Method for cleaning and deodorizing polyolefin resin after consumption

Abstract

The invention belongs to the technical field of plastic recovery, and discloses a method for cleaning and deodorizing polyolefin resin after consumption. The method comprises the steps of normal-temperature abrasive cleaning, microwave cleaning and the like, a specific abrasive cleaning agent and a specific microwave frequency are supplemented, the appearance performance of the polyolefin resin fragments after consumption can be improved, the unpleasant odor of the polyolefin resin fragments can be reduced, the material of the fragments is not affected, and the cleaned fragments have good mechanical properties and are beneficial to subsequent processing and utilization.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic recycling, and in particular relates to a method for cleaning and deodorizing post-consumer polyolefin resin. Background Art

[0002] With the rapid development of society, plastic has become one of the most widely used materials in the world due to its excellent plasticity. This is accompanied by the generation of massive amounts of plastic waste. In order to protect the ecological environment and improve resource utilization, the recycling and regeneration process of post-consumer waste plastics needs to be accelerated.

[0003] At present, the cleaning and deodorization technology of post-consumer polyolefin resins is relatively backward. Only a part of the pollutants are removed through simple cleaning and rinsing processes. It is difficult to achieve a high removal rate for embedded substances or stubborn pollution with weak volatility. At the same time, in order to improve the cleaning cleanliness of the materials, the existing cleaning and deodorization technology requires long-term high-temperature treatment, which can easily lead to the breakage of the molecular chains of recycled plastics, aging, yellowing, and precipitation of toxic substances.

[0004] The prior art discloses a method for recycling waste HDPE plastic barrels, which only removes soot, label paper and other debris on the surface of the plastic barrels through simple steps such as alkaline solution spraying and crushing, water friction cleaning, rinsing, and drying, but does not deeply remove stubborn stains and odors.

[0005] Therefore, it is necessary to develop a systematic cleaning and deodorization method operated at room temperature to remove the stubborn pollutants and odors of post-consumer polyolefin resins and prepare recycled polyolefin resin fragments with good appearance and low odor. Summary of the invention

[0006] In order to solve the technical problems in the prior art that it is difficult to remove stubborn pollutants and cleaning causes the material change and performance degradation of polyolefin resins, the present invention provides a cleaning and deodorizing method for post-consumer polyolefin resins, which integrates wet crushing, room temperature grinding and washing, microwave cleaning and other processes, and is supplemented by a specific cleaning agent, which has an ideal cleaning effect on stubborn pollutants and difficult-to-remove odors. At the same time, the method of the present invention will not affect the material of the polyolefin resin, while taking into account the mechanical properties of the polyolefin resin. The primary purpose of the present invention is to provide a cleaning and deodorizing method for post-consumer polyolefin resins.

[0007] Another object of the present invention is to provide application of the above method.

[0008] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0009] The present invention provides a method for cleaning and deodorizing post-consumer polyolefin resin, which comprises the following steps in sequence:

[0010] (1) grinding and washing at room temperature: the polyolefin resin fragments are subjected to grinding and washing in a first cleaning agent at room temperature to obtain grinding and washing fragments;

[0011] (2) Microwave cleaning: applying a second cleaning agent to the surface of the abrasive fragments, subjecting the fragments to microwave treatment and exhaust, thereby obtaining clean fragments;

[0012] Wherein, the first cleaning agent comprises the following components: 0.5-5wt% of at least one ester substance, 1-10wt% of at least one ether substance, and the rest is water;

[0013] The frequency of the microwave treatment is 2-10 GHz.

[0014] The present invention provides a method for cleaning and deodorizing post-consumer polyolefin resin, which includes the steps of normal temperature grinding and cleaning, microwave cleaning, etc., wherein:

[0015] (1) Room temperature grinding and washing: By soaking the crushed polyolefin resin fragments in a cleaning agent and grinding them with a grinding machine, the fragments can be fully rubbed with the cleaning agent and grinding equipment to remove most of the non-volatile pollutants such as beverages, medicines, oil stains and dust on the fragments, reducing the pressure of microwave cleaning, making the samples brighter and whiter, thereby increasing the L value and reducing the b value.

[0016] (2) Microwave cleaning is to evenly attach the cleaning agent to the surface of the scraps after grinding and washing, then place them in a microwave generator for microwave treatment, and then exhaust the air. This is to rapidly heat up the stubborn pollutants on the surface of the scraps and the attached cleaning agent. In a short period of time, the pollutants evaporate along with the cleaning agent to form gas, which is removed during the exhaust process. It is mainly used to deeply remove volatile stubborn pollutants that cannot be removed by the above two steps, remove odors, and reduce the odor level.

[0017] The microwave frequency has a considerable influence on the mechanical properties of polyolefin resin. The present invention controls the microwave frequency within the above range, which can take into account both the cleaning effect and the mechanical properties of the fragments, and is conducive to subsequent recycling.

[0018] Preferably, the ester substance is selected from at least one of butyl acetate, isobutyrate, ethylene glycol diacetate, glyceryl stearate, polyoxypropylene stearate, ethylene glycol stearate, lauric acid monoglyceride, oleic acid glyceride or ethylenediamine oleate, preferably glyceryl stearate.

[0019] Preferably, the ether substance is selected from at least one of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether or nonanol polyoxyethylene ether, octanol polyoxyethylene ether, decanol polyoxyethylene ether or lauryl alcohol polyoxyethylene ether, preferably nonylphenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether or nonanol polyoxyethylene ether.

[0020] Preferably, the method further comprises the following steps before step (1) of grinding and washing at room temperature:

[0021] (0) Wet crushing: The polyolefin resin is crushed in a first cleaning agent to obtain fragments of the polyolefin resin.

[0022] The present invention adopts wet crushing, in which collected post-consumer polyolefin resin is crushed, a cleaning agent is added during the crushing process, and the resin is crushed into fragments of a specified size, which is mainly used to remove a portion of residual contents on the surface. On the one hand, the contact area between the substrate and the cleaning agent can be increased, so that the cleaning agent can be more evenly attached to the substrate; on the other hand, volatile and non-volatile pollutants can be prevented from being embedded in the substrate due to friction and temperature rise during crushing, thereby reducing the difficulty of subsequent cleaning and deodorization.

[0023] Preferably, the second cleaning agent is selected from at least one of methanol, ethanol, isopropanol, tert-butanol, acetone, ether, tetrahydrofuran, methyl formate, n-propyl acetate or ethyl butyrate, preferably ethanol, acetone, isopropanol or tert-butanol.

[0024] The microwave cleaning agent selected by the present invention has a good removal effect on stubborn stains and odors, and has basically no effect on the material of the polyolefin resin and will not cause the collapse of the polyolefin resin structure.

[0025] Preferably, the size of the fragments is 8-16 mm.

[0026] Preferably, the scrubbing speed is 50-200 rpm, and the scrubbing time is 15-60 min.

[0027] Preferably, the microwave treatment time is 5 to 15 minutes.

[0028] Preferably, all the steps of microwave cleaning are repeated 1 to 10 times. Repeating all the steps of microwave cleaning is to ensure that the contaminants can be fully removed.

[0029] Preferably, the second cleaning agent is applied by at least one of spraying, soaking or rinsing, preferably spraying. Spraying allows the cleaning agent to fully and evenly soak the surface of the fragments and come into contact with the contaminants.

[0030] Preferably, the method further comprises the following steps:

[0031] (3) rinsing: washing the cleaned fragments with water to obtain rinsed fragments;

[0032] and / or,

[0033] (4) Drying: Drying the rinsed chips.

[0034] Rinsing is done by taking out the microwave-cleaned pieces, putting them in water, and stirring them to remove residual detergent. Drying is done by taking out the rinsed pieces and putting them in a baking device, where they are baked until dry by blowing hot air.

[0035] Preferably, the polyolefin resin includes PE or PP. Specifically, the PE includes HDPE; the PP includes copolymer PP or homopolymer PP. The method of the present invention is applicable to various types of PE or PP materials.

[0036] Preferably, the post-consumer polyolefin resin comprises bottles, cans, cups or barrels for containing liquid food, cleaning products or chemical products.

[0037] Preferably, the liquid food includes but is not limited to beverages, dairy products, juices, alcohol or edible seasonings; the cleaning products include but are not limited to personal care products, household cleaning products or industrial cleaning products; the chemical products include but are not limited to chemical raw materials.

[0038] The polyolefin resin of the present invention is used for solid packaging, and its contents include but are not limited to liquid food (beverages, edible seasonings, alcohol), cleaning products and chemical products. The main pollutants are residual contents and dust, such as dairy products, fruit juices, edible seasonings, alcohol, personal care products, household cleaning products, industrial cleaning products, chemical raw materials, etc.; the odor includes the odor of the contents themselves, the protein fermentation odor after long-term abandonment, the odor released by the degradation of the polyolefin resin, etc.

[0039] The present invention also protects the use of the above method for recycling post-consumer polyolefin resins.

[0040] The present invention also protects the use of the recycled material obtained by the above method in preparing hollow products, pipes or injection molded products made of polyolefin materials.

[0041] Preferably, the hollow article comprises a bottle, a can, a cup or a barrel.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The invention designs a method for cleaning and deodorizing post-consumer polyolefin resin by wet crushing, normal temperature grinding and washing, microwave cleaning and other processes.

[0044] The method of the present invention can remove more pollutants, so that the color of the regenerated polyolefin resin fragments is close to that of the original resin, thereby improving the color performance.

[0045] The method of the present invention can remove more volatile pollutants, so that the odor of the regenerated polyolefin resin fragments is close to that of the original resin, thereby improving the odor performance.

[0046] The present invention adopts room temperature grinding and microwave treatment to reduce the heat treatment time of the regenerated polyolefin resin fragments, which avoids the problem of substrate being affected by high temperature for a long time and then aging, and maintains the mechanical properties of the polyolefin resin fragments; on the other hand, it reduces energy consumption. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with examples. These examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually carried out according to conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of protection claimed by the present invention.

[0048] Some of the raw materials or reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0049] HDPE hollow bottle: used for rigid packaging of liquid food, including milk, beverages, cooking oil and seasonings;

[0050] PP hollow bottle: used for rigid packaging of liquid food, including milk, beverages, cooking oil and seasonings;

[0051] Glyceryl stearate: CAS number 31566-31-1, commercially available;

[0052] Nonylphenol polyoxyethylene ether: CAS number is 127087-87-0, commercially available;

[0053] Dodecylphenol polyoxyethylene ether: CAS number is 2201101-54-2, commercially available;

[0054] Nonanol polyoxyethylene ether: CAS number is 68213-23-0, commercially available;

[0055] Butyl acetate: CAS number is 123-86-4, commercially available;

[0056] Olein: CAS number 25496-72-4, commercially available;

[0057] Octylphenol polyoxyethylene ether: CAS number is 9036-19-5, commercially available;

[0058] Octanol polyoxyethylene ether: CAS number is 27252-75-1, commercially available;

[0059] Ethanol: Commercially available;

[0060] Acetone: commercially available;

[0061] Tert-Butanol: Commercially available;

[0062] Isopropyl alcohol: commercially available;

[0063] The first cleaning agent used in each embodiment and comparative example of the present invention includes the following formula:

[0064] Table 1 Formula of the first cleaning agent

[0065]

[0066] Table 1: Formula of the first cleaning agent

[0067] composition Cleaning agent 10 Cleaning agent 11 Cleaning agent 12 Cleaning agent 13 Glyceryl Stearate 2.5wt% 2.5wt% Butyl acetate 2.5wt% Olein 2.5wt% Nonylphenol polyoxyethylene ether 5wt% 5wt% Octylphenol polyoxyethylene ether 5wt% Octanol polyoxyethylene ether 5wt%

[0068] The testing methods and standards for the cleaning effects of the embodiments of the present invention and the comparative examples are as follows:

[0069] Cleaning effect (appearance): The cleaned HDPE fragments are injection molded into standard color plates, and then placed in a colorimeter to test the LAB value of the color plate. L represents luminosity, which is equivalent to brightness. Its value range is from 0 to 100. The higher the value, the higher the brightness. a represents the range from red to green, and b represents the range from blue to yellow. The value ranges of a and b are both from +120 to -120. The higher the b value, the yellower the color.

[0070] Cleaning effect (odor): tested according to PV3900-2000 standard, divided into six levels from 1 to 6. The lower the level, the smaller the odor.

[0071] Mechanical properties (elongation at break): tested in accordance with ISO 527 standard.

[0072] Examples and Comparative Examples

[0073] The cleaning and deodorizing methods of Examples 1 to 15 and Comparative Examples 1 to 9 include all or part of the following steps:

[0074] (0) Wet crushing: The HDPE hollow bottles are crushed in a first cleaning agent to obtain HDPE fragments, and the specific steps are: crushing the collected post-consumer HDPE hollow food packaging bottles, adding the first cleaning agent during the crushing process, and crushing them into HDPE fragments of a specified size;

[0075] (1) grinding and washing at room temperature: the HDPE fragments are subjected to grinding and washing at room temperature in the first cleaning agent to obtain grinding and washing fragments, and the specific steps are: immersing the crushed HDPE fragments in the first cleaning agent, grinding and washing them in a grinding and washing machine, so that the HDPE fragments are fully rubbed with the cleaning agent and the grinding and washing equipment;

[0076] (2) Microwave cleaning: applying a second cleaning agent to the surface of the ground and washed HDPE fragments, subjecting the fragments to microwave treatment and exhaust, to obtain clean fragments. The specific steps are: spraying the cleaning agent on the surface of the ground and washed HDPE fragments, then placing the fragments in a microwave generator chamber for microwave treatment, then exhausting the fragments, and repeating the above spraying-microwave treatment-exhausting process;

[0077] (3) rinsing: washing the cleaned fragments after microwave cleaning with water to obtain rinsed fragments, the specific steps are: taking out the HDPE fragments after microwave cleaning and putting them into water, stirring and washing to remove residual cleaning agent;

[0078] (4) Drying: Drying the rinsed chips. The specific steps are as follows: taking out the rinsed HDPE chips and placing them in a baking device, and baking them to a dry state by blowing hot air.

[0079] The steps of the cleaning and deodorizing method of Example 16 are consistent with the above-mentioned examples and comparative examples, except that the cleaning object is changed to PP hollow bottles.

[0080] The method parameters of each embodiment and comparative example are shown in Table 2-5:

[0081] Table 2 Method parameters of Examples 1 to 5

[0082]

[0083] Table 3 Method parameters of Examples 6 to 11

[0084]

[0085] Table 4 Method parameters of Examples 12 to 16

[0086]

[0087] Table 5 Method parameters of Comparative Examples 1 to 9

[0088]

[0089] The cleaning effects and mechanical properties of each embodiment and comparative example are shown in Table 6:

[0090] Table 6 Cleaning effect and mechanical properties of HDPE fragments obtained by the methods of each embodiment and comparative example

[0091]

[0092] Table 6 Cleaning effect and mechanical properties of HDPE fragments obtained by the methods of each embodiment and comparative example

[0093]

[0094] Table 6 Cleaning effect and mechanical properties of HDPE fragments obtained by the methods of each embodiment and comparative example

[0095]

[0096] As can be seen from Table 6, the HDPE or PP fragments cleaned by the methods of Examples 1 to 16 of the present invention have good cleaning effects and mechanical properties, with an L value of more than 87, a b value of less than 7, an odor level of less than 3.8, an elongation at break of the HDPE fragments of more than 610%, and an elongation at break of the PP fragments of 18%.

[0097] In Comparative Examples 1-2, only a single cleaning agent of ester or ether is used, and the cleaning effect is not as good as that of the compound cleaning agent, the yellowness is high, and the brightness is reduced; in Comparative Example 3, no room temperature grinding and washing step is set, most of the pollutants will remain on the HDPE, and the odor cannot be removed. On the one hand, the brightness of the HDPE after cleaning is low and the yellowness is high, and on the other hand, the pollutants penetrate into the interior of the HDPE, resulting in poor mechanical properties such as tensile strength and elongation at break; in Comparative Example 4, no microwave grinding and washing step is set, and the odor residue is still serious; in Comparative Example 5, the microwave frequency exceeds the range, resulting in poor mechanical properties of HDPE; in Comparative Examples 6-7, the content of any compound cleaning agent exceeds the range, resulting in excessive foam, affecting the cleaning effect, and the obtained fragments are reduced in yellowness, brightness, odor, etc.; in Comparative Example 8, wet crushing and room temperature grinding and washing use water as a cleaning agent, and the cleaning effect and mechanical properties are both inferior; in Comparative Example 9, microwave cleaning uses water as a cleaning agent, and the odor removal effect is poor.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for cleaning and deodorizing post-consumer polyolefin resins, comprising the following steps in sequence: (1) grinding and washing at room temperature: the polyolefin resin fragments are subjected to grinding and washing in a first cleaning agent at room temperature to obtain grinding and washing fragments; (2) Microwave cleaning: applying a second cleaning agent to the surface of the abrasive fragments, subjecting the fragments to microwave treatment and exhaust, thereby obtaining clean fragments; Wherein, the first cleaning agent comprises the following components: 0.5-5wt% of at least one ester substance, 1-10wt% of at least one ether substance, and the rest is water; The frequency of the microwave treatment is 2-10 GHz.

2. The method according to claim 1, characterized in that: The ester substance is selected from at least one of butyl acetate, isobutyrate, ethylene glycol diacetate, glyceryl stearate, polyoxypropylene stearate, ethylene glycol monostearate, glyceryl laurate, glyceryl oleate or ethylenediamine oleate.

3. The method according to claim 1, characterized in that The ether substance is selected from at least one of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether or nonanol polyoxyethylene ether, octanol polyoxyethylene ether, decanol polyoxyethylene ether or lauryl alcohol polyoxyethylene ether.

4. The method according to claim 1, characterized in that The method further comprises the following steps before step (1) of normal temperature grinding and washing: (0) Wet crushing: The polyolefin resin is crushed in a first cleaning agent to obtain fragments of the polyolefin resin.

5. The method according to claim 1, characterized in that The second cleaning agent is selected from at least one of methanol, ethanol, isopropanol, tert-butanol, acetone, ether, tetrahydrofuran, methyl formate, n-propyl acetate or ethyl butyrate.

6. The method according to claim 1, characterized in that The rotation speed of the scrubbing is 50-200 rpm.

7. The method according to claim 1, characterized in that The microwave treatment time is 5 to 15 minutes.

8. The method according to claim 1, characterized in that The method further comprises the following steps: (3) rinsing: washing the cleaned fragments with water to obtain rinsed fragments.

9. The method according to claim 8, characterized in that The method further comprises the following steps: (4) drying: drying the rinsed chips.

10. Use of the method according to any one of claims 1 to 9 in recycling post-consumer polyolefin resins.

Images