JPH0616835A - Polyethylene 2,6-naphthalate film - Google Patents

Abstract

PURPOSE:To obtain a polyethylene 2,6-naphthalate film of excellent recyclability by specifying the intrinsic viscosity and terminal carboxyl content after melting under specified conditions. CONSTITUTION:The film has an intrinsic viscosity equal to at least 80% of that before meLting when it is melted under the conditions of a temperature of 300-330 deg.C and a melting time of 5-30min, and a terminal carboxyl content of below 100eq/10<6>g after melting. The starting polyethylene 2,6-naphthalate is obtained by reacting 2,6-naphthalenedicarboxylic acid (ester) with ethylene glycol to obtain bis-beta-hydroxyethyl 2,6-naphthalate (oilgomer) and polycondensing it by heating in a vacuum.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyethylene-2,6-naphthalate film suitable for repeated recycling.

[0002]

2. Description of the Related Art Polyethylene-2,6-naphthalate film is produced by heating and melting a polyester composition as a raw material to form a film. Not 100%,
Some films will not be final products. By recycling and re-melting the film, which had to be discarded in the past, which had to be discarded, to form a film, the amount of expensive polyethylene naphthalate used was saved, greatly reducing the cost of the product and saving resources. Be useful. However, in the melt film-forming process of the polyethylene-2,6-naphthalate film, the melt temperature has to be set to a high temperature in terms of melt viscosity. Deterioration is remarkable. Also,
Since the formed film has a low intrinsic viscosity, when the film is melted again to form a film, it is necessary to increase the intrinsic viscosity again before melting. As a method of increasing the intrinsic viscosity again, it is usually adopted to make the film into fine chips and then to carry out solid phase polymerization. However, chip formation of this film is to melt the film once and form a strand with a kneading machine, etc., and finely cut this,
Here again, thermal degradation occurs. That is, the polymer undergoes a heat history of heating and melting at least twice before the polyethylene-2,6-naphthalate film is recycled and recycled, and at the final chip stage, the polymer structure is considerably deteriorated due to thermal deterioration. It is often destroyed and it becomes difficult to increase the intrinsic viscosity again by solid-state polymerization.

[0003]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that a polyethylene-2,6-naphthalate film satisfying a specific condition is suitable for repeated recycling. The present invention has been completed. That is, the gist of the present invention is that the melting temperature is 3
The intrinsic viscosity after melting is 80% or more of the value before melting under the conditions of 00 to 330 ° C. and the melting time of 5 to 30 minutes, and the amount of terminal carboxyl groups after melting is less than 100 equivalents / 10 ⁶ g. The present invention resides in a polyethylene-2,6-naphthalate film.

The present invention will be described in detail below. In the present invention, polyethylene-2,6-naphthalate means 2,6
-Naphthalenedicarboxylic acid or its ester, and polyester obtained by using ethylene glycol as a main starting material, but may contain other third component.
In this case, as the dicarboxylic acid component, for example, one type such as isophthalic acid, terephthalic acid, adipic acid, and sebacic acid can be used. As the glycol component, diethylene glycol, propylene glycol,
One or more of butanediol, 1.4-cyclohexanedimethanol and neopentyl glycol can be used. In any case, the polyethylene of the present invention
2,6-naphthalate is 80% of the repeating structural unit.
The above refers to a polyester having an ethylene-2.6-naphthalate unit.

Polyethylene-2,6-naphthalate, which is the raw material for the polyethylene-2,6-naphthalate film of the present invention, is polymerized with 2,6-naphthalenedicarboxylic acid or its ester and ethylene glycol as the main starting materials. It can be manufactured. That is, as the first step, 2,6-naphthalenedicarboxylic acid or its ester is first reacted with ethylene glycol to give bis-β-hydroxyethyl-2,6-
Naphthalate and / or its low polymer is obtained, which is further polycondensed as the second step.

The first step is usually accomplished by esterifying a dicarboxylic acid and a glycol, or by transesterifying a lower alkyl ester of a dicarboxylic acid and a glycol. In the present invention, any of these methods is used. Can also be adopted. The transesterification reaction is usually
2,6-Dimethylnaphthalate and an equimolar amount or more of ethylene glycol, preferably 1.5 to 3 times the molar amount of ethylene glycol are suitable catalysts such as Li, Na and M.
g, K, Ca, Zn, Sn, Pb, Ti, Mn, and the like metal carboxylic acid alcoholate, or in the presence of one or more kinds of hydrides, etc., in the range of 150-250 ℃ heating reaction Achieved by Particularly preferable as the catalyst is ethylene glycolate of these metals, which is produced by heating and dissolving acetates of Mg, Mn, and Ca in ethylene glycol.

The esterification reaction is usually carried out with 2,6-naphthalenedicarboxylic acid in an amount of 0.8 times or more, preferably,
It is achieved by reacting with 1.0 to 5 times the molar amount of ethylene glycol. In this case, unlike the transesterification reaction, a catalyst is not particularly required, but in order to increase the esterification reaction rate, a carboxylic acid alcoholate of a metal such as Na, Mg, Mn, Ge, or Sb, or a hydride or the like is used. One kind or two or more kinds can be added. Also in this case, particularly preferable to add is ethylene glycolate of these metals, which is formed from acetates of Mg, Mn and Ca and ethylene glycol.

In the second step following the first step, bis-β-hydroxyethyl-2,6-naphthalate and / or its low polymer obtained in the first step is heated under reduced pressure to carry out polycondensation to obtain a high polymer. A polymer is obtained. In this polymerization reaction, the system is gradually heated as the reaction progresses and the pressure is reduced, but the reaction temperature is usually 220 to 250 ° C. at the start of the reaction and finally 270 to 300 ° C. Is from atmospheric pressure at the start of the reaction to 5 mmHg or less, preferably 1 m
mHg or less. As the polymerization catalyst in the second step, antimony compounds, germanium compounds, titanium compounds and the like are used.

In order to obtain a raw material for a polyethylene-2,6-naphthalate film having excellent recyclability, the conditions of the second step are particularly preferable as the final temperature is 280 to 28.
The final pressure reduction degree is 0.5 mmHg or less at 5 ° C., and the polymerization reaction time is within 4 hours. Moreover, you may add a phosphorus compound as a heat stabilizer after completion | finish of a 1st process. As the phosphorus compound, phosphoric acid, phosphorous acid and their derivatives, for example, monomethyl phosphate, dimethyl phosphate, trimethyl phosphate, monoethyl phosphate, diethyl phosphate triethyl phosphate and the like can be used.

The polyethylene-2,6-naphthalate film of the present invention means at least a uniaxially oriented polyester film using such polyethylene-2,6-naphthalate as a starting material, and it is known as a method for producing the same. Any method can be used. For example, usually 295
After melt extruding into a sheet at 330 ° C, 40-80 ° C
After cooling and solidifying with an amorphous sheet, 130-170
It is possible to use a method in which longitudinal or transverse stretching is performed biaxially at a temperature of 4 to 20 times in the longitudinal or transverse direction sequentially or simultaneously, and then heat treatment is performed at 180 to 270 ° C. In the case of stretching in the machine direction and the transverse direction, each may be stretched in one stage, or may be stretched in multiple stages and a heat treatment section for orientation relaxation may be provided between the multi-stage stretches if necessary.

After biaxial stretching, it may be stretched again before being subjected to the heat treatment step of the next step. This re-stretching can be carried out in any of the longitudinal and lateral directions, or in both directions. Especially for high strength, after biaxial stretching, 140
A method of re-stretching 1.05 to 4.0 times in the machine and transverse directions at a temperature of ˜200 ° C. and then heat treating is often adopted. Particularly preferred production conditions for the film of the present invention are that the melting temperature at the time of melt extrusion into a sheet is 310 ° C. or lower, and
The residence time during melting is 15 minutes or less. Polyethylene
When reusing a 2,6-naphthalate film, the film is usually shredded and melted by heating to form chips. This chip may be used as it is for film formation, but if necessary, solid phase polymerization is carried out to increase the intrinsic viscosity of the chip. The solid phase polymerization is usually carried out under a nitrogen atmosphere or under reduced pressure under the conditions of a solid phase polymerization temperature of 240 to 260 ° C. and a solid phase polymerization time of 4 to 10 hours. In this case, the smaller the chip size, the higher the polymerization rate, but usually the volume is preferably 0.05 cm ³ or less.

The polyethylene-2,6-naphthalate film of the present invention has an intrinsic viscosity of 80% of the value before melting when melted under the conditions of a melting temperature of 300 to 330 ° C. and a melting time of 5 to 30 minutes. It is necessary that the amount of terminal carboxyl groups after melting is less than 100 equivalents / 10 ⁶ g. When the value of the intrinsic viscosity after melting under the above conditions is less than 80% of the value before melting, or when the amount of terminal carboxyl groups is 100 equivalents / 10 ⁶ g or more,
This film is shredded for recycling, and the intrinsic viscosity of chips when melted by heating and chipping is extremely low, and it is difficult to use it again for filming, and solid-phase polymerization is applied. However, the solid phase polymerization rate is extremely slow, which is not preferable.

The melting temperature of the film is 300 to 330.
After melting at a temperature of 5 ° C. for 5 to 30 minutes to form a lump with a volume of 0.05 cm ³ or less, under a nitrogen atmosphere, a solid phase polymerization temperature of 240 to 260 ° C. and a solid phase polymerization time of 4 to 8 hours It is preferable that the value of the intrinsic viscosity after the solid phase polymerization is 1.25 times or more the value before the solid phase polymerization. This value is 1.
If it is less than 25 times, the solid-phase polymerization time may be long when the chip is solid-phase polymerized after being shredded for recycling and being heat-melted into chips. The polyethylene-2,6-naphthalate film of the present invention may be added particles, if necessary, within a range not impairing the gist of the present invention, for example, inorganic particles such as kaolin, talc, calcium carbonate, silicon dioxide, aluminum oxide and cross-linking. It may contain organic particles such as polystyrene.

[0014]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The measuring methods and definitions of various physical properties and characteristics in the examples are as follows. In Examples and Comparative Examples, “part” means “part by weight”. (1) Intrinsic viscosity 1 g of a polymer was dissolved in 100 ml of a mixed solvent of phenol: tetrachloroethane = 1: 1 (weight ratio), and measured at 30 ° C. (2) Amount of terminal carboxyl groups HERBERT A. POHL (ANALYTICAL CHEMISTRY, 26 (10), 1614
(1954)). (3) Productivity of polyester film using recycled polyester chips The frequency of film breakage during film formation was evaluated according to the following criteria. ◯: Film rupture frequency was 1 time / 6 hours or less Δ: Film rupture frequency was 2 times / 6 to 5 times / 6 hours X: Film rupture frequency was 6 times / 6 hours or more

Example 1 (Production of Polyester) 100 parts of dimethyl naphthalene-2,6-dicarboxylate, 60 parts of ethylene glycol and 0.08 part of magnesium acetate tetrahydrate were placed in a reactor,
The temperature was raised by heating and the methanol was distilled off to carry out the transesterification reaction. It took 4 hours from the start of the reaction to raise the temperature to 225 ° C. to substantially end the transesterification reaction. Next, 0.2 part of the crosslinked polymer particles was added as an ethylene glycol slurry, and 0.03 part of phosphoric acid, 0.03 part of antimony trioxide, and 0.01 part of germanium oxide were further added, and the system temperature was set to 225 ° C. To 280 ° C,
At the same time, the polycondensation reaction was carried out by reducing the system pressure from atmospheric pressure to 0.3 mmHg.

The polycondensation reaction time is 3 hours and the intrinsic viscosity is 0.50.
Polyethylene-2,6-naphthalate of 2 was obtained. Then, the obtained polymer was subjected to solid-state polymerization at 240 ° C. for 5 hours in a nitrogen atmosphere to obtain polyethylene-2 having an intrinsic viscosity of 0.610.
6-naphthalate was obtained. (Production of polyester film)
A sheet was melt extruded at 95 ° C. from an extruder, and an amorphous sheet was obtained by using an electrostatic cooling method. The residence time of the polymer in the extruder at this time was 15 minutes. Then, it was stretched 2.6 times in the longitudinal direction at 140 ° C. and 4.2 times in the lateral direction with a tenter, and then re-longitudinal stretched at 160 ° C. in the longitudinal direction by 1.80 times, and then at 220 ° C. in the lateral direction by 1 time. ．Heat treatment is performed while making the width 10 times wider, and polyethylene with a thickness of 7 μm
A 2,6-naphthalate film was obtained. The intrinsic viscosity of the obtained film was 0.589.

(Production of Recycled Polyester Chips) The above film was shredded with a crusher, and the shredded film was melt-extruded at 330 ° C. into a strand form from an extruder to obtain chips. The residence time of the film in the extruder at this time was 30 minutes. The obtained chips had an intrinsic viscosity of 0.484 and a terminal carboxyl group content of 85 equivalents / 10 ⁶ g. (Solid-state polymerization of polyester chip) The obtained chip is
Since it was already a lump with a volume of 0.05 cm ³ or less,
Solid-state polymerization temperature 240 ° C., solid-state polymerization time 7 under nitrogen atmosphere
Solid phase polymerization was performed under the conditions of time. The value of the intrinsic viscosity of the chip after the solid-state polymerization was 0.601. (Production of polyester film using recycled polyester chips)

The solid-phase-polymerized chips were melt-extruded into a sheet form at 295 ° C. by an extruder, and an amorphous sheet was obtained by an electrostatic cooling method. The residence time of the polymer in the extruder at this time was 15 minutes. Then, the film was stretched 2.6 times in the machine direction at 140 ° C. and 4.2 times in the cross direction with a tenter, and then re-longitudinal stretched at 160 ° C. in the machine direction by 1.80 times, and then at 220 ° C. in the cross direction 1. Heat treatment was performed while the width was 10 times, and a polyethylene-2,6-naphthalate film having a thickness of 7 μm was obtained. The intrinsic viscosity of the obtained film was 0.585, which was comparable to the film when the polymer before regeneration was used. Further, no particular problem occurred during film formation.

Example 2 The polyethylene-2,6-naphthalate film before regeneration obtained in Example 1 was shredded by a crusher, and the shredded film was melted into a strand at 300 ° C. by an extruder. Extruded into chips. The residence time of the film in the extruder at this time was 10 minutes. The obtained chips had an intrinsic viscosity of 0.572 and a terminal carboxyl group content of 70 equivalents / 10 ⁶ g. The chips were further shredded with a crusher, and then melt-extruded into a sheet at 295 ° C. from the extruder as they were, to obtain a polyethylene-2,6-naphthalate film having a thickness of 7 μm in the same manner as in Example 1. The intrinsic viscosity of the obtained film was 0.560, which was comparable to the film when the polymer before regeneration was used. Further, no particular problem occurred during film formation.

Example 3 (Production of Polyester) Polyethylene-2,6-naphthalate was polymerized in the same manner as in Example 1 except that 0.02 part of manganese acetate tetrahydrate was used instead of magnesium acetate tetrahydrate. . The ultimate viscosity of the final polyester obtained after solid state polymerization was 0.611. (Production of Polyester Film) Using this polyester, a polyethylene-2,6-naphthalate film was produced in the same manner as in Example 1. The intrinsic viscosity of the obtained film was 0.593.

(Production of Recycled Polyester Chip) The above film was shredded with a crusher, and the shredded film was melt-extruded into a strand form at 330 ° C. from an extruder to obtain chips. The residence time of the film in the extruder at this time was 30 minutes. The obtained chips had an intrinsic viscosity of 0.524 and a terminal carboxyl group amount of 66 equivalents / 10 ⁶ g. (Solid-state polymerization of polyester chips) Since the obtained chips were already in the form of lumps with a volume of 0.05 cm ³ or less, solid-phase polymerization was performed under a nitrogen atmosphere at a solid-state polymerization temperature of 240 ° C. and a solid-state polymerization time of 4 hours. Polymerization was carried out. The value of the intrinsic viscosity of the chip after the solid phase polymerization was 0.603.

(Production of polyester film using recycled polyester chips)
Example 1 was melt-extruded into a sheet form from an extruder at 5 ° C.
A polyethylene-2,6-naphthalate film was produced in the same manner as in. The obtained film has an intrinsic viscosity of 0.5.
It was 89, which was comparable to the film when the polymer was used before reproduction. Further, no particular problem occurred during film formation.

Comparative Example 1 (Production of Polyester Film) The polymer obtained in Example 1 after solid phase polymerization of polyethylene-2,6-naphthalate before regeneration (intrinsic viscosity 0.610) was sheeted from an extruder at 340 ° C. It was melt-extruded into a sheet shape, and an amorphous sheet was obtained using an electrostatic applied cooling method. The residence time of the polymer in the extruder at this time was 5 minutes. Then, a polyethylene-2,6-naphthalate film was obtained in the same manner as in Example 1. The intrinsic viscosity of the obtained film was 0.529.

(Production of Recycled Polyester Chips) The obtained film was shredded with a crusher, and the shredded film was melt-extruded into a strand form at 300 ° C. from an extruder to obtain chips. The residence time of the film in the extruder at this time was 5 minutes. The obtained chips had an intrinsic viscosity of 0.396 and a terminal carboxyl group content of 109 equivalents / 10 ⁶ g.

(Solid-state Polymerization of Polyester Chip) The obtained chip was further shredded with a crusher to give a volume of 0.05 cm ³
After forming the following lumps, under a nitrogen atmosphere, the solid phase polymerization temperature 26
Solid phase polymerization was carried out under conditions of 0 ° C. and solid phase polymerization time. The intrinsic viscosity of the chip after 8 hours of solid-state polymerization was 0.492. Further, solid phase polymerization was continued for 8 hours under the same conditions, but the intrinsic viscosity of the chip was 0.493, which hardly increased. (Production of Polyester Film Using Recycled Polyester Chips) The solid-phase-polymerized chips were melt-extruded into a sheet at 295 ° C. from an extruder, and polyethylene-2,6-naphthalate film was prepared in the same manner as in Example 1. Attempts were made to produce it, but at the stage of melt extrusion into a sheet, the frequency of breakage of the sheet was remarkable and film formation was impossible.

Comparative Example 2 (Production of Polyester Film) The polyethylene-2,6-naphthalate unregenerated polymer obtained in Example 1 (intrinsic viscosity 0.610) was sheeted from an extruder at 335 ° C. It was melt-extruded into a sheet shape, and an amorphous sheet was obtained using an electrostatic applied cooling method. The residence time of the polymer in the extruder at this time was 8 minutes. Then, a polyethylene-2,6-naphthalate film was obtained in the same manner as in Example 1. The intrinsic viscosity of the obtained film was 0.557.

(Production of Recycled Polyester Chips) The above film was shredded with a crusher, and the shredded film was melt-extruded at 300 ° C. into a strand form from an extruder to obtain chips. The residence time of the film in the extruder at this time was 5 minutes. The obtained chips had an intrinsic viscosity of 0.460 and a terminal carboxyl group content of 103 equivalents / 10 ⁶ g. (Solid-state polymerization of polyester chips) The obtained chips are further shredded with a crusher to form a lump with a volume of 0.05 cm ³ or less, and then under a nitrogen atmosphere, a solid-state polymerization temperature of 260 ° C. and a solid-state polymerization time of 8 hours. Solid phase polymerization was carried out under the conditions of. Solid-state polymerization 8
The intrinsic viscosity of the chips after a lapse of time was 0.550. Further, solid phase polymerization was continued for 8 hours under the same conditions, but the intrinsic viscosity of the chip was 0.551, which hardly increased. (Production of Polyester Film Using Recycled Polyester Chips) The solid-phase-polymerized chips were melt-extruded into a sheet at 295 ° C. from an extruder, and polyethylene-2,6-naphthalate film was prepared in the same manner as in Example 1. Attempts were made to produce the film, but it was extremely difficult to produce the film because the frequency of breakage of the film was remarkable in the stretching step in the transverse direction.

Comparative Example 3 (Production of Polyester Film) The polyethylene-2,6-naphthalate pre-recycled polymer obtained in Example 3 (intrinsic viscosity 0.611) was sheeted at 340 ° C. from an extruder. It was melt-extruded into a sheet shape, and an amorphous sheet was obtained using an electrostatic applied cooling method. The residence time of the polymer in the extruder at this time was 5 minutes. Then, a polyethylene-2,6-naphthalate film was obtained in the same manner as in Example 1. The intrinsic viscosity of the obtained film was 0.539. (Production of Recycled Polyester Chip) The above film was shredded with a crusher, and the shredded film was melt-extruded into a strand form at 300 ° C. from an extruder to obtain chips. The residence time of the film in the extruder at this time was 5 minutes. The obtained chips had an intrinsic viscosity of 0.415.
And the amount of terminal carboxyl groups was 91 equivalents / 10 ⁶ g.

(Solid Phase Polymerization of Polyester Chip) The obtained chip was further shredded with a crusher to give a volume of 0.05 cm.
After lumps of ³ or less, solid phase polymerization temperature 2 under nitrogen atmosphere
Solid phase polymerization was performed under the conditions of 60 ° C. and solid phase polymerization time of 8 hours. The intrinsic viscosity of the chip after 8 hours of solid phase polymerization is 0.498.
Met. When solid phase polymerization was continued for 8 hours under the same conditions, the intrinsic viscosity of the chip rose to 0.602.

(Production of polyester film using recycled polyester chips)
Example 1 was melt-extruded into a sheet form from an extruder at 5 ° C.
An attempt was made to produce a polyethylene-2,6-naphthalate film in the same manner as in 1. However, the film sometimes broke in the transverse stretching step, and the productivity was insufficient. that's all,
The obtained results are summarized in Table 1 below.

[0031]

[Table 1]

[0032]

Industrial Applicability The film of the present invention has little deterioration in characteristics even when recycled, and has a high industrial value.

Claims (1)

[Claims] 1. A melting temperature of 300 to 330 ° C. and a melting time of 5
Polyethylene-2 characterized by having an intrinsic viscosity after melting of 80% or more of the value before melting under the condition of up to 30 minutes and having an amount of terminal carboxyl groups after melting of less than 100 equivalent / 10 ⁶ g. , 6-naphthalate film.