Foam rubber and cosmetics applicator

Abstract

Provided are foam rubber and a cosmetics applicator that are soft and glide smoothly on skin.　The foam rubber is produced from a composition containing a rubber polymer and an oil and / or fat that contains a fatty acid having at least 20 carbon atoms.

Description

Foam rubber and applicator for cosmetics

[0001] The present disclosure relates to foam rubber and an applicator for cosmetics.

[0002] In applicators such as puffs used when applying foundation to the skin, puffs etc. with a soft touch and good skin feel are preferably used.

[0003] For example, Patent Document 1 discloses a foam rubber produced by foam molding a mixture containing a raw material resin and fats and oils.

[0004] Japanese Patent Application Laid-Open No. 2002-20520

[0005] In the foam rubber of Patent Document 1, the softness was not sufficient and the skin feel was not sufficient either.

[0006] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a foam rubber and an applicator for cosmetics that are soft and have a good skin feel. The present disclosure can be realized in the following forms.

[0007] A foam rubber produced from a composition containing a rubber-based polymer and a fat or oil containing a fatty acid having 20 or more carbon atoms.

[0008] According to the present disclosure, a foam rubber and an applicator for cosmetics that are soft and have a good skin feel can be provided.

[0009] This is a perspective view showing an example of a cosmetic applicator. This is an optical microscope image of the surface of foam rubber when 3.2 parts by mass of high-erucine rapeseed oil is used as the oil. This is an optical microscope image of the surface of foam rubber when 6.4 parts by mass of high-erucine rapeseed oil is used as the oil. This is an optical microscope image of the surface of foam rubber when no oil is used. This is an optical microscope image of the surface of foam rubber when olive oil is used as the oil. In the photograph in Figure 2, lines (thick black lines) are drawn around the outer edges of multiple consecutive cells near the center. In the photograph in Figure 3, lines (thick black lines) are drawn around the outer edges of multiple consecutive cells near the center. In the photograph in Figure 4, lines (thick black lines) are drawn around the outer edges of multiple consecutive cells near the center. In the photograph in Figure 5, lines (thick black lines) are drawn around the outer edges of multiple consecutive cells near the center.

[0010] Herein are preferred examples of the present disclosure: [1] Foam rubber produced from a composition containing a rubber polymer and an oil or fat containing a fatty acid having 20 or more carbon atoms. [2] The foam rubber according to [1], wherein the content of the oil or fat is 1 part by mass or more and 20 parts by mass or less when the rubber polymer is 100 parts by mass. [3] The foam rubber according to [1] or [2], wherein the content of the fatty acid having 20 or more carbon atoms is 0.5 parts by mass or more and 17 parts by mass or less when the rubber polymer is 100 parts by mass. [4] A cosmetic applicator comprising the foam rubber according to any one of [1] to [3].

[0011] The disclosure is described in detail below. In this specification, when a numerical range is described using "-", it includes both the lower and upper limits unless otherwise specified. For example, the description "10-20" includes both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less". Furthermore, in this specification, the upper and lower limits of each numerical range can be combined in any way.

[0012] 1. Foam Rubber Foam rubber is manufactured from a composition (hereinafter also referred to as the rubber composition) containing a rubber-based polymer and an oil or fat containing a fatty acid with 20 or more carbon atoms. Foam rubber is also called latex foam. It is preferable that the foam rubber does not contain silicone oil.

[0013] (1) Rubber polymer The rubber polymer is not particularly limited. For example, one or more can be selected from the group consisting of acrylonitrile-butadiene rubber (NBR), isoprene rubber (IR), styrene-butadiene rubber (SBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), butadiene rubber (BR), butyl rubber (isobutylene-isoprene rubber (IIR)), and natural rubber (NR). Acrylonitrile-butadiene rubber (NBR), which has excellent weather resistance, oil resistance, abrasion resistance, and hygiene (inhibition of microbial growth), is preferably used.

[0014] (2) Oils and fats (fatty acid softeners) Oils and fats contain fatty acids with 20 or more carbon atoms.

[0015] From the viewpoint of making the texture of the foam rubber smoother, the content of fatty acids with 20 or more carbon atoms is preferably 0.5 parts by mass or more, more preferably 0.85 parts by mass or more, and even more preferably 1 part by mass or more, when the rubber polymer is 100 parts by mass. From the viewpoint of suppressing oils and fats from bleeding from the foam rubber and contaminating the surrounding area, the content of fatty acids with 20 or more carbon atoms is preferably 17 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less. From these viewpoints, the content of fatty acids with 20 or more carbon atoms is preferably 0.5 parts by mass or more and 17 parts by mass or less, more preferably 0.85 parts by mass or more and 10 parts by mass or less, and even more preferably 1 part by mass or more and 8 parts by mass or less.

[0016] The fatty acids contained in the oils and fats are preferably one or more selected from the group consisting of erucic acid (erucic acid), eicosenoic acid, arachidic acid, behenic acid (behenic acid), and lignoceric acid.

[0017] As the oil or fat, one or more types selected from the group consisting of high-erucine rapeseed oil and jojoba oil, which are rich in erucic acid (erucic acid) or eicosenoic acid, are preferred. The oil or fat may be used alone or in combination of two or more types.

[0018] High erucine rapeseed oil, for example, contains 40% or more erucic acid. Jojoba oil, for example, contains 10% or more erucic acid and 55% or more eicosenoic acid.

[0019] The oil and fat content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, when the rubber polymer is 100 parts by mass. The oil and fat content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less, from the viewpoint of suppressing oil and fat bleeding from the foam rubber and contaminating the surrounding area. From these viewpoints, the oil and fat content is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 2 parts by mass or more and 10 parts by mass or less, and even more preferably 3 parts by mass or more and 7 parts by mass or less.

[0020] (3) Other softening agents: Oils and fats function as softening agents. In addition to oils and fats, other softening agents may be incorporated into the rubber composition during the manufacture of foam rubber. Other softening agents are components that impart appropriate flexibility to the foam rubber. Other softening agents are not particularly limited. Examples of other softening agents include hydrocarbon process oils such as paraffinic process oils, naphthenic process oils, and aromatic process oils, as well as spindle oil and petrolatum. Paraffinic process oil is a process oil in which the proportion of carbon in paraffinic hydrocarbons is 50% by mass or more of the total carbon content per 100% by mass. Naphthenic process oil is a process oil in which the proportion of carbon in naphthenic hydrocarbons is 30% by mass or more and 45% by mass or less of the total carbon content per 100% by mass. Aromatic process oil is a process oil in which the proportion of carbon in aromatic hydrocarbons is 35% by weight or more of the total carbon content per 100% by mass.

[0021] From the standpoint of suppressing yellowing of foam rubber and further enhancing safety for the human body, paraffin-based process oils are preferred, and liquid paraffin is more preferred.

[0022] (4) The foaming agent rubber composition preferably contains a foaming agent. The foaming agent is not particularly limited. Examples of foaming agents include fatty acid salts such as potassium oleate, sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium castor oil soap, and potassium coconut oil soap; sarcosinate salts such as sodium lauroyl sarcosinate, sodium myristoyl sarcosinate, sodium oleyl sarcosinate, and sodium cocoyl sarcosinate; sulfates such as sodium coconut oil alcohol sulfate and sodium polyoxyethylene lauryl ether sulfate; sulfonates such as sodium dioctyl sulfosuccinate, sodium lauryl sulfoacetate, sodium dodecylbenzenesulfonate, and sodium α-olefin sulfonate; and cationic surfactants such as stearyldimethylammonium chloride and benzalkonium chloride.

[0023] The foaming agent content is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.5 parts by mass or more and 5 parts by mass or less, and even more preferably 0.8 parts by mass or more and 1.5 parts by mass or less, based on 100 parts by mass of rubber polymer.

[0024] (5) Foam stabilizers (5-1) Polyethyleneimine and its derivatives The rubber composition preferably contains polyethyleneimine and / or polyethyleneimine derivatives as foam stabilizers.

[0025] Polyethyleneimine (polyaziridine) is commonly referred to as polyethylene "imine," but may also be a copolymer of ethylenediamine, diethylenetriamine, or monoethanolamine with ethyleneimine. Polyethyleneimine can be obtained by known synthesis methods (for example, methods similar to those described in Japanese Patent Publication No. 49-33120, Japanese Patent Publication No. 43-8828, etc.). Specifically, for example, polyethyleneimine can be obtained by reacting ethyleneimine with a base amine such as ethylenediamine, diethylenetriamine, or monoethanolamine under the use of an acid catalyst such as hydrochloric acid, sulfuric acid, or p-toluenesulfonic acid. In addition, commercially available polyethyleneimine may be used as the polyethyleneimine in this disclosure. Examples of commercially available products include Epomin® SP series (manufactured by Nippon Shokubai Co., Ltd.), Lupasol series (manufactured by BASF Corporation), and LUGALVAN-G15000 (manufactured by BASF Corporation).

[0026] Furthermore, polyethyleneimine derivatives can also be used as foam stabilizers according to the present invention. Examples of such polyethyleneimine derivatives include epoxy-modified polyethyleneimine obtained by reacting polyethyleneimine with an epoxy compound such as epichlorohydrin, acrylic-modified polyethyleneimine obtained by reacting polyethyleneimine with an acrylic compound such as acrylonitrile, halogen-modified polyethyleneimine obtained by reacting polyethyleneimine with a halogen compound such as alkyl halide, isocyanate-modified polyethyleneimine obtained by reacting polyethyleneimine with an isocyanate compound such as alkyl isocyanate, and fatty acid-modified polyethyleneimine obtained by reacting polyethyleneimine with a fatty acid.

[0027] The polyethyleneimine and its derivatives described above can be used individually or in combination of two or more.

[0028] The amount of polyethyleneimine and / or polyethyleneimine derivatives blended varies depending on the type of rubber polymer, the vulcanization mechanism, and the crosslinking agent, but in a rubber composition, when the rubber polymer is 100 parts by mass, it is preferably 0.01 parts by mass or more and 20.0 parts by mass or less, more preferably 0.02 parts by mass or more and 15.0 parts by mass or less, and even more preferably 0.1 parts by mass or more and 10.0 parts by mass or less.

[0029] (5-2) The polyalkylene glycol derivative rubber composition preferably contains a polyalkylene glycol derivative as a foam stabilizer.

[0030] When using a derivative of polyalkylene glycol, the molecular weight of the polyalkylene glycol derivative is not particularly limited as long as it does not impair the purpose or effects of this disclosure.

[0031] In polyalkylene glycol derivatives, when using a block copolymer of ethylene oxide and alkylene oxide, the number of carbon atoms in the alkylene unit of the added alkylene oxide is not particularly limited, as long as it does not impair the purpose and effects of this disclosure. The alkylene unit in the polyalkylene glycol derivative that can be used in this technology can be a combination of C2 ethylene oxide and C3 or higher alkylene oxide. Examples of hydrophobic groups in polyalkylene glycol derivatives include aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and aromatic hydrocarbon groups having aliphatic side chains.

[0032] As derivatives of polyalkylene glycol, one can be used alone or two or more can be used in combination, as long as the purpose and effects of this disclosure are not impaired. Examples of derivatives of polyalkylene glycol include polyoxyalkylene alkyl ethers such as polyoxyalkylene monoalkyl ethers and polyoxyalkylenedialkyl ethers, polyoxyalkylene alkenyl ethers such as polyoxyalkylene monoalkenyl ethers and polyoxyalkylenedialkenyl ethers, polyoxyalkylene aryl ethers such as polyoxyalkylene monoaryl ethers and polyoxyalkylenediaryl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene glycol fatty acid esters such as polyoxyalkylene glycol monofatty acid esters and polyoxyalkylene glycol difatty acid esters, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylene alkylamines, and polyoxyalkylenediamines.

[0033] The amount of polyalkylene glycol derivative blended in the rubber composition is preferably 0.01 parts by mass to 20.0 parts by mass, more preferably 0.02 parts by mass to 15.0 parts by mass, and even more preferably 0.1 parts by mass to 10.0 parts by mass, based on 100 parts by mass of the rubber polymer.

[0034] (6) Vulcanizing agent The rubber composition preferably contains a vulcanizing agent. The vulcanizing agent has the function of vulcanizing (crosslinking) the rubber in order to ensure the elastic modulus of the foam rubber. The vulcanizing agent is not particularly limited. Examples of vulcanizing agents include sulfur, sulfur compounds, organic peroxides, phenol compounds, etc. As sulfur, for example, colloidal sulfur, finely powdered sulfur, etc., can be used. As sulfur compounds, for example, sulfur dichloride, dipentamethylenethuram tetrasulfide, etc., can be used. The vulcanizing agent may be used alone or two or more may be used in combination.

[0035] The amount of vulcanizing agent added varies depending on the type of rubber polymer, the vulcanization mechanism, and the crosslinking agent, but in a rubber composition, when the rubber polymer is 100 parts by mass, it is preferably 0.1 parts by mass or more and 15.0 parts by mass or less, more preferably 0.5 parts by mass or more and 10.0 parts by mass or less, and even more preferably 1.0 part by mass or more and 5.0 parts by mass or less.

[0036] (7) Vulcanization aid The rubber composition preferably contains a vulcanization aid. The vulcanization aid promotes the action of the vulcanizing agent. The vulcanization aid is not particularly limited. For example, inorganic compounds such as zinc oxide and magnesium oxide, organic substances such as stearic acid and amines can be used as vulcanization aids. One type of vulcanization aid may be used alone, or two or more types may be used in combination.

[0037] The amount of vulcanization aid added to the rubber composition is preferably 0.5 parts by mass or more and 10.0 parts by mass or less, more preferably 0.8 parts by mass or more and 8.0 parts by mass or less, and even more preferably 1.0 part by mass or more and 5.0 parts by mass or less, based on 100 parts by mass of rubber polymer.

[0038] (8) Vulcanization accelerator The rubber composition preferably contains a vulcanization accelerator. The vulcanization accelerator is used for purposes such as shortening the vulcanization time.

[0039] The vulcanization accelerator is not particularly limited. Examples of vulcanization accelerators include benzothiazoles, zinc dithiocarbamates, thirams, sulfenamides, and the like. The vulcanization accelerator may be used alone or in combination of two or more types.

[0040] Examples of benzothiazoles include 2-mercaptobenzothiazole and its salts (sodium salt, zinc salt, cyclohexylamine salt, dicyclohexylamine salt, etc.), 2-(4'-morpholinodithio)benzothiazole, 4-morpholyl-2-benzothiadyl disulfide, and 2-(N,N-diethylthiocarbamoylthio)benzothiazole.

[0041] Examples of zinc dithiocarbamates include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, and the like.

[0042] Examples of thiurams include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N,N'-dimethyl-N,N'-diphenylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like.

[0043] Examples of sulfenamides include N,N-diisopropyl-2-benzothiazylsulfenamide, N-t-butyl-2-benzothiazylsulfenamide, N-cyclohexyl-2-benzothiazylsulfenamide, N,N-dicyclohexyl-2-dinzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and the like.

[0044] When the rubber polymer is 100 parts by mass in the rubber composition, the compounding amount of the vulcanization accelerator is preferably 0.02 parts by mass or more and 20 parts by mass or less, more preferably 0.05 parts by mass or more and 15 parts by mass or less, and still more preferably 0.1 parts by mass or more and 10 parts by mass or less.

[0045] (9) Dispersant (emulsifier) The rubber composition may contain a dispersant (emulsifier). The dispersant serves to improve the dispersibility of rubber polymer particles and various additives in the rubber composition. By adding the dispersant, the rubber composition can be made uniform. Further, the dispersant can uniformly disperse the gas mixed into the rubber composition.

[0046] The dispersant is not particularly limited. Examples of the dispersant include anionic surfactants and nonionic surfactants. The dispersant may be used alone or in combination of two or more.

[0047] Examples of anionic surfactants include alkali metal salts of fatty acids, alkali metal salts of alkyl sulfonic acids, and alkali metal salts of alkylbenzene sulfonic acids.

[0048] Examples of nonionic surfactants include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene hydrogenated castor oil, and polyoxyethylene alkyl ethers.

[0049] The dispersant content in the rubber composition is preferably 0.02 parts by mass or more and 15 parts by mass or less, more preferably 0.05 parts by mass or more and 10 parts by mass or less, and even more preferably 0.1 parts by mass or more and 5 parts by mass or less, based on 100 parts by mass of rubber polymer.

[0050] As a dispersant, animal protein-based surfactants such as casein, glue, and albumin may also be used. The content of the animal protein-based surfactant as a dispersant in the rubber composition is preferably 0.001 parts by mass or more and 5 parts by mass or less, more preferably 0.005 parts by mass or more and 3 parts by mass or less, and even more preferably 0.01 parts by mass or more and 1 part by mass or less, based on 100 parts by mass of the rubber polymer.

[0051] (10) Anti-aging agents (antioxidants) The rubber composition may contain anti-aging agents (antioxidants). The anti-aging agents are not particularly limited. Examples of anti-aging agents include phenolic compounds (monophenolic compounds, bisphenolic compounds, trisphenolic compounds, polyphenolic compounds), diphenylamine compounds, condensates of aromatic amines and aliphatic ketones, imidazole compounds, etc. The anti-aging agent may be used alone or in combination of two or more types.

[0052] Examples of phenolic compounds include 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane and 4,4'-butylidenebis(6-tert-butyl-m-cresol).

[0053] Examples of diphenylamine compounds include N-phenyl-N'-(p-toluenesulfonyl)-p-phenylenediamine.

[0054] Examples of imidazole compounds include 2-mercaptobenzimidazole and its zinc salt.

[0055] The amount of the anti-aging agent in the rubber composition is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, more preferably 0.3 parts by mass or more and 3.0 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.0 part by mass or less, based on 100 parts by mass of the rubber polymer.

[0056] (11) Gelling agent The rubber composition may contain a gelling agent. The required amount of air and gelling agent can be added to the rubber composition and mixed thoroughly to create a bubbly state and gel to obtain a gel-like substance.

[0057] As the gelling agent mentioned above, liquids such as hexafluorosilicates including sodium fluorosilicide (SSF), potassium fluorosilicide, and calcium fluorosilicide, and cyclohexylamine salts such as cyclohexylamine acetate and sulfamate can be used in aqueous solution. The amount is preferably about 1 to 10 parts by mass per 100 parts by weight of the rubber polymer in the rubber composition. As the gelling agent, hexafluorosilicates, and especially sodium fluorosilicide, are particularly preferred because they allow for easy control of the reaction, such as the gelation start time.

[0058] (12) Other Additives In the foam rubber of the present disclosure, antimicrobial agents, fillers, colorants, fragrances, thickeners, antifungal agents, cooling agents, etc. may be used as additives to be added to the rubber composition, to the extent that they do not impair the effects of the present disclosure.

[0059] Examples of antibacterial agents include zinc pyrithione, parabens, and parahydroxybenzoic acid esters.

[0060] Examples of antifungal agents include organic antibacterial agents such as thiabendazole-based agents, nitrogen-sulfur-based agents, and inorganic antibacterial agents containing antibacterial metals in a porous material.

[0061] 2. Physical Properties of Foam Rubber (1) Apparent Density The apparent density of foam rubber (JIS K 7222:2005) is not particularly limited. From the viewpoint of making the foam rubber soft and fluffy against the skin, the apparent density of foam rubber is 0.08 g / cm³. ３ 0.30g / cm or more ３ The following is preferable: 0.10 g / cm³ ３ 0.20g / cm or more ３ The following is more preferable: 0.13 g / cm³ ３ 0.18g / cm or more ３ The following is even more preferable. The apparent density of the foam rubber is measured by the measurement method described later.

[0062] (2) The Asker F hardness of the Asker F hardness foam rubber is preferably 65 or less, more preferably 60 or less, and even more preferably 55 or less, from the viewpoint of making it soft and fluffy against the skin.

[0063] (3) Tensile strength The tensile strength of the foam rubber (JIS K 6400-5:2012) is preferably greater than 90 kPa, more preferably 120 kPa or higher, and even more preferably 150 kPa or higher, from the viewpoint of usability. The upper limit of the above tensile strength of the foam rubber is not particularly limited.

[0064] (4) The elongation of the foam rubber (JIS K 6400-5:2012) is preferably greater than 250%, more preferably 350% or more, and even more preferably 430% or more. The upper limit of the above elongation of the foam rubber is not particularly limited.

[0065] 3. Method for Manufacturing Foam Rubber The method for manufacturing foam rubber is not particularly limited. For example, the following manufacturing methods are preferably employed.

[0066] First, prepare the vulcanizing paste. Specifically, prepare the vulcanizing paste by adding a vulcanizing agent (e.g., sulfur), a vulcanizing aid (e.g., zinc oxide), a vulcanizing accelerator, an anti-aging agent, and a dispersant (e.g., sodium β-naphthalene sulfonic acid formalin condensate) to water.

[0067] Next, foam rubber is prepared. Specifically, a rubber composition is obtained by blending latex (emulsion) with vulcanizing paste, foaming agent, foam stabilizer, oils and fats, emulsifiers (e.g., casein protein, polyoxyethylene alkyl ether, etc.), and other additives (antibacterial agents, antifungal agents, etc.). Air is added to this composition, foaming is performed using a mixer, a gelling agent is added to solidify it, and then it is heated to produce foam rubber.

[0068] The gas used to create bubbles in the rubber composition is not particularly limited. Examples of gases that can be used include air and nitrogen. A mixer can be used as a method for creating bubbles. Suitable mixers include, for example, a Hobard mixer, a pin mixer, and an oak mixer. The vulcanization method is not particularly limited. Examples of vulcanization methods include steam vulcanization, hot air vulcanization, high-frequency vulcanization, and electron beam vulcanization.

[0069] 4. The foam rubber of the present disclosure can be suitably used in a cosmetic applicator 1. Figure 1 schematically shows an example of a cosmetic applicator 1.

[0070] The foam rubber disclosed herein has a pleasant feel against the skin and possesses excellent commercial value for applications that come into direct contact with the skin. When the foam rubber disclosed herein is used in the applicator 1, it is possible to provide an applicator that is soft, glides smoothly against the skin, and has a high cosmetic effect. The shape and structure of the cosmetic applicator 1 are not particularly limited, as long as it is used for the purpose of applying cosmetics. The foam rubber disclosed herein may be used in part of the applicator 1 or in the entirety of it. Suitable examples of cosmetic applicators 1 include puffs and brushes for liquid, cream, and powder foundations.

[0071] The following will provide a more detailed explanation using examples. 1. Preparation of Foam Rubber Various types of foam rubber were prepared using the compounding ratios shown in Table 1.

[0072]

[0073] Table 1 shows the details of the main ingredients below. (1) Raw materials - Rubber polymer: Acrylonitrile butadiene latex (NBR rubber) Nipol LX531B (manufactured by Nippon Zeon Co., Ltd.) - Foam stabilizer 1: Polyethyleneimine Epomin SP-006 (manufactured by Nippon Shokubai Co., Ltd.) - Foam stabilizer 2: Polyalkylene glycol derivative TNM-14Z (manufactured by Musashino Chemical Co., Ltd.) - Foaming agent: Potassium oleate oleate soap FR-14 (manufactured by Kao Corporation) - Vulcanizing agent: Sulfur fine powder 200 mesh (manufactured by Hosoi Chemical Industry Co., Ltd.) - Vulcanization aid: Zinc oxide (2 types of zinc oxide) (manufactured by Sakai Chemical Industry Co., Ltd.) - Vulcanization accelerator: Zinc salt of 2-mercaptobenzothiazole Noxellar MZ (manufactured by Ouchi Shinko Chemical Co., Ltd.) - Antioxidant: Phenolic antioxidant Adekastab AO-80 (manufactured by ADEKA Corporation) - Anti-aging agent: Bisphenolic antioxidant Nocrack NS-30 Emulsifier 1 (manufactured by Ouchi Shinko Chemical Co., Ltd.): Casein protein casein Dispersant (manufactured by Meggle Co., Ltd.): Sodium salt Demol N of β-naphthalene sulfonic acid formalin condensate Emulsifier 2 (manufactured by Kao Corporation): Polyoxyethylene alkyl ether emulsion 1135S-70 (manufactured by Kao Corporation): Pyrithione zinc Hokuside ZPT 48% dispersion Antifungal agent (manufactured by Hokko Sangyo Co., Ltd.): Thiabendazole Hokustar 25% sol (TBZ) Oils and fats (softeners) 1 (manufactured by Hokko Sangyo Co., Ltd.): Higheryl rapeseed oil Oils and fats (softeners) 2 (manufactured by Summit Oil Co., Ltd.): Jojoba oil (jojoba oil) Oils and fats (softeners) 3 (manufactured by Summit Oil Co., Ltd.): Olive oil (olive oil) Oils and fats (softeners) 4 (manufactured by J-Oil Mills Co., Ltd.): Cottonseed oil J-Oil Mills Co., Ltd. Gelling agent: Sodium silicic acid fluoride (sodium silicate) Shimonoseki Mitsui Chemicals Co., Ltd.

[0074] (2) Preparation of Foam Rubber Each foam rubber was specifically prepared as follows: (2.1) Example 1 (Preparation of Vulcanization Paste) The vulcanizing agent, vulcanization aid, vulcanization accelerator, antioxidant, and dispersant were added to water in the proportions shown in Table 1 and dispersed in a ball mill for 48 hours to prepare the vulcanization paste.

[0075] (Preparation of Foam Rubber) NBR latex rubber was used as the main raw material for the foam rubber. To 100 parts by mass of the rubber polymer contained in the latex mixture, a vulcanizing paste, a foaming agent, foam stabilizers 1 and 2, oil and fat 1 (higheryl rapeseed oil, 3.2 parts by mass), emulsifiers 1 and 2, and other additives (antibacterial agents, antifungal agents) were mixed according to the formulation shown in Table 1 to obtain a rubber composition (latex foam raw material). After adding air to this raw material and foaming it, foaming was performed using an oak mixer, a gelling agent was added and solidification occurred, and then it was heated at 100°C for 30 minutes to produce foam rubber.

[0076] (2.2) Example 2 Foam rubber was prepared in the same manner as in Example 1, except that the amount of oil 1 (high erucine rapeseed oil) was 6.4 parts by mass.

[0077] (2.3) Example 3 Foam rubber was prepared in the same manner as in Example 1, except that oil 2 (jojoba oil, 6.4 parts by mass) was used instead of oil 1 (high erucine rapeseed oil, 3.2 parts by mass).

[0078] (2.4) Comparative Example 1 Foam rubber was prepared in the same manner as in Example 1, except that oils and fats (softeners) were not used.

[0079] (2.5) Comparative Example 2 Foam rubber was prepared in the same manner as in Example 1, except that oil and fat 3 (olive oil, 6.4 parts by mass) was used instead of oil and fat 1 (high erucine rapeseed oil, 3.2 parts by mass).

[0080] (2.6) Comparative Example 3 Foam rubber was prepared in the same manner as in Example 1, except that oil and fat 4 (cottonseed oil, 3.2 parts by mass) was used instead of oil and fat 1 (high erucine rapeseed oil, 3.2 parts by mass).

[0081] (2.7) Comparative Example 4 Foam rubber was prepared in the same manner as in Example 1, except that oil and fat 4 (cottonseed oil, 6.4 parts by mass) was used instead of oil and fat 1 (high erucine rapeseed oil, 3.2 parts by mass).

[0082] 2. Evaluation Method The foam rubbers of Examples 1-3 and Comparative Examples 1-4 were evaluated as follows: (1) Evaluation Method for Surface Appearance of Foam Rubber The cell state (cell fineness) of the foam rubber was evaluated. Figures 2-5 are photographs of the surface of the foam rubbers of Examples 1 and 2 and Comparative Examples 1 and 2, respectively, taken using an optical microscope. The evaluation of surface appearance (cell roughness) is as follows: A: Cells are fine and there are few consecutive cells. B: Cell fineness is poor and there are many consecutive cells.

[0083] (2) Apparent density: The apparent density was measured in accordance with JIS K 7222:2005.

[0084] (3) The Asker F hardness of the Asker F hardness foam rubber was measured using an Asker hardness tester type F.

[0085] (4) Tensile strength The tensile strength of the foam rubber was measured in accordance with JIS K 6400-5:2012.

[0086] (5) The elongation of the foam rubber was measured in accordance with JIS K 6400-5:2012.

[0087] 3. Results The results are shown in Table 1. Figures 6-9 show photographs from Figures 2-5 with lines (thick black lines) drawn around the outer edges of multiple consecutive cells near the center. In the foam rubber of Examples 1 and 2, as shown in Figures 6 and 7, the cells were fine and there were few consecutive cells, resulting in a surface appearance evaluation of "A". The surface appearance evaluation of the foam rubber of Example 3 was also "A", although it is not shown in the illustration. In contrast, in the foam rubber of Comparative Examples 1 and 2, as shown in Figures 8 and 9, the cells were not fine enough and there were many consecutive cells, resulting in a surface appearance evaluation of "B". The surface appearance evaluation of the foam rubber of Comparative Examples 3 and 4 was also "B", although it is not shown in the illustration. By using high-erucine rapeseed oil or jojoba oil as the oil (softener), it was possible to produce foam rubber with finer cells and fewer consecutive cells compared to when no oil was used or when olive oil or cottonseed oil was used.

[0088] The Asker F hardness of the foam rubber in Examples 1-3 was about the same as that of the foam rubber in Comparative Example 1-4, and was sufficiently low. The tensile strength of the foam rubber in Example 1-3 was greater than that of the foam rubber in Comparative Example 1-4. It is generally known from experience that higher tensile strength results in better skin glide. Therefore, the foam rubber in Example 1-3 had better skin glide than the foam rubber in Comparative Example 1-4. Consequently, by using high-erucine rapeseed oil or jojoba oil as the oil (softener), it was possible to produce a softer foam rubber with better skin glide compared to when no oil was used or when olive oil or cottonseed oil was used.

[0089] The foam rubbers of Examples 1 and 2 had similar Asker F hardness and tensile strength. The amount of oil (high erucine rapeseed oil) added to Example 1 was half the amount added to Example 2. Therefore, it was found that when high erucine rapeseed oil is used as the oil, the amount added to produce a soft, smooth foam rubber can be reduced, and bleed-out can be easily suppressed.

[0090] 4. Effects of the Examples According to the above examples, a soft and smooth foam rubber can be provided.

[0091] This disclosure is not limited to the embodiments detailed above, and various modifications or alterations are possible.

[0092] 1. Cosmetic applicator

Claims

1. Foam rubber manufactured from a composition containing a rubber-based polymer and an oil or fat containing a fatty acid with 20 or more carbon atoms.

2. The foam rubber according to claim 1, wherein the oil content is 1 part by mass or more and 20 parts by mass or less when the rubber polymer is 100 parts by mass.

3. The foam rubber according to claim 1 or claim 2, wherein the content of the fatty acid having 20 or more carbon atoms is 0.5 parts by mass or more and 17 parts by mass or less when the rubber polymer is 100 parts by mass.

4. A cosmetic applicator comprising the foam rubber described in any one of claims 1 to 3.

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