Polypropylene composition, polypropylene and process for the preparation thereof, nonwoven fabric and process for the preparation thereof and use

Abstract

This invention relates to the field of polymers, specifically to a polypropylene composition, polypropylene and its preparation method, nonwoven fabric and its preparation method, and applications. The polypropylene composition is characterized by the following composition, based on the total weight of the polypropylene composition: the content of homopolymer polypropylene is 99.4-99.98 wt%, the content of antioxidant is 0.01-0.2 wt%, the content of degrading agent is 0.01-0.1 wt%, the content of acid absorbent is 0-0.1 wt%, and the content of slip agent is 0-0.2 wt%; the ash content of the homopolymer polypropylene is 30-100 ppm, and the odor level is 2-4. The polypropylene prepared from this composition not only has a low odor but also high fluidity and good spinnability. Meltblown fabric prepared from this polypropylene material has high filtration efficiency and hygienic properties.

Description

Technical Field

[0001] This invention relates to the field of polymers, specifically to a polypropylene composition, polypropylene and its preparation method, nonwoven fabric and its preparation method and application. Background Technology

[0002] The meltblown process for manufacturing nonwoven fabrics is a process in which melt is directly spun into a web. Meltblown nonwoven fabrics are often simply referred to as meltblown cloth. Meltblown fiber webs are ultrafine fibers with a large surface area, and therefore are widely used for filtration. Many types of raw materials are used for meltblown nonwoven fabrics; currently, over 90% use polypropylene (PP). This process requires a much higher melt flow rate (MFR) for the PP meltblown special material compared to spunbond nonwoven fabric raw materials, reaching 1000-2000 g / 10 min.

[0003] There are two main methods for preparing meltblown PP raw materials: (1) Direct polymerization of equipment to produce high-flow PP, which controls the molecular weight of PP by controlling the polymerization reaction process. This method is limited by factors such as catalyst and reaction conditions, and the stability of MFR is difficult to control, making it difficult to implement. (2) Chemical degradation to produce high melt flow index PP. Chemical degradation involves reacting PP with chemical degradation agents such as organic peroxides in a screw extruder, causing the PP molecular chains to break and reducing its molecular weight. However, many domestically produced meltblown special materials produced by degradation methods have problems such as strong odor, fluctuating melt flow index, and high ash impurities, resulting in coarse meltblown fabric fibers that are not only hard to the touch but also have low filtration efficiency. Most importantly, they have a strong odor and cannot be used to manufacture children's masks with high quality requirements, failing to meet the performance requirements of high-end protective materials such as masks.

[0004] CN 112679846A discloses a polypropylene meltblown material, its preparation method, and its application. The raw materials for preparing the polypropylene meltblown material include the following components by weight: 70-90 parts polypropylene resin, 10-30 parts thermoplastic elastomer, 0.1-1 parts degrading agent, and 0.1-1 parts antioxidant. The thermoplastic elastomer includes a hydrogenated styrene-butadiene block copolymer. The method yields polypropylene with a molecular weight filtration rate (MFR) of only 10-100 g / min, which cannot meet the requirements of meltblown nonwoven fabric preparation processes. Furthermore, it does not disclose the odor, molecular weight distribution, or other properties of the meltblown material, resulting in meltblown fabric with low filtration efficiency.

[0005] CN109503935A discloses a low-odor, high-transparency, ultra-high-flowability polypropylene, comprising 96%-99.89% polypropylene resin; 0.1%-2% free radical initiator; 0-0.2% lubricant; 0.01%-0.3% antioxidant; and 0-1.5% compounded transparent nucleating agent. The polypropylene resin used has a low melt index, and the amount of additives is high, resulting in high volatile matter, odor, and ash content in the prepared material. Furthermore, no further explanation or description is provided regarding the filtration efficiency and resistance of the meltblown fabric.

[0006] In summary, with the development of protective materials, developing a low-odor, high-flow, and good-spinnable polypropylene material, and meltblown fabric made from this polypropylene material with high filtration efficiency and hygienic performance to meet the needs of health and hygiene materials, has become an urgent technical problem to be solved. Summary of the Invention

[0007] The purpose of this invention is to overcome the aforementioned technical problems in the prior art and to provide a polypropylene composition, polypropylene and its preparation method, nonwoven fabric and its preparation method, and applications. This composition is a polypropylene material with low odor, high fluidity, and good spinnability. Meltblown fabric prepared from this polypropylene material has high filtration efficiency and hygienic properties.

[0008] To achieve the above objectives, a first aspect of the present invention provides a polypropylene composition, characterized in that the polypropylene composition comprises homopolymer polypropylene, an antioxidant, a degradation agent, and optionally an acid absorber and an optional slip agent; wherein,

[0009] Based on the total weight of the polypropylene composition, the content of the homopolymer polypropylene is 99.4-99.98 wt%, the content of the antioxidant is 0.01-0.2 wt%, the content of the degrading agent is 0.01-0.1 wt%, the content of the acid scavenger is 0-0.1 wt%, and the content of the slip agent is 0-0.2 wt%.

[0010] The homopolymer polypropylene has an ash content of 30-100 ppm and an odor level of 2-4.

[0011] A second aspect of the present invention provides a polypropylene obtained from the above-described polypropylene composition.

[0012] A third aspect of the present invention provides a method for preparing polypropylene, characterized in that the method comprises:

[0013] (1) A mixture is prepared by mixing homopolymer polypropylene, antioxidant, acid absorber and slip agent in a polypropylene composition;

[0014] (2) The mixture is mixed with the degradation agent in the polypropylene composition, extruded, granulated and dried to obtain polypropylene;

[0015] Wherein, the polypropylene composition is the polypropylene composition described in the first aspect.

[0016] A fourth aspect of the present invention provides a polypropylene prepared by the above-described preparation method.

[0017] The fifth aspect of the present invention provides a nonwoven fabric prepared from polypropylene as described in the second or fourth aspect.

[0018] A sixth aspect of the present invention provides a method for manufacturing a nonwoven fabric, characterized in that the method comprises:

[0019] Polypropylene is melt-blown spun to obtain the nonwoven fabric;

[0020] The polypropylene mentioned herein is the polypropylene described in the second or fourth aspect.

[0021] A seventh aspect of the present invention provides a method for manufacturing a nonwoven fabric, characterized in that the method comprises:

[0022] (1) A mixture is prepared by mixing homopolymer polypropylene, antioxidant, acid absorber and slip agent in a polypropylene composition;

[0023] (2) The mixture is mixed with the degradation agent in the polypropylene composition, extruded, granulated and dried to obtain polypropylene;

[0024] (3) The polypropylene is melt-blown spun to obtain the nonwoven fabric;

[0025] Wherein, the polypropylene composition is the polypropylene composition described in the first aspect.

[0026] The eighth aspect of the present invention provides a nonwoven fabric obtained by the method described in the sixth or seventh aspect.

[0027] The ninth aspect of the present invention provides the application of the nonwoven fabric described in the fifth or eighth aspect in protective materials.

[0028] Through the above technical solutions, the present invention provides a polypropylene composition, polypropylene and its preparation method, nonwoven fabric and its preparation method and application, which have the following beneficial effects:

[0029] In this invention, homopolymer polypropylene with an ash content of 30-100 ppm and an odor level of 2-4 is selected, preferably metallocene polypropylene. A polypropylene composition is prepared by combining it with other components. The polypropylene made from this polypropylene composition not only has a low odor but also high fluidity and good spinnability. The meltblown fabric made from this polypropylene material has high filtration efficiency and hygienic performance. Attached Figure Description

[0030] Figure 1 To obtain a fiber image of a nonwoven fabric under an electron microscope using Example 1;

[0031] Figure 2 For comparison, the fiber image of the nonwoven fabric obtained under an electron microscope was used in Example 3. Detailed Implementation

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] To achieve the above objectives, a first aspect of the present invention provides a polypropylene composition, characterized in that the polypropylene composition comprises homopolymer polypropylene, an antioxidant, a degradation agent, and optionally an acid absorber and an optional slip agent; wherein,

[0034] Based on the total weight of the polypropylene composition, the content of the homopolymer polypropylene is 99.4-99.98 wt%, the content of the antioxidant is 0.01-0.2 wt%, the content of the degrading agent is 0.01-0.1 wt%, the content of the acid scavenger is 0-0.1 wt%, and the content of the slip agent is 0-0.2 wt%.

[0035] The homopolymer polypropylene has an ash content of 30-100 ppm and an odor level of 2-4.

[0036] In this invention, by selecting homopolymer polypropylene with the above-mentioned specific properties and assembling it into the above-mentioned polypropylene composition, the resulting material has a low melting point, low odor, extremely low ash content, high purity, good hygiene, and good flowability, making it easy to process into meltblown fibers. The resulting meltblown fabric is soft, has high whiteness and fine fibers, high filtration efficiency, and no odor, making it well-suited for use in products with high odor requirements, such as baby masks.

[0037] According to the present invention, based on the total weight of the polypropylene composition, the content of the homopolymer polypropylene is 99.66-99.98 wt%, the content of the antioxidant is 0.05-0.15 wt%, the content of the degrading agent is 0.01-0.05 wt%, the content of the acid scavenger is 0-0.1 wt%, and the content of the slip agent is 0-0.2 wt%.

[0038] According to the present invention, the homopolymer polypropylene has an ash content of 30-90 ppm and an odor level of 2-3.

[0039] According to the present invention, the homopolymer polypropylene has a melt flow rate of 100-1000 g / 10 min at 230°C and 2.16 kg load.

[0040] Preferably, the homopolymer polypropylene has a melt flow rate of 500-1000 g / 10 min at 230°C and 2.16 kg load.

[0041] According to the present invention, the molecular weight distribution index of the homopolymer polypropylene is 2.5-3.5.

[0042] According to the present invention, the melting point of the homopolymer polypropylene is 148-152°C.

[0043] According to the present invention, the weight-average molecular weight of the homopolymer polypropylene is 7 × 10⁻⁶. 4 -16×10 4 .

[0044] Preferably, the homopolymer polypropylene has a weight-average molecular weight of 7 × 10⁻⁶. 4 -10×10 4 .

[0045] According to the present invention, the weight-average molecular weight is 50 × 10⁻⁶, based on the total weight of the homopolymer polypropylene. 4 -100×10 4 The proportion of this component is 0.2-0.5 wt%, and the weight-average molecular weight is less than 1×10⁻⁶. 4 The proportion of this component is 6-15 wt%.

[0046] Preferably, the weight-average molecular weight is 50 × 10⁻⁶, based on the total weight of the homopolymer polypropylene. 4 -100×10 4 The proportion of this component is 0.2-0.3 wt%, and the weight-average molecular weight is less than 1×10⁻⁶. 4 The proportion of this component is 6-10 wt%.

[0047] According to the present invention, the antioxidant is selected from phenolic antioxidants and / or phosphite antioxidants.

[0048] According to the present invention, the phenolic antioxidant is selected from at least one of pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenyl)benzene, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid and octadecyl β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, preferably pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and / or 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenyl)benzene.

[0049] According to the present invention, the phosphite antioxidant is selected from at least one of tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite and bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, preferably tris(2,4-di-tert-butylphenyl) phosphite.

[0050] According to the present invention, the degrading agent is selected from at least one of di-tert-butane peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane, and bis(tert-butylperoxy)dicumyl peroxide.

[0051] Preferably, the degrading agent is selected from 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and / or 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane.

[0052] According to the present invention, the acid absorbent is selected from at least one of sodium stearate, calcium stearate, zinc stearate and hydrotalcite.

[0053] Preferably, the acid absorbent is selected from hydrotalcite.

[0054] According to the present invention, the slip agent is selected from at least one of erucamide, oleamide and stearamide.

[0055] A second aspect of the present invention provides a polypropylene obtained from the above-described polypropylene composition.

[0056] In this invention, the MFR of the polypropylene is 1410-1980 g / 10 min, preferably 1460-1770 g / 10 min; Tm is 149-151 °C, preferably 149.7-150 °C; ash content is 30-50 ppm, preferably 30-40 ppm; volatile matter is 0.02-0.05 wt%, preferably 0.02-0.04 wt%; and odor grade is 2-3, preferably 2-2.5.

[0057] A third aspect of the present invention provides a method for preparing polypropylene, characterized in that the method comprises:

[0058] (1) A mixture is prepared by mixing homopolymer polypropylene, antioxidant, acid absorber and slip agent in a polypropylene composition;

[0059] (2) The mixture is mixed with the degradation agent in the polypropylene composition, extruded, granulated and dried to obtain polypropylene;

[0060] Wherein, the polypropylene composition is the polypropylene composition described in the first aspect.

[0061] During the use of the degradation agent of the present invention, a solution of the degradation agent can be selected according to the needs of use, such as purchasing a commercially available degradation agent solution.

[0062] According to the present invention, the extrusion conditions include: a temperature of 150-255°C; a rotation speed of 20-40 rpm; and a vacuum port negative pressure of 0.01-0.08 MPa.

[0063] Preferably, the extrusion conditions include: a vacuum port negative pressure of 0.03-0.05 MPa.

[0064] According to the present invention, the drying conditions include: a temperature of 80-100°C and a time of 30-120 min.

[0065] In the method for preparing polypropylene according to the present invention, a twin-screw extruder is preferably used. The length-to-diameter ratio of the screw in the twin-screw extruder is preferably 50-60, and the screw is preferably divided into 10-12 segments. Taking 12 segments as an example, the preferred temperatures for each segment are: 150-160℃, 190-210℃, 235-250℃, 235-250℃, 235-250℃, 235-250℃, 180-200℃, 160-180℃, 160-170℃, 160-170℃, and 160-170℃. The extruder is provided with two vacuum ports. Preferably, the vacuum port near the die head has a negative pressure of 0.02-0.03 MPa, and the other is preferably 0.03-0.05 MPa.

[0066] A fourth aspect of the present invention provides a polypropylene prepared by the above-described preparation method.

[0067] The fifth aspect of the present invention provides a nonwoven fabric prepared from polypropylene as described in the second or fourth aspect.

[0068] A sixth aspect of the present invention provides a method for manufacturing a nonwoven fabric, characterized in that the method comprises:

[0069] Polypropylene is melt-blown spun to obtain the nonwoven fabric;

[0070] The polypropylene mentioned herein is the polypropylene described in the second or fourth aspect.

[0071] According to the present invention, the conditions for meltblown spinning include: screw temperature of 180-255°C, hot tank outlet temperature of 250-270°C, spinneret temperature of 245-265°C, and receiving distance of 20-26cm.

[0072] In this invention, during the manufacturing process of nonwoven fabric, 1-5 wt% (based on the total amount of polypropylene) of electret masterbatch (such as: silica inorganic electret material, barium titanate (BaTiO3), zinc oxide (ZnO), aluminum oxide (Al2O3), titanium oxide (TiO2) and silicon nitride (Si3N4) and other oxides are added to polypropylene.

[0073] A seventh aspect of the present invention provides a method for manufacturing a nonwoven fabric, characterized in that the method comprises:

[0074] (1) A mixture is prepared by mixing homopolymer polypropylene, antioxidant, acid absorber and slip agent in a polypropylene composition;

[0075] (2) The mixture is mixed with the degradation agent in the polypropylene composition, extruded, granulated and dried to obtain polypropylene;

[0076] (3) The polypropylene is melt-blown spun to obtain the nonwoven fabric;

[0077] Wherein, the polypropylene composition is the polypropylene composition described in the first aspect.

[0078] In this invention, during the manufacturing process of the nonwoven fabric, polypropylene powder is preferably used for melt-blown spinning. This powder refers to a powder with a bulk density of 0.44-0.46 g / cm³. 3 Powder with an average particle size of 750-850μm and a melt flow rate of 100-1000g / 10min.

[0079] According to the present invention, the extrusion conditions include: a temperature of 150-255°C; a rotation speed of 20-40 rpm; and a vacuum port negative pressure of 0.01-0.08 MPa.

[0080] Preferably, the extrusion conditions include: a vacuum port negative pressure of 0.03-0.05 MPa.

[0081] According to the present invention, the drying conditions include: a temperature of 80-100°C and a time of 30-120 min.

[0082] According to the present invention, the conditions for meltblown spinning include: screw temperature of 180-255°C, hot tank outlet temperature of 250-270°C, spinneret temperature of 245-265°C, and receiving distance of 20-26cm.

[0083] The eighth aspect of the present invention provides a nonwoven fabric obtained by the method described in the sixth or seventh aspect.

[0084] The ninth aspect of the present invention provides the application of the nonwoven fabric described in the fifth or eighth aspect in protective materials.

[0085] Preferably, the nonwoven fabric is used in face masks.

[0086] The present invention will be described in detail below through embodiments.

[0087] In the following embodiments, unless otherwise specified, all raw materials used are commercially available.

[0088] (1) Polypropylene powder:

[0089] (a1) is a metallocene polypropylene powder, purchased from Beijing Yanshan Petrochemical, grade: MJ1T80, MFR is 800 g / 10 min, molecular weight distribution is 3, and weight average molecular weight is 8.8 × 10⁻⁶. 4 Based on the total weight of the homopolymer polypropylene, the weight-average molecular weight is 50 × 10⁻⁶. 4 -100×10 4 The proportion of this component is 0.2 wt%, and the weight-average molecular weight is less than 1 × 10⁻⁶. 4 It has a component content of 8 wt%, a melting point of 150℃, an ash content of 30 ppm, and an odor level of 2.

[0090] (a2) is a metallocene polypropylene powder, purchased from Beijing Yanshan Petrochemical, grade: MJ1T50, MFR is 500 g / 10 min, molecular weight distribution is 2.8, and weight average molecular weight is 10 × 10⁻⁶. 4 Based on the total weight of the homopolymer polypropylene, the weight-average molecular weight is 50 × 10⁻⁶. 4 -100×10 4 The proportion of this component is 0.3 wt%, and the weight-average molecular weight is less than 1 × 10⁻⁶. 4 It has a component content of 7 wt%, a melting point of 151℃, an ash content of 30 ppm, and an odor level of 2.

[0091] (a3) is a metallocene polypropylene powder, purchased from Beijing Yanshan Petrochemical, grade: MJ1H10, MFR is 1000 g / 10 min, molecular weight distribution is 3.2, and weight average molecular weight is 7 × 10⁻⁶. 4 Based on the total weight of the homopolymer polypropylene, the weight-average molecular weight is 50 × 10⁻⁶.4 -100×10 4 The proportion of this component is 0.2 wt%, and the weight-average molecular weight is less than 1 × 10⁻⁶. 4 It has a component content of 10 wt%, a melting point of 150℃, an ash content of 30 ppm, and an odor level of 2.

[0092] (a4) is a metallocene polypropylene powder, purchased from Beijing Yanshan Petrochemical, grade: MJ1T30, MFR is 300 g / 10 min, molecular weight distribution is 2.8, and weight average molecular weight is 13 × 10⁻⁶. 4 Based on the total weight of the homopolymer polypropylene, the weight-average molecular weight is 50 × 10⁻⁶. 4 -100×10 4 The proportion of this component is 0.3 wt%, and the weight-average molecular weight is less than 1 × 10⁻⁶. 4 It has a component content of 6 wt%, a melting point of 151℃, an ash content of 40 ppm, and an odor level of 2.

[0093] (a5) is polypropylene granules, purchased from Shanghai SECCO, grade: S2040, MFR: 35g / 10min, molecular weight distribution: 4, weight average molecular weight: 21×10⁻⁶. 4 Based on the total weight of the homopolymer polypropylene, the weight-average molecular weight is 50 × 10⁻⁶. 4 -100×10 4 The proportion of this component is 8 wt%, and the weight-average molecular weight is less than 1 × 10⁻⁶. 4 It has a content of 3 wt%, a melting point of 163℃, an ash content of 200 ppm, and an odor rating of 2.5.

[0094] (2) Copolymer polypropylene (b1): Purchased from Yanshan Petrochemical, grade 4220, with an MFR of 0.27 g / 10 min, a molecular weight distribution of 4.5, and a weight-average molecular weight of 80 × 10⁻⁶. 4 The weight-average molecular weight is 50 × 10⁻⁶. 4 -100×10 4 The proportion of this component is 45 wt%, and the weight-average molecular weight is less than 1 × 10⁻⁶. 4 It has a component content of 0.5 wt%, a melting point of 145℃, an ash content of 300 ppm, and an odor rating of 2.5.

[0095] In the following embodiments, the product performance testing is conducted using the following methods:

[0096] (1) Melt mass flow rate (MFR): Tested according to the method described in GB / T 3682.1-2018, at a temperature of 230℃ and a load of 2.16kg.

[0097] (2) Tm: Differential scanning calorimetry (DSC) was used to test the sample according to the method described in GB / T 19466.3-2004. Approximately 5 mg of the sample was heated to 200 °C at an initial temperature of 25 °C under N2 protection, and held at that temperature for 10 min to eliminate thermal history. The sample was then cooled to 50 °C at a cooling rate of 10 °C / min to obtain the crystallization temperature (TC) and heat of crystallization (ΔHC). The sample was then heated to 200 °C at a heating rate of 10 °C / min to obtain the melting point (Tm) and heat of fusion (ΔHm).

[0098] (3) Ash content: Tested according to the method described in GB / T 9345.1-2008.

[0099] (4) Volatile matter: Tested according to the method described in GB / T 2914-2008.

[0100] (5) Odor Rating: Add 10g ± 1g of the sample to a 1L glass container (equipped with an odorless seal and lid) and dry it in an oven at 40℃ ± 2℃ for 120min ± 10min. Remove the glass container from the oven and place it in a room free of any interfering odors to cool to room temperature. In a windless, odorless, and noise-free testing environment, open the lid of the glass container and have a team of five trained odor assessment personnel sequentially score the odor change, with each person smelling the odor for no more than 2 minutes. The odor rating should conform to the odor assessment form, and a half-level rating (e.g., 3.5) between two levels is permitted. If the five ratings differ by two levels or more, the test should be repeated.

[0101] Odor Evaluation Form

[0102] 1 Odorless 2 It has an odor, but no unpleasant odor. 3 It has a distinct odor, but no unpleasant odor. 4 It has a disturbing odor 5 It has a strong, interfering odor. 6 It has an unbearable odor.

[0103] (6) Fiber fineness: Tested according to the method described in GB / T 36422-2018.

[0104] (7) Filtration efficiency and gas resistance: Tested according to the method described in GB / T 32610-2016, with a ventilation rate of 32L / min.

[0105] (8) Molecular weight and distribution: The test was conducted in accordance with the method described in GB / T 36214.4-2018, Part 4, High Temperature Method, using o-dichlorobenzene as the solvent, and the sample dissolution and filtration temperature was 150℃.

[0106] Example 1

[0107] (1) Mix 10 kg of polypropylene (a1) powder with 5 g of antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] and 10 g of antioxidant tris(2,4-di-tert-butylphenyl) phosphite evenly to obtain a mixture.

[0108] (2) The mixture is added to the feeder of the twin-screw extruder. The material enters the twin screw through the feeder. 3g of the degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane liquid (concentration of 95wt%) is introduced from the liquid initiator injection port. It is melted by the screw and mixed evenly with the mixture. After extrusion, granulation and drying, polypropylene is obtained.

[0109] During processing, the screw's length-to-diameter ratio was 60, and the temperatures of each section were: 150℃, 195℃, 240℃, 240℃, 240℃, 240℃, 240℃, 180℃, 160℃, 170℃, 170℃, and 170℃. The rotation speed was 30 rpm. Vacuum port 1, located near the die head, had a negative pressure of 0.02 MPa; another vacuum port, number 2, had a negative pressure of 0.05 MPa. The drying conditions included a temperature of 90℃ and a time of 90 minutes. The performance test results of the obtained polypropylene are shown in Table 1.

[0110] Example 2

[0111] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0112] The amount of the degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane added is 5g.

[0113] The performance test results of the prepared polypropylene are shown in Table 1.

[0114] Example 3

[0115] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0116] The degradation agent used is 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane, and the addition amount is 5g.

[0117] The performance test results of the prepared polypropylene are shown in Table 1.

[0118] Example 4

[0119] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0120] Polypropylene (a1) was replaced with polypropylene (a2), and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane was selected as the degradation agent, with an addition amount of 7g.

[0121] The performance test results of the prepared polypropylene are shown in Table 1.

[0122] Example 5

[0123] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0124] Polypropylene (a1) was replaced with polypropylene (a3), and the amount of degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane added was 1.5g.

[0125] The performance test results of the prepared polypropylene are shown in Table 1.

[0126] Example 6

[0127] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0128] The amount of the degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane added is 6.5g.

[0129] The performance test results of the prepared polypropylene are shown in Table 1.

[0130] Example 7

[0131] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0132] Add 14g of slip agent erucamide and 5g of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane to the mixture.

[0133] The performance test results of the prepared polypropylene are shown in Table 1.

[0134] Example 8

[0135] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0136] Add 3g of hydrotalcite to the mixture.

[0137] The performance test results of the prepared polypropylene are shown in Table 1.

[0138] Example 9

[0139] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0140] Replace polypropylene (a1) with polypropylene (a4), and add 10g of the degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0141] The performance test results of the prepared polypropylene are shown in Table 1.

[0142] Comparative Example 1

[0143] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0144] Add 15g of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane as a degradation agent to the mixture.

[0145] The performance test results of the prepared polypropylene are shown in Table 1.

[0146] Comparative Example 2

[0147] Polypropylene was prepared using the same raw material ratio and preparation method as in Example 1, except that the antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], the antioxidant tris(2,4-di-tert-butylphenyl) phosphite, and the degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane were not added.

[0148] Comparative Example 3

[0149] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0150] Replace polypropylene (a1) with polypropylene (a5), and add 40g of the degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0151] The performance test results of the prepared polypropylene are shown in Table 1.

[0152] Comparative Example 4

[0153] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0154] The polypropylene (a1) was replaced with copolymer polypropylene (b1), and the amount of degradation agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane added was 95g.

[0155] The performance test results of the prepared polypropylene are shown in Table 1.

[0156] Comparative Example 5

[0157] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0158] The homopolymer polypropylene content is 95wt%, and 5wt% talc filler is added. The prepared polypropylene cannot be spun normally, the spinneret holes are severely blocked, and it cannot be spun into nonwoven fabric.

[0159] The performance test results of the prepared polypropylene are shown in Table 1.

[0160] Comparative Example 6

[0161] Polypropylene was prepared using the same raw material ratios and preparation methods as in Example 1, except that...

[0162] The content of the degradation agent is 0.2 wt%. The prepared polypropylene cannot be spun continuously, resulting in severe filament breakage and making it impossible to spin into nonwoven fabric.

[0163] The performance test results of the prepared polypropylene are shown in Table 1.

[0164] Application examples and comparative application examples

[0165] The polypropylene obtained in Examples 1-9 and Comparative Examples 1-6 was spun into nonwoven fabrics through the following steps:

[0166] Polypropylene was added to a feeder, along with 2 wt% titanium dioxide (TiO2), to prepare a 25 g nonwoven fabric. The screw temperatures were 180℃, 190℃, 235℃, 245℃, 255℃, and 255℃; the hot tank outlet temperature was 265℃; the spinneret temperatures were 265℃, 265℃, 265℃, 265℃, 255℃, 255℃, 255℃, 245℃, 245℃, 245℃, 255℃, 255℃, 255℃, 265℃, 265℃, and 265℃; the receiving distance was 22 cm; the main screw speed was 24 Hz; the suction fan speed was 1250 rpm; and the electret voltage was 55 kV.

[0167] The performance test results of the obtained nonwoven fabric are shown in Table 2.

[0168] Table 1

[0169] Example 1 1460 150 30 0.03 2.3 Example 2 1770 149.8 30 0.04 2.5 Example 3 1690 150 30 0.03 2.3 Example 4 1410 151 40 0.04 2.5 Example 5 1550 149 30 0.02 2 Example 6 1980 149.1 30 0.05 3 Example 7 1770 149.7 30 0.04 2.5 Example 8 1480 149.8 50 0.03 2.5 Example 9 1670 151 50 0.04 3.2 Comparative Example 1 2570 150.1 30 0.1 4 Comparative Example 2 850 150 30 0.03 2 Comparative Example 3 1430 164 200 0.2 4.5 Comparative Example 4 1400 145 300 0.3 5 Comparative Example 5 1260 152 50000 0.03 3.5 Comparative Example 6 3850 150.5 30 0.2 4.5

[0170] Table 2

[0171]

[0172]

[0173] The table shows that polypropylene has high processing fluidity while having lower odor and volatile matter content; its ash content and melting point are also lower, making it less prone to clogging the spinneret orifices and extending the spinneret's service life. The prepared fibers, after stretching, have a finer fiber fineness, resulting in a very soft fabric surface with high whiteness, low odor, high filtration efficiency, and low gas resistance, making it more suitable for the medical nonwoven fabric field where high odor levels and filtration efficiency are required.

[0174] from Figure 1 As can be seen from the results, the nonwoven fabric prepared in Application Example 1 has finer fibers, fewer filaments, and more uniform fibers. The filtration efficiency of this nonwoven fabric can reach 99.9%, and the gas resistance is low at only 26 Pa. In contrast, the nonwoven fabric prepared in Application Example 3 has coarser fibers, more filaments, and uneven fiber distribution. The filtration efficiency of this nonwoven fabric is only 95%, and the gas resistance is as high as 35 Pa.

[0175] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polypropylene composition, characterized in that, The polypropylene composition comprises homopolymer polypropylene, antioxidant, degradation agent, and optionally acid absorber and optional slip agent; wherein, Based on the total weight of the polypropylene composition, the content of the homopolymer polypropylene is 99.4-99.98 wt%, the content of the antioxidant is 0.01-0.2 wt%, the content of the degrading agent is 0.01-0.1 wt%, the content of the acid scavenger is 0-0.1 wt%, and the content of the slip agent is 0-0.2 wt%. The homopolymer polypropylene has an ash content of 30-100 ppm, an odor level of 2-4, a melt flow rate of 500-1000 g / 10 min at 230℃ and 2.16 kg load, a molecular weight distribution index of 2.5-3.5, and a weight-average molecular weight of 7 × 10⁻⁶. 4 -10×10 4 Based on the total weight of the homopolymer polypropylene, the weight-average molecular weight is 50 × 10⁻⁶. 4 -100×10 4 The proportion of this component is 0.2-0.5 wt%, and the weight-average molecular weight is less than 1×10⁻⁶. 4 The proportion of this component is 6-15 wt%.

2. The polypropylene composition according to claim 1, wherein, Based on the total weight of the polypropylene composition, the content of the homopolymer polypropylene is 99.66-99.98 wt%, the content of the antioxidant is 0.05-0.15 wt%, the content of the degrading agent is 0.01-0.05 wt%, the content of the acid scavenger is 0-0.1 wt%, and the content of the slip agent is 0-0.2 wt%. And / or, the homopolymer polypropylene has an ash content of 30-90 ppm and an odor level of 2-3.

3. The polypropylene composition according to claim 1, wherein, The homopolymer polypropylene has a melting point of 148-152℃.

4. The polypropylene composition according to claim 1, wherein, Based on the total weight of the homopolymer polypropylene, the weight-average molecular weight is 50 × 10⁻⁶. 4 -100×10 4 The proportion of this component is 0.2-0.3 wt%, and the weight-average molecular weight is less than 1×10⁻⁶. 4 The proportion of this component is 6-10 wt%.

5. The polypropylene composition according to claim 1, wherein, The antioxidant is selected from phenolic antioxidants and / or phosphite antioxidants.

6. The polypropylene composition according to claim 5, wherein, The phenolic antioxidant is selected from at least one of pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenylmethyl)benzene, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid and β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester; And / or, the phosphite antioxidant is selected from at least one of tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, and bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite.

7. The polypropylene composition according to claim 6, wherein, The phenolic antioxidant is selected from pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and / or 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenyl)benzene; And / or, the phosphite antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

8. The polypropylene composition according to claim 1, wherein, The degrading agent is selected from at least one of di-tert-butane peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane and bis(tert-butylperoxy)dicumyl peroxide; And / or, the acid absorbent is selected from at least one of sodium stearate, calcium stearate, zinc stearate and hydrotalcite; And / or, the slip agent is selected from at least one of erucamide, oleamide and stearamide.

9. The polypropylene composition according to claim 8, wherein, The degrading agent is selected from 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and / or 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane; And / or, the acid absorbent is hydrotalcite.

10. A polypropylene prepared from the polypropylene composition according to any one of claims 1-9.

11. A method for preparing polypropylene, characterized in that, The method includes: (1) The homopolymer polypropylene, antioxidant, acid absorber and slip agent in the polypropylene composition are mixed to obtain a compound; (2) The mixture is mixed with the degradation agent in the polypropylene composition, extruded, granulated, and dried to obtain polypropylene; The polypropylene composition is the polypropylene composition according to any one of claims 1-9.

12. The preparation method according to claim 11, wherein, The extrusion conditions include: temperature of 150-255℃; rotation speed of 20-40 rpm; and vacuum port negative pressure of 0.01-0.08 MPa. And / or, the drying conditions include: a temperature of 80-100°C; and a time of 30-120 min.

13. The preparation method according to claim 12, wherein, The extrusion conditions include: a vacuum port negative pressure of 0.03-0.05 MPa.

14. A polypropylene prepared by the preparation method according to any one of claims 11-13.

15. A nonwoven fabric made of polypropylene as described in claim 10 or claim 14.

16. A method for preparing a nonwoven fabric, characterized in that, The method includes: Polypropylene is melt-blown spun to obtain the nonwoven fabric; The polypropylene mentioned herein is the polypropylene as described in claim 10 or claim 14.

17. The preparation method according to claim 16, wherein, The conditions for meltblown spinning include: screw temperature of 180-255℃, hot tank outlet temperature of 250-270℃, spinneret temperature of 245-265℃, and receiving distance of 20-26cm.

18. A method for preparing a nonwoven fabric, characterized in that, The method includes: (1) The homopolymer polypropylene, antioxidant, acid absorber and slip agent in the polypropylene composition are mixed to obtain a compound; (2) The mixture is mixed with the degradation agent in the polypropylene composition, extruded, granulated, and dried to obtain polypropylene; (3) The polypropylene is melt-blown spun to obtain the nonwoven fabric; The polypropylene composition is the polypropylene composition according to any one of claims 1-9.

19. The preparation method according to claim 18, wherein, The extrusion conditions include: temperature of 150-255℃; rotation speed of 20-40 rpm; and vacuum port negative pressure of 0.01-0.08 MPa. And / or, the drying conditions include: a temperature of 80-100°C; and a time of 30-120 min; And / or, the conditions for meltblown spinning include: screw temperature of 180-255℃, hot tank outlet temperature of 250-270℃, spinneret temperature of 245-265℃, and receiving distance of 20-26cm.

20. The preparation method according to claim 19, wherein, The extrusion conditions include: a vacuum port negative pressure of 0.03-0.05 MPa.

21. A nonwoven fabric prepared by the preparation method according to any one of claims 16-20.

22. The use of the nonwoven fabric as described in claim 15 or 21 in protective materials.

23. The application according to claim 22, wherein, The application of nonwoven fabrics in face masks.

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