Powder of composite metal oxide, vulcanizing agent for rubber, rubber composition, and method for producing powder of composite metal oxide

Abstract

The present disclosure addresses the problem of providing powder of a composite metal oxide which is particularly useful as a vulcanizing agent for rubber.　The powder of a composite metal oxide according to the present disclosure comprises magnesium oxide and zinc oxide. The powder has a peak of the zinc oxide and a peak of the magnesium oxide in XRD. In the powder, the shift in the diffraction angle of the peak value of the magnesium oxide is within the range of ± 0.05° when compared with the peak value of a magnesium oxide single crystal.

Description

Composite metal oxide powder, rubber vulcanizing agent, rubber composition, and method for producing composite metal oxide powder

[0001] The present disclosure relates to a composite metal oxide powder, a rubber vulcanizing agent, a rubber composition, and a method for producing the composite metal oxide powder.

[0002] In order to produce rubber products, a vulcanizing agent, such as zinc oxide, and a vulcanization aid, such as magnesium oxide, are added to rubber raw materials. In addition, to improve the tendency of magnesium oxide to aggregate and its poor dispersibility, composite metal oxides containing magnesium oxide and zinc oxide, and rubber compositions containing the composite metal oxides, have been investigated.

[0003] For example, Patent Document 1 discloses the following composite metal oxide: Mg 1-x M 2+ x O (1) (wherein, M 2+ is Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ wherein x is a number in the range of 0.001<x<0.5).

[0004] Patent Document 2 discloses the following composite metal oxide: Mg 1-x M 2+ x O (1) (wherein, M 2+ is Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ and x is a number in the range of 0.001<x<0.5), and the BET specific surface area is 4 m 2 / g or less of a thermally conductive complex metal oxide that is a magnesium oxide-based solid solution.

[0005] JP-A-6-157032 JP-A-6-87979

[0006] Patent Documents 1 and 2 do not describe the structure of a composite metal oxide that has a specific X-ray peak according to the present disclosure, which is determined by powder X-ray diffraction (XRD). The present disclosure aims to provide a composite metal oxide powder that is particularly useful as a vulcanizing agent for rubber.

[0007] The present disclosure includes the following aspects. (First Disclosure) In this first disclosure, a composite metal oxide powder includes magnesium oxide and zinc oxide. In XRD, the powder has a peak for the zinc oxide and a peak for the magnesium oxide. In the powder, the peak value for the magnesium oxide has a diffraction angle shift within a range of ±0.05° compared to the peak value of magnesium oxide single crystal.

[0008] (Second Disclosure) The second disclosure relates to the first disclosure, wherein the composite metal oxide is represented by the following formula (1): Mg 1-x Zn x O is represented by formula (1): In formula (1), x satisfies 0.02≦x<0.5.

[0009] (Third Disclosure) The present third disclosure is the second disclosure, wherein x satisfies 0.15≦x≦0.25. (Fourth Disclosure) The present fourth disclosure is any of the first to third disclosures, wherein the powder has a t35 of 27 minutes or more and 38 minutes or less when 100 parts by mass of a chloroprene resin and 3 to 10 parts by mass of the powder are mixed and subjected to a Mooney scorch test at 125°C in accordance with JIS K 6300-1:2013.

[0010] (Fifth Disclosure) In this fifth disclosure, in the fourth disclosure, the powder has a t10 of 3.1 minutes or more and 4.0 minutes or less when 100 parts by mass of chloroprene resin and 3 to 10 parts by mass of the powder are mixed and subjected to a Mooney scorch test at 153°C in accordance with JIS K 6300-1:2013.

[0011] (Sixth Disclosure) The present sixth disclosure is a rubber vulcanizing agent containing the powder according to any one of Disclosures 1 to 5. (Seventh Disclosure) The present seventh disclosure is a rubber composition containing the rubber vulcanizing agent according to Disclosure 6 and a rubber raw material.

[0012] (Eighth Disclosure) This eighth disclosure relates to a method for producing a powder of a complex metal oxide. The production method includes a precipitation step, an aging step, a crushing step, and a calcination step. In the precipitation step, a water-soluble magnesium salt and an alkali are mixed to obtain a precipitate. In the aging step, the precipitate and a water-soluble zinc salt are mixed and aged to obtain a matured product. In the crushing step, the matured product is crushed. In the calcination step, the crushed matured product is calcined to obtain a complex metal oxide.

[0013] The composite metal oxide powder according to the present disclosure is particularly useful as a vulcanizing agent for rubber.

[0014] 1 shows the powder X-ray diffraction data of Powder No. 1.

[0015] The composite metal oxide powder, rubber vulcanizing agent, rubber composition, and method for producing the composite metal oxide powder according to the present disclosure are described in detail below. The composite metal oxide powder according to the present disclosure may be referred to as the "powder according to the present disclosure." The powder according to the present disclosure is a composite metal oxide powder and contains magnesium oxide and zinc oxide. In the present disclosure, the composite metal oxide refers to a metal oxide that combines magnesium oxide and zinc oxide. In other words, the composite metal oxide does not include a mixture of magnesium oxide and zinc oxide.

[0016] The powder according to the present disclosure has a zinc oxide peak and a magnesium oxide peak in powder X-ray diffraction (XRD). In the powder, the peak value of the magnesium oxide (200) plane has a diffraction angle (2θ) shift within a range of ±0.05° compared to the peak value of a magnesium oxide single crystal. When CuKα radiation is used as the X-ray source, the peak value of the diffraction angle (2θ) of the magnesium oxide (200) plane appears at around 42.9°.

[0017] In the magnesium oxide, the peak value of the (220) plane may be shifted in the diffraction angle (2θ) within a range of ±0.05° compared to the peak value of the magnesium oxide single crystal. When CuKα rays are used as the X-ray source, the peak value of the diffraction angle (2θ) of the (220) plane of the magnesium oxide single crystal appears at around 61.2°.

[0018] The powder X-ray diffraction (XRD) can be performed using CuKα radiation as the X-ray source, with a measurement range of 5 to 70°, a step width of 0.026°, and a measurement speed of 10 seconds / step. The CuKα radiation has a wavelength of 1.5418 Å. An example of an instrument used to perform the powder X-ray diffraction (XRD) is the Empyrean-DY1356 manufactured by Malvern Panalytical.

[0019] In the powder, the peak value of the diffraction angle (2θ) of zinc oxide may or may not be shifted from the peak value of the diffraction angle (2θ) of zinc oxide single crystal. In the powder, the peak value of the diffraction angle (2θ) of zinc oxide is preferably within a range of ±0.05° from the diffraction angle (2θ) of zinc oxide single crystal. As a result, for example, when the powder is used as a vulcanizing agent for rubber, the zinc oxide exposed on the outside of the magnesium oxide can promote initial vulcanization.

[0020] When the powder is used as a rubber vulcanizing agent, the amount of zinc oxide and magnesium oxide can be reduced compared to conventional systems that add zinc oxide and magnesium oxide, thereby contributing to the achievement of the SDGs (Sustainable Development Goals) adopted at the United Nations Summit.

[0021] The composite metal oxide is preferably represented by the following formula (1): Mg 1-x Zn x O is represented by formula (1). x preferably satisfies 0.02≦x, more preferably 0.05≦x, and even more preferably 0.15≦x. Also, x preferably satisfies x<0.5, more preferably x≦0.25, and even more preferably x≦0.2. This makes it easier for zinc oxide to be exposed to the outside of magnesium oxide.

[0022] The powder can be prepared by mixing 100 parts by mass of chloroprene resin with 3 to 10 parts by mass of the powder, and subjecting the mixture to a Mooney scorch test at 125°C in accordance with JIS K 6300-1:2013, "Unvulcanized Rubber—Physical Properties—Part 1: Determination of Viscosity and Scorch Time Using a Mooney Viscometer." This test may hereinafter be referred to as the "125°C Mooney Scorch Test." In the 125°C Mooney Scorch Test, the powder preferably has a t35 of 27 minutes or more, more preferably 29 minutes or more, and even more preferably 31 minutes or more. Furthermore, in the 125°C Mooney Scorch Test, the powder preferably has a t35 of 38 minutes or less, more preferably 37 minutes or less, and even more preferably 36 minutes or less. This ensures that when the powder is used as a rubber vulcanizing agent, the resulting rubber composition exhibits excellent storage stability and / or processing stability. It should be noted that "t35" means the scorch time (minutes) at which the Mooney reading rises 35M from the minimum viscosity: Vm. In the 125°C Mooney scorch test, it is preferable to use a sulfur-modified chloroprene resin.

[0023] The powder can be prepared by mixing 100 parts by mass of chloroprene resin with 3 to 10 parts by mass of the powder and subjecting the mixture to a Mooney scorch test at 153°C in accordance with JIS K 6300-1:2013. Hereinafter, this test may be referred to as the "153°C Mooney scorch test." In the 153°C Mooney scorch test, the powder preferably has a t10 of 3.1 minutes or more, more preferably 3.3 minutes or more, and even more preferably 3.4 minutes or more. Furthermore, in the 153°C Mooney scorch test, the powder preferably has a t10 of 4.2 minutes or less, more preferably 4.1 minutes or less, and even more preferably 4.0 minutes or less. This ensures that when the powder is used as a rubber vulcanizing agent, the rubber composition exhibits excellent curability. Note that "t10" refers to the scorch time (minutes) at which the Mooney reading rises by 10M above the minimum viscosity (Vm).

[0024] In the 153°C Mooney scorch test, the chloroprene resin preferably has the same properties as in the 125°C Mooney scorch test.

[0025] The particle size of the powder can be any particle size, and the preferred range varies depending on the application. For example, when the powder is used as a rubber vulcanizing agent, the powder preferably has a D50 of 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.6 μm or more. Also, when the powder is used as a rubber vulcanizing agent, the powder preferably has a D50 of 100 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less.

[0026] In this specification, D50 means the 50% particle size on a volume basis, and can be measured by a laser diffraction method. An example of an instrument used in the laser diffraction method is the laser diffraction scattering particle size distribution analyzer LMS-2000e manufactured by Seishin Enterprises.

[0027] The powder may have any BET specific surface area, and the preferred range may vary depending on the application. For example, when the powder is used as a vulcanizing agent for rubber, the powder preferably has a BET specific surface area of ​​10 m 2 / g or more, more preferably 15m 2 / g or more, and more preferably 20m 2 For example, when the powder is used as a vulcanizing agent for rubber, the powder preferably has a BET specific surface area of ​​300 m 2 / g or less, more preferably 280m 2 / g or less, and more preferably 250m 2 The BET specific surface area is measured, for example, by a high-speed specific surface area / pore distribution measuring device NOVA2000 manufactured by Yuasa Ionics Co., Ltd.

[0028] The powder according to the present disclosure does not need to be surface-treated. Alternatively, the powder according to the present disclosure may have particle surfaces treated with a surface treatment agent, for example, to improve dispersibility in the rubber raw material. Examples of the surface treatment agent include at least one of anionic surfactants, cationic surfactants, phosphate ester treatment agents, silane coupling agents, titanate coupling agents, aluminum coupling agents, silicone treatment agents, silicic acid, and water glass. Particularly preferred surface treatment agents are one or more selected from the group consisting of oleic acid, stearic acid, octanoic acid, and octylic acid. The amount of the surface treatment agent is 0.01 to 20% by mass, and preferably 0.1 to 15% by mass, based on the powder.

[0029] The surface treatment with the surface treatment agent can be carried out, for example, by charging the powder into a Henshiel mixer, and while stirring the powder at high speed, adding dropwise the surface treatment agent either as is or diluted with a solvent, and mixing the powder and the surface treatment agent.

[0030] The rubber vulcanizing agent according to the present disclosure includes the powder, in which zinc oxide is exposed on the outside of magnesium oxide, and therefore, when used as a rubber vulcanizing agent, the zinc oxide exposed on the outside of magnesium oxide can promote initial vulcanization.

[0031] The rubber composition according to the present disclosure includes the rubber vulcanizing agent and a rubber raw material. Examples of the rubber raw material include synthetic rubber raw materials. Examples of the synthetic rubber include acrylic rubber, ethylene propylene rubber (EPDM), butyl rubber, isoprene rubber, styrene butadiene rubber (SBR), nitrile rubber (NBR), and halogen-containing rubber. Examples of the halogen-containing rubber include at least one of chlorosulfonated polyethylene, fluororubber, brominated butyl rubber, and epichlorohydrin rubber.

[0032] In the rubber composition, the ratio of the rubber raw material to the rubber vulcanizing agent may vary depending on the type of rubber to be formed. The rubber vulcanizing agent is added in an amount of, for example, 0.001 to 20 parts by mass, preferably 0.01 to 10 parts by mass, per 100 parts by mass of the rubber raw material.

[0033] The rubber composition may further contain other additives in addition to the rubber vulcanizing agent. Examples of the additives include antioxidants, ultraviolet absorbers, antistatic agents, pigments, lubricants, crosslinking agents, vinyl chloride heat stabilizers, foaming agents, plasticizers, and fillers. Examples of the vinyl chloride heat stabilizers include at least one of organic zinc salts, β-diketones, organotins, phosphites, and partial esters of polyhydric alcohols.

[0034] The rubber vulcanizing agent according to the present disclosure is capable of vulcanizing raw rubber materials without adding other vulcanizing agents and / or vulcanization accelerators, but may further contain other vulcanizing agents and / or other vulcanization accelerators.

[0035] The mixing of the rubber raw material and the rubber vulcanizing agent is not particularly limited as long as they can be mixed. The mixing can be carried out using, for example, at least one of a single-screw extruder, a twin-screw extruder, a roll, and a Banbury mixer. The rubber composition can be molded by, for example, at least one of injection molding, extrusion molding, blow molding, press molding, rotational molding, calendar molding, sheet forming molding, transfer molding, lamination molding, and vacuum molding.

[0036] The powder according to the present disclosure has the same functions as conventional magnesium oxide, and is therefore useful in the above-mentioned rubber vulcanizing agent applications. In addition, the powder according to the present disclosure can be used in applications where magnesium oxide is used, such as at least one of an acid acceptor for resins, an acid acceptor for rubber, an acid neutralizer, a thickener for FRP, a heat stabilizer, a deodorizer, a light resistance improver, and a resin curing agent.

[0037] The method for producing a composite metal oxide powder according to the present disclosure includes a precipitation step, an aging step, a pulverization step, and a calcination step. In the precipitation step, a water-soluble magnesium salt and an alkali are mixed to obtain a precipitate. The precipitate contains magnesium hydroxide. Examples of the water-soluble magnesium salt include, but are not limited to, at least one of magnesium chloride, magnesium nitrate, magnesium acetate, and magnesium sulfate. From the viewpoint of suppressing aggregation of primary particles, the water-soluble magnesium salt is preferably magnesium chloride, magnesium nitrate, or magnesium acetate.

[0038] Examples of the alkali include hydroxides of alkali metals and hydroxides of alkaline earth metals. Examples of the alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Examples of the alkaline earth metal hydroxides include calcium hydroxide.

[0039] The alkali can be added in an amount appropriate for the water-soluble magnesium salt and the water-soluble zinc salt added in the aging step described below to form magnesium hydroxide and zinc hydroxide. The amount of alkali calculated to completely form magnesium hydroxide and zinc hydroxide from the water-soluble magnesium salt and water-soluble zinc salt is defined as 100 mol % (1.0 equivalent). In this case, the alkali is preferably added in an amount of 80 mol % (0.8 equivalent) or more, more preferably 90 mol % (0.9 equivalent) or more, and even more preferably 95 mol % (0.95 equivalent) or more. The alkali may be added in an amount of 100 mol % (1.0 equivalent) or more, but from the viewpoint of facilitating washing of at least one of the precipitate, the mixture, and the aged product, it is preferably added in an amount of 100 mol % (1.0 equivalent) or less.

[0040] In the aging step, the precipitate is mixed with a water-soluble zinc salt and aged to obtain an aged product. Examples of the water-soluble zinc salt include zinc chloride and / or zinc nitrate. The ratio of the precipitate to the water-soluble zinc salt can be appropriately adjusted according to the preferred molar ratio of Mg and Zn in the composite metal oxide. For example, when the composite metal oxide contains Mg,1-x Zn x When the precipitate has a chemical composition of 0, the precipitate can be mixed with a water-soluble zinc salt in a molar ratio of Mg:Zn of (1-x):x.

[0041] In the aging step, after mixing the precipitate with the water-soluble zinc, the mixture may be washed with, for example, deionized water, filtered, and then resuspended in, for example, water and / or an organic solvent, as needed, before aging. This allows impurities such as alkali metals and / or alkaline earth metals to be removed. For example, a homogenizer may be used for the resuspension.

[0042] In the aging step, the mixture is aged to form an aged product. The aging temperature is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 48°C or higher. The aging temperature is preferably 200°C or lower, more preferably lower than 100°C, and even more preferably 95°C or lower. This makes it easier to obtain the composite metal oxide powder. When the aging temperature is 100°C or higher, the aging step can be carried out under high pressure, for example, using an autoclave.

[0043] The aging temperature in the aging step is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more. The aging temperature is preferably 10 hours or less, more preferably 8 hours or less, and even more preferably 6 hours or less. The aged product can be dehydrated, filtered, and / or dried as necessary.

[0044] In the grinding step, the aged product is ground to form a ground aged product. The grinding of the aged product can be carried out using grinders known in the art. Examples of grinders include at least one of a jaw crusher, a gyratory crusher, a cone crusher, an impact crusher, a roll crusher, a cutter mill, a stamp mill, a ring mill, a roller mill, a jet mill, a hammer mill, a pin mill, a rotary mill, a vibratory mill, a planetary mill, and a ball mill.

[0045] In the calcination step, the pulverized aged product is calcined to obtain a composite metal oxide powder. Calcination of the aged product can be carried out by a method known in the art. Calcination of the aged product can be carried out at a temperature of preferably 300°C or higher, and more preferably 350°C or higher. Calcination of the coprecipitate can be carried out at a temperature of preferably 600°C or lower, and more preferably 550°C or lower. Calcination of the coprecipitate can be carried out for a time period of preferably 0.1 hour or longer, more preferably 0.5 hour or longer, and preferably 10 hours or shorter, and more preferably 6 hours or shorter.

[0046] The present disclosure will be described below using examples, but the present disclosure is not limited to these examples. [Example 1] 0.84 L of a magnesium chloride solution having a magnesium concentration of 1.0 mol / L was added to a reaction vessel. While stirring the magnesium chloride solution, sodium hydroxide having a sodium concentration of 2.0 mol / L was added to the reaction vessel so that the amount was 0.95 equivalents of magnesium, thereby obtaining Precipitate No. 1. Precipitate No. 1 was washed with deionized water, filtered, and then 2.97 L of deionized water was added and resuspended using a homogenizer, thereby obtaining Solution No. 1 of resuspended precipitate.

[0047] The resuspended precipitate, Solution No. 1, was placed in a container and stirred continuously while maintaining the temperature at 30°C. 0.16 L of a zinc chloride solution with a zinc concentration of 1.0 mol / L was added dropwise to the container over 30 minutes to obtain Mixture No. 1. Mixture No. 1 was aged at 80°C for 4 hours, filtered, dried, and pulverized in a ball mill, and then calcined at 400°C for 1 hour to obtain Composite Metal Oxide Powder No. 1.

[0048] The chemical composition of composite metal oxide powder No. 1 is Mg 0.8 Zn 0.2 The D50 of composite metal oxide powder No. 1 was 24.35 μm. The BET specific surface area of ​​composite metal oxide powder No. 1 was 128 m. 2 / g. Powder X-ray diffraction (XRD) data for composite metal oxide powder No. 1 is shown in Figure 1, along with powder X-ray diffraction (XRD) data for a commercially available product containing magnesium oxide single crystals. The commercially available product was Kyowamag 150 manufactured by Kyowa Chemical Industry Co., Ltd. In Figure 1, the peak corresponding to the (200) plane appears at approximately 42.9°, and the peak corresponding to the (220) plane appears at approximately 61.2°.

[0049] Comparative Example 1 Zinc oxide (Zinc Oxide Type 2, manufactured by Seido Chemical Industry Co., Ltd.) and magnesium oxide (Kyowamag 150, manufactured by Kyowa Chemical Industry Co., Ltd.) were mixed at a mass ratio of zinc oxide:magnesium oxide of 1:4 to form Powder No. 2.

[0050] [Comparative Examples 2 and 3] Powder No. 3 and Powder No. 4 were prepared in the same manner as in Comparative Example 1, except that the amount of zinc oxide was changed as shown in Table 1.

[0051] Comparative Example 4 Composite metal oxide powder No. 5 was produced in accordance with Example 1 of Patent Document 1. The specific production method is as follows: 3.0 L of a mixed solution of magnesium chloride and zinc chloride (magnesium concentration: 0.96 mol / L, zinc concentration: 0.05 mol / L) was charged into a reaction vessel. While stirring the mixed solution, 2.0 mol / L of sodium hydroxide was charged into the reaction vessel in an amount of 0.95 equivalents, the total equivalent of magnesium and zinc, to obtain coprecipitate No. 1. Coprecipitate No. 1 was washed with deionized water, filtered, and then added with deionized water and resuspended using a homogenizer to obtain resuspended coprecipitate No. 1.

[0052] The resuspended coprecipitate No. 1 was aged in an autoclave at 175°C for 12 hours, filtered, dried, pulverized in a ball mill, and then calcined at 450°C for 1 hour to obtain composite metal oxide powder No. 5. The chemical composition of composite metal oxide powder No. 5 was Mg 0.95 Zn 0.05 The D50 of composite metal oxide powder No. 5 was 0.90 μm. The BET specific surface area of ​​composite metal oxide powder No. 5 was 142 m2 / g.

[0053]

[0054] Example 2 100 parts by mass of chloroprene resin (PS-40A, manufactured by Denka Co., Ltd.), 0.5 parts by mass of stearic acid, 30 parts by mass of carbon black, and 4.0 parts by mass of Powder No. 1 were kneaded in a roll mill to form Rubber Composition No. 1.

[0055] To assess the storage stability of Rubber Composition No. 1, Vm, t5, and t35 were measured according to the 125°C Mooney scorch test described herein. The results are shown in Table 2. Rubber Composition No. 1 was molded into a 2 mm thick sheet, press-vulcanized at 153°C for 30 minutes, and then allowed to stand at room temperature for 24 hours to form Sheet No. 1. The properties of Sheet No. 1 were measured according to JIS K6251, "Vulcanized Rubber and Thermoplastic Rubber - Determination of Tensile Properties." The results are shown in Table 2.

[0056] In the tensile properties, "Tb" means "tensile strength at break." "Eb" means "elongation at break." "Se" means "tensile stress at a given elongation." For example, Se100 means tensile stress at 100% elongation.

[0057] The heat resistance of Sheet No. 1 was measured in accordance with JIS K6257:2017, "Vulcanized rubber and thermoplastic rubber - Determination of heat aging characteristics." The heating conditions were 120°C and 72 hours. The results are shown in Table 2.

[0058] The Shore A hardness of Sheet No. 1 was measured in accordance with JIS K6253-3:2012, Vulcanized and thermoplastic rubbers - Determination of hardness - Part 3: Durometer hardness. The results are shown in Table 2. The compression set (CS) of Sheet No. 1 was measured in accordance with JIS K6262:2013, Vulcanized and thermoplastic rubbers - Determination of compression set at room temperature, high temperature, and low temperature. The test temperature was 120°C, and the test time was 72 hours. The results are shown in Table 2.

[0059] [Examples 3 and 4] Rubber compositions No. 2 and No. 3 and sheets No. 2 and No. 3 were formed according to Example 2, except that the amount of powder No. 1 was changed as shown in Table 2. Their properties are shown in Table 2.

[0060] Comparative Examples 5 to 7 Rubber compositions No. 4 to No. 6 and sheets No. 4 to No. 6 were formed in the same manner as in Example 2, except that powder No. 1 was replaced with powders No. 2 to 4 in the amounts shown in Table 2. The properties of these compositions are shown in Table 2.

[0061] Comparative Example 8 Rubber Composition No. 7 and Sheet No. 7 were formed in the same manner as in Example 2, except that Powder No. 1 was replaced with Powder No. 5 in the amounts shown in Table 2. The properties of these compositions are shown in Table 2.

[0062] Comparative Example 9 100 parts by mass of chloroprene resin (PS-40A, manufactured by Denka Company Ltd.), 0.5 parts by mass of stearic acid, 30 parts by mass of carbon black, 5 parts by mass of zinc oxide (Zinc Oxide Type 2, manufactured by Seido Chemical Industry Co., Ltd.), and 4 parts by mass of magnesium oxide (Kyowamag 150, manufactured by Kyowa Chemical Industry Co., Ltd.) were kneaded using a roll mill to obtain rubber composition No. 8. Sheet No. 8 was formed from rubber composition No. 8 in the same manner as in Example 2. The properties of rubber composition No. 8 and sheet No. 8 are shown in Table 2.

[0063]

Claims

1. A powder of a composite metal oxide containing magnesium oxide and zinc oxide, In XRD, it has a peak of the zinc oxide and a peak of the magnesium oxide, The peak value of the magnesium oxide has a diffraction angle shift within a range of ±0.05° compared to the peak value of a magnesium oxide single crystal.

1. A composite metal oxide powder comprising:

2. The composite metal oxide has the following formula (1): Mg 1-x Zn x O of formula (1) In formula (1), x satisfies 0.02≦x<0.

5.

2. The powder of claim 1, wherein:

3. The powder according to claim 2 , wherein x satisfies 0.15≦x≦0.

25.

4. The powder according to claim 1, wherein when 100 parts by mass of a chloroprene resin and 3 to 10 parts by mass of the powder are mixed and subjected to a Mooney scorch test at 125°C in accordance with JIS K 6300-1:2013, the powder has a t35 of 27 minutes or more and 38 minutes or less.

5. The powder according to claim 4, wherein when 100 parts by mass of a chloroprene resin and 3 to 10 parts by mass of the powder are mixed and subjected to a Mooney scorch test at 153°C in accordance with JIS K 6300-1:2013, the powder has a t10 of 3.1 minutes or more and 4.0 minutes or less.

6. A vulcanizing agent for rubber, comprising the powder according to any one of claims 1 to 5.

7. A rubber composition comprising the rubber vulcanizing agent according to claim 6 and a rubber raw material.

8. a precipitation step of mixing a water-soluble magnesium salt with an alkali to obtain a precipitate; an aging step of mixing the precipitate with a water-soluble zinc salt and aging the mixture to obtain a aged product; a grinding step of grinding the aged product; a calcination step of calcining the pulverized aged product to obtain a composite metal oxide powder; A method for producing a powder of a composite metal oxide, comprising: