Plastic lubricant and preparation method thereof

Abstract

The invention discloses a plastic lubricant and a preparation method thereof, and belongs to the field of plastic processing aids. The lubricant comprises the following components in parts by weight: 50-70 parts of a basic lubricant with an optimized molecular structure, 10-30 parts of octadecanamide, 10-20 parts of calcium stearate, 0.3-1 part of nano titanium dioxide and the like. The basic lubricant is prepared by esterifying polyhydric alcohol and polyatomic acid and then grafting a fluorine-containing monomer, and the nano titanium dioxide is modified by a silane coupling agent. Through molecular structure optimization and auxiliary agent compounding, the problems of low light transmittance, poor lubricating efficiency, poor surface quality and the like of a traditional lubricant are solved, so that a transparent plastic product is high in light transmittance, the friction coefficient is reduced, the surface glossiness is improved, and the lubricant is suitable for processing plastics such as PET bottles and acrylic plates.

Description

Technical Field

[0001] This invention belongs to the field of plastic processing aids, specifically relating to a plastic lubricant and its preparation method. Background Technology

[0002] In the field of plastics processing, transparent plastic products such as PET beverage bottles, acrylic optical sheets, and polystyrene (PS) display panels are widely used in high-end fields such as food packaging, optical instruments, and electronic displays due to their high light transmittance, aesthetics, and functionality. These products have extremely high requirements for the light transmittance, surface smoothness, and processing stability of the raw materials. Plastic lubricants, as key additives for regulating processing performance, directly affect product quality and production efficiency.

[0003] Traditional plastic lubricants face multiple technical bottlenecks when applied to transparent products. Firstly, insufficient light transmittance: Many lubricants, due to poor molecular structure compatibility with the plastic matrix or the tendency of added inorganic fillers to agglomerate, create light scattering centers during processing, leading to decreased light transmittance and increased haze. For example, when ordinary stearic acid lubricants are used in PET bottle production, the light transmittance often fails to meet the requirement of ≥90% for optical-grade transparent materials. Secondly, lubrication efficiency needs improvement: Traditional lubricants have limited ability to reduce the coefficient of friction. High friction between the plastic melt and the screw / mold not only increases energy consumption (according to industry statistics, insufficient lubrication in traditional processes can increase injection molding machine energy consumption by 15%-20%), but also exacerbates mold wear, shortens equipment life, and causes uneven product wall thickness and dimensional deviations due to unstable melt flow. Thirdly, poor surface finishing: Some lubricants easily precipitate onto the product surface during high-temperature processing, forming white haze or oil spots, or uneven dispersion leads to fluctuations in surface gloss. For example, when unoptimized silicone-based lubricants are used in acrylic sheet extrusion, the surface gloss (60° gloss value) is usually below 80 GU, and regional haze often occurs, affecting the appearance of the product and subsequent printing, coating and other processes.

[0004] While existing technologies have attempted to improve surface properties by adding organosilicon additives or to enhance transparency by using nanofillers, they generally suffer from insufficient synergistic effects. Improving a single component cannot simultaneously resolve the contradictions between light transmittance, lubricity, and surface quality. Furthermore, some modification processes (such as simple physical blending) can easily lead to unstable lubricant performance, failing to meet the requirements of continuous industrial production. Therefore, developing a novel plastic lubricant that combines high transparency, efficient lubricity, and excellent surface modification effects has become a pressing technical challenge for the industry. Summary of the Invention

[0005] The purpose of this invention is to provide a plastic lubricant and its preparation method that improves the light transmittance, enhances lubrication efficiency, and improves surface gloss of transparent plastic products through molecular structure optimization, additive compounding, and high-efficiency lubrication formulation design.

[0006] To address the problems existing in the background technology, the following technical solution is adopted: A plastic lubricant, by weight, comprises: 50-70 parts of a molecularly optimized base lubricant, 10-30 parts of stearamide, 10-20 parts of calcium stearate, 0.3-1 parts of nano-titanium dioxide, 1-3 parts of organosilicon elastomer, and 0.5-2 parts of hindered amine light stabilizer; wherein the molecularly optimized base lubricant is prepared by grafting and modifying polyols and polyacids with fluorine-containing monomers after esterification reaction. This application improves the light transmittance of the product by modifying the base lubricant with fluorine-containing groups and combining it with nano-level transparent additives, effectively solving the problems of turbidity and high haze caused by traditional lubricants.

[0007] Furthermore, the polyol is pentaerythritol, and the polyacid is trimellitic anhydride.

[0008] Furthermore, the fluorinated monomer is perfluorooctyl ethyl acrylate.

[0009] A uniformly grafted fluorinated polyester skeleton is formed by reacting pentaerythritol, trimellitic anhydride and perfluorooctyl ethyl acrylate, which enhances compatibility with the plastic matrix, reduces surface energy, prevents precipitation and improves demolding lubrication efficiency.

[0010] Furthermore, the nano-titanium dioxide is nano-carbon dioxide with a particle size ≤50nm that has been surface-modified with a silane coupling agent, wherein the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane. Furthermore, the organosilicon elastomer is polydimethylsiloxane or organosilicon-acrylate copolymer or a combination thereof.

[0011] The dispersibility of nano-titanium dioxide is significantly improved after silane modification. When combined with organosilicon elastomers, it promotes the uniform spreading of lubricant on the surface of the product, eliminates fogging, and enhances light transmittance and surface smoothness.

[0012] Furthermore, the hindered amine light stabilizer is one or a mixture of bis(2,2,6,6-tetramethylpiperidinyl) sebacate (trade name Tinuvin 770), bis(1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate (trade name Chimassorb 944), bis(2,2,6,6-tetramethylpiperidinyl) adipate (Tinuvin 622), and poly(4-hydroxy-2,2,6,6-tetramethylpiperidinyl) succinate (trade name Hostavin NX890).

[0013] This application also discloses a method for preparing a plastic lubricant, comprising the following steps: (1) Polyols and polyacids react under the action of a catalyst to obtain a basic lubricant. Then, a fluorine-containing monomer is added to complete the grafting reaction to obtain a basic lubricant with optimized molecular structure. (2) Nano-titanium dioxide is surface modified with a silane coupling agent; (3) Mix the modified nano-titanium dioxide, organosilicon elastomer, hindered amine light stabilizer with the above-mentioned molecularly optimized basic lubricant and stir to disperse; (4) Add stearamide and calcium stearate, and continue stirring to obtain plastic lubricant. Furthermore, the catalyst is p-toluenesulfonic acid.

[0014] This application achieves three core performance enhancements through innovative design of the lubricant molecular structure and synergistic compounding of multiple components: First, it significantly improves the light transmittance of transparent plastic products. By modifying the base lubricant with fluorine-containing groups and combining it with nano-level transparent additives, the light transmittance of the products is improved, effectively solving the problems of turbidity and high haze caused by traditional lubricants, and meeting the optical requirements of high-end transparent products such as PET bottles and acrylic sheets. Second, it greatly enhances lubrication efficiency. The unique formula reduces the coefficient of friction between the plastic melt and processing equipment, reduces energy consumption, decreases mold wear rate, and stabilizes molding speed, significantly improving production efficiency and product dimensional consistency. Third, it significantly improves surface gloss. With the synergistic effect of organosilicon elastomers and modified additives, the lubricant is evenly distributed on the plastic surface, inhibiting precipitation and haze phenomena, improving the surface gloss of the products, and fundamentally optimizing the appearance quality and application value of transparent plastic products. Detailed Implementation

[0015] The present invention will be further described below through specific embodiments, but the scope of protection of this application is not limited to the embodiments. Example 1:

[0016] 1. Preparation of basic lubricants with optimized molecular structure: (1) Add 500g of pentaerythritol, 750g of trimellitic anhydride and 6g of p-toluenesulfonic acid (catalyst) to a reaction vessel equipped with a stirrer, thermometer and condenser. (2) Heat to 200℃ and stir for 5 hours under nitrogen protection to obtain polyester-based base lubricant; (3) Add 100g of perfluorooctyl ethyl acrylate to the polyester-type basic lubricant, heat to 220℃, add 1g of benzoyl peroxide as an initiator, react for 4 hours to complete the fluorine-containing monomer grafting modification, and obtain a basic lubricant with optimized molecular structure.

[0017] 2. Modification with nano-titanium dioxide: (1) Take 20g of nano titanium dioxide (particle size ≤50nm), add it to 100mL of anhydrous ethanol, and stir evenly.

[0018] (2) Add 4g of γ-methacryloxypropyltrimethoxysilane and sonicate at 70°C for 1.5 hours (ultrasonic power 300W).

[0019] (3) Filter and dry to obtain surface-modified nano-titanium dioxide.

[0020] 3. Preparation of plastic lubricant: The following raw materials are used: 600g of basic lubricant with optimized molecular structure; 200g of stearamide; Calcium stearate 160g; Modified nano titanium dioxide 6g; Organosilicon elastomer: 20g of polydimethylsiloxane and organosilicon-acrylate copolymer (mass ratio 1:1). Hindered amine light stabilizer: bis(2,2,6,6-tetramethylpiperidinyl) sebacate (trade name Tinuvin 770) 14g.

[0021] Preparation steps: (1) Heat the basic lubricant with optimized molecular structure to 90°C, add modified nano titanium dioxide, polydimethylsiloxane and organosilicon-acrylate copolymer and Tinuvin770, and stir and disperse for 1.5 hours (stirring speed 500 rpm).

[0022] (2) Add stearamide and calcium stearate, and continue stirring for 1 hour to obtain plastic lubricant. Example 2:

[0023] The following raw materials are used to prepare plastic lubricants: 500g of basic lubricant with optimized molecular structure; 300g of stearamide; Calcium stearate 176g; 4g of modified nano-titanium dioxide; Organosilicon elastomer: 12g of polydimethylsiloxane; Hindered amine light stabilizer: 8g of bis(1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate.

[0024] The preparation of the basic lubricant with optimized molecular structure and the preparation of modified nano-titanium dioxide, as well as other preparation methods, are the same as in Example 1. Example 3:

[0025] The following raw materials are used to prepare plastic lubricants: 700g of basic lubricant with optimized molecular structure; 100g of stearamide; Calcium stearate 147g; 10g of modified nano titanium dioxide; Organosilicon elastomer: 25g of organosilicon-acrylate copolymer Hindered amine light stabilizer: bis(2,2,6,6-tetramethylpiperidinyl) sebacate (trade name Tinuvin 770) 18g.

[0026] The preparation of the basic lubricant with optimized molecular structure and the preparation of modified nano-titanium dioxide, as well as other preparation methods, are the same as in Example 1.

[0027] Comparative Example 1: The base lubricant used is an ungrafted fluorinated monomer, and the remaining raw materials and preparation methods are the same as in Example 1.

[0028] Comparative Example 2: The nano-carbon dioxide was not surface modified with a silane coupling agent, and the remaining raw materials and preparation methods were the same as in Example 1.

[0029] Experiment: Data Testing of Plastic Lubricants Used in PET Bottles I. Experimental Objective The study aimed to verify the effects of plastic lubricants on light transmittance, lubrication efficiency, mold wear, and surface gloss improvement in PET bottle production, and to compare the technical differences between the examples and the comparative examples.

[0030] II. Sample Preparation 1. Mixing PET raw materials with lubricant Raw material ratio: PET resin (intrinsic viscosity 0.8 dL / g) 1000g Lubricant addition amount: 0.3% of the PET raw material mass (the corresponding lubricants were used in Examples 1-3 and Comparative Examples 1-2 respectively). Mixing method: Add PET particles and lubricant to a high-speed mixer (500 rpm) and mix for 10 minutes at 60°C to ensure that the lubricant is evenly adhered to the PET surface.

[0031] After mixing, the mixture is granulated by a twin-screw extruder (barrel temperature 240-260℃, screw speed 150rpm) to obtain PET masterbatch containing lubricant.

[0032] 2. Injection molding of PET preforms Equipment: Reciprocating screw injection molding machine; Process parameters: Barrel temperature: 250-260℃ (three-stage temperature control) Mold temperature: 40-60℃ Injection pressure: 80-100MPa Holding pressure: 50-60MPa (holding time 10s) Procedure: Inject the PET masterbatch into 500mL PET preforms (weight 28g, preform thickness 3mm). Prepare 1000 preforms for each lubricant group for subsequent blow molding.

[0033] III. Light transmittance test (GB / T2410-2008) 1. Sample preparation Cut a 2mm thick circular sheet (50mm in diameter) from the shoulder of the PET preform, and take 3 parallel samples for each group.

[0034] 2. Testing equipment Transmittance haze meter (model WGW-400, Shanghai Instrument & Electronic Physics); Calibration: Before testing, calibrate the instrument using a standard white board (99.5% transmittance) and a black board (0% transmittance).

[0035] 3. Testing Procedures Place the sheet into the sample cell and select a wavelength of 550nm (peak visible light). Read the transmittance value; test each sample three times and take the average value. Record data, accurate to 0.1%.

[0036] IV. Friction Coefficient Test (GB / T10006-2021) 1. Sample preparation Upper sample: PET melt cast film (made from bottle preform waste, thickness 0.1mm, size 100mm×20mm); Sample: 316L stainless steel plate (roughness Ra=0.8μm, size 100mm×50mm).

[0037] 2. Testing equipment Friction coefficient meter (model C600, Jinan Langguang); Environmental control: Test temperature 23±2℃, humidity 50±5%.

[0038] 3. Testing Procedures Fix the PET film to the upper slider (load 10N, contact area 20mm×20mm). The stainless steel plate is fixed to the test platform and moves horizontally at a speed of 100 mm / min. Record the dynamic friction coefficient. Test each sample 5 times and take the average value.

[0039] V. Mold Wear Test (GB / T10610-2009) 1. Test Object Injection mold: Mold for PET preform molding (material H13 mold steel, chrome plated). Measurement area: Annular groove at the neck of the mold preform (the area with the most severe wear). 2. Testing equipment Laser confocal microscope (Model KeyenceVK-X200) Surface profilometer (Model TaylorHobsonFormTalysurf) 3. Testing Procedures After producing 1000 PET preforms continuously, the mold is disassembled and the surface is cleaned with anhydrous ethanol. Five measurement points (72° apart) were selected in the neck groove, and a 10mm × 10mm area was scanned at each point; Compare the surface profiles before and after production, calculate the wear depth (μm), and take the average value of 5 points.

[0040] VI. Surface gloss test (GB / T8807-1988) 1. Test Sample Take 3 PET bottles (500mL) for each group.

[0041] 2. Testing equipment Three-angle gloss meter (model HG268, Beijing Normal University Optoelectronic Instrument Factory), 60° measurement angle.

[0042] 3. Testing Procedures Choose an unprinted area in the middle of the bottle, avoiding the mold line; Each bottle was measured at 3 locations (120° intervals), with the gloss meter perpendicular to the surface. Record the 60° gloss value (GU) and take the average of 9 data points.

[0043] VII. Experimental Data Recording and Processing

[0044] VIII. Results Analysis 1. Light transmittance: Synergistic effect of fluorine grafting and nano-modification The transmittance of Examples 1-3 was ≥92%, with Example 1 reaching 94.5%. However, the transmittance of Comparative Example 1 (ungrafted) was only 85.2% due to the poor compatibility between the base lubricant and the PET matrix, resulting in phase separation. Comparative Example 2 (unmodified nanoparticles) caused light scattering due to agglomerates (D90=500nm).

[0045] Differences between implementation examples: In Example 1, the base lubricant had a fluorine grafting rate of 12%, resulting in the best nanoparticle dispersion and the highest light transmittance. In Example 3, the proportion of base lubricant was increased to 70%, while the proportion of stearic acid additives was reduced, resulting in a slight decrease in light transmittance, but still exceeding 92%, demonstrating the influence of formulation ratio on light transmittance.

[0046] 2. Friction coefficient: Surface energy regulation by fluorine-containing groups The friction coefficients of Examples 1-3 were 0.28-0.30, which were 28.6%-33.3% lower than those of Comparative Example 1 (0.42), confirming that the surface energy of the lubricant was significantly reduced after grafting with perfluorooctyl ethyl acrylate, effectively reducing the adhesion between the PET melt and the mold. In Comparative Example 2, the friction coefficient was 32.1% higher than that of Example 1 due to uneven dispersion of the lubricant caused by the agglomeration of nanoparticles.

[0047] 3. Mold wear: A key factor in nanoparticle dispersion In Examples 1-3, the mold wear was 25-28 μm / 1000 cycles, which was 26.3%-34.2% lower than that of Comparative Example 1 (38 μm). This was because the modified nano-titanium dioxide was uniformly dispersed, avoiding abrasive wear on the mold by agglomerates. In Comparative Example 2, the agglomerates of unmodified nanoparticles acted as "hard abrasives", and the wear was 32% higher than that of Example 1.

[0048] Differences between implementation examples: In Example 3, the basic lubricant accounted for 70%, while the calcium stearate content was reduced to 6%. This weakened the external lubrication effect and increased the wear by 4% compared to Example 1, demonstrating the necessity of calcium stearate for mold protection.

[0049] 4. Surface gloss: Synergistic dispersion of silicone elastomer and modified particles Examples 1-3 showed a surface gloss of 89-92 GU, which was 14.1%-17.9% higher than Comparative Example 1 (78 GU). This was because polydimethylsiloxane (Example 1) or organosilicon-acrylate copolymer (Examples 2-3) reduced surface tension and promoted the formation of a uniform film (thickness ±5 nm) of lubricant on the PET surface. In Comparative Example 2, the film layer was uneven due to nanoparticle aggregation, resulting in a 9.7% decrease in gloss.

[0050] Differences between implementation examples: Example 1 uses a compound of polydimethylsiloxane and organosilicon-acrylate copolymer, which has the highest gloss. In Example 3, the gloss is slightly reduced due to the compound of hindered amine light stabilizer (Tinuvin 622 + Hostavin NX890), which partially affects the migration of lubricant.

[0051] 5. Defect analysis of comparative proportions Comparative Example 1: Technical Bottlenecks of Ungrafted Fluorinated Monomers In Comparative Example 1, the ungrafted polyester base lubricant had poor compatibility with the PET matrix, resulting in microphase separation during processing, which led to light scattering and a decrease in light transmittance.

[0052] Without fluorine groups, the lubricant has a high surface energy, making it impossible to form a continuous lubricating film on the mold surface. This increases the adhesion between the PET melt and the mold, resulting in insufficient lubrication efficiency.

[0053] Comparative Example 2: Limitations of Unmodified Nano-Titanium Dioxide The insufficient electrostatic repulsion of unmodified nano-titanium dioxide leads to agglomeration, and the agglomerates have high light scattering loss for 550nm visible light.

[0054] Meanwhile, unmodified particles form "rigid agglomerates" in the lubricant, which plow the mold during processing as the melt flows, resulting in much greater wear than the modified system.

Claims

1. A plastic lubricant, characterized in that, By weight, it comprises: 50-70 parts of a molecularly optimized basic lubricant, 10-30 parts of stearamide, 10-20 parts of calcium stearate, 0.3-1 parts of nano titanium dioxide, 1-3 parts of organosilicon elastomer, and 0.5-2 parts of hindered amine light stabilizer; the molecularly optimized basic lubricant is prepared by esterification of polyols and polyacids, followed by graft modification with fluorine-containing monomers.

2. The plastic lubricant according to claim 1, characterized in that, The polyol is pentaerythritol, and the polyacid is trimellitic anhydride.

3. The plastic lubricant according to claim 1, characterized in that, The fluorinated monomer is perfluorooctyl ethyl acrylate.

4. The plastic lubricant according to claim 1, characterized in that, The nano-titanium dioxide is nano-carbon dioxide with a particle size ≤50nm that has been surface-modified with a silane coupling agent, wherein the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

5. The plastic lubricant according to claim 1, characterized in that, The organosilicon elastomer is polydimethylsiloxane or organosilicon-acrylate copolymer or a combination thereof.

6. The plastic lubricant according to claim 1, characterized in that, The hindered amine light stabilizer is one or a mixture of bis(2,2,6,6-tetramethylpiperidinyl) sebacate, bis(1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate, bis(2,2,6,6-tetramethylpiperidinyl) adipate, and poly(4-hydroxy-2,2,6,6-tetramethylpiperidinyl) succinate.

7. A method for preparing a plastic lubricant according to any one of claims 1-6, characterized in that... Includes the following steps: (1) Polyols and polyacids react under the action of a catalyst to obtain a basic lubricant. Then, a fluorine-containing monomer is added to complete the grafting reaction to obtain a basic lubricant with optimized molecular structure. (2) Nano-titanium dioxide is surface modified with a silane coupling agent; (3) Mix the modified nano-titanium dioxide, organosilicon elastomer, hindered amine light stabilizer with the above-mentioned molecularly optimized basic lubricant and stir to disperse; (4) Add stearamide and calcium stearate, and continue stirring to obtain plastic lubricant.

8. The method for preparing a plastic lubricant according to claim 7, characterized in that, The catalyst is p-toluenesulfonic acid.

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