Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Reexamination Certificate
2002-05-03
2004-08-17
Wyrozebski, Katarzyna (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
C521S041000, C521S045500
Reexamination Certificate
active
06777453
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of reclaiming crosslinked rubber and to a molding of reclaimed rubber.
BACKGROUND ART
Heretofore, there has been known a reclaiming method wherein wastes of rubber moldings such as tire wastes etc., or scrap, defective moldings, etc. occurring in a process for producing rubber moldings, are converted into reclaimed rubber by applying heat and shear stress thereto.
According to the above reclaiming method, crosslinkages among rubber molecules constituting crosslinked rubber are cleaved by heat and shear stress, thus providing reclaimed rubber in a state similar to non-crosslinked rubber.
By re-crosslinking such reclaimed rubber singly and/or re-crosslinking a mixture which is formed by mixing new non-crosslinked rubber and the reclaimed rubber, moldings of the reclaimed rubber is formed, thus enabling recycling of crosslinked rubber.
A certain kind of crosslinked rubber generates decomposed products during reclamation, and a deterioration in qualities etc. may occur owing to the decomposed products. In the conventional reclaiming method, it was difficult to deal with the problem caused by the decomposed products.
Specifically, a certain kind of crosslinked rubber generates a malodorous gas during reclamation. To reclaim such crosslinked rubber, (1) the malodorous gas is subjected to combustion and deodorization in a combustion-type deodorizing unit and is released to the atmosphere as shown in JP-A 6-210633, and (2) malodorous components in the malodorous gas and in reclaimed rubber are continuously removed by heating in a heating oven as shown in JP-A 9-308951.
In the method (1), the malodorous gas could be removed from the gas released to the atmosphere during reclamation, but the malodorous gas remaining in the reclaimed rubber could not be removed. Accordingly, there was a problem that a bad smell is generated upon re-crosslinking of the reclaimed rubber or genrated from moldings of the re-crosslinked reclaimed rubber.
Removal of the malodorous gas by the method (2) is also unsatisfactory, and it was difficult in some cases to obtain reclaimed rubber applicable to articles used particularly in a closed space (e.g. in a room). Further, use of a heating oven made it difficult to apply the method to crosslinked rubber easily denatured by heating.
In a certain kind of crosslinked rubber in an embodiment different from the above, its decomposed products produced during reclamation react again with the crosslinked rubber in the process of reclamation to cause a deterioration in the qualities of reclaimed rubber. Further, the decomposed products can be a cause for premature crosslinkage to deteriorate scorch characteristics and storage stability.
The present invention was made in view of such conventional problems, and the object of the present invention is to provide a method of reclaiming crosslinked rubber wherein a reduction of qualities due to generation of decomposed products hardly occurs, and a molding of reclaimed rubber.
DISCLOSURE OF INVENTION
The present invention relates to a method of reclaiming crosslinked rubber, which includes introducing a degasification carrier and removing, together with the degasification carrier, decomposed products in crosslinked rubber, during a reclamation step of reclaiming crosslinked rubber by applying shear stress thereto and/or a subsequent step after the reclamation step.
The most remarkable feature of the present invention lies in removal of decomposed products together with the introduced degasification carrier.
According to this feature, the decomposed products are removed, thus scarcely remaining in crosslinked rubber in the process of reclamation and in reclaimed rubber. Accordingly, the deterioration in qualities of reclaimed rubber by the decomposed products and the inhibition of reclamation of crosslinked rubber by the decomposed products can be prevented.
According to the present invention, as described above, there can be provided a method of reclaiming crosslinked rubber wherein a reduction in qualities due to generation of decomposed products hardly occurs.
The process for introducing the degasification carrier and for removing decomposed products together with the degasification carrier is carried out preferably during reclamation of crosslinked rubber (see Embodiment 6). With this arrangement, the effect of the present invention can be secured.
As described later, cleavage of crosslinkages in crosslinked rubber is initiated by applying shear stress thereto, and almost simultaneously with the cleavage of crosslinkages, the decomposed products are also generated. Therefore, the effect of the present invention cannot be obtained if introduction and removal of the degasification carrier (degasification treatment) is conducted before decomposed products are generated, that is, before the cleavage of crosslinkages in crosslinked rubber is initiated. Accordingly, the degasification treatment should be carried out after a plasticizing step and/or a kneading step, which are described later. The degasification treatment may be repeated.
The decomposed products include e.g. malodorous components.
A certain kind of crosslinked rubber generates a malodorous gas during reclamation. As described above, it was difficult to remove the malodorous gas from such crosslinked rubber by the conventional method. The reclaiming method of the present invention can be applied to remove the malodorous components thereby improving the working environment during reclamation or during re-crosslinking of reclaimed rubber in forming moldings of reclaimed rubber (by rolling refining etc.)
Further, when the reclaimed rubber is formed into moldings of reclaimed rubber, the bad smell of the moldings of reclaimed rubber can be reduced, and thus the value of the moldings can be increased.
Further, the ratio of reclaimed rubber in moldings of the reclaimed rubber can be increased to improve the efficiency of recycling.
In addition, the processability of reclaimed rubber can be raised to improve crosslinking characteristics. Furthermore, the physical characteristics of reclaimed rubber moldings obtained from the reclaimed rubber can also be improved. Moreover, reclamation itself can also be promoted.
The crosslinked rubber generating malodorous gas as described above includes sulfur-vulcanized EPDM (ethylene propylene diene terpolymer), NR/SBR (blended rubber of natural rubber and styrene-butadiene rubber), SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber) etc.
When the crosslinked rubber generating a malodorous gas as described above is reclaimed, a deodorant may be added thereto. The malodorous gas can thereby be further reduced. The deodorant in this case can make use of perfumes such as vanillin and lignin and deodorants such as activated carbon and sepiolite.
Besides, rubbers such as acryl rubber generating amine compounds as decomposed products can be reclaimed by the production method of the present invention.
The amount of the degasification carrier added is preferably 0.02 to 20 parts by weight based on 100 parts by weight of crosslinked rubber. Decomposed products can thereby certainly removed. If the amount of the degasification carrier is less than 0.02 parts by weight, the effect is hardly obtained, while if the amount exceeds 20 parts by weight, the amount of the degasification carrier volatilized can be increased to make stable reclamation of crosslinked rubber difficult and to make removal of the degasification carrier incomplete, thus permitting a large amount of the degasification carrier to remain in the reclaimed rubber. The lower limit of the degasification carrier is preferably 0.1 part by weight, more preferably 0.5 part by weight. The upper limit thereof is preferably 7 parts by weight.
In the step of removing decomposed products together with the degasification carrier, techniques selected from heating degasification, degasification under reduced pressure, solvent cleaning, and bubbling are preferably used alone or in combination thereof.
The heating degasifi
Fukumori Kenzo
Fukuta Masahito
Honda Hidenobu
Matsushita Mitsumasa
Mouri Makoto
Kabushiki Kaisha Toyota Chuo Kenyusho
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wyrozebski Katarzyna
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