Water Based Aluminum Paste
Water Based Aluminum Paste is a pigment slurry that contains aluminum pigment flakes and water.
Introduction to Water Based Aluminum Paste
Environmental sustainability and efficiency are both of very high priority for ECKART. This is proven by our constant innovations in the field of water based aluminum paste for water based coatings systems.
ECKART developed with the products
- STAPA® HYDROXAL E
- STAPA® HYDROMIC
- STAPA® HYDROLUX
- STAPA® IL HYDROLAN
- STAPA® IL HYDROLAN S
- STAPA® HFG
Flake-shaped, “leafing” and “non-leafing” aluminum paste, which were stabilized in various different processing steps, in order to meet our customers’ highest demands. These pigments are not only water dispersible, but they also allow the formulation of gassing resistant and storable aqueous metallic lacquers based on aluminum pigments for various fields of application.
With the product HYDROSHINE, ECKART offers highly brilliant effect pigment dispersions for waterborne coatings. HYDROSHINE is based on the most advanced PVD aluminum pigments. Vacuum Metallized Pigments (VMP) allow the realization of unique mirror-like effects that offer manifold design options. They are produced in a special PVD (Physical Vapor Deposition) process which guarantees their captivating optical appearance.
STAPA® HFG, stands for Hydro Food Grade. The pigments are PAH free and compliant with various European standards regarding food contact. STAPA® HFG has also been approved by the FDA.
Under the product name HYDROPELLETS, ECKART offers aluminum pellets for solvent-borne coating systems. The usage of aluminum pellets makes the dispersion process easy, increases manufacturing efficiency and provides easy handling and dust-free dosage.
Direction for Processing
When using our water based aluminum paste for aqueous systems the same general recommendations apply as for conventional water based aluminum paste. To achieve the optimum pigment dispersion and develop the full potential characteristics of the metallic pigment, i.e. – brightness, brilliance, coverage and tinting strength, distinctiveness of image (DOI), flop (two tone) we recommend predispersing the water based aluminum paste in suitable solvents, i.e. – water, butyl glycol, methoxypropanol, isopropanol in a proportion 1:1 or 1:2.
At the same time, it is recommended to gradually add the solvent to the water based aluminum paste whilst stirring constantly. Upon completion of the solvent addition, the slurry may be stirred more thoroughly to ensure complete dispersion. In addition, some benefits may be observed upon holding the pigment/ solvent slurry for a period before any further processing is done. Please note the mixing blade should be close to the bottom of the mixing vessel in order to ensure complete dispersion of the pigment paste. The diameter of the mixing blade should be 1/2 to 3/4 the diameter of the mixing vessel.
Following is a recommended procedure:
- First add the aluminum pigment to the mixing vessel, then add solvent and if necessary – a wetting agent
- After thorough mixing, check for any undispersed pigment
- After thorough mixing has been achieved, other formulation components may be added.
- Addition of suitable wetting or dispersing agent can be beneficial.
Water based aluminum paste are compatible with a variety of anionic, cationic and nonionic emulsifiers.
In both solvent and waterborne coating systems, extensive mechanical stress due to high shear forces should be avoided. High shear may result in deforming and/or fracturing of the pigment particles. This damage will reduce the optical properties, gassing stability and overall shelf life of the product.
Low shear mixing blades are recommended, their diameters have to be adjusted to the size of the mixing vessel (see above). Suggested mixing speed for dissolver blades is 500 –800 rpm. Other parameters determining the performance of the aluminum pigmented coating material are the pH-value and the additives for adjustment of the pH-value in the coating material that influence shelf life and gassing stability.
· According to our own experience, coatings with a pH-range between 5–8 can be produced with sufficient stability by using
- STAPA® HYDROXAL E
- STAPA® HYDROMIC
- STAPA® HYDROLUX
- STAPA® HYDROLAN
However these limits are dependent on the binder system used and therefore testing and control of gassing is very important in both development and manufacture (the testing methods “boiling test” and “40°C test” are described in the annex).
In all cases the binder system has to be adjusted to the correct pH-value before blending with the water based aluminum paste slurry. When choosing suitable additives for the adjustment of the pH-value such as Ammonium Hydroxide, TEA, DMEA, AMP 90, TMEA and others, it should be considered that products like Ammonia or TEA have a more disadvantageous influence on the gassing stability than e.g. DMEA or AMP 90.
STAPA® HYDROXAL E / STAPA® HYDROXAL E Seed
The new E and E Seed series are free of APEO and meet the latest regulatory and technology standards.
HYDROXAL E types contain a biocide to prevent the water-containing pastes from fungal attack.
The two special HYDROXAL E Seed types are free from biocides – following the regulatory limits in the field of seed coatings.
Additionally available are water containing HYDROXAL DC and HYDROXAL M, which are as well APEO free and most suitable for use in decorative paints and for printing purposes.
STAPA® HYDROMIC - as the most current product development - enriches the portfolio of effect pigments for water-based coatings systems.
The pigments of the STAPA® HYDROMIC product series are additive-stabilized and free of APEO. In addition, they do not contain water and are thus ideally suited for airfreight.
All STAPA® HYDROLUX “non-leafing” water based aluminum paste are chrome treated in an unique manufacturing process. This development aims at very critical applications, whenever excellent gassing stability is required. STAPA® HYDROLUX also guarantees best results of adhesion/intercoat adhesion if the metallic pigmented coating is exposed to humidity tests.
STAPA® IL HYDROLAN
HYDROLAN is a silica encapsulated aluminum flake with long-term stability in water based coatings. This heavy-metal-free stabilization technology guarantees gassing stability and optical properties comparable to chromate passivated pigment types. The pigments are organically modified at their surface. They show high brilliance, whilst no degradation under high shear stress is observed. The product is stabilized without using a heavy metal compound.
The sandwich type structure of the silica encapsulated aluminum-flakes provides aluminum pigments with a high resistance to degradation. Simulation of the mechanical stress is afforded by means of a “Waring Blender Test*”. The shear stability of the pigments is divided into three levels, depending on the L values at 20°C (CIELAB):
∆L < 5: non degrading
∆L = 5–10: semi degrading
∆L > 10: degrading
Weathering and UV resistance
Comparable to untreated aluminum pigments.
Storage stability (at room temperature) of the silica coated aluminum flake type is 24 months.
*Waring Blender Test: A method to simulate the degradation resistance of effect pigment lacquers. The test, originally developed by an US located OEM manufacturer, allows comparisons of degradation resistance trends within short testing periods.
STAPA® IL HYDROLAN S Series Silica-Encapsulated Aluminum Pigments for Water-Based Coatings
The STAPA® IL HYDROLAN S series consists of the extremely thin silver- dollar pigments of the SILVERSHINE S series. STAPA® IL HYDROLAN S was developed especially for water-based coatings systems. A new heavy-metal-free stabilization procedure encapsulated conventional aluminum pigments with a transparent and homogeneous silica layer.
STAPA® IL HYDROLAN S closes the gap between conventional silver dollars and PVD pigments: The narrow particle size distribution results in a very bright, chrome-like appearance. From a functional point of view, STAPA® IL HYDROLAN S convinces with its extremely strong hiding power, an excellent gassing stability and a high shear stability.
Ultra Brilliant Effect Pigment Dispersions for Waterborne Coatings
HYDROSHINE is a highly brilliant effect pigment dispersion for waterborne coatings based on the most advanced PVD aluminum pigments. ECKART offers a choice of different technologies to meet customers' specific demands for gassing stability, humidity resistance and optical performance.
The following HYDROSHINE series are available:
HYDROSHINE WS 1000 series - Pigments available in different solvents.
HYDROSHINE WS 4021 - Passivated pigment for dark, chrome-like effects.
Pigments with heavy-metal-free encapsulation:
HYDROSHINE WS 3000 series - High chemical and hydrolysis resistance. Highly brilliant chrome-like effects.
HYDROSHINE WS 4001 - Darkest pigment within the HYDROSHINE WS portfolio, pronounced flop. Outstanding chemical resistance.
Depending on the desired effect, the typical pigmentation will vary between 0.5 % and 1.5 % (solid content of aluminum pigment). The pigment to binder ratio should be between 1:5 to 1:10.
STAPA® HFG – Hydro Food Grade Waterborne Coatings for the Direct Contact with Food
STAPA® HFG is a worldwide unique product innovation for water-borne coatings in the field of applications with direct food contact. HFG means Hydro Food Grade. The aluminum pigments used for this product are specially coated and stabilized.
STAPA® HFG is PAH free and compliant with various European standards regarding food contact. Amongst others, STAPA® HFG is in accordance with:
· FDA approval 175.300
· European standard for toys EN-71-3 (as of Nov. 2002)
For this reason, STAPA® HFG is perfectly suited for applications such as toys, packaging, can coatings or for the coating of cook-ware. This water-based product solution provides the desired expressive optics for your application: from a soft, greyish shade to high-sparkling effects.
HYDRO PELLETS – for safe and sustainable silver
The innovative HYDRO PELLETS silver pigments step up business efficiency and increase sustainability at the same time. Dosed automatically, the VOC free product allows safe handling and disperses easily.
It can be employed in waterborne systems for wall paints and industrial coatings. HYDRO PELLETS does not contain biocides or formaldehyde. As a result, it is classified as not dangerous according to GHS.
In addition to determining the quality criteria specified in the data sheets, the quality control applied in connection with the STAPA®/STANDART® metal pigments comprises comprehensive testing of optical aspects.
As a rule, the following tests are carried out:
- Tests on the pigment
- Tests in the application
The quality characteristics determined directly on the pigment are as follows:
- Sieve analysis (limit size particle sieving) according to DIN 53196 or ASTM 11
- Particle size distribution according to the laser granulometer method ISO 13320-1
In addition, for all pastes:
- Volatile or non-volatile content in accordance with DIN 55923
In addition, for water based aluminum paste for aqueous systems:
- Gassing stability (not standardized)
The tests for the optical quality characteristics of a paint application (visual and/or instrumental) include the following:
- metallic effect (flop)
- distinctiveness of image (DOI)
- color saturation
- tinting strength
- covering capacity
Boiling test ECKART test methods
Brief description of the boiling test
This test is a method to measure the gassing stability of aluminum pigments in water. Being measured is the time during which 1 g of aluminum (solid) produces 400 ml hydrogen at the temperature of the boiling liquid (mainly water, see below).
Attached is a schematic drawing of the apparatus with a list of the necessary equipment.
- 150 ml of dem. water is heated to boiling point (under reflux) in flask c.
- 1 g of aluminum as powder or paste (if using an aluminum-paste the non volatile content is to be considered) is dispersed in butyl glycol to get 10 g dispersion.
- Adjust the level of the sealing liquid in burette f with the leveling bottle G to the upper mark H.
- Add the aluminum dispersion to flask C and reclose tightly. Note time.
- To avoid an over pressure in the apparatus by the hydrogen evolution, the level of the sealing liquid in G and F should be adjusted by moving the leveling bottle G down. When the level of the equalized sealing liquid reaches the lower mark I; note time again. (We are using a magnetic fload valve and a time recorder to be time-independent).
- Switch off magnetic mixer A and heater B and open drip tube D.
Determination of particle size distribution with laser granulometer
The measurement of the particle size distribution (typical value), is standardized according to ISO 13320-1.
Besides hardware (equipment manufacturer and type) and software (computer program and plotting device), the results of the laser granulometer are highly dependent on the following parameters:
- way of dispersion
- dispersing devise
- dispersing medium
- dispersion energy
- dispersion time
The standard dispersion method applied to the specimen is by ultrasound. One can either use the built-in ultrasonic bath or preferably the specimen can be prepared in an external ultrasonic dispersion bath.
The higher the ultrasound frequency or the greater the energy concentration in the dispersing vessel, the “finer” the specimen will appear; this is because more super fine particles have been dispersed. In cases of an extremely high-energy concentration, super fine particles will be generated by mechanically breaking off from the original pigment.
The effect of the dispersion time is shown by the median value (D 50) falling as the dispersion time rises, i. e. once more the appearance of the specimen is “finer”.
Compared to the dispersion energy and time, the dispersion medium plays a relatively minor role; the medium generally used for QC purposes is isopropanol. The material properties of the device should be checked before using other solvents.
A detailed description of the testing method (test instruction) applied by ECKART can be obtained upon request.
Gassing sensibility test
1.1 300 ml gas washing bottle
1.2 Bubble counter with two chambers
1.3 Ground stopper
2.1 A 300 ml sample of the enamel containing aluminium flakes is filled into the gas washing bottle.
2.2 The bubble counter is attached to the gas washing bottle.
2.3 The lower chamber of the bubble counter is filled with 25 ml water through the side neck.
2.4 The assembled apparatus is placed in a 40 °C bath and allowed to reach equilibrium for 30 minutes.
2.5 When a constant temperature is established, the screw cap has to be securely tightened.
3.1 The volume of water displaced from the lower chamber equals the volume of gas (hydrogen) generated.
3.2 25 ml of generated gas in 30 days is the maximum acceptable level.
The technical specifications and other information in this leaflet reflect our current knowledge. They are solely intended as general information for our customers. Our customers still bear the responsibility for testing the products to ensure suitability for customers’ intended applications and meeting customers’ endues requirements. We reserve the right to alter product performance and specifications. Our technical consulting service is available for further advice, technical help in solving problems arising in manufacturing and applications, as well as with product formulations. The customer, however, is responsible for reviewing such data and recommendations prior to using them in an application. We assume no liability for the accuracy and completeness of the data presented on this leaflet or any other technical information we provide.