JPS6327581A - Adhesive sheet - Google Patents

Abstract

PURPOSE:To obtain an adhesive sheet capable of prevention of adhesive force reduction after being left to stand under moist heat or heating, for use in labels, stickers, etc., by coating specified amount of a metal ion-hindering agent on a metal compound-containing surface base material plane coming into contact with adhesive layer. CONSTITUTION:In an adhesive sheet made up of (A) a metal compound- containing surface base material, (B) an acrylic adhesive layer, and (C) a release paper, the surface of the component A coming into contact with the component B is coated with >=0.5(pref. >=0.7)g/m<2> of a metal ion-hindering agent (e.g. sodium tripolyphosphate), thus obtaining the objective adhesive sheet.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to general pressure-sensitive adhesive sheets such as labels and stickers, and more specifically to adhesive sheets containing metal compounds as the surface base material of labels and stickers. The present invention relates to a pressure-sensitive adhesive sheet made of high-quality paper, coated paper, polyvinyl chloride film, etc. and using an acrylic pressure-sensitive adhesive as the pressure-sensitive adhesive, which has a high shelf life under moist heat or heating conditions.

[Conventional technology]

Adhesive sheets such as labels and stickers are usually made of high-quality paper,
Base materials such as coated paper, polyvinyl chloride film, and polyethylene terephthalate film (hereinafter referred to as surface base materials), and rubber adhesives mainly composed of natural rubber or synthetic rubber, or alkyl acrylate and alkyl methacrylate. It consists of an acrylic adhesive made of a copolymer mainly composed of ester and a release paper that protects the adhesive.

A simple explanation of the process of processing adhesive sheets into labels, stickers, etc. First, a punching blade having a predetermined shape is used to insert the blade into the surface base material and the adhesive, leaving the release paper of the adhesive sheet. Next, unnecessary portions of the label or sticker (usually called lees or matrix) are removed, and so-called glazing is performed to leave the label or sticker on the liner paper. This process is a common process for manufacturing labels and stickers, but if the adhesive is not completely cut off during punching, the lees will break when the lees are removed, making it impossible to continuously manufacture labels and stickers. .

Acrylic adhesives are compared to rubber adhesives.

It is far superior in terms of ease of removal. Acrylic adhesives are copolymers mainly composed of alkyl acrylates and alkyl methacrylates, but the monomer composition may be changed or carboxyl groups in acrylic acid or methacrylic acid may be replaced with isocyanate, A wide range of adhesive properties can be developed by appropriately crosslinking with epoxy, melamine, aziridine, polyvalent metal chelate, etc.

As described above, acrylic pressure-sensitive adhesives are widely used as pressure-sensitive adhesives for pressure-sensitive adhesive sheets because of their excellent label processability and the ability to obtain a wide range of adhesive properties. However, on the other hand, it is known that in pressure-sensitive adhesive sheets whose surface base material contains a metal compound, when the pressure-sensitive adhesive sheets are left at high temperatures or under high temperature and humidity, the adhesive strength decreases to F1 degrees. .

The inventors of the present invention have completed the present invention as a result of intensive research into the cause of the decrease in adhesive strength and countermeasures thereof.

[Problem to be Solved by the Invention 1] Talc, calcium carbonate, and the like are used as fillers in the paper for high-quality paper, coated paper, etc. used as the surface base material. Particularly in recent years, there has been a strong tendency to use calcium carbonate to improve durability and reduce manufacturing costs through neutral papermaking.
By standing at 0°C and 85% relative humidity, the above metal compound dissociates, and the free metal ions that have entered the adhesive combine with acrylic acid or methacrylic acid to cause excessive crosslinking, resulting in the flow of the adhesive. This causes a decrease in adhesive strength, which in turn causes a decrease in adhesive strength. This phenomenon can be explained by the infrared absorption spectra of each adhesive before and after the decrease in adhesive strength.
This can be confirmed by the absorption near cm-', that is, the presence or absence of absorption due to the presence of ionized carboxyl groups.

A similar phenomenon occurs when polyvinyl chloride film is used as the surface substrate. In the case of polyvinyl chloride film, the metal stabilizer contained in the film penetrates into the adhesive together with the plasticizer when left at high temperatures, reacts with the acrylic acid or methacrylic acid in the adhesive, and causes over-crosslinking. It is.

[Means for solving problems]

The present invention was developed as a result of extensive research into a method for preventing the crosslinking reaction between metal ions entering from the surface base material and acrylic acid or methacrylic acid in the adhesive, and found that the use of a metal ion sequestering agent is extremely effective. This is what I discovered to be a method. Substances that sequester metal ions include phthalic acid and succinic acid.

Dibasic acids such as oxalic acid and aspartic acid, ethylenediaminetetramine (EDTA), condensed phosphates, and the like are known, but condensed phosphates are most effective for this purpose. As the condensed phosphate, sodium tripolyphosphate, acidic sodium metaphosphate, potassium pyrophosphate, sodium hexametaphosphate, sodium polyphosphate, potassium polyphosphate, potassium metaphosphate, etc. can be used.

The condensed phosphate salt is applied to the surface of the surface base material in contact with the adhesive layer.
0.5 g/n (or more, preferably 0.5 g/n) to the surface base material.
Applying 7 g/rrr or more can prevent metal ions from penetrating from the surface base material and prevent the adhesive strength of the acrylic adhesive from decreasing.0 The amount of condensed phosphate applied to the surface base material is 0.5 g/rrr. If the amount is less than -, the effect of preventing a decrease in adhesive strength is small. If the coating amount exceeds 1.2 g/rrr, although the effect of preventing a decrease in adhesive strength can be obtained, the adhesion between the surface substrate and the adhesive decreases6.Furthermore, when considering economic efficiency, it is not practical. When the surface substrate is a paper product such as high-quality paper or coated paper, the condensed phosphate may be coated with a water-soluble polymer (starch, carboxymethylcellulose).

It can be applied as an aqueous solution together with polyvinyl alcohol, etc.). The application location is a size press.

Examples include on-machine coaters such as calender rolls, and off-machine coaters, but there are no particular limitations. When the surface substrate is a film product such as a polyvinyl chloride film, the condensed phosphate may be applied together with an organic solvent-soluble resin (vinyl chloride/vinyl acetate copolymer, various acrylic binders).

Examples and effects obtained in the case where a coated paper containing 15% calcium carbonate was used as the surface base material and condensed phosphate was applied thereto using a starch aqueous solution will be described below. The present invention is not limited to these embodiments.

〔Example〕

Example 1 Coated paper (product name: SK coat, manufactured by Sanyo Kokusaku Pulp ■)
The surface in contact with the adhesive was coated with a mixed aqueous solution of sodium tripolyphosphate and starch at a coating amount of 1.0 g/m (coating amount of sodium tripolyphosphate: 0.8 g/rrr). Base material.

Comparative example 1 Surface base material of the vermilion coated paper used in Example 1.

Comparative Example 2 A mixed aqueous solution of sodium tripolyphosphate and starch was applied to the coated paper used in Example 1 at a coating amount of 0.6 g/I (the coating amount of sodium tripolyphosphate was 0-4 g/rrr).
) The surface base material is coated in such a way that it becomes

Comparative Example 3 A mixed aqueous solution of sodium tripolyphosphate and starch was applied to the coated paper used in Example 1 in a coating amount of 1.4 g/I (coating amount of sodium tripolyphosphate was 1-2 g/rrr).
The surface base material is coated to make it look like this.

Emulsion-type acrylic adhesive (product name: Toughtack 6)
01. Made by Sanyo Kokusaku Pulp ■) with release paper (product name: E
K120D2. 20g (manufactured by Souken Kako) in terms of solid content
/rrr, and after sufficiently drying with a hot air dryer, Example 1. Table 1 shows the adhesive strength of each of Comparative Examples 1 to 3 after being applied to the surface substrate and left under predetermined conditions. Furthermore, the first
The standing conditions and measurement conditions in the table were based on the methods shown below.

Normal standing: Each sample was left at 20°C and 65% RH for one week. Humid heat standing: Each sample was left at 40°C and 85% RH for one week.

A sample with an adhesive crab width of 20QIl was pasted on a polyethylene plate, crimped once with a roll with a 50mm load, and after 10 minutes, it was peeled off using a tensile tester at a tensile speed of 300m/min.The peel resistance was 10! Value converted to 11 width.

It can be seen from Example 1 and Comparative Example 1 in Table 1 that by applying sodium tripolyphosphate to the surface substrate, it is possible to prevent the adhesive strength from decreasing after being left in wet heat. In addition, if the amount of sodium tripolyphosphate applied is small (Comparative Example 2), the effect is insufficient, and if the amount applied is too large (Comparative Example 3), although the moist heat deterioration prevention effect is recognized, the adhesive strength after standing under normal conditions is lower than that of Example 3. Although it is slightly lower than that of , it is not to the extent that it lacks practicality, but it is not practical when considering economic efficiency.

Example 2 Polyvinyl chloride film containing barium zinc stabilizer (
Potassium pyrophosphate was added to acrylic resin (product name: Thermorack S-2000, manufactured by Soken Kako Co., Ltd.) on Viniban 80μ (manufactured by Band Kagaku Co., Ltd.) so that the amount of potassium pyrophosphate deposited was 1.0 g/rrr. surface base material coated on.

Comparative example 4 Polyvinyl chloride film surface base material used in Example 2.

Solution-type acrylic adhesive (product name: Cypinol AT-2
01L, manufactured by Siden Chemical Co., Ltd.) with release paper (trade name: E
K120D2. (manufactured by Soken Kako Co., Ltd.) in terms of solid content: 30 g
/rd, and after drying, it was attached to the surface substrate of Example 2 and Comparative Example 4, and the adhesive strength after being left under predetermined conditions is shown in Table 2.

Incidentally, the standing conditions and measurement conditions in Table 2 were based on the methods shown below.

Normally left unattended: Same conditions as above.

Leaving it heated: Each sample was left in an atmosphere of 70℃ for one week, and sticky crabs Same conditions as above.

Table 2 From the results shown in Table 2, applying potassium pyrophosphate to the surface substrate can prevent the adhesive strength from decreasing after being left to heat.
I understand.

〔Effect of the invention〕

Above is the example 1. As shown in Example 2, by applying a condensed phosphate to the surface base material, the combination of a surface base material containing a metal compound and an adhesive whose main components are an alkyl acrylate ester and an alkyl methacrylate ester can be applied. Alternatively, it was confirmed that it was possible to prevent the adhesive strength from decreasing after being left to heat.

Patent applicant: Sanyo Kokusaku Pulp Co., Ltd. Written amendment 6 September 12, 1986 7

Claims (1)

[Scope of Claims] 1. A pressure-sensitive adhesive sheet composed of a surface base material containing a metal compound, an acrylic adhesive layer, and a release paper, in which a metal ion sequestering agent is present on the surface of the surface base material in contact with the pressure-sensitive adhesive layer. 5
An adhesive sheet characterized by being coated with a coating of g/m^2 or more. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the metal ion sequestering agent is a condensed phosphate-based substance.