JP2010248276A - Rubber cement composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber cement composition capable of effectively reducing the amount of an organic solvent while preferably maintaining physical properties such as a bonding property and a coating property, and a pneumatic tire using the same. <P>SOLUTION: The rubber cement composition includes a carbon black and an organic solvent added to a rubber component containing a natural rubber obtained by applying a protein-removing process to a natural rubber latex. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber cement composition and a pneumatic tire using the same, and more particularly to a rubber cement composition suitable as an adhesive between tire rubber members and a pneumatic tire using the same.

  In general, a tire is formed by laminating or bonding a plurality of unvulcanized rubber members having different compounding compositions after molding the unvulcanized rubber members having different compounding compositions by a rolling roll or an extruder. In addition, it is manufactured by a precure method of further vulcanization. In the process of laminating the unvulcanized rubber member, in order to ensure sufficient adhesive strength and adhesive strength, a method of applying cement having excellent adhesiveness to the joint surfaces and drying the joint is generally used. Are known. For example, the tread is vulcanized and molded after pasting an unvulcanized tread rubber composition on the outer periphery of the tire body and joining both ends thereof. That is, the rubber cement composition is applied to the rubber to be bonded and pressure-bonded, and then the rubber is bonded by vulcanization bonding at a high temperature of about 120 to 170 ° C.

  Such a rubber cement composition is applied in a liquid form by blending an organic solvent with a rubber component such as natural rubber or synthetic rubber. As such a rubber cement composition, a specific butadiene rubber is blended to improve tackiness and adhesiveness (see Patent Document 1), or a specific silica dispersant based on styrene-butadiene rubber / natural rubber. To improve dispersibility with organic solvents by blending (see Patent Document 2), or by blending specific minerals and phenolic resins to bond between unvulcanized and vulcanized rubber of the same or different types Various compositions have been developed such as those for improving the properties (see Patent Document 3).

JP 2008-144014 A JP 2007-269893 A JP 2008-179732 A

  However, in any of these rubber cement compositions, natural rubber that can be employed as a rubber component is a normal untreated rubber, and its solution viscosity is still high. Therefore, when such natural rubber is used, a considerable amount of an organic solvent must be added to give a liquid form having a solution viscosity suitable as a rubber cement. Therefore, a volatile organic compound (VOC) It will go against discharge suppression.

  Accordingly, an object of the present invention is to provide a rubber cement composition capable of effectively reducing the amount of organic solvent while maintaining good physical properties such as adhesiveness and applicability, and a pneumatic tire using the same. It is said.

In order to solve the above-mentioned problems, the present inventors have found a rubber cement composition that employs natural rubber subjected to a specific treatment as a rubber component, and have completed the present invention.
That is, the rubber cement composition of the present invention comprises carbon rubber and an organic solvent mixed with a rubber component containing natural rubber obtained by deproteinizing natural rubber latex.

The natural rubber is a natural rubber latex obtained by partially deproteinizing the natural rubber so that the total nitrogen content in the natural rubber is 0.12 to 0.30% by mass. It is desirable that the product be solidified without being centrifuged and dried.
The Mooney viscosity (ML _{1 + 4} ) and stress relaxation time (T ₈₀ ) of the natural rubber preferably satisfy the following formulas (I) and (II).
40 ≦ ML _{1 + 4} ≦ 100 (I)
T ₈₀ <0.0035exp (ML _{1 + 4} /8.2)+20 (II)
[Where ML _{1 + 4} is the Mooney viscosity measured value at 100 ° C., T ₈₀ is the time (seconds) required to stop the rotor rotation immediately after ML _{1 + 4} measurement and the ML _{1 + 4} value is reduced by 80%. ). ].

It is preferable that the carbon black is blended in an amount of 20 to 80 parts by mass with respect to 100 parts by mass of the rubber component, and further a thermosetting resin is blended in an amount of 0.1 to 40 parts by mass. It may be.
The pneumatic tire of the present invention is characterized by using the rubber cement composition.

  According to the rubber cement composition of the present invention, the natural rubber adopted as the rubber component is subjected to a specific treatment, so that it not only has excellent adhesion performance but also has good operability such as applicability and workability. It is possible to effectively reduce the solution viscosity while fully exhibiting it, and it is possible to maintain a suitable solution viscosity even if the amount of the organic solvent is reduced. Therefore, it is possible to shorten the drying time by reducing the amount of the organic solvent, to contribute to the suppression of VOC emission, and to greatly contribute to the improvement of the atmospheric environment.

  Furthermore, if the rubber cement composition of this invention is employ | adopted, it will become possible to implement | achieve a high performance pneumatic tire.

Hereinafter, the present invention will be described in detail.
The rubber cement composition of the present invention comprises carbon rubber and an organic solvent mixed with a rubber component containing natural rubber obtained by deproteinizing natural rubber latex.

[Natural rubber]
The natural rubber used in the present invention is obtained by deproteinization treatment of natural rubber latex. The natural rubber latex used as a raw material is not particularly limited, and a field latex, a commercially available latex, or the like can be used.

  Deproteinization of natural rubber latex can be performed by a known method. For example, a decomposition treatment method using an enzyme, a method of repeatedly washing with a surfactant, a method of using an enzyme and a surfactant in combination, a transesterification method using sodium methoxide, sodium hydroxide, potassium hydroxide, etc. There is a saponification method using

  As the enzyme, a protease, a peptidase, a cellulase, a pectinase, a lipase, an esterase, an amylase, etc. can be used alone or in combination. The enzyme activity of these enzymes is suitably in the range of 0.1 to 50 APU / g.

  The amount of proteolytic enzyme added is suitably 0.005 to 0.5 parts by weight, preferably 0.01 to 0.2 parts by weight, based on 100 parts by weight of the solid component in the natural rubber latex. is there. If the amount of proteolytic enzyme added is less than the above lower limit, the protein degradation reaction may be insufficient. If the amount exceeds the upper limit, deproteinization will proceed excessively, resulting in a balance between the desired processability and physical properties. You may not be able to remove.

  In the present invention, when performing the proteolytic treatment, a surfactant may be added together with the proteolytic enzyme. As such surfactants, anionic, cationic, nonionic, amphoteric surfactants and the like can be added.

  In the present invention, the total protein content in the latex solid content is adjusted to 0.12 to 0.30% by mass, preferably 0.18 to 0.25% by mass, by the above deproteinization technique. Is desirable.

This nitrogen is derived from the nitrogen of the polypeptide bond. Determination of polypeptide binding may be performed by measuring the absorbance at 3280 cm ^-1 by a polypeptide bond proteins by infrared spectroscopy. Here, the total nitrogen content of 0.12% by mass means that the polypeptide bonds are decomposed by almost 80%. Moreover, the total nitrogen content of 0.30% by mass means that the polypeptide bonds are decomposed by about 20%. That is, it is desirable that such natural rubber latex is partially deproteinized.

When the total nitrogen content is within the above range, there is no risk of deterioration of physical properties such as mechanical properties and anti-aging properties, and the rubber viscosity is moderately reduced by the decomposition of peptide bonds, and a more preferable value of Mooney viscosity. Natural rubber having the following can be obtained. Furthermore, it contributes to an increase in the interaction between carbon black and rubber, and the dispersibility of carbon black in rubber can be improved.
The polypeptide degradation rate is preferably 20 to 80%, particularly preferably 30 to 70%.

  The natural rubber latex deproteinized as described above is preferably coagulated without centrifuging the non-rubber component. When the non-rubber component is centrifuged and solidified, the rubber physical properties such as aging resistance may be inferior. Further, it is desirable that the obtained rubber component is washed and then dried using a normal dryer such as a vacuum dryer, an air dryer or a drum dryer.

  In addition, from the viewpoint of improving the operability of the rubber cement composition, it is possible to shorten the input relaxation time. However, the natural rubber is partially deproteinized so that the branch point is selectively cut. It greatly contributes to the reduction of the stress relaxation time of natural rubber, imparts a suitable solution viscosity to the rubber cement composition, exhibits excellent operability, and shortens the drying time.

In the present invention, the stress relaxation time of natural rubber is defined by the relationship with the ML _{1 + 4} value at the time of Mooney viscosity measurement, and preferably satisfies both the following formulas (I) and (II).
40 ≦ ML _{1 + 4} ≦ 100 (I)
T ₈₀ <0.0035exp (ML _{1 + 4} /8.2)+20 (II)
[Where ML _{1 + 4} is the Mooney viscosity measured value at 100 ° C., T ₈₀ is the time (seconds) required to stop the rotor rotation immediately after ML _{1 + 4} measurement and the ML _{1 + 4} value is reduced by 80%. ). ]

  As described above, the natural rubber obtained through a specific treatment can effectively reduce the solution viscosity and not only improve the operability such as coating property but also reduce the blending amount of the organic solvent. This can also contribute to the improvement of VOC emission control measures.

[Rubber component]
The rubber component used in the rubber cement composition of the present invention includes the natural rubber. The specific natural rubber is desirably contained in 100% by mass of the rubber component in an amount of at least 20% by mass, preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass. If it is less than the lower limit, a rubber cement composition having desired physical properties may not be obtained.

  Examples of the rubber component used in combination with the specific natural rubber include normal natural rubber and diene synthetic rubber. Examples of the diene synthetic rubber include styrene-butadiene copolymer (SBR) and polybutadiene rubber (BR). , Polyisoprene rubber (IR), butyl rubber (IIR), ethylene-propylene copolymer, and mixtures thereof.

[Carbon black]
In addition to the rubber component, carbon black is blended in the rubber cement composition of the present invention. The carbon black is not limited by the particle size, and any carbon black can be selected and used from those conventionally used as reinforcing fillers for rubber. Specific examples include FEF, SRF, HAF, ISAF, and SAF.

  The amount of the carbon black is preferably 20 to 100 parts by mass, more preferably 30 to 50 parts by mass with respect to 100 parts by mass of the rubber component. In addition, you may use together fillers, such as a silica, an alumina, and aluminum hydroxide.

That is, when natural rubber subjected to the above deproteinization treatment is used, carbon black having a fine particle diameter having a nitrogen adsorption specific surface area of 80 m ² / g or more, or low structure carbon having a DBP oil absorption of 100 ml / 100 g or less. Even when black is blended, the dispersibility of carbon black can be improved compared to the case of using conventional natural rubber. Not only the operability of the rubber cement composition but also the wear resistance and low loss ( The physical properties such as low exothermic properties can also be greatly improved.

[Organic solvent]
The rubber cement composition of the present invention is formed by blending an organic solvent with the rubber component. That is, the natural rubber and carbon black are uniformly dispersed in the organic solvent, whereby the rubber cement composition is in a liquid state and imparts applicability. Since the rubber component can satisfactorily reduce the solution viscosity, the required physical properties of the rubber cement composition do not deteriorate even if the amount of the organic solvent is reduced as compared with the conventional rubber component. Examples of the organic solvent include rubber volatile oil, hexane, cyclohexane, petroleum ether, heptane, tetrahydrofuran and the like. In addition, the said organic solvent is what can melt | dissolve rubber | gum, and means what can contain the rubber | gum of 5 mass% or more in 100 mass% of solutions after melt | dissolving rubber | gum in this organic solvent. To do.

  Further, even when the blending amount of the organic solvent is reduced by 10% from the usual blending amount, good workability can be maintained by using the natural rubber. Thus, since it becomes possible to reduce the compounding quantity of an organic solvent effectively, it is effective also as a measure against VOC emission suppression.

[Rubber cement composition]
In addition to the rubber component, carbon black, and organic solvent, a resin may be added to the rubber cement composition of the present invention. Examples of such resins include petroleum resins, epoxy resins, and melamine resins made of C5 fraction and C9 fraction produced from phenol resin, naphtha and the like. Of these, phenol resins are preferred. By blending these resins, compatibility with rubber is improved, and adhesion between rubber members can be further improved.
When blending such a resin, the amount is 0.1 to 100 parts by weight, preferably 0.1 to 40 parts by weight, based on 100 parts by weight of the rubber component.

  The rubber cement composition further includes a compounding agent usually used in the rubber industry, such as a softening agent, an anti-aging agent, a coupling agent, a vulcanizing agent, a vulcanization accelerator, and a vulcanization acceleration aid. Etc. can be blended in a desired amount.

  The rubber cement composition of the present invention can be applied as an adhesive when bonding almost all rubber members in a pneumatic tire. At the time of coating, the rubber is bonded by brushing, bonding the rubber and the rubber, and then volatilizing the organic solvent. Further, during the subsequent vulcanization, it acts as a rubber and is bonded by vulcanization. Although the viscosity of the rubber cement composition of the present invention is effectively reduced, it is possible to reduce the organic solvent without deteriorating the coating property while maintaining such adhesion performance well. Therefore, it is a rubber cement composition that is most suitable for VOC emission suppression measures.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
The measurement of the total nitrogen content in natural rubber and the measurement of various physical properties such as Mooney viscosity and stress relaxation time were performed according to the following methods.

<Measurement of total nitrogen content>
The total nitrogen content was measured by the Kjeldahl method and determined as a ratio (mass%) to the total amount.

<< Mooney viscosity and stress relaxation time >>
The Mooney viscosity [ML _{1 +} 4/100 ° C.] was measured at 100 ° C. according to JIS K6300-1994. The stress relaxation time (T ₈₀ ) was measured as the time (seconds) required to stop the rotor rotation immediately after the ML _{1 + 4} measurement and reduce the ML _{1 + 4} value by 80%.

[Production Example 1: Production of natural rubber (NR-1)]
(I) Peptide bond decomposition process of natural rubber latex Anionic surfactant [“Demol” manufactured by Kao Co., Ltd., surfactant concentration is 2.5 mass%] 24.7 ml, protease (“Alkalase manufactured by Novozymes”) A solution was prepared by adding 0.06 g of 2.5 L, type DX ") and mixing.
Next, 1000 g of a natural rubber latex having a solid content of 20% by mass was kept constant at 40 ° C. in a water bath, the solution was added dropwise with stirring, and stirring was continued for 5 hours at the same temperature. Got.

(Ii) Coagulation / Drying Step The rubber obtained by acid coagulation is passed through a drum dryer set at 130 ° C. five times, and then dried at 40 ° C. for 8 hours in a vacuum dryer, and natural rubber (NR -1) was produced. Table 1 shows the measurement results of these various conditions and the total nitrogen content, Mooney viscosity, and stress relaxation time.

[Production Examples 2-3: Production of natural rubber (NR-2) to (NR-3)]
In Production Example 1, instead of protease, Production Example 2 uses peptidase (“Devitrase” manufactured by Soho Tsusho), Production Example 3 uses sodium hydroxide, and after obtaining each natural rubber latex (2), (3), Natural rubber (NR-2) and (NR-3) were produced by acid coagulation and drying. Table 1 shows the measurement results of these various conditions and the total nitrogen content, Mooney viscosity, and stress relaxation time.

[Production Example 4: Production of natural rubber (NR-4)]
In Production Example 1, the amount of protease added and the stirring time with natural rubber latex were changed to the conditions shown in Table 1 to obtain natural rubber latex (4), which was then coagulated and dried to produce natural rubber (NR-4). Manufactured. Table 1 shows the measurement results of these various conditions and the total nitrogen content, Mooney viscosity, and stress relaxation time.

[Production Example 5: Production of natural rubber (NR-5)]
Natural rubber latex (5) was obtained in the same manner as in Production Example 1. Subsequently, after centrifuging at a rotation speed of 7500 rpm using a latex separator SLP-3000 (manufactured by Saito Centrifuge Co., Ltd.), natural rubber (NR-5) was produced through a coagulation / drying process. Table 1 shows the measurement results of these various conditions and the total nitrogen content, Mooney viscosity, and stress relaxation time.

[Examples 1-7, Comparative Examples 1-4]
A rubber composition (RM-1 to RM-10) is prepared according to the formulation shown in Table 2, and an organic solvent (rubber volatile oil) shown in Table 3 is formulated to produce rubber cement compositions (A) to (K). did. Each evaluation was performed according to the following using the obtained rubber cement composition. The results are shown in Table 3.

<Evaluation of adhesiveness>
The evaluation of adhesiveness in an unvulcanized state was measured using a pickup type tackiness meter at room temperature. Evaluation was expressed as an index with Comparative Example 1 as 100. The larger the value, the better the result. In addition, the evaluation of the adhesiveness after vulcanization was carried out by performing a peeling test using a strograph, and the index was displayed with Comparative Example 1 as 100. The larger the value, the better the result.

《Solution viscosity》
The solution viscosity of the obtained rubber cement composition was measured using a Canon Fenske viscometer, the sample passage time was measured at 30 ° C., and Comparative Example 1 was set as 100. It shows that it is so favorable that a numerical value is small.

<Molding workability>
The obtained rubber cement composition was applied to a tire tread, and the ease of pasting at the splice part at the time of forming a pneumatic tire was evaluated in two stages, good / bad.

《Tuck over time》
After 1 hour from the formation of the pneumatic tire, the joining state of the splice part was visually evaluated in two stages of good / bad.

《Reverse buffing》
For the above vulcanized pneumatic tire, apply a rotary grinder in the direction of peeling the tread on the splice, and then remove the tread when the surface is shaved, and the exposed / exposed condition of the joint interface in two stages: good / bad Overall evaluation.

* 1: HAF carbon black * 2: N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine (NOCRACK 6C, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 3: N, N'-dicyclohexyl-2-benzothiazylsulfenamide (Noxeller DZ, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 4: Natural rubber (RSS # 3, total nitrogen content 0.47%, Mooney viscosity [ML _{1 +} 4/100 ° C] 73, stress relaxation time (T ₈₀ ) 62.5 seconds)
* 5: Natural rubber (total nitrogen content 0.47%, Mooney viscosity [ML _{1 +} 4/100 ° C] 69, stress relaxation time (T ₈₀ ) 51.5 seconds)
* 6: Polyisoprene rubber (total nitrogen content 0%, Mooney viscosity [ML _{1 +} 4/100 ° C] 78, stress relaxation time (T ₈₀ ) 26.0 seconds)
* 7: Compounding amount (parts by mass) with respect to 100 parts by mass of rubber component

According to Table 3, Examples 1-7 which employ | adopted the natural rubber obtained by a deproteinization process improve the adhesiveness at the time of non-vulcanization, and the adhesiveness after vulcanization compared with Comparative Examples 1-4. It can be seen that the viscosity of the rubber cement composition can be effectively lowered while being held, and the operability such as molding workability is excellent. In particular, Example 4, which employs the same rubber composition (rubber component) as Example 1, clearly shows that good adhesive performance can be maintained even if the blending amount of the organic solvent is reduced by 10% compared to Example 1. is doing.
Further, when Example 7 containing phenol resin and Comparative Example 4 are compared, Example 7 employing natural rubber obtained by deproteinization treatment is more effective in optimizing solution viscosity with phenol resin. You can see that

Claims (6)

  A rubber cement composition comprising a rubber component containing natural rubber obtained by deproteinizing natural rubber latex and carbon black and an organic solvent.   A natural rubber latex obtained by partially deproteinizing the natural rubber so that the total nitrogen content in the natural rubber is 0.12 to 0.30% by mass in the deproteinization treatment is used as a non-rubber component. The rubber cement composition according to claim 1, which is obtained by solidification without centrifugation and drying. The rubber cement composition according to claim 1 or 2, wherein a Mooney viscosity (ML _{1 + 4} ) and a stress relaxation time (T ₈₀ ) of the natural rubber rubber satisfy the following formulas (I) and (II):
40 ≦ ML _{1 + 4} ≦ 100 (I)
T ₈₀ <0.0035exp (ML _{1 + 4} /8.2)+20 (II)
[Where ML _{1 + 4} is the Mooney viscosity measured value at 100 ° C., T ₈₀ is the time (seconds) required to stop the rotor rotation immediately after ML _{1 + 4} measurement and the ML _{1 + 4} value is reduced by 80%. ). ].   The rubber cement composition according to any one of claims 1 to 3, wherein the carbon black is blended in an amount of 20 to 80 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition according to any one of claims 1 to 4, further comprising a resin in an amount of 0.1 to 40 parts by mass with respect to 100 parts by mass of the rubber component.   A pneumatic tire using the rubber cement composition according to any one of claims 1 to 5.