JPH07138544A - Pressure-sensitive acrylic adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title compsn. which has a stable cross-linkability and exhibits excellent adhesive properties, esp. resistance to peeling, in bonding low-polar adherends. CONSTITUTION:The title compsn. contains 100 pts.wt. acrylic copoymler obtd. by copolymerizing 99.5-90wt.% 2-18C alkyl (meth)acrylate with 0.5-10wt.% polymerizable unsatd. carboxylic acid, 5-40 pts.wt. pentaerythritol ester of polymerized rosin, and 0.01-5 pts.wt. aziridine compd. having at least two aziridine rinds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic pressure-sensitive adhesive composition suitable for use in adhesive processed products such as adhesive labels, adhesive tapes and adhesive sheets.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesives for pressure-sensitive adhesive products such as pressure-sensitive adhesive labels, pressure-sensitive adhesive tapes, pressure-sensitive adhesive sheets, etc. have mainly been acrylic pressure-sensitive adhesives containing acrylic copolymers, natural rubber, synthetic rubber, etc. A rubber-based pressure-sensitive adhesive containing as a main component is used.

The former acrylic pressure-sensitive adhesive is widely used because it has the advantage that the adhesive performance can be easily adjusted by selecting the monomer component of the acrylic copolymer.

However, ordinary acrylic pressure-sensitive adhesives do not have sufficient adhesive force to adherends having a low polarity surface such as polyethylene and polypropylene, and in order to deal with this, acrylic pressure-sensitive adhesives are used. A method of blending a tackifying resin with is generally used.

As an example of such an acrylic pressure-sensitive adhesive, 100 parts by weight of an acrylic copolymer, 2 to 50 parts by weight of pentaerythritol ester of polymerized rosin as a tackifying resin, and an isocyanate compound as a crosslinking agent are used. Is proposed (Japanese Patent Publication No. 5-60511), but in the case of this method, since an isocyanate compound is used as a crosslinking agent, it is affected by environmental conditions such as humidity. It is said that it takes a long time to crosslink, or the degree of crosslink itself lacks uniformity, and as a result, the adhesive properties of the pressure sensitive adhesive, such as holding power during heating and creep resistance, are insufficient or vary. There is a problem.

[0006]

In order to solve the above-mentioned conventional problems, the present invention has stable crosslinkability that is not affected by environmental conditions and productivity that the crosslinking reaction is terminated in a short time, and Acrylic pressure-sensitive adhesive composition that exhibits excellent adhesive properties to adherends, especially holding power and creep resistance when heated, and excellent adhesive properties to low-polar adherends, especially excellent peel resistance. The purpose is to provide things.

[0007]

The acrylic pressure-sensitive adhesive composition of the present invention comprises 99.5 to 90% by weight of a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 18 carbon atoms and a polymerizable non-polymerizable adhesive. Solid content 100 of acrylic copolymer obtained by copolymerizing with 0.5 to 10% by weight of saturated carboxylic acid
5 to 40 parts by weight of pentaerythritol ester of polymerized rosin and 0.01 to 0.5 parts by weight of an aziridine compound having two or more aziridine rings in one molecule are contained per part by weight. Therefore, the above object is achieved. In addition, in this invention, (meth) acryl shall mean acryl or methacryl.

The (meth) acrylic acid alkyl ester having 2 to 18 carbon atoms in the alkyl group used for the polymerization of the acrylic copolymer constituting the acrylic pressure-sensitive adhesive composition of the present invention includes (meth ) Acrylic acid ethyl ester, (meth) acrylic acid n-propyl ester, (meth) acrylic acid iso-propyl ester, (meth) acrylic acid n-butyl ester, (meth) acrylic acid n-
Octyl ester, (meth) acrylic acid 2-ethylhexyl ester, (meth) acrylic acid nonyl ester,
Examples thereof include (meth) acrylic acid dodecyl ester, and among them, acrylic acid ethyl ester, acrylic acid n-butyl ester, acrylic acid 2-ethylhexyl ester and the like are preferably used. When the number of carbon atoms of the alkyl group is outside the range of 2 to 18, the pressure-sensitive adhesive composition obtained is impaired in tackiness, which is not preferable.

Examples of the polymerizable unsaturated carboxylic acid used as a copolymerization component in the acrylic copolymer include (meth) acrylic acid and itaconic acid.

In the present invention, the copolymerization ratio of the above polymerizable unsaturated carboxylic acid needs to be in the range of 0.5 to 10% by weight, preferably 1 to 5% by weight. When the copolymerization ratio of the polymerizable unsaturated carboxylic acid is less than 0.5% by weight, the degree of crosslinking of the acrylic pressure-sensitive adhesive composition obtained does not increase, so that sufficient holding power and creep resistance are not expressed. On the contrary, when it exceeds 10% by weight, the initial adhesive strength of the obtained acrylic pressure-sensitive adhesive composition is lowered.

The acrylic pressure-sensitive adhesive composition of the present invention must contain a pentaerythritol ester of polymerized rosin as a tackifying resin.

The above-mentioned pentaerythritol ester of polymerized rosin is a tackifying resin containing a carboxyl group obtained by esterifying polymerized rosin obtained by polymerizing rosin to raise the melting point with pentaerythritol. Specific commercial products include commercial products. Name "Pencel D125", "Pencel D13
5 ”,“ Pencel D160 ”(above, manufactured by Arakawa Chemical Industry Co., Ltd.),“ Pentaline C ”(manufactured by Rika Hercules Co., Ltd.) and the like.

In the present invention, the content of the pentaerythritol ester of the polymerized rosin needs to be in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the solid content of the acrylic copolymer. If the content of the pentaerythritol ester of the polymerized rosin is less than 5 parts by weight based on 100 parts by weight of the solid content of the acrylic copolymer, the effect of adding the tackifying resin cannot be obtained, and if it exceeds 40 parts by weight, it is obtained. The initial adhesive strength and heat resistance of the acrylic pressure-sensitive adhesive composition are reduced.

The acrylic pressure-sensitive adhesive composition of the present invention needs to contain an aziridine compound having two or more aziridine rings in one molecule as a crosslinking agent.

Generally, an isocyanate compound is often used as a cross-linking agent for acrylic pressure-sensitive adhesives. However, an isocyanate compound non-selectively reacts with a hydroxyl group or a carboxyl group in an acrylic polymer, but since these reactions are easily affected by environmental conditions such as humidity, it takes a long time to crosslink. However, there is a drawback that the obtained pressure-sensitive adhesive has a large variation in adhesive properties. On the other hand, the aziridine-based compound having two or more aziridine rings in one molecule used in the present invention selectively and rapidly reacts with the carboxyl group in the acrylic copolymer, so that it can be used under environmental conditions such as humidity. Less affected,
There are advantages that the crosslinking proceeds stably in a short time and the adhesive properties of the obtained pressure-sensitive adhesive composition are also stabilized.

The aziridine compound is a compound having two or more aziridine rings in one molecule, and specifically, N, N'-diphenylmethane-4,4'-bis (1
-Aziridinecarboxamide), trimethylolpropane-tris-β-aziridinylpropionate, N,
Examples thereof include bifunctional or higher-functional aziridine compounds such as N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), but are not limited thereto.

In the present invention, the content of the aziridine compound must be in the range of 0.01 to 0.5 parts by weight based on 100 parts by weight of the solid content of the acrylic copolymer. If the content of the aziridine compound is less than 0.01 parts by weight based on 100 parts by weight of the solid content of the acrylic copolymer, the degree of crosslinking will be low and good heat resistance cannot be obtained. If it exceeds, the degree of cross-linking becomes too high and the initial adhesive strength is lowered.

The method of polymerizing the acrylic copolymer constituting the acrylic pressure-sensitive adhesive composition of the present invention is not special, and a usual solution polymerization method, emulsion polymerization method, dispersion polymerization method,
A known polymerization method such as a bulk polymerization method may be used, but a solution polymerization method is generally simple and suitable.

In the case of the solution polymerization method, for example, monomers having a predetermined composition are dissolved in an organic solvent such as ethyl acetate at a predetermined concentration, and a peroxide such as benzoyl peroxide or lauroyl peroxide is used as a polymerization catalyst. A desired acrylic copolymer solution can be easily obtained by carrying out a polymerization reaction at a temperature of about 60 to 80 ° C. for about 6 to 10 hours while stirring under nitrogen reflux.

The acrylic pressure-sensitive adhesive composition of the present invention may appropriately contain additives such as a plasticizer, a softening agent, a filler, a dye, a pigment and a stabilizer, as long as the object of the present invention is not impaired. May be.

The coating thickness of the pressure-sensitive adhesive composition of the present invention on a substrate when producing a pressure-sensitive adhesive product is not particularly limited, and depends on the type of the substrate and the use of the pressure-sensitive adhesive processed product. Generally, the film thickness after drying is 10 to 100 μm on one side.
A degree is preferable.

When the pressure-sensitive adhesive composition of the present invention is used in a pressure-sensitive adhesive tape, it may be a single-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on only one side of various base materials, or various base materials. It may be a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides. Furthermore, a non-support type adhesive tape that does not use a substrate may be used.

[0023]

In the acrylic pressure-sensitive adhesive composition of the present invention, since the aziridine compound is used as the crosslinking agent, the crosslinking proceeds stably and rapidly, so that the acrylic pressure-sensitive adhesive composition is excellent in stability and productivity. By bonding the carboxyl group present in the acrylic polymer and the pentaerythritol ester of the polymerized rosin through the aziridine compound which is a cross-linking agent,
By introducing the tackifying resin into the polymer chain to reduce the polarity of the tackifying resin as a whole, the adhesion to the low-polar adherend is improved. Further, since the tackifying resin having a bulky structure is introduced into the polymer chain, the elastic modulus of the pressure sensitive adhesive can be set high, and the pressure sensitive adhesive property, especially the peeling resistance can be improved.

[0024]

EXAMPLES In order to explain the present invention in more detail, examples will be given below. In addition, "part" in an Example means a "weight part."

(Example 1)

(A ) As shown in Example 1 in Table 1, 100 parts of ethyl acetate was placed in a reaction vessel equipped with a polymerization thermometer of an acrylic copolymer , a stirrer and a nitrogen inlet tube.
Acrylic acid 2-ethylhexyl ester (97 parts), acrylic acid (3 parts) and lauryl mercaptan (0.05 parts) as a chain transfer agent were added, and benzoyl peroxide (0.1 part) was further added as a polymerization initiator, while stirring under nitrogen reflux. Polymerization reaction was carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer solution having a solid content of 50%.

( B) Preparation of acrylic pressure-sensitive adhesive composition
Adult resultant acrylic copolymer solution, 200 parts (solid content 10
0 parts), a pentaerythritol ester of polymerized rosin “Pencel D160” as a tackifying resin (melting point 1
60 ° C., manufactured by Arakawa Chemical Industry Co., Ltd.) and 10 parts of N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide) as a cross-linking agent (trade name “HDU”, manufactured by Mutual Pharmaceutical Co., Ltd.). One part was mixed by stirring to obtain an acrylic pressure-sensitive adhesive composition having a solid content of 52.4%.

( C) Evaluation The obtained acrylic pressure-sensitive adhesive composition was coated on the release treated surface of the release paper so that the film thickness after drying would be 65 μm,
It was dried at 110 ° C. for 5 minutes. Then, the pressure-sensitive adhesive composition layer on the release paper was bonded to one surface of the non-woven fabric and pressure-bonded with a roll. Further, the same operation was performed on the other surface of the non-woven fabric to obtain a double-sided adhesive tape using the non-woven fabric as a base material.

The resulting double-sided pressure-sensitive adhesive tape was aged at 23 ° C. for 24 hours, and various adhesive properties of the double-sided pressure-sensitive adhesive tape were evaluated by the following methods.

Initial adhesive strength (against SUS) : JIS Z-
According to 1528 "Double-sided adhesive tape", double-sided adhesive tape cut into a width of 20 mm and a length of 100 mm has a thickness of 1.5 m.
m, width 25 mm, length 100 mm, cold-rolled stainless steel plate (SUS304 plate) with a bonding length of 75 mm, and allowed to stand in an atmosphere of 23 ° C.-65% RH for 20 minutes, then pulled using a Tensilon tester The 180-degree angle peel strength (g / 20 mm) was measured at a speed of 300 mm / min.

Initial adhesive strength (against polypropylene) : thickness of 2 mm, width of 25 m instead of cold rolled stainless steel plate
m, the same as the case of the initial adhesive force (against SUS) except that a polypropylene plate with a length of 100 mm was used, 1
The 80-degree angle peel strength (g / 20 mm) was measured.

Holding power (against SUS) : JIS Z-15
According to No. 28, a double-sided pressure-sensitive adhesive tape cut into a width of 20 mm and a length of 100 mm has a thickness of 1.5 mm, a width of 25 mm and a length of 10
A 0 mm cold rolled stainless steel plate (SUS304 plate) was attached with an adhesion length of 20 mm, left in an atmosphere of 23 ° C.-65% RH for 20 minutes, and further in an atmosphere of 80 ° C. for 20 minutes, and then a double-sided adhesive tape was used. Suspend vertically in a constant temperature dryer at 80 ° C and put 1k on the bottom edge of the double-sided adhesive tape.
A load of g was suspended and the sample was left vertically and the dropping time (minute) within 1 hour or the deviation distance (mm) after 1 hour was measured.

Constant load peeling retention force (against polypropylene
) : A double-sided adhesive tape cut into a width of 20 mm and a length of 100 mm is attached to a polypropylene plate having a thickness of 2 mm, a width of 25 mm and a length of 100 mm with an adhesive length of 50 mm, and 23
20 minutes in an atmosphere of -65% RH, then, with the double-sided adhesive tape on the lower side, both ends of the adhesive test piece were fixed and left horizontally in a constant temperature dryer at 60 ° C for 20 minutes. After that, a load of 80 g is hung on the non-adhesive end of the double-sided pressure-sensitive adhesive tape and a load in the 90 ° angle peeling direction is applied to drop it within 1 hour (minutes) or after 1 hour of peeling distance (mm). Was measured.

(Examples 2 to 3)

As shown in Examples 2 and 3 of Table 1,
Two kinds of acrylic pressure-sensitive adhesive compositions were obtained in the same manner as in Example 1 except that the compounding amount of the tackifying resin "Pencel D160" was changed.

The results of evaluating the two types of acrylic pressure-sensitive adhesive compositions obtained in the same manner as in Example 1 are shown in Table 1.

(Comparative Example 1)

As shown in Comparative Example 1 in Table 1, in the polymerization of the acrylic copolymer, the monomer composition was 70 parts of acrylic acid n-butyl ester, 29.7 parts of acrylic acid 2-ethylhexyl ester and 0 acrylic acid. An acrylic pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the amount was 0.3 part.

The acrylic pressure-sensitive adhesive composition obtained was evaluated in the same manner as in Example 1 and the results are shown in Table 1.

(Comparative Example 2)

As shown in Comparative Example 2 of Table 1, in the polymerization of the acrylic copolymer, the monomer composition was 70 parts of acrylic acid n-butyl ester, 15 parts of acrylic acid 2-ethylhexyl ester and 15 parts of acrylic acid. An acrylic pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except for the above.

The results of evaluation of the obtained acrylic pressure-sensitive adhesive composition in the same manner as in Example 1 are shown in Table 1.

(Comparative Examples 3 to 4)

As shown in Comparative Examples 3 and 4 of Table 1,
Two kinds of acrylic pressure-sensitive adhesive compositions were obtained in the same manner as in Example 1 except that the compounding amount of the tackifying resin "Pencel D160" was changed.

The results of evaluating the two types of acrylic pressure-sensitive adhesive compositions obtained in the same manner as in Example 1 are as shown in Table 1.

(Comparative Example 5)

As shown in Comparative Example 5 in Table 1, instead of "Pencel D160" as the tackifying resin, pentaerythritol ester "super ester A115" of disproportionated rosin (melting point 115 ° C, manufactured by Arakawa Chemical Industry Co., Ltd. An acrylic pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that (1) was used.

The results of evaluation of the resulting acrylic pressure-sensitive adhesive composition in the same manner as in Example 1 are shown in Table 1.

(Comparative Examples 6 to 7)

As shown in Comparative Examples 6 and 7 of Table 1,
Example 1 except that the compounding amount of the cross-linking agent "HDU" was changed.
In the same manner as above, two types of acrylic pressure-sensitive adhesive compositions were obtained.

The results of evaluating the two types of acrylic pressure-sensitive adhesive compositions obtained in the same manner as in Example 1 are as shown in Table 1.

(Comparative Example 8)

As shown in Comparative Example 8 in Table 1, the isocyanate compound "Coronate L" (active ingredient 55%, manufactured by Nippon Polyurethane Industry Co., Ltd.) was used as a cross-linking agent in place of "HDU", and in solid content. Acrylic copolymer 100
An acrylic pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that 2 parts of "Coronate L" was added to each part.

The results of evaluation of the obtained acrylic pressure-sensitive adhesive composition in the same manner as in Example 1 are shown in Table 1.

[0055]

[Table 1]

[0056]

As described above, the acrylic pressure-sensitive adhesive composition of the present invention has an adhesive force to a low-polar adherend,
In particular, since it has excellent peeling resistance, it can be suitably used for adhesive processed products for a wide range of applications.

Claims (1)

[Claims] 1. 99.5 to 90% by weight of a (meth) acrylic acid alkyl ester in which the alkyl group has 2 to 18 carbon atoms.
5 to 40 parts by weight and one molecule of pentaerythritol ester of polymerized rosin, based on 100 parts by weight of solid content of the acrylic copolymer obtained by copolymerizing 0.5 to 10% by weight of polymerizable unsaturated carboxylic acid. An acrylic pressure-sensitive adhesive composition containing 0.01 to 0.5 part by weight of an aziridine compound having two or more aziridine rings.