FIELD OF INVENTION

[001] This invention refers to a process of depolymerization of polypropylene (PP) and polyethylene (PE) through chemical recycling by employing the use of solvent of terpenic origin, particularly d-limonene, and a cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB). Instead, depoiymerization is performed using PP polymers and also low density (LOPE) and high density (HOPE) PE both post-consumption.

BACKGROUND

[002] Chemical recycling occurs through processes of depoiymerization by solvolysis (hydrolysis, alcoholysis, amylose), or by thermal methods (low and high temperature pyrolysis, gasification, hydrogenation) or by even thermal/catalytic methods (pyrolysis and the use of selective catalysts).

[003] Depoiymerization is the reversion of a polymer to its monomer, or to a smaller molecular weight polymer. This reversion may occur when the polymer is exposed to very high temperatures, to certain chemicals or moisture.

[004] There are several industrial chemical processes that have as objective to retrieve the plastic monomers by means of depoiymerization.

[005] Vicente, G. et al., 2009 (J. Anal. Appl. Pyrolysis, v. 85, pp. 366-371) studied the chemical recycling of polyethylene (PE) using phenol as solvent. The products obtained were linear hydrocarbons fractions (C ₅ -C ₁₂ ) as paraffinic compounds and a-olefins. It was found that the phenol promoted the plastic degradation and the PEAD conversion facilitating the formation of specific products; but with toxicity, which makes unfeasible its use in resins.

[006] The two-stage thermal depoiymerization was studied by Zassa, M. et al., 2010, J. Anal. Appl. Pyrolysis, v.87, pp.248-255, being the first step per PE melting and the second per volatilization effect through heating. In this study, the volatile products were observed at temperatures less than 450°C and with pyrolysis at temperatures above 800°C, with 85% to 75% values of gaseous products such as ethylene.

[007] ft was found that in the last four years the development of different methodologies of depolymerization of polyethylene, polypropylene and other polymers; as, for example, in Hamad, K. et al., 2013, Polymer Degradationand Stability, v.98, pp. 2801-2812, where a revision of all the methodologies currently used is made.

[008] XIAO, X. et al, 1994, Energy & Fueh, 8, pp. 113, reveals the chemical recycling of polypropylene (PP) using the depolymerization reaction with addition of liquefaction, since there was a release of hydrocarbon gases. Initially, the preparation of specific superacids catalysts, for example, iron oxides in a mixture of

polymer/catalyst (mass/mass) was made. In a second step, the PP and catalyst mixture was placed in a stainless steel autoclave reactor, being purged with nitrogen gas and pressurized with hydrogen gas to achieve a desired pressure. Then, the reactor was heated to the melting point of the mixture, between 350°C and 400'C, being further initiated the mechanical stirring. After the PP depolymerization reaction, paraffinic compounds from branched carbonic chain (C5-C12) were obtained.

[009] it is observed that in the methodologies of chemical depolymerization of PP and PE, understood in the literature, highly toxic solvents and highly carcinogenic, such as xylene, benzene and toluene are used.

[0010] The document US 6,031.142 discloses a method of pretreatment for polystyrene-containing materials to form a solution of polystyrene in a processing solvent from which the styrene in the polystyrene in materials is recovered. Materials are mixed with a solvent of environmentally acceptable pretreatment and have a boiling point lower than the processing solvent. The pretreatment solvent is selected from among the group consisting of d-limonene, l-limonene, dipentene, and their mixtures to dissolve the polystyrene and form a polystyrene solution in pretreatment solvent. Before the actual processing to recover the styrene, the pretreatment solvent is substantially replaced by the processing solvent to form the polystyrene solution in processing solvent. [0011] The document PI0402976-3 describes a method of recycling PET (Polyethylene terephthalate) packaging through depolymerization using hydrated ethanol and under supercritical conditions.

[0012] The document PI0605201-0 shows a process of obtaining oligomers from the bis-hydroxy-ethylene terephthalate (BHET) or bis-hydroxy-propylene terephthalate (BHPT) or bis-hydroxyethyl-ethylene terephthalate (BHEET) families, which are resulting from chemical recycling through Glycolysis of polyethylene terephthalate) (PET) reaction. In the aforementioned document, a prior preparation of the polymer is held, where the polymer is impregnated with a solution of Glycols, for example, ethylene glycol, propylene glycol, or mixtures thereof, in order to reduce the reaction time of depolymerization. Furthermore, several metal-based catalysts can be used such as those belonging to the group of alkali metals, alkaline-earth metals or, yet, transition metals such as, lanthanides and actinides. Instead, a solution of zinc acetate was used as a catalyst.

[0013] It is revealed a process for obtaining Terephthalic acid by means of PET chemical recycling in the document BR102013001662-4. In the referred method the cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) is used. Depolymerization is performed using the post-consumption PET previously clean with isopropyl alcohol, NaOH solution and in the presence of cationic surfactant CTAB, to obtain the Terephthalic acid (TPA) monomer. The cationic surfactant added worked as a catalyst, significantly reducing the reaction time from 6 hours to 1 hour and 50 minutes.

[0014] Spazzini, S. et o/., 29 ^th Annual Meeting of the Brazilian Society of Chemistry (SBQ), May/2006, no. AB-048, studied the polystyrene recycling through thermal depolymerization using solvents such as chloroform, benzene and toluene. The reaction occurred in stainless steel autoclaves with Teflon housings, where products were obtained, in great majority, as linear hydrocarbons and also aromatic and cyclic compounds.

[0015] A process for the depolymerization of acrylic polymers via catalytic pyrolysis is revealed in the document PI0500910-3, more specifically depolymerization of acrylic polymers via catalytic pyrolysis of acrylic acid monomer esters replaced or not, from a polymeric material. This process comprises contacting said polymer with the high accessibility zeolitic catalyst, under process conditions in order to separate and collect the resulting monomers of the depolymerization.

[0016] Achillas, D.S. et a/., in "Recent Advances in the Chemical Recycling of Polymers (PP, PS, LOPE, HOPE, PVC, PC, Nylon, PMMA)", reveal the use of limonene to dissolve EPS (expanded polystyrene). This solvent has the ability to dissolve EPS in large quantities, securely, and with negligible degradation of the polymer performance properties. Conventional melt separation methods cause to a big drop in the polymer molecular weight due to thermal degradation. Consequently, the PS (polystyrene) dissolved can be precipitated by the addition of a non-solvent to the mix. The solvent is evaporated to vacuum and reused.

[0017] The document PI0403740-5 discloses a process for chemical recycling of polyethylene terephthalate post consumption and equipment to perform said chemical recycling. This procedure includes the steps of (a) PET simultaneous flaked or granulated feeding and of depolymerization agent consisting of water, caustic soda, potash, soda ash or other appropriate alkali, or mixtures thereof; (b) PET melting and mixture of this material melted with the depolymerizing powered; (c) mixture of drag agent as nitrogen, carbon dioxide or another gas, or even water vapor; (d) separation of suspended material in the drag chain of molten material, which is purged to the power point, with partial disposal of this molten material; and (e) separation of Terephthalic acid and ethylene glycol solution.

[0018] This invention proposes a new methodology of PE and PP chemical recycling, by depolymerization reaction of bottles, plastic bags and disposable cups post- consumption, employing as a solvent the d-limonene and as reaction catalyst the cationic surfactant CTAB (Hexadecyltrimethylammonium Bromide). The use of surfactant molecules in interfacial and surface reactions represents a good alternative to the processes of PE and PP chemical depolymerization, and can optimize the time and the reaction temperature.

[0019] The CTAB choice is because of its use as one of the major cationic surfactants applied on the catalysis of reactions (Maniasso, N. - Quim. Nova, 24, p. 87 (2001)). [0020] This invention has considerable advantages facing the prior art. Its main advantage is the use of CTAB as a catalyst of the chemical reactions of PE and PP depolymerization. Therefore, this invention proposes a new chemical recycling process of these polymers using the d-limonene (green solvent) and a cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) in order to obtain a resin quickly and efficiently, reducing thus the reaction cost.

[0021] Thereby, this invention is more efficient in relation to the cost-benefit ratio when compared to the prior art due to having a smaller number of reaction steps and a simple and fast operating system.

ABSTRACT

[0022] In one embodiment, this invention describes a process of obtaining suppressing polyethylene resin through chemical recycling of PE comprising the steps of i) PE selection; ii) washing with detergent and water; iii) drying; iv) grinding; v) addition of terpenic solvent and cationic surfactant to the PE; vi) system heating and stirring; vii) obtaining oligomer products and adding additives; viii) characterization of the resin.

[0023] In one embodiment, this invention describes a process of obtaining suppressing polypropylene resin through chemical recycling of PP comprising the steps of i) PP selection; ii) washing with detergent and water; iii) drying; iv) grinding; v) addition of terpenic solvent and cationic surfactant to the PP; vi) system heating and stirring; vii) obtaining oligomer products and adding additives; viii) characterization of the resin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] This invention will now be described in reference to attached figures, in which:

[0025] Figure 1 illustrates the infrared spectrum for high and low density PE depolymerization;

[0026] Figure 2 illustrates the ESI (±)-MS spectra for EP oligomers;

[0027] Figure 3 illustrates the infrared spectrum for PP depolymerization; and

[0028] Figure 4 illustrates the ESI (±)-MS spectra for PP oligomers;

DETAILED DESCRIPTION OF THE INVENTION

[0029] The matter required of this invention will now be described in detail below, by way of example and not limited to, since both materials and methods per se herein revealed can comprise different details and procedures, without leaving the scope of the invention. Unless indicated otherwise, all parties and percentages are in weight, [0030] This invention proposes a new methodology of PE and PP chemical recycling by means of depolymerization reaction of materials such as bottles, plastic bags and disposable cups post-consumption.

[0031] in one embodiment, this invention describes a process of obtaining suppressing polyethylene resin through chemical recycling of PE comprising the steps of i) PE selection; ii) washing with detergent and water; iii) drying; iv) grinding; v) addition of terpenic solvent and cationic surfactant to the PE; vi) system heating and stirring; vii) obtaining oligomer products and adding additives; viii) characterization of the resin.

[0032] In one embodiment, this invention describes a process of obtaining suppressing polypropylene resin through chemical recycling of PP comprising the steps of i) PP selection; ii) washing with detergent and water; iii) drying; iv) grinding; v) addition of terpenic solvent and cationic surfactant to the PP; vi) system heating and stirring; vii) obtaining oiigomer products and adding additives; viii) characterization of the resin.

[0033] Oiigomer products obtained in processes of this invention are ethylene oligomer and propylene oligomer, respectively.

[0034] In this process, the cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) (0.01 mol/L) as reaction catalyst is preferably used. The CTAB improves the yield of the reaction in approximately 90%, when a proportion in volume of 50:30 mL of the mixture of terpenic solvent/cationic surfactant reacts with lg of PE.

[0035] instead, the terpenic solvent of the present invention is d-limonene.

[0036] In the process of this invention the additive is instead lignin.

[0037] For the procedure used in this invention, a stainless steel reactor with a 500 mL capacity and with an open pressure system was used.

[0038] At first, the PE material separation post-consumption was held, followed by the washing step where the material was washed with water, detergent and sterilized and dried in a stove at 40°C for 2 hours. Then, a grinding step was held, in Cutting Mills model SM 300, Retsch Gmbh brand, with 1500 rpm rotation, using a sieve with a particle size of 1 mm. In a stainless steel reactor, terpenic solvent have been added (20-50 mL, of Q.UALISOL), cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) (0.1 to 50 ml, 0.01 mol/L), of the Sigma-Aldrich brand, to the PE material obtained in grinding step (0.2 - 1 g). The reactor was heated at a temperature of 180°C, which was kept constant, under constant stirring and for a period of 40 minutes. After we add 10% of iignin to the oligomer product obtained (ethylene oligomer) in order to increase the viscosity of the final product.

[0039] After the PP material separation post-consumption, the material was washed with water, detergent and sterilized and dried in a stove at 40°C for 2 hours. Then, a grinding step was held, in Cutting Mills model SM 300, Retsch Gmbh brand, with 1500 rpm rotation, using a sieve with a particle size of 1 mm. In a stainless steel reactor, terpenic solvent have been added (20-50 ml, of QUALISOL), and cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) (0.1 to 50 ml, 0.01 mol/L), of the Sigma-Aldrich brand, and ferric sulfide (0.2g of the Vetec brand) to the PP material obtained in grinding step (0.2 - 1 g). The reactor was heated at a temperature of 150'C, which was kept constant, under constant stirring and for a period of 30 minutes. During the system stability, the separation of depoiymerization components in the form of ice bath occurs. After we add 10% of Iignin to the oligomer product obtained (propylene oligomer) in order to increase the viscosity of the final product.

[0040] Instead, the amount of cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) added in this invention is between 20 and 50 mL (0.01 g/mL).

[0041] Instead, the proportion of cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) for terpenic solvent is 1:1.

Example

[0042] The following example is offered by way of example in order to aid the understanding of this invention and should not be considered as limiting to its scope.

[0043] The assessment of PE and PP resins obtained and CTAB used as chemical catalyst in this process demonstrated the obtaining of a suitable and pure product. Results obtained are shown in the figures indicated.

[0044] EXAMPLE 1

[0045] The study of chemical depoiymerization was held to determine the efficiency of the d-limonene as solvent and CTAB as reaction catalyst. In order to analyze the surfactant action process efficiency, the volume of the CTAB in alkaline medium was kept constant and the results are presented in figures 1, 2, 3 and 4.

[0046] Figure 1 illustrates the infrared spectrum for high and low density PE depolymerization; Results show that the oligomers in products of high density HOPE, and low density LDPE depolymerization are in vibrational peaks of 2900 cm ^'1 and 1500 cm ^"1 corresponding to C-H and C=C groups, respectively.

(0047) Figure 2 shows the results of the ESI(±)-MS spectra for PE oligomers in positive and negative modes. The spectra also state the presence of oligomers with spaced peaks from 15 and 20 u with m/z 200-800 and an average molar mass distribution of approximately m/z 300 in the negative mode and m/z 255 in positive mode, respectively.

[0048] Figure 3 shows the infrared Spectrum for PP depolymerization indicating that oligomers are present in products of PP depolymerization, which are in vibrational peaks of 890 cm-1 to Groups C=C and of 2800-3100 cm-1 to Groups -CH2 and -CH3, respectively, which are consistent with those described by Lai, S. et al, JOURNAL OF MOLECULAR CATALYSIS A: CHEMICAL, V.26S, P.15-24, 2007.

[0049] Figure 4 corresponds to the ESI(±)-MS spectra for PP oligomers in the positive and negative modes. The spectra also state the presence of oligomers with spaced peaks from 15 and 20 u with m/z 200-800 and an average molar mass distribution of approximately m/z 250 in the negative mode and m/z 500, 520 and 550 in positive mode, respectively.