JPH0829560B2 - Multi-layer film molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a multilayer film having excellent strength properties by a coextrusion method using a thermal liquid crystal polymer and a polyester resin.

[Conventional technology]

In recent years, there has been an increasing demand for materials having excellent rigidity, heat resistance and dimensional stability regardless of whether they are fibers, films or molded products. Although polyester is excellent in rigidity and has come to be used in a wide range of applications, some products are required to have higher heat resistance and dimensional stability. Therefore, liquid crystal polyester, which has excellent heat resistance, has recently attracted attention. The one that has received particular attention is JPSPCEd 14 (197
6), 2043 and Japanese Examined Patent Publication No. 56-18016, after WJ Jackson announced a thermo-liquid crystalline polymer composed of polyethylene terephthalate and acetoxybenzoic acid. However, these liquid crystal polymers show a high degree of orientation in the molten state, resulting in a large anisotropy in mechanical properties, and when the film is formed, only a film having excessive molecular orientation in the longitudinal direction can be obtained. The late film is easy to tear vertically,
It was difficult to obtain a film that could be put to practical use.

Various methods have been proposed to solve the problem of the molecular orientation of the film. For example, uniaxially molecularly oriented films are laminated so that the orientation directions intersect with each other to obtain a high-strength film that has no directionality in strength, or a blow-up ratio (diameter The ratio of the diameter of the expanded cylindrical resin and the diameter of the annular slit of the die) is increased to make the degree of orientation in the longitudinal direction and the degree of orientation in the lateral direction equal, and to make the strength in the longitudinal and lateral directions uniform.

However, in the former method, since the films are laminated, not only the thickness of the film is increased, but also the laminating step is required in addition to the film forming step, and the operation is complicated. Since the latter method has a large blow-up ratio, bubbles (balloon-shaped parts in which air etc. is enclosed inside the cylindrical film to enlarge the diameter) burst and could not be obtained. However, there are drawbacks such as large thickness unevenness of the film.

In order to improve the above-mentioned problems of the prior art, the inventors of the present invention first used a rotary die capable of rotating the thermal liquid crystal polymer in the die lip and the core in mutually opposite directions, and inflated them while rotating at a specific rotational speed. We proposed a molding method that obtains a film that is almost equally oriented in the vertical and horizontal directions and that has excellent tensile strength by forming a film.

[Problems to be solved by the invention]

However, although the film obtained by the above-mentioned method has excellent tensile strength, its tear strength (particularly, notched tear strength) has not been sufficiently improved due to lack of toughness.

[Means for solving problems]

The present inventors have conducted extensive studies to solve the problems of the above-mentioned thermal liquid crystal polymer film, and as a result, provided a rotary die capable of rotating the thermal liquid crystal polymer and the polyester resin in mutually opposite directions. Using an inflation molding device (see Japanese Examined Patent Publication No. 54-44307), the rotary die is coextruded while being rotated at a specific rotational speed to form a multilayer film, so that the tensile strength is approximately equal in both longitudinal and lateral directions. It was found that a film excellent in both tear strength and tear strength can be obtained, and the present invention has been completed.

That is, the gist of the present invention is a thermal liquid crystal having a die lip and a core which are arranged through an annular slit and at least one of which is rotatable, and a plurality of resin supply holes which are respectively opened in the annular slit. When using an inflation molding apparatus having a die having a resin resin flow channel and a polyester resin flow channel, when coextruding while supplying the thermal liquid crystal polymer and the polyester resin in a state of being adjacent to the annular slit. , The die lip and the core are rotated in mutually opposite directions, or only one of them is rotated, and at that time, the rotation index (S) shown by the following formula (1) and the number of rotations shown by the following formula (2). A method for forming a multilayer film is characterized in that (N) and the relationship of 1 ≦ N / S ≦ 10 are satisfied.

However, G: Width of annular slit (m / m) MFI: Melt flow index of thermal liquid crystal polymer at molding temperature (g / 10 minutes) t: Thickness of film (m / m) BUR: Blow-up ratio D: Annular slit Diameter (m / m) N = die lip rotation speed (rpm) + core rotation speed (r.
pm) (2) The thermo-liquid crystal polymer usable in the present invention may be any polymer as long as it can be melt-molded and exhibits liquid crystallinity when melted. For example, the following [I] to [V] Of polyester, that is, [I] a substantial structural unit, Consisting of.

Consisting of.

(In the formula, X represents a C _{1 to} C ₅ hydrocarbon group, a halogen atom, an alkoxy group or a phenoxy group), (Wherein Y represents O, S, SO ₂ , CO, an alkylene group, or an alkylidene group or none, and R _{1 to} R ₈ represent a hydrogen atom, a halogen atom or a hydrocarbon group).

(In the formula, X represents a C _{1 to} C ₅ hydrocarbon group, a halogen atom, an alkoxy group or a phenoxy group), (Wherein Y represents O, S, SO ₂ , CO, an alkylene group or an alkylidene group or none, and R _{1 to} R ₈ represent a hydrogen atom, a halogen atom or a hydrocarbon group).

[V] a dicarboxylic acid unit represented by the general formula (J), (In the formula, at least 60 mol% or more of R ¹ is a 1,4-phenylene group, and 40 mol% or less is C other than 1,4-phenylene group.
Divalent aromatic hydrocarbon group having ₆ -C _16, a divalent alicyclic divalent aliphatic hydrocarbon group or a hydrocarbon group C ₁ -C ₄₀ of C ₄ -C _20. However, the hydrogen atom of the benzene ring of the aromatic hydrocarbon group (including 1,4-phenylene group) is a halogen atom,
It may be substituted with a C ₁ -C ₄ alkyl group or an alkoxy group) Glycol unit represented by the general formula (K) —O—R ² —O— (K) (wherein R is ² is a C _{1 to} C ₂₀ divalent aliphatic hydrocarbon group or C
₄ divalent an alicyclic hydrocarbon group) and the general formula (L) oxycarboxylic acid represented by Yunitsuto the -C ₂₀ (In the formula, at least 60 mol% or more of R ³ is a 1,4-phenylene group, and 40 mol% or less is C other than 1,4-phenylene group.
₆ represents a divalent aromatic hydrocarbon group having -C _16. However, the hydrogen atom of the benzene ring of the aromatic hydrocarbon group (including the 1,4-phenylene group) may be substituted with a halogen atom, a C ₁ -C ₄ alkyl group or an alkoxy group) A part of the oxycarboxylic acid unit (L) is bonded to a part of the glycol unit (K) by an ether bond to give a compound of the general formula (M) (Wherein, R ² and R ³ R ² in (K) and (L) formula
And R ³ have the same meaning) and the content of the dicarboxylic acid unit (J) is 10 to 40 mol%.
And the ratio (L) / {(J) + (L)} of the oxycarboxylic acid unit (L) to the total amount of the dicarboxylic acid unit (J) and the oxycarboxylic acid unit (L) is 30 to 80 mol%. The ratio (L) / {(K) + (L)} of the oxycarboxylic acid unit (L) to the total amount of the glycol unit (K) and the oxycarboxylic acid unit (L) is 30 to 80 mol%, The ratio (M) / (K) of the unit (M) to the glycol unit (K) is 0 to 50 mol%, and 0.5 g / dl of a 1: 1 (weight ratio) mixture of phenol and tetrachloroethane Logarithmic viscosity ηinh measured at a concentration of 30 ℃
Is a copolyester having a ratio of 0.4 dl / g or more.

Etc.

Furthermore, in addition to the above, the following [VI] to [XX]
Of polyester, that is, [VI] the substantial structural unit (Wherein X and Y are -H,-C1, shown -Br or -CH _3, Z
Is Or )).

(Wherein X and Y are -H,-C1 or CH ₃ are shown) made of.

Consisting of.

Consisting of.

Consisting of.

Consisting of.

Consisting of.

Consisting of.

Consisting of.

(Wherein X is C1, Br, showing a CH ₃₎ That Is a.

Consisting of.

Consisting of.

Consisting of.

Consisting of.

Etc. Among them, those shown in [I] to [V] are preferably used.

In the present invention, polyethylene terephthalate and a hydroxybenzoic acid or acetoxybenzoic acid as a thermo-liquid crystalline polymer are contacted and reacted in the presence of an acylating agent and, if necessary, in the presence of a catalyst, to produce a copolymerized oligomer, Copolymerized polyesters obtained by polymerization are particularly preferred. Acetic anhydride is preferable as the acylating agent, and the amount thereof used is preferably 1.25 times or more that of hydroxybenzoic acid.

As the method for producing the copolymerized polyester, for example,
Polyethylene terephthalate and hydroxybenzoic acid are put together with an acylating agent in a reaction vessel, reacted at 130 to 250 ° C for 30 minutes or more, preferably 1 to 3 hours to obtain a copolymer oligomer, and then polymerized at 240 to 300 ° C to obtain a product. obtain.

Alternatively, polyethylene terephthalate and hydroxybenzoic acid are first reacted at 130 to 250 ° C for 30 minutes, preferably 1 to 3 hours to form a copolymer oligomer, and then an acylating agent is added.
It is also possible to carry out reaction at 100 to 250 ° C for 30 minutes or more for acylation, and then to polymerize at 240 to 300 ° C to obtain a product.

At this time, an appropriate catalyst can be used in each stage. A tin compound (for example,
Stannous acetate) is effective, and zinc compounds (eg, zinc acetate) are effective in the last polymerization reaction. The amount of catalyst added is 50-5000 ppm, preferably 200-20, relative to the polymer produced.
It is 00 ppm.

The raw material supply ratio of polyethylene terephthalate and hydroxybenzoic acid for producing the above copolymerized polyester is 5 to 35 mol% of polyethylene terephthalate,
A proportion of 95-65 mol% hydroxybenzoic acid is preferred.

On the other hand, examples of the polyester resin include polyethylene terephthalate and polybutylene terephthalate.
Particularly, polyethylene terephthalate having a molecular weight of 5,000 or more, preferably 10,000 to 50,000 is suitable.

Examples of polyethylene terephthalate include homopolymers of terephthalic acid and ethylene glycol, and copolymers of terephthalic acid and ethylene glycol with which a third component is further copolymerized, and any of these can be used.
The third component is usually an aromatic dicarboxylic acid such as isophthalic acid or naphthalenedicarboxylic acid, an oxycarboxylic acid such as p-hydroxybenzoic acid, an alkylene glycol such as propylene glycol, tetramethylene glycol or neopentyl glycol, or a polyethylene glycol. Polyalkylene glycol or the like is used. The proportion of the third component in the copolymer is usually 15 mol% or less.

In addition, the inflation film used in the present invention can be used as a molding apparatus in any of the types normally used, but the molding die is different from a normal circular die, and includes an annular die and a core. A rotating die is used which can rotate in mutually opposite directions. An example of the die used in the present invention is shown in FIG.

In FIG. 1, the die is a resin for supplying a thermo-liquid crystal polymer to a movable die lip (2), a core (3) and the annular slit (1) which can be rotated in opposite directions via the annular slit (1). It is composed of a flow channel (4) and a resin flow channel (5) for supplying a polyester resin.

In the present invention, the thermal liquid crystal polymer and the polyester resin are molded under specific molding conditions by using the inflation film molding apparatus equipped with the above rotary die.

First, in the inflation molding apparatus, the thermo-liquid crystal polymer passes through the resin flow path (4) and then the resin supply hole a shown in FIG.
Further, the polyester resin is supplied to the annular slit (1) through the resin flow path (5) in a state of being adjacent to each other through the resin supply holes b in FIG. In this state, the movable die lip (2) and the core (3) are respectively rotated in the opposite directions, that is, in the opposite directions as shown by the arrows shown in FIG. 3, from the a in the annular slit (1). The thermal liquid crystal polymer (1) and the polyester resin (2) are pulled in the direction of rotation of the movable die lip (2) and the core (3), and are obliquely laminated as shown in FIG. By doing so, the bonding area of the thermal liquid crystal polymer from a and the polyester resin from b is increased, a strong bond is obtained, and the rotational speeds of the movable die lip (2) and the core (3) are adjusted. It is possible to obtain an arbitrary multi-layer film having a different number of laminated layers. The movable die lip (2)
Since the core (3) is rotated in the opposite direction, the film extruded from the annular slit (1) is oriented in a combined direction of the extruding direction and the rotating direction, so that the film as a whole is oblique. A molecularly oriented film is obtained.
The degree of molecular orientation of the film is appropriately selected and determined by adjusting the rotational speeds of the movable die lip and the core, the extrusion speed of the resin, and the take-up speed.

In the present invention, in order to produce a film having both excellent tensile strength and tear strength, the rotational speed of the movable die lip (2) and the core (3) (the movable die lip and the core are simultaneously rotated in opposite directions). In this case, the sum of the rotation speeds of both, or the rotation speed when only one of them is rotated) is greater than or equal to the value of the rotation index (S) represented by the following formula (1) and is equal to 10 of the S value. Not more than twice, preferably S
The value is adjusted to 1.2 times to 10 times, more preferably 3 times to 10 times the S value.

Where S: rotation index G: width of annular slit (m / m) MFI: melt flow index (g / 10 min) of thermotropic liquid crystal polymer at molding temperature t: film thickness (m / m) BUR: blow-up ratio D: Diameter of annular slit (m / m).

The above rotation index (S) is an important index of the molding operation conditions of the present invention, and the fluidity (MFI) of the resin used, the film thickness (t), the blow-up ratio (BUR), the slit width of the die used ( G) and the slit diameter (D) define the required minimum total rotational speed (rpm).

When the number of rotations defined above is smaller than the number of rotations (S), the strength of the film obtained is not much different from that of the conventional molded article with a high blow-up ratio, and the effect of the present invention is sufficiently exhibited. I don't get it. Further, the rotation speed is the rotation index (S)
When it is more than 10 times, the thermal liquid crystal polymer and the polyester resin are excessively oriented in the lateral direction to deteriorate the physical properties, and there is a possibility that it may cause a slight problem in terms of durability of the molding apparatus, which is not preferable.

In addition, the extrusion speed and the take-up speed of the resin are the speeds that are usually used in inflation molding.

The molding temperature in the coextrusion inflation molding of the thermal liquid crystal polymer and the polyester resin is a melt flow index of the thermal liquid crystal polymer is 20 g / 10 minutes or less, preferably 0.02 to 20 g / 10 minutes, more preferably 0.2 to It is performed at a temperature in the range of 10 g / 10 minutes. If the melt flow index is larger than the above upper limit, the stability of bubbles becomes poor,
Not preferred.

In the present invention, the melt flow index means that the above-mentioned thermal liquid crystal polymer is
The value (g / 10 minutes) measured according to SK 6760.

The blow-up ratio used in the present invention is about 0.6 to 5, preferably about 1 to 3.

The diameter (D) of the die is selected according to the relationship between the blow-up ratio and the product width and is not particularly limited.

The thickness (t) of the film to be formed is 2
˜300 μ, preferably in the range of 5 to 200 μ, and the layer ratio of thermionic liquid crystal polymer / polyester resin is in the range of 10/90 to 90/10.

The multi-layer film thus obtained has the strength, rigidity and dimensional stability characteristic of the thermal liquid crystal polymer, and also has the toughness of the polyester resin and excellent strength characteristics.

〔Example〕

Example 1 (1) Method for producing thermal liquid crystal polymer Polyethylene terephthalate oligomer (ηinh = 0.1
1dl / g) 28.8Kg (150mol) and p-hydroxybenzoic acid 4
8.3 kg (350 mol), 40.8 kg of acetic anhydride and 22.32 kg of stannous acetate were charged into a polymerization tank equipped with a stirrer, and the amount of nitrogen was adjusted to 3
After purging twice, heat the polymerization tank to 150 ° C, stir for 1 hour, and distill acetic acid at 170 ° C for 1 hour, then 240 ° C.
It was stirred for 1 hour. The temperature of the polymerization tank was further raised to 275 ° C and the pressure was gradually reduced while distilling out acetic acid. After 30 minutes, 0.15 mmHg
And Next, the polymerization system was returned to normal pressure with N ₂ , 40.8 g of zinc acetate dihydrate was added, and the mixture was stirred under a vacuum of 0.18 mmHg for 6 hours to complete the polymerization, withdrawn from the polymerization tank and pelletized with a pelletizer. .

(2) Multi-layer film forming method A Dersar 65φ extruder manufactured by Modern Machinery Co., Ltd. has an annular slit diameter of 100 mmφ, an annular slit width (die lip gear tip) of 0.7 mm, and the die lip and the core are opposed to each other through the annular slit. The thermal liquid crystal polymer obtained in the above (1) and the polyethylene terephthalate having a molecular weight of 20,000 were used by using an inflation molding apparatus equipped with a spiral rotary die (a rotary die having a shape shown in FIG. 1) capable of rotating in a direction. The resin is supplied from the resin supply holes a and b to the annular slit (1) through the resin flow paths (4) and (5), respectively. Molding temperature of 280 ℃, MFI of thermionic polymer at molding temperature of 2.0g / 10min, blow-up ratio (called BUR) 1.2,
A 50 μ multilayer film was produced by coextrusion under the conditions of a draft ratio of 12 and the number of revolutions shown in Table 1. The obtained film was evaluated by the following measuring methods. The results are shown in Table 1.

Measurement method Tensile strength Cut the film into strips and use a tensile tester to measure 500m
Tensile strength was measured at m / min, and the strength at which the film was cut was read. Measured according to JIS Z1702 Elmendorf tear strength JIS P8116-1973.

Definition of draft rate ρ _m : Specific volume upon melting ρ _f : Specific volume of film G: Die gear tape t: Film thickness BUR: Blow ratio Example 2 The same as Example 1 except that the rotation speed was changed to the conditions shown in Table 1. The film was molded. The results are shown in Table 1.

Comparative Example 1 A film was formed in the same manner as in Example 1 except that the rotation was stopped. The results are shown in Table 1.

Comparative Example 2 This is a case where the extrusion of PET was stopped and the liquid crystal polymer alone was molded in Example 1. The results are shown in Table 1.
Shown in

Comparative Example 3 A film was formed in the same manner as in Example 1 except that the rotation speed was changed to the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example 4 A film was formed in the same manner as in Example 1 except that the rotation speed was changed to the conditions shown in Table 1. The results are shown in Table 1.

[Effects of the Invention] According to the present invention, the tear strength of the thermo-liquid crystal polymer,
A film excellent in tensile strength and the like can be obtained, and the application range of the liquid crystal polymer is further expanded.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a die used in the present invention, and FIGS. 2 and 3 are partial plan views showing the arrangement of two types of die channels in the die. In the figure, (1) is an annular slit, (2) is a die slip,
(3) is a core, (4) is a resin flow path for thermal liquid crystal polymer,
(5) shows the resin flow paths for polyester.

Claims (1)

[Claims] 1. A thermal liquid crystal polymer having a die lip and a core arranged through an annular slit, at least one of which is rotatable, and a plurality of resin supply holes each opening in the annular slit. Using an inflation molding device having a die having a resin flow path and a resin flow path of a polyester resin, the co-extrusion molding is performed while co-extruding while supplying the thermal liquid crystal polymer and the polyester resin in the state of being adjacent to the annular slit. And the core are rotated in mutually opposite directions, or only one of them is rotated, and at that time, the rotation index (S) shown by the following formula (1) and the rotation speed (N shown by the following formula (2) ) And 1 satisfy the relationship of 1 ≦ N / S ≦ 10. However, G: Width of annular slit (m / m) MFI: Melt flow index of thermal liquid crystal polymer at molding temperature (g / 10 minutes) t: Thickness of film (m / m) BUR: Blow-up ratio D: Annular slit Diameter (m / m) N = rotation speed of die lip (rpm) + rotation speed of core (r.
pm) ・ ・ ・ (2)