JP2000265138A - Pressure sensitive adhesive composition and its adhesive sheets - Google Patents

Abstract

(57) [Problem] To provide a pressure-sensitive adhesive composition having excellent adhesiveness to a polyolefin-based adherend, particularly excellent curved surface adhesiveness, as an acrylic pressure-sensitive adhesive. SOLUTION: A monomer obtained by adding 0.5 to 10 parts by weight of a carboxyl group-containing unsaturated monomer to 100 parts by weight of an alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms. The copolymer of the mixture had an interfacial adhesion of 1.2 in a scratch test against polypropylene.
A pressure-sensitive adhesive composition comprising a tackifier resin of 7 kg / cm ² or more.

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 having excellent adhesion to a polyolefin-based adherend, particularly to a curved surface, and adhesive sheets thereof.

[0002]

2. Description of the Related Art In recent years, the range of use of pressure-sensitive adhesives has been widened, and the required characteristics and functions have been advanced, and the materials to be adhered have been diversified. For example,
For plastic adherends, it is easy to adhere until several years ago.
Polar adherends such as BS resin and acrylic resin were the mainstream, but now non-polar adherends such as polypropylene, which are more difficult to adhere to, are being used, and the automotive industry This tendency is particularly strong in the office automation and home appliance industries.

For such a polyolefin-based adherend, as an acrylic pressure-sensitive adhesive, for example, Japanese Unexamined Patent Publication (Kokai) No. 4-110376 discloses a method in which a specific acrylic polymer is mixed with an unsaturated rosin ester resin. Japanese Unexamined Patent Publication No. Hei 4-202391 discloses that a specific acrylic polymer is mixed with an alkylphenol resin, and Japanese Unexamined Patent Publication No. Hei 7-102229 discloses three types of acrylic polymers having different softening points. It has been proposed to mix a tackifying resin, and it is disclosed that these can improve the adhesion to a polyolefin-based adherend.

[0004]

However, the combination of the above-mentioned known acrylic polymer and tackifying resin cannot improve the adhesiveness to the polyolefin-based adherend. When the adhesive treatment is performed by bending to a polyolefin-based adherend, the adhesiveness to the adherend is poor, and peeling or falling off occurs in a short time. Atsuta.

In view of such circumstances, the present invention provides a pressure-sensitive adhesive composition having excellent adhesiveness to a polyolefin-based adherend, particularly excellent curved surface adhesiveness, and an adhesive sheet thereof as an acrylic pressure-sensitive adhesive. The purpose is to provide products.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above-mentioned object, and as a result, regarding the tackifying resin to be mixed with the acrylic polymer, the adhesiveness of the resin itself to polyolefin has been reduced. Focused attention, when a tackifying resin that shows a specific interfacial adhesion in a scratch test for polypropylene is blended with an acrylic polymer, a highly reliable pressure-sensitive adhesive composition with excellent adhesion to polyolefins, especially for curved surfaces And obtained the present invention.

That is, according to the present invention, 0.5 to 10 parts by weight of a carboxyl group-containing unsaturated monomer is added to 100 parts by weight of an alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms. A pressure-sensitive adhesive composition comprising a copolymer of a monomer mixture and a tackifier resin having an interfacial adhesion of 1.27 kg / cm ² or more in a scratch test for polypropylene. (1) and an adhesive sheet (claim 4) having an adhesive layer comprising the pressure-sensitive adhesive composition having the above structure on a support.

In the present invention, the alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms is preferably a (meth) acrylic acid having an alkyl group having 2 to 5 carbon atoms. Acid alkyl ester 20-90% by weight
Pressure-sensitive adhesive composition (claim 2), which is a mixture of an alkyl (meth) acrylate having an alkyl group having a carbon number in the range of 6 to 12 and 80 to 10% by weight (claim 2); In the test, the pressure-sensitive adhesive composition having the above-mentioned constitution in which the tackifier resin having an interfacial adhesion of 1.27 kg / cm ² or more is 5 to 60 parts by weight per 100 parts by weight of the copolymer (Claim 3) Can be provided.

The above-mentioned "scratch test for polypropylene" uses a scratch test, which is known as a method for evaluating the adhesion of a coating film, as an evaluation of the adhesion of the tackifier resin itself to polypropylene.
First, a 20% by weight toluene solution of a tackifying resin is applied on a polypropylene adherend by a spin coater at a rotation speed of 5,000 rpm for 20 seconds.
The sample is air-dried for at least one day to prepare a test piece having a thickness of 0.6 μm after drying. Next,
The test piece was set on a Shimadzu Scratch Tester SST-101 manufactured by Shimadzu Corporation.
Load speed 0.5 μm / s, amplitude 10 μm, feed speed 20
A scratch test was performed under the condition of μm / sec, and the strength (Kg / cm ² ) when the coating film made of the tackifying resin was peeled from the polypropylene adherend was read. And

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic polymer used in the present invention is obtained by adding a carboxyl group-containing unsaturated monomer to 100 parts by weight of a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 12 carbon atoms. It is a copolymer of a monomer mixture obtained by adding 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight. Examples of the carboxyl group-containing unsaturated monomer include (meth) acrylic acid, itaconic acid, and the like. By using these in the above ratio, a favorable result can be obtained in improving the adhesive properties.

The alkyl (meth) acrylate having an alkyl group having a carbon number in the range of 2 to 12 used as the main monomer includes ethyl (meth) acrylate and n-propyl (meth) acrylate. Alkyl (meth) acrylates having an alkyl group in the range of 2 to 5, such as n-butyl (meth) acrylate and t-butyl (meth) acrylate, and 2-ethylhexyl (meth) There are alkyl (meth) acrylates in which the alkyl group has 6 to 12 carbon atoms, such as acrylate, isooctyl (meth) acrylate, and isononyl (meth) acrylate. Species or two or more species are used.

Among these main monomers, particularly preferred are one or more of alkyl (meth) acrylates in which the alkyl group has 2 to 5 carbon atoms in the range of 20 to 90. %, Preferably 30 to 80% by weight, and 80 to 10% by weight, preferably 70 to 80% by weight of one or more alkyl (meth) acrylates having 6 to 12 carbon atoms in the alkyl group. -20% by weight. When an acrylic polymer obtained by using such a mixture is used in combination with a specific tackifier resin which is a feature of the present invention, it has an effect of improving the adhesiveness to polyolefin, especially the curved surface adhesiveness. Therefore, the present invention has an effect that the original adhesiveness can be better exhibited on a polar adherend such as a plastic plate or a metal plate such as an ABS resin or an acrylic resin.

In addition to the main monomer and the carboxyl group-containing unsaturated monomer, 2-hydroxyethyl (meth) acrylic acid is further used as a modifying monomer.
Hydroxy-containing unsaturated monomers such as tert-, 2-hydroxypropyl (meth) acrylate and hydroxyhexyl (meth) acrylate; nitrogen-containing unsaturated monomers such as (meth) acrylamide and acryloylmorpholin; methyl (Meth) acrylate, vinyl acetate, etc., and (meth)
A monomer that gives a polymer having a high glass transition point, such as acrylonitrile, styrene, vinylidene chloride and vinyl propionate, may be used in combination. In these modifying monomers, the alkyl group as the main monomer has 2 to 2 carbon atoms.
The ratio is usually preferably 50 parts by weight or less to 100 parts by weight of the alkyl (meth) acrylate in the range of 12.

In the present invention, such a monomer mixture is copolymerized in the presence of an appropriate radical polymerization initiator by known techniques such as solution polymerization, bulk polymerization, and emulsion polymerization. An acrylic polymer comprising a copolymer of the above monomer mixture is produced. The molecular weight of the polymer is not particularly limited, but generally the weight average molecular weight is preferably in the range of 100,000 to 1.5 million. Problems easily occur.

The tackifying resin used in the present invention has an interfacial adhesion of 1.27 kg / cm ² or more (usually up to 1.91 kg / cm ² ) in a scratch test on polypropylene.
The type is not limited as long as it shows the above-mentioned interfacial adhesion. Typical examples include rosin and derivatives thereof, and the latter derivatives include partially disproportionated or disproportionated rosin, hydrogenated rosin, maleic acid-modified rosin, polymerized rosin, metal salts thereof, and diethylene glycol. And esters with glycerin, pentaerythritol and the like. Among these, polymerized rosin esters are most preferred. In addition, α-pinene and β
Terpenes such as -pinene polymers, diterpene polymers, α-pinene-phenol copolymers and derivatives thereof, and coumarone-indene resins and derivatives thereof can also be used. It is preferable that these tackifying resins have a softening point of 80C or more, usually 100 to 170C.

In the present invention, the specific tackifying resin is an acrylic polymer 100 comprising the above-mentioned copolymer.
Usually 5 to 60 parts by weight, preferably 10 to 10 parts by weight
Used in a proportion of 50 parts by weight. If this amount is too small, good results cannot be obtained in the effect of the present invention, that is, improvement in adhesiveness to polyolefin, particularly in the case of curved surface adhesiveness, and when too large, problems tend to occur in properties such as holding power. .

In the present invention, if necessary, a tackifier resin other than the above or a known plasticizer may be used in combination with the above specific tackifier resin. However, the amount of the other tackifying resin or plasticizer used is not more than 50% by weight based on the total amount of the above specific tackifying resin so as not to impair the adhesiveness to polyolefin, particularly the curved surface adhesiveness. It is preferred that

The pressure-sensitive adhesive composition of the present invention contains the above-mentioned acrylic polymer and tackifying resin as essential components, and usually contains a crosslinking agent for improving cohesion. As the crosslinking agent, any conventionally known crosslinking agents such as an isocyanate crosslinking agent, a melamine crosslinking agent, an epoxy crosslinking agent, and a peroxide crosslinking agent can be used. The amount used is usually preferably 20 parts by weight or less based on 100 parts by weight of the acrylic polymer. Instead of using such a cross-linking agent, or after using the cross-linking agent, the cross-linking treatment can be performed by irradiation with an electron beam or ultraviolet rays.

The pressure-sensitive adhesive composition of the present invention may further contain, if necessary, conventionally known additives such as a plasticizer, a softener, a filler, a pigment and a dye. These additives may be used in a usual amount applied to a general pressure-sensitive adhesive.

In the present invention, such a pressure-sensitive adhesive composition is coated on a support, dried, and subjected to the above-mentioned crosslinking treatment, so that the support has an adhesive layer on one surface or both surfaces. Adhesive sheets such as tape and sheet.
As the support, conventionally known materials such as plastic film, paper, nonwoven fabric, and metal foil are used.

[0021]

Next, an embodiment of the present invention will be described in more detail. In the following, “parts” means “parts by weight”.

Example 1 A copolymer 1 having a weight average molecular weight of 450,000 obtained by solution polymerization of a monomer mixture comprising 70 parts of n-butyl acrylate, 30 parts of 2-ethylhexyl acrylate and 3 parts of acrylic acid.
In 00 parts, as a tackifying resin, polymerized rosin pentaerythritol ester having a softening point of 125 ° C. [Arakawa Chemical Co., Ltd.]
"Pencel D125", manufactured by Scratch Test for polypropylene, has an interfacial adhesion of 1.37 kg / cm ² ].
30 parts and 0.04 part of an epoxy-based crosslinking agent were added and uniformly stirred and mixed to prepare a solution of the pressure-sensitive adhesive composition. Next, the solution of the pressure-sensitive adhesive composition was applied to a release paper, and dried at 100 ° C. for 3 minutes to form an adhesive layer having a thickness of 75 μm. This adhesive layer was transferred to both sides of the nonwoven fabric to produce a double-sided adhesive sheet.

Example 2 A copolymer having a weight average molecular weight of 550,000 obtained by solution polymerization of a monomer mixture comprising 40 parts of n-butyl acrylate, 60 parts of 2-ethylhexyl acrylate and 3 parts of acrylic acid.
In 00 parts, as a tackifying resin, a polymerized rosin pentaerythritol ester having a softening point of 160 ° C. [Arakawa Chemical Co., Ltd.]
"Pencel D160" has a surface adhesion of 1.53 kg / cm ² in a scratch test on polypropylene].
30 parts and 0.035 part of an epoxy-based crosslinking agent were added and uniformly stirred and mixed to prepare a solution of the pressure-sensitive adhesive composition.
Using this pressure-sensitive adhesive composition solution, the following Example 1 was used.
In the same manner as in the above, a double-sided adhesive sheet was produced.

Example 3 The copolymer 10 obtained in Example 1 and having a weight average molecular weight of 450,000
In 0 parts, as a tackifying resin, polymerized rosin pentaerythritol ester having a softening point of 125 ° C. [“Pencel D125” manufactured by Arakawa Chemical Co., Ltd .; interfacial adhesion in a scratch test to polypropylene: 1.37 kg / cm ² ] 3
0 parts, terpene-phenol having a softening point of 130 ° C. [“YS Polystar T130” manufactured by Yashara Chemical Co., Ltd.
In a scratch test for polypropylene, 20 parts of an interfacial adhesive force of 1.01 kg / cm ² ] and 0.045 parts of an epoxy-based crosslinking agent were added, and the mixture was uniformly stirred and mixed to prepare a solution of the pressure-sensitive adhesive composition. Using this solution of the pressure-sensitive adhesive composition, a double-sided adhesive sheet was prepared in the same manner as in Example 1 below.

Example 4 The copolymer 10 obtained in Example 1 and having a weight average molecular weight of 450,000
In 0 parts, as a tackifying resin, polymerized rosin pentaerythritol ester having a softening point of 125 ° C. [“Pencel D125” manufactured by Arakawa Chemical Co., Ltd .; interfacial adhesion in a scratch test to polypropylene: 1.37 kg / cm ² ] 3
0 parts, Coumarone-indene having a softening point of 120 ° C. [“Esculon V120” manufactured by Nippon Steel Chemical Co., Ltd .;
7 kg / cm ² ] and 0.05 part of an epoxy-based crosslinking agent were added and uniformly stirred and mixed to prepare a solution of the pressure-sensitive adhesive composition. Using this solution of the pressure-sensitive adhesive composition, a double-sided adhesive sheet was prepared in the same manner as in Example 1 below.

Example 5 100 parts of n-butyl acrylate, 3 parts of acrylic acid, 5 parts of vinyl acetate, 0.1 of 2-hydroxyethyl acrylate
Of a monomer mixture consisting of 100 parts by weight of a monomer mixture having a weight average molecular weight of 500,000, and polymerized rosin pentaerythritol ester having a softening point of 128 ° C. as a tackifier resin [Rika Chemical Co., Ltd.] "Pentalin C" manufactured by
J ", 30 parts of an interfacial adhesive force in a scratch test with polypropylene of 1.59 kg / cm ² ], 5 parts of hydrogenated rosin methyl ester [" Harolin D "manufactured by Rika Hakires Co., Ltd.] as a plasticizer, Isocyanate crosslinking agent 2
The resulting mixture was uniformly stirred and mixed to prepare a solution of the pressure-sensitive adhesive composition. Using this solution, a double-sided adhesive sheet was prepared in the same manner as in Example 1 below.

Comparative Example 1 100 parts of a copolymer having a weight average molecular weight of 500,000 obtained by solution polymerization of a monomer mixture consisting of 100 parts of n-butyl acrylate, 3 parts of acrylic acid, and 5 parts of vinyl acetate was added to: Terpene phenol having a softening point of 130 ° C. [“YS Polystar T130” manufactured by Yasuhara Chemical Co., Ltd .;
8 kg / cm ² ] 30 parts, Coumarone-indene having a softening point of 120 ° C. [Esculon V12 manufactured by Nippon Steel Chemical Co., Ltd.
0 ", in a scratch test on polypropylene, the interfacial adhesion was 0.57 kg / cm ² ], 20 parts, isocyanate
G of a cross-linking agent were added, and the mixture was stirred and mixed uniformly to prepare a solution of the pressure-sensitive adhesive composition. Using this solution of the pressure-sensitive adhesive composition, a double-sided adhesive sheet was prepared in the same manner as in Example 1 below.

Comparative Example 2 A monomer mixture consisting of 100 parts of n-butyl acrylate and 1 part of acrylic acid was subjected to solution polymerization to give a weight average molecular weight of 5
A terpene phenol having a softening point of 130 ° C. (“YS Polyster T130” manufactured by Yashara Chemical Co., Ltd., an adhesive force of 1.08 kg / cm ² in a scratch test with polypropylene) was added to 100 parts of 100,000 copolymers. ] 50
And 0.03 part of an epoxy-based crosslinking agent, and uniformly stirred and mixed to prepare a solution of the pressure-sensitive adhesive composition. Using this solution of the pressure-sensitive adhesive composition, a double-sided adhesive sheet was prepared in the same manner as in Example 1 below.

Comparative Example 3 Copolymer 10 having a weight average molecular weight of 450,000 obtained in Example 1
In 0 parts, as a tackifying resin, a terpene phenol having a softening point of 130 ° C. [“YS Polystar T130” manufactured by Yashara Chemical Co., Ltd .; an interfacial adhesion of 1.08 kg / cm ² in a scratch test against polypropylene] 30
And 0.04 part of an epoxy-based crosslinking agent, and uniformly stirred and mixed to prepare a solution of the pressure-sensitive adhesive composition. Using this solution, a double-sided adhesive sheet was formed in the same manner as in Example 1 below.
Was made.

Each of the double-sided adhesive sheets of Examples 1 to 5 and Comparative Examples 1 to 3 was subjected to an adhesion test, a curved surface adhesion test, and a retention test by the following methods. These results were as shown in Table 1.

<Adhesion Test> A 25 μm-thick polyethylene terephthalate film was adhered to one side of a double-sided adhesive sheet, backed, cut into a width of 20 mm, and used as a test piece. After laminating to the adherend in one round trip, leaving it at 23 ° C for 30 minutes, pulling speed 300mm
At 180 ° / min, the 180 ° peel adhesion of the test piece was measured. The adherend used SUS304 and a polypropylene plate.

<Curved surface adhesion test> 90 mm × 10 in size
A single side of the double-sided adhesive sheet was attached to an A1 plate having a thickness of 0.4 mm and a thickness of 0.4 mm to form a test piece, which was bent and attached to a polypropylene cylinder having a diameter of 50 mm at 70 ° C. for 2 hours. The lifting (mm) of the test piece after that was measured.

<Holding force test> A 25 μm-thick polyethylene terephthalate film was adhered to one side of a double-sided adhesive sheet, backed and cut to a width of 10 mm to obtain a test piece. 10mm × 20mm
, The whole was hung down, and the test piece was left at a temperature of 80 ° C. for 1 hour with a load of 500 g applied to the lower end of the test piece, and the displacement distance (mm) of the test piece was measured.

[0034]

As is evident from the results in Table 1 above, the double-sided adhesive sheets of Examples 1 to 5 using the pressure-sensitive adhesive composition in which the specific tackifying resin was blended with the acrylic polymer were as follows: It can be seen that the adhesiveness to SUS304 and further to polypropylene are excellent, and particularly the curved surface adhesiveness to polypropylene can be sufficiently satisfied. On the other hand, in each of the double-sided adhesive sheets of Comparative Examples 1 to 3 using the pressure-sensitive adhesive composition not containing the specific tackifying resin, the adhesiveness to polypropylene, particularly the curved adhesiveness to polypropylene, Cannot be satisfied.

[0036]

As described above, in the present invention, by using a tackifying resin having an interfacial adhesion of 1.27 kg / cm ² or more in a scratch test for polypropylene, the adhesiveness to a polar adherend is improved. Needless to say, it is possible to provide a pressure-sensitive adhesive composition having excellent adhesiveness to polypropylene and other polyolefin-based nonpolar adherends, particularly excellent curved surface adhesiveness, and adhesive sheets thereof. In addition, in the present invention, when the tackifier resin is blended with the acrylic polymer, the interfacial adhesion of the tackifier resin itself to polypropylene is measured in advance by the above-described scratch test, and this is used as an index, and the polyolefin or the like is used as an index. Since the most effective tackifying resin can be easily selected according to the type of the adherend, it is possible to provide a pressure-sensitive adhesive composition having higher reliability than before and a bonding sheet thereof. .

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kazuyuki Yakura, 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Naoki Okochi, 1-2-1, Shimohozumi, Ibaraki-shi, Osaka F-term in Nitto Denko Corporation (reference) 4J004 AA04 AA10 AB01 CA01 CA08 CB01 CB02 CC02 EA05 4J040 BA202 DF041 DF051 DK012 DN072 EL012 GA03 GA05 GA07 GA12 GA13 GA17 GA22 JA09 JB09 KA26 LA01 LA06 LA08 MA11 MB10

Claims (4)

[Claims] 1. A monomer obtained by adding 0.5 to 10 parts by weight of a carboxyl group-containing unsaturated monomer to 100 parts by weight of an alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms. The copolymer of the body mixture had an interfacial adhesion of 1.2 in a scratch test against polypropylene.
A pressure-sensitive adhesive composition comprising a tackifier resin of 7 kg / cm ² or more. 2. An alkyl (meth) acrylate having an alkyl group having a carbon number of 2 to 12 and a (meth) acrylic acid alkyl ester having an alkyl group having a carbon number of 2 to 5 20 to 90. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the mixture is a mixture of 1 wt% and 80 to 10 wt% of a (meth) acrylic acid alkyl ester having an alkyl group having 6 to 12 carbon atoms. 3. 3. The method according to claim 1, wherein the tackifier resin having an interfacial adhesion of 1.27 kg / cm ² or more in a scratch test for polypropylene is 5 to 60 parts by weight per 100 parts by weight of the copolymer. Pressure-sensitive adhesive composition. 4. An adhesive sheet comprising an adhesive layer comprising the pressure-sensitive adhesive composition according to claim 1 on a support.