JPH0678094B2 - Heat-resistant bottle made of synthetic resin and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a synthetic resin heat-resistant bottle and a method for producing this bottle. More specifically, it has high heat resistance and gas barrier property. The present invention relates to a structure of a high polyethylene terephthalate resin bottle and a method for manufacturing the bottle.

[Conventional technology]

Polyethylene terephthalate resin (hereinafter simply referred to as PET) is used in a wide range of fields, especially in food container bottles, due to its excellent contents resistance, pollution resistance, gas barrier property, mechanical strength and transparency. Is used in large quantities.

Thus, PET bottles have many excellent properties, but they have low heat resistance and deform significantly when heated above 70 ° C.

For this reason, 120 ° C with food stored in the bottle
Such as retort foods that are left to heat for 30 minutes under the conditions
It has become extremely difficult to use it as a container for heat-treated food for sterilization, and it has been strongly desired to improve the heat resistance of this PET bottle.

Conventionally, as a means for improving the heat resistance of this PET bottle, PET has been used.
In order to increase the density of the blow mold for blow-molding the bottle-made body, the target heat-resistant temperature (if used in the retort food mentioned above
There is a method of blow molding a bottle by heating it to a temperature higher than 0 ° C).

[Problems to be solved by the invention]

However, in order to provide PET bottles with heat resistance of 120 ° C by this method, the mold temperature of the blow mold must be 140 ° C or higher. However, PET preforms are used for blow molding. When the heating temperature exceeds 120 ° C, thermal crystallization (whitening phenomenon) rapidly progresses, making blow molding into bottles impossible.

Also, considering the appropriate shapeability of the bottle, the mold temperature of the blow mold should be 15% higher than the resin heating temperature for blow molding.
It is necessary to set a temperature lower than ℃.

For this reason, the mold temperature of the blow mold is around 105 ° C for normal PET.
Biaxial stretch blow molding made upper limit for bottle molding,
It has been conventionally impossible to perform blow molding with the mold temperature of the blow mold being 140 ° C or higher.

The present invention was devised to eliminate the problems and dissatisfactions in the above-mentioned conventional examples, and provides a PET bottle body having excellent heat resistance and gas barrier properties, and a method for manufacturing this bottle body. It is intended.

[Means and Actions for Solving Problems]

Hereinafter, the present invention will be described with reference to the drawings showing an embodiment of the present invention.

The synthetic resin heat-resistant bottle 1 according to the present invention is made of a material obtained by mixing PET with nylon (hereinafter simply referred to as SM) which is synthesized with metaxylylenediamine and adipic acid as main components at a weight ratio of 10 to 30%. Axial stretch blow molding is performed.

The SM material mixed in the PET material is mixed in the sense that it complements the physical properties that are considered to be insufficient in the PET material, but if the mixing ratio of the SM material to the PET material is 10% or less, When the SM material does not sufficiently supplement the physical properties of the PET material, and when the mixing ratio of the SM material to the PET material is 30% or more, the excellent characteristics peculiar to the PET material are fully realized. There is a tendency that it cannot be put out.

That is, if the mixing ratio of the SM material is 10% or less, shrinkage occurs in the molded product when the mold temperature for molding is increased to improve heat resistance.

On the other hand, if the mixing ratio of the SM material is 30% or more, it becomes extremely difficult to control the wall thickness of the bottle during blow molding of the bottle.

For example, in the case of blow molding a bottle with PET material alone, if the mold temperature is raised to 105 ° C or higher, the shapeability is extremely deteriorated due to heat shrinkage and shrinkage occurs, but mixing SM material is necessary. As a result, the mixed SM material crystallizes and the entire molded product becomes hard, so even if the PET material tries to heat shrink,
The crystallized part of the material suppresses the heat shrinkage of this PET material, and it is possible to prevent shrinkage of the molded product, but when the mixing ratio of the SM material exceeds 30%, it is a primary molded product. Since the SM material is crystallized when the preform is heated, the preform blow-molded into the bottle becomes difficult to stretch, which makes it impossible to control the wall thickness distribution of the molded bottle.

Various methods are conceivable as the method for manufacturing the bottle 1 according to the present invention described above. Next, the most advantageous manufacturing method for sufficiently exerting the physical properties of the PET material will be described.

A preform, which is a primary molded product, is molded from a material in which SM is mixed with PET in an amount of 10 to 30% by weight.
In addition to heating to 140 ℃, the mold temperature of the blow mold is 100 to 200, which is 10 to 60 ℃ higher than the heating temperature of the preform.
The preform is biaxially stretch blow molded into a bottle while being heated to ℃.

That is, a mixing step A in which the SM material is mixed with the PET material in a weight ratio of 10 to 30%, a preform forming step B in which the PET material and the SM material are mixed, and the formed preform are The heating step C of heating to 90 to 140 ° C. and the blow molding step D of biaxially stretch blow molding the heated preform are sequentially performed.

It goes without saying that in each of the above-mentioned steps, the blow molding die for biaxial stretch blow molding is preheated to 100 to 200 ° C. at the same time as the heating step C.

The lower temperature limit for heating the preform was set to 90 ° C, which is the minimum temperature for achieving a smooth blow molding of the preform, as well as being above the Tg temperature of the PET and SM materials. This is because the maximum temperature is 14
The temperature is set to 0 ℃ because if the preform is heated to 140 ℃ or higher, the PET material will crystallize, making it impossible to perform stretch blow molding of the preform into the bottle 1. is there.

Similarly, the heating temperature of the blow mold is set to 100 to 200 ° C. in order to impart heat resistance to the bottle 1 to be stretch-blow molded, and the heating temperature of the blow mold is 100 ° C. or less. Therefore, it is impossible to impart sufficient heat resistance to the bottle body 1, and conversely, if the heating temperature of the blow mold is 200 ° C. or higher, the bottle body 1
This is because the stretch blow molding itself becomes difficult.

Further, the heating temperature of the preform is in the range of 90 to 140 ° C, preferably 110 to 130 ° C, and similarly, the mold temperature of the blow mold is in the range of 100 to 200 ° C. However, it is preferably in the range of 105 to 180 ° C.

The bottle 1 of the present invention thus formed is immersed in glycerin heated to 120 ° C. in a storage tank for 30 minutes without being capped and heated, and the bottle 1 is taken out from the glycerin. It was cooled with water and measured the change from before heating. The volume change rate of this bottle 1 was 0.5% or less,
From this, it was found that the bottle had sufficiently high heat resistance.

In addition, the heat resistance of this bottle 1 is SM for PET materials.
There was a tendency that the higher the mixing ratio of the materials, the better, and we were able to obtain the unexpected phenomenon that the shapeability was improved together with this improvement in heat resistance. It seems that the improvement and the improvement of the moldability are closely related to each other.

That is, as described above, crystallization of the SM material mixed in the PET material improves the shapeability, and the crystallized SM material improving the shapeability suppresses thermal contraction of the PET material. The heat resistance of the bottle body 1 as a molded product is improved.

〔Example〕

Next, an example of manufacturing the bottle 1 according to the present invention and an example of test results will be shown.

A preform is injection-molded with a mixed material in which a PET material dried to a moisture content of 0.005% or less and a SM material dried to a moisture content of 0.3% or less are mixed at a weight ratio of 20%, and this preform is 120 ° C. Using a blow mold heated to a mold temperature of 140 ° C., the bottle 1 was biaxially stretch blow molded at a blow molding time of 6.4 sec and a blow pressure of 36 kg / cm ² .

The molded bottle body 1 was semi-transparent with an ivory appearance and exhibited extremely good shapeability.

This bottle 1 was immersed in glycerin heated to 120 ° C for 30 minutes in the same manner as described above, and its heat resistance was tested. As a result, the rate of change in full-filled volume of bottle 1 was -0.48%. ， Exhibited extremely excellent heat resistance.

This bottle 1 was molded by changing the heating temperature of the preform, the blow molding time, and the blow pressure, while changing the heating temperature of the blow mold and the mixing ratio of the SM material to the PET material. Was tested, S
The heat resistance and shapeability tend to improve as the mixing ratio of M material increases, and the heat resistance tends to improve as the heating temperature of the blow mold increases.

Further, when the gas barrier property against oxygen of the molded bottle 1 was measured, it was found that the gas barrier property against oxygen was higher as the mixing ratio of the SM material was higher.

〔The invention's effect〕

As is clear from the above description, the present invention exhibits extremely high heat resistance, so that it is possible to use a PET bottle as a container for storing retort foods. Since the range of use could be greatly expanded and excellent shaping properties could be obtained, bottle molding could be successfully achieved and the number of defective products could be reduced. Since it can be manufactured by an existing molding device and molding operation, it exhibits many excellent effects such as its simple implementation.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a bottle according to the present invention. FIG. 2 is a block diagram showing an example of the manufacturing process of the present invention. DESCRIPTION OF SYMBOLS 1; Bottle, A; Mixing process, B; Preform molding process, C; Heating process, D; Blow molding process.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Ando 310 Minorita, Matsudo City, Chiba Yoshino Industry Co., Ltd. Chiba Plant (56) References JP-A-56-105936 (JP, A)

Claims (2)

[Claims] 1. A heat-resistant bottle made of synthetic resin biaxially stretch blow-molded from a material obtained by mixing polyethylene terephthalate resin with nylon synthesized mainly from metaxylylenediamine and adipic acid in a proportion of 10 to 30% by weight. 2. A preform, which is a primary molded product, is molded from a material in which a polyethylene terephthalate resin is mixed with nylon synthesized mainly from metaxylylenediamine and adipic acid in a proportion of 10 to 30%, and the preform is molded. 90 to
While heating to 140 ℃, the mold temperature of the blow mold is 10 ~ 60 ℃ higher than the heating temperature of the preform 100
A method for producing a synthetic resin heat-resistant bottle, wherein the preform is biaxially stretch blow-molded into a bottle while being heated to 200 ° C.