JPS6221835B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive adhesive, a method for producing the same, and an adhesive sheet. More specifically, the present invention relates to a long-tack thermal adhesive that is non-tacky at room temperature and remains tacky for a while even after being activated by heating and the heat source is removed, a method for producing the same, and an adhesive sheet.

Conventional labels, stickers, or sheets that use pressure-sensitive adhesives are always sticky and require release paper to prevent dust from adhering to them or to prevent them from accidentally adhering to other objects. However, in actual use, the release paper is discarded, which is undesirable from the viewpoint of material cost and resource saving. On the other hand, labels, stickers, or sheets using hot melt adhesives are non-adhesive at room temperature, but when activated by heat and the heat source is removed, the duration of adhesiveness is short, for example, several seconds, which poses problems in workability.

As an adhesive to solve the above-mentioned drawbacks, there is an example of a heat-sensitive adhesive prepared by blending a heat-sensitive material with a tackifying agent, as described in Japanese Patent Application Laid-Open No. 51-81832, but it is heat-activated. The disadvantage is that it takes too long, for example, several minutes. Also, JP-A-51-111246
There is a heat-activated adhesive composition prepared by blending a block copolymer of styrene and butadiene or styrene and isoprene with a tackifying agent and a crystalline plasticizer as described in the above publication. It has the disadvantage of poor workability, such as re-adhesion of cut surfaces when punching to create labels, stickers, or sheets.

The inventors of the present invention have found that they do not have the above disadvantages, that is, they are non-adhesive at room temperature, are heat activated in a short period of time, remain sticky for a while even when the heat source is removed after heat activation, and have good punching workability. The present invention was arrived at as a result of intensive studies aimed at obtaining a long-lasting heat-sensitive adhesive with excellent tackiness.

That is, the present invention provides a long-lasting tack heat-sensitive adhesive (No. 1 invention), the above (A), (B), (C) and (D) from 160 to
The method for producing the adhesive described above (second invention) is characterized in that the adhesive is heated and melted and mixed at a temperature of 200°C.

The crystalline plasticizer used in the present invention is solid at room temperature (melting point: usually 50-100°C, preferably 60-100°C).
℃), and has the feature that it melts in a short time when heated above its melting point and does not solidify easily even when the heat source is removed. Specific examples of such crystalline plasticizers include those described in () and () below, and mixtures of two or more thereof.

() Esters Aromatic dibasic acid diesters such as diphenyl phthalate, dicyclohexyl phthalate, dihydroabiethyl phthalate, and dimethyl isophthalate; Aliphatic polybasic acid esters such as tricyclohexyl citrate; ethylene glycol dibenzoate, tribasic acid esters, etc. Aromatic-basic acid esters of polyhydric alcohols such as trimethylolethane benzoate, glyceride tribenzoate, pentaerythritol tetrabenzoate, and sucrose benzoate; Fatty acid esters of polyhydric alcohols such as sucrose octaacetate; triphenyl Phosphate esters such as phosphatate, tri-p-tertbutylphenyl phosphate, etc. () Sulfonamide derivatives N-ethyltoluenesulfonamide, N-cyclohexyl-p-toluenesulfonamide, etc.

Among these, diesters of aromatic dibasic acids are preferred in terms of economy and performance as an adhesive, and dicyclohexyl phthalate is particularly preferred.

The ethylene-vinyl acetate copolymer used in the adhesive of the present invention usually has a vinyl acetate content of 10
~50% by weight, preferably 20-35% by weight can be used. If the vinyl acetate content is too low, the adhesive strength will decrease, and if it is too high, blocking will easily occur. Two or more types with different vinyl acetate contents (for example, 40 to 60% and 18 to 35% at 15:85)
A mixture (mixed at a ratio of ~85:15) can also be used. Melt index is usually 2-400g/
10 minutes, preferably 20 to 200 g/10 minutes.

The adhesion imparting resin is blended to improve adhesion upon heat activation. Such adhesion-imparting resins include terpene resins, aliphatic petroleum resins, aromatic petroleum resins, coumaron-indene resins, styrene resins, phenolic resins, terpene-phenolic resins, rosins and their derivatives (disproportionated, hydrogenated,
dehydrogenated products, esterified products), and combination systems of these [for example, combination systems of terpene resins and rosin derivatives (hydrogenated rosin, etc.)]. Suitable tackifying resins are those having a softening point of usually 40 to 130°C, preferably 70 to 120°C. Among these, preferred from the viewpoint of adhesiveness are terpene resins and/or aliphatic petroleum resins.

Furthermore, wax can be added to the adhesive of the present invention for the purpose of lowering the viscosity when melted and suppressing stickiness at room temperature. The wax usually has a melting point of 70 to 130°C, preferably 80 to 110°C, and a melt viscosity (140°C) of usually 50 to 10,000 cps, preferably 100 to 100°C.
7000cps is suitable.

Specific examples of such wax include hydrocarbon waxes such as paraffin wax, microcrystalline wax, low molecular weight polyethylene, and low molecular weight polypropylene; hydrocarbon waxes such as oxides of low molecular weight polyethylene or low molecular weight polypropylene. mineral waxes such as ozokerite; animal and vegetable waxes such as beeswax and rice sugar wax; and amide waxes such as stearic acid amide and ethylene bisstearamide.

Among these, hydrocarbon waxes are preferred, and low-molecular polyethylene is particularly preferred, since they do not impede adhesion and have good blocking resistance.

The adhesive of the present invention is an ethylene vinyl acetate copolymer.
For 100 parts by weight, tackifying resin is usually 40 to 150 parts by weight (preferably 50 to 100 parts by weight), crystalline plasticizer is usually 30 to 250 parts by weight (preferably 50 to 200 parts by weight), and wax is usually 0. ~70 parts by weight (preferably 20
~70 parts by weight). In the above formulation, if the adhesion imparting resin is less than 40 parts by weight, the adhesion upon heat activation will be insufficient, and if it is more than 150 parts by weight, it will become sticky at room temperature and is therefore impractical.

If the amount of crystalline plasticizer is less than 30 parts by weight, it will not be easily activated by heat and no lasting adhesive effect will be observed250
When the amount exceeds parts by weight, the adhesive strength decreases, which is not practical. Further, if the amount of wax exceeds 70 parts by weight, it is not preferable because it impairs adhesion. When the amount of wax is 20 to 70 parts by weight, it is even more effective because the tackiness at room temperature is suppressed and the viscosity when melted is lowered.

Also, based on the total amount of (A), (B), (C), and (D), (A) is 17
~59% by weight, especially 21-45% by weight, (B) 8-53% by weight, especially 11-37% by weight, (C) 8-64% by weight, especially 15-54% by weight, (D) 0 ~29% by weight, especially 4
~25% by weight is preferred.

In addition, to improve adhesion at low temperatures, elastomers are made of rubber-like polymers (styrene-butadiene rubber, butyl rubber, isoprene rubber, isobutylene rubber, nitrile rubber, acrylic rubber, urethane rubber, etc.) and thermoplastic resins (polyester, polyurethane rubber, etc.). , styrene-butadiene block copolymer, styrene-isoprene block copolymer, etc.) in a proportion of 30 parts by weight or less (preferably 20 parts by weight or less) per 100 parts by weight of the ethylene-vinyl acetate copolymer. It is also possible. If the amount of the above elastomer exceeds 30 parts by weight, the punching processability deteriorates when applied as an adhesive, making it impractical. Further, if necessary, antioxidants, fillers (barium sulfate, calcium carbonate, etc.), solvents, antiblocking agents, lubricants and other additives may be added.

The method for producing the adhesive of the present invention is not particularly limited.
It can be produced by heating and melting and mixing the above (A), (B), (C) and (D) in any order. For example (1)
Method (2) of blending all the components at the same time and heating and mixing (2) A method of heating and melting some of the components, then blending the other components and heating. Preferred is method (2), for example, a method in which (B), (C), and (D) are dissolved and then (A) is added and mixed. The temperature when heating is usually 160-200
It is ℃. It is also possible to dissolve at least a portion of the components [for example (D)] in a solvent (such as an aromatic hydrocarbon) and then mix them.

The adhesive thus obtained usually has a melting point of 50
-100°C, preferably 60-100°C. The viscosity is
It is usually about 5000 to 60000 cps at 160℃.

The adhesive of the present invention can be used in the same manner as conventional heat-sensitive adhesives.

For example, it can be applied directly to the substrate using a common hot melt coater. Examples of the base material include cellulosic sheet materials (such as paper), plastic sheets, films, and foils. Instead of hot melting, it can also be applied to the substrate as a solution in a solvent (aromatic hydrocarbon solvent, ketone solvent, ester solvent, chlorinated hydrocarbon solvent, etc.). Furthermore, adhesives in the form of films, tapes, etc. can be heated and melted between the substrates to make them adhere.

The base material coated with the adhesive of the present invention is not sticky at room temperature, so there is no need to worry about inadvertent adhesion, and it can be easily activated by heating with a hair dryer, iron, etc., and even after the heating source is removed. It also has the effect of maintaining adhesiveness for a while, and also has excellent workability because the cut surface does not re-adhere when punched into labels, stickers, etc.

The adhesive of the present invention can be used to bond various substrates, including cellulosic materials (paper, cellophane, etc.), plastics (polyester, polyvinyl chloride, polyethylene, polypropylene, ABS resin, polymethacrylate, polycarbonate, etc.), fibers, etc. It has excellent adhesion to products (woven fabrics, knitted fabrics, non-woven fabrics, etc.), wood, leather, metals (stainless steel, aluminum, etc.), glass, etc.

The adhesive of the present invention can be used in various applications such as packaging, shoe making, textile processing, metal structures, and electrical and electronic industries. The adhesive of the present invention is particularly useful for use as labels and stickers such as price and expiration date labels for fresh produce, labels and seals for cans and bottles, and for backing, such as wallpaper and carpet backing. Demonstrate.

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

Example 1 100 g of Evaflex #220 (ethylene vinyl acetate copolymer manufactured by Mitsui Petrochemicals, vinyl acetate content 28%, melt index 150 g/10 minutes), YS Resin A #800 (terpene resin manufactured by Cheap Crude Oil, softening point 80)
℃), 100 g of dicyclohexyl phthalate (manufactured by Osaka Organic Chemical Industry, melting point 64 °C), and 50 g of Mobil Wax 2305 (microcrystalline wax, melting point 77 °C, manufactured by Mobil Oil) in a glass beaker.
An adhesive was prepared by heating and mixing at 170°C.

The adhesive prepared by the above method has a coating amount of 25g/m ²
When it was melt-coated directly onto high-quality paper and left at room temperature for two weeks, the tackiness on the surface of the coated paper completely disappeared. The coated paper prepared by the above method was activated by heating at 120°C for 5 seconds, and then left at 20°C to measure the duration of stickiness. Adhesion was determined by whether or not the vinyl chloride stretch film was torn when the coated paper was attached to the vinyl chloride stretch film and then peeled off. As a result, the duration of stickiness was 1 hour.

Furthermore, the coated paper was activated by heating at 120℃ for 5 seconds.
Stainless steel plate (sus27) after being left at 20℃ for 10 minutes
The adhesive strength was measured by peeling at 180°C according to JIS C-2336 and found to be 2.5 kg/2.5 cm.

Example 2 Ultracene UE-750 (Toyo Soda ethylene vinyl acetate copolymer, vinyl acetate content 32% melt index 30 g/10 minutes) 100 g Alcon M-100
(Manufactured by Arakawa Chemical, _C9 hydrogenated petroleum resin, softening point 100
℃), 30 g of dicyclohexyl phthalate, and 30 g of Sunwax 171P (low molecular weight polyethylene wax manufactured by Sanyo Chemical Industries, softening point 105°C) were placed in a glass beaker and heated and mixed at 170°C to prepare an adhesive.

When the adhesive duration and adhesive strength of the adhesive prepared by the above method were measured by the method of Example 1, the adhesive duration was 10 minutes, and the adhesive strength to a stainless steel plate was 2.5 kg/2.5 cm.

Comparative example 1 100g of Ultrasen UE-750, Alcon M-
100 and 30 g of Sunwax 171P were placed in a glass beaker and heated and mixed at 170°C to prepare an adhesive.The adhesive duration was measured by the method of Example 1 and found to be 10 seconds or less.

Example 3 Ultrasen UE-750 100g, Alcon M-
100 70g, dicyclohexyl phthalate 200g,
Put 50g of Sanwatkusu 171P into a glass beaker.
An adhesive was prepared at 170° C. and the adhesive duration and adhesive strength were measured by the method of Example 1, and the adhesive strength was 1.5 kg/2.5 cm for 1 hour, respectively.

Claims (1)

[Scope of Claims] 1 Ethylene-vinyl acetate copolymer (A), tackifying resin (B), diphenyl phthalate, dicyclohexyl phthalate, dihydroabiethyl phthalate, dimethyl isophthalate, tricyclohexyl citrate,
Ethylene glycol dibenzoate, trimethylolethane tribenzoate, glyceride tribenzoate, pentaerythritol tetrabenzoate, sucrose benzoate, sucrose octaacetate, triphenyl phosphate, tri-p-tertbutyl phenyl phosphate Phate, N-ethyltoluenesulfonamide, N-cyclohexyl-p-toluenesulfonamide. Solid at room temperature, melts in a short time when heated above the melting point, and easily solidifies even when the heat source is removed. No crystalline plasticizer (C)
A long-lasting heat-sensitive adhesive containing wax (D) and wax (D). 2 (A) 100 parts by weight, hand (B) 40 to 150 parts by weight, (C)
The heat-sensitive adhesive according to claim 1, wherein (D) is 30 to 250 parts by weight and 0 to 70 parts by weight. 3. The heat-sensitive adhesive according to claim 1 or 2, wherein (D) is a hydrocarbon wax. 4. The heat-sensitive adhesive according to claim 3, wherein the hydrocarbon wax is low molecular weight polyethylene. 5. The heat-sensitive adhesive according to claim 1 or 4, wherein (B) is a terpene resin or/and an aliphatic petroleum resin. 6 Ethylene-vinyl acetate copolymer (A), tackifying resin (B), diphenyl phthalate, dicyclohexyl phthalate, dihydroabiethyl phthalate, dimethyl isophthalate, tricyclohexyl citrate,
Ethylene glycol dibenzoate, trimethylolethane tribenzoate, glyceride tribenzoate, pentaerythritol tetrabenzoate, sucrose benzoate, sucrose octaacetate, triphenyl phosphate, tri-p-tertbutyl phenyl phosphate Phate, N-ethyltoluenesulfonamide, N-cyclohexyl-p-toluenesulfonamide. Solid at room temperature, melts in a short time when heated above the melting point, and easily solidifies even when the heat source is removed. No crystalline plasticizer (C)
and wax (D) by heating and melting at a temperature of 160 to 200°C. 7 (A) 100 parts by weight, hand (B) 40 to 150 parts by weight, (C)
The method for producing a heat-sensitive adhesive according to claim 6, wherein (D) is 30 to 250 parts by weight and 0 to 70 parts by weight.