Isolated-cell rubber, method for producing same, and rubber for metal removal

Abstract

To provide a rubber for metal removal that is usable for removing molten metal from a heating tool without water wetting and that enables easy removal of metal remaining on a surface, and to provide an isolated-cell rubber serving as a base for the same and a method for producing the isolated-cell rubber.SOLUTION: An isolated-cell rubber 10 (or isolated-cell rubber) including a cured silicone rubber 11, wherein a plurality of isolated cells 13, each having at least one particle 12 disposed inside, are formed in the cured silicone rubber 11, and a water-soluble substance is dispersed therein.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a closed-cell rubber in which closed cells are formed in silicone rubber, a method for producing the same, and a rubber for metal removal. [Background technology]

[0002] BACKGROUND ART Pads have conventionally been used to remove solder from heating tools such as soldering irons, and specific examples thereof are disclosed in Patent Documents 1 and 2, for example. The pad disclosed in Patent Document 1 is made of a wood pulp sheet and is used in a wet, moisture-absorbing state, which prevents the pad from carbonizing or burning even when it comes into contact with a high-temperature heating tool or solder.

[0003] The pad disclosed in Patent Document 2 is made of silicone rubber, which makes it highly heat-resistant and does not require wetting with water. However, the pad described in Patent Document 2 is not designed to remove solder by rubbing a heated tool against its surface, so it cannot remove solder efficiently. In this regard, if a conventional urethane sponge pad is used after being wetted with water, the solder adhering to the heating tool can be easily removed by rubbing the heating tool against the surface of the pad on which the irregularities are formed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-195824 [Patent Document 2] Japanese Patent Application Publication No. 2018-24015 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a pad is wetted with water, the temperature of the heating tool drops significantly when the heating tool comes into contact with the pad, which requires time to heat up the heating tool, resulting in reduced work efficiency.Furthermore, the sudden drop in temperature of the heated heating tool can cause malfunctions in the heater part of the heating tool. Furthermore, once the flux used together with the solder adheres to the urethane sponge, it is virtually impossible to remove it from the urethane sponge. The problems caused by the rapid temperature drop of these heated tools are not limited to solder, but also apply to other molten metals.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a metal removal rubber that can be used to remove molten metal from a heated tool without wetting it with water and that can easily remove metal remaining on the surface, as well as the closed-cell rubber that forms the basis of the metal removal rubber and a method for producing the same. [Means for solving the problem]

[0007] The closed-cell rubber according to the first invention, which meets the above-mentioned objective, is a closed-cell rubber having a cured silicone rubber, in which a plurality of closed cells, each having at least one particle disposed inside, are formed in the cured silicone rubber, and a water-soluble substance is dispersed.

[0008] A method for producing closed-cell rubber according to a second invention that meets the above-mentioned objective comprises a first step of adding particles having a water-soluble substance attached thereto, the particles being partially or completely dissolved in a water-containing solvent, to uncured silicone rubber and mixing them to obtain a mixture in which the particles are dispersed throughout the silicone rubber; and a second step of heating the mixture while allowing the silicone rubber to cure, thereby evaporating the solvent contained in the mixture, and forming a plurality of closed cells in the cured silicone rubber, each with at least one of the particles disposed inside.

[0009] The third invention, which is in line with the above-mentioned object, provides a rubber for metal removal that has cured silicone rubber and has irregularities formed on part or all of its surface that remove molten metal from a heating tool. The cured silicone rubber has a plurality of closed cells formed therein, each with at least one particle disposed inside, and a water-soluble substance dispersed therein. [Effects of the Invention]

[0010] The closed-cell rubber of the first invention has multiple closed cells formed in the cured silicone rubber, so by cutting the closed-cell rubber, an uneven surface formed by the original closed cells is created, and this uneven surface can be used to remove molten metal. Because silicone rubber is more heat-resistant than conventional pads that are used by wetting it with water, it can be used to remove molten metal from a heated tool without wetting it with water, and experiments have confirmed that metal remaining on the uneven surface can be easily removed.

[0011] The method for producing closed-cell rubber according to the second invention is a method for producing the closed-cell rubber according to the first invention, and therefore corresponds to the closed-cell rubber according to the first invention. Furthermore, since the metal removal rubber according to the third invention has the same properties as the closed-cell rubber according to the first invention, this metal removal rubber can also be used to remove molten metal without wetting it with water, making it possible to easily remove metal remaining on the surface. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an explanatory diagram of a closed-cell rubber according to a first embodiment of the present invention. [Figure 2] FIG. 6 is an explanatory view of a rubber for metal removal according to a second embodiment of the present invention. [Figure 3] FIG. 10 is an explanatory diagram showing the results of comparing the mass change of a sample according to an example with the relative humidity. [Figure 4] 1A and 1B are stereomicroscope photographs of the cross section of a sample according to an example. [Figure 5]FIG. 10 is an explanatory diagram showing the results of measuring the temperature of a soldering iron brought into contact with a sample according to an example and a sample according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, embodiments of the present invention will be described with reference to the accompanying drawings to facilitate understanding of the present invention. As shown in Fig. 1, a closed-cell rubber 10 according to a first embodiment of the present invention has cured silicone rubber 11, in which a plurality of closed cells 13 are formed, each of which has at least one particle 12 disposed inside. A detailed description will be given below.

[0014] In this embodiment, the silicone rubber 11 is a room temperature curing type that reacts with moisture in the air and hardens at room temperature, but the silicone rubber 11 may also be one that is hardened by heat treatment, by adding platinum or the like, or by exposure to ultraviolet light.

[0015] The particles 12 may be porous particles, hollow particles, particles with an uneven surface, or the like, and may be, for example, one or more substances selected from the group consisting of zeolite, diatomaceous earth, shirasu balloons, carbon black, carbon nanotubes, graphene, silica gel, montmorillonite, kaolinite, pumice, shale, mesoporous silica, porous polymer beads, graphite, cellulose nanofiber, cork, and gamma alumina. When the particles 12 are hollow particles, it is desirable to use a type in which an opening communicating with the hollow portion is formed on the surface, because the water-soluble substance described below can enter the hollow portion.

[0016] Furthermore, a flame retardant such as aluminum hydroxide particles or magnesium hydroxide can be used in the particles 12. The closed-cell rubber 10 has flame retardancy even without using these flame retardants as the particles 12. However, from the perspective of improving the flame retardancy of the closed-cell rubber 10, it is possible to use aluminum hydroxide or magnesium hydroxide in the particles 12.

[0017] The closed-cell rubber 10 also has a water-soluble substance dispersed therein. The water-soluble substance may be one or more substances selected from the group consisting of calcium chloride, magnesium chloride, potassium carbonate, potassium pyrophosphate, magnesium perchlorate, calcium nitrate, magnesium nitrate, potassium acetate, urea, and potassium thiocyanate. These substances are deliquescent and have a solubility of 40 g / 100 g or more in water at 20°C.

[0018] The water-soluble substance does not need to be deliquescent, as long as it is soluble in a water-containing solution. The water-soluble substance may have a solubility of 5 g / 100 g or more in water (HO) at 20°C, for example. For example, one or more substances selected from the group consisting of potassium benzoate, trehalose, glucose, sucrose, aluminum phosphate, sodium dihydrogen phosphate, citric acid, and water-soluble oils may be used as the water-soluble substance. Furthermore, a water-soluble substance may be a mixture of a deliquescent substance and a non-deliquescent substance that is soluble in a water-containing solution.

[0019] Here, the closed-cell rubber 10 in this embodiment has no or almost no visible holes (craters) formed on the surface, as shown in Fig. 1. Therefore, even if a heated tool with molten metal on it is rubbed against the surface (flat surface) of the closed-cell rubber 10, the molten metal cannot be efficiently removed from the heated tool. In this regard, by cutting the area where the closed cells 13 of the closed-cell rubber 10 are formed, the cut surface is formed with irregularities with holes 14 provided in the locations where the closed cells 13 were previously. The holes 14 mentioned here have bottoms.

[0020] As shown in Fig. 2, a cut piece of closed-cell rubber 10 has an uneven surface 15 with unevenness formed thereon. Moreover, silicone rubber 11 has a high melting point and low surface tension. Therefore, the cut piece can be used as metal-removing rubber 20, which has this uneven surface 15 and is used to remove molten metal (e.g., molten solder) from a heating tool, even without wetting it with water. In other words, metal-removing rubber 20 can be used as something that can efficiently remove molten metal from a heating tool without being wetted with water. The metal removal rubber 20 shown in FIG. 2 has an uneven surface 15 (cut surface) that is a partial area of ​​the surface (if the metal removal rubber 20 is a hexahedron, for example, only one surface is uneven surface 15), but the entire surface of the metal removal rubber 20 may be uneven.

[0021] Therefore, the metal removal rubber 20 is a pad having hardened silicone rubber 11 and having irregularities formed on part or all of its surface for removing molten metal from a heated tool, and has multiple closed cells 13 formed therein, each with at least one particle 12 disposed inside, and a water-soluble substance dispersed therein. Depending on the cutting position of the closed-cell rubber 10, not only the holes 14 but also through-holes may be formed in the uneven surface 15 of the metal-removing rubber 20. Furthermore, it is also possible that the uneven surface 15 has no holes and only through-holes.

[0022] Here, the porosity of the closed-cell rubber 10 (the ratio of the space of the closed cells to the total volume of the closed-cell rubber 10) is preferably 40% or more and 85% or less. The porosity of the closed-cell rubber 10 corresponds to the size and number of holes 14 formed in the uneven surface 15 of the metal removal rubber 20 or the softness of the metal removal rubber 20, and it has been confirmed that if the porosity is too low or too high, the efficiency of removing molten metal from a heated tool by the metal removal rubber 20 decreases.

[0023] From the viewpoint of increasing the efficiency of removing molten metal from a heating tool by the metal removal rubber 20, the lower limit of the porosity of the closed-cell rubber 10 that forms the base of the metal removal rubber 20 is more preferably 45%, and even more preferably 50%. From the same viewpoint, the upper limit of the porosity of the closed-cell rubber 10 is more preferably 80%, and even more preferably 75%.

[0024] Next, a description will be given of a method for producing the closed-cell rubber 10. The water-containing composition 10 is produced by the following steps S1 to S4.

[0025] Process S1: A water-containing dissolving liquid is mixed with a water-soluble substance to dissolve the water-soluble substance partially or completely, and particles 12 are then added to the mixture, causing the partially or completely dissolved water-soluble substance to adhere (retain) to particles 12. Thus, particles 12 are capable of adhering to water-soluble substances. Hereinafter, unless otherwise specified, it is assumed that the water-soluble substance is partially or completely dissolved in the dissolving liquid.

[0026] Adhering the water-soluble substance to the particles 12 means that, if the particles 12 are porous, the water-soluble substance is attached to the surfaces and inside the pores of the particles 12 . An example of the dissolving liquid is water, but it is not limited thereto. When the dissolving liquid is water, it is preferable that the surfaces of the particles 12 are hydrophilic (non-water-repellent). From the viewpoint of increasing the amount of water-soluble substance that can be held by a unit amount of particles 12, particles 12 that themselves have a porous structure or particles 12 that fuse together to form aggregates with a complex structure, such as carbon black, are preferred.

[0027] Process S2: The particles 12 with the water-soluble substance attached are added to uncured silicone rubber 11, and the particles 12 and silicone rubber 11 are mixed using a stirrer or the like to obtain a mixture in which the particles 12 are dispersed in the uncured silicone rubber 11 (hereinafter, when simply referred to as "mixture," this mixture will be referred to). The uncured silicone rubber 11 referred to here means the state of the silicone rubber 11 in which the particles 12 are dispersed in the silicone rubber 11 by mixing the particles 12 and silicone rubber 11. Steps S1 and S2 correspond to the first step.

[0028] In step S2, when attempting to disperse particles 12 in uncured silicone rubber 11 while stably maintaining the state in which water-soluble substances are attached to particles 12, it is preferable to add particles 12 to uncured silicone rubber 11 in step S2 (first step) after mixing a hydrophobic liquid with uncured silicone rubber 11. The hydrophobic liquid referred to here refers to a liquid whose solubility in water at 20°C is less than 5 g / 100 g, and specific examples include benzene, hexane, kerosene, vegetable oil, toluene, xylene, and butyl acetate.

[0029] Process S3: While the curing (crosslinking) of the silicone rubber 11 in the mixture is progressing, the mixture is heated to evaporate the dissolving liquid contained in the mixture. The volume of the dissolving liquid expands due to the evaporation of the dissolving liquid, causing bubbles to form within the silicone rubber 11 as the curing progresses.

[0030] The heating temperature may be any temperature that generates bubbles within the silicone rubber 11 as it hardens, and may be below the boiling point. However, to ensure that the final closed-cell rubber 10 has a certain porosity or higher, it is preferable to heat the mixture in an atmosphere above the boiling point of the dissolving solution and evaporate the dissolving solution in a short period of time. In this regard, the heating temperature of the mixture is preferably at least 20°C (more preferably 30°C, and even more preferably 40°C) higher than the boiling point of the dissolving solution.

[0031] However, since the mixture needs to be heated at a temperature that does not thermally decompose the silicone rubber 11 and the particles 12, the heating temperature of the mixture is, for example, 300° C. or lower. When the closed-cell rubber 10 is formed into a specific shape, it is preferable to heat-treat the mixture by placing it in a mold corresponding to the shape. Here, in order to efficiently remove molten metal with the metal removal rubber 20 formed from the closed-cell rubber 10, it is preferable that the metal removal rubber 20 has a shape with corners (assuming that the corners are used as areas against which a heated tool is rubbed). A shape with corners is, for example, a rectangular parallelepiped shape as shown in Fig. 2, or a shape consisting of multiple cubes, such as one cube on the left side, a second cube diagonally in front and to the right of the first cube, and a third cube diagonally in front and to the left of the second cube.

[0032] Process S4: When the evaporation of the solvent and the curing of the silicone rubber are substantially completed, a closed-cell rubber 10 is obtained in which a large number (plurality) of closed cells 13 are formed in the cured silicone rubber 11. In this embodiment, "substantially completing evaporation of the solvent" means that substantially all of the solvent has evaporated. However, as long as closed cells 13 are ultimately formed in the closed-cell rubber 10, the heating treatment of the mixture may be terminated at a stage when the solvent remains in a liquid state in the closed-cell rubber 10.

[0033] When the closed-cell rubber 10 from which substantially all of the solvent had evaporated was observed, it was confirmed that substantially no solvent was present in the closed-cell rubber 10, that is, that the evaporated solvent did not remain within the closed cells 13 but was substantially entirely expelled to the outside of the mixture. Therefore, when the solvent was evaporated, through-holes should have been formed between the bubbles and in the outer wall of the mixture, through which the evaporated solvent could move toward the outside.

[0034] It is believed that these through holes are blocked by cross-linking of the silicone rubber 11, and as a result, a large number of closed cells 13 (cells that are not connected to other cells) are formed in the final closed-cell rubber 10, and there are no or almost no visible holes on the surface of the closed-cell rubber 10. In fact, when the closed-cell rubber 10 was cut and the cut surface was examined under a stereomicroscope, it was found that there were a few bubbles that were connected to each other by extremely thin channels, but the majority were closed bubbles 13 (i.e., bubbles that were not connected to other bubbles).

[0035] It was also confirmed by a stereomicroscope that at least one particle 12 was disposed inside substantially all or most of the closed cells 13. This means that the distribution of the closed cells 13 corresponds to the distribution of the particles 12. Thus, in step S4, a plurality of closed cells 13, each having at least one particle 12 disposed inside, are formed in the cured silicone rubber 11.

[0036] In this embodiment, the average particle size of particles 12 (measured by laser diffraction / scattering) is 10 nm or more and 100 μm or less, but particles 12 may have an average particle size of less than 10 nm or more than 100 μm as long as they are dispersed in silicone rubber 11 by stirring. However, from the viewpoint of dispersing particles 12 evenly in silicone rubber 11 and easily producing closed-cell rubber 10 in which closed cells 13 are uniformly distributed, it is preferable to use particles 12 with an average particle size of 200 μm or less. In this embodiment, step S3 and step S4 constitute a second step.

[0037] When a deliquescent water-soluble substance is used, the heat resistance temperature of the closed-cell rubber 10 is higher than when a non-deliquescent water-soluble substance is used. Therefore, when forming a metal removal rubber for removing molten metal from a heated tool based on the closed-cell rubber 10, it is preferable to use a deliquescent water-soluble substance. This is thought to be because the deliquescent water-soluble substance absorbs moisture from the atmosphere. It is also known that silicone rubber 11 has high water vapor permeability.

[0038] Furthermore, the manufacturing method for metal-removing rubber 20 is the same as the manufacturing method for closed-cell rubber 10 described above, except that it adds a step of removing a portion of the manufactured closed-cell rubber 10. The step of removing a portion of the closed-cell rubber 10 can be implemented by cutting the closed-cell rubber 10, scraping off a portion of the closed-cell rubber 10, dissolving a portion of the closed-cell rubber 10, or the like. [Example]

[0039] Next, an experiment conducted to confirm the effects of the present invention will be described. The closed-cell rubber used in the experiment (hereinafter referred to as "sample according to the example") was produced using the following materials: The heating temperature of the mixture was 140°C. Silicone rubber: 100g of Shin-Etsu Chemical Co., Ltd. sealant 45N Dissolution liquid: water 7g Water-soluble substance: Magnesium chloride 14g Particles for attaching water-soluble substances: 15g of diatomaceous earth Hydrophobic liquid: 20g of paint thinner (Sankyo Chemical Co., Ltd. Paint Thinner A(s))

[0040] The mass of the sample according to the example was measured once a day for 21 days from the date of manufacture, and the change in the measured value was compared with the change in the average relative humidity on the corresponding day announced by the Japan Meteorological Agency for the area where the sample according to the example was stored. The comparison results are shown in Figure 3. In Figure 3, the solid line indicates the mass of the sample according to the example, and the dashed line indicates the relative humidity. From the comparison results, it was confirmed that the mass of the sample according to the example changed in accordance with the change in relative humidity.

[0041] Next, the sample according to the example was cut, and the cut surface was observed under a stereomicroscope, and the stereomicroscope photographs are shown in Figures 4(A) and (B). In Figures 4(A) and (B), diatomaceous earth was confirmed at least in the area surrounded by the dashed line.

[0042] Furthermore, an experiment was conducted in which a soldering iron was brought into contact with each of the samples according to the embodiment and the comparative example in which the urethane sponge was wetted with water, and the surface temperature of the soldering iron was measured. The amount of water added to the sample according to the comparative example was 10.23 g, and the size of the sample according to the comparative example was 45 mm × 54 mm × 16 mm before water addition and 50 mm × 60 mm × 17 mm after water addition. No water was added to the sample according to the example.

[0043] The tip of a heated soldering iron (set to 300°C ± 5°C) was lightly pressed about 4 mm against a predetermined location on a sample (both the example and the comparative example) for 5 seconds, then the soldering iron was removed from the sample. After 25 seconds, the tip of the heated soldering iron was again lightly pressed about 4 mm against a different location on the sample for 5 seconds. This procedure was repeated for five different locations on the sample, and the temperature of the soldering iron tip was measured. The temperature was measured using a 1.6 mm diameter thermocouple (a K-type thermocouple manufactured by Hakko Electric Co., Ltd.) in contact with the tip of the soldering iron.

[0044] The measurement results are shown in Figure 5. From the measurement results shown in FIG. 5, it was confirmed that the sample according to the example was able to suppress the temperature drop of the soldering iron compared to the sample according to the comparative example.

[0045] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions that do not depart from the gist of the present invention are within the scope of application of the present invention. For example, closed cell rubber can be used in applications other than metal removal rubber. The porosity of the closed cell rubber may be less than 40% or more than 85%. [Explanation of symbols]

[0046] 10: Closed-cell rubber, 11: Silicone rubber, 12: Particles, 13: Closed-cell, 14: Holes, 15: Textured surface, 20: Rubber for metal removal

Claims

1. A closed cell rubber having a cured silicone rubber, a plurality of closed cells are formed in the cured silicone rubber, each having at least one particle disposed therein; A closed-cell rubber characterized by having a water-soluble substance dispersed therein.

2. 2. The closed-cell rubber according to claim 1, wherein the void ratio is 40% or more and 85% or less.

3. a first step of adding particles to which a water-soluble substance, which is partially or completely dissolved in a water-containing solution, is attached to uncured silicone rubber and mixing the particles to obtain a mixture in which the particles are dispersed in the silicone rubber; and a second step of heating the mixture to evaporate the solution contained in the mixture while proceeding with the curing of the silicone rubber, thereby forming a plurality of closed cells in the cured silicone rubber, each having at least one particle disposed inside.

4. 4. The method for producing closed-cell rubber according to claim 3, wherein the particles are introduced into the uncured silicone rubber in the first step after mixing the uncured silicone rubber with a hydrophobic liquid.

5. 5. The method for producing closed-cell rubber according to claim 3, wherein the water-soluble substance has deliquescent properties.

6. A metal removal rubber having hardened silicone rubber and having irregularities formed on a part or the entire surface thereof for removing molten metal from a heated tool, a plurality of closed cells are formed in the cured silicone rubber, each having at least one particle disposed therein; A rubber for metal removal characterized by having a water-soluble substance dispersed therein.

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