JPH08192421A - Liquid crystal polymer pellets and production thereof - Google Patents

Abstract

PURPOSE: To produce pellets excellent in properties by forming a liquid crystal polymer into a strip like article in a molten state and cooling and solidifying the strip like article to efficiently cut the same. CONSTITUTION: A liquid crystal polymer is formed into a strip like article in a molten state and this strip like article is cooled and solidified to be cut to produce pellets 11. At this time, the strip like article of which the cut cross section has a diameter of 1-6mm at the time of solidification is cut in the direction right-angled to the orientation direction of the polymer molecule in the presence of cooling water 10 when it is cooled to the temp. range from the m.p. of the liquid crystal polymer to the m.p. +80 deg.C to produce pellets wherein length is 1.0-5.0mm, a cut cross section has an oval shape with a long diameter of 2.0-8.0mm and a long diameter/short diameter length of 1.0-4.0, bulk specific gravity is 0.5-0.8kg/l and an angle of repose is 35-45 deg..

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a liquid crystalline polymer pellet and a method for producing the same. More specifically, the present invention relates to a method for producing a pellet having excellent properties by cooling and solidifying a liquid crystalline polymer as a string-like material from a molten state and efficiently cutting this.

[0002]

2. Description of the Related Art In recent years, since it can be melt-molded, it can be molded in the same manner as ordinary plastics and has liquid crystal properties such as high elasticity, high strength, low molding shrinkage, chemical resistance and self-extinguishing property. Polymers are receiving attention.

Conventionally, in the production of liquid crystalline polymers, a polymer in a molten state, which is usually obtained by a polycondensation reaction, is taken out of the reactor as a string-like substance, brought into contact with water at room temperature, completely cooled and solidified, and then taken out. The method of cutting into pellets with a cutter has been adopted.

[0004]

However, since the liquid crystal polymer generally has a low thermal conductivity, it requires a long cooling water tank for a long time to completely solidify the polymer, resulting in a large equipment volume. was there. In addition, since the completely solidified liquid crystalline polymer string has a tough and tough fibrous material, the cut surface is not uniform even if cut, leaving short threads (tails or whiskers) on the pellets. , Powdery substances are likely to be generated during cutting. If such short fibers or powdery substances are generated, the bulk density of the obtained pellets is lowered, and the pellet properties are also deteriorated such that the angle of repose is increased, and subsequent transportation and feed for drying and storage, glass, etc. In order to impregnate fibers such as fibers, pellet handling is poor at the time of feeding to a melt extruder or pellet feeding to a molding machine when molding pellets,
In addition, the processability such as trouble is not good. On the other hand, if you try to cut a string-like object that is insufficiently cooled in order to suppress the generation of powdery matter or short yarns as described above, not only is it difficult to cut, but the cut surface becomes irregular, and There was a problem that the molten core part of the string-like material became a pellet protruding in the length direction of the string-like material, and further uncut pellets in which the pellets were connected in a string were formed, which also deteriorates the pellet property. .

[0005]

Means for Solving the Problems As a result of diligent studies on the above-mentioned problems in producing pellets of a liquid crystalline polymer, the present inventors have found that the core of the string-like substance taken out from the polymer in a molten state is specific. It has been found that it is extremely effective to cut the string-like material in the presence of cooling water when the string-like object is cooled to reach the temperature range, and the present invention has been completed.

That is, the present invention is a pellet made of a liquid crystalline polymer capable of forming an anisotropic molten phase, and the pellet length cut in the direction perpendicular to the orientation direction of the polymer molecules is 1.0 to 5.0 mm. The cut cross section is elliptical, the major axis is 2.0 to 8.0 mm, the ratio of the major axis to the minor axis (major axis / minor axis) is 1.0 to 4.0, and the pellet is And a liquid crystal polymer pellet having a bulk specific gravity of 0.5 to 0.8 kg / liter and an angle of repose of 35 to 45 °. Further, according to the present invention, when a liquid crystalline polymer capable of forming an anisotropic molten phase is cooled and solidified from a molten state as a string-like material and cut into pellets by cutting the string-like material, the cut cross-sectional diameter when solidified is 1 ~ 6 mm
When the core of the cord is cooled within a temperature range of the melting point of the liquid crystalline polymer to 80 ° C. higher than the melting point, the cord is cut in the presence of cooling water. Item 1. A method for producing a liquid crystalline polymer pellet according to item 1.

The liquid crystalline polymer capable of forming an anisotropic molten phase to which the present invention is applied refers to a melt-processable polymer having a property capable of forming an optically anisotropic molten phase, and has a shear stress in a molten state. Upon receiving it, the polymer molecular chains have a regular parallel arrangement. Such polymer molecules are generally elongated, flattened, fairly stiff along the long axis of the molecule, and have multiple chain extension bonds, usually in either coaxial or parallel relationship. Is. The properties of the anisotropic molten phase can be confirmed by a conventional polarization inspection method using a crossed polarizer.
More specifically, the confirmation of the anisotropic molten phase can be performed by using a Leitz polarization microscope and observing the molten sample placed on the Leitz hot stage under a nitrogen atmosphere at a magnification of 40 times. The liquid crystalline polymer to which the present invention can be applied normally transmits polarized light and exhibits optical anisotropy when examined between orthogonal polarizers, even in a melt stationary state.

The liquid crystal polymer as described above is not particularly limited, but usually an aromatic polyester or an aromatic polyesteramide is preferable, and an aromatic polyester or a polyester partially containing the aromatic polyesteramide in the same molecular chain is also included. In range.

The liquid crystalline polymer to which the present invention can be applied is particularly preferably an aromatic polyester having as a constituent component at least one compound selected from the group consisting of aromatic hydroxycarboxylic acid, aromatic hydroxylamine and aromatic diamine. , An aromatic polyester amide.
More specifically, (1) a polyester mainly composed of one or more aromatic hydroxycarboxylic acids and their derivatives; (2) mainly (a) one or two aromatic hydroxycarboxylic acids and their derivatives. And above,
(b) one or more aromatic dicarboxylic acids, alicyclic dicarboxylic acids and their derivatives, and (c) at least one or two aromatic diols, alicyclic diols, aliphatic diols and their derivatives And (3) mainly (a) one or more aromatic hydroxycarboxylic acids and their derivatives, and (b) one or two aromatic hydroxyamines, aromatic diamines and their derivatives. A polyester amide comprising one or more kinds and (c) one or more kinds of an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid and a derivative thereof; (4) mainly
(a) 1 of aromatic hydroxycarboxylic acid and its derivative
One or more, and (b) one or more of an aromatic hydroxyamine, an aromatic diamine and a derivative thereof, and (c) one of an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid and a derivative thereof, or Examples thereof include polyesteramides composed of two or more kinds and (d) at least one kind or two or more kinds of aromatic diol, alicyclic diol, aliphatic diol and derivatives thereof. Further, if necessary, a molecular weight modifier may be used in combination with the above constituent components.

Preferable examples of specific compounds constituting the liquid crystal polymer to which the present invention can be applied include aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and 2,6- Dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 4,4 '
-Dihydroxybiphenyl, hydroquinone, resorcin, aromatic diols such as compounds represented by the following general formula [1] and general formula [2], terephthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 2,6 -Aromatic dicarboxylic acids such as naphthalenedicarboxylic acid and compounds represented by the following general formula [3], and aromatic amines such as p-aminophenol and p-phenylenediamine.

[0011]

Embedded image

A particularly preferred liquid crystalline polymer to which the present invention is applied is an aromatic polyester containing p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid as constituent units.

In the method for producing liquid crystalline polymer pellets of the present invention, the liquid crystalline polymer is cooled and solidified from a molten state as a string. The string-like material can be obtained, for example, by pressurizing and extruding the liquid crystalline polymer that has completed polycondensation from a nozzle provided at the bottom of the polymerization vessel. As a result, the liquid crystal polymer molecules are aligned in the length direction of the string-like material. The size of the string-like material is such that the cross-sectional diameter after solidification is usually in the range of 1 to 6 mm, preferably in the range of 3 to 5 mm.

In the method for producing the liquid crystalline polymer pellets of the present invention, the liquid crystalline polymer string in the molten state is cooled with cooling water, and the core temperature of the string is equal to or higher than the melting point of the liquid crystalline polymer. Cooling water when cooled to a temperature within a range of 80 ° C. or higher above the melting point, and more preferably when cooled to a temperature of 50 ° C. above the melting point and 60 ° C. above the melting point. Disconnect in the presence of. The melting point of the liquid crystalline polymer varies depending on the monomer composition of the polymer, but is usually 260 to
It is in the range of 360 ° C., and the temperature of the molten polymer when melt-extruded from a die or a nozzle to form a string-like material is higher than the melting point by about 5 ° C. or more, and usually in the temperature range of 300 to 400 ° C. The string-like material in the molten state is cooled by the cooling water as described above, but since it is solidified from the surface of the string-like object, the outer layer of the string-like object is formed at the time when the temperature of the core reaches the above range. The part is neither in a state in which solidification has proceeded extremely, nor in a molten state in which the cut surface is easily fluidized and the cut surface is deformed. Therefore, by cutting at the time when the temperature of the core of the string-like object at the time of cutting is cooled to the range of the temperature, the cutting is not difficult and the energy required for cutting is not excessive, and therefore the cutting blade is worn out. Can also be suppressed. When the temperature of the core is higher than the melting point by 80 ° C., the whole pellets obtained are not solidified so much, the pellet shape becomes poor when cut, the repose angle increases, and the bulk specific gravity decreases. . In the method for producing pellets of the present invention, the core of the string-like material at the time of cutting is still in a molten state, but since the cutting is performed in the cooling water in the present invention, the cooling of the core is also performed immediately after cutting from the cut surface. Begins. As a result, it is possible to prevent the molten core portion from becoming a pellet that protrudes after cutting, or prevent the pellets from sticking to the cutting blade due to the outer layer portion or the molten core portion. The generation of cut pellets can be almost suppressed.

In the present invention, the string-like material is cut when the core is cooled to the temperature range. If the temperature of the cooling water used for cooling is too low, the surface layer of the string-like material is rapidly cooled and solidification proceeds too much, and since the liquid crystalline polymer has a low thermal conductivity, the temperature difference between the core and the surface layer becomes large, and the protruding portion And pellets having a mustache are generated. On the other hand, if the cooling water temperature is too high, the outer layer portion of the string-like material is insufficiently solidified, so that it becomes difficult to cut the string-like material, and uncut pellets in the form of beads are likely to occur. Therefore, the cooling water temperature is usually in the range of 30 to 90 ° C., although the melting point of the target liquid crystalline polymer also varies.

In the present invention, the molten string-like material is cut after being cooled by the cooling water as described above, and the cooling time by the cooling water is the temperature at the start of cooling of the liquid crystalline polymer string-like object. , Melting point, diameter after solidification of the string-like material, cooling water temperature, etc., and may be appropriately selected so as to satisfy the requirements of the present invention. Although it is usually difficult to measure the temperature of the core during cutting, the thermal conductivity λ, the specific heat Cp, the density ρ, the resin temperature T, the cooling water temperature, and the contact time with the cooling water when the target liquid crystalline polymer is melted. Based on t and the diameter of the string-like object at the start of cooling, it can be easily calculated by the following basic equation [1] (r is a distance from the center of the string-like object) of unsteady heat conduction.

[0017]

[Equation 1]

Therefore, by setting some of these conditions, the setting range of the remaining conditions can be calculated. For example, the temperature of the string-like object at the start of cooling is 300 to
The temperature is 400 ° C., the cooling water temperature is 30 to 90 ° C., and the cooling time by the cooling water until cutting is 0.3 to 3 seconds, particularly preferably 0.7 to 2.0 seconds.

Since the cutting is performed in a direction perpendicular to the length direction of the string-like material, even if some disturbance occurs due to lateral run-out of the string-like material during cutting, the direction is almost perpendicular to the orientation direction of the polymer molecules. The pellets are cut into pieces. The cutting length (pellet length) in the molecular orientation direction is preferably 1 to 5
It is in the range of mm and can be adjusted by the speed of the rotary blade. Within this range, processability such as pellet feeding is also good. In addition, the cross section of the string-like object becomes elliptical due to the action of a take-up device and a cutter which will be described later at the time of cutting. The elliptical shape in the present invention includes a shape that is slightly deformed from an accurate ellipse, a shape that is close to a rectangle, and the like, because a string-shaped material whose surface is solidified and whose inside is molten is cut. The major axis is 2.0 to 8.0 mm, preferably 2.0 to 5.0 mm, and the ratio of major axis to minor axis (major axis / minor axis) is 1.0 to 4.0.
Is. It should be noted that, in the case of a pellet whose cut cross section is not exactly elliptical, the maximum width and the minimum width of the central portion of the cross section correspond to the major axis and minor axis of the ellipse, respectively. Further, when the ratio (major axis / minor axis) is 1.0, the cross section is circular, but the ellipse in the present invention also includes a circle in its definition. The pellets of the present invention thus obtained have excellent pellet properties not seen in the pellets conventionally obtained from liquid crystalline polymers, as a result of which the generation of uncut pellets and tails is almost suppressed. That is, the pellet has a bulk specific gravity of 0.5 to 0.8 kg / liter and an angle of repose of 35 to 45.
Each range is in the range of °, and the pellets are extremely excellent in handling.

The angle of repose in the present invention is an angle measured by a method called a tilt method. The tilting method is to insert a polymer pellet into a petri dish (inner diameter 70 mm, depth 12 mm) so as to correspond to about half of the internal volume and to perform the closest packing, close the lid of the petri dish, and close the cylindrical portion. Is placed on a horizontal surface, slowly rotated in the horizontal direction, and the inclination angle φ _r immediately before the internal pellet is broken by the rotation is measured. The measurement is performed 3 times and the average value is adopted.

The liquid crystalline polymer pellets of the present invention satisfy the above pellet properties even if they are produced by cutting as described above, but uncut pellets that may be slightly generated and mixed in By selecting and removing the pellets having tails with a sieve or the like, more excellent pellet properties can be obtained. The liquid crystalline polymer pellets of the present invention include those subjected to such a sorting treatment.

FIG. 1 is an example of a process diagram for explaining a pellet manufacturing method according to the present invention. In FIG. 1, 1 is the bottom (portion) of the polycondenser, 2 is a polymer extrusion die, 3 is a string-like material transfer / cooling water supply line, 4 is a string-like object, 5 is a string-like object transfer guide, and 6 is a string. Material cooling water spray, 7 string take-up roll, 8 string cutting rotary blade, 9 string cutting fixed blade, 10 cooling water, and 11 cut pellets. The liquid crystalline polymer produced in the polycondensator 1 is taken out as a molten string 4 from the extrusion die 2 provided at the bottom by a method such as pressurizing with an inert gas from the upper part of the polycondenser 1. . The taken out string-like object 4 descends into the string-like object guide 5 together with the cooling water 10 supplied from the line 3 and is cooled during that time. For cooling, cooling water from the spray 6 can also be used supplementarily. The string-like material that has descended from the guide 5 is cut in the cooling water 10 into the pellets 11 by the combination of the take-up roll 7, the cutting rotary blade 8 and the cutting fixed blade 9, and is transferred to the next process together with the cooling water 10.

FIG. 2 is a process diagram for explaining a conventional pellet manufacturing method. In the figure, 12 is a cooling water tank, 13 is a cutter, and 14 is a guide roll of a string-like object.

[0024]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

(Examples 1 to 4) A melting point of 280 ° C and a melt viscosity of 600 poises (300) containing p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid as constituent monomers.
¹ mm liquid crystal polyester with a shear rate of 1000 sec ^-1 ) at the bottom of the polycondenser is shown in Fig. 1 and has a diameter of 4 mm.
From the die (die) as a molten string at a resin temperature of 330 ° C., dropped into the horizontal part of the string guide 5 in FIG. It was flushed with the cooling water 10 to the inclined portion of the guide 5. And it cut | disconnected in water with the cutter provided in the same guide lower part. Cooling water temperature, contact time t with cooling water,
And the thermal conductivity λ (0.2 cal of the liquid crystalline polymer)
/ Cm ² · sec · ° C), specific heat (0.447cal / g)
· ° C.), determine the boundary conditions from density (1.28g / cm ^3), it was calculated the temperature of the strands of material core during cutting by the basic equations of the non-stationary heat conduction [1]. The properties of the obtained pellets are shown in Table 1. Further, the appearance of the obtained pellet having an elliptical cross-sectional shape was observed. As a result, pellets having a uniform cut surface and no generation of short yarns (tails) or powdery substances were obtained. Further, no uncut pellets that were linked were found.

[0026]

[Table 1]

(Comparative Example 1) In the same manner as in Example 1, the cord-like material of liquid crystalline polyester was taken out and cooled and cut by the equipment shown in FIG. The string-like material extruded from the die is 1
It is dropped into a warm water tank 12 at 45 ° C via an air layer of 0 cm, contacted with a freely rotating guide roll 14 and fed horizontally, and then contacted with a second guide roll 14 5 m away, and then fed upward, and a cutter. Cut at 13 and length 3.0
mm pellets. When the contact time with the cooling water was set to less than 4 seconds, the string-like material could not be cut or the cut pellets adhered to the blade of the cutter, etc., and the continuous operation of the cutter was significantly hindered. If the contact time is 4 seconds or more, the cross section of the cut pellet has a lot of tails (whiskers), the bulk specific gravity of the pellet is 0.55 kg / liter, the angle of repose is 45 °, and the pellet having poor flowability and the like is obtained. It was

[0028]

The liquid crystal polymer pellet manufacturing method of the present invention makes it possible to shorten the pellet manufacturing process and relatively reduce the wear of the cutter. Further, the obtained pellets of the present invention have less short yarns and powdery substances,
An object with a protruding core or an irregular cut surface,
Furthermore, there are few uncut pellets. Therefore, the bulk specific gravity is relatively large, and the angle of repose is also relatively small, so that it is excellent in processability such that troubles on the pellet feeding during the drying / storing step and during molding are less likely to occur.

[Brief description of drawings]

FIG. 1 is an example of a process diagram illustrating a pellet manufacturing method according to the present invention.

FIG. 2 is a process diagram illustrating a conventional pellet manufacturing method.

[Explanation of symbols]

 1 Bottom of polycondenser (part) 2 Polymer extrusion die 3 String-shaped material transfer / cooling water supply line 4 String-shaped material 5 String-shaped material transfer guide 6 String-shaped cooling water spray 7 String-shaped material take-up roll 8 String-shaped material Cutting rotary blade 9 String cutting fixed blade 10 Cooling water 11 Pellet 12 Cooling water tank 13 Cutter 14 Guide roll for string

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29K 105: 16

Claims (6)

[Claims] 1. A pellet made of a liquid crystalline polymer capable of forming an anisotropic molten phase, wherein the pellet length cut in a direction perpendicular to the orientation direction of polymer molecules is 1.0 to 5.
0 mm, the cut cross section is elliptical, the major axis is 2.0 to 8.0 mm, the ratio of major axis to minor axis (major axis / minor axis) is 1.0 to 4.0, A liquid crystalline polymer pellet characterized in that the bulk specific gravity of the pellet is in the range of 0.5 to 0.8 kg / liter and the angle of repose is in the range of 35 to 45 °. 2. The liquid crystalline polymer pellet according to claim 1, wherein the liquid crystalline polymer is an aromatic polyester or an aromatic polyesteramide. 3. The liquid crystalline polymer pellet according to claim 1, wherein the liquid crystalline polymer is a liquid crystalline polyester having p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid as constituent components. 4. A liquid crystal polymer capable of forming an anisotropic molten phase is cooled and solidified from a molten state as a string-like material, and when this is cut into pellets, the cut cross-sectional diameter when solidified is 1 Characterized in that a string-shaped material of ~ 6 mm is cut in the presence of cooling water when the core of the string-shaped material is cooled within a temperature range from the melting point of the liquid crystalline polymer to 80 ° C higher than the melting point. The method for producing a liquid crystalline polymer pellet according to claim 1. 5. The method for producing liquid crystalline polymer pellets according to claim 4, wherein the liquid crystalline polymer is a liquid crystalline polyester containing p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid as constituent components. 6. A liquid crystalline polymer having a melting point of 260 to 360.
The temperature range is 30 to 90 ° C., and the cooling time is 0.7 to 2.0 seconds for a string obtained from a molten polymer having a melting temperature of 5 to 60 ° C. higher than the melting point. The method for producing liquid crystalline polymer pellets according to claim 4 or 5, wherein the pellets are cooled after being cooled within the above range.