JPH0721107B2 - Polyester packaging material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester packaging material, and more specifically, to a polymer blend having excellent physical properties such as excellent gas permeation resistance and delamination-free mechanical strength and transparency. The present invention relates to a polyester packaging material.

[Prior Art] Polyethylene terephthalate is widely used for fibers, films, industrial resins and the like because of its excellent mechanical properties and chemical properties, but recently it has also been used for applications such as bottles, cups and trays. ing. In such applications, gas permeation resistance is required from the viewpoint of storage of contents, but polyethylene terephthalate has higher gas permeation resistance than polyolefin resins such as polyethylene, but is not necessarily sufficient compared with glass, aluminum, etc. It cannot be said to have gas permeation resistance.

Therefore, a method for improving the gas permeation resistance of polyethylene terephthalate has been studied and many proposals have been neglected.
For example, a method of coating or laminating polyester with a gas permeation resistant material such as polyvinylidene chloride, polyethylene-vinyl acetate saponified product, polyethylene isophthalate (JP-A-54-117565, JP-A-56-64839, JP-A-56-64839). Sho 59-39547, European Patent Publication 10582
5), a method of blending a gas permeable resistant material with polyester (JP-A-57-10640, EP-A-105826 and JP-A-59-196316), and the degree of orientation of a polyester molded article. A method of increasing the gas permeation resistance (JP-A-56-151648) has been proposed. However, the method of increasing the degree of orientation has a limit in improving the gas permeation resistance, and the method using the gas permeation resistant material has a problem in recovery and reuse after use.

In particular, in the method of coating or laminating polyvinylidene chloride or polyethylene-vinyl acetate saponified product, since a resin different from polyester is used together, adhesion to polyester is poor and delamination may occur, resulting in container Not only is transparency lost, but it is also disadvantageous in terms of recovery.

In addition, the method of coating or laminating polyethylene isophthalate does not have such a drawback because both layers are made of the same polyester, but even if laminated due to the hardness as a resin based on polyethylene isophthalate itself. In order to have brittleness and strength as a container, polyethylene terephthalate must have the same thickness as when it is used alone, and the advantage of the synthetic resin container, which is heavy and lightweight as a whole container, is lost. Will be. Moreover, the gas permeation resistance is not sufficient.

Also, a method of laminating polyglycolic acid (US Patent No.
No. 4,424,242), it is difficult to obtain a molded product having sufficient mechanical strength under the molding conditions of polyethylene terephthalate, and the gas permeation resistance is also insufficient.

Furthermore, polyalkylene isophthalate obtained by copolymerizing an aliphatic dicarboxylic acid having 4 to 12 carbon atoms has been proposed as a polyester for a packaging material replacing polyethylene terephthalate (US Pat. No. 4,403,090).
This polyester is not satisfactory for improving the gas barrier properties of polyethylene terephthalate packaging materials.

[Object of the Invention] An object of the present invention is to provide a polyester packaging material having excellent physical properties such as mechanical strength and transparency, and excellent gas permeation resistance.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a polyester system having excellent gas permeation resistance, which comprises a polyethylene terephthalate component and a polyethylene isophthalate component obtained by copolymerizing an aliphatic oxycarboxylic acid having 8 or less carbon atoms in an amount of 5 to 60 mol%. A packaging material made of a blend.

In the present invention, "polyethylene terephthalate" is a polyester containing terephthalic acid as a main acid component and ethylene glycol as a main glycol component. Polyethylene terephthalate may be copolymerized with other acid components and glycol components as long as the characteristics thereof are not impaired. Further, a polyfunctional compound such as trimellitic acid and pentaerythritol, or a monofunctional compound such as benzoic acid may be copolymerized within a range where the molecule is substantially linear.

The polyethylene terephthalate component is produced in exactly the same manner as ordinary polyethylene terephthalate. When used as a food packaging material, germanium oxide is preferable to antimony trioxide as a polymerization catalyst from the viewpoint of safety and health, but any material may be used as long as it meets the positive list of the Hygiene Council such as polyolefin.

The intrinsic viscosity of the polyethylene terephthalate component is preferably higher in terms of physical properties such as mechanical strength. Specifically 0.5 or more 1.5
The ratio is more preferably 0.6 or more.

The "copolymerized polyethylene isophthalate" useful for the packaging material of the present invention contains 95 to 40 mol% of ethylene isophthalate units and 5 to 60 mol% of aliphatic oxycarboxylic acid units having 8 or less carbon atoms. It was unexpectedly discovered that the gas permeation resistance was significantly improved by copolymerizing the aliphatic oxycarboxylic acid with polyethylene isophthalate.

When the copolymerization ratio is less than 5 mol%, brittleness due to isophthalic acid becomes remarkable, and the strength of the obtained packaging material may be insufficient. On the other hand, when the copolymerization ratio exceeds 60 mol%, the thermal stability at the time of molding and the physical properties of the molded article, particularly the mechanical strength, are reduced, which is not preferable. The copolymerization ratio of the aliphatic oxycarboxylic acid is preferably 10 to 50 mol%.

Examples of the aliphatic oxycarboxylic acid having 8 or less carbon atoms include glycolic acid, hydroacrylic acid (3-oxypropionic acid), 4-oxybutyric acid, 5-oxyvaleric acid, 6-oxycaproic acid, 7-oxyenanthic acid. , 8-oxycaprylic acid. Aliphatic oxycarboxylic acids are functional derivatives of these, for example, lower alkyl esters, lactones which are cyclically dehydrated by intramolecular dehydration (for example, β-propiolactone, γ-butyrolactone, δ-valerolactone, ε).
-Caprolactone and the like). Of these compounds, glycolic acid is most preferred. The intrinsic viscosity of the copolymerized polyethylene isophthalate is preferably
0.3 or more and 1.5 or less, more preferably 0.4 or more, and particularly preferably 0.45 or more.

As a matter of course, the above-mentioned copolymerized polyethylene isophthalate may contain other copolymerized components as long as the characteristics thereof are not impaired. In addition, glycerin, trimethylolpropane, pentaerythritol, trimellitic acid,
A polyfunctional compound such as trimesic acid, pyromellitic acid and tricarballylic acid, and a monofunctional compound such as o-benzoylbenzoic acid and naphthoic acid may be bonded within a range in which the polymer can be regarded as substantially linear. In particular, when the polyfunctional compound is copolymerized in an amount preferably in the range of 0.1 to 0.5 mol%, the creep resistance of the resulting molded article is improved, which is preferable.

Copolymerized polyethylene isophthalate can be produced in the same manner as polyethylene terephthalate. For example, esterification reaction is carried out using isophthalic acid, aliphatic oxycarboxylic acid and ethylene glycol, or lower alkyl ester of isophthalic acid (eg dimethyl ester), functional derivative of aliphatic oxycarboxylic acid (eg lower ester). Alkyl ester, lactone, etc.) and ethylene glycol are used for transesterification, and the obtained reaction product is further polycondensed. It can also be produced by the same method as above except that the addition of the aliphatic oxycarboxylic acid or its functional derivative is changed before the start of the polycondensation reaction. At that time, it is preferable to use an esterification catalyst, a transesterification catalyst, a polycondensation catalyst, a heat stabilizer and the like. As these catalysts and stabilizers, those known as catalysts and stabilizers for polyester, especially polyethylene isophthalate, can be used. If desired, other additives such as colorants, fluorescent whitening agents, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants and the like may be used.

Adjacent compounds are preferably used as heat stabilizers, in which case phosphorus is preferably used in an amount of 50 to 150 mmol%. Further, the antioxidant is preferably used in an amount of 0.1 to 1% by weight based on the weight of the copolymerized polyethylene isophthalate.

The packaging material of the present invention is formed by blending the above-mentioned polyethylene terephthalate component and the copolymerized polyethylene isophthalate component into an integral structure. In the polyester packaging material of the present invention, the copolymerized polyethylene isophthalate component is used as an aliphatic oxycarboxylic acid unit in an amount of 3 to 25 mol%, particularly 5 to 20 mol% of the total polyester.
Is preferably present in an amount such that

Examples of the packaging material of the present invention include bottles, cups, and the like.
A container obtained by a molding method involving stretching is exemplified.
Further, it may be a container obtained by deep drawing an unstretched sheet or a container obtained by stretching a pipe with a bottom. Further, it also includes a sheet or a tray-shaped one obtained by vacuum or pressure forming the sheet. As a method for obtaining these packaging materials, for example, in the case of a bottle, there are a conventionally known extrusion blow molding method and a biaxial stretch blow molding method, but the biaxial stretch blow molding method is advantageous. In the case of the biaxial stretch blow molding method, after the expandable geometric shape, that is, the container precursor molded body is heated to the stretching temperature, it is stretched by a stretch rod moving in the axial direction in the blow mold and the blowing of compressed gas. Stretching or heating the pipe precursor molded body that moves in the axial direction to the stretching temperature, stretches to the bottom after stretching due to the difference between the feeding speed and the take-up speed, and stretches in the circumferential direction by blowing compressed gas into a bottle shape. It can be shaped.

Further, heating of the container precursor molded body or the multilayer pipe precursor molded body can be carried out in a heating oven having a normal heating element such as a block heater or an infrared heater. When the packaging material is formed by blending, it is desirable that both components are melt-kneaded by an extruder to obtain a mixed pellet before molding the container precursor molded body, and then this is subjected to molding. Alternatively, the respective components can be formed into granules, which are then dry blended and directly subjected to molding.

[Effects of the Invention] The polyester packaging material of the present invention is excellent in gas permeation resistance and also in physical properties such as mechanical strength and transparency.

[Examples] The present invention will be specifically described below with reference to Examples. The characteristic values of the examples are measured by the following methods.

Intrinsic viscosity of polymer [η]: Calculated from solution viscosity of polymer o-chlorophenol solution measured at 35 ° C.

Bottle drop impact strength After filling 1000 g of water and 14 g of citric acid into the bottle, 14 g of sodium bicarbonate weighed in a polyethylene bag is inserted into the bottle mouth without being directly mixed with the citric acid aqueous solution in the bottle, and immediately , And capped with an aluminum cap. By bicarbonate is inserted into stoppered after the bottle and the citric acid solution is shaken bottle as fit Ri sufficiently mixed, and by which the CO _2, the aqueous solution which made Hoguse the CO ₂ press-welding is filled in the bottle It was in a state. The CO ₂ filled bottle was kept at 5 ° C., and after 24 hours, the bottom of the bottle was turned downward to 1.5.
The rate of bottle rupture when dropped on the concrete floor from a height of meters was investigated.

Carbon dioxide permeation resistance of bottles CO ₂ 4.0 times the same as in the case of the bottle drop strength measurement method.
After holding the CO ₂ filled bottle in which the Volume is dissolved under pressure in H ₂ O under an atmosphere of specified temperature and humidity for a specified period of time, transfer the filled bottle to an atmosphere of 20 ° C and keep the content liquid temperature at 20 ° C. The CO ₂ pressure in the bottle was measured to measure the remaining CO ₂ Volume.

Examples 1-3, Comparative Example 1 Polyester A: Dimethyl terephthalate 35 parts, ethylene glycol 22.4
Parts, 0.002 parts of tetrabutyl titanate into the reactor, 1
When heated to 50-240 ℃ and distilled 11.5 parts of methanol, 0.005 parts of phosphorous acid and 0.0045 parts of germanium dioxide were added 2
Raise the temperature to 50 to 280 ℃, gradually reduce the system pressure to 60 mm at 1 mmHg.
A minute reaction was performed to obtain a polymer of [η] 0.65. This further
Solid phase polymerization was carried out at 210 ° C. in a nitrogen stream to obtain polyethylene terephthalate of [η] 0.75. This is designated as polyester A.

Polyester B: Dimethyl isophthalate 17.5 parts, glycolic acid 6.86 parts,
Ethylene glycol 11.2 parts, tetrabutyl titanate 0.
Put 002 parts in a reactor, heat to 150-220 ℃, distill off methanol and water, add 0.005 parts phosphorous acid, 0.0045 parts germanium dioxide, raise the temperature to 240-260 ℃, gradually depressurize the system Then, the mixture was reacted at 1 mmHg for 90 minutes to obtain a polymer of [η] 0.74. This is designated as polyester B.

Polyester A was dried with hot air at 160 ° C. for 5 hours, and polyester B was vacuum dried at 50 ° C. for 24 hours, and both were blended at a predetermined ratio to obtain a bottle preform with a uniaxial single-layer injection molding machine. The molding conditions at this time were a cylinder temperature of 260 to 270 ° C, a mold temperature of 10 ° C, and an outer diameter of the body portion of 25 to 26 mm, a wall thickness of 3.5 mm, and a total length of 155 mm. It was done.

Next, preform heating temperature with a biaxial stretch blow molding machine.
Blow molding under conditions of 100-130 ℃, outer diameter of body is 82mm, and total height is 28
A blow bottle having a thickness of 0 mm, a wall thickness of 320 to 380 μm and an internal volume of 1040 to 1050 ml was obtained. The physical properties of this bottle are shown in Table 1.
For comparison, a bottle made of polyester A alone was molded, and the physical properties of this bottle are also shown in Table 1 as Comparative Example 1.

Claims (8)

[Claims] 1. A polyester packaging material formed by blending a polyethylene terephthalate component and a polyethylene isophthalate component obtained by copolymerizing an aliphatic oxycarboxylic acid having 8 or less carbon atoms in an amount of 5 to 60 mol% to form an integral structure. 2. The copolymerized polyethylene isophthalate component is present as an aliphatic oxycarboxylic acid unit in an amount of 3 to 25 mol% of the total polyester.
The polyester packaging material according to the item. 3. The polyester packaging material according to claim 2, wherein the copolymerized polyethylene isophthalate component is present as an aliphatic oxycarboxylic acid unit in an amount of 5 to 20 mol% of the total polyester. 4. The aliphatic oxycarboxylic acid is glycolic acid, hydroacrylic acid, 4-oxybutyric acid, 5-oxyvaleric acid, 6-oxycaproic acid, 7-oxyenanthic acid, 8-oxycaprylic acid and those. The polyester packaging material according to claim 1, which is selected from the functional derivatives of 5. The polyester packaging material according to claim 4, wherein the aliphatic oxycarboxylic acid is glycolic acid. 6. The polyester packaging material according to claim 1, wherein the copolymerization ratio of the aliphatic oxycarboxylic acid is 10 to 50 mol%. 7. The polyester packaging material according to claim 1, wherein the polyethylene terephthalate component has an intrinsic viscosity of 0.5 to 1.5. 8. The polyester packaging material according to claim 1, wherein the polyethylene isophthalate component has an intrinsic viscosity of 0.3 to 1.5.