JP6507074B2 - Crosslinked foam for reducing tire noise, and pneumatic tire - Google Patents

Description

  The present invention is used for a tire sound absorbing material capable of reducing noise associated with air column resonance (cavity resonance) in an air chamber of a tire, which is one of tire noise, without increasing tire mass. The present invention relates to a crosslinked foam containing an olefin / nonconjugated polyene copolymer.

  One of the tire noises is road noise having a frequency of about 50 to 400 Hz. The road noise is mainly caused by air column resonance (cavity resonance) generated in an air chamber of the tire (hereinafter referred to as "tire air chamber"). Air column resonance is a phenomenon in which a random vibration transmitted from the road surface to the tire vibrates the air in the tire air chamber, and as a result, a resonance phenomenon occurs near the air column resonance frequency of the tire air chamber to generate a resonance sound. .

  In order to solve this problem, Patent Document 1 below proposes a sponge material having a specific gravity of more than 0.06 and not more than 0.25 as a sponge material used for an assembly of a tire and a rim. Since the specific gravity of the material is large, the problem of increasing the weight of the tire remains.

  Patent Document 2 below proposes a sponge material made of urethane foam or the like having a specific gravity of 0.005 to 0.060. When the tire is stored alone, rain water, dew condensation water, etc. may stay inside the cavity inside the tire, and in this case, water may accumulate inside the sponge material mounted inside the cavity. When moisture is accumulated in the tire cavity and the inside of the sponge material, it is not easy to discharge or dry the moisture.

  Patent Document 3 below proposes that a resin film for water absorption prevention that can prevent water absorption be provided on a sponge material made of urethane foam or the like having a specific gravity of 0.005 to 0.060, but the resin film is adhesive It is necessary to fix to a sponge material using a tape or an adhesive, and this method increases the number of manufacturing steps, which inevitably increases the cost.

  In addition, as an example of a sound absorbing material for reducing tire noise using EPDM, which is excellent in durability and water resistance, Patent Document 4 below presents a foamed rubber containing many open cells with a single cell rate of 25% or less. However, there is no description of water absorption, and no description of specific gravity or thickness of the test piece at the time of measurement of sound absorption, and there is still room for improvement as a sound absorbing material for reducing tire noise.

Patent No. 5078907 JP 2005-254924 A JP, 2005-262921, A Japanese Patent Application Laid-Open No. 9-86114

  An object of the present invention is to provide a sound-absorbing material for a tire that has both excellent durability and sound absorption, can be manufactured at low cost, and does not increase the weight of the tire.

  According to the present invention, it is found that a cross-linked foam for tire noise reduction that can be manufactured at low cost can be obtained by adopting a specific composition and further controlling the density and water absorption rate of the foam. Thus, the present invention has been completed.

That is, the present invention relates to the following [1] to [7].
[1] A tire noise reduction foam molded body attached to the inner surface or rim portion of a tire tread of a pneumatic tire, comprising:
(A) 100 to 300 parts by mass of (B) filler, and (C) softener 20 to 100 parts by mass of the ethylene / α-olefin / non-conjugated polyene copolymer and 100 parts by mass of the (A) copolymer The sum of the content of (B) filler and (C) softener is at least 200 parts by mass with respect to 100 parts by mass of the (A) copolymer.
Apparent density is 60 kg / m ³ or less,
A crosslinked foam for tire noise reduction, which has a water absorption rate determined by the following water absorption rate measurement method of less than 200%.
(Measurement method of water absorption rate: The test piece consisting of the cross-linked foam for reducing tire noise was decompressed to -635 mmHg at a position of 50 mm below the water surface and held for 3 minutes, then returned to atmospheric pressure and water absorbed after 3 minutes progressed The weight of the specimen is measured, and the water absorption of the test piece is calculated from the following equation.
(Water absorption) [%] = {(W2-W1) / W1} × 100
W1: Weight of test piece before immersion (g)
W2: Weight of test piece after immersion (g)

[2] Ethylene / α-olefin / non-conjugated wherein the (A) ethylene / α-olefin / non-conjugated polyene copolymer has a strain hardening degree SH of 0.8 or more represented by the following formula [a] 100 parts by mass to 1 part by mass of the polyene copolymer (A-1) and 0 parts by mass of an ethylene / α-olefin / nonconjugated polyene copolymer (A-2) having a strain hardening degree SH of less than 0.8 The crosslinked foam for tire noise reduction according to the above-mentioned [1], comprising -99 parts by mass (based on a total of 100 parts by mass of the copolymer (A-1) and the copolymer (A-2)) .
SH = dlnλ / dε .. [a]
(Where λ = ηE (t, εH) // E (t, εL), where EE (t, εH) is the extensional viscosity in the non-linear region at time t measured at the extension rate εH, ηE (t, εL) ) Represents the elongational viscosity in the linear region at time t measured at an elongation rate εL less than εH, where ε represents the elongation rate εH, the Hencky strain at time t))

[3] The filler (B) is any one or a combination of two or more of carbon black, aluminum hydroxide, calcium carbonate, talc, clay, magnesium oxide, silica and mica. ] Or the crosslinked foam for tire noise reduction as described in [2].

[4] The crosslinked foam for tire noise reduction according to any one of the above [1] to [3], wherein the (C) softening material is paraffin oil.
[5] The crosslinked foam for tire noise reduction according to any one of the above [1] to [4], which has a thickness of 2 to 30 mm.

[6] A pneumatic tire formed by attaching the crosslinked foam for tire noise reduction according to any one of the above [1] to [5] to an inner surface or a rim of a tire tread.
[7] A pneumatic tire comprising the crosslinked foam for tire noise reduction according to any one of the above [1] to [5], which is formed between the inner surface of the tire tread and the crosslinked foam, or between the rim and the crosslinked foam. The pneumatic tire which has a clearance of 5-40 mm between foams.

  The crosslinked foam for reducing tire noise according to the present invention can be manufactured at low cost and can be reduced in weight by having a specific composition, density of foam and water absorption rate, and ethylene / α- Since the olefin / nonconjugated polyene copolymer is contained, weather resistance and heat and humidity resistance can be expected.

FIG. 1 is a graph showing the relationship between the 1/3 octave band center frequency and the normal incidence sound absorption coefficient in the case of 0 mm in the back air layer in Examples and Comparative Examples. FIG. 2 is a graph showing the relationship between the 1/3 octave band central frequency and the normal incidence sound absorption coefficient in the case of the back air layer 0, 20, 40 mm in Example 1. FIG. 3 is a graph showing the relationship between the 1 / octave band center frequency and the normal incidence sound absorption coefficient in the case of the back air layer 0, 20, 40 mm in Comparative Example 3. FIG. 4 is a graph showing the relationship between the 1/3 octave band center frequency and the normal incidence sound absorption coefficient in the case of the back air layer 0, 20, 40 mm in Comparative Example 4. FIG. 5 is a graph showing the relationship between the 1/3 octave band center frequency and the normal incidence sound absorption coefficient in the case of the back air layer 0, 20, 40 mm in Comparative Example 5.

The cross-linked foam for reducing tire noise attached to the tire tread inner surface or rim portion of the pneumatic tire of the present invention is
(1) (A) ethylene / α-olefin / nonconjugated polyene copolymer and (B) filler 100 to 300 parts by mass and (C) softener with respect to 100 parts by mass of the (A) copolymer And 20 to 100 parts by mass, and the sum of the contents of (B) filler and (C) softener is 200 parts by mass or more per 100 parts by mass of the (A) copolymer,
(2) The apparent density is 60 kg / m ³ or less,
(3) The water absorption coefficient determined by the following water absorption coefficient measurement method is less than 200%.

First, the composition which comprises the said crosslinked foam is demonstrated. [Composition which comprises a crosslinked foam]
The composition which comprises the said crosslinked foam contains the above-mentioned (A) ethylene-alpha-olefin nonconjugated polyene copolymer, (B) filler, and (C) softening agent.

(A) Ethylene / α-olefin / non-conjugated polyene copolymer (A) As α-olefin in ethylene / α-olefin / non-conjugated polyene copolymer, mention may be made of α-olefins having 3 to 20 carbon atoms it can. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, butene-1,4-methylpentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1 and undecene-1 , Dodecene-1, toldecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, nonadecene-1, eicosene-1, 9-methyl-decene-1, 11-methyl-dodecene-1, 12 And -ethyl-tetradecene-1 and the like. These α-olefins can be used alone or in combination of two or more.

  Examples of the non-conjugated polyene in the ethylene / α-olefin / non-conjugated polyene copolymer include, for example, non-conjugated polyene having 5 to 20, preferably 5 to 10 carbon atoms. 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,4-octadiene, 1,5-octadiene, 1,6-octadiene, 1,7-octadiene, 2-methyl-1,5- Hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, 4-ethylidene-8-methyl-1,7-nonadiene, 4,8-dimethyl-1,4,8-decatriene, Dicyclopentadiene, cyclohexadiene, dicyclooctadiene, methylene norbornene, 5-vinyl norbornene, 5-ethylidene-2-norbornene 5-methylene-2-norbornene, 5-vinylidene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5-norbornene And 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene and the like.

  (A) In the ethylene / α-olefin / nonconjugated polyene copolymer, the content of the structural unit derived from ethylene is preferably 40 to 72% by mass, more preferably 41 to 70% by mass, from the viewpoint of flexibility. More preferably, it is 42-65 mass%.

  (A) In the ethylene / α-olefin / nonconjugated polyene copolymer, the content of the structural unit derived from the nonconjugated polyene is preferably 4 to 16 from the balance between the processing stability at the time of foam molding and the vulcanization rate. It is mass%, more preferably 5 to 15 mass%, further preferably 6 to 14 mass%.

  (A) In the ethylene / α-olefin / nonconjugated polyene copolymer, the Mooney viscosity [ML1 + 4 (100 ° C.)] is preferably 8 to 80, from the balance between the processability at the time of foam molding and the foamability. Preferably it is 20-70, More preferably, it is 25-60.

  (A) In the ethylene / α-olefin / nonconjugated polyene copolymer, among the above-mentioned α-olefins, α-olefins having 3 to 10 carbon atoms are preferable, and in particular, propylene, 1-butene, 1-hexene, 1- Octene is preferred.

  (A) In the ethylene / α-olefin / nonconjugated polyene copolymer, preferred nonconjugated polyenes among the aforementioned nonconjugated polyenes are dicyclopentadiene, 5-vinylidene-2-norbornene, 5-ethylidene-2- Norbornene etc. are mentioned.

  In addition, (A) ethylene / α-olefin / nonconjugated polyene copolymer is an ethylene / α-olefin / nonconjugated polyene copolymer having a strain hardening degree SH of 0.8 or more represented by the following formula [a]: When 100 parts by mass to 1 part by mass of the polymer (A-1) is contained, a foam having a low apparent density can be stably obtained. That is, (A) ethylene / α-olefin / nonconjugated polyene copolymer is 100 parts by mass of ethylene / α-olefin / nonconjugated polyene copolymer (A-1) having a strain hardening degree SH of 0.8 or more. It is preferable to be composed of 1 part by mass and 0 parts by mass to 99 parts by mass of the ethylene / α-olefin / nonconjugated polyene copolymer (A-2) having a strain hardening degree SH of less than 0.8. Furthermore, the copolymer (A) is composed of 100 parts by mass to 50 parts by mass of the copolymer (A-1) and 0 parts by mass to 50 parts by mass of the copolymer (A-2), and further, a copolymer weight It is preferable to consist of 100 parts by mass to 80 parts by mass of the combined (A-1) and 0 parts by mass to 20 parts by mass of the copolymer (A-2).

  The ethylene / α-olefin / nonconjugated polyene copolymer (A-1) preferably has a strain hardening degree SH of 0.8 to 1.0, more preferably 0.8 to 0.9. The ethylene / α-olefin / nonconjugated polyene copolymer (A-2) preferably has a strain hardening degree SH of less than 0.8 and 0.1 or more.

SH = dlnλ / dε .. [a]
(Where λ = ηE (t, εH) // E (t, εL), where EE (t, εH) is the extensional viscosity in the non-linear region at time t measured at the extension rate εH, ηE (t, εL) ) Represents the elongational viscosity in the linear region at time t measured at an elongation rate εL less than εH, where ε represents the elongation rate εH, the Hencky strain at time t))
The strain hardening degree SH is a value indicating the degree of strain hardening of the elongation viscosity, as described in, for example, “The Journal of The Rheological Society of Japan, Vol. 31, No. (5), P 321-327”. In the present invention, as described in Examples described later, uniaxial elongational viscosity was measured under two conditions of a temperature of 140 ° C. and strain rates γ of 0.01 and 0.1 (1 / s) to determine a strain hardening degree SH. .
The ethylene / α-olefin / nonconjugated polyene copolymer (A-2) having a strain hardening degree SH of less than 0.8 may be produced by a conventionally known method, or a commercially available product may be used. Examples of commercially available products include “Mitsui EPT 3045” (trade name; manufactured by Mitsui Chemical Co., Ltd.), “Mitsui EPT 3092M” (trade name; manufactured by Mitsui Chemical Co., Ltd.), “Nordel IP 4640” (trade name; manufactured by Dow Chemical Co.), Vistalon 7500 "(trade name; manufactured by Exxon Mobil Chemical Co., Ltd.) and" Vistalon V8600 "(trade name; manufactured by Exxon Mobil Chemical Co., Ltd.).

(A) The strain hardening degree SH of the ethylene / α-olefin / nonconjugated polyene copolymer is adjusted to be 0.8 or more or less than 0.8 by the method described in JP-A-2013-234289. It is possible.
(B) Filler (B) As the filler, specifically, commercially available carbon black, carbon black surface-treated with a silane coupling agent, aluminum hydroxide, calcium carbonate, talc, clay, oxidized It is possible to use magnesium, silica, mica or the like singly or in combination of two or more. Among these fillers, as carbon black, “Asahi # 55 G”, “Asahi # 50 HG”, “Asahi # 15 G”, “Asahi # 60 G” (trade name, manufactured by Asahi Carbon Co., Ltd.), etc., calcium carbonate "Whiteton SB" (trade name, Shiroishi Calcium Co., Ltd.) and the like, and as aluminum hydroxide, "Higilight H-42M" (trade name, Showa Denko Co., Ltd.) etc. is preferable.

The content of the filler (B) is 100 to 300 parts by mass, preferably 120 to 280 parts by mass, and more preferably 140 to 100 parts by mass with respect to 100 parts by mass of the (A) ethylene / α-olefin / nonconjugated polyene copolymer. 260 parts by mass.
(C) Softener (C) As the softener, process oil such as paraffin oil (for example, “Diana Process Oil PS-430” (trade name: Idemitsu Kosan Co., Ltd.), etc., lubricating oil, liquid paraffin, petroleum oil Petroleum softeners such as asphalt and petrolatum; coal tar softeners such as coal tar and coal tar pitch; fatty oil softeners such as castor oil, linseed oil, rapeseed oil, soybean oil and coconut oil; honey Waxes such as wax, carnauba wax, and lanolin; fatty acids such as ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate, and zinc laurate or salts thereof; naphthenic acid, pine oil, and rosin or derivatives thereof; Terpene resin, petroleum resin, atactic polypropylene, and coumarone in Synthetic polymers such as Den resin; Ester softeners such as dioctyl phthalate, dioctyl adipate and dioctyl sebacate; Others, microcrystalline wax, liquid polybutadiene, modified liquid polybutadiene, liquid thiocol, synthetic hydrocarbon lubricating oil, tall Oil, and sub (factice) and the like. Among them, petroleum-based softeners are preferred, and in particular, process oils, among which paraffin oils are preferred. The above-mentioned softeners can be used alone or in combination of two or more.
The content of the softener (C) is 20 to 100 parts by mass, preferably 25 to 90 parts by mass, more preferably 30 to 80 parts by mass with respect to 100 parts by mass of the copolymer (A).

  In addition, if the sum of the content of (B) filler and (C) softener is smaller than 200 parts by mass with respect to 100 parts by mass of (A) ethylene / α-olefin / nonconjugated polyene copolymer, the production cost is The sum of the compounding amounts is preferably 200 or more per 100 parts by mass of the (A) copolymer. In addition, if the sum of the blending amounts of the (B) filler and the (C) softener is greater than 300 parts with respect to 100 parts by mass of the (A) copolymer, the elongation and tear strength of the foam are reduced. It is preferable that the sum of compounding quantities is 300 or less with respect to 100 mass parts of (A) copolymers. Therefore, the sum of the content of the (B) filler and the (C) softener is preferably 200 to 300 parts by mass, more preferably 210 to 290 parts by mass with respect to 100 parts by mass of the (A) copolymer. It is a part, More preferably, it is 220-280 mass parts.

Other components of the composition In order to obtain foams from the composition, in addition to (A) ethylene / α-olefin / nonconjugated polyene copolymer, (B) filler and (C) softener, foam Agents, vulcanizing agents (crosslinking agents), vulcanization accelerators can be added to the composition.

  As a foaming agent, inorganic foaming agents such as sodium bicarbonate and sodium carbonate; Nitroso compounds such as N, N'-dinitrosopentamethylenetetramine and N, N'-dinitrosotephthalamide; azodicarbonamide, azobisiso Azo compounds such as butyronitrile; hydrazide compounds such as benzenesulfonyl hydrazide and 4,4'-oxybis (benzenesulfonyl hydrazide); organic foaming agents such as azide compounds such as calcium azide and 4,4'-diphenyldisulfonyl azide It can be mentioned.

  The compounding amount of the foaming agent is 20 to 50 parts by mass, preferably 25 to 45 parts by mass, and more preferably 30 to 40 parts by mass with respect to 100 parts by mass of the copolymer (A). As the foaming agent, for example, commercially available Biniphor AC # 3M (trade name, Eiwa Kasei Kogyo Co., Ltd. azodicarbonamide (abbreviation ADCA)), Biniholl AC # 3 C-K2 (trade name, Eiwa Kasei Kogyo Co., Ltd. azodicarbonide) Amide (abbreviation ADCA), Biniholl AC # LQ (trade name, Eiwa Kasei Kogyo Co., Ltd. azodicarbonamide (abbreviation ADCA)), cell microphone C-2 (trade name, Sankyo Kasei Co., Ltd. azodicarbonamide (abbreviation ADCA)) , Cellular # D (trade name, Eiwa Kasei Kogyo Co., Ltd. N, N'- dinitroso pentamethylene tetramine (abbreviation DPT)), Cellular CK # 54 (trade name, Eiwa Kasei Kogyo Co., Ltd. N, N'- dinitroso pentamer) Methylenetetramine (abbr. DPT)), Cell Microphone #A (trade name, Sankyo Kasei Co., Ltd., N, N'-Di) Nitrosopentamethylenetetramine (abbreviation DPT), neocervone N # 1000 SW (trade name, Eiwa Chemical Industry Co., Ltd. 4,4'-oxybis (benzenesulfonyl hydrazide) (abbr. OBSH)), neocervone N # 1000 M (trade name, Eiwa Kasei Industrial Co., Ltd. 4,4'-oxybis (benzenesulfonyl hydrazide) (abbr. OBSH) etc. can be used.

  Moreover, you may contain a foaming adjuvant with a foaming agent. Examples of the foaming aid include organic acids such as salicylic acid, phthalic acid, stearic acid, oxalic acid and citric acid and salts thereof, urea and derivatives thereof and the like. The compounding amount of the foaming aid is 0.1 to 5 parts by mass, preferably 0.3 to 4 parts by mass with respect to 100 parts by mass of the copolymer (A). As the foaming aid, for example, commercially available cell paste K5 (trade name, Eiwa Kasei Kogyo Co., Ltd. urea), cell paste 101 W (trade name, Eiwa Kasei Kogyo Co., Ltd. urea), FE-507 (trade name, Eigawa Chemical Industries, Ltd. baking soda) etc. can be used.

  As a vulcanizing agent (crosslinking agent), a sulfur compound, an organic peroxide, a phenol resin, an oxime compound or the like can be used.

  Examples of sulfur compounds include sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, selenium dithiocarbamate and the like. As a sulfur compound, sulfur and tetramethylthiuram disulfide are preferable, and usually 0.3 to 10 parts by mass, preferably 0.5 to 5.0 parts by mass, further 100 parts by mass of the copolymer (A). Preferably, 0.7 to 4.0 parts by mass can be blended.

  Examples of the organic peroxide include dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2, 5-diethyl-2,5-di (t-butylperoxy) hexyne-3, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-dibutyl hydroperoxide etc. it can. Among these, dicumyl peroxide, di-t-butyl peroxide, and di-t-butylperoxy-3,3,5-trimethylcyclohexane are preferable. The blending amount of the organic peroxide is usually 0.001 to 0.05 mol, preferably 0.002 to 0.02 mol, more preferably 0.005 to 0. 100 mol of the copolymer (A). It is 015 mole.

  When using a sulfur-based compound as a vulcanizing agent, combined use of a vulcanization accelerator is preferable. As a vulcanization accelerator, N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N, N'-diisopropyl-2-benzothiazole sulfenamide, 2-mercapto Benzothiazole (for example, “Suncella M” (trade name, manufactured by Sanshin Chemical Industry Co., Ltd.), etc.), 2- (4-morpholinodithio) benzothiazole (for example, “Noxceler MDB-P” (trade name, Mishin) And others), 2- (2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4-morpholinothio) benzothiazole, and thiazole such as dibenzothiazyl disulfide; Guars such as diphenyl guanidine, triphenyl guanidine, diorsotryl guanidine Nidin system; acetaldehyde-aniline condensate, butyraldehyde-aniline condensate, aldehyde amine system; imidazoline system such as 2-mercaptoimidazoline; thiourea system such as diethylthiourea, dibutylthiourea etc .; tetramethylthiuram monosulfide, tetramethylthiuram disulfide etc. Thiuram-based compounds; Zinc dimethyldithiocarbamate, Zinc diethyldithiocarbamate, Zinc dibutyldithiocarbamate (eg, “Sancella PZ” (trade name, manufactured by Sanshin Chemical Industry Co., Ltd.), “Sunseller BZ” (trade name, Sanshin Chemical Industry Co., Ltd.) Dithio acid salts such as tellurium diethyldithiocarbamate; ethylenethiourea (eg, “SUNCERA BUR” (trade name, manufactured by Sanshin Chemical Industries, Ltd.), “SUNCELLER 22-C” (trade name, Thiourea series such as Shin Chemical Industry Co., Ltd.), N, N'-diethylthiourea etc .; 2-Mercaptobenzothiazole (eg, "Sunsera M" (trade name, Sanshin Chemical Industry Co., Ltd., etc.) Thiazole series Vulcanization accelerators include xanthates such as zinc dibutyl oxalate and the like.

  The compounding amount of these vulcanization accelerators is 0.1 to 20 parts by mass, preferably 0.2 to 15 parts by mass, and more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the copolymer (A). It is a mass part.

  A vulcanizing coagent can be used together with the vulcanizing agent. The vulcanization aid can be appropriately selected depending on the application, and can be used alone or in combination of two or more. Specific examples of the vulcanization aid include magnesium oxide and zinc oxide (for example, zinc oxide such as "META-Z102" (trade name, manufactured by Inoue Lime Industry Co., Ltd.)). The compounding amount is usually 1 to 20 parts by mass with respect to 100 parts by mass of the copolymer (A). Vulcanization aids further include quinone dioximes such as p-quinone dioxime; acrylics such as ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate; allyls such as diallyl phthalate and triallylisocyanurate; and other maleimides Divinyl benzene and the like can be mentioned.

  The composition may contain, in addition to the components described above, a processing aid, an activator, a hygroscopic agent, an anti-aging agent, and the like, as long as the object of the present invention is not impaired.

  As a processing aid, those generally blended with rubber as a processing aid can be widely used. Specifically, ricinoleic acid, stearic acid, palmitic acid, lauric acid, barium stearate, zinc stearate, calcium stearate or esters and the like can be mentioned. Of these, stearic acid is preferred. The processing aid can be suitably blended in an amount of 10 parts by mass or less, preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, based on 100 parts by mass of the copolymer (A) .

  The activator can be appropriately selected depending on the application, and can be used alone or in combination of two or more. Specific examples of the active agent include di-n-butylamine, dicyclohexylamine, mono-eranolamine, "Acting B" (trade name, manufactured by Yoshitsugu Pharmaceutical Co., Ltd.), "Acting SL" (trade name, Yoshishima Pharmaceutical Co., Ltd.) Amines); diethylene glycol, polyethylene glycol (eg, “PEG # 4000” (Lion Corporation)), lecithin, triarylate mellitate, zinc compounds of aliphatic and aromatic carboxylic acids (eg, “Struktolactivator 73 “Struktol IB 531” and “Struktol FA 541 (trade name, manufactured by Schill & Seilacher)” and the like; Zinc peroxide preparations such as “ZEONET ZP” (trade name, manufactured by Nippon Zeon Co., Ltd.); And ammonium hydroxide, synthetic hydrotalcite, special quaternary ammonium compounds (for example, “Arcard 2HT-F” (trade name, manufactured by Lion Akzo Co., Ltd.), and the like. Among these, polyethylene glycol (for example, "PEG # 4000" (manufactured by Lion Corporation)) and "Arcard 2HT-F" are preferable. The compounding amount of the activator is 0.2 to 10 parts by mass, preferably 0.3 to 5 parts by mass, and more preferably 0.5 to 4 parts by mass with respect to 100 parts by mass of the copolymer (A). .

  The hygroscopic agent can be appropriately selected depending on the application, and can be used alone or in combination of two or more. Specific examples of the hygroscopic agent include calcium oxide, silica gel, sodium sulfate, molecular sieve, zeolite, white carbon and the like. Among these, calcium oxide is preferred. The compounding amount of the hygroscopic agent is 0.5 to 15 parts by mass, preferably 1.0 to 12 parts by mass, and more preferably 1.0 to 10 parts by mass with respect to 100 parts by mass of the copolymer (A). .

Method of Preparing the Composition The composition comprises (A) an ethylene / α-olefin / non-conjugated polyene copolymer, (B) a filler and (C) a softener, and optionally mixing the other components. It can be prepared by
[Crosslinked foam]
The crosslinked foam of the present invention can be obtained by crosslinking and foaming the composition. An example of the cross-linking foaming is a method of extruding the composition using an extruder attached to a sheet-like die and forming the composition into a sheet. The resulting molded body is introduced into a vulcanizing tank, and heated at, for example, 100 to 250 ° C. for 5 to 60 minutes to perform crosslinking and foaming, whereby a sheet-like crosslinked foam (sponge) can be obtained.

The contents of (B) filler and (C) softener relative to (A) ethylene / α-olefin / non-conjugated polyene copolymer in the crosslinked foam of the present invention are the contents of these indicated for the composition and It is the same.
[Apparent density]
Apparent density of the crosslinked foam of the present invention, since the weight becomes heavier exceeds ^{60kg / m 3, 60kg / m} 3 or less. The lower limit of the density is not particularly limited, but when it is less than 20 kg / m ³ , stable production of a crosslinked foam is difficult, and elongation and strength decrease, so 20 kg / m ³ or more is preferable. The crosslinked foam having an apparent density of 60 kg / m ³ or less can be obtained, for example, by crosslinking and foaming the composition containing a crosslinking agent and a foaming agent, and in particular, as the (A) copolymer, the above-mentioned strain hardening degree The strain hardening is carried out using an ethylene / α-olefin / nonconjugated polyene copolymer (A-1) having an SH of 0.8 or more, and 100 parts by mass to 1 part by mass of the copolymer (A-1) 0 parts by mass to 99 parts by mass of ethylene / α-olefin / nonconjugated polyene copolymer (A-2) having a degree SH of less than 0.8 (provided that the copolymer (A-1) and the copolymer (A-) It can manufacture by using 20-50 mass parts of foaming agents with respect to a total of 100 mass parts of 2).

[Water absorption rate]
The water absorption rate of the crosslinked foam of the present invention is desirably less than 200%, preferably less than 150%, and more preferably less than 10%, as measured by the method described in the examples described later. If the water absorption rate by this measurement method is 200% or less, even if the tire is stored alone, the crosslinked foam does not absorb rainwater or condensation water, and water remains in the tire air chamber. There is no such thing.

  The water absorption rate of the crosslinked foam is cross-linked by using the ethylene / α-olefin / nonconjugated polyene copolymer (A-1) having the above-mentioned strain hardening degree SH of 0.8 or more as the A) copolymer. The gas generated during foaming is easily contained in the foam, and the proportion of closed cells is increased, so that it can be adjusted to 200% or less.

  The cross-linked foam of the present invention is a method of pressing the rubber foam between a pair of rotating rolls after cross-linking foaming (roll crush method) within a range that does not impair the low density and the water absorption rate. The foam breaking treatment may be performed using a conventionally known method such as a method of compressing and compressing (vacuum crush method), a method of punching with an infinite number of needles using a needle punch (needle punch method), and the like.

[Attachment of cross-linked foam to tire tread and rim]
The cross-linked foam of the present invention exhibits a very excellent effect as a sound absorbing material for reducing tire noise by attaching the cross-linked foam of the present invention to the inner surface or rim portion of a tire tread.
It does not specifically limit about the method to attach the crosslinked foam of this invention to a tire tread inner surface or a rim | limb part, A conventionally well-known method can be used. For example, there is a method in which the crosslinked foam of the present invention is adhered to the inner surface or rim portion of a tire tread with a synthetic rubber adhesive or an acrylic adhesive.

  When the crosslinked foam of the present invention is used as a sound absorbing material for reducing tire noise, the shape and thickness of the crosslinked foam are not particularly limited, and flat, rectangular, trapezoidal, and sinusoidal shapes can be exemplified. A simple flat plate shape is desirable from the viewpoint of manufacturing cost, and a sufficient sound absorbing effect can not be obtained when the thickness is thinner than 5 mm, and a weight is heavy when it is thicker than 30 mm. Is 8 to 25 mm, more preferably 10 to 20 mm.

  Moreover, as is clear from the sound absorption coefficient measurement described in the examples described later, when the crosslinked foam of the present invention has a gap (back air layer) behind its mounting portion, it absorbs sound compared to other sound absorbing materials Since the frequency band is largely shifted to the low frequency side and air column resonance in the tire air chamber can be greatly improved, 5 to 40 mm of between the tire tread inner surface and the cross-linked foam or between the rim and the cross-linked foam There can be gaps.

  The back air layer may have a partial gap between the rim and the cross-linked foam or the tire tread inner surface and the cross-linked foam, for example, the adhesive is not intentionally applied when using the adhesive. A back air layer can be created by providing parts and bending the cross-linked foam of the present invention into the parts.

Hereinafter, the present invention will be more specifically described based on examples, but the present invention is not limited to these examples. In the following description, "part" shows "mass part".
[(A) Ethylene / α-Olefin / Non-conjugated Polyene Copolymer]
As the copolymer (A), ethylene-propylene-nonconjugated polyene copolymer of the following EPDM (A-1) and EPDM (A-2) was used. These physical property values are summarized in Table 1.

EPDM (A-1):
Ethylene / propylene / non-conjugated polyene random copolymer (structural unit derived from ethylene) produced by the same method as in Example 1 of International Publication WO2010 / 064574 (the difference in the molar ratio was adjusted by the feed amount): 46% by mass, Structural unit content derived from 5-ethylidene-2-norbornene (ENB): 9.0% by mass, Structural unit content derived from 5-vinylidene-2-norbornene (VNB): 0.38 mass %, Mooney viscosity [ML 1 + 4 (100 ° C.)]: 33, SH: 0.9)
EPDM (A-2):
Ethylene / propylene / non-conjugated polyene random copolymer (content of structural unit derived from ethylene: 56% by mass, 5-ethylidene-2-norbornene (ENB) produced by the same method as the production example of International Publication WO2009 / 072553 Structural unit content derived from): 4.7% by mass, Mooney viscosity [ML 1 + 4 (100 ° C.)]: 39, SH: 0.2)

[Specific measurement method of strain hardening degree SH]
Uniaxial extensional viscosity was measured using MCR301 (manufactured by Anton Paar). The test pieces were subjected to hot press forming for 10 minutes under conditions of 190 ° C. using only EPDM to form a sheet having a thickness of 1 mm, then punched out into a strip having a width of 10 mm, and this is used for measurement It was. The measurement was performed under two conditions of a temperature of 140 ° C. and a strain rate γ of 0.01 and 0.1 (1 / s). The strain hardening degree SH was calculated from the obtained extensional viscosity according to the following formula [a].
SH = dlnλ / dε0.1 .. [a]
Here, λ = ηE (t, 0.1) / ηE (t, 0.01),
η E (t, 0.1): extensional viscosity at time t (s) measured at an extension rate of 0.1 (1 / s) η E (t, 0.01): at an extension rate of 0.01 (1 / s) Elongated viscosity ε 0.1 at time t (s) measured: elongation rate 0.1 (1 / s), Hencky strain at time t (s).

Example 1
100 parts of EPDM (A-1) and "META-Z102" as a vulcanization aid using MIXTRON BB MIXER (Kobe Steel, Ltd., BB-4 type, volume 2.95 L, rotor 4 WH) 8 parts of Inoue Lime Industry Co., Ltd., 1 part of stearic acid as a processing aid, 1 part of "PEG # 4000" (trade name: polyethylene glycol, manufactured by Lion Corporation) as an activator, "Hygolite as a filler 45 parts of H-42M (trade name; manufactured by Showa Denko KK) and 150 parts of "Whiteon SB" (trade name; manufactured by Shiroishi Calcium Co., Ltd.) as a softening agent "Diana Process Oil PS-430" (trade name; 50 parts of Idemitsu Kosan Co., Ltd. were kneaded. The kneading conditions were: rotor rotational speed: 50 rpm, floating weight pressure: 3 kg / cm ² , filling rate: 70%, kneading time: 5 minutes, and kneading discharge temperature: 145 ° C.

  Next, after confirming that the above composition reached a temperature of 40 ° C., using a 14-inch two-roll kneader, the above composition was subjected to a vulcanization accelerator “Sunseller M” (trade name; Sanshin Chemical Industry Co., Ltd.) 1.5 parts, as a vulcanization accelerator "Sunseller BZ" (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.) 1.5 parts, as a vulcanization accelerator "Sunseller PZ" (trade name; Sanshin Chemical Co., Ltd.) 1.5 parts of “Industrial Co., Ltd.”, 1.5 parts of “Sansera BUR” (trade name; manufactured by Sanshin Chemical Industries, Ltd.) as a vulcanization accelerator, 1.5 parts of sulfur as a vulcanizing agent, and a foaming agent 40 parts of “Binihole AC # LQ” (trade name; manufactured by Eiwa Kasei Kogyo Co., Ltd.) and 1 part of “Cell Paste K5” (trade name: manufactured by Eiwa Kasei Kogyo Co., Ltd.) as a foaming aid were kneaded. The kneading conditions were such that the roll temperature was front roll / back roll = 80 ° C./80° C., the roll peripheral speed was front roll / back roll = 13 rpm / 11.5 rpm, and the roll gap was 5 mm, and the kneading time was 15 minutes.

  The obtained kneaded product was extrusion-molded by a rubber extruder (manufactured by Three Leaf Manufacturing Co., Ltd.) having a diameter of 50 mm to obtain a sheet-like composition. The temperature conditions of the extruder were HD / C2 / C1 / SC = 80/70/60 / 50.degree. The composition was crosslinked and foamed at 180 ° C. for 8 minutes in a hot air vulcanization tank (manufactured by MICRO ELECTRONICS CO., LTD.) To obtain a crosslinked foam. The formulations used are shown in Table 2. Various measurements were carried out after storing the molded crosslinked foam for at least 72 hours in a room temperature environment.

[Method of measuring apparent density]
The cross-linked foam, including the cross-linked foam skin layer, was prepared into a flat cross-linked foam of 10 mm in thickness using a slicer, and then punched using a punching blade with a diameter of 100 mm to produce a disc-shaped test piece. The apparent density was measured using this test piece with reference to JIS K 7222. The results are shown in Table 4.

[Method of measuring water absorption rate]
A 20 mm × 20 mm test piece was punched out of the flat crosslinked foam having a thickness of 10 mm, and the stain on the surface of the test piece was wiped off with alcohol. The test piece was evacuated to -635 mmHg at a position of 50 mm below the water surface and held for 3 minutes. Subsequently, the pressure was returned to atmospheric pressure, and after 3 minutes, the weight of the absorbed test piece was measured, and the water absorption rate of the test piece was calculated from the following formula, and summarized in Table 4.
(Water absorption) [%] = {(W2-W1) / W1} × 100
W1: Weight of test piece before immersion (g)
W2: Weight of test piece after immersion (g)

[Sound absorption coefficient measurement]
Based on the above-mentioned 10 mm thick tabular cross-linked foam, in accordance with ISO 10534-2: 1998, Acoustics Determination of sound absorption coefficient and impedance in impedance tubes Part 2: Transfer-function method, 4206-T type acoustic tube (Bruel & Kjaer Vertical incident sound absorption coefficient for each 1/3 octave band is measured by adjusting the length of the back air layer using a thick tube with an inner diameter of 100 mmφ and measurement software (PULSE Material Testing Type 7758, manufactured by Bruel & Kjaer) did. The larger the value of the normal incidence sound absorption coefficient, the better the sound absorption. In addition, a back air layer means the clearance gap between the back of a foam crosslinked body, and a back hard wall. Table 4 shows the sound absorption coefficients at 200, 250, 315 and 400 Hz and their average value among the measurement data in the case of the back air layer 0 mm, and the average value of 0.07 or more is ○, 0.05 to 0.06. Δ, 0.05 or less was determined to be x. Here, a cross-linked foam satisfying the three criteria that the apparent density is 60 kg / m ³ or less, the water absorption coefficient is less than 200%, and the sound absorption coefficient judgment is ○ is taken as 総 合 as a comprehensive judgment. The foam cross-linked body which has an item which is not satisfied is considered as x as a comprehensive judgment. FIG. 1 shows the relationship between the 1/3 octave band center frequency and the normal incidence sound absorption coefficient when the back air layer is 0 mm. Further, the normal incidence sound absorption coefficient when the back air layer was 20 and 40 mm was similarly measured, and the result is shown in Table 5 and further shown in FIG. 2 together with the result when the back air layer is 0 mm.

Example 2
In the kneading by MIXTRON BB MIXER, a crosslinked foam was obtained in the same manner as in Example 1 except that 30 parts of Asahi # 50G was blended instead of the highlighte H-42M. The formulations used are shown in Table 2. The measurement results in the case of the back air layer 0 mm as shown in Example 1 are shown in Table 4 and FIG.

Comparative Example 1
In kneading with MIXTRON BB MIXER, a crosslinked foam was obtained in the same manner as in Example 1 except that 100 parts of the copolymer (A-2) was used instead of the copolymer (A-1). The formulations used are shown in Table 2. The measurement results in the case of the back air layer 0 mm as shown in Example 1 are shown in Table 4 and FIG.

Comparative Example 2
A crosslinked foam was obtained in the same manner as in Example 1 except that the blowing agent was reduced to 20 parts in kneading using a 14-inch two-roll kneader. The formulations used are shown in Table 2. The measurement results in the case of the back air layer 0 mm as shown in Example 1 are shown in Table 4 and FIG.

[Comparative examples 3 to 5]
A flexible polyurethane foam was produced using the following raw materials, and various physical properties were measured.
(Raw material for flexible polyurethane foam)
(I) Polyoxypropylene triol "ACTOCOL T-4000" (trade name; manufactured by Mitsui Chemicals, number average molecular weight 4,000)
(II) Polymer dispersed polyol "ACTOCOL POP-45" (trade name; manufactured by Mitsui Chemicals, Inc., hydroxyl value: 33, polymer content: about 40%)
(III) Trimethylolpropane "TMP" (trade name; manufactured by Mitsubishi Gas Chemical Co., Ltd.)
(IV) Foaming agent "water" (ion-exchanged water)
(V) Amine-based catalyst "DABCO 33LV" (trade name; manufactured by Air Products and Chemicals)
(VI) Tin octylate catalyst "DABCO T-9" (trade name; manufactured by Air Products & Chemicals)
(VII) Silicon-based foam stabilizer "SRX-294A" (trade name; manufactured by Toray Dow Corning Co., Ltd.)
(VIII) Toluene diisocyanate "TDI-80" (trade name; manufactured by Mitsui Chemicals, Inc.)

(Manufacture of urethane foam)
Among the components shown in Table 3 below, each component other than DABCO 33LV, DABCO T-9 and TDI-80 is stirred with a hand mixer, then DABCO 33 LV, DABCO T-9 is added, and after stirring for 5 seconds, TDI is immediately performed. -80 was added and mixed, and the mixture was charged into a foaming box and foamed and cured at room temperature. The resulting urethane foam was further allowed to stand at room temperature for 1 day, and then used for physical property measurement. The measurement results in the case of the back air layer 0 mm as shown in Example 1 are shown in Table 4 and FIG. Further, similarly to Example 1, the normal incidence sound absorption coefficient when the back air layer is 20 and 40 mm is similarly measured, and the result is shown in Table 5 together with the result when the back air layer is 0 mm. It showed to 3-5.

[result]
As can be seen from Table 4, the cross-linked foams described in Examples 1 to 2 are suitable as a sound absorbing material for reducing tire noise because they have low density, low water absorption, and good sound absorption characteristics. On the other hand, in Comparative Example 1, since the SH value of EPDM used is low, the balance between foaming and crosslinking is poor, the density of the crosslinked foam is high, and the sound absorption coefficient is low. Similarly, in Comparative Example 2, since the amount of the foaming agent is reduced, the foaming becomes insufficient, the density is high, and the sound absorption coefficient is low.

  Moreover, in Comparative Examples 3 to 5 in which a soft polyurethane foam-based sponge material is used for tire noise reduction, the water absorption coefficient is very large, regardless of the density of the material. Further, in Comparative Example 3 where the density is high, a good sound absorption coefficient is shown at 200 to 400 Hz, but in the low density Comparative Examples 4 and 5, the sound absorption coefficient at 200 to 400 Hz is low.

  The sound absorption coefficient at the time of setting the back air layer used as a clearance gap on the back surface of a crosslinked foam is shown in Table 5 and FIGS. As can be seen from these measurement results, in any of the sound absorbing materials, as the back air layer becomes larger, it can be seen that the Z-tone characteristics shift to the low frequency band, and in particular, the crosslinked foams of Examples 1 and 2 are tire air It is considered that the cross-linked foam of the present invention can greatly reduce air column resonance because the frequency of air column resonance generated indoors and the frequency band of sound absorption match well.

Claims (7)

A cross-linked foam for reducing tire noise, which is mounted on the inner surface or rim of a tire tread of a pneumatic tire, comprising:
(A) 100 to 300 parts by mass of (B) filler, and (C) softener 20 to 100 parts by mass of the ethylene / α-olefin / non-conjugated polyene copolymer and 100 parts by mass of the (A) copolymer The sum of the content of (B) filler and (C) softener is at least 200 parts by mass with respect to 100 parts by mass of the (A) copolymer.
Apparent density is 60 kg / m ³ or less,
A crosslinked foam for tire noise reduction, which has a water absorption rate determined by the following water absorption rate measurement method of less than 200%.
(Measurement method of water absorption rate: The test piece consisting of the cross-linked foam for reducing tire noise was decompressed to -635 mmHg at a position of 50 mm below the water surface and held for 3 minutes, then returned to atmospheric pressure and water absorbed after 3 minutes progressed The weight of the specimen is measured, and the water absorption of the test piece is calculated from the following equation.
(Water absorption) [%] = {(W2-W1) / W1} × 100
W1: Weight of test piece before immersion (g)
W2: Weight of test piece after immersion (g) The ethylene / α-olefin / nonconjugated polyene copolymer having a strain hardening degree SH of 0.8 or more represented by the following formula [a]: (A) ethylene / α-olefin / nonconjugated polyene copolymer 100 parts by mass to 1 part by mass of combined (A-1), and 0 parts by mass to 99 parts by mass of ethylene / α-olefin / nonconjugated polyene copolymer (A-2) having a strain hardening degree SH of less than 0.8 The crosslinked foam for tire noise reduction according to claim 1, which is composed of a part (however, the total of the copolymer (A-1) and the copolymer (A-2) is 100 parts by mass).
SH = dlnλ / dε .. [a]
(Where λ = ηE (t, εH) // E (t, εL), where EE (t, εH) is the extensional viscosity in the non-linear region at time t measured at the extension rate εH, ηE (t, εL) ) Represents the elongational viscosity in the linear region at time t measured at an elongation rate εL less than εH, where ε represents the elongation rate εH, the Hencky strain at time t))   The filler according to claim 1 or 2, wherein the filler (B) is one or more of carbon black, aluminum hydroxide, calcium carbonate, talc, clay, magnesium oxide, silica and mica. Crosslinked foam for tire noise reduction as described.   The crosslinked foam for tire noise reduction according to any one of claims 1 to 3, wherein the softener (C) is paraffin oil.   The crosslinked foam for tire noise reduction according to any one of claims 1 to 4, which has a thickness of 2 to 30 mm.   A pneumatic tire comprising the crosslinked tire foam for tire noise reduction according to any one of claims 1 to 5 attached to the inner surface or the rim of a tire tread.   A pneumatic tire comprising the crosslinked foam for tire noise reduction according to any one of claims 1 to 5, which is between the inner surface of the tire tread and the crosslinked foam, or the rim and the crosslinked foam. Pneumatic tire with a gap of 5 to 40 mm between.

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