Resin composition for soft bumpers

A resin composition for soft bumpers is disclosed, comprising (a) 100 parts by weight of a selectively hydrogenated block copolymer having at least two mono-alkenyl or mono-alkenylidene aromatic hydrocarbon polymer blocks having a number average molecular weight of from 5,000 to 15,000 and at least one partially or completely hydrogenated aliphatic conjugated diene hydrocarbon polymer block having a number average molecular weight of from 10,000 to 75,000, (b) from 10 to 100 parts by weight of an ethylene-propylene copolymer rubber having a Mooney viscosity of from 15 to 50 as measured at 100.degree. C. and an intrinsic viscosity of from 1.2 to 2.0 dl/g as measured in a xylene solution at 70.degree. C., (c) from 200 to 400 parts by weight of a propylene-ethylene block copolymer having a melt flow rate of from 10 to 30 g/10 min and an ethylene content of from 5 to 15% by weight, and (d) from 20 to 200 parts by weight of a non-aromatic diluent oil for rubber. The composition provides soft bumpers having improved appearance, such as gloss and surface uniformity, improved scratch resistance and excellent coating properties.

FIELD OF THE INVENTION 
This invention relates to a resin composition for soft bumpers. More 
particularly, it relates to a resin composition for soft bumpers having 
uniform appearance, excellent physical properties such as heat resistance, 
low-temperature resistance, weather resistance, etc., and excellent 
coating properties. 
BACKGROUND OF THE INVENTION 
With the increasing demands, particularly in the United States, for 
assurance of safety of automobiles and lightening of automobiles for 
energy saving, the conventionally employed metal bumpers have recently 
been replaced by urethane bumpers. 
The leading materials for the currently used urethane bumpers are RIM 
urethanes. Bumpers made of RIM urethane are characterized by high impact 
resistance, excellent energy absorbing properties, light weight, 
satisfactory moldability, wide freedom of design, excellent coating 
properties, and the like. 
On the other hand, RIM urethane-made bumpers are inferior in weather 
resistance, heat resistance, low-temperature resistance, and the like. 
Besides, RIM urethanes have productivity problems such that the molding 
cycle is long and the post-treatment takes much time and that scraps 
cannot be recycled, resulting in a great loss. 
In recent years, thermoplastic olefinic elastomers (hereinafter referred to 
TPO) have been developed as soft bumper materials which eliminate the 
above-described disadvantages of RIM urethane-made bumpers. TPO molded 
articles have a superiority over the RIM urethane molded articles in terms 
of weight, weather resistance, heat resistance and low-temperature 
resistance. Further, TPO not only has good processability on injection 
molding but also incurs a minimized loss of molding because scraps in 
molding can be recycled. 
However, TPO is inferior to RIM urethanes in terms of appearance of molded 
articles, particularly gloss and surface uniformity, and scratch 
resistance, and the application to be made of it is so limited. It has 
been, therefore, keenly demanded to solve these problems of appearance and 
physical properties of soft bumpers. 
SUMMARY OF THE INVENTION 
Accordingly, an object of this invention is to overcome the above-described 
problems and to provide a material for soft bumpers having greatly 
improved appearance, such as gloss and surface uniformity, scratch 
resistance, and the like and excellent coating properties while being 
compared advantageously with TPO in mechanical strength, heat resistance, 
low-temperature resistance, weather resistance and processability and 
productivity in injection molding. 
In the light of the above-described circumstances, the inventors have 
conducted intensive and extensive studies. As a result, it has now been 
found that the above object of this invention can be accomplished by 
compounding (a) a block copolymer having a specific structure comprising 
an aromatic hydrocarbon polymer and an aliphatic conjugated diene 
hydrocarbon polymer, (b) an ethylene-propylene copolymer rubber having a 
relatively low Mooney viscosity and a specific structure, (c) a 
propylene-ethylene block copolymer having a relatively high melt flow rate 
and a specific structure, and (d) a non-aromatic diluent oil for rubber at 
a specific compounding ratio. The present invention has thus been reached 
based on this finding. 
The gist of the present invention lies in use of a mixture comprising, as 
elastomer components, a hydrogenated block copolymer composed of (A) a 
mono-alkenyl or mono-alkenylidene aromatic hydrocarbon polymer block and 
(B) an aliphatic conjugated diene hydrocarbon polymer and a given 
proportion of an ethylene-propylene copolymer rubber having a specific 
structure. 
The present invention relates to a resin composition for soft bumpers, 
which comprises (a) 100 part by weight of a selectively hydrogenated block 
copolymer having (A) at least two mono-alkenyl or mono-alkenylidene 
aromatic hydrocarbon polymer blocks having a number average molecular 
weight of from 5,000 to 15,000 (hereinafter referred to block A) and (B) 
at least one partially or completely hydrogenated aliphatic conjugated 
diene hydrocarbon polymer block having a number average molecular weight 
of from 10,000 to 75,000 (hereinafter referred to block B), (b) from 10 to 
100 parts by weight of an ethylene-propylene copolymer rubber having a 
Mooney viscosity of from 15 to 50 as measured at 100.degree. C. and an 
intrinsic viscosity of from 1.2 to 2.0 dl/g as measured in a xylene 
solution at 70.degree. C., (c) from 200 to 400 parts by weight of a 
propylene-ethylene block copolymer having a melt flow rate of from 10 to 
30 g/10 min and an ethylene content of from 5 to 15% by weight, and (d) 
from 20 to 200 parts by weight of a non-aromatic diluent oil for rubber. 
DETAILED DESCRIPTION OF THE INVENTION 
In the block copolymer which can be used as component (a) of the resin 
composition of the invention, monomers constituting block A preferably 
include styrene, -methylstyrene, t-butylstyrene, etc., and monomers 
constituting block B preferably include butadiene, isoprene, etc. 
In the case when butadiene is used as a conjugated diene monomer for block 
B, the molecular chain of block B comprises a butadiene copolymer having a 
1-4 structure and a 1-2 structure. Upon hydrogenation, the double bond of 
this block copolymer is saturated to form a structure composed of an 
ethylene polymer segment resulted from the 1-4 structure and a butylene 
polymer segment resulted from the 1-2 structure. As a result, the block 
copolymer as component (a) has, for example, a styrene-ethylene 
butylene-styrene structure and is called SEBS. 
The number average molecular weight of block A ranges from 5,000 to 15,000, 
and that of block B ranges from 10,000 to 75,000. 
If the number average molecular weight of block A is less than 5,000 or 
that of block B is less than 10,000, the resulting resin compositions do 
not stand practical use as materials for automobile bumpers due to poor 
mechanical strength and low-temperature resistance, though possessing high 
flowability and high gloss. On the other hand, if the number average 
molecular weight of block A exceeds 15,000 or that of block B exceeds 
75,000, the resulting compositions exhibit satisfactory mechanical 
strength and low-temperature resistance but are inferior in flowability 
and appearance of molded products, such as gloss, and are, therefore, 
unsuitable as a substitute for RIM urethanes. 
There are many processes proposed for producing the block copolymer (a). 
According to a typical process as disclosed in Japanese Patent Publication 
No. 23798/65, mono-alkenyl or mono-alkenylidene aromatic hydrocarbons and 
aliphatic conjugated diene hydrocarbons are block-copolymerized in an 
inert solvent in the presence of a lithium catalyst or a Ziegler catalyst 
to thereby obtain a desired block copolymer (a). Hydrogenation of the 
block copolymer can be carried out in an inert solvent in the presence of 
a hydrogenation catalyst according to known processes as disclosed, e.g., 
in Japanese Patent Publication Nos. 8704/67, 6636/68 and 20814/71. The 
rate of hydrogenation is at least 50%, and preferably at least 80%, in 
block B and not more than 25% of the aromatic unsaturated bonds in block A 
are nuclear-hydrogenated. The thus produced partially or completely 
hydrogenated block copolymer is commercially available, typically under a 
trade name of KRATON-G manufactured by Shell Chemical Inc. (U.S.A.). 
The ethylene-propylene copolymer rubber (b) used in the present invention 
has a Mooney viscosity of from 15 to 50, and preferably from 20 to 45, as 
measured at 100.degree. C. and an intrinsic viscosity of from 1.2 to 2.0 
dl/g, and preferably from 1.2 to 1.7 dl/g, as measured in a xylene 
solution at 70.degree. C. If the Mooney viscosity is smaller than 15 and 
the intrinsic viscosity is smaller than 1.2 dl/g, the resulting molded 
products have largely reduced impact strength. If the Mooney viscosity is 
larger than 50 and the intrinsic viscosity is larger than 2.0 dl/g, 
appearance, particularly gloss, of the injection molded product is 
deteriorated. 
When the block copolymer (a) is used as a sole elastomer component, the 
molded products obtained therefrom have improved appearance, such as 
surface gloss, and other performance properties but are still insufficient 
in coating properties, particularly resistance to hot water and adhesion 
of the coating. On the other hand, when the ethylene-propylene copolymer 
rubber (b) is solely used as an elastomer component, the molded products 
are inferior in appearance, such as surface gloss, and scratch resistance. 
Accordingly, in the present invention, the ethylene-propylene copolymer 
rubber (b) is compounded in a proportion of from 10 to 100 parts by weight 
per 100 parts by weight of the block copolymer (a). If the proportion of 
the component (b) is less than 10 parts by weight, coating properties are 
insufficient. If it exceeds 100 parts by weight, appearance such as 
surface gloss, and scratch resistance become poor. A preferred proportion 
of the component (b) is from 30 to 80 parts by weight per 100 parts by 
weight of the component (a). 
The propylene-ethylene block copolymer (c) used in the present invention 
can be obtained by first polymerizing propylene in the presence of a 
Ziergler-Natta catalyst to form a polypropylene segment and then 
copolymerizing with a mixture of propylene and ethylene. The resulting 
block copolymer should have a melt flow rate of from 10 to 30 g/10 min and 
an ethylene content of from 5 to 15% by weight. 
If the melt flow rate of the block copolymer (c) is smaller than 10 g/10 
min, the resulting molded products are insufficient in surface gloss and 
uniform appearance. If it is larger than 30 g/10 min, the physical 
properties of the molded products, particularly impact strength, are 
deteriorated. A preferred melt flow rate of the component (c) is from 15 
to 30 g/10 min. 
If the ethylene content of the propylene-ethylene block copolymer (c) is 
less than 5% by weight, impact strength is deteriorated, and if it exceeds 
15% by weight, mechanical strength, such as modulus of elasticity in 
bending, is reduced. A preferred ethylene content in the component (c) 
ranges from 7 to 13% by weight. The term "ethylene content" as herein used 
is the one determined by infrared absorption spectrophotometry. 
The propylen-ethylene block copolymer (c) is compounded in a proportion of 
from 200 to 400 parts by weight per 100 parts by weight of the block 
copolymer (a). 
The non-aromatic diluent oil for rubber (d) used in the present invention 
means paraffinic and naphthenic hydrocarbon oils containing not more than 
30% by weight of aromatic hydrocarbons among mineral oils called process 
oils or extender oils that are used for the purpose of softening, 
extending or improving processability of rubbers. In general, these 
mineral oil diluents for rubbers are mixtures of aromatic rings, naphthene 
rings and paraffin chains. Those containing 50% or more of paraffin chains 
based on the total hydrocarbons are called paraffinic hydrocarbons; those 
containing 30 to 45% of naphthene ring hydrocarbons are called naphthenic 
hydrocarbons; and those containing 30% or more of aromatic hydrocarbons 
are called aromatic hydrocarbons. 
The paraffinic and naphthenic hydrocarbon oils are satisfactory in 
dispersing properties as compared with aromatic hydrocarbon oils. These 
non-aromatic diluent oils for rubbers usually have a dynamic viscosity of 
from 20 to 500 cst at 40.degree. C., a pour point of from -10.degree. to 
-15.degree. C., and a flash point of from 170.degree. to 300.degree. C. 
The amount of the diluent oil for rubber (d) to be compounded is from 20 to 
200 parts by weight, and preferably from 30 to 150 parts by weight, per 
100 parts by weight of the block copolymer (a). Amounts exceeding 200 
parts by weight reduce the modulus of elasticity in bending and heat 
resistance below levels required for bumpers and also cause bleeding of 
the oil to make the surface of molded product sticky. With amounts less 
than 20 parts by weight, flowability is insufficient and surface 
appearance of molded product is poor. 
The resin composition in accordance with the present invention preferably 
contains from 55 to 70% by weight of the propylene-ethylene block 
copolymer (c). The propylene-ethylene copolymer (c) exerts influences on 
mechanical properties of materials for soft bumpers, particularly modulus 
of elasticity in blending and thermal properties. More specifically, resin 
compositions for soft bumpers are required to have a modulus of elasticity 
in bending of from 2,000 to 5,000 kg/cm.sup.3, and preferably from 2,500 
to 4,000 kg/cm.sup.3, a notched Izod impact strength of a survival (no 
breakage) at -30.degree. C. and a heat sag of not more than 20 mm when 
heated at 120.degree. C. for 1 hour. Further, they are required to show 
satisfactory flowability in injection molding and to provide molded 
products having high gloss and uniform appearance. In order to satisfy 
these performance requirements, the resin compositions should have a melt 
flow rate of at least 10 g/10 min, and preferably at least 15 g/10 min. To 
this effect, the proportion of the propylene-ethylene copolymer (C) in the 
whole composition preferably ranges from 55 to 70% by weight. 
If the proportion of the propylene-ethylene copolymer (c) exceeds 70% by 
weight, the resulting composition has too a high modulus of elasticity in 
bending to retain its softness and also suffers from reduction in 
low-temperature impact strength and coating properties, thus failing of 
its object as a material for soft bumpers. On the other hand, proportions 
less than 55% by weight deteriorate heat resistance making heat treatment 
for coating difficult and, at the same time, reduce gloss and flowability. 
If desired, the resin composition according to the present invention can 
contain inorganic fillers as extenders for the purpose of reducing the 
cost of production. Fillers which can be used include calcium carbonate, 
talc, mica, barium sulfate, silica, clay, wollastonite, calcium hydroxide, 
titanium oxide, magnesium oxide, etc. In addition, carbon black, such as 
channel black, furnace black, etc., is also useful as a filler. 
The composition in accordance with the present invention can be obtained by 
uniformly mixing the above-described components at prescribed mixing 
ratios. Uniform mixing can be carried out by mechanically melt-kneading by 
the use of kneading machines commonly employed for thermoplastic resins, 
such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a 
two-roll mill, etc. The mixing of the components may be effected either 
all at once or in divided portions. The mixing in divided portions can be 
achieved by, for example, previously mixing the hydrogenated block 
copolymer (a) and the diluent oil for rubber (d) in a super mixer or a 
ribbon blender to thereby impregnate the diluent oil (d) into the 
hydrogenated block copolymer (a) and then adding the ethylene-propylene 
copolymer rubber (b) and the propylene-ethylene block copolymer (c) and, 
if any, other additives, followed by melt-kneading in a kneading machine. 
The above-described mixing method is preferred to achieve uniform mixing 
particularly in cases where the proportion of the diluent oil (d) is 
large. The melt-kneading is carried out at a temperature of from 
160.degree. to 260.degree. C. 
If desired, the composition of the present invention can further contain, 
in addition to the above-described basic components, other additives, such 
as antioxidants, thermal stabilizers, ultraviolet absorbents, lubricants, 
pigments, antistatic agents, copper poison inhibitors, flame retardants, 
neutralizing agents, plasticizers, nucleating agents, crosslinking agents, 
and the like. Of these compounding additives, antioxidants and ultraviolet 
absorbents are preferably used for the purpose of improving stability to 
oxidation and outdoor weather resistance that are especially important 
properties as resin compositions for soft bumpers. Examples of the 
antioxidants to be used include 2,6-di-t-butylphenol, 
2,6-di-t-butyl-4-ethylphenol, 
2,6-di-t-butyl-.alpha.-dimethylamino-p-cresol, 
6-(4-hydroxy-3,5-di-t-butylani-lino)-2, 4-bis-octylthio-1,3,5-triazine, 
2,6-di-t-butyl-4-methylphenol, 
tris-(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 
tetrakis-([methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]-meth 
ane, dilauryl dithiopropionate, etc. Examples of the ultraviolet absorbents 
to be used include 2-hydroxy-4-n-octoxybenzophenone, 
2-hydroxy-4-octadecyloxybenzophenone, 4-dodecyloxy-2-hydroxy-benzophenone, 
2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 
2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, 
bis-(2,6-dimethyl-4-piperidyl)-sebacate, etc. 
The resin compositions in accordance with the present invention have 
improved weather resistance, low-temperature resistance and productivity 
while retaining mechanical strength and energy absorption properties equal 
or superior to the conventional RIM urethane compositions, and also have 
improved surface gloss, appearance and scratch resistance while retaining 
mechanical strength, heat resistance, low-temperature resistance and 
weather resistance equal or superior to the thermoplastic olefinic 
elastomer compositions for bumpers. In other words, the resin compositions 
of the invention are epoch-making materials for soft bumpers which 
eliminate the disadvantages encountered with RIM urethanes and TPO while 
retaining favorable characteristics of both. The composition of the 
invention is particularly characterized by its high gloss which is not 
substantially reduced even after receiving washing treatment with 
1,1,1-trichloroethane that is given as a pretreatment for coating. 
The compositions of the present invention can be molded by any of the 
molding machines generally employed for thermoplastic resins, but are 
particularly suitable for injection molding to easily provide large-sized 
molded products having satisfactory appearance. 
Although the compositions of the present invention have been developed 
especially for use as soft bumpers, their excellent performance 
characteristics can be fully made use of in other applications, such as 
corner bumpers, sight shields, over-riders, bumper moles, side moles, and 
the like exterior automobile parts. 
This invention is illustrated in greater detail with reference to the 
following examples, but it should be understood that they are not intended 
to limit the present invention. The physical properties in these examples 
and comparative examples were determined in accordance with the following 
methods: 
(1) Melt Flow Rate: 
Measured in accordance with JIS K-7210. 
(2) Modulus of Elasticity in Bending: 
Measured in accordance with JIS K-7203. The specimen under test had a 
weight of 13 oz. and was molded by an injection molding machine. 
(3) Izod Impact Strength (notched): 
Measured in accordance with JIS K-7110 at 23.degree. C. and -30.degree. C. 
The specimen under test was prepared in the same manner as described in 
(2) above. 
(4) Gloss: 
Measured in accordance with ASTM D532-53T. The samples were molded by an 
injection molding machine into sheet specimen having a weight of 13 oz and 
a thickness of 3mm. 
(5) Hardness: 
Measured in accordance with ASTM D-2240. D-type. 
(6) Heat Sag: 
The samples were molded by an injection molding into a flat plate of 25 mm 
in width, 100 mm in length and 3 mm in thickness. The specimen under test 
was heated at 120.degree. C. for 1 hour in a heating oven, and the length 
of sag by gravity was measured. 
(7) Flow Mark: 
The samples were molded in a sheet of 100 mm in width, 400 mm in length and 
3 mm in thickness by an injection molding machine. Flow marks were 
visually observed and graded "excellent," "good" or "poor." 
(8) Scratch Resistance: 
The surface of the specimen was scratched with a coin (hundred-yen coin) 
fixed to a scratch tester (manufactured by Uwajima Seisakusho) under a 
load of 200 g at a linear speed of 100 mm/min. The scratch resistance was 
visually evaluated and graded "good," "medium" or "poor." 
In the following examples, all the parts, percents and ratios are by weight 
unless otherwise indicated.

EXAMPLE 1 
One hundred parts of a block copolymer comprising a polystyrene block A 
having a number average molecular weight of 8,500 and a completely 
hydrogenated butadiene block B having a number average molecular weight of 
45,000 in an A-B-A structure (hereinafter referred to as SEBS-1), 50 parts 
of an ethylene-propylene copolymer rubber having a Mooney viscosity of 35 
at 100.degree. C. and an intrinsic viscosity of 1.54 dl/g in a xylene 
solution at 70.degree. C. (hereinafter referred to as EPR-1), 300 parts of 
a propylene-ethylene block copolymer having a melt flow rate of 22 g/10 
min and an ethylene content of 8.5% with the propylene-ethylene copolymer 
segment having an ethylene content of 50% and an intrinsic viscosity of 
5.5 dl/g in a tetralin solution at 135.degree. C. (hereinafter referred to 
as PP-1) and 50 parts of Diana Process Oil PW-380 (paraffinic oil produced 
by Idemitsu Kosan Co., Ltd.; dynamic viscosity at 40.degree. C.: 381.6 
cst; average molecular weight: 746; ring analysis: C.sub.A =0%, C.sub.N 
=27.0%, C.sub.p =73.0%) were mixed. To 100 parts of the resulting mixture 
were added 0.3 part of Irganox.RTM. 1010 (antioxidant produced by 
Chiba-Geigy AG) and 0.2 part of Sanol.RTM. LS 770 (ultraviolet absorbent 
produced by Chiba-Geigy AG). The mixture was preliminary mixed in a super 
mixer for 5 minutes and then melt-kneaded in a Banbury mixer at 
190.degree. C. for 10 minutes. The resulting compound was extruded into 
pellets in a single-screw extruder, and the pellets were molded in an 
in-line screw type injection molding machine (manufactured by Sumitomo 
Heavy Industries, Ltd.) to prepare various specimens for measurement of 
physical properties. 
The coating properties of the resin composition was evaluated as follows. A 
flat plate specimen having a width of 100 mm, a length of 100 mm and a 
thickness of 3 mm was treated with 1,1,1-trichloroethane vapor and then 
spray-coated with a primer (RB-291H produced by Nippon Bee Chemical Co., 
Ltd.), followed by baking at 120.degree. C. for 15 minutes. A urethane 
topcoating (Flexthane.RTM. 101 produced by Nippon Bee Chemical Co., Ltd.) 
was then spray-coated thereon to a film thickness of 40 .mu.m. After 
allowing to stand for 10 minutes, the coating was baked at 120.degree. C. 
for 30 minutes. Three days later, the coated film was crosshatched with a 
knife to make 100 squares and subjected to Scotch tape test using an 
adhesive tape (Cellotape.RTM. produced buy Nichiban Co., Ltd.). The 
percent of squares remaining on the specimen was determined to evaluate 
initial adhesion. 
The resistance to hot water was evaluated by immersing the above-prepared 
coated sample in water at 40.degree. C. for 240 hours and then subjected 
to the same Scoth tape test as described above. 
The results of measurement of physical properties and coating properties 
are shown in Table 1. 
EXAMPLE 2 
The same procedure as described in Example 1 was repeated except replacing 
SEBS-1 with the same amount of a block copolymer comprising a polystyrene 
block A having a number average molecular weight of 9,000 and a completely 
hydrogenated butadiene block B having a number average molecular weight of 
60,000 in an A-B-A structure (hereinafter referred to as SEBS-2), changing 
the amount of EPR-1 to 15 parts and further using 35 parts of an 
ethylene-propylene copolymer rubber having a Mooney viscosity of 80 at 
100.degree. C. and an intrinsic viscosity of 2.50 (hereinafter referred to 
as EPR-2). The compound and physical properties of the resin composition 
are shown in Table 1. 
EXAMPLE 3 
The same procedures as described in Example 1 was repeated except using a 
1:1 blend of SEBS-1 and SEBS-2 in place of SEBS-1. The compound and 
physical properties of the resin composition are shown in Table 1. 
COMATIVE EXAMPLE 1 
The same procedure as described in Example 1 was repeated except using no 
EPR-1, changing the amount of PP-1 to 260 parts and changing the amount of 
Diana Process Oil PW-380 to 40 parts. The compound and the properties of 
the resin composition are shown in Table 1. 
COMATIVE EXAMPLE 2 
The same procedure as described in Example 1 was repeated except replacing 
EPR-1 with EPR-2. The compound and properties of the resin composition are 
shown in Table 1. 
COMATIVE EXAMPLE 3 
The same procedure as described in Comparative Example 1 was repeated 
except for replacing SEBS-1 with a block copolymer comprising a 
polystyrene block A having a number average molecular weight of 31,000 and 
a completely hydrogenated block B having a number average molecular weight 
of 13,000 in an A-B-A structure (hereinafter referred to as SEBS-3). The 
compound and the properties of the resin composition are shown in Table 1. 
COMATIVE EXAMPLE 4 
Fourty-five parts of an ethylene-propylene copolymer rubber having a Mooney 
viscosity of 70 at 100.degree. C. and an intrinsic viscosity of 2.40 dl/g, 
55 parts of a propylene homopolymer having a melt flow rate of 10 g/10 
min, 0.3 part of m-phenylene-bismaleimide and 30 parts of Diana Process 
Oil PW-380 were melt-kneaded in a Banbury mixer at 180.degree. C. for 10 
minutes, followed by pelletizing. To 100 parts of the pellets, 0.1 part of 
1,3-bis-t-butyl peroxyisopropylbenzene (Sunperox.RTM. TY-1.3-90 produced 
by Sanken Chemical Industrial Co., Ltd.) was mixed therewith in a tumbling 
mixer. The resulting compound was pelletized in a single-screw extruder 
having a diameter of 40 mm, and the pellets were molded in an in-line 
screw type injection molding machine to prepare specimens having a weight 
of 13 oz. The results of measurement of the physical properties and 
coating properties are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Comparative 
Comparative 
Comparative 
Comparative 
Example 
Example 
Example 
Example 
Example 
Example 
Example 
1 2 3 1 2 3 4 
__________________________________________________________________________ 
Compound (part by weight) 
(a) 
SEBS-1 100 50 100 100 
SEBS-2 100 50 
SEBS-3 100 
(b) 
EPR-1 50 15 50 
EPR-2 35 50 
(c) 
PP-1 300 300 300 260 300 260 
(d) 
Diana Process Oil 
50 50 50 40 50 50 
PW-380 
Physical Properties 
Melt Flow Rate (g/10 min) 
15 12 13 26 7 4 8 
Modulus of Elasticity 
2,900 
2,800 
2,800 
2,700 3,300 2,900 3,800 
in Bending (kg/cm.sup.3) 
Izod Impact Strength 
(notched) (kg .multidot. cm/cm) 
23.degree. C. NB* NB NB NB NB NB NB 
-30.degree. C. 
NB NB NB NB 6 NB 14 
Gloss (%) 65 60 62 70 38 35 45 
Heat Sage (mm) 
5 4 5 5 4 5 6 
Flow Mark excellent 
good excellent 
excellent 
poor poor poor 
Coating Property 
Initial Adhesion (%) 
100 100 100 100 100 100 100 
Resistance to 100 100 100 60 100 35 100 
Hot Water (%) 
Scratch Resistance 
good good medium 
good good good poor 
__________________________________________________________________________ 
(Note) NB: No breakage (survival) 
It can be seen from Table 1 above that the resin compositions according to 
the present invention are well-balanced in physical properties as having 
excellent appearance, such as gloss, flow mark, etc., and satisfactory 
coating properties and scratch resistance as compared with the comparative 
samples which do not fulfil all the requirements of the present invention. 
As described above, the present invention provides materials for soft 
bumpers, which produce molded products having markedly improved 
appearance, particularly gloss and surface uniformity, scratch resistance 
as well as excellent coating properties while possessing favorable 
characteristics of TPO, such as mechanical strength, heat resistance, and 
the like, and also processability and productivity in injection molding. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.