JP2658202B2 - Solventless composition for pressure sensitive adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention [Industrial Application Field] The present invention comprises a (meth) acrylate-based copolymer which is polymerized by active energy rays and exhibits high cohesive strength. The present invention relates to a solventless pressure-sensitive adhesive.

[Prior art and its problems]

Conventionally, acrylic ester copolymer pressure-sensitive adhesives or rubber pressure-sensitive adhesives have been widely used as solutions in organic solvents such as toluene and ethyl acetate. However, the use of the organic solvent has problems such as harm to the handler, fire danger, and environmental pollution, and a large amount of expense is required for measures to prevent these problems.

Therefore, recently, although an aqueous emulsion type pressure-sensitive adhesive has been widely used in the field of labels and the like in place of the organic solvent type pressure-sensitive adhesive, the aqueous emulsion type has poor drying properties and water resistance. There was a problem that the properties were insufficient.

On the other hand, as an alternative to the solution-type or emulsion-type pressure-sensitive adhesive, an adhesive layer can be formed by irradiation with active energy rays such as ultraviolet rays or electron beams. Solvent-free pressure-sensitive adhesives using a diluent as a diluent have been proposed, but in such solvent-free adhesives, the degree of polymerization of the polymer serving as the adhesive is not sufficiently increased, and the adhesive layer to be formed is There was a problem that the cohesive force was insufficient.

As means for solving the above problems, Japanese Patent Laid-Open No.
In 109873, a solventless pressure-sensitive adhesive composition comprising a copolymer of an alkyl acrylate and having a small amount of an olefinically unsaturated group in the molecule thereof, having a molecular weight of 1,000 to 50,000 is provided. Proposed. The pressure-sensitive adhesive composition, the olefinically unsaturated group present in the copolymer is polymerized by irradiation with active energy rays,
Since the molecular weight of the copolymer is further increased, a high cohesive force can be exhibited as an adhesive.

However, the solvent-free pressure-sensitive adhesive composition disclosed in Japanese Patent Application Laid-Open No. 57-109873 has a problem in coatability due to its high viscosity, and is practically one step away.

[Problems to be solved by the invention]

An object of the present invention is to provide a solvent-free composition for a pressure-sensitive adhesive which has a low viscosity, is excellent in coating properties, and exhibits high adhesive strength, holding power and tack when polymerized by an active energy ray.

(B) Configuration of the Invention [Means for Solving the Problems] As a result of intensive studies to solve the problems, the present inventors have a (meth) acryloyl group polymerizable by an active energy ray in the molecule. A solvent-free pressure-sensitive adhesive comprising a (meth) acrylate copolymer and a room-temperature liquid aromatic resin is low in viscosity and excellent in coating properties, and is obtained by using an aromatic resin comprising the copolymer. Found that they have almost the same cohesive strength as compared to pressure-sensitive adhesives not containing
The present invention has been completed.

That is, the present invention comprises the following copolymer (A) and aromatic resin (B), the former being 20 to 90% by weight and the latter being 80 to 10% by weight based on the total amount of both. Yes,
It is a solventless composition for pressure-sensitive adhesives that can be polymerized by irradiation with active energy rays.

Copolymer (A); (meth) acryloyl group having a molecular weight of 1000
The average number per molecule is 0.01 to 2 and the number average molecular weight is 1000 to 10
(Meth) acrylic acid ester-based copolymer of 0000.

Aromatic resin (B): a room temperature liquid-state aromatic resin which is a condensate of formaldehyde and an alkylbenzene having two or more alkyl groups bonded to a benzene ring and having a number average molecular weight of 200 to 1,000.

 Hereinafter, the present invention will be described in more detail.

[(Meth) acrylic acid ester-based copolymer] The (meth) acrylic acid ester-based copolymer constituting the solvent-free composition for pressure-sensitive adhesive of the present invention has a molecular weight of (meth) acryloyl group as described above. Average 0.01 per 1000
It is a (meth) acrylate-based copolymer having two and having a number average molecular weight of 1,000 to 100,000, and a more preferable content of the (meth) acryloyl group is 0.01 to 1,000 per molecular weight of the copolymer. The number is one, and the more preferable number average molecular weight is 5,000 to 50,000. As a method for producing such a (meth) acrylate-based copolymer, various known methods are known. For example, in the presence of a chain transfer agent,
It is composed of a radical polymerizable monomer containing a (meth) acrylic acid alkyl ester as a main component and having a group reactive with an epoxy group such as a carboxyl group, and optionally another copolymer monomer. A method of copolymerizing a monomer mixture to obtain a copolymer having a carboxyl group and having a number average molecular weight of 1,000 to 100,000, and subjecting the carboxyl group in the copolymer to an addition reaction of glycidyl (meth) acrylate or the like. .

As the alkyl (meth) acrylate serving as a main constituent unit of the copolymer, the alkyl group has 1 to 1 carbon atoms.
(Meth) acrylic acid alkyl esters in the range of 12 are preferred, and the amount used is preferably at least 50% by weight, more preferably at least 70% by weight, based on the total amount of all monomers to be subjected to polymerization. . When the amount of the alkyl (meth) acrylate used is less than 50% by weight, the tackiness of the adhesive layer formed by irradiation with active energy rays tends to be insufficient.

For the purpose of introducing a (meth) acryloyl group into the copolymer, a radical polymerizable monomer having a reactive group to be used in combination with the alkyl (meth) acrylate during the polymerization may be (meth) acrylic. Acids, unsaturated compounds having a carboxyl group such as itaconic acid and maleic acid can be used, and the preferred amount is 1 to 20% by weight based on the total amount of all monomers, and more preferably. Is 1 to 10% by weight.

The copolymerizable monomers that can be used together with the above essential monomers include acrylonitrile, hydroxyethyl (meth)
Examples include vinyl monomers such as acrylate and N-methylolacrylamide, and the preferred amount is 20% by weight or less based on the total amount of all monomers.

As chain transfer agents, n-butyl mercaptan, n-
And mercaptan-based chain transfer agents such as dodecyl mercaptan and thioglycolic acid ester. By adjusting the amount of the chain transfer agent used in the copolymerization, a polymer having a desired number average molecular weight can be easily produced.

The polymerization can be carried out by a conventional method employing a solution polymerization method or a suspension polymerization method using a conventional radical polymerization initiator.

The most common method for introducing a (meth) acryloyl group into a copolymer obtained by the above polymerization is to add glycidyl (meth) acrylate to the copolymer. Is carried out at a temperature of about 60 to 120 ° C. in an organic solvent such as toluene, if necessary, using a catalyst such as a tertiary amine or a quaternary ammonium salt. The proportion of the copolymer and glycidyl (meth) acrylate used in the addition reaction is appropriately selected according to the number of (meth) acryloyl groups to be introduced into the copolymer. It is preferable that a carboxyl group coexist in the copolymer having a (meth) acryloyl group introduced therein (hereinafter referred to as an active energy ray-reactive copolymer) used in the present invention. The average is preferably 0.5 to 40, and more preferably 1 to 20, per molecule. The carboxyl group in the active energy ray-reactive copolymer has an effect of increasing the anchoring property to the substrate. If the amount of the carboxyl group exceeds 40 per one molecule of the active energy ray-reactive copolymer, the tack tends to decrease.

(Meth) in active energy ray reactive copolymer
If the number of acryloyl groups exceeds an average of 2 per 1000 molecular weight of the copolymer, in the adhesive layer obtained by irradiation with active energy rays, the crosslinking density becomes too high,
The required tack is not obtained. Further, if the number average molecular weight of the copolymer is less than 1000, the desired holding force cannot be obtained because the cohesive force of the obtained adhesive is low, while if it exceeds 100,000, the viscosity is too high and the coating is performed. Can not.

In addition, the number average molecular weight in the present invention indicates a number average molecular weight in terms of polystyrene obtained by measurement by gel permeation chromatography.

(Aromatic resin)

In the present invention, the aromatic resin used in combination with the (meth) acrylate-based copolymer is, for example, an alkylbenzene having two or more alkyl groups bonded to a benzene ring such as trimethylbenzene such as mesitylene, xylene or diethylbenzene. A room temperature liquid aromatic resin having a number average molecular weight of 200 to 1000, more preferably a number, which is obtained by condensing formaldehyde with a benzene ring having a structure linked by methylene, acetal or ether bond, etc. It is an aromatic resin having an average molecular weight of 400 to 600. Examples of the aromatic resin include xylene resin Nicanol manufactured by Mitsubishi Gas Chemical Co., Ltd. and GP-Resin manufactured by General Petrochemical Industry Co., Ltd. .

If the number average molecular weight of the aromatic resin is less than 200, a sufficient cohesive force cannot be obtained as an adhesive, while if it exceeds 1,000, the viscosity of the obtained composition becomes high and coating becomes difficult.

Further, the use ratio of the (meth) acrylate copolymer and the aromatic resin should be 20 to 90% by weight and 80 to 10% by weight of the latter based on the total amount of both. More preferably, the former is 50 to 80% by weight and the latter is 50% by weight.
~ 20% by weight. If the proportion of the aromatic resin is less than 10% by weight, the viscosity of the resulting composition is too high to make coating difficult, while if it exceeds 80% by weight, the cohesive strength is insufficient.

The solvent-free composition for a pressure-sensitive adhesive of the present invention contains the aromatic resin and the (meth) acrylate copolymer as essential components, and if necessary, as a reactive diluent as shown below. You may apply | coat to a base material after mixing a vinyl-type oligomer. Vinyl oligomers suitable as diluents include polyethylene glycol monophenyl ether mono (meth) acrylate, polyethylene glycol monononyl ether mono (meth) acrylate), polypropylene glycol monononylphenyl ether mono (meth) acrylate, 2-hydroxy- 3-butoxypropyl (meth) acrylate, 2-hydroxy-3
-Hexyloxypropyl (meth) acrylate, 2-
Hydroxy-3-phenoxypropyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, monoacryloyloxyethyl succinate, monoacryloyloxyisopropyl succinate, monoacryloyloxyethyl maleate, monoacryloyloxy maleate Isopropyl ester, monoacryloyloxyethyl ethyl hexahydrophthalate, monoacryloyloxyethyl tetrahydrophthalate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, diacrylate of bisphenol S ethylene oxide adduct and bisphenol A ethylene oxide adduct No. The preferable addition amount is 50% by weight or less, more preferably 20% by weight or less, based on the total amount of all components of the adhesive composition.

Furthermore, in order to increase the storage stability of the solvent-free composition for a pressure-sensitive adhesive of the present invention, a small amount of a stabilizer can be used. Preferred examples of the stabilizer include hydroquinone, hydroquinone monomethyl ether, and t-butylhydroquinone. And phenols such as catechol and t-butyl catechol, quinones such as benzoquinone, naphthoquinone and diphenylbenzoquinone, phenothiazine, and copper salts. These stabilizers are preferably used in an amount of 0.001 to 0.5% by weight based on the total amount of all components of the adhesive composition.

In addition, various additives used in general pressure-sensitive adhesives, such as preservatives, rust inhibitors, pigments, plasticizers, fillers, antifreezing agents, high-boiling solvents, defoamers, tackifiers and leveling agents, etc. Can be appropriately added.

(Formation of adhesive layer)

The viscosity of the solvent-free composition for a pressure-sensitive adhesive of the present invention obtained by mixing the above components is about 5,000 to 20,000 cps, and is roll-coated on a substrate such as paper, plastic film or metal foil, It can be easily applied by a method such as coating or knife coating.

After coating on the substrate, active energy rays such as X-rays,
irradiating ionizing radiation such as γ-rays and electron beams or ultraviolet rays to further polymerize the (meth) acrylic ester-based copolymer by utilizing the (meth) acryloyl group attached to the copolymer As a result, an adhesive layer having desired cohesive strength, tackiness, tackiness and the like is formed. Irradiation conditions of the active energy rays such as the ionizing radiation and the ultraviolet ray may be in accordance with a conventional method. When the adhesive layer is formed by irradiating the ultraviolet ray, a known light such as benzoin is contained in the adhesive. It is preferable to add an appropriate amount of a polymerization initiator.

[Examples and Comparative Examples]

Next, the present invention will be described more specifically by showing Examples and Comparative Examples. In each of the examples, “parts” means “parts by weight”.

In addition, the evaluation of the adhesive properties of the adhesive obtained in each example,
The adhesive layer applied to a polyester film (thickness: 50μ) and then cured by irradiating with an electron beam (hereinafter referred to as EB) or ultraviolet rays (hereinafter referred to as UV) under the following conditions is used for the measurement method described below. By measuring the adhesion, holding power and tack.

EB irradiator: ESI "Electronic Curtain" Acceleration voltage: 170 KV Irradiation dose: 5 Mrad Oxygen concentration in atmosphere: 100 to 200 ppm UV irradiator: Ushio Electric Co., Ltd. "Unicure 4000" Lamp: 80 W / cm, ozone type High-pressure mercury lamp Reflector: Condensing type (light condensing on conveyor) Conveyor speed: 15 m / mm Initiator: 5% of 2-hydroxy-2-methylpropiophenone was mixed. The adhesive properties were measured by the following method.

<Adhesive Strength> A stainless steel plate was used as an adherend, and the adhesion was measured according to the 180-degree peeling method specified in JISZ-0237.

<Holding force> A stainless steel plate was stuck at 25 x 25 mm, and a time of 1 kg load was applied at 80 ° C until peeling off was measured. When held for 3 hours, the deviation width was measured.

<Tack> Measured according to the JISZ-0237 ball rolling method.

Examples 1 and 2 3 equipped with a stirrer, thermometer, cooler and dropping funnel
In a four-necked flask, 10 parts of toluene was charged and 70
The temperature was raised to ° C. After charging 9.0 parts of butyl acrylate (hereinafter referred to as "BA") and 0.5 part of acrylic acid (hereinafter referred to as "AA"), 86 parts of BA, 4.5 parts of AA, 0.3 part of n-dodecyl mercaptan 0.3 part, azobisisobutyro Nitrile (hereinafter “AIBN”)
) And 10 parts of toluene were continuously added dropwise over 4 hours to obtain a viscous liquid. Next, 3 parts of glycidyl methacrylate was added, and the mixture was stirred at a temperature of 90 ° C. for 6 hours to perform a reaction. The acrylate copolymer thus obtained has a number average molecular weight of 30,000 and has about 8 methacryloyl groups per molecule of the copolymer (about 0.27 per 1000 molecular weight of the copolymer). The copolymer had about 15 carboxyl groups per molecule.

The amount of the methacryloyl group in the copolymer was measured by nuclear magnetic resonance (NMR) spectroscopy, and the amount of the carboxyl group was the acid value obtained by titration as the amount of the carboxyl group. The solvent was removed from the copolymer solution, and 100 parts of the obtained copolymer was used as an aromatic resin (GP-5-5, manufactured by General Petrochemical Industry Co., Ltd.).
80 parts of a number average molecular weight (550) was mixed to prepare a pressure-sensitive adhesive. The viscosity of this adhesive was 12,000 cps. The adhesive properties were applied to a polyester film and irradiated with EB (Example 1) and UV (Example 2), and the adhesive properties are shown in Table 1.

Examples 3 and 4 An aromatic resin (GP-19, trade name, manufactured by General Petrochemical Co., Ltd., trade name: GP-19, number average molecular weight 44) was added to 100 parts of the copolymer of Example 1.
0) 80 parts were mixed. The viscosity of the obtained adhesive is 9,800 cps
Met. The adhesive properties after EB irradiation (Example 3) and UV irradiation (Example 4) are shown in Table 1.

Example 5 The above-mentioned GP-5-1 (40 parts) was mixed with 100 parts of the copolymer of Example 1. The viscosity of the obtained adhesive was 18,000 cps. E
The adhesive properties after B irradiation are shown in Table 1.

Examples 6 and 7 The mixing ratio of the copolymer of Example 1 and the aromatic resin GP-5-1 was changed to 100 parts of the former to 100 parts of the latter (Example 6).
An adhesive was obtained by changing the ratio of the former 100 parts to the latter 300 parts (Example 7). The viscosity of each obtained adhesive was Example 6: 10500 cps and Example 7: 7100 cps.

 Table 1 shows the adhesive properties of these adhesives after EB irradiation.

Example 8 Under the same conditions as in Example 1, a single loss mixture having a composition of 90 parts of BA and 10 parts of AA was polymerized, and an addition reaction was carried out to obtain a copolymer.

The copolymer has a number average molecular weight of 30,000, and has about 8 methacryloyl groups per molecule of the copolymer (the molecular weight of the copolymer is 10%).
The copolymer had about 30 carboxyl groups per molecule of the copolymer.

An adhesive was obtained by mixing 120 parts of an aromatic resin (trade name: GP-16, number average molecular weight: 400, manufactured by General Petrochemical Industries, Ltd.) with 100 parts of the above copolymer. The viscosity of the obtained adhesive is 82
It was 00cps. The adhesive properties after EB irradiation are shown in Table 1.

Examples 9 and 10 Under the same conditions as in Example 1, a monomer mixture having a composition of 99 parts of BA and 1 part of AA was polymerized, and an addition reaction was carried out to give a number average molecular weight of 30,000 and a methacryloyl group. Approximately 8 molecules per polymer (molecular weight of copolymer)
A copolymer having about 0.27 per 1000) and about 0.9 carboxyl groups per copolymer molecule was obtained.

An adhesive was obtained by mixing 120 parts of the aromatic resin GP-16 with 100 parts of the above copolymer. The viscosity of this adhesive was 9000 cps. The adhesive properties after irradiation with EB (Example 9) and UV (Example 10) are shown in Table 1.

Example 17 Under the same conditions as in Example 1, polymerization was carried out using 20 parts of toluene as a solvent, 90 parts of BA and 10 parts of AA as monomers, and 0.7 part of n-dodecyl mercaptan and 0.02 part of AIBN. Glycidyl methacrylate (12 parts) was added to the obtained polymer solution and reacted at 90 ° C. for 6 hours with stirring.

The number average molecular weight of the acrylate copolymer obtained by the above operation is 10,000, and the content of the methacryloyl group is about 16 per one molecule of the copolymer (about 1.6 per 1,000 of the molecular weight of the copolymer). And the content of carboxyl groups was about 7 per molecule of the copolymer.

Aromatic resin GP-5-1 was added to 100 parts of the copolymer.
Was added to prepare an adhesive. The viscosity of the obtained adhesive is 6500 cps, and the adhesive properties after EB irradiation are as follows: adhesive strength: 790 g
/ 25 mm, holding power: no displacement, tack: 4.

Examples 11 to 16 The adhesive prepared in Example 1 was further added with various vinyl oligomers described in Table 2 to evaluate the adhesive properties of the adhesives. The results are shown in Table 2. Was.

Comparative Example 1 Aromatic resin GP-5-1 was added to 100 parts of the copolymer of Example 1.
Were mixed to obtain an adhesive. The viscosity of this adhesive is 39
000 cps and its adhesive properties after irradiation with EB (Comparative Example 1) are as shown in Table 3.

Comparative Examples 2 and 3 The aromatic daughter resin (number average molecular weight 180) (Comparative Example 2) or the aromatic resin (number average molecular weight 1040) (Comparative Example 3) was used per 100 parts of the copolymer of Example 1. In this case also, 80 parts were mixed to obtain an adhesive. The viscosity of the adhesive of Comparative Example 2 is 7900 cp
s, and the viscosity of the adhesive of Comparative Example 3 was 36000 cps. The adhesive properties after EB irradiation are as shown in Table 3.

(C) Effects of the Invention The solvent-free composition for a pressure-sensitive adhesive of the present invention has a low viscosity without using an organic solvent, and can be easily applied to a base material such as paper or a plastic film by an ordinary coating method. It is possible to form a practically suitable adhesive layer that has a sufficiently large cohesive force represented by holding power and adhesive force, and can be formed into a high molecular weight by irradiation with an electron beam or ultraviolet light. Therefore, it can be preferably used for a wide range of applications without worrying about various problems caused by the organic solvent.

Claims (1)

(57) [Claims] (1) It comprises the following copolymer (A) and aromatic resin (B), and the former is 20 to 20 based on the total amount of both.
A solventless composition for a pressure-sensitive adhesive, which is 90% by weight and the latter is 80 to 10% by weight, and is polymerizable by irradiation with active energy rays. Copolymer (A); (meth) acryloyl group having a molecular weight of 1000
The average number per molecule is 0.01 to 2 and the number average molecular weight is 1000 to 10
(Meth) acrylic acid ester-based copolymer of 0000. Aromatic resin (B): a room temperature liquid-state aromatic resin which is a condensate of formaldehyde and an alkylbenzene having two or more alkyl groups bonded to a benzene ring and having a number average molecular weight of 200 to 1,000.