LOW-SOLVENT COATING SYSTEMS FOR TEXTILES

Abstract

Provided is a coating composition for the elastic coating of textile materials, comprising at least one blocked, isocyanate-terminated prepolymer (component A), the isocyanate-terminated prepolymer A) being prepared from a polyol component a) IN and an isocyanate component b), and the terminal isocyanate groups being blocked with dialkyl malonate and/or 3,5-dimethylpyrazole, and the isocyanate component b) containing 70 wt % of at least one aliphatic polyisocyanate and 30 wt % of at least one N aromatic polyisocyanate, based on the total weight of component b), at least one polyamine (component B) and 30 wt %, based on the total mass of the coating composition, of at least one organic solvent. Further provided are a method for coating substrates with the coating composition, and also the substrate obtainable in such a method, and, further, the use of the coating composition for producing elastic coatings or elastic films.

Claims

1.-15. (canceled)

16. A coating composition for the elastic coating of textile materials, comprising at least one blocked, isocyanate-terminated prepolymer (component A), the isocyanate-terminated prepolymer A) being prepared from a polyol component a) and an isocyanate component b), and the terminal isocyanate groups being blocked with dialkyl malonate and/or 3,5-dimethylpyrazole, and the isocyanate component b) containing 70 wt % of at least one aliphatic polyisocyanate and 30 wt % of at least one aromatic polyisocyanate, based on the total weight of component b), at least one polyamine (component B) and 30 wt %, based on the total mass of the coating composition, of at least one organic solvent.

17. The coating composition according to claim 16, wherein the terminal isocyanate groups of the isocyanate-terminated prepolymer A) come exclusively from the aliphatic polyisocyanates.

18. The coating composition according to claim 16, wherein the coating composition comprises 10 wt %, based on the total mass of coating composition, of at least one organic solvent.

19. The coating composition according to claim 16, wherein the terminal isocyanate groups of the prepolymer A) are blocked with dialkyl malonate.

20. The coating composition according to claim 16, wherein component B) comprises at least one diamine or consists exclusively of one or more diamines.

21. The coating composition according to claim 16, wherein component b) comprises 80 wt % of at least one aliphatic polyisocyanate and 20 wt % of at least one aromatic polyisocyanate, based on the total weight of component b).

22. The coating composition according to claim 16, wherein the ratio of the isocyanate groups in component b) to hydroxyl groups in component a) is 1.5:1.

23. The coating composition according to claim 16, wherein the polyol component a) comprises at least one polyol having a number-average molecular weight Mn of 2500 to 7000 g/mol, determined by means of GPC in tetrahydrofuran at 23 C., and an average functionality of hydroxyl groups of 1.8 to 3.5.

24. The coating composition according to claim 16, wherein the polyol component a) comprises or consists of a mixture comprising at least one polyol having a number-average molecular weight Mn of 2500 to 7000 g/mol, determined by means of GPC in tetrahydrofuran at 23 C., and having an average OH functionality of 1.8 to 3.5, and at least one polyol having a number-average molecular weight Mn of 300 to 1000 g/mol, determined by means of GPC in tetrahydrofuran at 23 C., and having an average OH functionality of 1.8 to 3.5.

25. The coating composition according to claim 16, wherein component b) has an average NCO functionality of 1.5 to 4.0.

26. The coating composition according to claim 16, wherein the weight ratio of component A) to component B) is 10:4.

27. A method for coating substrates, comprising applying the coating composition according to claim 16 to a substrate and crosslinking at 90 to 200 C.

28. The method according to claim 27, wherein the substrate is a textile material.

29. Coated substrate obtained by a method according to claim 27.

30. A method comprising utilizing the coating composition according to claim 16 for producing elastic coatings or elastic films.

Description

EXPERIMENTAL PART

Methods:

[0085] Data given in percent is based on mass, if not explicitly explained in a different way.

[0086] The concentration of isocyanate groups (NCO) have been determined by volumetric titration according to DIN EN ISO 11909.

[0087] All viscosity measurements have been carried out with a rheometer from Anton Paar, Germany (Physica MCR 301) according to DIN EN ISO 3219.

[0088] Viscosity 1: Viscosity of the prepolymer A) after having settled for at least 12 h at room temperature

[0089] Viscosity 2: Viscosity directly after addition of diamine

[0090] Viscosity 3: Viscosity 7 h after addition of diamine

[0091] The difference between viscosity 2 and viscosity 3 shows the pot life of the composition at room temperature.

[0092] The measurements of the 100% modulus, the elongation at break and the tensile strength are carried out according to DIN 53504.

Swelling in Water:

[0093] Free films are swollen in water over 24 hours at room temperature to determine the swelling rate. The change of the volume of the film after swelling is determined with a ruler. A film with a thickness of 0.1-0.2 mm is cut into a sample of 5050 mm and stored for 2 hours in water. The calculation of the swelling is carried out under the assumption that the change is proportional in all dimensions.

[0094] The number-average molecular weight Mn is determined by gel permeation chromatography (GPC) in tetrahydrofuran at 23 C. The procedure for this is in accordance with DIN 55672-1: Gel permeation chromatography, Part 1Tetrahydrofuran as eluent (SECurity GPC system from PSS Polymer Service, flow rate 1.0 ml/min; columns: 2PSS SDV linear M, 8300 mm, 5 m; RID detector). Calibration takes place using polystyrene samples of known molar mass. The number-average molecular weight is calculated with software assistance. Baseline points and evaluation limits are specified in accordance with DIN 55672 Part 1.

Description of Raw Materials:

[0095] All of the following raw materials were supplied by Covestro Deutschland AG

Polyol 1: Trifunctional polyether based on propylene oxide and ethylene oxide started with glycerol, number average molecular weight M.sub.n=6000 g/mol
Polyol 2: Trifunctional polyether based on propylene oxide and ethylene oxide started with glycerol, number average molecular weight M.sub.n=4800 g/mol
Polyol 3: Polypropylene oxide ether started with bisphenol A, number average molecular weight M.sub.n=560 g/mol
Polyol 4: Trifunctional polyether based on propylene oxide started with trimethylol propane, number average molecular weight M.sub.n=437 g/mol

Polyol 5:

[0096] Polyester polyol based on adipic acid, trimethylol propane, 1,6-hexane diol, iso-phthalic acid and phthalic acid, Mn=1200 g/mol

Polyisocyanate 1:

[0097] Hexamethylene-1,6-diisocyanate (HDI)

Polyisocyanate 2:

[0098] Isophorone diisocyanate (IPDI)

Polyisocyanate 3:

[0099] 4,4-Methylene-bis-(phenylisocyanate), pure 4,4-isomer (MDI)
Polyisocyanate 4: Polyisocyanate based on hexamethylene diisocyanate, concentration of free NCO-groups approximately 20%, Mn=655 g/mol
Polyisocyanate 5: Toluylene diisocyanate, isomeric mixture (20% 2,6-toluylene diisocyanate and 80% 2,4-toluylene diisocyanate)
Diamine 1: 4,4-Diamino-3,3-dimethylene dicyclohexylmethane (Laromin C 260, BASF, Germany)

[0100] All further raw materials were supplied by Sigma Aldrich and used without further purification if not mentioned otherwise.

General Procedure:

[0101] The polyol mixture is stirred at 100 C. for 1 hour at approximately 10 mbar to remove excess of water. If MDI is a part of the prepolymer the calculated amount of MDI is added at 65 C. and reacted until the NCO has fallen to zero. Afterwards, a mixture containing hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI) is added within 1-2 minutes at 90 C. and stirred until the theoretical NCO value is reached. If the experiment is carried out without MDI the HDI/IPDI-mixture is directly added to the polyol mixture at 90 C. and reacted until the theoretical NCO value has been reached. The prepolymer mixture is cooled to 60-65 C. If the reaction mixture contains the Polyisocyanate 4 this material is added to the NCO-prepolymer at this point.

[0102] The reaction of the free NCO groups with the blocking agent is carried out according to the two procedures which follow:

[0103] a) Blocking with Diethyl Malonate

[0104] At 60-65 C. a mixture of diethylmalonate and sodium methoxide solution (30% (w/w) in methanol) is added to the reaction mixture and stirred at this temperature until the NCO-value has dropped to zero. If the viscosity of the reaction mixtures is increasing significantly the given amount of solvent (methoxypropyl acetate (MPA)) is added during this reaction step. If the viscosity is not increasing very fast the amount of MPA is added after the reaction of the diethylmalonate with the isocyanate groups is complete (according to NCO titration).

[0105] In the final step di-n-butyl phosphate is added to neutralize the methoxide base.

[0106] b) Blocking with 3,5-Dimethyl Pyrazole

[0107] The reaction mixture is adjusted to 65 C. At this temperature 3,5-dimethyl pyrazole is added and reacted. Depending on the increase of the viscosity methoxypropyl acetate is added during the reaction to the mixture and stirred until the reaction with the isocyanate groups is complete (according to NCO titration).

[0108] Table 1 shows Examples 1 to 9 prepared according to procedures a) or b) and their compositions.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Amount Amount Amount Amount Amount Amount Amount Amount Amount Material (g) (g) (g) (g) (g) (g) (g) (g) (g) Polyol 1 765.0 765.0 612.2 0 546.5 765.0 765.0 0 0 Polyol 2 0 0 0 612.2 0 0 0 647.9 647.9 Polyol 3 47.9 47.9 47.9 47.9 34.2 47.0 47.9 61.7 61.7 Polyol 4 0 0 0 46.1 0 0 0 44.0 44.0 HDI 46.1 46.1 46.1 46.1 48.2 41.5 41.5 75.1 82.6 IPDI 64.8 64.8 64.8 64.8 67.8 64.8 64.8 105.9 116.4 MDI 0 0 0 0 0 7.2 7.2 0 0 Polyisocyan. 4 0 0 85.0 0 78.0 0 102.0 0 0 Diethyl 93.1 0 166.5 0 183.2 91.8 169.4 148.0 7.0 malonate Sodium 3.3 0 6.5 0 6.0 3.0 6.0 5.0 7.0 methoxide (30% in methanol) Methoxypropyl 112.0 52.0 55.0 44.0 55.0 55.0 65.0 58.0 60.0 acetate (9.9) (5.1) (5.1) (4.8) (5.4) (5.1) (5.1) (5.1) (5.0) (Content of solvent in wt. %) Di-n-butyl 1.5 0 3.2 0 3.0 1.5 3.0 2.5 3.5 phosphate 3,5-Dimethyl 0 50.7 0 55.8 0 0 0 0 0 pyrazole Viscosity 1 25.200 24.500 50.000 25.000 32.900 78.000 105.000 105.000 90.000 (mPas)
Evaluation of Prepolymer: Film Formation by Crosslinking with Diamine

[0109] The prepolymer (example 1 to example 9) is mixed with a stoichiometric amount of Diamine 1 and 3.0% of Additive for polyurethane-based synthetic leather (BYK Chemie GmbH, Germany) and 0.5% of Acronal L 700 (Acrylic resin in 50% ethyl acetate, plasticizer for coatings applications, BASF, Germany). The amount of Diamine 1 is calculated in a way that the mixture contains the same amount of amine and ester equivalents. The mixture is stirred for 3 minutes under vacuum. Then a film is generated on Bor supermatt paper with a blade (300 m wet). The film is dried according to the temperature programme which follows:

1 min 90 C., temperature increase from 90 C. to 130 C. within 1 minute
1 min 130 C., temperature increase from 130 C. to 160 C. within 2 minutes

5 min 160 C.

[0110] (curing carried out in a circulating air oven)

[0111] The viscosities and film properties were determined according to the above mentioned methods.

[0112] Table 2 summarizes the results of the measurements for examples 1 to 9 (corresponding to prepolymers 1 to 9).

[0113] The results of table 2 show that elastic films with a wide range of mechanical strengths and elastic properties can be designed with the technology of this invention. The pot life of the formulation allows the processing throughout a working day.

TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Viscosity 2 15.200 36.700 56.000 16.400 14.400 81.000 53.500 62.400 42.000 Start (mPas) Viscosity 3 30.500 61.400 71.400 20.000 32.900 106.000 80.000 108.000 71.000 after 7 hrs (mPas) 100% 0.68 0.40 0.82 1.16 2.80 0.70 2.03 1.98 3.03 Modulus (MPa) Tensile 2.66 2.4 3.56 10.92 3.6 5.85 8.66 6.7 12.08 Strength (MPa) Elongation 537 1040 992 1463 256 1068 488 719 707 at break (%) Swelling in 48 Film 26 19 19 33 19 13 0 Water (%) destroyed

Comparative Examples

[0114] Aliphatic Prepolymers Malonate-Blocked Crosslinked with Polyol 5

[0115] Crosslinking of selected malonate-blocked prepolymers is carried out with Polyol 5.

Procedure for Film Preparation:

[0116] The prepolymers from examples 3 (comparative example 1) or 7 (comparative example 2) and the Polyol 5 were mixed in a speedmixer at 3500 rpm for 1 minute. The amount of Polyol 5 is calculated in a way that the mixture contains the same amount of hydroxyl and ester equivalents.

[0117] Then a film is generated on polyethylene-coated paper with a blade (500 m wet). The film is dried according to the temperature programme which follows:

30 min 70 C.

10 min 90 C.

10 min 120 C.

10 min 150 C.

[0118] All obtained films are very soft and tacky. A sample for measuring the tear strength could not be prepared because the films were destroyed during delamination from the paper. Hence a diamine crosslinker is needed to generate films with a good mechanical stability.

Aromatic Prepolymer Malonate-Blocked: Determination of Pot Life in Combination with Diamine 1

Synthesis:

[0119] A polyol mixture out of 774.0 g polyol 1 and 48.4 g polyol 3 was stirred at 100 C. for 1 hour at approximately 10 mbar to remove excess of water. A mixture consisting of 69.4 g polyisocyanate 3 and 50.6 g polyisocyanate 5 is added to the mixture at 65 C. and stirred at this temperature until the theoretical NCO value has been reached. 60 g of this prepolymer was used for the blocking step with diethyl malonate.

[0120] A mixture of 60 g of the prepolymer prepared above and 7.0 g methoxypropyl acetate (MPA) was heated to 60 C. A mixture of 5.85 g diethylmalonate and 0.20 g sodium methoxide solution (30% (w/w) in methanol) is added to the reaction mixture and stirred at 60 C. until the NCO-value has dropped to zero.

[0121] In the final step 0.1 g di-n-butyl phosphate is added to neutralize the methoxide base.

Determination of Pot Life:

[0122] 15 g of the malonate-blocked prepolymer prepared above and 1.75 g of Diamine 1 were mixed in a speedmixer for 1 min at 3500 rpm. The amount of Diamine 1 is calculated in a way that the mixture contains the same amount of amine and ester equivalents. The starting viscosity of the prepolymer was 136.000 mPas, the addition of the low-viscous crosslinker amine should reduce the viscosity of the mixture. However, 2 minutes after preparation of the mixture the viscosity of this mixture increased to 875.000 mPas. After 30 min the viscosity increased to 1,100,000 mPas. The reaction of the two components at room temperature is very fast and hence the pot life of the composition is not sufficient for a technical application.