WO2005054344A1

WO2005054344A1 - Masterbatch

Info

Publication number: WO2005054344A1
Application number: PCT/AU2004/001709
Authority: WO
Inventors: John Scheirs; Stephen Michael Morriss; Lynden William Trickey; Noel Adrian Miller
Original assignee: John Scheirs; Stephen Michael Morriss; Lynden William Trickey; Noel Adrian Miller
Priority date: 2003-12-05
Filing date: 2004-12-03
Publication date: 2005-06-16

Abstract

The invention relates to a process for preparing a masterbatch, the process comprising compacting a feedstock into pellets, wherein the feedstock comprises waste toner powder. The masterbatch may be used in a method for colouring a thermoplastic polymer, the method comprising melt mixing the thermoplastic polymer with the masterbatch. The invention further relates to a masterbatch in the form of pellets comprising greater than 80 weight percent of waste toner powder.

Description

MASTERBATCH

Field of the Invention

The present invention relates generally to a masterbatch for colouring thermoplastic polymers, and is particularly concerned with the use of waste toner powder in a masterbatch.

Background of the Invention

Polymers are widely renowned for their versatility and durability. However, in their purest form most polymers are in fact quite unstable and have a dull unattractive colour. In order to enhance their practical utility, polymers are commonly compounded with additives such as antioxidants, UN-stabilisers, processing aids, dyes and pigments.

Compounding polymers with additives is generally performed by way of a melt mixing process such as extrusion. For convenience and efficiency of mixing, the additives are often provided in the form of a polymer concentrate, or "masterbatch" as it is commonly referred to in the art.

As used herein, the term "masterbatch" is intended to define a composition which comprises a polymer additive at a concentration that is higher than desired in a final polymer product, and which composition is subsequently melt mixed at a particular weight to weight ratio with a base thermoplastic polymer to produce the final polymer product having the desired amount of additive.

Masterbatches are commonly provided in the form of small granules or pellets and are prepared by melt mixing the desired additive(s) with a carrier polymer. To avoid problems associated with incompatibility, the carrier polymer is typically chosen such that it is the same as, or of the same general class as, the base polymer with which the masterbatch is to be melt mixed. For example, if the base polymer is polyethylene, the carrier polymer is preferably also polyethylene. Toner powder is a dry printing resin that generally has a particle size ranging from about 3 to 20 microns and is used in laser printers, photocopiers, fax machines and the like. Toner powder compositions vary, but in general they contain a binder component and a dye and/or pigment. By way of example only, black toner is mainly composed of a styrene- acrylate copolymer and carbon black and a yellow toner is mainly composed of a polyole resin and an organic dye.

WO 03/025046 proposes a process for producing a masterbatch for colouring thermoplastic polymers by melt mixing a carrier polymer, carbon black and waste toner powder. This process provides a means for recycling waste toner powder.

As acknowledged in WO 03/025046, a considerable quantity of waste toner powder is generated annually. This waste is derived primarily from toner manufacturers and from residual toner powder contained in spent toner cartridges. Waste toner powder can not generally be recycled for re-use as toner powder, and is therefore commonly disposed of in landfills. Disposal of the powder in this manner presents considerable disposal cost to the toner industry, and is of particular environmental concern to the community at large.

By the process proposed in WO 03/025046, the waste toner powder is used as a supplementary source of carbon black in the production of a masterbatch, with the fine particulate form of the toner being consolidated into more readily handled pellets or granules by melt mixing. Although the reference contemplates utilising up to 80 weight percent of waste toner in the masterbatch, it in fact teaches that use of more than about 50 weight percent of toner powder results in a masterbatch which is brittle and unsuitable for commercial use.

Accordingly, there remains an opportunity to develop a masterbatch which can accommodate high levels of waste toner powder.

Summary of the Invention

In one aspect, the present invention provides a process for preparing a masterbatch, the process comprising compacting a feedstock into pellets, wherein the feedstock comprises waste toner powder. In another aspect, the present invention provides a masterbatch comprising waste toner powder, the masterbatch being in the form of pellets formed by a compacting process.

In a further aspect, the present invention provides a masterbatch in the form of pellets comprising greater than 80 weight percent of waste toner powder.

It has been found that a masterbatch comprising greater than 50 weight percent of waste toner powder can be manufactured by using a compacting process. By the process of the invention, the masterbatch is provided in the form of pellets which can have a desirable balance of hardness. In particular, the pellets may be sufficiently durable to resist comminution during transport and handling, yet still capable of being readily "broken down" and dispersed upon being melt mixed with a base polymer. Through an ability to contain a high level of waste toner powder, a masterbatch in accordance with the invention can advantageously be formulated without any additional colouring agent or a carrier polymer. Thus, the invention can provide a highly efficient use of waste toner powder by enabling more than 80 percent by weight, or even up to 100 weight percent, to be incorporated in the masterbatch.

The ease with which the pellets of the masterbatch can be broken down and dispersed during melt mixing with a base polymer is believed to result from the pellets not being formed from a melt processing technique. In particular, the composition of the pellets is believed to retain a degree of particulate character from the un-compacted toner powder. This can enable the completion of pellet breakdown to be accomplished during the incorporation stage of melt mixing with the base polymer, without the application of additional energy. It can also enhance the colouring provided by use of the masterbatch. For example, in the case of black pigments, the pigment particle size determines to a large extent its degree of blackness or "jetness" in dispersed form. Accordingly, the greater ability to disperse such pigments enhances the colouring effect provided by them.

The use of compaction in preparing a masterbatch comprising waste toner powder is also believed to alleviate the problem of pellet embrittlement as described in WO 03/025046. Without wishing to be bound by theory, it is believed that toner powder has a tendency to become brittle upon being subjected to temperatures above its melting point. As melt processing techniques are generally performed at temperatures above the melt temperature of toner powders, toner based masterbatches prepared by these techniques are prone to being brittle and therefore commercially unusable, with the problem becoming more apparent as the toner content of the masterbatch increases.

Through compaction, the toner powder is not subjected to temperatures above the melting point of the binder component and the powder is therefore believed to retain some of its original elasticity. Thus, masterbatches in the form of pellets manufactured by this technique are typically not brittle. As a result, a commercially viable masterbatch in the form of pellets comprising greater than 80 weight percent toner powder can now be manufactured.

Detailed Description of the Invention

The masterbatch in accordance with the invention is in the form of pellets. As used herein, the term "pellet" is intended to denote a solid integral mass which is derived from the compaction of smaller particles.

As used herein, the terms "compacting" and "compaction" are intended to denote an act of applying pressure to the waste toner powder at a temperature below the melting point of the binder component so as to cause agglomeration of the powder particles and densification of the material. Variations on these words such as "compacted" shall be construed accordingly. Importantly, and as one skilled in the art would appreciate, the terms "compaction" and "compacting" are not intended to embrace a melt process such as melt extrusion.

The present invention provides an effective means for utilising waste toner powder. As used herein, the term "waste" toner powder refers to toner powder that is not used as a printing resin in printing applications. Typically, waste toner powder is derived from surplus or imperfect stock produced by toner manufacturers so will not be used as a printing resin in printing applications, and from residual toner contained in spent toner cartridges so has not been used as a printing resin in printing applications.

In order for the waste toner powder to be used in a masterbatch, it must be free of contaminants and impurities. Such contaminants and impurities may include metal, plastic or other fragments that are liberated during shredding or dismantling of toner cartridges or other packaging containing the waste toner powder. Accordingly, the waste toner powder is advantageously sieved and/or subjected to other fragment separating processes prior to compaction.

Compaction of the feedstock into pellets may be performed using any suitable apparatus that is capable of applying pressure to the toner powder so as to cause the powder to form a pellet. During compaction, binding of the toner powder particles, and any other components present, is effected by the pressure applied. The application of pressure is understood to increase interparticle interaction through both elastic and plastic deformation of the particles. The compaction may result in a degree of fusion at the grain boundaries of some particles. Other forces may also be involved.

Suitable compacting apparatus includes those which incorporate a die having one or more orifices through which the feedstock can be forced, with the pressure applied to the feedstock to force it through the die being provided by any suitable means. Examples of such apparatus include, but are not limited to, a pellet mill which utilises rollers for the application of pressure, and paste or powder extruders which utilise a rotary screw for the application of pressure.

Suitable apparatus also include those which exert pressure on the feedstock by applying pressure to it between two solid surfaces. An example of such apparatus includes, but is not limited to, a roll compactor. Roll compactors are commercially available from companies such as Hosokawa Bepex Corporation, USA. In such apparatus, feedstock can be squeezed between two counter rotating rollers to form dense sheets, the sheets can then be crushed and screened to yield a pelletised ^'product. The surfaces of the roller can be smooth or shaped, for example fluted, corrugated, waffled, knurled, etc. Compaction of the feedstock is preferably performed using a pellet mill. Pellet mills are commercially available from companies such as Amandus Kahl GMBH & Co., Germany. In such apparatus, a cylindrical pressing tool rolls over a layer of feedstock and forces it through a perforated die plate. As the feedstock is forced through the die plate, it emerges as a compacted strand which is fractured into pellets by a suitable means such as a rotating blade.

Unlike melt extrusion processes used for manufacturing conventional masterbatches, compaction of the feedstock does not require the application of heat through the use of electric heaters and the like. Furthermore, compaction of the feedstock does not result in the formation of a molten product. Such processing distinctions render not only masterbatch manufacture by compaction more energy efficient, but the resultant product easier to handle and the overall process less complicated.

Mechanical compaction apparatus suitable for use in the process of the invention will typically not have heating systems such as electric heaters coupled to thermostat controllers. Nevertheless, heat is likely to be generated by the compaction process itself. As most toner powders have a melting temperature above 100°C, the temperature of the waste toner powder within the feedstock reached during compaction preferably does not exceed about 100°C. More preferably the temperature of the waste toner powder within the feedstock reached during compaction does not exceed about 80°C, most preferably about 70°C. In a particularly preferred embodiment of the invention, the temperature of the toner powder reached during compaction is in the range of from 20°C to 70°C.

The temperature attained during compaction will primarily be determined by the net difference between the frictional heat generated and the heat lost from the apparatus. Those skilled in the compaction art will appreciate the numerous variables associated with heat loss/heat gain in compaction apparatus.

For example, in apparatus, such as a pellet mill, utilising a die plate, the length to diameter ratio of the orifice(s) in the die plate (aspect or compression ratio) will influence the temperature attained during a given compaction run. The smaller the aspect ratio, the lower the temperature attained. When such apparatus is used as a means for compacting the feedstock, the aspect ratio of the orifιce(s) preferably ranges from about 3:1 to about 6: 1. More preferably the aspect ratio is about 4:1.

As will be appreciated, the aspect ratio used will also influence the relative hardness of the pellets formed. Thus, aspect ratios below about 3:1 may result in pellets that are friable, whereas aspect ratios above 6:1 may result in pellets that are so hard that they can not be readily broken down and easily dispersed upon being melt mixed with a base polymer.

Another variable which can influence the temperature attained during compaction is the composition of the feedstock being compacted. The composition of toner powder may vary depending upon its source and colour. Also, additives such as lubricants, binders, damping agents and acid scavengers can be combined with the toner powder. Compositional details of the feedstock, and hence masterbatch, are discussed in more detail below.

Other variables such as feed rate and rotor speed can influence the temperature attained during compaction, but these variables are generally less significant.

During compaction of the feedstock, the heat generated by frictional forces and the heat lost from the equipment will typically reach a steady state and thereby provide a relatively constant compaction temperature. If the temperature reached during compaction becomes too high, those skilled in the art will appreciate the process parameters that can be adjusted in order to reduce the temperature. Alternatively, the compaction equipment can be cooled using conventional means.

Those skilled in the art will appreciate that height or gap adjustment between the rollers and the die plate in a pellet mill are important parameters in relation to the pressure applied during compaction. If the gap is too small then die plate wear can occur, and if the gap is too large a layer of toner can build up and the process may become less efficient. Preferably, the gap between the rollers and the die plate is from 0.01 to 1 mm, more preferably from 0.1 to 0.3 mm.

The pellets of masterbatch formed by compaction are in effect an agglomeration of smaller particles. The pellets can conveniently be formed into a diverse range of shapes and sizes. A common requirement of a masterbatch is that the pellet size is commensurate with the size of the base polymer with which the masterbatch is to be melt mixed. Providing the pellets of the masterbatch and base polymer with similar dimensions facilitates accurate metering and efficient dispersing during the melt mixing process. Accordingly, the pellets of the masterbatch in accordance with the invention preferably have dimensions within ±50 percent, preferably within ±30 percent, most preferably within ±20 percent, of the dimensions of the pellets of the base polymer with which the masterbatch is to be melt mixed.

Where the masterbatch has been prepared using a compactor which incorporates a die plate through which the pellets are forced, the pellets typically have a cylindrical shape. Preferably, such pellets have a diameter ranging from about 2mm to about 7mm, more preferably ranging from about 3mm to about 6mm, and a length preferably in the range of from about 1 to about 6 times the diameter, more preferably in the range of from about 1 to about 3 times the diameter.

As a preferred compacting device, a pellet mill is preferably equipped with a die plate containing circular orifices which have a diameter ranging from about 2mm to about 7mm, more preferably the orifices have a diameter of about 3mm. In operation the mill preferably runs at about 50 to 70kg/hr. The mill may operate at a nominal rotor speed of about 80 to about 250 rpm, preferably of about 80 to about 100 rpm.

Pellets formed by any compaction means will typically be sieved using an appropriately sized screen to remove fines. The fines can be collected and conveniently reused.

The masterbatch in accordance with the invention preferably has a "tapped" bulk density of at least 500 g/1, more preferably of at least 700 g/1. By "tapped" bulk density is meant that the bulk density is measured after tapping.

The masterbatch in accordance with the invention comprises waste toner powder. The composition of toner powder may vary depending on its source and colour. The composition of some common toner powders is as follows: Regular Black Toner

Regular black toner generally consists of a styrene-acrylate copolymer binder and carbon black along with optional smaller quantities of wax, dye and silica. For example:

Styrene acrylic copoly mer 48%

Carbon black 30%

Wax 15%

Silica 3%

Dye 4%

Commercial examples are:

Brother TN-6600 (Type A) CAS No.

Styrene acrylic copolymer 25767-47-9

Carbon black 1333-86-4

Wax 8002-74-2 Silica 7631-86-9

Dye 8005-02-05

Black Toner (Lanier) CAS No.

Styrene acrylic copolymer 25767-47-9 Carbon black 1333-86-4

Wax 8015-86-9

Dye 31714-55-3

Regular Coloured Toner

Regular coloured toner generally contains substantial quantities of polyole resin instead of the styrene-acrylate copolymer, and organic dyes instead of carbon black. The polyole content typically ranges from about 30 to 70 weight percent, and the dye content typically ranges from about 30 to 70 weight percent. By way of example only, some coloured toner compositions are: Cyan CAS No.

Polyole resin 186359-26-2 Organic dye 147-14-8 Organic salt 42405-40-3

Magenta CAS No. Polyole resin 186359-26-2 Organic dye 980-26-7 Organic salt 42405-40-3

Yellow CAS No. Polyole resin 186359-26-2 Organic dye 77804-81-0 Organic salt 42405-40-3

Black developer toner

Black developer toner generally contains magnetic iron oxide (MIO) or magnetic ferrite (MF) powder. A MIO toner generally has the following composition:

Styrene-acrylate copolymer 48%

Iron oxide 45% Polypropylene 4%

Silica 3%

Carbon black may also be present in an amount typically ranging up to 30 weight percent.

Commercial examples include:

Ricoh Developer (Type 3) CAS No. Iron oxide 1317-61-9

Styrene acrylic polymer 25767-47-9

Polyolefm 9003-07-0

Carbon black 1333-86-4 Ricoh Developer (Type 7) CAS No.

Iron oxide 1317-61-9

Styrene acrylic polymer 26655-10-7

Carbon black 1333-86-4

Wax 8015-86-9

Dye 31714-55-3

Ricoh PPC Developer (Type 1) CAS No. Ferrite powder 1317-38-0 1314-13-2 1309-37-1

Styrene acrylic polymer 25767-47-9 Carbon black 1333-86-4 Carnauba wax 8015-86-9

Ricoh Developer (Type 410) CAS No. Nickel zinc ferrite powder 12645-50-0 Styrene acrylic polymer 25036-19-5 Polyolefm 9003-07-0 Carbon black 1333-86-4

Coloured developer toner

Coloured developer toner also generally contains ferrite powder like its black counterpart, but it typically contains polyole resin, like the coloured toners above, instead of styrene acrylic polymer. A commercial example is:

Ricoh Colour Developer Type L CAS No. Ferrite powder 1317-38-0 1314-13-2 1309-37-1

Polyol resin 186359-26-2 Organic dye 77804-81-0 Organic salt 42405-40-3

In general, toner can been seen to contain a binder component and a colouring agent. The binder component is typically a polymer resin such as a styrene-acrylate copolymer or a polyole resin (ie polyolefm wax), optionally with a wax material such as paraffin wax, Fischer-Tropsch wax or carnauba wax. Fischer-Tropsch waxes are polymethylenes, synthetic hydrocarbons polymerised from natural gas. The colouring agents used are common dyes or pigments.

In preparing a masterbatch comprising waste toner powder it is particularly advantageous to maximise the amount of toner powder used. Masterbatches containing high levels of the toner powder not only have a higher concentration of the desired colouring agent, but they also utilise this source of waste material more efficiently. Advantageously, the masterbatch in accordance with the present invention is not limited by the amount of waste toner powder that it can contain. Preferably, the feedstock, and hence the masterbatch, contains greater than 80 weight percent of waste, toner powder, more preferably, at least 90 weight percent, most preferably at least 95 weight percent. The feedstock, and hence the masterbatch, may even consist essentially of waste toner powder (ie 100 weight percent).

The binder component present in the toner powder is particularly advantageous in the present invention in that it can function as a binding agent to assist consolidation of the pellet during compaction. Furthermore, the binder component has been found to act as a dispersing aid which facilitates dispersion of the toner particles upon the masterbatch being melt mixed with a base polymer. The binder components in waste toner powder have also been found to be compatible with a diverse range of polymers. Given that the masterbatch in accordance with the invention can be formulated without a carrier polymer, it can therefore advantageously be used as a universal masterbatch. By the term "universal" masterbatch is meant that the masterbatch may be melt mixed with a diverse range of polymers.

In addition to waste toner powder, the masterbatch in accordance with the invention may comprise other components. For example, it may be advantageous to include a lubricant. Suitable lubricants include, but are not limited to, glycerol monostearate, glycerine, butyl stearate, sorbitol, sorbitan esters, PEG (polyethylene glycol) fatty acid esters, ethoxylated glycerine esters, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monolaurate sorbitan tristearate, PEG-400 distearate, ethoxylated fatty amine, polyalkoxylene dioleate, tallowamine, PEG-600, cetyl alcohol, and combinations thereof. Inclusion of a lubricant with the toner powder can facilitate the compaction process by reducing friction, which in turn has the effect of increasing throughput and reducing compaction temperatures.

A binding agent can also be included in the masterbatch formulation. Suitable binding agents include, but are not limited, butyl stearate, ethylene bis-stearamide, polyethylene waxes, microcrystalline waxes, beeswax, paraffin wax, PEG-200, PEG- 1500, PEG-4000, PEG-6000, bisamide mixtures, erucamide, oleamide, metallocene waxes, acrylic-ethylene waxes, EVA waxes, Fischer Tropsch waxes and combinations thereof. Inclusion of a binding agent can facilitate consolidation of the toner particles and pellet formation.

Given the fine particle size of waste toner powder, it may be desirable to add a damping agent to the powder to reduce dusting during the compaction process. Suitable damping agents include, but are not limited to, glycerol monoleate, canola oil, glycerine, sorbitol, paraffin oil, castor oil, sunflower oil and combinations thereof.

Depending upon the intended application of the masterbatch, it may be beneficial to incorporate an acid scavenger in the masterbatch formulation. For example, where the masterbatch is to be melt mixed with a base polymer composition which includes a flame retardant, the melt mixing process may result in the degradation of the flame retardant and the release of acidic compounds such as a hydrogen halide. Under these circumstances, the presence of an acid scavenger in the masterbatch can prevent, or at least alleviate, the negative effects associated with the release of such acidic compounds. Suitable acid scavengers include, but are not limited to, hydrotalcite and epoxidised soybean oil (ESBO).

Those skilled in the art will appreciate that a component which functions as a lubricant may also function as a binder and/or a damping agent and/or an acid scavenger, and vice versa. Accordingly, it should be understood that the examples of lubricants, binders, damping agents and acid scavengers listed above are not necessarily limited to performing the task defined by the category they have been assigned to herein.

If desired, dyes and/or pigments may be added to the masterbatch formulation as additional colouring agent.

Additional components included in the masterbatch formulation such as lubricants, binders, damping agents and acid scavengers may be conveniently mixed with the waste toner powder prior to compaction in a ribbon blender or a high speed mixer to provide the feedstock. During the mixing process it is important that the additional components are thoroughly mixed with the toner powder to form a substantially homogeneous powdery blend or paste. To facilitate mixing, liquid components may be introduced as a spray under vacuum. The resultant mixture can then be fed into the compaction apparatus at a rate which achieves an acceptable pellet yield.

A lubricant may advantageously be included in the masterbatch formulationin an amount ranging, for example, up to about 20 weight percent, preferably from about 0.1 to about 20 weight percent, more preferably from about 0.5 weight percent to about 15 percent, most preferably from about 2 weight percent to about 5 weight percent.

A binder may advantageously be included in the masterbatch formulation in an amount ranging, for example, up to about 20 weight percent, preferably from about 0.1 weight percent to about 20 weight percent, more preferably from about 0.5 weight percent to about 15 percent, most preferably from about 2 weight percent to about 5 weight percent.

A damping agent may advantageously be included in the masterbatch formulation in an amount ranging, for example, up to about 20 weight percent, preferably from about 0.1 weight percent to about 20 weight percent, more preferably from about 0.5 weight percent to about 15 percent, most preferably from about 2 weight percent to about 5 weight percent.

An acid scavenger may advantageously be included in the masterbatch formulation in an amount ranging, for example, up to about 10 weight percent, preferably from about 0.1 weight percent to about 10 weight percent, more preferably from about 0.5 weight percent to about 8 weight percent, most preferably from about 3 weight percent to about 5 weight percent.

The inclusion of the aforementioned additional components in the feedstock at the indicated levels has advantageously been found to not adversely effect the "universal" character of the masterbatch.

Where other components are included in the masterbatch formulation, it will be important that they do not adversely interfere with the compaction process or the properties of the resulting pellets. Where a universal masterbatch is required, the other components, at the levels used, should also be compatible with a diverse range of base polymers.

As noted already, the masterbatch formulation preferably contains less than 50 weight percent, more preferably less than 20 weight percent, in total of components other than waste toner powder.

The masterbatch in accordance with the invention may be used for colouring thermoplastic polymers. In particular, the colouring agents in the waste toner powder are eminently suited for colouring most thermoplastic polymers. The ultimate colour provided by the masterbatch will be primarily dictated by the colour of the toner powder used in the masterbatch. Blending of two or more waste toner powders and/or of one or more waste toner powders with additional colouring agents can be used to create various shades of colour.

Accordingly, in a further aspect of the invention there is provided a method for colouring a thermoplastic polymer comprising melt mixing the thermoplastic polymer with the masterbatch according to the invention. The amount of masterbatch required to colour a thermoplastic base polymer will vary depending upon the intensity of colour required, the proportion of colouring agent in the waste toner and the amount of waste toner that is present in the masterbatch.

Melt mixing of the masterbatch with a thermoplastic base polymer can be performed using methods well known in the art. Preferably, melt mixing is achieved by continuous extrusion equipment such as twin screw extruders, single screw extruders, other multiple screw extruders and Farrel mixers.

Thermoplastic base polymers that can be coloured with the masterbatch include, but are not limited to, polyolefms such as polyethylene and polypropylene, PNC, nylons (polyamides), PET (and related polyesters), polycarbonate and commodity and engineering plastics in general.

The present invention is further described with reference to the following non-limiting Examples.

Examples

General masterbatch compacting conditions

After sieving, waste toner powder (type A) plus process additives (see below for formulation details) were mixed in a high speed mixer for about 5 minutes to produce a homogeneous blend in the form of a free flowing powder. The resulting powder blend was then transferred to a pellet mill (Amandus Kahl GMBH & Co. Model No. 14-175) operating at ambient temperature at a utilisation factor in the range of 0.75 to 1.8 kW. Various die plates with different aspect ratios (pressway length) were used. The temperature of the formulation during compaction did not reach 100°C. The resulting pellets were relatively hard, in the sense that considerable force was required to break them down into powder when subjected to manual compression. Therefore they could be handled with typical conveying equipment with minimal attrition. Dry sieving of the pelletized product with a Standard mesh screen indicated that the product consisted typically of about 96% pellets (+12 mesh) and 4% fines (-12 mesh). The pellets were cylindrical with a nominal diameter of 3 mm, a nominal length of 7 mm, and a particle compressive hardness of about 2.5 kg/cm (compressive hardness test method). The granules exhibited low dusting and good powder flow properties, and thus good metering and handling characteristics.

Example 1 Formulation:

Powdered polyolefm wax: 9.5 wt.%

Butyl stearate: 0.5 wt.%

Waste toner powder: 90 wt.%

Pressway ratio : 4 : 1

Tapped bulk density of pellets was 726 g/1.

Example 2 Formulation:

Powdered polyolefm wax: 8.0 wt.% Butyl stearate: 2.0 wt.%

Waste toner powder: 90 wt.%

Pressway ratio: 5:1

Tapped bulk density of pellets was 580 g/1.

Example 3 Formulation:

Powdered polyolefm wax: 2.0 wt.%

Calcium stearate: 2.0 wt.%

Canola oil: 2.0 wt.%

Waste toner powder: 94 wt.%

Pressway ratio: 4:1

Tapped bulk density of pellets was 665 g/1. Colouring a thermoplastic polymer with the masterbatch

The pellets prepared from the above compaction trials were used successfully as masterbatch in the production of black polyethylene film having uniform colour dispersion, good opacity and good tinctorial strength. In particular, the masterbatch from Example 1 was let down at 2% and at 10% in LDPE. The film was produced on a 45 mm diameter single-screw extruder with an L/D ratio of 18:1, and at a temperature in the range 180-190°C. Injection moulded plaques were also produced on a Boy 15 S injection moulding machine using standard plaque moulding conditions at 200°C.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia or elsewhere.

Claims

CLAIMS:

1. A process for preparing a masterbatch, the process comprising compacting a feedstock into pellets, wherein the feedstock comprises waste toner powder.

2. The process according to claim 1, wherein the feedstock is compacted using apparatus selected from a pellet mill, a paste or powder extruder and a roll compactor.

3. The process according to claim 2, wherein the pellet mill has a die plate with an orifice(s) having an aspect ratio ranging from about 3:1 to about 6: 1.

4. The process according to claim 3, wherein the aspect ratio is about 4: 1.

5. The process according to any one of claims 1 to 4, wherein the temperature of the waste toner powder reached during compaction does not exceed about 100°C.

6. The process according to any one of claims 1 to 5, wherein the feedstock comprises greater than 80 weight percent waste toner powder.

7. The process according to claim 6, wherein the feedstock comprises at least 90 weight percent waste toner powder.

8. The process according to claim 7, wherein the feedstock comprises at least 95 weight percent waste toner powder.

9. The process of according to claim 8, wherein the feedstock consists essentially of waste toner powder.

10. The process according to any one of claims 1 to 8, wherein the feedstock comprises one or more other components selected from lubricant, binder and dampening agent, each in an amount up to about 20 weight percent, and up to about 10 weight percent of acid scavenger.

11. The process according to claim 10, wherein the feedstock includes lubricant selected from glycerol monostearate, glycerine, butyl stearate, sorbitol, sorbitan esters, PEG (polyethylene glycol) fatty acid esters, ethoxylated glycerine esters, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monolaurate sorbitan - tristearate, PEG-400 disteafate, ethoxylated fatty amine, polyalkoxylene dioleate, tallowamine, PEG-600, cetyl alcohol, and combinations thereof.

12. The process according to claim 10, wherein the feedstock includes binder selected from butyl stearate, ethylene bis-stearamide, polyethylene waxes, microcrystalline waxes, beeswax, paraffin wax, PEG-200, PEG-1500, PEG-4000, PEG-6000, bisamide mixtures, erucamide, oleamide, metallocene waxes, acrylic-ethyl ene waxes, EVA waxes, and combinations thereof.

13. The process according to claim 10, wherein the feedstock includes dampening agent selected from glycerol monoleate, canola oil, glycerine, sorbitol, paraffin oil, castor oil, sunflower oil and combinations thereof.

14. The process according to claim 10, wherein the feedstock includes acid scavenger selected from hydrotalcite, epoxidised soybean oil and combinations thereof.

15. A masterbatch in the form of pellets formed by the process according to any one of claims 1 to 14.

16. The masterbatch according to claim 15, wherein the pellets have a cylindrical shape and a diameter ranging from about 2 mm to about 7mm.

17. The masterbatch according to claim 16, wherein the pellets have a length which is in the range of from about 1 to about 6 times the diameter.

18. The masterbatch according to any one of claims 15 to 17 having a tapped bulk density of at least 500 g/1.

19. A method for colouring a thermoplastic polymer, the method comprising melt mixing the thermoplastic polymer with the masterbatch according to any one of claims 15 to 18.

20. The method according to claim 19, wherein the thermoplastic polymer is selected from polyolefms, polyvinyl chloride, polyamides, polyesters and polycarbonates.

21. The method according to claim 19 or 20, wherein the masterbatch is used in an amount ranging from about 1 to about 25 weight percent.

22. A masterbatch in the form of pellets comprising greater than 80 weight percent of waste toner powder.

23. The masterbatch according to claim 22, which further comprises up to about 20 weight percent of one or more other components selected from lubricant, binder and dampening agent, and up to about 10 weight percent of acid scavenger.

24. The masterbatch according to claim 23 including lubricant selected from glycerol monostearate, glycerine, butyl stearate, sorbitol, sorbitan esters, PEG (polyethylene glycol) fatty acid esters, ethoxylated glycerine esters, -sorbitan monolaurate, sorbitan monopalmitate, sorbitan monolaurate sorbitan tristearate, PEG-400 distearate, ethoxylated fatty amine, polyalkoxylene dioleate, tallowamine, PEG- 600, cetyl alcohol, and combinations thereof.

25. The masterbatch according to claim 23 including binder selected from butyl stearate, ethylene bis-stearamide, polyethylene waxes, microcrystalline waxes, beeswax, paraffin wax, PEG-200, PEG- 1500, PEG-4000, PEG-6000, bisamide mixtures, erucamide, oleamide, metallocene waxes, acrylic-ethylene waxes, EVA waxes, and combinations thereof.

26. The masterbatch according to claim 23 including dampening agent selected from glycerol monoleate, canola oil, glycerine, sorbitol, paraffin oil, castor oil, sunflower oil and combinations thereof.

27. The masterbatch according to claim 23 including acid scavenger selected from hydrotalcite, epoxidised soybean oil and combinations thereof.

28. The masterbatch according to any one of claims 22 to 27 having a tapped bulk density of at least 500 g/1.