JPH0841107A - Method for reclaiming used vulcanized elastomeric material and composition for reclamation - Google Patents

Abstract

PURPOSE: To provide an effective process for reclaiming a used vulcanized elastomer material by treating used rubber chips with a vulcanization accelerator and a specific activator to delink or decompose the vulcanized network.

CONSTITUTION: A used vulcanized elastomer material is kneaded together with at least one compd. having a vulcanization accelerator function and at least one activator capable of initiating proton exchange at 70°C or lower to thereby delink or decompose the vulcanized network of the material, giving a revulcanizable elastomer material. At least one compd. selected from among zinc dimethyldithiocarbamate, 2-mercaptobenzothiazole, N-cyclohexyl-2- benzothiazolesulfenamide, tetraethylthiuram disulfide, guanidine compds., zinc dibutyldithiophosphate, etc., is pref. as the above vulcanization accelerator.

COPYRIGHT: (C)1996,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tires, molded articles, gloves, belts and the like, which are originally made from natural rubber or synthetic rubber vulcanized by a conventional sulfur accelerated vulcanization method or a combination thereof. The present invention relates to a recycling method and a recycling composition for recycling a used elastomer product.

[0002]

2. Description of the Related Art It is well known in the industry to recycle rubber regenerated from used rubber products, and about 20000 tonnes of rubber are recycled every year in the industry. Conventional rubber recycling methods use high temperatures and catalysts to digest the recycled elastomeric material, resulting in high energy consumption and significant degradation of the base polymer. Therefore, the regenerated rubber is inferior in physical properties and thus has limited applications. Typical reclaimed rubbers have tensile strengths of 5-6 MPa or less, while raw natural rubber of the same formulation can yield 20 MPa or more. In addition, the conventional method requires labor and requires difficult and complicated quality control and standardization.

The conventional method of reclaiming rubber consists mainly of taking vulcanized rubber crumbs, mixing them with the catalyst and exposing the mixture in the digester to temperatures above 170 ° C. for 4 to 6 hours. Next, the obtained material is kneaded until it becomes a sheet. Such reclaimed rubber products are used in small amounts with fresh rubber formulations as processing aids or diluents. The amount of recycled rubber in the mixture will adversely affect the physical and mechanical properties of the final vulcanizate.

Used tires and other rubber products are becoming environmental hazards worldwide. Therefore, there is a clear need for a satisfactory recycling law that addresses this ever-increasing environmental problem. The piles of used tires that currently exist worldwide are at risk of fire. Many attempts and approaches have been made to solve this environmental problem. Among these, the granulated tire piece is used as a road surface material, and the tire piece is burned to be used for energy generation. Hexamethylenetetramine and resorcinol tend to cleave the crosslinks of vulcanized rubbers in the presence of accelerators, which is reported in the literature distributed from Czechoslovakia (hereinafter "Czechoslovak method"). However, this method is uncontrollable and causes a change or decomposition in the produced recycled rubber. The mechanism of this reaction has not been described in detail, but it seems that the proton transfer reaction is involved in some way. Thus, none of the conventional methods or approaches have yet brought substantial progress in solving this cumbersome global problem.

[0005]

OBJECTS OF THE INVENTION The present invention provides a recycling method for effective recycling of used rubber products, which is an inexpensive method of cleaving the vulcanized network in used rubber pieces without excessively decomposing the backbone polymer. The purpose is to provide. The more such reclaimed rubber retains the physical and mechanical properties inherent to the original natural and synthetic rubbers, the wider the range of application of such reclaimed rubber in subsequent rubber production.

[0006]

DESCRIPTION OF THE INVENTION The present inventors have used used rubber product pieces to
A method has been developed that substantially transforms the material to properties close to those of new elastomers of similar formulation. This method is gentle, simple, and not harsh in energy or labor. We have reviewed the Czechoslovak method and developed a completely new method for the proton transfer reaction. However, our method does not use hexamine, which is a dangerous chemical to handle. Instead, we
It depends on the chemicals already used in the conventional rubber manufacturing process.

The present invention allows a novel chemistry to initiate proton exchange in a controlled manner at temperatures below 70 ° C., preferably below 50 ° C., thereby cleaving or degrading the vulcanized network of elastomeric materials. Based on the knowledge of using the composition.

Accordingly, the present invention provides a method for regenerating an elastomeric material from a vulcanized elastomeric material, ie, a vulcanized elastomeric material, together with one or more compounds having the action of a rubber accelerator. ℃
Treating with one or more activators capable of initiating proton exchange at the following temperatures, thereby cleaving or degrading the vulcanized network of vulcanized elastomeric materials:
A vulcanizable recycled elastomeric material is provided. The present invention also provides the cleaving or degrading composition described below.

The novel chemical composition of the present invention comprises one or more compounds having an action of a vulcanization accelerator and one activator.
It consists of two or more species. The compound is conventionally used as a vulcanization accelerator, and when used in combination with one or more activators capable of initiating proton exchange at a temperature of 70 ° C. or lower, the vulcanized network of vulcanized elastomeric material. It is possible to provide a vulcanizable regenerated elastomeric material by cleaving or breaking the bond. The compound having the action of the vulcanization accelerator is zinc dimethyldithiocarbamate (hereinafter referred to as "
ZDMC ”and zinc salt of thiocarbamates such as 2-mercaptobenzothiazole (hereinafter referred to as“ MB ”).
Abbreviated as "T") or its derivative in a molar ratio of 1: 1 to 1: 1.
Those consisting of 2 are preferred. This vulcanization accelerator is activated by one or more activators, preferably stearic acid and zinc oxide. Sulfur may be additionally added to these mixtures.

The preferred vulcanization accelerators ZDMC and MBT described above may be replaced by other accelerators, some of which are less active. The following are examples of known accelerators that can replace ZDMC and MBT, but not all. ZDMC includes zinc diethyldithiocarbamate (ZEDC), zinc dipropyldithiocarbamate, zinc dibutyldithiocarbamate (ZBDC) or zinc salt of dithiocarbamate such as zinc dibenzyldithiocarbamate (ZBDC), dibutyldithiophosphate zinc, and the like. It is replaced on a molar basis by zinc dialkyl phosphate or other chemicals that achieve a vulcanization promoting effect.

Similarly, MBT is another thiazole accelerator such as benzothiazyl disulfide (MBTS) or zinc 2-mercaptobenzothiazole (ZMBT),
Sulfenamide sulphenamides such as N-cyclohexyl-2-benzothiazole sulfenamide (CBS) or N-tert-butyl-2-benzothiazole sulfenamide (TBBS) Tetraethyl thiuram disulfide (TETD) , Tetramethylthiuram disulphide (TMTD) or tetrabenzyl thiuram disulphide (TBTD), thiuram promoters, nitrogen-based promoters such as guanidine, N, N'-diphenylguanidine, d-orthosultrylguanidine or 4 , 4'-Dithiomorpholine or other chemicals that achieve the action of vulcanization accelerators on a molar basis.

The molar ratio combination of MBT, MBT derivative or other promoter with ZDMC or ZDMC derivative is initiated by the presence of stearic acid and zinc oxide to initiate the proton exchange reaction. The presence of small amounts of sulfur has been found to promote ultimate vulcanization, but this is not essential. Similarly, the presence of the diol helps to disperse the powder and probably activates the mixture, but this too is not essential.

The novel chemical mixture, that is, the composition that cleaves and decomposes the vulcanized network bond, can be mixed with tire particles or other vulcanized elastomer particles (preferably 100 parts of rubber composition to 100 times rubber composition). 6 parts are mixed in a mill) The vulcanized network bond is efficiently decomposed, and as a result, the vulcanizable regenerated elastomer is ready for molding and vulcanization. The total kneading step is preferably carried out at a temperature below 70 ° C. for only 7-10 minutes. Alternatively, the cleaving / decomposing composition and the tire pieces may be mixed in advance and finally kneaded in an open mill.

Further, a method for making the cleavage / decomposition composition of the present invention easier to handle, that is, a method by a masterbatch method has been developed. The cleaving and decomposing composition is first mixed with new rubber or vulcanized rubber in a composition: rubber ratio of 90:10 to 4
Knead at a ratio of 0:60. This masterbatch mixture was mixed with vulcanized rubber pieces with a final composition: rubber ratio of 6:10.
They can be mixed at a ratio of 0. In the present specification, "part" means "part by weight".

[0015]

EXAMPLES The present invention will now be described in detail based on examples, but the present invention is not limited thereto. The formulation properties set forth below illustrate the manner in which the present invention is actually useful.

Example 1 The following substances are mixed in the stated proportions: 2-mercaptobenzothiazole (MBT) 20.0 parts zinc dimethyldithiocarbamate (ZDC) 6.0 parts stearic acid 2.0 parts zinc oxide 2. 0 parts Sulfur 1.5 parts Diethylene glycol 12.0 parts The powder is first mixed well with vigorous stirring, then diethylene glycol is added to make the entire composition of the invention a smooth paste. 3 pieces of tire piece 500g with 2 roll machine
Knead for minutes, then add 15 g of the composition. After kneading for a further 2 minutes, another 15 g of the composition is added. Finally 2
Kneading is performed for a minute with the roll gap narrowed. This time allows the formulation to be sheeted and is ready for vulcanization at 150 ° C. for 15-30 minutes. The properties of the vulcanizates prepared using 100% natural rubber tire pieces from Malaysia and Europe are shown in Table 1.

[0017]

[Table 1]

Example 2 In this example, the composition: vulcanized rubber pieces had a ratio of 6: 100 in a tire glove and a used glove obtained by granulating the paste-like composition described in Example 1. Mix in. The kneading and compounding steps are the same as described in Example 1. The kneading temperature should not exceed 70 ° C. The total kneading time should be 10 minutes or less. Table 2 shows the properties obtained from tire pieces and glove pieces. For comparison purposes, Table 2 shows the general properties obtained from the new rubber with filler (tire compound) and the new rubber without filler (pure gum compound).

[0019]

[Table 2]

Example 3 In this example, the pasty composition (as described in Example 1) is mixed with fresh rubber, tire pieces and glove pieces to obtain a masterbatch containing 90% and 50% paste.
The masterbatch thus produced is then separately mixed into tire pieces and glove pieces by the method described in Example 1,
In the case of a 0% paste masterbatch, 6.6 parts of the masterbatch is used for 100 parts of the vulcanized rubber and
In the case of a% paste masterbatch, a piece of rubber 100
Use 12 parts of masterbatch for each part. The characteristics obtained are shown in Table 3.

[0021]

[Table 3]

The above examples illustrate the diversion and effectiveness of the process of the present invention for obtaining recycled rubber blends regenerated from spent natural rubber, synthetic rubber vulcanizates or combinations thereof. Is. The resulting reclaimed rubber compound exhibits satisfactory levels of physical and mechanical properties. This formulation can be used directly in moldings or mixed with a new formulation. Examples of products obtained by ordinary molding or vulcanization methods using recycled elastomers are tires, mats, carpet underlays, electrical insulation layers, industrial tires, compounded or recycled tires (retreds).
And the like.

The masterbatch method can be further improved by using SBR instead of natural rubber. Careful control of the mixing, kneading and temperature during kneading of the compositions of the present invention can further improve the physical and mechanical properties of the final reclaimed blend from used tires and gloves. The following example shows an example where MBT was replaced with another accelerator.

Example 4 The following materials are mixed in the stated proportions. 1, benzothiazyl disulfide (MBTS) 27.8 parts 2, zinc-diethyldithiocarbamate (ZDEC) 7.6 parts 3, stearic acid 5.1 parts 4, zinc oxide 2.5 parts Ten parts are added to 100 parts of the tire flakes and 12.5 parts of the natural rubber described in Example 1. The relevant physical properties of the formulation are shown in Table 4.

[0025]

[Table 4]

Example 5 The following materials are mixed in the stated proportions. 1, N-cyclohexyl-2-benzothiazol sulhenamide (CBS) 43.9 parts 2, zinc diethyldithiocarbamate (ZDEC) 7.6 parts 3, stearic acid 5.1 parts 4, zinc oxide 2.5 parts 10 parts of the product are added to 100 parts of the tire flakes and 12.5 parts of the natural rubber described in Example 1. The relevant physical properties of this formulation are shown in Table 5.

[0027]

[Table 5]

Example 6 The following materials are mixed in the stated proportions. 1, N-tert-butyl-2-benzothiazol sulhenamide (TBBS) 39.8 parts 2, zinc diethyldithiocarbamate (ZDEC) 7.6 parts 3, stearic acid 5.1 parts 4, zinc oxide 2.5 parts This composition 10 parts of the product are added to 10 parts of the tire flakes and 12.5 parts of the natural rubber described in Example 1. The relevant physical properties of this formulation are shown in Table 6.

[0029]

[Table 6]

Although the present invention has been described above, it is obvious that the present invention can be varied in various ways. Such variations should not be considered as deviations from the scope of the present invention.
The novel features described above, which one of ordinary skill in the art will appreciate, give rise to various advantages. It should be noted that methacrylic acid may be used in addition to or instead of stearic acid. Also, instead of diethylene glycol, propylene glycol, dipropylene glycol or triethylene glycol and other suitable diols (which can be confirmed by simple experiments) can be used.

As mentioned above, aside from the compounds capable of achieving the action of vulcanization accelerators, the compounds within the scope of the claims of the present invention have been used up to now and as vulcanization accelerators. It is understood by those skilled in the art to include These are independent aspects encompassed by the present invention, whether or not included in the claims of the present invention. For example, the pasty composition of Example 1 can vary by plus or minus 20%, preferably by 10%.

Therefore, the chemical composition of the present invention comprises (a) Z
It comprises 4.8 to 7.2 parts of a component such as DMC and (b) 16 to 24 parts of a component such as MBT. The chemical composition also contains 1.6 to 2.4 parts of both stearic acid and zinc oxide. Further, it may contain 1.2 to 1.8 parts of sulfuric acid and 9.6 to 14.4 parts of a diol such as diethylene glycol. The invention also includes the chemical composition in the form of a paste or master badge, as described above.

[0033]

INDUSTRIAL APPLICABILITY According to the present invention, a vulcanized network structure in a used rubber piece can be cleaved without excessively decomposing a skeletal polymer, and a used rubber product can be effectively regenerated at low cost and recycled. it can. The obtained reclaimed rubber has properties close to the original physical and mechanical properties of the original natural and synthetic rubbers, and can be used as reclaimed rubber alone or mixed with new rubber as raw materials for various rubber products. be able to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Vitaly Abramovich Comer St. Russia, Russia. Petersburg 199057, Zeals Novoskaya You. , 62, apartment 2

Claims (19)

[Claims] 1. A used vulcanized elastomeric material which is one of compounds having a vulcanization accelerator action.
Or two or more and one or more activators capable of initiating proton exchange at a temperature of 70 ° C. or less, and kneading is thereby performed to cleave or decompose the vulcanized network of the vulcanized elastomeric material. A method for reclaiming a used vulcanized elastomer material, characterized in that a revulcanizable elastomeric material is obtained. 2. The regeneration method according to claim 1, wherein the vulcanization accelerator is selected from one or more of the following (a) to (f). (A) A zinc salt of a thiocarbamate selected from zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc dibutyldithiocarbamate and zinc dibenzylthiocarbamate. (B) 2-mercaptobenzothiazole, a derivative thereof,
And a compound selected from benzothiazyl disulfide. (C) Sulfenamides selected from N-cyclohexyl-2-benzothiazolesulfenamide and N-tert-butyl-2-benzothiazolesulfenamide (d) Tetraethylthiuramdisulfide, tetramethylthiuramdi Thiurams selected from sulfide and tetrabenzyl thiuram disulfide. (E) A nitrogen-based vulcanization accelerator selected from guanidines, N, N′-diphenylguanidine, di-orthosultrylguanidine and 4,4′-dithiomorpholine. (F) Dibutyldithiophosphate zincs of dibutyldithiophosphate zinc. 3. The regeneration method according to claim 2, wherein the component of the vulcanization accelerator is at least one of the following two compounds (a) and (b). (A) A zinc salt of a thiocarbamate selected from zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc dibutyldithiocarbamate and zinc dibenzyldithiocarbamate. (B) 2-mercaptobenzothiazole, a derivative thereof,
And a compound selected from benzothiazyl disulfide. 4. The regeneration method according to claim 3, wherein the molar ratio of the two vulcanization accelerators (a) and (b) is in the range of 1: 1 to 1:12. 5. The regeneration method according to claim 1, wherein the proton exchange is started in a controlled manner at a temperature of 50 ° C. or lower. 6. The regeneration method according to claim 1, wherein the activator component is stearic acid and zinc oxide. 7. The regeneration method according to claim 1, wherein sulfur is further present. 8. The ratio of the mixture of vulcanization accelerator and activator to the used elastomeric material is 40:60 to 90: 1.
A masterbatch having a ratio of 0 is used.
7. The reproducing method according to any one of 7. 9. Regeneration method according to claim 1, wherein the mixture of vulcanization accelerator and activator is mixed in a ratio of 60 parts by weight per 100 parts by weight of the used elastomeric material. 10. The masterbatch according to claim 8 is used and is prepared so that the ratio of masterbatch: elastomer material is 6: 100 as the mixture of vulcanization accelerator and activator: elastomer material. 9. The reproduction method described in 9. 11. The method of regenerating according to claim 1, wherein the vulcanized elastomeric material is a used elastomeric material, which is a natural rubber synthetic rubber or a mixture thereof. 12. Regeneration method according to claim 1, wherein the vulcanized elastomeric material is present in the form of small pieces. 13. Processing recycled elastomeric material,
13. Molded and / or vulcanized product to obtain products such as tires, car mats, carpet underlays, electrically insulating members or layers, industrial tires, pipes or retired tires. Reproduction method described in item. 14. A composition for reclaiming a used vulcanized elastomer material, which is capable of cleaving or decomposing a vulcanized network bond of a vulcanized elastomeric material containing one or more of the following vulcanization accelerators. (A) A zinc salt of a thiocarbamate selected from zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc dibutyldithiocarbamate and zinc dibenzylthiocarbamate. (B) 2-mercaptobenzothiazole, a derivative thereof,
And a compound selected from benzothiazyl disulfide. (C) Sulfenamides selected from N-cyclohexyl-2-benzothiazolesulfenamide and N-tert-butyl-2-benzothiazolesulfenamide (d) Tetraethylthiuramdisulfide, tetramethylthiuramdi Thiurams selected from sulfide and tetrabenzyl thiuram disulfide. (E) A nitrogen-based vulcanization accelerator selected from guanidines, N, N′-diphenylguanidine, di-orthosultrylguanidine and 4,4′-dithiomorpholine. (F) Dialkyldithiophosphate zincs. 15. The composition according to claim 14, which contains at least one of the following two vulcanization accelerators (a) and (b). (A) A zinc salt of a thiocarbamate selected from zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc dibutyldithiocarbamate and zinc dibenzyldithiocarbamate. (B) 2-mercaptobenzothiazole, a derivative thereof,
And a compound selected from benzothiazyl disulfide. 16. The composition according to claim 15, wherein the molar ratio of the two vulcanization accelerators (a) and (b) is in the range of 1: 1 to 1:12. 17. A composition according to any one of claims 14 to 16 which comprises an activator consisting of stearic acid and zinc oxide. 18. The method according to claim 14, further comprising sulfur.
The composition according to any one of 1. 19. A composition according to any one of claims 14 to 18, which is mixed in the form of a masterbatch in which the ratio of composition: spent vulcanized elastomeric material pieces is 40:60 to 90:10. Stuff.