p-hydroxybenzoic esters, plasticizer containing the same,...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof

Reexamination Certificate

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C528S271000, C528S272000, C528S288000, C528S292000, C528S322000, C524S292000, C524S295000, C524S310000, C525S420000, C525S422000, C525S433000, C428S034100, C428S035200, C264S512000, C264S513000, C264S514000, C264S515000, C264S563000, C560S001000, C560S008000, C560S076000

Reexamination Certificate

active

06348563

ABSTRACT:

TECHNICAL FIELD
The present invention relates to p-hydroxy-benzoic esters, polyamide resin plasticizers containing said p-hydroxybenzoic esters, and polyamide resin composition and polyamide resin molded articles containing said p-hydroxybenzoic esters.
More particularly, the present invention relates to p-hydroxybenzoic esters which are useful as plasticizers having good compatibility with a polyamide resin selected from the group consisting of nylon 11 and nylon 12, having low volatility, and having an excellent plasticizing effect; polyamide resin compositions containing the same, and polyamide resin molded articles which are obtainable by molding the polyamide resin composition and which have excellent flexibility, reservability, oil resistance, low-temperature impact resistance and high-temperature volatilization resistance.
BACKGROUND ART
Japanese Unexamined Patent Publication No. 1913/1994 filed by the inventors of the present invention broadly discloses a wide variety of p-hydroxybenzoic esters represented by the formula (2)
wherein R
2
represents an alkyl group, an alkenyl group, an optionally substituted cycloalkyl group, an aryl group or an aralkyl group; A
2
represents a C
2
-C
4
alkylene group; m is an integer of 1 to 20, and discloses that polyamide resin compositions containing said esters are excellent in compatibility at room temperature, good in mechanical properties, and capable of giving excellent molded articles with low-temperature resistance and oil resistance, and are useful as materials for hoses and tubes for automobiles.
More specifically, the publication discloses, as preferable examples of the esters represented by the above formula (2), butoxyethoxyethyl p-hydroxybenzoate, cyclohexyloxyethoxyethoxyethyl p-hydroxybenzoate, (p-nonylphenoxyethyl) p-hydroxybenzoate, and the working examples of said publication also disclose the use of butoxyethyl p-hydroxybenzoate and cyclohexyloxyethoxyethoxyethyl p-hydroxybenzoate.
The above Japanese Unexamined Patent Publication No. 1913/1994 exemplifies a variety of polyamide resins, particularly nylon 6, nylon 66, nylon 610, nylon 11, nylon 12 and copolymerized nylons.
In addition, for evaluating the properties of the molded articles (press sheet) obtained from said polyamide resin composition, the above Japanese Unexamined Patent Publication No. 1913/1994 discloses mechanical properties (tensile strength, elongation at break) evaluation according to ASTM D-638, low-temperature resistance evaluation according to Clash-Berg test, compatibility evaluation by measuring the amount of plasticizer bled out after leaving the press sheet to stand at 25° C. for 48 hours and oil resistance evaluation by measuring the weight loss after immersing the press sheet in gasoline at 25° C. for 48 hours.
Incidentally, due to recent improvement in performance and safety of automobiles, there is an increasing demand for increasing the strength of various parts. Fuel supply tubes and air brake hoses are also required to be more resistant to severe conditions. For example, the temperature of the engine room of a automobile in midsummer may be elevated to nearly 70-80° C., whereas it may be lowered to about −40° C. in winter. Generally, plasticizer in molded articles may volatilize at a high temperature, resulting in impaired physical properties such as mechanical properties and low-temperature resistance, and molded articles may also break upon impact at a low temperature. In order for the molded articles to withstand such environments, it is required that plasticizer does not volatilize at a high temperature (e.g. about 120° C.) out of the molded articles (hereinafter in the present description and claims referred to as “high-temperature volatilization resistance”) and that at lower temperatures (e.g. about −40° C.) the molded articles are not broken upon impact (hereinafter in the present description and claims referred to as “low-temperature impact resistance”).
However, in the above Japanese Unexamined Patent Publication No. 1913/1994, the properties of the molded article are evaluated in the normal environment. For example, reservability of the esters represented by the formula (2) in polyamide resins is determined based on the compatibility at room temperature. Additionally, the low-temperature resistance of said polyamide resin composition represents the flexible temperature of the resin, and therefore it is not an evaluation of breakage upon impact at lower temperatures.
Accordingly, the Japanese Unexamined Patent Publication No. 1913/1994 in no way gives a hint as to whether the molded article obtainable from the polyamide resin composition disclosed therein is excellent in terms of the above-mentioned high-temperature volatilization resistance and low-temperature impact resistance as recently required by the automobile industry.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a compound useful as a plasticizer which is capable of giving a polyamide resin molded article having excellent properties such as plasticizing ability, compatibility and reservability, particularly having excellent high-temperature volatilization resistance and low-temperature impact resistance, and to further enable the polyamide resin molded article having such excellent properties to be used in a broader range of environments.
The inventors of the present invention carried out extensive research to solve the above-mentioned problems. As a result, the present inventors found that when p-hydroxybenzoic esters, which have a specific structure different from those of the preferable compounds disclosed in the Japanese Unexamined Patent Publication No. 1913/1994, are used as a plasticizer for at least one polyamide resin selected from the group consisting of nylon 11 and nylon 12, there is obtained a molded article which is not only excellent in plasticizing ability, reservability and low-temperature resistance but also excellent in high-temperature volatilization resistance and low-temperature impact resistance. The present invention has been accomplished based on the above findings.
Thus, the present invention provides a p-hydroxybenzoic ester represented by the formula (1)
wherein R
1
represents a C
6
-C
10
straight-chain or branched-chain alkyl group, A
1
represents a C
2
-C
4
alkylene group, and n is an integer of 1 to 8.
The above compound of the formula (1) is not specifically disclosed in the above-mentioned Japanese Unexamined Patent Publication No. 1913/1994, and is a novel compound which acts, with high performance, as a plasticizer for a specific polyamide resin selected from the group consisting of nylon 11 and nylon 12.
The present invention also provides a plasticizer for at least one polyamide resin selected from the group consisting of nylon 11 and nylon 12, the plasticizer comprising a p-hydroxybenzoic ester represented by the above formula (1).
Furthermore, the present invention provides a polyamide resin composition comprising
(a) at least one polyamide resin selected from the group consisting of nylon and nylon 12; and
(b) at least one p-hydroxybenzoic ester represented by the formula (1)
wherein R
1
represents a C
6
-C
10
straight-chain or branched-chain alkyl group, A
1
represents a C
2
-C
4
alkylene group, and n is an integer of 1 to 8.
The present invention further provides a polyamide resin molded article obtainable by molding the above polyamide resin composition.
The present invention will be described below in detail.
p-Hydroxybenzoic Ester of the Formula (1)
The compound of the formula (1) for use in the present invention is a compound obtainable, for example, by subjecting p-hydroxybenzoic acid and a C
2
-C
4
alkylene oxide adduct of a C
6
-C
10
aliphatic alcohol (hereinafter sometimes referred to as “alkoxylated alcohol”) to a conventional esterification or ester-interchange reaction.
Examples of the aliphatic alcohol include C
6
-C
10
straight-chain or branched-chain aliphatic saturated alcohols or mixtures thereof, specifically, n-hexanol, n-heptanol, n-octanol,

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