MXPA99002279A

MXPA99002279A - Polyamide resin composition

Info

Publication number: MXPA99002279A
Application number: MXPA/A/1999/002279A
Authority: MX
Inventors: John Palmer Robert
Original assignee: Ei Du Pont De Nemours And Company
Priority date: 1996-09-10
Filing date: 1999-03-09
Publication date: 2000-02-02

Abstract

An improved polyamide resin composition for weldable moulded articles which comprises:(a) 99.9-30%by weight of a polyamide-containing compound;(b) 0.1-20%by weight of a plasticizing compound selected from the group consisting of esters of low molecular weight poly(ethylene glycol) having the formula (I):R-COO-(CH2CH2O)n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is 2 to 20;or long chain alkyl polyester of formula (II):HOOC-R-CO-(O-R'-O-CO-R-CO)n-O-R'-OH 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.

Description

COMPOSITION OF POLYAMIDE RESIN BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The invention relates to an improved polyamide resin composition comprising from 0.1 to 20% by weight of a plasticizer compound and molded hollow articles, which exhibit improved strength, i.e. burst pressure, which are produced by welding together discrete sections comprising the polyamide resin composition.

DESCRIPTION OF THE PREVIOUS TECHNIQUE It is known in the art to prepare resin compositions containing polyamide from which molded articles can be manufactured. Sometimes the requirements for the geometrical shape of the molded articles exceed the technical capabilities for molding such an article in one piece or the molding can only be carried out using a core molding process.

KEF 29453 lost relatively expensive and slow. As a result, alternative manufacturing processes have been developed to allow articles to be produced relatively complex by first molding parts of the article, for example two halves of the molded part of a hollow article, and in a second stage welding the halves together to form the desired article. Sometimes difficulties have been encountered, however, in the manufacture of articles with sufficient strength to withstand the forces encountered in the use of such welded articles. A typical example is with the air intake manifolds for the automotive industry. In particular, the breaking of the weld can be a problem in applications where the welded article is subjected to a high internal pressure. This can happen, for example, when the article is an air intake manifold on an internal combustion engine, and premature ignition of the engine. A further problem to be overcome, beside that of the weld rupture, is that in many cases the addition of compounds to the proposed thermoplastic resin composition to increase the strength of a weld in the final article may result instead of this to a decrease in some other important property of the molded article. Surprisingly, it has now been found that including a specific weight percentage of a plasticizer compound in polyamide resin compositions used for weldable molded articles results in significantly increased strength (as defined below), with minimal effect on other properties.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to an improved polyamide resin composition for weldable molded 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 plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula (TJ (___) R-COO- (CH2CH20) n-OC- R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (_____.) HOOC-R-CO- (O-R '-O-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R 'is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50, and (c) the remainder of the composition up to 100% is selected from one or more additive compounds. According to another aspect, the invention is an improvement in a polyamide-containing resin composition for weldable molded articles, wherein the improvement comprises incorporating into the polyamide-containing resin composition an effective amount of a plasticizer compound selected from the group consisting of of low molecular weight poly (ethylene glycol) esters having the formula (I) (I) R-COO- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (II.) HOOC-R-CO- (O-R '-0-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where 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 still another aspect, the present invention is a method for improving the weld strength of formed articles, wherein the articles are hollow and formed of discrete sections welded together and the sections consist essentially of a polyamide resin composition containing an effective amount of a plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula (I) (_D R-COO- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (II) HOOC-R-CO- (O-R '-O-CO-R-CO) "-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50.

According to still another aspect, the present invention is a hollow consisting essentially of a polyamide resin, article the article is comprised of two or more shaped sections discrete welded together, wherein the polyamide resin contains from 0.1 to 20% by Weight of a plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula (I) (I) R-COO- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (_____.) HOOC-R-CO- (O-R '-O-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, n is from 2 to 50. in a preferred embodiment of the invention, the molded article is an air intake manifold for the internal combustion engine, the composition of polyamide resin is polyamide 6/6, and plasticizer compound is present in an amount of from 0.5 to 5% by weight and is a poly (ethylene) low molecular weight terminated 2-ethylhexanoic acid, i.e. n = 9, or a polyester formed from the reaction of an acid C36 dicarboxylic acid and a glycol.

DETAILED DESCRIPTION The addition of plasticizers with polyamides to improve properties has been known in the art for a long time. A plasticizer is a material that causes a reduction in the glass transition temperature (Tg) of the polyamide. If the Tg is reduced below the temperature at which the module is measured, then the module will be significantly reduced. Water is an effective plasticizer for polyamides, but molecules of organic plasticizers can be added during manufacturing to avoid conditioning with moisture, or give a greater plasticizing effect. Plasticizers are typically added at a level of 5% or higher to give a significant increase in flexibility. This increase in flexibility (reduction in the energy needed to deform the material) results in a reduction in the strength of the product (energy needed to deform the material to a breaking point). Typically the strength of a molded thermoplastic article is measured by a method such as "Tensile Strength"; This is a measure of the maximum specific energy that can be applied to a properly molded test piece before it breaks or deforms. It is to be expected that for polyamide compositions containing plasticizer with increased flexibility the tensile strength will be reduced for the reasons given in the foregoing. This expected behavior would most likely have a negative effect on other methods of resistance measurement, in particular for welded thermoplastic hollow objects, the bursting pressure. The bursting pressure is determined by molding the sections of an article with a thermoplastic resin composition and then welding the sections, usually two pieces, together, thereby forming a hollow article included such as in the form of an air intake manifold. The resulting article is sealed and then pressurized until the break occurs in the weld; the breaking pressure is recorded in bars. The test has come to be accepted in the automotive industry as a criterion for the selection of material for welded thermoplastic articles and is proposed to indicate the EFFICIENCY of a material in a welded automotive component such as an air intake manifold when subjected to a loose and intense internal pressure, such as occurs during a premature ignition in an internal combustion engine. This test involve a tensile stress on the part, which increases until the break and is expected to vary in a manner similar to the tensile strength. Surprisingly, it has now been found that the burst pressure of molded welded hollow articles of the polyamide-containing compositions according to the present invention is significantly increased when even a relatively small amount of plasticizer compound is present in the resin composition. The unexpected behavior of such compositions provides a technical solution to the problems mentioned above, which could significantly increase the use of thermoplastic resins in environments where rigorous requirements are imposed on the behavior of welded articles in a complex manner. The polyamide-containing compound may comprise polyamides, amide copolymers and / or other monomers, mixtures of different polyamides, blends of polyamides with other thermoplastic polymers and / or mixtures of the aforementioned copolymers with a polyamide and / or mixtures of different copolymers with or without other thermoplastic polymers. Preferably, the polyamide-containing compound is selected from the group consisting of polyamides 6, 6/6, 4/6, semi-aromatic or aromatic polyamides, copolymers containing such polyamides and mixtures containing such polyamides. In a particularly preferred embodiment of the present invention the polyamide is polyamide 6/6, because the addition of a relatively small amount of plasticizer results in a thermoplastic resin composition with a substantially increased strength measured as burst pressure. Polyamide 6/6 is especially advantageous for use in applications such as automotive air intake manifolds due to its balance of properties including temperature and chemical stability. The exceptional weld strength of the molded compositions comprising both plasticizers and reinforcing fibers (in particular glass fibers) is most surprising in view of the fact that such a significant increase can be achieved when a relatively small amount of a plasticizer compound is present. present, which otherwise confers very little change to the properties of the material. In such a case, the tensile strength as well as other characteristic properties such as extensibility (elongation at break) are changed little compared to the increase in burst pressure. The plasticizer compound of the present invention is selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula (I) (_D R-COO- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (______ > HOOC-R-CO- (O-R '-O-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50.

A particularly preferred class of plasticizer compounds includes the low molecular weight poly (ethylene glycol) terminated in 2-ethylhexanoic acid, ie where n = 9, and long chain alkyl polyesters, in particular the polyester formed from the reaction of a C36 dicarboxylic acid and a glycol. The invention is further related to an improvement in a polyamide-containing resin composition, especially a polyamide 6/6 composition, for weldable molded articles, wherein the improvement comprises incorporating into the resin composition containing polyamide an effective amount of a plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula (I) I) R-C00- (CH2CH2O) n-0C-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (______) HOOC-R-CO- (O-R '-0-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50. According to yet another aspect, the present invention is a method for improving the welding strength of formed articles, wherein the articles are hollow and formed from discrete sections welded together and the sections consist essentially of a polyamide resin composition containing an effective amount of a plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula (I) (I) R-COO- (CH2CH20) n-0C-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (II.) HOOC-R-CO- (O-R '-O-CO-R-CO) "-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where 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 is comprised of two or more discrete shaped sections welded together, wherein the polyamide resin contains from 0.1 to 20% by weight of a plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula ( I_) (I) R-COO- (CH2CH20) O-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (II) HOOC-R-CO- (O-R '-O-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where 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 molded article is an air intake manifold for an internal combustion engine, the polyamide resin composition is polyamide 6/6, and the plasticizer compound is present in an amount from 0.5 to 5% by weight and is a low molecular weight poly (ethylene glycol) terminated in 2-ethylhexanoic acid, ie, where n = 9, which is commercially available as Plasthall® 809 (C. P. Hall) and Uniplex® 809 (Unitex). The plasticizer compound can also be a polyester formed from the reaction of a C36 dicarboxylic acid and a glycol, an example of which is commercially available as Priplast® 3155 (Unichema International). Other molded articles that can be produced from the polyamide-containing composition of the invention include automotive components, electrical and electronic components, aerospace components, sports and leisure time applications, in household and technical appliances, and in the automotive industry. the construction Preferably the polyamide resin composition according to the invention consists essentially of: (a) from 99.5-60% by weight of polyamide 6/6, (b) from 0.5-10% by weight of a plasticizer compound selected from a low molecular weight poly (ethylene glycol) terminated in 2-ethylhexanoic acid, where n = 9, and a polyester formed from the reaction of a C36 dicarboxylic acid and a glycol, and optionally, (c) from 20-40% by weight of a reinforcing compound, and (d) from 1-30% by weight of one or more additive compounds. More preferably, the plasticizer compound is present in the composition in an amount of 0.5-5% by weight, particularly when the composition comprises polyamide 6/6 as at least the main component of the polyamide-containing compound. An amount of less than 0.5% by weight of plasticizer compound in the resin in many cases does not result in a technically acceptable strength of welded articles molded with the use of such resin, although smaller amounts may result in an increase in strength (measured as burst pressure). An amount of more than 5% by weight of plasticizer compound can give rise to unwanted changes in properties of the thermoplastic resin composition, in particular, for technically demanding applications such as air intake manifolds, where the correct balance of properties of Welded thermoplastic molded sections are especially critical. Various types of reinforcing compounds can be used in the thermoplastic resin compositions according to the invention, for example minerals (such as talc, tonite waves, kaolin) and fibers. A wide variety of fibers can be used, both with respect to their dimensions and their chemical composition. The dimensions suitable for the fibers depend strongly on the type of application of the resin. However, in many applications fibers with an average relationship between dimensions (ratio of length to diameter) in the molding resin between 5 and 100 and a diameter of between 1 and 20 microns are suitable. Suitable types of fibers include both natural and man-made fibers, such as carbon, mineral, polymer and glass fibers. Suitable polymer fibers are polyaramide fibers. Particularly preferred fibers for welded articles with high strength are glass fibers. The fibers can be coated with for example a silane compound to improve their adhesion to the resin composition. The additive compounds referred to under (d9) of a preferred thermoplastic resin composition according to the invention as described above may be one or more optional compounds selected from a wide variety of compounds designed for different applications of the resin compositions. additive compounds may include flame retardants, impact modifiers, pigments, lubricants, antioxidants, and UV stabilizers and other stabilizers.There are various welding techniques for molded articles made from the pyrimetic polyamide resins of the type described herein, such as: hot plate welding, inductance welding (convective energy), resistance welding (tape welding), rotation welding, corner welding, ultrasonic welding and vibration welding, while all these welding techniques have their advantages (and disadvantages), it has been found that molded sections of complex shape made of a plasticized polyamide resin composition according to the invention are welded very effectively employing a vibration welding technique. The invention therefore also relates to vibration welded articles comprising at least two molded sections of a thermoplastic resin composition as described above. The invention is illustrated by the following Examples.

EXAMPLE 1 The composition A of thermoplastic resin (according to the invention) comprises 66.96% by weight of polyamide 6/6, 2.0% by weight of a plasticizer compound (low molecular weight poly (ethylene glycol) terminated in 2-ethylhexanoic acid), where n = 9), 30% by weight of glass fiber with an average length of 3 mm and an average diameter of 10 microns, 0.54% by weight of stabilizer and 2.0% by weight of a masterbatch containing black dye. The composition B of the plastics resin (comparative example, not according to the invention) comprises 68.96% by weight of the same type of polyamide 6/6 present in the composition A, without plasticizer, 30% by weight of the same type of fibers of glass, 0.54% by weight of stabilizer and 2.0% by weight of a master batch containing black colorant. The thermoplastic resin compositions A and B were both molded into two sections of an identical test box whose sections were subsequently joined together by vibration welding. Pressure was applied internally to the test box by drilling a hole by inserting a connection and pressurizing with oil using a pump connected to a pressure measuring device. The pressure at which the assembly exploded was recorded. The boxes were dry-welded after molding and left a day to equilibrate before the explosion test. The following table provides the results of the tests.

TABLE 1 As shown in the table, the standard deviation for the burst pressure test is significantly less than the substantial difference in burst pressure resistance between Experiment 1 according to the invention and Comparative Experiment 2. The experimental results additionally show that neither the results of the test for "Tensile Strength" or "Elongation to rupture" are an appropriate indication of resistance significantly increased in practical terms for applications where an increase of sudden pressure in articles can occur soldiers according to the invention, in particular air intake manifolds for internal combustion engines.

EXAMPLE 2 The formulations are as for Example 1, except that the plasticizer in composition C (according to the invention) is 2% of a polyester formed from the reaction of a C36 dicarboxylic acid and a glycol.

TABLE 2 EXAMPLE 3 Similar formulations were used as for Example 1 using the same type of plasticizer but with lower plasticizer contents and where compositions D and E are according to the invention.

TABLE 3 EXAMPLE 4 Composition F (according to the invention) comprises 53.21% by weight of a copolymer of polyamide 6/6 and polyamide 6 (85:15 ratio by weight), 15.0% by weight of polyamide 6, 2.0% by weight of a compound plasticizer (poly (low molecular weight ethylene glycol terminated in 2-ethylhexanoic acid), where n = 9), 30% by weight of the same type of glass fibers as in the above, 1.25% of a masterbatch containing black colorant and 0.54% stabilizer. Composition G (comparative example, not according to the invention) comprises 51.21% by weight of the same copolymer as in F, 15.0% by weight of the same type of polyamide 6, without plasticizer, 30% by weight of the same type of fibers of glass, 1.25% by weight of a master batch containing black dye and 0.54% stabilizer.

TABLE 4 EXAMPLE 5 Composition H (according to the invention) comprises 95.46% by weight of polyamide 6/6, 2.0% by weight of a plasticizer compound (low molecular weight poly (ethylene glycol) terminated in 2-ethylhexanoic acid, where n = 9), 0.54% by weight of stabilizer and 2.0% by weight of a master batch containing black dye. Composition I (comparative example, not according to the invention) comprises 97.46% by weight of the same type of polyamide 6/6, without plasticizer, 0.54% of stabilizer and 2.0% of a masterbatch containing black colorant. Compositions H and I do not contain reinforcing compounds such as glass fiber.

TABLE 5 Note that this Example 1 provides elongation to deformation, while in Examples 1-4 the elongation at break is provided. For the properties of the resin compositions without reinforcement such as H and I, the former was usually cited, while for reinforced materials, the latter was usually used. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

RE IVINDICATIONS Having described the invention as above, property is claimed as contained in the following:

1. An improved polyamide resin composition, characterized in that it comprises: (a) 99.9-30% by weight of a polyamide-containing compound; (b) 0.1-20% by weight of a plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters having the formula (I) (I) R-COO- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long-chain alkyl polyester of the formula (II) (II.) HOOC-R-CO- (O-R '-O-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50, and (c) the remainder of the composition up to 100% is selected from one or more additive compounds.

2. An improved method for preparing a polyamide resin composition, characterized in that the improvement comprises: incorporating into the polyamide-containing resin composition an effective amount of a plasticizer compound selected from the group consisting of low molecular weight poly (ethylene glycol) esters that have the formula (I_) (I) R-COO- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (II.) HOOC-R-CO- (O-R '-O-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50.

3. A method for improving the strength of welding in shaped articles, wherein the articles are formed of a polyamide resin composition containing an effective amount of a plasticizer compound selected from the group consisting of poly (ethylene glycol) esters of molecular weight low they have the formula (I) (I) R-COO- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (__U HOOC-R-CO- (O-R '-O-CO-R-CO) "-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50.

4. An article characterized in that it comprises a component formed of a polyamide resin composition, wherein the polyamide resin contains from 0.1 to 20% by weight of a plasticizer compound selected from the group consisting of poly (ethylene glycol) esters of low molecular weight that have the formula (I) (I) R-C00- (CH2CH20) n-OC-R wherein R is a branched or straight chain alkyl group having from 1 to 40 carbon atoms, and n is from 2 to 20; or a long chain alkyl polyester of the formula (II) (II) HOOC-R-CO- (O-R '-O-CO-R-CO) n-0-R' -OH wherein R is alkyl of 16 to 45 carbon atoms, R 'is alkyl of 2 to 6 carbon atoms, or, where R is an alkyl of 2 to 6 carbon atoms, R' is an alkyl of 16 to 45 carbon atoms, and n is from 2 to 50.

5. The article according to claim 4, characterized in that: a. the polyamide is polyamide 6/6, and b. the plasticizer compound is present in an amount from 0.5 to 5% by weight and is low molecular weight poly (ethylene glycol) terminated in 2-ethylhexanoic acid.

6. The article according to claim 4, characterized in that: a. the polyamide is polyamide 6/6, and b. The plasticizer compound is present in an amount from 0.5 to 5% by weight and is a polyester formed from the reaction of a C36 dicarboxylic acid and a glycol.

7. Shaped articles, characterized in that they comprise a polyamide resin composition prepared by the process according to claim 2.

8. Items formed, prepared by the processes according to claim 3.