JP2002363893A - Method for producing pseudo-bonding paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a pseudo-bonding paper having a stable adhesive property and a re-releasability. SOLUTION: In the method for producing the pseudo-bonding paper, a coating solution which includes a non-releasable adhesive base material, fine particle filler and a nonionic surfactant, not bonding in the usual condition but bonding after applying a specific condition and re-releasable after bonding, is applied to a base paper with forming a mono-layered freely falling vertical curtain of the coating solution and continuously running the paper base in a crossing direction of the curtain. The coating solution characteristically manifests <=40 mN/m of a static surface tension and includes precipitated silica having 1 to 8 μm of the average diameter of the coagulated particle measured by Coulter counter method and >=200 ml/100 g of linseed oil absorption measured by JIS K 5101 as the fine particle filler in amount of 20 to 50 wt.% in the coating solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing pseudo-bonded paper by curtain coating. More specifically, based on a non-peelable pseudo-adhesive, containing a fine particle filler and a nonionic surfactant, it is possible to bond when a certain condition is given without usually bonding, and peels after bonding. When forming a single-layer free-fall vertical curtain of a possible coating solution and applying it to a paper substrate continuously running across the free-fall vertical curtain, the static surface tension of the coating solution is 45 mN. / M or less, and the fine particle filler has an average agglomerated particle size of 1 by a Coulter counter method.
A precipitated silica having a linseed oil absorption of 200 ml / 100 g or more based on JIS K 5101;
The present invention also relates to a method for producing a pseudo-adhesive paper, wherein the precipitated silica is contained in the pseudo-adhesive layer in a solid content of 20 to 50% by weight.

[0002]

2. Description of the Related Art In recent years, while the amount of information transmitted by communication means such as communication and mail has increased, communication means requiring confidentiality such as personal information have been regarded as important.

Further, with the revision of the Postal Law, postcard systems having confidentiality have been put to practical use and have become widespread. A postcard system with confidentiality is to fold a reciprocating postcard with various information such as personal information folded and written on the inside,
The information is concealed by crimping the overlapped portion, mailed, and the recipient peels off the crimped portion and reads the concealed information. For example, a communication method that requires confidentiality includes a method in which a company notifies employees and a bank or a credit company notifies information having confidentiality to customers.

As such confidential communication means,
A paper using a pseudo-adhesive paper has been proposed and widely used. Pseudo-adhesive paper is made of a so-called non-peelable adhesive such as natural rubber, synthetic rubber, or rubber latex and a particulate filler that suppresses the adhesive force of the adhesive, on at least one side of the base paper. A pseudo-adhesion layer of a coating liquid comprising an agent is provided, and has a function of temporarily adhering but easily peeling off when necessary.

[0005]

On the other hand, as the development of environmentally friendly products is demanded in recent years, the mixing ratio of recycled pulp obtained by recycling various kinds of used paper on the base material of pseudo-adhesive paper is increased, and 100%. Pseudo-adhesive paper using recycled pulp as a base material is on the market. Although the base paper containing a high content of recycled pulp has improved opacity, the surface of the base paper becomes rough due to embrittlement of the recycled pulp fibers, and a blade coater that generates a shear force in the coating liquid during coating, etc. With the general-purpose coating method, unevenness is caused on the coated surface, causing unevenness in the adhesive force due to uneven coating.Even with an air knife coater, it is possible to obtain a uniform pseudo-adhesion layer due to uneven liquid absorption of the recycled pulp fiber and the air knife pattern. However, there is a problem that the adhesive strength varies.

An object of the present invention is to form a single-layer free-fall vertical curtain of a coating solution, continuously run a base paper across the free-fall vertical curtain, and form a uniform pseudo-adhesive layer on the base paper. By providing such a sheet, it is possible to provide a pseudo-adhesive sheet that satisfies stable adhesion and removability and is excellent in printability.

[0007]

Means for Solving the Problems The present inventors have found that the above object is based on the fact that a non-peelable adhesive is used as a base and a fine particle filler and a nonionic surfactant are used. To form a single-layer free-falling vertical curtain of a coating liquid that can be peeled off after bonding, and is applied to a paper substrate that is continuously running across the free-falling vertical curtain. In this case, the coating liquid has a static surface tension of 45 mN / m or less, and the fine particle filler has an average agglomerated particle diameter of 1 to 8 μm by a Coulter counter method.
m, linseed oil absorption based on JIS K 5101 is 20
It has been found that the problem can be solved effectively when the precipitated silica is 0 ml / 100 g or more, and the precipitated silica is contained in the coating solution at a solid content of 20 to 50% by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the static surface tension of a coating solution was determined using a Junois surface tensiometer (manufactured by Taihei Rika Kogyo Co., Ltd.) in an environment at a temperature of 23 ° C. and a humidity of 50% RH.

If the static surface tension exceeds 45 mN / m, the liquid film of the curtain becomes unstable, and the liquid film is cracked to produce an uncoated portion. In addition, even if the wettability with the paper base material is deteriorated and the coating liquid cannot be applied uniformly to the base paper or cracks are not visually observed, the pseudo-adhesive layer becomes non-uniform or uncoated portions occur. May occur, and stable production cannot be continued, resulting in a fatal defect.

[0010] If the uniformity of the curtain liquid film is impaired, the pseudo-adhesive strength of the portion with a small amount of application is reduced, and a problem occurs in the pseudo-adhesion of the pseudo-adhesive paper. The non-uniformity of the pseudo-adhesive layer causes pseudo-adhesion unevenness, tearing of the pseudo-adhesive paper, inadvertent peeling, and unevenness of the printed portion. The uncoated portion of the curtain liquid film cannot be bonded because the paper substrate is exposed, and the printing becomes uneven.

In the present invention, a non-peelable adhesive is used as a base, and a fine particle filler and a nonionic surfactant are contained.
Normally, bonding is performed when certain conditions are applied without bonding, and a pseudo-adhesive layer that can be peeled off after bonding is formed by coating. As the non-peelable adhesive in the coating solution for this purpose, a conventionally known non-peelable adhesive mainly composed of a natural rubber-based adhesive can be used without any problem.

Such natural rubber adhesives include, for example, natural rubber, natural rubber latex in which natural rubber is sulfur-free vulcanized and mixed with methyl methacrylate, or obtained by graft polymerization of natural rubber with methyl methacrylate. Natural rubber latex and the like.

In addition, the non-peelable adhesive may contain an acrylic-modified rubber latex or a mixture of a rubber latex and a protective colloid-based acrylic copolymer emulsion.

On the other hand, as the fine particle filler to be contained in the pseudo adhesive layer, precipitated silica is used. Since the precipitated silica has a porous cohesive structure, it incorporates natural rubber-based adhesive particles, which are the base material of the non-peelable adhesive, into the inside to prevent exposure of the base particles to ultraviolet rays. Moreover,
Precipitable silica is a fine particle filler having a buffering effect on pressurization due to its aggregated structure, and changes its shape when external pressure is applied. As a result, when an external pressure is applied to the pseudo adhesive layer, the surface of the pseudo adhesive layer has less irregularities. For this reason, the contact area between the pseudo-adhesives is increased, and the effect of increasing the adhesive force of the pseudo-adhesive layer is exhibited.

The precipitated silica used in the present invention has an average agglomerated particle size of 1 to 8 μm by a Coulter counter method (AP 50 μm) and an oil absorption of linseed oil according to JIS K 5101 of 200 ml / 100 g or more. When the average agglomerated particle diameter of the precipitated silica exceeds 8 μm, cracks in the curtain coater coating film cannot be visually observed, but fine elliptical or spot-shaped uncoated portions are generated, and removability is significantly impaired. Further, precipitated silica having a particle size of less than 1 μm has a problem that the dispersion density is low and the color density is low. Further, it is difficult to manufacture, and the price is high, which is not preferable in terms of cost.

The precipitated silica of the present invention has a linseed oil absorption of 200 ml / 100 g or more. Precipitated silica having a linseed oil absorption of 200 ml / 100 g or more has a high affinity with a natural rubber-based adhesive, and incorporates a large amount of natural rubber-based adhesive particles into the aggregated structure. As a result, the natural rubber-based adhesive particles are less likely to be exposed to ultraviolet light, the rate of decrease in the adhesive force of the pseudo-adhesive layer due to ultraviolet light is extremely small, and the adhesion remaining rate is improved. On the other hand, sedimentable silica having a linseed oil absorption of less than 200 ml has a low affinity for the natural rubber-based adhesive and has a small amount of the natural rubber-based adhesive incorporated into the aggregated structure. For this reason, the natural rubber-based adhesive particles are easily exposed to ultraviolet light, and the adhesion of the pseudo-adhesive layer due to ultraviolet light is significantly reduced.

In the case of gel-type silica having a different structure, the base particles cannot be incorporated into the aggregated structure. Decrease cannot be prevented. In addition, the pseudo-adhesive layer using gel type silica as a fine particle filler has a low adhesive strength, and therefore, unintended peeling is likely to occur.

The precipitated silica is contained in the pseudo adhesive layer in a solid content of 20 to 50% by weight. 2 precipitated silica
If the amount is less than 0% by weight, the adhesive force of the pseudo-adhesion surface becomes excessively high, and blocking between the adhesion surfaces easily occurs. Further, when the amount of the precipitated silica is excessively large, the stability of the coating liquid is impaired, the pseudo-adhesion is deteriorated, and the surface strength is reduced.

In addition to the above-mentioned precipitated silica, other types of fine particle fillers can be used in combination. Examples of the fine particle filler that can be used in combination include styrene beads, cereal starch, modified starch, other types of synthetic fine particle silica, calcium carbonate, and the like.

The nonionic surfactants used in the present invention include those having a structure of ether type, ether ester type, ester type, nitrogen-containing type and the like, and are added alone or in combination of two or more. .

In the present invention, specific examples of the nonionic surfactant which can be used include polyoxyethylene alkyl ether, polyoxyethylene ether, polyethylene glycol fatty acid ester, and polyoxyethylene fatty acid amide. Since the non-peelable adhesive is anionic, a nonionic surfactant is preferred because it does not cause a problem in thickening or formation of a free-falling vertical curtain by being contained.

The thickness of the pseudo adhesive layer is 5 to 20 μm, and the coating amount is in the range of ^{2 to} 30 g / m ² , preferably 3 to 15 g / m ² .

[0023]

The present invention will be described below with reference to examples of the present invention.
The present invention is not limited to these examples. In Examples, "parts" and "%" are parts by weight and% by weight, respectively, unless otherwise specified. <Adjustment of coating liquid> A natural rubber latex obtained by graft-polymerizing methyl methacrylate onto natural rubber is used as a coating liquid that can be bonded when certain conditions are given without being normally bonded and that can be peeled off after bonding. The pseudo-adhesive was prepared by changing the amounts and types of the fine particle filler and the surfactant to prepare coating liquids, and each coating liquid was applied by a free-fall vertical curtain coating method.

Example 1: Fine particle filler, Fine Seal T-32 (precipitated silica manufactured by Tokuyama Co.); average coagulated particle size by the Coulter counter method (AP 50 μm)
5 μm, linseed oil absorption based on JIS K 5101, 250 ml / 100 g, 30% by weight. The static surface tension was adjusted to 25 mN / m with a nonionic surfactant (Neugen ET102, manufactured by Daiichi Kogyo Seiyaku).

Example 2: Fine particle filler, Fine Seal X37 (precipitated silica manufactured by Tokuyama Co.); average coagulated particle diameter 2.7 by Coulter counter method (AP 50 μm)
μm, linseed oil absorption 2 based on JIS K 5101
30% by weight of 50 ml / 100 g. The static surface tension was adjusted to 25 mN / m with a nonionic surfactant (Neugen ET102, manufactured by Daiichi Kogyo Seiyaku).

Example 3 Fine particle filler, Carplex B312BM (precipitated silica manufactured by Shionogi Pharmaceutical Co., Ltd.); average coagulated particle diameter by a Coulter counter method (AP50 μm) 7.9 μm; 100 g of 20% by weight. Nonionic surfactant (Neugen ET115, manufactured by Daiichi Kogyo Seiyaku)
Adjust the static surface tension to 30 mN / m with.

Example 4: Fine particle filler, nip seal E
-1011 (precipitated silica manufactured by Nippon Silica Co.); average coagulated particle diameter 1.5 μm by Coulter counter method (AP 50 μm), linseed oil absorption based on JIS K 5101 250 ml / 100 g, 50% by weight. The static surface tension was adjusted to 30 mN / m with a nonionic surfactant (Neugen ET115, manufactured by Daiichi Kogyo Seiyaku).

Comparative Example 1: Fine particle filler, Fine Seal T-32 (precipitated silica manufactured by Tokuyama Co.); average coagulated particle diameter as determined by Coulter counter method (AP 50 μm)
5 μm, linseed oil absorption based on JIS K 5101, 250 ml / 100 g, 30% by weight. The static surface tension is
It was 48 mN / m.

Comparative Example 2: Fine particle filler, Toksir NP
(Precipitable silica manufactured by Tokuyama Co.); average coagulated particle diameter 11 μm by Coulter counter method (AP 50 μm), J
Linseed oil absorption based on ISK 5101 260 ml /
30% by weight of 100 g. Anionic surfactant (2% aqueous solution of sodium dialkyl sulfosuccinate)
Adjust the static surface tension to 32 mN / m with.

Comparative Example 3: Fine particle filler, Carplex EPS101 (precipitated silica manufactured by Shionogi Pharmaceutical Co., Ltd.); average coagulated particle diameter 1.5 μm by a Coulter counter method (AP50 μm), linseed oil absorption based on JIS K 5101 157 ml / 55% by weight of 100 g. The static surface tension was adjusted to 48 mN / m with an anionic surfactant (50% aqueous solution of funnel oil).

Comparative Example 4: NIPGEL AZ200 (silica gel manufactured by Nippon Silica Co.); average particle size 2.4 μm by Coulter counter method (AP: 50 μm), JI
Flaxseed oil absorption based on SK5101 330ml / 1
15% by weight of 00g. The static surface tension was adjusted to 47 mN / m with an anionic surfactant (50% aqueous solution of funnel oil).

Comparative Example 5: NIPGEL BY200 (silica gel manufactured by Nippon Silica Co.); average particle size 2.0 μm by Coulter counter method (AP: 50 μm), JI
Linseed oil absorption based on SK5101 220ml / 1
5% by weight of 00g. Nonionic surfactant (Neugen E
T102, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Adjusted to mN / m.

Comparative Example 6: Fine particle filler, NIPGEL
1. CX200 (silica gel manufactured by Nippon Silica Co.); average particle diameter by Coulter counter method (AP: 50 μm)
4 μm, linseed oil absorption of 115 ml / 100 g based on JIS K 5101 is 30% by weight. The static surface tension was adjusted to 25 mN / m with a nonionic surfactant (Neugen ET102, manufactured by Daiichi Kogyo Seiyaku).

The pseudo adhesive papers of Examples and Comparative Examples were
After being left for 30 minutes in an environment of 50 ° C. and 50% RH, it was pressure-compressed with a roll gap 14 (140 μm) using a mail sealer (MS-9100: manufactured by Dai Nippon Printing Co., Ltd.), and immediately thereafter, a T-peel test was performed. It measured using the machine.

Furthermore, a natural rubber latex obtained by graft-polymerizing methyl methacrylate onto natural rubber is used as a coating liquid that can be bonded when certain conditions are given without bonding and can be peeled off after bonding. Coating liquids were prepared by changing the amounts and types of the fine particle filler and the nonionic surfactant to this pseudo adhesive, and each coating liquid was applied by an air knife coating method and a blade coating method.

Comparative Example 7: Using the coating liquid of Example 1, coating was performed by an air knife coating method.

Comparative Example 8: The coating liquid of Example 1 was applied by a blade coating method.

Measuring method of peel strength after UV irradiation: The pseudo-adhesive papers of Examples and Comparative Examples were irradiated with an UV irradiator (UE0).
61-325-01k: 20 ° C., 50% RH using o-mercury type, manufactured by Eye Graphic Co., Ltd., output 6 KW)
UV irradiation under the environment of the mail sealer (MS9
100: manufactured by Dai Nippon Printing Co., Ltd.)
, And immediately after that, using a T-type peel tester,
The peel strength was measured.

In each of the examples and the comparative examples,
Table 1 shows the evaluation of the residual adhesion ratio, the blocking resistance, and the uniformity of the adhesive force.

[0040]

[Table 1]

[Liquid Film Cracking] The term "liquid film cracking" in the table was evaluated for the presence or absence of liquid film cracking during curtain coating.

[Residual Adhesion Ratio] The residual adhesive ratio in the table is the ratio of the peel strength after irradiation with ultraviolet rays when the peel strength before irradiation with ultraviolet rays is 100%. When the adhesive remaining ratio is 70
%, 50% to 70%, Δ, 50%
% Or less was evaluated as x.

[Blocking resistance] The blocking resistance in the table means that the present invention is subjected to form printing, and
The judgment was made as to whether or not inadvertent adhesion of the perforations was observed when the sheets were laminated. ○ without blocking, × with blocking.

[Uniformity of adhesive strength] The uniformity of adhesive strength in the table is an evaluation of the stability of the measured peel strength. The peel strength was measured 10 times, and the dispersion of each peel strength was not significant. Those having ± 25 g / 5 cm or less were evaluated as ○, those having ± 50 g / 5 cm or less were evaluated as Δ, and those exceeding ± 50 g / 5 cm were evaluated as x.

[0045]

As described in detail above, according to the present invention, Table 1
As is clear from the figure, the static surface tension of the coating solution was 45 mN.
/ M or less, and the fine particle filler has an average agglomerated particle diameter of 1 to 8 μm by a Coulter counter method, JIS
Linseed oil absorption based on K 5101 is 200 ml / 1
It has a stable adhesion and re-peelability, and is suitable for printing by containing 20 to 50% by weight of precipitated silica in solid content in the coating liquid. A pseudo adhesive paper is provided.

[0046]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a two-fold postcard.

FIG. 2 is an explanatory diagram of a partially folded postcard.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Support sheet, 2 ... Pseudo-adhesion layer, 3 ... Concealment information printing surface, 4 ... Address information

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D21H 23/48 D21H 23/48 F term (Reference) 2C005 WA03 4J004 AA03 AA05 AA10 AB01 CB02 CC02 CE03 EA06 FA01 FA10 4J040 CA011 CA031 CA061 DF001 DL031 HA126 HA306 HB13 HB30 HC10 JA01 JB05 KA03 KA23 KA42 LA03 LA06 MA09 NA10 NA21 PA21 4L055 AG18 AG52 AG71 AG88 AG92 AH02 AH29 AH37 AH50 BE08 CH10 CH30 EA10 EA32 EA40 FA13 FA30

Claims (1)

[Claims] Claims: 1. A non-peelable adhesive as a base, containing a particulate filler and a nonionic surfactant, which are usually not adhered but can be adhered when given certain conditions, and can be peeled after adhesion. A method for producing a pseudo-adhesive paper, comprising forming a single-layer free-falling vertical curtain of the following coating solution and applying it to a paper substrate continuously running across the free-falling vertical curtain. The coating liquid has a static surface tension of 45 mN / m or less, and the fine particle filler has an average agglomerated particle diameter of 1 to 8 μm by a Coulter counter method,
Linseed oil absorption based on JIS K 5101 is 200
ml / 100 g or more of sedimentable silica, and the sedimentable silica is contained in the coating solution in a solid content of 20 to 50% by weight.