[go: up one dir, main page]

WO2025158265A1 - Procédé de production de granulés de pigment redispersibles et granulés de pigment redispersibles associés - Google Patents

Procédé de production de granulés de pigment redispersibles et granulés de pigment redispersibles associés

Info

Publication number
WO2025158265A1
WO2025158265A1 PCT/IB2025/050573 IB2025050573W WO2025158265A1 WO 2025158265 A1 WO2025158265 A1 WO 2025158265A1 IB 2025050573 W IB2025050573 W IB 2025050573W WO 2025158265 A1 WO2025158265 A1 WO 2025158265A1
Authority
WO
WIPO (PCT)
Prior art keywords
pigment
polymeric
granules
particles
surfactant
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/IB2025/050573
Other languages
English (en)
Inventor
Marino Sergi
Giuseppe Zanella
Carolina Sylva Mariantonietta GASTONE
Roberto LEO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
REGIS Srl
Siof SpA Italiana Ossidi Ferro Soc
Original Assignee
REGIS Srl
Siof SpA Italiana Ossidi Ferro Soc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by REGIS Srl, Siof SpA Italiana Ossidi Ferro Soc filed Critical REGIS Srl
Publication of WO2025158265A1 publication Critical patent/WO2025158265A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/08—Treatment with low-molecular-weight non-polymer organic compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/22—Compounds of iron
    • C09C1/24—Oxides of iron
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/36—Compounds of titanium
    • C09C1/3607—Titanium dioxide
    • C09C1/3615—Physical treatment, e.g. grinding, treatment with ultrasonic vibrations
    • C09C1/3623—Grinding
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/36—Compounds of titanium
    • C09C1/3607—Titanium dioxide
    • C09C1/3669—Treatment with low-molecular organic compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/36—Compounds of titanium
    • C09C1/3692—Combinations of treatments provided for in groups C09C1/3615 - C09C1/3684
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/006—Combinations of treatments provided for in groups C09C3/04 - C09C3/12
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/04—Physical treatment, e.g. grinding, treatment with ultrasonic vibrations
    • C09C3/041—Grinding
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/04—Physical treatment, e.g. grinding, treatment with ultrasonic vibrations
    • C09C3/043—Drying, calcination
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/04—Physical treatment, e.g. grinding, treatment with ultrasonic vibrations
    • C09C3/045—Agglomeration, granulation, pelleting
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer

Definitions

  • This disclosure concerns a process for producing redispersible pigment granules, and redispersible pigment granules thereof.
  • Pigments are a key component in formulating and tinting coatings and plastics and play a critical role when it comes to performance. Pigments only develop their beneficial action when they are evenly distributed within matrices (vehicles), where they are in liquid solutions or melted forms. Most pigments are produced and marketed as dry powders that "agglomerate" due to mutual attraction and therefore present themselves as larger, fairly spherical entities. The destruction of these structures by mechanical forces in polymer solutions or melts, yielding a homogenous distribution of the single pigment particles, is called “dispersing". In that sense, dispersing is the elemental step in the production of any composite materials, especially in the case of coatings.
  • Pigment dispersions often are marketed in liquid form at relatively high pigment concentrations and are used in additive quantities to impart color to a wide variety of products.
  • the term "pigment dispersions” is often used synonymously with colorants, color concentrates, and pigment preparations. They are used to color many types of materials, such as paint and coatings or plastics. Applications include decorative and industrial applications, thermoset composites (powder coatings), inks, plastics, and textiles.
  • pigment dispersions are typically added to another material by either dispensing (volumetrically) or adding by weight (gravimetrically), which can be an automated or manual process.
  • Liquid pigment dispersions present several disadvantages, including a low environmental profile due to the relatively high content of VOCs (Volatile Organic Compounds) and biocides. Additionally, they pose challenges in maintaining clean workspaces and preventing mold infections. There is also the issue of pigment separation within liquid systems, leading to inaccurate dosing and fouling of dosing systems. The evaporation of solvents alters the concentration and viscosity of the liquid, further compromising dosing accuracy. Moreover, these dispersions have a short shelf-life.
  • Formulated or structured pigments in solid form also eliminate the issues presented when pigments are used as fine powders, such as: high dustiness; safety and health issues; product losses; low flow properties and handling (which impede controlled metering); low bulk density for packaging; caking over storage; etc.
  • structured solid pigments have to readily achieve a comparable degree of fineness when applied to the medium for which they are intended.
  • the object of this disclosure is to provide a process by which pigments can be produced in granular form that are readily dispersible in the final medium.
  • the present invention provides a discontinuous high-shear wet granulation process for producing redispersible pigment granules comprising the following steps: a. Providing at least one powder pigment in its natural aggregated and agglomerated form; b. Blending the at least one pigment with at least one insoluble grinding aid and/or disintegrant in powder form obtaining a blend; c. Dispergating the blend by applying a first liquid mixture comprising at least two non-polymeric surfactants by means of high-shear mixing, obtaining pigment particles with an average particle size lower than the average particle size of the pigment agglomerates and aggregates; d.
  • the present inventors found out that wet granulation of pigments performed in batch operated high shear mixers can attain semi-permanent aggregates in which dispergated pigment particles are still distinguished and are easily redispersible in the final medium.
  • Dispergation is meant a process of breaking down agglomerates or clusters of solid particles into their primary particles and smaller aggregates. Dispergation consists of two steps: 1. wetting the solid particles to reduce inter-particle forces and facilitate separation, and 2. shearing to physically break down agglomerates and distribute the particles. The outcome of dispergation is a wetted mixture of primary particles and smaller aggregates ready for further processing or incorporation into a medium. Dispergation is different from “dispersion”. "Dispersion” refers to the distribution and stabilization of solid particles within a medium to form a stable system where the particles remain suspended and do not re-agglomerate. The key steps of dispersion are: 1. wetting; 2.
  • dispersion breaking down and distributing particles throughout a medium, and 3. introducing stabilization mechanisms, like adding surfactants or modifying the zeta potential, to prevent particles from settling or re-agglomerating.
  • the outcome of the dispersion is a stable colloidal dispersion where solid particles are evenly distributed and maintained in suspension over time. While dispergation and dispersion relate to the distribution of particles, dispergation in the context of the present invention emphasizes the initial breakdown and the conditions under which particles may spontaneously disperse. On the other hand, dispersion generally refers to the broader process of distributing and stabilizing particles within a medium to ensure they remain suspended.
  • dispergation focuses on the initial breaking down of particle clusters
  • dispersion encompasses the broader process, ensuring not only distribution but also stabilization of particles within a medium.
  • references on dispergation please see Makarewicz, Edwin, and Agnieszka Michalik. "Research on the Influence of the Type of Surfactant and Concentrator in Aqueous Dispersion of Pigments” Journal of Surfactants and Detergents 17, no. 4 (July 2014): 773-84, https://doi.org/10.1007/sl l743-013- 1518-5; and Rusanov, A.I.
  • Redispersible pigments are pigments that, once dispersed in a medium and then dried or settled, can be redispersed back into the medium upon the addition of a suitable solvent without losing their properties.
  • the phrase "without losing their properties” signifies that redispersible pigments have the capability to return to their original state with all their inherent characteristics and qualities intact.
  • pigments When redispersing these pigments after they have dried or settled, they should maintain their essential properties, such as color, particle size, stability, and any other relevant attributes that make them suitable for their intended application. Essentially, it means that the pigment can be effectively restored to its initial state without any significant degradation or alteration of its desirable features.
  • the term "dispersible” primarily refers to the pigment's ability to be distributed throughout a medium without necessarily implying that it can be redispersed once settled or dried.
  • a key objective is to retain or improve the available surface area of the input pigment powders. This is because, for a given pigment, quality is not only a function of the purity and morphology of the pigment crystal structure, but it is also strongly dependent on the available surface area of the pigment particles. It is the interaction of the pigments with incident light that results in selective shares being removed (absorbed) from the white light and the remaining being scattered. The first property results in chroma, while the second is the prerequisite for good hiding power. The ability to produce chroma is then proportional to the pigment surface area which can interact with the light. This means that for a given pigment quantity the degree of selective absorption increases with decreasing particle size.
  • the High Shear Wet Granulation (HSWG) process is a well-established process largely used in the pharmaceutical sector for the production of oral solid dosage forms.
  • HSWG process is conventionally performed by spraying a liquid (normally referred to as binder) onto the particles as they are agitated in a high- shear mixer.
  • the liquid forms inter-particle bonds by a combination of capillary and viscous forces until more permanent bonds are formed by subsequent drying.
  • the present inventors modified the standard HSWG process to target the production of redispersible granular pigments (like for example titanium dioxide and iron oxides) optimized for paint and coatings applications.
  • the pigment is converted into a mechanically stable granular form that is easy to handle, store, and transport. Yet, this transformation is reversible as the granules are designed to effortlessly disperse again when introduced into a medium such as water for paints or resin for powder coatings.
  • the redispersibility unlocks the limitations traditionally associated with granular or powdered pigments.
  • Such a product attains the convenience of granules and the performance of a finely dispersed pigment.
  • the present invention provides a discontinuous high- shear wet granulation process for producing redispersible pigment granules comprising the following steps: a. Providing at least one powder pigment in its natural aggregated and agglomerated form; b. Blending the at least one pigment with at least one insoluble grinding aid and/or disintegrant in powder form obtaining a blend; c. Dispergating the blend with a first liquid mixture comprising at least two non-polymeric surfactants by means of high-shear mixing, obtaining pigment particles with an average particle size lower than the average particle size of the pigment agglomerates and aggregates of step a.; d.
  • step g. either in a high-shear mixer or, preferably, in a tumbler, and step h. in a fluid bed dryer, wherein the granulator is equipped with at least one impeller, at least one side-chopper, some nozzles for liquid spraying (into the granulator) and a vacuum pump.
  • the high-shear wet granulator usually equipped with at least one agitator/impeller that imparts high shear to particles for effective agglomeration, comprises one or more nozzles that spray liquid over the material bed.
  • the agitator/impeller typically features a three-blade impeller, and the motor is fitted with a variable frequency drive (VFD) for speed control throughout the granulation process, reaching blade tip speeds up to 15 m/s.
  • VFD variable frequency drive
  • the motor may also include a power or torque meter to assess the rheology of the wet mass.
  • the granulator may also comprise a secondary impeller, known as a chopper.
  • the chopper breaks down lumps during granule growth, and can be mounted either on the top or side of the vessel.
  • the granulator usually comprises a vacuum pump and a bag filter that are used for maintaining vacuum and filtering solids, respectively.
  • the granulator's bowl may also have a jacket for heating or cooling.
  • Granulators that can be used to implement the process of the present inventions are (i) Vertical Axis Granulators (having top or bottom-mounted agitators, with the vessel itself being cylindrical or tulip-shaped to enhance the impeller's roping action.
  • a HSWG apparatus may also comprise a set of sensors to detect physical quantities indicative of properties of the HSWG processing as well as a control unit coupled to the sensors and to the actuators in the HSWG apparatus to control operation thereof based on one or more of the sensed signals.
  • the pigment powders of step a. consist of aggregates/agglomerates of similar particles.
  • step c. In the dispergation phase (step c.) of the process, it is the magnitude of the cohesive forces between the individual particles that determine the extent of deagglomeration before the mechanical action (high shear mixing) is applied. But the most difficult part of the process to define is that concerned with the breakdown of the pigment aggregates and agglomerates into finer particles after all the available surface has been wetted with the first liquid mixture comprising at least two non-polymeric surfactants.
  • This step comprises two distinct phases, a first one of wetting the pigment powder with a mixture of surfactants, and a second one of high-shear mixing the wetted particles to obtain pigment particles with an average particle size lower than the average particle size of the pigment agglomerates and aggregates of step a.
  • Dispergation can be achieved through mechanical methods, such as milling and grinding, and chemical methods, such as the use of surfactants and polymers.
  • the present inventors discovered that the dispergation phase is greatly improved, in terms of robustness, by adding to the input pigment a small quantity of insoluble grinding aid(s) and/or disintegrant(s) in powder form (step b.).
  • the at least one insoluble grinding aid is selected from fumed silica, magnesium stearate, colloidal silicon dioxide, corn starch, calcium silicate, talc, sodium stearyl fumarate, stearic acid, and MCC microcrystalline cellulose.
  • the at least one disintegrant is selected from croscarmellose-sodium, sodium starch glycolate, crosslinked polyvinylpyrrolidone, carboxymethylcellulose, microcrystalline cellulose, naturally derived fibrous cellulose, magnesium silicate coprecipitated on chitin, magnesium aluminum silicate, potassium polacrilin (Amberlite), alginic acid, sodium alginate, gellan gum, xanthan gum, guar gum, chitosan and chitin derivatives.
  • step c. comprises (preferably consists of) two phases, wherein:
  • the first phase involves spraying the first liquid mixture on the pigment agglomerates and aggregates under vacuum and under high-shear mixing, and
  • the second phase involves stopping the spraying of the first liquid mixture and high-shear mixing under a mixing condition of a Froude number equal or greater than 20, under vacuum.
  • m is the angular velocity in (rad/s)
  • r is the radius of the rotation in meters (m)
  • g is the acceleration due to gravity in (m/s 2 ).
  • the spraying of the first liquid mixture is stopped when the amount of liquid sprayed onto the particles is sufficient to cover their surface with a surfactant adsorbed layer lower than 10 monolayers.
  • Monolayer adsorption refers to the process where a single layer of atoms or molecules adheres to a surface. This layer is exactly one atom or molecule thick. Calculating monolayer adsorption typically involves determining the surface area of the material and the size of the adsorbing molecules.
  • One common approach is to use the BET (Brunauer, Emmett, and Teller) method, which measures the amount of gas adsorbed onto a surface at different pressures to calculate the surface area and thus infer the surfactant amount needed for a monolayer.
  • BET Brunauer, Emmett, and Teller
  • the Rehbinder effect is an observed phenomenon in the spontaneous dispersion of solids in liquids, particularly relevant to the reduction of strength and hardness of solids in contact with surface-active media, like certain liquids. This effect contributes to increased mechanical wear or erosion.
  • surfaceactive agents surfactants
  • these agents adsorb onto the solid surface, modifying its surface energy and mechanical properties. This change makes the solid more susceptible to fracturing or disintegration under stress, leading to smaller particle fragments and enhanced dispersion in the liquid.
  • a monolayer within surface chemistry and materials science, is a single, continuous layer of atoms or molecules adsorbed onto a surface, each in direct contact with the surface and just one atom or molecule thick.
  • liquid molecules adsorb in one layer on the particle surface.
  • the adsorbed liquid volume significantly increases relative to the solid weight, illustrating how adsorbed liquid amounts can rapidly grow with more layers beyond the initial monolayer.
  • N n X A.
  • V mol a Single Surfactant Molecule Volume (V mol): Estimate this from the molecular weight and liquid density (e.g., water: 18 g/mol, 1 g/cm 3 ).
  • V Surfactant Monolayer Total Volume
  • the solid-air interface is replaced by one between solid and liquid.
  • the first liquid mixture comprises:
  • the claimed process starts with blending the powder pigments with the at least one insoluble grinding aid(s) and/or disintegrant(s) above described (step b.) while applying vacuum to the system.
  • step b. is carried out under vacuum, preferably at a pressure P equal to or lower than 0.85 bar, more preferably at a pressure P comprised between 0.4 and 0.05 bar.
  • step c. (dispergation phase) up to the completion of step e. (granulating polymeric binder addition).
  • roping flow refers to a specific flow pattern observed in the movement of powders, particularly in pneumatic conveying systems or similar environments. This regime is characterized by the formation of a concentrated, rope-like stream of powder particles that moves along the boundaries of the conveying medium, typically air. This state is achieved at a specific flow rate and pressure that results in the formation of this roping flow, where the particles behave almost like a fluid, ensuring effective and uniform dispersion as described by Iveson and Litster.
  • step c. is carried out at a powder flow regime corresponding to a Froude number of at least 20.
  • the side-chopper traditionally used to break large lumps of over-grown granules, is surprisingly effective during the dispergation phase when high shear is applied to break up agglomerates and aggregates.
  • the critical parameter to consider is the tip velocity, which can be calculated based on the chopper's diameter and rotational speed.
  • the chopper should be configured to achieve a tip velocity exceeding 1500 rpm, preferably up to 3000 rpm, while featuring a min three multi disk knife-type design with an outer diameter of at least 120 mm or greater.
  • a spray-flux number target for step c. is lower than 0.15.
  • the dimensionless spray-flux number (see K.P. Hapgood, D.J. Lister) is a critical parameter in the context of granulation processes. It quantifies the coverage of the powder surface by liquid droplets in relation to the movement of powder through the spray zone.
  • the spray-flux number can be expressed analytically as follows:
  • Q L be the liquid spray rate (volume per unit time, e.g., — ).
  • d be the average diameter of the droplets (e.g., in meters).
  • w be the width of the flat spray nozzle (e.g., in m).
  • v p be the velocity of the powder through the spray zone (e.g., in m/sf It can be estimated by the Froude number as v p « 0.15 ⁇ / r - r ⁇ g
  • the rate of wetted area coverage by droplets can be approximated as the product of the number of droplets per unit time and the average area covered by each droplet.
  • the area flux of powder through the spray zone can be defined as w x v p representing a linear measure of the powder flow through the spray zone.
  • the dimensionless spray-flux number can be represented as:
  • the given expression quantifies the density of droplets covering the powder surface in the granulation process, enabling the understanding and optimization of wetting and granulation efficiency.
  • step c. the first liquid mixture is sprayed in an amount ranging between 0.1 and 5%w, preferably between 0.5 and 2%w, with respect to dry pigment weight.
  • step c. the first liquid mixture is sprayed in an amount ranging between 1 and 10 monolayers, preferably between 1 and 3 monolayers, with respect to the total surface area of the particles.
  • step d. is initiated by deactivating the chopper and starting the addition of the second liquid mixture under the drop-penetration flow regime described earlier.
  • step d granules nuclei (seeds) are formed as pendular liquid bridges are initially established.
  • the wetting phase commences with the spraying of a liquid mixture (liq) onto the particles at a flow rate (V ) ranging between 0.5 and 5 kgiiq/kgsoi/h, preferably between 1.0 and 3 kgii q /kg so i/h with respect to unit mass of the dry pigment (sol).
  • step d the second liquid mixture is sprayed in an amount ranging between 5% and 40%wt, preferably between 10% and 25%wt with respect to the dry pigment weight.
  • step d. is carried out at a powder flow regime corresponding to a Froude number of at least 20.
  • step e. Adding of at least one granulating polymeric binder in solid form (powder or granules) into the system (step e.) is carried out while keeping the roping flow regime of the now-formed wetted mass unchanged. By keeping this flow regime unchanged, the binder is effectively mixed with the wetted particles, ensuring uniform granulation and efficient binding. This step allows achieving desired properties in the final product, such as consistent particle size, strength, and stability.
  • Such granulating polymeric binders are needed to form a more coherent mass at the intragranular level with a high degree of plasticity needed to ensure homogeneous, dense, dry granules with low friability, whilst ensuring adhesion and cohesion in the wet state, as well as, excellent plasticity and re-dispersibility after the granules are dried.
  • a stable structure of sufficient strength is thus formed in order to withstand the hydrophilic forces arising due to the evaporation of water.
  • a structure-forming 'cement' allows the pigment granules to be soluble in the medium into which it is desired to disperse the pigment in order to regenerate the fine particles.
  • a binder in the context of wet granulation is a substance used to impart cohesiveness to the granules, facilitating the formation and maintenance of their structure. Binders can be natural or synthetic, and they function by providing adhesive forces that bind the primary powder particles together. This results in the formation of larger, multi-particle entities known as granules.
  • a well-chosen binder will enhance the flow properties of the granules, improve compressibility, and ensure the uniformity of the final product, all while maintaining the desired release profile of the active ingredients.
  • a specific advantage offered by the granulating polymeric binder(s) is to contribute to minimizing the total amount of surfactants. This is particularly important given the adverse effect of excess surfactants on wet-scrubbing resistance and water permeability of the paint systems. Excess surfactant does not improve dispersion stability and may alter the water sensitivity of the resulting paint.
  • the granulating polymeric binder is selected from copovidone PVP-PVA copolymer; polyethylene glycol (PEG) in the range 400 to 10000 Da, preferably 4000; polyvinyl alcohol (PVOH); PEG-PVA; polyvinyl pyrrolidone (PVP); partially gelatinized starch (PGS); sodium carboxymethyl cellulose; cellulose ethers; starch; microcrystalline cellulose; hydroxypropyl methylcellulose; gelatin; acacia gum; sodium alginate; and mixtures thereof.
  • PEG-PVA polyethylene glycol
  • PVP polyvinyl pyrrolidone
  • PPS partially gelatinized starch
  • sodium carboxymethyl cellulose cellulose ethers
  • starch microcrystalline cellulose
  • hydroxypropyl methylcellulose gelatin
  • gelatin acacia gum
  • sodium alginate and mixtures thereof.
  • a very effective polymeric binder is copovidone PVP-PVA copolymer, a nonionic polymeric binder with high molecular weight (500-200,000 Da).
  • the obtained granules displayed a low water sensitivity and excellent gloss.
  • the granulating polymeric binder(s) is(are) either soluble or miscible in the liquid mixtures sprayed in steps c. and d.
  • the granulating polymeric binder(s) has(have) a Tg lower than 60° Celsius.
  • the granulating polymeric binder(s) is(are) added in dry form and in amounts ranging between 0.5% to 2%wt to dry pigment.
  • step f. The addition of the second liquid mixture (step f.) is then stopped as soon as pore saturation of min 80% is reached, indicating that the majority of the pores within the granules are filled with the liquid.
  • This level of saturation allows optimal granule formation, as it ensures sufficient wetness for granule growth while preventing excess liquid that could lead to over-wetting and undesirable agglomeration. In terms of granulation dynamics, this point corresponds to the formation of full funicular liquid bridges and the onset of capillary state formation in the granules.
  • step f. the second liquid mixture is sprayed in an amount ranging between 1% and 20%wt, preferably between 5% and 15%wt with respect to the dry pigment weight.
  • step f. the second liquid mixture (liq) is sprayed at a rate ranging between 0.1 and 3 kgii q /kg so i/h, preferably between 0.5 and 1.5 kgnq/kgsoi/h with respect to unit mass of the dry pigment (sol).
  • Step g. known as the 'massing' step, is preferably carried out in a tumbler, a device widely recognized in the art of granulation.
  • the granule growth behavior is intricately linked to the liquid content, especially as the saturation level approaches 80%.
  • the tumbler's mixing mechanism involving the free fall and tumbling of solid particles down its walls, plays a pivotal role in this process. This tumbling motion is particularly beneficial for granulation, promoting the coalescence and enlargement of granule size in a controlled and uniform manner.
  • Tumbler blenders used in this step, vary in shape, including cylindrical, rectangular, and with conical or bi-conical bottoms. Notably, these tumblers lack internal baffles or rotating parts, simplifying the construction and maintenance. The rotation speed and direction of these tumblers are adjustable, typically ranging from 4 to 20 rpm, allowing for precise control over the granulation process.
  • the bin blender features a removable container that facilitates easy transfer to subsequent processing stages.
  • the massing step is carried out in a cascading flow regime corresponding to a Froude number ⁇ 0.5.
  • wet granules are tumbled in a drum or vessel at a flow regime identified as cascading, corresponding to a Froude number ⁇ 0.5, the wet granules steadily coalesce without deteriorating the consolidation degree, conversely the porosity, achieved in the process, or even improving the particle size distribution.
  • This provides a means to improve the particle size and its distribution in an economical way.
  • the wet granules from step f. appear still surface-dry, but as minimum force is applied, liquid squeezes out to the surface promoting the coalescence.
  • wet granules of pigments are obtained with a very narrow particle size distribution (mono-modal) and a d50 that can range from 50 to 1000 microns with a variance of the distribution less than 0.25.
  • the d50 ranges from 100 to 200 microns.
  • the d50 of the obtained wet granules is normally lower and in the range of 50 to 100 microns.
  • wet granules post tumbling-growth are ready for the last phase of drying (step h.).
  • the best option is to dry them in a continuous fluid bed dryer where fines can be separated and collected, further improving the particle size distribution.
  • the fines can either be recycled back to the tumbler or the granulator.
  • the fluid bed dryer is fast, operates at a relatively low temperature, and by the effect of a bubbling gas only limited shear to the granules is applied. Very limited particle growth takes place in the fluid bed and the extraction of the liquid from the granules improves the final porosity of the product.
  • the fluid bed dryer operates on the fluidization principle: material in powder or granular form is suspended in a flow of hot air, passing through a perforated plate.
  • the air flow causes the particles to behave like a fluid, ensuring uniform drying.
  • the orientation of the perforated plate in the fluid bed ensures even distribution of hot air, promoting uniform drying throughout the batch.
  • Other types of dryers, continuous or discontinuous, are suitable for the task provided they do not apply high strain on the granules.
  • FIG. 1 A schematic representation of the process object of the present invention is provided in Figure 1.
  • a high shear wet granulation, HSWG apparatus comprises, in a manner per se known: a vessel comprising an internal volume (or space) 12 to perform HSWG granulation processing of (powder) materials inserted therein; at least one input duct (or filling spout or hatch 13) configured to couple the internal volume 12 of the vessel to a set of (buffer) tanks or volumes of powder materials Po, Pi, such as a first tank of at least one pigment powder (and/or filler) Pi and at least one second tank of solid powder Po (such as grinding aids, disintegrants, granulating polymeric binders); for instance, in case the first powder material comprises pigment powder, it is possible to synchronize, with respect to transition points of the HSWG processing, inserting a granulating polymeric binder in the volume 12 via a control unit CU, as discussed in the following; a mixer device 14, such as an agitator 14, comprising a rotating body (e.g., comprising
  • the liquid distribution sub-system L comprises at least one source of liquid substances LI, L2, and one or more nozzles 15, 17 coupled to the sources LI, L2 and configured to spray the at least one liquid substance over the bottom of the internal volume 12 after it has been filled with powder materials and after blending thereof.
  • the central body of the mixing device 14 is coupled to a set of blades (not visible in Figure 1), e.g. three helical blades forming a three-blade impeller.
  • blades not visible in Figure 1
  • the exemplified number and shape of blades of the agitator 14 is purely exemplary and in no way limiting as one or more embodiments may employ virtually any number of blades greater than two.
  • the agitator 14 in order to perform HSWG, has a diameter substantially equal to the diameter of the internal volume 12.
  • the apparatus 10 comprises a conventional vacuum pump 19 coupled to the apparatus 10 via the outlet of a bag filter installed thereon or on a sealing lid 18 of the internal space 12 of the apparatus 10.
  • the vacuum pump 19 is configured to vary (e.g., reduce) the pressure within the internal space 12 of the apparatus 10 based on process parameters/phases.
  • the granulator 10 may also comprise a jacket for heating or cooling the vessel, in a manner per se known.
  • powder pigments Pi are blended with additives Po like grinding aids and/or disintegrants while absolute pressure is dropped (via the vacuum 19) to favor air removal and improve milling efficiency.
  • torque meters suitable for coupling to a motor shaft driving the agitator 14 for a high shear wet granulator.
  • torque meters may be configured to measure the torque applied to the shaft in real-time, sampling the values at constant time intervals.
  • Conventional torque meters suitable for use in one or more embodiments may comprise strain gauge torque sensors, rotary torque transducers, in-line torque sensors, magnetic torque sensors, optical torque sensors, digital torque sensors and so on.
  • a method of determining an equilibrium point for the liquid-to-solid ratio (L/S) for the HSWG processing, thereby controlling the HSWG apparatus accordingly comprises: after introducing the first powder material Pi (such as a pigment, for instance) in the internal volume 12, spraying L at least one liquid substance thereon and computing a second derivative of the torque of the impeller 14 as a function the normalized cumulative liquid volume inside the processing space 12; and detecting transition points in the evolution of the torque profile by detecting zero-crossing points and local minima for the second derivative of the torque as a function of the normalized cumulative liquid volume.
  • Pi such as a pigment, for instance
  • the HSWG processing method further comprises: in response to detecting a first transition point (e.g., at a first zero crossing in the second derivative of the torque as a function of the normalized cumulative liquid volume), reducing (via the liquid distribution sub-system L) a flow rate of the liquid substance being sprayed L; preferably, also varying a pressure inside the internal volume 12 via the vacuum pump 19; and/or inserting the second powder material Po, such as a granulating polymeric binder, in response to detecting a second transition point (e.g., at a zero-crossing of the third derivative of the torque as a function of the normalized cumulative liquid volume); and/or stopping liquid spraying L in response to detecting a third process transition point (e.g. in response to the second derivative reaching a second zero-crossing after detecting a minimum value thereof).
  • a first transition point e.g., at a first zero crossing in the second derivative of the torque as a function of the normalized cumulative liquid volume
  • reducing via the liquid distribution
  • One or more embodiments exploit a process control approach that hinges on a detailed analysis of the mechanical forces at play during the granulation process.
  • One or more embodiments exploit the second derivative of torque with respect to the normalized cumulative volume of liquid sprayed. For instance, this parameter serves as a pivotal indicator for rheological transitions during the formation of wet granules.
  • HSWG processing may encompass various stages, such as:
  • a first processing phase (corresponding to step d.) comprising modulating operational parameters in response to detecting a change of sign in the second derivative (that is, a zero crossing of the function); for instance, such a first phase involves reducing the mass flow rate of the liquid being sprayed (the second liquid mixture) while adjusting the internal pressure to a threshold level (e.g., about 0.85 bar); this first processing phase facilitates maintaining consistency in the early stages of granulation;
  • a second processing phase (corresponding to step e.) involving adding the granulation polymeric binder in response to detecting that the second derivative reaches a minimum, corresponding to a zero crossing of the third derivative; introducing a pre-determined quantity of solid granulating polymeric binder into the HSWG apparatus at this point facilitates ensuring uniformity in the granulation process; - a third processing phase (corresponding to step f.) of transition to massing which is triggered when the second derivative of the torque as a function of the normalized cumulative liquid volume exhibits a second zero crossing; during the third phase, the completion of the second liquid mixture spraying phase is reached; stopping the liquid at this point correlates with the onset of capillary liquid bridges within the wet granules.
  • the strategic use of the second derivative of torque of the agitator 14 facilitates producing wet granules with high consistency in particle size distribution (PSD) and yield.
  • PSD particle size distribution
  • One or more embodiments provide an approach that facilitates improving quality in the formed wet granules for their intended application in pigment preparation, thereby enhancing their performance in paints and coatings.
  • the primary focus of the process object of the present disclosure is to obtain redispersible pigment granules based on colored and non-colored (i.e. white and black) pigments in both aqueous and non-aqueous media. Redispersibility of granules produced by the claimed process is strongly dependent on their size and more specifically their porosity.
  • the growth phase step g.
  • granules collide with each other and the process equipment to consolidate (densify).
  • the consolidation period corresponds to the total batch time, typically spanning several minutes.
  • the inventors discovered that the final pigment quality is influenced not only by the total amount of liquid content but also by the rate at which the liquid is added. For a specific formulation, in order to achieve optimal granule porosity, the duration of liquid addition is minimized, thereby ensuring the rate of addition is as rapid as feasible within process constraints.
  • the pigment content of the resulting granules is determined by the wettable surface area of the feed pigment particles in their finely divided form that can range from few sqm/g ( ⁇ 15 sqm/g) to hundreds of sqm/g (> 150 sqm/g). As a result, it is possible to obtain redispersible pigment granules with a pigment solid content from 40% to up to 97%wt.
  • the targeted average particle size of these granules is between 50 and 1000 microns, preferably between 100 and 200 microns.
  • redispersible pigment granules are polymeric binder(s), disintegrant(s), and grinding aids(s). No additional compounds as solvents, defoamers, antioxidants, biocides, etc. are required.
  • redispersibility is used herein to refer to the ability of pigment granules to re-disperse into a medium, either liquid or melt, to regenerate highly dispersed, stable colloidal dispersions.
  • Dispersibility has been defined as the ease with which the particles in the powder are distributed in a continuous medium so that each particle is completely surrounded by the medium, and no longer makes permanent contact with other particles. It is extremely difficult to calculate the minimum amount of energy required to separate the particles as yet no satisfactory theoretical treatment has been developed.
  • the fine grinding of solids to create new interfaces is greatly facilitated by the adsorption of non-polymeric and polymeric surfactants at structural defects in the pigment surface. These defects are normally present in the natural state and also appear as microcracks during the milling process. The decrease in the surface energy associated with the surfactant adsorption can be remarkable even rendering the colloidal state more stable than the condensed state.
  • the weakening of solids by adsorbed material is known as the Rehbinder effect.
  • surfactants can be adsorbed but the most practical and effective manner and the way which can be most generally predicted lies in the amphiphilic behavior of certain molecules (especially in aqueous medium).
  • amphiphilic character gives rise to adsorption in which the hydrophobic groups are oriented away from the water and the polar group towards it. Based on the nature of the solubilizing group, these agents are classified into anionic, cationic, and non-ionic types. When strong attractions are set up between the polar groups of a surfactant and specific groups on the surface of a solid phase, specific adsorption occurs. In such cases, adsorption with reversed orientation can occur, in which the hydrophobic groups are forced to orientate towards the aqueous phase. This is a highly specific phenomenon exploited in the process described herein.
  • Polymeric surfactants display a different adsorption mechanism compared to either amphipathic or specific adsorption.
  • surfactants modify the electric charge on surfaces, they can introduce steric barriers which increase the pigment stability and they can alter the adsorption characteristics of the pigment surface to increase the adsorption of polymeric materials in pigment systems (paints), thus increasing the barriers to flocculation.
  • the surface activity of a surfactant depends on the size and polarity of the lipophilic and hydrophilic groups in the molecule.
  • the inventors adopted the HLB (Hydrophile-Lipophile-Balance) system classification as a convenient yardstick to measure the surface activity of polymeric surfactants in pigment systems.
  • HLB Hydrophile-Balance
  • the main reason is that the required HLB values for a number of organic and inorganic pigments are constant in both aqueous and non-aqueous paint systems.
  • the polymeric surfactant(s) has(have) an HLB comprised in the range 8- 16
  • the polymeric surfactant(s) has(have) an HLB comprised in the range from 13 to well over 20.
  • the redispersible pigment granules are to be dispersed by the final user in an aqueous medium
  • good conditions for triggering the dispergation are achieved by the adsorption by the pigment of a liquid mixture of low viscosity non- polymeric non-ionic gemini-type and non-polymeric anionic surfactants of relatively low MW (between 200 and 2,000 g/mol, preferably ⁇ 800 g/mol, more preferably between 200 and 500 g/mol).
  • the non-polymeric surfactant small size their rate of adsorption is high relative to polymeric surfactants, and although in time the non-polymeric molecules could be replaced on the pigment surface by polymeric surfactants employed in steps d. and f.
  • the improved wetting obtained initially by these non-polymeric surfactants increases the rate of attainment of fine particles size and thus lowers the grinding energy.
  • the two non- polymeric surfactants used in the process are found to be synergistically and very effectively adsorbed on the surface of the powder pigments forming a partial monolayer molecular film of selectively adsorbed surfactant molecules which drop the contact angle and the surface tension of the water-vapour interface.
  • the non-polymeric anionic surfactant is replaced with a non-polymeric cationic or amphoteric one with comparable molecular weight.
  • Cationic or amphoteric surfactants offer considerable advantages in improving pigment dispersion, soft-texturing, and dispersibility in non-aqueous media.
  • Gemini-type surfactants also known as dimeric or bis-surfactants, are a unique class of surfactants characterized by having two hydrophilic head groups and two hydrophobic tail groups, linked by a spacer.
  • Non-polymeric gemini surfactants are those where the spacer does not contain a polymer chain. These surfactants are known for their high efficiency and effectiveness at lower concentrations compared to conventional monomeric surfactants.
  • Alkyl Chain Gemini Surfactants (Nature: Typically consist of two long alkyl chains connected by a short spacer. Features: High surface activity, good wetting, and foaming properties. Properties: Effective in reducing surface and interfacial tension, often used in formulations requiring strong wetting agents).
  • Ester-Linked Gemini Surfactants (Nature: Contain ester linkages in the spacer or tail group. Features: Biodegradable due to the ester bond, lower irritation potential. Properties: Useful in personal care and pharmaceutical applications where biodegradability and skin compatibility are important).
  • Amide-Linked Gemini Surfactants (Nature: Incorporate amide linkages in the spacer or tails. Features: Good stability, lower toxicity, and skin irritation. Properties: Suitable for applications requiring mild surfactants, such as in cosmetics and topical pharmaceutical formulations).
  • Sulfonate and Sulfate Gemini Surfactants (Nature: Sulfonate or sulfate groups as the hydrophilic head. Features: High solubility in water, strong cleansing ability. Properties: Often used in high-performance detergents and industrial cleaning agents).
  • Ethoxylated Gemini Surfactants (Nature: Contain ethylene oxide units in the spacer or head groups.
  • HLB Hydrophilic-lipophilic balance
  • Properties Versatile in applications ranging from emulsification to solubilization, used in cosmetics and pharmaceuticals).
  • Peptide-Based Gemini Surfactants (Nature: Incorporate peptide sequences in the spacer. Features: Biocompatibility, potential for specific interactions. Properties: interesting for biomedical applications, including drug delivery systems).
  • Acetylenic diols also known as molecular defoamers or nonionic gemini surfactants are a significant and unique category of surfactants that can be used for dispersion of solids like pigments and in defoaming applications.
  • Acetylenic diols have a unique structure characterized by an acetylenic (triple-bonded carbon) group and typically two hydroxyl groups. They are classified as nonionic surfactants and are known for their high surface activity and ability to reduce surface tension effectively.
  • acetylenic diols fit in the context of surfactants for pigment dispersion: Nature: Nonionic, with a unique molecular structure featuring acetylenic bonds.
  • the non-polymeric non-ionic gemini-type surfactant is 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD).
  • the non-polymeric anionic surfactant is selected from polymers based on: ethylenically unsaturated carboxylic acids (e.g., Poly(acrylic acid), poly(methacrylic acid), and copolymers of acrylic acid with other monomers such as acrylamide); polyurethane-based surfactants (e.g., Anionic polyurethane dispersions and anionic polyurethane-urea copolymers); acidic phosphoric, phosphonic, sulfuric, or sulfonic esters of poly ethers (e.g., Phosphate esters of polyethylene glycol, sulfonate esters of polypropylene glycol); polycondensation products of aromatic sulfonic acids with formaldehyde (e.g., Naphthalene sulfonate-formaldehyde condensates, benzene sulfonate-formaldehyde condensates).
  • formaldehyde e.g
  • the non-polymeric anionic surfactant is sodium bis-(2-ethylhexyl) sulfosuccinate. In one embodiment, the non-polymeric anionic surfactant is Disodium Alkyl Polyglucoside Citrate (A sugar-based green anionic surfactant derived from the esterification of citric acid with alkyl polyglucoside).
  • TMDD non-polymeric non-ionic gemini-type surfactant 2,4,7,9-tetramethyl- 5-decyne-4,7-diol
  • AOT anionic surfactant sodium bis-(2-ethyl-l- hexyl)s
  • the first liquid mixture comprises the non-polymeric non-ionic gemini-type surfactant in an amount ranging between 0.5%w and 20%w with respect to the dry pigment weight.
  • the first liquid mixture comprises the non-polymeric cationic or amphoteric surfactant in an amount ranging between 0.5%w and 20%w with respect to the dry pigment weight.
  • step c. the solid particles are kept under constant high-shear mixing for the entire stage, whereas the liquid addition is halted upon reaching the minimum wetting requirement to enhance the breakdown of the agglomerates and aggregates.
  • step d. the liquid spraying addition is resumed (step d.) but with the second liquid mixture comprising of at least one polymeric surfactant.
  • the process advances to the wetting-nucleation phase (step d.).
  • the surfactant mixture is composed of one or more polymeric surfactants.
  • the purpose of using these polymeric surfactants is to form a stabilizing steric or electrosteric barrier around the pigment particles and nuclei.
  • Non-ionic and anionic polymeric water-soluble surfactants are highly valuable in various applications.
  • Nonionic surfactants often based on polyethers, are preferred.
  • These nonionic surfactants can be in the form of unmixed polyalkylene oxides, block copolymers (including those with polypropylene oxide and polyethylene oxide blocks), or random copolymers.
  • These polyalkylene oxides are created by adding alkylene oxides to starter molecules such as aliphatic or aromatic alcohols, amines, carboxylic acids, carboxamides, and sulfonamides. The choice of the starter molecule and the extent of alkylene oxide addition determine the characteristics of the resulting surfactant, whose properties and utility in the field are widely known to the skilled man.
  • surfactant depends on the specific requirements of the paint formulation and its intended properties. Different surfactants may offer unique benefits, such as improved stability and dispersion, leading to enhanced paint quality.
  • the polymeric surfactant present in the second liquid mixture has a molecular weight comprised between 1500 and 20000 Daltons.
  • the polymeric surfactant is present in the second liquid mixture in an amount less than 2 %wt with respect to the dry pigment weight.
  • ammonium polyacrylate a low-viscosity polymeric anionic surfactant intended for paint products.
  • ammonium polyacrylate a low molecular weight ( ⁇ 3500 Da) ammonium polyacrylate (NHPA) has been extensively characterized as a dispersant for the colloidal powder processing of high solid content pigment dispersions.
  • the mechanism involves the adsorption of either uncharged polymers or the adsorption of charged polymers referred to as polyelectrolytes onto an electrostatically charged pigment surface.
  • NHPA is classed as a 'weak' polyelectrolyte, electro-steric dispersion is the proposed mechanism.
  • Polyelectrolytes are polymers that possess a charge that is present along the length of the polymer chain, as opposed to other polymers that have a charged species at one end of the molecule only.
  • a stable adsorption, corresponding to a loose loop and tail configuration, is reached at a relatively high concentration of NHPA (> 4 mg/g), yielding a favorable stabilizing barrier resisting drying.
  • NHPA polyethylene oxidepolypropylene oxide-polyethylene oxide
  • BAB non-ionic triblock
  • Pluronic®-F127 having an approximately MW of 12600 Daltons and a fully extended PEO segment length of - 40nm
  • the PEO block is hydrophilic and water soluble while the PPO block is hydrophobic and water insoluble.
  • PPO can form adducts with alcohols, glycols or amines to give an almost infinitely adjustable hydrophobic block which can then be further reacted with ethylene oxide (EO) to incorporate one or more hydrophilic entities into the molecule.
  • EO ethylene oxide
  • these triblock copolymers self-assemble into micelles with a hydrophobic PPO center core and a hydrophilic PEO outer shell that interfaces with water.
  • These nonionic copolymers are extensively used as steric stabilizers.
  • the stabilizing performance of a copolymer is controlled by the conformation of the adsorbed layer at the solid-liquid interface, influenced by the structure and MW of the macromolecule.
  • a steric stabilizer in a given situation depends principally on three factors. First, it must be well anchored to the particle surface such that it does not desorb or migrate laterally upon particle-particle interaction. Thus, block copolymers, whose solvent-incompatible blocks provide “anchors", are commonly used for this purpose. Second, the un-adsorbed portion of the block copolymer (the "buoy” moiety) must have good solvent compatibility. Since the solvent is selective for only the buoy moiety of the polymer, it is expected that at bulk concentrations yielding a plateau in the adsorbed amount, the copolymer remaining in solution will be in the form of micelles. Last, for effective steric stabilization, the buoy moiety must provide sufficient effective thickness to prevent the approach of the colloid pigment particles within range of the attractive van der Waals forces.
  • the nonionic polymeric surfactant present in the second liquid mixture is a non-ionic triblock BAB copolymer, wherein block B is hydrophilic, and block A is hydrophobic.
  • the second liquid mixture further comprises at least one anionic polymeric surfactant.
  • the at least one anionic polymeric surfactant is selected from sodium polyacrylate (A widely used anionic polymer, known for its thickening, dispersing, and emulsifying properties. It can form complexes with Pluronic F127, enhancing the stability and viscosity of formulations); Ammonium Polyacrylate (Similar to sodium polyacrylate but with ammonium counterions, offering different solubility and interaction characteristics with Pluronic F127); Polystyrene Sulfonate (PSS - A strong anionic polymer with sulfonate groups.
  • sodium polyacrylate A widely used anionic polymer, known for its thickening, dispersing, and emulsifying properties. It can form complexes with Pluronic F127, enhancing the stability and viscosity of formulations
  • Ammonium Polyacrylate Similar to sodium polyacrylate but with ammonium counterions, offering different solubility and interaction characteristics with Pluronic F127
  • CMC Carboxymethylcellulose
  • Alginates e.g., Sodium Alginate - Natural polysaccharides extracted from brown seaweeds, alginates can form gels and stabilize emulsions when mixed with Pluronic F127
  • Poly(methacrylic acid) PMAA - An anionic polymer with carboxylic acid groups, PMAA can interact with Pluronic Fl 27 to form hydrogels and improve the release profile of active agents in pharmaceutical formulations
  • Dextran Sulfate A sulfated polysaccharide that can provide high charge density and interact with the hydrophilic segments of Pluronic Fl 27, enhancing the solubilization of poorly soluble drugs
  • Sulfonated Polymers e.g., Sulfonated Poly(ether
  • the anionic polymeric surfactant present in the second liquid mixture has a molecular weight comprised between 2,000 and 15,000 Daltons.
  • the anionic polymeric surfactant is present in the second liquid mixture in an amount comprised between 0.5% and 2% with respect to dry pigment(s) weight.
  • the combination of polymeric, non-ionic and ionic surfactants mixture is widely used in many industrial processes to take advantage of their different properties.
  • the main characteristic of these liquid mixtures is that the nonionic and ionic surfactants often associate and form complexes via van der Waals forces, hydrogen bonding, electrostatic forces, and/or hydrophobic forces.
  • electrostatic effects contribute to excluding the polymers from the gap region, in addition to steric and/or entropic effects.
  • the bound ionic surfactant (NHPA) imparts a polyelectrolyte character to the otherwise neutral nonionic copolymer (F127).
  • F127 otherwise neutral nonionic copolymer
  • both NHPA and F127 are present in solution, the onset of the depletion force occurs at a very low concentration of NHPA in the presence of a mild concentration of F127 (10,000 ppm).
  • polymeric binders are added to the wetted pigment mass.
  • Such polymeric binders are needed to form a more coherent mass at the intragranular level with a high degree of plasticity needed to ensure homogeneous, dense, dry granules with low friability, whilst ensuring adhesion and cohesion between the pigment particles in the wet state, as well as, excellent plasticity and redispersibility after the granules are dried.
  • a stable structure of sufficient strength needs to be formed in order to withstand the hydrophilic forces arising due to the evaporation of water.
  • a structure-forming 'cement' allows the pigment granules to be soluble in the medium into which it is desired to disperse the pigment in order to regenerate the fine particles.
  • a specific advantage offered by the granulation polymeric binders is to contribute to minimizing the total amount of surfactants. This is particularly important given the adverse effect of excess surfactants on wet-scrubbing resistance and water permeability of the paint systems. Excess surfactant does not improve dispersion stability and may alter the water sensitivity of the resulting paint.
  • the at least one granulation polymeric binder is selected from PVP-PVA copolymer in the range 500-200,000 Da; polyethylene glycol (PEG) in the range 400-10,000 Da, preferably 4,000; polyvinyl alcohol (PVOH); PEG-PVA; polyvinyl pyrrolidone (PVP); partially gelatinized starch (PGS); sodium carboxymethyl cellulose; cellulose ethers.
  • PVP-PVA copolymer in the range 500-200,000 Da
  • PEG polyethylene glycol
  • PVOH polyvinyl alcohol
  • PVP polyvinyl pyrrolidone
  • PPS partially gelatinized starch
  • sodium carboxymethyl cellulose cellulose ethers.
  • the at least one granulation polymeric binder is added in an amount ranging between 0.5% to 2%wt to dry pigment.
  • a very effective granulation polymeric binder is PVP-PVA copolymer, a nonionic binder with high molecular weight (500-200,000 Da).
  • the obtained granules displayed a low water sensitivity and excellent gloss.
  • the process herein disclosed employs a weight ratio of the sum of the first and second liquid mixtures versus the weight of the dry powder pigment(s):
  • the powder pigment(s) has(have) a surface area lower than 150 sqm/g (BET).
  • the redispersible pigment granules resulting from the process object of the present disclosure show these features: solvent-free, residual moisture lower than 1% at the time of production (dryer outlet), typical mono-modal particle size distribution with a variance of the distribution lower than 0.25.
  • the redispersible pigment granules produced according to the process described herein comprise:
  • the pigments are preferably chosen from the oxides/hydroxides pigments, mixed metal oxides pigments, carbon black pigments, monoazos, naphtol AS, benzimidazolone, isoindolin(one)e, and polycyclic pigments.
  • a typical composition of the single redispersible pigment granule based on powder pigments with a surface area lower than 15 sqm/g is: pigment(s) 80 - 97 %wt; grinding aids(s) 0.1 - 2 %wt; disintegrant(s) 0.3 - 2 %wt; non-polymeric surfactant(s) 0.5 - 5 %wt; polymeric surfactant(s) 0.5 - 8 %wt; polymeric binder(s) 0 - 2 %wt; and residual moisture of less than 1% at the drying outlet.
  • a typical composition of the single redispersible pigment granule based on powder pigments with a surface area greater than 150 sqm/g is: - pigment(s) 40 - 80 %wt; grinding aids(s) 0.1 - 5 %wt; disintegrant(s) 0.3 - 5 %wt; non-polymeric surfactant(s) 0.5 - 20 %wt; polymeric surfactant(s) 0.5 - 25 %wt; - polymeric binder(s) 0 - 4 %wt; and residual moisture less than 1% at the drying outlet.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Glanulating (AREA)

Abstract

L'invention concerne un procédé discontinu de granulation par voie humide à cisaillement élevé pour la production de granulés de pigment redispersibles comprenant les étapes suivantes : a. fournir au moins un pigment en poudre sous sa forme naturelle agrégée et agglomérée ; b. Le mélange du ou des pigments avec au moins un auxiliaire de broyage insoluble et/ou un délitant sous forme de poudre pour obtenir un mélange ; c. la dispersion du mélange avec un premier mélange liquide comprenant au moins deux tensioactifs non polymères au moyen d'un mélange à cisaillement élevé, l'obtention de particules de pigment présentant une taille moyenne de particule inférieure à la taille moyenne des particules des agglomérats de pigment et des agrégats ; d. mouiller les particules de pigment avec un second mélange liquide comprenant au moins un tensioactif polymère sous mélange à cisaillement élevé et laisser les particules de pigment mouillées à nucléer ; e. ajout d'au moins un liant polymère de granulation sous forme solide aux particules de pigment mouillées sous mélange à cisaillement élevé, conduisant à la formation d'un lit solide cohésif de particules ; f. introduction du second mélange liquide sur le lit solide de particules sous mélange à cisaillement élevé, obtention de granulés de pigment mouillés ; g. masser les granulés de pigment mouillés pour croître par coalescence ; et h. sécher les granulés de pigment mouillés de l'étape g. pour obtenir des granulés de pigment redispersibles.
PCT/IB2025/050573 2024-01-23 2025-01-20 Procédé de production de granulés de pigment redispersibles et granulés de pigment redispersibles associés Pending WO2025158265A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT102024000001236 2024-01-23
IT202400001236 2024-01-23

Publications (1)

Publication Number Publication Date
WO2025158265A1 true WO2025158265A1 (fr) 2025-07-31

Family

ID=90468620

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2025/050573 Pending WO2025158265A1 (fr) 2024-01-23 2025-01-20 Procédé de production de granulés de pigment redispersibles et granulés de pigment redispersibles associés

Country Status (1)

Country Link
WO (1) WO2025158265A1 (fr)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0859036A1 (fr) 1997-02-14 1998-08-19 SCITEX DIGITAL PRINTING, Inc. Procédé pour améliorer la redispersibilité des encres à base de pigment pour l'impression par jet d'encre
US20030064098A1 (en) * 1999-12-08 2003-04-03 Kararli Tugrul T. Cyclooxygenase-2 inhibitor compositions having rapid onset of therapeutic effect
WO2008156948A2 (fr) * 2007-06-20 2008-12-24 Sun Chemical Corporation Pigments perlés à reflets lustrés multicolores
WO2017197467A1 (fr) * 2016-05-19 2017-11-23 Iluka Resources Limited Agglomération de fines de matériaux porteurs de titane
US20180327604A1 (en) * 2015-12-01 2018-11-15 Omya International Ag Method for the production of granules comprising surface-reacted calcium carbonate
JP2019500296A (ja) * 2015-10-16 2019-01-10 オムヤ インターナショナル アーゲー コポリマー添加剤を有する高固形分ｐｃｃ
EP3662895A1 (fr) * 2018-12-07 2020-06-10 Tillotts Pharma AG Procédé de fabrication de noyaux de comprimés réduisant le 5-asa sans sucre

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0859036A1 (fr) 1997-02-14 1998-08-19 SCITEX DIGITAL PRINTING, Inc. Procédé pour améliorer la redispersibilité des encres à base de pigment pour l'impression par jet d'encre
US20030064098A1 (en) * 1999-12-08 2003-04-03 Kararli Tugrul T. Cyclooxygenase-2 inhibitor compositions having rapid onset of therapeutic effect
WO2008156948A2 (fr) * 2007-06-20 2008-12-24 Sun Chemical Corporation Pigments perlés à reflets lustrés multicolores
JP2019500296A (ja) * 2015-10-16 2019-01-10 オムヤ インターナショナル アーゲー コポリマー添加剤を有する高固形分ｐｃｃ
US20180327604A1 (en) * 2015-12-01 2018-11-15 Omya International Ag Method for the production of granules comprising surface-reacted calcium carbonate
WO2017197467A1 (fr) * 2016-05-19 2017-11-23 Iluka Resources Limited Agglomération de fines de matériaux porteurs de titane
EP3662895A1 (fr) * 2018-12-07 2020-06-10 Tillotts Pharma AG Procédé de fabrication de noyaux de comprimés réduisant le 5-asa sans sucre

Non-Patent Citations (10)

* Cited by examiner, † Cited by third party
Title
CHI LIUYANMIN JIA: "Effect of Redispersible Latex Powder and Fly Ash on Properties of Mortar", COATINGS, vol. 12, no. 12, 2022, pages 1930, Retrieved from the Internet <URL:https://doi.org/10.3390/coatings12121930>
CHIU HSIEN-TANG ET AL: "Preparation, Particle Characterizations and Application of Nano-Pigment Suspension", POLYMER-PLASTICS TECHNOLOGY AND ENGINEERING, vol. 49, no. 15, 22 November 2010 (2010-11-22), US, pages 1552 - 1562, XP093191253, ISSN: 0360-2559, DOI: 10.1080/03602559.2010.512335 *
G.R. FEATS. LEVINE: "The Double-layer Interaction of Two Charged Colloidal Spherical Particles of a Concentrated Dispersion eina Medium of Low Dielectric Constant", JOURNAL OF COLLOID AND INTERFACE SCIENCE, vol. 54, no. 1, January 1976 (1976-01-01)
HAPGOOD, KAREN P.JAMES D. LITSTEREDWARD T. WHITEPAUL R. MORTDAMIAN G. JONES: "Dimensionless Spray Flux in Wet Granulation: Monte-Carlo Simulations and Experimental Validation", POWDER TECHNOLOGY, vol. 141, no. 1-2, March 2004 (2004-03-01), pages 20 - 30, Retrieved from the Internet <URL:https://doi.org/10.1016/j.powtec.2004.02.005>
KNIGHT, P.CJ.P.K SEVILLEA.B WELLMT INSTONE: "Prediction of Impeller Torque in High Shear Powder Mixers", CHEMICAL ENGINEERING SCIENCE, vol. 56, no. 15, August 2001 (2001-08-01), pages 4457 - 71, Retrieved from the Internet <URL:https://doi.org/10.1016/S0009-2509(01)00114-2>
MAKAREWICZEDWINAGNIESZKA MICHALIK: "Research on the Influence of the Type of Surfactant and Concentrator in Aqueous Dispersion of Pigments", JOURNAL OF SURFACTANTS AND DETERGENTS, vol. 17, no. 4, July 2014 (2014-07-01), pages 773 - 84, XP093062075, Retrieved from the Internet <URL:https://doi.org/10.1007/s11743-013-1518-5> DOI: 10.1007/s11743-013-1518-5
MALKIN, A. I.: "Regularities and Mechanisms of the Rehbinder's Effect", COLLOID JOURNAL, vol. 74, no. 2, April 2012 (2012-04-01), pages 223 - 38, XP035033511, Retrieved from the Internet <URL:https://doi.org/10.1134/S1061933X12020068> DOI: 10.1134/S1061933X12020068
REHBINDER, P. A.: "Formation of Structures in Disperse Systems", PURE AND APPLIED CHEMISTRY, vol. 10, no. 4, 1 January 1965 (1965-01-01), pages 337 - 58, Retrieved from the Internet <URL:https://doi.org/10.1351/pac196510040337>
RUSANOV, A.I: "Thermodynamics of Dispergation: Development of Rehbinder's Ideas", COLLOIDS AND SURFACES A: PHYSICOCHEMICAL AND ENGINEERING ASPECTS, vol. 160, no. 2, December 1999 (1999-12-01), pages 79 - 87, Retrieved from the Internet <URL:https://doi.org/10.1016/50927-7757(99)00353-2>
SARA R. GOMES DE SOUSAANTONIO J. FARIA BOMBARD, REDISPERSIBILITY IN MAGNETORHEOLOGICAL FLUIDS AND ITS RELEVANCE FOR MRF FORMULATIONS, Retrieved from the Internet <URL:https://arxiv.org/pdf/2302.07617.pdf>

Similar Documents

Publication Publication Date Title
Jin et al. Super stable foams stabilized by colloidal ethyl cellulose particles
Abend et al. Stabilization of emulsions by heterocoagulation of clay minerals and layered double hydroxides
Khoshkava et al. Effect of drying conditions on cellulose nanocrystal (CNC) agglomerate porosity and dispersibility in polymer nanocomposites
EP1995283B1 (fr) Préparations de pigments de consistance pâteuse ou sous forme de gel
Saleh et al. Wet granulation in a batch high shear mixer
Tong et al. Starch-based Janus particle: Fabrication, characterization and interfacial properties in stabilizing Pickering emulsion
JP2008291259A (ja) ペースト状またはゲル状の粘稠度の顔料調製物
JP2024501782A (ja) 均一バイオポリマー懸濁液、その製造プロセスおよびその使用
Wang et al. Association between the physical stability of flurbiprofen suspension and the interaction of HPMC/SDS
Shi et al. Silica particles with dynamic Janus surfaces in Pickering emulsion
Ouadaker et al. Porous granules by freeze granulation of Pickering emulsions stabilized with halloysite particles
TR201808779T4 (tr) Yüksek moleküler ağirlikli bi̇yopoli̇merleri̇n süper kri̇ti̇k akişkan muamelesi̇
WO2025158265A1 (fr) Procédé de production de granulés de pigment redispersibles et granulés de pigment redispersibles associés
Daradmare et al. Preparation of eco-friendly alginate-based Pickering stabilizers using a dual ultrasonic nebulizer spray method
Blanco et al. Organic–inorganic patchy particles as a versatile platform for fluid-in-fluid dispersion stabilisation
CA2888403A1 (fr) Pulverisation de nanoparticules sechees a froid et methode d&#39;utilisation associee
Kawazoe et al. Characterization of silicone oil emulsions stabilized by TiO2 suspensions pre-adsorbed SDS
CN112108075A (zh) 一种Pickering乳化剂及其制备方法与应用
Liu et al. Modification of microcrystalline cellulose enhanced by impact milling and solvothermal process and its Pickering emulsion
CA2923921C (fr) Nanoparticule et composites fonctionnels a gelification stabilisee d&#39;un sel ionique dans une matrice de polymeres hydrophobes
WO2009056114A2 (fr) Utilisation de poudres de polyéthylène-glycol et compositions contenant ces poudres
Wang et al. Preparation of cylinder-like polystyrene-silica composite particles
Jakubec et al. Formation of multi-compartmental drug carriers by hetero-aggregation of polyelectrolyte microgels
Jiang et al. Physicochemical characterization of nonionic surfactants in oil-in-water (O/W) nano-emulsions for new pesticide formulations
KR102116444B1 (ko) 구형 비드의 제조방법

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 25702043

Country of ref document: EP

Kind code of ref document: A1