JPH0711216A - Water-based pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain a water-based pressure-sensitive adhesive composition for the production of a tacky adhesive label or seal having excellent adhesivity and free from the generation of residual adhesive and scum breakage in processing. CONSTITUTION:This water-based pressure-sensitive adhesive composition contains (A) an emulsion of a (meth)acrylic acid ester copolymer having a glass transition temperature of -25 to -40 deg.C and composed mainly of a 4-14C alkyl (meth)acrylate, an alpha,beta-unsaturated carboxylic acid and a functional monomer containing two or more polymerizable double bonds in one molecule and (B) an emulsion of a tackifier resin having a softening point of >=151 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based pressure-sensitive adhesive composition, and more particularly to a water-based pressure-sensitive adhesive composition suitable as a pressure-sensitive adhesive used for pressure-sensitive adhesive labels and seals.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesives for pressure-sensitive adhesive labels / seals have been mainly rubber-based pressure-sensitive adhesives containing natural rubber or synthetic rubber as a main component, and acrylic copolymers as base polymers. Acrylic pressure sensitive adhesive is used.

As the acrylic pressure-sensitive adhesive, for example, Japanese Patent Publication No. 5-1314 discloses a pressure-sensitive adhesive containing an emulsion containing acrylic acid, vinyl acetate and alkyl (meth) acrylate as main components. Can be mentioned. Such acrylic pressure-sensitive adhesives are widely used because they have the advantage that the adhesiveness can be adjusted by selecting a monomer that is a component of the acrylic copolymer.

The adhesive labels and seals have various uses, and the adherend is spread to materials such as polyethylene that are difficult to adhere to, and there is a demand for a pressure-sensitive adhesive having high adhesive strength.

[0005]

[Problems to be solved] By the way, in an adhesive label / seal using an acrylic pressure-sensitive adhesive, after coating the release paper with the acrylic pressure-sensitive adhesive, a base material is superposed thereon, It is manufactured by cutting the base material and the adhesive layer from the upper surface of the base material with a cutter.

If the adhesive force of acrylic pressure-sensitive adhesives is too high, the adhesive label / seal processing step
There is a problem that the pressure sensitive adhesive remains on the release paper when the unnecessary parts are peeled off from the release paper after punching into the required shape (hereinafter referred to as adhesive residue), and the base material of the adhesive label / seal is paper. In the case of (1), when the unnecessary portion is peeled off from the release paper by winding, the unnecessary portion is torn in the middle (hereinafter referred to as scrap), and there is a problem that the work must be interrupted.

The present invention has been made in view of the above points, and has an excellent adhesive property, and does not cause adhesive residue or scraps in the adhesive label / seal processing step. The purpose is to provide a pressure-sensitive adhesive composition.

[0008]

The water-based pressure-sensitive adhesive composition of the present invention comprises a (meth) acrylic acid alkyl ester having an alkyl group of 4 to 14 carbon atoms and an α, β-unsaturated carboxylic acid. And a (meth) acrylic acid ester-based copolymer having a glass transition temperature of −25 ° C. to −40 ° C., which contains, as a main component, a functional monomer having two or more polymerizable double bonds in one molecule. And an emulsion of a tackifying resin having a softening point of 151 ° C. or higher.

The (meth) acrylic acid alkyl ester used in the present invention means an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester.

Examples of the (meth) acrylic acid alkyl ester having an alkyl group having 4 to 14 carbon atoms include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and lauryl (meth) acrylate. .

As the above α, β-unsaturated carboxylic acid,
Examples thereof include acrylic acid and methacrylic acid.

Examples of the functional monomer having two or more polymerizable double bonds in the above molecule include ethylene glycol dimethacrylate and triethylene glycol diacrylate.

In the (meth) acrylic acid ester-based copolymer emulsion used in the present invention, in addition to the above-mentioned monomers, methyl (meth) acrylate, ethyl (meth) acrylate, vinyl acetate, 2-hydroxyethyl (meth)
One or more ethylenically unsaturated monomers such as acrylate, styrene and acrylamide may be contained as a constituent component.

The (meth) acrylic acid ester-based copolymer emulsion contains, as a main component, a copolymer obtained by copolymerizing the above-mentioned monomers by ordinary emulsion polymerization.
The glass transition temperature (Tg) of the copolymer is -25 ° C to -40.
It is preferable to carry out the selection and combination of the monomers such that the temperature is in the range of ℃, preferably -30 ℃ to -40 ℃,
This increases the adhesive strength of the obtained adhesive.

Usually, as the Tg is designed lower, the adhesive strength of the adhesive can be increased. However, if the Tg is designed too low,
Adhesive residue and scrap scraps occur during the processing of adhesive labels and stickers.

Therefore, in order to obtain an excellent adhesive force without causing adhesive residue and scraps in the adhesive label / seal processing step, in the present invention, the acrylic ester copolymer emulsion is added with a softening point. Is blended with an emulsion of a tackifying resin having a temperature of 151 ° C. or higher.

The type of tackifying resin is not particularly limited,
Examples include natural resin type (rosin type, terpene type, etc.), synthetic resin type (petroleum type, xylene type, coumarone type, etc.). Particularly preferred is a rosin type (eg, a polymerized rosin ester type).

If the softening point of the tackifying resin is less than 151 ° C., it is necessary to add a large amount of the emulsion of the tackifying resin in order to obtain sufficient adhesive force, which causes adverse effects such as generation of aggregates. It is not preferable because it comes.

As the emulsifier used for emulsifying the tackifying resin, α-olefin sulfonate, alkyl sulfate, alkyl phenyl sulfate, polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene aralkyl phenyl ether sulfosuccinic acid are used. And anionic emulsifiers such as rosin soap; nonionic emulsifiers such as polyoxyethylene alkylphenyl ether.

The amount of the emulsifier added is not particularly limited, but is usually 1 in terms of solid content relative to 100 parts by weight of the tackifying resin.
It is preferably from 10 to 10 parts by weight, more preferably from 1 to 5 parts by weight. When the amount of the emulsifier added exceeds 10 parts by weight, the water resistance of the resulting water-based pressure-sensitive adhesive decreases, and when it is less than 1 part by weight, the stability of the tackifying resin emulsion during emulsification deteriorates.

The tackifying resin emulsion can be obtained, for example, by the following method: (1) The above-mentioned high softening point tackifying resin having a softening point of 151 ° C. or higher is used in a solvent such as benzene or toluene. After dissolution, the emulsifier and hot water are added, and the mixture is emulsified using a high-pressure emulsifier and then the solvent is removed under reduced pressure. (2) The softening point of the tackifying resin is about 90 ° C. or lower. A small amount of solvent such as benzene or toluene is mixed in, then the emulsifier is kneaded, and then hot water is gradually added to the emulsion to obtain a phase inversion emulsion to remove the solvent under reduced pressure or use as it is. Method (3) A method in which the tackifying resin is heated to a softening point or higher in an autoclave, an emulsifier is kneaded, and hot water is gradually added to perform phase inversion emulsification. What.

The method for producing the water-based pressure-sensitive adhesive composition of the present invention includes, for example, a method of mixing the above (meth) acrylic acid ester-based copolymer emulsion with the above tackifying resin emulsion; There is a method of reacting each monomer which is a constituent component of the (meth) acrylic acid ester-based copolymer in the presence of an emulsion.

The content of the tackifying resin emulsion is 100% by weight of the acrylic ester copolymer emulsion 100.
It is preferably 1 to 10 parts by weight in terms of solid content with respect to parts by weight. If it is less than 1 part by weight, sufficient adhesiveness cannot be imparted, and if it exceeds 10 parts by weight, adverse effects such as generation of agglomerates occur, which is not preferable.

In the water-based pressure-sensitive adhesive composition of the present invention, if necessary, a plasticizer, a tackifier, a thickener, a dispersant, a defoaming agent, a preservative, and a pH used in the pressure-sensitive adhesive. A regulator and the like can be added according to a conventional method.

The water-based pressure-sensitive adhesive composition of the present invention is used, for example, for producing pressure-sensitive adhesive labels and seals,
The obtained adhesive label / seal etc. can be widely used in the fields of printing, packaging, food, medical care, electronics, automobiles and the like.

Such a pressure-sensitive adhesive label / seal is prepared, for example, by applying the water-based pressure-sensitive adhesive composition of the present invention onto release paper, drying it to form an adhesive layer, and then onto a substrate such as paper. It can be obtained by stacking adhesive layers.

[0027]

Since the water-based pressure-sensitive adhesive composition of the present invention contains an emulsion of a tackifying resin having a softening point of 151 ° C. or more, sufficient adhesiveness can be imparted to the obtained water-based pressure-sensitive adhesive. The Tg of the (meth) acrylic acid ester-based copolymer is not designed too low. as a result,
It can be easily peeled from the release paper, and no adhesive residue or scraps are generated during the process of processing the adhesive label / seal.

[0028]

EXAMPLES In order to explain the present invention in more detail, examples will be given below.

The "parts" in the examples and comparative examples mean "parts by weight".

The method for preparing the tackifying resin emulsion used in this example and the comparative example, the method for preparing the adhesive label and the evaluation thereof are shown below.

<Preparation of Tackifying Resin Emulsion> [Tackifying Resin Emulsion (a)] 100 parts of polymerized rosin ester (softening point 160 ° C.) was added to 60 parts of toluene to give 10 parts.
After dissolving at 0 ° C. for about 1 hour, the mixture was cooled to 80 ° C., 3 parts of anionic emulsifier (sodium dodecylbenzene sulfonate) and 160 parts of water were added, and 7
Preliminary emulsification was performed by stirring at 5 ° C for about 1 hour. The preliminary emulsion thus obtained was emulsified by high pressure emulsification at a pressure of 300 kg / cm ² using a high pressure emulsifying machine (manton gaurin company). Next, 200 parts of the above emulsion was charged into a vacuum distillation apparatus, and vacuum distillation was performed for 6 hours under conditions of 50 ° C. and 100 mmHg to obtain a tackifying resin emulsion (a) made of a polymerized rosin ester having a softening point of 160 ° C.

[Tackifying Resin Emulsion (b)] Copolymerized petroleum resin (softening point 16
(B) a tackifying resin emulsion made of a copolymerized petroleum resin having a softening point of 165 ° C. by the same method as the method for preparing the tackifying resin emulsion (a) except that 5 ° C.) was used.
Got

[Tackifying Resin Emulsion (c)] A method similar to the method for preparing the tackifying resin emulsion (a) except that a disproportionated rosin ester (softening point 120 ° C.) was used in place of the polymerized rosin ester. At a softening point of 120
A tackifying resin emulsion (c) consisting of disproportionated rosin ester at 0 ° C was obtained.

<Preparation of pressure-sensitive adhesive label> The water-based pressure-sensitive adhesive composition was applied to a kraft paper-based release paper (craft paper laminated with polyethylene and subjected to silicone release treatment) with a doctor blade to form a film. It was applied so as to have a thickness of 75 μm and dried at 110 ° C. for 2 minutes. The pressure-sensitive adhesive layer on the release paper was overlaid on high quality paper (55 g / m ² ) and
The adhesive label was prepared by curing for 12 hours at 60 ° C and 60% RH. The thickness of the pressure sensitive adhesive layer was 20 μm.

<Evaluation> The obtained adhesive label was evaluated for its adhesive force and the force required for peeling from the release paper (hereinafter referred to as peeling force for the release paper) by the following method.

Adhesive strength: The adhesive layer of the adhesive label is 20
Affixed to the polyethylene film of the adherend under the conditions of ℃ and 60% RH, and apply a 2 kg roller on the adhesive label.
Regarding the test piece obtained by curing for 20 minutes after reciprocating, J
180 ° C peeling force (g / i according to IS Z 0237)
nch, pulling speed 300 mm / min) was measured.

Peeling force for release paper: Adhesive label 10c
Peeling force (g / 10 cm, pulling speed 5000 mm) when peeling m width from kraft paper release paper (180 ° peeling)
/ Min) was measured and used as the peeling force for the release paper. At this time, the presence or absence of adhesive residue was also visually observed.

(Examples 1 to 4) 40 parts of water was charged to a reaction vessel equipped with a thermometer, a stirrer and a nitrogen introducing tube, and charged to 65
The temperature was raised to ℃ and nitrogen substitution was performed. On the other hand, the monomers shown in Tables 1 and 2 were mixed with a molecular weight modifier (n-dodecyl mercaptan) to obtain a mixed monomer. Next, 0.6 part of an anionic emulsifier and 0.8 part of a nonionic emulsifier were dissolved in 30 parts of water, and the above mixed monomer was mixed and stirred to obtain an emulsified monomer. 1% by weight of this emulsified monomer and 0.4 part of ammonium persulfate as a polymerization initiator dissolved in 10 parts of water were charged into the above reaction vessel to start an initial reaction. After the completion of this initial reaction, the remaining emulsified monomer was dropped into the reaction vessel over 6 hours. After completion of the dropping, the mixture was aged for 3 hours and then cooled to terminate the reaction to obtain a (meth) acrylic acid ester-based copolymer emulsion.

To this (meth) acrylic acid ester-based copolymer emulsion, a tackifying resin emulsion of the type shown in Table 2 was mixed in the blending amount shown in Table 2 (parts in the table show the proportion of solid content). According to a conventional method, a thickener, a pH adjuster and the like were added to obtain an aqueous pressure-sensitive adhesive composition.

A pressure-sensitive adhesive label was produced by the above method using the obtained water-based pressure-sensitive adhesive composition, and its adhesive force and peeling force to release paper were evaluated.

Comparative Examples 1 to 8 The same as Example 1 except that the type of the (meth) acrylic acid copolymer emulsion and the type and blending amount of the tackifying resin emulsion were as shown in Table 2. An aqueous pressure-sensitive adhesive composition was obtained, a pressure-sensitive adhesive label was prepared, and its evaluation was performed.

Table 1 shows the types of constituent monomers of the (meth) acrylic acid copolymer emulsions used in the present examples and comparative examples, the compounding amounts thereof, and the Tg of the resulting emulsions.

Table 2 shows Examples 1 to 4 and Comparative Examples 1 to 8.
The amount of the constituent components of the water-based pressure-sensitive adhesive composition and the evaluation of the obtained pressure-sensitive adhesive label are shown.

[0044]

[Table 1]

[0045]

[Table 2]

As shown in Table 2, the water-based pressure-sensitive adhesive compositions of Examples 1 to 4 contained 900 to 950 g / inch.
While showing high adhesive strength, the peeling force against release paper is 3
It is extremely small, from 0 to 33 g / 10 cm. On the other hand, the water-based pressure-sensitive adhesive compositions of Comparative Examples 1 to 6 have a small peeling force with respect to the release paper, but have an adhesive force of 600 to 750 g / in.
There is a shortage of ch. The water-based pressure-sensitive adhesive compositions of Comparative Examples 7 and 8 have a high adhesive force, but have a large peel force of 43 to 45 g / 10 cm to the release paper. Therefore, Example 1
Only the water-based pressure-sensitive adhesive composition of ~ 4 has a high adhesive force, while leaving an adhesive residue in the process of processing an adhesive label / seal,
It is shown that it is suitable for use as a pressure-sensitive adhesive for pressure-sensitive adhesive labels and seals without the occurrence of scraps.

(Examples 5 to 8) 40 parts of water was charged in a reaction vessel equipped with a thermometer, a stirrer and a nitrogen inlet tube, and charged to 65
The temperature was raised to ℃ and nitrogen substitution was performed. On the other hand, the copolymer-constituting monomers shown in Tables 1 and 3 above were mixed with a molecular weight adjusting agent (n-
Dodecyl mercaptan) to prepare a mixed monomer. Next, 0.6 part of an anionic emulsifier and 0.8 part of a nonionic emulsifier were dissolved in 30 parts of water, and the above mixed monomer was mixed and stirred to prepare an emulsified monomer. Furthermore, a tackifying resin emulsion of the type and amount shown in Table 3 was added to this emulsified monomer,
An emulsified monomer containing tackifying resin was prepared. 1% by weight of this tackifying resin-containing emulsified monomer and 0.4 part of a polymerization initiator of ammonium persulfate dissolved in 10 parts of water were charged into the above reaction vessel to start the initial reaction. After the completion of this initial reaction, the remaining tackifying resin-containing emulsified monomer was dropped into the reaction vessel over 6 hours. After completion of dropping, the mixture was aged for 3 hours and then cooled to terminate the reaction to obtain a (meth) acrylic acid ester-based copolymer emulsion containing a tackifying resin.

To the (meth) acrylic acid ester-based copolymer emulsion containing the tackifying resin, a thickener, a pH adjuster and the like were added according to a conventional method to obtain a water-based pressure-sensitive adhesive composition.

Using the obtained water-based pressure-sensitive adhesive composition, a pressure-sensitive adhesive label was prepared by the above-mentioned method, and the adhesive force and the peeling force to release paper were evaluated.

Comparative Examples 9 to 16 Same as Example 1 except that the type and amount of tackifying resin emulsion and the type of (meth) acrylic acid copolymer emulsion were changed as shown in Table 3. Then, an aqueous pressure-sensitive adhesive composition was obtained, a pressure-sensitive adhesive label was prepared, and its evaluation was performed.

[0051]

[Table 3]

As shown in Table 3, the water-based pressure-sensitive adhesive compositions of Examples 5-8 contained 920-970 g / inch.
While showing high adhesive strength, the peeling force against release paper is 3
It is extremely small, 1 to 33 g / 10 cm. On the other hand, the water-based pressure-sensitive adhesive compositions of Comparative Examples 9 to 14 have a small peeling force with respect to the release paper, but have an adhesive force of 600 to 750 g / i.
There is a shortage of nch. The water-based pressure-sensitive adhesive compositions of Comparative Examples 15 and 16 have a high adhesive force, but have a large peel force to the release paper of 43 to 45 g / 10 cm. Therefore, only the water-based pressure-sensitive adhesive compositions of Examples 5 to 8 have high adhesive strength, but do not cause adhesive residue or scraps in the adhesive label / seal processing step to produce adhesive labels / seals. It shows that it is suitable as a pressure-sensitive adhesive.

[0053]

As described above, the water-based pressure-sensitive adhesive composition of the present invention has a high adhesive force and an extremely small peel force with respect to the release paper. Therefore, there is no risk of adhesive residue or scraps in the adhesive label / seal processing step, and it is possible to further improve the production speed thereof, which is particularly suitable as a pressure-sensitive adhesive for adhesive labels / seals. Used for.

Claims (1)

[Claims] 1. A (meth) acrylic acid alkyl ester having an alkyl group with 4 to 14 carbon atoms, an α, β-unsaturated carboxylic acid, and two or more polymerizable double bonds in one molecule. A (meth) acrylic acid ester-based copolymer emulsion having a glass transition temperature of −25 ° C. to −40 ° C. and a softening point of 151.
A water-based pressure-sensitive adhesive composition containing a tackifying resin emulsion having a temperature of not less than 0 ° C.