, neopentyl glycol, cyclohexanediol, 2,2-bis (4-hydroxycyclohexyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, diethylene glycol or dipropylene glycol, diamines such as ethylenediamine, Hydrazine, piperazine, isophoronediamine, toluenediamine, diaminodiphenylmethane as well as amino alcohols and optionally also water.

The isocyanate groups and the isocyanate-reactive hydroxyl and amino groups should be approximately equivalent molar Conditions are used. The ratio of the number of isocyanate groups to the total number of isocyanate-reactive groups Hydrogen atoms should be in the range between 0.9 and 1.2, preferably be between 1.0 and 1.1 »

Components A, B, C and D are said to be in such molar proportions are used that the ratio of the higher molecular weight hydroxy! compounds (A) to the sum of the diisocyanates (B) and to the sum of the compounds containing salt groups (C) and the low molecular weight chain extender (D) in the range of A: B: (C + D) = 1: 2: 1 to 1:14:13. The is particularly advantageous Range from 1: 4: 3 to 1: 10: 9 «

To accelerate the reaction of the diisocyanates, the usual and known catalysts such as dibutyltin dilaurate, tin (II) octoate or 1,4-diazabicyclo- (2,2,2) -octane, can also be used.

The preparation of the polyurethane compositions is carried out in a known manner by reacting the relatively high molecular weight PoIyhydroxylverbindungen with the diisocyanates and the low molecular weight chain-extending agents without salt groups in the melt or optionally in the presence of less than 100 ⁰ C boiling and water-miscible inert organic solvent optionally under

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Printing to a prepolymer with terminal isoeyanate groups.

The (cyclo) aliphatic and aromatic to be used according to the invention Diisocyanates (B) can either be mixed with one another or also one after the other in the order mentioned the higher molecular weight dihydroxy compounds (A) and the lower molecular weight Chain extenders (D) are implemented. Due to the different reactivity of the two diisocyanates it is often sufficient to use the diisocyanates as a mixture with one another. They become one after the other with the Hydroxy1 compounds A and D reacted, then it is essential to the invention, first the aromatic and then the (cycloaliphatic diisocyanate use to ensure that the reaction product is central segments of aromatic diisocyanate and chain extender (D) and terminal (cycloaliphatic isocyanate groups having. In the step-by-step reaction of the two diisocyanates, it is not essential before the (cyclo) aliphatic is added Diisocyanate to implement the aromatic diisocyanate completely, but the (cycloaliphatic diisocyanate can often added at a point in time at which only part of the aromatic diisoeyanate has reacted »

The polyurethane thus obtained having terminal aliphatic or eycloaliphatischen Isoeyanatgruppen is optionally miscible with water, below 100 ⁰ C boiling and inert towards Isoeyanatgruppen solvent (further) and washed at a temperature between 20 and 50 ⁰ C with a preferably aqueous solution of the under C mentioned salts of aliphatic aminocarboxylic or sulfonic acids added. The reaction of the salts with the isocyanate groups takes place spontaneously and, if the carboxylic or sulfonic acid salts contain more than one NH group per molecule, leads to chain lengthening. Water is stirred into the solution of the polyurethane thus obtained with built-in salt-like groups and the organic solvent is removed by distillation.

Finely divided, stable dispersions are obtained which are evaporated can optionally be concentrated. In general

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my preference is for solvent-free latices with a solids content of 30-50 %.

As low-boiling solvents, polar solvents which are inert towards isocyanate and which have boiling points below 100 ^° C. and are miscible with water, for example acetone, tetrahydrofuran or methyl ethyl ketone, are suitable.

The dispersions can be prepared, for example, according to the following general procedure: The higher molecular weight predominantly difunctional hydroxyl compounds (A) are first dehydrated at about 120 ° C in a water jet vacuum for 30 minutes, mixed with the chain extenders without salt groups (D) and optionally in the presence of solvents with a Mixture of the two diisocyanates (B) or reacted first with the aromatic and then with the (cyclo) -aliphatic diisocyanate at 50-130 ° C. to give a prepolymer with terminal isocyanate groups. The mass is then diluted with (further) solvent to such an extent that an approximately 30-50% solution results. The prepolymer solution is then treated with a solution of alkali metal salt of Diaminocarbon- or sulfonic acid in water has been added after completion of the reaction at 20 to 50 ⁰ C, the added according to the desired solids content of the produced dispersion calculated amount of water and the solvent distilled off in vacuo "

The dispersions obtainable in this way are finely divided and stable for more than 6 months even at tropical temperatures. You can after customary processes for films, foils, coatings, coatings, varnishes and impregnations of a wide variety of substrates are processed. The dispersions are particularly suitable for coating leather. They adhere very well to leather, are elastic, firm, tough and resistant to mechanical stress and give the leather a pleasant grip.

Depending on their intended use, the polyurethane dispersions can also be mixed with customary modifiers and additives can be combined, e.g. crosslinking agents, plasticizers, pigments, fillers, etc. They can also be combined with suitable dis-

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persions made of natural or synthetic polymers, for example Nitrocellulose, to be blended.

The parts mentioned in the examples and comparative experiments and Percentages are based on weight.

example 1

203 parts of a commercial polyester of adipic acid, hexanediol and neopentyl glycol with an OH number of 55 are dehydrated in a stirred flask at 130 ⁰ C and 20 Torr for 30 minutes. The polyester is cooled, dissolved in 200 parts of acetone, and 40.5 parts of 1,4-butanediol are added. A mixture of 69.7 parts of toluene diisocyanate (isomer ratio 2.4 / 2.6 = 80/20) and 33 »6 parts of hexamethylene diisocyanate and 0.02 part of dibutyltin dilaurate are then added. After stirring for 3 hours at 60 ° C., the mixture is diluted with 300 parts of acetone and cooled to room temperature. 19.3 parts of a 40 # strength aqueous solution of the equimolar addition product of ethylenediamine to sodium acrylate are stirred into the solution of the prepolymer thus obtained. After 20 minutes, 500 parts of water are added dropwise and the acetone is then distilled off under reduced pressure.

The result is a very finely divided, stable dispersion, which too does not tend to sediment during prolonged storage. If the dispersion is dried on glass plates, clear, high-gloss ones are obtained and very tough films which, according to DIN 53 504, have a tear strength of

ρ
330 kp / cm and an elongation at break of 720 % .

Comparative experiment la

203 parts of the polyester used in Example 1 are as described there dehydrated, dissolved in acetone and mixed with 36 parts of 1,4-butanediol. The amount of the chain extender butanediol is here reduced by the same molar amount compared to Example 1, by which the amount of chain extender containing salt groups is increased. So the total molar amount of chain extenders is

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the same for both attempts. After adding 10 ^ 1.4 parts of toluene diisocyanate (80/20) and 0.02 part of dibutyltin dilaurate is continued as in Example 1, but the opposite of Example 1 doubled amount (15.4 g, dissolved in 23 g water) des chain extender containing salt groups (addition product of Ethylenediamine to sodium acrylate) is used.

The dispersion obtained after the acetone has been distilled off is in spite of this the salt group content, which is doubled compared to Example 1, is very coarse and begins to sediment immediately. With less In the salt group content, this would of course be the case to an even greater extent. It is therefore useless for practical purposes.

Comparative experiment Ib

The comparative experiment la is repeated with the equimolar amount (100.8 parts) hexamethylene diisocyanate instead of toluene diisocyanate.

The prepolymer becomes insoluble in acetone after a short time and falls the end. A dispersion cannot be obtained with this.

The use of 1,4-butanediol as a chain extender is dispensed with here and, accordingly, instead of 100.8 parts, only 43.8 parts of hexamethylene diisocyanate are used, otherwise the result is same measures a finely divided, stable dispersion, but that provides very soft and therefore unsuitable for most purposes covers with a rubber-like handle.

Comparative experiment Ic

241.5 parts of the polyester from Example 1 are degassed and ^{reacted at 60 °} C. with 36 parts of toluene diisocyanate (TDI 80). The mass is diluted with 700 parts of acetone and a mixture of 50 parts of water, 3.76 parts of ethylenediamine, 4.26 parts of propane sultone and 19.6 parts of 10 ^ strength aqueous sodium hydroxide solution are added. 360 parts of deionized water are then added dropwise and the acetone is distilled off in vacuo.

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A dispersion is obtained which settles out after just a few hours.

Example 2

401 parts of a commercially available polyester made from adipic acid and ethylene glycol with a molecular weight of 2,000 are dehydrated and diluted with 124.9 parts of neopentyl glycol and 230 parts of acetone. Then 325 parts of 4.4 ^f -diisocyanatodiphenylmethane and 44.5 parts of isophorone diisocyanate are added with stirring, and stirring is continued for a further hour. The mass is diluted with 900 parts of acetone, cooled to room temperature and 38.5 parts of a 40% aqueous solution of the equimolar addition product of ethylenediamine to sodium acrylate are stirred in. After 30 minutes, 1350 parts of deionized water are slowly added dropwise and the acetone is stripped off under reduced pressure.

The result is a very finely divided, stable dispersion with a solids content of approx. 40 %. Samples mounted on glass plates dry at room temperature to form tough films which, according to DIN 53 504, have a tear strength of 24 N / mm, an elongation at break of 430 % and a tear strength according to DIN 53 775 of 56 kp / cm.

Comparative experiment 2a

Example 2 is repeated under the same conditions with the The difference is that instead of the isophorone diisocyanate, the equimolar amount, ie 34.85 parts of toluene diisocyanate (TDI 80), is used.

The dispersion produced in this way begins after just a few hours to sediment, a thick sediment has formed overnight. The dispersion made with 2 aromatic diisocyanates is therefore not useful in practice.

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Example 3

Example 2 is repeated with the difference that, instead of the polyester, 400 parts of polytetrahydrofuran of molecular weight 2,000 will be used. The water is added at 50 C, in addition 500 parts of tetrahydrofuran are added.

A finely divided, stable dispersion is obtained which dries up to tough, slightly opaque films at room temperature. A tear strength of 45.3 N / mm, an elongation at break of 385 % and a tear strength of 66 kp / cm are measured on the films.

Example 4

509 parts of a commercially available polyester of adipic acid, hexanediol and neopentyl glycol with an average molecular weight of 2,000 are dehydrated, 112.6 parts of 1,4-butanediol and 230 parts of acetone are added and 241.6 parts of toluene diisoeyanate (TDI 80) for 90 minutes at low boiling point of acetone stirred. Then 42.06 parts of hexamethylene diisocyanate and 0.2 part of dibutyltin dilaurate are added and stirring is continued for 90 minutes. The mixture is then diluted with 900 parts of acetone, and at 40 ⁰ C, 63.3 parts of a 32.8 # aqueous solution of sodium lysinate are stirred. After 20 minutes, 1250 ml of deionized water are slowly added dropwise with stirring and the acetone is distilled off under reduced pressure.

A finely divided, very stable dispersion with a solids content of 40 % which has not yet formed any sediment even after standing at room temperature for 6 months is obtained. Samples mounted on glass plates dry at room temperature to form clear, high-gloss and very tough films with a tear strength of 370 kp / cm and an elongation at break of 750 % ,

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Claims (1)

0 _: Z ₅ 32 235 Process for the production of emulsifier-free, aqueous polyurethane dispersions from dihydroxy compounds with a molecular weight of 500 to 5,000, diisocyanates, water-soluble salts of aliphatic aminocarboxylic or sulfonic acids with at least one hydrogen atom bonded to nitrogen and compounds without salt groups with at least 2 hydrogen atoms reactive towards isoeyanate groups and a molecular weight below 300 as chain extenders, by dissolving or dispersing the polyurethanes in aqueous-organic solvents and removing the organic solvent components, characterized in that the diisocyanate is a combination of aromatic and aliphatic or cycloaliphatic diisocyanates with 10 to 50 mol ^ (cycloj-aliphatischern proportion is used, and that either first the aromatic, after which the (cyclo) aliphatic diisocyanates, or both are used _{simultaneously, etc.} BASF Aktiengesellschaft 8 0 9 8 1 E / 0 3 7 2 _{BÄD 0} RieiNAL