METHOD OF TREATING A SUBSTRATE WITH A MULTIPLICITY OF SOLID

PARTICLES

[0001] Field of the Invention

[0002] The present invention relates to a method of treating a substrate using solid particles comprising a biodegradable polyester, it further relates to said solid particles.

[0003] Background to the Invention

[0004] The use of solid particles for treating substrates is increasingly being utilized in a number of areas of technology. The solid particles provide effective cleaning and processing and offer an economical advantage over many conventional treatment methods. PCT patent publication W02007/128962 discloses solid cleaning particles for the cleaning of substrates using solvent free methods to avoid environmental concerns associated with solvent processing. This publication teaches methods of treating substrates, particularly textiles, with Nylon 6,6 solid cleaning particles. This patent publication addresses environmental concerns which pertain to toxic and potentially environmentally harmful halocarbon solvents. PCT patent publication WO2014/167359 discloses a technology which comprises methods for treating animal substrates, such as leather, using for example polyethylene terephthalate (PET) polymeric particles with tanning agents. Both of the abovementioned patent publications clearly demonstrate economic and environmental advantages such as low water consumption and low energy use and these applications disclose that the particles are recovered and reused. Nylon 6,6 and PET do not readily degrade in the environment, but they can be used many times in the method and ultimately recycled with other nylon or PET materials.

[0005] That said, it was felt desirable by the present inventors that once the solid particles reach the end of their useful lifetime they could be released into the environment without any unwanted environmental damage and with short degradation times. Whilst many biodegradable materials exist, even these often take a good amount of time to degrade in the natural environment. Degradation can be especially slow in water when compared to degradation in soil. Of course, any material which might tend to be too quickly biodegradable would likely also not be usable for treating many batches of substrates. Thus, there was seen to be an inherent difficulty here.

[0006] The present inventors sought to retain (or ideally improve) the technical advantages seen with the existing technology and to provide a method in which the solid particles display an accelerated or quicker biodegradation in the environment whilst simultaneously retaining the prolonged use for treating multiple batches of substrates. [0007] The present inventors found that by initiating the degradation of the solid particles prior to releasing the solid particles to the environment the rates of degradation once in the environment are much accelerated.

[0008] The initiation of the degradation was found to be possible by several means. Degradation could be initiated by applying a physical degradation (e.g. heating) or by adding a degradation agent (e.g. an acid). Equally, initiation could be by effected by means of solid particles which additionally comprise a stimuli-responsive agent (such as a chalk or a photoacid generator) and apply a physical stimulation (light in the case of a photo-acid generator) or adding a chemical stimulant to which the stimuli-responsive agent responds (e.g. acid which dissolves a metal carbonate).

[0009] By utilising this approach, the present inventors found that it was possible to overcome the difficult tension between the desire to be able to reuse the solid particles many times to treat multiple batches of substrates, whilst simultaneously offering quick degradation in the natural environment.

[0010] Summary of the Invention

According to a first aspect of the present invention there is provided a method of treating a substrate comprising the steps of:

i. agitating a treatment composition comprising a liquid medium, the substrate and a multiplicity of solid particles comprising biodegradable polyester;

ii. optionally separating the solid particles comprising biodegradable polyester from the substrate;

iii. initiating the degradation of the solid particles;

wherein said solid particles have a size of from 1 mm to 100mm.

[0011] Methods

[0012] Physical degradation and degradation agent

[0013] The initiation in step iii. can be effected by exposing the solid particles to a physical degradation and/or adding a degradation agent.

[0014] Thus, the method is preferably one wherein step iii. comprises:

a. exposing the solid particles to a physical degradation so as to initiate degradation of the solid particles; and/or

b. adding to the solid particles a degradation agent, so as to initiate degradation of the solid particles. The degradation agent is suitably an agent which degrades the solid particles by chemical means, i.e. by one or more changes in the chemical composition of the solid particles. [0015] Preferably, step iii. of the first aspect of the present invention is performed in the presence of a phase transfer agent. Preferred phase transfer agents are surfactants. Preferred surfactants are nonionic, anionic, cationic and zwitterionic in nature. Cationic surfactants are especially suitable with preferred examples being long chain quaternary ammonium salts for example benzalkonium chloride.

[0016] The physical degradation and/or the degradation agent preferably act on the biodegradable polyester so as to initiate degradation. This is especially desirable in embodiments when the solid particles comprise no stimuli-responsive agent. More preferably the physical degradation and/or the degradation agent act on the ester linkages of the biodegradable polyester and most especially they cause hydrolysis of said ester linkages. This hydrolysis breaks down the biodegradable polyester chains and degrades the solid particles. In the case of physical degradation, it is preferred that a stimuli-responsive agent responds so as to initiate degradation of the solid particles, especially by hydrolysis of the ester linkages in the biodegradable polyester.

[0017] This method has the advantage that the solid particles can be free from any stimuli- responsive agent (as described below). So for example, the solid particles can consist exclusively of biodegradable polyester. Such solid particles are preferably free from any filler, preferably free from any inorganic filler.

[0018] Physical degradation

[0019] A preferred physical degradation is heating the solid particles. This is preferably performed in the presence of an aqueous liquid medium.

[0020] In order of increasing preference, the heating is to a temperature of at least 40°C, at least 50°C, at least 60°C, at least 70°C, at least 80°C or at least 90°C. Preferably the heating is to a temperature of no more than 100°C.

[0021] In order of increasing preference, the duration of the heating is no less than 1 second, no less than 30 seconds, no less than 1 minute, no less than 15 minutes, no less than 30 minutes, no less than 45 minutes and no less than 1 hour. In order of increasing preference, the duration of the heating is no more than 48 hours, no more than 36 hours, no more than 24 hours, no more than 16 hours, no more than 10 hours, no more than 8 hours, no more than 5 hours and no more than 3 hours.

[0022] The physical degradation can also comprise exposing the solid particles to radiation. This can be electromagnetic radiation and especially UV or gamma rays. The radiation can also be in the form of alpha particles or neutrons. Such radiation tends to break bonds in the solid particle quite randomly and energetically. [0023] Degradation agent

[0024] The degradation agent is preferably selected from an acid, a base, an oxidant and an enzyme. Mixtures of such degradation agents may be used. Of these, an acid or a base is preferred. Especially suitable acids are the organic acids (particularly acetic, citric, formic, oxalic) and the mineral acids (particularly sulfuric, hydrochloric, phosphoric and nitric). Suitable bases comprise metal hydroxides, especially the alkali metal hydroxides. Suitable oxidants include ozone, chlorine, oxygen, peroxides and hypohalites (e.g. hypochlorites). Suitable enzymes include esterases. Suitable bases include alkali metal hydroxides, oxides, hydrogen carbonates and carbonates.

[0025] The degradation agent is preferably added to the solid particles in a liquid medium which is aqueous.

[0026] When the degradation agent is acid, the pH of the aqueous liquid medium in step iii. is preferably below 7, more preferably below 5, especially below 3. The pH will typically be at least 1.

[0027] Once the degradation agent is added to the solid particles, the two are preferably permitted to contact for a time.

[0028] The time for contacting the degradation agent with the solid particles is in order of increasing preference at least 1 minute, at least 5 minutes, at least 10 minutes, at least 20 minutes and at least 30 minutes.

[0029] The time for contacting the degradation agent with the solid particles is in order of increasing preference no more than 24 hours, no more than 16 hours, no more than 8 hours, and no more than 5 hours.

[0030] In preferred embodiments, physical degradation (particularly by heating) and degradation by addition of a degradation agent (particularly an acid) are combined. This allows, for instance, acid hydrolysis of the biodegradable polyester to be much improved and accelerated.

[0031] Stimuli-responsive agent and method

[0032] The initiation in step iii. can be effected by use of solid particles comprising a stimuli- responsive agent. By utilising such solid particles, initiation can be effected by applying physical stimulation and/or a chemical stimulant to which the stimuli-responsive agent responds.

[0033] Thus, in this case, the method is preferably one wherein step iii. comprises:

a. exposing the solid particles to physical stimulation to which the stimuli-responsive agent responds, so as to initiate degradation of the solid particles; and/or b. adding to the solid particles a chemical stimulant to which the stimuli-responsive agent responds, so as to initiate degradation of the solid particles.

[0034] In order of increasing preference, the solid particles comprise at least 1wt%, at least 5wt%, at least 10wt%, at least 15wt% at least 20wt%, at least 30wt% and most especially at least 50wt% of stimuli-responsive agent.

[0035] In order of increasing preference, the solid particles preferably comprise no more than 90wt%, no more than 80wt% and no more than 70wt% of stimuli-responsive agent.

[0036] Preferably, the stimuli-responsive agent is or comprises a carbohydrate, an inorganic filler, a photo-acid generator, a latent acid or a mixture thereof. Of these, carbohydrates and inorganic fillers are preferred.

[0037] Preferred examples of carbohydrates include: monosaccharides (such as glucose, galactose and fructose), disaccharides (such as sucrose, lactose, maltose), malto- oligosaccharides (maltodextrins) and especially starch (more preferably amylose and/or amylopectin).

[0038] Preferred examples of inorganic fillers include a metal oxide, a metal hydroxide, a metal bicarbonate and especially a metal carbonate. Preferred carbonates include calcium carbonate and magnesium carbonate.

[0039] Examples of suitable metal oxides include zinc oxide and titanium dioxide, and whilst these inorganic fillers can decrease photodegradation in the environment they can helpfully promote both hydrolytic and enzymatic degradation. Thus, these stimuli-responsive agents are preferably paired with chemical stimulants which comprise acid or esterase.

[0040] Other suitable inorganic fillers include clays, metal silicates, metal sulfates and metal stearates.

[0041] Clays, metal silicates and metal sulfates have been found to be especially suitable as the stimuli-responsive agent when the solid particles are exposed to electromagnetic radiation (especially UV light) as the physical stimuli. These stimuli-responsive agents are thought to respond to light and to promote the degradation of the biodegradable polyester.

[0042] Metal stearates (especially iron and magnesium sulfate) have been found to be susceptible to respond to oxidation. Thus, such stimuli-responsive agents are preferably used in conjunction with a chemical stimulant which is an oxidizing agent. The preferred oxidizing agents are as mentioned above in reference to the degradation agent. The metal stearates are considered to work in conjunction with oxidizing agents to promote oxidative attack on the biodegradable polyester.

[0043] Preferred photo-acid generators include aryldiazonium salts, diarylhalonium salts and especially triarylsulfonium salts. [0044] Preferred latent acids are ammonium salts of strong acids especially strong organic acids such as sulfonic acid. A particularly preferred example is an ammonium salt of p-toluene sulfonic acid.

[0045] When a step iii. comprises exposing the solid particles to physical stimulation to which the stimuli-responsive agent responds, so as to initiate degradation of the solid particles, it is sufficient that the stimuli-responsive agent responds to promote subsequent degradation in the environment. Thus by example, when the stimuli-responsive agent is a photo-acid generator and light is used as the physical stimulation, the acid so generated within the solid particles will accelerate the degradation of the biodegradable polyester by promoting acid hydrolysis of the ester linkages. As a second example, when the stimuli-responsive agent is a latent acid and heat is used as the physical stimulation, the acid so generated within the solid particles will accelerate the degradation of the biodegradable polyester by promoting acid hydrolysis of the ester linkages. In either of these examples, some hydrolysis of the biodegradable polyester can be effected prior to release into the environment but this is not essential since the acid so generated is found to much accelerate environmental biodegradation.

[0046] When step iii. comprises adding to the solid particles a chemical stimulant to which the stimuli-responsive agent responds, so as to initiate degradation of the solid particles, it is preferred that the stimuli-responsive agent responds in such a way as to increase the number of pores within the solid particles. By example, when the stimuli-responsive agent is a carbohydrate and the chemical stimulant is an amylase, the enzymatic digestion of the carbohydrate within the solid particle causes pores to be formed within the solid particles. These pores increase the surface area and accessibility of the solid particle surface to water and to water ingress. Thus, whilst not wishing to be limited by any theory it is considered that the accelerated degradation in the environment results from an increase in the surface area and accessibility of water to the solid particle and the biodegradable polyester therein. As a second example, when the stimuli-responsive agent is an inorganic filler (especially a metal oxide, a metal hydroxide, a metal bicarbonate and especially a metal carbonate) and the chemical stimulant is an acid, the acid dissolution of the inorganic filler within the solid particle causes pores to be formed within the solid particles. These pores increase the surface area and accessibility of the solid particle surface to water and to water ingress and thus, by a mechanism similar to that described above, the degradation of the solid biodegradable polyester is accelerated once in the environment.

[0047] The stimuli-responsive agent can respond in different ways to the physical stimulation and/or to the addition of the chemical stimulant. [0048] Physical Stimulation

[0049] In one suitable method the solid particles comprise a stimuli-responsive agent which responds to physical stimulation.

[0050] Thus, for example when the stimuli-responsive agent is or comprises a photo-acid generator, the physical stimulation preferably is or comprises exposing the solid particles to electromagnetic radiation, which preferably generates an acid. The acid then initiates the hydrolytic degradation of the biodegradable polyester in the solid particles.

[0051] When the stimuli-responsive agent comprises a latent acid, the physical stimulation preferably comprises heating the solid particles. Preferably, the heating is to a temperature of at least 80°C, at least 90°C or at least 100°C. Preferably, the heating is to a temperature of no more than 200°C, more preferably no more than 150°C. In order of increasing preference, the heating is for at least 1 minute, at least 5 minutes, at least 15minutes, at least 30 minutes and at least 1 hours. In order of increasing preference, the heating is for no more than 48 hours, no more than 24 hours, no more than 16 hours and no more than 8 hours. The heating may be performed in air or more preferably in an inert atmosphere. Examples of suitable inert atmospheres include nitrogen and argon.

[0052] When the physical stimulation comprises exposing the solid particles to electromagnetic radiation the preferred stimuli-responsive agents include: photo-acid generators, clays, metal silicates and metal sulfates.

[0053] Chemical stimulation

[0054] In one suitable method the stimuli-responsive agent responds to a chemical stimulant. The chemical stimulant can, for example, dissolve or enzymatically digest the stimuli-responsive agent. The chemical stimulant may also work by oxidizing the stimuli-responsive agent.

[0055] Thus, for example, when the stimuli-responsive agent comprises a carbohydrate the chemical stimulant is preferably a carbohydrase (particularly amylase). In this way the carbohydrate is enzymatically digested.

[0056] Equally, when the stimuli-responsive agent comprises an inorganic filler (especially a metal oxide, hydroxide, bicarbonate or more especially a carbonate) the chemical stimulant is preferably an acid. In this way the stimuli-responsive agent is dissolved by acid. The chemical stimulant also serves as a degradation agent which can act to hydrolyse the biodegradable polyester. Thus, this method tends to degrade the solid particles in two ways.

[0057] When the stimuli-responsive agent is an inorganic filler (especially a metal oxide, hydroxide, bicarbonate or carbonate, and particularly a metal carbonate) it was surprisingly found that the solid particles were more resistant to hydrolysis and degradation in the treatment agitation step i. This facilitated agitation of more batches of substrates before the solid particle became unusable. The use of a chemical stimulant which is an acid permits the inorganic filler to be at least partially removed and thereby permits the solid particles and the biodegradable polyester to be more effectively initiated to degrade.

[0058] The chemical stimulant can be an acid, a base, an enzyme or an oxidant. These can be as preferred for the degradation agent. In the case of the enzyme, amylase is especially preferred for the chemical stimulant.

[0059] Solid particles comprising a biodegradable polyester

[0060] The solid particles are preferably prepared by extrusion. The biodegradable polymer and any optional stimuli-responsive agent can be combined in the extruder.

[0061] Biodegradable polyesters are a specific type of polyester that preferably break down after their intended purpose to yield natural by-products. In the case of poly(lactic acid), biodegradation produces lactic acid which is a natural product of anaerobic respiration and can be found in, for example, sour milk.

[0062] Preferably, the solid particles comprise at least 10wt%, preferably at least 20wt%, preferably at least 30wt% biodegradable polyester. The solid particles more preferably comprise at least 50wt%, at least 70wt%, at least 80wt%, at least 85wt% at least 90wt%, at least 95wt% and at least 99wt% of biodegradable polyester. Preferably, the remainder is the stimuli- responsive agent.

[0063] In some embodiments the solid particles consist of biodegradable polyester.

[0064] Preferably, when present the filler is inorganic. More preferably, the filler is an inorganic salt. A preferred inorganic salt is barium sulfate.

[0065] Preferably, the solid particles comprise no filler (and in particular no inorganic filler), and in this embodiment the solid particles can consist of biodegradable polyester. Such solid particles can be more readily formed into more spherical or ellipsoidal shapes which tend to separate from the substrate more readily. Additionally, such particles are more mechanically robust and less susceptible to abrasion than the corresponding particles containing fillers. Furthermore, such particles fully or completely degrade leaving no or little residues in the environment.

[0066] Preferably, at least some and more preferably all of the solid particles have a shape which is ellipsoidal or spheroidal as these shapes tend to be gentler to the substrate surface and tend to separate well from the substrate after performing the methods described herein. Most preferably, the solid particles have few or no edges or vertices. Preferably, the surfaces of the solid particles are entirely smooth. A preferred smooth surface comprises or consists of a curvilinear surface. Preferably, the solid particles have surfaces which are also initially free from pores, for example when viewed under an optical microscope, for example at 100x magnification.

[0067] Said solid particles comprising biodegradable polyester may be used in combination with solid particles comprising or consisting of other polymers. Preferably, however, at least 50% by number and more preferably all of the solid particles present comprise biodegradable polyester. When other polymers are present these are preferably also biodegradable (but not polyesters).

[0068] Preferably, the biodegradable polyester is insoluble in water. By insoluble we preferably mean having a solubility in water of less than 1wt%, more preferably less than 0.5wt%, especially less than 0.2wt%, and especially less than 0.1wt%. The solubility is preferably assessed in deionized water, preferably having a temperature of 20°C. The solubility is preferably assessed after immersing solid particles in water for a period of 24 hours. The pH of the deionized water is preferably from 5 to 7. In a preferred method the insolubility of the biodegradable polyester is established by: i. adding 1g of the biodegradable polyester to 10g of deionized water in a vial; ii. maintaining the temperature of the vial and its contents at 20°C for a period of 24 hours; iii. agitating the vial and its contents by rolling the vial on rollers; iv. isolating 1g of water after the 24 hours from the insoluble biodegradable polyester; v. drying the water so isolated in a sample container of exactly known weight by being placed in a vacuum oven at a temperature of 20°C and exposed to vacuum for a period of 24 hours; vi. weighing the dry sample container including any dry soluble biodegradable polyester and then calculating the weight of the dry soluble biodegradable polyester; vii. calculating the total amount of soluble biodegradable polyester and thereby the wt% of any soluble biodegradable polyester is established; viii. converting the wt% soluble biodegradable polyester into a wt% of insoluble biodegradable polyester. For the purposes of this method any mass of dry soluble polyester which is less than 0.0005g is regarded as being within experimental error equivalent to zero mass and therefore 100% insoluble.

[0069] In order of increasing preference, the solid particles preferably have a density of at least 0.5g/cm ³ , at least 0.75g/cm ³ , at least 0.9g/cm ³ , at least 1.0 g/cm ³ , at least 1.1g/cm ³ or at least 1.2g/cm ³ .

[0070] Preferably, the density of the solid particles is from 0.5g/cm ³ to 4.0g/cm ³ , more preferably from 1.0g/cm ³ to 3.0g/cm ³ , and especially from 1.1 g/cm ³ to 3.0g/cm ³ and most especially from 1.1 g/cm ³ to 1 5g/cm ³ .

[0071] Where the method of treating a substrate is a cleaning method then preferably the solid particles have lower densities so as to be kinder to the substrate, for example so as to lessen the tendency to damage or abrade the substrate. Thus, densities of no more than 3.0g/cm ³ , no more than 2.5g/cm ³ , no more than 1.8g/cm ³ , no more than 1.6g/cm ³ , no more than 1.5g/cm ³ , and no more than 1.4g/cm ³ are of value in cleaning methods according to the present invention. Thus, when the method of treating a substrate is a cleaning method then preferably the density of the solid particles is from 1.0g/cm ³ to 3.0g/cm ³ and especially from 1.1g/cm ³ to 1.5g/cm ³ .

[0072] Preferably, the solid particles are denser than the liquid medium, more preferably denser than water and especially more dense than water comprising relevant amounts of any optional additives.

[0073] In increasing preference, the solid particles preferably, have a size of no more than 50mm, no more than 40mm, no more than 30mm, no more than 25mm, no more than 20mm, no more than 15mm or no more than 10mm.

[0074] In increasing preference, the solid particles preferably, have a size of at least 2mm, at least 3mm, at least 4mm, at least 5mm, at least 6mm, at least 7mm, or at least 8mm.

[0075] Therefore, it is preferred that the solid particles have a size of from 1 mm to 40mm, more preferably from 1 mm to 30mm, especially from 2mm to 20mm, more especially from 3mm to 15mm and most especially from 4mm to 10mm.

[0076] The size is preferably a mean size, more preferably an arithmetic mean size. The arithmetic mean is preferably taken from a sample size of at least 100, at least 1 ,000 or at least 10,000 solid particles.

[0077] The size is preferably the longest linear dimension of the solid particle. The method of measuring the particle size is preferably performed by using callipers or a particle size measurement using image analysis, especially dynamic image analysis. A preferred apparatus for dynamic image analysis is a Camsizer as provided by Retsch. The mean size is preferably a number-weighted mean size.

[0078] The surface area of a solid particle is preferably from 10mm ² to 400mm ² , more preferably from 40mm ² to 200mm ² and especially from 50mm ² to 190mm ² .

[0079] Preferably, during step i. the ratio of solid particles to substrate is from 30:1 to 0.1 :1w/w (based on the dry mass of substrate), more preferably from 10:1 to 0.2:1w/w, with particularly favourable results being achieved with a ratio from 5:1 and 0.2:1w/w, and most particularly from 1 : 1w/w and 0.5: 1w/w.

[0080] Optional separation

[0081] Preferably step ii. in the method of the first aspect of the invention is not optional. Thus, preferably, the method of the present invention comprises the step (step ii.) separating the solid particles comprising biodegradable polyester from the substrate. [0082] This was found to be a preferred method as it prevents the substrate from being exposed to any chemicals or conditions used to initiate the degradation of the solid particles.

[0083] Re-use

[0084] Preferably, the solid particles are re-used, that is to say that they are used in the method of the first aspect of the present invention by repeating steps i. and ii. prior to step iii. Preferably this is achieved by performing steps i. and ii (which is not optional in this instance) many times using the same solid particles prior to performing step iii. In each step i. a fresh batch of substrate(s) is used.

[0085] In order of preference, steps i. and ii. are preferably repeated using the same solid particles at least 2, at least 3, at least 4, at least 5, at least 10, at least 20, at least 50, at least 100, at least 200, at least 300, at least 400 and at least 500 times prior to step iii. Preferably, steps i. and ii. are repeated no more than 10,000, especially no more than 5,000 times prior to step iii. It was especially surprising to the present inventors that solid particles as used in the present invention could survive so many repeated uses in the present method whilst simultaneously exhibiting the potential to initiate degradation in step iii effectively.

[0086] The present method can be used to treat many batches of substrate using the same solid particles.

[0087] Thus, preferably the method of the present invention is a method according to the first aspect of the present invention for treating multiple batches of substrates wherein a batch comprises at least one substrate, said method comprising the steps of:

i. agitating a treatment composition comprising a liquid medium, a first batch comprising at least one substrate and a multiplicity of solid particles comprising biodegradable polyester; ii. separating the solid particles comprising biodegradable polyester from the substrate(s); and said method further comprising the steps of:

(a) agitating a treatment composition comprising a liquid medium, a further batch comprising at least one substrate, and said solid particles separated in the preceding separation step; and

(b)separating the solid particles comprising biodegradable polyester from the substrate; optionally repeating steps (a) and (b) for subsequent batch(es) comprising at least one substrate.

[0088] The treatment procedure of an individual batch typically comprises the steps of agitating a treatment composition comprising the batch, said solid particles and said liquid medium in a treatment apparatus for a treatment cycle. A treatment cycle typically comprises one or more discrete treatment step(s), optionally one or more rinsing step(s), one or more step(s) of separating the solid particles from the treated batch (a“separation step”), optionally one or more extraction step(s) of removing liquid medium from the treated batch, optionally one or more drying step(s), and optionally the step of removing the treated batch from the apparatus.

[0089] Steps a) and b) are preferably performed at least 1 , at least 10, at least 100, at least 200 and at least 500 times prior to step iii. Preferably, steps a) and b) are repeated no more than 10,000, especially no more than 5,000 times prior to step iii.

[0090] The biodegradable polyester can be a copolymer but is preferably a homopolymer.

Polylactic acid obtained from polymerising lactic acid or lactide, more preferably lactide, is the preferred homopolymer.

[0091] A solid particle may comprise one or more different types of biodegradable polyester. Where a solid particle comprises more than one type of biodegradable polyester, these can be present within the same polymer molecule as a copolymer or they may be present as a physical blend of homopolymers or copolymers.

[0092] The method of the present invention as defined herein requires that a multiplicity of solid particles comprising biodegradable polyester is agitated with a liquid medium and a substrate. Such a multiplicity of solid particles may comprise one or more different types of biodegradable polyester. Where said multiplicity of solid particles comprises more than one type of biodegradable polyester, any given particle may comprise only one type of biodegradable polyester or more than one type of biodegradable polyester as described above.

[0093] Preferably, the biodegradable polyester is obtained by polymerizing one or more monomers at least one of which is selected from lactic acid (IUPAC 2-hydroxypropanoic acid), lactide, glycolic acid, hydroxy butyric acid, 3-hydroxy propionic acid, hydroxy valeric acid and caprolactone, including salts thereof. More preferably, the biodegradable polyester is obtained by polymerizing one or more monomers at least one of which is lactic acid or lactide, preferably lactide, including salts thereof.

[0094] Even more preferably, the biodegradable polyester is obtained by ring opening polymerisation of one or more monomers at least one of which is a cyclic ester, preferably lactide.

[0095] Salts may be of any kind without limitation but suitable salts for biodegradable polymers preferably include alkali metal salts (e.g. sodium, potassium and lithium salts), group II metal salts (especially magnesium and calcium) as well as ammonium and quaternary ammonium salts.

[0096] Preferably, the biodegradable polyester has a solidus of from 160°C and 250°C, more preferably from 160°C and 230°C. The solidus is the temperature of the onset of the melting phase of the biodegradable polyester. The solidus of the biodegradable polyester can be measured using known methodologies in the art, in particular using Differential Scanning Calorimetry (DSC).

[0097] Preferably, the glass transition temperature (Tg) of the biodegradable polyester is at least 50°C, more preferably at least 60°C. Preferably, the biodegradable polyester has a Tg of no more than 80°C, more preferably no more than 70°C.

[0098] Preferably, the melting point of the biodegradable polyester is from 100°C to 200°C, more preferably from 120°C to 180°C, especially from 140°C to 170°C and most especially from 150°C to 160°C.

[0099] It is preferred that the T g and melting point are established by conventional DSC techniques (preferably using a sample size of 5mg and a heating rate of 10°C/min). The value of Tg is preferably determined as the extrapolated onset temperature of the glass transition observed on the DSC scan (heat flow (W/g) against temperature (°C)), for instance as described in ASTM E1356-98. The melting point is suitably determined from the DSC scan as the peak endotherm of the transition.

[00100] Preferably, the biodegradable polyester comprises hydrolysable groups within the backbone of the polymer, wherein the backbone of the polymer is defined as the longest series of covalently bonded atoms.

[00101] Preferably, the biodegradable polyester comprises at least 1wt%, at least 5wt%, at least 10wt%, at least 20wt%, at least 30wt% and most especially at least 50wt% of alkyl esters, preferably wherein said alkyl esters are monomeric repeating units derived from the aliphatic compounds described above, namely lactic acid (IUPAC 2-hydroxypropanoic acid), lactide, glycolic acid, hydroxy butyric acid, 3-hydroxy propionic acid, hydroxy valeric acid and caprolactone, and more preferably wherein said alkyl esters are monomeric repeating units derived from lactic acid and lactide. The remaining components of the biodegradable polyester suitably comprise aryl ester or esters comprising both aryl and alkyl groups, preferably wherein said esters are monomeric repeating units derived from the aromatic group-containing compounds. Such alkyl esters and aryl-containing esters suitably form the backbone of the biodegradable polyester.

[00102] One simple method for determining the backbone composition is to fully hydrolyse the polyester by means of acid and optionally heating and then analysing the monomeric components, for instance by gel permeation chromatography (GPC). Alternatively, the biodegradable polyester composition can be established by NMR or mass spectrometry.

[00103] The biodegradable polyester comprises hydrolysable ester groups. By“ester group” we mean the -C(=0)-0- unit, which in the biodegradable polyester is bound at each end to a carbon atom. By“alkyl ester” we mean an -R-C(=0)-0- unit wherein R is an alkylene group. [00104] In one embodiment, the biodegradable polyester is polylactic acid or polylactide, i.e. a polyester characterised by the repeat unit -[CH(CH ₃ )-CO-0]-, and preferably having the formula CH ₃ -CH(0H)-C0-0-[CH(CH ₃ )-C0-0] _n -CH(CH ₃ )-C0-0H wherein n is an integer defined as the degree of polymerisation (wherein n suitably provides the preferred molecular weights referred to herein above).

[00105] The biodegradable polyester may be completely amorphous, completely crystalline or semi crystalline (i.e. containing both crystalline and amorphous regions). Typically, the biodegradable polyester is semi-crystalline. The biodegradable polyester is preferably at least partially amorphous.

[00106] The number-average molecular weight of the biodegradable polyester is the total weight of the polymer sample divided by the total number of molecules in the sample.

[00107] The number-average molecular weight is preferably established by GPC. The solvent is preferably tetrahydrofuran (THF). The standard used to calibrate the molecular weight is preferably polystyrene.

[00108] Preferably, the biodegradable polyester has a number-average molecular weight of at least 15,000 Daltons, more preferably at least 20,000 Daltons, even more preferably at least 30,000 Daltons and especially at least 40,000 Daltons.

[00109] It is especially preferred that the biodegradable polyester has a number-average molecular weight of from 30,000 Daltons to 500,000 Daltons.

[00110] Preferably, the biodegradable polyester has a number-average molecular weight of no more than 500,000, especially no more than 400,000, more especially no more than 300,000 and particularly no more than 200,000 Daltons.

[00111] Substrate

[00112] A substrate treated by the claimed method, within the scope of the present invention, may comprise any of the following, for example, plastics materials, paper, cardboard, metal, glass or wood.

[00113] Preferably, the substrate is pliable and may be flexible.

[00114] In a preferred embodiment, the substrate is or comprises a textile, a fibre, a yarn. These substrates are especially suited to cleaning or laundry methods.

[00115] In a further preferred embodiment, the substrate is or comprised an animal skin. Such substrates are especially suited to tanning or retanning methods. The animal skin may be in the form of a hide, a pelt, or untreated, partially or fully treated leather. The skin can be taken from a mature or juvenile animal. The animal may be a mammal, more preferably a ruminant and especially livestock such as goats, pigs, sheep and especially cows. It will be appreciated that human skins are not within the scope of the term“animal skins” in the context of the present invention.

[00116] When the substrate is or comprises a textile, the textile may comprise either a natural fibre, such as cotton, or a synthetic fibre, for example nylon 6,6 ora polyester, or a blend of natural and synthetic fibres.

[00117] The substrate can be soiled or clean prior to the method of treating according to the first aspect of the present invention. Preferably, the substrate is initially soiled.

[00118] When the method of treating comprises cleaning (or laundering), the substrate is preferably soiled before the method according to the first aspect of the present invention is performed, that is to say prior to the first step.

[00119] The soil, when present on the substrate, may be in the form of, for example, dust, dirt, foodstuffs, beverages, animal products such as sweat, blood, urine, faeces, and/or plant materials such as grass, and inks and paints.

[00120] Liquid Medium

[00121] Preferably, the liquid medium is aqueous. The liquid medium preferably, is or comprises water. Where water is used in conjunction with other liquids, these liquids may be organic liquids such as alcohols, esters, ethers, amides and the like.

[00122] In order of increasing preference, the liquid medium comprises at least 50wt%, at least 60wt%, at least 70wt%, at least 80wt%, at least 90wt%, at least 95wt% or at least 99wt% of water. Most preferably, the liquid medium consists of water and no other liquid components.

[00123] Preferably, the liquid medium has a pH range of from pH 3 to pH 13, preferably this pH is maintained during step i. The pH of the liquid medium is dependent on the substrate and application to which the method of treatment is applied, for example in a leather treatment, such as dye fixing in tanning, the pH typically will be under acidic conditions, below pH 7. While for leather treatment dye penetration methods the pH is preferably greater than pH 7. For laundry methods, to enhance fabric care milder conditions are preferred and typically the pH of the liquid medium is preferably in the range of from pH 7 to pH 12, more preferably from pH 8 to 12.

[00124] Applications

[00125] Preferably, treating is or comprises or consists of:

cleaning, more preferably laundering;

tanning or retanning; or

one or more of dyeing, abrading, fading, desizing and biofinishing. [00126] It will be appreciated that cleaning means cleaning the substrate. Similarly, tanning or retanning means tanning or retanning the substrate. Similarly, dyeing, abrading, fading, desizing and biofinishing all mean dyeing, abrading, fading, desizing and biofinishing the substrate.

[00127] Of these options, cleaning methods are especially preferred.

[00128] Preferably, when the method of treating a substrate is a cleaning method, such as a laundry method, the treatment composition preferably additionally comprises surfactant(s), and/or an enzyme(s). Preferably, said enzyme(s) is/are selected from a lipase, protease and amylase. Preferably, said surfactant(s) is/are selected from anionic, non-ionic, cationic, amphoteric and/or zwitterionic surfactants.

[00129] The treatment composition may additionally comprise a bleaching agent, examples of which include peroxides, hypochlorites and ozone.

[00130] Where the method of treatment is a cleaning method, such as laundry, then according to the present invention an excellent cleaning performance may be achieved whilst using significantly reduced levels of detergents and lower temperatures. Thus, as an example, methods concerned with garment cleaning according to the invention, may be carried out at temperatures not exceeding 65°C, and good performance is generally achieved at 5°C to 40°C. Though temperatures greater than 40°C can be used, generally this is not preferred.

[00131] Agitation

[00132] The agitation may be in the form of shaking, stirring, jetting and tumbling. Of these tumbling is especially preferred. Preferably, the treatment composition is placed into a rotatable treatment chamber which is rotated so as to cause tumbling. The agitation may be continuous or intermittent. Preferably, the agitation is performed for a period of from 1 minute to 600 minutes, more preferably, from 5 minutes to 180 minutes and even more preferably, from 20 minutes to 120 minutes.

[00133] Preferably, the agitation in step i. is performed at a temperature of at least 5°C, more preferably at least 10°C.

[00134] Preferably, the agitation in step i. is performed at a temperature of no more than 90°, more preferably no more than 80°C and especially no more than 70°C.

[00135] The agitation may be performed in an apparatus comprising a rotary chamber similar to that as described in PCT patent publications W02007/128962, WO2011/098815, WO2014/147389, and PCT/GB/2017/053815. [00136] Initiating degradation in step iii.

[00137] In step iii. the degradation of the solid particles is initiated. This does not mean that the degradation must be completed in step iii.

[00138] Especially when the solid particles comprise no stimuli-responsive agent, the term“initiated” preferably means that the solid particles are at least partially degraded.

[00139] Preferably, step iii. is performed to such an extent that any one or more of the following apply:

i. the number average molecular weight of the biodegradable polyester has reduced by at least 10%;

ii. the number average molecular weight of the biodegradable polyester is no more than 40,000;

iii. the solid particles have pores when they were initially non-porous;

iv. the solid particles become friable to pressure which can be exerted between human fingers;

v. the solid particles become gelatinous;

vi. at least 10wt% of the solid particles have been degraded into material having a size smaller than 1 mm;

vii. the solid particles have lost at least 0.5wt% during step iii.

[00140] Characteristics i. and ii. can be established by the GPC methods as mentioned above.

[00141] The existence of pores (characteristic iii.) in the solid particles are preferably established by optical microscopy at 100x magnification and by visual assessment. The present inventors have found that increasing the porosity of the solid particles is not desirable during steps i. and ii. of the method of the present invention but will very much assist in accelerating environmental degradation after step iii.

[00142] Characteristic vi. is readily established by accurately weighing the dry solid particles prior to step iii. After step iii. the solid particles are isolated using a mesh having a pore size of 1 mm. The so isolated particles are dried and reweighed.

[00143] Sending to the environment

[00144] Preferably, after step iii. the solid particles are sent into the environment.

[00145] The solid particles can be sent to degrade whilst in contact with soil and/or water. [00146] The solid particles preferably degrade whilst in contact with water, at a temperature of 20°C and at a pH of 6-8.

[00147] Preferably, the degradation initiated by the method of the present invention is such that no solid particles can be visually identified when 1g of the solid particles resulting from the method according to the present invention has been in submerged in 10g of water, at a temperature of 20°C and at a pH of 6-8 for a period of 5 years, 3 years, 2 years, 1 year, 6 months, more preferably 3 months and especially 1 month. In this way, the present inventors have provided a means to utilise solid particles comprising biodegradable polyesters which can be sent to the environment and which degrade markedly more rapidly than would otherwise be possible.

[00148] These tests can also be performed at 10°C or 5°C which are more stringent and demanding.

[00149] Particles

[00150] In a second aspect of the invention, there is provided a novel solid particle comprising, biodegradable polyester as described hereinabove, and particularly a novel solid particle comprising biodegradable polyester and a stimuli-responsive agent as described hereinabove.

[00151] In particular, the solid particle has a size of 1 mm to 100mm and comprises the biodegradable polyester and preferably also comprises the stimuli-responsive agent. The solid particles are preferably present in a multiplicity.

[00152] A multiplicity as used herein preferably means at least 100, more preferably at least 1 ,000 solid particles.

[00153] General

[00154] In the present invention, any items expressed in the singular are also intended to encompass the plural unless stated to the contrary. Thus, words such as“a” and“an” mean one or more.

[00155] The present invention will now be illustrated by the following non-limiting examples.

[00156] Examples

[00157] Materials

[00158] Polylactide material was obtained from Natureworks LLC under the tradename Ingeo 2003D.

[00159] The Polylactide material was hot melt extruded using a twin screw extruder and underwater cut into particles having an average size of 4 mm for one batch (hereinafter PLA - 1) and 6.5 mm for another batch (hereinafter PLA - 2). The size being the longest linear dimension. The polylactide within PLA - 1 had a number average molecular weight of approximately 56,000 Daltons. The polylactide within PLA - 2 had a number average molecular weight of approximately 73,000 Daltons. The molecular weights were determined by GPC using at 40°C in tetrahydrofuran.

[00160] Nylon 6 was twin screw extruded with barium sulphate in a weight ratio of 55wt% Nylon to 45wt% barium sulfate and underwater cut into particles having an average size of 4 mm for one batch (Nylon - 1) and 6 mm for another batch (Nylon - 2). The size again being the longest linear dimension.

[00161] The detergent used in the treating of the substrates was Pack 1 which is a detergent available from Xeros.

[00162] The substrate used in some of the treatments were EM PA 108 stain sheets which were obtained from Swissatest, these sheets had dimensions of approximately 12cm by 12cm and comprised a mixture of standard stains to be cleaned.

[00163] In order to add realistic levels of soiling into some treatments SBL2004 sebum sheets obtained from WFK were used. These add soil into the treatment step in a realistic way.

[00164] Cleaning Examples

[00165] Cleaning Example 1

[00166] A Xeros washing machine having a loading capacity of 25Kg of dry substrate as described in PCT patent publication WO 2011/098815 was used to treat (clean) the substrates in accordance with the present invention. The Xeros washing machine was loaded with a 20Kg load comprising a British Standard ballast comprising a mixture of towels (EMPA 351), sheets (EMPA352) and pillow cases (EMPA353). In addition, 6 EMPA 108 stain sheets, 10 sebum sheets both as described in the materials section were loaded into the Xeros washing machine.

[00167] Pack 1 detergent (250g) as described in the materials section was used for each wash load to assist the cleaning.

[00168] Solid particles (25kgs) in the form of PLA - 1 as described in the materials section were used.

[00169] Water was used as the liquid medium.

[00170] The treatment was cleaning which was performed for a period of 1 hour at a temperature of 20°C. The Xeros washing machine agitated (tumbled) the composition comprising the solid particles, the water, the substrate (EMPA 108 stain sheets) and the detergent (Pack 1).

[00171] The Xeros washing machine automatically separated the solid particles from the substrate towards the end of the 1 hour period and moved the solid particles to a separate sump. [00172] The washing machine contents were then unloaded. The EM PA 108 stain sheets were removed from the washload, ironed using a trouser press and left overnight to dry and acclimatise.

[00173] Test methodology

[00174] EMPA108 stain sheets obtained from Cleaning Example 1 were measured using a spectrophotometer from Konica Minolta with model number CM3600A. Each stain is measured 4x, twice on each side and an average Y value is recorded for each stain type. There were five stain types on each EMPA stain sheet. The“Sum of Y” value is then taken as the sum of each of the five average Y values for each stain.

[00175] Comparative Cleaning Example 1

[00176] Comparative Cleaning Example 1 was performed in exactly the same way as Cleaning Example 1 except that the solid particles were replaced with 25Kg of Nylon - 1 as described in the materials section.

[00177] Results

[00178] The Sum of Y values for Cleaning Example 1 and Comparative Cleaning Example 1 were as indicated below in Table 1.

[00179] Table 1

[00180] In this set of results a higher Sum of Y value indicates a better effectiveness of the cleaning.

These results showed that, within the error margins of experimentation, the cleaning performance of the present invention is at least as good if not better than the known art which uses non-biodegradable polymers such as Nylon.

[00181] Initiating Degradation 1

[00182] Initiation of the degradation of the solid particles PLA - 1 was effected by placing an exactly known weight of approximately 1 g of said particles in a container along with 100mls of a 1 M sodium hydroxide (base) solution containing 0.025g of benzalkonium chloride as a phase transfer agent (surfactant). The container contents were maintained at a temperature of 70 °C for a period of 1 hours, 2 hours and 4 hours. [00183] After each time period the solid particles were then removed from the container, strained to remove any excess sodium hydroxide solution, dried on a filter paper and then weighed. The mass loss was calculated as a %mass loss.

[00184] Results

[00185] The mass loss of the solid particles was a tabulated in Table 2.

[00186] Table 2

[00187] Higher mass loses indicate more extensive initiation of degradation.

[00188] Initiating Degradation 2

[00189] PLA - 1 solid particles were separated into two batches B1 , and B2 where the degradation was initiated in different ways.

[00190] For batch B1 the solid particles were submersed in water at a temperature of 50°C for a period of 28 days.

[00191] For batch B2 the solid particles were submersed in water at a temperature of 50°C for a period of 35 days.

[00192] The number averaged molecular weight of each batch of solid particles was remeasured after the initiation of the degradation using GPC.

[00193] Results

[00194] The number averaged molecular weight of each batch of solid particles was as indicated in Table 3.

[00195] Table 3

[00196] A lower number averaged molecular weight equates to a more significant degree of initiating the degradation of the solid particles. As might be expected prolonged initiation of degradation results in solid particles with a polyester having a low number averaged molecular weight.

[00197] Environmental Degradation

[00198] Exactly known amounts of solid particles B1 and B2 of around 1 g (each after initiating the degradation) were then subjected to environmental degradation. Each batch was further split into sub-batches the sub-batches were submersed in water at a temperature of 20°C (as found commonly in the environment) for a period of either 2 months or 4 months.

[00199] After the environmental degradation the solid particles were then isolated, strained to remove any excess water, dried on a filter paper, vacuum dried and then weighed.

[00200] The percentage mass loss was calculated for each sub-batch.

[00201] Results

[00202] The percentage mass loss for each sub-batch was as indicated in Table 4.

[00203] Table 4

[00204] A larger percentage mass loss corresponds to a faster environmental degradation of the solid particles. It was clearly demonstrated that after the initiation of degradation the environmental degradation was progressing well at a temperature of 20°C over a relatively short period of a few months.

[00205] T able 4 shows that with different extents of initiation of degradation the rate of environmental degradation can be controlled and accelerated.