JPH03265679A - Adhesive and manufacture of laminate by using it - Google Patents

Abstract

PURPOSE:To form an adhesive which does not produce any decomposition product of a photopolymerization initiator even when irradiated with ultraviolet rays for curing and is useful for obtaining a laminate excellent in appearance, strength, etc., by using a solution of an ultraviolet-curing resin and a specified photopolymerization initiator. CONSTITUTION:An adhesive formed from a solution of an ultraviolet-curing resin (e.g. a polyether polyurethane diacrylate obtained by reacting polyethylene glycol with tolylene diisocyanate and treating the reaction product with hydroxyethyl acrylate) and a photopolymerization initiator having isocyanato groups (e.g. 1-phenylisocyanato-2-hydroxy-2-methylpropan-1-one).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an adhesive using an ultraviolet curable resin and a method for producing a laminate using the adhesive.

[Prior art] Ready-made plastic films are attached to the surface of printed matter for the purpose of protecting the printed surface and giving a decorative finish, or films and sheets with different properties are attached to the surface of printed matter to provide a combination of various performances. Laminated sheets with adhesives attached are often used.

In the process of obtaining these laminates, adhesives based on curable resins are often used, such as adhesives based on two-component curable resins using isocyanate-curable polyether polyurethane resins, and adhesives based on UV-curable resins. Adhesives and the like are used that are made of a photoresist initiator and a polymerizable monomer component as a diluent.

[Problems to be Solved by the Invention] By the way, in adhesion using the two-component curable resin adhesive, after pressing the adhered object closely against the surface coated with the adhesive, It is necessary to go through a curing process that involves aging for about 10 days, and the manufacturing efficiency of the laminate is extremely low.As a result, it is not possible to meet quick delivery dates, and equipment for the aging process is required. Therefore, it is uneconomical.

In addition, when using an adhesive made of an ultraviolet curable resin and a photopolymerization initiator that uses a monomer component as a diluent, it is inevitable that low molecular weight substances remain due to the monomer component that is the diluent. This has become a hygiene problem for laminated sheets that are often used for packaging snack foods and the like.

Therefore, as an adhesive using an ultraviolet curable resin that does not have the problem of residual low molecular weight substances caused by the monomer components mentioned above, an adhesive with a high solid content consisting of a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator can be used. However, even in the laminated sheets obtained using this adhesive, the odor caused by the decomposition products of the photopolymerization initiator generated by irradiation with ultraviolet rays, such as cyclohexane, benzaldehyde, and methyl benzoate, is present. Due to these problems, it is not suitable as an adhesive for dry lamination.However, it is not suitable as an adhesive for dry lamination, and it also causes the adverse effects of the aforementioned decomposition products of the photopolymerization initiator and unreacted photopolymerization initiator bleeding onto the surface of the laminated sheet. For example, there are problems such as migration of the contents into the package formed by the laminated sheet, and a decrease in the heat sealing strength of the sealant film in the case of a laminated sheet in which the sealant film is laminated.

In contrast, the present invention does not require a long-term curing process due to aging when obtaining a laminate, and also does not use a diluent based on monomer components. There is no problem with residual materials,
Furthermore, we have developed an ultraviolet curable adhesive that is free from the harmful effects of decomposed products of photopolymerization initiators generated by irradiation of ultraviolet cotton and the harmful effects of residual unreacted photopolymerization initiators, and highly efficient laminates using the adhesives. We provide a method for manufacturing the same.

[Means for Solving the Problems] The adhesive of the first invention is made of a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator having an isocyanate group.

Furthermore, the method for producing a laminate according to the second aspect of the present invention includes coating the back surface of the base material with an adhesive made of a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator having an isocyanate group. After that, the solvent in the adhesive applied to the base material is evaporated, and then a sealant film with thermal welding performance is closely applied to the coated surface of the adhesive, and then ultraviolet cotton is irradiated. By doing this, a laminate is obtained.

Furthermore, the method for manufacturing a laminate according to the third invention is such that, in the method for manufacturing a laminate according to the second invention described above, a film having an ultraviolet transmittance of 250 to 400 nm of 20% or more is used as the sealant film. By utilizing this, a laminate can be obtained.

Moreover, the method for manufacturing a laminate according to the fourth aspect of the present invention is the method for manufacturing a laminate according to the third aspect of the present invention, in which the laminate is obtained by irradiating ultraviolet rays from the surface of the sealant film.

In the actual invention having the above configuration, the ultraviolet curable resin includes, for example, epoxy (meth)acrylate, polyurethane (meth)acrylate, polyolefin glycol (meth)acrylate, polyester (meth)acrylate, etc. with a molecular weight of 300 to 6000, preferably teeth,
1,000 to 3,000 oligomers having two or more polymerizable functional groups, specifically, one kind or a mixture of two or more kinds of oligomers having (meth)acrylic double bonds are used. .

The epoxy (meth)acrylate includes a reaction product of an epoxy resin having a glycidyl group at the end and (meth)acrylic acid, such as bisphenol-A type epoxy acrylate, and polyurethane (meth)acrylate.
Acrylate is a reaction product of a polyurethane resin having an isocyanate group at the end and a compound having a vinyl group and a hydroxyl group in the molecule, such as 2-hydroxyethyl (meth)acrylate, and a polyolefin glycol ( For meth)acrylate, for example, di(meth)acrylic acid ester of polyethylene glycol is used, and for polyester (meth)acrylate, a reaction of polyester with phthalic anhydride and diethylene glycol treated with (meth)acrylic acid is used for polyester (meth)acrylate. products etc. are used.

Furthermore, it goes without saying that the above-mentioned (meth)acrylic-modified oligomers may be a mixture thereof.

The photopolymerization initiator contained in the adhesive is a compound having an isocyanate group, such as an acetophenone photopolymerization initiator into which an isocyanate group is introduced,
Benzoin-based photopolymerization initiator, benzophenone-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, specifically, 1
Photopolymerization initiators such as -phenylisocyanate-2-hydroxy-2-methylpropan-1-one, benzoin isopropylisocyanate ether, benzoylbenzoic acid methyl isocyanate, 2-methylisocyanate thioxanthone, etc. are used.

For the photopolymerization initiator, if necessary, for example,
dimethylaminoethanol, triphenylphosphine,
Of course, a photosensitizer such as N,N-dimethylaniline or dimethylaminobenzoic acid ester may be used in combination.

Examples of the solvent in the adhesive include ethyl acetate, toluene, and methyl ethyl ketone.

Single solvents such as isopropyl alcohol, ethyl alcohol, methyl alcohol, and butyl alcohol, mixed solvents, and mixed solvents of the above alcohols and water are used. In the case of a water-alcohol mixed solvent, alcohol 100 A mixed solvent containing about 10 to 1000 parts by weight of water is used.

Note that when alcohol or a mixed solvent of water-alcohol is used as the solvent in the adhesive, the adhesive of the present invention and the method for producing a laminate using the adhesive do not have the problem of residual monomers mentioned above. At the same time, the special effect is that the problem of residual solvents can also be solved.

The adhesive of the present invention having the above composition usually includes a composition in which the photopolymerization initiator is contained in a proportion of 0.2 to 10 parts by weight and the solvent is contained in a proportion of approximately 50 to 1000 parts by weight based on 100 parts by weight of the resin component. For example, by coating methods such as gravure coating, direct roll coating, reverse roll coating, etc., 0% is applied to the adhesive coated surface of the base material.
．． 5-10gf resin component) Applicable to about 71.

In the method for producing a laminate of the present invention using the adhesive, the base material includes, for example, a biaxially stretched polypropylene film,
Monolayer films made of axially stretched polyester films, biaxially stretched polyamide films, etc., laminated films made of these films, and laminated films made of the above films and metal foils, paper, etc. are preferably used, and if necessary,
A base material that has been given design characteristics by printing or the like is used.

Further, the sealant film that is bonded to the base material using the above-mentioned adhesive includes, for example, a low-density polyethylene film.

Polyolefin resin films such as medium-density polyethylene film, high-density polyethylene film, ethylene-vinyl acetate copolymer film, ethylene-〇-olefin copolymer film, unstretched polypropylene film, etc. are used.

The method for manufacturing a laminate using the base material and a sealant film includes applying the above-mentioned adhesive to the base material surface, and then removing the solvent in the adhesive applied to the base material surface by, for example, blowing hot air. After that, the sealant film is brought into close contact with the surface coated with the adhesive, and ultraviolet rays are irradiated from the surface of the sealant film. Usually, a high-pressure mercury lamp or metal halide lamp is used. Ultraviolet irradiation treatment is performed using methods such as UV rays.

In addition, in the ultraviolet irradiation process, if the irradiation rate at the ultraviolet edge is too fast, the irradiation dose will be insufficient, resulting in insufficient curing of the adhesive, and if the irradiation rate is too slow, the ultraviolet The heat and ultraviolet rays from the edge lamp cause harmful effects on the sealant film, such as curling due to shrinkage of the film and a decline in heat sealing performance.
0 w/cm, irradiation speed: 20-150 m/win
It is preferable to irradiate with ultraviolet rays depending on the degree of irradiation.

[Examples] Hereinafter, specific configurations of the adhesive of the present invention and the method for manufacturing a laminate using the adhesive will be described with reference to Examples.

Example 1 An adhesive consisting of the following adhesive composition [1] was applied by a gravure roll coating method to the printed surface of a base material made of a two-wheel stretched polyester film having a thickness of 25 μ and which had been printed by reverse printing. Coating at a ratio of 3 g (resin component)/1, then blowing hot air at 80 ° C. for 2 seconds on the coated surface of the adhesive to evaporate and dry the isopropyl alcohol, which is the solvent in the adhesive, An adhesive coating layer made of ultraviolet curable resin was formed.

Ultraviolet curable resin [polyether-based polyurethane diacrylate prepared by treating the reaction product of polyethylene glycol and tolylene diisocyanate with hydroxyethyl acrylate: average molecular weight 3000] ...30tEI part photopolymerization initiator [1-Phenylsocyanate-2-monohydroxy-2-methylpropan-1-one]... lli parts Isopropyl alcohol... 69 parts by weight Next, on the surface of the coating layer of the adhesive made of the ultraviolet curable resin, A sealant film made of low density polyethylene film with a diameter of 40 μm was brought into contact and brought into close contact, and then thermocompression was performed using nip rolls.
+a, lamp length +90cm, Nippon Battery Co., Ltd.], distance to sealant film 11:10cm, irradiation speed (line speed during irradiation) = 100 m/n + in
The surface of the sealant film was irradiated with ultraviolet rays to obtain the desired product, the laminated sheet [a].

Comparative Example 1 Using the same base material as that used in Example 1, 3 g (resin component) of an adhesive having the following composition [2] was applied to the printed surface of the base material by gravure roll coating.
A laminated sheet [b] for comparison was obtained by the same process as the corresponding process of Example 1, except that the coating was applied at a ratio of 1/m''.

Ultraviolet curable resin [polyether-based polyurethane diacrylate prepared by treating the reaction product of polyethylene glycol and tolylene diisocyanate with hydroxyethyl acrylate: average molecular weight 3000] ...30 weight 1 part photopolymerization initiator [l-hydroxycyclohexylphenyl ketone (self-cleavage type photoinitiator)] 1 part by weight [benzyl dimethyl ketal self-cleavage type photoinitiator] ・・...1 part by weight Photosensitizer [p-dimethylaminobenzoic acid ethyl ester] ...1 part by weight Isopropyl alcohol ...69 parts by weight Comparative Example 2 Using the same base material as that used in Example 1, an isocyanate-curing polyether polyurethane resin [Takelac A-969, Takenate A-5] using ethyl acetate as a solvent was applied to the printing surface of the base material. : Takeda Pharmaceutical Co., Ltd.] was applied at a ratio of 3 g (resin component)/moisture by gravure roll coating, and the same adhesive as that used in Example 1 was applied to the coated surface. A laminated sheet [c] for comparison was obtained by closely adhering the low-density polyethylene resin films of 1 to 2 and compressing them with nip rolls, and then aging them at 40° C. for 7 days.

"Experiment 1" Each of the laminated sheets obtained in Example 1 and Comparative Examples 1 and 2 was cut into a narrow tape shape with a diameter of 15 mm, and then cut between the base material and a sealant film made of a low-density polyethylene film. , peeling angle 90 degrees, peeling speed 100 m+i/
+in. The adhesive strength' of each laminated sheet was obtained by measuring the peel strength when peeled off.

The results are shown in Table 1.

Table 1 "Experiment 2" The heat seal strength of each laminated sheet obtained in Example 1 and Comparative Examples 1 and 2 was measured.

The heat sealing strength of the laminated sheet is measured by attaching two laminated sheets so that the sealant film (low-density polyethylene film) sides of the laminated sheets are in contact with each other.
Fold it in half and use a sentinel heater to heat it.
After heat-pressure bonding at 60°C, 2 kg/cm" for 1 second, the sealant film surfaces of the obtained laminate were peeled at a peeling angle of 90 degrees and a peeling speed of 300 mm/min. It was obtained by measuring the peel strength when

In addition, each laminated sheet was left in a constant temperature bath at 37°C, a portion of the laminated sheet was taken out every week, and the heat seal strength was measured using the method described above. Changes in heat seal strength of sealant films were measured.

The results are shown in Table 2.

Note that the heat sealing strength of the laminate sheet [b] decreases over time due to decomposition products of the photopolymerization initiator contained in the adhesive and unreacted photopolymerization initiator over time. This is due to bleed-out on the sealant film surface over time.

"Experiment 3" Each of the laminated sheets obtained in Example 1 and Comparative Examples 1 and 2 was cut into 100 x 100 mm pieces, and 5 sheets of each type were placed in a 20-port RAA container with a public stopper. After the mixture was sealed in an Erlenmeyer flask and left in an oven at 40° C. for 1 hour, the odor inside each flask was evaluated by sensory evaluation.

The results are shown in Table 3.

Table 3 [Effects of the Invention] The adhesive of the present invention is composed of a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator having an isocyanate group, and the adhesive is applied to a base material. After coating, the solvent in the applied adhesive is evaporated, one of the six laminating materials is superimposed on the adhesive coated surface, and then ultraviolet rays are irradiated. A polymer'-network is gradually formed by the radical reaction and the reaction by the isocyanate group included in the photopolymerization initiator.

Therefore, upon irradiation with ultraviolet rays6, the photopolymerization initiator does not produce its decomposition products, and over time, the decomposition products and undecomposed products of the photopolymerization initiator appear on the surface of the resulting laminate. This will completely solve the problem of bleed-out of the photopolymerization initiator during the reaction.

[Effects of the Invention] In the adhesive of the present invention and the method for producing a laminate using the adhesive, the adhesive is irradiated with ultraviolet rays for curing the adhesive, and then photopolymerization in the adhesive is initiated. The decomposition products of the photopolymerization initiator are not generated in the agent, and there is no problem that decomposition products of the photopolymerization initiator and unreacted photopolymerization initiator bleed out onto the surface of the obtained laminate over time.

Therefore, the resulting laminate has problems with odor caused by decomposed products of the photopolymerization initiator, and bleed-out of decomposed products of the photopolymerization initiator and unreacted photoinitiator onto the surface of the laminate. It is possible to obtain a laminate that can be used as a packaging material without any problems, such as odor from the contents or migration of bleed-out substances to the contents.

In addition, there is no problem of bleed-out of decomposed products of the photopolymerization initiator or unreacted photopolymerization initiator onto the surface of the laminate, so the laminate obtained using conventional two-component curable resin adhesives is not affected. This is a laminate that exhibits adhesive strength that is comparable to the adhesive strength immediately after production, and this adhesive strength does not decrease over time after the production of the laminate, and can last for a long time. A maintained laminate is obtained.

In addition, since the adhesive of the present invention is made of a solvent solution of an ultraviolet curable resin, it is easy to adjust the viscosity of the adhesive used when applying the adhesive, and there is no odor caused by residual monomers and hygiene problems. A laminate with good quality and no problems can be obtained.

Furthermore, the adhesive of the present invention does not require an edging process in the bonding process using the adhesive, which is required when using a two-component hardening resin adhesive, and the manufacturing process can be extremely shortened. Therefore, it is possible to sufficiently respond to deliveries within a short period of time, and since the quality of the adhesion can be inspected immediately after the adhesion process, production control is easy. It is played.

Furthermore, the method for producing a laminate of the present invention exclusively effectively utilizes the characteristics of the adhesive of the present invention,
An efficient bonding method allows sealant films to be bonded without odor or hygiene problems caused by residual monomers, and whose heat-sealing performance does not deteriorate over time after the laminate is manufactured. A laminate is obtained.

Claims (1)

[Scope of Claims] 1. An adhesive comprising a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator having an isocyanate group. 2. After coating the adhesive described in claim 1 on the back side of the base material, the solvent in the applied adhesive is evaporated, and then the thermal welding performance is applied to the coated surface of the adhesive. 1. A method for producing a laminate, comprising: closely adhering a sealant film having a sealant film, and further irradiating with ultraviolet rays. 3. 250-400nm in sealant film
Claim 2 in which the ultraviolet transmittance of is 20% or more
2. Method for manufacturing a laminate described in Section 1. 4. The method for producing a laminate according to claim 3, wherein ultraviolet rays are irradiated from the surface of the sealant film.