Preparation method of polypropylene, polypropylene, low-odor polypropylene resin and preparation method of low-odor polypropylene resin

Abstract

The invention discloses a preparation method of polypropylene, polypropylene, low-odor polypropylene resin and a preparation method of the low-odor polypropylene resin, and belongs to the technical field of polypropylene resin. The preparation method of the polypropylene comprises the following steps: (1) mixing propylene, aluminum alkyl, a silane compound, a high-activity catalyst and a high-molecular nucleating agent, and carrying out propylene prepolymerization to obtain a propylene prepolymer; (2) mixing the propylene prepolymer with hydrogen and olefin, and carrying out propylene polymerization under heating and pressurization to obtain polypropylene; the olefin is selected from one or more of propylene, ethylene and alpha-olefin and at least contains propylene; according to the method, a high-activity catalyst and a high-molecular nucleating agent are added in the polypropylene synthesis process, so that the polypropylene resin prepared from the polypropylene has low odor and excellent rigidity and toughness.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene resins, and in particular to a method for preparing polypropylene, polypropylene and low-odor polypropylene resin and a preparation method thereof. Background Art

[0002] Polypropylene (PP) has excellent comprehensive mechanical properties, heat resistance, and easy processing and molding. It is widely used, including automotive interiors, household appliances, packaging materials, pipes, medical supplies, transparent containers, daily necessities, etc. With the improvement of living standards and the continuous enhancement of environmental awareness, people have increasingly stringent requirements on the safety of polypropylene products that they come into contact with in daily life, such as car seats and armrests; shells and parts of household appliances such as electric kettles, rice cookers, coffee machines, microwave ovens, fans, washing machines and refrigerators; shockproof and cushioning packaging for food packaging bags, bottle caps, precision instruments, electronic products, etc.; water pipes, floor heating pipes; medical syringes and infusion tubes; food containers, microwave tableware, beverage bottles; condiment containers, snack boxes, bathtubs, buckets, etc. Specifically, people require that the volatile organic compound (VOC) content of polypropylene materials be as low as possible during processing and use to ensure that no harmful substances or irritating odors are released, providing consumers with a more comfortable use experience.

[0003] The odor of polypropylene resin mainly comes from the following aspects: the catalytic system used in polymerization contains lipid compounds or peroxides with pungent odors; during the processing, a large number of additives such as small molecule nucleating agents, antioxidants, halogen absorbers, etc. will also have a certain pungent odor after passing through the high temperature of the screw; moreover, in the granulation process, the polypropylene resin melts at high temperature and is sheared to produce thermal cracking small molecule compounds, such as ketones and aldehyde compounds, which all have odors; in addition, plastic products may also be affected by environmental factors such as temperature, humidity, light, etc. during transportation, storage and use, leading to the generation of odors.

[0004] In order to reduce the odor of polypropylene materials, the existing method is usually to add odor adsorbents during the material processing and granulation process, and physically adsorb volatile small molecules through the porous structure of the adsorbent, and then filter out the odor adsorbent in the vacuum degassing process. Commonly used and effective odor adsorbents are microporous crystals, mainly including aluminosilicate types, diatomaceous earth types, magnesium silicate types, etc.

[0005] However, the above method has high preparation cost, complex processing, poor deodorization effect, and seriously affects product performance. Therefore, it is of great significance to study and develop a new type of low-odor polypropylene resin to solve the above technical problems. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing polypropylene, polypropylene and low-odor polypropylene resin and their preparation methods. The polypropylene is used to prepare polypropylene resin to obtain a polypropylene resin with low odor and excellent mechanical properties.

[0007] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for preparing polypropylene, comprising the following steps:

[0009] (1) mixing propylene, alkyl aluminum, a silane compound, a high-activity catalyst and a polymer nucleating agent to perform propylene prepolymerization to obtain a propylene prepolymer;

[0010] (2) mixing the propylene prepolymer with hydrogen and olefin, and polymerizing propylene under heating and pressure to obtain polypropylene;

[0011] The olefin is selected from one or more of propylene, ethylene, and α-olefin and contains at least propylene;

[0012] The high-activity catalyst is selected from one or more of HR, SP-4, CS-2, and BCZ-208;

[0013] The polymer nucleating agent is selected from one or more of polyvinylcyclopentane, polyvinylcyclohexane, polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene and polystyrene.

[0014] Preferably, the temperature of the prepolymerization in step (1) is -10°C to 20°C;

[0015] Preferably, the heating temperature in step (2) is 50°C-100°C;

[0016] Preferably, the pressurization pressure in step (2) is 1-5 MPa.

[0017] Preferably, the α-olefin is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene.

[0018] Preferably, the alkylaluminum is selected from one or more of triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum monochloride, diisobutylaluminum monochloride, dihexylaluminum monochloride and dioctylaluminum monochloride; more preferably, it is triethylaluminum, triisobutylaluminum or trihexylaluminum.

[0019] Preferably, the silane compound is selected from vinyl triethoxysilane, vinyl trimethoxysilane, methyl triethoxysilane, dimethyl dimethoxysilane, diethyl dimethoxysilane, dipropyl dimethoxysilane, diisopropyl dimethoxysilane, dibutyl dimethoxysilane, diisobutyl dimethoxysilane, di-tert-butyl dimethoxysilane, di-tert-hexyl dimethoxysilane, diphenyl dimethoxysilane, dicyclohexyl dimethoxysilane, dicyclopentyl dimethoxysilane, dimethyl diethoxysilane, diethyl diethoxysilane, dipropyl diethoxysilane, diisopropyl diethoxysilane, One or more of dibutyldiethoxysilane, diisobutyldiethoxysilane, di-tert-butyldiethoxysilane, di-tert-hexyldiethoxysilane, diphenyldiethoxysilane, dicyclohexyldiethoxysilane, dicyclopentyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, cyclopentylmethyldimethoxysilane, cyclopentyltrimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexyltrimethoxysilane, tert-hexyltrimethoxysilane, tert-butyltrimethoxysilane, and tert-hexyltrimethoxysilane; more preferably cyclohexylmethyldimethoxysilane or cyclohexyltrimethoxysilane.

[0020] The present invention also provides a polypropylene prepared by the above preparation method.

[0021] Preferably, the melt index of the polypropylene at 230°C and a load of 2.16 kg is 5-80 g / 10 min;

[0022] Preferably, the polypropylene contains a high activity catalyst at a concentration of 10-20 ppm; more preferably 10-15 ppm.

[0023] Preferably, the polypropylene contains a polymer nucleating agent at a concentration of 30-100 ppm.

[0024] The present invention also provides a low-odor polypropylene resin, which comprises the following components in parts by weight:

[0025] The above-mentioned polypropylene: 95-100 parts by weight;

[0026] Polyethylene or poly-α-olefin: 0 to 5 parts by weight;

[0027] Antioxidant: 0.1-0.3 parts by weight;

[0028] Halogen absorbent: 0.01-0.1 parts by weight;

[0029] Other additives: 0-0.3 parts by weight;

[0030] Wherein, the monomer α-olefin in the poly α-olefin is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene;

[0031] The antioxidant is composed of a primary antioxidant and an auxiliary antioxidant in a mass ratio of 1:(1-4); more preferably 1:(2-3).

[0032] The primary antioxidant is selected from one or more of antioxidant 2246, antioxidant 1010, antioxidant 1076, and antioxidant 1330; more preferably, antioxidant 1010 or antioxidant 2246.

[0033] The auxiliary antioxidant is selected from one or more of antioxidant 168, antioxidant 626, and antioxidant 9228; more preferably, antioxidant 168.

[0034] In the present invention, the antioxidant is further preferably 0.15 parts by weight.

[0035] Further preferably, the antioxidant is selected from antioxidant 1010 and antioxidant 168.

[0036] Further preferably, the mass ratio of the antioxidant 1010 to the antioxidant 168 is 1:2. Preferably, the halogen absorbent is selected from one or more of sodium stearate, calcium stearate, and zinc stearate, and more preferably calcium stearate.

[0037] Preferably, the low-odor polypropylene resin has a melt index of 5-80 g / 10 min at 230° C. and a load of 2.16 kg;

[0038] Preferably, the low-odor polypropylene resin has an odor grade of 3.5 or less and a volatile organic compound test value of ≤50 μg / g.

[0039] The present invention also provides a method for preparing the low-odor polypropylene resin, comprising the following steps:

[0040] The antioxidant, the halogen absorbent, other additives and the above-mentioned polypropylene are mixed, extruded through a twin-screw extruder, pelletized, and dried to obtain the low-odor polypropylene resin;

[0041] The screw temperature of each interval during extrusion of the twin-screw extruder is controlled between 170°C and 235°C, and the highest value of the interval temperature during extrusion must be greater than 230°C.

[0042] Compared with the prior art, the preparation method of polypropylene provided by the present invention comprises the following steps: (1) mixing propylene, alkyl aluminum, silane compound, high-activity catalyst and high-molecular nucleating agent to carry out propylene prepolymerization to obtain propylene prepolymer; (2) mixing the propylene prepolymer with hydrogen and olefin, and carrying out propylene polymerization under heating and pressure to obtain polypropylene; the olefin is selected from one or more of propylene, ethylene and α-olefin and contains at least propylene; the high-activity catalyst is selected from one or more of HR, SP-4, CS-2 and BCZ-208; the high-molecular nucleating agent is selected from one or more of polyvinyl cyclopentane, polyvinyl cyclohexane, polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene and polystyrene. The method adds high-activity catalyst and high-molecular nucleating agent in the process of polypropylene synthesis, so that the polypropylene resin prepared by the polypropylene has low odor and excellent rigidity and toughness. DETAILED DESCRIPTION

[0043] In order to further illustrate the present invention, the preparation method of polypropylene, polypropylene and low-odor polypropylene resin and the preparation method thereof provided by the present invention are described in detail below in conjunction with embodiments.

[0044] The unit ppm below represents 10 to the negative sixth power, which is a mass percentage, specifically the percentage of a substance in the mass of homopolymer or copolymer polypropylene. For example, HR / ppm in Example 1 in Table 1 below is 0.028 / 2000=0.000014=14ppm, and the same applies to the others.

[0045] Example 1

[0046] Preparation of polypropylene:

[0047] (1) adding 1 kg of propylene, 3 mL of triethylaluminum (1M), 0.06 mL of cyclohexylmethyldimethoxysilane, 0.028 g of high-activity catalyst HR and 0.06 g of polyvinylcyclohexane (PVCH) into a 3 L prepolymerization reactor at 10° C. to carry out propylene prepolymerization for 15 min to obtain a propylene prepolymer;

[0048] (2) The propylene prepolymer was transferred from the prepolymerization kettle to a 10 L polymerization kettle, 18 L of hydrogen and 2 kg of propylene were added, the temperature was increased, and propylene polymerization was carried out at 70° C. and a certain pressure for 1.5 h to obtain 2000 g of homopolypropylene.

[0049] Processing and granulation:

[0050] The materials were weighed according to the components and formulas provided in Table 1 (parts by weight, ppm means mass percentage, the same applies to the following embodiments and comparative examples), mixed evenly, and extruded and granulated in a twin-screw extruder with a length-to-diameter ratio of 60:1 and a diameter of 35 mm to obtain a low-odor polypropylene special material; wherein the temperatures in each zone of the extruder were: 180° C. for zone 1, 200° C. for zone 2, 230° C. for zone 3, 235° C. for zone 4, 210° C. for zone 5, and 190° C. for the die.

[0051] The performance test results are shown in Table 3.

[0052] Example 2

[0053] The only difference from Example 1 is that the amount of PVCH used in the preparation stage of polypropylene is 0.1 g, and 1900 g of homopolypropylene is obtained.

[0054] Example 3

[0055] The only difference from Example 1 is that the amount of PVCH used in the preparation stage of polypropylene is 0.18 g, and 1800 g of homopolypropylene is obtained.

[0056] Example 4

[0057] The only difference from Example 2 is that 0.024 g of high-activity catalyst SP-4 is used in place of high-activity catalyst HR in the preparation stage of polypropylene, and 1900 g of homopolypropylene is prepared.

[0058] Example 5

[0059] Preparation of polypropylene:

[0060] (1) adding 1 kg of propylene, 3 mL of triethylaluminum (1M), 0.06 mL of cyclohexylmethyldimethoxysilane, 0.028 g of high-activity catalyst HR and 0.11 g of polyvinylcyclohexane into a 3 L prepolymerization reactor at 10° C. to carry out propylene prepolymerization for 15 min to obtain a propylene prepolymer;

[0061] (2) The propylene prepolymer was transferred from the prepolymerization kettle to a 10 L polymerization kettle, 17 L of hydrogen and 2 kg of propylene were added, 140 g of ethylene was slowly and continuously added, the temperature was increased, and propylene polymerization was carried out at 70° C. and a certain pressure for 1.5 hours to obtain 2200 g of copolymerized polypropylene.

[0062] Processing and granulation:

[0063] The materials were weighed according to the components and formulas provided in Table 1, mixed evenly, and extruded and granulated in a twin-screw extruder with a length-to-diameter ratio of 60:1 and a diameter of 35 mm to obtain a low-odor polypropylene special material; wherein the temperatures of the various zones of the extruder were: 180°C in zone 1, 200°C in zone 2, 230°C in zone 3, 235°C in zone 4, 210°C in zone 5, and 190°C in the die.

[0064] Table 1 Compositions for preparing low odor polypropylene resins in Examples 1-5

[0065]

[0066] The polyethylene content of Example 5 in the above Table 1 is obtained by infrared detection of low-odor polypropylene resin, and the polypropylene content is 100 minus the polyethylene content; the amounts of HR, SP-4 and PVCH in the table are obtained by calculation (i.e., initial addition amount / prepared polypropylene output).

[0067] Comparative Example 1

[0068] Preparation of polypropylene:

[0069] (1) In a 3 L prepolymerization kettle at 10° C., 1 kg of propylene, 3 mL of triethylaluminum (1 M), 0.06 mL of cyclohexylmethyldimethoxysilane, and 0.028 g of a high-activity catalyst HR were sequentially added to carry out propylene prepolymerization for 15 min to obtain a propylene prepolymer;

[0070] (2) The propylene prepolymer was transferred from the prepolymerization kettle to a 10 L polymerization kettle, 18 L of hydrogen and 2 kg of propylene were added, the temperature was increased, and propylene polymerization was carried out at 70° C. and a certain pressure for 1.5 h to obtain 2010 g of homopolypropylene.

[0071] Processing and granulation:

[0072] According to the components and formula provided in Table 2 (compared with Example 1, 1 g of small molecule nucleating agent NA-21 is added), the materials are weighed and mixed evenly, and then extruded and granulated in a twin-screw extruder with a length-to-diameter ratio of 60:1 and a diameter of 35 mm to obtain a special polypropylene material (polypropylene material); wherein the temperatures in each zone of the extruder are: 180° C. for zone 1, 200° C. for zone 2, 230° C. for zone 3, 235° C. for zone 4, 210° C. for zone 5, and 190° C. for the die.

[0073] The performance test results are shown in Table 4.

[0074] Comparative Example 2

[0075] The only difference from Comparative Example 1 is that 0.2 g of high molecular nucleating agent PVCH is used instead of small molecular nucleating agent NA-21 during the granulation stage.

[0076] Comparative Example 3

[0077] The only difference from Example 3 is that 0.04 g of catalyst SP-2 is used instead of the high-activity catalyst HR in the preparation stage of polypropylene, and 0.2 g of PVCH is added to obtain 2000 g of homopolymer polypropylene. (Note: The activity of catalyst SP-2 is lower than that of catalyst SP-4 and HR catalyst)

[0078] Comparative Example 4

[0079] The difference from Comparative Example 1 is that 0.04 g of catalyst SP-2 is used in place of high-activity catalyst HR in the preparation stage of polypropylene to obtain 2100 g of homopolypropylene; and 1.05 g of small molecule nucleating agent NA-21 is added in the granulation stage.

[0080] Comparative Example 5

[0081] The step (1) of preparing polypropylene is the same as that of Comparative Example 4, and the step (2) of preparing polypropylene is the same as that of Example 5.

[0082] The granulation process was the same as that in Comparative Example 4.

[0083] Comparative Example 6

[0084] The only difference from Example 1 is that the temperatures of the extruder zones during the granulation stage are: 170°C in zone 1, 190°C in zone 2, 200°C in zone 3, 210°C in zone 4, 200°C in zone 5, and 180°C in the die.

[0085] Comparative Example 7 (Existing Technology for Preparing Low Odor Polypropylene)

[0086] The only difference from Comparative Example 4 is that 2 g of odor adsorbent nano silicon oxide is added during the granulation process to produce 2100 g of homopolypropylene.

[0087] Table 2 Comparative Examples 1-7 Preparation of Polypropylene Resin Materials

[0088]

[0089] The polyethylene content of Comparative Example 5 in Table 2 above is obtained by infrared detection of the polypropylene resin material, and the polypropylene content is 100 minus the polyethylene content; the amounts of HR, SP-2 and PVCH in the table are obtained by calculation (i.e., initial addition amount / prepared polypropylene output).

[0090] Table 3 Properties of low odor polypropylene resin materials prepared in Examples 1-5

[0091]

[0092]

[0093] Table 4 Properties of polypropylene resin materials prepared in Comparative Examples 1-7

[0094]

[0095] The odor level test in the above table is as follows: weigh (20±2)g of sample (the amount of sample is taken to cover the bottom of the odor bottle) and put it into the odor bottle; secondly, put the odor bottle containing the sample into an oven and store it at (80±2)℃ for 2h±10min; then, take the odor bottle out of the oven and cool it to 60±5℃ (it takes about 5min); finally, evaluate the odor of the cooled sample (specifically, 5 people evaluate the odor of the sample at the same time and take the average value), and the evaluation criteria are as follows:

[0096] Odor level Odor description 1 No odor 2 There is an odor, but it is not disturbing or irritating 3 There is a noticeable smell, but no disturbing or irritating smell 4 Disturbing, irritating odor 5 Has a strong disturbing and irritating smell 6 There is an unbearable smell

[0097] Volatile organic compound (VOC) test: The samples to be tested were tested by gas chromatography-mass spectrometry (GC-MS) using a thermal desorption-gas chromatography-mass spectrometer. The data in Table 3 show that the odor level of the low-odor polypropylene resin in Examples 1-5 is not higher than 3.0 (Note: the requirement is not higher than 3.5), and the VOC value is less than 50 μg / g. The odor level and VOC value of the homopolymer (Examples 1-4) and copolymer (Example 5) polypropylene resins are both low. At the same time, the flexural modulus of the homopolymer is ≥1890MPa, and the impact strength is ≥3.0KJ / m 2 This indicates that the low-odor homopolymer polypropylene resin of the present invention not only has low odor, but also has excellent rigidity and toughness.

[0098] Comparison of Comparative Example 1 with Examples 1-4 shows that when 500 ppm of small molecule nucleating agent is added in the granulation stage, the odor level and VOC value of the prepared polypropylene are greater than those of Examples 1-4, and do not meet the grade requirements of low-odor polypropylene.

[0099] The comparison between Comparative Example 2 and Example 3 shows that when the polymer nucleating agent is added to the polypropylene in the granulation stage, although the odor level and VOC value meet the requirements, the flexural modulus and impact strength of the product are low, and the product performance is poor.

[0100] The comparison between Comparative Example 3 and Example 3 shows that the low-activity catalyst replaces the high-activity catalyst, and the odor level and VOC value are slightly higher than the low-odor polypropylene index requirements.

[0101] Comparison between Comparative Example 4, Comparative Example 7 and Examples 1-4 shows that the prior art cannot simultaneously meet the requirements of product physical and mechanical properties, product odor level and VOC value. Comparative Example 4 is the prior art polypropylene preparation technology, the physical and mechanical properties meet the requirements, but the odor does not; Comparative Example 7 is the prior art low-odor polypropylene preparation technology, the odor meets the requirements, but the physical and mechanical properties deteriorate.

[0102] The comparison between Comparative Example 5 and Example 5 shows that the low-odor polypropylene preparation technology is also applicable to copolymer products; Comparative Example 5 adds a low-activity catalyst and a small molecule nucleating agent, and the added amount is relatively large, so the odor level and VOC value of Comparative Example 5 are higher than those of Example 5.

[0103] By comparing Comparative Example 6 with Examples 1-4, it can be seen that the granulation temperature of low-odor polypropylene needs to be higher than 230° C., otherwise the product performance will be affected.

[0104] In summary, the low-odor polypropylene resin provided by the present invention has low odor and excellent physical properties. The essential technical features of the preparation method of the low-odor polypropylene resin are: (1) a high-activity catalyst; (2) a polymer nucleating agent; (3) the polymer nucleating agent is added during the polymerization stage; and (4) the granulation temperature exceeds 230°C.

[0105] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing polypropylene, characterized in that: The following steps are involved: (1) mixing propylene, alkyl aluminum, a silane compound, a high-activity catalyst and a polymer nucleating agent to perform propylene prepolymerization to obtain a propylene prepolymer; (2) mixing the propylene prepolymer with hydrogen and olefin, and polymerizing propylene under heating and pressure to obtain polypropylene; The olefin is selected from one or more of propylene, ethylene, and α-olefin and contains at least propylene; The high-activity catalyst is selected from one or more of HR, SP-4, CS-2, and BCZ-208; The polymer nucleating agent is selected from one or more of polyvinylcyclopentane, polyvinylcyclohexane, polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene and polystyrene.

2. The preparation method according to claim 1, characterized in that: The temperature of the prepolymerization in step (1) is -10°C to 20°C; The heating temperature in step (2) is 50°C-100°C; The pressure applied in step (2) is 1-5 MPa.

3. The preparation method according to claim 1, characterized in that: The α-olefin is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene.

4. The preparation method according to claim 1, characterized in that: The alkylaluminum is selected from one or more of triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum monochloride, diisobutylaluminum monochloride, dihexylaluminum monochloride and dioctylaluminum monochloride; The silane compound is selected from vinyl triethoxysilane, vinyl trimethoxysilane, methyl triethoxysilane, dimethyl dimethoxysilane, diethyl dimethoxysilane, dipropyl dimethoxysilane, diisopropyl dimethoxysilane, dibutyl dimethoxysilane, diisobutyl dimethoxysilane, di-tert-butyl dimethoxysilane, di-tert-hexyl dimethoxysilane, diphenyl dimethoxysilane, dicyclohexyl dimethoxysilane, dicyclopentyl dimethoxysilane, dimethyl diethoxysilane, diethyl diethoxysilane, dipropyl diethoxysilane, One or more of diisopropyldiethoxysilane, dibutyldiethoxysilane, diisobutyldiethoxysilane, di-tert-butyldiethoxysilane, di-tert-hexyldiethoxysilane, diphenyldiethoxysilane, dicyclohexyldiethoxysilane, dicyclopentyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, cyclopentylmethyldimethoxysilane, cyclopentyltrimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexyltrimethoxysilane, tert-hexyltrimethoxysilane, tert-butyltrimethoxysilane, and tert-hexyltrimethoxysilane.

5. A polypropylene, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 4.

6. The polypropylene according to claim 5, characterized in that The melt index of the polypropylene at 230° C. and a load of 2.16 kg is 5-80 g / 10 min; The polypropylene contains a high-activity catalyst at a concentration of 10-20 ppm; The polypropylene contains a polymer nucleating agent with a concentration of 30-100 ppm.

7. A low-odor polypropylene resin, characterized in that: By weight, Includes the following ingredients: The polypropylene according to claim 5 or 6: 95 to 100 parts by weight; Polyethylene or poly-α-olefin: 0-5 parts by weight; Antioxidant: 0.1-0.3 parts by weight; Halogen absorbent: 0.01-0.1 parts by weight; Other additives: 0-0.3 parts by weight; Wherein, the monomer α-olefin in the poly α-olefin is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene; The antioxidant is composed of a primary antioxidant and an auxiliary antioxidant in a mass ratio of 1:(1-4); The primary antioxidant is selected from one or more of antioxidant 2246, antioxidant 1010, antioxidant 1076, and antioxidant 1330; The auxiliary antioxidant is selected from one or more of antioxidant 168, antioxidant 626, and antioxidant 9228.

8. The low-odor polypropylene resin according to claim 7, characterized in that: The halogen absorbent is selected from one or more of sodium stearate, calcium stearate and zinc stearate.

9. The low-odor polypropylene resin according to claim 7 or 8, characterized in that: The low-odor polypropylene resin has a melt index of 5-80 g / 10 min at 230° C. and a load of 2.16 kg; The low-odor polypropylene resin has an odor grade of 3.5 or less and a volatile organic matter test value of ≤50 μg / g.

10. The method for preparing the low-odor polypropylene resin according to any one of claims 7 to 9, characterized in that: The following steps are involved: The antioxidant, the halogen absorbent, other additives and the polypropylene according to claim 5 or 6 are mixed, extruded through a twin-screw extruder, pelletized, and dried to obtain the low-odor polypropylene resin; The screw temperature of each interval during extrusion of the twin-screw extruder is controlled between 170°C and 235°C, and the highest value of the interval temperature during extrusion must be greater than 230°C.

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