JPH028026A - Heat resistant hollow vessel - Google Patents

Abstract

PURPOSE:To obtain a heat resistant hollow vessel having a pearl-like surface gloss which has specific hot-water shrinkage factor by blow molding a composition in which the ratio of polyethylene terephthalate to methacrylic resin is specified. CONSTITUTION:Methacrylic resin to be used is mixed in a range of 1-20wt.% in polyethylene terephthalate resin. If it exceeds this range, its pearl-like surface gloss is scarcely generated, while if it exceeds 20wt.% or more, the mechanical properties of the obtained hollow vessel and particularly dropping impact strength is reduced. A preform is obtained by drying a composition composed of polyethylene terephthalate and methacrylic resin so that its water content is reduced to less than 0.01%, and then molding it by a normal injection or extrusion molding method. The vessel is obtained by blow molding the preform in a blowing mold heated to 120-190 deg.C, and its hot-water shrinkage factor is 3% or less.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a hollow container having a pearl-like surface gloss with excellent heat shrinkage resistance, and more specifically, a hollow container that enables high-temperature filling of fruit juice drinks, etc. It concerns containers.

[Prior Art] In recent years, plastic containers have come to be used as a substitute for glass containers.

Recently, polyethylene terephthalate has been developed with mechanical properties,
It has excellent chemical resistance, and has no effect on the human body due to lubricating agents such as polyvinyl chloride or residual monomers, and has a lower gas permeability for oxygen, carbon dioxide, etc. than polyethylene, polypropylene, etc., so it is suitable for foods and beverages. It has come to be used in large quantities for containers for products, cosmetics, etc.

[Problems to be Solved by the Invention] However, conventional hollow containers obtained by biaxially stretching and blowing preforms containing polyethylene terephthalate as a main component have low crystallinity and poor heat shrinkage resistance due to the use of low-temperature blow molds. Fruit juice drinks that require heat sterilization at high temperatures of 80 to 95 degrees Celsius must go through a cooling process before being filled, which means they are less workable. It has its drawbacks. For this reason, it is desired to manufacture containers with excellent heat shrinkage resistance, and as a method for improving the heat shrinkage resistance of such containers, the following methods are used: It has been proposed that heat treatment be applied at

In such a method, if the heat treatment temperature is low, such as 100 °C or less, or if the heat treatment time is not long enough to sufficiently relieve the residual internal stress of the preform even at a high temperature exceeding 100 °C, the heat treatment temperature is 80 °C or higher. It cannot withstand filling. In addition, if the heat treatment time is long enough to sufficiently relax the residual internal stress of the preform at a high temperature exceeding 100°C, high-temperature filling is possible but cloudy because the polyethylene terephthalate is crystallized. It has a poor appearance and has disadvantages in terms of decoration.

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted extensive research, and as a result of blow molding a resin composition in which a specific amount of methacrylic resin is blended with polyethylene terephthalate, the characteristics of polyethylene terephthalate can be improved. We have discovered that it is possible to obtain a heat-resistant hollow container that maintains properties such as chemical resistance and gas barrier properties, that allows filling of liquids at temperatures exceeding 80°C, and that also has a pearl-like surface gloss,
The present invention has been achieved.

That is, the present invention uses polyethylene terephthalate 80 to 99
This is a heat-resistant hollow container having a pearl-like surface gloss and a hot water shrinkage rate of 3% or less, which is obtained by blow molding a preform obtained from a polyethylene terephthalate resin composition consisting of a polyethylene terephthalate resin composition comprising 1% to 20% by weight of a methacrylic resin.

The polyethylene terephthalate used in the present invention is mainly composed of a terephthalic acid component and an ethylene glycol component, but a part of the terephthalic acid component is isophthalic acid, adipic acid, sebacic acid, naphthalene-1,4 - or - Dicarboxylic acids such as 2,6-dicarboxylic acid and diphenyl ether-4,4'-dicarboxylic acid, in which a portion of ethylene glycol is propylene glycol, butylene glycol, neopentyl glycol,
Copolymers substituted with glycol such as cyclohexane dimetatool and 2,2-bis(4-hydroxyphenyl)propane may also be used.

Polyethylene terephthalate can be obtained by ordinary polymerization methods such as polycondensation of terephthalic acid and ethylene glycol through transesterification or direct esterification. It is preferable to set it in the range of ~1.4. Here, it is also possible to increase the relatively low intrinsic viscosity by using a conventional solid phase polymerization method.

The intrinsic viscosity [η] of polyethylene terephthalate is 0.7
If a material with an intrinsic viscosity [y+] of 1.4 or more is used, the drop impact strength of the resulting container, especially at low temperatures, will be significantly reduced, which is undesirable.If a material with an intrinsic viscosity [y+] of 1.4 or more is used, the preform will be difficult to blow mold. When trying to obtain a hollow container, the molding processability becomes extremely difficult and the desired hollow container cannot be obtained.In addition, the intrinsic viscosity [η] is
It was determined from the solution viscosity measured at 25°C in a phenol/tetrachloroethane 50150 (weight ratio) solution.

The methacrylic resin used in the present invention may be a homopolymer of methyl methacrylate, a copolymer of 50 mol% or more of methyl methacrylate and another vinyl monomer, or a mixture of these polymers. Other vinyl-'0-Ex compounds to be copolymerized with methyl methacrylate include acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, acrylonitrile, methacrylonitrile, styrene, and α-methyl. Examples include styrene. Particularly preferred are homopolymers of methyl methacrylate or copolymers of methyl methacrylate and methyl acrylate or ethyl acrylate.

The methacrylic resin used in the present invention is 1 to 20% in the polyethylene terephthalate resin composition.
It is used in combination within the range of. If it deviates from this range, pearl-like surface gloss will be difficult to develop, and if the amount of methacrylic resin exceeds 2011i mass%, the mechanical properties of the resulting hollow container, especially the drop impact strength, will deteriorate. Therefore, the method for obtaining a polyethylene terephthalate composition consisting of polyethylene terephthalate and methacrylic resin is as follows:
Any method may be used, such as blending with chips after polyethylene terephthalate polymerization and extrusion, or blending in a hopper immediately before injection molding.

In addition, in the present invention, low-molecular substances may be added for the purpose of promoting crystallization and improving processability within a range that does not impair the purpose of the present invention, and fillers and reinforcing agents may be added to improve heat resistance to improve physical properties. There is no limit to the addition of antioxidants and the like, as well as colorants and the like.

The preform in the present invention is obtained by drying a composition comprising polyethylene terephthalate and a methacrylic resin until the water content becomes less than 0.01%, and then using a conventional injection molding method or extrusion molding method. Further, the hollow container of the present invention, which may be a preform with a bottom or a preform without a bottom, has a hot water shrinkage rate obtained by blow molding the preform described above in a blow mold heated to 120 to 190°C. 3% or less. The blow molding method at this time is not particularly limited, but a so-called biaxial stretch blow molding method is particularly preferable. By doing so, a strong hollow container can be obtained due to the stretching orientation.

Further, the temperature of the blow molding mold is heated to 120 to 190°C, preferably 150 to 170°C. If the mold temperature is less than 120°C, a sufficiently crystallized hollow container will not be obtained, and it will deform when filled with a liquid at a high temperature exceeding 80°C, and if the mold temperature exceeds 190°C, the hollow container will not be formed. This is not preferable because the hollow container is easily deformed when it is released from the blow mold. The degree of crystallinity of the body of the hollow container obtained by this method is preferably 30 to 60%, and by contacting with a blow mold for a time depending on the mold temperature, a hollow container suitable for the purpose can be obtained. Specifically, the method for obtaining the hollow container of the present invention, which allows the free-forming to be 80 to 1
Maintain temperature range of 60°C. In order to maintain the preform within this temperature range, the high-temperature preform obtained by melt molding is once cooled to about room temperature, and then the preform is rotated and heated uniformly using a heating heater such as an infrared heater. Use as appropriate.

Immediately thereafter, this preform is loaded into a blow molding mold heated to 120 to 190°C and stretched in the longitudinal direction with a stretching rod, or simultaneously with the stretching using compressed air,
The desired hollow container can be obtained by blowing and expanding the material at once in the same direction with a heated fluid such as nitrogen to achieve biaxial stretching and orientation, and then bringing it into contact with a heated blow mold for crystallization.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

The degree of crystallinity in the examples was calculated from the density determined in a density gradient tube of an aqueous sodium bromide solution at 30° C. using the following formula.

where, cm' dO: Density of methacrylic resin (g/cm3) Φ: m total fraction (-) of methacrylic resin The hot water shrinkage rate was determined as follows. That is, after measuring the bottle container obtained by molding, boiling water at 100° C. is filled into the bottle container.

Ten minutes after filling with boiling water, the boiling water was discarded, the volume of the bottle container was measured again, and the hot water shrinkage rate was determined using the following formula.

-B Hot water shrinkage rate = X100 (%) However, A is 1
Volume of bottle container before filling with boiling water at 00℃ (ml)
) B is the volume of the bottle container after discarding the 100℃ boiling water (
ml) In addition, the fracture height by the drop test was determined as follows. That is, the molded bottle was filled with water, the cap was occupied, and a drop test was conducted at 0° C. according to the ASTM D-2463-74C method to determine the fracture height.

In addition, the appearance was visually observed.

Examples 1-2, Comparative Examples 1-5 Polyethylene terephthalate (hereinafter abbreviated as PET) with an intrinsic viscosity [η] of 1.2 ml/g and polymethyl with an intrinsic viscosity of 0.4 measured in chloroform at 25°C Using a polyethylene terephthalate resin composition to which methacrylate homopolymer (hereinafter abbreviated as PMMA) was added in the amount shown in the table, the resin temperature was 280°C using an injection molding machine.
Under molding conditions of mold temperature 20℃, outer diameter 25mm, inner diameter 19
The preform was molded into a bottomed cylindrical preform with a length of 130 mm and a length of 130 mm.Next, the preform was placed in an infrared heater while rotating and heated uniformly so that the temperature of the preform reached 120 °C. The preform is inserted into a blow mold heated to the indicated temperature, compressed nitrogen is injected into the preform, and the molded body is brought into contact with the blow mold for 15 seconds while maintaining the internal pressure by stretch blowing. A hollow container with a surface stretching ratio of about 8 times was then obtained. Crystallinity, hot water shrinkage rate, fracture height and drop test results of the resulting bottles
The table shows the results of surface and appearance observation.

[Effects of the Invention] According to the present invention, properties such as chemical resistance and gas barrier properties, which are characteristics of polyethylene terephthalate, are maintained as they are,
Moreover, it has become possible to provide a heat-resistant hollow container having a pearl-like surface gloss and capable of being filled with liquid at temperatures exceeding 80°C.

Patent applicant: Mitsubishi Rayon Co., Ltd. Agent: Patent attorney Yoshizawa Takeo

Claims (1)

[Claims] A heat-resistant hollow body having a pearl-like surface gloss and a hot water shrinkage rate of 3% or less, which is obtained by blow molding a preform obtained from a polyethylene terephthalate resin composition consisting of 80 to 99% by weight of polyethylene terephthalate and 1 to 20% by weight of a methacrylic resin. container.