JP2007186583A - Highly damping rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly damping rubber that has high damping performance and can be produced with a simple composition and easy procedures. <P>SOLUTION: The rubber composition comprising acrylonitrile-butadiene rubber (preferably an amount of combined acrylonitrile is 30-50%) and inorganic acid salt of copper (II) (preferably copper sulfate anhydride) is heated preferably at 150-200°C for 10-60 minutes. The hysteresis loss of the highly damping rubber is set to 40-70% while the percentage of elongation applied to the highly damping rubber is 90% to the elongation applied when the highly damping rubber is broken. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high damping rubber.

In recent years, for example, in order to improve anti-vibration and damping performance for various industrial machines, home appliances, etc., and for example, seismic isolation performance for various buildings, development of high-damping rubber with excellent vibration energy damping performance has been actively conducted. It has become.
Conventionally, high damping rubber was obtained by blending raw materials rubber with various additives such as a crosslinking agent, filler (for example, carbon black, silica, etc.), softener, plasticizer, resin, high styrene rubber and the like. A high damping rubber composition is prepared by kneading and heat treatment.
Japanese Patent No. 3447643 Japanese Patent No. 2796044

However, conventional high-damping rubber compositions require a wide variety of additives, and are difficult to process. The preparation of high-damping rubber compositions and manufacturing processes for high-damping rubber (especially kneading, vulcanization, etc.) There was a problem that the process of (1) was complicated.
Accordingly, an object of the present invention is to provide a high-damping rubber that has a high damping performance and can be manufactured by a simple composition and a simple process.

In order to achieve the above object, the present invention provides:
(1) A high-damping rubber obtained by heating a rubber composition containing acrylonitrile-butadiene rubber and an inorganic acid salt of copper (II),
(2) The high attenuation rubber according to (1), wherein the inorganic acid salt of copper (II) is copper sulfate,
(3) The high-damping rubber according to (1) or (2), wherein the amount of bound acrylonitrile in the acrylonitrile-butadiene rubber is 30 to 50%,
(4) The high-damping rubber according to any one of (1) to (3), wherein the rubber composition is obtained by heating at 150 to 200 ° C. for 10 to 60 minutes.
(5) The hysteresis loss of the high damping rubber is 40 to 70% when the elongation given to the high damping rubber is 90% with respect to the elongation when the high damping rubber is cut. The high-damping rubber according to any one of (1) to (4),
I will provide a.

The above-mentioned “elongation when the high-damping rubber is cut” is the tensile test (tensile speed of 500 mm / min) defined in JIS K 6251 _{: 2004} “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. Dumbbell-shaped specimens taken from high-damping rubber (dumbbell-shaped No. 3 as defined in JIS K 6250, parallel part width 5 ± 0.1 mm, parallel part thickness 2.0 ± 0.2 mm, standard Elongation when the distance between lines (20 mm) is cut. Specifically, the difference ((L ₁ −L ₀ ) / mm) between the distance L ₁ (mm) between the marked lines when the dumbbell-shaped test piece is cut and the initial distance L ₀ (mm) between the marked lines. (L ₀ = 20 mm).

In addition, the hysteresis loss is obtained by using a strip-shaped test piece (width 5 mm, thickness 2 mm, distance between marked lines 40 mm) collected and manufactured from a high-damping rubber, as a pair of gripping tools (JIS B 7721) The rate of loss of mechanical energy (%) in one cycle of deformation and recovery when a tensile stress is applied by the following procedure with the distance between chucks being 80 mm).
The strip test piece fixed to the tensile tester is stretched until the elongation reaches a target elongation, that is, the difference between the distance L ₂ between the marked lines and the initial distance L ₀ between the marked lines. ((L ₂ −L ₀ ) / mm) is a previously measured difference between the distance L ₁ between the marked lines at the time of cutting the strip-shaped specimen and the distance L ₀ between the initial marked lines ((L ₁ − Pull at a pulling speed of 200 mm / min until 90% of L ₀ ) / mm). Next, immediately after the elongation of the strip-shaped test piece reaches the target elongation, unloading is performed at the same speed until the stress becomes zero.

  Hysteresis loss A (%) is surrounded by applied energy (0 point, curve a, point b, point e, and 0 point) from the stress-strain curve (see FIGS. 1 and 2) recorded in the series of operations described above. Area and the energy after one cycle of deformation and recovery (the area of the area surrounded by point 0, curve a, point b, curve c, point d and 0 point) is calculated by the following formula.

    A (%) = [(Area (0abcd0)) / (Area (0abe0))] × 100

  According to the present invention, it is necessary to blend a wide variety of additives such as a crosslinking agent, a filler (for example, carbon black, silica, etc.), a softener, a plasticizer, a resin, and a high styrene rubber with the raw rubber. However, a highly damped rubber having excellent damping performance can be produced by making the rubber composition for producing the highly damped rubber a simple composition and passing through simple steps of kneading and heat treatment.

The high-damping rubber of the present invention can be obtained by heating a rubber composition containing acrylonitrile-butadiene rubber and copper (II) inorganic acid salt.
Acrylonitrile-butadiene rubber (NBR) is not particularly limited. For example, a very high nitrile type or high nitrile type NBR with a large amount of bonded acrylonitrile, a low nitrile type with a low amount of bonded acrylonitrile, or a medium nitrile type NBR is known. Various NBRs can be used.

Among these, NBR is preferably a type having a large amount of bonded acrylonitrile from the viewpoint of increasing the number of crosslinking points.
The amount of bound acrylonitrile of NBR is preferably 30 to 50%, more preferably 35 to 50%.
Examples of such NBRs indicating the amount of bonded acrylonitrile include medium-high nitrile type (bonded acrylonitrile amount of 31% or more and less than 36%), high nitrile type (bonded acrylonitrile amount of 36% or more and less than 43%). ), Extremely high nitrile type (with a combined acrylonitrile amount of 43% or more).

Examples of copper (II) inorganic acid salts include compounds having an oxidation number of + II among copper and inorganic acid salts, such as copper sulfate, copper chloride (II), copper oxide (II). Etc. Of these, copper sulfate is preferable.
In addition, although the said copper (II) inorganic acid salt may take the form of a hydrate (hydrated salt), there exists a possibility that the crystal water in a hydrate may inhibit formation of the crosslinked structure of NBR. . For this reason, the inorganic acid salt of copper (II) is preferably an anhydride.

Therefore, copper (II) sulfate anhydride is particularly preferable among the above copper (II) inorganic acid salts.
The inorganic acid salt of copper (II) is blended in NBR and heat-treated, whereby the cyano group of NBR forms an intermolecular cross-linked structure (triazine structure) represented by the following reaction formula (1). It exhibits a catalytic action for the reaction and for the reaction in which the cyano group of NBR forms a ring structure by intramolecular cyclization schematically represented by the following formula (2).

    Reaction formula (1):

    Reaction formula (2):

(The above reaction formula schematically shows the intramolecular cyclization reaction, and the stoichiometric matching such as the number of hydrogen atoms bonded to the carbon atom is omitted.)
As shown in the above reaction formula (1), NBR forms an intermolecular cross-linked structure (triazine structure) using a copper (II) inorganic acid salt as a catalyst. This NBR cross-linked structure is a covalent cross-linked structure.

Moreover, it is thought that the said inorganic acid salt of copper (II) forms the crosslinked structure shown, for example by following (a)-(d) by mix | blending in NBR and heat-processing.
(A) A crosslinked structure by a coordinate bond between a cyano group of NBR and a copper (II) ion schematically represented by the following formula (3).
(B) A crosslinked structure by a coordinate bond between a triazine ring formed by intermolecular crosslinking of NBR and a copper (II) ion, schematically represented by the following formula (4).
(C) A crosslinked structure formed by a coordinate bond between a pyridine ring formed by NBR intramolecular cyclization and a copper (II) ion schematically represented by the following formula (5).
(D) a coordination bond between the cyano group of NBR and a copper (II) ion, a coordination bond between a triazine ring formed by intermolecular crosslinking of NBR and a copper (II) ion, and an NBR molecule A crosslinked structure containing two or more kinds of coordination bonds selected from the group consisting of coordination bonds between a pyridine ring formed by internal cyclization and a copper (II) ion.

(Note that the above formulas (3) to (5) schematically show cross-linking by coordination bonds, and the stoichiometric matching such as the number of hydrogen atoms bonded to carbon atoms is omitted. Yes.)
As described above, the above-mentioned NBR cross-linked structure is a cross-linked structure by a coordinate bond.
NBR intermolecular crosslinking reaction (triazine ring formation reaction) and NBR intramolecular cyclization reaction (pyridine ring formation reaction), and NBR cyano group and NBR molecule by the catalytic action of copper (II) described above In any case, the formation reaction of a coordination bond between a triazine ring formed by intercrosslinking or a pyridine ring formed by NBR intramolecular cyclization and a copper (II) ion is performed by NBR and copper (II). This is achieved by heat-treating a rubber composition containing the inorganic acid salt after kneading. In this way, a rubber composition containing NBR and a copper (II) inorganic acid salt is kneaded and heat-treated to obtain a highly attenuated rubber.

In addition, what kind of bridge | crosslinking state is formed by knead | mixing the rubber composition containing the inorganic salt of NBR and copper (II), and heat-processing, for example by observation by NMR etc. Can be determined.
Also, among the inorganic acid salts of copper (II), the amount not dispersed to the molecular level during the kneading treatment with NBR described later does not act as the central metal of the coordination bond in NBR. , Acts as a filler in NBR. Here, since the inorganic acid salt of copper (II) acting as a filler exists as an aggregate having a diameter of about 1 to 10 μm in NBR, the ratio of the inorganic acid salt of copper (II) acting as a filler is as follows. For example, it can be calculated by observing high-attenuation rubber with an electron microscope or the like.

  The compounding amount of the copper (II) inorganic acid salt is set according to the copper (II) ion (formula weight) in the copper (II) inorganic acid salt (molecular weight), and is particularly limited. However, for example, when the inorganic acid salt of copper (II) is copper sulfate (II) anhydride, the amount of copper sulfate (II) anhydride is preferably 1 to 100 parts by weight of NBR. It is 40 parts by weight, and more preferably 5 to 15 parts by weight.

  In this case, when the blending amount of copper (II) sulfate anhydride is less than 5 parts by weight with respect to 100 parts by weight of NBR, the crosslinking density of NBR is lowered or the reinforcing effect by copper (II) sulfate anhydride is obtained. It may become difficult to obtain, and there is a risk that the tensile strength of the high-damping rubber, the rubber hardness, etc. may be reduced. On the contrary, if the blending amount of copper (II) sulfate exceeds 15 parts by weight with respect to 100 parts by weight of NBR, the rubber hardness of the high-damping rubber becomes too high to be suitable for use as a damping member. There is a fear.

A rubber composition containing NBR and an inorganic acid salt of copper (II) may optionally further include, as a rubber component other than NBR, rubber such as natural rubber, chloroprene rubber, styrene butadiene rubber (SBR), etc. May be contained.
Moreover, the rubber composition containing NBR and copper (II) inorganic acid salt may further optionally contain a vulcanizing agent, a vulcanization accelerator, a filler, a reinforcing agent, and the like.

  Examples of the vulcanizing agent include sulfur, for example, organic sulfur-containing compounds such as N, N′-dithiobismorpholine, and organic peroxides such as benzoyl peroxide and dicumyl peroxide. Of these, sulfur and organic sulfur-containing compounds are preferable. Although the compounding quantity of a vulcanizing agent is not specifically limited, Preferably, it is 2 weight part or less with respect to 100 weight part of NBR.

  Examples of the vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetrakis (2-ethylhexyl) thiuram disulfide, tetramethylthiuram monosulfide (TMTM), Thiurams such as dipentamethylene thiuram tetrasulfide (TPTT), for example, 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), zinc salt of 2-mercaptobenzothiazole (ZnMBT), 2-mercaptobenzothiazole Cyclohexylamine salt (CMBT), 2- (N, N′-diethylthiocarbamoylthio) benzothiazole, 2- (4-morpholinodithio) benzothiazole, etc. Azoles such as pentamethylenedithiocarbamate piperidine salt (PPDC), pipecolyl dithiocarbamate pipecoline salt (PMPDC), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), zinc dibutyldithiocarbamate (ZnBDC), Zinc N-ethyl-N-phenyldithiocarbamate (ZnEPDC), zinc N-pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate (NaEDC), sodium dibutyldithiocarbamate (NaBDC), dimethyldithiocarbamate (CuMDC) ), Dithiocarbamic acid such as ferric dimethyldithiocarbamate (FeMDC) and tellurium diethyldithiocarbamate Such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N-oxydiethylene-2-benzothiazolylsulfen Sulfenamides such as amide (OBS) N, N′-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), such as trimethylthiourea (TMU), N, N′-diethylthiourea (DEU) Thioureas, for example, guanidines such as 1,3-diphenylguanidine (DPG), di-o-tolylguanidine (DOTG), 1-o-tolylbiguanide (OTBG), such as hexamethylenetetramine, n-butyraldehyde aniline Organic vulcanization accelerators such as slaked lime, oxide Examples thereof include inorganic vulcanization accelerators such as gnesium, titanium oxide, and resurge (PbO). These vulcanization accelerators may be used alone or in combination of two or more. Of the vulcanization accelerators exemplified above, thiurams and thiazoles are preferable. Although the compounding quantity of a vulcanization accelerator is not specifically limited, Preferably, it is 2 weight part or less with respect to 100 weight part of NBR.

Examples of the filler include inorganic fillers such as calcium carbonate, clay, barium sulfate, diatomaceous earth, mica, asbestos, graphite, and organic fillers such as recycled rubber, powder rubber, asphalt, styrene resin, and glue. Agents.
Examples of the reinforcing agent include inorganic reinforcing agents such as carbon black, silica-based or silicate-based white carbon, surface-treated precipitated calcium carbonate, magnesium carbonate, talc, clay, and the like, for example, coumarone indene resin, phenol Examples thereof include organic reinforcing agents such as resins and high styrene resins (styrene-butadiene copolymers having a high styrene content).

The blending amounts of the filler and the reinforcing agent are not particularly limited, and are appropriately set according to the strength and bulk required of the high damping rubber within a range where the damping performance of the high damping rubber is not impaired.
Further, the rubber composition containing NBR and an inorganic acid salt of copper (II) may further optionally include, for example, a vulcanization accelerating aid such as stearic acid, oleic acid, and cottonseed fatty acid, such as salicylic acid, anhydrous Aromatic organic acids such as phthalic acid and benzoic acid, for example, nitroso compounds such as N-nitrosodiphenylamine, N-nitroso-2,2,4-trimethyl-1,2-dihydroquinone, N-nitrosophenyl-β-naphthylamine Vulcanization retarders such as, for example, imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine, N, N′-di-β-naphthyl-p-phenylenediamine, N-phenyl-N′-isopropyl- Amines such as p-phenylenediamine, phenols such as di-tert-butyl-p-cresol, styrenated phenol Anti-aging agents such as fatty acids (eg stearic acid, lauric acid etc.), cottonseed oil, tall oil, asphalt material, paraffin wax, etc. softeners such as vegetable oils, mineral oils and synthetic oils, for example , Plasticizers such as dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate may be contained.

The kneading of the rubber composition containing NBR and an inorganic acid salt of copper (II) may be performed using, for example, various roll machines or mixers.
The processing time of the kneading process is preferably set to 5 to 20 minutes, for example, when kneading with a roll. If the kneading time is less than 5 minutes, the dispersibility of the copper (II) inorganic acid salt in NBR becomes poor, resulting in a decrease in crosslinkability and the accompanying physical properties of rubber (for example, rubber hardness, tensile strength). Etc.)). On the other hand, even when kneading for more than 20 minutes, no significant change is observed in the dispersibility of the inorganic salt of copper (II) in NBR, which is disadvantageous in terms of productivity and cost.

The heat treatment for the rubber composition containing NBR and copper (II) inorganic acid salt is preferably 150 to 200 ° C, more preferably 180 to 190 ° C, and preferably 10 to 60 minutes. Preferably, it may be performed for 20 to 30 minutes.
When the temperature during the heat treatment is lower than 150 ° C., it takes a long time to form a crosslinked structure, and thus the productivity of the high-damping rubber tends to decrease. On the other hand, if the temperature during the heat treatment exceeds 200 ° C., NBR may be deteriorated.

The high damping rubber thus obtained has a hysteresis loss of preferably 40 to 80% when the elongation given to the high damping rubber is 90% of the elongation when the high damping rubber is cut. Preferably, it is 50 to 70%, more preferably 60 to 70%.
The “elongation when the high-damping rubber is cut” and “hysteresis loss” are as described above.

The high damping rubber can be used, for example, as a raw material for producing damping members such as anti-vibration rubber, damping rubber, viscous body damper, damping isolator and the like.
The high-damping rubber has high damping performance, and can be manufactured with a simple composition and simple process. Therefore, it has excellent damping performance and low cost, and is a damping member suitable for various industrial machines and household appliances. Can be provided.

Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.
The components used in the following examples and comparative examples are as follows.
・ Acrylonitrile-butadiene rubber (NBR): 50% of bound acrylonitrile, trade name “DN003”, manufactured by Nippon Zeon Co., Ltd., copper sulfate (II) anhydride: manufactured by Wako Pure Chemical Industries, Ltd., sulfur: powdered sulfur, Tsurumi Made by Chemical Co., Ltd. ・ Vulcanization accelerator: Dibenzothiazyl disulfide (MBTS), trade name “Noxeller DM”, made by Ouchi Shinsei Chemical Co., Ltd. ・ Zinc flower: Zinc Hua 1, Mitsui Metal Mining Co., Ltd. Product / stearic acid: manufactured by Nippon Oil & Fat Co., Ltd. Example 1
After blending 100 parts by weight of NBR (bound acrylonitrile amount 50%) and 10 parts by weight of anhydrous copper (II) sulfate, the mixture was kneaded in a roll machine for 8 minutes at room temperature, and then at 190 ° C. in a press molding machine. A high-damping rubber was obtained by press molding (heat treatment) for 20 minutes.

Comparative Example 1
Formulated with 100 parts by weight of NBR (50% bound acrylonitrile), 2.5 parts by weight of sulfur, 1.6 parts by weight of vulcanization accelerator (MBTS), 5 parts by weight of zinc white, and 1 part by weight of stearic acid Then, after kneading for 8 minutes at room temperature in a roll machine, vulcanized rubber was obtained by press molding (heat treatment) at 160 ° C. for 30 minutes in a press molding machine.

Evaluation of Physical Properties From the high-damping rubber of Example 1 and the vulcanized rubber of Comparative Example 1, a dumbbell-shaped test piece (dumbbell-shaped No. 3 as defined in JIS K 6250, a width of a parallel portion of 5 ± 0.1 mm, respectively. , Parallel portion thickness 2.0 ± 0.2 mm, distance between marked lines 20 mm).
Next, the obtained dumbbell-shaped test piece was mounted on an autograph tensile tester (distance between chucks: 80 mm, manufactured by Shimadzu Corporation), and pulled at a pulling speed of 500 mm / min to cut the dumbbell-shaped test piece. The difference S ₁ ((L ₁ −20) / mm) between the distance L ₁ between the marked lines and the initial distance L ₀ (20 mm) between the marked lines was measured. Further, the elongation at break E _B (%) of the high damping rubber and the vulcanized rubber was calculated by the following formula.

E _B (%) = ((L ₁ −L ₀ ) / L ₀ ) × 100
Next, a strip-shaped test piece (width 5 mm, thickness 2 mm, distance between marked lines 40 mm) is mounted on the autograph tensile tester (distance between chucks 80 mm), and the elongation S _{2 of the} test piece (marked line of the test piece) The difference between the distance L ₂ and the initial distance L ₀ ((L ₂ −L ₀ ) / mm)) indicates that the distance L ₁ between the marked lines when the specimen is cut and the initial distance L ₀ between the marked lines. The tension was pulled at 200 mm / min until the difference S _{1 was} 90%.

Furthermore, immediately after the elongation of the test piece reached the target elongation, the load was unloaded at the same speed (tensile speed −200 mm / min) until the stress became zero.
FIG. 1 shows a stress-strain curve of the high attenuation rubber of Example 1 measured by the autograph tensile tester. Moreover, about the vulcanized rubber of the said comparative example 1, the stress-strain curve measured by the said autograph tensile testing machine is shown in FIG.

From the stress-strain curves shown in FIG. 1 and FIG. 2, hysteresis loss was measured for the high damping rubber of Example 1 and the vulcanized rubber of Comparative Example 1. As a result, the high damping rubber of Example 1 was 65%. there were. On the other hand, the vulcanized rubber of Comparative Example 1 was 21%.
The hysteresis loss A (%) is measured from the stress-strain curve shown in FIG. 1 and FIG. 2 with the applied energy (the area of the region surrounded by the zero point, the curve a, the point b, the point e, and the zero point). The energy (0 area, curve a, point b, curve c, point d, and area of the area surrounded by the 0 point) after one cycle of deformation and recovery was calculated and calculated by the following formula.

A (%) = [(Area (0abcd0)) / (Area (0abe0))] × 100
As for the vulcanized rubber of Comparative Example 1 and the high damping rubber of Example 1, further, a rubber hardness (JIS A; durometer hardness; JIS K 6253 _-1997), the tensile strength T _B (MPa; JIS K 6251 _{: 2004} ), the degree of swelling (%) with respect to toluene and the glass transition temperature T _g (° C.) were measured.

Further, the kneaded material containing NBR and copper sulfate prepared in Example 1 (that is, before crosslinking of the high-damping rubber of Example 1) and the NBR and sulfur prepared in Comparative Example 1 , Vulcanization accelerator, zinc white and stearic acid-containing kneaded product (that is, before vulcanization of the vulcanized rubber of Comparative Example 1), Mooney viscosity ML (1 + 4) at 130 ° C., The glass transition temperature T _g (° C.) was measured.

  These measurement results are shown in Table 1.

In Table 1, “ML (1 + 4), 130 ° C.” indicates the Mooney viscosity (viscosity after 1 minute, 4 minutes) measured at 130 ° C. "T _g" refers to the glass transition temperature (℃). “Hardness (JIS A)” indicates durometer hardness. “T _B ” indicates tensile strength (MPa). “E _B ” indicates elongation at break (%). “Swelling ratio” indicates the degree of swelling (%) with respect to toluene. “Hyst.loss” indicates hysteresis loss (%).

As shown in Table 1, it was found that the high damping rubber of Example 1 had significantly higher hysteresis loss and significantly better damping performance than the vulcanized rubber of Comparative Example 1. In addition, it was found that the high-damping rubber of Example 1 had higher tensile strength and elongation than the vulcanized rubber of Comparative Example 1, and good tensile strength.
The present invention is not limited to the above description, and various design changes can be made within the scope of the matters described in the claims.

3 is a graph showing a stress-strain curve of the high damping rubber obtained in Example 1. FIG. 3 is a graph showing a stress-strain curve of a vulcanized rubber obtained in Comparative Example 1.

Claims (5)

  A high-damping rubber obtained by heating a rubber composition containing acrylonitrile-butadiene rubber and copper (II) inorganic acid salt.   The high-damping rubber according to claim 1, wherein the copper (II) inorganic acid salt is copper (II) sulfate.   The high-damping rubber according to claim 1 or 2, wherein the acrylonitrile-butadiene rubber has a bound acrylonitrile amount of 30 to 50%.   The high-damping rubber according to claim 1, wherein the rubber composition is obtained by heating the rubber composition at 150 to 200 ° C. for 10 to 60 minutes. The hysteresis loss of the high damping rubber is 40 to 70% when the elongation given to the high damping rubber is 90% with respect to the elongation when the high damping rubber is cut. The high damping rubber according to any one of claims 1 to 4.

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