JPH0211685A - Solventless composition for pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To obtain a composition which is lowly viscous, excels in coatability, is polymerizable with actinic radiation and can produce a high adhesion, retentivity and tack by mixing a specified (meth)acrylate copolymer with an aromatic resin. CONSTITUTION:This solventless composition for pressure-sensitive adhesive comprises a copolymer (A) and on aromatic resin (B), in a ratio of A to B of 20-90 to 80-10 (by wt.%), and is polymerizable by irradiation with an actinic radiation. Said copolymer (A) has 0.01-2, on the average, per MW of 1000, (meth)acrylyol groups and a number-average MW of 1000-100000. The aromatic resin (B) is a normally liquid aromatic resin of a number-average MW of 200-1000, which is a condensate of formaldehyde with an alkylbenzene having at least two alkyl groups bonded to the benzene ring.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] The present invention consists of a (meth)acrylic acid ester copolymer that is polymerized by active energy rays and exhibits high cohesive strength. This invention relates to a solvent-free pressure-sensitive adhesive.

[Prior art and its problems]

Conventionally, acrylic ester copolymer-based pressure-sensitive adhesives or rubber-based pressure-sensitive adhesives have been used as solutions in organic solvents such as toluene and ethyl acetate. There are problems such as toxicity, fire danger, and environmental pollution, and a large amount of money is required to take preventive measures against these problems.

Therefore, recently, aqueous emulsion type pressure sensitive adhesives have been widely used in the field of labels etc. instead of the organic solvent type pressure sensitive adhesives mentioned above, but aqueous emulsion types have poor drying properties and water resistance. There was a problem of insufficient gender.

On the other hand, as an alternative to the above solution-type or emulsion-type pressure-sensitive adhesive, monomers such as acrylic acid alkyl esters can be used to form an adhesive layer by irradiation with active energy rays such as ultraviolet rays or electron beams. Solvent-free pressure-sensitive adhesives have been proposed that use a diluent as a diluent, but in such solvent-free adhesives, the polymerization degree of the adhesive polymer does not increase sufficiently, and There was a problem that the cohesive force of the adhesive layer was insufficient.

As a means to solve the above problems, JP-A-57-
No. 109873 (109873) describes a copolymer consisting of an acrylic acid alkyl ester, which has a small amount of olefinically unsaturated groups in its molecule, and has a molecular weight of 1000 to 50.
A solvent-free adhesive composition consisting of a copolymer of As a result, the molecular weight of the copolymer becomes even larger, so that it can exhibit high cohesive force as an adhesive.

However, the solvent-free pressure-sensitive adhesive composition disclosed in JP-A-57-109873 has a problem in coatability due to its high viscosity, and is not suitable for practical use.

[Problem to be solved by the invention]

The present invention aims to provide active energy with low viscosity and excellent coating properties.

(B) Structure of the Invention [Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have discovered that polymerizable (having a methane acryloyl group in the molecule) with active energy rays ( A solvent-free pressure-sensitive adhesive made of a meth)acrylic acid ester copolymer and an aromatic resin that is liquid at room temperature has a low viscosity and excellent coating properties. It was discovered that the cohesive force is almost the same as that of a pressure-sensitive adhesive that does not contain it, and the present invention was completed.

That is, the present invention consists of the following copolymer and aromatic resin (Bl), and the former is 2% based on the total amount of both.
The latter accounts for 80 to 10% by weight, and is a solvent-free composition for pressure-sensitive adhesives that can be polymerized by irradiation with active energy rays.

Copolymer (3); (meth)acryloyl group with molecular weight 10
A (meth)acrylic acid ester copolymer having an average of 0.01 to 2 molecules per 0.00 and a number average molecular weight of 1000 to 100000.

Aromatic resin (B) is a condensate of formaldehyde and an alkylbenzene in which two or more alkyl groups are bonded to a benzene ring, and is liquid at room temperature and has a number average molecular weight of 200 to 1000.

The present invention will be explained in more detail below.

The acrylic acid ester copolymer is as described above (meth)
The average molecular weight of acryloyl groups is 0.01 to 2 per 1000 g.
7 acrylic acid ester copolymer having a number average molecular weight of 1,000 to 100,000, and the more preferable content of (meth)acryloyl groups is the average content of (meth)acryloyl groups per 11,000 molecules of the copolymer. 0801 to 1, and a more preferable number average molecular weight is 5000 to 50000. Various known methods are known for producing such (meth)acrylic acid ester copolymers. In addition, a monomer mixture consisting of a radically polymerizable monomer having a group reactive with an epoxy group such as a carboxyl group, and other copolymerizable monomers as necessary is copolymerized, and a monomer mixture containing a carboxyl group is formed. An example of this method is to obtain a copolymer having a number average molecular weight of 1,000 to 100,000, and to add glycidyl (meth)acrylate or the like to the carboxyl groups in the copolymer.

The (meth)acrylic acid alkyl ester, which is the main structural unit of the above copolymer, has an alkyl group with 1 to 1 carbon atoms.
A (meth)acrylic acid alkyl ester in the range of 12 is preferable, and the amount used is preferably 50% by weight or more, more preferably 70% by weight or more based on the total amount of all monomers subjected to polymerization. . When the amount of (meth)acrylic acid alkyl ester used is less than 50% by weight,
The adhesive layer formed by irradiation with active energy rays tends to have insufficient tack.

For the purpose of introducing a (meth)acryloyl group into a copolymer, (meth)acrylic acid is a radically polymerizable monomer having a reactive group that should be used in combination with the above (meth)acrylic acid alkyl ester during polymerization. An unsaturated compound having a carboxyl group such as acid, itaconic acid and maleic acid can be used, and the preferred amount used is 1 to 20% by weight based on the total amount of all monomers, more preferably is 1 to 10% by weight. Copolymerizable monomers that can be used in combination with the above essential monomers include vinyl monomers such as acrylonitrile, hydroxyethyl (meth)acrylate, and N-methylolacrylamide, The preferred amount used is 20% by weight or less based on the total amount of all monomers.

Examples of the chain transfer agent include mercaptan chain transfer agents such as n-butylmercaptan, n-dodecylmercaptan, and thioglycolic acid ester. By adjusting the amount of chain transfer agent used in copolymerization, a polymer having a desired number average molecular weight can be easily produced.

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

The most common method for introducing (meth)acryloyl groups into the copolymer obtained by the above polymerization is to add glycidyl (meth)acrylate to the copolymer, and this addition reaction This is preferably carried out in an organic solvent such as toluene at a temperature of about 60 to 120° C. using a catalyst such as a tertiary amine or a quaternary ammonium salt if necessary. The ratio of the copolymer and glycidyl (meth)acrylate used in the addition reaction is appropriately selected depending on the number of (meth)acryloyl groups to be introduced into the copolymer.

It is preferable that a carboxyl group coexists in the (meth)acryloyl group-introduced copolymer used in the present invention (hereinafter referred to as active energy ray-reactive copolymer),
The number of carboxyl groups per molecule of the copolymer is preferably 0.5 to 40 on average, more preferably 1
~20 pieces. The carboxyl group in the active energy ray-reactive copolymer has the effect of increasing anchoring ability to the base material. When the amount of carboxyl groups exceeds 40 per molecule of the active energy ray-reactive copolymer, tack tends to decrease.

The number of (meth)acryloyl groups in the active energy ray-reactive copolymer is the molecule fit100 of the copolymer.
If the average number exceeds 2 per 0, the crosslinking density will become too high in the adhesive layer obtained by irradiation with active energy rays, making it impossible to obtain the necessary tack. In addition, if the number average molecular weight of the copolymer is less than 1,000, the cohesive force of the resulting adhesive will be low, making it impossible to obtain the desired holding power, while if it exceeds 100,000, the viscosity will be too high to coat. Can not.

In addition, the number average molecular weight in the present invention refers to the number average molecular weight in terms of polystyrene obtained by measurement by gel permeability solar chromatography.

[Aromatic resin]

In the present invention, the aromatic resin used in combination with the (meth)acrylic acid ester copolymer is an alkylbenzene in which two or more alkyl groups are bonded to a benzene ring such as trimethylbenzene such as mesitylene, xylene or diethylbenzene, etc. It is an aromatic resin that is liquid at room temperature and has a number average molecular weight of 200 to 1000, and has a structure in which benzene rings are linked by methylene, acetal, or ether bonds, etc., obtained by condensation with formaldehyde. Average molecular weight is 400-60
Examples of such aromatic resins include xylene resin dicanol manufactured by Mitsubishi Gas Chemical Co., Ltd. and gGP-Resin manufactured by General Petrochemical Co., Ltd.
etc.

If the number average molecular weight of the aromatic resin is less than 200, coating becomes difficult.

In addition, the ratio of the (meth)acrylic acid ester copolymer and aromatic resin used should be 20 to 90% by weight of the former and 80 to 10% by weight of the latter, based on the total amount of both. Yes, the former is more preferably 50 to 80 f
%, the latter becomes too much and coating becomes difficult, and on the other hand, if it exceeds 80% by weight, a (meth)acrylic acid ester copolymer is an essential component, but if necessary, a vinyl-based copolymer as shown below can be used as a reactive diluent. The oligomers may be mixed and then applied to the substrate. 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, and 2-hydroxy- 3-butoxypropyl (meth)acrylate, 2-hydroxy-5-hexyloxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate,
Dicyclopentenyloxyethyl (meth)acrylate, succinic acid monoacryloyloxyethyl ester, succinic acid monoacryloyloxyisoglobil ester,
Maleic acid monoacryloyloxyethyl ester, maleic acid monoacryloyloxyethyl ester, maleic acid monoacryloyloxyethyl ester, hexahydrophthalic acid monoacryloyloxyethyl ester, tetrahydrophthalic acid monoacryloyloxyethyl ester, polyethylene glycol diacrylate, polyglopylene glycol diacrylate, bisphenol S Examples include diacrylate of ethylene oxide adduct and bisphenol A ethylene oxide adduct. The preferred amount of the stabilizer added is 50% by weight or less based on the total amount of all constituent components of the adhesive composition, and to increase the preference, a small violet stabilizer can also be used, and a suitable stabilizer Examples include phenols such as hydroquinone, hydroquino/monomethyl ether, t-butylhydroquinone, catechol, and t-butylcatechol, 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 of all components of the adhesive composition.

- Various additives used in pressure-sensitive adhesives, such as preservatives, rust preventives, pigments, plasticizers, fillers,
An antifreeze agent, a high boiling point solvent, an antifoaming agent, a mesh firer, a leveling agent, etc. can be added as appropriate.

[Formation of adhesive layer]

It can be easily coated onto a substrate such as paper, plastic film, or metal foil by a method such as roll coating, die coating, or knife coating.

After coating the base material, active energy rays such as X-rays, γ
By irradiating ionizing radiation such as beams and electron beams or ultraviolet rays to utilize the (meth)acryloyl groups attached to the (meth)acrylate copolymer to further polymerize the copolymer. , to form an adhesive layer having desired cohesion, adhesion, tack, etc. The irradiation conditions for the above-mentioned ionizing radiation and active energy rays such as ultraviolet rays may be according to conventional methods. When forming an adhesive layer by irradiating ultraviolet rays, known light such as benzoin is added to the adhesive. It is preferable to add an appropriate amount of a polymerization initiator.

[Examples and comparative examples]

Next, the present invention will be explained in more detail by showing examples and comparative examples. Note that "parts" on each side mean "parts by weight."

In addition, to evaluate the adhesive properties of the adhesive obtained on each side, the adhesive was applied to a polyester film (thickness 50μ),
The adhesive layer was then cured by irradiation with electron beams (hereinafter referred to as EB) or ultraviolet rays (hereinafter referred to as UV) under the following conditions, and the adhesive strength, holding power, and tack were measured using the measurement methods shown below. Ta.

EB irradiation device: “Electro Curtain” made by ESI Acceleration voltage: 170 KV Irradiation dose: 5 Mrad Oxygen concentration in the atmosphere: 100-200 ppm UV irradiation device m: Ushio Inc. [Unikea 4000J lamp: 80 W/scratch, ozone type high-pressure mercury lamp Two reflector condensing type (light condensing on the conveyor) Conveyor speed: 15 ffl/Initiator: 5 units of 2-hydroxy-2-methylpropiophenone were mixed.The adhesive properties were determined by the following method.

Adhesive strength〉 Stainless steel plate is used as the adherend ~, JISZ-023
Measurement was carried out according to the specified 180 degree peeling method.

<Holding force> Stainless steel plates were laminated with 25×25101 plates, and a load was applied at 80° C. for 1 hour to measure the time until the plates peeled off.

When held for 3 hours, the deviation width was determined.

<tack> Measurement was performed according to the JISZ-0217 ball rolling method.

Example 1.2 3tA equipped with stirrer, thermometer, cooler and dropping funnel
Pour 10 parts of toluene into a flask and heat under nitrogen atmosphere.
The temperature was raised to 0°C. 90 parts of butyl acrylate (hereinafter referred to as BAJ), acrylic acid (hereinafter referred to as AAJ)
After preparing 0.5 parts, BA86 parts, AAJ, 5 parts, n-
0.3 parts of dodecyl mercaptan, 0.02 parts of azobisisobutyronitrile (hereinafter referred to as AIBNJ), 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 carry out a reaction. The acrylic ester copolymer thus obtained has a number average molecular weight of 30,000, and has approximately 8 methacryloyl groups per molecule of the copolymer (approximately 0.00 methacryloyl groups per 11,000 molecules of the copolymer. 27) and about 15 carboxyl groups per molecule of the copolymer.

The amount of methacryloyl groups in the copolymer is determined by nuclear magnetic resonance (N
The amount of carboxyl groups was measured by MR) spectroscopy, and the acid value obtained by titration was used as a measure of the carboxyl groups. The solvent was removed from this copolymer solution, and aromatic resin (trade name: GP-5-1 manufactured by General Petrochemical Industry @) was added to 100 parts of the obtained copolymer.
A pressure-sensitive adhesive was prepared by mixing 80 parts (number average molecular weight: 550). The viscosity of this adhesive was 12,000 cps. Table 1 shows the adhesive properties after applying the adhesive onto a polyester film and irradiating it with EB (Example 1) and UV (Example 2).

Example 6.4 100 parts of the copolymer of Example 1 was added with an aromatic resin (manufactured by General Petrochemical Corporation, trade name: GP-19, number average molecule Mk44).
0) 80 parts were mixed. The viscosity of the obtained adhesive was 9.8
It was 00cps. EB irradiation (Example 3) and UV
Table 1 shows the adhesive properties after irradiation (Example 4).

Example 5 40 parts of the above GP-5-1 was added to 100 parts of the copolymer of Example 1.
Parts were mixed. The viscosity of the obtained adhesive was 18.000
It was cps. Table 1 shows the adhesive properties after EB irradiation.

Examples 6 and 7 The mixing ratio of the copolymer of Example 1 and the aromatic resin GP-5-1 was 100 parts of the former to 100 parts of the latter (Example 6
), and the adhesive was obtained by changing the ratio of 100 parts of the former to 500 parts of the latter in Example 7). The viscosity of each adhesive obtained was 10,500 cps for Example 6 and 7,100 cps for Example 7, respectively.

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

Example 8 Under the same conditions as Example 1, 90 parts of BA and AAI
A monomer mixture having a composition of O parts was polymerized, and an addition reaction was further performed to obtain a copolymer.

The copolymer has a number average molecular weight of 50.000, has about 8 methacryloyl groups per molecule of the copolymer (about 0.27 per 1000 molecules of the copolymer), and has a carboxyl group It had about 30 molecules per molecule.

Add 100 parts of the above copolymer to an aromatic resin (General Petrochemical Co., Ltd. fA Pfa Product name CP-16 number average molecule i!
t400) were mixed to obtain an adhesive. The resulting adhesive had a viscosity of 8200 cps. Table 1 shows the adhesive properties after EB irradiation.

Example 9.10 Under the same conditions as Example 1, BA99 part 6 and AA
By polymerizing a single adhesion mixture having a composition of 1 part and further performing an addition reaction, the number average molecular weight can be obtained! 10000, methacryloyl, /l/ group (about 0.27 per 1000), and carboxyl group about 0 per 1 molecule of the copolymer.
．． A copolymer having 9 polymers was obtained.

Add 12 parts of aromatic resin GP-16 to 100 parts of the above copolymer.
An adhesive was obtained by mixing 0 parts. The viscosity of this adhesive is 90
It was 00cps. Table 1 after EB (Example 9) and UV (Example 10) irradiation Example 17 Under the same conditions as Example 1, using 20 parts of toluene as a solvent and 20 parts of Bi and 10 parts of AA as monomers,
0.7 parts of n-dodecyl mercaptan and AIB No.
02 parts were added to carry out polymerization. 12 parts of glycidyl methacrylate was added to the obtained polymer solution, and the temperature was 90°C.
The mixture was reacted with stirring for 6 hours.

The number average molecular weight of the acrylic ester copolymer obtained by the above procedure was 1oooo, and the content of methacryloyl groups was about 16 per molecule of the copolymer (about 1 per molecule of copolymer [1000-1]). .6), and the content of carboxyl groups was about 7 per molecule of the copolymer.

Aromatic resin GP-5-
1 was added to prepare an adhesive.

The viscosity of the obtained adhesive was 6,500 cps, and the adhesive physical properties after EB irradiation were 790 g/25 g of adhesive, no slippage during retention, and tack: 4.

Examples 11 to 16 Regarding adhesives obtained by adding various vinyl oligomers listed in Table 2 to the adhesive produced in Example 1,
The adhesive properties of each were evaluated and the results are shown in Table 2.

Comparative Example 1 Aromatic resin GP-5- was added to 100 parts of the copolymer of Example 1.
1 was mixed to obtain an adhesive. The viscosity of this adhesive is
The adhesive properties after EB (Comparative Example 1) irradiation are as shown in Table 6.

Comparative Examples 2 and 6 Per 100 parts of the copolymer of Example 1, either aromatic resin (number average molecule 1180) (Comparative Example 2) or aromatic resin (number average molecule f 1040) (Comparative Example 3) In the case of 800 parts, an adhesive was also obtained. The viscosity of the adhesive in Comparative Example 2 was 7,900 cps, and the viscosity of the adhesive in Comparative Example 3 was 36,000 cps. The adhesive physical properties after EB irradiation are as shown in Table 3.

Table 6 It has a low viscosity at best, can be easily coated on substrates such as paper and plastic films by ordinary coating methods, and can be made into a polymer by irradiation with electron beams or ultraviolet rays. The cohesive force represented by holding power and adhesion is sufficiently large to form a practically suitable adhesive layer, so it can be used in a wide range of applications without worrying about various problems caused by organic solvents. It can be preferably used.

Claims (1)

[Claims] 1. Consisting of the following copolymer (A) and aromatic resin (B), the former being 20 to 90% by weight and the latter 80 to 10% by weight, based on the total amount of both. A solvent-free composition for a pressure-sensitive adhesive that can be polymerized by irradiation with active energy rays. Copolymer (A); (meth)acryloyl group with a molecular weight of 10
A (meth)acrylic acid ester copolymer having an average of 0.01 to 2 molecules per 0.00 and a number average molecular weight of 1000 to 100000. Aromatic resin (B): An aromatic resin that is a condensate of formaldehyde and an alkylbenzene in which two or more alkyl groups are bonded to a benzene ring, and is liquid at room temperature and has a number average molecular weight of 200 to 1000.