Thermoplastic resin composition

Abstract

To provide a thermoplastic resin composition containing a vinylidene fluoride-based resin and core-shell particles, which achieves both transparency and elongation at low temperatures. [Solution] The solution contains a vinylidene fluoride resin and polymer particles. The polymer particles have a core particle (A) and a shell layer (B) located outside the core particle. (A) contains a rubber layer which is a reaction product of a vinyl monomer (a1) and a crosslinkable monomer (a2), where (a1) contains a (meth)acrylic acid ester and the glass transition temperature of the rubber layer is -20°C or lower. (B) contains an arbitrary graft layer (B1) with a glass transition temperature of -20°C or higher and less than 50°C, and a graft layer (B2) with a glass transition temperature of 50°C or higher, where (B1) / [(A)+(B1)+(B2)] is 0-10% by weight and [(A)+(B1)] / [(A)+(B1)+(B2)] is 30-70% by weight. The free polymer content in the polymer particles is 35% by weight or less.

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition containing a vinylidene fluoride-based resin, a film or molded article obtained by molding the resin composition, and a back sheet for solar cells or a solar cell module comprising the film. [Background Art]

[0002] From the viewpoint of creating clean energy, solar cells have attracted attention. A silicon-based solar cell, which is a typical solar cell, is generally configured such that solar cells are encapsulated with a thermoplastic resin such as ethylene-vinyl acetate copolymer (EVA), the surface irradiated with sunlight is covered with glass, and the back surface is protected with a back sheet (back surface protection sheet).

[0003] Such a back sheet for solar cells usually includes a resin sheet formed from a thermoplastic resin material. As the resin constituting the resin sheet, fluorine-based resins such as vinylidene fluoride-based resins are used, taking advantage of their high weather resistance, chemical resistance and the like.

[0004] Patent Document 1 describes that, for the purpose of suppressing discoloration under high temperature and high humidity, a film made of a resin composition obtained by blending a vinylidene fluoride-based resin with a methacrylate ester resin containing core-shell particles is used as a back sheet for solar cells.

[0005] Although not related to back sheets for solar cells, Patent Document 2 describes that in order to improve the thermodynamic stability of an ultraviolet absorber in a resin composition, a fluorine-based resin such as a vinylidene fluoride-based resin is blended with polymer particles having a core-shell structure whose core contains the ultraviolet absorber. [Prior Art Literature] [Patent Literature]

[0006] [Patent Document 1] International Publication No. 2014 / 057933 [Patent Document 2] Special Publication No. 2003-506546 [Overview of the project] [Problems that the invention aims to solve]

[0007] Until now, solar cells have primarily used a single-sided focusing method, but in order to improve solar energy conversion efficiency, the double-sided focusing method, which can generate electricity by focusing sunlight from both the front and back, is becoming mainstream. In conventional single-sided focusing methods, an opaque resin film with high weather resistance is used as the backsheet, but in double-sided focusing methods, the use of a highly transparent film is required.

[0008] Patent documents 1 and 2 describe the compounding of core-shell particles into a vinylidene fluoride resin. However, such compounding typically tends to reduce transparency due to the difference in refractive index between the two components. These documents do not address any studies on improving transparency, making it difficult to obtain highly transparent sheets.

[0009] Furthermore, since backsheets for solar cells are sometimes placed outdoors in low temperatures, they are required to exhibit high elongation at low temperatures to ensure strength at low temperatures.

[0010] In view of the above situation, the present invention aims to provide a thermoplastic resin composition that contains a vinylidene fluoride-based resin and core-shell particles, and that achieves both transparency and elongation at low temperatures. [Means for solving the problem]

[0011] The inventors of this invention diligently studied to solve the above problems and discovered that the problems could be solved by blending core-shell particles that satisfy specific conditions into a vinylidene fluoride-based resin, leading to the present invention.

[0012] In other words, the present invention relates to a thermoplastic resin composition comprising a vinylidene fluoride-based resin and polymer particles, The polymer particle comprises a core particle (A) and a shell layer (B) located outside the core particle. The core particle (A) contains a rubber layer which is a reaction product of a vinyl monomer (a1) and a crosslinkable monomer (a2). The vinyl monomer (a1) contains (meth)acrylic acid ester, The glass transition temperature of the rubber layer is -20°C or lower. The shell layer (B) includes an arbitrary graft layer (B1) having a glass transition temperature of -20°C or higher and less than 50°C, and a graft layer (B2) having a glass transition temperature of 50°C or higher. The weight ratio (B1) / [(A)+(B1)+(B2)] is between 0 and 10% by weight. The weight ratio [(A)+(B1)] / [(A)+(B1)+(B2)] is 30-70% by weight. This invention relates to a thermoplastic resin composition in which the free polymer content in the polymer particles is 35% by weight or less. The present invention also relates to a molded article or film obtained by molding the thermoplastic resin composition; a backsheet for solar cells including a layer made of the film; and a solar cell module including a solar cell element and the solar cell backsheet. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a thermoplastic resin composition that contains a vinylidene fluoride-based resin and core-shell particles, and that achieves both transparency and elongation at low temperatures. The thermoplastic resin composition according to the present invention can be molded into a molded article or a film. Taking advantage of its transparency and low-temperature elongation, the film can be particularly suitable for use as a backsheet for solar cells. [Modes for carrying out the invention]

[0014] Embodiments of the present invention are 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 in the claims. In addition, the respective configurations described below can be arbitrarily combined, and such combinations can also constitute one aspect of the present invention.

[0015] The thermoplastic resin composition according to the present disclosure contains at least a vinylidene fluoride-based resin as the thermoplastic resin, and polymer particles. The polymer particles function as a modifier for the vinylidene fluoride-based resin, particularly as an impact resistance modifier or an elongation modifier.

[0016] <Polymer Particles> The polymer particles have a core-shell structure including core particles (A) and a shell layer (B) located outside the core particles. Hereinafter, the polymer particles are also referred to as "core-shell type polymer particles".

[0017] Core particles (A) refer to particles located inside the core-shell type polymer particles. The shell layer (B) refers to a polymer layer located outside the core particles (A) so as to cover the surface of the core particles (A). Although the shell layer covers the surface of the core particles (A), it is not limited to one that covers the entire surface of the core particles, and only needs to cover at least a part of the surface of the core particles.

[0018] <Core Particles (A)> The core particles (A) include a rubber layer. Here, rubber refers to elastic rubber which is a material with a low elastic modulus composed of an organic material having a crosslinked structure. Since the polymer particles contain a rubber layer, impact resistance or high elongation can be imparted to the vinylidene fluoride-based resin by blending the polymer particles into the vinylidene fluoride-based resin.

[0019] The core particle (A) may consist of only a rubber layer, or may contain a polymer layer not corresponding to a rubber layer in addition to the rubber layer. In the latter case, the polymer layer may be present inside the rubber layer or outside the rubber layer.

[0020] The rubber layer is preferably the main component of the core particle (A). Specifically, the content ratio of the rubber layer in the core particle (A) may be 50 to 100% by weight, 70 to 100% by weight, 90 to 100% by weight, 95 to 100% by weight, or 99 to 100% by weight.

[0021] Further, the rubber layer may be composed of a layer of a single composition, or may be composed of a plurality of layers having different compositions from each other.

[0022] From the viewpoint of improving the impact resistance or elongation of the vinylidene fluoride-based resin, the glass transition temperature of the rubber layer is preferably -20°C or lower, more preferably -30°C or lower, still more preferably -40°C or lower, and particularly preferably -50°C or lower. The lower limit is not particularly limited, and may be, for example, -80°C or higher, -70°C or higher, or -60°C or higher. When the rubber layer is composed of a plurality of layers having different compositions from each other, the glass transition temperature of the rubber layer refers to the glass transition temperature of all of the plurality of layers.

[0023] Incidentally, the glass transition temperature of a polymer can be calculated using Fox's equation with reference to the values described in the Polymer Handbook (J. Brandrup, Interscience 1989). For example, the Tg of polymethyl methacrylate is 105°C, and the Tg of polybutyl acrylate is -54°C.

[0024] The rubber layer is formed from a reaction product of a vinyl monomer (a1) and a crosslinkable monomer (a2). (Vinyl monomer (a1)) The vinyl monomer refers to a compound that has one carbon-carbon unsaturated bond per molecule and has the ability to form a polymer through addition polymerization.

[0025] From the perspective of achieving both transparency and high elongation, the vinyl monomer (a1) contains at least a (meth)acrylic acid ester. Note that "(meth)acrylic" refers to both acrylic and methacrylic.

[0026] The (meth)acrylic acid ester is not particularly limited, but examples include alkyl (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; glycidyl (meth)acrylates such as glycidyl (meth)acrylate and glycidylalkyl (meth)acrylate; and alkoxyalkyl (meth)acrylates. The (meth)acrylic acid ester may be used alone or in combination of two or more types.

[0027] The number of carbon atoms in the ester portion of the (meth)acrylic acid ester is preferably 1 to 22, more preferably 1 to 18, even more preferably 2 to 12, and still more preferably 3 to 8.

[0028] The vinyl monomer (a1) may consist solely of the (meth)acrylic acid ester, or it may contain other vinyl monomers having one carbon-carbon unsaturated bond in one molecule. The other monomer is not particularly limited, but examples include aromatic vinyl compounds such as styrene and α-methylstyrene, vinyl cyanide compounds, vinyl halogenated compounds such as vinyl chloride and chloroprene, vinyl acetate, and alkenes such as ethylene and propylene.

[0029] In the vinyl monomer (a1), the content of the (meth)acrylic acid ester is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, even more preferably 80 to 100% by weight, even more preferably 90 to 100% by weight, and particularly preferably 95 to 100% by weight.

[0030] From the viewpoint of improving transparency, it is preferable that the vinyl monomer (a1) substantially does not contain vinyl monomers exhibiting a refractive index of 1.51 or higher as measured as a homopolymer. Here, "substantially contained" means that the content of vinyl monomers exhibiting 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 may be less than 0.1% by weight or less than 0.01% by weight. Examples of vinyl monomers exhibiting a refractive index of 1.51 or higher include aromatic vinyl compounds, vinyl cyanide compounds, and vinyl halogenated compounds.

[0031] From the viewpoint of controlling the glass transition temperature of the rubber layer to a low level to impart good elasticity to the rubber layer and imparting impact resistance or high elongation to the vinylidene fluoride resin, it is preferable to use an acrylic acid ester as the (meth)acrylic acid ester, and more preferably an alkyl acrylate ester. The number of carbon atoms in the alkyl group of the alkyl acrylate is preferably 1 to 22, more preferably 1 to 18, even more preferably 2 to 12, and even more preferably 3 to 8. In particular, it is preferable to use butyl acrylate and 2-ethylhexyl acrylate.

[0032] When an alkyl acrylate is used as the (meth)acrylic acid ester, the content of the alkyl acrylate in the vinyl monomer (a1) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, even more preferably 80 to 100% by weight, even more preferably 90 to 100% by weight, and particularly preferably 95 to 100% by weight. In this case, as the monomer other than the alkyl acrylate, a (meth)acrylic acid ester other than the alkyl acrylate may be used.

[0033] (Crosslinkable monomer (a2)) A crosslinkable monomer (a2) is a compound having two or more carbon-carbon unsaturated bonds in one molecule that can copolymerize with the vinyl monomer (a1). Specific examples include (meth)acrylates having an allyl group, such as allyl (meth)acrylate, allylalkyl (meth)acrylate, and allyloxyalkyl (meth)acrylate; polyfunctional (meth)acrylates having two or more (meth)acrylic groups, such as (poly)ethylene 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; and diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, and divinylbenzene.

[0034] In particular, from the viewpoint of transparency, it is preferable to use a crosslinkable monomer with a relatively low refractive index. Specifically, allyl methacrylate, butanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate are preferred, with allyl methacrylate being particularly preferred. Only one type of crosslinkable monomer (a2) may be used, or two or more types may be used in combination.

[0035] The amount of crosslinkable monomer (a2) used can be appropriately set from the viewpoint of improving impact strength or elongation, but specifically, it is preferably about 0.01 to 6 parts by weight per 100 parts by weight of vinyl monomer (a1). Within this range, it is easy to obtain a thermoplastic resin composition with good impact resistance or elongation. 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.

[0036] The average particle diameter of the core particles (A) is not particularly limited, but from the viewpoint of balancing impact resistance or elongation with transparency, it is preferable that the volume average particle diameter is in the range of 40 to 150 nm. Impact resistance or elongation tends to improve as the average particle diameter increases. From this viewpoint, the lower limit is preferably 50 nm or more, and more preferably 60 nm or more.

[0037] On the other hand, as the average particle size decreases, the haze tends to decrease and the transparency tends to increase. From this viewpoint, 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.

[0038] The average particle diameter of the core particles (A) referred to here means the average particle diameter of the polymer particles after synthesizing the core particles (A) but before synthesizing the shell layer (B). The average particle diameter of the polymer particles is a value measured using a particle diameter measuring device while the polymer particles are in their latex state, as shown in the Examples section. Furthermore, the particle size of the core particles (A) can be controlled by the type and amount of each monomer and crosslinkable monomer, the type and amount of initiators, reducing agents, emulsifiers, polymerization temperature, polymerization time, etc.

[0039] <Shell layer (B)> The shell layer (B) is a polymer layer located on the outside of the core particle (A), and is a layer located on the surface side of the core-shell type polymer particle. The shell layer (B) is preferably graft-bonded to the core particle (A), but may also contain components that are not graft-bonded. These components correspond to the free polymers described later.

[0040] By providing a shell layer (B), the compatibility between the core-shell type polymer particles and the vinylidene fluoride-based resin is improved, making it possible to disperse the core-shell type polymer particles in the resin composition as primary particles.

[0041] The shell layer (B) may include a graft layer (B1) with a glass transition temperature of -20°C or higher and less than 50°C, and a graft layer (B2) with a glass transition temperature of 50°C or higher. However, the graft layer (B1) is an arbitrary layer and may not be included. Furthermore, these graft layers may also contain components that are not graft-bonded.

[0042] The glass transition temperature of the graft layer (B1) should be between -20°C and 50°C, but the lower limit may be -10°C or higher, or 0°C or higher. The upper limit may be less than 40°C, less than 30°C, or less than 20°C.

[0043] 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, from the viewpoint of improving the stability of emulsion polymerization and the handling of core-shell polymer particles when they are recovered as powder. There is no particular upper limit, but it may be 105°C or lower, 100°C or lower, or 95°C or lower.

[0044] The polymer constituting the graft layer (B1) or graft layer (B2) is not particularly limited as long as it satisfies the glass transition temperature described above. However, from the viewpoint of having good compatibility with vinylidene fluoride resins, improving the dispersibility of core-shell type polymer particles in the vinylidene fluoride resin, and enhancing transparency, it is preferable that it be a polymer of at least one vinyl monomer selected from the group consisting of (meth)acrylic acid esters, aromatic vinyl compounds, and vinyl cyanide compounds.

[0045] The (meth)acrylic acid ester is not particularly limited, but examples include alkyl (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; glycidyl (meth)acrylates such as glycidyl (meth)acrylate and glycidylalkyl (meth)acrylate; and alkoxyalkyl (meth)acrylates.

[0046] The aromatic vinyl compound is not particularly limited, but examples include styrene, α-methylstyrene, p-methylstyrene, p-isopropylstyrene, o-chlorostyrene, p-chlorostyrene, and dichlorostyrene. Of these, styrene is preferred.

[0047] The vinyl cyanide compound is not particularly limited, but examples include acrylonitrile and methacrylonitrile. Of these, acrylonitrile is preferred.

[0048] From the viewpoint of compatibility with vinylidene fluoride resins, it is preferable that the graft layer (B1) or graft layer (B2) be composed of a polymer of monomer components containing at least (meth)acrylic acid ester. The total proportion of (meth)acrylic acid ester in the total monomers constituting the graft layer (B1) or graft layer (B2) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, even more preferably 90 to 100% by weight, and particularly preferably 95 to 100% by weight.

[0049] In particular, the polymer constituting the graft layer (B1) or graft layer (B2) is preferably a copolymer containing an acrylic acid ester and a methacrylic acid ester. In this case, the acrylic acid ester is preferably an alkyl acrylate, and in particular, an alkyl acrylate having 1 to 6 carbon atoms in the alkyl group is preferred. The methacrylic acid ester is preferably an alkyl methacrylate, and in particular, an alkyl methacrylic acid having 1 to 6 carbon atoms in the alkyl group is preferred. The ratio of the acrylic acid ester to the methacrylic acid ester can be appropriately set to satisfy the glass transition temperature described above.

[0050] From the viewpoint of improving the dispersibility of core-shell type polymer particles in vinylidene fluoride resin and enhancing 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.

[0051] From the viewpoint of improving transparency, it is preferable that the graft layer (B1) or graft layer (B2) is composed of a polymer of monomer components that substantially does not contain vinyl monomers having a refractive index of 1.51 or higher as measured as a homopolymer. Here, "substantially contained" means that the content of vinyl monomers having a refractive index of 1.51 or higher in the monomer components is 0% by weight or more and less than 1% by weight. The upper limit may be less than 0.1% by weight or less than 0.01% by weight. Examples of vinyl monomers having a refractive index of 1.51 or higher include aromatic vinyl compounds, vinyl cyanide compounds, vinyl halogenated compounds, and the like.

[0052] The graft layer (B1) or graft layer (B2) may be formed from a polymer having a crosslinked structure, but it is preferable that it be formed from a polymer without a crosslinked structure. That is, it is preferable that the graft layer (B1) or graft layer (B2) be formed from a polymer synthesized without using a crosslinkable monomer.

[0053] From the viewpoint of achieving high transparency, the weight ratio (B1) / [(A)+(B1)+(B2)] of the graft layer (B1) in the polymer particles is preferably 0 to 10% by weight. The upper limit is more preferably 8% by weight or less, and even more preferably 5% by weight or less. 3% by weight or less, or 1% by weight or less, is particularly preferred.

[0054] From the viewpoint of balancing transparency and high elongation, the total weight ratio of core particles (A) and graft layers (B1) in the polymer particles is preferably 30 to 70% by weight [(A) + (B1)] / [(A) + (B1) + (B2)]. By increasing the total weight ratio of core particles (A) and graft layers (B1), impact resistance or elongation can be improved. From this viewpoint, the lower limit may be 35% by weight or more, or 40% by weight or more. On the other hand, transparency can be increased by suppressing the total ratio of core particles (A) and graft layer (B1). From this perspective, the upper limit may be 65% by weight or less, 60% by weight or less, or 55% by weight or less.

[0055] Furthermore, from the viewpoint of improving impact resistance or elongation, the weight ratio of core particles (A) in the polymer particles is preferably 20 to 70% by weight [(A)] / [(A)+(B1)+(B2)]. By increasing the proportion of core particles (A), impact resistance or elongation can be improved. From this viewpoint, the lower limit may be 30% by weight or more, 35% by weight or more, or 40% by weight or more. On the other hand, transparency can be increased by suppressing the proportion of core particles (A). From this perspective, the upper limit may be 65% by weight or less, 60% by weight or less, or 55% by weight or less.

[0056] Furthermore, the proportion of the graft layer (B1), the total proportion of core particles (A) and the graft layer (B1), and the proportion of core particles (A) described above are values ​​calculated including the free polymer, which will be explained next.

[0057] From the viewpoint of achieving high transparency, the free polymer content in the polymer particles relating to this disclosure is preferably below a certain amount. Specifically, the free polymer content in the polymer particles is preferably 35% by weight or less. The 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, but may be, for example, 1% by weight or more, 5% by weight or more, or 10% by weight or more.

[0058] Here, "free polymer" refers to the polymer component of the shell layer (B) that is not grafted to the core particles (A). This free polymer can be separated from the polymer particles by dissolving the polymer particles in methyl ethyl ketone, reprecipitation the soluble component with methanol, and drying it. The specific method for measuring the free polymer content is described in the Examples section.

[0059] The content of the free polymer can be controlled by the type and amount of each monomer and crosslinkable monomer, the type and amount of initiators, reducing agents, emulsifiers, etc., the type and amount of chain transfer agents, polymerization temperature, polymerization time, etc.

[0060] The weight-average molecular weight of the free polymer is preferably 300,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less, from the viewpoint of achieving high transparency. The lower limit is not particularly limited, but may be, for example, 50,000 or more.

[0061] <Method for producing core-shell type polymer particles> In producing the core-shell type polymer particles, although not particularly limited, methods such as emulsion polymerization, miniemulsion polymerization, microemulsion polymerization, and soap-free emulsion polymerization can be used. Of these, emulsion polymerization is preferred.

[0062] The emulsifiers that can be used in emulsion polymerization are not particularly limited, and anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc., can be used. Dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives may also be used in combination.

[0063] The anionic surfactant is not particularly limited, but examples include the following compounds: fatty acid soaps such as 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-hardened beef tallow fatty acid sodium soap, castor oil potassium soap; and alkyl sulfurs such as sodium dodecyl sulfate, higher alcohol sodium sulfate, dodecyl sulfate triethanolamine, dodecyl sulfate ammonium, polyoxyethylene alkyl ether sulfate sodium, polyoxyethylene alkyl ether sulfate triethanolamine, polyoxyethylene alkylphenyl ether sulfate sodium, and 2-ethylhexyl sulfate sodium. Acid ester salts; sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate; sodium dialkylsulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate; sodium alkylnaphthalenesulfonate; sodium alkyldiphenyl ether disulfonate; potassium alkyl phosphate salts; phosphate ester salts such as sodium polyoxyethylene lauryl ether phosphate; sodium salts of naphthalenesulfonic acid formalin condensates; polycarboxylic acid type polymer anions; sodium acyl(tallow)methyltaurate; sodium acyl(coconut)methyltaurate; sodium cocoyl isethionate; sodium α-sulfo fatty acid ester salts; sodium amide ethersulfonate; oleyl sarcosine; sodium lauroyl sarcosinate; rosinic acid soap, etc.

[0064] The nonionic surfactant is not particularly limited, but examples include the following compounds: polyoxyethylene alkyl allyl ethers or polyoxyethylene alkyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene oleyl ether, and polyoxyethylene lauryl ether; polyoxyethylene sorbitan esters such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monostearate; polyoxyethylene fatty acid esters such as polyethylene glycol monolaurate, polyethylene glycol monostearate, and polyethylene glycol monooleate; and oxyethylene / oxypropylene block copolymers.

[0065] The cationic surfactant is not particularly limited, but examples include the following compounds: alkylamine salts such as coconutamine acetate, stearylamine acetate, octadecylamine acetate, and tetradecylamine acetate; and quaternary ammonium salts such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride, distearyldimethylammonium chloride, alkylbenzyldimethylammonium chloride, hexadecyltrimethylammonium chloride, and behenyltrimethylammonium chloride.

[0066] The aforementioned amphoteric surfactants are not particularly limited, but examples include the following compounds: alkyl betaines such as lauryl betaine, stearyl betaine, and dimethyl lauryl betaine; sodium lauryl diaminoethylglycine; amide betaine; imidazoline; lauryl carboxymethyl hydroxyethyl imidazolinium betaine, etc.

[0067] These emulsifiers may be used individually or in combination of two or more. Preferred emulsifiers are sodium dialkyl sulfosuccinate or surfactants having 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.

[0068] When employing emulsion polymerization, known polymerization initiators, namely 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate, can be used as thermal decomposition initiators.

[0069] In addition, a redox-type initiator can be used, which is a combination of an organic peroxide such as t-butyl peroxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and t-hexyl peroxide; an inorganic peroxide such as hydrogen peroxide, potassium persulfate, and ammonium persulfate; and at least one reducing agent selected from the group consisting of sodium formaldehyde sulfoxylate, glucose, transition metal salts such as iron(II) sulfate, chelating agents such as disodium ethylenediaminetetraacetate, and pyrophosphates such as sodium pyrophosphate.

[0070] When a redox-type initiator is used, polymerization can be carried out even at low temperatures in which the peroxide does not substantially decompose thermally, and the polymerization temperature can be set over a wide range, which is preferable. In particular, it is preferable to use organic peroxides such as cumene hydroperoxide, dicumyl peroxide, and t-butyl hydroperoxide as redox-type initiators. The amount of the initiator used, and the amounts of the reducing agent, transition metal salt, chelating agent, etc., when a redox-type initiator is used, may be within a known range. Surfactants may be used in addition, but this is also within a known range.

[0071] Any solvent that allows emulsion polymerization to proceed stably can be used as the solvent; for example, water can be suitably used.

[0072] The temperature during emulsion polymerization is not particularly limited, as long as the emulsifier is uniformly dissolved in the solvent, but for example, it is 40 to 90°C, preferably 45 to 85°C, and more preferably 49 to 80°C.

[0073] The core-shell type polymer particles can be manufactured by following the steps (I) to (III) in order. Step (I): First, a vinyl monomer (a1) and a crosslinkable monomer (a2) are polymerized in the presence of water, an emulsifier, and an initiator to form core particles (A) containing a rubber layer.

[0074] Step (II): A vinyl monomer and, if necessary, an initiator and / or emulsifier are added to the emulsion containing the formed core particles (A) to carry out polymerization and form a graft layer (B1) that coats the core particles (A). However, this step is optional.

[0075] Step (III): A vinyl monomer and, if necessary, an initiator and / or emulsifier are added to an emulsion containing polymer particles including the formed core particles (A) or graft layer (B1) to carry out polymerization, thereby forming a graft layer (B2) that covers the pre-core particles (A) or graft layer (B1), and obtaining the core-shell type polymer particles.

[0076] In each step, the polymerization reaction may be carried out in the presence of a chain transfer agent. This allows control of the molecular weight and free polymer content of the polymers forming each layer, thereby improving the impact resistance, elongation, or transparency of the thermoplastic resin composition. The chain transfer agent is not particularly limited, but examples include mercaptan-based chain transfer agents such as n-butyl mercaptan, n-octyl mercaptan, n-hexadecyl mercaptan, n-dodecyl mercaptan, n-tetradecyl mercaptan, sec-butyl mercaptan, sec-dodecyl mercaptan, and t-dodecyl mercaptan, as well as thioglycolic acid esters such as 2-ethylhexyl thioglycolate and thiophenols. The amount of the chain transfer agent used should be appropriately set considering the molecular weight of the polymers forming each layer.

[0077] After the core-shell polymer particles are formed, one or more coagulants selected from the group consisting of acids and salts are added to the latex to solidify it, and the core-shell polymer particles can be separated by heat treatment at a temperature of 40°C to 110°C, washing and dewatering, drying, and sieving with a sieve of a predetermined size.

[0078] <Resin composition> By incorporating the aforementioned core-shell type polymer particles into a vinylidene fluoride-based resin to form a resin composition, the impact resistance or elongation of the vinylidene fluoride-based resin can be improved.

[0079] The amount of core-shell type polymer particles in the resin composition according to this disclosure 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, per 100 parts by weight of vinylidene fluoride resin, from the viewpoint of balancing impact resistance or elongation with transparency.

[0080] <Polyvinylidene fluoride-based resin> A vinylidene fluoride resin refers to a homopolymer of vinylidene fluoride or a copolymer containing vinylidene fluoride. 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. You may use only one of these types, or you may use two or more types in combination.

[0081] In vinylidene fluoride-containing copolymers, the proportion of comonomers other than vinylidene fluoride to the total amount of monomer 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 possible to produce a polymer suitable for molded articles or films.

[0082] In the resin composition according to this disclosure, the vinylidene fluoride-based resin is more preferably at least one selected from the group consisting of vinylidene fluoride homopolymers and vinylidene fluoride-hexafluoropropylene copolymers having a ratio of hexafluoropropylene units of 15 mol% or less, from the viewpoint of heat resistance, melt moldability, mechanical properties, and chemical resistance.

[0083] In the resin composition relating to this disclosure, the content of vinylidene fluoride-based resin is preferably 40 to 99% by weight, more preferably 50 to 90% by weight, and even more preferably 60 to 85% by weight.

[0084] <Acrylic resin> The resin composition according to this disclosure preferably further contains an acrylic resin in addition to a vinylidene fluoride resin and polymer particles. This improves the compatibility between the vinylidene fluoride resin and the polymer particles, and also suppresses the crystallization of the vinylidene fluoride resin.

[0085] The acrylic resin may be any resin whose constituent units are vinyl monomers containing (meth)acrylic acid esters, and known thermoplastic acrylic resins can be used. In particular, thermoplastic acrylic resins containing structural units derived from methacrylate esters are preferred, and thermoplastic acrylic resins containing 30% by weight or more, more preferably 50% by weight or more, of alkyl methacrylate ester units with 1 to 4 carbon atoms in the alkyl group are preferred. From the viewpoint of thermal stability, methyl methacrylate is particularly preferred.

[0086] Other vinyl monomers copolymerizable with methyl methacrylate include, specifically, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, octyl methacrylate, glycidyl methacrylate, epoxycyclohexylmethyl methacrylate, dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and dicyclopentanyl methacrylate. 2,2,2-trifluoroethyl methacrylate, 2,2,2-trichloroethyl methacrylate, isobolonyl methacrylate, methacrylamide, N-methylol methacrylamide and other methacrylic acid esters; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, glycidyl acrylate, epoxycyclohexylmethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate Examples include acrylic acid esters such as ropil, acrylamide, and N-methylolacrylamide; carboxylic acids and their salts such as methacrylic acid and acrylic acid; vinyl cyanides such as acrylonitonyl and methacrylonitrile; vinylarenes 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 vinyls such as vinyl chloride, vinyl bromide, and chloroprene; vinyl esters such as vinyl formate, vinyl acetate, and vinyl propionate; alkenes such as ethylene, propylene, butylene, butadiene, and isobutylene; halogenated alkenes; and crosslinkable monomers such as allyl methacrylate, diallyl phthalate, triallyl cyanurate, monoethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and divinylbenzene. These vinyl monomers can be used individually or in combination of two or more types.

[0087] Other vinyl monomers copolymerizable with methyl methacrylate include (meth)acrylic acid esters (excluding methyl methacrylate) having 1 to 10 carbon atoms in the alkyl group.

[0088] From the viewpoint of optical properties, appearance, weather resistance and heat resistance, the acrylic resin preferably contains methyl methacrylate as a structural unit in an amount of 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, and other vinyl monomers copolymerizable with methyl methacrylate preferably in an amount of 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.

[0089] The amount of acrylic resin in the resin composition according to this disclosure is preferably 1 to 40 parts by weight, more preferably 3 to 30 parts by weight, and even more preferably 5 to 25 parts by weight, per 100 parts by weight of vinylidene fluoride resin, from the viewpoint of balancing impact resistance or elongation with transparency.

[0090] The thermoplastic resin composition may further contain thermoplastic resins other than vinylidene fluoride resins and acrylic resins, to the extent that transparency is not substantially impaired. Such thermoplastic resins are not particularly limited, but examples include vinyl chloride resins, polycarbonate resins, styrene-acrylonitrile copolymer resins (AS resins), amide resins, polyester resins, etc. These may be used individually or in combination of two or more.

[0091] The content of thermoplastic resins other than vinylidene fluoride resin and acrylic resin is not particularly limited, but may be 0 to 100 parts by weight, 0 to 50 parts by weight, 0 to 30 parts by weight, 0 to 10 parts by weight, 0 to 5 parts by weight, or 0 to 1 part by weight per 100 parts by weight of the total of vinylidene fluoride resin and acrylic resin. It may also be less than 1 part by weight.

[0092] The thermoplastic resin composition may optionally contain flame retardants, antibacterial agents, mold 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. These may be used individually or in combination of two or more.

[0093] In particular, phenolic, sulfuric, phosphorusic, and hindered amine-based antioxidants or stabilizers; benzophenone-based and benzotriazole-based ultraviolet absorbers; organopolysiloxanes, aliphatic hydrocarbons, esters of higher fatty acids and higher alcohols, amides or bisamides of higher fatty acids and their modified forms, oligoamides, and metal salts of higher fatty acids can be suitably added as internal and external lubricants.

[0094] The thermoplastic resin composition can be manufactured, for example, by mixing the core-shell polymer particles and the thermoplastic resin in the form of latex, slurry, solution, powder, pellets, or a combination thereof. When the core-shell polymer particles and the thermoplastic resin are latex, for example, the latex can be solidified into a slurry by adding an alkaline earth metal salt such as calcium chloride, magnesium chloride, or magnesium sulfate, or an alkali metal salt such as sodium chloride or sodium sulfate, or an inorganic or organic acid such as hydrochloric acid, sulfuric acid, phosphoric acid, or acetic acid, and then dehydrated and dried. Spray drying can also be used. In this case, some of the additives, such as stabilizers, can be added to the latex or slurry in the form of a dispersion.

[0095] The thermoplastic resin composition can be formed into a target molded article (especially a film) by mixing the core-shell type polymer particles and the thermoplastic resin powder, pellets, etc. with any additives as needed, using a known melt kneader such as a Banbarri mixer, roll mill, single-screw extruder, or twin-screw extruder, and then forming it into a target molded article (especially a film) using a known molding method such as injection molding, extrusion molding, or blow molding.

[0096] The thickness of the film formed from the thermoplastic resin composition according to this disclosure is not particularly limited, but may be, for example, about 1 μm to 2 mm.

[0097] The applications for the thermoplastic resin composition and its molded articles are not particularly limited, but they are preferably used in applications where transparency and low-temperature elongation can be utilized. While such applications are not particularly limited, they are preferably outdoor applications where transparency can be taken advantage of, and a suitable example is a backsheet for solar cells.

[0098] The following describes the specific configuration of the backsheet for solar cells related to this disclosure, and the solar cell module including said backsheet.

[0099] The backsheet for solar cells according to this disclosure may consist of a film molded from the resin composition according to this disclosure, or it may be a film on which one or more transparent substrates such as an electrically insulating resin film such as a polyethylene terephthalate film, a moisture-proof film, or a tempered glass plate are laminated. Adhesives may be used to bond the above films together.

[0100] The solar cell module including the backsheet for solar cells according to this disclosure is not particularly limited, but preferably comprises at least a surface protective material, a sealing material, solar cells, and a backsheet (backside protective material). Multiple solar cells are connected in series by wiring. A frame is arranged at the end or periphery of the solar cell module.

[0101] As a surface protective material, a transparent material is used to allow sunlight to pass through. While not particularly limited, examples include tempered glass sheets, transparent plastic sheets, single-layer or multi-layer transparent plastic films, or composite materials combining these.

[0102] The sealing material is not particularly limited as long as it is a transparent resin capable of sealing solar cells, but examples include ethylene-vinyl acetate copolymer (EVA), butyral resin, silicon resin, epoxy resin, and fluorinated polyimide resin. EVA is particularly preferred. A resin sheet can be used as the sealing material, in which case the solar cells can be sealed by sandwiching them between two resin sheets and heating and pressurizing them. Furthermore, when the sealing material is a resin sheet, the resin sheet can be compounded with the solar cell backsheet according to this disclosure before sealing the solar cells.

[0103] As described above, the backsheet can be a film molded from the resin composition according to this disclosure, or a laminate in which a transparent substrate is laminated to the film. Since the backsheet according to this disclosure is transparent, a solar cell module containing it can generate electricity by concentrating light from both the front and back surfaces, and can be suitably used as a double-sided concentrating type.

[0104] The following sections list preferred embodiments of this disclosure, but the present invention is not limited to these sections. [Item 1] A thermoplastic resin composition comprising a vinylidene fluoride-based resin and polymer particles, The polymer particle comprises a core particle (A) and a shell layer (B) located outside the core particle. The core particle (A) contains a rubber layer which is a reaction product of a vinyl monomer (a1) and a crosslinkable monomer (a2). The vinyl monomer (a1) contains (meth)acrylic acid ester, The glass transition temperature of the rubber layer is -20°C or lower. The shell layer (B) includes an arbitrary graft layer (B1) having a glass transition temperature of -20°C or higher and less than 50°C, and a graft layer (B2) having a glass transition temperature of 50°C or higher. The weight ratio (B1) / [(A)+(B1)+(B2)] is between 0 and 10% by weight. The weight ratio [(A)+(B1)] / [(A)+(B1)+(B2)] is 30-70% by weight. A thermoplastic resin composition in which the free polymer content in the polymer particles is 35% by weight or less. [Item 2] The thermoplastic resin composition according to item 1, wherein the vinyl monomer (a1) substantially does not contain a vinyl monomer having a refractive index of 1.51 or higher as measured as a homopolymer. [Item 3] The thermoplastic resin composition according to item 1 or 2, wherein the graft layer (B2) is composed of a polymer of monomer components containing (meth)acrylic acid ester. [Item 4] A thermoplastic resin composition according to any one of items 1 to 3, wherein the average particle diameter of the core particles (A) is 40 to 150 nm. [Item 5] A thermoplastic resin composition according to any one of items 1 to 4, further comprising an acrylic resin. [Item 6] A molded article obtained by molding a thermoplastic resin composition described in any one of items 1 to 5. [Item 7] A film obtained by molding a thermoplastic resin composition described in any one of items 1 to 5. [Item 8] A backsheet for solar cells, comprising a layer made of the film described in item 7. [Item 9] A solar cell module comprising a solar cell element and a solar cell backsheet as described in item 8. [Examples]

[0105] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0106] (Example of core-shell polymer particle manufacturing) (Manufacturing Example 1) In a pressure polymerizer equipped with a stirrer, 170 parts (parts by weight; the same applies hereafter) of pure water and 0.25 parts of sodium dioctyl sulfosuccinate as a surfactant were added while blowing nitrogen into the polymerizer. Next, while stirring the added raw materials, the oxygen inside the polymerizer was thoroughly removed by purging the gas inside with nitrogen. Then, the temperature of the solution in the pressure vessel was raised to 60°C. Subsequently, 0.006 parts of ethylenediaminetetraacetate disodium salt (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 t-butyl hydroperoxide (BHP) were added to the pressure vessel over 150 minutes. Polymerization was then carried out over 30 minutes to obtain core particles. The volume-average particle size of the core particles contained in the obtained aqueous latex was 70 nm. Subsequently, 0.36 parts of sodium dioctyl sulfosuccinate, a surfactant, was added, followed by the addition of a mixture of 7 parts BA, 73 parts MMA, 0.37 parts t-dodecyl mercaptan (t-DM), and 0.2 parts BHP into 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. Calcium chloride was added to the aqueous latex containing the obtained core-shell polymer particles and allowed to solidify. After heat treatment and dehydration of the solidified slurry, the polymer particles were washed with deionized water, and then dehydrated and dried again to obtain a powder of core-shell polymer particles (C1).

[0107] (Manufacturing example 2) 170 parts of pure water and 0.5 parts of sodium dioctyl sulfosuccinate as a surfactant were added to a pressure polymerizer equipped with a stirrer while blowing in nitrogen. Next, while stirring the added raw materials, the oxygen inside the pressure polymerizer was completely removed by purging the gas inside with nitrogen. Then, the temperature of the solution in the pressure vessel was raised to 60°C. Subsequently, 0.0064 parts of EDTA, 0.0016 parts of ferrous sulfate, and 0.11 parts of SFS were added to the pressure vessel. Then, 10 parts of BA, 0.1 parts of allyl methacrylate, and 0.016 parts of cumene hydroperoxide (CHP) were added to the pressure vessel over 50 minutes. Polymerization was then carried out over 15 minutes. Finally, 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 over 160 minutes. Subsequently, the reaction solution in the pressure polymerizer was maintained at 60°C for 30 minutes to carry out polymerization, and 0.13 parts of sodium dioctyl sulfosuccinate were added as a surfactant to obtain an aqueous latex containing core particles. The volume-average particle size of the core particles contained in the obtained aqueous latex was 60 nm. Next, a mixture of 51.3 parts MMA, 5.7 parts BA, and 0.21 parts t-DM was added to the glass reactor over 220 minutes as monomer components. Simultaneously with the addition of the monomer components (i.e., MMA and BA), the addition of 0.25 parts CHP to the glass reactor was started. 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 carry out polymerization, obtaining an aqueous latex containing core-shell polymer particles. Calcium chloride was added to the aqueous latex containing the obtained core-shell type polymer particles and allowed to solidify. After heat treatment and dehydration of the solidified slurry, the polymer particles were washed with deionized water, and then dehydrated and dried again to obtain a core-shell type polymer particle powder (C2).

[0108] (Manufacturing examples 3-11) A powder of core-shell polymer particles was obtained in the same manner as in Production Example 2, except that the amount of sodium dioctyl sulfosuccinate used and the type or amount of each component used in component (A) and component (B) were changed according to the formulation shown in Table 1.

[0109] (Manufacturing Example 12) In a pressure polymerizer equipped with a stirrer, 170 parts of pure water and 0.5 parts of sodium dioctyl sulfosuccinate as a surfactant were added while blowing in nitrogen. Next, while stirring the added raw materials, the oxygen inside the pressure polymerizer was completely removed by purging the gas inside with nitrogen. Then, the temperature of the solution in the pressure vessel was raised to 60°C. Subsequently, 0.0064 parts of EDTA, 0.0016 parts of ferrous sulfate, and 0.11 parts of SFS were added to the pressure vessel. Then, 10 parts of BA, 0.1 parts of allyl methacrylate, and 0.016 parts of cumene hydroperoxide (CHP) were added to the pressure vessel over 50 minutes. Polymerization was then carried out over 15 minutes. Finally, 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 over 110 minutes. Subsequently, the reaction solution in the pressure polymerizer was maintained at 60°C for 30 minutes to carry out polymerization, and 0.13 parts of sodium dioctyl sulfosuccinate were added as a surfactant to obtain an aqueous latex containing core particles. The volume-average particle size of the core particles contained in the obtained aqueous latex was 51 nm. Next, a mixture of 2 parts MMA, 3 parts BA, and 0.004 parts CHP was added to the glass reactor over 20 minutes as monomer components. Polymerization was then carried out over 30 minutes. Subsequently, a mixture of 55.8 parts MMA, 6.2 parts BA, and 0.4 parts t-DM was added to the glass reactor over 240 minutes. Simultaneously with the addition of the monomer components (i.e., MMA and BA), the addition of 0.28 parts CHP to the glass reactor was started. 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 carry out polymerization and obtain an aqueous latex containing core-shell polymer particles. Calcium chloride was added to the aqueous latex containing the obtained core-shell polymer particles and allowed to solidify. After heat treatment and dehydration of the solidified slurry, the polymer particles were washed with deionized water, and then dehydrated and dried again to obtain a powder of core-shell polymer particles (C3).

[0110] (Manufacturing examples 13-21) A powder of core-shell polymer particles was obtained in the same manner as in Production Example 12, except that the amount of sodium dioctyl sulfosuccinate used and the type or amount of each component used in component (A) and component (B) were changed according to the formulations described in Tables 1 and 2.

[0111] (Average particle diameter of core particles) The average particle size of the core particles was measured as the volume-average particle size in the core particle latex state. A Nanotrac Wave manufactured by Nikkiso Co., Ltd. was used as the measuring device.

[0112] (Free polymer content) 1.0 g of the obtained core-shell polymer particles was dissolved in 45 mL of methyl ethyl ketone, and the mixture was centrifuged for 1 hour at a rotation speed of 29,000 rpm for a total of three sets using a centrifuge (Hitachi Koki Co., Ltd., CP60E) to separate the insoluble and soluble components. The obtained soluble component was concentrated to 20 mL, reprecipitated in 200 mL of methanol, and vacuum-dried at 60°C and 600 Pa for 10 hours to obtain the free polymer. The weights of the obtained free polymer, insoluble matter, and soluble matter were measured, and the free polymer content was calculated using the following formula. Free polymer content (%) = {(weight of free polymers) / (weight of methyl ethyl ketone insoluble portion + weight of methyl ethyl ketone soluble portion)} × 100

[0113] (Weight average molecular weight) The free polymer obtained above was dissolved in tetrahydrofuran (THF), and the soluble portion was filtered through a 0.2 μm filter. The weight-average molecular weight was then determined using a high-speed GPC instrument (HLC-8220, manufactured by Tosoh Corporation). The measurement conditions were as follows. Sample solution: 20 mg of sample / 10 mL of THF Columns: 1 TSKguardcolumn SuperHZ-H and 2 TSKgel SuperHZM-H, manufactured by Tosoh Corporation. Column temperature: 40℃ Detector: Differential refractometer Flow rate: 0.35mL / min Injection volume: 10 μL, Calibration curve: Standard polystyrene

[0114] [Table 1]

[0115] [Table 2]

[0116] (Examples 1-13, Comparative Examples 1-9) [Creating a sheet] 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, and 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-blended and kneaded in a twin-screw extruder (TEX25SS manufactured by Japan Steel Works Ltd.) heated to a barrel temperature of 180-210°C at a screw rotation speed of 100 rpm, and then extruded to obtain pellets. However, in Comparative Example 1, core-shell polymer particles were not used, and the amount of acrylic resin was changed to 30 parts by weight. For the vinylidene fluoride resin, we used HAJ602 manufactured by Shandong Hua'an New Materials Co., Ltd., and for the acrylic resin, we used CM-207 (PMMA resin) manufactured by Chimei Industrial Co., Ltd.

[0117] After drying the obtained pellets in a dryer at 80°C for 5 hours, a 0.15 mm thick sheet was produced using a single-screw extruder (Toyo Seiki Co., Ltd. 2020C), a T-die molding machine (Toyo Seiki Co., Ltd. T150C), and a film take-up machine (Toyo Seiki Co., Ltd. FT2B15) in a Brabender (Toyo Seiki Co., Ltd. B3S150) under the following conditions: screw rotation speed of 100 rpm, molding temperature of 210-220°C, cooling roll temperature of 60°C, and take-up speed of 1 m / min.

[0118] [Tensile test] A 0.15 mm thick sheet prepared using the method described above was cut to the size of a JIS K7133-1 type test specimen, and its tensile properties (tensile fracture strain) were measured at -20°C at a test speed of 50 mm / min, in accordance with the JIS K7133 standard.

[0119] [Haze measurement] The haze value of a 0.15 mm thick sheet produced using the method described above was measured using an NDH-4000 manufactured by Nippon Denshoku Industries Co., Ltd., according to the method described in JIS K7105.

[0120] [Table 3]

[0121] [Table 4]

[0122] The following can be seen from Tables 3 and 4. In Examples 1 to 13, sheets were obtained that had low haze, high transparency, and high elongation at low temperatures. On the other hand, Comparative Example 1, which did not contain core-shell type polymer particles, showed insufficient elongation at low temperatures. Furthermore, in Comparative Examples 2 to 9, core-shell polymer particles with a large weight ratio of (B1) in the core-shell polymer particles (B1) / [(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 comprises a core particle (A) and a shell layer (B) located outside the core particle. The core particle (A) contains a rubber layer which is a reaction product of a vinyl monomer (a1) and a crosslinkable monomer (a2). The vinyl monomer (a1) contains a (meth)acrylic acid ester, The glass transition temperature of the rubber layer is -20°C or lower. The shell layer (B) includes an arbitrary graft layer (B1) having a glass transition temperature of -20°C or higher and less than 50°C, and a graft layer (B2) having a glass transition temperature of 50°C or higher. The weight ratio (B1) / [(A)+(B1)+(B2)] is between 0 and 10% by weight. The weight ratio [(A) + (B1)] / [(A) + (B1) + (B2)] is 30 to 70% by weight. A thermoplastic resin composition in which the free polymer content in the polymer particles is 35% by weight or less.

2. The thermoplastic resin composition according to claim 1, wherein the vinyl monomer (a1) substantially does not contain a vinyl monomer having 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 of monomer components containing (meth)acrylic acid ester.

4. The thermoplastic resin composition according to claim 1, wherein the average particle diameter of the core particles (A) is 40 to 150 nm.

5. The thermoplastic resin composition according to claim 1, further comprising an acrylic resin.

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

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

8. A backsheet for a solar cell, comprising a layer made of the film described in 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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