Method for deodorization from recycled high density polyethylene (HOPE)

Abstract

The invention relates to a method for removing odors from recycled plastics. The invention particularly relates to a method for removing bad odors from recycled high density polyethylene (HOPE) that includes the stages of heating, chemical washing, rinsing, drying and mixing.

Description

[0001] METHOD FOR DEODORIZATION FROM RECYCLED HIGH DENSITY POLYETHYLENE (HDPE)

[0002] Technical Field

[0003] The invention relates to a method for removing odors from recycled plastics.

[0004] The invention particularly relates to a method for removing bad odors from recycled high density polyethylene (HDPE) comprising the steps of heating, chemical washing, rinsing, drying and mixing.

[0005] State of the Art

[0006] Recycled plastics play a critical role in terms of environmental sustainability. Reprocessing plastic waste helps to protect natural resources and prevents environmental pollution by reducing the amount of waste. In this context, High Density Polyethylene (HDPE) has an important place in the recycling process. HDPE has a wide range of uses thanks to its durability and chemical resistance, and is also a highly efficient type of plastic in the recycling process. The recycled form of HDPE can be used in a wide range of products from water pipes to toys and packaging materials. However, recycled plastics have a problem such as having a bad odor.

[0007] Today, high density polyethylene (HDPE or PEHD) is one of the most widely used plastics. HDPE is used in a wide variety of rigid plastic applications. HDPE is suitable for regrinding, HDPE injection and blow molding applications. A plastic-free environment is impossible in workplaces, but less impact can be created with recyclable HDPE plastics. HDPE is a popular type of plastic that is easily found in many businesses. HDPE plastic consumables and other items are important to keep business operations running smoothly and cost-effectively.

[0008] Applications for recycled HDPE (R-HDPE) include non-food grade HDPE packaging, or in some cases food grade HDPE packaging. Commonly made from regrind HDPE, packaging includes shampoo bottles, milk bottles, bleach bottles, detergent bottles, chemical and cosmetic containers, recycling bins and shopping bags, beverage bottles, bottle caps, plastic items and more. Due to its high tensile strength, it is widely used in factories and warehouses. Non-food applications such as cable and wire sheathing can also be made from HDPE recycling. A very common recycled HDPE application is piping systems. The qualities that recycled high-density and low-density polyethylene (HDPE and LDPE) composites must meet for the production of pressure pipes and fittings for buried or above-ground applications are specified in the international standard ISO 4427. It can be quite tough, but is ideal for manufacturing hard shells such as computer cases. Recycled HDPE can also be used to produce plastic lumber as well as technical fibers for a variety of non-food applications, such as indoor and outdoor furniture, flower pots, floor tiles, and toys. To summarize, regrinding of HDPE can be used in non-food and packaging applications, such as textile fibers and furniture.

[0009] The different uses of HDPE plastics in the business world are summarized as follows:

[0010] • Containers and drums

[0011] • Boxes and pallets

[0012] • Utility pipes

[0013] • Thin film plastic shopping bags

[0014] • Household containers

[0015] • Cosmetic containers, such as face wash, shampoo, and conditioner

[0016] • Cleaning product containers, such as laundry detergent and all-purpose cleaners

[0017] • Hardscape materials, such as garden tools and planters

[0018] • Durable plastic floor tiles, crates, sheets, and film plastics

[0019] HDPE waste raw material is also often called HDPE scrap. Currently, HDPE is mainly recycled using the mechanical recycling approach. The type of HDPE raw materials or HDPE scrap can be generally classified into food-grade and non-food-grade HDPE, as well as post-consumer and post-industrial HDPE. Non-food-grade, post-consumer recycled HDPE (PCR HDPE or HDPE PCR) can be produced from any of the above-mentioned applications, such as cables, computer cases, and chemical containers. Commonly used HDPE raw materials are HDPE cans, foils, packaging, boxes, shampoo bottles, and pipes, among others.

[0020] Recycling of high-density polyethylene plastic (HDPE) plays a very important role in sustainable development. However, due to the material and processing properties of recycled HDPE and its odors, there are still obstacles to the use of recycled HDPE. The odor of recycled detergent bottle plastic has led to the rejection of most detergent manufacturers. Recently, some recycling businesses have adopted recycling with odor reduction processes that include the use of solvents, antimicrobial additives and odor extraction units in feeders and extruders. However, these processes affect the quality and cost of recycled plastic. Most small and medium-sized enterprises (SMEs) are negatively affected due to their limited models and resources. Moreover, many SMEs are reluctant to change their existing recycling operation units.

[0021] Recently, the removal of bad odors from recycled plastics has been carried out by plastic industries worldwide. Extensive research and development efforts are being carried out to provide the best experience to customers. New and innovative technologies are being introduced to meet industry standards and regulatory compliance for recycling plastic waste. New markets for recycling are emerging and industries are looking for assurance that plastic packaging waste can be reused as secondary raw materials in high-quality products. Bad odor is a major concern. It has been found that the substances that cause bad odors are not sufficiently removed by the traditional post-consumer HDPE recycling process that has been evaluated.

[0022] The current methods for minimizing odors in the art, such as the use of absorbents (e.g. activated carbon, zeolite, anthracite) or entrainers (e.g. water, alcohols), have been reported to be rarely profitable due to the need for additives specifically adapted to each application. Furthermore, biological odor treatment technologies such as biofilters do not prevent or reduce the odor of the material itself and are therefore the preferred method when aiming only at reducing air pollution. Previous studies on recycling processes, generally using multiple degassing systems for volatile organic compounds, different extraction techniques, specific washing methods or steam stripping as decontamination steps, have focused either on the investigation of the overall odor intensity by conventional olfactometry or on chemical analysis. Therefore, there is a need for methods that will provide simple, fast and effective odor removal from recycled HDPE in the state of the art.

[0023] An example of the known state of the art in the literature is document numbered KR101994313B1. The document in question relates to an apparatus for producing recycled plastics and a method for producing recycled plastics. The application in question describes a method for recycling plastics, where it is explained that odors can be eliminated in extruded recycled plastics by adding coal dust to the cooling water. However, the document does not currently mention a method for removing odors from recycled plastics, especially high-density polyethylene.

[0024] In conclusion, due to the above-mentioned drawbacks and the inadequacy of existing solutions on the subject, it has become necessary to make a development in the relevant technical field. Brief Description of the Invention

[0025] The present invention relates to a method for removing odors from recycled high density polyethylene (HDPE) that meets the above-mentioned requirements, eliminates all disadvantages and provides some additional advantages.

[0026] The primary purpose of the invention is to provide a method for removing bad odors caused by organic compounds present in and on the surface of the polymer matrix in recycled high density polyethylene (HDPE).

[0027] The purpose of the invention is to provide a recycled plastic product that is higher quality, VOC and odor-free, compared to recycled plastics obtained by conventional recycling.

[0028] One purpose of the invention is to increase the quality of recycled plastic and to enable it to be used in new areas such as the cosmetics and hygiene sector, etc.

[0029] Another purpose of the invention is to provide an environmentally friendly method that reduces production costs.

[0030] Another purpose of the invention is to reduce plastics in landfills.

[0031] In order to fulfill the above-mentioned purposes, the invention is a method for removing bad odors from recycled high density polyethylene (HDPE) and comprising the following process steps; i. Removal of bad odors from plastic by mixing recycled HDPE pellets at a temperature range of 80-120 °C, ii. Chemically washing the heated pellets in a water bath comprising deodorizing agent / s, iii. Rinsing HDPE pellets with pure water to remove chemicals, iv. Drying the rinsed pellets in a mechanical dryer, v. Blending and mixing the dried HDPE pellets with deodorizers to remove bad odors, vi. Taking the mixture in the extrusion line and turning it into pellets by melt mixing with the help of an endless screw.

[0032] The structural and characteristic features and all advantages of the invention will be understood more clearly thanks to the figures given below and the detailed explanation written by making references to these figures, and therefore the evaluation should be made by taking these figures and the detailed explanation into consideration. Figures to Help Understand the Invention

[0033] Figure 1 : The present invention is a schematic diagram of the procedure for performing odor removal in recycled high density polyethylene (HDPE).

[0034] Description of References

[0035] 1 . First reactor

[0036] 2. Second reactor

[0037] 3. Third reactor

[0038] 4. Dryer

[0039] 5. Mixing reactor

[0040] 6. Extruder

[0041] A: Odorous HDPE pellet

[0042] B: Odorless HDPE pellet

[0043] Detailed Description of the Invention

[0044] In this detailed description, the method of the invention is explained only for the purpose of better understanding the subject and in a way that does not create any limiting effect.

[0045] The invention is a series process in which malodorous organic compounds are removed from a series of HDPE pellets by means of both thermal and chemical washing and mixing techniques. The invention is a method for removing malodors in recycled high density polyethylene (HDPE) and comprises the following process steps; i. Mixing recycled HDPE pellets at a temperature range of 80-120 'C to remove bad odors from plastic, ii. Chemically washing heated pellets in a water bath containing deodorizing agent / s, iii. Rinsing HDPE pellets with pure water to remove chemicals, iv. Drying rinsed pellets in a mechanical dryer, v. Blending and mixing dried HDPE pellets with deodorizers to remove bad odors, vi. Taking the mixture in the extrusion line and turning it into pellets by mixing the melt with the help of an endless screw.

[0046] In the i) process step of the method, recycled HDPE pellets are mixed at a temperature range of 80-120 'C for preferably 10-70 minutes. In the i . process step, as a pre-process for target odor removal, the bad odors that are susceptible to volatilization and that are attached to the surface are removed by giving heat to the reactor at a certain temperature range.

[0047] In the process step ii) of the method according to the invention, the heated pellets are preferably chemically washed in a water bath comprising trisodium citrate dihydrate-sodium bicarbonate in a ratio of 1 :1 by weight. The temperature of the water bath is preferably in the range of 60-90cC.

[0048] In the process step iv) of the method according to the invention, the rinsed pellets are preferably dried in the temperature range of 50-80 'C for 3-12 hours.

[0049] In the process step v) of the method according to the invention, a vanillin-zinc ricinoleate solid mixture of 1 -15% by weight is added to the HDPE pellet and mixed. Here, the HDPE pellet and odor removers (vanillin-zinc ricinoleate solid mixture) are mixed at a speed of 200-500 rpm to obtain a homogeneous mixture.

[0050] In the method of the invention, the addition of different ratios of trisodium citrate dihydrate- sodium bicarbonate (step 2) and vanillin-zinc ricinoleate (step 5) chemicals to remove bad odors from HDPE pellets is the main reason for removing bad odors. In the process steps ii and iii, washing HDPE pellets with hot water and chemicals and then rinsing with pure water is one of the important processes. It is one of the supporting processes for removing volatile chemicals in the pellet before solid mixing. In step V, odor absorbing chemicals are added to HDPE pellets with bad odor organic compounds with the help of solid mixing and homogeneous mixing is provided before the melt process, which is an important step of the invention.

[0051] Figure 1 provides an example schematic diagram of the elements of the procedure for deodorization of recycled HDPE materials. In this step, the recycled HDPE pellets added to the first reactor (1 ) are heated to different temperatures (80-120cC) for different periods (I Q- 70 minutes) and mixed. In this process, the foul-smelling organic compounds that are also attached to the pellet surfaces and are prone to volatilization with heat are removed from the pellet surfaces. The first step is the preliminary removal process for the removal of foul-smelling volatile compounds from the pellets. In this process, gas is released from the top of the reactor with the help of ventilation to remove foul-smelling organic impurities. In the second step, the foul-smelling organic compounds are removed by a chemical wash in the second reactor (2). The selected wash temperatures are in the range of 60-90tC. In this step, the deodorization effect is increased by adding trisodium citrate dihydrate-sodium bicarbonate, preferably in a 1 :1 ratio, to the heated water bath. In the 3rd step, the HDPE pellets separated by filtration from different ratios of trisodium citrate dihydrate-sodium bicarbonate solution (1 trisodium citrate dihydrate vs. 0.5-5 sodium bicarbonate) are rinsed with pure water in the third reactor (3). In the 4th step, the rinsed pellets are dried by removing the water in the dryer (4) for 3-12 hours and at a temperature between 50-80cC. In the 5th step, different ratios of vanillin-zinc ricinoleate (1 vanillin vs. 0.5-10 zinc ricinoleate) solid mixture is added to eliminate small amounts of bad odors that may arise from trace amounts of bad-smelling organic compounds remaining in the molten HDPE pellets during extrusion using the mixing reactor (5). Here, 1 - 15% of the total HDPE pellet is added as a solid mixture. These solid mixtures are mixed at 200-500 rpm in this mixing reactor (5) to ensure homogeneous distribution in the main phase of HDPE pellets before extrusion. At the end of the homogeneous mixture in this reactor, the total mixture is taken to the extrusion line in Step 6 and turned into pellets by mixing the melt with the help of the endless screw. In Step 6, the extruded melt mixture leaves the extruder (6) in fiber form and is transferred to the fiber cutting system with the help of cold rollers to prepare pellets.

[0052] The method of the invention is based on the fact that with the help of all process steps, it facilitates the internal diffusion of volatile compounds depending on the operating temperature and time and mixing speed and time, as well as decreasing the boiling point of volatile organic compounds that are not mixed with water and increasing their evaporation from the polymer surface to the gas phase. The additional chemical additives used in these processes are designed in a way that they will not have a negative effect on the thermal, mechanical and other properties of the HDPE pellets after their bad odors are removed. It is avoided to damage the chemical and processing properties of HDPE pellets.

[0053] With the invention, a cleaner product is obtained, which is a higher quality, VOC and odor-free plastic compared to traditionally recycled recycled plastics. By increasing the quality of recycled plastics, new opportunities arise in the market for such plastics (e.g. packaging in the cosmetic and hygiene sectors). The method in question includes a completely environmentally friendly procedure.

[0054] The odor removal module in question is a hermetically closed circuit that allows heat recovery. The odor removal module can serve as an independent module of the recycling process. In this case, pellets recycled by other companies can be fed into the system to eliminate bad odors and increase the quality of the material.

[0055] The relationship between the steps of the said method and the odor removal of HDPE plastics was investigated through sensory evaluation. Finally, the resin pellet production and commercialization potential of deodorized recycled HDPE was investigated.

Claims

CLAIMS1. A method for removing bad odors from recycled high density polyethylene (HDPE), characterized by comprising; following process steps i. Removal of bad odors from plastic by mixing recycled HDPE pellets at a temperature range of 80-120 O, ii. Chemically washing the heated pellets in a water bath comprising deodorizing agent / s, iii. Rinsing HDPE pellets with pure water to remove chemicals, iv. Drying the rinsed pellets in a mechanical dryer, v. Blending and mixing the dried HDPE pellets with deodorizers to remove bad odors, vi. Taking the mixture in the extrusion line and turning it into pellets by mixing the melt with the help of an endless screw.

2. The method according to claim 1 , characterized in that; i) in the process step, the recycled HDPE pellets are mixed for 10-70 minutes at a temperature range of 80-120 tC.

3. The method according to claim 1 , characterized in that; ii) in the process step, the heated pellets are chemically washed in a water bath comprising trisodium citrate dihydrate-sodium bicarbonate in a ratio of 1 :1 by weight.

4. The method according to claim 1 or 3, characterized in that; ii) in the process step, the water bath temperature is in the range of 60-90<C.

5. The method according to claim 1 , characterized in that; iv) in the process step, the rinsed pellets are dried at a temperature range of 50-80 'C for 3-12 hours.

6. The method according to claim 1 , characterized in that; v) in the process step, 1 -15% by weight vanillin-zinc ricinoleate solid mixture is added to the HDPE pellet and mixed.

7. The method according to claim 1 , characterized in that; v) in the process step, HDPE pellets and odor removers are mixed at a speed of 200-500 rpm to obtain a homogeneous mixture.

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