JPH08225774A - Removable pressure-sensitive adhesive sheet - Google Patents

Abstract

PURPOSE: To obtain a removable and pressure-sensitive adhesive sheet which causes no loosening or removing, while it is applied to the substrate and shows excellent removability without staining of the substrate surface caused by breakage of the surface substrate or residual adhesive, when it is peeled off. CONSTITUTION: In a removable pressure-sensitive adhesive sheet comprising a releasing sheet, a pressure-sensitive adhesive layer and a surface substrate (laminated in this order), as an pressure-sensitive adhesive is used an adhesive which is obtained by combining an aqueous emulsion, as a main component, prepared by emulsion polymerization of monomers (a) through (d) described below with a polyglycidyl compound bearing 2 or more epoxy group so that the amount of the epoxy group becomes 0.5-2 equivalents per equivalent of the carboxyl groups in the copolymer where monomer (a) is 80-99wt.% of a (meth)acrylate ester having an alkyl of 8-12 carbon atom, monomer (b) is 0.3-10wt.% of (meth)acrylonitrile, monomer (c) is 0.1-5wt.% of α-unsaturated carboxylic acid and monomer (d) is 0-5wt.% of other copolymerizable monomers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a removable pressure-sensitive adhesive sheet used for price tags, labels for process control, etc., and particularly suitable for use as index labels for video cassettes, audio cassettes, floppy disks, etc. Regarding the seat.

[0002]

2. Description of the Related Art Adhesive sheets are used for labels, stickers, stickers, etc.
It is used after being processed into patches. The general structure of the pressure-sensitive adhesive sheet is one in which a pressure-sensitive adhesive layer is formed between a surface base material and a release sheet, and paper, film, metal foil or the like is used for the surface base material, and the release sheet is glassine. High-density base paper such as paper, clay-coated paper, polyethylene laminated base paper, etc. coated with a release agent such as a silicone compound or a fluorine compound is used. As the pressure-sensitive adhesive, various types of rubber-based, acrylic-based, vinyl ether-based emulsion, solvent or solventless pressure-sensitive adhesives are used. Such an adhesive sheet achieves the purpose of display, depending on the intended use of the product, and a permanent adhesive type that is permanently used while being attached to the adherend after being adhered to the adherend such as a product. There is a re-peeling type that is peeled off and discarded after doing. This latter type is a removable pressure sensitive adhesive sheet.

[0003]

Removable pressure-sensitive adhesive sheets are used for price tags whose prices are often replaced and labels for process control, but when those labels are finally peeled off, they are torn. It can be easily peeled off without leaving part of the surface substrate or adhesive on the adherend that is the product, that is, it has excellent removability that does not cause contamination of the adherend that damages the appearance of the adherend. Is basically required. It should be noted that the fact that the pressure-sensitive adhesive remains on the adherend in this way is simply referred to as adhesive residue. Further, there is an index label used for a video cassette, an audio cassette, a jacket of a floppy disk, etc. as a kind of the removable adhesive sheet.
With these labels, when new information is recorded on the tape or disc, the old label is peeled off and discarded, and a new label is applied. You need to have it. Furthermore, these index labels are liable to be lifted or flipped due to temperature changes in equipment such as video cassette decks, and such a phenomenon is directly related to the cause of mechanical failure such as cassette ejection failure. It is a big problem because it leads to.

The present invention solves the above problems, and when peeled off from an adherend, the appearance of the adherend is not spoiled by the breakage of the surface base material or the adhesive residue, and the excellent recontamination does not occur. An object of the present invention is to obtain a re-peelable pressure-sensitive adhesive sheet which exhibits releasability, floats when adhered to an adherend, and has no curl.

[0005]

[Means for Solving the Problems] Removable viscosity according to the present invention
The adhesive sheet is made by laminating a release sheet, an adhesive layer and a surface base material.
The removable adhesive sheet that has the adhesive layer
The following adhesives (a), (b), (c)
Milk the monomer composition consisting of (d) added as needed.
Polystyrene-equivalent number average molecular weight
Is 0.1 × 10 ^Four5.0 × 10^FourIs less than
And polystyrene equivalent weight average molecular weight and polystyrene
The number average molecular weight ratio is 40 to 800, and the average particle size is
100 ~ 500nm, glass transition temperature below -50 ° C
The main component is an aqueous emulsion of a copolymer,
0.5 equivalent of epoxy groups per equivalent of carboxyl groups
~ 2 equivalents with two or more epoxy groups.
It is special to use an adhesive containing a glycidyl compound.
To collect. (A) (Meth) acryl having an alkyl group having 8 to 12 carbon atoms
80-99% by weight of alkyl acid ester monomer (b) 0.3-10% by weight of (meth) acrylonitrile (c) 0.1-5% by weight of α, β-unsaturated carboxylic acid (d) 0 to 5% by weight of other copolymerizable monomers The number of epoxy groups in the polyglycidyl compound is 2 to 4
Is preferable. It is also preferable that the adhesive further contains a pigment.
Good.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors conducted the following studies and analyzes in order to solve the problems described above. Usually, a removable pressure-sensitive adhesive sheet is manufactured by applying a pressure-sensitive adhesive to a release paper, drying it, and then transferring the pressure-sensitive adhesive layer obtained by laminating the pressure-sensitive adhesive layer to a surface base material and applying pressure. The removable pressure-sensitive adhesive sheet is processed by die cutting or the like to form a removable pressure-sensitive adhesive label. In such a label, when the anchoring property of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer to the surface substrate is poor, the pressure-sensitive adhesive does not peel off from the adherend when peeled off from the adherend, and only the surface substrate peels off, leaving an adhesive residue. appear. On the contrary, if the anchoring property of the pressure-sensitive adhesive to the surface base material is too high, the opacity of the label lowers, so-called bleeding occurs, and the appearance of the surface base material is impaired. The bleeding is a state that can occur from the time when the pressure-sensitive adhesive layer comes into contact with the surface base material, regardless of whether or not the bleeding is in a state of being adhered to the adherend. On the other hand, when the adhesive strength of the pressure-sensitive adhesive to the adherend is reduced in order to improve the removability of the label, the adhesive strength with the surface base material is also reduced to cause adhesive residue, or the label floats due to temperature change, etc.
Causes curling. On the other hand, if the adhesive strength is excessively large, when paper is used as the surface base material, there is a possibility that paper breakage or the like may occur. As described above, in the removable pressure-sensitive adhesive label, the adhesive force of the pressure-sensitive adhesive to the adherend, the removability of the label from the adherend, and the appropriate penetrability of the pressure-sensitive adhesive to the surface substrate should be well balanced. Is required. The present inventors have repeated the above trials and various trials on the analysis, and when attached to an adherend, the label does not float or turn over, and has excellent removability at the time of peeling, and by bleeding. The present invention has been accomplished by finding a releasable pressure-sensitive adhesive sheet that is easy to manufacture without damaging the surface base material.

The expression of (meth) acrylic acid used in the present invention means acrylic acid and / or methacrylic acid, and the expression of (meth) acrylonitrile and the like is also the same. Specific examples of the (meth) acrylic acid alkyl ester monomer having 8 to 12 carbon atoms of the alkyl group used as the component (a) in the present invention include 2-ethylhexyl acrylate and 2-ethylhexyl methacrylate. Examples thereof include n-octyl acrylate, n-octyl methacrylate, isononyl acrylate, isononyl methacrylate, lauryl acrylate, and lauryl methacrylate. Preferred are 2-ethylhexyl acrylate, isononyl acrylate, and lauryl methacrylate.
Also, these (meth) acrylic acid esters may be used alone or 2
Combinations of more than one type can also be used.

Alkyl group having 8 to 12 carbon atoms (meta)
The amount of the acrylic acid alkyl ester monomer used is 80 to 99% by weight, preferably 8% by weight based on the total weight of the monomer mixture.
It is 5 to 99% by weight, more preferably 90 to 98% by weight. If it is less than 80% by weight, the adhesive force of the obtained adhesive to the adherend is too weak, causing problems such as label floating and curling. On the other hand, when it exceeds 99%, the adhesive force of the obtained adhesive to the adherend is too strong and paper tear occurs, and a part of the paper or the like remains attached to the adherend and the adherend is contaminated. Problem arises.

When the (meth) acrylic acid alkyl ester monomer having a carbon number other than 8 to 12 is used in an amount of 80 to 99% by weight based on the total weight of the monomer mixture, for example, butyl acrylate is used. In this case, the anchoring property of the pressure-sensitive adhesive to the surface base material is too high to impair the appearance of the surface base material, or the adhesive strength to the adherend is too strong, resulting in poor removability.

In the present invention, by using the (meth) acrylonitrile represented as the component (b) in a specific ratio, an adhesive which does not cause contamination of the adherend can be obtained. The amount of (meth) acrylonitrile used is 0.3
10 to 10% by weight, preferably 0.5 to 7% by weight, more preferably 0.7 to 5% by weight. Outside this range, the effect of preventing contamination of the adherend is small, and the adherend is likely to be contaminated due to paper breakage or adhesive residue.

Specific examples of the α, β-unsaturated carboxylic acid represented by the component (c) used in the present invention include acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. Acrylic acid and methacrylic acid are preferred. Also, these α and β
-Unsaturated carboxylic acid can be used individually or in combination of 2 or more types. The amount of the α, β-unsaturated carboxylic acid used is particularly important and is 0.1 to 0.1% based on the total weight of the monomer mixture.
It is 5% by weight, preferably 0.2 to 4% by weight, more preferably 0.3 to 3% by weight. Below 0.1% by weight,
The anchoring property of the adhesive to the surface base material is too high, and the appearance of the surface base material is impaired. On the other hand, if it exceeds 5% by weight, the anchoring property is too low and the removability is inferior, and the pressure sensitive adhesive is susceptible to humidity deterioration and the like.

The (meth) acrylic acid alkyl ester monomer having an alkyl group having 8 to 12 carbon atoms, represented by the component (d), (meth) acrylonitrile and α, β-
A specific example of the monomer copolymerizable with the unsaturated carboxylic acid is a vinyl monomer. Specific examples thereof include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate,
Acrylic acid alkyl ester and methacrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms such as butyl methacrylate, hydroxyethyl acrylate, hydroxyalkyl acrylate and hydroxyalkyl methacrylic acid such as hydroxyethyl methacrylate, methoxyacrylic acid methoxy Acrylic acid alkoxyalkyl esters and methacrylic acid alkoxyalkyl esters such as ethyl and ethoxymethyl acrylate, glycidyl acrylate and glycidyl acrylic acid and glycidyl methacrylic acid esters such as glycidyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, N Amides such as -methoxymethyl acrylamide and N-methoxybutyl acrylamide, styrene, - and the like aromatic unsaturated hydrocarbons such as methyl styrene. These may be used alone or in combination of two or more.

Alkyl group-containing (meth) acrylic acid alkyl ester monomers having 8 to 12 carbon atoms, (meth)
The amount of the acrylonitrile and the monomer copolymerizable with the α, β-unsaturated carboxylic acid used is 0 to 5% by weight based on the total weight of the monomer mixture. If it is 5% by weight or more, the adhesive force of the obtained adhesive to the adherend is too weak and the label floats,
The problem of turning over occurs.

In the present invention, the above monomer mixture is emulsion polymerized in water to prepare a copolymer emulsion. At that time, the polystyrene-equivalent number average molecular weight of the copolymer in the emulsion is particularly important, and is 0.1 × 10 ⁴ or more and 5.0 × 10 ⁴ or more.
Less, preferably 0.3 × 10 ⁴ or more and less than 4.5 × 10 ⁴ , more preferably 0.5 × 10 ⁴ or more and 4.0 × 10 ^4.
Is less than. If it is less than 0.1 × 10 ⁴ , the anchoring property of the pressure-sensitive adhesive to the surface base material is too high, and the appearance of the surface base material is impaired, or the adhesive strength to the adherend is too strong, and the removability is poor due to paper breakage. . On the other hand, when it is 5.0 × 10 ⁴ or more, the anchoring property becomes too low, and the re-peeling property is poor due to the adhesive residue, or the adhesive force is lowered to cause the label to float or turn over.

The ratio (Mw / Mn) of polystyrene equivalent weight average molecular weight to polystyrene equivalent number average molecular weight is 40 to 8.
00, preferably 50 to 700, more preferably 60
~ 600. Outside of this range, the label may be lifted or turned over, or the anchorage to the surface base material may be increased and the appearance of the surface base material may be impaired. Further, the average particle size of the copolymer particles in the emulsion is also important, and is 100 to 500 nm,
Preferably 150 to 450 nm, more preferably 18
It is 0 to 400 nm. If it is less than 100 nm, the anchoring property of the pressure-sensitive adhesive to the surface base material is too high and the appearance of the surface base material is impaired. If it exceeds 500 nm, the anchoring property is too low and the removability is poor due to the adhesive residue. In the present invention, the balance between the polystyrene reduced number average molecular weight and the average particle diameter of the copolymer is important, and the removability, the appearance of the surface base material, and the excellent adhesive strength were obtained by preparing the copolymer within the above range. A removable pressure-sensitive adhesive sheet is obtained.

The glass transition temperature of the copolymer constituting the pressure-sensitive adhesive used in the present invention is -50 ° C or lower, preferably -90.
C to -50C. If the glass transition temperature exceeds −50 ° C., the adhesive strength of the pressure-sensitive adhesive will be reduced, causing the label to float and turn over. In the present invention, the glass transition temperature Tg of the copolymer is calculated based on the following mathematical formula.

[0017]

[Equation 1]

Tg: Glass transition temperature of copolymer (absolute temperature display) Tg _i : Glass transition temperature of i-th monomer homopolymer (absolute temperature display) W _i : Weight fraction of i-th monomer

In the present invention, the above monomer mixture is copolymerized in water by emulsion polymerization. If the monomer mixture is polymerized by another polymerization method, for example, solution polymerization,
The anchoring property of the pressure-sensitive adhesive to the surface base material is too high and the appearance of the surface base material is impaired, or the adhesive force to the adherend is too strong and the removability is poor. The method of the polymerization treatment is not particularly limited as long as it is emulsion polymerization, and any of the commonly used methods can be used, for example, polyoxyethylene nonylphenyl ether, sodium lauryl sulfate, and an emulsifier such as sodium dodecylbenzenesulfonate. , A persulfate, azobisisobutylnitrile, a polymerization initiator such as peroxides, butyl mercaptan, dodecyl mercaptan, isopropyl alcohol, methanol, octyl thioglycolate, in an aqueous solution containing a molecular weight regulator such as carbon tetrachloride, After emulsifying the monomer mixture, a method of completing the polymerization reaction of the monomer mixture while continuously or intermittently supplying it to the reactor can be mentioned.

Adjustment of the number average molecular weight, the weight average molecular weight Mw / the number average molecular weight Mn ratio, the average particle diameter, and the glass transition temperature of the copolymer within the above ranges is a matter that can be easily performed by those skilled in the art. For example, if the amount of the molecular weight modifier (chain transfer agent) is increased, the molecular weight becomes smaller. By changing the type and amount of the molecular weight modifier or the amount of the emulsifier used, the Mw / Mn ratio can be increased. Can change,
The smaller the amount of emulsifier used, the larger the average particle size,
When the amount of component (a) used in the monomer composition is increased, Tg
Is reduced. If necessary, one or more additives such as a filler, a plasticizer, a tackifier, a thickener, a wetting agent, a defoaming agent, an alkali agent, and a stabilizer are added to this copolymer emulsion. However, even in that case, the copolymer component in the pressure-sensitive adhesive is a copolymer containing the above-mentioned additives as necessary in order to obtain good removability and prevent label floating. 60% by weight based on the solid content of the polymer emulsion
As described above, it is more preferable that the content is 80 to 99% by weight. Further, in order to increase the opacity of the removable pressure-sensitive adhesive sheet, a pigment as a filler is added in an amount of 0.5 to 20% by weight, more preferably based on the solid content of the copolymer emulsion containing the above additives as required. Is preferably contained in an amount of 1 to 10% by weight. This is one square meter of surface material
It is particularly effective when using paper of 00 g / m ² or less. As the pigment used as a filler, kaolin,
Examples thereof include talc, clay, titanium oxide, calcium oxide, calcium hydroxide, calcium carbonate, magnesium hydroxide, magnesium carbonate, zinc oxide, zinc carbonate, aluminum oxide and aluminum hydroxide. These may be used alone or in combination of two or more.

The copolymer emulsion thus obtained is mixed with a polyglycidyl compound having two or more epoxy groups in the molecule to give a pressure-sensitive adhesive, and is applied by a method using a known coater or the like as described later. However, since the pressure-sensitive adhesive is adjusted to have a viscosity suitable for its application by using the above-mentioned additives and the like, if necessary, the viscosity or solid content concentration of the copolymer emulsion itself is particularly limited. Instead, it can be appropriately selected from a wide range. Generally, it is convenient to set the solid content concentration of the copolymer emulsion to about 30 to 70% by weight. 30
If it is less than wt%, the efficiency will be poor when the adhesive layer is applied and dried,
This is because if it exceeds 70% by weight, the polymerization reaction becomes difficult.

The pressure-sensitive adhesive used in the present invention comprises a polyglycidyl compound having two or more epoxy groups as a cross-linking agent in the copolymer emulsion, wherein the epoxy group in the polyglycidyl compound is in the copolymer. It is prepared by adding 0.5 to 2 equivalents per equivalent of the carboxyl group. The number of epoxy groups is particularly preferably 2-4. If the number is one or less, crosslinking is not performed, the cohesive force of the pressure-sensitive adhesive does not increase, removability is poor, and bleeding easily occurs. When the number is 5 or more, the number of unreacted epoxy groups increases, so that the cohesive force of the pressure-sensitive adhesive decreases and the removability deteriorates.
When the blending amount of the polyglycidyl compound is less than 0.5 equivalent,
Since the adhesive force of the obtained pressure-sensitive adhesive is too strong on the adherend, an adhesive residue is generated and the adherend is contaminated. On the other hand, when it exceeds 2 equivalents, the anchoring property of the obtained pressure-sensitive adhesive to the substrate becomes poor.

Specific examples of the polyglycidyl compound used in the present invention include ethylene glycol or polyethylene glycol diglycidyl ether, propylene glycol or polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether,
1,6-hexanediol diglycidyl ether, dibromoneopentyl glycol diglycidyl ether, o
-Phthalic acid diglycidyl ester, glycerin polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether,
Examples thereof include polyglycerol polyglycidyl ether and sorbitol polyglycidyl ether.
Others, N, N, N ', N'-tetraglycidyl-m-
Xylene diamine, N, N, N ', N ", N" -pentaglycidyldiethylenetriamine, N, N, N',
N'-tetraglycidyl ethylenediamine etc. can also be used. These may be used alone or in combination of two or more. The pressure-sensitive adhesive of the present invention is formed by uniformly mixing the copolymer emulsion and the polyglycidyl compound by stirring or the like.

The pressure-sensitive adhesive thus obtained is applied and dried on the surface of the release agent layer of the release sheet or the back side of the surface base material to form a pressure-sensitive adhesive layer. The viscosity of the pressure-sensitive adhesive at the time of applying the pressure-sensitive adhesive is not particularly limited, and is appropriately adjusted by adding a thickener or the like to an appropriate viscosity according to a known coater as described later. The coating device for coating the pressure-sensitive adhesive on the release sheet or the surface substrate, for example, a reverse roll coater,
A knife coater, an air knife coater, a bar coater, a slot die coater, a lip coater, a reverse gravure coater and the like are used, and the coating amount of the adhesive is preferably in the range of about 5 to 50 g / m ^{2 in} dry weight. The above polyglycidyl compound is thus coated with the pressure-sensitive adhesive on the release agent layer surface of the release sheet to form a pressure-sensitive adhesive layer, and after the surface substrate is superposed on the pressure-sensitive adhesive layer to form the pressure-sensitive adhesive sheet of the present invention. By curing, a cross-linking reaction occurs, and a stable state is reached in which there is substantially no change in the physical properties of the pressure-sensitive adhesive layer. The curing condition is not particularly limited, but at 20 ° C. for about 1 week, 4
It is about 3 days at 0 ° C.

In the present invention, the surface substrate is not particularly limited, but for example, papers such as high-quality paper, crepe paper, water resistant paper, neutral paper and polyethylene films,
Films such as polyester film, biaxially oriented polyester film, polypropylene film, vinyl chloride film, polycarbonate film, polystyrene film, synthetic paper, non-woven fabric, etc., and art paper, coated paper, cast with various coating layers Examples thereof include coated sheets such as coated paper, heat-sensitive recording paper provided with various recording layers, ink jet recording paper, and thermal transfer recording image-receiving paper. Among them, the one using paper as the support is preferable from the viewpoints of cost and anchoring property of the adhesive to the surface substrate. Since the anchoring property of the pressure-sensitive adhesive is appropriately controlled as described above, the anchoring property becomes too strong even when paper is used as the support, that is, the appearance defect due to bleeding is extremely unlikely to occur. Therefore, the removable pressure-sensitive adhesive sheet of the present invention has an advantage that it is extremely easy to manufacture since it is less likely to be temporarily stored in a wound state or a laminated state where a large pressure is applied immediately after the sheet is manufactured. Regarding thermal paper, if the anchoring property of the pressure sensitive adhesive is excessive, the pressure sensitive adhesive component migrates to the heat sensitive recording layer, hinders the color developing function of the heat sensitive recording layer, and causes a decrease in color density (desensitization). However, since the pressure-sensitive adhesive used in the present invention has an appropriate anchoring property, since the pressure-sensitive adhesive component does not penetrate to the surface of the surface substrate, such a bad effect is less likely to occur.

When paper is used as the support for the surface base material, generally, if the internal bond strength, which is the strength between the paper layers, is weak, the top paper is likely to break when peeled. Therefore, JAPAN
Conventionally, it was necessary to use paper having an internal bond strength of about 0.315 kJ / m ² (150 ft · Lb / in ² ) or more determined according to TAPPI paper pulp test method No. _54-93 . However, since the pressure-sensitive adhesive used in the present invention is unlikely to cause label floating even though the adhesive strength to the adherend is weak, for example, paper with a relatively weak internal bond strength using a large amount of recycled pulp of waste paper is also used. it can. That is, paper with lower internal bond strength than the conventional one, specifically, 0.147 kJ / m ² (70
It can also be used with paper of about ft · Lb / in ² ).
It should be noted that, as the internal bond strength becomes stronger, there is no problem in terms of removability, but since the paper stiffness becomes too strong and label floating occurs or the printability deteriorates, the internal bond strength becomes 0.841 kJ. It is preferably less than / m ² (400 ft · Lb / in ² ). Such adjustment of the internal bond strength can be performed by selecting, combining, and the like of pulp fibers and internal addition aids in the paper stock used when making paper.

In addition to pulp fibers, the paper materials include fillers conventionally used, various anionic, nonionic, cationic or amphoteric retention improvers, drainage improvers and paper strength enhancers. An internal additive for papermaking such as an agent and an internal sizing agent can be appropriately added, and if necessary, a surface sizing agent can be used in combination. Further, the papermaking method is not particularly limited, and all papermaking methods such as an acidic papermaking method in which the papermaking pH is around 4.5, a so-called neutral papermaking method in which the papermaking pH is weakly acidic from about 6 to weakly alkaline about 9 Can be applied to the method, the paper machine is also a Fourdrinier paper machine, twin wire paper machine,
A cylinder paper machine, a Yankee paper machine or the like can be used as appropriate.

In the present invention, a primer layer may be provided between the surface base material and the pressure-sensitive adhesive layer, if necessary.
In particular, when a support having a low anchoring property such as a film is used as the support for the surface base material, it is preferable to provide a primer layer. Examples of the primer layer include magnesium hydroxide, magnesium carbonate, magnesium sulfate, calcium oxide, calcium hydroxide, calcium carbonate, satin white, calcium silicate, zinc oxide, titanium oxide,
Examples include pigments such as aluminum oxide, aluminum hydroxide, talc, and kaolin, and binders such as starch, polyvinyl alcohol, carboxymethyl cellulose, styrene / butadiene copolymer, acrylic copolymer, and vinyl acetate copolymer. .

For the primer layer, a coating liquid prepared by dispersing these pigments and a binder in water or an organic solvent (toluene, ethyl acetate, etc.) is applied to the back surface of the support of the surface substrate (that is, if there is no primer layer, it is adhered. On the surface that contacts the agent layer),
It can be obtained by coating and drying according to a conventional method. The ratio of the binder and the pigment in the coating liquid can be selected from a wide range and can be changed depending on the kind of the binder and the kind of the pigment, but generally, the binder and the pigment are used with respect to the total amount. It is preferably about 30 to 70% by weight and the pigment is about 70 to 30% by weight. Further, since the solid content concentration of the coating liquid is also adjusted so as to have a viscosity suitable for the coating method, the viscosity or solid content concentration of the coating liquid itself is not particularly limited and can be appropriately selected from a wide range. However, in general, the solid content concentration of the coating liquid is 30 to 70.
It is convenient to set it to about wt%. The coating amount of the coating liquid for forming the primer layer may vary depending on the type of pigment or binder used, the type of surface substrate, etc., but is generally about 0.1 to 10 g / m ^{2 on} a dry weight basis. Is preferred. When paper is used as a support for the surface base material, printing in which a coating layer containing a pigment as needed is provided on the front surface of the surface base material (that is, the surface that does not contact the pressure-sensitive adhesive layer). Coated sheets for ink jetting, ink jetting, thermal transfer, thermal recording, etc. are particularly preferable because their coating layers make it less likely that defective appearance due to bleeding of the pressure-sensitive adhesive will occur. These coating layers are formed by a conventional method. For example, it can be obtained by applying the coating liquid for these coating layers on the surface side of the paper support of the surface base material and drying.

The pigment used in the coating layer as required is not particularly limited, and examples thereof include kaolin and
Talc, clay, calcined clay, silica, titanium oxide, calcium oxide, calcium hydroxide, calcium carbonate, calcium sulfate, satin white, calcium silicate, magnesium hydroxide, magnesium carbonate, magnesium sulfate, magnesium silicate, zinc oxide, zinc carbonate, Examples thereof include zinc sulfate, aluminum oxide, aluminum hydroxide and aluminum silicate. Further, the binder used in the coating layer is not particularly limited, for example,
Starch, polyvinyl alcohol, casein, carboxymethyl cellulose, dextrin, methyl cellulose, styrene-butadiene copolymer, methyl methacrylate
Butadiene copolymer, vinyl chloride copolymer, ethylene
Examples thereof include vinyl chloride copolymers, vinylidene chloride copolymers, ethylene / vinylidene chloride copolymers, acrylic copolymers, vinyl acetate copolymers, ethylene / vinyl acetate copolymers. If necessary, an auxiliary agent such as a thickener, a dye, a defoaming agent, a dispersant or a wetting agent may be added to the coating liquid for forming a coating layer. When the coating layer contains a pigment, the ratio of the binder and the pigment can be selected from a wide range,
Although it may vary depending on the type of binder and the type of pigment, it is generally about 10 to 50% by weight of the binder and about 90 to 50% by weight of the pigment based on the total amount of the binder and the pigment.
It is preferably set to wt%. Further, since the solid content concentration of the coating liquid is also adjusted so as to have a viscosity suitable for the coating method, the viscosity or solid content concentration of the coating liquid itself is not particularly limited and can be appropriately selected from a wide range. However, in general, it is convenient that the solid content concentration of the coating liquid is about 30 to 70% by weight. The coating amount of the coating liquid for forming a coating layer may vary depending on the type of pigment or binder used, the type of surface substrate, etc., but generally it is 1 to 3 on a dry weight basis.
It is preferably about 0 g / m ² .

There is no particular limitation on the method for constructing the removable pressure-sensitive adhesive sheet in the present invention, and the pressure-sensitive adhesive layer is formed by applying the pressure-sensitive adhesive on the surface of the release agent layer of the release sheet and drying it. It is a general method of sticking and finishing, and in some cases, a method of applying a pressure sensitive adhesive to the back side of the surface base material and forming a pressure sensitive adhesive layer by drying, and laminating a release sheet there May be taken. As the release sheet, high-density base paper such as glassine paper, clay-coated paper, or kraft paper,
Polylaminated paper made by laminating polyethylene on high quality paper,
Used is a film or the like on which a fluororesin or silicone resin is applied in a dry weight of about 0.05 to 3 g / m ² and a release agent layer is formed by heat curing, ionizing radiation curing or the like.
As the coating device in this case, for example, a multi-stage roll coater, an air knife coater, a bar coater, an offset gravure coater, a direct gravure coater, or the like is used. Further, as the coating device when the adhesive is coated on the release sheet, for example, a reverse roll coater,
A knife coater, an air knife coater, a bar coater, a slot die coater, a lip coater, a reverse gravure coater, etc. are used, and the coating amount is 5 by dry weight.
A range of about 50 g / m ² is preferable.

The removable sheet of the present invention thus obtained is used for a wide range of purposes such as price tags, process control labels, index labels for video cassettes and audio cassettes. To use the removable sheet of the present invention,
The label (adhesive layer + surface base material) is peeled off from the release sheet, and this is attached to the adherend. When the information on the tape or disc is newly recorded, the old label is peeled off and discarded, and a new label is attached and used. The removable pressure-sensitive adhesive sheet of the present invention floats when adhered to an adherend and has no curling, and when peeled from the adherend, the appearance of the adherend is impaired due to tearing of the surface base material or adhesive residue and the adherend. It exhibits excellent removability without causing contamination, and does not damage the surface substrate by bleeding.

[0033]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these. Unless otherwise specified, all parts, proportions, coating amounts and the like in the examples are shown by solid content weight. Also"%"
Indicates solid content by weight unless otherwise specified.

It is basically used in preparing the removable pressure-sensitive adhesive sheets of Examples and Comparative Examples (method for producing pressure-sensitive adhesive).
And (a method for producing a removable pressure-sensitive adhesive sheet) will be described below.

(Production method of pressure-sensitive adhesive) Water and a polymerization initiator were charged into an autoclave equipped with a stirrer, a temperature controller and a reflux condenser, and the temperature was raised to 70 ° C. Next, a monomer mixture, a molecular weight modifier and an emulsifier were added, followed by stirring and emulsifying to prepare a pre-emulsion. The whole amount of this pre-emulsion was continuously added over 3 hours while stirring at 80 ° C. for emulsion polymerization. Then, stirring was further continued at 80 ° C. for 2 hours to complete the copolymerization. A 50% dispersion of titanium oxide as a pigment was added to this emulsion in an amount of 6% by weight as titanium oxide (solid content) based on the solid content of the copolymer emulsion, and the pH was adjusted to 8.5 with ammonia. Sodium polyacrylate as an agent
-60 (made by Rohm & Haas Co.) "to add viscosity (B
Type viscometer, No. 4 rotor, 60r. p. m) was adjusted to 4000 cps. Next, as a cross-linking agent, diglycerol polyglycidyl ether “Denacol EX-4
21 (manufactured by Nagase Kasei Co., Ltd., containing 90% by weight or more of diglycerol triglycidyl ether) is a ratio in which the carboxyl group in the copolymer in the emulsion and the epoxy group in the diglycerol polyglycidyl ether have the same equivalent weight. A pressure-sensitive adhesive was prepared by adding

(Preparation Method of Removable Adhesive Sheet) Using the above-mentioned adhesive and the surface base material, a commercially available polyethylene laminated release paper is separately provided with the above adhesive at a dry weight of 25 g.
After coating and drying so as to be / m ² , the pressure-sensitive adhesive layer surface and the back surface of the front surface substrate were attached to each other to prepare a removable pressure-sensitive adhesive sheet. The polyethylene-laminated release paper is obtained by heat-sealing a polyethylene layer with a thickness of about 15 μm on high-quality paper, and applying a release agent such as a silicone resin to the polyethylene layer and drying it.

Example 1 2-Ethylhexyl acrylate 9 as a monomer mixture
4.3 parts, acrylonitrile 5.0 parts, acrylic acid 0.
7 parts, 0.4 parts of sodium persulfate as a polymerization initiator, 0.02 parts of n-butyl mercaptan as a molecular weight modifier, 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier, and 1.0 of polyoxyethylene nonylphenyl ether. A pressure-sensitive adhesive was produced by the above method using 40 parts of water and 40 parts of water. Using the adhesive, 50 as a surface substrate
A releasable pressure-sensitive adhesive sheet was obtained using a μm polyester film. Example 2 A re-peelable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that high-quality paper having a surface area of 75 g / m ² was used as the surface substrate. Example 3 On the same high-quality paper of 75 g / m ^{2 as} the basis used in Example 2, 40 parts of kaolin and 40 parts of calcium carbonate were further added.
Part, and a pigment coating layer consisting of 20 parts of a styrene / butadiene copolymer emulsion are coated so that the dry weight is 10 g / m ^2, and then treated with a 4-stage super calender to obtain a coating having a paper thickness of 86 μm. A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that paper was used as the surface substrate. still,
The pressure-sensitive adhesive layer was formed on the surface of the surface base material opposite to the surface coated with the pigment.

Example 4 A releasable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that, as the surface base material, a high-quality paper having a weight of 75 g / m ² and having a weight of neutral paper was used. Example 5 A re-peelable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that the titanium oxide used in the above-mentioned (method for producing pressure-sensitive adhesive) was not used. Example 6 2-Ethylhexyl Acrylate 9 as Monomer Mixture
4.3 parts, acrylonitrile 3.0 parts, acrylic acid 0.
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 7 parts and 2.0 parts of N-methylolacrylamide were used.

Example 7 90.3 parts of isononyl acrylate as a monomer mixture,
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 5.0 parts of acrylonitrile, 0.7 parts of methacrylic acid, and 4.0 parts of butyl acrylate were used. Example 8 18.3 parts isononyl acrylate as a monomer mixture,
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 74.0 parts of lauryl methacrylate, 5.0 parts of acrylonitrile, 0.7 parts of acrylic acid, and 2.0 parts of methyl methacrylate were used. Example 9 2-Ethylhexyl Acrylate 9 as Monomer Mixture
Re-peel in the same manner as in Example 3 except that 2.5 parts, 3.3 parts of acrylonitrile, 0.7 parts of methacrylic acid, 3.0 parts of N-methylol acrylamide, and 0.5 parts of dimethylaminoethyl methacrylate were used. A pressure-sensitive adhesive sheet was obtained. Example 10 A releasable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 2 except that polyglycerol pentaglycidyl ether was used as the crosslinking agent.

Comparative Example 1 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of n-butyl mercaptan added as a molecular weight modifier was changed to 0.001 part. Comparative Example 2 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that the amount of n-butyl mercaptan added as a molecular weight modifier was changed to 0.001 part. Comparative Example 3 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that the addition amount of n-butyl mercaptan as a molecular weight modifier was changed to 0.5 part.

Comparative Example 4 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that the addition amount of sodium dodecylbenzene sulfonate as an emulsifier was changed to 0.2 part. Comparative Example 5 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that the addition amount of sodium dodecylbenzenesulfonate as an emulsifier was changed to 3.0 parts. Comparative Example 6 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 0.2 part of octyl thioglycolate was used as the molecular weight modifier instead of n-butyl mercaptan.

Comparative Example 7 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 0.02 part of octyl thioglycolate was used instead of n-butyl mercaptan as a molecular weight modifier. Comparative Example 8 Example except that diglycerol polyglycidyl ether was added as a cross-linking agent at a ratio of 6.0 equivalent of epoxy groups in diglycerol polyglycidyl ether to carboxyl groups in the copolymer in emulsion. Three
A releasable pressure-sensitive adhesive sheet was obtained in the same manner as in. Comparative Example 9 Example except that diglycerol polyglycidyl ether was added as a crosslinking agent at a ratio of 0.1 equivalent of epoxy groups in diglycerol polyglycidyl ether to carboxyl groups in the copolymer in emulsion. Three
A releasable pressure-sensitive adhesive sheet was obtained in the same manner as in.

Comparative Example 10 A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that allyl glycidyl ether was used instead of diglycerol polyglycidyl ether as a crosslinking agent. Comparative Example 11 2-Ethylhexyl acrylate 9 as a monomer mixture
7.2 parts, acrylonitrile 0.1 part, acrylic acid 0.
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 7 parts and 2.0 parts of N-methylolacrylamide were used. Comparative Example 12 2-Ethylhexyl Acrylate 8 as Monomer Mixture
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 2.3 parts, 15.0 parts of acrylonitrile, 0.7 parts of acrylic acid, and 2.0 parts of N-methylolacrylamide were used.

Comparative Example 13 2-Ethylhexyl Acrylate 3 as Monomer Mixture
0.0 parts, acrylonitrile 5.0 parts, acrylic acid 0.
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 7 parts and 64.3 parts of butyl acrylate were used. Comparative Example 14 2-Ethylhexyl acrylate 9 as a monomer mixture
A releasable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that 4.95 parts, acrylonitrile 3.0 parts, acrylic acid 0.05 part, and N-methylolacrylamide 2.0 parts were used. Comparative Example 15 2-Ethylhexyl Acrylate 8 as a monomer mixture
8.0 parts, acrylonitrile 3.0 parts, acrylic acid 7.
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3, except that 0 part and 2.0 parts of N-methylolacrylamide were used. Comparative Example 16 2-Ethylhexyl acrylate 6 as a monomer mixture
4.0 parts, acrylonitrile 4.0 parts, acrylic acid 0.
An adhesive sheet was obtained in the same manner as in Example 3 except that 7 parts, 29.3 parts of butyl acrylate and 2.0 parts of N-methylol acrylamide were used.

Regarding the pressure-sensitive adhesives used in Examples 1 to 10 and Comparative Examples 1 to 16, the polystyrene-equivalent number average molecular weight, the ratio of the polystyrene-equivalent weight average molecular weight and the polystyrene-equivalent number average molecular weight at the completion of the copolymerization of the pre-emulsion, The average particle diameter and the glass transition temperature were determined by the following methods. Table 1 shows the results. [Ratio of polystyrene reduced number average molecular weight, polystyrene reduced weight average molecular weight and polystyrene reduced number average molecular weight] Gel permeation chromatography device "HCL-"
8020 (manufactured by Tosoh Corporation) ". [Average particle diameter] It was measured using Nanosizer (manufactured by Coulter Co.). [Glass transition temperature] The glass transition temperature was calculated from the glass transition temperature of each monomer homopolymer based on the general formula 1 described above.

[0046]

[Table 1]

With respect to the removable pressure-sensitive adhesive sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 16, label floating, removability and bleed were evaluated by the following methods.
As for label floating and removability, the removability adhesive sheet is 23 ℃
Evaluation was performed after aging under an atmosphere of 65% RH for 2 weeks. The results are shown in Table 2.

[Label Lifting] Using a 3.5-inch floppy disk, a test piece was attached so as to have a folded portion of 180 degrees. In that state, the state of the test piece was observed after being left in an atmosphere of 70 ° C. for 7 days and further in an atmosphere of 23 ° C. and 65% RH for 24 hours. Label floating was evaluated based on the following criteria. A: No lift is seen at all B: Some lift is seen C: A lot of lift is seen D: The folded part is completely flipped up

[Removability] A test piece was attached to an ABS plate having a smooth surface and a 3.5-inch floppy disk, and 23
After leaving for 7 days in an atmosphere of 65 ° C RH, 300m speed
Peeling was performed at m / min and an angle of 180 degrees, and the state of the adherend was observed. The removability was evaluated according to the following criteria. A: Neither glue nor surface material remains on the adherend B: Some glue remains C: Some glue remains D: The surface material is broken and remains

[Bleed] A pressure of 1 kg / m ² was applied to the test piece immediately after the sample was prepared, and the bleeding state was observed after standing in an atmosphere of 25 ° C. for 24 hours. Bleed was evaluated according to the following criteria. A: No bleed at all B: Bleed a little C: Bleed quite a bit

[0051]

[Table 2]

[Other Evaluations] In Examples 2 to 10, all the surface base materials had an internal bond strength of 100 ft.
・ Although paper with a relatively low strength between the paper layers, such as Lb / in ^2, was used, the removability was all good. Further, in Example 5, since the pigment as a filler in the adhesive used was omitted, the opacity seems to be slightly inferior to that in Example 3,
There was no problem in practical use. In addition, in addition to the above-described examples, each releasable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that thermal transfer paper, inkjet paper, and thermal paper were used for the surface base material. Then, when each evaluation test was performed in the same manner as in Example 3, substantially the same evaluation results as in Example 3 were obtained. In Example 1, the removability of the smooth ABS plate was evaluated as B. This is because, in some samples, only a small amount of adhesive residue was observed.
The reason for this is that a polyester film was used as a support for the surface base material. When a polyester film provided with a primer layer was used, the evaluation of removability was A, which was the same as that when paper was used as the support of the surface base material.

[0053]

EFFECTS OF THE INVENTION The removable pressure-sensitive adhesive sheet of the present invention does not float when adhered to an adherend and does not curl up. When peeled from the adherend, the appearance of the adherend is improved by tearing of the surface base material or adhesive residue. It shows excellent removability without damaging the adherend to cause contamination of the adherend, and does not damage the surface substrate by bleeding.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C09J 163/00 JFK C09J 163/00 JFK

Claims (3)

[Claims] 1. A re-peelable pressure-sensitive adhesive sheet having a release sheet, a pressure-sensitive adhesive layer, and a surface base material laminated in this order, and as the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, the following (a), (b),
It is obtained by emulsion polymerization of a monomer composition comprising (c) and (d) which is added as necessary, and has a polystyrene reduced number average molecular weight of 0.1 × 10 ⁴ or more and 5.0 × 1.
Is less than 0 ⁴ , and the ratio of the polystyrene reduced weight average molecular weight to the polystyrene reduced number average molecular weight is 40 to 800,
Average particle size 100-500 nm, glass transition temperature-
Polyglycidyl having, as a main component, an aqueous emulsion of a copolymer having a temperature of 50 ° C. or lower, and having two or more epoxy groups so that the epoxy group is 0.5 to 2 equivalents per equivalent of carboxyl groups of the copolymer. A removable pressure-sensitive adhesive sheet, characterized in that a pressure-sensitive adhesive containing a compound is used. (A) 80 to 99% by weight of a (meth) acrylic acid alkyl ester monomer having an alkyl group with 8 to 12 carbon atoms (b) 0.3 to 10% by weight of (meth) acrylonitrile (c) α, β 0.1 to 5% by weight of unsaturated carboxylic acid (d) 0 to 5% by weight of other copolymerizable monomer 2. The removable pressure-sensitive adhesive sheet according to claim 1, wherein the polyglycidyl compound has 2 to 4 epoxy groups. 3. The removable pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive further contains a pigment.