JP3178882B2 - Photopolymerizable composition, polymerization method, and viscoelastic product obtained therefrom - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a (meth) acrylate-based photopolymerizable composition, and more particularly, to a homopolymer having a glass transition temperature of 35.degree.
e) relates to the formulation of a photopolymerizable composition containing a vinyl carboxylate monomer having a Q value of 0.45 or less, which indicates a monomer reactivity ratio, and a polymer obtained by irradiating the composition with light.

[0002]

2. Description of the Related Art As a viscoelastic product made of an acrylic polymer having excellent light resistance, weather resistance, oil resistance, etc., for example, acrylic adhesive, acrylic adhesive tape, acrylic adhesive sheet, double-sided adhesive tape, foaming Body-adhesive products are well known.

[0003] Acrylic pressure-sensitive adhesives have excellent light resistance, weather resistance, oil resistance, etc. because they contain an acrylic polymer as a main component, and acrylic pressure-sensitive adhesive tapes made of plastic film, paper, or the like as a surface substrate. Is widely used because of its excellent adhesive performance such as adhesive strength and cohesive strength, and aging resistance such as heat resistance and weather resistance.

A typical acrylic pressure-sensitive adhesive tape as such a viscoelastic product has conventionally been manufactured using a solution in which an acrylic pressure-sensitive adhesive is dissolved in an organic solvent. However, in this method, a large amount of energy is consumed to dry the pressure-sensitive adhesive solution applied or impregnated on the substrate at a high temperature, and a large-scale recovery device is required to prevent air pollution by a solvent. is there. In addition, since the solvent is easily ignited, there is a danger of fire, and a sufficient safety device is required for maintaining safety. For these reasons, there has been an increasing demand for replacing the method using an adhesive solution with another method.

[0005] As one of the methods, instead of forming an adhesive separately in a solvent and then forming a tape, a radical polymerization of an acrylic monomer compound is carried out by UV irradiation on a base material or a release material of the tape to form an adhesive. And there is a method of making a tape all at once.

[0006] This method began in Belgian Patent No. 675420 in 1961. However, the adhesive made by this method has poor cohesive strength and the like, so Martens (Marten
U.S. Pat.No. 4,181,752 by S. et al. uses a solvent-free photopolymerizable liquid composition containing a photopolymerization initiator such as benzoin methyl ether in a vinyl monomer containing an acrylate monomer as a main component. By controlling the intensity of the ultraviolet light (ultraviolet light having a wavelength of 300 to 400 nm
mW / cm ² of light intensity) and high molecular weight to improve. However, this improved method has a disadvantage that the production speed cannot be increased because the light intensity is kept low.

As one method for improving this, Japanese Patent Application No. 3-129326 discloses a method in which vinyl acetate is added to an acrylic monomer compound. This method uses vinyl acetate compared to acrylic monomer formulations.
Value (see Q. Co., published by Baifukan on June 20, 1975, published by Baifukan, edited by The Society of Polymer Science, p. 12, etc.) indicating the monomer reactivity ratio of Price and Price, the reactivity of the monomer itself is low. Although vinyl acetate remains low until the late stage of the reaction, the radicals formed by the reaction show high reactivity, so that the reaction can be completed more quickly.In addition, to increase productivity, increase the lamp intensity and increase the amount of initiator Even if such a high-speed reaction condition is set, a polymer having a low molecular weight is not generated, and therefore, the production speed can be increased.

[0008]

However, this method can increase the production speed, but the adhesive performance of the obtained adhesive tape is almost the same as that obtained without adding vinyl acetate.

It is an object of the present invention to provide a photopolymerizable composition for producing a viscoelastic product containing a photopolymerization initiator and containing substantially no solvent, and has both productivity (production speed) and adhesive performance. It is an object of the present invention to provide a novel photopolymerizable composition capable of producing an acrylic viscoelastic product maintained at a high level. Another object of the present invention is to provide a polymerization method having even lower odor and good physical properties as an adhesive.

[0010] Another object of the present invention is to provide a photopolymerizable composition.
An object of the present invention is to provide a polymer obtained from a product, that is, an acrylic viscoelastic product.

The present inventors have conducted intensive studies and found that, instead of adding vinyl acetate to a vinyl monomer containing an alkyl (meth) acrylate as a main component, the homopolymer has a glass transition temperature of 35 ° C. That's it, and Alfrey
It has been found that the above object can be achieved by blending a vinyl carboxylate monomer having a Q value indicating the monomer reactivity ratio of the monomer and the price of 0.45 or less, thereby completing the present invention.

Further, the above-mentioned photopolymerizable composition is irradiated with light, so that at least 5
After polymerizing 0% by weight, light with an intensity higher than this light is further irradiated, so that the amount of the vinyl carboxylate monomer remaining is small and the polymerization rate is large, and the adhesive properties when the adhesive tape is used. Have also found that a good polymer can be obtained, and have completed the present invention based on the findings.

[0013]

That is, according to the present invention, there are provided (a) a (meth) alkyl group having an alkyl group having 1 to 14 carbon atoms.
Selected from the group consisting of alkyl acrylates
At least one (meth) acrylate monomer 60-1
00% by weight and the (meth) acrylate monomer
Consisting of 0 to 40% by weight of other polymerizable vinyl monomers
100 parts by weight of vinyl monomer, (b) a glass transition temperature of the homopolymer 35 ° C. or higher
Q value indicating the monomer reactivity ratio between Alfrey and Price
Is less than or equal to 0.45
-40 parts by weight , and (c) 0.1-5.0 parts by weight of a photopolymerization initiator.
A photopolymerizable composition characterized by the above characteristics and a viscoelastic product obtained by irradiating the composition with light are provided.

Further, according to the present invention, the photopolymerizable composition is irradiated with light to polymerize at least 50% by weight or more of the vinyl monomer (a) component, and then the light intensity is lower than the light. By further irradiating the light with increased
A polymerization method is provided, wherein the polymerization reaction of the composition is substantially completed.

The components constituting the photopolymerizable composition according to the present invention and the method of photopolymerizing the composition will be described below.

(1) Each component vinyl monomer constituting the photopolymerizable composition (a) The vinyl monomer component used in the present invention is a (meth) acrylic acid having an alkyl group having 1 to 14 carbon atoms. It is composed of 60 to 100% by weight of at least one (meth) acrylate monomer selected from alkyl esters and 0 to 40% by weight of another vinyl monomer copolymerizable with the (meth) acrylate monomer. is there.

(Meth) acrylate monomer (meth) acrylate monomer is used for producing a known photopolymerized acrylic viscoelastic product.

As the (meth) acrylate monomer,
An alkyl acrylate or alkyl methacrylate having 1 to 14, preferably 4 to 12 carbon atoms in the alkyl group is used. Specific examples of these acrylate monomers include n-butyl (meth) acrylate,
Examples thereof include 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl (meth) acrylate.

These monomers may be used alone or in combination.
Used in combination of more than one species. From the viewpoint of the balance between adhesiveness and cohesiveness, the homopolymer generally contains an alkyl acrylate having a glass transition temperature of −50 ° C. or lower as a main component, and as a comonomer, a (meth) acrylic ester of a lower alkyl group or the vinyl It is preferable to use a system monomer.

Other vinyl monomers copolymerizable with other vinyl monomers (meth) acrylate monomers include, for example, acrylic acid, methacrylic acid, acrylamide, acrylonitrile, methacrylonitrile, N-substituted acrylamide, hydroxyethyl Examples include acrylate, carboxyethyl acrylate, N-vinylpyrrolidone, maleic acid, itaconic acid, N-methylolacrylamide, and hydroxyethyl methacrylate.

Particularly preferred among these vinyl monomers are acrylic acid, carboxyethyl acrylate and N-vinylpyrrolidone. These monomers have the effect of accelerating the polymerization reaction by themselves and have a small effect of reducing the molecular weight during the accelerating reaction.

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.

These vinyl monomers are used alone or in combination of two or more.

These (meth) acrylate monomers and vinyl monomers are composed of (meth) acrylate monomers 60
-100% by weight and 0-40% by weight of a vinyl monomer. If the amount of the vinyl-based monomer exceeds 40% by weight, the adhesive properties of the adhesive tape when used as an acrylic adhesive are undesirably reduced. The preferred compounding ratio is 75 to 98% by weight of the (meth) acrylate monomer and 2 to 25% by weight of the vinyl monomer.

The glass transition temperature (Tg) of the homopolymer is 3
Above 5 ° C and the monomer reactivity ratio of Alfrey and Price
Vinyl carboxylate having a Q value of 0.45 or less
-(B) The Q value indicating the monomer reactivity ratio between Alfrey and Price is, as understood from "copolymerization" (edited by the Society of Polymer Science, P.12), a specific free radical (radical) (for example, benzoyl radical). Etc.) and the reactivity of the monomer. Usually, when a monomer having a high Q value is compared with a monomer having a low Q value, the reactivity of the monomer having a low Q value is smaller. However, once the monomers have reacted with the free radicals and become radicals,
Generally, a radical generated from a monomer having a low Q value has higher reactivity with another specific monomer (for example, a styrene monomer) than a radical generated from a monomer having a high Q value.

That is, it can be said that the Q value indicates the degree of resonance stabilization of radical electrons in a monomer molecule. (A monomer having high resonance stability is likely to become a radical, but is difficult to react with other monomers.) As an example of the Q value, esters of acrylic acid are about 0.40 to 0.45, Acrylic acid is about 1.27, and carboxylic acid vinyl ester monomers are about 0.01 to 0.10.

Accordingly, specific examples of the vinyl carboxylate monomer having a glass transition temperature of 35 ° C. or higher and a Q value of 0.45 or lower for the homopolymer used in the present invention include vinyl benzoate (Tg: 75 ° C.). , Q value: 0.061), vinyl pivalate (Tg: 86 ° C., Q value: about 0.05),
And vinyl versatate (manufactured by Shell Chemical Co .; trade name “Vova 9”, Tg: 60 ° C., Q value: about 0.05) and the like. Of these, vinyl benzoate and vinyl pivalate are preferred. In particular, since vinyl pivalate, which is an aliphatic carboxylic acid, has a higher rate of residual monomer reduction in the latter stage of the reaction than vinyl benzoate, which is an aromatic carboxylic acid, the production rate and product quality (odor) are low. More desirable.

In the present invention, the vinyl carboxylate monomer (b) is a vinyl monomer (a) comprising the (meth) acrylate monomer and another vinyl monomer copolymerizable with the (meth) acrylate monomer. Can be used in an amount of 0.1 to 40 parts by weight based on 100 parts by weight in total. Preferably, 1 to 10 parts by weight can be used.

Photopolymerization initiator (c) Examples of the monofunctional photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [Darocur 2959: manufactured by Merck], α
-Hydroxy-α, α'-dimethylacetophenone [Darocur 1173: manufactured by Merck], acetophenone-based initiators such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone; benzoin ethers such as benzoin ethyl ether and benzoin isopropyl ether System initiators: ketal initiators such as benzyldimethyl ketal; and other examples include halogenated ketones, acylphosphinoxides, acylphosphonates, and the like.

The photopolymerization initiator comprises the monomer component (a) 1
0.1 to 5.0 parts by weight is added to 00 parts by weight. When the amount is less than 0.1 part by weight, the photopolymerization initiator is consumed in the early stage of polymerization by light energy, so that the unreacted monomer tends to remain, and only the monomer odor remains in the obtained polymer. But the cohesive strength is reduced. Conversely, if the amount exceeds 5.0 parts by weight, the polymerization reaction rate will increase, but the residual odor accompanying the decomposition of the photopolymerization initiator will increase,
In addition, the molecular weight of the obtained polymer varies greatly, and the adhesive performance also decreases. The preferred amount is 0.3 to 2.0.
Parts by weight.

Optional components that can be added to the photopolymerizable composition of the present invention
In partial-polymerizable crosslinking agent photopolymerizable composition of the present invention, the content in order to increase the cohesive force of a heat-resistant i.e. high temperatures, together with the photopolymerization initiator, the polyfunctional vinyl compound as the polymerizable cross-linking agent Preferably.

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

Such a crosslinking agent is generally blended in an amount of 5 parts by weight or less based on 100 parts by weight of the monomer component (a). By the incorporation of the cross-linking agent, cross-linking occurs between polymer molecules in the photopolymerization reaction, and the heat resistance of the polymer is improved. When the polymer is a pressure-sensitive adhesive tape, the cohesive force at a high temperature is increased, and the holding power is improved.

Tackifier Resin (Tackifier) The photopolymerizable composition according to the present invention is further referred to as a tackifier in order to impart a high level of tackiness to a viscoelastic product. A tackifier resin may be contained.

The tackifier used in the present invention includes rosin resins, modified rosin resins (hydrogenated rosin resins, disproportionated rosin resins, polymerized rosin resins, etc.), terpene resins, terpene phenol resins, and aromatic resins. modified terpene resins, C ₅ and C ₉ petroleum resins, and the like coumarone resin.

Other Additives The photopolymerizable composition according to the present invention may contain commonly used additives such as a thickener, a thixotropic agent, a bulking agent and a filler.

As the thickener, acrylic rubber, epichlorohydrin rubber, isoprene rubber, butyl rubber and the like are used.

As a thixotropic agent, colloidal silica, polyvinylpyrrolidone and the like are used.

As the extender, calcium carbonate, titanium oxide, clay and the like are used.

As the filler, inorganic hollow bodies such as glass balun, alumina balun and ceramic balun; organic spherical bodies such as nylon beads, acrylic beads and silicon beads; organic hollow bodies such as vinylidene balun and acrylic balun; polyester and rayon And a single fiber such as nylon.

(2) Photopolymerization method of photopolymerizable composition Preparation work before irradiation and light source In order to obtain a polymer using the photopolymerizable composition of the present invention, oxygen dissolved in the composition is usually used. To remove, purge with an inert gas such as nitrogen gas or add a compound having an oxygen removing effect such as phenyldiisodecyl phosphite, triisodecyl phosphite, stannous octoate. By the addition of such a compound, sufficient polymerization (curing) can be realized even if the oxygen concentration in the atmosphere is high to some extent.

When a pressure-sensitive adhesive tape is produced as a polymer, for example, the photopolymerizable composition is applied or poured onto a release paper, a release mold, or the like, or is formed from a plastic film, paper, cellophane, cloth, or nonwoven fabric. Or a substrate such as a metal foil. When the substrate is not impregnated, an adhesive tape without the substrate is obtained. When producing a sealing material 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 injecting, so that the work is performed smoothly,
It is preferable to increase the viscosity with a thickener. As another 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.

[0044] These coating, impregnating or pouring operations require a device devised so as not to come into contact with air (oxygen).

After coating, impregnating or pouring on a mold or a substrate,
The photopolymerizable composition is passed through a box replaced with an inert gas, and irradiated with light such as ultraviolet light or visible light through quartz glass, pyrex glass, or borate glass. Even in an inert gas atmosphere, the surface of the photopolymerizable composition applied to, impregnated with, or injected into a mold or base material can be covered with air (oxygen ) May be performed to prevent light from being emitted. In this case, it is preferable to add the compound having the oxygen removing effect.

Ultraviolet rays are usually used for light irradiation. As the ultraviolet lamp, one having an emission spectrum distribution at a light wavelength of 300 to 400 nm is used, and examples thereof include a chemical lamp, a black light lamp (trade name of Toshiba Electric Materials Co., Ltd.), a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, A metal halide lamp, a microwave excitation mercury lamp, or the like is used. Of these, the former two lamps are used to obtain a relatively low light intensity, and the latter five lamps are
Used to obtain relatively high light intensity.

Irradiation Method (Polymerization Method) The light intensity can be adjusted by adjusting the distance to the irradiation object and the voltage.
Generally, the irradiation time is about 0.5 to 100 mW / cm ² and the irradiation time is 1
It is about 0 seconds to 5 minutes.

By irradiation with light such as ultraviolet rays, a vinyl monomer component containing an alkyl (meth) acrylate 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 performed at a constant light intensity, but the physical properties of the obtained polymer may be adjusted more precisely by changing the light intensity in two or more steps. it can.

The invention of claim 3 is a polymerization method characterized in that the light intensity is changed in two steps. Specifically, the initial light intensity is generally set to about 0.5 to 100 mW / cm ² ,
The polymerization is carried out by irradiation for about 10 seconds to 5 minutes depending on the light intensity until the residual ratio of the vinyl monomer component (a) becomes 50% by weight or less, preferably 30% by weight or less.

Subsequently, irradiation is continued for a further 10 seconds to 5 minutes using light having an intensity higher than the initial intensity, preferably 1.1 times or more, more preferably 2 times or more, and the remaining monomer components and About 0.5 carboxylic acid monomer component
% By weight or less to substantially complete the polymerization reaction.

At this time, if the light intensity is increased while the residual ratio of the vinyl monomer component (a) exceeds 50%, a large amount of low molecular weight substances having a low glass transition temperature will be generated, and physical properties will be reduced. Will be invited.

[0053]

In the present invention, instead of blending vinyl acetate with the vinyl monomer (a) containing an alkyl (meth) acrylate as a main component, the homopolymer has a glass transition temperature of 35 ° C. or more, and By using a photopolymerizable composition containing a vinyl carboxylate monomer (b) having a Q value indicating a monomer reactivity ratio of Alfrey and Price of 0.45 or less, the residual amount of the vinyl carboxylate monomer is small, and It became possible to improve the adhesive properties while keeping the speed high.

The acrylic vinyl monomer component
After at least 50% by weight of (a) is polymerized, by irradiating more intense light, the residual amount of the vinyl carboxylate monomer is further reduced, and the odor is reduced while maintaining the adhesive properties of the adhesive tape. It has become possible to provide an improved polymerization method.

First, the reason why the polymerization rate is increased is that, as described above, a monomer having a low Q value has low reactivity of the monomer itself, and the monomer remains until late in the reaction, but radicals generated by the reaction have a high reactivity. This is considered to be because the reaction can be completed earlier.

The reason why the amount of the residual monomer in the aliphatic vinyl carboxylate monomer is smaller than that in the aromatic vinyl carboxylate monomer is that the latter is stabilized by the formation of complexed radicals and the polymerization rate is slowed down. On the other hand, it is considered that the former does not suffer from such polymerization inhibition. (For Complexed radicals, see V.Sta
nnett et al., Makromol. Chem. 73 , 177 (1974))

Further, the reason why the residual amount of the vinyl carboxylate is reduced by increasing the light intensity in the late stage of the polymerization is that the residual vinyl carboxylate at the end of the initial light irradiation can be more rapidly irradiated by the stronger light. It is considered to be consumed.

The reason why the adhesive property is improved is considered as follows. It is known that in the radical bulk polymerization, the molecular weight of the polymer formed late in the polymerization is generally low. Adhesives containing a large amount of low molecular weight polymers have poor adhesive properties, particularly poor cohesive strength. Therefore, it is considered that the conventional pressure-sensitive adhesive had low pressure-sensitive adhesive performance. However, when the glass transition temperature of the low molecular weight polymer is high, it is considered that the decrease in the cohesive force is small (since those having a high glass transition temperature are generally considered to be rich in cohesive force). Accordingly, the vinyl carboxylate monomer having a low Q value (0.45 or less) of the present invention remains until the late stage of polymerization, and the homopolymer has a high glass transition temperature (35 ° C. or more). However, there is little decrease in cohesion,
Therefore, it is considered that the adhesive properties are improved. (This may be considered to be the same effect as changing the tackifier incorporated in the acrylic pressure-sensitive adhesive from one having a low glass transition temperature to one having a high glass transition temperature.)

[0059]

Next, the present invention will be described in detail with reference to examples and comparative examples showing examples of the present invention. However, the present invention is not limited to these examples.

<Measurement method of physical properties of pressure-sensitive adhesive tape> Weight-average molecular weight of pressure-sensitive adhesive (measured only when no polymerizable cross-linking agent is added) by the following measurement method for double-sided pressure-sensitive adhesive tapes obtained in Examples and Comparative Examples , Residual monomer amount / reaction completion time, gel fraction / swelling degree, adhesive strength and holding power were measured.

(1) Weight-average molecular weight A sample was dissolved in tetrahydrofuran so that the concentration became 1.0% by weight, and left for 24 hours. The sample solution obtained by removing the insoluble matter was subjected to gel permeation chromatography (GPC) using a standard polystyrene as a standard, a general polymer using a refractive index detector, and a substituent having visible ultraviolet absorption. Was measured using a visible-ultraviolet detector. The GPC system used was a liquid sending device LC-9A, a refractive index detector RID-6A, and a visible-ultraviolet detector SPD-6A.
V, column oven CTO-6A, data analyzer C-
R4A (all manufactured by Shimadzu Corporation). GPC columns consist of three GPC-805 (exclusion limit: 4 million), GPC-805
One PC-804 (400,000 exclusion limit), GPC-801
(Exclusion limit 1500) One piece (all made by Shimadzu Corporation) was connected in this order and used. The measurement conditions were as follows: sample injection volume: 25 μl, eluate: tetrahydrofuran;
0 ml / min and the column temperature was 45 ° C.

(2) Amount of Residual Monomer and Reaction Completion Time 100 mg of an adhesive sample taken at regular intervals was dissolved in 5 ml of methyl acetate, 2 ml of this solution and 2 ml of an internal standard solution of 2-ethylhexyl methacrylate dissolved in methyl acetate. Was mixed to prepare a sample for measuring the amount of residual monomer (2-ethylhexyl acrylate, 2EHA). The measurement is
The separation was carried out using a separation column obtained by acid-treating chromosorb W carrying polyethylene glycol (trade name "20M" manufactured by Gas Chromo Industry Co., Ltd.) and a gas chromatograph (GC-6A, manufactured by Shimadzu Corporation) having a flame ionization detector. . Next, the ordinate is plotted on a semilogarithmic graph with the residual monomer (2EHA) amount and the abscissa being the reaction time.
The time when the amount of A became 0.3% by weight or less was defined as the reaction completion time. The amount of the residual vinyl carboxylate monomer was measured by preparing an internal standard solution of the monomer in the same manner as described above and by the same method as described above.

(3) Gel Fraction / Swelling Ratio 100 mg of an adhesive sample was dissolved in tetrahydrofuran,
What was left for a time 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 is 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. , 100-120mm from one end of the tape
Part was reciprocated once with a 2 kg roller, and attached.
Next, under the conditions of 23 ° C. and 65% RH, the other end of the tape was treated with an Instron tensile tester at a speed of 300 mm / min.
Peeling was performed in the direction of the 0-degree angle, and the peeling resistance at that time was measured and defined as the adhesive strength (g / 25 mm width).

(5) Holding force A 100 μm-thick aluminum foil was stuck on one side of the double-sided adhesive tape to form a 25-mm-wide adhesive tape, which was placed on a stainless plate polished with a No. 280 paper file. The part was reciprocated once with a 2 kg roller so that the adhesive area was 25 mm in width and 25 mm in length. next,
A 1 kg weight was fixed to the other end of the tape, suspended in an atmosphere of 80 ° C., the time required for the weight to fall together with the tape was measured, and the holding force (time) was determined.

Incidentally, the holding force is usually measured at 40 ° C., but the measurement was performed under severe conditions of 80 ° C. to shorten the measurement time. The measurement was performed for up to 40 hours.

[0067]

Example 1 2-ethylhexyl acrylate (2EH
A) 100 parts by weight of a monomer component consisting of 90% by weight, 8% by weight of N-vinylpyrrolidone (VP) and 2% by weight of acrylic acid (AA), 7 parts by weight of vinyl benzoate (VB), and a photopolymerization initiator 1.34 parts by weight of Darocure 2959 (trade name, manufactured by Merck) and 0.05 parts by weight of hexanediol diacrylate (HDDA) as a polymerizable cross-linking agent were added, and the mixture was stirred with a stirrer, mixed uniformly, and photopolymerized. The composition was obtained.

The resulting photopolymerizable composition was purged with nitrogen gas to remove dissolved oxygen, and then impregnated in a nylon nonwoven fabric on a transparent polyester film treated with a release agent, and the surface thereof was transparent as described above. Covered with polyester film. Next, an ultra-high pressure mercury lamp was used as a radiation source, and the light intensity of the irradiation surface was 28 mW / cm ² (365 nm).
Was irradiated with ultraviolet light for 2.0 minutes using a light intensity measuring device UVR-1 (manufactured by Tokyo Optical Machine Co., Ltd.) having the maximum sensitivity to produce a 220 μm-thick double-sided adhesive tape.

Table 1 shows the measurement results of the weight average molecular weight, the reaction completion time, the gel fraction, the degree of swelling, the adhesive strength and the holding power.
Shown in The weight-average molecular weight was measured for a polymer prepared under the same conditions as in the above formulation except that HDDA was not added in order to avoid the formation of a gel (Example 2, Comparative Example 1, 2 is the same).

The physical properties of the obtained tape were good in both adhesive strength and holding power, and sufficient performance was exhibited as a double-sided adhesive tape.

Example 2 Vinyl benzoate was converted to vinyl pivalate (VP
The same operation as in Example 1 was performed except that v) was replaced.
A double-sided adhesive tape was manufactured. Table 1 shows the measurement results. The physical properties of the obtained tape were as good as in Example 1,
Sufficient performance was exhibited as a double-sided pressure-sensitive adhesive tape, and a tape having a small amount of residual vinyl carboxylate and improved odor was obtained.

Comparative Example 1 A double-sided pressure-sensitive adhesive tape was produced in exactly the same manner as in Example 1, except that the vinyl carboxylate monomer was not blended. Table 1 shows the measurement results.

At this time, the completion time of the reaction was 1.4 minutes, which was longer than in the examples. Further, the weight average molecular weight was equivalent to that of the example. Regarding the physical properties of the obtained tape, the adhesive strength was the same as that of the tape of Example, but the holding power was 10%.
Time and time were low, resulting in insufficient performance as a double-sided adhesive tape.

The pressure-sensitive adhesive obtained here was softer as a viscoelastic material than the pressure-sensitive adhesive of the example from the feeling of finger touch. Is shown.

Comparative Example 2 A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1, except that 7 parts by weight of vinyl acetate (VAc) was added as a vinyl carboxylate monomer. Table 1 shows the measurement results.

At this time, the reaction completion time was 0.9 minutes, which was equivalent to that of Example 1 and earlier than Comparative Example 1. The gel fraction, swelling degree, and weight average molecular weight were the same as in Example 1. Regarding the physical properties of the obtained tape, the adhesive strength was equivalent to that of the tape of Example, but the holding power was as low as 15 hours, and only an insufficient performance as a double-sided adhesive tape was obtained.

It should be noted that the pressure-sensitive adhesive obtained here was softer as a viscoelastic material than the pressure-sensitive adhesive of the example from the feeling of finger touch. Is shown.

[0077]

[Table 1]

[0078]

Example 3 The photopolymerizable composition prepared in exactly the same manner as in Example 1 was irradiated with ultraviolet light at a light intensity of 28 mW / cm ² for 0.5 minutes (the amount of residual 2EHA at this point was 20% by weight). Irradiation was performed at 56 mW / cm ² for 1.5 minutes and photopolymerization was performed for a total of 2.0 minutes to produce a 220 μm-thick double-sided pressure-sensitive adhesive tape. Table 2 shows the measurement results of the properties.

The weight average molecular weight is 47 in the refractive index detector.
It was 280,000 in the visible-ultraviolet detector. This means that a large amount of the VB component is contained in the low molecular weight. In addition, the physical properties of the obtained tape were good in both adhesive strength and holding power, sufficient performance was exhibited as a double-sided adhesive tape, and the odor was smaller than that in Example 1.

[0080]

Example 4 Vinyl benzoate was replaced with vinyl pivalate (VP
The same operation as in Example 3 was performed except that v) was replaced.
A double-sided adhesive tape was manufactured. However, the amount of residual 2EHA at the time after 0.5 minute was 28% by weight. Table 2 shows the measurement results.

The physical properties of the obtained tape were as good as those of Example 3, and a sufficient performance as a double-sided pressure-sensitive adhesive tape was obtained, and a tape with extremely low odor was obtained.

[0082]

Comparative Example 3 Except that vinyl benzoate was not blended,
The same operation as in Example 3 was performed to produce a double-sided pressure-sensitive adhesive tape. However, the amount of residual 2EHA at the time after 0.5 minute was 26% by weight. Table 2 shows the measurement results.

At this time, the reaction completion time was 1.35 minutes, which was longer than in the examples. The gel fraction, the degree of swelling, and the weight average molecular weight were the same as those of the example, and the physical properties of the obtained tape were the same as those of the tape of the example, but the holding power was as low as 3 hours. Insufficient performance was obtained as a double-sided adhesive tape.

The adhesive obtained here is also softer as a viscoelastic material than the adhesive of the example from the sense of finger touch. Has been generated.

[Table 2]

[0085]

According to the photopolymerizable composition of the present invention, the vinyl polymer (a) containing an alkyl (meth) acrylate as a main component has a homopolymer having a glass transition temperature of 35 ° C. or higher. And the vinyl carboxylate monomer (b) having a Q value of 0.45 or less, which indicates the monomer reactivity ratio between Alfrey and Price, is blended, so that the polymerization reaction rate remains high,
The adhesive properties can also be improved. In particular, in the case of an aliphatic vinyl carboxylate monomer, the residual amount of the monomer can be reduced, so that the odor of the product is improved.

Further, according to the method for polymerizing the photopolymerizable composition of the present invention, the polymerization reaction rate is high, the adhesive property is maintained, and the residual amount of the vinyl carboxylate monomer can be further reduced. The effect of improving the odor caused by the monomer is remarkable.

The photopolymerizable composition or polymer obtained according to the present invention includes, for example, pressure-sensitive adhesive tapes, heat-sensitive adhesive sheets, sealing materials for buildings and automobiles, vibration damping materials,
It is useful for various uses such as an intermediate film.

Claims (4)

(57) [Claims] (1) An alkyl group having 1 to 14 carbon atoms.
A group consisting of certain alkyl (meth) acrylates
At least one (meth) acrylate
Nomer 60 to 100% by weight and the (meth) acrylate
Other vinyl monomers 0-40 copolymerizable with the monomers
And a vinyl monomer 100 parts by weight of the weight%, (b) a glass transition temperature of the homopolymer 35 ° C. or higher
Q value indicating the monomer reactivity ratio between Alfrey and Price
Is less than or equal to 0.45
Containing a 40 parts by weight, and 0.1 to 5.0 parts by weight (c) a photopolymerization initiator
A photopolymerizable composition, comprising: 2. (a) 60 to 100% by weight of at least one (meth) acrylate monomer selected from the group consisting of alkyl (meth) acrylates having 1 to 14 carbon atoms in the alkyl group; Other vinyl monomers copolymerizable with (meth) acrylate monomers 0 to 40
(B) vinyl benzoate or vinyl pivalate 0.1 to 4 parts by weight;
A photopolymerizable composition comprising: 0 parts by weight; and (c) 0.1 to 5.0 parts by weight of a photopolymerization initiator. 3. A viscoelastic product obtained by irradiating the photopolymerizable composition according to claim 1 with light . 4. The photopolymerizable composition according to claim 1, which is irradiated with light to polymerize at least 50% by weight or more of the vinyl-based monomer (a), and then has a higher intensity than the light. A polymerization method, wherein the polymerization reaction of the above composition is substantially completed by further irradiating the light with the increased temperature.