Method for producing acetalized ethylene vinyl alcohol copolymers

Abstract

The present invention relates to a method for producing a product of acetalization of an ethylene / vinyl alcohol copolymer, the method comprising acetalizing the ethylene / vinyl alcohol copolymer, wherein the ethylene / vinyl alcohol copolymer is a porous object.

Description

[Technical Field]

[0001] This patent application claims priority under the Paris Convention with respect to Japanese Patent Application No. 2021-067294 (filing date: April 12, 2021), which is incorporated herein by reference in its entirety. The present invention relates to a method for producing an acetalized ethylene vinyl alcohol copolymer, the acetalized ethylene vinyl alcohol copolymer, a resin sheet containing the acetalized ethylene vinyl alcohol copolymer as a resin component, an interlayer for laminated glass made from the resin sheet, and laminated glass containing the interlayer for laminated glass. [Background technology]

[0002] As methods for producing acetalized ethylene vinyl alcohol copolymers, there are known methods, including a method in which ethylene vinyl alcohol copolymer is dissolved in a solvent and acetalized in a homogeneous solution (hereinafter also referred to as the homogeneous method), and a method in which solid ethylene vinyl alcohol copolymer is immersed in an acetalization bath and acetalized in a heterogeneous system (hereinafter also referred to as the heterogeneous method) (Patent Documents 1 and 2). However, the homogeneous method requires a step of dissolving the ethylene vinyl alcohol copolymer in a solvent before acetalization, making it difficult to efficiently produce acetalized ethylene vinyl alcohol copolymers. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 1-74201 [Patent Document 2] Japanese Patent Application Publication No. 53-65386 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The heterogeneous method allows for the acetalization of ethylene vinyl alcohol copolymers without dissolving them in a solvent before acetalization. However, our studies have shown that acetalization using the heterogeneous method can sometimes result in the formation of a gel-like substance due to intermolecular crosslinking of the ethylene vinyl alcohol copolymer, and that the transparency of the resulting acetalized product decreases as a result of the formation of this gel-like substance.

[0005] Therefore, the present invention aims to provide a method for efficiently producing acetalized ethylene vinyl alcohol copolymers having excellent transparency. [Means for solving the problem]

[0006] The present inventors, after diligent research to solve the above problems, arrived at the present invention. That is, the present invention provides the following preferred embodiments. [1] A method for producing an acetalized product of an ethylene vinyl alcohol copolymer by acetalizing an ethylene vinyl alcohol copolymer, wherein the ethylene vinyl alcohol copolymer is a porous material. [2] The method according to [1], wherein the median diameter of the pores in the porous material is 0.005 μm or more. [3] The porous body having pores at the center of gravity of the porous body, according to the method of [1] or [2]. [4] The surface area of ​​the pores of the porous material is 25 m². 2 The method described in any of [1] to [3], wherein the amount is 1 / g or more. [5] The method according to any one of [1] to [4], wherein the ethylene content of the ethylene vinyl alcohol copolymer is 20 to 60 mol%. [6] The method according to any one of [1] to [5], wherein the average particle size of the porous material is 1 mm or more. [7] The porous body is in the form of pellets, according to any one of [1] to [6]. [8] The method according to any one of [1] to [7], wherein acetalization is carried out by a solid-liquid reaction. [9] The method according to any one of [1] to [8], wherein a dispersion containing an ethylene vinyl alcohol copolymer and a solvent is prepared, and an aldehyde and a catalyst are added to the dispersion in that order to acetalize it.

[10] The method according to [9], wherein the solvent includes water.

[11] An acetal of an ethylene vinyl alcohol copolymer, which is a porous material with a median pore size of 0.005 μm or more. A resin sheet containing an acetalized ethylene vinyl alcohol copolymer as described in

[12] and

[11] as a resin component.

[13] The resin sheet described in

[12] , wherein the storage modulus at 50°C and a frequency of 1 Hz is 20 MPa or more. An interlayer for laminated glass made of the resin sheet described in

[14] ,

[12] , or

[13] .

[15] Laminated glass comprising two glass plates and an interlayer for laminated glass as described in

[14] , disposed between the two glass plates. [Effects of the Invention]

[0007] According to the present invention, a method for efficiently producing acetalized ethylene vinyl alcohol copolymers having excellent transparency can be provided. [Modes for carrying out the invention]

[0008] [Method for producing acetalized ethylene vinyl alcohol copolymers] The present invention provides a method for producing an acetalized ethylene vinyl alcohol copolymer (hereinafter also simply referred to as "acetalized product"), which includes the step of acetalizing an ethylene vinyl alcohol copolymer (hereinafter also referred to as "EVOH").

[0009] <Ethylene vinyl alcohol copolymer> In this invention, the ethylene vinyl alcohol copolymer used for acetalization is a porous material. By using a porous ethylene vinyl alcohol copolymer (hereinafter also referred to as "EVOH porous material") as a raw material, even if solid EVOH is acetalized by a heterogeneous method, intermolecular crosslinking of EVOH is less likely to occur, and an acetalized EVOH product with excellent transparency can be obtained. This effect is thought to be because the acetalizing agent penetrates not only the solid surface of EVOH but also into the solid interior of EVOH through its pores, allowing for uniform acetalization of EVOH. As a result, the difference in the degree of acetalization between the solid surface and the interior of the acetalized product obtained by acetalization becomes small, and an acetalized product with a narrow distribution of acetalization degrees can be obtained.

[0010] In the present invention, the EVOH porous body refers to EVOH having a large number of pores. Furthermore, it is preferable that some or all of the pores have openings on the surface of the porous body.

[0011] In one embodiment of the present invention, from the viewpoint of uniformly acetalizing EVOH and easily improving the transparency of the obtained acetalized EVOH product, the median diameter of pores in the EVOH porous body is preferably 0.005 µm or more, more preferably 0.01 µm or more, and still more preferably 0.02 µm or more. In addition, since the porous body easily retains strength with the aforementioned median diameter, the porous body is less likely to collapse into powder during the production process of the acetalized product, as a result, clogging of the production line is less likely to occur, and from the viewpoint of easily producing the acetalized product efficiently, the median diameter is preferably 1 µm or less, more preferably 0.5 µm or less, still more preferably 0.2 µm or less, even more preferably less than 0.2 µm, particularly preferably 0.18 µm or less, even more particularly preferably 0.15 µm or less, and most preferably 0.12 µm or less. The median diameter of pores refers to the median diameter (d50) for all pores with a pore diameter in the range of 0.005 to 100 µm in the Log differential pore volume (logarithmic differential pore volume) distribution. The reason why the pore diameter is limited to the range of 0.005 to 100 µm in the pore distribution is that pore distribution for pores with a diameter larger than 100 µm mainly corresponds to voids between particles, and pore distribution for pores with a diameter smaller than 0.005 µm, which is near the lower measurement limit, includes pseudo-pores caused by compression or the like.

[0012] The median diameter of pores of the EVOH porous body can be adjusted by the production conditions of the porous body. For example, when producing an EVOH porous body by preparing a composition containing EVOH and at least one solvent selected from water and alcohols, extruding the composition into a coagulation liquid in a strand form to coagulate the composition, and cutting the obtained strand-shaped coagulated product, the median diameter of the porous body can be adjusted by the type and content of the solvent contained in the composition, the linear speed when extruding the composition, the extrusion temperature, the cooling rate, and the like. In addition, the median diameter of these pores can be measured by a pore distribution analyzer, for example, measured by the method described in the Examples.

[0013] In one embodiment of the present invention, the EVOH porous body preferably has pores in the center of gravity of the porous body. When the porous body has pores in the center of gravity, the acetalizing agent can penetrate into the interior of the EVOH solid, particularly to the center of gravity of the EVOH, so that EVOH can be uniformly acetalized. As a result, intermolecular crosslinking of EVOH is less likely to occur, and the transparency of the obtained acetalized EVOH is easily improved. In the present invention, the phrase that the porous body has pores in the center of gravity means that, in a cross-section of the porous body passing through the center of gravity of the porous body, when the shortest distance among the distances from the center of gravity of the cross-section to the surface of the porous body is defined as distance L, pores exist in a region within 50% of the distance L from the center of gravity of the cross-section.

[0014] In one embodiment of the present invention, from the viewpoint of uniformly acetalizing EVOH and easily improving the transparency of the obtained acetalized EVOH, in a cross-section of the EVOH porous body passing through the center of gravity of the porous body, when the shortest distance among the distances from the center of gravity of the cross-section to the surface of the porous body is defined as distance L, it is preferable that pores exist in a region within preferably 30%, more preferably within 20%, even more preferably within 10% of the distance L from the center of gravity of the cross-section.

[0015] In one embodiment of the present invention, from the viewpoint of uniformly acetalizing EVOH and easily improving the transparency of the obtained acetalized EVOH, the total pore area in the cross-section of the EVOH porous body passing through the center of gravity of the porous body is preferably 10 area% or more, more preferably 20 area% or more, still more preferably 30 area% or more, relative to the total cross-sectional area. In addition, from the viewpoint that the total pore area easily increases the strength of the porous body, as a result, the porous body is less likely to collapse in the production process of the acetalized product, and the acetalized product can be easily produced efficiently, the total pore area may be preferably 60 area% or less, more preferably 50 area% or less, relative to the total cross-sectional area.

[0016] A cross-section of the EVOH porous material passing through its center of gravity can be prepared using a single-edged razor or the like. Furthermore, the presence or absence of pores in this cross-section and the proportion of the total pore area can be confirmed and calculated by observing and analyzing electron microscope images of the cross-section.

[0017] In one embodiment of the present invention, the pore surface area of ​​the EVOH porous body in the range of 0.005 to 100 μm, as measured by the mercury intrusion method, is preferably 25 μm from the viewpoint of easily improving the transparency of the EVOH acetal. 2 / g or more, comfortably within 30m 2 It is 1 / g or more. Furthermore, the surface area of ​​the pores of the EVOH porous body is preferably 45m², from the viewpoint of easily suppressing adhesion between EVOH porous bodies during high-temperature washing in the manufacturing process of the EVOH porous body. 2 / g or less, more preferably 41m 2 / g or less, more preferably 39m 2 It is less than / g.

[0018] The pore surface area of ​​the EVOH porous material in the 0.005 to 100 μm range can be adjusted by the manufacturing conditions of the porous material. For example, similar to the method for adjusting the median diameter of the pores of the porous material, it can be adjusted by the type and content of solvent contained in the composition, the linear velocity when extruding the composition into the solidification solution, the extrusion temperature, and the cooling rate during solidification. Furthermore, the pore volume of the porous material can be measured using a pore distribution measuring device, for example, by the method described in the examples.

[0019] In one embodiment of the present invention, the pore volume of the EVOH porous body may be preferably 0.1 mL / g or more, more preferably 0.2 mL / g or more, and even more preferably 0.25 mL / g or more, from the viewpoint of uniformly acetalizing EVOH and improving the transparency of the resulting acetalized EVOH product. Furthermore, the pore volume may be preferably 1.0 mL / g or less, more preferably 0.5 mL / g or less, and even more preferably 0.3 mL / g or less, from the viewpoint of ease of handling. The pore volume of the EVOH porous body can be adjusted by the manufacturing conditions of the porous body. For example, similar to the method for adjusting the median diameter of the pores of the porous body, it can be adjusted by the type and content of solvent contained in the composition, the linear velocity when extruding the composition into the solidification solution, the extrusion temperature, and the cooling rate when solidifying. Furthermore, the pore volume of the porous body can be measured using a pore distribution measuring device, for example, by the method described in the examples.

[0020] In one embodiment of the present invention, the average particle size of the EVOH porous body may be preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 3 mm or more, from the viewpoint of ease of handling. Furthermore, the average particle size may be preferably 10 mm or less, more preferably 7 mm or less, and even more preferably 5 mm or less, from the viewpoint of facilitating uniform acetalization of EVOH and improving the transparency of the resulting acetalized product. The average particle size can be measured, for example, by the method described in the examples.

[0021] The shape of the EVOH porous body is not particularly limited and can be in the form of powder, pellets, flakes, beads, or irregular shapes. Among these, the porous body is preferably in the form of powder or pellets, and more preferably in the form of pellets. In this invention, a pellet-shaped porous body refers to a solid porous body having a substantially constant size, such as a spherical, cylindrical, elliptical prism, or polygonal prism, and its cross-section may be circular, elliptical, polygonal, etc.

[0022] In the present invention, when the EVOH porous body is in pellet form, the pellet-shaped porous body can be produced by extruding an ethylene vinyl alcohol copolymer composition into a solidification liquid to solidify it into strands, and then cutting the resulting strand-shaped solidified material to a predetermined length with a strand cutter or the like, or by directly cutting the ethylene vinyl alcohol copolymer composition in a molten state, as described below.

[0023] Examples of ethylene vinyl alcohol copolymers include those obtained by copolymerizing ethylene with a vinyl ester monomer and saponifying the resulting copolymer. In one embodiment of the present invention, the ethylene content of the ethylene vinyl alcohol copolymer (hereinafter also referred to as the ethylene unit content) is preferably 20 to 60 mol% with respect to the total monomer units constituting EVOH. Furthermore, from the viewpoint of easily improving the puncture resistance and moldability of the resulting acetal, the ethylene content may be more preferably 20 mol% or more, even more preferably 30 mol% or more, and particularly preferably 35 mol% or more. Also, from the viewpoint of easily improving the storage modulus of the resulting acetal, it may be more preferably 60 mol% or less, even more preferably 55 mol% or less, and particularly preferably 50 mol% or less.

[0024] The degree of saponification of EVOH is not particularly limited, but from the viewpoint of heat decomposition resistance, for example, it is preferably 95 mol% or more, more preferably 98 mol% or more, even more preferably 99 mol% or more, and particularly preferably 99.9 mol% or more. The upper limit of the degree of saponification is not particularly limited and may be, for example, 100 mol% or less.

[0025] The vinyl alcohol unit content of the ethylene vinyl alcohol copolymer may be preferably 40 mol% or more, more preferably 45 mol% or more, and even more preferably 50 mol% or more, relative to the total monomer units constituting EVOH, from the viewpoint of easily improving the storage modulus of the resulting acetal, and may be preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 65 mol% or less, from the viewpoint of easily improving the puncture resistance and moldability of the resulting acetal.

[0026] The copolymerization form of the ethylene vinyl alcohol copolymer is not particularly limited and may be any of the following: random copolymer, alternating copolymer, block copolymer, graft copolymer, etc.

[0027] In the present invention, the ethylene vinyl alcohol copolymer may contain, in addition to ethylene units, vinyl alcohol units, and vinyl ester units, monomer units derived from monomers copolymerizable with these units (hereinafter also referred to as other monomer units), to the extent that the effects of the present invention are not impaired. Examples of the other monomer units include α-olefins such as propylene, isobutylene, α-octene, and α-dodecene; unsaturated acids such as acrylic acid, methacrylic acid, methyl methacrylate, crotonic acid, maleic acid, and itaconic acid, or their anhydrides, salts, or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or their salts; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, and vinylidene chloride. If the ethylene vinyl alcohol copolymer contains other monomer units, their content may preferably be 15 mol% or less, more preferably 10 mol% or less.

[0028] The content of ethylene units, vinyl alcohol units, and optionally other monomer units in EVOH in the present invention can be determined by NMR measurement, for example, by the method described in the examples.

[0029] In one embodiment of the present invention, the melt flow rate (MFR) of the ethylene vinyl alcohol copolymer, measured in accordance with JIS K7210-1:2014 under conditions of 190°C and 2.16 kg, may preferably be 1 to 30 g / 10 min, more preferably 2 to 20 g / 10 min, and even more preferably 3 to 10 g / 10 min, from the viewpoint of easily suppressing thermal degradation of the resulting acetalized product during molding.

[0030] The method for producing a porous ethylene vinyl alcohol copolymer is not particularly limited and can be produced by known methods. As an example, a method for producing a pellet-shaped EVOH porous body will be described.

[0031] Pellet-shaped porous EVOH materials can be manufactured by, for example, the steps described in Japanese Patent Publication No. 11-293077 and Japanese Patent Publication No. 2002-121290, which involve preparing a composition containing an ethylene vinyl alcohol copolymer and at least one solvent selected from water and alcohol, extruding the composition in strand form into a solidification liquid, allowing it to solidify, and then cutting it, or by directly cutting the composition in a molten state.

[0032] The EVOH contained in the above composition can be obtained by copolymerizing ethylene with a vinyl ester monomer and saponifying the resulting copolymer. Examples of vinyl ester monomers used as raw materials for EVOH include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurylate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate. Among these, vinyl acetate is preferred. The method for copolymerizing ethylene and vinyl ester monomers is not particularly limited and may be carried out by conventionally known methods, such as solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc. The polymerization initiator that can be used in the copolymerization is a conventionally known polymerization initiator such as azo initiators, peroxide initiators, redox initiators, etc., which can be appropriately selected depending on the polymerization method. Saponification of copolymerization between ethylene and vinyl ester monomers can be carried out by conventionally known methods such as alcohol decomposition or hydrolysis using alkaline or acidic catalysts. Among these, saponification using methanol as a solvent and a caustic soda (NaOH) catalyst is preferred because it is simple.

[0033] The alcohol that may be included in the above composition is not particularly limited as long as it is a solvent that can dissolve EVOH, and examples include methanol, ethanol, propanol, isopropanol, etc. Among these alcohols, alcohols with a boiling point of 100°C or lower are preferred because they have a low boiling point and are easy to remove, and methanol is particularly preferred.

[0034] If the composition contains water as a solvent, it may be prepared by directly adding water to EVOH or to a composition containing EVOH and alcohol. Alternatively, it may be prepared by concentrating an EVOH alcohol solution obtained by dissolving EVOH in alcohol, and then adding water to the EVOH alcohol solution in an amount that does not cause EVOH to precipitate. Alternatively, water vapor may be introduced into EVOH or a composition containing EVOH and alcohol, and at least some of the alcohol may be discharged along with the water vapor to obtain a composition containing EVOH and water, or EVOH, water and alcohol.

[0035] The alcohol that can be used to prepare the EVOH alcohol solution is not particularly limited as long as it is a solvent that can dissolve EVOH, and examples include alcohols similar to those that can be contained in the above composition. Alcohols with a boiling point of 100°C or lower are preferred, and methanol is particularly preferred, because they have a low boiling point and are easy to remove. The alcohol content in the EVOH alcohol solution may be preferably 1 to 500 parts by mass, more preferably 5 to 200 parts by mass, per 100 parts by mass of EVOH.

[0036] When the composition contains water, the water content is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 50 parts by mass or more, per 100 parts by mass of EVOH, from the viewpoint of easily uniformly acetalizing EVOH and easily removing the neutralized salt produced by neutralization after the acetalization reaction. Furthermore, from the viewpoint of easily increasing the strength of the resulting porous body and thus easily producing acetalized products, the water content is preferably 500 parts by mass or less, more preferably 300 parts by mass or less, and even more preferably 200 parts by mass or less.

[0037] When the composition contains alcohol, the alcohol content is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 50 parts by mass or more, per 100 parts by mass of EVOH, from the viewpoint of easily uniformly acetalizing EVOH and easily removing the neutralized salt produced by neutralization after the acetalization reaction. Furthermore, from the viewpoint of easily increasing the strength of the resulting porous body and thus easily producing acetalized products, the alcohol content is preferably 500 parts by mass or less, more preferably 300 parts by mass or less, and even more preferably 200 parts by mass or less.

[0038] The coagulation solution used to solidify the aforementioned composition is not particularly limited as long as it is a solvent capable of solidifying EVOH, but it is preferable to use water, alcohol, or a mixed solvent of water and alcohol as the coagulation solution.

[0039] The temperature of the coagulation solution is preferably 0 to 50°C, more preferably 0 to 30°C, from the viewpoint of easily coagulating the composition sufficiently. Furthermore, the temperature of the composition when it is extruded into the coagulation solution is preferably 90 to 150°C, more preferably 100 to 140°C, from the viewpoint of the fluidity of EVOH. As described above, by extruding the composition into a solidification solution and allowing it to solidify, the resulting solidified body becomes a porous body with oriented pores.

[0040] The resulting strand-like solidified material can be cut, for example, using a strand cutter. By cutting the resulting strand-like solidified material with a strand cutter, pellet-shaped EVOH porous material can be obtained.

[0041] One method for obtaining a pellet-shaped EVOH porous body by directly cutting the composition in a molten state is to obtain a pellet-shaped EVOH porous body by extruding the molten material of the composition from an extruder using a hot-cut method or a hot-cut method in water. As described above, by extruding and pelletizing the molten material of the composition, the resulting pellets become porous bodies with oriented pores.

[0042] The method for producing the powdered EVOH porous body is not particularly limited, and for example, it may be obtained by crushing the pelletized porous body obtained by the above method using a pulverizer or the like.

[0043] The EVOH porous body may contain a solvent, but if the solvent is a good solvent for EVOH, it is preferable that the amount of good solvent in the EVOH is reduced by drying or other means to the extent that the pores of the EVOH porous body do not become clogged. If the solvent is a poor solvent for EVOH such as water, the EVOH porous body may contain 5 to 200 parts by mass of the poor solvent such as water per 100 parts by mass of the EVOH porous body.

[0044] <Acetalization> In this invention, since the EVOH used as a raw material is porous, intermolecular crosslinking of EVOH is less likely to occur even when acetalization is performed in a heterogeneous system, and an EVOH acetal with excellent transparency can be obtained. Therefore, in this invention, since there is no need to dissolve EVOH in a solvent before acetalization, the EVOH acetal can be produced efficiently. In the present invention, acetalization can be carried out by dispersing a solid porous EVOH material in a solvent and adding an acetalizing agent to the resulting EVOH dispersion.

[0045] In this invention, acetalization may be carried out by a solid-liquid reaction or by a dissolution reaction.

[0046] In the present invention, the method for carrying out acetalization by a solid-liquid reaction (hereinafter also referred to as the "solid-liquid method") refers to a method in which EVOH and the acetalized EVOH produced by acetalization are used as poor solvents for the acetalization reaction, thereby obtaining the resulting acetalized EVOH as a solid dispersed in a dispersion without dissolving EVOH and the acetalized EVOH in the solvent during the acetalization step.

[0047] The solvent for the acetalization reaction that can be used in the solid-liquid method is a poor solvent for EVOH and its acetal derivatives, preferably a water-containing solvent, more preferably water.

[0048] The method of acetalization by dissolution reaction (hereinafter also referred to as the "dissolution method") involves using a solvent that is a poor solvent for EVOH and a good solvent for the acetal product generated by acetalization as the solvent for the acetalization reaction. In this method, the acetal product generated as the reaction progresses is dissolved in the solvent during the acetalization step, and after the acetalization step, the generated acetal product is obtained as a solution dissolved in the solvent.

[0049] The solvent used in the dissolution method for the acetalization reaction is a poor solvent for EVOH and a good solvent for the acetalized product of EVOH. Examples of such solvents include alcohols and mixed solvents of alcohol and water. Preferred alcohols include methanol, ethanol, propanol, isopropanol, butanol, and isobutyl alcohol, which have a boiling point of 120°C or less. Among these, methanol is more preferred from the viewpoint of low solubility of EVOH and ease of drying. When a mixed solvent of alcohol and water is used as the solvent for the acetalization reaction, the ratio (alcohol:water (volume ratio)) in the mixed solvent is preferably 99.9:0.1 to 85:15, more preferably 97:3 to 87:13.

[0050] When water is used as the solvent for the acetalization reaction, it is classified as a solid-liquid method because water is a poor solvent for EVOH and its acetalized counterpart. On the other hand, when methanol is used as the solvent for the acetalization reaction, methanol may be a poor solvent for EVOH at low temperatures (e.g., below 60°C), but depending on the degree of acetalization, it can be a good solvent for the acetalized counterpart of EVOH, so it is classified as a dissolution method.

[0051] In one embodiment of the present invention, acetalization is preferably carried out by a solid-liquid reaction. By carrying out acetalization by a solid-liquid reaction, the resulting acetalized product can be separated from the reaction solution by filtration, making it easier to efficiently produce the acetalized product and to produce the acetalized product in high yield.

[0052] In one embodiment of the present invention, the EVOH content in the EVOH dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less, based on the total mass of the dispersion.

[0053] Examples of acetalizing agents include aldehydes. While there are no particular limitations on the aldehydes that can be used for acetalization, examples include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, benzaldehyde, isobutyraldehyde, 2-ethylhexylaldehyde, 2-methylbutyraldehyde, trimethylacetaldehyde, 2-methylpentylaldehyde, 2,2-dimethylbutyraldehyde, 2-ethylbutyraldehyde, and 3,5,5-trimethylhexylaldehyde. These aldehydes may be used individually or in combination of two or more. In one embodiment of the present invention, the aldehyde is preferably butyraldehyde, benzaldehyde, or isobutyraldehyde, from the viewpoint of easily improving the heat resistance and / or transparency of the resulting acetal. Furthermore, in one embodiment of the present invention, the aldehyde is preferably one that does not have a carboxyl group, from the viewpoint of easily improving the transparency of the resulting acetal.

[0054] The amount of aldehyde added to the EVOH dispersion is not particularly limited and can be adjusted as appropriate according to the desired degree of acetalization. In one embodiment of the present invention, the amount of aldehyde added may be preferably 1 to 40 parts by mass, more preferably 5 to 35 parts by mass, and even more preferably 10 to 30 parts by mass, per 100 parts by mass of EVOH, from the viewpoint of easily improving the transparency and impact resistance of the resulting acetalized product.

[0055] In one embodiment of the present invention, acetalization is preferably carried out in the presence of a catalyst, particularly an acidic catalyst. The acidic catalyst is not particularly limited and may be an organic acid or an inorganic acid. Examples of acidic catalysts include acetic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and carbonic acid. Among these catalysts, inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid are preferred because they easily increase the reaction rate of the acetalization reaction, facilitate washing from the resulting acetal product, and allow for efficient production of the acetal product.

[0056] The amount of catalyst added to the EVOH dispersion can be appropriately selected depending on the type of catalyst and the reaction temperature. For example, the catalyst concentration in the dispersion may be preferably 0.001 to 1.0 mol / L, more preferably 0.01 to 0.8 mol / L, and even more preferably 0.05 to 0.5 mol / L.

[0057] The method of adding the catalyst to the EVOH dispersion is not particularly limited; for example, the catalyst may be added to the EVOH dispersion all at once, or it may be added in multiple steps. From the viewpoint of obtaining an acetalized product with low haze and excellent transparency, it is preferable to add the catalyst to the EVOH dispersion in multiple steps, and particularly preferable to add it in two steps. When the catalyst is added to the EVOH dispersion in multiple stages, the amount of the first addition of catalyst is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, relative to the total amount added. If the amount of the first addition of catalyst is below the above upper limit, the distribution of the degree of acetalization becomes narrower, making it easier to improve the transparency of the resulting acetal product.

[0058] In a preferred embodiment of the present invention, acetalization is carried out by preparing a dispersion containing EVOH and a solvent, and adding an aldehyde and a catalyst to the dispersion, preferably in that order. By adding the aldehyde and catalyst to the dispersion in this order, the aldehyde permeates uniformly into the EVOH, allowing for uniform acetalization of the EVOH, thus improving the transparency of the resulting acetal product. In a preferred embodiment of the present invention, acetalization is preferably carried out by adding an aldehyde to a dispersion containing EVOH and a solvent, followed by adding the catalyst in multiple portions.

[0059] The reaction temperature for acetalization is preferably below the glass transition temperature of EVOH, from the viewpoint of easily maintaining the pores of the EVOH porous material. The reaction temperature may more preferably be 10 to 70°C, and more preferably 30 to 60°C. Furthermore, acetalization may be carried out in air, in an inert gas such as nitrogen gas or argon gas, and may be carried out under normal pressure, under pressurized pressure, or under reduced pressure.

[0060] After the acetalization reaction, the resulting reaction solution may be neutralized with an alkali as needed, and then the acetalized product may be separated and purified from the reaction solution by conventional separation methods, such as filtration, concentration, reprecipitation, and recrystallization. It is preferable to remove the neutralized salt produced by neutralization by washing or the like. The alkali that can be used for neutralization is not particularly limited and examples include sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium bicarbonate, and potassium carbonate.

[0061] [Acetalized EVOH] The acetalized EVOH obtained by the method of the present invention is uniformly acetalized and has excellent transparency because it does not easily have intermolecular crosslinking of EVOH.

[0062] The ethylene unit content of the acetalized material may preferably be 20 to 60 mol% relative to the total monomer units constituting the acetalized material. Furthermore, from the viewpoint of easily improving puncture resistance and moldability, the ethylene content may be more preferably 20 mol% or more, even more preferably 30 mol% or more, and particularly preferably 35 mol% or more. Also, from the viewpoint of improving the storage modulus and easily enhancing the self-supporting properties of the resin sheet containing the acetalized material as a resin component, it may be more preferably 60 mol% or less, even more preferably 55 mol% or less, and particularly preferably 50 mol% or less.

[0063] The content of vinyl alcohol units in the acetalized product may be preferably 12 mol% or more, more preferably 16 mol% or more, even more preferably 18 mol% or more, even more preferably 20 mol% or more, and particularly preferably 22 mol% or more, relative to the total unit content of the acetalized product, from the viewpoint of easily improving adhesion to substrates such as glass. Furthermore, from the viewpoint of easily improving the transparency of the resulting acetalized product, it may be preferably 79 mol% or less, more preferably 77 mol% or less, even more preferably 76 mol% or less, even more preferably 72 mol% or less, and particularly preferably 68 mol% or less.

[0064] The content of acetal units (acetalized vinyl alcohol units) in the acetalized product is preferably 1 mol% or more, more preferably 3 mol% or more, even more preferably 5 mol% or more, even more preferably 10 mol% or more, and particularly preferably 15 mol% or more, from the viewpoint of keeping the crystallinity of the acetalized product low and easily increasing transparency. Furthermore, from the viewpoint of easily increasing heat resistance, storage modulus, and adhesion to substrates such as glass, it is preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 55 mol% or less, even more preferably 50 mol% or less, and particularly preferably 45 mol% or less.

[0065] The acetalized product may contain other monomer units in addition to ethylene units, vinyl alcohol units, and acetal units (acetalized vinyl alcohol units), and optionally vinyl ester units, to the extent that it does not impair the effects of the present invention. Examples of other monomer units include monomer units similar to those that may be contained in EVOH. If the acetalized product contains other monomer units, their content is preferably 15 mol% or less, more preferably 10 mol% or less.

[0066] The content of each monomer unit in the acetalized product can be determined by NMR measurement, for example, by the method described in the examples.

[0067] The degree of acetalization of the acetalized product is preferably 0.4 mol% or more, more preferably 1.2 mol% or more, even more preferably 2 mol% or more, even more preferably 4 mol% or more, particularly preferably 6 mol% or more, particularly more preferably 8 mol% or more, and particularly still more preferably 10 mol% or more, and from the viewpoint of easily improving heat resistance, storage modulus, and adhesion to substrates such as glass, it is preferably 56 mol% or less, more preferably 48 mol% or less, even more preferably 44 mol% or less, even more preferably 40 mol% or less, and particularly preferably 36 mol% or less. In this invention, the degree of acetalization refers to the ratio of acetal units to the total content of vinyl ester units such as acetal units, vinyl alcohol units, and vinyl acetate units in the acetalized product. Specifically, in this invention, the degree of acetalization is given by the following formula, where k is the content of acetal units, l is the content of vinyl alcohol units, and m is the content of vinyl ester units: Acetalization degree (mol %) = {k / (k+l+m)} × 100 This can be determined by [method].

[0068] In one embodiment of the present invention, the acetalized material has high transparency, and the haze of the acetalized material is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less. Since the transparency of the acetalized material increases as the haze decreases, the lower limit is not particularly limited and may be, for example, 0.01% or more. The haze of the acetalized material can be measured using a haze meter in accordance with JIS K7136:2000, and can be measured, for example, by the method described in the examples.

[0069] In one embodiment of the present invention, the acetalized material exhibits excellent transparency (transparency during slow cooling) after being heated to 140°C and then slowly cooled from 140°C to 23°C at a rate of 0.1°C / min. Transparency during slow cooling can be evaluated by the haze during slow cooling (slow cooling haze). The slow cooling haze of the acetalized material is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less. Since a smaller haze increases the transparency of the resin sheet, the lower limit is not particularly limited and may be, for example, 0.01% or more. The slow cooling haze of the acetalized material can be determined by preparing a laminated glass having a resin sheet obtained from the acetalized material as an interlayer, heating the laminated glass to 140°C, and then slowly cooling from 140°C to 23°C at a rate of 0.1°C / min, and measuring the haze with a haze meter in accordance with JIS K7136:2000. For example, it can be determined by the method described in the examples.

[0070] In one embodiment of the present invention, the heat of fusion (ΔH) of the acetalized material is preferably 50 J / g or less, more preferably 40 J / g or less, and even more preferably 30 J / g or less, from the viewpoint of transparency, and the lower limit of the heat of fusion is not particularly limited and may be 0 J / g or more. In another embodiment of the present invention, the heat of fusion (ΔH) of the acetalized material is preferably 1 J / g or more, more preferably 5 J / g or more, and even more preferably 10 J / g or more, from the viewpoint of easily improving self-supporting properties in high-temperature environments. The heat of fusion can be measured by using a differential scanning calorimeter to heat a sample from 25°C to 230°C at a heating rate of 10°C / min until melted, then cooling it from 230°C to -30°C at a cooling rate of 10°C / min, and then heating it again from -30°C to 230°C at a heating rate of 10°C / min.

[0071] In one embodiment of the present invention, the melt flow rate (MFR) of the acetalized material, measured in accordance with JIS K7210-1:2014 under conditions of 190°C and 2.16 kg, is preferably 0.1 to 100 g / 10 min, more preferably 1 to 50 g / 10 min, even more preferably 2 to 30 g / 10 min, and particularly preferably 3 to 20 g / 10 min. When the MFR of the acetalized material is above the lower limit, it is easier to improve the moldability (fluidity) in an appropriate molding temperature range (e.g., 150 to 220°C), resulting in no need to excessively raise the molding temperature and making it easier to obtain a molded article with less discoloration. Furthermore, when the MFR is below the upper limit, it is easier to improve strength and impact resistance.

[0072] In one embodiment of the present invention, the glass transition temperature (Tg) of the acetalized product is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher, taking into account the balance between heat resistance and moldability. It may also be preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower, taking into account the balance between heat resistance and moldability. The Tg is the midpoint glass transition temperature determined from the DSC curve. The DSC curve is obtained by measuring the differential scanning calorimetry during the second heating cycle when the resin to be measured is heated to 230°C at a heating rate of 10°C / min in accordance with JIS K7121:2012, then cooled from 230°C to -30°C at a cooling rate of 10°C / min, and then heated again from -30°C to 230°C at a heating rate of 10°C / min.

[0073] In one embodiment of the present invention, the storage modulus (E') of the acetalized material measured by dynamic viscoelasticity measurement at 50°C and a frequency of 1 Hz is preferably 20 MPa or more, more preferably 30 MPa or more, even more preferably 60 MPa or more, and even more preferably 100 MPa or more, from the viewpoint of easily improving self-supporting properties. From the viewpoint of easily improving puncture resistance, it may be preferably 1500 MPa or less, more preferably 1200 MPa or less, and even more preferably 900 MPa or less. The storage modulus can be measured using a dynamic viscoelasticity measuring device, for example, by the method described in the examples.

[0074] In one embodiment of the present invention, the penetration energy of the acetalized material may be preferably 10 J or more, more preferably 12 J or more, and even more preferably 14 J or more, from the viewpoint of penetration resistance. The penetration energy is measured when the molten kneaded acetalized material is heated at 200°C and 50 kgf / cm². 2 A 0.8 mm thick sheet obtained by compression molding at a pressure of (50 MPa) for 5 minutes was used as the test specimen. The test was conducted using a drop-weight impact tester in accordance with ASTM D3763, under the conditions of a measurement temperature of 23°C, a load of 2 kg, and an impact velocity of 9 m / s. The SS curve area can be calculated from the area of ​​the SS curve from the moment the striker tip touches the specimen (sensing the test force) to the moment of penetration (when the test force returns to zero).

[0075] In one embodiment of the present invention, the acetal is preferably a porous material, and more preferably a porous material with a median pore diameter of 0.005 μm or more. Therefore, the present invention also includes acetal materials of EVOH that are porous materials with a median pore diameter of 0.005 μm or more.

[0076] In one embodiment of the present invention, the porous body of the acetalized material preferably has a pore structure similar to that of the EVOH porous body described above, which is the raw material for the acetalized material. The median diameter of the pores of the porous body of the acetalized material, the presence or absence of pores at the center of gravity of the porous body, the total pore area in the cross-section of the porous body passing through the center of gravity, the pore surface area, and the pore volume are similar to those described for the corresponding pore structures of the EVOH porous body. Furthermore, in one embodiment of the present invention, the average particle size and shape of the porous acetal material, including preferred forms, are similarly governed by the description of the average particle size and shape of the EVOH porous material.

[0077] The uses of the acetalized EVOH obtained by the method of the present invention are not particularly limited, and can be used in various fields, for example, as a packaging material. Such packaging materials can be used, for example, as containers with excellent oxygen barrier properties in the form of bags, tubes, cups, pouches, etc., for food, cosmetics, medical chemicals, toiletries, vacuum insulation boards, etc., or as gas barrier films for food packaging, gasoline tanks, vacuum insulation boards, heat pipes, etc. Furthermore, the acetalized EVOH in the present invention is also useful in paper processing agents such as fiber sizing agents, fiber treatment agents, fiber processing agents, sizing agents for textile products, clear coating agents for paper, pigment coating agents for paper, internal sizing agents for paper, and binders for overcoating thermal paper; pressure-sensitive adhesives, anti-fogging agents, paints, dispersants for organic and inorganic pigments, polymerization dispersion stabilizers for emulsions, polymerization dispersion stabilizers for PVC, adhesives for paper, wood, and plastics, binders for nonwoven fabrics, binders for fibers, binders for ceramics, binders for electrodes, binders for various building materials such as gypsum board and fiberboard, additives for cement and mortar, hot melt adhesives, resins for 3D printers, adhesives for display films, interlayer adhesives for ceramic laminates, adhesive compositions such as liquid glue and solid glue, separators for storage batteries, laminates with fluororesins, laminates with rubber such as tire inner liners, and composite laminates with fiber substrates. Furthermore, because the acetalized EVOH of the present invention has high transparency, it is useful as an interlayer for laminated glass, a film for agricultural greenhouses, a laminate with transparent resins such as resin glazing for vehicles, a laminate with antenna circuit boards, a protective film for glass surfaces, and various transparent containers for cosmetic applications.

[0078] [Resin composition] A resin composition may be obtained by adding other thermoplastic resins and additives as needed to the acetalized EVOH. The resin composition comprises the acetalized EVOH, and optionally other thermoplastic resins and additives.

[0079] From the viewpoint of transparency, the content of acetalized material in the resin composition may be preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may also be 100% by mass or less, based on the total mass of the resin composition.

[0080] Other thermoplastic resins that can be optionally included are not particularly limited and include, for example, polyolefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; ethylene-based ionomers; styrene-based resins such as polystyrene, styrene-maleic anhydride copolymer, high-impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, and MBS resin; methyl methacrylate polymers and methyl methacrylate-styrene copolymers; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamides such as nylon 6, nylon 66, and polyamide elastomers; polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, polyurethane, modified polyphenylene ether, polyphenylene sulfide, silicone-modified resins, acrylic rubber, acrylic thermoplastic elastomers, and silicone rubber; styrene-based thermoplastic elastomers such as SEPS, SEBS, and SIS; and olefin-based rubbers such as IR, EPR, and EPDM. These may be a single type or a combination of two or more types.

[0081] If the resin composition contains other thermoplastic resins, the content of the other thermoplastic resins can be appropriately selected within a range that does not impair the effects of the present invention, and the total content of the other thermoplastic resins may be preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on the total mass of the resin composition, from the viewpoint of easily improving transparency and impact resistance.

[0082] Examples of optional additives include plasticizers, antioxidants, UV absorbers, light stabilizers, adhesion modifiers, adhesion improvers, anti-blocking agents, pigments, dyes, and functional inorganic compounds. Among these additives, plasticizers, antioxidants, UV absorbers, adhesion modifiers, and adhesion improvers are preferred. These additives may be used individually or in combination of two or more types.

[0083] If the resin composition contains additives, the amount of additives may be preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, relative to the total mass of the resin composition, from the viewpoint of easily improving heat resistance, especially self-supporting properties in high-temperature environments, and easily suppressing the bleed-out of the additives.

[0084] Examples of plasticizers include triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, di-(2-butoxyethyl)-adipate (DBEA), di-(2-butoxyethyl)-sebacate (DBES), di-(2-butoxyethyl)-azelaic acid, di-(2-butoxyethyl)-glutarate, di-(2-butoxyethoxyethyl)-adipate (DBEEA), di-(2-butoxyethoxyethyl)-sebacate (DBEES), di-(2-butoxyethoxyethyl)-azelaic acid, and di-(2-butoxyethoxyethyl) Examples include di-glutaric acid esters, di-(2-hexoxyethyl)-adipate esters, di-(2-hexoxyethyl)-sebacate esters, di-(2-hexoxyethyl)-azelaic acid esters, di-(2-hexoxyethyl)-glutaric acid esters, di-(2-hexoxyethoxyethyl)-adipate esters, di-(2-hexoxyethoxyethyl)-sebacate esters, di-(2-hexoxyethoxyethyl)-azelaic acid esters, di-(2-hexoxyethoxyethyl)-glutaric acid esters, di-(2-butoxyethyl)-phthalate esters and / or di-(2-butoxyethoxyethyl)-phthalate esters. Among these plasticizers, it is preferable that the sum of the number of carbon atoms and oxygen atoms constituting the molecule is 28 or more. Examples of such plasticizers include triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, di-(2-butoxyethoxyethyl)-adipate, and di-(2-butoxyethoxyethyl)-sebacate. These plasticizers may be used individually or in combination of two or more.

[0085] When the resin composition contains a plasticizer, its content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less, per 100 parts by mass of the acetal. Furthermore, the plasticizer content may be preferably 0 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more.

[0086] Examples of antioxidants include phenolic antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants, among which phenolic antioxidants are preferred, and alkyl-substituted phenolic antioxidants are preferred. These antioxidants may be used individually or in combination of two or more.

[0087] Examples of phenolic antioxidants include acrylate compounds such as 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate or 2,4-di-t-amyl-6-(1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl)phenyl acrylate, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, octadecyl-3-(3,5-)di-t-butyl-4-hydroxyphenyl)propionate, and 2,2'-methylene-bis( 4-methyl-6-t-butylphenol), 4,4'-butylidene-bis(4-methyl-6-t-butylphenol), 4,4'-butylidene-bis(6-t-butyl-m-cresol), ethylenebis(oxyethylene)bis(3-(5-t-butyl-4-hydroxy-m-tolyl)propionate, 4,4'-thiobis(3-methyl-6-t-butylphenol), bis(3-cyclohexyl-2-hydroxy-5-methylphenyl)methane, 3,9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate (Luoxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate)methanetriethylene glycol bis(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate), also These are alkyl-substituted phenol compounds such as hexamethylenebis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 6-(4-hydroxy-3,5-di-t-butylanilino)-2,4-bis-octylthio-1,3,5-triazine, 6-(4-hydroxy-3,5-dimethylanilino)-2,4-bis-octylthio-1,3,5-triazine, 6-(4-hydroxy-3-methyl-5-t-butylanilino)-2,4-bis-octylthio-1,3,5-triazine or 2-octylthio-4,6-bis-(3,Examples include triazine group-containing phenolic compounds such as 5-di-t-butyl-4-oxyanilino)-1,3,5-triazine.

[0088] Examples of phosphorus-based antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, tris(dinonylphenyl) phosphite, tris(2-t-butyl-4-methylphenyl) phosphite, tris(cyclohexylphenyl) phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Examples include monophosphite compounds such as 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, and diphosphite compounds such as 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis(phenyl-di-alkyl(C12~C15) phosphite), 4,4'-isopropylidene-bis(diphenylmonoalkyl(C12~C15) phosphite), 1,1,3-tris(2-methyl-4-di-tridecyl phosphite-5-t-butylphenyl)butane or tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene phosphite. Among these, monophosphite compounds are preferred.

[0089] Examples of sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, lauryl stearyl 3,3'-thiodipropionate, pentaerythritol-tetrakis-(β-lauryl-thiopropionate), and 3,9-bis(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane.

[0090] If the resin composition contains an antioxidant, its content is preferably 0.001 to 5 parts by mass, more preferably 0.01 to 1 part by mass, per 100 parts by mass of the acetal.

[0091] Examples of UV absorbers include 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α'dimethylbenzyl)phenyl]-2H-benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, Examples include benzotriazole-based UV absorbers such as 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, or 2-(2-hydroxy-5-t-octylphenyl)benzotriazole, and benzoate-based UV absorbers such as 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate or hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate.

[0092] If the resin composition contains an ultraviolet absorber, its content may be preferably 10 to 50,000 ppm, more preferably 100 to 10,000 ppm, by mass relative to the acetal.

[0093] Examples of light stabilizers include hindered amine compounds such as 2,2,6,6-tetramethyl-4-piperidyl benzoate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate, 4-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)-1-(2-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl)-2,2,6,6-tetramethylpiperidine, or bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidine) sebacate.

[0094] Adhesion modifiers are additives that reduce adhesive strength. Examples of adhesion modifiers include those disclosed in International Publication No. 03 / 033583, preferably alkali metal salts and / or alkaline earth metal salts of organic acids. More preferably, potassium salts and magnesium salts of carboxylic acids having 1 to 16 carbon atoms, such as potassium acetate, magnesium acetate, magnesium propionate, magnesium butyrate, magnesium 2-ethylbutyrate, magnesium 2-ethylhexanoate, magnesium octoate, magnesium decanoate, and magnesium neodecanoate.

[0095] Examples of adhesion enhancers include silane coupling agents. Examples of silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyldiethoxysilane. These silane coupling agents may be used individually or in combination of two or more.

[0096] If the resin composition contains an adhesion modifier or adhesion improver, the amount thereof should be appropriately selected depending on the type of adhesion improver and the environment in which the laminated glass is used when the resin composition is used as an interlayer raw material for laminated glass. For example, the amount of adhesive pseudosolvent is preferably adjusted so that the adhesion strength of the resulting resin sheet to glass is generally 3 to 10 in the Pummel test (described in International Publication No. 03 / 033583, etc.), and is preferably adjusted to 3 to 6 when high penetration resistance is required, and to 7 to 10 when high glass shatter resistance is required. When high glass shatter resistance is required, it is also a useful method not to add an adhesion improver.

[0097] If the resin composition contains an adhesion improver, its content may be preferably 0.001 to 5 parts by mass, more preferably 0.01 to 1 part by mass, per 100 parts by mass of EVOH acetal.

[0098] Various additives may be added during the production of EVOH acetal products, or they may be added after the production of EVOH acetal products.

[0099] [Resin sheet] The present invention also includes resin sheets containing the acetalized EVOH as a resin component. In one embodiment of the present invention, the resin sheet has one or more layers (hereinafter also referred to as layer (x)) containing the acetalized EVOH as a resin component. Layer (x) is a layer made of the resin composition of the present invention, which optionally contains the acetalized EVOH and other thermoplastic resins and additives.

[0100] The resin sheet may consist only of layer (x), or it may be a laminate containing at least one layer (x). The laminate is not particularly limited, but examples include a laminate containing two or more layers (x), a laminate containing one or more layers (x) and one or more other layers, etc. If layer (x) or other layers consist of multiple layers, the resin or resin composition constituting each layer may be the same or different.

[0101] Examples of the aforementioned other layers include layers containing known resins. Examples of such resins include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, polytetrafluoroethylene, acrylic resin, polyamide, polyacetal, polycarbonate, and among polyesters, polyethylene terephthalate, polybutylene terephthalate, cyclic polyolefin, polyphenylene sulfide, polytetrachloroethylene, polysulfone, polyethersulfone, polyarylate, liquid crystal polymer, polyimide, thermoplastic elastomer, etc. The other layers may also contain one or more additives as needed, such as the aforementioned additives and heat-shielding materials (for example, inorganic heat-shielding fine particles or organic heat-shielding materials having infrared absorption capabilities).

[0102] In one embodiment of the present invention, from the viewpoint of preventing adhesion between resin sheets and improving degassing performance in the lamination process, the resin sheet of the present invention is preferably one having an uneven surface structure. Methods for providing the uneven surface structure include conventionally known methods, such as a method of providing a melt fracture structure by adjusting the extrusion conditions, or a method of imparting an embossed structure to the extruded sheet. The depth and shape of the embossing can be those of conventionally known methods.

[0103] The thickness of one layer (x) in the resin sheet is preferably 0.01 mm or more, more preferably 0.05 mm or more, even more preferably 0.10 mm or more, and also preferably 3 mm or less, more preferably 2.5 mm or less, even more preferably 2 mm or less, even more preferably 1.5 mm or less, and particularly preferably 1 mm or less. If the resin sheet has multiple layers (x), the thickness of each of the multiple layers (x) in the resin sheet may be the same or different.

[0104] The thickness of the resin sheet is preferably 0.1 mm or more, more preferably 0.4 mm or more, and even more preferably 0.7 mm or more, from the viewpoint of easily improving penetration resistance, and from the viewpoint of ease of handling, it is preferably 3 mm or less, more preferably 2.5 mm or less, even more preferably 2 mm or less, even more preferably 1.5 mm or less, and particularly preferably 1 mm or less. The thickness of the resin sheet is measured using conventionally known methods, such as contact-type or non-contact-type thickness gauges.

[0105] In one embodiment of the present invention, the haze of the resin sheet of the present invention is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less. Since a smaller haze increases the transparency of the resin sheet, the lower limit is not particularly limited and may be, for example, 0.01%. The haze of the resin sheet can be measured using a haze meter in accordance with JIS K7136:2000, and can be measured, for example, by the method described in the examples.

[0106] The resin sheet of the present invention also exhibits excellent transparency (transparency during slow cooling) after heating to 140°C and then slowly cooling from 140°C to 23°C at a rate of 0.1°C / min. Transparency during slow cooling can be evaluated by the haze during slow cooling (slow cooling haze). The slow cooling haze of the resin sheet of the present invention is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less. Since the transparency of the resin sheet increases as the haze decreases, the lower limit is not particularly limited and may be, for example, 0.01% or more. The slow cooling haze of the resin sheet can be determined by preparing a laminated glass having the resin sheet as an interlayer, heating the laminated glass to 140°C, and then slowly cooling from 140°C to 23°C at a rate of 0.1°C / min, and measuring the haze with a haze meter in accordance with JIS K7136:2000, for example, by the method described in the examples.

[0107] In one embodiment of the present invention, the storage modulus (E') of the resin sheet of the present invention, measured by dynamic viscoelasticity measurement at 50°C and a frequency of 1 Hz, is preferably 20 MPa or more, more preferably 30 MPa or more, even more preferably 60 MPa or more, and even more preferably 100 MPa or more, from the viewpoint of good self-supporting properties. Furthermore, from the viewpoint of easily improving puncture resistance, it may be preferably 1500 MPa or less, more preferably 1200 MPa or less, and even more preferably 900 MPa or less. The storage modulus can be measured using a dynamic viscoelasticity measuring device, for example, by the method described in the examples.

[0108] In one embodiment of the present invention, the resin sheet of the present invention may have a penetration energy of 10 J or more, more preferably 12 J or more, and even more preferably 14 J or more, from the viewpoint of penetration resistance. The penetration energy is measured at 200°C and 50 kgf / cm² for the molten kneaded acetal compound. 2A sheet, for example, with a thickness of 0.8 mm, obtained by compression molding at a pressure of (50 MPa) for 5 minutes, is used as the test specimen. The test is performed using a drop-weight impact tester in accordance with ASTM D3763, under the conditions of a measurement temperature of 23°C, a load of 2 kg, and an impact velocity of 9 m / s. The SS curve area can be calculated from the area of ​​the SS curve from the moment the striker tip touches the specimen (sensing the test force) to the moment of penetration (when the test force returns to zero).

[0109] From the viewpoint of preventing foaming during the manufacturing of laminated glass and preventing a decrease in adhesive strength to the substrate, a low water content is preferable for the resin sheet. The water content of the resin sheet is preferably 1% by mass or less, more preferably 0.9% by mass or less. Furthermore, from the viewpoint of adjusting the adhesive strength to the glass within an appropriate range and easily improving puncture resistance, the lower limit of the water content is preferably 0.1% by mass or more. The water content can be measured by coulometric titration.

[0110] [Method for manufacturing resin sheets] The method for producing the resin sheet of the present invention is not particularly limited. For example, the resin composition containing the acetalized material of the present invention may be formed into a sheet by known methods such as extrusion molding, press molding, blow molding, injection molding, and solution casting. Among the known methods, a preferred method involves supplying the acetalized material and, if necessary, additives to an extruder, kneading and melting the mixture, then extruding the resulting molten mixture from a die and taking it up with a taker to form a sheet. The resin temperature during extrusion is preferably 170 to 250°C, more preferably 180 to 240°C, and even more preferably 190 to 220°C. If the resin temperature during extrusion is below the above upper limit, the decomposition of the acetalized material is suppressed, making it difficult to color the sheet. If the resin temperature during extrusion is above the above lower limit, the acetalized material melts completely, making it easier to obtain a sheet with a good appearance and to suppress the generation of volatile substances. Furthermore, in order to efficiently remove volatile substances, it is preferable to remove them from the vent port of the extruder by reducing the pressure.

[0111] [Interlayer for laminated glass] The resin sheet of the present invention is suitably used as an interlayer film for laminated glass (hereinafter, also simply referred to as an interlayer film). Accordingly, the present invention encompasses an interlayer film for laminated glass composed of the resin sheet of the present invention. The interlayer film for laminated glass of the present invention is suitably used in various applications such as moving bodies including automobiles, buildings, and solar cells. In one embodiment of the present invention, the interlayer film for laminated glass of the present invention is excellent in transparency, self-supporting property, and adhesiveness to base materials such as glass, and thus is particularly suitably used as an interlayer film for laminated glass for structural materials.

[0112] [Laminated Glass] The present invention also encompasses a laminated glass comprising two glass plates and the interlayer film for laminated glass of the present invention disposed between the two glass plates. Since the laminated glass includes the interlayer film for laminated glass composed of the above resin sheet, it has excellent transparency.

[0113] As the glass plate to be laminated with the interlayer film, for example, inorganic glasses such as float glass, tempered glass, wired plate glass, and heat ray absorbing plate glass, as well as conventionally known organic glasses such as polymethyl methacrylate and polycarbonate can be used. These may be either colorless or colored. One of these may be used alone, or two or more thereof may be used in combination. The thickness of one glass plate is not particularly limited, and may be, for example, 1 to 10 mm, preferably 2 to 6 mm. Furthermore, the thicknesses of the two glass plates may be the same or different.

[0114] The laminated glass of the present invention can be produced by a conventionally known method. Examples thereof include a method using a vacuum laminator apparatus, a method using a vacuum bag, a method using a vacuum ring, and a method using nip rolls. After temporary adhesion by the above method, the assembly may be placed in an autoclave for final adhesion.

[0115] When a vacuum laminator apparatus is used, for example, 1×10 -6 ~1×10 -1Laminated glass can be manufactured by laminating a glass plate, an interlayer, and an optional layer (e.g., an adhesive resin layer) under reduced pressure of MPa at 60-200°C, particularly 80-160°C. A method using a vacuum bag or vacuum ring is described, for example, in European Patent No. 1235683, and is suitable for 2 × 10 -2 ~3×10 -2 Laminated glass can be manufactured by laminating a glass plate, an interlayer, and any other layer under a pressure of approximately MPa at a temperature of 100-160°C.

[0116] An example of a manufacturing method using nip rolls is a method in which a glass plate, an interlayer, and an arbitrary layer are laminated, a first temporary bonding is performed at a temperature below the flow initiation temperature of the acetalized material, and then compression is performed at a temperature close to the flow initiation temperature. Specifically, for example, this method involves heating to 30-70°C with an infrared heater, degassing with a roll, and then heating again to 50-120°C before compression with a roll to bond or temporarily bond the layers.

[0117] When the laminated glass is placed in an autoclave for further bonding after temporary bonding, the operating conditions for the autoclave process are appropriately selected depending on the thickness and composition of the laminated glass, but it is preferable to process it at a pressure of 1 to 1.5 MPa and a temperature of 130 to 145°C for 1 to 3 hours.

[0118] Because the acetalized material has high transparency, the laminated glass of the present invention exhibits excellent transparency. In one embodiment of the present invention, the haze of the laminated glass is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less. Since the transparency of the laminated glass increases as the haze decreases, the lower limit is not particularly limited and may be, for example, 0.01%. The haze of the laminated glass is measured using a haze meter in accordance with JIS K7136:2000.

[0119] In one embodiment of the present invention, the laminated glass of the present invention exhibits excellent transparency even after being heated to 140°C and then slowly cooled from 140°C to 23°C at a rate of 0.1°C / min. The haze (slow cooling haze) after heating the laminated glass to 140°C and then slowly cooling from 140°C to 23°C at a rate of 0.1°C / min is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less. Since a smaller haze increases the transparency of the laminated glass, the lower limit is not particularly limited and may be, for example, 0.01%. The slow cooling haze is also measured using a haze meter in accordance with JIS K7136:2000.

[0120] In one embodiment of the present invention, it is preferable that the laminated glass has excellent adhesion between the glass plate and the interlayer. In one embodiment of the present invention, the maximum shear stress measured by the compression shear strength test described in International Publication No. 1999 / 058334 is preferably 20 to 40 MPa, more preferably 22 to 38 MPa, and even more preferably 24 to 36 MPa. If the maximum shear stress is above the lower limit, the adhesion is sufficiently high, which tends to suppress the scattering of glass when the glass breaks, and if it is below the upper limit, it is easier to suppress the decrease in penetration resistance when the glass breaks.

[0121] The laminated glass of the present invention can be suitably used in automotive windshields, automotive side windows, automotive sunroofs, automotive rear windows, head-up display glass, laminates for facades, exterior walls and roofs, panels, doors, windows, walls, roofs, sunroofs, soundproof walls, display windows, balconies, railing walls and other building materials, partition glass members for conference rooms, solar panels, etc., but is not limited to these uses. [Examples]

[0122] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0123] The analytical methods and measurement methods for each physical property of the ethylene vinyl alcohol copolymer used as a raw material in the examples and comparative examples, and the evaluation methods for the resin sheet and laminated glass are shown below.

[0124] <Content and degree of acetalization of each monomer unit> The ethylene vinyl alcohol copolymers (EVOH1-5) used as raw materials in the examples and comparative examples, as well as the acetalized products of the ethylene vinyl alcohol copolymers obtained in the examples and comparative examples, were analyzed as follows to determine the content (in mol%) of ethylene units, vinyl alcohol units, and acetal units (acetalized vinyl alcohol units) in the ethylene vinyl alcohol copolymers and their acetalized products, and the degree of acetalization.

[0125] Ethylene vinyl alcohol copolymer was dissolved in dimethyl sulfoxide (DMSO) at 120°C, and the resulting DMSO solution was cooled to room temperature. Then, N,N-dimethyl-4-aminopyridine and acetic anhydride were added to the DMSO solution and stirred for 1 hour to allow the reaction to proceed. The copolymer was reprecipitated and washed from the resulting reaction solution using deionized water and acetone, and then dried to obtain ethylene vinyl acetate copolymer. The deuterated dimethyl sulfoxide (DMSO-d6) solution of the obtained ethylene vinyl acetate copolymer was measured using a 400 MHz proton NMR spectrometer with 256 cumulative measurements. From the resulting spectrum, the content of ethylene units (n) relative to the total monomer units constituting the ethylene vinyl alcohol copolymer was calculated from the intensity ratio of the methine proton peaks (1.1-1.9 ppm peaks) derived from ethylene units and vinyl acetate units, and the terminal methyl proton peak (2.0 ppm peak) derived from vinyl acetate units. Since ethylene units are not affected by the acetalization reaction, the ethylene unit content (n) in the ethylene vinyl alcohol copolymer is equal to the ethylene unit content (n) relative to the total monomer units constituting the acetalized EVOH obtained after acetalization. The content of vinyl alcohol units (l), vinyl acetate units (m), and acetal units (k) relative to the total monomer units constituting the acetalized EVOH was determined by the following method. A DMSO-d6 solution of the acetalized EVOH was measured using a 400 MHz proton NMR spectrometer with 256 cumulative measurements. From the obtained spectrum, the content of each monomer unit was calculated using the intensity ratio of the methine proton peaks (peaks from 1.0 to 1.8 ppm) derived from ethylene units, vinyl alcohol units, and vinyl acetate units, and the terminal methyl proton peaks (peaks from 0.8 to 1.0 ppm) derived from acetal units, as well as the ethylene unit content (n) of the ethylene vinyl alcohol copolymer.

[0126] The degree of acetalization of the acetalized EVOH was determined using the following formula, based on the content of vinyl alcohol units (l), vinyl acetate units (m), and acetal units (k) obtained above. Acetalization degree (mol %) = {k / (k+l+m)} × 100

[0127] <Melt Flow Rate (MFR)> The melt flow rate of the ethylene vinyl alcohol copolymer (after drying) used in the examples and comparative examples was measured in accordance with JIS K7210:2014 under conditions of 190°C and a 2.16 kg load.

[0128] <Median diameter of pores, surface area of ​​pores> After freeze-drying the ethylene vinyl alcohol copolymer porous bodies obtained in each of the production examples described below, or the EVOH acetalized materials obtained in the examples and comparative examples, at -80°C, 0.5 g was placed in a standard 5 cc powder cell (stem volume 0.4 cc), and the median diameter and pore surface area of ​​pores with a diameter in the range of 0.005 to 100 μm were measured using a micromeristic pore distribution analyzer (Shimadzu Corporation, Autopore V9620) under an initial pressure of 2.6 kPa. The median diameter of the pores is the median diameter (d50) for all pores with a diameter in the range of 0.005 to 100 μm in the log differential pore volume distribution. The mercury parameters were set to a mercury contact angle of 130 degrees and a mercury surface tension of 485 hynes / cm.

[0129] <Presence or absence of pores at the center of gravity of a porous material> Cross-sections of the porous bodies obtained in each of the manufacturing examples described below, perpendicular to the pore orientation direction (extrusion direction) passing through the center of gravity, were prepared using a single-edged razor while the porous bodies were frozen with liquid nitrogen. The prepared cross-sections of the porous bodies were observed using a scanning electron microscope (SEM, Hitachi High-Tech Corporation, SU-70) to evaluate whether each porous body had pores at its center of gravity.

[0130] <Average particle size> For 100g of ethylene vinyl alcohol copolymer obtained in Production Examples 1-5 described below, the average particle size of the measurement sample (freeze-dried EVOH porous pellets) was measured using Verder Scientific's "CAMSIZER XT". The average particle size was defined as the particle size at which the cumulative particle size distribution from the smallest particle size side of the circle equivalent particle size, calculated by dynamic image analysis in accordance with ISO 13322-2 (2006), reached 50% (by volume) (Q3 50.0%).

[0131] <Heat of fusion (ΔH)> The melted acetalized EVOH obtained in the examples and comparative examples were heated to a differential scanning calorimeter (DSC) (Mettler Toledo, TGA / DSC1 Star System) from 25°C to 230°C at a heating rate of 10°C / min to melt the samples. After cooling from 230°C to -30°C at a cooling rate of 10°C / min, the heat of fusion (ΔH) was measured when the samples were heated again from -30°C to 230°C at a heating rate of 10°C / min.

[0132] <Transparency> (Haze on resin sheets) Test specimens measuring 20 mm in length and 5 mm in width were cut from the resin sheets obtained in the examples and comparative examples. The haze of the obtained test specimens was measured using a haze meter (SH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136:2000. (Haze during slow cooling of laminated glass (slow cooling haze)) The laminated glass obtained in the examples and comparative examples was cut to a size of 25 mm x 25 mm to obtain test samples. The obtained test samples were heated to 140°C and then slowly cooled to 23°C at a rate of 0.1°C / min. The haze of the test samples after the slow cooling operation was measured using a haze meter (SH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136:2000.

[0133] <Self-supporting properties under high-temperature environments (storage modulus at 50°C)> Test specimens measuring 20 mm in length and 5 mm in width were cut from the resin sheets obtained in the examples and comparative examples, and the storage modulus (E') was measured using a dynamic viscoelasticity measuring device (manufactured by UBM Co., Ltd.) under the conditions of a measurement temperature of 50°C and a frequency of 1 Hz. The obtained value serves as an indicator of the self-supporting ability of the interlayer for laminated glass under high-temperature environments when the resin sheet is used as an interlayer for laminated glass.

[0134] In the examples and comparative examples, pelletized ethylene vinyl alcohol copolymers (EVOH1 to EVOH5) produced by the following methods were used as raw materials.

[0135] <Manufacturing Example 1> An EVOH solution containing 100 parts by mass of EVOH with an ethylene unit content of 44 mol% and a degree of saponification of 99.98 mol%, 60 parts by mass of methanol, and 40 parts by mass of water was continuously supplied from the top stage of a 10-stage tray column with a column diameter of 0.3 m, and steam was blown in from the bottom stage, bringing the EVOH solution into contact with the steam in a countercurrent. The temperature inside the column was 130°C and the pressure inside the column was 0.3 MPa. The hydrated EVOH obtained by contacting it with steam in a countercurrent was withdrawn from the bottom of the column. The temperature of the obtained hydrated EVOH was 120°C and the water content was 52.4% by mass. The methanol content was 0.02% by mass. Water-containing EVOH was supplied at 42 kg / hr to a twin-screw extruder with a back slit, and extruded under the following conditions through a die with a diameter of 3.0 mm and 8 holes attached to the end of the extruder. The molten material was cut with a hot cutter having two blades at a distance of 0.05 mm from the die to obtain flattened spherical pellets of porous EVOH. The flow rate of the cutter circulating water was 300 liters / min, and the rotation speed of the cutter blades was 3000 rpm. The resin temperature (outlet) at this time was 95°C, and the moisture content was 34% by mass. <Conditions for a twin-screw extruder> L / D: 14 Caliber: 30mm Screw: Full Flight Rotation speed: 300 rpm Cylinder temperature: 90℃ Die temperature: 120℃ The obtained EVOH porous material was washed with water at 50°C until the sodium acetate content reached 0.002% by mass (sodium equivalent), and the washing water was filtered off to obtain a flattened spherical pellet-shaped porous material of ethylene vinyl alcohol copolymer (EVOH1). The obtained EVOH1 was a flattened spherical pellet with an average particle diameter of 3.2 mm. Observation with an electron microscope revealed that the EVOH1 pellets had pores ranging in diameter from 0.003 μm to 100 μm, with a median diameter of 0.07 μm, pores located at the center of gravity of the porous body, and, in a cross-section of the porous body passing through its center of gravity, when the shortest distance L from the center of gravity of the cross-section to the surface of the porous body is defined as the distance L, pores were found in a region within 10% of the distance L from the center of gravity of the cross-section. Table 1 shows the median diameter, average particle diameter, and pore surface area of ​​the obtained EVOH1 pores.

[0136] <Manufacturing Example 2> A porous body of ethylene vinyl alcohol copolymer (EVOH2) in pellet form was obtained in the same manner as in Production Example 1, except that the ethylene content was set to 32 mol%. The obtained EVOH2 pellets were flattened and spherical with an average particle diameter of 3.2 mm. Observation with an electron microscope confirmed that the EVOH2 pellets had pores ranging in diameter from 0.003 μm to 100 μm, with a median diameter of 0.11 μm, and that pores were located at the center of gravity of the porous body and within 10% of the distance L from the center of gravity of the cross-section of the porous body. Table 1 shows the median diameter, average particle diameter, and pore surface area of ​​the obtained EVOH2 pores.

[0137] <Manufacturing Example 3> A porous body of ethylene vinyl alcohol copolymer (EVOH3) in pellet form was obtained in the same manner as in Production Example 1, except that the ethylene content was set to 27 mol%. The obtained EVOH3 pellets were flattened and spherical with an average particle diameter of 3.2 mm. Observation with an electron microscope confirmed that the EVOH3 pellets had pores ranging in diameter from 0.003 μm to 100 μm, with a median diameter of 0.11 μm, and that pores were located at the center of gravity of the porous body and within 10% of the distance L from the center of gravity of the cross-section of the porous body. Table 1 shows the median diameter, average particle size, and pore surface area of ​​the obtained EVOH3 pores.

[0138] <Manufacturing Example 4> The ethylene vinyl alcohol copolymer (EVOH1) obtained in Production Example 1 was fed into a twin-screw extruder and pelletized at a resin temperature of 100°C at the discharge port. The input rate of EVOH1 per unit time was 10 kg / hr. The specifications of the twin-screw extruder are shown below. <Conditions for a twin-screw extruder> L / D: 45.5 Caliber: 30mmΦ Screw: Fully meshing in the same direction Rotation speed: 300 rpm Die diameter: 3.0mmΦ Number of dice holes: 5 The obtained pellets were dried in a fluidized bed dryer at 100°C for 15 hours, and then dried in a static dryer at 100°C for another 15 hours to obtain pelletized ethylene vinyl alcohol copolymer (EVOH4). The obtained EVOH4 pellets were spherical with an average particle diameter of 2.9 mm, and observation with an electron microscope did not confirm that EVOH4 had pores. The average particle diameter and pore surface area of ​​the obtained EVOH4 are shown in Table 2.

[0139] <Manufacturing Example 5> The ethylene vinyl alcohol copolymer (EVOH2) obtained in Production Example 2 was pelletized and dried in the same manner as in Production Example 4 to obtain ethylene vinyl alcohol copolymer (EVOH5). The obtained EVOH5 pellets were spherical with an average particle diameter of 3.1 mm, and observation with an electron microscope did not confirm that EVOH5 had pores. The average particle diameter and pore surface area of ​​the obtained EVOH5 are shown in Table 2.

[0140] <Example 1> (Synthesis of acetalized ethylene vinyl alcohol copolymers) 100 parts by mass of the porous ethylene vinyl alcohol copolymer (EVOH2) obtained in Production Example 2 was dispersed in 377 parts by mass of water, and 20 parts by mass of isobutyraldehyde was added. The resulting dispersion was heated to 60°C under stirring. Stirring was continued for 2 hours to impregnate the dispersion of ethylene vinyl alcohol copolymer with isobutyraldehyde. Then, at 60°C, 10 parts by mass of 1 M hydrochloric acid was added to the dispersion to carry out the acetalization reaction. Two hours after the first addition of hydrochloric acid, 40 parts by mass of 1 M hydrochloric acid was added, and the acetalization reaction was carried out for a further 4 hours. The acetal product produced by acetalization was in a solid state. Then, the acetalization reaction was stopped by neutralizing the dispersion with 75 parts by mass of 1 M sodium hydroxide. To neutralize the solid interior of the acetal product, the dispersion was stirred at 60°C for a further 8 hours. The neutralized acetalized material was filtered off, and 500 parts by mass of deionized water was added to the acetalized material and stirred at 60°C for 6 hours to wash it. The acetalized material was filtered off again, and 500 parts by mass of deionized water was added to the acetalized material and stirred at 60°C for 6 hours to wash it a second time. The washing water was filtered off, and vacuum drying was carried out at 60°C for 8 hours to obtain 109 parts by mass (100% yield) of pelletized EVOH acetalized material. The ethylene unit content of the obtained EVOH acetalized material was 32 mol%, and the degree of acetalization was 29 mol%. Furthermore, the obtained EVOH acetalized material was a porous material having a pore structure similar to that of the raw material EVOH2.

[0141] The acetalized EVOH obtained above was melted and kneaded for 3 minutes at a chamber temperature of 200°C and a rotation speed of 100 rpm using a Laboplast Mill (Toyo Seiki Seisakusho Co., Ltd., "4M150"). The contents of the chamber were removed and cooled to obtain a molten mixture. The resulting molten mixture was heated at 210°C at a rate of 50 kgf / cm². 2 A resin sheet with a thickness of 0.8 mm was obtained by compression molding at a pressure of 50 MPa for 5 minutes. The obtained sheet was sandwiched between two 2.7 mm thick float glass sheets and placed in a vacuum laminator (Nisshinbo Mechatronics Co., Ltd. 1522N). The inside of the vacuum laminator was depressurized at 100°C for 1 minute. While maintaining the depressurized state and temperature, it was pressed at 30 kPa for 5 minutes to obtain a temporary bond. The obtained temporary bond was placed in an autoclave and treated at 140°C and 1.2 MPa for 30 minutes to obtain laminated glass.

[0142] <Examples 2-5> Pelletized EVOH acetals were obtained in the same manner as in Example 1, except that the type of ethylene vinyl alcohol copolymer used and the amount of aldehyde added were changed as shown in Table 1. The obtained EVOH acetals were porous bodies having a pore structure similar to that of the raw material ethylene vinyl alcohol copolymer. Using the obtained EVOH acetals, molten compound, resin sheet, and laminated glass were obtained in the same manner as in Example 1.

[0143] <Example 6> 100 parts by mass of the ethylene vinyl alcohol copolymer porous material (EVOH2) obtained in Production Example 2 was dispersed in 315 parts by mass of methanol, and the resulting dispersion was heated to 60°C under stirring. 40 parts by mass of 1 M hydrochloric acid was added to the dispersion, followed by 17 parts by mass of isobutyraldehyde, which was dispersed, and the acetalization reaction was carried out while maintaining the temperature at 60°C. As the reaction progressed, the EVOH2 dissolved, and a homogeneous solution was obtained. After holding the reaction for 6 hours from the start of the reaction, the acetalization reaction was stopped by neutralizing the reaction solution with 6.4 parts by mass of sodium bicarbonate. After neutralization, 500 parts by mass of methanol was added to the reaction solution to homogenize it, and then the reaction solution was added dropwise to 2000 parts by mass of ion-exchanged water to precipitate the acetal product produced by the acetalization reaction. The precipitated acetal product was filtered off and dispersed in ion-exchanged water. The resulting dispersion was stirred at 23°C for 15 minutes to wash off the acetal product with water, and the ion-exchanged water was filtered off. This washing and filtration process was repeated two more times. Subsequently, vacuum drying was performed at 60°C for 8 hours to obtain 102 parts by mass (yield 93%) of powdered EVOH acetal. The obtained EVOH acetal had an ethylene unit content of 32 mol% and a degree of acetalization of 25 mol%. Furthermore, the obtained EVOH acetal did not have pores. Using the acetalized EVOH obtained above, a molten compound, a resin sheet, and laminated glass were obtained in the same manner as in Example 1.

[0144] Table 1 shows the evaluation results of the molten compound, resin sheet, and laminated glass obtained in the examples.

[0145] [Table 1]

[0146] <Comparative Examples 1-2> Except for changing the type of ethylene vinyl alcohol copolymer used as a raw material and the amount of aldehyde added, as shown in Table 2, EVOH acetal was obtained in the same manner as in Example 1. Using the obtained EVOH acetal, a molten compound, a resin sheet, and laminated glass were obtained in the same manner as in Example 1.

[0147] <Comparative Example 3> 100 parts by mass of ethylene vinyl alcohol copolymer (EVOH4) obtained in Production Example 4 was dispersed in a mixed solvent of 500 parts by mass of methanol and 50 parts by mass of deionized water. The resulting dispersion was heated to 60°C under stirring to completely dissolve the copolymer. It took 1 hour for the copolymer to completely dissolve and become a homogeneous solution. 40 parts by mass of 1 M hydrochloric acid was added to the homogeneous solution of ethylene vinyl alcohol copolymer and stirred to mix. Then 33 parts by mass of isobutyraldehyde was added and the mixture was maintained at 60°C to carry out the acetalization reaction. After 6 hours from the start of the reaction, 6.4 parts by mass of sodium carbonate was added to neutralize the reaction and stop the acetalization reaction, obtaining a reaction solution containing the acetalized product. In the subsequent step of reprecipitation of the acetalized product generated by the acetalization reaction, 500 parts by mass of methanol was added to the reaction solution to reduce the precipitate size. 2000 parts by mass of deionized water was added dropwise to this diluted solution to precipitate the generated acetalized product. The precipitate was filtered off, dispersed again in ion-exchanged water, and stirred at 23°C for 15 minutes to wash the acetalized material, which was then filtered off. This washing and filtration process was repeated two more times. After this, vacuum drying was carried out at 60°C for 8 hours to obtain 102 parts by mass (yield 93%) of powdered EVOH acetalized material. The ethylene unit content of the obtained EVOH acetalized material was 44 mol%, and the degree of acetalization was 59 mol%. Using the obtained EVOH acetalized material, a molten compound, a resin sheet, and laminated glass were obtained in the same manner as in Example 1.

[0148] Table 2 shows the evaluation results for the molten compound, resin sheet, and laminated glass obtained in the comparative example.

[0149] [Table 2]

[0150] As shown in Table 1, in Examples 1 to 6, it was confirmed that even when the ethylene vinyl alcohol copolymer was not dissolved in the solvent before acetalization and acetalization was performed in a heterogeneous system, the resulting acetalized EVOH product exhibited excellent transparency. In contrast, as shown in Table 2, the acetalized EVOH products obtained in Comparative Examples 1 to 2 had low transparency. Furthermore, in Examples 1 to 6, the porous EVOH material used as a raw material had sufficient strength, and no blockage of the production line due to the porous material was observed. In Comparative Example 3, the process of dissolving ethylene vinyl alcohol in the solvent before acetalization required a long time. Moreover, the acetalized EVOH product obtained in Comparative Example 3 had a low storage modulus at 50°C and insufficient self-supporting ability in high-temperature environments.

[0151] <Examples 7-10> Pelletized ethylene vinyl alcohol copolymer acetals were obtained in the same manner as in Example 1, except that the type of ethylene vinyl alcohol copolymer used as a raw material and the reaction conditions were changed as shown in Table 3. The obtained ethylene vinyl alcohol copolymer acetals were porous bodies having a pore structure similar to that of the raw material ethylene vinyl alcohol copolymer. Using the obtained ethylene vinyl alcohol copolymer acetals, molten compound, resin sheet, and laminated glass were obtained in the same manner as in Example 1.

[0152] <Comparative Example 4> Except for changing the type of ethylene vinyl alcohol copolymer used as a raw material and the reaction conditions as shown in Table 3, EVOH acetal was obtained in the same manner as in Example 1. Using the obtained EVOH acetal, a molten compound, a resin sheet, and laminated glass were obtained in the same manner as in Example 1.

[0153] Table 3 shows the evaluation results of the molten compound, resin sheet, and laminated glass obtained in Examples 7-10 and Comparative Example 4.

[0154] [Table 3]

[0155] As shown in Table 3, in Examples 7-10, it was confirmed that even when the ethylene vinyl alcohol copolymer was not dissolved in the solvent before acetalization and acetalization was performed in a heterogeneous system, the resulting acetalized EVOH product exhibited excellent transparency. In contrast, the acetalized EVOH product obtained in Comparative Example 4 had low transparency. Furthermore, in Examples 7-10, the porous EVOH material used as a raw material had sufficient strength, and no blockage of the production line due to the porous material was observed.

Claims

1. A method for producing an acetalized product of an ethylene vinyl alcohol copolymer by acetalizing an ethylene vinyl alcohol copolymer, wherein the ethylene vinyl alcohol copolymer is a porous material, the acetalization is carried out by a solid-liquid reaction, and the haze of the acetalized product of the ethylene vinyl alcohol copolymer is 1% or less.

2. The method according to claim 1, wherein the median diameter of the pores in the porous material is 0.005 μm or more.

3. The method according to claim 1 or 2, wherein the porous body has pores at the center of gravity of the porous body.

4. The surface area of ​​the pores in the porous material is 25 m². ２ The method according to any one of claims 1 to 3, wherein the amount is 1 / g or more.

5. The method according to any one of claims 1 to 4, wherein the ethylene content of the ethylene vinyl alcohol copolymer is 20 to 60 mol%.

6. The method according to any one of claims 1 to 5, wherein the average particle size of the porous material is 1 mm or more.

7. The method according to any one of claims 1 to 6, wherein the porous body is in the form of pellets.

8. The method according to any one of claims 1 to 7, comprising preparing a dispersion containing an ethylene vinyl alcohol copolymer and a solvent, and adding an aldehyde and a catalyst in that order to the dispersion to perform acetalization.

9. The method according to claim 8, wherein the solvent includes water.

10. An acetalized ethylene vinyl alcohol copolymer having a porous structure with a median pore diameter of 0.005 μm or more and a haze of 1% or less.

11. The acetalized ethylene vinyl alcohol copolymer according to claim 10, wherein the heat of fusion (ΔH) is greater than 0 J / g.

12. The acetalized ethylene vinyl alcohol copolymer according to claim 10 or 11, wherein the ethylene unit content is 20 to 60 mol% relative to the total monomer units constituting the acetalized product.

13. The acetalized ethylene vinyl alcohol copolymer according to any one of claims 10 to 12, wherein the content of acetal units (acetalized vinyl alcohol units) is 1 to 70 mol% relative to the total monomer units constituting the acetalized product.

14. A resin sheet comprising an acetalized ethylene vinyl alcohol copolymer according to any one of claims 10 to 13 as a resin component.

15. The resin sheet according to claim 14, wherein the storage modulus at 50°C and a frequency of 1 Hz is 20 MPa or more.

16. An interlayer for laminated glass made of a resin sheet according to claim 14 or 15.

17. A laminated glass comprising two glass plates and an interlayer for laminated glass according to claim 16, disposed between the two glass plates.

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