Polycarbonate composition having low shrinkage rate, and preparation method therefor and use thereof

Abstract

A polycarbonate composition having a low shrinkage rate, and a preparation method therefor and a use thereof. The polycarbonate composition having a low shrinkage rate comprises the following components in parts by weight: 55-99.9 parts of a polycarbonate resin, 0.5-10 parts of a toughening agent, 0.1-2 parts of a spherical filler, and 5-30 parts of a composite flaky filler. The polycarbonate composition has a low shrinkage rate and excellent rigidity and toughness, and a product prepared from the polycarbonate composition has high weld line strength and good appearance, and can meet the quality requirements of processing technologies and post-assembly.

Description

A polycarbonate composition with low shrinkage, preparation method and application thereof Technical Field

[0001] The present invention relates to the field of engineering plastics, and more particularly to a polycarbonate composition with low shrinkage, a preparation method thereof, and applications thereof. Background Art

[0002] Polycarbonate materials are materials primarily composed of polycarbonate. Polycarbonate is an amorphous polymer that transforms into a transparent glass-like substance upon melting and cooling, exhibiting excellent optical and mechanical properties. Polycarbonate has a high melting point, is resistant to low temperatures, and exhibits low water absorption. It also exhibits excellent impact resistance, electrical insulation, and aging resistance, and is resistant to both inorganic and organic dilute acids.

[0003] With the trend of replacing steel with plastic, the application fields of plastic are becoming more and more extensive, so people's requirements for the dimensional accuracy of plastic parts are becoming increasingly stringent. Precision injection molding has become an important method of plastic molding, which is characterized by high precision of injection molded parts, including dimensional accuracy and repeatability. In order to meet the requirements of precision injection molding, it is necessary to develop polycarbonate materials with a low shrinkage rate (<0.3%). In addition, for important components in computers, video recorders, electronic display screens and color TVs, as well as application scenarios such as mechanical equipment housings, covers and frames, polycarbonate materials are also required to have excellent rigidity and toughness.

[0004] A Chinese patent titled "Aromatic Polycarbonate Resin Composition" reduces the shrinkage of the material by adding hollow microspheres to the aromatic polycarbonate resin, but its shrinkage can only reach 0.4-0.6%, which is still a relatively high level. In addition, due to the low strength of the one-dimensional hollow microspheres at the bonding line, the screw columns of the parts made of this material are prone to cracking, which in turn leads to low weld line strength, making it difficult to meet relevant application scenarios.

[0005] Therefore, it is necessary to solve the problems that the current polycarbonate material still has a high shrinkage rate, cannot have good rigidity and toughness at the same time, and has low weld line strength of the product.

[0006] Summary of the Invention

[0007] The primary objective of the present invention is to overcome the problems of existing polycarbonate materials, such as high shrinkage, inability to simultaneously provide good rigidity and toughness, and low weld line strength in finished parts. This polycarbonate composition is designed to provide a low-shrinkage polycarbonate composition. This polycarbonate composition exhibits low shrinkage, excellent rigidity and toughness, and produces finished parts with high weld line strength and a good appearance, meeting the quality requirements of various processing techniques and post-assembly processes.

[0008] A further object of the present invention is to provide a method for preparing the polycarbonate composition.

[0009] A further object of the present invention is to provide use of the polycarbonate composition in preparing display screens, housings or covers.

[0010] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0011] A polycarbonate composition with low shrinkage, comprising the following components in parts by weight:

[0012] The composite flaky filler is formed by compounding a first flaky filler and a second flaky filler in a mass ratio of 1:(0.33-3). The average particle size of the first flaky filler is 5-7 μm, and the average particle size of the second flaky filler is 0.5-2 μm. The average particle size of the first flaky filler can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, etc.; the average particle size of the second flaky filler can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, etc. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific values ​​within the above ranges.

[0013] Through numerous studies, the inventors of the present invention have discovered that adding a spherical filler and a composite flaky filler having a specific average particle size and mass ratio to a polycarbonate resin results in a polycarbonate composition having low shrinkage and excellent rigidity and toughness. This is because, on the one hand, compounding two flaky fillers of different average particle sizes increases the contact area between the matrix resin and the flaky filler through a size effect, forming a good riveted bond, thereby reducing the shrinkage of the polycarbonate composition to a certain extent. Furthermore, the addition of the spherical filler further amplifies the size effect by disrupting the orientation of the flaky filler through its rolling effect, resulting in smoother flow of the polycarbonate composition during injection molding and further reducing shrinkage (less than 0.3%). This, in turn, results in excellent dimensional stability of the polycarbonate composition parts. Furthermore, the size effect of the two flaky fillers of different average particle sizes synergizes with the spherical filler, resulting in good filler dispersion and a balanced rigidity and toughness of the polycarbonate composition, resulting in excellent rigidity and toughness. In addition, the combination of the composite flake filler and the spherical filler can also make the weld line strength of the polycarbonate composition product high (high clamping force of the metal screw column) and good appearance.

[0014] That is, the polycarbonate composition of the present invention has low shrinkage, excellent rigidity and toughness, and the weld line strength of the product is high and the appearance is good, and can meet the quality requirements of various processing techniques and post-assembly.

[0015] Preferably, the polycarbonate composition comprises the following components in parts by weight:

[0016] Polycarbonate resins, toughening agents and spherical fillers commonly used in the art can be used in the present invention.

[0017] Optionally, the polycarbonate resin is at least one of an aromatic polycarbonate resin and an aliphatic polycarbonate resin.

[0018] Optionally, the weight average molecular weight of the polycarbonate resin is 22,000 to 30,000.

[0019] The weight average molecular weight of the polycarbonate resin of the present invention can be measured by gel chromatography.

[0020] Preferably, the weight average molecular weight of the polycarbonate resin is 24,500 to 30,000.

[0021] Under the condition of the weight-average molecular weight, the obtained polycarbonate composition maintains good rigidity and toughness and low shrinkage, and has a higher clamping force for metal screw columns, thereby making the weld line strength of the product higher and the appearance better.

[0022] Preferably, the toughening agent is an ethylene copolymer toughening agent, including but not limited to EMA, EBA, EVA, etc.

[0023] More preferably, the toughening agent is ethylene-butyl acrylate copolymer (EBA).

[0024] By selecting ethylene-butyl acrylate copolymer as a toughening agent, the obtained polycarbonate composition has better toughness, lower shrinkage, and higher clamping force of metal screw columns.

[0025] Preferably, the mass ratio of the spherical filler to the composite flaky filler is 1:(15-50).

[0026] Optionally, the average particle size of the spherical filler is 0.2 to 45 μm, preferably 0.22 to 7.5 μm.

[0027] The average particle size of the spherical filler can be 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm and specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0028] Optionally, the spherical filler is at least one of glass microspheres, titanium dioxide or calcium carbonate.

[0029] Preferably, the first flaky filler is at least one of talc, flaky kaolin, montmorillonite, mica or flake glass powder, and the second flaky filler is at least one of talc, flaky kaolin, montmorillonite, mica or flake glass powder.

[0030] The first plate-like filler and the second plate-like filler may have the same or different compositions.

[0031] More preferably, the first flake filler is talc powder, and the second flake filler is talc powder.

[0032] Preferably, the polycarbonate composition further comprises 1 to 30 parts of a flame retardant, more preferably 8 to 14 parts.

[0033] Preferably, the polycarbonate composition further comprises 0.01 to 5 parts of an anti-dripping agent, more preferably 0.3 to 1 part.

[0034] In order to meet more application scenarios, when the present invention adds a flame retardant and an anti-drip agent, the polycarbonate composition of the present invention has good initial thin-wall flame retardancy (1.0mm V-0) while having low shrinkage, excellent rigidity and toughness, and high weld line strength of the workpiece. After double 85 wet heat aging treatment, it still has good thin-wall flame retardancy (1.0mm V-0). Among them, for the initial flame retardancy, the flammability test is carried out in accordance with the "Flammability Test of Plastic Materials, UL94-2022" regulations. The flame retardancy rating is derived based on the burning rate, extinguishing time, resistance to falling, and whether the falling is burning. The sample used for the test: 125mm length and 13mm width. The thickness of the present invention is selected as 1.0mm when conducting the test. According to the UL94 regulations, the flame retardancy rating of the material can be classified as (UL94-HB): V0, V1, V2, 5VA and 5VB. For flame retardancy after damp heat aging, the samples were first subjected to damp heat aging treatment in a constant temperature and humidity chamber with a temperature set at 85°C and a humidity of 85% for 500 hours, and then the flammability test was carried out according to the procedure of "Flammability Test of Plastic Materials, UL94-2022".

[0035] The present invention has no particular limitation on the flame retardant. Optionally, the flame retardant is at least one of bisphenol A bis(diphenyl phosphate), triphenyl phosphate, or resorcinol-bis(dibisphosphate).

[0036] The anti-drip agent of the present invention is not particularly limited. Optionally, the anti-drip agent is at least one of PTFE, a PTFE / SAN blend, a PTFE / PE blend, or a PTFE / ABS blend. Preferably, the polycarbonate composition further comprises 0.1 to 2 parts of other additives.

[0037] More preferably, the other auxiliary agent is at least one of an antioxidant or a lubricant.

[0038] Optionally, the antioxidant is at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, phosphite or n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0039] Optionally, the lubricant is at least one of polyol ester, polyethylene wax or montan wax.

[0040] The preparation method of the polycarbonate composition comprises the following steps:

[0041] The components are mixed, melt-extruded, and pelletized to obtain the polycarbonate composition.

[0042] Preferably, the preparation method comprises the following steps: stirring and mixing the components in a high-speed mixer, then melt-extruding in a twin-screw extruder, and granulating to obtain the polycarbonate composition.

[0043] More preferably, the stirring speed is 50 to 200 rpm; the aspect ratio of the twin-screw extruder is 36 to 60:1, the barrel temperature is 230 to 290° C., and the screw speed is 200 to 800 rpm.

[0044] The use of the polycarbonate composition in preparing display screens, housings or covers also falls within the protection scope of the present invention.

[0045] Optionally, the screen display is a computer screen, a video recorder screen or a color television screen.

[0046] Optionally, the housing is a mechanical equipment housing.

[0047] Optionally, the cover is a mechanical equipment cover.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The polycarbonate composition of the present invention has low shrinkage, excellent rigidity and toughness, and the weld line strength of the manufactured part is high and the appearance is good, and can meet the quality requirements of various processing techniques and post-assembly. DETAILED DESCRIPTION

[0050] In order to more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail through specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Various changes can be made within the scope of the rights of the present invention.

[0051] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0052] Polycarbonate 1#: PC 1300-10NP, LG, South Korea, weight average molecular weight 24500;

[0053] Polycarbonate 2#: PC 1300-03NP, LG, South Korea, weight average molecular weight 30,000;

[0054] Polycarbonate 3#: PC 1300-22NP, LG, South Korea, weight average molecular weight 22000;

[0055] Flame retardant: bisphenol A bis(diphenyl phosphate), commercially available;

[0056] Anti-drip agent: PTFE / SAN blend, commercially available;

[0057] Other additives: antioxidant 1076, commercially available;

[0058] Toughener 1#: Elvaloy-AC1125, DOW, EMA (ethylene-methyl acrylate copolymer);

[0059] Toughener 2#: Elvaloy PTW, DuPont, EBA (ethylene-butyl acrylate copolymer);

[0060] Toughening agent 3#: Evaflex EVA460, Mitsui DuPont, EVA (ethylene-vinyl acetate copolymer);

[0061] Toughener 4#: ABS POW HR181, Kumho, high rubber powder;

[0062] Spherical filler 1#: titanium dioxide, Chemours R-103, average particle size 0.22 μm;

[0063] Spherical filler 2#: titanium dioxide, TR50 2000 mesh, Guangdong Yuanlei Powder Co., Ltd., average particle size 6.5 μm;

[0064] Spherical filler 3#: titanium dioxide, TR50 300 mesh, Guangdong Yuanlei Powder Co., Ltd., average particle size 45 μm;

[0065] Spherical filler 4#: calcium carbonate, Filmlink 520, IMERYS, average particle size 2.7 μm;

[0066] First flaky filler 1#: talc powder, BHS-1250A, Xufeng, Haicheng, Liaoning; average particle size 6.5-7 μm;

[0067] First flaky filler 2#: talc powder, TYT-777, Liaoning Beihai Company, average particle size 5 μm;

[0068] Second flake filler 1#: talc powder, HTP Ultra 5L, Liaoning Aihai, average particle size 0.5 μm;

[0069] The second flake filler 2#: talc, HTP1, IMIFABI, average particle size 1.9 μm;

[0070] The fillers involved in the present invention can be directly purchased from the market to obtain spherical fillers and flaky fillers of corresponding particle sizes, or can be purchased from the market and then sieved or ground according to existing technologies to obtain spherical fillers and flaky fillers of corresponding particle sizes.

[0071] Composite flaky fillers 1 to 8#: homemade, with compositions as shown in Table 1; the preparation process is as follows: the first flaky filler and the second flaky filler are mixed to obtain the composite flaky filler.

[0072] Table 1 Formula of composite flake filler (parts by weight)

[0073] Unless otherwise specified, the components (such as adjuvants) used in the parallel examples and comparative examples are all the same commercially available products.

[0074] The properties of the polycarbonate compositions provided in the embodiments and comparative examples of the present invention were measured according to the following test methods:

[0075] Flexural modulus: 3.0mm flexural modulus is tested according to ASTM D790-2018 standard. After conditioning at room temperature of 25℃ and humidity of 50% for more than 48 hours, 5 pieces are tested and the average value is the final result.

[0076] Bending toughness: Measured by deflection, deflection is the linear displacement of a member's axis perpendicular to the axis, or the linear displacement of the midplane of a plate or shell perpendicular to the midplane, when subjected to force. A 3.2mm bending test is conducted according to ASTM D790-2018. After conditioning at 25°C and 50% humidity for at least 48 hours, the linear displacement of five members is measured and the average value is used as the final result. Larger values ​​indicate greater deflection and better bending toughness; smaller values ​​indicate less deflection and poorer bending toughness.

[0077] Shrinkage rate: The injection molding temperature is fixed at 265℃, the injection molding pressure is 50%, the injection molding speed is 50%, and a 2.0mm cross shrinkage rate plate is injection-molded. After injection molding, it is placed in an environment with a room temperature of 25℃ and a humidity of 50% for conditioning for more than 48 hours, and then measured and recorded by the secondary element to obtain the shrinkage rate.

[0078] Metal screw column bonding strength: Measure the clamping force (N) required to tighten (lock) the screw until it strips or breaks according to the GB / T 3098.9-2020 standard. Judge the strength based on the maximum clamping force (N) of the screw column. The lower the value, the poorer the bonding, and the higher the value, the better the bonding.

[0079] The polycarbonate compositions of the embodiments and comparative examples of the present invention were prepared as follows: Components were weighed according to their respective proportions, added to a high-pressure mixer, and stirred and blended to obtain a premix. The premix was then extruded in a twin-screw extruder, and melt-granulated to obtain the polycarbonate composition. The stirring speed was 150 rpm; the twin-screw extruder had an aspect ratio of 40:1, a barrel temperature of 230-290°C, and a screw speed of 600 rpm.

[0080] Examples 1 to 19

[0081] Examples 1 to 19 provide a series of polycarbonate compositions, the formulations of which are shown in Table 2, Table 3 and Table 4.

[0082] Table 2: Formulas of Examples 1 to 6 (parts by weight)

[0083] Table 3 Formulas of Examples 7 to 14 (parts by weight)

[0084] Table 4: Formulas of Examples 15 to 19 (parts by weight)

[0085] Comparative Example 1

[0086] This comparative example provides a polycarbonate composition, the formulation of which is different from that of Example 1 in that composite flaky filler 1# is replaced with composite flaky filler 7#.

[0087] Comparative Example 2

[0088] This comparative example provides a polycarbonate composition, the formulation of which is different from that of Example 1 in that composite flaky filler 1# is replaced with composite flaky filler 8#.

[0089] Comparative Example 3

[0090] This comparative example provides a polycarbonate composition, the formulation of which is different from that of Example 1 in that the composite flake filler is entirely composed of the first flake filler 1#.

[0091] Comparative Example 4

[0092] This comparative example provides a polycarbonate composition, the formulation of which is different from that of Example 1 in that the composite flake filler is entirely composed of the second flake filler 1#.

[0093] Comparative Example 5

[0094] This comparative example provides a polycarbonate composition, the formula of which is different from that of Example 1 in that the composite flake filler 1# is replaced with the same weight portion of spherical filler 1#, that is, the composite flake filler 1# is not added, and the amount of spherical filler 1# added is 16 parts by weight.

[0095] Comparative Example 6

[0096] This comparative example provides a polycarbonate composition, the formula of which is different from that of Example 1 in that the spherical filler 1# is replaced with the same weight parts of the composite flake filler 1#, that is, the spherical filler 1# is not added, and the amount of the composite flake filler 1# added is 16 parts by weight.

[0097] The properties of the polycarbonate compositions of the embodiments and comparative examples were measured according to the above-mentioned test methods. The test results are shown in Table 5.

[0098] Table 5 Performance test results of the polycarbonate compositions of various embodiments and comparative examples

[0099] As can be seen from Table 5, the polycarbonate compositions of Examples 1 to 19 have a flexural modulus exceeding 2900 MPa, a flexural toughness exceeding 15 mm, a shrinkage rate less than 0.3%, and a metal screw clamping force exceeding 3800 N. This indicates that the polycarbonate compositions of the present invention have excellent rigidity and toughness, low shrinkage, and high weld line strength and good appearance of the parts, meeting the quality requirements of various processing techniques and post-assembly.

[0100] The mass ratio of the composite flaky fillers added in Comparative Example 1 and Comparative Example 2 was inappropriate. The polycarbonate composition in Comparative Example 1 had a shrinkage of 0.3%, and the metal screw column clamping force was too weak. The metal screw column clamping force in Comparative Example 2 was also too weak. Comparative Example 3 used composite flaky fillers composed entirely of the first flaky filler, resulting in a polycarbonate composition with a too high shrinkage, low toughness, and too low metal screw column clamping force. Comparative Example 4 used composite flaky fillers composed entirely of the second flaky filler, resulting in a polycarbonate composition with a too high shrinkage and too low metal screw column clamping force. Comparative Example 5 did not add composite flaky fillers, resulting in a polycarbonate composition with too low rigidity and too high shrinkage. Comparative Example 6 did not add spherical fillers, resulting in a polycarbonate composition with too low toughness, too high shrinkage, and too low metal screw column clamping force.

[0101] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A polycarbonate composition with low shrinkage, characterized in that: The composition comprises the following components in parts by weight: The composite flaky filler is obtained by compounding a first flaky filler and a second flaky filler in a mass ratio of 1:(0.33-3), the average particle size of the first flaky filler is 5-7 μm, and the average particle size of the second flaky filler is 0.5-2 μm.

2. The polycarbonate composition according to claim 1, characterized in that: The polycarbonate composition comprises the following components in parts by weight:

3. The polycarbonate composition according to claim 1, characterized in that: The weight average molecular weight of the polycarbonate resin is 22,000 to 34,000.

4. The polycarbonate composition according to claim 1, characterized in that: The toughening agent is an ethylene copolymer toughening agent.

5. The polycarbonate composition according to claim 1, characterized in that: The mass ratio of the spherical filler to the composite flake filler is 1:(15-50).

6. The polycarbonate composition according to claim 1, characterized in that: The average particle size of the spherical filler is 0.2-45 μm.

7. The polycarbonate composition according to claim 1, characterized in that: The spherical filler is at least one of glass microbeads, titanium dioxide or calcium carbonate; the first flake filler is talcum powder, and the second flake filler is talcum powder.

8. The polycarbonate composition according to claim 1, characterized in that: The polycarbonate composition further comprises 1 to 30 parts of a flame retardant and 0.01 to 5 parts of an anti-dripping agent.

9. The method for preparing the polycarbonate composition according to any one of claims 1 to 8, characterized in that: The steps include: The components are mixed, melt-extruded and pelletized to obtain the polycarbonate composition.

10. Use of the polycarbonate composition according to any one of claims 1 to 8 in preparing display screens, housings or covers.

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