JP6982435B2 - Needle-shaped anhydrous magnesium carbonate, its production method, and resin composition - Google Patents

Description

The present invention relates to needle-shaped anhydrous magnesium carbonate, a method for producing the same, and a resin composition.

Anhydrous magnesium carbonate obtained by hydrothermal treatment of magnesium neutral carbonate _{(MgCO 3 · 3H 2 O)} ( magnesite, MgCO ₃₎ has a high thermal conductivity, water resistance and excellent in heat resistance, engineering plastics It is used as a heat conductive filler to be blended in (Patent Document 1). Such a resin composition is used in a place where heat is likely to be trapped, such as a member around an engine of an automobile or a member around a battery of a mobile phone. In addition, anhydrous magnesium carbonate has a low Mohs hardness, and has the features of low mold wear and excellent workability.

Japanese Unexamined Patent Publication No. 2005-272752

Anhydrous magnesium carbonate obtained by hydrothermal treatment has the above-mentioned advantages, but the shape of the particles is generally cubic, which makes it difficult to further develop applications. For example, even if it is used as a reinforcing filler for a resin, sufficient reinforcing property may not be obtained.

In order to improve the reinforcing property against bending and shearing, it is effective to make the particle shape into a needle shape, a rod shape, a fibrous shape or the like. Needle-shaped basic magnesium sulfate is added as such particles as a reinforcing filler for polypropylene resin used for car dashboards, bumpers and the like. However, basic magnesium sulfate has low weather resistance and decomposes to generate blisters, which limits its application to automobile exterior materials. Magnesium oxide obtained by firing acicular particles such as basic magnesium sulfate maintains an acicular particle shape, and has high thermal conductivity but low water resistance. Therefore, there is a demand for a filler having not only thermal conductivity, low mold wear resistance, and heat resistance, but also water resistance and reinforcing property.

An object of the present invention is to provide needle-shaped anhydrous magnesium carbonate having excellent reinforcing properties and water resistance, a method for producing the same, and a resin composition.

As a result of repeated diligent studies, the present inventor has found that the above-mentioned problems can be solved by adopting the following configuration, and has completed the present invention.

That is, the present invention relates to acicular anhydrous magnesium carbonate having an average major axis ratio to an average minor axis (hereinafter, also referred to as “aspect ratio”) of 5 or more in one embodiment.

Since the needle-shaped anhydrous magnesium carbonate has an aspect ratio of 5 or more, it is oriented when blended with a resin and exhibits anisotropy, and can exhibit excellent reinforcing properties. In addition, while exhibiting reinforcing properties, it is possible to exhibit the excellent water resistance of anhydrous magnesium carbonate. In addition, in this specification, "needle-like" literally includes not only needle-like shape but also rod-like shape, columnar shape, and fibrous shape.

In the needle-shaped anhydrous magnesium carbonate, the average major axis is preferably 10 μm or more. As a result, the continuity of orientation in the resin is enhanced, and the reinforcing property can be further improved.

_{In the needle-shaped anhydrous magnesium carbonate, it is preferable that the cumulative 50% diameter (d 50} ) in the particle size distribution obtained by the laser diffraction type particle size distribution meter is 5 μm or more and 200 μm or less on a volume basis. By setting the cumulative 50% diameter (d ₅₀ ) of the needle-shaped anhydrous magnesium carbonate within the above range, it is possible to improve the reinforcing property and to exhibit dispersibility and handleability.

After holding the needle-shaped anhydrous magnesium carbonate in an atmosphere of a temperature of 40 ° C. and a humidity of 75% for 30 hours, the water absorption rate represented by the following formula is preferably 5% or less.
Water absorption rate (%) = {(mass after holding-initial mass) / initial mass} x 100

By setting the water absorption rate of the needle-shaped anhydrous magnesium carbonate within the above range, the water resistance can be further improved.

In another embodiment, the present invention comprises a step of preparing acicular neutral magnesium carbonate having an average major axis to an average minor axis of 5 or more, and the acicular neutral magnesium carbonate in a carbon dioxide-containing atmosphere. The present invention relates to a method for producing acicular anhydrous magnesium carbonate, which comprises a step of heat treatment.

In the production method, the above-mentioned acicular anhydrous magnesium carbonate can be efficiently produced only by heat-treating the acicular neutral magnesium carbonate having a predetermined aspect ratio in a carbon dioxide-containing atmosphere. The reason for this is not clear, but it can be inferred as follows. In the conventional manufacturing method, when neutral magnesium carbonate is ignited, carbon dioxide is released and converted to magnesium oxide. In this production method, by performing heat treatment in an atmosphere where the carbon dioxide concentration in the reaction system is increased, carbon dioxide is taken in again after releasing carbon dioxide from neutral magnesium carbonate, and needle-like anhydrous magnesium carbonate is made efficient. Can be manufactured as a target.

It is preferable to carry out the heat treatment under atmospheric pressure at a temperature within the range of 450 ° C. or higher and 600 ° C. or lower. As a result, while promoting the phase conversion of neutral magnesium carbonate to acicular anhydrous magnesium carbonate, the release of carbon dioxide due to the decomposition of neutral magnesium carbonate is suitably suppressed, and acicular anhydrous magnesium carbonate can be produced more efficiently. Can be done.

It is preferable to carry out the heat treatment by heating to a temperature within the temperature range at a heating rate of 0.1 to 50 ° C./min and holding the heat treatment for 0 to 24 hours after reaching the temperature within the temperature range. As a result, the decomposition of neutral magnesium carbonate and the accompanying release of carbon dioxide can be suppressed at a high level.

In the production method, it is preferable that the average major axis reduction rate before and after the heat treatment represented by the following formula is 20% or less.
Average major axis reduction rate (%) = {(average major axis before heating-average major axis after heating) / average major axis before heating} x 100

Since water disappears during the phase conversion of acicular neutral magnesium carbonate to acicular anhydrous magnesium carbonate, some volume reduction is unavoidable. However, in this production method, since the needle-shaped neutral magnesium carbonate is heat-treated in a carbon dioxide-containing atmosphere, it is possible to suppress the volume decrease due to the release of carbon dioxide, and most of the volume of the needle-shaped neutral magnesium carbonate is covered. It can be phase-converted to acicular anhydrous magnesium carbonate while maintaining it.

The present invention relates to a resin composition in which, in a further embodiment, 5 to 600 parts by mass of the acicular anhydrous magnesium carbonate is blended with 100 parts by mass of the resin.

Since the resin composition contains needle-shaped anhydrous magnesium carbonate having a high aspect ratio, it can exhibit excellent strength and water resistance.

The resin is preferably at least one of ABS-based resin, polyethylene-based resin, polypropylene-based resin, polystyrene-based resin, polycarbonate-based resin, polyphenylene-based resin, polyester-based resin, and polyamide-based resin.

The present invention relates to a molded product containing the resin composition in still another embodiment.

The upper part is a chart of the X-ray diffraction pattern for the acicular anhydrous magnesium carbonate of Example 1 obtained by the XRD measurement, and the lower part is the X-ray diffraction pattern of the synthetic magnesite listed in the powder X-ray diffraction intensity database. It is a chart of. It is an SEM photograph of the needle-shaped anhydrous magnesium carbonate of Example 1. FIG.

《Needle-shaped anhydrous magnesium carbonate》
In the needle-shaped anhydrous magnesium carbonate (hereinafter, also referred to as “needle-shaped magnesite”) of the present embodiment, the ratio (aspect ratio) of the average major axis to the average minor axis may be 5 or more, preferably 8 or more. It is preferably 10 or more. The average major axis is the average major axis (μm) of the primary particles obtained by using the SEM photograph, and the average minor axis is the average minor axis (μm) of the primary particles obtained by using the SEM photograph. The aspect ratio is preferably 100 or less, more preferably 50 or less, from the viewpoint of dispersibility. By setting the aspect ratio of the needle-shaped magnesite within the above range, it is possible to improve the reinforcing property and the dispersibility in the resin.

The average major axis of the needle-shaped magnesite is preferably 10 μm or more, more preferably 20 μm or more, further preferably 30 μm or more, and particularly preferably 40 μm or more. The average major axis is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. By setting the average major axis of the needle-shaped magnesite in the above range, the continuity of orientation in the resin can be enhanced, the reinforcing property can be further improved, and the dispersibility, handleability, etc. can be further improved. ..

The average minor axis of the needle-shaped magnesite is preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 1.5 μm or more, and particularly preferably 2 μm or more. The average minor axis is preferably 20 μm or less, more preferably 10 μm or less, and further preferably 8 μm or less. By setting the average minor diameter of the needle-shaped magnesite within the above range, the strength of the particles themselves can be increased to improve the reinforcing property, and the dispersibility, handleability, and the like can be further improved.

_{The cumulative 50% diameter (d 50} ) on a volume basis in the particle size distribution obtained by the laser diffraction type particle size distribution meter of needle-shaped magnesite is preferably 5 μm or more and 200 μm or less. The cumulative 50% diameter (d ₅₀ ) is more preferably 8 μm or more, further preferably 10 μm or more. Further, the cumulative 50% diameter (d ₅₀ ) is more preferably 100 μm or less, and further preferably 50 μm or less. By setting the cumulative 50% diameter (d ₅₀ ) of the needle-shaped anhydrous magnesium carbonate within the above range, it is possible to improve the reinforcing property and to exhibit dispersibility and handleability.

After holding the needle-shaped magnesite in an atmosphere of a temperature of 40 ° C. and a humidity of 75% for 30 hours, the water absorption rate represented by the following formula is preferably 10% or less, and more preferably 5% or less. It is preferably 4% or less, and more preferably 4% or less.
Water absorption rate (%) = {(mass after holding-initial mass) / initial mass} x 100

By setting the water absorption rate in the above range in the needle-shaped magnesite, the water resistance can be further improved.

In the present embodiment, the apparent specific gravity of the needle-shaped magnesite is preferably 1 g / mL or less, more preferably 0.8 g / mL or less, still more preferably 0.5 g / mL or less. The apparent specific gravity of the needle-shaped magnesite is preferably 0.05 g / mL or more, more preferably 0.1 g / mL or more. By setting the apparent specific gravity of the needle-shaped magnesite within the above range, dispersibility and handleability can be improved. The apparent density can be measured according to JIS K-6220.

The needle-shaped anhydrous magnesium carbonate is _{a compound represented by MgCO 3} as a chemical formula, and the particles have the above-mentioned peculiar shape.

The needle-shaped magnesite of the present embodiment may contain an unavoidable impurity component derived from a raw material, a manufacturing method, or the like. Examples of the impurity component include Ca, Si, Fe, Al, and S. The content of these impurities is preferably 1% by mass or less in the needle-shaped magnesite particles in terms of each element.

The application of the needle-shaped magnetite of the present embodiment is not particularly limited, and for example, fillers and reinforcing materials for rubber products and resin products, insulating materials, heat conductive fillers, paints, clothing, friction materials, adhesives, etc. Examples include flame retardants, filter materials, thickeners and the like.

<< Manufacturing method of needle-shaped anhydrous magnesium carbonate >>
The method for producing needle-shaped anhydrous magnesium carbonate according to the present embodiment includes a step of preparing needle-shaped neutral magnesium carbonate having an average major axis ratio to an average minor axis of 5 or more, and the needle-shaped medium in a carbon dioxide-containing atmosphere. Includes a step of heat-treating magnesium carbonate. Further, after the heat treatment step, it is preferable to include a drying step of filtering the treatment dispersion liquid and drying the collected powder. Hereinafter, each step will be described.

(Preparation process)
In this process, as the raw material powder, to prepare a needle-like neutral magnesium carbonate ratio to the average minor axis of the average major axis is 5 or more _{(MgCO 3 · 3H 2 O)} . As a method for producing acicular neutral magnesium carbonate, which is a raw material powder, a known method can be adopted. For example, magnesium hydroxide is reacted with carbon dioxide gas to generate an aqueous solution of magnesium bicarbonate, and subsequently. Examples thereof include a method of heating to form acicular crystals.

A slurry is prepared by dispersing magnesium hydroxide powder in water. The slurry concentration may be set in consideration of the reaction efficiency with carbon dioxide gas in the next step, and the MgO concentration is about 1 to 20 g / L, preferably about 3 to 15 g / L. Magnesium bicarbonate can be obtained by setting this slurry to about 10 to 40 ° C., preferably about 15 to 30 ° C., and blowing carbon dioxide gas into the slurry to carry out a carbonation reaction between magnesium hydroxide and carbon dioxide gas. .. The flow rate of carbon dioxide gas may be appropriately set in consideration of reaction efficiency and the like, and is generally 0.5 to 50 L / min, preferably about 1 to 30 L / min. The carbonation reaction can be carried out using a known mixer equipped with a stirring blade.

Then, the obtained magnesium carbonate solution is heated and cured. During this curing, the particles grow into needles. The heating temperature is preferably 40 to 80 ° C, more preferably 50 to 70 ° C. The rate of temperature rise to the target temperature is preferably 0.1 to 10 ° C./min, more preferably 0.5 to 5 ° C./min. The curing (retention) time after reaching the target temperature is preferably 0.1 to 5 hours, more preferably 0.5 to 3 hours. Crystal growth can also be carried out using a known mixer equipped with a stirring blade. The aspect ratio and particle size of the target particles can be controlled by the heating temperature, the heating rate, the curing time and the stirring rate at the time of curing.

After the completion of the crystal growth reaction by curing, the raw material powder, needle-shaped neutral magnesium carbonate, can be obtained by dehydration and drying.

(Heat treatment process)
In this step, the needle-shaped neutral magnesium carbonate is heat-treated in a carbon dioxide-containing atmosphere. By performing heat treatment in an atmosphere with a high carbon dioxide concentration in the reaction system, the release of water from neutral magnesium carbonate is promoted, and at the same time, the uptake of carbon dioxide after the release of carbon dioxide is promoted, and the shape is needle-shaped. Magnesite can be produced efficiently. The heat treatment may be performed under atmospheric pressure or under pressure.

The heat treatment atmosphere is a carbon dioxide-containing atmosphere, and the carbon dioxide-containing atmosphere may be carbon dioxide alone or a mixed gas of carbon dioxide and another gas. The carbon dioxide concentration is not particularly limited as long as the concentration is such that carbon dioxide is taken in again after the carbon dioxide is released from the neutral magnesium carbonate. The carbon dioxide concentration in the carbon dioxide-containing atmosphere of the present embodiment is preferably 15% by volume or more, more preferably 20% by volume or more, still more preferably 25% by volume. The carbon dioxide concentration is preferably 100% by volume (that is, carbon dioxide alone), but may be 90% by volume or less, or 80% by volume or less. Examples of other gases include air, nitrogen, argon and the like.

When the heat treatment is performed under atmospheric pressure, it is preferably performed at a temperature within the range of 450 ° C. or higher and 600 ° C. or lower, and preferably at a temperature within the range of 480 ° C. or higher and 580 ° C. or lower. Such a heating temperature promotes the release of water from neutral magnesium carbonate to promote phase conversion to acicular magnesite, and preferably suppresses the release of carbon dioxide due to the decomposition of neutral magnesium carbonate, resulting in higher efficiency. Needle-shaped magnesite can be produced well.

The rate of temperature rise to the target temperature within the above temperature range is preferably 0.1 to 50 ° C./min, more preferably 0.5 to 20 ° C./min. Further, after reaching the target temperature within the above temperature range, it is preferably held for 0 to 24 hours, and more preferably 0.5 to 10 hours. By such a heating process, the decomposition of neutral magnesium carbonate and the accompanying release of carbon dioxide can be suppressed at a high level.

In the present embodiment, the average major axis reduction rate before and after the heat treatment represented by the following formula is preferably 20% or less, and more preferably 16% or less.
Average major axis reduction rate (%) = {(average major axis before heating-average major axis after heating) / average major axis before heating} x 100

Since water disappears during the phase conversion of acicular neutral magnesium carbonate to acicular anhydrous magnesium carbonate, some volume reduction is unavoidable. However, in the production method of the present embodiment, since the acicular neutral magnesium carbonate is heat-treated in a carbon dioxide-containing atmosphere, the volume reduction due to the release of carbon dioxide can be suppressed, and the volume of the acicular neutral magnesium carbonate can be suppressed. It can be phase-converted to acicular anhydrous magnesium carbonate while maintaining most of it.

The method for producing acicular anhydrous magnesium carbonate of the present embodiment may include steps other than the above-mentioned steps. For example, after the heat treatment step, a step of surface-treating the surface treatment agent by a known method may be included, if necessary.

As the surface treatment agent, a known compound used for the said application can be used. The surface treatment includes higher fatty acids, higher fatty acid alkaline earth metal salts, silane coupling agents, higher fatty acid esters consisting of fatty acids and polyhydric alcohols, higher fatty acid amides, and alcoholic phosphates consisting of phosphoric acid and higher alcohols. It is preferably carried out using at least one selected from the group consisting of esters. Since the surface of an inorganic material is generally hydrophilic, it has a low affinity with a resin or the like as a compound. It is possible to improve the dispersibility in the resin, improve the adhesiveness with the resin component, and maintain or improve the physical properties of the resin composition and the molded product. In addition, a surfactant can also be used as the surface treatment agent.

Examples of higher fatty acids include stearic acid, oleic acid, palmitic acid, linoleic acid, lauric acid, caprylic acid, behenic acid, montanic acid and the like. Examples of the higher fatty acid metal salt include stearate, oleate, palmitate, linoleate, laurate, caprylate, behenate, montanate and the like, and the types of metals include. Examples thereof include Na, K, Al, Ca, Mg, Zn and Ba.

Examples of the silane coupling agent include methacryloxy-based agents such as γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, and γ-methacryloxypropyltriethoxysilane. Vinyl-based products such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltri Epoxy-based materials such as ethoxysilane and β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane , N-β (aminoethyl) γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and other amino systems. ..

Examples of higher fatty acid esters include methyl laurate, methyl myristate, methyl palmitate, methyl stearate, methyl oleate, methyl erucate, methyl behenate, butyl laurate, butyl stearate, isopropyl myristate, isopropyl palmitate, and the like. There are monoesters such as octyl palmitate, octyl coconut fatty acid ester, octyl stearate, special beef fatty acid octyl ester, lauryl laurate, stearyl long stearate, long chain fatty acid higher alcohol ester, behenyl behenate, and cetyl myristate. Also, for example, neopentyl polyol long chain fatty acid ester, partial esterified product of neopentyl polyol long chain fatty acid ester, neopentyl polyol fatty acid ester, neopentyl polyol medium chain fatty acid ester, neopentyl polyol C9 chain fatty acid ester, dipentaerythritol long chain. Examples thereof include heat-resistant special higher fatty acid esters such as fatty acid esters and complex medium-chain fatty acid esters.

The alcohol phosphates include mono- and di-saturated alcohol phosphates such as mono-stearyl acid phosphate, di-stearyl acid phosphate, mono-lauryl acid phosphate, di-lauryl acid phosphate, mono-. Myristyl Acid Phosphate, Di-Myristyl Acid Phosphate, Mono-Palmityl Acid Phosphate, Di-Palmicyl Acid Phosphate, Mono-Arakil Acid Phosphate, Di-Arakil Acid Phosphate, Mono-Beher Acid Hoss Fate, di-behelic acid phosphate, mono-lignoceryl acid phosphate, di-lignoceryl acid phosphate and the like, using one or a mixture of mono and di-saturated alcohol phosphate esters. May be.

Examples of the higher fatty acid amide include stearic acid amide, oleic acid amide, palmitic acid amide, linoleic acid amide, lauric acid amide, caprylic acid amide, behenic acid amide, and montanic acid amide. Examples of the higher alcohol include octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol and the like. Examples of the hydrogenated oil include beef tallow hydrogenated oil and castor oil.

As the surfactant, a nonionic surfactant can be preferably used. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, and polyoxyethylene higher alcohol ether, and polyoxyethylene. Polyoxyethylene alkylaryl ethers such as nonylphenyl ether; polyoxyethylene derivatives; sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan sesquioleate. , Solbitan fatty acid esters such as sorbitan distearate; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate. , Polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate; polyoxyethylene sorbitol fatty acid esters such as tetraoleic acid polyoxyethylene sorbit; glycerol monostearate, glycerol monooleate, Glycerin fatty acid esters such as self-emulsifying glycerol monostearate; Polyoxyethylene fatty acid esters such as polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate: polyoxyethylene alkylamines; Polyoxyethylene hydrogenated castor oil; alkyl alkanolamide and the like can be mentioned.

A known dry method or wet method can be applied to perform surface treatment of needle-shaped magnesite using such a surface treatment agent. As a dry method, the powder of needle-shaped magnesite may be added in a liquid, emulsion or solid form with stirring by a mixer such as a Henschel mixer, and sufficiently mixed under heating or non-heating. .. As a wet method, needle-shaped magnesite powder is added to a non-aqueous solvent slurry in a solution state or an emulsion state, mechanically mixed at a temperature of, for example, about 1 to 100 ° C., and then dried or the like. The aqueous solvent may be removed. Examples of the non-aqueous solvent include isopropyl alcohol and methyl ethyl ketone. The amount of the surface treatment agent to be added can be appropriately selected, but when the dry method is adopted, the surface treatment level tends to be non-uniform compared to the wet method, so it is better to add a slightly larger amount than the wet method. good. Specifically, the range of 0.1 to 10 parts by mass is preferable with respect to 100 parts by mass of needle-shaped magnesite, and the range of 0.5 to 5 parts by mass is more preferable. When the wet method is adopted, the range of 0.1 to 10 parts by mass is preferable with respect to 100 parts by mass of needle-shaped magnesite, and 0.5 to 5 parts by mass is preferable from the viewpoint of sufficient surface treatment and prevention of aggregation of the surface treatment agent. The range of parts is more preferable.

The surface-treated needle-shaped magnesite can be subjected to washing with water, dehydration, granulation, drying, crushing, classification and the like, if necessary.

<< Resin composition >>
The resin composition in the present embodiment is a resin composition in which needle-shaped magnesite is blended with a resin. As the resin, a known resin can be appropriately set depending on the intended use and the like. For example, acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, polyethylene resin (linear polyethylene, low density polyethylene, high density polyethylene), polypropylene resin (homopolypropylene, propylene-ethylene random) Polymers, propylene-ethylene block copolymers, copolymers of propylene and other small amounts of α-olefins), ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, polystyrene-based resins, polybutadiene-based resins , Isoprene resin, ethylene-propylene rubber, ethylene-propylene rubber and other polyolefins, polyester resin (polybutylene terephthalate, polyethylene terephthalate), polyamide resin, polyacetal resin, syndiotactic polystyrene, polyphenylene resin (polyphenylene) Sulfide, polyphenylene ether, polyphenylene oxide), liquid crystal polymer, polyether ketone resin, polyether nitrile resin, polycarbonate resin, polysulfone resin, polyether sulfone resin, polyarylate resin, polyamideimide resin, poly There are etherimide-based resins and thermoplastic polyimide-based resins. Polyolefins are preferred from the standpoint of affinity with inorganic materials. It should be noted that these resins can be used alone or in combination of two or more. Above all, it is preferable that the resin is at least one of ABS-based resin, polyethylene-based resin, polypropylene-based resin, polystyrene-based resin, polycarbonate-based resin, polyphenylene-based resin, polyester-based resin, and polyamide-based resin.

In the above resin composition, needle-shaped magnesite is blended in an amount of 5 parts by mass or more and 600 parts by mass or less, preferably 10 parts by mass or more and 600 parts by weight or less, and more preferably 15 parts by mass or more with respect to 100 parts by mass of the resin. It is blended in an amount of 500 parts by weight or less, more preferably 20 parts by mass or more and 400 parts by weight or less. Since the needle-shaped magnesite of the present embodiment has a high aspect ratio, the reinforcing property of the resin can be improved.

In addition to the above components, other additives may be added to the above resin composition as long as the effects of the present invention are not impaired. Such additives include, for example, antioxidants, antioxidants, pigments, foaming agents, plasticizers, other fillers and reinforcing agents such as cubic-shaped magnesites, heat conductive fillers, flame retardants, and cross-linking agents. , Light stabilizers, UV absorbers, lubricants, lubricants, anti-aging agents, weather resistant agents, colorants, curing accelerators and the like. These additives may be blended alone or in combination of two or more. The blending amount of the other additives is not particularly limited from the viewpoint that the effect of the present invention may not be impaired, but it is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin.

Mixing and filling of needle-shaped magnesite and resin or the like can be obtained by a known kneading method or filling method. It is uniformly mixed by a machine, a revolving rotation type kneader, etc. It is also possible to knead while removing air bubbles in the resin composition using a device to which a defoaming effect is added. The obtained resin composition may be subjected to a crosslinking reaction by various methods such as heat treatment, electron beam treatment, and ultraviolet treatment. Examples of the cross-linking method include a chemical cross-linking method, an electron beam cross-linking method, and a silane cross-linking method.

<< Molded body >>
The molded product contains the resin composition. Such a molded product can be obtained by a known molding method after preparing a resin composition by blending a predetermined amount of needle-shaped magnesite or the like with a resin or the like. As such a molding method, it is molded by an extrusion molding machine, an injection molding machine, a blow molding machine, a press molding machine, a calendar molding machine or the like, a laminated molding machine, a doctor blade method or the like. Further, the obtained molded product may be subjected to a crosslinking reaction by various methods such as heat treatment, electron beam treatment, and ultraviolet treatment. Examples of the cross-linking method include a chemical cross-linking method, an electron beam cross-linking method, and a silane cross-linking method.

The molded product of the present embodiment can be used in various forms such as a film shape, a sheet shape, a plate shape, a lump shape, and a special shape, depending on various uses.

Since the molded body is formed of a resin composition containing the needle-shaped magnesite, it should be suitably applied to applications requiring high thermal conductivity, easy workability, heat resistance, water resistance, high strength, etc. Can be done. The use of the molded body is not particularly limited, and examples thereof include automobile members (engine peripheral members, bumpers, dashboards, etc.), mobile phone members (battery peripheral members, etc.) and the like.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

<Example 1>
(Raw material powder (magnesium neutral _carbonate: MgCO 3 · _3H 2 O) Preparation of)
Carbon dioxide gas was blown into the magnesium hydroxide slurry 20 L having an MgO concentration of 7 g / L at a gas flow rate of 15 L / min while stirring at 20 ° C. After confirming that the magnesium hydroxide was completely dissolved and the slurry became transparent, the blowing of carbon dioxide gas was stopped to obtain a magnesium bicarbonate solution. 20 L of the obtained magnesium carbonate solution was placed in a SUS container having a volume of 40 L, heated to 60 ° C. at a heating rate of 1 ° C./min while stirring, and cured for 1 hour. After curing, the suspension was filtered, washed with alcohol, air-dried for half a day, and then dried at a pressure of 50 Pa or less using a vacuum dryer for 24 hours. The obtained powder as a result of the identification and SEM photograph evaluation by XRD, it was confirmed that the needle-like MgCO ₃ · 3H ₂ O.

(Preparation of needle-shaped magnesite)
350 g of the above raw material powder was filled in a square crucible (200 mm × 200 mm × 100 mm) and fired by heating in an atmosphere of 100% by volume of carbon dioxide using an atmosphere furnace (atmospheric pressure, carbon dioxide flow rate 10 L / min). Baking was performed by raising the temperature to 540 ° C. at a heating rate of 1 ° C./min and holding it for 1 hour. As a result of identification by XRD and evaluation by SEM photograph, it was confirmed that the _{obtained powder was needle-shaped magnesite (MgCO 3).} FIG. 1 shows a chart of an X-ray diffraction pattern obtained by XRD measurement. The upper part is a chart of the X-ray diffraction pattern for the acicular anhydrous magnesium carbonate of Example 1 obtained by the XRD measurement, and the lower part is the X-ray diffraction pattern of the synthetic magnesite listed in the powder X-ray diffraction intensity database. It is a chart of. The actual measurement chart in the upper row and the chart in the database in the lower row correspond well, and it can be seen that the result of the example is magnesite. FIG. 2 shows an SEM photograph of the needle-shaped anhydrous magnesium carbonate of Example 1.

<Comparative Example 1>
70 L of a neutral magnesium carbonate suspension adjusted to an MgO concentration of 4.0% was placed in an autoclave with a capacity of 100 L and subjected to hydrothermal treatment at 180 ° C. for 5 hours while stirring. After the hydrothermal treatment, it was dried at 120 ° C. for 8 hours. As a result of identification by XRD and evaluation by SEM photograph, it was confirmed that the _{obtained powder was cubic magnesium carbonate (MgCO 3).}

<Comparative Example 2>
(Raw material powder (magnesium neutral _carbonate: MgCO 3 · _3H 2 O) Preparation of)
Needle-shaped neutral magnesium carbonate was prepared as a raw material powder by the same procedure as in Example 1.

(Preparation of needle-shaped magnesium oxide)
350 g of the above raw material powder was filled in a square crucible (200 mm × 200 mm × 100 mm) and fired in an electric furnace (atmosphere). The temperature was raised to 800 ° C. at a heating rate of 1 ° C./min and held for 3 hours for firing. As a result of identification by XRD and evaluation by SEM photograph, it was confirmed that the obtained powder was needle-shaped magnesium oxide (MgO).

<Evaluation>
The powders obtained in Examples and Comparative Examples were analyzed as follows. The evaluation results are shown in Table 1.

(1) Composition evaluation (XRD measurement)
The composition of the particles was measured and evaluated using an X-ray diffractometer (Rigaku Co., Ltd., RINT-2500) and integrated powder X-ray analysis software "PDXL2". The measurement conditions were a Cu radiation source (40 kV, 30 mA).

(2) Scanning electron microscope (SEM photograph); average major axis and minor axis of primary particles, aspect ratio)
Double-sided tape was attached on the aluminum sample table, and the sample powder was applied by tracing it with a spatula spatula. After the gold vapor deposition, the particle image of the sample powder was photographed at a magnification of 500 times using a scanning electron microscope (FE-SEM: S-4700 manufactured by Hitachi High-Technologies Corporation).

Using image analysis software (Image J), 50 particles in the photograph were randomly selected to determine the average major axis (μm) and average minor axis (μm) of the primary particles. Here, the major axis of the primary particle is the dimension of the particle in the direction in which the dimension of the particle is the largest (that is, the longest diameter) by measuring the dimension of the particle to be measured from each direction. The minor axis of the primary particle was the dimension of the particle in the direction in which the dimension of the particle was the smallest (that is, the shortest diameter) by measuring the dimension of the particle to be measured from each direction.

From the obtained average major axis and average minor axis, the aspect ratio was calculated based on the following formula.
Aspect ratio = average major axis / average minor axis

The average major axis and the average minor axis of the needle-shaped neutral magnesium carbonate, which is the raw material powder, were measured by the same procedure as above. Using the obtained values, the average major axis reduction rate was calculated based on the following formula.
Average major axis reduction rate (%) = {(average major axis before heating (raw material powder) -average major axis after heating (needle-shaped magnesite)) / average major axis before heating} x 100

(3) Cumulative 50% diameter 50 mL of ethanol was taken in a beaker with a capacity of 100 mL, about 0.2 g of sample powder was put in it, and ultrasonic treatment for 3 minutes (UD-201 manufactured by Tomy Seiko Co., Ltd.) was performed to prepare a dispersion. .. This dispersion was measured using a laser diffraction method-particle size distribution meter (Microtrac HRA Model 9320-X100 manufactured by Nikkiso Co., Ltd.), and the cumulative 50% diameter (d ₅₀ ) (μm) based on the volume in the obtained particle size distribution was obtained. ) Was asked.

(4) Water resistance (water absorption rate)
First, 1 g of the sample powder was placed in a Petri dish, and the Petri dish containing the sample powder was placed in a constant temperature and humidity chamber having a temperature of 40 ° C. and a humidity of 75% and held for 30 hours. The Petri dish was taken out from the constant temperature and humidity chamber, and the water absorption rate of the sample powder was measured based on the following formula. As for the target value, it was judged that the water resistance was good when the water absorption rate was 5% or less.
Water absorption rate (%) = {(mass after holding-initial mass) / initial mass} x 100

(5) Reinforcing property (measurement of flexural modulus)
a. Preparation of molded body for flexural modulus measurement After blending 15 parts by mass of sample powder with 100 parts by mass of polypropylene resin (PP, manufactured by Japan Polypropylene Corporation, BC6D), using a laboplast mill (Toyo Seiki Co., Ltd.), After melt-kneading at 180 ° C. for 5 minutes at a rotation speed of 50 rpm, the melt-kneaded product was cut to a diameter of about 5 mm or less with a shredder to prepare pellets. The pellet was injection molded using an injection molding machine (J-50E2, manufactured by Japan Steel Works, Ltd.) at an outlet temperature of 210 ° C. to obtain a test piece of 80 mm × 10 mm × 4 mm.

b. Measurement of flexural modulus The flexural modulus of the obtained test piece is determined by JIS. K. Measured based on 7171. Specifically, the 3382 type manufactured by Instron is used, and the A method that does not change the strain rate is adopted as the test method. The procedure was performed under the conditions of min, the radius of the indenter R1 = 5 mm, and the radius of the support base R2 = 5 mm. As for the target value, it was judged that the reinforcing property was good when the flexural modulus was 1.6 GPa or more.

From Table 1, the needle-shaped magnesite obtained in the examples was excellent in both reinforcing property and water resistance. On the other hand, the magnesium carbonate of Comparative Example 1 had a cubic shape, so that the reinforcing property was inferior. In Comparative Example 2, the reinforcing property was superior to that of Comparative Example 1, but the water resistance was inferior. From the above, the needle-shaped magnesite of the present invention can be suitably applied to various uses.

Claims (5)

A method for producing acicular anhydrous magnesium carbonate in which the ratio of the average major axis to the average minor axis is 5 or more.
It includes a step of preparing acicular neutral magnesium carbonate having a ratio of an average major axis to an average minor axis of 5 or more, and a step of heat-treating the acicular neutral magnesium carbonate in a carbon dioxide-containing atmosphere.
The heat treatment is performed under atmospheric pressure at a temperature within the range of 450 ° C. or higher and 600 ° C. or lower.
The heat treatment is carried out by heating to a temperature within the temperature range at a heating rate of 0.1 to 50 ° C./min and holding the heat treatment for 0.5 to 24 hours after reaching the temperature within the temperature range. A method for producing anhydrous magnesium carbonate. The method for producing acicular anhydrous magnesium carbonate according to claim 1 , wherein the average major axis reduction rate before and after the heat treatment represented by the following formula is 20% or less.
Average major axis reduction rate (%) = {(average major axis before heating-average major axis after heating) / average major axis before heating} x 100 A resin composition containing 5 to 600 parts by mass of acicular anhydrous magnesium carbonate having a ratio of an average major axis to an average minor axis of 5 or more with respect to 100 parts by mass of the resin. The resin, ABS resins, polyethylene resins, polypropylene resins, polystyrene resins, polycarbonate resins, polyphenylene resins, resins of claim 3 wherein at least one of polyester resin and a polyamide resin Composition. A molded product containing the resin composition according to claim 3 or 4.

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