JPS6258973B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester container with good heat shrinkage resistance. More specifically, the present invention relates to a polyester container that has excellent heat resistance, transparency, mechanical properties, etc. Polyester, particularly polyethylene terephthalate, is a polymer with excellent physical and chemical properties and has been widely used for fibers, films, and resins. Recently, containers made of polyester have been used for beverages, as they have excellent properties such as mechanical strength, gas barrier properties, transparency, and chemical resistance.
It is attracting attention for use in food and cosmetics. Methods for manufacturing polyester containers include extrusion blow molding, which has been conventionally used as a molding method for thermoplastic resin containers, or, for example, JP-A-47
Injection blow molding methods such as those disclosed in Japanese Patent Laid-open No. 4591-4591 and Japanese Patent Application Laid-Open No. 47-4592 are known. However, polyester containers made by this method have a drawback of poor mechanical strength such as impact strength. On the other hand, as a method for producing a polyester container with improved mechanical strength, the apparatus or method described in, for example, Japanese Patent Publication No. 12032/1983, Japanese Patent Publication No. 3907/1982, and Japanese Patent Publication No. 3007/1989 is used to produce polyester containers with improved mechanical strength. Furthermore, methods for manufacturing biaxially oriented polyester containers (so-called oriented blow molding method) are known, such as the method applied to JP-B-49-3073. ing. However, although the polyethylene terephthalate containers manufactured by these methods have excellent mechanical strength, they have the disadvantage of poor heat shrinkage resistance, and improvement thereof is desired. As a result of repeated studies on polyester containers with good heat shrinkage resistance that do not have such drawbacks, the present inventor found that the polyester constituting the container is a mixture of two types of polyesters with different intrinsic viscosities, and that the container body The inventors have discovered that a container in which the portion is made of polyester having a specific crystallization behavior has the desired properties, and has thus arrived at the present invention. That is, in the present invention, a substantially non-crystalline preform obtained by injection molding is molded into two parts using a blow mold.
A container made of polyester obtained by axial stretch blow molding, the polyester having an intrinsic viscosity of 0.65.
The above polyester A whose main repeating unit is ethylene terephthalate, and the polyester A
and a polyester B whose main repeating unit is ethylene terephthalate with an intrinsic viscosity different by at least 0.05, and the polyester B is blended in such a manner that the polyester B accounts for 2 to 50% by weight of the total polyester (the sum of polyester A and polyester B). A polyester container characterized in that the body portion of the container has an induction period of 10 seconds or less, or a half-crystallization time of 30 seconds or less, as determined by a depolarized intensity method crystallization rate meter. be. The polyester container of the present invention has an induction period of 10 seconds or less and/or a half-crystallization time of 30 seconds or less as determined by a depolarized intensity crystallization rate meter for the polyester constituting the body. Although this is necessary, if this induction period is longer than 10 seconds and the half crystallization time is longer than 30 seconds, the heat shrinkage resistance, which is the object of the present invention, will be poor. Further, it is preferable that the light transmittance of the body portion of the container is 50% or more; if it is less than this, the external appearance characteristics of the container and the mechanical characteristics such as impact strength will deteriorate. As a method for manufacturing the polyester container of the present invention, two types (or more) containing polyester A and polyester B, which have different intrinsic viscosities, are mixed in a conventional manner so that polyester B accounts for 2 to 50% by weight of the total viscosity. A method in which polyester B is mixed in a specified manner and then subjected to a predetermined melting process to form a polyethylene terephthalate (PET) container; in the above method, polyester B is partially crystallized to have a predetermined density and used after being mixed with polyester A. Method;
In the above method, polyester B is oriented to have a predetermined degree of orientation, and polyester A is
A method in which polyester B exhibits a high melting point is added to polyester A in the above method; and a method in which polyester B contains a crystallization nucleating agent in the above method. , a method in which it is added to polyester A, etc. can be exemplified. For example, in a method using a mixture of two or more types of PET with different intrinsic viscosities, 2.
~50% by weight of the polyethylene terephthalate (A)
and polyethylene terephthalate (B), which has an intrinsic viscosity of 0.05 or more and preferably has an intrinsic viscosity of 0.5 or more, at a temperature equal to or higher than the melting point of polyethylene terephthalate, preferably under conditions in which the time in the molten state does not exceed 2 minutes. After melting and mixing, the mixture is injected into a mold cooled to a temperature below the glass transition temperature (Tg) of polyethylene terephthalate to form a substantially amorphous bottomed preform; The preform is stretched in the axial direction in a blow mold at a temperature within a temperature range that allows stretching, and is then blown and expanded in the transverse direction to produce a polyester container in which at least a portion of the container body is biaxially oriented. The method is preferred. Furthermore, the temperature (T: °C) of the part of the blowing mold in contact with at least a part of the container body is expressed by the following formula (Tg-30)T(Tsp-50) (where Tg and Tsp are respectively polyethylene terephthalate (A Particularly preferred is a method of manufacturing a polyester container by maintaining the glass transition temperature (°C) and softening temperature (°C) of In addition, in the case of a method using PET with a predetermined density, for example, high-density PET with a chip surface density of at least 1.40 is mixed with low-density PET with a chip density of 1.33-1.37. It is preferable to use a mixture at a ratio of 90% by weight. Furthermore, in the case of a method using PET with a high degree of orientation added, the degree of plane orientation measured by a refractometer is 0.1 or more, and the temperature is 140°C to 180°C.
It is preferable to use one heated for 3 hours or more. Furthermore, when using PET with a predetermined melting point, add high melting point PET (for example, one with a melting point of 270°C or higher) obtained by repeating highly oriented PET and heat treatment at a temperature just below the melting point. A method using a mixture is preferred. Furthermore, in the case of a method using a crystallization nucleating agent added, for example, a phosphorus compound such as an alkali metal salt of an aliphatic carboxylic acid such as sodium montanate metal salt, or triphenyl phosphate is added to a bottomed preform. It is preferable to use a material added within a range where the light transmittance is 50% or more. If the light transmittance is lower than 50%, it is not preferable because the appearance (transparency) of the container is poor or, in some cases, stretching becomes impossible. The polyethylene terephthalate according to the present invention is mainly a homopolymer thereof, but a part of the terephthalic acid component is, for example, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, Aromatic dicarboxylic acids such as diphenylsulfonedicarboxylic acid; Alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, etc.; Aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, etc.: P-β -Hydroxyethoxybenzoic acid, ε-
and/or a portion of the ethylene glycol component, such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, Neopentylene glycol, diethylene glycol, 1,1-cyclohexane dimethylol, 1,
Other glycols such as 4-cyclohexanedimethylol, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4'-β-hydroxyethoxyphenyl)sulfonic acid and their functional derivatives. One or more polyfunctional compounds within 15 mol%, preferably within 5 mol%,
It may also be a copolymer copolymerized with substitution. These can be used alone or in combination of two or more. When polyethylene terephthalates having different intrinsic viscosities are mixed and used in the present invention, the intrinsic viscosity of polyethylene terephthalate (A) constituting the main component is 0.65 or more, preferably 0.65 to 1.0, particularly preferably 0.65 to 0.80. On the other hand, the polyethylene terephthalate (B) constituting the subcomponent is the same as the polyethylene terephthalate (A).
It is a polymer that has a difference of 0.05 or more from the intrinsic viscosity of , and has an intrinsic viscosity of 0.5 or more. Therefore, polyethylene terephthalate (B) may have a higher intrinsic viscosity than polyethylene terephthalate (A) as long as it satisfies the above-mentioned intrinsic viscosity. In particular, in this case, polyethylene terephthalate obtained by solid phase polymerization is preferable. It may also have a lower intrinsic viscosity than polyethylene terephthalate (A). The mixing ratio of polyethylene terephthalate (B) is
The amount is 2 to 50% by weight, preferably 5 to 50% by weight, based on the total amount with (A). Further, the difference in intrinsic viscosity between polyethylene terephthalate (A) and polyethylene terephthalate (B) is 0.05 or more. If this difference in intrinsic viscosity is less than 0.05, it is difficult to obtain the effect of improving heat shrinkage, which is the objective of the present invention. In addition, when using the above-mentioned method in the present invention, it is preferable to use the above-mentioned polyethylene terephthalate (A) as the polyethylene terephthalate, and polyethylene terephthalate (B) as the polyethylene terephthalate having a different density, degree of orientation, or melting point. Process and above~
It is preferable to use one that satisfies the following. In the polyester container of the present invention, a substantially amorphous bottomed preform (hereinafter referred to as preform) using the above-mentioned polyethylene terephthalate composition is molded into a blow mold at a specific temperature within a temperature range that allows stretching. Stretching in the axial direction so that at least a part of the container body is biaxially oriented while maintaining the
Moreover, the container exhibits improved performance such as heat shrinkage resistance obtained by blowing and expanding in the lateral direction. Here, "substantially amorphous preform" refers to a preform with good transparency in appearance,
For example, some of them have a light transmittance of 50% or more. This preform can be obtained, for example, by conventional injection molding. At that time, it is preferable that the mold be sufficiently cooled. This preform can also be obtained by extrusion molding.
Further, the above-mentioned "stretchable temperature range" is a range in which the outer surface temperature of the preform is from the glass transition temperature (Tg) of polyethylene terephthalate constituting the preform to (Tg + 100) °C, preferably from (Tg + 20) °C to (Tg + 50) °C. is within the range of
Furthermore, during blow molding, part of the blow mold temperature, that is, the part corresponding to the body of the container (Tg
-30)°C to (Tsp-50)°C (where Tsp is the softening point of polyethylene terephthalate), preferably in the range of (Tg-10)°C to (Tg-20)°C, and the stretching of the blow molded body The temperature of the mold corresponding to the parts with low magnification (for example, the shoulder and bottom of the bottle) is preferably below Tg. The degree of stretching (axial and transverse directions) is such that the refractive index in the thickness direction of the container body portion (i.e. cylindrical portion) after biaxial orientation is 1.48 to 1.53 or the area magnification of stretching is 4 to 16. It is preferable to double the amount. At that time, the stretching ratio in the horizontal direction is set to 1.2 times to 4 times.
It is preferable to increase the horizontal magnification from 2x to 10x. When the polyester container of the present invention is filled with hot water at 80°C, the internal volume decreases by only 7% or less. Moreover, the container has excellent drop impact resistance and heat shrinkage resistance. Furthermore, it has excellent transparency and gloss. When used as containers for food or cosmetics, they are characterized by little change in taste, little adhesion of odors, and little permeation of moisture, oxygen, and other substances. Hereinafter, the present invention will be explained in detail with reference to Examples. The measurement conditions for the main characteristic values are as follows. Induction period: Cut the sample from the body of the container,
The sample was sandwiched between glass plates approximately 0.2 mm thick, heated and melted at 290℃ for 3 minutes using a Kotaki Seisakusho MK-701 crystallinity meter, and then transferred to an oil bath at 140℃. Measure the change in depolarization intensity over time. The time period from when the sample is placed in the oil bath until the depolarization intensity starts to increase is defined as the induction period (seconds). Half-crystallization time: Measure the change in depolarization intensity over time in the same way as the induction period measurement above, and calculate the intensity when the depolarization intensity reaches equilibrium.
I ₀₀ , when the intensity in the induction period is I ₀ , the time from when the sample is put into the oil bath until the depolarized intensity reaches the intensity of I1/2 = (I ₀₀ + I ₀ )/2 is half the time. Let it be the crystallization time (seconds). Glass transition temperature (Tg): A sample melted at 290°C and then rapidly cooled to 0°C was measured using a differential calorimeter (PerkinElmer DSC-1 model) at a heating rate of 10°C/min. Intrinsic viscosity [ ]: ₀ - 35 using clophenol as a solvent
Measured in °C. Orientation degree (△n): A polarizing plate is installed in the Atsube refractometer,
The refractive index in the thickness direction and in the plane direction of a sample cut from the container was measured at a temperature of 25° C. using a sodium D line, and the difference between the two values was determined by calculation. Softening point (Tsp): Polymer chip (shape approx. 4mm x 4mm
× 2 mm) was treated at 140℃ for 1 hour and placed in a softening point tester, with a cross-sectional area of 1
A load of 1 kg was applied to a needle with a mm ² tip, the temperature was raised at a rate of 50°C/hr, the temperature at which the penetration depth reached 1 mm was measured, and that value was taken as the softening point. Light transmittance: Measure the light transmittance of a sample cut to a specified size using a Nippon Densoku Kogyo Digital Hazemeter (NDH-2D model). Density: Measured at 25°C using a density gradient tube made of carbon tetrachloride and n-heptane. Example 1 and Comparative Example 1 Polyethylene terephthalate (PET-A) with IV=0.71, Tg=77°C, Tsp=259°C and IV=
0.65, Tg = 82℃, Tsp = 259℃ in the form of chips with polyethylene terephthalate (PET-B) in the proportions shown in Table 1, and then dried at 160℃ for 4 hours in a dehumidifying dryer. The moisture in the chips
Dry chips of less than 0.01% were obtained. Using this dry chip, an 8-ounce injection molding machine (M-
A bottomed preform with a straight body diameter of 25 mm, a length of 175 mm, a wall thickness of 3.5 mm, and a weight of 50 gr was molded using a hot runner type two-cavity mold. The molding conditions are cylinder set temperature 265-270℃ (resin temperature at nozzle 285℃), injection pressure 500-700Kg/ ^cm2 ,
The molding cycle was 35 seconds, the temperature of the mold cooling water was 10 to 20°C, and the residence time of the resin in the cylinder of the injection molding machine was about 2 minutes. The obtained preform was substantially amorphous with good transparency. Using this preform, a stretch blow molding machine (RHB-L type machine manufactured by Cincinnati Milacron Co., Ltd.) was used to mold the shape of a commercially available 1st seasoning oil bottle with a body diameter of 75 mm at the top, 80 mm at the bottom, and 260 mm in height. A bottle was molded. The blow molding conditions at this time were as follows. Mold temperature: Shoulder 50~60℃, Body 80~100℃ (Upper 80~90℃, Lower 90~100℃)
℃) Bottom: Fill a bottle obtained under conditions of 50 to 60℃ or higher with 80℃ hot water, and leave it to cool until the liquid temperature drops to 20℃ or less.
The internal volume of the bottle was measured, and the volumetric shrinkage rate relative to the internal volume of the bottle before filling with hot water was measured. Further, a sample was cut from the body of the obtained bottle, and the induction period and half-crystallization time were measured using a depolarized intensity method crystallization rate meter, and the light transmittance was also measured.
The results are shown in Table-1.

[Table] Example 2 and Comparative Example 2 Polyethylene terephthalate (PET-A) with IV=0.65, Tg=82℃, Tsp=259℃ and IV=0.71,
Polyethylene terephthalate (PET-B) with Tg = 77°C and Tsp = 259°C was mixed in the proportions shown in Table 2, and then processed and molded in the same manner as in Example 1 to obtain a bottle with an internal volume of 1. This bottle has a body diameter
75mm, bottom 80mm, height 260mm. This bottle was evaluated in the same manner as in Example 1. The results are shown in Table-2.

[Table] Example 3 and Comparative Example 3 As PET-B, IV=0.86, Tg=84℃, Tm=
A bottle was molded in the same manner as in Example 1, except that polyethylene terephthalate with a surface density of 1.39 was used at 246°C and Tsp = 258°C. Table 3 shows the measurement results of the mixing ratio of PET-A and PET-B and the shrinkage rate of the bottle.
Shown below.

[Table] Example 4 and Comparative Example 4 As PET-B, IV=0.64, Tg=81℃, Tm=
253℃, Tsp=260℃, and the degree of plane orientation is approximately
Bottles were molded in the same manner as in Example 1, except that polyethylene terephthalate in the form of fine dried thin sheets with a density of about 0.1 and a density of about 1.37 was used, and the mold temperature and contact time with the mold were varied. The results are shown in Table 4.

【table】

Claims (1)

[Scope of Claims] 1. A container made of polyester obtained by biaxially stretching blow molding a substantially amorphous preform obtained by injection molding using a blow mold, wherein the polyester is A polyester A having a viscosity of 0.65 or more and whose main repeating unit is ethylene terephthalate, and a polyester B whose main repeating unit is ethylene terephthalate having an intrinsic viscosity different from that of the polyester A by at least 0.05, the polyester B being 2% of the total polyester. ~50
% by weight, and the induction period of the polyester constituting the body of the container is 10 seconds or less or the half-crystallization time is 30 seconds as determined by a depolarized intensity method crystallization rate meter. A polyester container characterized by: 2. The polyester container according to claim 1, wherein the body portion has a light transmittance of 50% or more.