JPH0813245A - Method for producing pulp-like material composed of thermoplastic liquid crystal resin - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a method for producing a pulp-like material made of a thermoplastic liquid crystal resin, which simplifies the pulp production process without using an oil agent, etc., which has conventionally been required. That's what it is. [Constitution] A thermoplastic liquid crystal resin capable of forming an anisotropic melt phase is heated at a temperature 10°C or more higher than the flow initiation temperature of the resin,
and extruding from a nozzle at a shear rate of 10 to 500 sec ^-1 , and pulverizing the obtained strands with a pulverizer to obtain a pulp-like material composed of a thermoplastic liquid crystal resin. law.

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a pulp-like material composed of a thermoplastic liquid crystal resin which forms an anisotropic melt phase. Useful as a reinforcing material for heat-resistant composite materials combined with thermosetting resins, as a substitute for asbestos as a friction material for automotive brake pads or clutch phasing, sliding materials, heat-resistant filters, chemical-resistant filters, etc. is.

[0002]

2. Description of the Related Art Conventionally, fibril pulp of aromatic aramid fibers is generally known as a pulp-like material composed of an organic substance. is clearly different from

[0003] In addition, since the aromatic aramid fiber has a high water absorption rate of 3 to 7%, especially when it is used in combination with a thermosetting resin, steam is generated from the aromatic aramid fiber during heat curing, resulting in a molded product. Blisters appear on the surface. Aromatic aramid fibers therefore require a drying step prior to use.

[0004] Japanese Patent Laid-Open No. ^1-201518 proposes a method for producing a pulp-like material made of thermotropic polyester. It is a method of producing a pulp-like material in a wet state using and is completely different from the method of the present invention.

[0005] Further, in this method, since the fibers or strands are wetted with water or an oil before pulverization, the manufacturing process becomes complicated. Moreover, when used as pulp, water and oils must be removed by drying, extraction, etc., and it is difficult to say that this is a method for obtaining pulp easily and inexpensively.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, simplify the pulp manufacturing process,
An object of the present invention is to provide a method for producing a useful pulp-like material.

[0007]

Means for Solving the Problems The inventors of the present invention have extensively researched pulp-like material production methods. The inventors have found that a pulp-like material having a good shape and being highly entangled can be produced, and have completed the present invention.

In the present invention, a thermoplastic liquid crystal resin capable of forming an anisotropic melt phase is melted at a temperature 10° C. or more higher than the flow initiation temperature of the resin and at a shear rate of 10 to 500 sec ⁻¹ or less. A method for producing a pulp-like material composed of a thermoplastic liquid crystal resin, characterized in that a pulp-like material is obtained by discharging from a nozzle and pulverizing the obtained strands. The invention is described in more detail below.

A particularly preferred example of the thermoplastic liquid crystal resin capable of forming an anisotropic melt phase used in the present invention consists of the following structural units (A), (B), (C) and (D), Structural unit (B) is substantially equal to the sum of structural units (C) and (D), and structural unit (A) is substantially equal to the sum of structural units (A), (B), (C) and (D) is 50 to 80 mol %, and the structural unit (C) is 50 to 100 mol % with respect to the sum of the structural units (C) and (D).

[0010]

[Chemical 7]

[0011]

[Chemical 8]

[0012]

[Chemical 9]

[0013]

[Chemical 10]

However, X in structural unit (D) is one or more selected from formula 1 below.

[0015]

[Chemical 11]

However, Ar in the above formula is one or more selected from formula 2 below.

[0017]

[Chemical 12]

Structural unit (A) is structural unit (A),
With respect to the total of (B), (C) and (D), when the total amount is 50 mol% or more, the obtained thermoplastic liquid crystal resin has excellent heat resistance, and when it is 80 mol% or less, the obtained thermoplastic liquid crystal resin Flow initiation temperature is not too high, making manufacturing and stranding easier.

Structural unit (C) is effective in improving melt moldability. The melt viscosity of the plastic liquid crystal resin is not too high, the melt moldability is easy, and a pulp-like material having a good shape can be obtained.

Further, it is desirable that the thermoplastic liquid crystal resin comprising the above structural units forms an anisotropic melting phase at 280 to 450.degree. A thermoplastic liquid crystal resin that forms an anisotropic molten phase at a temperature higher than 280° C. is unlikely to cause fusion during pulverization. A thermoplastic liquid crystal resin that forms an anisotropic melt phase at a temperature of 450° C. or lower is preferable because it facilitates melt molding.

The method for producing the thermoplastic liquid crystal resin capable of forming an anisotropic melt phase used in the present invention is not particularly limited, and can be produced according to conventionally known methods.

The following (a) to
Although the method of (d) can be mentioned, it is not limited to these production methods.

(a) A method of producing by a deacetic acid polycondensation reaction from aromatic dicarboxylic acids, diacetic esters of aromatic dihydroxy compounds and acetic esters of aromatic hydroxycarboxylic acids.

(b) A method in which aromatic dicarboxylic acids, aromatic dihydroxy compounds and aromatic hydroxycarboxylic acids are allowed to coexist with acetic anhydride to acetylate the phenolic hydroxyl groups, followed by a deacetic acid polycondensation reaction.

(c) A method of producing from a diphenyl ester of an aromatic dicarboxylic acid, an aromatic dihydroxy compound and a phenyl ester of an aromatic hydroxycarboxylic acid by a dephenol polycondensation reaction.

(d) The low-molecular-weight thermoplastic liquid crystal resin obtained by the methods (a) to (c) is solidified in air, in an inert gas atmosphere, or under reduced pressure at a temperature lower than the flow initiation temperature. A method of manufacturing by so-called solid phase polymerization, which is heated while maintaining the state.

Inorganic fillers such as talc, mica, clay and barium sulfate, and carbon pitch may be added to the thermoplastic liquid crystal resin as long as the objects of the present invention are not impaired. Additives such as pigments, lubricants and antioxidants may also be added.

In the present invention, a thermoplastic liquid crystal resin capable of forming an anisotropic molten phase is discharged from a nozzle at a temperature 10° C. or more higher than the flow initiation temperature of the resin and at a shear rate of 10 to 500 sec ^-1 . A pulp-like material having a good shape can be obtained by pulverizing the strands.

In the present invention, the flow initiation temperature is the melting point when a clear melting point is observed by a differential scanning calorimeter (DSC), and a hot stage is attached when a clear melting point is not observed by DSC. It refers to the temperature at which a part of the sample starts to flow when the sample is observed under a polarizing microscope while being heated.

In the present invention, the thermoplastic liquid crystal resin capable of forming an anisotropic melt phase is 10 degrees below the flow initiation temperature of the resin.
By discharging from the nozzle at a temperature higher than 10°C, it is possible to obtain a strand from which a pulp-like material having a good shape can be obtained. If the temperature is not at least 10°C higher than the flow initiation temperature of the resin, the melt viscosity of the thermoplastic liquid crystal resin is high.
Stranding becomes difficult. In addition, the resulting strands are not sufficiently oriented, and even if they are pulverized, a pulp-like material with a good shape cannot be obtained.

In the present invention, in order to obtain a pulp-like material having a good shape, it is necessary to discharge a thermoplastic liquid crystal resin capable of forming an anisotropic molten phase from a nozzle at a shear rate of 10 to 500 sec ^-1 . There is At a shear rate of 10 sec ^-1 or less, when the strand is pulverized, the fiber length becomes short and the strand becomes powdery, and a pulp-like material having a good shape cannot be obtained. At a shear rate of 500 sec ^-1 or more, the strands are pulverized to form a pulp-like material having a straight shape and less entanglement, which is not preferable. A particularly preferred shear rate is 50-2
00 sec ^-1 .

The extruder used for producing the strands may be either a single-screw type or a twin-screw type, as long as the cylinder temperature can be raised above the flow initiation temperature of the thermoplastic liquid crystal resin.

The shape of the nozzle is preferably circular, but is not particularly limited to this.

[0034] The strands can be pulverized as they are, but it is desirable to cut them into appropriate lengths and pulverize them. A general-purpose pelletizer is sufficient for cutting the strands, but a pelletizer capable of independently adjusting the strand take-up speed and the cutter speed is preferable because the L/D of the pellets can be adjusted. where L
is the length of the strand, and D is a numerical value obtained from the following equation. D=2×(S/π) ^1/2 S: Cross-sectional area of strand

[0035] the cut strand has a length of 1 mm or more;
If the L/D is 1 or more, a pulp-like material can be obtained, and if the length is 5 mm or more and the L/D is 5 or more, a pulp-like material having a better shape can be obtained.

Various pulverization methods can be used to obtain the pulp-like material, but dry pulverizers are preferred for pulverization from the viewpoints of efficiency, cost, etc. in the pulverization process. It is more preferable because the shape of the resulting pulp-like material is good. A rotary impact pulverizer is a pulverizer that pulverizes a resin or the like by impacting or shearing it with a pin that rotates in the pulverization chamber or a rotor with a special structure.

Examples of pulverizers having this type include Jiyu Pulverizer, New Cosmomizer (manufactured by Nara Machinery Co., Ltd.), Victory Mill, Fine Victory Mill (manufactured by Hosokawa Micron Corporation), Turbo Mill (Turbo Mill). Kogyo Co., Ltd.), Ultra Rotor (Co., Ltd.)
W. I. R. (manufactured by Makino Sangyo Co., Ltd.), and a fine mill (manufactured by Nippon Pneumatic Industry Co., Ltd.).

[0038] A wet grinder can also be used, but requires a drying step, which increases manufacturing costs. According to the present invention, by pulverizing with a dry pulverizer, a pulp-like material having a shape equal to or greater than that of a wet pulverizer can be obtained at a low production cost.

The pulp-like material produced by the above method can be used as a reinforcing agent for heat-resistant composite materials in combination with other thermoplastic resins or thermosetting resins, or as a substitute for asbestos for automotive brake pads or clutch phasing. friction materials, sliding materials, heat-resistant filters,
It is useful as a material for chemical resistant filters and the like.

[0040]

EXAMPLES The present invention will now be described in detail with reference to Examples, but the present invention is not limited to the following Examples. "Parts" described in the following examples and the like indicate "parts by weight". still,
Various measurements in Reference Example 1 were carried out by the following methods.

(1) Melting point differential scanning calorimeter (DSC) (manufactured by Seiko Electronics Co., Ltd., S
SC-560S type) is used, and about 10 mg of the sample is placed in a non-sealed aluminum container and placed in a nitrogen gas stream (30 ml/
The temperature was raised from 30° C. at a rate of 20° C./min at 20° C./min), and the temperature at which the endothermic peak was observed was taken as the melting point.

(2) Presence or absence of flow initiation temperature and anisotropic molten phase formation An optical microscope (manufactured by Nikon Corporation, trade name: Optiphot) equipped with a hot stage (manufactured by Colette Industry Co., Ltd.)
-pol), the sample was observed in the polarized state while the temperature was raised at a rate of 10°C/min. The temperature at which a part of the sample starts to flow was defined as the flow initiation temperature.

(3) Logarithmic Viscosity of Thermoplastic Liquid Crystal Resin Logarithmic viscosity [(lnηrel)/C] was measured at 60° C. as a pentafluorophenol solution having a concentration of 0.16 g/dl.

Reference Example 1 Production of LCP-A 1081 parts of p-acetoxybenzoic acid and 1,4 parts of p-acetoxybenzoic acid were added to a reactor equipped with a stirrer, thermometer, pressure gauge, nitrogen gas inlet tube, distillation head connected to a condenser, etc. -diacetoxybenzene 388 parts, N,N'-(4,4'-diphenyl ether)-bis-3,4'-dicarboximide benzoic acid 11
0 part of 2,6-naphthalenedicarboxylic acid and 389 parts of 2,6-naphthalene dicarboxylic acid were charged, and after purging with nitrogen three times, the temperature was raised to 200° C. while gently stirring and flowing a small amount of nitrogen into the reactor. After raising the temperature to 200°C, the stirring rate was increased and the mixture was heated stepwise to 240°C for 1 hour and 260°C for 1 hour.
1 hour at 280°C and 1 hour at 300°C. Then, the pressure inside the reactor was gradually reduced to 0.5 Tor.
The mixture was stirred at 300° C. for 1 hour, at 320° C. for 1 hour, and at 340° C. for 1 hour while maintaining a vacuum of r to complete the polymerization. After the polymerization was completed, the pressure inside the reactor was reduced to 2.5 kg/cm ² .
Then, take out the strand through the die from the exhaust bottom valve,
It was cut by a cutter to obtain pellets. This polymer (hereinafter referred to as LCP-A) had a melting point of 317° C., a flow initiation temperature of 312° C., and exhibited an anisotropic melting phase. The logarithmic viscosity was 4.2 g/dl.

Example 1 The LCP-A obtained in Reference Example 1 was extruded from a 4 mmφ nozzle attached to the tip of a 45 mm twin-screw extruder at 330° C. at a single hole discharge rate of 37 g/min. The resulting strand was cut into pellets with a length of 7 mm and a diameter of 1 mm using a pelletizer. The shear rate at this time was 70 sec ^-1 . These pellets are crushed by a small pulverizer A-10 manufactured by AICA Co., Ltd.
It was pulverized with a mold (dry type/rotary blade type). The resulting pulp was observed under a microscope. In addition, the resulting pulp and Table 1
are uniformly mixed with a home-use mixer, placed in a 35 mm diameter tablet molding mold, and subjected to a manual press at room temperature, a molding pressure of 50 kg/cm ² , and a pressure holding time of 1 minute. A cylindrical test piece was produced.

This test piece was subjected to a bending test using a Tensilon under the conditions of a crosshead speed of 1 mm/min and a span distance of 25 mm. The stress at the time of breakage of the test piece at this time was measured, and it was judged that the higher the stress, the stronger the entanglement of the pulp-like materials, the better the pulp shape, and the better the shape retention. Table 2 shows the results.

[0047] Table 1Pulp-like material Brass fiber Barium sulfate Graphite BT resin dust ⁽¹ ) 7 copies 43 copies 25 copies 10 copies 15 copies Note) (1) Phenol-modified xylene/formaldehyde resin novolac/epoxy From a cured product of resin/BT resin (bismaleimide triazine resin) = 70/30 200-100 mesh powder consisting of

Example 2 The LCP-A pellets obtained in Reference Example 1 were pulverized with a fine mill (dry, rotary impact type) manufactured by Nippon Pneumatic Industry Co., Ltd. Example 1 using the obtained pulp
A similar bending test was performed. Table 2 shows the results.

Comparative Example 1 The LCP-A obtained in Reference Example 1 was extruded at 330° C. from a 2 mmφ nozzle attached to the tip of a 45 mm twin-screw extruder at a single-hole discharge rate of 36 g/min. The resulting strand was cut into pellets with a length of 7 mm and a diameter of 1 mm using a pelletizer. The shear rate at this time is 550 sec ^-1
Met. These pellets are passed through a small pulverizer A-1 manufactured by Aica.
It was pulverized with type 0 (dry type, rotary blade type). The same bending test as in Example 1 was performed using the obtained pulp-like material. Table 2 shows the results.

Comparative Example 2 A strand of LCP-A discharged under the same conditions as in Example 1 was cut into pellets having a length of 2 mm and a diameter of 3 mm. The pellets were pulverized with a compact pulverizer A-10 (dry type, rotary blade type) manufactured by Aica. The same bending test as in Example 1 was performed using the obtained pulp-like material. Table 2 shows the results.

Reference Example 2 A bending test was conducted in the same manner as in Example 1, except that aromatic aramid fiber pulp was used in place of the thermoplastic liquid crystal resin pulp. Table 2 shows the results.

Table 2 Pulp shape ⁽²⁾ Length Thickness Branching Bending stress (kgf) Example 1 Medium thin High 3.3 Example 2 Long Thin High 5.5 Comparative example 1 Medium thick Low 1.6 Comparative example 2 Short Thin Less 0.9 Reference Example 2 Short Extra thin Considerably more 5.6 Note) (2) Length: Short: 3 mm or less Medium: 3 to 5 mm Length: 5 mm or more Thickness: Thin: 0.1 mm or less Thick: 0.1 mm or less 1 mm or more Branching: Many thin fibrils protruding from the pulp trunk

[0053]

INDUSTRIAL APPLICABILITY As is clear from the above detailed description and examples of the invention, the method for producing a pulp-like material comprising a thermoplastic liquid crystal resin according to the present invention does not require an oil agent or the like, which was necessary in the prior art. A useful pulp-like material can be produced in a simplified process with a shape retention equivalent to that of pulp made of aromatic aramid fibers without using a pulp, and its industrial significance is extremely high.

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Claims (5)

[Claims] 1. A thermoplastic liquid crystal resin capable of forming an anisotropic molten phase is discharged from a nozzle at a temperature 10° C. or more higher than the flow initiation temperature of the resin and at a shear rate of 10 to 500 sec ^-1 . and pulverizing the resulting strands with a pulverizer to obtain a pulp-like material from a thermoplastic liquid crystal resin. 2. A thermoplastic liquid crystal resin capable of forming an anisotropic melt phase comprises the following structural units (A), (B), (C) and (D), wherein the structural unit (B) is a structural unit ( C) and (D) substantially equal to the sum of structural units (A),
Structural unit (A) accounts for 50 to 80 mol% of the sum of (B), (C) and (D), and structural unit (C)
and the structural unit (C) is 50 to 1 with respect to the sum of (D)
A method for producing a pulp-like material comprising a thermoplastic liquid crystal resin according to claim 1, wherein the content is 00 mol %. [Chemical 1] [Chemical 2] [Chemical 3] [Chemical 4] However, X in the structural unit (D) is one or more selected from Formula 1 below. [Chemical 5] However, Ar in the above formula is one or more selected from Formula 2 below. [Chemical 6] 3. The thermoplastic liquid crystal resin capable of forming an anisotropic melt phase has a flow initiation temperature of 280 to 450.degree.
and a method for producing a pulp-like material comprising the thermoplastic liquid crystal resin according to claim 2. 4. The method for producing a pulp-like material comprising a thermoplastic liquid crystal resin according to claim 1, wherein a dry pulverizer is used as the pulverizer. 5. The method for producing a pulp-like material comprising a thermoplastic liquid crystal resin according to claim 1, wherein the strand has a length of 1 mm or more and an L/D of 1 or more. However, L is the length of the strand, and D is a numerical value obtained from the following formula. D=2×(S/π) ^1/2 S: Cross-sectional area of strand