JPH0112657B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester hollow container with excellent heat shrinkage resistance. In recent years, plastic containers have come to be used as an alternative to 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 plasticizers such as polyvinyl chloride or residual monomers.
In addition, since it has a lower gas permeability for oxygen, carbon dioxide, etc. and excellent transparency than polyethylene, polypropylene, etc., attempts have been made to use it in containers for foods, beverages, cosmetics, etc. However, polyester containers mainly made of polyethylene terephthalate have poor heat shrinkage resistance, especially biaxially oriented bottles that are not heat-treated at 60°C.
In a high-temperature atmosphere of 70°C or higher, problems arise such as thermal contraction of the container, deformation of the container, and change in volume. Therefore, there is a desire to develop a heat treatment technique that improves heat resistance, and although several heat treatment methods have been proposed so far, no economically effective method has yet been found. In view of the above-mentioned current situation, the present inventors conducted intensive studies to obtain a polyester hollow container with excellent heat shrinkage resistance. A hollow container containing a specific amount of a compound, and which is obtained by blow molding a bottomed preform whose body has a crystallinity within a specific range, satisfies the above characteristics. The present invention was achieved based on the discovery that this is the case. That is, the gist of the present invention is a hollow container made of a polyethylene terephthalate resin containing 0.002 to 0.5% by weight of at least one compound selected from the group consisting of kaolin, sodium benzoate, antimony trioxide, and titanium oxide. The crystallinity of the hollow container in the body is 1.0 to 10.0%.
The polyester hollow container is obtained by blow molding a bottomed preform. The polyethylene terephthalate resin used in the present invention is composed of terephthalic acid or its ester-forming derivatives (e.g., lower alkyl esters, phenyl esters, etc.) and ethylene glycol or its ester-forming derivatives (e.g., monocarboxylic acid ester, ethylene oxide, etc.). It is a polyester obtained by polymerization, and may be copolymerized with less than about 20 mol% of other dicarboxylic acid or glycol components. The polyester may also be copolymerized with a polyfunctional compound such as trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, etc. in an amount of less than 2 mol %.
Other dicarboxylic acid components used as the copolymerization component include phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acids,
Examples include aromatic dicarboxylic acids such as diphenoxyethane dicarboxylic acids, aliphatic or alicyclic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, decane dicarboxylic acid, cyclohexane dicarboxylic acid, and the like. Other glycol components used as other copolymerization components include aliphatic or alicyclic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neobentyl glycol, hexamethylene glycol, dodecamethylene glycol, cyclohexanedimethanol, etc. group glycols, bisphenols, hydroquinone, 2,2-bis(4-β-
Examples include hydroxyethoxyphenyl)propane and other aromatic diols. Also other pages
It is also possible to use oxyacids such as -hydroxyethoxybenzoic acid, ε-oxycaproic acid and the like. It is also possible to use lower alkyl esters of these oxyacids and other ester-forming derivatives. Furthermore, the polyethylene terephthalate resin in the present invention also includes a resin mixture in which a polyolefin resin such as polyethylene or polypropylene, a polystyrene resin, a polymethacrylic resin, etc. is blended with the above polyester in a range of 0.5 to 20% by weight. . The above-mentioned polyester preferably has an intrinsic viscosity [η] of 0.5 or more, preferably 0.55 or more, more preferably 0.6 or more. If a polyester having an intrinsic viscosity [η] of less than 0.5 is used, it is not preferable because the drop impact strength of the container will be significantly reduced.
The intrinsic viscosity [η] is a value determined from the solution viscosity measured at 25°C in a phenol/tetrachloroethane=50/50 (weight ratio) solution. Kaolin, sodium benzoate, antimony trioxide, and titanium oxide contained in the polyester hollow container of the present invention have a nucleating effect on polyethylene terephthalate and greatly contribute to heat shrinkage resistance. It is necessary that the hollow container contains at least one of the above-mentioned specific compounds, and if compounds other than those mentioned above are used, it is difficult to obtain a hollow container with excellent heat shrinkage resistance, which is the objective of the present invention. In addition, the content of at least one of these compounds in the hollow container is 0.002~
Must be 0.5% by weight and 0.002% by weight
If the amount is less than 0.5% by weight, the heat shrinkage resistance of the hollow container will not be sufficiently satisfactory, and if the amount exceeds 0.5% by weight, crystallization of the bottomed preform as described below will be promoted, making subsequent blow molding extremely difficult. Therefore, the desired hollow container cannot be formed. Further, the polyester hollow container of the present invention must be obtained by blow molding a bottomed preform whose body has a degree of crystallinity of 1.0 to 10.0%. The bottomed preform having a crystallinity of 1.0 to 10.0% in the body contains at least one compound selected from the above specific compound group having a nucleating effect on polyethylene terephthalate in a range of 0.002 to 0.5% by weight. It can be obtained by drying the polyethylene terephthalate resin contained therein until the water content becomes less than 0.01%, and then forming the desired bottomed preform by a conventional injection molding method, extrusion molding method, or the like. In this case, the specific compound having a nucleating effect can be added in a predetermined amount during polyester polymerization, blended with chips after polyester polymerization and extruded, or blended in a hopper immediately before injection molding. May be used. The degree of crystallinity in the body of the bottomed preform is 1.0.
-10.0%, and if it is less than 1.0%, the hollow container obtained by blow molding the preform will not have sufficient crystallinity and will have poor heat shrinkage resistance, which is not preferable. Also, the crystallinity
If the content exceeds 10.0%, it is difficult to blow mold the preform with a bottom, and the desired hollow container cannot be obtained. The polyester hollow container of the present invention is obtained by blow molding a bottomed preform having the above-mentioned characteristics, and the so-called biaxial stretch blow molding method is particularly preferred as the blow molding method at this time.
In this method, the bottomed preform is biaxially stretched and blown while being held in a temperature range that allows stretching and orientation, thereby increasing crystallization due to stretching and orientation, thereby producing a hollow container with significantly improved heat shrinkage resistance. The degree of crystallization of the hollow container due to this stretching orientation varies depending on the stretching ratio during biaxial stretching blowing, but the crystallinity is about 10.0 to 50.0%. The wall thickness of the bottomed preform used in carrying out the present invention can be arbitrarily changed depending on the form of the intended container and the area stretching ratio described below, but it is within the range of 1 to 12 mm from the viewpoint of moldability. It is preferable that there be. Specifically, the method for obtaining the polyester hollow container of the present invention is such that a bottomed preform having a degree of crystallinity within the above range is heated in advance to a temperature range of 80 to 150°C in order to enable subsequent blow-stretching orientation. Hold. In order to maintain the bottomed preform in this temperature range, the bottomed preform in a high temperature state obtained by melt molding is left to cool to the above temperature range, or the bottomed preform in a high temperature state is A method of uniformly heating the preform while rotating it with a heater such as an infrared heater after cooling the preform to about room temperature is appropriately used. Immediately thereafter, this bottomed preform is loaded into a blowing mold and stretched in the longitudinal direction with a stretching rod, or simultaneously with the stretching, it is simultaneously blown and expanded in the circumferential direction with a pressurized fluid such as compressed air or nitrogen. Biaxially stretched and oriented. Furthermore, if a method is adopted in which heat treatment is performed at the same time as the blowing expansion by heating the blowing mold during blowing expansion in the blowing mold, the content of the specific compound having the nucleating agent effect can be reduced to 0.002 to 0.1, for example. Even a small amount, such as % by weight, can produce a hollow container with satisfactory heat shrinkage resistance and slip resistance, and exhibits a remarkable effect. The polyester hollow container of the present invention has an areal stretching ratio of at least 3 times, preferably at least 4 times, particularly preferably at least 4 times that of the shoulder and body portions of the bottomed preform before stretching, to which the shoulders and body correspond. is required to be biaxially stretched and oriented six times or more. Further, the upper limit of the areal stretching ratio is preferably up to 25 times, more preferably up to 16 times. The polyester hollow container of the present invention has excellent mechanical strength and heat shrinkage resistance, and as a result of containing the above-mentioned specific compound, the containers are more likely to slip into each other than containers that do not contain this compound. It has excellent features such as reducing scratches caused by containers colliding with each other during transportation, and eliminating clogging between containers on the factory line where containers are filled with liquid. have The hollow container of the present invention can be used as a container for foods, beverages, cosmetics, and the like. The present invention will be specifically explained below using Examples.
The heat shrinkage rates in the examples were determined as follows. That is, after measuring the volume of the bottle obtained by molding, hot water at 70° C. is filled into the bottle. Two hours after filling with hot water, the hot water was discarded, the volume of the bottle container was measured again, and the thermal shrinkage rate was determined using the following formula. Heat shrinkage rate = AB/A x 100 (%) where A is the volume of the bottle before filling with 70℃ hot water (ml) B is the volume of the bottle after discarding the 70℃ hot water (ml) ) The degree of crystallinity was calculated from the density determined in an n-heptane/carbon tetrachloride density gradient tube at 30°C using the following formula. X=(12.125-1/δ×16.18)×100 However, X: Crystallinity (%) δ: Density (g/cm ³ ) Examples 1 to 15, Comparative Examples 1 to 20 [η] = 0.66, Softening point Kaolin, sodium benzoate, antimony trioxide, titanium oxide, etc. are first added to polyethylene terephthalate chips at 262℃.
After adding various amounts as shown in the table and tumbling, the chips were heated in a hot air dryer at 150°C for 5 hours to obtain dry chips. The moisture content of dried chips is 0.008
It was in weight%. This chip was molded into a bottomed cylindrical preform having an outer diameter of 25 mm, an inner diameter of 19 mm, and a length of 130 mm using an injection molding machine. Next, this preform is placed in an infrared heater while rotating, heated uniformly so that the temperature of the preform reaches approximately 105°C, and then inserted into a blow mold for molding, and compressed nitrogen is injected into the inside of the preform. Stretch blowing was performed to obtain a bottle with a surface stretching ratio of about 8 times. Table 1 shows the results of measuring the heat shrinkage rate of the obtained bottles. For comparison, Table 2 shows the results of the heat shrinkage rates of bottles molded in the same manner as above with no additives or with the addition of substances other than the compounds specified in the present invention.

【table】

【table】

[Table] Examples 13 to 24, Comparative Examples 21 to 40 A polyester resin prepared by blending 90% by weight of polyethylene terephthalate with 10% by weight of polymethyl methacrylate was heated and dried in a hot air dryer at 150°C for 5 hours. The moisture content of this dry blended polymer was 0.008% by weight. This dry blended polymer was molded into a preform containing the additives shown in Table 3 in the same manner as in Examples 1-12, and then molded into bottles in the same manner as in Examples 1-12. Table 3 shows the results of measuring the heat shrinkage rate of the obtained bottles. For comparison, Table 4 shows the results of the heat shrinkage rates of bottles molded in the same manner as above without any additives or with the addition of substances other than the compounds specified in the present invention.

【table】

【table】

【table】

Claims (1)

[Claims] 1 A hollow container made of a polyethylene terephthalate resin containing 0.002 to 0.5% by weight of at least one compound selected from the group consisting of kaolin, sodium benzoate, antimony trioxide, and titanium oxide, the hollow container having a body portion. The crystallinity of
A polyester hollow container obtained by blow molding a bottomed preform having a content of 1.0 to 10.0%.