JP2810540B2 - Pressure-sensitive adhesive composition for vibration damping material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition for a vibration damping material having both excellent adhesiveness and solvent resistance.

[Conventional technology]

In recent years, adhesives have been used in various applications in the form of tapes or sheets, and one of them is an adhesive for vibration damping materials for vibration reduction.

This type of adhesive is widely used as a means for reducing vibration and noise of automobile parts, various home appliances, etc., and exhibits good vibration damping properties at its use temperature.
Numerous studies have been made on temperature characteristics of vibration damping properties.

[Problems to be solved by the invention]

However, the required properties of the adhesive for vibration damping materials have been increasing year by year. For example, in precision equipment such as computers, solvent cleaning is performed to remove impurities and the like. There is a problem such as protrusion due to swelling, and an adhesive having excellent solvent resistance is desired.
To meet such demands, currently used adhesives for vibration damping materials are insufficient.

In view of such circumstances, the present invention has a good adhesive property that can be easily attached to various parts at room temperature, and has a solvent-resistant pressure-sensitive adhesive composition having excellent solvent resistance. It is intended to provide.

[Means for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and as a result, a specific cross-linked structure obtained by cross-linking a copolymer having a specific monomer composition by an appropriate means has been found to have both adhesiveness and solvent resistance. The inventors have found that they have excellent characteristics and are extremely suitable as pressure-sensitive adhesives for vibration damping materials, and have completed the present invention.

That is, the present invention relates to a main monomer 75 having an alkyl acrylate having an alkyl group having 8 to 12 carbon atoms.
~ 92 wt% and the glass transition temperature of the homopolymer (hereinafter, referred to as
A cross-linked structure of a copolymer with 25 to 8% by weight of a carboxyl group-containing monomer having a Tg of 50 ° C. or higher, and a solvent-insoluble component (hereinafter referred to as “CClF ₂ —Cl ₂ F”) in fluorinated ethane (CClF ₂ —Cl ₂ F). (Hereinafter, simply referred to as a solvent-insoluble component) is 95% by weight or more, and the T peel strength with respect to a SUS plate is 400 g / 20 mm width or more.

[Structure and operation of the invention]

Alkyl acrylate used in the present invention,
It has a long-chain alkyl group with 8 to 12 carbon atoms in the side chain. Due to its long side chain, the glass transition region that greatly affects the damping properties is wide, and high damping properties are provided over a wide range of temperatures. I do. Specifically, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, and the like are used.

In the present invention, the above-mentioned alkyl acrylate may be used alone as a main monomer, or the above-mentioned alkyl acrylate and another monomer copolymerizable therewith may be used as a main monomer as necessary. Good.
However, other copolymerizable monomers account for 30% of all monomers.
% By weight or less. If too much is used, the adhesiveness and vibration damping properties decrease. Specific examples include vinyl acetate, acrylonitrile, acrylamide, styrene or derivatives thereof.

Carboxyl group-containing monomer used in the present invention,
Since the homopolymer has a Tg of 50 ° C. or higher, preferably 80 to 190 ° C., it has a function of increasing the Tg of the polymer to a practical temperature range in the copolymerization with the alkyl acrylate, thereby providing an adhesive. In addition to imparting good vibration damping properties to the polymer, it has a carboxyl group as a polar group in the polymer molecule, and thus greatly contributes to improvement in adhesion to metals and the like. Specifically, acrylic acid, (anhydride) maleic acid, itaconic acid, fumaric acid, crotonic acid and the like are used.

In the present invention, the use ratio of the main monomer essentially including the alkyl acrylate and the carboxyl group-containing monomer is 75 to 92% by weight of the former main monomer and 25 to 8% by weight of the latter carboxyl group-containing monomer. It is particularly preferable that the content of the former main monomer is 80 to 90% by weight and the latter is a carboxyl group-containing monomer of 20 to 10% by weight.

When the carboxyl group-containing monomer exceeds 25% by weight,
The Tg of the copolymer becomes too high and the vibration damping property at a temperature as low as about 40 ° C. decreases, and the elasticity of the copolymer increases due to too many polar groups and the adhesion decreases. When the content is less than 8% by weight, the Tg of the copolymer becomes
Cannot be sufficiently increased, the vibration damping property at a high temperature of about 60 ° C. is reduced, and the effect of improving the adhesiveness cannot be obtained because the polar group is too small.

In the present invention, the main monomer and the carboxyl group-containing monomer essential for the above-mentioned alkyl acrylate are copolymerized in the above ratio, and the obtained copolymer is further subjected to a cross-linking treatment so that the solvent-insoluble content is 95% by weight. %
Thus, the crosslinked structure is preferably at least 96% by weight.

As a method for obtaining such a copolymer and a crosslinked structure thereof, generally, solution polymerization, emulsion polymerization,
A method in which a copolymer is obtained by a method such as suspension polymerization, and a crosslinking agent comprising a polyfunctional compound such as an isocyanate-based or epoxy-based compound is added to the copolymer to perform a crosslinking treatment.

However, in order to obtain a highly crosslinked type having a solvent-insoluble content of 95% by weight or more in this method, a large amount of a crosslinking agent must be used. There are problems that the viscosity becomes unapplicable and that the adhesion decreases due to an increase in the modulus of elasticity, and that good adhesion cannot be maintained.

In the present invention, a polyfunctional monomer is used as an internal cross-linking agent when forming a copolymer, and a monomer mixture containing the internal cross-linking agent is subjected to bulk polymerization with an ultraviolet ray or an electron beam. The above problem was solved by adopting the method of obtaining

According to this bulk polymerization, the reaction can be carried out in a monomer state or a low-viscosity prepolymer state, and the reaction can be easily controlled, so that there is no inconvenience in viscosity characteristics at the time of application to a substrate or the like. Moreover, in this method, even if the solvent insoluble content of the crosslinked structure is increased, a large decrease in the adhesiveness may be caused by the increase in the molecular weight of the produced polymer or the increase in the degree of freedom of the segment between the crosslinking points. It has a unique effect that it is not seen.

Examples of the polyfunctional monomer as an internal crosslinking agent used in such bulk polymerization include ethylene glycol diacrylate, pentaerythritol triacrylate, tetramethylolmethanetetraacrylate, and trimethylolpropane triacrylate.

The amount of the polyfunctional monomer used is usually based on 100 parts by weight of the total amount of the main monomer and the carboxyl group-containing monomer, which are essentially the above-mentioned alkyl acrylate.
It is preferred that the amount be 0.6 to 2.0 parts by weight. Insufficiently,
Sufficient cross-linking in which the solvent-insoluble content is 95% by weight or more cannot be obtained, and if it is excessive, the elastic modulus of the polymer becomes too large and the adhesiveness decreases.

Bulk polymerization is performed by irradiating an electron beam or ultraviolet light.In the case of ultraviolet irradiation, a photopolymerization initiator such as 1-hydroxycyclohexylphenyl ketone, benzyldimethyl ketal, or benzophenone is added to the monomer mixture in advance. Is good. The amount of addition may be generally about 0.1 to 10 parts by weight based on 100 parts by weight of the total amount of the main monomer essentially including the alkyl acrylate and the carboxyl group-containing monomer.

In the present invention, if the above-mentioned bulk polymerization is carried out on a release liner or a state coated on various substrates, after this polymerization, a solvent-insoluble component composed of a crosslinked structure of a copolymer is 95% by weight or more. , T peel strength against SUS plate is 400g /
A pressure-sensitive adhesive composition for a vibration damping material having a width of 20 mm or more, preferably 450 to 1,200 g / 20 mm width, which is excellent in both solvent resistance and adhesiveness, is obtained. It can be used as it is.

Such a tape-shaped or sheet-shaped pressure-sensitive adhesive composition has a loss coefficient indicating a vibration-damping performance at 40 ° C. to 60 ° C. of 0.05 or more, which is measured by a method described later, and is a very good vibration damping. It can be widely used as an adhesive for vibration damping materials for automobile parts, various home appliances, precision equipment, etc.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a pressure-sensitive adhesive composition for a vibration damping material that is excellent in both adhesiveness and solvent resistance.

〔Example〕

Next, examples of the present invention will be described in more detail. Hereinafter, "parts" indicates parts by weight. The solvent-insoluble content, T-peel strength and vibration damping property of the adhesive were measured in the following manner.

<Solvent-insoluble content> A sample of about 0.1 g was cut out, and Freon (Daiflon S-
3) Dip in room temperature for 5 days [this is a trade name of Freon-113, that is, ethane fluorinated ethane (CClF ₂ -CCl ₂ F)]. After immersion, the sample is pulled up with tweezers, transferred to an aluminum cup, and dried at 130 ° C. for 2 hours. From the change in weight after drying, the solvent-insoluble content was measured according to the following formula.

<T Peel Strength> A sample prepared to a thickness of 50 μm on a release liner is sandwiched between two SUS304 foils having a thickness of 50 μm, and is reciprocated once with a 2 kg rubber roller to be pressed. After leaving it for about 30 minutes, use Toyo Baldwin's Tensilon UMT-4-100 at 300 mm /
T peeling was performed at a speed of 23 minutes in an atmosphere of 23 ° C. and measured. The width of the test piece is 20 mm.

<Vibration Suppression> Measured by a mechanical impedance method using a measuring device manufactured by IMV. In the measurement, a loss coefficient was obtained from a transfer function at a resonance point near 1 KHz by a half-width method. The shape of the test piece is SUS304 (500μm thickness) for the base material and the present invention and comparative sample (50μm thickness) for the vibration damping material.
Was measured by a cantilever method using SUS304 (thickness of 50 μm) as a restraining material, with a length of 110 mm and a width of 20 mm.

Example 1 To 100 parts of a monomer mixture consisting of 90 parts of isoacrylic acrylate and 10 parts of acrylic acid, 2 parts of Irgakiure 184 (manufactured by Ciba-Geigy) was blended as a photopolymerization initiator, and the mixture was sufficiently purged with nitrogen. About 100mj / cm with mercury lamp
UV irradiation of ² was performed.

One part of trimethylolpropane triacrylate was added as an internal cross-linking agent to the obtained viscous material, and this was coated on a release liner at a thickness of 50 μm. Further, in order to eliminate the inhibition of polymerization by oxygen, the tape was covered with a PET (polyethylene terephthalate) release liner and irradiated with ultraviolet rays of about 1,400 mj / cm ² by a high-pressure mercury lamp to prepare a tape-shaped pressure-sensitive adhesive composition.

Example 2 A viscous substance was obtained in the same manner as in Example 1 except that 100 parts of a mixture consisting of 85 parts of 2-ethylhexyl acrylate and 15 parts of acrylic acid was used as the monomer mixture. Next, a tape-shaped pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that 2 parts of ethylene glycol acrylate was added as an internal crosslinking agent to this viscous material.

Example 3 Monomer mixture 100 consisting of 85 parts of 2-ethylhexyl acrylate, 5 parts of acrylonitrile and 10 parts of acrylic acid
3 parts of Irgaki Yua 651 (manufactured by Ciba Gaiki Co., Ltd.) as a photopolymerization initiator was added to each part, the atmosphere was sufficiently replaced with nitrogen, and UV irradiation of about 100 mj / cm ² was performed with a high-pressure mercury lamp.

To the obtained viscous material, 1.5 parts of pentaerythritol triacrylate was added as an internal crosslinking agent, coated on a release liner with a thickness of 50 μm, covered with a PET release liner, and 1,400 mj / Irradiation with ultraviolet light of cm ² was performed to produce a tape-shaped pressure-sensitive adhesive composition.

Comparative Example 1 A tape-shaped pressure-sensitive adhesive composition was produced in the same manner as in Example 1, except that 100 parts of a mixture consisting of 95 parts of isooctyl acrylate and 5 parts of acrylic acid was used as the monomer mixture.

Comparative Example 2 A tape-shaped pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that 0.2 part of trimethylolpropane triacrylate was added to the viscous material obtained in the same manner as in Example 2. Produced.

Comparative Example 3 A monomer mixture of 85 parts of isooctyl acrylate and 15 parts of acrylic acid was used, and a mixed solution obtained by adding 150 parts of ethyl acetate and 0.1 part of azobisisobutyronitotyl to 100 parts of the mixture was mixed in a nitrogen atmosphere. The solution was polymerized at 60 ° C. for about 7 hours to obtain a polymer solution.

One part of 1,3-bis (NN-diglycidylaminomethyl) cyclohexane was added to 100 parts of the obtained polymer solution to obtain a pressure-sensitive adhesive solution. This adhesive solution was applied on a release liner so that the thickness after drying was 50 μm, and dried at 120 ° C. for 5 minutes to prepare a tape-shaped pressure-sensitive adhesive composition.

For each of the pressure-sensitive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 3, the results measured for the solvent-insoluble content, T-peel strength, and vibration damping properties are as shown in Table 1 below. Atsuta.

When the laminated sample of SUS used in the measurement of the T peel strength was immersed in Freon for 5 days, the adhesive of the sample of Comparative Example 2 oozed from both sides, and after drying, the entire sample was contaminated. Others showed no staining after drying.

As is clear from the results shown in Table 1, the pressure-sensitive adhesive composition of the present invention has excellent adhesiveness and solvent resistance, and is extremely suitable as an adhesive for vibration damping materials.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Michio Mori 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (56) References JP-A-2-182773 (JP, A) JP-A Hei 2-3724 (JP, A) JP-A Hei 2-182773 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09J 133/04-133/10 C08F 220/10-220 / 18 C08F 20/10-20/18

Claims (1)

(57) [Claims] 1. A main monomer comprising 75 to 92% by weight of an alkyl acrylate having an alkyl group having 8 to 12 carbon atoms.
And a cross-linked structure of a copolymer having 25 to 8% by weight of a carboxyl group-containing monomer having a homopolymer having a glass transition temperature of 50 ° C. or higher.
In lF ₂ -CCl ₂ F) solvent-insoluble content of 95 wt% or more with respect, SU
A pressure-sensitive adhesive composition for a vibration damping material, wherein a T peel strength with respect to an S plate is 400 g / 20 mm width or more.