Preparation method for reducing odor grade of thin-wall injection molding polypropylene resin

Abstract

The invention discloses a preparation method for reducing the odor grade of thin-wall injection molding polypropylene resin. The preparation method comprises the following steps: firstly, performing extrusion granulation on a surfactant, a nucleating agent, calcium stearate, white carbon black and polypropylene to prepare master batches; and carrying out melt blending on the obtained master batch, polypropylene, a degradation agent and an antioxidant, and carrying out extrusion granulation to prepare the low-odor and high-melt-index thin-wall injection molding polypropylene resin. Wherein the natural surface active agent is tea saponin. The natural surfactant is added in the preparation of the master batch, so that rich microbubbles can be formed in a polymer extrusion molten state, and the rich microbubbles and volatile organic compounds in a melt are mutually extracted, so that the volatile organic compounds can be extracted by vacuumizing or adsorbed by white carbon black; therefore, the removal of small-molecule odor substances in the polyolefin resin material is realized. The method disclosed by the invention can be used for removing odor of various polyolefin finished product raw materials, can effectively improve the quality of polyolefin finished products, and has relatively high economic value and popularization value.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a preparation method for reducing the odor level of thin-wall injection molding polypropylene resin. Background Art

[0002] Polypropylene thin-wall injection molding has the characteristics of stable melt mass flow rate and high brightness. The melt index can be as high as 50-100g / 10min. Compared with ordinary injection molding products, thin-wall injection molding can significantly reduce processing temperature and improve production efficiency. The raw materials are healthier and safer, and the appearance of the finished product is more transparent. The high performance characteristics of thin-wall injection molding have made it a high value-added feature. Thin-wall injection molding polypropylene is mainly used in food packaging, medical devices, consumer electronics and the automotive industry. With the advancement of technology, the application scope of thin-wall injection molding polypropylene continues to expand, especially in terms of lightweight, environmental protection and cost-effectiveness.

[0003] At present, there are three methods for preparing polypropylene thin-wall injection molding: hydrogen adjustment method, production of high melt index polypropylene using new catalysts and controlled rheology method. Among them, the advantages of controlled rheology method are low production cost, wide adjustable range of melt index, narrow molecular weight distribution and flexible production. This method preferentially breaks the middle part of the macromolecular chain, thereby degrading more macromolecular parts, and the small molecule part does not change much, the content of intermediate components is increased, and the molecular weight distribution is narrowed. However, the controlled rheology method technology requires the addition of peroxide to degrade polypropylene to produce high-fluidity polypropylene products. In the process, small molecular by-products containing more initiator residues and free radical degradation will be formed, resulting in a high content of volatile organic compounds (VOC) in the product, and the odor level generally exceeds the industry hygiene requirements. With the continuous improvement of people's living standards and quality of life and the continuous enhancement of health and environmental awareness, as a polyolefin product closely related to human health, its odor parameters have become a key indicator for judging its product quality. Therefore, it is necessary to provide a low-odor high melt index thin-wall injection molding polypropylene. Summary of the invention

[0004] In order to overcome the problem of strong odor of traditionally produced high melt index thin-wall injection molding polypropylene, the present invention provides a preparation method for reducing the odor level of thin-wall injection molding polypropylene resin, and the obtained polypropylene resin has the characteristics of low odor level and narrow molecular weight distribution.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A low-odor, high-melt index, thin-wall injection-molded polypropylene, the preparation method of which comprises the following steps: 1) The surfactant, nucleating agent, calcium stearate, white carbon black and polypropylene are mixed, melt blended and extruded into granules to obtain a masterbatch; 2) The obtained masterbatch is mixed with polypropylene, a degradation agent and an antioxidant, melt-blended and extruded into granules to obtain a thin-wall injection molding polypropylene resin with low odor and high melt index.

[0006] Furthermore, the surfactant is tea saponin.

[0007] Furthermore, the nucleating agent is one or more of Milliken HPN-900ei, Shanghai Ruxia NA62A, and Guangzhou Chenghe Technology B801Q, preferably Milliken 900ei.

[0008] Furthermore, the polypropylene is homopolypropylene, copolymer polypropylene or a mixture of the two, and its melt index range is 2-8 g / 10 min (melt index is tested by GBT 3682-2000 method B, with a test temperature of 230° C. and a weight of 2.16 kg).

[0009] Furthermore, the degradation agent is a peroxide initiator, which specifically includes one or more of di-tert-butyl peroxide (DTBP), diisopropylbenzene peroxide, 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (Trigonox 301), and benzoyl peroxide, preferably 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane or Trigonox 301.

[0010] Furthermore, the antioxidant is antioxidant 1010, antioxidant 168 or a mixture of the two.

[0011] Furthermore, the weight ratio of the surfactant, the nucleating agent, calcium stearate, white carbon black and the polypropylene used in step 1) is 0.35:0.2:0.25:0.5:98.7.

[0012] Furthermore, in parts by weight, 1-30 parts of masterbatch, 40-80 parts of polypropylene, 0.01-1 parts of degradation agent, and 0.02-0.21 parts of antioxidant are used in step 2).

[0013] Furthermore, the mixing time in steps 1) and 2) is 10 minutes.

[0014] Furthermore, during step 2) mixing, the temperature inside the barrel should not be too high (T≤50°C) to avoid decomposition of the antioxidant (if the temperature is too high, mixing should be performed after it cools down).

[0015] Furthermore, the extrusion granulation in steps 1) and 2) adopts a twin-screw extruder, which is provided with 1 feeding port, 1 deashing port, 1 exhaust port and 12 processing areas; wherein the exhaust port is arranged in the second section close to the die head, the deashing port is arranged in the fourth section close to the die head, and a vacuum pump is arranged at the exhaust port to extract the volatile matter better and faster.

[0016] Furthermore, the aspect ratio of the twin-screw extruder is 44:1, and the processing temperature of each zone is: 80°C in the first section, 210°C in the second section, 230°C in the third to ninth sections, 210°C in the tenth section, and 180°C in the eleventh to twelfth sections; the operating pressure is -900~-980mbar, and the rotation speed is 300~450rpm.

[0017] The advantages of the present invention are: (1) The natural surfactant tea saponin will form a very rich microbubble in the polymer extrusion molten state. These rich microbubbles can be mutually extracted with the volatile organic matter in the melt, so that part of the volatile organic matter is adsorbed by white carbon black, and the other part is extracted by vacuum pumping, thereby achieving the removal of odorous small molecules in the polyolefin resin material.

[0018] (2) The addition of silica not only accelerates the process of mutual extraction between microbubbles and volatile organic compounds in the melt, but also adsorbs a portion of volatile organic compounds, thereby further achieving the removal of odorous small molecules in polyolefin resin materials.

[0019] (3) The high melt index thin-wall injection molding polypropylene prepared by the present invention has a melt index greater than 50g / 10min, a tensile strength ≥35MPa, and an elongation at break ≥25%. The performance is more stable. Compared with the existing high melt index polypropylene, it has lower volatiles and lower odor levels, is more beneficial to human health, and helps to improve people's quality of life.

[0020] (4) The method of the present invention meets environmental protection requirements, is environmentally friendly while effectively reducing the odor of polyolefin resins, and does not introduce new odorous impurities during the entire treatment process. It can be applied to the preparation of polyolefin products such as milk tea cups, high-end lunch boxes, automotive materials and fiber materials that have relatively high requirements for the odor level of polyolefin resins. DETAILED DESCRIPTION

[0021] A low-odor, high-melt index, thin-wall injection-molded polypropylene, the preparation method of which comprises the following steps: 1) By weight, 0.35 parts of tea saponin surfactant, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.7 parts of polypropylene were placed in a premixer and mixed for 10 minutes to make them uniform; 2) feeding the mixture obtained in step 1) through the feeding port of a twin-screw extruder for extrusion granulation, and then traction granulation to obtain masterbatch; 3) Add 1-30 parts of the obtained masterbatch, 40-80 parts of polypropylene, 0.01-1 parts of peroxide initiator, 0.01-0.06 parts of antioxidant 1010, and 0.01-0.15 parts of antioxidant 168 into a premixer and mix for 10 minutes to make it uniform; 4) The mixture obtained in step 3) is fed into the feed port of a twin-screw extruder for extrusion granulation, and then traction granulation is performed to obtain a low-odor and high-melt index thin-wall injection molding polypropylene resin.

[0022] The nucleating agent is one or more of Milliken HPN-900ei, Shanghai Ruxia NA62A, and Guangzhou Chenghe Technology B801Q. The polypropylene is homopolymer polypropylene, copolymer polypropylene, or a mixture of the two, and its melt index range is 2-8g / 10min (melt index is tested by GBT 3682-2000 method B, the test temperature is 230°C, and the weight is 2.16kg).

[0023] The length-to-diameter ratio of the twin-screw extruder used is 44:1, and it includes 12 processing areas. The processing temperature of each section is: 80°C for the first section, 210°C for the second section, 230°C for the third to ninth sections, 210°C for the tenth section, and 180°C for the eleventh to twelfth sections; the operating pressure is -900~-980mbar, and the rotation speed is 300~450rpm.

[0024] The following specific embodiments are combined to make the technical solutions and advantages of the present invention more clearly expressed. Those skilled in the art can make modifications or equivalent substitutions based on their understanding of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be included in the protection scope of the present invention.

[0025] The tea saponin used in the experiment was food grade, with a content of 98%, 80 mesh, and was a pure natural surfactant purchased from Danais Biological Co., Ltd.

[0026] The nucleating agent used in the experiment is Milliken HPN-900ei, the main component of which is carboxylic acid metal salts, purchased from Milliken Co.

[0027] The silica content used in the experiment is 99.8% and the specific surface area is 200m 2 / g, produced by Cabot Corporation, USA.

[0028] The polypropylene powder used in the experiment is H5035 powder produced by Sinochem Quanzhou Petrochemical, and its melt index range is 2~8g / 10min.

[0029] The antioxidants 1010 and 168 used in the experiment were purchased from Beijing Jiyi Chemical Co., Ltd. Example

[0030] 1) According to weight, 0.35 parts of natural surfactant tea saponin, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.7 parts of polypropylene powder were put into a premixer and mixed for 10 minutes; 2) The mixture obtained in step 1) is fed into the feed port of a twin-screw extruder, and extrusion granulation is performed by the extruder. The processing temperature of the extruder is: 80° C. for the first section, 210° C. for the second section, 230° C. for the third section to the ninth section, 210° C. for the tenth section, and 180° C. for the eleventh section to the twelfth section. The masterbatch is obtained by traction granulation.

[0031] 3) Add 78.7 parts of polypropylene powder, 0.8 parts of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, 0.05 parts of antioxidant 1010, 0.1 parts of antioxidant 168, and 20.35 parts of the prepared masterbatch into a premixer and mix for 10 minutes; 4) The mixture obtained in step 3) is fed into the feed port of a twin-screw extruder, and extrusion granulation is performed by the extruder. The processing temperature of the extruder is: 80° C. for the first section, 210° C. for the second section, 230° C. for the third section to the ninth section, 210° C. for the tenth section, and 180° C. for the eleventh section to the twelfth section. After traction and pelletization, a thin-walled injection molding polypropylene material with low odor and high melt index is obtained.

[0032] Comparative Example 1 In step 1), 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 99.05 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0033] Comparative Example 2 In step 1), 0.875 parts of natural surfactant soapberry fruit extract (40 wt%), 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.175 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0034] Comparative Example 3 In step 1), 1 part of natural surfactant cocamidopropyl betaine (35 wt%), 0.2 part of nucleating agent, 0.25 part of calcium stearate, 0.5 part of white carbon black and 98.05 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0035] Comparative Example 4 In step 1), 0.35 parts of natural surfactant saponin extract, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.7 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0036] Comparative Example 5 In step 1), 0.7 parts of surfactant alkyl polyglycoside APG-0810 (50%), 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.35 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0037] Comparative Example 6 In step 1), 0.35 parts of surfactant hexadecyltrimethylammonium bromide, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.7 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0038] Comparative Example 7 In step 1), 0.35 parts of surfactant sodium dodecylbenzene sulfonate, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.7 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0039] Comparative Example 8 In step 1), 0.35 parts of surfactant Tween, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.7 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0040] Comparative Example 9 In step 1), 0.35 parts of sodium carboxymethyl cellulose, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate, 0.5 parts of white carbon black and 98.7 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0041] Comparative Example 10 In step 1), 0.35 parts of natural surfactant tea saponin, 0.2 parts of nucleating agent, 0.25 parts of calcium stearate and 99.2 parts of polypropylene powder were put into a premixer and mixed for 10 minutes. The other steps were the same as in the embodiment.

[0042] The polypropylene materials prepared in the examples and comparative examples were subjected to an odor level test in accordance with VDA 270:2022.

[0043] Table 1 Odor rating results of examples and comparative examples

[0044] As can be seen from Table 1, the masterbatch made with tea saponin as a surfactant has the best effect in reducing the odor level of thin-walled injection molding plastics based on H5035, which can reduce the odor level from 3.5 (Comparative Example 1) to 2.0. In contrast. The masterbatch made with natural surfactants such as soapberry fruit extract, cocamidopropyl betaine or saponin extract also has a certain effect in reducing the odor level of thin-walled injection molding plastics (Comparative Examples 2-4), while the masterbatch made with alkyl polyglycoside APG-0810, hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, Tween, sodium carboxymethyl cellulose, etc. has a general effect in reducing the odor level of thin-walled injection molding plastics (Comparative Examples 5-9). In addition, it can be seen from the comparison between the embodiment and comparative example 10 that the addition of white carbon black can more effectively reduce the odor of thin-walled injection molding plastics, which may be due to the synergistic effect of white carbon black and tea saponin.

[0045] In order to further verify that the method of the present invention does not affect the mechanical properties of polyolefin resin materials while reducing the odor level, the mechanical properties of the polypropylene materials prepared in Example 1 and Comparative Example 1 were measured (tensile strength and elongation at break were measured in accordance with GB / T1040.2-2006). The results are shown in Table 2.

[0046] Table 2 Mechanical properties test results of samples

[0047] As can be seen from Table 2, the mechanical properties of the thin-walled injection molding polyolefin resin prepared by adding tea saponin and the mechanical properties of the thin-walled injection molding polyolefin resin prepared without adding tea saponin do not change significantly, indicating that the method of the present invention can be used to reduce the odor level of polyolefin resin materials without affecting their mechanical properties.

[0048] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for reducing the odor level of thin-wall injection molding polypropylene resin, characterized in that: The steps include: 1) The surfactant, nucleating agent, calcium stearate, white carbon black and polypropylene are melt-blended and then extruded and granulated to obtain a masterbatch; 2) The obtained masterbatch is melt-blended with polypropylene, a degradation agent and an antioxidant and then extruded into granules to obtain a thin-wall injection molding polypropylene resin with low odor and high melt index.

2. The method for reducing the odor level of thin-wall injection molding polypropylene resin according to claim 1, characterized in that: The surfactant is tea saponin.

3. The method for reducing the odor level of thin-wall injection molding polypropylene resin according to claim 1, characterized in that: The polypropylene is homopolymer polypropylene, copolymer polypropylene or a mixture thereof, and has a melt index range of 2-8 g / 10 min.

4. The method for reducing the odor level of thin-wall injection molding polypropylene resin according to claim 1, characterized in that: The degradation agent is a peroxide initiator.

5. The method for reducing the odor level of thin-wall injection molding polypropylene resin according to claim 1, characterized in that: The antioxidant is antioxidant 1010, antioxidant 168 or a mixture of the two.

6. The method for reducing the odor level of thin-wall injection molding polypropylene resin according to claim 1, characterized in that: The weight ratio of the surfactant, nucleating agent, calcium stearate, white carbon black and polypropylene used in step 1) is 0.35:0.2:0.25:0.5:98.

7.

7. The method for reducing the odor level of thin-wall injection molding polypropylene resin according to claim 1, characterized in that: In terms of weight, in step 2), 1-30 parts of masterbatch, 40-80 parts of polypropylene, 0.01-1 parts of degradation agent, and 0.02-0.21 parts of antioxidant are used.

8. The method for reducing the odor level of thin-wall injection molding polypropylene resin according to claim 1, characterized in that: The extrusion granulation adopts a twin-screw extruder with a length-to-diameter ratio of 44:1, including 12 processing areas. The processing temperature of each area is: 80°C in the first area, 210°C in the second area, 230°C in the third to ninth areas, 210°C in the tenth area, and 180°C in the eleventh to twelfth areas; its operating pressure is -900~-980mbar, and the rotation speed is 300~450rpm.

9. A thin-wall injection molding polypropylene resin with low odor and high melt index prepared by the method as claimed in claim 1.

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