Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a low-temperature resistance imp
prover for rubber and more particularly to a low-temperature resistance improver
for rubber which improves not only the low temperature resistance of rubber but
also its heat resistance and other physical and chemical characteristics.
With an increase in the range of the application and the use of
rubber goods in recent years, improved low-temperature resistance, particularly
low-temperature flexibility superior to that of conventional rubber goods are
required. Therefore, studies to improve the low-temperature resistance by, for
example, blending different rubbers with each other or adding a third component
have been made with considerable success. However, these methods have both
merits and demerits and no decisive method has yet been found.
For example, there is a method wherein natural rubber (hereinafter
referred to as NO) or polybutadiene rubber (hereinafter referred to as BY),
which are thought to have relatively good low-temperature resistance, is blended
with acrylonitrile/butadiene rubber (hereinafter referred to as NOR) or sheller-
prone rubber (hereinafter referred to as OR), which both have poor low-tempera-
lure resistance, to improve the low-temperature resistance of NOR or CR.
However, since a large quantity of NO or BY must be blended to improve the no-
distance sufficiently, and there is a problem in compatibility between rubbers,
physical and chemical characteristics peculiar to NOR or OR often deteriorate as
a result. In a method for improving low-temperature resistance by blending
different rubbers, it is scarcely possible to improve the low-temperature no-
distance of NO or styrene/butadiene rubber (hereinafter called as SIR).
A third component may be added. Ductile subacute (hereinafter
referred to as DOS), diisobutyl adipate (hereinafter referred to as DIVA) and
trioctyl phosphate are known as additives for OR and SIR, and dibutyl subacute
and DOS are known as additives for OR and NOR. However, improvement in low-
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I
temperature resistance is not sufficient. Therefore additives combining
superior low-temperature resistance with excellent heat resistance and other
physical and chemical characteristics are required in some fields. As an
example bottle owlet has considerably good low-temperature resistance but is
very poor in heat resistance. No low-temperature resistance improver satisfy-
in all the characteristics has been found.
We have made studies to find out an agent for improving the low-
temperature resistance of rubber as well as its heat resistance and other
various characteristics, and have surprisingly found that when a specified
Lo ester compound having a structure very close to that of known additives is
added to rubber, there can be obtained a rubber having excellent properties,
unattainable by known additives, such as satisfactory low-temperature resist-
ante, heat resistance and other physical and chemical characteristics. The
present invention is based on this finding.
According to one aspect of the present invention there is provided
a low-temperature resistance improver for rubber, comprising an ester derived
from an unsaturated Patty acid having 12 to I carbon atoms and at least one
hydroxyl compound selected from the group consisting of saturated alcohols having
6 to 12 carbon atoms, unsaturated alcohols having 14 to 18 carbon atoms and
glycols having 2 to 6 carbon atoms.
According to another aspect of the present invention there is provide
Ed a rubber comprising the above improver.
Examples of the saturated alcohols having 6 to 12 carbon atoms
used in the present invention include Huxley alcohol, 2-ethylhexyl alcohol,
n-octyl alcohol, n-decyl alcohol, and laurel alcohol. Preferred alcohols are
those having 8 to 10 carbon atoms.
Examples of the unsaturated alcohols having 14 to 18 carbon atoms
include myristoleyl alcohol and oilily alcohol.
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Examples of the glycols having 2 to 6 carbon atoms include ethylene
glycol, propylene glycol, diethylene glycol, neopentyl glycol, butanediol, and
hexanediol.
Examples of the unsaturated fatty acid having 12 to 24 carbon atoms
used in the present invention include lauroleic acid, oleic acid, elaidic acid,
erucic acid, linoleic acid, linoelaidic acid, eleostearic acid, myristoleic
acid, linolenic acid and tall oil fatty acid which is a mixture of the above-
listed acids. Among these acids, oleic acid and tall oil fatty acid are
preferred.
LO The esters of the present invention may be prepared from the above
described hydroxyl compounds and unsaturated fatty acids by any of conventional
methods. For example, they can be prepared by a dehydration-
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condensation reaction between the hydroxyl compounds
and the unsaturated fatty acids or an ester exchange
reaction between the hydroxyl compounds and lower
alkyd esters of the unsaturated fatty acids.
Examples of the esters suitable for use in -the
present invention include octal owlet, decal owlet,
tall oil fatty acid octal ester, oilily owlet,
ethylene glycol dwelt, 1,4-butanediol dwelt,
1,6-hexanediol dwelt, 2-ethylhexyl owlet, dodecyl
owlet, decal myristoleate, and oilily myristoleate,
among which octal owlet is preferred.
By adding the low-temperature resistance it
prover of the present invention to rubber, the low-
temperature resistance can be greatly improved while
other physical properties, particularly heat resistance,
can be maintained or improved.
Though it is not clear why the low-temperature
resistance improver of the present invention is superior
to conventional compounds, it is thought to be Sue to
wits chemical structure such as alkyd chain length, ester
linkage, or unsaturated bond.
In any case, the improver of the present invention
must be an ester derived from the hydroxyl compound
and the unsaturated fatty acid as specified above.
The effect of the present invention can not be obtained
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by an ester derived from other hydroxyl compounds or unsaturated fatty acids
than those specified above. For example, esters derived from a saturated
alcohol having five or less carbon atoms and the above-described unsaturated
fatty acid have unsatisfactory heat resistance, and unsaturated fatty acid
esters derived from a saturated alcohol having 13 or more carbon atoms or an
unsaturated alcohol other than those having 14 to 18 carbon atoms have unswept-
sfackory low-temperature resistance. Rosters derived from saturated fatty acids
also prove unsatisfactory.
The unsaturated fatty acid ester of the present invention is used
Lo in a quantity of 2.0 to 50 parts, preferably 5.0 to 30 parts by weight per 100
parts by weight of rubber. Inn the amount of the ester is less than 2.0 parts
by weight per 100 parts by weight of rubber, no sufficient effect on low-tempera-
lure resistance can be obtained, while when the amount exceeds 50 parts by
weight, physical properties of rubber, such as thermal resistance, are seriouslyaffected and such a large quantity is uneconomical.
The improver of the present invention can be applied to any rubbers
such as SIR, BRA NOR, CRY polyisoprene rubber, or ethylene/propylene rubber,
and the rubbers containing the improver may be vulcanized with sulfur and cross-linked by a peroxide.
The low-temperature resistance improver of the present invention
can be mixed with rubber to obtain a rubber blend composition by any of convent-tonal rubber kneading methods, for example, by means of open roll, Danbury mixeror kneader blender. Additives which are conventionally used in the rubber in-
cluster, such as vulcanizing agents, vulcanization accelerators, fillers,
softeners, antioxidant, or processing aids may be added.
The following examples are provided to illustrate the present in-
vent:Lon in more detail, but are not to be construed as limiting the present
Invention in any way.
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Examples 1 to 5 and Comparative Examples 1 to 5
Basic formulation
styrene/butadiene rubber SUB 1500) 100 parts by weight
carbon black (HA) 50
zinc white No. 3 3
starlike acid
vulcanization accelerator (DO)
vulcanization accelerator (D) 0.5
sulfur 1.75
Lo low-temperature resistance improver variable
(given in Table 1)
The above ingredients were mixed by means of an open roll. Vowel-
concision was carried out at 145C for 35 min. by means of a press. Tensile
test was carried out according to JIG K 6301 to obtain general physical
properties. Low temperature resistance was evaluated based on a low-temperature
flexibility test made according to ASTM D 10~3 by using a Clash-Berg testing
machine. Heat resistance was evaluated on the basis of a heating loss test of
a vulcanized sheet at 100C for I hr. For the purpose of comparison, a forum-
lotion wherein the low-temperature resistance improver was omitted from the
basic formulation and formulations wherein process oil (aromatic), DIVA, bottle
owlet or oilily Stewart was added in place of said improver were used as
Comparative Examples. The results are shown in Table 1.
It is apparent from Table 1 that Comparative Example 1 is inferior
in Low temperature resistance so that a low temperature resistance improver is
a usual ingredient in fields where such a resistance is required. Comparative
Example 2 shows the use of softeners most frequently used in the rubber induct-
rye but both the low temperature and heat resistance are very poor. Comparative
Example 3 shows the use of a known low-temperature plasticizer
I
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DIVA. The low-temperature and heat resistances are
relatively good, though considerably inferior to
those of Examples 1 to 5. The low-temperature nests-
lance of Comparative Example 4 is comparable but the
heat resistance is so poor that the formulation of
this Example can not be practically used. Come
parative Example 5 shows the use of a saturated fatty
acid unsaturated alcohol ester, which is considerably
inferior to Examples 1 to 5 in low-temperature nests-
lance.
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Examples 6 to 9 and Comparative Examples 6 to 9
Basic formulation
chloroprene rubber (neoprene type W) 100 parts by weight
magnesium oxide 4
antioxidant(N-phenyl-~-naphthylamine) 2
carbon black (SURF) 58
zinc white No. 3 5
vulcanization accelerator 0.5
(2-mercaptoimidazoline)
Starkey acid 0.5
low-temperature resistance improver 15
The ingredients described above were mixed
by means of an open roll. Vulcanization was carried
out at 150C for 30 mix by means of a press. For
the purpose of comparison, a formulation wherein
the low-temperature resistance improver was omitted
from the basic formulation and formulations wherein
myristyl Stewart, DOS or bottle owlet was added in
place of the improver of the present invention were
used as Comparative Examples. Physical properties
were evaluated in a similar manner to that of Example 1.
The results are shown in Table 2.
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