JPH0468074A - Acrylic self-adhesive composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an acrylic pressure-sensitive adhesive composition that has good tackiness at room temperature and maintains tackiness even at high temperatures. The acrylic pressure-sensitive adhesive composition of the present invention can be suitably used in various applications such as paint masking tapes and double-sided pressure-sensitive adhesive tapes (including pressure-sensitive adhesive sheets) that undergo a baking and high-temperature drying process after painting.

[Prior art] Acrylic adhesives generally have better heat resistance, weather resistance, aging resistance, transparency, etc. than rubber adhesives, and the polymer itself has adhesive properties. There is. Generally, in addition to the main monomer, the acrylic polymer used in an acrylic pressure-sensitive adhesive includes a functional group-containing monomer and various comonomers to improve properties such as cohesiveness and adhesiveness.

In particular, acrylic adhesives have weak internal cohesion, so
Usually, crosslinking is carried out using a crosslinking agent using a functional group-containing monomer that serves as a crosslinking point.

However, although conventional cross-linked acrylic adhesives have good adhesion at room temperature or relatively low temperatures, their adhesive strength rapidly decreases at high temperatures (80°C to 120°C).
It will peel off with the slightest force. In addition, to prevent softening at high temperatures, the crosslinking density is increased (then the adhesive becomes too hard and loses its tackiness).

Therefore, for example, when a paint masking tape made using a cross-linked acrylic adhesive is used for applications such as automobile painting, where baking after painting requires a drying process,
It tends to peel off under high temperature conditions, and improvements are needed.

In addition, double-sided adhesive tapes are applied to many objects in a wide range of fields such as the electrical industry, machinery industry, automobile/vehicle industry, and general office work, but there is a need for improved physical properties such as heat resistance and weather resistance. There is also a need to improve adhesives in response to these demands.

[Problems to be Solved by the Invention] The purpose of the present invention is to provide appropriate adhesive strength (temporary adhesive strength) at room temperature.
It is an object of the present invention to provide an acrylic pressure-sensitive adhesive having the following properties and exhibiting good adhesive strength even under high temperature conditions.

As a result of intensive research to overcome the problems of the prior art, the present inventors discovered a specific acrylic polymer that exhibits adhesive strength at high temperatures and a specific acrylic polymer that exhibits excellent adhesive strength at room temperature. It has been found that the above object can be achieved by using a pressure-sensitive adhesive composition comprising a polymer.

Moreover, this adhesive composition can be easily obtained as a uniform composition by polymerizing a monomer mixture forming the other acrylic polymer in the presence of one of these acrylic polymers. .

The present invention has been completed based on these findings.

[Means for Solving the Problems 1] Thus, according to the present invention, a monomer mixture containing a (meth)acrylic acid alkyl ester, a functional group-containing monomer, and optionally other radically polymerizable monomers is copolymerized. , the adhesive strength at 80°C to 120°C is 2.
00g/25mm or more of acrylic polymer (A), (
Obtained by copolymerizing a meth)acrylic acid alkyl ester, a functional group-containing monomer, and a heptamer mixture containing other radically polymerizable monomers as desired, at room temperature (23°C)
An acrylic polymer (B) having an adhesive force of 500 g / 25 mm or more, and the ratio of both (A)
: (B) is included in the range of 10:90 to 90:10 (1 ratio), and the adhesive strength at 80 to 120 ° C. is 100
Provided is an acrylic pressure-sensitive adhesive composition having a particle diameter of 100 g/25 mm or more.

The present invention will be explained in detail below.

(Monomer) The acrylic polymer (A) and the acrylic polymer CB) in the present invention are both monomer mixtures containing a (meth)acrylic acid alkyl ester, a functional group-containing monomer, and optionally other radically polymerizable monomers. Obtained by copolymerizing.

(Meth)acrylic acid alkyl esters are usually
(meth)acrylic acid alkyl esters of 01 to CI4, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-brobyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate , isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, inoctyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate , lauryl (meth)acrylate, tridecyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like.

Examples of functional group-containing monomers include monomers having carboxyl groups (including acid anhydrides) such as (meth)acrylic acid, itaconic acid, maleic acid, and maleic anhydride; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl Monomers having hydroxyl groups such as (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and propylene glycol mono(meth)acrylate; (
Monomers having an acid amide group such as meth)acrylamide; Monomers having a glycidyl group such as glycidyl (meth)acrylate; Monomers having a methylol group such as N-methylol(meth)acrylamide; dimethylaminoethyl methacrylate, tert-methacrylate Monomer having an amino group such as butylaminoethyl; N
-A monomer having an alkoxymethyl group such as butoxymethylacrylamide; and the like. Among these, carboxyl group-containing monomers and acid amide group-containing monomers are particularly preferred.

Examples of other radically polymerizable monomers include styrene, vinyl acetate, acrylonitrile, and N-vinylpyrrolidone.

(Acrylic polymer (A)) The acrylic polymer (A) used in the present invention is 80°C to 1
It is necessary that the adhesive strength at 20° C. be 200 g/25 mm or more, preferably 400 g/25 mm or more.

The acrylic polymer (A) is produced using the monomer mixture described above, but in order to develop adhesiveness at high temperatures, the glass transition temperature (Tg) of the polymer must be -20°C to
Each monomer component is selected so that the temperature is 60°C. Therefore, it is preferable that the main monomer contains a (meth)acrylate of a lower alkyl group. Further, in order to cause crosslinking and prevent softening and flow at high temperatures, it is necessary to use a functional monomer in combination.

This acrylic polymer (A) usually has no tackiness at room temperature and has an adhesive strength of 100 g/25 mm or less.

(Acrylic polymer (B)) The acrylic polymer (Bl) has an adhesive strength of 500 g/25 mm or more at room temperature (23°C), preferably 900 g/25 mm or more.
It is 25 mm or more.

The acrylic polymer (B) is produced using the monomer mixture described above, but in order to exhibit good adhesive strength at room temperature, the Tg of the polymer is -20°C or less, preferably -35°C.
Monomer components are selected as follows. Therefore, as raw monomers, those having a large number of carbon atoms in the alkyl group, such as 2-ethylhexyl acrylate, are usually used. Also, functional monomers are required for crosslinking.

This acrylic polymer (B) is usually heated at a temperature of 80°C to 120°C.
The adhesive force at high temperature of °C is below 60 g/25 mm.

(Composition) Mechanical blending of acrylic polymer (A) and acrylic polymer (Bl) usually tends to cause phase separation, so one of the polymers is prepared in advance and blended in the presence of the acrylic polymer (A). Preferably, the monomer mixture forming the other polymer is then polymerized.

That is, in the presence of the acrylic polymer (A), the monomer mixture forming the acrylic polymer (B) is copolymerized, or in the presence of the acrylic polymer (B), the acrylic polymer ( An acrylic pressure-sensitive adhesive composition is produced by copolymerizing the monomer mixture forming A).

Monomer mixtures containing acrylic monomers generally include
Polymerizes by radical polymerization. Although solution polymerization, emulsion polymerization, bulk polymerization, etc. are possible, solution polymerization is usually preferred. In addition, the monomer appropriate method, bulk charge polymerization method, etc. are employed.

As the polymerization solvent, common solvents such as ethyl acetate, acetone, benzene, toluene, and hexane can be used.

As the polymerization initiator, common peroxide-based initiators such as benzoyl peroxide and lauroyl peroxide,
Alternatively, an azo initiator such as azobisisobutyronitrile is used.

When one polymer is prepared in advance and a monomer mixture forming the other polymer is polymerized in its presence,
The first polymerization is performed for 8 to 10 hours, the second polymerization is performed for 12 to 16 hours, and the polymerization temperature is 60°C to 80°C, and it is preferable that the polymerization temperature in the second polymerization is relatively high.

Ratio of both (A): (Bl is 10:90-90:
10 (weight ratio), preferably 30 nia 0-70:30
It is.

If the acrylic polymer (A) is less than 10% by weight, the adhesive strength at high temperatures will be low, and conversely, if it exceeds 90% by weight, the adhesive strength at room temperature will be low.

The acrylic pressure-sensitive adhesive composition of the present invention usually contains a crosslinking agent. The crosslinking agent may be appropriately selected depending on the type of functional group of the functional group used, but in general, epoxy resins, melamine resins, urea resins, polyisocyanates, acid anhydrides, amine compounds, phenol compounds, and amino compounds are used. , aziridine compounds, metal oxides (organic acid metal salts, metal alkoxides, organometallic compounds, etc.).

In order to crosslink the acrylic polymer (A) and the acrylic polymer CB) at the same time, it is preferable to synthesize both using the same functional monomer.

Further, the functional monomer is preferably a carboxyl group-containing monomer or an acid amide group-containing monomer from the viewpoint of adhesive properties.

The acrylic adhesive composition of the present invention has an adhesive strength of 100 g/25 mm or more at 80 to 120°C.

If desired, a tackifier resin and various additives may be added.

The acrylic pressure-sensitive adhesive composition of the present invention can be used not only at room temperature but also at room temperature.
Since it has good tackiness at high temperatures, it can be suitably used, for example, as an adhesive for paint masking tapes and double-sided adhesive tapes.

(The following is a blank space) [Example] The present invention will be described in more detail with reference to Examples and Comparative Examples below. In addition, unless otherwise specified, parts and percentages are based on weight.

The physical properties of the adhesive were measured as follows.

<Adhesive strength> An adhesive obtained by adding a crosslinking agent to an acrylic polymer was applied onto a polyethylene terephthalate film (Lumirror #25, manufactured by Toshisha Co., Ltd.) base material to a dry thickness of 25 μm to form an adhesive tape. Created. A test piece of this adhesive tape (width 25
The peeling force (g/2
5 mm) was measured.

However, if the measurement temperature is 23℃, 2
After standing for 4 hours, it was measured in an atmosphere of 23°C and 65%RH,
In the case of 80℃, 100℃, 120℃, 30℃ at each temperature.
After standing for a minute, measurements were taken at that temperature.

<Tack> Measured according to the inclined pole tack (TIS Z-0237) method. A case where even a 1/32 inch diameter steel ball did not stay on the sticky surface was evaluated as no tack.

[Example 1] <Synthesis example of acrylic polymer (A)> Ethyl acrylate 93 parts Acrylic acid 7 parts Benzoyl peroxide 0.1 part Ethyl acetate
using 150 parts at 70°C by a conventional method.
Solution polymerization was carried out for an hour to obtain an ethyl acrylate-acrylic acid copolymer (Tg, -18°C).

Per 100 parts of the copolymer, 0.1 part of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., Tetrarad An adhesive tape was prepared by applying the adhesive tape to a dry thickness of .

This adhesive has no tack at room temperature (and the adhesive strength of the adhesive tape at high temperature is 660g/25m at 80℃).
m, 800g/25mm at 100℃, 760 at 120℃
g/25mm.

<Synthesis example of acrylic polymer (B)> Next, the above ethyl acrylate-acrylic acid copolymer 4
0 parts, 60 parts of a monomer mixture having the following composition were added, and further 0.06 parts of benzoyl peroxide and 60 parts of ethyl acetate were added, and copolymerization was carried out at 80° C. for 10 hours.

2-Ethylhexyl acrylate 83 parts Vinyl acetate 10 parts Acrylic acid
7 parts of obtained copolymer composition 1
0.00 parts, epoxy crosslinking agent (Tetralad X) 0.00 parts.
Add 1 part of polyethylene terephthalate film (
Lumirror #25) An adhesive tape was prepared by applying it to a dry thickness of 25 μm on a substrate.

The adhesive strength of this adhesive tape at room temperature (23℃) is 11
00g/25mm, adhesive strength at high temperature is 48 at 80℃
0g/25mm, 440g/25mm at 100℃, 12
It was 180 g/25 mm at 0°C, which was a high value.

[Comparative Example 1] Synthesis example of acrylic polymer (B)> 2-ethylhexyl acrylate 83 parts Vinyl acetate 10 parts acrylic acid
7 parts benzoyl peroxide 0.1 part ethyl acetate
150 parts In Example 1, in the absence of the ethyl acrylate-acrylic acid copolymer, 2-ethylhexyl acrylate, vinyl acetate, and acrylic acid were
An acrylic polymer was obtained by copolymerizing at ℃ for 15 hours (T
g; -37°C).

An adhesive was obtained by adding 0.1 part of an epoxy crosslinking agent (Tetralad Adhesive strength at room temperature (23℃) is 1200
g/25mm, adhesive strength at high temperature is 50g/25mm at 80℃
25mm, 20g/25mm at 100℃, 1 at 120℃
It was 0g725mm. Also, the tack was 6.

Although this acrylic polymer had excellent adhesiveness at room temperature, its adhesive strength at high temperatures was less than 60 g 725 mm, and it was easily peeled off.

[Comparative Example 2] All the monomer components used in Example 1 were used in the following proportions, and copolymerization was carried out simultaneously.

Ethyl acrylate 37.2 parts 2-ethylhexyl acrylate 49.8 parts Vinyl acetate
6 parts acrylic acid
7 parts benzoyl peroxide
0.1 part ethyl acetate 15
0 parts Copolymerization was carried out at 80°C for 15 hours by a conventional method,
An acrylic polymer was obtained.

An adhesive was obtained by adding 0.1 part of an epoxy crosslinking agent (Tetralad Adhesive strength at room temperature (23℃) is 1300
g/25mm, adhesive strength at high temperature is 50g/25mm at 80℃
25mm, 40g/25mm at 100℃, 1
It was 20 g/25 mm at 20°C. Also, the tack was 4.

This acrylic polymer has an adhesive strength of 6 parts g/2 at high temperatures.
It was 5 mm or less and could be easily peeled off.

[Example 2] <Synthesis example of acrylic polymer (A)> Butyl acrylate 50 parts Methyl methacrylate 38 parts N-vinylpyrrolidone 10 parts Acrylic acid
2 parts azobisisobutyronitrile
0.2 parts ethyl acetate 1
Polymerization was carried out using 50 parts at 70° C. for 8 hours in a conventional manner. (Tg, 1°C) 0.1% per 100 parts of copolymer was added to the obtained reaction solution.
A pressure-sensitive adhesive was obtained by adding an epoxy crosslinking agent (Tetrarad

The obtained adhesive tape did not tack at room temperature, but
Adhesive strength at high temperature is 940g/25mm at 80℃,
1000g/25mm at 100℃, 680g at 120℃
/25mm.

<Synthesis example of acrylic polymer (B)> Next, 70 parts of a monomer mixture having the following composition was added to 30 parts of the above copolymer, and further 0.07 parts of benzoyl peroxide and 70 parts of ethyl acetate were added. and copolymerization was carried out at 80° C. for 10 hours.

Butyl acrylate 94 parts Vinyl acetate 3 parts Acrylic acid
3 parts Epoxy crosslinking agent (Tetralad X) 0 per 100 parts of the obtained copolymer composition
．． 1 part was added and applied to a polyethylene terephthalate film (Lumirror #25) substrate to a dry thickness of 25 μm to prepare an adhesive tape.

The adhesive strength of this adhesive tape at room temperature (23℃) is 12
00g/25mm, adhesive strength at high temperature is 32 at 80℃
0g/25mm, 300g/25mm at 100℃, 12
It was 150g/25mm at 0°C, which was a high value.

[Example 3] <Synthesis example of acrylic polymer (B)> 2-ethylhexyl acrylate 93 parts acrylic acid 7 parts azobisisobutyronitrile 0.5 parts ethyl acetate
Polymerization was carried out using 150 parts at 70° C. for 8 hours in a conventional manner. (Tg; -43°C) 0.1% per 100 parts of copolymer was added to the obtained reaction solution.
A pressure-sensitive adhesive was obtained by adding an epoxy crosslinking agent (Tetrarad

The resulting adhesive tape has an adhesive strength of 1070g/at room temperature.
25mm, adhesive strength at high temperature is 80℃, 100℃,
60g/25mm at any temperature of 120℃
It was below.

<Synthesis example of acrylic polymer (A)> Next, to 10 parts, 50 parts, and 90 parts of the above copolymer, 90 parts, 50 parts, and 1 part of monomer mixtures having the following compositions were added, respectively.
Further, 0.09 parts, 0.005 parts, and 0.01 parts of benzoyl peroxide were added to each, and 90 parts, 50 parts, and 10 parts of ethyl acetate were added to each, and copolymerization was carried out at 80°C for 10 hours. I did it.

2-Ethylhexyl acrylate 50 parts Methyl methacrylate 38 parts Vinyl acetate
10 parts acrylic acid
0 parts of each epoxy crosslinking agent (Tetralad X) per 100 parts of each copolymer composition obtained.
．． 1 part was added and applied to a polyethylene terephthalate film (Lumirror #25) substrate at a dry thickness of 25 μm to prepare three types of adhesive tapes.

The adhesive strength of the three types of adhesive tapes obtained at each temperature was as shown in Table 1.

Table 1 Note that when a copolymer containing only a post-added monomer mixture (acrylic polymer (A), Tg: 3°C) is used, there is no tack at room temperature, and the adhesive strength of the adhesive tape at high temperature is 8.
720 g725mm at 0℃, 880g/2 at 100℃
5mm, and 1200g/25mm at 120°C.

[Example 4] Synthesis example of acrylic polymer (A)> Butyl acrylate 54 parts Methyl methacrylate 38 parts Acrylamide 8 parts Azobisisobutyronitrile 0.2 parts Ethyl acetate
Polymerization was carried out using 150 parts at 70° C. for 8 hours in a conventional manner. (Tg; 1°C) 1.5% per 100 parts of copolymer was added to the obtained reaction solution.
An adhesive was obtained by adding an isocyanate-based crosslinking agent (Coronate HL, manufactured by Nippon Polyurethane Industries, Ltd.), and applied to a polyethylene terephthalate film (Lumirror #25) base material to a dry thickness of 25 μm to create an adhesive tape. did.

The obtained adhesive tape did not tack at room temperature, but
Adhesive strength at high temperature is 150g/25mm at 80"C
, 600 g/25mm at 100℃, 4 at 120℃
It was 50 g/25 mm.

<Synthesis example of acrylic polymer (B)> Next, 50 parts of a monomer mixture having the following composition was added to 50 parts of the above copolymer, and further 0.05 parts of benzoyl peroxide and 50 parts of ethyl acetate were added. and copolymerization was carried out at 80° C. for 10 hours.

Butyl acrylate 85 parts Vinyl acetate 7 parts Acrylic acid
Copolymer composition 1 obtained in 8 parts
per 00 parts, isocyanate-based crosslinking agent (Coronate H
3 parts of L) was added and applied to a polyethylene terephthalate film (Lumirror #25) substrate to a dry thickness of 25 μm to prepare an adhesive tape.

The adhesive strength of this adhesive tape at room temperature (23℃) is 80
0g/25mm, adhesive strength at high temperature is 620 at 80℃
g/25mm, 460g/25mm at 100℃, 120
℃, which was 260 g/25 mm, which was a high value.

[Effects of the Invention] According to the present invention, an acrylic pressure-sensitive adhesive composition is provided that has appropriate adhesive strength at room temperature and exhibits good adhesive strength even under high temperature conditions.

The acrylic pressure-sensitive adhesive composition of the present invention is useful, for example, as a paint masking tape or double-sided pressure-sensitive adhesive tape, particularly as a pressure-sensitive adhesive in the field of pressure-sensitive adhesive tapes used under room temperature to high temperature conditions.

Claims (3)

[Claims] (1) Obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester, a functional group-containing monomer, and optionally other radically polymerizable monomers,
An acrylic polymer (A) having an adhesive force of 200 g/25 mm or more at ℃ to 120 ℃ and a monomer mixture containing a (meth)acrylic acid alkyl ester, a functional group-containing monomer, and optionally other radically polymerizable monomers are combined. Obtained by polymerization, the adhesive strength at room temperature (23°C) is 5.
00g/25mm or more of the acrylic polymer (B), the ratio (A):(B) of both is 10:90 to 90:1.
0 (weight ratio), and has an adhesive strength of 100 g/25 mm or more at 80 to 120°C. (2) Copolymerizing the monomer mixture forming the acrylic polymer (B) in the presence of the acrylic polymer (A), or copolymerizing the acrylic polymer in the presence of the acrylic polymer (B). The acrylic pressure-sensitive adhesive composition according to claim 1, which is obtained by copolymerizing the monomer mixture forming (A). (3) The acrylic adhesive composition according to claim 1 or 2, wherein the functional group-containing monomer is at least one selected from carboxyl group-containing monomers and acid amide group-containing monomers.