High-whiteness, low-warpage and high-heat-resistance polyester resin composition and preparation method thereof

Abstract

The invention discloses a high-whiteness, low-warpage and high-heat-resistance polyester resin composition and a preparation method thereof, and belongs to the field of polymer composite materials. On the first aspect, the invention relates to a polyester resin composition which comprises the following raw materials in parts by weight: 40-60 parts of PCT resin, 3-12 parts of PCT copolymerized modified resin and 3-12 parts of a reinforced filling material, wherein the reinforced filling material at least comprises glass fibers.

Description

Technical Field

[0001] The present invention relates to the field of polymer composite materials, and in particular to a high-whiteness, low-warpage, high-heat-resistant polyester resin composition and a preparation method thereof. Background Art

[0002] In recent years, light-emitting diodes (LEDs) have shown many advantages over traditional light sources, such as low power consumption, high luminous efficiency, high brightness, high reliability, rich colors, long life, miniaturization, and low cost. Therefore, they have rapidly replaced traditional light sources and become the mainstream lighting technology, and are widely used in various scenarios such as indoors and outdoors.

[0003] The LED production process begins by placing a surface-electroplated metal substrate into the injection mold cavity. An LED reflective bracket is then formed on the surface of the metal substrate through injection molding. The LED chip is then bonded to the metal substrate using solid crystals and wire bonding. Glue and curing are then performed to encapsulate the light-emitting chip, preventing it from being corroded by moisture, oxygen, and other factors, which could cause the light to die. Finally, the LED lamp beads are integrated and assembled into the final LED light source. The LED bracket is responsible for supporting and protecting the entire LED lamp bead, while also reflecting the light emitted by the lamp bead and improving the LED's lighting efficiency. Therefore, very high requirements are placed on the LED bracket's whiteness, reflectivity, and mechanical properties. Furthermore, the compatibility of the LED bracket with the sealing glue will directly affect the lifespan of the light-emitting chip. Therefore, the selection and optimization of LED bracket materials have become a very important topic in the LED industry.

[0004] LED reflective brackets typically undergo high-temperature processing such as encapsulation curing and reflow soldering (SMT), placing high demands on the material's heat resistance. Currently, the main materials used are PPA (high-temperature nylon) and high-temperature polyester PCT (polycyclohexane dimethanol terephthalate). However, because PPA resin exhibits significant yellowing at high temperatures, while PCT resin exhibits excellent yellowing resistance at high temperatures, PCT is the mainstream choice for high-power, high-brightness LED reflective brackets. However, to improve the bracket's whiteness and reflectivity, a large amount of white pigment must be added to the composite material, which reduces the material's toughness. Furthermore, to improve the bracket's mechanical reliability, glass fiber reinforcement is often required. However, PCT is a semi-crystalline material. After molding and heating, post-crystallization and the orientation effect of the glass fiber can cause the bracket to warp and deform, disrupting the bond between the bracket and the sealant. This significantly reduces the sealing of the LED lamp beads and seriously shortens the LED's service life.

[0005] The existing technology has improved the whiteness / reflectivity, aging resistance and light stability of PCT materials. Patent CN106084672A discloses a thermoplastic resin composition, which improves the reflectivity and yellowing resistance of the material by adding sodium phosphate. Patent CN105849190A discloses a thermoplastic resin composition, which, by adding a silicon-containing graft copolymer, gives the material excellent reflectivity, aging resistance and light stability. In addition, the existing technology has also improved the bonding between PCT materials and silica gel. Patent CN202010452425 uses a hyperbranched polyester with a specific molecular weight and carboxyl content together with PCT resin to prepare a PCT composition with excellent fluidity, and can effectively improve the bonding between the PCT reflective bracket and silica gel. However, the existing technology does not yet have an improvement solution for the decreased airtightness caused by the warping deformation of the PCT reflective bracket. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a polyester resin composition with high whiteness, low warpage and high heat resistance and a preparation method thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] The first aspect of the present invention relates to a polyester resin composition comprising the following raw materials in parts by weight:

[0009] 40-60 parts of PCT resin,

[0010] 3 to 12 parts of PCT copolymer modified resin,

[0011] 3 to 12 parts of reinforcing filling material;

[0012] Wherein, the reinforcing filling material at least includes glass fiber.

[0013] The PCT resin, namely polycyclohexanedimethanol terephthalate resin, is produced by the polycondensation reaction of terephthalic acid (TPA) and 1,4-cyclohexanedimethanol (CHDM).

[0014] The PCT resin is a high-temperature resistant polyester resin with a melting point of generally 280-295° C., and can withstand a high temperature of 260° C. during reflow soldering.

[0015] The PCT resin is commercially available and has been widely used in the field of LED lighting.

[0016] Preferably, the intrinsic viscosity of the PCT resin is 0.6 to 0.8 dL / g.

[0017] The PCT copolymer modified resin is obtained by copolymerizing a third or fourth monomer other than TPA and CHDM during the PCT polymerization process.

[0018] The PCT copolymer modified resin can be obtained by copolymerization with other dibasic acids except TPA.

[0019] The dibasic acid may be one or both of an aliphatic dibasic acid or an aromatic dibasic acid, specifically, one or both of succinic acid, adipic acid, sebacic acid, lauric acid, phthalic acid, isophthalic acid, and naphthalene dicarboxylic acid.

[0020] Preferably, PCTA resin obtained by copolymerizing and modifying PCT with isophthalic acid can be used.

[0021] The PCT copolymer modified resin can also be obtained by copolymerization with other diols except CHDM.

[0022] The diol may be one or both of an aliphatic diol or an aromatic diol. Specifically, it may be one or both of ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, hydroquinone bis(hydroxyethyl) ether, and resorcinol bis(hydroxyethyl) ether.

[0023] Preferably, PCTG resin can be obtained by copolymerizing PCT with ethylene glycol.

[0024] The PCT copolymer modified resin can improve some properties of the PCT resin itself to a certain extent by copolymerizing other resins with molecular chain segments, such as reducing crystallization ability, improving resin transparency, improving resin flow properties, lowering the melting point of the resin, changing the glass transition temperature, etc., thereby improving the processing performance of the resin and meeting different application fields.

[0025] The PCT copolymer modified resin is added to the PCT resin composition for blending and modification, and the LED reflector bracket obtained by injection molding exhibits better resistance to warping and deformation, and better maintains the structural stability of the reflector bracket, thereby ensuring the sealing and reliability of the LED lamp bead structure.

[0026] The PCT copolymer modified resin can reduce the crystallization ability of the PCT resin to a certain extent and improve the flow properties of the PCT resin composition, thereby reducing the warping deformation caused by post-crystallization and the orientation effect of the glass fiber after molding and heating.

[0027] The reinforcing filling material is one or a combination of two or more of glass fiber, wollastonite, potassium titanate whisker, kaolin, talc or mica.

[0028] The reinforcing filling material is preferably glass fiber.

[0029] The glass fiber generally requires a special surface treatment, which can be an inorganic coating, an organic coating, or a combination of inorganic and organic coatings. Preferably, the surface of the glass fiber is first coated with aluminum oxide, zirconium oxide, or silicon oxide, and then coated with a carboxylic acid, polyol, alkanolamine, or organosilane coupling agent.

[0030] The white pigment is selected from one or more of titanium dioxide, zinc oxide, zinc sulfide, and barium sulfate. Preferably, the white pigment is selected from one or more of titanium dioxide, zinc sulfide, and barium sulfate. More preferably, the white pigment is titanium dioxide.

[0031] The form of the titanium dioxide is not particularly limited, and various crystalline forms can be used, such as anatase, rutile, etc. However, rutile is preferred because it has a higher refractive index and lower photocatalytic activity, and has a better effect on improving the whiteness and light stability of the PCT polyester composition.

[0032] The titanium dioxide is subjected to a special surface treatment, which may be an inorganic coating treatment, an organic coating treatment, or a combination of inorganic coating and organic coating. Preferably, the surface of the titanium dioxide is first coated with aluminum oxide, zirconium oxide, or silicon oxide, and then coated with a carboxylic acid, a polyol, an alkanolamine, an organic silane coupling agent, or the like. This surface treatment method can, on the one hand, effectively prevent direct contact between the titanium dioxide and the polyester resin, thereby causing its photocatalytic degradation, and on the other hand, can enhance the organic bonding between the titanium dioxide and the polyester resin, thereby improving its dispersibility and the mechanical properties of the composite material.

[0033] The conventional auxiliary agents include one or a mixture of lubricants, release agents, nucleating agents, antioxidants, light stabilizers, fluorescent whitening agents, and flow modifiers.

[0034] The present invention also provides a method for preparing the above-mentioned polyester resin composition with high whiteness, low warpage and high heat resistance, comprising the following steps: uniformly mixing PCT resin, PCT copolymer modified resin and conventional additives in a high-speed mixer according to a proportion to obtain a mixture, and then adding the mixture through a main feed system, white pigment and reinforcing filler through a double-side feeding system to a twin-screw extruder, melt blending, and extrusion granulation to obtain a polyester resin composition with high whiteness, low warpage and high heat resistance.

[0035] Among them, in the melt blending process, the heating temperature of each zone is: zones 1 to 3, 280 to 300°C; zones 4 to 7, 270 to 290°C; zones 8 to 10, 275 to 295°C; and the die head, 280 to 300°C.

[0036] Beneficial effects of the present invention:

[0037] The present invention provides a high-whiteness, low-warpage, high-heat-resistant polyester resin composition and its preparation method. Compared with the existing technology, it has the following advantages:

[0038] The addition of PCT copolymer modified resin improves the fluidity of the PCT resin composition, enabling it to better meet the molding requirements of hundreds or even thousands of cavities per mold during injection molding. Furthermore, the PCT copolymer modified resin can, to a certain extent, reduce the crystallization capacity of the PCT resin and improve the flow properties of the PCT resin composition. This reduces warping caused by post-crystallization and glass fiber orientation effects after molding and heating. The injection-molded LED reflector bracket exhibits improved resistance to warping and deformation, better maintaining the structural stability of the reflector bracket, thereby ensuring the sealing and reliability of the LED lamp structure. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0040] In addition, unless otherwise specified, the preparation processes in the following examples are all conventional methods in the prior art and are therefore not described in detail. The parts in the following embodiments are all parts by weight.

[0041] The models and suppliers of the raw materials used in this embodiment are as follows:

[0042] PCT resin: PCT 36296, intrinsic viscosity 0.719 dL / g, Eastman Chemical Products.

[0043] PCT copolymer modified resin: PCTA GN071, Eastman Chemical Products.

[0044] Reinforcement filling material: Glass fiber OCV 995, Owens Corning Composites (OCV TM Reinforcements).

[0045] White pigment: titanium dioxide R105, average particle size: 0.31 μm, DuPont Co., Ltd.

[0046] Antioxidants: 1098 and 168 are both commercially available.

[0047] Lubricant: BN-500, Qingdao Bangni Chemical Co., Ltd.

[0048] The models and suppliers of the above raw materials are only for illustrating the sources and components of the raw materials used in the experiments of the present invention so as to fully disclose the information, and do not mean that the present invention cannot be realized by using other raw materials of the same type or raw materials provided by other suppliers.

[0049] Test method or standard:

[0050] Initial whiteness and reflectance: Measured using a Color Eye 7000A colorimeter. High-gloss panels, 60 mm long, 60 mm wide, and 2 mm thick, produced by injection molding, were used. The L value, reflecting the composite's initial whiteness, and the reflectance at a wavelength of 460 nm were measured. These two values ​​together evaluate the composite's light reflectivity when used as an LED reflector bracket.

[0051] Warping degree: Place the above-mentioned high-gloss board in a 180℃ oven and bake for 3 hours. After taking it out and cooling it naturally, use a feeler gauge to measure the warping height of the fixed corners of the high-gloss board.

[0052] Flowability test: The injection molding process is fixed at a temperature of 300°C, a speed / pressure of 50%, and a mold temperature of 80°C. A specific spiral mold is used for injection molding. The flow length ratio of the material is tested to evaluate the material's flowability.

[0053] Examples and Comparative Examples:

[0054] PCT 36296, PCTA GN071, titanium dioxide R105, glass fiber OCV 995, antioxidants 1098 and 168, and lubricant BN-500 were weighed according to the weight ratios listed in Table 1. PCT 36296, PCTA GN071, antioxidants 1098 and 168, and lubricant BN-500 were mixed uniformly in a high-speed mixer to obtain a mixture. This mixture was then added to a twin-screw extruder through the main feed port using a loss-in-weight scale. Simultaneously, titanium dioxide R105 and glass fiber OCV 995 were added to the twin-screw extruder through the side feed system using a loss-in-weight scale according to the ratios. The extruder heating temperature was set as follows: zones 1-3, 280-300°C; zones 4-7, 270-290°C; zones 8-10, 275-295°C; and die, 280-300°C. The above raw materials are fully melted and blended in a twin-screw extruder, and extruded into granules to obtain a polyester resin composition with high whiteness, low warpage and high heat resistance.

[0055] Table 1. Specific proportions of each component in Examples 1 to 6 and Comparative Examples 1 to 4 (parts by weight)

[0056]

[0057] Table 2. Performance test results of materials in Examples 1 to 6 and Comparative Examples 1 to 4

[0058]

[0059] The products prepared in the above examples and comparative examples were subjected to performance testing, and the results are listed in Table 2. A comparison of the results of Examples 1-5 and Comparative Example 1 shows that the addition of varying amounts of PCTA to the PCT polyester composition has minimal impact on mechanical properties. With increasing PCTA content, tensile strength, flexural strength, and flexural modulus decrease slightly, but notched impact performance improves slightly. This is due to the presence of a larger number of amorphous regions in PCTA, which enhances the flexibility of the molecular segments. The L value and reflectivity of the PCT polyester composition are significantly improved after the addition of PCTA, which is beneficial for LED reflective brackets, allowing LED lamp beads to achieve better initial brightness. The most critical thing is that after baking at 180°C for 3 hours, the warping degree of Examples 1 to 5 with the addition of PCTA is significantly better than that of Comparative Example 1, and as the PCTA content increases, the improvement effect of the warping degree gradually increases. This is because PCTA is amorphous and has excellent compatibility with PCT molecular segments. Adding it to the PCT polyester composition will destroy the crystallization behavior of some PCT molecules, thereby improving the warping deformation phenomenon caused by the post-crystallization behavior of PCT at high temperatures. This warping improvement can make the PCT reflective bracket less deformed under high temperature conditions, thereby better bonding with epoxy / silicone sealants, greatly improving the reliability of the LED lamp beads and extending their service life. However, continuing to increase the amount of PCTA does not bring better results. From the comparison results of Examples 1 to 5 and Comparative Examples 2 and 3, it can be seen that after adding more PCTA, although the mechanical properties of the PCT polyester composition are still within an acceptable range, its heat resistance is difficult to meet the requirement of HDT ≥ 260°C (1.8MPa), which will cause the LED reflector bracket to deform during subsequent reflow soldering, resulting in product failure. Therefore, the amount of PCTA added needs to be within a reasonable range. In addition, Example 6 and Comparative Example 4, which changed the addition ratio of glass fiber and white pigment, also showed similar patterns, which shows that the strategy of improving the warpage deformation of PCT polyester compositions by adding PCTA has good universality.

[0060] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0061] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A polyester resin composition, characterized in that Including the following raw materials by weight: 40-60 parts of PCT resin, 3 to 12 parts of PCT copolymer modified resin, 3 to 12 parts of reinforcing filling material; Wherein, the reinforcing filling material at least includes glass fiber.

2. The polyester resin composition according to claim 1, wherein The intrinsic viscosity of the PCT resin is 0.6-0.8 dL / g.

3. The polyester resin composition according to claim 1, wherein The PCT copolymer modified resin is obtained through lipid copolymerization.

4. The polyester resin composition according to claim 3, characterized in that The raw materials for the copolymerization reaction include one or both of an aliphatic dibasic acid and an aromatic dibasic acid.

5. The polyester resin composition according to claim 4, characterized in that The aliphatic dicarboxylic acid or aromatic dicarboxylic acid includes one or two of succinic acid, adipic acid, sebacic acid, lauric acid, phthalic acid, isophthalic acid, and naphthalene dicarboxylic acid.

6. The polyester resin composition according to claim 4, characterized in that The aliphatic diol or aromatic diol includes one or two of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, hydroquinone bishydroxyethyl ether, and resorcinol bishydroxyethyl ether.

7. The polyester resin composition according to claim 1, characterized in that The reinforcing filling material further comprises one or more of wollastonite, potassium titanate whiskers, kaolin, talc or mica.

8. The polyester resin composition according to claim 1, wherein Also includes white paint.

9. The polyester resin composition according to claim 1, wherein The white pigment includes one or more of titanium dioxide, zinc oxide, zinc sulfide, and barium sulfate.

10. A method for preparing a polyester resin composition, characterized in that: The following steps are involved: 40-60 parts by weight of PCT resin and 3-12 parts by weight of PCT copolymer modified resin are mixed, and then 3-12 parts by weight of reinforcing filler material including glass fiber are added and extruded to obtain the polyester resin composition.

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