JP2003277709A - Adhesive composition and adhesive product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition for obtaining an adhesive product having good tackifying power and excellent releasability. <P>SOLUTION: A polymer for the adhesive comprises a (meth)acrylate having 2-18C alkyl group, a nitrogen-containing monomer and a functional group- containing monomer as essential components, and is obtained from a monomer mixture (I) excluding a carboxy group-containing monomer. The monomer mixture (I) consists of a monomer component A and a monomer component B different in monomer composition from each other. The functional group- containing monomer is included in both monomer components A and B. The polymer is obtained by the steps of charging the monomer component A to a reactor, polymerizing it and charging the monomer component B to the reactor at the time when the polymerization rate of the monomer component A is under 50% and polymerizing it. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has excellent resistance to sticking to curved surfaces, shows a strong adhesive force, and can be applied to an adherend even if the adherend is left in a high temperature atmosphere for a long time. The present invention relates to a pressure-sensitive adhesive composition that can be peeled off cleanly from an adherend without being contaminated, and can form a pressure-sensitive adhesive layer with little change in pressure-sensitive physical properties over time, and such a pressure-sensitive adhesive product.

[0002]

2. Description of the Related Art Acrylic pressure-sensitive adhesives containing (meth) acrylic acid alkyl ester as a main constituent component have heat resistance, weather resistance, water resistance, oil resistance, etc. in addition to basic physical properties such as tack, adhesive strength and cohesive strength. It is widely used in adhesive products such as adhesive labels, sheets and tapes due to its excellent properties.

Generally, these adhesive products are a permanent adhesive type which is hardly peeled off after being adhered to an adherend, and a re-peelable type which is supposed to be peeled off again after being adhered to an adherend. They can be classified into molds, and in recent years, the amount of use of removable adhesive products has increased due to the necessity of environmental protection and recycling.

Adhesives used in removable adhesive products are
Even after a long time has been applied to the adherend,
It is required to be able to peel cleanly without causing contamination of adherend such as adhesive residue. Therefore, for example, if the cohesive force is improved by such means as increasing the crosslink density of the permanent adhesive type pressure-sensitive adhesive or increasing the glass transition temperature of the pressure-sensitive adhesive polymer, the adhesive residue disappears and the removability is improved. Is expected to improve. However, these methods have a problem that the removability is improved but the adhesive strength is reduced. The decrease in adhesive strength is particularly noticeable when the adhesive tape / label is attached to a curved surface, and the edge resistance of the adhesive tape / label floats, resulting in low adhesiveness to curved surfaces. Here, the term "good curved surface sticking resistance" means that a polypropylene column having a diameter of 15 mm (a cylinder may be used)
It means that the end of the tape does not float or peel off when the adhesive tape is attached to the surface of the tape over half the circumference and left for 3 days under normal conditions.

With respect to such problems, the present inventors have made various studies and reduced the adhesive residue by introducing a cross-linking reaction site into a low-molecular weight polymer formed at the end of the polymerization process (Japanese Patent Laid-Open No. 20-206).
No. 01-181347) An adhesive having a certain relationship between the gel fraction and the swelling rate does not cause adhesive residue (Japanese Patent Application No. 2000-300838). By synthesizing a gradient composition polymer showing a broad Tg, Achieves both improved adhesion to curved surfaces and prevention of adhesive residue (Japanese Patent Application No. 2001-353516 and Japanese Patent Application No. 2001-353517) A crosslinking system using a hydroxyl group is used to prevent the progress of the crosslinking reaction over time. We have applied for inventions such as securing the resistance to curved surface adhesion (Japanese Patent Application No. 2001-379030).

By the inventions disclosed in these applications,
We have succeeded in providing an adhesive product that has good adhesion to curved surfaces and that does not cause adhesive residue. However, for example, when a base material such as an aluminum (Al) vapor-deposited film having poor adhesiveness is used as a base material such as an adhesive tape, when the adhesive tape is attached to an adherend for a long time and then peeled off, ,
An interface peeling between the base material and the pressure-sensitive adhesive layer occurred, and a new problem of adhesive residue was caused in that the whole pressure-sensitive adhesive layer remained on the adherend side. In particular, when the industrial masking tape is peeled off at a very high peeling speed, such an adhesive residue phenomenon occurs.

This adhesive residue phenomenon, that is, the phenomenon of interfacial peeling between the substrate and the pressure-sensitive adhesive layer, is caused by the fact that the carboxyl group introduced into the pressure-sensitive adhesive polymer as a cohesive force securing component in the pressure-sensitive adhesive layer is It is considered that the cause is "adhesion enhancement" due to the formation of hydrogen bond with the adsorbed water existing on the surface to enhance the adhesive force with the adherend over time.

[0008]

Therefore, in the present invention, the introduction of the carboxyl group into the polymer for pressure-sensitive adhesive is stopped, and yet strong adhesive force is exhibited, the removability is excellent, and the curved surface adhesion resistance is high. Another object of the present invention is to provide a polymer for pressure-sensitive adhesives that can obtain excellent pressure-sensitive adhesive products.

[0009]

The first type of pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition essentially containing a polymer for pressure-sensitive adhesive and a crosslinking agent, wherein the polymer for pressure-sensitive adhesive is carbon. It is obtained from a monomer mixture (I) that contains (meth) acrylate having an alkyl group of number 2 to 18, a nitrogen atom-containing monomer, and a functional group-containing monomer as essential components and does not contain a carboxyl group-containing monomer. ,
The monomer mixture (I) is divided into a monomer component A and a monomer component B having different monomer compositions, and both of the monomer components A and B contain the above functional group-containing monomer. For the polymer, first, the monomer component A is charged into a reactor and polymerized, and after the polymerization of the monomer component A is started,
When the polymerization rate of the component does not exceed 50%, it is obtained by starting the polymerization of the monomer component B into the reactor, and the crosslinking agent reacts with the functional group of the functional group-containing monomer. The gist is that it is a compound having two or more functional groups in the molecule.

In the second type of pressure-sensitive adhesive composition, the pressure-sensitive adhesive polymer comprises a (meth) acrylate having an alkyl group having 2 to 18 carbon atoms, a nitrogen atom-containing monomer,
It is obtained from a monomer mixture (I) which contains a functional group-containing monomer as an essential component and does not contain a carboxyl group-containing monomer, and the monomer mixture (I) is
Monomer component A and monomer component B having different monomer compositions
And the monomer component C, and each of these monomer components A, B, and C contains the above functional group-containing monomer, and the adhesive polymer is prepared by first charging the monomer component A into a reactor. After the initiation of the polymerization of the monomer component A, and when the polymerization rate of the monomer A component does not exceed 50%, the monomer component B is fed to the reactor.
Of the monomer component B was completed and the polymerization rate of the monomer components A and B inside the reactor reached 80% or more, the monomer component C was further added to the reactor. It is obtained by carrying out polymerization, and the gist is that the cross-linking agent is a compound having two or more functional groups in the molecule capable of reacting with the functional groups of the functional group-containing monomer.

In each of the first and second types of pressure-sensitive adhesive compositions, a gradient composition polymer having no carboxyl group, a cohesive force secured by a nitrogen atom-containing monomer, and a crosslinking reaction By arranging the dots on the polymer in a well-balanced manner, we succeeded in suppressing adhesive residue (interfacial peeling between the base material and the adhesive layer) over time while maintaining various adhesive properties at good levels.

It is preferable that the monomer mixture (I) contains acrylonitrile as a nitrogen atom-containing monomer in order to secure cohesive force and increase adhesive force. Further, the functional group-containing monomer is a hydroxyl group-containing monomer,
Since the cross-linking agent is a compound having an isocyanate group and a cross-linking reaction occurs rapidly between them, it is possible to suppress the deterioration of the adhesive force with time.

The present invention also includes an adhesive product in which an adhesive layer obtained by crosslinking the above adhesive composition is formed on a substrate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The pressure-sensitive adhesive composition of the present invention can be classified into a first type and a second type according to the method of synthesizing a polymer for pressure-sensitive adhesive, and the pressure-sensitive adhesive which is the main component of the pressure-sensitive adhesive composition. Since the monomer mixture (I) that is a raw material of the polymer for use in common is common, first, various monomers that can be used as the monomer mixture (I) will be described. In addition,
The term “polymer”, unless otherwise specified as a “homopolymer”, means a copolymer or a terpolymer or more multi-component copolymer.

The monomer mixture (I) contains (meth) acrylic acid alkyl ester for exhibiting adhesive strength,
A nitrogen atom-containing monomer for imparting cohesive force and a functional group-containing monomer serving as a crosslinking point are used as essential components.

As the (meth) acrylic acid alkyl ester, those having an alkyl group having 2 to 18 carbon atoms are preferable, and for example, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, Cyclohexyl (meth) acrylate, acrylic acid (meth) 2
-Ethylhexyl, n-octyl (meth) acrylate,
Examples include isooctyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, and the like. These can use 1 type (s) or 2 or more types. Among them, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, which have a low Tg, are preferable. A monomer (high T
Even if it is combined with g), it does not exceed the upper limit of the Tg range suitable as a polymer for adhesives.

Specific examples of the nitrogen atom-containing monomer for imparting cohesive force include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylonitrile and the like, (meth) acrylamide,
N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N-methylolacrylamide,
N-methoxymethylacrylamide, N-ethoxyethylacrylamide, N- (n-butoxymethyl) acrylamide, dimethylaminopropylmethacrylamide,
Amido group-containing monomers such as t-butyl acrylamide are preferred, and one or more of these can be used as a mixture. Considering availability, polymerizability, properties of the obtained polymer, etc.,
Acrylonitrile, N-vinylpyrrolidone and acrylamide are preferred.

As the functional group-containing monomer, a monomer having no carboxyl group is used. This is for suppressing the above-mentioned adhesion progress. Specifically, it is not particularly limited as long as it is a monomer having a functional group capable of reacting with a cross-linking agent, and an epoxy group-containing monomer, an amino group-containing monomer, an isocyanate group-containing monomer and the like can be used. In order to complete the reaction and then prevent deterioration with time such as decrease in adhesive strength, it is possible to introduce a hydroxyl group into the adhesive polymer and use it in combination with a crosslinking agent having an isocyanate group. Due to their preference, it is recommended to use hydroxyl group-containing monomers.

Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate,
It is a polycaprolactone-modified product of (meth) acrylic acid-3-hydroxypropyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-4-hydroxybutyl, and (meth) acrylic acid-2-hydroxyethyl. "Plaxel F" series (manufactured by Daicel Chemical Industries Ltd.) and the like can be mentioned. Among them, 2-hydroxyethyl acrylate is inexpensive and easy to use. In addition, acrylic acid-
When 4-hydroxybutyl or "Placcel F" is used,
Since the hydroxyl group exists away from the main chain of the adhesive polymer, that is, at the tip of the longer side chain, steric hindrance due to the main chain can be eliminated, and the mobility of the hydroxyl group can be increased, resulting in cross-linking. The reaction efficiency with the agent can be improved.

The monomer mixture (I) for obtaining the pressure-sensitive adhesive polymer of the present invention preferably comprises the above-mentioned (meth) acrylic acid alkyl ester, a nitrogen atom-containing monomer, and a functional group-containing monomer. Since the (meth) acrylic acid alkyl ester is the main component, it is preferably used in an amount of 85% by mass or more in 100% by mass of the monomer mixture (I), and the nitrogen atom-containing monomer is preferably in the range of 1 to 10% by mass. The more preferable lower limit of the nitrogen atom-containing monomer is 2% by mass, and the more preferable upper limit thereof is 7% by mass.
The functional group-containing monomer is preferably in the range of 0.05 to 5% by mass. The more preferable lower limit of the functional group-containing monomer is 0.
It is 1% by mass. Further, in both the nitrogen atom-containing monomer and the functional group-containing monomer, if the lower limit of the preferable range is exceeded, the cohesive force may be insufficient. On the other hand, when the amount exceeds the upper limit of the above-mentioned preferred range, the cohesive force becomes too high, and the properties such as the curved surface sticking resistance and the adhesive force may deteriorate.

The monomer mixture (I) may contain other monomers. Specific examples of the other monomers include aromatic monomers such as styrene and α-methylstyrene; vinyl esters such as vinyl acetate and vinyl propionate, but are not particularly limited. These other monomers are preferably 0 to 20 mass% in 100 mass% of the monomer mixture (I). If it exceeds 20% by mass, Tg of the polymer for adhesives
Is not desirable because it rises and becomes hard.

In the present invention, when synthesizing the adhesive polymer, a special polymerization method is adopted so that a polymer having a gradient composition is formed. In order to improve the removability, the present inventors have a physical property that does not change in a wide temperature range from a low temperature to a high temperature or a degree of the change is small so that a wide peeling speed from low speed to high speed can be supported. It was found that a polymer for adhesives is preferable, and by gradually changing the copolymerization ratio to produce a polymer having a slightly different Tg, it is possible to synthesize a gradient composition polymer showing a broad Tg and tan δ as a whole polymer assembly. Successful (Japanese Patent Application No. 2000-353516, Japanese Patent Application 2000-353517)
issue). Also in the present invention, the gradient composition polymer polymerization method is adopted from such an idea.

The polymerization method of the adhesive polymer (hereinafter referred to as the first type adhesive polymer) used in the first type adhesive composition of the present invention means the monomer mixture (I).
Is divided into a monomer component A and a monomer component B having different compositions, the monomer component A is charged into a reactor, and at least after the polymerization of the monomer component A is started,
Is added dropwise or dividedly.

By starting the addition of the monomer component B after the polymerization of the monomer component A is started, a polymer consisting of only the monomer component A is formed before the addition of the monomer component B, and immediately after the addition of the monomer component A. A rich polymer is formed. By the end of the addition of the monomer component B, the remaining amount of the monomer component A is low, so a polymer rich in the monomer component B or a polymer consisting of only the monomer component B is formed. The finally obtained polymer is an aggregate of polymers having slightly different copolymerization compositions.

Since the gradient composition polymer is an assembly of polymers having slightly different copolymerization compositions, its Tg (ta
nδ or the peak of the DSC differential curve) is broader than the Tg of the polymer having a uniform composition as a whole because the Tg of the polymer having each composition is slightly different.

It is preferable to employ each monomer component so that the polymer formed only of the monomer component A (hereinafter polymer A) and the polymer formed only of the monomer component B (hereinafter polymer B) are incompatible. . This is because, when two kinds of monomer components capable of forming two kinds of polymers which are compatible with each other are polymerized by the polymerization method of the present invention, the above-mentioned polymer aggregate having a broad Tg cannot be obtained.

The polymer obtained by the polymerization method of the present invention is
Even if the polymer A and the polymer B are incompatible with each other, the copolymerization of the polymer A, the polymer B, and the various polymers having slightly different copolymerization compositions of A and B results in the copolymerization of A and B. The presence of various polymers having slightly different compositions results in polymers (mixtures) that are compatible as a whole. Specifically, a plurality of peaks corresponding to a plurality of Tg derived from polymers of two or more different compositions are overlapped with each other to give a polymer showing a broad (not sharp) peak. That is, the polymer for pressure-sensitive adhesive obtained by the polymerization method of the present invention comprises the polymer A and the polymer B, and
It becomes an aggregate of polymers having various different compositions to which polymers having a plurality of gradient compositions are added, and shows a stable compatible state due to the gradient composition, and thereby a polymer for pressure-sensitive adhesive excellent in removability which is an object of the present invention. Become. The monomer component B
It is possible that polymer A and / or polymer B will not be formed if the start of dropping is immediately after the start of polymerization of the monomer component A.

The obtained polymer may be completely compatible with each other or may have a microscopic sea-island structure (microdomain structure). However, if the dried polymer film is transparent, any of them may be used. .

Furthermore, it is preferable that both the monomer component A and the monomer component B contain a functional group-containing monomer, because the presence of an uncrosslinked polymer after forming the pressure-sensitive adhesive layer causes adhesive residue. Therefore, in order to make the compositions of the monomer component A and the monomer component B different from each other, the kind and amount of the (meth) acrylic acid alkyl ester as the main component may be appropriately selected so that the monomer components A and B are different. .

At the time of polymerization, it is necessary to first charge the reactor with the monomer component A. This is because when the monomer component A is also dropped, a gradient composition polymer cannot be obtained. Usually, it is easier to charge all of the monomer component A into the reactor all at once, but if the monomer component A has not been polymerized yet, it may be charged separately. It is also possible to interrupt the polymerization of the monomer component A once before the introduction of the monomer component B and to add the monomer component B after resuming the polymerization.

The concentration of the monomer component A (concentration of the monomer component A in the mixture with the solvent) at the charging stage is 3
0-80 mass% is preferable. If it is less than 30% by mass, the molecular weight of the polymer is difficult to increase, and if it is 80% by mass or more,
The amount of heat generated during polymerization is large, and it is not preferable because temperature control such as heat removal is difficult. The more preferable concentration of the monomer component A is 40 to 70% by mass. The monomer component A
The concentration of can be appropriately changed depending on the polymerization solvent. For example, when toluene or the like that easily causes chain transfer is used as the polymerization solvent, it is preferable to increase the concentration of the monomer component A in order to increase the molecular weight. However, it is recommended to use ethyl acetate, which causes less chain transfer, as the solvent in the initial stage of polymerization because the amount of heat generated increases and temperature control is difficult.

The initial addition of the monomer component B is carried out after the polymerization of the monomer component A charged in the reactor is started and when the polymerization rate does not exceed 50% (mass basis). When the polymerization rate of the monomer component A exceeds 50%, a considerable amount of the polymer A has already been produced in the reaction vessel, so that the amount of the monomer component A that is a polymerization partner of the monomer component B becomes relatively small. , It is not possible to obtain a gradient composition polymer. In this sense, it is recommended that the initial addition of the monomer component B is performed at a stage where the polymerization rate of the monomer component A is low. The polymerization rate is more preferably 20% or less, more preferably 10% or less, most preferably immediately after the initiation of the polymerization of the monomer component A. The polymerization start time can be measured by measuring the internal temperature of the polymerization container as the time when the heat generation due to the polymerization starts. Further, when the polymerization is carried out at the reflux temperature, it can be regarded as the time when the volatilization of the polymerization solvent becomes intense.

On the other hand, the monomer component B is preferably charged in three or more parts, most preferably dropwise. In order to broaden the Tg, it is preferable to add at a predetermined rate so that the monomer component B in the reaction vessel does not disappear, that is, the concentration of the monomer component B does not decrease above a predetermined amount. is there. Specifically, the residual amount of the monomer component B in the reactor is measured with time to calculate the consumption rate of the monomer component B, and the amount of the monomer component B to be added into the reactor is adjusted from the consumption rate. Then, although there is a slight time lag, the amount of the monomer component B present in the reactor can be made constant.

The ratios of the monomer component A and the monomer component B having different monomer compositions are not particularly limited as long as they are present (if one of them is not 0), but the total amount of both is 100% by mass. As a monomer component A of 10 to 90 mass% and a monomer component B of 90 to 10
It is preferably set to mass%. 20 to monomer component A
It is more preferable that the amount of the monomer component B is 80% by mass and the amount of the monomer component B is 80 to 20% by mass.

On the other hand, the polymerization method of the pressure-sensitive adhesive polymer used in the second type pressure-sensitive adhesive composition of the present invention (hereinafter referred to as the second type pressure-sensitive adhesive polymer) means the monomer mixture (I) The monomer component A, the monomer component B, and the monomer component C having different compositions are divided into three, and the monomer component A is charged into the reactor, and at least after the polymerization of the monomer component A is started, the monomer component B is added dropwise or dividedly. Then
When the polymerization rate of the monomer components A and B inside the reactor reaches 80% or more after the addition of the monomer component B is completed, the monomer component C is further added to the reactor to carry out the polymerization. .

A method is known in which a post-addition polymerization initiator (booster) is added into the reactor in order to increase the polymerization rate by reducing unreacted monomers in the latter stage of the polymerization. However, the amount of the post-addition initiator added is usually an excess amount with respect to the amount of the residual monomer in order to reduce the amount of the residual monomer as much as possible, so the polymer generated in the latter stage of the polymerization has a low molecular weight and causes the adhesive residue. Cheap. In this second type of polymerization method, a monomer component C mainly composed of a functional group-containing monomer is added to a reactor together with a post-addition initiator to introduce a functional group into a low molecular weight polymer, thereby forming a pressure-sensitive adhesive layer. The low molecular weight polymer in the medium is reliably crosslinked with a crosslinking agent to prevent adhesive residue. In this sense, the monomer component C needs to be charged into the reactor when the polymerization rate of the monomer components A and B in the reactor reaches 80% or more. The monomer component C is preferably added at a polymerization rate of 85% or more, and more preferably at a polymerization rate of 90% or more.

The respective conditions such as the composition of the monomer component A and the monomer component B, the timing of addition, and the amount ratio when polymerizing the adhesive polymer of the second type polymerize the adhesive polymer of the first type. You can do it just as you would. The monomer component C may partially contain other monomers, but from the viewpoint of introducing a functional group into a low molecular weight polymer, it is preferable that the monomer component C be composed of only a functional group-containing monomer. Thus hydroxyl group-containing monomers are most preferred.

The amount of the monomer component C is preferably as small as possible since it is added in the latter stage of the polymerization.
0.1 to 4.0 mass% is preferable in 100 mass% of the total of -C. If it is less than 0.1% by mass, the effect of addition is not exhibited, and the amount of functional groups introduced into the low molecular weight polymer may be insufficient. Further, for example, when only the hydroxyl group-containing monomer is used as the component C and added in an amount of more than 4.0% by mass, a homopolymer of the hydroxyl group-containing monomer is produced, and thus the compatibility with the gradient composition polymer decreases. The obtained polymer may become cloudy.
A more preferable lower limit is 0.2% by mass and an upper limit is 2% by mass.

In both cases of the first and second types of adhesive polymer, the polymerization is carried out by so-called solution polymerization in an organic solvent. This is because the solution polymerization method facilitates removal of the heat of polymerization during polymerization and has good operability. Specific examples of the solvent include aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate and butyl acetate; alicyclic hydrocarbons such as cyclohexane; hexane,
Examples thereof include aliphatic hydrocarbons such as pentane, but are not particularly limited as long as they do not inhibit the above polymerization reaction. These solvents may be used alone or in combination of two or more kinds for convenience. The amount of solvent used may be appropriately determined.

As the polymerization initiator, methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl hydroperoxide,
Cumene hydroperoxide, t-butyl peroxy octoate, t-butyl peroxy benzoate, lauroyl peroxide, trade name “Nyper BMT-K
40 "(manufactured by NOF CORPORATION; a mixture of m-toluoyl peroxide and benzoyl peroxide), azobisisobutyronitrile, trade name" ABN- "
E "[Japan Hydrazine Industry; 2,2'-azobis (2-
A known radical polymerization initiator such as an azo compound such as methylbutyronitrile)] can be used.

Polymerization initiators are required for the monomer component A and the monomer component B, and for the second type, for the monomer component C, those for the monomer component A are charged in the reactor and the monomer component B is used. And the monomer component C are preferably added together when the respective monomer components B and C are added. The polymerization initiators for the respective monomer components A to C may be the same or different, and in each case, two or more kinds of initiators may be mixed and used. Further, when the first type of polymer for pressure-sensitive adhesive is synthesized, the monomer component C is not added, so that the monomer component B
The post-addition initiator may be added alone after the completion of the addition. The total amount of initiator is based on the mass of the monomer.
It is preferably used so as to be 0.01 to 1% by mass. If the amount is too large, a high molecular weight polymer having excellent adhesive properties may not be obtained. From the viewpoint of adhesive properties, the weight average molecular weight Mw of the adhesive polymer as a whole is preferably 200,000 or more, more preferably 300,000 or more. The upper limit is not particularly limited, however, it is difficult to synthesize a polymer exceeding 2 million by solution polymerization, so 2 million or less is preferable, and 10 is preferable.
More preferably, it is at most 0,000.

The polymerization conditions such as the polymerization temperature and the polymerization time depend on, for example, the composition of each monomer component, the type of the polymerization solvent and the polymerization initiator, the required properties of the obtained pressure-sensitive adhesive polymer, the use of the pressure-sensitive adhesive and the like. It may be appropriately set depending on the situation, and is not particularly limited. The reaction pressure is also not particularly limited, and may be normal pressure (atmospheric pressure), reduced pressure, or increased pressure. The polymerization reaction is preferably performed in an atmosphere of an inert gas such as nitrogen gas.

In the above polymerization method, the use of polyvalent mercaptan which functions as a chain transfer agent is not preferable. When a polyvalent mercaptan is used, polymerization starts from the mercapto group portion to form a so-called star polymer, so that the molecular chain of the present invention is long and has a high molecular weight, and it is difficult to obtain a polymer having a gradient composition. This is because it is difficult to obtain a pressure-sensitive adhesive that satisfies removability and curved surface sticking resistance. In particular, the use of polyvalent mercaptans is not preferable in order to obtain a pressure-sensitive adhesive polymer that exhibits good adhesive properties at various peeling speeds. Of course, a mercaptan compound may be used for the purpose of controlling the polymerization rate, for example, as long as the effects of the present invention are not impaired. In this case, the amount of the mercaptan compound used is preferably 0 to 0.004 mass% with respect to the total amount of the monomer mixture (I). A more preferable upper limit is 0.00
It is 2% by mass, and more preferably 0.001% by mass.

The polymer A (polymer formed only from the monomer component A) and the polymer B (polymer formed from only the monomer component B) should have a Tg of -70 to -30 ° C. It is preferable to select the monomer composition of each monomer component. This is because when Tg is in this temperature range, good adhesive strength is exhibited at room temperature (23 ° C.). At this time, the other polymer preferably has a difference of 10 ° C. or more from the Tg of the polymer. This is because the wider the difference in Tg between the two, the broader the Tg when the polymer has a gradient composition and the better adhesive properties in a wide temperature range. However, if the Tg of the other polymer exceeds + 30 ° C, the adhesive strength of the obtained gradient composition polymer at room temperature decreases, so it is preferable to select the monomer component composition so as to be + 30 ° C or less. . The monomer component constituting the polymer having the lower Tg may be A or B. The monomer component C is in a small amount and is used for introducing a functional group into the low molecular weight polymer as described above, so that Tg varies depending on the monomer remaining in the system, and is not particularly limited.

The Tg of a polymer can be determined by DSC (differential scanning calorimeter), DTA (differential thermal analyzer), TMA (thermomechanical measuring device). Since it can be obtained from the ratio using the following calculation formula, it is preferable to determine the monomer composition of each monomer component using this calculated value as a guide. (1 / Tg) = (W ₁ / Tg ₁ ) + (W ₂ / Tg ₂ ) + ... +
(W _n / Tg _n)

In the formula, Tg represents the glass transition temperature (K), W ₁ , W ₂ , ... W _n represent the weight fraction of each monomer in the monomer component, and Tg ₁ , Tg ₂ ,. _n indicates the glass transition temperature (K) of a homopolymer of the corresponding monomer. The Tg of the homopolymer is "POLYMER
HANDBOOK "(4th edition; John Wiley & Sons, I
nc.)) and the like.

Next, specific examples of the pressure-sensitive adhesive composition of the present invention will be described. The pressure-sensitive adhesive composition of the present invention contains a first type or second type polymer for pressure-sensitive adhesive (hereinafter, simply referred to as “polymer for pressure-sensitive adhesive”) and a cross-linking agent.

As the cross-linking agent for cross-linking the pressure-sensitive adhesive polymer, one molecule of a functional group having the functional group-containing monomer and having reactivity with the functional group introduced into the pressure-sensitive adhesive polymer is used. A compound having two or more of them can be used. Examples of such a functional group include an isocyanate group, an epoxy group, an amino group, a methylol group, an alkoxymethyl group, an imino group, a metal chelate group, and an aziridinyl group, but the adhesive polymer has a hydroxyl group. In that case, it is preferable to use a polyfunctional isocyanate compound having two or more isocyanate groups in the molecule as a crosslinking agent.

As the polyfunctional isocyanate compound having two or more isocyanate groups, tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1, 5-naphthalene diisocyanate,
Diisocyanate compounds such as hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate and isophorone diisocyanate; buret polyisocyanate compounds such as "Sumijour N" (Sumitomo Bayer Urethane Co.); "Desmodur IL", " Desmodur HL "(all manufactured by Bayer AG), polyisocyanate compound having an isocyanurate ring known as" Coronate EH "(manufactured by Nippon Polyurethane Industry Co., Ltd.);" Sumijour L "(Sumitomo Bayer Urethane Co., Ltd.) Manufactured by Nippon Polyurethane Co., Ltd .; and the like; and adduct polyisocyanate compounds such as "Coronate L" and "Coronate L-55E" (both manufactured by Nippon Polyurethane Co., Ltd.). These may be used alone or in combination of two or more. Further, it is also possible to use a so-called blocked isocyanate obtained by inactivating the isocyanate group of these compounds with a masking agent having active hydrogen.

The amount of the cross-linking agent used is preferably 0.1 to 1 mass% of the cross-linking agent based on the adhesive polymer (solid content). If the amount is less than 0.1% by mass, the crosslinking may be insufficient, the crosslinking density may be low, and the cohesive force may be insufficient. If it exceeds 1% by mass, the crosslink density becomes too high, and properties such as curved surface sticking resistance and adhesive strength may deteriorate.

After the pressure-sensitive adhesive composition containing the above-mentioned pressure-sensitive adhesive polymer and the cross-linking agent as essential components is formed into a form according to various uses,
The adhesive product of the present invention can be obtained by a crosslinking reaction. The pressure-sensitive adhesive composition may optionally contain a tackifier in addition to the polymer for pressure-sensitive adhesive. As the tackifier, (polymerized) rosin type, (polymerized) rosin ester type, terpene type, terpene phenol type, coumarone type, coumarone indene type, styrene resin (oligomer)
System, xylene resin system, phenol resin system, petroleum resin system and the like. These can be used alone or in combination of two or more. Among these, a tackifier having a small number of carboxyl groups is preferable because it suppresses adhesion promotion, and a styrene-based oligomer “FTR6100” (manufactured by Mitsui Chemicals; softening point 96 to 97 ° C., acid value less than 1) is particularly preferable. is there.

Although the amount of the tackifier is not particularly limited,
It is usually 5 to 1 with respect to 100 parts by mass of the adhesive polymer.
It is preferably set to 00 parts by mass. If the addition amount of the tackifier is less than 5 parts by mass, the tackifying effect of the tackifier may not be exhibited. On the other hand, if the addition amount of the tackifier is more than 100 parts by mass, the tack may be decreased and the adhesive strength may be decreased. The range of 10 to 50 parts by mass is more preferable.

To the pressure-sensitive adhesive composition, if necessary, conventionally known additives such as a filler, a pigment, a diluent, an antiaging agent, an ultraviolet absorber and an ultraviolet stabilizer which are usually blended are added. May be. These additives may be one type or two types.
More than one species can be used. The amount of these additives added is
It may be appropriately set so as to obtain desired physical properties.

A pressure-sensitive adhesive composition prepared by mixing the polymer for pressure-sensitive adhesive with the above-mentioned cross-linking agent and, if necessary, the above-mentioned various additives, solvents, etc., can be prepared, for example, as a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive label, a pressure-sensitive adhesive tape, a double-sided tape or the like. It can be suitably used for the production of various adhesive products. Such adhesive products have no base material,
Alternatively, it is produced by forming a layer of the pressure-sensitive adhesive composition on a substrate and causing a crosslinking reaction.

As the substrate, conventionally known papers such as high-quality paper, kraft paper, crepe paper, glassine paper and the like; plastics such as polyethylene, polypropylene, polyester, polystyrene, polyethylene terephthalate, polyvinyl chloride, cellophane or the like. A of plastic
A metal vapor-deposited film of 1 or the like; fiber products such as woven fabric and non-woven fabric can be used. Examples of the shape of the base material include, but are not limited to, a film shape, a sheet shape, a tape shape, a plate shape, and a foam. A pressure-sensitive adhesive sheet, a pressure-sensitive adhesive tape, a pressure-sensitive adhesive label or the like can be obtained by applying the pressure-sensitive adhesive composition to one surface of the substrate by a known method.
Further, by applying the pressure-sensitive adhesive composition to release paper or the like in which a sheet-shaped material such as paper, synthetic paper, or plastic film is coated with the release agent, a baseless (single-layer structure) pressure-sensitive adhesive layer is formed. It can be obtained and used as a double-sided tape without a substrate. Moreover, the same or different adhesive composition may be applied to both surfaces of the above-mentioned substrate to form a double-sided tape.

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

After the pressure-sensitive adhesive composition is applied, the pressure-sensitive adhesive layer is formed on the substrate by drying. The drying temperature is not particularly limited. Depending on the use, the pressure-sensitive adhesive composition may be directly applied to the adherend. The pressure-sensitive adhesive product on which the pressure-sensitive adhesive layer is formed is preferably cured. The actual curing conditions do not have to be the same as the conditions for the holding power test, and the temperature, humidity, and time may be set appropriately. In order to suppress the change over time in characteristics after curing,
It is desirable to carry out curing under humidification to accelerate the crosslinking reaction.

On the surface of the pressure-sensitive adhesive layer formed on the substrate,
For example, release paper may be attached. The surface of the pressure-sensitive adhesive layer can be suitably protected and stored. The release paper is peeled off from the surface of the adhesive layer when using the adhesive product. When a pressure-sensitive adhesive layer is formed on one surface of a base material such as a sheet or tape, a known release agent may be applied to the back surface of the base material to form the release agent layer. By rolling the pressure-sensitive adhesive sheet (tape) in a roll shape with the pressure-sensitive adhesive layer inside, the pressure-sensitive adhesive layer comes into contact with the release agent layer on the back surface of the substrate, so the surface of the pressure-sensitive adhesive layer is protected. Saved.

[0059]

The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%" and "part" means "part by mass".

Synthesis Example 1 (Synthesis of Polymer Solution A1 for Adhesive) Ethyl acrylate (EA) 116 was placed in a four-necked flask equipped with a thermometer, a stirrer, an inert gas introducing tube, a reflux condenser and a dropping funnel. .04 parts, butyl acrylate (BA)
116.04 parts, acrylonitrile (AN) 7.2 parts and 2-hydroxyethyl acrylate (HEA) 0.7
Monomer component A consisting of 2 parts and ethyl acetate 196.
4 parts was added and the temperature was raised, and when the temperature reached 80 ° C., 0.48 part of a peroxide type initiator (Nyper BMT-K40: manufactured by NOF CORPORATION) was added to start polymerization. Monomer component A
At the same time as the initiation of polymerization (polymerization rate of less than 10%), BA34
Monomer component B consisting of 8.12 parts, AN10.8 parts and HEA1.08 parts, 0.72 parts of Niper BMT-K40, and 60.7 parts of ethyl acetate were added dropwise over one and a half hours to carry out the polymerization reaction. Continued. One hour after the dropping of the monomer component B was completed, the viscosity of the reaction product increased, so 390 parts of ethyl acetate was added as a diluting solvent.

After a further 2 hours, 1.8 parts of an azo polymerization initiator (ABN-E: manufactured by Nippon Hydrazine Industries Co., Ltd.) and 40 parts of ethyl acetate were added as a post-addition initiator, and further 4 parts were added.
The reaction continued for an hour. At the end of the polymerization, 212 parts of toluene was added for dilution. As a result, the solid content was 38.3% and the viscosity was 3
A polymer solution for adhesive (A1) having a viscosity of 5.3 Pa · s (25 ° C., B-type viscometer, the same applies hereinafter) and a weight average molecular weight of 65.9 × 10 ⁴ (GPC measurement: standard polystyrene conversion) was obtained.

The conditions for measuring the molecular weight by GPC are as follows. GPC measuring device: Liquid Chromatography Model 510 (Waters) Detector: M410 Differential refractometer Column: Ultra Styragel Linear (7.8 mm x 30 cm) Ultra Styragel 100A (7.8 mm x 30 cm) Ultra Styragel 500A (7.8 mm x) 30 cm) Solvent: THF (tetrahydrofuran) The sample concentration was 0.2%, and the injection amount was 200 microliter / time.

Synthesis Examples 2 to 3 (Polymer Solution A2 for Adhesive)
-Synthesis of A3) Polymerization was carried out in the same manner as in Synthesis Example 1 except that the monomer composition was changed as shown in Table 1 and HEA was added at once as the monomer component C at the same time as the addition of the post-addition initiator. Polymer solutions A2 to A3 were obtained. In all the synthesis examples, the polymerization rate immediately before the addition of the monomer component C and the post-addition initiator exceeded 90%.

Comparative Synthesis Examples 1 and 2 (Synthesis of Comparative Adhesive Polymer Solutions B1 and B2) Polymerization was carried out in the same manner as in Synthesis Example 1 except that the monomer composition was changed as shown in Table 1 to obtain a comparative adhesive composition. A polymer solution for agent B1 was obtained. Further, a polymer solution B2 for a pressure-sensitive adhesive for comparison was obtained in the same manner as in Synthesis Example 2.

[0065]

[Table 1]

Experiment No. 1 Adhesive polymer solution A1 was added to terpene phenol-based tackifier (“Tamanor 9
01 ”; manufactured by Arakawa Chemical Industry Co., Ltd .; softening point 120 to 135 ° C .;
After adding 20 parts of acid value 60 to 90) and adjusting the solid content to 35% with toluene, coronate L55E (polyisocyanate compound manufactured by Nippon Polyurethane Co .: solid content 55% to 100 parts of this solution). ) Was mixed and mixed well to prepare a pressure-sensitive adhesive composition. Using this composition, an adhesive strength test was conducted according to the method described below. The results are shown in Table 2.

Experiment No. 2 to 9 Experiment Nos. Except that the type of adhesive polymer solution, the type and amount of tackifier, and the amount of crosslinking agent were changed as shown in Tables 3 and 4. A pressure-sensitive adhesive composition was prepared in the same manner as in No. 1, and the performance was evaluated. The results are shown in Tables 2-3. The tackifier FTR6100 is a styrene oligomer (manufactured by Mitsui Chemicals, Inc .; softening point 96 to 97 ° C; acid value less than 1).

Experiment No. Experiment Nos. 10 to 13 except that the type of the polymer solution for the pressure-sensitive adhesive for comparison, the type and amount of the tackifier, and the amount of the crosslinking agent were changed as shown in Table 4. A pressure-sensitive adhesive composition was prepared in the same manner as in No. 1, and the performance was evaluated. The results are shown in Table 4.

[Method for preparing test piece] Al vapor-deposited polyethylene terephthalate film (thickness: 25 μm;
Hereinafter, the pressure-sensitive adhesive composition was applied using an Al vapor-deposited PET film) so that the thickness after drying was 35 μm, and then dried at 100 ° C. for 3 minutes. After that, release paper (made by San-A Kaken Co., Ltd., trade name K-80H
S) is attached and protected, then the temperature is 23 ° C and the relative humidity is 65.
After curing for 7 days in an atmosphere of%, an adhesive film (adhesive product) was obtained. This adhesive film was cut into a predetermined size to prepare a test piece. The release paper was peeled off during various measurement tests.

[Measurement method of holding power] A stainless steel plate (SUS304: hereinafter referred to as "SUS plate") specified in JIS G 4305 in an atmosphere of a temperature of 23 ° C and a relative humidity of 65%.
2), a 2 kg rubber roller is reciprocated 3 times to attach the adhesive film. The pasting area is 25 mm × 25 mm. After leaving this sample for 25 minutes, it is placed in a thermostat at 40 ° C. and suspended vertically. After 20 minutes,
Apply a 9.8N weight to the adhesive film. Therefore, the load is 1.568 N / cm ² . Apply a load, SU
Time until the adhesive film falls from the S plate, or 1
The deviation distance after 4 hours was measured. NC means that there was no deviation at all.

[Measurement Method of Initial Adhesion Strength] An adhesive film cut into a width of 25 mm and an appropriate length was prepared, and the SUS plate was reciprocated three times with a 2 kg rubber roller in an atmosphere of 23 ° C. and relative humidity of 65%. The adhesive film was pressure-bonded to the. Twenty-five minutes after crimping, speed 30 at
The strength at the time of peeling the adhesive film from the SUS plate by pulling the adhesive film in the direction of 180 ° at 0 mm / min was measured, and this peel strength was taken as the initial (after 20 minutes) adhesive force (N / cm).

[Measurement method of adhesive strength after 24 hours under normal conditions] An adhesive film was attached to a SUS plate in the same manner as in the initial adhesive strength measurement, and left in an atmosphere of a temperature of 23 ° C. and a relative humidity of 65% for 24 hours, and thereafter. A tensile test was performed in the same manner as the initial adhesive strength measurement to measure the peel strength. This value was taken as the adhesive force (N / cm) after 24 hours in the normal state.

[Measurement Method of Adhesive Strength after Acceleration of Heating] An adhesive film was attached to a SUS plate in the same manner as in the initial adhesive strength measurement and left at 70 ° C. for 7 days, then 23 ° C. and relative humidity 65.
%, The sample was allowed to stand for 1 hour in an atmosphere of 10%, and a tensile test was performed in the same manner as in the measurement of the initial adhesive strength to measure the peel strength. This value was defined as the adhesive force (N / cm) after accelerated heating (after 7 days).

[Evaluation of Adhesive Residue] In measuring the above-mentioned initial adhesive strength, normal adhesive strength and adhesive strength after heating, the adhesive residue of the adhesive was evaluated according to the following criteria. ○: No trace of adhesive remains △: Partially transferred to adherend ×: Entirely transferred to adherend

[Removability] An adhesive film was attached to a SUS plate in the same manner as in the initial adhesive strength measurement. About the thing adhered and left to stand at 80 degreeC for 24 hours, the adhesive film was quickly peeled by the hand to 90 degree direction with respect to the SUS board. The adhesive residue state at this time was evaluated according to the above criteria.

[Edge Lifting Resistance (Curved Surface Resistance)] At a temperature of 23 ° C. and a relative humidity of 65%, the length corresponds to a half circumference along the circumference of a polypropylene cylinder (diameter 15 mm). A test piece (label) having a width of 10 mm was attached and the floating state of the label was observed after 3 days. The floating state was judged based on the criteria shown in FIG.

[0077]

[Table 2]

[0078]

[Table 3]

[0079]

[Table 4]

From Tables 2 and 3, the pressure-sensitive adhesive products obtained from the pressure-sensitive adhesive composition of the present invention have a good balance of holding force, pressure-sensitive adhesive force, removability, and edge lift resistance (curved surface adhesion). I understand. However, in the pressure-sensitive adhesive using the polymer solutions B1 and B2 having a carboxyl group, especially when the adhesive force after heating for 7 days and the high-speed removability are checked, the broken state is between the base material on a part or the entire surface. And the adherend was contaminated (Table 4).

[0081]

Since the pressure-sensitive adhesive composition of the present invention contains a polymer for pressure-sensitive adhesive which uses a specific composition and a specific polymerization method as a main component, it can be re-peeled without contaminating an adherend,
Moreover, it was possible to obtain an adhesive product having excellent adhesion to curved surfaces and exhibiting strong adhesive strength.

[Brief description of drawings]

FIG. 1 is a diagram showing evaluation criteria of edge lift resistance.

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Claims (5)

[Claims] 1. A pressure-sensitive adhesive composition essentially comprising a pressure-sensitive adhesive polymer and a cross-linking agent, wherein the pressure-sensitive adhesive polymer comprises a (meth) acrylate having an alkyl group having 2 to 18 carbon atoms and a nitrogen atom. A monomer mixture (I) containing a monomer and a functional group-containing monomer as essential components and not containing a carboxyl group-containing monomer is obtained from the monomer mixture (I), wherein the monomer mixture (I) and the monomer component A have different monomer compositions. It is divided into component B, and both of these monomer components A and B contain the above functional group-containing monomer, and the polymer for pressure-sensitive adhesive is prepared by first charging the monomer component A into a reactor for polymerization. After the initiation of the polymerization of the monomer component A, and when the polymerization rate of the monomer A component does not exceed 50%, the monomer component B is charged into the reactor. Is obtained by initiating the polymerization, and the crosslinking agent is a compound having in the molecule two or more functional groups capable of reacting with the functional groups of the functional group-containing monomer. Composition. 2. A pressure-sensitive adhesive composition essentially comprising a pressure-sensitive adhesive polymer and a cross-linking agent, wherein the pressure-sensitive adhesive polymer contains a (meth) acrylate having an alkyl group having 2 to 18 carbon atoms and a nitrogen atom. A monomer mixture (I) containing a monomer and a functional group-containing monomer as essential components and not containing a carboxyl group-containing monomer is obtained from the monomer mixture (I), wherein the monomer mixture (I) and the monomer component A have different monomer compositions. It is divided into a component B and a monomer component C, and each of these monomer components A, B, and C contains the functional group-containing monomer, and the polymer for pressure-sensitive adhesive first comprises the monomer component A in a reactor. After the polymerization of the monomer component A is started and the polymerization rate of the monomer component A does not exceed 50%, the monomer is charged into the reactor. At the stage when the polymerization rate of the monomer components A and B inside the reactor reached 80% or more after the introduction of the monomer component B and the completion of the monomer component B, the monomer component C was further added to the reactor. A pressure-sensitive adhesive composition, which is obtained by adding and polymerizing, wherein the crosslinking agent is a compound having two or more functional groups in a molecule capable of reacting with the functional groups of the functional group-containing monomer. object. 3. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer mixture (I) contains acrylonitrile as a nitrogen atom-containing monomer. 4. The pressure-sensitive adhesive composition according to claim 1, wherein the functional group-containing monomer is a hydroxyl group-containing monomer, and the crosslinking agent is a compound having an isocyanate group. 5. A pressure-sensitive adhesive product comprising a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1 on a substrate.