Plastic and nonmetallic article shaping or treating: processes – Vacuum treatment of work – To degas or prevent gas entrapment
Patent
1999-03-25
2000-12-26
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Vacuum treatment of work
To degas or prevent gas entrapment
264143, 26421123, 366 75, 366 766, 366 77, 366 85, 366 88, 425198, 425203, 425204, 425208, B29C 4740, B29C 4764, B29C 4776
Patent
active
061653993
DESCRIPTION:
BRIEF SUMMARY
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a novel process for the preparation of toughened thermoplastics or polymer blends containing toughened thermoplastics, the thermoplastics or the polymer blends comprising
A) from 5 to 95% by weight of at least one water-moist elastomer component A containing up to 60% by weight of residual water,
B) from 5 to 95% by weight of at least one thermoplastic polymer B,
C) from 0 to 95% by weight of at least one further polymer C, and
d) from 0 to 70% by weight of additives D, if present, the further polymer C and, if present, the additives D in an extruder with mechanical dewatering of the elastomer component A.
The present invention furthermore relates to molding materials prepared by the process and the use of the molding materials for the production of films, fibers and moldings. Finally, the present invention relates to an extruder for the preparation of the thermoplastics.
BACKGROUND OF THE INVENTION
Particulate rubbers which may be grafted or ungrafted are frequently used as elastomer components for toughening thermoplastics or other plastics. Such rubbers are usually prepared in aqueous systems, for example by emulsion or suspension polymerization. The particles formed in the suspension polymerization or precipitated in the emulsion polymerization (for example by adding a coagulating precipitating agent) are as a rule washed with water and dewatered by a suitable dewatering method, such as sieving, pressing out, filtration, decanting, settling out, centrifuging or partial thermal drying, for example by means of a pneumatic dryer. Partial dewatering by spray drying is also possible. Partially dewatered products are obtained in every case.
DETAILED DESCRIPTION OF THE INVENTION
Frequently used graft rubbers are, for example, polybutadiene grafted with a styrene/acrylonitrile copolymer (SAN) and poly-n-butyl acrylate grafted with such a copolymer, or rubbers composed of a plurality of graft stages and based on butadiene, styrene, n-butyl acrylate, ethylhexyl acrylate, methyl methacrylate and/or acrylonitrile.
The residual water content of the rubber obtained after partial dewatering is up to 60% by weight and is usually removed by energy-intensive drying. The dried rubber obtained as a powder is finally incorporated into the thermoplastics present as powder or granules with melting, the end product being formed. Processes in which rubber polymers and matrix polymers are precipitated and dried together are also known. Owing to the content of fine dust, the rubber powder tends to undergo spontaneous ignition during the drying and the incorporation into the thermoplastics.
According to a proposal described in DE-A-20 37 784, partially dewatered graft rubber can be mixed into an SAN melt under superatmospheric pressure and a thermoplastic containing this graft rubber can be obtained with evaporation of the water. This process requires a relatively large amount of electrical energy.
EP-A 534 235 describes a process for the preparation of toughened thermoplastics by incorporating rubber subjected to partial mechanical dewatering into a thermoplastic above the softening point of the thermoplastic, the incorporation being effected in a main extruder and the partial dewatering of the rubber being carried out in a side extruder mounted at the side of the main extruder. The residual water remaining in the rubber is removed as steam during the incorporation, through devolatilization orifices present before and after the feed point. The disadvantage of this process is the necessity of operating two extruders for the preparation of the impact-resistant thermoplastic.
The German utility model DE-U 94 21 779 discloses an extruder for compounding moist material in which washed plastic wastes are pushed into the extruder using a stuffing device (stuffing screw). The water adhering to the chopped plastic pieces is removed through an opening in the extruder, the opening being provided with a screw to retain the plastic.
U.S. Pat. No. 5,151,026 describes an ex
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Bus Klaus
Czauderna Bernhard
Grabowski Sven
Guntherberg Norbert
Hofmann Jurgen
BASF - Aktiengesellschaft
Tentoni Leo B.
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