JPS6223028B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an adhesive film. Conventionally, adhesive films have been produced by coating a liquid mixture containing, for example, a thermal cross-linking agent and a polymer having an active group for the thermal cross-linking agent on a base film, and then applying a heating process to bond the thermal cross-linking agent and the polymer. react,
It is produced by crosslinking the polymer and evaporating the organic solvent contained in the mixture to form an adhesive film. However, in the manufacturing method of such a thermosetting adhesive film, the long drying time and use of a large amount of solvent for thermal cross-linking reaction and solvent evaporation are undesirable from the viewpoint of energy saving and resources, and the above-mentioned It is impossible to store a mixture containing a thermal cross-linking agent and a polymer for a long time because the reaction between the thermal cross-linking agent and the polymer proceeds gradually even at room temperature. There was a problem in that the cross-linking process did not proceed sufficiently by simply heating the adhesive film after the adhesive film was manufactured, so that the adhesive film had to be heated for several days after it was manufactured. In recent years, in order to improve these drawbacks, an attempt was made to produce an adhesive film by photopolymerizing and crosslinking a high solids composition containing vinyl groups, which was published in the Netherlands Patent No.
It is disclosed in the specification of No. 6601711, Japanese Unexamined Patent Publication No. 17942/1982, Japanese Patent Publication No. 5664/1983, etc. These can solve the problems mentioned above, but in order to utilize photopolymerization, it is essential to add a photoinitiator to the system.
This creates a new problem of poor compatibility since the system is highly solid. Furthermore, the curing performance of this product, which is related to the line speed of the adhesive film production line, cannot be said to be sufficiently advantageous for industrial implementation compared to existing solvent-based adhesive films. Furthermore, JP-A-55-27311 proposes curing a composition comprising a vinyl group-containing compound, a polyfunctional thiol compound, and a photoinitiator using actinic radiation, high-energy ionizing radiation, or the like. However, this is due to problems with the compatibility of the photoinitiator with the system, and products cured from such compositions have poor weather resistance due to the residual photoinitiator, and their characteristics are particularly large when exposed to light for a long time. It has the problem of undesirable changes and is still unsuitable for industrial implementation. In order to solve the above-mentioned problems, the present inventors have intensively studied electron beam-curable adhesive films that cure well without solvents and have excellent adhesive properties. It has been found that a composition containing a thiol compound can be cured well by electron beams and has good adhesive strength even without containing a photoinitiator. At the same time,
It has been found that such compositions exhibit excellent weather resistance, especially light resistance, since they are essentially free of photoinitiators. Furthermore, a polymer having only vinyl groups irradiated with an electron beam has low curing performance and low adhesive strength, and requires the presence of a polyfunctional thiol compound. Although the details of why the polyfunctional thiol compound contained in the photosensitive composition can promote electron beam curing and provide good adhesive strength are not clear, the SH group of the polyfunctional thiol compound has high sensitivity to electron beams. In addition, the reaction between vinyl groups and SH groups competes with the chain polymerization reaction between vinyl groups, and the reaction is similar to condensation polymerization, and as a result, the crosslinking distance of the cured product becomes longer. It is presumed that this is due to The present invention provides a method for producing an adhesive film that has good electron beam curability and adhesive strength, and has excellent weather resistance, particularly light resistance. Furthermore, the composition of the present invention, which does not contain a photoinitiator, also has the advantage that there is no need to consider special light shielding such as the use of a stable light or yellow lamp in the environment during the pre-curing processes such as compounding and coating. It is. In the present invention, on a film base material, a part of the glycidyl group of a copolymer obtained by copolymerizing a vinyl compound and a monomer having a glycidyl group,
An adhesive film is produced by reacting a monomer having a vinyl group and a carboxyl group, and polymerizes a composition containing a polymer having a vinyl group and a polyfunctional thiol compound and not containing a photoinitiator by irradiating electron beams. Regarding manufacturing methods. In the present invention, the above vinyl group-containing polymer used is obtained by copolymerizing a vinyl compound and a glycidyl group-containing monomer by a normal solution polymerization method in a suitable organic solvent, for example. It is produced by reacting a portion of the glycidyl groups of a copolymer with a monomer having a vinyl group and a carboxyl group in the presence of a polymerization inhibitor and a catalyst. Examples of the above-mentioned vinyl compounds include alkyl (meth)acrylate (meaning alkyl acrylate or alkyl methacrylate; the same applies hereinafter), vinyl acetate, acrylonitrile, styrene, butadiene, phthalic anhydride, acrylamide, N-t-butylacrylamide. , polymerizable derivatives of these compounds, etc. are used. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate,
Examples include acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, octadecyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of the monomer having a glycidyl group include glycidyl (meth)acrylate. Examples of the monomer having a vinyl group and a carboxyl group include (meth)acrylic acid. Furthermore, the composition of the present invention may contain at least one
A liquid addition polymerizable substance having two radically polymerizable unsaturated groups may be contained, for example, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, ethoxyethoxy Ethyl (meth)acrylate, polypropylene glycol mono(meth)acrylate,
Polyethylene glycol mono(meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 2-hydroxydodecyl (meth)acrylate, Aronix N-217A (trademark monoacrylate manufactured by Toagosei Chemical Co., Ltd.), Aronix M-5500 (Toagosei Co., Ltd.) Polyester monoacrylate (trademark manufactured by Kagaku Kogyo Co., Ltd.), acryloyloxyethyl hydrogen phthalate, 1,6-hexanediol (meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylol Methane tri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate, 1,
Examples include 3-butylene glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate. It is preferable that the glass transition temperature of the vinyl group-containing polymer of the present invention is 30° C. or less in order to obtain good adhesive properties. Further, the weight average molecular weight of the polymer is preferably in the range of 3000 to 10000,
If it is less than 3,000, the polymerization speed will decrease, and if it exceeds 10,000, the viscosity will be too high and high solids coating will tend to be difficult. Examples of polyfunctional thiol compounds to be included in the composition include ethanedithiol, butanedithiol, hexamethylenedithiol, decamethylenedithiol, ethylene glycol bis(thioglycolate), and ethylene glycol (β-methylcaptopropionate). , trimethylolpropane tris (thioglycolate), trimethylolpropane tris (β-mercaptopropionate), pentaerythritol tetrakis (thioglycolate), pentaerythritol tetrakis (β-mercaptopropionate), and the like. In the production method of the present invention, it is preferable to use 5 to 40 parts by weight of the polyfunctional thiol compound per 100 polymerized parts of the vinyl group-containing polymer in view of the characteristics of the resulting adhesive film. If it is less than 5 parts by weight, there is almost no effect, and if it exceeds 40 parts by weight, the speed of photocuring tends to decrease. In the present invention, the film base material on which the composition is applied is not particularly limited as long as it is not attacked by the composition, such as polyvinyl chloride film, polyester film, acetate film, polypropylene film, aluminum film, etc. Examples include foil, synthetic paper, and release paper. A known method may be used to apply the composition onto the film base material, such as a roll coater, kiss coater, knife coater, gravure coater, or the like. The composition of the present invention is applied onto a film base material as it is or with a solvent added thereto. As the solvent, toluene, methyl ethyl ketone, ethyl cellosolve, methylene chloride, etc. are used. After coating, irradiation is performed with an electron beam, which is emitted from various electron beam accelerators such as Kotscroft-Walton type, Van de Graaff type, Dynamicron type, linear type, resonant transformer type, and high frequency type. 1000keV,
Preferably, an electron beam in the range of 100 to 300 keV is used. The composition of the present invention may contain a chain transfer agent, a pigment, a dye, etc., if necessary. Next, the present invention will be explained in more detail with reference to Examples. Here, parts and % represent parts by weight and % by weight. Example 1 70 parts of toluene is poured into a four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a nitrogen gas blowing device, and the temperature is raised to 95°C. Then increase the temperature to 95℃
20.0 parts of ethyl acrylate while stirring,
Butyl acrylate 60.0 parts, glycidyl methacrylate 20.0 parts, azobisisobutyronitrile
A mixed solution consisting of 4.0 parts of triol and 10 parts of triol was added dropwise from the dropping funnel over 3 hours to obtain a terpolymer, followed by 0.2 parts of hydroquinone, 0.15 parts of benzyltrimethylammonium chloride, and 10 parts of acrylic acid.
The mixture consisting of
By continuing the reaction in this state for 14 hours, the viscosity decreased to approximately 50 cps/23℃ and the glass transition temperature decreased to -70.
A copolymer solution having a weight average molecular weight of about 5000 was obtained. A composition was prepared by adding 10.0 parts of butanedithiol to 300 parts of this material. (A) The above composition was applied onto a 60 μm thick polyethylene film using an applicator and dried by heating (80° C. for 3 minutes). A low-energy electron beam accelerator (Energy Science electrocurtain) was used under the condition of an oxygen concentration of 400 ppm.
An adhesive film was obtained by irradiating a curtain-shaped electron beam of 150 keV and 5 mA with a dose of 3.0 Mrad using a CB-150). The adhesive layer thickness of this product was 5 μm. Comparative Example (B) A composition obtained by removing butanediol from the above composition was irradiated with an electron beam in the same manner as above. however
In addition to the 3.0 Mrad dose, 5.0 Mrad dose was also used. The adhesive film sample piece prepared as described in (A) and (B) above was laminated on a 0.5 mm x 5 mm x 10 mm stainless steel plate with a weight of 2 kg, and was heated at 180 mm at a speed of 200 mm/min according to JIS C 2107.゜The adhesive force of peeling was measured. The results are shown in Table 1.

【table】

[Table] As is clear from Table 1, the presence of butanedithiol in the composition has a significant effect on the curing speed and adhesive strength at room temperature (23°C). "Good" electron beam curability in Table 1 above means that when a sample piece is laminated to a stainless steel plate under a pressure of 2 kg and peeled off after 7 days in a drying oven at 65°C, the peeling speed is This means that there is no migration, clouding, adhesion, etc. to the adherend stainless steel plate within the range of 1 to 10 ⁴ mm/min. Comparative Example 2 Sample pieces were obtained in the same manner as in Example 1 except that 10 parts of several types of photoinitiators were added to the composition of Example 1.
The results of measuring the adhesive strength and light resistance of this product are shown in Table 2 together with those of Example 1.

Table 2 shows that addition of a photoinitiator to the system has little effect on electron beam curability, but significantly deteriorates light resistance. Example 2 The polymer of Example 1 was subjected to solvent removal under reduced pressure (15 mmHg) at 50° C. for 6 hours using a rotary evaporator (Shida Kagaku Kiki Kogyo Co., Ltd. SPC type 5031). The residual solvent in this product was 0.1% or less. Add a certain amount of butanedithiol to 100 parts of this material and stir to obtain a composition. Table 3 shows the results of coating on a polyethylene film and evaluating the electron beam curability and adhesive strength as in Example 1.

[Table] Example 3 Table 4 shows the evaluation results when a compound other than butanedithiol was used as the polyfunctional thiol compound of Example 1. The number of parts added is based on components other than the solvent in the composition.
10 copies per 100 copies.

【table】

[Table] Example 4 Polymer subjected to solvent removal as in Example 2
To 100 parts, 10 parts of ethylene glycol bis(thioglycolate) and 10 parts of Aronix N-217A (monoacrylate manufactured by Toagosei Chemical Co., Ltd.) were added and stirred well. As a result, the adhesive film obtained had good curing properties and adhesive strength (23
℃) was also excellent. Example 5 An experiment was conducted in which Aronix N-217A in Example 4 was replaced with ethoxyethoxyethyl acrylate, and the results were as good as in Example 4. Example 6 Synthesis was carried out in the same manner as in Example 2 except that the number of parts of azobisisobutyronitrile in Example 1 was changed to 3.6 parts and the number of parts of acrylic acid was changed to 7 parts. The viscosity is approx.
A copolymer solution of 60 cps/23°C, glass transition temperature of about -65°C, and weight average molecular weight of 6000 was obtained. The following evaluation was carried out in the same manner as in Example 1. This product had good electron beam curability and excellent adhesive strength. According to the method for producing an adhesive film according to the present invention,
An adhesive film having good electron beam curability and adhesive strength is provided.

Claims (1)

[Scope of Claims] 1. A copolymer obtained by copolymerizing a vinyl compound and a monomer having a glycidyl group on a film base material has a monomer having a vinyl group and a carboxyl group as part of the glycidyl group. 1. A method for producing an adhesive film, which comprises irradiating a composition obtained by reacting a polymer having a vinyl group and a polyfunctional thiol compound and containing no photoinitiator with an electron beam to polymerize it. 2. The method for producing an adhesive film according to claim 1, wherein the polyfunctional thiol compound is contained in 5 to 40 parts by weight based on 100 parts by weight of the vinyl group-containing polymer.