JP3486698B2 - Pressure-sensitive adhesive composition and pressure-sensitive adhesive product - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive product having excellent initial adhesiveness, heat resistance and removability after heating.

[0002]

2. Description of the Related Art A conventional acrylic pressure-sensitive adhesive composition comprises a copolymer containing an adhesive vinyl monomer and a vinyl monomer containing active hydrogen. As the adhesive vinyl monomer, an alkyl acrylate ester having an alkyl group having 4 to 12 carbon atoms is used, and among them, C ₄ butyl acrylate and C ₈ 2-ethylhexyl acrylate are mainly used. . In particular, the copolymer obtained by using 2-ethylhexyl acrylate is
Since the glass transition point is lower than that of the copolymer obtained by using butyl acrylate, it is useful as a monomer exhibiting good initial adhesiveness. However, when 2-ethylhexyl acrylate is used as the main component of the tacky vinyl monomer, the resulting copolymer has a low glass transition point and thus a composition having sufficient heat resistance and removability after heating is obtained. It was not possible to achieve both initial adhesiveness and heat resistance of the composition. Meanwhile, acrylic acid alkyl esters of C _8, in addition to 2-ethylhexyl acrylate, acrylic acid n- octyl acrylate and iso-
Octyl and the like are known, but these acrylic acid n
-The copolymer obtained using octyl or iso-octyl acrylate has a glass transition point lower than that of the copolymer obtained using 2-ethylhexyl acrylate and thus is excellent in initial adhesion, but has a heat resistance It is considered to be inferior to the copolymer obtained by using 2-ethylhexyl acrylate, and 2 ethylhexyl acrylate is currently exclusively used as a C ₈ alkyl acrylate monomer.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a pressure-sensitive adhesive composition and a pressure-sensitive adhesive product which are excellent in initial adhesion, heat resistance and removability after heating. It is an issue.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have found that among C ₈ alkyl acrylate esters, n-octyl acrylate is particularly used. In the case of a polymer, performance that cannot be exhibited when 2-ethylhexyl acrylate or iso-octyl acrylate is used, that is, excellent initial adhesiveness, heat resistance and removability after heating are excellent. The inventors have found that a pressure-sensitive adhesive composition can be obtained, and completed the present invention. That is, according to the present invention, acrylic acid n-
Contains 10 to 99.9% by weight of octyl and 0.1 to 10% by weight of a copolymerizable vinyl monomer containing active hydrogen and 0 to 89.9% by weight of a copolymerizable vinyl monomer containing no active hydrogen. A pressure sensitive adhesive composition comprising a copolymer is provided. Further, according to the present invention, there is provided a pressure-sensitive adhesive product obtained by applying and drying the pressure-sensitive adhesive composition on a substrate.

The present invention uses n-octyl acrylate as the tacky vinyl monomer. 2-Ethylhexyl acrylate, which is generally used as a conventional tacky vinyl monomer, does not have a higher degree of polymerization or has a non-uniform co-polymerization coefficient when polymerized with other copolymerizable monomers due to the polymerizability. They tended to be coalesced, which was a factor that reduced heat resistance and removability. This has a glass transition point of 2 to 2 when the copolymer is measured by DSC (differential scanning calorimeter).
It can be presumed that the copolymer is heterogeneous by confirming at three places. When iso-octyl acrylate is copolymerized with another copolymerizable vinyl monomer, it has higher polymerizability than 2-ethylhexyl acrylate and tends to have a higher degree of polymerization or a uniform copolymer. Since its glass transition point is lower than that of the copolymer obtained by using 2-ethylhexyl acrylate, the heat resistance and the removability after heating tended to deteriorate. On the other hand, acrylic acid n-
Octyl has a polymerizable and glass transition point of acrylic acid is
It was considered to be similar to o-octyl, and when copolymerized with another copolymerizable vinyl monomer, the resulting copolymer also exhibits similar performance. However, the copolymer obtained by using n-octyl acrylate has better heat resistance and removability after heating than the copolymer obtained by using 2-ethylhexyl acrylate and iso-octyl acrylate. It has been found to show performance. That is, by using a copolymer using n-octyl acrylate as a main monomer, a pressure-sensitive adhesive composition having excellent initial adhesiveness, heat resistance and removability after heating can be obtained. It was found. The reason why this composition exhibits excellent heat resistance is considered to be due to the structure of the copolymer. That is, the gel fraction after crosslinking of the copolymer using n-octyl acrylate is higher than that of the copolymer using 2-ethylhexyl acrylate or iso-octyl acrylate after crosslinking. On the level. From this, it is considered that the cross-linking density of the copolymer using n-octyl acrylate is higher than that of the copolymer using other monomers, and thus shows good heat resistance and the like.

The copolymer used in the pressure-sensitive adhesive composition of the present invention (hereinafter, also simply referred to as a composition) must contain a copolymerizable vinyl monomer containing n-octyl acrylate and active hydrogen as polymerization components. It is a copolymer containing a copolymerizable vinyl monomer which is contained as a component and does not contain active hydrogen as necessary. The weight average molecular weight of this copolymer is in the range of 20,000 to 5,000,000, preferably 100,000 to 3,000,000. In this copolymer, the content ratio of n-octyl acrylate is 10 to 99.9% by weight, preferably 20.
˜99.9% by weight. When the content ratio of n-octyl acrylate is lower than the above range, the tackiness of the copolymer is reduced, and it becomes difficult to obtain a composition having excellent initial adhesiveness, which is not preferable. A copolymer having a content of n-octyl acrylate of 10 to 99.9% by weight, particularly 20 to 99.9% by weight, has excellent initial adhesiveness and heat resistance, and excellent removability after heating. It is possible to obtain a pressure sensitive adhesive composition. Generally, when a pressure-sensitive adhesive composition is heated, its adhesive force increases and it becomes difficult to peel again. However, the content ratio of n-octyl acrylate is set to 1 above.
By maintaining the content in the range of 0 to 99.9% by weight, particularly 20 to 99.9% by weight, a pressure-sensitive adhesive composition having removability equivalent to that before the heating is obtained even after the heating. Obtainable.

The content of the copolymerizable vinyl monomer containing active hydrogen is 0.1 to 10% by weight, preferably 0.1% by weight.
It is 5 to 5% by weight. When the content ratio of this monomer is higher than the above range, the copolymer becomes hard and causes problems such as a decrease in initial adhesiveness. On the other hand, when it is lower than the above range, the copolymer in the case of using a cross-linking agent is used. The crosslink density is lowered, and the heat resistance is lowered.

The content of the copolymerizable vinyl monomer containing no active hydrogen is 0 to 89.9% by weight, preferably 0.
~ 80% by weight. When the content of the copolymerizable vinyl monomer exceeds the above range, the adhesive strength after heating is increased, which causes a problem that the adhesive tape is difficult to peel off.

In the copolymerizable vinyl monomer containing active hydrogen used in the present invention, the active hydrogen includes hydrogen in a hydroxyl group, a carboxyl group, an amino group and the like, and preferably a hydrogen in the hydroxyl group or the carboxyl group. Is. Examples of such a monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, and itaconic acid; 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and the like. Unsaturated alcohol etc. are mentioned.

As the copolymerizable vinyl monomer containing no active hydrogen, various conventionally known vinyl monomers other than the above-mentioned monomers can be used. Examples of such vinyl monomers include alkyl acrylates other than n-octyl acrylate, such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, iso-octyl acrylate, isononyl acrylate, In addition to lauryl acrylate, stearyl acrylate, etc., methyl methacrylate, ethyl methacrylate,
Alkyl methacrylate such as octyl methacrylate, lauryl methacrylate and stearyl methacrylate;
Vinyl methyl ether, vinyl ethyl ether, vinyl inpropyl ether, vinyl n-propyl ether,
Alkyl vinyl ethers such as vinyl isobutyl ether, vinyl n-amyl ether, vinyl 2-ethylhexyl ether and vinyl n-octadecyl ether; alkyl vinyl esters such as vinyl acetate and vinyl propionate; styrene, vinyltoluene, acrylonitrile, acrylamide, methacryl Examples include ronitrile, methacrylamide, methyl vinyl ketone, allyl chloride and the like. The carbon number of the alkyl group in the acrylic acid alkyl ester, the methacrylic acid alkyl ester, the alkyl vinyl ether and the like is not particularly limited, but generally the carbon number is 1 to 22, preferably 1 to 18, and more preferably 1 to Twelve.

The above-mentioned copolymer can be obtained by polymerizing each monomer component in the presence of a radical polymerization initiator by a conventionally known method. The polymerization in this case can be carried out by any polymerization method such as bulk polymerization, suspension polymerization, solution polymerization and emulsion polymerization. For example, when carrying out the polymerization by a solution polymerization method, the monomer mixture is dissolved in an organic solvent, for example, ethyl acetate or toluene alone or in a mixture, and azobisisobutyronitrile or benzoyl peroxide is added as a polymerization initiator. By heating to 50 to 80 ° C. under an inert gas atmosphere, the copolymer can be obtained in 3 to 15 hours.

The pressure-sensitive adhesive composition of the present invention comprises a solution or dispersion (emulsion) of the above copolymer. As the organic solvent for obtaining the copolymer solution, any solvent can be used as long as it can dissolve the copolymer. Examples of such an organic solvent include fatty acid esters such as ethyl acetate, propyl acetate and butyl acetate; aromatic hydrocarbons such as benzene, toluene and xylene; halogenated aromatic hydrocarbons such as chlorobenzene and chlorotoluene; methyl ethyl ketone, Examples include ketone compounds such as methyl isobutyl ketone. The copolymer concentration in the solution is 10 to 80% by weight, preferably 20 to 60% by weight. As the solvent for obtaining the copolymer dispersion, a solvent that does not dissolve the copolymer, such as water or an aqueous solution, can be mentioned. The copolymer concentration in the dispersion is 10
-80% by weight, preferably 20-70% by weight.

A cross-linking agent is added to the composition of the present invention, if necessary. This cross-linking agent cross-links the copolymer to increase its cohesiveness and improve the heat resistance and removability of the composition. As the cross-linking agent, any one may be used so long as it can react with active hydrogen in the copolymer to cross-link the copolymer, and various conventionally known ones are used.
Moreover, a suitable solvent can be used if necessary.
As such a thing, the following can be mentioned, for example.

(1) Polyisocyanate compound Tolylene diisocyanate (3 mol) and trimethylolpropane (1 mol) adduct, hexamethylene diisocyanate (3 mol) and trimethylolpropane (1 mol) adduct, isophorone diisocyanate ( 3 mol)
And an addition product of trimethylolpropane (1 mol), an addition product of xylene diisocyanate (3 mol) and trimethylolpropane (1 mol), and the like. This polyisocyanate compound reacts with active hydrogen in the copolymer through the isocyanate group to crosslink the copolymer. (2) Polyepoxy compound Polyglycidyl ether compound such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerol polyglycidyl ether, sorbitol polyglycidyl ether; polyglycidyl ester such as phthalic acid diglycidyl ester, adipic acid diglycidyl ester Compounds: polyglycidyl amine compounds such as diglycidyl aniline, diglycidyl orthotoluidine, and tetraglycidyl ethylenediamine.
The polyepoxy compound reacts with active hydrogen in the copolymer through the epoxy group to crosslink the copolymer. (3) Polymethylol melamine Trimethylol melamine, hexamethylol melamine,
Methylated hexamethylolmelamine, ethylated trimethylolmelamine, butylated trimethylolmelamine, etc.
This polymethylolmelamine reacts with active hydrogen in the copolymer through the methylol group to crosslink the copolymer. (4) Metal compound di-iso-propoxy bis (acetylacetone) titanate, ethyl acetoacetate aluminum diisopropylate, aluminum isopropylate and the like. This metal compound reacts with active hydrogen in the copolymer through the metal ion to crosslink the copolymer.

The proportion of the cross-linking agent used for cross-linking the copolymer to give a cross-linked copolymer has a gel fraction of the cross-linked copolymer of 10 to 90%, preferably 40 to 80.
It is a ratio such that it becomes%. When the gel fraction of the cross-linked copolymer is lower than the above range, the heat resistance and removability of the composition are not sufficiently improved, while when it is higher than the above range, the initial adhesiveness is deteriorated. The reaction between the copolymer and the cross-linking agent is 0 to 150 ° C., preferably 20 to 40 ° C.
Can be performed at temperatures of. In this case, a suitable catalyst can be used in the crosslinking reaction, if necessary.

The composition of the present invention can be coated on a substrate and dried to give a pressure-sensitive adhesive product such as a pressure-sensitive adhesive sheet or pressure-sensitive adhesive tape. In this case, the composition can be applied to one side or both sides of the substrate. As the substrate, a conventionally known substrate generally used in the pressure sensitive adhesive field can be used. As such a substrate, for example,
Examples thereof include films and sheets of synthetic resins such as polyolefin resins, polyester resins, vinyl chloride resins, Japanese paper, and non-woven fabrics. The thickness of the pressure sensitive adhesive layer on the substrate is 0.
It is 5 to 100 μm, preferably 1 to 40 μm.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Polymerization method A flask equipped with a stirrer was charged with 26.67 parts by weight of ethyl acetate and azobisisobutyronitrile (A) as a polymerization initiator.
IBN) 0.06 parts by weight, n-octyl acrylate 9.
84 parts by weight, n-butyl acrylate 29.52 parts by weight,
2-Hydroxyethyl methacrylate 0.16 parts by weight and acrylic acid 0.48 parts by weight were charged, the temperature was raised with stirring, and the reaction was performed at 78 ° C. for 2 hours. Furthermore, ethyl acetate 1.
A solution prepared by dissolving 0.02 part by weight of AIBN in 00 parts by weight was charged at 2 hours and 4 hours of the reaction, and the mixture was heated at 78 ° C. for 6 hours.
The reaction was carried out for a time to obtain a copolymer. Toluene was added to the reaction solution as a diluting solvent to give a resin content of 40% by weight and a viscosity of 6500.
A cps resin solution (copolymer solution) was obtained. (2) Method for preparing adhesive tape 75% by weight of ethyl acetate, an adduct of tolylene diisocyanate (3 mol) and trimethylolpropane (1 mol) as a cross-linking agent, in 100 parts by weight of the resin solution (40% by weight solids solution) Add 2.0 parts by weight of the solution and apply it to a polyester film (thickness: 25 μm), and then apply 2
After being dried for a minute, an adhesive tape having a coating thickness of 25 μm (dry) was manufactured.

Examples 2 to 4 and Comparative Examples 1 to 9 By the same polymerization method as in Example 1, various copolymers were prepared by varying the compounding ratio of n-octyl acrylate and n-butyl acrylate. did. Next, various adhesive tapes were prepared by the same method as the adhesive tape preparation method of Example 1. For the purpose of comparison, the same polymerization method as in Example 1 was used.
Various copolymers were prepared by using monomers having different alkyl groups of ₈ acrylic acid alkyl esters. Next, an adhesive tape was produced by the same method as the adhesive tape production method of Example 1. Table 1 collectively shows the compounding ratio of the monomers in the copolymerization reaction and the solid content and viscosity of the obtained resin solution.

[0020]

[Table 1] n-OA: n-octyl acrylate i-OA: iso-octyl acrylate 2EHA: 2-ethylhexyl acrylate n-BA: n-butyl acrylate AA: acrylic acid 2HEMA: 2-hydroxyethyl methacrylate

Reference Example 1 With respect to the pressure-sensitive adhesive tapes obtained in Examples 1 to 4 and Comparative Examples 1 to 9, according to the methods described below, initial adhesiveness, heat resistance, removability, gel fraction and pressure-sensitive adhesive tape were obtained. The glass transition point was measured.

Initial Adhesion Property According to JIS Z 0237, the ball tack of the adhesive tape at 23 ° C. × 65% RH is measured. That is, place an adhesive tape (width 50 mm, length 150 mm or more) on an inclined surface of 30 degrees with the adhesive coated surface facing up, and 100 mm
The range of 100 mm from the lower end of the runway is used as the measurement unit.
A clean steel ball of 2/32 to 32/32 inch rolls along the runway, and is represented by a numerical value 32 times the maximum diameter of the steel ball that has stopped sticking for 5 seconds within the range of the measuring section.

Width of the heat-resistant adhesive tape is 25 m under the condition of 23 ° C. × 65% RH
A stainless steel plate (SUS-304) obtained by cleaning a test piece cut into a length of 120 mm and a length of 100 mm was cut into a size of 300 mm (mm / m) using a 2 kg rubber roller.
in) at 3 speeds and crimping, leaving for 1 hour, then 8
10 at 90 ° to the length of the adhesive tape at 0 ° C
A load of 0 g is applied, and the dropping time or the length of deviation after 1 hour is measured.

The releasable pressure-sensitive adhesive tape has a width of 25 m under the condition of 23 ° C. and 65% RH.
The test piece cut into m and 120 mm in length was placed on a stainless steel plate (SUS-304) using a 2 kg rubber roller and
The tape is reciprocated 3 times at a speed of 0 (mm / min), and after 1 hour, a 180 ° peeling force is measured at a tensile speed of 300 mm / min using a tensile tester defined in JIS B7721. This peeling force is the adhesive force in the normal state. In addition, one piece of the adhesive tape pressure-bonded to the stainless plate as described above
After heating at 30 ℃ for 1 hour, under the condition of 23 ℃ × 65% RH, using a tensile tester specified in JIS B 7721, at a tensile speed of 300 mm / min, 180 ° to the length direction of the adhesive tape. The peel force in the direction is measured. This peeling force is the adhesive force after heating. Furthermore, the occurrence of cloudiness due to the pressure sensitive adhesive remaining on the stainless steel plate after peeling the heated adhesive tape from the stainless steel plate was visually evaluated according to the following criteria. ○: No cloudiness occurred △: Some cloudiness occurred ×: Cloudiness occurred

The pressure-sensitive adhesive on the gel fraction pressure-sensitive adhesive tape is scraped off, and tetrahydrofuran (THF) is used as a solvent for extraction with Soxhlet for 6 hours. The filtration residue is dried under reduced pressure to obtain a gel component.
The gel fraction is calculated by the following formula from the weight ratio of the scraped pressure sensitive adhesive and the gel fraction.

Measurement of glass transition point The pressure-sensitive adhesive on the adhesive tape is scraped off and measured with a differential scanning calorimeter (DSC-200, manufactured by Seiko Electronics Co., Ltd.) under a temperature rising condition of 10 ° C./min. .

Test results The test results are shown in Table 2.

[0028]

[Table 2]

[0029]

As described above, the pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition of the present invention has excellent initial adhesiveness, heat resistance and removability after heating. The initial adhesiveness and heat resistance are compatible with each other.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-171120 (JP, A) JP-A-5-247420 (JP, A) JP-A-6-116536 (JP, A) JP-A-61- 261382 (JP, A) JP 61-261383 (JP, A) JP 5-59338 (JP, A) JP 6-128544 (JP, A) JP 6-1957 (JP, A) JP-A-6-54604 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09J 4/00-201/10

Claims (3)

(57) [Claims] 1. N-octyl acrylate 10-99.9.
Sensitivity of a copolymer containing 0.1 to 10% by weight of a copolymerizable vinyl monomer containing 1% by weight and active hydrogen and 0 to 89.9% by weight of a copolymerizable vinyl monomer containing no active hydrogen. Pressure-sensitive adhesive composition. 2. The pressure-sensitive adhesive composition according to claim 1, which contains a crosslinking agent containing two or more functional groups that react with active hydrogen. 3. A pressure-sensitive adhesive product obtained by applying and drying the pressure-sensitive adhesive composition according to claim 1 or 2 on a substrate.