JPH0155645B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention relates to an emulsion-type photocurable adhesive prepared by adding a photopolymerizable compound and a photopolymerization initiator to a base polymer emulsion obtained by emulsion polymerization of an alkyl (meth)acrylic ester. Regarding the manufacturing method. [Conventional technology] Pressure-sensitive adhesives that are normally sticky have been widely used to bond plastics, glass, metals, paper, etc., but it is said that high adhesive strength cannot be obtained due to low cohesive force. There were flaws. Therefore, photo-curable adhesives have been proposed to improve this drawback, and various emulsion-type photo-curable adhesives have been studied from the viewpoints of resource saving, energy saving, environmental hygiene, and the like. This photo-curable adhesive can increase the molecular weight of the base polymer by obtaining it through emulsion polymerization, so it exhibits relatively high cohesive force even before photo-curing, and even greater cohesive force after photo-curing. Because of this, it has attracted particular attention in recent years as an adhesive with high adhesive properties. [Problems to be Solved by the Invention] However, in this type of emulsion-type photocurable adhesive, in order to improve its photocurability, a relatively large amount of a photopolymerizable compound is added to the base polymer emulsion to initiate photopolymerization. Addition of such agents causes problems such as the stability of the emulsion is extremely reduced and the emulsion aggregates during storage and coating, making coating difficult and causing streaks. Furthermore, in order to avoid this problem, when the amount of emulsifier used during emulsion polymerization of the base polymer is increased, the stability of the emulsion is improved to some extent, but when this is applied to an adherend and photocured, There was a problem that the water resistance of the product was extremely reduced. Therefore, the object of the present invention is to solve these problems and provide an emulsion-type photocurable adhesive that has excellent emulsion stability and water resistance after photocuring. [Means for Solving the Problems] As a result of intensive studies in order to solve the above problems, the inventors have found that, in emulsion polymerization to obtain a base polymer, a method of stabilizing dispersion together with a commonly used emulsifier has been found. When a photopolymerizable compound and a photopolymerization initiator are added to the resulting base polymer emulsion, the stability of the emulsion is not impaired and the water resistance after photocuring is improved. This discovery led to this invention. That is, the present invention is directed to the use of a (meth)acrylic acid alkyl ester alone or a mixture of this monomer and other unsaturated monomers copolymerizable with an emulsifier and a water-soluble polymer having a weight average molecular weight of 10,000 or more. After emulsion polymerization in the presence of a dispersion stabilizer,
Emulsion-type photocuring with excellent emulsion stability and water resistance after photocuring, characterized by adding a photopolymerizable compound having at least one (meth)acryloyl group in one molecule and a photopolymerization initiator This invention relates to a method for producing a sticky adhesive. [Structure and operation of the invention] In this invention, the unsaturated monomer as a raw material used to obtain the base polymer emulsion has the properties of tackiness, adhesion, weather resistance, light resistance, and transparency that should be imparted to the adhesive. From these viewpoints, (meth)acrylic acid alkyl ester alone or a mixture of this monomer and other unsaturated monomers that can be polymerized are used. As the (meth)acrylic acid alkyl ester, for example, methyl (meth)acrylate, (meth)acrylate,
Ethyl acrylate, butyl (meth)acrylate,
(meth)pentyl acrylate, (meth)hexyl acrylate, (meth)octyl acrylate, (meth)
Nonyl acrylate, decyl (meth)acrylate,
Examples include dodecyl (meth)acrylate.
Among these, those in which the alkyl group has 2 to 12 carbon atoms are particularly preferred. Further, the alkyl group mentioned above may be linear or branched, and two or more types can be used in combination as necessary. Other unsaturated monomers that can be copolymerized with the above monomers include carboxyl group-containing unsaturated monomers such as (meth)acrylic acid, crotonic acid, maleic acid, and itaconic acid, and (meth)acryloyl phosphoric acid. Unsaturated monomers containing phosphate groups such as oxyethyl, (meth)acryloyloxypropyl phosphate, 2-hydroxyethyl (meth)acrylate, (meth)acrylate, etc.
Unsaturated monomers containing hydroxyl groups such as 2-hydroxypropyl acrylate, unsaturated monomers containing alkylamino groups such as N-N-dimethylaminoethyl (meth)acrylate, and N-tert-butylaminoethyl (meth)acrylate. Monomers, unsaturated monomers containing amide groups such as (meth)acrylamide, N-methylol (meth)acrylamide, n-butoxymethyl (meth)acrylamide, other (meth)acrylic acid glycidyl esters, (meth)acrylonitrile, Examples include unsaturated monomers such as vinyl acetate and styrene. The amount of these other unsaturated monomers added is in the range of 0 to 60 parts by weight based on 100 parts by weight of the above-mentioned (meth)acrylic acid alkyl ester. Used for purposes such as granting. In this invention, a base polymer emulsion is prepared by emulsion polymerization of the above-mentioned unsaturated monomers, but this emulsion polymerization is carried out in a conventional manner, except that a specific dispersion stabilizer is used in addition to a commonly used emulsifier. There is nothing particularly different. That is, the above-mentioned emulsifier and dispersion stabilizer may be added to an appropriate amount of water, and emulsion polymerization may be carried out according to a conventional method using a known polymerization initiator such as ammonium persulfate. As the emulsifier, anionic surfactants such as alkylbenzene sulfonates, alkylnaphthalene sulfonates, fatty acid salts, higher alcohol sulfate ester salts, dialkyl sulfosuccinic acids, and alkyl phosphate salts are used. The amount of this surfactant added varies depending on its type, but can generally be selected within the range of 0.1 to 5 parts by weight per 100 parts by weight of the unsaturated monomer. In order to improve the water resistance after photocuring, it is preferable to use the minimum amount that allows emulsion polymerization. The dispersion stabilizer, which is an important component of this invention and is used in combination with the emulsifier, has a weight average molecular weight of 10,000 or more,
It is a high molecular weight water-soluble polymer that does not form micelles, usually around 300,000. Specific examples include the following water-soluble polymers each having a weight average molecular weight of about 10,000 to 300,000. (a) Saponified polyvinyl acetate (saponification degree of 80% or more) RCOO (CmH ₂ O) nH or RCOO (CmH ₂ mO) nOCR [R: alkyl group with 1 to 18 carbon atoms,
m: An integer of 2 or more, usually up to 6, n: 50 or more, usually
An integer up to 3000] Polyalkylene glycol alkyl ester ha RO (CmH ₂ mO) nH or RO (CmH ₂ mO) nR [R: alkyl group with 1 to 18 carbon atoms,
m: An integer of 2 or more, usually up to 6, n: 50 or more, usually
An integer up to 3000] Polyalkylene glycol alkyl ether di [-(C _l H _2l O)-mCONH-R-NHCOO]-n
or [R, R': alkylene group with 1 to 6 carbon atoms, R'', R: alkyl group with 1 to 18 carbon atoms, l: integer from 2 to 6,
m: An integer from 1 to usually 30, n: Usually from 30 to 30
An integer up to 2000] Water-soluble polyurethane resin The amount of these dispersion stabilizers added is 100% of the unsaturated monomer.
It is generally preferable to use it in a range of 0.3 to 5 parts by weight. In this invention, the photopolymerizable compound having at least one (meth)acryloyl group in one molecule to be blended into the base polymer emulsion obtained as described above refers to a photopolymerizable compound having at least one (meth)acryloyl group in one molecule. Polyfunctional ones having at least one, preferably two or more methacryloyl or acryloyl groups, such as 1,4-butylene glycol di(meth)acrylate, 1,6
- hexane glycol di(meth)acrylate,
Monomers or epoxy (meth)acrylate such as neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate Examples include oligomers such as acrylate, urethane-modified (meth)acrylate, and oligoester (meth)acrylate, and two or more of these may be used in combination as necessary. The blending ratio of this photopolymerizable compound and the solid content of the base polymer emulsion is 10 to 80% by weight, preferably 30 to 70% by weight of the total amount of both.
It is preferable to adjust the amount to % by weight. Too much of the photopolymerizable compound is undesirable because the cohesiveness of the photocurable adhesive layer before irradiation with light is poor and adhesive oozes out to the sides, and too little is undesirable because sufficient curing cannot be obtained. . In this invention, the photopolymerization initiator used together with the photopolymerizable compound is not particularly limited as long as it promotes the photopolymerization reaction of the photopolymerizable compound. For example, benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, α-methylbenzoin, anthraquinones such as 1-chloroanthraquinone, 2-chloroanthraquinone, benzophenone, p-chlorobenzophenone, p-dimethyl Examples include benzophenones such as aminobenzophenone, sulfur-containing compounds such as diphenyl disulfide and tetramethylthiuram disulfide, and dimethylbenzyl ketal. The photopolymerization initiator is added in an amount of 0.05 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the total amount of the photopolymerizable compound and the solid content of the base polymer emulsion. When the photopolymerizable compound is liquid, the emulsion type photocurable adhesive consisting of the photopolymerizable compound, a photoinitiator, and a base polymer emulsion is prepared by directly applying the mixture of the photopolymerization compound and the photopolymerization initiator. Alternatively, the photopolymerizable compound may be added to the base polymer emulsion using a small amount of an organic solvent if necessary, or if the photopolymerizable compound is solid, it may be mixed with a small amount of a solvent or other liquid compound. It can be obtained by dissolving the mixture in the water and adding and mixing it according to the method described above. This adhesive has excellent stability as an emulsion even after the addition and mixing described above. Appropriate amounts of other compounding agents may be added to the emulsion-type photocurable adhesive of the present invention thus obtained, depending on the purpose. Examples of compounding agents include polymerization inhibitors that prevent thermal polymerization during production and reactions during storage, such as hydroquinone, hydroquinone monomethyl ether, tert-butylcatechol, p-benzoquinone, 2,5-tert-butylhydroquinone, and phenothiazine. , adhesion-imparting resins such as xylene resin and coumaron resin for the purpose of improving adhesive strength to the adherend surface, and triepoxypropylisocyanurate and butoxymethylated melamine for the purpose of improving cohesive strength before light irradiation. Examples include crosslinking agents such as. In use, the emulsion-type photocurable adhesive of the present invention can be cast onto a tape or sheet with high releasability such as low-adhesion resin-treated paper or plastic film, or on other releasable surfaces. It can be made into a tape or sheet by heating and drying. At this time, rayon nonwoven fabric,
A core material such as a nonwoven fabric such as a nylon nonwoven fabric or a cloth such as cheesecloth may be embedded. The above-mentioned tape or sheet having high releasability is used as it is as a releasable support that is peeled off and separated from the molded product during use. According to the sheet-like material of the photocurable adhesive obtained in this way, it can be interposed, for example, between at least one of the two articles to be joined, which is made of at least one or one having light transmitting ability, to temporarily bind both articles. After bonding, a light source such as a high-pressure mercury lamp, ultra-high-pressure mercury lamp, metal halide lamp, carbon arc lamp, or xenon lamp is used to pass through the above-mentioned light-transmitting article.
By performing light irradiation for 0.3 seconds or more, preferably 3 seconds or more and curing by photocrosslinking, both articles can be firmly bonded. Furthermore, even if this adhesive is immersed in humidified conditions or in water, the adhesive strength will not decrease much because the adhesive is highly water resistant. [Effects of the Invention] As described above, in this invention, by using a specific dispersion stabilizer together with a normal emulsifier when preparing a base polymer emulsion,
There is no risk of impairing the stability of the emulsion when a photopolymerizable compound, photopolymerization initiator, etc. are added after preparation of this emulsion, and it also contributes to improving the water resistance and moisture resistance of the cured adhesive layer after light irradiation. Can be done. [Examples] Examples of the present invention will be described below. In addition,
In the following, parts mean parts by weight. Example 1 2-ethylhexyl acrylate 60 parts Ethyl acrylate 35 parts Acrylic acid 2 parts -2-acryloyloxyethyl phosphate 3 parts Ion exchange water 100 parts Polypropylene glycol diethyl ether (weight average molecular weight approximately 10,000) 1.5 parts Dodecylbenzene Sodium sulfonate 1.5 parts Prepare the above composition in a 500ml flask,
After heating and stirring for 1 hour at 70℃ under inert gas, 0.1
of ammonium persulfate was added and the mixture was reacted at 70°C for 5 hours to obtain a base polymer emulsion. Next, to 100 parts of this emulsion (solid content), 50 parts of tetraethylene glycol dimethacrylate and 3 parts of benzoin isobutyl ether were added.
were gradually added dropwise to the emulsion while stirring rapidly and mixed uniformly to obtain an emulsion-type photocurable pressure-sensitive adhesive. Example 2 The same procedure as Example 1 was performed, except that the same amount of polyethylene glycol di-n-butyl ester (weight average molecular weight 18,000) was used instead of polypropylene glycol diethyl ether in the emulsion polymerization composition described in Example 1. An emulsion type photocurable adhesive was obtained in the same manner. Example 3 Example 3 except that the same amount of saponified polyvinyl acetate (weight average molecular weight 100000, degree of saponification 88%) was used instead of polypropylene glycol diethyl ether in the emulsion polymerization composition described in Example 1. An emulsion type photocurable adhesive was obtained in the same manner as in Example 1. Comparative Example 1 An attempt was made to obtain an emulsion type photocurable adhesive in the same manner as in Example 1, except that polypropylene glycol diethyl ether was not used in the emulsion polymerization composition described in Example 1. However, the emulsion agglomerated at the stage of adding the photopolymerizable compound and the photopolymerization initiator, and could not be used at all. Comparative Example 2 The composition for emulsion polymerization described in Example 1 except that polypropylene glycol diethyl ether was not used and the amount of sodium dodecylbenzenesulfonate used was changed from 1.5 parts to 3 parts.
An emulsion type photocurable adhesive was obtained in the same manner as in Example 1. Example 4 Butyl acrylate 80 parts Acrylonitrile 15 parts Methacrylic acid 5 parts Water-soluble polyurethane resin (trade name Coraclar PU85 manufactured by BASF) 2 parts Sodium hexaoxyethylene dodecyl ether sulfate 1.5 parts Ion-exchanged water 150 parts Using the above blended composition A base polymer emulsion was obtained in the same manner as in Example 1. Next, 60 parts of pentaerythritol triacrylate and 5 parts of dimethylbenzyl ketal were gradually added dropwise to 100 parts of this emulsion (solid content) while rapidly stirring the emulsion, and the emulsion was uniformly mixed. A sticky adhesive was obtained. The results of examining the emulsion stability of each emulsion-type photocurable adhesive according to Examples 1 to 4 and Comparative Example 2 are shown in the table below. In addition, each adhesive was placed on silicone-treated paper with a 50 μm thick nylon nonwoven fabric interposed as a core material, so that the thickness after drying was
It was applied to a thickness of 130 μm and dried at 100° C. for 5 minutes to produce a photocurable adhesive sheet. The following characteristics were evaluated for each sheet. The results are shown in the table below. <Stability of emulsion> Apply an emulsion-type photocurable adhesive onto silicone-treated paper and visually observe the presence or absence of agglomeration or streaking of the emulsion. If the case is △,
Cases where it was clearly recognized were evaluated as ×. <Peel adhesion strength> Thickness on one adhesive side of the photocurable adhesive sheet
20mm wide by pasting 50μm polyester sheet
20℃, 65°C
The adhesive strength of the polyester sheet was measured at 180° peeling at a peeling speed of 300 mm/min at %RH (before light irradiation). In addition, after irradiating ultraviolet rays for 5 seconds from a position 10cm away from the back of the polyester sheet with a high-pressure mercury lamp (80W/cm/1 lamp) on the polyester sheet and the stainless steel plate attached in the same manner as above,
After being left at ℃ for 24 hours, the adhesive strength was measured by peeling off at 180 degrees under the same conditions as described above (after irradiation with light). Furthermore, after the above ultraviolet irradiation, it was left at 20°C for 24 hours, and after being left at 60°C and 90% RH for 24 hours, it was peeled off at 180 degrees under the same conditions as above and the adhesive strength was measured (after light irradiation and storage under humidification). . <Tack> Roll a stainless steel ball onto the adhesive surface of a photocurable adhesive sheet from a run-up distance of 10 cm at 20℃ and 65% RH on a slope with an inclination angle of 30 degrees.
The ball number is shown as the largest ball (size = ball number x 1/36 inch) that stops at 10 cm.

[Table] As is clear from the above table, the emulsion-type photocurable adhesive of the present invention has excellent emulsion stability and sufficient adhesiveness to temporarily bond two articles to be joined before irradiation with light. It can be seen that the two articles can be firmly bonded together by light irradiation, and the water resistance after light irradiation is good.

Claims (1)

[Claims] 1. A (meth)acrylic acid alkyl ester alone or a mixture of this monomer and other unsaturated monomers copolymerizable with an emulsifier and a weight average molecular weight
After emulsion polymerization in the presence of a dispersion stabilizer consisting of 10,000 or more water-soluble polymers, a photopolymerizable compound having at least one (meth)acryloyl group in one molecule and a photopolymerization initiator are added. A method for producing an emulsion-type photocurable adhesive characterized by excellent emulsion stability and water resistance after photocuring. 2. The method for producing an emulsion type photocurable adhesive according to claim 1, wherein the emulsifier is an anionic surfactant. 3. Claim 1 or 2, wherein the dispersion stabilizer is at least one selected from saponified polyvinyl acetate, polyalkylene glycol alkyl ester, polyalkylene glycol alkyl ether, and water-soluble polyurethane resin. The method for producing the emulsion-type photocurable adhesive described above.