JPH04114079A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title composition having excellent bonding characteristics in a wide temperature range and improved adhesiveness to nonpolar materials to be bonded by blending a specific acrylic polymer with a specific amount of high-softening rosin-based tackifier. CONSTITUTION:(A) 100 pts.wt. acrylic polymer obtained by copolymerizing (i) 100 pts.wt. (meth)acrylic acid ester monomer (preferably 2-15C alkyl) with (ii) 2-40 pts.wt., preferably 5-20 pts.wt. acrylic acid ester of rosin and (iii) <=30 pts.wt., preferably 2-10 pts.wt. copolymerizable monomer [e.g. (meth)acrylic acid or 2-(meth)acrylic acid or propanesulfonic acid] is blended with (B) 5-50 pts.wt., preferably 10-35 pts.wt. rosin-based tackifier having >=105 deg.C, preferably 110-190 deg.C softening point.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an acrylic pressure-sensitive adhesive composition with improved adhesive properties, particularly a pressure-sensitive adhesive composition that is good for adhesion to non-polar adherends. It is about things.

[Prior Art and Problems to be Solved] In recent years, the range of use of pressure-sensitive adhesive compositions has expanded, and the required properties have also tended to become more sophisticated. In particular, when non-polar adherends such as polyethylene and polypropylene are used, sufficient adhesive properties cannot be obtained with conventional pressure-sensitive adhesives. In addition, the temperature range in which it can be used is expanded,
It is necessary to improve adhesion properties at higher temperatures than ever before, and of course adhesion properties at normal temperatures of 10 to 30°C are also required.

On the other hand, it is known that adhesion properties can be improved by adding a tackifier such as rosin resin or terpene phenol resin to acrylic pressure-sensitive adhesives for non-polar adherends. ing.

However, since the tackifier is usually a low molecular weight resin, the adhesive properties at high temperatures tend to decrease as the tackifier is added.

As a method to improve this, as described in JP-A-1-306483, the adhesive properties at high temperatures are improved by controlling the plasticization of the polymer using a tackifier that has poor compatibility with the base polymer. A technique has been proposed.

However, in this technique, because too much emphasis is placed on adhesive properties at high temperatures, the plasticization rate of the adhesive at normal temperatures becomes low and the adhesive properties to rough surfaces are impaired.

[Means for Solving the Problems] Therefore, as a result of intensive studies, the present inventors solved the above problems by using a polymer obtained by copolymerizing an acrylic monomer and an acrylic acid ester of rosin as the main component of a pressure-sensitive adhesive. By solving these problems, we have completed an acrylic pressure-sensitive adhesive composition that has excellent adhesive properties in a wide temperature range.

That is, the present invention relates to a pressure-sensitive adhesive composition, which contains (1) 100 parts by weight of (meth)acrylic ester monomer, (2) 2 to 40!1 parts of rosin acrylic ester, and (3) ) Contains 5 to 50 parts by weight of a rosin-based tackifier with a softening point of 105°C or higher per 100 parts by weight of an acrylic polymer obtained by copolymerizing 30 parts by weight or less of a copolymerizable monomer. It is something to do.

In the present invention, (meth)acrylic acid ester monomer (
As monomer (1)), the alkyl group of the aliphatic alcohol is an ethyl group, a butyl group, a 5ec-butyl group, an isobutyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a 2-ethylhexyl group, etc. Examples include esters of acrylic acid or methacrylic acid, and one or more of these may be used. Further, it is preferable that the alkyl group has 2 to 15 carbon atoms from the viewpoint of adhesive properties of the resulting pressure-sensitive adhesive.

Examples of the acrylic ester of rosin (monomer (2)) include ring-opening reaction products of carboxyl groups such as rosin, polymerized rosin, and hydrogenated rosin and epoxy groups such as glycidyl (meth)acrylate.

The acrylic ester of this rosin is, for example, JP-A-63
It can be obtained by the method described in JP-A-186783.

The polymerizable monomer (monomer (3)) copolymerized with the above monomers (1) and (2) includes (meth)acrylic acid,
Carboxyl group-containing monomers such as itaconic acid and crotonic acid, sulfonic group-containing monomers such as 2-(meth)acrylic acid propanesulfonic acid, and phosphoric acid group-containing monomers such as (meth)acrydoxyethyl phosphate. , hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, N
・N-dimethyl (ethyl) acrylate, bis-N-N
-Amino group-containing monomers such as dimethylaminoethyl maleate, amide group-containing monomers such as (meth)acrylamide and N-methylolacrylamide, epoxy group-containing monomers such as glycidyl (meth)acrylate, and acrylonitrile. Examples include nitrile group-containing monomers. These polymerizable monomers contribute to increasing the adhesive strength of the resulting pressure-sensitive adhesive, and one or more of them can be used.

In the present invention, 2 to 40 parts by weight of acrylic ester of rosin, preferably 5 to 20 parts by weight, and 30 parts by weight or less of polymerizable monomer, preferably 100 parts by weight of (meth)acrylic ester monomer. is blended in an amount of 2 to 10 parts by weight and copolymerized to obtain an acrylic polymer.

In addition, in the present invention, the above monomers (1), (
An acrylic polymer can also be obtained by copolymerizing a vinyl monomer with 2) and (3). Such vinyl monomers include vinyl acetate, vinylpyrrolidone,
Examples include vinyl propionate, styrene and its derivatives, and vinyl chloride, and one or more of these may be used. This vinyl monomer is the above-mentioned (
It is blended in an amount of 50 parts by weight or less, preferably 2 to 30 parts by weight, per 100 parts by weight of the meth)acrylic acid ester monomer.

This acrylic polymer can be synthesized using conventional methods.

The acrylic polymer itself synthesized in this manner is sticky at room temperature. Regarding the molecular weight, the weight average molecular weight measured from the molecular weight distribution curve by gel permeation chromatography (C, PC) method is about 100,000 or more in terms of polystyrene, preferably about 200,000 to 1,000,000. used.

In the present invention, the above copolymerized acrylic polymer has
A rosin-based tackifier with a softening point of 105°C or higher is blended.

This rosin-based tackifier is rosin or a derivative thereof, and has a softening point of 105°C or higher, preferably 110 to 19°C.
A temperature of 0°C is used. Examples of rosin derivatives include partially disproportionated or disproportionated rosin, water-added rosin, maleic acid-modified rosin, polymerized rosin, and formaldehyde-formed rosin, as well as their metal salts, diethylene glycol,
Examples include ester bonds with glycerin, pentaerythritol, and the like. This rosin-based tackifier was added in an amount of 5 parts by weight based on 100 parts by weight of the acrylic polymer.
~50 parts by weight, preferably 10 to 35 parts by weight.

Furthermore, in the present invention, in addition to the above-mentioned rosin-based tackifier, one having a softening point of less than 105'C can be used in combination to improve adhesive properties at low temperatures. This low softening point rosin tackifier is the above-mentioned high softening point (softening point 105°C or higher) rosin tackifier 100! The pressure-sensitive adhesive composition of the present invention, which is blended in an amount of 120 parts by weight or less, preferably 50 parts by weight or less, essentially contains the above-mentioned acrylic polymer and high softening point rosin tackifier. In addition to being contained as a component, a crosslinking agent may also be added to improve cohesive force. Examples of the crosslinking agent include conventionally known incyanate crosslinking agents, melamine crosslinking agents, epoxy crosslinking agents, peroxide crosslinking agents, and the like. The amount of this crosslinking agent used is preferably 20 parts by weight or less per 100 parts by weight of the acrylic pressure-sensitive adhesive. Furthermore, instead of using a crosslinking agent, or in addition to using a crosslinking agent, crosslinking can also be carried out by irradiation with electron beams or ultraviolet rays.

The pressure-sensitive adhesive composition of the present invention may also contain various conventionally known additives such as plasticizers, softeners, fillers, pigments, and dyes, if necessary. The amounts of these additives may be the amounts commonly used.

The reason why the adhesive properties of the pressure-sensitive adhesive composition of the present invention are improved is not necessarily clear, but by copolymerizing the acrylic ester of rosin with other monomers, it can be added to the copolymerized acrylic polymer. The compatibility of the rosin-based tackifier changes, and the flexibility of the acrylic polymer skeleton improves, resulting in better rough surface adhesion. This is thought to be because the cohesive force of the pressure adhesive composition as a whole decreases little at high temperatures.

〔Example〕

Hereinafter, the present invention will be explained based on examples. In addition, in the following, "part" means "part by weight".

Example 1 100 parts of butyl acrylate, rosin acrylic) li6
5 parts of 1 ester, 2 parts of acrylic acid, 0.4 parts of 2.2' azobisisobutyronitrile (AIBN), and 250 parts of ethyl acetate were put into four flasks and heated for 60 minutes under a nitrogen atmosphere.
Polymerization was carried out at ℃ for 10 hours.

Softening point: 120 for 100 parts of this acrylic polymer
30 parts of polymerized rosin and 4 parts of trifunctional isocyanate were added. This was applied onto a polyethylene terephthalate film with a thickness of 25 μm so that the thickness after drying was 50 μm, and dried at 100″C for 5 minutes to form an adhesive tape having a pressure-sensitive adhesive composition layer on the film. This adhesive tape was stored at 50° C. for 3 days to prepare a sample for evaluation.

Example 2 Substituted the rosin-based tackifier of Example 1, softening point 125°C
An adhesive tape and a sample for evaluation were obtained in the same manner as in Example 1 except that 40 parts of maleic acid-modified disproportionated rosin was added.

Example 3 Butyl acrylate 2 as a material for acrylic polymer
0 parts, 2-ethylhexyl acrylate 80 parts, acrylic acid ester of rosin 10 parts, acrylic acid 5 parts, AIB
An adhesive tape and an evaluation sample were prepared in the same manner as in Example 1, except that 4 parts of No. 4 and 268 parts of ethyl acetate were used, and the amount of polymerized rosin added was 20 parts.

Comparative Example 1 An adhesive tape and an evaluation sample were produced in the same manner as in Example 1, except that 100 parts of butyl acrylate, 2 parts of acrylic acid, 04 parts of ArBN, and 153 parts of ethyl acetate were used as the acrylic polymer materials.

Comparative Example 2 Butyl acrylate 2 as a material for acrylic polymer
Adhesive tapes and evaluation samples were prepared in the same manner as in Example 2, except that 0 parts, 80 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, 4 parts of AIB No., and 158 parts of ethyl acetate were used. The evaluation results of the comparative example are shown in Table 1 below.

Table 1 The test results in Table 1 were measured by the following method.

(a) Molecular weight Weight average molecular weight measured by GPC method and converted to polystyrene.

(b) Adhesive strength According to JIS Z-1522, a stainless steel plate and a polypropylene plate were used as adherends. The unit is g/20
It is mm.

(C) Anti-repulsion property A sample with a pressure-sensitive adhesive layer formed on release paper was
Cut it into 10x10 pieces and attach it to an aluminum plate of the same size with a thickness of 0.5 mm. Then peel off the release paper and
The sample was bonded to a cylinder made of 00 mm ABS resin at 23°C with the length direction of the sample in the circumferential direction. After that, it was left to stand for 1 hour, then held at 50° C. for 24 hours, and the length of the aluminum plate lifted was measured.

(b) An evaluation sample was bonded to a glass plate having a center line average roughness Ra of 3.2 μm at 23° C. by making one reciprocation of a 2 kg roll. Taking advantage of the fact that the adhesive part is transparent,
The adhesive area was measured by observing from the back side of the glass plate.

(e) Creep resistance phenol resin plate with mirror-like surface (30 x 120 x 3.
The adhesive area is 20 x 10 m at one end in the longitudinal direction (0 mm).
Samples for evaluation (width 10 mm) were bonded together so that the width was 10 mm, left for 30 minutes, and then heat-treated at 80° C. for 20 minutes. Next, set the phenolic resin plate vertically so that the side where the sample is attached is facing down, and attach the 500 mm to the other end of the sample.
A load of g was applied. In this state, the displacement distance of the sample from the phenol resin plate per hour was measured using a creep tester.

From Table 1, the pressure-sensitive adhesive composition of the present invention has excellent adhesive properties over a wide range of temperatures, excellent adhesive properties to curved surfaces, and excellent adhesive properties to rough surfaces, compared to the acrylic pressure-sensitive adhesive composition of the comparative example. You can see that

〔Effect of the invention〕

As mentioned above, the pressure-sensitive adhesive composition of the present invention uses acrylic acid ester of rosin as a component of the acrylic polymer, so it has excellent adhesion properties over a wide range of temperatures and can be applied to non-polar adherends. Good adhesion to.

Claims (3)

[Claims] (1) For 100 parts by weight of (meth)acrylic acid ester monomer, (2) 2 to 40 parts by weight of acrylic ester of rosin; (3) Contains 5 to 50 parts by weight of a rosin-based tackifier with a softening point of 105°C or higher per 100 parts by weight of an acrylic polymer obtained by copolymerizing 30 parts by weight or less of a copolymerizable monomer. Features: Pressure-sensitive adhesive composition.