INNOVATIVE HYDROPHILIC POLYISOCYANATES WITH IMPROVED STORAGE STABILITY

Abstract

The invention relates to innovative, water-dispersible, hydrophilic polyisocyanates and polyisocyanate mixtures, to a process for preparing them, to compositions comprising the hydrophilic polyisocyanates of the invention, and to their use as a starting component in the production of polyurethane plastics, more particularly as crosslinkers for water-soluble or water-dispersible film-forming, adhesives or sealant binders or binder components having groups which are reactive towards isocyanate groups.

Claims

1-15. (canceled)

16. A process for preparing hydrophilic polyisocyanates, comprising: reacting a prepolymer A which carries uretdione groups, with at least one emulsifier B, the emulsifier B comprising at least one ionogenic group which in the case of an acidic ionogenic group in water has a pK.sub.a>8 at room temperature or in the case of a basic ionogenic group has a pK.sub.b>8 at room temperature; wherein the emulsifier B is at least one sulphonate selected from the group consisting of hydroxyalkylsulphonates, hydroxypolyethersulphonates, aminoalkylsulphonates and aminopolyethersulphonates.

17. The process according to claim 16, further comprising reacting a polyisocyanate which carries uretdione groups with monomeric, oligomeric and/or polymeric compounds which contain hydroxyl groups, the prepolymer A being obtained and the compound which contains hydroxyl groups being selected from the group consisting of polyesters, polythioethers, polyethers, polycaprolactams, polyepoxides, polyesteramides, polyurethanes, low molecular weight dialcohols, low molecular weight trialcohols, low molecular weight tetraalcohols and monoalcohols.

18. The process according to claim 16, the prepolymer A having a free NCO content in the range from 0.2 wt % to 20 wt %, based on the total weight of the prepolymer A, and having a uretdione group content of 0.5 to 25 wt %, based on the total weight of the prepolymer A.

19. A hydrophilic polyisocyanate having at least one uretdione group, the polyisocyanate comprising at least one internal emulsifier preparable by a process according to claim 16.

20. A composition, comprising: C at least one hydrophilic polyisocyanate according to claim 19, and optionally water.

21. The composition according to claim 20, further comprising D a reactant for the hydrophilic polyisocyanate C, said reactant containing hydroxyl groups and being dispersible or emulsifiable or soluble in water, and optionally E an auxiliary and/or adjuvant, and optionally F a catalyst.

22. The composition according to claim 21, the reactant D being selected from the group consisting of polyethers, polyesters, polycarbonates, polyalkyd resins, polyacrylates, polyurethanes and polycaprolactones.

23. A polyurethane plastic, comprising: the hydrophilic polyisocyanate according to claim 19.

24. A crosslinker for water-soluble or water-dispersible film-forming binders, adhesives binders or sealant binders or binder components having groups which are reactive towards isocyanate groups, comprising: the hydrophilic polyisocyanate according to claim 19.

25. A polyurethane plastic, comprising: the composition according to claim 20.

26. Water-soluble or water-dispersible film-forming binders, adhesives binders or sealant binders or binder components having groups which are reactive towards isocyanate groups comprising: the composition according to claim 20.

27. A coating, adhesive bond or sealant produced using a composition comprising a polyisocyanate according to claim 19.

28. A method for producing a coating, adhesive bond or sealant, comprising applying a composition according to claim 20 to a substrate.

Description

EXAMPLES

Example a

Preparation of a Neutral, Non-Ionogenically Stabilized Uretdione (Not Inventive)

[0073] 223.9 g of IPDI uretdione (see example c1) were dissolved with 300.9 g of Polyglycol M350 (polyglycol monomethyl ether, Clariant) and 0.3 g of dibutyltin dilaurate (Aldrich) in 250 ml of acetone. After 15 hours under reflux, the solution was cooled. 250 g of this product were admixed with 262.5 g of fully demineralized water, with vigorous stirring in a dispermat (3000 rpm). The acetone was removed on a rotary evaporator at 40 mbar and 60° C., after which the product was filtered using a 50 μm filter. The latent NCO content was 4.59%, the solids about 46% and the viscosity 200 mPas.

[0074] After 8 weeks at 20° C. this aqueous dispersion had a latent NCO content of 3.0% and after 8 weeks at 50° C. a latent NCO content of 1.26%. The hydrophilization of uretdione-containing curing agents with polyethers therefore does not produce a storage-stable aqueous dispersion.

Example b

Preparation of a Non-Neutral, Ionogenically Stabilized Uretdione (Not Inventive)

[0075] 307.6 g of IPDI uretdione (see example c1) were dissolved in 180 ml of acetone and 0.3 g of dibutyltin dilaurate (Aldrich) was added. 112.4 g of dimethylaminopropylamine (DMAPA, Aldrich) were carefully added dropwise and the temperature was held at below 30° C. by cooling. After a subsequent reaction time of 1 hour, 200 g of this product were first neutralized with 23.8 g of acetic acid and then admixed with 163.8 g of fully demineralized water with vigorous stirring in a dispermat (3000 rpm). The acetone was removed on a rotary evaporator at 40 mbar and 60° C. after which the product was filtered using a 50 pm filter. The latent NCO content was 0.55% (theoretical 4.17%), the solids was about 46% and the viscosity was 200 mPas. Right at the start, therefore, the product does not have the expected NCO content. The hydrophilization of uretdione-containing curing agents with tertiary amino alkyl amines does not produce a storage-stable aqueous dispersion.

Example c

Preparation of the Uretdione-Containing Curing Agent C

[0076] c1) Preparation of a Uretdione Prepolymer from IPDI (Not Inventive)

[0077] Uretdione based on IPD1 was prepared in accordance with the instructions from DE 10 2005 036654. 10 000 g (45.0 mol) of isophorone diisocyanate (Vestanat IPDI, Evonik) were admixed with 200 g (2%) of 4-dimethylaminopyridine (DMAP) as catalyst at room temperature under dry nitrogen and with stirring. After 24 hours the reaction mixture, which had an NCO content of 27.2%, corresponding to a degree of oligomerization of 26.5%, was free from volatile constituents, without prior addition of the catalyst poison using a thin-film evaporator at a temperature of 160° C. and a pressure of 0.3 mbar. This gave a highly viscous, pale yellow-coloured uretdione polyisocyanate having a free NCO group content of 16.8% and a monomeric IPDI content of 0.3%. No isocyanurate structures were found in the .sup.13C NMR spectrum.

[0078] c2) Preparation of the Curing Agent C (Inventive)

[0079] 1050.6 g of IPDI uretdione (from preparation procedure c1) were dissolved with 95.5 g of trimethylolpropane (Aldrich) and 0.23 g of DBTL (dibutyltin dilaurate, Aldrich) in 1.4 l of acetone. After an hour of stirring under reflux (free NCO content: 3.64%), 103 g of butanol were added and heating under reflux was continued for 1.5 hours more, after which the free NCO content was 1.49%. After cooling, 151 g of Vestamin A95 (sodium hydroxide-neutralized, amine-containing alkylsulphonate, 50% in water, Evonik) were added dropwise as internal emulsifier. After the end of addition, heating at reflux was repeated for 1.5 hours and the product was then cooled. The free NCO content was 0.1%, the free amine number 0.2%.

[0080] 650 g of this product were admixed with 604 g of demineralized water with vigorous stirring in a dispermat (3000 rpm). The acetone was removed on a rotary evaporator at 40 mbar and 60° C. and the product was subsequently filtered using a 50 μm filter. The latent NCO content was 4.5%, the solids about 27% and the viscosity 163 mPas.

Example d

Preparation of the Water-Based Resin D (Not Inventive)

[0081] 829.5 g of Vestanat H.sub.12MDI (dicyclohexylmethylene diisocyanate, Evonik) and 169.4 g of dimethylolpropionic acid (Aldrich) were dissolved with 0.5 g of DBTL (dibutyltin dilaurate, Aldrich) in 1.1 l of acetone. After 12 hours under reflux, the batch was cooled and 57 g of 1,4-butanediol (Aldrich), 1363 g of Oxyester T1136 (liquid hydroxyl polyester with OHN:

[0082] 112, Evonik), 169 g of trimethyloipropane (Aldrich) and 0.8 g of DBTL (dibutyltin dilaurate, Aldrich) were added. After a further 18 hours of stirring under reflux, the NCO content had dropped to 0.1%. The acid number was 27 and the OH number was 82, based in each case on the solids.

[0083] 250 g of this product were neutralized with 7.6 g of dimethylaminoethanol and admixed with 8.2 g of a 10% strength solution of adipic hydrazide (Aldrich) in water. Then 345 g of fully demineralized water were added in a dispermat with vigorous stirring (3000 rpm). At the end a drop of triethylamine was added as well. The acetone was thereupon removed on a rotary evaporator at 40 mbar and 60° C., after which the product was filtered using a 50 μm filter. The solids was about 35%, the viscosity 190 mPas.

Example e

Storage Stability and Reactivity

[0084] e1) Storage of the Curing Agent

[0085] The curing agent C (latent NCO content 4.9%) was stored at 50° C. for 8 weeks. The stored variant is hereinafter abbreviated to C(g). The curing agent C(g) showed a latent NCO content of 4.6%.

[0086] e2) Storage of the Mixtures: 70.4 g of C +29.6 g of D

TABLE-US-00001 Initial value 8 w @ 50° C. NCO content 1.2% 0.9% Curing 30 min 180° C. Erichsen cupping [mm] >10 >10 Cross-cut [0-5] 0 0 MEK resistance [DR] >100 >100

[0087] e3) Mixture with Stored Curing Agent 70.4 g of C(g)+29.6 g of D

[0088] After the mixing of the stored curing agent C with D, the mixture is not stored any more. Here, therefore, only the initial figure was measured.

TABLE-US-00002 Value with stored curing agent C NCO content 1.1% Curing 30 min 180° C. Erichsen cupping [mm] >10 Cross-cut [0-5] 0 MEK resistance [DR] >100

[0089] Even after 8 weeks at 50° C. the reactivity is sufficient, irrespective of whether only uretdione-containing curing agent (e3) or the mixture as a whole (e2) was stored.

Example f

Catalyzed Systems

[0090] Owing to the catalyst, catalyzed systems possess a higher reactivity than the uncatalyzed systems tested in the examples indicated above. As a consequence of this they are also not so storage-stable, but cure even at much lower temperatures, which is more favourable for certain applications. The storage stability was therefore measured after curing at 130° C. for 30 minutes.

f1) Comparative Example

[0091] 163.2 g of the curing agent C from example c2) was mixed with stirring with 15 g of Voranol CP 450 (hydroxyl-containing polyether, Dow), 3.75 g of Poly G 55-37 (hydroxyl-containing polyether, Arch Chemicals), 5 g of fully demineralized water, 2 g of Byk 011 (additive, Byk-Chemie). This was followed by additions of 0.4 g of Byk 348 and 0.1 g of Byk 333 (additives, Byk-Chemie).

f2) Inventive Example

[0092] The mixture f1) was admixed with 3.62 g of 50% strength tetraethylammonium benzoate solution (catalyst, Sachem) and with 4.8 g of Polypox 1E700 8W (activator, hydrophilized bisphenol A diepoxide, UPPC, Dow).

[0093] Curing (30 min 130° C.)

TABLE-US-00003 f1* f2 Pendulum hardness [s] 53 193 MEK resistance [DR] 1-2 >100 * f1 is comparative example

[0094] Storage of f2

TABLE-US-00004 Initial value 8 w at RT Pendulum hardness [s] 193 204 MEK resistance [DR] >100 >100

[0095] Even after 8 weeks at room temperature the reactivity is unchanged in the case of f2.

[0096] The measurement values were determined as follows:

[0097] Erichsen cupping to DIN 53 156

[0098] Ball impact to ASTM D 2794-93

[0099] Pendulum hardness to DIN 53 157

[0100] Cross-cut to DIN 53 151

[0101] MEK resistance:

[0102] The methyl ethyl ketone resistance test is carried out by rubbing with an absorbent cotton ball soaked in methyl ethyl ketone under a weight of 1 kg until the coat dissolves. In this rubbing procedure, double rubs (DR) are counted. A figure of >100 therefore means that over more than 100 double rubs there was still no dissolution of the coat observable.