Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-10-30
2002-07-23
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S151000, C522S152000, C522S153000, C522S154000, C522S155000, C522S156000, C522S157000, C522S158000, C522S159000, C522S160000, C522S161000, C428S402000
Reexamination Certificate
active
06423760
ABSTRACT:
The present invention relates to a powdery rubber, more particularly, to a fully vulcanized powdery rubber having a controllable particle size, which can be in the order of nm, a process for preparation of and use of the powdery rubber.
It is well known that rubbers can be in the form of blocks, rods, powders, pellets, sheets or the like, and rubbers can be classified as vulcanized (including slightly vulcanized) and unvulcanized. The fully vulcanized powdery rubbers have hot been disclosed in literatures except the vulcanized powdery silicone rubber.
A lot of references disclosed the vulcanized powdery silicone rubber and preparation thereof. For example, U.S. Pat. No. 4,743,670 (May 10, 1988) disclosed a highly dispersed vulcanized powdery silicone rubber and preparation thereof. The powdery silicone rubber has a uniform particular shape and particle size, and a bulk resistance of greater than 10
13
&OHgr;·cm. The process for preparing the vulcanized powdery rubber comprises (1) preparing a dispersion of a heat-vulcanizable liquid silicone rubber composition in water at 0 to 25° C. in the presence of a surfactant, (2) dispersing the dispersion obtained in step (1) into a liquid at 50° C. or above to vulcanize the liquid silicone rubber composition into powders, and (3) separating the vulcanized powdery silicone rubber.
U.S. Pat. No. 4,742,142 (Apr. 6, 1987) disclosed a process for preparing a powdery silicone rubber which comprises heating a heat-vulcanizable composition with a liquid at 0 to 25° C., emulsifying the composition into water containing a surfactant, and then spraying the emulsion into a water bath at 25° C. or above to sufficiently vulcanize the components in the silicone rubber composition.
U.S. Pat. No. 4,749,765 (Jun. 7, 1988) disclosed a process for preparing a powdery silicone rubber having a uniform particle size, which comprises (1) mixing the components at −60 to 50° C. to prepare a liquid silicone rubber composition, (2) spraying the liquid silicone rubber composition into hot air at 80 to 200° C. to form particles, (3) vulcanizing the particles, and (4) recovering the result powdery silicone rubber.
U.S. Pat. No. 5,837,739 (Nov. 17, 1998) disclosed a vulcanized powdery silicone rubber and preparation thereof. The powdery silicone rubber has a high hydrophilicity and softness, and an average particle size of less than 500 micron. The process for preparing the powdery silicone rubber comprises (1) vulcanizing a vulcanizable silicone composition comprising a specific organopolysiloxane to form a vulcanized silicone rubber, and (2) drying the vulcanized silicone rubber by spraying. The vulcanization reaction to form the vulcanized silicone rubber can be addition reaction between the alkenyl groups and the silicon-bonded hydrogen atoms, condensation between the silicon-bonded hydroxyls and the silicon-bonded hydrogen atoms, reaction induced by an organo peroxide or UV rays.
Although vulcanized powdery silicone rubbers obtained by chemical cross-linking and preparation thereof were disclosed in the prior art, there have been no report on other fully vulcanized powdery rubber up to now.
The present inventors find after a long time and extensive research that a fully vulcanized powdery rubber can be obtained by irradiating a rubber latex and drying. The fully vulcanized powdery rubber obtained has a uniform and controllable particle size, which is substantially the same as the particle size of the rubber particles in the latex. The fully vulcanized powdery rubber can be used to produce roughened plastics and fully vulcanized thermoplastic elastomers, has a promising prospect and great economical significance.
Therefore, one object of the present invention is to provide a fully vulcanized powdery rubber.
Another object of the present invention is to provide a process for preparing the fully vulcanized powdery rubber.
Yet another object of the present invention is to provide a composition usable to produce toughened plastics and thermoplastic elastomers, which comprises the present fully vulcanized powdery rubber and a plastic.
Still another object of the present invention is to provide the use of the fully vulcanized powdery rubber for toughening plastics or preparing thermoplastic elastomers.
The present fully vulcanized powdery rubber is particulate rubber which has a gel content of 60% by weight or more, and is free-flowing without the need of a partitioning agent. The gel content is a common parameter well-known in the art to characterize the cross-linking degree of a rubber, and can be determined by a well-known method in the art. The present fully vulcanized powdery rubber has a gel content of at least 60% by weight, preferably at least 75% by weight, and most preferably at least 90% by weight. Additionally, the swell index is another common parameter to characterize the cross-linking degree of a rubber, and can be determined by a well-known method in the art. The present fully vulcanized powdery rubber has a swell index of not greater than 15, preferably not greater than 13. Furthermore, the present fully vulcanized powdery rubber is a free-flowing particulate rubber, and the free-flowing property can be achieved without the addition of a partitioning agent. Therefore, a partitioning agent is not necessary to be added into the present fully vulcanized powdery rubber. However, if desired, a partitioning agent can be added into the present fully vulcanized powdery rubber to improve further the free-flowing property and the anti-block property.
The present fully vulcanized powdery rubber has a controllable particle size, the average particle size is generally in the range of from 20 to 2000 nm, preferably from 30 to 1500 nm, and most preferably from 50 to 500 nm. In the context of the present application, the particle size is measured by Scanning Electron Microscopy (SEM).
In the present fully vulcanized powdery rubber, each particle is homogeneous, that is to say, the individual particle is uniform with respect to the composition, and a heterogeneous phenomenon, such as lamellar phase and phase-separation, etc., within the particles is not detectable with microscopy available nowadays.
There is no restriction on the kinds of the rubber for the present fully vulcanized powdery rubber, it can be any kind of rubber except silicone rubber vulcanized by chemical cross-linking method. The illustrative example thereof is natural rubber, styrene-butadiene rubber, carboxylated styrene-butadiene rubber, nitrile rubber, carboxylated nitrile rubber, chloroprene rubber, polybutadiene, acrylic rubber, butadiene-styrene-vinylpyridine rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, polysulfide rubber, acrylate-butadiene rubber, urethane rubber, or fluorine rubber.
The present fully vulcanized powdery rubber can be obtained by vulcanizing the corresponding rubber latex with irradiation. For example, the present fully vulcanized powdery rubber can be prepared by irradiating a rubber latex with a particle size in the range of from 20 to 2000 nm, which is market available or prepared by the inventors, in the presence or absence of a cross-linking agent, with a high-energy irradiation, to vulcanize it fully. The high-energy irradiation can be selected from gamma-rays, X-rays, UV rays, and high-energy electron beams, preferably gamma-rays. The irradiation dose can be 0.1 to 30 megarads, preferably 0.5 to 20 megarads. The fully vulcanized powdery rubber having a particle size which is substantially the same as the size of the rubber particles in the latex is obtained by drying the irradiated latex. The drying can be carried out in a spray dryer or by precipitation drying method. If the drying is carried out in a spray dryer, the inlet temperature can be controlled at 100 to 200° C., and the outlet temperature at 20 to 80° C.
In the present invention, there is no restriction on the rubber latex as starting material, and it can be selected from natural rubber latex, styrene-butadiene rubber latex, carboxylated styrene-butadiene rubber latex, nitrile rubb
Gao Jianming
Li Jiuqiang
Liu Yiqun
Qiao Jinliang
Shao Jingbo
China Petro-Chemical Corporation
Ladas & Parry
McClendon Sanza L.
LandOfFree
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