JPH11279333A - Highly hard crosslinked rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which generates substantially no carbon disulfide when crosslinked, is crosslinked in a good working atmosphere and gives a crosslinked rubber with a high hardness. SOLUTION: The composition contains (A) 1,2-polybutadiene wherein the vinyl bond content is 70% or larger, the degree of crystallinity is 5% or larger and the intrinsic viscosity [η] (determined in toluene at 30 deg.C) is 0.5 dl/g or larger and (B) at least one rubber chosen from the group consisting of a natural rubber, a diene synthetic rubber and a non-diene synthetic rubber in a weight ratio ((A)/(B)) of from 40/60 to 100/0. Furthermore, against 100 pts.wt. total amount of component (A) and component (B), (C) from 0 to 100 pts.wt. rubber softener, (D) from 0 to 600 pts.wt. filler, (E) from 10 to 100 pts.wt. sulfur, (F) from 5 to 40 pts.wt. thiazole vulcanization accelerator and (G) from 10 to 40 pts.wt. sulfenamide vulcanization accelerator, are contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for high hardness crosslinked rubber having low toxicity.

[0002]

2. Description of the Related Art Natural rubber, synthetic rubber, 1,2-polybutadiene and the like are used as cross-linked rubbers. In order to obtain particularly high hardness, high-hardness cross-linked products containing a large amount of sulfur (ebonite) are used. Formulations) are known. Most of the means for obtaining these crosslinked products are by hot pressing. Japanese Patent Publication No. 6-55555 discloses a method for obtaining a high-hardness crosslinked product using hot air. However, all of these formulations use a thiuram-based or dithiocarbamate-based accelerator, which is called a super-accelerator having a high crosslinking-acceleration power, as a main component as a means for obtaining a high-hardness crosslinked product. A large amount of carbon disulfide is generated in the cross-linking reaction using. Carbon disulfide is very toxic and is designated as a first class organic solvent, and the control concentration is specified as 10 ppm. Its toxicity is a strong paralytic effect, which can especially affect the nervous system and go crazy. It also affects the liver and kidneys. Therefore, in order to obtain a favorable working environment, it is necessary to establish a composition that does not use a thiuram-based or dithiocarbamate-based vulcanization accelerator or a composition in which a small amount is added.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a crosslinked rubber which can be crosslinked in a favorable working environment without substantially generating carbon disulfide at the time of crosslinking, and which has high hardness. To provide a rubber composition that can be used.

[0004]

According to the present invention, (A)
The vinyl bond content is 70% or more, the crystallinity is 5% or more, and the intrinsic viscosity [η] (in toluene, 30 ° C.) is 0.5 dl / g.
The above 1,2-polybutadiene and (B) at least one rubber selected from the group consisting of natural rubber, diene-based synthetic rubber and non-diene-based synthetic rubber other than the component (A) are 40/60. １００100/0 ((A) / (B)), and the components (A) and (B)
(C) 0-100 parts by weight of a rubber softener, (D) 0-600 parts by weight of a filler, based on 100 parts by weight of the total amount of the components.
(E) 10 to 100 parts by weight of sulfur, (F) 5 to 40 parts by weight of a thiazole vulcanization accelerator, and (G) 10 to 40 parts by weight of a sulfenamide vulcanization accelerator. The above object of the present invention is achieved by providing a composition for a high hardness crosslinked rubber. The present invention is described in detail below, and other objects, advantages and effects of the present invention will become apparent.

[0005] 1,2-polybutadiene as the component (A) blended in the composition of the present invention has a 1,1 polybutadiene content measured by ¹³ C-NMR method in order to obtain an appropriate hardness and shape conformability at the time of crosslinking. 2 Bond content is 70% or more, preferably 85%
As described above, the crystallinity measured by the X-ray diffraction method is 5% or more, preferably 10 to 40%. Although the molecular weight can be selected over a wide range, the intrinsic viscosity [η] (toluene, 30 ° C.) is 0.5 dl / g or more, preferably 0.7 dl / g in order to obtain a kneadable and high-hardness crosslinked product. ~
4.0 dl / g.

The rubber of the component (B) is a rubber other than the component (A) and is selected from natural rubber, diene-based synthetic rubber and non-diene-based synthetic rubber. The component (B) is used for improving the kneading processability of the composition of the present invention and adjusting the hardness of the uncrosslinked dough. If the above characteristics are satisfied only by the component (A), it is not always necessary to use the component. The mixing ratio of the component (A) and the component (B) is the weight ratio ((A) /
(B)) at 40/60 to 100/0, preferably 70 /
30 to 100/0. Excessive blending of component (B)
The result is poor shape followability, which is not preferable.

[0007] Typical examples of the rubber used for the component (B) include natural rubber (NR) and polyisoprene rubber (I).
R), styrene-butadiene rubber (SBR), polybutadiene rubber (BR), acrylonitrile rubber (NB
R), diene-based synthetic rubbers such as chloroprene rubber (CR), and ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), ethylene-butene rubber (EBM), and acrylic rubber (ACM, A
NM) and non-diene-based synthetic rubbers such as fluororubber. Preferred among these are NR, IR,
SBR, and BR. These can be used alone or in combination of two or more.

As the rubber softener (C), a mineral oil rubber softener generally called a process oil or extender oil is preferably used. The mineral oil-based rubber softener is usually a mixture of an aromatic ring compound, a naphthene ring compound and a paraffin chain compound.
Those having 50% or more of the total number of carbon atoms in the paraffin chain are called paraffinic and have a naphthene ring carbon number of 30 to
45% naphthenic, 30% aromatic carbon
More are called aromatics. The mineral oil-based rubber softener that can be used as the component (C) of the present invention is preferably a naphthene-based or aromatic-based softener among the above-mentioned categories from the viewpoint of compatibility with the component (A).

The amount of the softening agent (C) is from 0 to 10 parts by weight based on 100 parts by weight of the total amount of the components (A) and (B).
0 parts by weight, preferably 5 to 30 parts by weight. Excessive blending makes it difficult to obtain a high-hardness cross-linked product.
The kneading processability is not always good.

The filler of the component (D) is blended to reduce the cost of the blend and to improve the vibration damping performance by increasing the surface weight. Therefore, when the cost of the compound does not matter or when the vibration damping performance is not required, the compounding is not necessarily required. Examples of fillers that can be used include light calcium carbonate, heavy calcium carbonate, various surface-treated calcium carbonates, talc, magnesium hydroxide, mica,
Natural silicic acid, synthetic silicic acid, titanium oxide, glass fiber, carbon fiber, cotton floc and various carbon blacks can be used, but are not limited thereto. Among the fillers exemplified above, heavy calcium carbonate, light calcium carbonate, and talc are economically advantageous and preferred. These can be used alone or in combination of two or more. The mixing amount of the filler is up to 400 parts by weight, preferably up to 400 parts by weight, based on 100 parts by weight of the total of components (A) and (B). Excessive blending is inferior in sheeting due to poor kneading processability,
Even if sheeting can be performed, the surface texture of the crosslinked sheet becomes worse due to poor cohesion of the obtained uncrosslinked fabric.

The sulfur of the component (E) may be in any form as long as it functions as a crosslinking agent. Specifically, powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur and the like can be used. These can be used alone or in combination of two or more. The amount of sulfur is (A)
10 to 10 parts by weight of the total amount of the component and the component (B)
100 parts by weight, preferably 15 to 100 parts by weight, more preferably 20 to 100 parts by weight. If the amount is too small, a high-hardness crosslinked product cannot be obtained. If the amount is excessive, the possibility of causing a phenomenon such as deformation or destruction of the crosslinked material due to the reaction heat at the time of crosslinking increases.

The thiazole vulcanization accelerator of the component (F) is
By using a specific amount together with the sulfenamide-based vulcanization accelerator of the component (G) to be described later, (A)
The crosslinking reaction between the component and the component (B) proceeds stably and appropriately. As a result, a crosslinked product having high hardness is obtained. Since these vulcanization accelerators do not generate toxic carbon disulfide at the time of crosslinking, a good working environment can be maintained.
Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole and salts thereof (ZnMBT), 2-mercaptothiazoline, dibenzothiazyl sulfide (MBT
S), 2- (4'-morpholinodithio) benzothiazole, 2 (2,4-dinitrophenylthio) benzothiazole, 2- (2,6-dimethyl-4-morpholinothio)
Benzothiazole, 4-morpholinyl-2-dibenzothiazyl disulfide, 1,3-bis (2-benzothiazolylmercaptomethyl) urea and the like can be mentioned. These can be used alone or in combination of two or more. The compounding amount of the thiazole vulcanization accelerator is 5 to 40 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of the total of the components (A) and (B). If the amount is too small, a sufficient cross-linking reaction is not performed, so that a high-hardness cross-linked product cannot be obtained. Excessive blending further increases the hardness, but increases the possibility of causing phenomena such as deformation and breakage of the crosslinked product.

As the sulfenamide-based vulcanization accelerator of component (G), benzothiazyl-2-diethylsulfenamide, N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N, N-dicyclohexyl-
2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, N, N
-Diisopropyl-2-benzothiazylsulfenamide, N-tert-butyl-2-benzothiazylsulfenamide and the like. These may be used alone or in combination.
More than one species can be used in combination. The compounding amount of the sulfenamide-based vulcanization accelerator depends on the component (A) and the component (B).
10 to 40 parts by weight, based on 100 parts by weight of the total amount of the components,
Preferably it is 10 to 30 parts by weight. With an under formulation,
The rise of the vulcanization reaction is delayed. Excessive blending results in poor scorch stability and is not preferred.

In the present invention, a thiuram-based and dithiocarbamate-based vulcanization accelerator, which is a substance causing the generation of carbon disulfide, can provide a high-hardness crosslinked product without blending. However, since these vulcanization accelerators show excellent vulcanization accelerating power when added in small amounts to the components (F) and (G), the working environment is sufficiently improved and some toxicity is allowed. In some cases, small amounts of thiurams and / or
Alternatively, a dithiocarbamate vulcanization accelerator may be used. The mixing amount at that time is at most 3 parts by weight, preferably at most 2 parts by weight, based on 100 parts by weight of the total of the components (A) and (B). Excessive blending is undesirable because carbon disulfide is generated in non-negligible amounts. Also, scorch stability is reduced.

As the thiuram-based vulcanization accelerator which can be used, tetramethylthiuram monosulfide (TM
TM), tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram monosulfide, tetrabutylthiuram disulfide, N,
N'-dimethyl-N, N'diphenylthiuram disulfide, dipentamethylenethiuram monosulfide, dipentamethylenethiuram disulfide, dipentamethylenethiuram tetrasulfide, dipentamethylenethiuram hexasulfide, dicyclopentamethylenethiuram disulfide, mixed alkylthiuram Disulfide, a complex of activated disulfide and the like. Examples of the dithiocarbamate-based vulcanization accelerator that can be used include sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium di-n-butyldithiocarbamate, potassium dimethyldithiocarbamate, potassium di-n-butyldithiocarbamate, dimethyldithiocarbamine Zinc acid (ZnMDC), zinc pentamethylenedithiocarbamate, zinc ethylphenyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, complex salts of zinc dibutyldithiocarbamate and dibutylamine, dibenzodiyldithiocarbamine Zincate, zinc N-pentamethylenedithiocarbamate,
Zinc dimethylpentamethylenedithiocarbamate, a complex salt of zinc pentamethylenedithiocarbamate and piperidine, a zinc salt of ethylphenyldithiocarbamate, a complex zinc salt of dithiocarbamic acid, selenium dimethyldithiocarbamate, selenium diethyldithiocarbamate, tellurium diethyldithiocarbamate, copper dimethyldithiocarbamate, Iron dimethyldithiocarbamine, bismuth dimethyldithiocarbamate, dimethylammonium dimethyldithiocarbamate, dibutylammonium dimethyldithiocarbamate, N, N-dimethylcyclohexamine salt of diethylaminediethyldithiocarbamate, dibutyldithiocarbamate, piperidine pentamethylenedithiocarbamate, methylpentamethylenedithiocarbamate Pipericon etc. It is below.

The composition of the present invention may contain, if necessary, a compounding agent generally used in rubber compounding, for example, a vulcanization accelerator,
Tackifying resins, anti-aging agents, processing aids, coloring agents and the like can be added. In particular, vulcanization accelerating aids such as zinc oxide, magnesium oxide and fatty acids are preferably added from the viewpoint of facilitating the cross-linking reaction, and the tackifier resin is preferably added to obtain excellent shape following properties.

The method of mixing the components (A) to (G) and other compounding agents is not particularly limited, and is used for general rubber compounds such as Banbury type mixers, pressure kneaders, and open rolls. This is possible with a mixing method. The uncrosslinked compound obtained by any one of the above methods is formed into a sheet or the like using a calender roll, open roll, extruder, or the like, and then subjected to crosslinking in hot air. The crosslinking temperature is from 120 to 250 ° C, preferably from 130 to 250 ° C.
Crosslinking is carried out by heating in hot air in the range of 180 ° C. At the time of crosslinking, there is no particular need to apply pressure, and crosslinking can be performed under atmospheric pressure. In this case, the desired shape is created with a wooden mold, a viscosity mold, a mold, etc., and by placing the uncrosslinked sheet on the mold, the uncrosslinked sheet is softened by heat and conforms to the surface shape of the mold. Following, it is possible to carry out cross-linking molding to a desired shape. Further, it is also possible to use a tacky adhesive or the like at the time of cross-linking to further strengthen the adhesive force with the mold, and it is possible to integrate with the mold together with the cross-linking.

A high-hardness rubber crosslinked product can be obtained from the composition of the present invention, and it has excellent shape followability even when hot air crosslinking is performed under atmospheric pressure, and maintains a favorable working environment during crosslinking. it can. Therefore, the composition for a high-hardness crosslinked rubber of the present invention can be widely used for various linings, production of industrial articles, and the like.

[0019]

Next, the present invention will be described in more detail with reference to examples and comparative examples. In the examples and comparative examples, the methods for evaluating physical properties and the like and the components used are as follows.

[1] Evaluation method of physical properties (1) Seating property The composition mixed with the BR type Banbury mixer was
The following three-stage evaluation was performed according to the workability when performing sheeting with a thickness of 2 mm using a 0-inch test roll machine. ：: Sheeting can be easily performed to a predetermined thickness. Δ: Sheeting was performed to a predetermined thickness, but it was difficult. X: Sheeting cannot be performed to a predetermined thickness due to poor adhesion and poor cohesion. (2) Sagging test 1m thick with a 60mm diameter hole in 140 ° C oven
Place a 2mm thick uncrosslinked rubber sheet on the
After heating for a minute, the deformation distance (mm) at which the sheet fell into the hole was measured and evaluated. In addition, the sagging test shows that the larger the sag without sagging, the better the quality.If the sag is small, the shape following ability is insufficient, and in the case of sagging, the molten dough slips off on the inclined surface. Result.

(3) Uncrosslinked sheet hardness Measured with a JIS A type hardness meter. (4) Hardness of crosslinked product 2 mm thick on a 1 mm thick iron plate in a 140 ° C. oven
Was placed on the uncrosslinked rubber sheet for 30 minutes to carry out crosslinking, and then allowed to stand at 23 ° C. room temperature for 2 hours or more, and then measured with a Shore D hardness meter. (5) Carbon Disulfide Concentration An uncrosslinked rubber sheet was cut into 3 mm squares, approximately 2 g was precisely weighed in a 22 ml vial, the inside was replaced with nitrogen, sealed, heated at 140 ° C. for 30 minutes, and generated there. The carbon disulfide gas was measured by gas chromatography and gas chromatography / mass spectrometer, and the amount generated per gram of the uncrosslinked rubber sheet was calculated. (6) Scorch stability Using JSR Curastometer type III, swing angle 1 degree, 14
The measurement was performed under the condition of 0 ° C., and the time when the torque increased from the minimum torque by 2.5 kgf / cm ² was used as an index value. The scorch stability is an index of the storage stability of the product dough, and the larger the value, the better the scorch stability.

[2] Ingredients (1) JSR RB810: Equivalent to the component (A), JSR
Co., Ltd., vinyl bond content 90%, crystallinity 18
%, [Η] (toluene 30 ° C.) 1.25 dl / g (2) JSR SBR1502: corresponding to the component (B), J
(3) NR (RSS # 3): equivalent to component (B) (4) Heavy calcium carbonate: equivalent to component (D) (5) Naphthenic process oil: equivalent to component (C) ( 6) Synthetic petroleum resin: Coumarone (7) Vulcanization accelerator MBTS: Equivalent to (F) component (8) Vulcanization accelerator ZnMBT: Equivalent to (F) component (9) Vulcanization accelerator CBS: (G) component (10) Vulcanization accelerator ZnMDC: optional component (11) Vulcanization accelerator TMTM: optional component

EXAMPLE 1 1,2-Polybutadiene (JSR RB810, vinyl bond content 90%, crystallinity 18%, [η] (toluene 30 ° C.) 1.25) and other additives are shown in Table 1. The unvulcanized sheet which was mixed at a ratio with a Banbury mixer and sheeted to a thickness of 2 mm with a 10-inch test roll machine was evaluated for the items shown in Table 1. The results are shown in Table 1.

Examples 2 and 3 The same procedures as in Example 1 were carried out except that 100 parts by weight of 1,2-polybutadiene was used as the polymer component and the composition was changed as shown in Table 1. An unvulcanized sheet was prepared by the method described in the above and evaluated. The results are shown in Table 1.

Example 4 In Example 1, the blending amount of heavy calcium carbonate is shown in Table 1.
An unvulcanized sheet was produced and evaluated in the same manner as in Example 1 except that the sheet was changed as described in Example 1. The results are shown in Table 1.

Examples 5 to 7 Unvulcanized sheets were prepared and evaluated in the same manner as in Example 1 except that the type of the vulcanization accelerator was changed as shown in Table 1. Was done. The results are shown in Table 1.

Comparative Example 1 In Example 1, the polymer component used was 1,
An unvulcanized sheet was prepared and evaluated in the same manner as in Example 1 except that SBR1502 was used instead of 2-polybutadiene rubber. The results are shown in Table 2.

Comparative Example 2 The procedure of Example 1 was repeated except that the compounding amount of the rubber softener (naphthene-based process oil) was 200 parts by weight, and the sheeting was performed by pressing because the compound was soft and highly viscous. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 3 In Example 1, the amount of heavy calcium carbonate was changed to 15
An unvulcanized sheet was prepared and evaluated in the same manner as in Example 1 except that the amount was changed to 00 parts by weight. The results are shown in Table 2. Comparative Example 4 An unvulcanized sheet was produced and evaluated in the same manner as in Example 1, except that the amount of sulfur was changed to 2 parts by weight. The results are shown in Table 2.

Comparative Examples 5-9 Except that the amount of the vulcanization accelerator was changed to the amount shown in Table 2,
Evaluation was performed in the same manner as in Example 1. The result is
It is shown in the table.

[0031]

[Table 1]

[0032]

[Table 2]

From Table 1, it can be seen that the compositions of the present invention of Examples 1 to 7 can be easily sheeted, and are excellent in shape followability due to moderate dripping. Further, the obtained crosslinked product has a high hardness and an extremely small amount of highly toxic carbon disulfide is generated. Furthermore, it has excellent scorch stability. On the other hand, from Table 2, the compositions of Comparative Examples 1 to 9 have problems in at least one of the evaluation items, and are clearly inferior to the compositions of the present invention.

[0034]

According to the present invention, a high-hardness cross-linked rubber can be obtained from the composition for a high-hardness cross-linked rubber of the present invention, and a favorable working environment can be maintained. In addition, a mold is not required at the time of cross-linking, and the shape followability is excellent even with hot-air cross-linking under atmospheric pressure. Therefore, the composition for a high hardness crosslinked rubber of the present invention,
It can be widely used for various linings and industrial products.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 5/47 C08K 5/47 C08L 21/00 C08L 21/00

Claims (1)

[Claims] (A) a vinyl bond content of 70% or more, a crystallinity of 5% or more, and an intrinsic viscosity [η] (30% in toluene)
C) is 0.5 dl / g or more, and (B) at least selected from the group consisting of natural rubber, diene-based synthetic rubber, and non-diene-based synthetic rubber other than the component (A). 40 / 60-10 of one kind of rubber
0/0 weight ratio ((A) / (B)), and (C) rubber softener 0 to 10 with respect to 100 parts by weight of the total of components (A) and (B).
0 parts by weight, (D) 0 to 600 parts by weight of filler, (E) 10 to 100 parts by weight of sulfur, (F) thiazole vulcanization accelerator 5
A composition for a high-hardness cross-linked rubber, comprising-40 parts by weight and (G) 10-40 parts by weight of a sulfenamide vulcanization accelerator.