Thermoplastic resin composition

Abstract

This invention provides a thermoplastic resin composition comprising a vinylidene fluoride-based resin and core-shell particles, exhibiting both transparency and elongation at low temperatures. The thermoplastic resin composition comprises a vinylidene fluoride-based resin and polymer particles. The polymer particles have a core particle (A) and a shell layer (B) located outside the core particle. (A) comprises a rubber layer consisting of a reaction product of a vinyl monomer (a1) and a crosslinking monomer (a2), (a1) comprising (meth)acrylate, and the glass transition temperature of the rubber layer is below -20°C. (B) comprises any grafted layer (B1) with a glass transition temperature above -20°C and below 50°C, and a grafted layer (B2) with a glass transition temperature above 50°C, (B1) / [(A)+(B1)+(B2)] being 0-10% by weight, and [(A)+(B1)] / [(A)+(B1)+(B2)] being 30-70% by weight. The content of free polymer in the polymer particles is 35% by weight or less.

Description

Technical Field

[0001] The present invention relates to a thermoplastic resin composition comprising a vinylidene fluoride-based resin, a film or molded body formed from the resin composition, and a backsheet or solar cell module comprising the film. Background Technology

[0002] From the perspective of creating clean energy, solar cells have attracted much attention. As a representative type of solar cell, silicon-based solar cells are typically constructed by sealing the solar cell unit with a thermoplastic resin such as ethylene-vinyl acetate copolymer (EVA), covering the sun-exposed surface with glass, and protecting the back side with a backsheet (back protective sheet).

[0003] Such backsheets for solar cells typically comprise a resin sheet formed from a thermoplastic resin material. Fluoropolymer resins, such as vinylidene fluoride resins, are used as the resin constituting the resin sheet due to their high durability and chemical resistance.

[0004] Patent Document 1 describes a method for suppressing discoloration under high temperature and high humidity by using a thin film made of a resin composition consisting of a methacrylate resin containing core-shell particles in a vinylidene fluoride-based resin as a backsheet for solar cells.

[0005] Although not related to backsheets for solar cells, Patent Document 2 describes a method for improving the thermodynamic stability of ultraviolet absorbers in resin compositions by incorporating core-shell polymer particles in fluorinated resins such as vinylidene fluoride resins, the core of which contains ultraviolet absorbers.

[0006] Patent Document 1: International Publication No. 2014 / 057933

[0007] Patent Document 2: Japanese Patent Publication No. 2003-506546 Summary of the Invention

[0008] To date, solar cells have primarily used single-sided concentrating technology. To improve solar energy conversion efficiency, double-sided concentrating technology, which can concentrate light from the back in addition to the surface and generate electricity, is gradually becoming the mainstream. In previous single-sided concentrating methods, although durable but opaque resin films were used as backsheets, double-sided concentrating methods require the use of highly transparent films.

[0009] Patent documents 1 and 2 describe the incorporation of core-shell particles into vinylidene fluoride-based resins; however, in such incorporations, transparency typically tends to decrease due to the difference in refractive indices between the two components. Furthermore, these documents do not include research on improving transparency, making it difficult to obtain sheets with high transparency.

[0010] Furthermore, since the backsheets used for solar cells are sometimes placed outdoors at low temperatures, in order to ensure strength at low temperatures, they are also required to exhibit high elongation at low temperatures.

[0011] In view of the above-mentioned situation, the present invention aims to provide a thermoplastic resin composition comprising vinylidene fluoride resin and core-shell particles, which has both transparency and elongation at low temperature.

[0012] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by combining core-shell particles that meet specific conditions into vinylidene fluoride resin, the above-mentioned problems can be solved, thus completing the present invention.

[0013] This invention relates to a thermoplastic resin composition comprising a vinylidene fluoride-based resin and polymer particles.

[0014] The polymer particles described above have a core particle (A) and a shell (B) located outside the core particle.

[0015] The aforementioned nuclear particle (A) comprises a rubber layer consisting of a reactant of a vinyl monomer (a1) and a crosslinking monomer (a2).

[0016] The aforementioned vinyl monomer (a1) includes (meth)acrylates.

[0017] The glass transition temperature of the aforementioned rubber layer is below -20°C.

[0018] The aforementioned shell (B) includes any grafted layer (B1) with a glass transition temperature of -20°C or higher and less than 50°C, and a grafted layer (B2) with a glass transition temperature of 50°C or higher.

[0019] Furthermore, the weight ratio (B1) / [(A) + (B1) + (B2)] is 0 to 10% by weight.

[0020] The weight ratio [(A) + (B1)] / [((A) + (B1) + (B2)] is 30-70% by weight.

[0021] The content of free polymer in the above polymer particles is less than 35% by weight.

[0022] In addition, the present invention also relates to a molded body or film formed by molding the above-mentioned thermoplastic resin composition; a backsheet for a solar cell comprising a layer composed of the above-mentioned film; and a solar cell module comprising a solar cell element and the above-mentioned backsheet for a solar cell.

[0023] According to the present invention, a thermoplastic resin composition comprising vinylidene fluoride resin and core-shell particles can be provided, which also has transparency and elongation at low temperature.

[0024] The thermoplastic resin composition of the present invention can be molded into a molded body or a film. The film can take full advantage of its transparency and low-temperature elongation, making it particularly suitable for use as a backsheet for solar cells. Detailed Implementation

[0025] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and various modifications can be made within the scope defined by the claims. Furthermore, the various configurations described below can be combined arbitrarily, and such combinations can also be considered as a form of the present invention.

[0026] The thermoplastic resin composition disclosed herein comprises at least a vinylidene fluoride-based resin as a thermoplastic resin and polymer particles. The polymer particles function as a modifier for the vinylidene fluoride-based resin, particularly as an impact resistance improver or elongation improver.

[0027] <Polymer Particles>

[0028] The polymer particles described above have a core-shell structure comprising a nucleus (A) and a shell (B) located outside the nucleus. Hereinafter, these polymer particles will also be referred to as "core-shell polymer particles".

[0029] Nuclear particles (A) refer to particles located inside core-shell polymer particles.

[0030] The shell (B) refers to the polymer layer located outside the nuclear particle (A) in a manner that covers the surface of the nuclear particle (A). The shell covers the surface of the nuclear particle (A), but is not limited to covering the entire surface of the nuclear particle, as long as it covers at least a portion of the surface of the nuclear particle.

[0031] <Nuclear Particle (A)>

[0032] The nuclear particle (A) contains a rubber layer. Here, rubber refers to a material composed of organic materials with a cross-linked structure and a low elastic modulus, i.e., elastic rubber. Because the polymer particles contain a rubber layer, by incorporating the polymer particles into the vinylidene fluoride resin, the vinylidene fluoride resin can be endowed with impact resistance or high elongation.

[0033] The nuclear particle (A) may consist solely of a rubber layer, or it may contain a polymer layer that is not part of the rubber layer. In the latter case, the polymer layer may exist either inside or outside the rubber layer.

[0034] The rubber layer is preferably the main component of the core particle (A). Specifically, the rubber layer accounts for 50-100% by weight, 70-100% by weight, 90-100% by weight, 95-100% by weight, or 99-100% by weight of the core particle (A).

[0035] In addition, the rubber layer can be composed of a single layer or multiple layers with different compositions.

[0036] From the viewpoint of improving the impact resistance or elongation of vinylidene fluoride-based resins, the glass transition temperature exhibited by the aforementioned rubber layer is preferably below -20°C, more preferably below -30°C, further preferably below -40°C, and particularly preferably below -50°C. The lower limit is not particularly limited, and for example, it may be above -80°C, above -70°C, or above -60°C. It should be noted that when the rubber layer is composed of multiple layers with different compositions, the glass transition temperature of the rubber layer refers to the glass transition temperature of all the multiple layers combined.

[0037] It should be noted that the glass transition temperature of a polymer can be calculated using the values ​​recorded in the Polymer Handbook (J. Brandrup, Interscience 1989) and the Fox formula. For example, the Tg of polymethyl methacrylate is 105 °C, and the Tg of polybutyl acrylate is -54 °C.

[0038] The aforementioned rubber layer is formed from the reaction product of vinyl monomer (a1) and crosslinking monomer (a2).

[0039] (Vinyl monomers (a1))

[0040] Vinyl monomers are compounds that have a single carbon-carbon unsaturated bond in a molecule and the ability to form polymers through addition polymerization.

[0041] From the perspective of balancing transparency and high elongation, vinyl monomers (a1) contain at least (meth)acrylates. It should be noted that "(meth)acrylate" refers to both acrylic acid and methacrylic acid.

[0042] The aforementioned (meth)acrylates are not particularly limited, and examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, and other alkyl (meth)acrylates; phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and other (meth)acrylates containing aromatic rings; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; glycidyl (meth)acrylates such as glycidyl (meth)acrylate and glycidyl (meth)acrylate; and alkoxyalkyl (meth)acrylates. (Meth)acrylates can be used alone or in combination of two or more.

[0043] The number of carbon atoms in the ester portion of the (meth)acrylate is preferably 1 to 22, more preferably 1 to 18, even more preferably 2 to 12, and even more preferably 3 to 8.

[0044] The aforementioned vinyl monomer (a1) may consist solely of the aforementioned (meth)acrylate, or it may include other vinyl monomers having a single carbon-carbon unsaturated bond in one molecule. There are no particular limitations on these other monomers; examples include aromatic vinyl compounds such as styrene and α-methylstyrene, cyanide vinyl compounds, halogenated vinyl compounds such as vinyl chloride and chloroprene, vinyl acetate, ethylene, propylene, and other olefins.

[0045] In the above-mentioned vinyl monomer (a1), the content of the above-mentioned (meth)acrylate is preferably 50-100% by weight, more preferably 70-100% by weight, even more preferably 80-100% by weight, even more preferably 90-100% by weight, and particularly preferably 95-100% by weight.

[0046] From the viewpoint of improving transparency, it is preferable that the vinyl monomer (a1) substantially does not contain vinyl monomers with a refractive index of 1.51 or higher as measured as a homopolymer. Here, "substantially does not contain" means that the content of the aforementioned vinyl monomers with a refractive index of 1.51 or higher in the vinyl monomer (a1) is 0% by weight or more and less than 1% by weight. The upper limit is less than 0.1% by weight, or it may be less than 0.01% by weight. Examples of vinyl monomers with a refractive index of 1.51 or higher include aromatic vinyl compounds, cyanide vinyl compounds, and halogenated vinyl compounds.

[0047] From the viewpoint of imparting good elasticity to the rubber layer by controlling its glass transition temperature to a low level, and of imparting impact resistance or high elongation to the vinylidene fluoride-based resin, acrylates are preferred as the (meth)acrylates mentioned above, and alkyl acrylates are more preferred. The alkyl acrylate preferably has 1 to 22 carbon atoms in its alkyl group, more preferably 1 to 18 carbon atoms, further preferably 2 to 12 carbon atoms, and even more preferably 3 to 8 carbon atoms. In particular, butyl acrylate and 2-ethylhexyl acrylate are preferred.

[0048] When using alkyl acrylate as the above-mentioned (meth)acrylate, the content of alkyl acrylate in the vinyl monomer (a1) is preferably 50-100% by weight, more preferably 70-100% by weight, even more preferably 80-100% by weight, even more preferably 90-100% by weight, and particularly preferably 95-100% by weight. In this case, (meth)acrylates other than alkyl acrylate can also be used as monomers.

[0049] (Crosslinking monomer (a2))

[0050] Crosslinking monomer (a2) refers to a compound that can copolymerize with the aforementioned vinyl monomer (a1) and has two or more carbon-carbon unsaturated bonds in one molecule. Specific examples include allyl (meth)acrylates, allyl alkyl (meth)acrylates, allyl oxyalkyl (meth)acrylates, and other (meth)acrylates containing an allyl group; polyfunctional (meth)acrylates containing two or more (meth)acrylate groups, such as polyethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate; diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, and divinylbenzene.

[0051] From a transparency perspective, crosslinking monomers with relatively low refractive indices are preferred. Specifically, allyl methacrylate, butanediol dimethacrylate, tripropylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate are preferred, with allyl methacrylate being particularly preferred. As a crosslinking monomer (a2), only one type may be used, or two or more types may be used simultaneously.

[0052] The amount of crosslinking monomer (a2) used can be appropriately set from the viewpoint of improving impact strength or elongation. Specifically, it is preferably about 0.01 to 6 parts by weight relative to 100 parts by weight of vinyl monomer (a1). Within this range, thermoplastic resin compositions with good impact resistance or elongation are readily obtained. More preferably, it is 0.05 to 5 parts by weight, even more preferably 0.1 to 4 parts by weight, and particularly preferably 0.3 to 3 parts by weight.

[0053] The average particle size of the aforementioned nuclear particles (A) is not particularly limited, but from the viewpoint of balancing impact resistance or elongation with transparency, a volume average particle size in the range of 40 to 150 nm is preferred. Impact resistance or elongation tends to improve with increasing average particle size. From this viewpoint, a lower limit of 50 nm or more is preferred, and more preferably 60 nm or more.

[0054] On the other hand, as the average particle size decreases, there is a trend of reduced haze and increased transparency. From this point of view, the upper limit is preferably 120 nm or less, more preferably 100 nm or less, even more preferably 90 nm or less, and particularly preferably 80 nm or less.

[0055] The average particle size of the nucleus (A) mentioned here refers to the average particle size of the polymer particles after the synthesis of the nucleus (A) and before the synthesis of the shell (B). As shown in the examples, the average particle size of the polymer particles is the value measured using a particle size measuring device in the latex state of the polymer particles.

[0056] It should be noted that the particle size of the nuclear particles (A) can be controlled by the type and content of each monomer and crosslinking monomer, the type and content of initiator, reducing agent, emulsifier, etc., polymerization temperature, polymerization time, etc.

[0057] <Shell (B)>

[0058] The shell (B) is a polymer layer located outside the core particle (A), and is a layer located on the surface side of the aforementioned core-shell polymer particle. The shell (B) is preferably grafted onto the core particle (A), but may also contain ungrafted components. This component belongs to the free polymers described later.

[0059] By setting a shell (B), the compatibility between core-shell polymer particles and vinylidene fluoride resins can be improved, and the core-shell polymer particles can be dispersed in the resin composition as primary particles.

[0060] The shell (B) may include a grafted layer (B1) with a glass transition temperature of -20°C to less than 50°C and a grafted layer (B2) with a glass transition temperature of 50°C or higher. The grafted layer (B1) may be any layer or may be omitted. Furthermore, these grafted layers may also contain ungrafted components.

[0061] The glass transition temperature of the grafted layer (B1) can be above -20°C and below 50°C, with the lower limit also being above -10°C or above 0°C. The upper limit can also be below 40°C, below 30°C, or below 20°C.

[0062] From the viewpoint of improving the stability of emulsion polymerization and the operability when recovering core-shell polymer particles as powder, the glass transition temperature of the graft layer (B2) is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher. There is no particular upper limit, and it can be 105°C or lower, 100°C or lower, or 95°C or lower.

[0063] As for the polymer constituting the graft layer (B1) or graft layer (B2), there are no particular limitations as long as the glass transition temperature described above is met. From the viewpoint of good compatibility with vinylidene fluoride resins, improving the dispersibility of core-shell polymer particles in vinylidene fluoride resins, and improving transparency, polymers selected from at least one vinyl monomer selected from (meth)acrylates, aromatic vinyl compounds, and cyanide vinyl compounds are preferred.

[0064] The aforementioned (meth)acrylates are not particularly limited, and examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, and other alkyl (meth)acrylates; phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and other (meth)acrylates containing aromatic rings; hydroxyalkyl (meth)acrylates, 4-hydroxybutyl (meth)acrylate, and other hydroxyalkyl (meth)acrylates; glycidyl (meth)acrylates, glycidyl alkyl (meth)acrylates, and other glycidyl (meth)acrylates; and alkoxyalkyl (meth)acrylates, etc.

[0065] The aromatic vinyl compounds mentioned above are not particularly limited, and examples include styrene, α-methylstyrene, p-methylstyrene, p-isopropylstyrene, o-chlorostyrene, p-chlorostyrene, dichlorostyrene, etc. Among them, styrene is preferred.

[0066] The cyanide vinyl compound mentioned above is not particularly limited, and examples include acrylonitrile and methacrylonitrile. Acrylonitrile is preferred.

[0067] From the viewpoint of compatibility with vinylidene fluoride-based resins, the graft layer (B1) or graft layer (B2) is preferably composed of a polymer containing at least a monomeric component of (meth)acrylate. In the total monomer composition of the graft layer (B1) or graft layer (B2), the total proportion of (meth)acrylate is preferably 50-100% by weight, more preferably 70-100% by weight, further preferably 90-100% by weight, and particularly preferably 95-100% by weight.

[0068] Specifically, the polymer constituting the graft layer (B1) or graft layer (B2) is preferably a copolymer comprising acrylate and methacrylate. In this case, the acrylate is preferably an alkyl acrylate, and particularly preferably an alkyl acrylate with 1 to 6 carbon atoms in the alkyl group. The methacrylate is preferably an alkyl methacrylate, and particularly preferably an alkyl methacrylate with 1 to 6 carbon atoms in the alkyl group. The ratio of acrylate to methacrylate can be appropriately set to satisfy the glass transition temperature described above.

[0069] From the viewpoint of improving the dispersibility of core-shell polymer particles in vinylidene fluoride resins and improving transparency, the content of alkyl methacrylate in the polymer constituting the graft layer (B1) or graft layer (B2) is preferably 50 to 100% by weight, more preferably 70 to 90% by weight, and even more preferably 80 to 95% by weight.

[0070] From the viewpoint of improving transparency, the grafted layer (B1) or grafted layer (B2) is preferably composed of a polymer that substantially does not contain vinyl monomers with a refractive index of 1.51 or higher as measured as a homopolymer. Here, "substantially does not contain" means that the content of the aforementioned vinyl monomers with a refractive index of 1.51 or higher in the monomer component is 0% by weight or more and less than 1% by weight. The upper limit is less than 0.1% by weight, or it may be less than 0.01% by weight. Examples of vinyl monomers with a refractive index of 1.51 or higher include aromatic vinyl compounds, cyanide vinyl compounds, and halogenated vinyl compounds.

[0071] The graft layer (B1) or graft layer (B2) may be formed from a polymer having a cross-linked structure, but is preferably formed from a polymer without a cross-linked structure. That is, the graft layer (B1) or graft layer (B2) is preferably formed from a polymer synthesized without the use of cross-linking monomers.

[0072] From the viewpoint of achieving high transparency, the proportion of the graft layer (B1) in the polymer particles is preferably 0 to 10% by weight (B1) / [(A) + (B1) + (B2)]. More preferably, it is 8% by weight or less, and even more preferably 5% by weight or less. Particularly preferred are 3% by weight or less or 1% by weight or less.

[0073] From the viewpoint of balancing transparency and high elongation, the total ratio of the core particles (A) to the grafted layer (B1) in the polymer particles is preferably 30 to 70% by weight [(A) + (B1)] / [(A) + (B1) + (B2)] . By increasing the total ratio of the core particles (A) to the grafted layer (B1), impact resistance or elongation can be improved. From this viewpoint, the lower limit can be 35% by weight or more, or 40% by weight or more.

[0074] On the other hand, transparency can be improved by suppressing the total ratio of nuclear particles (A) to grafted layers (B1). From this perspective, the upper limit can be 65% by weight or less, 60% by weight or less, or 55% by weight or less.

[0075] Furthermore, regarding the proportion of the core particles (A) in the polymer particles, from the viewpoint of improving impact resistance or elongation, the weight ratio [(A)] / [(A) + (B1) + (B2)] is preferably 20 to 70% by weight. By increasing the proportion of core particles (A), impact resistance or elongation can be improved. From this viewpoint, the lower limit can be 30% by weight or more, 35% by weight or more, or 40% by weight or more.

[0076] On the other hand, transparency can be improved by suppressing the proportion of nuclear particles (A). From this perspective, the upper limit can be 65% or less by weight, 60% or less by weight, or 55% or less by weight.

[0077] It should be noted that the proportions of grafted layer (B1), the total proportion of nuclear particles (A) to grafted layer (B1), and the proportion of nuclear particles (A) described above are calculated values ​​that include the free polymer described below.

[0078] From the viewpoint of achieving high transparency, the content of free polymer in the polymer particles involved in this disclosure is preferably below a certain amount. Specifically, the content of free polymer in the polymer particles is preferably 35% by weight or less. The above content is preferably 30% by weight or less, more preferably 25% by weight or less, even more preferably 20% by weight or less, and particularly preferably 15% by weight or less. The lower limit is not particularly limited, and for example, it can be 1% by weight or more, 5% by weight or more, or 10% by weight or more.

[0079] Here, free polymer refers to the polymer component in the polymer constituting the shell (B) that has not been grafted onto the core particle (A). This free polymer can be separated from the polymer particles by dissolving the polymer particles in methyl ethyl ketone, reprecipitating the soluble component with methanol, and then drying it. Specific methods for determining the content of free polymer are described in the Examples section.

[0080] The content of the free polymer can be controlled by the types and contents of each monomer and crosslinking monomer, the types and contents of initiators, reducing agents, emulsifiers, etc., the types and contents of chain transfer agents, polymerization temperature, polymerization time, etc.

[0081] From the viewpoint of achieving high transparency, the weight-average molecular weight of the free polymer is preferably below 300,000, more preferably below 200,000, and even more preferably below 150,000. There is no particular limitation on the lower limit; for example, it can be above 50,000.

[0082] <Method for Manufacturing Core-Shell Polymer Particles>

[0083] There are no particular limitations in the manufacture of the aforementioned core-shell polymer particles; for example, emulsion polymerization, microemulsion polymerization, emulsion polymerization, and emulsion polymerization without emulsifiers (soap) can be used. Emulsion polymerization is preferred.

[0084] There are no particular limitations on the emulsifiers that can be used in emulsion polymerization; anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc., can be used. Additionally, dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives can also be used in combination.

[0085] The anionic surfactants mentioned above are not particularly limited, and examples include: potassium laurate, potassium coconut fatty acid, potassium myristate, potassium oleate, potassium oleate diethanolamine salt, sodium oleate, potassium palmitate, potassium stearate, sodium stearate, mixed fatty acid sodium soap, semi-cured tallow fatty acid sodium soap, castor oil potassium soap, and other fatty acid soaps; sodium lauryl sulfate, sodium higher alcohol sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and 2-ethylhexyl Alkyl sulfate salts such as sodium sulfate; sodium dodecylbenzene sulfonate and other alkylbenzene sulfonates; sodium dialkyl sulfosuccinate and other dialkyl sulfosuccinates; sodium alkyl naphthalene sulfonate; sodium alkyl diphenyl ether disulfonate; potassium alkyl phosphate; sodium polyoxyethylene lauryl ether phosphate and other phosphate salts; sodium salts of naphthalene sulfonic acid formaldehyde condensate; polycarboxylic acid type polymer anions; sodium acyl (tallow) methyl taurate; sodium acyl (coconut) methyl taurate; sodium cocoyl hydroxyethyl sulfonate; sodium α-sulfo fatty acid esters; sodium amide ether sulfonate; oleoyl sarcosine; sodium lauroyl sarcosine; rosin acid soap, etc.

[0086] The aforementioned nonionic surfactants are not particularly limited, and examples include the following compounds: polyoxyethylene nonylphenyl ether, polyoxyethylene oil-based ether, polyoxyethylene lauryl ether, and other polyoxyethylene alkyl allyl ethers or polyoxyethylene alkyl ethers; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, and other polyoxyethylene sorbitan esters; polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol monooleate, and other polyoxyethylene fatty acid esters; and oxyethylene / oxypropylene block polymers, etc.

[0087] The above-mentioned cationic surfactants are not particularly limited, and examples include: alkylamine salts such as coconutamine acetate, stearamine acetate, octadecylamine acetate, and tetradecylamine acetate; and quaternary ammonium salts such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, distearate dimethylammonium chloride, alkylbenzyldimethylammonium chloride, hexadecyltrimethylammonium chloride, and behenyltrimethylammonium chloride.

[0088] The amphoteric surfactants mentioned above are not particularly limited, but can be exemplified by the following compounds: alkyl betaines such as lauryl betaine, stearyl betaine, and dimethyl lauryl betaine; sodium lauryl diaminoethyl glycinate; amide betaine; imidazoline; and lauryl carboxymethyl hydroxyethyl imidazoline. Betaine, etc.

[0089] These emulsifiers can be used alone or in combination of two or more. Preferred emulsifiers are sodium dialkyl sulfosuccinate or surfactants with an oxyethylene structure, with sodium polyoxyethylene lauryl ether phosphate being particularly preferred. The average particle size of the polymer particles can be controlled by adjusting the amount of emulsifier used.

[0090] When using emulsion polymerization, well-known polymerization initiators such as 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate can be used as thermally decomposable initiators.

[0091] Alternatively, a redox initiator obtained by combining a peroxide with a reducing agent can be used. The peroxide may be an organic peroxide such as isopropyl tert-butyl peroxide, terpene hydrogen peroxide, cumene hydrogen peroxide, dicumene peroxide, tert-butyl hydrogen peroxide, di-tert-butyl peroxide, and tert-hexyl peroxide; or an inorganic peroxide such as hydrogen peroxide, potassium persulfate, and ammonium persulfate. The reducing agent is at least one selected from sodium formaldehyde sulfoxylate, glucose, transition metal salts such as ferric sulfate (II), chelating agents such as disodium ethylenediaminetetraacetate, and pyrophosphates such as sodium pyrophosphate.

[0092] When a redox initiator is used, polymerization can proceed at low temperatures where the peroxides do not substantially undergo thermal decomposition, and the polymerization temperature can be set over a wide range, which is therefore preferable. Specifically, organic peroxides such as cumene hydroperoxide, dicumene peroxide, and tert-butyl hydroperoxide are preferred as redox initiators. The amounts of the initiators used, as well as the amounts of reducing agents, transition metal salts, and chelating agents used when using redox initiators, are within known ranges. Surfactants can be added, and their amounts are also within known ranges.

[0093] As a solvent used in emulsion polymerization, any solvent that can stably carry out emulsion polymerization is acceptable; for example, water can be used appropriately.

[0094] The temperature during emulsification polymerization is not particularly limited as long as the emulsifier can be uniformly dissolved in the solvent. For example, it is 40 to 90°C, preferably 45 to 85°C, and more preferably 49 to 80°C.

[0095] Specifically, the aforementioned core-shell polymer particles can be manufactured by sequentially performing the following steps (I) to (III).

[0096] Process (I): First, vinyl monomers (a1) and crosslinking monomers (a2) are polymerized in the presence of water, emulsifier and initiator to form core particles (A) containing a rubber layer.

[0097] Step (II): Add vinyl monomers and, if necessary, initiators and / or emulsifiers to an emulsion containing the formed core particles (A) and polymerize to form a graft layer (B1) of the coated core particles (A). However, this step is optional.

[0098] Step (III): In an emulsion containing polymer particles containing the formed core particles (A) or graft layer (B1), a vinyl monomer and an initiator and / or emulsifier as needed are added and polymerized to form a graft layer (B2) covering the core particles (A) or graft layer (B1) to obtain the core-shell polymer particles.

[0099] In each process step, polymerization reactions can also be carried out in the presence of a chain transfer agent. This allows for control of the molecular weight and free polymer content of the polymers forming each layer, thereby improving the impact resistance, elongation, and transparency of the thermoplastic resin composition. There are no particular limitations on the chain transfer agent used; examples include thiol-based chain transfer agents such as n-butylthiol, n-octylthiol, n-hexadecylthiol, n-dodecylthiol, n-tetradecylthiol, sec-butylthiol, sec-dodecylthiol, and tert-dodecylthiol; thioglycolic acid esters such as 2-ethylhexyl mercaptoacetate; and thiophenol. The amount of the chain transfer agent used can be appropriately set considering the molecular weight of the polymers forming each layer.

[0100] After forming the core-shell polymer particles, one or more coagulants selected from acids and salts are added to the latex to coagulate it, for example, by heat treatment at a temperature of 40°C to 110°C, followed by washing, dehydration, drying, and sieving through a sieve of a specified size, thereby separating the core-shell polymer particles.

[0101] <Resin Composition>

[0102] By incorporating the aforementioned core-shell polymer particles into a vinylidene fluoride-based resin to prepare a resin composition, the impact resistance or elongation of the vinylidene fluoride-based resin can be improved.

[0103] From the viewpoint of balancing impact resistance or elongation with transparency, the amount of the core-shell polymer particles in the resin composition disclosed herein is preferably 1 to 60 parts by weight, more preferably 5 to 50 parts by weight, and even more preferably 10 to 40 parts by weight, relative to 100 parts by weight of vinylidene fluoride resin.

[0104] <vinylidene fluoride resins>

[0105] Vinylidene fluoride resins refer to homopolymers of vinylidene fluoride or copolymers containing vinylidene fluoride.

[0106] Examples of copolymers containing vinylidene fluoride include vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, and vinylidene fluoride-chlorotrifluoroethylene-hexafluoropropylene terpolymer.

[0107] You can use one of these, or you can use two or more together.

[0108] In copolymers containing vinylidene fluoride, the proportion of comonomers other than vinylidene fluoride in the total monomer content is preferably 15 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less. This improves the chemical resistance of the vinylidene fluoride-containing copolymer, making it suitable for molding or film production.

[0109] In the resin compositions disclosed herein, from the viewpoints of heat resistance, melt molding properties, mechanical properties, and chemical resistance, vinylidene fluoride resins are more preferably selected from at least one of vinylidene fluoride homopolymers and vinylidene fluoride-hexafluoropropylene copolymers in a ratio of 15 mol% or less.

[0110] In the resin composition disclosed herein, the content of vinylidene fluoride resin is preferably 40-99% by weight, more preferably 50-90% by weight, and even more preferably 60-85% by weight.

[0111] <Acrylic Resins>

[0112] In addition to the vinylidene fluoride resin and polymer particles, the resin composition disclosed herein preferably further comprises an acrylic resin. This improves the compatibility between the vinylidene fluoride resin and the polymer particles, and also suppresses the crystallization of the vinylidene fluoride resin.

[0113] The aforementioned acrylic resins can be any resins whose constituent units are vinyl monomers containing (meth)acrylates, and known thermoplastic acrylic resins can be used.

[0114] In particular, thermoplastic acrylic resins containing structural units derived from methacrylates are preferred, and thermoplastic acrylic resins containing 30% by weight or more, more preferably 50% by weight or more, alkyl methacrylate units having 1 to 4 carbon atoms are more preferred. From the viewpoint of thermal stability, methyl methacrylate is particularly preferred.

[0115] Other vinyl monomers that can copolymerize with methyl methacrylate include: ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, octyl methacrylate, glycidyl methacrylate, epoxycyclohexyl methacrylate, dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dicyclopentyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,2-trichloroethyl methacrylate, isobornyl methacrylate, methacrylamide, N-hydroxymethyl methacrylate, etc.; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, glycidyl acrylate, epoxycyclohexyl methacrylate, 2- Acrylates such as hydroxyethyl ester, 2-hydroxypropyl acrylate, acrylamide, and N-hydroxymethylacrylamide; carboxylic acids such as methacrylic acid and acrylic acid, and their salts; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinyl aromatics such as styrene, α-methylstyrene, monochlorostyrene, and dichlorostyrene; maleimides such as N-phenylmaleimide, N-cyclohexylmaleimide, and N-methylmaleimide; maleic acid, fumaric acid, and their esters; halogenated vinyl groups such as vinyl chloride, vinyl bromide, and chloroprene; vinyl esters such as vinyl formate, vinyl acetate, and vinyl propionate; olefins such as ethylene, propylene, butene, butadiene, and isobutylene; halogenated olefins; and crosslinking monomers such as allyl methacrylate, diallyl phthalate, triallyl cyanurate, monoethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and divinylbenzene. These vinyl monomers can be used alone or in combination of two or more.

[0116] As other vinyl monomers that can be copolymerized with methyl methacrylate, (meth)acrylates with alkyl groups having 1 to 10 carbon atoms are preferred (however, methyl methacrylate is an exception).

[0117] From the viewpoints of optical properties, appearance, durability, and heat resistance, it is appropriate that the above-mentioned acrylic resin contains, as a structural unit, methyl methacrylate, preferably 30 to 100% by weight, more preferably 50 to 100% by weight, even more preferably 50 to 99.9% by weight, and particularly preferably 50 to 98% by weight. Other vinyl monomers that can copolymerize with methyl methacrylate preferably contain 70 to 0% by weight, more preferably 50 to 0% by weight, even more preferably 50 to 0.1% by weight, and particularly preferably 50 to 2% by weight.

[0118] The amount of the acrylic resin in the resin composition disclosed herein, from the viewpoint of balancing impact resistance or elongation and transparency, is preferably 1 to 40 parts by weight relative to 100 parts by weight of the vinylidene fluoride resin, more preferably 3 to 30 parts by weight, and even more preferably 5 to 25 parts by weight.

[0119] The above-described thermoplastic resin composition may further contain thermoplastic resins other than vinylidene fluoride resins and acrylic resins, provided that transparency is not substantially impaired. Such thermoplastic resins are not particularly limited, and examples include vinyl chloride resins, polycarbonate resins, styrene-acrylonitrile copolymer resins (AS resins), amide resins, and polyester resins. Only one of these resins may be used, or two or more may be used in combination.

[0120] The content of thermoplastic resins other than vinylidene fluoride resins and acrylic resins is not particularly limited, but can be 0-100 parts by weight, 0-50 parts by weight, 0-30 parts by weight, 0-10 parts by weight, 0-5 parts by weight, or 0-1 parts by weight relative to a total of 100 parts by weight of vinylidene fluoride resins and acrylic resins. Alternatively, it can be less than 1 part by weight.

[0121] The above-mentioned thermoplastic resin composition may also contain, as needed, flame retardants, antibacterial agents, release agents, nucleating agents, plasticizers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, compatibilizers, pigments, dyes, antistatic agents, lubricants, etc. The amount of each additive can be appropriately determined by those skilled in the art. Only one of these additives may be used, or two or more may be used in combination.

[0122] Specifically, phenolic, sulfur-based, phosphorus-based, and hindered amine antioxidants or stabilizers may be added appropriately; benzophenone-based and benzotriazole-based ultraviolet absorbers; internal and external lubricants such as polyorganosiloxanes, aliphatic hydrocarbons, esters of higher fatty acids and higher alcohols, amides or diamides of higher fatty acids and their modifications, oligoamides, and metal salts of higher fatty acids.

[0123] The aforementioned thermoplastic resin composition can be manufactured, for example, by mixing the aforementioned core-shell polymer particles with the aforementioned thermoplastic resin in the form of latex, slurry, solution, powder, granules, or a combination thereof. When the aforementioned core-shell polymer particles and the aforementioned thermoplastic resin are a latex, it can be produced, for example, by adding alkaline earth metal salts such as calcium chloride, magnesium chloride, and magnesium sulfate, alkali metal salts such as sodium chloride and sodium sulfate, or inorganic or organic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and acetic acid to the latex to coagulate it into a slurry, which is then dehydrated and dried. Alternatively, a spray drying method can be used. In this case, a portion of the additives, such as stabilizers, can be added to the aforementioned latex or slurry in the form of a dispersion.

[0124] For the above-mentioned thermoplastic resin composition, any additives can be added as needed to the above-mentioned core-shell polymer particles and the above-mentioned thermoplastic resin powder, granules, etc., and the mixture can be mixed using a known melt mixing mill such as a Banbury mixer, roller mill, single-shaft extruder, or twin-shaft extruder. The mixture can then be shaped using known molding methods such as injection molding, extrusion molding, or blow molding to form the target molded body (especially a film).

[0125] The thickness of the film formed from the thermoplastic resin composition disclosed herein is not particularly limited, for example, it can be about 1 μm to 2 mm.

[0126] The use of the above-described thermoplastic resin composition and its molded articles is not particularly limited, but it is suitable for applications that utilize transparency and low-temperature elongation. Such applications are not particularly limited, but applications utilizing transparency outdoors are preferred; a preferred example is a backsheet for solar cells.

[0127] The following describes the specific structure of the backsheet for solar cells and the solar cell module including the backsheet involved in this disclosure.

[0128] The backsheet for solar cells disclosed herein can be composed of a thin film monomer formed from the resin composition disclosed herein. Alternatively, it can be formed by laminating one or more transparent substrates on the thin film, such as electrically insulating resin films like polyethylene terephthalate films, moisture-proof films, or reinforced glass sheets. Adhesives can also be used to bond the above films together.

[0129] The solar cell module including the backsheet for solar cells disclosed herein is not particularly limited, but preferably comprises at least a surface protective material, a sealing material, solar cell units, and a backsheet (backside protective material). Multiple solar cell units are connected in series via wiring. A frame is provided at the ends or periphery of the solar cell module.

[0130] As a surface protection material, transparent materials are used to allow sunlight to pass through. There are no particular limitations; for example, tempered glass sheets, transparent plastic sheets, single or multiple layers of transparent plastic films, or composite materials made by combining them can be used.

[0131] As a sealing material, there are no particular limitations as long as it is a transparent resin capable of sealing the solar cell unit. Examples include ethylene-vinyl acetate copolymer (EVA), butyral resin, silicone resin, epoxy resin, and fluorinated polyimide resin. EVA is particularly preferred. Resin sheets can be used as the sealing material. In this case, the solar cell unit can be sealed by clamping it between two resin sheets and applying heat and pressure. Alternatively, when the sealing material is a resin sheet, the resin sheet can be pre-composite to the solar cell backsheet disclosed herein before sealing the solar cell unit.

[0132] As described above, a thin film monomer formed from the resin composition disclosed herein, or a laminate formed by stacking a transparent substrate on the thin film, can be used as the backsheet. Since the backsheet disclosed herein is transparent, a solar cell module including the backsheet can generate electricity from the back side in addition to the surface, thus it can be appropriately used as a product with a double-sided light-concentrating method.

[0133] Preferred embodiments of this disclosure are set forth in the following items, but the invention is not limited to these items.

[0134] [Project 1] A thermoplastic resin composition comprising a vinylidene fluoride-based resin and polymer particles.

[0135] The aforementioned polymer particles have a core particle (A) and a shell (B) located outside the core particle.

[0136] The aforementioned nuclear particle (A) comprises a rubber layer consisting of a reactant of a vinyl monomer (a1) and a crosslinking monomer (a2).

[0137] The aforementioned vinyl monomer (a1) includes (meth)acrylates.

[0138] The glass transition temperature of the aforementioned rubber layer is below -20°C.

[0139] The aforementioned shell layer (B) comprises any grafted layer (B1) with a glass transition temperature of -20°C or higher and less than 50°C, and a grafted layer (B2) with a glass transition temperature of 50°C or higher.

[0140] Furthermore, the weight ratio B1 / [(A) + (B1) + (B2)] is 0 to 10% by weight.

[0141] The weight ratio [(A) + (B1)] / [(A) + (B1) + (B2)] is 30-70% by weight.

[0142] The content of free polymer in the above polymer particles is less than 35% by weight.

[0143] [Item 2] The thermoplastic resin composition according to Item 1, wherein the vinyl monomer (a1) is substantially free of vinyl monomers having a refractive index of 1.51 or higher as determined as a homopolymer.

[0144] [Item 3] The thermoplastic resin composition according to Item 1 or 2, wherein the grafted layer (B2) is composed of a polymer containing a monomeric component of (meth)acrylate.

[0145] [Item 4] The thermoplastic resin composition according to any one of Items 1 to 3, wherein the average particle size of the nuclear particles (A) is 40 to 150 nm.

[0146] [Item 5] The thermoplastic resin composition according to any one of Items 1 to 4, wherein it further comprises an acrylic resin.

[0147] [Item 6] A molded body is formed by molding the thermoplastic resin composition described in any one of Items 1 to 5.

[0148] [Item 7] A film formed by molding the thermoplastic resin composition of any one of Items 1 to 5.

[0149] [Item 8] A backsheet for a solar cell comprising a layer of the thin film described in Item 7.

[0150] [Item 9] A solar cell module comprising a solar cell element and a backsheet for a solar cell as described in Item 8.

[0151] Example

[0152] The present invention will be further described in detail below with examples, but the present invention is not limited to these examples.

[0153] (Example of manufacturing core-shell polymer particles)

[0154] (Manufacturing Example 1)

[0155] In a pressure-resistant polymerizer equipped with a stirrer, 170 parts by weight of pure water and 0.25 parts of sodium dioctyl sulfosuccinate as a surfactant were added while nitrogen was being blown in. Next, the gas inside the pressure-resistant polymerizer was replaced with nitrogen while stirring the added raw materials, thereby completely removing oxygen from the polymerizer. Then, the temperature of the solution in the pressure vessel was raised to 60°C. Then, 0.006 parts of disodium ethylenediaminetetraacetate (EDTA), 0.0015 parts of ferrous sulfate, and 0.15 parts of sodium formaldehyde sulfoxylate (SFS) were added to the pressure vessel. Then, 3 parts of methyl methacrylate (MMA), 27 parts of butyl acrylate (BA), 0.54 parts of allyl methacrylate, and 0.04 parts of tert-butyl hydroperoxide (BHP) were added to the pressure vessel over 150 minutes. Then, polymerization was carried out for 30 minutes to obtain core particles. The volume average particle size of the nuclear particles contained in the obtained water-based latex is 70 nm.

[0156] Then, after adding 0.36 parts of sodium dioctyl sulfosuccinate as a surfactant, a mixture of 7 parts BA, 73 parts MMA, 0.37 parts tert-dodecyl mercaptan (t-DM), and 0.2 parts BHP was added to a pressure vessel over 270 minutes. The reaction solution in the pressure polymerizer was then maintained at 60°C for 1 hour to carry out polymerization, yielding an aqueous latex containing core-shell polymer particles.

[0157] Calcium chloride was added to the obtained aqueous latex containing core-shell polymer particles to cause it to solidify. The solidified slurry was then heat-treated and dehydrated, and the polymer particles were washed with ion-exchanged water, followed by dehydration and drying again to obtain a powder of core-shell polymer particles (C1).

[0158] (Manufacturing Example 2)

[0159] In a pressure-resistant polymerizer equipped with a stirrer, 170 parts of pure water and 0.5 parts of sodium dioctyl sulfosuccinate (as a surfactant) were added while nitrogen was being purged. Next, while stirring the added raw materials, the gas inside the pressure-resistant polymerizer was replaced with nitrogen, thereby completely removing oxygen from the polymerizer. Then, the temperature of the solution in the pressure vessel was raised to 60°C. Then, 0.0064 parts of EDTA, 0.0016 parts of ferrous sulfate, and 0.11 parts of SFS were added to the pressure vessel. Then, over 50 minutes, 10 parts of BA, 0.1 parts of allyl methacrylate, and 0.016 parts of cumene hydroperoxide (CHP) were added to the pressure vessel. Then, polymerization was carried out for 15 minutes. Then, over 160 minutes, a mixture of 33 parts of BA, 0.83 parts of allyl methacrylate, and 0.054 parts of CHP was added to the pressure vessel. Then, the reaction solution in the pressure polymerizer was maintained at 60°C for 30 minutes for polymerization, and 0.13 parts of sodium dioctyl sulfosuccinate as a surfactant were added to obtain an aqueous latex containing core particles. The volume average particle size of the core particles in the obtained aqueous latex was 60 nm.

[0160] Next, after 220 minutes, a mixture of 51.3 parts MMA, 5.7 parts BA, and 0.21 parts t-DM was added as monomer components to the glass reactor. Simultaneously with the addition of the monomer components (MMA and BA), 0.25 parts CHP were added to the glass reactor. After the addition of CHP was complete, the temperature of the reaction solution in the glass reactor was maintained at 60°C for 30 minutes to carry out polymerization, yielding an aqueous latex containing core-shell polymer particles.

[0161] Calcium chloride was added to the obtained aqueous latex containing core-shell polymer particles to cause it to solidify. The solidified slurry was then heat-treated and dehydrated, and the polymer particles were washed with ion-exchanged water, followed by dehydration and drying again to obtain a powder of core-shell polymer particles (C2).

[0162] (Manufacturing Examples 3-11)

[0163] According to the formula recorded in Table 1, the amount of sodium dioctyl sulfosuccinate used, as well as the types or amounts of each component used in components (A) and (B), were changed. Otherwise, the same as in manufacturing example 2, a powder of core-shell polymer particles was obtained.

[0164] (Manufacturing Example 12)

[0165] In a pressure-resistant polymerizer equipped with a stirrer, 170 parts of pure water and 0.5 parts of sodium dioctyl sulfosuccinate (as a surfactant) were added while nitrogen was being purged. Next, while stirring the added raw materials, the gas inside the pressure-resistant polymerizer was replaced with nitrogen, thereby completely removing oxygen from the polymerizer. Then, the temperature of the solution in the pressure vessel was raised to 60°C. Then, 0.0064 parts of EDTA, 0.0016 parts of ferrous sulfate, and 0.11 parts of SFS were added to the pressure vessel. Then, over 50 minutes, 10 parts of BA, 0.1 parts of allyl methacrylate, and 0.016 parts of cumene hydroperoxide (CHP) were added to the pressure vessel. Then, polymerization was carried out for 15 minutes. Then, over 110 minutes, a mixture of 23 parts of BA, 0.58 parts of allyl methacrylate, and 0.038 parts of CHP was added to the pressure vessel. Then, the reaction solution in the pressure polymerizer was maintained at 60°C for 30 minutes for polymerization, and 0.13 parts of sodium dioctyl sulfosuccinate as a surfactant were added to obtain an aqueous latex containing core particles. The volume average particle size of the core particles in the obtained aqueous latex was 51 nm.

[0166] Next, after 20 minutes, a mixture of 2 parts MMA, 3 parts BA, and 0.004 parts CHP was added to the glass reactor as monomer components. Polymerization was then carried out for 30 minutes. Then, after 240 minutes, a mixture of 55.8 parts MMA, 6.2 parts BA, and 0.4 parts t-DM was added to the glass reactor. Simultaneously with the addition of the aforementioned monomer components (i.e., MMA and BA), 0.28 parts CHP were added to the glass reactor. After the addition of CHP was completed, the temperature of the reaction solution in the glass reactor was maintained at 60°C for 30 minutes to continue polymerization, yielding an aqueous latex containing core-shell polymer particles.

[0167] Calcium chloride was added to the obtained aqueous latex containing core-shell polymer particles to cause it to solidify. The solidified slurry was then heat-treated and dehydrated, and the polymer particles were washed with ion-exchanged water, followed by dehydration and drying again to obtain a powder of core-shell polymer particles (C3).

[0168] (Manufacturing Examples 13-21)

[0169] According to the formulations recorded in Tables 1 and 2, the amount of sodium dioctyl sulfosuccinate used, as well as the types or amounts of each component used in components (A) and (B), were changed, and otherwise, the same as in Manufacturing Example 12, a powder of core-shell polymer particles was obtained.

[0170] (Average particle size of nuclear particles)

[0171] The volume average particle size was determined as the average particle size of the nuclear particles in the form of a nuclear particle emulsion. The measuring apparatus used was a Nanotrac Wave manufactured by Nikkiso Corporation.

[0172] (Free polymer content)

[0173] 1.0 g of the obtained core-shell polymer particles were dissolved in 45 mL of methyl ethyl ketone (MEK). Centrifugation was performed using a centrifuge (Hitachi Koki Co., Ltd., CP60E) at 29,000 rpm for a total of three sets, each lasting one hour, to separate the insoluble and soluble components. The soluble component was concentrated to 20 mL and then precipitated in 200 mL of methanol. The precipitate was then vacuum-dried at 60 °C and 600 Pa for 10 hours to obtain the free polymer.

[0174] The weights of the obtained free polymer, insoluble components, and soluble components are determined, and the free polymer content is calculated according to the following formula.

[0175] Free polymer content (%) = {(weight of free polymer) / (weight of insoluble components of methyl ethyl ketone + weight of soluble components of methyl ethyl ketone)} × 100

[0176] (weight-average molecular weight)

[0177] The obtained free polymer was dissolved in tetrahydrofuran (THF). The soluble component was filtered through a 0.2 μm filter of the filtration system, and then the weight-average molecular weight was determined using a high-speed GPC apparatus (Tosoh Corporation, HLC-8220). The determination conditions were as follows: Sample solution: 20 mg sample / 10 mL THF

[0178] Chromatographic columns: Tosoh Corporation, one TSKguardcolumn SuperHZ-H and two TSKgelSuperHZM-H columns.

[0179] Column temperature: 40℃

[0180] Detector: Differential refractometer

[0181] Flow rate: 0.35 mL / min

[0182] Injection volume: 10 μL; Standard curve: Standard polystyrene

[0183]

[0184]

[0185] (Examples 1-13, Comparative Examples 1-9)

[0186] [Sheet production]

[0187] As shown in Tables 3 and 4, 70 parts by weight of vinylidene fluoride resin, 10 parts by weight of acrylic resin, 20 parts by weight of core-shell polymer particles, 0.1 parts by weight of AO-50 (manufactured by ADEKA) and 0.1 parts by weight of ADEKA2112 (manufactured by ADEKA) as stabilizers were dry-mixed and extruded using a twin-screw extruder (TEX25SS manufactured by Nippon Steel Corporation) heated to a barrel temperature of 180-210°C at a screw speed of 100 rpm to obtain granules. In Comparative Example 1, core-shell polymer particles were not used, and the amount of acrylic resin was changed to 30 parts by weight.

[0188] As a vinylidene fluoride-based resin, HAJ602 manufactured by Shandong Huaan New Materials Co., Ltd. was used; as an acrylic resin, CM-207 (PMMA resin) manufactured by Chi Mei Industrial Co., Ltd. was used.

[0189] The obtained granules were dried in a dryer at 80°C for 5 hours. Then, using a Brabender (Toyo Seiki B3S150), a single-shaft extruder (Toyo Seiki 2020C), a T-die forming machine (Toyo Seiki T150C), and a film traction machine (Toyo Seiki FT2B15), a sheet with a thickness of 0.15 mm was produced under the following conditions: screw speed 100 rpm, forming temperature 210-220°C, cooling roller temperature 60°C, and traction speed 1 m / min.

[0190] [Tension test]

[0191] The 0.15 mm thick sheet prepared by the above method is cut into test pieces of JIS K7133-1 shape. The tensile properties (tensile fracture strain) at -20℃ are determined by the method according to JIS K7133 standard at a test rate of 50 mm / min.

[0192] [Measurement of Haze]

[0193] The haze value of a 0.15 mm thick sheet produced by the above method was measured using an NDH-4000 manufactured by Nippon Denshoku Kogyo Co., Ltd., according to the method described in JIS K7105.

[0194]

[0195]

[0196] According to Tables 3 and 4, the following can be determined. In Examples 1 to 13, sheets with low haze, high transparency, and high elongation at low temperatures were obtained.

[0197] On the other hand, in Comparative Example 1, which did not incorporate core-shell polymer particles, the elongation at low temperatures was insufficient.

[0198] In addition, in Comparative Examples 2 to 9, core-shell polymer particles with a large weight ratio of (B1) to [(A) + (B1) + (B2)] were used, resulting in high haze and insufficient transparency.

Claims

1. A thermoplastic resin composition comprising a vinylidene fluoride-based resin and polymer particles, The polymer particle has a core particle A and a shell B located outside the core particle. The nuclear particle A comprises a rubber layer consisting of a reactant of vinyl monomer a1 and crosslinking monomer a2. The vinyl monomer a1 comprises (meth)acrylate. The glass transition temperature of the rubber layer is below -20°C. The shell layer B comprises any grafted layer B1 with a glass transition temperature above -20°C and below 50°C, and a grafted layer B2 with a glass transition temperature above 50°C. Furthermore, the weight ratio B1 / (A+B1+B2) is 0-10% by weight. The weight ratio (A+B1) / (A+B1+B2) is 30-70% by weight. The content of free polymer in the polymer particles is less than 35% by weight.

2. The thermoplastic resin composition according to claim 1, wherein, The vinyl monomer a1 substantially does not contain vinyl monomers with a refractive index of 1.51 or higher as measured as a homopolymer.

3. The thermoplastic resin composition according to claim 1, wherein, The graft layer B2 is composed of a polymer containing monomeric components of (meth)acrylate.

4. The thermoplastic resin composition according to claim 1, wherein, The average particle size of the nuclear particle A is 40–150 nm.

5. The thermoplastic resin composition according to claim 1, wherein, It further includes acrylic resins.

6. A molded article formed by molding the thermoplastic resin composition according to any one of claims 1 to 5.

7. A film formed by molding the thermoplastic resin composition according to any one of claims 1 to 5.

8. A backsheet for a solar cell comprising a layer formed of the thin film of claim 7.

9. A solar cell module comprising a solar cell element and a backsheet for a solar cell as described in claim 8.

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