Method for controlling melt index of polypropylene powder

Abstract

The invention belongs to the technical field of polypropylene material production, and particularly relates to a method for controlling the melt index of polypropylene powder, and the method for controlling the melt index of the polypropylene powder comprises the following steps: (1) recording hydrogen feeding amounts correspondingly required during production of n polypropylene powder with different melt indexes, n being greater than or equal to 6; (2) drawing a nonlinear fitting curve by using Origin software with the melt index in the step (1) as a vertical coordinate axis and the corresponding hydrogen feeding amount as a horizontal coordinate axis; the equation of the nonlinear fitting curve is y = a * xb. The method for controlling the melt index of the polypropylene powder has the beneficial effects that the thought is clear, the guiding effect is ideal, and the problems that the melt index of the polypropylene powder is slow to adjust and more transition materials are generated are effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene material production, and in particular relates to a method for controlling the melting index of polypropylene powder. Background Art

[0002] Polypropylene is a thermoplastic synthetic resin with excellent performance and is an indispensable necessity in people's daily life. In order to meet people's growing material needs, the downstream industries of polypropylene are provided with polypropylene products with low specific gravity, non-toxicity and easy processing to meet people's life needs in various aspects such as automobiles, household appliances, electronics, packaging, building materials and furniture. The downstream industries produce daily necessities for people's lives, which requires polypropylene products with different melt indexes. The melt index range of polypropylene products can reach 0.5g / 10min-1500g / 10min. At present, the production of polypropylene products with different melt indexes is adjusted according to the results of quality inspection and analysis. This method has the problems of slow adjustment speed, long time consumption, more transition materials and low efficiency. In order to improve the efficiency of product melt index adjustment and reduce the transition materials generated, the patent of this invention proposes a method for quickly adjusting and controlling the melt index of polypropylene powder. Summary of the invention

[0003] The present application provides a method for controlling the melt index of polypropylene powder, aiming to solve the problems of low efficiency, long time consumption and large amount of transition material in the prior art in adjusting the melt index of polypropylene powder.

[0004] The present application provides a method for controlling the melt index of polypropylene powder, comprising the following steps:

[0005] (1) Record the amount of hydrogen feed required for the production of n polypropylene powders with different melt indexes, where n ≥ 6;

[0006] (2) using Orign software to draw a nonlinear fitting curve with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis;

[0007] The equation of the nonlinear fitting curve is y=a*x^b.

[0008] The method for controlling the melt index of polypropylene powder described in the present application has clear ideas and ideal guiding effects, and effectively solves the problems of slow adjustment of the melt index of polypropylene powder and excessive generation of transition materials.

[0009] According to the method for controlling the melt index of polypropylene powder described in the present application, in step (1), the temperature of the polypropylene powder during production is 70-90°C.

[0010] According to the method for controlling the melt index of polypropylene powder described in the present application, in step (1), the pressure during the production of the polypropylene powder is 2-4 MPaG.

[0011] According to the method for controlling the melt index of polypropylene powder described in the present application, in step (1), the hydrogen feed amounts of the polypropylene powder production device producing the same melt index polypropylene powder under different loads are recorded respectively, and the average value is calculated as the hydrogen amount required for the production of the melt index polypropylene powder.

[0012] According to the method for controlling the melt index of polypropylene powder described in the present application, the device at different loads includes a device load of 40%-60%, a device load of 60%-80%, and a device load of 80%-100%.

[0013] According to the method for controlling the melt index of polypropylene powder described in the present application, the melt index of the polypropylene required for production is substituted into the equation to obtain the corresponding hydrogen feed amount for production.

[0014] According to the method for controlling the melt index of polypropylene powder described in the present application, the hydrogen feed amount is the hydrogen feed amount at a production temperature of 70-90°C.

[0015] According to the method for controlling the melt index of polypropylene powder described in the present application, the hydrogen feed amount is the hydrogen feed amount at a production pressure of 2-4 MPaG. DETAILED DESCRIPTION

[0016] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0017] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0018] The present application provides a method for controlling the melt index of polypropylene powder, comprising the following steps:

[0019] (1) Record the amount of hydrogen feed required for the production of n polypropylene powders with different melt indexes, where n ≥ 6;

[0020] (2) using Orign software to draw a nonlinear fitting curve with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis;

[0021] The equation of the nonlinear fitting curve is y=a*x^b.

[0022] The method for controlling the melt index of polypropylene powder described in the present application has clear ideas and ideal guiding effects, and effectively solves the problems of slow adjustment of the melt index of polypropylene powder and excessive generation of transition materials.

[0023] In some embodiments of the present application, in step (1), the temperature during the production of the polypropylene powder is 70-90°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0024] In some embodiments of the present application, in step (1), the pressure during the production of the polypropylene powder is 2-4 MPaG, such as 2 MPaG, 3 MPaG, 4 MPaG, etc.

[0025] In some embodiments of the present application, in step (1), the hydrogen feed amount of the polypropylene powder production device under different loads to produce the same melt index polypropylene powder is recorded respectively, and the average value is calculated as the hydrogen amount required for the production of the melt index polypropylene powder, so that the corresponding hydrogen feed amount required for the production of the melt index polypropylene powder is more accurate.

[0026] In some embodiments of the present application, the device at different loads includes a device load of 40%-60%, a device load of 60%-80%, and a device load of 80%-100%.

[0027] In some embodiments of the present application, the melt index of the polypropylene required for production is substituted into the equation to obtain the corresponding hydrogen feed amount for production.

[0028] In some embodiments of the present application, the hydrogen feed amount is a hydrogen feed amount at a production temperature of 70-90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0029] In some embodiments of the present application, the hydrogen feed amount is a hydrogen feed amount at a production pressure of 2-4 MPaG, such as 2 MPaG, 3 MPaG, 4 MPaG, etc.

[0030] The technical solution of the present application is further described below in conjunction with specific embodiments and drawings.

[0031] Example 1

[0032] A method for controlling the melt index of polypropylene powder comprises the following steps:

[0033] (1) When the polymerization reactor temperature is 80°C and 3.0MPaG:

[0034] The hydrogen feed amount corresponding to the production of a polypropylene product with a melt index of 1 g / 10 min at a load of 60%, 80%, and 100% was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 1 g / 10 min. The results are shown in Table 1.

[0035] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 2g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 2g / 10min. The results are shown in Table 1.

[0036] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 3g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 3g / 10min. The results are shown in Table 1.

[0037] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 4g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 4g / 10min. The results are shown in Table 1.

[0038] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 5g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 5g / 10min. The results are shown in Table 1.

[0039] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 6g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 6g / 10min. The results are shown in Table 1.

[0040] Table 1

[0041]

[0042]

[0043] (2) Using Orign software, with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis, a nonlinear fitting curve was drawn:

[0044] The equation of the nonlinear fitting curve is y=a*x^b, where a=0.01396, b=1.57687;

[0045] From the nonlinear curve fitting analysis, we can see that the number of points is 6, the degree of freedom is 4, the Reduced Chi-Sqr is 0.02393, the residual sum of squares is 0.0957, the R square (COD) is 0.99453, the adjusted R square is 0.99316, and the fitting status is successful (100). The Reduced Chi-Sqr value is very small, and the R square and adjusted R square are close to 1, indicating that the fitting effect is ideal.

[0046] (3) Substituting the required polypropylene melt index (required melt index is 7) into the equation, the corresponding hydrogen feed amount of 52 g is obtained. With this hydrogen feed amount, polypropylene is produced at a temperature of 80°C and a pressure of 3.0 MPaG.

[0047] Example 2

[0048] A method for controlling the melt index of polypropylene powder comprises the following steps:

[0049] (1) When the polymerization reactor temperature is 80°C and 3.0MPaG:

[0050] The hydrogen feed amount corresponding to the production of a polypropylene product with a melt index of 1 g / 10 min when the polymerization reactor load is 40%, 60%, and 80% is recorded respectively, and the average value is calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 1 g / 10 min. The results are shown in Table 2.

[0051] The corresponding hydrogen feed amount when the polymerization reactor load is 40%, 60%, and 80% to produce a polypropylene product with a melt index of 2g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 2g / 10min. The results are shown in Table 2.

[0052] The corresponding hydrogen feed amount when the polymerization reactor load is 40%, 60%, and 80% to produce a polypropylene product with a melt index of 3g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 3g / 10min. The results are shown in Table 2.

[0053] The corresponding hydrogen feed amount when the polymerization reactor load is 40%, 60%, and 80% to produce a polypropylene product with a melt index of 4g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 4g / 10min. The results are shown in Table 2.

[0054] The corresponding hydrogen feed amount when the polymerization reactor load is 40%, 60%, and 80% to produce a polypropylene product with a melt index of 5g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 5g / 10min. The results are shown in Table 2;

[0055] The corresponding hydrogen feed amount when the polymerization reactor load is 40%, 60%, and 80% to produce a polypropylene product with a melt index of 6g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 6g / 10min. The results are shown in Table 2.

[0056] Table 2

[0057] Melt index (g / 10min) 1 2 3 4 5 6 Hydrogen feed (g) 20 27 32 37 43 50

[0058] (2) Using Orign software, with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis, a nonlinear fitting curve was drawn:

[0059] The equation of the nonlinear fitting curve is y=a*x^b, where a=0.007610, b=1.7147;

[0060] From the nonlinear curve fitting analysis, we can see that the number of points is 6, the degree of freedom is 4, the Reduced Chi-Sqr is 0.07330, the residual sum of squares is 0.2932, the R square (COD) is 0.9833, the adjusted R square is 0.9791, and the fitting status is successful (100). The Reduced Chi-Sqr value is very small, and the R square and adjusted R square are close to 1, indicating that the fitting effect is ideal.

[0061] (3) Substituting the required polypropylene melt index (required melt index is 7) into the equation, the corresponding hydrogen feed amount of 54 g is obtained. With this hydrogen feed amount, polypropylene is produced at a temperature of 80° C. and a pressure of 3.0 MPa.

[0062] Example 3

[0063] A method for controlling the melt index of polypropylene powder comprises the following steps:

[0064] (1) When the polymerization reactor temperature is 80°C and 3.0MPaG:

[0065] The hydrogen feed amount corresponding to the production of a polypropylene product with a melt index of 2g / 10min at a load of 60%, 80%, and 100% was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 2g / 10min. The results are shown in Table 3.

[0066] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 4g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 4g / 10min. The results are shown in Table 3;

[0067] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 6g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 6g / 10min. The results are shown in Table 3;

[0068] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 8g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 8g / 10min. The results are shown in Table 3;

[0069] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 10g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 10g / 10min. The results are shown in Table 3;

[0070] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 12g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 12g / 10min. The results are shown in Table 3;

[0071] Table 3

[0072] Melt index (g / 10min) 2 4 6 8 10 12 Hydrogen feed (g) 23 35 47 59 75 90

[0073] (2) Using Orign software, with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis, a nonlinear fitting curve was drawn:

[0074] The equation of the nonlinear fitting curve is y=a*x^b, where a=0.06790, b=1.1550;

[0075] From the nonlinear curve fitting analysis, we can see that the number of points is 6, the degree of freedom is 4, the Reduced Chi-Sqr is 0.1601, the residual sum of squares is 0.6403, the R square (COD) is 0.9909, the adjusted R square is 0.9886, and the fitting status is successful (100). The Reduced Chi-Sqr value is very small, and the R square and adjusted R square are close to 1, indicating that the fitting effect is ideal.

[0076] (3) Substituting the required polypropylene melt index (required melt index is 7) into the equation, the corresponding hydrogen feed amount of 55 g is obtained. With this hydrogen feed amount, polypropylene is produced at a temperature of 80° C. and a pressure of 3.0 MPa.

[0077] Example 4

[0078] The only difference between Example 4 and Example 1 is that the temperature of the polymerization reaction is different when producing the polypropylene powder.

[0079] The specific steps are:

[0080] (1) When the polymerization reactor temperature is 75°C and 3.0MPaG:

[0081] The hydrogen feed amount corresponding to the production of a polypropylene product with a melt index of 1 g / 10 min when the polymerization reactor load is 60%, 80%, and 100% is recorded respectively, and the average value is calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 1 g / 10 min. The results are shown in Table 4.

[0082] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 2g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 2g / 10min. The results are shown in Table 4;

[0083] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 3g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 3g / 10min. The results are shown in Table 4.

[0084] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 4g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 4g / 10min. The results are shown in Table 4.

[0085] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 5g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 5g / 10min. The results are shown in Table 4;

[0086] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 6g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 6g / 10min. The results are shown in Table 4;

[0087] Table 4

[0088] Melt index (g / 10min) 1 2 3 4 5 6 Hydrogen feed (g) 21 26 34 40 44 59

[0089] (2) Using Orign software, with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis, a nonlinear fitting curve was drawn:

[0090] The equation of the nonlinear fitting curve is y=a*x^b, where a=0.02566, b=1.3536;

[0091] From the nonlinear curve fitting analysis, we can see that the number of points is 6, the degree of freedom is 4, the Reduced Chi-Sqr is 0.2612, the residual sum of squares is 1.0449, the R square (COD) is 0.9403, the adjusted R square is 0.9254, and the fitting status is successful (100). The Reduced Chi-Sqr value is very small, and the R square and adjusted R square are close to 1, indicating that the fitting effect is relatively ideal.

[0092] (3) Substituting the required polypropylene melt index (required melt index is 7) into the equation, the corresponding hydrogen feed amount of 63 g is obtained. With this hydrogen feed amount, polypropylene is produced at a temperature of 75° C. and a pressure of 3.0 MPa.

[0093] Example 5

[0094] The only difference between Example 5 and Example 1 is that the polymerization pressure is different when producing polypropylene powder.

[0095] The specific steps are:

[0096] (1) When the polymerization reactor temperature is 80°C and 3.2MPaG:

[0097] The hydrogen feed amount corresponding to the production of a polypropylene product with a melt index of 1 g / 10 min when the polymerization reactor load is 60%, 80%, and 100% is recorded respectively, and the average value is calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 1 g / 10 min. The results are shown in Table 5.

[0098] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 2g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 2g / 10min. The results are shown in Table 5;

[0099] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 3g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 3g / 10min. The results are shown in Table 5.

[0100] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 4g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 4g / 10min. The results are shown in Table 5.

[0101] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 5g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 5g / 10min. The results are shown in Table 5.

[0102] The corresponding hydrogen feed amount when the polymerization reactor load is 60%, 80%, and 100% to produce a polypropylene product with a melt index of 6g / 10min was recorded respectively, and the average value was calculated as the hydrogen feed amount required for the polymerization reactor to produce a polypropylene product with a melt index of 6g / 10min. The results are shown in Table 5.

[0103] Table 5

[0104] Melt index (g / 10min) 1 2 3 4 5 6 Hydrogen feed (g) 15 20 26 31 36 42

[0105] (2) Using Orign software, with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis, a nonlinear fitting curve was drawn:

[0106] The equation of the nonlinear fitting curve is y=a*x^b, where a=0.0200, b=1.533;

[0107] From the nonlinear curve fitting analysis, we can see that the number of points is 6, the degree of freedom is 4, the Reduced Chi-Sqr is 0.0345, the residual sum of squares is 0.138, the R square (COD) is 0.9921, the adjusted R square is 0.9901, and the fitting status is successful (100). The Reduced Chi-Sqr value is very small, and the R square and adjusted R square are close to 1, indicating that the fitting effect is ideal.

[0108] (3) Substituting the required polypropylene melt index (required melt index is 7) into the equation, the corresponding hydrogen feed amount of 46 g is obtained. With this hydrogen feed amount, polypropylene is produced at a temperature of 75° C. and a pressure of 3.2 MPa.

[0109] Melt index verification of polypropylene products obtained in Examples 1-5 of this application

[0110] The verification method is: when producing polypropylene products with a melt index of 7g / 10min, the theoretical simulation data is used to guide the actual operation. After actual verification, the feed amount required for the reactor is shown in Table 6:

[0111] Table 6

[0112] project Example 1 Example 2 Example 3 Example 4 Example 5 Melt index (g / 10min) 7 7 7 7 7 Simulation calculation of feed amount (g) 52 54 55 63 46 Actual hydrogen feed amount (g) 53 53 54 56 50

[0113] It can be seen from Table 6 that the theoretical simulation data of Examples 1, 2 and 3 are basically the same as the actual operation data, while there is a certain deviation between the theoretical simulation data of Examples 4 and 5 and the actual operation data, indicating that the reactor load and melt index have no effect on the hydrogen feed amount, and the pressure and temperature changes of the reactor have a greater impact on the hydrogen feed amount. However, the simulation data of Examples 4 and 5 are still relatively close to the actual operation data, which still has guiding significance for actual production work.

[0114] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for controlling the melt index of polypropylene powder, characterized in that: The following steps are involved: (1) Record the amount of hydrogen feed required for the production of n polypropylene powders with different melt indexes, where n ≥ 6; (2) using Orign software to draw a nonlinear fitting curve with the melt index in step (1) as the ordinate axis and the corresponding hydrogen feed amount as the abscissa axis; The equation of the nonlinear fitting curve is y=a*x^b.

2. The method for controlling the melt index of polypropylene powder according to claim 1, characterized in that: In step (1), the temperature during the production of the polypropylene powder is 70-90°C.

3. The method for controlling the melt index of polypropylene powder according to claim 1, characterized in that: In step (1), the pressure during the production of the polypropylene powder is 2-4 MPaG.

4. The method for controlling the melt index of polypropylene powder according to claim 1, characterized in that: In step (1), the hydrogen feed amounts of the polypropylene powder production device under different loads for producing the same melt index polypropylene powder are recorded respectively, and the average value is calculated as the hydrogen amount required for the production of the melt index polypropylene powder.

5. The method for controlling the melt index of polypropylene powder according to claim 1, characterized in that: The device has different loads including a device load of 40%-60%, a device load of 60%-80%, and a device load of 80%-100%.

6. The method for controlling the melt index of polypropylene powder according to claim 1, characterized in that: Substituting the melt index of the polypropylene required for production into the equation, the corresponding hydrogen feed amount for production is obtained.

7. The method for controlling the melt index of polypropylene powder according to claim 6, characterized in that: The hydrogen feed amount is the hydrogen feed amount at a production temperature of 70-90°C.

8. The method for controlling the melt index of polypropylene powder according to claim 6, characterized in that: The hydrogen feed amount is the hydrogen feed amount at a production pressure of 2-4 MPaG.