JP2000026663A - Sulfur vulcanizable rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sulfur vulcanizable rubber compositions which have a high rate of vulcanization and accordingly, a short vulcanization time and do not bring about undesirable properties on the vulcanized rubbers when vulcanized. SOLUTION: An elastomer having an olefinic unsaturation, a conventional amounts of a vulcanizing agent, an accelerator, and other conventional additives, and about 0.05 - about 5.0 phr methyltrialkylammonium salt represented by the formula (wherein R1, R2 and R3 are each independently 8-10C alkyl; and M is selected from the group consisting of Cl, Br, CH3SO4 and HSO4) are compounded by the conventional method to obtain a sulfur vulcanizable rubber composition whose vulcanization time can significantly be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the vulcanization of a sulfur vulcanizable rubber composition. More specifically, the present invention relates to a method for increasing the vulcanization rate of a sulfur vulcanizable rubber by adding a methyltrialkylammonium salt.

[0002]

2. Description of the Related Art The "rate of vulcanization" is defined as the rate at which rubber compound crosslinking and stiffness (modulus) development occur. As the rubber compound is heated, the properties of the rubber compound change from a soft plastic material to a tough elastic material accordingly. During the vulcanization process, a bridge is introduced that connects the long polymer chains of the rubber. As more crosslinking is introduced, the polymer chains become more tightly bound and the stiffness, or modulus, of the compound increases. Vulcanization rate is an important vulcanization parameter because vulcanization rate determines, in part, the time the compound must be vulcanized, or "vulcanization time." In the manufacture of vulcanized rubber articles, significant cost savings can be realized by reducing vulcanization time. By increasing the vulcanization rate, the vulcanization time required to satisfy the minimum vulcanization can be reduced. Extensive research has been done to reduce the vulcanization time of rubber to produce the above.

[0003]

Thus, there is a need for an improved method of increasing the rate of vulcanization without imparting undesired properties to the vulcanized rubber.

[0004]

SUMMARY OF THE INVENTION The present invention provides a sulfur vulcanizable rubber having the following formula:

[0005]

Embedded image

(Wherein R ¹ , R ² and R ³ independently represent 8 to 1)
An alkyl group having 0 carbon atoms, M is Cl,
It is selected from the group consisting of Br, CH ₃ SO ₄ and HSO ₄ . The present invention relates to a method for increasing the vulcanization rate of a rubber composition, comprising adding a methyltrialkylammonium salt represented by the formula Further, according to the present invention, there is disclosed a sulfur vulcanizable rubber composition comprising an olefinic unsaturation-containing elastomer, a sulfur-based vulcanizing agent, an accelerator and a methyltrialkylammonium salt selected from the above formula. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the use of methyltrialkyl ammonium salts as activators for sulfur vulcanizable rubber compositions. Particularly preferred methyl trialkyl ammonium salt is methyl trialkyl (C ₈ ~C ₁₀₎ ammonium hydrochloride, Sherex Ohio (Ohio) Dublin (Dublin) ·
Aliquo from the Sherex Chemical Company under Adogen® 464 and from Henkel Corporation of Minneapolis, Minnesota.
t: commercially available under the registered trademark 336. Methyltrialkylammonium salts are generally known as phase transfer catalysts and are described in U.S. Pat. No. 3,992,432. The entire description of this U.S. patent is incorporated herein by reference.

[0007] To facilitate handling, the methyltrialkylammonium salt may be deposited on a suitable carrier. Examples of carriers that can be used in the present invention include silica,
Carbon black, alumina, diatomaceous earth, silica gel and calcium silicate.

The use of methyltrialkylammonium salts does not appear to affect the distribution of crosslinks when used in combination with a primary and, optionally, a secondary accelerator. However, with increasing vulcanization rates, there is usually an increase in the efficiency of the vulcanizing chemical in the form of increased degree or state of vulcanization.

The present invention can be used to vulcanize sulfur vulcanizable rubbers or elastomers containing olefinic unsaturation. The phrase "rubber or elastomer containing olefinic unsaturation" is intended to encompass a wide variety of synthetic rubbers, as well as natural rubber and its various raw and regenerated varieties. Representative synthetic polymers are butadiene and homologs and derivatives thereof, such as the homopolymerized products of methylbutadiene, dimethylbutadiene and pentadiene, and also formed from butadiene or homologs or derivatives thereof and other unsaturated monomers. Copolymers such as Among the latter, acetylenes such as vinyl acetylene, olefins such as isobutylene copolymerizing with isoprene to form butyl rubber, vinyl compounds such as acrylic acid and acrylonitrile (polymerizing with butadiene to form NBR),
Methacrylic acid and styrene (the latter compound polymerizes with butadiene to form SBR), vinyl esters and various unsaturated aldehydes, ketones and ethers such as acrolein, methyl isopropenyl ketone and vinyl ethyl ether is there. Specific examples of the synthetic rubber include neoprene (polychloroprene), polybutadiene (including cis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene),
Copolymers of butyl rubber, 1,3-butadiene or isoprene with monomers such as styrene, acrylonitrile and methyl methacrylate, and also ethylene / propylene terpolymer known as ethylene / propylene / diene monomer (EPDM) And especially the ethylene / propylene / dicyclopentadiene terpolymer.

[0010] The activator used in the present invention can be added to the rubber by any conventional technique, for example by a mill or a Banbury. The amount of the methyltrialkylammonium salt can vary over a wide range depending on the type of rubber and other compounds present in the vulcanizable composition. The amount of methyltrialkylammonium salt will generally range from about 0.05 to about 5.0 phr.
Used in the range. A range from 0.1 to about 1.5 phr is preferred.

[0011] The vulcanization of rubber is generally about 100 ° C to 200 ° C.
At a temperature of Vulcanization is preferably carried out at about 110 ° C.
It is performed at a temperature in the range of 180 ° C. Any of the usual vulcanization methods can be used, for example heating in a press or mold, heating with superheated steam or hot air or in a salt bath.

In addition to the methyltrialkylammonium salt, other rubber additives can be incorporated into the sulfur vulcanizable material. Additives commonly used in rubber vulcanizates include, for example, carbon black, tackifier resins, processing aids, antioxidants, antiozonants, stearic acid, activators,
Wax, oil and peptizing agent
It is. As known to those skilled in the art, the particular additives described above will generally be used in conventional amounts, depending on the intended use of the sulfur-vulcanizable material. Typical loadings of carbon black are about 20 to 100 based on diene rubber.
It accounts for parts by weight (phr), preferably 50 to 70 phr. Typical amounts of tackifier resin are about 5 to 10 phr. Typical amounts of processing aids are about 1 to 5 phr. Typical amounts of antioxidants are from 1 to about 10 phr. Typical amounts of antiozonants are from 1 to about 10 phr. Typical amounts of stearic acid are 1 to about 2 phr. Typical amounts of zinc oxide are 2-5 phr. Typical amounts of wax are 1 to 5 phr. Typical amount of oil is 5-30p
hr. Typical amounts of disintegrant are 0.1 to 1 phr
It is. The presence and relative amounts of the above additives are not a feature of the present invention.

The vulcanization is performed in the presence of a sulfur-based vulcanizing agent.
Examples of suitable sulfur-based vulcanizing agents include elemental sulfur (free sulfur) or sulfur-providing vulcanizing agents, such as amine disulfides, polymeric polysulfides or sulfur olefin adducts. Preferably, the sulfur-based vulcanizing agent is elemental sulfur. As known to those skilled in the art, sulfur vulcanizing agents are used in amounts ranging from about 0.5 to 8 phr. 1.5-
A range of 2.25 phr is preferred.

Accelerators are used to control the time and / or temperature required for vulcanization and to improve the properties of the vulcanized rubber. In one embodiment, a single accelerator system can be used, ie, a primary accelerator. Primary accelerators are usually used in amounts ranging from about 0.5 to 2.0 phr. In another embodiment, primary accelerators generally used in large amounts (0.5-1.0 phr), and generally small amounts (0.05-0.1 phr) to improve and activate the properties of the vulcanized rubber. Combinations of two or more accelerators, which can consist of secondary accelerators used at 50 phr), can be used. Combinations of these accelerators are known to produce a synergistic effect on the final properties and are somewhat better than those produced by the use of either accelerator alone. In addition, delayed action accelerators that do not result from normal processing temperatures, but that provide sufficient vulcanization at normal vulcanization temperatures, can also be used. Suitable types of accelerators that can be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. The primary accelerator is preferably a sulfenamide. If a secondary accelerator is used, the secondary accelerator is preferably a guanidine, dithiocarbamate or thiuram compound.

[0015]

The following examples are given by way of illustration and do not limit the invention. Examples 1-11 Methyl trialkyl (C ₈ ~C _{1 0)} ammonium hydrochloride in varying amounts for those using an equivalent amount of tetraethylammonium hydrobromide these experiments as a comparative control (TEABr) (MTAAC) This is to compare the effectiveness of. MTAAC and TEABr were combined with 40 parts by weight of polyisoprene, 60 parts by weight of cis-1,4-polybutadiene, 0.5 phr of a primary accelerator and conventional amounts of carbon black, tackifiers, processing aids, Disintegrant,
Used in typical sidewall rubber stocks containing stearic acid, zinc oxide and sulfur. The various additives described above were compounded using conventional techniques. Vulcanization tests were carried out at 150 ° C. on a Monsanto Cure Rheometer according to ASTM test method D-2084-87. Compound scorch is ASTM D16
Measured according to 46-87. Table 1 shows the results of Examples 1 to 11.

[0016]

[Table 1]

The data in Table 1 show that the control compound (tetraethylammonium bromate) was t25 and t9.
A rating of 0 indicates little or no effect on vulcanization time. However, methyl trialkyl (C ₈ -C ₁₀ ) ammonium hydrochloride (MTAA)
The use of C) resulted in a significant reduction in vulcanization time. Methyl trialkyl to Example 12 to 19 sulfur vulcanizable rubber (C ₈ ~C ₁₀₎
Experiments (Examples 12 to 19) were performed to prove that the vulcanization rate was increased by the addition of ammonium salts. An experiment (Example 12, comparative control) was performed for comparison purposes. To demonstrate the effectiveness of using methyl trialkyl (C ₈ -C ₁₀₎ ammonium hydrochloride 68 wt% deposited on a calcium silicate, experiments (Examples 13 and 14)
Was done. Experiments (Examples 15 and 16) was performed to demonstrate the effectiveness of using 72 wt% of methyl trialkyl (C ₈ -C ₁₀₎ ammonium hydrochloride deposited on silica. Experiment (Example 17-19) were conducted to demonstrate the effectiveness of using methyl trialkyl (C ₈ -C ₁₀₎ ammonium methyl sulfate.
Various concentrations (phr) of methyltrialkylammonium salt, as well as 40 parts of polyisoprene, 60 parts of cis-
1,4-polybutadiene, 0.5 phr primary accelerator,
Eight rubber compounds were prepared using typical sidewall rubber stocks containing conventional amounts of carbon black, tackifiers, process oils, anti-disintegrants, stearic acid, zinc oxide and sulfur. The various additives described above were formulated using conventional techniques, and their samples were evaluated using the vulcanization procedures of Examples 1-11. Example 1 is shown in Table 2 below.
The vulcanization properties of the compounds of Nos. 2 to 19 were tabulated, with similar vulcanization conditions occurring for various vulcanization rates as seen at t25 and t90.

[0018]

[Table 2]

[0019] Example 13 to 19 demonstrates that methyl trialkyl (C ₈ ~C ₁₀₎ ammonium salt is effective for hyperactivity the vulcanization rate. That is, Examples 13 to
16 data, the use of various carriers indicates that it is not detrimental to the effectiveness of the methyl trialkyl (C ₈ ~C ₁₀₎ ammonium hydrochloride. Examples 17 to 19
Suggests that methyl trialkyl (C ₈ -C ₁₀ ) ammonium methyl sulfate is as effective as the other methyl trialkyl ammonium salts used in the present invention. Examples 20 to 21 Methyltrialkylammonium hydrochloride (MTAAC)
The following experiment was conducted to prove the activation of vulcanization. The formulation of Example 20 (comparative control) does not contain MTAAC, while the formulation of Example 21 has 0.30
phr of MTAAC. Both formulations had 20 parts by weight of natural rubber, 20 parts by weight of synthetic polyisoprene, 60 parts by weight of polybutadiene, 0.5 phr.
And typical sidewall rubber stocks containing conventional amounts of carbon black, wax, oil, anti-disintegrant, tackifier resin, stearic acid, zinc oxide and sulfur. The above various additives were blended, and the samples were vulcanized by compression molding at 150 ° C. for 18 minutes. The vulcanization properties were evaluated in the same manner as in Examples 1 to 11. ASTM method D41 for stress-strain characteristics
Tested by 2-87. Table 3 shows the results.

[0020]

[Table 3]

The above data show that the addition of methyltrialkylammonium hydrochloride reduces the cure time required to reach optimal vulcanization. The use of a methyltrialkylammonium salt is dependent on the crosslink density (v ×
As evidenced by the increase in 10 ⁴ ) and the 300% modulus, it improves the sulfur utilization but has little effect on the cross-link distribution. Examples 22-23 The following experiments were performed to demonstrate the effectiveness of MTAAC in another sulfur vulcanizable composition.

The formulation of Example 22 (comparative control) was MTA
No AC, whereas the formulation of Example 23 had 0.50 p
hr of MTAAC. Both formulations are 30
Parts by weight polybutadiene, 70 parts by weight SBR, 1 ph
r, a primary tread rubber containing 0.15 phr of a secondary accelerator and conventional amounts of carbon black, wax, oil, peptizer, stearic acid, anti-disintegrant, zinc oxide and sulfur It consisted of materials. The above various additives were blended, and the samples were
Vulcanized by compression molding at 18 ° C for 18 minutes. After vulcanization, these samples were evaluated using the test procedures of Examples 20-21. The data is shown in Table 4.

[0023]

[Table 4]

Examples 22 and 23 are polybutadiene / S
Demonstrates the effectiveness of MTAAC in BR blends. Examples 24 and 25 The following experiments were performed to demonstrate the effectiveness of MTAAC in another sulfur vulcanizable composition. The formulation of Example 24 (comparative control) did not contain MTAAC, while the formulation of Example 25 contained 0.2 phr of MTAAC. Both formulations contain 70 parts by weight of a medium vinyl content polybutadiene, 30 parts by weight of cis-1,4-polybutadiene, 1.1 phr of a primary accelerator, 0.16 phr of a secondary accelerator, and a conventional amount of carbon black. It consisted of a typical tread rubber stock containing wax, oil, anti-disintegrant, stearic acid, zinc oxide and sulfur. The various additives described above were compounded using conventional techniques.

These samples were evaluated by the vulcanization test procedure used in Examples 20 and 21. The data is shown in Table 5.

[0026]

[Table 5]

Examples 26-29 These experiments demonstrate the use of methyl trialkyl (C ₈ -C ₁₀ ) ammonium hydrochloride (MT) in the presence or absence of an accelerator.
AAC). Example 26-
The remaining ingredients of the 29 formulation were 50 parts by weight of SBR, 50
Parts by weight of polyisoprene, and the usual amount of oil (2
8.75 phr), carbon black (50 phr),
It consisted of a rubber stock containing zinc oxide (3 phr), sulfur (2 phr) and stearic acid (2 phr).
Example 26 used no accelerator or MTAAC. In Example 27, no accelerator was used, but 0.5
0 phr of MTAAC (68% by weight of Adgen 464 supported on a calcium silicate carrier) was used. Example 2
8 used 1.5 phr of accelerator, but MTAAC
Was not used. Example 29 used 1.5 phr of accelerator and 0.50 phr of MTAAC (as in Example 27). The various additives described above were compounded using conventional techniques. The vulcanization test is based on ASTM test method D-
15 with Monsanto vulcanization rheometer according to 2084
Performed at 0 ° C. The vulcanization properties are shown in Table 6 below.

[0028]

[Table 6]

Example 26 shows that very poor vulcanization occurs when neither MTAAC nor accelerator is used. The data in Example 27 show that the use of MTAAC in the absence of an accelerator does not result in any substantial vulcanization. The data in Example 28 shows a typical accelerator effect. The data of Example 29 shows that the accelerator and M
This shows a dramatic reduction in vulcanization time when using both TAAC activators.

Continuation of Front Page (71) Applicant 590002976 1144 East Market Street, Akron, Ohio 44316-0001, U.S.A. S. A. (72) Inventor Richard Michael Dosdocky, Clearview Road, Ravenna, 44266, Ohio, USA 3050 (72) Inventor Martin Paul Cohen 44313, Ohio, United States of America, Morewood Road, 3179

Claims (2)

[Claims] 1. A sulfur vulcanizable rubber composition comprising an elastomer having olefinic unsaturation, a vulcanizing agent, an accelerator and a methyltrialkylammonium salt represented by the following formula: Wherein R ¹ , R ² and R ³ are independently an alkyl group having 8 to 10 carbon atoms, and M is selected from the group consisting of Cl, Br, CH ₃ SO ₄ and HSO ₄ To be elected. 2. The composition of claim 1, wherein the methyltrialkylammonium salt is present in an amount ranging from about 0.05 to about 5.0 phr.