Patent Application
20080045641
Unless noted otherwise, all percentages are by weight.
Unless noted otherwise, all analytical measurements relate to temperatures of 23° C.
The reported viscosities were determined by means of rotational viscometry in accordance with DIN 53019 at 23° C. using a rotational viscometer from Anton Paar Germany GmbH, Ostfildern, DE.
NCO contents, unless expressly mentioned otherwise, were determined volumetrically in accordance with DIN-EN ISO-11 909.
The particle sizes reported were determined by means of laser correlation spectroscopy (instrument: Malvern Zetasizer 1000, Malvern Instr. Limited).
The solids contents were determined by heating of a weighed sample at 120° C. When constant weight was reached, the sample was weighed again to allow calculation of the solids content.
Monitoring for free NCO groups was carried out by means of IR spectroscopy (band at 2260 cm−1).
The adhesion was determined by means of DIN EN ISO 2409 crosshatch.
The König pendulum hardness was determined in accordance with DIN 53157.
Thermal yellowing was determined by the CIELAB method corresponding to DIN 6174.
Chemicals:
Desmodur® Z 4470 M/X:
Aliphatic polyisocyanate based on isophorone diisocyanate as a 70% strength solution in a mixture of methoxypropyl acetate and xylene (1/1), isocyanate content approximately 12%, Bayer MaterialScience AG, Leverkusen, DE.
Carbowax® 750:
Methoxypolyethylene glycol with an average molar mass of 750 g/mol from The Dow Chemical Company, Stade, Del.
Bayhydrol® A 145:
Water-dilutable, OH-functional polyacrylate dispersion, approximately 45% in water/solvent naphtha 100/2-butoxyethanol, neutralized with dimethylethanolamine, proportion approximately 45.6:4:4:1.4; OH content approximately 7.3%, Bayer MaterialScience AG, Leverkusen, DE
Bayhydrol® VP LS 2239:
Water-dilutable, hydroxyl-containing polyurethane dispersion, approximately 35% in water/NMP (60:5), OH content approximately 1.6%, Bayer MaterialScience AG, Leverkusen, DE
Bayhydur® VP LS 2240:
Hydrophilicized, blocked polyisocyanate crosslinker based on Desmodur® W, approximately 35% in water/MPA/xylene (56:4.5:4.5), NCO content (blocked) approximately 2.5%, Bayer MaterialScience AG, Leverkusen, DE
The other chemicals were purchased from the fine chemicals business of Sigma-Aldrich GmbH, Taufkirchen, DE.
Not inventive, preparation of a crosslinker dispersion blocked with butanone oxime
At 70° C. in a standard stirred apparatus with nitrogen blanketing, 359.0 g of Desmodur® Z 4470 M/X were admixed in succession with a solution of 4.7 g of dimethylolpropionic acid in 9.4 g of N-methylpyrrolidone (NMP), 37.5 g of Carboxwax® 750 and 3.39 g of neopentyl glycol. The batch was then heated to 80° C. and stirred until a constant NCO value of 8.02% (calculated: 8.27%) was reached. It was cooled to 70° C. Then 71.0 g of butanone oxime were added at a rate such that the temperature in the reaction vessel did not exceed 80° C. This was followed by further stirring at 80° C. until NCO groups were no longer detectable by IR spectroscopy, then by cooling to 70° C. and addition of 2.50 g of dimethylethanolamine. After further cooling to 60° C., the batch was dispersed with 570.8 g of deionized water at 25° C. It was conditioned at 50° C., stirred for 1 hour and left to cool to room temperature with stirring.
The properties of the resulting dispersion were as follows:
Not inventive, preparation of a crosslinker dispersion blocked with acetone oxime
At 70° C. in a standard stirred apparatus with nitrogen blanketing, 466.66 g of Desmodur® Z 4470 M/X were admixed with a solution of 13.1 g of dimethylolpropionic acid in 26.2 g of N-methylpyrrolidone (NMP). The batch was then heated to 80° C. and stirred until a constant NCO value of 9.12% (calculated: 9.17%) was reached. Then 48.75 g of Carbowax® 750 were added and the mixture was stirred at 75° C. until an NCO value of 7.84 (calculated: 7.87%) was reached. It was then cooled to 70° C. and thereafter 76.0 g of acetone oxime were added at a rate such that the temperature in the reaction vessel did not exceed 80° C. This was followed by further stirring at 80° C. until NCO groups were no longer detectable by IR spectroscopy, then by cooling to 70° C. and addition of 8.70 g of dimethylethanolamine. After further cooling to 60° C., the batch was dispersed with 1548 g of deionized water at 25° C. It was conditioned at 50° C., stirred for 1 hour and left to cool to room temperature with stirring.
The properties of the resulting dispersion were as follows:
Not inventive, preparation of a crosslinker dispersion blocked with caprolactam
At 70° C. in a standard stirred apparatus with nitrogen blanketing, 359.0 g of Desmodur® Z 4470 M/X were admixed in succession with a solution of 4.7 g of dimethylolpropionic acid in 9.4 g of N-methylpyrrolidone (NMP), 37.5 g of Carboxwax® 750 and 3.39 g of neopentyl glycol. The batch was then heated to 80° C. and stirred until a constant NCO value of 8.02% (calculated: 8.27%) was reached. It was cooled to 70° C. and then 92.3 g of ε-caprolactam were added. This was followed by further stirring at 100° C. until NCO groups were no longer detectable by IR spectroscopy, then by cooling to 70° C. and addition of 2.50 g of dimethylethanolamine. After further cooling to 60° C., the batch was dispersed with 770.53 g of deionized water at 25° C. It was conditioned at 50° C., stirred for 1 hour and left to cool to room temperature with stirring.
The properties of the resulting dispersion were as follows:
Inventive, preparation of a crosslinker dispersion blocked mixedly
At 70° C. in a standard stirred apparatus with nitrogen blanketing, 359.0 g of Desmodur® Z 4470 M/X were admixed in succession with a solution of 4.7 g of dimethylolpropionic acid in 9.4 g of N-methylpyrrolidone (NMP), 37.5 g of Carbowax® 750 and 3.39 g of neopentyl glycol. The batch was then heated to 80° C. and stirred until a constant NCO value of 8.24% (calculated: 8.27%) was reached. It was cooled to 70° C. and then 63.4 g of ε-caprolactam were added. Stirring was continued at 100° C. until a constant NCO value of 1.75% (calculated: 1.76%) was reached, followed by cooling to 75° C. and addition of 17.4 g of butanone oxime. Stirring was continued until NCO groups were no longer detectable by IR spectroscopy, then by cooling to 70° C. and addition of 2.50 g of dimethylethanolamine. After further cooling to 60° C., the batch was dispersed with 582 g of deionized water at 25° C. It was conditioned at 50° C., stirred for 1 hour and left to cool to room temperature with stirring.
The properties of the resulting dispersion were as follows:
Inventive, preparation of a crosslinker dispersion blocked mixedly
The procedure described in Example 4 was repeated but using 74.7 g of ε-caprolactam and 8.7 g of butanone oxime as blocking agents.
The properties of the resulting dispersion were as follows:
Inventive, preparation of a crosslinker dispersion blocked mixedly
The procedure described in Example 4 was repeated but using 52.1 g of ε-caprolactam and 26.1 g of butanone oxime as blocking agents.
The properties of the resulting dispersion were as follows:
Inventive, preparation of a crosslinker dispersion blocked mixedly
The procedure described in Example 4 was repeated but using 19.2 g of 3,5-dimethylpyrazole instead of butanone oxime as blocking agent.
The properties of the resulting dispersion were as follows:
Inventive, preparation of a crosslinker dispersion blocked mixedly
The procedure described in Example 4 was repeated but using 55.4 g of δ-valerolactam (instead of ε-caprolactam) and 17.4 g of butanone oxime as blocking agents.
The properties of the resulting dispersion were as follows:
For determination of the performance data, the blended coating materials of Examples 9 to 18 were formulated in accordance with Table 1, applied and cured. The performance data are contained in Table 2.
Table 1
Clearcoat materials 9 to 18 were prepared by mixing the blocked polyisocyanates with the polyol component in the ratio of their equivalent weights (BNCO:OH 1:1). To improve their adhesion, the coating materials include commercially customary additives (1.1%, calculated on the basis of solid binder).
The above clearcoat materials were applied to glass plates 3 mm thick, from Schlier & Hennes, using a coating knife from Deka (No. 120) and were baked in a forced-air oven at 170° C. for 30 minutes. This gave dry film thicknesses of approximately 25-30 μm.
Table 2:
The following technical properties were found:
a)Solvent resistance*
b)NaOH resistance*
c)Initial physical
d)Film hazing
a)Solvent resistance*
b)NaOH resistance*
c)Initial physical
d)Film hazing
Descriptions of Test Methods
a) Solvent Resistance
b) Sodium Hydroxide Resistance
c) Initial Physical Drying
d) Film Hazing
Requirements with Regard to the Individual Technical Properties:
Evaluation of Results:
With the non-inventive self-crosslinking baking systems it is not possible using the prior-art crosslinker dispersions to achieve a sufficient profile of properties in respect of initial physical drying, low thermal yellowing and absence of haze from the films (Examples 9-12). Even the blend of two non-inventive crosslinker dispersions shown in Example 13 (Example 1: oxime-blocked, Example 3: lactam-blocked) in the preparation of a self-crosslinking dispersion did not result in acceptable coatings.
Only when the inventive crosslinker dispersions were used, reacted with a lactam and with a further blocking agent (Examples 14-18), is it possible to achieve an optimum profile of the critical properties. The other film properties as well, such as the hardness of the coating film, solvent resistance and sodium hydroxide resistance, correspond to the requirements imposed on a high-value coating system.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102006038941.7 | Aug 2006 | DE | national |
