JPS6231015B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous dispersion that provides a film with excellent low-temperature thermal adhesion and blocking resistance, and a heat-sensitive adhesive sheet treated with the dispersion that can be thermally bonded even at low temperatures and has good blocking resistance. Various heat-sensitive adhesives are used to bond substrates that cannot be thermally bonded, such as paper, aluminum foil, and cellophane, which are widely used as packaging materials. Among them, thermoplastic resins are especially used from the viewpoint of non-pollution. Aqueous dispersions of are now widely used. A common method for using aqueous dispersions as adhesives is to
The aqueous dispersion is applied to the substrate and then dried to form a film on the substrate that has the property of adhering to the substrate by heat and pressure, thereby imparting thermal adhesive properties to the substrate. Adhesion of base materials coated with a film exhibiting thermal adhesive properties is carried out by applying heat and pressure to the coated surfaces or to the surface of another base material, depending on the purpose of use. In fact, it is preferable to be able to bond at a low temperature, both from the point of view of energy saving and also from the point of not requiring severe temperature control during the bonding process. Furthermore, industrially, bonding of substrates is carried out while the substrates are running at a constant speed, so being able to thermally bond them even at low temperatures makes it possible to thermally bond them while the substrates are running at high speeds. This results in high productivity. Furthermore, substrates treated with an aqueous dispersion and coated with a film are rarely thermally bonded as is, and in most cases they are simply peeled off, but in this case the film is highly adhesive. Blocking occurs between the coated (coating) surface and the substrate surface or equipment such as rolls, making it extremely difficult to handle and causing problems during the rolling process and subsequent processes (printing, filling, adhesion, etc.). This will impede stable operation. Therefore, the coating on the substrate must have good blocking resistance in addition to low-temperature thermal adhesion. Conventionally, aqueous dispersions of thermoplastic resins such as polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, and polyacrylic resins have been known as aqueous heat-sensitive adhesives with thermal adhesive properties. Most aqueous dispersions have the property that those that can be thermally bonded at low temperatures are easily blocked, and conversely, those that have good blocking resistance have a high temperature that allows thermal bonding. does not provide a coating that satisfies the performance of For this reason, the reality is that in consideration of practicality, a material with good blocking resistance is selected at the expense of thermal adhesion efficiency. As an improved method, wax emulsion, polyethylene emulsion,
Fine powders of cellulose, clay, silica, etc. are also used together as anti-blocking agents, but although these methods improve anti-blocking properties to some extent, they impair low-temperature thermal adhesion properties and are unsatisfactory. No results have been obtained. Furthermore, in JP-A-54-18689, an aqueous heat-sensitive adhesive composition was proposed in which a fatty acid ester of glycerin was used in combination with an ethylene copolymer with a high copolymerization content and a low heat softening temperature. However, in order to achieve the desired effect, it is necessary to use a resin with a high copolymerization content, which results in low strength of the resin itself and poor blocking resistance, so a large amount of fatty acid ester of glycerin should not be added. Therefore, although the temperature at which bonding is possible is low, the bonding strength is low. There are also problems with other practical properties of the coating, such as water resistance and heat resistance. Therefore, although it can be used simply as an adhesive between papers, it can also be used for applications that require sufficient adhesive strength.
For example, it cannot be used in the field of packaging that involves filling the contents, and can only be used for very limited special purposes. Recently, thermoplastic resins made of copolymers of ethylene and α,β-ethylenically unsaturated carboxylic acids, with some of the carboxylic acids neutralized with metal ions, so-called ethylene-based ionomer resins, have been developed to have anti-blocking properties. Because of its good properties, its aqueous dispersion has come to be used as a heat-sensitive adhesive for packaging materials, etc. However, since this ionomer resin has ionic bonds, it has good blocking resistance. Thermal fluidity becomes poor and there are problems with low-temperature thermal adhesion. The present inventors have conducted intensive research on water-based adhesives that can be thermally bonded at low temperatures (e.g. 70-90℃), have good blocking resistance, and have sufficiently high adhesive strength. If a specific ester compound is used in combination with an ethylene-based copolymer having a small amount of ethylene, the low-temperature thermal adhesion will be improved without impairing the excellent properties of the copolymer, and the aqueous dispersion will satisfy all of the above requirements. Heading: The present invention has been completed. That is, the present invention provides 97 to 85 mol% ethylene and 3 to 85 mol% ethylene.
An ethylene copolymer comprising 15 mol% of an α,β-ethylenically unsaturated carboxylic acid, or a part of the unsaturated carboxylic acid is an alkyl ester, the copolymer comprising at least 10% of the unsaturated carboxylic acid. The present invention provides an aqueous dispersion containing as main components a copolymer with a neutralized percentage and an aliphatic dibasic acid diester and/or a sulfosuccinic acid diester. Furthermore, a sheet treated with such an aqueous dispersion is provided. Next, the present invention will be explained in detail. The ethylene copolymer used in the present invention is 97~
85 mol %, preferably 95-90 mol % ethylene and 3-15 mol %, preferably 5-10 mol % α,β-ethylenically unsaturated carboxylic acid, optionally in which some of the carboxylic acids are alkyl It is an ethylene copolymer consisting of an ester and at least 10% of the α,β-unsaturated carboxylic acid is neutralized. If the ethylene content exceeds 97 mol %, it becomes difficult to produce a stable aqueous dispersion, and the low-temperature thermal adhesiveness becomes inadequate. On the other hand, 85 mol%
If it is less than that, the adhesive strength will be low and the blocking resistance will be poor. The content of alkyl ester in the ethylene copolymer is determined by the total amount of carboxylic acid groups in the copolymer (when expressed as R-COOX, R-
COO is a carboxylic acid group, X is H, metal or
It is preferable that the amount of NH ₄ and other alkali ions, and (representing an alkyl group) is 50% or less. When it exceeds 50%, it is difficult to obtain a stable aqueous dispersion and the adhesive strength becomes low. Examples of α,β-ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid. Examples of α,β-ethylenically unsaturated carboxylic acid alkyl esters include esters of the above-mentioned carboxylic acids such as methyl, ethyl, and butyl. These unsaturated carboxylic acids or alkyl esters thereof to be copolymerized with ethylene can be used alone or in combination of two or more. In addition, hydroxyethyl acrylate, acrylamide, maleic acid, etc. may be added as necessary for the purpose of adhesion, water dispersibility, blocking resistance, thermal adhesion, etc., to the extent that does not impair the effects of the present invention. Copolymers containing α,β-ethylenically unsaturated carboxylic acid derivatives such as imides, vinyl monomers such as vinyl acetate, vinyl alcohol, vinyl chloride, and styrene can also be used. Note that at least 10% of the total amount of carboxylic acid groups in the copolymer is neutralized. If the amount of neutralization is less than 10%, water dispersion becomes difficult. The optimal amount of neutralization varies depending on the type of neutralized substance and the amount of copolymerized components, and cannot be determined unconditionally, but if the amount of copolymerized components is small, the amount of neutralization should be increased, and conversely, if the amount of copolymerized components is large, the amount of neutralization should be In order to obtain a stable aqueous dispersion, it is preferable to lower the
It can be easily determined experimentally. Any neutralizing component may be used as long as it can neutralize the carboxylic acid and does not inhibit the stabilization of the aqueous dispersion, but from the viewpoint of practicality, alkali metals such as sodium and potassium and ammonium are preferred. Note that the degree of neutralization referred to in the present invention indicates the amount of neutralization of carboxylic acid in the copolymer when it exists as a dispersion. Therefore, when neutralizing with something that easily volatizes during drying (dehydration) after coating, such as ammonium neutralization, the amount of neutralized resin in the coating film is lower than that in the dispersion. Depending on the drying conditions, the amount of neutralization may be zero. Neutralization may be carried out at the time of preparing the resin, or may be carried out at the time of producing the aqueous dispersion. In the case of ammonium neutralization, it is preferably carried out when producing an aqueous dispersion from the viewpoint of volatility and odor. Such copolymers may be used alone or in combination of two or more for the purpose of controlling blocking resistance and low temperature adhesion. The above ethylene copolymers are ethylene/
When α,β-ethylenically unsaturated carboxylic acid ester copolymer is used as a starting material, for example,
When an ethylene/α,β-ethylenically unsaturated carboxylic acid copolymer is used as a starting material, it can be easily obtained by a known method such as in Japanese Patent Publication No. 39-6810. The aliphatic dibasic acid diesters used in the present invention include diesters obtained from an aliphatic dibasic acid and a monohydric alcohol, and polyester diesters obtained from an aliphatic dibasic acid, a dihydric alcohol, and a monocarboxylic acid. It is a basic acid diester. As an aliphatic dibasic acid, in the general formula HOOC-R-COOH, R is CH=CH, (CH ₂ ) _o , where n is 2 to
It is a dibasic acid that is an integer of 10. Examples include succinic acid, adipic acid, azelaic acid, and sebacic acid. Examples of the alcohol include monohydric and dihydric alcohols having 1 to 15 carbon atoms, such as ethanol, butanol, octanol, decanol, ethylene glycol, and propylene glycol. Monocarboxylic acids include fatty acids having 12 to 18 carbon atoms, such as lauric acid, palmitic acid, and stearic acid. Specific examples of aliphatic dibasic acid diesters include diesters of maleic acid such as dibutyl maleate and dioctyl maleate; diesters of fumaric acid such as dibutyl fumarate and dioctyl fumarate; dihexyl succinate, dioctyl succinate, etc. Diester of succinic acid; diethyl adipate,
Diesters of adipic acid such as dibutyl adipate, dioctyl adipate, diisodecyl adipate, octyl-decyl adipate, didecyl adipate, polypropylene adipate, polyester adipate; diesters of azelaic acid such as dibutyl azelaate and dioctyl azelate; sebacin Examples include diesters of sebacic acid such as dibutyl sebacate, dihexyl sebacate, dioctyl sebacate, octyl-decyl sebacate, polyethylene sebacate, polypropylene sebacate, and polyester sebacate. Such compounds are used as plasticizers for polyvinyl chloride and the like and are easily available. These aliphatic dibasic acid diesters can be used alone or in combination of two or more. All of these diesters exhibit their effects if the type and amount of coexisting resins are appropriately selected, but the preferred conditions can be easily determined through experiments. Among these diesters, diesters of adipic acid and diesters of sebacic acid are particularly preferred because they are produced on an industrial scale and the range of target resins that satisfy the performance is relatively wide. In addition, when the aqueous dispersion of the present invention is used in applications where the drying temperature after coating is high, or the time required for thermal adhesion after coating is long, and the volatilization of the diester is promoted, the boiling point is 200%. It is desirable to select a diester with a temperature above ℃. The sulfosuccinic acid diester used in the present invention has the following general formula:

It is shown by [Formula]. In the formula, R ₁ and R ₂ are alkyl groups having 1 to 20 carbon atoms, and may be the same or different. X
represents an alkali metal such as Na or K, or NH ₄ .
Such compounds can be easily obtained by the reaction of maleic acid, alcohol, and a sulfonating agent, and a diester type in which the esterified component of maleic acid is derived from glycol or hydroxyamine is also effective; A diester type derived from a monohydric alcohol is preferred from the viewpoint of stability and availability. Specific examples include sodium sulfodimethyl succinate, sodium sulfodibutyl succinate, sodium sulfodioctylsuccinate, and sodium sulfoditridecyl succinate. These compounds may be used alone or in combination of two or more if necessary. Note that these compounds may contain some monoesters and unreacted substances, but these monoesters and unreacted substances tend to hinder the stabilization of the aqueous dispersion and cause foaming, so avoid using them as much as possible. It is preferable to reduce the amount. In addition, these compounds are generally commercially available as aqueous solutions containing solvents such as methanol, ethanol, propylene glycol, butyl carbitol, etc., and are widely used as surfactants. Because it does not depend on the type of
It can be used with the solvent still in it, but it can also be used after removing the solvent if necessary. The aqueous dispersion of the present invention is prepared by mixing an aliphatic dibasic acid diester and/or a sulfosuccinic acid diester in a molten state or a solution state and blending the copolymer in advance. This is possible by emulsifying and dispersing the copolymer in water, or by emulsifying and dispersing the copolymer and these diesters together in water, but side reactions during mixing and hydrolysis of the blended diesters during emulsification and dispersion are possible. It is preferable to avoid this because it tends to cause a reaction. Generally, it is preferable to emulsify and disperse the copolymer in water in advance, and then blend the above-mentioned diester compound into the copolymer dispersion. The copolymer dispersion can be prepared by adding one or more of the copolymers as is or in the presence of an alkali for neutralization, as necessary to improve mechanical stability and wettability with the substrate during coating. It can be easily obtained by adding a small amount of a known anionic or nonionic surfactant for the purpose of improving the composition and dissolving or emulsifying it in water. The solids content of the copolymer in the dispersion is generally 20 to 60% by weight. On the other hand, aliphatic dibasic acid diesters and sulfosuccinic acid diesters are incorporated into the copolymer dispersion as they are or by emulsifying and dispersing them in water in the presence or absence of a small amount of an emulsifying dispersant. The amount of diester compound to be blended into the aqueous dispersion in order to achieve the purpose of the present invention varies slightly depending on the type of diester compound to be blended and the composition of the copolymer; On the other hand, if the pure content is at least 1 part by weight, the effect can be seen. Performance improves as the amount added increases, but when the amount exceeds a certain level, adhesive performance and stability of the dispersion deteriorate. The upper limit of the blending amount is approximately 10% when either aliphatic dibasic acid diester or sulfosuccinic acid diester is blended.
It is about 20 parts by weight, and when used in combination, performance is improved even when the amount is increased. In addition, when used in combination, it is preferable to use the aliphatic dibasic acid diester:sulfosuccinic acid diester in a weight ratio of 1:1 to 5:1 from the viewpoint of economy and stability. Considering the degree of improvement in adhesion and economic efficiency, the amount of these diester compounds blended is preferably in the range of 2 to 15 parts by weight. Generally speaking, when comparing the same blending amounts, the combination of aliphatic dibasic acid diester and sulfuccinic acid diester has better low-temperature thermal adhesion properties than the combination of either diester and sulfuccinic acid diester, and for example, adhesiveness is better than when using them alone. The minimum temperature will drop by about 5°C, and in some cases by about 10°C. The aqueous dispersion obtained in the present invention is characterized by containing the above-mentioned copolymer and an aliphatic dibasic acid diester and/or a sulfosuccinic acid diester as main components. Not only well-known additives such as surfactants, plasticizers, defoaming agents, antifoaming agents, thickeners, antistatic agents, anti-blocking agents, slip agents, and ultraviolet absorbers, but also for reducing costs and coatings. Polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, which are compatible with the aqueous dispersion of the present invention, may be added as necessary for the purpose of adjusting workability or for supplementary control of blocking properties and adhesion. ,polyethylene-
Known aqueous dispersions such as vinyl acetate and polyacrylic, as well as organic solvents such as ethanol and isopropyl alcohol for the purpose of accelerating drying, may be blended within a range that does not impede the properties aimed at by the present invention. The aqueous dispersion of the present invention can be applied to papers such as high-quality paper and synthetic paper, composite foils such as aluminum foil, cellophane, nonwoven fabrics,
It is useful for providing coatings on plastic sheets such as polyolefin and composite substrates of these substrates that have excellent blocking resistance, can be thermally bonded at low temperatures, and have high adhesive strength when bonded. . The method for forming a film on the substrate is to apply an aqueous dispersion to the substrate using an existing coating method used in general paper coating, such as a bar coater, air knife coater, roll coater, etc. Further, water can be evaporated through a conventional drying process. The amount of application varies depending on the smoothness and permeability of the base material, but it depends on the solid content.
If it is coated in an amount of 2 g/m ² or more, it is possible to obtain a heat-sensitive adhesive sheet that can be thermally bonded at low temperatures, which is the object of the present invention, and has good blocking resistance. The sheet treated with the aqueous dispersion of the present invention can be thermally bonded even at low temperatures, and when bonded, exhibits sufficiently high adhesive strength, and has a coating with excellent blocking resistance. It is easy to handle, there are no problems in the process from coating to adhesion, and it can be thermally bonded stably under high-speed running without the need for severe excessive adhesion control, producing high-quality products with high productivity. It can be manufactured stably. The heat-sensitive adhesive sheet of the present invention, which can be thermally bonded at low temperatures and has good blocking resistance, is useful in most applications that require thermal bonding; examples include confectionery products, foods, chemical products, It can be used as a packaging material for various contents such as household daily necessities and cosmetics, and can be used by printing the address and contents on the front side of the sheet with adhesive applied to the back side using a computer line printer, etc., then folding it in half and bonding it under heat. It is useful for making a single postcard, etc. EXAMPLES The content of the present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. In addition, the evaluation of the characteristics shown in the examples was performed by the following method unless otherwise specified. Each dispersion was coated on high-quality paper (75 g/m ² ) or aluminum foil (17 μm) using a bar coater and dried at 100° C. for 1 minute to obtain a heat-sensitive adhesive sheet. Thermal bonding was carried out at various temperatures by applying a load of 1 kg/cm ² for 1 second to the dispersion-coated surfaces of the heat-sensitive adhesive sheets obtained using a sentinel heat sealer. The method for evaluating adhesion is to cut a test piece from this adhesive sheet, and use a tensile tester to measure the strength (g/15 mm) at the time of peeling by pulling it in a direction of 90 degrees to the adhesive surface at a pulling speed of 200 mm/min. He did what he asked for. In addition, as another adhesion evaluation criterion, in the case of samples coated on high-quality paper, the degree of destruction of the paper layer upon peeling was determined. The evaluation was performed according to the following criteria. 〇: Almost the entire paper layer is destroyed upon peeling, △: Partial paper layer is destroyed upon peeling, ×: No paper layer is destroyed at all upon peeling. The blocking resistance was evaluated by applying a load of 0.5 kg/cm ² to the coated surfaces of aluminum foil (17μ) coated with approximately 5 g/m ² (solid content) or to the coated and non-coated surfaces together. The film was left in a constant temperature and humidity environment of 30°C and 60% humidity, and after 24 hours, it was peeled off by hand to evaluate the degree of blocking. Evaluation of blocking resistance was performed according to the following criteria. 〇: Almost no tackiness △: Slight tackiness ×: Considerable tackiness Example 1 Consists of 92 mol% ethylene and 8 mol% methacrylic acid, with 29% of the methacrylic acid converted to sodium ions. Aqueous dispersion of the copolymer (solids concentration 40% by weight, viscosity
130cps, sodium oleate amount based on solid weight
(containing 0.5%), 5 parts of a diester compound shown in Table 1 was added to 100 parts by weight of the copolymer. The resulting aqueous dispersion was placed on aluminum foil at 6 g/ ^m2.
(solid content), and the thermal adhesion and blocking resistance at low temperatures of this heat-sensitive adhesive sheet were measured. For comparison, a sheet treated with a dispersion containing no diester compound was also measured. The results are shown in Table 1. As is clear from the table, the adhesive sheet treated with the dispersion of the present invention can be thermally bonded even at 75°C, and has significantly improved low-temperature adhesion compared to the comparative example, and also has good blocking resistance. It is also found that the combination of an aliphatic dibasic diester and a sulfosuccinic acid diester further improves the low-temperature heat adhesion.

[Table] Example 2 Sodium sulfoditridecyl succinate was added to an ammonium-neutralized (neutralization degree 100%) dispersion (solid content concentration 40% by weight) of a copolymer of 91 mol% ethylene and 9 mol% acrylic acid. 5 parts of was added. The thermal adhesion and blocking resistance of the obtained dispersion were as follows.

[Table] Example 3 Dispersion of a copolymer of ethylene/methacrylic acid/methacrylic acid methyl ester with a composition ratio of 92/5/3 in mol% (approximately 65% of the total amount of carboxylic acid groups is neutralized with sodium ions) Liquid (solid content concentration 40% by weight)
7 parts of a pure emulsified dispersion of polyester adipate or an emulsified dispersion of polyethylene sebacate were added to 100 parts of the copolymer. The thermal adhesion and blocking resistance of the obtained dispersion were as follows.

[Table] Example 4 Copolymer of ethylene and methacrylic acid. (copolymerization ratio 95 mol%/5 mol%) and a copolymer of ethylene and acrylic acid (copolymerization ratio 91 mol%/9 mol%)
The mixing ratio of the two copolymers is former copolymer/latter copolymer = 7/3.
Emulsification of dioctyl azelaate in a dispersion (by weight) of Copolymerization weight of dispersion
5 parts, 10 parts, and 15 parts of each were added to 100 parts.
The thermal adhesion and blocking resistance of the obtained dispersion were as follows.

[Table] If the amount added is too large, the minimum temperature at which bonding is possible will be lower than when no additive is added, but the bonding strength will be lower.
In addition, oil droplets appeared after one week in the dispersion to which 15 parts were added, and a uniform coating film could not be obtained when applied to a substrate. Example 5 and Comparative Example 1 This comparative example illustrates that there is no effect even if the diester compound used in the present invention is combined with a dispersion of a resin other than the ethylene copolymer defined in the present invention. Dioctyl adipate was used as a diester compound, and 5 parts were added to 100 parts of the resin weight in the dispersion. After blending, the dispersion was applied to high-quality paper at 6 g/m ² (solid content), and the paper coated with the dispersion was subjected to a thermal adhesion test. The adhesiveness was evaluated by determining the degree of destruction of the paper layer when the adhesive surface was peeled off. The results are shown in Table 2. As is clear from the table, the thermal adhesiveness is not improved at all even when the resin is mixed with a resin other than the resin used in the present invention.
On the other hand, it can be seen that if it is blended with the resin specified in the present invention, it is significantly improved.

[Table] Example 6 and Comparative Example 2 This comparative example illustrates that there is no effect even if a substance other than the diester compound used in the present invention is blended into the ethylene copolymer dispersion defined in the present invention. . Additives shown in Tables 3 and 4 were added to the same dispersion as used in Example 1 in an amount of 5 parts or 10 parts per 100 parts of the resin weight in the dispersion. Each of the obtained blended dispersions was coated on high-quality paper at a solid content of about 5 g/m ² , and the treated sheets were thermally bonded to examine low-temperature thermal adhesion properties. The results are shown in Tables 3 and 4. The aliphatic dibasic acid diester used in the present invention is usually used as a plasticizer, but as shown in Table 3, no effect is observed even when other plasticizers are used. Furthermore, the sulfosuccinic acid diester used in the present invention is usually used as a surfactant, but
As shown in Table 4, no effect was observed even when various other surfactants were added. Even if the same sulfosuccinate ester is used, it has no effect in the case of a monoester.

【table】

【table】

[Table] Example 7 and Comparative Examples 3A-C Comparison of performance between the heat-sensitive adhesive composition proposed in JP-A-18689 and that of the present invention is illustrated. A dispersion with the composition shown in Table 5 (solid content concentration 40% by weight, all copolymers were sodium ion neutralized, degree of neutralization 30%) was prepared, and the thermal adhesion and blocking resistance of the dispersion were evaluated. . The results are shown in Table 6.

【table】

[Table] The copolymerization ratio of glycerin ester blended products is 10.
There is no effect when it is blended in a resin of less than mol % (Comparative Example A). When blended with a resin having a high copolymerization ratio (Comparative Example C), the thermal adhesion at low temperatures is improved, but the adhesive strength is significantly lower than that of the method of the present invention. Furthermore, since it is a resin with a low softening point, its blocking resistance is also somewhat inferior.

Claims (1)

[Scope of Claims] 1 Consists of 97 to 85 mol% ethylene and 3 to 15 mol% α,β-ethylenically unsaturated carboxylic acid, or a portion of the unsaturated carboxylic acid is an alkyl ester At least one type of ethylene copolymer in which at least 10% of the unsaturated carboxylic acid is neutralized, at least one type of aliphatic dibasic acid diester and/or sulfosuccinic acid. An aqueous dispersion containing at least one acid diester as a main component. 2. The dispersion according to claim 1, wherein the aliphatic dibasic acid diester is an adipic acid diester or a sebacic acid diester. 3. The dispersion according to claim 1, wherein the copolymer content is 20-60% by weight. 4 Diester content is 2-15 parts by weight (copolymer content
100 parts by weight). 5 When a fatty acid dibasic acid diester and a sulfosuccinic acid diester are used in combination, the relative ratio of each is 1:
A dispersion according to claim 1 in which the ratio is 1 to 5:1. 6 An ethylene copolymer consisting of 97 to 85 mol% ethylene and 3 to 15 mol% α,β-ethylenically unsaturated carboxylic acid, or a part of the unsaturated carboxylic acid is an alkyl ester. at least one copolymer in which at least 10% of the unsaturated carboxylic acids are neutralized; and at least one aliphatic dibasic acid diester and/or at least one sulfosuccinic acid diester. A heat-sensitive adhesive sheet treated with an aqueous dispersion mainly composed of seeds. 7. The sheet according to claim 6, wherein the aqueous dispersion has a solid content of 2 g/m ² or more.