JPH07278519A - Adhesive composition for lamination - Google Patents

Abstract

PURPOSE:To obtain a composition, comprising a mixture of an acrylonitrile- butadiene rubber with a urethane poly(meth)acrylate at a specific ratio, good in adhesion of a polyester film to a metallic plate and excellent in water resistance, processability, etc. CONSTITUTION:This composition comprises (A) 40-90 pts.wt. (preferably 50-80 pts.wt.) acrylonitrile-butadiene rubber with 20-50% combined acrylonitrile content and (B) 10-60 pts.wt. (preferably 20-50 pts.wt.) urethane poly(meth)acrylate having one or more carboxyl groups in one molecule. Furthermore, the component (B) is obtained by reacting (i) a polyol having carboxyl group such as dimethylolpropionic acid with (ii) a polyisocyanate such as tolylene diisocyanate and (iii) an acrylate or a methacrylate having OH group such as 2-hydroxyethyl (meth)acrylate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam curable adhesive used for laminating a polyester film on a metal plate.

[0002]

2. Description of the Related Art Conventionally, in the can manufacturing industry, coating of a solvent-based resin or a water-based resin has been performed on the inner surface and the outer surface of a can after it is manufactured. However, the coating on the outer surface of the can requires multiple coatings, and this coating process inevitably requires a long production line, and enormous energy is required to evaporate the solvent from the coating film. To do. A can manufacturing method that does not have such difficulties has been studied, and a technique of using a material obtained by laminating a polyester film on a metal plate as a material used for can manufacturing has been developed. As a method of laminating a polyester film on a metal plate, the invention of heat-sealing the polyester film is disclosed in JP-A-3-21.
Japanese Patent Laid-Open No. 5-438.
Japanese Patent No. 59 discloses an invention in which a polyester film and a metal plate are laminated using a thermosetting adhesive.

[0003]

When the polyester film as described above is heat-fused to a metal plate, or when the polyester film is laminated on the metal plate by using a hot melt adhesive, the metal plate of the polyester film is used. Surface treatment conditions of the metal plate used for adhesion performance to
Since it is greatly affected by the laminating conditions, precise process control is required to obtain a polyester film laminated metal plate having uniform properties. Further, in the case of making a film-laminated metal plate using a thermosetting adhesive, the time required to cure the adhesive requires a long time compared to the speed of a high-speed manufacturing line for cans, A long production line is required to correspond the two, resulting in enormous capital investment, a large factory space, and large energy consumption.

As a method for solving this problem, a technique of laminating a polyester film on a metal plate using an electron beam curing type adhesive has been developed. This method uses a small amount of energy, and a compact device can be used for high-speed canning. Since it can be applied to a production line, there is an advantage that a large production line for cans is not required as a whole. For example, in Japanese Unexamined Patent Publication (Kokai) No. 5-179205, an electron beam curable adhesive containing 100 parts by weight of a polyester resin and 2 to 200 parts by weight of a polyester oligomer having an unsaturated double bond or a polyurethane oligomer is used. , A method of obtaining a polyester film laminated metal plate by laminating a metal material and a polyester film and then curing the adhesive by electron beam curing. However, when the film-laminated metal plate produced by the above method is processed into a can and then retort-treated, the film laminated on the metal plate is peeled off.

[0005]

In order to solve the above problems, the present inventors have found that the adhesiveness to polyester films and metals is good, the water resistance and processability are excellent, and the electron beam curable resin is also used. Nitrile rubber, which has an excellent ability to relieve shrinkage stress when it cures, has good adhesion to polyester films and metals, has a large cohesive force after curing, and has excellent heat resistance. At least one or more carboxyl groups in the molecule. By combining urethane poly (meth) acrylate having a group, an adhesive for electron beam curable laminating is obtained that has excellent adhesion between the polyester film and the metal plate, and also excellent adhesion between the two after retort treatment. Therefore, the present invention has been completed.

That is, the present invention relates to (A) an acrylonitrile-butadiene rubber having a bound acrylonitrile content of 20 to 50%.
40 to 90 parts by weight, (B) urethane poly (meth) acrylate having at least one carboxyl group in the molecule 10
The adhesive composition for electron beam-curable laminating comprises -60 parts by weight.

Hereinafter, the adhesive composition of the present invention will be described in more detail. About Component (A) As the acrylonitrile-butadiene rubber which is the component (A), one having a bound acrylonitrile amount in the range of 20 to 50% is used. An electron beam curable adhesive using a nitrile rubber having a bound acrylonitrile content of less than 20% has a reduced adhesive force to a polyester film and a metal. On the other hand, the nitrile rubber containing more than 50% of bound acrylonitrile is
(B) Compatibility with urethane (meth) acrylate having a carboxyl group in the molecule that serves as component (B) decreases, and the stability of the resulting electron beam curable adhesive decreases, making it difficult to achieve stable performance. become. Acrylonitrile butadiene rubber which is the component (A) uses acrylic acid or methacrylic acid as a copolymerization component and is made into a polymer having a carboxyl group in the molecule. Good.

The molecular weight of the acrylonitrile butadiene rubber is not particularly limited, but in the case of a solid rubber, _one having a molecular weight distribution such that the Mooney viscosity ML _{1 + 4} 30 to 80 is preferable. When a low molecular weight liquid nitrile rubber is used, it is more preferable that it has a polymerizable unsaturated double bond at the molecular end or in the molecular chain and is crosslinked by electron beam curing.

The proportion of component (A) used is in the range of 40 to 90 parts by weight, preferably 50 to 80 parts by weight, in the adhesive of the present invention. A film-laminated metal plate made using an adhesive in which the amount of component (A) is less than 40 parts by weight reduces the adhesion of the film to the metal plate after can making, while the amount of component (A) is 90 parts by weight. The adhesive used in a ratio exceeding 0.1 has a small cohesive force, and the film-laminated metal plate made using the adhesive has a phenomenon in which both are separated by retort treatment after can making,
Its adhesiveness is reduced.

Component (B) The urethane poly (meth) acrylate having at least one carboxyl group in the molecule of component (B) is 1
A compound obtained by reacting a polyol having one or more carboxyl groups and two or more hydroxyl groups in a molecule, a polyisocyanate having two or more isocyanate groups in one molecule, and a (meth) acrylate having a hydroxyl group. is there.

One or more carboxyl groups and 2 in one molecule
Specific examples of the polyol having at least one hydroxyl group include dimethylolpropionic acid, dihydroxybenzoic acid, dihydroxyphenylacetic acid, dihydroxystearic acid, and the like, and the electron beam curable adhesive made using the component is a film. The adhesiveness between the metal plate and the metal plate is improved, the processability of the film-laminated metal plate obtained by using the adhesive is improved, and the retort processability after can making can be remarkably improved.

Specific examples of the polyisocyanate having two or more isocyanate groups in one molecule include tolylene diisocyanate, xylylene diisocyanate and 4,4 '.
-Diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and the like can be mentioned.

Specific examples of the (meth) acrylate having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like.

The proportion of the component (B) used is 10 to 60 parts by weight, preferably 20 to 50 parts by weight in the adhesive of the present invention. An adhesive containing less than 10 parts by weight of component (B)
The cohesive strength was insufficient, and the can made using the laminated metal plate made with this adhesive had poor adhesion of the film after retort treatment, while the adhesive with the content of component (B) exceeding 60 parts by weight. The laminated metal plate produced by using the agent has low adhesiveness after processing.

To the adhesive composition of the present invention, a solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, toluene or ethanol is added to adjust the viscosity for the purpose of improving workability during coating. You may. Further, in order to further improve the adhesiveness, a silane coupling agent such as γ-methacryloxypropyltrimethoxysilane, a phosphorus-containing monomer such as 2-acryloyloxyethyl acid phosphate, or the like in the adhesive composition, 2-
Highly polar monomers such as acryloyloxyethyl phthalate and acrylonitrile may be blended within a range that does not impair the object of the present invention. For the purpose of adjusting the crosslink density of the cured product of the adhesive of the present invention, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate and the like are used. You may mix | blend in the range which does not impair the objective of the invention. In addition, pigments such as titanium oxide and silica may be appropriately mixed depending on the purpose.

In the present invention, the polyester film laminated on the metal plate is preferably a stretched or unstretched polyethylene terephthalate film which has been subjected to surface treatment such as corona discharge treatment.

The metal plates used include hot-rolled steel plates, cold-rolled steel plates, tinplate, and various plated steel plates such as chin-free steel, zinc-plated steel plates, nickel-plated steel plates, and metal plates such as stainless steel plates and aluminum steel plates. It is more preferable that various kinds of surface treatments and primer treatments are carried out as needed.

The application of the adhesive composition of the present invention is carried out by a usual coating method such as roll coater, knife coater, gravure printing, spray coating, etc., on the polyester film or metal plate with a film thickness of 1 It is applied so as to be about 10 μm, and if a diluting solvent is added as necessary, the solvent is dried and removed. Then, the polyester film is laminated on a metal plate using a heating and pressing roll.

Next, from the polyester film side, 0.2 to
The adhesive layer is cured by irradiating it with an electron beam at an irradiation dose of 15 Mrad to obtain a polyester film laminated metal plate. If the irradiation dose is less than 0.2 Mrad, the curing of the adhesive layer does not proceed completely, and if the electron beam is irradiated with a dose exceeding 15 Mrad, the polyester film may be deteriorated, which is not preferable.

The present invention will be described in more detail below with reference to Examples and Comparative Examples. The abbreviations of the monomers and the abbreviations in the table are as follows. UA 1: Urethane diacrylate obtained by reacting dimethylolpropionic acid (1 mol) with 2,6-tolylene diisocyanate (2 mol) and 2-hydroxyethyl acrylate (2 mol) UM 1: Dihydroxystearin Urethane dimethacrylate UA 2: 2,6-tolylene diisocyanate (1 mol) obtained by reacting acid (1 mol), isophorone diisocyanate (2 mol) and 2-hydroxypropyl methacrylate (2 mol) , 2-
Urethane diacrylate obtained by reacting with hydroxyethyl acrylate (2 mol) EM 1: Bisphenol A diglycidyl ether (1 mol) and epoxy dimethacrylate PEA1 obtained by reacting methacrylic acid (2 mol): Polyester acrylate (trade name; manufactured by Aronix M-6200, Toagosei Kagaku Co.) AN amount: Acrylonitrile bound to acrylonitrile butadiene rubber

[0021]

Example 1 (1) Synthesis of Urethane Acrylate UA 1 Dimethylolpropionic acid was placed in a 2-liter four-necked flask.
134 g, tolylene diisocyanate 348 g, and methyl ethyl ketone 714 g as a diluting solvent were charged, and di-n-butyltin dilaurate 71 mg was added as a synthesis catalyst, and the temperature was 60 ° C.
After stirring for 5 hours at 2-hydroxyethyl acrylate
232 g was added, the temperature was raised to 70 ° C., and the mixture was further stirred for 8 hours to synthesize urethane acrylate UA 1. At this time, the reaction was traced using the IR spectrum of the reaction product, and it was confirmed that the isocyanate group had almost disappeared, and it was confirmed that a 50 wt% methyl ethyl ketone solution of urethane acrylate UA 1 was obtained. (2) Preparation of Adhesive Composition An adhesive composition was obtained by adding 80 parts by weight of a 50% by weight methyl ethyl ketone solution of UA 1 to 60 parts by weight of an acrylonitrile butadiene rubber having a bound acrylonitrile content of 40%. (3) Adhesion of Polyester Film and Metal Plate The adhesive composition synthesized in (2) was applied onto a polyester film subjected to corona discharge treatment using a bar coater so that the thickness after solvent drying was 2 μm. The film coated with the adhesive is left in a drying oven at 100 ° C for 20 seconds to remove the solvent from the adhesive layer, and then the dried film is heated to a roll temperature of 150 ° C and a roll pressure of 4 kg.
Laminated on chin-free steel under the condition of / cm ² .
Next, using an electron beam irradiation device, an electron beam of 1 Mrad was irradiated from the film side to obtain a polyester film-laminated metal plate. This film-laminated metal plate was evaluated by the following test methods, and the results are shown in Table 1. [Evaluation method] Cross-cut peeling test: conducted in accordance with JIS K 5400. Workability: From the film side of the polyester film laminated metal plate, use a cutter to reach the base material.
A notch having a length of cm was made in an X shape, and an intersection of the notches was pushed from the back side by 6 mm using an Erichsen tester (JIS B 7729) to evaluate the adhesiveness of the film. ◯: Does not peel. X: Peel from the intersection. Retort resistance: The pressure cooker test (125 ° C., 30 minutes) of the test piece after the workability test evaluated the adhesiveness after the retort treatment. ◯: Does not peel. X: The flower turns up from the intersection and peels off. Alternatively, the peripheral portion is peeled off like a tent.

[0022]

Examples 2 to 5 and Comparative Examples 1 to 7 Polyester film laminated metal plates were prepared in the same manner as in Example 1 except that the adhesive compositions shown in Table 1 were used, and their performance was evaluated. The results are also shown in Table 1.

[Table 1]

As is clear from Table 1, as shown in Examples 1 to 5, within the scope of the present invention, the cross-cut peeling test, workability, and retort resistance are satisfied. On the other hand, as shown in Comparative Example 1, when the amount of the component A used exceeds 90 parts by weight and the amount of the component B used is less than 10 parts by weight, the cohesive force is insufficient and the film is subjected to a retort resistance test after processing. Peels off. As shown in Comparative Example 2, when the amount of the component A used is less than 40 parts by weight and the amount of the component B used exceeds 60 parts by weight, the processability is insufficient and the film peels from the apex. As shown in Comparative Example 3, when the amount of bound acrylonitrile is less than 20%, the adhesiveness is lowered, and peeling occurs at the film interface or metal interface in the workability test.
As shown in Comparative Example 4, the amount of bound acrylonitrile was 50%.
If it exceeds, the adhesive composition will not dissolve uniformly. As shown in Comparative Examples 5 to 7, when another oligomer component was used instead of the component B, the adhesiveness to the substrate was insufficient, and the metal interface was peeled off in the cross-cut peeling test or the workability test.

[0024]

EFFECT OF THE INVENTION The adhesive of the present invention has excellent adhesiveness when producing a polyester film-laminated metal sheet, and the adhesiveness of the film-laminated metal sheet produced using the adhesive after processing into a can, It is an electron beam curable adhesive having excellent adhesiveness after retort treatment, and by using the adhesive of the present invention, the production of a polyester film laminated metal plate can be performed in a space-saving manner and with a reduced amount of energy used. It can be done by high-speed production.

Claims (1)

[Claims] 1. The amount of (A) bound acrylonitrile is 20 to 50%.
40-90 parts by weight of acrylonitrile butadiene rubber, (B)
An adhesive composition for an electron beam curable laminate, comprising 10 to 60 parts by weight of urethane poly (meth) acrylate having at least one carboxyl group in the molecule.