JP2016138196A - Resin composition and production method of the same, adhesive, and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a resin composition that has a significantly reduced amount of unreacted monomers while maintaining a desired molecular weight and that shows extremely preferable adhesive force when the composition is processed into an adhesive sheet, an adhesive obtained by using the composition, and an adhesive sheet using the adhesive.SOLUTION: The production method of a resin composition comprises successively performing the following steps: a first step of polymerizing a monomer (A) comprising at least a (meth)acrylic acid and a (meth)acrylate (A1) and having a double bond to obtain a polymer (B); and then a second step of mixing with a polyfunctional vinyl ether (D) having at least two vinyl ether groups in a solvent comprising alcohol (C) to allow unreacted monomers (A) to react.SELECTED DRAWING: None

Description

  The present invention relates to a resin composition and a method for producing the same, a pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet.

  Resin compositions obtained by polymerizing monomers such as (meth) acrylic acid esters are widely used in a wide range of industrial fields including adhesives and adhesives. However, on the other hand, a part of unreacted monomer remains in the resin composition, which may cause a problem of deterioration of working environment or use environment due to monomer-derived odor or the like. In addition, when an adhesive sheet produced using a resin composition containing such an unreacted monomer is attached to a human body or the like, the unreacted monomer can cause skin irritation. For use in applications, it is required to reduce the amount of unreacted monomer in the resin composition as much as possible.

  As a method for reducing the amount of unreacted monomer in the resin composition, a method of adding a scavenger monomer to the resin composition is known (Patent Documents 1 and 2). Patent Documents 1 and 2 describe examples in which a monofunctional vinyl ether compound and a polyfunctional (meth) acrylic acid ester compound are used as scavenger monomers, respectively. In any case, the unreacted (meth) acrylic acid ester monomer remaining in the composition has a higher radical polymerization reactivity than the scavenger monomer and is preferentially consumed. Reduced.

  However, in Patent Document 1 using a monofunctional vinyl ether compound as a scavenger monomer, about 0.7 parts by mass of the final unreacted monomer remains with respect to 100 parts by mass of the resin composition, which is sufficiently reduced. It can not be said. In addition, when more scavenger monomer is added, the amount of unreacted monomer may be reduced.However, since more unreacted material of the added scavenger monomer remains, the odor derived from the scavenger monomer is a problem. there were. That is, since the scavenger monomer is also in agreement with the unreacted monomer, it has been difficult to substantially reduce the amount of the unreacted monomer. In addition, when used as an adhesive, there is a risk of bleeding on the adherend due to unreacted scavenger monomers and a decrease in adhesive strength.

  On the other hand, when a polyfunctional (meth) acrylic acid ester compound is used as a scavenger monomer as in Patent Document 2, the volatility decreases due to an increase in the molecular weight of the scavenger monomer itself, and the scavenger monomer contains a plurality of (meth) acryloyl monomers. By having a group, the amount of unreacted scavenger monomer is reduced even when a large amount is added, so that the problem of odor can be improved. However, in general, when a radical polymerization initiator is used, a hydrogen abstraction reaction occurs from the resin, so that the scavenger monomer having a plurality of (meth) acryloyl groups acts as a crosslinking agent between the resins, and as a result, the resin There is a risk of increasing the molecular weight, and as a result, the resin composition is increased in viscosity or gelled, so that the amount added is substantially limited. That is, the amount of unreacted monomer could not be reduced sufficiently.

Special table 2009-520056 gazette JP-A-6-287529

  The problem to be solved by the present invention is a method for producing a resin composition that exhibits extremely good adhesive strength when it is made into an adhesive sheet by significantly reducing the amount of unreacted monomers while maintaining a desired molecular weight, and using the same Another object is to provide a pressure-sensitive adhesive obtained and the pressure-sensitive adhesive sheet.

  As a result of intensive studies to solve such problems, the present inventors have reached the present invention.

  That is, the present invention is a first step of obtaining a polymer (B) by polymerizing a monomer (A) having a double bond including at least (meth) acrylic acid and (meth) acrylic acid ester (A1), Production of a resin composition in which a second step of mixing a polyfunctional vinyl ether (D) having two or more vinyl ether groups in a solvent containing an alcohol (C) and reacting an unreacted monomer (A) is sequentially performed. Regarding the method.

  Moreover, this invention relates to the manufacturing method of the said resin composition which performs a 2nd process, after the conversion rate of a monomer (A) becomes 90% or more in a 1st process.

  Moreover, this invention relates to the manufacturing method of the said resin composition whose quantity of the unreacted monomer (A) in 100 mass parts of resin compositions is 0.1 mass part or less after a 2nd process.

  The present invention also relates to a resin composition obtained by any one of the above methods.

  The present invention also relates to a pressure-sensitive adhesive comprising the resin composition and a crosslinking agent.

  Moreover, this invention relates to the adhesive sheet which comprises the layer which comprises the said adhesive on a base material.

  According to the present invention, the amount of unreacted monomer is remarkably reduced while maintaining a desired molecular weight, and a resin composition exhibiting extremely good adhesive force when used in an adhesive sheet can be provided. Therefore, it was possible to provide a pressure-sensitive adhesive having a low content of unreacted monomer and a good pressure-sensitive adhesive force and a pressure-sensitive adhesive sheet thereof.

  Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. Not specific to the content.

<First step>
The first step is a step of obtaining a polymer (B) by polymerizing the monomer (A) having a double bond, and there is no particular limitation, and the polymer (B) can be obtained by a known radical polymerization reaction. The reaction may be solvent-free, but when used for a pressure-sensitive adhesive, it is preferable to use a solvent described later from the viewpoint of handling. The reaction may not use a radical polymerization initiator (hereinafter sometimes abbreviated as “polymerization initiator”) as in thermal polymerization, but a radical polymerization initiator described later is used from the viewpoint of molecular weight control. It is preferable. In addition, you may use well-known additives, such as a chain transfer agent.

<Monomer (A) having a double bond>
The monomer (A) having a double bond (hereinafter sometimes abbreviated as “monomer (A)”) contains at least (meth) acrylic acid and (meth) acrylic acid ester (A1), but is a radical polymerization reaction. As long as it is possible, there is no particular limitation, and monomers other than (meth) acrylic acid and (meth) acrylic acid ester (A1) may be included. Typical examples of the monomer (A) include monomers having at least one ethylenically unsaturated double bond such as acryloyl group, methacryloyl group, vinyl ether group, and vinyl group. The monomer (A) may have a plurality of ethylenically unsaturated double bonds in the same molecule. Moreover, when using with the crosslinking agent mentioned later in the form of an adhesive, it is preferable to use a part of monomer which has reactive functional groups, such as a hydroxyl group and a carboxyl group, which can react with a crosslinking agent.

<(Meth) acrylic acid and (meth) acrylic acid ester (A1)>
In the present invention, the monomer (A) includes (meth) acrylic acid and (meth) acrylic acid ester (A1). In this specification, acrylic acid and methacrylic acid are collectively referred to as (meth) acrylic acid, acrylate and methacrylate are collectively referred to as (meth) acrylate, acryloyl and methacryloyl are collectively referred to as (meth) acryloyl, and Sometimes abbreviated. In addition, (meth) acrylic acid and (meth) acrylic acid ester (A1) may be abbreviated as “monomer (A1)”.

  Examples of the (meth) acrylic acid ester having one double bond in the molecule include (meth) acrylic acid alkyl ester and (meth) acrylic acid ester having a hydroxyl group or a carboxyl group.

  Examples of the (meth) acrylic acid alkyl ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, (meth) Hexyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, (meth ) Palmityl acrylate, stearyl (meth) acrylate, and the like.

  Examples of the (meth) acrylic acid ester having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and (meth) acrylic acid 2. -Hydroxybutyl, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like.

  Examples of the (meth) acrylic acid ester having a carboxyl group include 2-carboxyethyl (meth) acrylate, 2-carboxypropyl (meth) acrylate, 3-carboxypropyl (meth) acrylate, and (meth) acrylic acid. 4-carboxybutyl, 2- (meth) acryloyloxyethyl hexahydrophthalate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxypropyl phthalate, 2- (meth) acryloyloxybutyl phthalate, 2- ( And (meth) acryloyloxyhexyl phthalate, 2- (meth) acryloyloxyoctyl phthalate, 2- (meth) acryloyloxydecyl phthalate, and the like.

  Moreover, as (meth) acrylic acid ester having one double bond in the molecule other than the above, (meth) acrylic acid in which (meth) acrylic acid and polyhydric alcohol such as ethylene oxide are partially transesterified. Examples include methoxypolyethylene glycol (meth) acrylate, ethoxypolyethyleneglycol (meth) acrylate, propoxypolyethyleneglycol (meth) acrylate, butoxypolyethyleneglycol (meth) acrylate, pentoxypolyethyleneglycol (meth) acrylate, methoxy Alkoxypolyalkylene glycol mono (meth) acrylates such as hexaethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, phenoxytetrae Glycol (meth) acrylates, aryloxy polyalkylene glycol mono (meth) acrylates such as methoxy hexaethylene glycol (meth) acrylate.

  Examples of the (meth) acrylic acid ester having two or more double bonds in the molecule include ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di ( (Meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1 , 10-decanediol di (meth) acrylate, di (meth) acrylates such as tricyclodecane dimethylol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, etc. Li (meth) acrylates.

<Monomer (A) having a double bond other than monomer (A1)>
Examples of the monomer (A) having one double bond in the molecule other than the monomer (A1) include (meth) acrylic acid amide, vinyl carboxylate, styrene, acrylonitrile, vinyl ether and the like.

  Examples of (meth) acrylic acid amide include (meth) acrylamide, N-methyl (meth) acrylamide, N-methylol (meth) acrylamide and the like.

  Examples of the vinyl carboxylate include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, and vinyl stearate.

  Examples of the vinyl ether include alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, and cyclohexyl vinyl ether.

  Examples of the monomer (A) having two or more double bonds other than the monomer (A1) include bis (meth) acrylamides such as N, N′-methylenebis (meth) acrylamide and N, N′-ethylenebis (meth) acrylamide. And the like. Moreover, the polyfunctional vinyl ether (D) mentioned later can also be used.

  The monomer (A) may be used alone or in combination of two or more. Moreover, the monomer (A) may be partially or completely neutralized with a basic compound such as a metal hydroxide or an amine.

  When the monomer (A) having two or more double bonds is polymerized in a solvent containing the alcohol (C), the polymer (B) by chain transfer to the alcohol (C) during the polymerization reaction. It is preferably used for the purpose of suppressing the decrease in molecular weight.

<Polymer (B)>
The polymer (B) is obtained by polymerizing the monomer (A). When used in the form of a pressure-sensitive adhesive using a cross-linking agent described later, a polymer obtained by partially using a monomer having a reactive functional group such as a hydroxyl group or a carboxyl group capable of reacting with the cross-linking agent, that is, a hydroxyl group or A polymer (B) having a reactive functional group such as a carboxyl group is preferred.

  The molecular weight of the polymer (B) is an important parameter that, when used in the form of an adhesive, for example, greatly affects various physical properties such as adhesive strength and holding power, and also affects the viscosity during coating. is there. The molecular weight of the polymer (B) is preferably from 50,000 to 1,000,000, more preferably from 200,000 to 800,000, although it depends on the substrate used, application or coating method. In order to obtain adhesive properties such as intended adhesive strength and holding power, or an appropriate coating viscosity, it is preferable that the desired molecular weight of the polymer (B) obtained in the first step is maintained after the second step. . The molecular weight change rate before and after the second step is preferably 140% or less, more preferably 110% or less.

<Polymerization initiator>
Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate and di (2-ethoxyethyl) peroxydi. Carbonate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl) peroxide and dipropionyl peroxide And organic peroxides such as diacetyl peroxide.

  Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile) and 2 , 2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile) and dimethyl 2,2'-azobis (2-methylpropionate) 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis [2- (2-imidazolin-2-yl) An azo compound such as propane].

  The polymerization initiators may be used alone or in combination of two or more. Although it depends on the boiling point of the solvent used, the polymerization temperature is preferably in the range of 60 to 90 ° C., and the polymerization time is preferably 5 to 12 hours. What is necessary is just to set the usage-amount of a polymerization initiator according to these superposition | polymerization temperature, superposition | polymerization time, the quantity of a monomer to be used, a composition, etc. Some organic peroxides have a strong hydrogen abstraction ability, but they are preferably used because the initiator efficiency is superior to that of azo compounds.

<Solvent>
The solvent is used for the purpose of handling in a liquid state in which the polymer (B) is dissolved and the handling property is excellent. The solvent may contain an alcohol (C) described later and is a solvent that can dissolve the polymer (B), and is not particularly limited as long as it does not significantly inhibit the radical polymerization reaction. Examples of solvents other than alcohol (C) include hydrocarbon solvents such as toluene, xylene, benzene, solvent naphtha, n-hexane, isohexane, cyclohexane, methylcyclohexane, normal heptane, isooctane, normal decane, acetone, methyl ethyl ketone, Ketone solvents such as methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, ethyl acetate, methyl acetate, butyl acetate, methoxybutyl acetate, cellosolve acetate, amyl acetate, n-propyl acetate, isopropyl acetate, methyl lactate, methyl lactate, ethyl lactate, butyl lactate, etc. Ester solvents such as isopropyl ether, methyl cellosolve, cellosolve, butyl cellosolve, dioxane, methyl t-butyl ether, butyl carbitol and the like, and N-methyl pyro Don, tetrahydrofuran, N, N- dimethylformamide, acetonitrile, dimethyl sulfoxide and the like. These solvents may be used alone or in combination of two or more. Especially, it is preferable that the solubility with respect to the high molecular weight polymer (B) is good, the viscosity is low, and the boiling point is low, since drying during the production of the pressure-sensitive adhesive sheet becomes easy. Examples of such a solvent include those having a molecular weight of 200 or less and a boiling point of 150 ° C. or less. Specifically, methanol, ethanol, isopropanol, methyl ethyl ketone, and ethyl acetate are preferable.

<Second step>
The second step is a step of mixing the polyfunctional vinyl ether (D) in a solvent containing the alcohol (C) after the first step and reducing the amount of the unreacted monomer (A) by radical polymerization reaction. . The polyfunctional vinyl ether (D) is subjected to the polymerization reaction together with the unreacted monomer (A) remaining in the resin composition starting from the radical generated from the radical polymerization initiator.

The radical polymerization reaction is performed using a polymerization initiator, and examples of the polymerization initiator include those exemplified in the first step. The polymerization initiators used in the first step and the second step may be the same or different. The polymerization initiator may be an uncleavable polymerization initiator that has not been consumed in the first step, or may be added in the second step.

  If some of the unreacted monomer remains in the resin composition in the resin production stage, for example, when used in the form of a pressure-sensitive adhesive, the pressure-sensitive adhesive sheet manufacturing environment due to the odor derived from the monomer and the deterioration of the usage environment become a problem. There is a case. Moreover, when using the adhesive sheet manufactured using the resin composition containing such an unreacted monomer, affixing on a human body etc., an unreacted monomer can also cause skin irritation. Therefore, in such use, it is required to reduce the amount of unreacted monomer in the resin composition as much as possible. The amount of unreacted monomer (A) remaining after the second step is preferably 0.2 parts by mass or less in 100 parts by mass of the resin composition, although it depends on the type, molecular weight, boiling point and the like of the monomer (A) used. 0.1 parts by mass or less is more preferable, and 0.05 parts by mass or less is more preferable.

<Alcohol (C)>
Examples of the alcohol (C) include aliphatic alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether. And glycol monoethers such as propylene glycol monoethyl ether and propylene glycol monoisopropyl ether.
Among these, those having a molecular weight of 200 or less and a boiling point of 150 ° C. or less are mentioned as preferred embodiments, and methanol, ethanol, and isopropanol are particularly preferable because the amount of unreacted monomers can be reduced without increasing the molecular weight in the second step.

  10-200 mass parts is preferable with respect to 100 mass parts of polymers (B), and, as for the usage-amount of alcohol (C) used for a 2nd process, 50-100 mass parts is more preferable. Moreover, you may use these alcohol (C) 1 type or in combination of 2 or more types.

<Polyfunctional vinyl ether (D)>
The polyfunctional vinyl ether (D) is not particularly limited as long as it is a compound having two or more vinyl ether groups in the molecule, and other double bond functional groups such as a (meth) acryloyl group, a hydroxyl group or a carboxyl group, etc. May have a reactive functional group. In the present specification, a group represented by “CH ₂ ═CH—O—” is referred to as a “vinyl ether group”.

  Examples of the polyfunctional vinyl ether (D) include 1,3-propanediol divinyl ether, 1,4-butanediol divinyl ether, 1,5-pentanediol divinyl ether, neopentyl glycol divinyl ether, 1,6-hexanediol. Alkanediol divinyl ethers such as divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, tricyclodecane dimethanol divinyl ether, hydrogenated bisphenol A divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol divinyl ether Such as alkylene glycol divinyl ethers, trimethylolpropane trivinyl ether, trimethylolpropane trivinyl ether There are no restrictions on the number of moles of ethylene oxide added (1 to 30 mole adducts are preferred. For example, trivinyl ethers such as Nippon Carbide, TMPEOTVE-30, ethylene oxide added mole number 3), and the like. .

  The number of functional groups of the polyfunctional vinyl ether (D) is preferably one having 2 to 6 vinyl ether groups in the molecule, and more preferably 2 to 3. Among them, the trimethylolpropane trivinyl ether ethylene oxide 3 mol adduct has good reactivity because it has a low molecular weight and excellent molecular mobility, while bleeding to the adherend when it is made into an adhesive sheet is likely to be suppressed. It is particularly preferably used from the viewpoint.

  What is necessary is just to determine as the usage-amount of polyfunctional vinyl ether (D) used at a 2nd process by the amount of the unreacted monomer (A) which remained at the 1st process. The smaller the amount of the unreacted monomer (A), the smaller the amount of the polyfunctional vinyl ether (D) may be used, which is preferable because the risk of increasing the molecular weight of the polymer (B) becomes smaller. Therefore, the second step is preferably performed after the conversion rate of the monomer (A) in the first step is 90% by mass or more, more preferably 95% by mass or more, and 98% by mass or more. More preferably, it is performed after The reaction time is not particularly limited and may be adjusted according to the reaction temperature, the amount of radical polymerization initiator consumed, etc., but is preferably 1 to 18 hours, more preferably 2 to 8 hours. Although there is no restriction | limiting in particular in reaction temperature, 20-150 degreeC is preferable from a viewpoint of a viscosity, reactivity, and the boiling point of alcohol (C) to be used, and 40-100 degreeC is more preferable.

<Adhesive>
Next, the pressure-sensitive adhesive of the present invention will be described. The pressure-sensitive adhesive of the present invention means one containing the resin composition of the present invention and a cross-linking agent described below.

<Crosslinking agent>
The crosslinking agent used in the pressure-sensitive adhesive of the present invention will be described. The crosslinking agent is used for the purpose of obtaining a pressure-sensitive adhesive that undergoes a crosslinking reaction with a reactive functional group such as a hydroxyl group or a carboxyl group in the polymer (B) and exhibits high elasticity and high adhesion.

  The crosslinking agent is a crosslinking agent that does not adversely affect the formation of a crosslinked structure even if it reacts with a reactive functional group such as a hydroxyl group or a carboxyl group in the polymer (B) in the pressure-sensitive adhesive and reacts with the alcohol (C). Metal chelate compounds and oxazoline compounds are preferred. You may manufacture an adhesive or an adhesive sheet using the crosslinking agent which consists of an isocyanate compound, an epoxy compound, etc. after removing alcohol (C) after a 2nd process.

(Metal chelate compound)
Examples of the metal chelate compound include aluminum, iron, copper, zinc, tin, titanium, titanium, nickel, antimony, magnesium, vanadium, chromium, zirconium, and other polyvalent metals such as 2,4-pentanedione and ethyl acetoacetate, Examples thereof include compounds coordinated with acetylacetone and the like. These metal chelate compounds easily react with alcohols, but have little influence on the formation of crosslinks because they are exchange reactions. In addition, when a metal chelate compound is used as a crosslinking agent, a coordination compound is used in order to further delay the reactivity with the reactive functional group in the polymer (B) and improve the storage stability in the coating liquid. You may use together. Examples of the coordinating compound include acetylacetone, dimethylglyoxime, oxine, dithizone, polyaminooxyacids such as ethylenediaminetetraacetic acid (also known as EDTA), oxycarboxylic acids such as citric acid, and condensed phosphoric acid. Among them, acetylacetone is preferable because it is soluble in alcohol and has volatility and is easy to remove.

(Oxazoline compound)
As the oxazoline compound, a compound having two or more oxazoline groups in the molecule is preferably used. For example, 2'-methylenebis (2-oxazoline), 2,2'-ethenebis (2-oxazoline), 2,2 ' -Ethenebis (4-methyl-2-oxazoline), 2,2'-propenebis (2-oxazoline), 2,2'-tetramethylenebis (2-oxazoline), 2,2'-hexamethylenebis (2-oxazoline) ), 2,2'-octamethylenebis (2-oxazoline), 2,2'-p-phenylenebis (2-oxazoline), 2,2'-p-phenylenebis (4,4'-dimethyl-2-) Oxazoline), 2,2′-p-phenylenebis (4-methyl-2-oxazoline), 2,2′-p-phenylenebis (4-phenyl-2-oxazoline) and the like. Door can be. Or copolymerization of vinyl monomers such as 2-isopropenyl-2-oxazoline and 2-isopropenyl-4,4-dimethyl-2-oxazoline with other monomers copolymerizable with these vinyl monomers It may be combined. Examples of these oxazoline group-containing copolymers include EPOCROS series of Nippon Shokubai Co., Ltd. Among these, WS-500 and 700 are preferable because of excellent compatibility with alcohol solvents.

  These crosslinking agents may be used alone or in combination of two or more.

  The amount of the crosslinking agent used in the present invention is such that the ratio between the number of moles of the functional group contained in the crosslinking agent and the number of moles of the reactive functional group capable of reacting with the crosslinking agent in the polymer (B) is In the case of applications such as labels and seals, it is preferable to use an amount of 0.05 to 0.6. In the case of applications such as a surface protective film, it is preferable to use an amount of 0.8 to 1.5.

<Additives>
The pressure-sensitive adhesive of the present invention includes, in addition to a crosslinking agent, a tackifier, a plasticizer, an antioxidant, an ultraviolet absorber, various stabilizers, a leveling agent, various drugs, and a filler that are generally used for pressure-sensitive adhesives. Various additives such as pigments and dyes may be added as necessary. These additives may be used alone or in combination of two or more, and the amount of the additive used is not particularly limited.

  Examples of tackifiers include terpene resins, aliphatic petroleum resins, aromatic petroleum resins, coumarone indene resins, phenol resins, terpene-phenol resins, rosin derivatives (rosin, polymerized rosin, hydrogenated rosin, and glycerin thereof. Well-known products such as esterified products with polyhydric alcohols such as pentaerythritol, resin acid dimers, etc. can be used. Known plasticizers such as phthalate esters and phosphate esters can be used as the plasticizer.

<Adhesive sheet>
Using the pressure-sensitive adhesive of the present invention, a pressure-sensitive adhesive sheet comprising a layer containing a pressure-sensitive adhesive on a substrate can be obtained. Here, a general description of the pressure-sensitive adhesive and the pressure-sensitive adhesive sheet will be given. The basic lamination structure of the pressure-sensitive adhesive sheet is a single-sided pressure-sensitive adhesive sheet such as a film-like base material / pressure-sensitive adhesive layer / peelable film, or a peelable film / pressure-sensitive adhesive layer / film-like base material / pressure-sensitive adhesive layer / peelable film. Such a double-sided pressure-sensitive adhesive sheet. At the time of use, the peelable film is peeled off and the pressure-sensitive adhesive layer is stuck on the adherend. The adhesive is not only tacky at the moment the pressure-sensitive adhesive layer touches the adherend during sticking, but also completely solidifies during sticking, unlike other adhesives. It is necessary to have a cohesive force for maintaining the sticking state while having a tack and appropriate hardness. Further, the cohesive force greatly depends on the molecular weight of the polymer (B).

  Adhesive strength is one of the methods for evaluating a pressure-sensitive adhesive sheet, and is evaluated by a method defined in JISZ0237: 2009. The adhesive strength varies depending on the adhesive, the substrate, the adherend, the measurement environment, etc., but it is necessary to obtain a desired adhesive strength suitable for the application. When used for labeling or the like, it is preferably 10 N / 25 mm or more, more preferably 12 N / 25 mm or more with respect to the stainless steel (SUS) substrate. During peeling, interfacial peeling may occur between the substrate / adhesive or between the adherend / adhesive, and cohesive failure may occur between the substrate, the adhesive, or the adherend. Interfacial peeling between the adherend / adhesive is preferred.

  Examples of the “base material” in the present specification include the following film-like base materials, paper, metal foil, vapor-deposited foil, foam, non-woven fabric, and those in which they are laminated. For example, polyhydroxyethene film, triacetylcellulose film, polypropene, polyethene, polycycloolefin, polyolefin resin film such as ethylene-vinyl acetate copolymer, polyester resin film such as polyethene terephthalate and polybutene terephthalate, polycarbonate Resin film, polynorbornene resin film, polyarylate resin film, propenoic acid resin film, polyphenylene sulfide resin film, polyethenylbenzene resin film, vinyl resin film, polyamide resin film , Polyimide resin films, plastic films such as oxirane resins, fine paper, kraft paper, glassine paper, art paper, coated paper, heat sensitive paper, moisture-proof Paper such as industrial paper, metal foil such as copper, aluminum, and stainless steel, composite sheet obtained by laminating the metal foil and plastic film, vapor deposition foil obtained by vapor deposition of aluminum, silica, etc., flat plate foam made of polyurethane or polyethylene And non-woven fabrics. In addition, any material can be used as long as it can secure the function of the pressure-sensitive adhesive sheet. The thickness of the substrate is preferably about 4 to 5000 μm. In particular, considering ease of handling, about 12 to 1000 μm is particularly favorable. The surface treatment of the base material may not be particularly treated, but is a dry treatment such as corona treatment, plasma treatment, flame treatment, electron beam irradiation, UV irradiation, etc., solvent washing, and easy adhesion coating treatment. A base material that has been treated may be used. Also suitable are coated paper, thermal paper, etc., on which various information is easily printed. Various additives such as various antioxidants, UV absorbers, light stabilizers, heat stabilizers, plasticizers, and lubricants may be mixed in the base material. Examples of the peelable film include those obtained by subjecting the surface of a film-like substrate such as cellophane, various plastic films, and paper to a release treatment with a silicone compound.

  There are no particular restrictions on the method for applying the adhesive to the peelable film, for example, Mayer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater. Various coating methods such as a coater and a spin coater can be mentioned. There is no restriction | limiting in particular in a drying method, The thing using hot air drying, infrared rays, and the pressure reduction method is mentioned. As drying conditions, although it depends on the crosslinked form of the pressure-sensitive adhesive, the film thickness, and the selected solvent, heating with hot air at about 60 to 180 ° C. is usually sufficient. Moreover, when applying an adhesive, a solvent can be added and a viscosity can be adjusted, or an adhesive can be heated and a viscosity can also be reduced. The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm in terms of film thickness when dried.

Specific examples of the present invention will be described below together with comparative examples, but the present invention is not limited to the following examples. In the following examples and comparative examples, unless otherwise specified, “part” and “%” represent “part by mass” and “% by mass”, respectively.

<Measurement of weight average molecular weight (Mw)>
The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC). As a measuring instrument, GPC (HPC-8020) manufactured by Tosoh Corporation was used. As the column, a Super HM-M and a Super HM-L manufactured by Tosoh Corporation were connected in series. In order to protect the column, insoluble matters were removed by using DISMIC13HP045AN (manufactured by Advantech Toyo Co., Ltd., hydrophilic PTFE membrane filter, pore diameter 0.45 micrometer) as a pretreatment of the sample solution. Measurement was performed at 40 ° C. using tetrahydrofuran (THF) as a solvent (eluent). The weight average molecular weight (Mw) was a converted value using polystyrene as a standard.

<Measurement of nonvolatile content in solution containing polymer (B)>
1 g of the solution containing the polymer (B) was weighed in a metal container and dried in a 150 ° C. oven for 20 minutes, and then the residue was weighed. The nonvolatile content was calculated as the ratio of the polymer (B) after drying to the solution containing the polymer (B) before drying.

<Measurement of unreacted monomer amount>
The amount of unreacted monomer in the resin composition was quantified by gas chromatography (GC17A, manufactured by Shimadzu Corporation) in accordance with the absolute calibration curve method of Japanese Industrial Standard (JIS) K0114: 2012. As a standard sample, an acetone solution of each monomer having a known concentration was prepared, and a calibration curve was prepared by gas chromatography. Separately, the synthesized resin composition was diluted with acetone, the diluted solution was measured by gas chromatography, and the amount of unreacted monomer was quantified.

<Calculation of monomer (A) conversion>
The conversion rate of the monomer (A) during the production of the polymer (B) was determined as the amount of monomer (A) consumed for polymerization in the first step relative to the amount of monomer (A) before the polymerization reaction. The conversion rate is the ratio obtained by dividing the difference between the total monomer (A) amount (W2) (part) and the unreacted monomer amount (W1) (part) by the total monomer (A) amount (W2) (part). Formula (1)
[(W2) − (W1)] / (W2) × 100 (%) (1)
Calculated by

<Manufacture of resin composition>
<First step>
(Synthesis Example 1)
A polymerization reaction apparatus equipped with a reaction tank, a stirrer, a thermometer, a reflux condenser, a dropping tank, and an air introduction tube was prepared. A mixture composed of the monomer (A), a solvent and a polymerization initiator shown below was charged into the reaction tank and the dropping tank at the following ratios. After replacing the air in the reaction tank with nitrogen gas, the temperature was raised to 80 ° C. in a nitrogen atmosphere while stirring to initiate the polymerization reaction. Next, the mixture in the dropping tank was dropped into the reaction tank over 1 hour. After completion of the dropping, the reaction was continued for 6 hours with further stirring. After completion of the reaction, the mixture was cooled to 25 ° C. to obtain a solution containing the polymer (B). The weight average molecular weight (Mw) of the obtained polymer was 330,000. The non-volatile content in the solution containing the polymer (B) was 50%. The amount of the unreacted monomer (A) was 0.40 part with respect to 100 parts of the solution containing the polymer (B), and the conversion rate of the monomer (A) was 99.2%.

[Reaction tank]
<Monomer (A)>
2-ethylhexyl acrylate 20 parts butyl acrylate 11 parts acrylic acid 0.8 parts 2-hydroxyethyl acrylate 0.1 part <solvent>
Ethanol 50 parts <Radical polymerization initiator>
Parroyl L (manufactured by NOF Corporation) 0.02 part [Drip tank]
<Monomer (A)>
2-ethylhexyl acrylate 74.0 parts butyl acrylate 40.0 parts acrylic acid 2.7 parts 2-hydroxyethyl acrylate 0.1 part ethylene glycol dimethacrylate 0.5 part <solvent>
Ethanol 100 parts <Radical polymerization initiator>
Parroyl L (manufactured by NOF Corporation) 0.05 parts

(Synthesis Examples 2 to 5)
A polymer was synthesized in the same manner as in Synthesis Example 1 except that the composition and reaction time in Table 1 were changed.

The abbreviations in Table 1 are as follows.
2EHA: 2-ethylhexyl acrylate BA: butyl acrylate AA: acrylic acid 2HEA: 2-hydroxyethyl acrylate EDMA: ethylene glycol dimethacrylate EtOH: ethanol EAc: ethyl perroyl acetate L: dilauroyl peroxide (manufactured by NOF Corporation)
TMPEOTVE-30: trimethylolpropane ethoxylate (number of moles of ethylene oxide added 1) trivinyl ether (Nippon Carbide)

<Second step>
Example 1
To the solution containing the unreacted monomer (A) and polymer (B) obtained in Synthesis Example 1, the polyfunctional vinyl ether (D) and radical polymerization initiator shown below are mixed in the following amounts, respectively. The resin composition was obtained by reacting at 3 ° C. for 3 hours. The amount of unreacted polyfunctional vinyl ether (D) in the resin composition after the second step (non-volatile content 50%) is 0.00 part, and the amount of unreacted monomer (A1) is 0.02 part. The amount of some unreacted monomer (A) was 0.02 part.

<Polymer (B)>
Synthesis Example 1 99.3 parts <Polyfunctional vinyl ether (D)>
Trimethylolpropane ethoxylate (number of moles of ethylene oxide added 1) trivinyl ether (manufactured by Nippon Carbide) 0.5 part <polymerization initiator>
Parroyl L (manufactured by NOF Corporation) 0.2 parts

(Examples 2 to 10, Comparative Examples 1 to 5)
Resin compositions were obtained in the same manner as in Example 1, except that the materials and compositions (blending amounts) in Table 2 were changed.

Abbreviations in Table 2 are as follows.
TMPEOTVE-30: trimethylolpropane ethoxylate (number of moles of ethylene oxide added 1) trivinyl ether (Nippon Carbide)
TMPEOTVE-60: Trimethylolpropane ethoxylate (2 moles of ethylene oxide added) trivinyl ether (manufactured by Nippon Carbide)
DEGDVE: diethylene glycol divinyl ether IPVE: isopropyl vinyl ether niper BW: benzoyl peroxide (manufactured by NOF Corporation)
AIBN: Azobisisobutyronitrile WS-500: Epocross WS-500 (Nippon Shokubai Co., Ltd. oxazoline group-containing copolymer, oxazoline compound, nonvolatile content 39%)

<Manufacture of adhesives>
(Examples 1-10, Comparative Examples 1-5)
With respect to 100 parts of the resin composition obtained in the second step, 2.05 parts of Epocross WS-500 (oxazoline group-containing copolymer, manufactured by Nippon Shokubai Co., Ltd., nonvolatile content 39%), which is an oxazoline compound, is used as a crosslinking agent. It mix | blended and diluted with ethyl acetate so that the non volatile matter of an adhesive might be 30 mass%, and the adhesive was obtained.

<Manufacture of adhesive sheet>
The obtained pressure-sensitive adhesive was coated on a release layer of a 38 μm thick polyethylene terephthalate release film [“SP-PET 382050” manufactured by Lintec Corporation, hereinafter referred to as “release film”] to a thickness of 25 μm after drying with a comma coater. After coating at a speed of 2 m / min, the coating was dried at 100 ° C. for 2 minutes, and a 50 μm thick polyester film (“E5100” manufactured by Toyobo Co., Ltd.) was pasted on the coated surface of the pressure-sensitive adhesive layer. Created. The obtained pressure-sensitive adhesive sheet was aged for 1 week in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and used for evaluation.

<Evaluation>
The resin compositions, pressure-sensitive adhesives, and pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 2.

<Evaluation method of unreacted monomer (A) amount>
The amount of unreacted monomer (A) measured after the second step and included in 100 parts of the entire resin composition was evaluated in the following four stages: ◎, ○, Δ, ×.
A: The amount of the monomer (A) is 0.05 parts by mass or less. Very good.
○: The monomer (A) amount exceeds 0.05 parts by mass and is 0.10 parts by mass or less. Good.
(Triangle | delta): A monomer (A) amount exceeds 0.10 mass part and is 0.20 mass part or less. Can be used.
X: A monomer (A) amount exceeds 0.20 mass part. Bad.

<Evaluation method of molecular weight change of polymer (B) before and after the second step>
The change in the molecular weight of the polymer (B) before and after the reaction in the second step was evaluated by the ratio (%) of the weight average molecular weight (Mw2) after the second step to the weight average molecular weight (Mw1) before the second step. That is, the following formula (2)
Mw2 / Mw1 × 100 (%) (2)
The molecular weight change was evaluated by the following three steps.
○: 95% or more and less than 110%. Good.
Δ: 110% or more and less than 140%. Can be used.
X: Less than 95%, 140% or more, or filter clogging during pretreatment. Bad.
In addition, the weight average molecular weight was calculated | required with the measuring method using the above-mentioned GPC.

<Evaluation method of adhesive strength of adhesive sheet>
According to JISZ0237: 2009, the obtained pressure-sensitive adhesive sheet was cut to a width of 25 mm, the release film was peeled off, and the surface of the pressure-sensitive adhesive layer that was exposed was attached to a stainless steel (SUS) substrate. The resistance when peeling was measured. The measurement was performed in a room at a temperature of 25 ° C. and a relative humidity of 50%, and was measured at a pulling speed of 300 mm / min. The adhesive strength was measured after being adhered to a substrate and left in a room at a temperature of 25 ° C. and a relative humidity of 50% for 24 hours. The adhesive strength was evaluated according to the following three steps.
○: 12 N / 25 mm or more. Good.
Δ: 10 N / 25 mm or more and less than 12 N / 25 mm. Can be used.
X: Less than 10 N / 25 mm, or cohesive failure of the pressure-sensitive adhesive layer. Bad.

  As is apparent from Table 2, in the examples of the present invention, a resin composition in which the amount of the unreacted monomer (A) is remarkably reduced while maintaining the desired molecular weight, and a pressure-sensitive adhesive sheet with good adhesive strength can be obtained. Became clear. On the other hand, the resin compositions of Comparative Examples 1 and 2 and Comparative Examples 4 and 5 have no problem in the molecular weight change in the second step, and the adhesive strength as an adhesive sheet is good, but the unreacted monomer ( A) The result was that the amount was large. In Comparative Example 3, the molecular weight of the polymer (B) was remarkably increased in the second step, resulting in poor adhesion due to poor coating properties due to thickening.

Claims (6)

  A first step of obtaining a polymer (B) by polymerizing a monomer (A) having a double bond containing at least (meth) acrylic acid and (meth) acrylic acid ester (A1), and then containing an alcohol (C) A method for producing a resin composition, wherein a second step of mixing a polyfunctional vinyl ether (D) having two or more vinyl ether groups in a solvent to react with an unreacted monomer (A) is sequentially performed.   The manufacturing method of the resin composition of Claim 1 which performs a 2nd process, after the conversion rate of a monomer (A) becomes 90% or more in a 1st process.   The method for producing a resin composition according to claim 1 or 2, wherein after the second step, the amount of the unreacted monomer (A) in 100 parts by mass of the resin composition is 0.1 parts by mass or less.   The resin composition obtained by the method in any one of Claims 1-3.   A pressure-sensitive adhesive comprising the resin composition according to claim 4 and a crosslinking agent.   A pressure-sensitive adhesive sheet comprising a layer comprising the pressure-sensitive adhesive according to claim 5 on a substrate.