JP2015189205A - Press bonding paper for confidential post card - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press bonding paper for a confidential post card having such a high surface strength that adhesive is not left out during operation of a printing machine, a printer or the like, and operability and quality are stabilized in order to correspond to higher speed of the printing machine or printer.SOLUTION: A press bonding paper for a confidential post card is configured such that a pressure-sensitive adhesive consisting essentially of adhesive base agent and fine particle filler is provided on at least one side of base paper. Therein, the pressure-sensitive adhesive contains nanofiber such as cellulose nanofiber.

Description

  The present invention relates to a pressure-sensitive adhesive sheet for confidential postcards.

What is called a “crimp postcard” instead of a sealed letter is widely used in many fields. This uses a paper (in the present invention, hereinafter referred to as a pressure sensitive postcard for confidential postcards) coated with a re-peelable pressure-sensitive adhesive that can be adhered by pressure, and prints the fixed information with a form printer. Next, after confidential information is printed with a non-impact printer such as an electrostatic recording method or an ink jet recording method, it is folded and folded in two or three and then mailed, and the receiver peels off the information surface and reads the information. is there.

The pressure-sensitive adhesive, as proposed in Patent Document 1, Patent Document 2, and Patent Document 3, is obtained by appropriately blending silica or starch particles having a specific particle size with an adhesive base, and the adhesive. By applying a strong pressure in a state where the layers are in contact with each other, the polymers are in close contact with each other by self-diffusion.

  However, because the speed of printing presses and printers is currently increasing, the adhesive drops off during running of the printing presses and printers, resulting in poor quality stability, and the printing presses and printers are soiled and operability is poor. The problem was pointed out.

Japanese Patent Publication No. 5-57117 Patent registration No. 2736838 Utility Model Registration No. 2518977

The present invention is a confidential postcard pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive mainly composed of an adhesive base and a fine particle filler is provided on at least one side of a base paper. It is an object of the present invention to provide a pressure-sensitive adhesive sheet for confidential postcards having a strong surface strength that prevents the adhesive from falling off.

  The present inventors have found that the above problem can be solved by blending nanofibers into a pressure-sensitive adhesive, and have completed the present invention.

  That is, the present invention relates to a confidential postcard pressure-sensitive adhesive paper in which a pressure-sensitive adhesive mainly composed of an adhesive base and a fine particle filler is provided on at least one of the base paper, the pressure-sensitive adhesive being nano The present invention relates to a pressure-sensitive adhesive paper for confidential postcards characterized by containing a fiber.

  The nanofiber is preferably a cellulose nanofiber.

  The pressure-sensitive adhesive paper for confidential postcards of the present invention has strong cohesive force and abrasion resistance of the adhesive film, so that the confidential postcards have strong surface strength that prevents the adhesive from being worn or dropped during running on a printing press or printer. A crimping paper is obtained.

The pressure-sensitive adhesive of the present invention is an adhesive that forms a so-called pressure-sensitive adhesive layer that does not adhere in a normal state but adheres by pressure and can be peeled off when necessary. As a main component, this is provided on at least one of the base papers to obtain a confidential postcard crimping paper.

The adhesive base consists of an adhesive main agent and an auxiliary adhesive. As the adhesive main agent, a natural rubber latex which is latex, a methyl methacrylate graft copolymer natural rubber latex called MG latex, an acrylic latex, or the like can be used. In addition, as an auxiliary adhesive, water-based SBR latex, NBR latex, urethane emulsion, ethylene / vinyl acetate copolymer emulsion, and the like are used, and water-soluble polyvinyl alcohol (hereinafter abbreviated as PVA) and its modification are also used as auxiliary adhesives. Products, polyvinylpyrrolidone, carboxymethyl cellulose (hereinafter abbreviated as CMC), various starches and modified products thereof, gelatin, casein, styrene / maleic anhydride copolymer, urethane, polyacrylamide and the like.

When nanofibers are blended with an adhesive base in the present invention, the adhesive does not wear or fall off during running of a printing press or printer, etc., because nanofibers have a reinforcing effect on the adhesive base ( It is presumed that the cohesive force and wear resistance of the adhesive film are enhanced as a result.

The blending ratio of the above-mentioned adhesive main agent and auxiliary adhesive affects the balance between the adhesive strength of the pressure-sensitive adhesive layer and the fixability to the base paper and the cohesive strength of the adhesive layer film, so adjust appropriately The mass ratio of the adhesive main agent and the auxiliary adhesive is preferably 97: 3 to 50:50. When the auxiliary adhesive is less than 3 parts by mass, the fixing property of the pressure-sensitive adhesive layer to the base paper is lowered, and conversely, when the auxiliary adhesive exceeds 50 parts by mass, Adhesive strength is reduced and appropriate peeling performance cannot be obtained.

In the pressure-sensitive adhesive of the present invention, a fine particle filler is blended. As the fine particle filler, it is preferable to use a fine particle filler having a small affinity with the adhesive and having a regular particle shape. Examples of such materials include calcium carbonate, clay, talc, silica, alumina, aluminum hydroxide, titanium oxide, zinc oxide, satin white, diatomaceous earth, glass powder, shirasu balloon, activated clay, cereal starch particles, and modifications thereof. And zeolite, microspherical acrylic resin, microspherical methacrylic resin, microspherical polyethylene, and plastic pigment. These fine particle fillers may be used alone or in combination of two or more.

In the pressure-sensitive adhesive of the present invention, the fine particle filler is blended in an amount of 30 to 300 parts by mass, preferably 50 to 250 parts by mass with respect to 100 parts by mass of the adhesive. If it is less than 30 parts by mass, the blocking resistance is lowered or the adhesive force is too strong to be easily peeled off, and if it exceeds 300 parts by mass, the adhesive force becomes too low, which is not preferable.

As the nanofiber used in the present invention, a nanofiber having a width of 1 to 3000 nm, preferably 5 to 1000 nm can be suitably used. The raw material of the nanofiber is not particularly limited. For example, polyurethane, polyester, polyethylene, polystyrene, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, aliphatic polyamide, semi-aromatic polyamide, aromatic polyamide, polyimide, nylon (registered trademark) , Polyacrylamide, polyacrylonitrile, cellulose, chitin, chitosan, collagen, polyvinyl alcohol, polylactic acid, polyphenylene sulfide, polymethylpentene, polyvinylidene fluoride, polyaniline, polycarbosilane, etc., and silica, carbon, fullerene, ceramic Inorganic materials such as alumina can be used. However, in the use of the pressure-sensitive adhesive paper for confidential postcards, colored ones may cause problems in appearance and are not preferable. In consideration of the color and the reinforcing effect, cellulose nanofibers are preferable.

The cellulose nanofiber used in the present invention has a width of 2 to 3000 nm, preferably 50 to 1000 nm, and a length of 1 to 500 μm. For example, Japanese Patent No. 3036354 (a method for producing fine fibrillated cellulose) , Japanese Patent No. 2967804 (ultrafine fibrillated cellulose and production method thereof, and coated paper production method and dyed paper production method using ultrafine fibrillated cellulose). However, it is not limited to the wet pulverization method as in the above two examples, and a dry pulverization method is also used. On the other hand, the wet paper pulverization method is preferable in order to sufficiently exhibit the reinforcing effect (filling effect). The average degree of polymerization of the cellulose nanofiber of the present invention is preferably 600 or more and 30000 or less, more preferably 600 or more and 5000 or less, and still more preferably 800 or more and 5000 or less.

  Examples of raw materials for cellulose nanofibers include chemical pulps such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood bleached sulfite pulp (NBSP), ground pulp (GP), and thermomechanical pulp (TMP). Non-wood pulp such as wood pulp such as machine pulp such as mechanical pulp such as mulberry, cinnamon, crust, and three-fold bast fiber pulp and cotton pulp, hemp, kenaf, rice, bagasse, bamboo, biocellulose such as bacterial cellulose, powdered cellulose, Microcrystalline cellulose, modified cellulose, regenerated cellulose and the like are used.

  The cellulose nanofibers of the present invention may be modified, and examples thereof include modification by TEMPO oxidation, cation modification, cation modification and anion neutralization, and water soaking modification. The modification may be performed before or after the production of cellulose nanofibers with respect to the raw material of cellulose nanofibers.

In the pressure-sensitive adhesive of the present invention, cellulose nanofibers are blended in the range of 0.5 to 50 parts by mass, preferably 2 to 30 parts by mass with respect to 100 parts by mass of the adhesive. If the amount is less than 0.5 parts by mass, the effect of enhancing the cohesive force and wear resistance of the adhesive film cannot be obtained. On the other hand, if the amount exceeds 50 parts by mass, the viscosity of the pressure-sensitive adhesive is too high, the coating suitability is unsuitable, and the adhesive strength is too low.

In the pressure-sensitive adhesive thus obtained, if necessary, additives commonly used for pressure-sensitive adhesives, such as tackifiers, viscosity modifiers, anti-aging agents, UV absorbers, stabilizers, preservatives Coloring agents, deodorants, antifoaming agents, dusting prevention agents, and the like can be added.

The pressure-sensitive adhesive of the present invention is applied to the base paper surface by a coating means such as a gravure coater, a roll coater, an air knife coater, a bar coater, a die coater, or a curtain coater. The amount of pressure-sensitive adhesive applied to the base paper surface is 1 to 30 g / m ² , preferably 3 to 15 g / m ² , more preferably 5 to 5 for adhesiveness and peelability of the pressure-sensitive adhesive layer. It is good to set it as 10 g / m < ² >.

As the base paper to which the pressure-sensitive adhesive of the present invention is applied, ordinary paper can be mainly used. This is usually 300-600 ml C.I. of papermaking pulp such as softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP). S. F. , And clay, kaolin, calcium carbonate, titanium oxide and other fillers, starch, PVA and other paper strength enhancers, melamine resin, urea resin, polyamide / epichlorohydrin, polyacrylamide and other wet strength agents, rosin Sizing agents such as sizing agents, alkyl ketene dimer sizing agents, fluorescent whitening agents, colored dyes and pigments, fixing agents, etc. are added as appropriate, using known paper machines such as circular paper machines and long paper machines. Based on a conventional method, paper is manufactured with a basis weight of 40 to 150 g / m ² . Further, it is also possible to appropriately apply a sizing agent, a paper strength enhancer and the like using a size press device during papermaking. Moreover, the coating layer which consists of a filler and a binder for improving smoothness can also be provided in the surface.

Further, as the base paper to which the pressure-sensitive adhesive of the present invention is applied, synthetic paper or synthetic films such as polyethylene, polyethylene terephthalate, polypropylene, and vinyl chloride can be used in addition to ordinary paper. When these synthetic films are used, the surface of the base paper is preferably subjected to surface treatment such as mat treatment or corona treatment.

An example of producing a postcard using the pressure-sensitive adhesive sheet for confidential postcards according to the present invention will be described in a three-fold type. The confidential postcard pressure-sensitive paper of the present invention is first slit into a predetermined width, wound up in a roll shape, and predetermined information is printed on the front and back surfaces thereof by a form printer. Next, sprocket holes are drilled at both ends to accurately feed the paper with a non-impact printer. Next, the address and information to be concealed are printed by a non-impact printer from various data stored in the computer. Next, the paper is continuously folded and bonded by applying a high pressure (usually 7 MPa or more) when passing between the rolls of the sealer, and then cut into a postcard one by one. As a result, the recipient can read the confidential information printed by peeling the crimped postcard. At this time, in order to facilitate peeling, a known method such as printing a release agent on the end portion can be appropriately applied.

Bonded paper for confidential postcards obtained by the present invention can be temporarily bonded in various forms such as bi-fold, tri-fold, cut-over, or overlap of separate bodies, but easy as needed Examples include postcards having a double-sided peelable surface, various forms, notices, and various cards.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely using an Example and a comparative example, the scope of the present invention is not limited to an Example. In addition, the following mass parts mean solid content conversion.

Manufacture of cellulose nanofiber: NBKP was used as a raw material, and beaten up to 300 ml CSF with a beater in advance to prepare a pulp slurry with a solid content concentration of 5%. Abrasive plate rubbing apparatus (trade name “Super Glinedel”, manufactured by Masuko Sangyo Co., Ltd.) Grain size: No. 46. Rotating abrasive plate speed: 1800 rpm. Abrasive plate clearance: 20 μm. Hopper The volume was reduced to 30 liters). The treated pulp slurry discharged from the abrasive plate rubbing part was continuously recirculated to the hopper to obtain finely fibrillated cellulose with a total refinement treatment time of 30 minutes. Next, after adjusting the solid content concentration of the aqueous suspension of fine fibrillated cellulose to 3%, a high pressure homogenizer (trade name “Nanomizer”, manufactured by Nanomizer Co., Ltd.) equipped with two discs was fed at a pressure of 1500 kg / Cellulose nanofibers were obtained by repeating the process of micronization by pumping at cm ² five times.

Manufacture of base paper: 20 parts by mass of softwood bleached kraft pulp, 80 parts by weight of hardwood bleached kraft pulp, 430 ml C.I. S. F. And adding 0.7 parts by mass of rosin sizing agent (trade name “Size Pine E”, manufactured by Arakawa Chemical Co., Ltd.) and 3.5 parts by mass of sulfuric acid band to adjust the stock. A paper having a basis weight of 85 g / m ² was made using a machine and adjusted to a thickness of 0.110 mm with a calendar to obtain a base paper.

(Example 1)
Methyl methacrylate (MMA) graft copolymer 100 mass parts of MMA graft copolymer natural rubber emulsion obtained by mixing 100 parts by weight of natural rubber (NR) and 17.6 parts by weight of MMA as a natural rubber latex Parts of SBR latex (trade name “Nipol LX430”, manufactured by Nippon Zeon Co., Ltd.) in an amount of 10 parts by weight with respect to 100 parts by weight of the adhesive base, silica gel (trade name “Fine Seal X37B”). ”, 25 parts by mass, manufactured by Tokuyama Corporation, 100 parts by mass, starch (trade name“ AS-225 ”, manufactured by Chiba Flour Milling Co., Ltd.), 5 parts by mass, PVA (trade name“ PVA117 ”, manufactured by Kuraray Co., Ltd.) The pressure-sensitive adhesive of the present invention was prepared by blending 3 parts by mass of cellulose nanofiber. The obtained pressure-sensitive adhesive was applied to both sides of the base paper using a die coater at a coating amount of 5.0 g / m ² to obtain a pressure-sensitive postcard paper for confidential postcards.

(Example 2)
A compressed postcard paper for confidential postcards was obtained in the same manner as in Example 1 except that the cellulose nanofibers of Example 1 were changed to 40 parts by mass.

(Comparative Example 1)
A compressed postcard paper for confidential postcards was obtained in the same manner as in Example 1 except that the cellulose nanofibers of Example 1 were excluded.

  The T-type peel adhesion immediately after production of the pressure-sensitive adhesive sheet for confidential postcards thus obtained, the surface strength by the printing test, and the wear resistance were evaluated by the following methods. The evaluation results are shown in Table 1.

(1) Measuring method of T-type peel adhesive strength; the obtained pressure-sensitive adhesive paper for confidential postcards was cut into a width of 25 mm and a length of 100 mm to prepare a sample, and the two samples were stacked to a length of 25 mm and 7 MPa. The above load was applied and crimped. In accordance with JISK6854, a peel adhesive strength test method for adhesives, T-type peel adhesive strength was measured using a universal testing machine (trade name “Tensilon”, manufactured by Orientec Co., Ltd.).
A: 100 to 150 (gf / 25 mm)
○: 150 to 200 (gf / 25 mm) or 50 to 100 (gf / 25 mm)
Δ: 200 to 300 (gf / 25 mm) or 30 to 50 (gf / 25 mm)
×: 300 (gf / 25 mm) or more or less than 30 (gf / 25 mm) A: Excellent, ○: Good, Δ: Acceptable, ×: Not acceptable

(2) Surface strength by printing test: When a pressure sensitive adhesive layer is printed on the ink tack 25 using the RI tester, the pressure sensitive adhesive layer adheres to the transfer roll. Whether or not to do so was visually observed. The transfer roll was transferred to A2 coated paper, and the color density was measured. Note that the amount of ink is printed so that the color density is 1.5 when printing is performed using A2 coated paper instead of the confidential postcard paper and the transfer roll at this time is further transferred to another A2 coated paper. Adjusted.
The coating layer does not adhere to the transfer roll at all: The coating layer adheres to the two-point transfer roll with a magnifying glass: The coating layer adheres to the one-point transfer roll with the naked eye: The color density of the zero-point transfer portion is 1 More than .4: The color density of the two-point transfer part is 1.0 to 1.4: The color density of the one-point transfer part is less than 1.0: The score of the evaluation result of the deposit on the zero-point transfer roll and the color density The total score with the evaluation result of
4 points: ◎, 3 points: ○, 2 points: Δ, 1 to 0 points: ×

(3) Abrasion resistance: Using a paperboard abrasion resistance tester, the surface of the adhesive layer when it was worn 100 times was visually judged to examine the degree of wear. As a result, the proportion of the destroyed area of the tested area is
In the case of 10% or less: ◎,
If 30% or less: ○,
If 50% or less: △,
When 51% or more: x.

(4) Based on the result of comprehensive evaluation or more, evaluation was performed as follows.
◎: Excellent, ○: Good, △: Acceptable, ×: Impossible The above (2) Surface strength by printing test and (3) Abrasion resistance are the substitute characteristics of surface strength in actual printers and printers. To do.

  The following can be seen from the results in Table 1.

  When cellulose nanofiber is blended, it is excellent in a printing test and an abrasion test, and as a result, a pressure-sensitive adhesive sheet for a confidential postcard having a strong surface strength that does not cause the adhesive to fall off during running on a printing press or a printer can be obtained.

Claims (2)

A pressure-sensitive adhesive paper for confidential postcards, wherein a pressure-sensitive adhesive mainly composed of an adhesive base and a fine particle filler is provided on at least one of the base paper, the pressure-sensitive adhesive containing nanofibers A featured postcard for confidential postcards. The pressure-sensitive adhesive paper for confidential postcards according to claim 1, wherein the nanofibers are cellulose nanofibers.