JP2006342458A - Nonwoven fabric made of liquid crystal resin fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonwoven fabric solving the alignment deviation caused by the formation of skin layer and core layer in a conventional liquid crystal resin fiber, suppressing partial fibrillation, and suitable e.g. as a substrate of a printed circuit board made of a liquid crystal resin fiber resistant to the lowering of strength in fibrillation, and having excellent strength and high-temperature dimensional stability and extremely small compressive deformation. <P>SOLUTION: The nonwoven fabric is composed of a liquid crystal resin composed of the following structural units (I), (II), (III), (IV) and (V) provided that the amount of the structural unit (I) is 65-80 mol% based on the sum of the structural units (I), (II) and (III), the amount of the structural unit (II) is 60-75 mol% based on the sum of the structural units (II) and (III), the amount of the structural unit (IV) is 60-92 mol% based on the sum of the structural units (IV) and (V), and the sum of the structural units (II) and (III) is essentially equimolar to the sum of the structural units (IV) and (V). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention solves the uneven distribution of orientation due to the formation of a skin layer core layer of a conventional liquid crystalline resin fiber, suppresses partial fibrillation, and when fibrillated, the liquid crystalline resin fiber is less likely to cause a decrease in strength or the like. The present invention relates to a non-woven fabric suitable for a circuit board substrate having excellent strength and dimensional stability at high temperature and having a very small amount of compressive deformation.

  Demand for liquid crystalline resins is growing, mainly for small precision molded products for electrical and electronic applications, taking advantage of their excellent heat resistance, fluidity, and electrical properties. In recent years, focusing on the high frequency characteristics, the use of films and non-woven fabrics as circuit board materials and IC substrates has been studied.

Especially for nonwoven fabrics, it is possible to obtain nonwoven fabrics with excellent dimensional stability and heat resistance by making use of the property that liquid crystalline resin is highly oriented by unidirectional shear flow such as spinning, and making highly oriented fibers nonwoven fabrics. It has been studied (for example, Patent Documents 1 to 3).
JP-A-10-325065 (pages 1 and 2) JP 2001-11731 A (pages 1 and 2) JP 2002-348768 (pages 1 and 2) JP 2003-166191 A (pages 1 and 2) JP 2004-100047 A (pages 1 and 2) JP 2004-270096 A (pages 1 and 2)

  However, the method described in Patent Document 1 is a method in which a liquid crystalline resin is spun and then stretched by 1.01 times or more. The liquid crystalline resin is molecularly oriented in one direction during spinning by shear flow. Since this occurs mainly in the skin layer, the part to be strengthened in stretching is limited to the skin layer subjected to tension. In such a fiber in which only the skin layer is oriented, the core layer has strength and dimensional stability. Since it does not contribute to sex, the effect obtained is not sufficient.

  Further, in the cited document 2, the absolute elongation of the liquid crystalline resin fiber is defined, but the obtained linear expansion coefficient is not sufficient, and the cited documents 3, 5 and 6 use a binder to increase the binding strength. However, its characteristics are lower than that of a non-woven fabric made only of liquid crystalline resin fibers.

  In Cited Document 4, micro glass fibers are added to improve the characteristics. However, since flexibility is emphasized in circuit boards and the like, a method of filling these inorganic fillers provides the desired characteristics. I can't.

  This invention makes it a subject to improve the dimensional stability and intensity | strength of a nonwoven fabric which are not enough with these methods.

  In order to solve the above-mentioned problems, the present inventors have studied in order to achieve the required high dimensional stability and strength with completely different ideas from these methods, and as a result, have reached the present invention.

That is, the present invention
(1) Consists of the following structural units (I), (II), (III), (IV) and (V), and the structural unit (I) is the sum of the structural units (I), (II) and (III) The structural unit (II) is 60 to 75 mol% based on the total of the structural units (II) and (III), and the structural unit (IV) is the structural unit (IV). And (V) is 60 to 92 mol%, and the total of structural units (II) and (III) and (IV) and (V) are substantially equimolar liquid crystal resin fibers Nonwoven fabric made of

  (2) The ratio (Is / Ic) between the orientation degree (Is) of the fiber surface of the liquid crystalline resin fiber constituting the nonwoven fabric and the orientation degree (Ic) of the fiber center portion is less than 1.2. Non-woven fabric.

  (3) When the liquid crystalline resin is melt-spun, the resin temperature is set to the melting point of the liquid crystalline resin + 20 ° C. or more, and the ambient temperature up to 30 cm just below the base is maintained in the temperature range of melting point−50 to melting point−10 ° C. After spinning, the liquid crystalline resin fiber obtained by stretching less than 1.005 times at a temperature not lower than the glass transition temperature of the liquid crystalline resin and not higher than -100 ° C. is cut into 2 to 10 mm, and wet papermaking or dry papermaking. A method for producing a non-woven fabric by forming a fiber web using any of the above methods, performing a fibrillation entanglement treatment, and then performing either a thermocompression treatment or a binder impregnation treatment.

  (4) The liquid crystalline resin comprises the following structural units (I), (II), (III), (IV) and (V), and the structural unit (I) is the structural units (I), (II) and ( The structural unit (II) is 60 to 75 mol% with respect to the total of structural units (II) and (III), and the structural unit (IV) is structural. 60 to 92 mol% based on the sum of units (IV) and (V), and the sum of structural units (II) and (III) and the sum of (IV) and (V) are substantially equimolar. The method to manufacture the nonwoven fabric of the said (3) description which is liquid crystalline resin.

  The non-woven fabric of the present invention has a liquid crystalline resin fiber constituting the non-woven fabric, which is less unevenly distributed in the fiber thickness direction, is difficult to fibrillate, and does not easily decrease in strength even when fibrillated. A non-woven fabric having higher strength and dimensional accuracy than a resin fiber non-woven fabric can be obtained, and it is most suitable for electrical / electronic applications such as circuit board substrates that require higher dimensional stability at higher temperatures and process pass strength.

  The nonwoven fabric of the present invention is composed of liquid crystalline resin fibers, and the liquid crystalline resin is a liquid crystalline resin composed of the following structural units (I), (II), (III), (IV) and (V). .

  The structural unit (I) is a structural unit generated from p-hydroxybenzoic acid, the structural unit (II) is a structural unit generated from 4,4′-dihydroxybiphenyl, and the structural unit (III) is generated from hydroquinone. The structural unit, the structural unit (IV) represents a structural unit generated from terephthalic acid, and the structural unit (V) represents a structural unit generated from isophthalic acid.

  The structural unit (I) is 65 to 80 mol%, more preferably 68 to 75 mol%, based on the total of the structural units (I), (II) and (III). Further, the structural unit (II) is 60 to 75 mol%, more preferably 65 to 73 mol%, based on the total of the structural units (II) and (III). Further, the structural unit (IV) is 60 to 70 mol%, more preferably 62 to 68 mol%, based on the total of the structural units (IV) and (V).

  In particular, when the structural unit (IV) is 62 to 68 mol% with respect to the total of the structural units (IV) and (V), the moldability, which is a characteristic of the present invention, is preferably expressed in a balanced manner.

  The sum of structural units (II) and (III) and (IV) and (V) is substantially equimolar, but an excess of carboxylic acid component or hydroxyl component is added to adjust the end groups of the polymer. May be. That is, “substantially equimolar” means that the unit constituting the polymer main chain excluding the terminal is equimolar, but the unit constituting the terminal is not necessarily equimolar.

  The liquid crystalline resin of the present invention includes 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 1,2-bis (phenoxy) ethane in addition to the components constituting the structural units (I) to (V). -4,4'-dicarboxylic acid, 1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 2,2 Aromatic dicarboxylic acids such as '-diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and dodecanedioic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, 3, 3', 5, 5'-tetramethyl-4,4'-dihydroxybiphenyl, t-butylhydroquinone, phenylhydroquinone, 2,6-dihydroxynaphthalene, 2,7- Hydroxynaphthalene, 2,2-bis (4-hydroxyphenyl) propane, 4,4'-dihydroxydiphenyl ether, chlorohydroquinone, 3,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxy Aromatic diols such as diphenyl sulfide, 4,4′-dihydroxybenzophenone and 3,4′-dihydroxybiphenyl, ethylene glycol, propylene glycol, 1,4-butanediol, cyclohexanedimethanol, 1,6-hexanediol, neopentyl Glycol, aliphatic such as 1,4-cyclohexanediol, alicyclic diol, 6-hydroxy-2-naphthoic acid, aromatic hydroxycarboxylic acid such as m-hydroxybenzoic acid, p-aminobenzoic acid, 6-amino- -Aromatic aminocarboxylic acids such as naphthoic acid, aromatic diamines such as 1,4-phenylenediamine, 4,4'-diaminobiphenyl, 2,6-diaminonaphthalene, aromatic hydroxylamines such as p-aminophenol, etc. The copolymer can be further copolymerized without departing from the specific composition ratio of the structural unit of the present invention as long as the characteristics of the present invention are not impaired.

  There is no restriction | limiting in particular in the manufacturing method of the said liquid crystalline resin used in this invention, It can manufacture according to the well-known polyester polycondensation method.

For example, in the production of the liquid crystalline resin, the following production method is preferably exemplified.
(1) A method for producing a liquid crystalline resin from p-acetoxybenzoic acid and 4,4′-diacetoxybiphenyl, diacetoxybenzene, terephthalic acid, and isophthalic acid by a deacetic acid condensation polymerization reaction.
(2) p-hydroxybenzoic acid and 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, isophthalic acid are reacted with acetic anhydride to acylate the phenolic hydroxyl group, and then the liquid crystalline resin is subjected to deacetic acid polycondensation reaction. How to manufacture.
(3) A method for producing a liquid crystalline resin from a phenyl ester of p-hydroxybenzoic acid and 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and diphenyl ester of isophthalic acid by a dephenol polycondensation reaction.
(4) A predetermined amount of diphenyl carbonate is reacted with p-hydroxybenzoic acid and aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid to form a diphenyl ester, and then aromatics such as 4,4'-dihydroxybiphenyl and hydroquinone. A method for producing a liquid crystalline resin by adding a group dihydroxy compound and dephenol polycondensation reaction.

  In particular, p-hydroxybenzoic acid and 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid are reacted with acetic anhydride to acylate the phenolic hydroxyl group, and then the liquid crystalline resin is removed by deacetic acid polycondensation reaction. The manufacturing method is preferred. Furthermore, the total amount of 4,4′-dihydroxybiphenyl and hydroquinone used and the total amount of terephthalic acid and isophthalic acid used are substantially equimolar. The amount of acetic anhydride used is preferably 1.10 equivalents or less, more preferably 1.05 equivalents or less, of the total of the phenolic hydroxyl groups of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl and hydroquinone. Preferably, the lower limit is 1.0 equivalent or more.

  When the liquid crystalline resin of the present invention is produced by a deacetic acid polycondensation reaction, a melt polymerization method is preferred in which the polycondensation reaction is completed by reacting under reduced pressure at a temperature at which the liquid crystalline resin melts. For example, in a reaction vessel having a predetermined amount of p-hydroxybenzoic acid and 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, isophthalic acid, acetic anhydride, a stirring blade, a distillation pipe, and a discharge port at the bottom. There is a method in which the reaction is completed by charging, heating while stirring in a nitrogen gas atmosphere to acetylate the hydroxyl group, then raising the temperature to the melting temperature of the liquid crystalline resin, and performing polycondensation under reduced pressure. The conditions for the acetylation are usually 130 to 300 ° C., preferably 135 to 200 ° C., usually 1 to 6 hours, preferably 140 to 180 ° C. for 2 to 4 hours. The polycondensation temperature is a melting temperature of the liquid crystalline resin, for example, in the range of 250 to 350 ° C., and preferably a melting point of the liquid crystalline resin + 10 ° C. or higher. The degree of vacuum during polycondensation is usually 0.1 mmHg (13.3 Pa) to 20 mmHg (2660 Pa), preferably 10 mmHg (1330 Pa) or less, more preferably 5 mmHg (665 Pa) or less. In addition, although acetylation and polycondensation may be performed continuously in the same reaction vessel, acetylation and polycondensation may be performed in different reaction vessels.

The obtained polymer is pressurized in the reaction vessel to, for example, approximately 1.0 kg / cm ² (0.1 MPa) at a temperature at which it melts, and discharged in a strand form from the discharge port provided in the lower portion of the reaction vessel. Can do. The melt polymerization method is an advantageous method for producing a uniform polymer, and an excellent polymer with less gas generation can be obtained, which is preferable.

  When the liquid crystalline resin of the present invention is produced, the polycondensation reaction can be completed by a solid phase polymerization method. For example, the polymer or oligomer of the liquid crystalline resin of the present invention is pulverized with a pulverizer, and the melting point of the liquid crystalline resin is -5 ° C to -50 ° C (for example, 200 to 300 ° C) under a nitrogen stream or under reduced pressure. A method of heating in the range for 1 to 50 hours, polycondensing to a desired degree of polymerization, and completing the reaction can be mentioned. Solid phase polymerization is an advantageous method for producing polymers with a high degree of polymerization.

  The polycondensation reaction of the liquid crystalline resin proceeds even without a catalyst, but metal compounds such as stannous acetate, tetrabutyl titanate, potassium acetate and sodium acetate, antimony trioxide, and magnesium metal can also be used.

  The liquid crystalline resin of the present invention preferably has a number average molecular weight of 3,000 to 25,000, more preferably 5,000 to 20,000, and more preferably 8,000 to 18,000. .

  The number average molecular weight can be measured by GPC-LS (gel permeation chromatography-light scattering) method using a solvent in which the liquid crystalline resin is soluble.

  Moreover, 1-200 Pa.s is preferable, as for the melt viscosity of the liquid crystalline resin in this invention, 10-200 Pa.s is more preferable, Furthermore, 10-100 Pa.s is especially preferable.

  The melt viscosity is a value measured by a Koka flow tester under the condition of the melting point of the liquid crystalline resin + 10 ° C. and the shear rate of 1,000 / s.

The liquid crystalline resin of the present invention preferably has a ΔS (melting entropy) defined by Formula 1 of 0.9 × 10 ⁻³ J / g · K or less, and such a liquid crystalline resin is non-oriented. Even in a close state, it exhibits a particularly high mechanical strength.
ΔS (J / g · K) = ΔHm (J / g) / [Tm (° C.) + 273] − [1]

  Here, Tm is an endothermic peak temperature (Tm1) observed when a polymer having been polymerized is measured at 20 ° C / min from room temperature in differential calorimetry, and then at a temperature of Tm1 + 20 ° C. This is the endothermic peak temperature (Tm2) observed when the sample is held for 5 minutes, then cooled to room temperature under a temperature drop condition of 20 ° C./min, and measured again under a temperature rise condition of 20 ° C./min. ΔHm is the endotherm The heat of fusion (ΔHm2) calculated from the peak area.

ΔS is preferably 0.9 × 10 ⁻³ J / g · K or less, more preferably 0.7 × 10 ⁻³ J / g · K or less, and even more preferably 0.5 × 10 10. ^-3 J / g · K or less.

  However, since ΔS is not 0 and does not become a negative value, it takes a real number range larger than 0.

  Although melting | fusing point (Tm2) of the liquid crystalline resin of this invention is not specifically limited, 280-360 degreeC is preferable and 300-340 degreeC is more preferable.

  In the measurement of ΔHm and Tm, when no peak is obtained, ΔS cannot be calculated, and it is interpreted that a liquid crystalline resin in which such a peak is not observed does not satisfy the above preferable range.

  When ΔS is in such a range, the molecular chain of the liquid crystalline resin exists in a very ordered state in the molten state and the solid state, and the molecular chain is not affected by high orientation during spinning. It is considered that a fiber having particularly excellent strength and dimensional stability can be obtained because of the small disturbance of the arrangement.

  The liquid crystalline resin of the present invention can be blended with a fine filler that does not interfere with fiber formation.

  The fine filler is preferably a granular filler having an average particle diameter of 10 μm or less or a fibrous filler having an average fiber length of 15 μm or less, an average fiber diameter of 3 μm or less, and a granular filler having an average particle diameter of 5 μm or less. More preferred.

  Examples of the fibrous filler include whisker fillers such as potassium titanate whisker, barium titanate whisker, aluminum borate whisker, and silicon nitride whisker.

  Examples of the particulate filler include mica, talc, kaolin, silica, glass beads, glass flakes, glass microballoons, clay, molybdenum disulfide, wollastonite, titanium oxide, zinc oxide, calcium polyphosphate and graphite. In particular, talc, silica, clay and the like are preferable, and silica is most preferable.

  As the silica, true spherical silica is preferable, and the average particle diameter is preferably 0.2 to 0.6 μm, and more preferably 0.3 to 0.5 μm. The number average particle diameter can be measured with a laser diffraction particle size distribution analyzer.

  The above-mentioned filler used in the present invention can be used by treating the surface thereof with a known coupling agent (for example, a silane coupling agent, a titanate coupling agent, etc.) or other surface treatment agents. .

  In addition, the liquid crystalline resin of the present invention includes an antioxidant and a heat stabilizer (for example, hindered phenol, hydroquinone, phosphites and substituted products thereof), an ultraviolet absorber (for example, resorcinol, salicylate), phosphorous acid. Colorants including salts, anti-coloring agents such as hypophosphite, lubricants and mold release agents (such as montanic acid and its metal salts, its esters, their half esters, stearyl alcohol, stearamide and polyethylene wax), dyes and pigments Carbon black, crystal nucleating agent, plasticizer, flame retardant (bromine flame retardant, phosphorus flame retardant, red phosphorus, silicone flame retardant, etc.), flame retardant aid, antistatic agent, etc. The conventional additive and a polymer other than the thermoplastic resin can be blended to further impart predetermined characteristics.

  The method of blending these additives is preferably by melt kneading, and known methods can be used for melt kneading. For example, using a Banbury mixer, rubber roll machine, kneader, single-screw or twin-screw extruder, etc., it can be melt kneaded at a temperature of 180 to 350 ° C., more preferably 250 to 320 ° C. to obtain a liquid crystalline resin composition. . In that case, 1) a batch kneading method with a liquid crystalline resin, an optional filler and other additives, and 2) a liquid crystalline resin composition containing a high concentration of other additives in the liquid crystalline resin ( Master pellet), and then adding other thermoplastic resins, fillers and other additives to the specified concentration (master pellet method), 3) one of liquid crystalline resin and other additives Any method may be used, such as a split addition method in which the part is kneaded once and then the remaining filler and other additives are added.

  It does not specifically limit as a method to manufacture the liquid crystalline resin fiber which comprises the nonwoven fabric of this invention, A well-known melt spinning method can be used.

  The fineness of the liquid crystalline resin fiber is not particularly limited as long as it can produce a non-woven fabric, but is preferably 5d (denier) or less for single fiber, and in papermaking, it is preferably 3d or less, more preferably 2d or less in terms of texture and density. More preferred.

  With respect to the single fiber strength, 1 to 20 cN / dtex is preferable, 4 to 15 cN / dtex is more preferable, and 9 to 14 cN / dtex is most preferable from the viewpoint of cutability during processing of the nonwoven fabric.

  When manufacturing non-woven fabrics, liquid crystalline resin fibers produced by melt spinning are made into long fibers or single fiber cut fibers, a web is formed on dry paper and wet paper, then needle punches and water jets, water streams (spun laces). The method of forming the web by spunbonding or melt-blowing can be used, and the method of entanglement of the short fiber cut fibers by the needle punch is preferable.

  At the time of forming the fiber web, it is also possible to perform a charging process such as corona discharge or a fiber opening process using compressed air.

  When manufacturing a wet nonwoven fabric, it is preferable to use a cut fiber having a single fiber length of 3d or less and a fiber length of 2 to 10 mm. If the cut length is too long, the pulp-like material is easily entangled and water dispersibility is lowered. If the cut length is too short, the entanglement between the pulp-like materials is small and sufficient strength cannot be obtained when processed into paper. You may add a dispersing agent to the obtained pulp-like thing.

  In terms of improving sheet formability, adhesion between fibers, flexibility and the like, it is preferable to use a binder component such as a binder fiber or a resinous binder in combination, and it is 1% by weight or more and 95% by weight based on the total amount of the nonwoven fabric. It is preferable to blend in an amount of not more than wt%, particularly not less than 2 wt% and not more than 50 wt%. Although the component which can be mix | blended is not specifically limited, For example, a polyethylene terephthalate, a polyparaoxybenzoic acid, a polyethyleneamide, a polyphenylene ketone, a polyimide, a polybiphenylimide, a phenol fiber, a polycarbonate fiber etc. are mentioned. An amine / epoxide binder can be preferably used because of its excellent heat resistance and electrical insulation.

  In the case of producing a dry nonwoven fabric, in the case of the liquid crystalline resin fiber of the present invention, a single fiber of 1 to 5d and a fiber length of about 15 to 110 mm are preferable. The presence or absence of crimp on the fiber is not particularly limited, but a fiber having a crimp is more preferable.

  When the liquid crystalline resin is in a molten state and the short fiber cut fiber is produced, it is preferable to control the alignment state of the liquid crystalline resin.

  In general, molten liquid crystal forming polyester has a very high crystallization speed and is easy to be oriented. Therefore, sufficient orientation crystallization occurs even when spinning at a relatively low speed and low draft. It is manufactured without a stretching process.

  Therefore, in the known liquid crystal melt spinning method, it is known that the draft limit is low, and the shear orientation when discharging from the nozzle determines the degree of orientation of the fiber. It is a well-known fact that is mainly oriented.

  Therefore, the center part (core part) in the fiber thickness direction is low-oriented, and the surface layer part (skin part) expresses the strength and dimensional stability of the fiber. When entanglement treatment such as water jet treatment or needle punch treatment is performed, the entanglement density is increased by fibrillation. However, the strength and dimensional stability are inevitably lowered by fibrillation of the skin layer.

  Therefore, in the present application, as a result of studying to eliminate the uneven distribution of the alignment strength in the thickness direction of the liquid crystalline resin fiber, it has been found that the uneven distribution can be eliminated by using a liquid crystalline resin having a specific composition. However, it can be brought closer to a more preferable form by the melt spinning method.

  That is, when the liquid crystalline resin is melt-spun, the resin temperature is set to the melting point of the liquid crystalline resin + 20 ° C. or higher, and the ambient temperature up to 30 cm just below the base is kept in the temperature range of melting point−50 to melting point−10 ° C. In the melt spinning, the high orientation of only the skin layer can be suppressed.

  The resin temperature is more preferably the melting point of the liquid crystalline resin + 25 ° C. or more, and the upper limit is + 40 ° C.

  The atmospheric temperature is more preferably a melting point of −35 ° C. to a melting point of −15 ° C.

  The spinning speed can be 500 to 6000 m / min, but high speed spinning of 1000 to 5000 m / min is preferable.

  The nozzle preferably has a small diameter, specifically 0.3 mmφ or less, more preferably 0.15 mmφ or less, in order to reduce the uneven distribution of shear orientation in the thickness direction.

  The nozzle shape may be a straight hole, or may be partially or entirely tapered, and a tapered nozzle is preferable from the viewpoint of spinning stability and orientation control.

  Spinning while applying compression with a taper nozzle is preferable because uneven orientation in the fiber thickness direction can be reduced.

  The taper length is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. The taper angle is preferably 1-30 °, more preferably 5-15 °.

  The melt-spun liquid crystalline resin fibers are less uneven in the orientation in the thickness direction and maintain a high atmospheric temperature until solidification, so that the skin layer has a loose molecular orientation equivalent to the core layer. Array part).

  The liquid crystalline resin fibers thus obtained have less loss of strength and dimensional stability when fibrillated than conventional liquid crystalline resin fibers, but more preferably the glass transition temperature of the liquid crystalline resin is not lower than the melting point-100 ° C. or lower. It is preferable to perform stretching less than 1.01 times at a temperature of.

  The glass transition temperature of the liquid crystalline resin is detected as a peak temperature of tan δ by a dynamic viscoelasticity measuring device (DMS) and is observed at about 50 to 250 ° C., and is preferably 100 ° C. or higher in the present invention, more preferably 110 ° C. or higher.

  The stretching temperature is more preferably not less than the glass transition temperature of the liquid crystalline resin and not more than the glass transition temperature of the liquid crystalline resin + 50 ° C. If the stretching temperature is too high, the orientation is relaxed, and if it is too low, a physical defect occurs depending on the tension, but this is not preferable.

  The draw ratio is more preferably less than 1.005. If the draw ratio is 1.01 or more, the residual strain becomes excessively large and the amount of thermal deformation becomes undesirably large.

  When heat treatment is performed to eliminate this residual strain, problems such as surface roughness occur, which is not preferable.

    By this very small amount of stretching, the remaining non-arranged portions are stretched by the force of the skin layer, the core layer, and the like, and liquid crystalline resin fibers that are highly oriented as a whole and have no uneven distribution are obtained. Further, this fiber has little residual strain and is excellent in dimensional stability.

  As a method of stretching, without winding up the spun liquid crystalline resin fiber, it is led to a tenter roll, and a method of stretching between rolls when the fiber temperature becomes the temperature in the cooling process, or after winding up once There is a method in which the film is heated and stretched by a stretching machine, but crystallization is promoted by re-heating, and therefore stretching while adjusting the temperature in the cooling step is preferable.

  Regarding the uneven distribution of the orientation, the ratio (Is / Ic) of the orientation degree (Is) of the fiber surface to the orientation degree (Ic) of the fiber center part is preferably less than 1.2, more preferably less than 1.1, More preferably, it is less than 1.05.

  The fiber orientation degree ratio (Is / Ic) is, for example, 2θ = 19 to 100 nm from the surface layer of the cross section obtained by cutting the fiber center with a microtome in the length direction using a RINT 2500 micro part X-ray diffractometer manufactured by Rigaku. The diffraction peak intensity in the direction parallel to the fiber length direction of the liquid crystalline resin observed at 20 ° is assumed to be Is, and the diffraction in the direction parallel to the fiber length direction of the liquid crystalline resin similarly observed at 100 nm in the central portion is performed. The peak intensity can be calculated as Ic.

  Thus, by controlling the orientation distribution in the thickness direction of the liquid crystalline resin fiber, the dimensional stability close to the theoretical strength of the liquid crystalline resin fiber and the theoretical linear expansion coefficient of the liquid crystalline resin is exhibited.

  By this method, since the liquid crystalline resin fibers are highly oriented without being unevenly distributed in all parts of the skin core, the conventional fibrillation phenomenon in which only the skin layer is fibrillated and the disappearance of the skin layer that is the strength development site associated therewith. It is difficult to cause a decrease in the single fiber strength due to the non-woven fabric, and when it is made into a non-woven fabric, it exhibits very high dimensional stability and strength, and even a liquid crystalline resin non-woven fabric without a binder has a very low compressive strain. A nonwoven fabric with high dimensional stability against external force and temperature change can be obtained.

  In any step after the melt spinning and after the web formation, the liquid crystalline fibers can be fibrillated using a homogenizer or the like to improve the entanglement efficiency.

  Since the liquid crystalline resin fiber of the present invention is less unevenly distributed between the skin layer and the core layer, the fibril is rarely peeled off from the fiber due to the treatment, and the fibril is hardly opened to produce cotton-like debris.

  The obtained fiber web can be made into a non-woven fabric by impregnating a binder or integrally bonded by heat treatment, and as the heat treatment, the whole or a part of the web can be integrally bonded by heat pressing or calendar treatment as appropriate. It is.

  Even in a high-temperature treatment such as a hot press temperature of 150 to 300 ° C., the liquid crystalline resin fiber according to the present invention does not substantially melt, and since it has excellent thermal heat resistance, it has no elongation and has excellent mechanical properties. A heat resistant nonwoven fabric having properties and dimensional stability can be obtained.

  Although the nonwoven fabric and liquid crystalline resin fiber of the present invention also have sufficient strength and elastic modulus, the performance can be further improved by relaxation heat treatment or tension heat treatment.

  The heat treatment can be performed in an inert gas atmosphere such as nitrogen, an active gas atmosphere containing oxygen such as air, or under reduced pressure. The heat treatment atmosphere is preferably a low-humidity gas having a dew point of −40 ° C. or less. The heat treatment is preferably performed in a temperature pattern in which the temperature is gradually increased from the melting point of the core component minus 40 ° C. or lower to the melting point of the sheath component or lower. Furthermore, the processing time is several minutes to several tens of hours depending on the target performance.

  Supply of heat during heat treatment is a method using a medium such as a gas, a method using radiation by a heating plate, an infrared heater, etc., a method of making contact with a heating roller, a heating plate, etc., an internal heating method using high frequency, etc. Etc. can be used. Further, the heat treatment may be performed under tension or non-tension depending on the purpose, and the shape may be a crushed shape, a tow shape (for example, placed on a metal net or the like), or may be continuously processed between rollers.

  The tension heat treatment is preferably performed at a temperature of the melting point of the core component minus 60 ° C. or less and under a tension of 5 to 50% of the cutting strength, and this treatment further improves the elastic modulus.

  The nonwoven fabric using the liquid crystalline resin fiber obtained by the present invention has little drop of fibrils even when fibrillated, and there is no orientation unevenness, so there is little reduction in strength and dimensional stability, and even at high temperatures. Since it has excellent shape stability and a small amount of compressive deformation, it can be used in various fields by taking advantage of these characteristics.

  For example, it is widely used for industrial materials, etc., and especially excellent for bearing wear materials, packing materials, gasket materials, filters, abrasives, insulating paper, heat-resistant paper, speaker cones, wiping cloths, resin reinforcing materials, etc. Demonstrate performance.

  Especially, since the nonwoven fabric using the liquid crystalline resin fiber obtained by this invention is excellent also in electrical insulation, mechanical performance, and dimensional stability, it can exhibit the performance outstanding in a circuit base material, electrical insulation paper, etc.

  Hereinafter, although an example explains the present invention still in detail, the gist of the present invention is not limited only to the following example.

(Reference Example 1)
In a 5 L reaction vessel equipped with a stirring blade and a distilling tube, 870 g (6.300 mol) of p-hydroxybenzoic acid, 327 g of 4,4′-dihydroxybiphenyl (1.890 mol), 89 g of hydroquinone (0.810 mol) , 292 g (1.755 mol) of terephthalic acid, 157 g (0.945 mol) of isophthalic acid and 1367 g of acetic anhydride (1.03 equivalent of the total of phenolic hydroxyl groups) were added at 145 ° C. with stirring in a nitrogen gas atmosphere. After reacting for hours, the temperature was raised to 330 ° C. over 4 hours. Thereafter, the polymerization temperature was maintained at 330 ° C., the pressure was reduced to 1.0 mmHg (133 Pa) in 1.0 hour, the reaction was continued for 90 minutes, and the polycondensation was completed when the torque reached 10 kgcm. Next, the inside of the reaction vessel was pressurized to 1.0 kg / cm ² (0.1 MPa), the polymer was discharged to a strand-like material via a die having one circular discharge port having a diameter of 10 mm, and pelletized by a cutter.

  In this liquid crystalline resin (A-1), the p-oxybenzoate unit was 70 mol% based on the total of the p-oxybenzoate unit, the 4,4′-dioxybiphenyl unit, and the 1,4-dioxybenzene unit. , 4′-dioxybiphenyl units are 70 mol% based on the total of 4,4′-dioxybiphenyl units and 1,4-dioxybenzene units, and terephthalate units are based on the total of terephthalate units and isophthalate units. It consists of 65 mol%, Tm (melting point of liquid crystalline resin) is 314 ° C., glass transition temperature (Tg) is 120 ° C., number average molecular weight is 12,000, using Koka type flow tester, temperature is 324 ° C., shear The melt viscosity measured at a speed of 1,000 / s was 15 Pa · s, the temperature was 334 ° C., and the melt viscosity measured at a shear rate of 1,000 / s was 12 Pa · s. .

  Note that the melting point (Tm) is maintained for 5 minutes at a temperature of Tm1 + 20 ° C. after observing the endothermic peak temperature (Tm1) observed when the polymer is measured at room temperature from 20 ° C./min in differential calorimetry. Then, after cooling to room temperature under a temperature drop condition of 20 ° C./minute, the endothermic peak temperature (Tm 2) observed when measuring again under a temperature rise condition of 20 ° C./minute was used.

  The glass transition temperature was determined as Tg by measuring the peak temperature of tan δ with a dynamic viscoelasticity measuring device (DMS).

  The molecular weight was measured by GPC-LS (gel permeation chromatography-light scattering) method using pentafluorophenol, which is a solvent in which the liquid crystalline resin is soluble, and the number average molecular weight was determined.

(Reference Example 2)
In a 5 L reaction vessel equipped with a stirring blade and a distillation tube, 994 g (7.20 mol) of p-hydroxybenzoic acid, 338.7 g (1.80 mol) of 6-hydroxy-2-naphthoic acid, and 965 g of acetic anhydride (1.05 equivalents of total phenolic hydroxyl groups) was added and reacted at 145 ° C. for 2 hours with stirring under a nitrogen gas atmosphere, and then heated to 330 ° C. over 4 hours. Thereafter, the polymerization temperature was maintained at 330 ° C., the polymerization temperature was maintained at 330 ° C., nitrogen was pressurized to 0.1 MPa, and the mixture was heated and stirred for 20 minutes. Thereafter, the pressure was released, the pressure was reduced to 133 Pa in 1.0 hour, the reaction was continued for 120 minutes, and the polycondensation was completed when the torque reached 15 kgcm. Next, the inside of the reaction vessel was pressurized to 0.1 MPa, the polymer was discharged to a strand through a die having one circular discharge port having a diameter of 10 mm, and pelletized by a cutter.

  This liquid crystalline resin (A-2) has a p-oxybenzoate unit of 80 mol%, a 6-oxy-2-naphthalate unit of 20 mol%, a Tm (melting point of the liquid crystalline resin) of 320 ° C., and a glass transition. The temperature is 105 ° C., the number average molecular weight is 11,100, the melt viscosity is 22 Pa · s, the temperature is 340 ° C., and the shear rate is 1000 / s, measured using a Koka flow tester at a temperature of 330 ° C. and a shear rate of 1000 / s. The measured melt viscosity was 14 Pa · s.

(Reference Example 3)
In a 5 L reaction vessel equipped with a stirring blade and a distillation tube, p-hydroxybenzoic acid 932 g (6.75 mol), 4,4′-dihydroxybiphenyl 419 g (2.25 mol), terephthalic acid 280 g (1.69 mol) ), 93 g (0.56 mol) of isophthalic acid and 1286 g of acetic anhydride (1.12 equivalent of total phenolic hydroxyl groups) were reacted at 155 ° C. for 2 hours, and then heated to 350 ° C. over 4 hours. Thereafter, the polymerization temperature was maintained at 320 ° C., nitrogen was pressurized to 0.1 MPa, and the mixture was heated and stirred for 20 minutes. Thereafter, the pressure was released, the pressure was reduced to 133 Pa in 1.0 hour, and the reaction was further continued for 30 minutes. When the torque reached 15 kgcm, the polycondensation was completed. Next, the inside of the reaction vessel was pressurized to 0.1 MPa, the polymer was discharged to a strand through a die having one circular discharge port having a diameter of 10 mm, and pelletized by a cutter.

  In this liquid crystalline resin (A-3), the p-oxybenzoate unit is 75 mol% with respect to the total of the p-oxybenzoate unit and the 4,4′-dioxybiphenyl unit, and the 4,4′-dioxybiphenyl unit. 25 mol% with respect to the total of p-oxybenzoate units and 4,4′-dioxybiphenyl units, terephthalate units with 75 mol% with respect to the total of terephthalate units and isophthalate units, melting point 335 ° C., glass transition The temperature was 110 ° C., the number average molecular weight was 12,800, the melt viscosity was 23 Pa · s, the temperature was 355 ° C., and the shear rate was 1000 / s, measured using a Koka flow tester at a temperature of 345 ° C. and a shear rate of 1000 / s. The measured melt viscosity was 15 Pa · s.

Example 1
Liquid crystal resin (A-1) taper nozzle with taper length of 10 mm and taper angle of 10 ° when the resin temperature is the melting point + 26 ° C. (340 ° C.) and the ambient temperature just 30 cm below the base is the melting point −24 ° C. (290 ° C.) Using a nozzle diameter of 0.1 mmφ, melt spinning was performed at a spinning speed of 2000 m / min.

It is introduced into the stretching section so that the fiber surface temperature is 150 ° C. at the time of introduction through a roller, and stretched 1.0035 times while maintaining a 150 ° C. atmosphere between the rollers, and has a fineness of 2 dtex and a strength of 13.5 cN / dtex. A liquid crystalline resin fiber was obtained. The fiber was cut into a length of 5 mm, and the resulting fiber was wet-papered and entangled with a needle punch to create a web with a basis weight of 70 g / m ³ .

  A thermal calendar process was performed at 230 ° C. and a linear pressure of 30 kg / cm to prepare a nonwoven fabric. The nonwoven fabric obtained by coating the nonwoven fabric with an epoxy resin adhesive, drying, and hot-pressing two sheets was evaluated.

  The following (1) to (5) were evaluated.

(1) Change in fibril drop weight (%)
The web weight before and after the needle punch was measured, the web weight after the needle punch was subtracted from the web weight before the needle punch, and the value divided by the web weight before the needle punch was defined as the fibril drop weight change (%). The decrease in weight corresponded to the weight of fine fibrils clogged with the wash water filter.

(2) Strength retention before and after fibrillation (%)
The retention rate of the single fiber strength before and after the homogenizer treatment was measured, and the strength retention rate before and after the treatment was determined. The single fiber strength was measured using fibers cut to a length of 50 mm, and measured using Tensilon UCT-100 manufactured by Orientec in accordance with JIS L1013.

(3) Nonwoven fabric strength (Kg / mm)
The tensile strength of the nonwoven fabric was evaluated according to JIS-P8116.

(4) Dimensional stability (ppm / ° C)
According to IPC TM650, the surface linear expansion coefficient of the non-woven fabric was measured to determine dimensional stability.

(5) Uneven distribution of orientation Liquid crystal observed using a RINT2500 micro-part X-ray diffractometer manufactured by Rigaku, with the fiber center cut by a microtome in the length direction from the surface to 100 nm from the surface layer at 2θ = 19 to 20 ° Orientation degree, where Is is the diffraction peak intensity in the direction parallel to the fiber length direction of the crystalline resin, and Is is the diffraction peak intensity in the direction parallel to the fiber length direction of the liquid crystalline resin of 100 nm in the center portion. The ratio (Is / Ic) was calculated.

Example 2
The atmospheric temperature 30 cm directly below the base of Example 1 was changed to a melting point of −44 ° C. (290 ° C.), and melt spinning was carried out under the same conditions except for stretching and production of a nonwoven fabric. Evaluation was performed in the same manner as in Example 1.

Example 3
The atmospheric temperature of 30 cm directly under the base of Example 1 was changed to a melting point of −12 ° C. (290 ° C.), and melt spinning was performed under the same conditions except for stretching and production of a nonwoven fabric. Evaluation was performed in the same manner as in Example 1.

Comparative Example 1
Tapered taper nozzle (nozzle diameter 0) with a taper length of 10 mm and a taper angle of 10 ° when the liquid crystalline resin (A-2) has a melting point of + 26 ° C. (346 ° C.) and an ambient temperature of 30 cm directly below the base is a melting point of −24 ° C. (296 ° C.). .1 mmφ) and melt spinning at a spinning speed of 2000 m / min.

Introduced into the stretching section so that the fiber surface temperature is 135 ° C. when introduced through the roller, and stretched 1.0035 times while maintaining a 135 ° C. atmosphere between the rollers,
A liquid crystalline resin fiber having a fineness of 2 dtex and a strength of 13.5 cN / dtex was obtained. The fiber was cut into a length of 5 mm, and the resulting fiber was wet-papered and entangled with a needle punch to create a web with a basis weight of 70 g / m ³ .

A thermal calendar process was performed at 230 ° C. and a linear pressure of 30 kg / cm to prepare a nonwoven fabric.
The nonwoven fabric obtained by coating the nonwoven fabric with an epoxy resin adhesive, drying, and hot-pressing two sheets was evaluated.

  Evaluation was performed in the same manner as in Example 1.

Comparative Example 2
The atmospheric temperature of 30 cm directly under the base of Comparative Example 1 was changed to 23 ° C. (room temperature), and melt spinning was performed under the same conditions except for stretching and production of a nonwoven fabric. Evaluation was performed in the same manner as in Example 1.

Comparative Example 3
Only the draw ratio of Comparative Example 1 was changed to 1.015, and melt spinning was carried out under the same conditions except that the draw and the nonwoven fabric were produced. Evaluation was performed in the same manner as in Example 1.

Comparative Example 4
Only the melt spinning temperature in Comparative Example 1 was changed to the melting point + 15 ° C. (335 ° C.), and melt spinning was performed under the same conditions except that the drawing and the nonwoven fabric were produced. Evaluation was performed in the same manner as in Example 1.

Comparative Example 5
Tapered taper nozzle (nozzle diameter 0) having a taper length of 10 mm and a taper angle of 10 ° when the liquid crystalline resin (A-3) has a melting point of + 26 ° C. (361 ° C.) and an ambient temperature of 30 cm directly below the base is a melting point of −24 ° C. (311 ° C.). .1 mmφ) and melt spinning at a spinning speed of 2000 m / min.

Introducing into the stretching section so that the fiber surface temperature is 140 ° C. at the time of introduction through a roller, stretching 1.0035 times while maintaining a 140 ° C. atmosphere between the rollers,
A liquid crystalline resin fiber having a fineness of 2 dtex and a strength of 13.5 cN / dtex was obtained. The fiber was cut into a length of 5 mm, and the resulting fiber was wet-papered and entangled with a needle punch to create a web with a basis weight of 70 g / m ³ .

A thermal calendar process was performed at 230 ° C. and a linear pressure of 30 kg / cm to prepare a nonwoven fabric.
The nonwoven fabric obtained by coating the nonwoven fabric with an epoxy resin adhesive, drying, and hot-pressing two sheets was evaluated.
Evaluation was performed in the same manner as in Example 1.

  As is clear from Table 1, the nonwoven fabric using the liquid crystalline resin of the present invention is less uneven in the fiber thickness direction than the nonwoven fabric using the liquid crystalline resin of the comparative example. Since the fibrils are not easily dropped and the strength decrease before and after fibrillation is small, the strength and dimensional stability of the nonwoven fabric are also high.

  Moreover, the nonwoven fabric of the Example had a small amount of compressive deformation, and its dimensions were stable against physical external forces.

  As described above, the non-woven fabric using the liquid crystalline resin fiber of the present invention in which the alignment control is performed by a special spinning method or stretching method using the liquid crystalline resin of the present invention is a circuit board base material in which these characteristics are required. Useful for.

Claims (4)

It consists of the following structural units (I), (II), (III), (IV) and (V), and the structural unit (I) is based on the sum of the structural units (I), (II) and (III) 65 to 80 mol%, structural unit (II) is 60 to 75 mol% based on the sum of structural units (II) and (III), and structural unit (IV) is structural units (IV) and (V ) And 60 to 92 mol% of the total of the structural units (II) and (III), and the total of (IV) and (V) is a liquid crystal resin that is substantially equimolar.

The ratio (Is / Ic) of the orientation degree (Is) of the fiber surface of the liquid crystalline resin fiber constituting the nonwoven fabric to the orientation degree (Ic) of the fiber center is less than 1.2. Non-woven fabric. When melt spinning the liquid crystalline resin, spinning was performed in a state where the resin temperature was the melting point of the liquid crystalline resin + 20 ° C. or more, and the ambient temperature up to 30 cm just below the die was maintained in the temperature range of melting point−50 to melting point−10 ° C. After that, the liquid crystalline resin fiber obtained by stretching less than 1.005 times at a temperature not lower than the glass transition temperature of the liquid crystalline resin and not higher than -100 ° C. is cut into a length of 2 to 10 mm, and either wet papermaking or dry papermaking is used. A method for producing a nonwoven fabric in which a fiber web is formed using any of the above methods and a fibrillation / entanglement treatment is performed, followed by either a thermocompression treatment or a binder impregnation treatment. The liquid crystalline resin is composed of the following structural units (I), (II), (III), (IV) and (V), and the structural unit (I) is composed of the structural units (I), (II) and (III). The structural unit (II) is 60 to 75 mol% based on the total of the structural units (II) and (III), and the structural unit (IV) is the structural unit (IV ) And (V) is 60 to 92 mol%, and the total of structural units (II) and (III) and (IV) and (V) are substantially equimolar. The method for producing a nonwoven fabric according to claim 3.