JPH08217894A - Transparent liquid crystal polyester resin film or sheet and its production - Google Patents

Abstract

PURPOSE: To obtain the subject film or sheet having high crystallizability, excellent heat resistance and transparency free from reduction in transparency under high-temperature conditions by molding a liquid crystal polyester resin in a low crystallinity index to give a film or a sheet and heat-treating the film or the sheet at a specific temperature. CONSTITUTION: This film or sheet is obtained by predissolving a liquid crystal polyester resin of the formula (Ph is 1,4-phenylene; Nh is 2,6-naphthalene) in a solvent, forming the solution into a film or a sheet by solidifying the end part of the film or the sheet or applying tension to it so as to raise surface smoothness and to make crystallinity index <=30% and heat-treating the film or the sheet at a temperature satisfying the formula Ta<Tcc [Ta is a heat- treating temperature ( deg.C); Tcc is a cooling crystallization temperature ( deg.C) measured by differential thermal analysis based on JIS-K7121 at 10 deg.C/min heating rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystalline polyester resin film, a sheet having a high crystallinity and a transparency which is not deteriorated under a high temperature condition and having excellent stability, and a method for producing the same. Is.

[0002]

BACKGROUND OF THE INVENTION Liquid crystalline polyester has excellent heat resistance, mechanical strength, dimensional stability,
It is also known to have low gas permeability and is used in a wide range of fields. The liquid crystalline polyester is considered to exhibit its excellent properties because it exhibits liquid crystallinity, and is considered to be a performance that is difficult to achieve with the isotropic nature of the resin. Further, the liquid crystalline polyester is characterized by having a so-called pearl luster due to its liquid crystallinity, and it has been extremely difficult to impart transparency. That is, in order to realize transparency, it is necessary to sacrifice the rigidity of the polymer skeleton, and if the rigidity is sacrificed, liquid crystallinity does not appear and excellent properties cannot be obtained. It was Also, the means for extremely reducing the crystallinity is
Although the present inventors have already tried using a solvent casting method to obtain a transparent film ("Plastics", Vol.41, No.9, pages 22 to 25), so-called pearls are easily obtained under high temperature. There is a problem that it becomes glossy and becomes opaque. That is, it was extremely difficult to develop heat resistance under high temperature conditions while maintaining transparency.

[0003]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the problem of stably obtaining excellent transparency while taking advantage of the excellent characteristics of liquid crystalline polyester resin. As a result, by heat-treating an extremely low crystallinity film under specific conditions, a film or sheet that does not lose its transparency even in a heated atmosphere without losing the original properties of the liquid crystalline polyester resin with high crystallinity The present invention has been completed and the present invention has been completed.
That is, the present invention is a liquid crystal polyester resin having a crystallinity of 30
Is a method for producing a transparent liquid crystalline polyester resin film or sheet having a haze value of 30% or less, which is characterized by heat-treating a film or sheet molded to have a haze value of 30% or less. . Formula (1) Ta <Tcc (° C) (however, Ta: heat treatment temperature (° C), Tcc: cold crystallization temperature of resin (° C measured by a differential thermal analysis method based on JIS K7121 at a heating rate of 10 ° C / min) )) Hereinafter, the structure of the present invention will be described in detail.

The liquid crystalline polyester used in the present invention is a type having a mesogen in the polymer main chain, that is, a main chain type liquid crystal polymer, from the viewpoint of the structure. Generally speaking, mesogen is a skeleton structure having rigidity that contributes to the development of liquid crystallinity, for example, a biphenylene skeleton, a skeleton having at least two benzene rings in a linear form such as a phenylbenzoate skeleton, And their nuclear substitutes, cyclic alkylenes, heterocycles, straight-chain fatty acids having a double bond, and the like. The liquid crystalline polyester resin used in the present invention has molecular orientation in a molten state and exhibits optical anisotropy. In the molecular orientation in this case, the molecules are arranged as a whole in the long axis direction of the molecule and the parallel direction thereof, and this axis and the inclination of the molecule do not necessarily have to match. The anisotropy observation in the molten state can be performed by a conventional polarization inspection method using a crossed polarizer. More specifically, the confirmation of the anisotropic molten phase was performed using a Leitz polarization microscope,
z The molten sample placed on the hot stage should be
It can be carried out by observing at double magnification. The polymers of the present invention, when examined between crossed polarisers, transmit polarized light and exhibit optical anisotropy, even in the melt stationary state. This can be observed as an optical pattern peculiar to the liquid crystal phase in a certain temperature range when gradually heated. Also, a phase-specific diffraction pattern can be observed in X-ray diffraction. In thermal analysis, a differential scanning calorimeter is generally used to measure entropy change and transition temperature of various phase transitions.
Liquid crystalline polymers suitable for use in the present invention tend to be insoluble in common solvents and therefore unsuitable for solution processing. However, these polymers can be easily processed by conventional melt processing methods. The liquid crystalline polymer used in the present invention is preferably an aromatic polyester and an aromatic polyesteramide, and a preferable example is also an aromatic polyester and / or a polyester partially containing the aromatic polyesteramide in the same molecular chain. Particularly preferably, aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine,
A liquid crystalline aromatic polyester and a liquid crystalline aromatic polyesteramide having at least one compound selected from the group of aromatic diamines as a constituent component. More specifically, 1) a polyester mainly composed of one or more aromatic hydroxycarboxylic acids and derivatives thereof 2) mainly a) one or more aromatic hydroxycarboxylic acids and derivatives thereof and b) Polyester consisting of one or more of aromatic dicarboxylic acids, alicyclic dicarboxylic acids and their derivatives and c) at least one or more of aromatic diols, alicyclic diols, aliphatic diols and their derivatives 3) Mainly a) one or more aromatic hydroxycarboxylic acids and their derivatives, and b) one or more aromatic hydroxyamines, aromatic diamines and their derivatives, and c) aromatic dicarboxylic acids and fats. Polyesteramide consisting of one or more of cyclic dicarboxylic acids and their derivatives 4) Mainly a) aromatic hydroxycarboxylic acids and And one or more kinds of derivatives thereof and b) one or more kinds of aromatic hydroxyamines, aromatic diamines and derivatives thereof and c) one kind of aromatic dicarboxylic acids, alicyclic dicarboxylic acids and derivatives thereof or Examples thereof include polyester amides consisting 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. For example, it is possible to use a monofunctional monomer, or to increase the carboxylic acid excess or the alcohol excess in order to break the molar balance between the acid and the alcohol, but the examples are not limited to these.
Preferred examples of the specific compound constituting the liquid crystalline polyester of the present invention include 2,6-naphthalenedicarboxylic acid and 2,6-
Naphthalene compounds such as dihydroxynaphthalene, 1,4-dihydroxynaphthalene and 6-hydroxy-2-naphthoic acid, 4,4′-diphenyldicarboxylic acid, biphenyl compounds such as 4,4′-dihydroxybiphenyl, p-hydroxybenzoic acid, Para-position-substituted benzene compounds such as terephthalic acid, hydroquinone, p-aminophenol and p-phenylenediamine, and their nucleus-substituted benzene compounds (substituents are selected from chlorine, bromine, methyl, phenyl, 1-phenylethyl), Meta-substituted benzene compounds such as isophthalic acid and resorcin. A preferred example of the specific compound is 2,6-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,
Naphthalene compounds such as 6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene and 6-hydroxy-2-naphthoic acid, biphenyl compounds such as 4,4′-diphenyldicarboxylic acid and 4,4′-dihydroxybiphenyl, the following general formula ( Compound represented by I), (II) or (III):

[0005]

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(However, X: a group selected from alkylene (C _{1 to} C ₄ ), alkylidene, -O-, -SO-, -SO _2- , -S-, -CO-, Y :-( CH ₂ ). _n- (n = 1 to 4), -O (CH ₂ ) _n O- (n = 1 to 4) selected group) The liquid crystalline polyester used in the present invention is the same as the above-mentioned constituent components. In addition, a polyalkylene terephthalate which does not partially show an anisotropic melt phase in the same molecular chain may be contained. In this case, the alkyl group has 2 to 4 carbon atoms.
Among the above-mentioned components, those containing one or more compounds selected from a naphthalene compound, a biphenyl compound and a para-substituted benzene compound as essential components are more preferable examples. Among the para-substituted benzene compounds, p-hydroxybenzoic acid, methylhydroquinone and 1-phenylethylhydroquinone are particularly preferred examples. Specific examples of compounds having an ester-forming functional group as a constituent and specific examples of polyesters forming an anisotropic melt phase which are preferable for use in the present invention are described in JP-B-63-36633. There is. The above aromatic polyesters and polyester amides also include
When dissolved in pentafluorophenol at a concentration of 0.1% by weight at 60 ° C, at least about 1.0 dl / g, for example about 1.0
An inherent viscosity (IV) of -10.0 dl / g is generally indicated.

The liquid crystalline polyester used in the present invention is
Although any polyester may be used as long as it exhibits liquid crystallinity, it preferably has a skeleton represented by the following formula (2). Formula (2) (-O-Ph-CO-) _m (-O-Nh-CO-) _n (however, Ph; 1,4-phenylene, Nh; 2,6-naphthalene) Furthermore, preferably liquid crystal polyester resin Is the formula
It has a skeleton represented by (2), and m + n in the formula is 50% or more of the total number of repeating units of the polymer, and the proportion of m is 40% or more of the total of m + n. It is a thing. Here, n may be 0. More preferably, m + n in the formula is 80% or more of the total number of repeating units of the polymer, and the proportion of m is m + n.
It is characterized by being 60% or more of the total of n. As for the monomer component constituting the skeleton of the liquid crystalline polyester resin, the one having less constituent components has higher order and the physical properties and various behaviors can be stably obtained, as compared with the multi-component system. On the other hand, if it is a single component, that is, a homopolymer, its rigidity is too high,
It has high crystallinity, and it is quite difficult to dissolve it in a solvent.
Therefore, the two-component system as described above is preferable in order to obtain physical properties as high as possible and easy to handle. In addition to the skeleton represented by the formula (2), aromatic hydroxycarboxylic acids such as hydroxydiphenylcarboxylic acid, diols such as aromatic diol and aliphatic diol, amines, amino alcohols and the corresponding aromatic compounds. Examples thereof include dicarboxylic acids such as dicarboxylic acids and aliphatic dicarboxylic acids.

In the present invention, to prepare a film or sheet formed by adjusting the crystallinity to a low level using a liquid crystalline polyester resin, the liquid crystalline polyester resin is previously dissolved in a solvent and the solvent is volatilized. It is preferable to use a method such as There are T-die method and inflation method which are usually used as a method for producing a film or sheet, but it is difficult to obtain a transparent liquid crystalline polyester resin film or sheet by these methods. Liquid crystalline polyesters are extremely sparingly soluble, but examples of suitable solvents include halogenated phenols such as pentafluorophenol, 3,5-bis (trifluoromethyl) phenol, orthochlorophenol, and the like or other And a mixture with a polar solvent. Further, since it is difficult to obtain the surface smoothness of the solvent cast film as it is, the edge of the film or the sheet is fixed or tension is applied until the solvent volatilization is completed to improve the surface smoothness. You should put it. For example, a film having a smooth surface can be obtained by a simple method such as fixing the end portion of the cast film before the solvent is completely volatilized and further volatilizing the solvent. When the liquid crystal polyester has a low isotropic transition point, a film or sheet may be obtained in which the crystallinity is adjusted to a low degree by rapidly cooling from the isotropic state. The low degree of crystallinity here generally means an amorphous state,
The crystallinity may be low as long as it guarantees transparency. A specific low degree of crystallinity corresponds to 30% or less.

A film formed by adjusting to a low crystallinity,
The sheet is heat treated at a temperature selected to satisfy the following formula (1). This is carried out by a method of immersing the film or sheet in a heating medium having a predetermined temperature such as hot water, a method of charging in a dryer at a predetermined temperature, a method of blowing warm air, a method of radiant heat such as infrared rays, and the like. Formula (1) Ta <Tcc (° C) (however, Ta: heat treatment temperature (° C), Tcc: cold crystallization temperature of resin (° C measured by a differential thermal analysis method based on JIS K7121 at a heating rate of 10 ° C / min) )) When the heat treatment temperature is higher than Tcc (° C.), rapid crystallization proceeds and the film or sheet becomes cloudy, which is not preferable. Further, if the heat treatment temperature is low, aging is required for an extremely long time, which is not preferable in terms of productivity, and the heat treatment temperature is preferably 50 ° C. or higher. The time required for the heat treatment varies depending on the composition of the liquid crystal polyester, for example, the content of hydroxybenzoic acid residues, the heat treatment temperature and the thickness of the film or sheet, but is generally about 5 minutes to 12 hours. The lower the heat treatment temperature or the thicker the film or sheet, the longer the heat treatment time. Also, the above formula (2)
In the case of the liquid crystalline polyester resin represented by, the higher the composition of either the hydroxybenzoic acid residue or the hydroxynaphthoic acid residue, that is, the closer the order is to a single component, the shorter the heat treatment time. The film or sheet is
Even if heating is performed at a higher temperature after heat treatment at a temperature selected so as to satisfy the formula (1), the decrease in transparency is small and the transparency is maintained stable. The transparent film and the sheet have a haze value of 30% or less when defined in a preferable range from the transparency, 180
It is practically desirable that the film has a haze value of 30% or less even if it is heat-treated at ° C. According to the present invention, it is possible to provide such a film or sheet. Incidentally, other thermoplastic resins and inorganic fillers may be supplementarily added and used in the composition of the present invention depending on the purpose within a range not impairing the effects of the present invention.

[0010]

As described above, the highly crystalline transparent film or sheet made of the liquid crystalline polyester resin obtained by the present invention is a low crystallinity film or sheet obtained by solvent casting or the like within a specific temperature range. The crystallinity is increased to the extent that the liquid crystalline polyester originally has by heat treatment without impairing the transparency, and has the following excellent effects. 1) High heat resistance of the resin, transparency does not decrease even under high temperature conditions of about 150 ° C, haze value of 30% or less is maintained, and the original liquid crystal polyester has excellent gas barrier properties and heat shrinkage resistance. Suitable for packaging materials for range cooking. 2) Since it imparts transparency without impairing mechanical properties, it can be used as a window glass protective film or the like. 3) Since it is transparent and has excellent mechanical properties, it is resistant to laser light and is excellent for various optical communication devices, especially the second harmonic generation device.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
The physical property evaluation methods and the like in the examples are as follows. (1) Melting point of liquid crystalline polyester resin, cold crystallization temperature, glass transition temperature Based on JIS K7121, liquid crystalline polyester resin pellets obtained by the method of Production Example are heated to a temperature of 10 by differential thermal analysis (DSC). It was measured at ° C / min. (2) Haze value A film or sheet was cut out and measured according to JIS K7105. (3) Surface smoothness The surface roughness Rz value (μm) of the film and sheet after the heat treatment was measured by a contour measuring instrument manufactured by Kosaka Laboratory Ltd. The smaller the Rz value, the smoother the surface. (4) Crystallinity After milling the film and sheet into fine particles of 60-mesh pass with a mill, freeze-grind them and use a tableting machine to obtain a diameter of 10 m / m and a thickness of 2 m / m.
The tablets of X-ray measurement equipment RAD-rB (Rigaku Denki Co., Ltd.) were used, and Cu-Kα = 1.5418A was used as the radiation source.
The measurement was performed in the diffraction angle range of 2θ = 5 ° -90 °. The crystallinity was calculated with reference to Ruland's report *. * ； LEAlexander, "X-Ray Diffraction Methods in Po
lymer Science ", JohnWiley & Sons. Inc., New York
(1973) (5) Oxygen permeability A film or sheet was cut out and measured according to JIS K7126. (6) How to make a transparent film with extremely low crystallinity Pellets of liquid crystalline polyester are dissolved in pentafluorophenol at about 80-100 ° C. After dissolution, the solution is allowed to cool, and when the temperature has dropped to around room temperature, chloroform is gradually added dropwise with stirring to bring the mixing ratio by weight to pentafluorophenol / chloroform = about 3/7. Next, the insoluble component is removed by filtering with a glass filter. The obtained polymer solution is poured into a flat Petri dish placed on a mercury plate, and a film is prepared in a desiccator adjusted to 27 ° C. After the film is formed, fix the end with a rubber band on the top of the beaker and volatilize the solvent to create a film with a smooth surface. The prepared film is subjected to Soxhlet extraction with acetone and vacuum dried at 80 ° C. (7) Evaluation of Heating of Low-Crystallinity Film and Evaluation of Transparency of Film After Heating Using a digital hot plate manufactured by Iuchi Co., Ltd., the film was treated under the predetermined temperature conditions shown in Table 1. The film was pressed with a glass plate during processing.

Production Example 1 (Synthesis of Polymer A) 275 parts by weight of acetoxybenzoic acid, acetoxynaphthoic acid
126 parts by weight and 0.01 part by weight of potassium acetate were charged into a reactor equipped with a stirrer and a distillation tube, respectively, and after sufficiently substituting with nitrogen, the temperature was raised to 150 ° C. under normal pressure and stirring was started.
Further, the temperature was gradually raised, and acetic acid produced as a by-product was distilled off. When the temperature reached 300 ° C, gradually reduce the pressure in the reactor and continue stirring at a pressure of 5 torr for 1 hour to obtain an intrinsic viscosity.
A liquid crystal polymer A of 7.0 was obtained. The polymer was subsequently pelletized. Production Example 2 (Synthesis of Polymer B) 178 parts by weight of acetoxybenzoic acid, acetoxynaphthoic acid
Charge 15 parts by weight, 75 parts by weight of diacetoxybiphenyl, 32 parts by weight of terephthalic acid, 0.01 part by weight of potassium acetate into a reactor equipped with a stirrer and a distillation tube, and after sufficiently replacing with nitrogen, up to 150 ° C under normal pressure. The temperature was raised and stirring was started.
Further, the temperature was gradually raised, and acetic acid produced as a by-product was distilled off. When the temperature reached 340 ℃, gradually reduce the pressure in the reactor and continue stirring at a pressure of 5 torr for 1 hour to obtain an intrinsic viscosity.
A liquid crystal polymer B of 6.2 was obtained. The polymer was subsequently pelletized. Examples 1 and 2 Using the polymers obtained in the above production examples, films were prepared and the above-mentioned properties were evaluated. The results are shown in Table 1. The film thickness of each polymer is 15μ for A and 17 for B.
It was μ. Example 3 A film was prepared in the same manner as in Example 1 except that the film was prepared by fixing the end of the film with a rubber band on the top of the beaker and applying no tension when the film was prepared. The results are shown in Table 1. Comparative Examples 1 and 2 The above physical properties were evaluated by changing the heat treatment conditions of the polymer films obtained by the above Production Examples. The results are shown in Table 1. Comparative Examples 3 and 4 (Method for producing T-die film) The polymer pellets obtained by the above-mentioned production example were rapidly cooled with a T-die type extruder of Labo Plastomill manufactured by Toyo Seiki Co., Ltd. to produce a 20μ film. The above physical properties were measured. The results are shown in Table 1. The temperature conditions of the T-die type extruder were as follows: A polymer in the cylinder at 330 ° C, T die at 290 ° C, B polymer in the cylinder at 370 ° C, and T die at 350 ° C. Further, Comparative Example 3 is heat treated, and Comparative Example 4 is not heat treated.

[0013]

[Table 1]

Claims (6)

[Claims] 1. A liquid crystal polyester resin having a crystallinity of 30.
% Of the film or sheet is heat-treated at a temperature satisfying the following formula (1), a method for producing a transparent liquid crystalline polyester resin film or sheet having a haze value of 30% or less. Formula (1) Ta <Tcc (° C) (however, Ta: heat treatment temperature (° C), Tcc: cold crystallization temperature of resin (° C measured by a differential thermal analysis method based on JIS K7121 at a heating rate of 10 ° C / min) )) 2. A liquid crystal polyester resin having a crystallinity of 30.
%, The crystallinity is adjusted to 30% or less by dissolving the liquid crystalline polyester resin in a solvent in advance, and volatilizing the solvent when producing a sheet, which is molded. The method for producing a liquid crystalline polyester resin film or sheet according to claim 1. 3. The end of the film or sheet is fixed or tensioned until the evaporation of the solvent is completed,
The method for producing a liquid crystalline polyester resin film or sheet according to claim 2, wherein the surface smoothness is increased. 4. The liquid crystalline polyester resin mainly has a skeleton represented by the following formula (2), wherein m + n is 50% or more of the total number of repeating units of the polymer, and
The method for producing a liquid crystalline polyester resin film or sheet according to any one of claims 1 to 3, wherein the proportion of m is 40% or more of the total of m + n. Formula (2) (-O-Ph-CO-) _m (-O-Nh-CO-) _n (however, Ph; 1,4-phenylene, Nh; 2,6-naphthalene) 5. The formula (2) wherein m + n is 80% or more of the total number of repeating units of the polymer, and the proportion of m is 60% or more of the total of m + n. 4. The method for producing a liquid crystalline polyester resin film or sheet according to 4. 6. A transparent liquid crystalline polyester resin film or sheet having a haze value of 30% or less, which is produced by the production method according to any one of claims 1 to 5.