JPH0129232B2 - - 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 period of time because the reaction between the thermal cross-linking agent and the polymer proceeds gradually even at room temperature. There is a problem in that the cross-linking reaction does not proceed sufficiently by simply heating after coating, so it is necessary to age the adhesive film for several days after producing it. 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. 17942/1983, 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 compound having a vinyl group, a polyfunctional thiol compound, and a photoinitiator using actinic radiation, high-energy ionizing radiation, or the like. However, this has 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 properties change significantly especially when exposed to light for a long time. There is a problem that it is undesirable, and it is still difficult to implement it industrially. 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, when only a polymer having a vinyl group is irradiated with an electron beam, the curing performance is low and the adhesive strength is low, and the presence of a polyfunctional thiol compound is required. 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 Based on these findings, the present inventors previously proposed a method for producing an adhesive film using a polyfunctional thiol compound. However, it has been found that although the number of adhesive films produced by this method is small, it has the problem of having a unpleasant odor characteristic of thiol compounds. The present inventors have arrived at the present invention which solves all the above-mentioned drawbacks by using a thiol compound obtained by reacting a dithiol with a diisocyanate. The present invention provides a method for producing an adhesive film that has good electron beam curability and adhesive strength, excellent weather resistance, especially light resistance, and is free from the unpleasant odor that thiol compounds tend to have. 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 safety lights or yellow lamps in the environment during pre-curing processes such as compounding and coating. It is. The present invention is an adhesive in which a composition containing a polymer having a vinyl group and a thiol compound obtained by reacting a dithiol with a diisocyanate and containing no photoinitiator is polymerized by irradiating it with an electron beam on a film base material. Concerning a film manufacturing method. As a method for preparing the polymer having a vinyl group used in the present invention, for example, the polymer obtained after copolymerizing a vinyl compound and a monomer having a glycidyl group by an ordinary solution polymerization method in a suitable organic solvent can be used. There is a method of introducing vinyl groups into a polymer by reacting a monomer having a vinyl group and a carboxyl group with a portion of the glycidyl groups of the copolymer 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, and the like 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 di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetra Methylolmethane 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 lower in order to obtain good adhesive properties. The weight average molecular weight of the polymer is preferably in the range of 3,000 to 10,000; if it is less than 3,000, the electron beam curing speed will decrease, and if it exceeds 10,000, the viscosity will be too high, making high solids coating difficult. The thiol compound obtained by reacting dithiol and diisocyanate used in the present invention is obtained by reacting dithiol and diisocyanate in an amount equal to or less than the equivalent amount of diisocyanate to dithiol. The reaction temperature is preferably in the range of 50 to 100°C. If necessary, a catalyst such as dibutyltin laurylate or dibutyltin oxide is used. If necessary, a solvent such as toluene, methyl ethyl ketone, ethylene glycol monoethyl ether, etc. is used. It is preferable to heat a solution containing dithiol and a catalyst, and drop an equivalent or less amount of diisocyanate thereto to carry out the addition reaction. Examples of dithiol include ethanediol,
Butanediol, hexamethylene dithiol, decamethylene dithiol, ethylene glycol bis(thioglycolate), ethylene glycol (β-
Mercaptopropionate), etc. Examples of the diisocyanate include trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and the like. In the production method of the present invention, in view of the characteristics of the resulting adhesive film, 5 to 40 parts by weight of a thiol compound obtained by reacting dithiol and diisocyanate is used for 100 parts by weight of a polymer having a vinyl group. It is preferable. 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.
An electron beam in the range of 1000 keV, preferably 100-300 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 (a) Synthesis of a thiol compound obtained by reacting dithiol and diisocyanate A 1,6-
2 moles of hexanediol dithiopropionate and 0.005 dibutyltin dilaurylate
Pour in the moles and raise the temperature to 60℃. Next, 1 mol of hexamethylene diisocyanate was added dropwise from the dropping funnel over 2 hours while keeping the temperature at 60°C and stirring. After the addition, the temperature was raised to 80°C and kept for 4 hours to form a pale yellow thiol compound at 500 cps/23°C. I got it. (b) Synthesis of polymers with vinyl groups Toluene was added to a four-necked flask equipped with a stirrer, thermometer, dropping funnel, and nitrogen gas blowing device.
Pour 70 parts and raise the temperature to 95℃. Next, add ethyl acrylate while stirring while keeping the temperature at 95℃.
A mixed solution consisting of 20.0 parts of butyl acrylate, 60.0 parts of glycidyl methacrylate, 4.0 parts of azobisisobutyronitrile, and 130 parts of triol was added dropwise from the dropping funnel over 3 hours.
Obtain the original copolymer, then add 0.2 hydrawaquinone
parts, benzyltrimethylammonium chloride 0.15
A mixture of 1 part and 10 parts of acrylic acid was added dropwise over 30 minutes, the temperature was raised to 100°C, and the reaction was continued in this state for 14 hours, resulting in a viscosity of approximately 50 cps/23
℃, glass transition temperature -70℃, weight average molecular weight approx.
5000 copolymer solution was obtained. 300 copies of this thing
10 parts of the thiol compound synthesized in (a) was added to prepare a composition. (c) Production of adhesive film 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.
CB-150) was irradiated with a curtain-shaped electron beam of 150 keV and 5 mA at a dose of 3.0 Mrad to obtain an adhesive film. The adhesive layer thickness of this product was 5 μm. Comparative Example 1 A composition obtained by removing the compound (a) from the above composition and adding 10 parts of butanedithiol instead was irradiated with an electron beam in the same manner as above to obtain an adhesive film. The sample piece of adhesive film prepared by the method described above was laminated on a 0.5 mm x 5 mm x 10 mm stainless steel plate with a weight of 2 kg, and the sample was laminated at a speed of 200 in accordance with JIS C 2107.
The adhesion force was measured at 180° peel in mm/min. The results are shown in Table 1.

[Table] As is clear from Table 1, the thiol compound of Example 1 obtained by reacting dithiol and diisocyanate is highly effective in reducing odor. "Good" electron beam curability in Table 1 above means that the 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. refers to one that does not cause any migration, clouding, transfer, 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】

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 vinyl group-containing polymer obtained in Example 1 was heated in a rotary evaporator (Shibata Kagaku Kiki Kogyo KK).
6 at 50℃ under reduced pressure (15mmHg) using SPC type 5031).
Solvent removal was carried out for hours. The residual solvent of this thing is 0.1
% or less. 100 copies of this product (a) of Example 1
A certain amount of the thiol compound synthesized in step 1 is added and stirred to form 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 A thiol compound was synthesized using a dithiol other than 1,6-hexanediol dithioproponic acid ester as the dithiol to be reacted with the diisocyanate in Example 1(a), and it was used to make an adhesive film. The evaluation results are shown in Table 4. The number of parts added was 10 parts per 100 parts of components other than the solvent in the composition.

[Table] Example 4 100 parts of the vinyl group-containing polymer used in Example 2 and subjected to solvent removal, 10 parts of the thiol compound synthesized in Example 1(a), and Aronix N-217A (mono manufactured by Toagosei Chemical Co., Ltd.) After adding 10 parts of acrylate and stirring well, the process from coating to a polyethylene film to evaluation of its properties was carried out in the same manner as in Example 1. As a result, the resulting adhesive film had good curing properties and adhesive strength (
℃) 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. Evaluation was conducted in the same manner as in Example 1 below. This product had good electron beam curability and excellent adhesive strength. Example 7 An adhesive film was obtained in the same manner as in Example 3 except that trimethylhexamethylene diisocyanate was used as the diisocyanate to be reacted with dithiol, and the same good results as in Example 3 were obtained. 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 composition containing a polymer having a vinyl group and a thiol compound obtained by reacting a dithiol with a diisocyanate and containing no photoinitiator is irradiated with an electron beam on a film base material. A method for producing an adhesive film characterized by irradiation and polymerization. 2 For 100 parts by weight of the polymer having a vinyl group,
The method for producing an adhesive film according to claim 1, wherein the thiol compound obtained by reacting dithiol and diisocyanate is contained in an amount of 5 to 40 parts by weight.