Rubber composition for sealing material and sealing material

Abstract

To provide a rubber composition for a sealing material, which has good roll processability and allows a sealing material having good normal-state physical properties and wear resistance and also having heat resistance and oil resistance to be produced.SOLUTION: The rubber composition for a sealing material contains an acrylic rubber and carbon blacks. The carbon blacks include a carbon black having a particle diameter of 100 nm or more and a carbon black having a particle diameter of less than 100 nm. The content of the carbon blacks is 30 pts.mass or more and 200 pts.mass or less based on 100 pts.mass of the acrylic rubber. The content of the carbon black having a particle diameter of 100 nm or more is 1 pt.mass or more and 100 pts.mass or less based on 100 pts.mass of the acrylic rubber. The content of the carbon black having a particle diameter of less than 100 nm is 29 pts.mass or more and 100 pts.mass or less based on 100 pts.mass of the acrylic rubber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for a seal, and further to a seal. [Background technology]

[0002] A vulcanizate of a rubber composition in which silica or glass fiber is blended with acrylic rubber has been proposed as a sealing material for use in sliding or rotating parts such as automotive oil seals (Patent Document 1). In addition, methods for improving the wear resistance of sealing materials have been proposed, such as adding a lubricating oil to the rubber composition that forms the sealing material, or subjecting the sealing material to a surface treatment in a post-process (Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-055832 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-348460 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-241868 Summary of the Invention [Problem to be solved by the invention]

[0004] Adding silica or glass fiber to a rubber composition containing acrylic rubber can deteriorate roll processability and mechanical properties. Adding lubricating oil to a rubber composition can deteriorate molding processability, increase raw material costs, and affect the types and contents of other components. Furthermore, applying surface treatment in a later process can increase production costs due to the increased number of processes and materials used for the surface treatment.

[0005] An object of the present invention is to provide a rubber composition for a seal which has good roll processability and enables the production of a seal having good normal physical properties and abrasion resistance. [Means for solving the problem]

[0006] The present invention provides the following rubber composition for a seal and the following seal. [1] A rubber composition for a seal material comprising an acrylic rubber and carbon black, The carbon black includes carbon black having a particle size of 100 nm or more and carbon black having a particle size of less than 100 nm, the content of the carbon black is 30 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the acrylic rubber, the content of the carbon black having a particle diameter of 100 nm or more is 1 part by mass or more and 100 parts by mass or less per 100 parts by mass of the acrylic rubber, The rubber composition for sealing materials, wherein the content of the carbon black having a particle diameter of less than 100 nm is 29 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the acrylic rubber. [2] The rubber composition for a seal according to [1], wherein the acrylic rubber includes a carboxyl group-containing acrylic rubber. [3] The rubber composition for seals according to [1] or [2], wherein the carbon black having a particle size of 100 nm or more is MT carbon black. [4] The rubber composition for seals according to any one of [1] to [3], wherein the carbon black having a particle size of less than 100 nm is at least one selected from the group consisting of FEF carbon black and HAF carbon black. [5] A sealant comprising a crosslinked product of the rubber composition for a sealant according to any one of [1] to [4]. [6] The sealing material according to [5], having a dynamic friction coefficient of 1.65 or less as measured in accordance with JIS K7218A. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a rubber composition for a seal that has good roll processability and enables the production of a seal having good normal physical properties and abrasion resistance. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0009] <Rubber composition for sealing materials> The rubber composition for a seal material contains acrylic rubber and carbon black, and the carbon black contains carbon black having a particle diameter of 100 nm or more and carbon black having a particle diameter of less than 100 nm. The content of the carbon black in the rubber composition for a seal material is 30 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the acrylic rubber. The content of the carbon black having a particle diameter of 100 nm or more in the rubber composition for a seal material is 1 part by mass or more and 100 parts by mass or less per 100 parts by mass of the acrylic rubber. The content of the carbon black having a particle diameter of less than 100 nm in the rubber composition for a seal material is 29 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the acrylic rubber.

[0010] (acrylic rubber) Acrylic rubber is a polymer having structural units derived from acrylic esters. The structural units derived from acrylic esters can be, for example, structural units derived from alkyl acrylate esters and structural units derived from alkoxyalkyl acrylate esters. Conventionally, hydrogenated nitrile rubber has been used in rubber compositions for sealing materials (see, for example, Patent Document 2). When a rubber composition for sealing materials contains acrylic rubber, the production costs tend to be reduced compared to hydrogenated nitrile rubber, and the heat resistance and oil resistance of the sealing material tend to be improved.

[0011] The structural unit derived from an alkyl acrylate ester is preferably a structural unit derived from an alkyl acrylate ester having an alkyl group containing 1 to 8 carbon atoms, more preferably a structural unit derived from an alkyl acrylate ester having an alkyl group containing 2 to 6 carbon atoms, and even more preferably a structural unit derived from an alkyl acrylate ester having an alkyl group containing 2 to 4 carbon atoms. Specific examples of structural units derived from alkyl acrylate esters include structural units derived from acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate. Of these, structural units derived from ethyl acrylate and n-butyl acrylate are preferred.

[0012] The structural unit derived from an alkoxyalkyl acrylate is preferably a structural unit derived from an alkoxyalkyl acrylate having an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a structural unit derived from an alkoxyalkyl acrylate having an alkoxyalkyl group having 2 to 6 carbon atoms, and even more preferably a structural unit derived from an alkoxyalkyl acrylate having an alkoxyalkyl group having 2 to 4 carbon atoms. Specific examples of structural units derived from an alkoxyalkyl acrylate include structural units derived from acrylic esters such as methoxymethyl acrylate, methoxyethyl acrylate, ethoxymethyl acrylate, 2-ethoxyethyl acrylate, 2-propoxyethyl acrylate, 2-butoxyethyl acrylate, 2-methoxypropyl acrylate, 2-ethoxypropyl acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 4-methoxybutyl acrylate, and 4-ethoxybutyl acrylate. Of these, a structural unit derived from methoxyethyl acrylate is preferred.

[0013] The content of structural units derived from acrylic acid esters in the acrylic rubber may be, for example, 5% by mass or more and 99.9% by mass or less, preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, more preferably 50% by mass or more, particularly preferably 70% by mass or more, and preferably 99.5% by mass or less, more preferably 99% by mass or less, based on the total structural units of the acrylic rubber.

[0014] From the viewpoint of heat resistance and resistance to slight water-containing oils, the acrylic rubber preferably contains structural units derived from unsaturated monomers having a carboxyl group. Examples of unsaturated monomers having a carboxyl group include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, 2-pentenoic acid, and cinnamic acid, unsaturated dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid, carboxylic anhydrides such as maleic anhydride and citraconic anhydride, butenedioic acid mono-chain alkyl esters such as monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, and mono-n-butyl maleate, butenedioic acid mono-cyclic alkyl esters such as monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclopentyl maleate, and monocyclohexyl maleate, and itaconic acid monoesters such as monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate, and monocyclohexyl itaconate. Among these, unsaturated dicarboxylic acid monoesters such as monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, monoethyl itaconate, monopropyl itaconate, monobutyl itaconate, etc. are exemplified. In this specification, (meth)acrylic acid means either methacrylic acid or acrylic acid.

[0015] When the acrylic rubber has a structural unit derived from an unsaturated monomer having a carboxyl group, the content of the structural unit in the acrylic rubber may be, for example, 0.1% by mass or more, preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less.

[0016] In addition to the above-mentioned structural units, the acrylic rubber may contain other monomer structural units copolymerizable therewith. Examples of such other structural units include structural units derived from methacrylate esters and structural units derived from other olefin-based monomers.

[0017] Commercially available acrylic rubbers can be used, such as Lacrestar CH and Lacrestar CT (both manufactured by Osaka Soda Co., Ltd.).

[0018] The acrylic rubber may be used alone or in combination of two or more kinds.

[0019] (carbon black) The content of carbon black in the rubber composition for a seal is usually 30 parts by mass or more and 200 parts by mass or less per 100 parts by mass of acrylic rubber. The amount of carbon black can be adjusted depending on the normal physical properties and abrasion resistance of the seal. The content of carbon black in the rubber composition for a seal is preferably 40 parts by mass or more and 150 parts by mass or less, more preferably 45 parts by mass or more and 120 parts by mass or less, even more preferably 50 parts by mass or more and 100 parts by mass or more, and particularly preferably 50 parts by mass or more and 95 parts by mass or less, per 100 parts by mass of acrylic rubber.

[0020] The carbon black includes both carbon black with a particle size of 100 nm or greater and carbon black with a particle size of less than 100 nm. By including both carbon black with a particle size of 100 nm or greater and carbon black with a particle size of less than 100 nm, sealants containing acrylic rubber tend to exhibit good normal physical properties and abrasion resistance while suppressing increases in hardness. This is presumably because the small-particle carbon black with relatively high reinforcing properties is incorporated into the gaps between the large-particle carbon black with relatively low reinforcing properties, improving the dispersibility of the carbon black and increasing the carbon black loading rate in the rubber composition for sealants (sealants), thereby improving normal physical properties and abrasion resistance. In this specification, particle size refers to the length of a straight line drawn so that the primary particle size of the carbon black particles measured in an image of the carbon black taken with an electron microscope is at its largest value.

[0021] Furthermore, the improved dispersibility of carbon black in the rubber composition for seals tends to improve roll processability during kneading in the compound preparation step.

[0022] Furthermore, as the filling rate of carbon black in the rubber composition for sealing materials increases, the proportion of acrylic rubber in the compound decreases, which tends to facilitate reduction in raw material costs.

[0023] Carbon black having a particle size of 100 nm or more may have an average particle size of, for example, 100 nm or more and 500 nm or less, preferably 200 nm or more and 490 nm or less. Carbon black having a particle size of 100 nm or more is preferably MT carbon black. In this specification, the average particle size refers to the arithmetic average of the primary particle sizes of 10 carbon black particles randomly selected from an image of carbon black photographed with an electron microscope.

[0024] The average particle size of MT carbon black can be, for example, 250 nm or more and 480 nm or less.

[0025] MT carbon black, for example, has a nitrogen adsorption specific surface area (N2SA) of 20m 2 / g or more 45m 2 The nitrogen adsorption specific surface area can be measured by the method described in JIS K6217-2:2001.

[0026] The MT carbon black may have a dibutyl phthalate (DBP) absorption of, for example, 70 ml / 100 g or more and less than 80 ml / 100 g. The dibutyl phthalate (DBP) absorption can be measured by the method described in JIS K6217-4:2008.

[0027] Commercially available MT carbon black can be used, such as "HTC#20" manufactured by Shin-Nichika Carbon Co., Ltd. and the "Thermax" series manufactured by Cancarb Limited.

[0028] The content of carbon black having a particle diameter of 100 nm or more is 1 part by mass or more and 100 parts by mass or less, preferably 2 parts by mass or more and 50 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less, and even more preferably 5 parts by mass or more and less than 20 parts by mass, per 100 parts by mass of acrylic rubber.

[0029] The carbon black having a particle size of less than 100 nm may have an average particle size of, for example, 5 nm or more and less than 100 nm, preferably 20 nm or more and 60 nm or less, and more preferably 28 nm or more and 50 nm or less. The carbon black having a particle size of less than 100 nm is preferably at least one selected from the group consisting of FEF carbon black and HAF carbon black.

[0030] FEF carbon black has an average particle size of 43 nm and a nitrogen adsorption specific surface area (N2SA) of 42 m 2 / g and DBP absorption capacity is 115 ml / 100 g. HAF carbon black has an average particle size of 28 nm and a nitrogen adsorption specific surface area (N2SA) of 77 m2 / g, and dibutyl phthalate (DBP) absorption can be 101 ml / 100 g.

[0031] Commercially available HAF carbon black and FEF carbon black can be used. Commercially available HAF carbon black products include "Diablack H" manufactured by Mitsubishi Chemical Corporation and "Seast 3" manufactured by Tokai Carbon Co., Ltd. Commercially available FEF carbon black products include "Seast GSO" manufactured by Tokai Carbon Co., Ltd. and "Asahi 60" manufactured by Asahi Carbon Co., Ltd.

[0032] The carbon black preferably contains only MT carbon black and at least one selected from the group consisting of FEF carbon black and HAF carbon black, and more preferably contains only MT carbon black, FEF carbon black, and HAF carbon black.

[0033] The content of carbon black having a particle diameter of less than 100 nm is 29 parts by mass or more and 100 parts by mass or less, preferably 30 parts by mass or more and 80 parts by mass or less, more preferably 40 parts by mass or more and 70 parts by mass or less, and even more preferably 45 parts by mass or more and 65 parts by mass or less, relative to 100 parts by mass of acrylic rubber.

[0034] The ratio of the mass of carbon black having a particle diameter of 100 nm or more to the mass of carbon black having a particle diameter of less than 100 nm is preferably 1 / 20 or more and 1 or less, more preferably 1 / 15 or more and 1 / 2 or less, and even more preferably 1 / 10 or more and 1 / 3 or less.

[0035] (Crosslinking agent) The crosslinking system of the acrylic rubber may be, for example, a polyamine crosslinking system. Examples of crosslinking agents used in the polyamine crosslinking system include ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenetetramine, p-phenylenediamine, cumenediamine, N,N'-dicinnamylidene-1,6-hexanediamine, ethylenediamine carbamate, and hexamethylenediamine carbamate.

[0036] Commercially available crosslinking agents can be used, such as "DIAC No. 1" (hexamethylenediamine carbamate) manufactured by Chemours.

[0037] The content of the crosslinking agent in the rubber composition for a seal material may be, for example, 0.1 to 10 parts by mass, and preferably 0.5 to 5.0 parts by mass, relative to 100 parts by mass of the acrylic rubber. Within this range, the crosslinking reaction can proceed sufficiently.

[0038] (additives) The rubber composition for sealing materials may contain additives, such as vulcanization accelerators, processing aids, and antioxidants. The additives may be used alone or in combination of two or more.

[0039] When the rubber composition for a seal contains additives, the total amount of the additives in the rubber composition for a seal may be an amount normally used in the field, for example, 50 parts by mass or less per 100 parts by mass of acrylic rubber, preferably 0.1 parts by mass or more and 25 parts by mass or less, more preferably 1 part by mass or more and 10 parts by mass or less.

[0040] Specific examples of the vulcanization accelerator include thiuram-based, thiazole-based, sulfenamide-based, thiourea-based, guanidine-based, and dithiocarbamate-based compounds.

[0041] Specific examples of processing aids include thermoplastic resins, liquid rubbers, oils, plasticizers, softeners, internal mold release agents, and tackifiers, such as stearic acid and zinc oxide. When the rubber component contains FKM, FEPM, or FFKM, it may contain a fluororesin or particles thereof as a filler, or a liquid fluororubber as a processing aid. When the rubber component contains EPM or EPDM, it may contain, for example, paraffinic oil as a processing aid.

[0042] Specific examples of the antioxidant include phenol derivatives, aromatic amine derivatives, amine-ketone condensates, benzimidazole derivatives, dithiocarbamic acid derivatives, thiourea derivatives, and the like.

[0043] The rubber composition for sealing materials can be prepared by uniformly kneading the above components using a kneader. Examples of kneaders that can be used include a mixing roll, a pressure kneader, and an internal mixer (Banbury mixer). In this case, among the various compounding components, components other than those contributing to the crosslinking reaction (crosslinking agent, vulcanization accelerator, etc.) may be kneaded uniformly first, and then the components contributing to the crosslinking reaction may be kneaded. The kneading temperature is preferably, for example, around room temperature.

[0044] (Application) A seal containing a crosslinked product of the rubber composition for a seal has good normal physical properties as well as excellent abrasion resistance, heat resistance, and oil resistance, and therefore can be used as a seal for a sliding part or a rotating part. The rubber composition for a seal is particularly suitable for a seal for an oil filter, which requires high heat resistance and oil resistance.

[0045] <Sealing material> The sealant includes a crosslinked product of the rubber composition for the sealant. The sealant can be produced by crosslinking (vulcanizing) and molding the rubber composition for the sealant. The crosslinking and molding methods can be conventionally known methods such as injection molding, compression molding, and transfer molding.

[0046] The heating temperature (primary crosslinking temperature) during molding may be, for example, 120°C or higher and 220°C or lower, and the heating time (primary crosslinking time) may be, for example, 0.5 minutes or higher and 120 minutes or lower. After vulcanization molding, secondary crosslinking may be performed. The secondary crosslinking temperature may be, for example, 120°C or higher and 280°C or lower, and the secondary crosslinking time may be, for example, 0.5 hours or higher and 24 hours or lower.

[0047] The sealing material preferably has an appropriate hardness, and for example, the A-type hardness according to JIS K 6253 may be, for example, 95 or less, preferably 60 to 80, and more preferably 65 to 75. When the hardness of the sealing material is within the above range, sealing properties tend to be easily maintained in sliding parts and rotating parts.

[0048] The sealing material may have a tensile strength of, for example, 10.5 MPa or more, preferably 11.0 MPa or more, more preferably 11.5 MPa or more, and usually 20 MPa or less, when its A-type hardness according to JIS K 6253 is 70. The sealing material may have an elongation of, for example, more than 220%, preferably 230% or more, more preferably 240% or more, and usually 350% or less, when its A-type hardness according to JIS K 6253 is 70. In this specification, tensile strength and elongation are measured in accordance with JIS K 6251.

[0049] The sealing material can be a packing used in a rotating part or a sliding part, a gasket used in a fixed part, etc. The shape of the sealing material is selected appropriately depending on the application, and a typical example is an O-ring with an O-shaped cross section. [Example]

[0050] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Roll processability] When the rubber composition for the sealing material was kneaded using a roll, those that did not stick to the roll were evaluated as "○", those that stuck to the roll were evaluated as "△", and those that stuck to the roll so much that carbon black could not be blended until the rubber hardness reached around 70 were evaluated as "×".

[0051] [Normal physical properties] The hardness of the sheet-form molded product was measured using a spring hardness tester as type A hardness in accordance with JIS K 6253. The tensile strength and elongation at break were measured using No. 3 dumbbell-shaped test pieces stretched at 500 mm / min using a Schopper tensile tester in accordance with JIS K 6251. All of these tests were carried out at 25°C.

[0052] [Wear resistance] The wear test was carried out in accordance with JIS K 7218A under the following conditions, and the dynamic friction coefficient and wear amount [mg] were measured. (Wear test conditions) Counterpart material: SS400 Rotation speed: 84 rpm Load: 120N Exam time: 1 hour

[0053] Example 1 Acrylic rubber, carbon black, processing aid, antioxidant, crosslinking accelerator, and crosslinking agent were kneaded on an open roll to form a full compound. The composition of each component is shown in Table 1. The resulting full compound was then thermally crosslinked at 170°C for 10 minutes (first crosslinking), and then at 180°C for 16 hours (second crosslinking) to obtain a rubber molded product. Test specimens were prepared from the resulting rubber molded product and evaluated. The evaluation results are shown in Table 1.

[0054] <Examples 2 to 4, Comparative Examples 1 to 3> Test specimens were prepared from the rubber molded products in the same manner as in Example 1, except that the compounding ingredients and compounding compositions were changed as shown in Table 1. The evaluation results are shown in Table 1.

[0055] [Table 1]

[0056] The details of the ingredients in Table 1 are as follows: Acrylic rubber 1: "Lacrestar CT" (carboxyl group-containing acrylic rubber) manufactured by Osaka Soda Co., Ltd. Acrylic rubber 2: "Lacrestar CH" (carboxyl group-containing acrylic rubber) manufactured by Osaka Soda Co., Ltd. MT carbon: CANCARB "Thermax N990 ULTRA-PURE" FEF carbon: "Seast GSO" manufactured by Tokai Carbon Co., Ltd. HAF carbon: "Diablack H" manufactured by Mitsubishi Chemical Corporation Crosslinking agent: Chemours "DIAC No. 1" (hexamethylenediamine carbamate) Crosslinking accelerator: "Noccela DT" (1,3-di-o-tolylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Processing aid 1: Kao Corporation's "Lunac S-50V" (stearic acid) Processing aid 2: "Phosphanol RL210" (polyoxyethylene stearyl ether phosphate) manufactured by Toho Chemical Industry Co., Ltd. Antioxidant: "Nocrac CD" [4,4'-bis(α,α-dimethylbenzyl)diphenylamine] manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0057] As shown in Table 1, the rubber compositions for sealing materials of Examples 1 to 4 had good roll processability. The resulting seals exhibited high tensile strength and elongation at a Shore A hardness of around 70, yet had low dynamic friction coefficients and small wear amounts. Furthermore, a comparison of the wear resistance of the rubber compositions for sealing materials of Examples 3 and 4 confirmed that the composition containing three types of carbon black tended to exhibit better results than the composition containing two types. In contrast, the rubber compositions for sealing materials of Comparative Examples 1 and 3 had poor roll processability. The resulting seals exhibited low tensile strength and elongation at a Shore A hardness of around 70, and the seals collapsed in the wear resistance test. Furthermore, the rubber composition for sealing material of Comparative Example 2 had poor roll processability, and the resulting seals exhibited poor normal physical properties and wear resistance. It can be seen that the seals produced from the sealing material rubber compositions of the present invention exhibited good roll processability and normal physical properties, and exhibited excellent wear resistance.

Claims

1. A rubber composition for a seal material, comprising an acrylic rubber and carbon black, The carbon black includes carbon black having a particle diameter of 100 nm or more and carbon black having a particle diameter of less than 100 nm, the content of the carbon black is 30 parts by mass or more and 130 parts by mass or less relative to 100 parts by mass of the acrylic rubber, the content of the carbon black having a particle diameter of 100 nm or more is 1 part by mass or more and 30 parts by mass or less relative to 100 parts by mass of the acrylic rubber, an amount of the carbon black having a particle size of less than 100 nm is 29 parts by mass or more and 100 parts by mass or less relative to 100 parts by mass of the acrylic rubber, The acrylic rubber of the rubber composition for sealing materials includes a carboxyl group-containing acrylic rubber.

2. 2. The rubber composition for sealing materials according to claim 1, wherein the carbon black having a particle size of 100 nm or more is MT carbon black.

3. 3. The rubber composition for sealing materials according to claim 1, wherein the carbon black having a particle size of less than 100 nm is at least one selected from the group consisting of FEF carbon black and HAF carbon black.

4. A seal comprising a crosslinked product of the rubber composition for a seal according to any one of claims 1 to 3.

5. The sealing material according to claim 4, which has a dynamic friction coefficient of 1.65 or less as measured in accordance with JIS K7218A.

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