JPH044126A - Manufacture of film - Google Patents

Abstract

PURPOSE:To obtain a film of a liquid crystalline polymer which possesses well- balanced high power and high elasticity in a crosswise direction and high uniformity, by a method wherein a specific thermotropic liquid crystalline polymer is oriented biaxially by an inflation method. CONSTITUTION:A liquid crystalline polymer to be used follows a measurement method ASTIM D-648 and a difference between thermal deformation temperatures measured under loads of 18.6 kg/cm<2> and 4.6 kg/cm<2> is within a range of 15 deg.C. As the liquid crystalline polymer which falls under this category and capable of performing melting and molding, a matter, which is a copolymer, for example, of p-hydroxybenzoic acid and polyethylene terephthalate and having a mol ratio of 50/50-70/30, can be mentioned. Although the same is made into a film by an inflation method, at the time of extrusion of a molten material through an annular slit die, a tubular film is expanded by applying external force to the inside of the tubular film to be obtained and the film is oriented by applying draft to also a receiving direction of the film. Then a draw ratio in the direction meeting at right angles with the receiving direction is made normally at least two times, preferably at least three times.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a high-performance film having high strength, high modulus of elasticity, and gas barrier properties.

(Prior Art) A thermotropic liquid crystal polymer has a rigid molecular skeleton and forms an anisotropic melt in a molten state.

This is because it has a unique multilayered structure called a self-reinforcing structure, which easily orients itself due to shear stress during processing.

Even unfilled resin exhibits extremely high strength and modulus of elasticity. Therefore, since the beginning of the development of thermotropic liquid crystal polymers (hereinafter referred to as liquid crystal polymers), studies have been conducted to apply them to yarns with high strength and high elastic modulus in order to take advantage of their characteristics. In recent years, it has begun to be put into practical use mainly for injection molding applications.

Furthermore, if we take advantage of this property of strong yet easy molecular orientation, we can create a film with high strength.

It has been predicted and investigated that a high performance film with a high modulus of elasticity will be obtained. but.

There are several problems to be solved in order to obtain practical films of liquid crystal polymers.

For example, a liquid crystal polymer film obtained by the T-die method, which is a common film-forming method, is strongly oriented in the drawing direction and has high strength in this direction.

Although it exhibits a high modulus of elasticity, its strength in the direction perpendicular to the pulling direction is extremely low, and it easily tears along the pulling direction, making it unusable except for special purposes. moreover,
If you try to stretch it as a post-process to make it biaxially oriented, it will already be strongly oriented in the extruded direction, so the strength in the direction perpendicular to the take-up direction will be low, and when stretched in this direction, The film may be torn.

Further, since the stretching temperature is close to the melting point, strict temperature control is required, making stretching as a post-process extremely difficult.

As described above, since the T-die method cannot substantially biaxially stretch the film, it is not possible to obtain a film of practical use.

The inflated film method has been considered as a film-forming method to solve this problem, and some experiments have already been carried out, and although it is not yet practical, biaxially stretched films have been obtained. Regarding the structure of the film obtained here, 9 For example, JP-A No. 61-241317 discloses that the film accumulates in multiple layers in the thickness direction, and in each layer, the molecular chains form a zigzag structure depending on the degree of stress applied. There is.

The inflation method is considered to be the most suitable method for biaxially stretching liquid crystal polymers because it can be applied to resins with low melt strength and can be stretched after extrusion molding but before solidification. However, the reason why a practical film is still not obtained by this method is its non-uniformity. When the liquid crystal polymer is extruded through a slit die, it becomes uneven in thickness before it solidifies, making it impossible to obtain a uniform film. This thickness unevenness is clearly different from that caused by poor adjustment of the die slit width, and has a much smaller period (pitch) than those. This non-uniformity becomes more noticeable when the stretching ratio is high.

(Problems to be Solved by the Invention) The present invention is based on the idea that liquid crystal polymers are expected to be applied to high-performance films, and various studies have been conducted. The purpose of the present invention is to solve the problem of not being able to obtain a uniform film due to uneven thickness.

(Means for Solving the Problems) In order to obtain a biaxially stretched uniform liquid crystal polymer film, the present inventors extruded a liquid crystal polymer through a slit die, and by the time the liquid crystal polymer was cooled and solidified. As a result of intensive research to solve the problem of uneven thickness, we found that it is possible to make a film using the inflation method using a liquid crystal polymer that has small differences in heat distortion temperature measured under different loads.

It was discovered that a biaxially oriented film of a liquid crystal polymer with high uniformity and practical use can be obtained, leading to the present invention. That is, 9 the present invention is r18. GKg/c/ and 4. G A film nolil characterized by biaxially aligning a thermotropic liquid crystal polymer whose heat distortion temperature difference measured under a load of Kg/c/ is within 15°C by an inflation method.
Construction method. ” is the gist.

The liquid crystal polymer used in the present invention conforms to ASTM D-848
According to the measurement method of 18. GKg/Crt and 4.6
The difference in heat distortion temperature measured under a load of Kg/crI is 15
It is a liquid crystal polymer that is within °C. Liquid crystal polymers are so named because they exhibit a state intermediate between crystal and liquid in their molten state, but after molding and before solidification, some crystallization occurs with some crystalline portions forming.

The fact that the difference in heat distortion temperature under different loads is small means that the material can be handled as if it were not a product. It is more preferable that the difference in heat distortion temperature is within 10°C.

The liquid crystal polymer used in the present invention can be anything that falls into this category and can be melt-molded.
Specific examples of such liquid crystal polymers include
A copolymer of p-hydroxybenzoic acid and polyethylene terephthalate with a molar ratio of 50,150 to 70/30 (7) disclosed in JP-A-18016, JP-A-18016-
210127, essentially the following structural formula (
1) to (II1), and the molar ratio of each structural unit is substantially equal to (1) and (I1).
) and (II1) are 9515 to 5/95, a liquid crystal polymer disclosed in JP-A-62-174228, consisting essentially of structural units represented by the following structural formulas (II1) and (IV), The molar ratio of (■) and (IV) is 951
Liquid crystal poly-OC-Ar2-CO-(
II) -O-Ar3-CO-(II1) (In the formula, +Arl and Ar4 are trivalent aromatic groups.

Ar2 and Ar3 represent divalent aromatic groups. however.

The aromatic group may have a substituent. )Special Public Showa 5G-
In the case of the liquid crystal polymer disclosed in Publication No. 1801G, those having a random structure are particularly preferred in order to obtain a uniform film. Among these liquid crystal polymers, it is preferable that the heat distortion temperature measured under a load of 4.6 kg/c1/ is 150°C or higher because it can be applied to applications that require heat resistance. This is achieved by some of the aromatic liquid crystal polymers. Furthermore, since it has extremely high flame retardancy among wholly aromatic liquid crystal polymers, it is disclosed in JP-A-83-210127 and JP-A-82-
Even if a plurality of liquid crystal polymers used in 174222 are blended, or a part of liquid crystal polymers that are outside the scope of the present invention are blended, as long as the effects of the present invention are not impaired. can be used.

In the present invention, general-purpose resins such as polyethylene, polypropylene, polystyrene, polyamide, polybutylene terephthalate,
Engineering plastics such as polyethylene terephthalate, polycarbonate, polyparaphenylene sulfide, polyacetal, polyphenylene oxide, super engineering plastics such as polysulfone, polyarylate, polyetherketone, polyetheretherketone, and flame retardants, stabilizers, and viscosity adjusters as required. It does not matter if additives such as laxatives are added.

In addition, since liquid crystal polymers generally have a low apparent melt viscosity for film formation, it is better to have a high melt viscosity for the film formation process. It is preferable that the apparent melt viscosity measured at shear rate is 1000 poise or more.
, 2000-10000 poise is particularly preferred.

The thickness unevenness of the film as used in the present invention is clearly different from that caused by, for example, improper adjustment of the die slit width, and is observed along the film taking direction. And this thickness unevenness is 9, for example, JIS
According to 80801 (197G), set the cutoff value to 2.
．． The center line average roughness (Ra
).

In the present invention, film formation is carried out by the inflated film method, and in this case, it is possible to use equipment normally used for film formation of polyolefins and the like.

That is, in one aspect of the present invention, a tubular film is melt-extruded using an annular slit die. Regarding the extrusion direction of the film, in addition to the method of pulling the film upward from the annular slit die, it is also possible to take the film vertically (downward).
Since liquid crystal polymers generally have low melt viscosity, downward extrusion is preferred in this case. When extruding the melt through the annular slit die, an external force is applied from the inside of the resulting tubular film to expand the tubular film, and a draft is also applied in the direction of take-up of the tubular film to stretch the film. In order to obtain a film with high strength and high modulus of elasticity, the drawing direction of the tubular film and the stretching ratio in the direction perpendicular to the drawing direction are usually 2 times or more, preferably 3 times or more.

In addition, in order to obtain a biaxially oriented film with high strength and high elastic modulus, the stretching ratio in each direction must be 3 times or more, and the stretching ratio in the pulling direction must be perpendicular to the pulling direction. It is preferable that the ratio of the stretching ratio in the direction is 0.2 or more.

(Function) In the present invention, a uniform film can be obtained. It is thought that the reason why the thickness of the liquid crystal polymer film is uneven is that microcrystals that are generated at the same time as the liquid crystal polymer is extruded and cooled act as nuclei, causing the thickness unevenness. It is thought that the method using a liquid crystal polymer with a small temperature difference and low crystallinity allows a uniform film to be obtained because no microcrystals are generated.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

The method for measuring the characteristic values is as follows.

9 Nippon Steel Newly Manufactured Type J-100S after fully drying the resins A to H obtained by the method described below.

A test piece having a length of 5 inches, a width of 1/2 inch, and a thickness of 1/8 inch was molded using an injection molding machine according to the suitability conditions of each resin. Then, using these test pieces, ASTM
18.6Kg/cze and 4 according to D-648
Each measurement was made under a load of J Kg/c).

Center line average roughness (Ra) Cut out 20 samples of 30 mm x 30 mm from the film.

For each sample, a stylus-type surface roughness measuring device (5 made by Koita Institute) was used.
JIS B 0Ei01 (197
According to [1i), the center line average roughness is measured under the conditions of measurement length 10 mm + cutoff value 2.5111 m. This operation was performed once for each of the 20 samples, and the third value from the largest of the obtained centerline average roughness values was taken as the representative value (hereinafter this value will simply be referred to as centerline average roughness). .

25℃, 65% RH using an autograph manufactured by Kano JILD
The tensile strength of the film in the bowing direction and in the direction perpendicular to the bowing direction was measured at a tensile speed of 5 mm/win in an atmosphere of .

Using a high-performance flow tester, the polymer was discharged at the extrusion temperature used for film formation, and the discharge amount Q (ml
/5ec), the apparent melt viscosity η and the apparent shear rate γ are calculated from the following formula.

η=πr' P/ (8IQ) γ=40/(πr3) However, 1: nozzle length (Cm), r: nozzle radius (am), P: pressure when extruding from the nozzle (dyne/C ) For each sample, change the pressure P when extruding from the nozzle,
The relationship between apparent shear rate γ and apparent melt viscosity η is determined. The extrapolated value of the apparent melt viscosity when the apparent shear rate γ was 103 sec-' was taken as a representative value (hereinafter this value will simply be referred to as the apparent melt viscosity).

Determination of liquid crystallinity Using a Leltz polarizing microscope with a hot stage, determination was made based on whether or not polarized light under crossed Nicols was allowed to pass through when each resin was heated to the extrusion temperature for film formation.

Next, specific methods for producing and obtaining eight types of resins A to H used in the Examples and Comparative Examples shown below will be shown.

Resin A p-bitroxybenzoic acid residue unit (P)IB) / terephthalic acid residue unit (TPA) / ethylene glycol residue polymerized according to the method described in Example 1 of Japanese Patent Publication No. 511i-180111i A resin whose molar ratio of units (EC) is 607/40/40. 25 of this resin
Apparent melt viscosity at 0°C and 270°C is 9!5 boids, respectively.

635 poise, and exhibited liquid crystallinity at both temperatures. In addition, the heat distortion temperature is 64°C (+8.Ei K
g/crl load) and 75°C (4.6 Kg/an? load).

Resin B p-hydroxybenzoic acid residue unit (PHB) / terephthalic acid residue unit (TP
A)/ethylene glycol residue unit (EC) molar ratio is 707/3G/30. The apparent melt viscosity of this resin at 280° C. was 834 voids, and it exhibited liquid crystallinity at this temperature. In addition, the heat distortion temperature is 89℃ (18,8
Kg/c1/load) and 102°C (4.8 Kg/cj load).

p-Hydroxybenzoic acid residue unit (PUB)/terephthalic acid residue unit (TPA) polymerized according to the method described in Example 1 of JP-A-63-2G632.
/ ethylene glycol residue unit (EC) molar ratio is 80
//20/20 resin. 300℃ of this resin
and the apparent melt viscosity at 320°C is 833, respectively.
Poise.

727 poise, and exhibited liquid crystallinity at both temperatures. In addition, the heat distortion temperature is 180℃ (18.6Kg/
c/load) and 210°C (4.6 Kg/Ct/load).

Adhesive ■1 9,10-dihydro-9 polymerized according to the method described in JP-A-82-174228, Example 1
-oxa-10-(2',5'-dihydroxyphenyl)phosphaphenanthrene-10-oxide residue unit/
A resin in which the molar ratio of terephthalic acid residue units/p-hydroxybenzoic acid residue units is 25/25/75.

The apparent melt viscosity of this resin at 330°C and 350°C is 1430 poise and 1010 poise, respectively.

It exhibited liquid crystallinity at both temperatures. In addition, the heat distortion temperature is 18.0℃ (1B, lli Kg/Ct/load) s 1
The temperature was 90°C (4, (fKg/C♂ load).

11. The powders of Resin C and Resin R, which had been thoroughly dried under reduced pressure, were premixed at a weight ratio of 50,150, and extruded at a temperature of 3 using a twin-screw extruder Labo Plastomill 20R200 manufactured by Toyo Seiki Co., Ltd.
20℃, screw rotation speed BOrp, discharge amount 5 kg
The mixture was extruded into strands at a speed of 1/hr, cooled with water, and then cut into pellets.

The apparent melt viscosity of the obtained pellets at 330°C was 8
20 poise, and exhibited liquid crystallinity at this temperature. Also,
Heat deformation temperature is 164℃ (1BJ Kg/awl load),
The temperature was 173°C (4 JKg/ctl load).

Resin F Resin resin and polyarylate resin (
Powders of "U Polymer JU-100" manufactured by Unitika were premixed at a weight ratio of 70/30, and extruded using a twin screw extruder Labo Plastomill 2OR200 manufactured by Toyo Seiki Co., Ltd. at a temperature of 330°C and a screw rotation speed of GO rpm + Discharge amount 4.
It was extruded into strands at 8 kg/hr, cooled with water, and then cut into pellets. The pellets obtained had an apparent melt viscosity of 1720 poise at 330°C, and exhibited liquid crystallinity at this temperature. In addition, the heat distortion temperature is 17B'C (18,6
Kg/Ct/load) and 185°C (4.8 Kg/c♂ load).

Tree MW G Diphenyl (2,5-dihydroxyphenyl)phosphine oxyto/phenylhydroquinone/
Terephthalic acid and acetic anhydride in a molar ratio of 25/75/1
0G/200, and dimethyltin maleate was added as a catalyst at a ratio of 4 to 1 mole of polyester structural unit.
X 10-' moles added, nitrogen atmosphere.

Normal pressure, 2 hours at 150℃, 2 hours at 250℃, and 2 hours at 250℃.
The reaction was carried out at 80°C for 2 hours. Then start depressurizing.

The reaction was carried out by successively increasing the temperature, and finally the temperature was raised to 320° C. for melt polymerization for a total of 10 hours.

The apparent melt viscosity of the obtained resin at 320°C was 105
It had 0 poise and exhibited liquid crystallinity at this temperature.

In addition, the heat distortion temperature is 179℃ (18, [i Kg/c)
load).

The temperature was 199°C (4.6 kg/CI load).

Resin H Polyplastics' liquid crystal polyester "Vectra J"
A-950° The apparent melt viscosity of this resin at 300°C was 670 voids, and it exhibited liquid crystallinity at this temperature.

In addition, the heat distortion temperature is 190℃ (18.6Kg/-load)
, 230°C (4.8 kg/c/load).

Example 1 Liquid crystal polymer A was sufficiently dried under reduced pressure, and it was
m, extrude downward through an annular slit die with a slit width of 1.5 mm, press nitrogen into the hollow part of this tubular film to rapidly expand the diameter of the tubular film at about 30 m below the die, and cool it sufficiently. After that, it was passed through nip rolls so that the stretching ratio in both the direction of take-up and the direction perpendicular to this was 6 times, as shown in Table 1.

Example 2 A film was obtained using Resin B as the liquid crystal polymer in the same manner as in Example except for the extrusion temperature. The characteristic values of the obtained film are shown in Table 1 together with the extrusion temperature during film formation.

Comparative Example 1 A film was obtained in the same manner as in Example 1 except for the extrusion temperature using Resin C as the liquid crystal polymer. The characteristic values of the obtained film are shown in Table 1 together with the extrusion temperature during film formation.

Examples 3-5. Comparative Examples 2 and 3 Films with a folding width of 470 mta and a thickness of 40 μm were obtained using five types of resins D-H under the same conditions and method as in Example 1 except for the respective extrusion temperatures. The characteristic values of the injection molded products and films of each resin are shown in Table 2 together with the temperature during film formation. However, in Comparative Example 3, when an attempt was made to expand the tubular film extruded from the slit die, holes were easily formed in the film and the film could not be stretched in a direction substantially perpendicular to the take-up direction. This phenomenon was similarly observed even when the extrusion temperature was increased from 300°C to 330°C. Further, when the film extruded from the slit die was cooled as it was, minute irregularities were observed on the entire surface of the film. Note that the center line average roughness of this unstretched film was 2.63 μm.

Examples 6-9. Comparative Example 4 Using liquid crystal polymer A, the influence of conditions for forming an inflatable film was investigated. That is, the resin was sufficiently dried under reduced pressure at 250°C, and the diameter was 50 mm, and the slit width was 1.5 m.
The tubular film is extruded downward through an annular slit die, and nitrogen is forced into the hollow part of the tubular film to rapidly expand the diameter of the tubular film at about 30 mm below the die.After cooling it sufficiently, it is passed through nip rolls to a predetermined size. A film having a thickness of about 35 μm was obtained with a stretching ratio of . At this time, the direction in which the film was taken off and the stretching ratio in the direction perpendicular to this direction were controlled by the amount of nitrogen supplied per unit time, which was press-injected from the hollow part, the speed at which the film was taken off, and the cooling rate. In Example 8, the tubular film was rapidly expanded at about 5 mm below the die, and in Example 9, the extrusion temperature was 270''C.

The characteristic values of the obtained film are shown in Table 3.

In Comparative Example 4, the draw ratio in the take-off direction is significantly higher than that in the direction perpendicular to the take-off direction, so it is difficult to say that it is biaxially oriented, but as shown by the center line average roughness, the thickness unevenness A small film was obtained.

Examples 1O-12. Comparative Example 5 Using liquid crystal polymer D, the influence of conditions for forming a blown film was investigated. That is, the resin was sufficiently dried under reduced pressure at 330°C, and the diameter was 50 mm, and the slit width was 1.5 H.
The tubular film is extruded downward through an annular slit die, and nitrogen is forced into the hollow part of the tubular film to rapidly expand the diameter of the tubular film at about 30 mm below the die.After cooling it sufficiently, it is passed through nip rolls to a predetermined size. A film having a thickness of about 45 μm at a stretching ratio was obtained. At this time, the direction in which the film was taken off and the stretching ratio in the direction perpendicular to this direction were controlled by the amount of nitrogen supplied per unit time, which was press-injected from the hollow part, the speed at which the film was taken off, and the cooling rate. Note that in Example I2, the extrusion temperature was 350°C.

The characteristic values of the obtained film are shown in Table 4.

In Comparative Example 5, the draw ratio in the drawing direction is significantly higher than that in the direction perpendicular to the drawing direction, so it cannot be said that it is biaxially oriented, but as shown by the center line average roughness, the thickness A film with small unevenness was obtained.

Comparative Examples 6 to 9 Using liquid crystal polymer C, the influence of conditions for forming an blown silicone film was investigated. In other words, the resin was thoroughly dried under reduced pressure at 300°C with a diameter of 50 mm and a slit width of 1.5 m.
The tubular film is extruded downward through an annular slit die, and nitrogen is forced into the hollow part of the tubular film to rapidly expand the diameter of the tubular film at about 30 mm below the die.After cooling it sufficiently, it is passed through nip rolls to a predetermined size. A film with a thickness of about 45 μm was obtained at a stretching ratio of . At this time, the direction in which the film was taken off and the stretching ratio in the direction perpendicular to this direction were controlled by the amount of nitrogen supplied per unit time, which was press-injected from the hollow part, the speed at which the film was taken off, and the cooling rate. In Comparative Example 9, the extrusion temperature was 320°C. Table 5 shows the characteristic values of the obtained film.

*MD is the pulling direction, and TD is the pulling direction. (Effects of the invention) The present invention provides high strength and high elastic modulus that are well-balanced in the pulling direction and in the direction perpendicular to this. While having
Practical liquid crystal polymer films with high uniformity can now be obtained. Due to its excellent dimensional stability, chemical resistance, and gas barrier properties, polyethylene terephthalate film is currently used in printer ribbons, thermal transfer films, speaker diaphragms, magnetic tape, barrier films, etc. It is expected that it will be widely used in applications where titration cannot be performed directly.

Patent applicant: Unitika Co., Ltd.

Claims (1)

[Claims] 1) A thermotropic liquid crystal polymer whose heat distortion temperature difference measured under a load of 18.6 Kg/cm^2 and 4.6 Kg/cm^2 is within 15°C is produced by an inflation method. A method for producing a film characterized by axial orientation. 2) The method for producing a film according to claim 1), wherein the film is a thermotropic liquid crystal polymer having a heat distortion temperature of 150° C. or higher when measured under a load of 4.8 Kg/cm^2. 3) The method for producing a film according to claim 1), wherein the thermotropic liquid crystal polymer is a wholly aromatic liquid crystal polymer.