JPH09272851A - Adhesive composition for confidential letter and confidential letter coated with the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition containing a specific latex and a powdery inorganic filler at a specific ratio, free from blocking trouble after the application of adhesive, having excellent printability, adhesive stability under pressure and openability of the confidential letter after pasting and free from blocking after peeling. SOLUTION: This adhesive composition contains (A) 100 pts.wt. (in terms of the resin component) of a polychloroprene latex (e.g. a copolymer latex containing >=60wt.% of a polychloroprene component having a glass transition temperature of 0 to -95 deg.C and having a resin concentration of 30-60%) and (B) 10-100 pts.wt. of a porous inorganic filler powder such as porous superfine silica powder. The composition is preferably further incorporated with (C) a light stabilizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel confidential communication document, typically an adhesive composition for confidential postcards, and a confidential composition which is obtained by applying the adhesive composition and which can be temporarily adhered by pressure and easily peeled off when necessary. It relates to correspondence documents (hereinafter simply referred to as confidential postcards).

[0002]

2. Description of the Related Art In recent years, with the revision of the Postal Law, a postcard system that has a lower postage rate than a sealed letter and has the same confidentiality as a sealed letter has been put into practical use and has begun to spread. This confidential postcard system prints or folds various information such as personal information or print information, print information, and various information that is inconvenient for others to know, and folds the postcards and overlaps them with various information surfaces. In this system, the information is concealed and mailed like a normal postcard, and the addressee who receives the information peels off the adhesive surface of the superposed sheets and reads the concealed information displayed.

In such a confidential postcard system,
After the sender has entered the information in the communication field, the information will not be leaked to other people and will be hidden, and after the recipient receives it,
Since it has to be opened again, it is necessary to make a peelable bond. Moreover, even if a person other than the recipient of the postcard peels off the confidential postcard, reads the information, and then rejoins it to eradicate the evidence of the prying eyes, it cannot be reattached unless a special pressure device is used. It is necessary to be.

In such a confidential postcard system,
It is necessary to releasably bond the concealment information display surface, but the conventional adhesive bonding method of this type is to provide an adhesive layer on one surface of a laminate of two transparent films releasably bonded together to form a release paper. Then, apply the adhesive layer coated to the concealment side paper piece, print the desired information on the concealment information display section or after printing, remove the release paper and put the concealment side paper piece on the concealment information display section side. The addressee who glued together and received is 2
A method is known in which the bonded surface of a sheet of transparent film is peeled off and the concealed information is read through the transparent film.

Further, Japanese Patent Application Laid-Open Nos. 5-69687 and 7-
As shown in 1872, there is also known a system in which a pressure sensitive adhesive is applied to a single information sheet, information is printed, and peeling after pressure bonding is easy, and concealed information is read.

[0006]

However, in the conventional method using a laminate of two transparent films that are releasably joined together, this laminate is inevitably costly, and at the time of use. The disadvantage is that the release paper has to be removed.

On the other hand, JP-A-5-69687 and JP-A-7-
1872, in the method of applying a pressure sensitive adhesive, since these pressure sensitive adhesives contain a rosin and a terpene-based tackifier, these adhesives act as a pressure sensitive adhesive, and thus If the agent-coated surfaces are pasted together, the bonded part cannot be peeled off once it has been bonded,
There is a drawback that a means for separately providing a non-peeling adhesive application surface with respect to a partial adhesion or pressure-sensitive adhesive application surface must be taken.

An object of the present invention is to solve the above drawbacks of the prior art and to provide an adhesive composition for a postcard having the following characteristics. Adhesive coated products should not block in inventory. Excellent printability on the adhesive coated surface. Must have a stable adhesive force by pressure. Being able to easily peel off the confidential postcard after adhesion. No blocking occurs after peeling.

[0009]

The present inventor has developed an adhesive composition comprising 100 parts by weight of polychloroprene latex (resin content) and 10 to 100 parts by weight of a porous inorganic filler powder as an adhesive for a postcard. It was found that the desired confidential postcard was obtained when used as. The present invention has been completed based on this new finding.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The confidential communication documents of the present invention include not only postcards but also various communication documents or sheets such as folding cards, stacking cards, and information hiding sheets.

The present invention will be described in more detail below. The polychloroprene latex used in the present invention is a polychloroprene latex or / and a modified polychloroprene latex.

The modified polychloroprene latex is a copolymer latex of chloroprene and vinyl monomer or a mixture of polychloroprene latex and vinyl polymer latex, and in particular, a copolymer latex having a polychloroprene component content of 60% by weight or more is used. preferable.

Vinyl monomers other than chloroprene include styrene, acrylic acid ester, methacrylic acid ester,
Acrylic acid, methacrylic acid, maleic acid ester, vinyl acetate, ethylene, vinyl chloride, butadiene and the like can be used alone or in combination of two or more.

In the present invention, the glass transition temperature (Tg) of polychloroprene is preferably 0 to -95 ° C, particularly preferably -25 to -80 ° C.

If the Tg is less than -95 ° C, the tackiness of the film after drying is large and the blocking resistance is poor.
Further, when Tg is higher than 0 ° C., the pressure-sensitive adhesive bonding between the dried adhesive coating products is insufficient.

The concentration of the polychloroprene latex is usually 30 to 60%.

The porous inorganic filler powder used in the present invention is a porous inorganic filler such as porous ultrafine silicic acid, hydrous fine silicic acid, diatomaceous earth, hydrous aluminum silicate, anhydrous aluminum silicate, zirconium silicate, hydrous magnesium silicate and zeolite. A powder can be mentioned as a typical example, and silicic acid is particularly preferable.

The average particle size of these porous inorganic filler powders is preferably 10 μm or less in terms of adhesiveness and peeling property. Especially in the porous inorganic filler powder, the average particle size is 1
Porous ultrafine silicic acid of 10 μm has good printability, adhesiveness,
Excellent in peeling property and blocking property.

The ratio of the polychloroprene latex to the porous inorganic filler powder in the present invention is 10 to 100 parts by weight, particularly 20 to 100 parts by weight of the resin component of the polychloroprene latex. -80 parts by weight is preferred.

At this time, if the amount of the porous inorganic filler powder is less than 10 parts by weight, the ink is not suitable for printing and the releasability tends to decrease. On the other hand, if the amount of the porous inorganic filler powder exceeds 100 parts by weight, the adhesive force tends to decrease.

A stabilizer may be added to the adhesive composition for confidential postcards of the present invention in an amount of 5% by weight or less, whereby thermal and photodegradation of a dry film of the adhesive composition is prevented. It improves the stability of the adhesive with the passage of time and more effectively exhibits the adhesive peeling property.

The stabilizer is a benzophenone-based, benzotriazole-based, oxalic acid anilide-based, cyanoacrylate-based, triazine-based ultraviolet absorber, or a compound having a piperazine ring, HALS (Nippon Ciba-Geigy product).
These light stabilizers can be used alone or in combination.

In the adhesive composition of the present invention, if necessary, various additives generally used in the adhesive field, such as a thickener, a water-soluble polymer, a tackifier, a defoaming agent, and an antiseptic agent are added. Agents, lubricants, antioxidants, plasticizers, crosslinking agents, fillers and the like can be added.

The adhesive composition of the present invention comprises a polychloroprene latex, a porous inorganic filler powder and, if necessary, a light stabilizer and other additives. It is preferable to adjust the viscosity according to the conditions to be applied, for example, the type of postcard, temperature, humidity, printing method, coating means, etc. before use. In the usual case, it is preferable to use at 10 to 1,000 mPa · s (at 30 ° C.).

From the viewpoint of adhesiveness and releasability, the coating amount of the confidential postcard adhesive of the present invention is 1 to 10 g / m ^{2 as} a dry coating amount.
Is preferred. If this dry coating amount is less than 1 g / m ² , pressure-sensitive adhesiveness tends to be impaired, and if it exceeds 10 g / m ² , releasability tends to be impaired.

The coating method is flexo, gravure,
It can be performed by a known adhesive application method such as a reverse roll or an air knife.

The pressure for masking information using the adhesive composition of the present invention is usually about 30 to 150 kg / cm ² ,
It is preferably about 40 to 100 kg / cm ² .

As the confidential postcard paper used in the present invention, for example, high-quality paper, synthetic paper, coated paper, laminated paper metal vapor-deposited paper, etc. can be used, and it can be used as a postcard and is not particularly limited.

The printing of the confidential postcard is performed on the front and back of the confidential postcard, but the printing may be performed before applying the adhesive for the confidential postcard, after applying the adhesive, and after drying.

Printing and printing methods include letterpress, offset, gravure, flexo, screen, electrophotographic method,
Printing can be performed by a known method such as a laser copy method, an inkjet method, or a thermal transfer method. Moreover, it goes without saying that there is no problem even if it is done by handwriting.

[0031]

[Examples] Specific examples will be described below.
The present invention is not limited by these examples.

[0032]

[Examples 1 to 3] 100 parts by weight of polychloroprene latex (Tg = -45 ° C) having a resin content of 50%, "Mizushikaru P-78A" (manufactured by Mizusawa Chemical Co., Ltd.), which is ultrafine powdered silicic acid.
Adhesives A, B and C were obtained by adding and mixing 10, 20 and 30 parts by weight of (average particle diameter: 3 μm), respectively. These adhesives A, B, and C were applied at 3 g / m ² (dry weight), and the dried postcards 1, 2, and 3 had blocking properties, printability, and
Table 1 shows the evaluation of pressure-sensitive adhesiveness and removability.

[0033]

Example 4 90 parts by weight of polychloroprene latex (Tg = -45 ° C.) having a resin content of 50% and styrene-butyl acrylate copolymer latex (Tg = 2) having a resin content of 50%.
100 parts by weight of modified polychloroprene latex blended with 10 parts by weight of 3 ° C., “Mizushikaru P-78A”
20 parts by weight, 5 parts by weight of anhydrous aluminum silicate and 2 parts by weight of titanium oxide were added and mixed to obtain an adhesive D. This adhesive D was applied at 8 g / m ² and the evaluation of the postcard 4 dried was shown in Table 1.

[0034]

Examples 5 to 6 100 parts by weight of polychloroprene latex (Tg = -45 ° C) having a resin content of 50% and 20 parts by weight of "Mizushikaru P-78A" were mixed in a mixed solution of 2 parts by weight of a benzotriazole type ultraviolet absorber or Light stabilizer (HALS
Adhesives E and F were obtained by adding and mixing 3 parts by weight (manufactured by Japan Ciba Gaiki). Tables 1 and 2 show the evaluation results of the confidential postcards 5 and 6 obtained by applying the adhesives E and F at 5 g / m ² .

[0035]

[Comparative Example 1] 100 parts by weight of natural latex having a resin content of 60% and 30 parts by weight of calcium carbonate were added and mixed to obtain an adhesive G.
I got This adhesive G was applied at 5 g / m ² (dry weight) and the evaluation of the postcard 7 dried was shown in Table 2.

[0036]

[Comparative Example 2] instead of the 30 parts by weight of calcium carbonate of Comparative Example 1 was applied to "Mizushikaru P-78A" 30 parts by weight adhesive H using at 5 g / m ² (dry weight), dried confidential postcard The evaluation of 8 is shown in Table 2.

[0037]

Comparative Example 3 100 parts by weight of polychloroprene latex (Tg = -45 ° C.) having a resin content of 50%, calcium carbonate 2
An adhesive I was obtained by adding and mixing 0 parts by weight. This adhesive I
Was applied at 3 g / m ² (dry weight), and the evaluation of the dried postcard 9 is shown in Table 2.

[0038]

Comparative Example 4 100 parts by weight of polychloroprene latex (Tg = -45 ° C.) having a resin content of 50%, "Mizushiru P-"
Adhesive J was obtained by adding and mixing 60 parts by weight of "78A". This adhesive J was applied at 3 g / m ² (dry weight), and the evaluation of the dried postcard 10 is shown in Table 2.

[0039]

Comparative Example 5 Adhesive 2 used in Example 2 was 15 g / m
Table 2 shows the evaluation of the confidential postcard 11 which was applied with ² (dry weight) and dried.

[0040]

[Table 1]

[0041]

[Table 2]

The evaluation of each confidential postcard is as follows. Evaluation 1) Blocking property: After depositing confidential postcards, the state of the confidential postcards was observed. ◎ ・ ・ ・ There is no blocking and you can take each confidential postcard one by one. △ ・ ・ ・ There is a feeling of resistance when taking the confidential postcard. × ・ ・ ・ The confidential postcard is broken.

Evaluation 2) Printability: Printing was performed by laser copying and the printing state was observed. ◎ ・ ・ ・ Printing is good △ ・ ・ ・ Partial printing is not possible × ・ ・ ・ Printing is not possible

Evaluation 3) Pressure Sensitivity: A pressure of 80 kg / cm ² was applied to the adhesive-coated surfaces of the confidential postcard to bond them, and the adhesiveness was confirmed. ◎ ・ ・ ・ Good adhesion × ・ ・ ・ No adhesion

Evaluation 4) Peelability: The confidential postcards laminated in Evaluation 3 were peeled by hand and the state was observed. ∘: Peeling is good, and there is no tearing of the confidential postcard and tearing of the print. △: No tearing of the paper due to peeling, but some peeling of the print occurs. Tears the paper --- it cannot be tested (adhesive was not used in the evaluation 3 test)

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[Procedure amendment]

[Submission date] July 10, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Adhesive composition for confidential communication documents and confidential communication documents coated with the same

Claims (4)

[Claims] 1. Polychloroprene latex (resin content) 1
An adhesive composition for confidential communication documents, which comprises 100 parts by weight of porous inorganic filler powder and 100 parts by weight of porous inorganic filler powder. 2. The adhesive composition for confidential communication documents according to claim 1, wherein the porous inorganic filler powder is porous ultrafine silica powder. 3. A light stabilizer is further contained.
An adhesive composition for confidential communication documents as described in 1. 4. The adhesive composition according to any one of claims 1 to 3 is applied to an adhesive surface, which is an information hiding surface of a confidential communication document.
-10 g / m ² application confidential communication document.