JP2648745B2 - Thermotropic liquid crystal polymer composition and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermotropic liquid crystal polymer composition and a method for producing the same.

Conventional technology and its problems Thermotropic liquid crystal polymer has a molecular structure (rigid linear molecule) even with resin alone, so its crystal structure is easily oriented at the time of molding, its mechanical strength in the flow direction is large, and its fluidity is high. It has attracted attention as a thermoplastic resin having excellent characteristics and a very small molding shrinkage in the flow direction, and is expected to be used in various fields of application.

However, such a thermotropic liquid crystal polymer has a large difference in strength and molding shrinkage between a flow direction and a direction perpendicular to the flow direction because a polymer chain is easily oriented at the time of molding (hereinafter, this is referred to as “anisotropic”). As a result, it is difficult to design the shape of the molded product, and the field of application is narrowed. Further, in many fields of use, there is a demand for a material having excellent heat resistance, various mechanical strengths or rigidity while maintaining the characteristics of the polymer such as flame retardancy, chemical resistance, and moldability. That is the fact.

Therefore, in recent years, attempts have been made to improve the anisotropy of the polymer by blending a powdery or flaky filler such as calcium carbonate, mica, and glass beads with the above polymer, and to strengthen the polymer with fibrous reinforcement such as glass fiber. Attempts have been made to improve the heat resistance, strength and stiffness of the polymer by blending agents. However, the former attempt has a fatal disadvantage that the impact resistance of the polymer is greatly reduced and the polymer becomes very brittle, and the latter attempt has an effect of improving the anisotropy of the polymer. In addition to poor surface quality, the surface smoothness, which is a characteristic of liquid crystal polymers, is impaired due to wear of the contact surface with processing machines and molds, and appearance of glass fiber embossed patterns on the surface of molded products. A serious drawback.

From this point of view, while improving the heat resistance, strength and rigidity of the thermotropic liquid crystal polymer, maintaining a good surface appearance, having a small anisotropy, and having little abrasion of a molding machine and a mold, the thermotropic liquid crystal. Polymer compositions have been developed (see, for example, JP-A-61-195156 and JP-A-62-81448). The former composition is obtained by adding a potassium titanate fiber (hereinafter referred to as "PTW"), which is a microfiber, to a wholly aromatic copolyester, which is a kind of thermotropic liquid crystal polymer, in particular, having a free potassium content of 0.025% or less. Is a composition containing 5 to 70% by weight of PTW. The latter composition is a composition obtained by blending 5-70% by weight of PTW with a thermotropic liquid crystal polymer.

However, these compositions have particularly low notched Izod impact strength (ie, poor impact resistance),
There is a fatal drawback of being brittle, and especially the latter composition is inferior in long-term heat resistance, and it is presently desired to solve such a drawback.

Means for Solving the Problems An object of the present invention is to provide a thermotropic liquid crystal polymer resin composition in which the impact resistance is greatly improved and the long-term heat resistance is improved, so as not to be expected with the conventional PTW reinforced material. It is to provide a manufacturing method thereof.

That is, the present invention provides a pH 6 to 8, X-ray diffraction chart 2θ = 1
A thermotropic liquid crystal polymer composition comprising 5 to 60% by weight of potassium 6-titanate fiber having a half width at a characteristic peak of 3.8% of 0.1 or less.

In the present invention, the thermotropic liquid crystal polymer refers to a polymer having liquid crystallinity (the molecular directions are aligned) in a molten state. As the thermotropic liquid crystal polymer used in the present invention, conventionally known ones can be widely used, and for example, a wholly aromatic (co) polyester, a wholly aromatic (co) polyesteramide, an aromatic-aliphatic copolyester, an aromatic polymer Azomethine, aromatic polyester carbonate and the like, which may be used alone or in combination of two or more.
More than one species may be used in combination.

A wholly aromatic (co) polyester and a wholly aromatic (co) polyesteramide have at least one aromatic ring in every monomer component constituting the polymer chain,
It is called wholly aromatic, and the polymer can exhibit liquid crystallinity in the molten phase because of its rigid molecular structure.
Such monomer components include hydroquinone, resorcin, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxybenzophenone, and 4,4'-dihydroxy. Diphenyl sulfide, 4,4 '
Aromatic diols such as -dihydroxydiphenylsulfone, 2,6-dihydroxynaphthoyl, p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, m-xylylenediamine, 4,4'-diaminodiphenyl, 4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl sulfide, 4,4'-
Aromatic diamines such as diaminodiphenyl sulfone, terephthalic acid, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxydiphenyl ether, 2,6-
Aromatic dicarboxylic acids such as dicarboxynaphthoyl, p-
Aromatic hydroxycarboxylic acids such as hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 4-hydroxycinnamic acid, p-aminobenzoic acid, 6
Examples thereof include aromatic aminocarboxylic acids such as -amino-2-naphthoic acid, but are not limited thereto.

A wholly aromatic (co) polyester and a wholly aromatic (co) polyesteramide are easily produced from these monomer components according to a conventional method. The wholly aromatic (co) polyester is prepared according to the method disclosed in, for example, JP-A-56-104932 and JP-A-57-44622. Each is manufactured according to the method disclosed in the specification of 4182842.

Specific examples of the aromatic-aliphatic (co) polyester include a copolymer of polyethylene terephthalate and p-hydroxybenzoic acid.

Specific examples of the aromatic polyazomethine include poly (nitrilo-2-methyl-1,4-phenylenenitriloethylidine-1,4-phenyleneethylidine), poly (nitrilo-
2-methyl-1,4-phenylene nitrilomethylidyne-1,4
-Phenylenemethylidine), poly (nitrilo-2-chloro-1,4-phenylenenitrilomethylidine-1,4-phenylenemethylidine) and the like.

As the aromatic polyester carbonates, those disclosed in, for example, US Pat. Nos. 4,107,143 and 4,284,57 are widely used.

The thermotropic liquid crystal polymer used in the present invention preferably has a weight average molecular weight of about 5,000 to about 200,000, particularly about 10,000 to about 50,000 as measured by gel permeation chromatography. If the weight-average molecular weight of the thermotropic liquid crystal polymer is too small, the mechanical properties of the obtained resin composition tend to decrease, while if the weight-average molecular weight of the polymer is too large, it is difficult to produce such a polymer. However, the melt viscosity of the polymer is increased, and the resulting resin composition tends to be difficult to mold and process.

The potassium titanate fiber blended in the composition of the present invention has a chemical formula of K ₂ O · 6TiO ₂ , has a pH of 6 to 8, preferably 6.5 to 7.5, and has an X-ray diffraction chart 2θ = 13.8 °. The half width at the characteristic peak is 0.1 or less, preferably 0.05
Highly crystalline potassium 6-titanate fiber (6-PTW)
It is. Here, the pH refers to a value measured at 20 ° C. after stirring a 1% by weight aqueous solution of PTW (using deionized water) for 10 minutes. The half-width at the characteristic peak of the X-ray diffraction chart 2θ = 13.8 ° is a value represented by W / H, where H is the peak height at 2θ = 13.8 ° and W is the peak width at 1 / 2H. . The latter value is an index indicating the crystallinity of the PTW, and indicates that the smaller the half width, the larger the crystallinity.

6-PTW having the above characteristic value used in the present invention is:
For example, it is manufactured according to the following method. That is, K ₂ O, K
₂ CO ₃ or the like K ₂ O component and TiO _2, TiO hydrothermal method from TiO ₂ component, such as _2-containing compound, a flux method, firing method, to produce a 6-PTW in accordance with a conventionally known method such as melting method, following To 700 ℃
After a heat treatment at the above high temperature to obtain a highly crystallized product having a half width at a characteristic peak of 2θ = 13.8 ° of 0.1 or less, desirably 0.05 or less, a crystalline system (6-PTW) is obtained by acid treatment and washing with water.
Without changing the pH, 6-PTW adjusted to a so-called neutral region of slightly acidic to slightly alkaline pH 6 to 8 can be obtained.

When the pH of 6-PTW used in the present invention exceeds 8, the thermotropic liquid crystal polymer is liable to undergo molecular chain breakage (thermal decomposition) at the time of heat melting (at the time of compounding and kneading and at the time of molding). As a result, the intended strength of the present invention cannot be achieved. On the other hand, if the pH is lower than 6, the effect of the acid remaining in 6-PTW not only deteriorates the appearance and mechanical strength of the molded product, but also causes corrosion of the processing machine and the mold. It is.

When the half-width of 6-PTW used in the present invention exceeds 0.1, the crystallinity is low even when the pH is adjusted to 8 or less by an acid treatment in the synthesis of 6-PTW, so that the crystallinity is low. K ₂ O
The components are easily transferred to the surface of 6-PTW, and therefore, when kneaded into the thermotropic liquid crystal polymer, dissolve in a small amount of water contained in the polymer and become alkaline with a pH of more than 8, thereby melting the polymer. High temperatures will hydrolyze the polymer chains, and
-Unsuitable because the reinforcing effect of PTW cannot be sufficiently exhibited.

If 6-PTW having the above characteristic values is used, the reinforcing effect is greater than that of high-dimension glass fiber, which was conventionally considered to have a large reinforcing effect.In particular, in the notched Izod impact strength, the conventional The Izod impact value is considerably lower than that of the GF-reinforced product, and the brittleness is brittle. "

Fiber diameter and fiber length of 6-PTW used in the present invention,
Although not particularly limited, the fiber diameter is usually 0.01 to 2
It is appropriate that the fiber length is about 2 to 500 μm, preferably about 5 to 100 μm, and the aspect ratio (fiber length / fiber diameter) is 10 or more.

The 6-PTW used in the present invention may not be treated with a surface treating agent, but is preferably treated with a surface treating agent. As such a surface treatment agent, γ
-Mercaptopropyltrimethoxysilane, β- (3,4
At least one selected from the group consisting of -epoxycyclohexyl) ethyltrimethoxysilane and N-phenyl-γ-aminopropyltrimethoxysilane is preferred. The use of 6-PTW treated with such a surface treatment agent has the advantage of facilitating subsequent supply to the melt mixer.

In the present invention, the compounding amount of 6-PTW is 6 to 60% by weight, preferably about 10 to 50% by weight, based on the total amount of the thermotropic liquid crystal polymer and 6-PTW. It is better to do so. If the amount of 6-PTW is less than 5% by weight, the resulting composition will have insufficient improvement in mechanical strength and rigidity (flexural modulus). On the other hand, when the blending amount of 6-PTW exceeds 60% by weight, 6-PTW itself is very bulky (apparent density 0.05 to 0.2 g / cc).
It is not practical because supply to the melt mixer becomes difficult.

In the thermotropic liquid crystal polymer composition of the present invention,
Antioxidants, heat stabilizers, ultraviolet absorbers, lubricants, mold release agents, coloring agents such as pigments, flame retardants, flame retardant assistants, antistatic agents, Ketjen within a range not to impair the object of the present invention. A conductivity-imparting agent such as black, a powdery filler such as calcium carbonate or a flaky (scale) filler such as mica, a reinforcing agent such as glass fiber or carbon fiber, and the like can also be appropriately compounded.

In producing the composition of the present invention, the compounding means is not particularly limited, and thermotropic liquid crystal polymer and 6-PT
W may be preliminarily mixed using a Henschel mixer, a tumbler mixer, or the like, or may be separately supplied to a melt mixer and melt-kneaded. In particular, in order to produce uniform-shaped pellets with good quantitative properties in a molding machine such as an injection molding machine, it is preferable to follow a rotary type mist cutting method. This method is a method in which a thermotropic liquid crystal polymer and 6-PTW are uniformly mixed by a melt mixer and then pelletized by a mist cut pelletizer.
More specifically, after the above-mentioned liquid crystal polymer and 6-PTW are uniformly melt-kneaded by a melt mixer, a rotary cutter that rotates at a high speed so as to be orthogonal to the die portion extruded in a strand shape is arranged, and provided at one end. Hot cutting may be performed with the cutting chamber filled with mist generated by mixing water and air from the nozzle. According to the study of the present inventor, once the melt is drawn into a strand in a usual manner, cooled in a water bath, and then pelletized with a general pelletizer, the thermotropic liquid crystal polymer crystallizes in the extrusion direction. Even if a shearing force is applied to a completely solidified state, the strands are broken into a wall-like shape, and it has been difficult to produce pellets such as those obtained with ordinary thermoplastic resins.

Effects of the Invention According to the present invention, there is provided a thermotropic liquid crystal polymer resin composition in which the impact resistance is greatly improved and the long-term heat resistance is improved to an extent that can not be expected with conventional PTW reinforced materials. Moreover, the composition of the present invention improves the heat resistance, strength and rigidity of the thermotropic liquid crystal polymer, maintains a good surface appearance, has small anisotropy,
The wear of the molding machine and the mold is small.

Examples Hereinafter, the present invention will be described more specifically with reference to Examples.

Examples 1 to 3 As a thermotropic liquid crystal polymer, a wholly aromatic polyester Vectra A950 (manufactured by Hoechst Celanese) was used.

Further, as a potassium titanate fiber, the half-value width at the characteristic peak of pH 6.8, X-ray diffraction chart 2θ = 13.8 ° is 0.02.
6-PTW [average fiber diameter 0.3 μm, average fiber length 15 μm
m] was used. The 6-PTW was prepared by adding β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane to 6-PTW in order to improve the supply of potassium titanate fiber and the wettability with the thermotropic liquid crystal polymer. −
The surface is treated by adding 1% by weight of PTW (pH value after surface treatment is 7.1).

Vectra A950 and 6-PTW were separately supplied from a main hopper and a side feeder of a twin-screw extruder [PCM45, manufactured by Ikegai Iron Works Co., Ltd.] so that the ratios of Examples 1 to 3 in Table 1 below were obtained. After melt-kneading at a cylinder temperature of 300 ° C, pelletizing at a circulating oil temperature of a die of 320 ° C using a mist cut pelletizer [PHR-100, manufactured by Ikegai Iron Works Co., Ltd.] A white egg-shaped uniform pellet was obtained.

The obtained pellets were subjected to an injection molding machine [FS-150N, manufactured by Nissei Plastic Industry Co., Ltd.] at a cylinder temperature of 290 ° C and a mold temperature of 80.
Each test piece was obtained by injection molding at ℃.

Tensile properties, bending properties, Izod impact strength (with notch) and heat distortion temperature are as per ASTM D-638, D-7
It measured according to 90, D-256, D-648. Further, the color difference ΔE between the test piece retained in an injection molding machine having a cylinder temperature of 290 ° C. for 15 minutes and the test piece before retention was measured using a colorimetric color difference meter [Z-
1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.], and the thermal stability of the test piece obtained in each example was evaluated.

 The results are shown in Table 1 below.

Comparative Examples 1 to 3 and Reference Example 1 In Comparative Example 1, Vectra A950 was injection molded as it was. In Comparative Examples 2 and 3, in the same manner as in Examples 1 to 3, Vectra A950 and the following potassium titanate fiber were melt-kneaded at a ratio of 70:30 (weight ratio), then pelletized, and injected similarly. A molded test piece was obtained.

Potassium titanate fiber used in Comparative Example 2: pH 9.2, 6-PTW having a half width at a characteristic peak of 0.113 in X-ray diffraction chart 2θ = 13.8 ° (fiber diameter and fiber length are those of Examples 1 to 3) The same as in Examples 1 to
The surface treated with the same silane coupling agent as in Example 3 (pH value after surface treatment is 9.8).

Potassium titanate fiber used in Comparative Example 3: HT-200 described in JP-A-61-19515 [6- (average fiber diameter 0.45 μm, average fiber length 22.5 μm, pH 8.2, half width 0.03) PTW that has been surface-treated with the same silane coupling agent as in Examples 1 to 3 (pH value after surface treatment is 8.5).

For each of the injection-molded test specimens of Comparative Examples 1 to 3, the same physical properties as those of the above-mentioned examples were measured.

For reference, a commercially available pellet (Vectra A-130, manufactured by Polyplastics) filled with 30% by weight of glass fiber was injection-molded in the same manner as above, and the same physical properties were measured.

 The results are shown in Table 1 below.

From Table 1 above, the following is clear. That is, the molded product of Example 2 shows higher mechanical strength than those of Comparative Examples 2 and 3. Especially in the notched Izod impact strength,
It is surprisingly 3 to 10 times that of the conventionally known PTW reinforced product, and has more than twice the high impact strength as compared with the glass fiber reinforced product of Reference Example 1.

Example 4 Aromatic-aliphatic polyester rod run LC500 [Unitika Ltd.] as a thermotropic liquid crystal polymer
Manufactured).

The same potassium titanate fibers as in Examples 1 to 3 were used.

Rod Run LC500 and 6-PTW were mixed at a ratio of 70:30 (weight ratio), and pellets were obtained in the same manner as in Examples 1-3.
Next, an injection molded test piece was prepared from this, and physical properties were evaluated.

Comparative Example 4 An injection molded test piece was obtained in the same manner as in Example 4 except that the potassium titanate fiber used in Comparative Example 2 was used as the potassium titanate fiber, and the physical properties were evaluated.

Various physical properties of the test piece of Example 4 and the test piece of Comparative Example 4 are shown below.

From the above results, it can be seen that when the 6-PTW of the present invention is used, the obtained molded product has high mechanical properties, has a large Izod impact strength, and has less thermal discoloration due to stagnation during molding.

Claims (4)

(57) [Claims] 1. A thermotropic liquid crystal polymer comprising 5 to 60% by weight of potassium 6-titanate fiber having a half width at a characteristic peak at pH 6 to 8 and an X-ray diffraction chart 2θ = 13.8 ° of 0.1 or less. Composition. 2. The composition according to claim 1, wherein the potassium titanate fiber has a pH of 6.5 to 7.5 and a half-width at a characteristic peak at 2θ = 13.8 ° in an X-ray diffraction chart is 0.05 or less. 3. The surface of a potassium titanate fiber is γ-mercaptopropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and N-
The composition according to claim or being treated with at least one member selected from the group consisting of phenyl-γ-aminopropyltrimethoxysilane. 4. A thermotropic liquid crystal polymer composition characterized in that the potassium 6-titanate fiber and the thermotropic liquid crystal polymer according to claim 1 are uniformly melt-kneaded by a melt mixer and then pelletized by a mist cut pelletizer. Method of manufacturing a product.