RECYCLING PLASTICS
20240254345 ยท 2024-08-01
Assignee
Inventors
Cpc classification
B29B17/02
PERFORMING OPERATIONS; TRANSPORTING
International classification
Abstract
This invention relates to the use of a surfactant for deinking plastic substrates. The invention also relates to a process for deinking plastic substrates with a deinking solution comprising the surfactant and a base.
Claims
1. Use of a surfactant to remove ink from plastic substrates, the surfactant being a trialkyl hydroxyalkyl ammonium salt.
2. Use of a surfactant according to claim 1, wherein the surfactant is present in a deinking solution, the deinking solution comprising the surfactant and a base; optionally wherein the deinking solution is an aqueous deinking solution.
3. A process for removing ink from a plastic substrate, wherein the process comprises: i) exposing the plastic substrate to an aqueous deinking solution comprising a base and a surfactant to provide a deinked plastic substrate, the surfactant being a trialkyl hydroxyalkyl ammonium salt.
4. The process of claim 3, wherein the surfactant has a structure according to formula (I): ##STR00004## wherein R.sup.1 is selected from C.sub.8-C.sub.20 alkyl, CH.sub.2Ph, and (CH.sub.2).sub.nOH; R.sup.2 is C.sub.1-C.sub.6 alkyl; R.sup.3 is C.sub.1-C.sub.6 alkyl; X.sup.? is an anion; and n is selected from 2, 3, 4, 5, or 6.
5. The process of claim 4, wherein R.sup.1 is C.sub.8-C.sub.20 alkyl.
6. The process of claim 4, wherein R.sup.2 and R.sup.3 are each C.sub.1-C.sub.3 alkyl.
7. The process of claim 4, wherein X.sup.? is selected from halide (F.sup.?, Cl.sup.?, Br.sup.?, I.sup.?), hydroxide (.sup.?OH), acetate (OC(O)Me) and sulphate (SO.sub.4.sup.?).
8. The process of claim 4, wherein n is 2.
9. The process of claim 4, wherein the surfactant has a structure according to formula (II): ##STR00005## wherein R.sup.1 is C.sub.12-C.sub.14 alkyl.
10. The process of claim 3, wherein the base is an inorganic base selected from LiOH, NaOH, KOH, Na.sub.2CO.sub.3, NaHCO.sub.3, K.sub.2CO.sub.3, and KHCO.sub.3;
11. The process of claim 3 wherein the base is NaOH.
12. The process of claim 3, wherein the surfactant is present in the deinking solution in an amount of from 0.025 wt % to 2 wt %.
13. The process of claim 3, wherein the base is present in the deinking solution in an amount of from 0.5 wt % to 10 wt %.
14. The process of claim 3, wherein the deinking solution further comprises an anionic detergent booster.
15. The process of claim 14, wherein the anionic detergent booster is selected from sodium lauryl sulfate (SLS), sodium lauryl ether sulfate (SLES), ammonium lauryl sulfate (ALS), and combinations thereof.
16. The process of claim 14, wherein the anionic detergent booster is present in an amount of from 0.1 to 2 wt %.
17. The process of claim 3, wherein the plastic substrate is selected from polypropylene (PP), polyethylene (PE), and low-density polyethylene (LDPE).
18. The process of claim 3, wherein the plastic substrate is a film.
19. The process of claim 3, wherein the surfactant is in contact with the plastic substrate for a period of 10 minutes or less.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0078] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:
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DETAILED DESCRIPTION
[0087] The terms deinking solution and aqueous deinking solution are used interchangeably throughout this description.
[0088] The terms deink, removal of ink, and ink removal are used interchangeably throughout this description to refer to the permanent separation of ink from a plastic substrate.
[0089] A deinked plastic substrate according to the present invention is any plastic substrate defined herein, wherein the amount of ink present on the plastic substrate is less than the amount of ink on the plastic substrate prior to it being exposed to the deinking solution.
[0090] The amount of ink remaining on a deinked plastic substrate may be less than 70%, less than 60%, less than 50%, less than 40%, less than 30%, less than 20%, or less than 10% of the amount of ink present on the plastic substrate prior to being exposed to the deinking solution. The ink may be completely removed from the plastic substrate, i.e. the plastic substrate may be fully deinked.
[0091] The amount of ink remaining on the deinked plastic may be determined by comparing the dry weight of the plastic substrate before and after the deinking has occurred. The amount of ink remaining on the deinked plastic may be determined by using a volatile solvent (such as acetone or IPA) to strip the surface of the plastic substrate. After stripping, both the solvent and the cleaned substrate are dried and the weight of removed ink is determined by the average weight loss of the plastic substrate and the weight of ink recovered.
[0092] For the avoidance of doubt, and unless otherwise explicitly disclosed (such as in the case of a deinked or fully deinked plastic substrate) a plastic substrate is a substrate comprising any non-zero amount of ink on at least one of its surfaces.
[0093] The term exposing the plastic substrate to an aqueous deinking solution, or variants thereof, means that the deinking solution is brought into contact with the plastic substrate.
[0094] The terms robust ink, more robust ink, or less robust ink refer to the relative strength of adhesion of an ink to the surface of the plastic substrate. A more robust ink will have a greater adhesion to a plastic substrate than a less robust ink.
[0095] The term alkyl, as used herein, refers to a linear or branched hydrocarbon chain. For example, the term C.sub.1-6 alkyl refers to a linear or branched hydrocarbon chain containing 1, 2, 3, 4, 5 or 6 carbon atoms.
[0096] Typically, the term alkyl refers to a linear hydrocarbon chain comprising from 8 to 20 carbon atoms. Typically, alkyl chains are unsubstituted, except where, in certain circumstances, an alkyl group may be substituted with a phenyl or hydroxy group.
[0097] A trialkyl hydroxyalkyl ammonium salt, as used herein, refers to a salt comprising a quaternary ammonium cation having three alkyl chains and one hydroxyalkyl chain, and an anion. A trialkyl hydroxyalkyl ammonium salt, as used herein, may also refer to a salt comprising a quaternary ammonium cation having three alkyl chains and one hydroxyalkyl chain, and an anion, wherein any one of the three alkyl chains may be substituted with a phenyl or hydroxy group.
[0098] A polyolefin, as used herein, refers to any polymer formed from alkene monomer units, i.e. any linear or cyclic hydrocarbon having one or more carbon-carbon double bonds. Typically said alkene monomers are polymerised by free radical polymerisation processes to form the polyolefin.
[0099] A multilayer film, as used herein, is a laminated structure comprising one or more layers of material, each independently selected from PE, PP, Nylon, PVDC, PET, and aluminium.
[0100] Throughout the description and claims of this specification, the words comprise and contain and variations of them mean including but not limited to, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
[0101] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
[0102] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.
[0103] Use of a surfactant according to the present invention, and the process of deinking a plastic substrate according to the present invention, give rise to substantial benefits in the recycling of plastic substrates. For example, the present invention provides improved deinking of plastic substrates such that food grade plastics are of sufficient quality following deinking that they can be added into virgin plastics (at 35 wt %) for reuse as food-grade plastic substrates.
EXAMPLES
Example 1
[0104] Approximately 100 kg of PP scrap rigid regrind with PP In Mould Labels (IML) was supplied from the manufacture of butter containers.
[0105] The PP scrap flakes were processed in a laboratory stirrer, according to the following operative conditions:
TABLE-US-00001 WASHING TEST # 16 Washing water (l) 3 L NaOH (%) 5% Surfactant (ml) Hydroxyethyl laurdimonium chloride (40 wt % solution) 50 ml Ratio water:detergent 60:1 Temperature (? C.) 85-90 Time (min) 10 samples PP scrap with PP labels (200 g)
[0106] After washing, samples were rinsed with cold water. To facilitate the evaluation of label removal, some flakes before and after washing were selected and visually evaluated. The results of the experiment can be seen in
[0107] PP IML were not removed from the surface of PP flakes. However, the writing and ink on PP IML was completely removed by the washing process.
[0108] The deinked plastic substrate was of a standard sufficient for reuse as food-grade plastic, according to German Food and Feed Code (LFGB) and European Framework Regulation (EC) No. 1935/2004.
Example 2
[0109] The process of Example 1 was repeated in a stainless steel cement mixer with 50 kg of PP scrap rigid regrind with PP IML. The mixing time remained at 10 minutes. All other conditions were scaled relative to Example 1.
[0110] As with Example 1, the process resulted in the complete removal of all print.
[0111] The deinked plastic substrate was of a standard sufficient for reuse as food-grade plastic, according to German Food and Feed Code (LFGB) and European Framework Regulation (EC) No. 1935/2004.
Example 3
[0112] LDPE films were washed to assess the removal of ink from these plastic substrates. The LDPE films were post-industrial films, i.e. plastic films received following production of the film. In other words, no-consumer use (including food exposure) of the film has occurred prior to being deinked.
[0113] The LDPE films were printed with resin acids and Rosin acids, fumarated esters with pentaerythritol. The films were printed with a loading of 0.5 g/m.sup.2 line colours, 1 g/m.sup.2 spot and 1.5 g/m.sup.2 white inks. The LDPE films were 55 microns thick.
[0114] The printed LDPE films were washed under the following conditions:
TABLE-US-00002 Deinking solution: 5% NaOH 0.3 wt % Hydroxyethyl laurdimonium chloride 2 L water Exposure time: 10 minutes Temperature of 65? C. deinking solution: Rinsing: Cold water Drying: Hot air
[0115] Samples that were removed, rinsed, and dried were visually analysed for remaining ink. The LDPE films were found to be completely deinked, i.e. no ink remained. The results of this experiment can be seen in
Example 4
[0116] 200 g of plastic substrate (50 g of 20 ?m thick PP film, 50 g of 50 ?m thick PP film, 100 g thermoformed PP) was processed in a laboratory stirrer, according to the following operative conditions:
TABLE-US-00003 WASHING TEST TEST 1 Washing water (l) 3 L NaOH (%) 3% Surfactant (ml) Hydroxyethyl laurdimonium chloride (40 wt % solution) 50 ml Ratio water:detergent 60:1 Temperature (? C.) 85 Time (min) 10
[0117] After washing, samples were rinsed with cold water. To facilitate the evaluation of label removal, some flakes before and after washing were selected and visually evaluated. The results of the deinking process are demonstrated in
[0118] The deinked plastic substrate was of a standard sufficient for reuse as food-grade plastic, according to German Food and Feed Code (LFGB) and European Framework Regulation (EC) No. 1935/2004.
Example 5
[0119] 200 g of plastic substrate (50 g of 20 ?m thick PP film, 50 g of 50 ?m thick PP film, 100 g thermoformed PP) was processed in a laboratory stirrer, according to the following operative conditions:
TABLE-US-00004 WASHING TEST TEST 4 Washing water (l) 3 L NaOH (%) 2% Surfactant (ml) Hydroxyethyl laurdimonium chloride (40 wt % solution) 150 ml Ratio water:detergent 20:1 Temperature (? C.) 60 Time (min) 10
[0120] After washing, samples were rinsed with cold water. To facilitate the evaluation of label removal, some flakes before and after washing were selected and visually evaluated. The results of the deinking process are demonstrated in
Example 6
[0121] 200 g of plastic substrate (50 g of 20 ?m thick PP film, 50 g of 50 ?m thick PP film, 100 g thermoformed PP) was processed in a laboratory stirrer, according to the following operative conditions:
TABLE-US-00005 WASHING TEST TEST 5 Washing water (l) 3 L NaOH (%) 2% Surfactant (ml) Hydroxyethyl laurdimonium chloride (40 wt % solution) 150 ml Ratio water:detergent 20:1 Temperature (? C.) 85 Time (min) 10
[0122] After washing, samples were rinsed with cold water. To facilitate the evaluation of label removal, some flakes before and after washing were selected and visually evaluated. The results of the deinking process are demonstrated in
Example 7
[0123] 200 g of plastic substrate (50 g of 20 ?m thick PP film, 50 g of 50 ?m thick PP film, 100 g thermoformed PP) was processed in a laboratory stirrer, according to the following operative conditions:
TABLE-US-00006 WASHING TEST TEST 6 Washing water (l) 3 L NaOH (%) 2% Surfactant (ml) Hydroxyethyl laurdimonium chloride (40 wt % solution) 50 ml Anionic detergent booster Sodium lauryl sulfate 25 ml Ratio water:detergent Temperature (? C.) 60 Time (min) 10
[0124] After washing, samples were rinsed with cold water. To facilitate the evaluation of label removal, some flakes before and after washing were selected and visually evaluated. The results of the deinking process are demonstrated in
Comparative Example 8
[0125] A deinking solution comprising 3 wt % NaOH and 2 wt % of one of the surfactants listed below was used to compare the deinking capabilities of several surfactants falling outside the scope of the present invention to that of a surfactant falling within the scope of the present invention. The deinking solution was heated to 70? C. and BOPP film or PP material was exposed to the solution for 2-3 hours.
TABLE-US-00007 Surfactant Result Benzalkonium chloride Deinking incomplete Alkyl dimethyl benzyl after 1 hour ammonium chlorides (C12-16) Alkyl dimethyl ethylbenzyl ammonium chloride (C12-14) Alkyl dimethyl ethylbenzyl ammonium chlorides (C12-18) Didecyldimethylammonium chloride Hydroxyethyl laurdimonium chloride Deinking complete after 10 minutes
[0126] The results of these experiments are shown in