AU627105B2 - Surface-treated fillers and rubber compositions containing the same - Google Patents

Description

Goo* 00 04 0 0 0.0 o 0 V 0 0 000 00 0 a o 00 0 0 0 on o 00 0~ PO *0 0,0 4 1 The present invention relates to a surfacetreated filler and rubber compositions containing the same.

Various fillers are added to rubbers for reducing a cost per unit volume, and improving the physical properties of crosslinked products.

For improving the physical properties of crosslinked rubbers as listed in how to uniformly disperse a filler in rubbers is important, and improvement in the disper- 10 sibility of the filler is being tried by selection of a rubber kneading method and the shape and surface treatment of the filler. Of these, the surface treatment is generally carried out with the aid of mainly various fatty acids, resin acids or their derivatives.

15 There are dispersing agents which have been given effects to improve the processability and tackiness of compounded rubbers at the same time with improvement in dispersibility. Further, there are instances in which, with the object of strengthening the reinforcing 20 property of fillers of weak reinforcing power such as calcium carbonate, treatment with a silane series or titanium series coupling agent or a copolymer resin styrene/maleic anhydride copolymer) is applied to calcium carbonate, thereby causing it to exhibit a reinforcing property equivalent to that of lower j" 1 8 t. io 1 .1 r :i 1 reinforcing carbon black [Interfaces Polym. Ceram. Met.

Matrix Compo's., (1988) Zhu Lu Zhang L.N. and Wu pp. 685-6921.

The conventional surface-treated fillers described above, however, have a problem that their reinforcing property has not satisfactorily been improved.

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I Cr *tC 4 11 It I I I I~ 4 An object of the present invention is to improve a poor reinforcing property of fillers such as calcium carbonate by applying a particular surface treatment.

The present inventors have extensively studied on a surface treatment technique for fillers and completed the present invention.

15 According to the present invention, there are provided a surface-treated filler characterized by consisting of a powdery product of an inorganic compound of which surface has been treated with a terpolymer comprising a repeating unit derived from ethylene, a repeating unit derived from at least one member selected from the group consisting of acrylates and methacrylates and a repeating unit derived from maleic anhydride, and a rubber composition comprising a rubber and the surface-treated filler.

The composition of the terpolymer preferably comprises 50 to 95% by weight of an ethylene unit, 4 to 49% by weight of a methacrylate unit, an acrylate unit or both and 0.5 to 10% by weight of a maleic anhydride

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2 1 unit. Fillers to be surface-treated with the terpolymer are preferably silica, calcium carbonate, talc and aluminum hydroxide.

Of the components of the terpolymer, specific examples of acrylates are ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tertbutyl acrylate, isobutyl acrylate, etc. Of these, ethyl acrylate is preferred.

Specific examples of methacrylates are ethyl a R"d 10 methacrylate, n-propyl methacrylate, isopropyl meth- So acrylate, n-butyl methacrylate, tert-butyl methacrylate, a isobutyl methacrylate, etc.

09" The foregoing proportions of the components o s of the terpolymer, i.e. 50 to 95% by weight for the ethylene unit, 4 to 49% by weight for the methacrylate unit, the acrylate unit or both and 0.5 to 10% by weight for the maleic anhydride unit, are preferred for the following reasons: When the ethylene unit is o less than 50% by weight, a tear strength-improving effect is sometimes not obtained, and when it is more s than 95% by weight to the contrary, the percent increase of tear strength tend to hit the ceiling and also the brittle temperature sometimes rises; and when the maleic anhydride unit is less than 0.5% by weight, a strength-improving effect is sometimes lost, and when iit is more than 10% by weight, production of the copolymer becomes sometimes difficult.

The method for producing the terpolymer used 3-

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1 I 1 in the present invention is not particularly limited, and the terpolymer is produced, for example, by a highpressure polymerization method.

The filler to be surface-treated is a powdery product of inorganic compounds such as silica, calcium carbonate, talc, aluminum hydroxide, etc. These fillers may be surface-treated in advance with a fatty acid or its derivatives. Commercially available fillers include Whiton SB (heavy calcium carbonate produced by Inoue Sekkai Kogyo Inc.), Novelight TT (calcium carbonate treated with a surface active agent produced by Nitto 0o40 S, Funka Kogyo Inc.), Nipsil VN (Silica produced by Nippon Silica Kogyo Inc.) and C-301 (aluminum hydroxide produced by Sumitomo Chemical Co., Ltd.).

15 For carrying out the surface treatment of the filler, there are a method comprising spraying a solution of the terpolymer in a solvent xylene) onto the a' 4filler or impregnating the fill,-r into the solution and Sheating the solution while stirring and mixing under 4t 20 normal pressure or reduced pressure to remove the solvent, and a method comprising mixing an emulsion of S' the terpolymer with the filler while stirring and removing water while heating and stirring the resulting mixture. When the surface area to adsorb the terpolymer of the filler is small, for example as in the case of calcium carbonate, the filler particles sometimes stick fast together in the form of a lump. However, such a lump-form filler can be used in a finely powdered form 4 1 by sufficiently removing the solvent or water from the filler and subjecting the dried filler to pulverization.

In this case, however, the reinforcing power is reduced as compared with fillers having a uniformly covered particle surface.

By the above surface treatment, at least a part of the surface of filler particles made of a powdery product of an inorganic compound is covered with a terpolymer.

The amount of the terpolymer applied to the surface of a powdery product of the inorganic compound 0969 0- is not particularly limited. However, it is preferably a at most 15.0% by weight, more preferably 0.9 to 12.0% 0000 OO by weight and most preferably 0.99 to 11.1% by weight o 15 based on the total weight of the inorganic compound and the terpolymer.

By suspending the resulting surface-treated o filler in water and spray-drying the suspension, it is possible to prepare a secondary aggregate of any ,j 20 desirable particle size.

The tear strength-improving effect obtained by S adding the filler surface-treated with the terpolymer to a compounded rubber is due to the interaction between the terpolymer and both the filler surface and rubber matrix.

For example, when the amount of the repeating unit derived from ethylene of the terpolymer is more than 95% by weight, the polar sites of the terpolymer to interact with the filler surface tend to untoleratively decrease. To the contrary, when the amount is less than 6by weight, the compatibility between the terpolymer and the rubber tends to be reduced, and also the proportion of the hydrophobic chain capable of interacting with the rubber molecules tends to decrease, whereby the physical properties of the vulcanized rubber are not sometimes expected to be improved.

As examples of the rubber component of the rubber composition, ethylene-a-olefin copolymer rubbers, ethylenea-olefine-nonconjugated diene terpolymer rubbers, styrenebutadiene rubbers, isoprene rubbers, acrylonitrilebutadiene copolymer rubbers, etc. can be used.

Particularly, it is effective to blend the surface-treated filler with an ethylene-a-olefin-nonconjugated diene terpolymer rubber, which has the lowest polarity among the foregoing rubber components. Specific examples of the aolefin in the ethylene-a-olefin-nonconjugated diene Sterpolymer rubber are propylene, 1-butene, l-pentene, 1hexene, etc. Specific examples of the diene compound in the terpolymer rubber are dicyclopentadiene, ethylidene S 20 norbornene, 1,4-hexadiene, methyltetrahydroindene and methylnorbornene.

The weight ratio of the rubber to the surfacetreated filler preferably ranges from 100:30 to 100:300, o more preferably 100:40 to 100:200, most preferably 100:50 to 100:150.

o o The rubber composition can be used molded into films, sheets, etc. without particular limitation.

j To the rubber composition using the filler of the present invention can be added if necessary reinforcing agents, other fillers, plasticizers, tackifiers, antioxidants, vulcanizing agents, vulcanization accelerators, etc.

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N AQ'* t^" i -TO^ 4 4 1 The surface-treated filler of the present invention can be widely used as a filler not only for rubbers but also for resins. For example, it can be added as a filler to olefinic resins such as polyethylene, polypropylene, etc.; olefinic copolymer resins such as ethylene-acrylate copolymer resins, ethylenemethacrylate copolymer resins, ethylene-vinyl alcohol copolymer resins, etc.; various polyester resins and carbonate resins. Further, known antioxidants, plasticizers, etc. may be added.

The present invention will be illustrated with 'o reference to the following examples. The number of 0 parts used in blending is by weight unless otherwise o stated.

9o o 0co Example 1 Heavy calcium carbonate (Whiton SB; a trade 0 name of Inoue Sekkai Kogyo Inc.) was added to a solution of a terpolymer of 75% by weight of ethylene, 22% by o 1 ,g weight of ethyl acrylate and 3% by weight of maleic anhydride (Bondine HX8020; a trade name of Sumika CDF S Co., Ltd.) in xylene. Xylene was removed by heating the mixture under reduced pressure, and then completely removed by vacuum-drying to obtain a surface-treated filler. At that time, the weight percentage of the terpolymer adsorbed in or adhered to the filler was controlled so as to be 4.8% by weight based on the total Sweight of the filler and the terpolymer.

According to the blending ratios shown in 7

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89: i -il-. i 1 Table 1, an ethylene-propylene-nonconjugated diene terpolymer rubber (Esprene® 522; a trade name of Sumitomo Chemical Co., Ltd.), the foregoing surfacetreated filler (surface-treated Whiton SB), stearic acid, zinc oxide, a process oil and calcium oxide were mixed and kneaded by means of a B/R type Banbury mixer.

To the kneaded product were added a vulcanizing agent (sulfur) and vulcanization accelerators (BZ, TT, DM) on a 10-inch roller. The resulting blend was shaped into a crosslinked rubber sheet of 2 mm in thickness by means of a 150-ton steam press (160°C x 30 min.).

The calculated value of the added amount in Table 1 refers to the amount (part by weight) of the terpolymer blended with the rubber, which terpolymer is 15 adsorbed in or adhered to the filler.

Table 2 shows the physical properties of vulcanized rubbers. The physical properties were measured according to Japanese Industrial Standard (JIS) K 6301.

0009 D 0 0000 o o e 0 oa^ 0 0 0 0 0 0 o D s e a 0 0 4 0000 o e 0 0*0 0 4 60 00f 0 6 0 00 0 0* 0 4 4 C 44t 1t t s n Example 2 The same procedure as in Example 1 was repeated except that the surface-treated filler was prepared by changing the concentration of the solution so that the weight percentage of the terpolymer adsorbed in or adhered to the filler was changed to 11.1% by weight, and that the blending proportion of the surface-treated filler in the rubber composition was changed to 55 parts -8 -'e 1 1 1 by weight. Table 2 shows the results.

Example 3 The same procedure as in Example 1 was repeated except that the surface-treated filler and its blending proportion in the rubber composition were changed to a surface-treated Novelight TT (calcium carbonate treated with a surface active agent) and 53 parts by weight, respectively, as shown in Table 1. Table 2 shows the results.

Example 4 The same procedure as in Example 2 was repeated except that the surface-treated filler and its blending proportion in the rubber compositon were changed to a surface-treated Novelight TT and 55 parts by weight, respectively, as shown in Table 1. Table 2 shows the s t results.

o 10 Example The same procedure as in Example 1 was repeated except that as shown in Table 1, the surface-treated filler and its blending proportion in the rubber composition were changed to a surface-treated Nipsil VN3 (silica produced by Nippon Silica Kogyo Inc.) and 53 parts by weight, respectively, and that the blending proportion of the process oil was changed to 20 parts by weight. Table 2 shows the results.

9- 1 Example 6 The same procedure as in Example 2 was repeated except that as shown in Table 1, the surface-treated filler and its blending proportion in the rubber com- 5 position were changed to a surface-treated Nipsil VN3 and 55 parts by weight, respectively, and that the Sblending proportion of the process oil was changed to parts by weight. Table 2 shows the results.

Comparative Example 1 «00 10 The same procedure as in Example 1 was repeated except that 50 parts by weight of Whiton SB was used as o+ ;a filler without being surface-treated as shown in Table 1. Table 2 shows the results.

as*4 Comparing Examples 1 and 2 with Comparative Example 1 demonstrates that the tear strength of the vulcanized rubber is greatly improved by using the filler having been surface-treated with the terpolymer.

fi Comparative Example 2 I The same procedure as in Example 3 was repeated except that 50 parts by weight of Novelight TT was used as a filler without being surface-treated as shown in Table 1. Table 2 shows the results.

Comparing Examples 3 and 4 with Comparative Example 2 demonstrates that in the case calcium carbonate treated with a surface active agent is used, the tear strength of the vulcanized rubber is greatly i S- 10 f I I t j j 1 4 4 #41W WI It *1 1 1* i*1 1 improved by using the surface-treated filler, either.

Comparative Example 3 The same procedure as in Example 5 was repeated except that 50 parts by weight of Nipsil VN3 was used as a filler without being surface-treated as shown in Table 1. Table 2 shows the results.

Comparing Examples 5 and 6 with Comparative Example 3 demonstrates that in the case silica is used, the tear strength of the vulcanized rubber is greatly 10 improved by using the surface-treated filler, either.

Example 7 An emulsion was prepared by using as the disperse phase a terpolymer of 80% by weight of ethylene, 18% by weight of ethyl acrylate and 2% by weight of maleic anhydride (Bondine® HX8290; a trade name of Sumika CDF Co., Ltd.). The emulsion and aluminum hydroxide (C-301; a trade name of Sumitomo Chemical Co., Ltd.) as a filler were mixed and dried with a Henschel mixer for carrying out the surface treatment of aluminum hydroxide. At that time, the weight percentage of the terpolymer adsorbed in or adhered to the filler was controlled so as to be 0.99% by weight.

According to the blending ratios shown in Table 3, an ethylene-propylene-nonconjugated diene terpolymer rubber (Esprene 505A; a trade name of Sumitomo Chemical Co., Ltd.), the foregoing surface-

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11 -c ~I 1 i i ;i-l~i 1 treated filler, stearic acid, zinc oxide and a process oil were kneaded by means of a B/R type Banbury mixer.

Thereafter, to the kneaded product were added a vulcanizing agent (sulfur) and vulcanization accelerators (BZ, TRA, TT, M) on a 10-inch roller. The resulting blend was shaped into a vulcanized rubber sheet of 2 mm in thickness by means of a 150-ton steam press (160 0 C x min.).

The calculated value of the added amount in Table 3 refers to the amount (part by weight) of the terpolymer blended with the rubber, which terpolymer o is adsorbed in or adhered to the surface-treated filler added.

ctcr *Table 4 shows the physical properties of vulcanized rubbers. The physical properties were measured according to Japanese Industrial standard (JIS) K 6301.

Example 8 J The same procedure as in Example 7 was repeated except that vulcanization was carried out in a peroxide i vulcanization system (dicumyl peroxide and TAIC) as shown in Table 3. Table 4 shows the results.

Example 9 The same procedure as in Example 7 was repeated except that aluminum hydroxide (C-3005; a trade name of Sumitomo Chemical Co., Ltd.) was used as a filler as -12 1 1 fc 11 1 shown in Table 3. Table 4 shows the results.

Example The same procedure as in Example 8 was repeated except that aluminum hydroxide (C-3005; a trade name of Sumitomo Chemical Co., Ltd.) was used as a filler as shown in Table 3. Table 4 shows the results.

Comparative Example 4 The same procedure as in Example 7 was repeated except that the filler was used without being surface- 10 treated as shown in Table 3. Table 4 shows the results.

4 t l «Comparative Example The same procedure as in Example 8 was repeated except that the filler was used without being surfacetreated as shown in Table 3. Table 4 shows the results.

Comparative Example 6 4 '1 The same procedure as in Example 9 was repeated except that the filler was used without being surfacetreated as shown in Table 3. Table 4 shows the results.

Comparative Example 7 The same procedure as in Example 10 was repeated except that the filler was used without being surfacetreated as shown in Table 3. Table 4 shows the results.

Comparing the results of Examples 7-10 with l' 13 i. C L 1 1 those of Comparative Examples 4-7 demonstrates that the tear strength of the vulcanized rubber is more greatly improved by using aluminum hydroxide surface-treated with the terpolymer than by using non-treated aluminum hydroxide. It also shows that application of the surface treatment on the filler exerts little adverse effect on the other physical properties of the vulcanized rubber. This conclusion can be applied to any of the sulfur vulcanization system (Examples 7 and 9 and Comparative Examples 4 and 6) and peroxide vulcanization system (Examples 8 and 10 and Comparative Examples 5 and 0 0 in other words, the conclusion does not depend upon S the type of the vulcanizing agent.

bo°a By blending a filler surface-treated with the "a 15 terpolymer of the present invention, the tear strength of vulcanized rubbers is greatly improved.

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0 MPMMRRFwmqa 0 a at a a 4. a Oat. at. aca oo'i o q oea *I a a a a a Table 1 Comparative SExamplNo. e Example Agent 2 3 4 5 6 1 2 3 Esprene® 522 1) 100 100 100 100 1 00 100 100 100 100 Stearic acid 1 1 1 1 1 1 1 1 1 Zinc oxide2 5 5 5 5 5 5 5 5 Whiton SB 50 3) Novelight TT 4 50 Nipsil VN3 Surface-treated Whiton SB 53 55 Surface-treated Novelight TT 53 55 Surface-treated Nipsil VN3 53 55 Process oil 110 10 10 10 20 20 10 10 Calcium oxide 10 10 10 10 10 10 10 10 Vulcanization accelerator BZ 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Vulcanization accelerator TT 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Vulcanization accelerator DM 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Sulfur 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Total 184 186 184 186 194 196 181 181 191 Weight percentage of terpolymer to surface-treated filler 4.8 11.1 4.8 11.1 4.8 11.1 Calculated value of added amount 2.7 5.5 2.7 5.5 2.7 5.5 0 0 0 F I -i a :r~fs Note: 1) Trade name of an ethylene-propylene-nonconjugated diene copolymer rubber produced by Sumitomo Chemical Co., Ltd.

2) Trade name of heavy calcium carbonate produced by Inoue Sekkai Kogyo Inc.

3) Trade name of calcium carbonate treated with a surface active agent produced by Nitto Funka Kogyo Inc.

4) Trade name of silica produced by Nippon Silica Kogyo Inc.

099 'o 5) Zinc di-n-butyldithiocarbamate, a vulcanization oo accelerator produced by Sumitomo Chemical Co., Ltd.

QQo' 6) Tetramethylthiuram disulfide, a vulcanization Poo accelerator produced by Sumitomo Chemical Co., Ltd.

7) Dibenzothiazyl disulfide, a vulcanization accelerator produced by Sumitomo Chemical Co., Ltd.

-16- 0 r"t Pse;~ei~sr~ apsaaa~I II I F i' ,^1 f r e bn C C in C B CCC be C0 CC C3OD C C C C C C C C C C C C C C Cj C C ~i C Ci C C C C C C CCCS C C Table 2 Physical properties of vulcanized rubber No. Example Comparative Exaple -Example Agent 1 2 3 4 5 6 1 2 3 Hardness according to JIS-A 55 56 56 56 70 68 58 48 72 100% Tensile stress (kg/cm 2 14 14 14 14 23 23 10 10 27 2 200% Tensile stress (kg/cm 23 21 21 21 36 37 13 13 39 300% Tensile stress (kg/cm 2 29 27 29 28 47 52 18 18 48 Tensile strength (kg/cm 2 40 34 46 35 123 197 32 33 61 Elongation at break 400 380 440 390 720 750 430 420 480 Tear strength (kg/cm) 18.8 19.7 20.6 19.8 46.6 53.1 12.9 12.5 36.3

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i 0 0 a p1 0 0S 0 O 0 pP a p 4o P apt .0 app CO0 0 o Q aQ 0a 00 p Pa 00 0 0 4- i P 0 P 0 al 0 4 Ppo a a Table 3 No. Example Comparative Example Agent 7 8 9 10 4 5 6 7 Esprene® 505A 1 100 100 100 100 100 100 100 100 Zinc oxide 5 5 5 5 5 5 5 Stearic acid 3 3 3 3 3 3 3 3 Process oil 10 10 10 10 10 10 10 C-301 2) 150 150 C-3005 3) 150 150 Surface-treated C-301 150 150 Surface-treated C-3005 150 150 Vulcanization accelerator BZ 1.5 1.5 1.5 1.5 Vulcanization accelerator TRA 0.5 0.5 0.5 0.5 Vulcanization accelerator TT 0.5 0.5 0.5 0.5 Vulcanization accelerator M 1.5 1.5 1.5 1.5 Sulfur 1.5 1.5 1.5 1.5 Dicumyl peroxide 2.7 2.7 2.7 2.7 TAIC 4) 2.0 2.0 2.0 Total 273.5 272.7 273.5 272.7 273.5 272.2 273.5 272.7 Weight percentage of terpolymer to 0.99 0.99 0.99 0.99 surface-treated filler Calculated value of added amount 1.5 1.5 1.5 1.5 0 0 0 0 i~ ;i Note: Surface-treated aluminum hydroxide: a product treated with Bondine® HX8290 emulsion.

1) Trade name of an ethylene-propylene-nonconjugated diene copolymer rubber produced by Sumitomo Chemical Co., Ltd.

2) Aluminum hydroxide produced by Sumitomo Chemical Co., Ltd.

3) Aluminum hydroxide produced by Sumitomo Chemical Co., Ltd.

o 4) Triallyl isocyanulate produced by Nihon Kasei Inc.

0o o 4 4 St I9 4'i1 4 a 4 i4 44 4 *4 I i- 19 Ii 1 4 4 4 4 44 44 0 4G 4 4 44 444 Ott a 0 0 0 0 a 3 J o 44 4 4 444 4 4 o 444i 444 Table 4 Physical properties of vulcanized rubber (press-vulcanized at 160 0

C)

Vulcani- Example Comparative Example zation time 7 8 9 10 4 5 6 7 (min.) Hardness according to 15 67 72 68 68 65 70 65 66 JIS-A 25 68 72 68 68 66 70 66 66 300% Tensile stress 15 29 27 21 24 (kg/cm 2 25 31 30 23 26 Tensile strength 15 53 44 56 57 49 43 54 42 (kg/cm 2 25 54 45 66 53 46 42 43 47 Elongation at break 15 470 280 430 320 490 290 450 290 25 450 270 440 300 460 280 400 290 Tear strength 15 20.0 19.8 20.0 19.0 17.0 14.1 16.8 13.9 (kg/cm) 25 19.7 19.4 20.2 16.0 15.5 12.8 16.2 15.9 Volume resistivity 25 15 4.6 11 1.0 8.6 0.75 0.13 0.16 (n.cm x 101 Oxygen index 25 26.1 25.1 28.0 26.4 26.7 25.6 28.4 27.0 I ^-aws Yh Lr I L -ii

Claims (6)

1. Asurface-treated filler characterized by consisting of a powdery product of an inorganic compound, the surface of which has been treated so that at least a part of the surface of filler particles is covered with a terpolymer, said terpolymer comprising a repeating unit derived from ethylene, a repeating unit derived from at least one member selected from the group consisting of acrylates and methacrylates and a repeating unit derived from maleic anhydride.

2. A surface-treated filler according to Claim 1, wherein the powdery product of the inorganic compound is selected from the group consisting of silica, talc, calcium carbonate and aluminium hydroxide.

3. A surface-treated filler according to any one of l Claims 1 and 2, wherein the surface of the powdery product of the inorganic compound has been treated with at most ~15.0% by weight of the terpolymer.

4. A surface-treated filler according to any one of Claims 1 to 3, wherein the surface of the powdery product of the inorganic compound has been treated with 0.9 to

12.0% by weight of the terpolymer. A surface-treated filler according to any one of 41 Claims 1 to 4, wherein the surface of the powdery product of the inorganic compound has been treated with 0.99 to 11.1% by weight of the terpolymer. 6. A surface-treated filler according to any one of ;Claims 1 to 5, wherein the terpolymer consists of 50 to 95% i by weight of a repeating unit derived from ethylene, 4 to 49% by weight of a repeating unit derived L ,ij, anhydride. 7. A surface-treated filler according to any one of Claims 1 to 6, wherein the terpolymer is an ethylene- ethyl acrylate-maleic anhydride terpolymer. 8. A rubber composition characterized by com- prising a rubber and a surface-treated filler consisting of a powdery product of an inorganic compound of which 0surface has been treated with a terpolymer comprising o a repeating unit derived from ethylene, a repeating unit derived from at least one member selected from the Ca group consisting of acrylates and methacrylates and a Srepeating unit derived from maleic anhydride. 9. A rubber composition according to Claim 8, wherein the rubber is an ethylene-propylene-nonconjugated l ac diene terpolymer rubber. A rubber composition according to any one of S "Claims 8 and 9, wherein the weight ratio of the rubber to the surface-treated filler ranges from 100:30 to 100:300. 11. A rubber composition according to any one of Claims 8 to 10, wherein the weight ratio of the rubber to the surface-treated filler ranges from 100:40 to 100:200. 12. A rubber composition according to any one of Claims 8 to 11, wherein the weight ratio of the rubber f Claims 8; to 11, wherein the weight ratio of the rubber N i 22 S- 10 to the surface-treated filler ranges from 100:50 to 100:150.

13. A vulcanized rubber obtained by vulcanizing the rubber composition according to any one of Claims 8 to 12. DATED THIS 5TH DAY OF FEBRUARY 1991 SUMITOMO CHEMICAL COMPANY, LIMITED By its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent o c Attorneys of Australia o 0 o a 4 a noq 04 0 aO t2ii3 23 aL o2 J I 4