JPH04298585A - Re-releasing pressure-sensitive adhesive composition capable of transfer coating - Google Patents

Abstract

PURPOSE:To obtain a pressure-sensitive adhesive excellent in re-releasing capacity and in transfer coating by incorporating an isocyanate compound in a synthetic resin emulsion obtained by copolymerizing a mixture of specific vinyl monomers. CONSTITUTION:A pressure-sensitive adhesive composition obtained by mixing a synthetic resin emulsion (A) formed by copolymerizing a vinyl monomer mixture containing a hydroxylated monomer represented by the formula (wherein R1 and R2 are each H or methyl; and n is 2-30) and a 4-12C alkyl (meth)acrylate with 0.1-20wt.% isocyanate compound (based on the solid matter in A), the content of the hydroxylated monomer in the monomer mixture being 2-50wt.%. When the number of carbon atoms of the (meth)acrylate is less than 4, the resulting synthetic resin composition has an inferior viscosity. Further, if the number exceeds 12, its dried file has no adhesiveness and hence the composition cannot be used.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is an adhesive that is useful as an adhesive for adhesive sheets or adhesive tapes using paper or plastic films as a support, and has excellent removability and is also excellent for transfer coating. The present invention relates to a drug composition. It is especially effective for paper base materials, and it increases the keying power (
It also has excellent anchorage ability.

0002

[Prior Art] Removable adhesives include adhesive sheets with paper or plastic film as a support, or adhesive tapes that can be easily peeled off when attached to various adherends. It is required that the adhesive does not remain on the adherend. Conventionally, solvent-based resins have been the mainstream for such removable pressure-sensitive adhesives, and emulsion-based resins have rarely been used because they are difficult to transfer coat, especially to paper. Although emulsion resins can be manufactured by directly coating them on paper, they have only been used for limited purposes due to problems such as paper shrinkage, wrinkling, and curling due to the absorption of water into the paper.

[0003] In order to enable transfer coating of emulsion resins to paper, attempts have been made to add cationic surfactants or plasticizers to emulsion resins, but these All adhesives remained on the adherend, making them extremely unsuitable as removable adhesives. In addition, attempts have been made to raise the glass transition temperature of the resin and to crosslink the particles of the synthetic resin emulsion in order to lower the adhesive strength to the adherend, but these methods all have a negative anchoring force to the paper. It is weak, and in extreme cases, the adhesive may transfer to the entire surface of the adherend during peeling, making it unsuitable as a removable adhesive.

0004

[Problems to be Solved by the Invention] As a result of intensive research to solve the above problems, the present inventors have found that transfer coating is possible, has excellent anchoring power to paper, and has an adhesive that can be applied to adherends. The inventors have discovered that a removable pressure-sensitive adhesive that leaves no residue or stains and can be easily peeled off upon peeling has been obtained, leading to the present invention.

[0005]

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

[0006]

[Formula, R1 and R2 are hydrogen atoms or methyl groups, n is 2
Copolymerization of a vinyl monomer mixture containing a hydroxyl group-containing monomer represented by (number of 1 to 30), and in which the content of the hydroxyl group-containing monomer in the monomer mixture is 2 to 50% by weight. Synthetic resin emulsion obtained by
0.1 of isocyanate compounds based on solid content)
The present invention relates to a removable pressure-sensitive adhesive composition which can be transferred and coated, and which contains up to 20% by weight.

The vinyl monomer mixture used to synthesize the synthetic resin emulsion contains the above-mentioned (meth)acrylic acid alkyl ester and the hydroxyl group-containing monomer as essential components, but if necessary, other unsaturated monomers may also be added. May contain. The (meth)acrylic acid alkyl ester used in the present invention is a (meth)acrylic acid alkyl ester in which the alkyl group has 4 to 12 carbon atoms. If the number of carbon atoms in the (meth)acrylic acid alkyl ester is less than 4, the resulting synthetic resin emulsion will have a disadvantage of poor viscosity, and if it exceeds 12, the dried film will lack adhesive strength and cannot be used. The number of carbon atoms in the alkyl group is 4
-12 (meth)alkyl esters include, for example,
Butyl acrylate, butyl methacrylate, acrylic acid-
Examples include 2-ethylhexyl, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, octyl acrylate, octyl methacrylate, etc.
These may be used alone or in combination of two or more. The (meth)acrylic acid alkyl ester whose alkyl group has 4 to 12 carbon atoms is 50 to 12 carbon atoms in the vinyl monomer mixture.
98% by weight, preferably 70-95% by weight.

In the present invention, in addition to the (meth)acrylic acid alkyl ester whose alkyl group has 4 to 12 carbon atoms, other unsaturated monomers copolymerizable with the (meth)acrylic 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 Acid, crotonic acid, arylsulfonic acid, sodium styrene sulfonate, sodium methacrylate sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, N-methylol (meth)acrylamide, (meth)acrylamide, (meth)acryl Glycidyl acid, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, (
2-methoxyethyl meth)acrylate, 2-ethoxyethyl (meth)acrylate, etc. can also 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 whose alkyl group has 4 to 12 carbon atoms.

Further, in the present invention, the hydroxyl group-containing monomer used together with the above (meth)acrylic acid alkyl ester has the general formula (1).

[Formula 3] (R1 and R2 are hydrogen atoms or methyl groups, n is 2
~30) It is expressed as follows.

Examples of the above-mentioned hydroxyl group-containing monomers include acrylic esters of polyethylene glycol, methacrylic esters of polyethylene glycol, acrylic esters of polypropylene glycol, and methacrylic esters 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.
It is. If the amount of the hydroxyl group-containing monomer used is less than 2% by weight, crosslinking with the isocyanate compound will be insufficient and the cohesive force necessary for removability will not be obtained, which is not preferable. In addition, if the amount of the hydroxyl group-containing monomer used exceeds 50% by weight, the crosslinking with the isocyanate compound will be too high and the cohesive force will become too high, resulting in a loss of adhesive strength, or the influence of the hydroxyl group-containing monomer will be too strong. Adhesive strength is low and undesirable.

[0011] The synthetic resin emulsion in the present invention is
The vinyl monomer mixture is obtained by emulsion polymerization according to a conventional method. That is, using an emulsifier, the vinyl monomer mixture is subjected to emulsion polymerization using a polymerization initiator in an aqueous layer. Examples of emulsifiers include anionic surfactants such as sodium sulfate ester of higher alcohols and sodium alkylbenzenesulfonate, nonionic surfactants such as polyoxyethylene nonylphenyl ether and polyoxyethylene lauryl ester, or the following general formula: (II), (I
A reactive emulsifier represented by II), (IV), (V), (VI),

0012

[Formula 4] (However, R1 is a hydrocarbon group that may have a substituent,
R2 represents hydrogen or a methyl group, and M represents Na or NH4. )

[0013]

[Chemical formula 5] (However, R1 is a hydrocarbon group that may have a substituent,
R2 represents hydrogen or a methyl group, and M represents Na or NH4. )

[0014]

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

[0015]

[Formula 7] (However, R1 is an alkyl group, alkenyl group, or aralkyl group having 4 to 18 carbon atoms, R2 is hydrogen or an alkyl group, alkenyl group, or aralkyl group having 4 to 18 carbon atoms, and A is a carbon number 2 -4 alkylene group or substituted alkylene group, n is a number from 2 to 200, and M is an alkali metal atom, NH4, or an alkanolamine residue.)

[0016]

[Chemical formula 8] (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. Two or more of these emulsifiers may be used in combination.

As the polymerization initiator, those commonly used in the emulsion polymerization of alkyl (meth)acrylic esters, such as ammonium persulfate, potassium persulfate, hydrogen peroxide solution, and t-butyl hydroperoxide. , permanganate, etc., or these with acidic sodium sulfite, hypo,
Redox catalysts that use reducing agents such as Rongalit, thiourea, organic oxysalts, and ferrous sulfate can be used as they are. Further, during emulsion polymerization, a neutralizing agent, an antifoaming agent, a stabilizer, a preservative, etc. may be added as necessary.

The isocyanate compound used in the present invention may be any compound having at least two isocyanate groups in the molecule, such as tolylene diisocyanate (TDI), 4,4'-diphenymethane diisocyanate (MDI), etc. ), crude MDI, xylylene diisocyanate (XDI), naphthylene-1,5-
Diisocyanate, hexamethylene diisocyanate (
HDI), hydrogenated TDI (HTDI), hydrogenated MDI (
HMDI), isophorone diisocyanate (IPDI)
, lysine diisocyanate (LDI), isopropylidene bis-4-cyclohexyl isocyanate, and other compounds;
A polymer thereof can be used. Moreover, blocked products of the above-mentioned isocyanate compounds can also be used. Two or more of these isocyanate compounds may be used in combination.

The blending ratio of the isocyanate compound is 0.1 to 2 in the synthetic resin emulsion (in terms of solid content).
0% polymerization, preferably 0.2 to 10% by weight. If the blending ratio of the isocyanate compound is less than 0.1% by weight based on the synthetic resin emulsion (in terms of solid content), crosslinking will be insufficient and the cohesive force necessary for removability will not be obtained, so it is preferable. do not have. Further, if the blending ratio of the isocyanate compound exceeds 20% by weight, the cohesive force becomes too high and the adhesive force becomes low, which is not preferable.

[0020] The removable pressure-sensitive adhesive composition of the present invention capable of transfer coating may optionally contain a plasticizer such as dibutyl phthalate or dioctyl phthalate, a tackifier such as rosin, terpene phenol, or petroleum resin, and talc. , fillers such as calcium carbonate, titanium white, zinc white, and additives such as thickeners may be added.

[0021]

[Examples] The present invention will be explained below with reference to Examples. In addition, parts and % in the examples mean polymerized parts and 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, methacrylic ester of polyethylene glycol (in general formula (1),
n is 7 to 9) 40 parts, a pre-emulsified emulsion of 10 parts of sodium dodecylbenzenesulfonate and 240 parts of water and 3%
50 parts of an aqueous potassium persulfate solution was simultaneously added dropwise over 3 hours. After the dropwise addition was completed, the reaction was continued for an additional hour. After the reaction was completed, the flask was cooled. The pH of the resulting synthetic resin emulsion was adjusted to 8 with 28% aqueous ammonia, and then the viscosity was adjusted to 10,000 using a high molecular weight ether nonionic surfactant and a polycarboxylic acid thickener.
cps to obtain a synthetic resin emulsion with a solid content of 55%. 3% of a self-emulsifying type of hexamethylene diisocyanate was blended into the obtained synthetic resin emulsion.

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

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

[Example 4] In Example 1, acrylic ester of polyethylene glycol (general formula (1)) was used instead of methacrylic ester of polyethylene glycol.
The procedure 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 same procedure as in Example 1 was repeated except that 80 parts of polyethylene glycol methacrylate was used.

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

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

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

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

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

[0033] The synthetic resin emulsions obtained in the above Examples and Comparative Examples were deposited on release paper in an amount of 25 g/m2 (
After drying at a temperature of 110° C. for 1 minute, it was transferred to high-quality paper with a basis weight of 55 g/m 2 . This adhesive sheet was evaluated for three adhesive properties, namely adhesive strength, tack, and holding power, and the state of contamination of the stainless steel plate was also evaluated. The results are shown in Table 1.

[0034]

[Table 1]

[Test method] (Adhesive strength) The adhesive sheet was pressure-bonded to a 25 mm wide stainless steel plate at 20° C. x 65% RH, and after 20 minutes, it was peeled off in a 180° direction at a tensile speed of 300 mm/min. The force required was measured and expressed in grams. (ball tuck) J. According to Dom method, 20℃ x 65%
At RH, a steel ball is rolled on a 10cm adhesive sheet on a 30° slope, and the largest ball that comes to rest, ball No. It was shown in (Holding force) A 25 mm x 25 mm portion of the adhesive sheet was pressed onto a stainless steel plate, a 1 kg load was applied at a temperature of 20° C., and the time until the load was dropped was measured and expressed in minutes. (Anchorability) Cut the sample into 25mm x 200mm, SU
One cycle consists of lightly stacking the sample on an S-304 plate, peeling it off by 50 mm in a 90° direction, and stacking it again. After 20 cycles, the anchoring properties are observed. Evaluation of anchoring properties ○…A state in which the adhesive does not peel off from the base material (high-quality paper) △…Intermediate state (a state in which the adhesive partially peels off from the base material (high-quality paper)) ×…A state in which the adhesive does not peel off from the base material (high-quality paper) ) After peeling off the sample (contaminated state) from the SUS-304 plate
Observe cloudiness and adhesive residue on the S-304 board. Evaluation of contamination state ○... When the sample is peeled off from the SUS, no adhesive is attached to the SUS △... When the sample is peeled off from the SUS, some adhesive is attached to the SUS ×... When the sample is removed from the SUS Most of it is still attached to the SUS when removed.

[0036]

Effects of the Invention The removable pressure-sensitive adhesive composition that can be transferred and coated according to the present invention is transfer-coated, has excellent anchoring power to paper, and prevents adhesive residue on adherends. No pollution,
Easy to peel off when peeling.

Claims (1)

[Claims] Claim 1: A (meth)acrylic acid alkyl ester in which the alkyl group has 4 to 12 carbon atoms and the general formula (1) [Formula 1]
] (In the formula, R1 and R2 are hydrogen atoms or methyl groups, and n is 2
Copolymerization of a vinyl monomer mixture containing a hydroxyl group-containing monomer represented by (number of 1 to 30), and in which the content of the hydroxyl group-containing monomer in the monomer mixture is 2 to 50% by weight. Synthetic resin emulsion obtained by
0.1 of isocyanate compounds based on solid content)
A removable pressure-sensitive adhesive composition capable of transfer coating, containing ~20% by weight.