JP7560481B2 - Resin composition and molded article using said composition - Google Patents

Description

The present invention relates to a resin composition and a molded article using the composition. More specifically, the present invention relates to a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer resin composition and a film- or sheet-shaped molded article using the same.

Tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers (hereinafter sometimes referred to as "THV resins") have excellent chemical resistance, contamination resistance, water repellency, insulating properties and low friction, and are therefore used in hoses and gaskets for transporting chemical liquids, oil, fuel, etc. In addition, THV resins can be formed into films by melt molding, and are therefore used in a variety of applications, such as component films for solar cells, release films and films for glass interlayers.

For example, Patent Document 1 discloses a release film mainly made of THV resin. The document also describes that the above-mentioned film is used as a release film in the semiconductor manufacturing process.

Furthermore, Patent Document 2 describes a fuel hose in which THV resin is used in a layer that requires low fuel permeability.

JP 2013-71382 A JP 2016-11715 A

However, when THV resin is melt-molded, it decomposes under high temperature conditions, which can easily generate acidic gases, raising concerns that this can cause deterioration and rust in the components used in the molding equipment. In other words, it is desirable to take special measures against the generation of acidic gases, but it is not desirable to melt-molde THV resin in general-purpose molding equipment that molds general thermoplastic resins without such measures. In addition, as a countermeasure as mentioned above, there is molding equipment with enhanced corrosion resistance, but considering costs, these measures are not necessarily easy to introduce.

On the other hand, to suppress the decomposition of the resin during melt molding, heat stabilizers made of organic substances such as antioxidants are sometimes added. However, because the melt molding temperature of THV resin is high, the heat stabilizer may evaporate, or the poor compatibility between THV resin and the heat stabilizer may cause the molded product to become cloudy and the appearance of the molded product to be impaired. Because THV resin has excellent chemical resistance and contamination resistance, it is expected to be used in applications that require good appearance, such as protective films for articles and building materials. For this reason, it is undesirable for the appearance of the molded product to deteriorate due to the effects of additives.

As described above, there is a need for the development of a THV resin composition that can be processed using general-purpose molding equipment and does not impair the appearance of the molded product.

In order to solve the above-mentioned problems, the present invention aims to provide a resin composition that can be melt molded using general-purpose molding equipment without impairing the appearance of the molded body, and a molded body using the composition.

The present inventors have discovered that, when dispersed in a THV resin, an inorganic acid acceptor can suppress clouding or yellowing when the resin composition is molded, maintaining the transparency of the molded article, and can also capture acidic gases produced by thermal decomposition of the THV resin, thereby preventing the diffusion of the acidic gases, and have arrived at the present invention.
<1> A resin composition comprising a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A) and an inorganic acid acceptor (B), wherein the content of the inorganic acid acceptor (B) in the resin composition is 0.01 to 0.1 parts by mass per 100 parts by mass of the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A).
<2> The resin composition according to <1>, wherein the inorganic acid acceptor (B) is at least one selected from the group consisting of a metal oxide, a metal hydroxide, a solid solution containing a plurality of kinds of metal oxides, a metal stearate, a hydrotalcite-type compound represented by the following formula (I), and a hydrotalcite-like layered compound exhibiting an anion exchange action:
Formula (I): M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _x/n・mH ₂ O(I)
(wherein M ²⁺ and M ³⁺ represent divalent and trivalent metal ions, respectively, A ^n- represents an n-valent anion, 0<x≦0.33, and m≧0.)
<3> A molded article obtained by molding the resin composition according to <1> or <2>.
<4> The molded article according to <3>, which is in the form of a sheet or a film.

According to the present invention, it is possible to provide a resin composition that can be melt molded using general-purpose molding equipment without impairing the appearance of the molded article, and a molded article using the composition.

The present invention will be described in detail below using embodiments, but the present invention is not limited to the embodiments shown below.

<THV resin composition>
The resin composition of the present embodiment (hereinafter, sometimes referred to as "THV resin composition") is a resin composition containing a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A) (hereinafter, sometimes referred to as "THV resin (A)") and an inorganic acid acceptor (B), and the content of the inorganic acid acceptor (B) in the resin composition is 0.01 to 0.1 parts by mass per 100 parts by mass of the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A).

The resin composition of the present embodiment uses a specific amount of inorganic acid acceptor (B) relative to the THV resin (A), thereby capturing acidic gases generated by decomposition of the THV resin (A) during melt molding and preventing their diffusion. In addition, unlike organic antioxidants, inorganic acid acceptors are less likely to volatilize even at the processing temperature of the THV resin (about 280°C or higher). Therefore, little acidic gas is generated during melt molding, and even when general-purpose molding equipment for molding general thermoplastic resins is used, there is little effect on members in the equipment.
In addition, organic antioxidants are poorly compatible with THV resins when mixed, and may cause clouding. On the other hand, inorganic acid acceptors are easily dispersed in THV resins, and have a refractive index relatively close to that of resins such as THV. This makes it possible to suppress clouding or yellowing when the resin composition is molded, and when the THV resin is molded into a molded article, the transparency of the THV resin molded article can be maintained without impairing the appearance of the article.

<Tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A)>
The tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A) (THV resin (A)) in this embodiment is a copolymer of tetrafluoroethylene (also known as "tetrafluoroethylene", hereinafter sometimes referred to as "TFE"), hexafluoropropylene (also known as "hexafluoropropylene", hereinafter sometimes referred to as "HFP"), and vinylidene fluoride (hereinafter sometimes referred to as "VDF").
The THV resin (A) is not limited to a copolymer consisting of three kinds of monomers, namely, TFE monomer, HFP monomer, and VDF monomer. That is, the THV resin (A) may contain other monomers in addition to the TFE monomer, HFP monomer, and VDF monomer. Examples of the other monomers include (perfluorohexyl)ethylene, (perfluorobutyl)ethylene, (perfluorooctyl)ethylene, and [4-(heptafluoroisopropyl)perfluorobutyl]ethylene, and the THV resin (A) also includes copolymers using these other monomers as the fourth monomer.

The monomer ratio (molar ratio of constituent units derived from each monomer) in the copolymerization of TFE monomer, HFP monomer, and VDF monomer in THV resin (A) is not particularly limited, but is preferably within the range of 90 or less of TFE monomer, 1 or more of HFP monomer, and 9 or more of VDF when the ratio of all monomers is taken as 100; more preferably, the ratio of TFE is 60 to 90, the ratio of HFP is 1 to 10, and the ratio of VDF is 9 to 30. When the ratio of TFE monomer is 90 or less, the ratios of HFP monomer and VDF monomer increase relatively, making it easier to soften and improving melt moldability. In addition, when the ratio of TFE monomer is 30 or more, a polytetrafluoroethylene-like structure is formed in part of the molecular chain, and the chemical resistance, weather resistance, antifouling properties, etc., characteristic of fluororesins are further improved.

The melting point of the THV resin (A) is not particularly limited, but from the viewpoint of heat resistance, it is preferably from 100°C to 250°C, and more preferably from 150°C to 250°C.
The glass transition temperature of the THV resin (A) is preferably from -10°C to 30°C, more preferably from 0°C to 20°C, from the viewpoint of flexibility when molded into a film or sheet.

The THV resin (A) may be a THV resin having any TFE/HFP/VDF ratio used alone, or may be a mixture of two or more THV resins having different TFE/HFP/VDF ratios.
Furthermore, resins other than the THV resin (A) may be added as necessary within a range that does not impair the transparency of the THV resin composition. In addition, a THV resin (A) that is a copolymer of three types of monomers such as TFE/HFP/VDF may be used in combination with a THV resin (A) that is a copolymer of TFE/HFP/VDF/a fourth monomer other than the above. Examples of resins other than the THV resin (A) include polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), polyperfluoroalkylvinyl ether (PFA), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and the like.
When the other resin is used, the content of the other resin in the THV resin composition is preferably 0.2 parts by mass or less, and more preferably 0.1 parts by mass or less, per 100 parts by mass of the THV resin (A).

<Inorganic Acid Acceptor (B)>
The THV resin composition of the present embodiment contains a specific amount of an inorganic acid acceptor relative to the THV resin (A).
Here, the term "inorganic acid acceptor" refers to an acid acceptor containing an inorganic compound. That is, the inorganic acid acceptor (B) is a general term for inorganic compounds that can capture acids such as acidic gases by taking in the acids or neutralizing the acids.

The inorganic acid acceptor (B) is not particularly limited, and can be appropriately selected from known inorganic compounds having an acid receiving function (acid capturing ability). However, the mechanism of acid capture in the inorganic acid acceptor (B) is not particularly limited. Among these inorganic acid acceptors, metal oxides, metal hydroxides, solid solutions containing multiple types of metal oxides, metal stearates, hydrotalcite-type compounds represented by the formula (I) described below, and hydrotalcite-like layered compounds exhibiting anion exchange function are preferred, and metal oxides, solid solutions containing multiple types of metal oxides, hydrotalcite-type compounds represented by the formula (I) described below, and hydrotalcite-like layered compounds exhibiting anion exchange function are particularly preferred.

In the resin composition of this embodiment, by adding a specific amount of these inorganic acid acceptors (B) to the THV resin, it is possible to suppress corrosion and deterioration of the molding equipment caused by acid gas generated by decomposition of the THV resin during melt molding, while maintaining the appearance of the molded product. Note that the inorganic acid acceptors (B) may be used alone or in combination of two or more types.

Examples of the inorganic acid acceptor (B) are not particularly limited, and include the inorganic compounds exemplified below. The inorganic acid acceptor (B) may contain the inorganic compound listed below as a main component and may also contain impurities.
Examples of metal oxides include magnesium oxide and zinc oxide.
Examples of metal hydroxides include magnesium hydroxide and barium hydroxide.
Examples of the metal stearates include calcium stearate and zinc stearate.
An example of a solid solution made of a plurality of metal oxides is a magnesium oxide-aluminum oxide solid solution.

In the hydrotalcite compound represented by the following formula (I), examples of the divalent metal ion include magnesium ion (Mg ²⁺ ) and zinc ion (Zn ²⁺ ), and examples of the trivalent metal ion include aluminum ion (Al ³⁺ ) and iron ion (Fe ³⁺ ). Examples of the n-valent anion include monovalent or divalent anions, and specific examples thereof include carbonate ion (CO ₃ ²⁻ ) and nitrate ion (NO ₃ ⁻ ). As such a hydrotalcite compound, a combination of magnesium ion, aluminum ion, and carbonate ion is preferred, and an example thereof includes hydrotalcite mainly composed of magnesium oxide-aluminum oxide.

Formula (I): M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _x/n・mH ₂ O
(wherein M ²⁺ and M ³⁺ represent divalent and trivalent metal ions, respectively, A ^n- represents an n-valent anion, 0<x≦0.33, and m≧0.)

Examples of hydrotalcite-like layered compounds that exhibit anion exchange activity include layered compounds obtained by calcining the hydrotalcite whose main components are magnesium oxide and aluminum oxide.

In addition, the refractive index of the inorganic acid acceptor (B) is preferably 1.9 or less, and more preferably 1.6 or less. If the refractive index is 1.6 or less, the difference in refractive index with the THV resin is not large, and clouding of the molded body can be effectively avoided.

The particle size of the inorganic acid acceptor (B) is not particularly limited, but from the viewpoints of maintaining the transparency of the THV resin molded body, the dispersibility of the acid acceptor, and the acid scavenging performance, it is preferable that the 50% average particle size is 0.1 μm to 1 μm, and 0.3 μm to 0.6 μm is more preferable.

The method of adding the inorganic acid acceptor (B) to the THV resin composition is not particularly limited, and it may be added in advance during the granulation process of the THV resin raw material, or it may be added while melt-mixing the unadded THV resin raw material and the inorganic acid acceptor (B) during the process of producing a sheet (molded body) of the THV resin composition.

The content of the inorganic acid acceptor (B) in the THV resin composition is 0.01 to 0.1 parts by mass per 100 parts by mass of the THV resin (A). When the content of the inorganic acid acceptor (B) is 0.1 parts by mass or less, it is possible to prevent the THV resin composition from becoming cloudy due to the acid acceptor and to prevent coloration due to thermal deterioration of the acid acceptor. Furthermore, when the content of the inorganic acid acceptor (B) is 0.01% by mass or more, a sufficient acid gas capture effect is obtained.

(others)
To the THV resin composition of the present embodiment, a plasticizer, a lubricant, an antistatic agent, an antifogging agent, a dripping agent, a hydrophilic agent, a liquid repellent agent, etc. can be added within a range that does not impair the transparency, color tone, glossiness, heat resistance, weather resistance, etc. and the effects of the present invention in practical use. Furthermore, these additives, etc. may be added when the THV resin composition is kneaded, or may be applied to the surface of a film or sheet (molded product) produced by molding the THV resin composition.
Furthermore, a pigment may be added to the THV resin composition of the present embodiment as necessary within a range that does not impair the heat resistance, weather resistance, etc., or the effects of the present invention in practical use.

<Method of manufacturing molded body>
The THV resin composition of the present embodiment can be molded into various shapes, for example, into a film or sheet. Here, a method for producing a film using the THV resin composition of the present embodiment will be described.

As a method for producing a film, a known method can be used, for example, a method of molding a resin composition by melt extrusion using an extruder and various T-dies such as a feed block die or a multi-manifold die. As an extruder, a single screw type, a twin screw type, a tandem type, etc. can be generally used, but a single screw type extruder is preferred in terms of preventing the resin from stagnation in the extruder system.

The screw shape used in the single-screw extruder is not particularly limited as long as it is configured to not cause excessive shear heating, but a full-flight screw is more preferred for melt extrusion without excessive shear.

The compression ratio of the screw is preferably in the range of 1.8 to 3.0, and more preferably 2.1 to 2.7. If the compression ratio is 1.8 or more, the THV resin is not sufficiently plasticized, and some of the resin is captured as unmelted material by the screen mesh, which can prevent the mesh from clogging and increasing the resin pressure. In addition, it can prevent unmelted material from being mixed into the sheet as a defect. Furthermore, if the compression ratio is 3.0 or less, it can also prevent the amount of acid gas generated from becoming too large due to excessive shear heat generation.

The ratio (L/D) of the screw length (L) to the screw (barrel) diameter (D) of the extruder is not particularly limited as long as the extruder has an L/D necessary and sufficient for plasticizing the THV resin, but is preferably 20 to 40, and more preferably 25 to 35. When the L/D is 20 or more, the resin can be sufficiently plasticized in the screw region, and the generation of unmelted material, which is a drawback and can be prevented from being mixed into the sheet, can be prevented. Furthermore, when the L/D is 40 or less, excessive shear is unlikely to be applied, and an increase in the amount of acid gas generated can be prevented.

A breaker plate may be provided between the tip of the extruder screw and the T-die. The aperture ratio of the breaker plate is preferably 40 to 60%, more preferably 42 to 58%. By setting the aperture ratio of the breaker plate to 40% or more, it is possible to suppress back pressure on the resin and to suppress retention of the resin in the extruder. In addition, by setting the aperture ratio to 60% or less, it is possible to stably maintain the number of defects in the film low for a long period of time.
The opening ratio is based on the portion exposed to the resin flow section of the extruder and means the area of the portion where the resin through holes are formed relative to the total area including the resin through holes.

The resin penetration diameter of the breaker plate is preferably 3.7 to 7.0 mm. By making the resin penetration diameter 3.7 mm or more, it is possible to reduce back pressure on the resin and prevent the resin from remaining in the extruder. Furthermore, by making it 7.0 mm or less, it is possible to keep the number of defects in the sheet consistently low for a long period of time.

The screen mesh arranged on the breaker plate is preferably a combination of two or more screen meshes with different mesh openings. The screen meshes may also be used in combination with screen meshes with the same mesh openings. In general, it is preferable to arrange the screen meshes with larger mesh openings and the screen meshes with smaller mesh openings in this order from the upstream side (near the screw) of the resin flow section to the downstream side (opening side of the breaker plate). Furthermore, it is preferable to arrange a mesh with a coarser mesh than the mesh with the smallest mesh opening downstream of the mesh with the smallest mesh opening in order to prevent the mesh from breaking due to resin pressure. Specifically, a coarser screen mesh with a larger mesh opening than the mesh with the smallest mesh opening can be introduced downstream of the screen mesh with the smallest mesh opening. The screen mesh is preferably arranged 10 to 100 mm downstream from the tip of the screw. In the sheet production of the THV resin composition of this embodiment, the minimum mesh opening of the screen mesh is preferably 0.03 to 0.2 mm, more preferably 0.03 to 0.15 mm. By making the minimum mesh opening of the screen mesh 0.03 mm or more, deterioration due to shear heat generation of the resin can be suppressed. Furthermore, by setting the minimum mesh size of the screen mesh to 0.2 mm or less, contamination of the resin, deteriorated raw materials, etc. can be reduced.
The screen mesh with large openings serves to remove coarse defects, and the openings are preferably 0.15 to 0.6 mm.

The flow path of the T-die used in film production is not particularly limited in shape as long as it is designed to prevent resin retention, but a coat hanger die is an example that can be used suitably. The main resin discharge directions are horizontal, or downward, perpendicular to the horizontal, but either form can be used suitably.

The temperature setting of the extruder used in film production varies depending on the type and fluidity of the THV resin, but is preferably 200 to 300°C, and more preferably 260 to 290°C, downstream of the extruder. If the temperature is 200°C or higher, the resin can be sufficiently plasticized, and if it is 300°C or lower, it is possible to prevent the generation of too much acid gas due to excessive heating.

The film extruded from the T-die in this way immediately comes into contact with the cooling roll close to the die and is taken up while being cooled. Since the THV resin partially crystallizes when cooled, if transparency is required, it is preferable to rapidly cool the film with the cooling roll before the crystallization proceeds from the molten state. The shortest distance between the exit of the T-die and the point where the film contacts the cooling roll is preferably 200 mm or less, more preferably 150 mm or less, and particularly preferably 100 mm or less. If the distance is 200 mm or less, the crystallization of the THV resin proceeds more than necessary, and the transparency of the sheet can be prevented from decreasing. On the other hand, if design, etc. are required, rolls engraved with designs, geometric patterns, etc. or embossed rolls can be used.

As a cooling method using a cooling roll, either of the following methods can be used: two rolls with hard surfaces such as hard chrome plating or diamond-like carbon are placed with a gap suitable for obtaining the desired film thickness, and the film-like molten resin is cooled by being brought into contact with the gap between them while being drawn up; or the hard-surfaced roll is pressed against a rubber roll such as silicone, and the film-like molten resin is cooled by being brought into contact with the gap between them while being drawn up.

The film taken up as described above is passed through appropriate guide rolls without damaging the film surface, slit to the desired width, and then wound up on a paper tube or the like in a sufficiently cooled state. During the process from when it is extruded from the die to when it is wound up on a paper tube or the like, the film surface may be subjected to a corona treatment, plasma treatment, or a surface chemical treatment using a chemical agent such as a silane coupling agent, or the above surface treatment may be carried out in a separate process.

In this specification, a sheet refers to something thicker and a film refers to something thinner, and no clear distinction is made between "sheet" and "film."

<THV resin molding>
The THV resin molded article can be suitably used in applications requiring excellent chemical resistance, weather resistance, and designability. The THV resin molded article can be used as a film or sheet alone, or as a laminate with another substrate.

In this specification, impaired appearance refers to poor dispersion and turbidity caused by the addition of too much acid acceptor, and brown coloration caused by thermal degradation of the acid acceptor. The aforementioned turbidity increases the haze value of the film measured in accordance with JIS K7105, but this value can be adjusted depending on the application by the manufacturing method, for example, by applying unevenness to the film surface with an embossed roll. In addition, intentional adjustment of the haze value is not treated as defective appearance.

Furthermore, in applications requiring transparency and design, such as signboard protection films and decorative films, the haze value of the film measured in accordance with JIS K7105 using a haze meter is preferably 5% or less, and more preferably 3% or less. When the haze value is 5% or less, sufficient visibility of patterns, designs, etc. placed under the THV resin composition film can be obtained.

In applications requiring transparency and design, the THV resin composition film preferably has a b ^{* value} of 2.0 or less, more preferably 1.0 or less, in the L ^* a ^* b ^* color system measured by a color difference meter. If the b ^* value exceeds 2.0, the film itself may be macroscopically recognized as yellow.

For example, the effect of reducing the generation of acidic gases when a sheet-shaped THV resin molded body is manufactured under high temperatures such as by extrusion molding can be confirmed using a device that measures the acidic gas concentration at any location. The measuring device is not particularly limited as long as it has sufficient quantitative accuracy. One example of a measuring device that can be used is an acidic gas concentration detector in which an acidic gas absorbent is filled in a glass tube, and a quantitative recovery of the gas and its gas concentration can be obtained. In the case of fluororesin, it is preferable to use a gas detector tube for hydrogen fluoride gas.

<Applications>
A molded article (for example, a film or sheet) obtained by molding the THV resin composition of the present embodiment can be used, for example, in the following applications.
- Wall materials, roofing materials, tent materials, membrane materials for buildings - Protective films for signs, road signs, and soundproofing walls - Decorative films, water-repellent films, oil-repellent films, snow-proof films, and ice-proof films used in the interior and exterior parts of automobiles, railway vehicles, aircraft, and ships

The present invention will be described in further detail below with reference to examples, but the present invention is not limited in any way to these examples.

<Ingredients>
The raw materials used in the present examples and comparative examples are shown below.
(THV resin)
- 3M "Dyneon THV Resin 815GZ" (melting point 225°C)

(Inorganic acid acceptor)
・Magnesium oxide: Kyowa Chemical Industry Co., Ltd. "Kyowamag MF150"
Magnesium oxide-aluminum oxide-based solid solution: "KW-2200" manufactured by Kyowa Chemical Industry Co., Ltd.
・Hydrotalcite compounds: ADEKA "ADEKA STAB AP-582"
・Hydrotalcite-type compound: Kyowa Chemical Industry Co., Ltd.'s "DHT-4C" (corresponding to a hydrotalcite-like layered compound that exhibits anion exchange properties)

(Antioxidants)
Phenolic antioxidant: "Irganox 1010" manufactured by BASF
Phenolic antioxidant: "Irganox 1076" manufactured by BASF
- Phenol-based antioxidant: "Sumilizer GA-80" manufactured by Sumitomo Chemical Co., Ltd.

Example 1
100 parts by mass of THV resin raw material ("Dyneon THV Resin 815GZ") was premixed with 0.01 parts by mass of magnesium oxide ("Kyowamag MF150"), and then the mixture was melt mixed at 280°C using a "Labo Plastomill Micro" manufactured by Toyo Seiki Seisakusho, and taken up with a metal cast roll to obtain a glossy film with a thickness of 0.05 mm.
The amount of acid gas generated during film preparation and the optical properties of the obtained film were measured and evaluated according to the standards described below. The results are shown in the table below.

<Examples 2 to 20 and Comparative Examples 1 to 16>
Sheets were produced in the same manner as in Example 1, except that the raw materials and the amounts added were changed as shown in Tables 2 to 6. The amount of acid gas generated during film production and the optical properties of the obtained films are also shown in Tables 2 to 6. In Tables 2 to 6, the amount of acid acceptor or antioxidant added indicates the amount of acid acceptor or antioxidant added relative to 100 parts by mass of the THV resin raw material.

<Film Evaluation>
(Measurement of acid gas generation amount)
Using a gas sampler (Kitagawa gas sampler AP-20; manufactured by Komyo Rikagaku Kogyo Co., Ltd.) and a hydrogen fluoride gas detector tube (Kitagawa gas detector tube No. 156S hydrogen fluoride; manufactured by Komyo Rikagaku Kogyo Co., Ltd.), the amount of acidic gas generated was measured i) at a position 10 mm directly above the vent port (degassing hole) provided in the above-mentioned "Labo Plastomill Micro"("immediately adjacent to the vent port" in the table below) and ii) at a position 1 m away from the lip of the T-die of the same device ("working environment" in the table below).

(Hayes)
The transparency of the resin sheet was judged based on the haze value measured in accordance with JIS K7105 using a haze meter "NDH7000" manufactured by Nippon Denshoku Industries Co., Ltd., and in accordance with the criteria described in the following Table 1. In the measurement, samples cut out from any five points of the resin sheet were used, and the arithmetic average value was adopted.

(Color tone: b ^* )
The b ^* in the L ^* a ^* b ^* color system was measured by a transmission method using ZE6000 manufactured by Nippon Denshoku Industries Co., Ltd. For the measured b ^* , the color tone of the resin sheet was evaluated according to the criteria listed in Table 1 below.

From the results of Examples 1 to 20, it was found that adding the inorganic acid acceptor in the amount shown in the table to THV resin provided excellent acid gas generation suppression capability without impairing the appearance.

From the results of Comparative Examples 1, 5, 8 and 11, it was found that when the amount of inorganic acid acceptor added was small, the film appearance was not impaired, but the amount of acid gas generation was insufficient.
It was also found that the appearance of the film was impaired when the amount of inorganic acid acceptor added was excessive in Comparative Examples 2 to 3, 6 to 7, 9 to 10, and 12 to 13. Furthermore, it was found that when an antioxidant containing an organic compound was added, the amount added was insufficient to suppress the generation of acidic gases, and the film became cloudy and the optical properties were impaired.

As described above, the THV resin composition of the present invention can suppress the acid gas generated during melt molding of THV resin by adding an inorganic acid acceptor without impairing the appearance. In other words, it is possible to melt mold THV resin using general-purpose molding equipment that is not corrosion-resistant equipment.

The disclosure of Japanese Patent Application No. 2019-224043, filed on December 11, 2019, is incorporated herein by reference in its entirety.
In addition, all publications, patent applications, and technical standards mentioned in the specification are herein incorporated by reference to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims (4)

A resin composition comprising a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A) and an inorganic acid acceptor (B), wherein the content of the inorganic acid acceptor (B) in the resin composition is 0.01 to 0.075 parts by mass per 100 parts by mass of the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (A). 2. The resin composition according to claim 1, wherein the inorganic acid acceptor (B) is at least one selected from the group consisting of a metal oxide, a metal hydroxide, a solid solution containing a plurality of types of metal oxides, a metal stearate, a hydrotalcite-type compound represented by the following formula (I), and a hydrotalcite-like layered compound exhibiting an anion exchange function.
Formula (I): M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _x/n・mH ₂ O(I)
(wherein M ²⁺ and M ³⁺ represent divalent and trivalent metal ions, respectively, A ^n- represents an n-valent anion, 0<x≦0.33, and m≧0.) A molded article made from the resin composition according to claim 1 or 2. The molded article according to claim 3, which is in the form of a sheet or film.