JPS6020428B2 - Radiation-curable pressure-sensitive adhesive composition - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a radiation-curable pressure-sensitive adhesive composition that has high cohesive strength and excellent adhesive properties. Conventionally, in pressure-sensitive adhesive tapes, desired cohesive force,
Polymers with relatively high molecular weight and high viscosity (i.e., natural rubber, synthetic rubber, etc.) to exhibit adhesive properties such as adhesive strength.
needed to be used. Therefore, during coating, it must be applied to the substrate as a solution in an organic solvent. However, since a large amount of the solvent used is evaporated, the drying process after coating requires a long time. Furthermore, the solvents used for the above purpose are volatile and flammable, and many of them have an adverse effect on the human body, so their use can lead to fire outbreaks and various pollution problems. In addition, from an economic standpoint as well as from the above-mentioned Tsurumi point of pollution prevention,
Solvent recovery equipment, which must be reinstalled, is generally expensive and requires a large space. Therefore, in recent years, from the viewpoints of so-called resource saving, energy saving, and pollution-free production, attention has been paid to the use of solvent-free sensitive E-adhesives. There are emulsion-type and hot-melt-type adhesives that can be used as key solvent solutions, but radiation-curable pressure-sensitive adhesives that use liquid oligomers are particularly in the spotlight. The reason for this is that radiation-curable pressure-sensitive adhesives do not, in principle, contain organic solvents, which are the disadvantages of solution-type pressure-sensitive adhesives, or can be made solvent-free, or even if they contain only a small amount. Furthermore, since radiation, which is a '1' active energy ray, is used, the curing (polymerization) reaction is fast;■ As the curing reaction progresses, hot life can be freely adjusted; Does not require a furnace;
This is because it has the following characteristics. However, even in the case of this radiation-curable pressure-sensitive adhesive, there are the following difficulties. That is, the polymerization (curing) reaction generally progresses to unsaturated double bonds due to the generated radicals after radiation irradiation, but the reaction rate is fast and excessive crosslinking is likely to occur. (As a result, the glass transition point increases.) Therefore, the formed film is brittle, and in extreme cases, polymerization shrinkage is large and cracks occur.
Examining the properties of the film in this state shows that it has high breaking strength, but has almost no elongation and does not exhibit rubber-like properties. On the other hand, if the absolute amount of unsaturated double bonds in the molecule is reduced in order to suppress excessive crosslinking, the reaction proceeds locally, resulting in insufficient cohesive force as a whole. As described above, it is difficult to appropriately control the curing reaction and maintain adhesive properties as a sensitive adhesive. Therefore, the present inventors have disclosed in Japanese Patent Publication No. 55-27311 that by adding a polyfunctional thiol compound to a compound having a vinyl group, it is well cured by radiation and has high cohesive force and adhesion. He discovered and proposed that it has a sexual nature. The details of why such a composition provides good adhesive strength are not clear, but it is believed that the SH group of the polyfunctional thiol compound has high radiation sensitivity, and that the reaction between the vinyl group and the SH group It is presumed that this competes with the chain polymerization reaction of the vinyl group, resulting in an increase in the distance between the crosslinking points of the magnetized material. However, in the case of pressure-sensitive adhesives made of compositions containing such thiol compounds, there is a problem in that even if they are sufficiently cured by radiation, they have a slight unpleasant odor characteristic of thiols. Therefore, as a result of further intensive research, it was found that the above drawbacks could be solved by using a reaction product of dithiol and alkyltin oxide, and the present invention was achieved. The present invention provides a pressure-sensitive adhesive that has good radiation curability and adhesive strength and does not have the unpleasant odor that thiol compounds tend to have. That is, in the present invention, a compound obtained by reacting a dithiol with an alkyl tin oxide is added to 0.5 parts by weight of a radiation-curable liquid oligomer 10 having a radically crosslinkable ethylenically unsaturated double bond in the molecule. 3 parts by weight of a radiation-curable pressure-sensitive adhesive composition. In the composition of the present invention, the compound formed by reacting dithiol and alkyltin oxide to be added is as follows. In other words, the unpleasant odor of dithiol is thought to be due to unreacted or hydrolyzed monofunctional thiol during synthesis. Therefore,
The thiol is generally removed by purification, such as by washing with water, but this is not sufficient. Furthermore, thiol has good reactivity with metals, especially tin compounds. As a result of the above, 0.1 to 1 mole of alkyltin oxide was added to 5 to 1 mole of dithiol.
It has been found that when the compound is reacted and made to have a high molecular weight while being heated uniformly for 2 hours or more at ~12 psi, the compound has almost no unpleasant odor even after the reaction and after irradiation with radiation. In the composition of the present invention, in view of the characteristics of the resulting adhesive tapes, 0.5 parts of the above reaction product of dithiol and alkyl tin oxide is added to 100 parts by weight of the radiation-curable liquid oligomer.
Preferably, ~3 parts by weight are used. If it is less than 0.5 parts by weight, there is almost no effect, and if it exceeds 3 parts by weight, the radiation curability may deteriorate. Examples of dithiols that can be used in the present invention include ethanedithiol, butanedithiol, hexamethylenedithiol, decanemethylenedithiol, ethylene glycol, bis(thioglycolate), and ethylene glycol (8-mercabutopropionate). Examples include xanedioldithiopropionate. Furthermore, an alkyl tin oxide is a compound represented by the formula [1]. Representative examples of the dialkyl tin oxide in [1] are dimethyl tin oxide, di-n-butyl tin oxide, di-lso-butyl tin oxide, and di-n-octyl tin oxide. etc.,

[0] is monomethyltin oxide, mono-n-butyltin oxide, mo/-n
-octyltin oxide, and [m] includes monomethyltin hydroxide, mono-n-butyltin hydroxide, mono-n-octyltin hydroxide, etc., but dialkyl of [1] is particularly effective in the present invention. It is tin oxide. Next, in the radiation-curable liquid oligomer having a radically bridged ethylenically unsaturated double bond in the molecule in the present invention, the primary mirror is an acrylic acid alkyl ester,
Oligomers copolymerized with alkyl methacrylate to a low degree of polymerization, polyol acrylate, polyester acrylate, urethane acrylate, epoxy acrylate, etc. have at least one unsaturated double bond per molecule, and the terminal Alternatively, it is an acrylic oligomer having a side chain, or a reactive prepolymer such as polybutadiene, polychloroprene, or polyisoprene. Moreover, the oligomer is liquid and solvent-free, and even if a solvent is used, only a small amount is used. Further, its viscosity is in the range of 1 picps to 5×1 picps at room temperature. In the present invention, particularly favorable results can be obtained with oligomers having highly reactive acrylic double bonds.
In addition, a tackifier may be added to this radiation-curable liquid oligomer, and if necessary, a softener, antioxidant, filler, pigment, etc. may be mixed therein. Radiation as used in the present invention refers to active energy rays, including ionizing radiation such as Q-rays, 8-rays, Y-rays, neutron beams, and accelerated electron beams, as well as ultraviolet rays. In the case of ionizing radiation, the dose can be used in the range of 0.5 to 5 MMd, or preferably about 1 to 2 MMd. Further, in the case of ultraviolet rays, the wavelength range is about 18 to 46 meters, and sources include high-pressure mercury lamps and the like. Further, depending on the case, a curing accelerator (sensitizer in the case of ultraviolet rays) may be included, but when irradiating, particular attention must be paid to the irradiation atmosphere. That is, since the generated radicals are inhibited by oxygen in the air, they may be replaced with an inert gas such as nitrogen depending on the case, but the film may be covered with a film or the like. This will be explained below using examples. Note that in the following, parts indicate parts by weight. Example 1, Comparative Examples 1 and 2 a Synthesis of high molecular weight thiol compound A three-necked flask equipped with a flask, a thermometer, and an injection port was prepared using 1.
1 mol of 6-hexanediol dithiopropionate is charged and the temperature is raised to 60q0. Next, while maintaining the temperature, the powdered gin-n-
0.5 mol of butyltin oxide was gradually injected over 30 minutes, and after the completion of the injection, the temperature was raised to 80 qo, and the temperature was kept for 3 hours for reaction to obtain a colorless and transparent high molecular weight thiol compound. b
Synthesis of radiation-curable oligomers Butyl acrylate 8 Anchorage, Glycidyl methacrylate 2
0 part was subjected to bulk polymerization in the presence of a catalyst to synthesize a solvent-free acrylic copolymer. The weight average molecular weight of the obtained liquid oligomer was approximately 500, and the static viscosity was 2×1 picps (30 qo). Then,
An acrylic radiation-curable liquid oligomer with an unsaturated double bond in the side chain was synthesized by adding one anchor of acrylic acid. 2 parts of the high molecular weight thiol compound synthesized in step (a) was added to 10 pieces of OIJ sesame synthesized as described above to prepare a radiation-curable pressure-sensitive adhesive composition. Next, as Comparative Example 1, a composition containing only the oligomer not containing the above-mentioned thiol compound was selected, and as Comparative Example 2, a composition to which 1 part of butanedithiol was added instead of compound a was selected, A comparison was made of film retention. The film is
Each composition was coated to a certain thickness (approximately 1 layer) on a silicone-treated paper pattern, and then heated in a nitrogen atmosphere (oxygen concentration 40×4) using a resonant transformer-type electron beam accelerator (EBG) with a maximum acceleration voltage of 2 MeV. By irradiating one dish core with one electron beam A generated, polymerization and reticular formation were performed. Then, the elongation rate and breaking strength of each film were measured using a Tensilon tensile tester. The results are shown in Table 1. In addition, the tensile strength is 200
Cape/minute (2pi○). Table 1 Film properties It was found that the composition of Example 1 showed sufficient rubber-like properties. Next, each composition was coated on a polyester film with a thickness of 0.025 mm (manufactured by Toray ■, trade name: Lumirror #25).
) was applied so that the thickness of the adhesive layer was 0.015 mm, and the adhesive force and cohesive force were measured by irradiating with an electron beam in the same manner as described above. The results are shown in Table 2. Table 2 Comparison of characteristics of adhesive tapes Measured according to JIS-C-2107 (adherent:
A heating acceleration test was conducted for 7 days on SUS430BA plate) 26yo, and the increase in adhesive strength was expressed in %. (The smaller the increase, the better) 3 Measure the deviation distance after 3 minutes at 20°C under a load of 500 minutes using a Bakelite plate. From the results, it is clear that the pressure-sensitive adhesive has excellent characteristics because it has no unpleasant odor due to thiol, has a certain cohesive force, and shows little change over time. Example 2, Comparative Example 2c Synthesis of high molecular weight thiol compound Synthesis was carried out by reacting 1 mole of decane methylene dithiol and 0.1 mole of di-n-octyltin oxide using the same apparatus as in Example 1a. d Synthesis of liquid oligomer 1 part of ethyl acrylate, 70 parts of butyl acrylate, and 2 parts of glycidyl methacrylate were polymerized in the same manner as in Example 1, and then 1 part of acrylic acid was added to radiation-cure the acrylic system. A type liquid oligomer was synthesized. Next, 2 parts of the thiol compound c was added to this oligomer to prepare a radiation-curable pressure-sensitive adhesive composition. Next, as Comparative Example 3, decane methylene dithiol was selected instead of the thiol compound in 1) and 1 part of it was added to prepare a composition. Each composition was applied to a 0.06 mm thick polyethylene ref film so that the adhesive layer had a thickness of 0.006 mm, and a linear filament type electron beam irradiation device (
Using an acceleration voltage of 16 V and a beam current of hA with a Lectro Curtain (trade name, manufactured by Energy Science Inc.) under a nitrogen atmosphere (oxygen concentration of 500 skin), an adhesive film for surface protection was manufactured and its characteristics were irradiated with ad electron beam. We conducted an evaluation. (Table 3) Table 3 Upper neck appearance as adhesive film characteristics 4)
The SUS board to which the adhesive film was attached was subjected to 8-skin Eriksen drawing according to JISB7777, and the state of natural peeling of the film was observed after one day at room temperature. From Table 3, it was found that the adhesive film for surface protection had no unpleasant odor, little change during elevation, and good squeezability.

Claims (1)

[Scope of Claims] 1. 0.1 to 1 mol of alkyltin oxide to 1 mole of dithiol to 100 parts by weight of a radiation-curable liquid oligomer having a radically crosslinkable ethylenically unsaturated double bond in the molecule.
A radiation-curable pressure-sensitive adhesive composition containing 0.5 to 30 parts by weight of a compound obtained by reacting 1 mole of the compound. 2 Radiation-curable liquid oligomers that have radically crosslinkable ethylenically unsaturated double bonds in their molecules are acrylic oligomers, and alkyl tin oxides have the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R has 1 carbon number. The radiation-curable pressure-sensitive adhesive composition according to claim 1, wherein the radiation-curable pressure-sensitive adhesive composition is a dialkyltin oxide represented by an alkyl group having an alkyl group of 1 to 10.