JPH0340059B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing polyester containers.
More specifically, the present invention relates to a method for manufacturing polyester containers that can omit the complicated operation of separating components other than polyester when effectively reusing used empty containers. In recent years, thermoplastic polyesters such as polyethylene terephthalate have been used for various packaging containers due to their excellent mechanical properties, gas barrier properties, chemical resistance, fragrance retention, transparency, hygiene, etc. There is. In containers made of thermoplastic polyester, the main body of the container is usually made of the thermoplastic polyester, but the container as a whole is used in a form that includes components made of components other than polyester. For example, in the case of pressurized containers such as carbonated drinks, they are used with polyethylene footrests attached. Such polyester containers are normally used as disposable containers, but from the viewpoint of resource conservation and environmental protection, it is desired to collect used empty containers and reuse them effectively. Methods for reusing such an empty container include reusing it as a polymer as a molding material, or decomposing it into terephthalic acid, which is the raw material for polyester, or its ester-forming derivative and ethylene glycol, purifying it, and then turning it into a polymer raw material. There is a known method for reusing it. but,
In either recycling method, components made of components other than polyester, such as the base, must be separated in advance. Further, as a method for separating components other than these polyesters, for example, a method of separating polyethylene in an aqueous solution using the difference in specific gravity can be considered. As a result of intensive studies on a method for manufacturing containers that can effectively recycle empty containers without performing such complicated separation operations, the inventors of the present invention have found that if a container is manufactured using a polyester base, the objective can be achieved. The present invention was achieved by discovering that polyester containers can be manufactured. That is, in the present invention, when attaching a leg base made of polyester whose main repeating unit is ethylene terephthalate to the bottom of a container made of thermoplastic polyester whose main repeating unit is ethylene terephthalate, the density is 1.40 g/cm ³ or less. This is a method for producing a polyester container, characterized in that a leg base made of polyester, preferably 1.38 g/cm ³ or less, is used. In the present invention, the thermoplastic polyester constituting the container body is mainly a homopolymer of polyethylene terephthalate, but a part of the terephthalic acid component is, for example, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, etc. acid, aromatic dicarboxylic acids such as diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, etc.; alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hecasahydroisophthalic acid, etc.; adipic acid, sebacic acid, azelaic acid, etc. Aliphatic dicarboxylic acids such as P-β-
With one or more other difunctional carboxylic acids such as oxyacids such as hydroxyethoxybenzoic acid, ε-oxycaproic acid, etc., and/or a portion of the ethylene glycol component, such as trimethylene glycol, tetramethylene glycol, hexa Methylene glycol, decamethylene glycol, neopentylene glycol, diethylene glycol, 1,1-cyclohexane dimethylol, 1,4-cyclohexane dimethylol, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis( 4′−
It may also be a copolymer substituted and copolymerized with one or more polyfunctional compounds of other glycols and functional derivatives thereof such as β-hydroxyethoxyphenyl)sulfonic acid. The proportion of copolymerized components in the copolymer is preferably up to about 10 mol%. In the present invention, the polyester constituting the footrest is mainly a homopolymer of polyethylene terephthalate, but a part of the terephthalic acid component and/or a part of the ethylene glycol component is replaced with a copolymer component to copolymerize it. It may also be a copolymer. Examples of this copolymerization component include the compounds listed as the copolymerization component of the thermoplastic polyester. The proportion of this copolymer component is preferably up to about 30 mol%. Additives such as inorganic additives and coloring agents may be added to the polyester constituting this footrest within a range that does not impair the characteristics of the present invention. In the present invention, the container (container body) made of thermoplastic polyester is mainly intended for use as a bottle-shaped container obtained by, for example, injection blow molding or extrusion blow molding. Oriented bottle-like containers are preferred. The footrest can have any structure as long as it allows the container body to stand on its own, but it is usually obtained by injection molding. In the present invention, an example of how the container body and the foot stand are attached is shown in the accompanying drawings. FIG. 1 is a partial side view and partial cross-sectional view of a polyester container in which a footrest is attached to the bottom of the container body, where 1 represents the container body and 2 represents the footrest. Further, FIGS. 2 and 3 are enlarged side views and partial cross-sectional views showing how the footrest is attached to the bottom of the container body. Reference numeral 3 indicates a recessed portion of the copper portion of the main body of the container, 4 indicates an upper end portion of a pedestal, and 5 and 6 indicate a thermal bonding portion or an adhesive layer. In the present invention, methods for attaching the leg base to the bottom of the container include softening or melting the upper end of the leg base and attaching it to the copper bottom of the container body; Preferably used are a method of bonding to a copper bottom, a method of attaching a footrest using a polyester adhesive, and the like. The polyester adhesive is preferably a copolyester having ethylene terephthalate as a repeating unit, and the content of the ethylene terephthalate repeating unit is preferably at least 30 mol %. Furthermore, when attaching the leg base, the density of the polyester portion of the leg base must be 1.40 g/cm ³ or less, and preferably 1.38 g/cm ³ or less. If the density of the polyester is higher than 1.40 g/cm ³ , it is not preferable because the adhesive strength is weak or the amount of deformation and shrinkage is small. In polyethylene terephthalate, a density of 1.40 g/cm ³ corresponds to a crystallinity of about 55%,
Further, 1.38 g/cm ³ corresponds to a crystallinity of about 40%. If the density of the base is low, in other words, if the degree of crystallinity is low, the following effects will occur when the base is attached to a container. As detailed above, when a part of the base is softened or melted using a high-temperature metal rod or the like and bonded to the container, the lower the density of the base, the lower the temperature.
Bonding can be done in a short time. On the other hand, the density is 1.40g/
If it exceeds cm ³ , it will be difficult to soften or melt, making it impossible to perform the installation process smoothly. Also, heat the top of the footrest with a high-temperature jig, etc.
Even when this part is deformed or contracted to connect the leg base and the container, if the density of the leg base is low, deformation occurs easily and operation becomes smooth. The difficulty of mounting when the density is high is similar to the difficulty of melting (softening) adhesion. Furthermore, even when adhesive is used to attach the contact portion of the container and the leg stand, the lower the density of the leg stand, the stronger the adhesive force between the leg stand and the adhesive. On the other hand, if the density of the base is high, the adhesive force will be weak and it may not be practical. When using a method of softening or melting the base, the temperature of the adhesive part of the base is higher than the glass transition temperature (Tg) of the polyester that makes up the base,
Preferably the temperature is 130°C or higher. If this temperature is lower than Tg, the adhesive force will be extremely weak, which is not preferable.
The upper limit of this temperature does not cause defects in appearance due to decomposition and discoloration of the polyester constituting the footrest. Alternatively, it is determined based on the fact that there are no holes in the bottom of the container, and any temperature range lower than this temperature is sufficient. Preferably, the melting point (Tm) of the polyester constituting the footrest is up to about 30°C. Further, when using a method of bonding by thermally deforming or heat shrinking the leg base, the heating temperature is at least Tg of the polyester constituting the leg base, preferably at least 100°C. If this temperature is lower than Tg, sufficient deformation and shrinkage will not occur, which is not preferable. The upper limit of the temperature is about Tm of polyester, but preferably about 200°C in order to prevent defects in appearance due to crystallization of thermally deformed parts. A preferred method for joining this foot stand to the bottom of the container is to make a recess as shown in 3 in the container body and push the upper end 4 of the foot stand into the recessed part 3 by thermal deformation, as shown in Fig. 2, for example. . In this method, a leg base having the portion shown in FIG. 2 (inwardly curved structure) may be manufactured in advance by injection molding or thermoforming, and the bottom of the container may be inserted into the leg base. Furthermore, when using a method of bonding the footrest with an adhesive, it is preferable to use a polyester-based adhesive as the adhesive, and in this case, the polyester composition includes a copolymer of up to about 70 mol% of the above-mentioned copolymer component. Preferred are copolyesters. An example of using an adhesive method or a thermal bonding method is shown in FIG. Hereinafter, the present invention will be explained in detail with reference to Examples. The measurement conditions for the main characteristic values are as follows. Glass transition temperature (Tg) and melting point (Tm): The sample was melted at 290℃ and then rapidly cooled to 0℃ using a differential calorimeter (PerkinElmer DSC-
1) at a heating rate of 10℃/min. Intrinsic viscosity [ ]: Measured at 35°C using o-chlorophenol as a solvent. Orientation degree (△n): Measure the refractive index in the thickness direction and plane direction of a sample cut from a container using a sodium D line at a temperature of 25°C using a polarizing plate attached to an Atpe refractometer. The difference was determined by calculation. Softening point (Tsp): Polymer chips (shape approx. 4mm x 4mm x 2mm)
The material treated at 140℃ for 1 hour was placed in a softening point tester, a load of 1kg was applied to a needle with a tip with a cross-sectional area of ^1mm2 , and the temperature was raised at a rate of 50℃/hr to determine the penetration depth. The temperature at which the temperature reached 1 mm was measured, and that value was taken as the softening point. Density (ρ): Measured at 25°C using a density gradient tube made from carbon tetrachloride and n-heptane. Example 1 and Comparative Example 1 Polyethylene terephthalate with =0.74, Tg = 77°C, and Tsp = 259°C was heated to 160°C in a dehumidifying dryer.
The chips were dried for 4 hours to obtain dry chips with a moisture content of 0.01% or less. Using this dry chip, an 8-ounce injection molding machine (M-100 model manufactured by Meiki Seisakusho) and a hot runner type two-cavity mold were used to mold the straight copper part with an outer diameter of 25 mm, a length of 175 mm, and a wall thickness of 3.5 mm. A bottomed preform weighing 50 gr was molded. The molding conditions are cylinder set temperature 265-270℃ (resin temperature at nozzle part)
285℃), injection pressure 500-700Kg/cm ² , molding cycle
The mold cooling water temperature was 10 to 20°C, and the residence time of the resin in the injection molding machine cylinder was about 2 minutes. The obtained preform was substantially amorphous with good transparency. Using this preform, a stretch blow molding machine (manufactured by Cincinnati Milacron Co., Ltd.)
RHB-L type machine), the diameter of the copper part is 80 mm, and the height is
A 260 mm round bottom 1 liter bottle-shaped container for carbonated beverages was molded. The blow molding conditions at this time were as follows. Preform outer surface temperature upon completion of preheating:
100-130℃ Blow pressure: Primary pressure 6Kg/cm ² G Secondary pressure 15-18Kg/cm ² G On the other hand, polyethylene terephthalate sheet with intrinsic viscosity 0.68, softening point 260℃, glass transition temperature 80℃, and wall thickness 2mm. After heating the mixture to about 100°C, a pedestal with a cylindrical inner diameter of about 82 mm and a bottom shape as shown in 4 in FIG. 3 was formed by vacuum forming. The density of the footrest is
It was 1.33 to 1.35 g/cm ³ . Next, after preliminarily attaching the foot stand to the bottom of the container, a heated metal rod with a smooth tip and having a diameter of 6 mm was pressed onto the part 5 or 6 in FIG. 3 to heat-bond it. Bonding was impossible when the temperature of the metal rod was lower than 802°C. Furthermore, when the density of the footrest was 1.41 g/cm ³ , the adhesive strength was weak even if the adhesive temperature was raised to the softening point temperature, and although we tried to melt the adhesive by increasing the temperature further, it took a long time to melt. , the adhesive part became discolored. Furthermore, the entire polyester container (with footrest) obtained in the above example was pulverized using a pulverizer, and after drying, 15% of glass fiber with a length of 3 mm was mixed, and an extruder was used to crush the container with a diameter of about 2 mm. The strands were extruded, cooled, and cut into lengths of about 2 mm to obtain glass fiber-filled pellets. Next, the pellets were molded into plate-shaped samples with a wall thickness of 0.5 mm using an injection molding machine. Table 1 shows the physical properties of the molded product. Further, after drying the pulverized product, a thread-like extrusion molded product with a thickness of 0.2 mm was formed using an extruder. This molding situation is shown in Table-1. On the other hand, for comparison, a similar molding was also attempted for a polyethylene container with a base similar to a polyethylene terephthalate bottle for carbonated drinks sold in the United States. The results are shown in Table 1.

[Table] As shown above, according to the container of the present invention, used empty containers can be recycled without complicated separation operations. Example 2 and Comparative Example 2 Intrinsic viscosity 0.68, softening point 260°C, glass transition temperature
Using dry chips of polyethylene terephthalate at 80 DEG C., legs having the structure shown in FIG. 3 and 2 were molded with the densities shown in Table 2 by varying the injection mold temperature. This pedestal was joined to the container obtained in Example 1 by deforming the top end of the pedestal using a metal jig heated to about 120° C. as shown in FIGS. 2 and 4. The results are shown in Table-2. Table 2 Density at the upper end of the footrest (g/cm ³ ) Deformation bondability 1.33 Good 1.38 〃 1.40 Slightly poor 1.41 Poor Example 3 Polyester bottle-shaped container obtained in Example 1 and polyester bottle-shaped container obtained in Example 1 Then, as an adhesive, polyethylene terephthalate copolyester (SP: 122°C) copolymerized with adipic acid in an amount of 55 mol% of the total acid component was used, and the adhesive was melted by heating. 3, 5 and 6, the bottle-shaped container and the base were immediately joined together, and the mixture was cooled and solidified. In this case, the footrest density is 1.38g/
Adhesion was good up to about 1.41g/cm ^{3 .}
In this case, the adhesive part was extremely easy to peel off due to impact.

[Brief explanation of drawings]

FIG. 1 is a partial side view and a partial cross-sectional view of a polyester container with a base. FIG. 2 is a partial side view and a partial cross-sectional view showing a state in which the leg base is joined to the bottom of the container. FIG. 3 is a partial side view and a partial cross-sectional view showing a state in which the leg base is thermally bonded to the bottom of the container.

Claims (1)

[Claims] 1. When attaching a leg made of polyester whose main repeating unit is ethylene terephthalate to the bottom of a container made of thermoplastic polyester whose main repeating unit is ethylene terephthalate, the density is 1.40 g/cm ³ A method for manufacturing a polyester container, characterized by using the following foot stand made of polyester. 2. A patent characterized in that, when attaching the leg base made of polyester, the upper end of the leg base is heated to a temperature equal to or higher than the glass transition temperature (Tg) of the polyester to soften or melt it and adhere it to the container. The manufacturing method according to claim 1. 3. A patent characterized in that, when attaching the leg base made of polyester, the upper part of the leg base is heated to a temperature equal to or higher than the glass transition temperature (Tg) of the polyester to deform or contract it and then join it to the container. The manufacturing method according to claim 1. 4. The manufacturing method according to claim 1, characterized in that when the leg base made of polyester is attached, the leg base is adhered to the container using a polyester adhesive.