JPH04366104A - Photopolymerizable composition - Google Patents

Abstract

PURPOSE:To provide a photopolymerizable composition for viscoelastic product production which contains a photopolymerization initiator, is substantially solvent-free, and has excellent application properties, and from which acrylic viscoelastic products having excellent tackiness can be produced. CONSTITUTION:The title composition comprises: (a) 60-98wt.% at least one acrylate monomer selected from the group consisting of alkyl acrylates and methacrylates in each of which the alkyl is 1-12C; (b) 2-40wt.% vinyl compound monomer having an unsaturated double bond which can copolymerize with the monomer (a); (c) a compound having two or more aziridine rings per molecule in an amount of 0.005-2 pts.wt. per 100 pts.wt. of the sum of the monomers (a) and (b); and (d) a photopolymerization initiator in an amount of 0.001-5 pts.wt. per 100 pts.wt. of that sum.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to acrylate-based photopolymerizable compositions, and more specifically, the formulation of photopolymerizable compositions that can maintain high levels of both coating properties and adhesive performance even under high-speed reaction conditions. and viscoelastic products obtained therefrom.

0002

[Prior art and problems to be solved] Viscoelastic products made of acrylic polymers include, for example, acrylic adhesives, acrylic adhesive tapes, acrylic adhesive sheets, double-sided adhesive tapes, and adhesive processed foam products. Are known.

[0003] Acrylic adhesives have acrylic polymers as their main component, so they have excellent light resistance, weather resistance, oil resistance, etc. Acrylic adhesive tapes have surface base materials such as plastic films and paper. is widely used because it has excellent adhesive properties such as adhesive strength and cohesive strength, and aging resistance properties such as heat resistance and weather resistance.

[0004] Taking acrylic adhesive tape as a typical example of these viscoelastic products, the adhesive tape is generally made of vinyl whose main component is an acrylate monomer such as an acrylic acid alkyl ester and/or a methacrylic acid ester. It is manufactured by applying or impregnating a base material with an adhesive solution obtained by solution polymerizing a system monomer in an organic solvent, or an emulsion obtained by emulsion polymerizing in an aqueous system, and then heating and drying this.

[0005] Among the above manufacturing methods, when an adhesive solution is used, a large amount of energy is consumed to dry the adhesive solution coated or impregnated on the base material at high temperature, and it is also difficult to prevent air pollution caused by the solvent. Therefore, large-scale recovery equipment is required. Moreover, since the solvent is easily flammable, sufficient safety equipment is required to maintain safety.

On the other hand, when an emulsion is used, more energy is required to evaporate water than when a solvent is used, and in terms of performance, water resistance is reduced due to the emulsifier mixed in during polymerization. Moreover, since water-soluble monomers cannot be used, the types of monomers are limited, and there is a drawback that it is difficult to meet the wide variety of needs required for adhesive tapes.

[0007] In order to solve these problems in tape manufacturing methods, a manufacturing method has been proposed in which acrylic monomers are polymerized in-situ using light. In order to put this method into practical use, problems regarding coating properties and adhesive performance must be solved. That is, in order to uniformly apply a composition mainly composed of monomers to a substrate, the viscosity of the composition must be about 100 to 20,000 cps, and the composition must be coated by some method before coating. It is necessary to thicken it.

JP-A No. 56-30410 describes one such viscosity increasing method in which a photopolymerizable composition placed in a storage container is partially irradiated with light until it reaches a coatable viscosity. A method of polymerizing (hereinafter referred to as partial photopolymerization thickening method) has been proposed. However, this method has a problem in that when the partial polymerization conversion rate is increased to 10% or more, the converted polymer ultimately has an adverse effect on the adhesive performance.

[0009] Also, in Japanese Patent Application Laid-Open No. 2-60981,
As another method of increasing the viscosity, a method of increasing the viscosity by adding acrylic rubber or epichlorohydrin rubber as a composition component is described. In this method, isoprene rubber and butyl rubber can also be used from the viewpoint of compatibility with the acrylic monomer. However, in this method of thickening using rubber, even if a multifunctional crosslinking agent is blended into the photopolymerizable composition and a crosslinking reaction is performed, the added rubber remains in the adhesive tape as a non-crosslinked substance, resulting in poor adhesive strength and cohesion. There is a problem with reducing power.

[0010] An object of the present invention is to provide a photopolymerizable composition for producing a viscoelastic product that contains a photopolymerization initiator and is substantially free of solvent, which has high coating properties and adhesive performance. The object of the present invention is to provide a novel photopolymerizable composition that can produce acrylic viscoelastic products with a high level of quality.

Another object of the present invention is to provide an acrylic viscoelastic product using the photopolymerizable composition.

0012

[Means for Solving the Problems] The present invention has been devised to achieve the above object, and includes an acrylate monomer (a) and a vinyl compound monomer (a) as monomer components.
By further incorporating an aziridine compound as a crosslinking agent as a third essential component into b), we obtained the knowledge that it is possible to obtain an acrylic viscoelastic product that maintains both coating properties and adhesive performance at a high level. It is complete.

That is, the photopolymerizable composition according to the present invention comprises (a) at least one acrylate selected from the group consisting of acrylic acid alkyl esters and methacrylic acid alkyl esters in which the alkyl group has 1 to 12 carbon atoms; 60 to 98% by weight of monomers, and (b)
2 to 40% by weight of a vinyl compound monomer having an unsaturated double bond copolymerizable with the acrylate monomer (a); and (c) the acrylate monomer (a).
and a compound having two or more aziridine rings in one molecule, which is blended in an amount of 0.005 to 2 parts by weight based on a total of 100 parts by weight of the vinyl compound monomer (b), and (d)
This is a photopolymerizable composition containing 0.001 to 5 parts by weight of a photopolymerization initiator.

[0014] Furthermore, the present invention provides a method of irradiating the composition with ultraviolet rays and simultaneously heating it to 60°C or higher.
Alternatively, after irradiating the composition with ultraviolet rays, the irradiated object is
It is an acrylic viscoelastic product obtained by heating above 0°C.

Each component constituting the photopolymerizable composition according to the present invention and a method for photopolymerizing the composition will be explained below.

Aziridine compound (crosslinking agent) In the present invention, in order to impart heat resistance and cohesive strength at high temperatures to the viscoelastic product, a third aziridine compound is added as a crosslinking agent to the above monomer composition system. Contain it as an essential ingredient.

Even if an aziridine compound is blended, a reactive composition thickened by partial photopolymerization thickening or rubber addition will only undergo the desired polymer growth reaction under photopolymerization reaction conditions, resulting in crosslinking. It can be controlled so that no reaction occurs. Therefore, the crosslinking reaction can be carried out simultaneously with this photopolymerization reaction or in the step of heating the composition after the photopolymerization reaction. That is,
Polymers produced by photopolymerization growth reactions with aziridine compounds during the heating process, polymers already produced by partial photopolymerization before photopolymerization, and thickener rubbers that have functional groups that react with aziridine compounds. can be crosslinked with each other.

[0018] As a result, the amount of non-crosslinked components can be reduced to a very low level, thereby eliminating the problem of adversely affecting the adhesive performance of viscoelastic products.

Compounds having two or more aziridine rings in one molecule having such crosslinking properties include 1,1
-Carbonylbisethyleneimine, polymethylenebisethyleneurea, polymethylenebisethyleneurethane, polymethylenebisethyleneimide, tris(1-aziridinyl)phosphinoxide, 2,4,3-triaziridinyl-1,3,5-triazine For example,

The aziridine compound is blended in an amount of about 0.005 to 2 parts by weight per 100 parts by weight of the unsaturated monomer. Preferably, the aziridine compound is blended in an amount of about 0.005 to 2 parts by weight per 100 parts by weight of the unsaturated monomer.

[0021] In addition to the above-mentioned aziridine compound, a polyfunctional vinyl compound can also be contained as a crosslinking agent in the same manner as in ordinary photopolymerization reactions.

Examples of such crosslinking agents 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 include polyester acrylate and urethane acrylate.

Such a crosslinking agent is generally contained in an amount of 5 parts by weight or less per 100 parts by weight of the monomer components. The combined use of an aziridine compound and such a crosslinking agent further improves the heat resistance of the viscoelastic product. When the viscoelastic product is an adhesive tape, the cohesive force at high temperatures increases and the holding power at high temperatures improves.

Acrylate Monomer The acrylate monomer is the main monomer component of the composition of the present invention and is used in the production of known photopolymerized acrylic viscoelastic products.

As the acrylate monomer, an acrylic acid alkyl ester or a methacrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms, preferably 4 to 12 carbon atoms is used. Specific examples of these acrylate monomers include n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and isononyl (meth)acrylate.

These monomers may be used alone or in combination of two or more. Considering the balance between adhesiveness and cohesiveness, the main component is usually an acrylic acid alkyl ester with a homopolymer glass transition temperature of -50°C or lower, and (meth) of a lower alkyl group is used as a comonomer.
It is preferable to use acrylic acid ester or the following vinyl monomer.

Vinyl monomers Other vinyl monomers that can be copolymerized with the acrylate monomer include, for example, acrylic acid, methacrylic acid,
Examples include acrylamide, acrylonitrile, methacrylonitrile, N-substituted acrylamide, hydroxyethyl acrylate, carboxyethyl acrylate, N-vinylpyrrolidone, maleic acid, itaconic acid, N-methylol acrylamide, and hydroxyethyl methacrylate.

Particularly preferred among these vinyl monomers are acrylic acid, carboxyethyl acrylate and N-vinylpyrrolidone. These monomers have the characteristics that they themselves have the effect of promoting the polymerization reaction and have a small effect of lowering the molecular weight during the accelerated reaction.

Also usable are vinyl monomers that form polymers with a low glass transition temperature, such as tetrahydrofurfuryl acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, fluorine acrylate, and silicone acrylate.

Photopolymerization initiator Examples of the monofunctional photopolymerization initiator include 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone [Darocur 2959: manufactured by Merck & Co., Ltd.];
α-Hydroxy-α,α'-dimethylacetophenone [Darocur 1173: manufactured by Merck & Co., Ltd.]; Acetophenone initiators such as methoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; Benzoin such as benzoin ethyl ether and benzoin isopropyl ether Ether initiators; ketal initiators such as benzyl dimethyl ketal; others include halogenated ketones, acylphosphinoxides, acyl phosphonates, and the like.

Tackifier The photopolymerizable composition according to the present invention may contain a tackifier called a tackifying resin.

[0032] The tackifier used here includes rosin resin, modified rosin resin, terpene resin,
Terpene phenol resin, aromatic modified terpene resin, C
5 and C9 petroleum resins, coumaron resins, etc.

Other Additives The photopolymerizable composition according to the present invention may contain commonly used additives such as thickeners, thixotropic agents, extenders and fillers.

[0034] As the thickener, acrylic rubber, epichlorohydrin rubber, isoprene rubber, butyl rubber, etc. are used.

As the thixotropic agent, colloidal silica, polyvinylpyrrolidone, etc. are used.

[0036] As the filler, calcium carbonate, titanium oxide, clay, etc. are used.

As fillers, inorganic hollow bodies such as glass balloons, alumina balloons and ceramic balloons; organic spherical bodies such as nylon beads, acrylic beads and silicon beads; organic hollow bodies such as vinylidene chloride balloons and acrylic balloons; polyester and rayon , single fibers such as nylon are used.

Photopolymerization process conditions The lamp used for light irradiation has a light wavelength of 400 nm.
Those having the following emission distributions are used, examples of which include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, and the like. Among these, ultra-high-pressure mercury lamps efficiently emit light in the active wavelength region of the initiator, and emit short-wavelength light that reduces the viscoelastic properties of the resulting polymer through crosslinking, and heat-evaporates the reaction composition. This is preferable because it does not emit much light with long wavelengths. Particularly, this effect of the lamp is exhibited in a so-called water-cooled type lamp in which a circulating water jacket is attached to the lamp.

The intensity of irradiation of the reactive composition by the lamp is a factor that influences the degree of polymerization of the resulting polymer, and is appropriately controlled depending on the performance of the desired product. When a common cleavage type initiator having an acetophenone group is blended, the illumination intensity is preferably in the range of 0.1 to 100 mw/cm2.

Photopolymerization in the present invention is inhibited by oxygen in the air or oxygen dissolved in the reactive composition. Therefore, light irradiation must be performed using a method that can eliminate the inhibition of oxygen reaction. One of the methods is
There is a method in which the reactive composition is covered with a film made of polyethylene terephthalate or Teflon to cut off contact with oxygen, and the composition is irradiated with light through this film. Alternatively, the composition may be irradiated with light through a light-transmitting window in an atmosphere in which oxygen is replaced with an inert gas such as nitrogen gas or carbon dioxide gas. In the latter method, in order to sufficiently complete the polymerization of the reactive composition to a degree of conversion of 99.7% or more, the oxygen concentration in the irradiation atmosphere must be 5000 ppm or less. The molecular weight of the polymer product obtained by photoirradiation of the composition decreases with increasing atmospheric oxygen concentration. In order to obtain a molecular weight comparable to that of a product obtained by polymerization in a completely inert atmosphere, the atmospheric oxygen concentration must be 1000 ppm or less. Furthermore, the extremely thin surface layer portion of the reactive composition is more susceptible to reaction inhibition by oxygen than the interior of the polymer, resulting in a decrease in cohesive force. In order for this surface layer to have the same degree of cohesiveness as the interior, the atmospheric oxygen concentration must be 300 ppm.
The following is desirable.

When light irradiation is carried out in the inert zone, a certain amount of inert gas is always introduced into this zone in order to keep the atmospheric oxygen concentration at a low level. This introduced gas generates an air current on the surface of the reactive composition, causing monomer evaporation. The airflow velocity required to keep this evaporation level low is preferably such that the relative velocity of the composition moving with the substrate in this zone is 1 m/sec or less, more preferably 0.1 m/sec or less. sec or less. If the airflow velocity is set to about 0.1 m/sec, evaporation due to the airflow can be substantially suppressed.

[0042]

[Function] By blending the aziridine compound, the blended composition of the present invention has a polymer concentration of 5% in the reactive composition thickened by partial photopolymerization thickening method, rubber addition, etc.
Even if the ratio is 60% or more, the same polymer and the polymer produced by the photopolymerization reaction can be crosslinked with each other.

[0043] As a result, the amount of non-crosslinked components can be significantly reduced, so that the adhesive performance of the viscoelastic product can be improved.

[0044]

[Example] Next, in order to specifically explain the present invention,
Examples illustrating an example of the present invention and some comparative examples illustrating comparison therewith will be listed, as well as performance test results of each viscoelastic product obtained. Note that % indicates weight %.

[Example 1] 950 g of 2-ethylhexyl acrylate, 50 g of acrylic acid, and 0.3 g of a photopolymerization initiator (manufactured by Merck & Co., trade name "Darocur 1173") were stirred and mixed in a separable flask until the mixture became uniform. rear,
Nitrogen gas was purged to remove dissolved oxygen. next,
When this composition was irradiated with ultraviolet light using a black light lamp, the temperature of the composition increased and the viscosity of the composition increased. When the temperature of the composition rose by 20°C, irradiation with ultraviolet rays was stopped. As a result, the conversion rate of the partially photopolymerized thickening composition obtained was 24.2%, and the viscosity was 400 cps.
Met.

To the thus obtained partially photopolymerized thickening composition, an aziridine compound (manufactured by Sogo Yakuko Co., Ltd., trade name "HDU") was added as a crosslinking agent to the total weight of 100% of 2-ethylhexyl acrylate and acrylic acid. 0.
After adding 05 parts by weight, it was coated onto a PET base material with a thickness of 38 microns using a comma coater so that the thickness was 35 μm. An ultra-high pressure mercury lamp is used as a radiation source in an inert zone with an oxygen concentration of 200 ppm, and the lamp intensity on the irradiated surface is 8 mw/cm2 (measured with a light intensity meter UVR-1 (manufactured by Tokyo Kogaku Kikai Co., Ltd.) with maximum sensitivity at 365 nm. The lamp height was set so that the intensity value was 100%, and ultraviolet rays were irradiated for 2 minutes. At this time, the residual monomer in the sample was 0.
．． 25%, and the gel fraction was 0%.

[0047] This sample was further heated to 0.5 at 100°C.
When irradiated with ultraviolet light for a minute, the gel fraction was 80%.

That is, it can be seen that the partially photopolymerized and thickened polymer and the subsequently photopolymerized polymer were crosslinked with each other during the heating process.

[Comparative Example 1] To the partially photopolymerized thickening composition obtained in Example 1, hexanediol diacrylate was added as a crosslinking agent instead of the aziridine compound to a total of 100 parts by weight of 2-ethylhexyl acrylate and acrylic acid. The same operation as in Example 1 was performed except that 0.05 part by weight was added.

That is, 0.05 parts by weight of hexanediol diacrylate as a crosslinking agent was added to the partially photopolymerized thickening composition obtained in Example 1 based on 100 parts by weight of the total of 2-ethylhexyl acrylate and acrylic acid. After that, it was coated onto a PET base material having a thickness of 38 microns using a comma coater so that the thickness was 35 μm. Oxygen concentration 20
Using an ultra-high pressure mercury lamp as a radiation source in an inert zone of 0 ppm, the lamp height was set so that the lamp intensity on the irradiated surface was 8 mw/cm2, and ultraviolet rays were irradiated for 2 minutes. The residual monomer of the sample at this time was 0.3%, and the gel fraction was 50%.

[0051] This sample was further heated to 0.5 at 100°C.
When irradiated with ultraviolet light for a minute, the gel fraction was 50%, and there was no change in crosslinking.

[Comparative Examples 2 to 4] To the partially photopolymerized thickening composition obtained in Example 1, the amount of the crosslinking agent hexanediol diacrylate was added per 100 parts by weight of the total of 2-ethylhexyl acrylate and acrylic acid. Various tape samples were prepared in the same manner as in Comparative Example 1, except that the amounts were 0.1, 0.2, and 0.3 parts by weight.

The gel fraction of the obtained tape sample was as follows. Comparative example Crosslinking agent amount (
Weight part) Gel fraction (%)
2 0.1
55 3
0.2 59
4 0.3
65
Although a large excess of 0.3 parts by weight of the crosslinking agent hexanediol diacrylate was added, it was confirmed that the partially photopolymerized and thickened polymer and the later photopolymerized polymer did not crosslink with each other.

[Examples 2 to 4] To the partially photopolymerized thickening composition obtained in Example 1, the crosslinking agent HDU was added in an amount of 0.000 parts per 100 parts by weight of the total of 2-ethylhexyl acrylate and acrylic acid. Various tape samples were prepared in the same manner as in Example 1 except that the amounts were changed to 0.07, 0.09 and 0.13 parts by weight.

[0055] The amount of residual monomer, holding power and sp adhesive strength in the obtained tape sample were measured. Measurement results,
It is shown together with the measurement results of Comparative Examples 5 to 7.

[Comparative Examples 5 to 7] To the partially photopolymerized thickening composition obtained in Example 1, the amount of crosslinking agent hexanediol diacrylate was added per 100 parts by weight of the total of 2-ethylhexyl acrylate and acrylic acid. te 0.07, 0.0
Comparative Example 1 except that it was changed to 9 and 0.13 parts by weight.
Various tape samples were prepared using the same procedure as above.

[0057] The amount of residual monomer, holding power and sp adhesive strength in the obtained tape sample were measured. The measurement results are shown in the table.

Crosslinking agent amount Residual monomer (%) Retention force (hr) SP adhesive force (g/25mm) Example 2 0.07
0.29 10.3
1050 3
0.09 0.28
100
1000 4 0.13
0.30 10
0 950
Comparative example 5 0.07
0.29 0.3
1000 6
0.09 0.28
0.4
900 7 0.13
0.30 0
．． 2 750
From these measurement results, when hexanediol diacrylate is used as a crosslinking agent, the amount added is 0.
It can be seen that even at 0.09 and 0.13 parts by weight, the retention force of the obtained tape sample is significantly lower than that of the tape sample using HDU as a crosslinking agent.

[0058]

Effects of the Invention Since the photopolymerizable composition of the present invention contains an aziridine compound, even when the composition is thickened for coating performance, it does not induce deterioration in adhesive performance due to the thickener. As a result, the composition of the present invention has excellent coating performance, and moreover, it is possible to produce a viscoelastic product with higher performance than the composition.

Furthermore, since the composition of the present invention can increase the conversion rate through partial photopolymerization without reducing adhesive performance, it is possible to reduce the monomer concentration that must be completed during post-photopolymerization. As a result, the reaction time in the production of viscoelastic products can be shortened, and the productivity of high-performance viscoelastic products can be increased.

Claims (2)

[Claims] Claim 1: (a) The number of carbon atoms in the alkyl group is 1
60 to 98% by weight of at least one acrylate monomer selected from the group consisting of acrylic acid alkyl esters and methacrylic acid alkyl esters of
and (b) 2 to 40% by weight of a vinyl compound monomer having an unsaturated double bond copolymerizable with the acrylate monomer (a), (c) the acrylate monomer (a) and the vinyl compound monomer (b). ) 0.005 to 2 parts by weight of a compound having two or more aziridine rings in one molecule, and (d) 0.001 to 5 parts by weight of a photopolymerization initiator. A photopolymerizable composition comprising: 2. By heating the composition according to claim 1 to 60° C. or higher at the same time as irradiating the composition with ultraviolet rays, or after irradiating the composition with ultraviolet rays, the irradiated object is heated to 60° C.
Acrylic viscoelastic product obtained by heating above ℃.