JP2000302891A - Polyester composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition for a film excellent in laminating properties and adhesion properties to a steel plate after retorted by incorporating silica particles containing a specific amount of a glycol component into a polyester composed mainly of an aromatic dicarboxylic acid and a glycol. SOLUTION: There is provided a composition comprising a polyester such as a polyethylene terephthalate, a polyethylene-2,6-naphthalene dicarboxylate or the like containing 0.02-1 wt.% of silica particles, which is obtained by polymerizing an aromatic dicarboxylic acid, a glycol component, a catalyst and silica particles having an average particle size of 0.01-3.0 μm and containing 0.05-15 wt.% of a glycol component. The composition is subjected to melt extrusion to form a film, which is stretched sequentially to give a biaxially stretched film having a thickness of 5-100 μm. The silica containing a glycol component is obtained by a heat treatment at150-200 deg.C of a silica powder, if necessary, surface-treated with a surfactant or the like, in a 2-20 wt.% slurry in ethylene glycol, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester composition for a metal plate laminated film and a 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 and a film.

[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. 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 a specific crystallinity. However, in recent years, as the speed of making cans has been increased, the ratio of forming cans from laminated steel sheets has been increasing, and further improvements in laminating properties, moldability, and adhesion between films and steel sheets have been desired. 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 due to the retort treatment after the can molding. The above proposals have not been able to satisfy these required characteristics comprehensively.

[0004]

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-laminated film and a film suitable for a metal can exhibiting adhesiveness.

[0005]

An object of the present invention is to provide a polyester comprising an aromatic dicarboxylic acid and a glycol as main components, wherein the glycol component is contained in an amount of from 0.05 to 0.05.
The object is achieved by a polyester composition for a metal plate-bonded film, which contains 20% by weight of silica particles. .

[0006]

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 which is obtained by copolymerizing an aromatic dicarboxylic acid component and / or a dicarboxylic acid component other than the glycol component and / or a glycol component constituting the polyester is preferable because the film has slipperiness, abrasion resistance, film and metal. 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, wear 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.

The silica particles in the present invention are not particularly limited, and examples thereof include aggregated silica and spherical silica. Further, as the glycol component in the silica particles in the present invention, ethylene glycol is preferable, and the content thereof is 0.05 to 15% by weight, preferably 0.1% by weight.
It is preferable that the content is 1 to 10% by weight from the viewpoints of moldability of the obtained polyester film, abrasion resistance during drawing / ironing, and adhesion to the steel sheet after retort.

[0010] A particle sample in the polymer for measuring the glycol component of the present invention is collected by centrifuging the particle and the polymer as a pretreatment. Hereinafter, a method of centrifuging the particles and the polymer will be described.

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. The completion of the separation is approximately 90 minutes, but this confirmation is performed, if necessary, when the light transmittance at 375 mμ of the liquid after the separation becomes a constant value higher than that before the separation. Since polymer particles may be mixed in the separated particles due to insufficient separation, O-chlorophenol at room temperature is added to the collected particles, and after substantially uniform dispersion, centrifugation is performed again. This operation needs to be repeated until the particles described below are dried and the melting point corresponding to the polymer can no longer be detected by scanning differential calorimetry on the particles. Finally, the separated particles thus obtained are vacuum-dried at 120 ° C. for 16 hours and weighed.

The average particle size of the silica particles in the present invention is 0.01 to 3.0 μm, preferably 0.05 to 3.0 μm.
The thickness of 2.0 μm is preferred from the viewpoint of the slipperiness, moldability, abrasion resistance at the time of drawing / ironing, and adhesion to the steel sheet after retorting. When the average particle diameter of the silica particles exceeds 3.0 μm,
Abrasion resistance during drawing / forming and adhesion to a steel sheet after retorting may be poor. If the average particle diameter is less than 0.01 μm, the resulting polyester film has poor slipperiness, which is not preferable because the film is damaged and the moldability is reduced.

The content of the silica particles with respect to the polyester is 0.02 to 1% by weight, preferably 0.05% by weight.
It is good in terms of slipperiness, moldability, abrasion resistance at the time of drawing / ironing, and adhesion to a steel sheet after retorting.
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. In some cases, the wear resistance during the drawing / ironing process and the adhesion to the steel sheet after retorting may be poor.

The method for producing 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.

As a method of causing the glycol component to be present in the silica particles by post-treatment, the silica particles are previously heated in a glycol slurry having a concentration of 2 to 20% by weight at a temperature of 150 to 200 ° C. for 1 to 5 hours. Processing is preferred. Further, the polyester film of the present invention may be used in combination with particles other than silica particles within a range that does not impair the effects of the present invention, whereby the resulting polyester film has slipperiness, moldability of metal cans, impact resistance, and resistance to impact. Abrasion and adhesion to the steel sheet after retort may be improved. Although such particles are not particularly limited, for example, inorganic particles include titanium oxide, zirconium oxide, aluminum oxide, calcium carbonate, talc, calcium sulfate, spinel, calcium phosphate, and the like, and organic particles or organic polymer particles. As cross-linked polystyrene particles, styrene-acrylic cross-linked particles, acrylic cross-linked particles, styrene-methacrylic cross-linked particles,
Examples include vinyl-based particles such as methacrylic cross-linked particles, and particles containing silicone, polytetrafluoroethylene, polyphenylester, phenolic resin, and the like as constituent components. The average particle size and content of the particles other than these composite oxide particles are not particularly limited, but the slipperiness of the obtained polyester film, the moldability of the metal can, the abrasion resistance during drawing / ironing molding. The average particle size is 0.005 to 3 μm from the viewpoint of the properties and adhesion to the steel sheet after retort.
m is preferable, and more preferably, 0.01 to 2 μm. The content is preferably 0.001 to 1% by weight, more preferably 0.005 to 0.5% by weight.

In mixing the silica particles with the polyester in the present invention, besides a method of directly adding the particles to the polymerization reaction system, for example, a method of kneading the particles into a molten polyester is also possible. 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.p. for maintaining 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 film strength is hardly reduced and crystallization is hardly caused, and no breakage or crack 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. The heat treatment temperature can be any temperature not lower than the crystallization temperature of the polyester and not higher than the softening point, but is preferably from 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.

Although the thickness of the film of the present invention is not particularly limited, it 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.

[0026]

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 characteristics Glycol The particles collected by centrifugation from the polymer are extracted in methyl alcohol at the boiling point of methyl alcohol for 10 hours. The extract was analyzed and quantified by gas chromatograph type GC-9A manufactured by Shimadzu Corporation.

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), and the image of the particles was processed by an image analyzer. 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 abrasion resistance was evaluated by a four-step method.

B. Heat resistance The molded metal can was heated at 210 ° C. for 5 minutes, the state of the film bonded to the metal can was observed, and the heat resistance was evaluated by a four-step method.

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 into 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.

The peel length of the film from the steel sheet after retorting was evaluated by a four-step method.

D. Wear resistance Laminated steel sheet is ironed and coiled by drawing machine and draw forming machine.
000 m (molding ratio (maximum thickness / minimum thickness) = 1.70,
Molded in the moldable temperature range, cans (diameter 6 cm, height 12
cm). At this time, the shaving amount of the film attached to the tool was measured and evaluated by a four-step method. 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, an ethylene glycol slurry containing 10 parts by weight of coagulable silica having an average particle diameter of 0.1 μm was heated at 195 ° C. for 2 hours, and then 1.5 parts by weight of the ethylene glycol slurry was added. The polyester is then subjected to a polycondensation reaction, and the polyester
After a solid phase polymerization reaction for a time, a polyester for a polyester film having an intrinsic viscosity of 0.72 dl / g was obtained. Particles were separated from the obtained polyester, and the amount of ethylene glycol in the particles was measured. As a result, it was 0.4% by weight. 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 was stretched 3.5 times in the longitudinal direction at 90 ° C. and then 3.5 times in the width direction at 105 ° C. Further, the biaxially stretched film was heat-treated at a constant length of 190 ° C. to obtain a 25 μm thick polyester film. Table 2 shows the film characteristics and the evaluation results. Slipperiness, heat resistance, abrasion resistance during drawing / ironing, and adhesion after retorting were all good. Examples 2 to 8 As shown in Table 1, the average particle size of silica, the amount added, the amount of ethylene glycol in the separated particles, and the intrinsic viscosity of the polyester composition were changed, and the polyester and polyester film were produced in the same manner as in Example 1. I got Table 2 shows the results of evaluating the characteristics of the obtained film. Both are slippery,
The abrasion resistance during the drawing / ironing process, the heat resistance, and the adhesion to the steel sheet after retorting were good. Comparative Example 1 As shown in Table 1, the properties of silica particles, the amount added, the amount of ethylene glycol in the separated particles, and the intrinsic viscosity of the polyester composition were changed without heating the ethylene glycol slurry of the particles. In the same manner as in Example 1, a polyester and a film were obtained. Table 2 shows the properties and evaluation results of the obtained film. All were inferior in any of the required properties of the present invention, such as slipperiness, heat resistance, abrasion resistance during drawing / ironing, and adhesion to a steel sheet after retorting. Example 9 Hydrolysis of alkyl silicate containing 1.5 μm of average particle diameter and 5% by weight of ethylene glycol as silica particles A polycondensation reaction was carried out in the same manner as in Example 1, except that 0.2% of spherical silica particles were contained. Solid-state polymerization reaction, specific year
69 dl / g of polyester was obtained. A polyester film was obtained from the polyester in the same manner as in Example 1.
The resulting film had good slipperiness, abrasion resistance during drawing / ironing, heat resistance, and adhesion to a steel sheet after retorting.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

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.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F071 AA45 AA46 AB26 AE17 AH05 BA01 BB06 BB08 BC01 4F100 AA20A AK41A BA01 JA20A JL11 YY00A 4J002 CF031 CF061 CF071 CF081 DJ016 FD010 FD016 GG00

Claims (5)

[Claims] 1. A polyester film comprising an aromatic dicarboxylic acid and a glycol as main constituents, wherein said polyester particle contains silica particles containing a glycol component in an amount of 0.05 to 15% by weight. Polyester composition. 2. The silica particles having an average particle size of 0.01 to 3.
The polyester composition for bonding metal plates according to claim 1, wherein the polyester composition has a thickness of 0 µm and a content of 0.02 to 1% by weight. 3. The polyester film for bonding metal plates according to claim 1, wherein the glycol component is ethylene glycol. 4. The polyester film according to claim 1, wherein the polyester composition is a copolymerized polyester composition. 5. A polyester film for laminating a metal plate, comprising the polyester composition according to claim 1.