JP3053673B2 - Photopolymerizable composition and polymer thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photopolymerizable composition and a polymer thereof, and more particularly, to an alkyl (meth) acrylate-based photopolymerizable composition containing an aminoalkyl (meth) acrylate. And a polymer obtained by polymerizing the photopolymerizable composition with light.

[0002]

2. Description of the Related Art Viscoelastic products made of acuruli-based polymers are excellent in light resistance, weather resistance, oil resistance, etc., for example, acrylic adhesives, acrylic adhesive tapes, acrylic adhesive sheets, double-sided adhesive tapes, and the like. It is used in a wide range of fields such as adhesive processed products of foams. In particular, acrylic pressure-sensitive adhesives are widely used because they are excellent in adhesive performance such as adhesive strength and cohesive strength, and aging resistance such as heat resistance and weather resistance.

[0003] The molecular weight of an acrylic polymer has a direct effect on its adhesive performance. Generally, in order to increase the cohesive force of an acrylic polymer, the molecular weight must be as high as 500,000 or more in terms of polystyrene equivalent weight average molecular weight by gel permeation chromatography (GPC). As another method for increasing the cohesive force, a method for increasing the degree of crosslinking of a polymer is known. However, the low-molecular-weight product hardly increases the degree of cross-linking compared to the high-molecular-weight product, and even if the degree of cross-linking increases, the adhesive force, which is an important physical property as an adhesive, is much lower than that of the high-molecular-weight product. Would.

[0004] Therefore, it has been common technical knowledge that an acrylic polymer to be used as an adhesive must have a high molecular weight and not a low molecular weight.

In recent years, it has been found that when a special monomer, a macromonomer having a weight average molecular weight of about 10,000 and an acrylic monomer is copolymerized, the polymer can be used as an adhesive even if the weight average molecular weight of the polymer by GPC is about 200,000. Was. This means that the polymer is a graft copolymer,
It is believed that the polymer is a comb-shaped polymer (JP-A-61-103971).

However, in this technique, the macromonomer obtained from the living polystyryllithium anion is expensive and the combination of the monomers is limited, so that there are limitations on the applicable applications.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photopolymerizable composition which satisfies physical properties as an adhesive even if it has a lower molecular weight than an acrylic polymer used in a conventional adhesive, An object of the present invention is to provide a polymer such as an adhesive obtained from the composition.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art, and as a result, have found that a vinyl monomer having an alkyl (meth) acrylate as a main component is substituted with an aminoalkyl (meth) acrylate. Using a photopolymerizable composition containing an ester, the polymer produced by photopolymerization of the polymer has a low GPC molecular weight, but it has been found that the polymer exhibits sufficient performance as a pressure-sensitive adhesive. Based on the above, the present invention has been completed.

[0009]

According to the present invention, (a)
100 parts by weight of a vinyl monomer having an alkyl (meth) acrylate as a main component, and (b) an aminoalkyl (meth) acrylate having a substituted alkyl group having an N, N-dialkylamino group as an alcohol moiety.
01 to 1 part by weight, and (c) photopolymerization initiator 0.1 to 5
A photopolymerizable composition is provided which contains parts by weight.

According to the present invention, there is provided a polymer obtained by irradiating the photopolymerizable composition with light. The polymer is added to the photopolymerizable composition in an amount of 0.5 to 10%.
Obtained by irradiating 0 W / cm ² ultraviolet rays,
The weight average molecular weight in terms of polystyrene by GPC is 2 to 6.
It has a pressure-sensitive adhesive performance of about 10,000. Hereinafter, the components of the present invention will be described in detail.

(Vinyl Monomer) In the present invention, a vinyl monomer having an alkyl (meth) acrylate as a main component is used as a main monomer component. The alkyl (meth) acrylate usually has 1 to 14 carbon atoms in the alkyl group, and is preferably used as a main component in the vinyl monomer at a ratio of preferably 60 to 100% by weight. Other vinyl monomers copolymerizable with the alkyl (meth) acrylate are preferably used in a proportion of 0 to 40% by weight.

As the alkyl (meth) acrylate, an alkyl acrylate or alkyl methacrylate having an alkyl group of usually 1 to 14, preferably 4 to 12 carbon atoms is used. Specific examples include n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl (meth) acrylate.

These are used alone or in combination of two or more. In general, the glass transition temperature of the homopolymer is -50 due to the balance between tackiness and cohesiveness.
It is preferable to use an alkyl acrylate at a temperature of not more than ° C as a main component, and to use a (meth) acrylic ester of a lower alkyl group or a vinyl monomer described below as a comonomer.

Other vinyl monomers which can be copolymerized with alkyl (meth) acrylates include, for example, acrylic acid, methacrylic acid, acrylamide, acrylonitrile, methacrylonitrile, N-substituted acrylamide, hydroxyethyl Acrylate, N-vinylpyrrolidone, maleic acid, itaconic acid, N-methylol acrylamide, hydroxyethyl methacrylate and the like can be mentioned.

Further, vinyl monomers forming a polymer having a low glass transition temperature, for example, vinyl monomers such as tetrahydrofurfuryl acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, fluorine acrylate and silicon acrylate can also be used.

The other vinyl monomers may be used alone or in combination of two or more. If the use ratio in the vinyl monomer component exceeds 40% by weight, the adhesive properties and the like as an acrylic adhesive are deteriorated. So
Not preferred.

[Aminoalkyl (meth) acrylate] Aminoalkyl (meth) acrylate having a substituted alkyl group having an N, N-dialkylamino group as an alcohol moiety is based on 100 parts by weight of the vinyl monomer. And 0.01 to 1 part by weight. If the compounding ratio is too small or too large, the intended purpose cannot be achieved. As a specific example, N, N-
Diethylaminoethyl (meth) acrylate, N, N-
Dimethylaminoethyl (meth) acrylate and the like can be mentioned.

(Photopolymerization Initiator) The photopolymerization initiator is blended in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the vinyl monomer.

Specific examples include, for example, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [Darocur-2959: manufactured by Merck],
acetophenones such as α-hydroxy-α, α′-dimethyl-acetophenone [Darocur-1173: manufactured by Merck], methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and benzoin such as benzoin ethyl ether and benzoin isopropyl ether Examples thereof include ethers, ketals such as benzyldimethyl ketal, and halogenated ketones, acylphosphinoxides, and acylphosphonates.

When the compounding ratio is less than 0.1 part by weight, the photopolymerization initiator is consumed in the early stage of the polymerization by light energy, so that unreacted monomers tend to remain, and not only the monomer odor remains but also , The cohesion decreases. vice versa,
When the amount exceeds 5 parts by weight, the polymerization reaction speed is increased, but the decomposition odor of the photopolymerization initiator is increased, the variation in molecular weight is increased, and the adhesive performance is reduced.

(Optional Components) The photopolymerizable composition of the present invention may optionally contain a crosslinking agent, an additive, and the like.

Polymerizable Crosslinking Agent The photopolymerizable composition of the present invention preferably contains a polymerizable crosslinking agent in order to impart heat resistance and cohesive strength at high temperatures.

Examples of such a polymerizable crosslinking agent include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di ( (Meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, other epoxy acrylate, polyester acrylate, urethane acrylate, etc. .

By generally containing 5 parts by weight or less of such a polymerizable crosslinking agent with respect to 100 parts by weight of the vinyl monomer component, cross-linking occurs between polymer molecules during the photopolymerization reaction, and The heat resistance of the polymer obtained is improved. When the polymer is a pressure-sensitive adhesive tape, the cohesive strength at high temperatures increases, and the holding power at high temperatures improves.

Other Additives In the present invention, commonly used additives such as a thickener, a thixotropic agent, a bulking agent and a filler may be added to the photopolymerizable composition. As a thickener, acrylic rubber,
Epichlorohydrin rubber and the like. Examples of the thixotropic agent include colloidal silica and polyvinylpyrrolidone.

Examples of the extender include calcium carbonate, titanium oxide, clay and the like. As fillers, inorganic hollow bodies such as glass balun, alumina balun, ceramic balun, organic spheres such as nylon beads, acrylic beads, silicon beads, organic hollow bodies such as vinylidene chloride, acrylic balun, polyester, rayon, nylon, etc. Monofilament and the like.

(Method for producing polymer) In order to obtain a polymer using the photopolymerizable composition of the present invention, an inert gas such as nitrogen gas is usually used to remove dissolved oxygen in the composition. Or a compound having an oxygen removing effect such as phenyldiisodecyl phosphite, triisodecyl phosphite or stannous octoate is added. By adding a compound having an oxygen removing effect, sufficient polymerization (hardening) can be realized even if the oxygen concentration in the atmosphere is high to some extent.

As a polymer, for example, in the case of producing an adhesive tape, the photopolymerizable composition is applied or poured onto a release paper, a release form, or the like, or is formed from a plastic film, paper, cellophane, cloth, or nonwoven fabric. Or impregnating or impregnating a substrate such as a metal foil. When the substrate is not impregnated, an adhesive tape without the substrate is obtained. When a sealing material is produced as a polymer, the photopolymerizable composition is injected into a strippable elongated mold or the like.

Applying the photopolymerizable composition to a mold or a substrate,
When impregnating or pouring, it is preferable to thicken with a thickener so that the work is performed smoothly. In addition, as a thickening method, for example, there is a method in which a part of the monomer component is polymerized in advance by irradiating a small amount of ultraviolet rays. For the application, impregnation or injection work, a device designed so as not to come into contact with air (oxygen) is used.

After being applied, impregnated, or injected into a mold or a substrate, the photopolymerizable composition is passed through a box replaced with an inert gas, and irradiated with ultraviolet light through quartz glass, pyrex glass, or borate glass. And irradiation of light such as visible light. Even in an atmosphere of an inert gas, by covering the surface of the photopolymerizable composition applied, impregnated or injected into a mold or a base material with a polyester film having releasability, air (oxygen ) May be applied to prevent irradiation with light. In this case, it is preferable to add a compound capable of removing oxygen.

Usually, ultraviolet light is used as the light.
As an ultraviolet lamp, usually, a wavelength of 300 to 400 nm
Although those having a spectral distribution in the region are used, specific examples include chemical lamps, black light lamps (trade names of Toshiba Electric Materials Co., Ltd.), low-pressure, high-pressure, ultra-high-pressure mercury lamps, metal halide lamps, and microwave-excited mercury. There are lamps. The first two lamps are used to obtain a relatively low light intensity, and the last five lamps are used to obtain a relatively high light intensity.

The light intensity is generally set to about 0.5 to 100 mW / cm ² and the irradiation time is set to about 10 seconds to 5 minutes by adjusting the distance to the irradiation object and the voltage.

By irradiation with light such as ultraviolet rays, a vinyl monomer component having a (meth) acrylate monomer as a main component is polymerized to obtain a polymer. With the above irradiation time (polymerization reaction time), the amount of the remaining monomer becomes about 0.5% by weight or less, and the polymerization reaction can be substantially completed.

The light irradiation may be carried out at a constant light intensity, but the physical properties of the polymer can be more precisely adjusted by changing the light intensity in two or more stages and irradiating. .

(Polymer or viscoelastic product) A photopolymerizable composition comprising a vinyl monomer component containing an alkyl (meth) acrylate as a main component and an aminoalkyl (meth) acrylate as described above. The weight average molecular weight in terms of polystyrene by GPC of a polymer produced by photopolymerization of is generally in the range of 20,000 to 600,000.

This GPC molecular weight range is very low compared to the molecular weight of a polymer used as a normal viscoelastic product of about 500 to 1,000,000, and is generally used as a viscoelastic product (especially an adhesive). However, the photopolymerizable composition of the present invention can be used as a normal viscoelastic product even if it has a low molecular weight.

The photopolymerizable composition of the present invention is useful for the production of various polymers such as pressure-sensitive adhesive tapes, heat-sensitive adhesive sheets, sealing materials for construction and automobiles, and interlayers for vibration-proof materials. is there.

[0038]

[Function] When a photopolymerizable composition in which (meth) acrylic acid aminoalkyl ester is blended with a vinyl monomer having (meth) acrylic acid alkyl ester as a main component,
Although the polymer obtained by photopolymerizing it has a low molecular weight, it exhibits sufficient performance as an adhesive. As described above, the reason for exhibiting physical properties as a pressure-sensitive adhesive even if the molecular weight is lower than that of a conventional pressure-sensitive adhesive is not necessarily clear, but is presumed as follows.

That is, the aminoalkyl (meth) acrylate compounded has not only the same (radical) polymerizability as the general alkyl acrylate but also the aminoalkyl (meth) acrylate. The alkylamino group has a moderate chain transfer property (a chain transfer agent having a large chain transfer constant, such as thiol, and a chain transfer constant that is negligible compared to the growth rate of a general alkyl acrylate). Between the polymer and the growth rate constant, but the chain transferability is not negligible, so that the polymer molecule of the system containing aminoalkyl (meth) acrylate is probably A polymer with a different number of chains and a shape different from that of the unpolymerized polymer (linear) It believed to be.

It is considered that when the number of side chains is large, the molecular volume becomes small even if they have the same molecular weight, and as a result, the molecular weight becomes low. However, since the polymer (viscoelastic body) is a group of macromolecules, those having many side chains are more entangled than the linear macromolecules due to the effects of entanglement and the like.
It seems to be about the same.

Therefore, when the aminoalkyl (meth) acrylate is blended, a polymer different from the polymer form of the conventional pressure-sensitive adhesive is formed, and even if its molecular weight is low, sufficient performance as a pressure-sensitive adhesive is obtained. It is thought to be expressed.

[0042]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples. For the double-sided pressure-sensitive adhesive tapes obtained in Examples and Comparative Examples, the weight-average molecular weight of the pressure-sensitive adhesive (measured only when no polymerizable crosslinking agent is added), the amount of residual monomers, the gel fraction, the degree of swelling, the adhesive strength, The holding power was measured. Each measuring method is shown below.

(1) Weight-average molecular weight A sample solution obtained by dissolving a sample in tetrahydrofuran so as to have a concentration of 1.0% by weight and removing the insoluble matter from the sample left for 24 hours was subjected to GPC based on standard polystyrene. Was measured using a refractive index detector.

As GPC, the liquid sending device is LC-9A,
Refractive index detector is RID-6A, column oven is CTO
-6A, and a system in which the data analyzer was C-R4A was used (all of the above were manufactured by Shimadzu Corporation). GPC columns consist of three GPC-805 (exclusion limit: 4 million), GP
One C-804 (400,000 exclusion limit), GPC-801
(Exclusion limit 1500) One (all above, manufactured by Shimadzu Corporation) was connected in this order and used. The measurement conditions were as follows: the sample injection amount was 25 μl, the eluent was tetrahydrofuran, and the amount of liquid sent was 1.0 ml / min. The column temperature was 45 ° C.

(2) Amount of Residual Monomer A gas chromatograph (GC-6A) equipped with a separation column obtained by acid-treating chromosorb W carrying polyethylene glycol (trade name: 20M, manufactured by Gaschrom Industry Co., Ltd.) and a flame ionization detector , Manufactured by Shimadzu Corporation)
It measured using. In addition, the measurement sample is the adhesive sample 1
2 mg from a solution of 00 mg dissolved in 5 cc of methyl acetate
c was collected and prepared by mixing 2 cc of this solution with 2 cc of an internal standard solution in which 2-ethylhexyl methacrylate was dissolved in methyl acetate.

(3) Gel Fraction / Swelling Ratio 100 mg of an adhesive sample was dissolved in tetrahydrofuran,
The sample left for 24 hours was filtered through a 200-mesh stainless steel filter. It was determined by measuring the weight of the swelled gel collected by filtration and the weight of a dried gel obtained by drying the swelled gel at 100 ° C. for 2 hours.

(4) Adhesive strength A 25 μm-thick polyester film was adhered to one side of a double-sided adhesive tape to form an adhesive tape having a width of 25 mm and a length of 300 mm. The adhesive tape was applied to a stainless steel plate polished with a # 280 paper file. , 100-120 length from one end of the tape
mm tape is reciprocated one time with a 2 kg roller and affixed. At 23 ° C. and 65% RH, the other end of the tape is applied with an Instron tensile tester at a speed of 300 mm / min.
Peeling was performed in the opposite direction at an angle of 80 degrees, and the peeling resistance at that time was measured to determine the adhesive strength (g / 25 mm width).

(5) Holding force A 100 μm-thick aluminum foil was adhered to one side of the double-sided adhesive tape to form an adhesive tape having a width of 25 mm.
One end of the tape was reciprocated once with a 2 kg roller so that the adhesive area became 25 mm in width and 25 mm in length on a stainless steel plate polished with a No. 280 file, and 1 kg of the other end of the tape was stuck. The weight was fixed, this was hung in an atmosphere of 80 ° C., and the time required for the weight to fall together with the tape was measured to obtain the holding force (time). The holding force is usually measured at 40 ° C., but the measurement was performed under severe conditions of 80 ° C. to reduce the measurement time, and the measurement was stopped at a maximum of 150 hours.

Example 1 82 parts by weight of 2-ethylhexyl acrylate (2EHA), 8 parts by weight of N-vinylpyrrolidone (VP), carboxyethyl acrylate (CE
A: 100 parts by weight of a monomer component consisting of 10 parts by weight of Radocure, 0.5 part by weight of N, N-dimethylaminoethyl acrylate (DMAEA), and Darocure 2959 (manufactured by Merck) 1 as a photopolymerization initiator. 0.34 parts by weight and 0.06 parts by weight of hexanediol diacrylate (HDDA) as a polymerizable cross-linking agent were added, and the mixture was stirred uniformly with a stirrer to produce a photopolymerizable composition.

The resulting photopolymerizable composition was purged with nitrogen gas to remove dissolved oxygen, and then impregnated into a nylon nonwoven fabric on a transparent polyester film treated with a release agent.
The plane was covered with the same film as above. Then
Using a super-high pressure mercury lamp, the light intensity is 14mW / c
Irradiation was performed at m ² (wavelength: 365 nm center) for 2.0 minutes to produce a 220 μm-thick double-sided pressure-sensitive adhesive tape.

The amount of residual monomers in the obtained polymer was 0.1.
3% by weight or less, gel fraction 65% by weight, swelling degree 50
And the weight average molecular weight was 130,000. The molecular weight at this time was determined by CE to avoid gel formation.
The measurements were made on a polymer made under the same conditions as above but with the exception of A and HDDA.

The physical properties of this double-sided adhesive tape are as follows.
When the holding force was 500 g / 25 mm and the holding force was 150 hours or more, both the adhesive force and the holding force were good, and sufficient performance as a double-sided adhesive tape was exhibited.

[Comparative Example 1] H was added without adding DMAEA.
0.20 parts by weight of DDA, light intensity of 100 mW / c
A tape was manufactured under the same conditions as in Example 1 except that m ² and the irradiation time were changed to 1.0 minute.

The amount of residual monomers in the obtained polymer was 0.1.
3% by weight or less, gel fraction 60% by weight, swelling degree 25
And the weight average molecular weight was 16 which was almost the same as in Example 1.
It was ten thousand. In this case, the molecular weight was measured for a polymer prepared under conditions excluding CEA and HDDA in order to avoid formation of a gel.

The physical properties of this double-sided pressure-sensitive adhesive tape were particularly poor, with a holding power of about 50 hours and a pressure of 500 g / 25 mm, and the performance as a double-sided pressure-sensitive adhesive tape was insufficient.

The holding force was an interface breakdown, and there was considerable variation among samples. From the feel of the finger, it is quite hard as a viscoelastic body,
This indicates that an unsuitable polymer was formed as an adhesive.

[Comparative Example 2] H2 was added without adding DMAEA.
0.10 parts by weight of DDA, light intensity of 100 mW / c
A tape was manufactured under the same conditions as in Example 1 except that m ² and the irradiation time were changed to 1.0 minute.

The amount of residual monomers in the obtained polymer was 0.1.
When the content was 3% by weight or less, the gel fraction and the degree of swelling were not measurable (a loose gel having a very high degree of swelling was formed), and the weight average molecular weight was 160,000, almost the same as in Example 1. In addition,
The molecular weight at this time is to avoid gel formation,
The measurements were made on polymers made under conditions excluding CEA and HDDA.

The physical properties of this double-sided pressure-sensitive adhesive tape are as follows:
300 g / 25 mm, and the holding force is a holding time of 0.1 hour,
In particular, the holding power was poor, and the performance as a double-sided pressure-sensitive adhesive tape was insufficient.

The holding power was cohesive failure. This also indicates that the viscoelastic body is very soft from a finger tactile sensation, lacks cohesion, and that an unsuitable polymer is formed as an adhesive.

[0061]

According to the present invention, a vinyl monomer containing an alkyl (meth) acrylate as a main component is
When a photopolymerizable composition containing (meth) acrylic acid aminoalkyl ester is used, sufficient performance as an adhesive can be exhibited even if the GPC molecular weight of the polymer produced by photopolymerizing the composition is low. .

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 220/18 C08F 2/48 C08F 220/34 C09J 4/02

Claims (2)

(57) [Claims] (1) 100 parts by weight of a vinyl monomer mainly composed of an alkyl (meth) acrylate, and (b) a substituted alkyl group having an N, N-dialkylamino group as an alcohol moiety. ) 0.01 to 1 part by weight of an aminoalkyl acrylate, and (c)
A photopolymerizable composition comprising 0.1 to 5 parts by weight of a photopolymerization initiator. 2. A polymer having a weight average molecular weight in terms of polystyrene of 20,000 to 600,000 as determined by gel permeation chromatography obtained by irradiating the photopolymerizable composition according to claim 1 with light.