JPS6336358B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a non-staining emulsion type pressure sensitive adhesive that has excellent anchoring power for synthetic resins, particularly polyolefin resins. More specifically, it relates to a pressure-sensitive adhesive whose main component is an aqueous emulsion obtained by homoemulsion polymerization or emulsion copolymerization of a vinyl unsaturated monomer using an allyl group- or methallyl group-containing sulfonate as an emulsifier. It is. Pressure-sensitive adhesives are generally used to manufacture adhesive materials such as adhesive tapes and adhesive sheets by coating and drying them on base materials such as paper, cloth, and plastic films. At this time, there is no problem when the base material is paper or cloth, but when using synthetic resins such as vinyl chloride resin and polyester resin, especially polyolefin resins such as polyethylene and polypropylene, the anchoring force of the pressure-sensitive adhesive is large. things become important. The anchoring force here refers to the adhesive force between the base material and an adhesive layer formed by applying and drying a pressure-sensitive adhesive onto the base material. In addition, when it comes to adhesive materials such as adhesive tapes and adhesive sheets, the surface of the adhesive layer is glass bottles,
It is important that the adhesive has adhesive properties to adherends such as plastic containers. This performance is generally understood to be broken down into adhesive strength, adhesion strength, and cohesive strength, and the performance of the adhesive material differs depending on the combination of these strengths. When the adhesive material is applied to the adherend,
The following strength relationship is essential: Adhesive force < Adhesive force < Cohesive force < Anchoring force. The reason why it is necessary to have the highest anchoring force is that if the anchoring force is small, when the adhesive material is applied to the adherend and then peeled off, the adhesive layer will remain on the adherend (glue will remain). This is because the remainder) causes a significant drawback in terms of handling and aesthetics. Conventionally, rubber-based resins have often been used as pressure-sensitive adhesives, but since their weather resistance is significantly poor, acrylic resins, which have good weather resistance, have since been used. However, since the acrylic resin used for this was a solvent type dissolved in a solvent, there was a risk of fire, toxicity, and pollution such as air pollution during the production of adhesive materials, so a water-based version was desired. Ta. As water-based adhesives, various water-based emulsion-type pressure-sensitive adhesives of acrylic resin have been proposed;
In both cases, the anchoring force against a base material made of synthetic resin, especially polyolefin resin, is weaker than that of the solvent type, so they have the drawback of leaving adhesive residue. In addition, when an adhesive material manufactured using such an emulsion-type pressure-sensitive adhesive is applied to an adherend and then peeled off, the emulsifier remaining in the adhesive layer may cause damage to the adherend, especially when it is peeled off. The disadvantage was that it caused clouding on the surface of painted objects and plastic products. Moreover, the water-resistant adhesive strength between the adhesive layer and the base material was also poor. As a result of research, the present inventors have found that when emulsion polymerization is carried out using a specific copolymerizable emulsifier, the resulting pressure-sensitive adhesive has outstanding anchoring power and water-resistant adhesion to synthetic resins, particularly polyolefin resins. The present invention was completed based on the discovery that there is no contaminating effect on adherends. That is, the present invention is based on the following general formula: or (In the formula, R ₁ is hydrogen or a methyl group, R ₂ is a hydrocarbon group or an organic group containing a hydrocarbon group having a substituent or an oxyalkyl group, and A is a carbon number of 2 to 4
n is 0 or a positive integer, M is an alkali or alkaline earth metal, ammonium, an organic amine base, or a quaternary ammonium base, m is M When a sulfonate containing an allyl group or a methallyl group is used as an emulsifier, the glass transition point is −30
Emulsification of vinyl unsaturated monomers or monomer mixtures containing 50% by weight or more of alkyl (meth)acrylates whose alkyl groups have 1 to 12 carbon atoms to form polymers or copolymers at temperatures below It is a pressure-sensitive adhesive whose main component is an aqueous emulsion obtained by polymerization. Note that the term "alkyl (meth)acrylate" as used herein refers to alkyl acrylate and/or alkyl methacrylate. The pressure-sensitive adhesive of the present invention is characterized by being an aqueous emulsion produced using a specific copolymerizable emulsifier as described above. The allyl group- or methallyl group-containing sulfonate used as an emulsifier in the present invention is a copolymerizable emulsifier that has extremely excellent emulsifying power for vinyl unsaturated monomers. Therefore, this emulsifier, like general emulsifiers and protective colloids, may be adsorbed to resin particles, or
Unlike emulsifiers that emulsify resin particles by existing in a dispersion medium, they copolymerize with resins to emulsify resin particles, but this emulsifier has extremely low homopolymerizability. On the other hand, since it exhibits good copolymerizability with vinyl unsaturated monomers, it exhibits sufficient emulsifying power even when used in a very small amount relative to the resin. Although it is not fully understood, this
We believe that the resulting pressure-sensitive adhesive has excellent anchoring power for polyolefin resin, water-resistant adhesion, and non-staining properties of adhesive materials made using this pressure-sensitive adhesive to adherends. ing. The allyl group- or methallyl group-containing sulfonic acid salt used in the present invention is produced by reacting a diester of maleic acid or fumaric acid containing at least one allyl group or methallyl group with a sulfite. Specific examples of diesters of maleic acid or fumaric acid containing at least one allyl group or methallyl group include diallyl ester, dimethallyl ester, allyl alkyl ester, allyl alkenyl ester, allyl phenyl ester of maleic acid or fumaric acid. In addition to relatively simple diesters such as allyl substituted phenyl ester, methallyl alkyl ester, methallyl alkenyl ester, and methallyl substituted phenyl ester, for example, polyethylene glycol, polypropylene glycol, alcohol alkylene oxide adducts, fatty acid alkylene oxide adducts, Mixed esters of compounds with terminal hydroxyl groups such as alkylphenol alkylene oxide adducts, aliphatic or aromatic amine alkylene oxide adducts, and allyl alcohol or methallyl alcohol, allyl alcohol or methallyl alcohol with ethylene oxide, propylene Single addition of alkylene oxides such as styrene oxide, alkylene oxides with substituents such as epichlorobidrin, or compounds with terminal hydroxyl groups obtained by random or block addition of these, and maleic acid or fumaric acid. Diesters produced by reaction with acids, and furthermore, the carboxyl group of one of maleic acid or fumaric acid forms an ester with an adduct of alkylene oxide or substituted alkylene oxide to allyl alcohol or methallyl alcohol, and the carboxyl group of the other carboxyl group Complex structures such as mixed esters in which the group forms an ester with other alcohols, phenols, glycols, or alkylene oxide adducts are also included. Examples of sulfites include acidic sodium sulfite, acidic potassium sulfite, acidic ammonium sulfite, acidic calcium sulfite, acidic magnesium sulfite, sodium metasulfite, potassium metasulfite, calcium metasulfite, sodium sulfite, ammonium sulfite, calcium sulfite, and the like. The vinyl unsaturated monomer used in the present invention is
A monomer containing 50% by weight or more of an alkyl (meth)acrylate whose alkyl group has 1 to 12 carbon atoms to form a polymer or copolymer with a glass transition point of -30°C or lower. In other words, the glass transition point of the polymer formed from vinyl unsaturated monomers is -30°C.
It is necessary to use them alone or in combination as follows. Specific examples of the alkyl (meth)acrylates in which the alkyl group has 1 to 12 carbon atoms include acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, butyl methacrylate; ―
Examples include methacrylates such as ethylhexyl methacrylate. Examples of vinyl unsaturated monomers that can be used in combination with the alkyl (meth)acrylate include acrylic acid,
Unsaturated carboxylic acids such as methacrylic acid; Unsaturated carboxylic acid amides such as acrylamide and methacrylamide; N-methylolacrylamide,
N-methylol unsaturated carboxylic acid amides such as N-methylol methacrylamide; unsaturated glycidyl compounds such as glycidyl acrylate and glycidyl methacrylate; alkylol compounds of unsaturated compounds such as hydroxyethyl acrylate and hydroxypropyl methacrylate; divinylbenzene Examples include vinyl unsaturated monomers having functional groups such as divinyl compounds such as. Furthermore, vinyl unsaturated monomers such as vinyl acetate, acrylonitrile, and methacrylonitrile may be used in combination. The aqueous emulsion, which is the main component of the pressure-sensitive adhesive of the present invention, uses the aforementioned allyl group- or methallyl group-containing sulfonate as an emulsifier, a radical polymerization initiator, a pH adjuster, and, if necessary, a polymer chain transfer agent. It can be obtained by homo-emulsion polymerization or emulsion copolymerization of the aforementioned unsaturated monomers in an aqueous phase in the presence of an agent. The polymerization method may be either a batch polymerization method or a continuous polymerization method. The polymerization reaction temperature is usually in the range of 30 to 90°C. The radical polymerization initiator is a water-soluble radical polymerization initiator used in ordinary emulsion polymerization, such as hydrogen peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, butyl hydroperoxide, etc., alone or in combination with L-ascorbic acid, Redox systems are used in combination with reducing agents such as sulfites, Rongalites, and ferrous sulfates. As the pH adjuster, acids such as hydrochloric acid, phosphoric acid, acetic acid, succinic acid, boric acid, and carbonic acid, and their salts, and bases such as alkali metal hydroxides, aqueous ammonia, and amines are used. As the polymerization chain transfer agent, mercaptan, carbon tetrachloride, chloroform, etc. can be used as necessary. As the emulsifier, the aforementioned allyl group- or methallyl group-containing sulfonate, a nonionic surfactant,
Anionic surfactants, protective colloids, etc. can also be used in combination, but needless to say, their use in large amounts is not allowed. The solids content of the aqueous emulsion used as the main component of the pressure-sensitive adhesive of the invention is at least 30% by weight.
As mentioned above, it is desirable that the solid content is preferably 45% by weight or more. Additives such as antifoaming agents, viscosity modifiers, fillers, preservatives, freeze stabilizers, crosslinking agents, plasticizers and tackifiers may be added to the pressure sensitive adhesive of the present invention as necessary. . The pressure-sensitive adhesive containing the aqueous emulsion of the present invention as a main component can be widely applied to adhesive tapes, adhesive sheets, adhesive labels, masking tapes, and the like. In particular, it can be used as a pressure-sensitive adhesive for surface protection sheets made of polyethylene or polypropylene sheets, making use of its excellent adhesion to polyolefin plastics with low polarity. The present invention will be explained below with reference to Examples, but is not limited thereto. Example 1 In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 150 parts by weight of water, 0.5 parts by weight of sodium acetate, and an allyl group-containing sulfonate represented by the chemical formula below as an emulsifier were added. 1.5 parts by weight was added, and then a monomer composition with the following composition: Butyl acrylate 87 parts by weight Methyl methacrylate 7 parts by weight Methacrylic acid 3 parts by weight N-butoxymethylol acrylamide
Add 3 parts by weight and 100 parts by weight, stir to emulsify the monomer composition, add 0.5 parts by weight of ammonium persulfate to start polymerization, and maintain the reaction temperature at about 70°C.
Emulsion polymerization is carried out for about 2 hours. After the reaction was completed, the mixture was aged at about 80° C. for 1 hour to obtain a pressure-sensitive adhesive consisting of an aqueous copolymer emulsion having a concentration of 40% by weight and a viscosity of 2 cP. Note that the glass transition point of the copolymer is -42°C. Example 2 In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 150 parts by weight of water, 0.5 parts by weight of sodium acetate, and an allyl group-containing sulfonate represented by the chemical formula below as an emulsifier were added. Next, a monomer composition having the following composition: Butyl acrylate 43 parts 2-ethylhexyl acrylate 43 parts by weight Acrylonitrile 7 parts by weight Acrylic acid 5 parts by weight Hydroxyethyl acrylate 2 parts by weight 100 parts by weight, Stir to emulsify the monomer composition, add 0.5 parts by weight of ammonium persulfate to start polymerization, maintain the reaction temperature at about 70°C,
Emulsion polymerization is carried out for about 2 hours. After the reaction was completed, the mixture was aged at about 80° C. for 1 hour to obtain a pressure-sensitive adhesive comprising an aqueous copolymer emulsion having a concentration of 40% by weight and a viscosity of 20 cP. Note that the glass transition point of the copolymer is -50°C. Example 3 In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 150 parts by weight of water, 0.5 parts by weight of sodium acetate, and an allyl group-containing sulfonate represented by the chemical formula below as an emulsifier were added. 1.0 parts by weight and 0.5 parts by weight of polyoxyethylene alkylphenol ether were charged, and then a monomer composition with the following composition was prepared: 2-ethylhexyl acrylate 82 parts by weight Vinyl acetate 14 parts by weight Methacrylic acid 3 parts by weight Glycidyl methacrylate 1 part by weight Add 100 parts by weight, stir to emulsify the monomer composition, add 0.5 parts by weight of ammonium persulfate to start polymerization, maintain the reaction temperature at about 70°C,
Emulsion polymerization is carried out for about 2 hours. After the reaction was completed, the mixture was aged at about 80° C. for 1 hour to obtain a pressure-sensitive adhesive comprising an aqueous copolymer emulsion having a concentration of 40% by weight and a viscosity of 60 cP. Note that the glass transition point of the copolymer is -55°C. Example 4 In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 150 parts by weight of water, 0.5 parts by weight of sodium acetate, and a methallyl group-containing sulfonate represented by the chemical formula below as an emulsifier were added. Add 1.5 parts by weight, then prepare a monomer composition with the following composition: 2-ethylhexyl acrylate 75 parts by weight Methyl methacrylate 18 parts by weight Acrylic acid 2.5 parts by weight N-butoxymethylol acrylamide
3 parts by weight divinylbenzene 0.5 parts by weight 100 parts by weight were charged, stirred to emulsify the monomer composition, and further added 0.5 parts by weight of ammonium persulfate to start polymerization, keeping the reaction temperature at about 70 ° C.
Emulsion polymerization is carried out for about 2 hours. After the reaction was completed, the mixture was aged at about 80° C. for 1 hour to obtain a pressure-sensitive adhesive consisting of an aqueous copolymer emulsion having a concentration of 40% by weight and a viscosity of 200 cP. Note that the glass transition point of the copolymer is -42°C. Comparative Example 1 Example 1 except that 1.5 parts by weight of polyoxyethylene alkyl phenol ether, a nonionic surfactant, was used instead of 1.5 parts by weight of the allyl group-containing sulfonate used as an emulsifier in Example 1. Similarly, the concentration is 40% by weight and the viscosity is
A copolymer aqueous emulsion of 20 cP was obtained. Comparative Example 2 Same as Example 2 except that 1.5 parts by weight of sodium dodecylbenzenesulfonate, an anionic surfactant, was used instead of 1.5 parts by weight of the allyl group-containing sulfonate used as an emulsifier in Example 2. An aqueous copolymer emulsion having a concentration of 40% by weight and a viscosity of 85 cP was obtained. Comparative Example 3 The same procedure as in Example 1 was carried out, except that 1.5 parts by weight of the sodium salt of sulfoethyl methacrylate, which was a polymerizable emulsifier, was used instead of 1.5 parts by weight of the allyl group-containing sulfonate used as the emulsifier in Example 1. An aqueous copolymer emulsion having a concentration of 40% by weight and a viscosity of 150 cP was obtained. Test Example The pressure sensitive adhesives obtained in Examples 1 to 4 and the copolymer aqueous emulsions obtained in Comparative Examples 1 to 3 were
It is applied to the corona discharge treated surface of 0.1 mm polyethylene film and polyester film so that the thickness after drying is 10μ, and the adhesive layer is heated and dried at 100℃ for 2 minutes to form an adhesive layer on the polyethylene film and polyester film. Formed. Using the polyethylene film and polyester film on which the adhesive layer has been formed, by the following method,
Anchorability tests and water resistance tests were conducted. The polyethylene film was subjected to an adhesive strength test, an adhesive strength test, and a weatherometer irradiation test. The test results were as shown in Table 1. (1) Anchoring ability test In order to examine the anchoring ability of the adhesive layer on polyethylene film and polyester film, the adhesive layer was crimped onto a 2 mm thick SUS24CP stainless steel plate and then rapidly separated. 〇…The adhesive layer does not peel off from the polyethylene film or polyester film. ×...The adhesive layer peels off from the polyethylene film or polyester film. (2) Water resistance test The polyethylene film and polyester film on which the adhesive layer was formed were immersed in water for 48 hours, and the adhesive layer was observed. 〇…The adhesive layer remains transparent and does not become cloudy. ×...The adhesive layer is cloudy. (3) Adhesion test A polyethylene film with a 10 cm long adhesive layer formed on a slope with a 30° inclination was fixed, and the film was placed above the slope.
A stainless steel ball was rolled at an initial speed of 0 from a position of 10 cm, and the ball with the maximum diameter that stopped on the adhesive layer was measured. (4) Adhesion test A polyethylene film with an adhesive layer formed on it was crimped onto a 2mm thick SUS24CP stainless steel plate.
A 180 degree peel test was conducted. (5) Weatherometer irradiation test A polyethylene film with an adhesive layer formed on it was crimped onto a 2mm thick SUS24CP stainless steel plate.
Using a weatherometer, the irradiation time until staining and adhesive residue on the surface of the adhesive layer on the stainless steel plate occurred was measured.

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Claims (1)

[Scope of Claims] 1. The number of carbon atoms in an alkyl group that forms a polymer or copolymer having a glass transition point of -30°C or lower using an allyl group- or methallyl group-containing sulfonate represented by the following general formula as an emulsifier. A pressure-sensitive adhesive whose main component is an aqueous emulsion obtained by emulsion polymerization of a vinyl unsaturated monomer containing 50% by weight or more of an alkyl (meth)acrylate having from 1 to 12 or a mixture of these monomers. or (In the formula, R ₁ is hydrogen or a methyl group, R ₂ is a hydrocarbon group or an organic group containing a hydrocarbon group having a substituent or an oxyalkyl group, and A is a carbon number of 2 to 4
n is 0 or a positive integer, M is an alkali or alkaline earth metal, ammonium, organic amine base, or organic quaternary ammonium base, m is M meaning valence or ionic valence)