JP6713735B2 - Masking tape - Google Patents

Description

TECHNICAL FIELD The present invention relates to a masking tape that can be used for coating purposes and the like.

2. Description of the Related Art Conventionally, a masking tape using a porous material such as Japanese paper or crepe paper as a base material has been used as a masking tape for coating applications such as buildings and vehicles. However, when a porous material is used as the base material, the dye, water, solvent, etc. contained in the paint are likely to soak into the base material, so that the adhesive will fall off from the base material when the masking tape is peeled off, and the adherend will be contaminated. There was a problem.
As a method for solving this problem, for example, Patent Document 1 proposes a masking tape in which a layer is formed by laminating a hot-melt resin on the surface of a paper base material, thereby suppressing penetration of a solvent or the like. ..

JP, 2009-40921, A

According to the masking tape described in Patent Document 1, it is possible to suppress penetration of a solvent and the like and to suppress contamination of the adherend to some extent, but the manufacturing cost is significantly increased as compared with the conventional masking tape. There was a problem. Therefore, it has been desired to develop a masking tape that can be manufactured at a lower cost and that can suppress contamination of adherends.
The present invention has been made in view of the above conventional problems, can be manufactured at low cost, and can suppress contamination of adherends even when a porous material such as paper is used as a substrate. We provide masking tape that can be used.

The gist of the present invention is a masking tape having a primer layer between a porous substrate and a pressure-sensitive adhesive layer, the primer layer being a layer formed of an aqueous acrylic emulsion.

According to the present invention, it is possible to provide a masking tape that can be manufactured at low cost and that can suppress contamination of an adherend even when a porous material such as paper is used as a base material.

The masking tape of the present invention is a masking tape having a primer layer between a porous substrate and a pressure-sensitive adhesive layer, the primer layer being a layer formed of an aqueous acrylic emulsion.
The masking tape of the present invention employs a novel structure in which a primer layer formed of a water-based acrylic emulsion is provided between the porous base material and the pressure-sensitive adhesive layer. On the other hand, even if a masking tape is applied, it becomes difficult for the solvent on the coated surface to soak into the porous base material, and as a result, the adhesive is prevented from falling off the base material and the adherend is prevented from being contaminated. it can. Further, the masking tape of the present invention can be manufactured relatively easily in a short time by using a general apparatus, so that the manufacturing cost can be kept low. Hereinafter, the present invention will be described in detail.

<Porous substrate>
The porous substrate that can be used in the present invention is not particularly limited as long as it is a porous material, but from the viewpoint that the masking tape can be easily cut by hand, wood pulp, cotton, hemp Examples thereof include natural fibers such as Manila hemp, Japanese paper, crepe paper, kraft paper, woven cloth, and non-woven cloth. Among these, Japanese paper, crepe paper, and kraft paper are preferable.

As the Japanese paper that can be used in the present invention, beaten wood pulp, and a paper obtained by mixing synthetic fibers with the wood pulp are preferable. Examples of the synthetic polymer forming the synthetic fiber include vinylon, nylon, polyester, polypropylene, and polyvinyl chloride.
The basis weight of the paper, from the viewpoint of improving the strength of the masking tape, preferably 15 g / m ² or more, more preferably 20 g / m ² or more, still more preferably 30 g / m ² or more, and preferably 60 g / m ² or less, more preferably 50 g/m ² or less, and further preferably 40 g/m ² or less.

Examples of the crepe paper that can be used in the present invention include natural pulp mainly composed of cellulose such as wood pulp, hemp pulp, and linter, and crepe paper obtained by mixing synthetic fibers such as vinylon with natural fibers. To be
From the viewpoint of improving the strength of the masking tape, the basis weight of the crepe paper is preferably 30 g/m ² or more, more preferably 40 g/m ² or more, still more preferably 45 g/m ² or more, and preferably 80 g/m ^2. m ² or less, more preferably 70 g/m ² or less, and further preferably 60 g/m ² or less.

Examples of the kraft paper that can be used in the present invention include, for example, unbleached kraft paper, semi-bleached kraft paper, bleached kraft paper, those that have been subjected to Clupak processing for imparting extensibility, and those that are wet. Examples thereof include those that have been subjected to wet strength processing to impart strength. Among these, the kraft paper that has been subjected to the Clupak process and the kraft paper that has been subjected to the wet strength process are preferable.
The basis weight of the kraft paper is preferably 20 g/m ² or more, more preferably 30 g/m ² or more, still more preferably 35 g/m ² or more, even more preferably 40 g/m ² from the viewpoint of improving the strength of the masking tape. The above is more preferably 45 g/m ² or more, and preferably 100 g/m ² or less, more preferably 90 g/m ² or less, and further preferably 80 g/m ² or less.

In the present invention, it is preferable to use a porous base material that has been subjected to a sealing treatment from the viewpoint of preventing the coating material from seeping into the porous base material. In the present invention, the porous base material is treated as a porous base material in the present invention even when the porous base material is no longer a porous material by subjecting it to a sealing treatment.
Examples of the sealing treatment include a method of impregnating a porous substrate with a sealing treatment agent such as an adhesive or a pigment.
As the adhesive used for the sealing treatment, polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, polyacrylate, starch, cellulose derivative, urethane resin, polyester resin, alkyd resin, melamine resin, styrene-butadiene copolymer latex (Hereinafter, also referred to as “SBR latex”), styrene-acrylic copolymer latex, (meth)acrylic resin, and the like.

Pigments used for the sealing treatment include inorganic pigments such as kaolin, aluminum hydroxide, heavy calcium carbonate, light calcium carbonate, titanium oxide, talc, satin white, calcium sulfate, barium sulfate, zinc oxide, and silica;
Organic pigments such as polypropylene resin, polyethylene resin, styrene resin, acrylic-styrene resin, urea-formalin resin, melamine-formalin resin, and benzoguanamine resin can be mentioned. The adhesives and pigments may be used alone or in combination of two or more.
Among these, styrene-butadiene copolymer latex, styrene-acrylic copolymer latex, and (meth)acrylic resin are preferable from the viewpoint of suppressing the penetration of the coating material into the porous material, and styrene-butadiene copolymer latex. , And (meth)acrylic resin are more preferably used together.

There is no particular limitation on the method of sealing the porous base material, but the method of immersing the porous base material in a treatment liquid prepared by dissolving or dispersing the sealing treatment agent in an organic solvent, water, or the like, or applying by hot melt Thus, a method of impregnating the porous base material with the filling treatment agent and the like can be mentioned. Among these, the method of immersing the porous base material in the treatment liquid in which the filling treatment agent is dissolved or dispersed is preferable from the viewpoint of safety and working environment. The porous base material impregnated with the treatment agent by being dipped in the treatment liquid may be dried for 1 to 30 minutes under the condition of about 40 to 130°C, if necessary.

The impregnated amount of the sealing agent per unit area of the porous substrate is preferably 1 g/m ² or more, more preferably 5 g/m ² or more, from the viewpoint of suppressing penetration of the solvent into the porous substrate. It is more preferably 7 g/m ² or more, and preferably 30 g/m ² or less, more preferably 20 g/m ² or less. The impregnated amount per unit area of the porous substrate can be calculated from the difference between the weight of the dried porous substrate after the sealing treatment and the weight of the porous substrate before the sealing treatment. it can.

<Primer layer>
The primer layer in the present invention is a layer provided between the porous base material and the pressure-sensitive adhesive layer, and is a layer formed of an aqueous acrylic emulsion.
As the water-based acrylic emulsion in the present invention, one or more selected from (meth)acrylic acid and (meth)acrylic acid ester is used as a raw material monomer, and the (meth)acrylic resin obtained by emulsion polymerization of the raw material monomer Emulsions are preferred. In addition, in this specification, "(meth)acrylic acid" means "acrylic acid" or "methacrylic acid", and "(meth)acrylic acid ester" means "acrylic acid ester" or "methacrylic acid ester". Means.
Examples of the raw material monomers (meth)acrylic acid and (meth)acrylic acid ester include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, Isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, (meth ) Phenyl acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, and dihydrodicyclopenta (meth)acrylate Dienyl and the like can be mentioned.
Among these, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferable, and acrylic acid and 2-ethylhexyl acrylate are more preferable.

The water-based acrylic emulsion in the present invention may use a monomer other than the (meth)acrylic acid and the (meth)acrylic acid ester as a raw material monomer, and examples thereof include an aromatic monomer and a carboxy group-containing vinyl monomer. To be
Examples of aromatic monomers include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, and 2,4-dibromostyrene.
Examples of the vinyl monomer containing a carboxy group include crotonic acid, maleic acid and its anhydride, fumaric acid, itaconic acid, unsaturated dicarboxylic acid monoalkyl ester (for example, monomethyl maleate, monoethyl fumarate, and mononormal butyl itaconic acid). Etc.
Further, as raw material monomers other than aromatic monomers and carboxy group-containing vinyl monomers, vinyl esters such as vinyl acetate and vinyl propionate; vinylidene halides such as vinylidene chloride vinylidene bromide; (meth)acrylonitrile; (meth) Glycidyl acrylate; (meth)acrylamide, N-methylol (meth)acrylamide, butoxymethyl (meth)acrylamide, and diacetone acryl amide.
As the raw material monomer other than the (meth)acrylic acid ester, an aromatic monomer is preferable, styrene and α-methylstyrene are more preferable, and styrene is still more preferable.

The water-based acrylic emulsion in the present invention may be a water-based acrylic emulsion of a (meth)acrylic acid polymer using only one or more selected from the (meth)acrylic acid and the (meth)acrylic acid ester as raw material monomers. It is good, but it is a water-based acrylic emulsion of a (meth)acrylic acid-based copolymer using at least one selected from the above-mentioned (meth)acrylic acid and (meth)acrylic acid ester, and a monomer other than that as a raw material monomer. It is preferable.
The water-based acrylic emulsion of a (meth)acrylic acid-based copolymer includes a structural unit derived from at least one selected from (meth)acrylic acid and a (meth)acrylic acid ester, and a structural unit derived from an aromatic monomer. A water-based acrylic emulsion of a copolymer having and is preferable, one or more structural units derived from at least one selected from (meth)acrylic acid and (meth)acrylic acid ester, and at least one selected from styrene and α-methylstyrene. A water-based acrylic emulsion of a copolymer having a structural unit derived from is more preferable.
More specifically, a water-based acrylic emulsion of an acrylic acid copolymer having a structural unit derived from acrylic acid and a structural unit derived from styrene and α-methylstyrene, derived from acrylic acid and -2 ethylhexyl acrylate. A water-based acrylic emulsion of an acrylic acid-based copolymer having a structural unit and a structural unit derived from styrene is more preferable.

When a monomer other than (meth)acrylic acid and (meth)acrylic acid ester is used as the raw material monomer, one kind selected from (meth)acrylic acid and (meth)acrylic acid ester in the (meth)acrylic acid-based copolymer The content of the structural unit derived from the above is preferably 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, and preferably 97% by mass or less, more preferably 96% by mass. % Or less, more preferably 95% by mass or less.

The glass transition point (Tg) of the (meth)acrylic resin constituting the water-based acrylic emulsion is preferably 0° C. or higher, more preferably 10° C. or higher, even more preferably 15° C. or higher, even more preferably 20° C. or higher, And, it is preferably 50° C. or lower, more preferably 45° C. or lower, further preferably 40° C. or lower, further preferably 35° C. or lower, still more preferably 30° C. or lower.

The weight average molecular weight of the (meth)acrylic resin constituting the water-based acrylic emulsion is preferably 100,000 or more, more preferably 200,000 or more, further preferably from the viewpoint of improving the adhesiveness and suppressing the contamination of the adherend. Is 300,000 or more, and from the viewpoint of suppressing the viscosity and improving the coating property, it is preferably 1 million or less, more preferably 900,000 or less, and even more preferably 800,000 or less.
In addition, the weight average molecular weight in this specification is the polystyrene equivalent weight average molecular weight obtained from the measurement of gel permeation chromatography (GPC).

The average particle size of the water-based acrylic emulsion is preferably 50 nm or more, more preferably 75 nm or more, further preferably 90 nm or more, still more preferably 100 nm or more, and preferably 300 nm or less, more preferably 250 nm or less, further preferably Is 200 nm or less.
In addition, in this specification, the average particle diameter of the water-based acrylic emulsion refers to the median diameter at 25° C. measured using a dynamic light scattering particle size distribution analyzer.
Examples of commercially available water-based acrylic emulsions include "Cybinol EK-61" manufactured by Saiden Chemical Co., Ltd.

The water-based acrylic emulsion used in the present invention can be produced by general emulsion polymerization. That is, water and a polymerization initiator are mixed and heated to 70 to 80° C., and then a reaction is carried out by dropping a mixture of a raw material monomer and an emulsifier, and after completion of the reaction, the reaction product is cooled to obtain an alkaline substance. The target water-based acrylic emulsion can be obtained by neutralizing with (for example, ammonia).

Examples of the emulsifier include anionic polymer emulsifiers such as fatty acid soap, rosin acid soap, alkyl sulfonate, alkylbenzene sulfonate, dialkylaryl sulfonate, alkyl sulfosuccinate, and polyoxyethylene alkyl sulfate.
Examples thereof include nonionic polymerization emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block copolymer.
The amount of the emulsifier used is preferably 0.3 to 3 parts by mass, more preferably 0.5 to 2.5 parts by mass, relative to 100 parts by mass of the raw material monomer.

Examples of the polymerization initiator include aqueous initiators such as potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide; and oil-based initiators such as tert-butyl hydrate-oxide and cumene hydroper-oxide.
The amount of the polymerization initiator used is preferably 0.1 to 0.7 parts by mass, and more preferably 0.2 to 0.6 parts by mass with respect to 100 parts by mass of the raw material monomer.

In emulsion polymerization, a chain transfer agent, a molecular weight modifier such as a polymerization terminator, and a polymerization rate modifier may be appropriately used to adjust the molecular weight.
Examples of the chain transfer agent include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, octyl mercaptan, n-tetradecyl mercaptan, and n-hexyl mercaptan, terpinolene, t-terpinene, α-methylstyrene dimer, ethyl xanthogen. Examples thereof include disulfide, diisopropyl xanthogen sulfide, aminophenyl sulfide, tetraethylthiuram disulfide and the like.
Examples of the polymerization terminator include hydroquinone (phenol), amine sulfur, hydroxylamine sulfate, ammonia, sodium hydroxide, potassium hydroxide and the like.

The method for forming the primer layer in the present invention is not particularly limited, and the primer layer can be formed by applying an aqueous acrylic emulsion. Examples of the coating method include a bar coater method, a Meyer bar method, an air knife method, a gravure method, and a reverse gravure method. Among them, the Meyer bar method is preferable.
After applying the water-based acrylic emulsion to the porous substrate, it may be dried under conditions of about 40 to 130° C. for 1 to 30 minutes, if necessary.

The thickness of the primer layer is preferably 0.5 μm or more, more preferably 0.7 μm or more, still more preferably 0.8 μm or more, from the viewpoint of improving the adhesion between the porous substrate and the pressure-sensitive adhesive layer. From the viewpoint of suppressing the cohesive failure of the primer layer, it is preferably 5 μm or less, more preferably 4 μm or less, still more preferably 3 μm or less.

<Adhesive layer>
The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer in the present invention is not particularly limited, and examples thereof include an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, and a polyether pressure-sensitive adhesive. Among these, the adhesive layer is preferably formed of an acrylic adhesive from the viewpoint of excellent high cohesiveness, high heat resistance, solvent resistance and the like.
Examples of the acrylic pressure-sensitive adhesive include solvent-type acrylic pressure-sensitive adhesives, water-based emulsion type acrylic pressure-sensitive adhesives, hot melt type acrylic pressure-sensitive adhesives, and photopolymerization type acrylic pressure-sensitive adhesives, which improve the adhesiveness. From the viewpoint of making it possible, an aqueous emulsion type acrylic pressure-sensitive adhesive is preferable.

The acrylic pressure-sensitive adhesive preferably contains a (meth)acrylic resin as a main component. Examples of the (meth)acrylic resin include (meth)acrylic resins obtained by homopolymerizing (meth)acrylic acid ester monomers, (meth)acrylic resins obtained by copolymerizing two or more kinds of (meth)acrylic acid ester monomers, and (meth ) A copolymer of an acrylic acid ester monomer and another vinyl monomer copolymerizable therewith, and the like.
Among these, a copolymer of a (meth)acrylic acid ester monomer and another vinyl monomer copolymerizable therewith is preferable.

As the (meth)acrylic acid ester monomer, those obtained by esterifying a primary or secondary alkyl alcohol having an alkyl group having 1 to 12 carbon atoms with (meth)acrylic acid are preferable, and examples thereof include (meth) ) Methyl acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t (meth)acrylate t -Butyl, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, Examples include dicyclopentadienyl (meth)acrylate and dihydrodicyclopentadienyl (meth)acrylate.

Examples of the other vinyl monomer copolymerizable with the (meth)acrylic acid ester monomer (hereinafter, also referred to as “other vinyl monomer”) include a carboxy group-containing monomer and a hydroxyl group-containing (meth)acrylic acid ester monomer. Can be mentioned.
Examples of the carboxy group-containing monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid.
Examples of the hydroxyl group-containing (meth)acrylic acid ester monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth)acrylic acid 2 -Hydroxybutyl, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl caprolactone-added (meth)acrylate.
Among these other vinyl monomers, a carboxy group-containing monomer is preferable, and acrylic acid is more preferable, from the viewpoint of easily controlling the molecular weight of the (meth)acrylic resin and from the viewpoint of improving the tackiness of the pressure-sensitive adhesive.

When the (meth)acrylic acid ester monomer is used in combination with another copolymerizable vinyl monomer, the content ratio of the structural unit derived from the (meth)acrylic acid ester monomer in the (meth)acrylic resin is determined by the pressure-sensitive adhesive layer. From the viewpoint of improving the adhesiveness of, preferably 50 mass% or more, more preferably 60 mass% or more, further preferably 70 mass% or more, even more preferably 80 mass% or more, even more preferably 90 mass% or more, It is more preferably 95% by mass or more, and from the viewpoint of suppressing the viscosity of the pressure-sensitive adhesive layer from becoming too high, preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and further preferably 99. It is not more than mass %.

When the (meth)acrylic resin contains a structural unit derived from a carboxy group-containing monomer, the content ratio thereof is preferably 0.1% by mass or more, and more preferably 0, from the viewpoint of improving the adhesiveness of the adhesive layer. It is 0.5% by mass or more, more preferably 1% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less.

Moreover, when the (meth)acrylic resin contains a structural unit derived from a hydroxyl group-containing (meth)acrylic acid ester monomer, the content ratio thereof is preferably 0.01 mass from the viewpoint of improving the tackiness of the pressure-sensitive adhesive layer. % Or more, more preferably 0.1% by mass or more, and preferably 0.5% by mass or less, more preferably 0.4% by mass or less.

The (meth)acrylic resin forming the pressure-sensitive adhesive layer is obtained by a radical reaction in the presence of a polymerization initiator together with the (meth)acrylic acid ester monomer and, if necessary, other vinyl monomer. A known method can be adopted as the polymerization method, and examples thereof include solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Of these, emulsion polymerization is preferable.

Examples of the emulsifier in the case of producing the (meth)acrylic resin constituting the pressure-sensitive adhesive layer by emulsion polymerization include fatty acid soap, rosin acid soap, alkyl sulfonate, alkylbenzene sulfonate, dialkylaryl sulfonate, alkyl sulfosuccinate. Anionic polymerization emulsifiers such as acid salts and polyoxyethylene alkyl ether sulfates;
Examples thereof include nonionic polymerization emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethyleneoxypropylene block copolymer.
Among these, anionic polymerization emulsifiers are preferable, polyoxyethylene alkyl ether sulfates are more preferable, and sodium polyoxyethylene lauryl ether sulfate (sodium laureth sulfate) is more preferable.
The amount of the emulsifier used is preferably 0.3 to 3 parts by mass, more preferably 0.5 to 2.5 parts by mass, relative to 100 parts by mass of the raw material monomer.

When the (meth)acrylic resin that constitutes the pressure-sensitive adhesive layer is produced by emulsion polymerization, examples of the polymerization initiator include aqueous initiators such as potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide; tert-butyl hydrate. -Oil-based initiators such as oxide and cumene hydroperoxide.
The amount of the polymerization initiator used is preferably 0.1 to 0.7 parts by mass, and more preferably 0.1 to 0.6 parts by mass, relative to 100 parts by mass of the raw material monomer.

Even in emulsion polymerization for producing a (meth)acrylic resin that constitutes the pressure-sensitive adhesive layer, a chain transfer agent for adjusting the molecular weight, and a molecular weight regulator such as a polymerization terminator, a polymerization rate regulator may be appropriately used. You can
Examples of the chain transfer agent include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, octyl mercaptan, n-tetradecyl mercaptan, and n-hexyl mercaptan, terpinolene, t-terpinene, α-methylstyrene dimer, ethyl xanthogen. Examples thereof include disulfide, diisopropylxanthogen sulfide, aminophenyl sulfide, tetraethylthiuram disulfide and the like.
Examples of the polymerization terminator include hydroquinone (phenol), amine sulfur, hydroxylamine sulfate, ammonia, sodium hydroxide, potassium hydroxide and the like.

The gel fraction of the (meth)acrylic resin constituting the pressure-sensitive adhesive layer is preferably 30% by mass or more, more preferably 35% by mass or more, further preferably 40% by mass or more, still more preferably 45% by mass or more, It is more preferably 50% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 85% by mass or less. When the gel fraction of the (meth)acrylic resin is within the above range, the tackiness is improved.
In addition, in this invention, the gel fraction of the (meth)acrylic resin which comprises an adhesive layer says what was measured by the following points. That is, the weight (Ag) of the (meth)acrylic resin is weighed and immersed in ethyl acetate at 23° C. for 24 hours. Then, the insoluble matter is filtered through a wire mesh of 200 mesh, the residue on the wire mesh is vacuum dried, and the weight (Bg) of the dried residue is measured and calculated by the following formula.
Gel fraction (mass %)=(B/A)×100

When the (meth)acrylic resin forming the pressure-sensitive adhesive layer has a hydroxyl group or a carboxy group in the resin column, a cross-linking structure may be formed between the main chains by using a cross-linking agent from the viewpoint of improving the tackiness.
Examples of the crosslinking agent include isocyanate crosslinking agents, aziridine crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking agents. Of these, epoxy crosslinking agents are preferable.

Examples of the epoxy crosslinking agent include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, 1,3-bis(N,N-diglycidylaminomethyl)toluene, N,N,N',N'-tetraglycidyl. -4,4-Diaminodiphenylmethane, N,N,N',N'-tetraglycidyl m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-diglycidyl n-hexane Etc.

When a cross-linking agent is used, its content is preferably 0.05 parts by mass or more, and more preferably 0.07 parts by mass or more, from the viewpoint of performing sufficient crosslinking with respect to 100 parts by mass of the (meth)acrylic resin. And is preferably 0.17 parts by mass or less, more preferably 0.15 parts by mass or less.

If necessary, the pressure-sensitive adhesive layer of the present invention further comprises a tackifying resin, a coupling agent, a filler, a bulking agent, a softening agent, a plasticizer, a surfactant, an antioxidant (antiaging agent), and a heat stability. You may contain 1 or more types of agents, a light stabilizer, an ultraviolet absorber, a coloring agent, etc.

In the present invention, the average thickness of the pressure-sensitive adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 15 μm or more, still more preferably 20 μm or more, from the viewpoint of improving adhesion to the adherend surface of the masking tape. Is more preferably 25 μm or more, and from the viewpoint of improving the unevenness followability of the pressure-sensitive adhesive layer, it is preferably 70 μm or less, more preferably 65 μm or less, still more preferably 60 μm or less.

The method for forming the pressure-sensitive adhesive layer in the present invention is not particularly limited, and after forming a coating film by applying a pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive by a roll method, an applicator method, a bar coater method, a knife coater method, or the like. If necessary, it may be dried for 1 to 30 minutes under the condition of about 40 to 130°C.

The masking tape of the present invention has a primer layer between the porous substrate and the pressure-sensitive adhesive layer, but other layers may be provided if necessary. Examples of other layers include a gas impermeable layer and the like.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
<Examples 1 to 6, Comparative Examples 1 and 2>
Example 1
An acrylic resin emulsion (New Nakamura Chemical Co., Ltd., Newcoat PV) and SBR latex (Nippon Zeon Co., Ltd., NIPPOL-LX110) were mixed at a mass ratio of 1:1 to prepare a sealing agent. A Washi paper having a basis weight of 35 g/m ² was dipped in this and then dried in a hot air drier at 110° C. for 3 minutes to obtain a sealed Washi paper base. The amount of impregnated acrylic resin emulsion and SBR latex after drying was 10 g/m ² .

[Formation of primer layer]
An acrylic primer agent (“Cybinol EK-61” manufactured by Saiden Chemical Co., Ltd.), which is a water-based acrylic emulsion, is applied to the Washi paper base material subjected to the sealing treatment with a Meyer bar so that the average thickness after drying is 1 μm. Then, a primer layer was formed on the sealing-treated porous base material by drying at 110° C. for 2 minutes with a hot air dryer.

[Production of adhesive]
45 parts by mass of water and 0.2 parts by mass of potassium persulfate were charged into a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a reflux cooling tube, and the atmosphere was replaced with nitrogen for 1 hour while stirring. Here, 96 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of methyl methacrylate, 2 parts by mass of acrylic acid, and 1 part by mass of sodium laureth sulfate emulsified with 150 parts by mass of water were added dropwise at 80° C. over 3 hours. Then, aging was carried out for 2 hours.
After aging, the mixture was cooled to room temperature and neutralized with 10% by mass aqueous ammonia to obtain a pressure-sensitive adhesive composed of an acrylic resin emulsion having a pH of 8.0.

[Formation of adhesive layer]
The pressure-sensitive adhesive produced by the above method was applied onto the primer layer with an applicator so that the thickness after drying was 30 μm, and dried at 110° C. for 5 minutes with a hot air drier to obtain a masking tape.

Example 2
A masking tape was obtained in the same manner as in Example 1 except that crepe paper having a basis weight of 55 g/m ² was used as the porous substrate.

Example 3
An epoxy-based crosslinking agent (“Tetrad C” manufactured by Mitsubishi Gas Chemical Co., Inc., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was added to 100 parts by mass of the solid content of the acrylic resin emulsion manufactured in Example 1. ) Was added and stirred to obtain a masking tape in the same manner as in Example 1 except that the pressure-sensitive adhesive layer was formed using the pressure-sensitive adhesive.

Example 4
A masking tape was obtained in the same manner as in Example 1 except that the sealing treatment was performed using only the acrylic resin emulsion without using the SBR latex.

Example 5
A masking tape was obtained in the same manner as in Example 1 except that the sealing treatment was performed using only the SBR latex without using the acrylic resin emulsion.

Example 6
An acrylic resin emulsion was produced in the same manner as in Example 1 except that 90 parts by mass of 2-ethylhexyl acrylate, 8 parts by mass of methyl methacrylate and 2 parts by mass of acrylic acid were used. A masking tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer was formed using the obtained acrylic resin emulsion.

Comparative Example 1
A masking tape was obtained in the same manner as in Example 1 except that the Japanese paper base material subjected to the sealing treatment described in Example 1 was not provided with the primer layer.

Comparative example 2
Except that a solvent-based primer agent (Nippon Shokubai Co., Ltd. "Polyment NK-350"), which is a non-aqueous acrylic emulsion, was used for the primer layer of the Washi paper base material subjected to the sealing treatment described in Example 1. A masking tape was obtained in the same manner as in Example 1.

Test method The surface of the wood, which was polished with #200 abrasive paper, was coated with a solvent-based lacquer paint (trade name: Lacquer Clear/Nippe Home Products) three times with a brush, and the masking tape was applied while only the surface was dry. I attached it. This is stored in a constant temperature and humidity room controlled at a temperature of 23±1° C. and a humidity of 50±5%, and after 24 hours, 48 hours and 72 hours, the masking tape is moved in the 90° direction. Was peeled off at a speed of about 1000 mm/min, and the contamination state of the adherend was evaluated by the following evaluation method. The results are shown in Table 1.

<Evaluation method>
◯ to × of evaluation are defined as follows.
⊚: There is no residue visually and no stickiness on the surface, and the resistance at the time of peeling the tape is small and the tape is easily peeled.
◯: No visible residue or stickiness on the surface, but the resistance when peeling the tape is slightly large.
Δ: There is no residue visually, and the surface is sticky.
X: There is a residue visually.

As is clear from the results shown in Table 1, the masking tape of the present invention can be manufactured at low cost, and suppresses contamination of adherends even when a porous material such as paper is used as a substrate. I know that I can do it.

Claims (5)

Has a primer layer between the porous substrate and a pressure-sensitive adhesive layer, wherein the primer layer is Ri layer der formed by aqueous acrylic emulsion,
A masking tape in which the porous base material is a porous base material subjected to a sealing treatment, and the sealing treatment is performed by impregnating the porous base material with a sealing treatment agent . The water-based acrylic emulsion is a water-based acrylic emulsion of a copolymer having a structural unit derived from at least one selected from (meth)acrylic acid and (meth)acrylic acid ester, and a structural unit derived from an aromatic monomer. The masking tape according to claim 1, which is The masking tape according to claim 1, wherein the primer layer has a thickness of 0.5 to 5 μm. The masking tape according to any one of claims 1 to 3, wherein the sealing agent contains an adhesive selected from a styrene-butadiene copolymer latex and a (meth)acrylic resin . The masking tape according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive.