A polyester resin composition, its preparation method and application

Abstract

This invention discloses a polyester resin composition, comprising, by weight, the following components: 100 parts PCT resin; 0-50 parts reinforcing material; and 0.1-0.8 parts hyperbranched polyester. The hyperbranched polyester has a molecular weight of 600-10000 g / mol and a hydroxyl value of 200-600 mg KOH / g. By adding specific parameters and a specific amount of hyperbranched polyester, this invention can improve the insufficient dimensional stability of PCT resin and inhibit cold crystallization.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a polyester resin composition, its preparation method, and its application. Background Technology

[0002] The invention of the light-emitting diode (LED) ushered in the era of semiconductor lighting for the lighting industry. LED light sources offer advantages such as high reliability, high luminous power, low power consumption, fast response time, long lifespan, low price, and rich colors. Following gas lighting, incandescent lamps, and fluorescent lamps, LEDs have become the next generation of mainstream lighting technology. With the development of the times and the advancement of technology, LEDs have been widely used in various fields such as streetlights, indoor lighting, backlit displays, automotive headlights, and landscape lighting.

[0003] LED reflectors are key components for reflecting LED light sources and require good dimensional stability and high-temperature resistance. PCT (polycarbonate) material is widely considered by those skilled in the art to possess excellent temperature resistance and transparency, making it particularly suitable for transparent LED brackets. However, researchers have found that because PCT is a semi-crystalline polymer, its cooling rate is extremely rapid under cold molding conditions. This insufficient molecular chain mobility leads to some molecular chains failing to crystallize in time, resulting in incomplete crystallization. When the injection-molded reflector bracket is dehumidified and baked at 160°C, exceeding the glass transition temperature of PCT, the material's molecular chains become mobile. Those molecular chains that did not crystallize in time will crystallize, forming cold crystals, causing shrinkage and deformation of the part and reducing the product's dimensional stability. Summary of the Invention

[0004] The purpose of this invention is to provide a polyester resin composition that has the advantages of good dimensional stability and inhibition of cold crystallization.

[0005] Another object of the present invention is to provide a method for preparing the polyester resin composition and its application.

[0006] This invention is achieved through the following technical solution: A polyester resin composition, by weight, comprises the following components: 100 parts of PCT resin; 0-50 parts of reinforcing material; Hyperbranched polyester, 0.1-0.8 parts; The molecular weight of hyperbranched polyester is 600~10000 g / mol, and the hydroxyl value is 200~600 mg KOH / g.

[0007] When the content of hyperbranched polyester exceeds 0.8 parts, further increasing the amount of hyperbranched polyester will actually slow down the inhibition of cold crystallization. When it exceeds 1.0 parts, the inhibition of cold crystallization decreases significantly, and dimensional stability also begins to decline.

[0008] Preferably, the content of hyperbranched polyester is 0.2 to 0.6 parts.

[0009] Preferably, the hyperbranched polyester has a molecular weight of 900~6000g / mol and a hydroxyl value of 300~560mg KOH / g.

[0010] The intrinsic viscosity of the PCT resin is 0.65~0.75 dL / g. The intrinsic viscosity test method is as follows: Weigh 0.5g of the sample, dissolve it in 100mL of 60 / 40 (wt / wt) phenol / tetrachloroethane, and then test the intrinsic viscosity using an Ubbelohde viscometer at a constant temperature of 25℃.

[0011] The reinforcing material is selected from at least one of glass fiber, wollastonite, potassium titanate whiskers, kaolin, talc, and mica.

[0012] The polyester composition obtained by the present invention has the following properties: inhibits cold crystallization, has a transverse shrinkage rate of less than or equal to 0.4% after baking at 160°C for 1 hour, a longitudinal shrinkage rate of less than or equal to 0.2%, and a cold crystallization enthalpy of less than or equal to 8.0 J / g.

[0013] The polyester resin composition of the present invention may also include, as needed, additives such as antioxidants, impact modifiers, flame retardants, fluorescent whitening agents, lubricants, plasticizers, thickeners, antistatic agents, nucleating agents, UV stabilizers, mold release agents, and dyes.

[0014] The preparation method of the above-mentioned polyester resin composition includes the following steps: melt blending PCT resin, hyperbranched polyester, and reinforcing material through a twin-screw extruder, followed by extrusion granulation to obtain the polyester resin composition. The temperature of the twin-screw extruder is set to 230~300℃. The above-mentioned polyester resin composition is used to prepare LED reflectors.

[0015] The present invention has the following beneficial effects: This invention involves adding a small amount of hyperbranched polyester (600-10000 g / mol, hydroxyl value 200-600 mg KOH / g) to PCT resin. The hydroxyl groups in the hyperbranched polyester can react with the free carboxyl groups at the ends of the PCT resin molecular chains, incorporating them into the molecular chains. After the hyperbranched polyester is incorporated into the molecular chains, the volume at the chain ends increases, the distance between molecular chains increases, and thus the molecular chain mobility and crystallization ability are improved. During cold molding, most of the molecular chains complete crystallization, resulting in more complete material crystallization. Therefore, during high-temperature dehumidification baking, although the molecular chains move, the number of uncrystallized molecular chains is extremely small, resulting in a low cold crystallization enthalpy, which inhibits the cold crystallization of the PCT resin composition and improves the dimensional stability of the polyester resin composition. Attached Figure Description

[0016] Figure 1 Schematic diagram of standard part for shrinkage rate test. Detailed Implementation

[0017] The present invention will be further illustrated below with reference to specific embodiments and comparative embodiments. The following specific embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments, and are not in particular limited to the types of raw materials used in the following specific embodiments.

[0018] The raw materials used in the following examples and comparative examples are commercially available products.

[0019] PCT Resin-A: Intrinsic viscosity: 0.719 dL / g, Eastman™ Chemical Products, PCT36296.

[0020] PCT resin-B: intrinsic viscosity: 0.65 dL / g, SK Chemicals, 0302; PCT resin-C: intrinsic viscosity: 0.75 dL / g, SK Chemicals, 0502; Hyperbranched polyester-A: molecular weight 920 g / mol, hydroxyl value 370 mg KOH / g, Wuhan Hyperbranched Resin Technology Co., Ltd. Hyperbranched polyester-B: molecular weight 5400 g / mol, hydroxyl value 490 mg KOH / g, Wuhan Hyperbranched Resin Technology Co., Ltd. Hyperbranched polyester-C: molecular weight 2400 g / mol, hydroxyl value 560 mg KOH / g, Wuhan Hyperbranched Resin Technology Co., Ltd. Hyperbranched polyester-D: molecular weight 1400 g / mol, hydroxyl value 240 mg KOH / g, Wuhan Hyperbranched Resin Technology Co., Ltd. Hyperbranched polyester-E: molecular weight 8400g / mol, hydroxyl value 160mg KOH / g, Wuhan Hyperbranched Resin Technology Co., Ltd. Hyperbranched polyester-F: molecular weight 500g / mol, hydroxyl value 670mg KOH / g, Wuhan Hyperbranched Resin Technology Co., Ltd. Hyperbranched polyester-G: molecular weight 11500 g / mol, hydroxyl value 230 mg KOH / g, Wuhan Hyperbranched Resin Technology Co., Ltd. Glass fiber: F7x28: NITTO BOSEKI, Japan; chopped glass fiber CSG3PA-820 composed of E-glass with a length of 3 mm, a main cross-sectional axis of 28 micrometers, a secondary cross-sectional axis of 7 micrometers, and an axis ratio of 4 (non-circular cross-section), 60wt%~67wt% silica, and 33wt%~40wt% alumina.

[0021] Preparation method of polyester resin composition in examples and comparative examples: PCT resin, glass fiber and hyperbranched polyester are mixed evenly, and then melt-blended and extruded granulated by a twin-screw extruder to obtain polyester resin composition. The temperature of the twin-screw extruder is set to 230~300℃.

[0022] Performance testing methods: (1) Enthalpy of cold crystallization: Weigh 0.01 g of polyester composition, place it in a crucible, and heat it to 340 °C at a rate of 10 °C / min using a differential scanning calorimeter (DSC). o C. The sample was held at 340℃ for 5 minutes, then the crucible was removed and rapidly immersed in liquid nitrogen for rapid cooling to simulate cold molding. The cooled sample was then removed and heated to 340℃ at a rate of 10℃ / min in DSC. The exothermic peak appearing in the range of 105℃~135℃ in the heating curve was the cold crystallization peak. The area of ​​the peak was integrated to obtain the enthalpy of cold crystallization.

[0023] (2) Shrinkage test: Inject the polyester composition into a part measuring 40mm × 80mm × 1.5mm, with the gate located at the center of the short side. Make four cross marks on the part, similar to the vertices of a rectangle (see the instruction manual). Figure 1 The distance between the centers of the two cross marks is 30mm and 70mm respectively, as shown below. Figure 1 As shown. Measure the actual distance L between the centers of the two crosshairs. A1 and L B1 Then bake it at 160℃ for 1 hour, and measure the distance L after baking. A2 and L B2 The lateral contraction rate is (L) A1 -L A2 ) / L A2The longitudinal shrinkage rate is (L) B1 - L B2 ) / L B2 .

[0024] Table 1: Content (parts by weight) of each component and performance test results of polyester compositions in Examples 1-6 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 PCT Resin-A 100 100 100 100 PCT Resin-B 100 PCT resin-C 100 Hyperbranched polyester content 0.4 0.4 0.4 0.4 0.4 0.4 Hyperbranched polyester number A A A A B C Fiberglass 10 10 10 10 10 Enthalpy of cold crystallization, J / g 5.2 5.1 5.4 5.2 3.5 4.4 Longitudinal shrinkage rate, % 0.29 0.30 0.28 0.40 0.25 0.27 Lateral shrinkage rate, % 0.14 0.15 0.14 0.20 0.11 0.13 As can be seen from Examples 1-3, the technical solution of this application is applicable to existing PCT resins that can be used in LED reflectors.

[0025] As can be seen from Example 4, the addition of glass fiber can improve dimensional stability and reduce cold crystallization enthalpy.

[0026] As can be seen from Examples 5 / 67, the preferred hyperbranched polyester has a molecular weight of 900~6000g / mol and a hydroxyl value of 300~560mg KOH / g.

[0027] Table 2: Content (parts by weight) of each component and performance test results of the polyester compositions in Examples 7-11 and Comparative Examples Example 7 Example 8 Example 9 Example 10 Example 11 PCT Resin-A 100 100 100 100 100 Hyperbranched polyester content D A A A A Hyperbranched polyester number 0.4 0.1 0.2 0.6 0.8 Fiberglass 10 10 10 10 10 Enthalpy of cold crystallization, J / g 6.7 7.8 5.5 5.4 8.0 Longitudinal shrinkage rate, % 0.33 0.39 0.31 0.30 0.39 Lateral shrinkage rate, % 0.17 0.19 0.16 0.15 0.20 As can be seen from Examples 1 / 8 / 9 / 10 / 11, the preferred amount of hyperbranched polyester added is 0.2 to 0.6 parts.

[0028] Continued from Table 2: Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 PCT Resin-A 100 100 100 100 100 Hyperbranched polyester content 1.3 0.4 0.4 0.4 Hyperbranched polyester number A E F G Fiberglass 10 10 10 10 10 Enthalpy of cold crystallization, J / g 15.8 12.4 9.2 8.6 9.8 Longitudinal shrinkage rate, % 0.61 0.52 0.43 0.42 0.44 Lateral shrinkage rate, % 0.34 0.27 0.22 0.21 0.23 As shown in Comparative Example 1 / 2, excessive addition of hyperbranched polyester does not significantly improve cold crystallization enthalpy and dimensional stability.

[0029] As can be seen from Comparative Examples 3 / 4 / 5, the molecular weight and hydroxyl value of hyperbranched polyester are not within the range of this application, and their effect on suppressing cold crystallization enthalpy and improving dimensional stability is not significant.

Claims

1. A polyester resin composition, characterized in that, By weight, it includes the following components: 100 parts of PCT resin; 0-50 parts of reinforcing material; Hyperbranched polyester 0.2-0.6 parts; The molecular weight of hyperbranched polyester is 600~10000 g / mol, and the hydroxyl value is 300-370 mg KOH / g; The polyester resin composition, after being baked at 160°C for 1 hour, has a transverse shrinkage rate of less than or equal to 0.4%, a longitudinal shrinkage rate of less than or equal to 0.2%, and a cold crystallization enthalpy of less than or equal to 8.0 J / g.

2. The polyester resin composition according to claim 1, characterized in that, The intrinsic viscosity of the PCT resin is 0.65~0.75 dL / g.

3. The polyester resin composition according to claim 1, characterized in that, The reinforcing material is selected from at least one of glass fiber, wollastonite, potassium titanate whiskers, kaolin, talc, and mica.

4. A method for preparing the polyester resin composition according to any one of claims 1-3, characterized in that, Includes the following steps: PCT resin, hyperbranched polyester, and reinforcing materials are melt-blended and extruded and granulated using a twin-screw extruder to obtain a polyester resin composition. The temperature of the twin-screw extruder is set to 230~300℃.

5. The application of the polyester resin composition according to any one of claims 1-3, characterized in that, Used to manufacture LED reflectors.

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