WO2020158064A1

WO2020158064A1 - Additive for pmma, and pmma resin composition

Info

Publication number: WO2020158064A1
Application number: PCT/JP2019/041089
Authority: WO
Inventors: 将志中村; 林田　浩一
Original assignee: 神島化学工業株式会社
Priority date: 2019-01-29
Filing date: 2019-10-18
Publication date: 2020-08-06
Also published as: JP7155029B2; JP2020121896A

Abstract

Provided are: an additive for PMMA which is not prone to compromise transparency or durability, and which produces an adequate improvement of surface hardness when added to PMMA; and a PMMA resin composition.　The present invention provides: an additive for polymethyl methacrylate (PMMA), used by being added to polymethyl methacrylate, the additive for PMMA containing, as a main component, synthetic analcime particles comprising synthetic analcime and/or an anhydride thereof; a PMMA resin composition containing the additive and polymethyl methacrylate (PMMA); and a molded article obtained by molding the PMMA resin composition.

Description

Additive for PMMA and PMMA resin composition

The present invention relates to an additive for PMMA containing, as a main component, synthetic analcime particles composed of synthetic analcime and/or its anhydride, and a PMMA resin composition containing the additive.

Polymethylmethacrylate (PMMA) is a highly transparent plastic, is easy to polish, cut, and cut, and is a resin that does not easily deteriorate, so it is used in various applications that take advantage of its transparency. However, the surface hardness is not sufficient as compared with glass or the like, and in applications such as automobile tail lamp covers, scratches due to car washing and the like pose a problem, which is a factor limiting applications.

Generally, in order to improve the strength and rigidity of a resin molded product, an inorganic filler is often used, but depending on the chemical composition of the inorganic filler, the shape of the fine particles, and the agglomerated structure, the effect of improving the surface hardness and strength is not sufficient. There is a problem that it becomes sufficient, and transparency and durability are impaired.

On the other hand, the synthetic analcime particles themselves are known as described in Patent Documents 1 and 2, and for example, silica, caustic alkali, and aluminum hydroxide or aluminate are hydrothermally mixed at a ratio commensurate with the composition of the analcime. It is known that it can be produced by reacting (see Patent Document 1).

Further, as applications of the synthetic analcime particles, Patent Document 1 describes an antiblocking agent for films and the like, and Patent Document 2 describes that it can be used as an antiblocking agent for various resin films. .. However, it has hitherto not been known that synthetic analcime particles can be used as an additive, especially for PMMA.

JP-A-60-186413 Japanese Patent Laid-Open No. 01-242413

By the way, there is a case where an inorganic filler is added to a highly transparent resin to give a deep natural stone-like texture to enhance designability, but when the resin is whitened, it becomes difficult to obtain a deep texture. .. Therefore, in order to improve the designability by adding the inorganic filler, it is desirable that the transparency be sufficiently maintained.

Therefore, an object of the present invention is to provide an additive for PMMA and a PMMA resin composition which, when added to PMMA, can sufficiently obtain the effect of improving the surface hardness and hardly impair transparency and durability.

As a result of extensive studies, the present inventor has used the synthetic analcime particles as an additive for PMMA, whereby the surface hardness of the obtained resin composition is sufficiently improved, and the transparency and durability are less likely to be impaired. This has led to the completion of the present invention.

That is, the additive for PMMA of the present invention is an additive for PMMA used by being added to polymethylmethacrylate (PMMA), and contains synthetic analcime particles and/or synthetic analcime particles composed of an anhydride thereof as a main component. It is characterized by

According to the additive for PMMA of the present invention, since it contains synthetic analcime particles composed of synthetic analcime and/or its anhydride as a main component, when used as an additive for PMMA, the refractive index of the particles is close to that of a resin. It is thought that transparency and durability are less likely to be impaired because of its high chemical stability. Further, it is considered that the particle shape and the agglomerated structure of the synthetic analcime particles also contribute to the improvement of the surface hardness and the maintenance of the transparency of the obtained resin composition.

For these reasons, it is preferable that the synthetic analcime particles have a volume-based cumulative 50% diameter (D50) of 1 to 200 μm in the particle size distribution obtained by a laser diffraction type particle size distribution analyzer.

Further, the synthetic analcime particles have a particle size distribution index (D10) obtained by a ratio of a cumulative 10% diameter (D10) and a cumulative 50% diameter (D50) on a volume basis in a particle size distribution obtained by a laser diffraction type particle size distribution meter. /D50) is preferably 1.0 to 1.5.

Furthermore, it is preferable that the synthetic analcime particles are composed of primary particles of a dodecahedron.

On the other hand, the PMMA resin composition of the present invention is characterized by containing the above-mentioned PMMA additive and polymethylmethacrylate (PMMA). According to the PMMA resin composition of the present invention, since it contains synthetic analcime particles as the main component, the refractive index of the particles is close to that of the resin and the chemical stability is high, so that it is difficult to impair transparency and durability. Conceivable. Further, it is considered that the particle shape and the agglomeration structure of the synthetic analcime particles also contribute to the improvement of the surface hardness of the obtained resin composition.

In the above, it is preferable to contain 0.1 to 200 parts by mass of the synthetic analcime particles with respect to 100 parts by mass of the polymethylmethacrylate.

The molded product of the present invention is characterized by being formed by molding the above PMMA resin composition. According to the molded product of the present invention, the effect of improving the surface hardness is sufficiently obtained, and the transparency and durability are less likely to be impaired.

1 is an SEM photograph of synthetic analcime particles obtained in Example 1 of the present invention. 3 is a SEM photograph of synthetic analcime particles obtained in Example 2 of the present invention. 3 is a powder X-ray diffraction pattern of the synthetic analcime particles obtained in Example 1 of the present invention.

<Additives for PMMA>
The PMMA additive of the present invention is used by being added to polymethylmethacrylate (PMMA). The additive can be used for improving surface hardness, strength, and design. That is, the additive can be used as a surface hardness improving agent, a reinforcing material, a design improving agent, or the like. When the resin is whitened by the additive, it becomes difficult to obtain a design property such as deep natural stone. Therefore, it is desirable that the transparency is maintained in order to improve the design property.

The additive for PMMA of the present invention contains, as a main component, synthetic analcime particles and/or synthetic analcime particles composed of an anhydride thereof. "Containing as a main component" means that it is usually contained in the additive in an amount of 80% by mass or more, preferably 90% by mass or more in the additive, and most preferably 100% by mass. .. Other components include surface treatment agents for synthetic analcime particles, and other additives for resins.

<Synthetic anal sim particles>
In the present invention, “synthetic analcime particle” refers to a particle composed of synthetic analcime and/or an anhydride thereof, and the synthetic analcime is typically represented by a composition formula of NaAlSi ₂ O ₆ ·H ₂ O. , Synthetic analcime anhydrides are typically represented by the composition formula of NaAlSi ₂ O ₆ . The synthetic analcime has a cubic crystal system, and the anhydrous synthetic analcime has a cubic crystal system.

In the present invention, by reducing particle agglomeration while having a narrower particle size distribution, from the viewpoint of improving the designability and surface hardness of the molded body, the synthetic analcime particles are primary particles that are a tetrahedron, or the corners of a tetrahedron are It is preferably composed of curved primary particles.

The typical chemical composition of the synthetic analcime particles is as follows: SiO ₂ 49 to 59% by mass, Al ₂ O ₃ 21 to 25% by mass, Na ₂ O 12 to 14% by mass, H ₂ O 7 to 10% by mass. % Is exemplified.

The cumulative 50% diameter (D50) on a volume basis in the particle size distribution obtained by a laser diffraction type particle size distribution analyzer for synthetic analcime particles has a sufficient effect of improving the surface hardness when added to PMMA, and improves transparency and durability. From the viewpoint of making it difficult to impair the property, the thickness is preferably 1 to 200 μm, more preferably 10 to 150 μm, and further preferably 20 to 100 μm. However, in order to improve the designability, it is particularly preferable that the cumulative 50% diameter (D50) is 20 to 100 μm.

Synthetic analcim particles have a cumulative 10% diameter (D10) from the viewpoint of improving the design and surface hardness of a molded article by reducing the particle aggregation while having a narrower particle size distribution by making the particle size distribution narrower. The particle size distribution index (D10/D50) determined by the ratio with the cumulative 50% diameter (D50) is preferably 1.0 to 1.5, more preferably 1.0 to 1.4, It is more preferably 1.0 to 1.3.

The refractive index of synthetic analcim particles is usually 1.48 to 1.49, and PMMA resin (refractive index 1.49) has a similar refractive index, so transparency is maintained by mixing with such resin. It is possible to improve the design of the molded product.

The synthetic analcime particles may contain impurities depending on the production method and the like. For example, compounds of metals such as iron, copper, manganese, chromium, cobalt, nickel and vanadium. The content of these impurities is preferably 0.5 mass% or less in terms of metal.
<Method for producing synthetic anal sim particle>
The synthetic analcime particles in the present invention can be produced by a known method. For example, it can be produced by mixing a silica raw material, a caustic alkali, and an aluminum raw material in a ratio corresponding to the composition of analcime, and hydrothermally reacting them. Mixing can be performed by, for example, a method of mixing the remaining raw materials with a caustic aqueous solution, or a method of previously mixing a silica raw material dissolved in a caustic aqueous solution and an aluminum raw material dissolved in a caustic aqueous solution. it can.

Examples of silica raw materials include amorphous silica powder, crystalline silica powder, colloidal silica, fumed silica, sodium silicate, phosphosilicate stone, cristobalite and colloidal silica.

Examples of caustic alkali include caustic soda (NaOH) and caustic potash (KOH). The concentration of caustic alkali in the caustic aqueous solution is preferably 0.1 M (mol/L) or more, more preferably 1 to 10 M, further preferably 2 to 5 M.

As the aluminum raw material, metal aluminum, aluminum oxide, aluminum hydroxide, aluminate, etc. may be mentioned.

The molar ratio adjusted during mixing is such that Na ₂ O/SiO ₂ is, for example, 0.5 to 5.0, preferably 0.7 to 3.0, and SiO ₂ /Al ₂ O ₃ is, for example, 2 to 50. , Preferably 3 to 20, and H ₂ O/Na ₂ O is, for example, 20 to 500, preferably 50 to 200. In the present invention, the molar ratio SiO ₂ /Al ₂ O ₃ is preferably from 1 to 10, and more preferably from 3 to 6, in order to obtain synthetic analcime particles having a narrow particle size distribution.

In the present invention, for example, in order to satisfy the above composition, each raw material is mixed to form a gel of alkali aluminosilicate, and the gel is homogenized by stirring and mixing, and then heated under normal pressure or hydrothermal conditions. By crystallizing under conditions, synthetic analcime particles can be obtained.

The hydrothermal treatment temperature is preferably 100 to 300°C, more preferably 150 to 250°C. The hydrothermal treatment time depends on the hydrothermal treatment temperature, but is preferably 1 to 100 hours, more preferably 3 to 50 hours.

In the present invention, from the viewpoint of efficiently forming a single phase of synthetic analcime particles, it is preferable to carry out hydrothermal treatment by mixing under heat and pressure. The hydrothermal treatment method is not particularly limited, but is usually performed in a heat resistant container such as an autoclave. The pressure inside the container during the hydrothermal treatment is not particularly limited, but is preferably 0.1 to 5.0 MPa, more preferably 0.2 to 4.0 MPa. When the hydrothermal treatment pressure is within this range, crystal growth and average particle size can be controlled within an appropriate range.

It is preferable that the slurry obtained by the hydrothermal treatment is vacuum-filtered to separate into a solid (cake) containing the synthetic analcime particles and a filtrate, and sufficiently washed with 20 times or more of the solid content of water. There is no particular limitation on the number of washings. This makes it possible to remove the water-soluble impurities contained in the slurry. The solid matter after washing with water may be dried in an oven or the like at 100 to 150° C. for 1 to 24 hours, and if necessary, the solid matter after drying may be dry pulverized or classified to obtain desired synthetic analcime particles. it can.

The surface of the synthetic analcime particles can be subjected to a surface treatment if necessary, and for example, metal soap, resin acid soap, various resins or waxes, silane-based or titanium-based coupling agents, silica coating, etc. are used. Can be surface treated.

A known dry method or wet method can be applied to the surface treatment of the synthetic analcime particles using such a surface treatment agent. As a dry method, the surface treatment agent may be added in a liquid, emulsion or solid state under stirring with a mixer such as a Henschel mixer, and the powder of the synthetic analcime particles may be sufficiently mixed with or without heating. As a wet method, a powder of synthetic analcime particles is added to a non-aqueous solvent slurry with a surface treatment agent in a solution state or an emulsion state, and the mixture is mechanically mixed at a temperature of, for example, about 1 to 100° C., and thereafter dried by a non-aqueous method. The solvent may be removed.

The amount of the surface treatment agent added can be appropriately selected, but is preferably in the range of 0.1 to 10 parts by mass, more preferably in the range of 0.5 to 5 parts by mass with respect to 100 parts by mass of the synthetic analcime particles. When the dry method is used, the surface treatment level tends to be non-uniform as compared with the wet method, so it is better to use a slightly larger amount than the wet method.

The surface-treated synthetic analcime particles can be washed with water, dehydrated, granulated, dried, crushed, and classified, if necessary.

In the case of producing synthetic analcime particles containing an anhydride of synthetic analcime, it is possible to obtain the synthetic analcime particles obtained by the above-mentioned method by heat treatment at a temperature of 350 to 1,000° C. for 1 to 24 hours. it can.

<Resin composition>
The resin composition of the present invention contains the additive for PMMA described above and polymethylmethacrylate (PMMA).

The PMMA may be a homopolymer of methyl methacrylate or a copolymer obtained by copolymerizing methyl methacrylate with another monomer. In that case, the copolymerization ratio of methyl methacrylate is preferably 50 mol% or more, more preferably 90 mol% or more, and most preferably 100 mol%.

Also, it may be a blend containing a homopolymer or copolymer of methyl methacrylate and another polymer. In that case, the content of the methyl methacrylate homopolymer or copolymer is preferably 50% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass in the total resin.

As other monomers to be copolymerized, alkyl methacrylate other than methyl methacrylate, alkyl acrylate, ester of methacrylic acid and phenol, ester of methacrylic acid and aromatic alcohol, aromatic vinyl monomer, vinyl cyanide Examples thereof include system monomers and conjugated diene monomers.

Specifically, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and other alkyl methacrylates excluding methyl methacrylate; Alkyl acrylate such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate; methacrylic acid such as phenyl methacrylate Ester with phenols; Methacrylic acid ester with methacrylic acid such as benzyl methacrylate and aromatic alcohol; Styrene, α-methylstyrene, 1-vinylnaphthalene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexyl Aromatic vinyl monomers such as styrene, 4-dodecyl styrene, 2-ethyl-4-benzyl styrene, 4-(phenylbutyl)styrene or halogenated styrene; vinyl cyanide mono-monomers such as acrylonitrile or methacrylonitrile Body; examples thereof include conjugated diene-based monomers such as butadiene and isoprene.

Other polymers to be blended include, for example, acrylic resins, ABS (acrylonitrile-butadiene-styrene copolymer) resins, polyethylene resins (linear polyethylene, low density polyethylene, high density polyethylene), polypropylene resins. Resin (homopolypropylene, propylene-ethylene random copolymer, propylene-ethylene block copolymer, copolymer of propylene and other small amount of α-olefin), ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer Examples thereof include polymers, polystyrene resins, polybutadiene resins, isoprene resins, polyolefins such as ethylene-propylene rubber and ethylene-propylene rubber. Among them, acrylic resins and the like are preferable from the viewpoint of compatibility with PMMA.

In the above resin composition, the content of synthetic analcime particles is adjusted according to the function as an additive. Generally, the synthetic analcime particles are added in an amount of 0.1 to 200 parts by mass per 100 parts by mass of the resin. It is preferably contained, more preferably 1 to 150 parts by mass, further preferably 5 to 100 parts by mass.

When giving a deep natural stone-like texture to enhance the design, it is preferable to contain 10 to 200 parts by mass, more preferably 50 to 150 parts by mass, of synthetic analcime particles per 100 parts by mass of the resin. To be included in.

Other additives may be added to the above resin composition in addition to the above components as long as the effects of the present invention are not impaired. Examples of such additives include antioxidants, antistatic agents, pigments, foaming agents, plasticizers, fillers, reinforcing agents, flame retardants, crosslinking agents, light stabilizers, ultraviolet absorbers, lubricants, lubricants, Antiaging agents, weathering agents, coloring agents, curing accelerators and the like can be mentioned. You may mix|blend these additives with 1 type(s) or 2 or more types. The amount of the other additives to be added is not particularly limited from the viewpoint that the effects of the present invention are not impaired, but it is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin.

The mixing and filling of the synthetic anal-sime particles and the resin and the like can be obtained by a known kneading method or filling method. , Orbital rotation type kneader, etc. It is also possible to carry out kneading while removing bubbles in the resin composition by using a device having a defoaming effect.

<Molded body>
The molded body contains the resin composition. Such a molded article can be obtained by a known molding method after blending a predetermined amount of synthetic analcime particles and the like with a resin to form a resin composition. As such a molding method, an extrusion molding machine, an injection molding machine, a blow molding machine, a press molding machine, a calender molding machine, etc., a lamination molding, a doctor blade method and the like can be used.

The molded product of this embodiment can be used in various forms such as a film form, a sheet form, a plate form, a lump form, and a special form according to various applications.

Since the molded product is formed of a resin composition containing synthetic analcime particles, it can be suitably applied to applications requiring surface hardness, transparency, heat resistance, water resistance and the like. The use of the molded product is not particularly limited, and examples thereof include bathtubs, washbasins, sinks, decorative boards, decorative plates, decorative films, automobile lamp covers, automobile lamp lenses, and the like.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The physical properties of the particles obtained in the examples and the effects as additives were evaluated as follows.

(Cumulative 50% diameter and cumulative 10% diameter)
50 mL of ethanol was placed in a 100-mL beaker, about 0.2 g of particles were put, and ultrasonic treatment (UD-201 manufactured by Tommy Seiko Co., Ltd.) for 3 minutes was performed to prepare a dispersion liquid. The dispersion was measured using a laser diffraction method-particle size distribution meter (Microtrac HRA Model 9320-X100, manufactured by Nikkiso Co., Ltd.), and the volume-based cumulative 50% diameter (D50) (μm) in the obtained particle size distribution was measured. And the cumulative 10% diameter (D10) (μm) were determined. Further, the particle size distribution index (D10/D50) was determined from these results.

(Particle shape)
The particle shape was evaluated by using an SEM (Hitachi High-Technologies Corporation, "Field Emission Scanning Electron Microscope S-4700") to obtain an observation image at a magnification of 1000 times. FIG. 1 shows a SEM photograph of the analcime particles obtained in Example 1, and FIG. 2 shows a SEM photograph of the analcime particles obtained in Example 2.

(Powder X-Ray Diffraction) An X-ray diffractometer (RINT-2500 manufactured by Rigaku Corporation) was used to perform measurement under the conditions of a Cu radiation source (40 kV, 30 mA).

(durability)
Using a PMMA (polymethylmethacrylate) resin (trade name: Sumipex MGSS, manufacturer: Sumitomo Chemical Co., Ltd.), add 150 parts by mass of particles to 100 parts by mass of the PMMA resin and use Labo Plastomill (manufactured by Toyo Seiki). The kneaded product obtained by melt-kneading at 220° C. for 5 minutes was placed in a mold having a space of 125 mm in length×13 mm in width×1 mm in thickness and press-molded at 220° C. to obtain a molded body of 125 mm in length×13 mm in width×1 mm in thickness. Created.

Immersing this molded body in warm water kept at 80°C, and confirmed the transparency within 1 hour, 3 hours, and 10 hours from the start of immersion. To check the transparency, place the molded object on the paper on which the characters (line thickness 0.5 mm, size 5 mm x 5 mm) are printed, and if the characters below can be identified, the character can be seen. When the distinction was difficult, it was marked with Δ, and when it was not visible at all, it was marked with x.

(Pencil hardness)
Using PMMA (polymethylmethacrylate) resin (trade name: Sumipex MGSS, manufacturer: Sumitomo Chemical Co., Ltd.), add 10 parts by mass of particles to 100 parts by mass of PMMA resin, and use Labo Plastomill (manufactured by Toyo Seiki). The kneaded product obtained by melt-kneading at 220° C. for 5 minutes was put in a mold having a space of 125 mm in length×13 mm in width×3 mm in thickness and press-molded at 220° C. to obtain a molded body of 125 mm in length×13 mm in width×3 mm in thickness. Created. As a comparative control, a molded body prepared in the same manner without containing particles was also evaluated.

Using this molded body, the pencil hardness was measured by the method according to JIS K5400. At that time, a pencil was set at 45 degrees on the wheeled block, and measurement was performed with a tip load of 750 g.

(Bending strength)
Using a PMMA (polymethylmethacrylate) resin (trade name: Sumipex MGSS, manufacturer: Sumitomo Chemical Co., Ltd.), 150 parts by mass of particles were added to 100 parts by mass of the PMMA resin, and a Labo Plastomill (manufactured by Toyo Seiki) was used. The kneaded product obtained by melt-kneading at 220° C. for 5 minutes was put in a mold having a space of 125 mm in length×13 mm in width×3 mm in thickness and press-molded at 220° C. to obtain a molded body of 125 mm in length×13 mm in width×3 mm in thickness. Created.

Bending strength (MPa) was measured based on JIS K7171 using a test piece punched from this molded body into a strip shape (13 mm x 120 mm).

(Creativity)
Using a PMMA (polymethylmethacrylate) resin (trade name: Sumipex MGSS, manufacturer: Sumitomo Chemical Co., Ltd.), 10 parts by mass of particles or 150 parts by mass of particles was added to 100 parts by mass of the PMMA resin, and Laboplast mill ( (Toyo Seiki) melt-kneaded at 220°C for 5 minutes to obtain a kneaded product, and put it in a mold having a space of 125 mm in length × 13 mm in width × 3 mm in thickness and press-mold at 220° C., 125 mm in length × 13 mm in width × thickness. A 3 mm molded body was prepared.

The designability was evaluated by confirming the transparency using the molded bodies having different particle contents. To check the transparency, place the molded object on the paper on which the characters (line thickness 0.5 mm, size 5 mm x 5 mm) are printed, and if the characters below can be identified, the character can be seen. When the distinction was difficult, it was marked with Δ, and when it was not visible at all, it was marked with x. In the case of ○, it was judged that there was a design property.

<Example 1> (Analsime small particle size product)
In a Teflon (registered trademark) autoclave device having a volume of 50 ml with a stirrer, a charged molar ratio of SiO ₂ /Al ₂ O ₃ =3.1, 25 ml of water so as to have a caustic concentration of 4 M, amorphous silica (Tosoh Corporation).・Silica Co., Ltd., VN3) 5.0 g, aluminum hydroxide (reagent) 1.0 g, sodium hydroxide (reagent) 4.8 g were added, and kept in a sealed state at 200° C. for 20 hours, under hydrothermal conditions. Reacted below. After that, the container is left to cool to room temperature, the semi-solid slurry obtained after the reaction is taken out, vacuum filtered with a Nutsche, and sufficiently washed with 20 times or more the volume of water relative to the solid content, and 120° C. And dried in a dryer for 10 hours to obtain analcime particles.

These particles have a cumulative 50% diameter (D50) of 21.0 μm and a particle size distribution index (D10/D50) of 1.3, and as shown in FIG. Met. Further, as shown in FIG. 3, the powder X-ray diffraction pattern of the synthetic analcime particles obtained in Example 1 showed a crystalline phase composed of a single phase of analcime.

<Example 2> (Analsime medium particle size product)
In Example 1, 5.0 g of colloidal silica (Snowtex O manufactured by Nissan Kagaku Co., Ltd.) was used instead of 5.0 g of amorphous silica in terms of silica (a molar ratio of charged SiO ₂ / Analsyme particles were obtained under the same conditions as in Example 1 except that Al ₂ O ₃ =3.1). This particle has a cumulative 50% diameter (D50) of 68.5 μm and a particle size distribution index (D10/D50) of 1.3, and as shown in FIG. The particles were of uniform shape.

<Example 3> (Analsime large particle size product)
In Example 1, 5.0 g of crystalline silica (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) was used instead of 5.0 g of amorphous silica in terms of solid content (the charge molar ratio was SiO.sub.2). ₂ /Al ₂ O ₃ =3.1), except that analcime particles were obtained under the same conditions as in Example 1. These particles have a cumulative 50% diameter (D50) of 122.3 μm and a particle size distribution index (D10/D50) of 1.4, and, as in Example 1, are particles of uniform shape composed of primary particles of a dodecahedron. Met.

<Comparative Example 1> (Taichite 3 μm product)
In a SUS container having a volume of 2 L, the molar ratio of the charged raw materials was set to Mg ²⁺ :Na ⁺ :CO ₃ ^2- :SO ₄ ^2- =1.0:7.9:3.1:2.0 ( SO ₄ ²⁻ /Mg ²⁺ ratio=2.0), water 200 g, basic magnesium carbonate powder (Kanjima Chemical Industry Co., Ltd., magnesium carbonate Venus) 58.4 g, anhydrous sodium carbonate (Fuji Film Wako Pure Chemical Industries, Ltd.) Manufactured by Reagent Special Grade 101.6 g, sodium hydrogencarbonate (Fuji Film Wako Pure Chemical Industries Ltd. reagent special grade) 40.4 g and Sodium Sulfate (Fuji Film Wako Pure Chemical Industries Ltd. reagent special grade) 179 g, The mixture was stirred at room temperature for 3 minutes at a stirring speed of 500 rpm and mixed to be uniform. 30 ml of the mixed slurry was put into a Teflon (registered trademark) autoclave device having a volume of 50 ml containing a stirrer, and the mixture was kept in a sealed state at 120° C. for 12 hours to react under hydrothermal conditions. The heating rate at this time was about 1° C./minute. Then, the container is allowed to cool to room temperature, the semi-solid slurry obtained after the reaction is taken out, vacuum filtered with a Nutsche, and sufficiently washed with 20 times or more the volume of water relative to the solid content, and at 120°C. It was dried in a dryer for 10 hours to obtain Thaichite particles having a cumulative 50% diameter (D50) of 3.2 μm.

<Comparative Example 2> (Taichite 150 μm product)
In Comparative Example 1, a 100 L autoclave container was charged so that the molar ratio of the raw materials charged was Mg ²⁺ :Na ⁺ :CO3 ^2- :SO4 ^2- =1:8.6:2.5:2.8. (SO4 ^2- /Mg ²⁺ ratio = 2.8), magnesium sulfate heptahydrate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., special grade reagent) 61.6 kg, anhydrous sodium carbonate (manufactured by Fuji Film Wako Pure Chemical Industries Ltd.) , 66.2 kg of reagent special grade) and 63.9 kg of sodium sulfate (Fuji Film Wako Pure Chemical Industries, Ltd. special grade reagent) were added, and the final liquid volume was adjusted to 75 L with water. After stirring at room temperature for 10 minutes to mix uniformly, the mixture was placed in an autoclave, stirred at 150 rpm, kept at 105° C. for 12 hours in a sealed state, and reacted under hydrothermal conditions. The heating rate at this time was 0.5° C./min. Then, the container was left to cool to room temperature, the slurry obtained after the reaction was taken out, and sieved with a stainless steel mesh having an opening of 75 μm, the cake remaining on the mesh was vacuum filtered with a Nutsche, and the solid content was removed. On the other hand, it was thoroughly washed with 20 times or more volume of water and dried in a dryer at 120° C. for 10 hours to obtain Taichite particles. This particle was a titite particle having a cumulative 50% diameter (D50) of 148.5 μm.

<Comparative Example 3> (20 μm magnesite product)
50 L of a neutral magnesium carbonate (MgCO ₃ .3H ₂ O) suspension prepared to a concentration of 0.3 mol/L was placed in an autoclave equipped with a stirrer having a capacity of 100 L, and hydrothermal treatment was carried out at 140° C. for 10 hours while stirring. .. The temperature rising rate at this time was 1° C./minute. The obtained suspension was dehydrated and then dried at 120° C. for 10 hours to obtain anhydrous magnesium carbonate (magnesite) particles having a cumulative 50% diameter (D50) of 20.6 μm.

<Comparative Example 4> (Boehmite 30 μm product)
1.0 kg of gibbsite (average particle size (D50) 35.4 μm, BET specific surface area 0.1 m ² /g, trade name: B-30, manufacturer: Almorix) was added to 4.0 L of pure water, A gibbsite suspension is prepared by stirring, poured into an autoclave having a 3 L capacity Hastelloy C-276 wetted part, and hydrothermally treated at 180° C. for 12 hours under stirring to obtain a cumulative 50% diameter ( D50) had a boehmite particle size of 28.7 μm.

Table 1 shows the results of the above-mentioned evaluations using the particles obtained in the above Examples and Comparative Examples.

<Evaluation result>
As shown by the results in Table 1, the analcime particles of Examples 1 to 3 were sufficiently effective in improving the surface hardness when added to PMMA, and were not likely to impair transparency and durability. On the other hand, in the case of the Taichite particles (Comparative Examples 1 and 2), the durability was impaired and the transparency was insufficient in terms of designability. Further, in the case of magnesite particles (Comparative Example 3) and in the case of boehmite particles (Comparative Example 4), the transparency was poor and the designability was poor.

Claims

An additive for PMMA used by being added to polymethylmethacrylate (PMMA), which is an additive for PMMA containing synthetic analcime and/or synthetic analcime particles composed of an anhydride thereof as a main component.
The additive for PMMA according to claim 1, wherein the synthetic analcime particles have a volume-based cumulative 50% diameter (D50) of 1 to 200 μm in a particle size distribution obtained by a laser diffraction type particle size distribution analyzer.
The synthetic analcime particles have a particle size distribution index (D10/D50) obtained by a ratio of a volume-based cumulative 10% diameter (D10) and a cumulative 50% diameter (D50) in a particle size distribution obtained by a laser diffraction particle size distribution analyzer. ) Is 1.0 to 1.5, and the additive for PMMA according to claim 1 or 2.
The additive for PMMA according to any one of claims 1 to 3, wherein the synthetic analcime particles are primary particles of a tetrahedron.
A PMMA resin composition comprising the PMMA additive according to any one of claims 1 to 4 and polymethylmethacrylate (PMMA).
6. The PMMA resin composition according to claim 5, which contains 0.1 to 200 parts by mass of the synthetic analcime particles with respect to 100 parts by mass of the polymethylmethacrylate.
A molded product obtained by molding the PMMA resin composition according to claim 5 or 6.