Frequently asked questions for

Automotive Refinish Coatings

Here are some of the most frequently asked questions with their answers from Automotive Refinish Coatings.

 

I have good experiences with LAPONITE RD, but I would like to improve the storage stability of the LAPONITE solution

To improve the storage stability, try a lower LAPONITE RD dosage to 2% or 2.5% and add after solving the LAPONITE the same amount of polypropylene glycole to the clear solution. As lower the LAPONITE RD​​​​​​​ content, as longer the storage stability of the solution. Important is also to work with very purified water which has very low conductivity / ion content.

Universal pastes based on Laropal A 81 + DISPERBYK 163 or DISPERBYK 161 are used in a mix system to produce final automotive metalic base coat for automotive refinish paint. The base coats consist of: 22-28% Uracron CR 226 XB50 24-29% of CAB 551-02 25% in BAc and max 20% of universal pigment pastes combinations - including Al or mica etc. Producing metallic base coats most of the shades show no problem. If there is CINQUASIA violet R NRT 201D and/or IRGAZIN blue A3RN / HOSTAPERM BLUE RL-01 in the pigment combination, we often but not always see flocculation in the stage of mixing components into the final base coat. Can you suggest a solution for such a problem? If there is no solution to stabilize these universal pastes so that they can be used in the polar system of metalic base coat, please suggest the formulation of pastes of Cinquasia violet R Nrt 201D and Indanthrons based on acrylic resin. Thank you very much for your prompt reply.

The phenomenon that you are describing is very well known in the base coat area. CAB often causes a problem, even so the pigments are well stabilized. There are two major points that you have to take care of: the pigment stabilization itself. For Irgazin Blue, I would recommend using 15% DISPERBYK-110 (solid additive on pigment), for Violet I, would recommend that you use 25% of DISPERBYK-2000 or DISPERBYK-2001. Unfortunately I cannot tell you which one will be the better choice, since this is very system-dependant. I would try DISPERBYK-2001 first. All three additives mentioned provide a better stability when CAB is added. Secondly, make sure that the CAB solution is added under higher shear forces (high-speed dissolver). A low incorporation speed (i.e. by stirrer) is often the reason for a reflocculation. A higher viscosity of the pigment concentrate before addition of CAB also helps to create higher shear forces. These suggestions should give you the results you are looking for.

We are using solspere 26000 for grinding of irgazine red and cinquasia violet with Tio2 and we observe viscosity pick-up more than double within 10 days of storage @ 30°C. Please advise a suitable additive to avoid pick-up in viscosity. For this resin, the system is polyester amino.

Please try DISPERBYK-2001 for Irgazine red and Cinquasia violet (calculation: 25% solid additive on pigment). Depending upon the TiO2 that you use, either DISPERBYK-110 (for basic treated TiO2) or DISPERBYK-180 (for acidic treated TiO2) is the best choice (1.5% solid additive on TiO2). If this is a co-grind (grinding all pigments together), calculate for each individual pigment and add the amount of wetting and dispersing additive accordingly.

One of our customers is not happy with the dispersability of one of our organic phtalocyanine pigment during grinding to make a waterborne paste. I am looking for an additive to improve the pigment dispersability.

Try DISPERBYK-2012, DISPERBYK-2014 and DISPERBYK-190 first. I recommend using 20-30% of active substance of the wetting and dispersing additive calculated on phthalocyanine pigment.

What is the best additive for increasing the low shear viscosity of auto polyester putty to prevent settling and sagging without affecting application viscosity?

Thank you for your request. We recommend the combination of two thixotropic agents: hydrophilic fumed silica such as Aerosil 200 in combination with a derivate of castor oil such as RHEOBYK-100 or RHEOBYK-7590. The efficiency of the Aerosil can be increased by adding approx. 20% RHEOBYK-R 605 based on Aerosil.
In amine accelerated putty’s, you can increase the filler load by approx. 10% to 15% by using our wetting and dispersing additive BYK-W 969 with 1% based on filler.
In cobalt accelerated putty’s, you can archive a filler increase of approx. 6% by using 1% BYK-W 966 on filler. If no filler increase is desired, you can only reduce the viscosity with those Additives. The result is a very smooth putty formulation without any settling or sagging problems. In general, the putty with BYK-W 966 exhibits a lower amount of separation.

Which dispersing agent would you recommend for dispersing Novoperm yellow HR70 in a polyester resin with low acid value? We currently use DISPERBYK-163 but are having a lot of problems with tension due to poor pigment wetting.

Normally, the DISPERBYK-163 is a useful additive for this pigment. In the case that you talk about a CAB-containing system, you may be better to try using DISPERBYK-2000 or DISPERBYK-2001. To achieve lower mill base viscosity, it is better to add 3-5 % n-Butanol into the mill base. The recommended additive dosage is 15 % additive solid on pigment. Technical Service Support

What do you suggest as sag control for ultra high solid clear coat for car repair? The system is composed of acrylic polyols resins, solvents like ButylAcetate, PMA, SS100 and Butylglicolacetate, and Isocyanate.

For improved sag resistance in the system you mention, you could try the following products: RHEOBYK-415, RHEOBYK-430,RHEOBYK-431. RHEOBYK-415 is a solution of a modified urea which gives temperature independent anti sag resistance. RHEOBYK-430 (solution of a high molecular urea modified medium-polar polyamide) and RHEOBYK-431 (solution of a high molecular urea modified non-polar polyamide) give you pseudoplastic flow behavior, fast viscosity recovery after application, and outstanding anti-sagging properties. Especially at temperature up to 50°C. However, the thickening effect always depends on the polarity of the solvents, therefore I recommend doing trials with all of the proposed additives and keeping the balance between sag resistance and leveling.

Please recommend a good additive for aluminum and pearl.

Due to limited information on your part, I can only give you some general recommendations. Generally speaking, for solvent-based systems you can use our products DISPERBYK-162 or DISPERBYK-110. DISPERBYK-162 is normally the better choice for aluminum pigments. However, for some grades of aluminum,DISPERBYK-110 is the way to go. For pearlescent pigments, in most cases DISPERBYK-110 is the first choice, followed by DISPERBYK-162. Dosage should be around 2-2.5 % (solid on pigment) for aluminum, and 1.5-3 % (solid on pigment) for pearlescent ones. For water-based systems, our suggestion is DISPERBYK-2060, DISPERBYK-192 or DISPERBYK-180, depending on the pigments. The amount of usage should be between 2-5 % (solid on solid pigment) for aluminum, and around 5 % (solid on solid pigment) for pearlescent pigments.

Please tell me any additive to improve wetting and dipersing of aluminum pigment.

Generally speaking, you could choose one of the following additives for this issue. If you're talking about a solvent-based system, which I presume you are, you can try either our DISPERBYK-162 and/or DISPERBYK-110 at a dosage between 2.0-2.5 (solid on pigment). Another important thing is the orientation of the aluminum flakes to achieve a uniform appearance (avoiding cloudiness). For this, we could propose the following additives: CERAFAK 103, CERAFAK 106, CERAFAK 110 (aromatic free), CERATIX 8561, CERATIX 8583 or CERATIX 8566 (aromatic free). If you're talking about water-based systems, our recommendation is our DISPERBYK-180 and/or DISPERBYK-192 or DISPERYK-2060 and, for the orientation, our AQUATIX-8421 in combination with Laponite-RD.

I have been asked to recommend a dispersion agent for a high surface area carbon black in a solvent-based automotive top coat. Have you any recommendations to pass on?

The additive type is highly depending on the type of pigment used. Our first recommendation would be DISPERBYK-2200, DISPERBYK-2000, DISPERBYK-2001. In base coat systems with a level of 70% additive solid on pigment. For top coats we recommend DISPERBYK-2013, DISPERBYK-2200, DISPERBYK-2014 or DISPERBYK-161 with the same level of addition. Also commercially available laboratory products (LP-products) are available, please get in contact with us in case these suggestions would be helpful.

I have problems with my water-borne pigment concentrates especially with carbon black. For certain reasons I have to add some thickener and cosolvent.

DISPERBYK-2012 and DISPERBYK-2014 is our first choice for resin-containing pigment grinds for both waterreducibles and emulsions. Slurry grind allows presence of amine, thickener, surfactant and co-solvent. Both products provides good stabilization of a wide range of pigments, mainly transparent and opaque organic pigments. With carbon blacks high jetness can be achieved. There is no negative impact on stability of pH-sensitive systems.

How can we avoid seeding when using LAPONITE-RD in waterborne base coat?

First LAPONITE has to be added slowly into demineralized water while stiring. This avoids the formation of gel particles. Also it is importatant only to add the LAPONITE solution as long as it is liquid. Postaddition of polypropylene glycole increases the using time of the LAPONITE solution drastically.

We develop a 2K refinish clear coat based on polyaspatic resins and struggle with the leveling of this sytem. Which additive do you recommend?

In most cases the best leveling in poly aspatic 2K clear coats are achieved by using quite polar modified silicones. An active one, which provides good substrate wetting and anti crater properties would be BYK-306. From the less active silicone BYK-326 and BYK-327 usually the most suitable one.

I use small quantaties of BYK-378 in may primer, but have wiping marks issues when the basecoat is applied on top. The primer is for wet on wet application.

Active silionces like BYK-378 can be used in small quantaties in primer surfacer to improve substrate wetting and anti crater properties as long the primer surfacer is sanded very well. In wet on wet (non-sandable) application the active silicone will lower the surface energy of the dried primer surfacer which cause the wiping marks. For such a application you better use BYK-3550 which lowers the surface tension quite similar to BYK-378 but will not impact the surface energy significant.

How can I get metallic orientation in water-borne refinish basecoat. I have good expierience with the EVA wax Cerafak-106 in solvent-borne but the EVA wax Aquacer-526 doesn't work for my waterborne system.

The mechanisem for metallic orientation in waterborne is quite different, becasue of the much slower evaperation speed of water. That mean the rheology of the paint is the key mechanisem for the effect pigment orientation. Therefore you need additives which provide pseudoplasticity with certain elastic parts to keep the flaces in the paint orientated. Here I like highly to recommend you to test the AQUATIX 8421. This wax provid you in the right dosage a good rheology profile for metallic orientation. But please keep in mind, that you should not adjust the applicaiton viscosity in flow cup, because this is not the right tool when psneudoplasticity is requisted. The adjustment have to be done with rotation viscosimeter. If higher flop values necessary you can combind the AQUATIX 8421​​​​​​​ with Laponite RD.

Even there is no demant for waterborne clear coats at the moment I like to ready for the future with such a system. Which levelling additives can you recommend for 2K waterborne clear coat.

For substrate wetting you should use 0.2-0.5% of a silicone surfactant like BYK-345, BYK-349 or BYK-3455. To increase the anti crater properties and for a certain surface slip I would further add some polymeric silicone like 0,1-0,2% BYK-331, BYK-333 or BYK-326.

For the stabilisation of the transparant iron oxid Sicotrans yellow 1916 I selected DISPERBYK-190. The resin free grind is very low viscos and also storage stable at 40°C but as soon I give this into the clear base coat the paint gells. What can I do.

DISPERBYK-190 is suitable to stabalize a very wide range of products in resin free slurry grind. Also for transparant iron oxides. The issue with this special type of pigments is that they contain iron iones, which cause the gelling of the waterborne resins. When you like to prevent the gelling you can add 1-5% DISPERBYK-102 into the slurry grind in combination with DISPERBYK-190 (approx. 25% additive solid on pigment). Please don't forget to adjust the pH of the slurry to the pH of your paint system before let down.

Sometimes I face wetting issues of my H2O base coat. How can I insure a sufficent wetting also of critical substrates.

The use of silicone surfactant like BYK-349, BYK-345 or BYK-347 insures a good substrate wetting. In cases of very low energetic surfaces you can try also BYK-3450 or BYK-3451.