Polypropylene composite material, door lock pull rod injection molded part and application thereof
By introducing fillers with negative thermal expansion and low humidity expansion into polypropylene composite materials, the dimensional instability problem of traditional polypropylene door lock rod materials under temperature and humidity changes is solved, achieving dimensional stability and mechanical strength in extreme environments and improving the reliability of door locks.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI MEILONGXIN PLASTIC MOULD ELECTRIC CO LTD
- Filing Date
- 2026-03-04
- Publication Date
- 2026-06-26
AI Technical Summary
Traditional polypropylene door lock levers are dimensionally unstable under temperature and humidity changes, causing them to jam or lock up. Existing improvements have failed to address the problem at its core.
Using polypropylene composite materials, including negative thermal expansion fillers such as rare earth tungstate, β-lithium nepheline, and aluminum titanate, and low moisture expansion fillers such as fumed silica, through modification treatment and specific proportions, a door lock pull rod injection molded part with stable dimensions under wide temperature range and humidity changes is prepared.
Under high temperature and high humidity or low temperature and low humidity environments, the diameter change rate of the door lock rod injection molded part is less than 5%, ensuring the reliability and service life of the door lock.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This application relates to the field of door lock rod material technology, specifically to a polypropylene composite material, a door lock rod injection molded part, and its application. Background Technology
[0002] As a core transmission component in mechanical door lock systems, the door lock lever precisely converts the torque of rotating the handle or key into the linear movement of the latch, directly affecting the operating feel, reliability, and lifespan of the door lock. Currently, door lock lever components are mainly made of polypropylene (PP) material through injection molding, which has advantages such as low cost, low density for lightweight design, and ease of processing, and can meet the basic functional requirements of door locks under normal conditions.
[0003] However, with the continuous expansion of the application areas of door lock products and the increasing complexity of the usage environment, the inherent defects of traditional flame-retardant PP pull rods have gradually become apparent. For example, since the linear thermal expansion coefficient of polypropylene material is usually higher than that of metal lock bodies and lock cylinders, the size of the pull rod will change with the fluctuation of ambient temperature and humidity. Especially in areas with large temperature differences between day and night or distinct seasonal climates, the precise fit between the plastic pull rod and the metal lock body will change due to thermal expansion and contraction, which can easily lead to malfunctions such as operation jamming, increased resistance, or even complete locking. In addition, since polypropylene material has a certain degree of hygroscopicity, the door lock pull rod products made from it may also deform due to moisture absorption and expansion in high humidity environments, causing malfunctions and affecting the user experience.
[0004] To address the aforementioned issues, the industry primarily improves door lock rod materials by increasing design tolerances, precisely controlling injection molding process parameters, or adding lubricating grease to metal contact areas. However, while these methods can alleviate the problems to some extent, they are reactive measures and fail to fundamentally resolve the dimensional instability caused by environmental changes.
[0005] Therefore, developing a new type of door lock rod material that can maintain high dimensional stability under wide temperature and humidity variations without sacrificing its mechanical strength and processing performance has become key to improving the environmental adaptability and reliability of mid-to-high-end door lock products. Summary of the Invention
[0006] To overcome the problems of poor dimensional stability of existing door lock rod materials under extreme conditions, which can easily cause door lock jamming or locking, this application provides a polypropylene composite material, a door lock rod injection molded part, and its application.
[0007] In a first aspect, this application provides a polypropylene composite material, which adopts the following technical solution: A polypropylene composite material comprising the following components in parts by weight: 90-110 parts of polypropylene resin, 15-25 parts of negative thermal expansion filler, 3-8 parts of low moisture expansion filler, 10-15 parts of reinforcing fiber, and 5-10 parts of other additives. The negative thermal expansion filler is selected from one or more of rare earth tungstates, β-lithium nepheline, and aluminum titanate; the negative thermal expansion filler is modified with a silane coupling agent at a temperature of 110-130℃ for 20-40 minutes; the amount of the silane coupling agent is 1-3 wt% of the negative thermal expansion filler. The low-moisture expansion filler has a specific surface area of 100-300 m². 2 / g of fumed silica.
[0008] This application utilizes polypropylene resin, negative thermal expansion filler, and low moisture expansion filler to prepare a polypropylene composite material with good environmental adaptability that is not easily deformed under high temperature and high humidity environments. This fundamentally solves the problem of dimensional instability caused by fluctuations in ambient temperature and humidity in existing traditional door lock rod materials. Specifically, the negative thermal expansion filler used in this application can generate a lattice contraction effect in the composite material, offsetting the thermal expansion of the polypropylene matrix and effectively preventing dimensional changes in the composite material. The low moisture expansion filler can reduce the hygroscopicity and moisture expansion of the composite material through physical barrier effects. Through the combined use of the above-mentioned negative thermal expansion filler and low moisture expansion filler, this application enables the door lock rod material to exhibit minimal gap changes with mating metal parts in a wide temperature range of -30℃ to 70℃ and a humidity range of 20-90% RH, effectively preventing problems such as door lock jamming or loosening and improving the reliability of door lock use. Furthermore, this application modifies the negative thermal expansion filler using a silane coupling agent at 110-130℃, which further improves the dispersibility of the negative thermal expansion filler in the resin matrix and the interfacial bonding force between the filler and the resin. Through synergistic reinforcement with reinforcing fibers, the composite material maintains good strength and toughness even with high filler content. In summary, the polypropylene composite material provided in this application has excellent dimensional stability, and the door lock pull rod injection molded parts made from it are not easily deformed in extreme and complex environments such as high temperature and high humidity, showing great application prospects.
[0009] In some embodiments, the negative thermal expansion filler is a mixture of rare earth tungstate and β-lithium nepheline.
[0010] In some embodiments, the weight ratio of the rare earth tungstate to β-nepheline is 1:(0.8-1.2).
[0011] In one specific embodiment, the weight ratio of the rare earth tungstate to β-lithium nepheline is 1:1.
[0012] Optionally, the low-moisture expansion filler has a specific surface area of 150-200 m². 2 / g of fumed silica.
[0013] In some embodiments, the specific surface area of the fumed silica can be 100-150 m². 2 / g, 100-180m 2 / g, 100-200m 2 / g, 100-300m 2 / g, 150-180m 2 / g, 150-200m 2 / g, 150-300m 2 / g、180-200m 2 / g、180-300m 2 / g or 200-300m 2 / g.
[0014] In one specific embodiment, the specific surface area of the fumed silica can be 100 m². 2 / g, 150m 2 / g、180m 2 / g、200m 2 / g or 300m 2 / g.
[0015] Optionally, the reinforcing fiber is chopped glass fiber with a length of 3-4 mm.
[0016] Optionally, the other additives are selected from one or more of compatibilizers, antioxidants, ultraviolet absorbers, and processing aids.
[0017] Optionally, the compatibilizer is maleic anhydride-grafted polypropylene; the antioxidant is a hindered phenolic antioxidant; the ultraviolet absorber is a benzotriazole ultraviolet absorber; and the processing aid is ethylene bis-stearamide or silicone masterbatch.
[0018] Secondly, this application provides a door lock lever injection molded part, which is injection molded from polypropylene composite material.
[0019] Optionally, the method for manufacturing the door lock lever injection molded part is as follows: Melt granulation: Mix all components of the composite material evenly and then melt extrude granulate; the extrusion temperature is: Zone 1 170±5℃, Zone 2 185±5℃, Zone 3 195±5℃, and die head 200±5℃; the screw speed is 280-310rpm, to obtain functional masterbatch with a particle size of 3-5mm. Injection molding: The dried functional masterbatch is injection molded. The barrel temperature is: 190±5℃ for the rear section, 205±5℃ for the middle section, 210±5℃ for the front section, and 205±5℃ for the nozzle; the mold temperature is 70-80℃; the injection speed is 10-40mm / s; and the injection pressure is 90-130MPa to obtain the door lock lever injection molded part.
[0020] Thirdly, this application provides the application of a door lock lever injection molded part in a door lock.
[0021] In summary, this application has the following beneficial effects: 1. This application uses one or more of rare earth tungstate, β-lithium nepheline, and aluminum titanate as negative thermal expansion fillers, and fumed silica as low humidity expansion fillers, and mixes them with polypropylene resin in a specific ratio. The injection-molded door lock rod has excellent dimensional stability. Its diameter change rate after being placed under high temperature and high humidity simulation conditions for 24 hours is only 1.31-3.75% (≤5%); and its diameter change rate after being placed under low temperature and dryness simulation conditions for 24 hours is only 0.78-2.88% (≤5%).
[0022] 2. This application further employs any two of rare earth tungstate, β-lithium nepheline, and aluminum titanate as negative thermal expansion fillers, and controls the specific surface area of fumed silica to be 150-200 m². 2 Within the range of / g, the obtained door lock lever injection molded parts have better dimensional stability. The diameter change rate after 24h under high temperature and high humidity simulation conditions is only 1.31-2.93% (≤3%), and the diameter change rate after 24h under low temperature and dryness simulation conditions is only 0.78-1.95% (≤2%). Detailed Implementation
[0023] This application provides a polypropylene composite material comprising the following components in parts by weight: 90-110 parts of polypropylene resin, 15-25 parts of negative thermal expansion filler, 3-8 parts of low moisture expansion filler, 10-15 parts of reinforcing fiber, 3-5 parts of compatibilizer, 0.5-1 part of antioxidant, 0.3-1 part of ultraviolet absorber, and 1-3 parts of processing aid. The low-moisture expansion filler has a specific surface area of 100-300 m². 2 / g of fumed silica; the negative thermal expansion filler is selected from one or more of rare earth tungstate, β-lithium nepheline, and aluminum titanate; the negative thermal expansion filler is modified with a silane coupling agent at a temperature of 110-130℃ for 20-40min; the amount of the silane coupling agent is 1-3wt% of the negative thermal expansion filler; the reinforcing fiber is chopped glass fiber with a length of 3-4mm.
[0024] This application also provides a door lock lever injection molded part, the preparation method of which includes the following steps: (1) Melt granulation: Polypropylene resin, negative thermal expansion filler, low moisture expansion filler, compatibilizer, antioxidant, ultraviolet absorber and processing aid are poured into a high-speed mixer and mixed at 300-500 rpm for 5-10 minutes to make the components initially dispersed evenly; then the mixture is fed into a twin-screw extruder, and the reinforcing fiber is introduced into the melt in the melting zone in the middle of the extruder through a side feeder. After melt extrusion granulation, water tank cooling and shaping, pelletizing by a pelletizer, and drying at 80-140℃ for 3-4 hours, functional masterbatch with a particle size of 3-5 mm is obtained; the temperature during melt extrusion granulation is: Zone 1 170±5℃, Zone 2 185±5℃, Zone 3 195±5℃, and die head 200±5℃; the screw speed is 280-310 rpm. (2) Injection molding: The functional masterbatch is placed in the injection molding machine and injected into a specific mold according to the following injection molding conditions. After holding pressure and cooling, the door lock pull rod injection molded part is obtained. During the injection molding process, the barrel temperature is: 190±5℃ for the rear section, 205±5℃ for the middle section, 210±5℃ for the front section, and 205±5℃ for the nozzle; the mold temperature is 70-80℃; the injection speed is 10-40mm / s; and the injection pressure is 90-130MPa.
[0025] In this application, the polypropylene resin is model K8003, purchased from Shanghai Liu Zhangyang Plastics Co., Ltd.; the rare earth tungstate is zirconium tungstate; β-lithium nepheline is purchased from Zibo Zhengxin Ceramic Technology Co., Ltd.; the silane coupling agent is KH550; and the low-moisture expansion filler has a specific surface area of 100 m². 2 / g, 150m 2 / g、180m 2 / g、200m 2 / g or 300m 2 / g of fumed silica; the reinforcing fiber is chopped glass fiber with a length of 3-4mm; the compatibilizer is maleic anhydride-grafted polypropylene, purchased from Dongguan Shengli New Materials Co., Ltd.; the antioxidant is hindered phenolic antioxidant 1010, purchased from Jiangsu Xinluda Polymer Materials Co., Ltd.; the ultraviolet absorber is benzotriazole ultraviolet absorber UV-327, purchased from Guangzhou Jingyi New Materials Co., Ltd.; the processing aid is ethylene bis-stearamide, purchased from Hubei Maidehao Biotechnology Co., Ltd.; the raw materials, reagents, solvents, etc. used in this application are all commercially available.
[0026] The following describes this application in further detail with reference to preparation examples, embodiments, and performance testing. Preparation Example 1
[0027] Preparation Example 1 provides a negative thermal expansion packing.
[0028] The negative thermal expansion filler in Example 1 is zirconium tungstate filler. The preparation method is as follows: 50g of zirconium tungstate filler is dried at 80℃ for 4h, and 0.5g of silane coupling agent is diluted with 100mL of ethanol. The ethanol dilution of silane coupling agent and the dried zirconium tungstate filler are added to a high-speed mixer and mixed at 400rpm for 10min. Then the mixture is reacted at 120℃ for 30min and dried to obtain zirconium tungstate filler. Preparation Example 2
[0029] Preparation Example 2 provides a negative thermal expansion packing.
[0030] The negative thermal expansion filler in Preparation Example 2 is zirconium tungstate filler, which differs from Preparation Example 1 in that the amount of silane coupling agent used is 1g. Preparation Example 3
[0031] Preparation Example 3 provides a negative thermal expansion packing.
[0032] The negative thermal expansion filler in Preparation Example 3 was zirconium tungstate filler, which differed from Preparation Example 1 in that the amount of silane coupling agent used was 1.5g. Preparation Example 4
[0033] Preparation Example 4 provides a negative thermal expansion packing.
[0034] The negative thermal expansion filler in Preparation Example 4 was β-lithium nepheline filler, which differed from Preparation Example 2 in that zirconium tungstate filler was replaced with an equal amount of β-lithium nepheline. Preparation Example 5
[0035] Preparation Example 5 provides a negative thermal expansion packing.
[0036] The negative thermal expansion filler in Preparation Example 5 is aluminum titanate, which differs from Preparation Example 2 in that the zirconium tungstate filler is replaced with an equal amount of aluminum titanate. Examples 1-5
[0037] Examples 1-5 each provide a door lock lever injection molded part.
[0038] The difference between the above embodiments is that the negative thermal expansion filler is derived from preparation examples 1-5.
[0039] The method for preparing the door lock lever injection molded part provided in Examples 1-5 includes the following steps: (1) Melt granulation: 100g of polypropylene resin, 20g of negative thermal expansion filler, and 5g of filler with a specific surface area of 180m² are melt-granulated. 2 / g of fumed silica, 4g of compatibilizer, 1g of antioxidant, 0.5g of UV absorber, and 2g of processing aid are added together into a high-speed mixer and mixed at 400rpm for 10min to initially disperse the components evenly. The mixture is then fed into a twin-screw extruder, while 15g of reinforcing fiber is introduced into the melt in the central melting zone of the extruder via a side feeder. After melt extrusion granulation, water cooling and shaping, and pelletizing, the mixture is dried at 120℃ for 4h to obtain functional masterbatch with a particle size of 5mm. The temperatures during melt extrusion granulation are: Zone 1 170℃, Zone 2 185℃, Zone 3 195℃, and die head 200℃; the screw speed is 300rpm. (2) Injection molding: The functional masterbatch is placed in the injection molding machine and injected into a specific mold according to the following injection molding conditions. After holding pressure and cooling, the door lock lever injection molded part is obtained. During the injection molding process, the barrel temperature is: 190℃ in the rear section, 205℃ in the middle section, 210℃ in the front section, and 205℃ in the nozzle; the mold temperature is 70-80℃; the injection speed is 30mm / s; and the injection pressure is 100MPa. Example 6
[0040] Example 6 provides a door lock lever injection molded part.
[0041] The difference between the above embodiment and Embodiment 2 is that the negative thermal expansion filler is a mixture of zirconium tungstate filler and β-lithium nepheline filler in a weight ratio of 1:1. Example 7
[0042] Example 7 provides a door lock lever injection molded part.
[0043] The difference between the above embodiment and embodiment 2 is that the negative thermal expansion filler is a mixture of zirconium tungstate filler and aluminum titanate in a weight ratio of 1:1. Example 8
[0044] Example 8 provides a door lock lever injection molded part.
[0045] The difference between the above embodiment and Embodiment 2 is that the negative thermal expansion filler is a mixture of aluminum titanate and β-lithium nepheline filler in a weight ratio of 1:1. Example 9
[0046] Example 9 provides a door lock lever injection molded part.
[0047] The difference between the above embodiment and Embodiment 2 is that the specific surface area of fumed silica is 100 m². 2 / g. Example 10
[0048] Example 10 provides a door lock lever injection molded part.
[0049] The difference between the above embodiment and Embodiment 2 is that the specific surface area of fumed silica is 150 m². 2 / g. Example 11
[0050] Example 11 provides a door lock lever injection molded part.
[0051] The difference between the above embodiment and Embodiment 2 is that the specific surface area of fumed silica is 200 m². 2 / g. Example 12
[0052] Example 12 provides a door lock lever injection molded part.
[0053] The difference between the above embodiment and Embodiment 2 is that the specific surface area of fumed silica is 300 m². 2 / g. Example 13
[0054] Example 13 provides a door lock lever injection molded part.
[0055] The difference between the above embodiment and Embodiment 2 is that the amount of some components added is as follows: the amount of negative thermal expansion filler added is 15g, the amount of low moisture expansion filler added is 8g, and the amount of reinforcing fiber added is 10g. Example 14
[0056] Example 14 provides a door lock lever injection molded part.
[0057] The difference between the above embodiment and Embodiment 2 is that the amount of some components added is as follows: the amount of negative thermal expansion filler added is 25g, the amount of low moisture expansion filler added is 3g, and the amount of reinforcing fiber added is 15g. Comparative Example 1
[0058] Comparative Example 1 provides a door lock lever injection molded part.
[0059] The difference between the above comparative example and Example 2 is that the amount of some components added is as follows: the amount of negative thermal expansion filler added is 8g, the amount of low moisture expansion filler added is 12g, and the amount of reinforcing fiber added is 20g. Comparative Example 2
[0060] Comparative Example 2 provides a door lock lever injection molded part.
[0061] The difference between the above comparative example and Example 2 is that the amount of some components added is as follows: the amount of negative thermal expansion filler added is 0g, the amount of low moisture expansion filler added is 25g, and the amount of reinforcing fiber added is 15g. Comparative Example 3
[0062] Comparative Example 3 provides a door lock lever injection molded part.
[0063] The difference between the above comparative example and Example 2 is that the amount of some components added is as follows: the amount of negative thermal expansion filler added is 25g, the amount of low moisture expansion filler added is 0g, and the amount of reinforcing fiber added is 15g. Performance testing
[0064] The dimensional stability of the door lock pull rod injection molded parts of Examples 1-14 and Comparative Examples 1-3 was tested, and the results are shown in Table 1 below. The experimental procedure is as follows: (1) Standard injection molded parts of door lock rods were prepared according to the methods of Examples 1-14 and Comparative Examples 1-3 (as shown in Figure 1). 15 parts were prepared in parallel for each example, divided into 3 groups of 5 parts each.
[0065] (2) Before the experiment, use vernier calipers to accurately measure the diameter of the middle section of the standard injection molded part of the door lock lever. Measure 3 times at different positions and take the average value as D0. (2) Place the standard injection molded parts of each door lock lever in a simulation test chamber for simulated extreme environment testing. After the simulation time is over, quickly measure the diameter of the standard injection molded parts of the door lock lever inside the chamber. Measure three times at different positions and take the average value as D1. Group 1: Standard condition test chamber (23℃, 50% RH) for 12 hours; Group 2: High temperature and high humidity test chamber (70℃, 90% RH) for 24 hours; Group 3: Low temperature and low humidity test chamber (-30℃, 20% RH) for 24 hours; (3) Calculate the diameter change rate Q of each door lock rod injection molded standard part before and after the simulation experiment, and take the average value of each group; the formula for calculating the diameter change rate Q is: Q (expansion) = (D1-D0) / D0×100% or Q (shrinkage) = (D0-D1) / D0×100%.
[0066] Table 1. Performance test results of the door lock lever injection molded parts of Examples 1-14 and Comparative Examples 1-3
[0067] According to the test results in Table 1, the diameter change rate of the door lock pull rod injection molded parts obtained in Examples 1-14 after being placed under high temperature and high humidity simulation conditions for 24 hours was 1.31-3.75%; the diameter change rate after being placed under low temperature and dryness simulation conditions for 24 hours was 0.78-2.88%. Therefore, this application demonstrates that by using one or more of rare earth tungstate, β-lithium nepheline, and aluminum titanate as negative thermal expansion fillers, and fumed silica as low humidity expansion fillers, and mixing them with polypropylene resin in a specific ratio, the injection-molded door lock pull rod parts obtained possess excellent dimensional stability. They are not easily deformed under high temperature and low temperature, and high humidity and low humidity environments, and can meet the requirements of high-end door locks.
[0068] The diameter change rate of the door lock lever injection molded part obtained by Comparative Example 1 after being placed under high temperature and high humidity simulation conditions for 24 hours was as high as 6.39%; the diameter change rate after being placed under low temperature and dryness simulation conditions for 24 hours was as high as 4.26%, indicating that the composition ratio of Comparative Example 1 was not good, especially the amount of negative thermal expansion filler added was too small, resulting in poor dimensional stability of the door lock lever injection molded part under high temperature and high humidity and low temperature and low humidity conditions.
[0069] The diameter change rate of the door lock pull rod injection molded parts obtained by Comparative Example 2-3 after being placed under high temperature and high humidity simulation conditions for 24 hours was as high as 3.83-10.71%; the diameter change rate after being placed under low temperature and dryness simulation conditions for 24 hours was as high as 4.26-6.35%. This indicates that the dimensional stability of the door lock pull rod injection molded parts obtained by Comparative Example 2-3 without the addition of negative thermal expansion filler or low humidity expansion filler is very poor, and they are prone to deformation under extreme environments.
[0070] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A polypropylene composite material, characterized in that, It includes the following components in parts by weight: 90-110 parts of polypropylene resin, 15-25 parts of negative thermal expansion filler, 3-8 parts of low moisture expansion filler, 10-15 parts of reinforcing fiber, and 5-10 parts of other additives. The negative thermal expansion filler is selected from one or more of rare earth tungstates, β-lithium nepheline, and aluminum titanate; the negative thermal expansion filler is modified with a silane coupling agent at a temperature of 110-130℃ for 20-40 minutes; the amount of the silane coupling agent is 1-3 wt% of the negative thermal expansion filler. The low-moisture expansion filler has a specific surface area of 100-300 m². 2 / g of fumed silica.
2. The polypropylene composite material according to claim 1, characterized in that, The low-moisture expansion filler has a specific surface area of 150-200 m². 2 / g of fumed silica.
3. The polypropylene composite material according to claim 1, characterized in that, The reinforcing fiber is chopped glass fiber with a length of 3-4 mm.
4. The polypropylene composite material according to claim 1, characterized in that, The other additives are selected from one or more of compatibilizers, antioxidants, ultraviolet absorbers, and processing aids.
5. The polypropylene composite material according to claim 4, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene; the antioxidant is a hindered phenolic antioxidant; the ultraviolet absorber is a benzotriazole ultraviolet absorber; and the processing aid is ethylene bis-stearamide or silicone masterbatch.
6. A door lock pull rod injection molded part, characterized in that, It is injection molded using the polypropylene composite material according to any one of claims 1-5.
7. The door lock pull rod injection molded part according to claim 6, characterized in that, The method for preparing the door lock pull rod injection molded part is as follows: Melt granulation: Mix all components of the composite material evenly and then melt extrude granulate; the extrusion temperature is: Zone 1 170±5℃, Zone 2 185±5℃, Zone 3 195±5℃, and die head 200±5℃; the screw speed is 280-310rpm, to obtain functional masterbatch with a particle size of 3-5mm. Injection molding: The dried functional masterbatch is injection molded. The barrel temperature is: 190±5℃ for the rear section, 205±5℃ for the middle section, 210±5℃ for the front section, and 205±5℃ for the nozzle; the mold temperature is 70-80℃; the injection speed is 10-40mm / s; and the injection pressure is 90-130MPa to obtain the door lock lever injection molded part.
8. The application of a door lock lever injection molded part as described in claim 6 or 7 in a door lock.