JP2024095210A - Resin composition, film, laminate, interlayer film for laminated glass, and laminated glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition which can suppress a decrease in hardness and impart superior impact resistance while maintaining original transparency of a resin, and to provide a film, a laminate, an interlayer film for laminated glass, and laminated glass using the resin composition.

SOLUTION: The resin composition contains a polyvinyl acetal and multilayer-structured particles. The multilayer-structured particles have a multilayer structure including a first hard layer, a soft layer, and a second hard layer in this order toward the outer surface. Each of the first hard layer and the second hard layer contains a polymer having a glass transition temperature of 25°C or higher. The soft layer contains a polymer having a glass transition temperature lower than 25°C. The film, the laminate, the interlayer film for laminated glass, and the laminated glass use the resin composition.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

This disclosure relates to a resin composition, as well as a film, a laminate, an interlayer film for laminated glass, and laminated glass that uses the resin composition.

A widely known type of laminated glass used in vehicle and architectural window panes is one in which an interlayer film for laminated glass is interposed between at least a pair of panes of glass and these are integrated together. Laminated glass is required to have properties such as transparency and impact resistance due to its intended use.

Conventionally, in order to ensure impact resistance, an interlayer film for laminated glass is known that uses a resin composition containing polyvinyl acetal, which has impact resistance. Patent Document 1 discloses a resin composition consisting of polyvinyl acetal and a multilayer structure polymer having a specific inner layer and outer layer.

JP 2003-40654 A

The laminated glass using the resin composition described in Patent Document 1 has improved impact resistance, but the hardness and haze value of the resin composition are unclear, and the balance of these performance groups (impact resistance, hardness, and haze) may be insufficient. Therefore, there has been a demand for the development of a resin composition with better performance.
An object of the present disclosure is to provide a resin composition that can suppress a decrease in hardness and impart superior impact resistance while maintaining the transparency inherent to the resin, and to provide a film, a laminate, an interlayer film for laminated glass, and laminated glass each using the same.

The resin composition, film, laminate, interlayer film for laminated glass, and laminated glass according to the present disclosure have the following configurations [1] to [12].
[1] A resin composition comprising: a polyvinyl acetal; and a multilayer-structured particle; the multilayer-structured particle has a multilayer structure including, in this order toward an outer surface, a first hard layer, a soft layer, and a second hard layer; each of the first hard layer and the second hard layer includes a polymer having a glass transition temperature of 25° C. or higher; and the soft layer includes a polymer having a glass transition temperature of lower than 25° C.
[2] The resin composition described in [1], wherein at least one or both of the first hard layer and the second hard layer contain a polymer having a structural unit derived from a methacrylic acid ester monomer.
[3] The resin composition according to [1] or [2], wherein the soft layer contains a polymer having a structural unit derived from an acrylic acid ester monomer.
[4] The resin composition according to any one of [1] to [3], wherein at least one or both of the first hard layer and the second hard layer contains a crosslinked body having a structural unit derived from a methacrylic acid ester monomer, and the soft layer contains a crosslinked body having a structural unit derived from an acrylic acid ester monomer.
[5] The multilayered particle contains the first hard layer in an amount of 5 to 55% by mass, the soft layer in an amount of 20 to 50% by mass, and the second hard layer in an amount of 5 to 65% by mass. [1] The resin composition according to any one of [4] to [5].
[6] The resin composition according to any one of [1] to [5], wherein the content mass ratio of the polyvinyl acetal to the multilayer structure particles is 50:50 to 90:10.
[7] The resin composition according to any one of [1] to [6], wherein the polyvinyl acetal is polyvinyl butyral.
[8] The resin composition according to any one of [1] to [7], further comprising 10 to 100 parts by mass of a (meth)acrylic acid ester polymer relative to 100 parts by mass of the multilayer structure particles.
[9] A film comprising the resin composition according to any one of [1] to [8].
[10] A laminate comprising the film according to [9].
[11] An interlayer film for laminated glass, comprising the resin composition according to any one of [1] to [8].
[12] A laminated glass comprising the interlayer film for laminated glass according to [11].

The present disclosure provides a resin composition that can suppress a decrease in hardness and impart superior impact resistance while maintaining the inherent transparency of the resin, as well as a film, laminate, interlayer film for laminated glass, and laminated glass that use the resin.

FIG. 2 is a schematic cross-sectional view of an example of a multilayered particle contained in a resin composition according to the present disclosure.

It is known to use other components such as plasticizers and metal components in combination with polyvinyl acetal, which has impact resistance. However, the use of these other components can result in whitening, reduced strength, and other problems that can reduce transparency and impact resistance compared to when polyvinyl acetal resin is used alone. Therefore, in Patent Document 1, impact resistance is improved by using a multilayer structure polymer (two-layer core-shell rubber) with specific inner and outer layers, but the performance balance between transparency and hardness may be insufficient.

On the other hand, the resin composition according to the present disclosure (hereinafter also referred to as the present resin composition) uses multilayer particles having a specific first hard layer, a soft layer, and a second hard layer, which are components other than the plasticizer and metal components that have been used conventionally. As a result, the present resin composition can suppress a decrease in hardness and exhibit the excellent impact resistance of polyvinyl acetal while maintaining the transparency inherent to the resin. Therefore, the present resin composition can provide films, laminates, intermediate films for laminated glass, and laminated glass with improved performance while maintaining transparency and hardness. There have been no examples of using polyvinyl acetal and multilayer particles having a specific three layers in combination, as in the present resin composition, and the effects obtained by the resin composition far exceeded expectations.

The following describes in detail an embodiment of the resin composition with reference to the drawings, but the present disclosure is not limited to this embodiment. In addition, the present disclosure can be modified in any manner without departing from the gist of the present disclosure.

<Resin Composition>
The resin composition includes polyvinyl acetal and multilayered particles. Here, as shown in FIG. 1, the multilayered particle 4 has a multilayered structure including a first hard layer 1, a soft layer 2, and a second hard layer 3 in this order toward the outer surface of the particle. In addition, both the first hard layer and the second hard layer include a polymer having a glass transition temperature of 25° C. or higher. The soft layer includes a polymer having a glass transition temperature of less than 25° C. The glass transition temperature of each layer of the multilayered particle can be determined by separating each layer of the multilayered particle and then measuring each layer with a differential scanning calorimeter (DSC). The temperature and heating rate at that time can be appropriately set according to the target sample. In addition, the glass transition temperature of each layer of the multilayered particle can be determined by measurement conditions in accordance with JIS K7121:2012. Specifically, a sample (e.g., materials constituting each layer) is heated once from room temperature (e.g., 25° C.) to 200° C., then cooled to −70° C. or lower, and then heated at a rate of 10° C./min from −70° C. to 200° C. to measure a DSC curve by differential scanning calorimetry. The midpoint glass transition temperature determined from the DSC curve measured during the second heating is regarded as the glass transition temperature of the sample.
In this way, by blending multilayered particles (e.g., a three-layered polymer as shown in FIG. 1 ) with polyvinyl acetal, the resin composition can suppress a decrease in hardness and improve impact resistance while maintaining the transparency of the resin composition, thereby solving the above-mentioned problems.

Each component contained in the resin composition will be described in detail below.
In this specification, the term "to" indicating a range of values means that the values before and after it are included as the lower and upper limits.
In this specification, the term "(meth)acrylic acid ester" refers to either or both of a methacrylic acid ester and an acrylic acid ester. The same applies to "(meth)acrylate" and "(meth)acrylic resin".

[Polyvinyl acetal]
As described above, polyvinyl acetal is contained in the resin composition in order to improve the impact resistance.
The content of polyvinyl acetal in the resin composition is preferably 40% by mass or more. If the content of polyvinyl acetal is 40% by mass or more, it is easy to impart appropriate corrosion resistance and adhesion. From the same viewpoint, the content of polyvinyl acetal is more preferably 50% by mass or more, and even more preferably 60% by mass or more. In addition, the content of polyvinyl acetal is preferably 96% by mass or less. If the content of polyvinyl acetal is 96% by mass or less, it is expected that the added components will improve the breaking strain. From the same viewpoint, the content of polyvinyl acetal is more preferably 90% by mass or less, and even more preferably 80% by mass or less.

Polyvinyl acetal is obtained by acetalizing polyvinyl alcohol, more specifically, by reacting the hydroxyl groups of polyvinyl alcohol with aldehydes in the presence of a catalyst.
Here, it is preferable to use polyvinyl acetal having an average acetalization degree of 40 to 90 mol%. If the average acetalization degree is 40 mol% or more, a suitable water absorption rate can be easily imparted. If the average acetalization degree is 90 mol% or less, the reaction time for obtaining polyvinyl acetal is easily kept within a suitable range, which is preferable in terms of the reaction process. From these viewpoints, the average acetalization degree is more preferably 60 to 85 mol%, and from the viewpoint of water resistance, it is even more preferably 65 to 80 mol%. The above average acetalization degree is a value based on the vinyl acetal component in the polyvinyl acetal described below.

Polyvinyl acetal is usually composed of a vinyl acetal component, a vinyl alcohol component, and a vinyl acetate component. The amount of each of these components can be measured, for example, according to JIS K 6728: 1977 "Testing Method for Polyvinyl Butyral" or by nuclear magnetic resonance (NMR) spectroscopy.

The polyvinyl acetal preferably has a vinyl acetate component content of 20 mol% or less. If the vinyl acetate component content is 20 mol% or less, blocking can be easily prevented during the production of the polyvinyl acetal, and the acetate group can be easily prevented from being hydrolyzed and modified into a carboxyl group under high temperature and high humidity conditions. From the same viewpoint, the vinyl acetate component content is more preferably 5 mol% or less, even more preferably 2 mol% or less, and particularly preferably 1.5 mol% or less.

Polyvinyl alcohol, which is the raw material of polyvinyl acetal, can be obtained, for example, by polymerizing a vinyl ester monomer and saponifying the resulting polymer. The method for polymerizing the vinyl ester monomer is not particularly limited, and conventionally known methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization can be applied. The polymerization initiator used during polymerization can be appropriately selected depending on the polymerization method used, and azo initiators, peroxide initiators, redox initiators, and the like can be used. For the saponification reaction, conventionally known methods such as alcoholysis and hydrolysis using an alkali catalyst or acid catalyst can be applied. Among these, the saponification reaction using methanol as a solvent and caustic soda (NaOH) as a catalyst is simple and most preferred.

From the viewpoint of keeping the blending ratio of the vinyl acetate component of the polyvinyl acetal within the above-mentioned range, the saponification degree of the raw material polyvinyl alcohol is preferably 80 mol% or more, more preferably 95 mol% or more, and even more preferably 98 mol% or more. The saponification degree of polyvinyl alcohol can be measured by a method conforming to JIS K 6726-1994 "Testing method for polyvinyl alcohol".

Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate. When polymerizing the vinyl ester monomers, they can also be copolymerized with other monomers such as α-olefins, as long as the scope of the present disclosure is not impaired.

The average degree of polymerization of the polyvinyl alcohol as a raw material is preferably 100 to 5000. If the average degree of polymerization of polyvinyl alcohol is 100 or more, the penetration resistance and creep resistance of the film obtained using the present resin composition, particularly creep resistance under high temperature and high humidity conditions such as 85°C and 85% RH (relative humidity), can be improved. On the other hand, if the average degree of polymerization is 5000 or less, the film obtained using the present resin composition can be more easily molded. From these viewpoints, the average degree of polymerization of polyvinyl alcohol is more preferably 400 to 3000, more preferably 600 to 2500, particularly preferably 700 to 2300, and most preferably 750 to 2000. The average degree of polymerization of polyvinyl alcohol can be measured, for example, based on JIS K 6726 "Polyvinyl Alcohol Test Method".
In addition, since the resin composition uses specific multilayered particles together with polyvinyl acetal, other components such as plasticizers and metal components may not be used, but these other components may be used. In addition, when using these other components, the resin composition can reduce the amount of these components used compared to conventional methods. Therefore, the resin composition can easily prevent the whitening phenomenon and strength reduction caused by these other components, which have been problems in the past.

From the viewpoint of improving the lamination suitability of the film obtained using this resin composition and obtaining a film with an even better appearance, it is preferable that the average polymerization degree of the polyvinyl acetal is as follows. That is, in a system to which no plasticizer is added, the average polymerization degree of the polyvinyl acetal is preferably 1500 or less, and more preferably 1100 or less. In addition, in a system to which a plasticizer is added, it is preferable to use a polyvinyl acetal with a higher average polymerization degree than in a system to which no plasticizer is added. Specifically, the average polymerization degree of the polyvinyl acetal is preferably 2500 or less, and more preferably 2000 or less.

The solvent used in the production of polyvinyl acetal is not particularly limited, but from the viewpoint of industrial mass production, it is preferable to use water. In this case, it is preferable to dissolve the raw material polyvinyl alcohol sufficiently at a high temperature, for example, a temperature of 90°C or higher, before the reaction. In addition, the concentration of the aqueous solution in which polyvinyl alcohol is dissolved (aqueous polyvinyl alcohol solution) is preferably 5 to 40% by mass. If the concentration of the aqueous polyvinyl alcohol solution is 5% by mass or more, productivity is likely to be improved. On the other hand, if the concentration of the aqueous polyvinyl alcohol solution is 40% by mass or less, stirring during the reaction is easy, and gelation due to intermolecular hydrogen bonds of polyvinyl alcohol is easily suppressed, and unevenness in the reaction can be easily prevented. From these viewpoints, the concentration of the aqueous polyvinyl alcohol solution is more preferably 6 to 20% by mass, and particularly preferably 7 to 15% by mass.

As described above, polyvinyl acetal can be produced by adding an aldehyde to an aqueous solution of polyvinyl alcohol and reacting it, and the catalyst used in this case may be either an organic acid or an inorganic acid. Examples of the catalyst include acetic acid, p-toluenesulfonic acid, hydrochloric acid, nitric acid, sulfuric acid, carbonic acid, and the like. Among these, it is preferable to use an acid selected from hydrochloric acid, nitric acid, and sulfuric acid as the catalyst, since a sufficient reaction rate is achieved and washing after the reaction is easy. In addition, it is more preferable to use hydrochloric acid as the catalyst, since it is easy to handle.
The catalyst concentration in the aqueous polyvinyl alcohol solution after the catalyst is added can be adjusted appropriately depending on the type of catalyst used, but in the case of hydrochloric acid, sulfuric acid, and nitric acid, it is preferably 0.01 to 5 mol/L. If the catalyst concentration is 0.01 mol/L or more, a moderate reaction rate can be easily maintained, and polyvinyl acetal having a desired degree of acetalization and desired physical properties can be easily obtained in a short time. Furthermore, if the catalyst concentration is 5 mol/L or less, the acetalization reaction is easily controlled, and the production of aldehyde trimers can be easily prevented. From these viewpoints, the catalyst concentration is more preferably 0.1 to 2 mol/L.

Here, as the aldehydes, for example, formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde, hexylaldehyde, benzaldehyde, etc. can be used. Among these, aldehyde compounds having 1 to 12 carbon atoms are preferred, saturated alkylaldehyde compounds having 1 to 6 carbon atoms are more preferred, and saturated alkylaldehyde compounds having 1 to 4 carbon atoms are particularly preferred. From the viewpoint of the mechanical properties of the film obtained by using the present resin composition, butylaldehyde is the most preferred aldehyde. That is, as the polyvinyl acetal, it is most preferred to use polyvinyl butyral.
The aldehydes may be used alone or in combination of two or more. In particular, it is preferable to use butyl aldehyde and acetaldehyde in combination, since the glass transition temperature of the polyvinyl acetal can be controlled. Furthermore, a small amount of polyfunctional aldehydes or aldehydes having other functional groups may be used in combination within a range of 20% by mass or less of the total aldehydes.

The procedure for the acetalization reaction can be any known method. For example, there is a method in which the above-mentioned catalyst is added to an aqueous solution of polyvinyl alcohol and then the aldehydes are added, or a method in which the above-mentioned aldehydes are added first and then the catalyst is added. Other examples include a method in which the aldehydes or catalyst are added all at once, gradually, or in portions, or a method in which a mixed solution of an aqueous solution of polyvinyl alcohol and an aldehyde or catalyst is added to a solution containing the catalyst or aldehydes.

The reaction temperature of the acetalization reaction can be appropriately selected and is not particularly limited. However, in order to improve the corrosion resistance of the film obtained using the present resin composition, from the viewpoint of producing a porous polyvinyl acetal that is easy to wash after the reaction, it is preferable to carry out the reaction at a relatively low temperature of 0 to 40°C until polyvinyl acetal particles are precipitated during the reaction, and more preferably at 5 to 20°C. If the reaction temperature is 40°C or lower, it is easy to prevent the polyvinyl acetal from fusing, and it is easy to produce a porous polyvinyl acetal. If the reaction temperature is 0°C or higher, it is preferable because the reaction system is easy to handle. In addition, after carrying out the reaction at a relatively low temperature of 0 to 40°C, the reaction temperature is preferably set to 50 to 80°C, and more preferably to 65 to 75°C, in order to drive the reaction and increase productivity.

As a method for removing the aldehydes and catalyst remaining after the acetalization reaction, a known method can be appropriately used. The polyvinyl acetal obtained by the reaction is neutralized with an alkali compound, but it is preferable to remove as much of the aldehydes remaining in the polyvinyl acetal as possible before neutralization. For this reason, a method of pushing the reaction under conditions that increase the reaction rate of the aldehydes, a method of thoroughly washing with water or a water/alcohol mixed solvent, or a method of chemically treating the aldehyde are useful. Examples of alkali compounds used for neutralization include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, and amine compounds such as ammonia, triethylamine, and pyridine. Among these, hydroxides of alkali metals, which have little effect on adhesion to glass, are particularly preferable.

[Multilayer structure particles]
Multilayer structure particles are used to prevent a decrease in hardness and impart excellent impact resistance while maintaining transparency.
The content of the multilayered particles in the resin composition is preferably 60% by mass or less. If the content of the multilayered particles is 60% by mass or less, the impact resistance and break resistance can be easily improved. From the same viewpoint, the content of the multilayered particles is more preferably 40% by mass or less, and even more preferably 30% by mass or less. In addition, the content of the multilayered particles is preferably 4% by mass or more. If the content of the multilayered particles is 4% by mass or more, it can contribute to improving the impact resistance and break resistance of the composition. From the same viewpoint, the content of the multilayered particles is more preferably 10% by mass or more, and even more preferably 15% by mass or more.

The multilayered particles 4 used in the present resin composition can be crosslinked rubber particles (core-shell rubber particles) having a multilayered structure (three-layered structure in FIG. 2) including a first hard layer 1, a soft layer 2, and a second hard layer 3 in this order toward the outer surface of the particle 4. The multilayered particles may have layers other than the above three layers, or may be composed of the above three layers, as long as the effects of the present disclosure can be obtained. Although multilayered particles may also be composed of two layers, in the present disclosure, by using multilayered particles including a specific three layers in the resin composition, films, laminated glass, etc. that have a better balance of hardness and impact resistance than when particles with a two-layered structure are used can be produced.

First hard layer The first hard layer, which is the inner layer (core) of the multilayer structure particle, contains a polymer (I) having a glass transition temperature of 25° C. or higher. The polymer (I) is not particularly limited as long as it has a glass transition temperature of 25° C. or higher, and any conventionally known polymer can be used.
However, from the viewpoint of hardness, the first hard layer preferably contains a polymer (eg, polymethacrylate) having a methacrylic acid ester unit (specifically, a structural unit derived from a methacrylic acid ester monomer).
More specifically, the polymer (I) preferably contains 80 to 99.95% by mass of alkyl methacrylate units, more preferably 85 to 98% by mass, and even more preferably 90 to 96% by mass, based on the total mass (100% by mass) of the polymer (I). By satisfying these content ranges, the hardness becomes better and more preferable. The alkyl methacrylate can be appropriately selected within a range in which the effects of the present disclosure can be obtained, but from the viewpoint of hardness, alkyl methacrylates having 1 to 8 carbon atoms in the alkyl group are preferred, and methyl methacrylate is particularly preferred. In addition, from the viewpoint of improving hardness, it is preferable that the polymer (I) has a crosslinked structure. More specifically, from the viewpoint of improving hardness, the first hard layer preferably contains a crosslinked body having a methacrylic acid ester unit (for example, a methacrylate crosslinked polymer).

In addition, from the viewpoint of having good hardness, the polymer (I) preferably has the following structural units with respect to the total mass of the polymer (I). That is, it is preferable to contain 0 to 19.95 mass% of alkyl acrylate units (specifically, structural units derived from alkyl acrylate monomers) in which the alkyl group has 1 to 8 carbon atoms, and 0.05 to 2 mass% of structural units derived from crosslinkable monomers. Furthermore, from the same viewpoint, it is more preferable to contain 2 to 15 mass% of alkyl acrylate units in which the alkyl group has 1 to 8 carbon atoms, and 0.05 to 1.5 mass% of structural units derived from crosslinkable monomers. Furthermore, from the same viewpoint, it is even more preferable to contain 4 to 10 mass% of alkyl acrylate units in which the alkyl group has 1 to 8 carbon atoms, and 0.1 to 1 mass% of structural units derived from crosslinkable monomers.
As the crosslinkable monomer, for example, a divinyl monomer such as allyl methacrylate can be used.
Furthermore, the polymer (I) may contain components other than those described above, as long as the effects of the present disclosure can be obtained.

Soft Layer The soft layer which becomes the intermediate layer (inner shell) of the multilayer structure particle contains a polymer (II) having a glass transition temperature of less than 25° C. The polymer (II) is not particularly limited as long as it has a glass transition temperature of less than 25° C., and a conventionally known polymer (for example, a crosslinked rubber polymer) can be used.
However, from the viewpoint of imparting flexibility and improving impact resistance, it is preferable that the soft layer contains a polymer (e.g., polyacrylate) having an acrylic acid ester unit (more specifically, a structural unit derived from an acrylic acid ester monomer).
More specifically, the polymer (II) preferably contains 70 to 98% by mass of alkyl acrylate units, more preferably 75 to 90% by mass, and even more preferably 80 to 85% by mass, based on the total mass (100% by mass) of the polymer (II). By satisfying the above content range, the polymer constituting the soft layer becomes a more flexible rubber material, and impact resistance can be easily imparted. The number of carbon atoms of the alkyl group in the alkyl acrylate unit is preferably 1 to 8. In addition, from the viewpoint of improving impact resistance, the polymer (II) preferably has a crosslinked structure. More specifically, from the viewpoint of improving impact resistance, the soft layer preferably contains a crosslinked body having an acrylic ester unit (for example, an acrylate crosslinked polymer).

Furthermore, polymer (II) preferably contains 2 to 30 mass %, more preferably 10 to 25 mass %, and even more preferably 15 to 20 mass % of structural units derived from a vinyl monomer (e.g., an aromatic vinyl monomer) relative to the total mass of polymer (II). By satisfying the above content range, the refractive index of polymer (II) can be easily adjusted to match that of the resin matrix, and high transparency can be easily imparted.
As the vinyl monomer, for example, an aromatic vinyl monomer such as styrene, or an aliphatic diene monomer such as butadiene can be used.

Furthermore, the polymer (II) preferably contains 1 to 5 mass %, more preferably 1 to 3 mass %, of structural units derived from a crosslinkable monomer based on the total mass of the polymer (II). By satisfying the above content range, an appropriate crosslink density can be easily obtained, and the behavior as a rubber material becomes better.
As the crosslinkable monomer, for example, a divinyl monomer such as allyl methacrylate can be used.
Furthermore, the polymer (II) may contain components other than those described above, as long as the effects of the present disclosure can be obtained.

Second Hard Layer The second hard layer which becomes the outer layer (shell) of the multilayer structure particle contains a polymer (III) having a glass transition temperature of 25° C. or higher. The polymer (III) is not particularly limited as long as it has a glass transition temperature of 25° C. or higher, and a conventionally known polymer (for example, a thermoplastic polymer) can be used.
However, from the viewpoint of compatibility with the resin matrix, the second hard layer preferably contains a polymer having a methacrylic acid ester unit (for example, polymethacrylate).
More specifically, the polymer (III) preferably contains 80 to 100% by mass of alkyl methacrylate units, more preferably 85 to 97% by mass, and even more preferably 90 to 96% by mass, based on the total mass (100% by mass) of the polymer (III). By satisfying these content ranges, compatibility with the resin matrix becomes better, which is preferable. The alkyl methacrylate monomer can be appropriately selected within a range in which the effects of the present disclosure can be obtained, but from the viewpoint of hardness, alkyl methacrylates having 1 to 8 carbon atoms in the alkyl group are preferred, and methyl methacrylate is particularly preferred. In addition, from the viewpoint of improving hardness, it is preferable that the polymer (III) has a crosslinked structure. More specifically, from the viewpoint of improving hardness, the second hard layer preferably contains a crosslinked body having a methacrylic acid ester unit (for example, a methacrylate crosslinked polymer).

In addition, polymer (III) preferably contains 0 to 20 mass %, more preferably 3 to 15 mass %, and even more preferably 4 to 10 mass % of alkyl acrylate units in which the alkyl group has 1 to 8 carbon atoms, based on the total mass of polymer (III). By satisfying the above content range, compatibility with the resin matrix is further improved.

From the viewpoint of transparency, it is preferable to select the polymers contained in each layer of the multilayered particles so that the difference in refractive index between adjacent layers is preferably less than 0.005, more preferably less than 0.004, and even more preferably less than 0.003.

From the viewpoint of achieving both hardness and impact resistance of the composition, the multilayered particle preferably contains 5 to 55% by mass of the first hard layer, 20 to 50% by mass of the soft layer, and 5 to 65% by mass of the second hard layer.
In the multilayered particle, from the viewpoint of achieving both hardness and impact resistance of the composition, the mass ratio of the first hard layer and soft layer to the second hard layer ((first hard layer + soft layer):second hard layer) is preferably 30:70 to 95:5, and more preferably 70:30 to 90:10.
The mass ratio of the first hard layer to the soft layer is preferably from 80:20 to 30:70, and more preferably from 70:30 to 50:50, from the viewpoint of achieving both hardness and impact resistance of the composition.

The average particle size of the multilayered particles is preferably 0.05 to 1 μm, more preferably 0.07 to 0.5 μm, even more preferably 0.1 to 0.4 μm, and particularly preferably 0.15 to 0.3 μm. By using multilayered particles having an average particle size within this range, toughness can be easily achieved with a small amount of compounding, and appropriate rigidity and surface hardness can be easily imparted. In this specification, the average particle size is the arithmetic mean value in the volume-based particle size distribution measured by a light scattering method.

The method for producing the multilayered particles is not particularly limited, and can be carried out by a known method. However, from the viewpoint of particle size control, it is preferable to use an emulsion polymerization method. Specifically, a seed particle is obtained by emulsion polymerization of a monomer constituting the first hard layer, which is the core, and then, in the presence of this seed particle, monomers constituting each layer (e.g., the soft layer and the second hard layer) are successively added, and polymerization is carried out up to the outermost layer (the second hard layer), thereby obtaining a multilayered particle.

Examples of emulsifiers used in emulsion polymerization include anionic emulsifiers such as dialkyl sulfosuccinates (e.g., sodium dioctyl sulfosuccinate, sodium dilauryl sulfosuccinate, etc.), alkyl benzene sulfonates (e.g., sodium dodecyl benzene sulfonate, etc.), and alkyl sulfates (e.g., sodium dodecyl sulfate, etc.); nonionic emulsifiers such as polyoxyethylene alkyl ethers and polyoxyethylene nonyl phenyl ethers; nonionic and anionic emulsifiers such as polyoxyethylene nonyl phenyl ether sulfates (e.g., sodium polyoxyethylene nonyl phenyl ether sulfate, etc.), polyoxyethylene alkyl ether sulfates (e.g., sodium polyoxyethylene alkyl ether sulfate, etc.), and alkyl ether carboxylates (e.g., sodium polyoxyethylene tridecyl ether acetate, etc.). These may be used alone or in combination of two or more. In addition, the average number of repeating units of ethylene oxide units in the exemplary compounds of nonionic emulsifiers and nonionic and anionic emulsifiers is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less, in order to maintain the appropriate foaming properties of the emulsifiers.

The polymerization initiator used in the emulsion polymerization is not particularly limited, and examples of initiators that can be used include persulfate-based initiators such as potassium persulfate and ammonium persulfate; and redox-based initiators such as persulfoxylate/organic peroxide, persulfate/sulfite, etc.

The separation and acquisition of multilayered particles from the polymer latex obtained by emulsion polymerization can be performed by known methods such as salting-out coagulation, freeze-coagulation, and spray drying. Among these, the salting-out coagulation and freeze-coagulation methods are preferred, and the freeze-coagulation method is more preferred, since impurities contained in the multilayered particles can be easily removed by washing with water. The freeze-coagulation method does not use a flocculant, so a film with excellent water resistance is easily obtained. In order to remove foreign matter mixed into the polymer latex before the coagulation step, it is preferable to filter the polymer latex with a wire mesh with an opening of 50 μm or less. From the viewpoint of facilitating uniform dispersion in melt-kneading with the resin matrix, it is preferable to extract the multilayered particles as aggregated particles of 1,000 μm or less, and more preferably as aggregated particles of 500 μm or less. The form of the aggregated particles is not particularly limited, and may be, for example, a pellet-like state in which the outermost layers are fused to each other, or a powder-like or granular powder.

[Other ingredients]
The present resin composition may contain various additives other than the above-mentioned components, such as polymer processing aids, ultraviolet absorbers, antioxidants, heat stabilizers, lubricants, antistatic agents, colorants, impact resistance aids, etc., as necessary, within the scope of the present disclosure. From the viewpoint of the mechanical properties and surface hardness of a film produced using the present resin composition, it is preferable that the amount of foaming agent, filler, matting agent, light diffusing agent, softener, and plasticizer added to the present resin composition is small (for example, 0.1 to 10% by mass in the resin composition).

Furthermore, the resin composition may contain other polymers in addition to the above-mentioned components, as long as the effects of the present disclosure are not impaired. Examples of such other polymers include 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; (meth)acrylic acid ester-based polymers such as polymethacrylate, polyacrylate, (meth)acrylate copolymer, and methyl methacrylate-styrene copolymer; polyethylene terephthalate; Examples of the rubber include polyester resins such as polybutylene terephthalate; polyamides such as nylon 6, nylon 66, and polyamide elastomers; polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyacetal, polyvinylidene fluoride, polyurethane, modified polyphenylene ether, polyphenylene sulfide, and silicone modified resins; acrylic rubber, silicone rubber; styrene-based thermoplastic elastomers such as SEPS, SEBS, and SIS; and olefin-based rubbers such as IR, EPR, and EPDM.
Among these, from the viewpoint of improving the break resistance of a film obtained using the present resin composition, it is preferable to use a (meth)acrylic acid ester polymer such as polymethacrylate, polyacrylate, and (meth)acrylate copolymer. The blending amount of the (meth)acrylic acid ester polymer in the present resin composition can be appropriately set, but from the viewpoint of improving the break resistance, it is preferable to contain 10 to 100 parts by mass of the (meth)acrylic acid ester polymer per 100 parts by mass of the multilayer structure particles.
Here, the (meth)acrylic acid ester polymer includes a methacrylic acid ester homopolymer, an acrylic acid ester homopolymer, a methacrylic acid ester copolymer (using a plurality of types of methacrylic acid esters), an acrylic acid ester copolymer (using a plurality of types of acrylic acid esters), an acrylic acid ester-methacrylic acid ester copolymer (for example, a methyl methacrylate-methyl acrylate copolymer), a copolymer of an acrylic acid ester and another component, a copolymer of a methacrylic acid ester and another component, and the like.

[Composition of Resin Composition]
In the present resin composition, the blending ratio (mass ratio) of the polyvinyl acetal and the multilayered particles is not particularly limited as long as the properties of the polyvinyl acetal itself are not impaired, and can be appropriately set. For the preferred content ratio of each component, please refer to the above explanation.

[Kneading method]
The method for preparing the resin composition is not particularly limited, and a known method can be appropriately used, but a method of melt-kneading and mixing each component is preferred. The mixing operation can be performed using a known mixing or kneading device such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer. In particular, from the viewpoint of kneading property and productivity, it is preferable to use a twin-screw extruder. The shear rate during melt-kneading is preferably 10 to 1,000/sec. The temperature during mixing and kneading is usually 150 to 320°C, preferably 200 to 300°C. When melt-kneading using a twin-screw extruder, it is preferable to use a vent and perform melt-kneading under reduced pressure or under a nitrogen gas flow from the viewpoint of suppressing coloring. In this way, the resin composition can be obtained, for example, in the form of pellets.

<Film, Laminate, Interlayer Film for Laminated Glass, and Laminated Glass>
The film according to the present disclosure (hereinafter, also referred to as the present film) contains the resin composition according to the present disclosure described above. The present film can be obtained by molding the present resin composition and can be composed of the present resin composition. The method for producing the present film is not particularly limited, and a known method can be used as appropriate. For example, the present film can be produced using a known method such as a T-die method, an inflation method, a melt casting method, or a calendar method. From the viewpoint of obtaining a film with good surface smoothness and low haze, it is preferable to include a step of melt-kneading the present resin composition, extruding it in a molten state from a T-die, and contacting both sides of the composition with a mirror-finished roll surface or a mirror-finished belt surface to mold it.

The present film produced using the present resin composition is excellent in transparency, load-bearing property, weather resistance, impact resistance, and corrosion resistance.
Taking advantage of these excellent properties, the present film may be used alone or as each layer (inner layer or outermost layer) constituting the laminate or as a part of those layers. The laminate according to the present disclosure (hereinafter also referred to as the present laminate) may include the present film, and its shape, configuration, use, etc. are not particularly limited. The present laminate preferably has a thermoplastic resin layer together with the present film. Examples of the thermoplastic resin constituting the thermoplastic resin layer include polycarbonate resin, polyethylene terephthalate resin, polyamide resin, polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, (meth)acrylic resin, ABS resin, ethylene-vinyl alcohol resin, polyvinyl butyral resin, polyvinyl acetal resin, styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, and acrylic thermoplastic elastomer.

Taking advantage of the excellent characteristics described above, the resin composition can also be suitably used as an interlayer film for laminated glass. Specifically, an interlayer film for laminated glass can be produced by inserting and laminating a film produced using the resin composition between two or more pieces of glass made of inorganic glass or organic glass. Such an interlayer film for laminated glass can be suitably used for laminated glass in which at least a portion of the film is in contact with a functional material.

The functional material preferably contains a metal. Examples of functional materials include heat sensors, light sensors, pressure sensors, thin-film capacitance sensors, liquid crystal display films, electrochromic functional films, heat-shielding materials, electroluminescent functional films, light-emitting diodes, cameras, IC tags, antennas, and electrodes and wiring for connecting them.

The present invention will be described in more detail below with reference to several examples, but the present disclosure is not limited to these examples in any way.
First, the methods for evaluating the films obtained in each example will be described below.

[Haze]
The film obtained in each example was cut into a size of 50 mm x 50 mm to prepare a test piece, and the haze (%) was measured at a temperature of 23°C according to the method in accordance with JIS K 7136.

[Impact resistance]
The film obtained in each example was placed in an impact tester (manufactured by Yasuda Seiki Seisakusho, product name: No. 181 Film Impact Tester). Then, the energy required to break the film was measured, and the impact resistance was evaluated from the value (J/mm) obtained by dividing the energy (J) by the film thickness (mm).

[Elastic modulus]
The film obtained in each example was cut into a rectangular piece of 10 mm x 60 mm, and a tensile test was performed at a speed of 20 mm/min using an autograph (manufactured by Shimadzu Corporation, product name: AG-IS 5kN). The distance between the chucks was 30 mm. The elastic modulus (MPa) was calculated from the slope of the obtained stress-strain curve in the initial elastic deformation region, and was used as an index for hardness evaluation.

[Production Example 1]
(Synthesis of Polyvinyl Butyral (PVB))
In a ² m3 reactor equipped with a stirrer, 1700 kg of a 7.5% by weight aqueous solution of PVA (polyvinyl alcohol; average degree of polymerization 1000, degree of saponification 99 mol%), 74.6 kg of butyl aldehyde, and 0.13 kg of 2,6-di-t-butyl-4-methylphenol were charged, and the whole was cooled to 14 ° C. To this, 160.1 L of a 20% by weight aqueous hydrochloric acid solution was added to start butyralization of PVA. 10 minutes after the end of the addition, the temperature was raised and the temperature was raised to 65 ° C. over 90 minutes, and the reaction was continued for another 120 minutes. After that, the PVB precipitated by cooling to room temperature was filtered, and then washed 10 times with 10 times the amount of ion-exchanged water relative to the PVB. Thereafter, the mixture was sufficiently neutralized using a 0.3% by weight aqueous sodium hydroxide solution, and further washed 10 times with 10 times the amount of ion-exchanged water relative to the PVB, dehydrated, and dried to obtain PVB. The refractive index of the obtained PVB was measured according to JIS K 7142, Method A, and found to be 1.491.

[Example 1]
(Preparation of multi-layered particles)
In a reactor equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a monomer inlet tube and a reflux condenser, 1050 parts by mass of ion-exchanged water, 0.3 parts by mass of sodium polyoxyethylene tridecyl ether acetate and 0.7 parts by mass of sodium carbonate were charged, and the inside of the reactor was fully replaced with nitrogen gas. Then, the inside temperature was set to 80°C. 0.25 parts by mass of potassium persulfate was added thereto and stirred for 5 minutes. 245 parts by mass of a monomer mixture consisting of 95.4% by mass of methyl methacrylate, 4.4% by mass of methyl acrylate and 0.2% by mass of allyl methacrylate was continuously dripped into the mixture over 60 minutes. After the dripping was completed, the polymerization reaction was carried out for another 30 minutes so that the polymerization conversion rate was 98% or more (synthesis of the first hard layer).
Next, 0.32 parts by mass of potassium persulfate was added to the reactor and stirred for 5 minutes. Then, 315 parts by mass of a monomer mixture consisting of 80.5% by mass of butyl acrylate, 17.5% by mass of styrene, and 2% by mass of allyl methacrylate was continuously dripped over 60 minutes. After the dripping was completed, the polymerization reaction was continued for another 30 minutes until the polymerization conversion rate reached 98% or more (synthesis of the soft layer).
Next, 0.14 parts by mass of potassium persulfate was added to the reactor and stirred for 5 minutes. Then, 140 parts by mass of a monomer mixture consisting of 95.2% by mass of methyl methacrylate, 4.4% by mass of methyl acrylate, and 0.4% by mass of n-octyl mercaptan was continuously dropped over 30 minutes. After the dropwise addition, the polymerization reaction was carried out for another 60 minutes so that the polymerization conversion rate was 98% or more (synthesis of the second hard layer), and a latex (A) containing multilayered particles was obtained. The emulsion was frozen to solidify the multilayered particles. The solidified product was then washed with water and dried to obtain a powder of multilayered particles. The glass transition temperatures of the first hard layer and the second hard layer contained in the multilayered particles, measured by the above-mentioned method, were 25°C or higher, and the glass transition temperature of the soft layer was less than 25°C. The mass proportions (mass %) of each layer in the multilayered particle were as follows: first hard layer: 35 mass %, soft layer: 45 mass %, and second hard layer: 20 mass %.

(Adjustment of Copolymer Particles (Dispersant))
A reactor equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a monomer inlet tube, and a reflux condenser was used. The reactor was filled with nitrogen. 2,700 parts by mass of ion-exchanged water was added to the reactor. Furthermore, 1.8 parts by mass of polyoxyethylene (EO=3) tridecyl ether sodium acetate (manufactured by Nikko Chemicals Co., Ltd.; product name: Nikkol ECT-3NEX) and 2.1 parts by mass of sodium carbonate were added. These were mixed and dissolved while stirring to obtain an aqueous medium with a pH of 8. The temperature of the aqueous medium was raised to a target temperature of 75°C.
Separately from the above, 2,000 parts by mass of a monomer mixture consisting of 92% by mass of methyl methacrylate, 7% by mass of methyl acrylate, 1% by mass of benzyl acrylate, and 0.42% by mass of n-octyl mercaptan, and 4.5 parts by mass of polyoxyethylene (EO=3) tridecyl ether sodium acetate were weighed out and placed in a specified container. These were mixed and dissolved in a beaker to prepare a monomer mixture to which an emulsifier had been added.
When the temperature of the aqueous medium in the reactor reached 75°C, 1.8 parts by mass of potassium persulfate was added to the reactor. The monomer mixture was then continuously fed at a rate of 1.43% by mass/min to carry out the polymerization reaction. Here, the total amount of the monomer mixture was taken as 100% by mass. After the entire amount of the monomer mixture was fed, the aqueous medium was stirred while being held at 75°C for 60 minutes to complete the polymerization reaction. After the polymerization was completed, the polymerization reaction product was cooled to 40°C and then filtered through a 325 mesh wire mesh to obtain a latex (B) containing copolymer particles (dispersant). The emulsion was frozen to coagulate the copolymer particles. The coagulated product was then washed with water and dried to obtain a powder of a (meth)acrylic copolymer. The resulting (meth)acrylic resin had a methyl methacrylate unit content of 92% by mass, a methyl acrylate and benzyl acrylate unit content of 8% by mass, a number average molecular weight of 38,000 and a glass transition temperature of 108°C.

(Preparation of mixed powder)
The obtained latexes (A) and (B) were mixed and then frozen to solidify. The mixture was then washed with water and dried to obtain a mixed powder containing multilayered particles. The mixing ratio was 67 parts by mass of multilayered particles and 33 parts by mass of copolymer particles. The average particle size of the multilayered particles was 0.23 μm, and the average particle size of the copolymer particles was 0.13 μm.

(Mixing and pressing of mixed powder and PVB)
The polyvinyl acetal used was the PVB obtained in Production Example 1. Then, 30 parts by mass of the mixed powder containing the multilayer structure particles (multilayer structure particles:copolymer particles=20:10 (mass ratio)) was added to 70 parts by mass of this PVB, and the mixture was melt-kneaded at a temperature of 210° C. for 3 minutes, and then press-molded at a temperature of 210° C. using a press molding machine to obtain a film having an average thickness of 0.1 mm.

[Example 2]
In Example 1, the mixed powder was not adjusted, but instead a powder of multilayer-structure particles was obtained by freezing, coagulation, washing with water, and drying. A film was produced in the same manner as in Example 1, except that the ratio during kneading was 80 parts by mass of PVB and 20 parts by mass of the powder of multilayer-structure particles.

[Comparative Example 1]
A film was produced in the same manner as in Example 1, except that the preparation of the mixed powder and the kneading of PVB were not performed, and only PVB resin was used alone.

The evaluation results for each example are shown in Table 1. The resin composition below indicates the blending ratio (blending ratio) of each component (PVB, multilayer structure particles, and copolymer particles) by mass.

The haze, impact resistance, and elastic modulus of the films obtained in the examples and comparative examples were measured. The haze value (%) and elastic modulus (MPa) in Examples 1 and 2 were almost the same as those in Comparative Example 1, and appropriate transparency and hardness were maintained. On the other hand, the impact resistance in Examples 1 and 2 was improved by about 1.5 times compared to Comparative Example 1, demonstrating the effect of adding multilayer structure particles.

From the above, it was found that the addition of multilayered particles can suppress the decrease in hardness and improve impact resistance while maintaining the transparency of the polyvinyl acetal resin composition without using plasticizers or metal salts. In addition, this resin composition has good processability and is likely to have excellent stability when formed into a film.

According to the present disclosure, it is possible to provide a resin composition that can suppress a decrease in hardness and impart superior impact resistance while maintaining the inherent transparency of the resin. Furthermore, it is possible to provide a film, a laminate, an interlayer film for laminated glass, and laminated glass using the resin composition that have these properties.

1 First hard layer 2 Soft layer 3 Second hard layer 4 Multilayer structure particles

Claims (12)

The present invention includes polyvinyl acetal and multilayer structure particles,
The multi-layered particle has a multi-layered structure including, from the outer surface thereof, a first hard layer, a soft layer, and a second hard layer in this order,
each of the first hard layer and the second hard layer contains a polymer having a glass transition temperature of 25° C. or higher;
The soft layer comprises a polymer having a glass transition temperature of less than 25° C.
A resin composition comprising: The resin composition according to claim 1, wherein at least one or both of the first hard layer and the second hard layer contains a polymer having a structural unit derived from a methacrylic acid ester monomer. The resin composition according to claim 1 or 2, wherein the soft layer contains a polymer having a structural unit derived from an acrylic acid ester monomer. At least one or both of the first hard layer and the second hard layer contain a crosslinked material having a structural unit derived from a methacrylic acid ester monomer,
The resin composition according to any one of claims 1 to 3, wherein the soft layer contains a crosslinked material having a structural unit derived from an acrylic acid ester monomer. The resin composition according to any one of claims 1 to 4, wherein the multilayered particle contains 5 to 55% by mass of the first hard layer, 20 to 50% by mass of the soft layer, and 5 to 65% by mass of the second hard layer. The resin composition according to any one of claims 1 to 5, wherein the mass ratio of the polyvinyl acetal to the multilayered particles is 50:50 to 90:10. The resin composition according to any one of claims 1 to 6, wherein the polyvinyl acetal is polyvinyl butyral. The resin composition according to any one of claims 1 to 7 further comprises 10 to 100 parts by mass of a (meth)acrylic acid ester polymer relative to 100 parts by mass of the multilayered particles. A film comprising the resin composition according to any one of claims 1 to 8. A laminate comprising the film according to claim 9. An interlayer film for laminated glass, comprising the resin composition according to any one of claims 1 to 8. Laminated glass comprising the interlayer film for laminated glass according to claim 11.

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