Glass bead aggregates

Abstract

The object of the present invention is to 3 The present invention provides a glass bead aggregate having both a low apparent density of 1000 or less and excellent compression resistance. The present invention provides an aggregate of glass beads having a glass composition that satisfies the following conditions: 48 mass%≦SiO2≦70 mass%, 5 mass%≦B2O3≦20 mass%, 1 mass%≦Al2O3≦10 mass%, 0.5 mass%≦CaO≦12 mass%, and 5 mass%≦(Li2O+Na2O+K2O)≦20 mass%, and has an apparent density of 1.20 to 1.80 g / cm 3 It is a collection of glass beads.

Description

[Technical Field]

[0001] The present invention relates to a glass bead aggregate. [Background technology]

[0002] Dispersing a glass filler in a resin matrix can improve the strength and dimensional accuracy of a resin molded body. Known fillers for this purpose include glass fillers in the form of flakes, fibers, powders, beads, and the like.

[0003] As the glass filler, for example, the composition of the glass contains iron oxide, and satisfies 0.005 mass%≦FeO≦0.30 mass%, 0.01 mass%≦T-Fe2O3≦0.80 mass% (where T-Fe2O3 is the total iron oxide converted to Fe2O3), and the iron oxide in the composition accounts for 0.005 mass%≦FeO≦0.30 mass%, 0.01 mass%≦T-Fe2O3≦0.80 mass%, and 2+ The ratio (by mass) of Fe 2+ / (Fe 2+ +Fe 3+ ) is 0.15 or more and 1.00 or less is known (see, for example, Patent Document 1).

[0004] Also known are inorganic oxide hollow microparticles formed from aluminum oxide, silicon oxide, and one or more oxides selected from alkali metal oxides, Group 2 element oxides, Group 4 element oxides, and boron oxide, which have a shell that defines a hollow chamber, the shell is porous, and has an average circularity of 0.85 or more, a shell thickness of 50 nm to 1 μm, and an average particle diameter of 0.5 to 20 μm (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 088488 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-23095 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors have found that the glass filler described in Patent Document 1 is solid and has a high apparent density. When dispersed in a resin matrix, the resin in which the glass filler is dispersed has a large mass per unit volume. On the other hand, the hollow microparticles described in Patent Document 2 are hollow, and therefore have a low apparent density. However, the hollow microparticles shown in the examples of Patent Document 2 have a maximum bulk density of 0.219 and a similarly low apparent density. This means that the shells that define the hollow chambers are thin, resulting in low mechanical strength. In conventional techniques, when a low apparent density is desired for a glass bead aggregate, compression resistance is reduced, making it difficult to achieve a good balance between low apparent density and compression resistance.

[0007] Therefore, the present invention is 1.80 g / cm 3 The main object of the present invention is to provide a glass bead aggregate having both a low apparent density of 1000 kJ / cm or less and excellent compression resistance. [Means for solving the problem]

[0008] The present inventors have conducted studies to solve the above problems and have found that a production method is adopted in which raw glass particles having a specific glass composition are mixed with carbon and supplied toward a combustion flame of a combustible gas to melt or soften the raw glass particles and generate spherical particles by surface tension, thereby achieving a glass density of 1.20 to 1.80 g / cm. 3 The inventors have found that the above-described manufacturing method can provide an aggregate of glass beads having excellent compression resistance despite a low apparent density of 1.20 to 1.80 g / cm. Specifically, the above-described manufacturing method provides a glass composition that satisfies the following conditions: 48% by mass ≦ ​​SiO ≦ 70% by mass, 5% by mass ≦ ​​B 2 O 3 ≦ 20% by mass, 1% by mass ≦ ​​Al 2 O 3 ≦ 10% by mass, 0.5% by mass ≦ ​​CaO ≦ 12% by mass, and 5% by mass ≦ ​​(Li 2 O + Na 2 O + K 2 O) ≦ 20% by mass. 3The present invention was completed through further investigations based on these findings.

[0009] That is, the present invention provides the following aspects. Item 1. 48 mass%≦SiO2≦70 mass%, 5 mass%≦B2O3≦20 mass%, 1 mass%≦Al2O3≦10 mass%, 0.5 mass%≦CaO≦12 mass%, and 5% by mass≦(Li2O+Na2O+K2O)≦20% by mass A collection of glass beads having a glass composition that satisfies the following: Apparent density 1.20 to 1.80 g / cm 3 It is a collection of glass beads. Item 2. A glass bead assembly according to Item 1, wherein the median diameter of the glass beads is 5 to 50 μm. Item 3. A method for producing a glass bead aggregate according to item 1 or 2, comprising: A first step of preparing a mixture of raw glass particles and carbon powder, the mixture having a glass composition satisfying 56 mass%≦SiO2≦68 mass%, 7 mass%≦B2O3≦15 mass%, 1 mass%≦Al2O3≦8 mass%, 0.5 mass%≦CaO≦10 mass%, and 6 mass%≦(Li2O+Na2O+K2O)≦18 mass%, and A second step of supplying the mixture prepared in the first step into a combustion flame of a combustible gas to spheroidize the raw glass particles. A method for producing a glass bead aggregate, comprising: Item 4. The production method according to Item 3, wherein the flammable gas is at least one alkane having 1 to 4 carbon atoms. [Effects of the Invention]

[0010] The glass bead aggregate of the present invention has an apparent density of 1.20 to 1.80 g / cm 3 and has excellent compression resistance, and can have a good balance between low apparent density and excellent compression resistance. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a spheronizing device used to produce glass bead aggregates in Examples 1 to 12 and Comparative Examples 1 to 8. [Figure 2] 1 is a microscope image of the glass bead aggregate obtained in Example 1. [Figure 3] 1 is a microscope image of the glass bead aggregate obtained in Example 2. [Figure 4] 1 is a microscope image of the glass bead aggregate obtained in Example 3. [Figure 5] 1 is a microscope image of the glass bead aggregate obtained in Example 4. [Figure 6] 1 is a microscope image of the glass bead aggregate obtained in Example 5. [Figure 7] 1 is a microscope image of the glass bead aggregate obtained in Example 6. [Figure 8] 1 is a microscope image of the glass bead aggregate obtained in Example 7. [Figure 9] 1 is a microscope image of the glass bead aggregate obtained in Example 8. [Figure 10] 1 is a microscope image of the glass bead aggregate obtained in Example 9. [Figure 11] 1 is a microscope image of the glass bead aggregate obtained in Example 10. [Figure 12] 1 is a microscope image of the glass bead aggregate obtained in Example 11. [Figure 13] 1 is a microscope image of the glass bead aggregate obtained in Example 12. DETAILED DESCRIPTION OF THE INVENTION

[0012] The glass bead aggregate of the present invention is an aggregate of glass beads having a glass composition that satisfies 48% by mass≦SiO2≦70% by mass, 5% by mass≦B2O3≦20% by mass, 1% by mass≦Al2O3≦10% by mass, 0.5% by mass≦CaO≦12% by mass, and 5% by mass≦(Li2O+Na2O+K2O)≦20% by mass, and has an apparent density of 1.20 to 1.80 g / cm 3 The glass bead aggregate of the present invention will be described in detail below.

[0013] 1. Glass composition The glass composition of the glass beads constituting the glass bead aggregate of the present invention satisfies the following conditions: 48% by mass≦SiO2≦70% by mass, 5% by mass≦B2O3≦20% by mass, 1% by mass≦Al2O3≦10% by mass, 0.5% by mass≦CaO≦12% by mass, and 5% by mass≦(Li2O+Na2O+K2O)≦20% by mass. Note that in the present invention, the glass composition is a composition (content of each component) determined in accordance with quantitative analysis specified in JIS K 0119:2008 "General rules for fluorescent X-ray analysis."

[0014] [SiO2] In the glass beads constituting the glass bead aggregate of the present invention, SiO2 is a component that plays a role in forming a glass network structure. The SiO2 content in the glass beads may be 48 to 70 mass %, preferably 50 to 68 mass %. By ensuring that the SiO2 content satisfies the above range, the glass beads can be provided with excellent compression resistance, while improving the moldability of the glass beads and the uniformity of the glass composition. In addition, the SiO2 content is 1.20 to 1.80 g / cm 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the SiO2 content in the glass beads is more preferably 54 to 65 mass %, and even more preferably 59 to 65 mass %.

[0015] [B2O3] In the glass beads constituting the glass bead aggregate of the present invention, B2O3 is a component that plays a role in forming the glass network structure and is also a component that adjusts the devitrification temperature and viscosity during glass formation. The B2O3 content in the glass beads may be 5 to 20 mass %, preferably 6 to 18 mass %. In addition, the content of B2O3 is 1.20 to 1.80 g / cm 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the content of B2O3 in the glass beads is more preferably 7 to 17 mass %, and even more preferably 8 to 14 mass %.

[0016] [Al2O3] In the glass beads constituting the glass bead aggregate of the present invention, Al2O3 is a component that plays a role in forming the glass network structure, and is also a component that adjusts the devitrification temperature and viscosity during glass formation while maintaining heat resistance. The Al2O3 content in the glass beads may be 1 to 10 mass%, preferably 1 to 8 mass%. Also, the content of Al2O3 is 1.20 to 1.80 g / cm 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the Al2O3 content in the glass beads is more preferably 1.5 to 8 mass %.

[0017] [CaO] In the glass beads constituting the glass bead aggregate of the present invention, CaO is a component that adjusts the devitrification temperature and viscosity during glass formation. The CaO content in the glass beads may be 0.5 to 12 mass%, preferably 0.8 to 8 mass%. In addition, the CaO content is 1.20 to 1.80 g / cm. 3 From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the CaO content in the glass beads is more preferably 0.8 to 7 mass %.

[0018] [Li2O+Na2O+K2O] In the glass beads constituting the glass bead aggregate of the present invention, Li2O, Na2O, and K2O are components that adjust the devitrification temperature and viscosity during glass formation. The content of the alkali metal oxides in the glass beads (the total content of Li2O, Na2O, and K2O) may be 5 to 20 mass%, preferably 5 to 18 mass%. In addition, the content of the alkali metal oxides in the glass beads is 1.20 to 1.80 g / cm 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the content of the alkali metal oxides in the glass beads (the total content of LiO, NaO, and KO) is more preferably 7 to 17 mass %.

[0019] [Na2O] In the glass beads constituting the glass bead aggregate of the present invention, the NaO content may be within a range that satisfies the content of the alkali metal oxides, for example, 3 to 20 mass%, preferably 4 to 17 mass%. 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the Na2O content in the glass beads is more preferably 5 to 16% by mass.

[0020] [K2O] In the glass beads constituting the glass bead aggregate of the present invention, the content of K2O may be within a range that satisfies the content of the alkali metal oxide, for example, 0 to 2 mass %, preferably 0.5 to 2 mass %.

[0021] [LiO] In the glass beads constituting the glass bead aggregate of the present invention, the Li2O content may be within a range that satisfies the alkali metal oxide content, and may be, for example, 0 to 0.1 mass %, more preferably 0 mass %.

[0022] [MgO] The glass beads constituting the glass bead aggregate of the present invention may contain MgO. The MgO content in the glass beads is, for example, 0 to 7 mass %, preferably 0 to 4 mass %, and more preferably 0 to 3 mass %.

[0023] [CO2] The glass beads constituting the glass bead aggregate of the present invention may contain CO. The CO content in the glass beads is, for example, 0 to 7 mass%, preferably 1 to 6 mass%, and more preferably 2 to 6 mass%.

[0024] [SO3] The glass beads constituting the glass bead aggregate of the present invention may contain SO3. The SO3 content in the glass beads is, for example, 0 to 0.5 mass%, preferably 0 to 0.3 mass%, and more preferably 0 to 0.2 mass%.

[0025] [Fe2O3] The glass beads constituting the glass bead aggregate of the present invention may contain Fe2O3. The content of Fe2O3 in the glass beads is, for example, 0 to 0.5% by mass, preferably 0 to 0.3% by mass. In addition, the content of Fe2O3 in the glass beads is 1.20 to 1.80 g / cm 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the content of Fe2O3 in the glass beads is more preferably 0.1 to 0.2 mass %.

[0026] [P2O5] The glass beads constituting the glass bead aggregate of the present invention may contain P2O5. The content of P2O5 in the glass beads is, for example, 0 to 0.3% by mass, preferably 0 to 0.2% by mass. In addition, the content of P2O5 in the glass beads is 1.20 to 1.80 g / cm 3From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the content of P2O5 in the glass beads is more preferably 0 to 0.1% by mass.

[0027] [BaO] The glass beads constituting the glass bead aggregate of the present invention may contain BaO. The content of BaO in the glass beads is, for example, 0 to 1.5% by mass, preferably 0.1 to 1.3% by mass. In addition, the content of BaO in the glass beads is 1.20 to 1.80 g / cm. 3 From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the content of BaO in the glass beads is more preferably 0.1 to 1.2 mass %.

[0028] [ZnO] The glass beads constituting the glass bead aggregate of the present invention may contain ZnO. The ZnO content in the glass beads is, for example, 0 to 0.3 mass%, preferably 0 to 0.2 mass%. Also, the ZnO content is 1.20 to 1.80 g / cm. 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the ZnO content in the glass beads is more preferably 0 to 0.1% by mass.

[0029] [Other ingredients] Furthermore, the glass beads constituting the glass bead aggregate of the present invention may contain other components, such as F, Cl, TiO2, MnO, Co2O3, NiO, Rb2O, SrO, ZrO2, SnO2, Sb2O3, I, CeO2, WO3, Cr2O3, Ga2O3, As2O3, Y2O3, Ag2O, Nb2O5, and Bi2O3, in addition to the above components. These components may be derived as unavoidable impurities from, for example, glass raw materials, glass composition manufacturing equipment, and glass composition molding equipment. In the glass beads constituting the glass bead aggregate of the present invention, the content of each of these other components is, for example, less than 1% by mass, preferably 0 to 0.1% by mass. The total amount of these other components is, for example, 0 to 1% by mass, preferably 0 to 0.5% by mass.

[0030] Specific embodiments of the glass composition of the glass beads constituting the glass bead aggregate of the present invention include glass composition A and glass composition B shown below.

[0031] 1-1.Glass composition A The following describes glass composition A. Glass composition A, which is one aspect of the glass composition of the glass beads that make up the glass bead aggregate of the present invention, can have a glass composition that satisfies 48% by mass≦SiO2≦63% by mass, 5% by mass≦B2O3≦20% by mass, 1% by mass≦Al2O3≦5% by mass, 3% by mass≦CaO≦12% by mass, and 10% by mass≦(Li2O+Na2O+K2O)≦20% by mass.

[0032] [SiO2] The SiO2 content in the glass composition A may be 48 to 63 mass%, preferably 50 to 63 mass%. 3 From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the content of SiO2 in the glass composition A is more preferably 54 to 61 mass %.

[0033] [B2O3] The content of B2O3 in the glass composition A may be 5 to 20 mass%, preferably 7 to 18 mass%. 3 From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the content of B2O3 in the glass composition A is more preferably 8 to 16 mass %.

[0034] [Al2O3] The content of Al2O3 in the glass composition A may be 1 to 5 mass%, preferably 1 to 3 mass%. 3 From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the content of Al2O3 in the glass composition A is more preferably 1.5 to 3.0 mass %.

[0035] [CaO] The CaO content in the glass composition A may be 3 to 12 mass %, preferably 4 to 10 mass %. 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the CaO content in the glass composition A is more preferably 5 to 8 mass %.

[0036] [Li2O+Na2O+K2O] The total content of Li2O, Na2O, and K2O in the glass composition A may be 10 to 20 mass%. 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the total content of Li2O, Na2O, and K2O in the glass composition A is preferably 12 to 18 mass %.

[0037] [Na2O] The content of Na2O in the glass composition A is, for example, 10 to 20 mass %, and preferably 13 to 17 mass %.

[0038] [K2O] The content of K2O in the glass composition A is, for example, 0 to 2 mass %, and preferably 0.1 to 1 mass %.

[0039] [LiO] The content of Li2O in the glass composition A is, for example, 0 to 0.1% by mass, and preferably 0% by mass.

[0040] [MgO] The content of MgO in the glass composition A is, for example, 1 to 7 mass %, preferably 1 to 4 mass %, and more preferably 1 to 3 mass %.

[0041] [CO2] The content of CO2 in the glass composition A is, for example, 0 to 7 mass %, preferably 1 to 6 mass %, and more preferably 2 to 6 mass %.

[0042] [SO3] The content of SO3 in the glass composition A is, for example, 0 to 0.5 mass %, preferably 0 to 0.3 mass %, and more preferably 0.1 to 0.2 mass %.

[0043] [Fe2O3] The content of Fe2O3 in the glass composition A is, for example, 0 to 0.5 mass %, preferably 0 to 0.3 mass %, and more preferably 0.1 to 0.2 mass %.

[0044] [P2O5] The content of P2O5 in the glass composition A is, for example, 0 to 0.3 mass%, preferably 0 to 0.2 mass%. 3 From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the content of P2O5 in the glass composition A is more preferably 0 to 0.1 mass %.

[0045] [BaO] The content of BaO in the glass composition A is, for example, 0 to 0.5 mass %, and preferably 0 to 0.1 mass %.

[0046] [ZnO] The content of ZnO in the glass composition A is, for example, 0 to 0.3 mass %, and preferably 0 to 0.2 mass %.

[0047] [Other ingredients] Furthermore, in addition to the above components, the glass composition A may contain other components such as F, Cl, TiO2, MnO, Co2O3, NiO, Rb2O, SrO, ZrO2, SnO2, Sb2O3, I, CeO2, WO3, Cr2O3, Ga2O3, As2O3, Y2O3, Ag2O, Nb2O5, and Bi2O3. These components may be unavoidable impurities, for example, derived from glass raw materials, glass composition manufacturing equipment, and glass composition molding equipment. In the glass beads constituting the glass bead aggregate of the present invention, the content of each of these other components is, for example, less than 1% by mass, preferably 0 to 0.1% by mass. The total amount of these other components is, for example, 0 to 1% by mass, preferably 0 to 0.5% by mass.

[0048] 1-2.Glass composition B The following describes glass composition B. Glass composition B, which is one aspect of the glass composition of the glass beads that make up the glass bead aggregate of the present invention, can have a glass composition that satisfies 60% by mass≦SiO2≦70% by mass, 5% by mass≦B2O3≦20% by mass, 5% by mass≦Al2O3≦10% by mass, 0.5% by mass≦CaO≦3% by mass, and 5% by mass≦(Li2O+Na2O+K2O)≦20% by mass.

[0049] [SiO2] The content of SiO2 in the glass composition B may be 60 to 70 mass%, preferably 63 to 68 mass%. 3From the viewpoint of suitably providing a lower apparent density within this apparent density range, the content of SiO2 in the glass composition B is more preferably 63 to 65 mass %.

[0050] [B2O3] The content of B2O3 in the glass composition B may be 5 to 20 mass %, preferably 10 to 15 mass %. 3 From the viewpoint of easily and suitably providing a lower apparent density within this apparent density range, the content of B2O3 in the glass composition B is more preferably 13 to 15 mass %.

[0051] [Al2O3] The content of Al2O3 in the glass composition B may be 5 to 10 mass%, preferably 6 to 9 mass%. 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the content of Al2O3 in the glass composition B is more preferably 7 to 9 mass %.

[0052] [CaO] The CaO content in the glass composition B may be 0.5 to 3 mass %, preferably 0.5 to 2 mass %. 3 From the viewpoint of suitably providing a lower apparent density within this apparent density range, the CaO content in glass composition B is more preferably 0.5 to 1.5 mass %.

[0053] [Li2O+Na2O+K2O] The total content of Li2O, Na2O, and K2O in the glass composition B may be 5 to 10 mass%, and preferably 5 to 9 mass%. 3From the viewpoint of suitably providing a lower apparent density within this apparent density range, the total content of Li2O, Na2O, and K2O in the glass composition B is more preferably 6 to 8 mass %.

[0054] [Na2O] The content of Na2O in the glass composition B is preferably 3 to 10 mass %, more preferably 3 to 8 mass %.

[0055] [K2O] The content of K2O in the glass composition B is preferably 0 to 2 mass %, more preferably 1 to 2 mass %.

[0056] [LiO] The content of Li2O in the glass composition B is preferably 0 to 0.1% by mass, and more preferably 0% by mass.

[0057] [MgO] The content of MgO in the glass composition B is, for example, 0 to 1 mass %, preferably 0 to 0.5 mass %, and more preferably 0 to 0.1 mass %.

[0058] [CO2] The content of CO2 in the glass composition B is, for example, 0 to 7 mass %, preferably 1 to 6 mass %, and more preferably 2 to 6 mass %.

[0059] [SO3] The content of SO3 in the glass composition B is, for example, 0 to 0.5 mass %, preferably 0 to 0.3 mass %, and more preferably 0 to 0.1 mass %.

[0060] [Fe2O3] The content of Fe2O3 in the glass composition B is, for example, 0 to 0.5 mass %, preferably 0 to 0.3 mass %, and more preferably 0 to 0.1 mass %.

[0061] [P2O5] The content of P2O5 in the glass composition B is, for example, 0 to 0.3 mass %, preferably 0 to 0.2 mass %, and more preferably 0 to 0.1 mass %.

[0062] [BaO] The content of BaO in the glass composition B is, for example, 0.3 to 1.5 mass %, preferably 0.7 to 1.5 mass %, and more preferably 1.0 to 1.4 mass %.

[0063] [ZnO] The content of ZnO in the glass composition B is, for example, 0 to 0.3 mass %, preferably 0 to 0.1 mass %, and more preferably 0 mass %.

[0064] [Other ingredients] Furthermore, in addition to the above components, the glass composition B may contain other components such as F, Cl, TiO2, MnO, Co2O3, NiO, Rb2O, SrO, ZrO2, SnO2, Sb2O3, I, CeO2, WO3, Cr2O3, Ga2O3, As2O3, Y2O3, Ag2O, Nb2O5, and Bi2O3. These components may be unavoidable impurities, for example, derived from glass raw materials, glass composition manufacturing equipment, and glass composition molding equipment. In the glass beads constituting the glass bead aggregate of the present invention, the content of each of these other components is, for example, less than 1% by mass, preferably 0 to 0.1% by mass. The total amount of these other components is, for example, 0 to 1% by mass, preferably 0 to 0.5% by mass.

[0065] 2. Characteristics of glass bead aggregates The apparent density of the glass bead aggregate of the present invention is 1.20 to 1.80 g / cm 3 However, from the viewpoint of achieving a lower apparent density, it is preferably 1.20 to 1.69 g / cm 3 , more preferably 1.20 to 1.45 g / cm 3The glass bead aggregate of the present invention can have excellent compression resistance despite having such a low apparent density. In order to satisfy such an apparent density, the glass bead aggregate may be produced by the production method described below.

[0066] In the present invention, the apparent density of a glass bead aggregate is a value measured under the following measurement conditions. First, a measuring cylinder and distilled water are prepared. The mass of the measuring cylinder is measured after filling it with distilled water at 20°C up to the 50 ml mark. Next, 15 to 20 g of glass bead aggregates are placed in an empty measuring cylinder, and distilled water at 20°C is further added up to the 50 ml mark, and the mass of the glass bead aggregates and the measuring cylinder filled with 50 ml of water are measured. The apparent density of the glass bead aggregate is calculated according to the following formula.

number

[0067] The particle diameter of the glass beads constituting the glass bead aggregate of the present invention is not particularly limited, but from the viewpoint of easily and suitably providing the aforementioned apparent density, the median diameter of the glass beads is 5 to 50 μm, preferably 5 to 20 μm, more preferably 10 to 18 μm, and even more preferably 11 to 15 μm. In the present invention, the median diameter of the glass beads is determined by collecting 30,000 or more glass beads from the glass bead aggregate and measuring the volume-based median diameter (D) in accordance with the method (Coulter counter method) described in "Method for measuring particle size distribution - Electrical detection zone method" specified in JIS Z 8832:2010. 50 The particle size of the glass beads in the glass bead aggregate of the present invention correlates with the particle size of the raw material glass particles used in the manufacturing method described below, and therefore, in order to satisfy the median size, the particle size and particle size distribution of the raw material glass particles used in the manufacturing method described below may be appropriately adjusted.

[0068] D of the glass beads constituting the glass bead aggregate of the present invention 10There are no particular limitations on the D of the glass beads constituting the glass bead aggregate of the present invention, but examples thereof include 1 to 25 μm, preferably 1 to 10 μm, more preferably 2 to 9 μm, and even more preferably 3 to 8 μm. 25 There are no particular limitations on the D of the glass beads constituting the glass bead aggregate of the present invention, but examples thereof include 2 to 35 μm, preferably 5 to 15 μm, more preferably 6 to 13 μm, and even more preferably 5 to 12 μm. 75 There are no particular limitations on the D of the glass beads constituting the glass bead aggregate of the present invention, but examples thereof include 5 to 60 μm, preferably 8 to 35 μm, more preferably 15 to 35 μm, and even more preferably 16 to 23 μm. 90 There are no particular limitations on the D of the glass beads, but examples thereof include 10 to 85 μm, preferably 11 to 45 μm, more preferably 20 to 40 μm, and even more preferably 20 to 35 μm. 10 , D 25 , D 75 , and D 90 are particle sizes at which the cumulative percentages are 10%, 25%, 75%, and 90%, respectively, in the volume cumulative particle size distribution measured in the same manner as the median size.

[0069] The sphericity of the glass beads constituting the glass bead aggregate of the present invention is not particularly limited, but from the viewpoint of further improving compression resistance while favorably providing the aforementioned apparent density, it is 95% or more, preferably 99% or more. To satisfy such a sphericity, it is sufficient to sufficiently soften the raw glass particles in a suspended state and to spheroidize them using surface tension in the spheroidizing step of the manufacturing method described below.

[0070] In the present invention, the sphericity of glass beads is a value measured by the following method. First, 500 or more glass beads are randomly selected from a glass bead aggregate. Next, each glass bead is observed at a magnification of 2000x using a digital microscope. Rounded glass beads with a sphericity (D1 / D2) calculated from the minimum length D1 and the maximum length D2 of 0.83 or more and free of acute angles or fusion between glass beads are defined as spherical, and the number of spherical glass beads is counted. The sphericity of the glass bead aggregate is calculated according to the following formula:

number

[0071] In a preferred embodiment of the glass bead aggregate of the present invention, at least some of the glass beads constituting the aggregate contain bubbles. That is, a preferred embodiment of the glass bead aggregate of the present invention includes glass beads containing bubbles and glass beads not containing bubbles. Here, in the present invention, bubbles refer to voids observed inside glass beads when the glass beads are observed at a magnification of 2000 times using a digital microscope. The bubble generation rate of the glass beads constituting the glass bead aggregate of the present invention is, for example, 5 to 50%, preferably 10 to 40%, and more preferably 10 to 30%.

[0072] In the present invention, the bubble generation rate is a value measured by the following method. First, 500 or more glass beads are randomly selected from a collection of glass beads. Each glass bead is observed at a magnification of 2000 times using a digital microscope to check for the presence or absence of bubbles. Glass beads containing even one bubble are considered bubble-generating glass beads, and the bubble generation rate is calculated according to the following formula.

number

[0073] The glass bead aggregate of the present invention is characterized by having excellent compression resistance despite the aforementioned low apparent density. In one embodiment of the glass bead aggregate of the present invention, the sphericity after a compression test in which the glass bead aggregate is compressed with a force of 2100 N is 99% or more, preferably 99.5%.

[0074] In the present invention, the sphericity after the compression test is a value measured by the following method. First, a cylindrical container (20 mm in diameter, 50 mm in length) is filled with glass bead aggregates until they overflow, and the cylindrical container is struck 40 times on each side to ensure that the glass bead aggregates are packed in tightly without any gaps. The supernatant liquid that overflowed from the glass bead aggregates in the cylindrical container is then leveled off. The container containing the leveled glass bead aggregates is placed under the upper jig (cylindrical, 20 mm in diameter) of a compression tester, aligned with the center of the upper jig, and a compression test is performed with a load range of 2 kN and a test speed of 3.0 mm / min, starting from the point where the upper jig and the glass bead aggregate come into contact, until the glass bead aggregates in the cylindrical container reach 2100 N. The sphericity of the glass beads that make up the compressed glass bead aggregate is measured using the method described above.

[0075] The glass bead aggregate of the present invention is also characterized by excellent compression resistance and a small difference in the sphericity of the glass beads before and after the compression test. In one embodiment of the glass bead aggregate of the present invention, the difference between the sphericity before the compression test and the sphericity after the compression test (sphericity before the compression test - sphericity after the compression test) is 3% or less, preferably 2% or less, and more preferably 1% or less.

[0076] 3. Manufacturing method of glass bead aggregates The method for producing the glass bead aggregate of the present invention is not particularly limited as long as it can have the above-mentioned glass composition and apparent density, but a suitable example is a production method including the following first and second steps. First step: A preparation step of preparing a mixture of raw glass particles and carbon powder, the mixture having a glass composition satisfying 56 mass%≦SiO2≦68 mass%, 7 mass%≦B2O3≦15 mass%, 1 mass%≦Al2O3≦8 mass%, 0.5 mass%≦CaO≦10 mass%, and 6 mass%≦(Li2O+Na2O+K2O)≦18 mass%. Second step: A spheroidizing step in which the mixture is fed into a combustion flame of a combustible gas to spheroidize the raw glass particles.

[0077] The first and second steps will be described below.

[0078] [1st step] In the first step, a mixture of raw glass particles and carbon powder that satisfies the glass composition of the glass bead aggregate of the present invention is prepared.

[0079] The glass composition of the raw glass particles used in the first step may be any as long as it satisfies the following conditions: 56% by mass≦SiO≦68% by mass, 7% by mass≦B2O3≦15% by mass, 1% by mass≦Al2O3≦8% by mass, 0.5% by mass≦CaO≦10% by mass, and 6% by mass≦(Li2O+Na2O+K2O)≦18% by mass. For example, glass composition a or glass composition b described below can be suitably used.

[0080] More specifically, examples of raw glass particles include the following: 56 mass%≦SiO2≦68 mass%, 7 mass%≦B2O3≦15 mass%, 1% by mass ≦ ​​Al2O3 ≦ 8% by mass, 0.5 mass%≦CaO≦10 mass%, 6 mass%≦(Li2O+Na2O+K2O)≦18 mass%, 5% by mass ≦Na2O≦17% by mass, 0.5 mass%≦K2O≦2.5 mass%, 0 mass%≦Li2O≦0.1 mass%, 0 mass%≦MgO≦3 mass%, 2.5 mass%≦CO2≦3.5 mass%, 0 mass%≦SO3≦0.2 mass%, 0 mass%≦Fe2O3≦0.2 mass%, 0 mass%≦P2O5≦0.05 mass%, 0 mass%≦BaO≦1.5 mass%, and Raw glass particles having a glass composition that satisfies 0 mass%≦ZnO≦0.05 mass%.

[0081] Furthermore, when producing an aggregate of glass beads that satisfy the above-mentioned glass composition A, the following raw glass composition a can be given as a specific example of the raw glass particles to be used. (Raw glass composition a) 56 mass%≦SiO2≦63 mass%, 7 mass%≦B2O3≦11 mass%, 1% by mass ≦ ​​Al2O3 ≦ 4% by mass, 5 mass%≦CaO≦10 mass%, 13 mass%≦(Li2O+Na2O+K2O)≦18 mass%, 14 mass%≦Na2O≦17 mass%, 0.5 mass%≦K2O≦1 mass%, 0 mass%≦Li2O≦0.1 mass%, 2 mass%≦MgO≦3 mass%, 2.5 mass%≦CO2≦3.5 mass%, 0.1 mass%≦SO3≦0.2 mass%, 0.1 mass%≦Fe2O3≦0.2 mass%, 0 mass%≦P2O5≦0.05 mass%, 0 mass%≦BaO≦0.1 mass%, and Raw glass particles having a glass composition that satisfies 0 mass%≦ZnO≦0.05 mass%.

[0082] Furthermore, when producing an aggregate of glass beads that satisfy the above-mentioned glass composition B, the following raw glass composition b can be given as a specific example of the raw glass particles to be used. (Raw glass composition b) 63 mass%≦SiO2≦68 mass%, 11 mass%≦B2O3≦15 mass%, 4% by mass ≦ ​​Al2O3 ≦ 8% by mass, 0.5 mass%≦CaO≦5 mass%, 6 mass%≦(Li2O+Na2O+K2O)≦13 mass%, 5% by mass ≦Na2O≦8% by mass, 1 mass%≦K2O≦2.5 mass%, 0 mass%≦Li2O≦0.1 mass%, 0 mass%≦MgO≦0.1 mass%, 2.5 mass%≦CO2≦3.5 mass%, 0 mass%≦SO3≦0.1 mass%, 0 mass%≦Fe2O3≦0.1 mass%, 0 mass%≦P2O5≦0.05 mass%, 1% by mass≦BaO≦1.5% by mass, and Raw glass particles having a glass composition that satisfies 0 mass%≦ZnO≦0.05 mass%.

[0083] The shape of the raw glass particles is not particularly limited, and may be, for example, fibrous, scaly, non-spherical, spherical, etc. Furthermore, the size of the raw glass particles may be appropriately set according to the particle diameter of the glass beads constituting the glass bead aggregate of the present invention, taking into account that the raw glass particles form a glass bead aggregate at least partially having bubbles, and for example, the median diameter of the raw glass particles is 1 to 30 μm, preferably 2 to 15 μm. The median diameter of the raw glass particles is a value measured under the same conditions as the median diameter of the glass beads constituting the glass bead aggregate of the present invention described above.

[0084] The type of carbon powder used in the first step is not particularly limited, but examples include carbon black, acetylene black, and ketjen black. These carbon powders may be used alone or in combination of two or more. Among these carbon powders, carbon black is a preferred example. The size of the carbon powder is not particularly limited, as long as it is large enough to adhere to the raw glass particles. Examples include carbon powders with an average particle diameter of 20 to 300 nm, preferably 30 to 75 nm. In the present invention, the average particle diameter of the carbon powder is measured using a transmission electron microscope (TEM). Specifically, 1.0 ml of purified water and 0.001 g of carbon powder are placed in a 1.5 ml microtube and stirred with a vortex mixer. The supernatant is dropped onto a TEM grid (400 mesh Cu) and dried to prepare a sample for TEM observation. This sample is observed using a transmission electron microscope at a magnification of 600,000 times to obtain an image. The major axis (maximum length) and minor axis (minimum length) of 50 randomly selected carbon particles that do not overlap each other in the image are measured. The average of the measured major and minor axes is then taken as the particle diameter of the measured carbon particles, and the sum of the particle diameters is divided by the number of measured carbon particles (total number of measurement data: 50) to calculate the average particle diameter of the carbon powder.

[0085] The mixing ratio of the raw glass particles and the carbon powder is not particularly limited, but for example, the carbon powder may be 0.1 to 3 parts by mass, preferably 0.2 to 1.5 parts by mass, and more preferably 0.5 to 1.0 parts by mass per 100 parts by mass of the raw glass particles.

[0086] The method for mixing the raw glass particles and the carbon powder is not particularly limited, but examples thereof include a method using a known mixer such as a dry powder mixer.

[0087] By mixing the raw glass particles with the carbon powder, a mixture is obtained in which the carbon powder adheres to the surfaces of the raw glass particles.

[0088] [Second process] In the second step, the mixture prepared in the first step is fed toward a combustion flame (flame) generated by a combustible gas to spheroidize the raw glass particles. In the second step, the raw glass particles fed toward the combustion flame melt or soften and become spherical particles due to surface tension.

[0089] The mixture can be supplied toward the combustion flame by dropping the mixture into the combustion flame or by ejecting the mixture toward the combustion flame together with a gas that carries the mixture (carrier gas).

[0090] The type of combustible gas that generates a combustion flame is not particularly limited, but is preferably an alkane gas having 1 to 4 carbon atoms. As the combustible gas, one type of alkane from among alkanes having 1 to 4 carbon atoms may be used alone, or two or more types of alkanes may be used in combination.

[0091] In order to generate a combustion flame, a combustion-supporting gas may be used in addition to the combustible gas. The combustion-supporting gas is a gas necessary to support the combustion of the combustible gas. The type of combustion-supporting gas is not particularly limited, but examples thereof include oxygen, oxygen-enriched air, and air. The ratio of the supply amount of the combustible gas to the supply amount of the combustion-supporting gas (supply amount of combustible gas / supply amount of combustion-supporting gas) is not particularly limited, but may be, for example, 0.09 to 0.60, preferably 0.09 to 0.50, and more preferably 0.09 to 0.30.

[0092] The second step can be carried out using an apparatus including a furnace for generating a combustion flame and a supply section for supplying the mixture, such as the apparatus disclosed in JP-A-11-199249.

[0093] The glass beads produced after the second step are cooled and collected to obtain the glass bead aggregate of the present invention.

[0094] Although not wishing to be limited in any way, the mechanism by which the glass bead aggregate of the present invention is obtained by carrying out the first and second steps is presumed to be as follows: The glass composition of the glass beads constituting the glass bead aggregate of the present invention is high in alkali metal oxide content. During the spheroidization of the raw glass particles in the second step, a combustion flame is generated by the combustion of a flammable gas. This combustion generates water (water vapor), and the water attached to the raw glass particles turns to water vapor due to the heat of combustion. It is believed that glass with a high alkali metal oxide content facilitates the diffusion of water into the molten glass during melting, and that the water diffused into the molten glass generates bubbles in the glass beads. Furthermore, it is believed that carbon attached to the raw glass particles acts as a reducing agent, promoting the diffusion of water and the reduction of metal oxides in the glass, thereby generating bubbles in the glass beads. Furthermore, it is believed that the combustion of the carbon generates carbon dioxide, which diffuses into the molten glass, generating bubbles in the glass beads. These factors are believed to enable the apparent density specified in the present invention to be satisfied.

[0095] 4. Uses of the glass bead aggregate of the present invention The use of the glass bead aggregate of the present invention is not particularly limited, and it can be used in various applications such as a glass bead filler, but a suitable example is a filler used by dispersing it in a resin. [Example]

[0096] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention should not be construed as being limited to these examples.

[0097] 1. Preparation of glass bead aggregates Example 1 (1) Preparation of a mixture of raw glass particles and carbon powder (first step) Fibrous raw glass particles having a median diameter D50 of 8.8 μm and the following composition a1 were prepared as raw glass particles. Carbon black (manufactured by Tokai Carbon Co., Ltd., product name: Carbon Black Seast SO, average particle diameter: 43 nm) was also prepared as carbon powder. The raw glass particles and carbon powder were mixed using a dry powder mixer RM-300HD / CD (Aichi Electric Co., Ltd.) so that the parts by mass of carbon powder per 100 parts by mass of raw glass particles and the mixing time satisfied the conditions shown in Table 8, thereby obtaining a mixture. In this mixture, the carbon powder adhered to the raw glass particles.

[0098] [Table 1]

[0099] (2) Spheroidization of raw glass particles (second process) The mixture obtained above was processed in a spheronization apparatus disclosed in Japanese Patent Application Laid-Open No. 11-199249 to spheroidize the raw glass particles with the carbon powder attached thereto, thereby obtaining glass bead aggregates. A schematic diagram of the spheronization apparatus used is shown in Figure 1. The mixture obtained above was placed in hopper 1 of the spheronization apparatus (Figure 1), discharged in fixed amounts by metering device 2, and transported by raw material carrier gas supplied from raw material carrier gas supply pipe 3 to burner 6. A gas of alkane having 1 to 4 carbon atoms (a combustible gas) and a combustion-supporting gas (air) were introduced from their respective supply sources into supply pipes 4 and 5 and supplied to burner 6. Burner 6 was installed within furnace 7 and configured to form a combustion flame within furnace 7. The mixture was sprayed toward the formed combustion flame by the raw material carrier gas, and the raw glass particles with the carbon powder attached thereto melted or softened, forming spherical particles due to surface tension. The spheroidized glass bead aggregates were cooled in the lower part of the spheroidizing furnace 7 and collected in a cyclone 8 and a bag filter 9. The ratio of the supply rate of the alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply rate of the combustion-supporting gas (air) (supply rate of the alkane gas having 1 to 4 carbon atoms / supply rate of the combustion-supporting gas), and the supply rate (g / min) of the raw glass particles with carbon powder attached to them into the furnace were set as shown in Table 8. The supply rate of the combustion-supporting gas (air) is the sum of the raw material carrier gas supplied from the raw material carrier gas supply pipe 3 and the combustion-supporting gas (air) supplied together with the combustible gas.

[0100] Example 2 Glass bead aggregates were produced under the same conditions as in Example 1, except that the feed rate (g / min) of the raw glass particles to which carbon powder was attached into the furnace was changed to the conditions shown in Table 8.

[0101] Example 3 A glass bead aggregate was produced under the same conditions as in Example 1, except that fibrous raw glass particles having the following composition a2 and a median diameter D50 of 9.7 μm were prepared as the raw glass particles, and the mass parts of carbon powder per 100 mass parts of the raw glass particles, the mixing time for mixing using a dry powder mixer, and the supply rate (g / min) of the raw glass particles with carbon powder attached to them into the furnace were changed to the conditions shown in Table 8.

[0102] [Table 2]

[0103] Example 4 Glass bead aggregates were produced under the same conditions as in Example 3, except that the mixing time using the dry powder mixer was changed to the conditions shown in Table 8.

[0104] Example 5 Glass bead aggregates were produced under the same conditions as in Example 3, except that the parts by mass of carbon powder per 100 parts by mass of raw glass particles was changed to the conditions shown in Table 8.

[0105] Example 6 A glass bead aggregate was produced under the same conditions as in Example 3, except that the mass parts of carbon powder per 100 mass parts of raw glass particles and the mixing time using a dry powder mixer were changed to the conditions shown in Table 8.

[0106] Example 7 Glass bead aggregates were produced under the same conditions as in Example 3, except that the parts by mass of carbon powder per 100 parts by mass of raw glass particles was changed to the conditions shown in Table 8.

[0107] Example 8 A glass bead aggregate was produced under the same conditions as in Example 3, except that the mass parts of carbon powder per 100 mass parts of raw glass particles and the mixing time using a dry powder mixer were changed to the conditions shown in Table 8.

[0108] Example 9 A glass bead aggregate was produced under the same conditions as in Example 1, except that fibrous raw glass particles having the following composition a3 and a median diameter D50 of 8.7 μm were prepared as the raw glass particles, and the supply rate (g / min) of the raw glass particles with carbon powder attached thereto into the furnace and the ratio of the supply rate of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply rate of combustion-supporting gas (air) (supply rate of alkane gas having 1 to 4 carbon atoms / supply rate of combustion-supporting gas) were changed to the conditions shown in Table 8.

[0109] [Table 3]

[0110] Example 10 A glass bead aggregate was produced under the same conditions as in Example 9, except that the amount (g / min) of raw glass particles with carbon powder attached thereto fed into the furnace and the ratio of the amount of alkane gas (combustible gas) with 1 to 4 carbon atoms fed to the amount of combustion-supporting gas (air) fed (amount of alkane gas with 1 to 4 carbon atoms fed / amount of combustion-supporting gas fed) were changed to the conditions shown in Table 8.

[0111] Example 11 A glass bead aggregate was produced under the same conditions as in Example 1, except that aspherical raw glass particles having the following composition b1 and a median diameter D50 of 2.3 μm were prepared as the raw glass particles, and the supply rate (g / min) of the raw glass particles with carbon powder attached to them into the furnace and the ratio of the supply rate of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply rate of combustion-supporting gas (air) (supply rate of alkane gas having 1 to 4 carbon atoms / supply rate of combustion-supporting gas) were changed to the conditions shown in Table 8.

[0112] [Table 4]

[0113] Example 12 A glass bead aggregate was produced under the same conditions as in Example 11, except that the ratio of the supply amount of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply amount of combustion-supporting gas (air) (supply amount of alkane gas having 1 to 4 carbon atoms / supply amount of combustion-supporting gas) was changed to the conditions shown in Table 8.

[0114] Comparative Example 1 (1) Preparation of raw glass particles As raw glass particles, fibrous raw glass particles having a median diameter D50 of 11.8 μm and the following composition a4 were prepared.

[0115] [Table 5]

[0116] (2) Spheroidization of raw glass particles The raw glass particles prepared above were spheroidized by treating them under the conditions shown in Table 9 using the spheroidizing device used in Example 1, to obtain glass bead aggregates.

[0117] Comparative Example 2 A glass bead aggregate was produced under the same conditions as in Comparative Example 1, except that raw glass particles were prepared that were non-spherical and had the composition b1 and a median diameter D50 of 2.3 μm, and the ratio of the supply amount of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply amount of combustion-supporting gas (air) (supply amount of alkane gas having 1 to 4 carbon atoms / supply amount of combustion-supporting gas) was changed to the conditions shown in Table 9.

[0118] Comparative Example 3 A glass bead aggregate was produced under the same conditions as in Comparative Example 2, except that the ratio of the supply amount of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply amount of combustion-supporting gas (air) (supply amount of alkane gas having 1 to 4 carbon atoms / supply amount of combustion-supporting gas) was changed to the conditions shown in Table 9.

[0119] Comparative Example 4 A glass bead aggregate was produced under the same conditions as in Comparative Example 3, except that raw glass particles prepared were non-spherical raw glass particles having the composition b1 and a median diameter D50 of 46.1 μm, and the ratio of the supply amount of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply amount of combustion-supporting gas (air) (supply amount of alkane gas having 1 to 4 carbon atoms / supply amount of combustion-supporting gas) was changed to the conditions shown in Table 9.

[0120] Comparative Example 5 A glass bead aggregate was produced under the same conditions as in Comparative Example 1, except that aspherical raw glass particles having the following composition S and a median diameter D50 of 24.7 μm were prepared as the raw glass particles, and the ratio of the supply amount of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply amount of combustion-supporting gas (air) (supply amount of alkane gas having 1 to 4 carbon atoms / supply amount of combustion-supporting gas) was changed to the conditions shown in Table 9.

[0121] [Table 6]

[0122] Comparative Example 6 Glass bead aggregates were produced under the same conditions as in Example 10, except that raw glass particles having a non-spherical shape and a median diameter D50 of 24.7 μm and composition S were prepared as raw glass particles.

[0123] Comparative Example 7 A glass bead aggregate was produced under the same conditions as in Comparative Example 1, except that fibrous raw glass particles having the following composition E and a median diameter D50 of 27.1 μm were prepared as raw glass particles, and the ratio of the supply amount of alkane gas (combustible gas) having 1 to 4 carbon atoms to the supply amount of combustion-supporting gas (air) (supply amount of alkane gas having 1 to 4 carbon atoms / supply amount of combustion-supporting gas) was changed to the conditions shown in Table 9.

[0124] [Table 7]

[0125] Comparative Example 8 A glass bead aggregate was produced under the same conditions as in Example 10, except that fibrous raw glass particles having composition E and a median diameter D50 of 27.1 μm were prepared as raw glass particles.

[0126] Comparative Example 9 Commercially available hollow glass beads (product name Glass Bubbles IM16K, manufactured by 3M Japan Ltd.) were prepared.

[0127] 2. Measurement of physical properties of glass bead aggregates 2-1. Measurement of apparent density A measuring cylinder and distilled water were prepared. The mass of the measuring cylinder filled with distilled water at 20°C up to the 50 ml mark was measured. Next, 15 to 20 g of glass bead aggregates were placed in an empty measuring cylinder, and distilled water at 20°C was further added up to the 50 ml mark. The masses of the glass bead aggregates and the measuring cylinder filled with 50 ml of water were measured. The apparent density of the glass bead aggregates was then calculated using the following formula (1).

number

[0128] 2-2. Measurement of the median diameter of glass bead aggregates Glass beads were collected from the glass bead aggregate so that there were 30,000 or more glass beads, and the volumetric D was measured according to the method (Coulter counter method) specified in JIS Z 8832:2010, "Method for measuring particle size distribution - Electrical detection zone method." 10 , D 25 , D 50 (Median diameter, D 75 , and D 90 was measured.

[0129] 2-3. Measurement of sphericity (before compression test) First, 500 or more glass beads were randomly selected from the glass bead aggregate. Next, each glass bead was observed at 2000x magnification using a digital microscope. Rounded glass beads with a sphericity (D1 / D2) of 0.83 or more, calculated from the minimum length D1 and the maximum length D2, and without acute angles or fusion between glass beads, were defined as spherical, and the number of spherical glass beads was counted. The apparent density of the glass bead aggregate was calculated using the following formula.

number

[0130] 2-4. Bubble generation rate First, 500 or more glass beads were randomly selected from the glass bead aggregate. Each glass bead was observed at 2000x magnification using a digital microscope to check for the presence of bubbles on the surface and inside the glass bead. Glass beads containing even one bubble were considered bubble-containing glass beads, and the bubble generation rate was calculated according to the following formula.

number

[0131] 2-5. Sphericity of glass bead aggregates after compression test A cylindrical container (20 mm in diameter, 50 mm in length) was filled to overflowing with glass bead aggregates, and each of the four sides of the cylindrical container was struck 40 times to ensure that the glass bead aggregates were packed tightly together. The supernatant liquid that overflowed from the cylindrical container was then leveled off. The container containing the leveled glass bead aggregates was placed under the upper jig (cylindrical, 20 mm in diameter) of a compression tester, aligned with the center of the upper jig, and a compression test was performed with a load range of 2 kN and a test speed of 3.0 mm / min, starting from the point where the upper jig and the glass bead aggregates contacted, until the glass bead aggregates in the cylindrical container were compressed to 2100 N. The sphericity (%) of the compressed glass bead aggregates was determined using the same method as described above.

[0132] 2-6. Difference in sphericity (%) of glass bead aggregates (before compression test) and after compression test The difference between the sphericity (%) of the glass bead aggregates (before the compression test) and that after the compression test was determined. A difference of 3% or less was deemed to be excellent in mechanical strength and to have passed the test.

[0133] 2-7. Glass composition of raw glass particles and glass bead aggregates The glass composition of the raw glass particles and glass bead aggregates was measured by X-ray fluorescence analysis. Specifically, the content (mass%) of each component was measured according to the quantitative analysis method specified in JIS K 0119:2008, "General Rules for X-ray Fluorescence Analysis." First, 5 g of raw glass particles or glass bead aggregates was crushed for 1 minute and 30 seconds in a crusher (CMT, TI-100). The crushed raw glass particles or glass beads were packed into a PVC ring for powder samples (Rigaku, 38 mm outer diameter × 30 mm inner diameter × 5 mm height) and pressed under 20 MPa to prepare a flat plate-shaped sample for quantitative analysis. The prepared sample for quantitative analysis was attached to the sample holder of the analyzer using a 30 mm diameter sample mask. The analytical equipment used was a wavelength dispersive X-ray fluorescence analyzer (Rigaku Corporation, ZSX Primus II), the measurement range was set to a circle with a diameter of 30 mm, the fundamental parameter method (FP method) was used as the quantitative method, and the prepared quantitative analysis samples were analyzed by SQX (Scan Quant X) analysis in EZ scan mode. The content (mass%) of each component in the material was measured.

[0134] 3. Measurement results of physical properties of glass bead aggregates The physical properties of the glass bead aggregates are shown in Tables 8 and 9. Microscope images of the glass bead aggregates obtained in Examples 1 to 12 are shown in Figures 2 to 13.

[0135] [Table 8]

[0136] [Table 9]

[0137] The glass bead aggregates (Examples 1 to 12) produced by feeding a mixture of raw glass particles of glass compositions a1 to a3 and b1 and carbon powder into a combustion flame and spheroidizing them had an apparent density of 1.20 to 1.80 g / cm 3 Despite the low sphericity of the glass bead aggregates, the difference between the sphericity (before the compression test) and the sphericity (%) after the compression test was 3% or less, and the glass bead aggregates had excellent compression resistance. In contrast, the glass bead aggregates (Comparative Examples 1 to 5 and 7) prepared by passing raw glass particles of glass compositions a4, b1, S and E individually through a combustion flame to spheroidize them had excellent compression resistance, but the apparent density was 1.80 g / cm. 3 The apparent density of the glass bead aggregates (Comparative Examples 6 and 8) produced by feeding a mixture of raw glass particles of glass compositions S and E and carbon powder into a combustion flame and spheroidizing the mixture showed an increase in apparent density compared to the case where raw glass particles of glass compositions S and E were used alone. Furthermore, the apparent density of commercially available hollow glass beads (Comparative Example 9) was 0.46 g / cm. 3 The difference in sphericity (%) between the glass bead aggregates (before the compression test) and after the compression test was 6.2%, indicating poor compression resistance.

[0138] That is, from these results, it can be seen that the glass has a composition that satisfies the conditions 48 mass%≦SiO2≦70 mass%, 5 mass%≦B2O3≦20 mass%, 1 mass%≦Al2O3≦10 mass%, 0.5 mass%≦CaO≦12 mass%, and 5 mass%≦(Li2O+Na2O+K2O)≦20 mass%, and has an apparent density of 1.20 to 1.80 g / cm 3 It was confirmed that an aggregate of glass beads satisfying the above conditions can have both a low apparent density and excellent compression resistance. It was also confirmed that an aggregate of glass beads having these properties can be obtained by mixing raw glass particles having a glass composition satisfying the following conditions: 56 mass%≦SiO2≦68 mass%, 7 mass%≦B2O3≦15 mass%, 1 mass%≦Al2O3≦8 mass%, 0.5 mass%≦CaO≦10 mass%, and 6 mass%≦(Li2O+Na2O+K2O)≦18 mass%, with carbon, and supplying the resulting mixture toward the combustion flame of a combustible gas to produce spherical particles. [Explanation of symbols]

[0139] 1 Hopper 2 Quantitative feeding device 3. Gas supply pipe for transporting raw materials 4 Supply pipe 5 Supply pipe 6 burners 7 Spheroidizing furnace 8. Cyclone 9. Bag filter

Claims

1. 48% by mass ≤ SiO 2 ≤70% by mass 5% by weight ≤ B 2 O 3 ≤20% by mass 1% by mass ≤ Al 2 O 3 ≤10% by mass 0.5% by mass≦CaO≦12% by mass, and 5% by mass ≤ (Li 2 O+Na 2 O+K 2 O) ≤ 20% by mass A collection of glass beads having a glass composition that satisfies the following: Apparent density of 1.20 to 1.80 g / cm 3 It is a collection of glass beads.

2. 2. The glass bead aggregate according to claim 1, wherein the median diameter of the glass beads is 5 to 50 μm.

3. 3. A method for producing a glass bead aggregate according to claim 1 or 2, comprising the steps of: 56% by mass≦SiO 2 ≦68% by mass, 7% by mass≦B 2 O 3 ≦15% by mass, 1% by mass≦Al 2 O 3 ≦8% by mass, 0.5% by mass≦CaO≦10% by mass, and 6% by mass≦(Li 2 O + Na 2 O+K 2 A first step of preparing a mixture of raw glass particles having a glass composition satisfying the following formula: O)≦18 mass% and carbon powder; and a second step of supplying the mixture prepared in the first step into a combustion flame of a combustible gas to spheroidize the raw glass particles; A method for producing a glass bead aggregate, comprising:

4. The method according to claim 3, wherein the flammable gas is at least one alkane having 1 to 4 carbon atoms.

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