Polypropylene composition, process for its preparation and use thereof

Abstract

The application discloses a polypropylene composition, a preparation method and application thereof, and belongs to the technical field of high polymer materials. The product comprises 59-71 parts of polypropylene resin, 20-40 parts of modified glass fiber, 1-5 parts of a compatilizer, 2-5 parts of micron inorganic material and 0.5-3 parts of nanometer inorganic light-shielding agent. The glass fiber is modified and its reserved length is limited, and two inorganic components with synergistic effect with the glass fiber are introduced, so that the product can realize excellent alkali-resistant and heat-resistant environment performance and appearance stability under the action of the three inorganic materials without introducing special environment-resistant agents or modification processes.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a polypropylene composition, its preparation method, and its application. Background Technology

[0002] Glass fiber reinforced polypropylene (GFRP) has advantages such as being non-toxic, lightweight, easy to process, and possessing good mechanical properties, and is currently widely used in washing appliances such as dishwashers and washing machines. However, feedback indicates that the performance of GFRP in this field still needs improvement. The main reason is that polypropylene, due to its structural instability, is easily degraded by external catalytic reactions. Washing appliances need to be used in a humid and hot environment containing detergents for extended periods, where polypropylene degrades even more rapidly. Furthermore, the glass fibers in these products have poor resistance to organic reagents, especially alkalis, ultimately leading to a significant decline in the integrity and appearance of the products.

[0003] To improve the service life of glass fiber reinforced polypropylene materials in humid and hot environments, various environmentally resistant agents such as antioxidants and light stabilizers have been introduced into the products. These modified products show significant improvement in initial stability under humid and hot organic environments. However, as the environmentally resistant agents hydrolyze, migrate, and are consumed, the environmental resistance of the products will decrease significantly. Furthermore, some anti-aging additives will generate colored groups after hydrolysis, further affecting the appearance of the products and the user experience. On the other hand, using high-performance and high-stability environmentally resistant agents or modifying the polypropylene matrix resin will significantly increase the production cost of the products. Summary of the Invention

[0004] Based on the deficiencies of the existing technology, the purpose of this invention is to provide a polypropylene composition. This product, by modifying the glass fibers it contains and limiting their retention length, and by introducing two inorganic components that have a synergistic effect with the glass fibers, enables the product to achieve excellent alkaline resistance to humid and hot environments and appearance stability simply through the action of three inorganic materials, without the need to introduce special environmentally resistant reagents or modification processes.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A polypropylene composition comprising the following components in parts by weight:

[0007] 59-71 parts polypropylene resin, 20-40 parts modified glass fiber, 1-5 parts compatibilizer, 2-5 parts micron-sized inorganic matter, and 0.5-3 parts nano-sized inorganic opacifier;

[0008] The modified glass fiber is a glass fiber modified by a modifying liquid including phosphate esters and sulfonic acid substances, and its retention length is 250-350 μm.

[0009] The average particle size of the micron-sized inorganic material is ≤6μm;

[0010] The nanoscale inorganic opacifier includes nanoscale titanium dioxide.

[0011] Preferably, the retained length of the modified glass fiber is the actual length of the modified glass fiber in the polypropylene composition product.

[0012] The method for testing the retention length of the modified glass fiber is as follows: First, the polypropylene composition particles or products are calcined at 650°C for 30 minutes to remove the resin matrix and retain the inorganic matter. The glass fiber is then screened by ultrasonic treatment. The glass fiber is then uniformly dispersed in water, and the retention length of the glass fiber is tested using a two-dimensional method.

[0013] In existing technologies, the public generally only focuses on the impact of the original length of the glass fiber used in the preparation of glass fiber reinforced polypropylene products on the processing performance and the performance of the processed products. However, they ignore the fact that during the subsequent production of parts, the glass fiber will undergo mechanical interaction with the matrix resin and various solid components during product processing. The glass fiber will be further squeezed and rubbed by the matrix resin and solid components. Glass fiber reinforced systems with weak interfacial interactions are prone to interfacial debonding, resulting in obvious fiber floating. This not only exposes some glass fibers to the outside to a certain extent, but also deteriorates the product's heat and oxygen aging resistance. On the one hand, it accelerates the erosion of glass fibers by the external environment, and on the other hand, the weak interfacial interaction accelerates the penetration of external oxygen, accelerates the oxidation and destruction of the resin, and causes severe discoloration of the product.

[0014] Therefore, in the technical solution of this invention, in the glass fiber reinforced polypropylene resin system, the modified glass fiber is pre-modified with phosphate esters and sulfonic acid substances to improve the product's solvent resistance, especially alkali resistance, and weaken the corrosive effect of organic solvent environment on the product. At the same time, two inorganic particles with specific contents and different sizes are introduced for compounding and the actual retention length of modified glass fiber in the product is controlled. The inorganic substances of specific sizes can weaken the interface defects between glass fiber and polypropylene resin, and also have a nucleating agent-like effect, which improves the crystallinity and density of polypropylene resin, and increases the resistance to external solvent penetration, so that the product can achieve ideal extraction resistance effect. Meanwhile, nano-sized titanium dioxide can improve its dispersion uniformity in the resin matrix based on mechanical action and improve its surface fiber floating phenomenon. In addition, nano-titanium dioxide has high whiteness and strong shielding of yellow band, which can, to a certain extent, cover up the color change phenomenon of the product in alkaline environment from the perspective of visual effect, so that the product exhibits excellent appearance stability in humid and hot environment, especially alkaline humid and hot environment. However, the introduction of nano-titanium dioxide will reduce the initial heat and oxygen aging resistance of the product to some extent, so too much should not be introduced. In addition, if too much is introduced, the resin encapsulation of the glass fiber will be weakened due to the excessive force, which will also reduce the extraction resistance.

[0015] Preferably, the polypropylene composition comprises the following components in parts by weight:

[0016] The mixture contains 60-65 parts polypropylene resin, 25-35 parts modified glass fiber, 2-4 parts compatibilizer, 2-5 parts micron-sized inorganic material, and 0.5-3 parts nano-sized inorganic opacifier.

[0017] More preferably, the polypropylene composition contains a polypropylene resin content of not less than 50 wt%.

[0018] Preferably, the micron-sized inorganic material includes at least one of micron-sized calcium carbonate and micron-sized silicate minerals; preferably, the silicate minerals include at least one of talc, montmorillonite, kaolinite, sepiolite, and mica.

[0019] More preferably, the average particle size of the micron-sized inorganic material is 2–6 μm.

[0020] More preferably, the average particle size of the micron-sized inorganic material is a range of one or any two of the following: 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, and 6μm.

[0021] The size of this inorganic material is larger than that of the nano-sized inorganic opacifier. In addition to forming a gradation effect with the nano-sized inorganic opacifier to avoid particle agglomeration, as mentioned above, if the size exceeds the limit, this inorganic material will not be able to act as a nucleating agent to induce polypropylene crystallization and increase density, and the alkali resistance extraction performance will be significantly reduced.

[0022] More preferably, the average particle size of the micron-sized inorganic material is 2.5 to 4 μm.

[0023] Within the specified range, micron-sized inorganic materials exhibit better dispersibility in the product, resulting in superior synergistic effects with inorganic components and better modification of polypropylene resin. Consequently, the product demonstrates better stability in alkali-resistant and humid environments.

[0024] Preferably, the average particle size of the nanoscale inorganic opacifier is 100–300 nm.

[0025] More preferably, the average particle size of the nanoscale inorganic opacifier is one or any two of the following: 100nm, 120nm, 140nm, 150nm, 180nm, 200nm, 220nm, 250nm, 280nm, 290nm, and 300nm.

[0026] More preferably, the average particle size of the nanoscale inorganic opacifier is 180–250 nm.

[0027] The method for testing the average particle size of the micron-sized inorganic matter and nano-sized inorganic opacifier in the polypropylene composition of the present invention is as follows: Using the GB / T 19077.1-2008 standard "Particle Size Analysis by Laser Diffraction," the particle size of the commercially available, ground, or sieved micron-sized inorganic matter and nano-sized inorganic opacifier is tested to obtain their average particle size. Although micron-sized inorganic matter and nano-sized inorganic opacifier are common inorganic fillers added to polypropylene products, in the technical solution of the present invention, their mechanism of action on glass fibers and polypropylene resin differs from conventional selection. After modification with phosphate esters and sulfonic acids, the rationally graded inorganic fillers better ensure the compatibility and dispersibility of glass fibers in the resin matrix, and do not cause particle agglomeration or glass fiber breakage, nor affect the coating effect of polypropylene resin on glass fibers or the whitening effect of the inorganic opacifier.

[0028] Preferably, the phosphate ester is a fatty alcohol phosphate ester;

[0029] More preferably, the fatty alcohol phosphate is a mixture of fatty alcohol polyoxyethylene ether phosphate and lauryl phosphate;

[0030] Preferably, the sulfonic acid is a mixture of dodecylbenzenesulfonic acid and sodium secondary alkyl sulfonate.

[0031] Different modifiers have varying effects on the compatibility of glass fibers in polypropylene resin and their ability to improve the resistance of glass fibers to external environments. After modifying glass fibers with the aforementioned phosphate esters and sulfonic acids, they do not weaken the compatibility of glass fibers in polypropylene resin, nor do they inhibit the interaction with other components in the product. They can also significantly improve the alkali resistance of glass fibers and significantly reduce the impact of the external environment on the product.

[0032] More preferably, the modified glass fiber is obtained by impregnating glass fiber in a modification solution containing phosphate esters and sulfonic acid substances.

[0033] More preferably, the temperature during immersion is room temperature, and the immersion time is 40 to 80 seconds.

[0034] More preferably, the solid-liquid ratio of the glass fiber to the solution is 1g:(10-200)mL.

[0035] More preferably, the modified liquid containing phosphate esters and sulfonic acid substances comprises the following components in parts by weight:

[0036] 15-25 parts of fatty alcohol polyoxyethylene ether phosphate, 3-8 parts of lauryl phosphate, 1-3 parts of dodecylbenzene sulfonic acid, and 3-8 parts of sodium secondary alkyl sulfonate.

[0037] More preferably, the modified liquid containing phosphate esters and sulfonic acid substances further includes the following components in parts by weight: 0.1 to 1 part of organosiloxane defoamer, 0.8 to 1.2 parts of epoxy compound hydrolysis stabilizer, 0.4 to 0.8 parts of aminosilane coupling agent, and 2.5 to 3.5 parts of epoxy emulsion.

[0038] It should be noted that, according to actual production needs, those skilled in the art can use the above-described impregnation method and the above-described formulation of solution to modify glass fibers to obtain modified glass fibers. Alternatively, other methods or solutions with other formulations can be used to modify glass fibers. For example, to improve the modification efficiency of glass fibers, those skilled in the art can use spraying, atomization, or other methods to directly adhere a solution containing phosphate esters and sulfonic acids to the surface of the glass fibers. To improve the uniformity and processability during impregnation, those skilled in the art can add 0.1 to 1 part of processing aids such as organosiloxane defoamers and 0.8 to 1.2 parts of hydrolytic stabilizers to the solution. As long as it does not affect the expected effect of the product, there are no restrictions.

[0039] More preferably, the epoxy compound hydrolysis stabilizer comprises 1,1,2,2-tetra(p-hydroxyphenyl)ethane tetraglycidyl ether epoxy resin.

[0040] More preferably, the aminosilane coupling agent comprises γ-aminopropyltriethoxysilane;

[0041] More preferably, the epoxy emulsion is an aqueous epoxy emulsion.

[0042] Preferably, the compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 1-1.5%.

[0043] Preferably, the polypropylene resin has a melt flow rate of 20-150 g / 10 min at 230°C and 2.16 kg load, according to ISO 1133-2011.

[0044] More preferably, the melt flow rate of the polypropylene resin at 230°C and 2.16 kg load is one or any two of the following values: 20 g / 10 min, 30 g / 10 min, 40 g / 10 min, 50 g / 10 min, 80 g / 10 min, 100 g / 10 min, 120 g / 10 min, and 150 g / 10 min.

[0045] Preferably, the polypropylene composition further includes 0-1 part of a processing aid;

[0046] More preferably, the processing aids include, but are not limited to, at least one of antioxidants and lubricants.

[0047] More preferably, the antioxidant includes at least one of hindered phenolic antioxidants, phosphite antioxidants, and sulfur antioxidants, more preferably a mixture of the three, wherein the mass ratio of the three is (0.8-1.2):(1.8-2.2):(0.8-1.2).

[0048] More preferably, the lubricant includes at least one of EBS amides, PE waxes, stearates, and pentaerythritol stearates.

[0049] Those skilled in the art know that when preparing polypropylene compositions, considering their processing effects and subsequent usage requirements, some common processing aids, such as antioxidants, lubricants, and antistatic agents, can be added to the product to improve its processing efficiency, antioxidant properties, and antistatic properties during use. Due to the special filler modification system in the product described in this invention, the product's resistance to alkaline and humid environments is significantly improved. Even if antioxidant components that may generate chromophores are introduced, the migration and consumption of antioxidants can be significantly suppressed based on the overall resin density and structural stability, thereby ensuring the product's appearance stability. As long as the expected effect of the product is not affected, the introduction of other processing aids besides those mentioned above is not a limitation.

[0050] Another object of the present invention is to provide a method for preparing the polypropylene composition, comprising the following steps:

[0051] The components are added to a screw extruder for melt extrusion and granulation to obtain the polypropylene composition.

[0052] Preferably, the temperature zones of the twin-screw extruder are set as follows: Zone 1: 110–130℃; Zone 2: 210–230℃; Zone 3: 210–230℃; Zone 4: 210–230℃; Zone 5: 210–230℃; Zone 6: 210–230℃; Zone 7: 210–230℃; Zone 8: 210–230℃; Zone 9: 210–230℃; Zone 10: 210–230℃; Screw speed: 400–500 rpm; Screw length-to-diameter ratio: (38–42):1.

[0053] Another object of the present invention is to provide the use of the polypropylene composition in the manufacture of washing appliances.

[0054] The polypropylene composition of this invention is based on its special filler system, with readily available raw materials, a simple production process, and high production cost-effectiveness. The product also exhibits strong appearance stability, a long service life, and high resistance to solvent environments, especially alkaline and humid heat environments. Tests show that after being continuously soaked in an alkaline solution at 70°C for 40 days, the product can maintain a powdery area ratio of no more than 5% after being left to stand at 150°C for over 1000 hours. It demonstrates extremely high stability in alkaline and humid heat environments, making it highly suitable for the preparation of plastic components in washing appliances that require direct contact with corrosive detergents (mostly alkaline detergents that damage glass fiber reinforced plastics) and involve certain heating scenarios.

[0055] The beneficial effect of the present invention is that it provides a polypropylene composition, which, by modifying the glass fibers contained therein and limiting their retention length, and by introducing two inorganic components that have a synergistic effect with the glass fibers, enables the product to achieve excellent alkaline resistance to humid and hot environments and appearance stability under the action of only three inorganic materials. Detailed Implementation

[0056] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0057] Examples 1-13

[0058] An embodiment of the polypropylene composition, its preparation method and application described in this invention, wherein the composition of the polypropylene composition is shown in Table 1.

[0059] The method for preparing the polypropylene composition includes the following steps:

[0060] The components are mixed evenly, and then melt-extruded and granulated in a screw extruder to obtain the polypropylene composition.

[0061] During melt extrusion of the component, the temperature zones of the screw extruder are set as follows: Zone 1: 120℃, Zone 2: 220℃, Zone 3: 220℃, Zone 4: 210℃, Zone 5: 210℃, Zone 6: 210℃, Zone 7: 210℃, Zone 8: 210℃, Zone 9: 210℃, Zone 10: 210℃. The screw speed is 400-500 rpm, and the screw length-to-diameter ratio is 40:1.

[0062] Comparative Examples 1-12

[0063] The only difference between each comparative example and the embodiment is the type and ratio of components, as shown in Table 2.

[0064] Comparative Example 13

[0065] The only difference between Comparative Example 13 and Example 1 is the screw speed during processing, which is 300-400 rpm, resulting in different retention lengths of glass fibers in the prepared products.

[0066] In the components described in each embodiment and comparative example,

[0067] The polypropylene resin is PP Z30S produced by Sinopec, which, according to ISO 1133-2011, has a melt flow rate of 24.76 g / 10 min at 230℃ and a crystallinity of 48.2% under a load of 2.16 kg. The modified glass fiber 1 is a self-made product, prepared by the following method:

[0068] Glass fiber was immersed in modified liquid 1 at a solid-liquid ratio of 1g:20mL and fully impregnated (at room temperature, impregnated for 60s without stirring). Then the solid and liquid were separated and the glass fiber was dried to obtain the modified glass fiber 1.

[0069] The glass fiber is ECS13-03-508A produced by Jushi, and the fiber length after grinding and sieving is 1 to 1.3 mm.

[0070] The modified liquid 1 is prepared from the following components in parts by weight:

[0071] 20 parts fatty alcohol polyoxyethylene ether phosphate, 5 parts lauryl phosphate, 2 parts dodecylbenzene sulfonic acid, 5 parts sodium secondary alkyl sulfonate, 0.3 parts organosiloxane defoamer, 1 part epoxy compound hydrolysis stabilizer, 0.5 parts aminosilane coupling agent, 3 parts epoxy emulsion and 63.2 parts water.

[0072] The epoxy compound hydrolysis stabilizer is TPGEE, 1,1,2,2-tetra(p-hydroxyphenyl)ethane tetraglycidyl ether epoxy resin, produced by Shandong Jiaying Chemical Technology Co., Ltd.

[0073] The aminosilane coupling agent is KH550, γ-aminopropyltriethoxysilane, produced by Hangzhou Jessica Chemical Co., Ltd.

[0074] The epoxy emulsion is waterborne epoxy emulsion JE-9064 produced by Changzhou Jien New Materials Co., Ltd.

[0075] The modified glass fiber 2 is a self-made product, differing from the modified glass fiber 1 only in that the modifying liquid 1 is replaced by the modifying liquid 2 during preparation. The modifying liquid 2 is prepared from the following components in parts by weight:

[0076] 18 parts fatty alcohol polyoxyethylene ether phosphate, 7 parts lauryl phosphate, 3 parts dodecylbenzene sulfonic acid, 4 parts sodium secondary alkyl sulfonate, 0.3 parts organosiloxane defoamer, 1 part epoxy compound hydrolysis stabilizer, 0.5 parts aminosilane coupling agent, 3 parts epoxy emulsion, and 63.2 parts water.

[0077] The modified glass fiber 3 is a self-made product, differing from the modified glass fiber 1 only in that the modifying liquid 1 is replaced by the modifying liquid 3 during preparation. The modifying liquid 3 is prepared from the following components in parts by weight:

[0078] 2 parts dodecylbenzene sulfonic acid, 5 parts sodium secondary alkyl sulfonate, 0.3 parts organosiloxane defoamer, 1 part epoxy compound hydrolysis stabilizer, 0.5 parts aminosilane coupling agent, 3 parts epoxy emulsion, and 88.2 parts water.

[0079] The modified glass fiber 4 is a self-made product, differing from the modified glass fiber 1 only in that the modifying liquid 1 is replaced by the modifying liquid 4 during preparation. The modifying liquid 4 is prepared from the following components in parts by weight:

[0080] 20 parts fatty alcohol polyoxyethylene ether phosphate, 5 parts lauryl phosphate, 0.3 parts organosiloxane defoamer, 1 part epoxy compound hydrolysis stabilizer, 0.5 parts aminosilane coupling agent, 3 parts epoxy emulsion and 70.2 parts water.

[0081] The modified glass fiber 5 is a self-made product, differing from the modified glass fiber 1 only in that the modifying liquid 1 is replaced by the modifying liquid 5 during preparation. The modifying liquid 5 is prepared from the following components in parts by weight:

[0082] 20 parts fatty alcohol polyoxyethylene ether phosphate, 5 parts lauryl phosphate, 7 parts sodium stearate, 0.3 parts organosiloxane defoamer, 1 part epoxy compound hydrolysis stabilizer, 0.5 parts aminosilane coupling agent, 3 parts epoxy emulsion and 63.2 parts water.

[0083] The modified glass fiber 6 is a self-made product, differing from the modified glass fiber 1 only in that the modifying liquid 1 is replaced by the modifying liquid 6 during preparation. The modifying liquid 6 is prepared from the following components in parts by weight:

[0084] 25 parts fatty alcohol polyoxyethylene ether, 2 parts dodecylbenzene sulfonic acid, 5 parts sodium secondary alkyl sulfonate, 0.3 parts organosiloxane defoamer, 1 part epoxy compound hydrolysis stabilizer, 0.5 parts aminosilane coupling agent, 3 parts epoxy emulsion, and 63.2 parts water.

[0085] The micron-sized inorganic material 1 is commercially available ultrafine talc powder HTP Ultra 5L with a purity ≥95% and an average particle size of 2.8 μm after sieving.

[0086] The micron-sized inorganic material 2 is commercially available talc powder TYT-777A, with an average particle size of 5.3 μm as measured.

[0087] The micron-sized inorganic material 3 is commercially available calcium carbonate AC-05N powder obtained by sieving, with a purity ≥95% and an average particle size of 4.5μm as measured.

[0088] The micron-sized inorganic material 4 is commercially available calcium carbonate AC-05N powder obtained by ball milling, with a purity ≥95% and an average particle size of 3.8μm as measured.

[0089] The micron-sized inorganic material 5 is commercially available calcium carbonate AC-05N powder obtained by ball milling, with a purity ≥95% and an average particle size of 2.6μm as measured.

[0090] The micron-sized inorganic material 6 is commercially available calcium carbonate AC-05N powder obtained by ball milling, with a purity ≥95% and an average particle size of 2.1 μm as measured.

[0091] The micron-sized inorganic material 7 is commercially available talc powder AH-1250N6 with a purity ≥95% and an average particle size of 13μm after sieving.

[0092] The micron-sized inorganic material 8 is commercially available calcium carbonate HX-1250 with a purity ≥95% and an actual measured average particle size of 8μm after sieving.

[0093] The nano-scale inorganic opacifier 1 is commercially available rutile titanium dioxide RCL-69 with a purity ≥95% and an average particle size of 240nm as measured.

[0094] The nano-scale inorganic opacifier 2 is commercially available rutile titanium dioxide TIKON 33 with a purity ≥95% and an average particle size of 290nm after sieving.

[0095] The nano-scale inorganic opacifier 3 is a powder obtained by ball milling nano-scale inorganic opacifier 2, and the measured average particle size is 250 μm.

[0096] The nano-scale inorganic opaque agent 4 is a powder obtained by ball milling nano-scale inorganic opaque agent 2, and the measured average particle size is 180 nm.

[0097] The nano-scale inorganic opacifier 5 is a powder obtained by ball milling nano-scale inorganic opacifier 2, and the measured average particle size is 140 nm.

[0098] The nanoscale filler is commercially available zinc sulfide HD-S, with an average particle size of 300 nm as measured.

[0099] The compatibilizer is maleic anhydride-grafted polypropylene AD-105 produced by Nanhai Baichen Polymer, with a grafting rate of 1.2%.

[0100] The processing aid is a mixture of hindered phenolic antioxidants and phosphite antioxidants, which are produced by BASF and contain antioxidants 1010, 168 and DSTDP in a mass ratio of 1:2:1.

[0101] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0102] The test method for the glass fiber retention length of the products in each embodiment and comparative example is as follows: each polypropylene composition particle or product is fired at 650°C for 30 minutes to remove the resin matrix and retain the inorganic matter. Glass fibers are screened by ultrasonic treatment. The glass fibers are uniformly dispersed in water. The retention length of the glass fibers is tested using a two-dimensional method.

[0103] Table 1

[0104]

[0105]

[0106] Table 2

[0107]

[0108] To verify the performance of the polypropylene composition described in this invention, the products prepared in each embodiment and comparative example were subjected to the following performance tests, with the specific steps as follows:

[0109] (1) Alkali extraction & thermal oxidation test: Each product was injection molded into a 50*80*2mm test square plate. First, a test square plate was placed in an oven at 150℃ and allowed to stand. The time R1 when the powdery area on the surface of the square plate reached 5% was recorded. Then, another test square plate prepared from a parallel sample was soaked in a sodium hydroxide solution at 70℃ and pH=11 for 40 consecutive days. Then, it was transferred to an oven at 150℃ and allowed to stand. The time R2 when the powdery area on the surface of the square plate reached 5% was recorded. The difference H between the thermal oxidation test time R1 and R2 of the sample before and after alkali extraction was calculated.

[0110] (2) Color difference test: Each product was injection molded into a test square plate of 50*80*2mm, and then continuously immersed in a sodium hydroxide solution of pH=11 at 70℃ for 40 days. The samples before and after immersion were tested according to ASTM D2244-21 standard. The color difference was tested using a colorimeter with a light source of D65 / 10° and a measuring aperture of 25.4mm.

[0111] The test results are shown in Tables 3 and 4.

[0112] Table 3

[0113]

[0114] Table 4

[0115]

[0116] As can be seen from Tables 3 and 4, the polypropylene composition of this invention has ideal appearance stability and resistance to alkaline and humid heat environments. After alkaline extraction and thermal oxidation, the time required for the powdered area to reach 5% can reach more than 1000 hours, and the difference H between the time required for thermal oxidation aging in the initial state can be maintained within 200 hours. This fully demonstrates that it has sufficient service life in alkaline and humid heat environments, making it very suitable for use in some washing appliances. At the same time, the product shows little color difference after alkaline extraction, which can be maintained within 5. This is mainly due to the modification of glass fiber and the control of its retention length in the product. It also requires the compounding of inorganic materials of specific size and function, so that even without special processes or the introduction of special environmentally resistant reagents, the expected effect can be achieved.

[0117] In contrast, traditional glass fiber reinforced polypropylene compositions, as shown in Comparative Example 1, suffer from poor alkali resistance due to the glass fiber's insensitivity and the polypropylene's susceptibility to degradation under the influence of solvents and thermal environments. This results in rapid pulverization and significant color variations after extraction. In such cases, simply introducing inorganic materials is insufficient to improve product performance, as shown in Comparative Example 2. Examples 1, 3, and Comparative Examples 5-8 demonstrate that glass fiber modification significantly impacts its alkali resistance, dispersibility, and compatibility. Modification using the phosphate esters and sulfonic acid substances specified in this invention significantly enhances the glass fiber's resistance to alkaline environments without affecting its dispersibility and compatibility. The resulting product exhibits significantly improved performance compared to Comparative Example 2. However, if either of these substances is absent, or if other substances with similar compositions are substituted, the equivalent effects of the product in these examples may not be achieved. The main reason is that phosphate esters can react chemically with the active sites on the surface of glass fibers through their functional groups, forming chemical bonds or strong physical adsorption, thereby enhancing the bonding force between glass fibers and the resin matrix. They also have good alkali resistance and remain stable under various alkaline conditions, without easily undergoing hydrolysis or decomposition reactions. On the other hand, sulfonic acid substances, when modified together with phosphate esters in the modification solution and glass fibers, will be converted into salts. These salts are generally weakly alkaline substances, which have good stability in alkaline environments. Furthermore, their polar ends will form strong chemical bonds with the surface of glass fibers. The non-polar alkane chains in sulfonic acid substances containing alkane chains can further effectively improve the compatibility between glass fibers and the resin matrix. Only through the combined effect of both can the product have sufficient alkali resistance in alkaline environments. As can be seen from Examples 1, 4-8, Comparative Examples 3, and Comparative Examples 9-10, the main function of micron-sized inorganic materials, besides controlling the retention length of glass fibers in the product, is to improve the crystallinity of the product. Without this component, the environmental resistance of the product will be greatly reduced. If the micron-sized inorganic materials are of a larger size, they will not be able to control the glass fibers and polypropylene resin. As shown in Comparative Examples 9 and 10, neither talc nor calcium carbonate can work synergistically with other components at a larger size. Furthermore, smaller size is not necessarily better for these micron-sized inorganic materials. In summary, an average particle size of 2.5-4 μm is the most effective.

[0118] Similarly, another type of inorganic material micron-sized opaque agent, as shown in Examples 1, 9-13, Comparative Example 4, and Comparative Example 12, has a mechanism of action that is not entirely the same as that of micron-sized inorganic materials. In addition to jointly regulating the retention length of glass fibers, it also needs to have a whitening effect. When this component is lacking, not only does the degradation rate of polypropylene in the product accelerate, but the product's service life is naturally shorter, and the appearance changes significantly. However, if only ordinary nano-sized fillers are introduced, as shown in Comparative Example 12, it cannot well guarantee the appearance stability of the product.

[0119] Meanwhile, as can be seen from Examples 1, 13-15 and Comparative Example 11, even with the presence of nano-level inorganic opacifiers, the product performance may not achieve the expected results. The amount of nano-level inorganic opacifiers added should not be excessive, as their introduction will cause a decrease in the initial heat and oxygen aging resistance of the product. It will also affect the dispersibility and compatibility of inorganic materials, reduce the effect on the retention length control of glass fibers, and ultimately lead to a decrease in the alkali resistance of the product. As shown in Comparative Example 11, not only is the difference between the extraction and the initial heat and oxygen aging test values ​​large, but the pulverization time after extraction-heat and oxygen aging is only 768 hours.

[0120] As can be seen from Example 1 and Comparative Example 13, the retained length of glass fibers in the polypropylene composition can be adjusted by adjusting the screw speed during preparation. Generally speaking, the higher the speed, the greater the shear force, and the smaller the retained length of the glass fibers. Even if the composition is the same, if the control scale of the glass fibers does not meet the requirements of the technical solution of the present invention, it will also be unable to achieve the ideal comprehensive performance.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polypropylene composition, characterized in that, The composition comprises the following components by weight: polypropylene resin 59~71 parts, modified glass fiber 20~40 parts, compatibilizer 1~5 parts, micron-sized inorganic substance 2~5 parts, nanometer-sized inorganic sunscreen 0.5~3 parts; the modified glass fiber is a glass fiber modified by a modifying liquid comprising phosphate ester and sulfonic acid, and the retained length thereof is 300~360 μm; the phosphate ester is a mixture of fatty alcohol polyoxyethylene ether phosphate and lauryl phosphate; the sulfonic acid is a mixture of dodecyl benzene sulfonic acid and sodium secondary alkyl sulfonate; the micron-sized inorganic substance has an average particle size ≤6 μm; the nanometer-sized inorganic sunscreen comprises nanometer-sized titanium dioxide.

2. The polypropylene composition according to claim 1, wherein the micron-sized inorganic substance comprises at least one of micron-sized calcium carbonate and micron-sized silicate mineral.

3. The polypropylene composition according to claim 2, characterized in that, the silicate mineral comprises at least one of talc, montmorillonite, kaolin, sepiolite and mica.

4. The polypropylene composition according to claim 2, wherein the polypropylene composition has a melt flow rate MFR2 (230 °C, 2.16 kg) of 0.1 to 10 g / 10 min. the micron-sized inorganic substance has an average particle size of 2~6 μm.

5. The polypropylene composition according to claim 4, wherein the polypropylene composition has a melt flow rate MFR2 (230 °C, 2.16 kg) of 0.5 to 5 g / 10 min. the micron-sized inorganic substance has an average particle size of 2.5~4 μm.

6. The polypropylene composition according to claim 1, wherein the polypropylene composition has a melt flow rate of 0.5 to 5 g / 10 min. the nanometer-sized inorganic sunscreen has an average particle size of 100~300 nm.

7. The polypropylene composition according to claim 1, wherein the polypropylene composition has a melt flow rate of 0.5 to 5 g / 10 min. the polypropylene resin has a melt flow rate of 20~150 g / 10 min at 230℃ under a load of 2.16 kg according to ISO 1133-2011.

8. The polypropylene composition according to claim 1, wherein the polypropylene composition has a melt flow rate of 0.5 to 5 g / 10 min. at 230°C under a load of 2.16 kg. the components of the polypropylene composition further comprise processing aid 0~1 part.

9. The polypropylene composition according to claim 8, wherein the polypropylene composition has a melt flow rate MFR2 (230 °C, 2.16 kg) of 0.5 to 5 g / 10 min. the processing aid comprises at least one of antioxidant and lubricant.

10. Process for the preparation of a polypropylene composition according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: adding the components into a screw extruder for melt extrusion granulation to obtain the polypropylene composition.

11. Use of the polypropylene composition according to any one of claims 1~9 in the preparation of a washing appliance.

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