LOW-VISCOUS ISOCYANATE PREPOLYMERS BLOCKED WITH PHENOLS OBTAINABLE FROM CASHEW NUTSHELL OIL, METHOD FOR THE PRODUCTION THEREOF AND USE THEREOF

Abstract

The present invention relates to novel solvent-free, blocked isocyanate prepolymers curing at room temperature, and to a method for the production thereof. Furthermore, the present invention relates to the use of said blocked isocyanate prepolymers for producing solvent-free reactive systems and to their use for producing adhesives, sealing compounds, casting compounds, molded parts or coatings, which are curing at room temperature.

Claims

1. A blocking agent comprising cardanol and cardol in a weight ratio of 92:8 to 100:0 and at least one compound of general formula 1 ##STR00005## in which R is C.sub.17H.sub.33-n, where n=0, 2 or 4, the compounds of formula 1 being present in a total amount of 0.1% to 3.0% by weight, based on the total weight of the blocking agent, and optionally at least one compound of general formula 2 ##STR00006## in which R is C.sub.15H.sub.31-n, where n=4 or 6, the compounds of formula 2, if present, being present in a total amount of not more than 1.8% by weight, based on the total weight of the blocking agent.

2. The blocking agent as claimed in claim 1, wherein the blocking agent has an OH value of from 184 to 206.

3. The blocking agent as claimed in claim 1 having a sulfur content of less than 15 mg/kg.

4. A process for producing blocked isocyanate prepolymers, comprising reacting at least one prepolymer bearing isocyanate groups obtained from the reaction of a composition comprising A. at least one aliphatic, cycloaliphatic, araliphatic and/or aromatic di- and/or polyisocyanate and B. at least one polyhydroxy compound with a blocking agent C as claimed in claim 1.

5. The process as claimed in claim 4, wherein component A comprises at least one di- and/or polyisocyanate based on naphthalene 1,5-diisocyanate, diisocyanatodiphenylmethane, poly(methylene phenyl isocyanate), diisocyanatomethylbenzene.

6. The process as claimed in claim 4, wherein component B comprises at least one polyhydroxy compound, having an OH functionality of 1.8 to 6.0 and a number-average molecular weight of from 1000 g/mol to 10 000 g/mol.

7. The process as claimed in claim 4, wherein component B comprises at least one polyether polyol that is a product of the addition of ethylene oxide and/or propylene oxide to propane-1,2-diol, propane-1,3-diol, glycerol, trimethylolpropane, ethylenediamine and/or pentaerythritol, or that is a polytetramethylene ether glycol obtained by polymerizing tetrahydrofuran.

8. The process as claimed in claim 1, wherein the at least one prepolymer bearing isocyanate groups obtained from the reaction of the composition comprising components A and B is, before reaction with component C, at least partially freed, by distillation, of unreacted di- and/or polyisocyanate of component A.

9. The process as claimed in claim 4, wherein the reaction of the composition comprising components A and B with component C takes place in the presence of a catalyst D1.

10. A blocked isocyanate prepolymer obtained by a process as claimed in claim 4.

11. The blocked isocyanate prepolymer as claimed in claim 10 having a viscosity, measured to DIN EN ISO 3219:1994-10 at 23° C., of less than 40 000 mPas.

12. A reactive system comprising a) at least one blocked isocyanate prepolymer as claimed in claim 10, b) at least one organic compound having at least 2 primary amino groups, c) optionally a compound having at least one oxirane group and an average oxirane functionality of >1, and d) optionally products from reactions of components a to c with one another, e) optionally catalysts, auxiliaries, and additives.

13. A method of producing a polyurethane plastic, comprising using the blocked isocyanate prepolymer as claimed in claim 10 to produce the polyurethane plastic.

14. A method of producing a coatings, in particular anti-corrosion coatings, adhesives, sealing compounds, potting compounds, primers or moldings, comprising using the reactive system of claim 12 to produce the coating.

15. A coating, in particular anti-corrosion coatings, adhesives, sealing compounds, potting compounds, primers and moldings comprising the blocked isocyanate prepolymer as claimed in claim 10.

16. A coated substrate, comprising a coating as claimed in claim 15 applied to a substrate.

Description

EXAMPLES

[0097] All percentages are based on weight unless otherwise noted.

[0098] The composition of the phenolic blocking agent was determined by gas chromatography. The measurement was carried out on an Agilent 6890 GC using an Optima 1 MS Accent column (30 m×0.25 mm×0.5 μm) and an MSD 5973 mass spectrometer detector. The carrier gas used was helium at a flow rate of 3 mL/min. The column temperature was 80° C. and was then increased at 6° C./min to 320° C. and held for 20 min on reaching the target temperature. The ionization energy for the GC/MS detection was 70 eV. Injection temperature was 270° C. with a split ratio of 20:1.

[0099] The sulfur content of the phenolic blocking agent was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). For this, the sample was first solubilized by microwave digestion. The optical spectroscopy was carried out using an ICP-OES instrument from Spectro (Arcos II) against certified standards. The principal detection line used for sulfur was the 180.731 nm line. To rule out possible interference, a second line (182.034 nm) was observed in parallel.

[0100] All viscosity measurements were recorded using a Physica MCR 51 rheometer from Anton Paar Germany GmbH (Germany) to DIN EN ISO 3219:1994-10 at a shear rate of 250 s.sup.−1.

[0101] NCO contents were determined titrimetrically to DIN EN ISO 11909:2007-05.

[0102] OH values were determined titrimetrically based on DIN 53240 part 2.

[0103] The tensile stress at break and elongation at break were determined based on DIN EN ISO 527-2:2012-06.

[0104] The further tear strength was determined to ISO 34-1:2016-06.

[0105] The Shore A and Shore D hardness tests were carried out to DIN 53505:2000-08.

[0106] Epilox T19-34/700 is a liquid epoxy resin based on bisphenol A and bisphenol F having an epoxy equivalent of 165-180 and a corresponding epoxy content of 23.9-26.1% (both values to DIN 16945:1989-03), obtainable from Overlack GmbH, Germany. Efka® SI 2008 is an additive for deaeration and defoaming, obtainable from BASF AG, Ludwigshafen, Germany, and TCD Diamine is octahydro-4,7-methano-1H-indenedimethylamine, Oxea, Marl, Germany

Example 1

[0107] a) 908.0 g of a polyether polyol having a functionality of 2 and an OH value of 56, produced by propoxylation of propylene glycol, was prepolymerized with 158.0 g of 2,4-diisocyanatotoluene/2,6-diisocyanatotoluene (ratio=80/20) for 3 hours at 90° C. until the theoretical NCO content of 3.6% was reached. To this was then added 324.0 g of phenolic blocking agent 1 (NX 2026, commercial product from Cardolite Specialty Chemicals Europe NV) having an OH value of 191 and containing cardanol and cardol in a weight ratio of 100:0, 1.7% of the compound of general formula (I), 0% of the compound of general formula (II) and a sulfur content of less than 10 ppm, catalyzed with 1.6 g of tin(II) octoate, and the mixture was stirred at 65° C. until the NCO content was below 0.4%.

[0108] 2.1 g of benzoyl chloride was then added and the mixture was stirred for a further 30 minutes.

[0109] The blocked isocyanate prepolymer thus obtained is characterized by the following characteristics:

TABLE-US-00001 Viscosity (23° C.) 27 500 mPas Content of free NCO 0.22%

[0110] b) 40 g of the blocked isocyanate prepolymer from a) was added with 40 g of Epilox T19-34/700, 0.8 g of oleic acid, 0.4 g of Efka® SI 2008, and 0.4 g of benzyl alcohol and stirred until a homogeneous mixture had formed. The TCD Diamine curing agent was then added and the mixture mixed again until homogeneous. The mixture was poured out in a layer approx. 1.5 mm thick. After a few hours a transparent,

[0111] highly elastic plastic material having the following mechanical characteristics was obtained: [0112] Tensile stress at break: 15.5 N/mm.sup.2 [0113] Elongation at break: 40.0% [0114] Further tear strength: 51.9 N/mm [0115] Shore A: 95 [0116] Shore D: 63

Examples 2 to 9

[0117] Further blocked isocyanate prepolymers were produced according to the process described in example 1 using various phenolic blocking agents. The resulting characteristics of the blocked isocyanate prepolymers and the mechanical characteristics resulting from the corresponding reactive systems are summarized in the table below.

TABLE-US-00002 TABLE 1 Overview of the examples 1 to 9 carried out: Example According to the invention Comparative 1 2 3 4 5 6 7 8 9 Blocking agent: NX-2026 (Cardolite Specialty x x x x Chemicals Europe N.V.) NX-2025 (Cardolite Specialty x x Chemicals Europe N.V.) GP-502 (Golden Cashew Products x Pvt. Ltd) Cardanol (Klaus F. Meyer GmbH) x x Cardanol:cardol 100:0 100:0 100:0 100:0 97:3 98:2 95:5 90:10 89:11 Compound 1 [%] 1.7 1.1 1.2 1.2 2.8 2.6 2.1 2.8 2.8 Compound 2 [%] 0.0 0.0 0.1 0.0 1.8 1.5 0.8 1.9 2.1 OH value 191 191 189 189 200 194 198 209 215 Sulfur [mg/kg] <12 <12 <12 <12 <12 <12 <12 18 31 Blocked isocyanate prepolymer: Viscosity [mPas] 27500 30300 26000 24100 25800 27300 33500 43000 52700 Content of free NCO [%] 0.22 0.29 0.27 0.25 0.27 0.35 0.24 0.33 0.27 Reactive system: Tensile stress at break [N/mm.sup.2] 15.5 20.2 20.7 18.3 16.8 19.7 19.7 20.6 21.9 Elongation at break [%] 40 23.2 33.5 26.8 19.4 29.5 22.8 25.1 29.6 Further tear strength [N/mm] 51.9 69.0 66.0 64.7 63.9 53.2 68.9 70.5 64.3 Shore A 95 93 93 98 97 95 92 94 89 Shore D 63 65 57 58 57 58 52 56 57