TWI843814B - Modified zirconium tungstate phosphate, negative thermal expansion filler and polymer composition - Google Patents

Abstract

The subject of the present invention is to provide a modified zirconium tungstate phosphate, which can effectively inhibit the dissolution of phosphorus ions even when in contact with water, can show excellent performance as a negative thermal expansion material, can be dispersed in polymer compounds such as resins, and can smoothly produce low thermal expansion materials containing negative thermal expansion fillers. A modified zirconium tungstate phosphate, wherein the surface of the zirconium tungstate phosphate particles is coated with an inorganic compound, and the inorganic compound contains one or more elements (M) selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe and Zr. The BET specific surface area of the zirconium tungstate phosphate particles is preferably 0.1 ^m2 /g to 50 ^m2 /g.

Description

Modified zirconium tungstate phosphate, negative thermal expansion filler and polymer composition

The present invention relates to a modified zirconium tungstate phosphate, a negative thermal expansion filler and a polymer composition using the same.

Generally speaking, a substance has the property of increasing in length or volume due to thermal expansion when the temperature rises. On the other hand, there are known materials that exhibit negative thermal expansion (hereinafter sometimes referred to as "negative thermal expansion materials") and have the property of decreasing in volume by the addition of heat. Materials that exhibit negative thermal expansion can be used together with other materials to suppress volume changes caused by thermal expansion of materials due to temperature changes, for example.

As materials showing negative thermal expansion, for example, β-eucryptite, zirconium tungstate (ZrW ₂ O ₈ ), zirconium tungstate phosphate (Zr ₂ WO ₄ (PO ₄ ) ₂ ), Zn _x Cd _1-x (CN) ₂ , manganese nitride, bismuth-nickel-iron oxide, and the like are known.

It is known that the linear expansion coefficient of zirconium tungstate phosphate particles is -3.4ppm/℃~-3.0ppm/℃ in the temperature range of 0℃~400℃, and the negative thermal expansion is large. By using the zirconium tungstate phosphate particles together with a material showing positive thermal expansion (hereinafter sometimes referred to as "positive thermal expansion material"), a low thermal expansion material can be produced (see Patent Documents 1~3). In addition, it is also proposed to use a polymer compound such as a resin as a positive thermal expansion material together with a negative thermal expansion material (Patent Documents 4~5).

[Prior art literature]

[Patent Literature]

[Patent document 1] Japanese Patent Publication No. 2005-35840

[Patent Document 2] Japanese Patent Publication No. 2015-10006

[Patent Document 3] International Publication No. 2017/61403 Manual

[Patent Document 4] Japanese Patent Publication No. 2015-38197

[Patent Document 5] Japanese Patent Publication No. 2016-113608

However, if zirconium tungstate phosphate comes into contact with water, phosphorus and other substances in the structure will dissolve in the form of ions, which may cause the following problems: reduced performance as a negative thermal expansion material, reduced electrical reliability when mixed with materials such as resins to make resin molded products, and corrosion of metal parts in contact with resin molded products.

Therefore, the purpose of the present invention is to provide a modified zirconium tungstate phosphate that inhibits the dissolution of phosphorus ions in zirconium tungstate phosphate into water and can be suitably used as a negative thermal expansion filler contained in a polymer compound, and a negative thermal expansion filler and a polymer composition using the same.

The inventors of the present invention have repeatedly conducted diligent research on the above-mentioned topic and found that by modifying the surface of zirconium tungstate phosphate particles by coating them with inorganic compounds containing specific elements, the elution of phosphorus ions can be effectively suppressed even when in contact with water. In addition, it was found that the modified zirconium tungstate phosphate is dispersed in a polymer compound such as a resin to produce a low thermal expansion material containing a negative thermal expansion filler, thereby completing the present invention.

That is, the present invention provides a modified zirconium tungstate phosphate, wherein the surface of the zirconium tungstate phosphate particles is coated with an inorganic compound, and the inorganic compound contains one or more elements (M) selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe and Zr.

In addition, the present invention provides a negative thermal expansion filler comprising the modified zirconium tungstate phosphate.

In addition, the present invention provides a polymer composition containing the negative thermal expansion filler and a polymer compound.

According to the modified zirconium tungstate phosphate of the present invention, even when in contact with water, the dissolution of phosphorus ions can be effectively suppressed, showing excellent performance as a negative thermal expansion material. In addition, the modified zirconium tungstate phosphate of the present invention can be dispersed in polymer compounds such as resins, and low thermal expansion materials containing negative thermal expansion fillers can be smoothly manufactured.

FIG1 is a scanning electron microscope image showing the shape of the zirconium tungstate phosphate particle sample 1.

Figure 2 is a scanning electron microscope image showing the shape of the zirconium tungstate phosphate particle sample 2.

Figure 3 is the thermogravimetry (TG) curve of zinc nitrate hexahydrate.

Figure 4 is the TG curve of zinc citrate dihydrate.

The present invention is described below based on a preferred embodiment. The modified zirconium tungstate phosphate (hereinafter also referred to as "modified ZWP") of the present invention is a zirconium tungstate phosphate particle (hereinafter also referred to as "ZWP particle") whose surface is coated with an inorganic compound (hereinafter sometimes referred to as "inorganic compound") containing one or more elements (M) selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe and Zr. That is, the modified ZWP of the present invention includes particles having a ZWP particle as a core material and a layer containing an inorganic compound formed on the surface of the particle. In the following description, when "N1~N2" (N1 and N2 are arbitrary numbers respectively) is recorded, it means "N1 or more and N2 or less" unless otherwise specified.

The inorganic compound contained in the modified ZWP may cover the entire surface of the ZWP particle without omission or only a portion of the surface of the particle. In the former case, the modified ZWP is in a state where the entire surface area of the ZWP particle is completely covered by the inorganic compound and the surface of the particle is not exposed. In the latter case, the surface of the modified ZWP includes a portion containing zirconium tungstate phosphate as a base and a portion containing the inorganic compound. In the case where the inorganic compound covers only a portion of the surface of the ZWP particle, the covered portion may be continuous, may be discontinuously covered in an island shape, or may be a combination of these.

The zirconium tungstate phosphate constituting the ZWP particles of the present invention is represented by the following general formula (1).

Zr _x (WO ₄ ) _y (PO ₄ ) _z (1)

(In the formula, x is 1.7≦x≦2.3, preferably 1.8≦x≦2.2, y is 0.85≦y≦1.15, preferably 0.90≦y≦1.10, z is 1.7≦z≦2.3, preferably 1.8≦z≦2.2)

The inorganic compound used in the present invention to coat the ZWP particles is an inorganic compound containing one or more elements (M) selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe and Zr. As the inorganic compound, oxides, hydroxides, carbonates, nitrates, sulfates, silicates, etc. containing the element (M) can be listed, and one or more of these inorganic compounds can be used. Among these, oxides or hydroxides containing the element (M) are particularly preferred from the viewpoint of being insoluble in water and having a higher inhibitory effect on eluted phosphorus ions.

In addition, as the element (M), among these, Zn, Al, Ca, and Ba are preferred, and inorganic compounds containing Zn are particularly preferred. The reason is that the film containing the Zn compound effectively inhibits the contact between ZWP and water, and the adsorption performance of phosphorus ions is also excellent. Therefore, the phosphorus ions eluted from ZWP are adsorbed by the Zn-containing compound in the film, thereby effectively inhibiting the elution of phosphorus ions from the modified ZWP.

The inorganic compound may be a complex oxide, complex hydroxide or complex salt containing two or more elements (M).

In the modified ZWP of the present invention, the coating amount (existence amount) of the inorganic compound relative to the ZWP particles is preferably 0.1 mass% to 10 mass%, more preferably 0.3 mass% to 5.0 mass%, and further preferably 0.5 mass% to 3.0 mass%, based on the element (M) contained in the inorganic compound. By having the coating amount in this range, the dissolution of phosphorus ions from the modified ZWP can be effectively suppressed, and the performance as a negative thermal expansion material can be improved. When used as a negative thermal expansion filler, the dispersibility in positive thermal expansion materials such as resins becomes good.

Regarding the coating amount of inorganic compounds, when the element (M) is Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co or Fe, it can be obtained by the following method: On the premise that these elements are not contained in the ZWP particles, the solution dissolved by nitric acid or hydrochloric acid is subjected to inductively coupled plasma (ICP) emission spectrometry to measure the amount of elements selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co and Fe. The accessory component elements contained in the ZWP particles and the inorganic elements coating the ZWP particles can be distinguished and quantified using scanning electron microscope (SEM)-energy-dispersion X-ray analysis (EDX), electron probe micro analysis (EPMA) and other methods.

From the perspective of improving the dispersibility or filling properties of the positive thermal expansion material, the ZWP particles as the raw material preferably contain elements other than P, W, Zr and O as the elements contained in the general formula (1) (hereinafter also referred to as "subsidiary component elements").

As the secondary component elements, for example, there can be listed: alkali metal elements such as Li, Na, and K; alkali earth metal elements such as Mg, Ca, Sr, and Ba; transition metal elements such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Nb, Mo, Ag, Hf, and Ta; rare earth elements such as La, Ce, Nd, Sm, Eu, Tb, Dy, Ho, and Yb; other metal elements other than transition metals such as Al, Zn, Ga, Cd, In, Sn, Pb, and Bi; semi-metal elements such as B, Si, Ge, Sb, and Te; non-metal elements such as S; halogen elements such as F, Cl, Br, and I, etc. These elements can be contained in the particles alone or in combination. Among these, from the viewpoint of further improving the dispersibility or filling characteristics of the positive thermal expansion material, the particles preferably contain at least one accessory element of Mg, Al and V.

From the perspective of producing a material having excellent negative thermal expansion and excellent dispersibility and filling characteristics in positive thermal expansion materials, the content of the accessory element in the ZWP particles is preferably 0.1 mass% to 3 mass%, and more preferably 0.2 mass% to 2 mass%, relative to the ZWP particles. When two or more accessory elements are contained, the content of the accessory element is calculated based on the total mass of the accessory element. In addition, the content of the accessory element in the modified ZWP can be set to the same range as described above. The content of the accessory element can be measured, for example, by a measuring device such as a fluorescent X-ray analyzer, by a powder pressing method, a molten glass bead method, or the like.

The particle shape of the modified ZWP is not particularly limited, and may be, for example, spherical, granular, plate-like, scaly, whisker-like, rod-like, filament-like, irregular gravel-like with one or more edges (hereinafter also referred to as "crushed"), or a combination thereof.

The modified zirconium tungstate phosphate of the present invention, which covers the surface of zirconium tungstate phosphate particles with an inorganic compound containing one or more elements (M) selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe and Zr, can effectively inhibit phosphorus from eluting from zirconium tungstate phosphate in the form of ions even when in contact with water, and can exhibit excellent performance as a negative thermal expansion material. In addition, the modified zirconium tungstate phosphate of the present invention can be uniformly dispersed in a polymer compound such as a resin, and as a result, a low thermal expansion material can be smoothly manufactured.

The following describes a preferred method for producing the modified ZWP of the present invention. The method for producing the modified ZWP is roughly divided into two steps: a step of obtaining ZWP particles by reacting a zirconium source, a tungsten source, and a phosphorus source, and a step of coating the surface of the obtained ZWP particles with an inorganic compound.

First, a zirconium source, a tungsten source, and a phosphorus source are reacted to obtain ZWP particles. The method for producing the ZWP particles used in the present invention is not particularly limited, and examples thereof include: (i) a method of calcining a mixture obtained by mixing zirconium phosphate, tungsten oxide, and a reaction accelerator such as MgO using a wet ball mill (for example, see Japanese Patent Publication No. 2005-35840); (ii) a method of calcining a mixture obtained by wet mixing a zirconium source such as zirconium chloride, a tungsten source such as ammonium tungstate, and a phosphorus source such as ammonium phosphate (for example, see Japanese Patent Publication No. 2015-10006); (iii) a method of calcining a mixture containing zirconium oxide, tungsten oxide, and diammonium dihydrogen phosphate (for example, see Materials Research Bulletin). Bulletin), 44 (2009), p.2045-2049); or (iv) a method of using a mixture of a tungsten compound and an amorphous compound containing phosphorus and zirconium as a reaction precursor and calcining the reaction precursor (for example, refer to the manual of International Publication No. 2017/061402).

From the viewpoint of facilitating the handling of the modified ZWP as a filler relative to a positive thermal expansion material, the BET specific surface area of the ZWP particles is preferably 0.1 m ² /g to 50 m ² /g, and more preferably 0.1 m ² /g to 20 m ² /g. The BET specific surface area of the modified ZWP can be set in the same range as described above. The BET specific surface area can be measured by the BET single point method, for example, using a BET specific surface area measuring device (manufactured by Quantachrome Instruments Co., Ltd., AUTOSORB-1).

From the same point of view, the average particle size of ZWP particles is preferably 0.02μm~50μm, and more preferably 0.5μm~30μm. In addition, the average particle size of the modified ZWP can be set to the same range as described above. The average particle size can be obtained by observing any 100 particles using a scanning electron microscope and taking the arithmetic mean of the maximum length of the particles in the scanning electron microscope image. The maximum length here refers to the length of the longest line segment among the line segments that cross the particle image. As the observation magnification, it is better to adjust the number of particles entering one field of view to 100~200.

There is no particular limitation on the shape of ZWP particles, and they may be spherical, granular, plate-like, scaly, whisker-like, rod-like, filament-like, crushed, or a combination thereof. ZWP particles may be granulated particles or ungranulated powder.

From the perspective of being able to easily control various properties such as the particle size, specific surface area, and particle shape by an industrially advantageous method and obtaining a modified ZWP having excellent negative thermal expansion, it is preferred to use ZWP particles produced by the method (iv) as a method for producing ZWP particles.

Next, the surface of the ZWP particles obtained by the above method is coated with an inorganic compound. This step can be performed by a wet method or a dry method.

When the inorganic compound coating treatment is performed by a wet method, for example, a dispersion (including a dissolved solution) containing the inorganic compound at a desired concentration may contain ZWP particles to prepare a slurry, and the slurry may be spray dried, or the slurry may be solid-liquid separated and the obtained solid component may be dried to obtain the target modified ZWP. The content of the inorganic compound in the dispersion (including a dissolved solution) may be appropriately adjusted so that the coating amount of the inorganic compound in the modified ZWP is within the above range. The concentration of the inorganic compound in the dispersion (including a dissolved solution) may be appropriately adjusted in consideration of workability.

When the inorganic compound coating treatment is performed by a dry method, for example, a mixing device such as a Henschel mixer or an air flow mill can be used to mix ZWP particles with the solid inorganic compound, or ZWP particles can be mixed with a dilution obtained by diluting the inorganic compound with a solvent, and then heated and dried as needed to obtain the target modified ZWP. In the dry method, the mixture of ZWP particles and the inorganic compound is directly used to produce the modified ZWP, so the amount of the inorganic compound added is roughly the same as the coating amount.

The coating treatment method in the dry method or wet method may also be a method of using an organic compound or inorganic salt containing the element (M) as a precursor of an inorganic compound, and converting the organic compound or inorganic salt into an oxide by heat treatment to a temperature above the decomposition temperature of the organic compound or inorganic salt in the heat treatment described below. The organic compound is not particularly limited as long as it can be converted into an oxide by heat treatment, and examples thereof include carboxylates of the element (M), alcoholates of the element (M), etc. For example, the carboxylic acid as the carboxylate may be any of a monocarboxylic acid and a polycarboxylic acid, and examples thereof include acetic acid, citric acid, gluconic acid, formic acid, lactic acid, etc. As inorganic salts, examples thereof include nitrates and carbonates of the element (M), etc. Furthermore, the amount of organic compound or inorganic salt used can be appropriately adjusted so that the coating amount of the inorganic compound in the modified ZWP is within the above range.

In addition, when the inorganic compound coating treatment is performed by a wet method, a water-soluble inorganic salt and an alkaline agent containing the element (M) are added to the slurry obtained by dispersing ZWP particles in water, and the pH is adjusted to 6-10, so that the hydroxide containing the element (M) is precipitated on the particle surface of the ZWP particles for coating. Furthermore, the content of the water-soluble inorganic salt containing the element (M) in the slurry can be appropriately adjusted so that the coating amount of the inorganic compound in the modified ZWP is within the above range.

The modified ZWP of the present invention manufactured in this way suppresses the elution of phosphorus ions from the modified ZWP even in the presence of water, and is suitable for use as a negative thermal expansion material. Regarding the modified ZWP of the present invention, when 1 g of the modified ZWP is heat-treated with 70 mL of water at 85°C for 1 hour, then cooled to 25°C and left to stand for 24 hours, the amount of phosphorus ions eluted per 1 g of modified zirconium tungstate phosphate is 100 μg or less, preferably 70 μg or less. The amount of phosphorus ions is measured as the total amount of phosphorus present in the eluate obtained by standing for 24 hours as described above, for example, using an ICP emission spectrometer.

It is preferred that a heat treatment be further performed after the coating treatment, whether the coating treatment is performed by a wet method or a dry method. The temperature of the heat treatment is preferably 250°C to 600°C, more preferably 300°C to 450°C, and the time of the heat treatment is preferably more than 30 minutes, more preferably 1 hour to 10 hours. In addition, the environment of the heat treatment can be any of a vacuum, an inert gas environment, or an atmospheric environment. By performing the heat treatment, the inorganic compound present on the surface of the ZWP particles becomes a dense structure, which can further inhibit the dissolution of phosphorus ions from the modified ZWP in the presence of water. As a result, a modified ZWP with excellent negative thermal expansion can be obtained.

The organic compound containing the element (M) and the inorganic salt of the element (M) as the precursor of the inorganic compound can be converted into the oxide of the element (M) by the heat treatment. The converted oxide of the element (M) existing on the surface of the ZWP particles forms a dense structure, further suppressing the elution of phosphorus ions from the modified ZWP in the presence of water. As a result, a modified ZWP with excellent negative thermal expansion can be obtained.

When heat treatment is performed, the temperature of the heat treatment is preferably a temperature higher than the decomposition temperature of the inorganic compound containing the element (M) when using a substance other than oxides and hydroxides or an organic compound containing the element (M). Furthermore, in the case of a water-containing salt, the decomposition temperature refers to the temperature at which the oxide is formed. By heat treatment at such a temperature, the compound containing the element (M) in the coating layer on the surface of the ZWP particles is converted into an oxide of the element (M), and the coating layer on the surface of the ZWP particles becomes a denser structure, which can further suppress the dissolution of phosphorus ions from the modified ZWP in the presence of water.

In addition, the modified ZWP of the present invention can further suppress the elution of phosphorus ions from ZWP, further improve the dispersibility or adhesion to polymer compounds, and prevent the reduction of electrical reliability of resin molded products and corrosion of metal parts caused by phosphorus ion elution. The surface of the modified ZWP particles is further treated with a hydrophobic compound. As the hydrophobic compound, coupling agents, higher fatty acids or metal salts of higher fatty acids can be listed. Among these, coupling agents are preferred in terms of further reducing the elution of phosphorus ions from ZWP and further improving the dispersibility or adhesion to polymer compounds.

In addition, for the sake of convenience, modified zirconium tungstate phosphate in which the surface of zirconium tungstate phosphate particles is coated with an inorganic compound containing one or more elements (M) selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe and Zr is sometimes referred to as "modified ZWP (1)".

In addition, below, the particle surface of ZWP (1) that has been further modified by coating with a coupling agent may be referred to as "modified ZWP (2)".

As coupling agents that can be used to modify ZWP (2), there can be listed silane-based coupling agents, aluminum-based coupling agents, titanium ester-based coupling agents, and zirconate-based coupling agents. One or more of these coupling agents can be used.

Examples of the silane coupling agent include silazanes such as hexamethyldisilazane; hydridosilanes such as trimethylsilane; halogenated silanes such as trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane; methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxy Alkyl alkoxysilanes such as propyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane; vinyl alkoxysilanes such as vinyltrimethoxysilane and vinyltriethoxysilane; methacryloyl-containing alkoxysilanes such as γ-methacryloxypropyltrimethoxysilane and γ-methacryloxypropylmethyldimethoxysilane ; γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane and other amino-containing alkoxysilanes; β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-Glyceryloxypropyl trimethoxysilane, γ-Glyceryloxypropyl methyl dimethoxysilane, γ-Glyceryloxypropyl triethoxysilane and other alkoxysilanes containing epoxy groups; vinyl triethoxysilane, γ-chloropropyl trimethoxysilane, γ-butyl propyl trimethoxysilane, N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane, γ-ureidopropyl triethoxysilane, aminofluorosilane, etc.

As aluminum coupling agents, for example, aluminum alcoholates such as ethyl acetylacetate aluminum diisopropoxide, methyl acetylacetate aluminum diisopropoxide, ethyl acetylacetate aluminum dibutyloxide, alkyl acetylacetate aluminum diisopropoxide, and aluminum chelates such as monoacetylacetylacetate bis(ethyl acetylacetate)aluminum, etc. can be cited.

As titanium ester coupling agents, there are: isopropyl triisostearate titanium ester, isopropyl tri-dodecylbenzenesulfonyl titanium ester, isopropyl tri(dioctyl pyrophosphate) titanium ester, tetraisopropyl(dioctyl phosphite) titanium ester, tetraoctyl di(di-tridecyl phosphite) titanium ester, tetrakis(2,2-diallyloxymethyl-1-butyl)di(di-tridecyl) titanium phosphite, bis(dioctyl pyrophosphate)oxyacetate titanium ester, bis(dioctyl pyrophosphate)ethylene titanium ester and other alkoxy titanium esters, etc.

Examples of zirconate coupling agents include zirconium alkoxides such as ethoxyzirconium stearate, zirconium chelate compounds such as zirconium tetraacetylacetonate or zirconium α-hydroxycarboxylate, zirconium soaps, zirconium acetate, etc.

In the present invention, among these coupling agents, when the obtained modified ZWP (2) is used as a negative thermal expansion material filler, silane-based coupling agents or titanium ester-based coupling agents are preferred from the viewpoint of excellent dispersibility or adhesion of polymer compounds and high effect of reducing the elution of phosphorus ions from ZWP.

The coating amount of the coupling agent in the modified ZWP (2) is preferably 0.05 mass% to 30 mass%, and more preferably 0.1 mass% to 10 mass%, relative to the modified ZWP (1). By having the coating amount in this range, the elution of zirconium ions, tungsten ions and phosphorus ions from the modified ZWP can be effectively suppressed, thereby improving the performance as a negative thermal expansion material.

As a method for coating the surface of modified ZWP (2) particles with a coupling agent, it can be carried out by a wet method or a dry method.

When the coupling agent is coated by a wet method, for example, the modified ZWP (1) is immersed in a dispersion (including a dissolved solution) containing the coupling agent at a desired concentration to prepare a slurry, and the slurry is spray-dried, or the slurry is solid-liquid separated and the solid component is dried to hydrolyze and condense the coupling agent. In this way, the target modified ZWP (2) can be obtained. The concentration of the coupling agent in the dispersion can be appropriately adjusted so that the coating amount in the modified ZWP (2) is within the above range.

When the coupling agent coating treatment is performed by a dry method, the modified ZWP (1) and the coupling agent are mixed using a mixing device such as a Henschel mixer or an air flow mill, or the modified ZWP (1) is mixed with a dilution obtained by diluting the coupling agent with a solvent, and then a heat treatment is performed under the above conditions as needed to hydrolyze and condense the coupling agent. In this way, the target modified ZWP (2) can be obtained. In the dry method, the mixture of the modified ZWP (1) and the coupling agent is directly used to produce the modified ZWP (2), so the coating amount of the coupling agent is roughly consistent with the value theoretically calculated from the amount of the coupling agent added.

The modified ZWP of the present invention obtained through the above steps can be directly used as a negative thermal expansion filler for manufacturing low thermal expansion materials in a dry state such as powder, or in a wet state such as by dispersing the powder in a solvent.

The negative thermal expansion filler of the present invention is a material containing the modified ZWP, and a polymer composition can be produced by mixing the negative thermal expansion filler with a polymer compound. Due to the high negative thermal expansion property of the modified ZWP, the polymer composition becomes a material with suppressed thermal expansion coefficient.

The polymer compound used in the polymer composition of the present invention is not particularly limited, but preferably a resin having positive thermal expansion. Examples of such resins include rubber, polyolefin resins, polycycloolefin resins, polystyrene resins, acrylonitrile-butadiene-styrene (ABS) resins, polyacrylate resins, polyphenylene sulfide resins, phenol resins, polyamide resins, polyimide resins, epoxy resins, silicone resins, polycarbonate resins, polyethylene resins, polypropylene resins, polyethylene terephthalate resins (PET resins), and polyvinyl chloride resins. These can be used individually or in combination.

The content of the negative thermal expansion filler in the polymer composition can be appropriately changed according to the type of polymer compound used, the purpose or purpose of the manufactured material, and is preferably 1 volume % to 90 volume % relative to the polymer composition. Similarly, the content of the polymer compound in the polymer composition is preferably 10 volume % to 99 volume % relative to the polymer composition.

In addition to negative thermal expansion fillers and polymer compounds, the polymer composition may further contain additives. Examples of additives include: antioxidants, heat stabilizers, ultraviolet absorbers, lubricants, stripping agents, colorants including dyes and pigments, flame retardants, crosslinking agents, softeners, dispersants, hardeners, polymerization initiators, inorganic fillers, etc. The content of additives is preferably 10% to 90% by volume relative to the polymer composition.

The polymer composition of the present invention can be manufactured by a known method. For example, when a curable resin is used as a polymer compound, the following methods can be cited: a method of mixing a negative thermal expansion filler, a curable resin (or a prepolymer) and an additive as required to form a molded body; or a method of pre-mixing a negative thermal expansion filler and an additive as required with one of the resin components to form a mixture, and then mixing the mixture with a curable resin (or a prepolymer) to form a molded body, etc.

In addition, when a thermoplastic resin is used as a polymer compound, there are the following methods: a method of using an extruder to melt and mix a negative thermal expansion filler and a thermoplastic resin to form a molded body; or a method of using an injection molding machine to mix a negative thermal expansion filler and a thermoplastic resin in a solid state to form a molded body.

The polymer composition of the present invention manufactured in this way effectively suppresses the thermal expansion rate due to the high negative thermal expansion of the modified ZWP used as a negative thermal expansion filler, making it a material that is not easily deformed by heat. In addition, the ion dissolution from the modified ZWP used as a negative thermal expansion filler is small, so it can be particularly used as a material for precision instruments such as packaging materials for electronic parts.

[Implementation example]

The present invention is described below by using examples, but the present invention is not limited to these examples.

<Preparation of Zirconium Tungstate Phosphate Particles (ZWP Particles)>

(1. ZWP particle sample 1)

15 parts by mass of commercially available tungsten trioxide (WO ₃ ; average particle size 1.2 μm) was placed in a beaker, and then 84 parts by mass of pure water and 1 part by mass of ammonium polycarboxylate salt were added as a dispersant to prepare a dispersion. The dispersion was stirred at room temperature (25°C) for 120 minutes using a three-one motor stirrer to prepare a 15% by mass slurry containing tungsten trioxide. The average particle size of the solid component in the slurry was 1.2 μm.

Next, zirconium hydroxide and 85 mass% phosphoric acid aqueous solution were added to the slurry at room temperature (25°C) in such a manner that the molar ratio of Zr:W:P in the slurry was 2.00:1.00:2.00 to prepare a reaction solution. The reaction solution was reacted for 2 hours at room temperature (25°C) under stirring. The total amount of the reaction solution after the reaction was dried at 200°C for 24 hours in the atmosphere to obtain a reaction precursor. The obtained reaction precursor was subjected to X-ray diffraction analysis, and only the diffraction peak of tungsten trioxide was observed.

Then, the obtained reaction precursor was calcined at 950°C for 2 hours in the atmosphere to obtain a white ZWP particle sample 1 as a calcined product. X-ray diffraction analysis was performed on the obtained ZWP particle sample 1, and the result showed that the sample 1 was a single-phase Zr ₂ (WO ₄ )(PO ₄ ) ₂ . The average particle size and BET specific surface area of the ZWP particle sample 1 are shown in Table 1. In addition, scanning electron microscope observation was performed, and the particle shape of the obtained ZWP particle sample 1 was a broken state as shown in FIG. 1 .

(2. ZWP particle sample 2)

15 parts by mass of commercially available tungsten trioxide (WO ₃ ; average particle size 1.2 μm) was placed in a beaker, and 84 parts by mass of pure water was added to prepare a dispersion. The dispersion was stirred at room temperature (25°C) for 120 minutes to prepare a 15% by mass slurry containing tungsten trioxide. The average particle size of the solid component in the slurry was 1.2 μm.

Next, zirconia hydroxide, 85 mass % phosphoric acid aqueous solution and magnesium hydroxide were added to the slurry at room temperature (25°C) so that the molar ratio of Zr:W:P:Mg in the slurry was 2.00:1.00:2.00:0.1 to prepare a reaction solution. The reaction solution was heated to 80°C and reacted for 4 hours under stirring. Thereafter, 1 mass part of ammonium polycarboxylate salt was added to the reaction solution after the reaction as a dispersant, and while stirring the solution, zirconia beads with a diameter of 0.5 mm were supplied to a media stirring bead mill (LMZ2 manufactured by Ashizawa Finetech) and wet pulverized at 2000 rpm for 15 minutes. The average particle size of the solid component in the reaction solution after wet grinding is 0.3μm.

Then, the wet-crushed reaction liquid was fed to a spray dryer set at 220°C at a feed rate of 2.4 L/h to obtain a reaction precursor. X-ray diffraction analysis of the obtained reaction precursor revealed that only the diffraction peak of tungsten trioxide was observed.

Finally, the obtained reaction precursor was calcined at 960°C for 2 hours in the atmosphere to obtain a white ZWP particle sample 2 as a calcined product. X-ray diffraction analysis of the obtained ZWP particle sample 2 showed that the sample 2 was a single-phase Zr ₂ (WO ₄ )(PO ₄ ) ₂ . The average particle size and BET specific surface area of the ZWP particle sample 2 are shown in Table 1. In addition, scanning electron microscope observation was performed, and the particle shape of the obtained ZWP particle sample 2 was spherical as shown in FIG. 2 .

(Implementation Example 1)

50 g of ZWP particle sample 1 and 3.5 g of 40 mass % zinc nitrate aqueous solution prepared using zinc nitrate hexahydrate were ground and mixed using an air flow mill (manufactured by Seishin Enterprise, A-O jet mill) to prepare a powder mixture, and the mixture was heated at 400°C for 1 hour in an atmospheric environment to obtain a modified ZWP in which the surface of the ZWP particles was covered with zinc oxide. The modified ZWP was in the form of crushed particles. The conditions of the air flow mill were set as powder feed rate: 3 g/min, thrust pressure: 0.6 MPa, and jet pressure: 0.6 MPa.

The TG curve obtained by measuring the zinc nitrate hexahydrate used by the following method is shown in Figure 3. As shown in the TG curve of Figure 3, it can be seen that zinc nitrate hexahydrate (molecular weight 297.49) decomposes at 310°C to form zinc oxide (molecular weight 81.40).

Therefore, it can be seen that the zinc nitrate present on the surface of the ZWP particles is converted into zinc oxide by the heat treatment at 400°C.

<TG curve measurement method>

Calculate the TG curve when the temperature is increased from 25℃ to 700℃ at 10℃/min in an atmospheric environment. The sample size is set to 5.6mg.

(Example 2)

1.63 g of zinc citrate dihydrate powder was used to replace 3.5 g of 40 mass % zinc nitrate aqueous solution, and the temperature of the powder mixture was set to 430°C. In addition, the same method as Example 1 was used to obtain a modified ZWP in which the surface of the ZWP particles was covered with zinc oxide. The modified ZWP was a crushed particle.

The TG curve obtained by measuring the zinc citrate dihydrate used by the above method is shown in Figure 4. As shown in the TG curve of Figure 4, it can be seen that zinc citrate dihydrate (molecular weight 610.43) decomposes at 430°C to form zinc oxide (molecular weight 81.40).

Therefore, it can be seen that zinc citrate dihydrate existing on the surface of ZWP particles is converted into zinc oxide by heat treatment at 430°C.

(Implementation Example 3)

Add 50g of ZWP particle sample 2 and 1.63g of zinc citrate dihydrate powder, use a mixer (laboratory mixer: Labo Milser) to mix at 20000rpm for 1 minute to make a powder mixture, heat the mixture at 430℃ in an atmospheric environment for 30 minutes to obtain a modified ZWP with the surface of the ZWP particles covered with zinc oxide. The modified ZWP is a spherical particle.

(Comparison Example 1 and Comparison Example 2)

Only ZWP particle sample 1 is used as comparative example 1, and only ZWP particle sample 2 is used as comparative example 2. That is, each comparative example uses only ZWP particles, and the surface of the particles is not coated with a zinc compound.

<Evaluation of physical properties>

(Evaluation of linear expansion coefficient of powder)

The particles obtained in the Examples and Comparative Examples were heated at a rate of 20°C/min using an X-ray Diffraction (XRD) device (Ultima IV manufactured by Rigaku) with a heating function, starting from 25°C and increasing the temperature to 100°C. Ten minutes after reaching the target temperature, the lattice constants of the sample with respect to the a-axis, b-axis, and c-axis were measured. Subsequently, the target temperature was set to 200°C, 300°C, and 400°C and the temperature was increased in sequence, and the lattice constants of the sample with respect to the a-axis, b-axis, and c-axis were measured at each temperature in the same manner as the above method. The obtained lattice volume change (cuboid) was linearly converted to obtain the linear expansion coefficient (ppm/°C) (refer to Journal of Materials Science (J.Mat.Sci.) (2000) 35, p.2451-2454). The results are shown in Table 2.

(Evaluation of the amount of dissolved P ions)

1 g of the particles obtained in the examples and comparative examples was added to 70 mL of pure water to prepare a test solution. The test solution was heated at 85°C for 1 hour, cooled to room temperature (25°C), and adjusted with pure water so that the test solution was 100 mL. The test solution was allowed to stand at 25°C for 24 hours, and then filtered to separate the solid and liquid of the test solution. The total P ion amount in the filtrate was measured using an ICP spectrophotometer and converted to the total P ion amount dissolved in 1 g of modified ZWP. The results are shown in Table 2.

As shown in Table 2, it can be seen that the modified ZWP of each embodiment has the same level of negative linear expansion coefficient compared with the particles of the comparative example, and the elution of ions from the particles is suppressed.

(Example 4 to Example 6)

The modified ZWP obtained in Examples 1 to 3 was used as a negative thermal expansion filler to produce a polymer composition. Specifically, a vacuum mixer (Thinky Defoaming Mixer ARV-310) was used to mix 5.8 g of a negative thermal expansion filler with 4.2 g of an epoxy resin (jER807 manufactured by Mitsubishi Chemical, epoxy equivalent 160~175) as a polymer compound at a rotation speed of 2000 rpm to produce a 30 volume % paste.

Next, 100 μL of a curing agent (Curezol manufactured by Shikoku Chemical) was added to the paste, mixed at a rotation speed of 1500 rpm using the vacuum mixer, and cured at 150°C for 1 hour to obtain the target polymer composition. The cross-section of the obtained polymer composition was observed using a scanning electron microscope, and it was confirmed that the modified ZWP as a negative thermal expansion filler was uniformly dispersed in the polymer composition in any embodiment.

(Reference Example 1)

The target polymer composition was obtained by the same method as in Example 6 except that 3.3 g of spherical fused silica (average particle size 10 μm, linear expansion coefficient 5×10 ^-7 /°C) was used instead of 5.8 g of modified ZWP as a negative thermal expansion filler to prepare a 30 volume % paste. The cross section of the obtained polymer composition was observed using a scanning electron microscope, and it was confirmed that the spherical fused silica particles were uniformly dispersed in the polymer composition.

<Evaluation of the linear expansion coefficient of the composition>

The polymer composition obtained in the embodiment and reference example was cut into a 5mm×5mm×10mm rectangular parallelepiped as a measurement sample. The measurement sample was measured using a thermomechanical analyzer (TMA; manufactured by NETZSCH, 4000SE) at a heating rate of 1°C/min to measure the linear expansion coefficient from 30°C to 120°C. The results are shown in Table 3.

As shown in Table 3, it can be seen that the polymer composition of each embodiment using the modified ZWP of the present invention as a negative thermal expansion filler is a material with a low linear expansion coefficient and is not easily deformed by heat.

(Implementation Example 7)

0.75 g of a titanium ester coupling agent (isopropyl triisostearyl titanium ester) was added to 50 g of the modified ZWP (modified ZWP (1)) obtained in Example 1, and the mixture was pulverized and mixed using an air flow mill (A-O jet mill manufactured by Seishin Corporation) to prepare a powder mixture. The mixture was heated at 110°C for 4 hours in an atmospheric environment to obtain a modified ZWP (2) sample in which the surface of the modified ZWP particles was coated with a titanium ester coupling agent. The modified ZWP (2) sample was a crushed particle. The conditions of the air flow mill were set as powder feed rate: 3 g/min, thrust pressure: 0.6 MPa, and jet pressure: 0.6 MPa.

In addition, the amount of P ions eluted from the obtained modified ZWP (2) sample was measured in the same manner as in Examples 1 to 3. The results are shown in Table 4.

(Implementation Example 8)

0.75 g of silane coupling agent (3-glycidyloxypropyltrimethoxysilane) was added to 50 g of the modified ZWP (modified ZWP (1)) obtained in Example 1, and the mixture was pulverized and mixed using an air flow mill (A-O jet mill manufactured by Seishin Corporation) to prepare a powder mixture. The mixture was heated at 110°C for 4 hours in an atmospheric environment to obtain a modified ZWP (2) sample in which the surface of the modified ZWP particles was coated with a silane coupling agent. The modified ZWP (2) sample was a crushed particle. The conditions of the air flow mill were set as powder feed rate: 3 g/min, thrust pressure: 0.6 MPa, and jet pressure: 0.6 MPa.

In addition, the amount of P ions eluted from the obtained modified ZWP (2) sample was measured in the same manner as in Examples 1 to 3. The results are shown in Table 4.

As shown in Table 4, it can be seen that in the modified ZWP (2) that was further treated with a coupling agent, the elution of ions from the particles was further suppressed.

(Example 9 and Example 10)

The modified ZWP (2) samples obtained in Examples 7 and 8 were used as negative thermal expansion fillers to prepare polymer compositions. Specifically, 5.8 g of negative thermal expansion fillers and 4.2 g of epoxy resin (jER807 manufactured by Mitsubishi Chemical, epoxy equivalent 160-175) as a polymer compound were mixed at a rotation speed of 2000 rpm using a vacuum mixer (Thinky Defoaming Mixer ARV-310) to prepare a 30 volume % paste.

Next, 100 μL of a curing agent (Curezol manufactured by Shikoku Chemical) was added to the paste, mixed at a rotation speed of 1500 rpm using the vacuum mixer, and cured at 150°C for 1 hour to obtain the target polymer composition. The cross-section of the obtained polymer composition was observed using a scanning electron microscope. As a result, it was confirmed that the modified ZWP (2) sample as a negative thermal expansion filler was uniformly dispersed in the polymer composition in any embodiment.

<Evaluation of the linear expansion coefficient of the composition>

The polymer composition obtained in Example 9 and Example 10 was cut into a 5 mm × 5 mm × 10 mm rectangular parallelepiped as a measurement sample. The measurement sample was measured using a thermomechanical analyzer (TMA; manufactured by NETZSCH, 4000SE) at a heating rate of 1°C/min to measure the linear expansion coefficient from 30°C to 120°C. The results are shown in Table 5.

As shown in Table 5, it can be seen that the polymer composition of each embodiment using the modified ZWP (2) of the present invention as a negative thermal expansion filler is a material with a low linear expansion coefficient and is not easily deformed by heat.

Claims (10)

A modified zirconium tungstate phosphate, wherein the surface of the zirconium tungstate phosphate particles is coated with an inorganic compound, wherein the inorganic compound contains one or more elements (M) selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe and Zr, wherein the coating amount of the inorganic compound relative to the zirconium tungstate phosphate particles is 0.1 mass% to 10 mass% based on the element (M) contained in the inorganic compound, and when 1 g of the modified zirconium tungstate phosphate is heated for 1 hour using 70 mL of water at 85°C, then cooled to 25°C and left to stand for 24 hours, the amount of phosphorus ions dissolved in 1 g of the modified zirconium tungstate phosphate is less than 100 μg. The modified zirconium tungstate phosphate as described in claim 1, wherein the BET specific surface area of the zirconium tungstate phosphate particles is 0.1 m ² /g to 50 m ² /g. The modified zirconium tungstate phosphate as described in claim 1 or claim 2, wherein the average particle size of the zirconium tungstate phosphate particles is 0.02μm~50μm. The modified zirconium tungstate phosphate as described in claim 1 or claim 2, wherein the zirconium tungstate phosphate particles further contain accessory element. The modified zirconium tungstate phosphate as described in claim 1 or claim 2, wherein the inorganic compound is an oxide and/or hydroxide containing the element (M). The modified zirconium tungstate phosphate as described in claim 5, wherein the element (M) is Zn. The modified zirconium tungstate phosphate as described in claim 1 or claim 2, wherein the surface of the zirconium tungstate phosphate particles is further coated with a coupling agent. The modified zirconium tungstate phosphate as described in claim 7, wherein the coupling agent is a silane-based coupling agent or a titanium ester-based coupling agent. A negative thermal expansion filler comprising modified zirconium tungstate phosphate as described in any one of claims 1 to 8. A polymer composition comprising a negative thermal expansion filler and a polymer compound as described in claim 9.