Masking tape

Abstract

To provide a masking tape that develops comparatively strong adhesion without dependence on finger touch sensation and that is also superior in re-peelability.SOLUTION: A masking tape comprising a base material and an adhesive layer provided on the base material, wherein the adhesive layer is formed from an adhesive composition containing a (meth)acrylic polymer and a crosslinking agent, and the adhesive layer has a probe tack area, measured under specific conditions, of 0.14 or more and 0.40 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a masking tape, and more particularly to a masking tape that exhibits relatively strong adhesive properties and also has excellent removability. [Background technology]

[0002] Masking tapes are used for fixing masking sheets, fixing surface protection materials, and protecting paint, etc. These masking tapes are used, for example, in construction and building materials, and are adhered to a wide range of surfaces, including concrete, metal, furniture, wallpaper, and cardboard.

[0003] In addition to the adhesive strength required for curing, masking tapes are required to have excellent removability so that they do not cause contamination of the adherend when peeled off after the work is completed.

[0004] For example, Patent Document 1 discloses a removable acrylic pressure-sensitive adhesive composition suitable for producing a pressure-sensitive adhesive tape used to temporarily secure protective sheets made of polypropylene cloth or the like. The acrylic pressure-sensitive adhesive composition contains a specific acrylic copolymer containing amide groups and hydroxy groups in the molecule but substantially no carboxyl groups, and a polyisocyanate compound derived from tolylene diisocyanate. The acrylic copolymer disclosed is one that contains 50 to 99.45 wt% of an acrylic acid ester having an alkyl group with 4 to 10 carbon atoms and a homopolymer Tg of −50°C or lower, 0.5 to 2 wt% of a monomer having an amide group, and 0.05 to 1 wt% of a monomer having a hydroxyl group.

[0005] Patent Document 2 discloses a hand-tearable adhesive tape for use in protective applications. The hand-tearable adhesive tape is formed by applying an acrylic adhesive composition consisting of a specific acrylic copolymer, a tackifier, and a crosslinking agent to a specific uneven surface of a polyolefin resin substrate film. Here, the acrylic copolymer consists of 1 to 10 wt% of a carboxyl group- or amino group-containing unsaturated monomer, 0 to 5 wt% of a hydroxyl group-containing unsaturated monomer, and 50 wt% or more of an alkyl ester of (meth)acrylic acid.

[0006] Patent Document 3 discloses a pressure-sensitive adhesive composition and masking tape that have good adhesive strength, cause minimal damage to the adherend when removed, and leave no adhesive residue. The pressure-sensitive adhesive composition comprises an acrylic ester polymer obtained by copolymerizing 80 to 99.9% by weight of a (meth)acrylic ester monomer having an alkyl group with 4 to 12 carbon atoms, 0.1 to 4% by weight of a polar group-containing monomer having a carboxy group, and 0 to 19.9% ​​by weight of another copolymerizable monomer, and a tackifier resin with a softening point of 95 to 160°C.

[0007] Patent Document 4 discloses a pressure-sensitive adhesive composition that has a good balance of adhesive strength and peeling performance and is intended for use in curing applications. The pressure-sensitive adhesive composition contains an acrylic resin, which is a polymer primarily composed of an acrylic acid alkyl ester monomer whose alkyl group has 5 or more carbon atoms, and a tackifier resin that includes a terpene resin and a xylene resin. This is said to prevent adhesive residue from being left on soft plastic resins when peeled off. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-119446 [Patent Document 2] Japanese Patent Application Publication No. 11-286664 [Patent Document 3] Patent No. 3864322 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-189842 Summary of the Invention [Problem to be solved by the invention]

[0009] In addition to adhesive strength and removability, tack, an indicator of the stickiness of the adhesive surface, is also an essential element for masking tape. Traditionally, at work sites where masking tape is used, skilled workers have evaluated tack by touching it with their fingers. In other words, there was no method for objectively quantifying and evaluating the tack of the above-mentioned masking tape. Therefore, when selecting a masking tape and calculating the amount to be used, it was necessary for skilled workers to test it using their finger touch.

[0010] Therefore, an object of the present invention is to provide a masking tape that exhibits relatively strong adhesiveness without relying on the feel of the fingers and also has excellent removability. [Means for solving the problem]

[0011] As a result of extensive research, the present inventors have found that there is a correlation between finger tactile sensation and probe tack, and have found that the above-mentioned problems can be solved. Note that Patent Documents 1 to 4 do not mention tack due to finger tactile sensation, and naturally do not mention the correlation between finger tactile sensation and probe tack.

[0012] The present invention has the following aspects. <<Aspect 1>> A substrate and a pressure-sensitive adhesive layer provided on the substrate, The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer and a crosslinking agent, and The pressure-sensitive adhesive layer has a probe tack area of ​​0.14 or more and 0.40 or less, measured under the following conditions: (conditions) The masking tape is subjected to a probe tack test under an environment of 23°C and 50% RH. The probe tack test is performed by attaching a stainless steel probe to the tape at a contact load of 1 N / cm. 2After contacting the stainless steel probe with the surface of the adhesive layer for 1 second at a contact speed of 10 mm / sec, the load when peeling the stainless steel probe from the adhesive layer is measured. The time from when the load starts to become positive until the probe is completely separated from the adhesive layer is defined as X (seconds). The maximum load within the time period of X is defined as Y (N). Using X and Y, the value expressed as [(X × Y) / 2] is defined as the probe tack area. <<Aspect 2>> The masking tape according to embodiment 1, wherein the value of X determined by the probe tack test is 0.06 to 0.13. Aspect 3 The masking tape according to <<Aspect 1>> or <<Aspect 2>>, wherein the value of Y determined by the probe tack test is 3.0 to 7.0. Aspect 4 The pressure-sensitive adhesive composition further contains at least one tackifying resin selected from the group consisting of a terpene phenol-based tackifying resin and a rosin-based tackifying resin, and The masking tape according to any one of <<Aspect 1>> to <<Aspect 3>>, wherein the tackifier resin is contained in an amount of 3 to 15 parts by mass per 100 parts by mass of the (meth)acrylic polymer. Aspect 5 The masking tape according to any one of "Aspect 1" to "Aspect 4," wherein the (meth)acrylic polymer is a polymer of a monomer component containing 45 to 80 mass% of a (meth)acrylic acid alkyl ester, the alkyl group of which has 5 to 12 carbon atoms. Aspect 6 The masking tape according to any one of <<Aspect 1>> to <<Aspect 5>>, wherein the (meth)acrylic polymer is a polymer of monomer components containing 0.5 to 8% by mass of a carboxyl group-containing monomer. Aspect 7 The masking tape according to any one of <<Aspect 1>> to <<Aspect 6>>, wherein the (meth)acrylic polymer is a polymer of monomer components containing 15 to 25% by mass of a hydroxyl group-containing monomer. DETAILED DESCRIPTION OF THE INVENTION

[0013] Masking tape The masking tape according to this embodiment comprises a substrate and a pressure-sensitive adhesive layer provided on the substrate. The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer and a crosslinking agent. The pressure-sensitive adhesive layer has a probe tack area of ​​0.14 to 0.40, which provides a masking tape that exhibits relatively strong adhesive properties and also has excellent removability. Furthermore, in addition to the adhesive properties and removability, the masking tape also achieves good tackiness.

[0014] The above-mentioned probe tack area of ​​the pressure-sensitive adhesive layer is a value measured under the following conditions. (conditions) The masking tape is subjected to a probe tack test under an environment of 23°C and 50% RH. The probe tack test is performed by attaching a stainless steel probe to the tape at a contact load of 1 N / cm. 2 After contacting the stainless steel probe with the surface of the adhesive layer for 1 second at a contact speed of 10 mm / sec, the load when peeling the stainless steel probe from the adhesive layer is measured. The time from when the load starts to become positive until the probe is completely separated from the adhesive layer is defined as X (seconds). The maximum load within the time period of X is defined as Y (N). Using X and Y, the value expressed as [(X × Y) / 2] is defined as the probe tack area.

[0015] More specifically, the above-mentioned probe tack test is carried out, and a graph is obtained in which the vertical axis represents load (N) and the horizontal axis represents time (seconds). First, the probe is brought into contact with the surface of the adhesive layer of the masking tape, and a contact load of 1 N / cm is applied. 2 When the probe is pressed against the adhesive layer at a contact speed of 10 mm / sec for 1 second, the load becomes negative. After that, when the probe begins to be peeled away from the surface of the adhesive layer at 10 mm / sec, the load becomes positive. If the probe continues to be peeled away, the load exceeds 0 and becomes positive. The time at which this positive value is taken as X1 (seconds). If the probe continues to be peeled away, the time at which the masking tape is completely peeled away and the load becomes 0 is taken as X2 (seconds). Furthermore, a load is generated when the probe is peeled away from the masking tape, and the maximum value of this load is taken as Y (N).

[0016] In the above probe tack test, a graph of an approximately triangular shape is obtained from time X1 to time X2. Therefore, [{(X2-X1)×Y)} / 2], i.e., {(X×Y) / 2}, is the area when the approximately triangle is regarded as a triangle. This value is referred to as the probe tack area in this specification.

[0017] The adhesive strength of the protective tape according to this embodiment to stainless steel, for example, is preferably 5 to 15 N / 25 mm. From the viewpoint of firmly adhering the protective tape to the adherend, the adhesive strength is preferably 6 N / 25 mm or more, and more preferably 7 N / 25 mm or more. From the viewpoint of removability, the adhesive strength is preferably 15 N / 25 mm or less, more preferably 14 N / 25 mm or less, and even more preferably 13 N / 25 mm or less.

[0018] The adhesive strength of the protective tape according to this embodiment to polyethylene is preferably 1 to 10 N / 25 mm. From the viewpoint of achieving the desired protective effect, the adhesive strength is preferably 1 N / 25 mm or more, and more preferably 3 N / 25 mm or more. From the viewpoint of removability, the adhesive strength is preferably 10 N / 25 mm or less, more preferably 7 N / 25 mm or less, and even more preferably 6 N / 25 mm or less.

[0019] The adhesive strength of the masking tape according to this embodiment to each substrate refers to a value measured by an adhesive strength test method in accordance with "8 Tensile strength and elongation" of JIS Z 0237:2009.

[0020] <Adhesive layer> The pressure-sensitive adhesive layer according to the present embodiment is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer and a crosslinking agent. In this specification, the term "(meth)acrylic polymer" refers to at least one of an acrylic polymer and a methacrylic polymer.

[0021] The above-mentioned probe tack area of ​​the adhesive layer in this embodiment is 0.14 or more and 0.40 or less, and the present invention has discovered that there is a correlation between the above-mentioned probe tack area and the tack measured by the finger touch of a skilled worker, making it possible to objectively and quantitatively evaluate the tack.

[0022] The probe tack area may be 0.14 or more and 0.40 or less. From the viewpoint of a balance between good tackiness and good removability, the probe tack area may be 0.14 or more, 0.15 or more, 0.18 or more, 0.20 or more, or 0.25 or more, or may be 0.40 or less, 0.39 or less, 0.38 or less, 0.30 or less, 0.25 or less, 0.20 or less, or 0.15 or less.

[0023] As mentioned above, the probe tack area is a value calculated by [(X × Y) / 2] using the values ​​of X (= X2 - X1) and Y determined in the probe tack test, and the value of X is preferably 0.06 to 0.13. However, from the viewpoint of a balance between imparting good tackiness to the masking tape and realizing good removability, the value of X can be set to 0.04 or more, 0.06 or more, 0.08 or more, or 0.10 or more, or can be set to 0.15 or less, 0.13 or less, 0.11 or less, 0.10 or less, or 0.09 or less.

[0024] The value of Y determined by the probe tack test is preferably 3.0 to 7.0. However, from the viewpoint of achieving a balance between imparting good tackiness to the masking tape and realizing good removability, the value of Y can be set to 3.0 or more, 4.0 or more, 5.0 or more, 6.0 or more, 8.0 or more, or 10.0 or more, or can be set to 15.0 or less, 13.0 or less, 11.0 or less, 10.0 or less, 9.0 or less, or 7.0 or less.

[0025] It is more preferable that the value of X determined by the probe tack test is 0.06 to 0.13 and the value of Y is 3.0 to 7.0.

[0026] The value of X can be adjusted, for example, by adjusting the monomer components (e.g., carboxyl group-containing monomers) constituting the (meth)acrylic polymer or the content of the tackifier resin contained in the pressure-sensitive adhesive composition. The value of Y can be adjusted, for example, by adjusting the monomer components constituting the (meth)acrylic polymer or the amount of crosslinking agent used in the pressure-sensitive adhesive composition.

[0027] The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer in this embodiment contains a (meth)acrylic polymer and a crosslinking agent, and may further contain a tackifier resin.

[0028] The thickness of the pressure-sensitive adhesive layer in this embodiment is, for example, 5 to 100 μm. Here, the thickness is preferably 5 μm or more, more preferably 10 μm or more, and is preferably 100 μm or less, more preferably 80 μm or less.

[0029] In this embodiment, the pressure-sensitive adhesive layer preferably has a gel fraction of 0 to 80%. While the gel fraction may be 0%, from the viewpoint of removability, the gel fraction is preferably greater than 0%, more preferably 40% or greater. Furthermore, the gel fraction is preferably 80% or less, more preferably 70% or less.

[0030] The gel fraction was calculated as follows. First, approximately 0.1 g of the adhesive layer was collected in a sampling bottle, and 30 mL of ethyl acetate was added to the bottle and shaken for 4 hours. The contents of the sample bottle were then filtered through a 200-mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 90°C for 2 hours to measure its dry weight. The dry weight thus obtained and the collected adhesive weight were used to calculate the gel fraction using the following formula. Note that the collected adhesive weight in the following formula is approximately 0.1 g, as described in the calculation method above. Gel fraction (%) = (dry weight / collected weight of adhesive) × 100

[0031] Examples of the monomer component constituting the (meth)acrylic polymer in this embodiment include (meth)acrylic acid alkyl esters, carboxy group-containing monomers, hydroxyl group-containing monomers, nitrogen atom-containing monomers, etc. The (meth)acrylic polymer may be a homopolymer consisting of one of these monomer components, or a copolymer consisting of two or more of these monomer components.

[0032] The (meth)acrylic polymer content in the solid content of the pressure-sensitive adhesive composition in this embodiment is preferably 60 to 99.9% by mass. Here, the content is preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more. The content is also preferably 99.9% by mass or less, more preferably 99.8% by mass or less, and even more preferably 99.7% by mass or less.

[0033] The monomer component constituting the (meth)acrylic polymer in this embodiment preferably contains a (meth)acrylic acid alkyl ester. From the viewpoint of imparting removability to the masking tape, the number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester can be 1 or more, 3 or more, 5 or more, 7 or more, or 10 or more, and from the viewpoint of imparting desired adhesive properties to the masking tape, the number of carbon atoms can be 20 or less, 15 or less, 12 or less, 10 or less, or 8 or less.

[0034] Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, iso-nonyl (meth)acrylate, n-decyl (meth)acrylate, iso-decyl (meth)acrylate, undeca(meth)acrylate, lauryl (meth)acrylate, n-stearyl (meth)acrylate, and iso-stearyl (meth)acrylate.

[0035] The (meth)acrylic polymer in this embodiment is preferably a polymer of a monomer component containing more than 50% by mass and not more than 99.5% by mass of a (meth)acrylic acid alkyl ester, with the (meth)acrylic acid alkyl ester content being more preferably 55 to 99% by mass, and even more preferably 60 to 98.5% by mass. Furthermore, the (meth)acrylic polymer is particularly preferably a polymer of a monomer component containing 45 to 80% by mass of a (meth)acrylic acid alkyl ester having an alkyl group with 5 to 12 carbon atoms. By using a (meth)acrylic acid alkyl ester having an alkyl group with 5 to 12 carbon atoms in an amount within the above range, a masking tape superior in terms of adhesive strength, maximum load in a probe tack test, and removability can be obtained.

[0036] The content of (meth)acrylic acid alkyl ester in the above monomer component can be 15% by mass or more, 30% by mass or more, 45% by mass or more, more than 50% by mass, 55% by mass or more, 60% by mass or more, 75% by mass or more, or 90% by mass or more, from the viewpoint of imparting removability to the masking tape, and the content can be 100% by mass or less, 99.5% by mass or less, 99% by mass or less, 98.5% by mass or less, 95% by mass or less, 90% by mass or less, 80% by mass or less, or 75% by mass or less, from the viewpoint of imparting desired adhesive properties to the masking tape.

[0037] In this embodiment, the monomer component constituting the (meth)acrylic polymer preferably contains a carboxyl group-containing monomer from the viewpoint of imparting desired adhesive properties to the protective sheet. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid; acid anhydride group-containing monomers such as phthalic anhydride and maleic anhydride; and carboxyl group-containing (meth)acrylates such as β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, succinic acid mono(meth)acryloyloxyethyl ester, and ω-carboxypolycaprolactone mono(meth)acrylate.

[0038] The (meth)acrylic polymer in this embodiment is preferably a polymer of a monomer component containing 0.5 to 8% by mass of a carboxyl group-containing monomer. The content of the carboxyl group-containing monomer in the monomer component may be 0% by mass or more, more than 0%, 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 1.5% by mass or more, 2.5% by mass or more, or 3.5% by mass or more, and the content may be 20% by mass or less, 10% by mass or less, 8.0% by mass or less, 5.0% by mass or less, 3.5% by mass or less, 2.5% by mass or less, 1.5% by mass or less, or 0.5% by mass or less.

[0039] In view of the ease of application and removability of the masking tape, the monomer component constituting the (meth)acrylic polymer in this embodiment preferably contains a hydroxyl group-containing monomer, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

[0040] The (meth)acrylic polymer in this embodiment is preferably a polymer of a monomer component containing 15 to 25% by mass of a hydroxyl group-containing monomer. The content of the hydroxyl group-containing monomer in the monomer component can be 0% by mass or more, more than 0%, 0.3% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, and the content can be 50% by mass or less, 30% by mass or less, 25% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, or 0.3% by mass or less.

[0041] The monomer components constituting the (meth)acrylic polymer in this embodiment may contain a nitrogen atom-containing monomer in order to improve the adhesive strength of the masking tape. Examples of the nitrogen atom-containing monomer include N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, N-hexyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, (meth)acryloylmorpholine, and cyano group-containing monomers.

[0042] In the (meth)acrylic polymer of the present embodiment, when containing a nitrogen atom-containing monomer, the content can be 0% by mass or more, more than 0% by mass, 0.3% by mass or more, 1.0% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, and the above content can be 50% by mass or less, 30% by mass or less, 25% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, or 0.3% by mass or less.

[0043] The (meth)acrylic polymer in the present embodiment preferably contains two or more selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group with 5 to 12 carbon atoms, carboxy group-containing monomers, and hydroxyl group-containing monomers as monomer components, and more preferably contains all three. Further, it is more preferable to contain 45 to 80% by mass of (meth)acrylic acid alkyl ester having an alkyl group with 5 to 12 carbon atoms, 0.5 to 8% by mass of carboxy group-containing monomer, and 15 to 25% by mass of hydroxyl group-containing monomer.

[0044] The weight average molecular weight (Mw) of the (meth)acrylic polymer in the present embodiment may be 400,000 or more, 500,000 or more, 600,000 or more, and may also be 2,000,000 or less, 1,800,000 or less, 1,500,000 or less.

[0045] The polydispersity (Mw / Mn) represented by the ratio of Mw to the number average molecular weight (Mn) of the (meth)acrylic polymer can be 15.0 or less, 10.0 or less, 8.0 or less, 6.0 or less, or 5.0 or less, and may also be 1.5 or more, 2.0 or more, 3.0 or more, or 4.0 or more. For example, the polydispersity of the (meth)acrylic polymer may be 1.5 or more and 15.0 or less, or 2.0 or more and 8.0 or less.

[0046] The weight average molecular weight and the number average molecular weight are determined by standard polystyrene conversion under the following conditions using GPC (gel permeation chromatography). <GPC measurement conditions> Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation) GPC column configuration: The following five columns (all manufactured by Tosoh) (1) TSK-GEL HXL-H (guard column) (2) TSK-GEL G7000HXL (3) TSK-GEL GMHXL (4) TSK-GEL GMHXL (5) TSK-GEL G2500HXL Sample concentration: 1.0 mg / cm 3 Dilute with tetrahydrofuran so that Mobile phase solvent: tetrahydrofuran Flow rate: 1.0cm 3 / min Column temperature: 40℃

[0047] The (meth)acrylic polymer can be produced by known methods, but is preferably produced by solution polymerization. Specifically, a reaction vessel is charged with monomer components and a polymerization solvent, and a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas. The mixture is heated to a reaction temperature of about 50 to 90°C and reacted for 4 to 20 hours. During the polymerization reaction, additional polymerization initiator, chain transfer agent, monomer components, and polymerization solvent may be added as needed.

[0048] Examples of the polymerization initiator include ordinary organic polymerization initiators, specifically peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as 2,2'-azobisisobutyronitrile. Among these, azo compounds are preferred.

[0049] Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis (2-Amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide].

[0050] The polymerization initiator may be used alone or in combination of two or more kinds. The amount of the polymerization initiator used is usually 0.01 to 5 parts by mass relative to 100 parts by mass of the monomer components. In this embodiment, the Mw of the (meth)acrylic polymer can be adjusted within an appropriate range.

[0051] In solution polymerization, examples of polymerization solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane. Polymerization solvents may be used alone or in combination of two or more.

[0052] Examples of chain transfer agents include cyanoacetic acid, bromoacetic acid, and alkyl esters thereof having 1 to 8 carbon atoms; aromatic compounds such as anthracene, phenanthrene, and fluorene; aromatic nitro compounds such as p-nitroaniline, nitrobenzene, and p-nitrobenzoic acid; benzoquinone derivatives such as benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone; borane derivatives such as tributylborane; halogenated hydrocarbons such as carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, and 3-chloro-1-propene; aldehydes such as chloral and furaldehyde; alkyl mercaptans having 1 to 18 carbon atoms; aromatic mercaptans such as thiophenol and toluene mercaptan; mercaptoacetic acid, alkyl esters of mercaptoacetic acid having 1 to 10 carbon atoms; hydroxyalkyl mercaptans having 1 to 12 carbon atoms; and terpenes such as pinene and terpinolene.

[0053] Examples of crosslinking agents in this embodiment include isocyanate compounds, epoxy compounds, and metal chelate compounds. Among these, isocyanate compounds are preferred from the viewpoint of exhibiting adhesive strength of the masking tape. The crosslinking agents may be used alone or in combination of two or more.

[0054] As the isocyanate compound, an isocyanate compound having two or more isocyanate groups in one molecule is usually used. The number of isocyanate groups in one molecule is preferably 2 to 8, more preferably 3 to 6. When the number of isocyanate groups is within the above range, it is preferable in terms of the efficiency of the crosslinking reaction between the (meth)acrylic polymer and the isocyanate compound.

[0055] Examples of diisocyanate compounds having two isocyanate groups per molecule include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of aliphatic diisocyanates include aliphatic diisocyanates having 4 to 30 carbon atoms, such as ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. Examples of alicyclic diisocyanates include alicyclic diisocyanates having 7 to 30 carbon atoms, such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate. Examples of aromatic diisocyanates include aromatic diisocyanates having 8 to 30 carbon atoms, such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

[0056] Examples of isocyanate compounds having three or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4',4"-triphenylmethane triisocyanate.

[0057] Examples of the isocyanate compound include multimers (e.g., dimers or trimers, biurets, and isocyanurates), derivatives (e.g., addition reaction products of polyhydric alcohols with two or more molecules of diisocyanate compounds), and polymers of the isocyanate compounds having two or more isocyanate groups. Examples of the polyhydric alcohols in the derivatives include low-molecular-weight polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol, as well as trivalent or higher alcohols; and high-molecular-weight polyhydric alcohols such as polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols.

[0058] Examples of such isocyanate compounds include a trimer of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, a biuret or isocyanurate of hexamethylene diisocyanate or tolylene diisocyanate, a reaction product of trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate (for example, a trimolecular adduct of tolylene diisocyanate or xylylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a trimolecular adduct of hexamethylene diisocyanate), polyether polyisocyanate, and polyester polyisocyanate.

[0059] Among isocyanate compounds, xylylene diisocyanate and hexamethylene diisocyanate crosslinking agents are preferred in terms of yellowing resistance, and tolylene diisocyanate crosslinking agents are preferred in terms of stress relaxation. Examples of xylylene diisocyanate crosslinking agents include xylylene diisocyanate and its multimers, derivatives, and polymers; examples of hexamethylene diisocyanate crosslinking agents include hexamethylene diisocyanate and its multimers, derivatives, and polymers; and examples of tolylene diisocyanate crosslinking agents include tolylene diisocyanate and its multimers, derivatives, and polymers.

[0060] Examples of epoxy compounds include compounds having two or more epoxy groups in the molecule, such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N'-diamineglycidylaminomethyl).

[0061] Examples of metal chelate compounds include compounds in which polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium are coordinated with alkoxides, acetylacetone, ethyl acetoacetate, etc. Specific examples include aluminum isopropylate, aluminum secondary butylate, aluminum ethyl acetoacetate diisopropylate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate.

[0062] The content of the crosslinking agent in the pressure-sensitive adhesive composition in this embodiment is preferably 0.05 to 10 parts by mass per 100 parts by mass of the (meth)acrylic polymer. From the viewpoint of the removability of the masking tape, the content is preferably 0.05 parts by mass or more, more preferably 0.10 parts by mass or more, and even more preferably 0.15 parts by mass or more. From the viewpoint of the adhesive properties of the masking tape, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less.

[0063] In view of the adhesiveness between the pressure-sensitive adhesive layer and the substrate, the crosslinking agent in this embodiment preferably contains an isocyanate compound. Examples of the isocyanate compound include L-45 and Y-75 (both manufactured by Soken Chemical & Engineering Co., Ltd.).

[0064] In addition to the (meth)acrylic polymer and crosslinking agent, the pressure-sensitive adhesive composition of the present embodiment may further contain other components within the scope of the present invention, such as a tackifier resin, an antistatic agent, a silane coupling agent, an ultraviolet absorber, an antioxidant, a plasticizer, an antifoaming agent, a filler, a softener, and a wettability adjuster.

[0065] The tackifying resin, which is an optional component, is a resin having a specific softening point, and is preferably included from the viewpoint of adhesiveness. The softening point is preferably, for example, 95 to 160°C. Here, the softening point is preferably 95°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher, and is preferably 160°C or lower, and more preferably 150°C or lower.

[0066] Examples of the tackifying resin include terpene phenol-based tackifying resins, rosin-based tackifying resins, terpene-based tackifying resins, and petroleum-based resins having 5 to 9 carbon atoms. Among these, at least one of terpene phenol-based tackifying resins and rosin-based tackifying resins is preferred.

[0067] In this embodiment, the content of the tackifier resin in the pressure-sensitive adhesive composition is preferably 3 to 15 parts by mass per 100 parts by mass of the (meth)acrylic polymer. From the viewpoint of obtaining sufficient adhesiveness, the content is preferably 3 parts by mass or more, more preferably 4 parts by mass or more, and even more preferably 5 parts by mass or more. From the viewpoint of tackiness, the content is preferably 15 parts by mass or less, more preferably 14 parts by mass or less, and even more preferably 13 parts by mass or less.

[0068] When at least one of a terpene phenol-based tackifying resin and a rosin-based tackifying resin is contained as the tackifying resin, the content of the tackifying resin is preferably 3 to 15 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer, as described above. When two or more types of resins are contained as the tackifying resin, the total content thereof is preferably within the above range.

[0069] <Base material> Examples of the substrate that constitutes the masking tape according to this embodiment include plastic, flat yarn cloth, nonwoven fabric, paper, and metal foil.

[0070] Examples of plastics include polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polyethylene terephthalate, polyamide, polyurethane, polycarbonate, and ethylene-vinyl acetate copolymer.

[0071] The nonwoven fabric may be made of one or more synthetic resin fibers selected from polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polyethylene terephthalate, polyamide, polyurethane, polycarbonate, and ethylene-vinyl acetate copolymer, and the fibers are thermally bonded and constrained.

[0072] The thickness of the substrate is, for example, 10 to 1000 μm.

[0073] Furthermore, when the masking tape according to this embodiment is wound and used, it is not necessary to place a release paper or the like on the adhesive layer, but this does not in any way exclude the possibility of providing a release layer on the adhesive layer.

[0074] The curing tape according to this embodiment can be used, like ordinary curing tapes, as a masking tape for spraying mortar, paint, etc. In particular, the curing tape according to this embodiment has good adhesion to various adherends such as metal, wood, and plastic, has excellent hiding and / or protective effects, leaves little residue when peeled off after use, and causes little damage to the adherend when peeled off, resulting in excellent removability.

[0075] <Making method of masking tape> The masking tape according to this embodiment has a pressure-sensitive adhesive layer on the above-mentioned substrate. The pressure-sensitive adhesive layer can be obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition, specifically by crosslinking at least the (meth)acrylic polymer with a crosslinking agent.

[0076] Examples of protective tapes include single-sided adhesive sheets having a substrate and the above-mentioned adhesive layer formed on one side of the substrate, and adhesive sheets in which a release-treated plastic film is attached to the side of the adhesive layer that is not in contact with other layers of these adhesive sheets.

[0077] The pressure-sensitive adhesive layer is formed, for example, as follows: The pressure-sensitive adhesive composition is applied to the release-treated surface of a release-treated plastic film or to a substrate, and dried typically at 60 to 120°C, preferably 70 to 110°C, typically for 1 to 10 minutes, preferably 2 to 5 minutes, to form a coating film. Subsequently, when the composition is applied to a release-treated plastic film, a substrate is laminated to the coating film on the side without the release-treated plastic film; when the composition is applied to a substrate, a release-treated plastic film is laminated to the coating film. Subsequently, the composition is aged for typically one day or more, preferably 2 to 10 days, typically in an environment of 5 to 60°C, preferably 15 to 50°C, typically 30 to 70% RH, preferably 40 to 70% RH. Crosslinking under the aging conditions described above allows for efficient formation of a crosslinked product.

[0078] The masking tape may be produced by applying the pressure-sensitive adhesive composition to a substrate, drying the composition, and then winding the composition around a core with the substrate side facing outward, followed by aging.

[0079] The pressure-sensitive adhesive composition can be applied by, for example, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, or the like.

[0080] <<Mask tape evaluation method>> The present invention also relates to a new method for evaluating masking tapes. Specifically, by using the probe tack area measured under the following conditions, it is possible to evaluate masking tapes that achieve the desired curing properties and have excellent removability without relying on tactile sensation. (conditions) The masking tape is subjected to a probe tack test at 23°C and 50% RH. The probe tack test is performed by attaching a stainless steel probe to the tape with a contact load of 1 N / cm. 2After contacting the stainless steel probe with the surface of the adhesive layer for 1 second at a contact speed of 10 mm / sec, the load required to peel the probe from the adhesive layer is measured. The time when the load begins to become positive is defined as X1 (seconds), and the time when the probe completely separates from the adhesive layer is defined as X2 (seconds). The maximum load during the time from X1 to X2 is defined as Y (N). Using X and Y, the value expressed as [(X × Y) / 2] is the probe tack area.

[0081] The details of the probe tack test are as described in detail above in the section "Making Tape," and the preferred embodiments are also the same.

[0082] For example, the probe tack area is preferably 0.14 or more, more preferably 0.14 to 0.40. Furthermore, in [(X×Y) / 2] representing the probe tack area, the value of X is preferably 0.06 to 0.13, and the value of Y is preferably 3.0 to 7.0.

[0083] The evaluation method according to this embodiment makes it possible to objectively quantify tackiness without relying on the tactile sensation of a skilled worker. [Example]

[0084] The present invention will be explained in more detail in the following examples, but the present invention is not limited thereto.

[0085] <Production example> Examples 1 to 7, Comparative Examples 1 and 2 A flask was charged with 100 parts by mass of ethyl acetate, and each of the monomers listed in the "monomer components" section of "(meth)acrylic polymer" in Table 1 was added in the amounts listed in Table 1, as well as 0.08 parts of n-dodecyl mercaptan as a chain transfer agent. The numerical values ​​for the blended components listed in Table 1 represent parts by mass. This solution was heated to 78°C with stirring, and then 0.03 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and polymerization was carried out at 80°C for 4 hours to prepare a (meth)acrylic polymer solution.

[0086] A crosslinking agent and an optional tackifying resin shown in Table 1 were blended with 100 parts by mass of the solid content of the (meth)acrylic polymer solution obtained above so that the blending ratios, converted into solid content, were the ratios shown in Table 1, and the mixture was thoroughly mixed to obtain a pressure-sensitive adhesive composition.

[0087] The adhesive composition obtained above after defoaming was applied to a polyethylene terephthalate (PET) film substrate using a doctor blade so that the thickness after drying would be 25 μm. The coating was then dried at 90° C. for 3 minutes to remove the solvent, yielding a masking tape comprising a substrate and an adhesive layer on the substrate. A release-treated PET film was attached to the surface of the adhesive layer opposite the substrate to prevent contamination until each evaluation was performed.

[0088] The abbreviations for each component in Table 1 are as follows: (Meth)acrylic polymer, monomer component BA: butyl acrylate 2EHA: 2-ethylhexyl acrylate AA: acrylic acid HEA: 2-hydroxyethyl acrylate AM: acrylamide Crosslinking agent L-45: Isocyanate crosslinking agent (manufactured by Soken Chemical Industries, Ltd.) E-5CM: Epoxy crosslinking agent (manufactured by Soken Chemical Industries, Ltd.) Tackifying resin A-100: Rosin-based tackifying resin (Super Ester A-100, manufactured by Arakawa Chemical Industries) G-100: Terpene phenol tackifying resin (YS Polystar G-100, manufactured by Yasuhara Chemical)

[0089] [Table 1]

[0090] "evaluation" <Probe tack test> Each of the masking tapes of Examples 1 to 7 and Comparative Examples 1 and 2 was cut to a size of 15 mm x 15 mm, and the release-treated PET film was peeled off to prepare a test specimen. The test specimen was attached to a test jig with a load of 20 g, and a probe tack test was performed under the conditions described above. The test was performed using a probe tack tester (TE-6001, manufactured by Tester Sangyo Co., Ltd.), and the probe tack area [(X x Y) / 2] was calculated using a data logger (multi-input data logger NR-500, manufactured by Keyence Corporation). The results are shown in Table 1 under "Evaluation" in the "Probe Tack Test" column as "X (seconds)," "Y (N)," and "Area," respectively.

[0091] <Adhesive strength> Each masking tape from Examples 1 to 7 and Comparative Examples 1 and 2 was cut to a size of 25 mm x 100 mm, and the release-treated PET film was peeled off to prepare a test specimen. The adhesive layer of the test specimen was attached to a SUS (stainless steel) plate, and the adhesive strength was measured in accordance with JIS Z 0237:2009. Specifically, the test specimen was pressed against the SUS plate using three reciprocating strokes of a 2 kg roller, and then left for 20 minutes in an environment of 23°C and 50% RH. The end of the test specimen was then pulled and peeled off at a peel angle of 180° from the SUS plate surface at a peel rate of 300 mm / min, and the peel strength per 25 mm width was measured as adhesive strength. The results are shown in Table 1 under "Adhesive Strength (N / 25 mm)" in the "Evaluation" section.

[0092] <Removability> After the above evaluation of <Adhesive strength>, the adherend (SUS plate) was visually inspected, and removability was evaluated according to the following criteria. 〇: No adhesive residue or marks are visible △: Slight traces of adhesive can be seen ×: Adhesive residue remains on the adherend

[0093] <Finger feel> Test specimens were prepared by peeling off the release-treated PET film from each of the protective tapes of Examples 1 to 7 and Comparative Examples 1 and 2. The adhesive layer of each test specimen was checked for tactile feel (finger tack) by two skilled workers, and compared with the tactile feel of a commercially available protective tape (Pyollan (registered trademark) Tape, Y-09-GR for painting and construction protection, manufactured by Diatex), and the tactile feel was evaluated according to the following criteria. The results are shown in the "tactile feel" column under "Evaluation" in Table 1. ◎: Stronger tack than Piolant Tape 〇: Equivalent to Piolantape △: Slightly weaker tack than Piolantape ×: Clearly weaker tack than Piolant Tape

[0094] As can be seen from Table 1, there is a good correlation between the probe tack area and the finger tactile feel. For example, comparing the results of Example 1 and Comparative Example 1, Comparative Example 1 has a probe tack area of ​​less than 0.14, so despite having lower adhesive strength than Example 1, it has poorer removability. Furthermore, comparing the results of Example 1, Example 4, and Comparative Example 2, it can be seen that, despite having similar adhesive strength, the larger the probe tack area, the better the finger tactile feel and removability. In this way, it was confirmed that the masking tape according to this embodiment, which has an adhesive layer with a probe tack area of ​​0.14 or more, can achieve the desired masking and also has excellent removability.

Claims

1. A substrate and a pressure-sensitive adhesive layer provided on the substrate, the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer and a crosslinking agent, The pressure-sensitive adhesive layer has a probe tack area of ​​0.14 or more and 0.40 or less, measured under the following conditions: (conditions) The masking tape is subjected to a probe tack test under an environment of 23°C and 50% RH. The probe tack test is performed by attaching a stainless steel probe to the tape at a contact load of 1 N / cm. ２ After the stainless steel probe is brought into contact with the surface of the adhesive layer at a contact speed of 10 mm / sec for 1 second, the load required to peel the stainless steel probe from the adhesive layer is measured. The time from when the load starts to become positive until the probe completely separates from the adhesive layer is defined as X (seconds). The maximum load within the time period X is defined as Y (N). Using X and Y, the value expressed by [(X × Y) / 2] is defined as the probe tack area.

2. The masking tape according to claim 1, wherein the value of X obtained by the probe tack test is 0.06 to 0.

13.

3. The masking tape according to claim 1 or 2, wherein the Y value obtained by the probe tack test is 3.0 to 7.

0.

4. The pressure-sensitive adhesive composition further contains at least one tackifying resin selected from the group consisting of a terpene phenol-based tackifying resin and a rosin-based tackifying resin, and The masking tape according to claim 1 or 2, wherein the tackifier resin contains 3 to 15 parts by mass per 100 parts by mass of the (meth)acrylic polymer.

5. The (meth)acrylic polymer is a polymer of a monomer component containing 45 to 80% by mass of a (meth)acrylic acid alkyl ester having an alkyl group with 5 to 12 carbon atoms. The masking tape according to claim 1 or 2.

6. The masking tape according to claim 1 or 2, wherein the (meth)acrylic polymer is a polymer of a monomer component containing 0.5 to 8% by mass of a carboxy group-containing monomer.

7. The masking tape according to claim 1 or 2, wherein the (meth)acrylic polymer is a polymer of a monomer component containing 15 to 25% by mass of a hydroxyl group-containing monomer.

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