JP4737661B2 - Methacrylic resin molded product, its manufacturing method, and front plate - Google Patents

Description

  The present invention relates to a methacrylic resin molded article having excellent weather resistance, which has a sharp blocking characteristic with respect to wavelengths in the harmful ultraviolet region of sunlight, and allows maximum transmission of useful sunlight.

  In general, methacrylic resins mainly composed of methyl methacrylate units are used in various fields such as lighting covers, automotive parts, signboards, ornaments, and miscellaneous goods because of their excellent weather resistance and excellent transparency.

  Conventionally, in order to improve the weather resistance of a methacrylic resin, methods using various ultraviolet absorbers are known. For example, Patent Document 1 discloses a technique using a benzotriazole ultraviolet absorber and a benzophenone ultraviolet absorber. The molded article containing a large amount of the benzotriazole-based ultraviolet absorber has high weather resistance, but when it is provided on the front surface of the photovoltaic element, many photovoltaic elements are formed of silicon, and light between 350 nm and 1100 nm is used. Therefore, there is a problem that power generation efficiency is lowered by shielding even light that can be used for power generation by the photovoltaic element.

On the other hand, Patent Document 2 discloses a technique for improving weather resistance without using an ultraviolet absorber. However, although the molded product transmits a large amount of light that can be used for power generation by the photovoltaic element, there is a problem in that it yellows due to long-term outdoor use and the light transmittance decreases.
JP-A-61-215660 Japanese Examined Patent Publication No. 2-61485

  Development of a methacrylic resin that does not have these disadvantages, transmits more light that can be used for power generation, and does not decrease transmittance due to yellowing of the methacrylic resin for long-term outdoor use is expected.

  An object of the present invention is to solve this problem.

  As a result of intensive studies, the present inventors have found that a photovoltaic device is obtained by using a (co) polymer containing a methyl methacrylate unit in combination with a specific ultraviolet absorber and, if necessary, a hindered amine light stabilizer. It has been found that more light that can be used for power generation in Japan is transmitted, and that the methacrylic resin turns yellow and does not decrease the transmittance in long-term outdoor use.

The gist of the present invention is that 100 parts by mass of methacrylic resin containing 60 to 100% by mass of methyl methacrylate units and 0 to 40% by mass of other copolymerizable vinyl monomer units, and 2- ( At least one of 2-hydroxy-4-n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine and 2-hydroxy-4-octyloxybenzophenone 0.005 and a ~ 0.045 parts by weight, and the light transmittance at a wavelength of 340nm is 20% or less in the thickness range 0.5 to 5 mm, consisting of methacrylic resin molded article light transmittance at a wavelength of 380nm is 70% or more Located on the front plate of the photovoltaic element .

  The aforementioned methacrylic resin molded article is preferably produced by polymerizing a polymerizable raw material containing an ultraviolet absorber in a mold and peeling it from the mold.

  The methacrylic resin molded article of the present invention is useful because it causes less yellowing when used outdoors for a long period of time and transmits more light that can be used for power generation in a photovoltaic device.

  In the methacrylic resin molded product of the present invention, the light transmittance at a wavelength of 340 nm in the thickness range of 0.5 to 5 mm is 20% or less, and the light transmittance at a wavelength of 380 nm is 70% or more.

  When the light transmittance at a wavelength of 340 nm is 20% or less, the weather resistance of the molded product is improved. The light transmittance is preferably 5% or less, and more preferably lower.

  When the light transmittance at a wavelength of 380 nm is 70% or more, light that can be used for power generation when used for the front plate of the photovoltaic element is effectively transmitted, and the power generation efficiency is increased. The light transmittance is preferably 75% or more. The upper limit of the light transmittance is preferably 93% or less.

  In order to obtain a resin molded product having this physical property, a molded product is formed by molding a resin composition containing 0.005 to 0.15 parts by mass of an ultraviolet absorber having a maximum absorption wavelength of 300 nm or less per 100 parts by mass of a methacrylic resin. It is preferable that

As an ultraviolet absorber having a maximum absorption wavelength of 300 nm or less, 2- (2-hydroxy-4-
n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3
5-triazine, 2-hydroxy-4-octyloxybenzophenone. 2- (2-hydroxy-4-n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine and 2-hydroxy-4 per 100 parts by weight of methacrylic resin -A resin molded article comprising a resin composition containing 0.005 to 0.15 parts by mass of at least one of octyloxybenzophenone . 2- (2-hydroxy-4-n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine is particularly preferable.

  More preferably, the content of the ultraviolet absorber in the methacrylic resin molded product of the present invention is appropriately adjusted for each thickness of the molded product. For 100 parts by weight of the methacrylic resin, the thickness of the molded product is used to calculate the content of “UV absorber = (0.04 to 0.07 (part by weight)) ÷ thickness of the methacrylic resin molded product (mm)”. It is most preferable to use it in an addition amount within a range. When the content of the ultraviolet absorber is not less than the minimum mass part calculated by calculation, the weather resistance of the methacrylic resin molded product due to the wavelength in the harmful ultraviolet region can be improved. On the other hand, when the content of the ultraviolet absorber is equal to or less than the maximum mass part calculated by calculation, light that can be used for power generation in the photovoltaic element is effectively transmitted, and the power generation efficiency is increased. Here, the “thickness of the methacrylic resin molded product” means a thickness in a direction in which light is transmitted in a form using the methacrylic resin molded product.

  The methacrylic resin molded product of the present invention can be extruded by mixing an appropriate amount of an ultraviolet absorber with methacrylic resin pellets and beads. In addition, an appropriate amount of an ultraviolet absorber may be mixed with a polymerizable raw material containing methyl methacrylate, which is a raw material for methacrylic resin, to form a molded product. In order to obtain a molded article having a high molecular weight and high mechanical strength, it is preferable to mix a suitable amount of an ultraviolet absorber with a polymerizable raw material containing methyl methacrylate, which is a raw material for methacrylic resin, to form a molded article.

  The methacrylic resin molded product of the present invention has a sharp blocking characteristic against the wavelength of harmful ultraviolet rays of sunlight, and is very useful as a methacrylic resin molded product with excellent weather resistance that allows the maximum transmission of useful sunlight. It is.

  UV absorbers 2- (2-hydroxy-4-n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine and 2-hydroxy-4-octyl By containing at least one of oxybenzophenone, the weather resistance can be improved while transmitting useful light, but the weather resistance of the resulting composition can be further improved by using a hindered amine light stabilizer in combination.

  The content of the hindered amine light stabilizer used in the present invention is preferably in the range of 0.01 to 1 part by mass (based on the mass of the methacrylic resin, that is, 100 parts by mass), and 0.05 to 0.5 parts by mass. The range of is more preferable. When the content of the hindered amine light stabilizer is 0.01 parts by mass or more, the weather resistance is improved. On the other hand, when the content of the hindered amine light stabilizer is 1 part by mass or less, deterioration of mechanical properties, which is an excellent characteristic of the composition, can be prevented.

  Examples of the hindered amine light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [ 2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-hydroxyphenyl) propionyloxy]- 2,2,6,6-tetramethylpiperidine, bis (1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, 4-benzoyloxy-2,2,6,6-tetra And methyl piperidine. Among them, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (1-octyloxy-2,2) , 6,6-tetramethyl-4-piperidyl) sebacate, the most preferred of which is bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate.

  Hereinafter, a production method for obtaining a molded product by polymerizing a polymerizable raw material containing an ultraviolet absorber will be described.

(Monomer)
The monomer used in the present invention may be methyl methacrylate alone, or a monomer mixture of methyl methacrylate and another vinyl monomer copolymerizable with methyl methacrylate. (In the present invention, even a single monomer may be referred to as a “monomer mixture” for convenience).

(Other copolymerizable monomers)
Other vinyl monomers copolymerizable with methyl methacrylate (vinyl monomers other than methyl methacrylate) are not particularly limited. Examples of such vinyl monomers include ethyl methacrylate, isopropyl methacrylate, t-butyl methacrylate, s-butyl methacrylate, n-butyl methacrylate, amyl methacrylate, octyl methacrylate, 2-methacrylic acid 2- Methacrylic acid esters other than methyl methacrylate having 1 to 12 carbon atoms of cycloalkyl group such as ethylhexyl, lauryl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and alkyl groups containing benzyl group; bornyl methacrylate; Methacrylic acid esters having an alkyl group or alicyclic hydrocarbon group having 8 to 20 carbon atoms such as isobornyl methacrylate, 1-menthyl methacrylate, adamantyl methacrylate and dimethyladamantyl methacrylate; acrylic acid Chill, ethyl acrylate, isopropyl acrylate, butyl acrylate, t-butyl acrylate, amyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, etc. Acrylic esters of styrene; vinyl aromatics such as styrene, α-methyl styrene, paramethyl styrene, isopropenyl styrene, vinyl toluene; unsaturated nitriles such as acrylonitrile, methacrylonitrile; methacrylic acid, acrylic acid, maleic anhydride Examples thereof include, but are not limited to, unsaturated carboxylic acids such as acids; polyunsaturated compounds such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and divinylbenzene. These monomers can be used alone or in combination of two or more as required.

  The composition of the monomer that can be used in the present invention is usually 60 to 100% by mass of methyl methacrylate (based on the whole monomer) and 0 to 40% by mass of other copolymerizable vinyl monomers. Range. The use amount of the copolymerizable vinyl monomer is preferably 10% by mass or less as a use amount that does not impair the original physical properties of the methacrylic resin obtained by polymerization.

  In the present invention, the monomer mixture can be subjected to polymerization. However, a mixture of the monomer mixture and a polymer of the monomer mixture (hereinafter, such a mixture is sometimes referred to as “syrup” as appropriate). There is no problem even if it is subjected to polymerization.

  In order to shorten the production time and make it difficult to cause appearance defects, it is preferable to use syrup having a preliminarily increased polymerization rate of the monomer mixture, and the polymerization rate is 5 considering the handling of syrup and mixing of additives. It is preferable to be in the range of ˜40% by mass.

  The kind and addition amount of the ultraviolet absorber used in the present invention include those described above. It is preferable to adjust the addition amount as described above depending on the thickness of the obtained molded product.

  The kind and addition amount of the hindered amine light stabilizer used in the present invention include those described above.

  The kind and addition amount of the hindered amine light stabilizer used in the present invention include those described above.

(Method for producing methacrylic resin molded product)
The methacrylic resin molded product of the present invention is, for example, an ultraviolet absorber and, if necessary, a hindered amine light stabilizer added to the above monomer mixture or syrup and mixed to form a polymerizable raw material, which is injected into a mold. It can be produced by polymerization.

  The template that can be used in this case is not particularly limited. In the present invention, for example, a plate-like body such as tempered glass, a chrome-plated plate, or a stainless plate and a gasket such as soft vinyl chloride, or the same as described in Japanese Patent Publication No. 52-30885. A mold composed of two endless belts traveling in the direction at the same speed and gaskets traveling at the same speed as both endless belts at both end portions on the opposite surface side can be used.

  The mold surface may have a shape having minute irregularities.

(Radical polymerization initiator)
In the present invention, the polymerization initiator or polymerization initiation method that can be used when polymerizing the monomer mixture or syrup is not particularly limited. In the present invention, it is preferable to use a radical polymerization initiator.

  As the radical polymerization initiator usable in the present invention, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 2,2′- Azo polymerization initiators such as azobis- (2,4-dimethylvaleronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), benzoyl peroxide, bis (4-t-butylcyclohexyl) peroxydi Organic peroxides such as carbonate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxypivalate, etc. It is done. These polymerization initiators can be used alone or in combination or in combination of two or more as required.

  The addition amount of the radical initiator is preferably in the range of 0.01 to 0.5 parts by mass per 100 parts by mass of the monomer mixture or syrup. If the amount of radical initiator added is too small, the polymerization is not completed due to insufficient initiator, and therefore unreacted monomers tend to increase and the weather resistance of the molded product tends to deteriorate. On the other hand, when there is too much addition amount of a radical initiator, it will become easy to produce a surface defect in a molded article.

(Additive)
The monomer mixture or syrup can be added with various additives used in producing a normal methacrylic resin or a modified product thereof, if necessary. Examples of the additive herein include dyes and pigments used for coloring; stabilizers such as antioxidants; flame retardants, chain transfer agents, crosslinking agents, release agents, and the like.

(Polymerization temperature)
The polymerization temperature in the present invention varies depending on the type of polymerization initiator used, but is generally preferably 40 to 170 ° C. Furthermore, it is preferable to perform polymerization at a two-stage polymerization temperature in which the first stage is 40 to 90 ° C. and the second stage is 100 to 140 ° C.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

  In addition, the physical property evaluation in an Example was performed based on the following method.

1) Light transmittance The light transmittance at each wavelength of a test piece cut out from a resin molded product was measured using an ultraviolet-visible spectrophotometer UVmini-1240 manufactured by Shimadzu Corporation.

2) Electrical output characteristics A plate made of a methacrylic resin molded product was disposed on the upper surface of Showa Shell Sekiyu made solar cell module GT1618-MF, and the electrical output characteristics were measured using an AM1.5 light source.

  In addition, a result is described by the relative value which set the output characteristic before the weather resistance test of Example 1 to 100, evaluation before a weather resistance test arrange | positions a molded article single board, and evaluation after a weather resistance test is a weather resistance test. Several subsequent molded product pieces were placed and measured.

3) Weather resistance test As an accelerated exposure test that is close to long-term outdoor use, a sunshine weatherometer (manufactured by Suga Test Instruments Co., Ltd.) was used under conditions where there was rain at 63 ° C for 12 minutes in one cycle of 60 minutes. The test piece cut out from the molded article was exposed for 2000 hours.

4) Yellowness measurement The yellowness of the test piece after the weather resistance test was measured according to JIS K 7103.

[Example 1]
100 parts by mass of methyl methacrylate was supplied to a 50 liter SUS304 reactor equipped with a condenser, a thermometer and a stirrer and heated while stirring, and when the internal temperature reached 80 ° C., 2, 2 ′ -By adding 0.05 parts by mass of azobis- (2,4-dimethylvaleronitrile) (based on the mass of methyl methacrylate), further heating to an internal temperature of 90 ° C and holding for 8 minutes, then cooling to room temperature A syrup having a polymerization rate of about 22% by mass measured by a reprecipitation method and a viscosity at 20 ° C. of 1.5 Pa · s measured by a B-type viscometer was obtained.

  Next, 0.2 parts by mass of t-hexyl peroxypivalate as a radical polymerization initiator and 0.016 parts by mass of 2-hydroxy-4-octyloxybenzophenone as an ultraviolet absorber were added to 100 parts by mass of this syrup. Then, after stirring and degassing under reduced pressure at −90 kPa for 5 minutes, two tempered glass plates opposed to each other at an interval of about 4 mm were injected into a mold fixed by a clamp through a polyvinyl chloride gasket.

  The mold in which syrup was injected in this manner was immersed in warm water at 78 ° C. for 30 minutes to be polymerized and cured, then heat-treated in a 135 ° C. air heating furnace for 60 minutes and cooled to 90 ° C. The methacrylic resin molded product having a thickness of 3 mm was obtained by removing the frame.

  A test piece was cut out from the obtained resin molded product, one was measured for light transmittance and electrical output characteristics, and the other was measured for yellowing and electrical output characteristics after the weather resistance test. The obtained results are shown in Table 1.

[Comparative Example 1]
In the same manner as in Example 1, except that 0.01 part by mass of 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole was added instead of the ultraviolet absorber used in Example 1. A resin molded product was obtained. Table 1 shows the results of various evaluations performed on test pieces cut out from the obtained molded product.

[Comparative Example 2]
A resin molded product was obtained in the same manner as in Example 1 except that the ultraviolet absorber used in Example 1 was not added. Table 1 shows the results of various evaluations performed on test pieces cut out from the obtained molded product.

[Example 2]
100 parts by mass of syrup as in Example 1, 0.065 parts by mass of 2,2′-azobis- (2,4-dimethylvaleronitrile), and 2- (2-hydroxy-4-n-octyl) as an ultraviolet absorber After adding 0.034 parts by mass of (oxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, the mixture was stirred to obtain syrup. The syrup thus obtained was degassed under reduced pressure at -90 kPa for 5 minutes, and then injected through a polyvinyl chloride gasket into a mold in which two opposed SUS304 plates were clamped and fixed. .

  The mold in which syrup is injected in this manner is immersed in warm water at 78 ° C. for 30 minutes, polymerized and cured, then heat-treated in an air heating furnace at 125 ° C. for 60 minutes, cooled to 90 ° C., and then removed from the mold. As a result, a methacrylic resin molded product having a thickness of 2 mm was obtained.

  Table 1 shows the results of various evaluations performed on test pieces cut out from the obtained molded product.

[Comparative Example 3]
A resin molded article was obtained in the same manner as in Example 2 except that 0.018 parts by mass of ethyl-2-cyano-3,3-diphenyl acrylate was added instead of the ultraviolet absorber used in Example 2. It was. Table 1 shows the results of various evaluations performed on test pieces cut out from the obtained molded product.

[Example 3]
96 parts by mass of methyl methacrylate and 4 parts by mass of butyl acrylate are supplied to the same reactor as that used in Example 1, and 0.06 parts by mass of n-dodecyl mercaptan (methyl methacrylate and acrylic acid) are used as a molecular weight regulator. (Based on the total mass of butyl acrylate), and then with stirring, when the internal temperature reached 80 ° C., 0.02 part by weight of 2,2′-azobis- (2,4-dimethylvaleronitrile) (methacrylic acid) (The total mass of methyl acrylate and butyl acrylate) was added, and further heated to an internal temperature of 90 ° C. and held for 13 minutes, and then cooled to room temperature, whereby the polymerization rate measured by the reprecipitation method was about 26% by mass A syrup having a viscosity of 2 Pa · s at 20 ° C. measured with a B-type viscometer was obtained.

  Next, 0.08 parts by mass of 2,2′-azobis- (2,4-dimethylvaleronitrile), which is a radical polymerization initiator, and 2- (2-hydroxy-4-n-octyloxy) are added to 100 parts by mass of this syrup. Phenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine 0.045 parts by mass, bis (2,2,6,6-tetramethyl-) as a hindered amine light stabilizer After adding 0.2 parts by mass of 4-piperidyl) sebacate, the mixture was stirred, degassed under reduced pressure at -90 kPa for 5 minutes, and then two SUS304 facing each other at intervals of about 1.3 mm via a polyvinyl chloride gasket. The plate was poured into a mold fixed with a clamp.

  The mold in which syrup is injected in this way is immersed in warm water at 78 ° C. for 30 minutes, polymerized and cured, then heat-treated in a 130 ° C. air heating furnace for 60 minutes and cooled to 90 ° C., and then the mold is removed. Thus, a methacrylic resin molded product having a thickness of 1 mm was obtained.

  Table 1 shows the results of various evaluations performed on test pieces cut out from the obtained molded product.

[Comparative Example 4]
The hindered amine light stabilizer used in Example 3 was not added, and 2- (2-hydroxy-4-n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3 A resin molded product was obtained in the same manner as in Example 3 except that the amount of addition of, 5-triazine was changed to 0.003 parts by mass. Table 1 shows the results of various evaluations performed on test pieces cut out from the obtained molded product.

[Comparative Example 5]
The amount of 2- (2-hydroxy-4-n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine added in Comparative Example 4 was 0.2. A resin molded product was obtained in the same manner as in Comparative Example 4 except that the mass parts were changed. Table 1 shows the results of various evaluations performed on test pieces cut out from the obtained molded product.

Explanation of abbreviations MMA: methyl methacrylate unit BA: butyl acrylate unit UVA-1: 2-hydroxy-4-octyloxybenzophenone UVA-2: 2- (2-hydroxy-4-n-octyloxyphenyl) -4, 6-bis (2,4-dimethylphenyl) -1,3,5-triazine UVA′-3: 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole UVA′-4: ethyl-2- Cyano-3,3-diphenyl acrylate HALS-1: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate

  The methacrylic resin molded product of the present invention is suitable for a front plate of a photovoltaic element.

Claims (3)

  100 parts by mass of a methacrylic resin containing 60 to 100% by mass of methyl methacrylate units and 0 to 40% by mass of other copolymerizable vinyl monomer units, and 2- (2-hydroxy-4-) as an ultraviolet absorber 0.005 to 0.045 parts by mass of at least one of n-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine and 2-hydroxy-4-octyloxybenzophenone In front of a photovoltaic device comprising a methacrylic resin molded product having a light transmittance of 20% or less at a wavelength of 340 nm in a thickness range of 0.5 to 5 mm and a light transmittance of 380 nm of 70% or more. Face plate.   Furthermore, the front plate of the photovoltaic element which consists of a methacrylic resin molded product of Claim 1 containing 0.01-1 mass part of hindered amine light stabilizers. The front plate of a photovoltaic element comprising the methacrylic resin molded product according to claim 1, wherein the content of the ultraviolet absorber satisfies the following formula with respect to 100 parts by mass of the methacrylic resin.
UV absorber content = (0.04-0.07 (parts by mass)) / methacrylic resin molded product thickness (mm)