A poly-lactic acid matte skin feel masterbatch and a preparation method thereof

Abstract

The application provides a matte skin-feeling polylactic acid master batch and a preparation method thereof. Polylactic acid is used as a carrier, and an epoxy acrylate modified polylactic acid modifier, nano-extinction powder, skin-feeling micro powder and multifunctional additive are compounded. The master batch is added in polylactic acid base material at 1%~5%, so that the surface gloss of the product is lower than 10GU (60° angle), a delicate and smooth matte effect is presented, a silky smooth and warm and moist touch is given, and good dispersibility, processing fluidity and biodegradability are also provided.

Description

Technical Field

[0001] This application relates to the field of polylactic acid technology, specifically to a polylactic acid matte skin-feel masterbatch and its preparation method. Background Technology

[0002] Polylactic acid (PLA), a fully biodegradable material derived from renewable plant resources, possesses excellent transparency, mechanical strength, and processability, making it widely used in packaging, tableware, 3D printing, fibers, and plastic products. However, pure PLA suffers from significant drawbacks, including excessively high surface gloss (typically >80 GU at 60°), resulting in a glaring appearance, easy fingerprint visibility, a lack of premium matte finish, and a stiff, dry feel, lacking the soft, smooth, and skin-friendly texture. This leads to a poor user experience when used in daily necessities, electronic product casings, and cosmetic packaging. Directly adding inorganic matting agents can cause agglomeration and uneven dispersion in the system, leading to a significant decrease in the mechanical properties of the products. Furthermore, common matting / feel modifiers have poor compatibility with PLA, easily precipitating and migrating, affecting appearance and stability.

[0003] Existing technologies mostly use a single filler (calcium carbonate, talc) for matting, or only add silicone oil and wax to improve the feel, making it difficult to achieve a comprehensive effect of low gloss matting, delicate skin feel, good dispersion and mechanical retention at the same time, and lack a dedicated PLA-based masterbatch system.

[0004] Therefore, preparing a high-efficiency, stable, and compatible polylactic acid matte skin-feel masterbatch is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This application provides a polylactic acid matte skin-feel masterbatch, which uses polylactic acid as a carrier and is compounded with organosilicon elastomer, nano-matte powder, skin-feel micro powder and multifunctional additives. The masterbatch is added to the polylactic acid matrix at 1% to 5%, which can make the surface gloss of the product less than 10 GU (60° angle), presenting a delicate frosted matte effect, while giving it a silky smooth, warm and skin-friendly touch, and also has good dispersibility, processing flowability and biodegradability.

[0006] In a first aspect, this application provides a polylactic acid matte skin-feel masterbatch, comprising the following components in parts by weight: The composition includes 100 parts of primary polylactic acid resin, 8-18 parts of PBAT degradable resin, 15-20 parts of epoxy acrylate modified polylactic acid modifier, 40-60 parts of matting agent, 12-22 parts of skin-feel powder, 7-13 parts of interface stabilizer, 0.4-0.7 parts of coupling agent, 0.6-1.0 parts of antioxidant, 1.0-1.8 parts of lubricant, and 0.4-0.8 parts of anti-hydrolysis agent; the matting agent is composed of nano-silica and polymethylsilsesquioxide. The powder is composed of alkylene and nano-talc, wherein the weight ratio of nano-silica, polymethylsilsesquioxane and nano-talc is 1:(0.5~1.0):(0.5~1.0); the skin-feeling micro powder is composed of polyethylene wax micro powder, maleic anhydride grafted wax micro powder and polytetrafluoroethylene micro powder, wherein the weight ratio of polyethylene wax micro powder, maleic anhydride grafted wax micro powder and polytetrafluoroethylene micro powder is 1:(0.4~0.8):(0.3~0.7).

[0007] This application provides a polylactic acid (PLA) matte finish masterbatch, comprising PLA resin, PBAT degradable resin, epoxy acrylate modified PLA modifier, matting agent, skin-feel powder, and interface stabilizer, coupling agent, lubricant, antioxidant, and anti-hydrolysis agent. PLA resin and PBAT serve as the matrix resin and flexibility-regulating components, ensuring compatibility between the masterbatch and the PLA matrix while maintaining mechanical properties. Interface stabilizer, coupling agent, and various additives are used to improve dispersibility and processing stability during melt mixing.

[0008] It should be understood that the skin-feeling micro powder is mainly used to improve tactile stability and low friction. The amount of masterbatch added to the polylactic acid matrix is ​​low, and the content of polytetrafluoroethylene micro powder in the whole system is extremely low, so it has little impact on the final biodegradability of the material.

[0009] During their research, the inventors discovered that polylactic acid (PLA) materials inherently have a hard surface and a dry feel. Existing PLA matting masterbatches typically rely on inorganic powders such as nano-silica and talc to form a microscopic uneven structure on the product surface, causing diffuse reflection of incident light and thus reducing surface gloss. While this method can achieve a certain matting effect, nano-silica and nano-talc are hard inorganic powders with high surface hardness and strong polarity, resulting in limited interfacial compatibility with the PLA matrix. Under high-filling conditions, they are prone to agglomeration, localized enrichment, or surface exposure, leading to a noticeable roughness, graininess, powderiness, and dryness on the product surface. In other words, simply using hard inorganic powders for matting easily results in a "low-gloss but poor-feeling" surface, making it difficult to simultaneously meet the requirements of low gloss and a smooth, skin-like feel for PLA products. To address the roughness, powdery feel, and dryness caused by the aforementioned hard inorganic matting powders, this application introduces polymethylsilsesquioxane into an inorganic matting system composed of nano-silica and nano-talc. Polymethylsilsesquioxane possesses a silicon-oxygen framework and organic methyl surface characteristics, combining the soft tactile feel of organosilicon materials with the surface-modifying effect of microsphere powders. On one hand, polymethylsilsesquioxane can work with nano-silica and nano-talc to construct a micro / nano matting structure, ensuring the product surface still maintains the diffuse reflection interface required for reduced gloss. On the other hand, polymethylsilsesquioxane can distribute between the hard inorganic powders, softening and modulating the hard, rough interface formed by nano-silica and nano-talc, reducing the powdery, grainy, and dry feel caused by direct exposure of hard particles. Therefore, by introducing polymethylsilsesquioxane, this application transforms the traditional hard inorganic powder matting interface into a softened micro / nano matting interface, improving the smooth tactile feel of the product surface while maintaining low gloss.

[0010] However, the inventors further discovered that while polymethylsilsesquioxane (PMSA) can improve the roughness and dryness caused by hard inorganic powders, its introduction introduces new interfacial stability issues. Specifically, the surface of PMSA is predominantly composed of organosilicon structures, lacking sufficiently strong interfacial bonding with the polylactic acid (PLA) matrix. Furthermore, in systems containing high levels of inorganic powders such as nano-silica and nano-talc, PMSA primarily serves as a softening transition and surface feel modifier. If it cannot be stably anchored between the inorganic powder and the PLA matrix, it is prone to local migration, segregation, peeling, or discontinuous distribution during high-temperature melting processing, strong shear mixing, or long-term use. These phenomena cause local instability or collapse of the softened micro / nano matting interface originally constructed by PMSA, leading to localized gloss recovery, decreased smoothness, uneven feel, and even affecting powder dispersion and masterbatch processing stability. In other words, the introduction of polymethylsilsesquioxane solved the problem of the first layer of tactile sensation caused by hard inorganic powders, but at the same time brought about the problem that the softened interface was difficult to maintain stably in the long term.

[0011] To address the issue of insufficient interfacial stability resulting from the introduction of polymethylsilsesquioxane, this application further introduces an epoxy acrylate-modified polylactic acid modifier. This modifier uses polylactic acid as its main chain segment, thus exhibiting good compatibility with the first polylactic acid resin and avoiding migration or precipitation as easily as common small-molecule interfacial additives. Simultaneously, this modifier contains epoxy active groups, enabling interfacial interactions with the silanol groups on the surface of polymethylsilsesquioxane, the silanol groups on the surface of nano-silica, and the polar groups in polylactic acid, PBAT, or maleic anhydride grafted components. Therefore, the epoxy acrylate-modified polylactic acid modifier can form a reactive interfacial bond between the polylactic acid matrix, PBAT-degradable resin, hard inorganic matting agent, and polymethylsilsesquioxane.

[0012] Through the aforementioned interfacial bonding effect, the epoxy acrylate-modified polylactic acid modifier can more stably anchor polymethylsilsesquioxane between nano-silica, nano-talc, and the polylactic acid matrix, reducing the migration, segregation, and interfacial peeling of polymethylsilsesquioxane during processing and use. This results in a more continuous, uniform, and stable softened micro / nano matting interface. In other words, the epoxy acrylate-modified polylactic acid modifier not only solves the problem of insufficient interfacial stability that may arise after the introduction of polymethylsilsesquioxane, but also further enhances the softening and regulating effect of polymethylsilsesquioxane on hard inorganic matting powders, enabling polymethylsilsesquioxane to more fully and persistently reduce the hard particle feel and improve the powdery and dry feel.

[0013] Meanwhile, the introduction of epoxy acrylate-modified polylactic acid modifier can also improve the processing and dispersion state of highly filled systems. The masterbatch in this application contains high levels of matting and skin-feeling powders, resulting in numerous system interfaces and high melt flow resistance, which easily leads to difficulties in powder dispersion and localized agglomeration. Because the epoxy acrylate-modified polylactic acid modifier combines the compatibility of polylactic acid segments with the reactivity of epoxy, it can improve the wetting and interfacial bonding between the powder and the resin matrix during melt mixing, reducing the uneven dispersion of hard inorganic powders, polymethylsilsesquioxane, and skin-feeling powders, thereby improving the processing stability of the masterbatch and the uniformity of the finished product.

[0014] Furthermore, the skin-feel powder in this application is obtained by compounding polyethylene wax micropowder, maleic anhydride grafted wax micropowder, and polytetrafluoroethylene micropowder in a specific ratio. Polyethylene wax micropowder and polytetrafluoroethylene micropowder can reduce the surface friction coefficient of the product, improving surface smoothness and a delicate feel. Maleic anhydride grafted wax micropowder can form a low-friction synergistic system with polyethylene wax micropowder and polytetrafluoroethylene micropowder, and its maleic anhydride graft structure can also create interfacial interactions with polylactic acid systems, epoxy acrylate-modified polylactic acid modifiers, interface stabilizers, or coupling-treated powder interfaces, thereby reducing the tendency for waxes and fluorine-containing micropowders to migrate freely. Therefore, the skin-feel powder is less likely to migrate alone to the product surface to form a continuous low surface energy layer, reducing problems such as precipitation, stickiness, gloss restoration, and decreased feel.

[0015] In some embodiments, the preparation method of the epoxy acrylate modified polylactic acid modifier includes the following steps: 100 parts of second polylactic acid resin, 5-10 parts of glycidyl methacrylate and 0.1-0.5 parts of dicumyl peroxide are mixed evenly and added to a twin-screw extruder. After melt extrusion reaction, the extrudate is water-cooled, granulated and dried to obtain epoxy acrylate modified polylactic acid modifier.

[0016] Among the methods mentioned above, epoxy acrylate modified polylactic acid modifiers are prepared by melt grafting, which enables glycidyl methacrylate to be more uniformly distributed and bound to the polylactic acid chain segments. This avoids the problems of uneven local reaction, volatilization loss, or unstable metering in subsequent masterbatch processing that occur when liquid or small molecule reactive monomers are added directly. This method can be used to prepare epoxy acrylate modified polylactic acid modifiers.

[0017] In some embodiments, the interface stabilizer is composed of maleic anhydride-grafted polylactic acid and an epoxy chain extender, wherein the weight ratio of maleic anhydride-grafted polylactic acid to epoxy chain extender is 1:0.2~0.4.

[0018] Among the aforementioned methods, maleic anhydride-grafted polylactic acid (PLA), with PLA segments as the main component, can maintain good compatibility with PLA resin. Its maleic anhydride grafting groups can improve the interfacial bonding and wetting dispersion of matting powders such as nano-silica, polymethylsilsesquioxane, and nano-talc, as well as skin-feel powder and PBAT in the PLA system, reducing powder agglomeration, white spots, streaks, and phase separation. Epoxy chain extenders contain epoxy functional groups, which can react or interact with the terminal carboxyl groups or terminal hydroxyl groups in PLA and PBAT, thereby improving the bonding strength of the PLA / PBAT system and the powder / resin interface, and inhibiting the decline in mechanical properties caused by the degradation of PLA molecular chains during melt processing. By controlling the ratio of maleic anhydride-grafted polylactic acid to epoxy chain extender at 1:0.2–0.4, sufficient interfacial wetting and dispersion stabilization are ensured, while providing a moderate chain-extending effect. Simultaneously, excessive epoxy chain extender is avoided, which can lead to excessively high melt viscosity, decreased processing fluidity, or localized gelation. This allows the masterbatch to maintain good dispersibility, processing stability, and retained mechanical properties even in systems with high matting and skin-feel powder contents.

[0019] In some embodiments, the coupling agent is one or more of aminosilane coupling agents, epoxysilane coupling agents, methacryloxysilane coupling agents, or vinylsilane coupling agents.

[0020] In some of the above methods, coupling agents are used to improve the interfacial compatibility between inorganic powders and organic resins, promote the uniform dispersion of powders in polylactic acid systems, and reduce agglomeration.

[0021] In some embodiments, the antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants, wherein the mass ratio of the hindered phenolic antioxidants to the phosphite antioxidants is 1:0.5~1.

[0022] In some of the aforementioned methods, hindered phenolic antioxidants are mainly used to capture free radicals generated during the melt processing of polylactic acid, PBAT, and silicone elastomers, inhibiting thermo-oxidative aging reactions. Phosphite antioxidants can decompose peroxides formed during processing, reducing their further initiation of polymer chain degradation. The combined use of these two antioxidants can form a synergistic stabilizing system of primary and secondary antioxidants, improving the thermal stability of the masterbatch during twin-screw extrusion, high-shear compounding, and subsequent molding processes. Maintaining a mass ratio of hindered phenolic antioxidants to phosphite antioxidants of 1:0.5–1 effectively inhibits thermo-oxidative degradation and discoloration during polylactic acid processing, while also helping to maintain the material's molecular weight and melt stability, thereby reducing mechanical property degradation, processing fluctuations, and surface defects caused by degradation.

[0023] In some embodiments, the lubricant is composed of two or more of glyceryl stearate, ethylene bis-stearamide, erucamide, and silicone lubricants.

[0024] In some of the aforementioned methods, lubricants can provide internal and external lubrication between polylactic acid resin, PBAT resin, matte powder, and skin-feel powder, reducing frictional resistance and shear heat in the melt mixing process of highly filled systems, and improving material flowability and extrusion stability. Specifically, glyceryl stearate and ethylene bis-stearamide are beneficial for improving powder wetting and dispersion in the resin, reducing agglomeration; erucamide and silicone lubricants can further reduce friction between the melt and the surfaces of equipment and products. By compounding two or more lubricants, processing flowability, powder dispersion, and surface smoothness can be balanced, reducing defects such as flow marks, streaks, and graininess generated during melt extrusion and molding, thus contributing to a stable matte skin-feel effect in the masterbatch.

[0025] In some embodiments, the anti-hydrolysis agent is a carbodiimide-based anti-hydrolysis agent.

[0026] In some of the aforementioned processes, polylactic acid (PLA) and PBAT are susceptible to hydrolysis due to trace amounts of moisture during drying, melt extrusion, and subsequent processing, leading to a decrease in molecular weight, reduced melt strength, and loss of mechanical properties. Carbodiimide-based anti-hydrolysis agents can react with carboxyl groups or acidic end groups generated by hydrolysis in the system, reducing the risk of further catalytic hydrolysis by these acidic end groups, thereby inhibiting the processing degradation of PLA and PBAT. By adding carbodiimide-based anti-hydrolysis agents, the stability of the masterbatch during high-temperature processing can be improved, reducing melt fluctuations, increased brittleness, and decreased tensile strength caused by hydrolysis. This allows the masterbatch to maintain good processing stability and retain good mechanical properties even when containing a high proportion of matting and skin-feeling agents.

[0027] In some embodiments, the polylactic acid resin has a melt index of 10-30 g / 10 min at 190°C and 2.16 kg.

[0028] In some of the above methods, controlling the melt index of polylactic acid resin within this range is beneficial for the masterbatch to have both appropriate fluidity and melt strength during the melt mixing process, so that it can fully wet and coat functional components such as matting powder, skin-feel powder and organosilicon elastomer, thereby improving the dispersion uniformity of each component in the polylactic acid system.

[0029] Secondly, this application provides a method for preparing a polylactic acid matte skin-feel masterbatch, comprising the following steps: S1. Provide the raw material for the polylactic acid matte skin-feel masterbatch described in any embodiment of the first aspect; S2. Vacuum dry the matte powder and skin-feel powder to obtain dried matte powder and dried skin-feel powder; S3. Add the other raw materials to a high-speed mixer and mix, then add the dried matte powder and the dried skin-feel powder, and continue mixing until uniform to obtain a premix; S4. The premixed material is added to a twin-screw extruder, and after melt mixing, extrusion, and granulation, polylactic acid matte skin-feel masterbatch is obtained.

[0030] In some embodiments, a method for preparing a polylactic acid matte skin-feel masterbatch is characterized by comprising the following steps: S1. Provide the raw material for the polylactic acid matte skin-feel masterbatch described in any embodiment of the first aspect; S2. Vacuum dry the matte powder and skin-feel powder at a temperature range of 60~80℃ for 2~4h to obtain dried matte powder and dried skin-feel powder; S3. Add the other raw materials to a high-speed mixer and mix for 3 to 7 minutes at a temperature range of 40 to 50°C. Then add the dried matte powder and the dried skin-feel powder and continue mixing for 8 to 12 minutes until uniform to obtain a premix. S4. The premixed material is added to a twin-screw extruder, melt-mixed and extruded, granulated under a water temperature ≤25℃, and then dehydrated, dried and sieved to obtain polylactic acid matte skin-feel masterbatch.

[0031] According to this application, the polylactic acid matte skin-feel masterbatch is prepared by pre-drying, stepwise mixing, and twin-screw melt mixing. First, the matte powder and skin-feel powder are vacuum dried at 60-80°C for 2-4 hours, which effectively reduces the moisture content in nano-silica, polymethylsilsesquioxane, nano-talc, and the skin-feel powder. This reduces the hydrolytic degradation of the first polylactic acid resin, PBAT-degradable resin, and epoxy acrylate-modified polylactic acid modifier during subsequent melt processing, and lowers the risk of powder agglomeration or uneven dispersion due to moisture content. During the mixing process, the first polylactic acid resin, PBAT degradable resin, epoxy acrylate modified polylactic acid modifier, interface stabilizer, coupling agent, antioxidant, lubricant, and anti-hydrolysis agent are premixed at 40-50℃ for 3-7 minutes to allow the resin components, reactive interface control components, and various additives to be initially dispersed. Then, the dried matting powder and skin-feel powder are added and mixed for another 8-12 minutes. This facilitates the full wetting, coating, and pre-dispersion of the matting powder and skin-feel powder by the resin and interface stabilizing components, reduces the direct agglomeration of hard inorganic powders such as nano silica and nano talc, and promotes full contact between the epoxy acrylate modified polylactic acid modifier and the polymethylsilsesquioxane and powder interface. Subsequent melt mixing, extrusion, and low-temperature water-cooled granulation using a twin-screw extruder further improves the dispersion uniformity of the multi-component system. This allows the epoxy acrylate-modified polylactic acid modifier to more fully exert its interfacial regulation effect in the molten state, thereby enhancing the continuity and stability of the softened micro-nano matte interface formed by polymethylsilsesquioxane. Controlling the granulation water temperature at ≤25℃ facilitates rapid masterbatch setting, reduces adhesion and deformation, and lowers the risk of degradation caused by heat retention. Ultimately, a uniformly dispersed, processing-stable polylactic acid matte masterbatch with low gloss, a delicate skin feel, and stable hand feel is obtained.

[0032] Compared with the prior art, the beneficial effects of this application are at least as follows: 1. This application addresses the problem that hard inorganic matting powders such as nano-silica and nano-talc powder can easily cause roughness, powderiness, and dryness on the surface of polylactic acid (PLA) products. It introduces polymethylsilsesquioxane to form a softening micro / nano matting interface. Furthermore, to address potential issues such as insufficient interfacial bonding, inadequate distribution stability, and diminished softening effect after the introduction of polymethylsilsesquioxane, an epoxy acrylate-modified PLA modifier is further introduced. Through its compatibility with the PLA system and the interfacial interaction of the epoxy active groups, the anchoring stability of polymethylsilsesquioxane between the hard inorganic powder and the PLA matrix is ​​improved. This not only solves the new problems but also further enhances the softening matting effect of polymethylsilsesquioxane.

[0033] 2. This application also forms a skin-feel system by compounding polyethylene wax micro powder, maleic anhydride grafted wax micro powder and polytetrafluoroethylene micro powder, so that the surface of the product can obtain better smoothness and delicate touch, and reduce the migration, precipitation and gloss recovery of skin-feel components.

[0034] In summary, this application enables polylactic acid matte skin-feel masterbatch to maintain low gloss while possessing a delicate skin feel, good dispersion stability, durable hand feel, and good retention of mechanical properties. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0036] Figure 1 The surface morphology of the test film prepared by adding the masterbatch obtained in Example 1 to a PLA substrate is shown in the image. Figure 2 The surface morphology of the test film prepared by adding the masterbatch obtained in Comparative Example 1 to a PLA substrate is shown in the image. Figure 3 The surface morphology of the test film prepared by adding the masterbatch obtained in Comparative Example 2 into a PLA substrate is shown in the figure. Figure 4 The surface morphology of the test film prepared by adding the masterbatch obtained in Comparative Example 3 to a PLA substrate is shown in the figure. Figure 5 The surface morphology of the test film prepared by adding the masterbatch obtained in Comparative Example 4 to a PLA substrate is shown in the figure. Figure 6 The surface morphology of the test film prepared by adding the masterbatch obtained in Comparative Example 5 into a PLA substrate is shown. Detailed Implementation

[0037] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0038] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0041] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0042] First polylactic acid resin: melt flow index (MFR) = 20 g / 10 min (190℃ / 2.16 kg), brand: NatureWorks, model: 2003D; Second polylactic acid resin: melt flow index MFR=10g / 10min (190℃ / 2.16kg), brand: Haizheng, model: Revode190; PBAT resin: Melt flow index (MFR) = 5 g / 10 min (190℃ / 2.16 kg), Brand: Haizheng; Nano silica: Hydrophobic nano silica with an average particle size of 100 nm; Polymethylsilsesquioxane: Polymethylsilsesquioxane micro powder with an average particle size of 2μm; Nano-talc: average particle size 150nm; Polyethylene wax micro powder: average particle size 5μm; Maleic anhydride-grafted wax micron powder: average particle size 5μm, maleic anhydride grafting rate 1.0wt%; Polytetrafluoroethylene micro powder: average particle size 4μm; Maleic anhydride-grafted polylactic acid: melt flow index (MFR) = 10 g / 10 min (190℃ / 2.16 kg), maleic anhydride grafting rate 0.8 wt%; Epoxy chain extender: Brand: BASF, Model: JoncrylADR-4370; Coupling agent: KH-550; Antioxidant: composed of hindered phenols (1010) and phosphites (168) in a mass ratio of 3:2; Lubricant: composed of glyceryl stearate, ethylene bis-stearamide, erucamide and silicone lubricant in a mass ratio of 3:2:2:1; Anti-hydrolysis agents: Polycarbodiimide anti-hydrolysis agents Epoxidized soybean oil: Epoxidation value: 6.05%.

[0043] Preparation Example 1 Preparation of epoxy acrylate modified polylactic acid modifier: Mix 100 parts of polylactic acid resin II, 7.5 parts of glycidyl methacrylate (GMA), and 0.3 parts of dicumyl peroxide (DCP) as follows: First, mix DCP and GMA to obtain a mixture; then, while stirring, spray the mixture evenly onto the surface of polylactic acid resin II particles, continue stirring for 5-10 minutes to allow the mixture to be fully absorbed by the resin particles, and let it stand for 15 minutes to obtain a premix. The premixed material is added to a twin-screw extruder for a melt grafting reaction. The extruder temperatures are set as follows: Zone 1 160℃, Zone 2 170℃, Zone 3 175℃, Zone 4 180℃, and Die Head 175℃; the screw speed is 150~200 rpm. After the material is melt-mixed and reacted in the twin-screw extruder, the extrudate is obtained. The extrudate is granulated by water cooling, and the resulting granules are placed in a vacuum drying oven and dried under vacuum at 60°C for 8 hours to obtain epoxy acrylate modified polylactic acid modifier.

[0044] Example 1 Preparation of polylactic acid matte skin-feel masterbatch: S1. Preparation of raw materials: 100 parts of first polylactic acid resin, 13 parts of PBAT resin, 18 parts of epoxy acrylate modified polylactic acid modifier, 20 parts of nano silica, 15 parts of polymethylsilsesquioxane, 15 parts of nano talc, 8.5 parts of polyethylene wax powder, 5 parts of maleic anhydride grafted wax powder, 4 parts of polytetrafluoroethylene powder, 7.5 parts of maleic anhydride grafted polylactic acid, 2.5 parts of epoxy chain extender, 0.55 parts of coupling agent, 0.8 parts of antioxidant, 1.4 parts of lubricant, and 0.6 parts of anti-hydrolysis agent; wherein the epoxy acrylate modified polylactic acid modifier is the epoxy acrylate modified polylactic acid modifier obtained in Preparation Example 1.

[0045] S2. The first polylactic acid resin, PBAT resin, nano silica, polymethylsilsesquioxane, nano talc, polyethylene wax micro powder, maleic anhydride grafted wax micro powder and polytetrafluoroethylene micro powder are placed in a vacuum drying oven and dried at 70°C for 3 hours to obtain dried powder. S3. Add epoxy acrylate modified polylactic acid modifier, maleic anhydride grafted polylactic acid, epoxy chain extender, coupling agent, antioxidant, lubricant and anti-hydrolysis agent to a high-speed mixer and mix at 45°C for 5 min; then add the dry powder obtained in step S2 and continue mixing for 10 min to obtain a premix. S4. The premixed material is added to a twin-screw extruder for melt mixing and extrusion granulation. The twin-screw extruder has an L / D ratio of 45:1, and the temperatures from zone one to the die head are 110℃, 140℃, 160℃, 170℃, and 175℃ respectively. The screw speed is 200 rpm, and the vacuum degree is -0.095 MPa. The extrudate is then underwater pelletized at a water temperature of 22℃, followed by dehydration, drying, and sieving to obtain a polylactic acid matte finish masterbatch.

[0046] Comparative Example 1 Preparation of polylactic acid matte skin-feel masterbatch: Similar to Example 1, except that 15 parts of polymethylsilsesquioxane were replaced with 15 parts of nano-silica.

[0047] Comparative Example 2 Preparation of polylactic acid matte skin-feel masterbatch: It is largely the same as Example 1, except that 18 parts of epoxy acrylate modified polylactic acid modifier are replaced with 18 parts of first polylactic acid resin.

[0048] Comparative Example 3 Preparation of polylactic acid matte skin-feel masterbatch: It is largely the same as Example 1, except that 18 parts of epoxy acrylate modified polylactic acid modifier are replaced with 18 parts of second polylactic acid resin.

[0049] Comparative Example 4 Preparation of polylactic acid matte skin-feel masterbatch: Similar to Example 1, except that 15 parts of polymethylsilsesquioxane were replaced with 15 parts of nano-silica, and 18 parts of epoxy acrylate modified polylactic acid modifier were replaced with 18 parts of first polylactic acid resin.

[0050] Comparative Example 5 Preparation of polylactic acid matte skin-feel masterbatch: The method is largely the same as in Example 1, except that 18 parts of epoxy acrylate modified polylactic acid modifier are replaced with 5.5 parts of epoxy soybean oil and 12.5 parts of second polylactic acid resin.

[0051] Test section Sample preparation: The polylactic acid matte skin-feel masterbatch prepared in each example and comparative example was added to the polylactic acid substrate at a ratio of 3wt%. A polylactic acid test film was prepared by a three-layer co-extrusion casting process. The total thickness of the film was 50μm. The structure was designed as ABA type, that is, the upper surface layer (layer A) and the lower surface layer (layer B) are functional layers, and the core layer (layer B) is a support layer.

[0052] The specific preparation method is as follows: The polylactic acid matte skin-feel masterbatch and polylactic acid substrate were mixed evenly at a mass ratio of 3:97 to form the surface layer (layer A) raw material; a first polylactic acid resin was used as the core layer (layer B) raw material; the surface layer raw material and the core layer raw material were respectively fed into three extruders of their respective casting units, and after being melted and plasticized, they were co-extruded through a three-layer co-extrusion die; the surface layer extruder temperature was set as follows: zone 1 110℃, zone 2 160℃, zone 3 170℃, and die head 175℃; the core layer extruder temperature was set as follows: zone 1 120℃, zone 2 170℃, zone 3 180℃, and die head 175℃; the co-extruded melt was cast and cooled by a cooling roller (cooling roller temperature was 25℃) to obtain an ABA three-layer polylactic acid test film, wherein the surface layer thickness accounted for 20% of the total film thickness (i.e., approximately 5μm per layer), and the core layer thickness accounted for 60% of the total film thickness (i.e., approximately 30μm).

[0053] Surface morphology observation: The surface morphology of each test film was observed using a Keyence super depth-of-field digital microscope (model VHX-X1F). The results are as follows: Figures 1-6 As shown.

[0054] Gloss test: The 60° gloss of the sample was tested according to the method described in the national standard GB / T8807-1988 Test method for mirror gloss of plastics. The results are shown in Table 1. Skin feel test: The samples were placed in a dark box and evaluated by touch. The evaluation level was divided into excellent, good, fair, and poor. "Excellent" means smooth to the touch, with no obvious dryness, powdery or sticky feeling; "Good" means relatively smooth to the touch, with a slight dryness or powdery feeling; "Fair" means fair to the touch, with obvious dryness, powdery or uneven smoothness; "Poor" means rough to the touch, with obvious dryness, powdery or sticky feeling. Each sample was evaluated by 10 people, and the results were based on more than 50% of the evaluations. The results are shown in Table 1. Appearance: The surface condition of the film was observed manually to detect white spots / streaks / graininess. The results are shown in Table 1. Stability: The sample was placed in a 70℃ forced-air drying oven and left to stand for 7 days. After being taken out, it was placed at room temperature for 2 hours. Then, the surface of the film was observed for white fog, oil spots, stickiness, powder, crystal points or other visible precipitates. The results are shown in Table 1.

[0055] Table 1

[0056] According to Example 1 and Comparative Example 1, Figure 1 and Figure 2 The comparison shows that the introduction of polymethylsilsesquioxane can improve the surface feel degradation caused by the matting effect of hard inorganic powders alone. This is because nano-silica and nano-talc are hard inorganic powders. While increasing their dosage alone can form the micro-nano rough structure required for matting, it can also easily produce a grainy, powdery, and dry feel due to the high hardness of the powder and insufficient interfacial compatibility. Polymethylsilsesquioxane, on the other hand, has an organosilicon-oxygen framework and relatively soft organic surface characteristics. It can be distributed between nano-silica and nano-talc, softening and transitioning the rough interface formed by the hard inorganic powders. This transforms the matting structure from a simple accumulation of hard inorganic powders to a softened micro-nano matting interface composed of inorganic powders and organosilicon microspheres, thus reducing the unpleasant feel caused by direct exposure of hard particles while maintaining the matting effect.

[0057] According to Example 1 and Comparative Examples 2-3, Figure 1 and Figure 3 , 4 The comparison reveals that the effect of the epoxy acrylate-modified polylactic acid (PLA) modifier does not originate from the addition of PLA resin, but rather from the interfacial regulation effect formed by the PLA-compatible segments and epoxy active groups. This is because, while Comparative Examples 2 and 3 retained polymethylsilsesquioxane, replacing the epoxy acrylate-modified PLA modifier with either the first or second PLA resin resulted in a lack of epoxy active structures in the system capable of interacting with the PLA, nano-silica, and PLA / PBAT interface. This makes it difficult for the PLA to be stably anchored between the rigid inorganic powder and the PLA matrix. Therefore, although the PLA can provide some softening effect, its distribution stability and interfacial bonding are insufficient, leading to discontinuities or decreased stability in the softened micro / nano matting interface. In contrast, the epoxy acrylate-modified PLA modifier in Example 1 enhances the aforementioned interfacial bonding, enabling the PLA to more stably exert its softening and matting effect.

[0058] According to Example 1 and Comparative Example 4 Figure 1 and Figure 5The comparison shows that Comparative Example 4 removed both polymethylsilsesquioxane and epoxy acrylate-modified polylactic acid modifiers. The system mainly relied on hard inorganic powders such as nano-silica and nano-talc for matting, lacking the softening and adjustment of the interface of hard inorganic powders, as well as the reactive interface stabilization effect on the softened matting structure. Therefore, it is easy to form a matting surface with direct exposure of hard particles, powder agglomeration, and insufficient interfacial bonding. In contrast, Example 1 first softens the hard inorganic matting interface with polymethylsilsesquioxane, and then enhances the interfacial bonding between polymethylsilsesquioxane, polylactic acid matrix, and inorganic powders with epoxy acrylate-modified polylactic acid modifier, thereby forming a more continuous and stable softened micro-nano matting interface.

[0059] According to Example 1 and Comparative Example 5, Figure 1 and Figure 6 The comparison shows that epoxy acrylate-modified polylactic acid (PLA) modifiers cannot be simply replaced by ordinary small-molecule epoxy compounds. This is because, although epoxidized soybean oil contains epoxy groups, its molecular structure lacks compatibility and anchoring stability with the PLA matrix. In highly filled PLA systems, it is prone to local migration or precipitation, making it difficult to maintain a stable and continuous interaction at the interface between polymethylsilsesquioxane, inorganic powder, and the PLA matrix. In contrast, epoxy acrylate-modified PLA modifiers possess both PLA-compatible segments and epoxy active groups, allowing for better dispersion in PLA systems and a stable interfacial interaction between polymethylsilsesquioxane and the powder interface. This more effectively maintains the continuity and stability of the softened micro / nano matting interface.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A polylactic acid matte skin-feel masterbatch, characterized in that, Includes the following components by weight: 100 parts of primary polylactic acid resin, 8-18 parts of PBAT degradable resin, 15-20 parts of epoxy acrylate modified polylactic acid modifier, 40-60 parts of matting agent, 12-22 parts of skin-feel powder, 7-13 parts of interface stabilizer, 0.4-0.7 parts of coupling agent, 0.6-1.0 parts of antioxidant, 1.0-1.8 parts of lubricant, and 0.4-0.8 parts of anti-hydrolysis agent; The matting powder is composed of nano-silica, polymethylsilsesquioxane and nano-talc, and the weight ratio of nano-silica, polymethylsilsesquioxane and nano-talc is 1:(0.5~1.0):(0.5~1.0). The skin-feel powder is composed of polyethylene wax micro powder, maleic anhydride grafted wax micro powder and polytetrafluoroethylene micro powder, and the weight ratio of the polyethylene wax micro powder, maleic anhydride grafted wax micro powder and polytetrafluoroethylene micro powder is 1:(0.4~0.8):(0.3~0.7).

2. The polylactic acid matte skin-feel masterbatch according to claim 1, characterized in that, The preparation method of the epoxy acrylate modified polylactic acid modifier includes the following steps: 100 parts of second polylactic acid resin, 5-10 parts of glycidyl methacrylate and 0.1-0.5 parts of dicumyl peroxide are mixed evenly and added to a twin-screw extruder. After melt extrusion reaction, the extrudate is water-cooled, granulated and dried to obtain epoxy acrylate modified polylactic acid modifier.

3. The polylactic acid matte skin-feel masterbatch according to claim 1, characterized in that, The interface stabilizer is composed of maleic anhydride-grafted polylactic acid and an epoxy chain extender, wherein the weight ratio of maleic anhydride-grafted polylactic acid to epoxy chain extender is 1:0.2~0.

4.

4. The polylactic acid matte skin-feel masterbatch according to claim 1, characterized in that, The coupling agent is one or more of aminosilane coupling agents, epoxysilane coupling agents, methacryloxysilane coupling agents, or vinylsilane coupling agents.

5. The polylactic acid matte skin-feel masterbatch according to claim 1, characterized in that, The antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants, wherein the mass ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:0.5~1.

6. The polylactic acid matte skin-feel masterbatch according to claim 1, characterized in that, The lubricant is composed of two or more of the following: glyceryl stearate, ethylene bis-stearamide, erucamide, and silicone lubricants.

7. The polylactic acid matte skin-feel masterbatch according to claim 1, characterized in that, The anti-hydrolysis agent is a carbodiimide-based anti-hydrolysis agent.

8. The polylactic acid matte skin-feel masterbatch according to claim 1, characterized in that, The polylactic acid resin has a melt index of 10-30 g / 10 min at 190°C and 2.16 kg.

9. A method for preparing a polylactic acid matte skin-feel masterbatch, characterized in that, Includes the following steps: S1. Providing raw materials for the polylactic acid matte skin-feel masterbatch according to any one of claims 1 to 8; S2. Vacuum dry the matte powder and skin-feel powder to obtain dried matte powder and dried skin-feel powder; S3. Add the other raw materials to a high-speed mixer and mix, then add the dried matte powder and the dried skin-feel powder, and continue mixing until uniform to obtain a premix; S4. The premixed material is added to a twin-screw extruder, and after melt mixing, extrusion, and granulation, polylactic acid matte skin-feel masterbatch is obtained.

10. The method for preparing a polylactic acid matte skin-feel masterbatch according to claim 9, characterized in that, Includes the following steps: S1. Providing raw materials for the polylactic acid matte skin-feel masterbatch according to any one of claims 1 to 8; S2. Vacuum dry the matte powder and skin-feel powder at a temperature range of 60~80℃ for 2~4h to obtain dried matte powder and dried skin-feel powder; S3. Add the other raw materials to a high-speed mixer and mix for 3 to 7 minutes at a temperature range of 40 to 50°C. Then add the dried matte powder and the dried skin-feel powder and continue mixing for 8 to 12 minutes until uniform to obtain a premix. S4. The premixed material is added to a twin-screw extruder, melt-mixed and extruded, granulated under a water temperature ≤25℃, and then dehydrated, dried and sieved to obtain polylactic acid matte skin-feel masterbatch.

Images