A plastic aluminum pigment and its preparation method

Abstract

This invention discloses a plastic aluminum pigment and its preparation method. The plastic aluminum pigment comprises the following raw materials in weight percentages: 60-80% aluminum silver paste, 3-10% carrier agent, 2-3% antioxidant, 3-10% dispersant, and 3-20% adhesive. The carrier agent facilitates the coating of dispersant and antioxidant onto the aluminum sheet surface, forming a protective layer to prevent molten plastic adhesion and improve the appearance of the plastic product. The antioxidant prevents the aluminum pigment from oxidizing and turning black, and avoids thermo-oxidative aging of the carrier agent, thus extending the service life of the plastic material. The dispersant reduces friction between the raw material and the screw, effectively solving problems such as product blackening, flow lines, or particle formation. The adhesive agent ensures that the dried powder is evenly coated on its surface, effectively preventing aluminum pigment powder dust, improving dispersion, and resulting in more uniform color mixing. Vacuum drying removes 99.5% of the mineral oil from the aluminum silver paste, meeting environmental protection requirements.

Description

Technical Field

[0001] This invention relates to the field of aluminum pigment technology, and in particular to an easily dispersible plastic aluminum pigment and its preparation method. Background Technology

[0002] Plastics are widely used in all aspects of production and daily life. Adding aluminum pigments to plastics can give plastic parts a metallic appearance. The method of use is to pre-mix the aluminum pigments with plastic particles (such as PP, ABS, etc.) evenly and then directly injection mold them; or to first extrude them into plastic masterbatches through an extruder before use.

[0003] Traditional aluminum pigments, also known as aluminum silver paste or aluminum silver powder, contain 20-40 wt% solvent. Direct injection molding can leave chemical residues, which does not meet certain national or international standards, thus limiting their application scenarios. In addition, during injection molding or extrusion, traditional aluminum pigments are not resistant to screw shear and are not easy to disperse, easily resulting in problems such as blackening, flow lines, or particles.

[0004] Therefore, how to overcome the shortcomings of traditional aluminum pigments, such as poor shear resistance, poor dispersibility, and environmental unfriendliness, is an urgent problem to be solved in the industry. Summary of the Invention

[0005] This invention addresses the technical problems of traditional aluminum pigments, such as poor shear resistance, poor dispersibility, and environmental unfriendliness, by providing a mineral oil-free, easily dispersible, and shear-resistant plastic aluminum pigment and its preparation method.

[0006] To address the aforementioned technical problem, this invention provides a plastic aluminum pigment comprising the following raw materials by weight percentage: Aluminum silver paste 60-80%, carrier agent 3-10%, antioxidant 2-3%, dispersant 3-10%, adhesive 3-20%.

[0007] Preferably, the aluminum silver paste is an oil-based aluminum silver paste prepared by ball milling, and the median particle size of the aluminum silver paste is 5-65 μm.

[0008] Preferably, the carrier is a petroleum wax, particularly a fully refined paraffin wax that has undergone deep refining.

[0009] Preferably, the antioxidant is at least one of hindered phenolic antioxidants, aminocarboxylic acid chelating agent solutions, or low-volatility organophosphates.

[0010] Preferably, the dispersant is at least one of amide, oleamide, ethylene bis-stearamide, or N,N-ethylenebis-alkydamide.

[0011] Preferably, the adhesive is at least one of low molecular weight polyethylene, high-density oxidized polyethylene, low-density oxidized polyethylene, or ethylene-acrylic acid copolymer.

[0012] This invention also proposes a method for preparing plastic aluminum pigment, comprising the following steps: Step 1: Weigh and prepare various raw materials for plastic aluminum pigment according to the formula. Add the carrier agent to the aluminum silver paste and stir and knead for 0.5-1 hours to obtain the first mixture. Add the antioxidant and the dispersant to the first mixture. You can choose to heat it to 50-70℃ for better fusion. Stir and knead for 3-4 hours to obtain the second mixture. Step 2: Place the second mixture into a vacuum drying oven for drying. To improve drying efficiency, the second mixture can be extruded into strips or sheets or other shapes with a large surface area. The vacuum drying temperature is 70-90℃ and the drying time is 10-12 hours to obtain the dried material. Step 3: Stir and mix the dried material with the adhesive for 0.5-1 hour to obtain the plastic aluminum pigment.

[0013] This invention utilizes a carrier agent to facilitate the coating of dispersants and antioxidants onto the surface of aluminum sheets, forming a protective layer. This also prevents melt adhesion of plastics and improves the appearance quality of plastic products. The antioxidant prevents aluminum pigments from oxidizing and turning black during processing, avoids thermo-oxidative aging of carrier agents and other raw materials, and extends the service life of plastic materials. In the preparation of masterbatches, the dispersant reduces friction between the raw material and the screw, enhances shear resistance, improves the color development of aluminum pigments, and improves the dispersion quality of aluminum pigments, effectively solving problems such as blackening, flow lines, or particle formation in products. In direct injection molding applications, it can increase injection speed, reduce the temperature gradient of the molded part, and weaken thermal stress and shrinkage deformation rate. The adhesive agent allows the dried powder to be evenly coated on the outer surface of the adhesive particles, forming a fine sand-like product, effectively preventing aluminum pigment powder dust and improving safety during storage and use. During use, the fine sand-like product adheres more easily to plastic particles, resulting in better dispersion and more uniform color mixing.

[0014] The carrier, dispersant, and adhesive selected in this invention also have a synergistic effect of external lubrication. The three raw materials work together to further improve the dispersion quality of pigments, reduce pigment agglomeration, and give the product a good appearance and gloss. The vacuum drying process used in the preparation of this invention effectively removes mineral oil from the aluminum silver paste, achieving a removal rate of 99.5% or higher, which is more environmentally friendly and broadens the application range of aluminum pigments. Attached Figure Description

[0015] Figure 1 Photographs of samples prepared using existing plastic aluminum pigments; Figure 2 A photograph of a sample prepared using the plastic aluminum pigment of Example 1 of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the invention and do not constitute a limitation thereof.

[0017] To address the aforementioned problem, this invention provides a plastic aluminum pigment comprising the following raw materials in the indicated weight percentages: Aluminum silver paste 60-80%, carrier agent 3-10%, antioxidant 2-3%, dispersant 3-10%, adhesive 3-20%.

[0018] Depending on the requirements, different raw material ratios can be used to prepare plastic aluminum pigments, such as, but not limited to, the formulations with weight percentages of the five examples given in Table 1 below: Table 1

[0019] The present invention also proposes a method for preparing the aforementioned plastic aluminum pigment, the steps of which are as follows: Step 1: Weigh each raw material according to the raw material ratios of the five embodiments shown in Table 1. Add the carrier agent to the aluminum silver paste and stir and knead for 0.5-1 hour to obtain the first mixture; then add the antioxidant and dispersant to the first mixture, heat to 50-70℃ to better integrate the raw materials, and stir and knead for 3-4 hours to obtain the second mixture.

[0020] Step 2: Place the second mixture into a vacuum drying oven for drying. The second mixture can be extruded into strips or flakes, or other shapes with a large surface area, to improve drying efficiency. The vacuum drying temperature is 70-90℃, and the drying time is 10-12 hours, yielding the dried material. The dried material is in a loose strip or flake state and can be easily crushed into powder.

[0021] Step 3: Stir and mix the dried material with the adhesive for 0.5-1 hour to obtain plastic aluminum pigment with powdered aluminum pigment uniformly coated on the outer surface of the adhesive particles.

[0022] In this invention, the carrier agent makes it easier for the dispersant, antioxidant, etc., to coat the surface of the aluminum sheet, thus protecting the aluminum sheet. In application, the carrier agent also reduces the melt viscosity of the plastic, improves melt flowability, prevents melt adhesion, and improves the appearance quality of the plastic product. Another function of the carrier agent is to increase the viscosity of the system, allowing the material to retain its original shape after drying and preventing dust generation.

[0023] The antioxidant in this invention can prevent aluminum pigments from oxidizing and turning black during processing, and can also prevent thermal oxidative aging of other additives such as carriers, and can extend the service life of plastic materials and maintain their physical properties.

[0024] In this invention, the dispersant reduces friction between pigments and substrates, screws, and other equipment during the preparation of masterbatches, enhances shear resistance, prevents aluminum flake curling, and improves the color development of aluminum pigments. It also reduces the size and number of aluminum pigment agglomerates, improving the dispersion quality of the aluminum pigments. When applied directly in injection molding, it can increase injection speed, reduce the temperature gradient of the molded part, and weaken thermal stress and shrinkage deformation rate.

[0025] This invention uses an adhesive as a core, allowing powdered aluminum pigment to be uniformly coated onto the adhesive particles, forming a fine-grained product. This fine-grained product effectively prevents aluminum pigment powder from becoming dusty, improving safety during storage and use. During use, the fine-grained product adheres more easily to plastic particles, exhibiting better dispersion and more uniform color mixing.

[0026] The carrier, dispersant, and adhesive used in this invention have a synergistic effect, all of which provide external lubrication, further improving the dispersion quality of pigments, reducing pigment agglomeration, and giving the product a good appearance and gloss.

[0027] The present invention uses a vacuum drying process to effectively remove mineral oil from aluminum silver paste, with a removal rate of 99.5% or higher, which is more in line with environmental protection requirements and thus expands the application range of aluminum pigments.

[0028] The aforementioned traditional aluminum pigment is known as "aluminum silver paste." Its application in plastics presents two major problems. 1. The problem of containing petroleum solvents such as mineral oil. This invention solves this problem through vacuum drying and verifies it by measuring the solid content.

[0029] 2. The problem of difficulty in dispersion. This invention solves this problem through formulation, and verifies it by checking for pitting on test plates.

[0030] Traditional aluminum silver paste consists of aluminum powder, solvent, and additives. It is generally produced using a wet ball milling method. Specifically, spherical or near-spherical aluminum powder is sprayed onto the surface, along with additives such as erucic acid and oleic acid, and organic solvents such as mineral oil, solvent oil, heavy aromatics, and isopropanol. The milling media consists of 1-5mm steel balls, and the milling time is approximately 8-30 hours. Through prolonged and continuous milling, the spherical aluminum powder is stretched into flake-like aluminum powder, exhibiting a silvery-gray metallic luster. The milled flake-like aluminum powder undergoes a sieving process to achieve a more uniform particle size, followed by solid-liquid separation (filtration) to obtain a filter cake. Finally, the filter cake is kneaded together with appropriate surface treatment agents and organic solvents to obtain an aluminum silver paste product with a solids content of approximately 60-70%.

[0031] The aforementioned traditional aluminum pigment was used as a control sample.

[0032] The following is a comparative analysis of the five embodiment samples and control samples of the present invention.

[0033] 1. Testing performance parameters: Mineral oil content Testing equipment: Moisture meter Detection Method: The mineral oil in the silver paste of the example sample and the control sample were heated separately to evaporate the mineral oil. The samples before and after evaporation were weighed, and the mineral oil content was calculated from the weight difference. In practice, 3-5g of the example and control sample were taken sequentially and placed in a measuring dish. The detection temperature was set to 120℃, and the constant weight time was set to 90 seconds. That is, the weight of the material should not change within 90 seconds to avoid inaccurate calculation results due to insufficient drying of the mineral oil.

[0034] Testing standard: Mineral oil content 1% or less Actual results: The mineral oil content in the aluminum silver paste of the control example ranged from 70-80%. The mineral oil content in the five embodiments of this invention ranged from 0.2-0.6%. The mineral oil content of this invention meets the standard of less than 1%. Testing showed that this invention effectively removes mineral oil from aluminum silver paste.

[0035] 2. Detection performance parameters: Dispersion Detection method: The sample from the embodiment and the control sample were mixed with PP respectively, and then processed into test plates using an injection molding machine. The actual dispersion of the sample was checked by observing the pits, particles, or other dispersion conditions on the test plates. In specific implementation, 2% of the weight of the sample from the embodiment or control sample was added to the PP from the embodiment and control sample, mixed and shaken well, and then processed into test plates using an injection molding machine.

[0036] Testing standards: Uniformly dispersed, without pitting or particles.

[0037] Testing equipment: Injection molding machine Actual results: The test plates of the control examples usually had 3-5 pits, while those of the embodiments of the present invention did not.

[0038] like Figure 1 The image shown is a comparison image of a plastic aluminum pigment printing plate. Many small dots can be seen within the circles. Figure 2 The image shown is a stencil image of the plastic aluminum pigment from Embodiment 1 of the present invention. No pitting is visible. Clearly, the present invention exhibits good dispersibility.

[0039] This invention addresses two major challenges in the application of traditional aluminum pigments (i.e., untreated aluminum silver paste) in plastics: poor dispersibility and solvent content. The invention solves the solvent problem through vacuum drying and the dispersibility problem through formula adjustments. Furthermore, the use of an adhesive eliminates the dust problem, resulting in a fine, granular product that is both easily dispersed and dust-free. In practical use, this invention achieves easy dispersibility, dust-free production, and solvent-free properties. This broadens its applicability, making it suitable for food-grade plastics and shear-resistant (suitable for mixing with other colors to create masterbatches). These characteristics are significantly superior to existing technologies.

[0040] The above description is merely a specific embodiment of the present invention. It should be noted that any modifications, equivalent substitutions, and variations made within the spirit and framework of the present invention should be included within the protection scope of the present invention.

Claims

1. A plastic aluminum pigment, characterized in that, The raw materials include the following weight percentages: Aluminum silver paste 60-80%, carrier agent 3-10%, antioxidant 2-3%, dispersant 3-10%, adhesive 3-20%.

2. The plastic aluminum pigment as described in claim 1, characterized in that, The aluminum silver paste is an oil-based aluminum silver paste prepared by ball milling, and the median particle size of the aluminum silver paste is 5-65μm.

3. The plastic aluminum pigment as described in claim 1, characterized in that, The carrier agent is petroleum wax.

4. The plastic aluminum pigment as described in claim 1, characterized in that, The antioxidant is at least one of hindered phenolic antioxidants, aminocarboxylic acid chelating agent solutions, or low-volatility organophosphates.

5. The plastic aluminum pigment as described in claim 1, characterized in that, The dispersant is at least one of amide, oleamide, ethylene bis-stearamide, or N,N-ethylenebis-alkydamide.

6. The plastic aluminum pigment as described in claim 1, characterized in that, The adhesive is at least one of low molecular weight polyethylene, high-density oxidized polyethylene, low-density oxidized polyethylene, or ethylene-acrylic acid copolymer.

7. A method for preparing a plastic aluminum pigment as described in any one of claims 1 to 6, comprising the following steps: Step 1: Weigh and prepare the various raw materials for the plastic aluminum pigment according to the formula, add the carrier agent to the aluminum silver paste and stir and knead to obtain the first mixture; add the antioxidant and the dispersant to the first mixture, heat to the set temperature, and stir and knead to obtain the second mixture. Step 2: Place the second mixture into a vacuum drying oven for drying to obtain a dried material; Step 3: Mix the dried material with the adhesive to obtain the plastic aluminum pigment.

8. The preparation method according to claim 7, characterized in that, In step 1, the carrier agent is added to the aluminum silver paste and stirred and kneaded for 0.5-1 hours to obtain the first mixture; the set temperature is 50-70℃, and then stirred and kneaded for 3-4 hours to obtain the second mixture.

9. The preparation method according to claim 7, characterized in that, In step 2, the vacuum drying temperature is 70-90℃ and the drying time is 10-12 hours to obtain the dried material.

10. The preparation method according to claim 7, characterized in that, In step 3, the dried material and the adhesive are stirred and mixed for 0.5-1 hour to obtain the plastic aluminum pigment.

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