JPH08100157A - Heat-sensitive tacky sheet - Google Patents

Abstract

PURPOSE: To obtain the subject sheet excellent in the balance between blocking resistance and adhesiveness, having untacky property at ordinary temperature, exhibiting tackiness by heating and useful for label, etc., by vroviding a heat- sensitive tacky layer comprising a thermoplastic resin a rabid plasticizer and polyolefin fine particles an a substrate. CONSTITUTION: This sheet is obtained by providing a heat-sensitive tacky agent layer comprising (A) a thermoplastic resin such as a styrene-isoprene copolymer or a vinyl acetate-ethylene-styrene copolymer, (B) a solid plasticizer such as di(cylo)hexyl phthalate or benzoic aid sucrose and (C) polyolefin fine particles such as fine-particle aqueous dispersion containing a thermoplastic elastomer, a low-density polyolefin, an ionomer, a vinyl acetate-based copolymer polyolefin or a low-molecular weight polyolefin as a raw material on a substrate such as a film, paper or a metal foil. Furthermore, average particle diameter of the components B and C are preferably each <=4μm and 4-10μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive pressure-sensitive adhesive sheet which has a surface which is non-tacky at room temperature but which exhibits tackiness when heated and is used as a label or the like.

[0002]

2. Description of the Related Art Conventionally, labels such as soft drinks, alcoholic beverages, and glass bottles such as chemical bottles have been labeled with a water-soluble adhesive such as casein or starch on the back side of a substrate by an automatic labeler or the like. A method of sticking, or a method of sticking a label of a general pressure-sensitive adhesive sheet having a structure in which a top paper, a pressure-sensitive adhesive layer, and a release sheet are sequentially laminated using an automatic labeler or the like is adopted. However, for a label with a water-soluble adhesive, when the water-soluble adhesive is applied to the back surface of the base material, the label curls and wrinkles or floats occur on the label after it is attached to the glass bottle, resulting in a defective label and spoiling its appearance. There was a problem. On the other hand, a label of a pressure-sensitive adhesive sheet having a general structure is usually used by peeling off the release sheet, but the peeled release sheet is difficult to collect and reuse, and is almost always discarded. In recent years, attention has been paid to resource saving and environmental problems, and a heat-sensitive adhesive sheet that does not require a release sheet has been receiving attention.

Generally, a heat-sensitive adhesive sheet has a structure in which a heat-sensitive adhesive is applied on one surface of a base material, and is usually used as a label by printing on the other surface of the base material. The heat-sensitive adhesive is based on three components: a thermoplastic resin, a solid plasticizer, and a tackifier. It is non-adhesive at room temperature, but it is activated when heated by a labeler or oven equipped with a heating device. The adhesiveness is developed. Usually, the activation temperature is 50
C. to 150.degree. C., and in this temperature range, the solid plasticizer in the heat-sensitive adhesive starts to melt and gives the thermoplastic resin adhesiveness. The melted solid plasticizer is crystallized slowly and the stickiness is maintained for a long time. Therefore, it is used by sticking it to a glass bottle or the like while having the stickiness. Further, the tackifier is added to enhance the adhesive function.

Even if the heat-sensitive adhesive sheet is continuously stuck to the glass bottle with a labeler or the like provided with a heating device, it is like a method of applying a water-soluble adhesive to the back surface of the label and sticking it to the glass bottle. There is no problem of a bad label. Further, unlike the above-mentioned general pressure-sensitive adhesive sheet, there is an advantage that the release sheet is not used and thus the production can be performed at low cost, which is advantageous from the viewpoint of resource saving and environmental problems.

However, the heat-sensitive adhesive sheet is often stored in a wound state or in a state where several sheets are stacked, and in this case, blocking occurs when the temperature is higher than room temperature. There is a problem. Normally, the solid plasticizer is present in the state of being exposed on the surface of the heat-sensitive adhesive, and when storing it in the state of winding or stacking multiple sheets, the surface of the heat-sensitive adhesive and the printed surface are It has an effect of preventing a certain substrate surface from adhering. For example, a method of preventing blocking by increasing the average particle size of the solid plasticizer of the heat-sensitive adhesive (JP-A-62-1)
No. 64777) has been proposed. However, if the average particle size of the solid plasticizer is increased, there is a problem that the solid plasticizer does not melt completely when activated at a normal activation temperature and the adhesive function is insufficient when used as a label,
In addition, there is a problem that it takes time to activate until a sufficient adhesive function is obtained at a normal activation temperature.

Further, there is also a method (Japanese Patent Laid-Open No. 3-91586) in which a thermoplastic resin, a solid plasticizer, and a tackifier are made into a heat-sensitive adhesive composition and further polymer microspheres are added to prevent blocking. Has been proposed,
Even such a heat-sensitive adhesive sheet will cause blocking if it is stored in a wound state at a temperature higher than room temperature for a long time. The current situation is that the problem of blocking has not yet been solved in the heat-sensitive adhesive sheet.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a heat-sensitive pressure-sensitive adhesive sheet which has excellent blocking resistance, and when used as a label, a sufficient adhesive function can be obtained even when activated at a normal activation temperature. To do.

[0008]

The present inventors have determined that the main cause of blocking is the tackifier, and the heat-sensitive material is used so that the conventional adhesive function can be obtained without using the tackifier. As a result of diligent research on the constitution of the heat-sensitive adhesive layer, the heat-sensitive adhesive sheet obtained by coating and drying the heat-sensitive adhesive mainly composed of thermoplastic resin, solid plasticizer and polyolefin fine particles on the substrate Found to prevent blocking. Further, when a high adhesive function is required when used as a label, without adding a tackifier, the average particle diameter of the solid plasticizer,
It has been found that by adjusting the average particle diameter of the polyolefin fine particles, a high adhesive function can be obtained and a heat-sensitive adhesive sheet having good blocking resistance can be obtained.

The present invention is a heat-sensitive adhesive sheet characterized in that a heat-sensitive adhesive layer comprising a thermoplastic resin, a solid plasticizer and polyolefin fine particles is provided on a substrate.
Further, the present invention is a heat-sensitive adhesive sheet, wherein the solid plasticizer has an average particle size of 4 μm or less. Further, the present invention is the heat-sensitive adhesive sheet, wherein the polyolefin fine particles have an average particle size of 4 to 10 μm.

[0010]

The type of thermoplastic resin used in the heat-sensitive adhesive of the present invention includes styrene-isoprene copolymer, vinyl acetate-ethylene-styrene copolymer, vinyl acetate-
Ethylene copolymer, vinyl acetate-ethylene-vinyl chloride copolymer, vinyl acetate-ethylene-acrylic acid ester copolymer, vinyl acetate-acrylic acid ester copolymer,
Examples thereof include ethylene-vinyl chloride copolymer, (meth) acrylic acid ester copolymer, NBR, and SBR.

The glass transition temperature of the thermoplastic resin is in the range of -35 ° C to 60 ° C, preferably -30 ° C to
30 degreeC, More preferably, it is -20 degreeC-30 degreeC. If the glass transition temperature of the thermoplastic resin is lower than -35 ° C, there is a problem that the thermoplastic resin has tackiness even at room temperature. Also, 6
If the temperature exceeds 0 ° C, there is a problem that tackiness is hard to appear.

Examples of solid plasticizers used in heat-sensitive adhesives include dihexyl phthalate (melting point 65 ° C.), dicyclohexyl phthalate (melting point 63 to 65 ° C.), dihydroabietyl phthalate (melting point 65 ° C.), isophthalic acid. Dimethyl (melting point 66-67 ° C), sucrose benzoate (melting point 98
℃), ethylene glycol dibenzoate (melting point 70 ℃),
Trimethylolethane tribenzoate (melting point 73 ° C), pentaerythritol tetrabenzoate (melting point 95 ° C), sucrose octaacetate (melting point 89 ° C), tricyclohexyl citrate (melting point 57 ° C), N-cyclohexyl-p-toluene. Examples thereof include sulfonamide (melting point 86 ° C.).

The average particle size of the solid plasticizer is preferably 4 μm or less. If the average particle size exceeds 4 μm, the heat transfer during heat activation is slow and the adhesive function may be insufficient. If the adhesive function is insufficient, conventionally, it is sufficient to add a tackifier, but this is avoided because blocking tends to occur, and it is solved by making the average particle diameter of the solid plasticizer finer. Most preferably, the average particle size of the solid plasticizer is 2 μm or less. As a method of pulverizing the solid plasticizer to an intended average particle diameter, a ball mill,
It is preferable to use a crusher such as a sand mill.

Examples of the types of raw materials for the polyolefin fine particles contained in the heat-sensitive adhesive include thermoplastic elastomers, low-density polyolefins, ionomers, vinyl acetate copolymer polyolefins, and low-molecular weight polyolefins. And these raw materials have an average particle size of 4 to 1
It is preferable to use polyolefin fine particles which have been made into a finely divided aqueous dispersion having a particle size of 0 μm. For example, it is possible to select and use commercially available materials such as Chemipearl (manufactured by Mitsui Petrochemical Industry Co., Ltd.), Hi-Tech (manufactured by Toho Chemical Industry Co., Ltd.), and Polylon (manufactured by Chukyo Yushi-Seiyaku Co., Ltd.). The average particle diameter of the polyolefin fine particles is 4 μm.
If it is less than the above range, it becomes difficult to prevent blocking. On the other hand, if it exceeds 10 μm, the adhesive function may be deteriorated even if the average particle diameter of the solid plasticizer is 1 μm or less. The more preferable average particle diameter of the polyolefin fine particles is 4 to 6 μm.

The mixing ratio of the thermoplastic resin and the solid plasticizer in the heat-sensitive adhesive is 50 to 300 solid parts by weight of the solid plasticizer relative to 100 parts by weight of the thermoplastic resin. When the amount of the solid plasticizer is less than 50 parts by weight, there is a problem that the tackiness as a heat-sensitive adhesive is less likely to appear and the adhesive strength is poor. Further, when the solid plasticizer exceeds 300 solid parts by weight, there is a problem that the time for which the pressure-sensitive adhesive has the tackiness becomes short. In addition, the proportion of the polyolefin fine particles contained in the heat-sensitive adhesive is 10% by weight of the thermoplastic resin.
20 to 200 solid parts by weight relative to 0 solid parts by weight.
If the proportion of the polyolefin fine particles is less than 20 solid parts by weight with respect to 100 solid parts by weight of the thermoplastic resin, it is impossible to prevent blocking, and if it exceeds 200 solid parts by weight, the adhesive function becomes poor. is there. The best proportion of polyolefin fine particles capable of preventing blocking without deteriorating the adhesive function is 30 to 100 solid parts by weight with respect to 100 solid parts by weight of the thermoplastic resin.

The coating amount of the heat-sensitive adhesive is preferably 5 to 50 g / m ^{2 in} dry weight. More preferably 10
Is about 30 g / m ² . Incidentally, if the coating amount is less than 5 g / m ² , there is a problem that it cannot be used as a label because a sufficient adhesive force cannot be obtained when the label is attached to a glass bottle or the like. On the other hand, when it exceeds 50 g / m ² , the adhesive function is saturated and the economy is poor.

The heat-sensitive adhesive is applied onto a substrate by brush coating, spray coating, screen printing, coating applicator, gravure printing, offset printing, letterpress printing, Mayer bar coater, kiss roll coater, lip coater, It is carried out by various coating devices such as a direct roll coater, an offset roll coater, a gravure roll coater, a reverse roll coater, a rod coater, a blade coater and an air knife coater.

Drying can be carried out by a conventional method combined with the above-mentioned apparatus for coating. In addition, when drying, it must be performed at a temperature lower than the melting point of the solid plasticizer. This is because if the solid plasticizer is dried at a temperature higher than the melting point of the solid plasticizer, the solid plasticizer melts during the drying and the heat-sensitive adhesive layer becomes tacky. For the above reasons, it is generally preferable that the drying temperature is 50 ° C. or lower. The heat-sensitive adhesive may be colored with a coloring agent such as a coloring dye before being applied.

Examples of the material of the substrate used in the heat-sensitive adhesive sheet of the present invention include papers, films, metal foils and the like. A barrier layer may be provided on the surface to which the heat-sensitive adhesive is applied in order to reinforce the strength or prevent the heat-sensitive adhesive from penetrating into the substrate and deteriorating the adhesive function. When used as a label, printability and the like are required. In particular, when used as a label to be attached to a glass bottle containing a liquid such as soft drink, alcoholic beverage, and chemical bottle, it is preferable to use a substrate having excellent water resistance.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
In the examples, "parts by weight" means "parts by weight of solid" unless otherwise specified.

[Preparation of Solid Plasticizer] As the solid plasticizer used in the following Examples and Comparative Examples, dicyclohexyl phthalate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) was used, which was mixed with a nonionic surfactant, Use a ball mill that has been pulverized to each average particle size.

[0022]

Example 1 [Preparation of heat-sensitive adhesive] 100 parts by weight of SBR (trade name: P4626, manufactured by Sumitomo Dow Co., Ltd., glass transition temperature 9 ° C.) as a thermoplastic resin, and an average particle diameter of 1 as a solid plasticizer
200 parts by weight of dicyclohexyl phthalate of μm, 40 parts by weight of a thermoplastic elastomer of polyolefin fine particles (trade name: Chemipearl A-100, manufactured by Mitsui Petrochemical Co., Ltd., average particle size 4 μm) and water are uniformly mixed to obtain a solid content. A heat-sensitive adhesive having a concentration of 50% was obtained.

(Preparation of Thermosensitive Adhesive Sheet) 84.9m 2
One side of g / m ² double-sided art paper (trade name: S Kinbo <73>, manufactured by Shin Oji Paper Co., Ltd.) was coated with the heat-sensitive adhesive obtained above using a reverse roll coater in a dry weight of 2
2 g / m ^{2 was} applied and dried at 40 ° C. to obtain a heat-sensitive adhesive sheet.

[0024]

Example 2 A thermosensitive adhesive was prepared in the same manner as in Example 1 except that 200 parts by weight of dicyclohexyl phthalate having an average particle diameter of 3 μm was used instead of dicyclohexyl phthalate having an average particle diameter of 1 μm in the preparation of the heat sensitive adhesive. Got the sheet.

[0025]

Example 3 In preparation of a heat-sensitive adhesive, a low molecular weight polyolefin (trade name: Chemipearl W-308, Mitsui Petrochemical Industry Co., Ltd.) was used instead of the thermoplastic elastomer (trade name: Chemipearl A-100) of polyolefin fine particles. A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 40 parts by weight of the product (average particle size 7 μm) was used.

[0026]

[Example 4] In the preparation of a heat-sensitive adhesive, a vinyl acetate-ethylene copolymer (trade name: Sumikaflex 20) was used instead of the thermoplastic resin SBR (trade name: P4626).
(Sumitomo Chemical Co., Ltd., glass transition temperature -12 ° C)
A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 100 parts by weight was used.

[0027]

Example 5 In the preparation of a heat-sensitive adhesive, 200 parts by weight of dicyclohexyl phthalate having an average particle size of 6 μm was used in place of dicyclohexyl phthalate having an average particle size of 1 μm, and a thermoplastic elastomer of polyolefin fine particles (trade name: Chemipearl) was used. A-100) was replaced with 40 parts by weight of a low molecular weight polyolefin (trade name: Chemipearl W-308, manufactured by Mitsui Petrochemical Co., Ltd., average particle size 7 μm), and heat-sensitive adhesive was carried out in the same manner as in Example 1. Got the sheet.

[0028]

Example 6 In the preparation of a heat-sensitive adhesive, a low molecular weight polyolefin (trade name: Chemipearl W-100, Mitsui Petrochemical Industry Co., Ltd.) was used instead of the thermoplastic elastomer (trade name: Chemipearl A-100) of polyolefin fine particles. A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 40 parts by weight of a product having an average particle diameter of 3 μm) was used.

[0029]

[Example 7] In the preparation of a heat-sensitive adhesive, a vinyl acetate-based copolymerized polyolefin (trade name: Chemipearl V-100, Mitsui Petrochemical Co., Ltd.) was used instead of the thermoplastic elastomer (trade name: Chemipearl A-100) of polyolefin fine particles. A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 40 parts by weight manufactured by Kogyo Co., Ltd., average particle diameter 12 μm) was used.

[0030]

[Comparative Example 1] In the preparation of a heat-sensitive adhesive, a vinyl acetate-ethylene copolymer (trade name: Sumikaflex 200, manufactured by Sumitomo Chemical Co., Ltd.) was used instead of SBR (trade name: P4626) as a thermoplastic resin. Glass transition temperature-1
2 ° C.) 100 parts by weight, and as a tackifier, a rosin-based tackifier (trade name: Super Ester E-71
0, manufactured by Arakawa Chemical Industry Co., Ltd.) A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 100 parts by weight was added.

[0031]

[Comparative Example 2] In the preparation of a heat-sensitive adhesive, fine particles of polyolefin were not used, and a vinyl acetate-ethylene copolymer (trade name: Sumikaflex 20 was used as a thermoplastic resin.
0, Sumitomo Chemical Co., Ltd., glass transition temperature -12
℃) 100 parts by weight, average particle diameter 15μ as a solid plasticizer
A thermosensitive adhesive sheet was obtained in the same manner as in Example 1 except that 200 parts by weight of dicyclohexyl phthalate of m and water were uniformly mixed to obtain a thermosensitive adhesive having a solid content concentration of 50%.

[0032]

Comparative Example 3 In the preparation of the heat-sensitive adhesive, 100 parts by weight of vinyl acetate-ethylene copolymer (trade name: Sumikaflex 200, Sumitomo Chemical Co., Ltd., glass transition temperature -12 ° C.) as a thermoplastic resin, 200 parts by weight of dicyclohexyl phthalate having an average particle size of 25 μm as a solid plasticizer, and a rosin-based tackifier as a tackifier (trade name:
Super Ester E-710, Arakawa Chemical Industry Co., Ltd.)
A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 100 parts by weight and water were uniformly mixed to obtain a heat-sensitive adhesive having a solid content concentration of 50%.

[0033]

[Comparative Example 4] In the preparation of the heat-sensitive adhesive, starch granules (trade name: Glyco B, trade name: Chemipearl A-100) were used instead of the thermoplastic elastomer of polyolefin fine particles (trade name: Chemipearl A-100).
A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 40 parts by weight of Ezaki Glico Co., Ltd., average particle size 20 μm) was used.

"Evaluation" The obtained heat-sensitive adhesive sheet was evaluated for adhesive function and blocking resistance. [Adhesive Function] The heat-sensitive adhesive sheet was heat-activated for 10 seconds in an oven heated to 100 ° C., and was adhered to a glass plate within 3 minutes after heat activation. After 2 hours, the adhesive force was measured at an angle of 180 degrees at a speed of 0.3 m / min, and judged according to the following criteria. ◯: 800 g / 25 mm or more, excellent in adhesive function. B: Adhesive strength is 500 g / 25 mm or more, and the adhesive function has no practical problem. X: The adhesive strength is less than 500 g / 25 mm, and the adhesive function is poor.

[Blocking Resistance] The heat-sensitive adhesive sheet was wound and treated for 3 days at 50 ° C. to evaluate the occurrence of blocking. ◯: What was not blocked. Δ: A little blocking, but practically no problem. X: Blocking and practically problematic. [Comprehensive Evaluation] Based on the results of the adhesion function and the blocking resistance, a comprehensive evaluation was evaluated as Δ, a particularly excellent quality was evaluated as ○, and a practically unusable product was evaluated as ×. Table 1 shows the results.

[0036]

[Table 1]

[0037]

As is clear from Table 1, the heat-sensitive adhesive sheet has a good balance between blocking resistance and adhesive function. Further, it is a heat-sensitive adhesive sheet having a sufficient adhesion function even if it is activated at a normal activation temperature without using a tackifier by adjusting the average particle size of solid plasticizer and polyolefin fine particles. .

Claims (3)

[Claims] 1. A heat-sensitive adhesive sheet comprising a base material and a heat-sensitive adhesive layer comprising a thermoplastic resin, a solid plasticizer and polyolefin fine particles. 2. The heat-sensitive adhesive sheet according to claim 1, wherein the solid plasticizer has an average particle diameter of 4 μm or less. 3. The polyolefin fine particles have an average particle size of 4 to 4.
The heat-sensitive adhesive sheet according to claim 1, which has a thickness of 10 μm.