Method for producing polymer material, molding or polymerizable semi-product

Abstract

To provide a method for producing a molded body that utilizes a photopolymerization reaction of a vinyl monomer, does not use a photoinitiator, and becomes a thickness incapable of producing with a short wave length UV light of wavelength of 172 to 254 nm, and a method for producing a polymer material to which such producing method is applied.SOLUTION: The present invention utilizes a photopolymerization reaction of vinyl monomers and is a method for producing polymer materials, molded articles, or polymerizable semi-finished products, characterized by causing a reaction material containing vinyl monomers to undergo photopolymerization under conditions that satisfy all of the following (a) to (c): (a) substantially free of both a photopolymerization initiator and a photosensitizer in the reaction material; (b) the photopolymerization reaction is conducted in a container; (c) the wavelength of the irradiation light is 300 nm or greater.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polymer material, a molding or a polymeric semi-finished product. [Background technology]

[0002] In recent years, lighting using light guides has become widely used in automobile headlamps, taillamps, interior lighting, and other applications due to changes in design and the increase in electric vehicles. These require extremely high light transmittance to minimize light attenuation due to the optical path length, and polymers obtained by polymerizing (meth)acrylic esters and the like are primarily used. Furthermore, molding methods using photocurable resins have been widely adopted to manufacture similar optical components such as microlenses and prism sheets, resulting in the production of a variety of products. However, decomposition products and unreacted materials from the photopolymerization initiators and photosensitizers used in these products remain in the polymer, reducing transmittance. Therefore, photocurable resins are unable to achieve the required light transmittance for light guides. Furthermore, photocurable resins can sometimes cause problems such as odor generation, coloration, and reduced durability due to the decomposition products, as well as concerns about their effects on the human body.

[0003] Several reports have been published on photopolymerization without photoinitiators or photosensitizers, avoiding the drawbacks inherent in photopolymerization initiators. For example, Patent Document 1 and Non-Patent Documents 1 and 2 describe polymerization reactions using short-wavelength ultraviolet light in the 172-254 nm range. However, in the case of thick molded bodies such as light guides, light irradiated onto the reaction mixture attenuates as it travels from the irradiated surface to the interior according to the Beer-Lambert law. Therefore, at these wavelengths where the absorbance of the reaction mixture is high, the photochemical reaction proceeds only near the irradiated surface and not within the interior. Therefore, polymerization reactions using these short-wavelength ultraviolet lights are limited to curing thin films, making it difficult to produce thick molded bodies. Furthermore, according to the UV exposure limit and harmful effects of wavelengths specified in JIS Z8812, the use of short-wavelength ultraviolet light below 300 nm is harmful to the human body and undesirable for the working environment.

[0004] One method for manufacturing optical components involves polymerizing vinyl compounds such as acrylic esters in a reactor to form a polymer, which is then molded by injection molding or other techniques. In this case, the polymer is typically produced by a polymerization reaction using a thermal polymerization initiator. Azo-based initiators such as azobisisobutyronitrile and peroxides such as benzoyl peroxide are commonly used as thermal polymerization initiators, but these initiators also reduce optical transmittance. Therefore, polymerization without a thermal polymerization initiator is considered effective for achieving higher transmittance. As one such example, Patent Document 2 describes a method for producing highly transmittant polymers by bulk polymerization at high temperatures (235°C to 310°C) without the use of a polymerization initiator. However, this method has limitations on the melt viscosity of the products that can be produced, and the range of composition and molecular weight is limited, making it impossible to obtain polymers suitable for the production of optical reactive materials. Furthermore, this method requires extremely high-temperature and high-pressure reaction conditions, requiring specialized equipment and resulting in high capital investment.

[0005] Known molding methods utilizing the polymerization reaction of acrylic monomers include RTM molding, RIM molding, and monomer casting. For example, large molded bodies are produced by the monomer casting method using methyl methacrylate. However, methyl methacrylate monomers have low viscosity, and if introduced directly into a mold, they can leak from the air vent or harden and clog the air vent. Therefore, they are first prepolymerized in a reaction vessel separate from the mold, or mixed with a separately polymerized polymer to form a viscous syrup, which is then introduced into the mold (see, for example, Patent Documents 3 and 4). A method using photopolymerization to produce this syrup has also been reported (see Patent Document 5). According to Patent Document 5, the production of this syrup using a photopolymerization initiator has a fast reaction rate and high productivity, but the reaction occurs explosively, making it difficult to produce a uniform acrylic syrup with the desired conversion rate. To solve this problem, a molecular weight modifier or the like is required. In other words, this method is not only difficult to control the reaction, but also suffers from reduced light transmittance due to various additives, making it insufficient for practical use. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6292242 [Patent Document 2] U.S. Patent No. 4,414,370 [Patent Document 3] Patent No. 7146154 [Patent Document 4] Patent Publication No. 2021-172775 [Patent Document 5] Patent No. 6523442 [Non-patent literature]

[0007] [Non-Patent Document 1] Nuclear Instruments and Methods in Physics Research Section B, 236(1-4), pp.195-200. [Non-patent document 2] Polymer International, 68(1), pp.79-82. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for producing a molded article that utilizes the photopolymerization reaction of a vinyl monomer, does not use a photopolymerization initiator, and has a thickness that cannot be produced using short-wavelength ultraviolet light of 172 to 254 nm, and a method for producing a polymer material or a polymerizable semi-finished product that applies such a production method. [Means for solving the problem]

[0009] As a result of extensive research aimed at solving the above problems, the present inventors have discovered a method for producing a polymer material or a molded article using a photochemical reaction, which is substantially free of photopolymerization initiators and photosensitizers, and uses ultraviolet or short-wavelength visible light with a wavelength of 300 nm or more, which is relatively less harmful to the human body, to efficiently proceed with a photochemical reaction deep within the reaction mixture, and have completed the present invention. Specifically, the present invention provides the following.

[0010] (1) The present invention utilizes the photopolymerization reaction of a vinyl monomer, and is a method for producing a polymer material or a molded article, characterized in that a reactive material containing a vinyl monomer is photopolymerized under conditions that satisfy all of the following conditions (a) to (c): (a) The reaction material is substantially free of both photopolymerization initiators and photosensitizers. (b) The photopolymerization reaction takes place in a container. (c) The wavelength of the light to be irradiated is 300 nm or more.

[0011] (2) The present invention also provides the production method according to (1), which further satisfies the following condition (d): (d) When contained in the container, the optical path length of the light irradiated onto the reaction material is 1 mm or more.

[0012] (3) The present invention also relates to the production method according to (1) or (2), wherein the vinyl monomer contains at least one selected from the group consisting of (meth)acrylic acid, (meth)acrylic acid derivatives, styrenes, vinyl esters, vinyl amides, vinyl ethers, and ethenes in an amount exceeding 50% by mass relative to the total mass of the vinyl monomer. In the present invention, "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid."

[0013] (4) The present invention also provides the method according to any one of (1) to (3), wherein the container is a tank type or a pipe type.

[0014] (5) The present invention also provides the method according to any one of (1) to (4), wherein the light source for the photopolymerization reaction is a light-emitting diode.

[0015] (6) The present invention utilizes the photopolymerization reaction of a vinyl monomer, and is also a method for producing a polymerizable semi-finished product, characterized in that a reactive material containing a vinyl monomer is photopolymerized under conditions that satisfy all of the following conditions (a) to (c): (a) The reactive material is substantially free of both a photopolymerization initiator and a photosensitizer. (b) The photopolymerization reaction takes place in a container. (c) The wavelength of the light to be irradiated is 300 nm or more.

[0016] (7) The present invention also provides a method for producing a polymerizable semi-finished product according to the above item (6), which satisfies the following condition (d): (d) The length of the optical path irradiated onto the reaction material when contained in the container is 1 mm or more. [Effects of the Invention]

[0017] According to the present invention, there are provided a method for producing a molded article that utilizes the photopolymerization reaction of a vinyl monomer, does not use a photopolymerization initiator, and has a thickness that cannot be produced using short-wavelength ultraviolet light of 172 to 254 nm, as well as a method for producing a polymer material or a polymerizable semi-finished product that applies such a production method. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 shows ultraviolet-visible (UV-Vis) spectra for each of the molded articles of Example 1 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a first embodiment and a second embodiment of the polymer material or molded article of the method for producing a polymer material or molded article of the present invention will be described. Of these, the first embodiment is a method for producing a molded article, and the second embodiment is a method for producing a polymer material. In addition, one embodiment of the method for producing a polymerizable semi-finished product of the present invention will also be described.

[0020] <First embodiment of the present invention> First, a first embodiment of the present invention will be described. The first embodiment of the present invention utilizes the photopolymerization reaction of a vinyl monomer, and is a method for producing a molded article, characterized in that a reactive material containing a vinyl monomer is photopolymerized under conditions that satisfy all of the following conditions (a) to (c): (a) The reaction material is substantially free of both photopolymerization initiators and photosensitizers. (b) The photopolymerization reaction takes place in a container. (c) The wavelength of the light to be irradiated is 300 nm or more.

[0021] As mentioned above, to polymerize a vinyl monomer to obtain a molded article, a photopolymerizable composition (a photopolymerization initiator and a photosensitizer are added to a vinyl monomer) or a thermally polymerizable composition (a thermally polymerizable composition) is prepared by adding a thermally polymerizable initiator to a vinyl monomer. The composition is then filled into a mold, and the vinyl monomer contained in the composition is polymerized by light irradiation (the former composition) or heating (the latter composition) to form a cured molded article. However, when a molded article is prepared using this method, the resulting molded article contains impurities such as decomposition products or unreacted products of the photopolymerization initiator or thermally polymerized initiator. The presence of these impurities reduces the light transmittance of the molded article. Furthermore, as proposed in Patent Documents 1 and 2, it is possible to polymerize a thin film of a vinyl monomer by irradiating it with short-wavelength ultraviolet light (172 nm to 254 nm) without using a photopolymerization initiator. However, this method is unsuitable for preparing molded articles because it is limited to thin films.

[0022] In this regard, the present inventors have unexpectedly found that when a vinyl monomer containing substantially no photopolymerization initiator or photosensitizer is placed in a container having a certain thickness to allow a light path during irradiation and the container is irradiated with ultraviolet or short-wavelength visible light having a wavelength of 300 nm or more, the vinyl monomer placed in the container is cured to form a molded article conforming to the shape of the container. This is quite unexpected, considering the common technical knowledge that a polymerization initiator is essential for the polymerization of a vinyl monomer.

[0023] The reason for this unexpected reaction is not entirely clear. However, similar curing does not occur easily in thin films. For curing to occur, the container containing the vinyl monomer must have a certain thickness and be irradiated with light over that thickness. The following explanation is inferred: Vinyl monomer molecules have very low absorption efficiency for ultraviolet or short-wavelength visible light with wavelengths of 300 nm or longer. Therefore, even when irradiated with such light, almost no chemical reaction occurs due to light absorption. However, there is still a very small probability that molecules may undergo a chemical reaction, i.e., polymerization, upon exposure to such light. In a thin film, where the optical path length of ultraviolet or visible light is short, polymerization reactions hardly occur due to the very small probability. However, a container with a certain thickness allows for the optical path length of such light to be extended, and vinyl monomer molecules may be present that initiate polymerization due to the accumulation of very small probabilities. Thus, once a vinyl monomer polymerization reaction occurs at a certain point within the container, the polymerization reaction propagates due to the properties of radical reactions. Furthermore, the polymerization reaction may be accelerated by the reaction heat generated at the same time. Ultimately, the vinyl monomer contained in the container becomes a cured product conforming to the shape of the container. This cured product does not contain decomposition products or unreacted products of the photopolymerization initiator or photosensitizer, and is composed only of polymerized vinyl monomers, and therefore exhibits good light transmittance.

[0024] As described above, the polymerization of vinyl monomers in the present invention involves polymerizing a reactive material containing a vinyl monomer through a photoreaction, and is characterized in that (a) the reactive material contains substantially no photoinitiator or photosensitizer, (b) the photopolymerization reaction is carried out in a container, and (c) the wavelength of the irradiated light is 300 nm or longer. These points will be explained below.

[0025] The vinyl monomer used in the present invention may be, without particular limitation, a compound having a vinyl group polymerizable by radical polymerization. Examples of such compounds include (meth)acrylic acid, (meth)acrylic acid derivatives, styrenes, vinyl esters, vinyl amides, vinyl ethers, and ethenes. These vinyl monomers may be used alone or in combination of two or more. The term "(meth)acrylic acid derivative" refers to a compound that, when considered as the parent compound, has been modified by introducing a functional group, oxidizing, reducing, or substituting atoms to such an extent that the polymerizability inherent to (meth)acrylic acid is not lost. Examples of such (meth)acrylic acid derivatives include (meth)acrylate, (meth)acrylamide, and (meth)acrylonitrile.

[0026] Examples of acrylic acid and acrylic acid derivatives include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, nonyl acrylate, isodecyl acrylate, lauryl acrylate, stearyl acrylate, isostearyl acrylate, isobornyl acrylate, dicyclopentanyl acrylate, 2-hydroxyethyl acrylate, methoxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, ethoxyethoxyethyl acrylate, benzyl acrylate, phenoxyethyl acrylate, polyethylene glycol acrylate, methoxypoly Examples of the acrylic acid derivative include ethylene glycol acrylate, ethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, neopentyl glycol diacrylate, ethylene oxide-modified bisphenol A diacrylate, trimethylolpropane triacrylate, ethylene oxide-modified trimethylolpropane triacrylate, glycerin triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, acrylamide, N-alkylacrylamide, and acrylonitrile. In addition to these low-molecular-weight compounds, compounds with a molecular weight sufficient to be called oligomers or polymers and having one or more acryloyl groups as side chains are also considered to be acrylic acid derivatives in the present invention.

[0027] Examples of methacrylic acid and methacrylic acid derivatives include methacrylic acid, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, nonyl methacrylate, isodecyl methacrylate, lauryl methacrylate, stearyl methacrylate, isostearyl methacrylate, isobornyl methacrylate, dicyclopentanyl methacrylate, 2-hydroxyethyl methacrylate, methoxyethyl methacrylate, hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, ethoxyethoxyethyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, Examples of methacrylic acid derivatives include methacrylic acid derivatives such as methacrylic acid acrylate, polyethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, ethylene oxide-modified bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, ethylene oxide-modified trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, methacrylamide, and methacrylonitrile. In addition to these low-molecular-weight compounds, compounds having a molecular weight sufficient to be called an oligomer or polymer and having one or more methacryloyl groups as a side chain are also considered to be methacrylic acid derivatives in the present invention.

[0028] Examples of styrenes include styrene, methylstyrene, α-methylstyrene, ethylstyrene, indene, acetoxystyrene, hydroxystyrene, divinylbenzene, benzocyclobutene, and vinylpyridine.

[0029] Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl benzoate.

[0030] Examples of vinylamides include N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone.

[0031] Examples of vinyl ethers include vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl hexyl ether, 2-ethylhexyl vinyl ether, vinyl cyclohexyl ether, phenyl vinyl ether, and ethylene glycol vinyl ether.

[0032] Examples of ethenes include ethylene, propylene, butylene, butadiene, isobutene, pentene, and methylpentene.

[0033] In the present invention, a reactive material containing the vinyl monomer is prepared and used in the photoreaction. This reactive material may be the vinyl monomer alone, i.e., the vinyl monomer itself, or may contain pigments, dyes, various fillers, various solvents, various additives such as antifoaming agents and surfactants, polymers for adjusting viscosity, etc. Alternatively, the vinyl monomer may be irradiated with ultraviolet or short-wavelength visible light of 300 nm or more, and a semi-polymerized product that is not completely cured may be placed in a container of a desired shape and cured by irradiating it with ultraviolet or short-wavelength visible light of 300 nm or more.

[0034] As already mentioned, the reactive material containing the vinyl monomer is substantially free of both a photopolymerization initiator and a photosensitizer. "Substantially free" means that the reactive material does not contain a photopolymerization initiator or a photosensitizer to such an extent that photopolymerization occurs mainly from the photopolymerization initiator or the photosensitizer, and the content of these components can be, for example, about 10 ppm by mass.

[0035] The shape of the container in which the photopolymerization reaction is performed may be selected according to the shape of the desired molded product. In this case, the thickness of the optical path portion of the container in which the photopolymerization reaction is performed, through which ultraviolet or short-wavelength visible light with a wavelength of 300 nm or more passes, i.e., the optical path length irradiated onto the vinyl monomer-containing reactive material, is preferably 1 mm or more, and more preferably 5 mm or more. As already mentioned, the probability that vinyl monomer molecules will absorb ultraviolet or short-wavelength visible light with a wavelength of 300 nm or more and cause a polymerization reaction is extremely low. Therefore, it is necessary to make the optical path length irradiated onto the vinyl monomer-containing reactive material relatively long to maximize this probability and facilitate the polymerization reaction. An optical path length irradiated onto the vinyl monomer-containing reactive material of 1 mm or more is preferable because sufficient curing of the vinyl monomer-containing reactive material can be expected.

[0036] The container in which the photopolymerization reaction is performed has its wall formed of a material that transmits light of the wavelength used in the reaction, or has a window or hole formed in some part of the container for the purpose of light irradiation. The light-transmitting material is not particularly limited as long as it transmits light of the wavelength used for irradiation, and examples include borosilicate glass, quartz, sapphire, etc. It is also possible to provide a lens, a diffusion plate, a prism sheet, etc. in the irradiation area to improve irradiation efficiency. Materials other than the irradiation area can be used without particular limitation as long as they are not corroded by the reaction material contained therein. It is also possible to provide a light reflecting or scattering mechanism on the container wall surface other than the irradiation area. Since ultraviolet or short-wavelength visible light with a wavelength of 300 nm or more is used in the present invention, it is not necessarily necessary to use expensive quartz or sapphire as the container in which the photopolymerization reaction is performed, and inexpensive borosilicate glass can be used.

[0037] As described above, the light used for irradiation is ultraviolet or short-wavelength visible light with a wavelength of 300 nm or more. Generally, ultraviolet light has a wavelength of up to about 380 nm, and light with wavelengths greater than that is considered visible light. The upper limit of the wavelength of the short-wavelength visible light used in the present invention can be about 450 nm, more preferably about 430 nm, and even more preferably about 410 nm. Therefore, the light used for irradiation in the present invention can be said to be light with a wavelength of about 450 nm or less, provided that it has a wavelength of 300 nm or more. Note that ultraviolet light with a wavelength of less than 300 nm is absorbed and attenuated near the irradiated surface and does not sufficiently reach the inside of the container containing the reactive material, resulting in no curing.

[0038] Preferred examples of light sources for irradiation include xenon lamps, high-pressure mercury lamps, metal halide lamps, excimer lamps, and light-emitting diodes, which have emission wavelengths and practical output suitable for the present invention. Light-emitting diodes are more preferred in terms of emission efficiency. Furthermore, in the case of light sources with multiple emission wavelengths, such as mercury lamps, they may include ultraviolet or short-wavelength visible light with wavelengths of 300 nm or more, and may also include other wavelengths. Light irradiation can be performed by varying the intensity depending on the reaction conditions, by intermittently irradiating, by changing the wavelength during the reaction, or by simultaneously irradiating with multiple wavelengths. Furthermore, light irradiation can be programmed to control the reaction rate, molecular weight, and reaction heat generation.

[0039] The atmosphere in the vessel in which the photoreaction is carried out can be appropriately selected depending on the reaction. Since oxygen inhibition occurs in polymerization reactions using vinyl monomers, from this viewpoint, it is preferable to make the vessel an inert atmosphere of nitrogen, argon, carbon dioxide, or the like. Furthermore, it is desirable to remove dissolved oxygen contained in the vinyl monomer and solvent used in advance.

[0040] <Second embodiment of the present invention> Next, a second embodiment of the present invention will be described. The second embodiment of the present invention utilizes the photopolymerization reaction of a vinyl monomer and is a method for producing a polymer material, characterized by photopolymerizing a reaction material containing a vinyl monomer under conditions satisfying all of the following conditions (a) to (c): The first embodiment and the second embodiment differ only in that the former produces a molded product, while the latter produces a polymer material. The production method in the second embodiment involves irradiating a reaction material containing a vinyl monomer with ultraviolet or short-wavelength visible light having a wavelength of 300 nm or more, which is the same as the first embodiment. Therefore, in the description of the second embodiment, the same parts as those in the first embodiment will be omitted, and the differences will be mainly described. (a) The reaction material is substantially free of both photopolymerization initiators and photosensitizers. (b) The photopolymerization reaction takes place in a container. (c) The wavelength of the light to be irradiated is 300 nm or more.

[0041] The polymer material produced in this embodiment refers to a polymer of a vinyl monomer used as a molding material for producing plastic products by means of injection molding or the like, a coating material such as paint, or a curable material such as an adhesive or pressure-sensitive adhesive.

[0042] From the viewpoint of mass production, preferred examples of reaction apparatus for producing polymer materials include tank-type reactors and tubular reactors. Both batch and continuous reaction systems are applicable. The reactor in which the photopolymerization reaction is performed has walls made of a material that transmits light of the wavelength used in the reaction, or a window or hole for light irradiation is formed in a portion of the container. The light-transmitting material is not particularly limited as long as it transmits light of the wavelength used for irradiation, but borosilicate glass, quartz, sapphire, etc. are preferred. To improve irradiation efficiency, lenses, diffusers, prism sheets, etc. can be provided in the irradiation area. Materials other than the irradiation area can be used without particular limitation as long as they are not corroded by the reaction material contained therein. It is also possible to provide a light reflecting or scattering mechanism on the container wall surface other than the irradiation area. Since ultraviolet or short-wavelength visible light with a wavelength of 300 nm or more is used in the present invention, expensive quartz or sapphire is not necessarily required for the container in which the photopolymerization reaction is performed; inexpensive borosilicate glass can be used.

[0043] As described above, the light used for irradiation is ultraviolet or short-wavelength visible light with a wavelength of 300 nm or more. Generally, ultraviolet light has a wavelength of up to about 380 nm, and light with wavelengths greater than that is considered visible light. The upper limit of the wavelength of the short-wavelength visible light used in the present invention can be about 450 nm, more preferably about 430 nm, and even more preferably about 410 nm. Therefore, the light used for irradiation in the present invention can be said to be light with a wavelength of about 450 nm or less, provided that it has a wavelength of 300 nm or more. This is as explained in the first embodiment above.

[0044] From the viewpoint of uniform progress and control of the reaction, it is preferable to provide a stirring mechanism in a tank reactor. There are no limitations on the stirring method, but in the case of a tank reactor, a rotary stirring blade or the like is a preferred example. For the same reason, it is also preferable to provide a mechanism for promoting mixing of the reaction materials in a tubular reactor, in which case a static mixer or a dynamic mixer is preferred. Since temperature changes often occur due to heat generation or endothermism caused by the reaction, it is also possible to provide a temperature control mechanism such as a jacket or coil regardless of whether the reactor is a tank reactor or a tubular reactor.

[0045] A solvent may be further added to the reaction material containing the vinyl monomer. By producing a polymer material in a state containing a solvent, it is possible to prevent the reaction mixture from curing during the production of the polymer material. When producing a polymer material in a state containing a solvent, the solvent can be distilled off after the polymerization reaction by light irradiation is completed, thereby recovering a solid polymer material.

[0046] The reactor can be operated under pressure or under reduced pressure. The reactor can be operated in a batch mode, a feed mode in which the reaction materials and solvent are added as the reaction proceeds, a semi-batch mode, or a continuous mode.

[0047] The vinyl monomers that can be used in this embodiment, the reaction materials containing them, and the light source for irradiating ultraviolet or short-wavelength visible light are the same as those described in the first embodiment, and therefore will not be described here.

[0048] <Method of manufacturing polymerizable semi-finished products> Next, one embodiment of the method for producing a polymerizable semi-finished product of the present invention will be described. The method for producing a polymerizable semi-finished product of the present invention is similar to the method for producing a polymer material or molded article of the present invention in that a polymerization reaction of the vinyl monomer is carried out by irradiating a reactive material containing a vinyl monomer with ultraviolet or short-wavelength visible light having a wavelength of 300 nm or more. However, it differs in that the polymerization reaction is stopped midway to obtain a semi-finished product in a state where further polymerization reaction is possible. Therefore, in the description of the method for producing a polymerizable semi-finished product of the present invention, the explanation of the parts common to the method for producing a polymer material or molded article of the present invention will be omitted and the differences will be mainly described.

[0049] The method for producing a polymerizable semi-finished product of the present invention utilizes the photopolymerization reaction of a vinyl monomer, and is characterized in that a reactive material containing a vinyl monomer is photopolymerized under conditions that satisfy all of the following conditions (a) to (c): (a) The reactive material is substantially free of both a photopolymerization initiator and a photosensitizer. (b) The photopolymerization reaction takes place in a container. (c) The wavelength of the light to be irradiated is 300 nm or more.

[0050] As described above, the method for producing a polymerizable semi-finished product of the present invention does not involve carrying out the polymerization reaction until it becomes a polymer material or a molded product, but rather terminates the polymerization reaction midway to obtain a polymerizable semi-finished product in a state in which further polymerization reactions are possible. Many of these polymerizable semi-finished products exhibit viscous properties and can be used as polymerizable adhesives by adding a photopolymerization initiator or a thermal polymerization initiator, or to form molded products. Furthermore, they can also be used for these purposes by irradiating them with ultraviolet or short-wavelength visible light having a wavelength of 300 nm or more, as described above, without adding a photopolymerization initiator or a thermal polymerization initiator.

[0051] As such polymerizable semi-finished products, those called acrylic syrup or acrylic syrup are commercially available. While these commercially available products are produced by adding a polymerization initiator to a (meth)acrylic monomer, the polymerizable semi-finished products of the present invention are prepared without using a polymerization initiator, and therefore provide adhesives and molded articles with higher transparency than those obtained by using commercially available products. [Example]

[0052] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples. In the following examples and comparative examples, a spot-type UV-LED irradiator 8332C manufactured by CCS Inc. was used as the light irradiation device. This irradiator can irradiate light at wavelengths of 280 nm, 365 nm, 385 nm, or 405 nm by switching the head.

[0053] [Example 1] The polymerization inhibitor was removed from isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd., product name IBXA) by known means, and 0.9 g of the resulting solution was placed in a 10 mm resin cell for UV-Vis measurement. Dissolved oxygen was removed by nitrogen bubbling, and then LED light with a wavelength of 365 nm was irradiated from the side at 100% output at room temperature to cure the entire interior of the cell, yielding the molded article of Example 1. In this test, the resin cell served as a mold, and the optical path length was 10 mm.

[0054] [Comparative Example 1] The polymerization inhibitor was removed from isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., product name IBXA) by known means, and 0.01 parts by mass of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals Co., Ltd., Irgacure 369) was added to 100 parts by mass of the resulting mixture to form a curable composition. This curable composition was irradiated with LED light in the same manner as in Example 1, to obtain a molded product of Comparative Example 1.

[0055] Comparative Example 2 The polymerization inhibitor was removed from isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., product name IBXA) by known means, and 0.5 parts by mass of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals Co., Ltd., Irgacure 369) was added to 100 parts by mass of the resulting mixture to prepare a curable composition. This curable composition was irradiated with LED light in the same manner as in Example 1, to obtain a molded product of Comparative Example 2.

[0056] [Light transmittance measurement of molded bodies of Example 1 and Comparative Examples 1 and 2] The UV-Vis spectrum was measured for each of the molded articles of Example 1 and Comparative Examples 1 and 2, and the transmittance at 310 nm and 400 nm was also determined. The chart of the obtained UV-visible absorption spectrum is shown in Figure 1, and the transmittance at wavelengths of 310 nm and 400 nm is shown in Table 1.

[0057] [Table 1]

[0058] As shown in FIG. 1 and Table 1, in Example 1, even though no photopolymerization initiator was present, curing was achieved by irradiation with ultraviolet light to obtain a molded product, and it can be seen that this molded product exhibited higher light transmittance than the molded products of Comparative Examples 1 and 2.

[0059] [Example 2] The polymerization inhibitor was removed from trimethylolpropane triacrylate (manufactured by Osaka Organic Chemical Industry Ltd., product name TMPTA) by known means (hereinafter, trimethylolpropane triacrylate from which the polymerization inhibitor has been removed will be referred to as TMPTA). 1.0 g of this was placed in a quartz vial with an inner diameter of 10 mm, and dissolved oxygen was removed by bubbling with nitrogen. After that, the molded article of Example 2 was cured by irradiating it with LED light having a wavelength of 365 nm from the side at 100% output for 60 seconds at room temperature.

[0060] Comparative Example 3 Light irradiation was carried out for 60 seconds using the same procedure as in Example 2, except that LED light with a wavelength of 280 nm (output 100%) was used instead of LED light with a wavelength of 365 nm. As a result, only a film-like cured product was formed on the irradiated surface, but the entire product was not cured, and no molded product was obtained. This is thought to be because TMPTA has a high absorption efficiency of ultraviolet light at a wavelength of 280 nm, so only the TMPTA present near the irradiated surface absorbed the light and formed a film-like cured product, and the light did not reach the interior.

[0061] [Example 3] A 32 mm inner diameter Pyrex (registered trademark) screw tube was charged with 6.0 g of a 25 mass % cyclohexane solution of n-butyl acrylate from which the polymerization inhibitor had been removed by a known means (hereinafter, n-butyl acrylate from which the polymerization inhibitor had been removed will be referred to as BA), and a magnetic stirrer bar. After removing dissolved oxygen by nitrogen bubbling, the contents were irradiated from the side with LED light at 100% output and a wavelength of 365 nm for 8 hours at room temperature while stirring, to obtain a viscous polymer solution. 1 The conversion rate calculated using H-NMR was 58.4%. The transmittance of this viscous polymer solution was measured using a quartz cell for UV-Vis measurements, and was 99.97% at a wavelength of 400 nm and 96.90% at a wavelength of 310 nm.

[0062] [Example 4] Except for using LED light with a wavelength of 385 nm (output 100%) instead of LED light with a wavelength of 365 nm, light irradiation was carried out for 8 hours in the same manner as in Example 3. As a result, a viscous polymer solution similar to that in Example 3 was obtained. 1 The conversion rate calculated using H-NMR was 49.9%. The transmittance of this viscous polymer solution was measured using a quartz cell for UV-Vis measurements, and was 99.90% at a wavelength of 400 nm and 96.12% at a wavelength of 310 nm.

[0063] Comparative Example 4 The light irradiation was carried out for 8 hours in the same manner as in Example 3, except that LED light with a wavelength of 280 nm (output 100%) was used instead of LED light with a wavelength of 365 nm. As a result, no change in viscosity was observed.1 No polymer peaks were detected in H-NMR measurements.

[0064] Comparative Example 5 To a 30 mass % cyclohexane solution of BA, 1.0 mol % relative to BA (2.5 mass parts relative to 100 mass parts of BA) of benzoyl peroxide was added, and thermal polymerization was carried out at 70°C for 2 hours under a nitrogen stream to obtain a viscous polymer solution. 1 The conversion rate calculated using H-NMR was 98.9%. The transmittance of this viscous polymer solution was measured using a quartz cell for UV-Vis measurements, and was 98.60% at a wavelength of 400 nm and 51.29% at a wavelength of 310 nm.

[0065] [Example 5] 0.80 g of tert-butyl acrylate (t-BA) and 0.35 g of 1,4-dioxane were placed in a Pyrex (registered trademark) polymerization tube with an inner diameter of 13 mm and a stirring bar placed therein, and after removing dissolved oxygen by freeze degassing, the mixture was irradiated with LED light having a wavelength of 405 nm at 100% output for 1 hour while stirring. 1 The conversion rate was determined to be 32% by H-NMR. The number-average molecular weight Mn of the resulting polymer was 175,000, and the molecular weight distribution Mw / Mn was 2.64.

[0066] [Example 6] A 6 mm diameter hole was drilled in a 5 mm thick silicone rubber plate, which was then attached to a CaF2 plate. BA was inserted, and the CaF2 plate was then placed on top. LED light with a wavelength of 365 nm was then irradiated from above. A solvent-insoluble gel-like cured product was obtained after 60 minutes of light irradiation at room temperature. The optical path length in Example 6 was 5 mm.

[0067] [Example 7] A 5 mm thick silicone rubber sheet with a 6 mm diameter hole was attached to a quartz glass slide, the hole was filled with TMPTA, and then a quartz glass slide was placed on top of it. LED light with a wavelength of 365 nm was irradiated at 100% output for 10 minutes. As a result, a cylindrical, cured molded product of Example 7 was obtained. The optical path length in Example 7 was 5 mm.

[0068] [Example 8] The LED light was irradiated in the same manner as in Example 7, except that a 2 mm thick silicone rubber was used instead of the 5 mm thick silicone rubber. As a result, a cylindrical cured molded product of Example 8 was obtained. The optical path length in Example 8 was 2 mm.

[0069] [Example 9] The LED light was irradiated in the same manner as in Example 7, except that a 1 mm thick silicone rubber was used instead of the 5 mm thick silicone rubber. As a result, a cylindrical cured molded product of Example 9 was obtained. The optical path length in Example 9 was 1 mm.

[0070] [Example 10] A Pyrex (registered trademark) screw tube with an inner diameter of 32 mm was charged with 6 g of isobornyl acrylate (IBXA) and a stirring bar, and the tube was then sealed with a septum cap. While stirring the contents with a magnetic stirrer, nitrogen was passed through a syringe needle at a rate of 40 mL / min to remove oxygen, and then the container was irradiated with LED light (100% output) at a wavelength of 365 nm from the side of the container for 10 minutes while stirring to prepare a polymerizable semi-finished product (acrylic syrup). The conversion rate of IBXA in this polymerizable semi-finished product was calculated using the following formula: 1 The H-NMR analysis revealed that it was 12%.

[0071] 1-hydroxycyclohexyl phenyl ketone (Tokyo Chemical Industry Co., Ltd.) was dissolved in this polymerizable semi-finished product at a concentration of 0.26% by mass as a photopolymerization initiator to prepare a photocurable composition. A 5 mm thick silicone rubber sheet with a 6 mm diameter hole was attached to a quartz glass slide. The prepared photocurable composition was placed in the hole, and then covered with a quartz glass slide. LED light with a wavelength of 365 nm was irradiated at 100% output for 15 seconds. As a result, a cured product corresponding to the shape of the hole was obtained. This demonstrates that the polymerizable semi-finished product obtained in Example 10 can be used in the same way as commercially available acrylic syrup.

Claims

1. A method for producing a polymer material or a molded article, which utilizes the photopolymerization reaction of a vinyl monomer, and is characterized by photopolymerizing a reactive material containing a vinyl monomer under conditions that satisfy all of the following conditions (a) to (c): (a) The reactive material is substantially free of both a photopolymerization initiator and a photosensitizer. (b) The photopolymerization reaction is carried out in a container. (c) The wavelength of the irradiated light is 300 nm or more.

2. The method according to claim 1, further satisfying the following condition (d): (d) The length of the optical path irradiated onto the reaction material when the reaction material is contained in the container is 1 mm or more.

3. 2. The method according to claim 1, wherein the vinyl monomer contains at least one selected from the group consisting of (meth)acrylic acid, (meth)acrylic acid derivatives, styrenes, vinyl esters, vinyl amides, vinyl ethers, and ethenes in an amount exceeding 50% by mass based on the total mass of the vinyl monomers.

4. 2. The method according to claim 1, wherein the container is a tank or a tube.

5. 2. The method according to claim 1, wherein the light source for the photopolymerization reaction is a light-emitting diode.

6. A method for producing a polymerizable semi-finished product, which utilizes the photopolymerization reaction of a vinyl monomer, is characterized by photopolymerizing a reactive material containing a vinyl monomer under conditions that satisfy all of the following conditions (a) to (c): (a) The reactive material is substantially free of both a photopolymerization initiator and a photosensitizer. (b) The photopolymerization reaction is carried out in a container. (c) The wavelength of the irradiated light is 300 nm or more.

7. The method according to claim 6, further satisfying the following condition (d): (d) The length of the optical path irradiated onto the reaction material when the reaction material is contained in the container is 1 mm or more.

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