JPH0976336A - Production of polyester bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyester bottle excellent in ultraviolet cut-off properties and reduced in shrinkage with the elapse of time. SOLUTION: A perform composed of polyester consisting of 1-5mol% of an ethylene-2, 6-naphthalate unit and 99-95mol% of an ethylene terephthalate unit is heated at temp. higher than 110 deg.C and lower than (low temp. crystallizing temp. -10 deg.C) and subjected to blow stretching molding in a blow mold of which the inner surface temp. is set to 60-90 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester bottle which is excellent in blocking ultraviolet rays and has a small shrinkage over time.

[0002]

2. Description of the Related Art Conventionally, a polyester bottle made of a polyester resin represented by polyethylene terephthalate (hereinafter sometimes simply referred to as PET) has excellent transparency, surface gloss, impact resistance, rigidity and gas barrier property. Utilizing its characteristics, it is widely used as a container for various foods.

[0003]

However, polyethylene terephthalate has an insufficient ultraviolet ray blocking property for long-term packaging of brewed liquor and edible oil, and is relatively shrunk over time, that is, during storage and transportation in the summer. There has been a problem that a phenomenon in which the content capacity is reduced with the passage of a long time is observed.

The present invention solves the above problems and provides a method for producing a polyester bottle which is excellent in ultraviolet ray blocking property and has a small shrinkage over time.

[0005]

SUMMARY OF THE INVENTION The present invention provides an ethylene-
A preform composed of a polyester containing 1 to 5 mol% of 2,6-naphthalate units and 99 to 95 mol% of ethylene terephthalate units was prepared at a temperature higher than 110 ° C. and at a temperature (low temperature crystallization temperature −10 ° C.) or lower. Heat
It is a method for producing a polyester bottle, which comprises performing blow stretch molding in a blow molding mold having a mold inner surface temperature of 60 to 90 ° C.

In the present invention, 1 to 5 mol%, preferably 1 to 3 mol%, of ethylene-2,6-naphthalate unit is necessary relative to the total amount of ethylene-2,6-naphthalate unit and ethylene terephthalate unit. To be done.

1 ethylene-2,6-naphthalate unit
If it is less than mol%, the ultraviolet ray blocking property is insufficient, and it is 5 mol%.
If it exceeds the above range, the effect of improving the ultraviolet blocking property reaches a ceiling, and the transparency of the blow stretch-molded polyester bottle deteriorates.

The polyester in the present invention includes a polyester having ethylene-2,6-naphthalate as a main constituent unit (hereinafter sometimes referred to as PEN) and a polyester having ethylene terephthalate as a main constituent unit (hereinafter sometimes referred to as PET). It is obtained by melt-mixing and.

The PEN and PET before melt-mixing may be those obtained by copolymerizing components other than the respective main constitutional units in an amount of 5 mol% or less.

The polyester of the present invention contains ethylene-2,6-naphthalate units and ethylene terephthalate units in an amount of 1 to 5 mol%, preferably 1 to 3 mol% of ethylene-2,6-naphthalate units. It can also be obtained by copolymerizing so that

The polyester of the present invention thus obtained has an intrinsic viscosity of 0.5 to 1.0, preferably 0.6.
It is in the range of 0.9, and a preform can be obtained by a usual injection molding method.

In the present invention, a preform is obtained at a temperature higher than 110 ° C. (low temperature crystallization temperature-
It is necessary to heat to a temperature of 10 ° C.) or lower.

When the temperature is 110 ° C. or lower, the shrinkage rate with time becomes larger than 0.3%, while the low temperature crystallization temperature is −10.
When the temperature is higher than 0 ° C, the preform is whitened due to crystallization and softened, and it becomes difficult to perform blow molding with high accuracy.

In the present invention, in order to realize a very small shrinkage with time and obtain a transparent polyester bottle, it is necessary to carry out blow stretch molding in a blow molding mold having a mold inner surface temperature of 60 to 90 ° C.

When the mold inner surface temperature is lower than 60 ° C., the shrinkage factor with time becomes larger than 0.3%, while when the mold inner surface temperature exceeds 90 ° C., the blow molded polyester bottle is blow molded. The above range is necessary because thermal deformation is likely to occur when taking out from the mold.

Furthermore, the preform is heated at a temperature higher than 110 ° C., which is higher than before, and blow-molded in a blow-molding mold having an inner mold surface temperature of 60 to 90 ° C. Since the preform wall is easily stretched, not only a polyester bottle that is well fit to the blow mold but also faithful to the mold can be obtained, but at the same time as the blow stretch molding, the preform wall is attached to a separate handle installed in the blow mold. There is also an effect that it is easy to perform so-called outsert molding, which is to wind and attach.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the method of measuring physical properties used is as follows.

1) Intrinsic viscosity A 50/50 mixed solvent of phenol / tetrachloroethane was used for measurement at 30 ° C.

2) UV blocking property A sample was cut out from the body of the bottle and manufactured by Hitachi Ltd. 2
The light transmittance was measured in the ultraviolet wavelength region using a 28 type spectrophotometer, and the 0 portion was taken as the cutoff wavelength.

3) Preform temperature: The preform divided in half is heated in a closed state, and immediately before blow stretching, the outer surface of the preform and the open inner surface are measured with an infrared radiation thermometer. It measured and calculated | required the average value of both.

4) Shrinkage with time A polyester bottle after blow stretching is subjected to 20 ° C. and 60% R
After storing at H for 24 hours, measure the full-injection volume before use (use water at 20 ° C), and then store at 40 ° C, 60% RH for 7 days, The amount of decrease in the full-injection volume due to the treatment was expressed as a percentage with respect to the full-injection volume before the treatment and used as the time-dependent shrinkage rate.

5) Low temperature crystallization temperature (Tcc) The temperature was raised from room temperature at 10 ° C./min, and the exothermic peak temperature due to crystallization was measured.

6) Haze A sample was cut out from the body of the bottle and measured with a haze meter.

[0024]

【Example】

[Experimental Examples 1 to 6] Polyethylene terephthalate having an intrinsic viscosity of 0.84 and polyethylene-2 having an intrinsic viscosity of 0.64,
After drying the 6-naphthalate chips with hot air at 170 ° C. for 3 hours, the polyethylene-2,6-naphthalate content was reduced to 0.
Both are mixed within a range of up to 7 mol%, melt-blended at a cylinder set temperature of 280 ° C. using a TEX30C twin-screw extruder manufactured by Nippon Steel Co., Ltd., and then rapidly cooled after discharge to give an intrinsic viscosity of 0.68. ˜0.74 of the blended chips of Experimental Examples 1 to 6 were obtained.

This blended chip was dried with hot air at 170 ° C. for 3 hours, and then it was weighed with an IS-90B injection molding machine manufactured by Toshiba Machine Co., Ltd., having a weight of 62 g, an outer diameter of the body part of 33 mm, a wall thickness of 3.5 mm and a total length of 155 mm. I got a reform.

This bottomed preform was heated at 105 ° C. for 120
The mold surface temperature is 7 after heating to ℃ and mounting a separate handle in the mold.
In a blow mold at 0 ° C, it is stretched in the axial direction by a stretching rod and is stretched in the circumferential direction by applying an internal pressure of 27 kg / cm2. The outer diameter of the body is 105 mm, the total height is 300 mm, and the wall thickness of the body is 0.2. A bottle with a handle of 0.4 mm and an internal capacity of 1.8 liters was obtained.

Table 1 shows the results of measuring the ultraviolet blocking property, the time-dependent shrinkage ratio, and the haze of these bottles with handles.

[0028]

[Table 1] As shown in Table 1, in the case of Experimental Example 1 which was heated at 120 ° C., the preform of only polyethylene terephthalate could not be whitened and molded due to thermal crystallization.
Molding is possible with Experimental Example 2 at ℃ and low temperature, but UV blocking property is 3
It is not sufficient to cut off below 10 nm, and the shrinkage rate with time is 0.36
% And more than 0.3%.

Polyethylene-2,6-naphthalate 1
In Experimental Examples 3 to 5 in which both are mixed in a range of 5 mol%, the ultraviolet blocking property is improved to 360 to 370 nm or less,
The aging shrinkage rate is also 0.22 to 0.26%, which is excellent at 0.3% or less. Further, in Experimental Examples 3 to 5, the preform heating temperature was 105 ° C, which was lower than that of Experimental Example 2 at a low temperature. The winding of the preform wall was also good.

Polyethylene-2,6-naphthalate 7
In Experimental Example 6 in which both of them were mixed so as to be mol%, the haze was as large as 2.3 and the transparency was poor.

[Experimental Examples 7 to 11] Next, an intrinsic viscosity of 0.84
Of polyethylene terephthalate and polyethylene-2,6-naphthalate with an intrinsic viscosity of 0.64
After drying with hot air at 70 ° C for 3 hours, polyethylene-2,6
-Mixing both so that the naphthalate content is 3 mol%,
Using a TEX30C twin-screw extruder manufactured by Japan Steel Works, Ltd., melt blending was performed at a cylinder setting temperature of 280 ° C., and then the mixture was discharged and then rapidly cooled to obtain chips of Experimental Examples 7 to 12 having an intrinsic viscosity of 0.7.

This blended chip was dried with hot air at 170 ° C. for 3 hours, and then it was weighed with an IS-90B injection molding machine manufactured by Toshiba Machine Co., Ltd., having a weight of 62 g, a body outer diameter of 33 mm, a wall thickness of 3.5 mm, and a total length of 155 mm. I got a reform.

This bottomed preform was heated at 105 ° C. for 113 seconds.
℃, 123 ℃, and attached a separate handle in the mold,
In a blow mold having a mold surface temperature of 70 ° C., heated to 123 ° C., in a blow mold having a mold surface temperature of 55 to 95 ° C., axially stretched with a stretching rod, and an internal pressure of 27 kg / cm 2 was applied to form a circle. Circumferentially stretched body outer diameter 105 mm, total height 30
0 mm, body thickness 0.2 to 0.4 mm, internal capacity 1.8
A liter bottle with a handle was obtained.

Table 2 shows the results of measuring the ultraviolet blocking property, haze, and time-dependent shrinkage of these bottles with handles.

[0035]

[Table 2] As shown in Table 2, even in the preform having the same polyethylene-2,6-naphthalate content of 3 mol%, in Experimental Example 7 in which the preform heating temperature was 105 ° C., the aging shrinkage rate was as large as 0.38 and the preform for the handle was large. The wrapping around the wall was not perfect.

Preform heating temperature is 113 to 123 ° C.
In Experimental Examples 8 and 9 molded in a blow molding mold having a mold surface temperature of 70 ° C., the UV blocking property was improved to 370 nm or less, and the shrinkage ratio with time was 0.20 to 0.24%, 0.3. %, And in Experimental Examples 8 and 9, the winding of the preform wall around the handle was better than in Experimental Example 7 in which the preform heating temperature was as low as 105 ° C.

However, the preform heating temperature is 123 ° C.
However, the experimental example 10 using the blow molding die having the mold surface temperature of 55 ° C. and the low temperature has a large shrinkage ratio of 0.40, and the experimental example 11 using the blow molding die having the mold surface temperature of 95 ° C. and the high temperature.
Had a large thermal deformation when the bottle was taken out from the blow mold.

[0038]

INDUSTRIAL APPLICABILITY According to the present invention, a preform made of a polyester containing 1 to 5 mol% of ethylene-2,6-naphthalate units and 99 to 95 mol% of ethylene terephthalate units is used at a temperature higher than 110 ° C. (Temperature of -10 ° C) or lower, and the temperature of the inner surface of the mold is 60 to 9
Since it is a method for producing a polyester bottle, which comprises performing blow stretch molding in a blow molding mold at 0 ° C.,
A polyester bottle having excellent ultraviolet blocking properties, small shrinkage over time, and high transparency can be obtained, and when the handle is attached, the preform wall is wrapped around the handle well.

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Claims (1)

[Claims] 1. 1 to 5 mol% of ethylene-2,6-naphthalate units and 99 of ethylene terephthalate units.
A preform made of polyester containing 95 to 95 mol% was heated at a temperature higher than 110 ° C (low temperature crystallization temperature-10
(° C) or lower, and blow stretch-molding in a blow molding mold having a mold inner surface temperature of 60 to 90C.