JP2002069235A - Process for mastication of natural rubber, and natural rubber obtained by this mastication process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for masticating a natural rubber capable of decreasing the gel portion without lowering the molecular weight and also of improving the processability, and to provide a natural rubber obtained by this mastication process. SOLUTION: The mastication process for a natural rubber is carried out by adding an ester from an aromatic polycarboxylic acid having in the molecule at least one carboxylic group bonding to an aromatic ring and a (poly) oxyalkylene derivative, to a natural rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for masticating natural rubber which can reduce the amount of gel without lowering the molecular weight and further improve the processability, and a natural rubber obtained by the method. About.

[0002]

2. Description of the Related Art In general, rubber products such as tires, belts and hoses are mixed with various compounding agents such as vulcanizing agents and reinforcing agents. Therefore, a mastication step of raw rubber (natural rubber) as a raw material is indispensable. Generally, the meaning of mastication is to impart sufficient plasticity by applying mechanical shearing force to raw rubber. This mastication facilitates the mixing and kneading operation (operation of uniformly kneading the various compounding agents into the raw rubber) by facilitating the dispersion of various compounding agents such as a vulcanizing agent and a filler, and is also a post-process. In rolling, extrusion, etc., it plays a role in facilitating these operations, such as stabilizing dimensions, cleaning skin, and making scorching difficult.

[0003] In this mastication, the molecular weight is reduced due to molecular cutting of raw rubber by simple mechanical mastication such as a roll machine or a closed kneader, and the rubber is plasticized. Kneading requires a great deal of power, labor and time. Therefore, it is generally well known that a mastication accelerator (peptizer) is used in the mastication step of raw rubber.

Hitherto, thiophenol or disulfide substituted with an aromatic ring has been used as a mastication accelerator. However, the use of this mastication accelerator promotes plasticization and lowers the viscosity of the rubber, but at the same time, cuts the molecular chains and vulcanizes the rubber. There is an issue in that

On the other hand, in natural rubber, molecular chains are entangled,
There is a gel due to the reaction between the functional groups in the isoprene chain of the natural rubber or between such a functional group and the non-rubber component in the natural rubber, and this gel component increases the viscosity of the raw rubber (for example, storage curing).
Alternatively, this is a cause of poor dispersion of the rubber compounding agent. Although the gel content is reduced by ordinary mastication, the same problem as described above occurs because the molecular chains are simultaneously cut.

As a technique for selectively reducing the gel amount without lowering the molecular weight of natural rubber as described above, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 11-209406 a specific aromatic polycarboxylic acid derivative. At least one selected from
It discloses an additive for masticating natural rubber consisting of seeds.
However, the additives for kneading natural rubber described in this publication have not been conventionally used as a technique for selectively reducing the amount of gel without lowering the molecular weight of natural rubber. At present, there is a demand for a technology for reducing the amount.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems and the current state of the prior art described above, and is intended to solve the problem. The present invention is intended to further reduce the gel amount without lowering the molecular weight of natural rubber. Another object of the present invention is to provide a method for masticating natural rubber which can also improve processability, and a natural rubber obtained by the method for masticating.

[0008]

Means for Solving the Problems The present inventors have found that an ester of a specific aromatic polycarboxylic acid and a (poly) oxyalkylene derivative can significantly reduce the gel amount without reducing the molecular weight of natural rubber, Furthermore, they have found that the processability can be improved, succeeded in obtaining the desired method for masticating natural rubber and the natural rubber obtained by the method, and have completed the present invention.

That is, the present invention resides in the following (1) to (8). (1) An ester (a) of an aromatic polycarboxylic acid and a (poly) oxyalkylene derivative having at least one carboxyl group bonded to an aromatic ring in a molecule is added to natural rubber to perform the reaction. Natural rubber mastication method. (2) The method for masticating natural rubber according to (1), wherein the ester of the component (a) is supported on a solid and added to natural rubber. (3) The method for masticating natural rubber according to (2), further comprising adding at least one kind (b) selected from the group consisting of (poly) oxyalkylene derivatives, alcohols and fatty acid esters thereof. (4) The component (b) has a melting point of 20 ° C. or less, and
The method for masticating natural rubber according to the above (3), wherein the boiling point is 150 ° C. or higher. (5) The method for masticating natural rubber according to any one of the above (1) to (4), wherein the ester of the component (a) is a compound represented by the following general formula (I).

Embedded image (6) A method for masticating natural rubber, comprising adding 0.05 to 20 parts by weight of the ester described in (1) or (5) to 100 parts by weight of natural rubber. (7) The natural rubber according to any one of the above (3) to (6), wherein the amount of the component (b) is 20% by weight or less based on the ester of the component (a). Kneading method. (8) A natural rubber obtained by the method for masticating a natural rubber according to any one of the above (1) to (7).

[0010]

Embodiments of the present invention will be described below in detail. The method for masticating the natural rubber of the present invention (hereinafter, referred to as
The method of the present invention) comprises adding an ester (a) of an aromatic polycarboxylic acid and a (poly) oxyalkylene derivative having at least one carboxyl group bonded to an aromatic ring in a molecule to natural rubber. It is characterized by carrying out.

The ester of the component (a) used in the method of the present invention is obtained from an aromatic polycarboxylic acid and a (poly) oxyalkylene derivative, and has at least one carboxyl group bonded to an aromatic ring in the molecule. It is not particularly limited as long as it has one, but is preferably a compound represented by the following general formula (I).

Embedded image

In the above formula (I), more preferably, n + p is 2 or 3, R ¹ is an alkylene group having 2 to 4 carbon atoms, and R ² is an alkyl group or alkenyl group having 2 to 28 carbon atoms. Yes, more preferably n = 1, p = 1,
R ¹ is an ethylene group, R ² is an alkyl or alkenyl group having 2 to 28 carbon atoms, and particularly preferably, m is 1 to 1
0, n = 1, p = 1, R ¹ is an ethylene group, and R ² is 8 carbon atoms
~ 18 alkyl groups or alkenyl groups.

The ester of component (a) used in the method of the present invention can be obtained by reacting (i) a divalent or higher valent aromatic carboxylic acid or its anhydride with (ii) a (poly) oxyalkylene derivative. Can be. Examples of the divalent or higher aromatic carboxylic acid (i) include divalent aromatic carboxylic acids such as phthalic acid, phthalic anhydride, and naphthalenedicarboxylic acid or anhydrides thereof, trimellitic acid, and trimellitic anhydride. Such as trivalent aromatic carboxylic acids or anhydrides thereof, pyromellitic acid and pyromellitic anhydride;
Examples thereof include a divalent aromatic carboxylic acid and an anhydride thereof. From the viewpoint of cost, a divalent or trivalent aromatic carboxylic acid or an anhydride thereof is preferable, and phthalic anhydride is particularly preferable. The (poly) oxyalkylene derivative of the above (ii) is, for example, a derivative having a (poly) oxyalkylene group having an average degree of polymerization of 1 or more and having one or more hydroxyl groups. It is a derivative having a (poly) oxyalkylene group having one, and particularly preferably a derivative having a (poly) oxyalkylene group having one hydroxyl group. Examples of the (poly) oxyalkylene derivative include ether types such as (poly) oxyalkylene alkyl ether; ester types such as (poly) oxyalkylene fatty acid monoester; ether ester types such as (poly) oxyalkylene glycerin fatty acid ester; Examples thereof include nitrogen-containing types such as (poly) oxyalkylene fatty acid amide and (poly) oxyalkylenealkylamine. The (poly) oxyalkylene derivative of the present invention is preferably an ether type or an ester type, and particularly preferably an ether type.

Examples of the ether type (poly) oxyalkylene derivative include polyoxyethylene lauryl ether, polyoxyethylene decyl ether, polyoxyethylene octyl ether, polyoxyethylene len-2-ethylhexyl ether, and polyoxyethylene polyoxypropylene. Lauryl ether, polyoxypropylene stearyl ether, polyoxyalkylene such as polyoxyethylene oleyl ether, polyoxyalkylene aliphatic ether containing unsaturation, polyoxyethylene benzyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene penylation Examples thereof include polyoxyethylene aromatic ethers such as phenyl ether, and polyoxyalkylene aliphatic ethers are preferable. Further, it is preferably a polyoxyethylene alkyl or alkenyl ether, and particularly preferably, the average degree of polymerization of the polyoxyethylene is 10 or less, and the alkyl group or alkenyl group has 8 to 18 carbon atoms. Specifically, polyoxyethylene is converted to PO
E (n) is abbreviated, and the average degree of polymerization is shown in parentheses. POE (3) octyl ether, POE (4) 2
-Ethylhexyl ether, POE (3) decyl ether, POE (5) decyl ether, POE (3) lauryl ether, POE (8) lauryl ether, POE
(1) Stearyl ether and the like.

In the method of the present invention, the above-mentioned ester, that is, an ester serving as an additive for kneading natural rubber, preferably at least one selected from the compounds represented by the above-mentioned general formula (I) is added to 100% by weight of natural rubber. Part, 0.
It is desirable to add 0.5 to 20 parts by weight for mastication. The reason why the amount of the ester is defined as 0.05 to 20 parts by weight with respect to 100 parts by weight of the natural rubber is that when the amount is 0.05 to 20 parts by weight, the fracture characteristics of the vulcanized rubber are reduced. This is because the desired effects of the present invention can be sufficiently obtained without causing any adverse effects such as a decrease in the density.

In the method of the present invention, the type of natural rubber used, for example, RSS (ribbed smoked sheet), TS
R (Technical Standard Rubber), grade (grade)
For example, the compounding amount of the ester varies within the above range, but within this range, preferably from 1 to 5 from the viewpoint of cost handling, and the effect of increasing the amount. Parts, more preferably 1-3
Desirably, parts by weight are used.

Further, in the method of the present invention, when the ester of the component (a) is added, it is preferable that the ester is supported on a solid in order to improve workability in a factory. The fixing used herein is not particularly limited, and examples thereof include inorganic compounds such as silica, aluminum hydroxide, clay, calcium carbonate, and talc; and organic compounds such as carbon black, stearic acid, wax, and an antioxidant. . Among these, silica or carbon black is preferable.
In addition, when the component (a) is carried, dust may flutter. Therefore, in order to suppress this, the component (b) is selected from (poly) oxyalkylene derivatives, alcohols and fatty acid esters thereof. At least one of them. This compound tatami mat of the component (b)
The amount is preferably 20% by weight or less, more preferably 5 to 10% by weight, based on the ester of the component (a). (B)
It is preferred that the components have a melting point of 20 ° C. or lower and a boiling point of 150 ° C. or higher. The melting point of the component (b) is preferably 20 ° C. or less from the viewpoint of suppressing dust during mastication, and the boiling point is preferably 150 ° C. or more from the viewpoint of safety during mastication.

The (poly) oxyalkylene derivative as the component (b) is the same as the above (ii) (poly) oxyalkylene derivative, and includes ether type, ester type, ether ester type and nitrogen-containing type. Preferred are ether-type and ester-type polyoxyalkylene derivatives. The alcohol as the component (b) is not particularly limited, but is preferably an aliphatic alcohol having 8 to 20 carbon atoms, such as octyl alcohol, 2-ethylhexyl alcohol, decyl alcohol, and lauryl alcohol. Oleyl alcohol, stearyl alcohol, ethylene glycol, caprylic alcohol and the like. In addition, fatty acid esters of these alcohols are preferably used.

Among the above-mentioned components (b) used in the method of the present invention, ether-type or ester-type polyoxyethylene derivatives or ethylene glycol fatty acid esters are particularly preferred. Specifically, orioxyethylene is converted to PO
E (n), where n is the average degree of polymerization, POE
(3) Lauryl ether, POE (5) decyl ether, POE (4) oleyl ether, POE (10) monolaurate, POE (10) monooleate, ethylene glycol dioleate, POE (9) dicaprylate and the like. .

In the method of the present invention, the above-mentioned esters may be used alone or in combination of two or more. In addition, thiophenol or thiophenol which is usually used as a peptizing accelerator (a peptizing agent) may be used. Disulfides and the like may be used in place of the ester of the present invention. It is necessary that the compounding amount of these mastication accelerators is 10% by weight or less of the compounding amount of the ester of the present invention. If the content exceeds 10% by weight, the adverse effect of molecular chain scission becomes large, and the destructive properties and the like of the vulcanized rubber obtained by vulcanization are undesirably reduced.

The method of the present invention may be carried out by adding each of the above-mentioned components to natural rubber using a mastication machine, and the optimum range of rotation speed, mastication temperature, mastication time, etc. for the mastication machine. Is selected. Examples of the mastication machine include a roll machine, a closed kneader, a Gordon plasticizer, and the like.For example, when a roll machine is used, a roll interval, a roll rotation ratio, a roll rotation speed, and the like are in an optimal range. Is selected. The mastication start temperature is from 60 to 85 ° C, preferably from 70 to 80 ° C, and the mastication time is from 60 to 120 seconds, preferably from 80 to 100 seconds, depending on the rubber application and the like. desirable. According to the method of the present invention configured as described above, the amount of the polymer gel can be reduced without reducing the molecular weight of the natural rubber, and
By increasing the slip between molecules, the workability of molding can be improved, and a decrease in the physical properties of the unvulcanized rubber or the vulcanized rubber can be suppressed.

The natural rubber obtained by the method of the present invention is entangled with the molecular chains in the natural rubber, and the functional groups in the isoprene chain of the natural rubber, or such functional groups and the non-rubber component in the natural rubber. Since the gel resulting from the reaction (1) is removed, the gel amount is selectively reduced without reducing the molecular weight of natural rubber. Therefore, by using this natural rubber (plastic processing), it is possible to easily disperse various compounding agents such as a vulcanizing agent and a filler in the mixing and kneading process. , Non-pro kneading blending and kneading oils, anti-aging agents, etc., and then sulfur, vulcanization accelerator etc. Furthermore, in the subsequent processes such as rolling and extrusion, these operations can be performed extremely easily and efficiently, such as stabilizing the dimensions, cleaning the skin, and making scorching difficult. The fracture characteristics of the vulcanized rubber obtained as described above will not be reduced. The obtained natural rubber can be suitably used for rubber products such as conveyor belts, belts, hoses, etc., in addition to pneumatic tires.

[0023]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 6 and Comparative Examples 1 to 5, Preparation of masticated rubber (natural rubber)] The mastication conditions were determined by using a Banbury mixer with the blending contents (parts by weight) shown in Table 1 below, with a start temperature of 80 ° C. For 90 seconds. The gel amount (%), molecular weight and Mooney viscosity (processability) of the obtained masticated rubber were measured by the following methods. The results are shown in Table 1 below. In addition, RSS3 was used for natural rubber. The ester is represented by the above general formula (I) (described in the margin of Table 1).
Was used.

(Measurement of gel amount of masticated rubber) The gel amount of masticated rubber was measured by immersing 0.2 g of rubber in 60 cc of toluene and leaving it at room temperature for 24 hours. Thereafter, the gel component was separated by a centrifugal separator, the solvent was volatilized by a reduced-pressure drier, and the gel weight was measured. The smaller the gel amount,
This indicates that the amount of the polymer gel is degraded.

(Measurement of molecular weight of masticated rubber) The molecular weight of masticated rubber was determined by dissolving 0.03 g of rubber in 30 cc of THF (tetrahydrofuran) and leaving it at room temperature for 24 hours, followed by GPC (GEL PERMEATION CHROMATOG) manufactured by TOSOH.
RAPH).

(Mooney viscosity of masticated rubber (ML1 +
4. Measurement of processability) The processability (viscosity) of masticated rubber is
MOONEY VISCOME manufactured by SHIMADZU
It measured at 100 degreeC using TER SMV201, and set it as the value after 5 minutes.

[0028]

[Table 1]

As is clear from the results in Table 1, the masticated rubbers (natural rubber compositions) of Examples 1 to 6 which fall within the scope of the present invention.
It was found that, compared to Comparative Examples 1 to 5, which were out of the range of the present invention, the amount of the polymer gel could be reduced without lowering the molecular weight, and the processability could be improved. When viewed individually, Comparative Example 1 is a case of a natural rubber composition without mastication, and in this case, the gel amount is large, and Comparative Example 2 is a case of a natural rubber composition with normal mastication. In this case, too, it can be seen that the gel amount is large and the molecular weight is also reduced. Further, Comparative Examples 3 and 4 are the cases of natural rubber compositions which were masticated by adding a normal deflocculant. In these cases, the gel amount was reduced, but the molecular weight was also significantly reduced. I understand. Comparative Example 5 was a case where the compound (aromatic polycarboxylic acid derivative) described in JP-A-11-209406 was used [when m in formula (I) was out of the range of the present invention]. The amount of gel is smaller than Comparative Examples 1 to 3, and the same effect as that of the present invention is recognized. However, the present invention is more effective at the same compounding amount (comparing Example 2 and Reference Example). It turns out that the effect is great. In contrast, Examples 1 to 6 are natural rubber masticated using an ester serving as the mastication additive of the present invention,
In this case, it was found that the gel amount could be significantly reduced without lowering the molecular weight, and the processability could be further improved.

Next, the dust suppressing effect of the component (b) when the component (a) was carried was examined. As the component (a) ester, the type A of Example 2 was used, and as a solid, silica (manufactured by Nippon Silica Industry Co., Ltd., trade name “Nipsil AQ”)
As the component (b), ethylene glycol diolate (melting point −6 ° C., boiling point 250 ° C. or more) is used. As the component (1), the component (a) supported on an equal weight solid is:
As (2), a composition was prepared in which 8 parts by weight of the component (b) was added to 100 parts by weight of the component (a), and the solid was supported on an equal weight of the component (a). In addition to natural rubber, respectively, that is, natural rubber 1 as a component (a)
2 parts by weight per 00 parts by weight were added, and mastication was performed to examine the state of dust. The amount of dust in the mastication is significantly reduced when (2) is used, compared to when (1) is used, and the dust suppression effect of adding the (b) component is reduced. I was able to confirm. The gel weight, molecular weight, and Mooney value were the same as in Example 2 in each case.

[0031]

According to the method of the present invention, there is provided a method for masticating natural rubber which can reduce the amount of gel without lowering the molecular weight of natural rubber and further improve the processability.
According to the present invention, there is provided a natural rubber capable of reducing the gel amount without lowering the molecular weight of the natural rubber and further improving the processability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/10 C08K 5/10 5/12 5/12 9/12 9/12 C08L 71/02 C08L 71 / 02 // C08C 4/00 C08C 4/00 B29K 7:00 B29K 7:00 (72) Inventor Masaaki Dobashi 1334 Minato, Wakayama, Wakayama Pref. Kao Corporation Research Laboratory (72) Inventor Tetsuo Takano, Wakayama, Wakayama 1334 F-term in Kao Corporation Laboratory (Reference) 4F070 AA05 AC36 AC38 AC43 AC65 AE02 EA04 4F201 AA46 AB07 AB19 AP16 AR06 BA01 BA09 BC01 BC37 BK14 BK75 4J002 AC011 EC037 EC067 ED036 ED037 ED066 EH037 EH146EH 010G 156 E076

Claims (8)

[Claims] 1. A method of adding an ester (a) of an aromatic polycarboxylic acid and a (poly) oxyalkylene derivative having at least one carboxyl group bonded to an aromatic ring in a molecule to natural rubber. Characteristic method of masticating natural rubber. 2. The method for masticating natural rubber according to claim 1, wherein the ester of the component (a) is supported on a solid and added to natural rubber. 3. The method for masticating natural rubber according to claim 2, further comprising adding at least one kind (b) selected from the group consisting of (poly) oxyalkylene derivatives, alcohols and fatty acid esters thereof. 4. The method for masticating natural rubber according to claim 3, wherein the melting point of the component (b) is 20 ° C. or lower and the boiling point is 150 ° C. or higher. 5. The method of masticating natural rubber according to claim 1, wherein the ester of the component (a) is a compound represented by the following general formula (I). Embedded image 6. A method for masticating natural rubber, comprising adding 0.05 to 20 parts by weight of the ester according to claim 1 to 100 parts by weight of natural rubber. 7. The blending amount of the component (b) is the same as the component (a)
The method for masticating natural rubber according to any one of claims 3 to 6, wherein the amount is 20% by weight or less based on the ester of the component. 8. A natural rubber obtained by the method for masticating a natural rubber according to any one of claims 1 to 7.