Method for reducing odor grade of polyolefin resin material by utilizing supercritical extraction

Abstract

The invention discloses a method for reducing the odor grade of a polyolefin resin material by utilizing supercritical extraction, which mainly adopts a supercritical CO2 extraction technology and takes an ethanol solution containing a Chinese honeylocust fruit extract as a carrying agent to realize removal of odor small molecular substances in the polyolefin resin material so as to realize preparation of low-odor and low-VOC (Volatile Organic Compounds) polyolefin. The method does not need post-processing, can be used for refining and purifying various polyolefin finished product raw materials, and has high popularization value.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a method for reducing the odor level of polyolefin resin material by using supercritical extraction. Background Art

[0002] Polyolefin materials are widely used in defense, energy, automobiles, construction, packaging, textiles, medical and other fields, and have become one of the important materials supporting social development. With the continuous improvement of people's living standards and quality of life and the increasing awareness of health and environmental protection, the odor parameters of polyolefin materials have become the key indicators for judging the quality of products such as automotive interiors, sanitary materials, and food packaging materials. Therefore, it is necessary to find a method that can effectively reduce the odor level of polyolefin resins. Summary of the invention

[0003] In order to improve the problem of strong odor of polyolefin materials, the present invention proposes a method of reducing the odor level of polyolefin resin materials by supercritical extraction, which can effectively solve the dilemma that existing polyolefin materials have a strong odor and cannot enter the high-end polyolefin field.

[0004] To achieve the above object, the present invention adopts the following technical solution: A method for reducing the odor level of polyolefin resin material by supercritical extraction comprises the following steps: 1) Add polyolefin resin material into CO2 extraction kettle; 2) The carrier and liquid CO2 are heated and pressurized into a supercritical state and then sent into an extraction kettle for extraction; 3) The material flowing out of the extraction kettle is sent to the vacuum separation kettle to separate the small molecular substances. The separated gaseous fluid is cooled to liquid and then sent to the extraction kettle for recycling; at the same time, the remaining material in the extraction kettle is collected to obtain a low-odor, low-VOC polyolefin resin material.

[0005] Furthermore, the carrying agent in step 2) is prepared by mixing sapodilla extract and anhydrous ethanol in a mass ratio of 1:20.

[0006] Furthermore, in step 3), the amount of the carrying agent used is 50-500 ml per 1-2 kg of polyolefin resin material treated.

[0007] Furthermore, the extraction pressure in step 2) is 10-30 MPa and the extraction time is 10-60 min.

[0008] The present invention innovatively combines the natural surfactant saponin extract and supercritical CO2 extraction for the first time to reduce the odor of polyolefin resin. Saponin extract is a pure natural surfactant that forms abundant microbubbles in the supercritical CO2 extraction kettle, which can be mutually extracted with volatile organic compounds, more effectively assisting SC-CO2 in removing small molecules from polyolefins.

[0009] The significant advantages of the present invention are: (1) Supercritical CO2 extraction has moderate supercritical conditions (critical temperature 31.1℃, critical pressure 7.38MPa), and CO2 itself is a non-toxic, cheap, clean solvent that can be recycled. At the same time, its intermolecular force with small molecules is strong (CO2 is easily miscible with small molecules), while its intermolecular force with polymers is very weak. By utilizing this principle, small molecules generated during the processing of polyolefins can be removed from the system. In addition, the pure natural surfactant saponin extract will form abundant microbubbles in the supercritical CO2 extraction kettle, which can be extracted with volatile organic compounds, more effectively assisting SC-CO2 in removing small molecules from polyolefins, thereby achieving the preparation of low-odor, low-VOC resin products.

[0010] (2) According to the method of the present invention, the odor level of polyolefin resin powder at 80°C can be reduced to 2.0 or below (using VDA270:2022 standard) within 10 minutes, and the odor level of polyolefin resin pellets at 80°C can be reduced to 2.5 or below (using VDA270:2022 standard) within 15 minutes. In addition, since the supercritical CO2 used is reduced to gaseous state and separated from the air when the pressure and temperature are restored to normal temperature and pressure, the obtained low-odor polyolefin resin does not need to be dried and post-processed, which saves time and cost significantly.

[0011] (3) The method of the present invention meets environmental protection requirements, is environmentally friendly while effectively reducing the odor of polyolefin resins, and does not introduce new odorous impurities during the entire treatment process. It can be used in the refining and purification of polyolefin finished raw materials such as bottle cap materials, high-end lunch boxes, automotive materials and fiber materials that have relatively high requirements for the odor level of polyolefin resins. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of a treatment device for reducing the odor level of polyolefins according to the present invention. DETAILED DESCRIPTION

[0013] A method for reducing the odor level of polyolefin resin material by supercritical extraction, wherein the device used is as follows Figure 1 , including CO2 cylinder, filter, flow meter, refrigeration system, carrying agent tank, mixing tank, heating device, extraction kettle and separation kettle.

[0014] Among them, CO2 cylinders are used to store gaseous CO2; the filter contains filtering materials such as silica gel, which plays a filtering role; the flow meter is used to display instantaneous flow and cumulative flow; the refrigeration system is composed of a water-cooled fully enclosed refrigeration compressor unit, a cold box, etc.; the carrying agent tank is used to store the carrying agent; the mixing tank is used to mix the carrying agent and liquid CO2; the heating device is used to heat the extraction kettle and the separation kettle.

[0015] At the same time, both the extraction kettle and the separation kettle can be one-stage or multi-stage.

[0016] The specific processing steps for reducing the odor level of polyolefin resin materials using this device are as follows: 1) Add polyolefin resin material (powder or pellets) into the extraction kettle; 2) Open the valve of the CO2 cylinder, let the CO2 gas pass through the filter to filter out impurities, monitor the flow rate through the flow meter, and then enter the refrigeration system to cool into liquid CO2; 3) Open the valve of the carrier tank, so that the carrier enters the mixing tank together with the liquid CO2 through the pump, and then is heated and pressurized into a supercritical state by the heating device and sent to the extraction kettle for extraction; 4) The material flowing out of the extraction kettle is sent to the separation kettle to separate the small molecular substances. The separated gaseous fluid is filtered and cooled into liquid and then sent to the extraction kettle for recycling; at the same time, the remaining material in the extraction kettle is collected to obtain a low-odor, low-VOC polyolefin resin material.

[0017] The amount of the carrying agent in step 3) is 50-500 ml per 1-2 kg of polyolefin resin material. The carrying agent is prepared by mixing sapodilla extract and anhydrous ethanol at a mass ratio of 1:20. The extraction pressure is 10-30 MPa and the extraction time is 10-60 min.

[0018] The following specific embodiments are combined to make the technical solutions and advantages of the present invention more clearly expressed. Those skilled in the art can make modifications or equivalent substitutions based on their understanding of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be included in the protection scope of the present invention.

[0019] The polypropylene used in this embodiment is H5035 and 5502 produced by Sinochem Quanzhou Petrochemical.

[0020] The sapodilla extract used in this example was purchased from Xi'an Feida Biological, and its product specification was 20:1. It was sieved through an 80-mesh sieve before use.

[0021] Example 1 1) Add 2 kg of polyolefin resin H5035 powder into the extraction kettle; 2) Open the valve of the CO2 cylinder, let the CO2 gas pass through the filter to filter out impurities, monitor the flow rate through the flow meter, and then enter the refrigeration system to cool into liquid CO2; 3) Add 0.07 parts of saponin extract to 4 parts of anhydrous ethanol by mass to mix as a carrier; open the valve of the carrier tank, and pump 100 mL of the carrier into the mixing tank together with liquid CO2, and then heat and pressurize it into a supercritical state through a heating device and enter the extraction kettle; 4) The extraction pressure is set to 10 MPa. After 10 minutes of extraction in the extraction kettle, the outflowing supercritical fluid is sent to the separation kettle to separate the small molecular substances. The separated gaseous fluid is filtered and cooled to liquid state and then sent to the extraction kettle for recycling. At the same time, the remaining materials in the extraction kettle are collected to obtain low-odor, low-VOC polyolefin resin.

[0022] Comparative Example 1 1) Add 2 kg of polyolefin resin H5035 powder into the extraction kettle; 2) Open the valve of the CO2 cylinder, let the CO2 gas pass through the filter to filter out impurities, monitor the flow rate through the flow meter, and then enter the refrigeration system to cool into liquid CO2; 3) Use anhydrous ethanol as a carrier; open the valve of the carrier tank, pump 100 mL of the carrier into the mixing tank together with liquid CO2, and then heat and pressurize it into a supercritical state through a heating device before entering the extraction kettle; 4) The extraction pressure is set to 10 MPa, and the extraction is carried out in the extraction kettle for 30 minutes. The outflowing supercritical fluid is sent to the separation kettle to separate the small molecular substances. The separated gaseous fluid is filtered and cooled to liquid state and then sent to the extraction kettle for recycling; at the same time, the remaining materials in the extraction kettle are collected to obtain the treated polyolefin resin.

[0023] Comparative Example 2 In step 4), the extraction pressure was set to 20 MPa, and the extraction was carried out in the extraction kettle for 30 min. Other operations were the same as those in Comparative Example 1.

[0024] Comparative Example 3 In step 4), the extraction pressure was set to 30 MPa, and the extraction was carried out in the extraction kettle for 30 min. Other operations were the same as those in Comparative Example 1.

[0025] Comparative Example 4 In step 4), the extraction pressure was set to 30 MPa, and the extraction was carried out in the extraction kettle for 60 min. Other operations were the same as those in Comparative Example 1.

[0026] Comparative Example 5 By mass, 0.07 parts of cationic surfactant hexadecyltrimethylammonium bromide was added to 4 parts of anhydrous ethanol to mix as a carrier, and other operations were the same as in Example 1.

[0027] Comparative Example 6 By mass, 0.07 parts of anionic surfactant sodium dodecyl sulfate was added to 4 parts of anhydrous ethanol to mix as a carrier, and other operations were the same as in Example 1.

[0028] Comparative Example 7 According to the mass proportion, 0.07 parts of nonionic surfactant Tween 20 was added to 4 parts of anhydrous ethanol to mix as a carrier, and the other operations were the same as those in Example 1.

[0029] Comparative Example 8 By mass, 0.07 parts of natural surfactant tea saponin was added to 4 parts of anhydrous ethanol to mix as a carrier, and other operations were the same as in Example 1.

[0030] Comparative Example 9 By weight, 0.2 parts of natural surfactant cocamidopropyl betaine (purity of 35 wt%) was added to 4 parts of anhydrous ethanol to mix as a carrier, and other operations were the same as in Example 1.

[0031] Comparative Example 10 By mass, 0.175 parts of natural surfactant soapberry fruit extract (purity 40wt%) was added to 4 parts of anhydrous ethanol to mix as a carrier, and other operations were the same as Example 1.

[0032] Example 2 1) Add 2 kg of polyolefin resin 5502 pellets into the extraction kettle; 2) Open the valve of the CO2 cylinder, let the CO2 gas pass through the filter to filter out impurities, monitor the flow rate through the flow meter, and then enter the refrigeration system to cool into liquid CO2; 3) Add 0.07 parts of saponin extract to 4 parts of anhydrous ethanol by mass to mix as a carrier; open the valve of the carrier tank, and pump 100 mL of the carrier into the mixing tank together with liquid CO2, and then heat and pressurize it into a supercritical state through a heating device and enter the extraction kettle; 4) The extraction pressure is set to 10 MPa, and the extraction is carried out in the extraction kettle for 15 minutes. The outflowing supercritical fluid is sent to the separation kettle to separate the small molecular substances. The separated gaseous fluid is filtered and cooled to liquid state and then sent to the extraction kettle for recycling. At the same time, the remaining materials in the extraction kettle are collected to obtain low-odor, low-VOC polyolefin resin.

[0033] Comparative Example 11 1) Add 2 kg of polyolefin resin 5502 pellets into the extraction kettle; 2) Open the valve of the CO2 cylinder, let the CO2 gas pass through the filter to filter out impurities, monitor the flow rate through the flow meter, and then enter the refrigeration system to cool into liquid CO2; 3) Use anhydrous ethanol as a carrier; open the valve of the carrier tank, pump 100 mL of the carrier into the mixing tank together with liquid CO2, and then heat and pressurize it into a supercritical state through a heating device before entering the extraction kettle; 4) The extraction pressure is set to 20 MPa, and the extraction is carried out in the extraction kettle for 30 minutes. The outflowing supercritical fluid is sent to the separation kettle to separate the small molecular substances. The separated gaseous fluid is filtered and cooled to liquid state and then sent to the extraction kettle for recycling; at the same time, the remaining materials in the extraction kettle are collected to obtain the treated polyolefin resin.

[0034] The polyolefin resins obtained by the above-mentioned embodiments and comparative examples were subjected to an odor level test using the VDA270-2022 standard. The results are shown in Table 1.

[0035] Table 1 Comparison of odor levels of samples obtained under different treatment conditions

[0036] From the comparison of Example 1 and Comparative Examples 1-4 in Table 1, it can be seen that adding a surfactant saponin extract to the carrier can reduce the pressure and time of supercritical extraction. When a surfactant saponin extract is added to the carrier, the odor level of 5035 powder can be reduced from 3.5 to 2.0 within an extraction pressure of 10MPa and an extraction time of 10min, while pure ethanol is used as a carrier, and the same effect can be achieved under the conditions of an extraction pressure of 30MPa and an extraction time of 60min. At the same time, it can also be seen from the comparison of Example 2 and Comparative Example 11 that adding a surfactant saponin extract to the carrier can reduce the odor level of 5502 pellets from 3.5 to 2.5 within an extraction pressure of 10MPa and an extraction time of 15min, while pure ethanol is used as a carrier, and the odor level of 5502 pellets can be reduced from 3.5 to 3.0 at an extraction pressure of 20MPa and an extraction time of 30min. This shows that the use of saponin extract in the carrier can effectively reduce the pressure and time of supercritical extraction.

[0037] In addition, by comparing Example 1 with Comparative Examples 5-10, it can be seen that, compared with adding cationic surfactant hexadecyltrimethylammonium bromide, anionic surfactant sodium dodecylbenzenesulfonate and natural surfactant tea saponin, natural surfactant cocamidopropyl betaine and soapberry fruit extract to the carrier, adding saponin extract to the carrier has a better effect in reducing the odor level of polyolefin resin, while adding non-ionic surfactant Tween 20 to the carrier has basically no effect in reducing the odor level of polyolefin resin.

[0038] In order to further verify that the method of the present invention does not affect the mechanical properties of polyolefin resin materials while reducing the odor level of the polyolefin resin materials, the mechanical properties and melt index of the polyolefin resins obtained by the treatment of Example 1 and Comparative Example 1 were measured. The results are shown in Table 2.

[0039] Table 2 Comparison of mechanical properties and melt index results of samples obtained under different treatment conditions

[0040] As can be seen from Table 2, the mechanical properties and molecular weight distribution of the polyolefin resin obtained by adding the surfactant saponin extract to the carrier for supercritical CO2 extraction did not change significantly from those of the 5035 raw material. This shows that the method of the present invention can be used to reduce the odor level of the polyolefin resin material without affecting its mechanical properties.

[0041] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for reducing the odor level of polyolefin resin material by supercritical extraction, characterized in that: The following steps are involved: 1) Add polyolefin resin material into the extraction kettle; 2) The carrier and liquid CO2 are heated and pressurized into a supercritical state and then sent into an extraction kettle for extraction; 3) The material flowing out of the extraction kettle is sent to the separation kettle to separate the small molecular substances, and the remaining material in the extraction kettle is collected at the same time, so as to obtain a low-odor, low-VOC polyolefin resin material.

2. The method for reducing the odor level of polyolefin resin material by supercritical extraction according to claim 1, characterized in that: Step 2) The carrier is prepared by mixing the saponin extract and anhydrous ethanol in a mass ratio of 1:

20.

3. The method for reducing the odor level of polyolefin resin material by supercritical extraction according to claim 1, characterized in that: In step 3), the amount of the carrying agent is 50-500 ml for every 1-2 kg of polyolefin resin material treated.

4. The method for reducing the odor level of polyolefin resin material by supercritical extraction according to claim 1, characterized in that: The extraction pressure in step 2) is 10-30 MPa and the extraction time is 10-60 min.

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