Negative thermal expansion material, method for producing same, negative thermal expansion material composition, and composite material

Abstract

A purpose of the present invention is to provide a negative thermal expansion material including a zinc-phosphorus composite oxide having excellent negative thermal expansion properties.　The negative thermal expansion material includes a composite of a zinc-phosphorus composite oxide and a calcium pyrophosphate salt, and is characterized in that the zinc-phosphorus composite oxide includes a zinc-phosphorus composite oxide represented by a general formula (1) (ZnxMyPz1Ot1), and the calcium pyrophosphate salt includes a calcium pyrophosphate salt represented by a general formula (2) (Caw1Aw2Pz2Ot2).

Description

Negative thermal expansion material, method for manufacturing the same, negative thermal expansion material composition, and composite material

[0001] This invention relates to a negative thermal expansion material that contracts in response to temperature rise, a method for producing the same, a negative thermal expansion material composition containing the negative thermal expansion material, and a composite material.

[0002] Many materials increase in length or volume due to thermal expansion when their temperature rises. In contrast, there are also materials that exhibit negative thermal expansion, where their volume decreases when heated (hereinafter sometimes referred to as "negative thermal expansion materials").

[0003] It is known that materials exhibiting negative thermal expansion can be used in conjunction with other materials to suppress changes in the thermal expansion of the material due to temperature changes.

[0004] Examples of materials exhibiting negative thermal expansion include β-eucryptite, zirconium tungstate (ZrW2O8), zirconium tungstate phosphate (Zr2WO4(PO4)2), and Zn x CD 1-x (CN)2, manganese nitride, bismuth nickel iron oxide, etc. are known examples.

[0005] The linear thermal expansion coefficient of zirconium tungstate is -3.4 to -3.0 ppm / °C in the temperature range of 0 to 400°C, and it is known to have high negative thermal expansion. By using zirconium tungstate in combination with a material that exhibits positive thermal expansion (hereinafter sometimes referred to as "positive thermal expansion material"), it is possible to manufacture a material with low thermal expansion (see Patent Documents 1-2, etc.). It has also been proposed to use a negative thermal expansion material in combination with a polymer compound such as a resin, which is a positive thermal expansion material (see Patent Document 3, etc.).

[0006] Furthermore, Patent Document 3 proposes a zinc-phosphorus composite oxide of Zn2P2O7 and a negative thermal expansion material obtained by substituting a portion of the Zn in the zinc-phosphorus composite oxide with at least one element selected from Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, La, Ta, W, and Bi, or by substituting a portion of the P with at least one element selected from Al, Si, V, Ge, and Sn.

[0007] Japanese Patent Application Laid-Open No. 2005-35840, Japanese Patent Application Laid-Open No. 2015-10006, Pamphlet of International Publication No. 2022 / 114004

[0008] The zinc phosphate composite oxide in which a part of Zn2P2O7 and zinc in Patent Document 3 are replaced with other metals has a smaller linear expansion coefficient than zirconium tungstate phosphate, can be produced from a more inexpensive raw material system, and can be industrially advantageously produced, and has advantages such as excellent water resistance.

[0009] In the search for a material having excellent negative thermal expansibility, the inventors have found that a composite of a specific zinc phosphate composite oxide and a specific calcium pyrophosphate has excellent negative thermal expansibility as compared with those obtained by using, respectively, alone the zinc phosphate composite oxide in which a part of Zn2P2O7 and zinc are replaced with other metals, and have completed the present invention.

[0010] Accordingly, an object of the present invention is to provide a negative thermal expansion material containing a zinc phosphate composite oxide having excellent negative thermal expansibility.

[0011] That is, the present invention (1) is a composite of a zinc phosphate composite oxide and a calcium pyrophosphate salt, and the zinc phosphate composite oxide is represented by the following general formula (1): Zn x M y P z1 O t1 (1) (In the formula, M represents one or more elements selected from Mg, Ca, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. x represents 0.0 < x ≤ 2.0, y represents 0.0 ≤ y < 2.0, z1 represents 1.7 ≤ z1 ≤ 2.3, and t1 represents 6.00 ≤ t1 ≤ 8.00. However, 1.7 ≤ x + y ≤ 2.3.) and includes a zinc phosphate composite oxide represented by the formula, and the calcium pyrophosphate salt is represented by the following general formula (2): Ca w１ A ｗ２ P z2 O t2 (2) The present invention provides a negative thermal expansion material characterized by containing a calcium pyrophosphate salt represented by the formula: (wherein A represents one or more metallic elements selected from Mg, Cu, Fe, Zn, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w1 represents 1.7 ≤ w1 ≤ 2.3, w2 represents 0 ≤ w2 ≤ 1.0, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.00 ≤ t2 ≤ 8.00. However, 1.7 ≤ w1 + w2 ≤ 2.3.)

[0012] Furthermore, the present invention (2) provides a negative thermal expansion material of (1), characterized in that the composite has a core-shell structure, the core contains a zinc-phosphorus composite oxide represented by the general formula (1), and the shell contains a calcium pyrophosphate salt represented by the general formula (2).

[0013] Furthermore, the present invention (3) provides a negative thermal expansion material according to (1) or (2), characterized in that the zinc-phosphorus composite oxide represented by the general formula (1) is Zn2P2O7.

[0014] Furthermore, the present invention (4) provides any of the negative thermal expansion materials according to (1) to (3), characterized in that the calcium pyrophosphate salt represented by the general formula (2) is Ca2P2O7.

[0015] Furthermore, in the present invention (5), the coefficient of thermal expansion between 100 and 150°C is -25 × 10 -6 The present invention provides a negative thermal expansion material characterized by having a temperature of 1 / K or less, according to any of (1) to (4).

[0016] Furthermore, the present invention (6) has a thermal expansion coefficient between 100 and 150°C of -80 × 10 -6 The present invention provides a negative thermal expansion material characterized by having a temperature of / K or less, as described in any of (1) to (5).

[0017] Furthermore, the present invention (7) provides any of the negative thermal expansion materials (1) to (6) characterized in that when X-ray diffraction measurements are performed using Cu-Kα as an X-ray source, the peak top of the main peak is observed to be between 29 and 30°, with 2θ = 29.66 to 29.73°.

[0018] Furthermore, the present invention (8) provides any of the negative thermal expansion materials (1) to (7) characterized in that the average particle size is 0.1 to 100 μm.

[0019] Furthermore, the present invention (9) relates to a BET specific surface area of ​​0.05 to 50 m². 2 The present invention provides a negative thermal expansion material characterized by being / g, which is any of (1) to (8).

[0020] Furthermore, the present invention (10) is based on the following general formula (1) Zn x M y P z1 O t1 (1) Zinc phosphorus composite oxide particles represented by the following general formula (2) Ca ｗ１ A w２ P z2 O t2 (2) (In the formula, A represents one or more metallic elements selected from Mg, Cu, Fe, Zn, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w1 represents 1.7 ≤ w1 ≤ 2.3, w2 represents 0 ≤ w2 ≤ 1.0, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.00 ≤ t2 ≤ 8.00, where 1.7 ≤ w1 + w2 ≤ 2.3.) The present invention provides a method for producing a negative thermal expansion material, characterized by calcining a mixture containing a Ca source, a P source, and an A source added as necessary, which are raw materials for producing a calcium pyrophosphate salt represented by [formula].

[0021] Furthermore, the present invention (11) provides a method for producing a negative thermal expansion material according to (10), characterized in that the zinc-phosphorus composite oxide represented by the general formula (1) is obtained by calcining a reaction precursor containing at least zinc pyrophosphate.

[0022] Furthermore, the present invention (12) comprises any of the negative thermal expansion materials (1) to (9) and the following general formula (3) Cu ｗ３ M' ｗ４ P ｚ３ O ｔ３ (3) The present invention provides a negative thermal expansion material composition characterized by containing a copper pyrophosphate salt represented by the formula (wherein M' represents a metallic element with an atomic number of 11 or greater other than Cu and V; w3 represents 1.7 ≤ w3 ≤ 2.3, w4 represents 0 ≤ w4 ≤ 1.0, z3 represents 1.7 ≤ z3 ≤ 2.3, and t3 represents 6.00 ≤ t3 ≤ 8.00, provided that 1.7 ≤ w3 + w4 ≤ 2.3).

[0023] Furthermore, the present invention (13) relates to a case where the copper pyrophosphate represented by the general formula (3) is Cu ２ P ２ O ７ The present invention provides the negative thermal expansion material composition described in (12), characterized in that it is such.

[0024] Furthermore, the present invention (14) provides a composite material characterized by comprising any of the negative thermal expansion materials (1) to (9) or the negative thermal expansion material composition of (12), and a positive thermal expansion material.

[0025] Furthermore, the present invention (15) provides a composite material of (14) characterized in that the positive thermal expansion material is at least one selected from metal, alloy, glass, ceramics, rubber, and resin.

[0026] According to the present invention, it is possible to provide a negative thermal expansion material containing a zinc-phosphorus composite oxide that exhibits excellent negative thermal expansion properties.

[0027] X-ray diffraction pattern of the negative thermal expansion material sample of Example 1. X-ray diffraction pattern of the negative thermal expansion material sample of Example 2. X-ray diffraction pattern of the negative thermal expansion material sample of Comparative Example 1. Relationship diagram between thermal shrinkage rate (%) and temperature (°C) of ceramic molded bodies using the negative thermal expansion material samples of Examples 1-2 and Comparative Example 1. Relationship diagram between thermal shrinkage rate (%) and temperature (°C) of compacted molded bodies of the negative thermal expansion material composition sample of Example 3 and the negative thermal expansion material sample of Example 2.

[0028] The present invention will be described below based on its preferred embodiments. The negative thermal expansion material of the present invention is a composite of a zinc-phosphorus composite oxide and a calcium pyrophosphate salt, wherein the zinc-phosphorus composite oxide is of the following general formula (1): Zn x M y P z1 O t1 (1) A zinc phosphorus composite oxide represented by the formula (wherein M represents one or more elements selected from Mg, Ca, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. x represents 0.0 < x ≤ 2.0, y represents 0.0 ≤ y < 2.0, z1 represents 1.7 ≤ z1 ≤ 2.3, and t1 represents 6.0 ≤ t1 ≤ 8.0, where 1.7 ≤ x + y ≤ 2.3) is included. The calcium pyrophosphate salt is of the following general formula (2): Ca w１ A ｗ２ P z2 O t2 (2) The product is characterized by containing a calcium pyrophosphate salt represented by the formula: (wherein A represents one or more metallic elements selected from Mg, Cu, Fe, Zn, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w1 represents 1.7 ≤ w1 ≤ 2.3, w2 represents 0 ≤ w2 ≤ 1.0, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.00 ≤ t2 ≤ 8.00. However, 1.7 ≤ w1 + w2 ≤ 2.3.)

[0029] The negative thermal expansion material of the present invention is a composite of a zinc-phosphorus composite oxide and a calcium pyrophosphate salt. The negative thermal expansion material of the present invention is a composite of a zinc-phosphorus composite oxide mainly containing a zinc-phosphorus composite oxide represented by general formula (1) and a calcium pyrophosphate salt mainly containing a calcium pyrophosphate salt represented by general formula (2).

[0030] In general formula (1), M is an element that may be included as needed to further adjust the negative thermal expansion properties. M represents one or more elements selected from Mg, Ca, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. In the present invention, M is preferably Mg, Mn, or Cu, as these elements exhibit particularly excellent negative thermal expansion properties.

[0031] In general formula (1), x is 0.0 < x ≤ 2.0. From the viewpoint of excellent negative thermal expansion characteristics, x is preferably 1.5 ≤ x ≤ 2.0, and particularly preferably 1.6 ≤ x ≤ 2.0.

[0032] In general formula (1), y is 0.0 ≤ y < 2.0. From the viewpoint of excellent negative thermal expansion characteristics, y is preferably 0 ≤ y ≤ 1.9, and particularly preferably 0 ≤ y ≤ 1.8.

[0033] In general formula (1), z1 is 1.7 ≤ z1 ≤ 2.3. From the viewpoint of excellent negative thermal expansion characteristics, z1 is preferably 1.8 ≤ z1 ≤ 2.2, and particularly preferably 1.9 ≤ z1 ≤ 2.1.

[0034] In general formula (1), t1 is 6.0 ≤ t1 ≤ 8.0. From the viewpoint of excellent negative thermal expansion characteristics, t1 is preferably 6.5 ≤ t1 ≤ 7.5, and particularly preferably 6.2 ≤ t1 ≤ 7.2.

[0035] However, in general formula (1), x + y is 1.7 ≤ x + y ≤ 2.3. Preferably, x + y is 1.8 ≤ x + y ≤ 2.2, as this provides better negative thermal expansion characteristics.

[0036] In general formula (2), A is an element that may be included as needed to further adjust the negative thermal expansion properties. A represents one or more metallic elements selected from Mg, Cu, Fe, Zn, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho, of which Cu and Zn are particularly preferred from the viewpoint of having particularly excellent negative thermal expansion properties.

[0037] In general formula (2), w1 is 1.7 ≤ w1 ≤ 2.3. From the viewpoint of also having excellent negative thermal expansion characteristics, w1 is 1.8 ≤ w1 ≤ 2.2, and particularly preferably 1.9 ≤ w1 ≤ 2.1.

[0038] In general formula (2), w² is 0 ≤ w² ≤ 1.0. From the viewpoint of also having excellent negative thermal expansion characteristics, w² is 0 ≤ w² ≤ 0.9, and particularly preferably 0 ≤ w² ≤ 0.8.

[0039] In general formula (2), z² is 1.7 ≤ z² ≤ 2.3. From the viewpoint of excellent negative thermal expansion characteristics, z² is preferably 1.8 ≤ z² ≤ 2.2, and particularly preferably 1.9 ≤ z² ≤ 2.1.

[0040] In general formula (2), t2 is 6.0 ≤ t2 ≤ 8.0. From the viewpoint of also having excellent negative thermal expansion characteristics, t2 is preferably 6.5 ≤ t2 ≤ 7.5, and particularly preferably 6.2 ≤ t2 ≤ 7.2.

[0041] However, in general formula (2), w1 + w2 is 1.7 ≤ w1 + w2 ≤ 2.3. w1 + w2 is preferably 1.8 ≤ w1 + w2 ≤ 2.2, as this provides better negative thermal expansion characteristics.

[0042] The calcium pyrophosphate salt represented by general formula (2) has a lower phase transition temperature than the zinc-phosphorus composite oxide represented by general formula (1). In the negative thermal expansion material of the present invention, by compounding the zinc-phosphorus composite oxide represented by general formula (1) with the calcium pyrophosphate salt represented by general formula (2), which has an even lower phase transition temperature, the material exhibits excellent negative thermal expansion properties.

[0043] Examples of composite forms related to the negative thermal expansion material of the present invention include: a) a simple mixture of zinc phosphorus composite oxide particles represented by general formula (1) and calcium pyrophosphate salt particles represented by general formula (2); b) a composite having a core-shell structure, comprising a core containing zinc phosphorus composite oxide represented by general formula (1) and a shell containing calcium pyrophosphate salt represented by general formula (2) covering all or part of the surface of the core; c) a composite having a core-shell structure, comprising a core containing calcium pyrophosphate salt represented by general formula (2) and a shell containing zinc phosphorus composite oxide represented by general formula (1) covering all or part of the surface of the core; and d) a composite in which particles containing zinc phosphorus composite oxide represented by general formula (1) and particles containing calcium pyrophosphate salt represented by general formula (2) are bonded together.

[0044] In embodiment b), the core is formed of a zinc-phosphorus composite oxide mainly comprising a zinc-phosphorus composite oxide represented by general formula (1). That is, in embodiment b), the core may be formed of only the zinc-phosphorus composite oxide represented by general formula (1), or it may be formed of a zinc-phosphorus composite oxide represented by general formula (1) containing Ca, A elements and / or other impurity elements derived from the calcium pyrophosphate salt represented by general formula (2) due to the method for producing the negative thermal expansion material of the present invention, in a range that does not produce the effects of the present invention, for example, in a range of 5% by mass or less relative to the zinc-phosphorus composite oxide represented by general formula (1). Also, in embodiment b), the shell is formed of a calcium pyrophosphate salt mainly comprising a calcium pyrophosphate salt represented by general formula (2). In other words, in form b), the shell may be formed solely of the calcium pyrophosphate salt represented by general formula (2), or it may be formed of the calcium pyrophosphate salt represented by general formula (2) containing Zn, M and / or other impurity elements derived from the zinc-phosphorus composite oxide represented by general formula (1) as a result of the method for producing the negative thermal expansion material of the present invention, in a range that does not produce the effects of the present invention, for example, in a range of 5% by mass or less relative to the calcium pyrophosphate salt represented by general formula (2).

[0045] In embodiment c), the core is formed mainly of a calcium pyrophosphate salt containing the calcium pyrophosphate salt represented by general formula (2). That is, in embodiment c), the core may be formed only of the calcium pyrophosphate salt represented by general formula (2), or it may be formed of a calcium pyrophosphate salt represented by general formula (2) containing Zn element, M element and / or other impurity elements derived from the zinc phosphorus composite oxide represented by general formula (1) as a result of the method for producing the negative thermal expansion material of the present invention, in a range that does not produce the effects of the present invention, for example, in a range of 5% by mass or less relative to the calcium pyrophosphate salt represented by general formula (2). Also, in embodiment c), the shell is formed mainly of a zinc phosphorus composite oxide containing the zinc phosphorus composite oxide represented by general formula (1). In other words, in form c), the shell may be formed solely of a zinc-phosphorus composite oxide represented by general formula (1), or it may be formed of a zinc-phosphorus composite oxide represented by general formula (1) containing Ca, A elements and / or other impurity elements derived from a calcium pyrophosphate salt represented by general formula (2) as a result of the method for producing a negative thermal expansion material of the present invention, in a range of 5% by mass or less relative to the zinc-phosphorus composite oxide represented by general formula (1), in a range that does not produce the effects of the present invention.

[0046] d) includes a composite of core particles consisting only of zinc-phosphorus composite oxide represented by general formula (1), or core particles consisting of zinc-phosphorus composite oxide represented by general formula (1) containing Ca, A elements and / or impurity elements derived from the calcium pyrophosphate salt represented by general formula (2) due to the manufacturing method of the negative thermal expansion material of the present invention, in a range of 5% by mass or less relative to the zinc-phosphorus composite oxide represented by general formula (1), and coated particles consisting only of calcium pyrophosphate salt represented by general formula (2) that are attached to cover part or all of the surface of the core particles, or attached particles consisting of calcium pyrophosphate salt represented by general formula (2) containing Zn elements, M elements and / or other impurity elements derived from the zinc-phosphorus composite oxide represented by general formula (1) due to the manufacturing method of the negative thermal expansion material of the present invention, in a range of 5% by mass or less relative to the calcium pyrophosphate salt represented by general formula (2). Furthermore, d) includes a composite of core particles consisting solely of a calcium pyrophosphate salt represented by general formula (2), or core particles consisting of a calcium pyrophosphate salt represented by general formula (2) containing Zn, M, and / or other impurity elements derived from the zinc phosphorus composite oxide represented by general formula (1) due to the manufacturing method of the negative thermal expansion material of the present invention, in a range that does not exhibit the effects of the present invention, for example, in a range of 5% by mass or less relative to the calcium pyrophosphate salt represented by general formula (2), and coated particles consisting solely of the zinc phosphorus composite oxide represented by general formula (1) that are attached to cover part or all of the surface of the core particles, or attached particles consisting of the zinc phosphorus composite oxide represented by general formula (1) containing Ca, A, and / or other impurity elements derived from the calcium pyrophosphate salt represented by general formula (2) due to the manufacturing method of the negative thermal expansion material of the present invention, in a range that does not exhibit the effects of the present invention, for example, in a range of 5% by mass or less relative to the zinc phosphorus composite oxide represented by general formula (1).

[0047] Of the above embodiments, b) a composite having a core-shell structure comprising a core containing a zinc-phosphorus composite oxide represented by general formula (1) and a shell containing a calcium pyrophosphate salt represented by general formula (2) covering all or part of the surface of the core is preferred from the viewpoint of having excellent negative thermal expansion properties.

[0048] In the negative thermal expansion material of the present invention, it is preferable, particularly from the viewpoint of excellent negative thermal expansion properties, that the zinc-phosphorus composite oxide represented by general formula (1) is Zn2P2O7 and the calcium pyrophosphate salt represented by general formula (2) is Ca2P2O7.

[0049] The thermal expansion coefficient of the negative thermal expansion material of the present invention between 100 and 150°C is -25 × 10 -6 / K or less, preferably -30 x 10 -6 It is less than or equal to / K, and there are no particular restrictions on the lower limit, but it is approximately -170 × 10 -6 / K or higher, preferably -150 x 10 -6 The coefficient of thermal expansion is 1 / K or higher. In the negative thermal expansion material of the present invention, when combined with a positive thermal expansion material, the coefficient of thermal expansion between 100 and 150°C is particularly preferably -30 × 10, in that the coefficient of thermal expansion makes it easier to cancel out the positive expansion. -6 ~-150 x 10 -6 / K. Furthermore, the negative thermal expansion material of the present invention is a zinc-phosphorus composite oxide represented by general formula (1) which is Zn ２ P ２ O ７ The coefficient of thermal expansion between 100 and 150°C in this case is Zn ２ P ２ O ７ As long as it is smaller than when used alone, it is not limited, but -80 × 10 -6 / K or less, preferably -82 x 10 -6 / K or less, and there are no particular restrictions on the lower limit, but it is approximately -170 × 10 -6 / K or higher, preferably -150 x 10 -6 It is above / K. Furthermore, when combined with a positive thermal expansion material, the coefficient of thermal expansion is more likely to cancel out the positive expansion, so the coefficient of thermal expansion between 100 and 150°C is particularly preferably -82 × 10 -6 ~-150 x 10 -6 It is K.

[0050] In the present invention, the degree of volume reduction due to temperature rise between 100 and 150°C is determined by the following procedure.

[0051] First, 0.05 g of propylene carbonate is added to 1.00 g of the sample and ground and mixed in a mortar for 3 minutes. Then, 0.15 g is weighed out and the entire amount is filled into a φ6 mm mold. Next, a powder molded body is produced by molding with a pressure of 0.5 t using a hand press. The obtained powder molded body is heated in an electric furnace to 700°C in 3 hours and held for 4 hours to produce a ceramic molded body. Next, the thermal expansion coefficient of the produced ceramic molded body is measured using a thermomechanical measuring device (NETZSCH JAPAN TMA4000SE). The measurement conditions are a nitrogen atmosphere, a load of 10 g, and a temperature range of 50°C to 225°C, and measurements are taken twice repeatedly. The thermal expansion coefficient between 100°C and 150°C in the second repeated measurement is taken as the thermal expansion coefficient of the negative thermal expansion material.

[0052] The content ratio of the zinc-phosphorus composite oxide represented by general formula (1) and the calcium pyrophosphate salt represented by general formula (2) in the composite of the negative thermal expansion material according to the present invention is preferably 0.002 to 0.50, and particularly preferably 0.005 to 0.30, for the molar ratio of the calcium pyrophosphate salt represented by general formula (2) to the zinc-phosphorus composite oxide represented by general formula (1) (calcium pyrophosphate salt represented by general formula (2) / zinc-phosphorus composite oxide represented by general formula (1)). Having a molar ratio of calcium pyrophosphate salt represented by general formula (2) / zinc-phosphorus composite oxide represented by general formula (1) within the above range enhances effects such as excellent negative thermal expansion.

[0053] In the negative thermal expansion material of the present invention, when X-ray diffraction measurements are performed using Cu-Kα as the X-ray source, it is preferable that the peak top of the main peak is observed at 2θ = 29.66 to 29.73° when 2θ is between 29 and 30°. Conventional negative thermal expansion materials made of zinc-phosphorus composite oxides in which a portion of the zinc in Zn2P2O7 is replaced with other metal elements show that when X-ray diffraction measurements are performed using Cu-Kα as the X-ray source, the peak top of the main peak is observed at around 2θ = 29.65°, which is smaller than 29.66°, when 2θ is between 29 and 30°. In contrast, in the negative thermal expansion material according to the present invention, the peak top of the main peak is observed at 2θ = 29.66 to 29.73° when 2θ is between 29 and 30°.

[0054] The BET specific surface area of ​​the negative thermal expansion material of the present invention is not particularly limited, but is preferably 0.05 to 50 m². 2 / g, particularly preferably 0.10 to 10m 2 / g, more preferably 0.20 to 8m 2 The value is / g. The fact that the BET specific surface area of ​​the negative thermal expansion material falls within the above range makes it easier to handle when using the negative thermal expansion material as a filler for resins, glass, etc. In this invention, the BET specific surface area of ​​the negative thermal expansion material is a value measured using the BET single-point method with a fully automatic specific surface area measuring device, Macorb (manufactured by Mountec).

[0055] The average particle diameter of the negative thermal expansion material of the present invention is not particularly limited, but is the average particle diameter determined by scanning electron microscopy, preferably 0.1 to 100 μm, particularly preferably 0.2 to 80 μm, and even more preferably 0.2 to 20 μm. Having the average particle diameter of the negative thermal expansion material within the above range makes it easier to handle when using the negative thermal expansion material as a filler for resins, glass, etc. In this invention, the average particle diameter of the negative thermal expansion material was determined by the arithmetic mean of the particle diameters of 50 particles arbitrarily extracted at a magnification of 1000x using scanning electron microscopy. At this time, the particle diameter of each particle refers to the largest length (maximum length) of the line segment that crosses the two-dimensional projection image of the particle.

[0056] The particle shape of the negative thermal expansion material of the present invention is not particularly limited and may be spherical, granular, plate-like, flaky, whisker-like, rod-like, filamentous, or crushed.

[0057] In the negative thermal expansion material of the present invention, the thermal expansion coefficient between 80 and 200°C is -20 × 10 -6 / K or less, preferably -23 × 10 -6 It is less than or equal to / K, and there are no particular restrictions on the lower limit, but it is approximately -100 × 10 -6 / K or higher, preferably -80 x 10 -6 The coefficient of thermal expansion is 1 / K or higher. In the negative thermal expansion material of the present invention, when combined with a positive thermal expansion material, the coefficient of thermal expansion between 80 and 200°C is particularly preferably -23 × 10⁻¹⁰, as this makes it easier to cancel out the positive expansion. -6 ~-80 x 10 -6It is K.

[0058] In this invention, the thermal expansion coefficient between 80 and 200°C is determined by the following procedure. First, 0.05 g of propylene carbonate is added to 1.00 g of the sample and ground and mixed in a mortar for 3 minutes. Then, 0.15 g is weighed out and the entire amount is filled into a φ6 mm mold. Next, a powder molded body is produced by molding with a pressure of 0.5 t using a hand press. The obtained powder molded body is heated to 700°C in an electric furnace for 3 hours and held for 4 hours to produce a ceramic molded body. Next, the thermal expansion coefficient of the produced ceramic molded body is measured using a thermomechanical measuring device (for example, TMA4000SE manufactured by NETZSCH JAPAN). The measurement conditions are a nitrogen atmosphere, a load of 10 g, and a temperature range of 50°C to 225°C. Measurements are taken twice repeatedly in the temperature range of 50°C to 225°C, and the thermal expansion coefficient between 80 and 200°C from the second measurement is taken as the thermal expansion coefficient of the negative thermal expansion material.

[0059] Hereinafter, a preferred method for producing a negative thermal expansion material in the present invention will be described, specifically a method for producing a composite having the aforementioned b) core-shell structure, comprising a core containing a zinc-phosphorus composite oxide represented by general formula (1), and a shell containing a calcium pyrophosphate salt represented by general formula (2) that covers all or part of the surface of the core. The method for producing a negative thermal expansion material in the present invention is as follows: General formula (1) Zn x M y P z1 O t1 (1) A zinc phosphorus composite oxide represented by the following general formula (2): Ca w１ A ｗ２ P z2 O t2 (2) (In the formula, A represents one or more metallic elements selected from Mg, Cu, Fe, Zn, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w1 represents 1.7 ≤ w1 ≤ 2.3, w2 represents 0 ≤ w2 ≤ 1.0, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.00 ≤ t2 ≤ 8.00, where 1.7 ≤ w1 + w2 ≤ 2.3.) The method is characterized by calcining a mixture containing a Ca source, a P source, and an A source added as needed, which are necessary for producing the calcium pyrophosphate salt represented by [formula].

[0060] In other words, the negative thermal expansion material of the present invention is manufactured by a manufacturing method comprising the following steps A and B. Step A: A step of preparing a raw material mixture containing a zinc-phosphorus complex oxide represented by general formula (1) and a Ca source, a P source, and an A source added as needed for the production of a calcium pyrophosphate salt represented by general formula (2). Step B: A step of calcining the raw material mixture to obtain a negative thermal expansion material.

[0061] Regarding the various physical properties of the zinc-phosphorus composite oxide represented by the general formula (1) in step A, from the viewpoint of facilitating handling when using the negative thermal expansion material as a filler for resins, glass, etc., the average particle size determined by scanning electron microscopy is preferably 0.1 to 100 μm, more preferably 0.2 to 80 μm.

[0062] The BET specific surface area of ​​zinc-phosphorus composite oxides represented by general formula (1) is 0.05 to 50 m². 2 / g, preferably 0.1 to 10m 2 Having a value of / g is preferable from the viewpoint of facilitating handling when using negative thermal expansion materials as fillers for resins, glass, etc.

[0063] In the method for producing a negative thermal expansion material of the present invention, the zinc-phosphorus composite oxide represented by general formula (1) in step A is preferably obtained by the following steps from the viewpoint of being able to produce a negative thermal expansion material industrially advantageously. Step 1: A step of preparing a reaction precursor containing Zn, P and M element to be added as needed. Step 2: A step of calcining the reaction precursor to obtain a zinc-phosphorus composite oxide represented by general formula (1).

[0064] The first step is to prepare a reaction precursor containing Zn, P, and M element, which may be added as needed.

[0065] The reaction precursor can be produced by mixing a Zn compound, a phosphorus compound, and an M-element-containing compound, which may be added as needed.

[0066] Zn compounds are compounds containing a Zn atom. Examples of Zn compounds include zinc salts of organic carboxylic acids such as zinc gluconate, zinc citrate, zinc acetate, and zinc lactate, zinc salts of mineral acids, zinc oxides, zinc hydroxides, zinc phosphates, and zinc pyrophosphates.

[0067] A phosphorus compound is a compound containing a phosphorus atom. Phosphoric acid is preferred as the phosphorus compound. Furthermore, compounds containing both a Zn source and a P source, such as zinc phosphate and zinc pyrophosphate, can also serve as both Zn and phosphorus compounds.

[0068] The M-element-containing compounds added as needed are compounds containing the M element. Examples of M-element-containing compounds include M carbonates, M oxides, M hydroxides, M halides, and M carboxylates. Examples of M carboxylates include gluconates, citrates, oxalates, acetates, and lactates.

[0069] The reaction precursor in the first step preferably contains at least zinc pyrophosphate, as this makes it easier to obtain a reaction precursor in which each raw material is uniformly dispersed in an inexpensive and simple operation, and also makes it easier to obtain a single-phase zinc-phosphorus complex oxide represented by general formula (1) by X-ray diffraction by calcination of the obtained reaction precursor in the second step described later. The zinc pyrophosphate may be hydrated or anhydrous.

[0070] Furthermore, when producing Zn2P2O7 in which y in general formula (1) is 0, the reaction precursor containing at least zinc pyrophosphate contains only zinc pyrophosphate. On the other hand, when producing a zinc-phosphorus complex oxide represented by general formula (1) that contains element M, the reaction precursor contains zinc pyrophosphate, a phosphorus compound, and an element M compound.

[0071] In the first step, it is preferable to adjust the content of the zinc compound, phosphorus compound, and M-containing compound as appropriate so that the molar ratios of Zn, P, and M in the reaction precursor are equal to the composition of the zinc-phosphorus complex oxide represented by general formula (1). When using zinc phosphate or zinc pyrophosphate as the zinc compound, it is preferable to prepare the reaction precursor while also considering the amount of phosphorus atoms in the zinc compound.

[0072] In the first step, a mixing treatment of zinc compounds, phosphorus compounds, and M-element-containing compounds may be performed as needed. This mixing treatment can be carried out wet or dry.

[0073] When performing a wet mixing process, the reaction precursor can be obtained by drying the entire volume to remove the solvent.

[0074] Furthermore, in the first step, the composition of the reaction precursor obtained by removing the completely dried solvent after the wet mixing treatment is approximately the same as the atomic molar ratio of Zn, P, and M at the time of each raw material charge and the composition of the zinc-phosphorus complex oxide represented by general formula (1).

[0075] The second step involves calcining the reaction precursor prepared in the first step to obtain a zinc-phosphorus complex oxide represented by general formula (1).

[0076] The firing temperature in the second step is preferably 300 to 900°C, more preferably 500 to 800°C. On the other hand, if the firing temperature in the second step is below the above range, the formation of the zinc-phosphorus composite oxide represented by general formula (1) tends to be insufficient, and if it exceeds the above range, it tends to become a solidified sintered body. The firing time in the second step is not particularly limited, and firing should be carried out for a sufficient time until the zinc-phosphorus composite oxide represented by general formula (1) is formed.

[0077] The formation of the zinc-phosphorus complex oxide represented by general formula (1) can be confirmed, for example, by checking whether a single-phase zinc-phosphorus complex oxide represented by general formula (1) is obtained by X-ray diffraction analysis.

[0078] In the second step, in most cases, the calcination time is 0.5 hours or more, preferably 2 to 20 hours, and almost all of the reaction precursor can be converted into the zinc-phosphorus complex oxide represented by the general formula (1).

[0079] The firing atmosphere in the second step is not particularly limited and may be an inert gas atmosphere, a vacuum atmosphere, an oxidizing gas atmosphere, or air.

[0080] In the second step, firing may be performed once, or multiple times as desired. For example, in order to make the powder properties uniform, the material may be fired once, then crushed, and the crushed material may be fired again.

[0081] After firing, the material can be cooled as needed and crushed, pulverized, classified, etc., as required.

[0082] The Ca source for step A is a compound containing the element Ca. Examples of Ca sources include calcium carbonates, oxides, hydroxides, halides, and carboxylates. Examples of calcium carboxylates include calcium gluconates, citrates, oxalates, acetates, and lactates.

[0083] The P source in step A is a compound containing a P atom. Phosphate is preferred as the P source. In addition, compounds containing both a Ca source and a P source, such as calcium phosphate and calcium pyrophosphate, can also serve as both a Ca source and a P source.

[0084] The A source added as necessary in step A is a compound containing element A. Examples of A sources include carbonates of A, oxides of A, hydroxides of A, halides of A, and carboxylates of A. Examples of A carboxylates include gluconic acid, citrate, oxalate, acetate, and lactate.

[0085] In step A, it is preferable to adjust the mixing amounts of the Ca, P source and A source appropriately so that the molar ratios of Ca, P, and A in the raw material mixture are equal to the composition of the calcium pyrophosphate salt represented by general formula (2).

[0086] In step A, it is preferable to adjust the mixing amounts of the zinc-phosphorus composite oxide represented by general formula (1), Ca source, P source, and A source so that the amount of calcium pyrophosphate salt represented by general formula (2) that is produced is 0.1 to 20 parts by mass, preferably 0.2 to 15 parts by mass, relative to 100 parts by mass of the zinc-phosphorus composite oxide represented by general formula (1) in the negative thermal expansion material produced.

[0087] In step A, the mixing treatment of the zinc-phosphorus composite oxide represented by general formula (1), Ca source, P source, and A source can be carried out wet or dry.

[0088] In the case of wet mixing, it is preferable to obtain the raw material mixture by drying the entire amount to remove the solvent.

[0089] Step B is a step in which the raw material mixture prepared in Step A is calcined to obtain a composite of a zinc-phosphorus complex oxide represented by general formula (1) and a calcium pyrophosphate salt represented by general formula (2), that is, the negative thermal expansion material of the present invention.

[0090] The firing temperature in step B is preferably 300 to 850°C, more preferably 350 to 800°C. On the other hand, if the firing temperature in step B is below the above range, the formation of the calcium pyrophosphate salt represented by general formula (2) tends to be insufficient, and if it exceeds the above range, it tends to solidify by sintering. The firing time in step B is not particularly limited, and firing should be carried out for a sufficient time until the calcium pyrophosphate salt represented by general formula (2) is formed.

[0091] The formation of the calcium pyrophosphate salt represented by general formula (2) can be confirmed, for example, by observing whether the peak top of the main peak is observed in X-ray diffraction analysis when 2θ is between 29 and 30°, specifically between 2θ = 29.66 and 29.73°.

[0092] In step B, the negative thermal expansion material of the present invention can often be obtained by firing for 0.5 hours or more, preferably 1 to 10 hours.

[0093] The firing atmosphere in step B is not particularly limited and may be an inert gas atmosphere, a vacuum atmosphere, an oxidizing gas atmosphere, or air.

[0094] In step B, firing may be performed once, or multiple times as desired. For example, in order to make the powder properties uniform, the material may be fired once, then crushed, and the crushed material may be fired again.

[0095] After firing, the material is cooled as appropriate, and if necessary, crushed, pulverized, classified, etc., to obtain a negative thermal expansion material which is a composite having a core with a core-shell structure and containing a zinc-phosphorus composite oxide represented by general formula (1), and a shell containing a calcium pyrophosphate salt represented by general formula (2) that covers all or part of the surface of the core.

[0096] Furthermore, as a method for obtaining a composite of the zinc-phosphorus composite oxide particles represented by general formula (1) and calcium pyrophosphate salt particles represented by general formula (2) as described above, one method is to mix the zinc-phosphorus composite oxide represented by general formula (1) and the calcium pyrophosphate salt represented by general formula (2) using mechanical means in which strong shear force is applied, either dry or wet. Also, as a method for producing a composite having the core-shell structure described above, comprising a core containing calcium pyrophosphate salt represented by general formula (2) and a shell containing zinc-phosphorus composite oxide represented by general formula (1) covering all or part of the surface of the core, one method is to calcine a mixture containing the calcium pyrophosphate salt represented by general formula (2) that will form the core and the reaction precursor of the zinc-phosphorus composite oxide represented by general formula (1) obtained in the first step described above, at 300 to 850°C. Furthermore, as a composite, a method for producing a composite in which particles containing a zinc-phosphorus composite oxide represented by general formula (1) and particles containing a calcium pyrophosphate salt represented by general formula (2) are bound together is to heat-treat a homogeneous mixture of particles of the zinc-phosphorus composite oxide represented by general formula (1) and particles of the calcium pyrophosphate salt represented by general formula (2) at 300 to 850°C.

[0097] The average particle size of the negative thermal expansion material obtained by the method for producing the negative thermal expansion material of the present invention is preferably 0.1 to 100 μm, particularly preferably 0.2 to 80 μm, and even more preferably 0.2 to 20 μm, and the BET specific surface area is 0.05 to 50 m². 2 / g, particularly preferably 0.10 to 10m 2 / g, more preferably 0.20 to 8m 2 The value is / g. It is preferable that the average particle diameter and / or BET specific surface area of ​​the negative thermal expansion material are within the above range, as this facilitates handling when using the negative thermal expansion material as a filler in resins, glass, etc.

[0098] Further, the negative thermal expansion material according to the present invention may have its particle surface subjected to surface treatment, if necessary, for the purpose of improving the resin dispersibility and the moisture resistance of the negative thermal expansion material. Further, the method for producing a negative thermal expansion material according to the present invention may, if necessary, perform a surface treatment on the negative thermal expansion material obtained by performing the second step B for the purpose of improving the resin dispersibility and the moisture resistance of the negative thermal expansion material.

[0099] Examples of the surface treatment include a method of coating the particle surface with an inorganic compound containing one or more elements selected from a silane coupling agent, a titanate coupling agent, a fatty acid or its derivative, Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe, and Zr (see, for example, WO2020 / 095837 pamphlet, WO2020 / 261976 pamphlet, WO2019 / 087722 pamphlet, and JP-A-2020-147486). Further, these may be appropriately combined for the surface treatment.

[0100] The thermal expansion coefficient of the negative thermal expansion material obtained by performing the method for producing a negative thermal expansion material of the present invention between 100 and 150 °C is -25 × 10 -6 / K or less, preferably -30 × 10 -6 / K or less. The lower limit is not particularly limited, but is generally -170 × 10 -6 / K or more, preferably -150 × 10 -6 / K or more. In the negative thermal expansion material of the present invention, the thermal expansion coefficient between 100 and 150 °C is particularly preferably -30 × 10 -6 to -150 × 10 -6 / K in that it is easier to cancel out the positive expansion of the thermal expansion coefficient when combined with a positive thermal expansion material. Incidentally, the negative thermal expansion material of the present invention has a zinc phosphorus composite oxide represented by the general formula (1) having Zn ２ P ２ O ７ When it is, the thermal expansion coefficient between 100 and 150 °C is not limited as long as it is smaller than when Zn ２ P ２ O ７ is used alone, but is -80 × 10 -6 / K or less, preferably -82 × 10 -6 / K or less, and the lower limit is not particularly limited, but is generally -170×10 -6 / K or more, preferably -150×10 -6 / K or more. Also, in terms of making it easier for the positive thermal expansion to cancel out when combined with a positive thermal expansion material, the thermal expansion coefficient between 100 and 150 °C is particularly preferably -82×10 -6 ~-150×10 -6 / K.

[0101] Further, the thermal expansion coefficient of the negative thermal expansion material obtained by carrying out the method for producing the negative thermal expansion material of the present invention between 80 and 200 °C is -20×10 -6 / K or less, preferably -23×10 -6 / K or less, and the lower limit is not particularly limited, but is generally -100×10 -6 / K or more, preferably -80×10 -6 / K or more. In the negative thermal expansion material of the present invention, in terms of making it easier for the positive thermal expansion to cancel out when combined with a positive thermal expansion material, it is particularly preferably -23×10 -6 ~-80×10 -6 / K.

[0102] Further, in the negative thermal expansion material of the present invention, a rapid volume decrease may be observed as the temperature rises. For example, in the case of the composite (1) where the zinc phosphorus composite oxide represented by the general formula (1) is Zn2P2O7 and the calcium pyrophosphate salt represented by the general formula (2) is Ca2P2O7, a rapid volume decrease is likely to occur as the temperature rises in the temperature range of 100 to 150 °C. When a rapid volume decrease occurs as the temperature rises, in a composite material containing a negative thermal expansion material and a positive thermal expansion material, the positive thermal expansion material may not be able to follow the rapid volume decrease of the negative thermal expansion material, and as a result, it may be difficult to achieve a zero thermal expansion rate or a low thermal expansion rate of the composite material containing the negative thermal expansion material. In order to suppress this rapid volume decrease, in the present invention, the following general formula (3) is further added to the negative thermal expansion material of the present invention: Cu ｗ３ M’ ｗ４ P ｚ３ O ｔ３(3) (In the formula, M' represents a metallic element other than Cu with an atomic number of 11 or higher. w3 represents 1.7 ≤ w3 ≤ 2.3, w4 represents 0 ≤ w4 ≤ 1.0, z3 represents 1.7 ≤ z3 ≤ 2.3, and t3 represents 6.00 ≤ t3 ≤ 8.00. However, 1.7 ≤ w3 + w4 ≤ 2.3.) By incorporating a copper pyrophosphate salt represented by this formula and using it as a negative thermal expansion material composition, for example, compared to composite (1), it is possible to obtain a negative thermal expansion material that shows a gradual volume decrease with increasing temperature between 100 and 150°C, and furthermore, consistently exhibits excellent negative thermal expansion properties over a wide temperature range between -30 and 150°C.

[0103] The negative thermal expansion material composition of the present invention contains the negative thermal expansion material of the present invention described above and copper pyrophosphate represented by the general formula (3).

[0104] In general formula (3), M' is an element that may be included as needed to further adjust the negative thermal expansion properties. M' represents a metallic element other than Cu with an atomic number of 11 or higher, and is preferably one or more selected from, for example, Zn, Ga, Fe, Mg, Co, Mn, Ba, Ca, and Al.

[0105] In general formula (3), w3 is 1.7 ≤ w3 ≤ 2.3. From the viewpoint of also having excellent negative thermal expansion characteristics, w3 is 1.8 ≤ w1 ≤ 2.2, and particularly preferably 1.9 ≤ w1 ≤ 2.1.

[0106] In general formula (3), w4 is 0 ≤ w4 ≤ 1.0. From the viewpoint of also having excellent negative thermal expansion characteristics, w4 is 0 ≤ w4 ≤ 0.9, and particularly preferably 0 ≤ w4 ≤ 0.8.

[0107] In general formula (3), z3 is 1.7 ≤ z3 ≤ 2.3. From the viewpoint of excellent negative thermal expansion characteristics, z3 is preferably 1.8 ≤ z3 ≤ 2.2, and particularly preferably 1.9 ≤ z3 ≤ 2.1.

[0108] In general formula (3), t3 is 6.0 ≤ t3 ≤ 8.0. From the viewpoint of also having excellent negative thermal expansion characteristics, t3 is preferably 6.5 ≤ t3 ≤ 7.5, and particularly preferably 6.2 ≤ t3 ≤ 7.2.

[0109] However, in general formula (3), w3 + w4 is 1.7 ≤ w3 + w4 ≤ 2.3. Preferably, w3 + w4 is 1.8 ≤ w3 + w4 ≤ 2.2, as this provides better negative thermal expansion characteristics.

[0110] The preferred physical properties of the copper pyrophosphate salt represented by general formula (3) are a BET specific surface area of ​​0.2 to 8.0 m². ２ / g, preferably 0.3 to 7.0 m ２ A particle size of 0.2 to 10 μm, preferably 0.3 to 8.0 μm, is preferable from the viewpoint of easily obtaining a uniform mixture with the negative thermal expansion material of the present invention, resulting in good fluidity and improved dispersibility in the positive thermal expansion material when used as a filler.

[0111] Copper pyrophosphate represented by general formula (3) can be easily produced, for example, by carrying out the following steps 1' to 2'. Step 1': A step of preparing a reaction precursor containing Cu, P and M' element to be added as needed. Step 2': A step of calcining the reaction precursor to obtain copper pyrophosphate represented by general formula (3).

[0112] The first step is to prepare a reaction precursor containing Cu, P, and, if necessary, an additional M' element.

[0113] The reaction precursor can be produced by mixing a Cu compound, a phosphorus compound, and an M' element-containing compound, which may be added as needed.

[0114] Cu compounds are compounds containing a Cu atom. Examples of Cu compounds include copper salts of organic carboxylic acids such as copper gluconate, copper citrate, copper acetate, and copper lactate, copper salts of mineral acids, copper oxides, copper hydroxides, copper phosphates, and copper pyrophosphates.

[0115] A phosphorus compound is a compound containing a phosphorus atom. Phosphoric acid is preferred as the phosphorus compound. Furthermore, compounds containing both a copper source and a phosphorus source, such as copper phosphates and copper pyrophosphates, can serve as both Cu compounds and phosphorus compounds.

[0116] The M' element-containing compound added as needed is a compound containing the M' element. Examples of M' element-containing compounds include M' carbonates, M' oxides, M' hydroxides, M' halides, and M' carboxylates. Examples of M' carboxylates include gluconates, citrates, oxalates, acetates, and lactates.

[0117] The reaction precursor in step 1' preferably contains at least copper pyrophosphate, as this makes it easier to obtain a reaction precursor in which each raw material is uniformly dispersed in an inexpensive and simple operation, and also makes it easier to obtain a single-phase copper-phosphorus composite oxide represented by general formula (3) by X-ray diffraction by calcination of the obtained reaction precursor in step 2' described later. The copper pyrophosphate may be hydrated or anhydrous.

[0118] Furthermore, when producing Cu2P2O7 in which W4 in general formula (3) is 0, the reaction precursor containing at least copper pyrophosphate contains only copper pyrophosphate. On the other hand, when producing a copper pyrophosphate salt represented by general formula (3) that contains element M', the reaction precursor contains copper pyrophosphate, a phosphorus compound, and an element M' compound.

[0119] In step 1', it is preferable to adjust the content of the copper compound, phosphorus compound, and M' element-containing compound as appropriate so that the molar ratios of Cu, P, and M in the reaction precursor are equal to the composition of copper pyrophosphate represented by general formula (3). When using copper phosphate or copper pyrophosphate as the copper compound, it is preferable to prepare the reaction precursor while also considering the amount of phosphorus atoms in the copper compound.

[0120] In the first step, a mixing treatment of copper compounds, phosphorus compounds, and M' element-containing compounds may be performed as needed. This mixing treatment can be carried out wet or dry.

[0121] When performing a wet mixing process, the reaction precursor can be obtained by drying the entire volume to remove the solvent.

[0122] Furthermore, in step 1', the composition of the reaction precursor obtained by removing the completely dried solvent after the wet mixing treatment is approximately the same as the atomic molar ratio of Cu, P, M' and the copper pyrophosphate salt represented by general formula (3) at the time of each raw material charge.

[0123] Step 2' is a step in which the reaction precursor prepared in Step 1' is calcined to obtain a copper pyrophosphate salt represented by general formula (3).

[0124] The firing temperature in step 2' is preferably 550 to 850°C, more preferably 600 to 800°C. On the other hand, if the firing temperature in step 2' is below the above range, the formation of the copper pyrophosphate salt represented by general formula (3) tends to be insufficient, and if it exceeds the above range, it tends to become a solidified sintered body. The firing time in step 2' is not particularly limited, and firing should be carried out for a sufficient time until the copper pyrophosphate represented by general formula (3) is formed.

[0125] The formation of copper pyrophosphate represented by general formula (3) can be confirmed, for example, by checking whether single-phase copper pyrophosphate represented by general formula (3) is obtained by X-ray diffraction analysis.

[0126] In the second step, in most cases, the calcination time is 1 hour or more, preferably 1.5 to 8 hours, and almost all of the reaction precursor can be converted to the copper pyrophosphate salt represented by the general formula (3).

[0127] The firing atmosphere in step 2' is not particularly limited and may be an inert gas atmosphere, a vacuum atmosphere, an oxidizing gas atmosphere, or air.

[0128] In the second step, firing may be performed once, or multiple times as desired. For example, in order to make the powder properties uniform, the material may be fired once, then crushed, and the crushed material may be fired again.

[0129] After firing, the material can be cooled as needed and crushed, pulverized, classified, etc., as required.

[0130] The amount of copper pyrophosphate represented by general formula (3) is set to 5 to 150 parts by mass, preferably 10 to 140 parts by mass, of the negative thermal expansion material of the present invention per 100 parts by mass of the copper pyrophosphate. This suppresses, for example, the rapid volume decrease of the negative thermal expansion material of the present invention with increasing temperature, and furthermore, it is possible to obtain a negative thermal expansion material that consistently exhibits excellent negative thermal expansion properties over a wide temperature range of -30 to 150°C.

[0131] The negative thermal expansion material composition of the present invention can be manufactured, for example, by mixing the negative thermal expansion material of the present invention with copper pyrophosphate. This mixing process may be carried out by either a dry or wet method, but the dry method is preferred because it is easier to manufacture. In the case of dry mixing, there are no particular limitations as long as a uniform mixing process can be carried out, and mixing devices such as high-speed mixers, super mixers, turbosphere mixers, Eilich mixers, Henschel mixers, Nauter mixers, ribbon blenders, V-type mixers, conical blenders, jet mills, cosmo-mizers, paint shakers, bead mills, and ball mills can be used. At the laboratory level, mixing with a household mixer or mortar and pestle is also sufficient.

[0132] The negative thermal expansion material or negative thermal expansion material composition of the present invention is used as a powder or a paste. When using the negative thermal expansion material or negative thermal expansion material composition of the present invention as a paste, the negative thermal expansion material or negative thermal expansion material composition of the present invention is mixed and dispersed in a solvent and / or a low-viscosity liquid resin and used in paste form. Alternatively, the negative thermal expansion material or negative thermal expansion material composition of the present invention may be dispersed in a solvent and / or a low-viscosity liquid resin, and further, if necessary, a binder, flux, dispersant, etc., may be included and used in paste form.

[0133] The negative thermal expansion material or negative thermal expansion material composition of the present invention is used as a positive thermal expansion material in combination with various organic or inorganic compounds to form a composite material. The composite material of the present invention comprises the negative thermal expansion material or negative thermal expansion material composition of the present invention and a positive thermal expansion material.

[0134] Organic compounds used as positive thermal expansion materials are not particularly limited, but include rubber, polyolefins, polycycloolefins, polystyrene, ABS, polyacrylate, polyphenylene sulfide, phenolic resins, polyamide resins, polyimide resins, epoxy resins, silicone resins, polycarbonate resins, polyethylene resins, polypropylene resins, polyethylene terephthalate resins (PET resins), polyurethane resins, and polyvinyl chloride resins. Inorganic compounds used as positive thermal expansion materials include silicon dioxide, silicates, graphite, sapphire, various glass materials, concrete materials, and various ceramic materials.

[0135] Since the composite material of the present invention contains a negative thermal expansion material or negative thermal expansion material composition of the present invention which has excellent negative thermal expansion properties, it is possible to achieve a negative thermal expansion coefficient, zero thermal expansion coefficient, or low thermal expansion coefficient by adjusting the blending ratio with other compounds.

[0136] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. (X-ray diffractometer) In the examples, measurements were performed using an X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation) under the following measurement conditions. Radiation source: Cu-Kα Tube voltage: 40kV Tube current: 40mA Scanning speed: 1° / sec Smoothing: Weighted averaging method Kα2 removal: Intensity ratio 0.5

[0137] <Preparation of Zn2P2O7 Sample> (ZNP1 Sample) Zinc pyrophosphate trihydrate (Zn2P2O7·3H2O, average particle size 1.2 μm) was calcined at 700°C for 4 hours. X-ray diffraction analysis of the calcined powder revealed single-phase α-Zn2P2O7. The average particle size of the obtained Zn2P2O7 sample was 1.1 μm and the BET specific surface area was 0.6 m². 2The result was / g. The average particle size of the Zn2P2O7 sample was determined by the average value of 50 particles arbitrarily extracted at a magnification of 1000x using a scanning electron microscope. (ZNP2 sample) Zinc pyrophosphate trihydrate (Zn2P2O7·3H2O, average particle size 1.2 μm) was calcined at 625°C for 1.5 hours. X-ray diffraction analysis of the calcined powder revealed single-phase α-Zn2P2O7. The average particle size of the obtained Zn2P2O7 sample was 1.5 μm and the BET specific surface area was 1.0 m². 2 The result was / g. The average particle size of the Zn2P2O7 sample was determined by the average value of 50 particles arbitrarily extracted at a magnification of 1000x using a scanning electron microscope.

[0138] (Example 1) <Step A> Zn prepared as described above ２ P ２ O ７ 5,000 g of sample (ZNP1), 0.1977 g of calcium monohydrogen phosphate dihydrate (average particle size 1.9 μm), and 10 mL of pure water were thoroughly ground and mixed in a mortar. The entire amount was then dried at 130°C. <Step B> The resulting dried powder was calcined at 700°C for 4 hours. X-ray diffraction analysis of the calcined powder revealed α-Zn ２ P ２ O ７ Only peaks originating from were observed (Figure 1). This was found in the negative thermal expansion material sample (core: Zn ２ P ２ O ７ Shell: Ca ２ P ２ O ７ )

[0139] (Example 2) <Step A> Zn prepared as described above ２ P ２ O ７ 5,000 g of the sample (ZNP2) and 0.1448 g of calcium monohydrogen phosphate dihydrate (average particle size 1.9 μm) were thoroughly ground and mixed in a mortar. <Step B> The resulting mixed powder was calcined at 700°C for 1.5 hours. X-ray diffraction analysis of the calcined powder revealed α-Zn ２ P ２ O ７ Only peaks originating from were observed (Figure 2). This was found in the negative thermal expansion material sample (core: Zn ２P ２ O ７ Shell: Ca ２ P ２ O ７ )

[0140] (Comparative Example 1) The Zn2P2O7 sample prepared above was used as a negative thermal expansion material sample (Zn2P2O7). The X-ray diffraction pattern is shown in Figure 3.

[0141] (Physical Property Evaluation) For the samples obtained in the examples and comparative examples, the average particle size, BET specific surface area, main peak at 2θ = 29-30° measured by an X-ray diffractometer, and thermal expansion coefficient were measured. The average particle size and thermal expansion coefficient were measured as described below. The results are shown in Tables 1 and 2.

[0142] (Average particle size) The average particle size of the negative thermal expansion material sample was determined by the average value of 50 particles arbitrarily extracted at a magnification of 1000x during scanning electron microscopy observation.

[0143] [Measurement of Thermal Expansion Coefficient] (Preparation of Ceramic Molded Body) 0.05 g of propylene carbonate was added to 1.00 g of the sample and ground and mixed in a mortar for 3 minutes. Then, 0.15 g was weighed out and the entire amount was filled into a φ6 mm mold. Next, a powder molded body was prepared by molding it with a pressure of 0.5 t using a hand press. The obtained powder molded body was heated in an electric furnace to 700°C in 3 hours and held for 4 hours to prepare a ceramic molded body. The thermal expansion coefficient of the prepared ceramic molded body was evaluated between 80 and 200°C and between 100 and 150°C as described below.

[0144] (Measurement of thermal expansion coefficient between 80 and 200°C) The thermal expansion coefficient of the fabricated ceramic molded body was measured using a thermomechanical measuring device (NETZSCH JAPAN TMA4000SE). The measurement conditions were nitrogen atmosphere, load of 10g, and temperature range of 50°C to 225°C, and measurements were taken twice. The thermal expansion coefficient between 80 and 200°C from the second measurement was taken as the thermal expansion coefficient of the negative thermal expansion material sample. Figure 4 shows the relationship between the thermal shrinkage rate (%) and temperature (°C) of the negative thermal expansion material sample.

[0145] (Measurement of thermal expansion coefficient between 100 and 150°C) The thermal expansion coefficient of the fabricated ceramic molded body was measured using a thermomechanical measuring device (NETZSCH JAPAN TMA4000SE). The measurement conditions were a nitrogen atmosphere, a load of 10g, and a temperature range of 50°C to 225°C, and measurements were taken twice repeatedly. The thermal expansion coefficient between 100 and 150°C in the second measurement was taken as the thermal expansion coefficient of the negative thermal expansion material sample.

[0146]

[0147]

[0148] <Copper pyrophosphate sample (Cu ２ P ２ O ７ Preparation of (CUP1 sample) copper pyrophosphate trihydrate (Cu ２ P ２ O ７ 3H ２ O (average particle size 1.0 μm) was calcined at 700°C for 1.5 hours. X-ray diffraction analysis of the calcined product revealed single-phase Cu ２ P ２ O ７ This was Cu ２ P ２ O ７ The sample was used. Also, the obtained Cu ２ P ２ O ７ The average particle size of the sample was 2.1 μm, and the BET specific surface area was 0.7 m². 2 It was / g. ２ P ２ O ７ The average particle size of the sample was determined by the average value of 50 particles arbitrarily extracted at a magnification of 1000x using a scanning electron microscope.

[0149] (Example 3) Cu prepared above ２ P ２ O ７100 parts by mass of sample (CUP1) and 41 parts by mass of the negative thermal expansion material sample obtained in Example 2 were thoroughly mixed in a mortar to obtain the negative thermal expansion material composition sample. <Measurement of linear expansion coefficient (thermal expansion coefficient)> The obtained negative thermal expansion material composition sample was subjected to thermal expansion measurements in the range of -30 to 150°C, -30 to 25°C, and 90 to 130°C as described below. (Preparation of compacted molded body) 1.00 g of the negative thermal expansion material composition sample was crushed and mixed in a mortar for 3 minutes, then 0.15 g was weighed out and the entire amount was filled into a φ6 mm mold. Next, a compacted molded body was prepared by molding with a pressure of 10 MPa using a hand press. The thermal expansion coefficient of the prepared compacted molded body was measured using a thermomechanical measuring device (NETZSCH JAPAN TMA4000SE). Measurements were taken twice under the conditions of a nitrogen atmosphere, a load of 10 g, and a temperature range of -35°C to 170°C. The thermal expansion coefficients for the second measurement were calculated for the ranges of -30°C to 150°C, -30°C to 25°C, and 90°C to 130°C. Similarly, compacted bodies were prepared from the negative thermal expansion material sample obtained in Example 2, and the thermal expansion coefficients for the ranges of -30°C to 150°C, -30°C to 25°C, and 90°C to 130°C were calculated. The results are shown in Table 3. Figure 5 shows the relationship between the thermal shrinkage rate (%) and temperature (°C) of the compacted bodies. Table 3 and Figure 5 show that the negative thermal expansion material of Example 2 does not exhibit negative thermal expansion properties at least between -30 and 25°C, and a rapid volume decrease is observed with increasing temperature between 100 and 150°C. Example 3, a negative thermal expansion material composition obtained by further adding copper pyrophosphate to the negative thermal expansion material sample of Example 2 of the present invention, exhibits consistently excellent negative thermal expansion properties over a wide temperature range of -30 to 150°C, and furthermore, compared to the negative thermal expansion material sample of Example 2, it shows a more gradual volume decrease with increasing temperature between 100 and 150°C.

Claims

1. A complex of zinc-phosphorus complex oxide and calcium pyrophosphate salt, wherein the zinc-phosphorus complex oxide is of the following general formula (1): Zn x M y P z1 O t1 (1) A zinc phosphorus composite oxide represented by the formula (wherein M represents one or more elements selected from Mg, Ca, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. x represents 0.0 < x ≤ 2.0, y represents 0.0 ≤ y < 2.0, z1 represents 1.7 ≤ z1 ≤ 2.3, and t1 represents 6.00 ≤ t1 ≤ 8.00, where 1.7 ≤ x + y ≤ 2.3) is included. The calcium pyrophosphate salt is of the following general formula (2): Ca w１ A ｗ２ P z2 O t2 (2) A negative thermal expansion material characterized by containing a calcium pyrophosphate salt represented by the formula: (wherein A represents one or more metallic elements selected from Mg, Cu, Zn, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w1 represents 1.7 ≤ w1 ≤ 2.3, w2 represents 0 ≤ w2 ≤ 1.0, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.00 ≤ t2 ≤ 8.

00. However, 1.7 ≤ w1 + w2 ≤ 2.3.) 2. The negative thermal expansion material according to claim 1, characterized in that the composite has a core-shell structure, the core contains a zinc-phosphorus composite oxide represented by the general formula (1), and the shell contains a calcium pyrophosphate salt represented by the general formula (2).

3. The negative thermal expansion material according to claim 1 or 2, characterized in that the zinc-phosphorus composite oxide represented by the general formula (1) is Zn2P2O7.

4. The negative thermal expansion material according to claim 1 or 2, characterized in that the calcium pyrophosphate salt represented by the general formula (2) is Ca2P2O7.

5. The negative thermal expansion material according to claim 1 or 2, characterized in that the thermal expansion coefficient between 100 and 150 °C is -25×10 -6 / K or less.

6. The coefficient of thermal expansion between 100 and 150°C is -80 × 10⁻⁶ -6 The negative thermal expansion material according to claim 3, characterized in that it is less than or equal to / K.

7. The negative thermal expansion material according to claim 1 or 2, characterized in that when X-ray diffraction measurements are performed using Cu-Kα as an X-ray source, the peak top of the main peak is observed at 2θ = 29.66 to 29.73° when 2θ is between 29 and 30°.

8. The negative thermal expansion material according to claim 1 or 2, characterized in that the average particle size is 0.1 to 100 μm.

9. BET specific surface area is 0.05 to 50 m². 2 The negative thermal expansion material according to claim 1 or 2, characterized in that it is / g.

10. The following general formula (1) Zn x M y P z1 O t1 (1) Zinc phosphorus composite oxide particles represented by the following general formula (2) Ca ｗ１ A w２ P z2 O t2 (2) (In the formula, A represents one or more metallic elements selected from Mg, Cu, Fe, Zn, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w1 represents 1.7 ≤ w1 ≤ 2.3, w2 represents 0 ≤ w2 ≤ 1.0, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.00 ≤ t2 ≤ 8.00, where 1.7 ≤ w1 + w2 ≤ 2.3.) A method for producing a negative thermal expansion material, characterized by firing a mixture containing a Ca source, a P source, and an A source added as necessary, which are raw materials for producing a calcium pyrophosphate salt represented by [formula].

11. The method for producing a negative thermal expansion material according to claim 10, characterized in that the zinc-phosphorus composite oxide represented by the general formula (1) is obtained by calcining a reaction precursor containing at least zinc pyrophosphate.

12. A negative thermal expansion material according to claim 1 or 2, and the following general formula (3) Cu ｗ３ M' ｗ４ P ｚ３ O ｔ３ (3) A negative thermal expansion material composition characterized by containing a copper pyrophosphate salt represented by the formula (wherein M' represents a metallic element other than Cu with an atomic number of 11 or greater, w3 represents 1.7 ≤ w3 ≤ 2.3, w4 represents 0 ≤ w4 ≤ 1.0, z3 represents 1.7 ≤ z3 ≤ 2.3, and t3 represents 6.00 ≤ t3 ≤ 8.00, provided that 1.7 ≤ w3 + w4 ≤ 2.3).

13. The copper pyrophosphate represented by the general formula (3) is Cu ２ P ２ O ７ The negative thermal expansion material composition according to claim 12, characterized in that it is the same as the one described above.

14. A composite material characterized by comprising a negative thermal expansion material according to claim 1 or a negative thermal expansion material composition according to claim 12, and a positive thermal expansion material.

15. The composite material according to claim 14, characterized in that the positive thermal expansion material is at least one selected from metal, alloy, glass, ceramics, rubber, and resin.

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