JPH0819395B2 - Removable adhesive composition capable of transfer coating - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a pressure-sensitive adhesive which is useful as a pressure-sensitive adhesive for a pressure-sensitive adhesive sheet or pressure-sensitive adhesive tape having a paper or plastic film as a support, and has extremely excellent removability and at the same time excellent transfer coating Agent composition. It is especially effective for paper base materials and has excellent keying force (anchoring force) to paper.

[0002]

2. Description of the Related Art Removable pressure-sensitive adhesives can be easily peeled when a pressure-sensitive adhesive sheet having a paper or plastic film as a support or a pressure-sensitive adhesive tape is attached to various adherends and peeled off. It is required that the adhesive does not remain on the adherend. Conventionally, solvent-based resins have been the mainstream for such re-peelable pressure-sensitive adhesives, and emulsion-based resins have hardly been used because transfer coating on paper is particularly difficult. Emulsion-based resins can also be produced by direct coating on paper, but they have been used only for limited applications because of problems such as paper shrinkage, wrinkling, and curling due to absorption of moisture into the paper.

In order to enable transfer coating of an emulsion resin onto paper, it has been attempted to add a cationic surfactant or a plasticizer to the emulsion resin. The pressure sensitive adhesive remained on all adherends and was extremely unsuitable as a re-peelable pressure sensitive adhesive. Further, in order to reduce the adhesive strength to the adherend, methods of increasing the glass transition temperature of the resin and crosslinking the inside of the particles of the synthetic resin emulsion have been tried, but all of them have an anchoring force for paper. It was weak and, in the extreme case, the adhesive may migrate to the entire surface of the adherend during peeling, and it was unsuitable as a removable adhesive.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies aimed at solving the above problems, the present inventors have found that transfer coating is possible, excellent anchoring power to paper, and adhesive to an adherend. The present invention has been accomplished by finding that a removable pressure-sensitive adhesive can be easily peeled at the time of peeling without any residue or contamination.

[0005]

[Means for Solving the Problems] That is, the present invention provides a (meth) acrylic acid alkyl ester having an alkyl group with 4 to 12 carbon atoms and a general formula (1).

[0006]

Embedded image (In the formula, R ₁ and R ₂ are hydrogen atoms or methyl groups, and n is 2 to
A vinyl-based monomer mixture containing a hydroxyl-containing monomer represented by the formula (1), wherein the content of the hydroxyl-containing monomer in the monomer mixture is 2 to 50% by weight. An isocyanate compound was added to the synthetic resin emulsion (solid content conversion) obtained by
The present invention relates to a re-peelable pressure-sensitive adhesive composition which is blended in an amount of 1 to 20% by weight and which can be transfer coated.

The vinyl-based monomer mixture used for synthesizing the synthetic resin emulsion contains the above-mentioned (meth) acrylic acid alkyl ester and a hydroxyl group-containing monomer as essential components, but other unsaturated monomers may be added as necessary. May be included. The (meth) acrylic acid alkyl ester used in the present invention is a (meth) acrylic acid alkyl ester having an alkyl group with 4 to 12 carbon atoms. If the carbon number of the (meth) acrylic acid alkyl ester is less than 4, there is a drawback that the viscosity of the obtained synthetic resin emulsion is inferior. The number of carbon atoms in the alkyl group is 4
As the (meth) alkyl ester of ~ 12, for example,
Butyl acrylate, butyl methacrylate, acrylic acid-
2-ethylhexyl, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, octyl acrylate, octyl methacrylate and the like,
You may use these 1 type or in mixture of 2 or more types. The (meth) acrylic acid alkyl ester having an alkyl group with 4 to 12 carbon atoms is 50 in the vinyl-based monomer mixture.
~ 98 wt%, preferably 70-95 wt%.

In the present invention, in addition to the (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms, other unsaturated monomers copolymerizable with the (meth) acrylic acid ester, such as ( (Meth) methyl acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, styrene, vinyl acetate, vinyl propionate, vinyl methyl ether, vinylpyrrolidone, vinyl chloride, butadiene, acrylonitrile, (meth) acrylic acid, itaconic acid, maleic anhydride, Maleic acid, crotonic acid,
Aryl sulfonic acid, sodium styrene sulfonate, sodium methacrylic sulfonate, 2-acrylamido-2-
Methyl propane sulfonic acid, N-methylol (meth) acrylic amide, (meth) acrylic amide, (meth)
Glycidyl acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate,
2-Methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate and the like can be used in combination.
The amount of the other copolymerizable unsaturated monomer used is 50% by weight or less of the amount of the (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms.

In the present invention, the hydroxyl group-containing monomer used together with the (meth) acrylic acid alkyl ester is represented by the general formula (1)

Embedded image (In the formula, R ₁ and R ₂ are hydrogen atoms or methyl groups, and n is 2 to
30).

Examples of the hydroxyl group-containing monomer include acrylic acid ester of polyethylene glycol, methacrylic acid ester of polyethylene glycol, acrylic acid ester of polypropylene glycol, and methacrylic acid ester of polypropylene glycol. The amount of the hydroxyl group-containing monomer used is 2 to 50% by weight, preferably 5 to 30% by weight in the vinyl monomer mixture. When the amount of the hydroxyl group-containing monomer used is less than 2% by weight, the crosslinking with the isocyanate compound becomes insufficient and the cohesive force required for removability cannot be obtained, which is not preferable. Also, the amount of hydroxyl group-containing monomer used is 50% by weight.
If it exceeds, the crosslinking with the isocyanate-based compound is too sufficient and the cohesive force becomes too high, the adhesive force is lost, or the influence of the hydroxyl group-containing monomer is too strong, and the adhesive force is small, which is not preferable.

The synthetic resin emulsion in the present invention is
The vinyl-based monomer mixture can be obtained by emulsion polymerization according to a conventional method. That is, the emulsifier is used to emulsion-polymerize the vinyl-based monomer mixture in a water layer with a polymerization initiator. As the emulsifier, anionic surfactants such as sodium sulfate ester of higher alcohol and sodium alkylbenzene sulfonate, nonionic surfactants such as polyoxyethylene nonylphenyl ether and polyoxyethylene lauryl ester, or the following general formula (II), (III), (I
V), (V), (VI) represented by a reactive emulsifier,

[0012]

[Chemical 4] (However, R ₁ is a hydrocarbon group which may have a substituent,
R ₂ is hydrogen or a methyl group, and M is Na or NH ₄ . )

[0013]

Embedded image (However, R ₁ is a hydrocarbon group which may have a substituent,
R ₂ is hydrogen or a methyl group, and M is Na or NH ₄ . )

[0014]

[Chemical 6] (However, A is an alkylene group having 2 to 4 carbon atoms, m is a number from 0 to 100, and X is hydrogen or nonion, or an anionic hydrophilic group.)

[0015]

[Chemical 7] (However, R ₁ is an alkyl group, alkenyl group, or aralkyl group having 4 to 18 carbon atoms, R ₂ is hydrogen or an alkyl group, alkenyl group, or aralkyl group having 4 to 18 carbon atoms, and A is 2 to 4 carbon atoms. Alkylene group or substituted alkylene group, n is a number from 2 to 200, and M is an alkali metal atom, NH ₄ , or an alkanolamine residue.)

[0016]

Embedded image (However, A is an alkylene group having 2 to 4 carbon atoms, and n
Is a number from 0 to 100. ) Etc. can be used. You may use these emulsifiers in mixture of 2 or more types.

As the polymerization initiator, those generally used in emulsion polymerization of (meth) acrylic acid alkyl ester, for example, ammonium persulfate, potassium persulfate, hydrogen peroxide solution, t-butyl hydroperoxide. , Permanganate, etc., or acidic sodium sulfite, hypo,
A redox catalyst that uses a reducing agent such as Rongalit, thiourea, an organic oxy salt, and ferrous sulfate together can be used as it is. In addition, in the emulsion polymerization, a neutralizing agent, a defoaming agent, a stabilizer, a preservative and the like may be added if necessary.

The isocyanate compound used in the present invention may be any compound having at least two isocyanate groups in the molecule. For example, tolylene diisocyanate (TDI), 4.4'-diphenylmethane diisocyanate (MDI). ), Crude MDI, xylylene diisocyanate (XDI), naphthylene-1,5-
Diisocyanate, hexamethylene diisocyanate (HDI), hydrogenated TDI (HTDI), hydrogenated MDI
(HMDI), isophorone diisocyanate (IPD
Compounds such as I), lysine diisocyanate (LDI), and isopropylidene bis-4-cyclohexyl isocyanate, and polymers thereof can be used. In addition, blocked products of the above isocyanate compounds can also be used. You may use these isocyanate type compounds in mixture of 2 or more types.

The mixing ratio of the isocyanate compound is 0.1 to 2 with respect to the synthetic resin emulsion (solid content conversion).
It is 0% by weight, and preferably 0.2 to 10% by weight. When the compounding ratio of the isocyanate compound is less than 0.1% by weight based on the synthetic resin emulsion (solid content conversion), the crosslinking is insufficient and the cohesive force required for removability cannot be obtained, which is preferable. Absent. Further, when the compounding ratio of the isocyanate compound exceeds 20% by weight, the cohesive force becomes too high and the adhesive force becomes small, which is not preferable.

The removable transferable pressure-sensitive adhesive composition of the present invention includes, if necessary, a plasticizer such as dibutyl phthalate and dioctyl phthalate, a tackifier such as rosin, terpene phenol and petroleum resin, and talc. , Calcium carbonate, titanium white, zinc white, and the like, and additives such as a thickener may be added and used.

[0021]

The present invention will be described below with reference to examples. The parts and% in the examples mean polymerized parts and% by weight, unless otherwise specified.

Example 1 150 parts of water was placed in a 1-liter four-necked flask and heated to 80 ° C. Next, 510 parts of 2-ethylhexyl acrylate and methacrylic acid ester of polyethylene glycol (in the general formula (1),
n is 7 to 9) 40 parts, an emulsion obtained by previously emulsifying 10 parts of sodium dodecylbenzenesulfonate and 240 parts of water, and 3%
50 parts of potassium persulfate aqueous solution of was added dropwise over 3 hours at the same time. After the dropping was completed, the reaction was further performed for 1 hour. After the reaction was completed, the flask was cooled. The pH of the obtained synthetic resin emulsion was adjusted to 8 with 28% ammonia water, and then the viscosity was 10,000 with a high molecular weight ether type nonionic surfactant and a polycarboxylic acid type thickener.
It was adjusted to cps to obtain a synthetic resin emulsion having a solid content of 55%. 3% of a self-emulsifying type of hexamethylene diisocyanate was blended with the obtained synthetic resin emulsion.

Example 2 In Example 1, acrylic acid-2 was used.
The procedure was exactly the same, except that the same amount of butyl acrylate was used instead of ethylhexyl.

Example 3 In Example 1, acrylic acid-2 was used.
The procedure was exactly the same, except that the same amount of octyl acrylate was used instead of ethylhexyl.

Example 4 In Example 1, instead of the methacrylic acid ester of polyethylene glycol, an acrylic acid ester of polyethylene glycol (general formula (1)
Was carried out in exactly the same manner except that n was 7 to 9).

[Example 5] The same procedure as in Example 1 was repeated except that the self-emulsifying type of hexamethylene diisocyanate was changed to 6%.

Example 6 The procedure of Example 1 was repeated, except that the amount of methacrylic acid ester of polyethylene glycol was changed to 80 parts.

[Comparative Example 1] The same procedure as in Example 1 was repeated except that 2-hydroxyethyl methacrylate was used instead of the methacrylic acid ester of polyethylene glycol.

[Comparative Example 2] The same procedure as in Example 1 was repeated except that methacrylic acid was used instead of the methacrylic acid ester of polyethylene glycol.

[Comparative Example 3] In Example 1, acrylic acid 2-
The same procedure was carried out except that 220 parts of ethylhexyl and 330 parts of methacrylic acid ester of polyethylene glycol were used. In this case, gelation occurred during the reaction.

[Comparative Example 4] The procedure of Example 1 was repeated, except that diphenylmethane-bis-4,4'-NN ethylene urea was used instead of the self-emulsifying type of hexamethylene diisocyanate.

[Comparative Example 5] The procedure of Example 1 was repeated, except that the self-emulsifying type of hexamethylene diisocyanate was not used.

The synthetic resin emulsions obtained in the above-mentioned Examples and Comparative Examples were deposited on a release paper in an amount of 25 g / m 2.
^{It was} applied so that it would be ² (dry), dried at a temperature of 110 ° C. for 1 minute, and then transferred to a high-quality paper having a basis weight of 55 g / m ² . With respect to this pressure-sensitive adhesive sheet, the three physical properties of the pressure-sensitive adhesive, that is, the pressure-sensitive adhesive strength, the tackiness, and the holding power were evaluated, and the contamination state on the stainless steel plate was evaluated. The results are shown in Table 1.

[0034]

[Table 1]

[Test Method] (Adhesion) The pressure-sensitive adhesive sheet was pressure-bonded to a stainless steel plate having a width of 25 mm at 20 ° C. and 65% RH, and after 20 minutes, peeled in a 180 ° direction at a pulling speed of 300 mm / min. The force sometimes required was measured and displayed in g. (Ball tack) J. According to Dom method, 20 ℃ × 65%
In RH, a steel ball is rolled on a 10 cm pressure-sensitive adhesive sheet with a slope of 30 °, and the largest ball that is stationary reaches No. Indicated by. (Holding power) A 25 mm × 25 mm portion of the pressure-sensitive adhesive sheet was pressure-bonded to a stainless steel plate, a load of 1 kg was applied at a temperature of 20 ° C., and the time until the load dropped was measured and displayed in minutes. (Anchoring property) Cut the sample into 25 mm x 200 mm and
Lightly stacking on the S-304 plate, peeling 50 mm in the direction of 90 °, and stacking again for 1 cycle, and anchoring property after 20 cycles is observed. Evaluation of anchorage ○: Adhesive cannot be peeled from base material (quality paper) △… Intermediate state (adhesive is partially peeled from base material (quality paper)) ×… Adhesive is base material (quality paper) )) Is completely peeled off (contamination state). After the sample is peeled from the SUS-304 plate, cloudiness and adhesive residue on the SUS-304 plate are observed. Evaluation of Contamination State ◯: When the sample was peeled from SUS, no adhesive was attached to SUS △ ... When the sample was peeled from SUS, when it was partially attached to SUS × ... Sample from SUS Most of it adheres to the SUS when peeled off

[0036]

EFFECT OF THE INVENTION The removable transferable pressure-sensitive adhesive composition obtained by the present invention can be transfer-coated, has excellent anchoring power to paper, and has no adhesive residue on an adherend. No pollution,
Can be easily peeled off.

Continuation of front page (56) Reference JP-A-3-54285 (JP, A) JP-A-56-149467 (JP, A) JP-A-2-617 (JP, A) JP-A-62-104824 (JP , A) JP 61-268711 (JP, A) JP 57-51773 (JP, A) JP 4-198210 (JP, A)

Claims (1)

[Claims] 1. A (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms and a compound represented by the general formula (1): (In the formula, R ₁ and R ₂ are hydrogen atoms or methyl groups, and n is 2 to
A vinyl-based monomer mixture containing a hydroxyl-containing monomer represented by the formula (1), wherein the content of the hydroxyl-containing monomer in the monomer mixture is 2 to 50% by weight. An isocyanate compound was added to the synthetic resin emulsion (solid content conversion) obtained by
A re-peelable pressure-sensitive adhesive composition capable of transfer coating, containing 1 to 20% by weight.