JP2867366B2 - Acrylic pressure-sensitive adhesive composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive composition. More specifically, it relates to an acrylic pressure-sensitive adhesive composition having excellent peel resistance and tack, particularly excellent low-temperature tack.

2. Description of the Related Art Pressure-sensitive adhesive compositions used for labels, adhesive tapes, double-sided adhesive tapes, etc. are used in consideration of their use environment, etc. Properties, color tone, transparency, etc. are required. Therefore, an adhesive composition containing an acrylic polymer as a main component has hitherto been awarded.

By the way, in general, an acrylic pressure-sensitive adhesive composition has insufficient peeling resistance to various adherends simply with an acrylic polymer, so that a rosin ester, a C9 petroleum resin,
It is used as a composition containing a tackifier resin such as a terpene resin and a so-called pure monomer resin represented by a copolymer of styrenes. However, the tackifying resin is an acrylic pressure-sensitive adhesive composition having excellent peel resistance if the amount of addition is increased, but has the disadvantage that tack, particularly at low temperatures, is significantly reduced. I have.

By the way, in the fields of automobiles, light electrical appliances, construction, printing, and the like, there is a tendency that required performance for pressure-sensitive adhesives is increased. That is, there is a demand for excellent tackiness from room temperature to low temperature, high peeling resistance, and performance such as cohesion in a high temperature range. Among these, the cohesive strength in the high temperature region can be easily solved by a method such as increasing the amount of the crosslinking monomer or the amount of the crosslinking agent to increase the crosslinking density of the acrylic polymer. However, as described above, high peel resistance and tack, particularly low-temperature tack, are mutually contradictory properties, and an acrylic pressure-sensitive adhesive composition excellent in both of them has not been obtained at present.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an acrylic pressure-sensitive adhesive composition having high peel resistance and excellent tackiness, particularly low-temperature tackiness, without impairing adhesive properties such as cohesive strength.

Means for Solving the Problems The present inventors have conducted intensive studies focusing on tackifying resins blended in acrylic copolymers in order to solve the problems of the prior art, and as a result, have found that a high hydroxyl value is obtained. The present inventors have found that the above problems can be completely solved when a resin acid ester having the same is used as a tackifier resin, and have completed the present invention.

That is, the present invention provides an acrylic pressure-sensitive adhesive composition containing an acrylic polymer and a tackifier resin as main components, wherein the tackifier resin is obtained by reacting a resin acid and a polyhydric alcohol. And a resin acid ester having a hydroxyl value of 50 to 100.

In the acrylic pressure-sensitive adhesive composition of the present invention, an acrylic polymer is used as a base polymer. The composition of the acrylic polymer is not particularly limited, and various known acrylic esters and / or methacrylic esters (hereinafter abbreviated as (meth) acrylic esters).
A homopolymer or a copolymer having as a main component can be used as it is. Specific examples of the (meth) acrylate include methyl (meth) acrylate, (meth)
Examples include ethyl acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Furthermore, (meth) acrylic acid, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide, or the like may be used in combination as a crosslinkable monomer. Further, if desired, other copolymerizable monomers such as vinyl acetate and styrene can be used in combination to the extent that the adhesive properties of the (meth) acrylate polymer are not impaired. The glass transition temperature of these acrylic polymers containing (meth) acrylic acid ester as a main component is not particularly limited, but is usually -70 to 0 ° C, preferably -60.
The temperature is preferably in the range of -10 ° C. Glass transition temperature is 0 ℃
If it is too high, the tack is significantly reduced, which is not preferable. If the temperature is lower than −70 ° C., the peeling resistance tends to decrease.

The acrylic polymer is prepared by dissolving the (meth) acrylic acid ester alone or in combination with a copolymerizable monomer in an appropriate solvent, and using various known azo- or peroxide-based initiators. Can be easily produced by a so-called solution polymerization method in which a solution is added and heated. It can also be produced by other polymerization methods.

As the tackifier resin used in the acrylic pressure-sensitive adhesive composition of the present invention, it is essential to use a resin acid ester having a hydroxyl value of 50 to 100. Preferably 60-
It has a hydroxyl value of 90. When the hydroxyl value is less than 50, the peel resistance of the acrylic pressure-sensitive adhesive composition tends to decrease, and when the hydroxyl value exceeds 100, when a crosslinking agent that undergoes a crosslinking reaction with a hydroxyl group is used. The performance of the acrylic pressure-sensitive adhesive composition, particularly the cohesive strength, tends to be significantly reduced.

Such a resin acid ester is obtained by reacting a resin acid and a polyhydric alcohol.

Resin acids include resin acid monomers such as rosins, and rosins include gum rosin, wood rosin, tall oil rosin and the like. The resin acid preferably contains 5% by weight or more of a resin acid dimer. More preferably, it is at least 10% by weight. When the content of the resin acid dimer is 5% by weight or more, the low temperature tack is particularly excellent.

Here, the resin acid dimer is generally called a polymerized rosin, and refers to a dimer of a resin acid monomer such as a rosin. The method for producing the resin acid dimer is not particularly limited, and a known method can be employed. For example, a resin acid monomer such as rosin includes a catalyst such as sulfuric acid, hydrogen fluoride, aluminum chloride, and titanium tetrachloride. A method in which the reaction is carried out in a solvent such as toluene or xylene at a temperature of about 40 to 160 ° C. for about 1 to 5 hours can be mentioned. The reaction product varies depending on the reaction temperature, reaction time, etc., and a resin acid dimer alone in which the resin acid monomer is completely dimerized, or a mixture of an unreacted resin acid monomer and a resin acid dimer can be considered.
Either case may be used. In the present invention, it is preferable that the resin acid dimer is contained in the resin acid in an amount of 5% by weight or more. When the reaction product is a mixture, the dimerization ratio of the resin acid monomer is preferably 5% by weight or more.

In preparing the resin acid containing the resin acid dimer of the present invention, the resin acid dimer alone may be used, or a predetermined amount of the resin acid monomer may be added to a mixture of the unreacted resin acid monomer and the resin acid dimer. Can be added.

Specific examples of the resin acid dimer include tall oil-based polymerized rosin (trade name “Silva Tack 140”, manufactured by Arizona Chemical Co., Ltd.), wood-based polymerized rosin (trade name “Dymarex”, Hercules Co., Ltd.), gum-based polymerized rosin, etc. Is raised.

The polyhydric alcohol may be appropriately selected in consideration of the molecular weight and softening point of the resin acid ester. For example, dihydric alcohols such as ethylene glycol, diethylene glycol and triethylene glycol, trihydric alcohols such as glycerin, pentaerythritol, and dihydric alcohol Tetraerythritol, polyglycerol, and other tetravalent or higher alcohols.

As the method for producing the resin acid ester, a normal esterification reaction may be employed.For example, a resin acid and a polyhydric alcohol may be used in the presence or absence of a solvent at 250 to 280 ° C.
A method of performing a heat dehydration reaction for about 1 to 8 hours may be used. Here, an aromatic solvent such as Hensen, toluene and xylene is preferably used as the solvent.

Further, the ratio of charged resin acid and polyhydric alcohol is not particularly limited, but the hydroxyl value of the obtained resin acid ester is
It must be in the range of 60-100. Usually, it is better to use an amount of polyhydric alcohol having a hydroxyl group equivalent to 1.4 to 2 equivalents to the carboxyl group equivalent of the resin acid. Further, the softening point of the resin acid ester is preferably from 80 to 140 ° C.

The blending ratio of the acrylic polymer and the tackifier resin is preferably about 5 to 40% by weight of the tackifier resin to about 60 to 95% by weight of the acrylic polymer on a solid basis. When the content of the acrylic polymer is less than 60% by weight, there is almost no tackiness and it is difficult to use as a pressure-sensitive adhesive. Tends to be lower.

The acrylic pressure-sensitive adhesive composition of the present invention does not include a crosslinking agent such as a polyisocyanate compound, a polyamine compound, a melamine resin, a urea resin, and an epoxy resin as essential components, but further improves cohesive strength and heat resistance. It can be used for any purpose. In particular, a polyisocyanate compound is preferable, and any of various known compounds can be used.
Examples thereof include 1,6-hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate.

Further, in the acrylic pressure-sensitive adhesive composition of the present invention, a filler, an antioxidant, an ultraviolet absorber and the like can be appropriately used as needed. Further, various known tackifier resins can be used in combination as long as the performance of the tackifier resin of the present invention is not impaired.

Effects of the Invention According to the present invention, it is possible to provide an acrylic pressure-sensitive adhesive composition that is excellent in high peel resistance and tackiness, particularly low-temperature tackiness, without impairing adhesive properties such as cohesive strength.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. In each example, all parts and percentages are by weight unless otherwise specified.

Production Example 1 (Production of Acrylic Polymer) 57 parts of ethyl acetate, 33 parts of toluene, 97 parts of butyl acrylate, and 3 parts of acrylic acid were charged into a reactor equipped with a stirrer, a cooling pipe, a dropping funnel, and a nitrogen introduction pipe. After that, the temperature was raised under a nitrogen stream until the temperature in the system reached about 75 ° C. Then, about 3 hours were added dropwise from a dropping funnel previously charged with 0.5 parts of azobisisobutyronitrile and 10 parts of ethyl acetate into the system, and the polymerization reaction was completed by keeping the same temperature for 5 hours. An acrylic polymer having a content of 49.6% and a viscosity (23 ° C.) of 11,000 cps was obtained.

Production Example 2 (Production of acrylic polymer) Exactly the same as Production Example 1 except that the mixing ratio of the acrylic monomer in Production Example 1 was changed to 73 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, and 2 parts of acrylic acid. To obtain an acrylic polymer having a solid content of 49.4% and a viscosity (23 ° C.) of 8000 cps.

Production Example 3 (Production of tackifying resin) In a reactor equipped with a stirrer, a cooling pipe, a water separator and a nitrogen introduction pipe, 40 parts of gum rosin, tall oil-based polymerized rosin (trade name “Silva Tack 140”, dimer amount 80) Weight%) 60
And 14 parts of pentaerythritol, and then heated under a nitrogen stream until the temperature in the system reached 250 ° C. 2 at the same temperature
After reacting for an hour, the temperature was further raised to 280 ° C., and the reaction was continued at the same temperature for 7 hours. Thereafter, low-boiling fractions were removed under reduced pressure to obtain pentaerythritol rosin ester. The softening point was 122.5 ° C., the acid value was 16.3, the hydroxyl value was 70, and the color tone (Gardner) was 11.

Production Examples 4 to 13 (Production of Tackifying Resin) The same procedure as in Production Example 3 was carried out except that the charged amounts of the resin acid and the polyhydric alcohol were changed as shown in Table 1.

Example 1 After sufficiently kneading 80 parts (in terms of solid content) of the acrylic polymer obtained in Production Example 1 and 20 parts of the resin acid ester obtained in Production Example 3, a polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., 1.2 parts of brand name "Coronate L")
A cross-linked acrylic pressure-sensitive adhesive composition was obtained. The obtained acrylic pressure-sensitive adhesive composition was dried on a 38 μm-thick polyester film with a dice-type applicator to a dry film thickness of 70 μm.
Then, the solvent was removed from the adhesive composition to prepare a sample tape, and various tests were performed by the following methods.

(Performance Test of Acrylic Pressure-Sensitive Adhesive Composition Tape) The sample tape was aged for one week and aged, and then evaluated by the following test method. The evaluation results are shown in Table 2.

Peeling Resistance A sample tape (25 mm wide × 50 mm long) was attached to a polypropylene plate, and a load of 200 g was applied in the 90 ° peeling direction at 40 ° C., and the time until the weight dropped was measured.

Using tack sample tape, ASTM the D-2979 "probe tack method" probe tack measuring machine according to, adhesion rate and pull-off speed is 10 mm / sec, adhesion load 100 gf / cm ^2, contact time 1 second The detachment resistance at 0 ° C. and 23 ° C. was measured.

Cohesive force A sample tape (25 mm × 25 mm) was attached to a stainless steel plate, and 1 kg load was applied at 40 ° C., and the displacement after 1 hour was measured.

Examples 2 to 8 and Comparative Examples 1 to 4 In the same manner as in Example 1, except that the composition of the acrylic polymer and the tackifying resin was changed as shown in Table 2, various cross-linking types were used. An acrylic pressure-sensitive adhesive composition was obtained. The evaluation results are shown in Table 2.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yumi Ogawa, Arakawa Chemical Industry Co., Ltd., 3-4-233 Imafukuminami, Joto-ku, Osaka-shi, Osaka (72) Yoshihiro Kodama Yoshihiro Kodama, Imafuku-minami, Joto-ku, Osaka-shi, Osaka 3-43-3 Arakawa Chemical Industries Co., Ltd. Laboratory Examiner Yoshihide Kawakami (56) References JP-A-63-256672 (JP, A) JP-A-64-16882 (JP, A) JP-A-58- 98371 (JP, A) JP-A-1-284577 (JP, A) JP-A-3-146658 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09J 133/04-133 / 14,193 / 04

Claims (3)

(57) [Claims] 1. An acrylic pressure-sensitive adhesive composition containing an acrylic polymer and a tackifier resin as main components, wherein the tackifier resin is obtained by reacting a resin acid and a polyhydric alcohol. And an acrylic pressure-sensitive adhesive composition, wherein the resin acid ester has a hydroxyl value of 50 to 100. 2. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the resin acid ester has a hydroxyl value of 60 to 90. 3. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the resin acid is a resin acid containing 5% by weight or more of a resin acid dimer.