JP2003176474A - Adhesive composition and adhesive product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive product excellent in adhesiveness to a curved surface and having a small property change with the lapse of time. <P>SOLUTION: The adhesive composition essentially comprises a polymer for the adhesive and a crosslinking agent, wherein the composition gives an adhesive tape sample by coating the composition on 50 μm thickness polyethylene terephthalate base film to form 30 μm dry-base thickness adhesive layer, and the obtained sample shows 0.5-5.5 h falling time when measured the retentivity at 80°C under 1.568 N/cm<SP>2</SP>load after holding the sample for 7 days under conditions of 23°C and 65% relative humidity (RH) and, as well, after holding the sample for 7 days under the conditions of 23°C and 65% RH and then for 20 days at 40°C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent resistance to sticking to curved surfaces and having little change in pressure-sensitive adhesive property over time, and to 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 basic properties such as tack, adhesive strength, cohesive strength (holding power), heat resistance,
It is widely used for adhesive products such as adhesive labels, sheets, and tapes because it has excellent weather resistance, water resistance, oil resistance, etc.

In the case of an acrylic pressure-sensitive adhesive, it is common to introduce a hydroxyl group into a polymer for pressure-sensitive adhesive and crosslink it with an isocyanate group-containing crosslinking agent to improve the above properties. This cross-linking system is used because the reaction between the hydroxyl group and the isocyanate group takes place relatively quickly. However, in a short time such as applying the pressure-sensitive adhesive composition to a film substrate or the like and heating and drying, it is always difficult to complete the cross-linking reaction because of the usual chemical reaction,
For the purpose of minimizing changes in physical properties of the adhesive product, the adhesive product is usually left (cured) at 20 to 30 ° C. for about one week in a humid environment. This curing completes the cross-linking reaction and suppresses changes in physical properties after shipment as a product.

However, if a carboxyl group is introduced into the pressure-sensitive adhesive polymer, there is a problem in that even after the curing is completed, the crosslinking gradually progresses and the physical properties change with time. In particular, for applications requiring curved surface sticking resistance, the molecular design of the polymer for pressure-sensitive adhesive and the amount of cross-linking agent are adjusted so that the softening pressure-sensitive adhesive can be obtained by setting the cross-linking density to a low level. Nevertheless, there is a problem that if the crosslink density increases even a little during curing, the resistance to sticking to curved surfaces is extremely reduced. Here, the curved surface adhesion resistance is good, for example, when a pressure-sensitive adhesive tape sample is stuck on a surface of a polypropylene cylinder (cylinder may be used) having a diameter of 15 mm for half a round and left for 3 days under normal conditions,
It means that the end of the tape does not float or peel off.

The carboxyl group is introduced into the adhesive polymer by copolymerizing, for example, acrylic acid in order to form a hydrogen bond and improve the cohesive force of the adhesive. It is considered that the above physical property changes occur due to the reaction with the unreacted isocyanate group-containing crosslinking agent.

When the use of the carboxyl group-containing monomer is stopped in order to suppress the change in the above physical properties, the cohesive force cannot be secured, and when the amount of the cross-linking agent is simply increased to increase the cohesive force, the adhesive force is lowered. Therefore, it is currently very difficult to select the composition of the pressure-sensitive adhesive for ensuring the resistance to sticking to curved surfaces.

[0007]

In the present invention, the ultimate goal is to obtain an adhesive product having excellent resistance to curved surface sticking. However, with respect to sticking curved surface, the radius of curvature of the cylinder for sticking the sample is large. In this case, the test method is such that all the samples remain adhered well, and if the radius of curvature of the cylinder is reduced, the ends of all the samples will float, resulting in disqualification. is there.

Therefore, the present inventors first found a characteristic equivalent to the curved surface sticking resistance, and found out what degree of the characteristic the curved surface sticking resistance can be made to be good. The subject was to find a suitable pressure-sensitive adhesive composition for obtaining a pressure-sensitive adhesive that does not change over time while satisfying the above conditions.

[0009]

The pressure-sensitive adhesive composition according to the present invention, which has solved the above-mentioned problems, is a pressure-sensitive adhesive composition essentially containing a polymer for pressure-sensitive adhesive and a cross-linking agent, which comprises a polyethylene terephthalate film having a thickness of 50 μm. A pressure-sensitive adhesive tape sample was prepared by applying a pressure-sensitive adhesive composition on one surface of the base material so that the thickness of the pressure-sensitive adhesive layer after drying was 30 μm, and producing a pressure-sensitive adhesive tape sample. %, A drop time when the holding power was measured at 80 ° C. under a load of 1.568 N / cm ² , after leaving it for 7 days in an atmosphere of 23%,
1.568 for the sample after being left for 7 days in an atmosphere of ℃ and relative humidity of 65%, and further left at 40 ° C. for 20 days
The summary is that the dropping time when the holding power is measured at 80 ° C. under a load of N / cm ² is 0.5 to 5.5 hours in each case.

The present inventors have found that the holding power test at 80 ° C. shows a good correlation with the resistance to sticking to curved surfaces, and that the holding power test at 80 ° C. is 0 even after curing and after acceleration of heating after curing. It was found that those that fall in 0.5 to 5.5 hours have appropriate softness and exhibit excellent curved surface adhesion resistance,
The above configuration has been reached.

In preparing the above-mentioned adhesive tape sample,
After applying the pressure-sensitive adhesive composition to the polyethylene terephthalate film, and drying at 100 ° C. for 3 minutes, the pressure-sensitive adhesive layer is covered with a release paper (“K-80HS”; manufactured by San-A Kaken Co., Ltd.) to cure. went. A detailed test method for holding power will be described later.

The Tg of the pressure-sensitive adhesive polymer, which is the main component of the pressure-sensitive adhesive composition of the present invention, is preferably -55 ° C. or less, whereby good curved surface sticking resistance can be obtained. Specifically, the adhesive polymer is obtained from a monomer mixture containing (meth) acrylate having an alkyl group having 2 to 18 carbon atoms, a nitrogen atom-containing monomer, and a functional group-containing monomer as essential components. It is a preferred embodiment of the pressure-sensitive adhesive composition that the crosslinking agent is a compound containing a functional group capable of reacting with the functional group-containing monomer. The functional group-containing monomer is a hydroxyl group-containing monomer,
It is particularly preferable that the crosslinking agent is a compound having an isocyanate group. The present invention also includes an adhesive product provided with an adhesive layer made of the adhesive composition of the present invention.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION
It was found that there is a good correlation with the holding power test at 0 ° C. Measurement at temperatures lower than 80 ° C and load of 1.568
If it is smaller than N / cm ² , no significant difference is produced and no correlation with the curved surface sticking property is observed, which is not preferable. The base material was a thick (50 μm) polyethylene terephthalate (PET) film. Furthermore, the sample was cured at 25 ° C. and 65% RH for 7 days, but in order to understand the change in physical properties after curing, the sample after being left at 40 ° C. for 20 days in a dry state was also treated as after curing. Similarly, a holding power test at 80 ° C. was performed.

A pressure-sensitive adhesive tape sample was prepared by applying a pressure-sensitive adhesive composition to a PET film having a thickness of 50 μm so that the thickness after drying was 30 μm, and heating at 100 ° C. for 3 minutes. The pressure-sensitive adhesive layer was covered with a release paper (“K-80HS”; manufactured by San-A Kaken Co., Ltd.) and cured.

The holding power test at 80 ° C. was carried out using S as an adherend.
Using a US304 stainless steel plate, the procedure is as follows. In an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%, a 2 kg rubber roller is reciprocated 3 times to press-bond the adhesive tape sample to a stainless steel plate. The pasting area is 25 mm × 25 mm. After leaving it for 25 minutes, it is hung vertically in a holding power tester set at 80 ° C. and left for 20 minutes. After 20 minutes, the sample is weighted (suspended) with a weight of 9.8N. Therefore, the load is 1.568 N / cm ² . And
After the weight is applied, the time until the sample falls from the stainless steel plate is measured.

In the present invention, the holding power test result (falling time) at 80 ° C. according to the above method is 0.5 hours for both the sample after curing and the sample after standing for 20 days at 40 ° C. after curing. Must be 5.5 hours. Within this range, the adhesion to curved surfaces is good, and the adhesive force, especially the adhesive force to the polyolefin-based hardly adherend, is also good.

Those that fall in less than 0.5 hours have insufficient cohesive strength, and therefore the adhesive causes cohesive failure during the curved surface sticking resistance test and loses the rigidity of the substrate. Is not preferable. Those that do not fall even after more than 5.5 hours are unfavorable because they are too cross-linked from the viewpoint of resistance to sticking to a curved surface and the ends of the sample float.
The lower limit of the fall time is more preferably 1 hour, and further preferably 2 hours. Further, the more preferable upper limit of the dropping time is 5 hours, and further preferably 4 hours. In addition, even if one of the fall times after curing and after being left at 40 ° C. for 20 days after curing is included in the above range, if either is not included, it is determined that the sample has a large temporal change. As such, it is not preferred in the present invention.

Next, specific examples of preferable pressure-sensitive adhesive compositions for satisfying the above requirements will be described. The pressure-sensitive adhesive composition of the present invention contains at least a polymer for pressure-sensitive adhesive and a crosslinking agent. The term “polymer”, unless otherwise specified as “homopolymer”, represents a copolymer or a terpolymer or more multicomponent copolymer.

The adhesive polymer of the present invention has a Tg of -5.
It is preferably 5 ° C or lower. This is because if the Tg is higher than -55 ° C, the requirements for the holding power test may not be satisfied even if the amount of the crosslinking agent is reduced. More preferable Tg
Has an upper limit of -60 ° C. The Tg of the polymer is DSC (differential scanning calorimeter), DTA (differential thermal analyzer), T
It can be determined by MA (thermo-mechanical measuring device).
It can also be calculated from the Tg (K) of the homopolymer and the mass fraction of the monomer using the following calculation formula. It is preferable to determine the monomer composition by 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 a glass transition temperature (K), and W ₁ , W ₂ ,
... W _n represents the mass fraction of each monomer in the monomer component, and Tg ₁ , Tg ₂ , ... Tg _n represent the glass transition temperature (K) of the homopolymer of the corresponding monomer. In addition, the Tg of homopolymer is "POLYMER HANDBO
The numbers described in publications such as "OK" (4th edition; published by John Wiley & Sons, Inc.) may be used.

When synthesizing a polymer for pressure-sensitive adhesives, a (meth) acrylic acid alkyl ester for expressing a pressure-sensitive adhesive force, a monomer containing a functional group serving as a crosslinking point, and a monomer for imparting cohesive force It is preferable to use and in combination.

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, 2-ethylhexyl acrylate (-70 ° C) having a low Tg is preferable. This is because even if it is combined with a monomer (high Tg) for imparting cohesive force, it does not exceed the preferable upper limit of Tg.

The functional group-containing monomer is not particularly limited as long as it is a monomer having a functional group capable of reacting with a crosslinking agent, and an epoxy group-containing monomer, an amino group-containing monomer,
Isocyanate group-containing monomers can also be used,
In order to complete the cross-linking reaction during curing and prevent the physical properties from changing with time, it is necessary to introduce a hydroxyl group into the adhesive polymer and use it in combination with a cross-linking agent having an isocyanate group. Due to their preference, it is recommended to use hydroxyl group-containing monomers. Since the carboxyl group-containing monomer causes the above-mentioned change with time after curing, it is preferable to refrain from using it.

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.

As the monomer for imparting cohesive force, a nitrogen atom-containing monomer is preferable. Specifically, N
-Vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylonitrile, etc.,
(Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ethoxyethyl Acrylamide, N- (n
Amido group-containing monomers such as -butoxymethyl) acrylamide, dimethylaminopropyl methacrylamide, and t-butyl acrylamide are mentioned as preferable ones, and among these, one kind or a mixture of two or more kinds can be used. N-vinylpyrrolidone and acrylamide are preferable in consideration of availability, polymerizability, and characteristics of the obtained polymer.

The monomer mixture for obtaining the adhesive polymer of the present invention is preferably a combination of a (meth) acrylic acid alkyl ester, a monomer having a functional group serving as a crosslinking point, and a nitrogen atom-containing monomer. (Meta)
85% by mass because acrylic acid alkyl ester is the main component
It is preferable to use the above. The functional group-containing monomer is 0.
The range of 05-5 mass% is suitable. The more preferable lower limit of the functional group-containing monomer is 0.1% by mass. Further, 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. If both the functional group-containing monomer and the monomer for imparting cohesive force are below the lower limit of the above preferred range, the cohesive force may be insufficient and the dropping time in the above-mentioned holding force test may be faster than 0.5 hours. . On the other hand, when the amount exceeds the upper limit of the above-mentioned preferable range, the cohesive force becomes too high, and the drop time in the holding power test may exceed 5.5 hours.

The monomer mixture 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 contained in each monomer component in an amount of 0 to 20.
It is preferably set to mass%. If it exceeds 20% by mass,
It is not preferable because the Tg of the adhesive polymer increases and becomes hard.

The method for polymerizing the adhesive polymer is not particularly limited, but so-called solution polymerization is preferably carried out 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; aliphatic hydrocarbons such as hexane and pentane. Examples thereof include, but are not particularly limited as long as they do not inhibit the above polymerization reaction. Only one kind of these solvents may be used, or two or more kinds thereof may be appropriately mixed and used. 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. A post-addition initiator (booster) may be added in the latter stage of the polymerization for the purpose of reducing the amount of residual monomers.

It is preferable to use the initiator in a total amount of 0.01 to 1% by mass based on the mass of the monomer. If the amount is too large, a high molecular weight polymer having excellent adhesive properties may not be obtained. In terms of adhesive properties,
The weight average molecular weight (Mw) of the adhesive polymer is preferably 200,000 or more, more preferably 300,000 or more. Although the upper limit is not particularly limited, it is difficult to synthesize a polymer of more than 2 million by solution polymerization.
10,000 or less is more preferable. Speaking of curved surface resistance, 5
Most preferably, it is from 0,000 to 700,000. Therefore, if necessary,
A known chain transfer agent such as a mercapto compound may be used. The molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

The polymerization conditions such as the polymerization temperature and the polymerization time depend on, for example, the composition of the monomer mixture, the type of the polymerization solvent and the polymerization initiator, the required properties of the obtained adhesive polymer, the use of the adhesive, and the like. There is no particular limitation as long as it is set appropriately. 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.

As the cross-linking agent for cross-linking the polymer for pressure-sensitive adhesive, one molecule of the functional group which the functional group-containing monomer has and has reactivity with the functional group introduced into the polymer for pressure-sensitive adhesive 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 a factor which greatly affects the drop time requirement of the above-mentioned holding force test. It is preferable to use the functional group of the crosslinking agent in an amount of 0.2 to 4.0 equivalents based on 1 equivalent of the functional group (crosslinking point) of the adhesive polymer. The crosslinker has a functional group of 0.2
If the amount is less than the equivalent, the crosslinking may be insufficient, the crosslinking density may be low, and the cohesive force may be insufficient. If it exceeds 4.0 equivalents, the crosslink density becomes too high, and the dropping time in the holding power test may exceed 5.5 hours.

It is necessary to appropriately increase or decrease the amount of the cross-linking agent used within the above range depending on the kind of the polymer for pressure-sensitive adhesive so that the requirement of the holding time of the dropping force can be satisfied. For example, when the Tg of the pressure-sensitive adhesive polymer is high or the molecular weight is high, or when the pressure-sensitive adhesive polymer uses many monomers for imparting cohesive force, it is preferable to reduce the amount of the crosslinking agent. In addition, the above-mentioned acrylic acid-4
-When hydroxybutyl or "Plaxel F" is used as the functional group-containing monomer of the polymer for pressure-sensitive adhesives, the reaction between the hydroxyl group in the polymer and the cross-linking agent proceeds efficiently.
It is desirable that the amount of the cross-linking agent is about half as compared with the case where the polymer is synthesized using -hydroxyethyl. Furthermore, when using a tackifier having a functional group capable of reacting with the cross-linking agent, the amount of the cross-linking agent may be determined in consideration of consumption of the cross-linking agent in the tackifier. It should be noted that the functional group of the tackifier is not so highly reactive due to steric hindrance or the like.

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 type, xylene resin type, phenol resin type, petroleum resin type, etc. Is mentioned.
These can be used alone or in combination of two or more.

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, from pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, pressure-sensitive adhesive tapes, double-sided tapes, etc. 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 and glassine paper; plastics such as polyethylene, polypropylene, polyester, polystyrene, polyethylene terephthalate, polyvinyl chloride, cellophane; woven fabrics Textile products such as cloth 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.

[0044]

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".

Experiment No. 1 Into a four-necked flask equipped with a thermometer, a stirrer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel, acrylic acid-2-
Ethylhexyl (2EHA) 95.7 parts, acrylic acid-
40 parts of a monomer mixture consisting of 0.3 parts of 2-hydroxyethyl (HEA) and 4.0 parts of N-vinylpyrrolidone (NVP) and 40 parts of ethyl acetate were added and the temperature was raised to 84 ° C. By the way, 0.04 parts of a peroxide type initiator (Nyper BMT-K40: manufactured by NOF CORPORATION) was added to initiate polymerization. 10 minutes after the initiation of the polymerization, 9 parts of a mixture of 60 parts of the remaining monomer mixture, 40 parts of ethyl acetate and 0.06 part of Niper BMT-K40 was mixed.
It dripped uniformly over 0 minutes. Polymerization was continued at reflux temperature.

90 minutes after the dropping of the monomer was completed, an azo type polymerization initiator (ABN-
E: 0.3 part of Japan Hydrazine Industry Co., Ltd. and 50 parts of toluene were added, and the reaction was terminated by aging for 90 minutes. As a result, the solid content was 44.9% and the viscosity was 4400.
A polymer solution for pressure-sensitive adhesive having a mPa · s (25 ° C., B-type viscometer, the same below) and a weight average molecular weight (Mw) of 62.2 × 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 c)
m) Ultra Styragel 100A (7.8 mm x 30 cm) Ultra Styragel 500A (7.8 mm x 30 cm) Solvent: THF (tetrahydrofuran) Sample concentration was 0.2%, and injection volume was 200 microliters / dose.

To the above-mentioned adhesive polymer solution, toluene 2 was added.
0 parts and tackifier ("Pencel D-160"; manufactured by Arakawa Chemical Industry Co., Ltd .; polymerized rosin ester type; hydroxyl value 42) 20
The mixture with the parts was added to obtain a tackifier-containing polymer solution. To 100 parts of this tackifier-containing polymer solution,
As a cross-linking agent, 1.0 part (wet) of Coronate L-55E (polyisocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd .: solid content: 55%) was added and well stirred to prepare an adhesive composition. Crosslinker NCO to polymer OH
The equivalent ratio (NCO / OH) of is 2.27.

Experiment No. Experiment Nos. 2 to 9 except that the monomer composition was changed as shown in Table 1. A pressure-sensitive adhesive composition was prepared in the same manner as in 1.

Experiment No. Experiment No. 10 except that the monomer composition was changed as shown in Table 1, the amount of ethyl acetate as the initial charging solvent was changed to 50 parts, and the amount of ethyl acetate for dropping was changed to 30 parts. A pressure-sensitive adhesive composition was prepared in the same manner as in 1.

[0051]

[Table 1]

In the above table, Tg (° C.) is a calculated value obtained from the above formula. The following Tg (K) of the homopolymer was used for the calculation.

2EHA: 2-ethylhexyl acrylate 203K BA: Butyl acrylate 217K HEA: 2-hydroxyethyl acrylate 258K 4HBA: 4-hydroxybutyl acrylate 224K NVP: N-vinylpyrrolidone 451K AAM: Acrylamide 426K AAA : Acrylic acid 379K Experiment No. 1-No. Using the pressure-sensitive adhesive composition obtained in No. 10, a sample was prepared by the following method, and each property was evaluated. The results are shown in Table 2.

[Preparation Method of Sample] After using a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., thickness: 50 μm) as a substrate, the pressure-sensitive adhesive composition was applied so as to have a thickness after drying of 30 μm. And dried at 100 ° C. for 3 minutes. After that, a release paper (manufactured by San-A Kaken Co., Ltd., trade name K-80HS) was attached to the surface of the pressure-sensitive adhesive layer to protect it, and then 7 in an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%.
I was cured for a day. Each measured value of the sample after curing is shown in Table 2 as "initial". Also, after curing, 4 more
The samples after being left for 20 days in a dry state at 0 ° C. are shown in Table 2 as “aging”.

[Measurement Method of Holding Power] The holding power test at 80 ° C. was carried out as follows using a SUS304 stainless steel plate as an adherend. In an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%, a 2 kg rubber roller is reciprocated 3 times to press-bond the adhesive tape sample to a stainless steel plate. The pasting area is 25 mm × 25 mm. 80 after leaving for 25 minutes
Suspend vertically in a holding force tester set at ℃, 20
Leave for minutes. After 20 minutes, the sample is weighted with 9.8N. Therefore, the load is 1.568 N / cm ² . Then, the time from the application of the weight to the dropping of the sample from the stainless steel plate was measured. When the sample did not fall after 24 hours, it was shown as “> 24” in Table 2. In addition, the ratio of the elapsed time to the initial drop time "Age / Initial"
Are also shown in Table 2. Further, the holding power test at 40 ° C. (only in the initial stage) was also performed in the same manner as at 80 ° C. except that the holding power tester set to 40 ° C. was used.

[Measurement Method of Adhesive Strength (Initial)] The SUS plate and the polyethylene plate (PE plate) were used as adherends.
The sample was attached to an adherend with a 2 kg rubber roller in an atmosphere of 23 ° C. and a relative humidity of 65%, and pressure-bonded so that the rubber roller makes a total of 3 reciprocations on the sample. 25 after crimping
After 30 minutes, in the atmosphere of 23 ° C. and relative humidity of 65%, the film part of the adherend and the sample (the part to which the adhesive is not applied) are respectively gripped using a tensile tester, and the speed is 300 mm.
The peel strength of the sample was measured by pulling the sample in the direction of 180 ° at a speed of / min and peeling the sample from the adherend.

[Curved surface resistance] temperature 23 ° C., relative humidity 6
Polypropylene cylinders (diameter 15
mm) along the circumference of a circle, a width of 10
A sample (label) of 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.

[0058]

[Table 2]

From Table 2, Experiment No. 1 to 5 have a drop time in a holding power test at 80 ° C. after curing (initial),
Both after curing and after standing for heating (aging) were included in the specified range (0.5 to 5.5 hours) of the present invention, and the curved surface adhesion resistance was also excellent at rank 5. On the other hand, Experiment No. 6 ~
In No. 10, both in the initial stage and the aging period, the specified range (0.
5 to 5.5 hours), the surface resistance to curved surfaces is poor. From this, it was confirmed that there is a good correlation between the holding power test result at 80 ° C. and the curved surface adhesion resistance.

Experiment No. In Nos. 1 to 4, the amount of HEA and the amount of the cross-linking agent were appropriate, so that the fall time in the holding power test at 80 ° C could be set within the target range. In addition, the experiment No.
Since 5H used 4HBA, it is considered that the resin was appropriately crosslinked even when the amount of the crosslinking agent was small. Experiment No. 6 and experiment N
o. From the comparison of No. 1, It can be seen that No. 6 has insufficient cohesive force because the amount of the crosslinking agent is small. On the contrary, the experiment No.
In No. 7, the amount of crosslinking agent was too large. Experiment No. Since acrylic acid was used for 8 and 9, the change with time was remarkable, which was not desirable as a product. In addition, the experiment No. In No. 10, since 4HBA having a high crosslinking efficiency was used and BA having a Tg higher than 2EHA as a main component, the adhesive was too hard even if the amount of the crosslinking agent was small, and the cohesive force became excessive. To be

[0061]

EFFECTS OF THE INVENTION By using the drop time in the holding power test at 80 ° C. as a guide, it is possible to provide an adhesive product which has little change in properties over time and is excellent in curved surface sticking resistance.

[Brief description of drawings]

FIG. 1 is a diagram showing an evaluation standard of curved surface sticking resistance.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4J004 AA10 AA14 AB01 BA02 CA03                       CA06 CB01 CB02 CB04 EA05                       FA01 FA06 FA08                 4J040 DF041 DF051 DF061 DF101                       EF071 EF241 EF291 EF301                       HB41 HC14 HD02 JB09 KA12                       LA02 LA06 MB10

Claims (5)

[Claims] 1. A pressure-sensitive adhesive composition essentially comprising a pressure-sensitive adhesive polymer and a cross-linking agent, wherein a polyethylene terephthalate film having a thickness of 50 μm is used as a substrate, and one side of the substrate has a thickness of the adhesive layer after drying. Thirty
The pressure-sensitive adhesive composition was applied and dried to a thickness of μm to prepare a pressure-sensitive adhesive tape sample, and the sample was allowed to stand for 7 days in an atmosphere of 23 ° C. and relative humidity of 65%, and then a load of 1.568 N / cm ² was applied. Multiply by 8
The drop time when the holding power was measured at 0 ° C. and the sample after being left for 7 days in an atmosphere of 23 ° C. and 65% relative humidity, and further for 20 days at 40 ° C.
The pressure-sensitive adhesive composition is characterized in that the fall time when the holding power is measured at 80 ° C. under a load of 68 N / cm ² is 0.5 to 5.5 hours. 2. The T of the polymer for pressure-sensitive adhesive in the pressure-sensitive adhesive composition.
The pressure-sensitive adhesive composition according to claim 1, wherein g is −55 ° C. or lower. 3. A pressure-sensitive adhesive polymer is obtained from a monomer mixture containing a (meth) acrylate having an alkyl group having 2 to 18 carbon atoms, a nitrogen atom-containing monomer, and a functional group-containing monomer as essential components. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the cross-linking agent is a compound having a functional group capable of reacting with the functional group-containing monomer. 4. The pressure-sensitive adhesive composition according to claim 3, 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 comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 4.