JP2005048102A - Rubber composition containing modified calcium carbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer composition having an excellent mechanical property. <P>SOLUTION: The rubber composition is produced by combining to at least one sort of a 100 pts.wt. rubber component selected from a natural rubber and a diene-based rubber, (1) carbon black and/or silica and (2) a modified calcium carbonate having (i) a silica layer, (ii) an organic acid layer prepared by a treatment using at least one sort of agent selected from the group consisting of a fatty acid, fatty acid salt, fatty acid ester, resin acid, resinate and resin acid ester and (iii) a silane coupling agent layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition having excellent mechanical properties that can be used as a tire raw material. The present invention also relates to a tire obtained from the rubber composition.

  Conventionally, carbon black has been mainly used as a filler for tire rubber compositions. However, in order to meet the recent demand for fuel efficiency reduction in the automobile industry, a part of carbon black is replaced with a silica-based filler, especially silica, thereby reducing fuel consumption (reducing rolling resistance) and wet grip. It has been considered to improve the balance.

  However, a rubber composition using both carbon black and silica has a higher viscosity of (1) unvulcanized rubber and (2) self-aggregation of silica than a rubber composition containing only conventional carbon black. Since it is high, its dispersion is not easy, (3) the silica has a high Mohs hardness, and there is a problem that the wear of processing machines such as rubber kneaders and molding machines may become severe. Furthermore, the rubber composition using both carbon black and silica needs to use a large amount of an expensive silane coupling agent together with silica in order to develop tire characteristics comparable to a rubber composition containing only carbon black. There was also a problem in terms of cost.

  As means for solving such problems, attempts have been made to blend various fillers such as calcium carbonate into the polymer composition (Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, (See Patent Document 5, etc.).

  As is well known, calcium carbonate is widely used as a rubber extender, reinforcing agent, etc., and a rubber composition containing calcium carbonate has a low viscosity in an unvulcanized state, and a rubber containing silica. Compared to the composition, there is an advantage that the winding property on a roll or the like is good. Furthermore, since calcium carbonate has a weakly alkaline pH, the rubber composition containing calcium carbonate has an advantage that it does not inhibit vulcanization.

However, if calcium carbonate is used in a large amount for improving the properties of the rubber composition as it is, there is a problem that the mechanical properties of the rubber composition are deteriorated.
Japanese Patent Laid-Open No. 11-269307 JP 09-194634 A JP 09-077915 A JP 09-150606 A Japanese Patent Laid-Open No. 10-087896

  The main object of the present invention is to obtain a rubber composition having excellent unvulcanized rubber properties and vulcanized rubber properties.

  The inventor has intensively studied for the purpose of obtaining a rubber composition having excellent physical properties. As a result, a rubber composition in which a specific amount of carbon black and / or silica and modified calcium carbonate having a specific structure is blended with at least one rubber selected from natural rubber and diene-based synthetic rubber is desired. As a result, the present invention has been completed.

  That is, the present invention includes the following rubber composition and molded article.

Item 1. A rubber composition comprising the following components 1 and 2 with respect to 100 parts by weight of at least one rubber selected from natural rubber and diene-based synthetic rubber;
Component 1: 40 to 100 parts by weight of any one of (1) to (3) selected from the group consisting of (1) carbon black, (2) silica, and (3) a mixture of carbon black and silica,
Component 2: 0.5 parts by weight or more and less than 20 parts by weight of modified calcium carbonate having a silica layer and a silane coupling agent layer.

Item 2. A rubber composition comprising the following components 1 and 2 with respect to 100 parts by weight of at least one rubber selected from natural rubber and diene-based synthetic rubber;
Component 1: 40 to 100 parts by weight of any one of (1) to (3) selected from the group consisting of (1) carbon black, (2) silica, and (3) a mixture of carbon black and silica ,
Component 2: (i) Silica layer, (ii) Organic acid layer obtained by treatment with at least one selected from the group consisting of fatty acids, fatty acid salts, fatty acid esters, resin acids, resin acid salts and resin acid esters And (iii) 0.5 parts by weight or more and less than 20 parts by weight of the modified calcium carbonate having a silane coupling agent layer.

  Item 3. Item 1. The component 1 is (3) a mixture of carbon black and silica, and the mixing ratio of carbon black: silica is 0.5: 99.5 to 99.5: 0.5 by weight. Rubber composition.

Item 4. Item 1. The rubber composition according to any one of Items 1 and 2, wherein Component 1 is (2) silica and further contains the following Component 3;
Component 3: 0.1-30 weight% of silane coupling agent with respect to compounding quantity of silica.

Item 5. Item 1. The rubber composition according to any one of Items 1 to 3, wherein Component 1 is a mixture of (3) carbon black and silica, and further contains Component 3 below:
Component 3: 0.1-30 weight% of silane coupling agent with respect to compounding quantity of silica.

  Item 6. Item 6. A molded body obtainable by molding the rubber composition according to any one of Items 1 to 5.

  Hereinafter, the present invention will be specifically described. In the present specification, “%” and “part” represent “% by weight” and “part by weight” unless otherwise specified.

The rubber rubber, at least one rubber selected from natural rubber and diene-based synthetic rubber is used.

  The natural rubber is not particularly limited as long as it is a rubbery polymer obtained from natural plants and has a cis-1,4-polyisoprene structure in terms of chemical structure.

  As the diene synthetic rubber, a crosslinkable diene rubber can be used. Specific examples of the diene synthetic rubber include, for example, cis-1,4-polyisoprene, emulsion polymerization styrene butadiene copolymer, solution polymerization styrene butadiene copolymer, low cis-1,4-polybutadiene, and high cis. 1,4-polybutadiene, ethylene-propylene-diene copolymer, chloroprene, halogenated butyl rubber, acrylonitrile-butadiene rubber and the like.

  Among the rubbers mentioned above, natural rubber, cis-1,4-polyisoprene, emulsion polymerized styrene butadiene copolymer, solution polymerized styrene butadiene copolymer, low cis-1,4-polybutadiene, and high cis-1,4. -Polybutadiene is particularly preferably used.

  As the rubber, one kind selected from the above-mentioned natural rubber or diene-based synthetic rubber may be used alone, or two or more kinds may be mixed and used. The mixing ratio can be appropriately set according to required characteristics.

  Further, for the purpose of improving workability and the like, an oil-extended rubber obtained by previously blending an extender oil with the rubber may be used.

Ingredient 1:
Component 1 blended in the rubber composition of the present invention is either (1) carbon black alone, (2) silica alone, or (3) a mixture of carbon black and silica.

  The blending ratio of Component 1 with respect to the rubber composition is 40 to 100 parts by weight with respect to 100 parts by weight of rubber, and is appropriately adjusted in order to obtain desired physical properties.

  Hereinafter, the cases (1) to (3) will be described separately.

(1) Carbon black As the carbon black used in the present invention, those usually used for rubber reinforcement can be used.

Without limitation carbon BET specific surface area of the black, especially, in particular, preferably has a BET specific surface area of more than 70m ² / g by a nitrogen adsorption method, it is more preferably a ^{70~220m 2 / g, 70~200m 2 /} g Are more preferred.

  A carbon black having a BET specific surface area in the above range is particularly preferable in that the dispersibility of the carbon black is good and the reinforcing properties such as tensile properties, tear strength, and abrasion resistance are excellent.

  When component 1 is (1) carbon black alone, the compounding amount of carbon black is 40 to 100 parts by weight, preferably 40 to 90 parts by weight, and more preferably 40 to 80 parts by weight with respect to 100 parts by weight of rubber. .

  When the blending amount of the carbon black is within the above range, it is particularly preferable in that the workability is not deteriorated due to the increase in Mooney viscosity and the reinforcing properties such as wear resistance and tensile properties are excellent.

(2) Silica As silica used in the present invention, those usually used for rubber reinforcement can be used. Specific examples of silica include wet silica and dry silica.

Silica, BET specific surface area of more than 20 m ² / g by a nitrogen adsorption method, more preferably a 20 to 400 m ² / g, more preferably suitably used those 30~300m ² / g.

  A silica having a BET specific surface area in the above range is particularly preferable in terms of good dispersibility of silica and excellent reinforcing properties such as tensile properties, tear strength, and abrasion resistance.

  When component 1 is (2) silica alone, the amount of silica is 40 to 100 parts by weight, preferably about 40 to 90 parts by weight, per 100 parts by weight of rubber.

  When the blending amount of silica is within the above range, it is preferable in that the workability does not decrease due to an increase in Mooney viscosity and the reinforcing properties such as wear resistance and tensile properties are excellent.

(3) Mixture of carbon black and silica (3) As a mixture of carbon black and silica used in the present invention, a mixture of (1) carbon black and (2) silica according to a known method is used. .

  When Component 1 is a mixture of (3) carbon black and silica, the mixing ratio of carbon black and silica is 0.5: 99.5 to 99.5: 0.5, preferably 10:90 in weight ratio. -90: 10, More preferably, it is 30: 70-70: 30.

  When Component 1 is a mixture of (3) carbon black and silica, the amount of the mixture is 40 to 100 parts by weight, preferably about 40 to 90 parts by weight, per 100 parts by weight of rubber.

  When the blending amount of the mixture of carbon black and silica is within the above range, it is preferable in that the workability does not deteriorate due to an increase in Mooney viscosity and the reinforcing properties such as wear resistance and tensile properties are excellent.

Ingredient 2:
Modified calcium carbonate Modified calcium carbonate is blended as component 2 in the rubber composition of the present invention.

The modified calcium carbonate in the present invention is a modified calcium carbonate obtained by adding two layers of a silica layer and a silane coupling agent layer to calcium carbonate as a raw material, or silica layer, fatty acid, fatty acid salt, fatty acid ester, resin It is a modified calcium carbonate provided with three layers of an organic acid layer and a silane coupling agent layer obtained by treatment with at least one selected from the group consisting of acids, resin acid salts and resin acid esters.
In the present invention, “layer” means calcium carbonate or partially modified calcium carbonate (that is, modified calcium carbonate having one or two of a silica layer, a silane coupling agent layer, and an organic acid layer). As long as it has a structure that covers all or a part of the surface, there is no particular limitation, and it is not always necessary to continuously cover the entire surface.
In the modified calcium carbonate of the present invention, the structure of the surface layer is (1) a portion in which the silica layer, the organic acid layer, and the silane coupling agent layer are laminated in this order, and (2) the silica layer and the silane coupling agent layer in this order. The part which laminated | stacked the part which laminated | stacked in order of (3) a silica layer and an organic acid layer, and the part which (4) silica layer, the organic acid layer, and the silane coupling agent layer existed individually (in single layer) were mixed. It is estimated that it contains.

  The thickness of the layer is not particularly limited, and the thickness of each layer can be appropriately adjusted for the purpose of obtaining desired physical properties.

-Raw material calcium carbonate In this invention, there is no restriction | limiting in particular in the kind of calcium carbonate used as a raw material, A well-known heavy calcium carbonate, synthetic | combination (precipitation) calcium carbonate, etc. can be used.

  Heavy calcium carbonate raw materials are known to use naturally produced calcium carbonate, such as roller mill, high-speed rotary mill (impact shear mill), container drive medium mill (ball mill), medium stirring mill, planetary ball mill, jet mill, etc. It can be prepared by grinding by a dry or wet grinding method.

  Synthetic (precipitating) calcium carbonate can be obtained according to a known method such as lime milk-carbon dioxide reaction method, calcium chloride-soda ash reaction method, lime milk-soda ash reaction method. An example of the lime milk-carbon dioxide reaction method is as follows: raw limestone is burned with coke or petroleum fuel (heavy oil or light oil), natural gas, LPG, etc. to obtain quick lime, which is hydrated and hydroxylated. Calcium carbonate can be produced by bubbling and reacting carbon dioxide gas generated during combustion with calcium slurry. By setting the conditions for the carbon dioxide reaction, desired submicron order fine particles can be obtained. In addition to this, a zinc salt that can be converted into zinc hydroxide by hydrolysis is added to the calcium hydroxide slurry, and at the same time, carbon dioxide gas is bubbled and reacted, so that calcium carbonate finer than the above calcium carbonate is added. A manufacturing method can also be applied (Japanese Patent No. 401044).

Although the BET specific surface area of the raw material calcium carbonate in the present invention is not particularly limited, it is usually about 5 to 120 m ² / g. A more preferable range is about 20 to 110 m ² / g, and a further preferable range is about 50 to 100 m ² / g.

  Here, the BET specific surface area can be calculated by detecting the amount of nitrogen gas adsorbed on calcium carbonate based on the gas adsorption method.

  When the BET specific surface area of raw material calcium carbonate is too large, it is necessary to increase the amount of fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt or resin acid ester used. Since the fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt and resin acid ester also have a function as a softening agent, the reinforcing effect on rubber may be impaired. On the other hand, if the BET specific surface area of calcium carbonate as a raw material is too small, the effect of refining the filler particles is reduced, and the reinforcing effect when blended with rubber may be reduced.

  The particle diameter of the raw material calcium carbonate in the present invention is not particularly limited as long as a desired effect is obtained, and can be appropriately selected from a wide range.

  However, generally, when observed with a scanning electron microscope, the primary particle size of the raw material calcium carbonate particles is preferably about 0.01 to 0.5 μm, preferably about 0.02 to 0.4 μm. More preferably.

-Silica layer In this invention, a silica layer is a layer obtained by processing with a silica hydrosol.

  As the silica hydrosol used in the present invention, one produced according to a known method can be used. For example, silica hydrosol obtained by an acid decomposition method can be used. Amorphous silica formed by adding inorganic acid such as hydrochloric acid and sulfuric acid, aluminum sulfate, organic acid such as acetic acid and acrylic acid, and other acidic substances such as carbon dioxide and sulfurous acid to sodium silicate solution Hydrosols can be used. Alternatively, a silica hydrosol produced by a dialysis method in which sodium silicate is produced through a semipermeable membrane can be used. Moreover, the silica hydrosol produced | generated by the ion exchange method using an ion exchange resin can also be used.

As a method of treating calcium carbonate with silica hydrosol, for example, an active silica hydrolyzate formed by adding an aqueous solution of sodium silicate having an appropriate concentration to a calcium carbonate slurry and dropping an acidic substance such as an inorganic acid or an organic acid while stirring. A method of treating the surface of calcium carbonate with a sol can be mentioned.
When a silica hydrosol prepared in advance is used, it can be treated by adding the silica hydrosol to the calcium carbonate slurry and stirring vigorously.

  As the calcium carbonate slurry, one having a solid concentration of 0.5 to 20%, preferably about 1 to 15% is used. The concentration of the sodium silicate aqueous solution is about 1 to 40%. The ratio of the sodium silicate concentration to the solid content concentration of the calcium carbonate slurry is about 11.3% to 200%.

Silica in the silica hydrosol basically adheres to calcium carbonate almost quantitatively.
The amount of silica hydrosol used in the present invention attached to calcium carbonate is not particularly limited, but the amount of silica obtained by silica hydrosol attached to calcium carbonate is solid relative to 100 parts by weight of calcium carbonate as a raw material. In terms of minutes, it is usually about 0.5 to 15 parts by weight, more preferably about 1 to 12 parts by weight, and still more preferably about 2 to 10 parts by weight. The amount of adhesion is appropriately adjusted according to the BET specific surface area of calcium carbonate to be adhered.

  When the amount of silica with respect to calcium carbonate is too small, the reaction site sufficient to bind a silane coupling agent to be described later decreases, so that there is a possibility that desired rubber physical properties cannot be expressed. On the other hand, if the amount of silica is too large, excess silica hydrosol will be present in the solution in addition to adhering to the calcium carbonate surface, so the silica hydrosol will strongly agglomerate and solidify the calcium carbonate during drying. , Coarse particles that are difficult to grind increase. The calcium carbonate filler containing such coarse particles may reduce the tear strength, flex crack resistance, etc. of the polymer.

Organic acid layer In the present invention, the organic acid layer is a layer obtained by treating with at least one selected from the group consisting of fatty acids, fatty acid salts, fatty acid esters, resin acids, resin acid salts and resin acid esters. is there.

The fatty acid used in the present invention includes saturated or unsaturated fatty acids having about 6 to 24 carbon atoms, particularly 10 to 20 carbon atoms.
Examples of saturated or unsaturated fatty acids having about 6 to 24 carbon atoms include stearic acid, palmitic acid, lauric acid, behenic acid, oleic acid, erucic acid, linoleic acid, and the like. In particular, stearic acid, palmitic acid, lauric acid, and oleic acid are preferable. You may use these in mixture of 2 or more types.

  Examples of the fatty acid salt include alkali metal salts such as sodium salts and potassium salts of saturated or unsaturated fatty acids having about 6 to 24 carbon atoms, particularly 10 to 20 carbon atoms.

  Examples of the fatty acid ester include saturated fatty acids having about 6 to 24 carbon atoms, especially 10 to 20 carbon atoms, and alcohols having about 6 to 18 carbon atoms, especially saturated fats having 10 to 18 carbon atoms. An ester with a group alcohol.

Examples of the treatment method using fatty acids, fatty acid salts and / or fatty acid esters include the following methods.
First, the fatty acid is saponified while being heated in an alkali metal aqueous solution such as NaOH aqueous solution or KOH aqueous solution (to form a metal salt such as Na salt or K salt) to form a solution. The amount of the aqueous alkali metal solution is not particularly limited as long as it is an amount necessary for saponification of fatty acid. The concentration of the aqueous alkali metal solution is about 1 to 40%, preferably about 1 to 20%.
Next, the calcium carbonate aqueous suspension on which the silica layer is formed is heated in advance to 30 to 50 ° C., and the above-mentioned solution-like fatty acid soap is added to the suspension, and the mixture is stirred and mixed. Then, an organic acid layer containing a fatty acid and / or a fatty acid salt is formed. In the case where soap such as fatty acid Na is used as it is, an aqueous solution heated in advance is prepared and treated in the same manner as described above. The addition ratio of the fatty acid soap to the aqueous suspension of calcium carbonate is about 10 to 70%, preferably about 10 to 50%.

  Moreover, it can also process using a fatty acid, without saponifying. For example, the organic carbonate layer containing a fatty acid is obtained by stirring the calcium carbonate in which the silica layer is formed in a powder state while heating it to a temperature equal to or higher than the melting point of the fatty acid, adding the fatty acid thereto, stirring and mixing. Can be formed.

Examples of the resin acids used in the present invention include abietic acids such as abietic acid, dehydroabietic acid and dihydroabietic acid or polymers thereof, disproportionated rosin, hydrogenated rosin, polymerized rosin, and salts thereof (for example, alkali Metal salts, alkaline earth metal salts) or esters (for example, rosin pentaerythritol ester, glycerol ester, hydrogenated rosin methyl ester, triethylene glycol ester, pentaerythritol ester). Among these, abietic acid and dehydroabietic acid are preferable.
As a treatment method using a resin acid, a resin acid salt and / or a resin acid ester, the same method as that for a fatty acid, a fatty acid salt and / or a fatty acid ester can be employed. Specifically, the resin acid is saponified (made into a metal salt such as Na salt or K salt) while heating in an alkali metal aqueous solution such as NaOH aqueous solution or KOH aqueous solution to form a solution. The amount of the alkali metal aqueous solution is not particularly limited as long as there is an amount necessary for saponification of the resin acid. The concentration of the aqueous alkali metal solution is about 1 to 40%, preferably about 1 to 20%.
Next, the aqueous suspension of calcium carbonate on which the silica layer is formed is heated to 30 to 50 ° C. in advance, and the solution-like resin acid soap is added to the suspension and stirred to mix. Then, an organic acid layer containing a resin acid and / or a resin acid salt is formed. The ratio of the resin acid soap to the aqueous calcium carbonate suspension is about 10 to 70%, preferably about 10 to 50%.

  In the case of using soap such as resin acid Na as it is, an aqueous solution of resin acid soap heated in advance is prepared and treated in the same manner as described above. Further, the treatment can be performed using the resin acid without saponification. For example, the calcium carbonate in which the silica layer is formed is stirred in a powder state while heating to a temperature higher than the melting point of the resin acid, and the resin acid is added to this, and the mixture is stirred and mixed. An acid layer can be formed.

  The amount of the organic acid layer, that is, the amount of at least one selected from the group consisting of fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt and resin acid ester is not particularly limited, The amount is usually about 0.5 to 20 parts by weight per 100 parts by weight of calcium carbonate. More preferably, it is about 1-15 weight part, More preferably, it is about 2-12 weight part.

-Silane coupling agent layer The silane coupling agent layer in this invention is a layer obtained by processing with a silane coupling agent.

  Examples of the silane coupling agent used in the present invention include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxy. Silane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltrimethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacrylic Roxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylme Rudimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, bis- (3- [triethoxysilyl] -propyl) -tetrasulfane (TESPT), bis -(3- [Triethoxysilyl] -propyl) -disulphane and the like can be mentioned.

  In particular, γ- (2-aminoethyl) aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, bis- ( 3- [Triethoxysilyl] -propyl) -tetrasulfane, bis- (3- [triethoxysilyl] -propyl) -disulfane are preferably used.

  In the present invention, the method for treating calcium carbonate using a silane coupling agent is not particularly limited, and various conventionally known surface treatment methods can be applied.

  When the calcium carbonate having a silica layer and an organic acid layer is a dry powder, for example, while stirring the calcium carbonate powder in a mixer, a silane coupling agent is dropped or sprayed using a spray or the like. A method of applying a silane coupling agent to the surface of calcium carbonate can be applied. In this case, you may heat-dry after surface treatment as needed.

  When calcium carbonate having a silica layer and an organic acid layer is obtained in a suspension state, a water-soluble silane coupling agent is added to the suspension, and the silane coupling agent is applied to the surface of the calcium carbonate. Surface treatment is carried out by adsorption, and then the treated product is filtered off and dried, whereby modified calcium carbonate treated with a silane coupling agent can be produced. In addition, when calcium carbonate having a silica layer and an organic acid layer formed on the surface or calcium carbonate treated with a silane coupling agent is a suspension, a stirrer or A wet grinding machine such as a bead mill or a sand mill may be used.

  The adhesion amount of the silane coupling agent that constitutes the silane coupling agent layer is not particularly limited, but is usually about 0.05 to 10 parts by weight, preferably 0, with respect to 100 parts by weight of calcium carbonate as a raw material. About 0.05 to 5 parts by weight, more preferably about 0.1 to 3 parts by weight. The amount of adhesion is appropriately adjusted according to the BET specific surface area of calcium carbonate to be adhered.

-Modified calcium carbonate Of the modified calcium carbonate of the present invention, the modified calcium carbonate having a silica layer and a silane coupling agent layer is obtained by using the above-described silica hydrosol on the raw calcium carbonate or treated calcium carbonate. It can manufacture by performing a process and the process by a silane coupling agent.

  Moreover, it has the organic acid layer and silane coupling agent layer which are obtained by processing with at least 1 sort (s) chosen from the group which consists of a silica layer, a fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt, and resin acid ester. The modified calcium carbonate can be produced by subjecting calcium carbonate as a raw material or treated calcium carbonate to the above-described treatment with silica hydrosol, treatment with an organic acid, and treatment with a silane coupling agent.

  The method for producing the modified calcium carbonate of the present invention will be specifically described. For example, the modified calcium carbonate having three layers of a silica layer, an organic acid layer, and a silane coupling agent layer has the following steps. Can be manufactured.

  (1) A step of forming a silica layer on the surface of calcium carbonate by adding silica hydrosol to the calcium carbonate slurry, (2) fatty acid, fatty acid salt, fatty acid ester in the calcium carbonate slurry provided with this silica layer A step of forming an organic acid layer by adding at least one selected from the group consisting of a resin acid, a resin acid salt, and a resin acid ester; (3) dehydrating the calcium carbonate slurry formed with the silica layer and the organic acid layer And (4) a method comprising a step of forming a silane coupling agent layer by surface-treating the obtained calcium carbonate particles with a silane coupling agent. By this method, a modified calcium carbonate having (i) a silica layer, (ii) an organic acid layer, and (iii) a silane coupling agent layer on the surface of calcium carbonate particles as a raw material can be obtained.

  The modified calcium carbonate having (i) a silica layer, (ii) an organic acid layer, and (iii) a silane coupling agent layer comprises: (i) a silica layer and (ii) fatty acid, fatty acid salt, fatty acid ester, resin A calcium carbonate having an organic acid layer composed of at least one selected from the group consisting of an acid, a resin acid salt and a resin acid ester, and a silane coupling agent, for example, a silane coupling agent blended as component 3, are separately rubber. It can also be produced in a rubber composition by blending into the composition and kneading.

  For example, by adding partially modified calcium carbonate having (i) a silica layer and (ii) an organic acid layer to the rubber, and further adding a silane coupling agent as component 3 to the rubber, and then mixing the rubber, Examples of the composition include a method for producing a modified calcium carbonate having (i) a silica layer, (ii) an organic acid layer, and (iii) a silane coupling agent layer. Alternatively, by adding the silane coupling agent of component 3 to the rubber and then adding the partially modified calcium carbonate having (i) silica layer and (ii) organic acid layer to the rubber, and then mixing them, the rubber composition Examples thereof include a method for producing a modified calcium carbonate having (i) a silica layer, (ii) an organic acid layer, and (iii) a silane coupling agent layer.

  As described above, when (i) the partially modified calcium carbonate having the silica layer and (ii) the organic acid layer and the silane coupling agent are added separately to the polymer, they are added after mixing each other. Thus, the silane coupling agent is adsorbed on the surface of the partially modified calcium carbonate having (i) the silica layer and (ii) the organic acid layer, and (i) the silica layer, (ii) the organic acid layer, and (iii) ) Modified calcium carbonate having three silane coupling agent layers will be formed in the rubber composition.

  When (i) a modified calcium carbonate having a silica layer and (ii) an organic acid layer and a silane coupling agent are separately added to the rubber composition, (i) a silica layer, (ii) an organic acid layer and (Iii) The amount of the silane coupling agent that forms the modified calcium carbonate having a silane coupling agent layer is about 0.05 to 10 parts by weight, preferably about 0.07 to 5 parts by weight, with respect to 100 parts by weight of the raw material calcium carbonate. More preferably, it is about 0.1 to 3 parts by weight.

The BET specific surface area of the modified calcium carbonate in the present invention is not particularly limited, but is usually about 4 to 110 m ² / g. A more preferable range is about 15 to 100 m ² / g, and a further preferable range is about 40 to 90 m ² / g.

  The BET specific surface area can be calculated by detecting the amount of nitrogen gas adsorbed on calcium carbonate based on the gas adsorption method.

  If the BET specific surface area of the modified calcium carbonate is too large, the reinforcing effect on rubber may be impaired. On the other hand, if the BET specific surface area of the modified calcium carbonate is too small, the effect of refining the filler particles is reduced, and the reinforcing effect when blended with rubber may be reduced.

  The particle diameter of the modified calcium carbonate in the present invention can be set as appropriate for the purpose of obtaining a desired effect.

  However, in general, when observed with a scanning electron microscope, the size of the modified calcium carbonate particles is preferably about 0.01 to 0.6 μm of the primary particle diameter, and about 0.02 to 0.5 μm. It is more preferable that

Ingredient 3:
Silane Coupling Agent In the present invention, when silica is blended as component 1, it is preferable to blend a rubber composition with a silane coupling agent as component 3 in combination with silica. When molding a product that requires high-grade physical properties such as a tire using a rubber composition, a composition in which silica is blended with rubber does not have a strength comparable to that of a rubber composition blended with carbon black. The disadvantage is that compression set and permanent elongation are inferior.

  When combined with silica and a silane coupling agent, the modulus and wear resistance of the rubber composition are improved to be comparable to the rubber composition containing carbon black, and rolling resistance when the rubber composition is molded into a tire. , Grip performance is improved.

  The form of the silane coupling agent is not particularly limited, and may be in the form of a liquid single substance having a purity of 100%, or in the form of a composition impregnated with a powder such as carbon black, calcium carbonate, or silica. It is good.

  When a silane coupling agent is blended as Component 3, the blending amount of the silane coupling agent is 0.1 to 30% by weight, preferably 1 to 20% by weight, more preferably 3 to 3%, based on the blending amount of silica. 10% by weight.

The compounding amount of silica means the total amount of component 1 when component 1 is only silica, and the amount corresponding to the mixing ratio of silica in component 1 when component 1 is a mixture of carbon black and silica. .

Rubber composition The rubber composition of the present invention uses, as the rubber component, carbon black and / or silica as component 1, modified calcium carbonate as component 2, and silica or silica mixture as component 1. It can be obtained by blending the silane coupling agent as component 3.

  As specific embodiments, the following can be considered.

Aspect 1: Example of rubber composition comprising 100 to 100 parts by weight of rubber, Component 1: 40 to 100 parts by weight of carbon black, Component 2: 0.5 to 18 parts by weight of modified calcium carbonate Rubber composition of the present invention As a first aspect of the product, carbon black is used as component 1 and (2) (i) a silica layer as component 2 with respect to 100 parts by weight of at least one rubber component selected from natural rubber and diene synthetic rubber. (Ii) an organic acid layer obtained by treating with at least one selected from the group consisting of fatty fatty acids, fatty acid salts, fatty acid esters, resin acids, resin acid salts and resin acid esters, and (iii) silane coupling agents The composition which mix | blended the modified calcium carbonate which has a layer is mentioned.

  The rubber composition of the first aspect can be produced by blending carbon black and modified calcium carbonate with at least one rubber selected from natural rubber and diene synthetic rubber, and then kneading. .

  The order of addition (compounding) of carbon black and modified calcium carbonate is not particularly specified, modified carbon carbonate may be blended after blending carbon black, and carbon black is blended after blending modified calcium carbonate. Alternatively, carbon black and modified calcium carbonate may be blended at the same time.

  The compounding amount of carbon black in the first embodiment is about 40 to 100 parts by weight, preferably 40 to 90 parts by weight, and more preferably 40 to 80 parts by weight with respect to 100 parts by weight of the rubber component. The amount of the modified calcium carbonate is about 0.5 to 18 parts by weight, preferably about 1 to 18 parts by weight, and more preferably about 3 to 15 parts by weight with respect to 100 parts by weight of the rubber component. .

  In the first aspect, when the blending amount of carbon black and modified calcium carbonate is within the above range, permanent elongation and bending resistance are maintained while maintaining the processability of the rubber composition and the mechanical properties as the rubber composition. A particularly excellent effect is exhibited in that the cracking property and Mooney scorch time can be improved.

Aspect 2: Component 100: Silica 40-80 parts by weight, Component 2: Modified calcium carbonate 0.5-15 parts by weight, Component 3: Silica coupling agent 0 with respect to 100 parts by weight of rubber Example of rubber composition containing 1 to 30% by weight As a second embodiment of the rubber composition of the present invention, 100 parts by weight of at least one rubber selected from natural rubber and diene synthetic rubber is used. By treating with at least one selected from the group consisting of silica as component 1, (i) silica layer, (ii) fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt and resin acid ester as component 2 Examples thereof include an organic acid layer obtained, (iii) modified calcium carbonate having a silane coupling agent layer, and a composition containing a silane coupling agent as component 3.

  The rubber composition of the second aspect can be produced as follows.

  For example, after blending silica and a silane coupling agent into at least one rubber selected from natural rubber and diene-based synthetic rubber, (i) silica layer, (ii) fatty acid, fatty acid salt, fatty acid ester, resin acid, Compounding an organic acid layer obtained by treating with at least one selected from the group consisting of a resin acid salt and a resin acid ester, and (iii) a modified calcium carbonate having a silane coupling agent layer, and then kneading. Can be manufactured.

  Moreover, it obtains by processing with at least 1 sort (s) chosen from the group which consists of (i) silica layer, (ii) fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt, and resin acid ester as follows. It can also be produced using calcium carbonate having two organic acid layers.

  For example, after blending silica and a silane coupling agent into at least one rubber selected from natural rubber and diene-based synthetic rubber, (i) silica layer, (ii) fatty acid, fatty acid salt, fatty acid ester, resin acid, It can manufacture by mix | blending the modified calcium carbonate which has an organic acid layer obtained by processing by at least 1 sort (s) chosen from the group which consists of a resin acid salt and resin acid ester, and then knead | mixing.

  In addition, at least one rubber selected from natural rubber and diene-based synthetic rubber includes silica, and (i) silica layer, (ii) fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt, and resin acid ester. It can manufacture by mix | blending the silane coupling agent after mix | blending the modified calcium carbonate which has an organic acid layer obtained by processing by at least 1 sort (s) chosen from the group which consists of, and then knead | mixing.

  As described above, when (i) the modified calcium carbonate having the silica layer and (ii) the organic acid layer and the silane coupling agent are separately added to the rubber, they should be mixed after adding each. The silane coupling agent is adsorbed on the surface of the partially modified calcium carbonate having (i) a silica layer and (ii) an organic acid layer, and (i) a silica layer, (ii) an organic acid layer, and (iii) A modified calcium carbonate having three silane coupling agent layers is formed, and a rubber composition containing the modified calcium carbonate is produced.

  The compounding amount of silica in the second embodiment is about 40 to 80 parts by weight, preferably 40 to 70 parts by weight with respect to 100 parts by weight of the rubber component, and the compounding amount of the modified calcium carbonate is 100 parts by weight of the rubber component. It is about 0.5-15 weight part with respect to a weight part, Preferably it is about 1-15 weight part, More preferably, it is about 3-15 weight part. The amount of the silane coupling agent is about 0.1 to 30% by weight, preferably about 1 to 20% by weight, and more preferably about 3 to 10% by weight with respect to the amount of silica.

  (I) Two layers having an organic acid layer obtained by treating with at least one selected from the group consisting of a silica layer, (ii) fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt and resin acid ester When the modified calcium carbonate is added to rubber and the silane coupling agent of component 3 is used to form a three-layer modified calcium carbonate, the blending amount of the silane coupling agent is based on the blending amount of silica, Preferably it is about 0.1-35 weight%, More preferably, it is about 0.1-33 weight%.

  In the second embodiment, when the blending amounts of silica, silane coupling agent and modified calcium carbonate are in the above range, the rubber composition is obtained without impairing the processability of the rubber composition and the mechanical properties as the rubber composition. It has particularly excellent effects in that it can improve physical properties of unvulcanized rubber such as Mooney scorch time of the product, and can further improve tear strength and permanent elongation.

  You may add a well-known compounding agent to the rubber composition of this invention as needed. For example, other fillers such as silica, clay and aluminum hydroxide can be used in combination as appropriate. Furthermore, process oils such as naphthenic oil, paraffin oil and aroma oil, antioxidants, anti-aging agents, activators, additives such as stearic acid, zinc oxide and wax, vulcanizing agents such as sulfur and vulcanization accelerators, etc. Can also be blended as desired.

  The rubber composition of the present invention is produced by kneading, heating, extruding, etc., rubber, carbon black or silica, modified calcium carbonate, silane coupling agent, and other compounding agents selected as necessary. it can.

  The kneading conditions are not particularly limited, and various conditions such as the input volume to the kneading apparatus, the rotational speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading apparatus, and the like depending on the purpose. It can be selected as appropriate. The kneading apparatus is not particularly limited, and either a closed type or an open type can be used. For example, a known kneading apparatus that is usually used for kneading a rubber composition, specifically, a Banbury mixer (registered trademark) ), Intermix (registered trademark), kneader, roll and the like.

  There are no particular limitations on the heating conditions, and various conditions such as the heating temperature, the heating time, and the heating apparatus can be appropriately selected according to the purpose. As a heating apparatus, the roll machine etc. which are normally used for the heating of a rubber composition are mentioned, for example.

  Extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion apparatus, and extrusion temperature can be appropriately selected according to the purpose. As an extrusion apparatus, the extruder etc. which are normally used for extrusion of a rubber composition are mentioned, for example. The extrusion temperature can be determined as appropriate.

  The rubber composition of the present invention is suitably used in various fields such as industrial materials, OA equipment field, automobile field and the like.

  In particular, since it is excellent in processability and reinforcing properties, it can be suitably used as a tread rubber composition for tires.

Molded body The molded body of the present invention can be obtained by molding the rubber composition by any of various known molding methods.

  Examples of the molding method used in the present invention include calendar processing, extrusion processing, and raw manufacturing.

  Further, after the above molding, a vulcanized rubber molded body can be obtained by methods such as mold molding vulcanization, plate vulcanization, direct / indirect steam vulcanization, and high-frequency heating continuous vulcanization. There are no particular limitations on the vulcanizing apparatus, system, conditions, etc., and they can be selected appropriately according to the purpose. For example, as a device for performing vulcanization, a molding vulcanizer using a mold usually used for vulcanizing a rubber composition for a tire can be used. Further, as a vulcanization condition, the vulcanization temperature is usually 100 to 190 ° C.

  The molded article of the present invention is excellent in terms of storage stability (Mooney scorch time), improvement in flex crack resistance, improvement in tear strength, and the like because the specific component is blended in a specific ratio. It is effective and can be usefully used as a tire tread, sidewall, industrial belt, or the like.

  The rubber composition of the present invention has excellent effects in both physical properties of unvulcanized rubber and physical properties of vulcanized rubber.

  A rubber composition containing a combination of carbon black and modified calcium carbonate is particularly effective in that it can improve the flex crack resistance of the vulcanized rubber properties without impairing the storage stability of the unvulcanized rubber. Have

  In addition, a composition containing a combination of silica and a silane coupling agent and modified calcium carbonate improves the storage stability of unvulcanized rubber without impairing the mechanical strength of a rubber composition containing only silica. It has a particularly excellent effect in that it is remarkably improved.

  The rubber composition of the present invention has such excellent properties and can be usefully used for various applications.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these Examples.

Examples 1-2 and Comparative Examples 1-4
Using a pressure kneader and an 8-inch two-roll, the samples shown in Table 1 or Table 2 were mixed in the prescribed proportions in Table 1 or Table 2, respectively, and Examples 1 to 2 and Comparative Examples 1 to 4 were mixed. A rubber composition was obtained. These rubber compositions were subjected to press vulcanization based on the optimum vulcanization time tc (90) calculated by a vulcanization degree tester (manufactured by JSR, Cura Toast, test temperature 160 ° C.), and the thickness was 2 mm. The rubber sheet and the test piece described in the evaluation method described later were prepared.

  In Examples 1-2 and Comparative Examples 1-4, the following were used as components.

  Oil-extended SBR: JSR 1778N (23.5% bound styrene, 100 parts by weight of styrene butadiene rubber with 37.5 phr of extended oil), manufactured by JSR Corporation.

  Carbon black: Asahi # 80, ISAF, manufactured by Asahi Carbon Co., Ltd.

  Silica: White carbon, Nipsil AQ, manufactured by Nippon Silica Industry Co., Ltd.

-Modified calcium carbonate: The modified calcium carbonate is composed of (i) silica layer, (ii) fatty acid, fatty acid salt, fatty acid ester, resin acid, resin acid salt and resin acid ester prepared by the following method. A modified calcium carbonate having an organic acid layer obtained by treatment with at least one selected from the group and (iii) a silane coupling agent layer was used.
A synthetic calcium carbonate slurry having a BET specific surface area of 75 m ² / g was heated to 40 ° C. with good stirring. To 100 parts by weight of the synthetic calcium carbonate in the slurry, 7 parts by weight of an aqueous solution of sodium silicate (sodium silicate (193-08185) manufactured by Wako Pure Chemical Industries, Ltd.)) diluted 10 times with water at room temperature was added. A dilute aqueous hydrochloric acid solution was introduced in an amount necessary for neutralizing sodium silicate to form a silica layer on the calcium carbonate surface. Next, sodium hydroxide was added, and the mixture was saponified by heating and stirring at 90 ° C. (fatty acid mixture containing oleic acid, stearic acid, palmitic acid, etc. (manufactured by Wako Pure Chemical Industries, oleic acid (159-00246)) 5 parts by weight of stearic acid (199-10995) and palmitic acid (165-00102)) are added, followed by dehydration, drying and grinding to obtain a calcium carbonate powder (calcium carbonate A) having a silica layer and a fatty acid layer. It was.
While stirring the obtained calcium carbonate A with a mixer, 2.0 parts by weight of bis- (3- [triethoxysilyl] -propyl) -tetrasulfane (manufactured by Degussa) with respect to 100 parts by weight of the calcium carbonate A , Si69) was sprayed, and the mixture was further stirred for 10 minutes, and then heated and dried at 100 ° C. for 60 minutes to obtain a modified calcium carbonate having three layers of a silica layer, an organic acid layer, and a silane coupling agent layer. .

  Silane coupling agent: bis- (3- [triethoxysilyl] -propyl) tetrasulfane, Si69, manufactured by Degussa.

  -Zinc oxide: Zodo Chemical, two types of zinc oxide.

  -Stearic acid: Lunac S-50 made by Kao.

  -Naphthenic oil: NP-24, Idemitsu Kosan Co., Ltd.

  Anti-aging agent: NOCRACK 224, manufactured by Ouchi Shinsei Chemical Co., Ltd.

  ・ Vulcanization accelerator 1: Noxeller D, manufactured by Ouchi Shinsei Chemical Co., Ltd.

  -Vulcanization accelerator 2: Noxeller CZ, manufactured by Ouchi Shinsei Chemical Co., Ltd.

  ・ Sulfur: Made by Hosoi Chemical, powdered sulfur.

About the rubber sheet obtained from the rubber composition of Evaluation Examples 1-2 and Comparative Examples 1-4, Mooney scorch time was investigated as an unvulcanized rubber physical property. Further, as physical properties of vulcanized rubber, tests on tensile test, tear test, hardness, permanent elongation, and bending crack resistance were performed.

1. Mooney scorch time
In accordance with the method defined in JIS K 6300, measurement was performed using a Mooney viscometer manufactured by Shimadzu Corporation. The test temperature was 125 ° C., the measurement was started 1 minute after the preheating, and the time until the torque was increased by 5 points was measured.

2. Tensile test (modulus, tensile strength)
According to the method defined in JIS K 6251, the following test items at 23 ° C. were measured using a shopper tensile strength tester.

300% modulus: Tensile strength at 300% elongation Tensile strength: Value obtained by dividing the load at cutting by the cross-sectional area of the test piece The modulus indicates the tensile strength against elongation, and the tensile strength is the strength against the load of the sample. Indicates.

3. Hardness
According to the method prescribed in JIS K 6253, measurement was performed using a type A durometer made by Kobunshi Keiki.

4). Tear strength The tear strength was measured at 23 ° C. using a shopper tensile tester according to the method defined in JIS K 6252. The specimen used was a crescent type (with a notch). The larger this value is, the harder it is to break by cracking and chipping caused by accidental defects.

5. Permanent elongation Dumbbell-shaped No. 1 was used and the marked line was 40 mm. Above 1. 50% of the elongation at the time of cutting in the tensile test was extended and held in this state for 30 minutes. After 30 minutes, the external force was removed and the mixture was allowed to stand for another 30 minutes, and the residual elongation at this time was measured. As a result, the residual elongation relative to the original length (40 mm) was expressed as a percentage. This means that the smaller the value, the less strain due to stress remains, and an improvement (decrease) in rolling resistance when used as a tire tread rubber composition is predicted.

6). Bending Crack Resistance According to the method defined in JIS K 6260, the number of bendings (cycles) until the crack length during bending was changed from 2 mm to 10 mm was measured using a Demacha bending tester manufactured by Ueshima Seisakusho. The thickness of the test piece used was 6.3 mm, and the bending reciprocation was 300 times per minute. The movement distance of the specimen gripper was 57 mm, and the maximum distance between the grippers was 75 mm. It is preferable that the number of bendings is large. If the number of times of bending is small, the appearance of the tire surface may be damaged or chipping may occur.

  The results obtained for the evaluation method are shown in Tables 1 and 2.

As is clear from the results in Table 1, it was found that the rubber composition of Example 1 had a longer Mooney scorch time than the rubber compositions of Comparative Examples 1 and 2.
The rubber composition of Comparative Example 1 had a short Mooney scorch time, low tear strength, and low flex crack resistance. The rubber composition of Comparative Example 2 had good tear strength and flex crack resistance, but the improvement range of Mooney scorch time was small, and the modulus was slightly reduced.

As is clear from the results of Table 2, it was found that the rubber composition of Example 2 had a longer Mooney scorch time than the rubber compositions of Comparative Examples 3-4.
The rubber composition of Comparative Example 3 had a short Mooney scorch time and poor processability. The rubber composition of Comparative Example 4 had a short Mooney scorch time and a slight decrease in tensile strength.

Claims (6)

A rubber composition comprising the following components 1 and 2 with respect to 100 parts by weight of at least one rubber selected from natural rubber and diene-based synthetic rubber;
Component 1: 40 to 100 parts by weight of any one of (1) to (3) selected from the group consisting of (1) carbon black, (2) silica, and (3) a mixture of carbon black and silica,
Component 2: 0.5 parts by weight or more and less than 20 parts by weight of modified calcium carbonate having a silica layer and a silane coupling agent layer. A rubber composition comprising the following components 1 and 2 with respect to 100 parts by weight of at least one rubber selected from natural rubber and diene-based synthetic rubber;
Component 1: 40 to 100 parts by weight of any one of (1) to (3) selected from the group consisting of (1) carbon black, (2) silica, and (3) a mixture of carbon black and silica ,
Component 2: (i) Silica layer, (ii) Organic acid layer obtained by treatment with at least one selected from the group consisting of fatty acids, fatty acid salts, fatty acid esters, resin acids, resin acid salts and resin acid esters And (iii) 0.5 parts by weight or more and less than 20 parts by weight of the modified calcium carbonate having a silane coupling agent layer. Component 1 is (3) a mixture of carbon black and silica, and the mixing ratio of carbon black: silica is 0.5: 99.5 to 99.5: 0.5 by weight. The rubber composition as described. The rubber composition according to claim 1, wherein component 1 is (2) silica and further contains the following component 3;
Component 3: 0.1-30 weight% of silane coupling agent with respect to compounding quantity of silica. The rubber composition according to any one of claims 1 to 3, wherein the component 1 is a mixture of (3) carbon black and silica, and further contains the following component 3.
Component 3: 0.1-30 weight% of silane coupling agent with respect to compounding quantity of silica. The molded object obtained by shape | molding the rubber composition in any one of Claims 1-5.