JP2841303B2 - Foaming resin composition and foamed molded article thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a resin composition useful for foaming use, particularly for in-mold foam molding, and a foam made from the composition, particularly useful for buffer packaging. The present invention relates to a foam molded article.

[Conventional technology]

It is widely known that a molded article obtained by molding polystyrene foam beads is easily broken. Several attempts have been made to improve the fragility of the molded styrene foam beads and the poor recovery of the compression strain. For example, (1) a method of generally adding a polyethylene resin or butadiene rubber having high crack resistance to a polystyrene resin and mixing them by a mechanical method to obtain a foaming resin composition;
(2) JP-B-51-46536 and JP-A-55-52331 disclose a method for obtaining a resin composition for foaming using a high-impact polystyrene resin (hereinafter, referred to as a HIPS resin).
JP-A-54-154471 and JP-A-54-158467 disclose mixing a polystyrene resin or a HIPS resin with a block copolymer resin of styrene and butadiene (hereinafter referred to as SB resin) by a mechanical method. A method for obtaining a foamed resin composition,
(4) JP-A-54-119563 and JP-A-57-111330 disclose the graft weight of polyethylene resin or a copolymer resin of ethylene and vinyl acetate (hereinafter referred to as EVA resin) with polystyrene. A method for obtaining a resin composition for foaming using a united resin is described.

[Problems to be solved by the invention]

However, in the method (1) of obtaining a foaming resin composition by mixing a polystyrene resin with a resin having high crack resistance such as a polyethylene resin or butadiene rubber,
The resin to be added has different thermal properties from the polystyrene resin,
In addition, as a result of the poor mixing property and the inability to obtain a homogeneous mixed composition, when the foaming resin composition is impregnated with a volatile organic blowing agent by a method described later to form a foamable resin composition, extremely high foaming properties are obtained. However, there was a problem that a foamed molded article having a high magnification required for a buffer packaging material could not be obtained. The above (2)
In the method of obtaining a resin composition for foaming with the HIPS resin, it is generally known that the HIPS resin alone exhibits high crack resistance, but a foam molded article obtained from this HIPS resin by a method described below is not necessarily required. High crack resistance as seen with the HIPS resin alone was not obtained, and was not at all satisfactory.

Also, in relation to the amount of the rubber component in the HIPS resin and the crack resistance, it is well known that an increase in the amount of the rubber component increases the crack resistance, but the HIPS resin is generally used for its manufacturing method. The maximum amount of butadiene that can be added to the total HIPS resin is about 15% by weight at the maximum, and for this reason there is a limit to the improvement in crack resistance. Further, in the method (3) of mixing the HIPS resin with the SB resin having more crack resistance by a mechanical method, the rigidity of the added SB resin itself is extremely low, so that the crack resistance and the compressive strength characteristics are simultaneously improved. There was a problem that I could not be satisfied. Furthermore, in the method of (4) for obtaining a foaming resin composition using a polyethylene resin or an EVA resin and a polystyrene graft polymer resin, the target level required for the obtained foamed molded article to have crack resistance is required. In order to increase the amount of olefin components such as polyethylene resin and EVA resin, it is necessary to increase the amount of olefin components to at least 30% by weight based on the total resin amount. When a foaming agent is impregnated to obtain a foamable resin composition, and when foamed particles are obtained by the method described below, it is difficult to obtain a foam molded product having a very low foaming agent holding property and a stable quality, and a mechanical strength. Since the proportion of the olefin component having a low characteristic is high, there is a problem that the obtained molded foam has low compressive strength characteristics.

Accordingly, the present invention is intended to solve all of the above-mentioned disadvantages, and an object of the present invention is to provide a resin composition which is excellent in holding properties of a foaming agent and is easily foamed into a foamed article having a high foaming property. It is an object of the present invention to provide a foam having excellent compressive strength, crack resistance and compressive strain recovery when the foamed article is formed, which is excellent for use in buffer packaging.

[Means for solving the problem]

The present invention relates to (1) a block copolymer of a vinyl aromatic compound and a conjugated diene compound, in which most of the double bonds derived from the conjugated diene are hydrogenated and saturated, and a high-impact polystyrene resin. And a total rubber component amount that is a sum of a rubber component in the copolymer resin and a rubber component in the high-impact polystyrene resin is 10 to 25% by weight, and The ratio of the rubber component amount in the copolymer resin to the total rubber component amount is 10
To 60% by weight,
And (2) a block copolymer of a vinyl aromatic compound and a conjugated diene compound, wherein the block copolymer is derived from a conjugated diene.
A resin composition obtained by mixing a copolymer resin and a high-impact polystyrene resin in which most of the heavy bonds are hydrogenated and saturated, and a rubber component in the copolymer resin and a rubber in the high-impact polystyrene resin The total rubber component amount, which is the sum of the components, is 10 to 25% by weight, and the ratio of the rubber component amount in the copolymer resin to the total rubber component amount is 10 to 60%.
A large number of foamed particles made of a resin composition which is
A foamed molded article that is fused and integrated at its surface.

 Hereinafter, the present invention will be described in detail with reference to the drawings and the like.

The main feature of the present invention is to use a mixture of HIPS resin and HSB resin.

(Operation)

FIG. 1 is an experimental drawing that clearly shows the significance of using the resin composition of the present invention. That is, the horizontal axis in FIG. 1 shows the amount of the total rubber component with respect to the total resin amount in weight percent. This means that in the mixing of the HIPS resin and the HSB resin each containing a rubber component, the mixing ratio is represented by the total rubber amount.

The vertical axis is (foaming agent holding time), (compression strain recovery amount),
The evaluation from three viewpoints of [compression strength] is shown. That is, FIG. 1 shows that the [compression strength] and the [foaming agent holding time] decrease with an increase in the total rubber component amount and become significantly worse when the total rubber component amount exceeds 25% by weight. . However, [the amount of recovery of compression strain] is contradictory to the above-mentioned item 2, and decreases with a decrease in the total rubber component amount. Further, when the total rubber component amount is less than 10% by weight, it is shown to be significantly deteriorated, and It can be seen that a composition with improved properties is obtained. And from the viewpoint of simultaneously satisfying three of [compressive strength] and [foaming agent holding time] and [compressive strain recovery amount], which show properties that are contradictory in relation to the total rubber component amount, It is desirable to select a composition having a range indicated by a dotted line shown in FIG. 1, that is, a composition having a total rubber component amount of 10 to 25% by weight.

FIG. 2 shows HSB in the total rubber component in the resin composition of the present invention.
FIG. 4 is an experimental view showing the significance of the amount occupied by a rubber component of a resin.
That is, the horizontal axis in FIG. 2 shows the amount of the rubber component of the HSB resin occupied by the weight percentage relative to the total rubber component amount, and the vertical axis shows the evaluation from two viewpoints of [crack amount] and [expansion ratio]. . According to FIG. 2, the [expansion ratio] is improved as the rubber content of the HSB resin in the total rubber content is reduced, and particularly when the rubber component content of the HSB resin is 10% by weight or less, it is significantly improved. It is. On the other hand, the (crack amount), contrary to the (expansion ratio), greatly deteriorates with a decrease in the amount of the rubber component of the HSB resin, and particularly when the rubber component amount of the HSB resin is less than 10% by weight, it becomes extremely large and deteriorates. It is.

That is, it can be understood that the improvement point corresponding to the target can be taken out by the ratio of the HSB rubber component amount to the total rubber component amount in the composition. In this way, the foaming ratio and the amount of cracking, which show contradictory properties in relation to the amount of rubber of the HSB resin, are 2
From the viewpoint of simultaneously satisfying the two requirements, it is desirable to adjust the range of the dotted line shown in FIG. 2, that is, the amount of the rubber component in the HSB resin to be in the range of 10 to 60% by weight based on the total rubber amount. I understand.

As described above, according to the foamed molded article of the resin composition for foaming of the present invention, even when the amount of the total rubber component in the total amount of the resin is small, it is extremely high [crack resistance] and excellent [recovery of compression strain]. ] Was obtained. The mechanism by which such an effect occurs is not necessarily clear, but may be considered as follows. That is, the HIPS resin and the HSB resin that constitute the resin composition for foaming have high mutual compatibility and are uniformly mixed. HI to be the main subject
The PS resin itself has high rigidity and crack resistance. (C) The HSB resin used has extremely high crack resistance. It is believed that the synergistic effect provided by the homogeneous mixing of HIPS resin and HSB resin having these properties.

Table 1 shows the significance of using the HIPS resin and the HSB resin in the present invention. As a result, the effects of the present invention are clearly shown in light of the prior art. That is, according to the resin composition of the present invention and the foam molded article obtained therefrom, as shown in Example 1, the evaluation that all the evaluation items were extremely poor (indicated by X in the table)
No excellent performance was observed in a wide range of the ratio of the total rubber component to the total resin amount. still,
Practically, the ratio of the total rubber component to the total resin amount is 10
It illustrates the fact that it is desirable to choose from a range of ~ 25 weight percent.

The HIPS resin used in the present invention is not particularly limited, but preferably has a generally used rubber component amount of 3 to 15% by weight based on the total HIPS resin amount.
Further, the HSB resin used is preferably such that the amount of the vinyl aromatic compound component in the total amount of the HSB resin is 20 to 80% by weight and the degree of saturation by hydrogenation of the double bond derived from the conjugated diene is preferably 80%. It is good to select from among those having a percentage of at least 90%, more preferably at least 90%. When the amount of the vinyl aromatic compound component is less than 20% by weight, the mixture with the HIPS resin is slightly poor and a homogeneous mixture is hardly obtained, and when the amount of the vinyl aromatic compound component exceeds 80% by weight, the expensive HSB resin is used. The amount to be added increases, which is disadvantageous in cost. Furthermore, the HS obtained when the saturation degree of the conjugated diene compound component to be hydrogenated is less than 80% is obtained.
This is because the rigidity of the B resin is slightly inferior, and as a result, the compression strength of the foamed molded article decreases.

In the present invention, the `` total amount of rubber component relative to the total amount of resin '' and `` the amount of rubber component of HSB resin relative to the total amount of rubber component '' can be adjusted by changing the types of HIPS resin and HSB resin used and the compounding thereof. I can do it.

In the present invention, the HIPS resin and the HSB resin are blended at the respective required ratios, and then continuously supplied to an extruder, mixed homogeneously while being heated and melted in the extruder, and formed into a thread-like shape through pores provided in a die of the extruder. Immediately after being extruded into water, it is cooled in a cooling bath containing water, and is cut in the length direction by a rotary cutter while being sandwiched and taken up by two upper and lower drive rolls to obtain a particulate foaming resin composition. .

The method for obtaining a foamed molded article from the resin composition for foaming of the present invention is as follows. That is, the foaming resin particles are impregnated with a volatile organic foaming agent such as pentane, butane, and monochlorodifluoroethane to obtain particles of the foamable resin composition. In addition, the method of impregnating the volatile organic foaming agent is as follows:
For example, put the particles of the foaming resin composition in an autoclave, add a volatile organic foaming agent to this, fill up and seal, then impregnate by heating and pressing or particles of the foaming resin composition. After being heated and melted in the extruder, the volatile organic blowing agent is injected through a blowing agent supply line that is separately connected to the extruder, and sufficiently mixed with the foaming resin composition in a molten state,
After that, it is extruded into a thread form from the pores provided in the die part of the extruder, and is cut directly in the length direction by a rotary cutter while being picked up by two upper and lower drive rolls while being cooled by a cooling bath containing water. A method of obtaining particles of the foamable resin composition is used.

Next, the particles of the expandable resin composition are heated and foamed with a known foaming machine for polystyrene foam beads using steam to form foamed particles. Incidentally, the expansion ratio of the obtained expanded particles is based on the weight of the particles of the expandable resin composition to be put into a foaming machine.
When the expandable resin particles expand to a target volume in a foaming machine, the supply of steam is automatically stopped to stop foaming, and a target expansion ratio is obtained.

Further, the obtained foamed particles are fused into one body by a known automatic molding machine for polystyrene foam beads to obtain a foam molded body.

〔Example〕

 Next, the present invention will be described with reference to examples.

In addition, the measuring method and evaluation method in the following Examples and Comparative Examples are as follows.

<Measurement method> Expansion ratio Approximately 5 g of expanded particles are weighed to two or less places to determine the exact weight (W). Next, about 50 to 100 cc of water is poured into a glass graduated cylinder whose minimum scale unit is 1 cc, and the tip is a circular wire mesh plate whose tip is slightly smaller than the diameter of the graduated cylinder and has a length of about 15 at the center thereof. A pressing tool of upright foam beads with a fixed wire of about 30 cm is immersed, and the water level (V ₀ ) at that time is read.

Next, the foaming particles whose weight was assured except for the pressing tool were placed in a measuring cylinder, and the water level (V) was read again in a state of being completely submerged by the pressing tool, and the expansion ratio was obtained by the following.

Blowing agent content Approximately 5 g of expandable resin particles, the weight is weighed down to the second decimal place and the confirmed upper part is opened,
Transfer to a cylindrical glass container having a low area of 78.5 cm ² and a height of 10 cm, and weigh to the second decimal place to confirm the weight.
Further, the resin particles are put together with the glass container into a vacuum deaerator controlled at 100 ° C., degassed at a degree of vacuum of −700 mmHg for 60 minutes, then taken out, left to cool in a chamber for 5 minutes, weighed to the second decimal place and weighed. Was determined as follows.

The amount of cracks In accordance with JIS-Z-0235 and the drop impact test method, as shown in FIG. The drop impact body 2 having a rectangular parallelepiped wooden shape falls almost at the center in the longitudinal direction of the plate-like foam molded body 1 and over the entire surface in the width direction. The relationship between the maximum amount of compressive strain and the crack size was determined. Further, to clarify these relationships, the maximum compressive strain was plotted on the horizontal axis and the crack size was plotted on the vertical axis, and arranged on a graph. Next, from the obtained graph, the crack size at the time when the maximum compressive strain was 60% with respect to the original thickness dimension of the plate-like foamed molded product 1 was obtained, and the crack amount was obtained as follows.

S: Crack amount (%) H: Crack size (cm) T: Thickness size of plate-like foamed molded product (cm) Amount of recovery of compressive strain A test specimen having a length, width and thickness of 50 mm x 50 mm x 50 mm was subjected to a 25% compression test according to JIS K-6767 repeated compression set test, and determined as follows.

R: recovered amount of compression set (mm) R _1: 25% -compression of the thickness (mm) R _2: thickness after recovery _{(mm) R = R 2 -R} 1 Compressive Strength JIS Z-0234 Compression Test According to the method, a test specimen of 100 mm × 100 mm × 50 mm in length × width × thickness is 10 mm per minute in the thickness direction
The compressive stress value (kg / cm ² ) at the time of compressive strain of 25% with respect to the thickness is defined as the compressive strength.

<Evaluation method> High foaming performance (Effect A) Expandable resin composition particles made by impregnating 100 g of resin with 10 g of pentane as a foaming agent are used as foaming beads for polystyrene foaming machine (Sekisui Koki Seisakusho Co., Ltd., SKK After heating and foaming at a steam temperature of 98 ° C. for 50 seconds at −50), drying was performed in a dryer at 50 ° C. for 20 minutes, and the foaming ratio was confirmed by a measuring method of the foaming ratio.

Foaming agent retention performance (Effect B) The same foaming resin particles as used in the above-mentioned section on evaluation of high foaming performance were subjected to a foaming machine for polystyrene foam beads (SKK-50, manufactured by Sekisui Koki Seisakusho Co., Ltd., SKK-50). After the foamed particles are doubled, the foamed particles are left for about 24 hours in a container at room temperature where the humidity is almost completely removed by a dryer, and after the moisture on the surface and the inside of the foamed particles are almost completely removed. After taking out, the foaming agent content was immediately confirmed by the measuring method of the foaming agent content. Further, the foaming agent content is confirmed in the same manner every three hours, and the relationship between the standing time and the foaming agent content is shown. The foaming agent content ranges from 8 (g / 100 g resin) to 4 (g / 100 g resin). The required time for halving was confirmed, and the foaming agent holding performance was determined as follows.

Cracking resistance (Effect C) The same expanded particles as those used in the evaluation of the foaming agent holding performance were subjected to plate-like expansion using an automatic bead expanded polystyrene molding machine (Piony-75, manufactured by Kasahara Kogyo Co., Ltd.). Molded body (Length x width x thickness is 300mm x 300mm x 50mm, bulk density is 25kg
/ m ³ ) was obtained and determined as follows by the method for measuring the amount of cracks.

Compressive strength characteristics (Effect D) The same foamed molded article as used in the above section on the evaluation of crack resistance was determined as follows by the method of measuring the compressive strength.

Compressive strain recovery performance (Effect E) Using the same foamed molded article used in the evaluation of the cracking performance, the compression strain recovery amount was determined as follows.

Example 1 In this experiment, when a foamable resin composition was obtained by impregnating a volatile organic foaming agent into the foaming resin composition of the present invention, the obtained foamable resin composition exhibited high foaming performance and foaming properties. It is intended to prove the fact that a foamed molded article obtained from these expandable resin particles has excellent crack resistance, compressive strength characteristics and compressive strain recovery properties.

An HSB resin [manufactured by Asahi Kasei Kogyo Co., Ltd., trade name: Tuftec] having a saturation degree of 99% or more of a conjugated diene compound component to be hydrogenated with a HIPS resin [manufactured by Asahi Kasei Kogyo Co., Ltd .; trade name: Styrone-HIPS] Were mixed in the composition ratio corresponding to the experiment number in the order of the experiment number, and after each well mixed by a drum type blender, the mixed resin was melt-kneaded in an extruder separately from the pores provided in the die portion. The mixture was extruded into a thread, immediately cooled through a cooling bath storing cooling water, and cut in the length direction by a rotary cutter while being sandwiched between two upper and lower drive rolls and taken out to obtain particles of the resin composition for foaming. Next, these particles are separately provided with a pressure-supplying device for the blowing agent in the order of the experiment number, and a connection line from the pressure-supplying device is connected so as to communicate with the melt kneading section in the extruder cylinder. It is supplied to an extrusion impregnation device equipped with a resin cooling device at the head and a die device having a large number of resin outflow holes, and while mixing and kneading in the extruder, pentane is fed from the foaming agent pressurization supply device to the resin 100 weight Parts by weight to a ratio of 10 parts by weight with a pump, and while kneading and mixing with the resin, it is cooled to an appropriate temperature by a cooling device, extruded into a thread form from a number of pores provided in a die device, and immediately, It is cut in the length direction with a rotary cutter while being pulled between two upper and lower drive rolls through a cooling bath containing water at almost room temperature, and the dimensions are about 1.0 mm in diameter and 4.0 mm in length Particles of the resin composition were obtained. From the particles of the foamable resin composition, particles of the foamable resin composition and a foamed molded article were obtained by the method described above and evaluated. Table 1 shows the evaluation results.

Comparative Example 1 A polystyrene resin [manufactured by Asahi Kasei Kogyo Co., Ltd., trade name: Stylon GP-680] and a polystyrene resin [manufactured by Asahi Kasei Kogyo Co., Ltd., Suntec LD-2115], the composition ratios corresponding to the experiment numbers shown in Table 2 The particles of the foamable resin composition were obtained in exactly the same manner as in Example 1 except that
Was evaluated in exactly the same manner. Table 2 shows the evaluation results.

Comparative Example 2 A HIPS resin containing a butadiene component corresponding to the experiment number shown in Table 2 [trade name: Styrone HIPS manufactured by Asahi Kasei Kogyo Co., Ltd.] was prepared, and foaming properties were obtained in exactly the same manner as in Example 1. Example 1 A resin composition particle and a foam molded article were obtained.
Was evaluated in exactly the same manner. Table 2 shows the evaluation results.

Comparative Example 3 HIPS resin [manufactured by Asahi Kasei Kogyo Co., Ltd., trade name; Stylon-HIPS, rubber component content 7% by weight] and SB resin [Asahi Kasei Kogyo Co., Ltd., trade name; tufprene, rubber component content 50 wt. %) Were blended in the composition numbers corresponding to the experiment numbers shown in Table 2 to obtain particles of the foamable resin composition and a foamed molded product in the same manner as in Example 1.
Was evaluated in exactly the same manner. Table 2 shows the evaluation results.

Comparative Example 4 EVA resin (manufactured by Mitsui Polychemicals, Inc., trade name: Evaflex P-607) particles, water, magnesium carbonate,
Siegmill peroxide was blended as follows to obtain a blended intermediate liquid.

EVA resin 1,000 parts by weight Water 2,000 parts by weight Magnesium carbonate 5 parts by weight Diegyl peroxide 10 parts by weight Sodium dodecylbenzenesulfonate 1 part by weight Styrene monomers obtained by adding and dissolving oxide at a concentration of 1% by weight were blended as follows to obtain three kinds of blended liquids.

Thereafter, the mixed liquid 2 was transferred to each of the 5 autoclaves, sealed, heated with stirring, and kept at 70 ° C. for 5 hours to impregnate the resin particles with styrene.
° C and gradually maintained at each temperature for 4 hours and 30 minutes at the same temperature, and simultaneously with the polymerization reaction of styrene, the binding reaction between styrene and EVA resin, and also the crosslinking reaction of EVA resin, followed by cooling. The styrene-EVA copolymer resin particles were taken out.

The amounts of styrene contained in these resin particles were respectively 83, 75, and 70 weight percent in order. The method for determining the amount of styrene is to determine the amount of residual styrene in the liquid remaining in the autoclave after the completion of the reaction, and to determine the amount of impregnation in the EVA resin based on the difference from the amount of styrene added before the reaction. I can do it. Further, 2,000 g of each styrene-EVA copolymer resin particle was placed in each of 5 pressure-resistant containers, and heated under pressure at 80 ° C. in a pentane-filled liquid, and about 15 parts by weight of pentane was added to 100 parts by weight of the resin. After impregnation, the mixture was cooled and taken out to obtain expandable resin particles. Next, the foaming resin particles were allowed to stand at room temperature and dried while the foaming agent was reduced while drying. The foaming agent content was regularly confirmed by the above-described method for confirming the foaming agent content. When the agent content reached 10 parts by weight with respect to 100 parts by weight of the resin, evaluation was made in the same manner as in Example 1.
Table 2 shows the evaluation results.

Comparative Example 5 Expandable resin particles were obtained from a polystyrene resin (trade name: Stylon GP-680, manufactured by Asahi Kasei Corporation) and evaluated in the same manner as in Example 1. Table 2 shows the evaluation results.

[Effects of the Invention] The present invention has the above-described configuration, and when it is viewed as a resin composition, when it is to be used as a foam, it has excellent holding properties of a foaming agent, and it is easy to obtain a highly foamed molded article. This has the effect. Further, when viewed as the obtained foamed molded article, there is an advantage that the foamed molded article has both crack resistance, compressive strength characteristics, and recovery from compression strain, and is excellent in buffer packaging use. It is an excellent invention that can be used for buffer packaging of lightweight and easily breakable contents such as audio equipment or communication equipment, and plays a large role in the industrial world.

[Brief description of the drawings]

1 and 2 are experimental views showing the contents of the invention. FIG. 3 is a view showing a crack test method, and FIG. 3 (A) is a front view when a falling impact body with a weight is dropped, and FIG. 3 (B).
The figure is a front view of the test piece after the crack test is performed. In FIG.
1 is a foam molded article, 2 is a drop impact body, 3 is a weight, 4 is a crack of the foam molded article, indicates a crack size (cm), and indicates a thickness (cm) of the foam molded article.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08J 9 / 14,9 / 16 C08L 51 / 04,53 / 02 C08J 9/228

Claims (2)

(57) [Claims] 1. A block copolymer of a vinyl aromatic compound and a conjugated diene compound, wherein a high-impact polystyrene resin and a copolymer resin in which most of the double bonds derived from the conjugated diene are hydrogenated and saturated are used. A resin composition obtained by mixing, wherein a total rubber component amount which is a sum of a rubber component in the copolymer resin and a rubber component in the high impact polystyrene resin is 10 to 25% by weight, and A foaming resin composition, wherein a ratio of a rubber component amount in the polymer resin to the total rubber component amount is 10 to 60% by weight. 2. A block copolymer of a vinyl aromatic compound and a conjugated diene compound, wherein a high-impact polystyrene resin and a copolymerized resin in which most of the double bonds derived from the conjugated diene are hydrogenated and saturated. A resin composition obtained by mixing, wherein a total rubber component amount which is a sum of a rubber component in the copolymer resin and a rubber component in the high impact polystyrene resin is 10 to 25% by weight, and A foam molded article obtained by fusing and integrating a large number of foamed particles made of a resin composition having a ratio of the rubber component amount in the polymer resin to the total rubber component amount of 10 to 60% by weight on the surface thereof .