Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-06-15
2003-03-11
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06531527
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a viscosity-stabilizer-containing natural rubber latex and natural rubber which have an excellent viscosity stabilizing effect and a production process for a viscosity-stabilizer-containing natural rubber.
2. Description of the Related Art
In general, a natural rubber latex is produced in tropical countries such as Thailand, Malaysia and Indonesia. Natural rubber latices produced are subjected to treatments such as coagulating and drying to form natural rubbers and then the natural rubbers are classified according to species and grades.
A natural rubber is used widely in a large quantity in the rubber industry and the tire industry because of excellent physical properties thereof.
A natural rubber immediately after its production has a Mooney viscosity as low as 60 to 70, but the Mooney viscosity goes up to the vicinity of 90 to 100 during several months while it is stored and transported after the production (called storage hardening).
It is supposed that one of the causes of storage hardening of a natural rubber is attributable to the fact that a heterogeneous bond (an aldehyde group and the like) in an isoprene chain of a natural rubber is reacted with proteins and amino acids contained in a natural rubber, whereby cross-linking takes place to cause gelation (an increase in a gel quantity) (a mechanism thereof is not distinctly elucidated in literatures).
Gelation in a natural rubber deteriorates processability thereof. In general, a natural rubber has preferably a larger molecular weight from a viewpoint of physical properties, and a reduction in the molecular weight results in exerting an adverse effect on physical properties of the natural rubber. These molecular weight and gel quantity depend largely on the drying condition of the natural rubber after washed with water and the subsequent storing state of the natural rubber.
Known as viscosity stabilizers for preventing the storage hardening described above are hydroxylamine sulfate (NH
2
OH.H
2
SO
4
), semicarbazide (NH
2
NHCONH
2
), hydroxylamine, dimedone (1,1-dimethylcyclohexane-3,5-dione) and a hydrazide.
However, it is observed that when the respective compounds are used in a small amount, though varied depending on the compounds, a viscosity stabilizing effect is small from the beginning, or the viscosity is increased from a certain period, and therefore a problem resides in that the sufficient viscosity stabilizing effect has not yet been obtained.
On the other hand, the present applicant has applied a patent of a process for producing a natural rubber having a viscosity stabilizing effect by adding a viscosity stabilizer to a natural rubber immediately after dried (Japanese Patent Laid-Open No. Hei 7-48404, Japanese Patent Laid-Open No. Hei 7-48405 and Japanese Patent Laid-Open No. Hei 8-67703).
The production processes for a natural rubber which are disclosed in these official gazettes provide natural rubbers having an excellent viscosity stabilizing effect. In the production processes thereof, a viscosity stabilizer is added to a natural rubber without being diluted, and a problem resides in that dispersibility of the viscosity stabilizer added is not constant, so that a natural rubber latex or a natural rubber having an excellent viscosity stabilizing effect has not yet been obtained in a certain case.
It is disclosed in British Patent 1472064 to add a hydrazide compound which is emulsified using xylene as a solvent to a latex. However, aromatic compounds such as xylene are not preferred since an effect thereof exerted on human bodies and the environment is concerned.
The present invention is intended to solve the foregoing problems on conventional techniques, and an object of the present invention is to provide a natural rubber latex and a natural rubber which displays an excellent viscosity stabilizing effect, and a production process for a viscosity-stabilizer-containing natural rubber by further improving dispersibility of a viscosity stabilizer in them.
SUMMARY OF THE INVENTION
Intensive investigations repeated by the present inventors have resulted in finding that obtained are a natural rubber latex and a natural rubber which are excellent in a viscosity stabilizing effect by adding a specifically treated viscosity stabilizer which has good dispersibility and a good viscosity stabilizing effect to a natural rubber latex or a natural rubber up to immediately after drying (it may be added during drying), and researches further continued have resulted in successfully obtaining a production process for a natural rubber latex which meets the object described above and a viscosity stabilizer-containing natural rubber. Thus, the present invention has been completed.
That is, the present invention comprises the following items (1) to (17).
(1) A production process for a viscosity-stabilizer-containing natural rubber comprising a step of adding a viscosity stabilizer liquid diluted with a solvent to a natural rubber.
(2) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (1), wherein the natural rubber described above is a natural rubber latex.
(3) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (1), wherein the natural rubber described above is a natural rubber after it was coagulated.
(4) The production process for a viscosity-stabilizer-containing natural rubber as described in any of the above items (1) to (3), wherein the viscosity stabilizer liquid is an emulsion.
(5) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (3), wherein the viscosity stabilizer liquid is an organic solution or an aqueous solution.
(6) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (4), wherein the emulsion was prepared by further adding water to a viscosity stabilizer organic solution.
(7) The production process for a viscosity-stabilizer-containing natural rubber as described in any of the above items (1) to (6), wherein the solvent is an aliphatic chain compound.
(8) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (7), wherein the aliphatic chain compound described above is an aliphatic polyhydric alcohol.
(9) The production process for a viscosity-stabilizer-containing natural rubber as described in any of the above items (1) to (8), wherein the viscosity stabilizer described above is a hydrazide compound.
(10) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (9), wherein the hydrazide compound described above is represented by the following general Formula (I):
R—CONHNH
2
(I)
wherein R represents an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms or an aryl group having 3 to 30 carbon atoms.
(11) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (10), wherein the viscosity stabilizer is at least one selected from the group consisting of acetohydrazide, propionohydrazide, butyrohydrazide, laurohydrazide, palmitohydrazide, stearohydrazide, cyclopropane carbohydrazide, cyclohexane carbohydrazide, cycloheptane carbohydrazide, benzohydrazide, o-toluohydrazide, m-toluohydrazide, p-toluohydrazide, p-methoxybenzohydrazide, 3,5-dimethylbenzohydrazide and 1-naphthohydrazide.
(12) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (4), wherein the viscosity stabilizer emulsion has a concentration of 3 to 50% by weight.
(13) The production process for a viscosity-stabilizer-containing natural rubber as described in the above item (5), wherein the viscosity stabilizer solution has a concentration of 20 to 80% by weight.
(14) A viscosity-stabilizer-containing natural rubber latex prepared by adding a viscosity stabilizer dissolved in an aliphatic ch
Hashimoto Takatsugu
Kijima Ken
Toratani Hirotoshi
Bridgestone Corporation
Cain Edward J.
LandOfFree
Viscosity-stabilizer-containing natural rubber latex and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Viscosity-stabilizer-containing natural rubber latex and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Viscosity-stabilizer-containing natural rubber latex and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3060036