JPS5847346B2 - Method for manufacturing containers and container lids made of coated metal structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing containers and container lids made of coated metal structures.

In recent years, in the field of paints, solvent-free paints have been developed as so-called pollution-free paints.

These solvent-free paints include paints that have the fluidity necessary for painting and that polymerize to form a coating film under the action of light, radiation, or catalysts, and paints that are based on powdered thermoplastic resins. It has been known.

However, these solvent-free paints are not fully satisfactory in terms of the durability of the coating film formed, the corrosion resistance against metal substrates, the extraction resistance, or the processability of the coated material.

For example, paints based on thermoplastic resins generally have unsatisfactory adhesion to metal substrates such as steel plates, and also have insufficient corrosion resistance, which can cause damage to the paint film, especially when processing coated metal materials. Or dogs with a tendency to peel.

For example, when using a steel plate substrate as a steelmaking material,
It is necessary to subject the can body material to severe processing such as drawing, drawing/ironing, flanging, seaming, etc., and known thermoplastic resin-based paints suffer from damage to the paint film under such processing conditions. This may cause peeling or peeling.

Furthermore, when paints made of thermoplastic resins are used as paints for the inside of chisels, the amount of components extracted into the food contents is generally small, giving the food a so-called poly-odor and tending to impair the flavor. This tendency becomes even greater when the canned food is sterilized by heat (retort sterilization).

The present inventors formed a chromium-containing coating layer mainly composed of nonmetallic chromium, which will be described in detail later, on the surface of a metal substrate, and
Thermoplastic polyester or polyester ether, which will be detailed later, is selected as the thermoplastic resin for coating.1. , and when the thermoplastic polyester or polyester ether is thermally fused to the metal substrate via the chromium-containing coating layer, the coated metal structure that is formed has excellent coating film adhesion and corrosion resistance of the metal substrate. Furthermore, it has been found that this coated metal structure exhibits excellent workability without causing damage or peeling of the coating even when subjected to brutal processing.

The inventors further found that the above-mentioned coated metal structure exhibits corrosion resistance even after processing and heating, particularly after being formed into a container and undergoing hot water treatment such as retort 7 sterilization. It has been found that the material is outstandingly superior and useful as a material for containers.

According to the present invention, the substrate made of metal and the amount of chromium coated on at least one surface of the metal substrate are 0.005 to 0.5 μ/da'' in terms of chromium, and 70% or more in terms of chromium is A substantially amorphous coating layer consisting of non-metallic chromium of chromium oxide or hydrated chromium oxide, and an orthochloromethane coating layer heat-sealed to a metal substrate via the chromium-containing coating layer. 1.0 in phenol? / 100m
The concentration of l and the intrinsic viscosity measured at 30°C are 0.7 to 2.
．． A coated metal structure consisting of a coating layer of plastic polyester or polyester ether is heated to a temperature in the range of 8.
There is provided a method for producing a container or a container lid, characterized in that the container or container lid is subjected to drawing forming or ladder forming so that at least the inner surface of the container becomes the surface coated with the thermoplastic polyester or polyester ether.

According to the present invention, many advantages are achieved by heat-sealing the above-mentioned thermoplastic polyester or polyester ether to a metal substrate via a chromium-containing coating layer mainly composed of non-metallic chromium on the metal substrate. .

First, the thermoplastic polyester or polyester ether used in the present invention can be applied directly onto a surface-treated metal substrate in the form of a melt by a method known as extrusion lamination, or applied as a film, powder, etc. on a surface-treated metal substrate. It can be applied as a coating film by fusing it on the spot, etc., without using solvents that cause air pollution, and without the need for processes such as baking. It has the ability to form a protective coating film with uniform properties without coating defects.

Additionally, in connection with the presence of a specific amount of chromium-containing coating layer in the coated metal structure of the present invention, it is possible to directly heat an untreated metal substrate, such as an untreated steel plate (crack plate). Compared to the case where plastic polyester or polyester ether is thermally fused, the adhesiveness of the coating layer and the corrosion resistance of the metal substrate are significantly superior.

Moreover, the adhesion of the coating and the corrosion resistance of the metal substrate mentioned above are
In connection with the coating of thermoplastic polyester or polyester ether, it is also satisfactorily achieved when the surface of the metal substrate is subjected to a very mild chromic acid treatment, which is different from the conventionally known tin-free steel. .

Thus, according to the present invention, compared to conventional coated metal structures made of tin-free steel (TFS), the processing process can be streamlined and simplified, processing costs can be reduced, and the power efficiency can be improved. becomes.

Furthermore, the coated structure of the present invention not only has excellent processability or formability, but also maintains the adhesion of the coating and the corrosion resistance of the metal substrate even after severe processing of the coated structure. .

When a structure in which a conventional chromium-coated steel sheet containing a metallic chromium layer (so-called tin-free steel) is coated with an organic resin is subjected to drawing forming, the metal layer becomes hard and hard.
Unable to follow the plastic flow of the steel matrix, there was a large rack.

On the other hand, even if the structure of the present invention, which is made of a steel substrate and is coated with a specific organic resin through a chromium film that does not contain metallic chromium and is essentially -L-amorphous, is subjected to drawing processing, the chromium film will not be removed. The material is made of thin, substantially amorphous chromium with good processability, and in conjunction with the use of a specific polyester coating layer, it is difficult for cracks to enter, and even if they do, they are limited to very few racks.

Note that changes in the chromium coating layer before and after these processes can be easily confirmed by, for example, observation using a transmission electron microscope.

As a result, in coated structures after drawing using tin-free steel, the adhesion between the organic resin and nine-free steel and corrosion resistance are poor due to the large rack, but the coated structures of the present invention It has the advantage that it is less affected by cracks and its adhesion to steel sheets and corrosion resistance remain intact even after processing.

In addition, when drawing a coated structure made of tin-free steel, the hard metal chromium layer damages not only the organic coating but also the drawing punch and die, and the scratches on the surface of these tools can subsequently damage the inner and outer surfaces of the container. Due to the damage, it was not possible to continuously produce high-quality containers.

In connection with the selection of a specific chromium coating and organic resin during drawing, the coated structure of the present invention not only has excellent adhesion to the steel plate and corrosion resistance as described above, but also
There were no scratches on the surface of the drawing punch or die, making high-speed can manufacturing possible for the first time.

Squeezing force ``When the container wall is further ironed afterwards, the above-mentioned difference between conventional products and crystal becomes even more pronounced.

Moreover, these characteristics also make it possible for the film to withstand long-term contact with fumes or liquids containing acids, alkalis, or salts that are highly corrosive to metals, through the coating.
Furthermore, it will not be lost even when it comes into contact with hot water, such as in retort sterilization in difficult packing.

In summary, the coated metal structure of the present invention is useful as containers, especially containers for filling and storing food products, and does not give the contents a metallic odor such as iron due to corrosion, or prevents the contents from being stored. It doesn't lower your sexuality.

Furthermore, the above-mentioned coating made of thermoplastic polyester or polyester needle has excellent extraction resistance and does not impart any foreign odor such as so-called poly odor to the food contents.
It does not compromise the subtle flavors of food.

One of the important features of the present invention is that the metal is coated with a chromium-containing coating layer mainly composed of non-metallic chromium with a chromium coating amount in a specific range of 0.005 to 0.5 m9/dm2 in terms of chromium. The novel finding is that the substrate has outstanding adhesion to the thermoplastic polyester or polyester ether coating layer.

First, the chromium-containing coating layer in the present invention has a chromium coating amount of 0.005 mg/dmj or more in terms of chromium (unless otherwise specified, the chromium coating amount has this meaning), particularly 0.005 mg/dmj or more.
It must be thrown at 01 m9/dm or more and 0.5cm/(1m or less, especially 0-3my/dm or less.

When the amount of chromium coated is less than the above range, the adhesion or adhesion of the thermoplastic polyester or copolyester to the metal substrate is considerably reduced compared to the case of the present invention, and the adhesion after processing or hot water treatment is significantly reduced. There is a tendency for the adhesive properties to decrease significantly.

Further, when the amount of chromium coating is larger than the above range, the workability of the coated structure tends to be low due to the fact that the chromium-containing coating layer is mainly composed of nonmetallic chromium.

Thus, according to the present invention, by setting the amount of chromium coating within the above-mentioned range, - a coating structure with excellent adhesion of the resin coating after processing and excellent corrosion resistance of the metal substrate can be achieved, compared to a case outside the above-mentioned range; You can get things.

The most suitable chromium-containing coating layer for the purpose of the present invention is 0.05
It has a chromium coating amount of 0.2 to 0.2 m9/'dm.

Furthermore, it is important that the chromium-containing coating layer of the present invention is mainly composed of nonmetallic chromium in order to form a thermoplastic polyester or polyester ether coating that can withstand severe processing and hot water treatment.

Conventionally, as the chromium-containing coating layer formed on the surface of a metal substrate, a metallic chromium layer (chromium plating layer), a nonmetallic chromium layer of chromium oxide or aqueous chromium oxide, or a combination thereof has been known. There is.

When comparing the same chromium coating amount in terms of chromium, a non-metallic chromium layer has better adhesion to an organic resin coating than a metallic chromium layer, but a non-metallic chromium layer has better corrosion resistance than a metallic chromium layer. It is also believed that non-metallic chromium layers have poorer adhesion to metal substrates than metallic chromium layers. It was believed that it was necessary to interpose a considerable amount of metallic chromium layer between the two.

Furthermore, it has been thought that if the amount of chromium coated is considerably large, generally 0.8 .mu./dm or more, excellent corrosion resistance of the metal substrate and adhesion of the coating film cannot be obtained.

On the other hand, in the present invention, a specific thermoplastic polyester or polyester ether is selected as the coating,
And by setting the amount of chromium coating within the range mentioned above,
Even when the chromium-containing coating layer consists essentially only of nonmetallic chromium, a coated structure with excellent coating adhesion, corrosion resistance to the metal substrate, and workability can be exceptionally obtained, which is explained above. Considering conventional common sense, this is quite surprising.

Nonmetallic chromium, which is the main component of the chromium-containing coating layer, consists of chromium oxide or chromium hydrated oxide that is physically or chemically bonded to the metal substrate. Chromium exists in trivalent, hexavalent, or a mixed state of these (including oxides).

A chromium-containing coating layer which is particularly suitable for the purposes of the present invention consists essentially of non-metallic chromium, generally at least 70% in terms of chromium, of chromium oxide or aqueous chromium oxide, and which is substantially non-metallic. It is crystalline (amorphous).

Of course, the chromium-containing coating layer of the present invention can have a metallic chromium layer as an underlayer (an intervening layer between a metallic substrate and a non-metallic chromium layer) depending on the type of means for forming it, that is, the type of processing means. The amount of such a metallic chromium layer is preferably 30% or less, particularly 10% or less of the chromium-containing coating layer.

According to the present invention, since the total amount of chromium coated is small, the cost for coating is low, and since the chromium-containing coating is substantially composed of non-metallic chromium, chromic acid etc. can be reduced to metallic chromium. This eliminates the need for electrolytic energy for electrolysis, and as a result, a significant advantage is achieved in that a coated metal structure with excellent adhesion, corrosion resistance, and workability can be provided at a low cost.

In the present invention, the metal substrate for forming the above-mentioned chromium-containing coating layer on the surface may be any metal substrate on which such a coating layer can be formed, such as untreated steel, various plated plates of light metals such as aluminum, and various alloys. etc. can be mentioned.

Depending on the application, these metal substrates include foil or sheet substrates, as well as angle materials, knee beams, tubes,
It can be used to form a chromium-containing coating layer in the form of various shapes such as pipes and rods, and molded products such as wires and ropes.

The invention is particularly suitable for untreated steel (black plate) or aluminum foils with a thickness in the range from 3 to 150 microns, in particular from 5 to 100 microns, and in particular from 0.1 to Q.
It can be particularly suitably applied to coating untreated steel plates or aluminum plates in the range of 57 nM.

The chromium-containing coating layer in the present invention can be formed by any method except for the above-mentioned limitations.

For example, the formation of the chromium-containing coating layer is performed using chromic anhydride (Cr
It can be carried out by using an aqueous solution containing 03), by dipping treatment, spraying treatment, coating treatment with a roller or various coaters, electrolytic treatment, or the like.

Any composition can be used as the aqueous solution containing chromic anhydride, but in order to effectively form the above-mentioned chromium-containing coating layer, the CrO3 content should be 10 g/.e or less, especially 0.0 g/.e or less. Preferably, relatively dilute aqueous solutions of 5 to 5 g/l are used.

In the production of conventionally known electrolytic chromic acid treated steel sheets, CrO3
Is the content between 40 and 200? A bath in the range of /l is generally used, but the formation of the chromium-containing coating layer of the present invention is characterized by the use of a solution that is more dilute than known electrolytic chromic acid treatment baths. be.

To this aqueous solution containing chromic anhydride, various additives are added at 5% per chromic anhydride in order to adjust the amount of chromium coating, the properties of the chromium-containing coating layer, and the stratification state, depending on the treatment method used. In particular, it can be contained in an amount of 1% or less.

For example, in order to adjust the adhesion of the chromium-containing coating layer to the metal substrate, sulfate ions, nitrate ions, halide ions,
Acid anions such as halogen oxygen acid ions and halide acid ions can be present, and cobalt, molybdenum, tungsten, nickel, zinc, etc. can be added to metal cations or metal oxygen for the purpose of modifying the chromium-containing coating layer. It can be present in the form of acid ions, and monohydric or polyhydric alcohols such as ethanol, propatool, ethylene glycol, phlopylene gelicol, diethylene glycol, glycerin, sorbitol, mannitol, pentaerythritol, citric acid, tartaric acid, etc. , maleic acid,
Organic acids such as acetic acid, benzoic acid, sepacic acid, adipic acid, salicylic acid, benzenesulfonic acid, naphthalenedisulfonic acid, phthalic acid, etc. can be present.

Furthermore, there is no particular problem even if these aqueous baths contain alkali metals such as sodium and potassium, and ammonium ions as impurities.

Also, chromium sulfate (III) is added to the bath as a source of chromium.
), an inorganic or organic acid salt of chromium such as chromium sulfate can also be contained.

The temperature at which the chromic anhydride solution and the metal substrate are brought into contact can vary widely, generally within the range from 30°C to the boiling point of said solution, but it is preferred to use temperatures between 40 and 95°C, particularly at high temperatures. In terms of efficiency, it is preferable to make contact at the sides.

In order to adjust the contact temperature between the chromic acid anhydride solution and the metal substrate to the above temperature, 1) maintain the temperature of the treatment bath at a constant temperature, 2) adjust the temperature of the metal substrate to the above temperature or slightly higher than the above temperature. It is preferable to use means such as holding the temperature at 100%, or 2 combining the above 2 and 3.

The time period for which the anhydrous chromic acid solution and the metal substrate are brought into contact may be such that a chromium coating amount within the above-mentioned range can be obtained, and although this time varies depending on the treatment temperature and composition of the treatment solution, it is generally 0. Relatively short times, such as 0.02 to 10 seconds, especially 0.05 to 5 seconds, are sufficient.

For example, when a metal substrate such as a rolled steel plate is brought into contact with a chromic acid solution, the rolling oil is degreased from the rolled steel plate by means known per se, and then the steel plate is subjected to a pickling process known per se. After that, it is added to the chromic acid treatment described above.

In this case, the steel plate immediately after degreasing and pickling treatment is generally at a temperature of 20 to 80°C, but it is thermoeconomical to make these operations continuous and perform the chromic acid treatment while the steel plate is within the contact temperature range mentioned above. It is preferable in this respect.

Chromic acid treatment of a metal substrate such as a steel plate can be carried out by simply immersing the metal substrate in a bath having the above-described composition and temperature for a predetermined period of time in a continuous or batch manner.

Alternatively, the coating can be carried out by spraying a chromic acid solution having the above-mentioned composition onto the surface of the metal substrate, or by applying it by a known coating means such as a roller or a coater.

A major feature of the chromium-containing coating layer of the present invention is that it can be easily formed by dipping, spraying, or coating in a short time without using any special electrolytic means.

When a metal substrate is immersed in a bath of chromic anhydride solution,
If desired, a mild electrolytic treatment can be performed using the metal substrate as a cathode.

In this case, it is generally desirable that the current density be in the range of 5 A/d i or less so that a chromium-containing coating layer consisting mainly of nonmetallic chromium is formed.

The metal substrate treated with chromic acid can be dried as is and used for coating with thermoplastic polyester or polyester ether, which will be described later, but generally the metal substrate after treatment is washed with water to remove free chromic acid. After removing and then drying, it is preferable to subject it to the coating step described below.

In the present invention, the presence of a small to trace amount of a chromium-containing coating layer on the surface of a metal substrate can be confirmed by various analytical means.

For example, the presence of a chromium-containing coating layer can be easily confirmed by fluorescent X-ray analysis of the coated metal substrate or by applying it to an X-ray microanalyzer, and can be quantitatively determined from the intensity at that time. .

Further, the fact that the chromium-containing coating layer is made of nonmetallic chromium can be confirmed by eluting the coating layer with a hot alkali and then performing atomic absorption spectroscopy.

Furthermore, it can be confirmed by an electron microscope that the chromium-containing coating layer is mainly a non-metallic chromium layer.

Another feature of the invention is that in orthochlorophenol 1.
A thermoplastic polyester or polyester ether having a concentration of 0 g/100 ml and an intrinsic viscosity in the range of 0.7 to 2.8 measured at 30° C. is thermally bonded to a metal substrate provided with the above-mentioned chromium-containing coating layer. It is used selectively as a protective coating.

The polyester resin used in the present invention is significantly different from conventional polyester paints, which are all thermosetting type, in that it is thermoplastic.

That is, conventional thermosetting polyester paints consist of a homogeneous liquid composition of a relatively low molecular weight unsaturated polyester having an ethylenic double bond and a polymerizable ethylenically unsaturated monomer.

A composition made of this composition is applied to a substrate and then cured to form a coating film by the action of light, ionizing radiation, heat, a catalyst, or the like.

Not only do such paints require special curing methods, but the resulting paint film has a moderate hardness but lacks toughness and flexibility, making it difficult to subject the coated structure to various treatments. difficult to do.

On the other hand, the resin made of polyester or polyester ether used in the present invention is a high molecular weight thermoplastic polymer obtained by highly condensing a dibasic acid component and a glycol component in advance. It does not have the drawbacks of thermosetting polyester paints mentioned above.

Furthermore, when the thermoplastic polyester or polyester ether mentioned above is heat-sealed to a metal substrate with a chromium-containing coating layer, it exhibits exceptional adhesion and corrosion protection compared to other heat-sealable protective coatings. Imparts the coated structure with the combined properties of flexibility and processability.

For example, it is widely known that a thermoplastic resin such as a polyolefin, an ionomer, or a polyvinyl chloride resin is heat-sealed as a protective coating onto a metal substrate on which a chromium-containing coating layer has been conventionally provided.

However, even though these thermoplastic resins can be thermally bonded to the substrate, they lack the corrosion resistance of metal substrates and the ability to retain the flavor of the contents. After this, the adhesion or adhesion of the film significantly decreases (see Comparative Examples described below).

On the other hand, the thermoplastic polyester or polyester ether used in the present invention has excellent corrosion resistance of the substrate and processability of the coated structure, and also has excellent adhesion of the coating after processing or hot water treatment, and It has surprisingly excellent anti-corrosion properties and ability to retain the flavor of the contents.

*The thermoplastic polyether or polyester ether used in the present invention has excellent adhesion, flexibility, anticorrosion properties, and the combined properties of , which is desirable in terms of its properties after processing.

The polyester or polyester ether used in the present invention generally has the following formula, where R1 is a divalent hydrocarbon group, and at least 66 mol%, particularly 85 mol% or more of the hydrocarbon group R1 is p-
Preferably it is a phenylene group, each of R2 and R3 is a divalent aliphatic hydrocarbon group, R2 and R3 may be the same or different, preferably at least 45 mol% of the groups R2 and R3 , especially 55 mol% is a tetramethylene group, p and q are numbers of 1 or more, m and n are halo or a number of 1 or more, and when one of m and n is zero, the other shall be a number greater than or equal to 1.

It consists of the unit -C.

In the general formula Ichishijiki, the divalent hydrocarbon group R1 includes a straight chain or branched alkylene group having 2 to 13 carbon atoms, a cycloalkylene group having 4 to 12 carbon atoms, and a cycloalkylene group having 6 to 15 carbon atoms. It can consist of an arylene group.

From the viewpoint of corrosion resistance, extraction resistance and mechanical properties of the coating film, it is most preferable that all divalent hydrocarbon groups R1 are arylene groups, but up to 34 mol% of all divalent hydrocarbon groups R1 It is permissible to substitute the above alkylene group or cycloalkylene group.

Examples of arylene groups other than p-phenylene include 0- or m-phenylene group, naphthylene group, and where CH2 4 is a direct bond, or 10-1 CH(CH3) --C(CH3)2 -1 or -NH-
The following groups can be mentioned, which represent divalent bridging groups such as groups.

In addition, with alkylene groups R2 and R3, the number of carbon atoms is 2
Among these, linear alkylene groups are preferred.

As the divalent aliphatic hydrocarbon group, groups other than alkylene groups, within a range not exceeding 55 mol% of the total glycol components,
For example, an aliphatic hydrocarbon containing an aromatic ring or a saturated ring such as a 0-1m- or p-xylene group or a 1,4-dimethylenecyclohexylene group as an intermediate group may be contained.

In the polyester or polyester ether used in the present invention, glycols may be (a) contained in a form bonded to all C dibasic acids, that is, in the form of ester repeating units, or (b) contained entirely in ester ether repeating units. (C) A portion may be contained in the form of ester repeating units and the remaining portion may be contained in the form of polyether glycol and dibasic acid combined, that is, in the form of ester ether repeating units. You can leave it there.

In the case of Haa), in the general formula (1), the repeating number n of the ester ether unit is zero or p in the ester ether unit is 1, and the polyester is a homopolyester or a copolyester, and all ester repeats. I will warn you from asking.

Suitable examples of such polyesters and copolyesters are as follows.

Polytetramethylene terephthalate, polytetramethylene/ethylene terephthalate, polytetramethylene terephthalate/isophthalate, polytetramethylene/ethylene terephthalate/'isophthalate, polytetramethylene 27' ethylene terephthalate 1.
/Hexahide terephthalate 1.

bb), in the general formula (1), the number of repeats m of the ester unit (4) is zero, and the number of repeats of the ether unit is 2 or more, and this polyester ether is an ester ether monomer. Contains only B).

It is desirable to select the repeating number p of the ether unit so that the average molecular weight of the polyether glycol is in the range of 200 to 4000, and within this range, the average molecular weight of the polyether glycol is in the range of 400 to 2.
It is preferable to select p to be in the range of 000.

Suitable examples of such polyester ethers are as follows.

Polyoxytetramethylene terephthalate; Polyoxytetramethylene/ramethylene/oxyethylene terephthalate, polyoxytetramethylene/oxyethylene terephthalate/isophthalate.

In the aspect of the present invention (former Utlc), the general formula (
In 1), both m and n are numbers greater than or equal to 1, and p
is a number greater than or equal to 2.

In this case, ester unit N and ester ether single DB)
There are no particular restrictions on the form of bonding, and this polymer may be in the form of a block copolymer as shown in the general formula or a random copolymer as shown in the general formula.

Repeating number p of ether units in ester ether single QB)
is the number of carbon atoms in the glycol constituting the polyether (group R
Generally, p is selected so that the average molecular weight of the polyether glycol is in the range of 200 to 4,000, and the average molecular weight of polyether glycol is in the range of 400 to 2,000. Good.

In the embodiment of the present invention using polymers of the polyester-ether type (Mac), if tel-ramethylene glycol is included, this component is incorporated into the esdel ether units [B) in the form of a polyether. Alternatively, it can be incorporated into the ester unit (4) in the form of an ester.

Of course, a combination of these two can also be adopted.

In this specification, when the degree of polymerization of polyether glycol is p, calculations are made by considering this polyether glycol as pmol of glycol.

Suitable examples of such copolyesters are as follows.

Te1'ramethylene terenotalate/'polyoxytetramethylene terephthalate copolymer, Te1'ramethylene terenotalate/'polyoxyethylene terephthalate/copolymer, ethylene terephthalate/polyoxytetramethylene Terephthalate 1/copolymer, detramethylene terephthalate/polyoxytetramethylene terephthalate/polyoxyethylene terephthalate copolymer, polytetramethylene terephthalate/polytetramethylene glycol block copolymer, polytetramethylene terephthalate/ Polytetramethylene glycol/polyethylene glycol block copolymer, polytetramethylene terephthalate/polypropylene glycol/polytetramethylene glycol/polyethylene glycol block copolymer.

The molecular weight of the polyester or polyester ether in the present invention is 1.0 in orthochlorophenol? /1
Intrinsic viscosity measured at a concentration of 0 ml and at 30°C
ηsp/C: ηsp: specific viscosity, C is concentration] is in the range of 0.7 to 2.8, more preferably 1.0 to 20, which improves adhesion to metal substrates, processability, and mechanical properties. This is important in that respect.

If this intrinsic viscosity is lower than the above range, the mechanical properties of the coating film will be poor compared to those in the range of the present invention, and if it is higher than the above range, the processability of the resin itself or the properties of the coating film will be poor. Processability deteriorates.

Furthermore, by selecting this intrinsic viscosity within the above range,
A desirable combination of excellent adhesion and processability to metal substrates is achieved.

The polyester or polyester ether used in the present invention varies depending on the composition ratio of the ester unit to the ester ether unit and the way of bonding, but the polyester or polyester ether is 130 to 2
It is desirable to have a softening temperature of 50° C., particularly preferably 150 to 235° C., in view of the balance between heat resistance and thermal adhesion of the coating.

Polyester or polyester ether with a softening temperature higher than 250°C may cause thermal deterioration of the polymer when thermally bonded to a metal substrate, and it may take a long time to fuse or cool the polyester, making it difficult to paint or Coating efficiency is undesirable, and such polyesters generally lack coating processability.

On the other hand, polyesters and polyester ethers whose softening temperature is lower than 130° C. may cause blocking of the film, and may also cause defects in the extraction resistance and heat resistance of the film.

The above-mentioned polyester or polyester ether polymer comprises a dicarboxylic acid or an ester-forming functional derivative thereof, a diol or an ester-forming functional derivative thereof, and a poly(oxyalkylene) glycol or It is produced by condensation polymerization of at least one functional derivative thereof using a method known per se.

In this case, it is preferred that at least 66 mol% of the dicarboxylic acid component is terephthalic acid and that at least 45 mol% of the total glycol component, including those used in the form of poly(oxyalkylene) glycols, is tetramethylene glycol. It is desirable that

Dicarboxylic acids that can be used in combination with terephthalic acid include isophthalic acid, diphenyl-4゜4' dicarboxylic acid, adipic acid, sebacic acid, hexahydroterentalic acid, etc., and diols include tetramethylene glycol, ethylene glycol, propylene glycol,
Examples include 1,4-cymethylene hexylene glycol and the like.

In addition, for the purpose of adjusting the physical properties of the polyester or copolyester to be formed, following a method known per se,
A monofunctional or trifunctional alcohol or carboxylic acid can be added within a range that satisfies the molecular weight (or viscosity) and softening temperature conditions of the present invention.

Furthermore, additives such as alkali and alkali metal fatty acid salts can be added according to methods known per se.

When synthesizing a homopolyester or copolyester consisting only of the ester single DA), at least one dicarboxylic acid component of the formula (a) and at least one diol component of the formula b) are reacted. That's fine.

In addition, when a certain homopolyester ether or copolyester ether is synthesized from only the ester ether unit B), at least one dicarboxylic acid component of the above Ma) and at least one polyester of the above c) What is necessary is to react with an oxyalkylene glycol component.

Of course, in this case, before the reaction or in the reaction system, the formula (
The dicarboxylic acid component a) and the diol component of formula (b) may be reacted to form a bishydroxy ester, and this bishydroxy ester may be reacted with the polyoxyalkylene glycol q c).

Furthermore, when synthesizing a polyester ether from an ester unit and an ester ether unit B), the three components of formulas (a), (b) and 'fic) described above may be reacted.

In this case, there is no particular restriction on the order in which the polyester-ether type polymer is synthesized.

For example, a polyester may be synthesized from the dicarboxylic acid component of the above 1iEQa) and the glycol of the above formula (b), and the polyester glycol may be reacted with the polyether glycol of the above formula (c), or the polyester ether may be reacted first. The three of formulas (a), (b), and (C) may be mixed and polycondensed.

The aforementioned polyesters or polyester ethers can be applied by any means to the metal substrate provided with the chromium-containing coating.

For example, this polyester or polyester ether can be applied by a method called extrusion lamination, which consists of extruding the polyester or polyester ether in a molten state into a thin film on the surface of a metal substrate provided with a chromium-containing coating layer.

At this time, the polyester or polyester ether in the present invention has excellent processability not only in the film state but also in the molten state, so the extrusion temperature of the resin and the movement speed of the treated metal substrate are adjusted. By doing so, it is possible to provide very thin coating layers, for example 10 microns or less.

Alternatively, the above-mentioned polyester may be extruded into a film by a film-forming method known per se, such as a T-die method or an inflation method, stretched uniaxially or biaxially as desired, and then this film is attached to the metal substrate. It can also be fused to the surface of

Alternatively, the polyester described above can be formed into a powder by means known per se, and this powdered polyester can be applied to the treated metal substrate by means such as fluidized dipping, electrostatic coating, powder spraying or the like.

The polyester of the present invention can of course be applied to the treated metal substrate in the form of a solution or dispersion, but in this case the advantages of the present invention of streamlining and pollution-free coating processes would be lost.

The temperature at which thermoplastic polyester or polyester ether is fused varies depending on the type of polyester or polyester ether, but is generally 18Q to 3
It is desirable to select an appropriate heat fusion temperature from the range of 0.0°C, particularly from 200 to 280°C.

The polyester coating is applied to at least a portion of the surface of the metal substrate provided with the chromium-containing coating layer, and more preferably to the entire surface of the substrate.

The thickness of the polyester coating layer is not particularly limited as long as there are no coating defects such as pinholes. For example, according to the present invention, coating defects such as pinholes may occur even when the coating thickness is as thin as 1 micron. It is a remarkable advantage that properties such as flexibility and ductility necessary for processing the coating layer are not lost even when the coating thickness is as thick as 300 microns.

However, making the coating too thin causes problems in terms of reliability of corrosion resistance, and making it too thick causes problems in terms of economic efficiency.
Preferably, the coating is applied to a thickness of microns, especially 15 to 200 microns.

As shown in FIG. 1, the coated structure of the present invention comprises a metal substrate 1 such as steel or aluminum, and chromium-containing coating layers 2, 2 mainly composed of nonmetallic chromium bonded to the surface of the substrate.
The thermoplastic polyester or polyester ether coating layers 3, 3 are heat-sealed to the metal substrate via the chromium-containing coating layer.

This coated structure has a structure in which a specific thermoplastic polyester or polyester ether coating layer is thermally fused to a metal substrate via a specific chromium-containing coating layer, so it can be drawn in the form of a coated structure. Various types of processing such as ironing, flange processing, and bending processing can be easily performed, and even after these processings, excellent coating adhesion and corrosion resistance of the metal substrate are maintained.

For example, a steel plate (D
However, according to the present invention, by pre-coating the above-mentioned polyester or polyester ether with a chromium-containing coating layer, bending process of Not only is it possible to bend the molded product, but the molded product that has been bent in this way also exhibits excellent corrosion resistance in salt water tests and storage tests in actual cans filled with foodstuffs.

Furthermore, even when this coated structure is subjected to hot water heat treatment at 100 to 150°C for 1 minute to 2 hours, it exhibits excellent coating film adhesion and corrosion resistance of the metal substrate, as shown in the examples below. is never lost.

Thus, the coating structure of the present invention can be used as a variety of container materials by taking advantage of these excellent properties.

In this case, the above-mentioned coated metal structure is formed into a container by means known per se so that the thermoplastic polyester or polyester ether coating layer is on the inner surface.

-L The coated metal structure described above is formed into a container with seamless sides by drawing or ironing.

In this case, the above-mentioned coated metal structure is subjected to at least one drawing process between a drawing die and a punch, and is integrally connected to the side body part with no seam on the side surface and the side body part without a seam. Then, if desired, the side body portions are ironed to form a container with seamless sides.

Since the coated structure of the present invention has excellent workability, it is defined by the following formula, where D is the minimum diameter of the coated metal structure subjected to drawing processing, and d is the minimum diameter of the punch. The drawing process can be performed so that the drawing ratio (RD) is in the range of 1.1 to 3.0, especially 1.2 to 28, and in the following formula, 1o is the thickness of the metal material before ironing. Yes, t1
Generally speaking, the ironing rate (Rl), which is defined as the residual board thickness after ironing, is in the range of 10 to 50% for one stage of ironing and 10 to 80% for the entire ironing process. It can be subjected to ironing process.

FIG. 2 shows an example of a lateral seamless container according to the present invention,
The container consists of a side body part 8 with no side seams and a bottom part 9 seamlessly connected to the side body part.

The bottom part 9 has substantially the same thickness as the coated metal material used, while the side body part 8 has a thickness of the coated metal material used, depending on whether it has been subjected only to drawing or ironing. or less than the thickness of the material.

This container with seamless sides can be domed, neck-in-beaded, and flanged if necessary.
It can be formed into a can body that can be double-sealed with the can lid.

The coated metal structure of the present invention also has excellent processability, so it can be easily formed into various container lids, such as crowns, screw caps, twist-off caps, peelable camps, can lids, etc. In both cases the same advantages as with containers are achieved.

In particular, when the coated metal structure of the present invention is used as a can lid, it can be processed very easily to attach an opening mechanism such as an easy-open mechanism, and its excellent anti-corrosion properties are maintained. This is also a significant advantage.

The coated metal structure of the present invention can be easily formed or processed into these various forms of containers, has excellent adhesion of the coating film after processing and corrosion resistance of the metal substrate, and has excellent coating components that are not extracted by food. In addition, it is excellent in retaining the flavor of the contents, and these characteristics are not lost even when subjected to harsh treatments such as heat sterilization.

Further, since the coating in the coated structure of the present invention has excellent thermal adhesion, finishing such as thermal fusion of a printed film is easy.

The invention is illustrated in the following examples.

Example 1 After electrolytically degreasing and pickling a twice-cold-rolled steel plate with a thickness of 0.17 mm,
The samples were immersed in a bath containing 12/l of chromic anhydride at 93 DEG C. for the times shown in Table 1 to obtain samples having chromium coatings having compositions A1 to A6.

Terephthalic acid 157.7 parts (0.95 mol), isophthalic acid 8.3 parts (0.05 mol), 1.4 tetramethylene glycol 82.5 parts (0.90 mol), ethylene glycol 6.2 parts A 30μ thick film of copolyester (intrinsic viscosity 1.85) consisting of (0.10 mol) was melt-bonded at 250°C to the surfaces of various steel plates shown in Table 1 to create polyester-coated steel plates, and the films shown in Table 2 were Tested.

Table 2 shows the results of various characteristic tests on these samples.

As Comparative Example 1, thickness Q. A 171 lr/L twice cold rolled steel plate was used.

In Comparative Example 2, a 30μ thick polypropylene (Profax manufactured by Hercules) was applied to the A3 treated steel plate in Table 1.
Comparative Example 3 is a coated steel plate in which a film was melt-bonded at 250°C, and Comparative Example 3 is a coated steel plate in which a steel plate treated in the same manner as in Example 3 is coated with an epoxy paint for cans to a thickness of 5 μm.

Comparative Example 4 is a commercially available tain-free film with a thickness of 0.17 mm.
Steel was used.

From Example 1 and Comparative Example 4, it can be seen that the amorphous chromium hydrated oxide coating of the present invention is particularly superior to the coating containing metallic chromium when processed and used. To investigate the cause of this, changes in the surface coating before and after drawing were observed using a transmission electron microscope.

Chromium content 0. 15 m9/d m, steel plate with the coating of the present invention having a proportion of amorphous chromium of 100% (Example 1)
, A3) and the amount of chromium 1 1 5 mp/. (1, l
A commercially available TFS (tein free steel) having a coating containing 73% amorphous chromium was subjected to drawing processing, and a sample was taken from a portion with a drawing ratio of 1.5.

For the sample, the thermoplastic polyester coating layer was previously dissolved and removed in orthochromic phenol, and then the sample was immersed in 5% nital to dissolve the base steel, and only the chromium coating layer was taken out and observed with a transmission electron microscope.

The surface coating of the product of the present invention has no cracks even after drawing, but commercially available TFS has many cracks observed in the form of a white net after drawing.

In particular, cracks become large in the critical crystalline region of the metallic chromium layer.

It is believed that the presence of metallic chromium (crystalline substance) makes it easier for cracks to form during processing, thereby deteriorating corrosion resistance.

Example 2 A twice-cold-rolled steel plate having a thickness of 0.26 mm was degreased and pickled, and then immersed in a bath containing 12/l of chromic acid anhydride at a temperature of 70°C for 1 second.

This is added to polytetramethylene terephthalate (intrinsic viscosity 1
．． 75) A 35 μ film was melt-bonded at 260° C., and then formed into a fully open edge with a diameter of 202 mm by a conventional method.

This was subjected to the same treatment and polyester coating with a thickness of 0.17 mm, and then re-drawn (drawing ratio 2.3). After filling baby food into a can body with a height of 45.5++ m, 2
It was sealed and sterilized by heavy wrapping.

After storage at 50° C. for 6 months, the can was opened and the rust was observed, the state of the polyester coating was observed, the contents were subjected to a play bar test, and leached iron was measured, all of which showed good results.

In addition, the amount of chromium film at this time is 0.15■ in terms of chromium amount.
/ d m” (Ratio of non-metallic chromium/chromium is 100%
)Met.

Example 3 After degreasing and pickling steel foil with a thickness of 100μ, chromic anhydride 52
/l, sulfuric acid 0.05g/l, immersion treatment for 5 seconds in a bath at 50°C, chromium content equivalent: 0.121n9/d m
' (Ratio of nonmetallic chromium/chromium was 100%) was obtained.

A 50μ film of polyethylene terephthalate/isophthalate (intrinsic viscosity 1.80) was placed on both sides of this at 240°C.
Melt and glue the length 15crIL x width 10crIL x height 3
．． It was molded into a square container with 5 flanges.

After filling this with meatballs, heat-sealing with 30μ steel foil treated and coated in the same way, heating and pressure sterilization.
It was stored for 6 months in 'c.

This was opened, and the inner surface of the container was inspected, and the characteristics of the contents and leached iron were measured, but no abnormalities were found in any of them.

Example 4 Aluminum 'M (JISH-I N-3) with a thickness of 60μ
0 -H-0) cumic anhydride 101/. e,
Sulfuric acid 0.0 0 7? /l, borohydrofluoric acid 0.00
5? /'l, immersion treatment for 3 seconds in a bath with a bath temperature of 45°C, and chromium-converted Xo. A chromium coating of os/d m (nonmetallic chromium/chromium ratio is 100%) was obtained.

Terephthalic acid 80 parts, sebacic acid 15 parts, adipic acid 5 parts
This polyester consists of a dibasic acid consisting of
) 60μ film on both sides of this aluminum foil at 240℃
From blank size 12Qgφ, inner diameter 6
It was drawn into a cup with a diameter of 5 mm, a height of 30 mm, and a flange width of 31 rL1IL.

After filling this with sausage, it was heat-sealed with a 100 μm aluminum foil treated and coated in the same manner, sterilized by heating and pressure, and then stored at 50° C. for 6 months.

This was opened and the inner surface of the container was observed and the characteristics of the contents and the amount of eluted aluminum were measured, but no abnormalities were found in any of them.

Example 5 Polyethylene glycol (molecular weight approximately 1500) and polyethylene glycol (molecular weight approximately 900) shown in Table 3 were used.
), ■ Polyester di-7-yl synthesized by transesterification and condensation from 4-tetramethylene glycol and dimethyl terephthalate (intrinsic viscosity and glycol component (
Table 3 shows the percentage of tetramethyle/glycol component (in terms of mole)) which was formed into a film having a thickness of 40 μm using a film forming machine.

This film was treated with chromic anhydride o. 5? /l, chlorine ion 0.1'? 0.17mm thick chromium film with a chromium equivalent of 0.2cm/dm (non-metallic chromium/chromium ratio is 100%). Twice cold rolled steel plate 240~ **270℃
It was melted and glued.

Add this to a three-time squeeze can with a diameter of 301 and a height of 1 1 3 crrL (
Table 4 shows the test results after molding to a drawing ratio of 2.7), filling with fruit cocktail, sterilizing, and storing at 50°C for 6 months.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the coated metal structure of the present invention, and FIG.
The figure is a sectional view showing an example of a seamless container with a side surface manufactured from the coated metal structure of the present invention, in which reference numeral 1 is a metal substrate, 2 is a chromium-containing coating layer, and 3 is a thermoplastic polyester or polyester ether. The covering layer, 8 represents the side body part, and 9 represents the bottom part.

Claims (1)

[Scope of Claims] 1. A substrate made of a metal, and an amount of chromium coated on at least one surface of the metal substrate, in terms of metallic chromium.
005 to 0-5 '%'/d rri', and a substantially amorphous chromium-containing coating layer in which 70% or more in terms of chromium is made of nonmetallic chromium such as chromium oxide or hydrated chromium oxide; Heat-sealed to a metal substrate via a chromium-containing coating layer,
1.0′ in orthochlorophenol? Intrinsic viscosity measured at 7100ml concentration and 30°C is 0.7 to 2.8
A coated metal structure with a coating layer of thermoplastic polyester or polyester ether in the range of A method for producing a container or a container lid comprising a coated metal structure.