阅读说明：本技术 一种利用超临界co2制备高纯聚丙烯的方法 (By using supercritical CO2Method for preparing high-purity polypropylene ) 是由 王家纯 李贵生 付红生 张丕生 于 2021-08-19 设计创作，主要内容包括：本发明属于高纯聚丙烯制备技术领域,公开一种利用超临界CO-(2)制备高纯聚丙烯的方法。将待处理原料聚丙烯分散到乙醇中,获得分散液；然后将分散液转移至超临界装置中,向超临界装置中注入二氧化碳,在超临界条件下搅拌3-6h,自然冷却至室温后卸压；将超临界处理后的体系分离,洗涤后干燥,得到高纯聚丙烯。本发明突破传统的聚合物洗涤方法,在超临界二氧化碳条件下,采用乙醇纯化商业化聚丙烯粒料,脱灰技术环保无污染,在能源转换领域有重大的应用前景。(The invention belongs to the technical field of high-purity polypropylene preparation, and discloses a method for preparing polypropylene by using supercritical CO 2 A method for preparing high-purity polypropylene. Dispersing raw material polypropylene to be treated into ethanol to obtain dispersion liquid; then transferring the dispersion liquid into a supercritical device, injecting carbon dioxide into the supercritical device, stirring for 3-6h under the supercritical condition, naturally cooling to room temperature, and releasing pressure; and separating the system after the supercritical treatment, washing and drying to obtain the high-purity polypropylene. The invention breaks through the traditional polymer washing method, adopts ethanol to purify the commercial polypropylene granules under the condition of supercritical carbon dioxide, has environment-friendly and pollution-free deliming technology, and has great application prospect in the field of energy conversion.)

1. By using supercritical CO₂The method for preparing high-purity polypropylene is characterized by comprising the following steps: dispersing the polypropylene to be treated into ethanol to obtainObtaining dispersion liquid; then transferring the dispersion liquid into a supercritical device, injecting carbon dioxide into the supercritical device, stirring for 3-6h under the supercritical condition, naturally cooling to room temperature, and releasing pressure; and separating the system after the supercritical treatment, washing and drying to obtain the high-purity polypropylene.

2. The method of claim 1 using supercritical CO₂The method for preparing high-purity polypropylene is characterized by comprising the following steps: the dosage ratio of the raw material polypropylene to be treated and the ethanol is (50-150) g to (100-200) mL.

3. The method of claim 1 using supercritical CO₂The method for preparing high-purity polypropylene is characterized in that the parameters of the supercritical conditions are as follows: the temperature is 60-100 deg.C, and the pressure is 15-20 Mpa.

4. The method of claim 1 using supercritical CO₂The method for preparing high-purity polypropylene is characterized by comprising the following steps: the volume part of the ethanol is 50-90 v%.

5. The method of claim 1 using supercritical CO₂The method for preparing high-purity polypropylene is characterized by comprising the following steps: the separation mode is filtration.

6. The method of claim 1 using supercritical CO₂The method for preparing high-purity polypropylene is characterized by comprising the following steps: when washing, the washing is carried out for several times by alternately adopting absolute ethyl alcohol and water.

Technical Field

The invention belongs to the technical field of high-purity polypropylene preparation, and particularly relates to a method for preparing polypropylene by using supercritical CO₂A method for preparing high-purity polypropylene.

Background

Polypropylene (PP) is a polyolefin widely used in industry and life, and is prepared by polymerizing propylene monomers under the action of a catalyst, and is classified into isotactic polypropylene, syndiotactic polypropylene and atactic polypropylene according to methyl arrangement positions. The ash content of polypropylene refers to the metal and non-metal oxides remaining from the PP after complete combustion. The ash in PP mainly comes from main catalyst, cocatalyst, electron donor, additive, system impurity and the like, and the main chemical element components are titanium, magnesium, aluminum, chlorine and the like. In practical applications, such as electronic appliances, medicines, foods, textiles, etc., polypropylene is required to have a low ash content (generally less than 0.0080%). For severe application environments, the lower the ash content of polypropylene, the better, such as PP films for high voltage capacitors. At present, the preparation of high-purity polypropylene mainly depends on the subsequent deashing treatment of the obtained PP granules, generally adopts a solvent washing mode, needs a large amount of chemical solvents and has low deashing efficiency. In the preparation and application of high-purity polypropylene, in order to reduce the production cost and achieve the purpose of green environmental protection, the challenges of utilizing simple and easily available green solvents and exploring a simpler washing and deashing technology are still required.

Disclosure of Invention

In view of the above-mentioned drawbacks and disadvantages of the prior art, it is an object of the present invention to provide a method for utilizing supercritical CO₂A method for preparing high-purity polypropylene.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for preparing high-purity polypropylene (ash content is less than or equal to 10 ppm) by using a supercritical fluid technology comprises the following steps: dispersing raw material polypropylene to be treated into ethanol to obtain dispersion liquid; then transferring the dispersion liquid into a supercritical device, injecting carbon dioxide into the supercritical device, stirring for 3-6h under the supercritical condition, naturally cooling to room temperature, and releasing pressure; and separating the system after the supercritical treatment, washing and drying to obtain the high-purity polypropylene.

Preferably, the dosage ratio of the raw material polypropylene to be treated and the ethanol is (50-150) g to (100-200) mL.

Preferably, the parameters of the supercritical conditions are: the temperature is 60-100 deg.C, and the pressure is 15-20 Mpa.

Preferably, the volume part of the ethanol is 50-90 v%.

Preferably, the separation means is filtration.

Preferably, the washing is carried out several times by alternately washing with absolute ethanol and water.

The invention provides a method for utilizing supercritical CO₂In the method for preparing the high-purity polypropylene, ethanol and water solvent molecules can enter the expanded PP polymer network structure under the assistance of carbon dioxide in a supercritical high-pressure environment, and due to the solvation effect, impurities such as residual catalyst and the like wrapped in a polymer chain are dissolved in a washing solvent and are efficiently removed along with stirring.

The invention directly processes the commercial polypropylene granules, realizes polypropylene deliming by using supercritical carbon dioxide as a medium, has higher efficiency than the method of directly washing by using a chemical solvent, and can effectively reduce the washing time and the use of harmful solvents. In the whole PP purification process, the method is simple and easy to implement, environment-friendly and pollution-free, and has great application prospects in the fields of capacitors, batteries and the like.

Compared with the prior art, the invention has the following advantages:

the invention breaks through the traditional polymer washing method, adopts ethanol to purify the commercial polypropylene granules under the condition of supercritical carbon dioxide, has environment-friendly and pollution-free deliming technology, and has great application prospect in the field of energy conversion.

Drawings

FIG. 1 is an optical photograph (right side) of a raw polypropylene (left side) and a high purity polypropylene prepared in example 1 of the present invention.

Figure 2 is an XRD characterization of the starting polypropylene (left) and the high purity polypropylene prepared in example 1 of the present invention.

Detailed Description

In order to make the invention clearer and clearer, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

100 g of commercial polypropylene (PP) pellets (provided by original chemical Co., Ltd., ash content of about 0.0020 wt%) were added to 150 mL of 75 v% ethanol and stirred to obtain a dispersion, and then the dispersion was transferred to a supercritical reaction tank; injecting carbon dioxide into the supercritical reaction kettle to enable the supercritical reaction kettle to reach a supercritical state, wherein the temperature is 80 ℃, the pressure is 16 MPa, and performing deliming washing by magnetic stirring for 3 hours; and then naturally cooling to room temperature, releasing carbon dioxide for pressure relief, separating the PP subjected to supercritical treatment by adopting a filtering mode, alternately washing the PP for 3 times by using absolute ethyl alcohol and purified water, and drying the obtained PP in an oven at 60 ℃ to obtain the high-purity polypropylene.

The optical photo of the prepared high-purity polypropylene is shown in figure 1, and the polypropylene granules still keep granular in macroscopic view, and the surface of the polypropylene granules is not obviously damaged; the XRD representation of the prepared high-purity polypropylene is shown in figure 2, and the crystal form of the PP can be well maintained and is an alpha spherulite structure.

Comparative example 1

The difference from example 1 is that: treating without supercritical conditions; the method comprises the following specific steps: 100 g of commercial polypropylene pellets (provided by original chemical Co., Ltd., ash content of 0.0024 wt%) were added to 150 mL of 75 v% ethanol, stirred and dispersed to obtain a dispersion, and then the dispersion was transferred to a supercritical reaction vessel; without CO filling ₂Gas is magnetically stirred for 3 hours at the temperature of 80 ℃ for deliming and washing; and naturally cooling to room temperature, separating by adopting a filtering mode, alternately washing by using absolute ethyl alcohol and purified water for 3 times respectively, and drying the obtained PP in an oven at 60 ℃.

Comparative example 2

The difference from example 1 is that: example 1 was followed using "20 v% ethanol" instead of "75 v% ethanol".

The ash content of the raw materials, the products obtained in example 1 and comparative example 1 was measured by the direct calcination method (temperature 850 ℃ C.) in GB/T9345.1-2008, and is shown in Table 1.