JP2001164221A - Removable adhesives and adhesive sheets - Google Patents

Abstract

(57) [Problem] To provide a re-peelable aqueous dispersion-type pressure-sensitive adhesive and a pressure-sensitive adhesive sheet which have a small increase in adhesive force with respect to an adherend such as a metal plate with the lapse of time and are easily peelable without adhesive residue. It is intended to be provided without increasing the types. A weight-average molecular weight of at least 5 × 10 ⁴ -5 obtained by aqueous emulsion polymerization of a monomer mixture comprising at least a (meth) acrylate and a vinyl monomer having a functional group copolymerizable therewith. Aqueous dispersion (A) in the range of less than × 10 ⁵ , also having a weight average molecular weight of 5
Aqueous dispersion (B) having × 10 ⁵ or more, also having a gel, having a gel content of 95% or less of the whole, and having a weight average molecular weight of sol content of 5 × 10 ⁵ or more (C) To
(A) is 10 to 90% by weight, and (B) is 10 to
90% by weight, or (A) is 10 to 90% by weight,
Provided is a removable aqueous dispersion-type pressure-sensitive adhesive and a pressure-sensitive adhesive sheet characterized in that (C) can be arbitrarily mixed in a range of 10 to 90% by weight and can be adjusted to a specific storage modulus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film for a metal plate and a resin molded product, a protective film for an electronic component, a masking tape for coating, an adhesive memo, a disposable, using a water-dispersed acrylic copolymer. The present invention relates to a removable pressure-sensitive adhesive used for various uses such as a warmer, and pressure-sensitive adhesive sheets in the form of a sheet or a tape.

[0002]

2. Description of the Related Art For example, a surface protective film is used to temporarily protect the surface of a product such as a metal plate, a plastic plate, and a painted plate in order to prevent the surface from being damaged, contaminated, and corroded during transportation, storage, processing, and the like. After this purpose is achieved, it is peeled off. Therefore, the surface protection film is used for transporting products,
It is required that the product does not adhere and peel during storage and processing, while it can be easily peeled off when the product is used.

[0003] Similarly, a masking tape for coating is required to be able to be easily peeled off after application without being adhered and peeling off after coating and leaving no adhesive residue.

On the other hand, acrylic pressure-sensitive adhesives have been widely used instead of conventional rubber-based pressure-sensitive adhesives in view of their excellent adhesive properties and weather resistance. In addition, from the viewpoints of environmental measures, resource saving, and safety, the development of aqueous dispersion-type acrylic pressure-sensitive adhesives that do not use organic solvents has been progressing, and their use has been increasing.

[0005] In some cases, an aqueous dispersion type removable pressure-sensitive adhesive is used for the surface protective film. However, in the case of a conventional product, the pressure-sensitive adhesive is broken after pasting it on a metal plate or the like. This has the disadvantage that glue residue may be left on the surface of products such as metal plates.

Further, in the conventional removable water-dispersed pressure-sensitive adhesive, as the wettability with respect to the adherend progresses, the adhesive strength is increased due to the surface roughness, and the adhesive strength may change over time. For this reason, when the surface protective film using the re-peelable pressure-sensitive adhesive is used for a product such as a metal plate, the peeling force is heavy and it is difficult to peel off. did.

As described above, the conventional surface protective film using a removable adhesive based on an aqueous dispersion of an acrylic copolymer exhibits a time-dependent increase in adhesive strength after being attached to a metal plate or the like. There are also problems such as a large time required for the peeling operation and the occurrence of adhesive residue, a temperature dependency of the peeling force, and an influence of the surface roughness of the adherend.

Conventionally, as a countermeasure against these problems, it has been often the case that a change is made to the monomer composition of the aqueous dispersion-type removable pressure-sensitive adhesive. However, changing the monomer composition also increases the number of types of pressure-sensitive adhesives indefinitely, which makes the product group complicated and disadvantageous in terms of cost.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to improve the conventional problems, and has a small increase in adhesive force to an adherend such as a metal plate with the passage of time, and can be easily peeled off without adhesive residue. It is an object of the present invention to provide a removable aqueous dispersion-type pressure-sensitive adhesive and a pressure-sensitive adhesive sheet without increasing the types of pressure-sensitive adhesives.

[0010]

Means for Solving the Problems The inventors of the present invention have found that the cause of adhesive residue of a surface protective pressure-sensitive adhesive sheet having a removable aqueous dispersion-type pressure-sensitive adhesive layer is attributable to the destruction of boundaries between polymer particles, ie, grain boundaries. We paid attention to that. In order to prevent the destruction of the grain boundaries, a method of creating a more uniform pressure-sensitive adhesive layer by strengthening the interaction between the particles or improving the fusion between the particles and eliminating the grain boundaries is considered. Can be In order to freely control the peeling force, for example, a means of mixing at least two or more of a soft aqueous dispersion polymer containing a large amount of low molecular weight polymer and a hard aqueous dispersion polymer containing a large amount of high molecular weight polymer or gel at an arbitrary ratio. Can be considered.

From such a viewpoint, as a result of diligent studies to achieve the above object, a removable adhesive based on an aqueous dispersion of an acrylic copolymer having excellent properties such as weather resistance and environmental hygiene. By mixing an aqueous dispersion consisting of a linear polymer of relatively low molecular weight, which has no gel in the polymer particles, the fusion property between the particles is improved, and the elasticity can be freely adjusted by selecting the mixing ratio. It was found that the rate could be adjusted to control peeling. Further, this aqueous dispersion was more effective when the particle diameter was smaller than that of other aqueous dispersions whose fusion property was desired to be improved.

Based on these findings, the present invention provides a product group having a wide range of peeling force by using only aqueous dispersions of several kinds of acrylic polymers and freely adjusting the elastic modulus only by the mixing ratio thereof. I do.

That is, the present invention provides at least (meth)
A weight-average molecular weight of 5 × 10 ⁴ obtained by subjecting an acrylic ester and a monomer mixture comprising a functional group-containing vinyl monomer copolymerizable therewith to an aqueous emulsion polymerization.
Aqueous dispersion in the range of less than to 5 × 10 ⁵ (A), also water-based dispersion having a weight average molecular weight of 5 × 10 ⁵ or more (B), in terms of solid content (A) is 10 to 90 wt%,
(B) is a pressure-sensitive adhesive obtained by mixing arbitrarily in the range of 10 to 90 wt%, and finally has a storage elastic modulus of 20 to 100 N /
cm ² , 20 to 100 N / cm ² at 23 ° C., 1 to 100 N at 100 ° C.
Provided is a removable aqueous dispersion-type pressure-sensitive adhesive characterized by being adjustable in the range of 30 N / cm ² (claim 1).

Further, the present invention provides a gel obtained by subjecting a monomer mixture comprising at least a (meth) acrylic acid ester and a functional group-containing vinyl monomer copolymerizable therewith to an aqueous emulsion polymerization. 95 minutes
wt% or less, and the weight average molecular weight of the sol is 5 × 10 ⁵
The above aqueous dispersion (C) and the above (A) were converted into (A)
Is 10 to 90 wt% in terms of solid content, and (C) is 10 to 90 wt%
%, And finally has a storage elastic modulus of 20 to 100 N / cm ² at 0 ° C. and 20 to 100 N / cm ² at 23 ° C.
100 N / cm ^2, related to removable pressure-aqueous dispersion type pressure-sensitive adhesive, wherein the adjustable range of 1~30N / cm ² at 100 ° C. (Claim 2). (Here, the sol molecular weight is the molecular weight of the polymer eluted in ethyl acetate after immersing the polymer in ethyl acetate for a certain period of time.)

In the aqueous dispersions (A) and (B), the average particle diameter is in the range of 0.01 to 1 μm, and the aqueous dispersion (A) is equal to or less than the aqueous dispersion (B). The present invention relates to the removable aqueous dispersion pressure-sensitive adhesive according to claim 1, which has an average particle diameter (claim 3).

The aqueous dispersions (A) and (C) each have an average particle diameter in the range of 0.01 to 1 μm, and the aqueous dispersion (A) has an average particle size equal to or less than that of the aqueous dispersion (C). The present invention relates to the removable aqueous dispersion pressure-sensitive adhesive according to claim 2, which has an average particle diameter (claim 4).

Further, the functional group-containing vinyl monomer contains a carboxyl group as a functional group (claim 5), and the functional group-containing vinyl monomer containing a carboxyl group is selected from acrylic acid and methacrylic acid. (Claim 6).

Further, there is provided a removable pressure-sensitive adhesive sheet characterized in that the removable aqueous dispersion-type pressure-sensitive adhesive according to any one of claims 1 to 6 is provided on one or both sides of a substrate (claim 7).

[0019]

Aqueous dispersion in Detailed Description of the Invention The present invention (A), (B) and (C), a) the general formula ^{_{(1) CH 2 = CR 1}} COOR 2 ... (1) ( In the formula, R ¹ Is hydrogen or a methyl group, and R ² is 2-1 carbon atom.
4 alkyl group. )) As the main monomer, and b) a functional group-containing vinyl monomer copolymerizable therewith as an essential component, and if necessary, c) the above a and b A monomer mixture obtained by adding a monomer copolymerizable with the component is used, and these are obtained by subjecting them to aqueous dispersion polymerization, particularly emulsion polymerization, by a known method.

Here, the aqueous dispersion (A) in the present invention
Has a weight average molecular weight in the range of 5 × 10 ^{4 to} less than 5 × 10 ⁵ , (B) has a weight average molecular weight of 5 × 10 ⁵ or more, preferably 5 × 10 ^{5 to} 5 × 10 ⁶ , and (C) ) Has a gel, the gel content is 95% by weight or less of the whole, and the weight average molecular weight of the sol content is 5 × 10 ⁵ or more, preferably 5 × 10 ^{5 to} 5
× 10 ⁶ . (Here, the sol molecular weight is the molecular weight of the polymer eluted in ethyl acetate after immersing the polymer in ethyl acetate for a certain period of time.)

The (meth) acrylate of the component a is
When the alkyl group (R ² in the general formula (1)) is an ethyl group, a propyl group, a butyl group, an isobutyl group, an isoamyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an isooctyl group, an isononyl group, an isodecyl group, or the like. Is an alkyl ester of acrylic acid or methacrylic acid.
One or more of these (meth) acrylates are used depending on the purpose and use.

These (meth) acrylates are
It is preferable to use 60 to 99 parts by weight based on 100 parts by weight of the total monomer mixture. If the amount is less than 60 parts by weight, the adhesive properties may be impaired.

The functional group-containing vinyl monomer of the component b is
Stabilization of the polymer particles in the aqueous dispersion obtained by emulsion polymerization, improving the adhesion of the pressure-sensitive adhesive layer to the substrate,
Further, it is a monomer for improving the initial adhesion to the adherend, and is a monomer copolymerizable with the (meth) acrylic acid ester of the component a. Those having a carboxyl group, a sulfonic acid group, a phosphoric acid group or the like as a functional group can be used, and those having a carboxyl group are particularly preferably used.

Examples of the vinyl monomer having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid,
Maleic acid, crotonic acid, and the like can be used, and acrylic acid and methacrylic acid are preferably used particularly in view of high copolymerization reactivity, dispersion stability of polymer particles, and mechanical stability. One or more of these may be used depending on the purpose and application.

Examples of the vinyl monomer containing a sulfonic acid group include 2-acrylamido-2-methylpropanesulfonic acid and 4-styrenesulfonic acid. For example, 2-hydroxyethyl acryloyl phosphate,
Examples include compounds such as 2-hydroxypropylacryloyl phosphate, and one or more compounds are used depending on the purpose and use.

The monomer comprising the functional group-containing vinyl monomer is used in an amount of 1 part by weight based on 100 parts by weight of the total monomer mixture.
Preferably, it is used in an amount of up to 40 parts by weight. If the amount is less than 1 part by weight, the effect is difficult to obtain, and if it exceeds 40 parts by weight, the adhesive properties may be impaired.

In the present invention, a monomer (component (c)) copolymerizable with the above components (a) and (b) can be added according to the required characteristics. These are cyclohexyl (meth) acrylate, benzyl (meth) acrylate, vinyl acetate, styrene, glycidyl (meth) acrylate,
2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methyl (meth) acrylate, N- (meth) acryloylmorpholine, N-
(Meth) acryloylpyrrolidone, N, N-dimethyl (meth) acrylamide, N-vinyl-2-pyrrolidone and the like are included. One or more of these can be used as needed.

The amount of the component (c) can be appropriately selected depending on the type of each monomer. However, in order to develop good pressure-sensitive adhesiveness, the glass transition temperature of the resulting polymer is usually -20 ° C. or lower. It is desirable to determine the amount to be used.

Further, by using a polyfunctional acrylic monomer in addition to the above-mentioned component c, it is possible to carry out cross-linking in advance in the polymerization stage to obtain an aqueous dispersion (C) having a gel inside the particles. Examples of the polyfunctional acrylic monomer include methylenebisacrylamide, 1,6-hexanediol (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, and pentaerythritol di (meth)
Acrylates, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythrol hexa (meth) acrylate and the like can be mentioned. These polyfunctional acrylic monomers can be emulsified and dispersed in water together with a (meth) acrylic acid ester, a functional group-containing vinyl monomer and other monomers, an emulsifier, and the like, and subjected to emulsion polymerization. The amount of these used is usually preferably 2 parts by weight or less based on 100 parts by weight of the solid content of the acrylic polymer.

In the present invention, as a method for preparing an aqueous dispersion (C) having a gel inside the particles, a persulfate such as ammonium persulfate or potassium persulfate is used as a polymerization initiator described later. When used, a gel can be generated by causing a cross-linking reaction between polymer chains during emulsion polymerization.

In the present invention, the gel content of the aqueous dispersion (C), that is, the ratio of the gel to the solid content of the acrylic polymer needs to be 95% by weight or less. It is not preferable because it may extremely decrease.

In the present invention, the method of emulsion polymerization is not particularly limited, and a monomer mixture emulsified and dispersed in water is charged all at once.
Alternatively, emulsion polymerization can be performed by an arbitrary method such as a dropping method depending on the purpose and application. In this emulsion polymerization, it is desirable to use a nonionic surfactant and / or an anionic surfactant as an emulsifier. The amount to be used is 0.3 to 30 parts by weight in the case of a nonionic surfactant or an anionic surfactant alone, based on 100 parts by weight of the total monomer amount mixture, depending on the required particle size. When used together, the former is 0.2 to 20 parts by weight, and the latter is 0.1
To 10 parts by weight.

Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acid esters, and polyoxyethylene fatty acid esters. Used. On the other hand, as anionic surfactants, alkyl sulfates, alkyl benzene sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phosphates and the like are used.

In the present invention, the average particle diameter of each aqueous dispersion is desirably adjusted to 0.01 to 1 μm, and the average particle diameter of the aqueous dispersion (A) is adjusted to the aqueous dispersions (B) and (C). It is desirable that the average particle diameter is not more than the average particle diameter. Here, when each average particle diameter is smaller than 0.01 μm, the viscosity of the aqueous dispersion increases, and it is difficult to obtain a smooth pressure-sensitive adhesive layer at the time of coating. May be reduced, and adhesive residue may be caused at the time of re-peeling.

The polymerization initiator used in the present invention is not particularly limited.
2'-azobis (2-amidinopropionamidine) dihydrochloride, 2,2'-azobis (4-methoxy-2,4- {methylvaleronitrile), 2,2'-azobis [2- (2-imidazoline- 2-yl) propane] dihydrochloride, 2,2′-azobis [2-
(2-Imidazolin-2-yl) propane] azo such as disulfate dihydrate, dimethyl 2,2′-azobis (2-methylpropionate), and 4,4′-azobis (4-cyanovaleric acid) System initiators, persulfates such as ammonium persulfate and potassium persulfate, benzoyl peroxide,
Organic peroxides such as t-butyl hydroperoxide, and redox initiators such as persulfate and sodium bisulfite, etc., are used, and one or more of them are used depending on the purpose and use.

In the present invention, a chain transfer agent may be used to adjust the molecular weight of the acrylic polymer. The chain transfer agent is not particularly limited, and examples thereof include 1-dodecanethiol, mercaptoacetic acid, 2-mercaptoethanol, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. One or two or more are used depending on the purpose and application.

The acrylic aqueous dispersions (A), (B) and (C) in the present invention are preferably those in which the solid content of the acrylic polymer is adjusted in the range of 30 to 65% by weight. By adjusting to this range, appropriate viscosity is obtained and handling becomes easy.

The removable aqueous dispersion pressure-sensitive adhesive used in the present invention comprises an aqueous dispersion (A) containing an acrylic polymer having a weight average molecular weight in the range of 5 × 10 ^{4 to} less than 5 × 10 ^5, and a weight average molecular weight. Is 5 × 10 ⁵ or more, preferably 5 × 10 ⁵ to
Aqueous dispersion (B) containing an acrylic polymer of 5 × 10 ⁶ , in terms of solid content, (A) is 10 to 90 wt%, preferably 20 to 80 wt%, and (B) is 10 to 90 wt%, preferably Is characterized by being mixed in the range of 20 to 80% by weight.

Alternatively, as another form, the aqueous dispersion (A)
Has a gel, and the gel content is 95% by weight or less of the whole,
The sol component can be mixed with an aqueous dispersion (C) containing an acrylic polymer having a weight average molecular weight of 5 × 10 ⁵ or more, preferably 5 × 10 ^{5 to} 5 × 10 ^6. It is characterized in that it is arbitrarily mixed within a range of from 90 to 90 wt%, preferably from 20 to 80 wt%, and (C) within a range of from 10 to 90 wt%, preferably from 20 to 80 wt%. (Here, the molecular weight of the sol is determined by immersing the polymer in ethyl acetate for a certain period of time,
The molecular weight of the polymer eluted in ethyl acetate. )

In general, high molecular weight polymers have relatively high cohesion, which is advantageous for applications requiring cohesion of the polymer. However, contrary to this, the diffusion of the polymer decreases as the molecular weight increases. The decrease in the diffusion tends to decrease the fusion property between the polymer particles based on the aqueous dispersion and the film-forming property accompanying the fusion. As a result, a grain boundary remains in the pressure-sensitive adhesive layer, causing breakage between particles during processing. This problem is caused by an aqueous dispersion composed of polymer particles having a relatively high molecular weight [aqueous dispersion (B) in the present specification].
Is mixed with an aqueous dispersion composed of polymer particles having a relatively low molecular weight [aqueous dispersion (A) in the present specification] to maintain the high cohesive force of the high molecular weight polymer while maintaining the high molecular weight polymer. It can be improved by improving the fusion property due to the diffusivity.

A decrease in the fusion property or film-forming property of the polymer particles can be considered in the case where a gel exists in the polymer particles [aqueous dispersion (C) in the present specification]. Improvement can be achieved by mixing an aqueous dispersion composed of low molecular weight polymer particles.

These effects appear when the ratio of (A) is 90% by weight or less in terms of solid content. If it exceeds this, the cohesive strength is reduced, although the fusibility is maintained. The wettability is increased, which may cause adhesive residue and an increase in adhesive strength during processing. On the other hand, when the ratio of (A) is less than 10% by weight in terms of solid content, it is difficult to substantially obtain the effect of improving the fusibility, which is not preferable.

The weight average molecular weight of (A) is 5 × 10 ⁴
The preferably not observed improvement in fusion due to high diffusion of the low molecular weight material in (A) for its own insufficient cohesive strength lead to adhesive residue and adhesive force increase at the time of processing, also 5 × 10 ⁵ or more but less than Absent.

Further, the weight average molecular weight of (B) is 5 × 10
^If it is less than ⁵ , the high cohesion of the high molecular weight body is not maintained, which is not preferable.

Similarly, when the weight average molecular weight of the sol component (C) is less than 5 × 10 ⁵ , the high cohesion of the high molecular weight product is not maintained, which is not preferable.

In addition, it is more effective that the average particle size of the low molecular weight polymer particles for improving the fusion property is equal to or smaller than the average particle size of the high molecular weight polymer particles and the gel-containing polymer particles. In the present invention, the aqueous dispersions (A), (B) and (C) each have an average particle diameter in the range of 0.01 to 1 μm, and the average particle diameter of (A) is (B) and (C). )) Is desirable. This takes into account that the smaller particles have a larger specific surface area, so that the contact area of the small particles with the surface of the large particles also increases, so that fusion between the particles occurs effectively.

For the purpose of improving the cohesiveness and the bonding strength between polymer particles, it is important to post-add a particle external crosslinking agent to the thus-prepared removable aqueous dispersion-type pressure-sensitive adhesive. . As such a particle external cross-linking agent, those conventionally used can be used. For example, a water-soluble melamine resin compound such as “Watersol S-695” (manufactured by Dainippon Ink Co., Ltd.), “Aqua Aqueous isocyanate compounds such as "Nate" (manufactured by Nippon Polyurethane Industry Co., Ltd.), "Takenate" and "Takelac" (manufactured by Takeda Pharmaceutical Co., Ltd.), and water-soluble compounds such as "Epomin" (manufactured by Nippon Shokubai Kogyo Co., Ltd.) Water-dispersible aziridine compounds such as ethyleneimine (aziridine) compounds, "Chemite DZ-22" (manufactured by Nippon Shokubai Co., Ltd.), and ethyleneimines (aziridines) such as "Polyment" (manufactured by Nippon Shokubai Kogyo Co., Ltd.) ) -Based compounds, "Nissan TEPIC" (manufactured by Nissan Chemical Co., Ltd.),
Aqueous epoxy compounds such as "Epolite" (manufactured by Kyoeisha Chemical Co., Ltd.), and aqueous oxazoline compounds such as "Epocross WS-500" (manufactured by Nippon Shokubai Kogyo Co., Ltd.).

These cross-linking agents may have a total solid content of 10% of the aqueous dispersions (A) and (B) or the acrylic polymer of (A) and (C) depending on the purpose, application and monomer composition of the polymer.
0.01 to 20 parts by weight relative to 0 parts by weight is desirable.
If the amount is less than 0.01 part by weight, it is difficult to obtain the effect.
When the amount is more than the weight part, a substantially unreacted crosslinking agent remains, which may undesirably contaminate the adherend at the time of peeling.

Furthermore, in the present invention, two types of aqueous dispersions (A) and (B) having different molecular weights, or
(A) and (C) are arbitrarily mixed within a predetermined range,
Finally, the storage modulus is 20 to 100 N / cm ² at 0 ° C., preferably 20 to 70 N / cm ² , and 20 to 100 N at 23 ° C.
/ Cm ² , preferably 20 to 70 N / cm ² , 1 to 100 ° C.
It can be adjusted in a range of 30 N / cm ² , preferably 5 to 25 N / cm ² . Here, "finally" means that two kinds of aqueous dispersions having different molecular weights are mixed together, and the above-mentioned external crosslinking agent for particles and, if necessary, additives described later are blended to form an adhesive mixture. Refers to the state of application and drying. The method for preparing the pressure-sensitive adhesive film for measuring the storage elastic modulus was described in the working examples described later.

By adjusting the storage elastic modulus within a predetermined range at each temperature, the obtained pressure-sensitive adhesive composition shows good removability, and the elastic modulus can be freely adjusted from a high elastic modulus to a low elastic modulus. Thus, it is possible to obtain a re-peelable pressure-sensitive adhesive sheet of low peel force type to high peel force type.

At each temperature, if the storage elastic modulus is lower than the lower limit, the peeling force becomes too high, which is not suitable for re-peeling, and if the storage elastic modulus is higher than the upper limit, an appropriate peeling force cannot be obtained. Is also not preferred.

In the present invention, in addition to the aqueous dispersions (A), (B) and (C), the particle external cross-linking agent or the particle internal cross-linking agent, if necessary, an inorganic powder may be used. A commonly used additive such as a filler such as a metal powder, a pigment, and a colorant may be blended. The amount of these additives used may be a commonly used amount.

The peelable pressure-sensitive adhesive sheets having the water-dispersible pressure-sensitive adhesive prepared as described above are coated on one or both sides of the substrate with the pressure-sensitive adhesive and dried to obtain a film having a thickness of usually 1%.
An adhesive layer having a thickness of about 100 μm is formed to form a sheet or a tape. In order to apply the pressure-sensitive adhesive composition on the base material, a coating method such as roll coating, screen coating, and gravure coating may be used. Alternatively, the pressure-sensitive adhesive composition may be applied to a release paper having a surface subjected to a release treatment, dried by heating, and then transferred to a substrate to form a pressure-sensitive adhesive layer. For the base material, depending on the purpose of use, various known films such as a polyethylene film, a polyester film, and the like, usually a plastic film having a thickness of 10 to 300 μm, a nonwoven fabric, a woven fabric, a porous member such as a mesh, a metal foil and the like A material of a material is used.

[0054]

According to the present invention, an aqueous dispersion composed of low-molecular-weight polymer particles having a high polymer diffusibility and an aqueous dispersion composed of high-molecular-weight polymer particles or gel-containing polymer particles which are expected to have high cohesion are mixed. This makes it possible to obtain a removable water-dispersed pressure-sensitive adhesive with improved fusibility while making use of the characteristics of a high molecular weight polymer and a gel. Furthermore, the mixing ratio of these aqueous dispersions allows the elastic modulus to be freely adjusted from a high elasticity adhesive to a low elasticity adhesive with a small number of aqueous dispersion polymers, and a high peeling strength of a low peeling force type re-peelable pressure-sensitive adhesive sheet. A re-peelable pressure-sensitive adhesive sheet of a peeling force type can be obtained. The re-peelable pressure-sensitive adhesive sheet using these pressure-sensitive adhesives has no adhesive residue after peeling, and has good re-peelability.

[0055]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Here, “parts” means “parts by weight”.

Reference Examples 1 to 3
Various types of aqueous dispersions were prepared. In addition, each weight average molecular weight, gel fraction, and average particle diameter were measured by the following methods.

[Measurement of Molecular Weight] The aqueous dispersion was coated on a release paper and dried at 80 ° C. for 5 minutes.
% Tetrahydrofuran solution was prepared. The adhesive composition having a gel is immersed in ethyl acetate for a certain period of time, and after filtration of insoluble matter, the filtrate is dried. Tetrahydrofuran is added to the residue (eluate of ethyl acetate) to prepare a 0.1 wt% tetrahydrofuran solution. did. This was filtered through a polytetrafluoroethylene membrane having a pore size of 0.45 μm, and the molecular weight was measured by GPC (gel permeation chromatography) using the filtrate. Measurement conditions: eluent THF, liquid transfer volume 1.0 ml
/ min, column temperature 38 ° C, converted to standard polystyrene

[Measurement Method for Gel Content] The aqueous dispersion was applied on release paper and dried at 80 ° C. for 5 minutes to obtain a pressure-sensitive adhesive composition. After the pressure-sensitive adhesive composition was weighed and immersed in ethyl acetate for a certain period of time, the insoluble matter was filtered, the ethyl acetate was dried, and the ethyl acetate insoluble matter was weighed. The gel content was calculated by the following equation. Gel content (wt%) = (weight of ethyl acetate insoluble content / weight before immersion in ethyl acetate) × 100

[Average Particle Size] A diluent of the aqueous dispersion was prepared, and the average particle size was measured using a laser diffraction / scattering type particle size distribution analyzer (LA-910) manufactured by Horiba, Ltd.

Reference Example 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer, 59 parts of butyl acrylate, 40 parts of butyl methacrylate, and acrylic acid
1 part of a monomer mixture, 2,2 ′ as a polymerization initiator
-Azobis (2-amidinopropionamidine) dihydrochloride 0.02 part, 1-dodecanethiol 0.15 part as a chain transfer agent, 1.5 parts polyoxyethylene nonyl phenyl ether as an emulsifier, and polyoxyethylene nonyl phenyl ether After 1.5 parts of ammonium sulfate and 100 parts of water were emulsified and dispersed, emulsion polymerization was carried out to obtain an aqueous dispersion (A). The polymer had a weight average molecular weight of 3.5 × 10 ⁵ and an average particle size of 0.1.
μm.

Reference Example 2 A reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer was charged with 59 parts of butyl acrylate, 40 parts of butyl methacrylate and acrylic acid.
1 part of a monomer mixture, 2,2 ′ as a polymerization initiator
-Azobis (2-amidinopropionamidine) dihydrochloride 0.02 part, 1-dodecanethiol 0.05 part as a chain transfer agent, 0.3 parts polyoxyethylene nonyl phenyl ether as an emulsifier, and polyoxyethylene nonyl phenyl ether Ammonium sulfate 0.
After emulsifying and dispersing 3 parts and 100 parts of water, emulsion polymerization was carried out to obtain an aqueous dispersion (B). The obtained polymer had a weight average molecular weight of 30 × 10 ⁵ and an average particle size of 0.5 μm.

Reference Example 3 In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer, 59 parts of butyl acrylate, 40 parts of butyl methacrylate, and acrylic acid
After emulsifying and dispersing 1 part of a monomer mixture, 0.3 parts of ammonium persulfate as a polymerization initiator, 1 part of polyoxyethylene nonyl phenyl ether as an emulsifier, and 1 part of ammonium polyoxyethylene nonyl phenyl ether sulfate, and 100 parts of water. Emulsion polymerization, aqueous dispersion (C)
I got It has a gel content of 75
%, The weight average molecular weight of the sol component was 10 × 10 ⁵ , and the average particle size was 0.3 μm.

[Examples 1 to 6, Comparative Examples 1 to 3] In the following Examples and Comparative Examples, an aqueous dispersion-type pressure-sensitive adhesive composition having the following composition was prepared and was directly coated on a 60 μm-thick polyethylene film. The resultant was coated and dried to obtain a pressure-sensitive adhesive layer having a thickness of 5 μm to obtain a pressure-sensitive adhesive sheet.

Example 1 The aqueous dispersion (A) obtained in Reference Example 1 and the aqueous dispersion (B) obtained in Reference Example 2 were polymer ratio in terms of solid content, (A) :( B) = 20wt%: 80wt%
And an oxazoline group-containing water-soluble crosslinking agent (Nippon Shokubai Co., Ltd.) per 100 parts of the polymer solid content of the mixture.
Was manufactured by mixing 3 parts of “Epocross WS500” manufactured by Epson Corporation and a re-peelable aqueous dispersion-type pressure-sensitive adhesive was prepared.

Example 2 The aqueous dispersion (A) obtained in Reference Example 1 and the aqueous dispersion (B) obtained in Reference Example 2 were polymer ratio in terms of solid content, (A) :( B) = 50wt%: 50wt%
And an oxazoline group-containing water-soluble crosslinking agent (Nippon Shokubai Co., Ltd.) per 100 parts of the polymer solid content of the mixture.
Was manufactured by mixing 3 parts of “Epocross WS500” manufactured by Epson Corporation and a re-peelable aqueous dispersion-type pressure-sensitive adhesive was prepared.

Example 3 The aqueous dispersion (A) obtained in Reference Example 1 and the aqueous dispersion (B) obtained in Reference Example 2 were polymer ratio in terms of solid content, (A) :( B) = 80wt%: 20wt%
And an oxazoline group-containing water-soluble crosslinking agent (Nippon Shokubai Co., Ltd.) per 100 parts of the polymer solid content of the mixture.
Was manufactured by mixing 3 parts of “Epocross WS500” manufactured by Epson Corporation and a re-peelable aqueous dispersion-type pressure-sensitive adhesive was prepared.

Example 4 The aqueous dispersion (A) obtained in Reference Example 1 and the aqueous dispersion (C) obtained in Reference Example 3 were polymer ratio in terms of solid content, (A) :( C) = 20wt%: 80wt%
And an oxazoline group-containing water-soluble crosslinking agent (Nippon Shokubai Co., Ltd.) per 100 parts of the polymer solid content of the mixture.
Was manufactured by mixing 3 parts of “Epocross WS500” manufactured by Epson Corporation and a re-peelable aqueous dispersion-type pressure-sensitive adhesive was prepared.

Example 5 The aqueous dispersion (A) obtained in Reference Example 1 and the aqueous dispersion (C) obtained in Reference Example 3 were polymer ratio in terms of solid content, (A) :( C) = 50wt%: 50wt%
And an oxazoline group-containing water-soluble crosslinking agent (Nippon Shokubai Co., Ltd.) per 100 parts of the polymer solid content of the mixture.
Was manufactured by mixing 3 parts of “Epocross WS500” manufactured by Epson Corporation and a re-peelable aqueous dispersion-type pressure-sensitive adhesive was prepared.

Example 6 The aqueous dispersion (A) obtained in Reference Example 1 and the aqueous dispersion (C) obtained in Reference Example 3 were polymer ratio in terms of solid content, (A) :( C) = 80wt%: 20wt%
And an oxazoline group-containing water-soluble crosslinking agent (Nippon Shokubai Co., Ltd.) per 100 parts of the polymer solid content of the mixture.
Was manufactured by mixing 3 parts of “Epocross WS500” manufactured by Epson Corporation and a re-peelable aqueous dispersion-type pressure-sensitive adhesive was prepared.

Comparative Example 1 100 parts of the aqueous dispersion (A) obtained in Reference Example 1 was added to 100 parts of the polymer solid content of this dispersion.
Per part, 3 parts of an oxazoline group-containing water-soluble crosslinking agent (“Epocross WS500” manufactured by Nippon Shokubai Co., Ltd.) was mixed to prepare a re-peelable aqueous dispersion-type pressure-sensitive adhesive.

Comparative Example 2 100 parts of the aqueous dispersion (B) obtained in Reference Example 2 was mixed with 100 parts of the polymer solid content of this dispersion.
Per part, 3 parts of an oxazoline group-containing water-soluble crosslinking agent (“Epocross WS500” manufactured by Nippon Shokubai Co., Ltd.) was mixed to prepare a re-peelable aqueous dispersion-type pressure-sensitive adhesive.

Comparative Example 3 100 parts of the aqueous dispersion (B) obtained in Reference Example 3 was added to 100 parts of the polymer solid content of this dispersion.
Per part, 3 parts of an oxazoline group-containing water-soluble crosslinking agent (“Epocross WS500” manufactured by Nippon Shokubai Co., Ltd.) was mixed to prepare a re-peelable aqueous dispersion-type pressure-sensitive adhesive.

[Evaluation] The storage elastic modulus of the pressure-sensitive adhesive obtained in each of Examples and Comparative Examples, and the pressure-sensitive adhesive test, the removability test, and the adhesive residue test (processing) of the pressure-sensitive adhesive sheet made of these pressure-sensitive adhesives Test) was measured by the following method, and the results of the storage modulus were summarized in Table 1, and the adhesion test, removability test and adhesive residue test (processing test) of the pressure-sensitive adhesive were summarized in Table 2.

[Adhesion Test] A test piece of 20 mm × 100 mm (width × length = flow direction of coating) was sampled from the obtained pressure-sensitive adhesive sheet, and 2 kg of the test piece was placed on a stainless steel plate (SUS430BA) as an adherend. The pressure roller was reciprocated once and pressed. After leaving at 23 ° C. for 20 minutes, the pulling speed 3
Under the conditions of 00 mm / min, 23 ° C. and 65% RH, the force required for peeling was measured by 180 ° peeling.

[Removability Test] A test piece of 20 mm × 100 mm (width × length = flow direction of coating) was sampled from the obtained pressure-sensitive adhesive sheet, and 2 kg was applied to a stainless steel plate (SUS430BA) as an adherend. Was reciprocated once and pressed. After standing at 23 ° C. for 24 hours, the tensile speed 3
180 ° under the conditions of 00mm / min., 23 ° C, 65% RH
The force required for peeling was measured by peeling.

[Glue Residue Test (Processing Test)] Width 30 m
m, length 100mm, thickness 1.0mm stainless steel plate (S
US430BA) was used as an adherend, and a tape-shaped material sampled from the obtained pressure-sensitive adhesive sheet and having substantially the same size as the adherend was pressure-bonded by reciprocating a 5 kg pressure roller once. 23
The specimen was left for 24 hours in an atmosphere of 65 ° C. and 65% RH.

The test piece was placed on a mold having a recess of 8 mm width and R = 1.0 mm having an inverted triangular cross section so that the adhesive tape was in contact with the recess side.
That is, a 90 ° bending test was performed with a press machine from above the side where the pressure-sensitive adhesive sheet of the adherend was not bonded. Then, when the adhesive tape was peeled off from the test piece, the adhesive residue on the adherend was examined. When there was no glue residue, it was evaluated as ○, when there was partial glue residue, it was evaluated as Δ, and when there was glue residue on the entire surface, it was evaluated as x.

[Measurement of Storage Elastic Modulus] The pressure-sensitive adhesives of Examples and Comparative Examples were applied on a polyethylene sheet and dried.
An adhesive film having a thickness of about 10 μm for measuring storage elastic modulus was prepared. The obtained pressure-sensitive adhesive film was laminated to produce a pressure-sensitive adhesive plate having a thickness of about 1.5 mm, punched out into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates from above and below, and scanning the temperature to determine the viscosity. The storage modulus was measured from the elasticity measurements.

[0079]

[Table 1]

[0080]

[Table 2]

As shown in Table 1, various elastic moduli can be adjusted depending on the type and the mixing ratio of the aqueous dispersion.

Further, as shown in Table 2, only by mixing two kinds of different aqueous dispersions, a wide range from high adhesion type to low adhesion type can be obtained. In the adhesive residue test, adhesive residue was observed in Comparative Example 1 due to insufficient cohesive force, and in Comparative Examples 2 and 3, adhesive residue considered to be due to breakage of grain boundaries. On the other hand, in Examples 1 to 6, it can be seen that the adhesive dispersibility was improved by mixing the aqueous dispersion (A) composed of low molecular weight polymer particles. This can be expected that the addition of the low molecular weight polymer improved the diffusivity and the fusion property. Even with the high adhesion type (Example 3), the adhesive residue was relatively good. Further, it can be seen that these examples have a small increase in the peeling force and no problem with respect to the removability.

Continued on the front page F term (reference) 4J004 AA10 AB01 CA04 CA06 CA08 CB01 CC02 EA05 FA04 4J040 DF011 DF041 DF051 DG001 DJ011 DJ021 GA05 GA07 GA08 GA17 GA22 GA25 GA27 JA03 JA09 JB09 LA01 LA03 LA06 MA02 NA05 NA19 PA42

Claims (7)

[Claims] 1. A water-based emulsion polymerization of a monomer mixture comprising at least a (meth) acrylate and a functional group-containing vinyl monomer copolymerizable therewith, and having a weight average molecular weight of 5 × 10 ⁴ to aqueous dispersion in the 5 × 10 under ⁵ range (a), also a weight-average molecular weight of 5
A pressure-sensitive adhesive obtained by arbitrarily mixing the aqueous dispersion (B) having a content of × 10 ⁵ or more in the range of 10 to 90% by weight and (B) in the range of 10 to 90% by weight in terms of solid content. Has a storage modulus of 20-100 N / cm ² at 0 ° C. and 20-100 N at 23 ° C.
Releasable aqueous dispersion type pressure-sensitive adhesive, wherein the adjustable range of 1~30N / cm ² in N / cm ^2, 100 ℃. 2. A gel obtained by aqueous emulsion polymerization of a monomer mixture comprising at least a (meth) acrylic acid ester and a functional group-containing vinyl monomer copolymerizable therewith. The aqueous dispersion (C) having a weight average molecular weight of 5 × 10 ⁵ or more of the sol component and the above-mentioned (A), wherein (A) is 10 to 90 wt% in terms of solid content, (C ) Is an adhesive which is arbitrarily mixed in the range of 10 to 90% by weight, and finally has a storage elastic modulus of 0 ° C.
20 to 100 N / cm ² at 23 ° C and 20 to 100 N / cm 2
^{2. A} removable aqueous dispersion type pressure-sensitive adhesive characterized in that it can be adjusted within a range of 1 to 30 N / cm ² at 100 ° C. (Here, the sol molecular weight is the molecular weight of the polymer eluted in ethyl acetate after immersing the polymer in ethyl acetate for a certain period of time.) 3. The aqueous dispersions (A) and (B) each have an average particle diameter in the range of 0.01 to 1 μm, and the aqueous dispersion (A) is equal to or less than the aqueous dispersion (B). 2. The removable aqueous dispersion pressure-sensitive adhesive according to claim 1, having an average particle diameter. 4. The aqueous dispersions (A) and (C) each have an average particle diameter in the range of 0.01 to 1 μm, and the aqueous dispersion (A) is equal to or less than the aqueous dispersion (C). The removable aqueous dispersion pressure-sensitive adhesive according to claim 2, which has an average particle diameter. 5. The functional group-containing vinyl monomer contains a carboxyl group as a functional group.
5. The removable aqueous dispersion pressure-sensitive adhesive according to any one of items 4 to 4. 6. The functional group-containing vinyl monomer containing a carboxyl group is selected from acrylic acid and methacrylic acid.
The removable aqueous dispersion-type pressure-sensitive adhesive according to claim 5. 7. A removable pressure-sensitive adhesive sheet comprising the substrate and the water-dispersible pressure-sensitive adhesive according to claim 1 provided on one or both sides of a substrate.