Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-04
2002-07-09
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06417254
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel and useful granulated diacetal composition, a process for preparing the same, and polyolefin resin composition and molded articles prepared with use of the diacetal composition.
BACKGROUND ART
Diacetals, typically dibenzylidene sorbitol and nuclearly substituted products thereof, are functional agents widely used as nucleating agents for polyolefin resins, gelling agents for various fluids or the like.
Conventional commercial products of diacetals are in the form of bulky fine powders having an apparent specific gravity of about 0.1 to 0.2. A method has been proposed wherein a diacetal powder is further pulverized into an ultrafine powder for improving the dissolution of the diacetal powder in polyolefin resins (Japanese Unexamined Patent Publication No. 145431/1994).
Ultrafine powders have poor transferability because of their small apparent specific gravity of 0.1 or less, and are liable to cause bridging in piping or hoppers and likely to generate dust which increases the risk of dust explosion. Further, they tend to agglomerate to form solid cakes during storage, lacking in storage stability.
Similarly, fine powders of diacetals are likely to generate dust when added to resins or fluids. Since the powders have stacking property (strong adhesion between the particles), they have poor flow property and tend to cause bridging in piping or hoppers. Further, they are likely to agglomerate during storage.
It has been therefore necessary to take sufficient measures for improving the transferability and storage stability of fine powders, for preventing dust explosion, and for maintaining working environment free from dust. However, no method is known which solves the problems of diacetal powders with respect to transferability, dust, storage stability, etc.
Incidentally, a process for granulating additives for plastics are known. DE 3639874 discloses a process and apparatus for preparing a granular additive by mixing an additive such as filler, nucleating agent, coloring agent, UV absorber, antioxidant, light stabilizer or the like with a carrier or binder which is active at 100° C. or lower, and compressing the mixture at 100° C. or lower. However, said publication does not specify the kinds of the nucleating agent and binder. Accordingly, the disclosed technique is not one proposed for improving transferability and for taking dust-preventive measures with respect to a specific compound.
Japanese Examined Patent Publication No. 423/1989 and Japanese Unexamined Patent Publication No. 126352/1989 describe that a powdery diacetal composition comprising diacetal particles coated with a higher fatty acid can be obtained by adding a powdery diacetal to an aqueous emulsion containing a higher fatty acid, stirring the mixture, and separating the powder, followed by drying, and that resin compositions containing the diacetal composition are improved in transparency, rigidity, and like properties.
Japanese Unexamined Patent Publication No. 245843/1996 teaches a powdery composition comprising a diacetal particles as intimately mixed with a carboxylic acid amide or behenic acid, the powdery composition being prepared by mixing a diacetal powder with a solution or dispersion of carboxylic acid amide or behenic acid in a solvent and removing the solvent; or a powdery diacetal composition comprising diacetal particles which are coated with carboxylic acid amide on the surface, the powdery diacetal composition being prepared by adding a diacetal powder to a liquid emulsion of carboxylic acid amide and evaporating the solvent for drying. The publication discloses that use of carboxylic acid amide particularly lowers the melting point of the diacetal and enables molding at lower temperatures.
However, the above powdery compositions are liable to agglomerate during storage by fusion or the like, since the coating material has a relatively low melting point or is likely to undergo secondary crystallization. Furthermore, the flow property or transferability of the powdery compositions are not remarkably improved partly because the compositions have a small apparent specific gravity of up to 0.38.
Stated more specifically, according to the processes of Japanese Examined Patent Publication No. 423/1989 and Japanese Unexamined Patent Publication No. 126352/1989, the surfaces of diacetal particles are coated with a higher fatty acid. However, the flow property of the powdery composition was insufficient partly because of its small apparent specific gravity of about 0.3. Further, the composition is very liable to agglomerate at about 60° C. or under load.
According to the process of Japanese Unexamined Patent Publication No. 245843/1996, a solvent is essential in the mixing step, necessitating use of a large solvent recovery system and mixing apparatus. Thus, the process is of economically low value. Furthermore, the resulting powdery composition has an insufficient flow property partly because the composition has a small apparent specific gravity of about 0.3 due to the pores which have been made presumably when the solvent is removed.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide, by an economical process, a novel and useful diacetal composition in the form of a commercial product, which is excellent in workability in automatic metering and the like, is highly safe in respects of prevention of dust generation, prevention of explosion, and the like, is excellent in transferability in piping or hoppers, is easily handled without generating dust, and is good in storage stability, while not impairing the resin-modifying properties, solubility or dispersibility in molten resins and characteristics of gelling ability which are inherently possessed by diacetals.
The present inventor conducted extensive researches to solve the above problems, and considered that if a composition comprising a diacetal as an essential component is formed into fine particles (or ultrafine particles) or grains having an apparent specific gravity of 0.4 or more, in particular 0.5 or more, without using a special large apparatus for solvent recovery or the like, then the transferability would be improved and the dust problem would be solved, and the size of containers for storing or transporting a diacetal powder would become compact.
On the other hand, there was concern that the increase in the apparent specific gravity, achieved by forming the diacetal into grains, would impair the resin-modifying properties, solubility or dispersibility in molten polyolefin resins or characteristics of gelling ability which are inherently possessed by diacetals, because a large apparent specific gravity resulting from granulation would be considered to be incompatible with good solubility or dispersibility in molten polyolefin resins. For example, it was considered that if a diacetal powder was formed into grains by compression, the diacetal crystals constituting the particles of the diacetal powder would aggregate more densely and the dispersibility or solubility in molten polyolefin resins would decrease.
Under the circumstances, the inventor carried out further extensive research, and found that a granulated diacetal composition having an increased apparent specific gravity and good storage stability and transferability can be obtained by mixing a diacetal powder with a melt of a specific binder (not in the form of a solution or dispersion of the binder in water, an organic solvent or like liquid medium, that is to say, without using such a liquid medium which is required to be recovered during the production process) and molding the resulting mixture into grains or by pulverizing the obtained grains. It has also been found that surprisingly the obtained granulated composition, in spite of having an increased apparent specific gravity, has improved dispersibility or solubility in molten polyolefin resins, and therefore achieves the above object.
Thus, the inventor found that the above object can be achieved by granulated diacetal composition or pulverizatio
Larson & Taylor PLC
Mulcahy Peter D.
New Japan Chemical Co. Ltd.
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