Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1997-02-25
2001-07-17
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S322000, C525S419000, C524S538000, C524S539000, C524S556000, C524S558000, C524S559000, C524S569000, C524S606000, C428S357000, C428S364000, C428S394000, C428S395000
Reexamination Certificate
active
06262221
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an improved polyamide resin composition which includes from 0.1 to 20% by weight of a plasticising compound and to moulded hollow articles, which exhibit improved strength, i.e., burst pressure, that are produced by welding together discreet sections comprising said polyamide resin composition.
2. Description of Prior Art
It is known in the art to prepare polyamide-containing resin compositions from which moulded articles can be manufactured. Sometimes the requirements for the geometric shape of the moulded articles exceed the technical capabilities for moulding such an article in one piece or the moulding can only be carried out using a relatively costly and slow lost-core moulding process. As a result, alternative manufacturing processes have been developed to enable relatively complex-formed articles to be produced by first moulding parts of the article, for instance two half shells of a hollow article, and in a second step welding the shells together to form the desired article.
Difficulties have sometimes been encountered, however, in manufacturing articles with a sufficient strength to withstand the forces encountered in the utilization of such welded articles. A typical example is with air inlet manifolds for the automotive industry. In particular, weld failure can be a problem in applications where the welded article is subjected to an elevated internal pressure. This can happen, for example, when the article is an air intake manifold on an internal combustion engine, and the engine backfires.
An additional problem to overcome, besides that of weld failure is that in many cases the addition of compounds to the thermoplastic resin composition intended to increase the strength of a weld in the final article, may lead instead to a decrease in some other important property of the moulded article.
Surprisingly, it has now been found that including a specific weight percentage of a plasticising compound in polyamide resin compositions used for weldable moulded articles results in a significantly increased strength (as defined hereinafter), with minimal effect on other properties.
SUMMARY OF THE INVENTION
The present invention relates to an improved polyamide resin composition for weldable moulded articles, especially hollow articles, which comprises:
(a) from 99.9-30% by weight of a polyamide-containing compound,
(b) from 0.1-20% by weight of a plasticising compound selected from the group consisting of esters of low molecular weight poly(ethylene glycol) having the formula (I)
R—COO—(CH
2
CH
2
O)
n
—OC—R (I)
wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is 2 to 20; or a long chain alkyl polyester of formula (II)
HOOC—R—CO—(O—R′—O—CO—R—CO)
n
—O—R′—OH (II)
wherein R is alkyl of 16 to 45 carbon atoms, R′ is alkyl of 2 to 6 carbon atoms, or, wherein R is an alkyl of 2 to 6 carbon atoms, R′ is an alkyl of 16 to 45 carbon atoms, and n is 2 to 50, and
(c) the balance of the composition up to 100% being selected from one or more additive compounds.
According to another aspect, the invention is an improvement in a polyamide-containing resin composition for weldable moulded articles, wherein the improvement comprises incorporating into said polyamide-containing resin composition an effective amount of a plasticising compound selected from the group consisting of esters of low molecular weight poly(ethylene glycol) having the formula (I)
R—COO—(CH
2
CH
2
O)
n
—OC—R (I)
wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is 2 to 20; or a long chain alkyl polyester of formula (II)
HOOC—R—CO—(O—R′—O—CO—R—CO)
n
—O—R′—OH (II)
wherein R is alkyl of 16 to 45 carbon atoms, R′ is alkyl of 2 to 6 carbon atoms, or, wherein R is an alkyl of 2 to 6 carbon atoms, R′ is an alkyl of 16 to 45 carbon atoms, and n is 2 to 50.
According to yet another aspect, the present invention is a method for improving the weld strength of shaped articles where the articles are hollow and formed from discreet sections welded together and the sections consist essentially of a polyamide resin composition which contains an effective amount of a plasticising compound selected from the group consisting of esters of low molecular weight poly(ethylene glycol) having the formula (I)
R—COO—(CH
2
CH
2
O)
n
—OC—R (I)
wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is 2 to 20; or a long chain alkyl polyester of formula (II)
HOOC—R—CO—(O—R′—O—CO—R—CO)
n
—O—R′—OH (II)
wherein R is alkyl of 16 to 45 carbon atoms, R′ is alkyl of 2 to 6 carbon atoms, or, wherein R is an alkyl of 2 to 6 carbon atoms, R′ is an alkyl of 16 to 45 carbon atoms, and n is 2 to 50.
According to yet another aspect, the present invention is a hollow article consisting essentially of a polyamide resin, the article being comprised of two or more discreet shaped sections welded together, wherein the polyamide resin contains from 0.1 to 20% by weight of a plasticising compound selected from the group consisting of esters of low molecular weight poly(ethylene glycol) having the formula (I)
R—COO—(CH
2
CH
2
O)
n
—OC—R (I)
wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is 2 to 20; or a long chain alkyl polyester of formula (II)
HOOC—R—CO—(O—R′ —O—CO—R—CO)
n
—O—R′ —OH (II)
wherein R is alkyl of 16 to 45 carbon atoms, R′ is alkyl of 2 to 6 carbon atoms, or, wherein R is an alkyl of 2 to 6 carbon atoms, R′ is an alkyl of 16 to 45 carbon atoms, and n is 2 to 50.
In a preferred embodiment of the invention, the moulded article is an air intake manifold for an internal combustion engine, the polyamide resin composition is polyamide 6/6, and the plasticising compound is present in an amount of from 0.5 to 5% by weight and is a 2-ethyl hexanoic acid terminated low molecular weight poly(ethylene glycol), i.e., n=9, or a polyester formed from the reaction of a C
36
dicarboxylic acid and a glycol.
DETAILED DESCRIPTION
The addition of plasticisers to polyamides for improving properties has been known in the art for a long time. A plasticiser is a material which causes a reduction in the glass transition temperature (Tg) of the polyamide. If the Tg is reduced to below the temperature at which the modulus is measured, then the modulus will be significantly reduced. Water is an effective plasticiser for polyamides but organic plasticiser molecules can be added during manufacture to avoid moisture conditioning, or give a greater plasticising effect. Plasticisers are typically added at a level of 5% or greater to give a significant increase in flexibility. This increase in flexibility (reduction in energy necessary to deform the material) results in a reduction in the strength of the product (energy necessary to deform the material to breaking point).
Typically the strength of a moulded thermoplastic article is measured by one method as “Tensile Strength”; this is a measure of the maximum specific energy which can be applied to an appropriately moulded test piece before it breaks or yields.
It is to be expected that for plasticiser-containing polyamide compositions with increased flexibility the tensile strength will be reduced for the reasons given above.
This expected behavior would most likely have a negative effect on other methods of measuring strength, in particular for welded thermoplastic hollow objects, the burst pressure.
Burst pressure is determined by moulding the sections of an article with a thermoplastic resin composition and then welding the sections, usually two pieces, together, thus forming an enclosed hollow article such as in the shape of an air intake, or inlet, manifold. The resulting article is sealed and then pressurized until failure occurs at the weld; the failure pressure is recorded in bars. The te
E. I. DuPont de Nemours and Company
Hampton-Hightower P.
LandOfFree
Polyamide resin composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyamide resin composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyamide resin composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2464123