Polyesterurethane elastomers and process for their production

Details Polyesterurethane elastomers and process for their production Polyesterurethane elastomers and process for their production

2000-11-16

2003-06-17

Short, Patricia A. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S411000, C525S438000, C525S439000, C525S440030, C525S444000, C528S076000, C528S083000

Reexamination Certificate

active

06579952

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an ester elastomer having good flexibility and excellent mechanical characteristics at high temperature, particularly excellent creep resistance at high-temperature and a process for its production.
PRIOR ART
With the increased consciousness of ecology, the substitution of recyclable materials for conventional materials is progressing at an accelerated rate in various industries. Thermoplastic elastomers (TPE) have attracted attention as recyclable rubbery materials for many years but as the concept of eco-friendliness is given greater emphasis of late, those materials have come to be used more and more frequently in many applications in automotive and other industries.
Among thermoplastic elastomers, polyester elastomers (hereinafter referred to as TPEE) are outstanding in mechanical strength, heat resistance, wear resistance, and flexural fatigue resistance so that they are broadly used in various industries, particularly in automotive industry. However, TPEE has the disadvantage of (1) high hardness beyond the usual rubber hardness region and, hence, low flexibility and (2) large compressive set at large deformation and/or high temperature and consequent lack of creep resistance. As such, improvements in these aspects have been demanded.
In order to impart flexibility to TPEE, it is necessary to reduce the proportion of the hard segment component which is to shoulder physical crosslinking and a technology for decreasing the hard segment component has been proposed in Japanese Kokai Publication Hei-2-88632, for instance. However, the application of the technique leads to a reduction in the block property of the hard segment component, with the result that the melting point of the resin is depressed and the mechanical properties at high temperature are also sacrificed. With regard to creep resistance, too, a technology for increasing the degree of polymerization to improve the creep resistance has been disclosed in Japanese Kokai Publication Sho-52-121699, for instance, but the consequent improvements in mechanical characteristics are limited and it was also difficult to reconcile creep resistance with flexibility.
SUMMARY OF THE INVENTION
The present invention has for its object to provide an ester elastomer having a high block of the hard and soft segment components, high flexibility, and good mechanical properties at high temperature, particularly high temperature creep resistance and a process for producing said ester elastomer.
The present invention, in a first aspect, relates to an ester elastomer which comprises a block copolymer comprising a polyester copolymer (A) and a polymer having hydroxyl groups at both terminal ends (B) (hereinafter referred to sometimes as hydroxyl-terminated polymer) which are coupled to each other through the intermediary of an urethane component (C) containing a group of general formula (1);
—O—CO—NH—R
1
—NH—CO—O—  (1)
(wherein R
1
represents an alkylene group containing 2 to 15 carbon atoms, —C
6
H
4
—, —C
6
H
4
—CH
2
—, —C
6
H
4
—CH
2
—C
6
H
4
— (where —C
6
H
4
— represents phenylene)) and/or a group of general formula (2);
—O—CO—NH—R
2
—NH—CO—  (2)
(wherein R
2
represents an alkylene group containing 2 to 15 carbon atoms, —C
6
H
4
—, —C
6
H
4
—CH
2
— or —C
6
H
4
—CH
2
—C
6
H
4
— (wherein —C
6
H
4
— represents phenylene)),
where said polyester copolymer (A) consisting of 50 to 95 weight % of a short-chain polyester component (a1) comprising a group of general formula (3);
—CO—R
3
—CO—O—R
4
—O—  (3)
(wherein R
3
represents a bivalent aromatic hydrocarbon group containing 6 to 12 carbon atoms; R
4
represents an alkylene group containing 2 to 8 carbon atoms) as a recurring unit and 50 to 5 weight % of a long-chain polyester component (a2) comprising a group of general formula (4);
—CO—R
5
—CO—O—L—  (4)
(wherein R
5
represents a bivalent aromatic hydrocarbon group containing 6 to 12 carbon atoms; L represents an oligomer component (L) having a glass transition temperature of not higher than 20° C. and a number average molecular weight of 500 to 5000) as a recurring unit, said hydroxyl-terminated polymer (B) having a glass transition temperature of not higher than 20° C., a number average molecular weight of 500 to 5000, and the absolute difference |&dgr;B-&dgr;L| [where &dgr;B represents the solubility parameter of said hydroxyl-terminated polymer (B) and &dgr;L represents the solubility parameter of said oligomer component (L) of said long-chain polyester component (a2)] being not greater than 0.5.
The present invention, in a second aspect, relates to a process for producing an ester elastomer which comprises melt kneading 100 parts by weight of the polyester copolymer (A) comprising 50 to 95 weight % of the short-chain polyester component (a1) and 50 to 5 weight % of the long-chain polyester component (a2), said long-chain polyester component (a2) containing the oligomer component (L) having a glass transition temperature of not higher than 20° C. and a number average molecular weight of 500 to 5000, 50 to 500 parts by weight of the hydroxyl-terminated polymer (B) having a glass transition temperature of not higher than 20° C. and a number average molecular weight of 500 to 5000, the absolute difference |&dgr;B-&dgr;L| ([where &dgr;B represents the solubility parameter of said hydroxyl-terminated polymer (B) and &dgr;L represents the solubility parameter of said oligomer component (L) of said long-chain polyester component (a2)] being not greater than 0.5, and 10 to 100 parts by weight of the isocyanate compound (C′).
The present invention, in a third aspect, relates to an ester elastomer having a surface hardness of 60 to 90 and a 72-hour compressive set at 120° C. of not greater than 90%.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is now described in detail.
Referring to the first aspect of the invention, the polyester copolymer (A) comprises of 50 to 95 weight % of a short-chain polyester component (a1) of the general formula (3) shown above and 50 to 5 weight % of a long-chain polyester component (a2) of the general formula (4) shown above.
The above polyester copolymer (A) generally consists of recurring units of short-chain polyester component (a1) and long-chain polyester component (a2).
In the above general formula (3) representing said short-chain polyester component (a1), R
3
represents a bivalent aromatic hydrocarbon group containing 6 to 12 carbon atoms and R
4
represents an alkylene group containing 2 to 8 carbon atoms.
Preferably said short-chain polyester component (a1) may for example be polybutylene terephthalate, polybutylene 2,6-naphthalate, or polyethylene 2,6-naphthalate, for those compounds contribute to the formation of ester elastomers having satisfactory creep resistance at high temperature. Particularly when polybutylene 2,6-naphthalate or polyethylene 2,6-naphthalate is used, a remarkable improvement is obtained in creep resistance at high temperature.
The long-chain polyester component (a2) is represented by general formula (4), and contains said oligomer component (L) having a glass transition temperature of not higher than 20° C. and a number average molecular weight of 500 to 5000 as a constituent unit. In the above general formula (4), R
5
represents a bivalent aromatic hydrocarbon group of 6 to 12 carbon atoms.
The oligomer component (L) mentioned above, when it exists as an independent substance, has hydroxyl groups at both termini thereof, and in the long-chain polyester component (a2), each of the two termini is in the form of an ester bond. This oligomer component (L) may for example be a polyether, aliphatic polyester, polylactone, polycarbonate, polyolefin, polybutadiene, polyisoprene, polyacrylate, polysiloxane, and other compounds which have hydroxyl groups at both termini. Among the above-mentioned oligomers, the polyether, aliphatic polyester, polylactone and polycarbonate are preferred because of high reactivity.
When the oligomer

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