Ink Jet Ink Formulation Filtration

Pigmented Inks
The key objective in filtration of pigmented ink for thermal ink jet printing is to remove oversized pigments and agglomerates, while classifying the dispersion for maximum printhead performance. It is imperative to keep filtration costs low while meeting this goal. Pall recommends the PROFILE® II  or Profile Star filters for prefiltration and final filtration of pigmented inks. Final filtration requirements typically range from 0.3 to 1.0 micron.

Dye-Based Inks
Dye-based inks differ in chemical composition from pigmented inks, and thus have different filtration requirements. In addition to insoluble dye elements, gelatinous residues and other contaminants, the potential presence of bacteriological matter may cause premature printhead failure. For effective and economical removal of these contaminants, Pall recommends two-stage filtration. Prefiltration options include the Profile II  or NEXIS®  depth filters while the WATER-FINE^TM  0.2 µm membrane filter is best for final filtration.

Industrial Marking Inks for General Use
Industrial marking systems require high-efficiency filtration for contaminant removal that ensures proper operation without nozzle deflections or plugging.  Therefore, ink filtration to 1 µm absolute is essential to assure printer performance. For most aqueous, ketone and alcohol formulations, the Profile II  and Nexis Series  filters are most suitable.

Inks for High-Resolution Industrial Marking Applications
Pall has a wide range of filtration options for fine filtration of high-resolution inks. Please contact the ink jet team at Pall for a recommendation for your specific ink chemistry.

Pigmented Solvent-Based Inks
For filtration of pigmented solvent-based ink jet inks for piezo printing, Pall recommends filtration to 1.5 µm absolute. This provides for excellent protection of the printhead and outstanding ink shelf life. The Profile Star, POLY-FINE® XLD  and ULTIPOR GF PLUS® filters are recommended based on specific chemical compatibility.

UV Curable Ink Jet Inks
The application of UV curable technology to the ink jet printing market offers many advantages such as image durability and fade resistance. These unique inks require filter technology with low-pressure drop characteristics due to high viscosities. Excellent gel capture and retention are also critical for proper printhead performance. Pall Profile Star or Poly-Fine XLD  filters are recommended for most formulations, while those higher in temperature should use the Ultipor GF Plus filter.

Proper filtration of both dye and pigmented ink jet colorants is critical for high-quality final ink formulation.  Colorants that are properly filtered will facilitate final ink formulation and enhance the overall ink performance in the printer. Pall recommends filtration at 0.5 µm absolute with the Profile II  filter for pigmented colorants. Two-stage filtration is suggested for dye-based colorants with the Profile II  or Nexis  depth cartridges as prefilters. Water-Fine  0.2 µm membrane elements may be used as final filters.

Initial Formulation Trials to Full Production
Proper selection and coordination of the filtration scheme, starting with the first formulation trials, assures the launch of high-performance ink at an economical cost.

Selection of the best filtration technology begins during ink formulation. Preliminary ink formulations that are filtered properly will have better performance and an improved chance of being successful with minimal changes. In addition, filterability testing during pilot-scale manufacturing will help determine filter usage and allow optimization of the total filtration process.
 
From small disc filters to one-inch test filters and housings to capsule filters, we provide products and services to support the ink jet laboratory needs of our customers.

Pall offers two exceptional melt-blown polypropylene depth filter options with absolute retention ratings from 0.3 to 200 µm. These filters are ideal for classification of ultra-fine pigment dispersions and as cost-effective prefilters for final ink formulations.

Nexis Series
Nexis polypropylene filters utilize a revolutionary melt-blowing technique called CoLD (Co-located Large Diameter) fiber technology. This patented process integrates large-diameter CoLD fibers within the fine fiber filtration matrix to provide outstanding structural strength, resistance to contaminant unloading and exceptionally long service life.


Nexis Series


Filtration zones with CoLD fibers.

Profile II 
Profile II filters feature a continuously tapered prefiltration section and a constant pore size final filtration section that yields excellent service life. They are available in polypropylene, nylon and polyphenylene sulfide with filtration efficiencies to 0.3 µm absolute.


Profile II

High-efficiency membrane filters are available for fine filtration of ink jet inks.

Varafine™ and Water-Fine Series
These high-efficiency filters incorporate patented highly asymmetric polysulfone membrane to provide absolute-rated filtration with superior flow rates and long life cycles. The uniquely manufactured membrane consists of very open pores on the upstream side for less flow restriction and lower pressure drops, while the downstream cut-off layer has smaller pores for the finest filtration.


Highly asymmetric polysulfone membrane.

Ultipor® N66®
This filter is made from a pure, naturally hydrophilic nylon membrane, which has exceptional chemical and solvent compatibility and extremely low extractables. The membrane is cast on a nonwoven support material for added strength and integrity. The Ultipor N66 filter is specifically engineered for reliable, economical fine filtration.

The Pall family of pleated, fibrous products includes both resin-bonded microfiber and melt-blown polymeric options.

Ultipor GF Plus
These filters feature a resin-bonded inorganic microfiber matrix in a high area pleated configuration. The resin binder ensures a rigid structure and imparts a positive zeta potential in aqueous, low ionic solutions, thus enhancing contaminant removal. With retention ratings from 0.1 to 40 µm, they are available in a wide range of configurations and hardware choices.

Poly-Fine II Series
These pleated filter cartridges utilize chemically resistant polypropylene media and hardware. The filter media, manufactured directly by Pall just for filtration applications, offers long service life with low pressure losses and retention ratings to 0.2 µm. The Poly-Fine II filter is an ideal choice for dye-based inks.


Poly-Fine II Series

Pall has developed several innovative filters that combine the classification characteristics of pleated filters with the gel-removal traits of depth filters. These filters work well in pigmented ink applications that are higher in viscosity.

 

Profile Star Series 
This filter combines the exceptional dirt-holding capacity of Profile II depth filters with the high flow rates of traditional pleated filters. The pleated-depth design features a graded pore structure to maximize void volume and service life, while providing excellent removal of gels and agglomerates. The Profile Star filter media minimizes removal of desirable colorant while efficiently removing oversized contaminant and is available in polypropylene or nylon.



Poly-Fine XLD Series 
These Extended-Life depth filters feature proprietary polypropylene media, manufactured directly by Pall, for effective capture of deformable contaminant. This pleated-depth filter provides long life, high flow rates and low pressure drops, while capturing gels, and other contaminants.