JP2002146166A - Polyester composition and film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain polyester film for metal plate lamination that has excellent heat resistance, slipperiness, high abrasion resistance on reduction/ironing work and high adhesion to steel plate after retorting and shows good adhesion to metal plate. SOLUTION: The objective polyester film mainly comprises aromatic dicarboxylic acid and glycol and characteristically includes silica particles having the IR ratio of <=3.0 according to the following formula: IR ratio = νA/νB (1) (wherein νA is the maximum absorption intensity of FT-IR at 1650-1800 cm-1, and νB is the maximum absorption intensity of FT-IR at 750-900 cm-1). The polyester film-laminated metal plates according to this invention can be fabricated to cans for drinks, cans for food and the like and suitably used in the market.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyester composition for a metal plate laminated film. More specifically, for containers manufactured by molding having a combination of slipperiness, heat resistance, abrasion resistance during drawing / ironing, and adhesiveness after retorting, especially for polyester films suitable for bonding metal plates. It relates to a composition.

[0002]

2. Description of the Related Art Conventionally, various types of thermosetting resins, such as epoxy and phenolic resins, dissolved or dispersed in a solvent have been applied to the inner and outer surfaces of a metal can to prevent corrosion. Coating has been widely practiced. However, such a method of coating the thermosetting resin requires a long time for drying the paint, and has unfavorable problems such as a decrease in productivity and environmental pollution due to a large amount of an organic solvent.

As a method of solving these problems, there is a method of laminating a polyester film on a steel plate, an aluminum plate, or a metal plate obtained by subjecting the metal plate to various surface treatments such as plating. When a metal can is manufactured by laminating a film or molding a laminated metal plate of the film, the polyester film is required to have the following characteristics. (1) Being excellent in laminating property to a metal plate. (2) Excellent adhesion to the metal plate. (3) It is excellent in moldability and does not cause defects such as pinholes after molding. (4) Excellent adhesion after retort. (5) The polyester film does not peel, crack, or pinhole due to impact on the metal can. (6) Excellent wear resistance during drawing / ironing. (7) The scent component of the contents of the can is not adsorbed on the polyester film, and the flavor of the contents is not impaired by the elution component or odor of the polyester film.

[0004] Many proposals have been made to solve these requirements. For example, Japanese Patent Application Laid-Open No. 2-57339 discloses a copolymerized polyester film having specific crystallinity. However, in recent years, with the increase in can making speed, the forming ratio of the polyester film in the can making process of a laminated steel sheet has been increasing, and further improvement in laminating properties, moldability, and adhesion between the film and the steel sheet is desired. ing. In particular, when the increase in the molding ratio is achieved by drawing / ironing, abrasion resistance represented by abrasion of particles in the film becomes a problem. In addition, when the molding ratio is increased, there is a problem that the adhesion between the film and the steel sheet is reduced particularly by the retort treatment after the can molding. The above suggestions
These required characteristics are no longer totally satisfactory.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide excellent laminating properties, abrasion resistance at the time of drawing / ironing work, and a steel sheet after retorting. An object of the present invention is to provide a polyester composition for a metal bonded film suitable for a metal can exhibiting adhesiveness.

[0006]

An object of the present invention is to provide a polyester composition containing an aromatic dicarboxylic acid and a glycol as main components, and having an IR ratio represented by the following formula (1) of 3.0 or less. This is achieved by a polyester composition for a metal plate bonded film, characterized by containing the silica particles of the above.

IR ratio = νA / νB (1) where: νA: 1650 to 1800 cm− ^{1 of} FT-IR
Absorption intensity at νB: Maximum absorption intensity at 750-900 cm- ¹ of FT-IR

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the present invention is composed of a dicarboxylic acid component and a glycol component, for example, an esterification or transesterification reaction of a dicarboxylic acid or an ester-forming derivative thereof with a glycol, and a subsequent reaction. It is produced by a polycondensation reaction. The type of polyester is not particularly limited as long as it can be formed into a molded product such as a film. For example, polyethylene terephthalate, polytetramethylene terephthalate, polyhexamethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate and the like can be mentioned. Of these, polyethylene terephthalate, polyethylene-2,6- Naphthalenedicarboxylate is preferred in terms of laminating properties, moldability, adhesion between the film and the steel sheet, abrasion resistance during drawing / ironing, and adhesion after retorting. Further, in the present invention, the polyester is obtained by copolymerizing an aromatic dicarboxylic acid component and a dicarboxylic acid component other than the glycol component and / or a glycol component constituting the polyester. It is particularly preferable from the viewpoint of adhesion to a plate. Examples of the dicarboxylic acid component copolymerizable with the above-mentioned polyester include, for example, terephthalic acid,
Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-
Examples thereof include aromatic dicarboxylic acids such as sulfoisophthalic acid, aliphatic dicarboxylic acids such as adipic acid and dimer acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Of these dicarboxylic acid components, it is preferable to copolymerize at least one component selected from isophthalic acid, 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acid, and more preferably, isophthalic acid and naphthalenedicarboxylic acid. Are preferred in terms of lamination properties, formability, adhesion between the film and the steel sheet, abrasion resistance during drawing / ironing, and adhesion to the steel sheet after retort.

The glycol component copolymerizable with the above-mentioned polyester is, for example, ethylene glycol,
Aliphatic glycols such as triethylene glycol, polyethylene glycol, polytetramethylene glycol, propanediol, butanediol, and hexanediol;
Examples include aromatic glycols such as bisphenol A and bisphenol S, and alicyclic glycols such as cyclohexane dimethanol. Among these glycol components, at least one kind selected from aliphatic glycols and alicyclic glycols It is preferable to copolymerize the components,
More preferably, ethylene glycol and cyclohexane dimethanol are preferable in terms of laminating properties, moldability, adhesion between the film and the steel sheet, abrasion resistance, and adhesion to the steel sheet after retorting.

The above dicarboxylic acid component and glycol component may be used alone or in combination of two or more. These copolymer components are preferably copolymerized in an amount of 1 to 30 mol% with respect to all the acid components constituting the copolymerized polyester, from the viewpoint of adhesion to a metal plate, and more preferably from 3 to 25 m.
ol%, more preferably 5 to 20 mol%. When the copolymerization amount is less than 1 mol%, the adhesion to the metal plate is poor, and the film is peeled off or the impact resistance is poor due to accelerated crystallization of the film in the production process of the metal can. is there. On the other hand, if it exceeds 30 mol%, the melting point may be low, resulting in poor heat resistance.

In the present invention, the IR ratio is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. It is preferable in terms of abrasion resistance during ironing and adhesion to a steel sheet after retorting.

The particle sample for measuring the IR ratio of the present invention is collected by centrifuging the particles and the polymer as a pretreatment. Hereinafter, a method of centrifuging the particles and the polymer will be described.

[0013] 50 g of the polymer composition was sampled, and
-Add 450 g of chlorophenol and stir with 100
After the temperature was raised, the polymer portion was allowed to stand for 1 hour to dissolve the polymer portion. However, under these conditions, when the polymer is not sufficiently dissolved, for example, when the polymer is highly crystallized, the polymer composition can be melted once and quenched as a sample under the above-mentioned melting conditions. Then, the solution is filtered through a G-3 glass filter to remove unnecessary substances other than the dust contained in the polymer or the added particles, and the weight is subtracted from the sample amount. Equipped with a rotor for Hitachi Koki SCR20B high-speed centrifuge for separation, the above solution was used for every 10 centrifuge tubes.
After injecting 0CC, the rotor is rotated at 4500 rpm, and after confirming that there is no abnormal rotation, the rotation speed is increased to 16000 rpm and the particles are centrifuged at this rotation speed for 90 minutes. After the separation is completed, the separated particles may contain a polymer component due to insufficient separation, so that O-chlorophenol at room temperature is added to the collected particles, and after substantially uniform dispersion,
Perform centrifugation again. Confirmation of separation between the polymer and the particles is carried out when the light transmittance at 375 mμ of the liquid after the separation becomes a constant value higher than that before the separation.

This operation needs to be repeated until the particles described below are dried and the melting point corresponding to the polymer cannot be detected by scanning differential calorimetry. Finally,
The separated particles thus obtained are vacuum-dried at 120 ° C. for 16 hours and weighed.

As the added particles in the present invention, silica particles are preferred from the viewpoint of film winding property and slipperiness, and particularly, aggregated silica particles are preferred, but single silica particles and the like are also included. Further, the silica particles or the slurry containing the silica particles is subjected to a heat treatment in the range of 150 ° C. to 250 ° C. for 1 to 10 hours, thereby changing the affinity between the particles and the polyester and the crystallization characteristics of the polyester, and changing the steel sheet after retorting. It is preferable in that it improves the adhesiveness with the adhesive.

The average particle diameter of the silica particles in the present invention is from 0.01 to 3.0 μm, more preferably from 0.05 to 2.0 μm. It is preferable from the viewpoints of abrasion resistance at the time of drawing / ironing forming and adhesion to a steel sheet after retort. If the average particle diameter of the silica particles exceeds 3.0 μm, the abrasion resistance at the time of drawing / forming and the adhesion to the steel sheet after retorting are inferior. If the average particle size is less than 0.01 μm, the resulting polyester film will have poor slipperiness, which will damage the film and lower the moldability.

The content of the silica particles with respect to the polyester is from 0.02 to 1% by weight, and the content of the silica film is preferably from 0.05 to 0.5% by weight. Abrasion resistance during molding,
It is more preferable from the viewpoint of adhesiveness to the steel sheet after retort. When the content is less than 0.02% by weight, the slipperiness is not sufficiently exhibited, and when the content exceeds 1% by weight, the particles are agglomerated with each other to form coarse particles and the surface roughness of the film. And the abrasion resistance during drawing / ironing and the adhesion to the steel sheet after retorting are inferior.

The method for producing the silica particles is not particularly limited, and examples thereof include a dry method and a wet method.
Examples of the production of dry silica include a thermal decomposition method of a silicon halide, a thermal decomposition method of a silicate compound, and a thermal decomposition method of an organic silicon compound. Examples of the production of wet silica include a method of decomposing sodium silicate with an acid, a method of decomposing sodium silicate with an ammonium salt or an alkali salt, generating an alkaline earth metal silicic acid from sodium silicate, and decomposing with an acid. Examples thereof include a method of converting into silicic acid and a method of hydrolyzing alkyl silicate to form silicic acid.

Such silica particles can be subjected to a surface treatment as long as the effects of the present invention are not impaired.
As the surface treatment agent, for example, sodium dodecylbenzenesulfonate, anionic surfactants such as sodium lauryl sulfate, polyoxynonylphenol ether, nonionic surfactants such as polyethylene glycol monostearate, polyvinyl alcohol, polyvinyl pyrrolidone, Water-soluble synthetic polymers such as polyethylene glycol; water-soluble natural polymers such as gelatin and starch; water-soluble semi-synthetic polymers such as carboxymethyl cellulose; silane and titanium coupling agents; Phosphorus compounds such as acids, phosphonic acids and derivatives thereof can be used.

Further, the polyester film of the present invention may be used in combination with particles other than silica particles within a range not to impair the effects of the present invention, so that the resulting polyester film has slipperiness, moldability of a metal can, and impact resistance. Properties, abrasion resistance, and adhesion to a steel sheet after retort may be improved. Such particles are not particularly limited, for example, as inorganic particles, titanium oxide, zirconium oxide, aluminum oxide, calcium carbonate, talc, calcium sulfate, spinel, calcium phosphate, etc.
As organic particles or organic polymer particles, crosslinked polystyrene particles, styrene / acrylic crosslinked particles, acrylic crosslinked particles, styrene / methacrylic crosslinked particles, vinyl particles such as methacrylic crosslinked particles, silicone, polytetrafluoroethylene, Examples include particles containing polyphenylester, phenolic resin and the like as constituent components. Average particle size of particles other than these composite oxide particles,
The content is not particularly limited, but the average is determined from the viewpoint of the slipperiness of the obtained polyester film, the moldability of the metal can, the abrasion resistance during drawing / ironing, and the adhesion to the steel sheet after retorting. The particle size is preferably in the range of 0.005 to 3 μm, and more preferably in the range of 0.01 to 2 μm. The content is preferably 0.001 to 1% by weight, more preferably 0.005 to 0.5% by weight.

The mixing of the silica particles with the polyester in the present invention can be carried out by, for example, kneading the particles into a molten polyester, in addition to the method of directly adding the particles to the polymerization reaction system. The timing of addition to the former polymerization reaction system is optional, but is preferably before the transesterification reaction or after the esterification reaction and before the start of the polycondensation reaction under reduced pressure. In the case of the latter kneading, a method of kneading particles into a polyester in a powder state or a method of directly kneading while reducing the pressure in a slurry state may be used.

The polyester of the present invention has an acetaldehyde content of 25 p in order to maintain good taste characteristics of the contents.
pm or less, preferably 15 ppm or less. The method for reducing the content of acetaldehyde to 25 ppm or less is not particularly limited. For example, in order to remove acetaldehyde generated by thermal decomposition when producing a polyester by a polycondensation reaction or the like, the polyester obtained by a method of heat-treating the polyester under a reduced pressure or an inert gas atmosphere at a temperature equal to or lower than the melting point of the polyester. Can be formed into a film. Preferably, the polyester is formed into a film by solid-phase polymerization of the polyester at a temperature of 150 ° C. or more and a melting point or less under reduced pressure or an inert gas atmosphere.

In producing the polyester for obtaining the polyester film of the present invention, conventionally known reaction catalysts and coloring inhibitors can be used. Examples of the reaction catalyst include alkali metal compounds and alkaline earth metal compounds. , A zinc compound, a lead compound, a manganese compound, a cobalt compound, an aluminum compound, and the like, and examples of the coloring inhibitor include a phosphorus compound. Examples of the catalyst used when polymerizing the polyester composition of the present invention include at least one compound selected from germanium, antimony, and titanium. Examples of the antimony compound include antimony trioxide, antimony acetate and the like. Also, as the titanium compound,
For example, titanium tetrabutoxide, titanium acetate and the like can be mentioned. Preferred examples of the germanium compound include amorphous germanium oxide, crystalline germanium oxide, a solution in which germanium oxide is dissolved in glycol in the presence of an alkali metal or a compound thereof, and a solution in which germanium oxide is dissolved in water.

The intrinsic viscosity of the polyester film in the present invention is preferably 0.50 dl / g or more in that the strength of the film and the crystallization hardly occur, and no breakage or cracking occurs during the molding of the metal can. 2.0 dl / g or less is preferable from the viewpoint of facilitating stretching in the film forming step. A more preferred range of the intrinsic viscosity is 0.55
To 1.5 dl / g, and a particularly preferred range is 0.60 to 1.
0 dl / g.

Further, additives such as an antioxidant, a plasticizer, an antistatic agent, a weathering agent and a terminal blocking agent can be appropriately used in the polyester film of the present invention, if necessary.

The polyester film of the present invention comprises:
It may be an unstretched sheet or a stretched film stretched uniaxially or biaxially.

The polyester film of the present invention can be formed by any conventionally known method. For example, in the case of a biaxially stretched film, a method in which a polyester raw material is sufficiently dried, then supplied to an extruder, melt-extruded on a casting drum to form an unstretched film, and then the unstretched film is biaxially stretched simultaneously or sequentially. Is mentioned. In the case of sequential biaxial stretching, the stretching order may be such that the film is oriented in the longitudinal direction and the width direction, or vice versa. Further, in the sequential biaxial stretching, stretching in the longitudinal direction or the width direction can be performed twice or more. The stretching ratio in the longitudinal direction and the width direction of the film can be arbitrarily set in accordance with the desired degree of orientation, strength, elastic modulus, etc. of the film, but is preferably 2.5 to 5.0 times. Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased, and may be the same. The stretching temperature can be any temperature within the range of the glass transition temperature of the polyester or higher and the crystallization temperature or lower, but is usually 80 to 150.
C is preferred. After the biaxial stretching, the film can be subjected to a heat treatment. This heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. Heat treatment temperature is above the crystallization temperature of polyester,
Any temperature below the softening point can be used, but it is preferably 120 to 240 ° C. The heat treatment time can be arbitrarily set, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction.

The polyester film of the present invention may be a film in which a polyester layer different from the polyester constituting the film of the present invention is laminated on at least one side of the film. In particular, a film in which a polyester layer having a melting point difference of 5 to 50 ° C. with respect to the melting point of the polyester constituting the film of the present invention is laminated is preferable because the adhesiveness to a metal plate, impact resistance and heat resistance are improved. When a polyester layer having a melting point difference of 5 to 50 ° C. is laminated on a metal plate in the laminated film, the heat resistance is improved when the polyester layer is higher than the melting point of the polyester of the present invention, and the adhesiveness and resistance when the polyester layer is lower than the melting point. Improves impact properties. Further, in the case of forming a laminated film, additives such as particles, catalysts, antioxidants, plasticizers, antistatic agents, weathering agents, terminal blocking agents and the like can be used as needed in the laminated portion.

The thickness of the film of the present invention is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 80 μm, in consideration of the laminating property to a metal plate and the moldability of a metal can. Is 15-50μ
m.

[0030]

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

(1) Particle Properties IR ratio Particles collected by centrifugation from polymer
Rat Laboratories FT-IR Type FTS-40
At 1650-1800 cm ^-1 and 750-
Read each maximum absorption intensity at 900 cm ^-1 ,
The IR ratio was calculated.

B. Average particle size The polyester film is subjected to plasma low-temperature incineration to expose the particles.

This was observed with a scanning electron microscope (SEM), the image of the particles was processed with an image analyzer, and the number of particles was changed to 5,000 or more at different observation points, and the volume average diameter was determined.

(2) Polyester Properties Intrinsic viscosity of polyester film The polyester film was dissolved in orthochlorophenol and measured at 25 ° C.

(3) Film characteristics Observe the condition of the film attached to the metal can after molding,
The occurrence of scratches and shavings was evaluated.

B. Wear resistance Laminated steel sheet is ironed and coiled by drawing machine and draw forming machine.
000m molding ratio (maximum thickness / minimum thickness) = 1.70, molded in moldable temperature range, can (diameter 6cm, height 12c)
m). At this time, the shaving amount of the film attached to the tool was measured and evaluated.

C. Adhesiveness after retort A TFS steel sheet (thickness of about 0.
2 mm), and quenched in a 70 ° C. water bath. The laminated steel sheet was cut to a width of 30 mm, and only a part of the steel sheet was cut while leaving a part of the film.
A 0 g weight was hung and retort treatment was performed at 125 ° C. for 25 minutes.

Evaluation was made based on the peel length of the film from the steel sheet after retort.

Example 1 76 parts by weight of terephthalic acid, 10.4 parts by weight of isophthalic acid, and 42 parts by weight of ethylene glycol were charged into a reaction vessel to carry out an esterification reaction. Subsequently, 0.01 parts by weight of phosphoric acid and 0.012 parts by weight of germanium dioxide were added,
Further, as shown in Table 1, 1.5 parts by weight of an ethylene glycol slurry containing 10 parts by weight of coagulable silica having an average particle diameter of 0.1 μm was added, and a polycondensation reaction was performed to obtain a polyester for a polyester film. Next, the polyester was subjected to solid-state polymerization at 190 ° C. for 8 hours under reduced pressure to obtain an intrinsic viscosity of 0.70 dl / g polyester. The particles were separated from the obtained polyester, and the IR ratio of the particles was measured. As a result, it was 0.8. The properties and evaluation results of the polyester are shown in Table 1. The polyester was melt-extruded on a casting drum using an extruder under the conditions of a melting temperature of 270 ° C. and a residence time of 20 minutes to obtain an unstretched film. This unstretched film is 3.5 times longer at 90 ° C. in the longitudinal direction, then 10 times.
The film was stretched 3.5 times in the width direction at 5 ° C. Further, the biaxially stretched film was heat-treated at a constant length of 190 ° C. to obtain a polyester film having a thickness of 25 μm.
Slipperiness, abrasion resistance during drawing / ironing, and adhesion after retorting were all good.

Examples 2 to 7 Polyester and polyester were prepared in the same manner as in Example 1 except that the particle size of silica, the amount added, the IR ratio of the separated particles and the intrinsic viscosity of the polyester composition were changed as shown in Table 1. A film was obtained and the results of characteristic evaluation were shown. In each case, the sliding property, the wear resistance during drawing / ironing and the adhesion to the steel sheet after retorting were good.

Comparative Examples 1 to 5 As shown in Table 1, the properties of the silica particles, the amount added, the IR ratio of the separated particles, and the intrinsic viscosity of the polyester composition were changed. A film was obtained, and the results of evaluating the characteristics of the film were shown. All of these were inferior in any of the required properties of the present invention, such as slipperiness, abrasion resistance during drawing / ironing, and adhesion to a steel sheet after retort.

[0042]

[Table 1]

[0043]

The polyester film for bonding metal sheets of the present invention has excellent heat resistance, slipperiness, abrasion resistance during drawing / ironing, good adhesion after retorting, and good taste characteristics of the contents. The metal plate laminated with the polyester film of the present invention can be suitably used for metal cans such as beverage cans and food cans manufactured by molding.

Continued on the front page F-term (reference) 4F071 AA45 AA45X AA46 AA46X AA76X AB26 AE17 AF22 AF27 AF29 AF45 AF53 AF58 AH05 BA01 BB06 BB08 BC01 4F100 AA20A AA20H AB01B AB03 AK42A AK42J AL01A BA01 BA02J01 J01 GB02 J01 GB01 CF061 CF071 CF081 DJ016 FA086 FD016 GF00 GG01

Claims (4)

[Claims] 1. A polyester comprising an aromatic dicarboxylic acid and a glycol as main components, and having a particle diameter of 0.0
It contains silica particles having a particle size of 1 to 3.0 μm, the content is 0.02 to 1% by weight, and the IR ratio represented by the following formula (1) is 3.0 or less. Polyester composition for metal plate laminated film. IR ratio = νA / νB (1) where νA: FT-IR of ^{1650~1800cm-1}
Absorption intensity at νB: Maximum absorption intensity at 750-900 cm- ¹ of FT-IR 2. The polyester composition according to claim 1, wherein the polyester is a copolyester. 3. A film comprising the polyester composition according to claim 1. 4. The film according to claim 3, which is for laminating a metal plate.