JPH04202586A - Pressure-sensitive adhesive composition for vibration damping material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pressure-sensitive adhesive composition for vibration damping materials that has excellent adhesive properties and solvent resistance.

[Conventional technology]

In recent years, adhesives have been used in the form of tapes or sheets for various purposes, one of which is adhesives for vibration damping materials.

This type of adhesive is widely used as a means to reduce vibration and noise in automobile parts, various home appliances, etc., and exhibits good vibration damping properties at the operating temperature. Many studies have been conducted on the characteristics.

[Problem to be solved by the invention]

However, the required properties for adhesives for splitting materials are increasing year by year, and for example, in precision equipment such as computers, solvent cleaning is performed to remove impurities. There are problems such as extrusion caused by adhesives, and an adhesive with excellent solvent resistance is desired. The currently used adhesives for damping materials are insufficient to meet these demands.

In view of these circumstances, the present invention provides a pressure-sensitive adhesive composition for vibration damping materials that has good adhesive properties that can be easily attached to various parts at room temperature and has excellent solvent resistance. is intended to provide.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the present inventors have discovered that a specific crosslinked structure obtained by crosslinking a copolymer with a specific monomer composition by appropriate means has both adhesive properties and solvent resistance. It was discovered that this adhesive has excellent properties and is extremely suitable as a pressure-sensitive adhesive for vibration damping materials, leading to the completion of the present invention.

That is, the present invention provides a raw monomer 7 which essentially includes an acrylic acid alkyl ester having an alkyl group having 8 to 12 carbon atoms.
5 to 92% by weight and 25 to 8% by weight of a carboxyl group-containing monomer whose homopolymer glass transition temperature (hereinafter referred to as Tg) is 50°C or higher, and is insoluble in solvents. 95% by weight or more, S
This invention relates to a pressure-sensitive adhesive composition for vibration damping material, which has a T-peel strength of 400 g/20 m width or more against a US plate.

[Structure and operation of the invention] The acrylic acid alkyl ester used in the present invention has a long-chain alkyl group with 8 to 12 carbon atoms in its side chain, and due to its long side chain, it has a large effect on vibration damping properties. It has a wide glass transition region, giving it high splitting properties over a wide range of temperatures. Specifically, isooctyl acrylate,
2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, etc. are used.

In the present invention, the above acrylic acid alkyl ester may be used alone as a raw monomer, or if necessary, the above acrylic acid alkyl ester and another monomer copolymerizable therewith may be used in combination as a raw monomer. good. However, other monomers that can be copolymerized are
It is preferable that the amount is less than % by weight, and if too much is used, adhesiveness and vibration damping properties will deteriorate. Specific examples include vinyl acetate, acrylonitrile, acrylamide, styrene or derivatives thereof.

The carboxyl group-containing monomer used in the present invention has a homopolymer Tg of 50°C or higher, preferably 80 to 19
0°C, it has the effect of raising the Tg of the polymer to a practical temperature range when copolymerized with acrylic acid alkyl ester, thereby imparting good vibration damping properties to the adhesive, as well as strengthening the polymer molecules. Since it has a carboxyl group as a polar group, it greatly contributes to improving the adhesion to metals and the like. Specifically, acrylic acid, maleic acid (anhydride), itaconic acid, fumaric acid, crotonic acid, etc. are used.

In the present invention, the ratio of the main monomer that essentially includes the above-mentioned acrylic acid alkyl ester 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. Particularly preferably, the former raw monomer 80
It is preferable that the amount of the latter carboxyl group-containing monomer is 20 to 10% by weight relative to 90% by weight.

When the carboxyl group-containing monomer exceeds 25% by weight,
If the Tg of the copolymer becomes too high, vibration damping properties at temperatures as low as 40° C. will decrease, and if the number of polar groups increases too much, the elastic modulus of the copolymer will increase, resulting in a decrease in adhesiveness. In addition, if it is less than 8% by weight, the Tg of the copolymer cannot be sufficiently increased, resulting in a decrease in vibration damping properties at temperatures as high as 60°C, and the amount of polar groups is too small, making it difficult to improve adhesion. I can't get it.

In the present invention, the above-mentioned raw monomer that essentially includes the acrylic acid alkyl ester and the carboxyl group-containing monomer are copolymerized in the above ratio, and the resulting copolymer is further crosslinked to reduce the solvent-insoluble content to 95% by weight. %
The crosslinked structure is preferably 96% by weight or more.

As a method for obtaining such a copolymer and its crosslinked structure, the copolymer is generally obtained by a method such as solution polymerization, emulsion polymerization, or suspension polymerization, and then a polyfunctional compound such as an isocyanate type or an epoxy type is added to the copolymer. A method of crosslinking treatment by adding a crosslinking agent consisting of:

However, in order to create a highly crosslinked type with a solvent insoluble content of 95% by weight or more using this method, a large amount of crosslinking agent must be used. There are problems such as a viscosity that makes it impossible to coat, and a decrease in adhesion due to an increase in elastic modulus, making it impossible to maintain good adhesive properties.

In the present invention, a polyfunctional polymer is used as an internal crosslinking agent when producing a copolymer, and a monomer mixture containing this internal crosslinking agent is bulk-polymerized with ultraviolet rays or electron beams, and the copolymer is simultaneously produced and crosslinked. The above problem was solved by adopting a method of obtaining a structure.

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 problem in terms of viscosity properties when coating on a substrate. Moreover, with this method, even if the solvent-insoluble content of the crosslinked structure is increased, the adhesiveness does not significantly decrease, probably due to the increased wettability caused by the higher molecular weight of the resulting polymer and the degree of freedom of the segments between the crosslinking points. It exhibits a unique effect of being invisible.

Examples of polyfunctional monomers used as internal crosslinking agents in such bulk polymerization include ethylene glycol diacrylate, pentaerythritol triacrylate, tetramethylolmethanetetraacrylate, and trimethylolpropane triacrylate.

The amount of this polyfunctional monomer to be used is usually 0.6 to 2.0 parts by weight based on 100 parts by weight of the total amount of the main monomer essentially including the acrylic acid alkyl ester and the carboxyl group-containing monomer. It is better to do so. If the amount is too small, sufficient crosslinking with a solvent-insoluble content of 95% by weight or more cannot be obtained, and if it is too large, the elastic modulus of the polymer becomes too large (too much, resulting in decreased adhesiveness).

Bulk polymerization is carried out by irradiating electron beams or ultraviolet rays, but in the case of ultraviolet irradiation, a photopolymerization initiator such as 1-hydroxycyclohexylphenyl ketone, benzyl dimethyl ketal, hensifenone, etc. is added to the mixture in advance. It is better to leave it there. The amount added is usually 0.1 to 1 part by weight, based on 100 parts by weight of the main monomer that essentially includes the above-mentioned acrylic acid alkyl ester and the carboxyl group-containing monomer.
It is enough to add about 0 parts by weight.

In the present invention, if the above-mentioned bulk polymerization is carried out on a release liner or coated on various substrates, after this polymerization, the solvent-insoluble content of the crosslinked structure of the copolymer is 95% by weight or more. , T peel strength against SUS plate is 4
00g/20m width or more, preferably 450 to 1,200
A pressure-sensitive adhesive composition for splitting materials having a width of 10 g/20 g/20 and excellent in both solvent resistance and adhesiveness is obtained, and this composition can be used as is in the form of a tape or sheet.

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

〔Effect of the invention〕

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

〔Example〕

Next, examples of the present invention will be described in more detail. Hereinafter, parts refer to parts by weight.

In addition, the solvent-insoluble content, T-peel strength, and vibration damping properties of the adhesive were measured in the following manner.

<Solvent-insoluble matter> Cut out approximately 0.1 g of sample and add Freon (Daiflon 5).
-3) at room temperature for 5 days. After immersion, the sample was pulled up with tweezers, transferred to an aluminum cup, and dried at 130°C for 2 hours. Based on the weight change after drying, the solvent-insoluble content was measured according to the following calculation formula.

<T Peel Strength> A sample prepared on a release liner to a thickness of 50 μm was sandwiched between two sheets of SUS304 foil having a thickness of 50 μm, and was pressed with a 2 kg rubber roller by making one reciprocation. After leaving it for about 30 minutes, Toyo Balduin Tensilon UMT-4
-100 at a speed of 300 mm/min in an atmosphere of 23° C. for measurement. The width of the test piece is 20 mm.

<Vibration damping properties> Measured using a mechanical impedance method using a measuring device manufactured by IMV. In the measurement, the loss coefficient was obtained from the transfer function using the half-width method at a resonance point near IKHz.

The shape of the test piece was as follows: 5US304 (500 μm thick) was used as the base material, and samples of the present invention and comparison (500 μm thick) were used as the damping material.
5TJS304 (50μm thickness) as a restraining material.
m thickness), length 110 mm, radius 20
Measurements were made using the cantilever beam method.

Example 1 2 parts of Irgacure 184 (manufactured by Ciba Geigy) was added as a photopolymerization initiator to 100 parts of a monomer mixture consisting of 90 parts of isooctyl acrylate and 10 parts of acrylic acid.
1 part, thoroughly purged with nitrogen, and heated with a high-pressure mercury lamp for about 1 part.
Ultraviolet irradiation was performed at 00+++j/-.

One part of trimethylolpropane triacrylate as an internal crosslinking agent was added to the resulting viscous material, and this was coated onto the release liner in a thickness of 50 parts m. Further, in order to eliminate the polymerization limit due to oxygen, the material was covered with a PET (polyethylene terephthalate) release liner and irradiated with ultraviolet rays of about L400+nj/- using a high-pressure mercury lamp to prepare a tape-shaped pressure-sensitive adhesive composition.

Example 2 A viscous material 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, Example 1 was prepared, except that 2 parts of ethylene glycol diacrylate was added as an internal crosslinking agent to this viscous material.
A tape-shaped pressure-sensitive adhesive composition was prepared in the same manner as above.

Example 3 Seven-mer mixture 1 consisting of 85 parts of 2-ethylhexyl acrylate, 5 parts of acrylonitrile, and 10 parts of acrylic acid
00 parts, Irgacure 65 as a photopolymerization initiator
1 (manufactured by Ciba Geigy), the mixture was sufficiently purged with nitrogen, and irradiated with ultraviolet rays at about 100 mj/cj using a high-pressure mercury lamp.

To the resulting viscous material, 1.5 parts of pentaerythritol triacrylate as an internal crosslinking agent was added, coated on a release liner to a thickness of 50 μm, covered with a PET release liner, and heated with a high-pressure mercury lamp for 1.5 parts. .400mj/cn!
A tape-shaped pressure-sensitive adhesive composition was prepared by irradiating the sample with ultraviolet rays.

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 parts of trimethylolpropane triacrylate was added to the viscous material obtained in the same manner as in Example 2. I made something.

Comparative Example 3 Using a monomer mixture of 85 parts of isooctyl acrylate and 10 parts of acrylic acid, a mixed solution of 150 parts of ethyl acetate and 0.1 part of azobisisobutyronitrile was added to 100 parts of this mixture under nitrogen gas. Solution polymerization was carried out in an atmosphere 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 onto a release liner to a dry thickness of 50 μm, and dried at 120° C. for 5 minutes to produce a tape-shaped pressure-sensitive adhesive composition.

The results of measuring the solvent-insoluble content, T-peel strength, and vibration damping properties of the pressure-sensitive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 3 above are as shown in Table 1 below. there were.

In addition, when the SUS bonded sample used in measuring the T-peel strength was immersed in Freon for 5 days, the adhesive seeped out from both sides of the comparative sample @2, and the entire sample was contaminated even after drying. No contamination was observed in the other items after drying.

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

Patent applicant: Nitto Denko Corporation

Claims (1)

[Claims] (1) 75 to 92% by weight of the main monomer which is essentially an acrylic acid alkyl ester with an alkyl group having 8 to 12 carbon atoms
and 25 to 8% by weight of a carboxyl group-containing monomer whose homopolymer glass transition temperature is 50°C or higher, and a crosslinked structure of a copolymer with a solvent-insoluble content of 95% by weight.
T-peel strength against SUS plate is 400g at weight% or more
A pressure-sensitive adhesive composition for vibration damping material, characterized in that the width is 20 mm or more.