JPH0939183A - Multilayered polyester sheet and its molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet which is free from the defects of a conventional PET(polyethylene terephthalate) sheet, and has excellent properties such as the ease of winding at the time of forming a film, secondary working of the sheet into a container and heat resistance under high temperature and high humidity. SOLUTION: This multilayered polyester sheet consists of a blended resin composition of 45-80 pts.wt. PEN resin with a limiting viscosity of 0.6-0.9 and 20-55 pts.wt. PEN resin with a limiting viscosity of 0.4-0.7 for the skin layer of the sheet, and PET resin with a limiting viscosity of 0.6-0.9 for the core layer. The weight ratio of the skin layer to, the core layer is 10:90-40:60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer polyester sheet and a molded article made of the same. More specifically, the present invention relates to a polyester sheet having a multi-layer structure, which is transparent and can efficiently obtain a container having excellent dimensional stability in a high-temperature and high-humidity atmosphere, and a molded article made of the same.

[0002]

2. Description of the Related Art Polyesters, especially polyethylene terephthalate (hereinafter referred to as PET), are excellent in mechanical properties, heat resistance, chemical resistance, dimensional stability and the like.
Widely used as film and plastic. Recently, molded products made from PET sheets as raw materials can be easily molded and have good transparency, gloss, and gas barrier properties, so attempts to use them as containers for packaging various products have been made. Has been done.

However, these packaging containers are unstable under high temperature and high humidity as compared with conventional containers made of vinyl chloride, and it is necessary to improve this point. The packaging container made of the above-mentioned sheet made of PET deforms when left in a high humidity atmosphere for a long time even at a temperature below the glass transition temperature. For example, a blister case for household appliances for export is often found in the cabin of a ship during transportation, which is relatively high temperature (60 ° C) and humidity (90% RH).
It has a drawback that it is deformed when left inside for a long time, and its improvement has been desired.

On the other hand, polyethylene naphthalate (hereinafter P
PET), as already known in JP-A-47-34694 and JP-A-47-35087.
It is superior in heat resistance, weather resistance, and gas barrier property compared to, and is useful as a resin for producing fibers, films, and other molded articles.

JP-A-50-74652 discloses PET.
Although a polyester sheet with improved heat resistance and weather resistance has been proposed by blending PEN with PEN, this blend sheet has excellent heat resistance, but on the other hand, since the elongation decreases due to the incorporation of PEN, a sheet during film formation is used. There is a drawback that cracks are likely to occur when wound into a roll or when the sheet is secondarily processed.

[0006]

The object of the present invention is to eliminate the drawbacks of the sheet made of PET as described above, to have the same heat resistance under high temperature and high humidity as a vinyl chloride container and at the time of film formation. It is intended to provide a sheet having excellent windability, and excellent workability for secondary processing into containers and the like.

[0007]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors for such a purpose, as a result of providing reinforcing layers made of a mixture of PET resin and PEN resin on both sides of a main constituent layer made of PET resin, The present invention has been accomplished by finding that a multi-layered structure sheet having excellent heat resistance, improved sheet winding property, and improved secondary processability can be obtained.

That is, the present invention provides a multilayer polyester sheet, wherein the multilayer polyester sheet has 45 to 80 parts by weight of a PET resin having an intrinsic viscosity of 0.6 to 0.9 and an intrinsic viscosity of 0.4 to 0.7. What is claimed is: 1. A multilayer polyester sheet comprising a skin layer made of a resin composition containing 20 to 55 parts by weight of a PEN resin and a core layer made of a PET resin having an intrinsic viscosity of 0.6 to 0.9. The present invention relates to a multilayer polyester sheet having a layer weight ratio of 10:90 to 40:60 and a molded article made of the same.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The PET resin used in the present invention includes terephthalic acid or its ester-forming derivative (eg lower alkyl ester) and ethylene glycol or its ester-forming derivative (eg monocarboxylic acid ester ethylene oxide). And) are obtained by polycondensation of (1) and (3) by a known method, but may contain other copolymerization components within a range not impairing the original physical properties.

Examples of such a copolymerizable component include aromatic dicarboxylic acids such as isophthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic rings such as 1,4-cyclohexanedicarboxylic acid. Group dicarboxylic acids, diethylene glycol, 1,4-butanediol, neopentyl glycol, diols such as 1,4-cyclohexanedimethanol, and polyalkylene glycols such as polyethylene glycol and polytetraethylene oxide glycol. The amount of these copolymer components is usually 10 mol% or less, preferably 5 mol%.
It is the following.

The PEN resin used in the present invention is 2,6
-Product obtained by polycondensing naphthalenedicarboxylic acid or its ester-forming derivative (for example, lower alkyl ester) and ethylene glycol or its ester-forming derivative (for example, monocarboxylic acid ester ethylene oxide) by a known method However, other copolymerization components may be contained within a range that does not impair the original physical properties.

Examples of such a copolymerizable component include aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and 1,4.
An alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, diethylene glycol, 1,4-butanediol,
Examples include neopentyl glycol, diols such as 1,4-cyclohexanedimethanol, and polyalkylene glycols such as polyethylene glycol and polytetraethylene oxide glycol. The blending amount of these copolymerization components is usually 10 mol% or less, preferably 5 mol% or less.

In the present invention, the PET resin used for the skin layer of the multilayer polyester sheet has an intrinsic viscosity of 0.6 to 0.9, preferably 0.7 to 0.9. If the intrinsic viscosity is lower than 0.6, the thermoformed article becomes opaque because the crystallization rate of the obtained sheet is high. In addition, the production of PET resin having an intrinsic viscosity higher than 0.9 requires solid-state polymerization for a long time, which increases the production cost, which is not preferable.

In the present invention, the intrinsic viscosity of the PEN resin used for the skin layer of the multilayer polyester sheet is 0.4 to 0.7. When the intrinsic viscosity is lower than 0.4, the physical properties of the obtained sheet are remarkably deteriorated, and the production of a PEN resin having an intrinsic viscosity higher than 0.7 requires solid phase polymerization for a long time, resulting in high production cost. Is not preferable.

In the present invention, the resin composition used for the skin layer of the multilayer polyester sheet comprises 45 to 80 parts by weight of PET resin and 20 to 55 parts by weight of PEN resin. If the PEN resin content is less than 20 parts by weight, the heat resistance is not sufficiently improved, and if it exceeds 55 parts by weight, the difference in glass transition temperature (thermoforming temperature) from the core layer made of PET resin becomes large. Molding becomes difficult. Further, the PEN resin has a high weight composition ratio, resulting in a high cost.

As a method for obtaining the resin composition, any method can be adopted, but the PET resin and the PEN resin are kneaded under melting in advance by using a twin-screw kneader or the like and pelletized, and the sheet extrusion is carried out. At that time, it is preferable to add it to the extruder.

In the present invention, the intrinsic viscosity of the PET resin used for the core layer of the multilayer polyester sheet is 0.
It is 6-0.9, preferably 0.7-0.9. If the intrinsic viscosity is lower than 0.6, the thermoformed article becomes opaque because the crystallization rate of the obtained sheet is high. In addition, the production of PET resin having an intrinsic viscosity higher than 0.9 requires solid-state polymerization for a long time, which increases the production cost, which is not preferable.

The multi-layered polyester sheet of the present invention is a substantially unstretched sheet obtained by the usual film forming means of the above composition. The unstretched sheet of the present invention has a density of 1.34 g / cm ³ or less and is a substantially amorphous material. If the density of the sheet is greater than 1.34 g / cm ³ ,
It is not preferable because the transparency of the sheet is lowered and the impact strength of the sheet is lowered. Such an amorphous polyester sheet can be obtained by melt-mixing the composition of the present invention with an extruder and then discharging it from a general multi-layer extrusion die and quenching it with a cooling drum.

The multilayer polyester sheet of the present invention is a three-layer sheet having skin layers on both sides of a core layer. The weight ratio of the skin layer and the core layer is 10:90.
˜40: 60, preferably 20: 80-3
It is more preferably 0:70. When the weight ratio of the skin layer is less than 10% by weight, heat resistance is not sufficiently improved, and when it exceeds 40% by weight, PEN is used.
There is a drawback that the cost becomes high because the weight composition ratio of the resin becomes high.

The multilayer polyester sheet of the present invention is
As described above, it is a three-layer sheet having skin layers on both sides of the core layer, but if the ratio of the skin layers on both sides is extremely different, the unevenness of the sheet surface becomes remarkable during film formation, which is not preferable. Weight ratio is 40:60 to 50: 5
It is preferable to set the range to 0.

The molded article of the present invention is obtained by thermoforming the multilayer polyester sheet of the present invention. Thermoforming is performed by heating and softening the sheet and pressing it against the desired mold to remove air in the gap between the mold and the material and then adhering it to the mold by atmospheric pressure, or by forming the sheet into a mold by compressed air at atmospheric pressure or higher. It is possible to apply pressure molding for close contact and molding that uses vacuum and pressure together.

[0022]

INDUSTRIAL APPLICABILITY The multilayer polyester sheet of the present invention and the molded article made thereof have excellent transparency and heat resistance under high temperature and high humidity, and can be widely used as a substitute for a vinyl chloride container.

[0023]

The present invention will be described in more detail with reference to the following examples. In addition, the measurement of the main physical property value in an Example was performed by the method shown below. (1) Intrinsic viscosity (IV) 0.5 g of a sample was dissolved in 50 ml of a mixed solvent of 60% by weight of phenol and 40% by weight of 1,1,2,2-tetrachloroethane, and measured at 20 ° C. (2) Density (ρ) The sample was submerged in a density gradient tube made of carbon tetrachloride and n-heptane, and measured at 23 ° C. (3) Haze value Using a sheet piece having a thickness of 600 μm, JIS-K7105
It was measured according to. (4) Elongation Using a sheet piece having a thickness of 600 μm, JIS-K7113
The elongation at break (%) obtained by the measurement according to the above method was determined.

Examples 1 and 2 Comparative Example 1 80 parts by weight of PET resin of ethylene glycol and terephthalic acid having an intrinsic viscosity of 0.74, ethylene glycol and 2,6-naphthalenedicarboxylic acid having an intrinsic viscosity of 0.50. 20 parts by weight of PEN resin and screw diameter of 30
Melt blending was performed using a mm biaxial kneader to obtain a pelletized resin composition (A). Using a multilayer sheet extruder with an 80 cm wide T-die equipped with three single-screw extruders,
The resin composition (A) as a raw material was used as a skin layer, and the intrinsic viscosity of ethylene glycol and terephthalic acid was 0.1.
A PET resin of No. 85 was used in the ratio shown in Table 1 for the core layer to extrude a three-layer sheet having a thickness of 0.6 mm. Extruder cylinder temperature is 280 ℃, T die temperature is 290 ℃,
The temperature of the cooling roller was 30 ° C. The sheet was wound into a roll, but no breakage or cracking occurred. Table 1 shows the measurement results of the intrinsic viscosity, the density, the transparency (haze), and the elongation of the obtained sheet.

Further, the formability was evaluated by the preheating time width of the sheet required to obtain a molded product having good shapeability. As the evaluation criteria, the one having a preheating time width of 10 seconds or more was (◯) and the one having a preheating time width of 10 seconds or less was (x). The obtained molded product is treated at 60 ° C. and 9
It was left in a high temperature and high humidity atmosphere of 0% RH for a maximum of 250 hours, and the appearance was inspected for deformation and heat resistance was evaluated. The evaluation standard is that the shrinkage in the depth direction is less than 5% (○), 5%
The above was designated as (x). Table 2 shows the cracking occurrence state during film formation, the moldability, and the evaluation results of heat resistance.

Examples 3 and 4 Comparative Example 2 In Examples 1, 2 and Comparative Example 1, the resin composition used for the skin layer was made of ethylene glycol and terephthalic acid, respectively, and the intrinsic viscosity was 0.74. Parts and ethylene resin and 55 parts by weight of PEN resin composed of 2,6-naphthalenedicarboxylic acid having an intrinsic viscosity of 0.50 are blended using a twin-screw kneader having a screw diameter of 30 mm to prepare a resin composition (B). Made the same evaluation. The above results are summarized in Tables 1 and 2.

[0027]

[Table 1]

[0028]

[Table 2]

Comparative Example 3 In Example 1, the resin composition used for the skin layer had an intrinsic viscosity of ethylene glycol and terephthalic acid of 0.
80 parts by weight of PET resin of 50 and 20 parts by weight of PEN resin of ethylene glycol and 2,6-naphthalenedicarboxylic acid having an intrinsic viscosity of 0.50 were used, and the screw diameter was 30.
Resin composition (C) blended using a mm biaxial kneader
The test was conducted in the same manner as described in Example 1 except that

Comparative Example 4 In Example 1, the resin used for the core layer was P composed of ethylene glycol and terephthalic acid and having an intrinsic viscosity of 0.50.
The test was performed in the same manner as described in Example 1 except that the ET resin was used instead.

Comparative Example 5 In Example 1, the resin composition used for the skin layer had an intrinsic viscosity of 0.
The PET resin of 50 and the resin used for the core layer also have the same intrinsic viscosity of ethylene glycol and terephthalic acid of 0.
The test was performed in the same manner as described in Example 1 except that the PET resin was changed to 50.

Comparative Example 6 In Example 1, the resin composition used in the skin layer was the resin composition (B) described in Example 3, and the resin used in the core layer was also the resin composition described in Example 3. The test was conducted in the same manner as described in Example 1 except that (B) was used. Frequent cutting of the sheet occurred when the sheet was wound into a roll. The above results are summarized in Tables 3 and 4.

[0033]

[Table 3]

[0034]

[Table 4]

Claims (3)

[Claims] 1. A polyethylene terephthalate resin 45 to 80 parts by weight having an intrinsic viscosity of 0.6 to 0.9 and a polyethylene naphthalate resin 20 to 20 having an intrinsic viscosity of 0.4 to 0.7.
A multilayer polyester sheet comprising a skin layer made of a resin composition obtained from 55 parts by weight and a core layer made of a polyethylene terephthalate resin having an intrinsic viscosity of 0.6 to 0.9, the weight of the skin layer and the core layer. Ratio is 10: 9
A multi-layered polyester sheet having a thickness of 0 to 40:60. 2. The polyethylene naphthalate resin is 2,
6-naphthalenedicarboxylic acid as a dicarboxylic acid component,
The multilayer polyester sheet according to claim 1, which is an aromatic polyester containing ethylene glycol as a diol component. 3. A polyester molded product comprising the sheet according to claim 1.