A method and apparatus for processing a bioplastic derived from cellulosic fabric scraps

Abstract

There is provided a method and apparatus for processing a bioplastic that can be used in multiple industries such as, for example, food / non-food applications, apparel industry applications, retail store packaging and so forth. It is preferable that the present invention is able to enable replacement / reduction of use of conventional non- biodegradable plastic originating from petrochemicals.

Description

[0001] A METHOD AND APPARATUS FOR PROCESSING A BIOPLASTIC DERIVED FROM CELLULOSIC FABRIC SCRAPS

[0002] Field of the Invention

[0003] The present invention relates to a method and apparatus for processing a bioplastic, specifically from cellulosic fabric scraps.

[0004] Background

[0005] In the present day, clothing and trends rapidly evolve, such that there is now a concept of “fast fashion”, where users who wish to be seen at the forefront of fashion typically buy clothing several times per season, and not just once for each climate season of the year.

[0006] Unfortunately, this has led to a situation where clothing is perceived to be disposable, as users typically encounter issues storing the clothing that they have purchased. This can be a sustainability issue as fast fashion often involves use of fabric which includes non-biodegradable components. Only a small percentage of clothes are recycled into new garments.

[0007] Much of the technical difficulty in recycling worn-out clothes back into new clothing comes down to their composition. The majority of clothes in our wardrobes are made from a blend of textiles, with polyester being the most widely used fibre. The reason for polyester's prevalence is the low cost of fossil-based synthetic fibres, making them a popular choice for fast fashion brands which prioritise price above all else. As one would appreciate, the non-biodegradable components in the disposed apparel have an adverse effect on the earth, and it is desirable if such non-biodegradable components could be replaced by biodegradable components and consequently, lead to more sustainable practices. Summary

[0008] In a first aspect, there is provided a method for preparing a bioplastic derived from cellulosic fabric scraps, the method comprising: shredding a pre-determined weight of cellulose fabric; mixing shredded cellulose fabric with a sulphuric acid solution; filtering the sulphuric acid solution, retaining acidic shredded cellulose fabric; washing the acidic shredded cellulose fabric with dilute sodium hydroxide solution to produce a neutral cellulose solution; washing the neutral cellulose solution with distilled water on a plurality of repetitions to form a washed cellulose mixture; and drying the washed cellulose mixture using a desiccate to form a powder.

[0009] In a second aspect, there is provided a method for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the method comprising: adding a resin to the bioplastic powder; mixing the resin with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; adding at least one compatibilizer via dosing to the resin and bioplastic powder to form a mixture; mixing the mixture at a second mixing rate, a second temperature, and a second duration; adding refined cellulose to the mixture in accordance with a predetermined resin to reinforcement ratio; mixing the refined cellulose with the mixture at a third mixing rate, a third temperature, and a third duration; and forming a uniform batch of pellets.

[0010] In a third aspect, there is provided a method for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the method comprising: adding cellulose to the bioplastic powder; mixing the cellulose with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; adding at least one compatibilizer via dosing to the cellulose and bioplastic powder to form a mixture; mixing the mixture at a second mixing rate, a second temperature, and a second duration; adding resin to the mixture in accordance with a predetermined resin to reinforcement ratio; mixing the resin with the mixture at a third mixing rate, a third temperature, and a third duration; and forming a uniform batch of pellets.

[0011] In a fourth aspect, there is provided an apparatus for preparing a bioplastic derived from cellulosic fabric scraps, the apparatus being configured to: shred a pre-determined weight of cellulose fabric; mix shredded cellulose fabric with a sulphuric acid solution; filter the sulphuric acid solution, retaining acidic shredded cellulose fabric; wash the acidic shredded cellulose fabric with dilute sodium hydroxide solution to produce a neutral cellulose solution; wash the neutral cellulose solution with distilled water on a plurality of repetitions to form a washed cellulose mixture; and dry the washed cellulose mixture using a desiccate to form a powder.

[0012] In a fifth aspect, there is provided an apparatus for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the apparatus being configured to: add a resin to the bioplastic powder; mix the resin with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; add at least one compatibilizer via dosing to the resin and bioplastic powder to form a mixture; mix the mixture at a second mixing rate, a second temperature, and a second duration; add refined cellulose to the mixture in accordance with a predetermined resin to reinforcement ratio; mix the refined cellulose with the mixture at a third mixing rate, a third temperature, and a third duration; and form a uniform batch of pellets.

[0013] In a sixth aspect, there is provided an apparatus for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the apparatus being configured to: add cellulose to the bioplastic powder; mix the cellulose with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; add at least one compatibilizer via dosing to the cellulose and bioplastic powder to form a mixture; mix the mixture at a second mixing rate, a second temperature, and a second duration; add resin to the mixture in accordance with a predetermined resin to reinforcement ratio; mix the resin with the mixture at a third mixing rate, a third temperature, and a third duration; and form a uniform batch of pellets. In a seventh aspect, there is provided an apparatus configured to produce a bioplastic film from bioplastic pellets, the apparatus comprising: an extruder configured to operate at a first speed and a first temperature; a thickness controller configured to operate at a second speed and a second temperature; a constrictor configured to operate at a third speed and a third temperature; and a winder configured to operate at a fourth speed and a fourth temperature.

[0014] It will be appreciated that the broad forms of the invention and their respective features can be used in conjunction, interchangeably and / or independently, and reference to separate broad forms is not intended to be limiting.

[0015] Brief Description of the Drawings A non-limiting example of the present invention will now be described with reference to the accompanying drawings, in which:

[0016] FIG 1 provides a preferred embodiment of a process flow for a method of preparing a bioplastic;

[0017] FIG 2 provides a preferred embodiment of a process flow for a method of preparing bioplastic pellets;

[0018] FIG 3 provides preferred embodiment of an apparatus for processing a bioplastic;

[0019] FIG 4 shows an example apparatus for processing a bioplastic; and

[0020] FIG 5 shows a table of different types of pellets that can be produced by the method of FIG 2.

[0021] Detailed Description

[0022] There is provided a method and apparatus for processing a bioplastic that can be used in multiple industries such as, for example, food / non-food applications, apparel industry applications, retail store packaging and so forth. It is preferable that the present invention is able to enable replacement / reduction of use of conventional non- biodegradable plastic originating from petrochemicals. This can be carried out by incorporating a waste material, for example, pre-consumer garment industry fabric scraps, in the production of bioplastics which take lesser time to get composted. Alternatively, pre-consumer garment industry fabric scraps can also be upcycled in terms of usage to facilitate circularity in the fashion value chain.

[0023] Referring to FIG 1 , there is shown a method 100 of preparing a bioplastic derived from cellulosic fabric scraps, for example, cotton, viscose, lyocell and modal fibers. Cellulosic fabric scraps are desirable as the method 100 is configured to process cellulose. At step 105, scraps of cellulose fabric are shredded. The scraps of cellulose fabric are typically pre-consumer garment industry scraps. A weight of the scraps of cellulose fabric is at least 8kg.

[0024] At step 110, a 10% sulphuric acid solution is prepared by continuous stirring. The sulphuric acid solution is formed by 98% sulphuric acid (30ml) and distilled water (3.06L). Typically, this ratio is maintained during preparation of the sulphuric acid solution if more or less of the solution is required.

[0025] At step 115, a sample of the shredded fabric scrap is weighed, and in this embodiment, 8kg of the shredded fabric scrap is typically required.

[0026] At step 120, the sample of the shredded fabric scrap and the 10% sulphuric acid solution are mixed. This can be carried out for about a duration of 2.5hrs and at about a temperature of 85°C.

[0027] At step 125, the acid solution is filtered, leaving an acidic cellulose filtrate behind.

[0028] At step 130, the acidic cellulose filtrate is neutralized by washing with dilute sodium hydroxide solution to produce a neutral cellulose solution. For example, the dilute sodium hydroxide solution is dilute caustic soda solution, and the amount required is about 30L.

[0029] At step 135, the neutral cellulose solution is washed repeatedly (at least 4 times) with distilled water to form a washed cellulose mixture. Typically, about 20L of distilled water is used.

[0030] At step 140, drying of the washed cellulose mixture is carried out using a desiccate in order to form a powder. In some embodiments, the powder may undergo crushing. The powder is then stored in airtight containers.

[0031] It is desirable that the cellulose based bioplastic powder produced by the method 100 can be employed in place of conventional non-biodegradable plastic originating from petrochemicals. The use of the cellulose based bioplastic primarily aids in cost reduction, decrease in time taken to form compost, and also marginally increases tensile strength of the material. In addition, it also preserves water vapor permeability of the material. The bioplastic powder can be used in multiple applications such as, for example, food / non-food applications, apparel industry applications, retail store packaging and so forth. The cellulose based bioplastics resultant from the powder can be made into a lightweight material which demonstrates good tensile strength. In addition, the cellulose content of the material also enables the better biodegrability.

[0032] It should be noted that the method 100 can be carried out by one apparatus, or a combination of various apparatus.

[0033] Referring to FIG 2, there is shown a method 200 for preparing bioplastic pellets, the bioplastics preferably being produced by the method 100. The method 200 can be used to produce at least four different types of pellets, as shown in FIG 5. In the various pellets shown in FIG 5, the resin used is polybutylene succinate (PBS), and the reinforcing material is microcrystalline cellulose. However, differences of the pellets arise due to use of different compatibilizers and different “resin to reinforcement material” ratios. It should be appreciated that the compatibilizers are used in order to create a suitable bond between the PBS resin and the cellulose. The compatibilizers used can include, for example, glycerine, stearic acid, soybean oil, PEG-1500 coating, and so forth. The compatibilizers are used to enhance compatibility with resins, and ensures strength and thin-ness of the material. Typically glycerine is used as a compatibilizer to make more flexible composite films required for highly flexible packaging. Similarly, stearic acid is used as a compatibilizer to make more smoother and uniform composite films required for visually attractive flexible packaging. Soybean oil is used as a compatibilizer to make more transparent and extensible films required for flexible packaging with good optical transparency. Finally, PEG-1500 is used as a compatibilizer to make films that have good tensile strength required for sturdy flexible packaging. In addition, the “resin to reinforcement material” ratios can range from 3:1 to 5:1 , which have been determined to provide consistent material characteristics. These ratios are desirable for preferred bonding between the cellulose and the PBS resin, whereby any variation in the ratio would cause deterioration of final product quality.

[0034] At step 205, either resin or cellulose is added as per desired “resin to reinforcement material” ratios, for example as shown in FIG 5. The resin can be PBS.

[0035] At step 210, mixing is carried out at low speed, for example, mixing is done at an RPM of 250, for a duration of about 15 minutes. The temperature is also maintained at around 45°C.

[0036] At step 215, at least one compatibilizer is added via dosing, where the compatibilizers used can include, for example, glycerine, stearic acid, soybean oil, PEG-1500 coating, and so forth. For example, the at least one compatibilizer comprises 20% of a weight of the cellulose. Stearic acid and PEG-1500 coating is added at 1.5-2% of the weight of the fillers, while soybean oil is added at 10% of the weight of the resin. Dosage of compatibilizers is calculated with respect to an amount of cellulose fillers.

[0037] At step 220, further mixing is carried out at a high speed, for example, mixing is done at an RPM of 550, for a duration of about 5 to 15 minutes. The temperature is also maintained at around 75°C to 95°C.

[0038] At step 225, if PBS was added at step 205, then refined cellulose is added as per desired “resin to reinforcement material” ratios, for example as shown in FIG 5. Similarly, if cellulose was added at step 205, then PBS is added as per desired “resin to reinforcement material” ratios, for example as shown in FIG 5.

[0039] At step 230, mixing is then carried out at a higher speed, for example, mixing is done at an RPM of 1000, for a duration of about 20 minutes. The temperature is also maintained at around 75°C to 95°C. At step 235, a uniform mixture of pellets formed from the preceding steps is then loaded to a twin screw extruder 300 as shown in FIG 3 to produce fiber strands. The extruder configured to produce filler or compound masterbatches. Temperature and motor speed is a crucial factor here. For a motor RPM of 65-80 rpm, a substantially constant temperature profile is maintained for all the heating zones of the extruder. It should be appreciated that the extruder 300 carries out a sequence of processes including feeding, melting, dispersing, homogenizing and discharging.

[0040] The method 200 is configured to produce filament strands with a diameter of at least 4 mm. However if an extruder head of the extruder 300 is changed, pipes, cylinders or other type of profiles can also be produced, depending on desired application.

[0041] It should be noted that the method 200 can be carried out by one apparatus, or a combination of various apparatus. The method 200 can be used to produce cylindrical pipes or rectangular profiles. It can also be used to make flat films of high thickness. The method 200 is used as it ensures desirable mixing of resins and fillers and other chemicals to produce consistent products.

[0042] Referring to FIG 4, there is shown an apparatus 400 for processing a bioplastic. The apparatus 400 is a film blowing machine. The pellets produced from the method 200 can be used with the apparatus 400 to produce a film output. Subsequently, the film can be used for applications like for example, blow molded bottles, sheet extrusion for plates, lamination material for packaging, and so forth.

[0043] The apparatus 400 comprises an extruder 410, a thickness controller 420, a constrictor 430, and a winder 440.

[0044] A preferred set-up of the apparatus 400 will include the following parameters:

[0045] - the extruder 410 at 25-60 RPM;

[0046] - the thickness controller 420 at 10-25 RPM;

[0047] - the constrictor 430 at 39-50 RPM; and

[0048] - the winder 440 at 39-50 RPM.

[0049] In addition, respective stages of the extruder 410 are set as:

[0050] - stage 1 : 145°C;

[0051] - stage 2: 155°C;

[0052] - stage 3: 165°C; and

[0053] - stage 4: 175°C.

[0054] The parameters above are subsequently able to provide a film with the following parameters:

[0055] - tensile strength of at least 20MPa;

[0056] - horizontal tearing strength of at least 2000MPa;

[0057] - vertical tearing strength of at least 3000MPa;

[0058] - elongation of at least 200%;

[0059] - thickness of about 0.03mm;

[0060] - density of 1 .3 - 1 .4 g / cm3;

[0061] - melt flow index of at least 7;

[0062] - sealing strength of at least 2800MPa;

[0063] - biodegradation period of 150 days; and

[0064] - retention of properties after 4 instances of melt-extrusions.

[0065] The apparatus 400 is configured to produce films which are lightweight, have high tensile strength and are biodegradable. Apparatus 400 can be only used to produce films in a desirable manner which leads to efficiency and productivity.

[0066] Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

[0067] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for preparing a bioplastic derived from cellulosic fabric scraps, the method comprising: shredding a pre-determined weight of cellulose fabric; mixing shredded cellulose fabric with a sulphuric acid solution; filtering the sulphuric acid solution, retaining acidic shredded cellulose fabric; washing the acidic shredded cellulose fabric with dilute sodium hydroxide solution to produce a neutral cellulose solution; washing the neutral cellulose solution with distilled water on a plurality of repetitions to form a washed cellulose mixture; and drying the washed cellulose mixture using a desiccate to form a powder.

2. The method of claim 1 , wherein the acid solution is formed by 98% sulphuric acid (30ml) and distilled water (3.06L).

3. The method of either claim 1 or 2, wherein the pre-determined weight of cellulose fabric is at least 8kg.

4. The method of any of claims 1-3, wherein the dilute sodium hydroxide solution is dilute caustic soda solution.

5. The method of any of claims 1-4, further including crushing the powder.

6. A method for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the method comprising: adding a resin to the bioplastic powder; mixing the resin with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; adding at least one compatibilizer via dosing to the resin and bioplastic powder to form a mixture; mixing the mixture at a second mixing rate, a second temperature, and a second duration; adding refined cellulose to the mixture in accordance with a predetermined resin to reinforcement ratio; mixing the refined cellulose with the mixture at a third mixing rate, a third temperature, and a third duration; and forming a uniform batch of pellets.

7. A method for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the method comprising: adding cellulose to the bioplastic powder; mixing the cellulose with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; adding at least one compatibilizer via dosing to the cellulose and bioplastic powder to form a mixture;mixing the mixture at a second mixing rate, a second temperature, and a second duration; adding resin to the mixture in accordance with a predetermined resin to reinforcement ratio; mixing the resin with the mixture at a third mixing rate, a third temperature, and a third duration; and forming a uniform batch of pellets.

8. The method of either claim 6 or 7, wherein the first mixing rate is 250 RPM, the first temperature is 45°C, and the first duration is 15 minutes.

9. The method of either claim 6 or 7, wherein the second mixing rate is 550 RPM, the second temperature is between 75°C to 95°C, and the second duration is between 5 to 15 minutes.

10. The method of either claim 6 or 7, wherein the third mixing rate is 1000 RPM, the third temperature between 75°C to 95°C, and the third duration is 20 minutes.11 . The method of any of claims 6 to 10, wherein the resin is PBS.

12. The method of any of claims 6 to 11 , wherein the at least one compatibilizer is a substance selected from a group consisting of: glycerine, stearic acid, soybean oil, and PEG-1500 coating.

13. The method of any of claims 6 to 12, wherein the predetermined resin to reinforcement ratio is selected from a group consisting of: 5:1 , 3:1 and 4:

1.

14. An apparatus for preparing a bioplastic derived from cellulosic fabric scraps, the apparatus being configured to: shred a pre-determined weight of cellulose fabric; mix shredded cellulose fabric with a sulphuric acid solution; filter the sulphuric acid solution, retaining acidic shredded cellulose fabric; wash the acidic shredded cellulose fabric with dilute sodium hydroxide solution to produce a neutral cellulose solution; wash the neutral cellulose solution with distilled water on a plurality of repetitions to form a washed cellulose mixture; and dry the washed cellulose mixture using a desiccate to form a powder.

15. An apparatus for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the apparatus being configured to: add a resin to the bioplastic powder; mix the resin with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; add at least one compatibilizer via dosing to the resin and bioplastic powder to form a mixture; mix the mixture at a second mixing rate, a second temperature, and a secondduration; add refined cellulose to the mixture in accordance with a predetermined resin to reinforcement ratio; mix the refined cellulose with the mixture at a third mixing rate, a third temperature, and a third duration; and form a uniform batch of pellets.

16. An apparatus for preparing bioplastic pellets from a bioplastic powder derived from cellulosic fabric scraps, the apparatus being configured to: add cellulose to the bioplastic powder; mix the cellulose with the bioplastic powder at a first mixing rate, a first temperature, and a first duration; add at least one compatibilizer via dosing to the cellulose and bioplastic powder to form a mixture; mix the mixture at a second mixing rate, a second temperature, and a second duration; add resin to the mixture in accordance with a predetermined resin to reinforcement ratio; mix the resin with the mixture at a third mixing rate, a third temperature, and a third duration; and form a uniform batch of pellets.

17. An apparatus configured to produce a bioplastic film from bioplastic pellets, the apparatus comprising: an extruder configured to operate at a first speed and a first temperature; a thickness controller configured to operate at a second speed and a second temperature; a constrictor configured to operate at a third speed and a third temperature; and a winder configured to operate at a fourth speed and a fourth temperature.

18. The apparatus of claim 17, wherein the first speed is between 25-60 RPM, and the first temperature is 145°C.

19. The apparatus of claim 17, wherein the second speed is between 10-25 RPM, and the second temperature is 155°C.

20. The apparatus of claim 17, wherein the third speed is between 39-50 RPM, and the third temperature is 165°C.

21. The apparatus of claim 17, wherein the fourth speed is between 39-50 RPM, and the fourth temperature is 175°C.

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