Reusable plastic package cleaning agent and application thereof

Abstract

The invention provides a reusable plastic package cleaning agent and application thereof. The reusable plastic package cleaning agent can provide larger oleophylic space and stripping force; the interfacial tension between oil and water systems is reduced, and the free energy under the interface action is reduced, so that an oil phase attached to the surface of a plastic material is more easily stripped out. The uncontrollability of multiple oleophylic contact points of the multi-branched-chain surfactant is inhibited by adjusting the proportional relation of the dosage of the single-branched-chain surfactant and the dosage of the multi-branched-chain surfactant, and synergistic compounding of different surfactants is achieved. Compared with a surfactant with a single long-chain structure, the compound surfactant has the advantages that the oil stain removal is quicker and more stable, so that the efficient cleaning effect is realized.

Description

Technical Field

[0001] The invention relates to the technical field of plastic product recycling, in particular to a plastic lunch box cleaning agent which can be reused multiple times. Background Art

[0002] With the prevalence of fast food culture, the use of various plastic packaging has become more frequent, such as plastic lunch boxes (PP, PS), milk tea boxes, beverage bottles and other disposable plastic packaging products. However, due to the chemical properties of the material itself, it is not easy to degrade. A large amount of discarded plastic waste has increased the environmental burden. Whether it is landfill or incineration, it will have a serious negative impact on the ecosystem. It often takes a very long time to rely solely on its own degradation. The safe, effective and environmentally friendly way is to recycle and reuse it so that chemical materials can be recycled for a second time.

[0003] Compared with new materials that have not been used, the performance degradation of recycled plastics is difficult to avoid, and the more impurities it contains, the more serious the performance degradation. Especially for plastic lunch boxes, there are often a lot of food residues, oil stains and other impurities attached to them, which cannot be effectively reused by simple recycling. Therefore, the recycling process of plastics usually includes steps such as crushing, cleaning, and granulation, among which the cleaning process is particularly important. Without a thorough cleaning step, a large amount of oil stains, food residues and other impurities are attached to the surface of the recycled plastic. The plastic obtained after granulation has poor mechanical properties, turbidity, glossiness, etc. The application of recycled materials is limited, the reusability is not high, and the value of recycled plastics is greatly reduced. Therefore, choosing a suitable plastic cleaning agent is the key to recycling plastic products.

[0004] Patent 20141078340.2 discloses a waste plastic bottle cleaning agent, which mainly includes 16-20 parts of sodium tripolyphosphate, 11-15 parts of citric acid, 11-15 parts of lactic acid, 23-26 parts of phosphoric acid, 11-15 parts of sodium alkylbenzene sulfonate, and 70-90 parts of water. It can be used to clean plastic bottles, but its synthesis process is complicated and the effect of removing oil stains in daily life is not ideal.

[0005] Patent 20151030200.6 provides a plastic cleaning agent, which is composed of the following weight percentage components: 10-20% ethylmethylbenzene, 10-30% diethylbenzylamine, 30-40% diethylenetriamine, and 20-40% ethylmethylbenzene. Although it can simply and efficiently remove stains on the plastic surface, a large amount of wastewater is generated during the cleaning process, the decontamination efficiency is low, and the oily components on the plastic surface cannot be quickly and thoroughly removed, and the decontamination efficiency is obviously insufficient.

[0006] Patent 201811430562.4 has developed an environmentally friendly, recyclable and reusable plastic cleaning powder, which reduces the discharge of COD-containing wastewater and can be recycled. However, the cleaning powder only uses a single non-ionic surfactant, sodium polyoxyethylene fatty alcohol ether sulfate (AEO), which seriously degrades the performance of the plastic and is not conducive to the further effective utilization of the plastic.

[0007] Due to the lipophilic nature of the plastic packaging structure, stains on the surface are highly adherent and difficult to remove. Therefore, the current technical challenges for cleaning agents are to effectively separate stains from plastic lunch boxes without destroying the chemical properties of the plastic surface and to control COD wastewater discharge. Summary of the invention

[0008] In order to solve the deficiencies in the prior art, the present invention provides a plastic packaging cleaning agent that can be reused multiple times, which can efficiently peel off and remove stains on the plastic surface, meet the later plastic recycling performance requirements, and at the same time the cleaning agent can be recycled, will not generate a large amount of industrial wastewater, and reduces the environmental load.

[0009] The cleaning agent uses the synergistic effect between anions and non-ions as the main agent, and the auxiliary agents such as alkaline substances, penetrants, and activation promoters improve the permeability of oil stains and enhance the compatibility between surfactants; the addition of sodium oxide salt can remove harmful microorganisms, prevent the growth of bacteria on the plastic surface, play a role in sterilization and disinfection, and further ensure the effective utilization of recycled plastic products.

[0010] The invention designs the oil-stain stripping strength through the structural characteristics of anionic and nonionic surfactants, and through experiments it is found that under the condition of satisfying a specific anionic and nonionic surfactant dosage ratio, the oil-stain stripping effect of the cleaning agent is significantly better than that of a single type of surfactant; the activation promoter can disperse the oil phase in a fine manner, thereby solving the problem of uneven distribution of multi-branched nonionic surfactants, and the mechanical properties of the renewable plastic particles obtained after cleaning are excellent, the surface of the plastic packaging after cleaning is smooth and odorless, and the plastic is not chemically damaged during the cleaning process, and the light transmittance and mechanical properties are excellent, and the recycled plastic particles have broad application prospects.

[0011] The purpose of the present invention can be achieved through the following technical scheme: a plastic packaging cleaning agent that can be reused multiple times, which includes, by weight: 50-80 parts of surfactant a, 5-10 parts of alkaline substance b, 10-20 parts of sodium oxide salt c, and 5-15 parts of penetrant d.

[0012] Furthermore, the surfactant a includes a C12-C18 nonionic surfactant and / or anionic surfactant; wherein the nonionic surfactant is: one of sorbitan monostearate and sorbitan tristearate; preferably sorbitan tristearate; the anionic surfactant is: one of sodium octadecenoate and sodium dodecylbenzene sulfonate; preferably sodium octadecenoate.

[0013] More preferably, in the surfactant a, the weight ratio of the nonionic surfactant to the anionic surfactant is 1:1-4, preferably 1:3.

[0014] The alkaline substance b is sodium hydroxide and / or potassium hydroxide.

[0015] The oxidized sodium salt c is sodium persulfate.

[0016] The penetrant d is a C12-C18 long-chain fatty acid, preferably one or more of palmitic acid, α-linolenic acid, and stearic acid.

[0017] The cleaning agent further comprises 5-15 parts of an activation promoter e, which is selected from one or more of coconut fatty acid diethylamide, triethanolamine, and diethanolamine, preferably a mixture of coconut fatty acid diethylamide and triethanolamine, wherein the weight ratio of the two in the mixture is 1:1.

[0018] In addition, the present invention also provides a process for using a cleaning agent, and the specific process is as follows:

[0019] S1. Select plastic food packaging and add it to the mechanical crusher for crushing;

[0020] S2. The cleaning agent and water are prepared into a cleaning solution in proportion and set aside;

[0021] S3. Immersing the crushed plastic in a cleaning solution, and setting an ultrasonic step for ultrasonic cleaning;

[0022] S4. The cleaned plastic fragments are sprayed with clean water;

[0023] S5. The fragments are air-dried, and the washing wastewater is collected. 10-20 parts of a precipitation promoter are added to promote the formation of solids. The aqueous phase is obtained by standing and stratifying to remove impurities, and the aqueous phase is further re-added to S2 for recycling;

[0024] S6. The air-dried plastic fragments are added to an extruder for granulation to obtain renewable plastic particles.

[0025] Among them, plastic food packaging chooses one of polypropylene lunch boxes, polypropylene milk tea cups, polystyrene lunch boxes, polyethylene milk boxes, polyethylene films, and PET plastic water bottles.

[0026] The preparation ratio of the cleaning agent to water is 1g:(10-50)g, the ultrasonic cleaning time is 5-30min, and the spray treatment time is 1-10min.

[0027] In the use process, the precipitation promoter is one or more of sodium chloride and sodium sulfate.

[0028] The present invention has the following beneficial effects:

[0029] (1) The present invention selects a C12-18 long-chain surfactant, and the hydrophobic group is better extended in the oil phase, providing a larger lipophilic space and stripping force; under the staggered entanglement of multi-arms and long-chain alkyl groups, the surfactant molecules between the oil and water phases are arranged closely, further reducing the interfacial tension between the oil and water systems, and the free energy under the interface action is reduced, so that the oil phase attached to the surface of the plastic material is easier to be stripped off.

[0030] (2) The present invention suppresses the uncontrollability of the multi-branched surfactant having multiple lipophilic contact points by adjusting the ratio of the single-branched surfactant to the multi-branched surfactant, thereby achieving a synergistic combination of different surfactants. Compared with a single long-chain surfactant, the selection of the compound surfactant can remove oil stains more quickly and stably, thereby achieving an efficient cleaning effect.

[0031] (3) The use of the activation promoter and penetrant of the present invention promotes the oil-water interface effect of the cleaning system, disperses the oil into droplets of smaller particle size, and further disperses the oil phase droplets through the spatial size effect, which makes up for the uneven interface arrangement defect of the multi-branched surfactant, which is beneficial to the rapid capture and thorough stripping of the oil stains. The obtained recycled plastic has a high mechanical property retention rate and has good reusability.

[0032] (4) The present invention uses a recycling method to reuse the wastewater after washing, which eliminates the discharge of wastewater rich in COD, ensuring the recycling of plastics without bringing additional burden to the green ecology. At the same time, the use of precipitation promoter sodium chloride or sodium sulfate improves the stratification effect through the salting-out effect by increasing the sodium ion concentration of the system, and obtains the water phase more quickly and effectively. The impurities are thoroughly precipitated, and the water phase obtained by stratification is clear and transparent without obvious visible objects dispersed in the water phase, thereby providing a basis for the recycling of the washing liquid. DETAILED DESCRIPTION

[0033] The present invention will be further described with reference to specific embodiments below, but the embodiments do not limit the present invention in any form. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0034] Synthesis Example 1-8

[0035] The composition of the plastic packaging cleaning agent that can be reused multiple times is shown in Table 1. According to the amount of each component shown in Table 1, the target cleaning agent is mixed and prepared.

[0036] Table 1:

[0037]

[0038] Comparative Synthesis Example 1

[0039] Compared with Example 2, in this comparative example, 20 parts of sp65 and 60 parts of sodium octadecenoate are replaced by 80 parts of sp65, and the formulation of other components is the same as that of Example 2.

[0040] Comparative Synthesis Example 2

[0041] Compared with Example 2, in this comparative example, 20 parts of sp65 and 60 parts of sodium octadecenoate are replaced by 80 parts of sodium octadecenoate, and the formulation of other components is the same as that of Example 2.

[0042] Comparative Synthesis Example 3

[0043] Compared with Example 2, the components of this comparative example are 20 parts of sp65 and 60 parts of sodium octadecenoate are replaced by 60 parts of sp65 and 20 parts of sodium octadecenoate, and the formulation of other components is the same as that of Example 2.

[0044] Comparative Synthesis Example 4

[0045] Compared with Example 2, this comparative example lacks an activation promoter in the components, and the other components are the same as those in Example 2.

[0046] Comparative Synthesis Example 5

[0047] Compared with Example 2, this comparative example lacks a penetrant in the components, and the other components are the same as those in Example 2.

[0048] Comparative Synthesis Example 6

[0049] Compared with Example 2, in this comparative example, 5 parts of triethanolamine and 5 parts of coconut fatty acid diethylamide are replaced by 20 parts of triethanolamine, and the other components are the same as those in Example 2.

[0050] Specific test examples (Examples 1-8, Comparative Examples 1-6)

[0051] Test content: The steps for using the plastic packaging cleaning agent that can be reused multiple times are as follows:

[0052] S1. Select a plastic lunch box made of polypropylene and put it into a mechanical crusher to crush it into a size of less than 2cm;

[0053] S2. The cleaning agent and water in Synthesis Example 1-8 and Comparative Synthesis Example 1-6 were prepared into a cleaning solution in a ratio of 1g: 20g for standby use;

[0054] S3. Immerse the crushed plastic in a cleaning solution and set an ultrasonic step for ultrasonic cleaning for 10 minutes;

[0055] S4. The cleaned plastic fragments were sprayed with clean water for 5 minutes;

[0056] S5. The fragments were air-dried, and the washing wastewater was collected. 10 parts of sodium chloride was added to promote the formation of solids. The aqueous phase was obtained by standing and stratifying to remove impurities, and the aqueous phase was further re-added to S2 for recycling;

[0057] S6. The air-dried plastic pellets are added to an extruder for granulation to obtain renewable plastic pellets.

[0058] The stain removal rate test method is as follows:

[0059] Take a fixed amount of clean, unused polypropylene plastic lunch boxes and crush them, weigh the total weight of the fragments, and record it as M1; take out the fragments after completely immersing them in edible soybean oil, drain them until no liquid drips, and weigh the total weight of the fragments, which is recorded as M2; wash the fragments according to steps S2-S5 in the corresponding embodiments 1-8 and comparative examples 1-6, until the fragments are naturally air-dried to ensure that there is no moisture, and weigh the total weight of the fragments, which is recorded as M3.

[0060] Stain removal rate = (M2-M3) / (M2-M1)×100%.

[0061] Further, the renewable plastic particles obtained in Examples 1-8 and Comparative Examples 1-6 were subjected to tensile strength, impact strength and light transmittance tests, with the tensile strength test standard referring to GB / T 1040.2-2006, the notched impact strength test standard referring to GB / T1843-2008, and the light transmittance test standard referring to GB / T 2410-2008. The test results are shown in Table 2.

[0062] Table 2:

[0063]

[0064]

[0065] According to the experimental results, the plastic packaging cleaning agent prepared by the present invention and which can be reused multiple times has a stain removal rate greater than 97.3% and a light transmittance of more than 79.3%. In addition, the mechanical property retention rate is maintained at more than 90%, and the impact strength retention rate can reach up to 98.1%. That is, while meeting the stain removal rate, it not only ensures the light transmittance of the product, but also inhibits the attenuation of the mechanical property strength, making the application field of renewable plastics wider and no longer limited to the use of recycled materials in the cheap and low-end market.

[0066] In addition, the present invention further studies the influence of the cleaning agent on the physical and chemical properties of the plastic packaging during the cleaning process and the residual condition of the cleaning agent itself (except for oil stains). Therefore, Example 2 with the best comprehensive performance in Table 2 is selected as the cleaning agent of the present invention and unused PP raw materials for experiments, that is, the same steps S1-S6 as Example 2 are selected to experiment on the unused PP raw materials, and the performance changes of the PP raw materials and the residual condition of the cleaning agent are tested.

[0067] Comparative example: The cleaning powder was prepared using the component raw materials in Example 1 of Patent 201811430562.4, and was mixed with water in a ratio of 1g:20g to prepare a cleaning liquid to clean the PP raw material. The above cleaning steps are the same as S2-S6 of the present invention.

[0068] The test method for the residual rate of cleaning agent is as follows:

[0069] Take a fixed amount of clean, unused PP raw material and crush it, weigh the total weight of the fragments, and record it as m1; wash the fragments according to steps S2-S5 until the fragments are naturally air-dried to ensure that there is no moisture, and weigh the total weight of the fragments, and record it as m2.

[0070] Cleaning agent residual rate = (m2-m1) / m1×100%.

[0071] The test results are shown in Table 3:

[0072] Table 3:

[0073]

[0074]

[0075] From the test results of blank PP raw materials, the residual cleaning agent components on the plastic packaging after cleaning with the cleaning agent of the present invention contain only 0.02%, and the residual components harmful to the human body are far lower than the national standard, which greatly guarantees the application prospects of recycled plastic products, such as those that can contact food; and the mechanical properties after cleaning are almost unaffected, which also shows that the cleaning agent will not cause obvious structural damage to the plastic itself, further expanding the applicable market for recycled plastics.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A plastic packaging cleaning agent that can be reused multiple times, comprising, by weight: 50-80 parts of surfactant a, 5-10 parts of alkaline substance b, 10-20 parts of sodium oxide salt c, 5-15 parts of penetrant d.

2. The cleaning agent according to claim 1, wherein the surfactant a comprises a C12-C18 nonionic surfactant and / or an anionic surfactant; wherein the nonionic surfactant is: one of sorbitan monostearate and sorbitan tristearate; preferably sorbitan tristearate; the anionic surfactant is: one of sodium octadecenoate and sodium dodecylbenzene sulfonate; preferably sodium octadecenoate. More preferably, in the surfactant a, the weight ratio of the nonionic surfactant to the anionic surfactant is 1:1-4, preferably 1:

3.

3. The cleaning agent according to claim 1, wherein the alkaline substance b is sodium hydroxide and / or potassium hydroxide. The cleaning agent according to claim 1 , wherein the sodium oxide salt c is sodium persulfate.

5. The cleaning agent according to claim 1, wherein the penetrant d is a C12-C18 long-chain fatty acid, preferably one or more of palmitic acid, α-linolenic acid, and stearic acid.

6. cleaning agent according to claim 1, wherein also contains 5-15 parts of activation promoter e, it is selected from one or more of coconut fatty acid diethylamide, triethanolamine, diethanolamine, preferably a mixture of coconut fatty acid diethylamide and triethanolamine, in which the weight ratio of the two is 1:

1.

7. The use process of the cleaning agent according to claim 1, the specific process is as follows: S1. Select plastic food packaging and add it to the mechanical crusher for crushing; S2. The cleaning agent and water are prepared into a cleaning solution in proportion and set aside; S3. Immersing the crushed plastic in a cleaning solution, and setting an ultrasonic step for ultrasonic cleaning; S4. The cleaned plastic fragments are sprayed with clean water; S5. The fragments are air-dried, and the washing wastewater is collected. 10-20 parts of a precipitation promoter are added to promote the formation of solids. The aqueous phase is obtained by standing and stratifying to remove impurities, and the aqueous phase is further re-added to S2 for recycling; S6. The air-dried plastic fragments are added to an extruder for granulation to obtain renewable plastic particles.

8. According to the process of claim 7, the plastic food packaging is selected from one of polypropylene lunch boxes, polypropylene milk tea cups, polystyrene lunch boxes, polyethylene milk boxes, polyethylene films, and PET plastic water bottles.

9. According to the process of claim 7, the ratio of the cleaning agent to water is 1g:(10-50)g, the ultrasonic cleaning time is 5-30min, and the spray treatment time is 1-10min.

10. According to the process of claim 7, the precipitation promoter is one or more of sodium chloride and sodium sulfate.

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