Process for the hydrogenation of conjugated diene polymers having alcoholic hydroxyl groups

A process for the hydrogenation of conjugated diene polymers having alcoholic hydroxyl groups, is provided. In the process, reduced nickel is used as a catalyst and an ether or a mixture of an ether and a hydrocarbon is used as a solvent for the hydrogenation reaction whereby elimination of the group rarely occurs with a very high hydrogenation rate being attained.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for hydrogenating conjugated diene 
polymers having hydroxyl or carboxyl groups, or groups derived from the 
carboxyl group at high hydrogenation rates without damaging the groups 
present in the conjugated diene polymers. 
2. Description of the Related Art 
Among conjugated diene polymers having hydroxyl or carboxyl groups, or 
groups derived from the carboxyl group (which polymer may be hereinafter 
referred to simply as "modified polymer" and which group may be referred 
to simply as "substituent"), conjugated diene polymers having a 
substituent at one or both ends are useful for reacting with diisocyanate 
compounds to form moldings with a high resistance to hydrolysis. 
Alternatively, conjugated diene polymers having substituents in the 
molecular chain exhibit good rubber elasticity and can be cured by means 
of sulfur or peroxides. Moreover, the polymers may undergo various 
modifications depending upon the type of functional group in the polymers. 
As will be appreciated from the above, it is known that a variety of 
functions can be imparted to the conjugated diene polymers by introducing 
certain functional groups into the polymers. The carbon-carbon double bond 
in the conjugated diene polymer serves as an important reaction site when 
the functional groups are introduced into the polymer, but will cause the 
weatherability, light resistance and heat resistance of the resultant 
modified polymer to lower. In order to improve the weatherability, light 
resistance and heat resistance, it is considered to hydrogenate the 
carbon-carbon double bond in the presence of a catalyst. 
Known catalysts for the hydrogenation used for the hydrogenation reaction 
of the carbon-carbon double bond are those of nickel, palladium, ruthenium 
and the like (Japanese Laid-open Patent Application Nos. 50--90694 and 
52--111992 and United States Patent No. 4107225). However, when modified 
polymers are hydrogenated by the use of these catalysts, there are 
encountered problems in that the hydrogenation reaction does not proceed 
at all by the presence of the substituents, the hydrogenation rate lowers 
considerably, or the chemical structure of the substituent changes or the 
substituent is eliminated from the modified polymer. Since the palladium 
or ruthenium catalyst is expensive, its application to the hydrogenation 
reaction of modified polymers brings about an increase of production 
costs, thus being disadvantageous from the industrial viewpoint. 
An object of the present invention is to provide a process for the 
hydrogenation of modified polymers which solve the prior-art problems. 
Another object of the invention is to provide a process for the 
hydrogenation of modified polymers which has a high hydrogenation rate and 
in which substituents present in the modified polymers are not damaged. 
Other objects, features and advantages of the invention will become 
apparent from the following description. 
SUMMARY OF THE INVENTION 
The present inventors made intensive studies on a process for the 
hydrogenation of conjugated diene polymers (modified polymers) having 
alcoholic hydroxyl or carboxyl groups or groups derived from the carboxyl 
group (substituents), in which the hydrogenation reaction was carried out 
at a high hydrogenation rate without causing any chemical change or 
elimination of the substituents. As a result, it was found that when a 
so-called reduced nickel catalyst was used and a solvent used for the 
hydrogenation was an ether or a mixed solvent of an ether and a 
hydrocarbon, the hydrogenation velocity became high with a high 
hydrogenation rate and the elimination of the substituents was not brought 
about. The present invention is accomplished based on the above finding. 
A prominent feature of the invention resides in the hydrogenation of 
modified polymers in which a reduced nickel catalyst is used and a solvent 
for the hydrogenation is an ether or a mixture of an ether and a 
hydrocarbon. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The modified polymers to which the hydrogenation process of the invention 
is applied are conjugated diene polymers having substituents in the 
molecule. Examples of the modified polymers include those polymers 
obtained by polymerizing monomers, such as 1,3-butadiene, 1,3-pentadiene, 
isoprene, 2,3-dimethylbutadiene, phenylbutadiene and the like, by various 
known processes. The polymers may be not only homopolymers of the 
conjugated diene monomers indicated above, but also copolymers of two or 
more of conjugated diene monomers and copolymers of the conjugated diene 
monomers and vinyl monomers. For the copolymerization of two or more of 
the conjugated diene monomers, the ratio of these monomer ingredients may 
be arbitrary without limitation. Examples of the vinyl comonomers include 
styrene, vinyltoluene, alpha-methylstyrene, vinylnaphthalene, cumarone, 
indene, vinylpyridine, vinylfuran, acrylonitrile, ethyl acrylate, methyl 
acrylate, methyl methacrylate, hydroxyethyl acrylate, hydroxyethyl 
methacrylate, acrylic acid, methacrylic acid and the like. These 
comonomers are used in an amount of not larger than 95 wt%, preferably not 
larger than 80 wt%, of the total monomer. 
As the number of substituents contained in the modified polymer increases, 
the substituents are more likely to eliminate by the hydrogenation 
reaction with a higher degree of deactivation of the hydrogenation 
catalyst. The number of the substituents is preferably from 1 to 100 in 
one molecule of the polymer. 
In the practice of the invention, the groups derived from the carboxyl 
group include an acid anhydride group, an imido group, an amido group, an 
ester group, a haloacyl group, a metal salt or ammonium salt of a carboxyl 
group, and the like. 
Although the process of the invention can be applied irrespective of the 
number average molecular weight (Mn) of modified polymers, the number 
average molecular weight is preferably in the range of from 500 to 
200,000. In view of the case where conjugated diene polymers having a 
substituent at ends thereof are used, for example, as a starting material 
for moldings, a preferred number average molecular weight is in the range 
of from 500 to 50,000, more preferably from 700 to 30,000. Oligomers 
having a molecular weight of not larger than 500 are disadvantageous in 
that moldings obtained from the oligomers after hydrogenation are 
deficient in flexibility. Moreover, the hydrogenated products of 
conjugated diene polymers having a substituent at ends thereof and a 
molecular weight of not less than 50,000 are also disadvantageous in that 
the resultant molding has small physical strength and the hydrogenated 
products are poor in moldability. 
In consideration of the case where hydrogenated products of conjugated 
diene polymers having substituents in the molecule are formulated, for 
example, as a modifier for plastics, a preferred number average molecular 
weight of the modified polymer is in the range of from 5,000 to 200,000, 
more preferably from 10,000 to 150,000. When the molecular weight is less 
than the above range, polyolefin compositions to which the hydrogenated 
product of a modified polymer is added as a modifier for plastics involve 
problems that the mechanical strength is liable to lower or the 
hydrogenated product is apt to bleed on the surfaces of a molding during 
storage over a long time. On the other hand, when the molecular weight is 
over the above range, not only flexibility is not imparted to polyolefin 
compositions, but also an effect of improving coating properties is 
unfavorably small. By blending with a compound having a favorable range of 
molecular weight, the melt viscosity during the course of melting and 
kneading lowers with improved workability. 
The number average molecular weight used herein is a number average 
molecular weight calculated as styrene from a gel permeation 
chromatography (GPC). 
Among modified polymers used in the present invention, conjugated diene 
polymers having a substituent at ends thereof can be obtained by various 
processes. For instance, one or more of conjugated diene monomers or a 
mixture of a conjugated diene monomer and a vinyl monomer may be 
radical-polymerized in the presence of a catalyst including an azobis 
compound having a functional group, e.g. 
.beta..beta.'-azobis(.beta.-cyano)-n-propanol, 
.delta.,.delta.'-azobis(.delta.-cyano)-n-pentanol, 
4,4'-azobis(4-cyanopentanoic acid), dimethyl-2,2'-azobis(2-methylpropionic 
acid), 2,2'-azobis(2-methylpropionamido)dihydrate or the like, or a 
peroxide such as hydrogen peroxide, cyclohexane peroxide, 
methylcyclohexanone peroxide or the like. An experimental procedure of the 
polymerization using isoprene as the monomer is particularly described 
below. 300 g of hexane as a solvent, 68 g of isoprene as a monomer and 44 
g of cyclohexanone peroxide as a catalyst [having a chemical formula, 
##STR1## 
commercial name, Perhexa H 50% Product (Nippon Oils and Fats Co., 
Ltd.)]are charged into a one liter autoclave and heated to 80.degree. C. 
while agitating for polymerization over 20 hours to obtain hydroxyl 
group-containing polyisoprene (yield 65%, Mn =5,500, OH value 21 mg/g). 
The conjugated diene polymers having a substituent at ends thereof may be 
prepared by polymerizing the above-mentioned monomers or monomer mixture 
in the presence of a catalyst made of an alkali metal such as sodium, 
lithium or the like, and adding an alkylene oxide, epichlorohydrin or the 
like to the polymerization system to introduce hydroxyl groups into the 
polymer. 
The conjugated diene polymers having substituents in the molecular chain 
may also be obtained by various processes. For instance, there is a 
process in which a polymer having carbon-carbon double bonds is obtained 
by polymerization and substituents are added to the polymer by 
polymerization reaction. More particularly, one or more of conjugated 
diene monomers or a mixture of a conjugated diene monomer and a vinyl 
monomer is polymerized by ordinary polymerization procedures such as anion 
polymerization, radical polymerization and the like to obtain a polymer. 
The thus obtained polymer is subsequently subjected to a process as 
described, for example, in Japanese Laid-open Patent Application No. 
55--133403 or 57--16003, in which maleic anhydride is added to the 
conjugated diene polymer. 
Alternatively, another process may be used in which a conjugated diene 
monomer and a monomer having a substituent are copolymerized. More 
specifically, one or more of conjugated diene monomers or a mixture of a 
conjugated diene monomer and a vinyl monomer and a monomer having a 
substituent are subjected to ordinary polymerization such as anion 
polymerization, radical polymerization or the like. The monomers having a 
carboxyl group include, for example, acrylic acids such as acrylic acid, 
methacrylic acid, crotonic acid, isocrotonic acid, oleic acid, fumaric 
acid, maleic acid, itaconic acid and the like. The monomers having an acid 
anhydride group include acid anhydrides such as maleic anhydride, itaconic 
anhydride and the like. The monomers having an imido group include 
maleimides such as N-phenylmaleimide, N-(p-chlorophenyl)maleimide and the 
like. The monomers having an amido group include acrylamide, 
methacrylamide and the like. The monomers having an ester group are alkyl 
or aryl esters of the above-indicated carboxylic acids and carboxylic 
anhydrides. Additionally, the monomers having a haloacyl group include 
acryloyl chloride, methacryloyl chloride, maloyl dichloride and the like. 
When the modified polymers obtained by these processes are hydrogenated by 
using reduced nickel as a catalyst and an ether solvent or a mixed solvent 
of an ether solvent and a hydrocarbon solvent, the hydrogenation proceeds 
efficiently and readily without elimination of any substituents. 
The reduced nickel catalyst used in the present invention can be obtained 
according to known procedures in which nickel oxide, nickel hydroxide or 
basic nickel carbonate is heated for reduction in a stream of hydrogen. 
The reduced nickel catalyst is usually employed as supported on a carrier 
such as carbon, alumina, silica, diatomaceous earth or the like. The 
reduced nickel catalyst may be a carrier on which 2 to 30 wt% of a 
co-catalyst such as of zirconium, an alkali metal or an alkaline earth 
metal and the balance of nickel have been supported. The nickel should be 
supported in an amount of from 20 to 60 wt%, preferably from 30 to 50 wt%. 
Reduced nickel catalysts which surfaces are partially oxidized, are 
commercially sold, for example, under the designations of SN-100, SN-150 
and SN-300 available from Sakai Chemical Industry Co., Ltd. Since these 
catalysts have good stability, their use is recommended. 
Aside from the reduced nickel catalyst, there are known, as the 
hydrogenation catalyst used for the hydrogenation reaction, a Raney nickel 
catalyst as a nickel catalyst and a palladium catalyst. However, the Raney 
nickel catalyst is liable to ignite in air, with the difficulty that close 
attention is required in handling. In addition, when the Raney nickel 
catalyst is used for hydrogenation of modified polymers in an ether 
solvent, a high hydrogenation rate cannot be attained as is particularly 
shown in Comparative Examples 2, 5 and 9. On the other hand, when 
hydrogenation of modified polymers in an ether is effected using a 
palladium catalyst, elimination of substituents is considerable as is 
particularly shown in Comparative Examples 7 and 11. 
The ethers used in the present invention as a solvent include linear ethers 
such as ethyl ether, n-butyl ether, isopropyl ether, diisoamyl ether and 
the like, phenol ethers such as phenyl ether, anisole, phenetole, amyl 
phenyl ether and the like, and cyclic ethers such as tetrahydrofuran, 
tetrahydropyran, dioxane, trioxane and the like. Of these, the cyclic 
ethers are preferred. The hydrocarbons used in combination with the ethers 
include, for example, hexane, heptane, octane, cyclohexane, 
methylcyclohexane, benzene, toluene, xylene and the like. 
The mixing ratio of the ether and the hydrocarbon depends upon the types of 
solvents and an intended velocity of the hydrogenation reaction. In 
general, the amount of the ether in the mixed solvent is from 1 to 100 
wt%, preferably from 10 to 100 wt%. 
If cyclohexane is used singly for the hydrogenation reaction, a final 
hydrogenation rate is low, as is particularly shown in Comparative 
Examples 1 and 8, even when a reduced nickel catalyst is used. 
Although it may occur to one that an alcohol is used as the solvent, 
elimination of substituents becomes considerable as is shown in 
Comparative Examples 3 and 10. Moreover, the use of an alcohol is 
disadvantageous from the industrial viewpoint in that because it 
considerably lowers the solubility of the polymer, a substantial amount of 
a solvent required to increase the solubility of the polymer has to be 
added in a catalystremoving step after completion of the hydrogenation 
reaction. 
The hydrogenation reaction temperature is generally selected from a range 
of from room temperature to 200.degree. C. Preferably, the temperature 
ranges from 80.degree. C. to 180.degree. C. If the reaction temperature is 
lower than room temperature, the hydrogenation velocity lowers to a 
significant extent. Over 200.degree. C., the substituent unfavorably 
changes its chemical structure or is eliminated substantially. 
The hydrogenation rate of the polymer is changed depending upon the 
purpose, and is determined by measurement of an iodine value of polymer 
prior to and after the hydrogenation to obtain a polymer with a 
predetermined hydrogenation rate. 
The amount of the reduced nickel catalyst used is in arbitrarily selected 
from a range of from 1 to 30 parts by weight, preferably from 1 to 20 
parts by weight, calculated as nickel, based on 100 parts by weight of a 
starting modified polymer. 
Hydrogen may be used as a flow system at normal pressures or may be used 
under a pressure of from 1 to 300 kg/cm.sup.2. The hydrogenation reaction 
may be effected by any procedures including those using a fixed bed, a 
suspension procedure and the like. 
In the practice of the invention, at least 50% and ordinarily 70% of 
unsaturated sites of a starting modified polymer is hydrogenated. 
The hydrogenation velocity is fast and the number of substituents per one 
molecule rarely changes as compared with that of the starting polymer. 
The hydrogenated product of the modified polymer obtained according to the 
invention may be used as a cured product through various crosslinking 
agents in which the substituents present in the polymer serve as 
crosslinking sites. Useful crosslinking agents include epoxy compounds, 
metal compounds, amine compounds, organic isocyanate compounds, polyhydric 
alcohols, halides and the like. 
The hydrogenated products of the modified polymers obtained in the 
invention may also be used as rubber or modifiers for plastics. For 
applications, additives such as thermal stabilizers, UV absorbers, 
pigments and lubricants may be added, if necessary, in amounts not larger 
than 50 wt% of the hydrogenated product. Moreover, fillers or 
reinforcements such as talc, mica, glass fibers and the like may be used 
along with the hydrogenated product for the rubber or plastic modification 
.

The present invention is described in detail by way of examples, which 
should not be construed as limiting the invention. 
In the examples, the hydrogenation rate is determined by measuring an 
iodine value of a modified polymer and calculating the rate from the 
following equation. 
##EQU1## 
wherein 
A: an iodine value of a modified polymer prior to hydrogenation, and 
B: an iodine value of the modified polymer after the hydrogenation. 
EXAMPLE 1 
100 g of polyhydroxypolyisoprene (Mn=2,600, OH value=45.3 mg/g) obtained by 
radical polymerization with hydrogen peroxide, 10 g of reduced nickel 
(amount of supported nickel 40%, carrier: diatomaceous earth) and 200 g of 
tetrahydrofuran used as a reaction solvent were charged into a one liter 
autoclave, followed by substitution of the air in the system with a 
purified nitrogen gas and heating to 150.degree. C. in 30 minutes. At the 
time when a stationary state of 150.degree. C. was attained, a highly pure 
hydrogen gas was supplied into the autoclave, after which the 
hydrogenation reaction was effected while keeping the inner pressure of 
the system at 50 kg/cm. After the reaction continued over a certain time, 
the resultant hydrogenated polymer was withdrawn and the catalyst was 
removed by filtration, followed by removal of the solvent by distillation 
to obtain a hydrogenated product. 
The results of analysis of the thus obtained hydrogenated product are shown 
in Table 1. 
EXAMPLE 2 
50 g of polyisoprene terminated with a hydroxyl group at both ends which 
had been obtained by poly isoprene by the use of an anion polymerization 
initiator composed of a naphthalene/sodium compound and adding ethylene 
oxide and then water (Mn =10,000, OH value=10.5 mg/g), 3 g of reduced 
nickel (amount of supported nickel 40%) and 200 g of 1,4-dioxane were 
charged into a one liter autoclave, followed by hydrogenation reaction in 
the same manner as in Example 1. 
The results of analysis of the resultant hydrogenated product are shown in 
Table 1. 
EXAMPLE 3 
The hydrogenation reaction was effected in the same manner as in Example 1 
except that a mixed solvent made of 70 wt% of ethyl ether and 30 wt% of 
cyclohexane was used. The results of analysis of the resultant 
hydrogenated product are shown in Table 1. 
EXAMPLES 4-7 
The hydrogenation reaction was carried out under conditions indicated in 
Table 1, with the results shown in Table 1. 
EXAMPLE 8 
The hydrogenation reaction was effected in the same manner as in Example 1 
except that the reduced nickel catalyst used was one available from Sakai 
Chemical Industry Co., Ltd., under the commercial name of SN-300. The 
results are shown in Table 1. 
COMATIVE EXAMPLE 1 
The hydrogenation reaction was effected in the same manner as in Example 1 
except that 200 g of cyclohexane was used instead of tetrahydrofuran, 
thereby obtaining a hydrogenated product. The results of analysis of the 
thus obtained hydrogenated product are shown in Table 2. 
From the results, it was found that a final hydrogenation rate was low when 
the cyclohexane was used. 
COMATIVE EXAMPLE 2 
The hydrogenation reaction was effected in the same manner as in Example 1 
except that 10 g of Raney nickel was used instead of the reduced nickel, 
thereby obtaining a hydrogenated product. The results of analysis of the 
thus obtained product are shown in Table 2. 
From the results, it was found that a final hydrogenation rate was low when 
the Raney nickel catalyst was used. 
COMATIVE EXAMPLE 3 
The hydrogenation reaction was effected in the same manner as in Example 1 
except that isopropyl alcohol was used as the solvent. The results of 
analysis of the resultant hydrogenated product are shown in Table 2. 
From the results, it was found that in the hydrogenation reaction using 
isopropyl alcohol as the solvent, elimination of the hydroxyl groups was 
considerable. 
COMATIVE EXAMPLES 4-7 
The hydrogenation reaction was effected under conditions indicated in Table 
2, with the results shown in Table 2. 
TABLE 1 
__________________________________________________________________________ 
Example 
1 2 3 4 5 6 7 8 
__________________________________________________________________________ 
Modified Polymer: 
polyisoprene (g) 100 50 100 100 -- -- 50 100 
polybutadiene (g) 
-- -- -- -- 100 100 -- -- 
number average molecular weight 
2,600 
10,000 
2,600 2,600 2,800 
2,800 
10,000 2,600 
OH value (mg/g) 45.3 
11.0 
45.3 45.3 44.2 
44.2 
11.0 45.3 
Hydrogenation Conditions: 
catalyst: amount (g) 
10 3 10 10 10 10 3 3 
solvent: 
kind THF DOx Et.sub.2 /CHx 
DOx/CHx THF DOx DOx/CHx 
THF 
(70/30 wt %) 
(60/40 wt %) (60/40 wt %) 
amount (g) 200 200 200 200 200 200 200 200 
reaction temp. (.degree.C.) 
150 150 150 150 150 150 150 150 
pressure of hydrogen (kg/cm.sup.2 G) 
50 50 50 50 50 50 50 50 
time (Hrs.) 6 6 6 6 6 6 6 6 
Hydrogenated Polymer: 
hydrogenation rate (%) 
96 99 94 98 97 94 93 97 
OH value (mg/g) 45.1 
10.6 
45.2 45.1 44.0 
43.9 
10.7 45.0 
__________________________________________________________________________ 
In the "kind of solvent", THF: tetrahydrofuran, DOx: 1,4dioxane, Et.sub.2 
O: ethyl ether, and CHx: cyclohexane. 
TABLE 2 
__________________________________________________________________________ 
Comparative Example 
1 2 3 4 5 6 7 
__________________________________________________________________________ 
Modified Polymer: 
polyisoprene (g) 100 100 100 100 50 -- 100 
polybutadiene (g) 
-- -- -- -- -- 100 -- 
number average molecular weight 
2,600 
2,600 
2,600 
2,600 10,000 
2,800 
2,600 
OH value (mg/g) 45.3 
45.3 
45.3 
45.3 11.0 
44.2 
45.3 
Hydrogenation Conditions: 
catalyst: 
type (1) A B A A B A C 
amount (g) 10 10 10 10 3 10 3 
solvent: 
kind (2) CHx THF IPA IPA/CHx 
THF CHx THF 
(70/30 wt %) 
amount (g) 200 200 200 200 200 200 200 
reaction temp. (.degree.C.) 
150 150 150 150 150 150 150 
pressure of hydrogen (kg/cm.sup.2 G) 
50 50 50 50 50 50 
50 
time (Hrs.) 6 6 6 6 6 6 6 
Hydrogenated Polymer: 
hydrogenation rate (%) 
42 46 87 53 42 45 89 
OH value (mg/g) 44.1 
41.3 
18.3 
21.2 10.5 
43.2 
22.0 
__________________________________________________________________________ 
(1) In the "kind of catalyst", A: reduced nickel, B: Raney nickel, C: 5% 
palladiumon-carbon catalyst. 
(2) In the "kind of solvent", THF: tetrahydrofuran, DOx: 1,4dioxane, 
Et.sub.2 O: ethyl ether, CHx: cyclohexane, and IPA: isopropyl alcohol. 
EXAMPLE 9 
Polyisoprene having a number average molecular weight of 31,000 when 
determined by GPC was obtained by anion polymerization using 
n-butyllithium as a catalyst. 100 g of the polymer and 9.8 g of maleic 
anhydride (MAn) were agitated at 180.degree. C. in a stream of nitrogen 
for 10 hours to effect the addition reaction, thereby obtaining a maleic 
anhydride adduct of the polyisoprene. The amount of the added MAn was 
determined by measurement of an acid value, from which it was confirmed 
that 9 wt% of the MAn was added. 
100 g of the maleic anhydride adduct of the polyisoprene, 10 g of reduced 
nickel (amount of supported nickel 40%, carrier: diatomaceous earth), and 
200 g of tetrahydrofuran as a reaction solvent were charged into a one 
liter autoclave, followed by substitution of the system with a purified 
nitrogen gas and heating to 150.degree. C. in 30 minutes. At the time when 
a stationary state of 150.degree. C. was attained, a highly pure hydrogen 
gas was supplied to the autoclave and the hydrogenation reaction was 
effected for 6 hours while keeping the inner pressure of the system at 100 
kg/cm.sup.2. After allowing to cool, the reaction solution was withdrawn, 
from which the catalyst was removed by filtration, followed by drying in 
vacuum to obtain a hydrogenated product of the maleic anhydride-containing 
polyisoprene. The hydrogenation rate of the hydrogenated product was found 
to be 89%. The measurement of the acid value revealed that elimination of 
the MAn from the polymer by the hydrogenation reaction did not occur. 
EXAMPLE 10 
Polyisoprene having a carboxyl group at both ends and a number average 
molecular weight of 11,000 when determined by GPC was obtained by radical 
polymerization using 4,4'-azobis(4-cyanopentanoic acid) having a carboxyl 
group at both ends. The measurement of an acid value of the polyisoprene 
revealed that the acid value was 10.1 mg/g. 
Subsequently, the general procedure of Example 9 was repeated except that 
100 g of polyisoprene terminated with a carboxyl group at both ends, 10 g 
of reduced nickel (amount of supported nickel 40%, carrier: diatomaceous 
earth) and 200 g of 1,4-dioxane were used, thereby obtaining a 
hydrogenated product of the polyisoprene terminated with a carboxyl group 
at both ends. The hydrogenation rate was 96% and the acid value of the 
hydrogenated product was 9.6 mg/g. 
EXAMPLE 11 
A hydrogenated product of maleic anhydride-containing polyisoprene was 
obtained in the same manner as in Example 9 except that 200 g of 
1,4-dioxane was used as a reaction solvent for the hydrogenation reaction. 
The hydrogenation rate was 92% and the amount of the addition of the MAn 
was 8.8 wt%. 
EXAMPLE 12 
A hydrogenated product of maleic anhydride-containing polyisoprene was 
obtained in the same manner as in Example 9 except that a mixed solvent of 
120 g of 1,4-dioxane and 80 g of cyclohexane was used as a reaction 
solvent for the hydrogenation reaction. The hydrogenation rate was 87% and 
the amount of the addition of the MAn was 8.5 wt%. 
EXAMPLE 13 
Polyisoprene having a number average molecular weight of 69,000 when 
determined by GPC was obtained by anion polymerization using 
n-butyllithium as a catalyst. 100 g of the polymer and 17.5 g of 
N-phenylmaleimide (PMI) were agitated at 180.degree. C. in a stream of 
nitrogen for 15 hours to effect the addition reaction, thereby obtaining 
an N-phenylmaleimide adduct of the polyisoprene. The amount of the added 
MAn was measured by the Kjaldahl method, from which it was confirmed that 
15 wt% of the PMI was added. 
The hydrogenation reaction was effected in the same manner as in Example 9 
except that 100 g of the N-phenylmaleimide adduct of the polyisoprene was 
used, thereby obtaining a hydrogenated product of the 
N-phenylmaleimide-containing polyisoprene. The hydrogenated product had a 
hydrogenation rate of 92%. It was confirmed by the Kjaldahl method that 
any elimination of the PMI from the polymer by the hydrogenation reaction 
did not occur. The hydrogenation rate of the hydrogenated product was 
found to be 89%. The measurement of the acid value revealed that 
elimination of the MAn from the polymer by the hydrogenation reaction did 
not occur. 
EXAMPLE 14 
A hydrogenated product of the N-phenylmaleimide-containing polyisoprene was 
obtained in the same manner as in Example 13 except that 200 g of 
1,4-dioxane was used as a reaction solvent for the hydrogenation reaction. 
The hydrogenation rate was 98% and the amount of the addition of the PMI 
was 14.1 wt%. 
EXAMPLE 15 
A hydrogenated product of the N-phenylmaleimide-containing polyisoprene was 
obtained in the same manner as in Example 13 except that a mixed solvent 
of 140 g of 1,4-dioxane and 60 g of cyclohexane was used as a reaction 
solvent of the hydrogenation reaction. The hydrogenation rate was 91% and 
the amount of the addition of the PMI was 14.9 wt%. 
COMATIVE EXAMPLE 8 
The hydrogenation reaction was effected in the same manner as in Example 9 
except that 200 g of cyclohexane was used, instead of the tetrahydrofuran, 
as a reaction solvent for the hydrogenation reaction. The resultant 
polymer had a hydrogenation rate of 29% and an amount of the addition of 
the MAn of 8.2 wt%. 
The above results revealed that a final hydrogenation rate was low when 
using the cyclohexane. 
COMATIVE EXAMPLE 9 
The hydrogenation reaction was effected in the same manner as in Example 9 
except that 10 g of Raney nickel was used instead of the reduced nickel 
catalyst. The resultant polymer had a hydrogenation rate of 12% and an 
amount of the addition of the MAn of 8.0 wt%. 
From the above results, it was found that the final hydrogenation rate was 
low for the Raney nickel catalyst. 
COMATIVE EXAMPLE 10 
The hydrogenation reaction was effected in the same manner as in Example 13 
except that isopropyl alcohol was used instead of the tetrahydrofuran as a 
reaction solvent of the hydrogenation reaction. The resultant polymer had 
a hydrogenation rate of 76% and an amount of the addition of the PMI of 9 
wt%. 
From the above results, it was found that with the isopropyl alcohol, 
elimination of the PMI from the polymer was considerable. 
COMATIVE EXAMPLE 11 
The hydrogenation reaction was effected in the same manner as in Example 13 
using 2 g of a palladium (5 wt%)-on-carbon catalyst instead of the reduced 
nickel as a catalyst. The resultant polymer had a hydrogenation rate of 
23% and an amount of the addition of the PMI of 12 wt%. 
From the above results, it was found that with the palladium-carbon 
catalyst, the final hydrogenation rate was low and elimination of the PMI 
from the polymer was considerable.