Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1991-02-19
1994-04-26
Kight, III, John
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 63, 525 55, 525154, C08G 6391
Patent
active
053067690
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a novel acetal copolymer and a process for producing it. More particularly, the present invention relates to an acetal copolymer which comprises a polyacetal and a particulate crosslinked polymer other than a polyacetal which has a functional group and has an average particle size of 0.01-10 .mu.m, said polyacetal and particulate crosslinked polymer being reaction bonded through said functional group, and a process for producing an acetal copolymer which comprises homopolymerizing formaldehyde or trioxane or copolymerizing formaldehyde or trioxane with a cyclic ether in the presence of a polymer other than a polyacetal which has a functional group and has an average dispersion particle size of 0.01-2,000 .mu.m.
BACKGROUND TECHNIQUE
Recently, there has been a great demand for polyacetals as engineering plastics because of their superior mechanical characteristics, fatigue characteristics and frictional wear characteristics. However, with diversification of uses and demand for enhancement of functions of polyacetals, properties possessed by polyacetals cannot satisfy all of the requirements.
In order to improve this point, extensive research has been conducted on modification of polyacetals, for example, a polymer alloying technique where a polyacetal and a resin other than a polyacetal are blended or a technique to modify the skeleton by introducing a component other than a polyacetal into the main chain of a polyacetal.
For example, as an example of the polymer alloying technique, EP-A-115373 discloses that a composition obtained by adding to a polyacetal an acrylic multi-phase interpolymer having a two-phase structure and having a particle size of 10-100 .mu.m is excellent in impact resistance.
However, the acrylic multi-phase interpolymer disclosed in the above patent publication has a rigid thermoplastic phase as the outermost phase and since affinity of this outermost phase to a polyacetal is insufficient, the composition cannot be said to be sufficient in high impact resistance required for engineering plastics. Further, the composition has the defect that impact resistance in a specific direction decreases significantly depending on processing conditions.
Specifically, impact resistance in a specific direction decreases when processing is conducted under conditions which apply orientation to the multi-phase interpolymer dispersed in the polyacetal in processing such as injection molding, extrusion molding, and blow molding. For example, in a weld portion which is formed by joining molten resins to each other in a mold for injection molded products, impact resistance in a specific direction of the molded product, namely, weld strength greatly decreases. This phenomenon occurs due to the fact that the multi-phase interpolymer dispersed in the polyacetal is not uniformly dispersed in all portions of the molded product, but non-uniform un-uniform dispersion such as agglomeration or orientation occurs in the molded product.
Therefore, impact resistance of the composition disclosed in the above patent publication is non-uniform and compositions having mechanical properties excellent in isotropy cannot be obtained.
The mechanical properties excellent in isotropy in the present invention mean mechanical properties which show no reduction in tensile characteristics and impact resistance in a specific direction in any portion, especially a weld portion, of molded products and having uniformity.
Examples of the technique to modify the skeleton for solving the above problems are as shown below.
For example, U.S. Pat. No. 4,535,127 discloses that graft copolymers having a structure where a polyacetal is grafted on elastomers such as modified ethylene-propylene copolymer and modified styrene-butadiene copolymer have high impact resistance.
Moreover, U.S. Pat. No. 4,535,127 discloses that A-B-A triblock copolymers comprising polyacetal units (A) and elastomer units (B) have excellent impact resistance.
However, in these processes, normally, copolymerization is ca
REFERENCES:
patent: 4535127 (1985-08-01), Matsuzaki et al.
Derwent Abstract, No. 76:06478X [04], of JP-B-50 039709, Dec. 18, 1975 (Daicel K. K.).
Derwent Abstract, No. 73:47693U [34], of JP-A-48 001095, JP-B-52 049035, Dec. 14, 1977 (Daicel Co. et al.).
Hata Tadashige
Matsuzaki Kazuhiko
Sone Tatsuo
Asahi Kasei Kogyo Kabushiki Kaisha
Jones Richard
Kight III John
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