Polypropylene thin-wall injection molding material and thin-wall injection molding product made therefrom

Abstract

The present invention provides a polypropylene thin-wall injection molding compound comprising a polypropylene resin and a sorbitol compound. The polypropylene resin is homopolypropylene or polypropylene containing 2% by weight or less of butene. By adding the sorbitol compound to the polypropylene resin, the haze of the polypropylene thin-wall injection molding compound can be reduced while maintaining a low content of the sorbitol compound under high-temperature thin-wall injection molding conditions, resulting in thin-wall injection molding products having improved mechanical, thermal, and optical properties. The present invention also provides polypropylene thin-wall injection molding products produced at high temperatures from the polypropylene thin-wall injection molding compound.

Description

Technical Field

[0001] The present invention relates to a polypropylene thin-wall injection molding material and also relates to a thin-wall injection molding product prepared from the thin-wall injection molding material. Background Art

[0002] As one of the five most widely produced and consumed general-purpose plastics, polypropylene boasts the advantages of being non-toxic, inexpensive, and easy to process. Polypropylene injection molding has broad application prospects in food packaging, medicine and hygiene, daily necessities, electronics, and other fields. It can be used to produce packaging products such as food storage boxes, medicine boxes, and takeout containers, as well as plastic containers such as storage boxes and lockers.

[0003] In recent years, packaging products, plastic containers, mechanical devices, high-precision devices, etc. have gradually developed towards thin-walled or even ultra-thin-walled products. As one of the most widely used varieties of polypropylene, polypropylene thin-wall injection molding products are mainly disposable fast food boxes, bowls, plates and plastic water cups, aviation cups and other food packaging products. These products have the characteristics of heat resistance, non-water absorption, corrosion resistance, mildew resistance, long service life and beautiful appearance.

[0004] In the field of thin-wall injection molding, thin-wall generally refers to products with a wall thickness of ≤1mm. Compared with large-scale injection molding and precision injection molding, thin-wall injection molding has different requirements for injection speed, material fluidity, and material crystallization speed.

[0005] With the further demand for production efficiency in the thin-wall injection molding field, polypropylene thin-wall injection molding is required to be quickly processed and injection molded at high temperatures. However, the polypropylene thin-wall injection molding materials in the existing technology are mainly used at injection molding processing temperatures below 250°C, which can no longer meet the requirements of resisting mechanical shear and thermal oxidation degradation during processing and injection molding at high temperatures. As a result, thin-wall injection molded products have the defect of high haze, making it difficult to obtain thin-wall injection molded products with excellent optical properties.

[0006] The existing technology for producing polypropylene thin-walled injection molding compounds uses calcium hexahydrophthalate as an additive. Since this additive decomposes at high temperatures, it causes a loss of haze in thin-walled injection molding products, making it difficult to produce products with excellent optical properties. In addition, if you want to maintain good haze, you need to increase the amount of additive added, which increases costs. Summary of the Invention

[0007] In response to the aforementioned shortcomings of the prior art, one objective of the present invention is to provide a low-haze, highly transparent thin-walled polypropylene injection molding compound. The inventors of the present invention have discovered that existing thin-walled injection molding compounds struggle to produce thin-walled injection molded products with a haze level that meets application requirements at high temperatures. The present invention is unique in that it utilizes a specific polypropylene resin material and a specific sorbitol compound to maintain excellent optical properties even at high temperatures, particularly above 230°C, such as injection molding temperatures between 230°C and 380°C, particularly between 280°C and 380°C.

[0008] The first object of the present invention is to provide a polypropylene thin-wall injection molding compound, comprising a polypropylene resin and a sorbitol compound, wherein the polypropylene resin is homopolymerized polypropylene and / or polypropylene containing ≤2 wt% of butene.

[0009] Preferably, the invention relates to a thin-walled injection molding material suitable for preparing injection molding products with a wall thickness of 0.2 mm to 1 mm, and more preferably relates to a thin-walled injection molding material suitable for preparing injection molding products with a wall thickness of 0.3 mm to 0.5 mm.

[0010] Preferably, the isotacticity of the homopolypropylene is greater than or equal to 96%.

[0011] Preferably, the polypropylene resin has a melt index (MFR) greater than 60 g / 10 min (measured under test conditions of 230° C. and a test load of 2.16 kg). During thin-wall injection molding, to ensure complete cavity filling, the polypropylene resin filling rate must be greater than the resin cooling rate in the injection channel. Under high-temperature injection molding conditions for thin-wall injection molding, a polypropylene resin with good fluidity is required. The inventors have discovered that selecting a melt index (MFR) greater than 60 g / 10 min can meet the requirement for good fluidity of polypropylene thin-wall injection molding materials at high temperatures.

[0012] Preferably, the weight average molecular weight of the polypropylene resin is 1.30×10 5 -1.6×10 5 , the molecular weight distribution range is 6.5-9.0. The inventors found that under high temperature, high shear thin-wall injection molding conditions, in order to ensure complete mold filling and fast mold filling speed, it is necessary to select a polypropylene resin with a low weight average molecular weight and a wide molecular weight distribution. However, this will also lead to a decrease in the mechanical properties of polypropylene thin-wall injection molding materials. Therefore, it is particularly important to select a polypropylene resin with a suitable weight average molecular weight and molecular weight distribution. The inventors found that the weight average molecular weight of the polypropylene resin is 1.30×10 5 -1.6×10 5 The molecular weight distribution range is 6.5-9.0, which can meet the processing performance and mechanical properties of thin-wall injection molding products.

[0013] In existing technologies, some raw material manufacturers use macro-modification of polyethylene and polypropylene to improve the toughness of homopolypropylene, but this still fails to address the shortcomings of long-term heat stability. Other raw materials use copolymerization of propylene monomer and a small amount of ethylene (1-4%). The ethylene monomer is randomly distributed within the long propylene chain, reducing the polymer's crystallinity and melting point, while improving the material's impact resistance, heat resistance, and aging resistance. However, as a thin-walled injection molding compound, its overall performance still needs to be improved, especially in optical properties such as haze.

[0014] Preferably, the polypropylene is selected from polypropylene containing 0.5-2 wt% butene; more preferably, a polypropylene resin containing 0.7-1.5 wt% butene. The inventors have discovered that polypropylene containing a certain amount of butene segments, combined with a sorbitol compound, can be injection molded at high temperatures to produce thin-walled injection molding compounds with satisfactory optical and mechanical properties. This may be because the specific butene segment content in the polypropylene resin reduces crystallinity while improving the dispersion of the sorbitol compound in the polypropylene resin matrix, resulting in excellent optical properties for the resulting thin-walled injection molding compound.

[0015] Furthermore, the chemical formula of the sorbitol compound is:

[0016]

[0017] Wherein, R1, R2, and R3 are independently selected from H, C1-C6 alkyl, C2-C6 alkenyl, C1-C6 alkoxy, hydroxyl or halogen atom.

[0018] Examples of the C1-C6 alkyl group include, but are not limited to, methyl, ethyl, propyl, and butyl; examples of the C2-C6 alkenyl group include, but are not limited to, vinyl, allyl, 1-butenyl, and 2-butenyl; examples of the C1-C6 alkoxy group include, but are not limited to, methoxy, ethoxy, propoxy, and butoxy, and the halogen atom is selected from F, Cl, Br, or I.

[0019] The sorbitol compound is an α-crystalline compound, and the sorbitol compound is determined using GB / T 19077-2016, and has the following characteristics:

[0020] -Specific surface area greater than or equal to 1.5m 2 / g;

[0021] -Surface area average particle size greater than or equal to 1.3 μm;

[0022] The volume average particle size is greater than or equal to 3.4 μm.

[0023] The inventors have discovered that by selecting a sorbitol compound with the aforementioned specific specific surface area, surface area average particle size, and volume average particle size, multiple fine crystal nuclei can be formed within a polypropylene resin matrix, promoting crystallization and refining the spherulite size of the polypropylene resin. This, in turn, reduces the haze of the polypropylene thin-wall injection molding compound and improves its optical properties. Furthermore, the sorbitol compound with these specific parameters can be well dispersed within the specifically selected polypropylene resin of the present invention, further improving the optical properties of the polypropylene thin-wall injection molding compound.

[0024] Furthermore, the sorbitol compound is selected from one or more of 1,3,2,4-bis-O-(3,4-dimethylbenzylidene)-D-sorbitol, 1,3,2,4-di-p-methylbenzylidene sorbitol, 1,3,2,4-di-p-chlorobenzylidene sorbitol and 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonanol.

[0025] The concentration of the sorbitol compound in the polypropylene resin is 400-1500 ppm, preferably 600-1500 ppm. The polypropylene resin of the present invention contains a small amount of butene, and a relatively small amount of sorbitol compound can be used to obtain a thin-walled injection molded product with excellent optical properties.

[0026] In a preferred embodiment of the present invention, the polypropylene thin-wall injection molding material further comprises 2,5-diaminopyrimidine-4-carboxylate. More preferably, the mass ratio of the sorbitol compound to the 2,5-diaminopyrimidine-4-carboxylate is 5-10:1-2, and the 2,5-diaminopyrimidine-4-carboxylate is selected from its sodium salt and / or potassium salt.

[0027] Polypropylene is a semi-crystalline polymer with incomplete crystallization. Especially in the rapid injection molding process at high temperature, due to the fast molding speed, the macromolecular segments do not have enough time to adjust their structure, resulting in incomplete crystallization. The refractive index of the crystalline region and the non-crystalline region is different, which will increase the haze and reduce the transmittance, affecting the optical properties of the product.

[0028] The inventors unexpectedly discovered that by adding a certain amount of 2,5-diaminopyrimidine-4-carboxylate to a polypropylene thin-wall injection molding compound, the polypropylene thin-wall injection molding compound of the present invention, when injection molded at a high temperature of 280-380°C, with a relatively low amount of sorbitol compound added, completely crystallizes the obtained thin-wall injection molding compound, and the optical properties not only do not decline, but are actually improved to a certain extent.

[0029] In a more preferred technical solution of the present invention, the sorbitol compound and 2,5-diaminopyrimidine-4-carboxylate are compounded in a mass ratio of 4-6:1-1.5, and the obtained polypropylene resin has the best comprehensive performance of the thin-wall injection molding compound.

[0030] Furthermore, the thin-wall injection molding compound may further include one or more additives such as an acid absorber, an antioxidant, an antistatic agent, a colorant, a lubricant or a dispersant, etc., which are added according to specific needs.

[0031] The acid absorber is selected from one or more of sodium myristate, sodium laurate, sodium stearate, potassium myristate, potassium laurate, potassium stearate, zinc myristate, zinc stearate, calcium myristate, calcium stearate, calcium laurate, and zinc laurate.

[0032] The antioxidant is selected from one or more of antioxidant 1010, antioxidant 168, antioxidant 1790, antioxidant 626, antioxidant 3114, antioxidant DBHA, and antioxidant DBHB. Preferably, antioxidant 168 and antioxidant 1010 are compounded in a mass ratio of 1-2:1-2.

[0033] The lubricant is selected from one or more of ethylene bisstearamide (EBS), stearamide, oleamide, erucamide, calcium stearate, zinc stearate, high boiling point paraffin, microcrystalline paraffin, fatty acid, PE wax and the like.

[0034] The antistatic agent is selected from one or more of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate, stearyl trimethyl quaternary ammonium hydrochloride, stearamidopropyl dimethyl hydroxyethyl quaternary ammonium nitrate, potassium p-nonyl diphenyl ether sulfonate, sodium p-nonyl phenoxy propane sulfonate, dibutyl oleamide, hexamethylphosphoric triamide, etc.

[0035] A second object of the present invention is to provide a method for preparing the above-mentioned thin-walled injection molding compound, comprising uniformly blending a polypropylene resin and a sorbitol compound to obtain a blend. Optionally, one or more additives such as an acid absorber, an antioxidant, an antistatic agent, a colorant, a lubricant, or a dispersant may be added to the blend. The above-mentioned blend is then extruded and granulated through an extruder to obtain a thin-walled injection molding compound.

[0036] The process of extrusion granulation is well known in the art, and granulation is performed according to the "SHJ-20 Twin-Screw Extruder Operating Procedures" at a granulation temperature of 190-220°C.

[0037] The third object of the present invention is to provide a thin-walled injection molded product obtained by processing the thin-walled injection molding material at a processing temperature of 230-380°C, in particular a thin-walled injection molded product obtained at a processing temperature of 280-380°C.

[0038] A fourth object of the present invention is to provide a use of a sorbitol compound for reducing the haze value of a polypropylene thin-wall injection molding compound when injection molded at 230-380°C, particularly for reducing the haze value of a polypropylene thin-wall injection molding compound when injection molded at 280-380°C, wherein the polypropylene thin-wall injection molding compound is as described above.

[0039] The present invention also provides thin-walled injection molding products, particularly thin-walled injection molding products with a wall thickness of ≤1 mm (preferably 0.3 mm-0.5 mm). The polypropylene thin-walled injection molding product provided by the present invention has a haze value according to GB / T2410 of 50% or less, preferably 45% or less, more preferably 40% or less, and most preferably 35% or less, and further preferably 30% or less, 25% or less, or 20% or less, when injection molding a 1 mm sample at 230-280°C; and a haze value according to GB / T2410 of 50% or less, preferably 45% or less, more preferably 40% or less, and most preferably 35% or less, and further preferably 30% or less, 25% or less, or 20% or less, when injection molding a 1 mm sample or an injection molding product with a thickness of <1 mm (preferably 0.3 mm-0.5 mm) at 280-380°C.

[0040] The thin-walled injection molded articles of the present invention can be produced by known processes such as injection molding, extrusion blow molding, and injection stretch blow molding. These molded articles can be formed into desired shapes and used in resin molded articles such as automotive parts, mechanical parts, and food packaging. Specifically, the thin-walled injection molded articles are useful in the following applications: Examples of thin-walled injection molded articles include food containers, disposable lunch boxes, crates, buckets, household items, furniture, drinking cups, lids and seals, and other injection molded articles.

[0041] The thin-wall injection molding material of the present invention selects homopolymer polypropylene with a specific melt index, weight-average molecular weight and molecular weight distribution and an isotacticity greater than or equal to 96%, and particularly selects a polypropylene resin containing a certain amount of butene as a raw material, and combines it with a sorbitol compound with specific physical property parameters. At a high-temperature processing temperature, a thin-wall injection molding product with low haze can be obtained.

[0042] Since thin-walled injection molding materials can be injection molded at high temperatures, processing time is shortened and work efficiency is increased, and the resulting thin-walled injection molded products have excellent optical properties and low haze, the thin-walled injection molding materials provided by the present invention have great production advantages and commercial value.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] (1) The thin-walled injection molded product prepared by the present invention using a specific polypropylene resin as a raw material and a specific sorbitol compound can achieve better optical properties with a smaller amount of sorbitol compound.

[0045] (2) The inventors also unexpectedly discovered that the compounding of 2,5-diaminopyrimidine-4-carboxylate and sorbitol compounds as auxiliary agents, especially the compounding of sorbitol compounds and sodium 2,5-diaminopyrimidine-4-carboxylate in a mass ratio of 4-6:1-1.5, further improved the optical properties of thin-walled injection molded products under high temperature processing conditions, especially the haze was significantly reduced.

[0046] (3) The thin-walled injection molding compound containing sorbitol compounds of the present invention can meet the needs of thin-walled injection molding products of different thicknesses. DETAILED DESCRIPTION

[0047] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0048] Examples 1-12

[0049] In the thin-wall injection molding compound formulations of Examples 1-10 and Comparative Examples 1-3, the raw materials used are as follows:

[0050] Polypropylene A1: PPH K1870-B base material from Shaanxi Yanchang Zhongmei Yulin Energy Chemical Co., Ltd., containing 1wt% butene, MFR 70g / 10min, weight average molecular weight M w =1.56×10 5 , molecular weight distribution is 7.0.

[0051] Polypropylene B1: Brand is PPH MN60 base material of Luoyang Petrochemical, homopolymer polypropylene with isotacticity greater than or equal to 96%, MFR is 60g / 10min, weight average molecular weight M w =1.60×10 5 , the molecular weight distribution is 6.5.

[0052] Polypropylene B2: Brand is Guangzhou Petrochemical's PPH S990 base material, homopolymer polypropylene with an isotacticity greater than or equal to 96%, MFR of 90g / 10min, and a weight average molecular weight of M w =1.30×10 5 , the molecular weight distribution is 9.0.

[0053] The sorbitol compound is selected from 1,3-O-2,4-di(3,4-dimethylbenzylidene)sorbitol:

[0054] Sorbitol compound A1: 1,3,2,4-bis-O-(3,4-dimethylbenzylidene)-D-sorbitol, produced by Chenghe Technology, brand NA-98, with a specific surface area of 3.75 m2 / g, a surface area average particle size of 1.602 μm, and a volume average particle size of 8.920 μm;

[0055] Sorbitol compound A2: 1,3,2,4-bis-O-(3,4-dimethylbenzylidene)-D-sorbitol, commercial product 1, with a specific surface area of 3.49 m2 / g, a surface area average particle size of 1.720 μm, and a volume average particle size of 3.529 μm;

[0056] Additive B: calcium hexahydrophthalate, commercial product 2;

[0057] Additive C: sodium 2,5-diaminopyrimidine-4-carboxylate;

[0058] Acid absorbent: calcium stearate;

[0059] Antioxidants: Antioxidant 1010, Antioxidant 168.

[0060] The polypropylene thin-wall injection molding compounds of Examples 1-10 and Comparative Examples 1-3 were prepared using the components in parts by mass in Table 1-2 in the following steps:

[0061] (S1) mixing the raw materials in a mixer according to the formula in Table 1-2 to obtain a blend;

[0062] (S2) The blend is pelletized through an extruder according to the "SHJ-20 twin-screw extruder operating procedures" at a pelletizing temperature of 190-220° C. to obtain a thin-walled injection molding compound.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067]

[0068] Performance testing:

[0069] The thin-walled injection molding materials of Examples 1-10 and Comparative Examples 1-3 were injection molded into strips at 250° C. in an injection molding machine to obtain Examples 1A-10A and Comparative Examples 1A-3A. The injection molding machine was HTF90W1 from Haitian Plastic Machinery Co., Ltd. The injection molding working conditions were: injection speed 40 mm / s, injection pressure 30 bar, injection time 2 s, holding pressure 30 bar, holding time 15 s, and the relevant properties were tested, as shown in Tables 3 and 4.

[0070] Table 3

[0071]

[0072]

[0073] Table 4

[0074]

[0075] The thin-walled injection molding materials of Examples 1-10 and Comparative Examples 1-3 were injection molded into strips in an injection molding machine at 280° C. to obtain Examples 1B-10B and Comparative Examples 1B-3B, and their related properties were tested, as shown in Tables 5 and 6.

[0076] Table 5

[0077]

[0078] Table 6

[0079]

[0080] The thin-walled injection molding materials of Examples 1-10 and Comparative Examples 1-3 were injection molded into samples or injection molded products in an injection molding machine at 300° C. to obtain Examples 1C-10C and Comparative Examples 1C-3C, and their relevant properties were tested, as shown in Tables 7-9.

[0081] Table 7

[0082]

[0083] Table 8:

[0084]

[0085] Table 9:

[0086]

[0087] The thin-walled injection molding materials of Examples 1-6 were injection molded into disposable lunch boxes with a thickness of 0.3 mm in an injection molding machine at 350° C. to obtain Examples 1D-6D, and their optical properties were tested. See Table 10 for details.

[0088] Table 10

[0089]

[0090] The thin-walled injection molding materials of Examples 1-6 were injection molded into disposable lunch boxes with a thickness of 0.3 mm in an injection molding machine at 380° C. to obtain Examples 1E-6E, and their optical properties were tested. See Table 11 for details.

[0091] Table 11

[0092]

[0093] Comparing the examples and comparative examples in Table 3, it can be seen that the thin-walled injection molding plastics containing 1200 ppm and 1500 ppm of sorbitol compounds have lower haze than the thin-walled injection molding plastics containing 2000 ppm of organic carboxylate compounds, indicating that sorbitol compounds have a more favorable effect on the optical properties of thin-walled injection molding plastics.

[0094] Comparisons of Tables 3, 5, and 7, and Tables 4, 6, and 8, show that as processing temperature increases, the crystallization temperature, flexural modulus, and heat distortion temperature of thin-walled injection molding compounds containing sorbitol compounds increase, while their haze further decreases. In contrast, as processing temperature increases, the crystallization temperature, flexural modulus, and heat distortion temperature of thin-walled injection molding compounds containing organic carboxylates decrease to a certain extent, while their haze increases to a certain extent. This indicates that thin-walled injection molding compounds containing sorbitol compounds are more capable of high-temperature processing, while organic carboxylates, due to their lack of high-temperature resistance, further deteriorate the optical, mechanical, and thermal properties of these thin-walled injection molding compounds.

[0095] By comparing Table 9, Table 10 and Table 11, it can be seen that as the processing temperature of the polypropylene thin-wall injection molding material increases from 300°C to 380°C, the haze of the obtained polypropylene thin-wall injection molding material generally shows a trend of first decreasing and then slightly increasing, but the haze at 380°C still remains at a satisfactory level.

[0096] By comparing Examples 3A-4A, 3B-4B, 3C-4C with Examples 7A-8A, 7B-8B, 7C-8C, it can be seen that the sorbitol compounds that meet the specific parameters of the present invention all have lower haze, better mechanical properties and thermal properties.

[0097] Comparison of Examples 9A-10A with Examples 5A-6A shows that increasing the MFR of homopolypropylene reduces the haze of the thin-walled injection molding compound while also decreasing its mechanical properties. This indicates that increasing the MFR of homopolypropylene enhances processing fluidity, which in turn improves the dispersion of the sorbitol compound in the matrix, leading to improved optical properties of the thin-walled injection molding compound.

[0098] As shown in Table 9, the thin-walled injection molding compound containing sorbitol compounds has better haze as the thickness decreases, meeting the application needs of a wider range of thin-walled injection molding products.

[0099] Examples 11-12

[0100] According to the formula in Table 1 above, the difference is that a certain amount of additive C2,5-diaminopyrimidine-4-carboxylate sodium is also added to the thin-wall injection molding compound. The formula of each component by weight is shown in Table 12 below:

[0101] Table 12

[0102]

[0103]

[0104] The materials of Examples 11-13 were mixed uniformly in a mixer to obtain a blend, which was then extruded and granulated in an extruder under the same conditions to obtain a thin-walled injection molding compound. Test specimens were injection molded in an injection molding machine at processing temperatures of 250°C, 280°C, and 300°C, respectively, and relevant properties were tested. The results are shown in Table 13 below:

[0105] Table 13

[0106]

[0107] The data in Table 11 show that when a certain amount of sodium 2,5-diaminopyrimidine-4-carboxylate is added to the sorbitol compound as the compounding additive C, the resulting thin-walled injection molding compound exhibits little change in performance at temperatures of 250°C and 280°C. However, at a high-temperature injection molding machine operating temperature of 300°C, the resulting injection-molded strips exhibit significantly lower haze than the injection-molded strips obtained at 300°C in Example 4A, and the mechanical properties are also slightly improved. This indicates that the compounding of the sorbitol compound and sodium 2,5-diaminopyrimidine-4-carboxylate exerts a synergistic effect, significantly improving the optical properties of thin-walled injection-molded products molded at high temperatures (280-380°C).

[0108] According to the formula of Example 12 in Table 12, disposable lunch boxes were injection molded at high temperatures of 350°C and 380°C using the same method, and the optical properties were tested. The results are shown in Table 14 below:

[0109] Table 14

[0110]

[0111] As shown in Table 14, the haze of the polypropylene thin-walled injection molding compound obtained by the present invention continues to decrease when molded at a high temperature of 350°C compared to 300°C. The haze does not begin to increase until 380°C, but remains at a satisfactory level. This indicates that the polypropylene injection molding compound provided by the present invention is very suitable for thin-walled products, such as disposable lunch boxes.

Claims

1. A polypropylene thin-wall injection molding compound for preparing thin-wall injection-molded products, comprising a polypropylene resin and a sorbitol compound, wherein the polypropylene resin is homopolypropylene having an isotacticity of 96% or greater and / or polypropylene containing 2 wt% or less butene, and wherein the polypropylene resin has a melt index (MFR) greater than 60 g / 10 min, measured under test conditions of a temperature of 230° C. and a test load of 2.16 kg. The polypropylene thin-wall injection molding compound has a haze value of less than 50% according to GB / T 2410 when injection-molding a 1 mm sample at 230-280° C. and a haze value of less than 50% according to GB / T 2410 when injection-molding a 1 mm sample or an injection-molded product having a diameter less than 1 mm at 280-380° C. The polypropylene thin-wall injection molding compound further comprises sodium 2,5-diaminopyrimidine-4-carboxylate, and the mass ratio of the sorbitol compound to the sodium 2,5-diaminopyrimidine-4-carboxylate is 5-10:1-2.

2. The polypropylene thin-wall injection molding material according to claim 1, characterized in that: The weight average molecular weight of the polypropylene resin is 1.30×10 5 -1.6×10 5 , the molecular weight distribution range is 6.5-9.

0.

3. The polypropylene thin-wall injection molding material according to claim 2, characterized in that: The polypropylene resin is a polypropylene resin with a butene content of 0.5-2wt%.

4. The polypropylene thin-wall injection molding material according to claim 1, characterized in that: The general chemical formula of the sorbitol compound is: Wherein, R1, R2, and R3 are independently selected from H, C1-C6 alkyl, C2-C6 alkenyl, C1-C6 alkoxy, hydroxyl or halogen atom.

5. The polypropylene thin-wall injection molding material according to claim 4, characterized in that: The sorbitol compound is an α-crystalline compound, and the sorbitol compound is determined using GB / T 19077-2016, and has the following characteristics: -Specific surface area greater than or equal to 1.5m 2 / g; -Surface area average particle size greater than or equal to 1.3 μm; - The volume average particle size is greater than or equal to 3.4 μm.

6. The polypropylene thin-wall injection molding material according to claim 1, characterized in that: The concentration of the sorbitol compound in the polypropylene resin is 400-2000 ppm.

7. The polypropylene thin-wall injection molding material according to claim 1, characterized in that: The mass ratio of the sorbitol compound to sodium 2,5-diaminopyrimidine-4-carboxylate is 4-6:1-1.

5.

8. The polypropylene thin-wall injection molding material according to claim 1, characterized in that: The polypropylene thin-wall injection molding compound may further include one or more of an acid absorber, an antioxidant, an antistatic agent, a colorant, a lubricant or a dispersant.

9. The method for preparing the polypropylene thin-wall injection molding compound according to claim 1 or 8, comprising the following steps: The polypropylene resin and the sorbitol compound are uniformly blended to obtain a blend. One or more of an acid absorber, an antioxidant, an antistatic agent, a colorant, a lubricant or a dispersant may also be added to the blend. The blend is then extruded and granulated through an extruder to obtain a polypropylene thin-wall injection molding compound.

10. A thin-walled injection molded product obtained by processing the polypropylene thin-wall injection molded material according to claim 1 at a processing temperature of 230-380°C.

11. Use of the polypropylene thin-wall injection molded product according to claim 10 in resin molded products such as automobile parts, mechanical parts, and food packaging.

12. A use of a sorbitol compound for reducing the haze value of a polypropylene thin-wall injection molding compound during injection molding at 230-380°C, characterized in that: The polypropylene thin-wall injection molding material is as described in claim 1.

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