CN111004519B

CN111004519B - Low dielectric liquid crystal polyester composition and preparation method thereof

Info

Publication number: CN111004519B
Application number: CN201911322304.9A
Authority: CN
Inventors: 金良文
Original assignee: Jiangmen Dengzhongtai Engineering Plastics Co ltd
Current assignee: Jiangmen Dengzhongtai Engineering Plastics Co ltd
Priority date: 2019-12-20
Filing date: 2019-12-20
Publication date: 2021-08-03
Anticipated expiration: 2039-12-20
Also published as: CN111004519A

Abstract

The embodiment of the invention provides a low dielectric liquid crystalline polyester composition and a preparation method thereof, wherein the low dielectric liquid crystalline polyester composition comprises 40-90% of LCP (A) and 10-60% of LCP (B) fibers, wherein the melting point of the LCP is more than or equal to 280 ℃, the dielectric constant is lower than 3.5, the dielectric loss tangent angle is lower than 0.002, and the melting point of the LCP (B) fibers is higher than the melting point of the LCP (A) by more than 30 ℃. The low dielectric liquid crystal polyester composition has good flowing property, the dielectric constant is lower than 3.5, the dielectric loss tangent angle is lower than 0.002, and the tensile strength is higher than 150Mpa, so that the temperature resistance requirement of an SMT (surface mount technology) process is met.

Description

Low dielectric liquid crystal polyester composition and preparation method thereof

Technical Field

The invention belongs to the technical field of dielectric materials, and particularly relates to a low dielectric liquid crystal polyester composition and a preparation method thereof.

Background

Dielectric materials, also known as dielectrics, are electrically insulating materials. There are high dielectric materials and low dielectric materials, depending on the properties. With the rapid advance of electronic information technology, electronic products are being developed toward light weight, high performance and multiple functions, and development of low dielectric constant (Dk <3) materials with good performance is increasingly required.

First, with the advent of the 5G era, the communication frequency is becoming higher and the requirement for the transmission stability of electrical signals is becoming higher, and therefore the dielectric properties of materials are becoming higher and higher, and it is required that the dielectric constant (Dk) and the dielectric loss tangent angle (Df) of materials are as low as possible and are substantially stable over a wide frequency range. Secondly, due to the miniaturization of electronic communication products, the plastic material is required to have excellent processability and high strength. Furthermore, due to the Surface Mount Technology (SMT) and environmental requirements, lead-free wave-soldering is generally used in the industry for processing, and the material is required to have stable performance at a temperature of over 260 ℃, not deform and not decompose, and therefore, the material is required to have high temperature resistance.

Liquid Crystal Polymer (LCP) refers to a wholly aromatic condensation Polymer having relatively rigid and linear Polymer chains. When these polymers melt, they orient to form a liquid crystal phase. Liquid crystal polymers constitute a family of thermoplastics with a unique set of properties, among which the most well known applications are wholly aromatic polyesters (LCP in the present invention refers specifically to wholly aromatic polyesters). They perform very well in harsh environments, show high thermal resistance, high chemical resistance, low water absorption and extremely high dimensional stability. The dielectric properties remain relatively stable over a wide frequency range and temperature range. However, pure LCP resin has low mechanical strength, and thus is usually compounded with other materials and then injection molded to be applied to various fields.

The LCP fiber is formed by melting LCP resin, spraying the molten LCP resin from a spinneret of a melt spinning assembly, forming a melt trickle after the melt is sprayed from the spinneret, and solidifying and forming the melt trickle in air below the spinneret. Then post-treating to further improve the mechanical strength of the fiber material.

The continuous fiber reinforced thermoplastic Composite (CFRTP) technology is a composite produced by uniformly impregnating a thermoplastic resin and continuous fibers with the continuous fibers as a reinforcing material and the thermoplastic resin as a matrix. Optional reinforcing materials include glass fibers, carbon fibers, aramid fibers, plant fibers, and basalt fibers. The resin matrix can be selected from PP, PE, PA6, PA66, PC, PET, TPU, PPS, PEEK, etc. The reinforcing material can be in a unidirectional form or a fabric form according to different product performances and molding requirements. The continuous fiber reinforced thermoplastic composite material technology mainly comprises the following steps according to different infiltration processes: 1. a hybrid yarn dipping method; 2. a melt impregnation method; 3. powder impregnation method; 4. solution impregnation method. The mixed fiber yarn dipping method is that the thermoplastic fiber and the reinforced fiber are mutually dispersed evenly by a certain method, then the fiber is combined into a bundle, and then the thermoplastic fiber is heated in the forming process to be melted and evenly coated on the reinforced fiber, so as to prepare the continuous fiber reinforced thermoplastic composite material.

The melting impregnation method is that the resin is melted under the action of a screw machine and enters an impregnation molten pool, then the pre-dispersed fibers are sent into the infiltration molten pool, the long fibers are re-dispersed and infiltrated in the molten pool, and then the continuous fiber reinforced thermoplastic composite material is obtained by extrusion from a die, cooling and granulation.

The powder impregnation method is to adhere thermoplastic resin powder to the dispersed fibers, then to melt and mold the thermoplastic resin powder, and to heat and melt the thermoplastic resin powder and uniformly coat the thermoplastic resin powder on the reinforcing fibers, so as to obtain the continuous fiber reinforced thermoplastic composite material.

The solution impregnation method is to mix and dissolve the thermoplastic resin and a specific solvent to obtain a solution with obviously reduced viscosity, impregnate the fiber with the solution with low viscosity to obtain the solution impregnated fiber, and then volatilize the solvent to obtain the continuous fiber reinforced thermoplastic composite material.

For the preparation of low dielectric, high strength and high temperature resistant materials, in the prior art, low dielectric fillers and wholly aromatic polyester are mostly blended to prepare low dielectric compositions. For example, patent CN 106633860a describes a method for preparing a low dielectric material by blending glass fiber, ultra-high molecular weight polyethylene and wholly aromatic polyester. However, the composition has a risk of foaming deformation when subjected to SMT processing due to the low melting point of the ultra-high molecular weight polyethylene. Patent CN 109705577a describes a method for preparing a low dielectric material by blending PPS resin, hollow glass beads, low dielectric glass fibers and a toughening agent. The dielectric constant can be reduced to 3 or less, but since the melting point of the PPS resin itself is low, about 280 degrees, there is a risk of foaming deformation during SMT processing. Moreover, the mechanical properties of the material are poor, since the reinforcing effect of the hollow glass microspheres is too low.

At present, no solution which can enable the material to simultaneously meet the performances of high temperature resistance, high fluidity, low dielectric constant and high strength exists in the market.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a low dielectric liquid crystalline polyester composition and a preparation method thereof.

According to the low dielectric liquid crystal polyester composition disclosed by the embodiment of the first aspect of the invention, the low dielectric liquid crystal polyester composition is prepared from a composition consisting of LCP (A) and LCP (B) fibers by adopting a continuous fiber reinforcement technology, has good flow property, a dielectric constant of less than 3.5, a dielectric loss tangent angle of less than 0.002, a tensile strength of more than 150MPa, and low density, and meets the temperature resistance requirement of an SMT (surface mount technology) process.

According to the embodiment of the first aspect of the invention, the low dielectric liquid crystalline polyester composition comprises LCP, and the preparation raw materials of the LCP comprise the following components in percentage by mass:

LCP (A): 40 to 90%, and

lcp (b) fibers: 10-60%;

the melting point of the LCP is more than or equal to 280 ℃, the dielectric constant is lower than 3.5, and the dielectric loss tangent angle is lower than 0.002;

the melting point of the LCP (B) fiber is more than 30 ℃ higher than that of the LCP (A).

According to some embodiments of the invention, the LCP has a hydroxyl end group content of 20 to 100 equivalents/mole.

According to some embodiments of the invention, the LCP has a carboxyl end group content of 20 to 80 equivalents/mole.

According to some embodiments of the present invention, the lcp (b) fibers are wound using a winding roller having a thermal expansion coefficient 10% to 800% greater than that of the lcp (b) fibers.

According to some embodiments of the invention, the LCP (B) fibers and the take-up roller are maintained at a vacuum of less than 500Pa and at a temperature of 200-400 ℃ but less than the melting point of the LCP (B) fibers for 1-36 hours.

According to some embodiments of the invention, the LCP (B) fibers have a diameter of 5 to 20 μm.

According to some embodiments of the invention, the lcp (b) fiber strength is greater than 20.0 cN/dtex.

According to some embodiments of the present invention, the preparation raw material includes at least one of fibrous silica, porous silica, fluorosilicone glass, amorphous polytetrafluoroethylene, tragedy fluorine polyimide, hollow glass beads, porous polytetrafluoroethylene, porous alumina, zeolite-polyimide composite porous material, and BN/SICO composite porous material.

The preparation method of the low dielectric liquid crystal polyester composition comprises the following steps:

s1: uniformly mixing the preparation raw materials except the LCP (B) fiber, and plasticizing and melting the mixture at 280-440 ℃ by using an extruder to obtain a first melt;

s2: inputting the first melt into a preheated impregnation tank, and inputting LCP (B) fibers into the impregnation tank for dispersed impregnation, wherein the temperature of the impregnation tank is 280-380 ℃, but the temperature of the impregnation tank is lower than the melting point of the LCP (B) fibers, and the impregnation time is 1-30 min, so as to obtain a second melt;

s3: and drawing the second melt out of the impregnation tank, cooling and pelletizing to obtain the low dielectric liquid crystalline polyester composition.

According to some embodiments of the present invention, the dipping tank in step S2 is composed of 1-20 contact type dipping grooved rollers, the diameter of the dipping rollers is 3-50 mm, and the distance between the dipping rollers is 10-100 mm.

According to some embodiments of the invention, the LCP comprises in its structure at least one structural repeat unit of an aromatic hydroxycarboxylic acid repeat unit, an aromatic diol repeat unit, and an aromatic dicarboxylic acid repeat unit.

The aromatic hydroxycarboxylic acid repeating units are derived from at least one member selected from the group consisting of: 2-hydroxy-3-naphthoic acid, 2-hydroxy-6-naphthoic acid, 1-hydroxy-5-naphthoic acid, p-hydroxybenzoic acid, m-hydroxybenzoic acid, 4-hydroxy-4' -carboxydiphenyl ether, and aromatic hydroxycarboxylic acids in which a part of the hydrogen atoms in the aromatic ring of these aromatic hydroxycarboxylic acids is replaced with a substituent selected from the group consisting of alkyl groups, aryl groups, and halogen atoms. In the production of the LCP, the aromatic hydroxycarboxylic acid may be used alone, or two or more of the aromatic hydroxycarboxylic acids may be used in combination.

The aromatic hydroxycarboxylic acid unit is preferably p-hydroxybenzoic acid or 2-hydroxy-6-naphthoic acid, and more preferably 2-hydroxy-6-naphthoic acid, from the viewpoint of obtaining excellent properties such as high heat resistance, high fluidity, low dielectric constant, and low loss.

The aromatic dicarboxylic acid repeating units are derived from at least one member selected from the group consisting of: 2,6 '-naphthalenedicarboxylic acid, isophthalic acid, terephthalic acid, 4, 4' -biphenyldicarboxylic acid, 4,4 '-dicarboxylic acid-diphenylsulfide, 4, 4' -dicarboxylic acid-diphenylether and aromatic dicarboxylic acids in which a part of hydrogen atoms in the aromatic ring of these aromatic dicarboxylic acids is replaced by a substituent selected from the group consisting of an alkyl group, an aryl group and a halogen atom. In the production of the LCP, the aromatic dicarboxylic acid may be used alone, or two or more of the aromatic dicarboxylic acids may be used in combination.

The aromatic dicarboxylic acid unit is preferably terephthalic acid, isophthalic acid, 4,4 '-biphenyldicarboxylic acid and 2, 6' -naphthalenedicarboxylic acid, and more preferably 4,4 '-biphenyldicarboxylic acid and 2, 6' -naphthalenedicarboxylic acid, from the viewpoint of obtaining excellent properties such as high heat resistance, high fluidity, low dielectric constant, and low loss.

The aromatic diol repeating units are derived from at least one member selected from the group consisting of: 2,6 ' -dihydroxynaphthalene, 1,5 ' -dihydroxynaphthalene, 4,4 ' -dihydroxybiphenyl, 4,4 ' -dihydroxybenzophenone, 1, 2-bis (4-hydroxyphenyl) ethane, 4,4 ' -dihydroxydiphenyl ether, 4,4 ' -dihydroxydiphenyl sulfone, 4,4 ' -dihydroxydiphenyl sulfide, bis (4-hydroxyphenyl) methane, resorcinol, hydroquinone and aromatic diols in which a part of the hydrogen atoms in the aromatic ring is replaced with a substituent selected from the group consisting of an alkyl group, an aryl group and a halogen atom. In the production of the LCP, the aromatic diol may be used alone, or two or more of the aromatic diols may be used in combination.

The aromatic diol unit is preferably 4,4 '-dihydroxybiphenyl and hydroquinone, and more preferably 4, 4' -dihydroxybiphenyl, from the viewpoint of obtaining excellent properties such as high heat resistance, high fluidity, low dielectric constant, and low loss.

The LCP according to the invention may also be end-capped by any end-capping agent. In the polycondensation reaction, active functional groups are generally present at both ends of the formed polymer, and when proper functional groups are present, the molecular chain ends of the polymer can still continue to participate in the reaction, so that the chain grows up, and in order to eliminate the activity of the terminal groups, monofunctional compounds can be added to eliminate the terminal functional groups, so that the terminal blocking effect is called, and the monofunctional compounds are conventionally called terminal blocking agents, namely terminal blocking agents. The capping agent is optionally selected from any mono-reactive group species thereof capable of reacting under polycondensation reaction conditions to yield an ester/amide bond, such as a monocarboxylic acid, a monoamine, a monoalcohol or a monophenol, and the like.

The monocarboxylic acid used as the end-capping agent is not particularly limited as long as it is a monocarboxylic acid reactive with a hydroxyl group, and examples thereof include: aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, pivalic acid, caproic acid, caprylic acid, tridecanoic acid, lauric acid, palmitic acid, myristic acid, and stearic acid; aromatic monocarboxylic acids such as benzoic acid, α -naphthoic acid, β -naphthoic acid, methylbenzoic acid, methylnaphthoic acid, and phenylacetic acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid and cyclopentanecarboxylic acid; and any mixtures thereof, and the like. Among them, benzoic acid is preferable from the viewpoints of reactivity, stability of the capped end, price, and the like.

The monoamine used as the end-capping agent is not particularly limited as long as it is a monoamine reactive with a carboxyl group, and examples thereof include: aliphatic monoamines such as methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, butylamine, dibutylamine, hexylamine, octylamine, decylamine, and stearylamine; aromatic monoamines such as aniline, diphenylamine, benzylamine, and naphthylamine; alicyclic monoamines such as dicyclohexylamine and cyclohexylamine; and any mixtures thereof, and the like. Among them, aniline, benzylamine, hexylamine, octylamine, decylamine, cyclohexylamine are preferable from the viewpoints of reactivity, high boiling point, stability of the end-capped terminal, and price.

The monool used as the end-capping agent is not particularly limited as long as it is reactive with a carboxyl group, and examples thereof include: alicyclic monoalcohols such as bicyclohexanol and cyclohexanol; aliphatic monoalcohols such as methanol, dimethanol, ethanol, diethanol, propanol, dipropanol, butanol, dibutanol, hexanol, octanol, decanol, and stearyl alcohol; and any mixtures thereof, and the like. Among them, hexanol, cyclohexanol, octanol, and decanol are preferable from the viewpoints of reactivity, high boiling point, stability of a capped end, and price.

The monophenol used as the end-capping agent is not particularly limited as long as it is reactive with a carboxyl group, and examples thereof include: phenol, diphenol, cresol, naphthol, and the like. Among them, phenol is preferable from the viewpoints of reactivity, high boiling point, stability of the end-capped terminal, and price.

The blocking agent is preferably monophenol from the viewpoint of obtaining excellent properties such as high heat resistance, high fluidity, low dielectric constant, and low loss.

The amount of the unit derived from the end-capping agent is preferably 0.5 to 5 mol%, more preferably 0.8 to 3.5 mol%, based on the dicarboxylic acid unit. The desired terminal hydroxyl group content is 20 to 100 equivalents/mole. When the content of the terminal hydroxyl group is more than 100 equivalents/mole, the reactivity is too high, foaming is easily caused by high-temperature degradation of the material, and the dielectric constant is high. When the content of terminal hydroxyl groups is less than 20 equivalents/mole, the reactivity is too low, and the bonding force between the LCP (A) and the LCP (B) fibers is reduced, resulting in a lower strength of the composition. The desired carboxyl end group content is 20 to 80 equivalents/mole. When the content of the terminal carboxyl group is more than 80 equivalents/mole, the reactivity is too high, foaming is easily caused by high-temperature degradation of the material, and the dielectric constant is high. When the carboxyl end group content is less than 20 equivalents/mole, the reactivity is too low, and the bonding force between the LCP (A) and the LCP (B) fibers is reduced, resulting in a lower strength of the composition.

The liquid crystalline polymer resin of the composition according to the present invention can be produced using a catalyst including a metal compound and a nitrogen-containing heterocyclic compound. Mention may be made, by way of example, of metal compound catalysts such as: metal salts of organic acids such as sodium acetate, potassium acetate, calcium acetate, magnesium acetate, zinc acetate, and ferrous acetate; nitrogen-containing heterocyclic compound catalysts, such as: 1-methylimidazole, 1-ethylimidazole and 4- (dimethylamino) pyridine.

Preferred catalysts are 1-methylimidazole and 1-ethylimidazole which are nitrogen-containing heterocyclic compound catalysts, from the viewpoint of obtaining excellent properties such as high heat resistance, high fluidity, low dielectric constant, and low loss. The amount of catalyst added is 0.01% to 1% based on the total weight of the repeating unit precursor.

Preferably, the liquid crystal polymer resin according to the present invention is preferably manufactured by a method comprising the steps of: an acylation reaction step, a polymerization reaction step and a solid-phase tackifying step.

A first step of acylation reaction of the phenolic hydroxyl group of the aromatic hydroxycarboxylic acid and the phenolic hydroxyl group of the aromatic diol with a fatty acid anhydride to obtain an acylated aromatic dicarboxylic acid and an acylated aromatic diol.

The fatty acid anhydride is selected from the group consisting of: acetic anhydride, 2-ethylhexanoic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, and the like. They may be used in combination of 2 or more. From the viewpoint of cost and source stability, acetic anhydride is preferable.

The amount of the fatty acid anhydride used is preferably in the range of 1.05 to 1.2 times equivalent based on 1 mole of the phenolic hydroxyl groups in total in the aromatic phenolic hydroxyl groups and the aromatic diol. When the amount of the fatty acid anhydride is too large, the color of the liquid-crystalline polyester is darkened. When the amount of the fatty acid anhydride is too small, the acylation reaction may not be smoothly and completely performed and the unreacted aromatic dihydroxy carboxylic acid or aromatic diol may remain in the polymerization step to be performed next, so that the polymerization reaction may not be efficiently performed. If the acylation reaction does not proceed sufficiently, the non-acylated raw material monomer may sublimate, and the fractionator used in the polymerization may be clogged.

Preferably, a certain amount of fatty acid is added at the same time when the raw material monomer, the end-capping agent, the catalyst and the fatty acid anhydride are charged into the reaction apparatus. The fatty acid is selected from the group consisting of: acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, 2-ethylhexanoic acid, monofluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, glutaric acid, maleic acid, succinic acid, and the like. They may be used in combination of 2 or more. From the viewpoint of cost and source stability, acetic acid is preferred.

The fatty acid is added in an amount of 10 to 50 parts per hundred based on the total weight of the fatty acid anhydride. The addition amount of the fatty acid is less than 10 parts per hundred, which is not favorable for the dispersion of raw material monomers, end capping agents, catalysts and the like in the fatty acid anhydride. The addition of the fatty acid is higher than 50 parts per hundred, which is not beneficial to the reaction efficiency and increases the energy consumption.

The reaction temperature of the acylation reaction is preferably in the range of 140 ℃ to 160 ℃ and the reaction time is preferably in the range of 1 to 5 hours.

A second polymerization step of polymerizing the acylated aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid and acylated aromatic diol by transesterification to obtain a liquid crystalline polyester of low polymerization degree. In the polymerization step, transesterification of the monomers is carried out. The polymerization reaction is preferably carried out under a high temperature condition, and the polymerization reaction is preferably carried out while raising the temperature inside the polymerization vessel to a range of 280 to 400 ℃ at a rate of 0.3 to 5 ℃/min.

In order to make the transesterification conversion rate in the polymerization reaction as high as possible, the fatty acid produced as a by-product and the unreacted fatty acid anhydride are preferably evaporated and distilled out of the reaction system by a fractionator or the like. It is also possible to condense a part of the raw material monomer vaporized or sublimed together with the fatty acid by refluxing a part of the distilled fatty acid, so that the monomer can be returned to the reactor, ensuring that the compounding ratio of the reaction system is maintained in a desired range.

When the temperature reaches the highest reaction temperature, vacuum pumping or inert gas introduction can be selected to further promote the forward progress of the reaction and increase the molecular weight of the liquid crystal polymer resin in the polymerization reaction step.

And thirdly, heating the solid low-polymerization-degree liquid crystal polyester in vacuum or inert gas flow to obtain a liquid crystal polymer with higher molecular weight. The solid-phase tackifying step is a method of cooling the resin obtained in the polymerization step, making the resin into powder or granules having a uniform particle size, and heat-treating the resin for 1 to 20 hours in an inert gas atmosphere or under reduced pressure. The heat treatment temperature is 30-80 ℃ lower than the melting point of the liquid crystal polymer.

The intrinsic viscosity of the liquid crystal polymer resin is in the range of 2 to 15 deciliters/gram, and more preferably in the range of 3 to 10 deciliters/gram. When a liquid crystal polymer resin having an intrinsic viscosity of 2 dl/g or more is used, the mechanical properties of the resulting composition become good. Further, when a liquid crystal polymer resin having an intrinsic viscosity of 15 dl/g or less is used, the moldability of the obtained composition is good. The intrinsic viscosity can be determined according to ISO-1628-5 using an 50/50(v/v) mixture of pentafluorophenol and hexafluoroisopropanol.

More than one liquid crystalline polymer may be used in the composition according to the invention.

The weight percentage of the lcp(s) (a) in the total weight of the liquid crystalline polyester composition is at least 40 wt%, preferably at least 50 wt%, and more preferably at least 60 wt%. Furthermore, the weight percentage of the lcp(s) (a) in the total weight of the liquid crystalline polyester composition is at most 90 wt%, preferably at most 80 wt%, and most preferably at most 70 wt%.

The liquid crystalline polymer suitable for spinning in the present invention is not particularly required, and is preferably produced according to the compounding ratio and process of the above LCP. However, from the viewpoint of low dielectric constant, high strength and spinning advantage, the intrinsic viscosity of the liquid crystal polymer is preferably in the range of 4 to 10 dl/g, more preferably 5 to 8 dl/g. Dk is less than 3.0 and Df is less than 0.002. The melting point is higher than 310 ℃ and lower than 400 ℃. The content of the terminal hydroxyl groups is 20 to 120 equivalents/mole, and the content of the terminal carboxyl groups is 20 to 120 equivalents/mole.

The aromatic polyester fiber of the present invention can be produced by a known spinning method, and preferably by melt spinning. The equipment for melting and spinning consists of a double-screw extruder, a melt pump, a filter, a spinneret and a winder.

The twin-screw extruder preferably has a maximum heating temperature of up to 400 c and more preferably a maximum heating temperature of 450 c. The temperature during the spinning is generally set to a temperature not lower than the melting point of the aromatic polyester but lower than the thermal decomposition temperature. Since the melting point of the aromatic polyester is more than 280 ℃, if the heating temperature is too low, the resin cannot be melted well, which is not favorable for spinning.

The heating mode adopts electric heating or heat-conducting oil heating, and preferably adopts heat-conducting oil indirect heating. All heating parts are preferably heated by heat conduction oil, so that the heating process is more gentle and uniform. So as to stabilize the solution and improve the stability and yield of spinning.

The diameter of the spinneret is preferably 0.1 to 0.5mm, and more preferably 0.2 to 0.4 mm. When the diameter of the spinneret is larger than 0.5mm, it is not favorable to obtain a desired fiber diameter because the stretching ratio of the LCP resin is low. When the diameter of the spinneret is less than 0.1mm, the spinning yield is liable to be lowered.

The filtering mesh number of the filter is preferably 60-500 meshes, and more preferably 120-300 meshes. The filter has a filtering mesh number lower than 60 meshes, and the spinneret holes are easily blocked by gel substances or impurities. The filtering mesh number of the filter is higher than 500 meshes, which easily causes the pressure before the filter to be too high.

The winding speed of the winding machine is preferably 300-2000 m/min, and more preferably below 600-1800 m/min.

The thermal expansion coefficient of the winding roller is preferably 10-800% larger than that of the LCP fiber, and more preferably 50-500%. This facilitates the expansion of the take-up drum during heat treatment to further stretch the LCP fibers and further improve fiber strength. When the thermal expansion coefficient of the winding roller is preferably not more than 10% than that of the LCP fibers, the reinforcing effect is not obvious. When the thermal expansion coefficient of the winding roller is preferably more than 800% higher than that of the LCP fibers, fiber breakage is easy to occur in the post-treatment process.

The strength of the primary yarn spun by the equipment in the mode is generally lower, the application requirement cannot be met, and the strength is generally further improved by heat treatment. The heat treatment process of the invention is to heat the fiber to 200-400 ℃ in a heat transfer oil heat transfer heating mode under the negative pressure state of less than 500Pa, but less than the melting point of LCP (B) fiber, and maintain the temperature for 1-36 hours. Because the heat treatment temperature is always below the melting point of the LCP, the condition that the fibers are melted and bonded can be well avoided. Due to the fact that the LCP is heated in the vacuum state, the phenomenon that the LCP is aged by thermal oxidation in the high-temperature state can be well avoided. The heat-treated fibers are preferably rewound on paper tubes again, which facilitates storage and transport and subsequent stable addition of the composition.

The diameter of the fiber obtained by the heat treatment is preferably 5 to 20 μm, and more preferably 7 to 14 μm; the fiber strength is preferably 20.0cN/dtex or more, more preferably 40.0cN/dtex or more; the elongation is preferably 0.5% or more, more preferably 1.0% or more; the elastic modulus is preferably 500cN/dtex or more, more preferably 800cN/dtex or more.

More than one LCP fiber may be used in the composition according to the invention.

The weight percentage of the LCP (B) fiber or fibers in the total weight of the liquid crystalline polyester composition is at least 10 wt%, preferably at least 20 wt%. Furthermore, the weight percentage of the LCP (B) fiber or fibers in the total weight of the liquid crystalline polyester composition is at most 60 wt%, preferably at most 50 wt%.

According to some embodiments of the present invention, the liquid crystalline polyester composition may further comprise a low dielectric filler including an inorganic low dielectric constant material, an organic low dielectric constant filler, a porous low dielectric constant material, and a composite low dielectric constant material. Wherein the inorganic low dielectric constant material is fluorosilicone glass, alumina, porous silicon, forsterite, silicon nitride, aluminum nitride, silicon oxide, etc. From the viewpoint of enhancing and lowering the dielectric properties, fibrous silica, porous silica and fluorosilicone glass are preferable.

The organic low dielectric constant filler refers to polyvinyl aryl compound, polyimide, polyaryl hydrocarbon, polyaryl ether, parylene, polypropylene, polyethylene, fluorine doped polyimide, amorphous polytetrafluoroethylene, fluorine doped polyarylether, methyl silsesquioxane, diethoxysilane, norbornene, hydrogen silsesquioxane, fluorine doped benzoxazole polymer, fluorine doped benzoxazine polymer and the like. From the viewpoint of enhancement, high temperature resistance and reduction of dielectric properties, amorphous polytetrafluoroethylene and tragedy fluorine polyimide are preferable.

The porous low-dielectric constant material refers to hollow glass microspheres, porous silsesquioxane, porous polyimide, porous polyethylene, porous polytetrafluoroethylene, porous polysiloxane, porous alumina, porous forsterite and the like. From the viewpoint of reinforcement, high temperature resistance and reduction of dielectric properties, hollow glass beads, porous polytetrafluoroethylene and porous alumina are preferable.

The composite low dielectric constant material refers to zeolite-polyimide composite porous material, BN/SICO composite porous material, polystyrene-silicon oxide composite material and polyimide-silicon oxide composite material. From the viewpoint of reinforcement, high temperature resistance and reduction of dielectric properties, zeolite-polyimide composite porous materials and BN/SICO composite porous materials are preferred.

The weight percentage of the low dielectric filler in the total weight of the liquid crystalline polyester composition of the invention is generally at least 1 wt%, preferably at least 3 wt%. Furthermore, the weight percentage of the low dielectric filler in the total weight of the liquid crystalline polyester composition of the invention is generally at most 50 wt%, preferably at most 40 wt%.

The liquid crystal polyester composition of the present invention may further contain other components such as a lubricant, an antistatic agent, an antioxidant, a heat stabilizer, a light stabilizer, and a plasticizer. When other components are blended in the liquid crystal polyester composition of the present invention, the amount thereof is preferably 5 wt% or less with respect to the mass of the whole liquid crystal polyester composition of the present invention.

The low dielectric liquid crystal polyester composition provided by the embodiment of the invention has at least the following technical effects:

the low dielectric liquid crystal polyester composition has good flowing property, the dielectric constant is lower than 3.5, the dielectric loss tangent angle is lower than 0.002, and the tensile strength is higher than 150Mpa, so that the temperature resistance requirement of an SMT (surface mount technology) process is met.

The process for preparing the low dielectric liquid crystalline polyester composition of the present invention may employ continuous fiber reinforced thermoplastic Composite (CFRTP) technology, which is well known in the art. The impregnation process is not particularly limited, but a melt impregnation method is preferably employed.

According to a second aspect of the invention, a method for preparing a low dielectric liquid crystalline polyester composition comprises the steps of:

Step S2 the steeping vat comprises 1 ~ 20 steeping vat moulds, and wherein the steeping vat mould includes: the device comprises a contact type dipping roller system mould, a non-contact type dipping roller system mould, a tooth system dipping mould and a bending runner structure dipping mould. Contact impregnation roller system molds are preferred.

The structure of the impregnation roller can be a circular roller, a grooved roller, a flat roller and a convex roller. Grooved rolls are preferred.

The diameter of the dipping roller is 3-50 mm. Preferably 5 to 30 mm.

The distance between the impregnating rollers is 10-100 mm. Preferably 20-80 mm.

The traction speed of the impregnation roller is 10-1000 mm/s. Preferably 20 to 800 mm/s.

The preparation method of the low dielectric liquid crystal polyester composition provided by the embodiment of the invention at least has the following technical effects:

the preparation method has simple steps and non-harsh process.

Detailed Description

The following are specific examples of the present invention, and the technical solutions of the present invention will be further described with reference to the examples, but the present invention is not limited to the examples.

Melting Point

The temperature was raised at a rate of 10 ℃ per minute from 50 ℃ in a nitrogen atmosphere using a differential scanning calorimeter, and the peak temperature of the melting peak appearing was determined as the melting point (. degree. C.). When there are a plurality of melting peaks, the peak temperature of the melting peak at the highest temperature is determined as the melting point.

Tensile Properties

Tensile properties were tested according to ISO 527. The test temperature was 23 ℃ and the test rate was 2 mm/min.

Notched impact strength

According to ISO 179. The test was performed using a type a notch (0.25mm base radius) and type 1 specimen size (length 80mm, width 10mm, thickness 4 mm). Samples were cut from the center of the multi-purpose strip using a single gear milling machine. The test temperature was 23 ℃.

Thin wall flow length

A mould with a spiral vent having a periphery of 0.5 x 10mm was provided for injection moulding. The screw length was measured by injection molding at a molding temperature at which the melting point of the polyamide composition was 20 ℃. When the difference of the flow length of the three continuous dies is not more than 5 percent, taking the average value of the three values as the flow length of the thin wall.

Number of blisters in reflow soldering

The mold for injection molding is 21mm long, 22mm wide, 1-2 mm thick and 8 in one mold. Each composition was injection molded 25 times for a total of 200 samples according to standard injection molding conditions. The wave-soldering temperature is 260-280 ℃, and the retention time at 280 ℃ exceeds 60 seconds. The number of blisters or deformations in the appearance of the part was visually checked. The high temperature resistance of the material was evaluated.

Dielectric constant

The material was molded into 80 x 0.9mm block samples using an injection molding machine and the dielectric constant was measured according to IEC 60250 test standard at a frequency of 10 GHz. The test temperature was 23 ℃.

Tangent angle of dielectric loss

The material was molded into 80 x 0.9mm block samples using an injection molding machine and tested for dielectric loss tangent angle at 10GHz frequency according to IEC 60250 test standard. The test temperature was 23 ℃.

Preparation of LCP (A1)

In a reactor equipped with a stainless steel type C stirrer, a torque meter, a nitrogen introduction tube, a thermometer, a pressure gauge and a reflux condenser, 1027.5g of 4-hydroxybenzoic acid (HBA), 470g of 6-hydroxy-2-naphthoic acid (HNA), 1122g of acetic anhydride, 200.0g of acetic acid were charged. The reactor was purged by evacuation and flushing with dry nitrogen and 0.3g of 1-methylimidazole was added. The temperature was raised to 150 ℃ over 60 minutes with stirring at 150rpm under nitrogen blanket and refluxed for 60 minutes by holding at this temperature. After 13.0g of phenol had been added to the reactor, the temperature was increased to 340 ℃ within 120 min. During this time, the by-product acetic acid was removed by distillation. After keeping the temperature at 340 ℃ for 30min, the pressure is gradually reduced to about 100pa within 20min, the vacuum is maintained until the torque is increased by more than 30%, the reaction is ended, and the prepolymer is taken out. The obtained prepolymer was cooled to room temperature and then pulverized by a crusher. The pulverized prepolymer is subjected to solid phase polymerization by: heating from room temperature to 230 deg.C for 3 hours, heating from 230 deg.C to 265 deg.C for 3 hours at negative pressure of 200Pa, and maintaining at 265 deg.C for 10 hours. The liquid crystalline polymer thus obtained is referred to as LCP (a 1). LCP (A1) was tested to have a melting point of 300 deg.C, an intrinsic viscosity of 5.5dl/g, a Dk of 2.9, a Df of 0.0012, 32 equivalents/mole of carboxyl end groups and 45 equivalents/mole of hydroxyl end groups.

Preparation of LCP (A2)

In a reactor equipped with a stainless steel type C stirrer, a torque meter, a nitrogen introduction tube, a thermometer, a pressure gauge and a reflux condenser, 1027.5g of 4-hydroxybenzoic acid (HBA), 470g of 6-hydroxy-2-naphthoic acid (HNA), 1122g of acetic anhydride were charged. The reactor was purged by evacuation and flushing with dry nitrogen and 0.3g of potassium acetate was added. The temperature was raised to 150 ℃ over 60 minutes with stirring at 150rpm under nitrogen blanket and refluxed for 60 minutes by holding at this temperature. The temperature was raised to 340 ℃ within 120 min. During this time, the by-product acetic acid was removed by distillation. After keeping the temperature at 340 ℃ for 30min, the pressure is gradually reduced to about 100pa within 20min, the vacuum is maintained until the torque is increased by more than 30%, the reaction is ended, and the prepolymer is taken out. The obtained prepolymer was cooled to room temperature and then pulverized by a crusher. The pulverized prepolymer is subjected to solid phase polymerization by: heating from room temperature to 230 deg.C for 3 hours, heating from 230 deg.C to 265 deg.C for 3 hours at negative pressure of 200Pa, and maintaining at 265 deg.C for 10 hours. The liquid crystalline polymer thus obtained is referred to as LCP (a 2). The LCP (A2) was tested to have a melting point of 300 deg.C, an intrinsic viscosity of 6.5dl/g, a Dk of 3.2, a Df of 0.0023, 89 equivalents/mole of carboxyl end groups and 102 equivalents/mole of hydroxyl end groups.

Preparation of LCP (B1) fibers

Into a reactor equipped with a stainless steel type C stirrer, a torque meter, a nitrogen introduction tube, a thermometer, a pressure gauge and a reflux condenser were charged 685g of p-hydroxybenzoic acid, 311g of terephthalic acid, 104g of isophthalic acid, 465g of biphenol, 1071g of acetic anhydride, 400.0g of acetic acid. The reactor was purged by evacuation and flushing with dry nitrogen and 0.18g of 1-methylimidazole was added. The temperature was raised to 150 ℃ over 80 minutes with stirring at 300rpm under nitrogen and refluxed for 3 hours by holding at this temperature. After 13.0g of phenol had been added to the reactor, the temperature was increased to 360 ℃ within 120 min. During this time, the by-product acetic acid was removed by distillation. After keeping the temperature at 360 ℃ for 30min, the pressure is gradually reduced to about 100pa within 20min, the vacuum is maintained until the torque is increased by more than 30%, the reaction is ended, and the prepolymer is taken out. The obtained prepolymer was cooled to room temperature and then pulverized by a crusher. The pulverized prepolymer is subjected to solid phase polymerization by: the mixture was heated from room temperature to 260 ℃ for 4 hours, from 260 ℃ to 295 ℃ for 5 hours at a negative pressure of 100Pa, and held at 295 ℃ for 6 hours. The aromatic polyester thus obtained was used as a base resin for the next step of producing fibers. The melting point was found to be 340 ℃, the intrinsic viscosity was 6.5dl/g, Dk was 3.0, Df was 0.0015, carboxyl end groups were 25 equivalents/mole, hydroxyl end groups were 43 equivalents/mole, and the coefficient of thermal expansion was 1.5 x 10-5.

The aromatic polyester in 150 degrees C vacuum dryer drying for 12 hours, after the water content to 10ppm, by using a twin screw extruder melt extrusion, using a gear pump metering, the resin supply to the spinning pack. The spinning temperature from the outlet of the extruder to the spin pack at this time was 360 ℃ and the number of filter meshes of the filter was 240. The resin was discharged at a discharge rate of 18 cc/min using a spinneret having 58 holes with a hole diameter of 0.25 mm. 58 monofilaments were simultaneously wound at 800m/min on an aluminum alloy reel (thermal expansion coefficient 2.5 x 10-5) to obtain a preliminary aromatic polyester fiber. Next, the heat treatment was carried out under a negative pressure of 100Pa for 6 hours from room temperature to 280 ℃ and 6 hours from 280 ℃ to 310 ℃ and held at 310 ℃ for 18 hours. After the heat treatment, the LCP (B1) fiber was obtained by rewinding the paper tube from the heat-treated bobbin at 400 m/min. The fiber diameter is 10 mu m and the fiber strength is 35 cN/dtex; the elongation was 0.87% and the modulus of elasticity was 950 cN/dtex.

Preparation of LCP (B2) fibers

The aromatic polyester in 150 degrees C vacuum dryer drying for 12 hours, after the water content to 10ppm, by using a twin screw extruder melt extrusion, using a gear pump metering, the resin supply to the spinning pack. The spinning temperature from the outlet of the extruder to the spinning pack at this time was 360 ℃ and the number of filtration meshes of the filter was 200. The resin was discharged at a discharge rate of 18 cc/min using a spinneret having 58 holes with a hole diameter of 0.05 mm. 58 monofilaments were simultaneously wound at 500 m/min on a stainless steel reel (thermal expansion coefficient 1.5 x 10-5) to obtain a preliminary aromatic polyester fiber. Subsequently, the fiber was heat-treated in nitrogen at 310 ℃ for 10 hours. After the heat treatment, the LCP (B2) fiber was obtained by rewinding the paper tube from the heat-treated bobbin at 400 m/min. The fiber diameter is 15 mu m and the fiber strength is 21 cN/dtex; the elongation was 0.42% and the modulus of elasticity was 450 cN/dtex.

Example 1

The embodiment provides a preparation method of a low dielectric liquid crystal polyester composition, which comprises the following steps:

s1: plasticizing and melting 70 parts by weight of LCP (A1) by a double extruder to obtain a first melt, wherein the plasticizing temperature is 320 ℃;

s2: inputting the first melt into a grooved roller contact type impregnation roller system die head (4 impregnation rollers with the diameter of 25mm and the distance of 30mm), inputting 30 parts by weight of LCP (B1) fibers into the impregnation die head, impregnating for 3min, and setting the temperature of an impregnation tank at 325 ℃ to obtain a second melt;

s3: and drawing the second melt out of the dipping die at the speed of 300mm/s, cooling and pelletizing to obtain the low dielectric liquid crystal polyester composition. The test results are reported in table 1.

Example 2

s1: uniformly mixing 60 parts by weight of LCP (A1) and 10 parts by weight of hollow glass beads, adding the mixture into a double-extruder, plasticizing and melting to obtain a first melt, wherein the plasticizing temperature is 315 ℃;

s3: and drawing the second melt out of the dipping die at the speed of 200mm/s, cooling and pelletizing to obtain the low dielectric liquid crystalline polyester composition. The test results are reported in table 1.

Example 3

s1: uniformly mixing 60 parts by weight of LCP (A1) and 10 parts by weight of low-dielectric glass fiber, adding the mixture into a double extruder, and plasticizing and melting the mixture to obtain a first melt, wherein the plasticizing temperature is 320 ℃;

Example 4

s1: adding 60 parts by weight of LCP (A1) into a double-extruder for plasticizing and melting to obtain a first melt, wherein the plasticizing temperature is 325 ℃;

s2: inputting the first melt into a grooved roller contact type impregnation roller system die head (4 impregnation rollers with the diameter of 25mm and the distance of 30mm), inputting 40 parts by weight of LCP (B1) fibers into the impregnation die head, impregnating for 3min, and setting the temperature of an impregnation tank at 325 ℃ to obtain a second melt;

Example 5

s1: adding 50 parts by weight of LCP (A1) and 50 parts by weight of LCP (A2) into a double extruder for plasticizing and melting to obtain a first melt, wherein the plasticizing temperature is 325 ℃;

s2: inputting the first melt into a grooved roller contact type impregnation roller system die head (5 impregnation rollers with the diameter of 25mm and the distance of the impregnation rollers of 30mm), inputting 50 parts by weight of LCP (B1) fibers and 50 parts by weight of LCP (B2) fibers into the impregnation die head, impregnating for 5min, and setting the temperature of an impregnation tank to 325 ℃, thus obtaining a second melt;

Comparative example 1

and (2) uniformly mixing 70 parts by weight of LCP (A2) and 30 parts by weight of hollow glass beads, adding the mixture into a double extruder for plasticizing and melting, wherein the plasticizing temperature is 325 ℃, and carrying out water-cooling bracing and then granulating to obtain the low dielectric liquid crystalline polyester composition. The test results are reported in table 2.

Comparative example 2

and (2) uniformly mixing 70 parts by weight of LCP (A2) and 30 parts by weight of low dielectric glass fiber, adding the mixture into a double extruder for plasticizing and melting, wherein the plasticizing temperature is 335 ℃, and carrying out water-cooling bracing and then dicing to obtain the low dielectric liquid crystalline polyester composition. The test results are reported in table 2.

Comparative example 3

s1: adding 70 parts by weight of LCP (A1) into a double-extruder, plasticizing and melting to obtain a first melt, wherein the plasticizing temperature is 325 ℃;

s2: inputting the first melt into a grooved roller contact type impregnation roller system die head (4 impregnation rollers with the diameter of 25mm and the distance of 30mm), and inputting 30 parts by weight of LCP (B2) fibers into the impregnation die head at the temperature of 355 ℃ to obtain a second melt;

s3: and drawing the second melt out of the dipping die at the speed of 200mm/s, cooling and pelletizing to obtain the low dielectric liquid crystalline polyester composition. The test results are reported in table 2.

Comparative example 4

s1: adding 70 parts by weight of PP into a double-extruder for plasticizing and melting to obtain a first melt, wherein the plasticizing temperature is 215 ℃;

s2: inputting the first melt into a grooved roller contact type impregnation roller system die head (4 impregnation rollers with the diameter of 25mm and the distance of 30mm), and inputting 30 parts by weight of LCP (B1) fibers into the impregnation die head at the temperature of 225 ℃ to obtain a second melt;

The test results are shown in tables 1 and 2 below.

TABLE 1

TABLE 2

Claims

1. The low dielectric liquid crystalline polyester composition is characterized by comprising LCP, wherein the LCP is prepared from the following raw materials in percentage by mass:

LCP (A): 40 to 90%, and

lcp (b) fibers: 10-60%;

the melting point of the LCP (B) fiber is more than 30 ℃ higher than that of the LCP (A);

the LCP (B) fiber is rolled by a rolling roller with the thermal expansion coefficient being 10-800 percent larger than that of the LCP fiber;

and the LCP (B) fibers and the rolling roller are kept for 1-36 hours at the vacuum degree of less than 500Pa and at the temperature of 200-400 ℃ but less than the melting point of the LCP (B) fibers.

2. The low dielectric liquid crystalline polyester composition according to claim 1, wherein the LCP has a terminal hydroxyl group content of 20 to 100 equivalents/mole.

3. The low dielectric liquid crystalline polyester composition of claim 1, wherein the LCP has a carboxyl end group content of 20 to 80 equivalents/mole.

4. The low dielectric liquid crystalline polyester composition according to claim 1, wherein the LCP (B) fiber has a diameter of 5 to 20 μm.

5. The low dielectric liquid crystalline polyester composition of claim 1, wherein the lcp (b) fiber strength is greater than 20.0 cN/dtex.

6. The low dielectric liquid crystalline polyester composition of claim 1, wherein the preparation raw material comprises at least one of fibrous silica, porous silicon, fluorosilicone glass, amorphous polytetrafluoroethylene, tragedo-fluorine polyimide, hollow glass beads, porous polytetrafluoroethylene, porous alumina, zeolite-polyimide composite porous material, and BN/SICO composite porous material.

7. The method for preparing a low dielectric liquid crystalline polyester composition according to any one of claims 1 to 6, comprising the steps of:

8. The method for preparing a low dielectric liquid crystalline polyester composition according to claim 7, wherein the dip tank in the step S2 comprises 1 to 20 contact dip grooving rollers, the diameter of the dip roller is 3 to 50mm, and the distance between the dip rollers is 10 to 100 mm.