Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1986-12-15
1989-04-11
Anderson, Harold D.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
525420, 528300, C08G 6944
Patent
active
048207969
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a transparent polyamide elastomer. More particularly, the present invention relates to a transparent polyamide elastomer of the polyether-ester-amide type which is composed of polycapramide as the hard segment and polyoxytetramethylene glycol as the soft segment and has a low hardness belonging to crosslinked rubber and a high strength so that it is preferably used in the field particularly requiring flexibility and transparency such as hoses, tubes, films and sheetings.
BACKGROUND ART
In recent years, thermoplastic elastomers such as polyamide elastomers and polyester elastomers have begun to come rapidly into use, for example, in mechanical parts, sheetings, and hoses, because of their excellence in physical properties such as water resistance, heat resistance, mechanical strength, and low temperature characteristics and also in moldability promising an improvement in productivity.
Of the thermoplastic elastomers, known polyamide elastomers include a polyether-ester-amide type and a polyether-amide type. In both types, nylons such as 12-nylon and 6-nylon are used as the polyamide constituent, the former nylon being chiefly used in commercial products. On the other hand, as the polyether constituent, use may be made of polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, mixtures thereof, or block copolymers thereof. Of these compounds, polyoxytetramethylene glycol is chiefly used in view of water resistance, mechanical strength, and low temperature characteristics.
Elastomers having such physical properties as flexibility, high mechanical strength, and transparency are preferably employed as useful industrial materials such as, for example, sheetings, films, and tubings. However, because of being mainly of the 12-nylon type which is relatively good in the miscibility between the hard segment and the soft segment, the polyamide elastomers currently being on the market have a relatively high Shore hardness of 40D to 70D. A soft nylon elastomer having a Shore hardness of 60A to 40D, as in the case of crosslinked rubbers, has not yet been known.
In order to decrease the hardness of the elastomer, it is a common practice to reduce the content of polyamide constituting the hard segment. If it is attempted in such a manner to prepare an elastomer of the 12-nylon type, the cohesive force in the polyamide domain will be rapidly decreased, thereby forming a product of a low mechanical strength or of a low melting point and, hence, a product having low heat resistance. If 6-nylon is used in the hard segment, it seems probable to obtain a tough product owing to a large cohesive force in the hard domain even in the case of a low 6-nylon content. However, in preparing an elastomer having a hard segment of 6-nylon and a soft segment of polyoxytetramethylene glycol, the low miscibility between the two materials tends to cause a coarse phase separation during polymerization, forming a polymerization system of milky white appearance and the resulting polyamide elastomer becomes opaque and pale yellowish white in color accompanied with reduced mechanical strengths. This tendency becomes more marked with increased number average molecular weights of polyoxytetramethylene glycol. When the number average molecular weight of polyoxytetramethylene glycol is 800 or below, an elastomer formed which is opaque but has a relatively high strength. However, owing to the low molecular weight of the polyoxytetramethylene glycol; the resulting elastomer is very limited in composition, thus making it difficult to obtain a product of well-balanced physical properties. When the number average molecular weight of polyoxytetramethylene glycol is 1,000 or above, there is formed only an elastomer which is of low strength and the elastomer is fragile. For this reason, a polyamide elastomer having a hard segment of 6-nylon and a soft segment of polyoxytetramethylene glycol has not yet been put to practice
Such an elastomer is separated into a soluble portion and an ins
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Aoshima Atsushi
Nakamura Mikihiko
Suzuki Yoshio
Anderson Harold D.
Asahi Kasei Kogyo Kabushiki Kaisha
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