JPH03231982A - Adhesive and production of laminate using the adhesive - Google Patents

Abstract

PURPOSE:To provide an adhesive comprising a solvent solution containing an UV-curing resin and a photo-polymerization initiator having acryloyl group, free from the odor and hygienic problems caused by residual monomers and resistant to the lowering of adhesivity with time after the production of a laminate. CONSTITUTION:The objective adhesive is composed of a solvent solution containing (A) an UV-curing resin consisting of preferably a (meth)acrylic oligomer (mixture) containing double bond and having a molecular weight of 1,000-3,000 and (B) an acetophenone, benzoin, thioxanthone or benzophenone-type photo-polymerization initiator having acryloyl group. The above solvent is e.g. ethyl acetate, toluene, methyl ethyl ketone, isopropanol, ethanol or their mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial 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 made of a photopolymerization initiator and a polymerizable monomer component as a diluent are used.

[Problems to be Solved by the Invention] By the way, in the case of adhesion using the two-component curable resin adhesive, the object to be adhered is pressed closely against the surface coated with the adhesive, and then the adhesive is It is necessary to go through a curing process of aging for about 10 days, and the manufacturing efficiency of the laminate is extremely low, which not only makes it impossible to meet quick delivery dates, but also requires equipment for the aging process. , 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 with laminated sheets using this adhesive, there is an odor problem due to decomposition products of the photopolymerization initiator produced by irradiation with ultraviolet rays, such as cyclohexane, benzaldehyde, and methyl benzoate. It is not suitable as an adhesive for lamination, and moreover, it has the disadvantage of causing the aforementioned decomposition products of the photopolymerization initiator and unreacted photopolymerization initiator to bleed out onto the surface of the laminated sheet. There are problems such as migration to the contents inside the package and a decrease in the heat sealing strength of the sealant film in the case of a laminated sheet of the sealant film.

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 of residual materials,
Furthermore, we have developed an ultraviolet curable adhesive that does not have the harmful effects of decomposed products of photopolymerization initiators generated by ultraviolet irradiation or the harmful effects of residual unreacted photopolymerization initiators, and highly efficient laminates using such adhesives. A manufacturing method is provided.

[Means for Solving the Problems] The adhesive of the invention of Section 1 is made of a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator having an acryloyl group.

In addition, the method for manufacturing a laminate according to the invention of Section 2 is such that after applying an adhesive from a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator having an acryloyl group to the back surface of the base material, , the solvent in the adhesive coated on the base material is evaporated, then a sealant film having thermal welding performance is closely attached to the coated surface of the adhesive, and then ultraviolet rays are irradiated to form the laminate. This is what you get.

Furthermore, the method for manufacturing a laminate according to the invention of Section 3 uses a film having an ultraviolet transmittance of 20% or more in the range of 250 to 400 nm as the sealant film in the method for manufacturing a laminate according to the invention of Section 2 described above. By doing this, a laminate is obtained.

Further, the method for manufacturing a laminate according to the invention in Section 4 is to obtain a laminate by irradiating ultraviolet rays from the sealant film surface in the method for manufacturing a laminate according to the invention in Section 3 described above.

In the present invention having the above structure, the ultraviolet curable resin has a molecular weight of 300 to 6,000. Preferably,
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.
The 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, for example, 2-hydroxyethyl (meth)acrylate. For example, polyolefin glycol (meth)acrylate-1-
Di(meth)acrylic acid ester of polyethylene glycol is used, and for polyester (meth)acrylate, a reaction product obtained by treating a polyester of phthalic anhydride and diethylene glycol with (meth)acrylic acid is 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 photopolymerization initiator having an acryloyl group, such as an acetophenone photopolymerization initiator into which an acryloyl group has been introduced, a benzoin photopolymerization initiator, and thioxanthone. type photopolymerization initiator, benzophenone type photopolymerization initiator, specifically,
4-(2-acryloyl-oxyethoxy)-phenyl-2-hydroxy 2-propyl ketone, alkylated benzophenone ether 2-acryloyl-benzophenone, 3-acryloyl-benzophenone, 4-acryloyl-benzophenone, 2-acryloyl-2-benzoyl Benzoet, 3-acryloyl-2-benzoylbenzoate, 4-acryloyl-2-pendiylbenzoate-1-,3,3-dimethyl-2-acryloyl-4-
Photopolymerization initiators such as methoxy-benzophenone, 3,3-dimethyl-4-acryloyl-4-methoxy-benzophenone, and 3,3-dimethyl-5-acryloyl-4-methoxy-benzophenone 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.6 Examples of the solvent in the adhesive include ethyl acetate, toluene, and methyl ethyl ketone.

Single solvents and mixed solvents such as isopropyl alcohol, ethyl alcohol, methyl alcohol, butyl alcohol,
Furthermore, a mixed solvent of the alcohol and water is used, and in the case of a water-alcohol mixed solvent, a mixed solvent containing about 10 to 1000 parts by weight of water to 100 parts by weight of alcohol 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., 0.5~L
Applicable to about og (resin component)/m2.

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 ray irradiation process, if the ultraviolet ray irradiation rate is too fast, the irradiation dose will be insufficient and the adhesive will not be sufficiently cured, and if the irradiation rate is too slow, the ultraviolet lamp The heat and ultraviolet rays from the sun cause problems such as curling of the sealant film due to shrinkage of the film and a decrease in heat sealing performance.
20 w/cm, irradiation speed = 20-150 m/min
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 biaxially stretched polyester film having a thickness of 25 μm and which had been printed by reverse printing. 3 g (resin component)/l112, and 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, A coating layer of ultraviolet curable resin was formed.

Qi acid l UV curable resin [Polyether-based polyurethane diacrylate prepared by treating the reaction product of polyethylene glycol and tolylene diisocyanate with hydroxyethyl acrylate, average publication! 3000] 30 parts by weight Photopolymerization initiator [4-(2-acryloyl-oxyethoxy)phenyl-2-hydroxy-2-propyl ketone... 1 part by weight Isopropyl alcohol... 69 parts by weight Next, the above-mentioned ultraviolet curing A sealant film made of a low-density polyethylene film with a thickness of 40 μm was brought into contact with the surface of the adhesive coating layer made of mold resin, and was further pressed with a nip roll.
Lamp length: 90cm, distance to sealant film, 10cm, irradiation speed (Nippon Battery Co., Ltd.)
Ultraviolet rays were irradiated at a line speed of 100 m/min (line speed during irradiation) from the sealant film surface to obtain the desired product, the laminated sheet [a] 8 Comparative Example 1 Base material used in Example 1 above Using the same base material as above, 3 g of adhesive consisting of the following composition [2] was applied to the printing surface of the base material by gravure roll coating method (resin component).
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 /m'.

Contact Qi 8 Sei 2 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 parts by weight Photopolymerization initiator [1-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 Groups used in Example 1 above Using the same base material as the base material, incyanate-curing polyether polyurethane resin using ethyl acetate as a solvent [Takelac A-969, Takenate A-5 = Takeda Pharmaceutical Co., Ltd.] ] was applied in an amount of 3g (resin component) to 7m2 using the gravure roll coating method, and the same low-density polyethylene resin film as that used in Example 1 was closely attached to the coated surface. A laminated sheet [c] for comparison was obtained by crimping with nip rolls and then aging at 40° C. for 7 days.

"Experiment 1" After cutting each of the laminated sheets obtained in Example 1 and Comparative Examples 1 and 2 into a narrow tape shape with a width of 15 mm, the laminate sheet was cut into a narrow tape shape with a width of 15 mm, and then the laminate sheet was cut into a narrow tape shape with a width of 15 mm, and then the laminate sheet was cut into a narrow tape shape with a width of 15 mm. , peeling angle 90 degrees, peeling speed 100 mm/m
in. The adhesive strength of each laminated sheet was obtained by measuring the peel strength when the sheet was 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 determined by attaching two laminated sheets so that the sealant film (low-density polyethylene film) surfaces of the laminated sheets are in contact with each other.
Fold it in half and use a sentinel heater to heat it.
60℃, 2 kg/cm2. After heat-pressure bonding under heat sealing conditions for 1 second, the peel strength is measured when the sealant film surfaces of the obtained laminate are peeled at a peel angle of 90 degrees and a peel rate of 300 Im/min. It was obtained by

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 were measured.

The results are shown in Table 2.

Table 2 0 The decrease in heat-sealing strength of the laminated sheet [bl] as time passes is 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 200 mf2 triangle with a stopper. Seal it in a flask and place it in an oven at 40°C.
After standing for a period of time, the odor inside each flask was evaluated by sensory evaluation.

The results are shown in Table 3.

Table 1 [Operations and 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 acryloyl group, and the adhesive initiates photopolymerization by irradiation with ultraviolet rays. No decomposition products of the agent are generated.

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. No problems, no odor or build-up to the contents;
- A laminate that can be used as a packaging material without problems such as migration to the contents of products can be obtained.

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. A laminate can be obtained that exhibits an adhesive force that is comparable to the adhesive force immediately after manufacture, and in which the adhesive force does not decrease over time after the laminate is manufactured.

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, as is the case when using a two-component curable resin adhesive, and the manufacturing process can be simplified. Since the time is extremely short, it can be delivered within a short period of time, and the quality of the bond can be inspected immediately after the bonding process.
Functions and effects such as easy production management are achieved.

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.

4

Claims (1)

[Scope of Claims] 1. An adhesive comprising a solvent solution containing an ultraviolet curable resin and a photopolymerization initiator having an acryloyl 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.