Hydrotalcites are a class of anionic clays with general formula:

[M(II)_1-x M(III)_x (OH)₂]^x+(An-)_x/n * mH₂O

where M(II) can be: Mg, Zn, Fe, Co, Ni, Mn,Cu, Ca; while M(III) can be: Al, Fe, Co, V; (generally 0,2 ≤ x ≤ 0,4); A can be an inorganic or organic anion with n- charge (where n = 1, 2, 3, 4); m are the moles of water (generally 0,4 ≤ x ≤ 1).

They are a class of compounds with a structure similar to the hydrotalcites with comparable reactivity of the interlamellar region. The main characteristic of these lamellar solids is the presence of the bivalent metal while the trivalent metal (like aluminum) is absent. The general formula is:

[M(II)_1−x M(II)_1+x(OH)_3(1-y)]⁺(Aⁿ⁻)_(1+3y)/n * mH₂O

where M(II) can be Mg, Zn, Fe, Co, Ni, Mn, Cu, Ca; (with 0 ≤ x < 1; 0 ≤ y < 1); A can be be an inorganic or organic anion with n- charge (con n = 1, 2, 3, 4); m are the moles of water (generally 0,5 ≤ m ≤ 1).

In the last thirty years the chemistry of phosphates and phosphonates of tetravalent metals with lamellar structure and general formula M(IV)H₂P₂O₈ * nS (where M= Zr, Ti, Hf, Sn, Ge, Ce, Th; X= P, As; nS= moles of co-intercalated solvent) has grown, so much to require a new classification.

Such lamellar compounds are usually divided into two main classes:

I) M(IV) phosphate and phosphonate with alfa structure, having general formula:

M(IV)(O₃PR)_x(O₃PR’)_2-x

where R and R’ are monovalent organic or inorganic radicals (i.e. H, OH, -CH3, -C₆H₅ ecc.) amd M(IV) is a tetravalent metal like.

II) M(IV) phosphate-diidrogen phosphate, M(IV) phosphate-phosphonate and M(IV) phosphate-phosphinate with gamma structure, having general formula:

M(IV)(PO₄) (O₂PRR’),

where R and R’ are monovalent organic or inorganic radicals (i.e. H, OH, -CH3, -C₆H₅ ecc.) and M(IV) is a tetravalent metal like Zr, Ti, Hf, Ce, Th, Sn.

They consist of synthetic and mineral clays with lamellar structure and general formulas:

A₃Si₂O₅(OH)₄ e A₃Si₄O₁₀(OH)₂

where A can be Ca, Mg, Al, Na, Fe, Ti, Li, K, Ba.

Particularly interesting are the lamellar systems in which Si is partially replaced by a trivalent metal such as Al, because the formation of negative charges in the layers produces aluminosilicates capable of exchanging cationic species by intercalation reactions.

Silica is one of the most abundant minerals in nature and has many industrial uses.

Parallel to the conventional silica of mineral origin, numerous synthetic approaches have been developed to obtain new materials with peculiar properties and suitable for many research and industrial applications.

Micro and nano-structured silicas with ordered and controlled porosity are some examples of such synthetic derivatives.

All the additives can be modified through the intercalation/inclusion of organic molecules with the aim of compatibilize the fillers with the polymeric matrices of interest and maximize the performances.

The organic modification allows the increase of the interlayer distance of the materials creating an environment compatible with the polymer. This favours the diffusion of the polymer chains into the interlayered region during the mixing process of the additive.

In fact, the greater are the interaction between the polymer and the organic modifier of the layered solids the greater is the tendency of the additive to exfoliate and homogeneously disperse in the polymeric matrix forming a nanocomposite material. The organic modification is a fundamental step in the production of layered solids because from the dispersion/exfoliation degree depends the surface of contact between the polymer and the additive and then the efficacy of the filler to improve the properties of the final composite material.

The intercalation/hosting of organic molecules in the lamellar solids allows the insertion of special functionalities in the additives very useful to confer new properties in the composites which are absent in the neat polymers.

Thus the organic modification is an effective tool for the preparation of multifunctional additives able to exert nanostructurant effects and to produce composite material with the following properties:

» anti-UV
» antistatic
» antifog
» anticorrosion
» antifouling
» antioxidant
» antibacterial
» magnetic
» optic
» biomedical
» catalytic

Lamellar hydrotalcites and hydroxide double salts are used for the intercalation/inclusion of anionic or deprotonable species.

Lamellar matrices of phyllosilicates, phosphates and phosphonates are used for the intercalation/ inclusion of cationic or protonable species.

Silicas and silicates are generally used as such or as matrices for the inclusion/encapsulation of neutral species.

All the synthetic lamellar solids are prepared through original methods developed by the company, starting from salts of Mg, Zn, Al, Zr (or other metals) and using only water as solvent. The strict control of the synthesis parameters allows The preparation of materials with high purity, but also offers the possibility to modulate the degree of crystallinity, the dimensions and the size distribution of the particles (generally 0.1 – 50 μm), the surface area (typically 20-200 m²/g) and the porosity of the material.

Using intercalation techniques, it is possible to modify the hydrophobic/hydrophilic character of the materials, in order to compatibilize them with the polymers and industrial processes of interest, but also to introduce specific functional groups in the additives.

Prolabin & Tefarm’s R&D department is always looking for new synthetic approaches in order to improve its ability to develop new products for industrial applications. We search, in collaboration with our partners and customers, the most appropriate solution to technological and production needs.

For this reason, Prolabin & Tefarm is able to supply, in addition to additives, also masterbatch formulations based on polymers and resins of interest and/or customized compounds for each application.

To achieve the desired efficacy and functionality the formulations are prepared properly combining various fillers, exploiting the synergistic action of the conventional additives with the PT-Clay additives. A brief but non-exhaustive list of synergistic additives is reported below:

» Graphene
» Expanded graphite
» Micro and nanostructured tubular fillers
» Aluminosilicates
» Mineral fillers
» Conductive fillers