JP3448464B2 - Method for dispersing crosslinked rubber particles, dispersion, and curable adhesive composition - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for dispersing crosslinked rubber particles suitable for use in a photocurable pressure-sensitive adhesive, a dispersion obtained by the dispersion method, and a curable pressure-sensitive adhesive composition. More specifically, the present invention relates to a method for dispersing crosslinked rubber particles, a dispersion, and a curable pressure-sensitive adhesive composition, which allow the crosslinked rubber particles to be uniformly dispersed in an acrylic / epoxy pressure-sensitive adhesive.

[0002]

2. Description of the Related Art Epoxy adhesives are widely used mainly for structural adhesives because they are inexpensive and can obtain a strong shear adhesive force. However, since the cured product of the epoxy adhesive is hard and brittle, the peel strength with respect to the adherend was not sufficient. Therefore, in order to increase the peel strength of the epoxy adhesive, a method of blending a flexible polymer component with the epoxy adhesive has been widely used from the past.

For example, when a flexible polymer component such as acrylonitrile-butadiene rubber (NBR), acrylic rubber, urethane rubber, acrylic resin or urethane resin is mixed with an epoxy compound, the above polymer is added to the sea of the epoxy compound. By forming a so-called "sea-island structure" in which islands are present, it has been attempted to perform stress relaxation in the cured product of the epoxy adhesive and thereby increase the peel strength.

However, as the polymer component,
When a liquid polymer was mixed, the size of islands formed was different depending on the curing conditions of the epoxy compound, and the adhesive performance tended to be unstable.

Therefore, in order to stabilize the shape of "islands", a method is known in which a polymer component is previously made into fine particles and further intramolecularly crosslinked. That is, it is said that by dispersing these crosslinked fine particles in an epoxy adhesive, the peel strength can be improved and the adhesive physical properties can be stabilized.

[0006] Generally, the smaller the particle size of the "island",
It is said to have a high effect of stabilizing the adhesive properties. In particular, the crosslinked rubber particles having a functional group that reacts with the epoxy group on the surface are finally incorporated into the network structure of the multifunctional epoxy compound, which is the main component of the epoxy adhesive, due to the three-dimensional crosslinkage, so that the adhesive strength and heat resistance are improved. It is said that the property is enhanced (for example, “Journal of the Japan Adhesion Society, Vol.31 No.11 (19
95) 471-478 ").

On the other hand, an acrylic pressure-sensitive adhesive is generally composed mainly of an alkyl acrylate polymer having a low glass transition point. Acrylic pressure-sensitive adhesives have the advantages of higher heat resistance and weather resistance and easier control of adhesive performance than rubber-based pressure-sensitive adhesives. Therefore, although the acrylic pressure-sensitive adhesive is often used for double-sided tapes and the like, it is possible to easily bond the members, but it is not possible to obtain the heat resistance and the adhesive strength as high as those of the adhesive.

[0008] Therefore, a latent curing component is blended in the pressure-sensitive adhesive so that pressure-sensitive adhesiveness can be easily adhered at the time of bonding, and reaction curing is performed after bonding to obtain heat resistance and adhesive strength comparable to those of the adhesive. So-called tacky adhesives have been proposed.

In particular, as the acrylic / epoxy adhesives, various curing methods such as a heat curing type, a light curing type and a moisture curing type have been proposed.
However, even in the acrylic / epoxy adhesives, it is difficult to obtain sufficient peel strength because the epoxy component after curing is hard. Therefore, a method has been proposed in which cross-linking rubber particles are mixed with an acrylic / epoxy adhesive to increase the peeling force, as in the case of the epoxy adhesive (JP-A-7-138550).

However, the crosslinked rubber particles generally have low dispersibility in an acrylic polymer and it is difficult to uniformly disperse them in the acrylic / epoxy adhesive.

[0011]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method for easily and uniformly dispersing crosslinked rubber particles capable of softening a cured product to enhance peel strength in an acrylic / epoxy adhesive / adhesive component. An object of the present invention is to provide a dispersion obtained by the dispersion method, and a curable adhesive composition using the dispersion.

[0012]

The method for dispersing crosslinked rubber particles according to the invention as defined in claim 1 is a method for dispersing crosslinked rubber particles having a functional group capable of reacting with an epoxy group and a monofunctional epoxy compound in an organic solvent. It is characterized in that after mixing and reacting a functional group which reacts with an epoxy group, it is mixed with an acrylic polymer.

The invention described in claim 2 is the same as claim 1
It is a crosslinked rubber particle dispersion obtained by the method for dispersing crosslinked rubber particles according to 1. A third aspect of the present invention is a curable pressure-sensitive adhesive composition comprising the crosslinked rubber particle dispersion according to the second aspect, a polyfunctional epoxy compound and a photocationic polymerization initiator.

The details of the present invention will be described below. Claim 1
The method for dispersing crosslinked rubber particles according to the invention described in 1), by grafting an epoxy compound component having compatibility with an acrylic polymer to the crosslinked rubber particles, thereby increasing the compatibility between the crosslinked rubber particles and the acrylic polymer, and crosslinking. It is characterized in that the dispersibility of rubber particles is enhanced.

Therefore, as the crosslinked rubber particles, those having a functional group (reactive functional group) which reacts with an epoxy group on the surface are used. The reactive functional group is not particularly limited as long as it can react with an epoxy group, and examples thereof include COOH group, OH group, vinyl ether group, glycidyl group, episulfide group, ethyleneimine group, and mercapto group. Can be mentioned.

The material of the crosslinked rubber particles is not particularly limited as long as it can perform the stress relaxation action in the cured adhesive, but is not limited to NBR, acrylic rubber,
Silicone rubber, urethane rubber or the like can be used. Specifically, for example, product name: manufactured by Nippon Synthetic Rubber Co., Ltd.
XER91 (COOH group-containing crosslinked NBR), same name: XER71 (epoxy group-containing crosslinked NBR), same name: DHS2S (COOH group-containing crosslinked acrylic rubber)
Can be used.

The particle size of the crosslinked rubber particles is 100 in terms of primary particle size.
It is preferably not more than 10 μm, more preferably 10 μm
m or less. When the particle diameter of the crosslinked rubber particles is more than 100 μm, when the obtained crosslinked rubber particles are dispersed in an acrylic / epoxy adhesive, the peel strength of the cured adhesive may not be sufficiently increased.

The crosslinked rubber particles having a reactive functional group are first mixed with a monofunctional epoxy compound in an organic solvent. As the monofunctional epoxy compound, alkyl glycidyl ether, phenol glycidyl ether, cresyl glycidyl ether and modified products thereof can be used, but the monofunctional epoxy compound is not particularly limited as long as it is compatible with an acrylic polymer. Not something.

The organic solvent is not particularly limited as long as it is a medium capable of reacting the reactive functional group with the monofunctional epoxy compound when the crosslinked rubber particles and the monofunctional epoxy compound are mixed. Is 40 to 200 ° C
It is preferable to use a moderate organic solvent. If the boiling point is lower than the above range, the volatility is high and handling at room temperature becomes difficult. If the boiling point exceeds the above range, the coating film may be insufficiently dried and the adhesiveness may be lowered. Examples of such an organic solvent include acetone and methyl ethyl ketone (ME
K), methyl isobutyl ketone (MIBK), ethyl formate, butyl formate, methyl acetate, ethyl acetate, butyl acetate, toluene, p-xylene, n-hexane, cyclohexane, chloroform, carbon tetrachloride, etc. Can be used. The general organic solvent is described in detail in "Solvent Handbook" published by Kodansha.

The specific steps for mixing the crosslinked rubber particles with a monofunctional epoxy compound in an organic solvent and reacting the reactive functional groups are not particularly limited, but preferably, first, the organic solvent is used. A method is used in which the crosslinked rubber particles are uniformly dispersed therein, and then a monofunctional epoxy compound is appropriately added. Regarding the amount of the organic solvent, it is desirable that the amount of the crosslinked rubber particles is an appropriate amount so that the crosslinked rubber particles can be dispersed to a desired particle size. The temperature at which the crosslinked rubber particles and the monofunctional epoxy compound are reacted can be freely adjusted within the range of room temperature to the boiling point of the solvent.

In order to enhance the reaction between the crosslinked rubber particles having the reactive functional group and the monofunctional epoxy compound,
A reaction catalyst such as triphenylphosphine may be added.

Regarding the reaction between the crosslinked rubber particles and the monofunctional epoxy compound, the reaction rate of the reactive functional groups in the crosslinked rubber particles is preferably 10 to 90 mol%, preferably 30 to 70 mol%. It is desirable to react so that If the above reaction rate is less than 10 mol%, the dispersed particle size of the crosslinked rubber particles becomes large, and the peel strength of the cured adhesive of the curable pressure-sensitive adhesive containing the crosslinked rubber particles may not be sufficiently increased. If it exceeds 90 mol%, the crosslinked rubber particles are hard to be incorporated into the three-dimensional network structure of the epoxy when the adhesive is cured, and the heat resistance may decrease.

When the crosslinked rubber particles and the monofunctional epoxy compound are mixed in an organic solvent, the mixing ratio of the crosslinked rubber particles and the monofunctional epoxy compound cannot be uniquely determined because they differ depending on the respective types. As described above, the reaction rate of the reactive functional groups in the crosslinked rubber particles is selected so as to be 10 to 90 mol%, more preferably 30 to 70 mol% of the whole.

According to the first aspect of the invention, the crosslinked rubber particles and the monofunctional epoxy compound are mixed in an organic solvent to react a reactive functional group, and then mixed with an acrylic polymer.

As the acrylic polymer, any suitable acrylic polymer used in acrylic / epoxy adhesives can be used and is not particularly limited. However, an alkyl (meth) acrylate polymer or copolymer conventionally used for constituting an acrylic / epoxy pressure-sensitive adhesive is more preferable, and an alkyl having 1 to 12 carbon atoms in the alkyl group is more preferable. An alkyl (meth) acrylate copolymer of (meth) acrylate and a vinyl monomer copolymerizable therewith is used.

After the crosslinked rubber particles and the monofunctional epoxy compound are mixed and reacted in an organic solvent, the ratio of the acrylic polymer at the time of mixing the acrylic polymer is not particularly limited, and the ratio before and after curing is not limited. It may be appropriately determined according to the desired adhesive and physical properties.

In the invention described in claim 1, as described above, the crosslinked rubber particles and the monofunctional epoxy compound are preliminarily reacted with each other, and the epoxy compound component having high compatibility with the acrylic polymer is grafted to the crosslinked rubber particles. It will be. Therefore, the compatibility between the crosslinked rubber particles and the acrylic polymer is enhanced, and the crosslinked rubber particles having a small particle size are uniformly dispersed in the acrylic polymer to obtain the dispersion according to the invention of claim 2. .

A curable pressure-sensitive adhesive composition according to the invention of claim 3 is characterized by using the dispersion according to the invention of claim 2, wherein the dispersion and the polyfunctional epoxy compound are used. And a photocationic polymerization initiator.

The above polyfunctional epoxy compound is acrylic /
It is used for constituting the curing component of the epoxy-based curable pressure-sensitive adhesive, and such a polyfunctional epoxy compound is not particularly limited, but a polyfunctional epoxy compound is preferably used. Can be used. Further, as the polyfunctional epoxy compound, bisphenol A
Type or bisphenol type such as bisphenol F type, novolak type such as phenol novolak type or cresol novolak type, glycidyl ether type, glycidyl amine type and alicyclic epoxy can be used.

The above-mentioned photo-cationic polymerization initiator is activated by being irradiated with light to generate a photo-cationic polymerization-initiating substance. Since it can start the polymerization by irradiation of light, it has a relatively low energy. Polymerization can be initiated.

As the above-mentioned light, microwaves, infrared rays, visible light, ultraviolet rays, X-rays, γ-rays, etc. can be used, but generally they are easy and convenient to handle, and relatively high energy can be obtained. Ultraviolet rays that can be used are preferably used. More preferably, ultraviolet rays having a wavelength of 200 to 400 nm are used.

The above-mentioned ultraviolet rays can be irradiated by using an appropriate light source such as a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp or the like. The cationic photopolymerization initiator may be either an ionic photoacid generating type or a nonionic photoacid generating type.

Examples of the ionic photoacid generating type include aromatic diazonium salts, aromatic halonium salts, onium salts of aromatic sulfonium salts, and organometallic complexes such as iron-allene complexes, titanocene complexes and arylsilanol-aluminum complexes. Kind of things can be mentioned. More specifically, for example, Optomer SP-150 (manufactured by Asahi Denka Kogyo), Optomer SP-170 (manufactured by Asahi Denka Kogyo), U
VE-1014 (manufactured by General Electronics Co.), C
A commercially available compound such as D-1012 (manufactured by Sartomer) can be used.

As the nonionic photoacid generating type, nitrobenzyl ester, sulfonic acid derivative, phosphoric acid ester, sulfonic acid derivative, phenolsulfonic acid ester, diazonaphthoquinone, N-hydroxyimide sulfonate, etc. may be used. it can.

The above-mentioned cationic photopolymerization initiator may be used alone or in combination of two or more kinds, and is cured in a plurality of stages using a plurality of cationic photopolymerization initiators having different effective active wavelengths. Good.

Further, other photopolymerization initiators such as photoradical polymerization initiators or photoanionic polymerization initiators may be used in combination. In this case, the wavelength of light that activates the photoradical polymerization initiator or the photoanion polymerization initiator does not necessarily have to be the same as the wavelength that activates the photocationic polymerization initiator.

The above photocationic polymerization initiator is used in the curable adhesive composition according to the third aspect of the invention in an amount of 0.001 to 1 mol with respect to 1 mol of the functional group of the polyfunctional epoxy compound.
It is preferable to blend in the range of 10 mol%. 0.00
If the amount is less than 1 mol%, the cationic photopolymerization may not proceed sufficiently and the curing speed may be slow. If the amount is more than 10 mol%, the curing due to the light irradiation may proceed too fast and the adherend may not be adhered. The work time until pasting may be restricted.

Further, in the curable pressure-sensitive adhesive composition according to the third aspect of the present invention, in addition to the above-mentioned dispersion, polyfunctional epoxy compound and photocationic polymerization initiator, a range that does not impair the object of the present invention. In order to improve the adhesiveness, other polymer components such as other acrylic resin, urethane resin, polyester resin, olefin resin, styrene resin, silicone resin and rubber may be blended, and known tackifying resin You may mix | blend a filler, etc. suitably.

The curable pressure-sensitive adhesive composition according to the third aspect of the invention can be used in an appropriate form depending on the place of use. That is, it is possible to coat the adherend as a curable pressure-sensitive adhesive and to cure it by irradiating it. Alternatively, the curable pressure-sensitive adhesive composition may be processed into a sheet and used in the same manner as the double-sided pressure-sensitive adhesive tape.

(Operation) In the method for dispersing crosslinked rubber particles according to the first aspect of the present invention, first, the crosslinked rubber particles having a functional group capable of reacting with an epoxy group and a monofunctional epoxy compound are mixed in an organic solvent. As a result, the reactive functional group reacts, and an epoxy compound component having excellent compatibility with the acrylic polymer is grafted on the surface of the crosslinked rubber particles. Therefore,
Next, when the acrylic polymer is mixed, since the compatibility of the crosslinked rubber particles with the acrylic polymer is enhanced, the crosslinked rubber particles having a small particle size are uniformly dispersed in the acrylic polymer. A dispersion according to the invention described is obtained.

The curable pressure-sensitive adhesive composition according to the third aspect of the present invention contains the above dispersion, a polyfunctional epoxy compound, and a cationic photopolymerization initiator. In the dispersion, the crosslinked rubber particles are acrylic. Since it is uniformly and finely dispersed in the polymer, even in the curable pressure-sensitive adhesive composition,
The crosslinked rubber particles are evenly dispersed throughout the acrylic / epoxy adhesive. Therefore, when the curable adhesive composition is irradiated with light and the polyfunctional epoxy compound is photocationically polymerized and cured, the stress of the cured product is uniform due to the uniformly dispersed crosslinked rubber particles having a small particle size. And the peel resistance is improved.

[0042]

The present invention will be described in more detail by giving non-limiting examples of the present invention.

(Example 1) As a crosslinked rubber particle having a reactive functional group which reacts with an epoxy group, trade name: XER91 (COOH group-containing crosslinked NBR: manufactured by Nippon Synthetic Rubber Co., Ltd .:
The average particle size of 80 nm) was dispersed in methyl ethyl ketone so that the concentration was 10% by weight. In this case, the dispersed particle size of the crosslinked rubber particles was 80 nm. 60 this dispersion
Alkyl glycidyl ether (manufactured by Asahi Denka Co., Ltd., trade name: ED502) as a monofunctional epoxy compound while stirring at ℃
2 parts by weight of S) was added to 100 parts by weight of the crosslinked rubber particles, and the mixture was reacted for 1 hour. It was also confirmed by neutralization titration that 56 mol% of the COOH groups of the crosslinked rubber particles had reacted. At this time, the dispersed particle size of the crosslinked rubber particles is 8
It was 0 nm.

(Example 2) As in Example 1, except that DHS2S (COOH group-containing crosslinked acrylic rubber, average particle size 80 nm) manufactured by Japan Synthetic Rubber Co., Ltd. was used as the crosslinked rubber particles. To obtain a crosslinked rubber particle dispersion. The dispersed particle size of the crosslinked rubber particles is 80 nm,
The reaction rate of H group was 49 mol%.

Comparative Example 1 Example 1 was repeated except that the monofunctional epoxy compound was not used.
Same as. The dispersed particle size of the crosslinked rubber particles was 80 nm.

Comparative Example 2 Example 2 was repeated except that the monofunctional epoxy compound was not used.
A dispersion was obtained in the same manner as in. The dispersed particle size of the crosslinked rubber particles was 80 nm.

Comparative Example 3 The crosslinked rubber particles were not dispersed,
An alkyl glycidyl ether as a monofunctional epoxy compound was mixed with MEK.

(Evaluation of Examples and Comparative Examples) Examples 1 and 2
And 5 parts by weight of the solid content of each of the dispersions obtained in Comparative Examples 1 and 2 or the monofunctional epoxy compound solution obtained in Comparative Example 3, respectively, a bisphenol A type epoxy compound as a polyfunctional epoxy compound (Yukaka Shell Epoxy Co., Ltd. Made by trade name: Epicoat 828) 45 parts by weight, polyethyl acrylate (Mw = 620,000, 40% by weight ethyl acetate solution) as a non-volatile content of 50 parts by weight, a cationic photopolymerization initiator (Asahi Denka Co., Ltd., trade name: SP170, 1.5 parts by weight of aromatic sulfonium antimony salt) was mixed and stirred with a high-speed stirrer for 1 minute to obtain a curable adhesive composition.

With respect to each of the obtained curable pressure-sensitive adhesives, the average particle size of the crosslinked rubber particles and the adhesive strength were evaluated in the following manner. Average particle size of crosslinked rubber particles: The average particle size of the crosslinked rubber particles was measured by a laser light scattering particle size measuring device manufactured by Horiba Ltd.

A transparent polyethylene naphthalate (PEN) film having a thickness of 100 μm and a final thickness of 100 μm is added.
The curable tacky adhesive was applied to give m, and dried in a gear oven at 100 ° C. for 10 minutes to volatilize the solvent. After that, another PEN film is attached on the curable adhesive layer, and ultraviolet rays with a wavelength of 365 nm are applied by an ultra-high pressure mercury lamp.
Irradiation with an intensity of J / cm ² caused photocationic polymerization and curing to obtain a sample. After that, the PEN films are joined to each other with a curable adhesive to cut the sample into a width of 20 mm, and a T-type peeling test is performed to obtain 50 mm.
The adhesive force was measured by peeling under the condition of / min. The results are shown in Table 1 below.

[0051]

[Table 1]

As is clear from Table 1, in Comparative Examples 1 and 2, since the crosslinked rubber particles were not previously reacted with the monofunctional epoxy compound, the average of the crosslinked rubber particles in the curable adhesive composition was found. Very large particle size of 250 μm or more, and the adhesive strength of the curable adhesive is 900 g / 20 mm
Was low. On the other hand, in Examples 1 and 2, the cross-linked rubber particles are preliminarily reacted with the monofunctional epoxy compound to enhance the compatibility with the acrylic polymer. It can be seen that the average particle diameter of the crosslinked rubber particles is as small as 10 μm or less, and therefore the crosslinked rubber particles having a fine particle diameter are uniformly dispersed throughout. Also, the adhesive strength was significantly increased to 2200 g / 20 mm or more.

[0053]

According to the invention of claim 1, the crosslinked rubber particles having a functional group capable of reacting with an epoxy group are
The polyfunctional epoxy compound is mixed in an organic solvent, the reactive functional group is reacted, and the epoxy compound component is grafted onto the crosslinked rubber particles. Since this epoxy compound component has excellent compatibility with the acrylic polymer, when mixed with the acrylic polymer, the crosslinked rubber particles having a small particle size are uniformly dispersed throughout.

Therefore, it is possible to obtain the crosslinked rubber particle dispersion according to the present invention in which the crosslinked rubber particles having a small particle size are uniformly dispersed. Therefore, when a curable tacky-adhesive agent using an acrylic pressure-sensitive adhesive component is formed using the dispersion according to the invention of claim 2, the stress in the final cured adhesive product is a uniform cross-linked structure. It is relieved by the action of rubber particles. Therefore, it becomes possible to provide a curable pressure-sensitive adhesive having high peel resistance.

The curable pressure-sensitive adhesive composition according to the invention of claim 3 contains the dispersion according to the invention of claim 2, a polyfunctional epoxy compound, and a photocationic polymerization initiator. . In this dispersion, since the crosslinked rubber particles are uniformly dispersed in the acrylic polymer with a small particle size, the cationic resin is used for photo-cationic polymerization of the polyfunctional epoxy compound in the curable adhesive composition. When the cured adhesive is obtained by causing the curing, the peel strength of the cured adhesive can be surely increased. That is, in an acrylic / epoxy curable adhesive, not only can it be easily attached to an adherend by utilizing its pressure-sensitive adhesive property and can be easily cured by irradiation of light, but the final adhesive cured product can also be obtained. It is also possible to effectively increase the peel strength, that is, the adhesive force.

Claims (3)

(57) [Claims] 1. A crosslinked rubber particle having a functional group capable of reacting with an epoxy group and a monofunctional epoxy compound are mixed in an organic solvent to react the functional group capable of reacting with the epoxy group with the epoxy group, followed by acryl. A method for dispersing crosslinked rubber particles, which comprises mixing with a base polymer. 2. A crosslinked rubber particle dispersion obtained by the method for dispersing crosslinked rubber particles according to claim 1. 3. A crosslinked rubber particle dispersion according to claim 2,
A curable pressure-sensitive adhesive composition comprising a polyfunctional epoxy compound and a cationic photopolymerization initiator.