Multilayer plate, multilayer plate decomposition / recovery method, and (METH)acrylic resin composition recycling method

Abstract

Provided is a multilayer plate including a glass fiber-reinforced (meth)acrylic resin layer (B) with a (meth)acrylic resin layer (A) disposed on at least one surface thereof. Also provided are: a multilayer plate decomposition / recovery method that pyrolyzes multilayer plates (including recycled multilayer plates) at 380℃ or higher and recovers a (meth)acrylic acid ester by separating a volatile component from solid matter; and a recycling method that recycles a (meth)acrylic resin composition that forms multilayer plates (including recycled multilayer plates).

Description

Multilayer board, method for disassembling and recovering multilayer boards, and recycling method for (meth)acrylic resin composition

[0001] The present invention relates to multilayer boards, a method for disassembling and recovering multilayer boards, and a method for recycling (meth)acrylic resin compositions.

[0002] (Meth)acrylic resin has excellent weather resistance and moldability, and is easy to color, so it has been used in a variety of applications as a resin molded product, and its applications are expanding. For example, by taking advantage of the excellent properties of (meth)acrylic resin, its application as a substitute material for other resins or non-resin materials is being considered in applications where other resins were previously used, or where non-resin materials such as glass or metal were previously used. Resin molded products formed from (meth)acrylic resin ((meth)acrylic resin molded products) generally do not have sufficient impact resistance or rigidity, and technologies to improve these are being considered. For example, glass fiber reinforced (meth)acrylic resin, which is a (meth)acrylic resin mixed with glass fibers to form a resin molded product, can be mentioned. Patent document 1 proposes an automotive sunroof in which the main body (1) is formed from a surface-hardened glass fiber reinforced acrylic resin plate, as a (meth)acrylic resin molded product for use as a glass substitute using such glass fiber reinforced (meth)acrylic resin.

[0003] Jitszen No. 59-085721

[0004] When manufacturing (meth)acrylic resin molded articles, it is possible to mold the (meth)acrylic resin in one step, such as by injection molding. However, from the standpoint of handling, productivity, and depending on the application, a method is frequently used in which (meth)acrylic resin sheets are first produced as semi-finished products (intermediate products), and then heat-processed to produce (meth)acrylic resin molded articles as finished products. Furthermore, (meth)acrylic resin molded articles are sometimes heat-processed to fine-tune their shape and dimensions, and even to recycle them. For this reason, excellent heat-processability is required for (meth)acrylic resin molded articles and (meth)acrylic resin sheets (in this invention, (meth)acrylic resin molded articles include (meth)acrylic resin sheets, but in this and the next paragraph, they will be described as different for the purpose of explaining the manufacturing method). In addition, (meth)acrylic resin molded articles and (meth)acrylic resin sheets used in various applications pose a risk of causing secondary damage to people or property if they are damaged or shattered when subjected to impact, and the resulting fragments scatter. Therefore, (meth)acrylic resin molded articles and (meth)acrylic resin sheets are required to have properties that make them resistant to damage or shattering even when subjected to impact, and that prevent fragments from scattering even if they do break or shatter (hereinafter sometimes simply referred to as "shatter prevention properties"). However, Patent Document 1 does not consider shatter prevention properties or heat processability.

[0005] Incidentally, in recent years, with the soaring prices of resources and the growing awareness of environmental issues, the practical application of technologies for recovering resin molded products used in various applications and recycling the resin molded products themselves or their materials (resins) is progressing. This is also true for (meth)acrylic resin molded products and (meth)acrylic resin sheets. Recycling methods for (meth)acrylic resin and its molded products include, for example, material recycling, which involves remolding the recovered molded products to produce new ones; chemical recycling, which involves recovering and polymerizing (meth)acrylic acid esters and other components that make up (meth)acrylic resin from the recovered molded products to obtain (meth)acrylic resin; and thermal recycling, which utilizes the recovered molded products as fuel. Among these, material recycling has significant advantages in reducing environmental impact and building a circular economy because it reuses the recovered molded products ((meth)acrylic resin) as they are. However, recovered molded products usually have reduced physical properties and characteristics compared to unused (meth)acrylic resin. Therefore, achieving material recycling of recovered molded products is not easy, and currently they are recycled chemically or thermally.

[0006] The present invention aims to provide a multilayer board with excellent shatterproof properties and thermal processability. Furthermore, the present invention aims to provide a method for decomposing and recovering a multilayer board (including recycled multilayer boards) to recover (meth)acrylic acid esters, and a recycling method for recycling a (meth)acrylic resin composition from a multilayer board (including recycled multilayer boards).

[0007] In other words, the object of the present invention has been achieved by the following means: <1> A multilayer plate comprising a glass fiber reinforced (meth)acrylic resin layer (B) having a (meth)acrylic resin layer (A) on at least one surface. <2> The multilayer plate according to <1>, wherein the (meth)acrylic resin layer (A) is a resin layer of a (meth)acrylic resin composition (A) containing (meth)acrylic resin and hard inorganic particles. <3> The multilayer plate according to <2>, wherein the hard inorganic particles include silica particles. <4> The multilayer plate according to any one of <1> to <3>, wherein the (meth)acrylic resin layer (A) does not contain fibrous glass filler. <5> The multilayer board according to any one of <1> to <4>, wherein the glass fiber reinforced (meth)acrylic resin layer (B) is a resin layer of a (meth)acrylic resin composition (B) comprising a (meth)acrylic resin in which the content of structural units derived from (meth)acrylic acid ester is 90 to 99.985 mol% and the content of structural units derived from (meth)acrylic acid is 0.015 to 9.0 mol% based on the total content of all structural units of 100 mol%, and a fibrous glass filler. <6> The multilayer board according to any one of <1> to <5>, wherein the (meth)acrylic resin layer (A) has a thickness of 30 to 500 μm. <7> A recycling method for recycling a (meth)acrylic resin composition forming a multilayer board, comprising recovering the (meth)acrylic resin composition from the multilayer board described in any one of <1> to <6> above or from the recycled multilayer board described below, and mixing the recovered (meth)acrylic resin composition with unused (meth)acrylic resin and unused fibrous glass filler. (Recycled multilayer board) A recycled multilayer board having a (meth)acrylic resin layer (A) on at least one side of a glass fiber reinforced (meth)acrylic resin layer (B) made of a recycled (meth)acrylic resin composition containing the (meth)acrylic resin composition recovered from the multilayer board described in any one of <1> to <6> above, unused (meth)acrylic resin and unused fibrous glass filler. <8> A method for decomposing and recovering a multilayer board, comprising decomposing the multilayer board described in any one of <1> to <6> above with heat of 380°C or higher and recovering (meth)acrylic acid ester by separating volatile components and solid matter.

[0008] The present invention can provide a multilayer board with excellent shatterproof properties and thermal processability. Furthermore, the present invention can provide a method for decomposing and recovering a multilayer board (including a recycled multilayer board) to recover (meth)acrylic acid esters, and a recycling method for recycling a (meth)acrylic resin composition from a multilayer board (including a recycled multilayer board).

[0009] In the present invention and this specification, "(meth)acrylic resin" means either or both of acrylic resin and methacrylic resin. The same applies to "(meth)acrylic acid ester" and "(meth)acrylic acid."

[0010] In the present invention and this specification, the bonding mode (arrangement of structural units) of two or more structural units in a copolymer that becomes a resin or elastomer is not particularly limited and includes, for example, random bonding (random copolymer), block bonding (block copolymer), alternating bonding (alternating copolymer), graft bonding (graft copolymer), etc. In the present invention and this specification, when describing content, physical properties, etc., by indicating numerical ranges, when the upper and lower limits of the numerical range are described separately, either upper and lower limit can be appropriately combined to form a specific numerical range. On the other hand, when multiple numerical ranges expressed using "~" are set and described, the upper and lower limits that form the numerical range are not limited to a specific combination of the upper and lower limits described before and after "~" as a specific numerical range, but can be a numerical range obtained by appropriately combining the upper and lower limits of each numerical range. In the present invention and this specification, a numerical range expressed using "~" means a range that includes the numbers described before and after "~" as the lower and upper limits.

[0011] In the present invention and this specification, "unused (meth)acrylic resin" refers to (meth)acrylic resin that has not been used in the preparation of (meth)acrylic resin compositions or the manufacture (molding) of multilayer boards, etc. Examples include (meth)acrylic resin obtained by polymerization or its isolated and purified product, and commercially available (meth)acrylic resin. "Recovered (meth)acrylic resin" means (meth)acrylic resin recovered from waste materials such as residues generated in the preparation of (meth)acrylic resin compositions (including recycled (meth)acrylic resin compositions), waste materials such as fragments, defective products, and residues generated in the manufacture of multilayer boards (including recycled multilayer boards), and multilayer boards (including recycled multilayer boards) discarded by consumers. On the other hand, "recycled (meth)acrylic resin" means (meth)acrylic resin that contains recovered (meth)acrylic resin and can be reused (recycled) in the preparation of new (meth)acrylic resin compositions, etc. The same applies to each component used in the preparation of the (meth)acrylic resin composition of the present invention.

[0012] Furthermore, "unused (meth)acrylic resin composition" refers to a (meth)acrylic resin composition that has not been molded into a multilayer board or the like, and an example of such a composition is a (meth)acrylic resin composition obtained by preparation. "Recovered (meth)acrylic resin composition" means a (meth)acrylic resin composition that has been recycled and recovered by conventional methods and conditions, preferably by the recovery process of the (meth)acrylic resin composition recycling method of the present invention, from waste generated in the preparation of (meth)acrylic resin compositions (including recycled (meth)acrylic resin compositions), waste generated in the manufacture of multilayer boards (including recycled multilayer boards), and multilayer boards (including recycled multilayer boards) discarded by consumers. On the other hand, "recycled (meth)acrylic resin composition" means a (meth)acrylic resin composition that contains the above-mentioned recovered (meth)acrylic resin composition and can be reused for the manufacture of new multilayer boards, etc. In the present invention, the above-mentioned waste and multilayer boards to be recovered include those that contain a recovered (meth)acrylic resin composition that has been recovered at least once. Therefore, in the present invention, recycled (meth)acrylic resin encompasses both forms: one containing recycled (meth)acrylic resin recovered once, and one containing recycled (meth)acrylic resin recovered two or more times. Similarly, the recycled (meth)acrylic resin composition of the present invention encompasses both forms: a resin composition containing a recycled (meth)acrylic resin composition recovered once, and a resin composition containing a recycled (meth)acrylic resin composition recovered two or more times. In the case of a resin composition containing a recycled (meth)acrylic resin composition recovered two or more times, in order to distinguish it from the recycled (meth)acrylic resin composition to be prepared, a resin composition containing a recycled (meth)acrylic resin composition that has already been regenerated (previous generation) and is used in the preparation of this resin composition may be called a "recycled (meth)acrylic resin composition."

[0013] Furthermore, "unused multilayer boards" refer to multilayer boards that were manufactured but not used as resin components in products, semi-finished products, etc. "Recovered multilayer boards" refer to multilayer boards that have been recovered as waste generated during the manufacture of multilayer boards, etc., and multilayer boards that have been discarded by consumers and then recovered. On the other hand, "recycled multilayer boards" refer to multilayer boards that include a glass fiber reinforced (meth)acrylic resin layer formed from a recycled (meth)acrylic resin composition. The same applies to molded articles, which will be discussed later.

[0014] In the present invention and this specification, "(meth)acrylic resin" may include "unused (meth)acrylic resin," "recovered (meth)acrylic resin" as described later, and "recycled (meth)acrylic resin" as described later. However, unless otherwise specified, "(meth)acrylic resin" shall be used as a term meaning "unused (meth)acrylic resin." Similarly, "(meth)acrylic resin composition" may include "unused (meth)acrylic resin composition," "recovered (meth)acrylic resin composition" as described later, and "recycled (meth)acrylic resin composition" as described later. However, unless otherwise specified, "(meth)acrylic resin composition" shall be used as a term meaning "unused (meth)acrylic resin composition." However, when "(meth)acrylic resin composition" means a recycled (meth)acrylic resin composition, the content of recovered (meth)acrylic resin composition in 100% by mass of the recycled (meth)acrylic resin composition shall be, for example, less than 1% by mass. Furthermore, the term "multilayer board" can encompass "unused multilayer boards," "recovered multilayer boards," and "recycled multilayer boards," but unless otherwise specified, "multilayer board" is used to mean "unused multilayer boards."

[0015] [Multilayer board] The multilayer board of the present invention is a multilayer board comprising a glass fiber reinforced (meth)acrylic resin layer (B) having a (meth)acrylic resin layer (A) on at least one surface. This multilayer board is a multilayer board having a (meth)acrylic resin layer (sometimes called a "surface layer") (A) on at least one surface of a glass fiber reinforced (meth)acrylic resin layer (sometimes called a "base layer") (B). The multilayer board of the present invention can be described as a laminate of a surface layer (A) and a base layer (B). The multilayer board of the present invention includes a multilayer board having a surface layer (A) on one surface of the base layer (B) (for convenience, referred to as a "two-layer board") and a multilayer board having a surface layer (A) on both surfaces of the base layer (B) (for convenience, referred to as a "three-layer board"). In the multilayer board of the present invention, the base layer (B) and the surface layer (A) may each have a single-layer structure or a multi-layer structure. Furthermore, the multilayer board of the present invention may have layers that do not correspond to either the base layer (B) or the surface layer (A), such as a coloring layer, a printed layer, a water-repellent layer, an adhesive layer, a primer layer, etc. In a three-layer board, the two surface layers (A) may be the same or different.

[0016] The multilayer board of the present invention is typically in the form of a board (including sheet or film), and may be either a long board or a short board (single-sheet board or strip board). The multilayer board of the present invention can be used as a material for molded articles formed into shapes, forms, and dimensions suitable for the application.

[0017] The total thickness of the multilayer board of the present invention is determined appropriately according to the application and other factors, and is not particularly limited, but is usually 0.1 to 10.0 mm, preferably 0.2 to 5.0 mm, and more preferably 0.3 to 3.0 mm. The thickness of the surface layer (A) is not particularly limited and is determined appropriately considering the total thickness of the multilayer board. For example, the thickness of the surface layer (A) is preferably 10 to 800 μm, more preferably 30 to 600 μm, even more preferably 30 to 500 μm, and particularly preferably 50 to 500 μm. Each surface layer (A) in a three-layer board may have the same thickness or different thicknesses. The thickness of the base layer (B) is not particularly limited and is determined appropriately considering the total thickness of the multilayer board and the thickness of the surface layer (A), etc. For example, the thickness of the base layer (B) can be 500 to 6000 μm, preferably 800 to 5000 μm, and more preferably 1000 to 3000 μm. In the multilayer board of the present invention, the ratio of the total thickness of the surface layer (A) to the thickness of the base layer (B) [total thickness of surface layer (A) / thickness of base layer (B)] is not particularly limited and can be, for example, 0.01 to 1, and preferably 0.02 to 0.8.

[0018] The multilayer board of the present invention has a surface layer (A) and a base layer (B) each formed from a (meth)acrylic resin composition described later, and the multilayer board as a whole is a non-thermosetting board that does not exhibit the property of curing by heat, and preferably is an uncured board that has not been cured by heat, light, or other curing agents or polymerization initiators. Furthermore, the multilayer board of the present invention as a whole can be softened or melted by heating and has excellent thermal workability (e.g., hot press workability, (free) blow moldability). In this respect, the multilayer board of the present invention can be said to have thermoplasticity as a whole.

[0019] The multilayer board of the present invention has excellent thermal processability and shatter prevention properties, and furthermore, the (meth)acrylic resin composition (B) forming the base layer (B) and the (meth)acrylic resin composition (A) forming the surface layer (A) can be recycled (materially), and the (meth)acrylic acid ester in each (meth)acrylic resin composition can also be recovered and recycled (chemically).

[0020] The multilayer board of the present invention can be used in a variety of applications, taking advantage of the above-mentioned excellent characteristics. For example, in addition to the conventional applications of (meth)acrylic resin, it can be used as a material for applications requiring shatterproof properties and heat processability, outdoor applications, and as a substitute for various resins such as ABS resin, and as a substitute for glass, etc. Examples include: exterior and body components for vehicles such as pillars and front fenders; interior components for vehicles such as instrument panel covers; battery components such as battery housings; optical components such as lenses, display protective plates, optical films, and light guide plates; office automation equipment; components for cosmetic containers and building components (interior components); housings for electrical products; and components installed outdoors where shatterproof properties are required (for example, signs, soundproof walls, resin exterior wall sheets for agricultural greenhouses, roofing materials for carports and garages, etc.).

[0021] [Base layer (B)] The base layer (B) consists of a glass fiber reinforced (meth)acrylic resin layer and is formed in layers of a (meth)acrylic resin composition (B) containing the (meth)acrylic resin (B) and fibrous glass filler described later. In the multilayer plate of the present invention, by forming the base layer (B) with a (meth)acrylic resin composition (B) containing the (meth)acrylic resin and fibrous glass filler, excellent shatterproof properties and high thermal processability can be achieved. The base layer (B) is a non-thermosetting layer and is preferably an uncured layer that has not been cured by heat, light, or other curing agents or polymerization initiators. Furthermore, it is preferable that the base layer (B) is thermoplastic.

[0022] <(Meth)acrylic resin composition (B)> The (meth)acrylic resin composition (B) that forms the base layer (B) (in this invention, this may be referred to as the "base layer resin composition") contains (meth)acrylic resin (B) and fibrous glass filler. The components contained in the base layer resin composition (B) will be described below. Each component contained in the base layer resin composition (B) may be one type or two or more types.

[0023] ((meth)acrylic resin (B)) The (meth)acrylic resin (B) contained in the base layer resin composition (B) is a resin made of a polymer containing structural units derived from (meth)acrylic acid esters (in the present invention, also referred to as "(meth)acrylic acid ester structural units"), and includes resins made of copolymers containing structural units derived from (meth)acrylic acid esters and various copolymer structural units described later. Examples of (meth)acrylic resin (B) include resins made of a homopolymer containing only one type of (meth)acrylic acid ester structural unit, resins made of copolymers containing two or more types of (meth)acrylic acid ester structural units, and resins made of copolymers containing at least one type of (meth)acrylic acid ester structural unit and at least one type of copolymer structural unit. In terms of scattering prevention properties and heat processability, resins made of copolymers containing two or more types of (meth)acrylic acid ester structural units and resins made of copolymers containing at least one type of (meth)acrylic acid ester structural unit and at least one type of copolymer structural unit are preferred, and resins made of copolymers containing at least one type of (meth)acrylic acid ester structural unit and at least one type of copolymer structural unit are more preferred. Each of the above copolymers may contain one or more of the other structural units described later. An example of a resin consisting of a copolymer containing two or more (meth)acrylic acid ester structural units is the (meth)acrylic resin (A) contained in the (meth)acrylic resin composition (A) that forms the (meth)acrylic resin layer (A).

[0024] In each of the above copolymers, it is preferable that at least one (meth)acrylic acid ester structural unit comprises at least one acrylic acid ester structural unit and at least one methacrylic acid ester structural unit. The copolymer structural unit is not particularly limited as long as it is derived from a compound copolymerizable with (meth)acrylic acid ester, and examples include structural units derived from (meth)acrylic acid described later, structural units containing ring structures, and other structural units.

[0025] The content of (meth)acrylic acid ester structural units in the polymer ((meth)acrylic resin) is not particularly limited and is determined appropriately according to each copolymer. For example, the content of (meth)acrylic acid ester structural units is usually 50 mol% or more, but preferably 85 mol% or more, and more preferably 90 mol% or more, based on the total content of all structural units constituting the polymer (100 mol%). On the other hand, the upper limit of the above content can be 100 mol%, but it is preferably 99.985 mol% or less. The content of (meth)acrylic acid ester structural units is not limited to the above example, and depending on the structural units contained in the copolymer, it may be the content described later for each copolymer.

[0026] As the (meth)acrylic resin (B) contained in the resin composition (B) for the base layer, a resin composed of a copolymer having a (meth)acrylate structural unit and a structural unit derived from (meth)acrylic acid (also referred to as "(meth)acrylic acid structural unit" in the present invention) is preferable in that it can enhance the anti-scattering property without impairing the thermoformability. This copolymer may further have a structural unit containing a ring structure described later and other structural units. A preferable copolymer (resin) having a (meth)acrylic acid structural unit can preferably exhibit excellent anti-scattering properties in a multilayer board of a (meth)acrylic resin when used in combination with a fibrous glass filler, and can also exhibit excellent impact resistance and rigidity as appropriate. This copolymer preferably contains 90 to 99.985 mol% of a structural unit derived from a (meth)acrylate and 0.015 to 9.0 mol% of a structural unit derived from (meth)acrylic acid with respect to the total content of 100 mol% of all the structural units forming the (meth)acrylic resin.

[0027] The (meth)acrylic resin contained in the resin composition (B) for the base layer may be one kind or two or more kinds. For example, it can be a mixture of a resin composed of a copolymer having a (meth)acrylic acid structural unit and a resin composed of a copolymer having no (meth)acrylic acid structural unit (for example, the above-mentioned homopolymer, a copolymer containing two or more (meth)acrylate structural units, etc.). When the resin composition (B) for the base layer contains two or more (meth)acrylic resins, regarding the properties and physical properties of the (meth)acrylic resin (B), for example, the content of each structural unit, it only needs to conform to the content described later for the whole of the two or more (meth)acrylic resins, and each (meth)acrylic resin may or may not conform.

[0028] - Structural unit derived from (meth)acrylic acid ester - The (meth)acrylic acid ester that leads to the structural unit derived from (meth)acrylic acid ester is not particularly limited, and examples include (meth)acrylic acid alkyl ester, (meth)acrylic acid aryl ester, etc., and (meth)acrylic acid alkyl ester is preferred. The alkyl group constituting the (meth)acrylic acid alkyl ester is not particularly limited, but an alkyl group having 1 to 8 carbon atoms is preferred.

[0029] Examples of the acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, tert-butyl acrylate, sec-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, lauryl acrylate, benzyl acrylate, etc. The acrylic acid ester preferably contains methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, tert-butyl acrylate, sec-butyl acrylate, iso-butyl acrylate, or 2-ethylhexyl acrylate, and more preferably contains methyl acrylate.

[0030] Examples of the methacrylic acid alkyl ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, sec-butyl methacrylate, iso-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, benzyl methacrylate, etc. The methacrylic acid ester preferably contains methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, sec-butyl methacrylate, iso-butyl methacrylate, or 2-ethylhexyl methacrylate, and more preferably contains methyl methacrylate.

[0031] The (meth)acrylic acid ester may have substituents. The (meth)acrylic resin may contain one or more structural units derived from the above (meth)acrylic acid ester.

[0032] - Structural units derived from (meth)acrylic acid - The (meth)acrylic acid used to derive structural units derived from (meth)acrylic acid is not particularly limited, and examples include acrylic acid and methacrylic acid, with methacrylic acid being preferred. The (meth)acrylic acid may have substituents. The (meth)acrylic resin (B) may contain one or more of the above-mentioned structural units derived from (meth)acrylic acid.

[0033] - Structural units containing ring structures - (meth)acrylic resin (B) may contain ring structures in its main chain. In the present invention, "containing (incorporating) a ring structure in the main chain of (meth)acrylic resin" means that a substructure bonded to a carbon atom constituting the carbon chain that forms the main chain of the (meth)acrylic resin forms a ring structure together with this carbon atom. It is preferable that this ring structure is incorporated into the main chain of the (meth)acrylic resin by having a structural unit containing a ring structure. Since the structural unit containing a ring structure affects the impact resistance and rigidity of the (meth)acrylic resin (B) and the shatterproof properties of the multilayer plate of the present invention, it may be included or not, taking these factors into consideration. When (meth)acrylic resin (B) contains a structural unit containing a ring structure, it is preferable to include one or more structural units containing a ring structure made of a cyclic anhydride compound, and more preferably to include a structural unit containing a ring structure made of a glutaric acid anhydride compound, in order to achieve excellent shatterproof properties. On the other hand, if the (meth)acrylic resin does not contain structural units containing a ring structure, the structural units containing a ring structure that are not included are preferably structural units containing a ring structure made of a glutaric acid anhydride compound, more preferably structural units containing a ring structure made of a cyclic anhydride compound, and even more preferably structural units containing the following ring structures.

[0034] The ring structure is not particularly limited. For example, a ring structure composed of cyclic imides such as maleimide and glutarimide; a ring structure composed of cyclic acid anhydrides such as maleic anhydride and glutaric anhydride; a ring structure composed of cyclic amides (such as a lactam ring structure, etc.); a cyclic ester ring structure such as a ring structure composed of lactone, etc. can be mentioned. Examples of the cyclic acid anhydride include acid anhydrides of unsaturated carboxylic acids, and preferably, maleic anhydride, itaconic anhydride, etc. can be mentioned. Examples of maleimide include N-substituted maleimides such as phenylmaleimide, cyclohexylmaleimide, and methylmaleimide. Each compound forming the above ring structure may have an appropriate substituent. The ring structure (structural unit including the ring structure) possessed by the (meth)acrylic resin may be one kind or two or more kinds.

[0035] Examples of the structural unit having a ring structure composed of glutarimide and the structural unit having a ring structure composed of glutaric anhydride include, for example, the structural unit represented by the following formula (A).

[0036]

[0037] In formula (A), R １ and R ２ each independently represent a hydrogen atom or an alkyl group, and R ３ represents a hydrogen atom or a substituent. X １ represents an oxygen atom or a nitrogen atom. When X １ is an oxygen atom, n is 0, and when X １ is a nitrogen atom, n is 1. The alkyl group that can be taken as R １ and R ２ , and the substituent that can be taken as R ３ are not particularly limited. For example, the content regarding formula (1) described in JP-A-2022-158606 can be appropriately referred to, and its content is incorporated herein as it is as a part of the description of this specification. In the present invention, in the structural unit having a ring structure represented by formula (A), two R １ are methyl groups, two R ２ are hydrogen atoms, and X １It is preferable that the structural unit has a ring structure consisting of glutaric acid anhydride, in which the oxygen atom is located.

[0038] Examples of structural units having a ring structure composed of maleimide and structural units having a ring structure composed of maleic anhydride include the structural unit represented by the following formula (B).

[0039]

[0040] In equation (B), R ４ and R ５ R independently represents a hydrogen atom or a methyl group. ６ X is a hydrogen atom or substituent, ２ X is either an oxygen atom or a nitrogen atom. ２ When it is an oxygen atom, n is 0, X ２ When R is a nitrogen atom, n is 1. ６ The substituents that can be taken are not particularly limited, and for example, the contents of formula (2) described in Japanese Patent Application Publication No. 2022-158606 can be appropriately referred to, and those contents are incorporated as part of the description herein. In the present invention, the structural unit having a ring structure represented by formula (B) is R ４ and R ５ Both are hydrogen atoms, X ２ It is preferable that the structural unit has a ring structure consisting of maleic anhydride, which is an oxygen atom.

[0041] The ring structure consisting of a lactone and the ring structure consisting of a cyclic amide (pyrrolidinone) are not particularly limited, and for example, the contents of the lactone ring structure and pyrrolidinone ring structure described in Japanese Patent Application Publication No. 2022-158606 can be appropriately referenced, and their contents are incorporated as part of the description herein.

[0042] The (meth)acrylic resin (B) may contain one or more structural units including the above-mentioned ring structure. The ring structure included in the main chain of the (meth)acrylic resin can be formed by appropriate methods, for example, by the various methods described in Japanese Patent Application Publication No. 2022-158606, and the contents described in Japanese Patent Application Publication No. 2022-158606 are incorporated as is as part of this specification.

[0043] - Other Structural Units - (meth)acrylic resin (B) may contain other structural units that do not fall under any of the (meth)acrylic acid ester structural units, (meth)acrylic acid structural units, or structural units containing ring structures. The compounds (monomers) that lead to other structural units are not particularly limited as long as they are copolymerizable with (meth)acrylic acid esters, etc., and include monofunctional monomers having one polymerizable carbon-carbon double bond in the molecule, and polyfunctional monomers having two or more polymerizable carbon-carbon double bonds in the molecule. Examples of such monofunctional monomers include aromatic vinyl compounds such as styrene and α-methylstyrene; vinyl cyanide compounds such as (meth)acrylonitrile and (meth)acrylamide; and unsaturated carboxylic acids such as maleic acid and itaconic acid (excluding (meth)acrylic acid and anhydrides of unsaturated carboxylic acids). Examples of polyfunctional monomers include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethylolpropane triacrylate; alkenyl esters of unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate, and allyl cinnamate; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, and triallyl isocyanurate; and aromatic polyalkenyl compounds such as divinylbenzene. The (meth)acrylic resin may contain one or more of the above-mentioned other structural units.

[0044] The (meth)acrylic resin (B) includes acrylic resin and methacrylic resin, and methacrylic resin is preferred in terms of excellent anti-scattering properties and heat-processability, and methacrylic resin consisting of a copolymer of at least one methacrylic acid ester, methacrylic acid, and appropriately copolymerized structural units and / or other structural units is more preferred. The methacrylic resin preferably contains methyl methacrylate, and more preferably contains methyl acrylate. In this invention, methacrylic resin refers to a resin that contains structural units derived from methacrylic monomers such as methacrylic acid esters and methacrylic acid in a higher content than structural units derived from acrylic monomers such as acrylic acid esters and acrylic acid.

[0045] The content of each structural unit in the total 100 mol% of all structural units constituting the (meth)acrylic resin (B) contained in the base layer resin composition (B) is set as appropriate, but is preferably set within the following ranges. In the total content of all structural units constituting the (meth)acrylic resin (B) of 100 mol%, the content of (meth)acrylic acid ester structural units is preferably 90 to 99.985 mol%, more preferably 90 to 99.8 mol%, even more preferably 90 to 99.0 mol%, particularly preferably 92 to 98.0 mol%, and most preferably 93.0 to 97.0 mol%, in order to achieve excellent anti-scattering properties while maintaining excellent heat processability. In the total content of all structural units constituting (meth)acrylic resin (B) at 100 mol%, the content of (meth)acrylic acid structural units tends to contribute particularly strongly to improving the anti-scattering properties, and in order to achieve excellent anti-scattering properties while maintaining excellent heat processability, it is preferably 0.015 to 9.0 mol%, more preferably 0.05 to 9.0 mol%, even more preferably 0.1 to 9.0 mol%, particularly preferably 0.2 to 8.0 mol%, and most preferably 0.3 to 5.0 mol%.

[0046] If the (meth)acrylic resin composition (B) contains a resin other than (meth)acrylic resin (B), the content (mass%) of (meth)acrylic acid structural units in the total resin can be calculated from the product of the content (mass%) obtained by converting the content (mol%) in the above-mentioned (meth)acrylic resin (B) to a mass basis and the content (mass%) of (meth)acrylic resin (B) in the total resin. The content (mass%) of (meth)acrylic acid structural units in the total resin is not particularly limited, but in order to achieve excellent anti-scattering properties while maintaining excellent heat processability, it can be, for example, 0.01 to 10 mass%, preferably 0.1 to 10.0 mass%, more preferably 0.2 to 8.0 mass%, and even more preferably 0.3 to 5.0 mass%.

[0047] In the total content of all structural units constituting the (meth)acrylic resin (B), the content of structural units including ring structures is not particularly limited and is determined appropriately considering the balance between shatter prevention properties and heat processability. For example, when the (meth)acrylic resin (B) contains structural units including ring structures, the content of structural units including ring structures in the total content of 100 mol% can be, for example, 10 to 80 mol%, and preferably 20 to 60 mol%. On the other hand, when the (meth)acrylic resin (B) contains a small amount of structural units including ring structures, the content of structural units including ring structures in the total content of 100 mol% is preferably 1.0 mol% or less, more preferably 0.7 mol% or less, and even more preferably 0.5 mol% or less, considering the balance between shatter prevention properties and heat processability. The lower limit of the content of structural units including ring structures is greater than 0 mol%, and can be, for example, 0.001 mol% or more. The content of structural units having a ring structure, particularly those consisting of glutaric acid anhydride compounds, is determined appropriately considering the presence or absence of other structural units having a ring structure, the content of the aforementioned structural units having a ring structure, etc., but it is preferable that it be within the above range.

[0048] In the total content of all structural units constituting the (meth)acrylic resin (B), which is 100 mol%, the content of other structural units is appropriately determined according to the application, properties, etc., and for example, it is preferably 0.1 to 1.0 mol%, more preferably 0.2 to 0.8 mol%, and even more preferably 0.3 to 0.7 mol%.

[0049] The content of each component can be calculated from the amount of compound used to produce each component for polymerization, and can also be measured by known methods. For example, the component derived from (meth)acrylic acid is measured by the nuclear magnetic resonance spectrum in the examples described later. １３ This can be calculated by measuring C-NMR. If the (meth)acrylic resin (B) contains two or more of each component, the above content of each component shall be the total content of the two or more components.

[0050] The properties and physical characteristics of (meth)acrylic resin (B) are not particularly limited and are determined appropriately according to the application and the characteristics of the multilayer sheet (e.g., shatterproof properties, heat workability). For example, the weight-average molecular weight of (meth)acrylic resin is not particularly limited, but 5 × 10 ４ ~2 x 10 ５ It can be done this way.

[0051] (Meth)acrylic resin (B) can be a commercially available product or a synthetically produced product. When synthesizing (meth)acrylic resin, it can be produced by polymerizing (meth)acrylic acid ester, and optionally (meth)acrylic acid, a compound that leads to a structural unit containing a ring structure, and optionally other compounds that lead to other structural units, using conventionally known methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. In the method for producing (meth)acrylic resin, additives such as polymerization initiators, chain transfer agents, and suspension stabilizers may be used. The polymerization temperature is not particularly limited and can be, for example, 110 to 190°C.

[0052] (Fibrous glass filler) The fibrous glass filler contained in the base layer resin composition (B) is not particularly limited and may be in any shape, such as roving, chopped strand, middle fiber, glass beads, surfacing mat, chopped strand mat, satin weave, lattice weave, plain weave, open plain weave, twill weave, or net. The glass material forming the fibrous glass filler is not particularly limited and preferably uses, for example, quartz glass, borosilicate glass, fluorosilica glass, alkali-free glass, alkali-containing glass (e.g., soda glass), potassium lime glass, lead glass, etc. As the fibrous glass filler, alkali-free glass fibers such as E-GF, S-GF, T-GF, and alkali-containing glass fibers such as C-GF are preferably used. When surface treating the glass material, the surface treatment agent is not particularly limited and various coupling agents can be used, with silane-based coupling agents being preferred.

[0053] The shape of the fibrous glass filler is not particularly limited as long as it is fibrous; for example, its cross-sectional shape can be circular, elliptical, or flattened.

[0054] The size of the fibrous glass filler is not particularly limited and can be set as appropriate. For example, one preferred fiber length is 0.5 to 10 mm, and another preferred fiber length is 0.1 to 10 mm. The fiber diameter is preferably 3 to 25 μm. In this invention, when using commercially available fibrous glass filler, the fiber length and fiber diameter of the fibrous glass filler can be taken from catalog values.

[0055] As a fibrous glass filler, silicon dioxide (SiO₂) ２ ) 35-100% by mass, aluminum oxide (Al ２ O ３ ) 0-30% by mass, boron oxide (B ２ O ３ Preferably, the mixture contains 0 to 15% by mass of the above-mentioned substance and 0 to 65% by mass of other substances (such as magnesium oxide, zinc oxide, and barium oxide).

[0056] (Other Components) The (meth)acrylic resin composition (B) may contain components other than those described above (hereinafter sometimes referred to as "other components"). Other components are not particularly limited and include components that can be commonly used in resin compositions, such as release agents, anti-adhesion agents, ultraviolet absorbers, lubricants, antioxidants, plasticizers, antistatic agents, dyes (pigments), neutralizing agents, ultraviolet absorbers, lubricants, nucleating agents, adhesives, anti-fogging agents, anti-blocking agents, melt flow rate modifiers, and solvents. The (meth)acrylic resin composition (B) may also contain hard inorganic particles, which will be described later. Examples of release agents include higher fatty acid esters, higher aliphatic alcohols, higher fatty acids, higher fatty acid amides, higher fatty acid metal salts, and fatty acid derivatives. Examples of ultraviolet absorbers include benzophenone ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, benzotriazole ultraviolet absorbers, malonic acid ester ultraviolet absorbers, and oxalanilide ultraviolet absorbers. Examples of antioxidants include phenolic antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants. Examples of lubricants include silicone oil and polysiloxane compounds. Examples of antistatic agents include conductive inorganic particles, tertiary amines, quaternary ammonium salts, cationic acrylic acid ester derivatives, and cationic vinyl ether derivatives. The (meth)acrylic resin composition (B) may contain one of each of the other components, or two or more of each component. In the present invention, the above-mentioned other components may be mixed with the (meth)acrylic resin (B) during the preparation of the (meth)acrylic resin composition (B), or may be pre-mixed with the (meth)acrylic resin (B) prior to the preparation of the (meth)acrylic resin composition (B).

[0057] The (meth)acrylic resin composition (B), particularly the recovered (meth)acrylic resin composition (B) and the recycled (meth)acrylic resin composition (B), may contain components that were present in the surface layer (A), such as hard inorganic particles described later. The content of hard inorganic particles in the (meth)acrylic resin composition (B) is not particularly limited and can be appropriately set within a range that maintains the excellent shatterproof properties and heat-processability described in the present invention when a multilayer board is manufactured, for example, it can be 10% by mass or less.

[0058] (Composition of (meth)acrylic resin composition (B)) The (meth)acrylic resin composition (B) only needs to contain the (meth)acrylic resin and the fibrous glass filler described above, and the content of each component (composition of the composition) is not particularly limited and is appropriately determined according to the application, the characteristics of the multilayer plate (e.g., shatterproof properties, heat workability), etc., and is preferably set within the following range, for example. The total content of (meth)acrylic resin (B) and fibrous glass filler in 100 parts by mass of the (meth)acrylic resin composition (B) is not particularly limited, but is preferably 50 parts by mass or more, more preferably 70 to 100 parts by mass, and even more preferably 75 to 95 parts by mass, in order to achieve excellent shatterproof properties while maintaining heat workability. The content of (meth)acrylic resin in (meth)acrylic resin composition (B) is preferably 10 to 90 parts by mass per 100 parts by mass of the total content of (meth)acrylic resin (B) and fibrous glass filler, in order to achieve excellent shatterproof properties while maintaining heat workability, and more preferably 60 to 85 parts by mass, and even more preferably 70 to 80 parts by mass, in order to achieve an even higher level of balance between heat workability and shatterproof properties. The content of fibrous glass filler in (meth)acrylic resin composition (B) is preferably 1 to 40 parts by mass per 100 parts by mass of the total content of (meth)acrylic resin (B) and fibrous glass filler, in order to achieve excellent shatterproof properties while maintaining heat workability, and more preferably 10 to 35 parts by mass, and even more preferably 15 to 30 parts by mass, in order to achieve an even higher level of balance between heat workability and shatterproof properties. In the (meth)acrylic resin composition (B), the ratio of the (meth)acrylic resin content to the fibrous glass filler content [(meth)acrylic resin content / fibrous glass filler content] is appropriately determined considering the above-mentioned contents, and can be, for example, 65 / 35 to 90 / 10, and preferably 70 / 30 to 85 / 15.

[0059] The total content of other components in 100 parts by mass of (meth)acrylic resin composition (B) is appropriately determined within a range that does not impair the effects of the present invention, and can be, for example, 0.5 parts by mass or less. The content of each component in 100 parts by mass of (meth)acrylic resin layer (B) is the same as the content of each component in 100 parts by mass of glass fiber reinforced (meth)acrylic resin composition (B) (excluding the solvent).

[0060] (Preparation of (meth)acrylic resin composition (B)) (meth)acrylic resin composition (B) can be manufactured by known methods and is usually prepared by mixing or kneading (meth)acrylic resin (B), fibrous glass filler, and other components as appropriate. The mixing and kneading methods are not particularly limited and any conventionally known methods such as melt kneading can be used. Conventional mixers and kneaders can be used as equipment for mixing and kneading, such as single-screw kneaders, twin-screw kneaders, multi-screw extruders, Henschel mixers, Banbury mixers, kneaders, and roll mills. If it is necessary to increase the rotational speed in the kneading method, a high-shear processing device can be used, for example. The kneading temperature is not particularly limited and can be set as appropriate considering the selected components, their quantities, properties, etc., for example, it can be 200 to 280°C. In the preparation of the (meth)acrylic resin composition (B), recovered components (e.g., recovered (meth)acrylic resin) and recycled components (e.g., recycled (meth)acrylic resin) can be used as components; however, in the present invention, unused components are usually used.

[0061] [Surface Layer (A)] The surface layer (A) consists of a (meth)acrylic resin layer and is formed in layers with a (meth)acrylic resin composition (A) containing the (meth)acrylic resin (A) described later. In the multilayer plate of the present invention, by forming the surface layer (A) with the (meth)acrylic resin composition (A), excellent shatterproof properties and thermal workability can be achieved together with the base layer (B). It is preferable that the (meth)acrylic resin composition (A) contains (meth)acrylic resin (A) and hard inorganic particles, in that it is possible to improve scratch resistance (scratch resistance) while maintaining the thermal workability and shatterproof properties of the multilayer plate. The surface layer (A) is a non-thermosetting layer and is preferably an uncured layer that has not been cured by heat, light and other curing agents or polymerization initiators. It is also preferable that the surface layer (A) is thermoplastic. The surface layer (A) may be a glass fiber reinforced (meth)acrylic resin layer containing fibrous glass filler, or it may be a glass fiber unreinforced (meth)acrylic resin layer that does not contain fibrous glass filler. In the present invention, "not containing fibrous glass filler" includes a configuration in which the (meth)acrylic resin composition forming the surface layer (A) contains less than 1 part by mass of (meth)acrylic resin per 100 parts by mass of (meth)acrylic resin.

[0062] <(Meth)acrylic resin composition (A)> The (meth)acrylic resin composition (A) that forms the surface layer (A) (in this invention, this may be referred to as the "surface layer resin composition") contains (meth)acrylic resin (A) and preferably contains hard inorganic particles. The components contained in the surface layer resin composition (A) will be described below. Each component contained in the surface layer resin composition (A) may be one type or two or more types.

[0063] ((meth)acrylic resin (A)) The (meth)acrylic resin (A) contained in the surface layer resin composition (A) is a resin consisting of a polymer containing structural units derived from (meth)acrylic acid ester, and includes resins consisting of copolymers containing structural units derived from (meth)acrylic acid ester and various copolymer structural units and other structural units described later. Examples of (meth)acrylic resin (A) include resins consisting of a homopolymer containing only one type of (meth)acrylic acid ester structural unit, and resins consisting of copolymers containing two or more types of (meth)acrylic acid ester structural units. In terms of anti-scattering properties and heat processability, resins consisting of copolymers containing two or more types of (meth)acrylic acid ester structural units are preferred, and resins consisting of copolymers containing at least one type of acrylic acid ester structural unit and at least one type of methacrylic acid ester structural unit are more preferred. Each of the above copolymers may contain one or more of the other structural units described later. The (meth)acrylic resin (A) may or may not contain the structural units and / or ring structures derived from the above-mentioned (meth)acrylic acid.

[0064] The content of (meth)acrylic acid ester structural units in the polymer ((meth)acrylic resin) is not particularly limited and can be determined as appropriate. For example, the content of (meth)acrylic acid ester structural units is usually 50 mol% or more, but preferably 85 mol% or more, and more preferably 90 mol% or more, based on the total content of all structural units constituting the polymer (100 mol%). On the other hand, the upper limit of the above content can be 100 mol%, but it is preferably 99 mol% or less.

[0065] The (meth)acrylic resin composition (A) that forms the surface layer (A) may contain one or more types of (meth)acrylic resins. If the resin composition (A) for the surface layer contains two or more types of (meth)acrylic resins, the properties and physical characteristics of the (meth)acrylic resins (A), such as the content of each structural unit, only need to conform to the content described later for the two or more types of (meth)acrylic resins as a whole, and each (meth)acrylic resin may or may not conform to the content.

[0066] - Structural units derived from (meth)acrylic acid esters - The (meth)acrylic acid esters used to derive structural units derived from (meth)acrylic acid esters are not particularly limited, and examples include alkyl (meth)acrylates and aryl (meth)acrylates, with alkyl (meth)acrylates being preferred. The alkyl group constituting the alkyl (meth)acrylate is not particularly limited, but an alkyl group having 1 to 8 carbon atoms is preferred.

[0067] Examples of alkyl acrylates include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, lauryl acrylate, and benzyl acrylate. The acrylic acid ester preferably contains methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, or 2-ethylhexyl acrylate, and more preferably contains methyl acrylate.

[0068] Examples of alkyl methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, sec-butyl methacrylate, iso-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, and benzyl methacrylate. The methacrylic acid esters preferably include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, sec-butyl methacrylate, iso-butyl methacrylate, or 2-ethylhexyl methacrylate, and more preferably include methyl methacrylate.

[0069] The (meth)acrylic acid ester may have substituents. The (meth)acrylic resin (A) may contain one or more structural units derived from the above (meth)acrylic acid ester.

[0070] - Structural units derived from (meth)acrylic acid - The structural units derived from (meth)acrylic acid are not particularly limited and are the same as those in (meth)acrylic resin (B) above.

[0071] - Structural units including ring structures - Structural units including ring structures are not particularly limited and are the same as those in the (meth)acrylic resin (B) described above.

[0072] - Other structural units - Other structural units are not particularly limited and are the same as those in (meth)acrylic resin (B) above.

[0073] The (meth)acrylic resin (A) includes acrylic resin and methacrylic resin, with methacrylic resin being preferred in terms of anti-scattering properties and heat-processability, methacrylic resin consisting of a copolymer containing structural units derived from at least one methacrylic acid ester is more preferred, and methacrylic resin consisting of a copolymer containing structural units derived from at least one acrylic acid ester and structural units derived from at least one methacrylic acid ester is even more preferred. The methacrylic resin preferably contains methyl methacrylate, and more preferably contains methyl acrylate. The (meth)acrylic resin (A) is particularly preferred as a methacrylic resin consisting of a copolymer containing structural units derived from one or more acrylic acid esters containing methyl acrylate and structural units derived from one or more methacrylic acid esters containing methyl methacrylate, and most preferably as a methacrylic resin consisting of a copolymer containing structural units derived from methyl acrylate and structural units derived from methyl methacrylate.

[0074] The content of each structural unit in the total 100 mol% of all structural units constituting the (meth)acrylic resin (A) contained in the (meth)acrylic resin composition (A) that forms the surface layer (A) is set as appropriate, but is preferably set within the following range. In the total 100 mol% of all structural units constituting the (meth)acrylic resin (A), the content of (meth)acrylic acid ester structural units is usually 50 mol% or more in terms of heat processability and anti-scattering properties, but is preferably 85 to 100 mol%, and more preferably 90 to 100 mol% or more.

[0075] When (meth)acrylic resin (A) is an acrylic resin, the content of acrylic acid ester structural units is preferably 50 to 100 mol%, more preferably 65 to 98 mol%, and even more preferably 80 to 90 mol%, out of a total content of all structural units constituting the acrylic resin. When the acrylic resin contains methacrylic acid ester structural units, the content of methacrylic acid ester structural units is preferably 10 mol% or less, more preferably 1 to 9 mol%, and even more preferably 2 to 8 mol%, out of a total content of all structural units constituting the acrylic resin.

[0076] When (meth)acrylic resin (A) is methacrylic resin, the methacrylic acid ester structural units are preferably 50 to 100 mol%, more preferably 65 to 98 mol%, and even more preferably 80 to 90 mol%, out of a total content of 100 mol% of all structural units constituting the methacrylic resin. When the methacrylic resin contains acrylic acid ester structural units, the content of acrylic acid ester structural units is preferably 10 mol% or less, more preferably 1 to 9 mol%, and even more preferably 2 to 8 mol%, out of a total content of 100 mol% of all structural units constituting the methacrylic resin.

[0077] (Meth)acrylic resin (A) may contain (meth)acrylic acid structural units, but it is preferable that it does not. In the present invention, "(meth)acrylic resin (A) does not contain (meth)acrylic acid structural units" includes the embodiment in which the content of (meth)acrylic acid structural units in the total content of all structural units constituting (meth)acrylic resin (A) is 0 mol%, and the embodiment in which it is greater than 0 mol% and less than 0.015 mol%. (Meth)acrylic resin (A) may contain structural units including ring structures, but it is preferable that it does not. In the present invention, "(meth)acrylic resin (A) does not contain structural units including ring structures" includes the embodiment in which the content of structural units including ring structures in the total content of all structural units constituting (meth)acrylic resin (A) is 0 mol%, and the embodiment in which it is greater than 0 mol% and less than the lower limit when (meth)acrylic resin (B) contains fewer structural units including ring structures. In the total content of all structural units constituting the (meth)acrylic resin (A), which is 100 mol%, the content of other structural units is appropriately determined according to the application, properties, etc., and for example, it is preferably 0.01 to 2.0 mol%, more preferably 0.1 to 1 mol%, and even more preferably 0.2 to 0.8 mol%.

[0078] The content of each component can be calculated or measured in the same manner as for (meth)acrylic resin (B). If (meth)acrylic resin (A) contains two or more of each component, the above content of each component shall be the total content of the two or more components.

[0079] The properties and physical characteristics of the (meth)acrylic resin (A) are not particularly limited and are determined appropriately according to the application and the characteristics of the multilayer sheet (e.g., shatterproof properties, heat workability). For example, the weight-average molecular weight of the (meth)acrylic resin is not particularly limited, but is 5 × 10⁻⁶. ４ ~2 x 10 ５ It can be done this way.

[0080] (Meth)acrylic resin (A) can be a commercially available product, or a synthetically produced product can be used as appropriate. The synthesis method and conditions for (meth)acrylic resin (A) are the same as those for (meth)acrylic resin (B).

[0081] (Hard Inorganic Particles) The resin composition (A) for the surface layer preferably contains hard inorganic particles. If the resin composition (A) for the surface layer contains hard inorganic particles, the scratch resistance of the surface layer (A), and by extension the multilayer plate of the present invention, can be further improved. As hard inorganic particles, spherical hard inorganic particles are preferred. In the present invention, the hard inorganic particles may be any hard inorganic particles, such as metal oxides, metal carbides, and metal silicates. Here, "metal elements" include metal elements belonging to groups 1 to 14 of the periodic table, as well as so-called "metalloid elements" belonging to groups 14 to 17 of the periodic table, such as silicon, germanium, antimony, tellurium, and bismuth. The hard inorganic particles may contain one or more metal elements. When the hard inorganic particles contain two or more metal elements, they may be called composite oxides, composite carbides, etc. Examples of metal oxides include titanium oxide (silica), aluminum oxide (alumina), zirconium oxide, silica-titania, and magnesium oxide (magnesia). Examples of metal carbides include silicon carbide. Examples of metal element silicates include zirconium silicate. As hard inorganic particles, metal oxide particles are preferred, and particles of silica, zirconium oxide, and silica-titania are more preferred. Note that hard inorganic particles differ from the fibrous glass fillers described above in that they are particles, preferably spherical particles.

[0082] The particle size (median diameter) of hard inorganic particles is preferably 100 to 1500 nm, more preferably 100 to 1000 nm, and even more preferably 100 to 500 nm, from the viewpoint of improving scratch resistance. The particle size (median diameter) of hard inorganic particles can be determined, for example, by a laser diffraction particle size distribution analyzer. The equipment used to measure particle size is not particularly limited. Examples of equipment that can measure particle size include Nikkiso's "Microtrac," Horiba's "LA," Cirrus's "CILAS," Malvern's "Mastersizer," and Beckman Coulter's "LS." The median diameter that can be measured by the measurement method using a laser diffraction particle size distribution analyzer is also called d50, and refers to a predetermined particle size at which, when the powder is divided in half, the volume of the side with larger particle size and the volume of the side with smaller particle size are equal.

[0083] By setting the average particle size of the hard inorganic particles within the above range, it is possible to improve both scratch resistance and transparency while maintaining excellent shatterproof properties and heat processability. In this invention, the average particle size refers to the median diameter (d50).

[0084] The silica particles are not particularly limited. The refractive index of the silica particles (refractive index when irradiated with light of a wavelength of 589 nm at 25°C) is preferably 1.47 to 1.60, more preferably 1.47 to 1.52, and even more preferably 1.47 to 1.50. The refractive index of the silica particles can be adjusted to any suitable refractive index by changing the composition ratio of silicon to other elements in the silica particles. The refractive index of the silica particles can be measured by any suitable conventional method known, such as the immersion method. By setting the refractive index of the silica particles within the above range, transparency can be further enhanced while maintaining excellent shatterproof properties and heat processability.

[0085] Silica particles can be produced by conventionally known and suitable manufacturing methods such as flame melting, flame hydrolysis, and sol-gel methods.

[0086] As silica particles, commercially available products can be used. Examples of such commercially available products include "AdmaFine SO-C2" manufactured by Admatex Corporation, "Snowtex O" manufactured by Nissan Chemical Industries, Ltd., and "Sunsphere NP-30" manufactured by AGC SI-TEC Corporation.

[0087] (Other Components) The (meth)acrylic resin composition (A) may contain components other than those described above (hereinafter sometimes referred to as "other components"). The other components that the (meth)acrylic resin composition (A) may contain are not particularly limited and include, for example, fibrous glass fillers and the components described in the section on other components that the (meth)acrylic resin composition (B) may contain. Examples of fibrous glass fillers include the fibrous glass fillers described in the section on (meth)acrylic resin composition (B). In the present invention, it is preferable that the (meth)acrylic resin composition (A) and the (meth)acrylic resin layer (A) do not contain fibrous glass fillers. The statement that the (meth)acrylic resin composition (A) and the (meth)acrylic resin layer (A) do not contain fibrous glass fillers means that the content of fibrous glass fillers in 100 parts by mass of the (meth)acrylic resin composition (A) or the (meth)acrylic resin layer (A) is 1 part by mass or less.

[0088] (Composition of (meth)acrylic resin composition (A)) The (meth)acrylic resin composition (A) only needs to contain the (meth)acrylic resin described above, and the content of each component (composition of the composition) is not particularly limited and is appropriately determined according to the application, the characteristics of the multilayer board (e.g., shatterproof properties, heat workability), etc., and is preferably set within the following range, for example. The content of (meth)acrylic resin (A) in 100 parts by mass of the (meth)acrylic resin composition (A) is not particularly limited, but is preferably 50 parts by mass or more, more preferably 70 to 100 parts by mass, and even more preferably 75 to 95 parts by mass, in order to achieve excellent shatterproof properties while maintaining heat workability.

[0089] The content of hard inorganic particles in the (meth)acrylic resin composition (A) is not particularly limited and can be determined as appropriate. The content of hard inorganic particles is preferably 0.001 to 5 parts by mass, more preferably 0.01 to 5 parts by mass, even more preferably 0.01 to 1 part by mass, and particularly preferably 0.03 to 0.45 parts by mass, per 100 parts by mass of (meth)acrylic resin. The content of hard inorganic particles in the methacrylic resin composition (A) can be measured, for example, using the ICP-AES method. By setting the content of hard inorganic particles to 0.001 parts by mass or more, a multilayer board can be made that has excellent shatterproof properties and heat processability, as well as high scratch resistance. Furthermore, by setting the content of hard inorganic particles to 5 parts by mass or less, a multilayer board can be made that has excellent shatterproof properties and heat processability, as well as high transparency. In other words, by keeping the content of hard inorganic particles within the above range, it is possible to improve both scratch resistance and transparency, as well as water resistance, while maintaining excellent shatterproof properties and heat processability. The content of hard inorganic particles may also be the blending concentration of hard inorganic particles when melt-mixing the (meth)acrylic resin and hard inorganic particles. The blending concentration value and the content value are generally the same. From the viewpoint of accuracy, it is preferable to measure the content of hard inorganic particles by the ICP-AES method.

[0090] The content of metal oxides, particularly silica particles, in the (meth)acrylic resin composition (A) can be appropriately determined considering the content of the hard inorganic particles, and it is preferable, for example, to be within the same range as the content of the hard inorganic particles.

[0091] The total content of other components in 100 parts by mass of (meth)acrylic resin composition (A) is appropriately determined within a range that does not impair the effects of the present invention, and can be, for example, 0.5 parts by mass or less. The content of fibrous glass filler in 100 parts by mass of (meth)acrylic resin composition (A) is appropriately determined considering the total content of the other components mentioned above, and is preferably within the above range. The content of each component in 100 parts by mass of (meth)acrylic resin layer (A) is the same as the content of each component in 100 parts by mass of (meth)acrylic resin composition (A) (excluding the solvent).

[0092] (Preparation of (meth)acrylic resin composition (A)) (Meth)acrylic resin composition (A) can be manufactured by known methods and is usually prepared by mixing or kneading (meth)acrylic resin (A), the hard inorganic particles and other components as appropriate. The mixing and kneading methods are not particularly limited and, for example, the mixing and kneading methods described above in the preparation of (meth)acrylic resin composition (B) can be used. In the preparation of (meth)acrylic resin composition (A), recovered components (e.g., recovered (meth)acrylic resin) and recycled components (e.g., recycled (meth)acrylic resin) can be used as each component, but in the present invention, unused components are usually used.

[0093] [Method for Manufacturing Multilayer Boards] The multilayer board of the present invention can be manufactured by laminating a base layer and a surface layer. The method for manufacturing a multilayer board by laminating a base layer and a surface layer is not particularly limited, and it may be manufactured by laminating the base layer and surface layer separately using a conventional method, but in terms of workability and other factors, a method of manufacturing the base layer and surface layer by co-extrusion is preferred.

[0094] Methods for separately producing the base layer and surface layer include, for example, melt extrusion, in which each resin layer is melt-extruded using an extruder and at least one side of the resulting plate-like material is brought into contact with a roll or belt to form it into a plate; and press molding, in which each (meth)acrylic resin composition is formed into a plate using a heated press device.

[0095] One method for producing multilayer sheets by co-extrusion is to use multiple uniscrew, twin-screw, or multi-screw extruders to melt-knead a (meth)acrylic resin composition (B) that forms the base layer (B) and a (meth)acrylic resin composition (A) that forms the surface layer (A), and then laminate them via a feed block or multi-manifold die. Here, each (meth)acrylic resin composition that forms the base layer (B) or the surface layer (A) can be used as pellets obtained by mixing components such as (meth)acrylic resin in a supermixer, and then melt-kneading the resulting mixture in an extruder. The conditions for melt extrusion, heating press, and melt-kneading can be appropriately selected to melt or soften the (meth)acrylic resin in each (meth)acrylic resin composition, for example, the heating temperature can be set to 200 to 290°C. Other conditions, such as the discharge speed (extrusion speed) and screw rotation speed, can be appropriately set according to the composition and physical properties of each (meth)acrylic resin composition. After co-extrusion, the sheets are cooled. The cooling method is not particularly limited, and known cooling methods such as air cooling, water cooling, and forced cooling with a cooler can be applied. The cooling conditions, such as the cooling rate and cooling temperature, can be appropriately set according to the composition and physical properties of each (meth)acrylic resin composition.

[0096] [[Molded Article]] A molded article using the multilayer sheet of the present invention (for convenience, referred to as "the molded article of the present invention") may be a plate-shaped molded article made of the multilayer sheet of the present invention itself, or it may be a molded article obtained by molding or processing the multilayer sheet of the present invention into a predetermined shape and dimensions according to the application. Furthermore, the molded article of the present invention may be a molded article made of the multilayer sheet of the present invention and other members.

[0097] [Method for Manufacturing a Molded Article] The method for manufacturing the molded article of the present invention is not particularly limited, and known molding methods can be applied. For example, the multilayer sheet of the present invention can be molded and processed by press molding, blow molding, etc. Since the multilayer sheet of the present invention is thermoplastic and has excellent thermoprocessability, thermal processing such as press molding and (free) blow molding can be preferably applied. The molding conditions and processing conditions are not particularly limited as long as the multilayer sheet of the present invention can be molded and processed, and can be appropriately set according to the physical properties of the multilayer sheet of the present invention. In addition, in the method for manufacturing the molded article, recovered (meth)acrylic resin compositions and recycled (meth)acrylic resin compositions can also be used as the (meth)acrylic resin composition.

[0098] [[Method for Disassembling and Recovering Multilayer Boards]] The multilayer boards of the present invention may be disposed of or incinerated, but from the viewpoint of reducing environmental burden (environmental protection) and building a circular economy (sustainable society), recycling is desirable. The inventors have investigated and found that (meth)acrylic acid esters can be recovered and recycled from the multilayer boards of the present invention by the following method.

[0099] In the multilayer board decomposition and recovery method of the present invention (sometimes simply referred to as "the decomposition and recovery method of the present invention"), the multilayer board of the present invention is decomposed at a temperature of 380°C or higher, and the obtained volatile components and solid matter are separated. By this decomposition and recovery method of the present invention, the (meth)acrylic acid ester contained in each (meth)acrylic resin composition forming the base layer and surface layer can be chemically recycled. In the decomposition and recovery method of the present invention, the heating temperature (decomposition temperature) of the multilayer board should be 380°C or higher, and can be appropriately determined according to the type of (meth)acrylic resin contained in the (meth)acrylic resin composition (boiling point, decomposition temperature, etc.). For example, the temperature at which the (meth)acrylic resin decomposes and the obtained (meth)acrylic acid ester becomes gaseous is preferred, specifically, 385°C or higher is preferred, and 390°C or higher is more preferred. The upper limit of the heating temperature is not particularly limited, for example, 500°C or lower is preferred, and 460°C or lower is more preferred. The heating time is not particularly limited and can be appropriately determined according to the degree of decomposition of the (meth)acrylic resin. For example, the heating time can be 5 to 20 minutes. In this way, the (meth)acrylic resin contained in the (meth)acrylic resin composition forming the multilayer board of the present invention can be thermally decomposed into (meth)acrylic acid ester.

[0100] In the decomposition and recovery method of the present invention, the obtained volatile components and solid matter are separated during or after the thermal decomposition of the (meth)acrylic resin. Various known separation methods can be applied to this separation, but it is preferable to separate the gas and solid at the above decomposition temperature, with the (meth)acrylic acid ester in a gaseous state as a volatile component and the other components as solid matter.

[0101] In the decomposition and recovery method of the present invention, steps other than the decomposition and separation steps described above may also be performed. For example, these include a step of purifying the recovered (meth)acrylic acid ester and a step of cutting a multilayer plate made of the (meth)acrylic resin composition of the present invention.

[0102] The decomposition and recovery method of the present invention allows for the decomposition and recovery of the multilayer board and (meth)acrylic resin composition of the present invention through the simple steps of decomposition and separation described above. Specifically, (meth)acrylic acid esters can be separated and recovered from the multilayer board and (meth)acrylic resin composition of the present invention.

[0103] The decomposition and recovery method of the present invention can also be applied to molded articles of the present invention. For example, similar to the multilayer boards of the present invention, (meth)acrylic acid esters can be recovered and recycled from molded articles of the present invention (including off-spec products, manufacturing intermediates, manufacturing waste, or used recovered products) by the method described above. Furthermore, the decomposition and recovery method of the present invention can also be applied to recovered multilayer boards and recycled multilayer boards, as well as recovered molded articles and recycled molded articles, as described later. In this case, (meth)acrylic acid esters can be recovered and recycled by the method described above, with the target of application being the multilayer boards or molded articles described above instead of the multilayer boards of the present invention.

[0104] [[Recycled (meth)acrylic resin composition]] A recycled (meth)acrylic resin composition is a resin composition containing a recovered (meth)acrylic resin composition, preferably a composition recycled by the recycling method for (meth)acrylic resin compositions of the present invention. The recovered (meth)acrylic resin composition includes one or more types of recovered (meth)acrylic resin compositions recovered from the multilayer board of the present invention (corresponding to the recycled multilayer board described above), and the recycled (meth)acrylic resin composition recovered from the recycled multilayer board of the present invention. That is, the recovered (meth)acrylic resin composition includes recovered (meth)acrylic resin compositions recovered from waste generated in the preparation of the (meth)acrylic resin composition of the present invention, waste generated in the manufacture of the multilayer board of the present invention, and multilayer boards of the present invention discarded by consumers, and further includes recovered (meth)acrylic resin compositions recovered from waste generated in the preparation of already recycled (meth)acrylic resin compositions, waste generated in the manufacture of recycled multilayer boards, and recycled multilayer boards discarded by consumers.

[0105] The recycled (meth)acrylic resin composition (as appropriate, referred to as "the recycled (meth)acrylic resin composition of the present invention") is a resin composition comprising a (meth)acrylic resin composition recovered and recycled from the multilayer board of the present invention, or the recycled multilayer board of the present invention (corresponding to the recycled multilayer board described above), and unused (meth)acrylic resin (B) and unused fibrous glass filler as virgin material. The recycled (meth)acrylic resin composition of the present invention can satisfy the excellent level of shatterproof properties and heat-processability exhibited by the multilayer board of the present invention, even if it contains the recovered (meth)acrylic resin composition. The recycled (meth)acrylic resin composition, in particular the recycled (meth)acrylic resin composition obtained by the recycling method of the (meth)acrylic resin composition of the present invention, can be used as a material for forming the multilayer board of the present invention, and is particularly preferably used as a (meth)acrylic resin composition for forming the base layer (B) of the multilayer board.

[0106] In the recycled (meth)acrylic resin composition of the present invention, the recovered (meth)acrylic resin composition may contain each component as a whole (present, scattered) or independently. The source of the recovered (meth)acrylic resin composition contained in the recycled (meth)acrylic resin composition of the present invention and the number of recoveries (recycling count) of the multilayer board containing the recovered (meth)acrylic resin composition are not particularly limited. For example, the number of recoveries of the recovered (meth)acrylic resin composition (recovered multilayer board) is preferably set within a range in which the recycled multilayer board satisfies excellent levels of shatterproof properties and thermal processability. The number of recoveries depends on the composition and physical properties of the recycled (meth)acrylic resin composition, for example, but as an example, it is preferably 2 to 10 times in terms of shatterproof properties and thermal processability. When the recycled (meth)acrylic resin composition of the present invention contains a recovered (meth)acrylic resin composition that has been recovered multiple times, the recovered (meth)acrylic resin composition contained in the recycled (meth)acrylic resin composition of the present invention may be a recovered (meth)acrylic resin composition recovered the same number of times, or it may be a plurality of different types of recovered (meth)acrylic resin compositions recovered the same number of times.

[0107] The unused (meth)acrylic resin contained in the recycled (meth)acrylic resin composition of the present invention is not particularly limited, and any suitable (meth)acrylic resin can be used. However, in terms of shatterproof properties and heat processability, it is preferable to include the (meth)acrylic resin (B) used in the (meth)acrylic resin composition (B) that forms the base layer (B), that is, a (meth)acrylic resin in which the content of structural units derived from (meth)acrylic acid ester is 90 to 99.985 mol% and the content of structural units derived from (meth)acrylic acid is 0.015 to 9.0 mol% based on a total content of 100 mol% of all structural units. Details of the (meth)acrylic resin are as described above. Furthermore, the unused fibrous glass filler contained in the recycled (meth)acrylic resin composition of the present invention is not particularly limited, but it is preferable to include the fibrous glass filler used in the (meth)acrylic resin composition (B) that forms the base layer (B). The recycled (meth)acrylic resin composition of the present invention may also contain other unused components. These unused components are the same as the other components used in the (meth)acrylic resin composition (B) that forms the base layer (B). Each component contained in the recycled (meth)acrylic resin composition of the present invention may be one type or two or more types.

[0108] [Composition of Recycled (Meth)acrylic Resin Composition] The recycled (meth)acrylic resin composition of the present invention may contain the above-mentioned recovered (meth)acrylic resin composition, unused (meth)acrylic resin, and unused fibrous glass filler, and the appropriate composition (contained components and their content) is determined according to the application, the characteristics of the multilayer board (e.g., shatterproof properties, heat workability), etc. The composition of the recycled (meth)acrylic resin composition of the present invention (regardless of the number of times the contained recovered (meth)acrylic resin composition has been recovered, encompassing the composition of the recycled (meth)acrylic resin composition of the present invention; the same applies hereinafter) is preferably such that it satisfies a preferred range as an excellent level in the evaluation of shatterproof properties and heat workability in the examples described later. The composition of the recycled (meth)acrylic resin composition of the present invention (the content of (meth)acrylic resin and fibrous glass filler) is more preferably such that it satisfies the composition range described above for the (unused) (meth)acrylic resin composition that forms the base layer (B), and it may also be the same composition as the (unused) (meth)acrylic resin composition that forms the base layer (B). The composition of the (unused) (meth)acrylic resin composition that forms the base layer (B) is as described above.

[0109] In this invention, the term "same composition" refers to the identity of both the (meth)acrylic resin and the fibrous glass filler components, and does not concern the identity of other components. Furthermore, while the (meth)acrylic resin and fibrous glass filler may deteriorate due to recycling of the (meth)acrylic resin composition of this invention, in this invention, the identity of the components is determined by their identity in an unused state.

[0110] Since the multilayer board of the present invention has a surface layer (A) in addition to a base layer (B), the (meth)acrylic resin ((meth)acrylic resin composition) recovered from the multilayer board of the present invention is a mixture of the (meth)acrylic resin forming the base layer (B) and the (meth)acrylic resin forming the surface layer (A), and the composition of the (meth)acrylic resin (types and / or content of structural units) may change.

[0111] In the recycled (meth)acrylic resin composition of the present invention, it is preferable that the content of fibrous glass filler derived from the recovered (meth)acrylic resin composition and the content of unused fibrous glass filler contained in the recycled (meth)acrylic resin composition are the same, in order to achieve an excellent level of both anti-shattering properties and heat-processability. That is, it is preferable that the content of recovered fibrous glass filler contained in the recovered (meth)acrylic resin composition as a percentage of 100 parts by mass of the total recovered (meth)acrylic resin and recovered fibrous glass filler is the same as the content of unused fibrous glass filler as a percentage of the total unused (meth)acrylic resin and unused fibrous glass filler contained in the recycled (meth)acrylic resin composition. In this case, the above content of recovered fibrous glass filler and the above content of unused fibrous glass filler can each be within the same range as the content of (unused) fibrous glass filler in the (meth)acrylic resin composition (B) that forms the base layer (B). For example, in the recycled (meth)acrylic resin composition of the present invention, in order to achieve an excellent balance between anti-scattering properties and heat-processability, it is preferable that the content of unused fibrous glass filler in a total of 100 parts by mass of unused (meth)acrylic resin and unused fibrous glass filler is 1 to 40 parts by mass, and the more preferable range and even more preferable range are as described above.

[0112] In the recycled (meth)acrylic resin composition of the present invention, the content of the recovered (meth)acrylic resin composition, the content of the unused (meth)acrylic resin, and the content of the unused fibrous glass filler are not particularly limited and can be set as appropriate. For example, in the recycled (meth)acrylic resin composition, of the total content of the recovered (meth)acrylic resin composition, unused (meth)acrylic resin, and unused fibrous glass filler at 100% by mass, the content of the recovered (meth)acrylic resin composition is preferably 1 to 99% by mass, more preferably 3 to 90% by mass, even more preferably 5 to 80%, and particularly preferably 10 to 70%, in order to achieve an excellent balance between shatterproof properties and heat processability. At this time, the content of the recovered (meth)acrylic resin and the content of the recovered fibrous glass filler in the recovered (meth)acrylic resin composition can be set as appropriate, but it is preferable that the total of the content of the unused (meth)acrylic resin and unused fibrous glass filler equals the above-mentioned content in (meth)acrylic resin composition (B). Furthermore, in the recycled (meth)acrylic resin composition, the total content of unused (meth)acrylic resin and unused fibrous glass filler in 100% by mass of the total content of the recovered (meth)acrylic resin composition, unused (meth)acrylic resin, and unused fibrous glass filler is preferably 1 to 99% by mass, more preferably 10 to 97% by mass, even more preferably 20 to 95%, and particularly preferably 30 to 90%, in order to achieve an excellent balance between shatterproof properties and heat processability. At this time, the content of unused (meth)acrylic resin and unused fibrous glass filler in the above total content can be set as appropriate, but it is preferable that the total of the recovered (meth)acrylic resin and recovered fibrous glass filler present in the recovered (meth)acrylic resin composition equals the above content in (meth)acrylic resin composition (B).

[0113] If the recycled (meth)acrylic resin composition of the present invention contains other unused components, the content of these other unused components is not particularly limited and can be set as appropriate. The recycled (meth)acrylic resin composition of the present invention may also contain hard inorganic particles derived from the surface layer (A) of the recovered multilayer board. The content of hard inorganic particles that the recycled (meth)acrylic resin composition may contain is not particularly limited, but for example, it can be 5 parts by mass or less per 100 parts by mass of (meth)acrylic resin, and a preferred content can be the same as the above content of hard inorganic particles in the (meth)acrylic resin composition (A) that forms the surface layer (A).

[0114] [Preparation of Recycled (Meth)acrylic Resin Composition] The recycled (meth)acrylic resin composition of the present invention can be prepared in the same manner as the preparation of the (meth)acrylic resin composition (B) that forms the base layer (B), except that it uses a recovered (meth)acrylic resin composition, unused (meth)acrylic resin, unused fibrous glass filler, and other unused components as appropriate. In the present invention, it is preferable to prepare the recycled (meth)acrylic resin composition by the recycling method of the present invention described later. The unused components used in the preparation of the recycled (meth)acrylic resin composition of the present invention may be mixed individually with the recovered (meth)acrylic resin composition, or they may be mixed as a mixture of two or more unused components that have been mixed in advance.

[0115] [[Recycled Multilayer Board and Method for Manufacturing the Same]] In the present invention, the recycled (meth)acrylic resin composition can be recovered and collected in the form of a multilayer board, in which case the recycled (meth)acrylic resin composition can also be called a recycled multilayer board. This recycled multilayer board can be manufactured using a recovered multilayer board, an unused (meth)acrylic resin, an unused fibrous glass filler, and other unused components as appropriate, to prepare a base layer resin composition (B) and a surface layer resin composition (A). The recycled multilayer board is the same as the multilayer board of the present invention except that the recycled (meth)acrylic resin composition is used as the base layer resin composition (B).

[0116] [Recycled Molded Article and Method for Manufacturing the Same] The recycled molded article is a molded article made of recycled multilayer boards using the recycled (meth)acrylic resin composition of the present invention described above. The recycled molded article of the present invention has excellent scattering prevention properties and heat processability, and also has the excellent feature that the recycled (meth)acrylic resin composition and recycled multilayer boards can be recycled (materially) again, and the (meth)acrylic acid esters can be recovered and recycled (chemically) again. For this reason, the recycled molded article of the present invention can be used for various applications, just like the molded article of the present invention. The form, shape and dimensions of the recycled molded article of the present invention are the same as those of the molded article of the present invention. The method for manufacturing the recycled molded article of the present invention is not particularly limited and is the same as the method for manufacturing the molded article of the present invention, except that the recycled (meth)acrylic resin composition or recycled multilayer board of the present invention is used.

[0117] [Recycling Method] The recycling method for (meth)acrylic resin compositions of the present invention (sometimes simply referred to as "the recycling method of the present invention") is a method for recycling (meth)acrylic resin compositions that form multilayer boards (material recycling). In the recycling method of the present invention, the target of recycling is mainly the (meth)acrylic resin composition that forms the base layer (B), but unless the surface layer (A) is removed from the multilayer board in advance, the (meth)acrylic resin composition that forms the surface layer (A) is also included. The recycling method of the present invention was completed after finding that even if the (meth)acrylic resin composition forming the multilayer board of the present invention has been recovered once or multiple times, the properties of the (meth)acrylic resin composition before recovery are not significantly impaired, and by using it in combination with unused (meth)acrylic resin composition and unused fibrous glass filler, a recycled multilayer board exhibiting desired shatterproof properties and heat-processable properties can be formed.

[0118] In the recycling method of the present invention, a recycled multilayer board that has already been recycled can be used as the object to be processed, and in this case, the (meth)acrylic resin composition can be recycled repeatedly multiple times. That is, one or more types of multilayer boards can be appropriately selected from the multilayer board of the present invention and the recycled multilayer board of the present invention as the multilayer board used in the recycling method of the present invention. The number of recycling cycles (number of recovery cycles) of the recycled multilayer board used in the recycling method of the present invention is not particularly limited and can be appropriately determined within a range in which the (meth)acrylic resin forming the recycled multilayer board satisfies the composition (particularly the content of structural units) of the unused (meth)acrylic resin (B) described above, that is, within a range in which the multilayer board formed using the obtained recycled multilayer board exhibits excellent shatterproof properties and thermal workability. The number of recycling cycles can be, for example, the same as the number of recovery cycles of the recovered multilayer board described above.

[0119] [Recovery Process] In the recycling method of the present invention, first, the (meth)acrylic resin composition is recovered from at least one of the multilayer board of the present invention and the recycled multilayer board of the present invention. The recovery method and conditions are not particularly limited, and the (meth)acrylic resin composition forming the multilayer board may be melted and mixed and recovered as a molten mixture (including strands, pellets, etc.). However, it is preferable to recover and collect the multilayer board in its original form in order to suppress the deterioration of its properties. In this case, the recovered (meth)acrylic resin composition and the recovered multilayer board are synonymous, and the recycling method of the present invention can also be called a multilayer board recycling method. The source from which the multilayer board is recovered is not particularly limited.

[0120] [Mixing Step] In the recycling method of the present invention, the recovered (meth)acrylic resin composition (multilayer board), unused (meth)acrylic resin (B), and unused fibrous glass filler are then mixed to prepare a recycled (meth)acrylic resin composition. The mixing method and mixing conditions at this time are not particularly limited, but the mixing method and kneading method used in the preparation of the (meth)acrylic resin composition (B) can be suitably employed. The recovered multilayer board can be crushed or pulverized as appropriate. In addition, other unused components may be added in the above-mentioned amounts. Each component to be mixed may be one type or two or more types.

[0121] In the present invention, the recycled multilayer board prepared as described above can be subjected to the recovery step and mixing step again to obtain a recycled multilayer board that has been recycled multiple times. That is, in the recycling method of the present invention, the recovery step and the mixing step can be repeated multiple times, with a molding step and a usage step interspersed as appropriate. The number of times recycling is performed can be appropriately determined within a range in which the recycled multilayer board that has been recycled multiple times exhibits excellent shatterproof properties and heat workability, and can be the same as the number of recovery steps for the recovered (meth)acrylic resin composition described above.

[0122] As described above, a recycled (meth)acrylic resin composition can be prepared. When the obtained recycled (meth)acrylic resin composition is used in a multilayer board, particularly as the base layer (B), it can achieve both excellent shatterproof properties and thermal processability.

[0123] In the recycling method of the present invention, in addition to the above-mentioned recovery step and mixing step, other steps may be included. Other steps include, for example, a step of washing the recovered multilayer board and a step of crushing the recovered multilayer board. In the recycling method of the present invention, in addition to multilayer boards, the molded articles of the present invention and recycled molded articles may also be processed.

[0124] The following are examples of the present invention, but the present invention is not limited thereto.

[0125] [Preparation or manufacture of (unused) (meth)acrylic resin] <Preparation of methacrylic resin PM1> As methacrylic resin PM1 (sometimes simply referred to as "resin PM1"), commercially available ALTUGLAS HT121 (trade name, manufactured by ARKEMA) was used. Hereinafter, methacrylic resin PM1 will be referred to as methacrylic resin HT121.

[0126] <Production of Methacrylic Resin PM2> A mixture of 97.5 parts by mass of methyl methacrylate (sometimes referred to as "MMA") and 2.5 parts by mass of methyl acrylate (sometimes referred to as "MA"), along with 0.016 parts by mass of 1,1-di(tert-butylperoxy)cyclohexane and 0.16 parts by mass of n-octyl mercaptan, was continuously supplied to a polymerization reactor equipped with a stirrer, and the polymerization reaction was carried out at 175°C with an average residence time of 43 minutes. Next, the reaction solution (partial polymer) discharged from the polymerization reactor was preheated, and then supplied to a defoliation extruder to vaporize and recover the unreacted monomer components, thereby obtaining pelletized methacrylic resin PM2 (sometimes simply referred to as "resin PM2").

[0127] <Production of Methacrylic Resin PM3> A mixture of 94.5 parts by mass of methyl methacrylate and 5.5 parts by mass of methyl acrylate, along with 0.016 parts by mass of 1,1-di(tert-butylperoxy)cyclohexane and 0.16 parts by mass of n-octyl mercaptan, were continuously supplied to a polymerization reactor equipped with a stirrer, and the polymerization reaction was carried out at 175°C with an average residence time of 43 minutes. Next, the reaction solution (partial polymer) discharged from the polymerization reactor was preheated, and then supplied to a defoliation extruder to vaporize and recover the unreacted monomer components, thereby obtaining pelletized methacrylic resin PM3 (sometimes simply referred to as "resin PM3").

[0128] For the prepared or manufactured methacrylic resins PM1 to PM3, the nuclear magnetic resonance spectra were measured under the following conditions ( １３¹³C-NMR (C-NMR) was measured, and the molar ratio of each component was calculated by taking the integral value of each peak in the resulting NMR chart. Specifically, a nuclear magnetic resonance spectrometer (Brker Avance 600 (product name), (10 mm cryoprobe)) was used. １３ The content was determined by measuring 13C-NMR. Deuterated chloroform was used as the measurement solvent, and the measurement was performed by the inverse gate proton decoupling method. The chemical shift value standard was chloroform. The MMA content was determined from the integral value of the peak with a chemical shift of 173.0–180.4 ppm. The methacrylic acid (MAA) content was determined from the integral value of the peak with a chemical shift of 180.4–188.0 ppm. The content of the glutaric anhydride structure formed by the cyclization condensation of MMA and MAA was determined from the integral value of the peak with a chemical shift of 170.0–173.0 ppm. The results are shown in Table 2. - Measurement conditions for nuclear magnetic resonance spectrum - Resonance frequency: 400 MHz Measurement temperature: 27°C Pulse repetition time: 20 seconds Number of integrations: 4000 Sample concentration: 300 mg / 2.5 mL Solvent: CDCl ３

[0129]

[0130] In Table 1, "MA" indicates the content of structural units derived from methyl acrylate (unit: mol%), "MMA" indicates the content of structural units derived from methyl methacrylate (unit: mol%), "MAA" indicates the content of structural units derived from methacrylic acid (unit: mol%), and "Ring structure" indicates the content of structural units including a ring structure made of glutaric anhydride (unit: mol%).

[0131] [Preparation of hard inorganic particles (silica particles)] The following silica particles were prepared as hard inorganic particles: AdmaFine SO-C2: trade name, average particle size (median diameter): 0.5 μm, manufactured by Admatex Co., Ltd.

[0132] [Preparation of Fibrous Glass Filler] The following fibrous glass filler was prepared as the fibrous glass filler. <Fibrous Glass Filler (T-289)> ESC03T-289: Product name, chopped strand, fiber diameter 13 μm, fiber length 3.0 mm, circular cross-section, manufactured by Nippon Electric Glass Co., Ltd.

[0133] <Manufacturing of Methacrylic Resin Composition (1) (Melting and Kneading)> The methacrylic resin PM2 manufactured as described above and silica particles in an amount of 1 part by mass per 99 parts by mass of the methacrylic resin were added as raw materials and mixed. Then, using a twin-screw extruder (model: TEX30SS-30AW-2V, manufactured by Japan Steel Works Co., Ltd.), the mixture was melt-kneaded under the following kneading conditions to extrude it into strands, solidified by water cooling, and cut with a strand cutter to obtain pellet-shaped methacrylic resin composition (1) (sometimes simply referred to as "resin composition (1)"). (Conditions for melting and kneading) The temperature of the extruder was set to 200°C, 200°C, 210°C, 220°C, 230°C, 240°C, 240°C, and 250°C for the eight heaters spaced apart from each other between the raw material inlet and outlet, starting from the raw material inlet side. The screw rotation speed and raw material input speed were as follows. Screw rotation speed: 200 rpm; Raw material input speed: 14 kg / hour

[0134] <Preparation of Methacrylic Resin Composition (2) (Melting and Kneading)> Methacrylic resin PM1 (4 parts by mass), PM2 (76 parts by mass), and fibrous glass filler (T-289) (20 parts by mass) were melt-kneaded using a single-screw extruder (model: VS40, manufactured by Tanabe Plastics Co., Ltd.) under the following melt-kneading conditions, extruded into strands, solidified by water cooling, and cut with a strand cutter to obtain pellet-shaped methacrylic resin composition (2) (sometimes simply referred to as "resin composition (2)"). The content of each component in the total methacrylic resin in methacrylic resin composition (2) was 96.925 mol% for MMA, 2.85 mol% for MA, 0.2 mol% for MAA, and 0.025 mol% for structural units including ring structures, based on a total of 100 mol% of all components. (Conditions for melting and kneading) For the extruder temperature, five heaters were spaced apart from each other between the raw material inlet and outlet, and were set to 200°C, 220°C, 230°C, 250°C, and 260°C, respectively, from the raw material inlet side. Kneading was performed at a screw rotation speed of 70 rpm.

[0135] [Examples 1-3 and Comparative Examples 1 and 2] Using the unused (meth)acrylic resin or (unused) (meth)acrylic resin composition described above, (unused) multilayer plates were prepared and evaluated.

[0136] <Examples 1-3 and Comparative Example 1> A φ25 mm single-screw extruder was used to produce the surface layer (A), and a φ40 mm single-screw extruder was used to produce the base layer (B). Co-extrusion was performed to produce two types of three-layer plates (Examples 1 and 2), two types of two-layer plates (Example 3), or single-layer plates (Comparative Example 1) corresponding to the multilayer plates shown in Table 2. The resins or resin compositions used to produce the surface layer (A) and base layer (B) are as shown in Table 2. Lamination was performed using a feed block installed upstream of the T-die. The resin or resin composition for the surface layer (A) and the resin or resin composition for the base layer (B) were laminated in the feed block and then passed through the T-die. The plate-like material exiting the die was cooled by three mirror-polishing rolls (upper, middle, and lower). The temperature of the extruder and T-die was set to 250-260°C, and the surface temperatures of the polishing rolls were set to 90°C, 95°C, and 105°C from the first roll (upstreammost). The thickness of each layer was adjusted by the extruder's discharge rate. Specifically, the discharge rate of the φ25 mm extruder was adjusted so that the surface layer (A) of one layer had a predetermined thickness (300 μm), and the discharge rate of the φ40 mm extruder was further adjusted so that the thickness of the entire multilayer sheet and the single-layer sheets was 3 mm, thereby manufacturing the multilayer sheet. Two-layer sheets of type 2 were manufactured by closing one side of the flow path of the φ25 mm extruder. Single-layer sheets were manufactured using only the φ40 mm extruder, without using the φ25 mm extruder, so that the sheet thickness was 3 mm.

[0137]

[0138] <Comparative Example 2> (Preparation of a single-layer plate made of polymethacrylic resin by thermosetting) A polymerizable composition was prepared by vacuum degassing a polymerizable mixture obtained by mixing 99.86 parts by mass of methyl methacrylate partial polymer syrup (containing about 5% by mass of polymethyl methacrylate), 0.07 parts by mass of 2,2'-azobisisobutyronitrile (AIBN: radical polymerization initiator), 0.05 parts by mass of sodium di(2-ethylhexyl)sulfosuccinate (release agent), 0.01 parts by mass of 1-methyl-4-isopropylidene-1-cyclohexene (polymerization regulator), and 0.01 parts by mass of 2-(2-hydroxy-5-methylphenyl)benzotriazole (ultraviolet absorber). Next, 20 parts by mass of fibrous glass filler (T-289) was added to 80 parts by mass of this polymerizable composition and stirred to obtain a polymerizable composition (3) containing glass fibers. Next, two 10 mm thick, 300 mm square pieces of glass were placed facing each other, and a 3 mm thick flexible polyvinyl chloride gasket (sealant) was sandwiched between the two surfaces to form a cell. The polymerizable composition containing the prepared glass fibers was then injected into the hollow portion of this cell. This cell was placed horizontally in a polymerization tank using a heat transfer medium and left to stand for a while. After that, it was heated at 60°C for 8 hours, and then at 110°C for 1 hour to carry out the polymerization reaction and polymerize and harden the polymerizable composition.

[0139] The multilayer sheets produced in Examples 1 to 3 and the single-layer sheets produced in Comparative Examples 1 and 2 were evaluated based on the following method.

[0140] [Evaluation of Shatterproof Characteristics] A shatterproof test was conducted using the manufactured multilayer or single-layer plates with a DuPont drop weight test (0.15 kg load, 1 m height). The evaluation of shatterproof characteristics was based on whether no large fragments scattered ("OK" - pass) or whether large fragments scattered ("NG" - fail). The results are shown in Table 3.

[0141] [Evaluation of Thermal Processability] The manufactured multilayer or single-layer sheets were heated in an oven at 180°C for 15 minutes, then removed. A ring-shaped mold was placed on the sheet, and air was blown onto the back of the mold at 10 MPa to evaluate whether it expanded into a dome shape with the ring mold as the rim. The thermal processability (formability) was evaluated as "OK" (pass) if the multilayer or single-layer sheet could be formed into a dome shape, and "NG" (fail) if it did not expand into a dome shape and burst midway through the process. The results are shown in Table 3.

[0142] [Evaluation of Scratch Resistance] Using the manufactured multilayer or single-layer plates, scratch resistance was evaluated using the "steel wool scratch test" and the ratio of the "gloss at a gloss measurement angle of 60°" before and after the "steel wool scratch test," i.e., the "residual percentage of gloss value" calculated by the following formula. A higher residual percentage indicates better scratch resistance. Formula: Residual percentage of gloss (Gloss loss 60°) = Gloss after scratch test (Gloss 60° (Before)) ÷ Gloss before scratch test (Gloss 60° (After)) × 100 (%)

[0143] The "steel wool scratch test" was conducted using commercially available equipment, specifically the "Planar Abrasion Tester PA-2A" manufactured by Daiei Chemical Precision Machinery Co., Ltd. Specifically, the "steel wool scratch test" was conducted using a flat test piece of a predetermined size (length 145 mm x width 60 mm x thickness 3 mm) cut from a manufactured multilayer or single-layer plate, under the following conditions: friction stroke: 140 mm, test speed: 15 cm / sec, number of reciprocations of the test stand: 10 reciprocations, test load: 1000 g, friction surface: 2 cm x 2 cm, steel wool: #0000. The "steel wool scratch test" was conducted multiple times (3 times), and the average value obtained was adopted as the measured value. The "residual percentage of gloss value" was calculated by measuring the "gloss at a gloss measurement angle of 60°" in accordance with JIS Z 8741 using a conventionally known and suitable device capable of measuring gloss for both the test specimens subjected to the "steel wool scratch test" and the test specimens before the "steel wool scratch test" was performed, as described above. Specifically, the "gloss at a gloss measurement angle of 60°" was measured using a commercially available device, the "Portable Gloss Meter GM268Plus" manufactured by KONICA MINOLTA. In evaluating scratch resistance, the surface layer (A) side of each test specimen was used as the test surface, and for the test specimen of Comparative Example 2, the side opposite the side where the glass filler had settled was used as the test surface.

[0144] [Decomposition and Recovery Test] The manufactured multilayer or single-layer boards were recovered, and their chemical recyclability (chemical recyclability) was evaluated to determine whether the methyl methacrylate (MMA) component could be recovered. Specifically, each manufactured multilayer or single-layer board was cut to approximately 2 mm x 2 mm, then thermally decomposed in a tubular furnace at 450°C for 10 minutes. The resulting decomposition products were measured by GC-MS, and the detected components were qualitatively analyzed. During this thermal decomposition, volatile components were generated, and a black solid substance remained on the combustion board inside the tubular furnace. As a result of measuring the volatile components by GC-MS, the main component recovered was methyl methacrylate (MMA). If the MMA component could be separated from the fibrous glass filler, it was judged as "OK" (pass), and if the MMA component could not be separated from the fibrous glass filler, it was judged as "NG" (fail). The results are shown in Table 3.

[0145]

[0146] [Evaluation of the recyclability of the (meth)acrylic resin composition] The multilayer board manufactured in Example 1 was crushed into fine pellet pieces. Then, 70 parts by mass of these crushed pellets (recovered multilayer board), 21.9 parts by mass of unused methacrylic resin composition (2), and 8.1 parts by mass of unused fibrous glass filler (total content including the fibrous glass filler contained in the recovered multilayer board was 20 parts by mass) were pre-blended into pellets and fed into a φ40 mm single-screw extruder. At the same time, the methacrylic resin composition (1) was fed into a φ20 mm single-screw extruder and co-extruded to produce a recycled multilayer board with two types and three layers. The obtained recycled multilayer board was evaluated for its shatterproof properties, heat workability, and scratch resistance in the same manner as in Example 1, and it was confirmed that similar results were obtained.

[0147] The results shown in Tables 1 to 3 indicate the following: The single-layer plate of Comparative Example 1, formed with methacrylic resin PM3 that does not contain fibrous glass filler, showed thermal workability, but in the DuPont drop weight test, the single-layer plate broke (cracked), with sharp edges and large fragments scattering, indicating poor shatter prevention properties. This single-layer plate did not show sufficient scratch resistance. Similarly, the single-layer plate of Comparative Example 2, formed with a thermosetting polymerizable composition (3) containing fibrous glass filler, passed the shatter prevention test, but was thermoset and did not show sufficient thermal workability. In contrast, the multilayer plates of Examples 1 to 3, having a surface layer (A) and a base layer (B) as defined in the present invention, all exhibited excellent shatter prevention properties, thermal workability, and scratch resistance. It was also found that methyl methacrylate in each methacrylic resin constituting the multilayer plates of Examples 1 to 3 could be recovered by heating them to a predetermined temperature. Furthermore, even when the multilayer board from Example 1 was recovered (the methacrylic resin composition was recovered), and the recycled resin composition obtained by mixing it with unused components was used as the methacrylic resin composition for the base layer (B), the resulting recycled multilayer board maintained the excellent shatterproof properties, heat workability, and scratch resistance exhibited by the multilayer board from Example 1 (unused). From the above results, it was found that the multilayer board of the present invention can be suitably used in various applications by utilizing the above-mentioned excellent properties, and moreover, material recycling and chemical recycling are possible.

Claims

1. A multilayer board comprising a glass fiber reinforced (meth)acrylic resin layer (B) having a (meth)acrylic resin layer (A) on at least one surface.

2. The multilayer board according to claim 1, wherein the (meth)acrylic resin layer (A) is a resin layer of a (meth)acrylic resin composition (A) containing (meth)acrylic resin and hard inorganic particles.

3. The multilayer plate according to claim 2, wherein the hard inorganic particles include silica particles.

4. The multilayer board according to claim 1, wherein the (meth)acrylic resin layer (A) does not contain fibrous glass filler.

5. The multilayer board according to claim 1, wherein the glass fiber-reinforced (meth)acrylic resin layer (B) is a resin layer of a (meth)acrylic resin composition (B) comprising a (meth)acrylic resin having a content of 90 to 99.985 mol% of structural units derived from (meth)acrylic acid ester and a content of 0.015 to 9.0 mol% of structural units derived from (meth)acrylic acid, and a fibrous glass filler, based on a total content of 100 mol% of all structural units.

6. The multilayer board according to claim 1, wherein the (meth)acrylic resin layer (A) has a thickness of 30 to 500 μm.

7. A recycling method for recycling a (meth)acrylic resin composition forming a multilayer board, comprising: recovering the (meth)acrylic resin composition from a multilayer board according to any one of claims 1 to 6 or from the recycled multilayer board described below; and mixing the recovered (meth)acrylic resin composition with unused (meth)acrylic resin and unused fibrous glass filler. <Recycled Multilayer Board> A recycled multilayer board having a (meth)acrylic resin layer (A) on at least one surface of a glass fiber reinforced (meth)acrylic resin layer (B) made of a recycled (meth)acrylic resin composition containing the (meth)acrylic resin composition recovered from a multilayer board according to any one of claims 1 to 6, unused (meth)acrylic resin, and unused fibrous glass filler.

8. A method for decomposing and recovering a multilayer board, comprising decomposing the multilayer board according to any one of claims 1 to 6 by heating it to 380°C or higher, and recovering (meth)acrylic acid ester by separating volatile components and solid matter.

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