JPH07292344A - Heat-sensitive tacky agent and heat-sensitive tacky sheet - Google Patents

Abstract

PURPOSE:To obtain the subject tacky agent, excellent in chalking resistance and bonding characteristics and enabling an improvement, etc., in a working environment by blending an aqueous dispersion of a melt mixture of a solid plasticizer with a tackifier with an aqueous dispersion of a thermoplastic resin. CONSTITUTION:This heat-sensitive tacky agent is obtained by blending an aqueous dispersion of a mixture prepared by previously melt mixing (A) 100 pts.wt. solid plasticizer (preferably dicyclohexcyl phthalate) with (B) 5-100 pts.wt. tackifier (e.g. a terpene resin) with (C) an aqueous dispersion of a thermoplastic resin (e.g. a styrene-butadiene copolymer). The aqueous dispersion of the mixture of the components (A) with (B) is obtained by, e.g. melt mixing the components (A) with (B) at 80-180 deg.C, then adding water containing a dispersing agent to the resultant mixture while stirring the mixture, producing a W/O type emulsion, subsequently dropping warm water into the emulsion while vigorously stirring the emulsion, carrying out the phase inversion of the emulsion and further allowing the inverted emulsion to stand for several days and dispersing the prepared emulsion in a dispersing machine.

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 and a heat-sensitive adhesive sheet, which retain their adhesiveness for a while even after removing the heating source.

[0002]

2. Description of the Related Art Conventional heat-sensitive adhesives are often used as water-dispersed adhesives, as represented by known delayed tack adhesives, in order to maintain the adhesiveness after the onset of adhesion. For example, "Adhesive Handbook" (12th Edition, Showa 55)
(Published by Kobunshi Shuppankai), 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 heat-sensitive adhesive is applied to a paper such as high-quality paper, coated paper, art paper, vapor-deposited paper or a plastic substrate such as PET film to obtain a heat-sensitive adhesive sheet, which is made of metal, glass or plastic. It is used by sticking it as a label on the surface of the. However, a heat-sensitive adhesive sheet obtained by coating a conventional heat-sensitive adhesive on a substrate is
Depending on the conditions such as the drying and storage temperatures, there is a problem that powder spraying (chalking) of the solid plasticizer is observed on the surface of the coated adhesive layer. If choking occurs, the powder of the solid plasticizer will be scattered during the work, which will worsen the working environment.In addition, the labeler will malfunction due to the powder during labeling, or the powder will print labels. Various problems such as adhesion to the surface occur.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive adhesive having excellent choking resistance and adhesive properties.

[0005]

That is, the present invention relates to an aqueous dispersion ([I] liquid) of a mixture in which 5 to 100 parts by weight of a tackifier is pre-melt mixed with 100 parts by weight of a solid plasticizer.
Provided are a heat-sensitive adhesive characterized by being blended with an aqueous dispersion of a thermoplastic resin ([II] liquid), and a heat-sensitive adhesive sheet obtained by coating the substrate with the heat-sensitive adhesive. To do.

In the present invention, the liquid [I] and the liquid [II] are 20 to 200 parts by weight, preferably 20 to 200 parts by weight, of the thermoplastic resin of the liquid [II] per 100 parts by weight of the solid plasticizer of the liquid [I]. 30-140
It is preferable that the solid content ratio is part by weight. If it is blended outside this range, sufficient adhesive properties cannot be obtained.

The cause of choking is that the solid plasticizer is slightly melted in the drying step and is present as powder on the surface of the pressure-sensitive adhesive layer due to recrystallization and crystal growth over time. It is possible that it will come to mind. In the case of the heat-sensitive adhesive of the present invention using an aqueous dispersion of a mixture in which a solid plasticizer and a tackifier are previously melt mixed, the solid plasticizer that causes choking does not exist alone, and It is presumed that, because the solid plasticizer is melt-mixed, crystal growth of the solid plasticizer is suppressed, and choking is less likely to occur.

The aqueous dispersion ([I] liquid) of the mixture obtained by previously melt-mixing the solid plasticizer and the tackifier can be prepared, for example, by the following method. That is, in a device that can heat and stir the solid plasticizer and tackifier, 60 to 210 ℃
, Preferably in the range of 80 to 180 ° C. to obtain a mixture of the plasticizer and tackifier in the molten state. The tackifier to be mixed is not limited to a solid tackifier, and may be mixed in an aqueous dispersion such as an emulsion, but it is preferable to use a solid tackifier for handling. When an aqueous dispersion of a tackifier is used, it is preferable to first dry and remove water and then mix and heat with a solid plasticizer, or heat while mixing with a solid plasticizer to dry and then melt. Good. When an aqueous dispersion of tackifier is used, the solid content of tackifier is 5 to 100 parts by weight per 100 parts by weight of the solid plasticizer.
It is blended in a proportion that makes it part by weight.

When water containing a dispersant is added while stirring the mixture of the solid plasticizer and tackifier thus obtained, the water is a dispersed phase and the mixture of the plasticizer and the tackifier is continuous. A phase W / O emulsion is formed. In this case, the viscosity increases depending on the mixing ratio. Also,
The amount of water is 60 to 90% by weight, preferably 70 to 90% by weight, based on the total amount (mixture of plasticizer and tackifier in molten state + water). Prepare to be 85% by weight.

Next, hot water (the amount of warm water is such that the concentration of the mixture of the plasticizer and the tackifier is 5 to 80% by weight, preferably 20 to 70% by weight) is added dropwise with vigorous stirring.
The emulsion inverts, water becomes the continuous phase and an O / W emulsion is produced in which the mixture of plasticizer and tackifier is the dispersed phase. Here, immediately after cooling the aqueous dispersion of the mixture of the plasticizer and the tackifier, since the mixture of the plasticizer and the tackifier remains in a molten state, it is immediately changed to a thermoplastic resin emulsion or the like. When the pressure-sensitive adhesive is prepared by mixing, the coated product retains its tackiness and cannot be used as a raw material for the heat-sensitive pressure-sensitive adhesive. Therefore, when an aqueous dispersion of a mixture of a plasticizer and a tackifier is left to stand for several days, it contains water or is semi-solidified in a state where it is phase separated from water to some extent. However, in this case, the form differs depending on the mixing ratio of the solid plasticizer, tackifier and water, heating temperature, dropping time or cooling rate. When this is dispersed using a disperser, a fine aqueous dispersion of a mixture (solid) of a plasticizer and a tackifier is obtained.

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.

Tackifiers that are melt mixed with solid plasticizers include
It is used in a solid content ratio of 5 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the solid plasticizer. Examples of the tackifier include terpene resin, aliphatic petroleum resin, aromatic petroleum resin, coumarone-indene resin, styrene resin, phenol resin, terpene-phenol resin, rosin derivative (rosin, polymerized rosin, hydrogenated rosin And their esters with glycerin, pentaerythritol and the like, resin acid dimers and the like).

The aqueous dispersion of the thermoplastic resin ([II] liquid) is not limited to the emulsion type obtained by emulsion polymerization of the thermoplastic resin, but the polymer obtained by solution polymerization or emulsion polymerization is again dissolved in water. As a result, the thermoplastic resin is dispersed in water, such as a type dispersed using a dispersant or the like, a type dissolved in a solvent and dispersed in water and used as it is, or a type dispersed by evaporating the solvent to disperse in water. If it is dispersed in, it can be used regardless of the manufacturing process.

Examples of the thermoplastic resin include acrylic acid ester, styrene-acrylic acid ester, styrene-
Butadiene, ethylene-vinyl acetate, vinyl acetate, vinyl acetate-acrylic acid ester, ethylene-vinyl chloride,
Examples thereof include polymers such as ethylene-acrylic acid ester, ethylene-acrylic acid, butadiene, urethane, styrene-isoprene, and acrylonitrile-butadiene.
Among them, those having a glass transition temperature of −5 ° C. or higher, more preferably 0 ° C. or higher are excellent in blocking resistance and therefore are preferably used.

The solid plasticizer, tackifier or thermoplastic resin can be used as a mixture of two or more kinds. That is, as the solid plasticizer, dicyclohexyl phthalate and diphenyl phthalate, dicyclohexyl phthalate and dihexyl phthalate, dicyclohexyl phthalate and dihydroabietyl phthalate, dicyclohexyl phthalate and dimethyl isophthalate, dicyclohexyl phthalate and sucrose benzoate, Dicyclohexyl phthalate and ethylene glycol dibenzoate, dicyclohexyl phthalate and trimethylolethane tribenzoate, dicyclohexyl phthalate and triglyceride tribenzoate, dicyclohexyl phthalate and pentaerythritol tetrabenzoate, dicyclohexyl phthalate and sucrose octaacetate, phthalate Acid dicyclohexyl and tricyclohexyl citrate, dicyclohexyl phthalate and N-sic Can be used in two or dicyclohexyl phthalate, three or more of a mixture of diphenyl phthalate and dihexyl phthalate, etc. and hexyl -p- toluenesulfonamide or the like.

The tackifier may also be a terpene resin, an aliphatic petroleum resin, an aromatic petroleum resin or coumarone.
Indene resin, styrene resin and phenol resin,
Terpene-phenol resin and rosin derivative, terpene resin and rosin derivative, aliphatic petroleum resin and rosin derivative, aromatic petroleum resin and rosin derivative, coumarone-indene resin and rosin derivative, styrene resin and rosin derivative, phenol resin and It can be used in a mixture of two kinds with a rosin derivative or the like, or three kinds or more with a rosin derivative, an aliphatic petroleum resin, an aromatic petroleum resin and the like.

Further, the thermoplastic resin includes acrylic acid ester and styrene-acrylic acid ester, styrene-butadiene and ethylene-vinyl acetate, vinyl acetate and vinyl acetate-acrylic acid ester, ethylene-vinyl chloride and ethylene-acrylic acid ester, Ethylene
Acrylic acid and butadiene, urethane and styrene-isoprene, styrene-butadiene and acrylic acid ester, styrene-butadiene and styrene-acrylic acid ester, styrene-butadiene and vinyl acetate, styrene-butadiene and vinyl acetate-acrylic acid ester, styrene-butadiene And ethylene-vinyl chloride, styrene-butadiene and ethylene-acrylic acid esters, styrene-butadiene and ethylene-acrylic acid, styrene-butadiene and butadiene, styrene-butadiene and urethane, styrene-
2 with butadiene and styrene-isoprene, styrene-butadiene and acrylonitrile-butadiene, etc.
It can be used in a mixture of three or more kinds of styrene-acrylic acid ester, styrene-butadiene and ethylene-vinyl acetate.

In addition to the above, a filler and the like can be added to the heat-sensitive adhesive of the present invention within a range that does not impair the object of the present invention. Examples thereof include titanium oxide, alumina, kaolin, talc, colloidal silica and alumina sol. Inorganic substances, paraffins, natural waxes, synthetic waxes, organic substances such as natural oils and fats, and resin powders can also 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. Furthermore, if necessary, a dispersant,
Defoaming agents, thickeners, etc. can also be used.

[0019]

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] With the formulation shown in Table 1, a solid plasticizer and a solid tackifier were previously melt-mixed at 120 ° C, and a mixed dispersant for a maleic acid resin and polyvinyl alcohol was stirred while stirring the mixed liquid. Aqueous solution was added. Next, warm water was added with vigorous stirring to obtain an aqueous dispersion having a particle size of about 3 μm, in which water was the continuous phase and the mixture of the plasticizer and the tackifier was the dispersed phase. After naturally cooling this aqueous dispersion, it is left in a thermostatic chamber at 25 ° C. for 3 days, the dispersion is semi-solidified into a cake, and then dispersed by a ball mill to prepare an aqueous dispersion of a mixed solid of a plasticizer and a tackifier ( [I] solution) was prepared. Next, the liquid [I], the aqueous dispersion of the thermoplastic resin (the liquid [II]) and the additives were added and mixed and stirred for 5 minutes to prepare a pressure-sensitive adhesive.

Comparative Example 1 With the formulation shown in Table 1, a solid plasticizer was melted at 120 ° C. in advance, and an aqueous solution of a dispersant was added while stirring the melt. Next, warm water was added with vigorous stirring to obtain an aqueous dispersion having a particle size of about 3 μm in which water was the continuous phase and the plasticizer was the dispersed phase, and the aqueous dispersion of the plasticizer was then processed in the same manner as in the example. Was produced. Next, the above-mentioned aqueous dispersion of plasticizer, aqueous dispersion of tackifier, aqueous dispersion of thermoplastic resin ([II] liquid) and additives are added,
Mixing and stirring were performed with a mixer for minutes to prepare a heat-sensitive adhesive. [Comparative Examples 2 to 3] Adhesives were prepared according to the formulations shown in Table 1 by the method described in Examples.

The pressure-sensitive adhesives obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were directly coated on a single-sided art paper at a coating amount of 20 g / m ² and dried at 45 ° C. for 30 seconds. did. No tackiness could be confirmed in the dried state. Table 1 shows the results of evaluation of the adhesive force, the holding force, and the chalking property of the coated product.

[0022]

[Table 1] * 1 Ethylene-vinyl acetate copolymer * 2 Styrene-butadiene copolymer * 3 Solid content ratio

The adhesive strength, holding power and chalking property of the coated product were evaluated by the following methods. Adhesion: After heating the coated product at 120 ° C for 25 seconds to develop its adhesiveness, it is immediately attached to a stainless steel plate and a glass plate, and the adhesion strength is measured by peeling 180 degrees according to JIS K-6848. It was judged according to the following criteria. However, the glued part was 100 mm. ◎ ・ ・ 800g / 25mm or more ○ ・ ・ ・ ・ ・ ・ 500g / 25mm or more, less than 800g / 25mm × ・ ・ ・ ・ ・ ・ less than 500g / 25mm

Holding power; after the appearance of tackiness by heating,
Quickly attach the adhesive coating to the stainless steel plate, and
The creep test was conducted according to SK-6848, and the judgment was made according to the following criteria. However, the gluing part was 25 mm. ◎ ・ ・ 2000sec or more ○ ・ ・ ・ ・ ・ ・ 1000sec or more, less than 2000sec × ・ ・ ・ ・ ・ ・ less than 1000sec

Chalking property: The coating material dried at 45 ° C for 30 seconds is further heated at 50 ° C for 4 minutes and stored at 25 ° C. After 3 days and 7 days, the coated surface is rubbed with a black cloth 3 times back and forth. The surface condition of the black cloth was observed and evaluated according to the following criteria. ◎ ・ ・ Almost no white powder is attached. ○ ・ ・ ・ ・ ・ ・ White powder can be wiped off lightly. △ ・ ・ ・ ・ ・ ・ Part of the black cloth turns white. × ・ ・ ・ ・ The entire black cloth becomes white.

[0026]

EFFECTS OF THE INVENTION According to the present invention, as compared with the pressure-sensitive adhesive sheet coated with the conventional heat-sensitive pressure-sensitive adhesive, the chalking resistance is improved, the time for developing the pressure-sensitive adhesiveness is not increased, and the adhesive strength and the holding power are not increased. A pressure-sensitive adhesive sheet that can satisfy practical characteristics has come to be obtained. In addition, the industrial significance of being able to improve the working environment, reduce machine failures, and reduce the adhesion of powder to the printing surface of the label is extremely great.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Kameyama 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd. (72) Akira Kikuchi 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. A tackifier for 100 parts by weight of a solid plasticizer.
Aqueous dispersion ([I] liquid) of a mixture prepared by pre-melt mixing 5 to 100 parts by weight, and an aqueous dispersion of thermoplastic resin ([II])
Liquid) and a heat-sensitive adhesive. 2. The liquid [I] and the liquid [II] contain 20 parts of the thermoplastic resin of the liquid [II] per 100 parts by weight of the solid plasticizer of the liquid [I].
The heat-sensitive adhesive according to claim 1, wherein the solid content ratio is ˜200 parts by weight. 3. A heat-sensitive adhesive sheet obtained by applying the heat-sensitive adhesive according to claim 1 or 2 onto a substrate.