WO2018002653A1

WO2018002653A1 - Recycled siliceous mineral

Info

Publication number: WO2018002653A1
Application number: PCT/GB2017/051931
Authority: WO
Inventors: Alex COE; Becky PRALL; Robert EADE; David Moseley; Pankaj Chauhan; Anabelle Huguette Renée LEGRIX; Andrew Curtis
Original assignee: Imerys Minerals Limited
Priority date: 2016-07-01
Filing date: 2017-06-30
Publication date: 2018-01-04
Also published as: GB201611523D0

Abstract

A recycled siliceous mineral, a method of making a recycled siliceous mineral and uses of the recycled siliceous mineral as a functional filler, for example in paint compositions, for example for use as a matting agent without detrimentally affecting opacity, colour and/or scrub resistance of the paint composition.

Description

RECYCLED SILICEOUS MINERAL TECHNICAL FIELD The present invention relates generally to a recycled siliceous mineral (e.g. perlite and/or diatomaceous earth (DE)) and the use of the recycled siliceous mineral as a functional filler in various compositions (e.g. in paint compositions). The recycled mineral may, for example, be used as a matting agent. In other words, the recycled mineral may be used to decrease the gloss of compositions. The recycled mineral may, for example, provide the compositions with similar opacity and/or colour and/or scrub resistance in comparison to compositions comprising a corresponding non-recycled siliceous matting agents. The present invention further relates to methods of making the recycled siliceous mineral and methods of making compositions comprising the recycled siliceous mineral.

BACKGROUND

Particulate minerals are used for a wide range of applications including, for example, as fillers in compositions such as plastic, paper and paint. Siliceous minerals such as perlite and DE are often used as filters, for example in the food and beverage, agriculture and oil industries due to their porous structures. It is desirable to provide further applications for minerals after their initial use in order to reduce waste. It is thus desirable to provide alternative and/or improved methods for recycling minerals and alternative and/or improved recycled minerals. The recycled minerals may, for example, be used in various applications and may, for example, provide alternative or improved properties.

SUMMARY In accordance with a first aspect of the present invention there is provided a recycled siliceous mineral comprising equal to or less than about 0.5 wt% carbon and/or having a L^* whiteness equal to or greater than about 75. In accordance with a second aspect of the present invention there is provided a method for recycling a siliceous mineral, the method comprising heating a used siliceous mineral to remove water and organic matter. The method may, for example, make a recycled siliceous mineral according to any aspect or embodiment of the present invention.

In accordance with a third aspect of the present invention there is provided a recycled siliceous mineral made by the method of any aspect or embodiment of the present invention.

In accordance with a fourth aspect of the present invention there is provided a paint composition comprising a recycled siliceous mineral. The recycled siliceous mineral may, for example, be according to any aspect or embodiment of the present invention. In accordance with a fifth aspect of the present invention there is provided the use of a recycled siliceous mineral as a functional filler. The recycled siliceous mineral may, for example, be according to any aspect or embodiment of the present invention.

In accordance with a sixth aspect of the present invention there is provided the use of a recycled siliceous mineral as a filler in a paint composition. The recycled siliceous mineral may, for example, be according to any aspect or embodiment of the present invention.

In accordance with a seventh aspect of the present invention there is provided the use of a recycled siliceous mineral to decrease the gloss of a paint composition. In other words, there is provided the use of a recycled siliceous mineral as a matting agent. The recycled siliceous mineral may, for example, be according to any aspect or embodiment of the present invention. In certain embodiments of any aspect of the present invention, the siliceous mineral comprises equal to or less than about 0.1 wt% carbon.

In certain embodiments of any aspect of the present invention, the siliceous mineral is recycled DE and/or recycled perlite. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral is derived from a filter cake.

In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a LOI equal to or less than about 2.5 wt% or equal to or less than about 0.5 wt%.

In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a L^* whiteness equal to or greater than about 80.

In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a b^* yellowness equal to or greater than about 1 or equal to or greater than about 2 or equal to or greater than about 10. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has an oil absorbency ranging from about 40 g/100g to about 70 g/100g. In certain embodiments, the recycled siliceous mineral has an oil absorbency ranging from about 45 g/100g to about 70 g/100g. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a d₅o ranging from about 10 μηι to about 40 μηι. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a d₉o ranging from about 20 μηι to about 70 μηι. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a d₅o ranging from about 1 1 μηι to about 13 μηι. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a d₉₀ ranging from about 36 μηι to about 40 μηι. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a bulk density ranging from about 0.1 g/cm³ to about 1 g/cm³. In certain embodiments, the recycled siliceous mineral has a bulk density ranging from about 0.2 g/cm³ to about 0.6 g/cm³. In certain embodiments of any aspect of the present invention, the recycled siliceous mineral has a pH ranging from about 8 to about 1 1 .

In certain embodiments of any aspect of the present invention, the recycled siliceous mineral is made by heating a used siliceous mineral to a first temperature to remove water and then heating to a second higher temperature to remove organic matter. In certain embodiments, the recycled siliceous mineral is made by heating a used siliceous mineral to a temperature ranging from about 200°C to about 300°C and maintaining a temperature within this range for a period of time and then heating the used siliceous mineral to a temperature ranging from about 600°C to about 1 100°C and maintaining a temperature within this range for a period of time. In certain embodiments, the siliceous mineral is maintained at a temperature ranging from about 200°C to about 300°C for a period of time ranging from about 5 minutes to about 60 minutes. In certain embodiments, the siliceous mineral is maintained at a temperature ranging from about 600°C to about 1 100°C for a period of time ranging from about 5 hours to about 6 hours.

In certain embodiments, the heating is carried out by microwave assisted heating. In certain embodiments, the recycled siliceous mineral is milled or screened after the heating step(s).

In certain embodiments, the used siliceous mineral is not treated prior to the heating step(s).

In certain embodiments, the maximum temperature that the siliceous mineral is heated to is determined by performing thermogravimetric analysis (TGA) on a sample of the used siliceous mineral and heating to a temperature at which at least 99 wt% of the organic matter is removed.

In certain embodiments, the used siliceous mineral is DE and the DE is heated to a temperature ranging from about 900°C to about 1 100°C. In certain embodiments, the used siliceous mineral is DE and the DE is heated to a temperature of about 1000°C. In certain embodiments, the DE is heated to a temperature ranging from about 900°C to about 1 100°C for a period of time ranging from about 5 hours to about 6 hours.

In certain embodiments, the used siliceous mineral is perlite and the perlite is heated to a temperature ranging from about 600°C to about 700°C. In certain embodiments, the used siliceous mineral is perlite and the perlite is heated to a temperature of about 650°C. In certain embodiments, the DE is heated to a temperature ranging from about 600°C to about 700°C for a period of time ranging from about 5 hours to about 6 hours. In certain embodiments of any aspect of the present invention, a paint composition according to any aspect or embodiment of the present invention has a gloss at 85° ranging from about 0.5 % to about 5 %.

In certain embodiments of any aspect of the present invention, a paint composition according to any aspect or embodiment of the present invention has a L^* whiteness equal to or greater than about 95.

In certain embodiments of any aspect of the present invention, a paint composition according to any aspect or embodiment of the present invention has an opacity of at least about 80 % when measured using a wet film thickness of 60 μηι.

Certain embodiments of the present invention may provide one or more of the following advantages: · desired colour characteristics (e.g. brightness, L^* whiteness, b^* yellowness);

• desired opacity;

• desired (e.g. decreased) gloss;

• desired scrub resistance;

• decreased waste;

· more efficient method of recycling siliceous mineral.

The details, examples and preferences provided in relation to any particular one or more of the stated aspects of the present invention apply equally to all aspects of the present invention. Any combination of the embodiments, examples and preferences described herein in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein, or otherwise clearly contradicted by context. DETAILED DESCRIPTION

The present invention is based on the surprising finding that a used siliceous mineral such as a siliceous mineral derived from a filter cake, can be processed such that it is suitable for use as a matting agent (i.e. to decrease gloss), for example a matting agent in paint compositions. In certain embodiments, the recycled siliceous mineral can be used as a matting agent without substantially affecting the colour (e.g. whiteness), opacity and/or scrub resistance of the composition (e.g. paint composition) (e.g. in comparison to a paint composition that does not comprise a matting agent). In certain embodiments, the recycled siliceous mineral can be used as a matting agent in place of a non-recycled siliceous matting agent in a composition (e.g. paint composition) and still obtain similar gloss (e.g. within 10%), colour (e.g. whiteness), opacity and/or scrub resistance characteristics.

Recycled Siliceous Mineral

There is provided herein a recycled siliceous mineral comprising equal to or less than about 0.5 wt% carbon and/or having a L^* whiteness equal to or greater than about 75. The recycled siliceous mineral may, for example, be a dry mineral or may be an aqueous mineral slurry.

A recycled siliceous mineral is a waste siliceous mineral that has been used for one purpose and then processed to make it suitable for use for a further purpose (whether the same or different to the first purpose). A recycled siliceous mineral is not a siliceous mineral that has been obtained from its source. A recycled siliceous mineral is not a siliceous mineral that has been obtained from its source and processed to make it suitable for a first use.

The siliceous mineral prior to recycling may, for example, have been used as a filter. For example, the siliceous mineral prior to recycling may have been used as a filter in liquid/solid separation processes. For example, the siliceous mineral prior to recycling may have been used as a filter in food or beverage production (e.g. water, beer, wine, oil, pectin, sugar, vinegar, alcohol, gelatin), pharmaceutical production, chemical production or oil filtration. The siliceous mineral prior to recycling may, for example, be used to separate components especially particulate matter from solutions, fluids, and fluid suspensions. For example, solid particulate matter from fermentation processes may include cells, cell debris, protein aggregates, and other components that can be separated from the remaining solutions, thus clarifying the solution. The mineral prior to recycling may, for example, be a filter cake. Thus, the recycled siliceous mineral may, for example, be derived or obtained from a filter cake. The term "filter cake" refers to the material through which a product has been filtered and thus comprises both the filter material (i.e. including the siliceous mineral) and any debris that was prevented from passing through the filter material (e.g. particulate matter, organic matter). Where water was removed from the siliceous mineral prior to filtration, the filtration process may re-introduce water to the mineral.

A siliceous mineral is any mineral comprising greater than 50 wt% silica (Si0₂). The siliceous mineral may, for example, be selected from quartz, tridymite, cristobalite, coesite, stishovite, zeolite, diatomaceous earth (DE), perlite and combinations thereof. For example, the siliceous mineral may be DE and/or perlite. For example, the siliceous mineral may be DE.

Diatomaceous earth (also called "DE" or "diatomite") is generally a sediment enriched in biogenic silica (i.e. silica produced or brought about by living organisms) in the form of siliceous skeletons (frustules) of diatoms. Diatoms are a diverse array of microscopic, single-celled, golden-brown algae generally of the class Bacillariophyceae that possess an ornate siliceous skeleton of varied and intricate structures comprising two valves that, in the living diatom, fit together much like a pill box. DE may be obtained from a saltwater or freshwater source. Natural diatomaceous earth is, in general, a sedimentary biogenic silica deposit comprising the fossilized skeletons of diatoms, one-celled algae-like plants that accumulate in marine or fresh water environments. The DE generally has honeycomb silica structures, which may, for example, give DE a useful porous structure that makes it suitable for filtration applications. The DE may thus also have useful characteristics such as high absorptive capacity, high surface area, chemical stability and/or low bulk density.

The DE may, for example, comprise about 80 wt% to about 90 wt% silica. For example, the DE may comprise about 90 wt% silica. The DE may, for example, further comprise various metal oxides, for example selected from one or more of Al, Fe, Ca and Mg oxides. For example, the DE may comprise about 1 wt% to about 5 wt%, for example from about 2 wt% to about 4 wt% alumina (Al₂0₃). For example, the DE may comprise from about 0.1 wt% to about 4 wt%, for example from about 0.5 wt% to about 2 wt% iron oxide.

The DE may, for example, comprise one or more natural impurities such as clay and organic matters. Prior to its first use, the DE may undergo one or more chemical and/or physical modification processes which may, for example, remove one or more natural impurities. Physical modification processes include, for example, milling, drying and classifying. Chemical modification processes include, for example, silanization and calcination. Alternatively, prior to its first use, the DE may be unprocessed following mining or extraction. Perlite is a natural glass, also known as volcanic glass, which is formed by the rapid cooling of siliceous magma or lava. Most natural glasses are chemically equivalent to rhyolite. Natural glasses which are chemically equivalent to trachyte, dacite, andesite, latite, and basalt are known but are less common. The term "obsidian" is generally applied to dark, most often black, massive natural glasses that are rich in silica (i.e.,Si0₂). Obsidian glasses may be classified into subcategories according to their silica content, with rhyolitic obsidians (containing typically about 73% Si0₂ by weight) as the most common (Berry et al., 1983).

Perlite ore is a hydrated natural glass containing typically about 72-75% Si0₂, 12-14% Al₂0₃, 0.5-2% Fe₂0₃, 3-5 % Na₂0, 4-5% K₂0, 0.4-1 .5% CaO (by weight), and small concentrations of other metallic elements. Perlite ore is distinguished from other natural glasses by a higher content (2-10% by weight) of chemically bonded water, the presence of a vitreous, pearly luster, and characteristic concentric or arcuate onion skin-like (i.e., perlitic) fractures. Perlite products may be prepared by methods disclosed herein which may include milling, screening, and thermal expansion. The perlite products can possess commercially valuable physical properties such as high porosity, low bulk density, and chemical inertness. Depending on the quality of the perlite ore and the method of processing, expanded perlite products can be used as filter aids, lightweight insulating materials, filler materials, horticultural and hydroponic media, and chemical carriers.

The processing of perlite can include comminution of the ore (crushing and grinding), screening, thermal expansion, milling, and air size separation of the expanded material to meet the specification of the finished product and other methods known in the art. For example, perlite ore is crushed, ground, and separated to a predetermined particle size range (e.g., passing 30 mesh), then the separated material is heated in air at a temperature of 870-1 l OCO in an expansion furnace (cf. Neuschotz, 1947; Zoradi, 1952), where the simultaneous softening of the glass and vaporization of contained water leads to rapid expansion of glass particles to form a frothy glass material with a bulk volume up to 20 times that of the unexpanded ore. The expanded perlite is then separated to meet the size specification of the final product.

Expanded perlite includes one or more cells, or parts of cells, in which a cell is essentially a void space partially or entirely surrounded by walls of glass, usually formed from expansion of gases when the glass is in a softened state. The presence of gas-filled or vacuous cells in a given volume of glass results in lower centrifuged wet density than for the same volume of solid glass. If cells are closed and air is entrapped, the particles of perlite may float on liquid. Fracturing of perlite, for example, by milling, can create an intricate cellular structure that retains the characteristic of low wet density and also provides useful features for filtration and functional filler applications. The expanded perlite products can be used in a variety of filtration applications. The term "filtration" is used herein in the conventional sense and refers to the removal of particulate matter from a fluid in which the particulate matter is suspended. An exemplary filtration process is one which comprises the step of passing the fluid through a filter aid material supported on a septum (e.g. mesh screen, membrane, or pad). The intricate cellular structure of expanded perlite is particularly effective for the physical entrapment of particles in filtration processes. The perlite products can be applied to a septum to improve clarity and increase flow rate in filtration processes, in a step sometimes referred to as "precoating." Perlite products are also can be added directly to a fluid as it is being filtered to reduce the loading of undesirable particulate at the septum while maintaining a designed liquid flow rate, in a step often referred to as "body feeding". Depending on particular separation involved, the perlite products may be used in precoating, body feeding, or both. The perlite products, especially those which are surface treated, also may provide pre-selected properties during filtration that can further enhance clarification or purification of a fluid.

The recycled siliceous mineral may, for example, have a loss-on-ignition (LOI) equal to or less than about 2.5 wt%. For example, the recycled siliceous mineral may have a LOI equal to or less than about 2.4 wt% or equal to or less than about 2.3 wt% or equal to or less than about 2.2 wt% or equal to or less than about 2.1 wt% or equal to or less than about 2 wt% or equal to or less than about 1 .9 wt% or equal to or less than about 1 .8 wt% or equal to or less than about 1 .7 wt% or equal to or less than about 1 .6 wt% or equal to or less than about 1 .5 wt% or equal to or less than about 1 .4 wt% or equal to or less than about 1 .3 wt% or equal to or less than about 1 .2 wt% or equal to or less than about 1 .1 wt% or equal to or less than about 1 wt% or equal to or less than about 0.9 wt% or equal to or less than about 0.8 wt% or equal to or less than about 0.7 wt% or equal to or less than about 0.6 wt% or equal to or less than about 0.5 wt%. For example, the recycled siliceous mineral may have a LOI ranging from about 0.01 wt% to about 2.5 wt% or from about 0.1 wt% to about 2 wt% or from about 0.2 wt% to about 1 .5 wt% or from about 0.3 wt% to about 1 wt%.

Where the recycled siliceous mineral is DE, the DE may have a LOI ranging from about 1 wt% to about 2.5 wt% or from about 1 .5 wt% to about 2.5 wt% or from about 1 .5 wt% to about 2.3 wt% or from about 1 .8 wt% to about 2.2 wt% or from about 1 .9 wt% to about 2.1 wt%.

Where the recycled siliceous mineral is perlite, the perlite may have a LOI ranging from about 0.1 wt% to about 1 wt% or from about 0.2 wt% to about 0.8 wt% or from about 0.3 wt% to about 0.6 wt% or from about 0.4 wt% to about 0.5 wt%.

Loss-on-ignition is measured by combusting a sample of the mineral until its mass ceases to change and measuring the change in mass of the sample. The recycled siliceous mineral may, for example, comprise equal to or less than about 0.5 wt% carbon. For example, the recycled siliceous mineral may comprise equal to or less than about 0.4 wt% or equal to or less than about 0.3 wt% or equal to or less than about 0.25 wt% or equal to or less than about 0.2 wt% or equal to or less than about 0.1 wt% or equal to or less than about 0.09 wt% or equal to or less than about 0.08 wt% or equal to or less than about 0.07 wt% or equal to or less than about 0.06 wt% or equal to or less than about 0.05 wt% or equal to or less than about 0.04 wt% or equal to or less than about 0.03 wt% carbon. For example, the recycled siliceous mineral may comprise from about 0.001 to about 0.5 wt% carbon or from about 0.01 to about 0.1 wt% carbon.

The wt% carbon in the recycled siliceous mineral may, for example, be determined using a LECO SC-632 Carbon and Sulphur Determinator instrument, which is designed to measure the carbon and sulphur content by combustion and dispersive infra-red detection.

The recycled siliceous mineral may, for example, have a L^* whiteness equal to or greater than about 75. For example, the recycled siliceous mineral may have a L^* whiteness equal to or greater than about 76 or equal to or greater than about 77 or equal to or greater than about 78 or equal to or greater than about 79 or equal to or greater than about 80 or equal to or greater than about 81 or equal to or greater than about 82 or equal to or greater than about 83 or equal to or greater than about 84. For example, the recycled siliceous mineral may have a L^* whiteness up to about 95 or up to about 94 or up to about 93 or up to about 92 or up to about 91 or up to about 90 or up to about 89 or up to about 88 or up to about 87 or up to about 86 or up to about 85. For example, the recycled siliceous mineral may have a L^* whiteness ranging from about 75 to about 95 or from about 75 to about 85 or from about 80 to about 90.

Where the recycled siliceous mineral is DE, the DE may have a L^* whiteness ranging from about 80 to about 90, for example from about 82 to about 88, for example from about 83 to about 97, for example about 84 to about 85. Where the recycled siliceous mineral is perlite, the perlite may have a L^* whiteness ranging from about 75 to about 90, for example from about 75 to about 85, for example from about 78 to about 82, for example about 80 to about 82. The recycled siliceous mineral may, for example, have a b^* yellowness equal to or greater than about 1 . For example, the recycled siliceous mineral may have a b^* yellowness equal to or greater than about 2 or equal to or greater than about 3 or equal to or greater than about 4 or equal to or greater than about 5 or equal to or greater than about 6 or equal to or greater than about 7 or equal to or greater than about 8 or equal to or greater than about 9 or equal to or greater than about 10 or equal to or greater than about 1 1 or equal to or greater than about 12 or equal to or greater than about 13 or equal to or greater than about 14. The recycled siliceous mineral may, for example, have a b^* yellowness ranging from about 1 to about 20 or from about 2 to about 18 or from about 3 to about 17 or from about 4 to about 16.

Where the recycled siliceous mineral is DE, the DE may have a b^* yellowness ranging from about 1 to about 10 or from about 2 to about 8 or from about 3 to about 6 or from about 4 to about 6. For example, the DE may have a b^* yellowness of about 5. Where the recycled siliceous mineral is perlite, the perlite may have a b^* yellowness ranging from about 5 to about 20 or from about 10 to about 20 or from about 12 to about 18 or from about 14 to about 16.

The L^* whiteness and the b^* yellowness index are derived respectively from the white- black axis and blue-yellow axis of the CIE (Commission Internationale d'Eclairage) 1976 colour space diagram. L^* whiteness and b^* yellowness of the siliceous material may be measured using a Datacolor Elrepho 450X spectrophotometer, or instrument of similar capabilities (illuminant D65/10⁰). The recycled siliceous mineral may, for example, have a brightness equal to or greater than about 40 %. For example, the recycled siliceous mineral may have a brightness equal to or greater than about 45 % or equal to or greater than about 50 % or equal to or greater than about 55 % or equal to or greater than about 60 %. For example, the recycled siliceous mineral may have a brightness equal to or less than about 100 % or equal to or less than about 90 % or equal to or less than about 80 %.

Brightness is the percentage of light reflected by a body compared to that reflected by a perfectly reflecting diffuser, measured at a nominal wavelength of 457 nm with a Datacolor Elrepho 450X spectrophotometer, or instrument of similar capabilities. This reflectance value is known as the ISO Brightness.

The recycled siliceous mineral may, for example, have an oil absorbency ranging from about 40 g/100g to about 70 g/100g. For example, the recycled siliceous mineral may have an oil absorbency ranging from about 41 g/100g to about 70 g/100g or from about 42 g/100g to about 70 g/100g or from about 43 g/100g to about 70 g/100g or from about 44 g/100g to about 70 g/100g or from about 45 g/100g to about 70 g/100g. For example, the recycled siliceous mineral may have an oil absorbency ranging from about 40 g/100g to about 65 g/100g or from about 40 g/100g to about 60 g/100g or from about 40 g/100g to about 55 g/100g or from about 40 g/100g to about 50 g/100g. For example, the recycled siliceous mineral may have an oil absorbency ranging from about 50 g/100g to about 70 g/100g or from about 55 g/100g to about 70 g/100g or from about 60 g/100g to about 70 g/100g.

Oil absorbency is measured according to ASTM D281 .

The recycled siliceous mineral may, for example, have a bulk density ranging from about 0.1 g/cm³ to about 1 g/cm³. The recycled siliceous mineral may, for example, have a bulk density ranging from about 0.2 g/cm³ to about 0.9 g/cm³ or from about 0.3 g/cm³ to about 0.8 g/cm³ or from about 0.4 g/cm³ to about 0.7 g/cm³. Bulk density is the mass of the mineral divided by the total volume it occupies.

The recycled siliceous mineral may, for example, have a pH ranging from about 8 to about 1 1 , for example from about 9 to 1 1 . For example, where the recycled siliceous mineral is DE, the DE may have a pH ranging from about 8 to about 10, for example from about 9 to about 10. For example, where the recycled siliceous mineral is perlite, the perlite may have a pH ranging from about 9 to about 10. The recycled siliceous mineral may, for example, have a d₅o ranging from about 10 μηι to about 40 μηι. For example, the recycled siliceous mineral may have a d₅o ranging from about 12 μηι to about 38 μηι or from about 14 μηι to about 36 μηι or from about 16 μηι to about 34 μηι or from about 18 μηι to about 32 μηι or from about 20 μηι to about 30 μηι or or from about 15 μηι to about 25 μηι or from about 20 μηι to about 25 μηι.

The recycled siliceous mineral may, for example, have a d₅o ranging from about 10 μηι to about 15 μηι. For example, the recycled siliceous mineral may have a d₅o ranging from about 1 1 μηι to about 14 μηι or from about 1 1 μηι to about 13 μηι. For example, the recycled siliceous mineral may have a d₅o of about 12 μηι.

The recycled siliceous mineral may, for example, have a d₅o ranging from about 20 μηι to about 40 μηι. For example, the recycled siliceous mineral may have a d₅o ranging from about 25 μηι to about 35 μηι. For example, the recycled siliceous mineral may have a d₅o of about 40 μηι.

The recycled siliceous mineral may, for example, have a d₉o ranging from about 20 μηι to about 70 μηι. For example, the siliceous mineral may have a d₉o ranging from about 25 μηι to about 65 μηι or from about 30 μηι to about 60 μηι or from about 35 μηι to about 55 μηι or from about 40 μηι to about 50 μηι or from about 50 μηι to about 60 μηι.

The recycled siliceous mineral may, for example, have a d₉₀ ranging from about 36 μηι to about 40 μηι. For example, the recycled siliceous mineral may have a d₉₀ ranging from about 36.5 μηι to about 39.5 μηι or from about 37 μηι to about 39 μηι or from about 37.5 μηι to about 38.5 μηι. For example, the recycled siliceous mineral may have a d₉₀ of about 38 μηι.

The recycled siliceous mineral may, for example, have a d₉₀ ranging from about 35 μηι to about 75 μηι. For example, the recycled siliceous mineral may have a d₉₀ ranging from about 35 μηι to about 65 μηι or from about 40 μηι to about 60 μηι or from about 40 μηι to about 50 μηι. For example, the recycled siliceous mineral may have a d₉₀ of about 72 μηι. The recycled siliceous mineral may, for example, have a d₅o ranging from about 1 1 .5 μηι to about 12.5 μηι and a d₉o ranging from about 37.5 μηι to about 38.5 μηι. The recycled siliceous mineral may, for example, have a d₅o ranging from about 1 1 .8 μηι to about 12.2 μηι and a d₉o ranging from about 38 μηι to about 38.5 μηι.

Unless otherwise stated, particle size properties referred to herein for the inorganic particulate materials are as measured by the well-known conventional method employed in the art of laser light scattering, using a CILAS 1064 instrument (or by other methods which give essentially the same result). In the laser light scattering technique, the size of particles in powders, suspensions and emulsions may be measured using the diffraction of a laser beam, based on an application of Fraunhofer theory. Such a machine provides measurements and a plot of the cumulative percentage by volume of particles having a size, referred to in the art as the 'equivalent spherical diameter' (e.s.d), less than given e.s.d values. The d₅o is the value determined in this way of the particle e.s.d at which there are 50% by volume of the particles which have an equivalent spherical diameter less than that d₅o value. The term d₉o is the particle size value less than which there are 90% by volume of the particles.

The recycled siliceous mineral may, for example, have a surface area ranging from about 0.5 m²/g to about 12 m²/g, for example from about 0.5 m²/g to about 1 1 m²/g or from about 1 m²/g to about 9 m²/g or from about 1 m²/g to about 8 m²/g or from about 1 m²/g to about 7 m²/g or from about 1 m²/g to about 6 m²/g or from about 1 m²/g to about 5 m²/g or from about 1 m²/g to about 4 m²/g or from about 1 m²/g to about 3 m²/g or from about 1 m²/g to about 2 m²/g. For example, the recycled siliceous mineral may have a surface area ranging from about 1 .2 m²/g to about 2 m²/g or from about 1 .3 m²/g to about 1 .9 m²/g or from about 1 .4 m²/g to about 1 .8 m²/g. For example, the recycled siliceous mineral may have a surface area ranging from about 1 .5 m²/g to about 2 m²/g or from about 1 .6 m²/g to about 1 .9 m²/g or from about 1 .7 m²/g to about 1 .8 m²/g.

The surface area of the mineral is measured using the BET method by quantity of nitrogen adsorbed on the surface of said particles so as to form a monomolecular layer completely covering said surface (measurement according to the BET method, AFNOR standard X1 1 -621 and 622 or ISO 9277). The recycled siliceous mineral may, for example, result in a paint having one or more of the properties described below.

Compositions Comprising Recycled Siliceous Mineral

There is also provided herein compositions, for example coating and paint compositions comprising a recycled siliceous mineral. The recycled siliceous mineral may, for example, be according to any aspect or embodiment described herein. The coating and paint compositions may, for example, comprise from about 0.5 wt% to about 10 wt% of the recycled siliceous mineral. For example, the coating and paint compositions may comprise from about 1 wt% to about 9 wt% or from about 2 wt% to about 8 wt% or from about 3 wt% to about 7 wt% or from about 3 wt% to about 6 wt% or from about 3 wt% to about 5 wt% of the recycled siliceous mineral. For example, the coating and paint compositions may comprise from about 1 wt% to about 5 wt% or from about 1 wt% to about 3 wt% of the recycled siliceous mineral. For example, the recycled siliceous mineral may be perlite and the coating or paint compositions may comprise from about 1 wt% to about 3 wt% of the siliceous mineral. For example, the recycled siliceous mineral may be DE and the coating or paint compositions may comprise from about 3 wt% to about 5 wt%, for example about 5 wt%, of the siliceous mineral.

In addition to the recycled siliceous mineral, the coating and paint formulations may comprise further components commonly found in coating and paint compositions respectively. For example, the coating and paint compositions may further comprise a pigment. The pigment provides the primary colour of the coating or paint, whether white or a colour shade. The term includes finely ground, natural or synthetic, inorganic or organic, insoluble dispersed particles which, when dispersed in a liquid vehicle, i.e., solvent, may provide, in addition to colour, many of the desired properties of a coating or paint, such as opacity, hardness, durability and corrosion resistance. Suitable pigments include, for example, titanium dioxide, carbon black, calcium sulphate, iron oxide, and the copper-complex phthalo blue. Other suitable pigments for providing colour will be readily apparent to persons skilled in the art. The coating or paint compositions may comprise one or more further additives selected from, for example, rheology modifier, thickener, defoamer or anti-foamer, biocide, pH adjuster (e.g. alkali or alkali earth metal hydroxide), binder, and antifreeze coalescent. Suitable anti-foamers and defoamers include, for example, blends of surfactants, tributyl phosphate, fatty polyoxyethylene esters plus fatty alcohols, fatty acid soaps, silicone emulsions and other silicone containing compositions, waxes and inorganic particulates in mineral oil, blends of emulsified hydrocarbons and other compounds sold commercially to carry out this function.

Suitable biocides include, for example, oxidizing biocides such as chlorine gas, chlorine dioxide gas, sodium hypochlorite, sodium hypobromite, hydrogen, peroxide, peracetic oxide, ammonium bromide/sodium hypochlorite, or non-oxidising biocides such as GLUT (Glutaraldehyde, CAS No 90045-36-6), ISO (CIT/MIT) (Isothiazolinone, CAS No 55956-84-9 & 961 18-96-6), ISO (BIT/MIT) (Isothiazolinone), ISO (BIT) (Isothiazolinone, CAS No 2634-33-5), DBNPA, BNPD (Bronopol), NaOPP, CARBAMATE, THIONE (Dazomet),EDDM - dimethanol (O-formal), HT - Triazine (N-formal), THPS - tetrakis (O-formal), TMAD - diurea (N-formal), metaborate, sodium dodecylbenene sulphonate, thiocyanate, organosulphur, sodium benzoate and other compounds sold commercially for this function.

Suitable rehology modifiers include cellulose-derived rheology modifiers, for example, microfibrillated cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose or a mixture thereof. Suibtale non-cellulose-derived rheology modifiers include one or more of emulsion copolymers, dicyanamide, triols, polyoxyethylene ether, urea, sulphated castor oil, polyvinyl pyrrolidone, sodium alginate, xanthan gum, and sodium silicate.

The paint composition may further include dye. The distinction between powders which are pigments and those which are dyes is generally considered to be on the basis of solubility: pigments being insoluble and dispersed in the material, dyes being soluble or in solution when used. The coating or paint composition, may, for example, have a lower gloss than a coating or paint composition that is identical except it does not comprise the recycled siliceous mineral. For example, the coating or paint composition may have a gloss that is at least about 3 percentage points or at least about 5 percentage points or at least about 10 percentage points or at least about 15 percentage points or at least about 20 percentage points lower than the gloss of a coating or paint composition that is identical except that it does not comprise the recycled siliceous mineral.

The coating or paint composition may, for example, have a similar (e.g. + or - 2 percentage points or + or - 1 percentage point or + or - 0.5 percentage points) gloss to a coating or paint composition that is identical except that it comprises a corresponding non-recycled siliceous mineral in place of the recycled siliceous mineral.

The coating or paint composition may, for example, have a gloss at 85° ranging from about 0.5 % to about 5 %. For example, the coating or paint composition may have a gloss at 85° ranging from about 0.5 % to about 4.5 % or from about 0.5 % to about 4 % or from about 0.5 % to about 3.5 % or from about 0.5 % to about 3 % or from about 0.5 % to about 2.5 % or from about 0.5 % to about 2 % or from about 1 % to about 2 %. Gloss at 85° is measured according to ISO 2813.

The coating or paint composition may, for example, have an opacity that is similar (e.g. + or - 5 percentage points or + or - 2 percentage point or + or - 1 percentage points or + or - 0.5 percentage points) to the opacity of a coating or paint composition that is identical except that it does not comprise the recycled siliceous mineral.

The coating or paint composition may, for example, have an opacity that is similar (e.g. + or - 5 percentage points or + or - 2 percentage point or + or - 1 percentage points or + or - 0.5 percentage points) to the opacity of a coating or paint composition that is identical except that it comprises a corresponding non-recycled siliceous mineral in place of the recycled siliceous mineral.

The coating or paint composition may, for example, have an opacity of at least about 80 % when measured using a wet film thickness of 60 μηι. For example, the coating or paint composition may have an opacity of at least about 82 % or at least about 85 % or at least about 88 % or at least about 90 % or at least about 92 % or at least about 94 % or at least about 95 % or at least about 96 % or at least about 97 % or at least about 98 % or at least about 99 % when measured using a wet film thickness of 60 μηι. For example, the coating or paint composition may have an opacity up to about 100 % when measured using a wet film thickness of 60 μηι.

The coating or paint composition may, for example, have an opacity of at least about 98 % when measured using a wet film thickness of 200 μηι. The coating or paint composition may, for example, have an opacity of at least about 98.5 % or at least about 99 % or at least about 99.5 % when measured using a wet film thickness of 200 μηι. For example, the coating or paint composition may have an opacity up to 100 % when measured using a wet film thickness of 200 μηι. Opacity is measured according to ISO 2814.

The coating or paint composition may, for example, have a L^* whiteness that is similar (e.g. + or - 5 units or + or - 2 units or + or - 1 unit or + or - 0.5 units) to the L^* whiteness of a coating or paint composition that is identical except that it does not comprise the recycled siliceous mineral.

The coating or paint composition may, for example, have a L^* whiteness that is similar (e.g. + or - 5 units or + or - 2 units or + or - 1 units or + or - 0.5 units) to the L^* whiteness of a coating or paint composition that is identical except that it comprises a corresponding non-recycled siliceous mineral in place of the recycled siliceous mineral.

The coating or paint composition may, for example, have a L^* whiteness that is at least about 95. For example, the coating or paint composition may have a L^* whiteness that is at least about 95.5 or at least about 96 or at least about 96.5 or at least about 97.

L^* whiteness is measured according to ISO 7724.

The coating or paint composition may, for example, have a scrub resistance that is similar (e.g. + or - 2 mg/cm² or + or - 1 mg/cm² or + or - 0.5 mg/cm²) to the scrub resistance of a coating or paint composition that is identical except that it does not comprise the recycled siliceous mineral.

The coating or paint composition may, for example, have a scrub resistance that is similar (e.g. + or - 2 mg/cm² or + or - 1 mg/cm² or + or - 0.5 mg/cm²) to the scrub resistance of a coating or paint composition that is identical except that it comprises a corresponding non-recycled siliceous mineral in place of the recycled siliceous mineral.

A corresponding non-recycled siliceous mineral refers to the same siliceous mineral as the recycled siliceous mineral (e.g. if the recycled mineral is perlite, a corresponding non-recycled siliceous mineral is perlite) and has a d₅o that is within 2 μηι (i.e. + or - 2 μηι) of the d₅o of the recycled siliceous mineral.

Method for Recycling a Siliceous Mineral

There is also provided herein a method for recycling a siliceous mineral. The siliceous mineral is a siliceous mineral that has been used for a first purpose (i.e. a used siliceous mineral). The used siliceous mineral is not siliceous mineral that has been obtained from its source. The siliceous mineral may, for example, have been used in a method of filtration, for example as described above. Thus, the siliceous mineral may, for example, be a filter cake.

The method comprises heating the used siliceous mineral to remove water and organic matter. The method may, for example, comprise heating to a first temperature and then heating to a second higher temperature. The method may, for example, comprise heating to a first temperature to remove water and then heating to a second higher temperature to remove organic matter.

The method may, for example, comprise first heating to a temperature of at least about 200°C for a period of time. The method may, for example, comprise first heating a temperature ranging from about 200°C to about 300°C for a period of time. The temperature may, for example, range from about 210°C to about 290°C, for example from about 220°C to about 280°C, for example from about 230°C to about 270°, for example from about 240°C to about 260°C. The period of time may, for example, be at least about 5 minutes or at least about 10 minutes or at least about 15 minutes. The period of time may, for example, range from about 5 minutes to about 60 minutes, for example from about 5 minutes to about 45 minutes, for example from about 5 minutes to about 30 minutes, for example from about 5 minutes to about 20 minutes, for example from about 5 minutes to about 15 minutes, for example from about 10 minutes to about 15 minutes, for example about 15 minutes.

The method may, for example, comprise heating to a temperature (e.g. second temperature) of at least about 600°C for a period of time. The method may, for example, comprise heating to a temperature (e.g. second temperature) ranging from about 600°C to about 1 100°C for a period of time. The temperature may, for example, range from about 600°C to about 900°C or from about 600°C to about 800°C or from about 600°C to about 700°C, or from about 620°C to about 680°C or from about 640°C to about 660°C, for example about 650°C. The temperature may, for example, range from about 800°C to about 1 100°C or from about 900°C to about 1 100°C or from about 950°C to about 1050°C. The period of time may, for example, be at least about 5 hours or at least about 5.5 hours or at least about 6 hours. The period of time may, for example, range from about 5 hours to about 8 hours or from about 5 hours to about 7 hours or from about 5 hours to about 6 hours, for example about 5.5 hours.

Where the siliceous mineral is DE, the method may comprise heating to a temperature (e.g. second temperature) ranging from about 800°C to about 1 100°C or from about 850°C to about 1050°C or from about 900°C to about 1 100°C or from about 950°C to about 1050°C.

Where the siliceous mineral is perlite, the method may comprise heating to a temperature (e.g. second temperature) ranging from about 600°C to about 800°C or from about 600°C to about 750°C or from about 600°C to about 700°C or about 650°C to about 700°C.

The highest temperature at which the siliceous mineral is heated may, for example, be determined by first performing thermogravimetric analysis (TGA) on a sample of the siliceous mineral. The sample of siliceous mineral is heated at a constant rate (e.g. 10°C per minute) and the change in mass over time (and temperature) is determined. The highest temperature at which the siliceous mineral is heated may, for example, be a temperature at which at least about 99 wt% of organic matter is removed. The highest temperature at which the siliceous mineral is heated may, for example, be no more than about 50°C or 40°C or 30°C or 20°C higher than the temperature at which at least about 99 wt% of organic matter is removed.

The used siliceous mineral may, for example, be unprocessed prior to heating. The heating may, for example, be performed in an oven (e.g. a kiln or furnace, e.g. a rotary kiln). The heating may, for example, be performed using microwave-assisted heating.

The method may further comprising milling and/or screening to obtain a desired particle size distribution (e.g. a di₀, d₅o and/or d₉o as defined above).

The recycled siliceous mineral disclosed herein may, for example, be made by the method described herein, including all combinations thereof.

The method may, for example, further comprise combining (e.g. by mixing) appropriate amounts of the recycled siliceous mineral with appropriate amounts of other components of a paint or coating composition to make a paint or coating composition. The coating or paint composition may, for example, further be applied to a substrate.

Uses of Recycled Siliceous Mineral

The recycled siliceous minerals disclosed herein may, for example, be used as a filler in various compositions including, for example, paper, plastics (polymers), rubber, construction materials and coating or paint compositions. The recycled siliceous minerals may, for example, be used as a functional filler in these compositions to affect one or more properties of the composition such as gloss, brightness, whiteness, yellowness, opacity, viscosity and scrub resistance. The recycled siliceous mineral may, for example, be used in a coating or paint composition to obtain a coating or paint composition in accordance with any embodiment described herein. The recycled siliceous minerals may, for example, be used as a filter or in a filtration system. In particular, the recycled siliceous minerals disclosed herein may be used as a filler in paint compositions. The recycled siliceous mineral may, for example, affect the gloss and/or opacity and/or colour (e.g. whiteness) and/or scrub resistance of the paint composition.

For example, the recycled siliceous mineral may be used as a matting agent to decrease the gloss of the paint composition. For example, the recycled siliceous mineral may be used to decrease the gloss of a paint composition in comparison to a paint composition that is identical except that it does not comprise the recycled siliceous mineral. For example, the recycled siliceous mineral may be used to decrease the gloss of a paint composition by at least about 3 percentage points or at least about 5 percentage points or at least about 10 percentage points or at least about 15 percentage points or at least about 20 percentage points in comparison to a paint composition that is identical except that it does not comprise the recycled siliceous mineral.

For example, the recycled siliceous mineral may be used to replace a matting agent present in a paint composition. For example, the recycled siliceous mineral may be used to replace a matting agent present in a paint composition to obtain a paint composition that has a gloss that is similar (e.g. + or - 2 percentage points or + or - 1 percentage point or + or - 0.5 percentage points) to the gloss of the paint composition with the original matting agent. For example, the recycled siliceous mineral may be used to replace a corresponding non-recycled siliceous mineral in a paint composition to obtain a paint composition that has a gloss that is similar (e.g. + or - 2 percentage points or + or - 1 percentage point or + or - 0.5 percentage points) to the gloss of the paint composition comprising the corresponding non-recycled siliceous mineral.

For example, the recycled siliceous mineral may be used to provide a paint composition with a gloss at 85° ranging from about 0.5 % to about 5 %. For example, the recycled siliceous mineral may be used to provide a paint composition with a gloss at 85° ranging from about 0.5 % to about 4.5 % or from about 0.5 % to about 4 % or from about 0.5 % to about 3.5 % or from about 0.5 % to about 3 % or from about 0.5 % to about 2.5 % or from about 0.5 % to about 2 % or from about 1 % to about 2 %. For example, use of the recycled siliceous mineral in a paint composition may not significantly affect the opacity of the paint composition. For example, use of the recycled siliceous mineral in a paint composition may not change the opacity of the paint composition by more than about 5 percentage points (i.e. + or - 5 percentage points) or by more than about 2 percentage points or by more than about 1 percentage point or by more than about 0.5 percentage points in comparison to a paint composition that is identical except that it does not comprise the recycled siliceous mineral.

For example, use of the recycled siliceous mineral to replace another matting agent (e.g. a corresponding non-recycled siliceous mineral) in a paint composition may not significantly affect the opacity of the paint composition. For example, use of the recycled siliceous mineral in a paint composition to replace another matting agent (e.g. a corresponding non-recycled siliceous mineral) may not change the opacity of the paint composition by more than about 5 percentage points (i.e. + or - 5 percentage points) or by more than about 2 percentage points or by more than about 1 percentage point or by more than about 0.5 percentage points in comparison to a paint composition that is identical except that it comprises a corresponding non-recycled siliceous mineral in place of the recycled siliceous mineral. For example, use of the recycled siliceous mineral in a paint composition may provide a paint composition having an opacity of at least about 80 % when measured using a wet film thickness of 60 μηι. For example, use of the recycled siliceous mineral in a paint composition may provide a paint composition having an opacity of at least about 82 % or at least about 85 % or at least about 88 % or at least about 90 % or at least about 92 % or at least about 94 % or at least about 95 % or at least about 96 % or at least about 97 % or at least about 98 % or at least about 99 % when measured using a wet film thickness of 60 μηι. For example, the coating or paint composition may have an opacity up to about 100 % when measured using a wet film thickness of 60 μηι. For example, use of the recycled siliceous mineral in a paint composition may provide a paint composition having an opacity of at least about 98 % when measured using a wet film thickness of 200 μηι. For example, use of the recycled siliceous mineral in a paint composition may provide a paint composition having an opacity of at least about 98.5 % or at least about 99 % or at least about 99.5 % when measured using a wet film thickness of 200 μηι. For example, the coating or paint composition may have an opacity up to about 100 % when measured using a wet film thickness of 200 μηι.

Opacity is measured according to ISO 2814. For example, use of the recycled siliceous mineral in a paint composition may not significantly affect the L^* whiteness of the paint composition. For example, use of the recycled siliceous mineral in a paint composition may provide a paint composition that has a similar L^* whiteness (e.g. + or - 5 units or + or - 2 units or + or - 1 unit or + or - 0.5 units) to the L^* whiteness of a coating or paint composition that is identical except that it does not comprise the recycled siliceous mineral.

For example, use of a recycled siliceous mineral to replace another matting agent (e.g. a corresponding non-recycled siliceous mineral) in a paint composition may provide a paint composition that has a similar L^* whiteness (e.g. + or - 5 units or + or - 2 units or + or - 1 unit or + or - 0.5 units) to the L^* whiteness of a coating or paint composition that is identical except that it comprises the other matting agent (e.g. a corresponding non-recycled siliceous mineral).

For example, use of a recycled siliceous mineral in a paint composition may provide a paint composition having a L^* whiteness of at least about 95. For example, use of a recycled siliceous mineral in a paint composition may provide a paint composition having a L^* whiteness of at least about 95.5 or at least about 96 or at least about 96.5 or at least about 97. For example, use of the recycled siliceous mineral in a paint composition may not significantly affect the scrub resistance of the paint composition. For example, use of the recycled siliceous mineral in a paint composition may not change the scrub resistance of a paint composition by more than 2 mg/cm² (i.e. + or - 2 mg/cm²) or by more than 1 mg/cm² or by more than 0.5 mg/cm² in comparison to a paint composition that is identical except that it does not comprise the recycled siliceous mineral.

For example, use of the recycled siliceous mineral to replace another matting agent (e.g. a corresponding non-recycled siliceous mineral) in a paint composition may provide a paint composition that has a similar scrub resistance (e.g. + or - 2 mg/cm² or + or - 1 mg/cm² or + or - 0.5 mg/cm²) to the scrub resistance of a coating or paint composition that is identical except that it comprises the other matting agent (e.g. a corresponding non-recycled siliceous mineral). EXAMPLES

Example 1

A diatomaceous earth (DE) filter cake and a perlite filter cake were used to prepare recycled siliceous mineral for use in paint.

Thermogravimetric analysis (TGA) was carried out on a sample of each filter cake to find the optimum temperature for recycling. During TGA, the samples were heated to 1000°C at 10°C per minute in an air atmosphere and the weight loss of each sample was recorded with time. Table 1 shows the change in mass within particular temperature ranges for the DE filter cake. Table 2 shows the change in mass within particular temperature ranges for the perlite filter cake.

Table 1.

Table 2.

It was decided to heat the DE filter cake to 1000°C and the perlite filter cake to 650°C. The untreated filter cakes were heated in conductive ceramic containers in a kiln having 4 universal burners (2 on each side) which fire horizontally under the load. The burner positions are alternated to provide uniform heat distribution. The kiln was programmed to ramp up to 300°C initially, then dwell for 15 minutes and then ramp up again to target temperature (1000°C for DE and 650°C for perlite) at 10°C per minute and maintain the target temperature for 6 hours (DE) or 5 hours (perlite). After the specified duration, the kiln was turned off and allowed to cool to ambient temperature.

The products were characterised as shown below. Apparent density is the mass of a dried powder divided by its volume using water as a displacing medium. VIO, YEL, L^*, A^* and B^* were measured using a Datacolor EIrepho 450X spectrophotometer as described above for L^* and b^*. Scrub resistance is measured according to BS 7719.

Table 3.

Table 4.

AI2O3 Si0₂ K₂0 Fe₂0₃ Ti0₂ CaO MgO Na₂0 LOI

Recycled DE XRF Analysis

2.7 83.78 0.42 1 .42 0.35 5.31 0.41 3.07 2.05 Table 5.

Table 6.

The milled/screened recycled minerals described in Tables 3 and 5 above were incorporated into a paint composition. Control paint compositions comprising a non- recycled perlite or DE having the characteristics shown in Table 7 below were also prepared. The formulation of the paint is shown in Table 8 below. The paint compositions had a pigment volume concentration (PVC) of 75 %. The paint incorporating recycled perlite was screened at 90 μηι prior to testing. Since the screened recycled perlite product has only approximately 2 vol% of particles larger than 90 μηι, the screening of the paint only removes about 2 % of the large particles. The predicted d₉₀ of the screened paint is about 70 μηι and the predicted d₅o is about 39 μηι. Table 7.

Table 8.

Wt%

Tioxide TR92 10

Perlite or DE 3

Calcium Carbonate 27

Dispex N40 0.35

10% Calgon S 0.5

Ammonia 0.15

Natrosol 250 MR 0.36

Acticide MBS 0.1

Nopco NDW 0.2

Propylene Glycol 1

Water 38.44

Ropaque Ultra E 5

Texanol 1 .4

Acronal S790 1 1 .5

Acrysol TT935 : Water 1 : 2 1

Total 100.0 Opacity, scrub resistance, L^*, b^*, a^* and gloss at 20°, 60° and 85° of the paint compositions was determined. The results are shown in Table 9 below.

Table 9.

Example 2

Samples of the screened recycled perlite used in Example 1 above were jet milled by hand-feeding the material into a TROST Air Impact Pulveriser (Jet Mill - Model TX 41585) using the pressure setting specified below and different feed rates. Table 10 shows the particle size distributions obtained. It was found that the material can be milled to provide different d₅o values depending on the conditions used. Table 10.

Pressure

Material Processina Settina dm (urn) dsn (urn) dsn (urn)

(DSl)

Screened

- 14 40 72 <250 μηι

Jet Milled 20/10 8 27 47

Jet Milled,

Higher Feed 20/10 11 32 62

Perlite

Rate

Jet Milled,

Higher Feed 30/10 8 25 45 Rate

Jet Milled 30/10 7 21 38

The following numbered paragraphs define particular embodiments of the present invention:

1 .A recycled siliceous mineral:

comprising equal to or less than about 0.5 wt% carbon; and/or having a L^* whiteness equal to or greater than about 75.

2. The recycled siliceous mineral of paragraph 1 , wherein the recycled siliceous mineral comprises equal to or less than about 0.1 wt% carbon.

3. The recycled siliceous mineral of paragraph 1 or 2, wherein the recycled siliceous mineral has a L^* whiteness equal to or greater than about 80.

4. The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral has a b^* yellowness equal to or greater than about 1 or equal to or greater than about 2 or equal to or greater than about 10.

5. The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral has an oil absorbency ranging from about 40 g/100g to about 70 g/1 OOg, for example from about 45 g/1 OOg to about 70 g/1 OOg.

6. The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral has a d₅o ranging from about 10 μηι to about 40 μηι. 7. The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral has a d₉o ranging from about 20 μηι to about 70 μηι.

8. The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral has a bulk density ranging from about 0.1 g/cm³ to about 1 g/cm³, for example from about 0.2 g/cm³ to about 0.6 g/cm³.

9. The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral has a pH ranging from about 8 to about 1 1 . 10. The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral is diatomaceous earth (DE) or perlite. 1 1 . The recycled siliceous mineral of any preceding paragraph, wherein the recycled siliceous mineral is derived from a filter cake.

12. A method for recycling a siliceous mineral, the method comprising heating a used siliceous mineral to remove water and organic matter.

13. The method of paragraph 12, wherein the method comprises heating to a first temperature to remove water from the used siliceous mineral and then heating to a second higher temperature to remove organic matter from the used siliceous mineral.

14. The method of paragraph 12 or 13, wherein the method comprises:

first heating the used siliceous mineral to a temperature ranging from about 200°C to about 300°C and maintaining a temperature within this range for a period of time; and

then heating the used siliceous mineral to a temperature ranging from about 600°C to about 1 100°C and maintaining a temperature within this range for a period of time. 15. The method of paragraph 14, wherein the siliceous mineral is maintained at a temperature ranging from about 200°C to about 300°C for a period of time ranging from about 5 minutes to about 60 minutes.

16. The method of paragraph 14 or 15, wherein the siliceous mineral is maintained at a temperature ranging from about 600°C to about 1 100°C for a period of time ranging from about 4 hours to about 7 hours, for example from about 5 hours to about 6 hours.

17. The method of any one of paragraphs 12 to 16, wherein the method further comprises milling or screening the recycled siliceous mineral.

18. The method of any one of paragraphs 12 to 17, wherein the used siliceous mineral is not treated prior to heating. 19. The method of any one of paragraphs 14 to 18, wherein the temperature ranging from about 600°C to about 1000°C that the used siliceous mineral is heated to is determined by performing thermogravimetric analysis on a sample of the used siliceous mineral and heating to a temperature at which at least 99 wt% of the organic matter is removed. 20. The method of any one of paragraphs 12 to 19, wherein the heating is carried out using microwave assisted heating.

21 . The method of any one of paragraphs 12 to 20, wherein the used siliceous mineral is diatomaceous earth (DE) or perlite.

22. The method of any one of paragraphs 12 to 21 , wherein used siliceous mineral is derived from a filter cake.

23. The method of any one of paragraphs 12 to 22, wherein the used siliceous mineral is DE and the used siliceous mineral is heated to a temperature ranging from about 900°C to about 1 100°C, for example about 1000°C.

24. The method of paragraph 23, wherein the used siliceous mineral is DE and the used siliceous mineral is heated to a temperature ranging from about 900°C to about 1 100°C, for example about 1000°C, for a period of time ranging from about 5 hours to about 6 hours.

25. The method of any one of paragraphs 12 to 22, wherein the used siliceous mineral is perlite and the used siliceous mineral is heated to a temperature ranging from about 600°C to about 700°C, for example about 650°C.

26. The method of paragraph 25, wherein the used siliceous mineral is perlite and the used siliceous mineral is heated to a temperature ranging from about 600°C to about 700°C, for example about 650°C, for a period of time ranging from about 5 hours to about 6 hours.

27. The method of any one of paragraphs 12 to 26, wherein the recycled siliceous mineral is according to any one of paragraphs 1 to 1 1 . 28. A recycled siliceous mineral made by the method of any one of paragraphs 12 to 27. A paint composition comprising a recycled siliceous mineral. The paint composition of paragraph 29, wherein the recycled siliceous mineral is according to any one of paragraph 1 to 1 1 or is made by the method of any one of paragraphs 12 to 27. The paint composition of paragraph 29 or 30, wherein the paint composition has a gloss at 85° ranging from about 0.5 % to about 5 %. The paint composition of any one of paragraphs 29 to 31 , wherein the paint composition has a L^* whiteness equal to or greater than about 95. The paint composition of any one of paragraphs 29 to 32, wherein the paint composition has an opacity of at least about 80 % when measured using a wet film thickness of 60 μηι. Use of a recycled siliceous mineral as a functional filler. Use of a recycled siliceous mineral as a filler in a paint composition. Use of a recycled siliceous mineral to decrease the gloss of a paint composition. The use of any one of paragraphs 34 to 36, wherein the recycled siliceous mineral is according to any one of paragraphs 1 to 1 1 or is made by the method of any one of paragraphs 12 to 27.

Claims

1 .A recycled siliceous mineral:

comprising equal to or less than about 0.5 wt% carbon; and/or having a L^* whiteness equal to or greater than about 75;

wherein the recycled siliceous mineral is recycled diatomaceous earth and/or recycled perlite.

2. The recycled siliceous mineral of claim 1 , wherein the recycled siliceous mineral is derived from a filter cake.

3. The recycled siliceous mineral of any preceding claim, wherein the recycled siliceous mineral comprises equal to or less than about 0.1 wt% carbon.

4. The recycled siliceous mineral of any preceding claim, wherein the recycled siliceous mineral: a) has a L^* whiteness equal to or greater than about 80; and/or b) has a b^* yellowness equal to or greater than about 1 or equal to or greater than about 2 or equal to or greater than about 10; and/or c) has an oil absorbency ranging from about 40 g/100g to about 70 g/100g, for example from about 45 g/100g to about 70 g/100g; and/or d) has a d₅o ranging from about 10 μηι to about 40 μηι; and/or e) has a d₉o ranging from about 20 μηι to about 70 μηι; and/or f) has a bulk density ranging from about 0.1 g/cm³ to about 1 g/cm³, for example from about 0.2 g/cm³ to about 0.6 g/cm³; and/or g) has a pH ranging from about 8 to about 1 1 .

5. A method for recycling a siliceous mineral, the method comprising heating a used siliceous mineral to remove water and organic matter, wherein the used siliceous mineral is a used diatomaceous earth and/or used perlite.

6. The method of claim 5, wherein the method comprises heating to a first temperature to remove water from the used siliceous mineral and then heating to a second higher temperature to remove organic matter from the used siliceous mineral.

7. The method of claim 5 or 6, wherein the method comprises:

first heating the used siliceous mineral to a temperature ranging from about 200°C to about 300°C and maintaining a temperature within this range for a period of time, for example ranging from about 5 minutes to about 60 minutes; and

then heating the used siliceous mineral to a temperature ranging from about 600°C to about 1 100°C and maintaining a temperature within this range for a period of time, for example from about 4 hours to about 7 hours, for example from about 5 hours to about 6 hours.

8. The method of any one of claims 5 to 7, wherein the method further comprises milling or screening the recycled siliceous mineral.

9. The method of any one of claims 5 to 8, wherein the used siliceous mineral is not treated prior to heating.

10. The method of any one of claims 5 to 9, wherein used siliceous mineral is derived from a filter cake.

1 1 . The method of any one of claims 5 to 10, wherein the recycled siliceous mineral is according to any one of claims 1 to 4.

12. A recycled siliceous mineral made by the method of any one of claims 5 to 1 1 .

13. A paint composition comprising a recycled siliceous mineral, for example wherein the recycled siliceous mineral is according to any one of claims 1 to 4 or is made by the method of any one of claims 5 to 12.

14. The paint composition of claim 13, wherein the paint composition a) has a gloss at 85° ranging from about 0.5 % to about 5 %; and/or b) has a L^* whiteness equal to or greater than about 95; and/or c) has an opacity of at least about 80 % when measured using a wet film thickness of 60 μηι.

15. Use of a recycled siliceous mineral as a filler, for example as a filler in a paint