JP4753564B2 - Removable pressure-sensitive recording paper - Google Patents

Description

  The pressure-sensitive adhesive composition of the present invention is an adhesive that does not adhere at normal temperature and normal pressure, can be adhered by pressurization, and can be removed again when necessary, and a releasable pressure-bonding using the adhesive It relates to recording paper.

  In recent years, confidential postcards have become widespread as means for notifying personal information such as savings and balances from banks, credit companies, insurance companies, government agencies, and the like. For confidential postcards, pressure sensitive adhesive is applied to the substrate, common information is printed by offset printing, gravure printing, etc., personal information is printed by laser beam method, ink jet method, etc. It is possible to obtain information by adhering by adding, mailing to each individual, and then re-peeling.

  When the confidential postcard with re-peelable pressure-sensitive recording paper is mailed, or when it gets wet with rainwater etc. in a mailbox, it should be peeled off at the interface of the pressure-sensitive adhesive, but the paper layer peels off and the information to be notified to the recipient can be read. It turns out that there is a fault that it disappears. In addition, if it gets wet for a long time, the strength of the paper surface will become extremely weak, and if you touch it lightly with your fingers etc., the paper surface will tear and the information on the address will disappear There are also cases where the postcard is broken and the function as a confidential postcard is lost when it is severe.

  As the behavior when the paper gets wet with water, the conventional general paper base material that does not improve the strength when wet occurs, the strength of the paper between the paper itself decreases, and the adhesive strength of the adhesive gets wet. Improvement is the main cause of the problem of paper tearing during peeling. In view of this, there is a proposal that a water-resistant treatment layer is provided on a base material or that the base material itself is water-resistant so that the paper is not torn even when wet by rainwater or the like. However, this method has a drawback that the paper cannot be separated again at the time of recycling by increasing the wet strength of the paper substrate.

  Conventionally, methyl methacrylate graft copolymer natural rubber adhesives have been mainly used for pressure sensitive adhesives, but they are inferior in ultraviolet resistance (UV) performance, moisture resistance performance, and heat resistance performance. The UV irradiation reduces the adhesive strength, and also deteriorates with time as represented by yellowing, decreased adhesive strength and curing (hereinafter referred to as aging phenomenon), and the performance change is remarkable. For this reason, there has been a problem that it peels off naturally during mailing, etc., and the information of the third party is touched and the original function as a confidential postcard cannot be performed. Therefore, in order to improve the adhesive performance, it has been proposed to use a highly stable SBR resin or ethylene-vinyl acetate resin as an adhesive instead of a natural rubber adhesive. (See Patent Documents 2 to 4)

  However, although SBR resin is more stable than natural rubber adhesive, the disadvantage is that the unsaturated bond in the molecule is broken when UV irradiation is performed during offset printing, resulting in a change in molecular structure and adhesion performance. There is a problem such as lowering. In addition, since the SBR resin has low hydrophilicity, there is a problem that the suitability of IJ decreases when the blending amount increases.

  The ethylene-vinyl acetate resin is excellent in stability such as UV resistance and heat resistance and suitability for IJ, but as a disadvantage, the ink component used in the offset printing process is different from the unreacted acrylic monomer in the resin. Since it is easy to react, since the ink of the printed part reacts with the coating layer on the opposite surface when the pressure bonding is performed, there is a problem that the content becomes difficult to read. Furthermore, since ethylene-vinyl acetate resin has a problem that water resistance is inferior, there is a problem that the peel strength decreases with time due to moisture due to humidity.

Japanese Patent Laid-Open No. 7-309086 (page 1-4) JP 2000-318353 A (0001, paragraphs 0008 to 0025) JP 2001-335762 (paragraphs 0001 and 0006 to 0033) Japanese Patent Laying-Open No. 2003-160764 (paragraphs 0001 and 0007 to 0015)

  Accordingly, the object of the present invention is to provide various information, etc., using UV curable ink on the releasable pressure-sensitive recording paper, and undesired transfer or adhesion force to the opposing surface by fixing the ink by UV irradiation. When there is no decline, it has a stable adhesive force, and even if the paper gets wet due to rain water during mailing, it does not break the paper, and it can be re-separated because it can be separated again, and the recipient intentionally peels it off Is to provide an information recording sheet that can provide a uniform and fine peeling feeling and can be peeled smoothly.

The releasable pressure-sensitive recording paper according to the present invention has a pressure-sensitive adhesive layer that does not exhibit tackiness and adhesiveness at room temperature and normal pressure, and exhibits adhesiveness when pressed, and can be peeled after pressure bonding on at least one side. In addition to the synthetic silica and the cationic resin as the dye fixing agent, the modified vinyl alkanoate / ethylene copolymer aqueous emulsion represented by the following general formula ( A pressure sensitive adhesive prepared by mixing A) and an acrylic copolymer emulsion (B) at a blending ratio (B) / (A) of 0.10 to 0.70, and wet tensile strength (JIS P 8113: 1998) relates to a releasable pressure-sensitive recording sheet characterized in that it is 1.0 kgf / 15 mm (MD) to 1.2 kgf / 15 mm (MD).

（式中、Ｒ^１、Ｒ^２及びＲ^３は、それらの合計の炭素数が６以上の直鎖のアルキル基であり、Ｒ^１、Ｒ^２及びＲ^３の少なくとも１つはメチル基を表す）
本発明は、アクリル共重合体系エマルジョン（Ｂ）の他に、前記一般式で表される変性アルカン酸ビニル・エチレン共重合体の水性エマルジョン（Ａ）を合成シリカ１００重量部に対して５０〜２００重量部含み、該変性アルカン酸ビニル・エチレン共重合体水性エマルジョン（Ａ）と該アクリル共重合体系エマルジョン（Ｂ）との配合比（Ｂ）／（Ａ）が０．１０〜０．７０である感圧接着剤組成物にも関する。

(Wherein R ¹ , R ² and R ³ are linear alkyl groups having a total carbon number of 6 or more, and at least one of R ¹ , R ² and R ³ represents a methyl group)
In the present invention, in addition to the acrylic copolymer emulsion (B), an aqueous emulsion (A) of a modified vinyl alkanoate / ethylene copolymer represented by the above general formula is added in an amount of 50 to 200 with respect to 100 parts by weight of synthetic silica. The blending ratio (B) / (A) of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion (A) and the acrylic copolymer emulsion (B) is 0.10 to 0.70. It also relates to a pressure sensitive adhesive composition.

  By adopting such a configuration, the releasable pressure-sensitive recording paper of the present invention has no decrease in re-peeling strength due to irradiation of an ultraviolet lamp, and even if the paper gets wet in the middle of mailing such as rain, To provide a releasable pressure-sensitive recording sheet that is recyclable because the strength of the paper and the pressure-sensitive adhesive layer does not decrease even if water penetrates into the inside from the front and back surfaces and the edge of the peripheral edge, and the paper can be separated again. did it.

The present invention will be described in detail below, but the present invention is not limited to these embodiments.
In the pressure-sensitive adhesive layer that is formed by the pressure-sensitive adhesive coating liquid of the releasable pressure-sensitive recording paper of the present invention and is capable of accepting ink for inkjet printing, the color developability, bleeding, and water resistance by the inkjet method, and the process ink In order to satisfy offset printing suitability and re-peelability with UV curable inks, etc., it is important to select the chemicals that are the main components, such as modified vinyl alkanoate / ethylene copolymer aqueous emulsion, acrylic copolymer emulsion, etc. A combination of a cationic resin and synthetic silica is a material that satisfies these conditions.

  Examples of the acrylic copolymer emulsion include acrylic copolymer emulsions such as acrylic ester and styrene / acryl. Also, methyl methacrylate graft copolymer system natural rubber emulsion combined with acrylic copolymer emulsion is printing ink acceptability, surface strength, printing durability, blocking resistance, heat resistance, water resistance, pigment fixing property. Etc. to improve.

  The acrylic copolymer emulsion is preferably dispersed with a water-soluble resin emulsion. In the present invention, it is preferable that at least 5 to 200 parts by weight of the water-soluble resin emulsion is contained with respect to 100 parts by weight of the acrylic copolymer emulsion.

  Water-soluble resin emulsion dispersed in acrylic copolymer emulsion is polyvinyl alcohol, carboxymethylmerulose, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, ethylene / maleic anhydride copolymer, styrene / maleic anhydride copolymer , Methyl vinyl ether-maleic anhydride copolymer, isobutylene / maleic anhydride copolymer, and other known water-soluble polymers can be appropriately selected and used. These resins may be used alone or in combination of two or more. In the present invention, it is preferable to use polyvinyl alcohol which is excellent in ultraviolet resistance, printability, blocking resistance, water resistance and the like.

  In the present invention, the non-releasable adhesive for the pressure-sensitive adhesive layer is a blending ratio (B) / (A) of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion (A) and the acrylic copolymer emulsion (B). ) Is an adhesive layer containing as a main component an adhesive mixed at a ratio of 0.10 to 0.70.

The blending ratio (B) / (A) of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and the acrylic copolymer emulsion needs to be adjusted appropriately. This is because if the amount of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion is excessive, the occurrence of blocking increases, and the paper-like touch is impaired, and the conveyance trouble in the printer and the printing press is likely to occur. Further, when the paper is wet, the water-resistant adhesive strength becomes unstable, and the paper base material is easily broken, and yellowing and re-peeling strength change due to ultraviolet rays occur. On the other hand, if there is an excessive amount of acrylic copolymer emulsion, ink bleed is likely to occur in the ink-jet quality, and when it is peeled again, the ink is transferred to the opposite surface of the print surface, which makes it possible to interpret the information on the opposite surface. It will cause trouble.

  More preferably, by adjusting the content of the acrylic copolymer emulsion used in the pressure-sensitive adhesive layer to a range of 5% to 30% by weight, the stability of water-resistant adhesive strength, wear resistance, and UV resistance Thus, a pseudo adhesive layer having excellent elasticity and easy re-peeling can be obtained.

  When the content of the acrylic copolymer emulsion is 5% by weight or less, the printing strength at the time of offset printing is lowered, and the coating layer is peeled off by ink and the paper is peeled off. In addition, the adhesive strength due to the deterioration of natural rubber due to ultraviolet irradiation becomes unstable. If it is 30% by weight or more, surface stickiness and blocking may occur.

Cationic resin is used as a dye fixing agent that fixes direct dyes, acid dyes or reactive dyes to paper. Silica pigments are cationically activated by their cationic properties, and anionic ink jet inks are fixed by ionic bonds. It is effective in making it contain, and is contained in order to impart water resistance of the water-based ink. As the cationic resin in the present invention, polyamine resins such as polyamines, polyalkylamines and modified polyamines, polyamide / epoxy resins, amine / epichlorohydrin condensation resins and the like can be used. It is particularly desirable to use an amine / epichlorohydrin condensation resin. The cationic resin contained in the coating layer per unit area of the printed sheet is preferably 0.1 to 4.0 g / m ² by dry weight. When the cationic resin is less than 0.1 g / m ² , the water-resistant effect of the water-based ink is insufficient, and when it exceeds 4.0 g / m ² , the transfer of the water-based ink to the opposite surface is remarkable. Because it becomes.

  Although synthetic silica or gel synthetic silica can be used as synthetic silica, for the purpose of improving re-peeling strength, synthetic silica is a secondary aggregation particle of ultrafine silica that has excellent cushioning properties during pressure bonding. It is preferred to use silica. This is because the secondary agglomerated particles of the gel method synthetic silica are hard because they are dense, and the cushioning property is inferior to that of the gel method synthetic silica. Since the re-peeling strength is improved by using the precipitation method synthetic silica, when the same re-peeling strength as the pressure-sensitive adhesive layer containing the gel method silica is obtained, the pressure roller can be reduced by widening the clearance of the pressure roller. Therefore, it is possible to obtain a releasable pressure-sensitive recording sheet that does not cause ink transfer to the opposite surface. The precipitated synthetic silica is more preferably one having an average particle size of 3 to 4 μm. This is because the inkjet ink is taken into the pores of the secondary agglomerated particles.

  In the present invention, in order to adjust the cushioning property or the ink-absorbing property of the ink jet ink, the gel method synthetic silica may be mixed with the precipitation method synthetic silica and used.

  In a mixture of an emulsion, for example, a modified vinyl alkanoate / ethylene copolymer aqueous emulsion and an acrylic copolymer emulsion, the cationic resin is in the range of 5 to 80 parts by weight with respect to 100 parts by weight of the precipitated synthetic silica. By adding the precipitation method synthetic silica and the cationic resin and coating and drying, coloring, bleeding and water resistance of the ink-jet ink are sufficiently satisfied.

  Further, other coating pigments such as titanium oxide, kaolin, clay, calcium carbonate, talc, plastic pigment, barium sulfate, aluminum hydroxide and the like may be used in combination as appropriate. The combined use with wheat starch having an average particle size of about 20 μm is most preferable because it forms an uneven state with two different peaks on the surface of the pressure-sensitive adhesive layer, and gives blocking resistance while improving re-peeling strength. However, other starches having an average particle size of about 20 μm, such as potato, tapioca, corn, etc., or silica, kaolin, clay, talc, calcium carbonate, aluminum hydroxide, titanium oxide, plastic pigment, etc. It can be used together as appropriate.

  Various additives may be included in the pressure-sensitive adhesive coating liquid, and leveling agents, antifoaming agents and antifoaming agents, waxes to improve post-processability, Fluorescent dyes for improving the whiteness due to visual sensation, so-called antistatic agents composed of surfactants and inorganic salts for imparting conductivity can be contained. In addition, dispersants, printability improvers, lubricants, water repellents, penetrants, thickeners, anti-aging agents, ultraviolet absorbers, dyes, dye fixing agents, sizing agents, paper strength enhancers, as necessary Additives such as water retention agents, deodorants, antiseptics, and antifungal agents can be used in combination according to the purpose.

  Furthermore, for the purpose of improving printing strength (surface strength), oxidized starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, soy protein, synthetic protein, casein, etc., as well as vinyl acetate, methyl methacrylate / butadiene emulsion, styrene A butadiene-based emulsion, an acrylic / butadiene-based emulsion, or the like can be included as necessary.

  Further, it has been found that the problem as described above that occurs when wet in rainwater for a long time can be solved by using a wet paper strength enhancer in combination with the paper base, and the wet tensile strength (JIS P 8113) is 1. It is necessary to make the paper so as to fall within the range of not less than 0.0 kgf / 15 mm (MD) and not more than 1.2 kgf / 15 mm (MD).

  As the wet paper strength enhancer, any of known wet paper strength enhancers such as melamine resin, urea resin, polyamide / epichlorohydrin, and polyacrylamide can be used, and after making a paper base material, wet tensile strength (JIS P 8113). ) Is 1.0 kgf / 15 mm (MD) or more and 1.2 kgf / 15 mm (MD) or less. When the wet tensile strength is less than 1.0 kgf / 15 mm (MD), the paper is torn when it is wet for a long time. If the wet tensile strength exceeds 1.2 kgf / 15 mm (MD), the paper will not be torn even if it is wet for a long time, but re-disaggregation at the time of recycling becomes impossible.

The above-mentioned pressure-sensitive adhesive coating solution capable of offset printing and ink-jet ink can be applied by a general coater such as an air knife coater, roll coater, blade coater, rod blade coater, bar coater or die coater. However, it is desirable that the coating amount be adjusted in the range of 3 to 15 g / m ² in terms of dry weight. The reason why the coating amount is limited to the above range is that when the amount is 3 g / m ² or less, as the ink receiving layer for ink jet and the offset ink receiving layer, the ink receiving amount is reduced, and the visual quality such as the print quality and the printing finish is reduced. This is because the water-resistant fixing property of the ink-jet ink and the adhesive strength as a pressure-sensitive adhesive layer are lowered, which is not preferable. On the other hand, when the coating amount exceeds 15 g / m ² , the visual appearance such as the print quality and the printed finish is improved, but the practicality is inferior from the economical viewpoint, the writing property is poor, and paper dust is generated. This is not preferable because the adhesive strength as a pressure-sensitive adhesive layer is too strong and the paper surface of the printed surface is destroyed.

Example:
The present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited to these examples. In addition, “parts” and “%” shown in the production examples, examples, and comparative examples indicate parts by weight and% by weight unless otherwise specified.

Production Example 1: Production of Modified Vinyl Alkanoate / Ethylene Copolymer Aqueous Emulsion Disperse 10 parts of partially saponified polyvinyl alcohol (saponification degree 88, degree of polymerization 500) in 200 parts of ion-exchanged water, and dissolve by heating. A high-pressure reactor was charged. After replacing the air in the kettle with ethylene, the ethylene pressure was adjusted to 3.9 MPa, and the temperature was raised to 65 ° C. while stirring. 407 parts of VV-9 (vinyl alkanoate monomer, manufactured by Shell, carbon number 9) were emulsified with 250 parts of a 20% partially saponified polyvinyl alcohol (saponification degree 88, polymerization degree 500) solution, and a 2% ammonium persulfate aqueous solution. 40 parts and 20 parts of 2% sodium bisulfite were dropped into the kettle over 5 hours to carry out the reaction. After maintaining at 65 ° C. for 2 hours after that, 120 parts of ion exchange water was fed to the reaction kettle, then 50 parts of butyl acrylate, 10 parts of 5% t-butyl peroxide aqueous solution and 10 parts of 3% sodium bisulfite were added dropwise over 1 hour. Then, after maintaining at 65 ° C. for 1 hour, the reaction was terminated by cooling. The non-volatile content of the obtained emulsion was 50.5%. The product corresponds to an aqueous emulsion of the modified vinyl alkanoate-ethylene copolymer of Chemical Formula 1.

Coating and drying a pressure sensitive adhesive coating liquid having the following composition on a paper substrate having a wet tensile strength of 1.0 kgf / 15 mm (MD) so that the dry coating amount is 10 g / m ² per side. Thus, a releasable pressure-sensitive recording paper was prepared, and this was designated as Example 1.
100 parts of precipitated synthetic silica,
50 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion of Production Example 1
Viniblanc VA-757 (acrylic copolymer emulsion) 5 parts,
35 parts of cationic resin.
A pressure-sensitive adhesive coating liquid having the above composition was applied to both sides of the paper substrate and dried to prepare a releasable pressure-sensitive recording paper.

  A re-peelable pressure-sensitive recording paper was prepared in the same manner as in Example 1 except that the acrylic copolymer emulsion was changed to 35 parts with the pressure-sensitive adhesive coating solution of Example 1, and this was designated as Example 2. .

  Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution in Example 1 was changed to 200 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 20 parts of the acrylic copolymer emulsion. A pressure-sensitive adhesive recording paper was prepared and used as Example 3.

  Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating liquid of Example 1 was changed to 200 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 140 parts of the acrylic copolymer emulsion. A pressure-sensitive adhesive recording paper was prepared and used as Example 4.

  A re-peelable pressure-sensitive recording paper was prepared in the same manner as in Example 1 except that the paper base material having a wet tensile strength of 1.2 kgf / 15 mm (MD) was changed in Example 1, and this was designated as Example 5. .

(Comparative Example 1)
Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution in Example 1 was changed to 40 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 4 parts of the acrylic copolymer emulsion. A pressure-sensitive adhesive recording paper was prepared and used as Comparative Example 1.

(Comparative Example 2)
Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution in Example 1 was changed to 250 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 25 parts of the acrylic copolymer emulsion. A pressure-sensitive adhesive recording paper was prepared and used as Comparative Example 2.

(Comparative Example 3)
Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution of Example 1 was changed to 50 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 4 parts of the acrylic copolymer emulsion. A pressure-sensitive adhesive recording paper was prepared and used as Comparative Example 3.

(Comparative Example 4)
Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution of Example 1 was changed to 50 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 40 parts of the acrylic copolymer emulsion. A pressure-sensitive adhesive recording paper was prepared and used as Comparative Example 4.

(Comparative Example 5)
Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution of Example 1 was changed to 200 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 15 parts of the acrylic copolymer emulsion. A pressure-bonding recording paper was prepared and used as Comparative Example 5.

(Comparative Example 6)
Re-peeling in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution in Example 1 was changed to 200 parts of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion and 150 parts of the acrylic copolymer emulsion. A pressure-sensitive adhesive recording paper was prepared and used as Comparative Example 6.

( Example 7: Comparative example of the invention of claim 1 )
Except that the paper substrate of Example 1 was changed to a wet tensile strength of 0.8 kgf / 15 mm (MD), a releasable pressure-sensitive recording sheet was prepared in the same manner as in Example 1, and this was compared with Comparative Example 7 Also called .

( Example 8: Comparative Example of the Invention of Claim 1 )
Except that the paper substrate of Example 1 was changed to a wet tensile strength of 1.4 kgf / 15 mm (MD), a releasable pressure-sensitive recording paper was prepared in the same manner as in Example 1, and this was compared with Comparative Example 8. Also called .

(1) Peel strength test: The obtained releasable pressure-sensitive recording paper is cut into a width of 100 mm and a length of 100 mm, and the coated surfaces are overlapped with each other and a dry sealer (Pressle Econo: manufactured by Toppan Foams Co., Ltd.) is used. And pressure bonded. Next, the width direction center part of this sample was cut | judged to 25 mm width, and 23 degreeC and 50% R. H. Peeling strength gf / 25mm is obtained by peeling with a strograph M-1 type (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a speed of 300 mm / min and a peeling angle of 90 ° (T-type peeling) under an environment.
A: 100 to 150 g / 25 mm,
A: Less than 50 to 100 g / 25 mm is a practical level peel strength.
Δ: 20 to less than 50 g / 25 mm;
X: 0 to less than 20 g / 25 mm is not practical because the peel strength is weak.

(2) UV resistance test: The coated surface of the obtained releasable pressure-sensitive recording paper is irradiated with ultraviolet rays of 50 mJ / cm ² , and then the peel strength of 90 ° peel strength is measured by the method as described above.
(Double-circle): Since the adhesive force of 80-100% is hold | maintained, it is in a practical use level.
○: Since the adhesive force of 60 to less than 80% is maintained, it is at a practical level.
(Triangle | delta): Since the adhesive force of 40 to less than 60% is hold | maintained, it is not a practical use level.
X: 0 to less than 40% adhesive strength is maintained, so it is not at a practical level.

(3) Printability test: The coated surface of the obtained releasable pressure-sensitive recording paper
Using an RI-3 type printing aptitude tester (manufactured by Meisei Seisakusho), the ink density, printing durability and the like were visually observed and evaluated. The case where there was no peeling of the coating layer with ink or paper was marked as ◎, ○, Δ, ×.

(4) Non-impact printing (NIP) printability test: The coated surface of the obtained removable pressure-sensitive recording paper
A test print pattern (character, line, solid) was printed using a laser beam printer (LASER SHOT LBP-950, manufactured by Canon Inc.) and evaluated by visual sensation. The clear images and prints obtained were marked with ◎, ○, Δ, and ×.

(5) Inkjet (IJ) printability test: The coated surface of the obtained releasable pressure-sensitive recording paper
Cytex 1040 black ink was injected into an ink cartridge of an inkjet printer (HP DeskJet 560J, manufactured by Hewlett Packard), and a test print pattern (characters, lines, solid) was printed and evaluated by visual feeling. The clear images and prints obtained were marked with ◎, ○, Δ, and ×.

(6) Wet tensile strength (MD) of paper substrate:
The paper substrate was immersed in water for 5 minutes and then measured according to JIS P8113.

(7) Paper tearing test at the time of opening in a water-immersed state: In a peel strength test, a releasable pressure-sensitive recording paper that is pressure-bonded at a width of 100 mm and a length of 100 mm,
After being immersed in water for 2 hours, the sample was opened in a wet state, and evaluated based on the degree of occurrence of the paper layer breakage of the paper substrate, not the pressure-sensitive adhesive layer (coating layer). The papers that were not torn were evaluated as 、, ○, △, and ×. X means that the paper is severely torn.

(8) Re-peelability of paper: The obtained re-peelable pressure-sensitive recording paper
Using a standard disaggregator according to JIS P 8209, the mixture was dissolved in hot water at 50 ° C. at a caustic concentration of 0.5% (vs. pulp), and the disaggregation treatment was carried out for 10 minutes at a disaggregation concentration of 1%. ○ indicates complete disaggregation, and x indicates disaggregation.

  The test was conducted by the above method, and the evaluation results are shown in Table 1 below.

  As is apparent from Table 1, (B) / (A) is a blending ratio (B) / (A) of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion (A) and the acrylic copolymer emulsion (B). Are within the range of 0.1 to 0.7, and the wet tensile strength of the paper substrate is 1.0 to 1.2 kgf / 15 mm. It can be seen that there is no deterioration in peel strength, no paper breakage occurs when wet with water, and there is an excellent effect that the re-peelable pressure-sensitive recording paper can be re-disaggregated.

  In contrast, the wet tensile strength of the paper substrate is 1.0 kgf / 15 mm, but the mixing ratio of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion (A) and the acrylic copolymer emulsion (B) ( B) / Comparative Examples 1 to 6 where (A) is outside the range of 0.1 to 0.7 have the same physical properties such as re-peeling strength and IJ quality, but the paper breaks after 2 hours of water immersion. In the test, the paper base material can be tolerated, but since the coating layer peels off from the paper base material due to water swelling, the confidential information becomes unreadable. In Comparative Example 7, since the paper substrate was low in wet tensile strength, paper breakage occurred in the paper tear test after immersion in water for 2 hours. In Comparative Example 8, because the paper substrate was high in wet tensile strength. In the paper tear test after 2 hours of water immersion, no paper tear occurred, but it was impossible to re-disaggregate the releasable pressure-sensitive recording paper.

  The releasable pressure-sensitive recording paper of the present invention contains a pressure-sensitive adhesive in which a modified vinyl alkanoate / ethylene copolymer aqueous emulsion (A) and an acrylic copolymer emulsion (B) are mixed, and a blending ratio (B ) / (A) is not less than 0.10 and not more than 0.70, there is no decrease in re-peeling strength due to irradiation with an ultraviolet lamp, and the wet tensile strength (JIS P 8113) of the paper substrate is 1.0 kgf. / 15mm (MD) to 1.2kgf / 15mm (MD), when the paper gets wet, such as when it rains during mailing, water enters the inside from the front and back surfaces of the paper and the edge of the periphery. However, the strength of the paper and the pressure-sensitive adhesive layer does not decrease, and the paper can be re-disaggregated to provide a releasable pressure-sensitive adhesive recording paper that can be recycled.

Claims (2)

In a releasable pressure-sensitive adhesive recording paper having at least one side of a pressure-sensitive adhesive layer that does not exhibit tackiness and adhesion at normal temperature and normal pressure but does not exhibit adhesiveness when pressed and can be peeled after pressure bonding. In addition to the synthetic silica and the cationic resin as the dye fixing agent, the modified vinyl alkanoate / ethylene copolymer aqueous emulsion (A) and the acrylic copolymer emulsion (B) represented by the following general formula: Containing a pressure sensitive adhesive mixed at a blending ratio (B) / (A) of 0.10 to 0.70, and the wet tensile strength (JIS P 8113) of the paper substrate is 1.0 kgf / 15 mm (MD) Re-peelable pressure-sensitive recording paper, characterized by being -1.2 kgf / 15 mm (MD).

(Wherein R ¹ , R ² and R ³ are linear alkyl groups having a total carbon number of 6 or more, and at least one of R ¹ , R ² and R ³ represents a methyl group) In addition to the acrylic copolymer emulsion (B), the aqueous emulsion (A) of the modified vinyl alkanoate / ethylene copolymer according to claim 1 is contained in an amount of 50 to 200 parts by weight based on 100 parts by weight of the synthetic silica, The blending ratio (B) / (A) of the modified vinyl alkanoate / ethylene copolymer aqueous emulsion (A) and the acrylic copolymer emulsion (B) is 0.10 to 0.70. Pressure sensitive adhesive composition.