Recycling pigments from textile

Abstract

The present disclosure is directed to methods producing microparticle pigments from coloured waste textiles. The method comprises the processing of the waste textiles to produce textile snippets which can subsequently be missed with water to produce a textile snippet-water slurry which is further processed to obtain the microparticle pigments in water. The present disclosure is further directed to microparticle pigments comprising recycled textiles and products, such as dyes, produced using the microparticle pigments.

Description

Recycling pigments from textileTechnical Field

[0001] The present invention relates to producing microparticle pigments from coloured waste textiles.Background

[0002] Recycling waste textiles is essential for addressing the growing environmental and resource challenges posed by the fast fashion and large volumes produce by the textile industries. As the demand for clothing and textiles continues to rise, so does the volume of waste generated, much of which ends up in landfills or incinerators, contributing to pollution and greenhouse gas emissions. Recycling textiles not only reduces the strain on natural resources by conserving raw materials like water, energy, and fossil fuels but also minimizes the environmental impact by diverting waste from landfills. Moreover, using textile wastes can be transformed into new products, creating a circular economy that supports sustainability. Embracing textile recycling and repurposing is crucial for reducing waste, lowering carbon footprints, and promoting a more responsible and eco-friendly approach to consumption and production.

[0003] The traditional manufacture of colour (dyes and pigments) poses significant environmental risks due to the extensive use of toxic chemicals and large volumes of water in the dyeing process. Most synthetic dyes are derived from petrochemicals and contain hazardous substances like heavy metals and aromatic compounds, which can leach into soil and water systems, causing contamination and harm to aquatic life. Additionally, the dyeing process often requires large amounts of water, which, when discharged as wastewater, carries these pollutants into rivers and oceans, leading to water pollution and disruption of local ecosystems. The energy-intensive nature of colour production also contributes to carbon emissions, exacerbating climate change. The environmental footprint of traditional colour manufacturing highlights the urgent need for more sustainable practices, such as the development of eco- friendly dyes, improved wastewater treatment, and innovations in dyeing techniques that reduce resource consumption and pollution.

[0004] Efforts to recycle textiles and repurpose them into pigments have shown promise in reducing environmental impact while offering economic benefits. By converting colouredwaste textiles into pigments, the need for virgin raw materials is diminished, which in turn conserves resources and reduces the environmental burden associated with colour production and disposal. These recycled pigments can be used not only for re-colouring textiles but also in a variety of other industries, including printing packaging, in art and craft colour, as coloured fillers in various materials and providing coloured coatings. This cross-sector application extends the life cycle of textiles and minimizes waste, promoting a circular economy. Economically, the process creates new revenue streams from materials that would otherwise be discarded, reducing costs for manufacturers and fostering innovation in sustainable product development. Moreover, by decreasing reliance on traditional dyeing methods, which are often resource-intensive and polluting, the use of recycled pigments contributes to a reduction in water and energy consumption, as well as a lower carbon footprint. This approach supports both environmental sustainability and economic growth, aligning with broader goals of reducing industrial waste and promoting responsible consumption.

[0005] Attempts in this field have included the work through WO2017 / 072718A1, which discloses a process of recycling waste textile to produce a dye suitable for dyeing and printing. This document further discloses it can produce dye powders with a Dv90 ranging from 100 to 150 micrometers. Dye particles are usually in the range of less than 1 nm and soluble in water or dispersed in water in colloidal form as in the case of disperse dyes. In the case of pigments, particles are sub-micron or few micrometers and this size range ensures they can disperse well on fibre surface, and do not separate during storage and during applications pass through screens in the case of screen printing or do not block nozzles during digital printing. It would not be possible or technically viable for pigment particles above 100 microns to achieve a good result for printing, and dyeing is not practical if not dissolved in water or solvent. It is not clear whether the dye produced is soluble or not or requires additional pre-treatment or posttreatment and any of those required for application and fixation are environment friendly or not. In addition, this method requires the use of chemicals by applying a reactive substance to the textile fibres to make the textile fibres more fragile to produce pigments, wherein the reactive substance comprises colloidal silicic acid. While applying a reactive substance like colloidal silicic acid to textile fibres can be effective in making the fibres more fragile for recycling purposes, this method appears to have some drawbacks. One concern is that colloidal silicic acid, while useful in breaking down fibres, can be difficult to handle and control during the process, potentially leading to inconsistent results. Additionally, there are environmental and health considerations to take into account. If not properly managed, colloidal silicic acidcould pose risks, such as exposure to fine particles that could be harmful if inhaled which might lead to the risks of developing serious silica-related diseases in the workforce, such as: silicosis, lung cancer, chronic obstructive pulmonary disease, etc.. Moreover, the chemical treatment could generate waste or byproducts that require careful disposal to avoid environmental contamination. In addition to that, chemical process often requires heat treatment which is not energy efficient or change the colour of textiles and pigments produced from such textiles. A similar attempt is also found in CN 109811558 B, which also requires chemical treatment of the fibres. These challenges highlight the need for careful consideration and management when using any chemical based reactive substances in textile recycling processes.

[0006] Although there have been applications of using radiation such as electron beam to treat biomass, these target different applications such as converting or breaking down the original fibres into low molecular weight sugars such as in US 8,877,472 B2. Attempts have also been made to use high energy electro-beam radiation to treat pure cellulose and to create micro-nano size cellulose particles (CN 104294693 A). However, this document applies electro-beam radiation directly to cellulose rather than coloured textiles and focuses solely on the end particle size and structure. As a result, it does not take into account the colour change, which is crucial in pigment generation and manufacture.

[0007] With this in mind, the present disclosure seeks to mitigate at least one or more of the problems above, as well as providing an alternative textile recycling process with improved properties for industrial application. In addition, the present disclosure, in part, also seeks to provide an alternative method to produce pigments that may overcome some of the disadvantages associated with the known methods described above.

[0008] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.SummaryGeneral terms

[0009] In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments. It is understood that other embodiments may be utilised and structural changes may be made without departing from the scope of the present disclosure.

[0010] With regards to the definitions provided herein, unless stated otherwise, or implicit from context, the defined terms and phrases include the provided meanings. Unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired by a person skilled in the relevant art. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Furthermore, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[0011] All publications discussed and / or referenced herein are incorporated herein in their entirety.

[0012] Throughout this disclosure, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e., one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. For example, reference to “a” includes a single as well as two or more; reference to “an” includes a single as well as two or more; reference to “the” includes a single as well as two or more and so forth.

[0013] Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the examples, steps, features, methods, compositions, coatings, processes, and coated substrates, referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features.

[0014] The term “and / or”, e.g., “X and / or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning.

[0015] As used herein, the phrase “at least one of’, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of’ means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, and without limitation, “at least one of item A, item B, and item C” may mean item A; item B; item C; item A and item B; item A and item C; item B and item C; item A, item B, and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example and without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

[0016] As used herein, the term “about”, unless stated to the contrary, typically refers to + / - 10%, for example + / - 5%, of the designated value.

[0017] Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to a “second” item does not require or preclude the existence of lower-numbered item (e.g., a “first” item) and / or a higher-numbered item (e.g., a “third” item).

[0018] It is to be appreciated that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination.

[0019] Throughout the present specification, various aspects and components of the invention can be presented in a range format. The range format is included for convenience and should not be interpreted as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range, unless specifically indicated. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 5, from 3 to 5 etc., as well as individual and partial numbers within the recited range, for example, 1, 2, 3, 4, 4.5 or 5, unless where integers are required or implicit from context.This applies regardless of the breadth of the disclosed range. Where specific values are required, these will be indicated in the specification.

[0020] Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The phrase “consisting of’ means the enumerated elements and no others.

[0021] The phrase “substantially consists of’, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%.

[0022] The reference to “substantially free” generally refers to the absence of that compound or component in the composition other than any trace amounts or impurities that may be present, for example this may be an amount by volume % in the total composition of less than about 3%, 2% 1%, 0.1%, 0.01%, 0.001%, or 0.0001%.

[0023] Throughout the document, the terms ‘pigment’ includes pigment with dye containing inside the fibre particles.

[0024] Throughout the document, the terms ‘textile’ and ‘fabric’ are used interchangeably and may be considered synonymous in meaning.

[0025] Throughout the document, the terms ‘textile’ and ‘waste textile’ and ‘recycled textile’ are used interchangeably and may be considered synonymous in meaning.Method, Process and the Product

[0026] An object of the invention is to provide a method to produce a pigment from waste textiles. The pigment produced contains a dye inside fibre particles. Traditionally, it is normally not possible to use pigments for dyeing as dyes are much smaller, dissolve in water and can therefore penetrate inside fibre whereas traditional pigments are larger in size and sit on fibre surface and can only bound by a binder. However, pigments produced by this invention are unlike traditional pigments. Pigments produced by this invention contain a dye inside the fibre particle and do not come out during particle fabrication stage or after application but as thesepigment particles are small enough to be used in printing process such screen printing and form a stable ink without separation during storage and application.

[0027] According to one aspect of the present invention, there is provided a process of producing pigments from textiles or waste textiles, the process comprising: cutting and / or shredding the textiles into textile snippets; mixing the textile snippets with water to produce a textile snippet-water slurry; milling the textile snippet-water slurry to produce a microparticle pigment-water mixture.

[0028] Preferably, the process of recycling waste textiles further comprises applying a radiation treatment to the waste textiles prior to cutting and / or shredding the waste textiles into textile snippets;

[0029] Preferably, the process of converting waste textiles to pigments further comprises applying a radiation treatment to the textiles before or after the cutting, or before or after shredding the waste textile into textile snippets, or any time prior to the milling.

[0030] Preferably, the radiation treatment is Gamma treatment. More preferably, the applied dose of Gamma treatment is up to 250 kGy. In particular, the dose of Gamma treatment applied to the waste textile is in the range of 25-500 kGy, or preferably 50-400 kGy, or preferably 50- 300 kGy, or more preferably 50-250 kGy, or more preferably 75-250 kGy.

[0031] Preferably, the radiation treatment is Electron beam. More preferably, the applied dose of Electron beam is 250 kGy. In particular, the dose of Electron beam treatment applied to the waste textile is in the range of 25-500 kGy, or preferably 50-400 kGy, or preferably 50-300 kGy, or more preferably 50-250 kGy, or more preferably 75-250 kGy.

[0032] Preferably, the textiles are first cut into small pieces prior to be fed into the cutting mill or a granulator. More preferably, the coloured textiles are first cut into small pieces in a shape with a length around 10 mm, or around 20 mm, or around 30 mm, or around 40 mm, or around 50 mm, or around 60 mm, or around 70 mm, or around 80 mm, or around 80 mm, or around 90 mm, or around 100 mm, Preferably, the textiles are cut into small pieces in a shape with a width similar to its length and in the range of 10 mm, or around 20 mm, or around 30 mm, or around 40 mm, or around 50 mm, or around 60 mm, or around 70 mm, or around 80 mm, or around 90 mm, or around 100 mm, Alternatively, the textiles can also be cut into smallpieces in a shape with a width slightly shorter than its length, for example, 5 mm shorter than the length, or 10 mm shorter than the length, or 15 mm shorter than the length, or 20 mm shorter than the length, or 30 mm shorter than the length, or 40 mm shorter than the length, or 50 mm shorter than the length. Preferably, the textiles are cut into 20-50 mm square or in the vicinity of this size range and shape, or more preferably, the textiles were cut into 30-40 mm square or in the vicinity of this size range and shape.

[0033] Preferably, the textiles are first cut into small pieces into a shape of square, a rectangle, a circle, an ellipse, or any other random shapes.

[0034] Preferably, the process comprises cutting the textile into textile snippets or fragments in a size range of 0.25-6 mm length fibres, more preferably 0.5-4 mm, or more preferably 0.5- 2 mm, or more preferably 1-2 mm. This step maybe done either in a cutter mill or granulator with grid to allow pieces smaller than size of grid like 1 mm, 2mm to pass through.

[0035] Preferably, resulting textile snippets are mixed with water with a ratio in the range of 200 gram of textile snippets per 1 L water. More preferably, the ratio of mixture of textile snippets and water might be selected from any one of the following ranges: 1:5, 1:7.5, 1: 10, 1: 15, 1 :20, 1:25. Preferably, to a mixture with ratio between snippets and water of 1:7.5 to 1: 15.

[0036] The mixture of textile snippets and water, or the pigment-water slurry, is then fed into a milling machine to be milled into textile particles, or pigment-water mixture with finer pigment particles. Preferably, the milling machine is ball mill, a stirred media mill, a sand mill, or any other mill that are suitable for milling the mixture.

[0037] Preferably, milling includes the use of a media mill, more specifically a stirred media mill.

[0038] Preferably, depending on the model of the mills that are available in the market, without any prior pre-treatment, the milling time applied to mill the snippet-water slurry into pigment-water mixture is preferably 0.5-6 hours, 1-6 hours, 1-5 hours, 1-4 hours, 1-3 hours, or more preferably around 0.5 hour, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, ...etc., depending on the different materials and particle size requirement.

[0039] With radiation pre-treatment, and depending on the mills that are available in the market, the milling time applied to mill the snippet-water slurry into micrometre pigment-watermixture can be greatly reduced. Preferably the milling time can be reduced to 0.5-4 hours, 0.5- 3 hours, 0.5-2 hours, 0.5-1 hour, or more preferably, around 0.2 hour, 0.5 hour, 1 hour, 1.5 hours, 2 hours, 3 hours or 4 hours to achieve the same or similar result as above to the process without radiation treatment.

[0040] Another parameter that might be considered and used in a stirred media mill is the selection of ball size as well as the media used in the mill. Various of media can be used but preferably ceramic media and more specifically zirconia media can achieve better results. Preferably, a 2-10 mm ball, or more preferably a 4-6 mm ball can be used during the milling.

[0041] By milling the snippet-water slurry, the formed pigment particles are almost spherical which is a big advantage for subsequent printing as well as other applications as cohesiveness and flow properties are significantly different compared to dry milled particles. This approach also ensures control of particle shape and improve particle flow and dispersion to enable efficient printing and diverse applications including applications other than the printing and dying on textiles.

[0042] Depending on the end use or application, the resultant microparticle pigment-water mixture may be further processed.

[0043] To obtain wet pigment microparticles, vacuum filtration might be used. By applying vacuum filtration, the textile particles would present in the form of a “paste” that can be used for water-based medium and applications as pigments. Optionally, centrifuge including continuous centrifuge or decanting can also be used to separate most of the water from the pigments. If drier powder or drier pigments are to be obtained through this method, then the paste can be further dried through a drier followed by dry mill via any known process in the art.

[0044] For obtaining dry pigment powders of sphere-like morphology, spray-drying may also be used to spray-dry the mixture directly without removing excess of water. By applying spraydrying, the textile particles would be in a “powder” form for use in water based or non-water- based applications as pigments. Optionally, a filtering step might be used prior to spray-drying to remove or further disperse any lumps or agglomerates.

[0045] Pigments produced, depending on the milling time, are measured with a Dv50 in the range of 1-30 microns, typically 1-20 microns, more typically 5-10 microns and more typically 5-8 microns. Dv90 are measured in the range of 10-50 microns and more typically 15-20microns. 10% are finer particles which are between 0.5-5 microns, and typically 1 micron. To avoid any doubt, all measurements are volume-based distribution. Size distribution is critical for printing as particles are required to pass through the screen. Generally, it requires the particles to be in the range below 50 microns or much lower for quality printing including screen printing. It is clear the pigments produced by the method disclosed in this invention fall right within in this range.

[0046] Microparticle pigments produced by above method and process would have dyes contained inside. These microparticle pigments, unlike traditional pigments that require binder to be bound to fibres, are small enough to disperse well into fibre for fabric printing or pigment dyeing processes.

[0047] According to a further aspect of the present invention, there is provided a process of deriving pigments from textiles or waste textile, the process comprising: sorting the textiles into groups of textiles with similar colours; cutting or shredding the textiles into textile-snippets; mixing the textile -snippets with water to produce textile snippet-slurry; milling the textile snippet-water slurry to produce a microparticle pigment-water mixture; applying a radiation treatment to the textile at any step prior to the milling.

[0048] Preferably, sorting the textiles involves grouping textiles according to fibre types, blend types, similar colour range, as well as the colour depth such like light, medium and dark. These powders then after pigment formation can be mixed to decide the desired depth and shade of the pigments.

[0049] Similar approaches and settings are to be applied to steps involving cutting, shredding, milling, radiation and drying as discussed above.

[0050] Most importantly, the microparticle pigments produced containing dyes from the original textile and are small enough to form a stable printing ink for storage and application for direct printing on fibrous materials such as textiles, fabrics, papers and the like, such as screen printing. These microparticle pigments also make some other applications possible, for example, when use for coating such as knife coating or use as fillers for coloured products made from plastics, polymers, rubbers, etc., where it’s possible to mix with a traditional binderfor being used as paint or ink applied on varied materials other than textiles or other fibrous materials.

[0051] Microparticle pigments produced, depending on the milling time, are measured with a Dv50 in the range of 1-30 microns, typically 1-20 microns, more typically 5-10 microns and more typically 5-8 microns. Dv90 are measured in the range of 10-50 microns and more typically 15-20 microns. 10% are finer particles which are between 0.5-5 microns, and typically 1 micron. To avoid any doubt, all measurements are volume based distribution. Size distribution is critical for printing as particles are required to pass through the screen, or mix well with binder in polymers if used as fillers. Generally it requires the particles to be in the range below 20 microns or much lower for quality printing including screen printing. It is clear the pigment produced by the method disclosed in this invention fall right within in this range.

[0052] Pigments produced comprise recycled textiles. In other words, the pigments produced from textiles comprise textile microparticles or microparticles recycled from textiles or waste textiles.

[0053] Pigments produced have dyes contained inside, wherein the dyes are from the original textile. In a preferred embodiment, pigments or the microparticle pigments produced are controllable in size and shape. In one embodiment, the formed pigment particles are almost spherical.Description of the Drawings

[0054] Various embodiments of the present disclosure will be further described and illustrated, by way of example only, with reference to the accompanying drawings as follows:Figure 1 is a flow chart showing the steps of deriving pigments from recycled textiles.Figure 2 shows an example of the cutting of waste textile into textile snippets.Figure 3 shows an example of forming snippet-water slurry, milling, and forming pigments.Figure 4 shows an example of removing water from pigments via either filtration or spraydrying to result in paste-form pigments (b) and powder-form pigments (c).Figure 5 shows the bursting strength of a group of samples after Gamma treatment and Electron Beam treatment.Figure 6 shows the bursting strength of a group of samples after Gamma treatment of different doses.Figure 7 shows the reduction of milling time to produce pigment-water mixture with pigments in the range of 0.5 microns after applying Gamma treatment of different doses to both cotton(a) and wool (b).Figure 8 are SEM images of attritor-milled cotton after 6 hours without radiation treatment (a)-(b) and after 2 hours of gamma radiation treatment (c)-(d).Figure 9 are SEM images of attritor-milled wool after 6 hours without radiation treatment (a)- (b) and after 2 hours of gamma radiation treatment (c)-(d).Figure 10 are SEM images of attritor-milled cotton after 2 hours of milling under different doses of gamma treatment: 75kGy (a); 150 kGy (b); and 250 kGy (c).Figure 11 are SEM images of attritor-milled wool after 2 hours of milling under different doses of gamma treatment: 75kGy (a); 150 kGy (b); and 250 kGy (c).Figure 12 shows coloured snippets (a), microparticle pigments in paste form obtained from vacuum filtration (b), and microparticle pigment powder obtained from spray-drying (c).Figure 13 are images of products obtained from using resultant microparticle pigments in textile printing, for example using any of available techniques in the field, such as screen printing.Figure 14 show the excellent miscibility and blending characteristics with polymers through either melt blending or mixing with solvent based solution and curing.Figure 15 shows products obtained from using the pigments as artwork paint for painting on varied mediums: ceramics; paper; and canvas.Detailed DescriptionMaterials

[0055] Textiles containing natural fibres, synthetic fibres, regenerated fibres, or a combination of one or more fibres can be converted using the steps and methods described herein. The textiles include, but are not limited to, cotton, wool, mungo, shoddy, silk, polyester,nylon, acrylic, polyamide cellulose, and the like. Waste textiles include fabric from clothing textiles, home textiles, or any other textiles comprising one or more of the materials above.Method

[0056] In one embodiment, textile, for example waste textiles, were first cut into small pieces which then fed into a cutting mill to be shredded into snippets. Any cutting methods that are known in the art can be used to cut the textiles into pieces. In one example, a batch of 200 grams of fabric were cut into small pieces of roughly 70 mm x 80 mm, more or less in the similar range, and then fed into a cutting mill to be granulated into snippets.

[0057] In one example, a Fritsch Pulverisette 19 cutting mill was used to cut or shred the cut fabric piece into snippets. In one example, the batch of 200 grams of 70 mm x 80 mm fabric pieces were fed into the cutting mill. The cutting mill was set to 1 mm grid to result in snippets in the size range of 1 mm. The cutting mill was run for about 20 min to result in 200 grams of snippets. In one example, with a granulator of 1 mm grid, a production rate of 1 kg / min can be achieved. It is to be noted that, this number cannot be seen as the limitation to the production rate, depending on any available shredders in the market, a larger shredder can work even faster.

[0058] Figure 2 shows the images of cut fabric pieces and resultant snippets after processing the fabric pieces via the cutting mill.

[0059] In one embodiment, the obtained snippets were mixed with water to make snippetwater slurry. In one example, followed by above, the batch of 200 grams of snippets were mixed with 2 L of water (100 g / L).

[0060] In one embodiment, the slurry was fed into a stirred media mill for milling into pigments. Different size distribution of pigments might be obtained depending on the milling time, snippets to media ratio, media size. In one example, the stirred mill was run up to 6 hours to obtain pigments of average 5 microns. In one example, the power consumption of the mill was 3 H.P., 2.24 kW, with total electricity consumption at 2.24x7=15.68 kWh (6 hours of milling with 1 hour of cleaning time).

[0061] In one example, radiation treatment was applied to pre-treat the textiles. With more detailed information discussed later in this document, with same setting, the milling time can be reduced to 2 hours to achieve the same results and to obtain pigments of average 5 microns.

[0062] In one example, chilled water is circulated through the jacket of the mill to keep the process temperature down and not used in the milling liquid. The attritor was run for 6 hours with power set at 2150W, with total electricity consumption of 2150x6 / 1000=12.9 kWh.

[0063] Figure 3 shows the mixed snippet-water slurry (Figure 3(a)) is being treated by the stirred mill (Figure 3(b)) to generate pigments-water mixture (Figure 3(c)).

[0064] In one embodiment, a sieve maybe used after milling to remove or to disperse any agglomerates, lumps, aggregates, and the like from the pigment-water mixture. This step is optional and more preferable if producing powder-form pigments via spray-drying in the following step. In one example, a sieve of 100 pm might be used. As would be expected by a person skilled in the art, any standard sieve might be used for the same purpose.

[0065] In one embodiment, a vacuum pump was used to carry out vacuum filtration of the pigments. The purpose of this step is to remove water from pigments. By using the vacuum filtration, a paste-form of pigments were obtained, as shown in Figure 4(b). In one example, a common vacuum pump with power of 145 W was used, which is capable of extracting 4L of water within 4 hours from the milled pigment-water mixture.

[0066] In one embodiment, to generate powder-form pigment particles, spray-drying method might be used. In one example, Buchi Mini Spray Dryer B-290 Basic model was used. For one example, this model was able to reach a sample output of 3 L / hour with yields up to 80-85%. Under this rate, pigment-water mixture was run through this model for 3 hours and results in 100 grams of powder-form pigments, shown in Figure 4(c). The total power consumption for 200 grams of powder-form pigments was roughly about 17.4 kWh for this model.

[0067] In one embodiment, radiation is applied to a batch of waste textile as a pre-treatment. The purpose of the radiation pre-treatment is to reduce fibre molecules thereby enabling faster size reduction during milling.

[0068] In one example, a dose of 250 kGy of Gamma radiation and a dose of 250 kGy Electron Beam are each applied to a series of 200 g batches of waste textile fabric each comprising cotton, wool, polyester, and polyamide.

[0069] ASTM D3786 was used to test the bursting strength of textile fabrics after the radiation pre-treatment to understand the impact of radiation on strength of fabric. ASTM D3786 is a standard measurement for the measurement of Bursting Strength of Textile Fabrics. During thetest, fabric specimen is clamped over an expandable diaphragm; the diaphragm is expanded to the point of specimen rupture. The difference between the total pressure required to rupture the specimen and the pressure required to inflate the diaphragm is reported as the bursting strength.

[0070] Figure 5 shows the test results among a group of samples comprising cotton, wool, polyester and polyamide. A set of samples of the same materials have also been tested as a control group.

[0071] It is clearly shown in Figure 5(a) that the bursting strength of each sample after radiation treatment is greatly reduced comparing to the Control group. In particular, the group of polyamide shows most significant reduction in bursting strength after Gamma treatment, followed by the cotton group, which are consistent with the strength loss shown in Figure 5(b).

[0072] Overall, Gamma treatment is relatively more effective in reducing the fabric strength comparing to the Electron beam under the same dose and conditions, depending on the varied materials used, the effectiveness might vary. Nevertheless, both radiation pre-treatments would result in treated fabric with significant strength loss.

[0073] In one example, a dose of 75 kGy, 150 kGy, and 250 kGy of Gamma radiation are respectively applied to waste textile as pre-treatments for comparison. In one example, a batch of the waste textile are comprising mainly cotton, and another batch of the waste textile are comprising wool. Similar as above, ASTM D3786 was used to test the bursting strength of textile fabrics after the radiation pre-treatment.

[0074] Figure 6 shows the test results among a group of samples comprising cotton, wool, polyester and polyamide. A set of samples of same materials have also been tested as a control group.

[0075] It is clear from Figure 6 that, 250 kGy Gamma radiation has the most significant effect to reduce the strength of polyamide, followed by the cotton group. Nevertheless, the higher the dose, the greater the effect in destroying the fabric strength.

[0076] Figure 7 shows the reduction in milling time to mill the textile into particles with diameter in the range of 0.5 microns for being treated as pigments for subsequent applications.

[0077] 2-3 hours milling is sufficient instead of 6 hour of milling even with 75 kGy of Gamma pre-treatment compared to the control group for both cotton and wool. Note that, from the previous results in Figures 5-6, wool clearly has much less strength loss comparing to cotton.However, the results of Figure 7 suggest even for wool with the lowest dose of 75 kGy, it can reduce the milling time to 2-3 hours to achieve a pigment particle size of average 5 microns. Therefore, although the higher dose the greater effect in reducing the textile strength, by taking into account energy consumption and safety requirements, a high dose of radiation might not be necessary. For industrial applications, balance between the milling time and radiation dose may also be considered.

[0078] To further demonstrate the effect of radiation treatment, Figure 8 shows the attritor- milled cotton without radiation treatment (Figure 8(a)) and with 250 kGy Gamma treatment (Figure 8(b)). Figure 8 demonstrates that similar results or even more fine pigments were obtained after 2 hours of milling for Gamma radiation treated textiles (Figure 8(b)) as compared to the control group in Figure 8(a) which shows pigment particles obtained after 6 hour of attritor-milling.

[0079] Similar results for wool can be also in Figure 9. Figure 9 shows the attritor-milled cotton without radiation treatment (Figure 9(a)) and with 250 kGy Gamma treatment (Figure 9(b)). The control group as in Figure 9(a) shows the obtained pigment particles after 6 hour of attritor-milling. Similar results were obtained after 2 hours of milling for Gamma radiation treated textiles (Figure 9(b)).

[0080] Figure 10 shows the attritor-milled cotton pigments after 75 kGy, 150 kGy, and 250 kGy of Gamma treatment. After 2h of attritor-milling, pigment particles all successfully milled into particles in the range of 0.5 microns, with 250 kGy treated sample with less aggregations.

[0081] Similar results were also obtained for wool under the same treatment condition.

[0082] It might be noted that there would be colour change due to radiation treatment. Table 1 below shows the results of colour change for a group of samples under different dose of Gamma treatments. The results show in increase in CIE L and decrease in K / S with increased dose of Gamma treatment. CIE L stands for the he CIELAB colour space, and K / S means the ratio between Absorption coefficient (K) and Scattering coefficient (S).

[0083] High doses of Gamma treatment would have the effect on reducing colour strength or change colour significantly which would then impact pigment quality. Therefore, a balance is needed between colour change and strength change. For example, a dose range between 50 kGy-300 kGy, or more preferably between 75 kGy to 250 kGy has been found efficient inreducing the milling time while with least adverse effect on the colour quality depending on colour in pigments.

[0084] Table 1 below shows an example of Colour Change due to radiation. In this table, CIE L stands for the he CIELAB colour space, and K / S means the ratio between Absorption coefficient (K) and Scattering coefficient (S). It can be seen that with different materials, such as cotton, the increase in radiation strength from 75 kGy to 250 kGy might have greater effect in colour change but not have significant decrease in milling time; while for wool, while the radiation greatly reduces the milling time, the differences in the dosage have little effect on the color change. For example, if it’s required to keep the CIE L change under 20% or preferably under 10%, this can be achieved through a balance of the milling time. For example, with pure cotton material, by keeping the radiation below 150 kGy, the milling time can be kept below 2.5 hours, comparing to no pre-treatment (6 hours) or 250 kGy treatment (>30% change with only 0.5 hour reduction in milling). To a person skilled in the art, when working on different materials, or different combinations of materials, depending on the requirements of targeted pigments of different applications, would understand to balance out the selection of doses and the need of reducing the milling time when considering energy and time consumption as well as other additional cost during the industrial applications. For example, the requirement of colour accuracy of the printing industry would be normally higher comparing to the paint used by artists who normally mix colours to create unique shades during their creations.

[0085] Table 1 Example of Colour Change due to radiationApplications

[0086] Pigments recycled from above process can be applied to various of applications, including not only replied for fabric dyeing, but also can be explored for printing, art and craft paint formulations, paint for wood and other applications, printing paper and packaging and filler for synthetic polymers and rubbers and other materials. Figure 12 shows examples of coloured snippets (a), and microparticle pigments in paste form obtained from vacuum filtration (b) and microparticle pigment powder obtained from spray-drying (c). Colours produced include varied greens, yellow, orange, blue, red, etc., any person skilled in the art would understand mixing the relevant colour to achieve any desired colours for applications in dyeing, printing or colouring.

[0087] Figure 13 shows examples of using the resultant microparticle pigments in textile printing using any of available techniques in the field, such as screen printing.

[0088] The recycled pigments are compatible with a range of traditional paint medium, including watercolours, acrylics, oils, and inks. They are also miscible with polymers through either melt or curing. On the bottom right of Figure 14, buttons made of polymers were dyed into orange and blue using the microparticle pigments.

[0089] Figure 15 also shows use the pigments as artwork paint used by artist painting on varied mediums, such as ceramics, paper and canvas.

Claims

Claims1. A process of producing pigments from textiles, the process comprising: cutting and / or shredding the textiles into textile snippets; mixing the textile snippets with water to produce a textile snippet-water slurry; milling the textile snippet-water slurry to produce a microparticle pigment-water mixture.

2. The process of producing pigments from textiles of Claim 1, further comprising applying a radiation treatment to the textiles.

3. The process of producing pigments from textiles of Claim 2, wherein the radiation treatment is applied to pre-treat waste textile prior to cutting and / or shredding the waste textile into textile snippets.

4. The process of producing pigments from textiles of Claim 2, wherein the radiation treatment is applied at any step prior to the milling.

5. The process of producing pigments from textiles of any one of the preceding claims, wherein the radiation treatment is Gamma treatment or Electron-beam treatment.

6. The process of producing pigments from textiles of any one of the preceding claims, wherein the radiation treatment is a dose of radiation of up to 250 kGy, preferably in a range of 25-500 kGy.

7. The process of producing pigments from textiles of Claim 6, wherein the dose of radiation is in a range of 75-250 kGy.

8. The process of producing pigments from textiles of Claim 1, further comprising removing at least a portion of water from the microparticle pigment-water mixture, wherein the removing at least a portion of water comprises one or more of: filtration, filtering, centrifuge, spray-drying, decanting, or a combination thereof.

9. The process of producing pigments from textiles of any one of the preceding claims, wherein the textiles are waste textiles.

10. Microparticle pigments produced from textiles using the process of any one of the preceding claims, wherein the microparticle pigments have dye contained inside, and wherein the microparticle pigments are small enough to penetrate inside fibre and function as dyes for dying, colouring and / or printing.

11. The microparticle pigments produced from textiles of Claim 10, wherein the microparticle pigments have a Dv50 in a range of 1-30 micrometers, or a Dv90 in a range of 10-50 micrometers.

12. The microparticle pigments produced from textiles of Claim 10, wherein the microparticle pigments have a Dv50 in a range of 5-8 micrometers, or a DV90 in a range of 15-20 micrometers.

13. Pigments produced from a process according to any one of claims 1-9.

14. Microparticle pigments produced from textiles, wherein the microparticle pigments comprise dyes from the textiles, and wherein the textiles include recycled textiles or waste textiles.

15. Pigments comprising textile microparticles.

16. Pigments comprising recycled textiles.

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