Patent Application
20240317993
The present invention relates to a polyester resin composition, a method of preparing the same, and a molded article manufactured using the same. More particularly, the present invention relates to a polyester resin composition being capable of minimizing deformation and maintaining flatness even under high temperature environments by maintaining the balance between mechanical properties and heat resistance and thus being suitable for automotive parts having an integrated complex structure, and a molded article including the polyester resin composition.
Polybutylene terephthalate resins (hereinafter referred to as “PBT” resins) and polyethylene terephthalate resins (hereinafter referred to as “PET” resins), which are polyester resins, have excellent mechanical and electrical properties and excellent physical and chemical properties, and thus are widely used in various fields such as automobiles, electrical and electronic devices, and office equipment.
Recently, as electric vehicles and autonomous driving technology are developed, the number of automotive parts manufactured using PBT or PET is increasing, and integration of these parts is progressing.
However, in summer, when an automobile is exposed to sunlight outdoors and the temperature inside the automobile exceeds 80° C., there is a problem in that automobile parts are severely bent, that is, bending deformation occurs. In addition, even when bending of automotive parts is not severe, there still is a problem in that the level of flatness when an automobile is shipped from a factory cannot be maintained.
Therefore, there is a need to develop a polyester resin composition suitable for automotive parts having an integrated complex structure due to excellent low bending properties thereof, and automotive housing parts including a molded article manufactured using the polyester resin composition.
Therefore, the present invention has been made in view of the above problems, and it is one object of the present invention to provide a polyester resin composition being capable of minimizing deformation and maintaining flatness even under high temperature environments by maintaining the balance between mechanical properties and heat resistance and thus being suitable for automotive parts having an integrated complex structure.
It is another object of the present invention to provide a method of preparing the polyester resin composition.
It is yet another object of the present invention to provide a molded article manufactured using the polyester resin composition.
In accordance with one aspect of the present invention, provided is a polyester resin composition, including:
A weight ratio (PET:layered clay mineral) of the polyethylene terephthalate (PET) resin to the layered clay mineral can be 1:0.9 to 1.8.
A weight ratio (PBT:PET) of the polybutylene terephthalate (PBT) resin to the polyethylene terephthalate (PET) resin can be 1:0.3 to 1.5.
The polybutylene terephthalate resin can have a weight average molecular weight (Mw) of 20,000 to 100,000 g/mol, and can have a melting point of 200 to 240° C. as measured using a Differential Scanning calorimeter (DSC).
The polyethylene terephthalate resin can have a melting point of 200 to 270° C. as measured using a DSC.
A weight ratio (reinforcing fiber:layered clay mineral) of the reinforcing fiber to the layered clay mineral can be 1:0.1 to 0.3.
The reinforcing fiber can be a glass fiber.
The glass fiber can include 20 to 65% by weight of silica; 1 to 40% by weight of aluminum oxide; 10 to 60% by weight of calcium oxide; and 5% by weight or less of one or more selected from among iron oxide, magnesia, sodium oxide, iron, and boron oxide, and can have a diameter of 7 to 15 μm and a length of 3 to 6 mm.
The layered clay mineral can include one or more selected from among mica, montmorillonite, bentonite, kaolinite, hectorite, fluorohectorite, saponite, beidellit, nontronite, stevensite, vermiculite, halloysite, volkonskoite, sauconite, magadiite, kenyaite, and hydrotalcite.
The polyester resin composition can include one or more additives selected from among a heat stabilizer, a UV stabilizer, a lubricant, a plasticizer, a flame retardant, a flame retardant aid, a colorant, a release agent, a pigment, a dye, a transesterification inhibitor, an antistatic agent, an antibacterial agent, a processing aid, a metal deactivator, a fluorine-based anti-dripping agent, and a coloring masterbatch.
Based on 100% by weight of all components (polybutylene terephthalate resin+polyethylene terephthalate resin+reinforcing fiber+layered clay mineral+additives) constituting the polyester resin composition, the additives can be included in an amount of 0.1 to 5% by weight.
When measuring height difference in a height direction before and after leaving a specimen having dimensions of 200 mm×100 mm×2T in width, length, and thickness at 100° C. for 30 minutes, the polyester resin composition can have a height difference of 0.25 mm or less.
The polyester resin composition can have a flexural modulus of 8,120 MPa or more as measured according to ISO 178.
The polyester resin composition can have a heat deflection temperature (HDT) of 190° C. or higher as measured under 1.80 MPa according to ISO75-1/2.
In accordance with another aspect of the present invention, provided is a method of preparing a polyester resin composition, including:
The layered clay mineral can include one or more selected from among mica, montmorillonite, bentonite, kaolinite, hectorite, fluorohectorite, saponite, beidellite, nontronite, stevensite, vermiculite, halloysite, volkonskoite, sauconite, magadiite, kenyaite, and hydrotalcite.
In accordance with yet another aspect of the present invention, provided is a molded article, including:
the above-described polyester resin composition.
The molded article can be a part for electronic control units including an engine control unit, a transmission control unit (TCU), an electronic stability control (ESC) system, an airbag control system, a tire pressure monitoring system (TPMS), and a passive occupant detection system (PODS); a cover thereof; or a cover part thereof.
When a polyester resin composition according to the present invention is prepared, since the structure and content of a polyethylene terephthalate resin mixed with a polybutylene terephthalate resin are adjusted and the weight ratio between glass fiber and a specific layered clay mineral is adjusted, the balance between mechanical strength and heat resistance can be greatly improved, and flatness can be maintained, and deformation can be minimized even under high temperature environments. Thus, the polyester resin composition is applicable to automotive parts having an integrated complex structure. In addition, when the polyester resin composition is used, manufacturing cost can be reduced.
Accordingly, the polyester resin composition of the present invention can be applied to parts for electronic control units (ECUs) including an engine control unit, a transmission control unit (TCU), an electronic stability control (ESC) system, an airbag control system, a tire pressure monitoring system (TPMS), and a passive occupant detection system (PODS); the covers thereof; or the cover parts thereof.
Hereinafter, the present invention will be described in more detail to aid in understanding of the present invention.
The terms and words which are used in the present specification and the appended claims should not be construed as being confined to common meanings or dictionary meanings but should be construed as having meanings and concepts matching the technical spirit of the present invention in order to describe the present invention in the best fashion.
In the present invention, it is to be understood that, unless stated otherwise, when a part “comprises” any element, the part can include other elements without excluding other elements.
In this description, unless otherwise specified, “content” is given in % by weight.
In this description, the term “low bending properties” refers to maintaining the height dimension of a specimen when the specimen is left for a certain period of time under a high temperature condition with respect to the height dimension of the specimen immediately after preparation. When variation in height dimension is close to zero, the low bending properties are excellent. In addition, when there is no variation in the average height dimension between specimens, the low bending properties are excellent. The present inventors confirmed that, to prepare a
material applicable to parts for automotive electronic control units including an engine control unit, a transmission control unit (TCU), an electronic stability control (ESC) system, an airbag control system, a tire pressure monitoring system (TPMS), and a passive occupant detection system (PODS); the covers of the parts; or parts included in the covers, when a base resin consisting of a polybutylene terephthalate resin and a polyethylene terephthalate resin was mixed with predetermined components capable of minimizing deformation even under high temperature conditions in a predetermined content ratio, the balance between mechanical strength and heat resistance was greatly improved, and deformation was minimized, and flatness was maintained even under high temperature environments. In particular, the present inventors confirmed that the composition of the present invention was suitable for automotive e parts having an integrated complex structure. Based on these results, the present inventors conducted further studies to complete the present invention.
In one embodiment of the present invention, a polyester resin composition including a polybutylene terephthalate resin, a polyethylene terephthalate resin, a reinforcing fiber, and a layered clay mineral is provided.
The polyethylene terephthalate resin includes one or more selected from among 1,4-cyclohexanedimethanol, isophthalic acid, and butanediol.
The weight ratio (PET:layered clay mineral) of the polyethylene terephthalate (PET) resin to the layered clay mineral is 1:0.9 to 1.8.
The layered clay mineral includes one or more selected from among mica, montmorillonite, bentonite, kaolinite, hectorite, fluorohectorite, saponite, beidellite, nontronite, stevensite, vermiculite, halloysite, volkonskoite, sauconite, magadiite, kenyaite, and hydrotalcite.
The polyester resin composition of the present invention can maintain flatness and minimize deformation even under high temperature environments by controlling the structure of the polyethylene terephthalate resin mixed with the polybutylene terephthalate resin, and adjusting the weight ratio between the reinforcing fiber and the layered clay mineral.
Hereinafter, each component constituting the polyester resin composition of the present invention will be described in detail.
According to one embodiment of the present invention, the polyester resin composition includes a polybutylene terephthalate resin. As described above, by including the polybutylene terephthalate resin in the polyester resin composition, physical properties required for automotive parts can be realized.
In one embodiment of the present invention, as the polybutylene terephthalate resin, a polybutylene terephthalate resin obtained by polycondensation through direct esterification or transesterification of 1,4-butanediol, and terephthalic acid or dimethyl terephthalate can be used.
The polybutylene terephthalate (PBT) resin included as a base resin of the polyester resin composition of the present invention can have a repeat unit of Chemical Formula 1 below.
In Chemical Formula 1, n represents an integer greater than or equal to 50, as a specific example, an integer from 50 to 200.
In one embodiment of the present invention, to increase the impact strength of the polyester resin composition, a copolymer obtained by copolymerizing the polybutylene terephthalate resin and an impact strength enhancing compound such as polytetramethylene glycol, polyethylene glycol, polypropylene glycol, aliphatic polyester, aliphatic polyamide, and the like, or a modified polybutylene terephthalate resin obtained by reacting the polybutylene terephthalate resin with the impact strength enhancing compound can be used.
In one embodiment of the present invention, for example, the polybutylene terephthalate resin has an intrinsic viscosity (n) of 0.6 dl/g to 1.8 dl/g, 0.7 dl/g to 1.3 dl/g, or 0.9 dl/g to 1.3 dl/g as measured according to ASTM D2857. When the intrinsic viscosity of the polybutylene terephthalate resin is within this range, a polyester resin composition having excellent physical property balance between mechanical properties and processability can be obtained.
The intrinsic viscosity (n) can be measured at 20° C. using a filtrate obtained by dissolving a sample to be measured in methylene chloride using an Uberode-type viscosity tube.
For example, the polybutylene terephthalate resin can have a weight average molecular weight of 20,000 g/mol to 100,000 g/mol, 30,000 g/mol to 90,000 g/mol, 40,000 g/mol to 80,000 g/mol, or 50,000 g/mol to 70,000 g/mol. Within this range, mechanical properties can be improved.
When measuring weight average molecular weight, a sample having a concentration of 1 wt % is prepared by putting tetrahydrofuran (THF) and a compound in a 1 ml glass bottle. Then, after filtering a standard sample (polystyrene) and the sample through a filter (pore size: 0.45 μm), the filtered samples are injected into a GPC injector. Then, the molecular weight and molecular weight distribution of the compound can be obtained by comparing the elution time of the sample with the calibration curve of the standard sample. At this time, Infinity II 1260 (Agilient Co.) can be used as measuring instrument, and flow rate can be set to 1.00 mL/min and column temperature can be set to 40.0° C.
For example, the polybutylene terephthalate resin can have a melting point of 200 to 240° C. or 210 to 230° C. as measured using a DSC. Within this range, mechanical properties can be maintained even under high temperature conditions.
In one embodiment of the present invention, in the base resin including the polybutylene terephthalate resin and the polyethylene terephthalate resin, the polybutylene terephthalate resin can be included in an amount of 28 to 50% by weight, 30 to 50% by weight, or 30 to 45% by weight. When the polybutylene terephthalate resin is included in an amount less than the range, due to decrease in solidification rate during injection molding, problems such as increased cycle time can occur. When the polybutylene terephthalate resin is included in an amount exceeding the range, bending deformation can be severe under high temperature conditions.
Polymerization methods commonly practiced in the art to which the present invention pertains can be used to prepare the polybutylene terephthalate resin. In addition, commercially available polybutylene terephthalate resins can be used when the polybutylene terephthalate resins conform to the definition of the polybutylene terephthalate resin according to the present invention.
According to one embodiment of the present invention, the polyester resin composition includes a polyethylene terephthalate resin. As described above, by including the polyethylene terephthalate resin in the polyester resin composition, physical properties required for automotive parts and the cover parts thereof can be implemented. According to one embodiment of the present invention,
as the polyethylene terephthalate resin, conventional polyethylene terephthalate resins can be used, and as a specific example, a co-polyethylene terephthalate polymer can be preferably used.
The polyethylene terephthalate resin included in the polyester resin composition of the present invention can have a repeat unit of Chemical Formula 2 below.
In Chemical Formula 2, m represents an integer greater than or equal to 1, as a specific example, an integer from 40 to 160.
In one embodiment of the present invention, to increase the impact strength of the polyester resin composition, a copolymer obtained by copolymerizing the polyethylene terephthalate resin and an impact strength enhancing compound such as polytetramethylene glycol, polyethylene glycol, polypropylene glycol, aliphatic polyester, aliphatic polyamide, and the like, or a modified polyethylene terephthalate resin obtained by reacting the polyethylene terephthalate resin with the impact strength enhancing compound can be used.
For example, the impact strength enhancing compound can include 1,4-cyclohexanedimethanol, isophthalic acid, and butanediol.
The impact strength enhancing compound can be included in an amount of 5 to 45 mol % or 10 to 40 mol % as a unit constituting the skeleton of the polyethylene terephthalate resin.
In one embodiment of the present invention, considering the processability and mechanical properties of the polyethylene terephthalate resin, the polyethylene terephthalate resin can have an intrinsic viscosity (IV, n) of 0.5 to 1 dl/g, preferably 0.6 to 1.0 dl/g as measured according to ASTM D2857. When the intrinsic viscosity of the polyethylene terephthalate resin is within this range, a polyester resin composition capable of providing excellent low bending properties can be obtained.
For example, the polyethylene terephthalate resin can have a melting point of 200 to 270° C. or 230 to 250° C. as measured using a DSC. Within this range, mechanical properties can be maintained under high temperature conditions.
In one embodiment of the present invention, based on a total weight of the polyester resin composition, the polyethylene terephthalate resin can be included in an amount of 20 to 40% by weight, 20 to 35% by weight, or 23 to 35% by weight. Within this range, by adjusting the content of the polyethylene terephthalate resin, the mechanical properties of the polyester-based composition can be improved, and excellent low bending properties can be provided.
Polymerization methods commonly practiced in the art to which the present invention pertains can be used to prepare the polyethylene terephthalate resin. In addition, commercially available polyethylene terephthalate resins can be used when the polyethylene terephthalate resins conform to the definition of the polyethylene terephthalate resin according to the present invention.
In one embodiment of the present invention, by including a reinforcing fiber in the polyester resin the physical properties, such as tensile composition, strength and flexural strength, of a molded article including the polyester resin composition can be improved.
According to one embodiment of the present invention, a glass fiber can be used as the reinforcing fiber. The glass fiber can be used in combination with other inorganic fibers, such as carbon fiber, basalt fiber, and the like, and/or natural fibers, such as kenaf, hemp, and the like.
In one embodiment of the present invention, the cross-section of the glass fiber can have a shape such as a circle, a rectangle, an oval, a dumbbell, or a rhombus. The glass fiber can have a diameter of 7 to 20 μm or 7 to 15 μm and a length of 2 to 6 mm or 3 to 6 mm. Within this range, excellent mechanical property balance can be implemented. For example, the diameter and the length can be an average diameter and an average length, respectively.
The diameter and length of the glass fiber can be measured by methods commonly used in the art. For example, the diameter and length of the glass fiber can be measured using a scanning electron microscope (SEM).
Specifically, the diameters and lengths of 50 glass fiber strands can be measured, and the average value thereof can be calculated based on the measurement results.
The cross-section of the glass fiber can have a shape such as a circle, a rectangle, an oval, a dumbbell, or a rhombus.
During fiber production or post-treatment process, the glass fiber can be treated with a sizing agent or a coupling agent.
The sizing agent is mainly used to form good strands, and the coupling agent improves adhesion between the glass fiber, the polybutylene terephthalate resin, and the polyethylene terephthalate resin. When the coupling agent is appropriately selected and used in consideration of the types of a polybutylene terephthalate e resin, a polyethylene terephthalate resin, and a glass fiber, excellent physical properties can be imparted to the polyester resin composition.
Methods of using the sizing agent can include a method of directly treating the glass fiber with the sizing agent and a method of adding the sizing agent to the polybutylene terephthalate resin or the polyethylene terephthalate resin. To sufficiently exhibit the performance of the sizing agent, the content thereof should be appropriately selected.
For example, the sizing agent can include amine-based sizing agents, acrylic sizing agents, and silane-based sizing agents such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(beta-aminoethyl) γ-aminopropyltriethoxysilane, γ-methacryloxypropyl triethoxysilane, γ-glycidoxypropyl trimethoxysilane, and β(3,4-epoxyethyl) γ-aminopropyl trimethoxysilane.
In particular, the glass s fiber of the present substrate preferably contains silica because silica can provide rigidity and mechanical properties.
For example, silica can be included in the glass fiber in an amount of 20 to 65% by weight, preferably 25 to 60% by weight, more preferably 30 to 55% by weight. Within this range, by adjusting the content of the glass fiber, the impact resistance and mechanical properties of the polyester-based composition can be improved. When silica is included in an amount less than the range, the effect of improving heat resistance and mechanical properties according to the addition of the glass fiber can be insignificant. When silica is included in an amount exceeding the range, low bending properties can be significantly deteriorated.
In addition, aluminum oxide can be included in the glass fiber in an amount of, for example, 1 to 40% by weight or 5 to 30% by weight.
In addition, calcium oxide can be included in the glass fiber in an amount of, for example, 10 to 60% by weight or 20 to 50% by weight.
In addition, one or more selected from among iron oxide, magnesia, sodium oxide, iron, and boron oxide can be included in an amount of 5% by weight or less, or 0.001 to 5% by weight.
In one embodiment of the present invention, the input amount of the reinforcing fiber can be greater than the input amount of the polyethylene terephthalate resin. In this case, the effect of reinforcing an injection product can be further increased.
As a specific example, based on a total weight of the polyester resin composition, the reinforcing fiber can be included in an amount of 20.5 to 30% by weight or 23 to 28% by weight. Within this range, by adjusting the content of the reinforcing fiber, the tensile strength and flexural strength of a molded article manufactured using the polyester resin composition can be improved.
For example, a layered clay mineral according to the present invention can include one or more selected from among mica, montmorillonite, bentonite, kaolinite, hectorite, fluorohectorite, saponite, beidellite, nontronite, stevensite, vermiculite, halloysite, volkonskoite, sauconite, magadiite, kenyaite, and hydrotalcite. In the case of using the layered clay mineral, the layered clay mineral can provide excellent low bending properties by serving as a filler and reducing the aspect ratio by the crystal structure of the polymers constituting the base resin and the reinforcing fiber.
Based on a total weight of the polyester resin composition, the layered clay mineral can be included in an amount of 2 to 30% by weight, 5 to 15% by weight, or 5 to 10% by weight. Within this range, deterioration of physical properties such as mechanical strength due to destruction of the reinforcing fiber by the layered clay mineral can be prevented, and thus excellent physical properties can be maintained.
The polyester resin composition of the present invention can include the polybutylene terephthalate resin and the polyethylene terephthalate resin in a weight ratio (PBT:PET) of 1:0.9 to 1.8. Within this range, low bending properties can be improved while maintaining mechanical properties.
For example, the weight ratio (PBT:PET) of the polybutylene terephthalate resin to the polyethylene terephthalate resin can be 1:0.9 to 1.6 or 1:1 to 1.4. Within this range, low bending properties can be improved while maintaining mechanical properties. When the weight ratio thereof is less than the range, severe bending deformation can occur under high temperature conditions. When the weight ratio thereof exceeds the range, due to decrease in solidification rate during injection molding, problems such as increased cycle time can occur.
In the polyester resin composition of the present invention, the input amount of the reinforcing fiber can be greater than the input amount of the layered clay mineral. In this case, solidification rate can be increased, and low bending properties can be improved.
For example, the reinforcing fiber can be included in an amount such that a weight ratio (reinforcing fiber:layered clay mineral) of the reinforcing fiber to the layered clay mineral is 1:0.1 to 0.3 or 1:0.15 to 0.25.
The polyester resin composition of the present invention can further include one or more additives selected from among a heat stabilizer, a UV stabilizer, a lubricant, a plasticizer, a flame retardant, a flame retardant aid, a colorant, a release agent, a pigment, a dye, a transesterification inhibitor, an antistatic agent, an antibacterial agent, a processing aid, a metal deactivator, a fluorine-based anti-dripping agent, and a coloring masterbatch.
In one embodiment of the present invention, based on a total weight of the polyester resin composition, the additives can be included in an amount of 0.1 to 5% by weight, 0.1 to 3% by weight, or 0.1 to 1% by weight. Within this range, the intrinsic properties of the additives can be expressed without deterioration in the physical properties of the resin composition.
As the heat stabilizer, phenolic heat stabilizers and hindered amine-based compounds can be used. As a specific example, the phenolic heat stabilizer can be pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate).
Specifically, based on a total weight of the polyester resin composition, the heat stabilizer can be included in an amount of 0.1 to 5% by weight, 0.1 to 3% by weight, or 0.1 to 1% by weight. Within this range, by adjusting the content of the heat stabilizer, the impact strength of the polyester resin composition can be excellent, the heat resistance thereof can be excellent due to an increase in heat deflection temperature, and the melt flow index thereof can be reduced.
In the present invention, as the phenolic compound, Hindered Phenolic Antioxidant 1010 can be used.
The hindered amine end group of the hindered amine-based compound can react with end groups of polymers constituting the base resin to impart hydrolysis resistance. Specifically, when using the hindered amine-based compound, gas generation during molding of the polyester-based composition can be effectively suppressed.
For example, the hindered amine-based compound can be a halogen-free alkoxy hindered amine having a weight average molecular weight of 2,200 to 2,300 g/mol. As a specific example, the hindered amine-based compound can be poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-s-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino] (CAS number: 71878-19-8).
Based on a total weight of the polyester resin composition, the hindered amine-based compound can be included in an amount of 0.1 to 5% by weight, 0.1 to 3% by weight, or 0.1 to 1% by weight. Within this range, by adjusting the content of the hindered amine-based compound, required physical properties can be implemented without impairing the hydrolysis resistance effect provided by the chain extender described above.
The lubricant can be olefin wax, and serves to help the polyester resin composition maintain excellent releasability and injection properties.
The olefin wax can be a polymer having a low melt viscosity and can be an oily solid having sliding properties and plasticity. For example, the olefin wax can include at least one selected from among polyethylene wax and polypropylene wax, and commercially available olefin wax can be used.
In one embodiment of the present invention, based on a total weight of the polyester resin composition, the lubricant can be included in an amount of 0.1 to 5% by weight, 0.1 to 3% by weight, or 0.1 to 1% by weight. Within this range, excellent releasability and injection properties can be provided.
The polyester resin composition can include a plasticizer that facilitates chain folding during crystal formation, such as glycerol, to control crystallization by increasing the point of a crystal nucleus.
The polyester resin composition can be preferably a polyester resin composition for cover parts of automotive parts. In this case, in addition to general parts, the automotive parts include electronic control units (ECUs) including an engine control unit, a transmission control unit (TCU), an electronic stability control (ESC) system, an airbag control system, a tire pressure monitoring system (TPMS), and a passive occupant detection system (PODS), the covers thereof, and the cover parts thereof.
When measuring height difference in the height direction before and after leaving a specimen having dimensions of 200 mm×100 mm×2T in width, length, and thickness at 100° C. for 30 minutes, the polyester resin composition of the present t invention can have a height difference of 0.25 mm or less, 0.01 to 0.25 mm, or 0.05 to 0.25 mm. Within this range, deformation at all points of a molded article can be minimized under high temperature conditions, thereby improving low bending properties. Here, the height of the molded article is 12 mm, and the thickness thereof is 2T.
For example, the polyester resin composition can have a flexural modulus of 8, 120 MPa or more, as a specific example, 8,120 to 9,000 MPa, preferably 8,130 to 8,250 MPa as measured according to ISO 178. Within this range, low bending properties can be provided under high temperature conditions while maintaining mechanical properties.
For example, the polyester resin composition can have a Charpy impact strength of 6.6 KJ/m2 or more, as a specific example, 6.6 to 7.5 kJ/m2, as a preferred example, 6.6 to 6.9 kJ/m2 as measured according to ISO 179. Within this range, low bending properties can be provided under high temperature conditions while maintaining mechanical properties.
For example, the polyester resin composition can have a heat deflection temperature (HDT) of 190° C. or higher, as a specific example, 190 to 205° C., as a preferred example, 190 to 200° C. as measured under a load of 1.80 MPa according to ISO 75-1/2. Within this range, low bending properties can be provided under high temperature conditions while maintaining mechanical properties.
The polyester resin composition according to the present invention can be prepared by a method known in the art. For example, the polyester resin composition can be prepared in the form of pellets by a method of melt-extruding a mixture of components and additives in an extruder, and the pellets can be used to manufacture injection-molded articles and extrusion-molded articles.
In one embodiment of the present invention, the pellets are injected or extruded at a temperature of 240 to 300° C. or 250 to 290° C. In addition, when injecting the pellets, the temperature of a mold is preferably 60 to 120° C. When the mold temperature is 60° C. or less, appearance can be deteriorated. When the mold temperature is 120° C. or higher, the pellets can stick to the mold, reducing releasability and increasing cooling rate. Specifically, the mold temperature can be 60 to 100° C., 70 to 90° C., or 75 to 85° C. Within this range, even when the temperature of a mold is controlled during injection molding, bending deformation at all points of an injection-molded article can be minimized, thereby improving low bending properties.
According to one embodiment of the present invention, in the process of injection-molding the injection-molded article, the injection rate of a melt product containing the polyester resin composition can be 20 to 100 mm/s. Specifically, in the process of injection-molding the injection-molded article, the injection rate of a melt product containing the polyester resin composition can be 20 to 90 m/s, 20 to 80 mm/s, or 30 to 60 mm/s. Within this range, even when the temperature of a mold is controlled during injection molding of the injection-molded article, bending deformation at all points of the injection-molded article can be minimized, thereby improving low bending properties.
For example, a method of preparing the polyester resin composition of the present invention includes a step of kneading and extruding the polyester resin composition including the polybutylene terephthalate resin, the polyethylene terephthalate resin, the reinforcing fiber, the layered clay mineral, and the additives. In this case, the physical property balance between rigidity, processability, and low bending properties can be excellent.
According to another embodiment of the present invention, a molded article manufactured using the above-described polyester resin composition is provided.
In particular, the molded article can be a part for automotive electronic control units (ECUs) including an engine control unit, a transmission control unit (TCU), an electronic stability control (ESC) system, an airbag control system, a tire pressure monitoring system (TPMS), and a passive occupant detection system (PODS), the cover thereof, or the cover part thereof.
The part for electronic control units, the cover thereof, or the cover part thereof can be manufactured by a method including a step of excluding and injecting the polyester-based composition at a molding temperature of 230 to 300° C., preferably 250 to 290° C. Within this range, a product without defects can be obtained, the manufacturing time can be shortened, and the manufacturing cost can be reduced.
Within this range, by adjusting the impact strength, tensile strength, and flexural strength of the molded article, the impact resistance and durability of the molded article can be improved.
In describing the polyester resin composition of the present invention, the method of preparing the same, and the molded article including the same, it should be noted that other conditions or equipment not explicitly described herein can be appropriately selected within the range commonly practiced in the art without particular limitation.
Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. Also, in the present invention, % means % by weight unless otherwise defined.
The components constituting the polyester resin composition are as follows.
Here, “%” means “% by weight”.
According to the contents shown in Table 1 below, the polybutylene terephthalate resin (A), the polyethylene terephthalate resins (B-1) to (B-3), the reinforcing fiber (C), talc (D-1), mica (D-2), calcium carbonate (D-3), the heat stabilizer (E-1), the lubricant (E-2), and the carbon black masterbatch (E-3) were mixed and melt and kneaded at 250 to 290° C. using a twin-screw extruder (L/D=42, ϕ=40 mm) to prepare a polyester resin composition in the form of pellets. Based on 100% by weight in total of the polyester resin composition, 0.8% by weight in total of the components (E-1) and (E-2) was added.
After drying the pelletized resin at 120° C. for more than 4 hours, the resin was injected at an injection temperature of 260 to 290° C., a mold temperature of 80° C., and an injection rate of 40 mm/s using a 280-ton electric injection machine (Sumitomo Co.) to prepare a specimen having dimensions of 200 mm×100 mm×2T in width, length, and thickness, and the specimen was stored at room temperature.
The properties of specimens prepared in Examples 1 and 2 and Comparative Examples 1 to 6 were measured according to the following methods, and the results are shown in Table 1 below.
As shown in Table 1, in the case of Examples 1 and 2 according to the present invention including a polybutylene terephthalate resin, a polyethylene terephthalate resin including an isophthalic acid monomer, a reinforcing fiber, mica, and additives in a specific content ratio, the balance between mechanical strength and heat resistance was maintained, and bending deformation was minimized under high temperature conditions, thereby greatly improving low bending properties.
On the other hand, in the case of Comparative Example 1 including a polybutylene terephthalate resin, a polyethylene terephthalate resin not including an isophthalic acid monomer, a reinforcing fiber, talc, and additives, heat resistance was further improved, but low bending properties were not improved.
In addition, in the case of Comparative Example 2 in which a reinforcing fiber was added in an inappropriate content ratio compared to mica, mechanical strength was poor, and low bending properties were not improved.
In addition, in the case of Comparative Example 3 using a polyethylene terephthalate resin not including an isophthalic acid monomer, mechanical strength was poor, and low bending properties were not improved.
In addition, in the case of Comparative Example 4 including a small amount of a polybutylene terephthalate resin and an excess of a polyethylene terephthalate resin not including an isophthalic acid monomer, heat resistance was significantly reduced, and low bending properties were not improved.
In addition, in the case of Comparative Example 5 including a polybutylene terephthalate resin; a polyethylene terephthalate resin not including an isophthalic acid monomer, a reinforcing fiber, calcium carbonate, and additives, mechanical strength was significantly reduced, and low bending properties were not improved.
In addition, in the case of Comparative Example 6 including an excess of a polybutylene terephthalate resin and a small amount of a polyethylene terephthalate resin including an isophthalic acid monomer, low bending properties were deteriorated.
In conclusion, the present invention provides a polyester resin composition suitable as a material for parts for automotive electronic control units including an engine control unit, a transmission control unit (TCU), an electronic stability control (ESC) system, an airbag control system, a tire pressure monitoring system (TPMS), and a passive occupant detection system (PODS); the covers thereof, or the cover parts thereof. According to the present invention, by controlling the structure and content of a polyethylene terephthalate resin mixed with a polybutylene terephthalate resin and adjusting the weight ratio of a reinforcing fiber to a layered clay mineral, the balance between mechanical strength and heat resistance can be maintained, and flatness can be maintained even under high temperature environments, thereby minimizing deformation. Thus, the polyester resin composition of the present invention can be applied to automotive parts, the covers thereof, or the cover parts thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0011940 | Jan 2022 | KR | national |
| 10-2023-0001101 | Jan 2023 | KR | national |
This application is a National Stage Application of International Application No. PCT/KR2023/000183 filed on Jan. 5, 2023, which claims priority to Korean Patent Application No. 10-2022-0011940, filed on Jan. 27, 2022, and Korean Patent Application No. 10-2023-0001101, re-filed on Jan. 4, 2023, based on the priority of the above patent, in the Korean Intellectual Property Office, the disclosures of each of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2023/000183 | 1/5/2023 | WO |
