Adhesives and adhesive tapes

Abstract

To provide an adhesive which has high flame retardancy and high adhesion.SOLUTION: An adhesive contains an acrylic resin (A), a crosslinking agent (B) an a flame retardant (C), wherein a solubility parameter (SP value) of the acrylic resin (A) is 10 (cal / cm3)1 / 2 or less, and the flame retardant (C) contains a phosphate-based flame retardant.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive and an adhesive tape, and more particularly to an adhesive having excellent flame retardancy and adhesive strength, and an adhesive tape using this adhesive. [Background technology]

[0002] Conventionally, flame-retardant pressure-sensitive adhesive tapes have been developed by adding a flame retardant to the pressure-sensitive adhesive layer. For example, Patent Document 1 discloses that adding an ammonium phosphate flame retardant to an acrylic resin can provide a flame-retardant pressure-sensitive adhesive tape that does not generate halogen gas or phosphine gas and has excellent flame retardancy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-189753 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the adhesive tape disclosed in Patent Document 1 uses a relatively large amount of flame retardant, and therefore the adhesive strength is insufficient.Furthermore, the flame retardancy is insufficient for use as an adhesive tape for fixing aircraft components, which requires even higher flame retardancy.

[0005] Under these circumstances, the present invention aims to provide an adhesive having high flame retardancy and high adhesiveness, and an adhesive tape using this adhesive. [Means for solving the problem]

[0006] However, the present inventors have conducted extensive research in light of the above circumstances and have found that the solubility parameter (SP value) is 10 (cal / cm 3 ) 1 / 2The inventors have found that by using the following acrylic resin in combination with a phosphate ester flame retardant as a flame retardant, it is possible to obtain an adhesive that has excellent flame retardancy and, in contrast to the usual case where an adhesive containing a flame retardant has a reduced adhesive strength, has a higher adhesive strength than an adhesive that does not contain a flame retardant, and have completed the present invention.

[0007] That is, the present invention provides a pressure-sensitive adhesive containing an acrylic resin (A), a crosslinking agent (B), and a flame retardant (C), wherein the solubility parameter (SP value) of the acrylic resin (A) is 10 (cal / cm 3 ) 1 / 2 and the flame retardant (C) contains a phosphate ester flame retardant. The content of the flame retardant (C) is 1 to 8 parts by weight based on 100 parts by weight of the acrylic resin (A). The first aspect of the present invention is an adhesive.

[0008] A second aspect of the present invention is an adhesive tape having a substrate and an adhesive layer containing the above-mentioned adhesive on at least one surface of the substrate. In the present invention, the term "tape" also includes "film" and "sheet."

[0009] The reason why the present invention provides the above-mentioned effects is not clear, but the following reasons are considered: The solubility parameter (SP value) of the acrylic resin (A) is 10 (cal / cm 3 ) 1 / 2 When the ratio is equal to or less than 1, the compatibility between the acrylic resin (A) and the phosphate ester flame retardant is good, and the phosphate ester flame retardant is easily dissolved in the acrylic resin (A). This is thought to improve the flame retardancy by uniformly dispersing the phosphate ester flame retardant in the acrylic resin (A), and also improve the adhesiveness by softening the acrylic resin (A). [Effects of the Invention]

[0010] The pressure-sensitive adhesive of the present invention has excellent flame retardancy and adhesiveness, and therefore the pressure-sensitive adhesive tape of the present invention using this pressure-sensitive adhesive also has excellent flame retardancy and adhesiveness, and therefore the pressure-sensitive adhesive tape of the present invention can be suitably used as a pressure-sensitive adhesive tape such as a double-sided pressure-sensitive adhesive tape for fixing aircraft components that require even higher flame retardancy. DETAILED DESCRIPTION OF THE INVENTION

[0011] The configuration of the present invention will be described in detail below, but these are merely examples of preferred embodiments.

[0012] adhesive The pressure-sensitive adhesive of the present invention contains an acrylic resin (A), a crosslinking agent (B), and a flame retardant (C). Each of the components used in the pressure-sensitive adhesive of the present invention will be described in detail below.

[0013] <Acrylic resin (A)> Examples of the acrylic resin (A) used in the present invention include a homopolymer of alkyl (meth)acrylate and a copolymer obtained by polymerizing a copolymerizable monomer copolymerizable with the homopolymer. Each monomer unit that can constitute the acrylic resin (A) will be described below. In this specification, (meth)acrylate refers to acrylate or methacrylate, and (meth)acrylic acid refers to acrylic acid or methacrylic acid.

[0014] [Hydroxyl Group-Containing Monomer (a1) Unit] The acrylic resin (A) preferably contains units of a hydroxyl group-containing monomer (a1). Examples of copolymerizable monomers for forming the hydroxyl group-containing monomer (a1) unit include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; N-methylol (meth)acrylate; Examples of suitable monomers include hydroxyl group-containing (meth)acrylamides such as tert-acrylamide, N-hydroxyethyl(meth)acrylamide, and N-methylolpropane(meth)acrylamide, primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethylphthalate, secondary hydroxyl group-containing monomers such as 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 3-chloro-2-hydroxypropyl(meth)acrylate, and 2-hydroxy-3-phenoxypropyl(meth)acrylate, and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl(meth)acrylate. These monomers can also be referred to as hydroxyl group-containing (meth)acrylic acid ester monomers.

[0015] Among these, primary hydroxyl group-containing monomers are preferred because of their excellent reactivity with crosslinking agents, and (meth)acrylic acid hydroxyalkyl esters are more preferred, with 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate being particularly preferred.

[0016] The hydroxyl group-containing monomer (a1) units are useful because they form crosslinking points with the crosslinking agent (B), described below, particularly the isocyanate-based crosslinking agent (b1). The content of the hydroxyl group-containing monomer (a1) units is usually 0.01 to 5 wt%, preferably 0.05 to 3 wt%, and more preferably 0.05 to 2 wt%, based on the total weight of the acrylic resin (A). If the amount of the monomer (a1) units is too small, the flame retardancy tends to decrease, while if the amount is too large, the adhesive strength tends to decrease. The content of the hydroxyl group-containing monomer (a1) units can be adjusted by the blending ratio of the monomers when producing the acrylic resin (A), and can be analyzed by NMR or the like.

[0017] [(Meth)acrylic acid monomer (a2) unit] The acrylic resin (A) preferably also contains (meth)acrylic acid monomer (a2) units. The content of the (meth)acrylic acid monomer (a2) units is usually 0.1 to 5 wt %, preferably 0.5 to 4.5 wt %, and more preferably 1 to 4 wt %, based on the total weight of the acrylic resin (A). If the (meth)acrylic acid monomer (a2) units are too few, the adhesive strength tends to decrease, whereas if they are too much, the viscosity of the coating liquid tends to increase, resulting in decreased coatability.

[0018] [Alkyl (meth)acrylate ester monomer (a3) ​​unit] The acrylic resin (A) preferably also contains units of an alkyl (meth)acrylate monomer (a3) ​​having an alkyl group having 4 to 24 carbon atoms. The copolymerizable monomer for forming such alkyl(meth)acrylate monomer (a3) ​​units may be any alkyl(meth)acrylate monomer having an alkyl group having 4 to 24 carbon atoms. In particular, it is preferable to use both an alkyl(meth)acrylate monomer (a3-1) having an alkyl group having 4 to 7 carbon atoms and an alkyl(meth)acrylate monomer (a3-2) having an alkyl group having 8 to 24 carbon atoms. An alkyl(meth)acrylate monomer having an alkyl group with 4 to 24 carbon atoms and also having a hydroxyl group is classified as a hydroxyl group-containing monomer (a1).

[0019] Examples of the alkyl(meth)acrylate monomer (a3-1) having an alkyl group having 4 to 7 carbon atoms include n-butyl(meth)acrylate, t-butyl(meth)acrylate, isobutyl(meth)acrylate, n-hexyl(meth)acrylate, etc. Among these, n-butyl(meth)acrylate is preferred from the viewpoints of easy availability and economical efficiency.

[0020] Examples of the alkyl (meth)acrylate monomer (a3-2) having an alkyl group having 8 to 24 carbon atoms include 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, isotridecyl (meth)acrylate, myristyl (meth)acrylate, isomyristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, etc. Among these, alkyl (meth)acrylates having an alkyl group having 8 to 12 carbon atoms are preferred, and 2-ethylhexyl (meth)acrylate is particularly preferred, due to their low polarity and low glass transition temperature.

[0021] The content of the monomer (a3) ​​units is usually 55 to 98% by weight, preferably 70 to 97% by weight, and more preferably 80 to 95% by weight, based on the total weight of the acrylic resin (A). If the content of the monomer (a3) ​​units is too small, the adhesive strength tends to decrease, whereas if the content of the monomer (a3) ​​units is too large, the adhesive strength and holding power tend to decrease.

[0022] When the monomer (a3-1) and the monomer (a3-2) are used in combination, the ratio of the monomer (a3-1) units to the monomer (a3-2) units is preferably (a3-1) / (a3-2)=15 / 85 to 85 / 15 by weight, more preferably 25 / 75 to 75 / 25, even more preferably 30 / 70 to 70 / 30, particularly preferably 40 / 60 to 60 / 40, and especially preferably 45 / 55 to 55 / 45. If the ratio of the monomer (a3-1) units is too small, the holding power tends to decrease, and if it is too large, the flame retardancy tends to decrease.

[0023] [Other monomer (a4) units] The acrylic resin (A) may contain other monomer (a4) units, such as alkyl (meth)acrylate monomer (a4-1) units having an alkyl group with 1 to 3 carbon atoms, cyclic structure-containing monomer (a4-2) units, and vinyl ester monomer (a4-3) units having 3 to 10 carbon atoms. The above-mentioned monomers (a4-1) to (a4-3) are collectively referred to as "other monomers (a4)." Furthermore, even if a monomer falls under the category of "other monomers (a4)," if it also has a hydroxyl group, it is classified as a hydroxyl-containing monomer (a1).

[0024] Examples of copolymerizable monomers for forming the alkyl(meth)acrylate monomer (a4-1) units having an alkyl group having 1 to 3 carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, etc. Among these, methyl(meth)acrylate and ethyl(meth)acrylate are preferred.

[0025] The copolymerizable monomer for forming the cyclic structure-containing monomer (a4-2) unit is usually a (meth)acrylic monomer having a substituent containing a cyclic structure, and examples thereof include heterocycle-containing (meth)acrylates having a heterocycle such as a morpholine ring, a piperidine ring, a pyrrolidine ring, or a piperazine ring, such as N-(meth)acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and also phenyl(meth)acrylate, phenoxyethyl(meth)acrylate, and the like. Other examples of the (meth)acrylate include phenyl diethylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, isobornyl (meth)acrylate, and biphenyloxyethyl (meth)acrylate. Other examples of the (meth)acrylate that are not (meth)acrylic monomers include styrene and α-methylstyrene. Among these, heterocycle-containing (meth)acrylates having a morpholine ring are preferred due to their well-balanced properties, and N-(meth)acryloylmorpholine is particularly preferred due to its availability and safety.

[0026] Examples of copolymerizable monomers for forming the vinyl ester monomer (a4-3) units having 3 to 10 carbon atoms include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, etc. Among these, vinyl acetate is preferred because of its easy availability.

[0027] The content of the other monomer (a4) units is usually 11% by weight or less, preferably 10% by weight or less, and more preferably 8% by weight or less, based on the total acrylic resin (A). If the content of the other monomer (a4) units is too high, the adhesive strength to the adherend tends to decrease. The lower limit of the content of the other monomer (a4) units is usually 0% by weight, but 1% by weight is preferred.

[0028] [Further other monomer (a5) units] The acrylic resin (A) may further contain other monomer (a5) units, if necessary. Examples of copolymerizable monomers for forming the other monomer (a5) units include functional group-containing monomers such as acetoacetyl group-containing monomers, isocyanate group-containing monomers, glycidyl group-containing monomers, amino group-containing monomers, and amide group-containing monomers, as well as other copolymerizable monomers.

[0029] Examples of the acetoacetyl group-containing monomer include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate.

[0030] Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

[0031] Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and allyl glycidyl (meth)acrylate.

[0032] Examples of the amino group-containing monomer include a monomer having an ethylenically unsaturated double bond and an amino group (unsubstituted or substituted amino group). For example, mono-substituted amino group-containing (meth)acrylic acid esters such as aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, and aminoisopropyl (meth)acrylate, and (meth)acrylic acid esters of N-alkylaminoalkyl such as N-(t-butyl)aminoethyl (meth)acrylate; di-substituted amino group-containing (meth)acrylic acid esters such as N,N-dialkylaminoalkyl (meth)acrylic acid esters such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate. dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminopropyl(meth)acrylamide, and quaternized salts of these amino group-containing monomers; amino group-containing styrenes such as p-aminostyrene; styrenes having a dialkylamino group such as 3-(dimethylamino)styrene and dimethylaminomethylstyrene; dialkylaminoalkyl vinyl ethers such as N,N-dimethylaminoethyl vinyl ether and N,N-diethylaminoethyl vinyl ether; allylamine, 4-diisopropylamino-1-butene, trans-2-butene-1,4-diamine, and 2-vinyl-4,6-diamino-1,3,5-triazine.

[0033] The amide group-containing monomer includes a monomer having an ethylenically unsaturated double bond and an amide group (a group having an amide bond). For example, (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, N-isobutyl(meth)acrylamide, Ns-butyl(meth)acrylamide, Nt-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, diacetone(meth)acrylamide, N,N'-methylenebis(meth)acrylamide, and N-(1,1-dimethyl-3-oxobutyl)(meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-diisobutyl(meth)acrylamide, and N,N-di(s-butyl)(meth)acrylamide. N,N-dialkyl(meth)acrylamides such as N,N-di(t-butyl)(meth)acrylamide, N,N-dipentyl(meth)acrylamide, N,N-dihexyl(meth)acrylamide, N,N-diheptyl(meth)acrylamide, N,N-dioctyl(meth)acrylamide, N,N-diallyl(meth)acrylamide, and N,N-ethylmethylacrylamide; dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminopropyl(meth)acrylamide; substituted amide group-containing monomers such as N-vinylacetamide, N-vinylformamide, (meth)acrylamidoethylethyleneurea, and (meth)acrylamido-t-butylsulfonic acid; alkoxy group-containing (meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide; and quaternized salts of these amide group-containing monomers.

[0034] Examples of the other copolymerizable monomers include monomers containing an alkoxy group or an oxyalkylene group, such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and polypropylene glycol mono(meth)acrylate; acrylonitrile, methacrylonitrile, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyl trimethylammonium chloride, and dimethyl allyl vinyl ketone.

[0035] The other monomer (a5) can be used to adjust the physical properties depending on the application, provided that the effect of the present invention is not impaired. For example, the content of the other monomer (a5) units is usually 10% by weight or less, with the lower limit usually being 0% by weight, based on the total weight of the acrylic resin (A).

[0036] The acrylic resin (A) can be obtained by polymerizing one or more monomers selected from the above monomers (a1) to (a5). For example, the acrylic resin (A) can be obtained that preferably contains the above monomer (a1) unit, more preferably the monomer (a2) unit, even more preferably the monomer (a3) ​​unit, and particularly preferably the monomer (a4) unit, and if necessary, the monomer (a5) unit. The monomers (a1) to (a5) can be used alone or in combination of two or more types.

[0037] As the polymerization, it is preferable to employ solution polymerization, since it allows the acrylic resin (A) to be produced safely and stably with any monomer composition.

[0038] Such solution polymerization can be carried out according to a conventional method. For example, the monomers (a1) to (a5) and a polymerization initiator are mixed or added dropwise to an organic solvent, and polymerization can be carried out under reflux or at 50 to 98°C for 0.1 to 20 hours. The acrylic resin (A) polymerized in an organic solvent is an organic solvent-based acrylic resin.

[0039] As the polymerization initiator, a conventional radical polymerization initiator can be used. Specific examples include azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile; and peroxide-based polymerization initiators such as benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, and cumene hydroperoxide. These polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator used is usually 0.001 to 5 parts by weight per 100 parts by weight of the copolymerization components.

[0040] [Solubility parameter (SP value)] In the present invention, the acrylic resin (A) has a solubility parameter (SP value) of 10 (cal / cm 3 ) 1 / 2 Below 9.9 (cal / cm 3 ) 1 / 2 Less than or equal to 9.8 (cal / cm 3 ) 1 / 2 The present invention is characterized by the following: SP value is 10(cal / cm 3 ) 1 / 2 If the SP value exceeds 7 (cal / cm), the flame retardancy and adhesiveness will decrease. 3 ) 1 / 2 and preferably 8 (cal / cm 3 ) 1 / 2 , more preferably 8.5 (cal / cm 3 ) 1 / 2 , and more preferably 9.0 (cal / cm 3 ) 1 / 2 , and particularly preferably 9.5 (cal / cm 3 ) 1 / 2 is.

[0041] The SP value can be calculated from the evaporation energy (ΔE), molar volume (ΔV) and molar ratio of the (meth)acrylic acid alkyl ester monomer and copolymerizable monomer that constitute the acrylic resin (A), and specifically, can be calculated by the following formula (1).

[0042] SP value (cal / cm 3 ) 1 / 2 = (ΔE / ΔV) 1 / 2 (1) ΔE=(x × ΔEx / Mx) + (y × ΔEy / My) + (n × ΔEn / Mn) × (1 / C) ΔV=(x × ΔVx / Mx) + (y × ΔVy / My) + (n × ΔVn / Mn) × (1 / C) C=(x / Mx) + (y / My) + (n / Mn) x: content of monomer X relative to the copolymerization components (% by weight) ΔEx: Vaporization energy of monomer X ΔVx: Molar volume of monomer X Mx: molecular weight of monomer X y: content of monomer Y relative to the copolymerization component (% by weight) ΔEy: Evaporation energy of monomer Y ΔVy: Molar volume of monomer Y My: Molecular weight of monomer Y n: content of monomer N in copolymerization components (% by weight) ΔEn: Vaporization energy of monomer N ΔVn: Molar volume of monomer N Mn: molecular weight of monomer N C: Molar ratio of acrylic resin (A)

[0043] The SP value of acrylic resin (A) is 10 (cal / cm 3 ) 1 / 2The following method may be exemplified by a method of adjusting the type and content of the monomers (a1) to (a5), particularly the type and content of the functional group-containing monomer.

[0044] [Average molecular weight] The weight-average molecular weight of the acrylic resin (A) is usually 100,000 to 5,000,000, preferably 300,000 to 1,500,000, and more preferably 400,000 to 900,000. If the weight-average molecular weight is too small, durability tends to decrease, while if it is too large, adhesive strength tends to decrease.

[0045] The dispersity (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, and particularly preferably 7 or less. If the dispersity is too high, the durability of the pressure-sensitive adhesive layer tends to decrease and foaming and the like tends to occur easily. From the viewpoint of production limitations, the dispersity is preferably 1.1 or more, more preferably 3 or more, and even more preferably 4 or more.

[0046] The weight-average molecular weight of the acrylic resin (A) is a weight-average molecular weight converted into a standard polystyrene molecular weight. The weight-average molecular weight was measured by a high-performance liquid chromatograph (manufactured by Japan Waters, Inc., "Waters 2695 (main body)" and "Waters 2414 (detector)") using a Shodex GPC KF-806L column (exclusion limit molecular weight: 2 × 10 7 Separation range: 100 to 2 × 10 7 The number average molecular weight can be measured using three columns in series (theoretical plate number: 10,000 / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm), and the number average molecular weight can also be measured using the same method.

[0047] [Glass transition temperature] The glass transition temperature (Tg) of the acrylic resin (A) is usually −80 to 10° C., preferably −70 to −10° C., and more preferably −65 to −20° C. If the glass transition temperature is too high, tackiness tends to be insufficient, and if it is too low, heat resistance tends to decrease.

[0048] The glass transition temperature (Tg) is a value calculated by applying the glass transition temperature and weight fraction of each of the monomers constituting the acrylic resin (A) to the following Fox's formula when the monomers are made into homopolymers.

[0049]

number

[0050] Tg: Glass transition temperature (K) of acrylic resin (A) Tga: Glass transition temperature of the homopolymer of monomer A (K) Wa: weight fraction of monomer A Tgb: Glass transition temperature of the homopolymer of monomer B (K) Wb: weight fraction of monomer B Tgn: Glass transition temperature (K) of the homopolymer of monomer N Wn: weight fraction of monomer N (Wa+Wb+···+Wn=1)

[0051] Here, the glass transition temperature when the monomers constituting the acrylic resin (A) are made into a homopolymer is usually a value measured by a differential scanning calorimeter (DSC) according to a method in accordance with JIS K7121-1987 or JIS K6240, or a value listed in a catalog.

[0052] The viscosity of the acrylic resin (A) is usually adjusted with a solvent or the like, and the acrylic resin (A) solution is used for coating. From the viewpoint of ease of handling, the viscosity of the acrylic resin (A) solution is preferably 500 to 20,000 mPa·s / 25°C, more preferably 1,000 to 18,000 mPa·s / 25°C, and even more preferably 2,000 to 15,000 mPa·s / 25°C. If the viscosity is too high, the fluidity tends to decrease, making handling difficult, while if the viscosity is too low, coating of the adhesive solution tends to be difficult. The solution concentration in this case is usually 10 to 70% by weight.

[0053] The solvent that can be used to adjust the viscosity is not particularly limited as long as it dissolves the acrylic resin (A), and examples thereof include ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic solvents such as toluene and xylene; and alcohol solvents such as methanol, ethanol, and propyl alcohol. Among these, ethyl acetate and methyl ethyl ketone are preferred, and ethyl acetate is more preferred, in terms of solubility, drying properties, cost, etc. Among these solvents, any one of them may be used alone, or two or more may be used in combination.

[0054] The viscosity of the acrylic resin (A) solution is measured by a rotational viscometer method using a B-type viscometer, with the resin solution adjusted to a temperature of 25°C.

[0055] <Crosslinking agent (B)> Examples of the crosslinking agent (B) used in the present invention include an isocyanate-based crosslinking agent (b1), an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, a melamine-based crosslinking agent, an aldehyde-based crosslinking agent, an amine-based crosslinking agent, and a metal chelate-based crosslinking agent.

[0056] The isocyanate-based crosslinking agent (b1) contains at least two isocyanate groups, and examples thereof include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Examples of such crosslinking agents include biurets and isocyanurates of these crosslinking agents, as well as adducts formed by reaction with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Adducts of tolylene diisocyanate and trimethylolpropane are particularly preferred. These crosslinking agents can be used alone or in combination.

[0057] Examples of the epoxy crosslinking agent include aliphatic epoxy crosslinking agents such as ethylene glycol diglycidyl ether, trimethylolpropane diglycidyl ether, and diglycidylamine; alicyclic epoxy crosslinking agents such as 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, and N,N,N',N'-tetraglycidyl-m-xylylenediamine; aromatic epoxy crosslinking agents such as diglycidylaniline; and heterocyclic epoxy crosslinking agents such as 1,3,5-tris-(2,3-epoxybutyl)isocyanurate, 1,3,5-tris-(3,4-epoxybutyl)isocyanurate, and 1,3,5-tris-(4,5-epoxypentyl)isocyanurate. Among these, alicyclic epoxy crosslinking agents are preferred. These may be used alone or in combination of two or more.

[0058] Examples of the aziridine crosslinking agent include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine, and trimethylolpropane tri-β-(2-methylaziridine)propionate.

[0059] Examples of the melamine-based crosslinking agent include melamine; methylolmelamine derivatives such as amino group-containing methylolmelamine obtained by condensing melamine with formaldehyde, imino group-containing methylolmelamine, and hexamethylolmelamine; and alkylated methylolmelamines such as partially or completely alkylated methylolmelamine and imino group-containing partially or completely alkylated methylolmelamine obtained by reacting a methylolmelamine derivative with a lower alcohol such as methyl alcohol or butyl alcohol to partially or completely etherify the methylolmelamine derivative.

[0060] Examples of the aldehyde crosslinking agent include aldehyde compounds that liberate aldehyde in an aqueous solution, such as formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde, glyoxal, glutaraldehyde, dialdehyde starch, hexamethylenetetramine, 1,4-dioxane-2,3-diol, 1,3-bis(hydroxymethyl)-2-imidazolidine, dimethylol urea, N-methylol acrylamide, urea formalin resin, and melamine formalin resin, as well as aromatic aldehyde compounds such as benzaldehyde, 2-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, and m-hydroxybenzaldehyde.

[0061] Examples of the amine-based crosslinking agent include 4,4'-methylene-bis(2-chloroaniline) (hereinafter abbreviated as "MOCA"), modified MOCA, and diethyltoluenediamine.

[0062] Examples of the metal chelate crosslinking agent include chelate compounds in which the metal atom is aluminum, zirconium, titanium, zinc, iron, tin, etc., and aluminum chelate compounds are preferred from the viewpoint of performance. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethyl acetoacetate, diisopropoxyaluminum monolauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, and diisopropoxyaluminum monoisostearyl acetoacetate.

[0063] In the present invention, one or more crosslinking agents selected from the above-mentioned crosslinking agents can be used as the crosslinking agent (B). However, it is preferable that the crosslinking agent (B) contains at least an isocyanate-based crosslinking agent (b1). A crosslinking agent (B) containing only the isocyanate-based crosslinking agent (b1) or a crosslinking agent (B) containing the isocyanate-based crosslinking agent (b1) and one or more other crosslinking agents can be used. The content of the isocyanate-based crosslinking agent (b1) in the crosslinking agent (B) is preferably 50% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95 to 100% by weight, based on 100% by weight of the crosslinking agent (B).

[0064] The crosslinking agent (B) reacts with the functional groups in the acrylic resin (A) to form a crosslinked structure. By using an isocyanate-based crosslinking agent (b1) as the crosslinking agent (B), the effect of improving flame retardancy when the flame retardant (C) is contained is further increased. The reason why the flame retardancy improvement effect is further increased is not clear, but it is thought that the reaction between the isocyanate-based crosslinking agent (b1) and the functional groups, particularly the hydroxyl groups, in the acrylic resin (A) allows the formation of a pressure-sensitive adhesive layer with a high crosslinking density, and therefore the addition of a small amount of flame retardant (C) can improve flame retardancy.

[0065] The content of the crosslinking agent (B) is preferably 0.1 to 5.0 parts by weight, more preferably 0.15 to 0.8 parts by weight, even more preferably 0.18 to 0.5 parts by weight, and particularly preferably 0.2 to 0.4 parts by weight, relative to 100 parts by weight of the acrylic resin (A). If the content is too low, the holding power tends to decrease, and if it is too high, the adhesive power tends to decrease. The crosslinking agent (B) is usually used after being diluted with a solvent or the like, and the above content indicates the substantial (solid content) content of the crosslinking agent excluding the solvent or the like. Furthermore, the crosslinking agent (B) contained in the pressure-sensitive adhesive of the present invention may have the same structure as the unreacted crosslinking agent when mixed with the acrylic resin (A), or may have a structure that has reacted with a functional group in the acrylic resin (A). Therefore, the content of the crosslinking agent (B) contained in the pressure-sensitive adhesive of the present invention refers to the content of both the unreacted and reacted crosslinking agent structures, and is equivalent to the content of the crosslinking agent (B) when mixed with the acrylic resin (A) during preparation of the pressure-sensitive adhesive of the present invention.

[0066] <Flame retardant (C)> The flame retardant (C) used in the present invention contains at least a phosphate ester-based flame retardant (c1). The phosphate ester-based flame retardant (c1) is preferably a non-halogen flame retardant, and examples thereof include aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, and tributyl phosphate; aromatic phosphate esters such as triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate, 2-naphthyl diphenyl phosphate, cresyl di-2,6-xylenyl phosphate, tris(t-butylated phenyl)phosphate, tris(isopropylated phenyl)phosphate, and triaryl isopropyl phosphate; and aromatic condensed phosphate esters such as (1,3-phenylenedioxy)bis(diphenyl phosphonate), bisphenol A bis(diphenyl phosphate), and 1,3-phenylene bis(di-2,6-xylenyl phosphate). Among these, aromatic condensed phosphate esters are preferred in that they provide good dispersibility in the acrylic resin (A).

[0067] Specific examples of non-halogen phosphate ester flame retardants include "DAIGUARD-880," "DAIGUARD-580," and "DAIGUARD-610" (all manufactured by Daihachi Chemical Industry Co., Ltd.).

[0068] Specific examples of aromatic condensed phosphate ester products include "CR-733S," "CR-741," and "PX-200" (all manufactured by Daihachi Chemical Industry Co., Ltd.), with "PX-200" being particularly preferred because of its good dispersibility in the acrylic resin (A). "CR-733S" contains (1,3-phenylenedioxy)bis(diphenylphosphonate), "CR-741" contains bisphenol A bis(diphenyl phosphate), and "PX-200" contains 1,3-phenylenebis(di-2,6-xylenyl phosphate).

[0069] Flame retardants other than the phosphate ester flame retardant (c1) are not soluble or compatible with the acrylic resin (A), making it difficult to disperse them uniformly in the acrylic resin (A). Therefore, it is necessary to increase the amount of flame retardant to achieve sufficient flame retardancy, which results in a decrease in the adhesive strength of the acrylic resin (A). In contrast, the phosphate ester flame retardant (c1) and the SP value of 10 (cal / cm 3 ) 1 / 2 In the pressure-sensitive adhesive containing the following acrylic resin (A), it is believed that the acrylic resin (A) is softened by the phosphate ester flame retardant (c1), which can actually improve the adhesive strength. However, in the present invention, a flame retardant other than the phosphate ester flame retardant (c1) may be contained as the flame retardant (C) within the range that does not impede the achievement of the object of the present invention.

[0070] The content of the flame retardant (C), in terms of the content of the phosphate ester flame retardant (c1), is preferably 1 to 50 parts by weight, more preferably 2 to 40 parts by weight, even more preferably 3 to 25 parts by weight, particularly preferably 4 to 18 parts by weight, especially preferably 4 to 16 parts by weight, and even more preferably 4 to 8 parts by weight, relative to 100 parts by weight of the acrylic resin (A). If the content of the flame retardant (C) is too high, it is thought that some of the flame retardant (C) will remain undissolved in the acrylic resin (A), which tends to reduce the adhesiveness of the pressure-sensitive adhesive tape, whereas if the content is too low, the flame retardancy tends to be insufficient.

[0071] <Tackifier (D)> The pressure-sensitive adhesive of the present invention may further contain a tackifier (D), which is not an essential component, in order to further enhance the excellent physical properties of the acrylic resin (A). As the tackifier (D), a resin compatible with the acrylic resin (A) is used, and examples thereof include rosin-based resins, terpene-based resins, xylene-based resins, phenol-based resins, coumarone-based resins, and petroleum-based resins. These tackifiers (D) may be used alone or in combination of two or more. Among these, rosin-based resins, terpene-based resins, and petroleum-based resins are preferred, and will be specifically described below.

[0072] Examples of the rosin-based resin include rosin ester resins obtained by hydrogenating, disproportionating, dimerizing, or adding an acid to a raw rosin, followed by esterification with glycerin or pentaerythritol, and rosin phenol resins obtained by adding phenol to the raw rosin. The use of any of these rosin-based resins allows the acrylic resin (A) to further exhibit its excellent physical properties. Among these, preferred are disproportionated rosin esters obtained by disproportionating the raw rosin and esterifying it with glycerin or pentaerythritol to adjust the softening point to a range of 70 to 130°C, polymerized rosin esters obtained by dimerizing the raw rosin and esterifying it with pentaerythritol to adjust the softening point to a range of 110 to 170°C, and rosin phenols obtained by adding phenol to the raw rosin to adjust the softening point to a range of 120 to 160°C.

[0073] The terpene resin is a general term for compounds based on the isoprene principle and represented by the molecular formula (C5H8)n. Examples of the tackifier (D) used in the present invention include resins obtained by homopolymerizing or copolymerizing monoterpenes (e.g., α-pinene, β-pinene, limonene, etc.) using a Friedel-Crafts catalyst. Specific examples of resins obtained by homopolymerizing or copolymerizing monoterpenes include α-pinene resins, β-pinene resins, dipentene resins, terpene phenol resins, aromatic modified terpene resins, and hydrogenated terpene resins obtained by hydrogenating these resins. Among these, terpene phenol resins are preferred because of their good compatibility with the acrylic resin (A). Any of the terpene phenol resins can further enhance the good physical properties of the acrylic resin (A), but particularly preferred are those having a softening point of 90 to 170°C and a hydroxyl value of 20 to 250 (mgKOH / g), and even more preferred are those having a softening point of 100 to 150°C and a hydroxyl value of 50 to 150 (mgKOH / g).

[0074] The petroleum-based resins are obtained, for example, by polymerizing and then hydrogenating C4-C5 and C9-C11 fraction monomers produced by thermal decomposition of naphtha or the like. Depending on the type of raw material fraction, examples include pure monomer-based resins, aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, and hydrogenated petroleum-based resins. The use of any of these petroleum-based resins allows the acrylic resin (A) to further exhibit its excellent physical properties. Among these, those with a softening point in the range of 90 to 130°C are preferred, and copolymers of styrene-based monomers and aliphatic monomers are more preferred.

[0075] The softening point of the tackifier (D) can be measured by the ring and ball method of JIS K 2531, and the hydroxyl value can be measured by potentiometric titration in accordance with JIS K 0070.

[0076] When the pressure-sensitive adhesive of the present invention contains a tackifier (D), the content of the tackifier (D) is usually 1 to 50 parts by weight, preferably 5 to 30 parts by weight, and more preferably 5 to 20 parts by weight, per 100 parts by weight of the acrylic resin (A). However, the tackifier (D) may be blended in an appropriate amount depending on the physical properties required of the pressure-sensitive adhesive, and the content of the tackifier (D) is not limited to the above range.

[0077] <Other ingredients> The adhesive of the present invention may contain other components, such as resin components other than the acrylic resin (A), acrylic monomers, polymerization inhibitors, antioxidants, corrosion inhibitors, crosslinking accelerators, radical generators, peroxides, UV absorbers, plasticizers, pigments, stabilizers, fillers, various additives such as radical scavengers, metals, and resin particles, as long as the effects of the present invention are not impaired. These may be used alone or in combination of two or more. In addition to the above, the adhesive may contain small amounts of impurities contained in the manufacturing raw materials of the adhesive components.

[0078] When the pressure-sensitive adhesive of the present invention contains other components, the content of the other components is preferably 5 parts by weight or less, more preferably 1 part by weight or less, and even more preferably 0.5 parts by weight or less, per 100 parts by weight of the acrylic resin (A). The lower limit is usually 0 parts by weight. If the content is too high, compatibility with the acrylic resin (A) decreases, and durability tends to decrease. However, for additives (pigments, fillers, metal and resin particles, etc.) that do not exhibit their effects at the above-mentioned contents, an appropriate amount may be added within a range that exhibits the effects of the additive without inhibiting the effects of the present invention.

[0079] The pressure-sensitive adhesive of the present invention is a pressure-sensitive adhesive composition containing the above-mentioned acrylic resin (A), crosslinking agent (B), flame retardant (C), and optionally a tackifier (D), and further other components, in which at least a portion of the composition is crosslinked. That is, it includes not only cases in which almost the entire pressure-sensitive adhesive composition is crosslinked, but also cases in which a portion of the pressure-sensitive adhesive composition is in an uncrosslinked state, and cases in which a portion of the pressure-sensitive adhesive composition is crosslinked. The pressure-sensitive adhesive or pressure-sensitive adhesive composition in which the acrylic resin (A) is an organic solvent-based acrylic resin is an organic solvent-based pressure-sensitive adhesive or organic solvent-based pressure-sensitive adhesive composition. The method for producing the pressure-sensitive adhesive composition is not particularly limited, but in addition to the commonly known mechanical kneading dispersion method, known methods such as solvent dispersion method and ultrasonic dispersion method can be used as necessary.

[0080] The pressure-sensitive adhesive of the present invention preferably has a gel fraction of 20% by weight or more, more preferably 30% by weight or more, and even more preferably 40% by weight or more, in order to increase the holding power. The gel fraction can be adjusted by adjusting the type and content of the crosslinking agent (B). The upper limit of the gel fraction is preferably 70% by weight, more preferably 60% by weight, and even more preferably 50% by weight. If the gel fraction is too low, the holding power tends to decrease, and if the gel fraction is too high, the peel strength tends to decrease. In this specification, the gel fraction is determined by the method described in the examples below.

[0081] adhesive tape The pressure-sensitive adhesive tape of the present invention has a substrate and a pressure-sensitive adhesive layer on at least one surface of the substrate, and this pressure-sensitive adhesive layer contains a pressure-sensitive adhesive obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition. For example, the pressure-sensitive adhesive composition is dissolved in a solvent such as ethyl acetate to prepare a pressure-sensitive adhesive composition solution for coating so that the solid content concentration is 10 to 70% by weight, and this solution is applied to a substrate and dried, whereby the pressure-sensitive adhesive composition is crosslinked to form a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive, thereby producing a pressure-sensitive adhesive tape.

[0082] The method for producing such a pressure-sensitive adhesive tape is not particularly limited, and known production methods can be used. For example, the pressure-sensitive adhesive tape of the present invention can be produced by a method in which a pressure-sensitive adhesive composition solution is applied to one side of a substrate, and the substrate is then laminated onto the surface of the pressure-sensitive adhesive layer formed by drying, or by a method in which a pressure-sensitive adhesive composition solution is applied to one side of a release liner, and the substrate is then laminated onto the surface of the pressure-sensitive adhesive layer formed by drying. Among these, the method in which a pressure-sensitive adhesive composition solution is applied to one side of a release liner, and the substrate is then laminated onto the surface of the pressure-sensitive adhesive layer formed by drying is preferred from the standpoint of handling, etc.

[0083] The substrate is preferably hand-tearable, and the surface of the hand-tearable substrate may be appropriately subjected to a known or conventional surface treatment, for example, a physical treatment such as corona discharge treatment or plasma treatment, or a chemical treatment such as a primer treatment. The substrate is not particularly limited and may be any known substrate, such as rayon cloth, cotton cloth, polyester cloth, a cloth made of a blend of rayon and polyester, a nonwoven fabric, a flat yarn cloth, or a laminated film in which a plastic film or the like is laminated on a flat yarn cloth. Among these, a substrate having a flat yarn cloth is preferred because of its high tensile strength in the longitudinal direction. The pressure-sensitive adhesive tape of the present invention using a substrate having a flat yarn cloth can further have excellent flame retardancy and ease of hand tearing. The term "substrate having flat yarn cloth" conceptually includes not only the flat yarn cloth itself but also a laminated film in which a plastic film or the like is laminated to the flat yarn cloth.

[0084] Flat yarn cloth is a woven fabric made by cutting a film called flat yarn into strips and stretching it to give it strength, and the flat yarns are woven together. Usually, the crossings of the flat yarns that cross the fabric vertically and horizontally are fixed by heat fusion to prevent misalignment. As the material for the flat yarn, an olefin resin such as polyethylene or polypropylene is preferred, polyethylene is more preferred, and high-density polyethylene is even more preferred.

[0085] Using a substrate in which a plastic film is laminated to a flat yarn cloth is preferred because it provides stable adhesive strength and releasability. This is thought to be because, in the case of double-sided adhesive tapes, the plastic film prevents the adhesive on one side from penetrating the substrate and mixing with the adhesive on the other side, and inhibits the migration of additives contained in the adhesive on one side, such as crosslinking agents, flame retardants, and plasticizers, to the adhesive on the other side. Furthermore, laminating a plastic film to a flat yarn cloth improves hand-tearability and the linearity of the fracture surface, possibly due to smooth propagation of the fracture point. A polyethylene film is preferred as the plastic film to be laminated to the flat yarn cloth, and a low-density polyethylene film is more preferred.

[0086] Furthermore, the substrate in which a plastic film is laminated onto a flat yarn cloth is preferably lightweight, and the plastic film is preferably thin. The thickness of the plastic film is preferably 10 to 80 μm. The plastic film may be laminated onto only one side of the flat yarn cloth, or onto both sides. Regarding the method of laminating the film onto the flat yarn cloth, extrusion lamination is preferred because it can be made lighter without using an adhesive.

[0087] The thickness of the substrate containing the flat yarn cloth is preferably 10 to 200 μm, more preferably 50 to 100 μm, and even more preferably 60 to 90 μm. If the thickness is too thin, hand tearability will improve but defects such as the inclusion of wrinkles during the production of the adhesive tape will tend to increase, while if the thickness is too thick, defects during the production of the adhesive tape will decrease but a greater force will be required to cut, and hand tearability will tend to decrease.

[0088] Examples of the release liner include paper obtained by laminating a film such as polyethylene onto glassine paper, kraft paper, or clay-coated paper; paper coated with a resin such as polyvinyl alcohol or an acrylic ester copolymer; and synthetic resin film obtained by coating a release agent such as a fluorine-based resin or a silicone-based resin onto a synthetic resin film such as polyester or polypropylene. Among these, paper release liners are preferred because they are easily torn by hand, and the basis weight of the base paper is 40 to 120 g / m 2 , preferably 50 to 80 g / m 2 A paper release liner having the following structure is particularly preferred. Furthermore, the thickness of such a release liner is preferably 40 to 180 μm, more preferably 60 to 140 μm, and even more preferably 80 to 120 μm. If the thickness is too thin, wrinkles may occur during winding, making production difficult, while if the thickness is too thick, hand tearability may decrease.

[0089] The coating device used when coating the PSA composition on one side of the substrate or release liner can be any commonly used coating device, such as a roll knife coater, die coater, roll coater, bar coater, gravure roll coater, reverse roll coater, dipping coater, blade coater, etc.

[0090] The thickness of the pressure-sensitive adhesive layer after drying is preferably 5 to 200 μm, more preferably 10 to 150 μm, and even more preferably 15 to 130 μm. If the thickness is too thick, it tends to be difficult to apply the pressure-sensitive adhesive composition, and if the thickness is too thin, sufficient adhesive strength tends to be difficult to obtain.

[0091] The pressure-sensitive adhesive tape of the present invention may be a single-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on one side of a substrate, or a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on each side of a substrate. Furthermore, both pressure-sensitive adhesive layers of the double-sided pressure-sensitive adhesive tape may be pressure-sensitive adhesive layers having the same composition, or pressure-sensitive adhesive layers having different compositions. Furthermore, both pressure-sensitive adhesive layers may contain the pressure-sensitive adhesive of the present invention, or only one of the pressure-sensitive adhesive layers may contain the pressure-sensitive adhesive of the present invention.

[0092] When a release liner is laminated on the adhesive layer of a double-sided adhesive tape, it is preferable to select the release liners laminated on both sides so that they have different peel strengths, in order to improve workability. For example, workability can be improved by selecting a release liner with a lighter peel strength on the side of the double-sided adhesive tape that is applied first than on the side of the double-sided adhesive tape that is applied second.

[0093] The drying conditions for drying the pressure-sensitive adhesive composition solution may be any conditions that allow the solvent and residual monomers in the pressure-sensitive adhesive composition to be dried and removed, and allow the functional groups of the acrylic resin (A) to react with the crosslinking agent (B) to form a crosslinked structure. Drying conditions such as 60 to 120°C for about 1 to 5 minutes are preferred. After drying, the sheet-like substrate laminated with the pressure-sensitive adhesive layer is aged to further promote the crosslinking reaction.

[0094] The pressure-sensitive adhesive tape of the present invention may be in the form of a roll or in the form of sheets, or may be further processed into various shapes. When the adhesive tape is a double-sided adhesive tape in a sheet state, it is preferable that a release liner be provided on the surface of both of the two adhesive layers, and when it is in a roll state, it is preferable that a release liner be provided on the surface of only one of the two adhesive layers.

[0095] The adhesive tape produced by the above method not only has high adhesiveness but also high flame retardancy, and therefore can be suitably used as an adhesive tape for fixing aircraft components that require high flame retardancy. Examples of aircraft components include carpets, vinyl chloride sheets, flooring, wall materials, etc. Particularly preferred are carpets, vinyl chloride sheets, and flooring. Examples of the carpet include known carpets used inside aircraft, specifically carpets using nylon fibers or olefin fibers. Examples of vinyl chloride sheets include hard vinyl chloride sheets with a relatively low content of plasticizer (softener), and soft vinyl chloride sheets with a relatively high content of plasticizer (softener). Examples of flooring materials include metal alloys such as aluminum alloys and titanium alloys, composite materials of glass reinforced fiber and epoxy resin, and composite materials of glass reinforced fiber and phenolic resin. Furthermore, when the pressure-sensitive adhesive tape of the present invention is in the form of a double-sided pressure-sensitive adhesive tape, it can be used to bond two or more types of aircraft components together. Examples of combinations of aircraft components that can be bonded together using the double-sided pressure-sensitive adhesive tape include a combination of flooring and carpet. [Example]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0097] First, various acrylic resins (A) were prepared as follows. The weight average molecular weight, dispersity, viscosity, glass transition temperature, and SP value of the acrylic resin (A) were measured according to the methods described above.

[0098] <Acrylic resin (A)> Prior to the production of the acrylic resin (A), the following copolymerization components (monomers) to be used in the production were prepared. Monomer (a1): 2-hydroxyethyl methacrylate Monomer (a2): acrylic acid Monomer (a3-1): n-butyl acrylate Monomer (a3-2): 2-ethylhexyl acrylate Monomer (a4): Vinyl acetate

[0099] [Production of acrylic resin (A-1)] In a reactor equipped with a thermometer, a stirrer, and a reflux condenser, 0.1 parts of 2-hydroxyethyl methacrylate (a1), 2.9 parts of acrylic acid (a2), 46 parts of n-butyl acrylate (a3-1), 46 parts of 2-ethylhexyl acrylate (a3-2), 5 parts of vinyl acetate (a4), 40 parts of ethyl acetate as a solvent, and 0.1 parts of azobisisobutyronitrile as a polymerization initiator were charged, and the temperature was raised with stirring, and polymerization was carried out for 9 hours at the reflux temperature of the ethyl acetate (mixture). The reaction mixture was then diluted with toluene to obtain an acrylic resin (A-1) solution with a solids content of 45%. The weight-average molecular weight of the resulting acrylic resin (A-1) was 600,000, the dispersity was 4.8, the glass transition temperature was -57°C, and the SP value was 9.65 (cal / cm 3 ) 1 / 2 The viscosity of the acrylic resin (A-1) solution was 7,500 mPa·s / 25°C.

[0100] [Production of acrylic resin (A-2)] A reactor equipped with a thermometer, a stirrer, and a reflux condenser was charged with 0.1 parts of 2-hydroxyethyl methacrylate (a1), 8 parts of acrylic acid (a2), 91.9 parts of n-butyl acrylate (a3-1), 60 parts of ethyl acetate as a solvent, and 0.05 parts of azobisisobutyronitrile as a polymerization initiator. The mixture was heated with stirring and polymerized for 9 hours at the reflux temperature of the ethyl acetate (mixture). The reaction mixture was then diluted with toluene to obtain an acrylic resin (A-2) solution with a solids content of 35%. The weight-average molecular weight of the resulting acrylic resin (A-2) was 870,000, the dispersity was 4.91, the glass transition temperature was -48.2°C, and the SP value was 10.06 (cal / cm 3 ) 1 / 2 The viscosity of the acrylic resin (A-2) solution was 7,000 mPa·s / 25°C.

[0101] [Production of acrylic resin (A-3)] A reactor equipped with a thermometer, stirrer, and reflux condenser was charged with the copolymerization components 0.2 parts 2-hydroxyethyl methacrylate (a1), 3 parts acrylic acid (a2), 93.8 parts 2-ethylhexyl acrylate (a3-2), 3 parts vinyl acetate (a4), 40 parts ethyl acetate as solvent, 15 parts acetone, and 0.12 parts azobisisobutyronitrile as polymerization initiator. The mixture was heated with stirring and polymerized at the reflux temperature of the ethyl acetate mixture for 7 hours. Then, 3 parts of Mighty Ace G-125 (a terpene-based resin, manufactured by Yasuhara Chemical Co., Ltd.) and 2 parts of Nikanol H-80 (a xylene-based resin, manufactured by Mitsubishi Gas Chemical Co., Ltd.) were added as tackifiers (D). The reaction mixture was diluted with toluene and ethyl acetate to obtain an acrylic resin (A-3) solution with a solids content of 40%. The weight-average molecular weight of the obtained acrylic resin (A-3) was 600,000, the polydispersity was 4.7, the glass transition temperature was -65°C, and the viscosity of the acrylic resin (A-3) solution was 6,000 mPa·s / 25°C.

[0102] <Flame retardant (C)> The following flame retardants (C) were prepared: Aromatic condensed phosphate ester flame retardant (c1): Aromatic condensed phosphate ester (manufactured by Daihachi Chemical Industry Co., Ltd., product name "PX-200") Aromatic condensed phosphate ester flame retardant (c2); (manufactured by Daihachi Chemical Industry Co., Ltd., product name "CR-733S") Non-halogen condensed phosphate ester flame retardant (c3): (manufactured by Daihachi Chemical Industry Co., Ltd., product name "DAIGUARD-880") Non-halogen condensed phosphate ester flame retardant (c4): (manufactured by Daihachi Chemical Industry Co., Ltd., product name "DAIGUARD-580")

[0103] <Crosslinking agent (B)> The following crosslinking agent (B) was prepared: Isocyanate-based crosslinking agent (b1): Tosoh Corporation, Coronate L-55E (solid content 55%)

[0104] Example 1 [Preparation of double-sided adhesive tape] A pressure-sensitive adhesive composition solution was prepared by adding 0.5 parts of an isocyanate-based crosslinking agent (b1), 5 parts of an aromatic condensed phosphate ester-based flame retardant (c1), and an appropriate amount of ethyl acetate to 100 parts of the solid content of the acrylic resin (A-1), and mixing until homogeneous. The pressure-sensitive adhesive composition solution was then applied to a paper release liner (Shinomura Chemical Industry Co., Ltd., trade name "SSW-53FOAG"; base paper basis weight 93 g / m 2 This solution was applied to the heavy release surface of (1) using an applicator so that the thickness after application was 110 μm, and then dried at 80°C for 5 minutes to produce a paper release liner (1) with an adhesive layer (I). Next, 2.75 parts of an isocyanate-based crosslinking agent (b1) and an appropriate amount of ethyl acetate were added to 100 parts of the solid content of the acrylic resin (A-3) and mixed until uniform. The mixture was then coated on another paper release liner (Shinomura Chemical Industry Co., Ltd., trade name "SSW-53FOAG"; base paper basis weight 93 g / m 2 The adhesive layer (II) was applied to the light release surface of the paper release liner (2) using an applicator so that the thickness after coating was 35 μm, and then dried at 80° C. for 3 minutes to produce a paper release liner (2) with an adhesive layer (II). Furthermore, a lightweight substrate (manufactured by Diatex Co., Ltd.: weight 47 g / m) was prepared by laminating a low-density polyethylene film on one side of a high-density polyethylene flat yarn cloth. 2 The adhesive side of the paper release liner (1) with the adhesive layer (I) was bonded to the side not laminated with the low-density polyethylene film (thickness: 62 μm), and then the adhesive side of the paper release liner (2) with the adhesive layer (II) was bonded to the opposite side of the substrate (the low-density polyethylene film side). This was then subjected to a heat aging treatment in a dryer at 40°C for 7 days to obtain a double-sided adhesive tape of Example 1.

[0105] Example 2 and Reference Examples 1 to 5 > Example 2 was prepared in the same manner as in Example 1, except that the type and content of the flame retardant (C) in the pressure-sensitive adhesive layer (I) were changed as shown in Table 1. and Reference Examples 1 to 5 A double-sided adhesive tape of this size was obtained.

[0106] <Comparative Example 1> A double-sided pressure-sensitive adhesive tape of Comparative Example 1 was obtained in the same manner as in Example 1 above, except that the flame retardant (C) was not contained in the pressure-sensitive adhesive layer (I).

[0107] <Comparative Example 2> A double-sided pressure-sensitive adhesive tape of Comparative Example 2 was obtained in the same manner as in Example 1 above, except that the acrylic resin (A-1) in the pressure-sensitive adhesive layer (I) was changed to acrylic resin (A-2), and the content of crosslinking agent (B) was 0.65 parts and the content of flame retardant (C) was 15 parts per 100 parts of the solid content of acrylic resin (A-2).

[0108] <Comparative Example 3> A double-sided pressure-sensitive adhesive tape of Comparative Example 3 was obtained in the same manner as in Comparative Example 2 above, except that the flame retardant (C) was not contained in the pressure-sensitive adhesive layer (I).

[0109] The double-sided pressure-sensitive adhesive tapes obtained in the above Examples and Comparative Examples were subjected to the following evaluation tests. The results are summarized in Table 1.

[0110] <180° peel strength> The paper release liner (2) of the double-sided adhesive tape obtained above was peeled off, and the adhesive layer (II) was backed with a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10"; thickness 25 μm). The double-sided adhesive tape was then cut to a width of 25 mm and a length of 150 mm to prepare a test piece. Next, a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10"; thickness 38 μm) cut to a width of 25 mm and a length of 180 mm was bonded to the adhesive layer exposed by peeling off about 3 cm of one end of the paper release liner (1) covering the adhesive layer (I) on the measurement surface of the test piece, and the bonded portions were fixed with a stapler. The adherends used were test plates of SUS-BA plates (bright annealed stainless steel plates) that had been subjected to a heat drying treatment at 175°C for 1 hour. The paper release liner (1) was peeled from the test piece, and the adhesive layer (I) of the test piece was attached to the test plate. A 2 kg roller was then moved back and forth twice at a speed of 10 mm / s to bond the adhesive. After bonding, the test piece was left to stand for 1 minute in an atmosphere of 23°C and 50% RH. The free end of the test piece was then folded back 180° and peeled off 30 mm. In the same atmosphere, the test plate was secured to the lower chuck and the edge of the polyethylene terephthalate film secured to the upper chuck of the peel strength tester. The double-sided adhesive tape was peeled off from the adherend at a peel angle of 180° and a speed of 300 mm / min to measure the 180° peel strength (N / 25 mm).

[0111] <Gel fraction> As a sample for measuring the gel fraction, in the double-sided adhesive tapes prepared in the Examples and Comparative Examples, the paper release liner (2) with the adhesive layer (II) was removed from the substrate (manufactured by Diatex Co., Ltd.: weight 47 g / m 2 In the same manner as above, except that the adhesive tape was not laminated onto a substrate (62 μm thick), an adhesive tape having only the adhesive layer (I) on one side was prepared. In addition, the gel fraction of the adhesive layer (I) of an adhesive tape having only the adhesive layer (I) on one side is theoretically the same as the gel fraction of the adhesive layer (I) of a double-sided adhesive tape having the adhesive layer (I) and the adhesive layer (II). A 200-mesh SUS wire mesh large enough to encase the adhesive tape is prepared, and its weight is measured (α). The paper release liner (1) is peeled off from the adhesive tape, and the tape is wrapped in the aforementioned SUS wire mesh, and the weight of the tape and the wire mesh is measured (β). After immersion in toluene maintained at 23°C for 48 hours, the tape is thoroughly dried, and the weight of the tape and the wire mesh is measured (γ). After immersion, the tape is removed from the wire mesh, and the remaining adhesive layer (I) is removed, and the weight of the substrate is measured (δ). The above weights are measured in grams (g). Subtraction was carried out as shown in the following formula, and the weight percentage of the adhesive component after immersion relative to that before immersion was determined as the gel fraction. [Formula] Gel fraction (%) = (weight of tape after immersion including the weight of SUS wire mesh (γ) - weight of substrate (δ) - weight of SUS wire mesh (α)) / (weight of tape before immersion including the weight of SUS wire mesh (β) - weight of substrate (δ) - weight of SUS wire mesh (α)) x 100

[0112] <Flammability test> The test was conducted in accordance with the flammability test specified in 14 CFR Part 25 Appendix F Part I Section (a)(1)(ii), which is the flame retardancy standard for items used on aircraft, and a pass / fail result was determined.

[0113] [Table 1]

[0114] From the results in Table 1 above, the SP value is 10 (cal / cm 3 ) 1 / 2 The following acrylic resin (A-1) is used, and a phosphate ester flame retardant ( c1) Example 1 using and 2 The adhesive tape of Example 1 has high flame retardancy and adhesive strength. and 2 The adhesive tape had a higher adhesive strength than the adhesive tape of Comparative Example 1 which did not contain the flame retardant (C).

[0115] In contrast, the SP value of acrylic resin is 10 (cal / cm3 ) 1 / 2 The adhesive tape of Comparative Example 2, which used a larger acrylic resin (A-2), was insufficient in flame retardancy and also had insufficient adhesive strength. In addition, the SP value of the acrylic resin is 10 (cal / cm 3 ) 1 / 2 The adhesive tape of Comparative Example 3, which used a larger acrylic resin (A-2) and did not contain any flame retardant (C), naturally not only lacked flame retardancy but also had insufficient adhesive strength.

[0116] In addition, Example 1 and 2 Since the fabric has a flat yarn cloth as a base material, it has excellent hand tearability. [Industrial Applicability]

[0117] The pressure-sensitive adhesive of the present invention can be used to obtain a pressure-sensitive adhesive having high flame retardancy and high adhesiveness. Therefore, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing this pressure-sensitive adhesive is highly expected to be used, in particular, as a pressure-sensitive adhesive tape for fixing aircraft components, because of its excellent flame retardancy and adhesiveness.

Claims

1. A pressure-sensitive adhesive comprising an acrylic resin (A), a crosslinking agent (B), and a flame retardant (C), The solubility parameter (SP value) of the acrylic resin (A) is 10 (cal / cm ３ ) １／２ The flame retardant (C) contains a phosphate ester-based flame retardant, The pressure-sensitive adhesive contains the flame retardant (C) in an amount of 1 to 8 parts by weight based on 100 parts by weight of the acrylic resin (A).

2. The pressure-sensitive adhesive according to claim 1 , wherein the crosslinking agent (B) contains an isocyanate-based crosslinking agent.

3. The pressure-sensitive adhesive according to claim 1 or 2, wherein the acrylic resin (A) contains a hydroxyl group-containing monomer unit.

4. The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the phosphate ester-based flame retardant is an aromatic condensed phosphate ester.

5. An adhesive tape comprising a substrate and an adhesive layer comprising the adhesive according to any one of claims 1 to 4 on at least one surface of the substrate.

6. 6. The adhesive tape of claim 5, wherein the substrate comprises a flat yarn cloth.

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