Double-coated titanium dioxide and preparation method and application thereof

Abstract

The present application relates to a kind of double-layer coated titanium dioxide and its preparation method and application, the double-layer coated titanium dioxide includes the following components by weight parts: hydrophilic titanium dioxide 100 parts, first organic modifier 1-4 parts and second organic modifier 1-4 parts;The crystal form of the hydrophilic titanium dioxide is rutile;The first organic modifier includes tetraethoxysilane;The second organic modifier includes C8-C16 long-chain silane coupling agent;The first organic modifier, second organic modifier are sequentially coated on the surface of hydrophilic titanium dioxide.The rutile hydrophilic titanium dioxide is used as raw material in the present application, after being double-layer coated by specific organic modifier, the hydrophobicity of titanium dioxide, the uniformity of coating, the compactness can be improved, so that its thermal stability when being used for PC coloring is significantly improved, in addition, color contrast under ultraviolet marking is also improved to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of pigment modification technology, and in particular to a double-coated titanium dioxide, its preparation method, and its application. Background Technology

[0002] Polycarbonate (PC), as a high-performance engineering plastic, is widely used in electronics, automotive, and optical devices due to its excellent mechanical properties, transparency, and thermal stability. However, the ester groups in its molecular backbone are sensitive to water, acids, and alkalis, and are prone to hydrolysis, leading to chain breakage and affecting the long-term durability of the material. Titanium dioxide (TiO2) is often introduced as a white pigment in the coloring or modification of polycarbonate. However, titanium dioxide itself has hydrophilic properties, especially in the presence of its highly photocatalytic anatase crystal form. Under light and humidity conditions, the hydrolytic degradation of the ester groups may be accelerated, resulting in a significant reduction in the material's thermal stability and marking contrast. Therefore, developing titanium dioxide pigments suitable for polycarbonate systems has significant scientific research value and practical application significance.

[0003] CN103044972A discloses an organic surface modification method for improving the hydrophobicity of anatase titanium dioxide. The method involves adding an organosilicon material (a mixture of one, two, or three of the following: a trialkoxyalkylene silane, a hydroxyl-terminated hydrogen-containing polysiloxane, or a methyl-terminated hydrogen-containing polysiloxane) to deionized water, then adding unmodified anatase titanium dioxide, followed by slurry preparation, drying, and pulverization. The resulting titanium dioxide exhibits significantly improved hydrophobicity. However, this titanium dioxide is only suitable for hydrophobic modification and cannot meet the requirements for polycarbonate coloring.

[0004] CN107805321A discloses a method for preparing a titanium dioxide pigment specifically for polycarbonate. The method involves inorganically coating primary titanium dioxide produced by the chlorination process with silicon dioxide and aluminum oxide, followed by organic surface treatment with amino-modified polysiloxane. This significantly improves the mechanical properties when applied to PC. However, this method involves both inorganic and organic coating processes, making it complex.

[0005] Therefore, providing a simple and readily available titanium dioxide pigment suitable for PC systems, and improving coloring stability and marking contrast, is an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a double-coated titanium dioxide, its preparation method, and its applications. This invention uses rutile hydrophilic titanium dioxide as raw material, and after double-coating with a specific organic modifier, it can improve the hydrophobicity of the titanium dioxide and the uniformity and density of the coating, significantly enhancing its thermal stability when used for PC coloring. Furthermore, the color contrast under ultraviolet marking is also improved to some extent.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a double-coated titanium dioxide, wherein the double-coated titanium dioxide comprises the following components by weight: 100 parts of hydrophilic titanium dioxide, 1-4 parts of a first organic modifier, and 1-4 parts of a second organic modifier. The first organic modifier may be, for example, 1 part, 2 parts, 3 parts, 4 parts, etc., and the second organic modifier may be, for example, 1 part, 2 parts, 3 parts, 4 parts, etc.

[0008] The hydrophilic titanium dioxide has a rutile crystal form. The first organic modifier includes tetraethoxysilane; The second organic modifier includes a C8-C16 long-chain silane coupling agent; The carbon number of the C8-C16 long-chain silane coupling agent can be, for example, C8, C10, C12, C14, C16, etc.

[0009] The first organic modifier and the second organic modifier are sequentially coated on the surface of the hydrophilic titanium dioxide.

[0010] In this invention, the hydroxyl groups on the surface of hydrophilic titanium dioxide allow the tetraethoxysilane in the first organic modifier to form a dense silica coating film after hydrolysis and condensation, thereby improving the chemical stability of the titanium dioxide. Then, a long-chain silane coupling agent is used to hydrophobically modify the monolayer-coated titanium dioxide, forming a double-layer-coated titanium dioxide. When the resulting double-layer-coated titanium dioxide is used for PC coloring, its thermal stability is significantly improved, and its color contrast under UV marking is also somewhat improved.

[0011] Preferably, the hydrophilic titanium dioxide has a TiO2 content of 94-98 wt%, a pH of 6-8, and a specific gravity of 4.0-4.2.

[0012] Preferably, the C8-C16 long-chain silane coupling agent includes any one or a combination of at least two of the following: n-octyltriethoxysilane, n-octyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, perfluorooctyltriethoxysilane, or perfluorodecyltrimethoxysilane.

[0013] In a second aspect, the present invention provides a method for preparing double-coated titanium dioxide according to the first aspect. The method for preparing double-coated titanium dioxide according to the present invention is a conventional method in the art, including but not limited to wet coating, dry coating or vapor deposition.

[0014] Preferably, the preparation method includes the following steps: (1) The first organic modifier and water are mixed and hydrolyzed to obtain solution one; the hydrophilic titanium dioxide and solution one are mixed and homogenized, and then dried to obtain single-layer coated titanium dioxide; (2) The second organic modifier and water are mixed and hydrolyzed to obtain solution two; the single-layer coated titanium dioxide and solution two are mixed and homogenized, and then dried to obtain the double-layer coated titanium dioxide.

[0015] In this invention, the organic coating modification adopts homogeneous stirring coating, which is a simple method. The dried product is loose, delicate and free of lumps, and has good coating uniformity.

[0016] Preferably, the homogenization time in steps (1) and (2) is 20-30 min each independently.

[0017] The homogenization time can be independent, for example, 20 min, 22 min, 25 min, 28 min, 30 min, etc.

[0018] Preferably, the preparation method includes the following steps: (1) The first organic modifier is sprayed onto the hydrophilic titanium dioxide, stirred and then dried to obtain a single-layer coated titanium dioxide. (2) The second organic modifier is sprayed onto the single-layer coated titanium dioxide, stirred and dried to obtain the double-layer coated titanium dioxide.

[0019] Thirdly, the present invention provides an application of the double-coated titanium dioxide according to the first aspect in polycarbonate coloring.

[0020] Fourthly, the present invention provides a polycarbonate composition comprising, by weight, the following components: 98.5 parts of polycarbonate and 1-8 parts of the double-coated titanium dioxide described in the first aspect.

[0021] The double-coated titanium dioxide can be, for example, 1 part, 2 parts, 4 parts, 6 parts, 8 parts, etc.

[0022] Preferably, the polycarbonate composition further comprises 0.5-2 parts by weight of chain extender.

[0023] The chain extender may be, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, etc.

[0024] Preferably, the chain extender comprises any one or a combination of at least two of the following: a copolymer of styrene-acrylonitrile-glycidyl methacrylate, an epoxy group chain extender, or a grafted oxazoline group chain extender.

[0025] In this invention, the introduction of chain extender can repair the molecular chain breakage that may occur in PC resin during processing, and can also indirectly affect the coloring effect of titanium dioxide and the final comprehensive performance of the product. It can play a synergistic role with double-coated titanium dioxide in improving the final product performance.

[0026] Preferably, the polycarbonate composition further includes 0.1-5 parts by weight of additives.

[0027] The additive may be, for example, 0.1 parts, 0.5 parts, 1 part, 2 parts, 3 parts, 5 parts, etc.

[0028] Preferably, the additives include any one or a combination of at least two of toughening agents, antioxidants, or lubricants.

[0029] The toughening agent includes any one or a combination of at least two of methyl methacrylate-butadiene-styrene-acrylic acid copolymer, ABS and its high-rubber powder or acrylate rubber.

[0030] Preferably, the antioxidant comprises hindered phenolic antioxidants and / or phosphite antioxidants, preferably any one or a combination of at least two of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, or octadecyl-3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate.

[0031] Preferably, the lubricant comprises any one or a combination of at least two of pentaerythritol stearate, glyceryl stearate, or ethylene bis-stearamide.

[0032] Fifthly, the present invention provides a method for preparing a polycarbonate composition according to the fourth aspect, the method comprising: mixing the components, performing melt extrusion, cooling granulation, and injection molding to obtain the polycarbonate composition.

[0033] Preferably, the temperature of the melt extrusion is 250-280°C.

[0034] The temperature of the melt extrusion can be, for example, 250°C, 260°C, 270°C, 280°C, etc.

[0035] Preferably, the injection molding temperature is 280-310℃.

[0036] The injection temperature can be, for example, 280℃, 290℃, 300℃, 310℃, etc.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The double-coated titanium dioxide provided by the present invention can be used as a white colorant in polycarbonate, which significantly improves its thermal stability. In addition, the color contrast under ultraviolet marking is also improved to a certain extent.

[0038] (2) The preparation process of double-coated titanium dioxide provided by the present invention is simple. The inexpensive hydrophilic titanium dioxide can be used as a colorant for PC after a simple organic modification process, and the added value can be improved. Detailed Implementation

[0039] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0040] The raw materials used in the following embodiments and application examples are as follows: 1. Hydrophilic titanium dioxide Hydrophilic titanium dioxide 1: Purchased from Jiangxi Tianguang Titanium Industry Co., Ltd., brand name TIKON 33, rutile crystal titanium dioxide prepared by sulfuric acid method; Hydrophilic titanium dioxide 2: Purchased from Guangxi Lanxing Dahua Chemical Co., Ltd., brand name DHA-100, anatase titanium dioxide prepared by the sulfuric acid method; 2. First organic modifier Tetraethoxysilane, purchased from Anhui Zesheng Technology Co., Ltd., CAS No. 78-10-4, purity 99 wt%; 3. Second organic modifier Second organic modifier 1: n-octyltriethoxysilane, purchased from Beijing Innocare Technology Co., Ltd., CAS No. 2943-75-1, purity 97%; Second organic modifier 2: hexadecyltrimethoxysilane, purchased from Tianjin Xiens Biochemical Technology Co., Ltd., CAS No. 16415-12-6, purity 98%; 4. Other modifiers Other modifier 1: Tetramethoxysilane, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No. 681-84-5, purity ≥98%; Other modifier 2: Sodium metasilicate nonahydrate, purchased from Anhui Zesheng Technology Co., Ltd., CAS No. 13517-24-3, purity 98%; 5. Polycarbonate resin Polycarbonate resin (PC resin): Grade PC 2220, purchased from Wanhua Chemical Group Co., Ltd., melt flow index (300℃ / 1.2Kg) under ASTM D1238 test standard (300℃ / 1.2Kg): 19 g / 10min, density 1.2 g / cm³. 3 ; 6. Chain extenders Chain extender 1: A copolymer of styrene-acrylonitrile-glycidyl methacrylate, purchased from Shanghai Rizhisheng Fine Chemical Co., Ltd., brand name SAG-008, CAS number: 29762-66-1, concentration 99-100wt%; Chain extender 2: Grafted oxazoline group type chain extender, purchased from Shanghai Puzhan Industrial Co., Ltd., brand name PZ-1050; 7. Additives MBS toughening agent: methyl methacrylate-butadiene-styrene-acrylic acid copolymer, purchased from Foshan Ruishan Group Co., Ltd., brand name M-521; Antioxidant 1: Octadecyl-3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate, CAS No.:2082-79-3, purchased from BASF Applied Chemicals Co., Ltd., Shanghai, China, brand name IRGANOX 1076; Antioxidant 2: Tris(2,4-di-tert-butyl)phenyl phosphite, CAS No.:31570-04-4, purchased from Sanfeng Chemical Co., Ltd., Linyi City, Shandong Province, brand name SONOX 168; Lubricant: Pentaerythritol stearate, purchased from Jiangsu Wannapu New Material Technology Co., Ltd., brand name PETS-AP.

[0041] Examples 1-9, Comparative Examples 1-10 Examples 1-9 and Comparative Examples 1-10 respectively provide a double-layer / single-layer coated titanium dioxide, and the raw materials and their weight parts are shown in Table 1-2.

[0042] The preparation method of the double-layer coated titanium dioxide in Examples 1-8 and Comparative Examples 7-8 includes the following steps: (1) Mix the first organic modifier (or other modifier 1) with half of the total amount of deionized water, stir and hydrolyze to obtain solution one; mix the hydrophilic titanium dioxide with solution one, stir homogenously for 25 min, and then dry at 105℃ to obtain single-layer coated titanium dioxide. (2) Mix the second organic modifier with the remaining deionized water, stir and hydrolyze to obtain solution two; mix the single-layer coated titanium dioxide with solution two, stir homogenously for 25 min, and then dry at 105°C to obtain the double-layer coated titanium dioxide.

[0043] The preparation method of the double-coated titanium dioxide in Example 9 includes the following steps: (1) First, put the hydrophilic titanium dioxide into a mixing tank, and then spray the first organic modifier onto the titanium dioxide while stirring. After stirring evenly, bake at 105℃ for 2 hours to obtain single-layer coated titanium dioxide. (2) Put the single-layer coated titanium dioxide into a mixing tank, and spray the second modifier onto the titanium dioxide while stirring. After stirring evenly, bake at 105℃ for 2 hours to obtain double-layer coated titanium dioxide.

[0044] The preparation methods of the monolayer coated titanium dioxide in Comparative Examples 1-6 include the following steps: The first organic modifier / second organic modifier and deionized water were mixed and stirred for hydrolysis. Then, hydrophilic titanium dioxide was added, and the mixture was stirred homogenously for 25 minutes. After drying at 105°C, a single-layer coated titanium dioxide was obtained.

[0045] The preparation method of the double-coated titanium dioxide in Comparative Example 9 includes the following steps: (1) Mix other modifier 2 with half of the total amount of deionized water, stir and hydrolyze to obtain solution one; mix hydrophilic titanium dioxide with solution one, adjust the pH to 7 with dilute hydrochloric acid, stir homogenously for 25 min, and then dry at 105℃ to obtain single-layer coated titanium dioxide. (2) Mix the second organic modifier with the remaining deionized water, stir and hydrolyze to obtain solution two; mix the single-layer coated titanium dioxide with solution two, stir homogenously for 25 min, and then dry at 105°C to obtain the double-layer coated titanium dioxide.

[0046] The preparation method of the double-coated titanium dioxide in Comparative Example 10 includes the following steps: (1) Mix the second organic modifier with half of the total amount of deionized water, stir and hydrolyze to obtain solution one; mix the hydrophilic titanium dioxide with solution one, stir homogenously for 25 min, and then dry at 105℃ to obtain single-layer coated titanium dioxide. (2) Mix the first organic modifier and the remaining deionized water, stir and hydrolyze to obtain solution two; mix the single-layer coated titanium dioxide with solution two, stir homogenously for 25 min, and then dry at 105°C to obtain the double-layer coated titanium dioxide.

[0047] Hydrophobicity test: Take a small amount of modified titanium dioxide, flatten the surface of the powder with a coverslip, drop a drop of water with a syringe needle, and observe the contact state between the water and the titanium dioxide: if the water droplet is immersed in the powder, it is hydrophilic; if the water droplet is hemispherical, it is hydrophobic; if the water droplet is spherical, it is superhydrophobic.

[0048] Table 1 Table 2 Application Example 1-13, Comparative Application Example 1-12 Application Examples 1-13 and Comparative Application Examples 1-12 each provide a polycarbonate composition, the components of which and their weight parts are shown in Tables 3-4.

[0049] The method for preparing the polycarbonate composition includes: mixing the components, melting and extruding them through a twin-screw extruder at 280°C, cooling and granulating them, and injection molding them at 300°C to obtain the polycarbonate composition.

[0050] The obtained polycarbonate composition was subjected to the following performance tests, and the results are summarized in Table 3-4.

[0051] (1) Thermal stability assessment: The color sample was injected at 300℃. The remaining granules were left in the injection molding machine for 5 minutes before injection molding. The color was tested using a spectrophotometer and the color difference DE1 before and after the heat retention was compared. (2) Marking effect evaluation: Marking was performed using a 355nm ultraviolet laser marking machine (3W). The marking parameters were: pulse width 25us, frequency 25KHz, speed 1800mm / s. Color was tested using a spectrophotometer, and the color difference DE2 before and after marking was compared.

[0052] Table 3 Table 4 As can be seen from Tables 3-4, the double-layer coated titanium dioxide provided by this invention can improve the hydrophobicity of titanium dioxide and the uniformity and density of the coating, thus significantly improving its thermal stability when used for PC coloring. In addition, the color contrast under ultraviolet marking is also improved to a certain extent. Specifically, based on Comparative Application Example 1, the color difference DE1 of the injection-molded color plate after 5 minutes of heat retention decreased from 2.34 to 0.27-0.45, and the contrast of ultraviolet laser marking was also improved to a certain extent, with the contrast DE2 increasing from 37.28 to 41.32-42.31.

[0053] As can be seen from Application Examples 1-9, the color and thermal stability of titanium dioxide are significantly improved after double-layer coating. This is because tetraethoxysilane can form a dense silica coating film on the surface of titanium dioxide, improving its chemical and thermal stability. Furthermore, the modified titanium dioxide also improves the contrast of laser marking when applied to PC. This is because the material's stability is improved, the amount of small molecule gases produced by degradation is reduced, and foaming during marking is decreased, thus increasing blackness.

[0054] As shown in Application Examples 3 and 11 and 13, the introduction of a certain amount of chain extender can help improve the performance of PC. This is because it can repair the molecular chain breakage that may occur in PC resin during processing, and can also indirectly affect the coloring effect of titanium dioxide and the final comprehensive performance of the product. A comparison between Application Example 11 and Comparative Application Example 9 shows that using chain extender alone has no significant effect on improving the performance of colored PC; it needs to be used in conjunction with modified titanium dioxide to achieve a synergistic effect.

[0055] As shown in Application Example 3 and Comparative Application Examples 2-6, the titanium dioxide coated with the second organic modifier alone shows a slight improvement in the thermal stability of the color after injection molding, but the effect is not significant. As shown in Application Example 3 and Comparative Application Example 7, the coating with the first organic modifier alone does not significantly improve performance. This is because the surface coated with tetraethoxysilane still has hydrophilic properties, and the introduced moisture will lead to PC degradation. As shown in Application Example 3 and Comparative Application Example 8, when anatase titanium dioxide is used, the improvement in the thermal stability of the color plate after injection molding is not significant, and the marking contrast is low. This is because the anatase crystal structure is not dense enough, has poor stability, and is prone to phase transformation at high temperatures, thus its performance is inferior to rutile titanium dioxide. As can be seen from the comparison between Application Example 3 and Comparative Application Examples 10-11, if tetraethoxysilane is replaced with tetramethoxysilane or sodium metasilicate nonahydrate, the performance deteriorates. This is because tetramethoxysilane reacts too quickly, resulting in a loose silica structure with many defects, making it difficult to form a dense coating layer. Sodium metasilicate nonahydrate requires a precise pH to react and introduces impurity ions, making it difficult to control the density of the silica structure formed. As can be seen from the comparison between Application Example 3 and Comparative Application Example 12, the performance is worse after changing the order of the modifiers. This is because the silica product formed after the hydrolysis and condensation reaction of tetraethoxysilane has hydrophilic properties, which introduces moisture and leads to PC degradation.

[0056] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A double-layer coated titanium dioxide, characterized in that, The double-coated titanium dioxide comprises the following components by weight: 100 parts of hydrophilic titanium dioxide, 1-4 parts of the first organic modifier, and 1-4 parts of the second organic modifier. The hydrophilic titanium dioxide has a rutile crystal form. The first organic modifier includes tetraethoxysilane; The second organic modifier includes a C8-C16 long-chain silane coupling agent; The first organic modifier and the second organic modifier are sequentially coated on the surface of the hydrophilic titanium dioxide.

2. The titanium dioxide according to claim 1, characterized in that, The C8-C16 long-chain silane coupling agent includes any one or a combination of at least two of the following: n-octyltriethoxysilane, n-octyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, perfluorooctyltriethoxysilane, or perfluorodecyltrimethoxysilane.

3. A method for preparing double-layer coated titanium dioxide according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) The first organic modifier and water are mixed and hydrolyzed to obtain solution one; the hydrophilic titanium dioxide and solution one are mixed and homogenized, and then dried to obtain single-layer coated titanium dioxide; (2) The second organic modifier and water are mixed and hydrolyzed to obtain solution two; the single-layer coated titanium dioxide and solution two are mixed and homogenized, and then dried to obtain the double-layer coated titanium dioxide.

4. The application of a double-coated titanium dioxide according to claim 1 or 2 in polycarbonate coloring.

5. A polycarbonate composition, characterized in that, The polycarbonate composition comprises, by weight, the following components: 98.5 parts polycarbonate and 1-8 parts of the double-coated titanium dioxide as described in claim 1 or 2.

6. The polycarbonate composition according to claim 5, characterized in that, The polycarbonate composition further includes 0.5-2 parts by weight of chain extender; Preferably, the chain extender comprises any one or a combination of at least two of the following: a copolymer of styrene-acrylonitrile-glycidyl methacrylate, an epoxy group chain extender, or a grafted oxazoline group chain extender.

7. The polycarbonate composition according to claim 5, characterized in that, The polycarbonate composition further includes 0.1-5 parts by weight of additives; Preferably, the additives include any one or a combination of at least two of toughening agents, antioxidants, or lubricants.

8. The polycarbonate composition according to claim 7, characterized in that, The toughening agent includes any one or a combination of at least two of methyl methacrylate-butadiene-styrene-acrylic acid copolymer, ABS and its high-rubber powder or acrylate rubber.

9. The polycarbonate composition according to claim 7, characterized in that, The antioxidants include hindered phenolic antioxidants and / or phosphite antioxidants, preferably any one or a combination of at least two of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, or octadecyl-3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate. Preferably, the lubricant comprises any one or a combination of at least two of pentaerythritol stearate, glyceryl stearate, or ethylene bis-stearamide.

10. A method for preparing a polycarbonate composition according to any one of claims 5-9, characterized in that, The preparation method includes: mixing the components, melting and extruding, cooling and granulating, and injection molding to obtain the polycarbonate composition.

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