WO2017133332A1 - Liquid crystal polyester, moulding composition consisting thereof and use thereof - Google Patents

Abstract

Disclosed are a liquid crystal polyester, a moulding composition consisting thereof and a use thereof, composed of repeating structural units of formulae [I]-[V], wherein dynamic thermo-mechanical analysis (DMA) is used for testing, and the liquid crystal polyester satisfies: the storage modulus release rate ΔG, as defined in following formula (1), is greater than or equal to 95.0% to less than or equal to 99.4%. (1) ΔG＝[G(-50)-G(melting point)]/G(-50)*100%. The DMA storage modulus release rate ΔG of the liquid crystal polyester of the present invention is greater than or equal to 95.0% to less than or equal to 99.4%. The liquid crystal polyester and the moulding composition prepared from the liquid crystal polyester have a relatively high fluidity, an excellent melting property, and a high moulding stability for small-size thin-walled mouldings, and are particularly suitable for applying to thin-walled electric pieces.

Description

Liquid crystal polyester and molding composition composed thereof and application thereof Technical field

The present invention relates to the field of polymer materials, and in particular to a liquid crystal polyester and a molding composition composed thereof and an application thereof.

Background technique

Thermotropic Liquid Crystal Polymer (TLCP) is a high performance special engineering plastic with excellent mechanical properties, good fluidity, heat resistance, chemical resistance, flame retardancy and electrical insulation properties. Currently in electronics and small It is widely used in precision thin-walled parts and other fields. The preparation thereof is usually carried out by a high-temperature melt polymerization method, but due to the self-polymerization of the HBA, HNA or the like, or the branching reaction of the molecular chain, the melt processing property and physical properties of the final liquid crystal product are poor, especially the resin. The fluidity is seriously affected, which leads to the mold filling dissatisfaction in the molding process of the liquid crystal polyester molding composition, which seriously affects the application of the liquid crystal polymer in the thin-walled parts of electronic appliances.

Research on inhibiting the self-polymerization of HBA and controlling the occurrence of side reactions such as cross-linking during high-temperature polymerization has been a major issue in research and industry, such as the patents CN1673249A, CN104004170 A, CN104098760A, CN104098761A mentioned by adding 4-A The method of inhibiting decarboxylation and self-polymerization of HBA by a method such as benzenesulfonic acid, water, or acetic acid has a certain effect on the intrinsic viscosity of the liquid crystal polymer.

As the above patents, the intrinsic viscosity of liquid crystal polyesters has become a common means in the industry to characterize the relative molecular mass and molecular chain motion characteristics of liquid crystal polyesters, and indirectly reflects the fluidity of the final liquid crystal polyester. However, the difference in intrinsic viscosity is not the only factor affecting the fluidity of the polymer. The structure or ratio of raw material monomers, the degree of self-polymerization of monomers, the change of molecular weight and molecular chain sequence structure, the uniformity of molecular segments, the degree of entanglement or branching of molecular chains, the mobility of molecular chains and The crystal structure and speed, the preparation process, etc. all have an effect on the fluidity of the polymer.

Dynamic thermomechanical analysis (DMA), which is commonly used to characterize the change in modulus of a plastic article with temperature, reflects the mobility of the molecular chain, and the greater the degree of entanglement and branching of the self-polymerized product and molecular chain, The more branched cross-linking points, the weaker the molecular chain's ability to move, resulting in high storage modulus. The present applicant has continuously studied and found that when the storage modulus release rate ΔG of the liquid crystal polyester is within a specific range, the liquid crystal polyester is significantly weakened due to self-polymerization or molecular chain branching crosslinking, and the molecular chains are arranged in an orderly manner. Therefore, it exhibits excellent processing fluidity and mechanical properties.

Summary of the invention

SUMMARY OF THE INVENTION A primary object of the present invention is to provide a liquid crystal polyester having high fluidity, which has a storage modulus release rate ΔG within a specific range and which has remarkably improved processing fluidity.

Another object of the present invention is to provide a molding composition comprising the above liquid crystal polyester.

The invention is achieved by the following technical solutions:

A liquid crystal polyester composed of repeating structural units of the following formulas [I]-[IV]:

The amount of the structural unit [I] derived from p-hydroxybenzoic acid is 30 mol% or more and 72 mol% or less based on 100 mol% of the total of the repeating units; and the structural unit derived from 6-hydroxy-2-naphthoic acid [II] The amount is 1 mol% or more and 7.5 mol% or less; the total amount of the structural unit [III] derived from terephthalic acid and the structural unit [IV] derived from isophthalic acid is 10 mol% or more and 38 mol% or less. The amount of the structural unit [V] derived from 4,4'-biphenol is 10 mol% or more and 31 mol% or less; the structural units [I], [II], [III], [IV] and The sum of the mole percentages of [V] is 100;

The dynamic thermomechanical analysis DMA test is adopted, and the liquid crystal polyester is heated from the initial temperature of -50 ° C to a heating rate of 3 ° C / min, the amplitude is 30 μm, and the frequency is 1 Hz, and the initial temperature is -50. The storage modulus of °C is denoted as G(-50), and the storage modulus at the melting point is denoted as G (melting point), and the liquid crystal polyester satisfies the storage modulus release rate ΔG defined by the following formula (1) 95.0% to less than or equal to 99.4%,

(1) ΔG = [G (-50) - G (melting point)] / G (-50) * 100%.

The physical meaning of the DMA storage modulus release rate ΔG is the change in the ability of the liquid crystal polyester molecular chain to store energy during the process of moving from low temperature to melting point. For the ideal molecular chain without interaction, the molecular chain without entanglement or branching of the liquid crystal polyester when the temperature reaches the melting point, the energy stored in the molecular chain movement should be completely released, that is, the storage modulus release rate reaches 100%. At this time, the ideal molecular chain movement has no friction and other resistance, showing perfect fluidity. However, the actual synthetic liquid crystal polyester is different in the structure or proportion of the raw material monomer, the degree of self-polymerization of the monomer, the change of the molecular weight and the molecular chain sequence structure, the uniformity of the molecular segment, the degree of entanglement or branching of the molecular chain. Molecular chain The dynamic capacity and the speed of the crystal structure and speed, the preparation process and many other factors affect the molecular chain structure of the final prepared liquid crystal polyester, so the energy generated during the movement cannot be completely released. , leading to a decline in liquidity.

According to the research, when the DMA storage modulus release rate ΔG of the liquid crystal polyester is 95.0% or more to 99.4% or less, the HBA or HNA self-polymerization or molecular chain branching crosslinking is obviously weakened, and the comparison is performed. It has high fluidity and excellent melting characteristics, and has high molding stability of small-sized thin-walled molded articles. When ΔG is less than 95.0%, molecular chain branching and crosslinking are increased, and processing fluidity is inferior.

In order to complete the preparation of a high-flow liquid crystal polyester of the present invention, the liquid crystal polyester has a melt viscosity of 9 Pa.s-35 Pa.s, preferably 15 Pa.s-30 Pa.s, and the melt viscosity is tested by a capillary rheometer. The temperature was greater than the melting point of 0-30 ° C, the shear rate was 1000 S ^-1 , and the die was measured using a die having an inner diameter of 1 mm and a length of 40 mm.

The melting point of the liquid crystal polyester should be as high as possible from the viewpoint of heat resistance, but the melting point of the liquid crystal polymer of the present invention is 310 ° C to 390 ° C in consideration of the heating ability of the molding apparatus during melt processing of the polymer. It is preferably 330 ° C to 380 ° C. The melting point is measured by DSC, and the temperature is raised from the room temperature to the highest temperature of the melting point +30 ° C at a temperature rising rate of 20 ° C / min. After staying at this temperature for 3 min, the temperature is lowered to room temperature at a rate of 20 ° C / min, and the test sample is tested. After staying at room temperature for 3 min, the temperature was raised again to the highest temperature of the melting point + 30 ° C at a heating rate of 20 ° C / min to obtain a second melting curve of the liquid crystal polyester, and the melting peak of the curve was selected as the melting point.

The content of each structural unit of the present invention can be calculated by measuring 500 mg of the liquid crystal polyester or a molding composition thereof into a 25 ml volumetric flask, and adding 2.5 ml of a NaOH/CH ₃ OH solution having a concentration of 5 mol/L, and then 10 ml of water-removing dimethyl sulfoxide was added. At 60 ° C, nitrogen atmosphere, thoroughly hydrolyzed and shaken for more than 18h, dissolved in water and acidified with hydrochloric acid, and then freeze-dried. An appropriate amount of the hydrolyzate was taken into an NMR (nuclear magnetic resonance) test tube, and 1H-NMR measurement was carried out, and the peak area ratio derived from each structural unit was calculated.

The method for preparing the above liquid crystal polyester of the present invention comprises the following steps:

a, under nitrogen pressure, with p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-biphenol, terephthalic acid and isophthalic acid as raw materials, in the acylating agent The acylation reaction is carried out under the action of maintaining the pressure at 0.2 MPa to 0.6 MPa;

b. After the acylation reaction is completed, the pressure in the reaction vessel is reduced to 10KPa-30KPa, and acetic acid and unreacted acetic anhydride molecules are rapidly discharged from the rectification column. When the acetic acid receiving amount reaches 50% or more of the theoretical value, the rapid Raising to 200 ° C or above, maintaining the reduced pressure conditions and the temperature of the reaction system is programmed to the maximum temperature of the reaction, and then further reducing the pressure to 50 Kpa - 100 Kpa, melt polycondensation to obtain a prepolymer;

c. The prepolymer is cooled and solidified and granulated, and solid phase polymerization is carried out in a solid phase polymerization vessel to obtain liquid crystal polyester granules.

The phenolic hydroxyl group contained in the above raw material monomer is preferably acylated with a fatty acid anhydride before melt polycondensation. For fatty acid anhydride It is not particularly limited, and any of acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, 2-ethylhexanoic anhydride, dichloroacetic anhydride, dibromoacetic anhydride, difluoroacetic anhydride, maleic anhydride, and succinic anhydride can be used. Alternatively, it may be used in combination of two or more kinds. From the viewpoint of production cost, acetic anhydride, propionic anhydride or butyric anhydride is preferred, and acetic anhydride is more preferred. The molar ratio of the amount of the fatty acid anhydride to the phenolic hydroxyl group used is (1 to 1.2): 1, and the amount of the fatty acid anhydride is preferably 1.02 to 1.10 equivalents from the viewpoint of producing lower degassing and soldering resistance.

In the above preparation method of the liquid crystal polyester, the first stage is an acylation reaction stage, and the acylating agent acylates the phenolic hydroxyl group of the main monomer component, and the main feature of the acylation process is that nitrogen is passed through the acylation process. The pressure of the reactor is maintained at 0.2 MPa to 0.6 MPa in a pressurized manner, wherein the magnitude of the holding pressure is not particularly limited, but the acylation reaction temperature must be controlled within the acylation temperature range required by the process, and the purpose is to pressurize The method makes the acetic anhydride and the acetic acid product boil vigorously, and the acetic acid is generated by the self-polymerization reaction of the hydroxybenzoic acid acylate to increase the volume of the acetic acid gas, and the increase of the pressure causes the chemical reaction to proceed toward the decrease of the gas volume, so the self The poly-reaction is moderately inhibited, and the boiling acetic anhydride increases the probability of collision with the monomer, ensuring the balance of the acylation reaction of the phenolic hydroxyl group. The second stage is a transesterification polymerization stage. The whole reaction process is a decompression reaction, and the pressure is reduced to 10KPa-30KPa, wherein the decompression is achieved by vacuum pumping. The pressure is not particularly limited, but must be programmed. Rate requirements. After the acylation is finished, the acetic acid molecules are required to be quickly discharged to meet the requirements of rapid temperature rise. Due to the nitrogen pressure in the acylation stage, the acetic acid molecules are vaporized into a large amount of mist, and then evacuated by a vacuum pump to make a large amount of acetic acid and Unreacted acetic anhydride is discharged from the reaction vessel, and the discharged acetic acid flows into the acetic acid receiving tank through the heat exchanger cooling action. When the acetic acid receiving amount reaches 50% of the theoretical value, the heating rate is increased to make the reaction of the reaction kettle. The temperature is rapidly raised to 200 ° C or higher, and a condensation reaction of an acylating group of a phenolic hydroxyl group with a carboxylic acid group is carried out to suppress self-polymerization of the monomer. In the transesterification polymerization stage, the pressure is reduced, and when the reaction temperature reaches the maximum temperature of the reaction, the degree of vacuum of the reactor is increased, and then further reduced to 50 Kpa-100 Kpa, so that by-products such as phenol and other small molecules are produced. Continuous discharge from the reaction vessel under the action of reduced pressure reduces the probability of molecular chain rearrangement or branching, thereby reducing the branched crosslinking reaction of the molecular chain.

The acylation reaction is usually carried out at 100 ° C to 180 ° C for 30 minutes to 20 hours, preferably at 120 ° C to 160 ° C for 40 minutes to 5 hours. The melt polycondensation can be carried out under the action of a catalyst, and the catalyst can be a conventionally known catalyst for polyester polymerization, and can be a metal salt catalyst such as potassium acetate, sodium acetate, magnesium acetate, zinc acetate, antimony trioxide, Tetrabutyl titanate and the like.

The melt polycondensation can be carried out under an inert gas atmosphere; the polycondensation can be carried out in a batch or continuous manner or in a combination. After the acylation reaction is completed, the temperature is raised at a rate of 0.1 ° C / min to 150 ° C / min, the reactor is rapidly heated to 200 ° C or above, and enters the melt polycondensation stage; the melt polycondensation is carried out at a temperature range of 130 ° C to 400 ° C, preferably The temperature is in the range of 160 ° C to 370 ° C, wherein the highest reaction temperature is more preferably the melting point of the liquid crystal polyester + 30 ° C.

The polymerization vessel used for the melt polycondensation may be a polymerization vessel having a known shape. Preferably, a vertical polymerization tank is used, which may be a turbine blade, a twin propeller blade, a multi-stage paddle blade, preferably a turbine blade.

After the melt polycondensation, the melt viscosity of the prepolymer is preferably 10 Pa·s or less from the viewpoint of easily discharging the prepolymer in a molten state from the polymerization tank. The melt viscosity was measured by a Dynisco LCR7000 capillary rheometer. The test temperature was 30 ° C above the melting point, the shear rate was 1000 S ^-1 , and the die was measured using a die having an inner diameter of 1 mm and a length of 40 mm.

After the melt polycondensation, the discharge of the prepolymer is preferably carried out under an inert atmosphere such as a nitrogen atmosphere, that is, by adding an inert gas to the polymerization vessel and increasing the pressure, the occurrence of side reactions can be suppressed, and the molecular weight of the prepolymer is inhibited from increasing. Large (inhibits the melt viscosity of the prepolymer). The apparatus for discharging the prepolymer in a molten state may select a valve, an extruder, and a gear pump to solidify the prepolymer while continuously conveying it in one direction, and may use a wire cutter or a sheet downstream in the conveying direction. The cutter or pulverizer cuts or pulverizes. The prepolymer particles or powder obtained after cutting or crushing are not particularly limited, and are preferably from 0.1 mm to 5 mm.

Further, the acylation reaction and the transesterification polymerization may be carried out continuously in the same reactor or in different reaction vessels.

The solid phase polymerization is preferably carried out under a vacuum of 0.1 Pa to 50 KPa or under an inert protective gas such as nitrogen, and the polymerization temperature is about 0 to 340 ° C, and the reaction time is 0.5 to 40 hours. The solid phase polymerization can be carried out in a static state with or without stirring.

According to a large amount of experimental data according to the present invention, the self-polymerization of the monomer mainly occurs under low temperature conditions, such as a temperature below 200 ° C, and the branching and crosslinking reaction of the molecular chain is mainly concentrated under high temperature conditions, such as above 300 ° C; Therefore, using the preferred preparation process to control the reaction of the two temperature segments is the key to controlling the structural arrangement of the molecular chain sequence, and is also the key to ensure that the prepared liquid crystal polyester has good processing fluidity. The invention adopts the improved preparation process, effectively controls the reaction of each temperature section, and avoids the processing fluidity problem caused by monomer self-polymerization or molecular chain branching crosslinking. And the experimental data was found that the liquid crystal polyester prepared by the process of the present invention and the molding composition thereof were tested by DMA for storage modulus, and when the DMA storage modulus release rate ΔG was in a preferred range, it was exhibited. Higher fluidity, but when the DMA storage modulus release rate ΔG is lower than the preferred range of the present invention, molecular chain branching crosslinking increases, and processing fluidity deteriorates.

The main characteristic of the adjusted polymerization process is to divide the reaction into two stages. The first stage is the acylation stage of the monomer, and the pressure is maintained in the acylation process, and the pressure is maintained at 0.2 MPa-0.6 MPa; The second stage is a transesterification polymerization stage, in which the whole process of the reaction is a reduced pressure reaction, and the pressure is reduced to 10 KPa to 30 KPa. The purpose of the process of combining the pressure and pressure reduction is to effectively solve the problems of a series of side reactions generated in the two reaction temperature ranges, thereby preparing a liquid crystal polyester having excellent processing fluidity and a molding composition thereof.

The present invention also provides a liquid crystal polyester molding composition comprising 30 parts by weight to 99.9 parts by weight of a liquid crystal polyester, 1 part by weight to 70 parts by weight of the reinforcing filler and 0 to 20 parts by weight of other auxiliary agents and/or other polymers;

The liquid crystal polyester is composed of repeating structural units of the following formulas [I] to [IV]:

The amount of the structural unit [I] derived from p-hydroxybenzoic acid is 30 mol% or more and 72 mol% or less based on 100 mol% of the total of the repeating units; and the structural unit derived from 6-hydroxy-2-naphthoic acid [II] The amount is 1 mol% or more and 7.5 mol% or less; the total amount of the structural unit [III] derived from terephthalic acid and the structural unit [IV] derived from isophthalic acid is 10 mol% or more and 38 mol% or less. The amount of the structural unit [V] derived from 4,4'-biphenol is 10 mol% or more and 31 mol% or less, and the structural units [I], [II], [III], [IV] and The sum of the mole percentages of [V] is 100;

The dynamic thermomechanical analysis DMA test is adopted, and the liquid crystal polyester is heated from the initial temperature of -50 ° C to a heating rate of 3 ° C / min, the amplitude is 30 μm, and the frequency is 1 Hz, and the initial temperature is -50. The storage modulus of °C is denoted as G(-50), and the storage modulus at the melting point is denoted as G (melting point), and the liquid crystal polyester satisfies the storage modulus release rate ΔG defined by the following formula (1) 95.0% to less than or equal to 99.4%,

(1) ΔG = [G (-50) - G (melting point)] / G (-50) * 100%.

The liquid crystal polyester molding composition of the present invention is also affected by the filler due to the addition of various fillers. It exhibits slightly lower fluidity than the resin, resulting in a slight decrease in the storage modulus release rate ΔG of the molding composition, but comparative test data found that when the storage composition has a storage modulus release rate ΔG of 91.0% or more When it is 99.0% or less, the processing fluidity is still superior to the liquid crystal polyester composition in the comparative test.

The liquid crystal polyester molding composition of the present invention is subjected to a dynamic thermomechanical analysis DMA test, and the liquid crystal polyester molding composition is heated from a starting temperature of -50 ° C to a temperature of 3 ° C / min and an amplitude of 30 μm. When the temperature is raised to the melting point at a frequency of 1 Hz, the storage modulus at an initial temperature of -50 ° C is denoted as G (-50), and the storage modulus at the melting point is denoted as G (melting point), and the liquid crystal polyester is molded. The composition satisfies the storage modulus release rate ΔG defined by the following formula (1) of 91.0% or more and 99.0% or less,

(1) ΔG = [G (-50) - G (melting point)] / G (-50) * 100%.

Wherein, the reinforcing filler has a fibrous shape with an average length of 0.01 mm to 20 mm, preferably 0.1 mm to 6 mm; and an aspect ratio of 5:1 to 2000:1, preferably 30:1 to 600:1. When the size of the selected fibrous reinforcing filler is within the above range, the liquid crystal polyester composition exhibits not only good melt processing fluidity but also high heat distortion temperature and high rigidity.

If the content of the reinforcing filler is too low, the mechanical properties of the liquid crystal polyester molding composition are poor; the content of the reinforcing filler is too high, and the surface of the liquid crystal polyester molding composition has a serious floating fiber, which affects the appearance of the product. The content of the reinforcing filler is preferably from 10 parts by weight to 50 parts by weight, more preferably from 15 parts by weight to 40 parts by weight;

The reinforcing filler is an inorganic reinforcing filler or an organic reinforcing filler.

The inorganic reinforcing fillers include, but are not limited to, glass fibers, potassium titanate fibers, metal clad glass fibers, ceramic fibers, wollastonite fibers, metal carbide fibers, metal curable fibers, asbestos fibers, alumina fibers, silicon carbide. One or more of fibers, gypsum fibers or boron fibers, preferably glass fibers. The use of the glass fiber not only improves the moldability of the liquid crystal polyester composition, but also improves mechanical properties such as tensile strength, flexural strength or flexural modulus, and improves heat resistance such as heat of molding of the thermoplastic resin composition. Deformation temperature.

The organic reinforcing fillers include, but are not limited to, liquid crystal polyester fibers and/or carbon fibers.

The reinforcing filler has a non-fibrous shape and an average particle diameter of 0.001 μm to 50 μm. When the average particle diameter of the reinforcing filler is less than 0.001 μm, the liquid crystal polyester resin may have poor melt processability; when the average particle diameter of the reinforcing filler is increased Greater than 50 μm will result in poor surface appearance of the injection molded article. It is selected from the group consisting of potassium titanate whiskers, zinc oxide whiskers, aluminum borate whiskers, talc, carbon black, gypsum, asbestos, zeolite, sericite, kaolin, montmorillonite, clay, hectorite, synthetic mica, Aluminosilicate, silica, titania, alumina, zinc oxide, zirconium oxide, iron oxide, calcium carbonate, magnesium titanate, dolomite, aluminum sulfate, barium sulfate, magnesium sulfate, calcium carbonate, mica, quartz powder One or more of magnesium hydroxide, calcium hydroxide, aluminum hydroxide, glass beads, ceramic beads, boron nitride or silicon carbide.

In the liquid crystal polyester composition of the embodiment of the present invention, it may be selected from an antioxidant, a heat stabilizer, an ultraviolet absorber, a lubricant, a mold release agent, a dye-containing or a dye, or a range which does not impair the effects of the present invention. A usual processing aid in colorants, plasticizers, and antistatic agents for pigments. Or other polymers of liquid crystal polyester or liquid crystal polyester may be blended, and the other polymer may be a wholly aromatic or semi-aromatic thermotropic liquid crystal polymer, an aromatic or semi-aromatic polyamide. One or more of polyetheretherketone, polyethersulfone, polyolefin homopolymer or copolymer. By such a combination, predetermined characteristics can be further imparted.

The method of blending the reinforcing filler, the processing aid, and the like in the liquid crystal polyester according to the embodiment of the present invention is not particularly limited, and a dry blending, a solution mixing method, or a polymerization of a liquid crystalline polyester may be used for addition, melt mixing. In the refining or the like, it is preferably melt-kneaded. For example, a kneader, a uniaxial or biaxial extruder, a rubber roller machine or the like, wherein a twin screw extruder is preferably used. The temperature of the melt-kneading is not less than the melting point of the liquid crystal polyester, and the melting point is +50 ° C or lower.

As a kneading method, a liquid crystal polyester, a reinforcing filler, and other processing aids may be used for kneading from a post-loading machine; liquid crystal polyester and other processing may also be introduced from a post-loading machine. Auxiliary agent, a method of adding a reinforcing filler from a side feeder for kneading, or preparing a liquid crystal polyester composition masterbatch containing a liquid crystal polyester and other processing aid at a high concentration, and then polymerizing the mother particle and the liquid crystal The ester or the reinforcing filler is a method of kneading to obtain a predetermined concentration.

The liquid crystal polyester composition of the embodiment of the present invention is injection-molded, and is subjected to injection molding, compression molding, extrusion molding, blow molding, press molding, and the like. The molded article described herein may be various molded articles such as injection molded articles, extrusion molded articles, press molded articles, sheets, tubes, unstretched films, uniaxially stretched films, and biaxially stretched films, and may be undrawn. Various kinds of filaments such as stretched silk and super drawn yarn. In the case of injection molding, the effects of the present invention can be remarkably obtained, and therefore it is preferable.

The molded article formed by the liquid crystalline polyester or liquid crystal polyester molding composition obtained by the present invention can be applied to various gears, various housings, sensors, LED lamps, connectors, sockets, resistors, relays. Housing, relay base, relay winding bobbin, switch, coil shaft, capacitor, variable capacitor housing, optical pickup, resonator, various terminal boards, transformers, plugs, printed wiring boards, tuners, speakers, Microelectronics represented by microphones, headphones, small motors, head mounts, power modules, housings, semiconductors, liquid crystal display components, FDD brackets, FDD chassis, HDD components, motor brush holders, parabolic antennas, computer-related components, etc. Parts, VTR parts, TV parts, irons, hair dryers, rice cooker parts, microwave oven parts, audio parts, audio, laser discs, optical discs and other voice equipment parts, lighting parts, refrigerator parts, air conditioning parts, typewriter parts, word processors Parts, such as households, corporate electrical parts, office computer related parts, electricity Machine-related parts, facsimile related parts, copier related parts, washing jig, oilless bearings, stern bearings, underwater bearings, and other bearings, the motor unit Parts, mechanical parts represented by igniters, typewriters, etc., optical equipment represented by microscopes, binoculars, cameras, clocks, etc., precision mechanical related parts; alternator terminals, alternator connectors, IC adjustment Valves, dimmer potentiometer bases, exhaust valves, and other valves, fuel associated, exhaust systems, various types of suction systems, inlet nozzle vents, intake manifolds, fuel pumps, engine cooling Water joint, vaporizer body, vaporizer separator, exhaust gas sensor, cooling water sensor, oil temperature sensor, throttle position sensor, crank position sensor, air flow meter, brake pad wear sensor, air conditioner thermostat base, air conditioner In-vehicle motor insulators such as motor insulators and power windows, heater warm air flow control valves, radiator motor brush holders, water pump impellers, turbine blades, wiper motor related components, distributors, starter switches, starter relays Wiring harness for transmission, window washer nozzle, air conditioner panel switch substrate, fuel-related electromagnetic Coil, fuse connector, horn terminal, electrical component insulation board, stepper motor rotor, lamp ring, lamp holder, light reflector, lamp housing, brake piston, solenoid line shaft, engine oil filter, ignition Automobiles, vehicle-related components, and the like, such as a device casing, are particularly useful in printed wiring boards, small-sized thin-walled electronic devices, and the like.

Compared with the prior art, the invention has the following beneficial effects:

(1) The present invention has found that the liquid crystal polyester of the present invention has a DMA storage modulus release rate ΔG of 95.0% or more and 99.4% or less, has high fluidity, and has excellent melting characteristics, and is a small-sized thin-walled molded article. The molding stability is high.

(2) In the whole synthesis process, the invention can effectively control the acylation efficiency of the hydroxyl group by combining the polymerization process of pressurization and decompression, and effectively prevent the monomer from self-polymerization, the entanglement of the molecular chain, and the branching during the polymerization process. The occurrence of side reactions such as cross-linking controls the ordered arrangement of the molecular chains of the liquid crystal polyester, and a liquid crystal polyester having a high fluidity and a molding composition thereof are prepared.

(3) The preparation method of the invention is simple in operation, easy to obtain, short in production cycle, and suitable for industrial production.

detailed description

The other raw materials, acylating agents, catalysts, glass fibers, mica and calcium stearate used in the examples of the present invention are all commercially available.

The necessary performance characterization and testing methods in the present invention:

(1) Melting point: measured by DSC 200 F3 manufactured by NETZSCH Co., Ltd., and raised from room temperature to a maximum temperature of melting point + 30 ° C at a heating rate of 20 ° C / min, and stay at this temperature for 3 min and then at 20 ° C / The rate of min was cooled to room temperature, and the test sample was allowed to stand at room temperature for 3 min, and then heated again to the highest temperature of the melting point + 30 ° C at a heating rate of 20 ° C / min to obtain a second melting curve of the polyester, and the melting peak of the curve was selected. It is the melting point.

(2) Storage modulus release rate ΔG: Obtained by Q800 DMA test from Ta Company of the United States. Observed from the initial temperature of -50 °C, the temperature rise rate is 3 °C/min, the amplitude is 30um, and the frequency is 1Hz. When the temperature is raised to the melting point, the storage modulus at the initial temperature of -50 ° C is recorded as G (-50), the storage modulus at the melting point is recorded as G (melting point), and the storage modulus is released. The rate ΔG is calculated as follows:

ΔG=[G(-50)-G(melting point)]/G(-50)*100%.

(3) Fluidity: The fluidity of the liquid crystal polyester is characterized by the length of the strip-shaped sheet injection molded body of the width * thickness of 5 * 0.45 mm, the injection temperature is near the melting point, and the average length of the injection molded body through 30 rod-shaped sheets The fluidity of the liquid crystal polyester and its molding composition was measured as a parameter. Under the same injection molding conditions, the longer the length of the rod-shaped sheet injection molded body, the better the fluidity.

(4) Melt viscosity: The test was carried out using a Dynisco LCR7001 capillary rheometer with a die diameter of 1 mm and a length of 40 mm. The liquid crystal polyester had a viscosity at a shear rate of 1000 s ^-1 at a temperature of 20 ° C above the melting temperature of 20 ° C. For melt viscosity.

Example 1

The following monomer raw materials, acylating agents, and catalysts were placed in a polymerization apparatus equipped with a stirrer, a reflux condenser, a monomer feed port, a nitrogen gas inlet, a thermometer, and a torque sensor.

(I) p-hydroxybenzoic acid 1298.4 g (47 mol%) HBA

(II) 62.9 g (3 mol%) HNA of 6-hydroxy-2-naphthoic acid

(III) terephthalic acid 731 g (22 mol%) TA

(IV) 99.7 g (3 mol%) of isophthalic acid IA

(V) 4,4'-biphenoldiol 931.1 g (25 mol%) BP

Acylation agent: 2001 g of acetic anhydride

Catalyst: Magnesium acetate 103 mg

After the completion of the feeding, the atmosphere in the reaction vessel was completely replaced with nitrogen, the temperature of the reaction system was raised to 140 ° C under a nitrogen atmosphere, and the nitrogen pressure was maintained at 0.2 MPa, and the temperature was maintained at reflux for 2 hours to carry out an acylation reaction; acylation After the reaction is completed, the vacuum pump is opened to reduce the pressure in the reactor to 10KPa-30KPa, and the acetic acid and unreacted acetic anhydride molecules are quickly discharged from the rectification column to meet the requirements of rapid heating process, when the acetic acid receiving amount reaches 50% of the theoretical value. When the amount is above 5%, the temperature is rapidly raised to 200 ° C, the reduced pressure condition is maintained, and the reaction system is heated to a maximum temperature of 360 ° C in 6 hours, during which the acetic acid, particularly phenol, and the like, which cause molecular chain rearrangement and branching, are small. The molecule is then depressurized to 50 KPa in 30 minutes; when the stirring torque reaches a predetermined value, the reaction is considered to be completed, at which time the product in the reactor is taken out; after cooling the product to room temperature, it is pulverized by a pulverizer, and then under vacuum. Heating from room temperature to 300 ° C in less than 200 Pa and maintaining at this temperature for 10 hours; observing the product obtained by the above method by a polarizing microscope It is now a liquid crystal polymer which exhibits optical anisotropy in a molten state. The melting temperature, melt viscosity, storage modulus release rate, and length of the rod-shaped injection molded body of the liquid crystal polyester are shown in Table 1.

Example 2-5: According to the formulation of Table 1, after the acylation reaction was completed, the vacuum pump was used to decompress the pressure in the reactor to 10 KPa to 30 KPa, and the acetic acid and unreacted acetic anhydride molecules were quickly discharged from the rectification column to meet the rapid requirements. The temperature rise process requires that when the acetic acid receiving amount reaches 50% or more of the theoretical value, the temperature is rapidly raised to 210 ° C, the reduced pressure condition is maintained, and the reaction system is heated to a maximum temperature of 370 ° C in 6 hours, during which the acetic acid is continuously discharged, especially a by-product small molecule such as phenol which causes molecular chain rearrangement and branching, and then reduced to 60 KPa in 30 minutes; the rest is the same as in Example 1; the melting point, melt viscosity, storage modulus release rate of the liquid crystal polyester, rod shape The fluid lengths are listed in Table 1.

Example 6-12: According to the formulation of Table 1, after the acylation reaction is completed, the vacuum pump is used to decompress the pressure in the reactor to 10 KPa to 30 KPa, and the acetic acid and unreacted acetic anhydride molecules are rapidly discharged from the rectification column to meet the rapid requirements. The temperature rise process requires that when the acetic acid receiving amount reaches 50% or more of the theoretical value, the temperature is rapidly raised to 220 ° C, the reduced pressure condition is maintained, and the reaction system is heated to a maximum temperature of 380 ° C in 6 hours, during which the acetic acid is continuously discharged, especially a by-product small molecule such as phenol which causes molecular chain rearrangement and branching, and then reduced to 70 KPa in 30 minutes; the rest is the same as in Example 1; the melting point, melt viscosity, storage modulus release rate of the liquid crystal polyester, rod shape The fluid lengths are listed in Table 1.

Comparative Example 1-3: After the completion of the charging, the atmosphere in the reaction vessel was completely replaced with nitrogen, and the temperature of the reaction system was raised to 140 ° C under a nitrogen atmosphere, and the temperature was refluxed for 2 hours to carry out an acylation reaction; the acylation reaction was completed. Thereafter, the acetic acid and the unreacted acetic anhydride molecules are discharged from the side of the rectification column, and the temperature is raised and the reaction system is heated to a maximum temperature of 360 ° C in 6 hours, during which the acetic acid is continuously discharged, and then the pressure is reduced to 30 KPa in 30 minutes; After the stirring torque reaches a predetermined value, the reaction is considered to be completed, at which time the product in the reactor is taken out; after cooling the product to room temperature, it is pulverized by a pulverizer, and then heated from room temperature to 300 ° C in a vacuum of less than 200 Pa in 10 hours. And maintaining at this temperature for 10 hours; the product obtained by the above method was observed by a polarizing microscope, and it was found to be a liquid crystal polymer which can exhibit optical anisotropy in a molten state. The melting point, melt viscosity, storage modulus release rate, and length of the rod-shaped injection molded body of the liquid crystal polyester are shown in Table 1.

Table 1

It can be seen from the above results that in the embodiment, the storage modulus release rate ΔG is greater than or equal to 95.0% to 99.4% of the liquid crystal polyester, and the length of the rod-shaped injection molded body is significantly higher than that of the comparative example, indicating that the liquid crystal polyester in the embodiment has High liquidity.

In addition, it can be seen from the examples and the comparative examples that even in the case where the raw material monomers have the same structure, the same ratio, and the melt viscosity is similar, the liquid crystal polyester in the range of different storage modulus release rates has a molecular chain structure due to its molecular chain structure. The difference in the length of the rod-shaped injection molded body is that the liquid crystal polyester having a different storage modulus release rate exhibits different fluidity.

Examples 13-24, Comparative Examples 4-7: Preparation of Liquid Crystalline Polyester Molding Compositions

According to the ratio of Table 2, the liquid crystal polyesters of Examples 1-12 and Comparative Examples were vacuum dried at 150 ° C for 12 hours or more, and then the resin and the auxiliary agent were supplied from the main feed port of the twin-screw extruder by a high-speed mixer. Adding to the extruder, adding glass fiber and mica, calcium stearate and other additives to the extruder from the feed port of the twin-screw extruder according to the ratio, and mixing and selecting the appropriate barrel temperature Extrusion, granulation, cooling and solidification in an annular cooling air of a sufficiently long air flow to obtain a liquid crystal polyester composition; respectively testing the melting point, melt viscosity, storage modulus release rate, and rod-shaped injection molded body of the liquid crystal polyester composition The length test results are listed in Table 2.

Table 2

It can be seen from the results of Table 2 that since the liquid crystal polyester resin having a storage modulus release rate ΔG of 95.0% or more and 99.4% or less is used, the molecular chain structure changes greatly, and the liquid crystal polyester mold of the embodiment is used. The fluidity of the plastic composition is significantly higher than that of the comparative example, and is particularly suitable for use in thin-walled electronic parts.

Claims (15)

1. A liquid crystal polyester composed of repeating structural units of the following formulas [I]-[IV]:

   

   The amount of the structural unit [I] derived from p-hydroxybenzoic acid is 30 mol% or more and 72 mol% or less based on 100 mol% of the total of the repeating units; and the structural unit derived from 6-hydroxy-2-naphthoic acid [II] The amount is 1 mol% or more and 7.5 mol% or less; the total amount of the structural unit [III] derived from terephthalic acid and the structural unit [IV] derived from isophthalic acid is 10 mol% or more and 38 mol% or less. The amount of the structural unit [V] derived from 4,4'-biphenol is 10 mol% or more and 31 mol% or less; the structural units [I], [II], [III], [IV] and The sum of the mole percentages of [V] is 100;

   The dynamic thermomechanical analysis DMA test is adopted, and the liquid crystal polyester is heated from the initial temperature of -50 ° C to a heating rate of 3 ° C / min, the amplitude is 30 μm, and the frequency is 1 Hz, and the initial temperature is -50. The storage modulus of °C is denoted as G(-50), and the storage modulus at the melting point is denoted as G (melting point), and the liquid crystal polyester satisfies the storage modulus release rate ΔG defined by the following formula (1) 95.0% to less than or equal to 99.4%,

   (1) ΔG = [G (-50) - G (melting point)] / G (-50) * 100%.
2. The liquid crystal polyester according to claim 1, wherein the liquid crystal polyester has a melt viscosity of 9 Pa.s to 35 Pa.s, preferably 15 Pa.s to 30 Pa.s, and the melt viscosity is tested by a capillary rheometer. The test temperature is greater than the melting point of 0-30 ° C, the shear rate is 1000 S ^-1 , and the die is measured using a die having an inner diameter of 1 mm and a length of 40 mm.
3. The liquid crystal polyester according to claim 1, wherein the liquid crystal polyester has a melting point of 310 ° C to 390 ° C, preferably It is selected from 330 ° C to 380 ° C, and the melting point is measured by DSC. The temperature is raised from the room temperature to the highest temperature of the melting point + 30 ° C at a heating rate of 20 ° C / min. After staying at this temperature for 3 min, then at 20 ° C / min. The rate was lowered to room temperature, and the test sample was allowed to stand at room temperature for 3 min and then heated again at a temperature increase rate of 20 ° C/min to a maximum temperature of the melting point + 30 ° C to obtain a second melting curve of the liquid crystal polyester, and the melting peak of the curve was selected. It is the melting point.
4. The method for preparing a liquid crystal polyester according to any one of claims 1 to 3, comprising the steps of:

   a, under nitrogen pressure, with p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-biphenol, terephthalic acid and isophthalic acid as raw materials, in the acylating agent The acylation reaction is carried out under the action of maintaining the pressure at 0.2 MPa to 0.6 MPa;

   b. After the acylation reaction is completed, the pressure in the reaction vessel is reduced to 10KPa-30KPa, and acetic acid and unreacted acetic anhydride molecules are rapidly discharged from the rectification column. When the acetic acid receiving amount reaches 50% or more of the theoretical value, the rapid Raising to 200 ° C or above, maintaining the reduced pressure conditions and the temperature of the reaction system is programmed to the maximum temperature of the reaction, and then further reducing the pressure to 50 Kpa - 100 Kpa, melt polycondensation to obtain a prepolymer;

   c. The prepolymer is cooled and solidified and granulated, and solid phase polymerization is carried out in a solid phase polymerization vessel to obtain liquid crystal polyester granules.
5. The method for preparing a liquid crystal polyester according to claim 4, wherein in the step a, the temperature of the acylation reaction is from 100 ° C to 180 ° C, preferably from 120 ° C to 160 ° C, and the reaction time is from 30 minutes to 20 ° C. The hour is preferably 40 minutes to 5 hours.
6. The method for preparing a liquid crystal polyester according to claim 4, wherein in the step b, after the acylation reaction is completed, the temperature is raised at a rate of 0.1 ° C / min to 150 ° C / min, and the reactor is rapidly heated to 200 ° C. Or above, entering the melt polycondensation stage, the temperature of the melt polycondensation is from 130 ° C to 400 ° C, preferably from 160 ° C to 370 ° C.
7. The method for preparing a liquid crystal polyester according to claim 4, wherein in the step c, the solid phase polymerization is carried out under a vacuum of 0.1 Pa to 50 KPa or under an inert protective gas such as nitrogen, and the polymerization temperature is 0. ~340 ° C, the reaction time is 0.5 hours to 40 hours.
8. A liquid crystal polyester molding composition comprising the liquid crystal polyester according to any one of claims 1 to 3, comprising 30 parts by weight to 99.9 parts by weight of the liquid crystal polyester, 1 part by weight to 70 parts by weight of the reinforcing filler, and 0-20 parts by weight of other auxiliaries and/or other polymers;

   The liquid crystal polyester is composed of repeating structural units of the following formulas [I] to [IV]:

   

   The amount of the structural unit [I] derived from p-hydroxybenzoic acid is 30 mol% or more and 72 mol% or less based on 100 mol% of the total of the repeating units; and the structural unit derived from 6-hydroxy-2-naphthoic acid [II] The amount is 1 mol% or more and 7.5 mol% or less; the total amount of the structural unit [III] derived from terephthalic acid and the structural unit [IV] derived from isophthalic acid is 10 mol% or more and 38 mol% or less. The amount of the structural unit [V] derived from 4,4'-biphenol is 10 mol% or more and 31 mol% or less; the structural units [I], [II], [III], [IV] and The sum of the mole percentages of [V] is 100;

   The dynamic thermomechanical analysis DMA test is adopted, and the liquid crystal polyester is heated from the initial temperature of -50 ° C to a heating rate of 3 ° C / min, the amplitude is 30 μm, and the frequency is 1 Hz, and the initial temperature is -50. The storage modulus of °C is denoted as G(-50), and the storage modulus at the melting point is denoted as G (melting point), and the liquid crystal polyester satisfies the storage modulus release rate ΔG defined by the following formula (1) 95.0% to less than or equal to 99.4%,

   (1) ΔG = [G (-50) - G (melting point)] / G (-50) * 100%.
9. The liquid crystal polyester molding composition according to claim 8, wherein the liquid crystal polyester has a melt viscosity of 9 Pa.s to 35 Pa.s, preferably 15 Pa.s to 30 Pa.s, and a melt viscosity of a capillary tube. For the rheometer test, the test temperature was greater than the melting point of 0-30 ° C, the shear rate was 1000 S ^-1 , and the die was measured using a die having an inner diameter of 1 mm and a length of 40 mm.
10. The liquid crystal polyester molding composition according to claim 8, wherein the liquid crystal polyester has a melting point of from 310 ° C to 390 ° C, preferably from 330 ° C to 380 ° C, and the melting point is measured by DSC, from room temperature. The temperature was raised to the highest temperature of the melting point +30 ° C at a heating rate of 20 ° C / min. After staying at this temperature for 3 min, the temperature was lowered to room temperature at a rate of 20 ° C / min. The test sample was allowed to stand at room temperature for 3 min and then again at 20 The heating rate of °C/min is raised to the highest temperature of the melting point +30 °C, and the second melting curve of the liquid crystal polyester is obtained. The melting peak of the curve is selected as the melting point.
11. The liquid crystal polyester molding composition according to claim 8, wherein the reinforcing filler has a shape of a fiber The average length is from 0.01 mm to 20 mm, preferably from 0.1 mm to 6 mm; the aspect ratio is from 5:1 to 2000:1, preferably from 30:1 to 600:1; and the content of the reinforcing filler is preferably 10 Parts by weight to 50 parts by weight, more preferably 15 parts by weight to 40 parts by weight; the reinforcing filler is an inorganic reinforcing filler or an organic reinforcing filler, including but not limited to glass fibers, potassium titanate fibers, metal bags One or more of a layer of glass fiber, ceramic fiber, wollastonite fiber, metal carbide fiber, metal curable fiber, asbestos fiber, alumina fiber, silicon carbide fiber, gypsum fiber or boron fiber, preferably glass fiber; The organic reinforcing fillers include, but are not limited to, liquid crystal polyester fibers and/or carbon fibers.
12. The liquid crystal polyester molding composition according to claim 8, wherein the reinforcing filler has a non-fibrous shape and an average particle diameter of from 0.001 μm to 50 μm selected from the group consisting of potassium titanate whiskers and zinc oxide. Whiskers, aluminum borate whiskers, talc, carbon black, gypsum, asbestos, zeolite, sericite, kaolin, montmorillonite, clay, hectorite, synthetic mica, aluminosilicate, silica, titanium oxide , alumina, zinc oxide, zirconium oxide, iron oxide, calcium carbonate, magnesium titanate, dolomite, aluminum sulfate, barium sulfate, magnesium sulfate, calcium carbonate, mica, quartz powder, magnesium hydroxide, calcium hydroxide, hydroxide One or more of aluminum, glass beads, ceramic beads, boron nitride or silicon carbide.
13. The liquid crystal polyester molding composition according to claim 8, wherein the other auxiliary agent is selected from the group consisting of an antioxidant, a heat stabilizer, a UV absorber, a lubricant, a mold release agent, a colorant, and a plasticizer. Or one or more of antistatic agents.
14. The liquid crystal polyester molding composition according to any one of claims 8 to 13, characterized in that the liquid crystal polyester molding composition is heated from a starting temperature of -50 ° C by a dynamic thermomechanical analysis DMA test. When the temperature is 3 ° C / min, the amplitude is 30 um, and the temperature is raised to the melting point at a frequency of 1 Hz, the storage modulus at the initial temperature of -50 ° C is recorded as G (-50), and the storage modulus at the melting point is recorded as G (melting point), the liquid crystal polyester molding composition satisfies the storage modulus release rate ΔG defined by the following formula (1) of 91.0% or more and 99.0% or less,

    (1) ΔG = [G (-50) - G (melting point)] / G (-50) * 100%.
15. Use of the liquid crystal polyester molding composition according to any one of claims 8 to 14 in the field of electronic and electrical.