JP5601695B2 - Surface-treated calcium carbonate and rubber composition - Google Patents

Description

  The present invention relates to surface-treated calcium carbonate and a rubber composition containing the same.

  Among calcium carbonates, calcium carbonate fine particles having a particularly small particle diameter are known to improve the tear strength, flex resistance, heat generation and the like of a rubber composition when used in combination with carbon black. In order to strengthen the interaction with rubber, calcium carbonate is known in which a silica layer is formed on the surface of calcium carbonate and surface-treated with a silane coupling agent and a fatty acid, and such surface-treated calcium carbonate is used. Thus, it is known that a rubber composition for tire tread having good processability and weather resistance and having physical properties equivalent to those of a silica-containing rubber composition can be obtained (Patent Document 1).

  Also, by mixing surface-treated calcium carbonate, silica, silane coupling agent, and secondary aliphatic amine or tertiary aliphatic amine, the decrease in reinforcement and wear resistance is suppressed, and silica dispersion Has been proposed (Patent Document 2) that improves the wettability and makes it possible to achieve both wet skid performance and low rolling resistance.

JP 2004-51774 A JP 2007-99896 A

  An object of the present invention is to provide a surface-treated calcium carbonate that can be made into a rubber composition having a low exothermic temperature, a long scorch time, and a high tensile strength when blended with rubber, and a rubber composition containing the same. There is.

  In the surface-treated calcium carbonate of the present invention, the surface of calcium carbonate has at least one organic acid selected from fatty acids and resin acids, and at least one amine selected from secondary aliphatic amines and tertiary aliphatic amines. It is characterized by the surface treatment.

  By blending the surface-treated calcium carbonate of the present invention with rubber such as natural rubber or synthetic rubber, a rubber composition having a low exothermic temperature, a long scorch time, and a high tensile strength can be obtained.

  The average primary particle diameter of calcium carbonate in the present invention is preferably in the range of 0.01 to 1.0 μm, and more preferably in the range of 0.02 to 0.4 μm. When the average primary particle diameter is too large, there are cases where a sufficient reinforcing effect cannot be obtained when blended with rubber. On the other hand, if the average primary particle size is too small, dry agglomeration may occur, dispersibility in rubber may be reduced, and the reinforcing effect may be impaired. The average primary particle diameter of calcium carbonate can be measured with, for example, a scanning electron microscope.

  The amount of amine treated in the surface-treated calcium carbonate of the present invention is preferably 0.1 to 5 parts by weight, more preferably 0.1 to 4 parts by weight, with respect to 100 parts by weight of calcium carbonate. Preferably it is 0.1-3 weight part. If the amount of amine processed is too small, there may be cases where the suppression of heat generation and the effect of delaying the scorch time cannot be obtained sufficiently. If the amount of amine processed is too large, the scorch time will be shortened and the tensile strength will decrease. There is a case.

  The treatment amount of the organic acid in the surface-treated calcium carbonate of the present invention is preferably 0.5 to 8 parts by weight, more preferably 1 to 5 parts by weight, further preferably 100 parts by weight of calcium carbonate. 2 to 5 parts by weight. If the treatment amount of the organic acid is too small, the calcium carbonate particles may dry and agglomerate and the dispersibility may be lowered. If the treatment amount of the organic acid is too large, the rubber becomes soft and the reinforcing property may be lowered. is there.

  The treatment amount of amine and the treatment amount of organic acid can be appropriately adjusted depending on the primary particle diameter of calcium carbonate to be treated.

  The rubber composition of the present invention is characterized in that 0.5 to 100 parts by weight of the surface-treated calcium carbonate of the present invention is blended with 100 parts by weight of natural rubber or synthetic rubber.

  The rubber composition of the present invention has a low exothermic temperature, a long scorch time, and a high tensile strength.

  If the amount of the surface-treated calcium carbonate is too large, the fluidity of the rubber is reduced, so that the processability is deteriorated. Or the problem that hardness becomes high too much also arises. Moreover, when there are too few compounding quantities of surface treatment calcium carbonate, the heat | fever temperature is low, the scorch time is long, and the physical property of this invention that a tensile strength is high may not be obtained. The amount of the surface treated calcium carbonate is more preferably 1 to 60 parts by weight, and further preferably 5 to 40 parts by weight.

  The surface-treated calcium carbonate of the present invention can be made into a rubber composition having a low exothermic temperature, a long scorch time, and a high tensile strength when blended with rubber.

  Hereinafter, the surface-treated calcium carbonate and rubber composition of the present invention will be described in more detail.

<Calcium carbonate>
The calcium carbonate used as the raw material used for the surface-treated calcium carbonate of the present invention is not particularly limited, and for example, conventionally known calcium carbonate can be used. Such materials include synthetic (precipitating) calcium carbonate, heavy calcium carbonate, and the like.

  Synthetic (precipitating) calcium carbonate can be obtained by 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 mixed with coke or petroleum fuel (heavy oil, 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 co-firing with calcium slurry. By setting the conditions for the carbon dioxide reaction, desired submicron order fine particles can be obtained.

  Heavy calcium carbonate raw material is a publicly known raw calcium carbonate that is produced by using a roller mill, a high-speed rotary mill (impact shear mill), a container drive medium mill (ball mill), a medium stirring mill, a planetary ball mill, a jet mill, etc. It can be adjusted by grinding by a dry or wet method.

<Amine>
In the present invention, the surface of calcium carbonate is surface-treated with at least one amine selected from secondary aliphatic amines and tertiary aliphatic amines.

  Examples of the secondary aliphatic amine include dialkyl secondary amines having an alkyl group having 8 to 36 carbon atoms, preferably 8 to 20 carbon atoms.

  Examples of the tertiary aliphatic amine include dimethylalkyl tertiary amine and methyldialkyl tertiary amine having an alkyl group having 10 to 36 carbon atoms, preferably 10 to 20 carbon atoms. In particular, dimethylalkyl tertiary amine is preferably used.

<Organic acid>
The surface-treated calcium carbonate of the present invention is surface-treated with the above amine and at least one organic acid selected from fatty acids and resin acids. Either the fatty acid or the resin acid may be surface-treated, or the surface treatment may be performed using both the fatty acid and the resin acid.

  Examples of the fatty acids used in the present invention include saturated and unsaturated fatty acids having 6 to 24 carbon atoms, salts or esters thereof, and the like.

  Examples of the saturated or unsaturated fatty acid having 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 preferably used. You may use these in mixture of 2 or more types.

  Examples of the fatty acid salt include alkali metal salts and alkaline earth metal salts.

  Examples of fatty acid esters include esters of saturated or unsaturated fatty acids having 6 to 24 carbon atoms with lower alcohols having 6 to 18 carbon atoms.

  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 (alkali metal salts). , Alkaline earth metal salts) or esters. Among these, abietic acid and dehydroabietic acid are particularly preferably used.

<Surface treatment>
In the present invention, the amine and the organic acid are surface-treated on the surface of calcium carbonate. The order of surface treatment is not particularly limited, and the amine may be treated after treating the organic acid, or the organic acid may be treated after treating the amine. Moreover, you may process an amine and an organic acid simultaneously.

  However, when synthetic (precipitating) calcium carbonate having a small average primary particle size is used as calcium carbonate, calcium carbonate tends to aggregate, and therefore it is preferable to treat the amine after treating the organic acid. Examples of the method for treating fatty acids and resin acids include the following methods.

  The fatty acid or the resin acid is saponified while heating in an aqueous alkali metal solution such as an aqueous NaOH solution or an aqueous KOH solution to form a metal salt solution such as an Na salt or K salt. Next, an aqueous suspension of calcium carbonate is heated to 30 to 50 ° C. in advance, and an alkali metal aqueous solution of a fatty acid or resin acid is added to the suspension and mixed by stirring. The surface is treated with fatty acid or resin acid.

  The treatment can also be performed using a fatty acid or resin acid without saponification as described above. For example, treating calcium carbonate with fatty acid or resin acid by stirring while heating to a temperature equal to or higher than the melting point of fatty acid or resin acid, adding fatty acid or resin acid to this, stirring and mixing. Can do. Similarly, the fatty acid or the resin acid ester is used, and the calcium carbonate is stirred while being heated to the melting point or higher, and the fatty acid or the resin acid ester is added thereto for surface treatment.

  The method for surface treatment of amine is not particularly limited, and various surface treatment methods can be used.

  When an amine is treated on calcium carbonate treated with an organic acid, it can be treated by the following method.

  When the calcium carbonate treated with the organic acid is a dry powder, for example, while stirring the calcium carbonate powder in a mixer, the amine is added dropwise or sprayed using a spray or the like, thereby calcium carbonate. An amine can be surface-treated. In this case, you may heat-dry after surface treatment as needed.

  When calcium carbonate treated with an organic acid is obtained in the form of a suspension, the surface treatment can be performed by adding an amine to the suspension and adsorbing the amine on the surface of the calcium carbonate. . Surface treatment calcium carbonate is obtained by drying after the treatment.

  When calcium carbonate treated with organic acid or calcium carbonate treated with amine is a suspension, it is treated with a wet grinder such as a stirrer, bead mill, or sand mill in order to perform the treatment uniformly. May be.

  The specific surface treatment method has been described above, but the surface treatment method for the surface-treated calcium carbonate of the present invention is not limited to the above-described one.

<Rubber composition>
Examples of the natural rubber and synthetic rubber used in the present invention include the following.

  Natural rubber is a rubbery polymer obtained from natural plants, and the shape, color tone, etc. are not particularly limited as long as it has a cis-1,4-polyisoprene structure in terms of chemical structure.

  Synthetic rubbers include, for example, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, acrylonitrile butadiene rubber, butyl rubber, halogenated butyl rubber, ethylene propylene rubber, urethane rubber, silicone rubber, fluorine rubber, chlorosulfonated polyethylene, epichloro Examples include hydrin rubber and polysulfide rubber.

  The rubber composition of the present invention can be produced by blending the surface-treated calcium carbonate of the present invention with natural rubber or synthetic rubber.

  As a method of blending surface-treated calcium carbonate with natural rubber or synthetic rubber, a closed-type kneader such as a Banbury mixer or a pressure kneader, a method of blending surface-treated calcium carbonate while kneading rubber with an open roll, etc. Is mentioned.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

Example 1
A fatty acid was used as the organic acid for surface treatment of calcium carbonate. As the fatty acid, a fatty acid mixture (all manufactured by Wako Pure Chemical Industries, Ltd.) containing oleic acid, stearic acid, and palmitic acid was used. This fatty acid mixture was added to an aqueous sodium hydroxide solution and heated and stirred at 90 ° C. to prepare an aqueous sodium solution of fatty acid.

  A synthetic calcium carbonate slurry (solid content concentration 8% by weight) having an average primary particle diameter of 20 nm when observed with a scanning electron microscope was heated to 40 ° C. with good stirring. To this slurry, the above-mentioned aqueous fatty acid sodium solution was added so as to be 1.5 parts by weight as a fatty acid with respect to 100 parts by weight of calcium carbonate. After addition, the mixture was stirred, dehydrated with a filter press, and dried at 80 ° C. using a box dryer. The obtained dried product was pulverized using a micron mill pulverizer to obtain a fatty acid-treated calcium carbonate.

  While stirring the obtained fatty acid-treated calcium carbonate powder with a mixer, a secondary aliphatic amine (made by Lion Corporation, trade name “Armin 2C” so that it becomes 0.3 parts by weight with respect to 100 parts by weight of calcium carbonate. ”, Dicocoalkylamine) was dissolved by heating and then sprayed. After stirring and mixing for 10 minutes, the mixture was pulverized with a micron mill to obtain a surface-treated calcium carbonate powder.

(Example 2)
Surface-treated calcium carbonate was obtained in the same manner as in Example 1 except that the amount of the secondary aliphatic amine was 1.5 parts by weight with respect to 100 parts by weight of calcium carbonate.

(Example 3)
Surface-treated calcium carbonate was obtained in the same manner as in Example 1 except that the amount of the secondary aliphatic amine was 3 parts by weight with respect to 100 parts by weight of calcium carbonate.

Example 4
As the amine, a tertiary aliphatic amine (manufactured by Lion, trade name “Armin DMMCD”, N, N-dimethylcocoalkylamine) is used in place of the secondary aliphatic amine. Thus, surface treated calcium carbonate was obtained.

(Example 5)
A surface-treated calcium carbonate was obtained in the same manner as in Example 4 except that the amount of the tertiary aliphatic amine was 1.5 parts by weight.

(Example 6)
A surface-treated calcium carbonate was obtained in the same manner as in Example 4 except that the amount of the tertiary aliphatic amine was 3 parts by weight.

(Example 7)
Surface treated calcium carbonate was obtained in the same manner as in Example 1 except that the amount of fatty acid treated was 3 parts by weight.

(Example 8)
Surface treated calcium carbonate was obtained in the same manner as in Example 1 except that the amount of fatty acid treated was 5 parts by weight.

Example 9
Surface-treated calcium carbonate was obtained in the same manner as in Example 2 except that calcium carbonate having an average primary particle size of 30 nm was used.

(Example 10)
Resin acid was used as the organic acid. As the resin acid, abietic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used. Surface-treated calcium carbonate was obtained in the same manner as in Example 7, except that a sodium resin aqueous solution was used instead of the fatty acid sodium aqueous solution.

(Comparative Example 1)
A surface-treated calcium carbonate was obtained in the same manner as in Example 1 except that a primary aliphatic amine (manufactured by Lion, trade name “Armin CD”, cocoalkylamine) was used instead of the secondary aliphatic amine. .

(Comparative Example 2)
A surface-treated calcium carbonate was obtained in the same manner as in Comparative Example 1 except that the treatment amount of the primary aliphatic amine was 1.5 parts by weight.

(Comparative Example 3)
A surface-treated calcium carbonate was obtained in the same manner as in Comparative Example 1 except that the treatment amount of the primary aliphatic amine was 3 parts by weight.

(Comparative Example 4)
In the same manner as in Example 1, a fatty acid surface-treated calcium carbonate was prepared and used as it was without being surface-treated with an amine. In addition, when mix | blending with rubber | gum, a secondary aliphatic amine was added in rubber | gum so that it might become 1.5 weight part with respect to 100 weight part of calcium carbonate.

(Comparative Example 5)
Instead of calcium carbonate having an average primary particle size of 20 nm, a slurry of synthetic calcium carbonate (product name “Silver W”, manufactured by Shiroishi Kogyo Co., Ltd.) whose primary particles have an average major axis of 1.5 μm (1500 nm) is used. A surface treatment with sodium was carried out to obtain a dry powder, and this dry powder was treated with a secondary aliphatic amine in the same manner as in Example 2 to obtain a surface-treated calcium carbonate.

(Preparation of rubber composition)
100 parts by weight of the surface-treated calcium carbonate obtained in the above examples and comparative examples are blended with 100 parts by weight of styrene butadiene rubber (SBR, manufactured by JSR, trade name “1502”), and further to 100 parts by weight of styrene butadiene rubber. On the other hand, 5 parts by weight of zinc white, 1 part by weight of stearic acid, 1.2 parts by weight of vulcanization accelerator DM (dibenzothiazole disulfide), 0.2 part by weight of vulcanization accelerator TS (tetramethylthiuram monosulfide), and sulfur 2 parts by weight were added and kneaded with two rolls to obtain an unvulcanized rubber.

  As described above, in Comparative Example 4, the secondary aliphatic amine was added when kneading with a roll.

  The obtained unvulcanized rubber was subjected to a curast meter to obtain an optimum vulcanization time tc (90), and press crosslinking was performed at this time to obtain a press vulcanized sheet.

  Using the obtained press vulcanized sheet, Mooney scorch time, tensile strength, and HBU (exothermic temperature) were measured as follows.

<Mooney coach time>
According to the method prescribed | regulated to JIS (Japanese Industrial Standards) K6300, it measured using the Mooney viscometer 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.

<Tensile strength>
According to the method prescribed in JIS K 6251, the tensile strength at 23 ° C. (value obtained by dividing the load at the time of cutting by the cross-sectional area of the test piece) was measured using a shopper tensile strength tester.

<Measurement of HBU (exothermic temperature)>
According to the method prescribed | regulated to JISK6265, the exothermic temperature and permanent set were measured from the initial temperature of 40 degreeC using the flexometer. As a test piece, a cylindrical shape having a diameter of 17.80 mm and a height of 25.0 mm was used, a static compression stress of 1 MPa, a stroke of 1800 times per minute, a stroke of 4 m / m was given, and heat generation after 25 minutes passed. The temperature (Δt) was measured.

  The measurement results are shown in Tables 1 and 2.

  As is clear from the results shown in Table 1, the rubber compositions using the surface-treated calcium carbonate of Examples 1 to 10 according to the present invention have a low exothermic temperature, a long scorch time, and a high tensile strength.

  On the other hand, in Comparative Examples 1 and 2 using the surface-treated calcium carbonate in which the primary aliphatic amine was surface-treated, the rubber composition was destroyed in the HBU measurement test. Moreover, in the comparative example 3, it turns out that a scorch time becomes very short and it is inferior to storage stability.

  Or, as is clear from the comparison between Example 2 and Comparative Example 4, Comparative Example 4 in which the secondary aliphatic amine was not used for the surface treatment of calcium carbonate and was added during the kneading process of the rubber is The exothermic temperature is higher than 2. Moreover, the scorch time is shortened and the tensile strength is reduced. This shows that a rubber composition having a low exothermic temperature, a long scorch time, and a high tensile strength can be obtained by using calcium carbonate surface-treated with an amine according to the present invention.

  In Comparative Example 5, light calcium carbonate having an average major axis of 1.5 μm is used, but it can be seen that the tensile strength and heat generation temperature are poor.

  As described above, it is understood that a rubber composition having a low exothermic temperature, a long scorch time, and a high tensile strength can be obtained by using the surface-treated calcium carbonate according to the present invention. Although the detailed reason for obtaining such an effect is not clear, it is considered that the amine can be efficiently and uniformly distributed in the rubber by treating the surface of calcium carbonate with the amine.

  Further, according to the present invention, since the amine is treated on the calcium carbonate surface in advance, it is not necessary to add the amine when kneading the rubber, and the working efficiency can be improved.

  In the above embodiment, the example in which the surface-treated calcium carbonate of the present invention is blended with the SBR rubber has been shown, but the present invention is not limited to this, and may be blended with other natural rubber and synthetic rubber. it can.

Claims (5)

Characterized in that the surface of calcium carbonate, in which the at least one amine selected from secondary aliphatic amines and tertiary aliphatic amines, surface-treated with at least one selected salt or these salts of fatty acids and resin acids Surface treatment calcium carbonate.   The surface-treated calcium carbonate according to claim 1, wherein the average primary particle diameter of the calcium carbonate is in the range of 0.01 to 1.0 µm.   The surface-treated calcium carbonate according to claim 1 or 2, wherein the treatment amount of the amine is 0.1 to 5 parts by weight with respect to 100 parts by weight of calcium carbonate. At least one processing amount selected salt or these salts of fatty acids and resin acids are, relative to 100 parts by weight of calcium carbonate, any one of the preceding claims, characterized in that 0.5 to 8 parts by weight 2. The surface-treated calcium carbonate according to item 1.   A rubber composition comprising 0.5 to 100 parts by weight of the surface-treated calcium carbonate according to any one of claims 1 to 4 based on 100 parts by weight of natural rubber or synthetic rubber.