JP2001049216A - Pressure-sensitive adhesive composition and pressure- sensitive adhesive article using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure-sensitive adhesive composition containing a pressure- sensitive polymer obtained by polymerizing a monomer component essentially consisting of an alkyl (meth)acrylate by the use of a polymeric polymerization initiator having a specified structure while realizing an increase in the molecular weight of the polymer and reduction in low-molecular-weight products in the polymerization step, and improvement in both pressure-sensitive adhesiveness and cohesive force. SOLUTION: This composition contains a pressure-sensitive adhesive polymer obtained from a monomer component essentially consisting of an alkyl (meth)acrylate. The pressure-sensitive adhesive polymer is obtained by polymerizing the monomer component in the presence of such an amount of a polymeric polymerization initiator having a structure represented by formula I (wherein R1 is a divalent linear hydrocarbon group; and m is 3 or greater) and/or formula II (wherein R2 and R3 are each a linear or cyclic hydrocarbon group optionally containing an ethylene group on the chain; and n is 2 or greater) in the main chain as to give an active oxygen concentration of 5-300 ppm. The pressure-sensitive adhesive polymer is one having a weight- average molecular weight Mw of at least 200,000 and an Mw/Mn ratio of at most 6 (wherein Mn is the number-average molecular weight).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive product which have good balance between cohesive force and adhesive force, and have excellent performance such as curved surface adhesion.

[0002]

2. Description of the Related Art Acrylic pressure-sensitive adhesives containing alkyl (meth) acrylate as a main constituent are heat-resistant, weather-resistant, water-resistant, oil-resistant, etc. in addition to basic physical properties such as tack, adhesion and cohesion. It is widely used for pressure-sensitive adhesive labels, sheets, tapes and the like. In recent years, the applications of these pressure-sensitive adhesive products have been increasing more and more, and therefore, further improvement in the properties of the pressure-sensitive adhesive is required.

[0003] Among the above three basic physical properties of the pressure-sensitive adhesive, the adhesive strength and the cohesive strength are known as contradictory physical properties. That is,
When the adhesive strength is improved, the cohesive strength is reduced, and when the cohesive strength is increased, the adhesive strength is reduced. Therefore, it is quite difficult to improve the physical properties of both while maintaining the balance between them.

In order to improve the cohesive force while maintaining a high adhesive force, the polymer constituting the adhesive is not easily cross-linked three-dimensionally, but the polymer itself is increased in molecular weight to secure a high adhesive force. It has been found that a method of minimizing a low molecular weight substance, which is a factor of deteriorating cohesion, is useful.

As a method for increasing the molecular weight of an acrylic polymer for an adhesive, there are a method of increasing the monomer concentration in a polymerization system and a method of decreasing the concentration of a polymerization initiator.
The polymer is likely to be three-dimensional. When the polymer becomes three-dimensional, it becomes insoluble in a solvent and cannot be applied to a substrate or the like as an adhesive.

[0006] On the other hand, as the polymerization reaction proceeds, the monomer concentration and the initiator concentration in the polymerization system decrease, and the probability that the two meet each other decreases, so that the monomer remains in the system by all means. It is not recommended to mix the residual monomer in the polymer because it often causes an unpleasant odor of the adhesive product or is a irritant or toxic compound. Separation from polymers is not possible in terms of energy and cost, and is almost impossible.

From this point of view, a method is usually employed in which a post-addition polymerization initiator called a booster is added to the system immediately before the end of the polymerization, and the residual monomers are forcibly polymerized to make them harmless. In this case, the amount of the booster for the residual monomer is considerably larger than the amount of the initiator for the monomer in the early stage of the polymerization reaction, in consideration of the probability that the residual monomer and the initiator meet, and the necessity of reliably polymerizing the residual monomer. It is currently being added. However, since there will be a large amount of initiator for a small amount of monomer, the resulting polymer after the booster addition will be mostly of very low molecular weight. And this low molecular weight substance causes the cohesive force of the pressure-sensitive adhesive to decrease.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art. As a final object, it is intended to increase the molecular weight of a polymer for a pressure-sensitive adhesive and to reduce the molecular weight of a low molecular weight product in a polymerization step. The aim was to reduce the pressure and simultaneously improve the adhesion and cohesion.

[0009]

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer obtained from a monomer component essentially containing an alkyl (meth) acrylate, A high-molecular-weight polymerization initiator represented by the following general formula (1) and / or (2) wherein the adhesive polymer has a structure represented by the following general formula (1) and / or (2) in the main chain: A polymer obtained by polymerization using a polymer having a weight average molecular weight of 200,000 or more and a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn): Mw / Mn of 6 or less. Have a gist.

[0010]

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(In the formula, R ¹ represents a divalent chain hydrocarbon group, and m represents a natural number of 3 or more.)

[0012]

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(Wherein R ² and R ³ are the same or different,
It represents a chain or alicyclic hydrocarbon group which may contain an ethynylene group in the chain, and n represents a natural number of 2 or more. ).

By using the above-mentioned high molecular polymerization initiator, it is possible to increase the molecular weight of the adhesive polymer and to reduce the amount of low-molecular-weight substances in the polymerization step, and to provide an adhesive composition excellent in both adhesive and cohesive properties. We were able to.

It is preferable that the adhesive polymer is polymerized by using the high molecular weight polymerization initiator such that the active oxygen concentration is 5 to 300 ppm based on the total weight of the monomer component. If the amount of the polymerization initiator is too large, a high-molecular-weight adhesive polymer cannot be obtained.

The above-mentioned adhesive polymer is preferably obtained without adding a post-addition polymerization initiator, which is added just before the end of the polymerization to improve the polymerization rate. The standard of the preferable polymerization rate is 93% or more, more preferably 96%.
% Or more. The present invention also includes a pressure-sensitive adhesive product obtained by using the pressure-sensitive adhesive composition according to the present invention.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The pressure-sensitive adhesive composition of the present invention contains a pressure-sensitive adhesive polymer polymerized using a high-molecular-weight polymerization initiator having a structure represented by the above general formula (1) or (2). Have the biggest point where you do. In the present invention, the term “polymer” includes not only a homopolymer but also a binary or more copolymer such as a copolymer and a terpolymer.

The high molecular weight polymerization initiator having the structure represented by the above general formula (1) or (2) in the molecule has 3 in the main chain.
It is a relatively high molecular weight organic peroxide having more than one peroxide moiety. Therefore, even after one peroxide is cleaved to initiate polymerization and cause a growth / termination reaction, the peroxide is still cleaved at the terminal of the produced polymer. As a result, the polymerization reaction continues from the polymer terminal again, and a high molecular weight product having a linearly increased molecular weight can be obtained. For this reason, the adhesive polymer of the present invention has a considerably higher molecular weight than a conventionally known polymer obtained by using a polymerization initiator having one or two peroxide groups in one molecule. High molecular weight polymers have more entanglements in the polymer molecular chains themselves,
It is particularly effective for improving adhesive properties such as curved surface adhesiveness. From this viewpoint, in the present invention, it is preferable to carry out polymerization using only the above-mentioned high molecular type polymerization initiator, but it is excluded to use a conventionally known polymerization initiator in combination to the extent not deviating from the object of the present invention. Not something.

When the above-mentioned high molecular type polymerization initiator is used, since the produced polymer itself has a peroxide, there is a high probability that the monomer and the peroxide will meet even in the latter half of the polymerization reaction. , The generation of low molecular weight substances is eliminated.
Furthermore, since the amount of residual monomer is reduced, it is not necessary to add a post-addition initiator, and from this point, there is no need to worry about the formation of a low-molecular-weight product that reduces the cohesive force of the adhesive polymer.

The high molecular weight polymerization initiator used in the present invention has a structure represented by the following general formula (1) and / or (2) in the main chain skeleton.

[0021]

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(In the formula, R ¹ represents a divalent chain hydrocarbon group, and m represents a natural number of 3 or more.)

[0023]

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(Wherein R ² and R ³ are the same or different,
It represents a chain or alicyclic hydrocarbon group which may contain an ethynylene group in the chain, and n represents a natural number of 2 or more. ).

The polymer type polymerization initiator has a molecular weight of about 450 to 20,000 and has three or more peroxide groups in the molecule. The chain hydrocarbon group in the above general formula has a meaning including linear and branched, and preferably has 4 to 30 carbon atoms. An ethynylene group is -C≡C-. Specific examples of the repeating unit represented by the general formula (1) include the following structures. Since these have one peroxide group in the repeating unit, a high molecular weight polymerization initiator having three or more of these structures in the main chain can be used.

[0026]

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Specific examples of the repeating unit represented by the general formula (2) include the following structures. Since these include two peroxide groups in the repeating unit, a polymer type polymerization initiator having two or more of these structures in the main chain can be used.

[0028]

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[0029]

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The high molecular weight polymerization initiator has an active oxygen concentration of 5 to 300 based on the total weight of the monomer components.
It is preferable to use it so that it becomes ppm. When the amount of the polymerization initiator is lower than 5 ppm, the polymerization reaction does not proceed smoothly,
If the content exceeds 300 ppm, the high-molecular-weight adhesive polymer intended for the present invention is not produced. A more preferred lower limit is 10 ppm. A more preferred upper limit is 100p
pm, and a more preferred upper limit is 50 ppm.

When a conventionally known polymerization initiator having two or less peroxide groups in one molecule is used in combination,
The total active oxygen concentration is in the range of 5 to 300 ppm, and the amount of the conventional polymerization initiator is suppressed to 50% by weight or less of the weight of the high molecular weight polymerization initiator. It is more preferably not more than 10% by weight, and still more preferably not used. If many conventional polymerization initiators are used, the high-molecular-weight adhesive polymer intended for the present invention cannot be obtained.

The high molecular weight adhesive polymer intended for the present invention has a weight average molecular weight (Mw) of 200,000 or more. Since the polymerization is carried out using the above-mentioned polymer type polymerization initiator, 200,000 or more polymers can be easily obtained.
If Mw is smaller than 200,000, the adhesive properties are inferior, and the larger the Mw, the better. The ratio of the weight average molecular weight Mw to the number average molecular weight (Mn): Mw / M
n becomes 6 or less. Mw / Mn indicates the spread of the molecular weight distribution, and it can be said that the smaller this value, the sharper the molecular weight distribution of the polymer. In the present invention, the use of the high-molecular-weight polymerization initiator produces a high-molecular-weight adhesive polymer and suppresses the production of low-molecular-weight products.
Therefore, the Mw / Mn of the adhesive polymer of the present invention is 6 or less. The molecular weight is a value in terms of polystyrene measured by gel permeation chromatography (GPC) (Mw and Mn, the same applies hereinafter).

[0033] A monomer component essentially containing an alkyl (meth) acrylate is polymerized by using the above-mentioned high-molecular type polymerization initiator. As the alkyl (meth) acrylate, those having 1 to 12 carbon atoms in the alkyl group are preferable. For example, methyl (meth) acrylate,
Ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, (meth) acryl Isooctyl acid, dodecyl (meth) acrylate,
And stearyl (meth) acrylate. One or more of these can be used. The content of the alkyl (meth) acrylate in the monomer component is preferably from 70 to 99.9% by weight.

The monomer component may contain a monomer having a functional group in addition to the alkyl (meth) acrylates. The functional group-containing monomer is used for introducing a functional group which becomes a reaction point with a crosslinking agent described later into the adhesive polymer.

Specific examples of the functional group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic anhydride, maleic acid, 2-acryloyloxyethylsuccinic acid, 2-acryloyloxyethylphthalic acid, Carboxyl group-containing monomers such as acryloyloxyethyl hexahydrophthalic acid; 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic acid 4 -Hydroxybutyl,
Hydroxyl group-containing monomers such as “Placcel F” series (manufactured by Daicel Chemical Industries, Ltd.), which is a polycaprolactone modified product of 2-hydroxyethyl (meth) acrylate;
Glycidyl (meth) acrylate, an alicyclic epoxy group-containing monomer "Cyclomer" series (manufactured by Daicel Chemical Industries, Ltd.), epoxy group-containing monomers such as methyl glycidyl (meth) acrylate; dimethylaminoethyl (meth) acrylate Amino group-containing monomers such as diethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide; isocyanate group-containing monomers such as 2-methacryloyloxyethyl isocyanate and methacryloyl isocyanate; 2-vinyl-2-oxazoline, 2-vinyl -4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-
Oxazolinyl group-containing monomers such as isopropenyl-2-oxazoline and 2-isopropenyl-4-methyl-2-oxazoline, β-chloro (or bromo) ethyl vinyl ether, monochloro (or bromo) vinyl acetate, α-chloro (or bromo ) Methyl acrylate, 3
And halogen-containing monomers such as -chloro (or bromo) -2-hydroxypropyl methacrylate.

The above functional group-containing monomers can be used alone or in combination of two or more. The isocyanate group has reactivity with an amino group, a hydroxyl group and a carboxyl group, and the epoxy group has a reactivity with an amino group, a hydroxyl group and a carboxyl group. Has a reactivity with an amino group and a carboxyl group, an amino group has a reactivity with a hydroxyl group and a carboxyl group, and an oxazolinyl group has a reactivity with a carboxyl group. Introducing two or more functional groups having the same into the same adhesive polymer is not preferred because it causes gelation. Two or more functional groups that are not reactive with each other can coexist.

In the monomer component, the amount of the functional group-containing monomer is preferably 0.1 to 10% by weight.
If it is less than 0.1% by weight, the crosslinking point is too small, the crosslinking density is insufficient, and the cohesive strength tends to be insufficient. On the other hand, if it exceeds 10% by weight, the crosslinking density becomes too high and the cohesive force becomes too high, so that the adhesive strength and the resilience resistance decrease, which is not preferable.

The monomer component may contain other monomers in addition to the alkyl (meth) acrylate and the functional group-containing monomer. Specific examples of other monomers include aromatic monomers such as styrene and α-methylstyrene; vinyl esters such as vinyl acetate and vinyl propionate; N-group-containing monomers such as N-vinylpyrrolidone and acryloylmorpholine; Examples thereof include nitrile group-containing monomers such as acrylonitrile; and amide monomers such as (meth) acrylamide and N-methylolacrylamide, but are not particularly limited. These other monomers are present in the monomer component from 0 to
It is preferably 20% by weight. If the content is more than 20% by weight, the Tg of the adhesive polymer increases and becomes hard, so that properties such as adhesive strength and repulsion resistance are reduced, which is not preferable.

The tacky polymer according to the present invention preferably has tackiness at room temperature. From the viewpoint of the balance between tack and tackiness, the polymer has a glass transition temperature (Tg) of -65 ° C. after polymerization. It is preferable to select the monomers exemplified above so that the temperature is -30C. Tg is D
It can be determined by SC (differential scanning calorimeter) or TMA (thermomechanical analyzer). It is convenient if the calculated value obtained by the following equation is used as a guide. (1 / Tg) = (W 1 / Tg 1) + (W 2 / Tg 2) + ... +
(W _n / Tg _n)

[0040] In the formula, Tg represents the glass transition temperature _{(K), W 1, W} 2, ... W n represents a weight fraction in a monomer component of each _{monomer, Tg 1, Tg 2, ...} Tg _n indicates the glass transition temperature (K) of the homopolymer of the corresponding monomer. Note that the Tg of the homopolymer is “POLYMER
Handbook 3rd Edition "(John Wiley & Sons, I
nc.) may be used. Some specific examples of Tg of the homopolymer are as follows.
For example, 106 ° C. for polyacrylic acid, 8 ° C. for polymethyl acrylate, 22 ° C. for polyethyl acrylate, −54 ° C. for butyl polyacrylate, −70 ° C. for poly (2-ethylhexyl acrylate), 2-hydroxyethyl acrylate) is -15C, poly (2-hydroxyethyl methacrylate) is 55C, polymethyl methacrylate is 105C, polyvinyl acetate is 32C, polyacrylonitrile is 125C, and polystyrene is 100C. ° C.

In polymerizing the monomer component with a high molecular weight polymerization initiator, a conventionally known polymerization method can be adopted, and the polymerization method is not particularly limited. For example, a solution polymerization method, a bulk polymerization method, or the like can be used, and the solution polymerization method is industrially preferable. This is because the solution polymerization method can easily remove the heat of polymerization during polymerization and has good operability.

In the solution polymerization method and the bulk polymerization method, both a method of performing polymerization by batch charging and a method of performing polymerization while dropping a monomer can be adopted. In the case of polymerization by batch charging, it is preferable that the polymerization initiator is not added to the polymerization system except at the time of the initial charging, but the polymerization initiator may be added if it is a small amount in the first half of the polymerization.

In the present invention, the use of the high molecular weight polymerization initiator can increase the molecular weight of the adhesive polymer and reduce the residual monomer to increase the polymerization rate.
It is preferable not to add a so-called post-addition polymerization initiator which is added immediately before the end of the polymerization (for example, at a stage where the conversion exceeds 90%). This is because a low molecular weight substance may be generated.

However, in the present invention, since the amount of the residual monomer just before the end of the polymerization is extremely small, even if a small amount of the post-addition polymerization initiator is added, the polymerization is carried out using only the conventionally known polymerization initiator. The amount of low-molecular-weight substances generated is extremely small as compared with the case where the post-addition polymerization initiator is added. Therefore, if the Mw / Mn does not exceed 6 and does not adversely affect the adhesive properties, a post-addition polymerization initiator may be added. The amount of the post-addition polymerization initiator is not more than half (weight) and more preferably not more than 1/10 (weight) of the polymerization initiator added to the polymerization vessel in the initial stage of polymerization. is there. The time of addition of the post-addition polymerization initiator,
The stage where the conversion exceeds 90%, more preferably the stage where the conversion exceeds 95%.

On the other hand, in the method of polymerizing while dropping the monomer, the polymerization initiator is usually dropped together with the monomer. Therefore, it is preferable not to add the polymerization initiator after the dropping of the monomer is completed. As long as the object of the present invention is not impaired as described above, the post-addition polymerization initiator is not more than half (weight), preferably not more than 1/10, of the total amount of the polymerization initiator added before the completion of the monomer dropping. May be added.

Specific examples of the solvent used in the solution polymerization include aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate and butyl acetate;
Examples thereof include alicyclic hydrocarbons such as cyclohexane; and aliphatic hydrocarbons such as hexane and pentane, but are not particularly limited as long as the polymerization reaction is not inhibited. These solvents may be used alone or in a combination of two or more. Note that the amount of the solvent used may be appropriately determined.

The reaction conditions such as the reaction temperature and the reaction time are conveniently determined according to, for example, the composition of the monomer component, the polymerization method, the required properties of the (meth) acrylic adhesive polymer to be obtained, the use of the adhesive, and the like. What is necessary is just to set and it is not specifically limited. Also, the reaction pressure is not particularly limited, and may be any of normal pressure (atmospheric pressure), reduced pressure, and increased pressure. The polymerization reaction is desirably performed in an atmosphere of an inert gas such as a nitrogen gas.

In the present invention, a high polymerization rate can be achieved because the polymerization is carried out using a high molecular weight polymerization initiator. A preferable standard of the polymerization rate is 93% or more, and more preferably 96% or more.

The pressure-sensitive adhesive composition of the present invention contains the above-mentioned pressure-sensitive adhesive polymer as a main component. In addition to the adhesive polymer, if necessary, a crosslinking agent capable of reacting with the functional group introduced into the adhesive polymer by the functional group-containing monomer may be included. By using a crosslinking agent, the adhesive strength and cohesive strength of the pressure-sensitive adhesive composition can be further improved. The crosslinking agent is not particularly limited as long as it is a compound having two or more functional groups capable of reacting with the adhesive polymer per molecule. Specific examples of the crosslinking agent include a polyfunctional epoxy compound, a polyfunctional melamine compound, a polyfunctional isocyanate compound, a metal crosslinking agent,
Aziridine compounds, oxazoline compounds, mercapto compounds, and the like.

The polyfunctional epoxy compound is not particularly limited as long as it has two or more epoxy groups per molecule. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6- Hexanediol diglycidyl ether, bisphenol A / epichlorohydrin type epoxy resin, N, N, N ', N'-tetraglycidyl-
m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine and the like. These polyfunctional epoxy compounds are effective when the adhesive polymer contains an amino group or a carboxyl group.

The polyfunctional melamine compound is not particularly limited as long as it is a compound having two or more functional groups of one of an amino group, a methylol group, an alkoxymethyl group and an imino group per molecule. , Hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine and the like. These polyfunctional melamine compounds are effective when the adhesive polymer contains a hydroxyl group and / or a carboxyl group.

As the polyfunctional isocyanate compound, 1
The compound is not particularly limited as long as it has two or more isocyanate groups per molecule. For example, tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate, xylylene diisocyanate, meta Xylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate,
Diisocyanate compounds such as hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate; buret polyisocyanate compounds such as "Sumidur N" (manufactured by Sumitomo Bayer Urethane Co.); "Desmodur IL", "Desmodur H"
L "(both manufactured by Bayer AG)," Coronate EH "(manufactured by Nippon Polyurethane Industry Co., Ltd.) and other polyisocyanate compounds having an isocyanurate ring;" Sumidur L "(manufactured by Sumitomo Bayer Urethane)
And adduct polyisocyanate compounds such as "Coronate L" (manufactured by Nippon Polyurethane Industries, Ltd.). These can be used alone or in combination of two or more. Also, a so-called blocked isocyanate obtained by reacting an isocyanate group of these compounds with a masking agent having active hydrogen and inactivating them may be used. These polyfunctional isocyanate compounds are effective when an amino group, a hydroxyl group, and a carboxyl group are introduced into the adhesive polymer.

The metal crosslinking agent is not particularly limited. For example, metals such as aluminum, zinc, cadmium, nickel, cobalt, copper, calcium, barium, titanium, manganese, iron, lead, zirconium, chromium, tin, etc. Metal chelate compounds coordinated with acetylacetone, methyl acetoacetate, ethyl acetoacetate, ethyl lactate, methyl salicylate, and the like. These are effective when the adhesive polymer contains a carboxyl group and / or a hydroxyl group, or an epoxy group.

The aziridine compounds include N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, bisisophthaloyl-1 −
(2-methylaziridine), tri-1-aziridinyl phosphoxide, N, N'-diphenylethane-
4,4'-bis (1-aziridinecarboxamide) and the like. These are effective when the adhesive polymer contains a carboxyl group or an epoxy group.

Examples of the oxazoline compound include the “Epocross” series (manufactured by Nippon Shokubai Co., Ltd.), and these are effective when the adhesive polymer contains a carboxyl group.

As mercapto compounds, 1,6-dimercaptohexane, dimercaptodiethyl ether,
Aliphatic polymercapto compounds such as 2,2-dimercaptodiethylsulfide; 3,4-dimercaptotoluene;
Bis (4-mercaptophenyl) sulfide, 4-te
rt-butyl-1,2-benzenethiol, 1,5- or 2,7-dimercaptonaphthalene, 2,4-dimercapto-6-dibutylamino-1,3,5-triazine, 2,4-dimercapto-6 -Phenylamino-1,
3,5-triazine, 2,4-dimercapto-6-dimethylamino-1,3,5-triazine, 2,4-dimercapto-6-octylamino-1,3,5-triazine, 2,4-dimercapto- 6-octylamino-1,
Aromatic polymercapto compounds such as triazinethiol compounds such as 3,5-triazine and 2,4-dimercapto-6-dioctylamino-1,3,5-triazine are exemplified. These are effective when the adhesive polymer contains an epoxy group, an oxazolinyl group, or a halogen group.

The amount of the crosslinking agent in the pressure-sensitive adhesive composition of the present invention can be appropriately set according to the amount of the functional group introduced into the pressure-sensitive adhesive polymer. Usually, adhesive polymer 1
0.1 to 10 parts by weight per 100 parts by weight is preferred. If the amount of the crosslinking agent used is less than 0.1 part by weight, the crosslinking density may be insufficient and the cohesive strength may be insufficient.
This is because if added in excess of 0 parts by weight, the crosslink density becomes too high and the adhesive strength is reduced. A more preferred range is 0.5 to 5 parts by weight.

The adhesive polymer according to the present invention has a high molecular weight and exhibits excellent adhesive strength. However, if necessary, a tackifier may be contained in the adhesive composition according to the application. As the tackifier, (polymerized) rosin,
(Polymerization) Rosin ester type, terpene type, terpene phenol type, coumarone type, coumarone indene type, styrene resin type, xylene resin type, phenol resin type, petroleum resin type and the like can be mentioned. These can be used alone or in combination of two or more.

The amount of the tackifier in the pressure-sensitive adhesive composition is not particularly limited, but is usually preferably 5 to 100 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive polymer. If the amount of the tackifier is less than 5 parts by weight, the effect of improving the adhesive strength by the tackifier may not be exhibited. on the other hand,
If the amount of the tackifier is more than 100 parts by weight,
There is a possibility that tackiness is reduced and adhesive strength is reduced. 10
More preferably, the amount is in the range of 50 parts by weight to 50 parts by weight.

The pressure-sensitive adhesive composition of the present invention may further contain, if necessary, a conventionally known filler, pigment, diluent, antioxidant, ultraviolet absorber, ultraviolet stabilizer, etc. Additives can be blended. One or more of these additives can be used. Further, a polymer polymerized with a conventionally known polymerization initiator may be added and mixed as long as the object of the present invention is not impaired. The amounts of these additives may be appropriately set so as to obtain desired physical properties.

The pressure-sensitive adhesive composition of the present invention contains the pressure-sensitive adhesive polymer of the present invention as an essential component and, if necessary, a cross-linking agent, an additive and the like, but the mixing timing and method are not particularly limited.

The pressure-sensitive adhesive composition having the above constitution can be applied to any use in which a known pressure-sensitive adhesive composition is used. For example, the production of various pressure-sensitive adhesive products such as pressure-sensitive adhesive sheets, pressure-sensitive labels, pressure-sensitive adhesive tapes, and double-sided tapes Can be suitably used. Such a pressure-sensitive adhesive product is manufactured without a substrate or by forming a layer of a pressure-sensitive adhesive composition on a substrate. As the base material, high quality paper, kraft paper, crepe paper,
Conventionally known papers such as glassine paper; plastics such as polyethylene, polypropylene, polyester, polystyrene, polyethylene terephthalate, polyvinyl chloride, and cellophane; and fiber products such as woven fabric and nonwoven fabric can be used.
The shape of the substrate includes, for example, a film, a sheet, a tape, a plate, and a foam, but is not particularly limited. A pressure-sensitive adhesive sheet, a pressure-sensitive adhesive tape, a pressure-sensitive adhesive label and the like can be obtained by applying the pressure-sensitive adhesive composition of the present invention to one surface of a substrate by a known method. Further, by applying the pressure-sensitive adhesive composition to a release paper or the like in which a release agent is applied to a sheet-like material such as paper, synthetic paper, or a plastic film, a substrate-less (single-layer structure) pressure-sensitive adhesive can be obtained. It can be used as a double-sided tape without a base material. Alternatively, a double-sided tape may be formed by applying the same or different pressure-sensitive adhesive composition to both surfaces of the substrate.

The method of applying the pressure-sensitive adhesive composition to the substrate is not particularly limited, and a known method such as a roll coating method, a spray coating method, and a dipping method can be employed. In this case, any of a method of directly applying the pressure-sensitive adhesive composition to the substrate, a method of applying the pressure-sensitive adhesive composition to release paper or the like, and then transferring the coated material onto the substrate can be adopted.

After the pressure-sensitive adhesive composition is applied, it is dried to form a pressure-sensitive adhesive layer on the substrate. The drying temperature is not particularly limited, but when a pressure-sensitive adhesive composition to which a cross-linking agent is added is applied, the cross-linking reaction proceeds during drying. Is preferred. In some applications, the pressure-sensitive adhesive composition may be directly applied to an adherend.

For example, release paper may be attached to the surface of the pressure-sensitive adhesive formed on the base material. The surface of the pressure-sensitive adhesive can be suitably protected and preserved. The release paper is peeled off from the adhesive surface when using the adhesive product. In the case where a pressure-sensitive adhesive surface is formed on one side of a base material such as a sheet or a tape, a known release agent may be applied to the back surface of the base material to form a release agent layer. By winding the pressure-sensitive adhesive sheet (tape) into a roll with the pressure-sensitive adhesive layer inside, the pressure-sensitive adhesive layer comes into contact with the release material layer on the back of the base material, so that the pressure-sensitive adhesive surface is protected and preserved. You.

[0066]

The present invention will be described in detail with reference to the following examples, but the scope of the present invention is not limited to these examples. Unless otherwise specified, “%” indicates “% by weight” and “parts” indicates “parts by weight”. Evaluation of various adhesive properties is based on JIS Z 0
According to No. 023, the following method was used.

[Method of preparing test piece] Polyethylene terephthalate (manufactured by Toray Industries, Inc., thickness 50 μm) as a base material
Was used to apply the pressure-sensitive adhesive composition to a thickness of 25 μm after drying, followed by drying at 100 ° C. for 3 minutes to prepare a pressure-sensitive adhesive film. After the release paper (manufactured by San-A Kaken Co., Ltd., trade name: K-80HS) was adhered and protected on the surface of the adhesive, it was cured for 7 days in an atmosphere at a temperature of 23 ° C. and a relative humidity of 65%. The cured adhesive film was cut into a predetermined size to prepare a test piece.

[Measurement Method of Holding Force] A stainless steel plate (SUS30) was used in an atmosphere at a temperature of 23 ° C. and a relative humidity of 65%.
4: Hereafter referred to as “SUS board”), the sticking area is 25 mm
An adhesive film test piece is stuck so as to be × 25 mm. After standing for 25 minutes, the SUS plate to which the test piece is adhered is placed in a thermostat at 80 ° C. and suspended vertically. After a lapse of 20 minutes, a 1 kg load is applied to the test piece and SUS
The time required for the test piece to fall from the plate or the displacement distance after 24 hours was measured.

[Measurement Method of Adhesive Strength] In an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%, a width of 25 mm was applied to a SUS plate as an adherend.
mm adhesive film test piece was stuck. The sticking was performed by reciprocating the test piece three times with a rubber roller having a weight of 2 kg. Twenty-five minutes after the application, the strength (180-degree peeling adhesive force) when one end of the test piece was peeled from the SUS plate in the 180-degree direction at a speed of 300 mm / min.

[Method of Measuring Ball Tack] A temperature of 23 ° C.
The measurement was performed using an inclined ball tacking device (ball rolling device) under an atmosphere of a relative humidity of 65%. The runway and the adhesive surface measurement part were 100 mm, and the inclination angle was 30 degrees.

[Rebound Resistance] A 15 mm × 30 mm adhesive film test piece was stuck on a stainless steel cylinder having a diameter of 20 mm, and left at 40 ° C. for 24 hours. The evaluation criteria were as follows: ○ when the pressure-sensitive adhesive film test piece sheet did not peel off at all from the cylinder, Δ when the edge part peeled off a little, and × when the test piece almost peeled except for a part. did.

Example 1 A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet tube, a reflux condenser, and a dropping funnel was charged with 227.28 parts of butyl acrylate, 12 parts of acrylic acid,
A monomer component consisting of 0.72 parts of hydroxyethyl,
300 parts of ethyl acetate were charged. Stir under a stream of nitrogen,
Maintained at 82 ° C., as a polymerization initiator, a polymer type polymerization initiator having a structure represented by the following formula (where p is a natural number of 2 or more) in the main chain (“Polyper CH”: NOF Corporation) 30% solution of ethylbenzene; active oxygen amount 3.05
% / 30% solution; 10 hour half-life temperature 75 ° C) 0.24
Part and a mixed solution of 5.5 parts of ethyl acetate were added to the flask,
The polymerization was started. The polymerization was terminated 16 hours after the start of the reaction.

[0073]

Embedded image

Solids 43.1%, viscosity 12100 mPa
• An adhesive polymer solution having an s (25 ° C., B type viscometer, the same applies hereinafter) and a weight average molecular weight of 86.7 × 10 ⁴ (GPC measurement: standard polystyrene conversion) was obtained. To 100 parts (solid content 43.1%) of this adhesive polymer solution, "Coronate L55E" (a polyisocyanate compound manufactured by Nippon Polyurethane Co., Ltd .: solid content 55%) was added as a crosslinking agent in an amount of 0.1%.
Six parts were mixed to prepare a pressure-sensitive adhesive composition 1. Table 1 summarizes data on the composition, reaction conditions, molecular weight, and the like of the monomer components, and the results of evaluating the adhesive properties by the above-described method.

Examples 2 to 4 The same reactions and operations as in Example 1 were carried out except that the monomer component composition, reaction conditions, and the like were changed as shown in Table 1, to obtain pressure-sensitive adhesive compositions 2 to 4. . Table 1 summarizes data on the monomer component composition, reaction conditions, molecular weight, and the like, and the results of evaluating the adhesive properties by the above-described method.

Comparative Example 1 In a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet tube, a reflux condenser and a dropping funnel, 227.28 parts of butyl acrylate, 12 parts of acrylic acid,
A monomer component consisting of 0.72 parts of hydroxyethyl and 300 parts of ethyl acetate were charged. Stir under a stream of nitrogen, 8
Maintained at 2 ° C., a low molecular weight organic peroxide having a molecular weight of 256 and having one peroxide group in the molecule as a polymerization initiator (“Niper BMT-K40”: manufactured by NOF Corporation;
(Xylene 40% solution; active oxygen content 3.01% / 40% solution; 10-hour half-life temperature 73.1 ° C) A mixed solution of 0.243 parts and ethyl acetate 7 parts was added to initiate polymerization. The polymerization was terminated 16 hours after the start of the reaction. Solids 42.
3%, viscosity 10090 mPa · s, weight average molecular weight 7
1.2 × 10 ⁴ comparative adhesive polymer solutions were obtained. To 100 parts of this solution (solid content: 42.3%), 0.6 parts of the above-mentioned “Coronate L55E” was mixed as a crosslinking agent to prepare a comparative pressure-sensitive adhesive composition 1. Table 1 summarizes data on the composition, reaction conditions, molecular weight, and the like of the monomer components, and the results of evaluating the adhesive properties by the above-described method.

Comparative Example 2 A comparative pressure-sensitive adhesive composition 2 was obtained in the same manner as in Comparative Example 1, except that the monomer component composition, the reaction conditions and the like were changed as shown in Table 1. Table 1 summarizes data on the monomer component composition, reaction conditions, molecular weight, and the like, and the results of evaluating the adhesive properties by the above-described method.

Comparative Example 3 275.1 parts of 2-ethylhexyl acrylate, 24 parts of acrylic acid, 2 parts of acrylic acid were placed in a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet tube, a reflux condenser and a dropping funnel. -A monomer component consisting of 0.9 parts of hydroxyethyl and 300 parts of ethyl acetate were charged. The mixture was stirred under a nitrogen stream and kept at 82 ° C., and the above polymerization initiator “Niper BM
A mixed solution of 0.3 parts of “T-K40” and 7 parts of ethyl acetate was added to initiate polymerization. Five hours after the start of the reaction, 10 parts of ethyl acetate and 0.3 part of 2,2′-azobis (2-methylbutyronitrile) (manufactured by Nippon Hydrazine Industries, Ltd .; hereinafter, abbreviated as ABNE) as a post-addition polymerization initiator. Additional reaction continued for another 5 hours. As a result, the solid content was 48.0.
%, Viscosity 4050 mPa · s, weight average molecular weight 25.0
× 10 ⁴ comparative adhesive polymer solutions were obtained. To 100 parts of this solution (solid content: 48.0%), 1.5 parts of the above-mentioned “Coronate L55E” was mixed as a cross-linking agent to prepare a comparative pressure-sensitive adhesive composition 3. Table 1 summarizes data on the composition, reaction conditions, molecular weight, and the like of the monomer components, and the results of evaluating the adhesive properties by the above-described method.

In Table 1, the names of the respective compounds are abbreviated as follows. The numbers on the left are the Tg (K) values of homo-adhesive polymers listed in the Adhesive Polymer Handbook. BA: butyl acrylate 219K 2EHA: 2-ethylhexyl acrylate 203K HEA: 2-hydroxyethyl acrylate 258K Polyper CH: high molecular type polymerization initiator of the above structural formula BMT-K40: "Niper BMT-K40" low molecular type organic Peroxide ABNE: 2,2'-azobis (2-methylbutyronitrile)

[0080]

[Table 1]

As is evident from Table 1, all of the examples of the present invention have a large Mw and a small Mw / Mn, produce a high molecular weight polymer of interest, and generate low molecular weight substances. It was found that was suppressed. In Example 1, since the main monomer was BA, Mw was considerably larger than in Examples 2 to 4 of the 2EHA system.
On the other hand, Comparative Examples 1-2 using conventional "Niper BMT-K40" having only one peroxide in one molecule
In this example, Mw was low, Mw / Mn was large, and the polymerization rate was low as compared with the examples using the same monomer. Further, in Comparative Example 3 in which polymerization was carried out by a conventional method using a post-addition polymerization initiator, the polymerization rate was high, but Mw / Mn
This indicates that a large amount of low molecular weight substances was generated.

Reflecting the results of the above polymerization, the pressure-sensitive adhesive films of the examples were balanced in holding power, adhesive power, and tack, and were excellent in repulsion resistance. However, the pressure-sensitive adhesive film of Comparative Example was inferior in repulsion resistance, and in particular, Comparative Example 3 using the post-addition polymerization initiator resulted in no curved surface adhesion.

[0083]

According to the present invention, since the adhesive polymer is obtained by using the high molecular type polymerization initiator, the obtained adhesive polymer has a high molecular weight. In addition, since the polymerization rate could be increased without using the post-addition polymerization initiator, the generation of low molecular weight substances which adversely affect the cohesion was suppressed. As a result, it was possible to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive product excellent in both performance of pressure-sensitive adhesive strength and cohesive force and excellent in rebound resistance.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasumasa Tanaka 5-8 Nishiburi-cho, Suita-shi, Osaka Nippon Shokubai Co., Ltd. F-term (reference) 4J004 AA10 AB01 CA02 CA03 CA04 CA05 CA06 CB02 CB03 CC02 FA01 FA04 FA08 4J015 BA03 4J040 DF041 DF051 DN022 EL032 KA12 LA06 MA09 MA10 MB09 4J100 AB02Q AB03Q AG02Q AG04Q AJ01P AJ02P AJ09P AK32P AL03P AL04P AL08P AL08Q AM02Q AM15Q AM17Q AQ08Q BA03P BA16PBA03P01 BC03 BC03

Claims (4)

[Claims] 1. A pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer obtained from a monomer component essentially containing a (meth) acrylic acid alkyl ester, wherein the pressure-sensitive adhesive polymer has the following general formula (I) in its main chain: A polymer obtained by polymerization using a high molecular weight polymerization initiator having a structure represented by 1) and / or (2), and having a weight average molecular weight of 200,000 or more and a weight average molecular weight (Mw ) And the number average molecular weight (Mn): Mw / Mn is 6 or less. Embedded image (In the formula, R ¹ represents a divalent chain hydrocarbon group, and m represents a natural number of 3 or more.) (In the formula, R ² and R ³ are the same or different and represent a chain or alicyclic hydrocarbon group which may contain an ethynylene group in the chain, and n represents a natural number of 2 or more.) 2. The pressure-sensitive adhesive polymer is polymerized by using the high-molecular-weight polymerization initiator with respect to the total weight of the monomer component so that the active oxygen concentration becomes 5 to 300 ppm. Item 6. The pressure-sensitive adhesive composition according to Item 1. 3. The adhesive polymer according to claim 1, wherein the adhesive polymer is obtained without adding a post-addition polymerization initiator, which is added just before the end of the polymerization for improving the polymerization rate.
The pressure-sensitive adhesive composition according to item 1. 4. A pressure-sensitive adhesive product obtained by using the pressure-sensitive adhesive composition according to claim 1.