Home > Applications > Industrial Coatings

Polyurethane top coats for industrial coatings- for long lasting high quality surfaces

One- and two-component polyurethane coating systems are particularly suitable for top coats on high-quality industrial goods. They feature great physical and optical properties and have an excellent durability. Depending on their final application they can be classified in these categories:

Industrial Topcoats
Topcoats	Single coat finishes Direct-to-metal (DTM)	Clearcoats	Structural and special effect coats
Pigmented one- or two-component topcoats in multi-layer applications - based on solvents, waterbased or as high solid systems	Must have the combined properties of a primer and top coat - Must have very high performance regarding humidity barrier, corrosion protection and weather resistance combined with good adhesive properties ==> Polyaspartics	Unpigmented top coats - with good transparency and resistance, must be non-yellowing	Metallic coatings with special effects or surface structures
As one-component (air-drying or stoving) or two-component system - solvent or water based, high solid or UV-curing system

The selection of the coating system depends among other considerations on the size and geometry of the parts to be coated. Generally, air-drying one-component or two-component polyurethane coatings are used when the parts are too big or too complex for one-component stoving coatings. Waterborne and high solids are the choice, when both, a high quality of the coating and the reduction of solvents are important considerations. Production facilities and parts permitting, UV curing top coats can be an alternative. Since UV curing takes place very quickly, the parts can immediately be used for subsequent processing.

For highly efficient coating processes the polyaspartic acids (Polyaspartics) take a very important role. With polyaspartics films can be applied in high thickness, in one pass and bubble-free, replacing several coating layers compared to classical coating systems. Even 1-coat applications are possible with these products (direct-to-metal, DTM). Their high solid character and the rapid film building are additional advantages. Find out more in the section Corrosion protection - Polyaspartics and in the Technology section under High Solid Systems.

New developments in the field of waterborne two-component polyurethane dispersions enable the formulation of low-VOC systems that are well within the VOC limits set by current legislation and offer users maximum freedom in the choice and quantity of co-solvent used. The most common raw materials to be used in these topcoats are polyacrylate and polyurethane dispersions with 2,5 - 5 % OH-content. A higher OH-content of up to 5% (in some cases even more) results in a considerably higher crosslinking density, allowing coating films with extremely good chemical resistance (like for anti-graffiti coatings, ect.). With rapidly drying coating systems based on polyacrylates, particularly with the "internally activated" dispersions, the efficiency of the coating process can be significantly increased without any adverse effects on processing time. Energy costs can be saved (lower oven temperatures compared to standard systems), thereby improving the CO2 balance. Also, in numerous applications it has been proven, that waterbased two-component polyurethane topcoats show the same characteristics as those of comparable solventborne polyurethane coatings, e.g. an excellent early water resistance and solvent resistance, as well as the desired optical properties.

In some applications there is a trend towards single-coat finishes or "Direct-to-metal", primarily for cost reasons (e.g. time for the coating process). These coatings combine the corrosion protection properties of a primer with the surface properties of a classic topcoat. In these waterbased 2K polyurethane single coat finishes Bayhydrol® A polyacrylate dispersions have been shown to be particularly advantageous.

Examples from a wide range of products suitable for industrial coatings

Polyurethanes for one- and two-component waterborne systems

Waterbased dispersions:

	Type	Solids in %	% OH on solids	Viscosity mPas at 23°C	Characteristics
Polyacrylate dispersions
Bayhydrol® A 145	Polyacrylate dispersion	45	3.3	950	Good pigment wetting, high shear resistance, for high-gloss topcoats with good adhesion and good resistance against solvents and water
Bayhydrol® A XP 2469	Polyacrylate dispersion	45	2.5	1500	for cost efficient 2K polyurethane industrial coatings with a good property profile, high gloss
Bayhydrol® A 2470	Polyacrylate dispersion	45	3.9	2000	For clear- and top coats with good resistance properties
Bayhydrol® A XP 2770	Polyacrylate dispersion	44,5	3.9	2000	Low VOC variant of Bayhydrol A 2470 without flash point
Bayhydrol® A 2601	Polyacrylate dispersion	45	3.9	2000	For clear- and top coats with good resistance properties and very fast drying
Bayhydrol® A 2695	Polyacrylate dispersion	42	5.0	2500	For clear- and top coats with very good resistance properties (anti-graffiti properties)
Polyurethane dispersions
Bayhydrol® U XP 2750	Polyurethan dispersion	43	3.6	1000	Hydrophilic crosslinker in combination with HDI-based greades to enhance drying properties
Bayhydrol® U XP 2766	Polyurethan dispersion	44,5	3.9	2000	For clearcoats and topcoats with very high gloss and hardness, ideal for mixing with other dispersions to increase gloss, free of co-solvent
Polyester polyurethane dispersions
Bayhydrol® UH 245	Polyester polyurethane dispersion	45	2.3	850	For air and force drying high gloss coatings with good corrosion protection properties
Bayhydrol® UH XP 2592	Polyester polyurethan dispersion	45	2.1	300	For air and force-drying high gloss coatings with good corrosion protection

Polyisocyanate crosslinkers for waterbased:

	Type	Solids in %	% NCO on solids	Viscosity mPas at 23°C	Characteristics
Bayhydur® 3100	HDI polyisocyanate	100	17.4	2800	Hardener also as additive for high-quality waterborne coatings
Bayhydur® 304	HDI polyisocyanate	100	17.4	2800	Hardener also as additive for high-quality 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
Bayhydur® XP 2759	IPDI polyisocyanate	70	15.7	6500	Hydrophilic crosslinking partner in combination with HDI grades for improving drying behaviorl
Desmodur® N 3600	HDI trimer	100	23.0	1200	For high solid coatings, high gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3900	HDI trimer	100	23.5	730	Forhigh-solids coatings, high gloss, chemical and weather resistance, good lichtfastness 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

Polyurethanes for one-component waterborne stoving systems

Dispersions:

	Type	Solids in %	% OH on solids	Viscosity mPas at 23°C	Characteristics
Polyester dispersions
Bayhydrol® E 356	Oil free saturated polyester	57	1.5	9500	In combination with melamine resins for very elastic systems, for dip and spray coating
Polyacrylate dispersions
Bayhydrol® A 145	Polyacrylate Dispersion	45	3.3	950	Good pigment wetting and high shear stability, for high-gloss topcoats with good adhesion and resistance against water and solvents
Bayhydrol® A 2227/1	Polyester- Polyacrylate- Dispersion	42	3.8	1500	For stoving systems with high whiteness retention
Polyester polyurethane dispersions
Bayhydrol® UH 245	Polyester polyurethane dispersion	45	2.3	850	For air and force drying primers with good corrosion protection properties
Bayhydrol® UH XP 2592	Polyester polyurethane dispersion	45	2.1	300	For air and force drying primers with good corrosion protection properties

Polyisocyanate crosslinkers for one-component waterbased stoving systems:

	Type	Solids in %	% NCO on solids	Viscosity mPas at 23°C	Characteristics
Bayhydur® BL XP 2706	Hydrophilic, blocked polyisocyanate	41	3.4 blocked on supply form	1200	In combination with Bayhydrol®-Polyols for lightfast one-component polyurethane stoving coatings or as additive for stoving systems, shows high reactivity and now thermal yellowing

Self-crosslinking urethanes:

	Type	Solids in %	pH	Viscosity mPas at 23°C	Characteristics
Bayhytherm® 2817 XP	Self-crosslinking W-urethane	40	8	850	For waterborne one-component-stoving systems for improved elasticity and adhesion, good stone chip resistance
Bayhytherm® 3146	Self-crosslinking HDI-urethane	46	7.9	700	As binder for waterborne one-component stoving systems, high reactivity, no thermal yellowing

Some starting formulations (examples)

RR 6050

Waterborne one-component polyurethane stoving top coat (Bayhydrol® E 155)

Polyurethanes for one-component solventbased systems

	Type	Solids in %	% OH on solids	Viscosity mPas at 23°C	Characteristics
Desmophen® T 1665 SN/IB	saturated polyester polyol	65	2.6	2700	Very good weather resistance, high elasticity but tough resistant to scratching and abrasion

Polyurethanes for two-component solventbased systems

	Type	Solids in %	% NCO or OH on solids	Viscosity mPas at 23°C	Characteristics
Desmophen® 670 BA	Polyester polyol	80	4.4 OH	3000	With Desmodur® N 75 or N 3390 for very weather resistant films, which stay very 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 75 MPA/X	HDI biuret	75	22.0 NCO	250	High gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3390 BA/SN	HDI trimer	90	21.8 NCO	550	High gloss, good chemical and weather resistance, lightfast, good mechanical resistance

The Desmodur® N grades above might be combined with hydroxy acrylates.

A starting formulation:

RR 6052	Two-component polyurethane top coat (Desmodur® N 3390/ Desmophen® 670)

Polyaspartic acids (Polyaspartics) for hitgh solid systems

	Solids in %	Equivalent weight	Viscosity mPas at 25°C	Reactivity
Desmophen® NH 1520	100	290	~ 1200	+
Desmophen® NH 1420	100	279	~ 1500	++
Desmophen® NH 1220	100	230	< 100	++++
Desmophen® NH 1521	90 % in BA	326	~ 150	+

Some suitable polyisocyanate crosslinker (examples)

	Solids in %	Viscosity mPas at 23°C	NCO-Content [%]	Functionality
Desmodur® N 3900	100	730	23,5	3,1
Desmodur® N 3600	100	1200	23	3,1
Desmodur® N 3390 BA	90 in Butylacetat	500	19,6	3,5
Desmodur® N 75 BA	75 in Butylacetat	170	16,5	3,8

more information on Polyaspartics

Take a look at this in-depth information, which could be interesting for your application:

	Dispersions - Products and Applications		Polyisocyanates and Prepolymers: Products and Applications
	Bayhydrol® A - designed for high Performance - engineered for Success		Resins - Polyols and Aspartics for reaction with Polyisocyanates
	Toolbox for waterborne 2K Polyurethane-Coating-Systems		UV-Systems: Products and Applications