A silicone oil modified polypropylene composite material and a preparation method thereof

Abstract

This invention relates to the field of polypropylene technology, specifically to a silicone oil-modified polypropylene composite material and its preparation method. The material undergoes a stepwise pre-reaction process: first, aminopropyl-terminated polydimethylsiloxane reacts with maleic anhydride-grafted polypropylene to form an internally anchored organosilicon phase; then, it reacts with 2,4-dihydroxybenzophenone, hydroxyethoxypropyl-terminated polydimethylsiloxane, and tetrabutyl titanate to construct an anti-UV interface layer. Simultaneously, 2-hydroxy-4-n-octyloxybenzophenone is pre-dispersed in hydroxyethoxypropyl-terminated polydimethylsiloxane and added after the formation of the main melt along with a hindered amine light stabilizer, forming a lubricating-light-absorbing composite functional phase on the surface. This composite material maintains a stable coefficient of friction, low surface roughness, minimal color change, and high mechanical property retention even after long-term UV exposure, making it suitable for outdoor components requiring long-term self-lubrication and weather resistance.

Description

Technical Field

[0001] This invention relates to the field of polypropylene technology, and in particular to a silicone oil-modified polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene (PP) materials are widely used in fields such as outdoor equipment and automotive exteriors, where materials are exposed to sunlight for extended periods, due to their excellent overall performance and cost advantages. However, PP itself has poor resistance to ultraviolet (UV) aging. Under prolonged sunlight exposure, it is prone to molecular chain breakage and surface oxidation, leading to embrittlement, discoloration, surface roughening, and even cracking, severely affecting its service life and appearance. To improve weather resistance, a common practice is to add UV absorbers and hindered amine light stabilizers to PP. For example, the technology disclosed in CN102040767B, which involves co-extruding various stabilizing agents with PP, can delay material aging to some extent. However, this technology mainly focuses on maintaining the basic mechanical properties and color of the material, without fully considering the impact on the surface characteristics. Especially for moving parts subject to friction and wear, changes in the surface state directly affect performance.

[0003] On the other hand, to reduce the coefficient of friction of polypropylene and achieve self-lubrication, the industry typically employs methods such as direct blending with lubricants like silicone oil, as disclosed in CN101696302A. This method can effectively reduce frictional resistance in the initial stage, but simply blended silicone oil has poor compatibility with polypropylene and is prone to migration and precipitation during processing and use, resulting in insufficient durability of the lubrication effect. More importantly, when such self-lubricating materials are exposed to outdoor sunlight, the photo-oxidative degradation of the material surface and the migration and loss of lubricant mutually exacerbate each other: microcracks and roughening formed by surface oxidation disrupt the continuity of the lubricating film, accelerating lubrication failure; while the loss or changes in the distribution of lubricating components may expose the matrix more directly to ultraviolet light, accelerating the aging process.

[0004] Therefore, existing weather-resistant modification and self-lubricating modification technologies are relatively independent. Simply combining them—i.e., attempting to directly add a weather-resistant stabilizer system to self-lubricating polypropylene—often fails to achieve synergistic effects. Additives with different properties may interfere with each other during processing, affecting dispersion and final positioning; their effects may also be mutually restrictive. For example, the lubricating phase migrating to the surface may hinder the enrichment and function of UV absorbers on the surface, while some stabilizers may also affect the interfacial behavior of the lubricating phase. The resulting material often fails to meet expectations in terms of long-term tribological performance, surface integrity, and mechanical property retention after light exposure, thus failing to satisfy the demands of outdoor applications requiring long-term, stable self-lubrication. The fundamental problem lies in the failure to construct a microstructure that allows lubrication and anti-photoaging functions to coexist and synergistically function within and on the surface of the material over a long period. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a silicone oil modified polypropylene composite material and its preparation method, so as to overcome the defects of the prior art in which the lubrication performance and light aging resistance of polypropylene materials are difficult to balance, and the lubrication performance drops sharply after light exposure, and to provide a composite material that can maintain low friction, low wear and good surface integrity before and after light exposure.

[0006] To achieve the above objectives, the present invention provides a silicone oil-modified polypropylene composite material, which is prepared from the following raw materials in parts by mass: 760-850 parts polypropylene;

[0007] The pre-reactant is prepared by pre-reacting 120-180 parts of maleic anhydride-grafted polypropylene and 3-8 parts of aminopropyl-terminated polydimethylsiloxane, followed by further pre-reaction with 4-8 parts of 2,4-dihydroxybenzophenone, 8-12 parts of hydroxyethoxypropyl-terminated polydimethylsiloxane and 0.8-1.2 parts of tetrabutyl titanate.

[0008] A mobile dispersion formed by pre-dispersing 12-20 parts of hydroxyethoxypropyl-terminated polydimethylsiloxane and 4-10 parts of 2-hydroxy-4-n-octyloxybenzophenone; 4-8 parts hindered amine light stabilizer; 0.8-1.2 parts hindered phenolic antioxidant; and 0.8-1.2 parts phosphite antioxidant.

[0009] Preferably, the maleic anhydride-grafted polypropylene and the aminopropyl-terminated polydimethylsiloxane are pre-reacted under nitrogen protection at 175-185°C and 55-70 rpm, wherein the maleic anhydride-grafted polypropylene is first melted for 2 min, and then the aminopropyl-terminated polydimethylsiloxane is added dropwise within 1 min, and the mixing continues for 5-7 min.

[0010] Preferably, the further pre-reaction is carried out under nitrogen protection at 188-195°C and 55-65 rpm, wherein the 2,4-dihydroxybenzophenone is added first and mixed for 1.5-2.5 min, then the hydroxyethoxypropyl-terminated polydimethylsiloxane and the tetrabutyl titanate are added and mixed for another 5-7 min, and then maintained at -0.075±0.005 MPa for 1.5-2.5 min.

[0011] Preferably, the fluid dispersion is obtained by heating the hydroxyethoxypropyl-terminated polydimethylsiloxane to 78-85°C, adding the 2-hydroxy-4-n-octyloxybenzophenone, and continuing to stir for 15-25 minutes.

[0012] Preferably, the hindered amine light stabilizer is Tinuvin 770 DF, the hindered phenolic antioxidant is Irganox 1010, and the phosphite antioxidant is Irgafos 168.

[0013] Preferably, the polypropylene is PPH-T03, the maleic anhydride-grafted polypropylene is EPOLENE E-43P, the aminopropyl-terminated polydimethylsiloxane is DMS-A32, and the hydroxyethoxypropyl-terminated polydimethylsiloxane is MCR-C18.

[0014] Furthermore, the present invention also provides a method for preparing a silicone oil-modified polypropylene composite material, comprising the following steps: (1) After heating hydroxyethoxypropyl-terminated polydimethylsiloxane, 2-hydroxy-4-n-octyloxybenzophenone was added and stirred to obtain a mobile dispersion; (2) Under nitrogen protection, maleic anhydride-grafted polypropylene is pre-reacted with aminopropyl-terminated polydimethylsiloxane to obtain the first pre-reaction material; (3) The first pre-reactant is further pre-reacted with 2,4-dihydroxybenzophenone, hydroxyethoxypropyl-terminated polydimethylsiloxane and tetrabutyl titanate to obtain the second pre-reactant; (4) Polypropylene, the second pre-reactant, hindered phenol antioxidant and phosphite antioxidant are melt-extruded, and hindered amine light stabilizer and the flow dispersion are added after forming a continuous melt. The mixture is then extruded and granulated to obtain the silicone oil modified polypropylene composite material.

[0015] Preferably, in step (4), the melt extrusion adopts a co-rotating twin-screw extruder with temperature zones of 173-178℃, 178-183℃, 183-188℃, 188-193℃, 193-198℃, 198-203℃, 198-203℃ and 193-198℃ respectively, and the screw speed is 210-235 rpm; after a continuous melt is formed in zone 4, the hindered amine light stabilizer is side-fed in zone 5, the flowing dispersion is added at the liquid injection port in zone 6, and vacuum degassing is performed in zone 7.

[0016] The beneficial effects of this invention are: First, by pre-reacting aminopropyl-terminated polydimethylsiloxane with maleic anhydride-grafted polypropylene, a chemically anchored organosilicon phase is formed within the material. This structure serves as a foundation, providing not only initial lubrication but, more importantly, laying the groundwork for the subsequent construction of a more stable interface layer and preventing rapid loss of silicone oil.

[0017] Secondly, in the second pre-reaction stage, 2,4-dihydroxybenzophenone is first introduced, followed by hydroxyethoxypropyl-terminated polydimethylsiloxane and tetrabutyl titanate. This stepwise operation facilitates the construction of an interface layer with both flexibility and UV resistance around the anchored organosilicon phase. This interface layer can effectively block ultraviolet light from penetrating deep into the internal matrix, reducing photoaging of the main material. At the same time, its flexibility helps to buffer stress and maintain surface integrity.

[0018] Finally, by pre-dispersing 2-hydroxy-4-n-octyloxybenzophenone in hydroxyethoxypropyl-terminated polydimethylsiloxane added later and injecting it after the main melt is formed, a lubricating-light-absorbing composite functional phase is formed on the outermost layer of the material in synergy with a side-fed hindered amine light stabilizer. This composite phase preferentially accumulates on the surface, providing continuous lubrication while efficiently absorbing and dissipating ultraviolet light energy, maximizing the protection of the surface from photo-oxidative damage, thereby maintaining the continuity of the lubricating film and the smoothness of the surface over a long period.

[0019] In summary, this invention enables the material to achieve excellent initial self-lubricating properties while significantly improving its resistance to light aging, ensuring stable friction coefficient, minimal color change, low surface roughness, and high mechanical property retention after long-term ultraviolet irradiation. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0021] Raw material source and model: Polypropylene was purchased from Sinopec, model PPH-T03 (T30S); maleic anhydride-grafted polypropylene was purchased from Westlake, model EPOLENE E-43P; aminopropyl-terminated polydimethylsiloxane was purchased from Gelest, model DMS-A32; hydroxyethoxypropyl-terminated polydimethylsiloxane was purchased from Gelest, model MCR-C18; 2,4-dihydroxybenzophenone was purchased from Tokyo Chemical Industry Co., Ltd., model D0573; 2-hydroxy-4-n-octyloxybenzophenone was purchased from Tokyo Chemical Industry Co., Ltd., model H0288; hindered amine light stabilizer was purchased from BASF, model Tinuvin 770 DF; hindered phenolic antioxidant was purchased from BASF, model Irganox 1010; phosphite antioxidant was purchased from BASF, model Irgafos. 168; Tetrabutyl titanate was purchased from Sigma-Aldrich, model number 244112.

[0022] Example 1: Step 1: Place 800g of polypropylene and 150g of maleic anhydride-grafted polypropylene in an 80℃ vacuum drying oven and dry for 4 hours; place 6g of 2,4-dihydroxybenzophenone, 6g of 2-hydroxy-4-n-octyloxybenzophenone, 6g of hindered amine light stabilizer, 1g of hindered phenol antioxidant and 1g of phosphite antioxidant in a 60℃ vacuum drying oven and dry for 2 hours; heat 15g of hydroxyethoxypropyl-terminated polydimethylsiloxane to 80℃ and stir, slowly add 6g of 2-hydroxy-4-n-octyloxybenzophenone, continue stirring for 20 minutes to obtain a flowing dispersion, and seal for later use.

[0023] Step 2: Under nitrogen protection, 150g of maleic anhydride-grafted polypropylene was added to a torque rheostat mixer and melted at 180℃ and 60rpm for 2min; then 5g of aminopropyl-terminated polydimethylsiloxane was added dropwise over 1min, and the mixture was continued to be mixed for 6min. The mixture was then discharged, cooled, and pelletized to obtain the first pre-reaction material.

[0024] Step 3: Add all the first pre-reacted material obtained in Step 2 back into the torque rheostat mixer and mix for 2 min at 190℃, 60 rpm, and nitrogen protection; first add 6 g of 2,4-dihydroxybenzophenone and mix for 2 min, then add 10 g of hydroxyethoxypropyl-terminated polydimethylsiloxane and 1 g of tetrabutyl titanate, and continue mixing for 6 min; then vacuum to -0.08 MPa at 190℃ and maintain for 2 min, discharge, cool, and pelletize to obtain the second pre-reacted material;

[0025] Step 4: Final reactive extrusion is performed using a co-rotating twin-screw extruder. The temperature zones are set sequentially to 175℃, 180℃, 185℃, 190℃, 195℃, 200℃, 200℃, and 195℃, with the screw speed set to 220 rpm. 800g of polypropylene, all of the second pre-reactant obtained in Step 3, 1g of hindered phenolic antioxidant, and 1g of phosphite antioxidant are added to the main feed port. After a continuous melt is formed in Zone 4, 6g of hindered amine light stabilizer is added to the side feed port in Zone 5. All of the flowing dispersion prepared in Step 1 is added to the liquid injection port in Zone 6. Vacuum exhaust is activated in Zone 7, with the vacuum level controlled at -0.09MPa. The melt is extruded through the die head, water-cooled, and pelletized to obtain the silicone oil-modified polypropylene composite material.

[0026] Example 2: Step 1: Place 850g of polypropylene and 120g of maleic anhydride-grafted polypropylene in a vacuum drying oven at 78℃ and dry for 3 hours; place 4g of 2,4-dihydroxybenzophenone, 4g of 2-hydroxy-4-n-octyloxybenzophenone, 4g of hindered amine light stabilizer, 0.8g of hindered phenolic antioxidant and 0.8g of phosphite antioxidant in a vacuum drying oven at 58℃ and dry for 2 hours; heat 12g of hydroxyethoxypropyl-terminated polydimethylsiloxane to 78℃ and stir, slowly add 4g of 2-hydroxy-4-n-octyloxybenzophenone, continue stirring for 15 minutes to obtain a flowing dispersion, and seal for later use.

[0027] Step 2: Under nitrogen protection, 120g of maleic anhydride-grafted polypropylene was added to a torque rheostat mixer and melted for 2 minutes at 175℃ and 55rpm. Then, 3g of aminopropyl-terminated polydimethylsiloxane was added dropwise over 1 minute, and the mixture was continued to be mixed for 5 minutes. The mixture was then discharged, cooled, and pelletized to obtain the first pre-reaction material.

[0028] Step 3: Add all the first pre-reacting material obtained in Step 2 back into the torque rheostat mixer and mix for 2 minutes at 188°C, 55 rpm, and nitrogen protection. First, add 4 g of 2,4-dihydroxybenzophenone and mix for 1.5 minutes, then add 8 g of hydroxyethoxypropyl-terminated polydimethylsiloxane and 0.8 g of tetrabutyl titanate, and continue mixing for 5 minutes. Then, vacuum the mixture to -0.07 MPa at 188°C and maintain it for 1.5 minutes. Discharge, cool, and pelletize to obtain the second pre-reacting material.

[0029] Step 4: Final reactive extrusion is performed using a co-rotating twin-screw extruder. The temperature zones are set sequentially to 173℃, 178℃, 183℃, 188℃, 193℃, 198℃, 198℃, and 193℃, with a screw speed of 210 rpm. 850g of polypropylene, all of the second pre-reactant obtained in Step 3, 0.8g of hindered phenolic antioxidant, and 0.8g of phosphite antioxidant are added to the main feed port. After a continuous melt is formed in Zone 4, 4g of hindered amine light stabilizer is added to the side feed port in Zone 5. All of the flowing dispersion prepared in Step 1 is added to the liquid injection port in Zone 6. Vacuum exhaust is activated in Zone 7, with the vacuum level controlled at -0.08 MPa. The melt is extruded through the die head, water-cooled, and pelletized to obtain the silicone oil-modified polypropylene composite material.

[0030] Example 3: Step 1: Place 820g of polypropylene and 140g of maleic anhydride-grafted polypropylene in a vacuum drying oven at 79℃ and dry for 3.5h; place 5g of 2,4-dihydroxybenzophenone, 5g of 2-hydroxy-4-n-octyloxybenzophenone, 5g of hindered amine light stabilizer, 0.9g of hindered phenol antioxidant and 0.9g of phosphite antioxidant in a vacuum drying oven at 59℃ and dry for 2h; heat 13g of hydroxyethoxypropyl-terminated polydimethylsiloxane to 79℃ and stir, slowly add 5g of 2-hydroxy-4-n-octyloxybenzophenone, continue stirring for 18min to obtain a flowing dispersion, and seal for later use.

[0031] Step 2: Under nitrogen protection, 140g of maleic anhydride-grafted polypropylene was added to a torque rheostat mixer and melted for 2 minutes at 178℃ and 58rpm. Then, 4g of aminopropyl-terminated polydimethylsiloxane was added dropwise over 1 minute, and the mixture was continued to be mixed for 5.5 minutes. The mixture was then discharged, cooled, and pelletized to obtain the first pre-reaction material.

[0032] Step 3: Add all the first pre-reacting material obtained in Step 2 back into the torque rheostat mixer and mix for 2 min at 189°C, 58 rpm, and nitrogen protection. First, add 5 g of 2,4-dihydroxybenzophenone and mix for 2 min, then add 9 g of hydroxyethoxypropyl-terminated polydimethylsiloxane and 0.9 g of tetrabutyl titanate, and continue mixing for 5.5 min. Then, vacuum the mixture to -0.075 MPa at 189°C and maintain it for 2 min. Discharge, cool, and pelletize to obtain the second pre-reacting material.

[0033] Step 4: Final reactive extrusion is performed using a co-rotating twin-screw extruder. The temperature zones are set sequentially to 174℃, 179℃, 184℃, 189℃, 194℃, 199℃, 199℃, and 194℃, with the screw speed set to 215 rpm. 820g of polypropylene, all of the second pre-reactant obtained in Step 3, 0.9g of hindered phenolic antioxidant, and 0.9g of phosphite antioxidant are added to the main feed port. After a continuous melt is formed in Zone 4, 5g of hindered amine light stabilizer is added to the side feed port in Zone 5. All of the flowing dispersion prepared in Step 1 is added to the liquid injection port in Zone 6. Vacuum exhaust is activated in Zone 7, with the vacuum level controlled at -0.085MPa. The melt is extruded through the die head, water-cooled, and pelletized to obtain the silicone oil-modified polypropylene composite material.

[0034] Example 4: Step 1: Place 780g of polypropylene and 170g of maleic anhydride-grafted polypropylene in a vacuum drying oven at 82℃ and dry for 4.5h; place 7g of 2,4-dihydroxybenzophenone, 8g of 2-hydroxy-4-n-octyloxybenzophenone, 7g of hindered amine light stabilizer, 1.1g of hindered phenol antioxidant and 1.1g of phosphite antioxidant in a vacuum drying oven at 62℃ and dry for 2.5h; heat 17g of hydroxyethoxypropyl-terminated polydimethylsiloxane to 82℃ and stir, slowly add 8g of 2-hydroxy-4-n-octyloxybenzophenone, continue stirring for 22min to obtain a flowing dispersion, and seal for later use.

[0035] Step 2: Under nitrogen protection, 170g of maleic anhydride-grafted polypropylene was added to a torque rheostat mixer and melted at 182℃ and 63rpm for 2min; then 6g of aminopropyl-terminated polydimethylsiloxane was added dropwise over 1min, and the mixture was continued to be mixed for 6.5min. The mixture was then discharged, cooled, and pelletized to obtain the first pre-reaction material.

[0036] Step 3: Add all the first pre-reacting material obtained in Step 2 back into the torque rheostat mixer and mix for 2 min at 192℃, 62 rpm, and nitrogen protection. First, add 7 g of 2,4-dihydroxybenzophenone and mix for 2 min, then add 11 g of hydroxyethoxypropyl-terminated polydimethylsiloxane and 1.1 g of tetrabutyl titanate, and continue mixing for 6.5 min. Subsequently, vacuum the mixture to -0.085 MPa at 192℃ and maintain it for 2 min, then discharge, cool, and pelletize to obtain the second pre-reacting material.

[0037] Step 4: Final reactive extrusion is performed using a co-rotating twin-screw extruder. The temperature zones are set sequentially to 176℃, 181℃, 186℃, 191℃, 196℃, 201℃, 201℃, and 196℃, with a screw speed of 230 rpm. 780g of polypropylene, all of the second pre-reactant obtained in Step 3, 1.1g of hindered phenolic antioxidant, and 1.1g of phosphite antioxidant are added to the main feed port. After a continuous melt is formed in Zone 4, 7g of hindered amine light stabilizer is added to the side feed port in Zone 5. All of the flowing dispersion prepared in Step 1 is added to the liquid injection port in Zone 6. Vacuum exhaust is activated in Zone 7, with the vacuum level controlled at -0.09 MPa. The melt is extruded through the die head, water-cooled, and pelletized to obtain the silicone oil-modified polypropylene composite material.

[0038] Example 5: Step 1: Place 760g of polypropylene and 180g of maleic anhydride-grafted polypropylene in an 85℃ vacuum drying oven and dry for 5 hours; place 8g of 2,4-dihydroxybenzophenone, 10g of 2-hydroxy-4-n-octyloxybenzophenone, 8g of hindered amine light stabilizer, 1.2g of hindered phenol antioxidant and 1.2g of phosphite antioxidant in a 65℃ vacuum drying oven and dry for 2.5 hours; heat 20g of hydroxyethoxypropyl-terminated polydimethylsiloxane to 85℃ and stir, slowly add 10g of 2-hydroxy-4-n-octyloxybenzophenone, continue stirring for 25 minutes to obtain a flowing dispersion, and seal for later use.

[0039] Step 2: Under nitrogen protection, 180g of maleic anhydride-grafted polypropylene was added to a torque rheostat mixer and melted at 185℃ and 70rpm for 2min; then 8g of aminopropyl-terminated polydimethylsiloxane was added dropwise over 1min, and the mixture was continued to be mixed for 7min. The mixture was then discharged, cooled, and pelletized to obtain the first pre-reaction material.

[0040] Step 3: Add all the first pre-reacting material obtained in Step 2 back into the torque rheostat mixer and mix for 2 min at 195℃, 65 rpm, and nitrogen protection; first add 8 g of 2,4-dihydroxybenzophenone and mix for 2.5 min, then add 12 g of hydroxyethoxypropyl-terminated polydimethylsiloxane and 1.2 g of tetrabutyl titanate, and continue mixing for 7 min; then vacuum to -0.09 MPa at 195℃ and maintain for 2.5 min, discharge, cool, and pelletize to obtain the second pre-reacting material;

[0041] Step 4: Final reactive extrusion is performed using a co-rotating twin-screw extruder. The temperature zones are set sequentially to 178℃, 183℃, 188℃, 193℃, 198℃, 203℃, 203℃, and 198℃, with a screw speed of 235 rpm. 760g of polypropylene, all of the second pre-reactant obtained in Step 3, 1.2g of hindered phenolic antioxidant, and 1.2g of phosphite antioxidant are added to the main feed port. After a continuous melt is formed in Zone 4, 8g of hindered amine light stabilizer is added to the side feed port in Zone 5. All of the flowing dispersion prepared in Step 1 is added to the liquid injection port in Zone 6. Vacuum exhaust is activated in Zone 7, with the vacuum level controlled at -0.095MPa. The melt is extruded through the die head, water-cooled, and pelletized to obtain the silicone oil-modified polypropylene composite material.

[0042] Comparative Example 1: The difference from Example 1 is that 5g of aminopropyl-terminated polydimethylsiloxane is not added in step 2; and to maintain a consistent total feed amount, an additional 5g of polypropylene is added to the main feed inlet in step 4. All other conditions are the same as in Example 1.

[0043] Comparative Example 2: The difference from Example 1 is that: in step 2, the pre-reaction of 150g of maleic anhydride-grafted polypropylene and 5g of aminopropyl-terminated polydimethylsiloxane is not performed; in step 2, only 150g of maleic anhydride-grafted polypropylene is mixed at 180°C, 60rpm, and nitrogen protection for 9 minutes, then discharged, cooled, and pelletized to obtain the first pre-reaction material; the 5g of aminopropyl-terminated polydimethylsiloxane is replaced by adding 800g of polypropylene, all of the second pre-reaction material obtained in step 3, 1g of hindered phenolic antioxidant, and 1g of phosphite antioxidant simultaneously at the main feed port in step 4. All other conditions are the same as in Example 1.

[0044] Comparative Example 3: The difference from Example 1 is that the amount of aminopropyl-terminated polydimethylsiloxane added in step 2 is changed from 5g to 10g; and to maintain a consistent total feed amount, 5g less polypropylene is added at the main feed inlet in step 4. All other conditions are the same as in Example 1.

[0045] Comparative Example 4: The difference from Example 1 is as follows: In step 3, after mixing at 190°C, 60 rpm, and nitrogen protection for 2 minutes, 6 g of 2,4-dihydroxybenzophenone, 10 g of hydroxyethoxypropyl-terminated polydimethylsiloxane, and 1 g of tetrabutyl titanate were added simultaneously, and mixing continued for 8 minutes; subsequently, a vacuum was drawn to -0.08 MPa at 190°C and maintained for 2 minutes. The remaining conditions were the same as in Example 1.

[0046] Comparative Example 5: The difference from Example 1 is as follows: 15g of hydroxyethoxypropyl-terminated polydimethylsiloxane is not added in step 1; 25g of hydroxyethoxypropyl-terminated polydimethylsiloxane and 1g of tetrabutyl titanate are added in step 3; and only 6g of 2-hydroxy-4-n-octyloxybenzophenone heated to 80°C is added to the liquid injection port in zone 6 of step 4. All other conditions are the same as in Example 1.

[0047] Comparative Example 6: The difference from Example 1 is that in step 1, 6g of 2-hydroxy-4-n-octyloxybenzophenone is not pre-dispersed in 15g of hydroxyethoxypropyl-terminated polydimethylsiloxane; in step 4, the 15g of hydroxyethoxypropyl-terminated polydimethylsiloxane is still added through the liquid injection port in zone 6, while the 6g of 2-hydroxy-4-n-octyloxybenzophenone is added simultaneously through the main feed port along with 800g of polypropylene, all of the second pre-reaction material obtained in step 3, 1g of hindered phenolic antioxidant, and 1g of phosphite antioxidant. All other conditions are the same as in Example 1.

[0048] Comparative Example 7: The difference from Example 1 is that in step 4, 6g of hindered amine light stabilizer is added through the main feed inlet, instead of through the side feed inlet in zone 5. All other conditions are the same as in Example 1.

[0049] Performance testing: Sample preparation and conditioning: The samples were obtained from the granules of Examples 1-5 and Comparative Examples 1-7. Each granule was dried in a vacuum drying oven at 80℃ for 4 hours. Multipurpose Type 1A tensile specimens and strip specimens were prepared using an injection molding machine according to GB / T 17037.1-2019. The temperatures of each zone of the barrel were set to 190℃, 200℃, 205℃, and 210℃, respectively; the nozzle temperature was 210℃; the mold temperature was 40℃; the injection pressure was 80MPa; the holding pressure was 55MPa; the holding time was 10s; and the cooling time was 30s. The resulting strip specimens were 80mm × 10mm × 4mm in size. One portion was machined into Type A notched specimens for notched impact testing of simply supported beams, and the other portion was machined into 30mm × 7mm × 4mm rectangular specimens for sliding friction and wear testing. Separately, each granule was preheated at 190℃ for 5 minutes, then pressed at 10 MPa for 3 minutes in a flat vulcanizing machine, and cooled to room temperature under the same pressure to obtain 100 mm × 100 mm × 2 mm flat plate samples for fluorescence ultraviolet aging, yellow index, and surface roughness testing. Simultaneously, one set each of tensile test specimens and A-notch impact test specimens of the same specifications were prepared for mechanical property testing after fluorescence ultraviolet aging. All samples were conditioned for 24 hours at 23℃ and 50% relative humidity before testing.

[0050] Fluorescent UV aging treatment: Tests were conducted according to GB / T 16422.1-2019 and GB / T 16422.3-2022. 2mm flat plate specimens, type 1A tensile specimens, and type A notched impact specimens were fixed on the sample holder of the fluorescent UV aging chamber, with the light-receiving surface facing the lamp tube. The specimen spacing, installation direction, and light-receiving surface were kept consistent. This application uses a UVA-340 lamp tube, with an irradiance of 0.76 W / (m²) at 340 nm. 2 The samples were subjected to UV irradiation (nm) for 8 hours followed by 4 hours of condensation, with the blackboard temperature controlled at 60±3℃ during the UV irradiation phase and 50±3℃ during the condensation phase. The total aging time was set to 500 hours. After aging, the samples were placed at 23℃ and 50% relative humidity for 4 hours before subsequent tests were performed on friction and wear, yellow index, surface roughness, tensile strength, and notched impact strength of a simply supported beam.

[0051] Sliding friction coefficient: Tested according to GB / T 3960-2016 using a ring-block friction and wear testing machine. The sample size is 30mm×7mm×4mm. The paired steel ring is made of GCr15 with an outer diameter of 40mm, a surface hardness of 60-64HRC, and a surface roughness Ra controlled between 0.2-0.4μm. Before the test, the sample and steel ring surfaces were wiped with anhydrous ethanol and allowed to dry naturally for 10min. Dry friction conditions were used, with a load of 200N and a steel ring rotation speed of 200rpm. The test was conducted continuously for 60min, and the friction coefficient curve was recorded in real time. The average value of the last 30min was taken as the stable friction coefficient. Each sample was tested separately for unaged samples and samples aged for 500h. Each condition was tested in parallel 5 times.

[0052] Tensile strength and retention rate: The test was conducted in accordance with GB / T 1040.2-2022, using type 1A tensile specimens, at 23℃, with a tensile speed of 50 mm / min. Five parallel samples were tested for each sample, including the unaged sample and the sample aged for 500 h. The average tensile strength was recorded, and the tensile strength retention rate was calculated as (tensile strength after aging / tensile strength before aging) × 100%.

[0053] Notched impact strength and retention rate of simply supported beams: The test was conducted in accordance with GB / T 1043.1-2018, using 80mm×10mm×4mm type A notched specimens, at a test temperature of 23℃, using a lateral impact method, and the pendulum energy was set to 5.5J; 10 parallel samples were tested for each sample, including unaged specimens and specimens aged for 500h, and the average notched impact strength of simply supported beams was recorded. The impact strength retention rate was calculated as (notched impact strength of aged simply supported beams / notched impact strength of unaged simply supported beams) × 100%.

[0054] Yellow index and its variation: The test was conducted in accordance with GB / T 39822-2021. Unaged plate samples and plate samples aged for 500h were selected. The yellow index was measured on the same spectrophotometer. The light source conditions were set to D65 and the field of view was set to 10°. Five points were measured at different positions on the light-receiving surface of each sample, and the average value was taken.

[0055] Surface roughness: Tested according to GB / T 1031-2016 and GB / T 10610-2009. Unaged flat plate samples and flat plate samples aged for 500h were selected. The light-receiving surface was used as the test surface. A stylus-type surface roughness tester was used for measurement. The cutoff wavelength was set to 0.8mm, the evaluation length was set to 4.0mm, and the measurement speed was set to 0.5mm / s. Five parallel test lines were selected in the area more than 10mm away from the edge of the sample. The surface roughness Ra was recorded and the average value was taken.

[0056] Table 1 Performance Test Results

[0057] Sample Initial coefficient of friction Coefficient of friction after aging Initial tensile strength / MPa Tensile strength retention rate after aging / % Initial Charpy notched impact strength / (kJ / m 2 ) Impact strength retention rate after aging / % Initial yellow index Yellow index after aging Initial surface roughness Ra / μm Surface roughness Ra / μm after aging Example 1 0.182 0.194 31.8 91.8 4.5 88.6 2.0 5.6 0.126 0.169 Example 2 0.197 0.226 30.7 88.4 4.1 84.8 1.8 6.9 0.132 0.194 Example 3 0.186 0.199 31.4 91.1 4.4 87.9 1.9 5.9 0.129 0.173 Example 4 0.179 0.211 32.0 89.6 4.3 86.3 2.1 6.4 0.137 0.186 Example 5 0.175 0.236 30.9 87.1 4.2 83.6 2.4 7.4 0.144 0.208 Comparative Example 1 0.271 0.398 31.9 76.8 3.7 71.5 1.9 13.8 0.131 0.352 Comparative Example 2 0.248 0.341 31.2 79.4 4.0 74.1 2.0 11.7 0.135 0.301 Comparative Example 3 0.191 0.287 30.5 82.7 4.2 78.3 2.5 10.1 0.151 0.247 Comparative Example 4 0.214 0.309 30.9 81.9 4.1 76.8 2.2 10.8 0.148 0.262 Comparative Example 5 0.232 0.328 30.8 80.6 4.0 75.0 2.3 12.4 0.146 0.281 Comparative Example 6 0.204 0.279 31.0 83.6 4.2 77.9 2.1 9.5 0.141 0.236 Comparative Example 7 0.196 0.264 31.3 84.8 4.3 79.0 2.1 8.7 0.138 0.223

[0058] Data Analysis: As can be seen from the data in Table 1, the silicone oil-modified polypropylene composite material prepared by the present invention maintains a high mechanical level of the polypropylene matrix while having a low initial coefficient of friction, a small increase in friction after photoaging, small changes in yellow index and surface roughness, and a high retention rate of tensile strength and notched impact strength of simply supported beams. This indicates that the material is suitable for polypropylene components that require both low friction operation and long-term resistance to photoaging. The reason is speculated to be that aminopropyl-terminated polydimethylsiloxane first undergoes a first pre-reaction with maleic anhydride-grafted polypropylene to form an internally anchored organosilicon phase; then 2,4-dihydroxybenzophenone, hydroxyethoxypropyl-terminated polydimethylsiloxane, and tetrabutyl titanate are added stepwise to further construct an interfacial light-resistant flexible layer; then, with the subsequent injection of 2-hydroxy-4-n-octyloxybenzophenone and hydroxyethoxypropyl-terminated polydimethylsiloxane, the side feeding of hindered amine light stabilizer, and the subsequent addition of hindered phenolic antioxidant and phosphite antioxidant, a surface restricted migration lubrication-light-absorbing composite phase can be formed, thereby maintaining a relatively continuous lubricating film and a relatively complete surface structure before and after light exposure.

[0059] As can be seen from the data in Table 1 for Example 1, Comparative Example 1, and Comparative Example 2, the lack of aminopropyl-terminated polydimethylsiloxane, or the absence of a first pre-reaction with maleic anhydride-grafted polypropylene, resulted in a more significant deterioration in the coefficient of friction, yellowing index, and surface roughness after aging. The tensile strength and notched impact strength retention of simply supported beams also decreased simultaneously. The presumed reason is that the former struggles to form an internally anchored organosilicon phase, while the latter, although containing organosilicon, struggles to establish a stable, confined migration lubrication structure, making it more difficult to maintain the continuity of the lubricating film after light exposure.

[0060] As can be seen from the data in Table 1 for Example 1 and Comparative Example 3, simply increasing the amount of aminopropyl-terminated polydimethylsiloxane in the pre-reaction stage resulted in a decrease in overall performance, including friction, yellowing index, surface roughness, and mechanical retention rate after aging. This may be because the first pre-reaction stage excessively consumed the polar sites on the maleic anhydride-grafted polypropylene, weakening the space for the subsequent stepwise construction of the interface between 2,4-dihydroxybenzophenone, hydroxyethoxypropyl-terminated polydimethylsiloxane, and tetrabutyl titanate. This resulted in a surface lubricating phase that, while easier to form, was less stable.

[0061] As can be seen from the data in Table 1 for Example 1 and Comparative Example 4, when 2,4-dihydroxybenzophenone, hydroxyethoxypropyl-terminated polydimethylsiloxane, and tetrabutyl titanate were added simultaneously, the initial properties of the material were acceptable, but after aging, many indicators were significantly worse than those of Example 1, especially the surface structure retention and mechanical retention. It is speculated that this is because, after the stepwise addition was changed to simultaneous addition, 2,4-dihydroxybenzophenone had difficulty functioning effectively in the already formed organosilicon interface, and hydroxyethoxypropyl-terminated polydimethylsiloxane was more prone to local enrichment, resulting in insufficient construction of the interfacial light-resistant flexible layer.

[0062] As can be seen from the data in Table 1 for Examples 1, 5, and 6, the subsequent liquid injection does not merely serve to add components, but is crucial for the formation of the surface-confined migration lubrication-light-absorbing composite phase. In Comparative Example 5, hydroxyethoxypropyl-terminated polydimethylsiloxane was moved to the second pre-reaction stage, and only 2-hydroxy-4-n-octyloxybenzophenone was added in the subsequent stage. This indicates that the lack of a subsequent organosilicon carrier reduces the continuity of the surface lubricating film and the appearance stability after light exposure. Although Comparative Example 6 retained the subsequent organosilicon injection, 2-hydroxy-4-n-octyloxybenzophenone was no longer pre-dispersed, resulting in uneven distribution of the active sites in the light-exposed surface, and significant friction and roughening after aging. Both examples demonstrate that hydroxyethoxypropyl-terminated polydimethylsiloxane and 2-hydroxy-4-n-octyloxybenzophenone only achieve a significant synergistic effect (1+1>2) when they are pre-dispersed in the subsequent stage and jointly enter the surface.

[0063] As can be seen from the data in Table 1 for Example 1 and Comparative Example 7, simply changing the addition of the hindered amine light stabilizer from side-feeding to main-feeding did not significantly alter the initial properties of the material. However, after aging, the friction, yellow index, surface roughness, and both mechanical properties decreased. The main reason for this is likely that, because the hindered amine light stabilizer enters the high-temperature main melt earlier, it is more prone to loss of effective components or shift in its distribution position during the initial processing, resulting in a decrease in its effective retention on the light-receiving surface of the final product.

[0064] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A silicone oil-modified polypropylene composite material, characterized in that, It is prepared from the following raw materials in parts by mass: 760-850 parts polypropylene; The pre-reactant is prepared by pre-reacting 120-180 parts of maleic anhydride-grafted polypropylene and 3-8 parts of aminopropyl-terminated polydimethylsiloxane, followed by further pre-reaction with 4-8 parts of 2,4-dihydroxybenzophenone, 8-12 parts of hydroxyethoxypropyl-terminated polydimethylsiloxane and 0.8-1.2 parts of tetrabutyl titanate. A mobile dispersion formed by pre-dispersing 12-20 parts of hydroxyethoxypropyl-terminated polydimethylsiloxane and 4-10 parts of 2-hydroxy-4-n-octyloxybenzophenone; 4-8 parts hindered amine light stabilizer; 0.8-1.2 parts hindered phenolic antioxidant; and 0.8-1.2 parts phosphite antioxidant.

2. The silicone oil-modified polypropylene composite material according to claim 1, characterized in that, The maleic anhydride-grafted polypropylene and the aminopropyl-terminated polydimethylsiloxane are pre-reacted under nitrogen protection at 175-185°C and 55-70 rpm. The maleic anhydride-grafted polypropylene is first melted for 2 min, and then the aminopropyl-terminated polydimethylsiloxane is added dropwise over 1 min, and the mixture is continued to be mixed for 5-7 min. The further pre-reaction is carried out under nitrogen protection at 188-195°C and 55-65 rpm. The 2,4-dihydroxybenzophenone is first added and mixed for 1.5-2.5 min, then the hydroxyethoxypropyl-terminated polydimethylsiloxane and the tetrabutyl titanate are added and the mixture is continued to be mixed for 5-7 min. The mixture is then maintained at -0.075±0.005 MPa for 1.5-2.5 min.

3. The silicone oil-modified polypropylene composite material according to claim 1, characterized in that, The fluid dispersion is obtained by heating the hydroxyethoxypropyl-terminated polydimethylsiloxane to 78-85°C, adding the 2-hydroxy-4-n-octyloxybenzophenone, and continuing to stir for 15-25 minutes.

4. The silicone oil-modified polypropylene composite material according to claim 1, characterized in that, The hindered amine light stabilizer is Tinuvin 770 DF, the hindered phenolic antioxidant is Irganox 1010, and the phosphite antioxidant is Irgafos168.

5. The silicone oil-modified polypropylene composite material according to claim 1, characterized in that, The polypropylene is designated as PPH-T03.

6. The silicone oil-modified polypropylene composite material according to claim 1, characterized in that, The grade of the maleic anhydride-grafted polypropylene is EPOLENE E-43P.

7. The silicone oil-modified polypropylene composite material according to claim 1, characterized in that, The grade of the aminopropyl-terminated polydimethylsiloxane is DMS-A32.

8. The silicone oil-modified polypropylene composite material according to claim 1, characterized in that, The grade of the hydroxyethoxypropyl-terminated polydimethylsiloxane is MCR-C18.

9. A method for preparing a silicone oil-modified polypropylene composite material according to any one of claims 1-8, characterized in that, Includes the following steps: (1) After heating hydroxyethoxypropyl-terminated polydimethylsiloxane, 2-hydroxy-4-n-octyloxybenzophenone was added and stirred to obtain a mobile dispersion; (2) Under nitrogen protection, maleic anhydride-grafted polypropylene is pre-reacted with aminopropyl-terminated polydimethylsiloxane to obtain the first pre-reaction material; (3) The first pre-reactant is further pre-reacted with 2,4-dihydroxybenzophenone, hydroxyethoxypropyl-terminated polydimethylsiloxane and tetrabutyl titanate to obtain the second pre-reactant; (4) Polypropylene, the second pre-reactant, hindered phenol antioxidant and phosphite antioxidant are melt-extruded, and hindered amine light stabilizer and the flow dispersion are added after forming a continuous melt. The mixture is then extruded and granulated to obtain the silicone oil modified polypropylene composite material.

10. The method for preparing the silicone oil-modified polypropylene composite material according to claim 9, characterized in that, In step (4), the melt extrusion adopts a co-rotating twin-screw extruder with temperature zones of 173-178℃, 178-183℃, 183-188℃, 188-193℃, 193-198℃, 198-203℃, 198-203℃ and 193-198℃ respectively, and the screw speed is 210-235 rpm. After the continuous melt is formed in zone 4, the hindered amine light stabilizer is side-fed in zone 5, the flowing dispersion is added at the liquid injection port in zone 6, and vacuum degassing is performed in zone 7.