HIGHLY DISPERSIBLE SILICA FOR RUBBERS AND THE PROCESS FOR OBTAINING IT

• US 20120041128A1
• Filed: 10/11/2009
• Published: 02/16/2012
• Est. Priority Date: 10/06/2008
• Status: Abandoned Application

• Current Assignee: Dimona Silica Industries Ltd.
• Original Assignee: Dimona Silica Industries Ltd.
• Inventors: Kosso, Raisa Avgustovna
• Application Number:
  US12/998,278
• Publication Number:
  US 20120041128A1
• Time in Patent Office: Days
• US Class Current: 524/493
• CPC Class Codes: B60C 1/0016 Compositions of the tread
• CPC Class Codes: C01B 33/18 Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof preparation of aerogels by dehydrating gels C01B33/158; treatment to enhance the pigmenting or filling properties C09C
• CPC Class Codes: C01B 33/193 of aqueous solutions of silicates
• CPC Class Codes: C08K 3/36 Silica
• CPC Class Codes: C08K 5/548 containing sulfur C08K5/5477 takes precedence
• CPC Class Codes: C08L 21/00 Compositions of unspecified rubbers
• CPC Class Codes: C08L 2666/08 Homopolymers or copolymers according to C08L7/00 - C08L21/00; Derivatives thereof
• CPC Class Codes: C08L 9/00 Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• CPC Class Codes: C08L 9/06 Copolymers with styrene
• CPC Class Codes: Y02P 20/141 Feedstock

Abstract

The present invention relates to a precipitated silica for elastomers and, more particularly, to a new highly dispersible and highly reinforcing precipitated silica for elastomers. The invention further provides the process for its production and rubber products made therefrom.

Claims

1. A highly dispersible silica characterized by a D_A coefficient which ranges from 0.4 to 0.6, wherein D_A is calculated according to Formula I:

D_A=1−

(CDBP/DBP₀)  

 

Formula I

wherein

DBP₀ is the dibutyl phthalate absorption of a primary uncompressed sample of said silica, as measured according to ASTM D-2441 test; and

CDBP is the dibutyl phthalate absorption after compression of said silica, as measured according to ASTM D-3493 test, said test being modified to a pressure of 40 MPa.

2. The highly dispersible silica of claim 1, further characterized by one or more of the following properties:

a) A BET specific surface area ranging from about 130 to 200 m²/gram; and

/or

b) A CTAB specific surface area ranging from about 100 to 200 m²/gram; and

/or

c) a BET to CTAB ratio ranging from about 1 to about 1.15; and

/or

d) a DBP absorption of a primary uncompressed sample ranging from about 200 ml/100 grams to about 350 ml/100 grams; and

/or

e) a DBP absorption of a compressed silica sample ranging from about 100 ml/100 grams to about 220 ml/100 grams.

14. A reinforced elastomer comprising an elastomer and particles of the highly dispersible silica of claim 1.

15. The reinforced elastomer of claim 14, wherein said elastomer is selected from a styrene butadiene rubber, a soluble styrene butadiene rubber, a butadiene rubber, a natural rubber or their any mixture or combination thereof.

16. The reinforced elastomer of claim 14, characterized by at least one of the following properties:

a) a modulus 100% which is higher than 2.05 MPa;

b) a modulus 300% which is higher than 9 MPa;

c) a reinforcement index ((M₃₀₀−

M₁₀₀) G′

at 0.7%) which is over 23;

d) a rebound of tread rubber being higher than 31%; and

e) an elongation which is lower than 540%.

17. A tire tread comprising an elastomer and the highly dispersible silica of claim 1.

18. The tire tread of claim 17, having a rolling resistance which is smaller than 0.1 and/or an ice grip which is larger than 0.0009.

19. A rubber mixture comprising the highly dispersible silica of claim 1.

20. The rubber mixture of claim 19, for use in the manufacturing of a tire having a rolling resistance which is smaller than 0.1 and/or an ice grip which is larger than 0.0009, said rubber mixture comprising a rubber and a reinforcing filler comprising the highly dispersible silica characterized by a D_A coefficient which ranges from 0.4 to 0.6, wherein D_A is calculated according to Formula I:

D_A=1−

(CDBP/DBP₀)  

 

Formula I

wherein

DBP₀ is the dibutyl phthalate absorption of a primary uncompressed sample of said silica, as measured according to ASTM D-2441 test; and

CDBP is the dibutyl phthalate absorption after compression of said silica, as measured according to ASTM D-3493 test, said test being modified to a pressure of 40 MPa.

3. A process of producing highly dispersible silica, said process comprising:

(a) Preparing an initial diluted silicate solution in a reaction vessel by mixing an alkali silicate with water to obtain a mixture having an initial volume of 20% to 50% of the final precipitation volume, and heating said mixture under stirring; and

(b) Precipitating silica by simultaneously adding additional alkali silicate solution and an acidifying agent to said reaction vessel, such that the rate of addition of said additional silicate solution is regulated to be;

5 to 25% of the overall silicate volume added at a rate V₁,

25 to 40% of the overall silicate volume added at a rate V₂,

25 to 40% of the overall silicate volume added at a rate V₃, and

20 to 30% of the overall silicate volume added at a rate V₄,

such that V₁ is smaller than any one of V₂, V₃ and V₄ and at least two of V₁-V₄ are different than 0 liters/minute, thereby obtaining a highly dispersible silica suspension;

(c) filtering and/or washing said precipitated highly dispersible silica suspension, thereby obtaining a precipitated silica cake.

4. The process of claim 3, wherein said silica is characterized by a D_A coefficient which ranges from 0.4 to 0.6, wherein D_A is calculated according to formula I:

D_A=1−

(CDBP/DBP₀)  

 

Formula I

wherein DBP₀ is the dibutyl phthalate absorption of a primary uncompressed sample of said silica, as measured according to ASTM D-2441 test; and

CDBP is the dibutyl phthalate absorption after compression of said silica, as measured according to ASTM D-3493 test, said test being modified to a pressure of 40 MPa.

5. The process of claim 3, wherein V₁<

V₂ and V₃≦

V₄.

6. The process of claim 3, wherein said process further comprises drying and/or granulating said precipitated silica cake.

7. The process of claim 3, wherein said alkali silicate is sodium silicate.

8. The process of claim 3, wherein said acidifying agent is a carbonic acid.

9. The process of claim 8, wherein said carbonic acid is a carbon dioxide (CO₂) gas or a carbon dioxide air/gas mixture.

10. The process of claim 3, wherein an overall duration of silica precipitation is at least 75 minutes long.

11. The process of claim 3, further comprising, prior to said filtering and/or washing, aging said precipitated silica at a temperature which is at least 10°

C. to 20°

C. lower than the reaction temperature.

12. A system for the preparation of highly dispersible silica, said system comprising a reaction vessel to which, after insertion of an initial volume of silicate solution, additional diluted silicate solution is added simultaneously with an acidifying agent,

wherein the initial volume of said silicate solution ranges from 20% to 50% of the final volume of said solution;

further wherein the rate of addition of the initial 5% to 25% of the overall of silicate solution is conducted at a rate V₁ which is smaller than the rate of addition of the remaining silicate solution; and

further wherein the pH level in said vessel is maintained constant by regulating the addition rate of said acidifying agent.

13. The system of claim 12, wherein the highly dispersible silica prepared by said system is characterized by a D_A coefficient which ranges from 0.4 to 0.6, wherein D_A is calculated according to formula I:

D_A=1−

(CDBP/DBP₀)  

 

Formula I

wherein DBP₀ is the dibutyl phthalate absorption of a primary uncompressed sample of said silica, as measured according to ASTM D-2441 test; and

CDBP is the dibutyl phthalate absorption after compression of said silica, as measured according to ASTM D-3493 test, said test being modified to a pressure of 40 MPa.