JP2564469B2 - Polyester packaging material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester packaging material, and more particularly to a polyester packaging material having a multi-layer structure having excellent gas permeation resistance and excellent physical properties such as mechanical strength and transparency without delamination.

[0002]

2. Description of the Related Art Polyethylene terephthalate is widely used for fibers, films, industrial resins and the like due to its excellent mechanical properties and chemical properties, but recently it has also been used for applications such as bottles, cups and trays. Has been. In such applications, gas permeation resistance is required from the viewpoint of storage of contents, but polyethylene terephthalate has high gas permeation resistance as compared with polyolefin resins such as polyethylene, but is not necessarily as good as glass, aluminum, etc. It cannot be said that it has sufficient gas permeation resistance.

Therefore, methods for improving the gas permeation resistance of polyethylene terephthalate have been investigated and many proposals have been made. For example, a method of coating or laminating polyester with a gas permeation resistant material such as polyvinylidene chloride, polyethylene-vinyl acetate saponified product, or polyethylene isophthalate (JP-A-54-117565 and JP-A-56-64839). Sho 59-39
No. 547, European Patent Publication No. 105825), and a method of blending a gas-permeable material with polyester (Japanese Patent Laid-Open No. 57-10640, European Patent Publication No. 105826, and Japanese Patent Laid-Open No. 59-19631).
No. 6), a method for improving the gas permeation resistance by increasing the degree of orientation of a polyester molded article (JP-A-56-151648).
No. gazette) is 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, polyvinylidene chloride and polyethylene
In the method of coating or laminating a vinyl acetate saponified product, since a resin different from polyester is used together, adhesion with polyester is poor and delamination occurs, and as a result, the transparency of the container is lost. It is also disadvantageous in terms of recovery.

Further, in the method of coating or laminating polyethylene isophthalate, both layers are made of the same polyester, so there is no such drawback, but due to the hardness as a resin based on polyethylene isophthalate itself. It is fragile even if laminated, and in order to have strength as a container, it is necessary to make polyethylene terephthalate as thick as the case of using it alone, and the advantage of a synthetic resin container characterized by being heavy and lightweight as a whole container is It will be lost. Furthermore, the gas permeation resistance is not sufficient.

Further, in the method of laminating polyglycolic acid (US Pat. No. 4,424,242), it is difficult to obtain a molded article having sufficient mechanical strength under the molding conditions of polyethylene terephthalate, and it is The gas permeability is also insufficient.

Further, 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. 4,40).
No. 3,090), but this polyester is not satisfactory for improving the gas barrier properties of polyethylene terephthalate packaging materials.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyester packaging material having excellent physical properties such as mechanical strength and transparency and excellent gas permeation resistance.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention comprises a polyethylene terephthalate component and an aliphatic oxycarboxylic acid having 8 or less carbon atoms in an amount of 5 to 5.
It is a polyester packaging material having excellent gas permeation resistance, which contains a polyethylene isophthalate component copolymerized at 60 mol%.

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.

This polyethylene terephthalate component is
It 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 of the present invention is preferably high in view of physical properties such as mechanical strength. Specifically, it is 0.5 or more and 1.5 or less, and 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. contains. 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 product, particularly the mechanical strength are deteriorated, which is not preferable. The copolymerization ratio of the aliphatic oxycarboxylic acid is preferably 10-
50 mol%.

As the aliphatic oxycarboxylic acid having 8 or less carbon atoms, glycolic acid, hydroacrylic acid (3-oxypropionic acid), 4-oxybutyric acid, 5-oxyvaleric acid,
6-oxycaproic acid, 7-oxyenanthic acid, 8-
Examples include oxycaprylic acid. Aliphatic oxycarboxylic acids are functional derivatives of these, for example, lower alkyl esters, lactones that are cyclically dehydrated by intramolecular dehydration (for example, β-propiolactone, γ-butyrolactone, δ-parerolactone, ε-caprolactone, etc.). ) May be sufficient. 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. Also, glycerin,
Polyfunctional compounds such as trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid and tricarballylic acid, o-benzoylbenzoic acid,
A monofunctional compound such as naphthoic acid may be bound within the 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 obtained molded article is improved, which is preferable.

Copolymerized polyethylene isophthalate can be prepared in a manner similar to polyethylene terephthalate. For example, an esterification reaction is carried out using isophthalic acid, an aliphatic oxycarboxylic acid and ethylene glycol, or a lower alkyl ester of isophthalic acid (eg dimethyl ester), a functional derivative of an aliphatic oxycarboxylic acid (eg lower alkyl). (Ester, lactone, etc.) and ethylene glycol to carry out a transesterification reaction, and further polycondensate the obtained reaction product to produce the compound. 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 of polyester, particularly polyethylene isophthalate, can be used. If desired, other additives such as colorants, optical brighteners, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants and the like may be used.

A phosphorus compound is preferably used as the heat stabilizer, and in this 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 comprises the above-mentioned polyethylene terephthalate component and copolymerized polyethylene isophthalate component formed in a multilayer structure. In the polyester packaging material of the present invention, the copolymerized polyethylene isophthalate component is present as an aliphatic oxycarboxylic acid unit in an amount of 3 to 25 mol%, particularly 5 to 20 mol% of the total polyester. preferable.

When the polyester packaging material of the present invention is formed into a multi-layer structure, its layer formation is not particularly limited, and the number of layers is not particularly limited, but in practice, it is at most 5 layers, preferably up to 3 layers. It may have a configuration of. In general, the polyethylene terephthalate component is preferably formed as the innermost layer of the packaging material, and in the case of a three-layer structure, the copolymerized polyethylene isophthalate component may be formed as the intermediate layer.

Examples of the packaging material of the present invention include bottles, cups, and other containers obtained by a molding method involving stretching. Further, it may be a container obtained by deep drawing an unstretched sheet, or a container in which a pipe is bottomed and stretched. 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, an expandable geometric shape, that is, a container precursor molded body is heated to a stretching temperature, and then, by a stretch rod moving axially in a blow mold and blowing a compressed gas. Stretching, or heating the pipe precursor molded body that moves in the axial direction to the stretching temperature, and after stretching due to the difference between the feeding speed and the take-up speed to bottom, stretched in the circumferential direction by blowing compressed gas into a bottle shape. It can be shaped.

The container precursor molding having a multi-layer structure can be formed by sequentially molding the inner layers one by one using a conventional injection molding machine or a molding machine having a plurality of melt injection devices, or by forming a plurality of injection cylinders. Using a molding machine having the above, by injecting the melted polyethylene terephthalate and the copolymerized polyethylene isophthalate in a single mold once, continuously and alternately at different timings, or almost simultaneously, By injecting polyethylene terephthalate into the inner and outer surface layers, and by injecting the later-injected copolymerized polyethylene isophthalate into the intermediate layer, or by bottoming one end of a multilayer pipe formed by a multilayer extruder. can get.

Next, 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. The stretching temperature in the case of the multi-layered container precursor molded body is almost the same as the stretching temperature of the container precursor molded body made of polyethylene terephthalate alone.

[0024]

The polyester packaging material of the present invention is excellent in gas permeation resistance as well as in physical properties such as mechanical strength and transparency. Further, the polyester packaging material of the present invention having a multi-layered structure further has an excellent property that there is no delamination.

[0025]

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": o of polymer
-Calculated from the solution viscosity of the chlorophenol solution measured at 35 ° C.

Drop impact strength of bottles Sodium bicarbonate 14 filled with 1000 g of water and 14 g of citric acid in a bottle and then weighed in a polyethylene bag
g was inserted into the mouth of the bottle without being directly mixed with the citric acid aqueous solution in the bottle, and immediately capped with an aluminum cap. By the sodium bicarbonate and citric acid inserted into stoppered after the bottle is shaken bottle to suit 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 rate of bottle rupture was examined when the bottle bottom was faced downward and dropped from the height of 1.5 meters onto the concrete floor surface.

Carbon dioxide gas permeation resistance of bottles CO in the same manner as in the method for measuring drop strength of bottles.
₂ 4.0 times the volume of CO ₂ dissolved in H ₂ O under pressure
Predetermined temperature filling bottles, transferred filled bottle to the atmosphere of 20 ° C. after holding for a predetermined time in an atmosphere of a predetermined humidity, the contents liquid temperature remains by measuring the bottle CO ₂ pressure in the state is 20 ° C. CO ₂ Volume Was measured.

However, CO ₂ Volume = VCO ₂ / VH ₂ O VH ₂ O: H ₂ O liquid volume in the bottle VCO ₂ : 0 of CO ₂ dissolved in the H ₂ O liquid phase in the bottle
Gas-equivalent volume at 1 ° C. and 1 atmosphere [Examples 1 to 4, Comparative Example 1] Polyester A: 35 parts of dimethyl terephthalate, 22.4 parts of ethylene glycol, and 0.002 part of tetrabutyl titanate were placed in a reactor, After heating to 150 to 240 ° C. and distilling 11.5 parts of methanol, phosphorous acid of 0.1.
005 parts, 0.0045 parts germanium dioxide were added,
Raise the temperature to 250-280 ° C and gradually reduce the system pressure to 1
The reaction was carried out at mmHg for 60 minutes to obtain a polymer of [η] 0.65. This was further subjected to solid phase polymerization in a nitrogen stream at 210 ° C. to obtain [η] 0.75 polyethylene terephthalate. This is designated as polyester A.

Polyester B: 17.5 parts of dimethyl isophthalate, 6.86 parts of glycolic acid, 11.2 parts of ethylene glycol and 0.002 parts of tetrabutyl titanate are put in a reactor and heated to 150 to 220 ° C., and methanol is added. And water are distilled off, 0.005 parts of phosphorous acid and 0.0045 parts of germanium dioxide are added, the temperature is raised to 240 to 260 ° C., the system is gradually reduced in pressure, and the system is reacted at 1 mmHg for 90 minutes. ] 0.74 polymer was obtained. This is designated as polyester B.

Multi-layer molding In a three-layer injection molding machine having two cylinder parts, one of which is inside the other, polyester A (hot air drying at 160 ° C. for 5 hours) is used at a cylinder temperature of 270 to 280 ° C. and polyester B (50 ° C.). (Vacuum drying for 24 hours) at a cylinder temperature of 200 to 220 ° C., the polyester B enters the inside of the polyester A, and the amount thereof is changed to a ratio as shown in Table 1 by adjusting the injection amount. Co-injected at ℃, polyester A inner and outer layers, polyester B has a three-layer structure of the intermediate layer, the outer diameter of the body 25-26 m
m, wall thickness 3.5 mm, total length 155 mm to obtain a cylindrical preform with one end having a bottom.

The preform was blow-molded with a biaxial stretch blow molding machine at a preform heating temperature of 100 to 130 ° C. to obtain a body outer diameter of 82 mm, a total height of 280 mm, and a body wall thickness of 32.
A bottle having a volume of 0 to 380 μm and an internal volume of 1040 to 1050 ml was obtained.

Table 1 shows the drop impact strength and carbon dioxide gas permeation resistance of the polyester multilayer bottle thus obtained.

For comparison, a multi-layer bottle consisting of polyester A alone was molded, and the physical properties of this bottle are also shown.

In Examples 3 and 4, although the amount of oxyacid in the bottle was increased, the amount of residual CO ₂ was decreased because the bottle volume increased due to creep.

[0036]

[Table 1]

[Examples 5 and 6] In Example 3, the ratio of glycolic acid in the polyester B is shown in Table 1 as Examples 5 and 6.
In the same manner as in Example 3 except that the ratio of polyester B in the bottle was changed to 30% by weight, the physical properties of the bottle when a biaxially stretched multilayer bottle was prepared are also shown in Table 1.

[Examples 7 to 9] In Example 3, in the production of polyester B, the amount of phosphorous acid added after transesterification was 0.0148 parts (100 mm based on all acid components).
Polymer B (Example 7) changed to ol%) and further pentaerythrityl tetrakis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate] is added to the polymer B in an amount of 0.2% by weight.
(Example 8) and trimellitic anhydride 0.0 at the beginning of the reaction
Biaxially oriented multilayer bottles were made in the same manner as in Example 3 except that Polymer B (Example 9) added with 69 parts (0.2 mol% based on all acid components) was used. The physical properties of this bottle are shown in Table 1.

In the case of Examples 7 and 8, the impact stability of the bottle was increased because the thermal stability of the polymer B was increased. In the case of Example 9, the creep property was improved and the amount of residual CO ₂ was increased. I found out that

Examples 10 to 15 and Comparative Examples 2 and 3 The same as Example 1 except that various oxyacids shown in Table 2 were used in place of glycolic acid in the production of polyester B in Example 1. Made a biaxially stretched bottle.

The bottle performance is shown in Table 2.

[0042]

[Table 2]

Claims (8)

(57) [Claims] 1. A polyethylene terephthalate component and 5 to 60 mol% of an aliphatic oxycarboxylic acid having 8 or less carbon atoms
A polyester packaging material having excellent gas permeation resistance, which is formed in a multilayer structure with a copolymerized polyethylene isophthalate component. 2. The packaging material according to claim 1, wherein 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. 3. The 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 packaging material according to claim 1, which is selected from the functional derivatives of 5. The packaging material according to claim 4, wherein the aliphatic oxycarboxylic acid is glycolic acid. 6. The packaging material according to claim 1, wherein the copolymerization ratio of the aliphatic oxycarboxylic acid is 10 to 50 mol%. 7. The packaging material according to claim 1, wherein the polyethylene terephthalate component has an intrinsic viscosity of 0.5 to 1.5. 8. The packaging material according to claim 1, wherein the polyethylene isophthalate component has an intrinsic viscosity of 0.3 to 1.5.