JPH06116374A - Copolymer polyester and film for laminating to metallic plate - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer for metallic cans, etc., consisting of an aromatic dicarboxylic acid and a glycol component containing a polyoxyalkylene glycol, and containing germanium element and having good flavor property, heat resistance and impact resistance. CONSTITUTION:This copolymer poster containing 1.0-500ppm germanium element, excellent in flavor, heat resistance and impact resistance and useful for film, etc., for laminating to metallic plates such as metallic cans is obtained by heating an aromatic dicarboxylic acid component such as dimethyl terephthalate or dimethyl isophthalate and a glycol component such as ethylene glycol containing 0.05-20wt.% polyoxyalkylene glycol component such as diethylene glycol to 150-235 deg.C in the presence of manganese acetate under stirring and carrying out an ester interchange reaction while distilling methanol, and adding trimethyl phosphate and germanium dioxide thereto and reducing pressure in the reactional system to 0.5mmHg, and simultaneously heating these components to 20 deg.C to carry out polycondensation reaction.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a copolyester and a film for laminating metal plates. More specifically, the present invention relates to a copolymerized polyester and a film for laminating metal plates, which are excellent in flavor, heat resistance and impact resistance, particularly in flavor and are suitable for a metal can produced by molding.

[0002]

2. Description of the Related Art Conventionally, a thermosetting resin has been mainly coated for the purpose of preventing corrosion on the inner and outer surfaces of a metal can. However, the coating of the thermosetting resin has problems that it takes a long time to dry the coating composition, productivity is deteriorated, and a large amount of the organic solvent is scattered, which is not preferable in terms of environmental hygiene.

As a method of solving these problems, a method of laminating a polyester film on a metal plate is performed. When a metal plate laminated with a polyester film is formed into a metal can, the polyester film is required to have the following characteristics. Drying after can making,
The laminated polyester film should not be crystallized or deteriorated by heating such as print baking and retort sterilization treatment, so that peeling, shrinkage, cracks, pinholes, etc. of the film do not occur (heat resistance). The polyester film should not be peeled off or cracked by impact on the metal can (impact resistance). The scent component of the contents of the metal can is adsorbed on the polyester film, or the odor of the polyester film does not impair the flavor of the contents (flavor). There has been an eager desire to develop a polyester film that comprehensively satisfies the various required characteristics as described above. Many proposals have been made to solve these requirements, for example, JP-A-64-
Japanese Patent No. 22530 discloses a polyester film having a specific density and plane orientation coefficient, and Japanese Patent Application Laid-Open No. 2-57339 discloses a copolyester film having a specific crystallinity. However, these proposals cannot comprehensively satisfy the various required properties of the film for metal cans, and cannot be said to be at a sufficiently satisfactory level particularly with respect to flavor property.

[0004]

The object of the present invention is to solve the above-mentioned problems of the prior art, and to bond metal plates excellent in flavor property, heat resistance, impact resistance, especially flavor property. To provide polymerized polyesters and films.

[0005]

The above-mentioned object of the present invention is to provide a copolyester having an aromatic dicarboxylic acid and a glycol as main constituents, wherein a polyoxyalkylene glycol component is contained in an amount of 0.05 to 20% by weight and germanium. It can be achieved by a copolyester and a film for laminating metal plates, which is characterized by containing 1.0 to 500 ppm of an element.

The copolyester in the present invention means
A polyester obtained by copolymerizing a polyester composed of an aromatic dicarboxylic acid component and a glycol component with an aromatic dicarboxylic acid component constituting the polyester, a dicarboxylic acid component other than the glycol component and / or a glycol component. Examples of the polyester copolymerized with the dicarboxylic acid component and / or the glycol component include conventionally known polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polycyclohexylene dimethylene terephthalate and polyethylene naphthalate. Of these, polyethylene terephthalate and polyethylene naphthalate are particularly preferable.

The dicarboxylic acid component and / or glycol component which is copolymerized with the above-mentioned polyester is, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid. , Diphenyl ether dicarboxylic acid, 5-sulfoisophthalic acid, aromatic dicarboxylic acid such as phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid Alicyclic dicarboxylic acid and the like. Of these dicarboxylic acid components, isophthalic acid and naphthalenedicarboxylic acid are particularly preferable. These dicarboxylic acid components may be alkyl esters or the like. Examples of the glycol component include ethylene glycol, propanediol, butanediol,
Examples thereof include aliphatic glycols such as pentanediol, hexanediol and neopentyl glycol, aromatic glycols such as bisphenol A and bisphenol S, and alicyclic glycols such as cyclohexanedimethanol. Neopentyl glycol among these glycol components. , Cyclohexanedimethanol is particularly preferred. The above dicarboxylic acid component and glycol component may be used alone or in combination of two or more. The copolymerization amount is preferably 1.0 to 30 mol% with respect to the total acid component and / or the total glycol component of the polyester, and more preferably 5.
0 to 20 mol%, particularly preferably 7.0 to 15 mol
%. If the copolymerization amount is less than 1.0 mol%, crystallization tends to occur, so that impact resistance is poor, and if it exceeds 30 mol%, the melting point is low and heat resistance is poor.

As long as the effects of the present invention are not impaired, the copolymerized polyester is added with a polyfunctional compound such as trimellitic acid, trimesic acid, trimethylolpropane or p-
An oxycarboxylic acid such as oxybenzoic acid may be copolymerized.

The copolymerized polyester in the present invention must contain the polyoxyalkylene glycol component in an amount of 0.05 to 20% by weight, preferably 0.1 to 10%.
%, More preferably 0.3 to 5% by weight. If the content of the polyoxyalkylene glycol component is less than 0.05% by weight, the effect of improving the flavor property is not sufficient, and if it exceeds 20% by weight, the melting point becomes low and the heat resistance becomes poor. The method of incorporating the polyoxyalkylene glycol component into the polyester is not particularly limited, and any conventionally known method can be adopted. Examples of such a method include a method of adding a polyoxyalkylene glycol compound at an arbitrary stage before the completion of the polycondensation reaction, a method of mixing the polyoxyalkylene glycol compound with an acid component and / or a glycol component as a starting material of polyester, and the like. Is mentioned. The polyoxyalkylene glycol compound is not particularly limited, but a compound having a number average molecular weight of 4000 or less is preferable, and a compound having a number average molecular weight of 1000 or less is preferable from the viewpoint of improving the flavor property. Examples of such compounds include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol and polytetramethylene glycol. Of these, diethylene glycol is particularly preferable. The polyoxyalkylene glycol component in the present invention usually contains a diethylene glycol component that is a by-product during the production of a polyester containing ethylene glycol as the glycol component.

The copolymerized polyester of the present invention must contain germanium element in an amount of 1.0 to 500 ppm, preferably 5.0 to 300 ppm, and more preferably 10 to 100 ppm. If the amount of germanium element is less than 1.0 ppm, the effect of improving the flavor property is not sufficient, and if it exceeds 500 ppm, foreign matters are generated in the copolyester and it easily becomes a crystal nucleating agent and crystallizes, so that the impact resistance deteriorates. Or, the heat resistance is lowered, and the coloring of the polyester is increased. The copolyester of the present invention can improve the flavor property by incorporating the above-mentioned specific amount of germanium element into the polyester. The method of incorporating the germanium element into the polyester is not particularly limited and may be any conventionally known method, but usually, at any stage before the production of the polyester is completed, it is possible to add a germanium compound as a polymerization catalyst. preferable. Examples of such a method include a method in which a powder of a germanium compound is added as it is, or, as described in JP-B-54-22234, a germanium compound in a glycol component which is a starting material of a copolyester. And the like. Examples of the germanium compound, germanium dioxide, germanium hydroxide containing crystal water, or germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium alkoxide compounds such as germanium ethylene glycoloxide, germanium phenolate, germanium β-naphtholate, etc. Examples thereof include phosphorus-containing germanium compounds such as germanium phenoxide compounds, germanium phosphate and germanium phosphite, and germanium acetate.

The melting point of the copolyester of the present invention is preferably 150 ° C. or higher from the viewpoint of showing heat resistance that can withstand heat treatment such as drying in a can making process and printing / baking, and the copolyester has an appropriate crystallinity. In order to obtain a film excellent in keeping and impact resistance, it is preferably 250 ° C or lower. A more preferable melting point range is 170 ° C to 240 ° C, and a particularly preferable range is 180 ° C to 230 ° C.

The intrinsic viscosity of the copolyester in the present invention is preferably 0.50 dl / g or more in that the strength and crystallization of the polyester film are unlikely to occur and breakage and cracks do not occur during molding of a metal can. 2.0 dl in terms of facilitating stretching in the film forming process
/ G or less is preferable. A more preferable range of the intrinsic viscosity is 0.55 to 1.5 dl / g, and a particularly preferable range is 0.6.
It is 0 to 1.0 dl / g.

In producing the copolyester of the present invention, any conventionally known method can be employed without any particular limitation. As an example, a case will be described where an isophthalic acid component is copolymerized with polyethylene terephthalate, diethylene glycol is used as the polyoxyalkylene glycol component, and germanium dioxide is added as the germanium compound. The transesterification reaction is carried out while distilling methanol out of the reaction system, preferably in the presence of a catalyst, for dimethyl terephthalate, dimethyl isophthalate, ethylene glycol and diethylene glycol. Subsequently, germanium dioxide is added, and ethylene glycol is distilled out of the reaction system under high temperature and reduced pressure to carry out a polycondensation reaction to obtain a copolyester. Also,
A method in which terephthalic acid, isophthalic acid, ethylene glycol, or diethylene glycol is used as a raw material for producing a polyester to carry out an esterification reaction, and then germanium dioxide is added to carry out a polycondensation reaction can also be adopted. In addition, after the transesterification or esterification reaction, a polycondensation reaction is performed until a certain degree of polymerization is obtained, and then the obtained low polymer is further polycondensed at a temperature lower than its melting point under reduced pressure or an inert gas stream. A phase polymerization method may be used.

In producing the copolyester of the present invention, conventionally known reaction catalysts and anti-coloring agents can be used, and examples of the reaction catalysts include alkaline earth metal compounds, zinc compounds, lead compounds and manganese. Compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and the like. Examples of the coloring preventing agent include phosphorus compounds and the like.

Further, in producing the copolymerized polyester of the present invention, additives such as an antioxidant, a plasticizer, an antistatic agent, a weathering agent and a terminal blocking agent can be appropriately used if necessary. The film made of the copolyester in the present invention may be an unstretched sheet or a uniaxially or biaxially stretched film.

The copolyester film of the present invention comprises
The film can be formed using any conventionally known method.
For example, in the case of a biaxially stretched film, the copolymerized polyester described above is sufficiently dried and then supplied to an extruder, and melt-extruded onto a casting drum to obtain an unstretched film,
Then, a method of biaxially stretching the unstretched film simultaneously or sequentially can be mentioned. In the case of sequential biaxial stretching, the stretching order may be the longitudinal direction of the film, the transverse direction of the film, or vice versa. Furthermore, in the sequential biaxial stretching,
It is also possible to perform stretching in the longitudinal direction or the width direction twice or more. The stretching ratio in the longitudinal direction and the width direction of the film can be arbitrarily set according to the degree of orientation, strength, elastic modulus, etc. of the target film, but is preferably 2.5 to
It is 5.0 times. Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased or may be the same. The stretching temperature may be any temperature in the range of not less than the glass transition temperature of polyester and not more than the crystallization temperature, but it is usually preferably 80 to 150 ° C. Further, the film can be heat-treated after the biaxial stretching. This heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature above the crystallization temperature of the polyester and below the softening point, but it is preferably 120 to 240 ° C. The heat treatment time may be arbitrary, but it is usually preferably 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction.

The thickness of the copolyester film of the present invention is not particularly limited, but considering the laminating property to a metal plate and the molding processability of a metal can, it is preferably 5 to 100 μm, more preferably 10 to 80 μm. Particularly preferably 1
It is 5 to 50 μm.

The copolymerized polyester film in the present invention may be a laminated film composed of the same kind or two or more kinds of polyester.

[0019]

The present invention will be described in detail with reference to the following examples. The properties of polyester and film were measured and evaluated by the following methods.

(1) Content of polyoxyalkylene glycol component in polyester It was quantified by 13 C-NMR measurement.

(2) Content of Germanium Element in Polyester The content of germanium element was determined by fluorescent X-ray measurement from a calibration curve of the intensity of fluorescent X-ray.

(3) Intrinsic viscosity of polyester Dissolve polyester in orthochlorophenol and prepare 25
It was measured at ° C.

(4) Melting point of polyester Crystallization of polyester chips was performed at 16 ° C. by a differential scanning calorimeter (DSC-2 type manufactured by Perkin-Elmer).
It was measured at a temperature rising rate of min.

(5) Flavor of Polyester Film A polyester film cut into a size of 15 cm × 15 cm was added to a perfume aqueous solution (d-limonene 20 ppm aqueous solution).
The film was soaked for a day, and then the film was heat treated at 80 ° C. for 30 minutes, and the adsorbed amount of d-limonene per 1 g of the film was quantified by gas chromatography to evaluate the flavor property of the film.

(6) Heat Resistance of Polyester Film A molded metal can is heated at 210 ° C. for 5 minutes, and the state of the film attached to the metal can is observed. Was accepted. 1st grade: No peeling or shrinkage of the film. Grade 2: Peeling and shrinkage occur slightly on the film. Grade 3: Peeling and shrinkage of the film occur. 4th grade: Film peeling and shrinkage are remarkable.

(7) Impact resistance of polyester film A molded metal can was filled with water and dropped from a height of 1 m onto marble. Ten metal cans were dropped, each metal can was subjected to an electric current test (ERV test), and impact resistance was evaluated according to the following criteria, and grade 2 or higher was passed. The current-carrying test is a test in which a dropped metal can is filled with a 1% sodium chloride aqueous solution, and the current value flowing when a voltage of 6 V is applied to the electrode and the metal can provided in the aqueous solution. Class 1 ... 9 or more with a current value of 0.2 mA or less. Class 2 ... 7 to 8 with a current value of 0.2 mA or less. Class 3 ... Less than 7 with a current value of 0.2 mA or less.

Example 1 132 parts by weight of dimethyl terephthalate, 18 parts by weight of dimethyl isophthalate (12 parts by weight based on the total acid component of polyester)
mol%), 96 parts by weight of ethylene glycol, 3.0 parts by weight of diethylene glycol, and 0.05 parts by weight of manganese acetate are charged into a flask equipped with a rectification column and a distilling condenser, and heated to 150 to 235 ° C. with stirring to produce methanol. The ester exchange reaction was carried out while distilling. After distilling out almost the theoretical amount of methanol, trimethyl phosphate 0.0
3 parts by weight, 0.04 parts by weight of germanium dioxide were added and the reaction mass was transferred to a reactor equipped with a distillation condenser.
Then, the pressure inside the reactor was gradually reduced to 0.5 mmHg while stirring, and the temperature was raised to 290 ° C. to carry out a polycondensation reaction. As shown in Table 1, the copolyester obtained had an intrinsic viscosity of 0.70 dl / g, a melting point of 224 ° C., a diethylene glycol component amount of 2.5% by weight, and a germanium element amount of 51 ppm.

After the polyester chips were dried, they were melt extruded on a casting drum using an extruder to obtain an unstretched film. This unstretched film at 90 ° C
3.5 times in the longitudinal direction, and then in the width direction at 105 ° C.
It was stretched 5 times. Furthermore, this biaxially stretched film is
It heat-processed at 90 degreeC, and obtained the 25-micrometer-thick polyester film. Table 1 shows the evaluation results of the flavor, heat resistance, and impact resistance of this polyester film. As is clear from these results, it has excellent flavor, heat resistance and impact resistance.

Example 2 Copolymerized polyester was polymerized in the same manner as in Example 1 without adding diethylene glycol to form a biaxially stretched film. Table 1 shows the characteristic evaluation results of the copolyester and the film. As is clear from these results, it has excellent flavor, heat resistance and impact resistance.

Examples 3 to 5 Copolymerized polyesters were polymerized in the same manner as in Example 1 except that the amounts of diethylene glycol, germanium dioxide added and the intrinsic viscosity were changed to form biaxially stretched films. Table 1 shows the characteristic evaluation results of the copolyester and the film. From these results, it can be seen that the copolyester of the present invention has excellent flavor, heat resistance and impact resistance.

Example 6 Instead of diethylene glycol, the number average molecular weight was 100.
A copolymerized polyester was polymerized in the same manner as in Example 1 except that 3.7 parts by weight of polyethylene glycol of No. 0 was added to produce a biaxially stretched film. Analysis of this copolyester revealed that it contained 2.5% by weight of polyethylene glycol component and 1.5% by weight of diethylene glycol component. When the characteristics of this copolyester film were evaluated, it had excellent flavor, heat resistance and impact resistance.

Example 7 Instead of dimethyl isophthalate as a copolymerization component, 1,
A biaxially stretched film was produced by polymerizing the copolyester in the same manner as in Example 1 except that 4-cyclohexanedimethanol (10 mol% based on the total glycol component of the polyester) was used. Table 1 shows the characteristics of the copolyester and the evaluation results of the characteristics of the film. As is clear from these results, it had excellent flavor, heat resistance and impact resistance.

Comparative Example 1 Antimony trioxide was replaced with germanium dioxide in an amount of 0.
A copolyester was polymerized in the same manner as in Example 1 except that 063 parts by weight was added to produce a biaxially stretched film. Table 1 shows the characteristic evaluation results of the copolyester and the film. As a result, the copolyester did not contain a germanium element, and thus the flavor of the film was poor.

Comparative Example 2 A copolymerized polyester was polymerized in the same manner as in Example 1 except that 61 parts by weight of diethylene glycol and 60 parts by weight of ethylene glycol were added to produce a biaxially stretched film. When the characteristics of the copolymerized polyester and the film were evaluated, a polyoxyalkylene glycol component,
Since the melting point was out of the range of the present invention, the flavor, heat resistance and impact resistance of the film were inferior.

Comparative Example 3 Copolymerized polyester was polymerized in the same manner as in Example 1 except that 0.0007 parts by weight of germanium dioxide and 0.063 parts by weight of antimony trioxide were added to produce a biaxially stretched film. This copolymerized polyester was inferior in the flavor property, heat resistance, and impact resistance of the film because the content of germanium was out of the range of the present invention.

Comparative Example 4 A biaxially stretched film was produced by polymerizing a copolyester in the same manner as in Example 1 except that 0.39 parts by weight of germanium dioxide was used. This copolymerized polyester was inferior in flavor heat resistance and impact resistance of the film because the content of germanium was out of the range of the present invention.

Comparative Example 5 A biaxially stretched film was produced by polymerizing a copolyester in the same manner as in Example 1 except that dimethyl isophthalate was not copolymerized. The properties of this copolyester and the properties of the film are shown in Table 1. As is clear from these results, the flavor, heat resistance and impact resistance were poor.

[0038]

[Table 1] The abbreviations in the table are as follows. PAG: polyoxyalkylene glycol Ge: germanium IPA: isophthalic acid DEG: diethylene glycol PEG: polyethylene glycol CHDM: 1,4-cyclohexanedimethanol

[0039]

EFFECT OF THE INVENTION The copolymerized polyester and film for laminating metal plates of the present invention have flavor, heat resistance, impact resistance,
In particular, it has excellent flavor and can be suitably used for a metal can produced by molding.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // C08L 67:02

Claims (4)

[Claims] 1. A copolyester mainly composed of an aromatic dicarboxylic acid and a glycol, characterized by containing 0.05 to 20% by weight of a polyoxyalkylene glycol component and 1.0 to 500 ppm of a germanium element. A copolyester for laminating metal plates. 2. The copolyester for laminating metal plates according to claim 1, wherein the polyoxyalkylene glycol component is diethylene glycol. 3. The melting point of the copolyester is 150 to 25.
The copolyester for laminating metal plates according to claim 1, which has a temperature of 0 ° C. 4. A film comprising the copolyester for laminating metal plates according to claim 1, 2 or 3.