JP5008934B2 - Removable water-based adhesive composition and information carrying sheet using the same - Google Patents

Description

  The present invention relates to an aqueous adhesive composition that does not leave stickiness on an information description surface after peeling, and an information carrying sheet using the same.

  Traditionally, sealed letters have been used to send information that needs to be sent in a concealed state, but it can be mailed with the information inside the V-type or Z-type postcard, glued, and kept in the concealed state. Postcards have been used and are collectively referred to as information carrying sheets. The performance required for such information-carrying sheets is that the adhesive surface does not peel off during mailing, that the peeled surface does not re-adhere easily, that there is no paper breakage during peeling, and that the peeled surface is tacked after peeling. Is not left and is not sticky.

  Currently, pressure-sensitive adhesives or heat-sensitive adhesives are mainly used to meet the requirement that the peeled surface does not easily re-adhere, but it is necessary to dry after applying the adhesive or after bonding However, there is a problem in terms of information concealment because the manufacturing process becomes complicated due to the need for pressurization and heating, and although it is not easily re-adhered in a normal state, it can be re-adhered by pressurization or heating. It was.

In contrast, the present inventors have proposed an aqueous adhesive composition containing an acrylic resin emulsion, a vinyl acetate resin emulsion, a wax emulsion, and a silicone oil emulsion as essential components, and an information carrying sheet using the same. (Patent Document 1). This is applied by applying the adhesive composition to at least one of the substrates facing each other and bonding them together in a wet state, and does not require drying after applying the adhesive. When peeled off, it does not re-adhere even when pressurized, heated or moistened, so it has excellent information concealment performance. However, depending on the type of paper used, there is room for improvement in that paper breakage occurs at the time of peeling, making it difficult to read information, and that some stickiness remains after peeling.
Japanese Patent Application No. 2005-287621

  The problem of the present invention is that it can be bonded without drying, pressing and heating after applying the adhesive in the bonding process, and once peeled off, it can be re-bonded even if pressurized, heated or moistened. And providing an adhesive composition and an information carrying sheet suitable for the production of an information carrying sheet that has excellent information concealment performance, does not break paper when peeled, and does not have stickiness after peeling.

  An adhesive composition comprising a vinyl acetate resin emulsion, a plasticizer, and fatty acid calcium, and an information carrying sheet produced using the adhesive composition.

  The aqueous adhesive composition of the present invention and the carrier sheet using the same are applied by applying the adhesive composition to at least one surface of the substrate facing each other and bonding them in a wet state. Since it is not necessary to perform drying, pasting pressure application, or heating after applying the adhesive in the process, the information carrying sheet manufacturing process can be simplified and energy saving. Also, once peeled off, the information-carrying sheet does not re-adhere even if it is pressurized, heated or moistened, and has excellent information concealing performance. Therefore, it can be suitably used for mailing personal information.

  The vinyl acetate resin emulsion constituting the adhesive composition of the present invention is synthesized by emulsion polymerization of vinyl acetate in the presence of an emulsifier. As the emulsifier, polyvinyl alcohol having a polymerization degree of about 300 to 4000 and a saponification degree of about 86 to 99.5% is preferably used, but a water-soluble polymer such as hydroxyethyl cellulose, a surfactant, or the like can also be used. As the unsaturated monomer, only vinyl acetate may be used, or an unsaturated monomer copolymerizable with vinyl acetate within a range that does not impair the original performance, such as acrylic acid, may be copolymerized. . However, when an ethylene vinyl acetate copolymer resin emulsion obtained by copolymerizing vinyl acetate and ethylene is used, since stickiness remains after the information carrying sheet is peeled off, ethylene is not preferable as a copolymerization monomer. Moreover, when acrylic acid ester is copolymerized, stickiness may remain depending on the amount used, so it is preferable not to use it. As the polymerization initiator, a persulfate such as ammonium persulfate, a peroxide such as hydrogen peroxide, an azo compound, or the like may be used, and a reducing agent such as tartaric acid, sodium bisulfite, or ascorbic acid may be used in combination. The polymerization can be performed at about 60 to 85 ° C.

  In the adhesive composition of the present invention, the plasticizer has an effect of improving peelability and preventing paper breakage or printing layer destruction. A preferred plasticizer includes dialkylene glycol dibenzoate, with dipropylene glycol dibenzoate being more preferred. By adding 10 parts by weight or more of a plasticizer with respect to 100 parts by weight of the solid content of the vinyl acetate resin emulsion, the effect of improving the peelability appears clearly, and becomes more remarkable at 30 parts by weight or more. If the amount exceeds 100 parts by weight, the printed layer may be destroyed at the time of peeling, or stickiness may remain after peeling.

  Fatty acid calcium is mainly a calcium salt of a fatty acid having 12 to 18 carbon atoms, and has a role of improving peelability in the adhesive composition of the present invention. Usually, calcium stearate (carbon number 18) is used, but in an industrial production method, calcium stearate may be obtained as a mixture of a calcium salt of a fatty acid having a small number of carbon atoms or a fatty acid having an unsaturated bond. Such a mixture may be used. Since fatty acid calcium has low water solubility, it is preferably used as an aqueous dispersion emulsified with a surfactant or the like. By adding 20 parts by weight or more of fatty acid calcium in a solid content with respect to 100 parts by weight of the solid content of the vinyl acetate resin emulsion, the effect of improving the peelability appears clearly, and becomes more remarkable at 50 parts by weight or more. In addition, when it exceeds 200 weight part, there exists a tendency for adhesive force to fall, and it may peel during mailing depending on a use.

  In addition to the essential components described above, a surfactant, an aqueous polymer solution, an antifoaming agent, a preservative, etc. may be added to the adhesive composition for the purpose of adjusting various physical properties and imparting performance required for individual applications. it can.

  Hereinafter, the present invention will be described more specifically based on examples. In addition, this invention is not limited to an Example at all.

Synthesis of vinyl acetate resin emulsion 280 parts of water was charged into a flask equipped with a stirrer, thermometer, heater, reflux condenser and 12 parts of partially saponified polyvinyl alcohol (B-05, trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.) Then, 6 parts by weight of intermediate saponified polyvinyl alcohol (manufactured by Denki Kagaku Kogyo Co., Ltd., H-17) was dispersed in water, heated to 80 ° C. and stirred for 2 hours to dissolve. While maintaining the liquid temperature at 80 ° C., 0.5 parts by weight of tartaric acid was added, and a polymerization initiator solution in which 0.5 parts by weight of 35% hydrogen peroxide solution was dissolved in 10 parts of water and 220 parts of vinyl acetate monomer were added. The solution was added dropwise over 3 hours. After completion of the addition, polymerization was further performed for 1 hour, followed by cooling to obtain a vinyl acetate resin emulsion.

Example 1
Example 1 A blend of 75 parts by weight of the vinyl acetate resin emulsion, 20 parts by weight of dipropylene glycol dibenzoate as a plasticizer, and fatty acid calcium (manufactured by Nisshin Chemical Laboratory Co., Ltd., containing 55% non-volatile content and calcium stearate) An adhesive composition was obtained.

Examples 2-5, Comparative Examples 1-4
In addition to the compounding material described in Example 1, # 59 (manufactured by Denki Kagaku Kogyo Co., Ltd., glass transition temperature -18 ° C., non-volatile content 56%, trade name) as an ethylene vinyl acetate copolymer resin emulsion, D- as an acrylic resin emulsion Each adhesive composition shown in Table 1 was obtained by blending 32 (manufactured by Gantz Kasei Co., Ltd., glass transition temperature-30 ° C., non-volatile content 55%, trade name). The formulation in Table 1 is parts by weight.

Test Evaluation quality paper (Kokuyo Co., Ltd., copy paper KB9TN, basis weight 75 g / m ²⁾ applying the adhesive composition to at coating weight 10 g / m ^2, in 0.4N using a 20cm width hand roller Pressurized and repeated twice. After curing at room temperature for 1 day, the test piece was prepared by cutting the adhesive surface of the test piece into a width of 25 mm.
<Peelability>
The specimen was peeled off and the peeled state was observed. (○: Good with no paper breakage or destruction of the printed layer, ×: No paper breakage but printing layer breakage, XX: Paper breakage)
<Tack>
The peeled surface after peeling was touched with a finger to confirm the presence or absence of tack. In addition, the thing whose peelability became xx could not be evaluated. (○: No or almost no tack, Δ: Slightly tack, ×: Clear tack)

  In Examples 1 to 5, good peeling properties were obtained, and there was no tack after peeling. In Comparative Examples 1 and 2, an ethylene vinyl acetate copolymer resin emulsion and an acrylic resin emulsion were used in place of the vinyl acetate resin emulsion, respectively, but there was a printed layer breaking portion at the time of peeling, and tack remained after peeling. Comparative Examples 3 and 4 were obtained by removing dipropylene glycol dibenzoate and fatty acid calcium, respectively, but were not usable at all because paper breakage occurred at the time of peeling.

Claims (2)

An adhesive composition comprising 10 to 100 parts by weight of a plasticizer and 20 to 200 parts by weight of fatty acid calcium in a solid content with respect to 100 parts by weight of a solid content of the vinyl acetate resin emulsion. An information carrying sheet manufactured using the adhesive composition according to claim 1 .