U.S. patent application number 15/507848 was filed with the patent office on 2017-09-07 for rubber-metal adhesion promoter, rubber composition, and tire.
The applicant listed for this patent is DIC Corporation, National University Corporation, Iwate University. Invention is credited to Hidetoshi Hirahara, Takayuki Odashima, Shujiro Otsuki.
Application Number | 20170253722 15/507848 |
Document ID | / |
Family ID | 55459119 |
Filed Date | 2017-09-07 |
United States Patent
Application |
20170253722 |
Kind Code |
A1 |
Otsuki; Shujiro ; et
al. |
September 7, 2017 |
RUBBER-METAL ADHESION PROMOTER, RUBBER COMPOSITION, AND TIRE
Abstract
A rubber-metal adhesion promoter characterized by including: a
metal salt (1) of a carboxylic acid which is a metal salt of an
aliphatic carboxylic acid having 2 to 25 carbon atoms and in which
the metal is bismuth, copper, antimony, silver or niobium; or a
compound (2) represented by the following general formula (A):
[wherein Z represents a structure selected from the following
formulae (z-1) to (z-4); M represents bismuth, copper, antimony,
silver or niobium; (RCOO) represents a residue of an aliphatic
carboxylic acid having 2 to 25 carbon atoms; and x represents the
valence of M minus 1]. ##STR00001##
Inventors: |
Otsuki; Shujiro;
(Ichihara-shi, JP) ; Odashima; Takayuki;
(Ichihara-shi, JP) ; Hirahara; Hidetoshi;
(Morioka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DIC Corporation
National University Corporation, Iwate University |
Tokyo
Morioka-shi |
|
JP
JP |
|
|
Family ID: |
55459119 |
Appl. No.: |
15/507848 |
Filed: |
September 9, 2015 |
PCT Filed: |
September 9, 2015 |
PCT NO: |
PCT/JP2015/075592 |
371 Date: |
March 1, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 53/124 20130101;
C07C 53/128 20130101; C08K 5/55 20130101; C08K 5/52 20130101; B60C
1/00 20130101; C08K 5/098 20130101; B60C 9/0007 20130101; C08K
5/098 20130101; C08L 21/00 20130101; C08K 5/55 20130101; C08L 21/00
20130101 |
International
Class: |
C08K 5/098 20060101
C08K005/098; C07C 53/128 20060101 C07C053/128; C07C 53/124 20060101
C07C053/124; B60C 1/00 20060101 B60C001/00; B60C 9/00 20060101
B60C009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 12, 2014 |
JP |
2014-187070 |
Claims
1. A rubber-metal adhesion promoter comprising: a metal salt (1) of
a carboxylic acid which is a metal salt of an aliphatic carboxylic
acid having 2 to 25 carbon atoms and in which the metal is bismuth,
copper, antimony, silver or niobium; or a compound (2) represented
by the following general formula (A): [Chemical Formula 1]
[(RCOO).sub.xMO].sub.3Z (A) [wherein Z represents a structure
selected from the following formulae (z-1) to (z-4); ##STR00004##
wherein M represents bismuth, copper, antimony, silver or niobium;
(RCOO) represents a residue of an aliphatic carboxylic acid having
2 to 25 carbon atoms; and x represents an integer of {(valence of
M)-1}].
2. The rubber-metal adhesion promoter according to claim 1, wherein
said metal salt (1) of the carboxylic acid is included, and the
metal in the metal salt (1) of the carboxylic acid is bismuth or
copper.
3. The rubber-metal adhesion promoter according to claim 1, wherein
said metal salt (1) of the carboxylic acid is included, and the
aliphatic carboxylic acid in the metal salt (1) of the carboxylic
acid is an aliphatic monocarboxylic acid or an aliphatic
dicarboxylic acid.
4. The rubber-metal adhesion promoter according to claim 3, wherein
the aliphatic carboxylic acid in said metal salt (1) of the
carboxylic acid is a saturated aliphatic monocarboxylic acid having
2 to 20 carbon atoms.
5. The rubber-metal adhesion promoter according to claim 4, wherein
the carboxylic acid in said metal salt (1) of the carboxylic acid
is 2-ethylhexanoic acid, neodecanoic acid, hexadecanoic acid or
octadecanoic acid.
6. The rubber-metal adhesion promoter according to claim 1, wherein
said compound (2) is included, and M in the compound (2) is bismuth
or copper.
7. The rubber-metal adhesion promoter according to claim 1, wherein
said compound (2) is included, and Z in the compound (2) is a
structure represented by said formula (z-1).
8. The rubber-metal adhesion promoter according to claim 1, wherein
said compound (2) is included, and (RCOO) in the compound (2) is a
residue of a saturated aliphatic monocarboxylic acid having 2 to 20
carbon atoms.
9. The rubber-metal adhesion promoter according to claim 8, wherein
(RCOO) in said compound (2) is a residue of 2-ethylhexanoic acid, a
residue of neodecanoic acid, a residue of hexadecanoic acid or a
residue of octadecanoic acid.
10. The rubber-metal adhesion promoter according to claim 1, which
is used for adhering rubber and a steel cord.
11. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 1; and a rubber component.
12. The rubber composition according to claim 11, which contains
0.01 to 10 parts by mass of said rubber-metal adhesion promoter
with respect to 100 parts by mass of said rubber component.
13. A tire comprising a steel cord/rubber composite including the
rubber composition according to claim 11 and a steel cord.
14. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 2; and a rubber component.
15. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 3; and a rubber component.
16. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 4; and a rubber component.
17. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 5; and a rubber component.
18. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 6; and a rubber component.
19. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 7; and a rubber component.
20. A rubber composition comprising: the rubber-metal adhesion
promoter according to claim 8; and a rubber component.
Description
TECHNICAL FIELD
[0001] The present invention relates to a rubber-metal adhesion
promoter, and a rubber composition and a tire using the same. More
specifically, the present invention relates to an adhesion promoter
capable of exerting a high adhesive force between rubber and a
metal, which is equivalent to or higher than that of a
cobalt-containing adhesion promoter, without containing cobalt
associated with concerns over toxicity; and a rubber composition
and a tire using the same.
BACKGROUND ART
[0002] Conventionally, in order to enhance the performance of
automobile tires, belt conveyors and the like, for example, steel
cord or the like that is plated with brass has been used as a
reinforcing material. In order to improve the adhesive force
between the reinforcing material and natural rubber or synthetic
rubber, the rubber contains an adhesion promoter. As the adhesion
promoter, an organic acid cobalt metal soap (for example, cobalt
stearate, cobalt naphthenate, cobalt tallate, cobalt boron metal
soap, or the like) has been frequently used because of favorable
adhesive properties with the steel cord and the rubber.
[0003] However, cobalt compounds such as the aforementioned organic
acid cobalt metal soaps are listed in Group 2B which is said to be
"possibly carcinogenic to humans" in the list of carcinogenic risks
classified by the International Agency for Research on Cancer. In
addition, since metallic cobalt which is a raw material of various
cobalt compounds is a rare metal, its supply is unstable. As
described above, cobalt compounds (organic acid cobalt metal soaps)
using a raw material which is suspected to be carcinogenic and also
unstable in supply tend to be avoided although adhesive properties
with rubber and the metal (steel cord) are favorable, and there is
a demand for alternative adhesion promoters (non-cobalt based
adhesion promoters).
[0004] As a non-cobalt based adhesion promoter, for example, an
adhesion promoter containing boron or phosphorus has been known.
More specifically, for example, an adhesion promoter having a
structure containing three atoms of nickel or bismuth bonded to
boron or phosphorus via an oxygen atom and having both a residue of
an aromatic carboxylic acid and a residue of an aliphatic
carboxylic acid has been known (see, for example, Patent Document
1). However, the adhesion promoter disclosed in Patent Document 1
has a problem in that the adhesive force when adhering the rubber
and the metal is not sufficient.
CITATION LIST
Patent Document
[0005] [Patent Document 1] Japanese Unexamined Patent Application,
First Publication No. Hei 4-230397
SUMMARY OF INVENTION
Technical Problem
[0006] The problem to be solved by the present invention is to
provide an adhesion promoter capable of exerting a high adhesive
force between rubber and a metal than a cobalt-containing adhesion
promoter without containing cobalt which is associated with
concerns over toxicity; and a rubber composition and a tire using
the same.
Solution to Problem
[0007] As a result of intensive investigations in order to solve
the above problems, the present inventors have found the followings
that led to the completion of the present invention: i.e., a metal
salt of an aliphatic carboxylic acid having 2 to 25 carbon atoms in
which the metal is bismuth, copper, antimony, silver or niobium
becomes an adhesion promoter capable of exerting a high adhesive
force between rubber and a metal, rather than a cobalt-containing
adhesion promoter, without containing cobalt that is of concern for
toxicity; and one having a specific structure containing any one of
bismuth, copper, antimony, silver, or niobium which is bonded to
boron or phosphorus via an oxygen atom, and having a residue of an
aliphatic carboxylic acid in combination also becomes an adhesion
promoter capable of exerting a high adhesive force between rubber
and a metal, as compared with the one positively having an aromatic
carboxylic acid residue as disclosed in the aforementioned Patent
Document 1.
[0008] That is, the present invention includes the following
aspects.
[0009] [1] A rubber-metal adhesion promoter characterized by
including: a metal salt (1) of a carboxylic acid which is a metal
salt of an aliphatic carboxylic acid having 2 to 25 carbon atoms
and in which the metal is bismuth, copper, antimony, silver or
niobium; or a compound (2) represented by the following general
formula (A):
[Chemical Formula 1]
[(RCOO).sub.x(MO].sub.3Z (A)
[in the formula, Z represents a structure selected from the
following formulae (z-1) to (z-4);
##STR00002##
M represents bismuth, copper, antimony, silver or niobium; (RCOO)
represents a residue of an aliphatic carboxylic acid having 2 to 25
carbon atoms; and x represents an integer of {(valence of
M)-1}].
[0010] [2] The rubber-metal adhesion promoter according to the
above [1], wherein the aforementioned metal salt (1) of the
carboxylic acid is included, and the metal in the metal salt (1) of
the carboxylic acid is bismuth or copper.
[0011] [3] The rubber-metal adhesion promoter according to the
above [1] or [2], wherein the aforementioned metal salt (1) of the
carboxylic acid is included, and the aliphatic carboxylic acid in
the metal salt (1) of the carboxylic acid is an aliphatic
monocarboxylic acid or an aliphatic dicarboxylic acid.
[0012] [4] The rubber-metal adhesion promoter according to the
above [3], wherein the aliphatic carboxylic acid in the
aforementioned metal salt (1) of the carboxylic acid is a saturated
aliphatic monocarboxylic acid having 2 to 20 carbon atoms.
[0013] [5] The rubber-metal adhesion promoter according to the
above [4], wherein the carboxylic acid in the aforementioned metal
salt (1) of the carboxylic acid is 2-ethylhexanoic acid,
neodecanoic acid, hexadecanoic acid or octadecanoic acid.
[0014] [6] The rubber-metal adhesion promoter according to the
above [1], wherein the aforementioned compound (2) is included, and
M in the compound (2) is bismuth or copper.
[0015] [7] The rubber-metal adhesion promoter according to the
above [1] or [6], wherein the aforementioned compound (2) is
included, and Z in the compound (2) is a structure represented by
the aforementioned formula (z-1).
[0016] [8] The rubber-metal adhesion promoter according to the
above [1], [6] or [7], wherein the aforementioned compound (2) is
included, and (RCOO) in the compound (2) is a residue of a
saturated aliphatic monocarboxylic acid having 2 to 20 carbon
atoms.
[0017] [9] The rubber-metal adhesion promoter according to the
above [8], wherein (RCOO) in the aforementioned compound (2) is a
residue of 2-ethylhexanoic acid, a residue of neodecanoic acid, a
residue of hexadecanoic acid or a residue of octadecanoic acid.
[0018] [10] The rubber-metal adhesion promoter according to any one
of the above [1] to [9], which is used for adhering rubber and a
steel cord.
[0019] [11] A rubber composition characterized by including: the
rubber-metal adhesion promoter according to any one of the above
[1] to [10]; and a rubber component.
[0020] [12] The rubber composition according to the above [11],
which contains 0.01 to 10 parts by mass of the aforementioned
rubber-metal adhesion promoter with respect to 100 parts by mass of
the aforementioned rubber component.
[0021] [13] A tire characterized by having a steel cord/rubber
composite including the rubber composition according to the above
[11] or [12] and a steel cord.
Advantageous Effects of Invention
[0022] The rubber-metal adhesion promoter of the present invention
is, despite being a non-cobalt based promoter, capable of exerting
a higher adhesive force between rubber and a metal than a
cobalt-containing adhesion promoter, especially even under wet heat
conditions. By using the adhesion promoter of the present
invention, it is possible to easily obtain a rubber composition
capable of suitably producing automobile tires, belt conveyors and
the like exhibiting strong adhesion between the steel cord and the
rubber.
DESCRIPTION OF EMBODIMENTS
[0023] A rubber-metal adhesion promoter of the present invention is
characterized by containing a metal salt (1) or a compound (2) as
described above. Hereinafter, the metal salt (1) will be described
in detail.
[0024] The metal salt (1) of a carboxylic acid in the present
invention is a metal salt of an aliphatic carboxylic acid having 2
to 25 carbon atoms. Here, the metal species is bismuth, copper,
antimony, silver or niobium. Among the metal species, bismuth,
copper, antimony or silver is preferable, and bismuth or copper is
more preferable, since an adhesion promoter capable of achieving a
favorable adhesion between the steel cord and the rubber even under
wet heat conditions is obtained.
[0025] In the present invention, when an aliphatic carboxylic acid
having less than 2 carbon atoms is used, it is not preferable
because it is difficult to form an adhesion promoter excellent in
compatibility with the rubber, and as a result, it becomes
difficult to obtain an adhesion promoter that exerts a high
adhesive force between the rubber and the metal. In addition, when
a carboxylic acid having more than 25 carbon atoms is used, it is
not preferable because it is difficult to synthesize the metal salt
(1), and as a result, it becomes difficult to obtain an adhesion
promoter that exerts a high adhesive force between the rubber and
the metal.
[0026] As the aliphatic carboxylic acid having 2 to 25 carbon
atoms, for example, an aliphatic monocarboxylic acid and an
aliphatic dicarboxylic acid can be preferably exemplified. Here, in
the present invention, the number of carbon atoms of the aliphatic
carboxylic acid refers to the number of carbon atoms including
those of the carboxyl group.
[0027] Examples of the aliphatic carboxylic acid having 2 to 25
carbon atoms include saturated aliphatic monocarboxylic acids and
unsaturated aliphatic monocarboxylic acids. Examples of the
saturated aliphatic monocarboxylic acid include ethanoic acid,
propanoic acid, butanoic acid, pentanoic acid, hexanoic acid,
2-ethylhexanoic acid, heptanoic acid, octanoic acid, nonanoic acid,
isononanoic acid, decanoic acid, neodecanoic acid, dodecanoic acid,
tetradecanoic acid, hexadecanoic acid, heptadecanoic acid,
octadecanoic acid, eicosanoic acid, docosanoic acid, tetracosanoic
acid and naphthenic acid.
[0028] Examples of the unsaturated aliphatic monocarboxylic acid
include 9-hexadecenoic acid, cis-9-octadecenoic acid,
11-octadecenoic acid, cis, cis-9,12-octadecadienoic acid,
9,12,15-octadecatrienoic acid, 6,9,12-octadecatrienoic acid,
9,11,13-octadecatrienoic acid, eicosanoic acid, 8,11-eicosadienoic
acid, 5,8,11-eicosatrienoic acid, 5,8,11,14-eicosatetraenoic acid,
tung oil acid, linseed oil acid, soybean oil acid, resin acid, tall
oil fatty acid, rosin acid, abietic acid, neoabietic acid,
palustric acid, pimaric acid and dehydroabietic acid.
[0029] Examples of the aliphatic dicarboxylic acid having 2 to 25
carbon atoms include saturated aliphatic dicarboxylic acids and
unsaturated aliphatic dicarboxylic acids. Examples of the saturated
aliphatic dicarboxylic acid include oxalic acid, malonic acid,
succinic acid, glutaric acid and adipic acid.
[0030] Examples of the unsaturated aliphatic dicarboxylic acid
include fumaric acid and maleic acid.
[0031] Among the aforementioned carboxylic acids, saturated
aliphatic monocarboxylic acids are preferable because they hardly
affect adversely the sulfur crosslinking of the rubber, and as a
result, a rubber cured product having less adverse effects on the
rubber physical properties which is used for automobile tires, belt
conveyors and the like can be obtained. Among the saturated fatty
acids, a saturated aliphatic monocarboxylic acid having 2 to 20
carbon atoms is preferable, and 2-ethylhexanoic acid, neodecanoic
acid, hexadecanoic acid or octadecanoic acid is more
preferable.
[0032] The metal salt (1) of a carboxylic acid in the present
invention can be obtained, for example, by the following
method.
[0033] Production Method 1: A production method in which an
aliphatic carboxylic acid (a) having 2 to 25 carbon atoms is
directly reacted with at least one selected from an oxide (b-1) of
a metal (bismuth, copper, antimony, silver or niobium), a hydroxide
(b-2) of a metal (bismuth, copper, antimony, silver or niobium) and
a carbonate (b-3) of a metal (bismuth, copper, antimony, silver or
niobium) (direct method).
[0034] Production Method 2: A production method in which, after
reacting an aliphatic carboxylic acid (a) having 2 to 25 carbon
atoms with sodium hydroxide in the presence of water to obtain a
sodium salt of an aliphatic carboxylic acid, the sodium salt of the
aliphatic carboxylic acid is reacted with at least one selected
from a sulfate (c-1) of a metal (bismuth, copper, antimony, silver
or niobium), a chloride (c-2) of a metal (bismuth, copper,
antimony, silver or niobium) and a nitrate (c-3) of a metal
(bismuth, copper, antimony, silver or niobium) (double
decomposition method).
[0035] Examples of the oxide (b-1) of the metal (bismuth, copper,
antimony, silver or niobium) used in the above Production Method 1
include bismuth(III) oxide, copper(I) oxide, copper(II) oxide,
antimony(III) oxide, antimony(V) oxide, silver(I) oxide, silver(II)
oxide, silver(III) oxide, niobium(IV) oxide and niobium(V) oxide.
Examples of the hydroxide (b-2) of the metal (bismuth, copper,
antimony, silver or niobium) include copper(II) hydroxide and the
like. Examples of the carbonate (b-3) of the metal (bismuth,
copper, antimony, silver or niobium) include bismuth(III)
carbonate, bismuth(III) subcarbonate and copper(II) carbonate.
[0036] Examples of the sulfate (c-1) of the metal (bismuth, copper,
antimony, silver or niobium) used in the above Production Method 2
include copper(II) sulfate and the like. Examples of the chloride
(c-2) of the metal (bismuth, copper, antimony, silver or niobium)
include bismuth(III) oxychloride, copper(T) chloride, copper(II)
chloride, antimony(III) chloride, antimony(V) chloride, silver(I)
chloride and niobium(V) chloride. Examples of the nitrate (c-3) of
the metal (bismuth, copper, antimony, silver or niobium) include
bismuth(III) nitrate, bismuth(III) subnitrate and silver(I)
nitrate.
[0037] In the above Production Method 1, the reaction temperature
at the time of reacting the aliphatic carboxylic acid (a) having 2
to 25 carbon atoms with the compounds (b-1) to (b-3) is usually
from 50 to 150.degree. C. In addition, the reaction time is usually
from 1 to 20 hours.
[0038] In the above Production Method 2, the reaction temperature
at the time of reacting the aliphatic carboxylic acid (a) having 2
to 25 carbon atoms with sodium hydroxide in the presence of an
organic solvent is usually from 20 to 100.degree. C. In addition,
the reaction time is usually from 1 to 5 hours.
[0039] In the above Production Method 2, the reaction temperature
at the time of reacting the sodium salt of an aliphatic carboxylic
acid with the compounds (c-1) to (c-3) is usually from 20 to
100.degree. C. In addition, the reaction time is usually from 1 to
5 hours.
[0040] In the Production Method 2, after reacting the sodium salt
of the aliphatic carboxylic acid with the compounds (c-1) to (c-3),
an aqueous layer in the reaction system is separated. Thereafter,
by removing the solvent present in the oil layer by distillation
under reduced pressure, the rubber-metal adhesion promoter (fatty
acid metal salt) of the present invention can be obtained.
[0041] Next, the compound (2) represented by the general formula
(A) in the present invention will be described in detail. (RCOO) in
the compound (2) represents a residue of an aliphatic carboxylic
acid having 2 to 25 carbon atoms. The residue of an aliphatic
carboxylic acid having less than 2 carbon atoms is unlikely to
become an adhesion promoter excellent in compatibility with the
rubber, and as a result, it becomes difficult to obtain an adhesion
promoter that exerts high adhesive force between the rubber and the
metal, and is therefore not preferable. In addition, not only it is
difficult to synthesize the compound (2) with the residue of a
carboxylic acid having more than 25 carbon atoms, but also it is
difficult to disperse in the rubber or adsorb to the surface of the
steel cord. As a result, it becomes difficult to obtain an adhesion
promoter that exerts high adhesive force between the rubber and the
metal, and is therefore not preferable. Here, in the present
invention, the number of carbon atoms of (RCOO) refers to the
number of carbon atoms including those of the carboxyl group.
[0042] As the residue of the aliphatic monocarboxylic acid having 2
to 25 carbon atoms, for example, a residue of an aliphatic
monocarboxylic acid can be preferably exemplified. As these
residues, for example, a residue derived from the aliphatic
monocarboxylic acid described above can be preferably
exemplified.
[0043] Among the residues of the aliphatic carboxylic acid, the
residues of a saturated aliphatic monocarboxylic acid is preferred
since it does not crosslink with the rubber and can further develop
the performance as the adhesion promoter by further promoting
dispersion in the vicinity of the steel cord or adsorption to the
surface of the steel cord. Among the residues of a saturated
aliphatic monocarboxylic acid, a residue of a saturated aliphatic
monocarboxylic acid having 2 to 20 carbon atoms is preferable, and
a residue of 2-ethylhexanoic acid, a residue of neodecanoic acid, a
residue of hexadecanoic acid or a residue of octadecanoic acid is
more preferable.
[0044] M in the compound represented by the general formula (A) is
a metal species, and more specifically, is bismuth, copper,
antimony, silver or niobium. Among the metal species, bismuth,
copper, antimony or silver is preferable, and bismuth or copper is
more preferable, since an adhesion promoter capable of achieving a
favorable adhesion between the steel cord and the rubber even under
wet heat conditions is obtained.
[0045] Further, x in the compound (2) represented by the general
formula (A) is an integer of {(valence of M)-1}.
[0046] Z in the compound (2) represented by the general formula (A)
is a structure selected from the following formulae (z-1) to
(z-4).
##STR00003##
[0047] Among the above structures, the structure represented by the
above formula (z-1) is preferable because it is easy to obtain an
adhesion promoter that exerts high adhesive force between the
rubber and the metal.
[0048] For example, the compound (2) represented by the general
formula (A) can be produced by a method of mixing and heating an
aliphatic carboxylic acid (a) having 2 to 25 carbon atoms; a boric
acid ester (d-1) of a lower alcohol having 1 to 5 carbon atoms, a
metaboric acid ester (d-2) of a lower alcohol having 1 to 5 carbon
atoms, a phosphoric acid ester (d-3) of a lower alcohol having 1 to
5 carbon atoms or a phosphite ester (d-4) of a lower alcohol having
1 to 5 carbon atoms; an acid (e) capable of forming a volatile
ester with a lower alcohol residue of 1 to 5 carbon atoms present
in the esters (d-1) to (d-4); and a metal compound M(f) as a metal
source, and removing the resulting volatile ester.
[0049] As the monocarboxylic acid (a), for example, the
aforementioned aliphatic monocarboxylic acids having 2 to 25 carbon
atoms and the like can be mentioned.
[0050] Examples of the boric acid ester (d-1) of a lower alcohol
include trimethyl borate, triethyl borate, tripropyl borate and
tributyl borate. Examples of the metaboric acid ester (d-2) of a
lower alcohol include trimethyl metaborate, triethyl metaborate,
tripropyl metaborate and tributyl metaborate. Examples of the
phosphoric acid ester (d-3) of a lower alcohol include methyl
phosphate, ethyl phosphate, propyl phosphate and butyl phosphate.
Examples of the phosphite ester (d-4) of a lower alcohol include
methyl phosphite, ethyl phosphite, propyl phosphite and butyl
phosphite.
[0051] As the metal compound M (f) serving as the metal source, for
example, the oxide (b-1), the hydroxide (b-2), the carbonate (b-3)
and the like described above can be used.
[0052] Examples of the acid (e) include ethanoic acid, propanoic
acid and butanoic acid.
[0053] The proportion of the metal compound M (f) used as the metal
source is, for example, from 20 to 100 parts by mass per 100 parts
by mass of the aliphatic carboxylic acid (a) having 2 to 25 carbon
atoms. In addition, the proportion of the above (d) used is, for
example, from 10 to 50 parts by mass per 100 parts by mass of the
aliphatic carboxylic acid (a) having 2 to 25 carbon atoms. Further,
the proportion of the acid (e) used is, for example, from 10 to 50
parts by mass per 100 parts by mass of the aliphatic carboxylic
acid (a) having 2 to 25 carbon atoms.
[0054] Among the above production methods, the production method
including a first step of mixing and heating an aliphatic
carboxylic acid (a) having 2 to 25 carbon atoms, an acid (e)
capable of forming a volatile ester with a lower alcohol residue of
1 to 5 carbon atoms present in the ester (d) and a metal compound M
(f) as a metal source to obtain a reaction product; followed by a
second step of adding, after removing water from the reaction
system containing the reaction product, the aforementioned esters
(d-1) to (d-4) to the reaction system from which the water has been
removed, and allowing the reaction product to react with the esters
(d-1) to (d-4) reactant, is preferable because it is possible to
prevent the hydrolysis of the esters (d-1) to (d-4) by the water
produced in the first step, and as a result, it is possible to
efficiently produce the compound (2) in the present invention.
[0055] In the above production method, the temperature for reacting
the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms, the
esters (d-1) to (d-4), the acid (e) and the metal compound M (f)
is, for example, from 100 to 250.degree. C., and preferably from
150 to 220.degree. C. In addition, the reaction time is, for
example, from 1 to 20 hours, and preferably from 1 to 5 hours.
[0056] The rubber composition of the present invention is
characterized by containing the adhesion promoter of the present
invention and a rubber component. As the rubber component, for
example, diene-based rubber can be used. Examples of the
diene-based rubber include natural rubber (NR) and diene-based
synthetic rubber. Examples of the diene-based synthetic rubber
include isoprene rubber (IR), butadiene rubber (BR), styrene
butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR),
ethylene propylene diene rubber (EPDM), chloroprene rubber (CR) and
acrylonitrile butadiene rubber (NBR). Among these rubber
components, NR which is easy to elongate and crystallize and
excellent in fracture properties is preferable.
[0057] In the rubber composition according to the present
invention, a filler such as carbon black or silica can be blended
as a reinforcing agent.
[0058] The carbon black is not particularly limited, and for
example, carbon black of SAF, ISAF, HAF or FEF type can be used,
and two or more types of these may be used in combination. The
amount of the carbon black added is not particularly limited, but
it is preferably from 20 to 100 parts by mass, and more preferably
from 40 to 80 parts by mass with respect to 100 parts by mass of
the diene-based rubber.
[0059] Examples of the silica include wet silica (hydrous silicic
acid), dry silica (anhydrous silicic acid) and surface treated
silica. In the case of adding silica, the added amount thereof is
not particularly limited, but it is preferably 0 parts by mass or
more and 40 parts by mass or less, and more preferably 0.1 parts by
mass or more and 20 parts by mass or less, with respect to 100
parts by mass of the diene-based rubber.
[0060] Sulfur as a vulcanizing agent is usually added to the rubber
composition according to the present invention. The added amount of
sulfur is preferably from 1 to 10 parts by mass, and more
preferably from 2 to 8 parts by mass with respect to 100 parts by
mass of the diene-based rubber. Examples of sulfur include powdered
sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur and
oil-treated sulfur, and are not particularly limited.
[0061] A vulcanization accelerator can be added to the rubber
composition of the present invention. As the vulcanization
accelerator, for example, a sulfenamide-based vulcanization
accelerator can be mentioned. Here, examples of the sulfenamide
vulcanization accelerator include N-cyclohexyl-2-benzothiazole
sulfenamide (CZ, JIS abbreviation: CBS),
N-tert-butyl-2-benzothiazole sulfenamide (NS, JIS Abbreviation:
BBS), N-oxydiethylene-2-benzothiazole sulfenamide (OBS),
N,N-diisopropyl-2-benzothiazole sulfenamide (DPBS) and
N,N-dicyclohexyl-2-benzothiazole sulfenamide (DZ, JIS abbreviation:
DCBS).
[0062] The content of the vulcanization accelerator is preferably
from 1 to 12 parts by mass, more preferably from 2 to 10 parts by
mass, and even more preferably from 3 to 9 parts by mass, with
respect to 100 parts by mass of the rubber component.
[0063] In addition to the above components, various compounding
agents can be arbitrarily added to the rubber composition according
to the present invention. Examples of such compounding agents
include stearic acid, wax, oil, antioxidants and processing
aids.
[0064] The rubber composition of the present invention can be
prepared by kneading using a mixer such as a Banbury mixer or a
kneader that is commonly used.
[0065] The rubber composition of the present invention can be
suitably used, in particular, as a rubber composition for covering
various steel cords. In particular, it is preferably used as a
rubber composition for covering (topping) a steel cord used as a
reinforcing material for a pneumatic tire such as a belt layer, a
carcass layer, a chafer layer and the like, and a steel cord
topping sheet is produced by a topping device such as a steel
calender in accordance with a conventional method and this is used
as a tire reinforcing member and molded and vulcanized in
accordance with a conventional method, thereby a tire having a
steel cord/rubber composite can be produced.
[0066] The content of the rubber-metal adhesion promoter according
to the present invention in the rubber composition of the present
invention is preferably from 0.01 to 10 parts by mass, and more
preferably from 1 to 6 parts by mass, with respect to 100 parts by
mass of the rubber component.
EXAMPLES
[0067] Hereinafter, the present invention will be described in
detail by referring to Examples of the present invention and
comparing them with Comparative Examples. In the Examples and
Comparative Examples, unless stated otherwise, "parts" and "%"
refer to mass-referenced values.
Synthesis Example 1 [Adhesion Promoter (1-1): Synthesis of Metal
Salt (1-1)]
[0068] 400 g of 2-ethylhexanoic acid and 134 g of antimony(III)
oxide were charged into a flask, and the resulting mixture was
heated and stirred at 120.degree. C. for 2 hours. Then, the
resultant was dried under reduced pressure at 120.degree. C. for 1
hour to obtain a metal salt (1-1) used in the present invention. It
should be noted that the metal salt (1-1) can also be said to be an
adhesion promoter (1-1) of the present invention containing the
metal salt (1-1).
Synthesis Example 2 (Adhesion Promoter (1-2): Synthesis of Metal
Salt (1-2))
[0069] A metal salt (1-2) used in the present invention was
obtained in the same manner as in Synthesis Example 1 except that
483 g of neodecanoic acid was used in place of 400 g of
2-ethylhexanoic acid. It should be noted that the metal salt (1-2)
can also be said to be an adhesion promoter (1-2) of the present
invention containing the metal salt (1-2).
Synthesis Example 3 (Adhesion Promoter (1-3): Synthesis of Metal
Salt (1-3))
[0070] 483 g of neodecanoic acid and 43 g of niobium(II) oxide were
charged into a flask, and the resulting mixture was heated and
stirred at 120.degree. C. for 2 hours. Then, the resultant was
dried under reduced pressure at 120.degree. C. for 1 hour to obtain
a metal salt (1-3) used in the present invention. It should be
noted that the metal salt (1-3) can also be said to be an adhesion
promoter (1-3) of the present invention containing the metal salt
(1-3).
Synthesis Example 4 [Adhesion Promoter (2-1): Synthesis of Compound
(2-1)]
[0071] 233 g of bismuth(III) oxide was added to a mixed acid of 63
g of acetic acid and 342 g of neodecanoic acid, and then the
resulting mixture was heated and stirred at 120.degree. C. for 2
hours. Then, after drying the resultant under reduced pressure at
120.degree. C. for 1 hour, 80 g of tributyl borate was reacted with
the produced bismuth metal salt, and butyl acetate produced as a
by-product was distilled off to obtain a compound (2-1) used in the
present invention. It should be noted that the compound (2-1) can
also be said to be an adhesion promoter (2-1) of the present
invention containing the compound (2-1).
Synthesis Example 5 (Adhesion Promoter (2-2): Synthesis of Compound
(2-2))
[0072] A compound (2-2) used in the present invention was obtained
in the same manner as in Synthesis Example 4 except that 80 g of
copper(II) oxide was used in place of 233 g of bismuth(III) oxide.
It should be noted that the compound (2-2) can also be said to be
an adhesion promoter (2-2) of the present invention containing the
compound (2-2).
Synthesis Example 6 (Adhesion Promoter (2-3): Synthesis of Compound
(2-3))
[0073] A compound (2-3) used in the present invention was obtained
in the same manner as in Synthesis Example 4 except that 146 g of
antimony(III) oxide was used in place of 233 g of bismuth(III)
oxide. It should be noted that the compound (2-3) can also be said
to be an adhesion promoter (2-3) of the present invention
containing the compound (2-3).
Synthesis Example 7 (Adhesion Promoter (2-4): Synthesis of Compound
(2-4))
[0074] A compound (2-4) used in the present invention was obtained
in the same manner as in Synthesis Example 4 except that 124 g of
silver(II) oxide was used in place of 233 g of bismuth(III) oxide.
It should be noted that the compound (2-4) can also be said to be
an adhesion promoter (2-4) of the present invention containing the
compound (2-4).
Synthesis Example 8 (Adhesion Promoter (2-5): Synthesis of Compound
(2-5))
[0075] A compound (2-5) used in the present invention was obtained
in the same manner as in Experimental Example 4 except that 125 g
of niobium(IV) oxide was used in place of 233 g of bismuth(III)
oxide. It should be noted that the compound (2-5) can also be said
to be an adhesion promoter (2-5) of the present invention
containing the compound (2-5).
Comparative Synthesis Example 1 [Adhesion Promoter (2'-1):
Synthesis of Comparative Compound (2'-1)]
[0076] 210 g of neodecanoic acid, 147 g of propionic acid and 300 g
of xylene were charged into a reaction flask and heated to
50.degree. C. with mechanical stirring. 171 g of cobalt(II)
hydroxide was added thereto, and the temperature was raised to
90.degree. C. with mechanical stirring to produce a mobile blue
liquid. Further, heat was applied and the reaction water was
removed by xylene loading using a Dean & Stark trap. After the
temperature reached 140.degree. C., 73 g of benzoic acid dissolved
in 150 g of xylene was gradually added to the reaction mixture, and
the produced water was continuously removed.
[0077] After completion of the water removal, xylene was removed by
short path distillation to a maximum temperature of 155.degree. C.,
and a vacuum was applied to complete the removal. 138 g of tributyl
borate was added thereto. The reaction mixture was heated to
190.degree. C. and refluxed for 3 hours. 220 g of n-butyl
propionate was then removed by distillation at the maximum
temperature of 220.degree. C., and a vacuum was applied to complete
the ester removal to obtain a comparative compound (2'-1).
[0078] The comparative compound (2'-1) was a hard blue solid
represented by the following formula:
B(OCoOCOB')(OCoOCOA').sub.2
[In the formula, OCOA' is a neodecanoic acid ester, and OCOB' is a
benzoic acid ester]. It should be noted that the comparative
compound (2'-1) can also be said to be a comparative adhesion
promoter (2'-1) containing the comparative compound (2'-1).
Example 1 (Preparation of Rubber Composition of the Present
Invention)
[0079] 100 parts of natural rubber (grade: RSS 1), 4 parts of the
adhesion promoter (1-1), 50 parts of carbon black (SEAST G-S
manufactured by Tokai Carbon Co., Ltd.), 5 parts of oil (Dutrex R
manufactured by Shell Chemicals Japan Ltd.), 8 parts of zinc white,
1 part of an antioxidant (Nocrac 810NA manufactured by Ouchi Shinko
Chemical Industrial Co., Ltd.), 5 parts of insoluble sulfur, 2
parts of stearic acid and 0.5 parts of a vulcanization accelerator
(Nocceler CZ, manufactured by Ouchi Shinko Chemical Industrial Co.,
Ltd.) were kneaded at 40.degree. C. to obtain a rubber composition
(1) of the present invention. A cured product (test piece) of a
rubber composition in which a steel cord was sandwiched was
prepared using the obtained rubber composition (1), and the
adhesive properties between the steel cord and rubber were
evaluated. The method for preparing a test piece and the method for
evaluating the adhesive properties are shown below. In addition,
the evaluation results are shown in Table 1.
<Method for Preparing Test Piece>
[0080] The rubber composition (1) was subjected to a heat treatment
by a double test roller to prepare a rubber sheet having a width of
100 mm, a thickness of 6 mm and a length of 100 mm. Two rubber
pieces having a width of 10 mm, a thickness of 6 mm and a length of
60 mm were cut out from the rubber sheet. A 1.times.4.times.0.25 mm
steel cord plated with brass (Cu 65%, Zn 35%) was sandwiched
between the aforementioned two rubber pieces and vulcanized at
160.degree. C. for 10 minutes to prepare a rubber composition test
piece to which the steel cord was adhered.
<Evaluation Method of Adhesive Properties>
[0081] A pulling test was conducted by a method in accordance with
ASTM D2229 using the aforementioned test piece, and the adhesive
force between the rubber and the steel cord was measured. For the
measurement of the adhesive force, the following three types of
measurements were carried out.
[0082] Initial adhesive force: A test piece was prepared by
vulcanization under the above vulcanization conditions, and
measurements were conducted after 24 hours.
[0083] Adhesive force after hygrothermal aging test: The test piece
vulcanized under the above vulcanization conditions was subjected
to water immersion aging by being immersed in hot water at
90.degree. C. for 72 hours, and then the adhesive force was
measured.
[0084] Adhesive force after heat aging test: The test piece
vulcanized under the above vulcanization conditions was left to
stand at 110.degree. C. for 72 hours to measure the adhesive
force.
[0085] It should be noted that the measured values of the above
three adhesive forces are relative adhesive force values when the
adhesive forces of a comparative metal salt (1'-2) described later
are taken as 100.
Examples 2 to 15
[0086] Rubber compositions (1) to (15) were obtained in the same
manner as in Example 1 except that the metal salts (1-1) to (1-10)
or the compounds (2-1) to (2-5) [adhesion promoters of the present
invention] shown in Table 1 were used. An evaluation test of
adhesive properties was carried out in the same manner as in
Example 1, and the results are shown in Table 1. It should be noted
that in Examples 2 to 15, the amounts of the respective metal salts
(1-1) to (1-10) or the compounds (2-1) to (2-5) used were added so
that the metal molar concentrations in the rubber compositions were
the same.
TABLE-US-00001 TABLE 1 Metal Salt (1) or Compound (2) (Adhesion
Promoter) Adhesion after aging test Metal Salt or Synthesis Amount
used Initial Adhesion after Adhesion after Compound Example Metal
salt name or compound name (parts) Adhesion hygrothermal aging test
heat aging test Ex. 1 (1-1) Synthesis Antimony(III)
2-ethylhexanoate 4.0 110 105 120 Example 1 Ex. 2 (1-2) Synthesis
Antimony(III) neodecanoate 4.7 108 110 115 Example 2 Ex. 3 (1-3)
Synthesis Niobium(IV) neodecenoate 5.7 101 105 102 Example 3 Ex. 4
(1.4) Bismuth(III) 2-ethylhexanoate 4.7 128 114 120 Ex. 5 (1-5)
Copper(II) 2-ethylhexanoate 3.0 122 115 144 Ex. 6 (1-6) Silver(I)
2-ethylhexanoate 1.8 108 110 112 Ex. 7 (1-7) Niobium(IV)
2-ethylhexanoate 4.8 103 110 108 Ex. 8 (1-8) Bismuth(III)
neodecanoate 5.4 125 120 125 Ex. 9 (1-9) Copper(II) neodecanoate
3.5 120 118 122 Ex. 10 (1-10) Silver(II) neodecanoate 3.3 104 108
110 Ex. 11 (2-1) Synthesis Bismuth(III) boron neodecanoate 4.2 122
120 130 Example 4 Ex. 12 (2-2) Synthesis Copper(II) boron
neodecanoate 2.2 115 125 128 Example 5 Ex. 13 (2-3) Synthesis
Antimony(III) boron neodecanoate 3.5 112 120 125 Example 6 Ex. 14
(2-4) Synthesis Silver(II) boron neodecanoate 2.2 105 120 120
Example 7 Ex. 15 (2-5) Synthesis Niobium(IV) boron neodecanoate 4.6
102 118 110 Example 8
Comparative Examples 1 to 12 (Preparation of Comparative Rubber
Compositions)
[0087] Comparative rubber compositions (1') to (12') were obtained
in the same manner as in Example 1 except that the metal salts
(1'-2) to (1'-11) or the compound (2'-1) [comparative adhesion
promoters] and the compound (2'-2) shown in Table 2 were used. An
evaluation test of adhesive properties was carried out in the same
manner as in Example 1, and the results are shown in Table 2. It
should be noted that in Comparative Examples 1 to 12, the amounts
of the respective metal salts (1'-2) to (1'-11) or the compounds
(2'-1) to (2'-2) used were added so that the metal molar
concentrations in the rubber compositions were the same.
TABLE-US-00002 TABLE 2 Metal Salt (1') or Compound (2') (Adhesion
Promoter) Adhesion after aging test Metal Salt or Synthesis Metal
salt name or Amount used Initial Adhesion after Adhesion after
Compound Example compound name (parts) Adhesion hygrothermal aging
test heat aging test Comp. Ex. 1 (1'-2) Cobalt(II) 2-ethylhexanoate
2.7 100 100 100 Comp. Ex. 2 (1'-3) Iron(II) 2-ethylhexanoate 3.8 25
25 20 Comp. Ex. 3 (1'-4) Manganese(II) 2-ethylhexanoate 2.9 24 27
18 Comp. Ex. 4 (1'-5) Yttrium(II) 2-ethylhexanoate 3.7 24 26 16
Comp. Ex. 5 (1'-6) Magnesium(II) 2-ethylhexanoate 3.2 23 27 20
Comp. Ex. 6 (1'-7) Zinc(II) 2-ethylhexanoate 2.1 21 22 17 Comp. Ex.
7 (1'-8) Lead(II) 2-ethylhexanoate 4.0 19 22 18 Comp. Ex. 8 (1'-9)
Strontium(II) 2-ethylhexanoate 3.9 12 16 10 Comp. Ex. 9 (1'-10)
Calcium(II) 2-ethylhexanoate 3.4 10 12 10 Comp. Ex. 10 (1'-11)
Barium(II) 2-ethylhexanoate 4.6 7 10 5 Comp. Ex. 11 (2'-1)
Comparative Cobalt(II) boron (neodecanoate + 3.3 75 80 80 Synthesis
benzoate) Example 1 Comp. Ex. 12 (2'-2) Cobalt(II) boron
neodecanoate 1.9 100 102 101
INDUSTRIAL APPLICABILITY
[0088] The present invention is used, for example, in automobile
tires, belt conveyors and the like in order to promote adhesion
between rubber and a metal to enhance the performance.
* * * * *