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Polyurethane top coats for commercial vehicles – extremely resistant in every climate

Outstanding mechanical properties in extreme weather conditions have made two-component polyurethane systems the top coats of choice for commercial vehicles. They are resistant against harsh weather conditions, dust, dirt, aggressive chemicals and solvents. Their optical appearance remains as good as new even after years. Polyurethane systems show their performance in demanding applications like aircraft coating, where an extreme UV- and temperature resistance are essential.

For the production of high solid systems and waterborne coatings Bayer MaterialScience provides polyurethane raw materials like polyol dispersions, low-viscosity and hydrophilized polyisocyanates for waterborne systems, polyester polyols as well as polyisocyanate hardeners.

Some polyurethane raw materials for commercial vehicle top coats:

Waterborne two-component systems

Polyacrylate / Polyurethane dispersions:

	Type	Solids in %	% OH on solids	Viscosity mPas at 23°C	Characteristics
Bayhydrol® A 145	Polyacrylate dispersion	45	3.3	950	Good pigment wetting properties, high shear stability for high-gloss topcoats with good adhesion and resistance to solvents and water
Bayhydrol® A 2470	Polyacrylate dispersion	45	3.9	2000	For clear- and top coats with good resistance properties
Bayhydrol® A 2601	Polyacrylate dispersion	44.5	3.9	2000	For clearcoats and topcoats with good resistance properties and very rapid drying without adverse effect on pot life
Bayhydrol® A 2695	Polyacrylate dispersion	45	5.0	2500	For clear- and top coats with very good resistance properties (anti graffiti properties)
Bayhydrol® A XP 2770	Polyacrylate dispersion	45	3.9	2000	Low-VOC variant of Bayhydrol A 2470 without flash point
Bayhydrol® A 2809 XP	Polyacrylate dispersion	47	3.3	1300	low VOC, high gloss, good chemical resistance, good adhesion on different substrates
Bayhydrol® UH XP 2592	Polyester polyacrylate dispersion	45	2.1	300	For waterborne air- and force-drying, high-gloss coatings offering a high degree of corrosion protection
Bayhydrol® U XP 2750	Polyurethane dispersion	43	3.6	1000	For clearcoats and topcoats with outstanding weathering resistance properties
Bayhydrol® U XP 2766	Polyurethane dispersion	40	4.0	3000	For clearcoats and topcoats with very high gloss and high hardness, ideal for mixing with other dispersions to increase gloss, free of co-solvent

Polyisocyanate crosslinkers for waterbased dispersions:

	Type	Solids in %	% NCO on solids	Viscosity mPas at 23°C	Characteristics
Bayhydur® 3100	HDI polyisocyanate	100	17.4	2800	Hardener component, also as an additive for high-grade waterborne coatings
Bayhydur® 304	HDI polyisocyanate	100	18.2	4000	Hardener component, also as an additive for high-grade waterborne coatings
Bayhydur® XP 2655	HDI polyisocyanate	100	21.2	3500	As a hardener component for two-component polyurethane systems that can be very easily incorporated and as an additive for high-quality waterborne coating systems
Bayhydur® XP 2487/1	HDI polyisocyanate	100	20.6	5400	As a hardener component for two-component polyurethane systems that can be easily incorporated and as an additive for high-quality waterborne coating systems with good chemical resistance
Bayhydur® XP 2759	IPDI polyisocyanate	70	11.0	6500	Hydrophilic crosslinking partner in combination with HDI grades for improving drying behavior
Desmodur® N 3600	HDI trimer	100	23.0	1200	For waterborne two-component and high-solids coatings gloss, chemical and weathering resistance, good lightfastness and high mechanical stability
Desmodur® N 3800	HDI trimer	100	11.0	6000	Mixed with Bayhydur® and Desmodur® grades to flexibilize waterborne two-component polyurethane systems
Desmodur® N 3900	HDI trimer	100	23.5	730	For waterborne two-component and high-solids coatings that can be easily incorporated, with high gloss, chemical and weathering resistance, good lightfastness and high mechanical stability

Some starting formulations:

STIT 2421/1	Waterborne 2K PUR topcoat, glossy (Bayhydrol® A 2695 / Bayhydrol® U XP 2766 / Desmodur® N 3900)

STIT 2539	Waterborne 2K PUR clearcoat, selfhealing (Bayhydrol® U XP 2750 / Bayhydrol® A 2601 / Bayhydur® XP 2655

STIT 2159/2	Waterborne 2K PUR topcoat, glossy (Bayhydrol® A 2470 / Desmodur® N 3900)

STIT 2283/2	Waterborne 2K PUR topcoat, white (Bayhydrol® A XP 2770 / Bayhydur® 304)

STIT 2405/1	Waterborne 2K PUR topcoat, glossy (Bayhydrol® A 2470 / Bayhydur® 304)

STIT 2422/1	Waterborne 2K PUR topcoat, glossy (Bayhydrol® A 2470 / Bayhydur® XP 2487/1)

STIT 2625/2	Waterborne 2K PUR topcoat, glossy (Bayhydrol® U XP 2766 / Bayhydur® 304 / Bayhydur® XP 2759)

Solventborne two-component-systems

	Type	Solids in %	% NCO or OH on solids	Viscosity mPas at 23°C	Characteristics
Desmophen® 650 MPA	Polyester polyol	65	8.2 OH	20 000	In combination with Desmodur® N 75 MPA for coatings with outstanding UV resistance, gloss, weather resistance, good chemical and abrasion resistance
Desmophen® 651 MPA	Polyester polyol	65	8.5 OH	14 500	In combination with Desmodur® N 75 MPA or N 3390 BA for coatings with outstanding UV resistance, gloss, weather resistance, good chemical and abrasion resistance
Desmophen® 670	Polyester polyol	100	4.3 OH	2200	In combination with Desmodur® N 75 MPA or N 3390 BA for highly weather resistant films, which remain elastic at low temperatures
Desmophen® 680 X	Polyester polyol	60	3.0 OH	2750	High gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3300	HDI-trimer	100	21.8 NCO	3000	For high solid coatings, high gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3400	HDI-trimer	100	21.8 NCO	150	For high solid coatings, high gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3600	HDI-trimer	100	23.0 NCO	1200	For high solid coatings, high gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3800	HDI-trimer	100	11.0 NCO	6000	Hardener component for weather resistant coating systems, for High Solids coatings
Desmodur® N 3390 BA/SN	HDI-isocyanurate	90	21.8 NCO	550	High gloss, high chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® Z 4470 BA	IPDI-trimer	70	17.0 NCO	600	Hard, high gloss, chemical resistance and weather resistance, lightfast, good mechanical resistance, in combination with Desmodur® N grades
Desmodur® N 75 MPA	HDI-biuret	75	22.0 NCO	250	Good chemical resistance and weather resistance, very high gloss and outstanding mechanical properties

Suitable combination partners are polyols like hydroxy polyacrylates.

Some starting formulations

RR 4572	Two-component polyurethane top coat (Desmodur® N 75 / Desmophen® 650/ Desmophen® 651)

RR 4505	Two-component polyurethane clear coat (Desmodur® N 75 / Desmophen® 650/ Desmophen® 651)

Solvent-reduced "Very High Solid" systems with polyaspartics

The lowest possible solvent content, or rather a maximum solid content can be achieved with a combination of reactive thinners and low-viscosity polyisocyanates (polyaspartates) plus a polyol. These "Very high solid" systems contain less than 250g/l of solvent.

	Type (Solids)	Reactivity	Equivalent Weight	Viscosity mPas at 23°C	Characteristics
Desmophen® NH 1521	Polyaspartate (90%)	+	356	150	For top coats and clear coats, in combination with Desmophen NH 1420
Desmophen® NH 1520	Polyaspartate (100%)	+	290	1600 (bei 25°)	For top coats and clear coats, in combination with Desmophen NH 1420
Desmophen® NH 1420	Polyaspartate (100%)	++	279	1500 (bei 15°)	For clear coats and fillers, in combination with Desmophen NH 1521
Desmophen® NH 1220	Polyaspartate (100%)	++++	230	< 100 (bei 25°)	For putties and elastomers, in combination with Desmophen NH 1420

+ low reactivity ++++ high reactivity

Starting formulations for Very High Solid Systeme are available on Polyaspartics or by request.

For more in-depth information have a look at these brochures:

Dispersions Products MS00063641	PIC / Prepo Products MS00063645	Polyol Products MS 00063643
. 2K WB Toolbox MS00063580	. .Bayhydrol A MS00063642	. Polyaspartics MS00051641