Method for producing rubber foam

Abstract

To provide a technology that enables improvement in the dimensional stability of rubber foam.SOLUTION: The present technology provides a method for producing rubber foam, the method including: a crosslinking and foaming step in which a composition for producing rubber foam that contains a rubber component is subjected to crosslinking and foaming; a cutting step in which the rubber foam obtained through the crosslinking and foaming step is cut; and a heating step in which the rubber foam obtained through the cutting step is heated. The present technology makes it possible to achieve further reduction of the curing period required until the rubber foam attains dimensional stability.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present technology relates to a method for producing a rubber foam. [Background technology]

[0002] Foams made with rubber components are widely used in a variety of fields, from construction, machinery, home appliances, transportation, and packaging to daily necessities, toys, and miscellaneous goods. Various developments are underway to improve quality and add new functions to them according to each field and purpose.

[0003] It is known that closed-cell rubber foams, among other rubber foams, shrink over time after production. This is because gas trapped inside the cells during crosslinking and foaming is released over time. To prevent dimensional changes in rubber foams after production, a shrink-removal process is generally carried out during the production of rubber foams.

[0004] For example, Patent Document 1 discloses a method for producing a rubber foam in which a rubber composition containing a rubber component is foamed in two stages, and then shrink-reducing is performed in a gear oven at 70°C for 10 hours. Patent Document 2, for example, discloses a method for producing a rubber foam in which a rubber composition containing a rubber component is press-vulcanized, and then the rubber composition is placed in a hot air dryer (70°C for 2 hours) and heated to shrink-reducing. Furthermore, Non-Patent Document 1 describes a method called shrink-reducing, in which certain sponge products are produced by leaving the product at around 70°C for a long period of time to complete shrinkage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 02-278635 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-213615 [Non-patent literature]

[0006] [Non-Patent Document 1] Journal of the Society of Rubber Science and Technology of Japan, Vol. 74, No. 10 (2001), pp. 386-391 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, when foams using rubber components used in various fields are produced, a shrink-removal process is carried out to prevent dimensional changes in the produced rubber foam. However, the reality is that there is a demand for a further reduction in the curing period required for the dimensions to stabilize.

[0008] Therefore, a main object of the present technology is to provide a technology that can improve the dimensional stability of a rubber foam. [Means for solving the problem]

[0009] As a result of intensive research into technologies that can improve the dimensional stability of rubber foam, the inventors of the present application unexpectedly succeeded in significantly shortening the curing period required for the dimensions of rubber foam to stabilize by changing the way they think about the order of manufacturing processes that had previously been commonly used, and thus completed the present technology. That is, the present technology includes a crosslinking and foaming step of crosslinking and foaming a rubber foam production composition containing a rubber component; a cutting step of cutting the rubber foam that has been subjected to the cross-linking and foaming step; a heating step of heating the rubber foam that has been subjected to the cutting step; The present invention provides a method for producing a rubber foam having the above structure. In the production method according to the present technology, the heating step can be carried out in an atmosphere at a temperature of 40°C or higher and 150°C or lower. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments for implementing the present technology will be described below. The embodiments described below are examples of typical embodiments of the present technology, and any of the embodiments can be combined. Furthermore, the scope of the present technology will not be interpreted narrowly by these embodiments.

[0011] 1. Manufacturing method of rubber foam The method for producing a rubber foam according to the present technology includes a crosslinking and foaming step, a cutting step, and a heating step. Furthermore, as needed, steps performed in general methods for producing rubber foams, such as a kneading step and a curing step, can be freely combined as long as the effects and advantages of the present technology are not impaired. Below, each material and each step used in the production method according to the present technology will be described in detail. Each step will be described in chronological order.

[0012] (1) Composition for producing rubber foam In the method for producing a rubber foam according to the present technology, a rubber foam is produced using a composition for producing a rubber foam. The composition for producing a rubber foam used in the present technology can contain a rubber component, a blowing agent, a foaming aid, a crosslinking agent, a crosslinking accelerator, a crosslinking accelerator aid, a filler, a reinforcing material, a softener, a processing aid, and various other components that can be used in producing a rubber foam depending on the purpose.

[0013] (1-1) Rubber component The rubber component used in this technology is a vulcanizable resin component. As the rubber component that can be used in this technology, one or more rubber components that can be used in rubber foams can be freely selected and used as long as the function and effect of this technology are not impaired. Examples include natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), and silicone rubber (SI). Among these, in this technology, it is preferable to use a rubber component containing ethylene-propylene-diene rubber (EPDM) as the rubber component, due to environmental considerations.

[0014] (1-2) Foaming agent A foaming agent can be used in the composition for producing a rubber foam used in the present technology. As the foaming agent that can be used in the present technology, one or more foaming agents that can be used in rubber foams can be freely selected and used as long as the action and effect of the present technology are not impaired.

[0015] Examples of blowing agents that can be used in this technology include organic and inorganic thermal decomposition type chemical blowing agents. Examples of organic blowing agents include nitroso compounds such as N,N'-dinitrosopentamethylenetetramine (DPT), azo compounds such as azodicarbonamide (ADCA), metal azodicarboxylates (e.g., barium azodicarboxylate), and azobisisobutyronitrile (AIBN), hydrazine derivatives such as hydrazodicarbonamide, 4,4'-oxybis(benzenesulfonylhydrazide), and toluenesulfonylhydrazide (TSH), and semicarbazide compounds such as toluenesulfonylsemicarbazide. Examples of inorganic blowing agents include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and anhydrous monosodium citrate.

[0016] Among these, in the present technology, it is preferable to use an organic blowing agent as the blowing agent, and among the organic blowing agents, it is preferable to use a nitroso compound, and among the nitroso compounds, it is preferable to use N,N'-dinitrosopentamethylenetetramine (DPT).

[0017] The amount of foaming agent used in the composition for producing rubber foams according to the present technology can be freely set as long as it does not impair the functions and effects of the present technology. In the present technology, the lower limit of the amount of foaming agent in the composition for producing rubber foams is, for example, 0.5 parts by mass or more, preferably 1.0 parts by mass or more, and more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. Setting the lower limit of the amount of foaming agent used within this range can improve foamability during foam production and the physical properties of the produced foam.

[0018] In the present technology, the upper limit of the amount of the foaming agent in the composition for producing a rubber foam, relative to 100 parts by mass of the rubber component, is, for example, 30 parts by mass or less, preferably 25 parts by mass or less, and more preferably 20 parts by mass or less. Setting the upper limit of the amount of the foaming agent used within this range can prevent molding defects due to excessive foaming and also contribute to cost reduction.

[0019] (1-3) Foaming aid The composition for producing a rubber foam used in the present technology can contain a foaming aid. As the foaming aid that can be used in the present technology, one or more foaming aids that can be used in rubber foams can be freely selected and used, as long as the action and effect of the present technology are not impaired.

[0020] Examples of foaming aids that can be used in the present technology include urea-based aids such as urea, metal oxides, and fatty acid metal salts. Examples of metal oxides include zinc oxide, zinc chloride, zinc acetate, zinc nitrate, lead oxide, dibasic lead phosphite, and tribasic lead sulfate. Examples of fatty acid metal salts include zinc stearate, lead stearate, magnesium stearate, and calcium stearate. Among these, it is preferable to use urea as the foaming aid in the present technology.

[0021] The amount of foaming aid used in the composition for producing a rubber foam used in the present technology can be freely set as long as it does not impair the functions and effects of the present technology. The lower limit of the amount of foaming aid in the composition for producing a rubber foam is, for example, 1 part by mass or more, preferably 2 parts by mass or more, and more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. By setting the lower limit of the amount of foaming aid within this range, the foaming rate during production can be adjusted, thereby improving foamability.

[0022] The upper limit of the amount of foaming aid in the composition for producing a rubber foam, per 100 parts by mass of the rubber component, is, for example, 15 parts by mass or less, preferably 13 parts by mass or less, and more preferably 11 parts by mass or less. Setting the upper limit of the amount of foaming aid used within this range can improve foamability by adjusting the foaming rate during production and also contribute to cost reduction.

[0023] (1-4) Crosslinking agent A crosslinking agent can be used in the composition for producing a rubber foam used in the present technology. As the crosslinking agent that can be used in the present technology, one or more crosslinking agents that can be used in rubber foams can be freely selected and used, as long as the action and effect of the present technology are not impaired.

[0024] The crosslinking agent that can be used in the present technology is a sulfur-based crosslinking agent for sulfur crosslinking. Examples of the sulfur-based crosslinking agent that can be used in the present technology include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, as well as organic sulfur-containing compounds such as tetramethylthiuram disulfide and N,N-dithiobismorpholine, which can release active sulfur under crosslinking conditions to crosslink rubber. Among these, in the present technology, it is preferable to use sulfur as the sulfur-based crosslinking agent.

[0025] The amount of crosslinking agent used in the composition for producing rubber foams according to the present technology can be freely set as long as it does not impair the functions and effects of the present technology. The lower limit of the amount of crosslinking agent in the composition for producing rubber foams is, for example, 0.2 parts by mass or more, preferably 0.4 parts by mass or more, and more preferably 0.6 parts by mass or more, per 100 parts by mass of the rubber component. By setting the lower limit of the amount of crosslinking agent within this range, sufficient crosslink density can be achieved, thereby improving foamability. Furthermore, the mechanical properties of the rubber foam can be improved.

[0026] The upper limit of the amount of crosslinking agent in the composition for producing a rubber foam, per 100 parts by mass of the rubber component, is, for example, 10.0 parts by mass or less, preferably 8.0 parts by mass or less, and more preferably 6.0 parts by mass or less. By setting the upper limit of the amount of crosslinking agent within this range, blooming of the molded article can be suppressed.

[0027] (1-5) Crosslinking accelerator A crosslinking accelerator can be used in the composition for producing a rubber foam according to the present technology. As the crosslinking accelerator that can be used in the present technology, one or more crosslinking accelerators that can be used in rubber foams can be freely selected and used, as long as the action and effect of the present technology are not impaired.

[0028] Examples of crosslinking accelerators that can be used in the present technology include thiazoles (e.g., 2-mercaptobenzothiazole, dibenzothiazyl disulfide, etc.), thiurams (e.g., tetramethylthiuram disulfide, tetramethylthiuram monosulfide, etc.), dithiocarbamic acids (e.g., sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, etc.), guanidines (e.g., diphenylguanidine, di-o-tolylguanidine, etc.), sulfenamides (e.g., , benzothiazyl-2-diethylsulfenamide, N-cyclohexyl-2-benzothiazylsulfenamide, etc.), xanthogenic acids (e.g., sodium isopropyl xanthogenate, zinc isopropyl xanthogenate, etc.), aldehyde ammonias (e.g., acetaldehyde ammonia, hexamentylenetetramine, etc.), aldehyde amines (e.g., n-butylaldehyde aniline, butylaldehyde monobutylamine, etc.), thioureas (e.g., diethylthiourea, trimethylthiourea, etc.), dithiophosphate-based crosslinking accelerators, etc. Among these, in the present technology, it is preferable to use thiazoles and thiurams as crosslinking accelerators from the viewpoint of adjusting the timing of the foaming rate and the vulcanization rate, etc.

[0029] The amount of crosslinking accelerator used in the composition for producing a rubber foam used in the present technology can be freely set as long as it does not impair the functions and effects of the present technology. The lower limit of the amount of crosslinking accelerator in the composition for producing a rubber foam is, for example, 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and more preferably 0.2 parts by mass or more, per 100 parts by mass of the rubber component. By setting the lower limit of the amount of crosslinking accelerator within this range, the crosslinking rate can be increased, gas leakage can be suppressed, and foamability during production can be improved. In addition, the mechanical properties of the rubber foam can be improved.

[0030] The upper limit of the amount of crosslinking accelerator in the composition for producing a rubber foam, relative to 100 parts by mass of the rubber component, is, for example, 10 parts by mass or less, preferably 7 parts by mass or less, and more preferably 5 parts by mass or less. Setting the upper limit of the amount of crosslinking accelerator within this range can prevent the crosslinking rate from increasing too much, resulting in non-foaming, and improve moldability.

[0031] (1-6) Crosslinking accelerator A cross-linking accelerator aid can be used in the rubber foam production composition for producing the rubber foam according to the present technology. As the cross-linking accelerator aid that can be used in the present technology, one or more cross-linking accelerator aids that can be used in rubber foams can be freely selected and used, as long as the action and effect of the present technology are not impaired.

[0032] Examples of crosslinking accelerators that can be used in the present technology include metal oxides such as zinc oxide (active zinc oxide), magnesium oxide, etc. Among these, in the present technology, it is preferable to use zinc oxide as the crosslinking accelerator from the viewpoint of adjusting the timing of the foaming rate and the vulcanization rate.

[0033] The amount of crosslinking accelerator used in the rubber foam production composition used in the present technology can be freely set as long as it does not impair the functions and effects of the present technology. The lower limit of the amount of crosslinking accelerator in the rubber foam production composition is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 1.0 parts by mass or more, per 100 parts by mass of the rubber component. By setting the lower limit of the amount of crosslinking accelerator within this range, the crosslinking rate can be increased, gas leakage can be suppressed, and foamability during production can be improved. In addition, the mechanical properties of the rubber foam can be improved.

[0034] The upper limit of the amount of crosslinking accelerator in the composition for producing a rubber foam is, for example, 15 parts by mass or less, preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component. Setting the upper limit of the amount of crosslinking accelerator in this range can prevent the crosslinking rate from increasing too much, resulting in non-foaming, and can improve moldability. This can also contribute to cost reduction.

[0035] (1-7) Filler A filler can be used in the composition for producing a rubber foam used in the present technology. As the filler that can be used in the present technology, one or more fillers that can be used in rubber foams can be freely selected and used, as long as the action and effect of the present technology are not impaired.

[0036] Examples of fillers that can be used in the present technology include inorganic fillers such as calcium carbonate such as heavy calcium carbonate, magnesium carbonate, calcium hydroxide, silicic acid and its salts, clay, talc, mica powder, bentonite, silica, alumina, aluminum silicate, aluminum powder, etc. Among these, in the present technology, it is preferable to use silicic acid salts such as hydrated aluminum silicate as the filler.

[0037] The amount of filler used in the composition for producing rubber foams used in the present technology can be freely set as long as it does not impair the functions and effects of the present technology. The lower limit of the amount of filler in the composition for producing rubber foams is, for example, 5 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component. Setting the lower limit of the amount of filler in this range can contribute to cost reduction.

[0038] The upper limit of the amount of filler in the composition for producing a rubber foam, relative to 100 parts by mass of the rubber component, is, for example, 100 parts by mass or less, preferably 80 parts by mass or less, and more preferably 70 parts by mass or less. Setting the upper limit of the amount of filler within this range can improve the mechanical properties of the rubber foam and suppress a decrease in foamability, etc.

[0039] (1-8) Reinforcement A reinforcing material can be used in the composition for producing a rubber foam used in the present technology. As the reinforcing material that can be used in the present technology, one or more reinforcing materials that can be used in rubber foams can be freely selected and used as long as the action and effect of the present technology are not impaired. Examples of reinforcing materials that can be used in the present technology include carbon blacks such as acetylene black, furnace black, and channel black.

[0040] The amount of reinforcing material used in the composition for producing a rubber foam used in the present technology can be freely set as long as it does not impair the functions and effects of the present technology. The lower limit of the amount of reinforcing material in the composition for producing a rubber foam is, for example, 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component. Setting the lower limit of the amount of reinforcing material within this range can improve mixability during production and also improve the mechanical strength of the rubber foam.

[0041] The upper limit of the amount of reinforcing material in the composition for producing a rubber foam, relative to 100 parts by mass of the rubber component, is, for example, 90 parts by mass or less, preferably 80 parts by mass or less, and more preferably 70 parts by mass or less. By setting the upper limit of the amount of reinforcing material within this range, low hardness can be achieved.

[0042] (1-9) Softener A softener can be used in the composition for producing a rubber foam used in the present technology. As the softener that can be used in the present technology, one or more softeners that can be used in rubber foams can be freely selected and used as long as the action and effect of the present technology are not impaired.

[0043] Examples of softeners that can be used in the present technology include naphthenic process oil, paraffinic process oil, wax, liquid paraffin, rosin, chroman resin, polybutene, asphalt, plasticizer, etc. Among these, in the present technology, it is preferable to use naphthenic process oil as the softener.

[0044] The amount of softener used in the composition for producing rubber foam used in the present technology can be freely set as long as it does not impair the functions and effects of the present technology. The lower limit of the amount of softener in the composition for producing rubber foam is, for example, 10 parts by mass or more, preferably 15 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component. By setting the lower limit of the amount of softener within this range, a rubber foam with lower hardness can be produced.

[0045] The upper limit of the amount of the softener in the composition for producing a rubber foam, relative to 100 parts by mass of the rubber component, is, for example, 100 parts by mass or less, preferably 90 parts by mass or less, and more preferably 80 parts by mass or less. Setting the upper limit of the amount of the softener within this range can improve kneadability during production.

[0046] (1-10) Processing aids The composition for producing a rubber foam used in the present technology may contain a processing aid. The use of a processing aid can improve processability during production.

[0047] The processing aid that can be used in the present technology can be freely selected from one or more processing aids that can be used in general rubber compositions, as long as the purpose and effects of the present technology are not impaired. Examples of processing aids that can be used in the present technology include fatty acids such as stearic acid, fatty acid esters, fatty acid amides, fatty alcohols, and metal salts of fatty acids. Among these, in the present technology, it is preferable to use fatty acids such as stearic acid and fatty acid esters as processing aids.

[0048] The amount of processing aid used in the composition for producing rubber foam used in the present technology can be freely set as long as it does not impair the purpose and effects of the present technology. The lower limit of the amount of processing aid in the composition for producing rubber foam can be set to, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 1.0 parts by mass or more, per 100 parts by mass of the rubber component. Setting the lower limit of the amount of processing aid within this range can further improve kneading processability during production.

[0049] The upper limit of the amount of processing aid in the composition for producing a rubber foam can be set to, for example, 10 parts by mass or less, preferably 8 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. By setting the upper limit of the content of the processing aid within this range, a decrease in the strength of the produced rubber foam can be prevented.

[0050] (1-11)Other In the composition for producing a rubber foam used to produce a rubber foam according to the present technology, one or more components that can be used in rubber foams can be freely selected and used as other components depending on the purpose, as long as the action and effect of the present technology are not impaired.

[0051] Examples of components that can be used in the rubber foam according to the present technology include foam stabilizers, stabilizers, colorants, antioxidants, dispersants, ultraviolet absorbers, and flame retardants.

[0052] (2) Mixing process In the production method according to the present technology, a kneading step can be performed. The kneading step is a step of kneading the raw materials of the composition for producing a rubber foam described above. Specifically, all or a part of the raw materials of the composition for producing a rubber foam can be kneaded using a kneading machine such as a kneader, a Banbury mixer, or a roll mixer.

[0053] The kneading step can be carried out in a plurality of stages. Specifically, for example, the components other than the crosslinking agent, crosslinking accelerator, foaming agent, foaming auxiliary, etc. are first kneaded primarily, and then the crosslinking agent, crosslinking accelerator, crosslinking accelerator auxiliary, foaming agent, foaming auxiliary, etc. are added to the obtained primary kneaded mixture and kneaded secondarily.

[0054] When kneading is performed in two stages, the conditions for the first kneading can be set, for example, at a temperature of 50°C to 180°C and for a kneading time of 3 to 30 minutes, etc. The conditions for the second kneading can be set, for example, at a temperature of 20°C to 80°C and for a kneading time of 3 to 30 minutes, etc.

[0055] (3) Cross-linking and foaming process The crosslinking and foaming step is a step of crosslinking and foaming the rubber foam-producing composition. The conditions for crosslinking and foaming can be freely set as long as they do not impair the functions and effects of the present technology.

[0056] The temperature condition is, for example, 100° C. or higher, preferably 120° C. or higher, more preferably 125° C. or higher. The upper limit of the temperature is, for example, 220° C. or lower, preferably 210° C. or lower, more preferably 200° C. or lower.

[0057] The pressure condition is, for example, 0.1 MPa or more, preferably 0.2 MPa or more, more preferably 0.5 MPa or more. The upper limit of the pressure is, for example, 20 MPa or less, preferably 18 MPa or less, more preferably 17 MPa or less.

[0058] The time condition is, for example, 1 minute or more, preferably 2 minutes or more, more preferably 5 minutes or more, and even more preferably 6 minutes or more. The upper limit of the time is, for example, 100 minutes or less, preferably 60 minutes or less, and more preferably 50 minutes or less.

[0059] Crosslinking and foaming can be carried out in multiple stages. For example, after primary crosslinking and foaming, the heating temperature can be further increased to sequentially carry out secondary crosslinking and foaming. When crosslinking and foaming are carried out in two stages, the conditions for primary crosslinking and foaming can be set, for example, at a temperature of 100°C to 160°C and for 3 to 70 minutes. The conditions for secondary crosslinking and foaming can be set, for example, at 140°C to 220°C and for 3 to 70 minutes.

[0060] (4) Cutting process The cutting step is a step of cutting the rubber foam that has undergone the cross-linking and foaming step. In conventional methods for producing rubber foams, the cross-linking and foaming step is followed by heating to remove shrinkage, and then cutting is performed. However, in the present technology, the cutting step is performed before the heating step, which will be described later, and as will be shown in the examples that will be described later, this has succeeded in significantly shortening the time it takes for the dimensions of the produced rubber foam to stabilize.

[0061] The specific conditions for the cutting process can be freely combined with general methods as long as they do not impair the functions and effects of the present technology.

[0062] (5)Heating process The heating step is a step of heating the rubber foam that has been through the cutting step, and is a step that has conventionally been called a shrink-reducing step. In conventional methods for producing rubber foams, the shrink-reducing step is carried out after the cross-linking and foaming step, and then cutting is carried out. However, in the present technology, the cutting step is carried out after the cross-linking and foaming step, and then the heating step is carried out. As will be shown in the examples below, this technology has succeeded in significantly shortening the time it takes for the dimensions of the produced rubber foam to stabilize.

[0063] Various conditions in the heating step can be freely set as long as they do not impair the functions and effects of the present technology. The lower limit of the heating temperature in the heating step is, for example, 40°C or higher, preferably 50°C or higher, and more preferably 60°C or higher. By setting the lower limit of the heating temperature within this range, it is possible to improve the efficiency of releasing gas accumulated inside the cells. The upper limit of the heating temperature in the heating step is, for example, 150°C or lower, preferably 140°C or lower, and more preferably 130°C or lower. By setting the upper limit of the heating temperature within this range, it is possible to prevent extreme shrinkage during the heating step.

[0064] The lower limit of the heating time in the heating step is, for example, 1 hour or more, preferably 2 hours or more, and more preferably 3 hours or more. By setting the lower limit of the heating time within this range, it is possible to efficiently release gas accumulated inside the cell. The upper limit of the heating time in the heating step is, for example, 48 hours or less, preferably 24 hours or less, and more preferably 12 hours or less. By setting the upper limit of the heating time within this range, it is possible to shorten the manufacturing process.

[0065] (6)Curing process The curing step is a step in which the rubber foam produced through the heating step is left to stand, thereby stabilizing the dimensions of the rubber foam.

[0066] The rubber foam produced by the production method according to the present technology can be cured in 5 days or less, during which the difference in dimensions between the rubber foam produced after the heating step and the rubber foam produced 21 days later remains 0.5% or less. In other words, the present technology can shorten the curing period required for the dimensions of the produced rubber foam to stabilize. The curing step is preferably carried out at room temperature, for example, from 5 to 35°C.

[0067] The curing step is a step of leaving the product without any particular heating, but if the temperature of the storage environment is low, for example, in a cold region or in winter, the storage environment can be heated as needed. When the storage environment is heated, it is preferable to heat it to a temperature lower than the heating temperature in the heating step. Furthermore, if the temperature of the storage environment is high, for example, in a tropical region or in summer, the storage environment can be cooled as needed.

[0068] 2. Applications of rubber foam The high quality of the rubber foam produced using the production method according to the present technology can be utilized for a wide variety of applications in a wide range of fields, including sealing materials, cushioning materials, sound-absorbing materials, heat insulating materials, vibration-damping materials, dust-proofing materials, and fillers. The foam can be used in a wide range of fields, including construction, vehicles, aircraft, transportation, home appliances, electronic devices, packaging, daily necessities, clothing, medicine, furniture, bedding, household goods, and cosmetics. [Example]

[0069] The present technology will be described in more detail below based on examples. Note that the examples described below are examples of typical examples of the present technology, and the scope of the present technology should not be construed as being narrow.

[0070] In this example, the influence of differences in manufacturing methods on the physical properties of rubber foams was examined.

[0071] (1) Raw materials The raw materials shown in Table 1 below were used.

[0072] [Table 1]

[0073] (2) Manufacturing of rubber foam [Example 1] to [Example 3] The rubber foam raw materials shown in Table 1 were mixed and roll-kneaded to prepare a composition for producing a rubber foam, which was then crosslinked and foamed by heating and pressurization. The rubber foam that had undergone the crosslinking and foaming step was cut into a thickness of 5 mm and a 300 mm square, and then heated under the conditions shown in Table 2 below to produce a rubber foam.

[0074] [Comparative Example 1] The rubber foam raw materials shown in Table 1 were mixed and roll-kneaded to prepare a composition for producing a rubber foam, which was then crosslinked and foamed by heating and pressure. The rubber foam that had undergone the crosslinking and foaming step was heated under the conditions shown in Table 2 below, and then cut into a thickness of 5 mm and a 300 mm square to produce a rubber foam.

[0075] [Reference example 1] The rubber foam raw materials shown in Table 1 were mixed and roll-kneaded to prepare a composition for producing a rubber foam, which was then crosslinked and foamed by heating and pressure. The rubber foam that had undergone the crosslinking and foaming step was cut into a thickness of 5 mm and a 300 mm square to produce a rubber foam.

[0076] (3) Measurement of curing days The dimensional change rate of the produced rubber foam was measured from immediately after production until 21 days later. The period until the difference in dimensions of the rubber foam after 21 days became 0.5% or less was defined as the curing period.

[0077] (4) Results The results are shown in Table 2 below. [Table 2]

[0078] (5) Discussion As shown in Table 2, in Examples 1 to 3 in which heating was carried out after cutting, the curing period was significantly shorter than in Comparative Example 1 in which cutting was carried out after heating.

Claims

1. a crosslinking and foaming step of crosslinking and foaming a rubber foam-producing composition containing a rubber component; a cutting step of cutting the rubber foam that has been subjected to the cross-linking and foaming step; a heating step of heating the rubber foam that has been subjected to the cutting step; The method for producing a rubber foam, comprising:

2. The method for producing a rubber foam according to claim 1 , wherein the heating step is carried out in an atmosphere having a temperature of 40° C. or higher and 150° C. or lower.

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