JP2852690B2 - Resin-coated steel sheet for drawn and ironed cans and drawn and ironed cans - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resin-coated steel sheet for drawn and ironed cans and a drawn and ironed can.

(Prior art) Conventionally, it is remarkably excellent in workability against drawing and ironing, and it is possible to perform ironing at a high ironing rate of 60% or more with a resin coating on the inner surface, Japanese Patent Application Laid-Open No. 60-186863 proposes a resin-coated steel sheet for a drawn and ironed can which can obtain a drawn and ironed can excellent in adhesion, corrosion resistance and appearance properties of a resin film by drawing and ironing.

The proposal consists of a coating layer of a thermoplastic resin such as polyethylene terephthalate resin, which can be oriented on the outermost surface that should be inside when drawn and ironed and has a barrier property against corrosive components, and adheres under this coating layer. A drawn ironing can having an inorganic oxide film layer such as hydrated chromium oxide as a base and having a plated layer of a spreadable metal such as Sn on a surface to be an outer side when the drawn iron is made into a drawn iron. Resin-coated steel sheet.

(Problems to be Solved by the Invention) In order to obtain a drawn and ironed can having excellent adhesion, corrosion resistance and appearance characteristics of the resin film by drawing and ironing such a resin-coated steel sheet for a drawn and ironed can, As specified in the above-mentioned publication, at the time of drawing and ironing, the coated resin of the resin-coated steel sheet for drawn and ironed cans is drawn at an appropriate stretching temperature (lower than the crystallization temperature of the resin and a glass transition temperature (Tg) within ± 30 ° C). Temperature, for example, 40 to 100 ° C if the resin is PET resin)
On the other hand, the resin-coated steel sheet for drawn and ironed cans, which is manufactured by a known extrusion lamination method or the like and is subjected to the drawn and ironed step, is usually at room temperature. There is a problem that a preheating step must be added.

The present invention, even when subjected to drawing and ironing at room temperature without preheating the resin-coated steel sheet, is remarkably excellent in workability against drawing and ironing, and the ironing rate is 60% in a state where the resin coating is provided on the inner surface. Ironing at a high ironing rate as described above becomes possible, and the resin-coated steel sheet for drawn ironing can, which can obtain a drawn ironed can excellent in adhesion and corrosion resistance of the resin film, and also has the above characteristics The purpose is to provide a drawn and ironed can.

(Means for Solving the Problems) The gist of the present invention is as follows.

(1) One side of a steel plate having Sn plating on both sides is coated with an amorphous polyester resin layer, and the crystalline polyester resin and the amorphous polyester resin are further subjected to a heat melting reaction on the resin layer by the following formula. Define alloying rate less than 50% (0%
). A resin-coated steel sheet for drawn and ironed cans, characterized by being coated with a thermoplastic polyester resin layer.

T _m1 or T _g1 : Melting point or glass transition temperature of the raw material crystalline polyester resin T _m2 or T _g2 : Melting point or glass transition when the raw material crystalline polyester resin and amorphous polyester resin are completely heated and melted Temperature, that is, the melting point or glass transition temperature of the random copolymer polyester resin having the same monomer composition _Tm3 or _Tg3 : the melting point or glass transition temperature of the thermoplastic polyester resin (2) The crystal is formed on one side of the Sn-plated steel sheet on both sides The thermoplastic polyester resin and the amorphous polyester resin are subjected to a heat-melting reaction, coated with a thermoplastic polyester resin layer having an alloying ratio defined by the following formula of 50% or more and less than 100%, and furthermore, the resin layer is coated with a crystalline resin. A resin-coated steel sheet for drawn and ironed cans, characterized by being coated with a polyester resin layer.

T _m1 or T _g1 : Melting point or glass transition temperature of the raw material crystalline polyester resin T _m2 or T _g2 : Melting point or glass transition when the raw material crystalline polyester resin and amorphous polyester resin are completely heated and melted Temperature, that is, the melting point or the glass transition temperature of the random copolymer polyester resin having the same monomer composition. (3) On one side of a Sn-plated steel sheet on both sides, a crystalline polyester resin and an amorphous polyester resin are subjected to a heat melting reaction, It is covered with a thermoplastic polyester resin layer having an alloying ratio defined by the following formula of 50% or more and less than 100%, and further, on the resin layer, a crystalline polyester resin and an amorphous polyester resin are subjected to a heat melting reaction to obtain the following. A resin coating for drawing and ironing cans, characterized by being coated with a thermoplastic polyester resin layer having an alloying ratio defined by the formula of less than 50% (excluding 0%). Covered steel plate.

T _m1 or T _g1 : Melting point or glass transition temperature of the raw material crystalline polyester resin T _m2 or T _g2 : Melting point or glass transition when the raw material crystalline polyester resin and amorphous polyester resin are completely heated and melted Temperature, that is, the melting point or glass transition temperature of the random copolymer polyester resin having the same monomer composition _Tm3 or _Tg3 : the melting point or glass transition temperature of the thermoplastic polyester resin (4) For the drawn ironing can of item 1, 2 or 3 above A drawn and ironed can characterized by being drawn and ironed so that the resin-coated surface of the resin-coated steel sheet is the inner surface of the can.

The above _Tm1 , _Tm2 , _Tm3 or _Tg1 , _Tg2 , _Tg3 are melting points or glass transition temperatures obtained by raising the temperature at 10 ° C./min using a differential thermal analyzer (Perkin Elmer-7 type). It is. In addition, the difference between crystalline and non-crystalline is determined by using a differential thermal analyzer in the same manner as that of the crystalline polyester, the crystalline polyester, and the polyester that expresses only the glass transition temperature or the peak of the glass transition temperature and melting point. Those which do not appear are called amorphous polyesters.

Examples of the crystalline polyester include polyethylene terephthalate (hereinafter abbreviated as PET), polybutylene terephthalate (hereinafter abbreviated as PBT), polyethylene naphthalate (hereinafter abbreviated as PEN), and copolymers thereof. Without being limited to these, it refers to a thermoplastic polyester having a melting point of at least 200 ° C.

Examples of the amorphous polyester include polyethylene isophthalate (hereinafter abbreviated as PEI), polyethylene terephthalate copolyester of 30 mol% of cyclohexane / dimethanol, polyethylene terephthalate of 20 mol% or more of isophthalic acid, polyarylate, polyester polycarbonate and the like. However, the glass transition temperature is not limited to 20 ° C. or higher, preferably 40 ° C.
The above amorphous thermoplastic polyester is referred to.

 Hereinafter, the contents of the present invention will be described in more detail.

The present inventors coated various thermoplastic resins on one side of a known surface-treated steel sheet having Sn plating on both sides by a known method, and squeezed and ironed the inner surface of the can so as to become a resin-coated surface at room temperature. Go to make cans.

First, the present inventors, as a thermoplastic resin, known PET
And a resin in a known amorphous state was used. However, a normal temperature resin-coated steel sheet manufactured according to a known method was not able to withstand 60% or more of the draw ironing targeted by the present inventors even if it could withstand mild drawing and ironing. After considering the reason,
If only ordinary amorphous PET was used, PET was initially amorphous in the process of processing the resin during drawing and ironing.
Was partially crystallized by processing, and was considered to be unbearable because it was crystallized for subsequent processing. Therefore, the present inventors have developed PEI as a non-crystalline polyester resin.
The same processing was performed using. Although this PEI was amorphous, it exhibited excellent properties for drawing as expected,
In the subsequent ironing process, the resin adheres to the punch for processing (ironing is usually performed by pressing a metal between three dies with a punch and ironing between the punch / die), and the resin is applied from the inner surface of the can. At the same time as peeling, the can body could not be removed from the punch (called strip-out). In addition, PET or PET, PE which simply mixed PEI
I. The same drawing and ironing process was further performed using the mixture, but no satisfactory results were obtained. That is, when the content of the crystallized resin is large, the processability is inferior, and when the content of the amorphous resin is large, the strip-out property is poor. Nothing satisfying both sexes was obtained.

Therefore, the present inventors, on the Sn plating layer of the steel plate, the amorphous polyester resin layer having good workability (adhesion),
With the idea of laminating a crystalline polyester resin layer having a good strip-out property on the resin layer, the drawability and ironing workability were investigated using various amorphous polyester resins and crystalline polyester resins. In any combination, peeling occurred between the lower amorphous polyester resin layer and the upper crystalline polyester resin layer during drawing or ironing.

The cause was presumed to be that the characteristics of the lower resin and the upper resin were significantly different, so the present inventors improved the resin composition of the upper or lower layer to prevent separation between the upper and lower resin layers, and to process the resin. Properties and strip-out properties during processing. That is, when an amorphous polyester resin having good processability (adhesion) is used for the lower layer, a characteristic resin between the upper and lower resin layers can be obtained by employing a special resin that is appropriately crystallized by resin stretching during processing as the upper layer resin. , The separation between the upper and lower resin layers was prevented, and the strip-out property during processing was ensured.

When a crystalline polyester resin with good strip-out properties is used for the upper layer, a special resin that does not crystallize as much as possible by resin stretching during processing is used as the lower layer resin to reduce the characteristic difference between the upper and lower resin layers, The separation between layers was prevented and the workability of the resin was ensured.

Furthermore, by adopting a special resin that is appropriately crystallized by the resin stretching during the above processing as the upper resin, and adopting a special resin that does not crystallize as much as possible by the resin stretching during the above processing as the lower resin, the upper and lower resin characteristics difference To prevent peeling between the upper and lower resin layers, and ensure the workability of the resin and the strip-out property during the processing.

The moderately crystallized special resin to be used as the upper layer resin is obtained by incompletely heat-melting a crystalline polyester resin and an amorphous polyester resin, and has an alloying ratio defined by the above formula. Less than 50% (but not including 0%) of thermoplastic polyester resin.

The special resin which does not crystallize as much as possible to be used as the lower layer resin is a resin obtained by incompletely heat-melting a crystalline polyester resin and an amorphous polyester resin, and has an alloying ratio defined by the above-mentioned formula. It is a thermoplastic polyester resin of 50% or more and less than 100%.

A thermoplastic polyester resin having an alloying ratio of 100% is an amorphous polyester resin, and a thermoplastic polyester resin having an alloying ratio of 0% is a crystalline polyester resin.

 Next, the reasons for limiting the constituent elements of the invention will be described.

First, the alloying rate of the side of the steel sheet that comes into contact with the Sn plating layer, that is, the lower layer thermoplastic polyester resin, should be 50% or more and 100%
When the alloying ratio is less than 50%, the above Sn
Poor adhesion to the plating layer, drawing and ironing,
In particular, if the ironing rate is 65% or more, the crystalline portion of the coating resin increases, and the adhesion to the Sn plating layer, that is, the workability of the resin cannot be ensured. This is because it is an amorphous polyester resin, and if the alloying ratio is 100%, peeling between the upper and lower resin layers cannot be prevented.

Next, the alloying ratio of the thermoplastic polyester resin of the upper layer, which is in contact with the punch at the time of drawing and ironing, was limited to less than 50% (but not including 0%).
If the content is more than 50%, the amorphous portion of the coating resin increases, the apparent melting temperature decreases, and the strip-out property is greatly deteriorated. The thermoplastic polyester resin having an alloying ratio of 0% is a crystalline polyester resin. Yes, alloying rate 0
% Cannot prevent the separation between the upper and lower resin layers.

When the crystalline polyester resin and the amorphous polyester resin are heated and melted to form an alloy, the mixing ratio (amorphous polyester resin ポ リ エ ス テ ル total amount of polyester resin ×
100) is preferably 50 to 90% when manufacturing a thermoplastic polyester resin having an alloying ratio of 50% or more and less than 100% for the lower layer, and the alloying ratio for the upper layer is 50%.
When producing less than (but not including 0%) a thermoplastic polyester resin, it is preferably 10 to 50% in terms of production efficiency.

In addition, the resin coating (lamination) thickness of the lower and upper layers,
The thickness of the plating layer is not limited at all, and the thickness can be appropriately applied according to the processing conditions.However, according to the results of the present inventors, the Sn plating thickness was 2.8 g / m ² , and the total ironing rate was 60%.
% Or more, the thickness of the upper resin layer is 3 μm in thickness before processing in order to ensure strip-out property with the punch.
When the thickness is less than 3 μm, part of the resin in the lower layer is fused to the punch by the heat generated during drawing and ironing, and good strip-out properties cannot be secured.

(Examples) Hereinafter, the content of the present invention will be described with specific examples based on examples.

Using a two-layer extruded T-die on the Sn plating layer on one side of a steel sheet (sheet thickness 0.30 mm, hardness T-1 equivalent) having a Sn plating layer of 2.8 g / m ² per side on both sides, as shown in Table 1. Lower layer 20μm, upper layer 20μm thermoplastic polyester resin, total 40μ
m. The resin melting temperature at the T-die at this time is 265-3
It was 00 ° C, and the steel sheet temperature during coating was 150 to 200 ° C. In addition, a steel sheet coated with resin by a T-die
It was quenched to 0 ° C or less. The reason for the rapid cooling is to prevent crystallization of the resin at a high temperature.

The room temperature resin-coated steel sheet thus obtained is drawn and ironed under the following molding conditions so that the inner surface of the can becomes the resin-coated surface to produce a drawn ironed can. To evaluate the properties, a 1.0% saline solution was placed in a can, and the current flowing when a voltage of +6 V was applied using the platinum disposed in the center of the can as the anode and the platinum as the cathode was measured (hereinafter, referred to as the following). , QTV test). Similarly, for the purpose of evaluating the soundness of the inner surface of the can, a solution containing 20 g / sulfuric acid and 50 g / copper sulfate (CuSO ₄ 7H ₂ O) was placed in the can and left for 10 minutes.
The solution was removed, and Cu precipitated after washing with water (if the solution was a chemical plating solution of Cu and there was a defect in the resin layer, iron was eluted from the defect and Cu was replaced and plated) was observed (hereinafter referred to as sulfuric acid). Abbreviated as copper test).

These results are shown in Table 2 together with the evaluation results of the strip-out property and the results of observation of the inner surface of the can after drawing and ironing.

<Molding conditions> 1. Resin temperature just before drawing and ironing: normal temperature 2. Blank diameter: 137mmφ 3. Drawing condition: 1st drawing ratio H / D = 33 / 86mmφ 2nd drawing ratio H / D = 50 / 65mmφ 4. Ironing punch diameter : 3-stage ironing 65.5mmφ 5. Total ironing rate: 70.5% (Effect of the Invention) As described above, the resin-coated steel sheet for drawn and ironed cans obtained by using the thermoplastic polyester resin composition of the present invention has an extremely excellent inner surface even when subjected to drawing and ironing at room temperature. Pre-heating process of resin-coated steel sheets for drawn ironing cans, which is indispensable for can-manufacturers, required for conventional drawn-ironing cans that can be obtained using conventional thermoplastic resin because they can produce drawn ironed cans with characteristics Can be omitted, and can manufacturing cost can be reduced.

Continued on the front page (72) Inventor Koji Niimi 61-2, Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Petrochemical Industry Co., Ltd. (72) Takayuki Hiraoka 6-Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture No. 1-2 in Mitsui Petrochemical Industry Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) B32B 15/08 B21D 22/28

Claims (4)

(57) [Claims] A steel sheet coated on both sides with Sn plating is coated on one side with an amorphous polyester resin layer, and the crystalline polyester resin and the amorphous polyester resin are heated and melted on the resin layer. A resin-coated steel sheet for drawing and ironing cans, which is coated with a thermoplastic polyester resin layer having an alloying ratio defined by the formula of less than 50% (excluding 0%). T _m1 or T _g1 : Melting point or glass transition temperature of the raw material crystalline polyester resin T _m2 or T _g2 : Melting point or glass transition when the raw material crystalline polyester resin and amorphous polyester resin are completely heated and melted Temperature, that is, melting point or glass transition temperature of random copolymer polyester resin having the same monomer composition T _m3 or T _g3 : melting point or glass transition temperature of thermoplastic polyester resin 2. A hot melt reaction of a crystalline polyester resin and an amorphous polyester resin on one side of a steel plate having Sn plating on both sides, so that the alloying ratio defined by the following formula is 50% or more.
Coated with a thermoplastic polyester resin layer of less than 0%,
A resin-coated steel sheet for drawn and ironed cans, wherein the resin layer is further coated with a crystalline polyester resin layer. T _m1 or T _g1 : Melting point or glass transition temperature of the raw material crystalline polyester resin T _m2 or T _g2 : Melting point or glass transition when the raw material crystalline polyester resin and amorphous polyester resin are completely heated and melted Temperature, that is, the melting point or glass transition temperature of the random copolymer polyester resin having the same monomer composition 3. A crystalline polyester resin and an amorphous polyester resin are subjected to a hot-melt reaction on one side of a steel plate having Sn plating on both sides, and an alloying ratio defined by the following formula is set to 50% or more.
Coated with a thermoplastic polyester resin layer of less than 0%,
Further, on the resin layer, a thermoplastic polyester resin layer in which a crystalline polyester resin and an amorphous polyester resin are subjected to a heat melting reaction to make an alloying ratio defined by the following formula less than 50% (not including 0%). A resin-coated steel sheet for drawn and ironed cans characterized by being coated. T _m1 or T _g1 : Melting point or glass transition temperature of the raw material crystalline polyester resin T _m2 or T _g2 : Melting point or glass transition when the raw material crystalline polyester resin and amorphous polyester resin are completely heated and melted Temperature, that is, melting point or glass transition temperature of random copolymer polyester resin having the same monomer composition T _m3 or T _g3 : melting point or glass transition temperature of thermoplastic polyester resin 4. A drawn and ironed can which is drawn and ironed so that the resin-coated surface of the resin-coated steel sheet for a drawn and ironed can according to claim 1, 2 or 3 is an inner surface of the can.