Method for reducing odor grade of polyolefin resin material through post-treatment

Abstract

The invention discloses a method for reducing the odor grade of a polyolefin resin material through post-treatment, which mainly comprises the following steps of: preparing cocamidopropyl betaine, alkyl glycoside and water into a carrying agent, and removing odor small molecular substances in the polyolefin resin material through a supercritical CO2 extraction technology, so as to prepare low-odor low-VOC (Volatile Organic Compounds) polyolefin. The method disclosed by the invention can be used for removing the odor of various polyolefin finished product raw materials and effectively improving the quality of the polyolefin finished product, so that the method has relatively high economic value and 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 through post-processing. 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] The object of the present invention is to provide a method for reducing the odor level of polyolefin resin material by post-treatment, which can remove the odor of various polyolefin finished raw materials and effectively improve the quality of the obtained polyolefin resin material.

[0004] To achieve the above object, the present invention adopts the following technical solution: A method for reducing the odor level of a polyolefin resin material by post-treatment, comprising the following steps: 1) Add polyolefin resin material into CO2 extraction kettle; 2) Mixing cocamidopropyl betaine, alkyl glucoside and water to prepare a carrier; 3) The carrier and liquid CO2 are heated and pressurized into a supercritical state and then sent into an extraction kettle for extraction; 4) After extraction, the material in the extraction kettle is collected to obtain a low-odor, low-VOC polyolefin resin material.

[0005] Furthermore, the mass ratio of cocamidopropyl betaine, water and alkyl glycoside used is 10:200:1.

[0006] Furthermore, the alkyl glycoside is specifically APG-0810.

[0007] Furthermore, the amount of the carrying agent is 50-500 ml per 1-2 kg of polyolefin resin material treated.

[0008] Furthermore, in step 3), the extraction pressure is 10-30 MPa and the extraction time is 10-30 min, preferably 10 MPa and 15 min.

[0009] The present invention innovatively uses the aqueous solution of natural surfactants cocamidopropyl betaine and alkyl glycoside as a carrier and supercritical CO2 extraction to reduce the odor of polyolefin resin. Cocamidopropyl betaine is a pure natural amphoteric surfactant, and alkyl glycoside is a degradable, non-toxic and non-irritating non-ionic surfactant. The combination of the two can produce a synergistic effect and effectively assist SC-CO2 in removing small molecules from polyolefins.

[0010] 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; coupled with the synergistic effect of cocamidopropyl betaine and alkyl glucoside, SC-CO2 can be more effectively assisted in removing small molecules from polyolefins, thereby achieving the preparation of low-odor, low-VOC resin products.

[0011] (2) According to the method of the present invention, the odor level of the polyolefin resin powder at 80°C can be reduced to level 2.5 or below (using VDA270:2022 standard) within 15 minutes. Since the supercritical CO2 used is reduced to a gaseous state and released 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.

[0012] (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 milk tea cups, 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

[0013] Figure 1 This is a schematic diagram of a post-treatment device for reducing the odor level of polyolefins according to the present invention. DETAILED DESCRIPTION

[0014] A method for reducing the odor level of polyolefin resin material by post-treatment, 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.

[0015] Among them, CO2 cylinders are used to store gaseous CO2; the filter contains silica gel and other filtering materials, which play a filtering role; the flow meter is used to display the 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. Both the extraction kettle and the separation kettle can be one or more sections.

[0016] The specific processing steps for reducing the odor level of polyolefin resin materials using this device are as follows: 1) Mix cocamidopropyl betaine, water and alkyl glucoside in a mass ratio of 10:200:1 to prepare a carrier, and store the mixture in a carrier tank; 2) Add polyolefin resin material (powder or pellets) into the extraction kettle; 3) 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; 4) 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; 5) 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] Wherein, the amount of the carrying agent in step 4) is 50-500 ml per 1-2 kg of polyolefin resin material. The extraction pressure is 10-30 MPa and the extraction time is 10-30 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 polyolefin resin material used in this embodiment is a polypropylene powder material used for milk tea cups.

[0020] The cocamidopropyl betaine used in this embodiment has a purity of 35 wt % and was purchased from Guangzhou Chaorun Chemical Co., Ltd.

[0021] The APG-0810 used in this example has a purity of 50 wt % and was purchased from Jiangsu Wanqi Biotechnology Co., Ltd.

[0022] Example 1 1) Add 0.2 parts of cocamidopropyl betaine and 0.02 parts of APG-0810 to 4 parts of pure water as a carrier, and store in a carrier tank; 2) Add 2kg of milk tea cup polypropylene powder into the extraction kettle; 3) 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; 4) Open the valve of the carrier tank, pump 100mL of carrier into the mixing tank together with liquid CO2, and then heat and pressurize it into a supercritical state through the heating device before entering the extraction kettle; 5) The extraction pressure is set to 10 MPa. After 15 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.

[0023] Comparative Example 1 In step 1), pure water is used as a carrier, and other operations are the same as in Example 1.

[0024] Comparative Example 2 In step 1), 0.15 parts of APG-0810 were added to 4 parts of pure water by mass to mix as a carrier, and other operations were the same as in Example 1.

[0025] Comparative Example 3 In step 1), 0.2 parts of cocamidopropyl betaine are added to 4 parts of pure water by mass and mixed as a carrier, and other operations are the same as in Example 1.

[0026] Comparative Example 4 In step 1), 0.175 parts of soapberry fruit extract (purity of 40 wt%) were added to 4 parts of pure water as a carrier, and other operations were the same as in Example 1.

[0027] Comparative Example 5 In step 1), 0.175 parts of soapberry fruit extract (purity of 40 wt%) and 0.02 parts of APG-0810 were added to 4 parts of pure water as a carrier, and other operations were the same as in Example 1.

[0028] Comparative Example 6 In step 1), 0.07 parts of hexadecyltrimethylammonium bromide are added to 4 parts of pure water by mass to mix as a carrier, and other operations are the same as in Example 1.

[0029] Comparative Example 7 In step 1), 0.07 parts of hexadecyltrimethylammonium bromide and 0.02 parts of APG-0810 were added to 4 parts of pure water by mass and mixed as a carrier, and other operations were the same as in Example 1.

[0030] Comparative Example 8 In step 1), 0.07 parts of sodium dodecylbenzene sulfonate are added to 4 parts of pure water by mass to mix as a carrier, and other operations are the same as in Example 1.

[0031] Comparative Example 9 In step 1), 0.07 parts of sodium dodecylbenzene sulfonate and 0.02 parts of APG-0810 were added to 4 parts of pure water by mass and mixed as a carrier, and other operations were the same as in Example 1.

[0032] 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.

[0033] Table 1 Comparison of odor levels of samples treated with different carriers

[0034] It can be seen from Table 1 that after the polypropylene powder (raw material) was subjected to supercritical CO2 extraction using pure water as a carrier, the 80°C odor level of the powder was reduced from 4.5 to 3.5, while the 80°C odor level of the powder obtained by using only an alkyl polyglycoside aqueous solution as a carrier for extraction in Comparative Example 2 was also reduced to 3.5, indicating that using only an alkyl polyglycoside aqueous solution as a carrier has no obvious effect in reducing the odor level of polyolefins. From the comparison of comparative examples 3-9, it can be seen that under the same extraction pressure and extraction time, cocamidopropyl betaine, nonionic surfactant soapberry fruit extract, cationic surfactant hexadecyl trimethyl ammonium bromide, anionic surfactant sodium dodecylbenzene sulfonate or an aqueous solution of soapberry fruit extract, hexadecyl trimethyl ammonium bromide, sodium dodecylbenzene sulfonate and alkyl glycoside are added to the carrier respectively, and the odor level of polypropylene powder (raw material) at 80°C is reduced from 4.5 to 3.0 at most, while Example 1 can reduce the odor level of polypropylene powder at 80°C from 4.5 to 2.5, which shows that the carrier is a cocamidopropyl betaine and alkyl glycoside aqueous solution can effectively reduce the odor level of polypropylene powder in milk tea cups. The reason for the analysis may be that compared with other surfactants, alkyl glycosides can produce better synergistic effects with the amphoteric surfactant cocamidopropyl betaine, and thus can more effectively assist SC-CO2 in removing small molecules from polyolefins.

[0035] 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, the mechanical properties and melt index of Example 1 and the raw materials not extracted by the supercritical CO2 extraction device were measured. The results are shown in Table 2.

[0036] Table 2 Comparison of mechanical properties and melt index results of samples obtained under different treatment conditions

[0037] As can be seen from Table 2, the mechanical properties, molecular weight distribution, melting point and crystallization point of the obtained polyolefin resin are not significantly different from those of the polypropylene powder raw material when the aqueous solution of cocamidopropyl betaine and alkyl glycoside is used as a carrier to perform supercritical CO2 extraction on the polyolefin resin. This shows that the method of the present invention can effectively reduce the odor level of the polyolefin resin material without affecting its mechanical properties.

[0038] 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 post-treatment, characterized in that: Cocamidopropyl betaine, alkyl glycoside and water are mixed as a carrier, and the polyolefin resin is subjected to supercritical CO2 extraction to remove the odorous small molecules in the polyolefin resin.

2. The method for reducing the odor level of polyolefin resin material by post-treatment according to claim 1, characterized in that: The mass ratio of cocamidopropyl betaine, water and alkyl glycoside used is 10:200:

1.

3. The method for reducing the odor level of polyolefin resin material by post-treatment according to claim 1 or 2, characterized in that: The alkyl glycoside is specifically APG-0810.

4. The method for reducing the odor level of polyolefin resin material by post-treatment according to claim 1, characterized in that: The amount of the carrying agent is 50-500 ml for every 1-2 kg of polyolefin resin material treated.

5. The method for reducing the odor level of polyolefin resin material by post-treatment according to claim 1, characterized in that: The supercritical CO2 extraction is performed at a pressure of 10-30 MPa and a time of 10-30 min.

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