JP3497878B2 - Heat-sensitive adhesive sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is non-tacky at room temperature but develops tackiness upon heating, and
The present invention relates to a heat-sensitive adhesive sheet that retains adhesiveness for a while even after removing a heating source.

[0002]

2. Description of the Related Art Conventional pressure-sensitive adhesives for heat-sensitive pressure-sensitive adhesive sheets are used as water-dispersed pressure-sensitive adhesives, as typified by known delayed tack type pressure-sensitive adhesives, in order to maintain the pressure-sensitive adhesiveness after the development of the pressure-sensitive adhesiveness. In many cases. For example, "Adhesion Handbook" (No.
As described in 12th edition, 1980, published by Kobunshi Kogyokai), the composition has a basic skeleton of a thermoplastic resin, a tackifier and a solid plasticizer. Thermoplastic resins are the source of tackiness and adhesiveness. In addition, since solid plasticizers are solid at room temperature, they do not impart plasticity to the resin, and because they melt and swell or soften the resin when heated, they develop tackiness when heated to non-tacky adhesives at room temperature. Acts to cause. At this time, when the tackifier is present, the tackiness becomes more remarkable, and the practical properties are improved.

The pressure-sensitive adhesive is applied onto a paper such as high-quality paper, coated paper, art paper, vapor-deposited paper or a plastic substrate sheet such as PET film to produce a heat-sensitive adhesive sheet. The heat-sensitive adhesive sheet is used by heating it at the time of use to develop the adhesiveness and sticking it on a metal, glass or plastic surface as a label or the like. However, when the heat-sensitive adhesive sheet is attached by using a machine (labeler) for attaching to various objects while heating the heat-sensitive adhesive layer of the heat-sensitive adhesive sheet to develop the adhesiveness,
When an accident such as a sticking error occurs, it becomes necessary to easily remove the heat-sensitive adhesive sheet. In this case,
In the heat-sensitive adhesive sheet using the conventional heat-sensitive adhesive,
In particular, when the base material sheet is paper, there is a problem that the base material is broken and wasteful such as washing and discarding again occurs.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive adhesive sheet that can be easily reattached when an attachment error or the like occurs.

[0005]

That is, the present invention provides a heat-sensitive adhesive sheet obtained by coating a base sheet with a heat-sensitive adhesive containing a thermoplastic resin, a tackifier and a solid plasticizer, The sheet is heated to develop adhesiveness and adhered to the adherend after 15 minutes, and the adhesive force is 40 g / 25 mm or more and 300 g / 25 mm
Hereinafter, and adhesion after sticking 24 hours to provide a heat-sensitive adhesive sheet, characterized in that it is 600 g / 25 mm or more.

[0006] The heat-sensitive adhesive sheet is heated to develop the adhesiveness, and the adhesive force after attachment to the adherend for 15 minutes is 300 g / 25 mm or less.
There, in order to heat-sensitive adhesive sheet is not peeled off naturally is 40 g / 25 mm or more. Adhesive strength 15 minutes after application is 300g / 25
If it exceeds mm , the substrate breaks when the substrate sheet is paper. Further, when the base material sheet is plastic such as PET film, the base material does not break, but adhesive residue phenomenon occurs on the sticking surface at the time of re-adhesion, and re-cleaning of the sticking surface is required. Cannot be easily reattached. Paste 15
When the adhesive strength after 40 minutes is less than 40g / 25mm, the adhesive strength is weak and the heat-sensitive adhesive sheet is not sufficiently adhered to the adherend, and even if it can be adhered, the holding power is weak and not practical. . On the other hand, when the adhesive strength after adhesion for 24 hours is less than 600 g / 25 mm, the adhesive strength with time is weak and the phenomenon such as spontaneous peeling of the heat-sensitive adhesive sheet occurs, which is not practical.

The mixing ratio of the thermoplastic resin, the tackifier and the solid plasticizer in the heat-sensitive adhesive is 10 to 200 parts by weight of the tackifier with respect to 100 parts by weight of the thermoplastic resin as a solid content ratio.
A range of 50 to 500 parts by weight of solid plasticizer is preferred. Further, the solid content ratio is preferably 20 to 120 parts by weight of the tackifier and 70 to 350 parts by weight of the solid plasticizer with respect to 100 parts by weight of the thermoplastic resin.

When the tackifier exceeds 200 parts by weight or the solid plasticizer is added to 100 parts by weight of the thermoplastic resin,
If the amount exceeds 00 parts by weight, the heat-sensitive adhesive sheet is heated to develop the adhesiveness and the adhesive force after 15 minutes of application to the adherend is improved.
Since it exceeds 300g / 25mm , re-adhesion is not easy. On the other hand, for 100 parts by weight of the thermoplastic resin, 10
When the amount is less than 50 parts by weight or when the solid plasticizer is less than 50 parts by weight, the heat-sensitive adhesive sheet is heated to develop the adhesiveness and the adhesive force after attachment to the adherend for 15 minutes is 40 g / 25 mm. Since it is less than the range, the adhesive strength is weak and it will peel off naturally.

Examples of thermoplastic resins include acrylic acid ester, styrene-acrylic acid ester, styrene-butadiene, ethylene-vinyl acetate, vinyl acetate, vinyl acetate-acrylic acid ester, ethylene-vinyl chloride, ethylene-acrylic acid ester. , Ethylene-acrylic acid,
Examples thereof include polymers such as butadiene, urethane, styrene-isoprene, and acrylonitrile-butadiene. In order to facilitate the re-adhesion after the heat-sensitive adhesive sheet is heated to develop the adhesiveness and adhered to the adherend, a hard thermoplastic resin, that is, a glass transition temperature of -5 ° C or higher is used. A plastic resin is preferably used. However, if the glass transition temperature is too high, the film-forming property is deteriorated, so 50 ° C. or lower is preferable. Furthermore, when the thermoplastic resin is mixed and used, the glass transition temperature of the thermoplastic resin after mixing is
It is preferably −5 ° C. or higher, and more preferably 50 ° C. or lower from the viewpoint of film-forming property.

Conventionally known tackifiers can be used as the tackifier for improving the tack performance of the pressure-sensitive adhesive, but when the softening temperature is low, the heat-sensitive pressure-sensitive adhesive sheet is heated to develop the tackiness and the adherend is adhered. Since the adhesive strength increases 15 minutes after application,
It is preferable that the softening temperature is 80 ° C or higher. Examples of tackifiers include terpene resins, aliphatic petroleum resins, aromatic petroleum resins, coumarone-indene resins, styrene resins,
Examples thereof include phenol resins, terpene-phenol resins, and rosin derivatives (rosin, polymerized rosin, hydrogenated rosin and their esters with glycerin, pentaerythritol, etc., resin acid dimers, etc.).

Examples of the solid plasticizers include diphenyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dihydroabietyl phthalate, dimethyl isophthalate, sucrose benzoate, ethylene glycol dibenzoate, trimethylolethane tribenzoate, and trimethyl triethane. Benzoic acid glyceride, tetrabenzoic acid pentaerythritol, sucrose octaacetate, tricyclohexyl citrate, N-cyclohexyl
Examples thereof include -p-toluenesulfonamide, but dicyclohexyl phthalate is preferable. The particle size of the solid plasticizer is
The surface condition of the coated surface is considerably affected, and further, the thermal activation time is prolonged, so that it is preferably adjusted to 10 μm or less.

The above-mentioned thermoplastic resin, tackifier and solid plasticizer can be used alone or in a mixture of two or more kinds. In the heat-sensitive adhesive used in the present invention, in addition to this, a filler or the like may be added within a range not hindering the object of the present invention, particularly to suppress the adhesive force immediately after sticking (after 15 minutes). it can. As the filler and the like, for example,
Inorganic substances such as titanium oxide, alumina, kaolin, talc, colloidal silica, and alumina sol, organic substances such as paraffin, natural wax, synthetic wax, natural fats and oils, and resin powder can be used. Further, a solvent, a liquid plasticizer or the like may be added for the purpose of improving the film forming property of the coating film. Further, if necessary, a dispersant, a defoaming agent, a thickener, etc. can be used.

The heat-sensitive adhesive can be used as the heat-sensitive adhesive sheet of the present invention by applying it on a substrate sheet as an aqueous emulsion or an organic solvent solution or by hot-melt coating. Further, in addition to coating the entire surface of the base material sheet, partial coating and the like can be performed for the purpose of suppressing the total adhesive force immediately after sticking.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. However, the scope of the present invention is not limited to the following examples. In the examples, “part” means “part by weight”,
% Represents% by weight. [Examples 1 to 7 and Comparative Examples 1 to 5] With the formulation shown in Table 1, first, a solid plasticizer, a maleic acid-based resin solution and water were put in a ball mill, and after crushing for 24 hours, a tackifier, a thermoplastic The resin emulsion and additives were added and mixed and stirred for 5 minutes to prepare an adhesive. The obtained adhesive,
On the back side of single-sided art paper or on PET film,
The coating amount was applied as shown in, and dried at 45 ° C for 30 seconds. No tackiness could be confirmed in the dried state. With respect to the coated product, the adhesive strength (15 minutes and 24 hours after application), the state of breakage of the base material, and the holding power were evaluated. The results are shown in Table 1.
Shown in.

[0015]

[Table 1] * 1 Styrene-butadiene copolymer * 2 Ethylene-vinyl acetate copolymer

The evaluation method of the coated product is shown below. Adhesiveness: The coated material is heated at 120 ° C for 25 seconds to develop tackiness, and then rapidly adhered to a stainless steel plate or glass plate, and after 15 minutes and 24 hours, peeled 180 degrees according to JIS K-6848. The adhesive strength was measured by, and the peeled state was observed, and the judgment was made according to the following criteria. However, the glued part was 100 mm. Peeling condition 1 ... Does not break the paper substrate. 2 ・ ・ Paper base material breaks. A: The base material does not break and no adhesive residue remains. B ... ・ The base material does not break, but adhesive remains.

Holding power: The coated material is heated at 120 ° C. for 25 seconds to develop tackiness, and then rapidly adhered to a stainless steel plate or a glass plate and subjected to a creep test according to JIS K-6848. It was judged according to the standard. However, the glued part was 25 mm. ◎ ・ ・ 2000sec or more ○ ・ ・ ・ ・ ・ ・ 1000sec or more, less than 2000sec × ・ ・ ・ ・ ・ ・ less than 1000sec

[0018]

According to the present invention, it has become possible to obtain a heat-sensitive adhesive sheet which can be easily reattached immediately after being attached. If you make a mistake when using the labeler,
The industrial significance of being able to re-paste easily and being able to pursue economic benefits with resource saving is:
It is extremely large.

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Makoto Kameyama 2-3-3 Kyobashi, Chuo-ku, Tokyo Within Toyo Inki Manufacturing Co., Ltd. (72) Akira Kikuchi 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd. (56) Reference JP-A-1-193381 (JP, A) JP-A-63-154781 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09J 7/02

Claims (4)

(57) [Claims] 1. A heat-sensitive adhesive sheet obtained by applying a heat-sensitive adhesive containing a thermoplastic resin, a tackifier and a solid plasticizer on a substrate sheet to heat the sheet to develop the adhesiveness. The adhesive strength after 15 minutes of adhesion to the adherend is 40 g / 25
mm or more and 300g / 25mm or less , and the adhesive strength 24 hours after application
A heat-sensitive adhesive sheet that is 600 g / 25 mm or more. 2. The glass transition temperature of the thermoplastic resin is -5 ° C.
The heat-sensitive adhesive sheet according to claim 1, which has a temperature of 50 ° C or lower. 3. The heat-sensitive adhesive sheet according to claim 1, wherein the thermoplastic resin is a styrene-butadiene copolymer. 4. The heat-sensitive adhesive sheet according to claim 1, wherein the thermoplastic resin is an acrylic polymer.