CA2130476A1 - Extrusion or blow-moulding of polyamide compositions - Google Patents
Extrusion or blow-moulding of polyamide compositionsInfo
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- CA2130476A1 CA2130476A1 CA 2130476 CA2130476A CA2130476A1 CA 2130476 A1 CA2130476 A1 CA 2130476A1 CA 2130476 CA2130476 CA 2130476 CA 2130476 A CA2130476 A CA 2130476A CA 2130476 A1 CA2130476 A1 CA 2130476A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
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- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
Abstract
A blow moulding process in which a parison is formed from a polyamide composition and an extrusion process in which a profile is extruded from a polyamide compositon are disclosed. The polyamide composition comprises (a) 55-90 % by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at least 40; and (b) 10-45 % by weight of a polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer. Each of the grafted polymer and ungrafted polymer are independently selected from the polyolefins having a melt index of less than 10 dg/min. The polyolefin of the grafted polymer is grafted with 0.1-5.0 % by weight of an ethylenically unsaturated carboxylic acid or anhydride.
The grafted polymer is 25-100 % by weight of the polymer of (b).
The composition exhibits a relative increase in melt viscosity at low shear stress compared to the polyamide of (a). The compositons may be used in the blow moulding of for example bottles, containers and hollow under-the-hood automotive components and in the extrusion of for example rods, tubing, cable jacketing and other profiles.
The grafted polymer is 25-100 % by weight of the polymer of (b).
The composition exhibits a relative increase in melt viscosity at low shear stress compared to the polyamide of (a). The compositons may be used in the blow moulding of for example bottles, containers and hollow under-the-hood automotive components and in the extrusion of for example rods, tubing, cable jacketing and other profiles.
Description
WO 94/13740 PCT/CA93/0050~
-1 2t30q(~
EXTRUSION OR BLOW-MOULDIN~ OF POLYAMIDE COMPOSITIQ~S
The present invention relates to extrusion and blow-moulding processe~ using polyamide compositions and to such compositions, and e~pecially to improvements therein. In particular, the invention relates to extrusion and blow-moulding processes in which the polyamide compositions have increased melt viscosity at low stress levels to impart melt sag resistance and moderately low viscosity at high stress levels, to impart improved extrudability.
. Polyamides may be fabricated into a wide variety of products. The compositions used must have melt viscosity characteristics that are appropriate to the process being used, as discussed in published European patent application 0 295 906 of D.S. Dykes and K.D. Ruhnemann, published 1988 December 21. The use of compositions of polyamides and epoxides $n extrusion processes is disclosed therein. Polyamide compo~itions for blow moulding are disclosed in U.S. Patent 5 122 570 of P.M.
Subramanian, issued 1992 June 16, such compositions being semi-crystalline poly~mide, selected toughening agent and an anhydride-rich ethylene copolymer~
Blow moulding and extrusion are important processing operations used in the manufacture of finish~d articles from polymaric compo~itions. Blow moulding is the process normally used for the manufacture of hollow articles for example bottles, jugs and the like, from thermoplastic polymers e.g. polyethylene, polypropylene and polyvinyl chloride. Blow moulding processes are finding increasing use in the manufacture of engineering and structural components, for example automotive under-the-hood components e.g. fluid reservoirs, resonators and the like, which have to be manufactured from so-called engineering polymers e.g. polyamides. Extrusion `~L3047~ 2 processes are used for making continuous profiles for example pipe, tubing or other profiles of a specific cross-sectional shape. For automotive and other critical end-use applications, such extrusion procQsses utilize engineering polymers.
Both blow moulding and extrusion processes require polymer compositions with unique rheological characteristics for commercially acceptable operation.
In blow moulding processes, molten polymer is extruded vertically from an annular die into a cavity between two halves of a mould, in the form of a tube known as a parison. The mould is then closed, capturing the parison between the halves of the mould. Air is blown into the parison to force the molten polymer into contact with and to the shape of the walls of the mould. The melt is cooled by circulation of a cooling fluid through cbannels with~n the walls of the ~ould, after which the moulded part is removed. During extrusion and until it is captured by the halves of the mould, the parison undergoes deformation characterized by extension or stretching of the parison under the influence of its own weight; as the only influence on the parison is its weight, the deformation occurs under low levels of stress. For successful operation of the process, the polymer ~ust exhibit sufficiently high melt viscosity under low stress that the parison is able to support itself without extensive drawing, sagging or thinning in localized areas.
In an extrusion process, polymer melt is extruded Ifrom a die in the form of a continuous profile which then enters a cooling chamber for solidification. The travel of the extrudate from the die to the cooling chamber is usually free from any surface, and in order to preserve the desired cross-sectional shape the extrudate needs to 3S be able to support itself without undergoing excessive :
0~7~
sagging. As with blow moulding processes, this also requires a polymer that has a sufficiently high melt viscosity under low levels of stress.
While hiqh melt viscosity at,low stress levels is required for the above processes, a moderately low melt vi~cosity i8 required under high levels of stre~, and correspondingly high rates of flow, encountered in the extruder and die. A melt viscosity that is too high under these condition~ leads to excessive pressure build-up and requires high torgues for extrusion, which ultimately limits the rate of throughput obtainable from the extruder. Very high melt viscosity under these conditions may also lead to a phenomenon known as melt fracture where tbe surface of the extrudate becomes rough and wavy making the process difficult to operate and the résultant parts unacceptable.
The ctress acting on a melt parison in a blow^
moulding process Dr on melt exudate during its travel from the die to the cooling chamber in an extrusion proce-s is extensional in nature. However, it is ; extremely difficult to characterize melt viscosity of a polymer over a wide range of extensional stress, and melt viscosity measurements are ~o~monly carried out over a wlde range of shear stress.
2S Polyamides are characterized by low melt viscosity under both high and low shear stress i.e. they tend to have poor melt sag resistance. Techniques that increase the melt viscosity under low shear streæs alco tend to increase the melt viscosity under high shear stress, with ~1 ,30 ! the result that the resultant polyamide compositions tend to be unacceptable for blow moulding or extrusion ;~proc2sses. Preferred characteristics for blow moulding -~~ and extrusion are high viscosity at low shear stress and oderately low melt viscosity under high shear stress 3`5 ;~lèvels.
WO 94/13740 PCT/CA93/00~03 ~3~ t~ 6 Polyamide compositions suitable for blow moulding and extrusion processes h~ve how been found.
Accordingly, the pre'sent invention provides a blow moulding process in which a parison is formed from a polyamide composition, characterized in that said composition ~omprises:
(a) SS-90~ by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at least 40; and :~- (b) 10-45% by weight of a polymer selected from the;~ group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently ;; sel~cted from polyolefins having a mel~ index of less ~ than 10 dg/min, the polyolefin of ~aid grafted poly~er -~ having ~een grafted with 0.1-S~OS by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b);
and said composition exhibiting a relative increase in melt viscocity at low shear stress compared to the polyamide of (a).
~5 The present invention also provide~ an extrusion process in which a profile is extruded from a polyamide co~position, characterized in that said composition comprises:
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) :~ polyamides that are soluble in formic acid and which havean RV measured .in formic acid of at least 40; and (b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of wo 94~13740 2 t 3 0 1 7 ~ PCT/CA93/00~03 grafted polymer and ungrafted polymer, e~ch of s~id grafted polymer and ungr~fted polymer being independently ~elected from polyolefins having a melt index of less than 10 dg/min, the polyolefin of said grafted polymer S having been grafted with 0.1-5.0% by weight of an ethylenically un~aturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viæcosity at low shear stress compared to the polyamide of (a)-~; n preferred e~bodiments of the processes of the invention, the polyamide haæ an amine end group content of at least 30 equivalents/10~ grams of polymer.
The present inv ntion also provides a polyamide composition comprising:
(a) 55-90% by w~ight of a polya~ide selected fro~
the group consi~ting of (i) polyamides having a weight average molecular weight of gre~ter than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in for~ic acid of at least 40; and b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said 2s ~rafted polymer and ungrafted polymer being independently selected from polyolefins having a malt index of less ~han 10 dg/min, the polyolefin of said grafted polymer having been grafted with 0.1-5.0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, ,; 30 Ithe grafted polymer being 2S-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity ~t low shear stress compared to the polyamide of (~) ~ In a preferred embodiment of the composition of the ,, ~,, i., , ~,~3~6 - 6-invention, the polyamide has an amine end group content of at least 30 eguivalents/l06 grams of polymer.
Tn the drawing, Fig. 1 illustrates melt vi~cosity-shear stress~data for a number of compositions of Ex~mple I.
The invention rel~tes to polyamide compositions and their use in certain proces~e~ viz. blow moulding and extrusion proce~es. The polyamide i~ ~ conden~ation polymer, commonly known as ~nylon", having recurring units of aliphatic and/or aromatic amide groups in the molecular chain. Examples of aliphatic polyamides are nylon 6, nylon 66, nylon 610, nylon 612, and their related copolymers e.g. nylon 6/66. Aromatic polya~ides may be formed from aromatic acids e.g. terephthalic ~5 and/or isophthalic acids, especially in which the diamine is hex~methylene diamine, 2-methyl pentamethylene di~mine, dodec~methylene diamine and/or other related branched and unbra~ched diamines. The polyamide forms 55-90% by weight of the composition, especially 60-85% of the composition.
In one embodiment of the invention, the polyamides used in the composition have a weight average molecular weight of greater than 25 000. Polyamides with a weight ~ve~ge molecular weight of less than 25 000 generally will not exhibit an acceptable melt vi~cosity at low she~r rates. Preferably, the weight a~erage ~olecular weight is less than 100 000, especially less than 50 000 for acceptable melt viscosity under high shear i.e.
during extrusion.
! In another embodiment, the polyamides are soluble in formic acid, and the molecular weight of the polymers may be characterized in terms of relative viscosity (RV), which is defined as the ratio of the viscosity of an 8.4%
solution of tbe polymer (by weight) in 90% formic acid solvent to the viscosity of the formic acid solvent at W094/137~ 213 U ~ 7 6 PCT/CA93/00503 room temperature. In this embodiment, the polyamides used in the compositions have an RV of at least about 40;
such polymers are commercially avail~ble e.g. as injection moulding grade nylon polymers. Polymers with an RV of le~s than 40 will generally not exhibit an acceptable melt viscosity at low shear rates. The RV
should be less than 200, preferably less than 100, for acceptable melt viscosity under high shear e.g. during extrusion.
The polyamide preferably has an amine end group content of at leaæt 30 equivalentR/l06 grams of polymer, especially at least 35 equivalents/l06 grams of polymer, for acoeptable co~patibilization of the polyamide and polyolefin phases of the composition by the acid or anhydride-grafted polymers. At lower amine end group contents, the compatibilization of the nylon and polyolefin phases ~ay be inadeguate; this can manifest itself as, for exa~ple, insufficient enhancement of low shear viscosity or poor pinch-off strength in the blow ; 20 moulded parts. Poor pinch-off strength occurs when two p~rts e.g. the two halvès, of a finished blow moulded article are not bonded together wit~ ~deguate strength, and the two halves may be readily pulled ~part.
The polyolefins used in the present invention may be polyethylene, polypropylene, copolymers of two or more of ethylene, propylene, butene, hexene, octene, butadiene, hexadiene and related monomers, or olefinic t~ermoplastic ~; elastomers. The polyolefins preferably have a low melt index i.e. a high melt viscosity; melt index is measured - 30 !by the procedure of ASTM D-1238, at tQmperatures appropriate to the particular polymer. T~e melt index of the polyolefin should be less than about lO dg/min, preferably less than about 2 dg/min. ~t is preferred to u~e ~polyolefin with a density of less than about 0.~4 35- glcm3, especially less than about 0.935 g/cm3, to improve ' C~,~3~916 - 8 -modification of the rheology of the composition and increase toughness of the fabricated articles. In espQcially preferred embodiments, at lea6t part of the polyolefin is a low modulus el~6tomeric polymer e.g.
s ethylene/propylene/diene ~EPDM) thermoplastic elastomer, to improve modification oi the rheology of the compocition and incrQase toughness.
The compatibilization between the nylon and polyolefin phafies is achieved by the use of lo functionalized or grafted polymers that are reactive and/or comparative with both the nylon and polyolefin phases. The grafted polymers are polyolefins, as defined above, that have been grafted with acid and/or anhydride group-containing monomers. Examples of the acids and lS anhydrides, which ~ay be mono-, di or polycarboxylic acids, are acrylic acid, methacrylic acid, maleic acid, fum~ric acid, itaconic acid, crotonic acid, itaconic^
anhydride~, maleic anhydride, and substituted maleic anhydr~de e.g. dimethyl maleic anhydride or citraconic anhydride, nadic anhydride, nadic methyl anhydride and tetrahydric phthalic anhydride. Examples of the derivatives of the unsaturated acids are salts, amides, imides and esters e.g. mono- and disodium maleate, acrylamide, maleimide, glycidyl me~h~crylate and diethyl fumaraSe. The preferred gr~fting mono~er i8 maleic anhydride. Such polymers should also have high viscosity, as characterized by low melt index which has to be measured at a temperature appropriate to the particular polymer. A melt index of less than about 10 dg/min is acceptable for the grafted polyolefins, with melt indices of less than 2 dg/min being preferred~ The acid and/or anhydride graft level should be in the range of about 0.1%-5%, especi~lly 0.3-4%, by weight. A method for the grafting of ethylenically unsaturated carboxylic acids or anhydrides onto polyolefins is described in U.S.
`:
:
WO94/137~ 21~ O Pcr/c~93/oosn3 Patent 4 612 155 of R.A. Zelonka and C.S. Wong, issued 1986 September 16. It is preferred to use grafted polymer with a density of less than 0.94 g/cm3, especially les~ than ~bout 0.935 g/c~3, to improve modification of S the rheoloqy of the compo~ition and incrQase toughness of the r~bricated article. It i8 especially preferred that at l~st part of the gra~ted polymer ~ a gr~fted low moldulu~ elastomeric polymer e.g. ethylene-propylene-diene tEPDM) thermoplastic e~astomer qrafted with acid ~nd/or anhydride group-containing monomers, to improve modification of the rheology of the composition and to increase toughness.
The polyolefins and grafted polymer are used in amount such that the ratio is in the range of about 0:1 to 3:1, by weight, especially 0.2 to 2.5~ start]
Fillers aild reinforcements used for improving physical mechanical properties of thermoplastic polymer6 may ~l~o be incorporated into the compositions. ~xamples of ~uch reinforcements and fillers are glass fibres, glass flakes, qlas~ ~pheres, particulate minerals e.g.
calc~um carbonate, talc, mica, wolla~tonite, clay, silica and the like, minerals ~ynthetic fibre~ e.g. calcium sulphate fibreæ, aramid fibres etc. The fillers and reinforcements, generally tend to incr~ase the melt viscosity at low shear rates to higher Yalues than f or the equi~alent unfilled or unreinforced compositions, and - thus provide even greater resistance to ~elt sagging.ta~]
The compositions may be prepared using conventional apparatus for the mixing ~nd blending of polymer compositions, examples of which are single and multiple screw extruders, internal batch and continuous mixers, roll mills, kneaders and the like. Alternatively, the compositions may be prepared by dry mixing the components 3s together, and melt fabricating the resulting mixtures ~r~ ~ - 10 -directly into articles using blow moulding or extrusion processes.
The compositions may be used in blow moulding and extrusion processes e.g. in the manufacture of bottles, S containers, hollow under-the-hood automotive components and o~her blow moulded article~, and in the manufacture of rods, tubing, cable ~ackets and other extruded profiles.
The invention i8 illustrated by the following examples.
, ~ml21~
The shear rate - melt viscosity curves were deter~ined for the polymer compositions list~d below, at temperatures appropriate to the polymers in the compo~ition~ and using a Kayness capillary vi~cometer.
Further details and the shear rate-melt viscosity data ar~ t~bulated in Table I.
The.composition were:
Composition (a) is a comparative composition that is an in~ection ~oulding grade nylon 6 having a relative ~ viscosity (RV) of Sl;
- ~ Composition tb) i8 a comparative composition that is.an .~ injection moulding grade nylon 66 having an RV of 52;
Composition (c) i8 a comparative composition th~t is an extrusion grade nylon 6 with an RV of 140;
Composition (d) is a comparative composition that is an extrusion grade nylon 6 with an RV o 253;
;~ Composition (e) is a comparative composition that is an extrusion grade nylon 6 with an RV of 285;
IComposition (f) is a blend, on a weight b~sis, of (i) 59.75% Nylon 66 having an RV of 52 and an amine end level of 55 equivalent/106 gm, (ii) 25% polyethylene having a melt index of 0~6 dg/min and a density of 0.919 g/cm3, iii) 15~ of a grafted polyethylene having a melt index of about 2 dg/min, a density of 0.92 g/cm3 and containing 0 4 7 ~i approximately 1% grafted maleic anhydride, and ( iv) O . 25%
of thermal stabilizers;
Composition (g) is a blend, on a weight basis, of (i) 59.75% nylon 6 having ~n RV of 46 and ~mine end ~evel of 23 equiv~lents/106 gm, ~ii) 25% polyethylene having ~ melt index of 1.4 dg/min ~nd ~ density of 0.92 g/cm3, tiii) 10%
grafted polyethylene ~aving ~ melt index of about 2 dg/min, a density of 0.92 g/cm3 and containing ~pproximately 1% grafted maleic ~nhydride, (iv) 5%
grafted ethylene-propylene-diene thermoplastic elastomer containing approximately 1.7% grafted fumaric acid, and (v) 0.25% of thermal stabilizers;
Composition (h) is a blend, on a weight basis, of (i)69.75% nylon 6 having an RV of 48 and amine end level of 37 equivalents/10~ gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min ~nd a density of 0.92 g/c~, (iii) 6.5% grafted polyethylene with a melt index of about 2 dg/min, ~ density of about 0.92 g/cm3 and containing approximately 1% grafted maleic anhydride, (iv) 6.5% grafted ethylene-propylene-diene thermoplastic ela~tomer containlng approximately 1.7% grafted fumaric . acid, (v) 4.4% black pigment concentrate, and (vi) 0.25%
of therm~l ~tab~lizer~;
Composition (i) i5 a blend, on a weight ba~is, of (i) 69.75% nylon 6 ha~ing an RV of 67 and amine end level of 51 eguivalents/106 gm, (ii) 13% polyethylene with a melt index of 1.4 dg/min and a density of 0.92 g/cm3, (iii) 6.5~ grafted polyethylene with a melt index ~f about 2 dg/min, a density of ~bout 0.92 gJcm3 ~nd containing approximately 1% grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene therMoplastic elastomer with approximately 1.7% grafted fumaric acid, (v) 4,4%
black pigment concentrate, and (vi) 0.25% of thermal stabilizers;
~3~ - 12 -Composition (~) is a blend, on a weight basis, of (i) 69.75% nylon 6 having an RV of 140 and amine end level of 36 equivalents/10~ gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min ~nd a density of 0.92 g/cm3, (iii) 6~5% gr~fted polyethylene having a melt index of about 2 dg/min, a den~ity of ~bout 0.92 g/cm3 and containing approximately 1~ grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene thermoplastic el~stomer having approximately 1.7% grafted fumaric ~cid, (v) 4.4%
black pigment concentrate, and (vi) 0.25% of thermal ~tabilizer~;
Composition (k) is a blend, on a weight basis, of (i) 69.75% nylon 6 having an RV of 78 and amine end level of 14 equivalents/10~ gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min and a density of 0.92 glcm3, (iii) 6.5% grafted polyethylene having a melt index of about 2 dg/min, a density of about 0.92 g/cm3 and containing pproximately 1% grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene thermoplastic elastomer with approximately 1.7% grafted fumaric ~cid, (v) 4.4%
~ black pigment concentrate, and (vi) 0.25% of thermal ;~ stabilizers; and Composition tl) is a blend, on a weight basis, of (i) 69.75~ nylon 6 having an RV an amine end level of 23 equivalents/106 gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min and a density of 0.92 gfcm3~ (iii) .5% grafted polyethylene having a melt index o~ about 2 dg/min, a density of about 0.92 g~cm3 and containing approximately 1% grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene thermoplastic elastomer having approximately 1.7% grafted fumaric acid, (v) 4.4%
black pigment concentrate, and tvi) 0.25% thermal stabilizers.
In the above compositions, the polyethylene was an :
ethylene/butene-l copolymer containing 6.7~ butene-1 The same type of polymer was used for the grafted polymer. The EPDM elastomer contained 70~ by weight of ethylene, 26S by weight of propylene and 4~ by weight of hexadiene.
The above compositions were prepared by dry mixing the components of th- co~position, ~nd then ~elt blending the resultant ~ixture in a Werner ~ Pfleiderer 53 mm twin screw extruder at 250 rp~. For compositions based on nylon 6, a temperature profi~e of 210-C in the feed section, 230-235-C in the barrel section and 235C at the die was used. For composit~ons based on nylon 66, a temperature profile of 240-C in the feed section, 270-280-C in the barrel section and 280-C at the die was used. The resulting poly~er melt was pelletized to obtain the composition in the form of pellets.
Compositions were evaluated in blow moulding and extrusion processes. Blow ~oulding evaluation was carried out using a blow ~oulding apparatus with an accumulator head of 1.4 kg capacity and a representative mould for an automotive plenum chamber. Extrusion evaluation was carried out by making nominally 6 mm diameter tubing. A melt temperature of about 228C was ; used for nylon 6 compositions, and a melt temperature of ~5 about 265C wa~ used for ~ylon 66 compositions.
Compositisns (a) and (b) are comparative examples of low RV nylon 6 ~nd nylon 66 compositions that are intended for use in injection moulding apparatus. T~e melt viscosities are extremely low, compared with i 30 Icompositions required for blow moulding and extrusion.
Thus, these compositions are unsuitable for blow moulding and extrusion process.
Compositions (c~, (d) and (e) are comparative examples of nylon 6 compositions having higher R~ values -35 ~ ~than`Compositions (a) and (b), and were evaluated in blow 0~ 14 -~oulding processes. Compositions (c) and (d) were difficult to blow mould because the melt viscosities of these compositions at low levels of stress were not sufficiently higb to;prevent excessive sagging of the S melt parison. Compositions (e) exhibited extremely high melt viscosity, which mado the composition difficult to oxtrude into a parison at a~ceptable rates; however, the parison exhibitod excellent resistance to sagging under its own weight.
Compositions tf), (g), (h) and (i) illustrate the prQsent invention. Compositions (f) and ~g) were evaluated in small diameter tubing extrusion process.
oth compositions were processed successfully into tubing with nominal di~meter of about 6 mm.
lS Compositions (h) and (i) were evaluated in thè blow ~ moulding operation, and comp~red ~gainst high RV nylon 6 - co~positions (c), (d) and (e). In a blow moulding operation involving the samo size of parison, tbe stress acting on the parison due to the weight of tbe parison ~ .-will be the same for all compositions, thereby providing a comparison at common levels of stress.
In a blow moulding process, Compositions (h) and (i) exhibited excellent re~istance to melt sagqing, and yet were easy to extrude at high tbroughput. It took less than half the time to extrude suf~icient melt to make the blow moulded parts, aæ compared with the time required for Composit~on (e). Composition (i) exhibited even greater resistance to sagging than (h), due to tho higher RV of the nylon 6 composition.
, 30 I Composition (;) is similar to Composition (b), except that it is based on nylon 6 with a substantially higher ~V. This composition exhibited extremely high melt viscosity at high shear stress, and was extremely difficult to extrude into parisons.
Composition (i) is also similar to Composition (h), , ~
- 15- 213~0q7~
except that it is based on nylon 6 with higher Rv but a lower level of amine ends. Blow moulding evaluation of this composition showed that although it has sufficiently bigh viscosity at low stress levels to exhibit good s resi~tance to melt parison sagging, it lacked so-called pinch-o~f strength, which i8 defined as the stress nQcessary to pull apart two halves of th~ ~oulded article ;~ bonded by pinch-o~ in the mould cavity, a~ter the ;~ article has been ~oulded.
Composition ~1) is similar to (h), being based on nylon 6 with a low level of amine ends. While t is po~sible to blow mould this composition, its resistance to sagging of the par~son was not as great as that of ::~
either of Compositions (h) or (i).
Figure 1 illustrates melt viscosity - sbear stre~s relationships for Compositions (c), (d), (e), (h and (i). In the case of the high RV nylon 6 composit~ons (c), (d) and (e),-the ~elt viscosity curve flattens out towards the low shear tress end, and the viscosity does not show a rapid rise as the shear stress is reduced;
consequently, any attempt to increase the melt viscosity at low stress by increasing the molecular weight i.e.
increasing RV, also increases the mel~ viscosity under high ~hear stress lev~ls thereby making the composition difficult to extrude. In contrast, Compositions (h) and (i) exhibit a completely different behaviour, characterized by a steep viscosity curve with the melt viscosity rising sharply as the shear stress is reduced.
Such high viscosity at low shear stress levels provides lexcellent resist~nce to melt sagging or drawing of the parison during a blow moulding operation. On the other hand, the melt viscosity drops to low values at high shear stress, below tbat of Compositions (c), (d) or (e), , ~ .
which allows for relatively easy extrusion of material.
~ Thus,~the present invention provides a way of modifying ,, W094/137~ PCT/CA93/00503 .~304~ - 16 -rheology of relatively low molecular weight polyamides such that the resistance to melt sagging is improved without comprising the ease of extrusion.
TABLE I
Shear Rate - Viscos~ty Relationships Comp. Temp.<~ - Shear Rate (1/~ -->
(-C) 0.087 0.174 0~26 0.347 0.52 1 2 (a) 240 (c) 240 4270 3440 3420 (d) 240 13470 10110 10720 (e)~ 240 36830 31890 30090 2g640 26570 19310 (f) 280 (g) 240 (h) 240 35030 23130 18260 15380 12870 8910 6890 (i) 240 53890 35920 33080 29420 24100 16020 (;) 240 (k) 240 (1) 240 S~ear Rate - Viscosity Relationships (cont.) Comp. Temp. <~ Shear Rate (1/8)~
(C) 10 30 50 100 25~ 300 S00 1000 (a) 240 480 460 390 340 210 (c) 240 3340 2220 2190 172~ 114~ 1080 710 490 ~d~ 240 S570 3720 2560 1570 1080 (e) 240 ~220 4370 3020 1440 990 ~.F.**
(f) 280 3000 1600 850 450 240 (g) 24~ 2540 1380 1010 6~0 410 280 (h) 240 4180 2110 1520 970 6S0 (i) 240 6430 3700 2840 1930 1130 430 (j) 240 8510 4920 2420 M.F.** M~F.**
(k) 240 3080 1900 1130 650 340 (1) 24Q 23B0 1520 970 570 290 WO 94113740 PCT/CA93/00~03 - 17 - 2130~7~
Shear Rate - Viscosity Relationships (cont.) Comp. Temp. <----------Shear Rate (1/s)---------->
(C) 25 1~0 350 830 1200 (b) 280 250 270 230 190 170 s Note: Data for Composition (e) i~ representative data, as melt v~scosity data was changing during measurement.
MF - melt fracture occurred.
Viscosity i8 reported in Pa.s The amples of the compo~itions wero dried at 80-C
for two hours in a de~umidified drier to moisture levels below 0.05S by weight prior to measurements being conducted.
The dat~ represent apparent viscosity and shear stress; 8agley and ~obinowitch corrections were not applied.
- E~ple II
Short qlaæs fibre reinforced compositions were prepared by melt blending and uniformly dispersing ~ ~ var~ OU8 levels of short glass fibres into Composition (h) ; o~ Ex~mple I. On a weight basis, these compositions were nom~nally as ~ollows:
Composition (m) 87% Composition (h) 13% short of Example 1 glass fibres Compo ition (n) 80~ Composition ~h) 20~ short of Examp~e 1 glass fibres Composition (o) 75% Composition (h) 25% short of Exampl~ 1 glass fibres Composition (p) 70~ Composition (h) 30S short 3S of Example 1 glass fibres The melt blending and glass dispersion was carried out in a 53 mm~Werner and Pfleiderer twin screw extruder running at 200 rpm using a temperature profile of 210C
; in the feed section, 230-235C in the barrel section and ,~
wos4/137~ PCT/CA~3/00~03 ~3~4~G -18 -2350C at the die. In each case, the resulting ~elt was pelletized to obtain the composition in the form of pellets.
The shear rate-viscosity relationships for these S compositions wer~ d~e~t.~rminad using a Kayne~ capillary viscometer at 24QC. The dat~ are tabulated in Tabla II.
TABLE II
Shear Rate - vis~08ity Relationsh~p~
Comp.~ ----Shear Rate (l/s)~ ------>
0.52 1 2 10 50 100 250 500 (m) 51000 29000 1900 8400 3400 2200 1200 740 (n) 70000 40000 26000 10600 3900 2500 1400 900 (o) 61000 35000 23000 9900 3700 ~400 1400 940 (p) 63000 31000 21000 1050~ 3700 2400 1400 sO0 Viscosity is reported in units of P~. 8 The ~amples ~f the compositions were dried at 80OC
for two hours in a dehumidified drier to moisture levels below 0.05% by weight prior to measurements being conducted.
The data represent ~pp~rent viscosity and shear stress; Bagley and Ro~inowitch corrections were not ~pplied.
Compositions were evaluated in the blow moulding process of Example I. The mould used was de~igned to produce hollow rectangul~ p~ques ~ea~uring roughly 42 x 10 x 5 cm. It had inserts to produce either textured sections or two qu~re draw pockets measurin~
approximately 3.8 x 3.8 x 0.6 cm and 1.9 x 1.9 x 0.6 cm on one side of the blow moulded parts. The draw pockets provide a measure of the ability of the composition to be drawn into features representing sharp changas in geometry. A melt temperature of about 235C was used for blow moulding evaluation of all of the compositions.
- 19 _ 2130~76 All of the compositions exhibited excellent resistance to melt sagging. Compared to the unreinforced compo~ition (h) of Example 1, the above composition exhlbited signlficantly lower die swell in the thickness and dia~eter of the pari~on. All the co~positions were able to produce good blow ~oulded p~rts when the textured insert was u~ed in the ~ould. When th- in~ert with ~quare draw pocket~ wa~ u~ed, compo~itionR (m) and (n) produced good parts. In case of compo~itions (o~ and (p), the draw pockete were not ~harply defined and had thin rounded corners. This indicate~ a reduced drawability o~ the melt at higher glass loadings.
-1 2t30q(~
EXTRUSION OR BLOW-MOULDIN~ OF POLYAMIDE COMPOSITIQ~S
The present invention relates to extrusion and blow-moulding processe~ using polyamide compositions and to such compositions, and e~pecially to improvements therein. In particular, the invention relates to extrusion and blow-moulding processes in which the polyamide compositions have increased melt viscosity at low stress levels to impart melt sag resistance and moderately low viscosity at high stress levels, to impart improved extrudability.
. Polyamides may be fabricated into a wide variety of products. The compositions used must have melt viscosity characteristics that are appropriate to the process being used, as discussed in published European patent application 0 295 906 of D.S. Dykes and K.D. Ruhnemann, published 1988 December 21. The use of compositions of polyamides and epoxides $n extrusion processes is disclosed therein. Polyamide compo~itions for blow moulding are disclosed in U.S. Patent 5 122 570 of P.M.
Subramanian, issued 1992 June 16, such compositions being semi-crystalline poly~mide, selected toughening agent and an anhydride-rich ethylene copolymer~
Blow moulding and extrusion are important processing operations used in the manufacture of finish~d articles from polymaric compo~itions. Blow moulding is the process normally used for the manufacture of hollow articles for example bottles, jugs and the like, from thermoplastic polymers e.g. polyethylene, polypropylene and polyvinyl chloride. Blow moulding processes are finding increasing use in the manufacture of engineering and structural components, for example automotive under-the-hood components e.g. fluid reservoirs, resonators and the like, which have to be manufactured from so-called engineering polymers e.g. polyamides. Extrusion `~L3047~ 2 processes are used for making continuous profiles for example pipe, tubing or other profiles of a specific cross-sectional shape. For automotive and other critical end-use applications, such extrusion procQsses utilize engineering polymers.
Both blow moulding and extrusion processes require polymer compositions with unique rheological characteristics for commercially acceptable operation.
In blow moulding processes, molten polymer is extruded vertically from an annular die into a cavity between two halves of a mould, in the form of a tube known as a parison. The mould is then closed, capturing the parison between the halves of the mould. Air is blown into the parison to force the molten polymer into contact with and to the shape of the walls of the mould. The melt is cooled by circulation of a cooling fluid through cbannels with~n the walls of the ~ould, after which the moulded part is removed. During extrusion and until it is captured by the halves of the mould, the parison undergoes deformation characterized by extension or stretching of the parison under the influence of its own weight; as the only influence on the parison is its weight, the deformation occurs under low levels of stress. For successful operation of the process, the polymer ~ust exhibit sufficiently high melt viscosity under low stress that the parison is able to support itself without extensive drawing, sagging or thinning in localized areas.
In an extrusion process, polymer melt is extruded Ifrom a die in the form of a continuous profile which then enters a cooling chamber for solidification. The travel of the extrudate from the die to the cooling chamber is usually free from any surface, and in order to preserve the desired cross-sectional shape the extrudate needs to 3S be able to support itself without undergoing excessive :
0~7~
sagging. As with blow moulding processes, this also requires a polymer that has a sufficiently high melt viscosity under low levels of stress.
While hiqh melt viscosity at,low stress levels is required for the above processes, a moderately low melt vi~cosity i8 required under high levels of stre~, and correspondingly high rates of flow, encountered in the extruder and die. A melt viscosity that is too high under these condition~ leads to excessive pressure build-up and requires high torgues for extrusion, which ultimately limits the rate of throughput obtainable from the extruder. Very high melt viscosity under these conditions may also lead to a phenomenon known as melt fracture where tbe surface of the extrudate becomes rough and wavy making the process difficult to operate and the résultant parts unacceptable.
The ctress acting on a melt parison in a blow^
moulding process Dr on melt exudate during its travel from the die to the cooling chamber in an extrusion proce-s is extensional in nature. However, it is ; extremely difficult to characterize melt viscosity of a polymer over a wide range of extensional stress, and melt viscosity measurements are ~o~monly carried out over a wlde range of shear stress.
2S Polyamides are characterized by low melt viscosity under both high and low shear stress i.e. they tend to have poor melt sag resistance. Techniques that increase the melt viscosity under low shear streæs alco tend to increase the melt viscosity under high shear stress, with ~1 ,30 ! the result that the resultant polyamide compositions tend to be unacceptable for blow moulding or extrusion ;~proc2sses. Preferred characteristics for blow moulding -~~ and extrusion are high viscosity at low shear stress and oderately low melt viscosity under high shear stress 3`5 ;~lèvels.
WO 94/13740 PCT/CA93/00~03 ~3~ t~ 6 Polyamide compositions suitable for blow moulding and extrusion processes h~ve how been found.
Accordingly, the pre'sent invention provides a blow moulding process in which a parison is formed from a polyamide composition, characterized in that said composition ~omprises:
(a) SS-90~ by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at least 40; and :~- (b) 10-45% by weight of a polymer selected from the;~ group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently ;; sel~cted from polyolefins having a mel~ index of less ~ than 10 dg/min, the polyolefin of ~aid grafted poly~er -~ having ~een grafted with 0.1-S~OS by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b);
and said composition exhibiting a relative increase in melt viscocity at low shear stress compared to the polyamide of (a).
~5 The present invention also provide~ an extrusion process in which a profile is extruded from a polyamide co~position, characterized in that said composition comprises:
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) :~ polyamides that are soluble in formic acid and which havean RV measured .in formic acid of at least 40; and (b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of wo 94~13740 2 t 3 0 1 7 ~ PCT/CA93/00~03 grafted polymer and ungrafted polymer, e~ch of s~id grafted polymer and ungr~fted polymer being independently ~elected from polyolefins having a melt index of less than 10 dg/min, the polyolefin of said grafted polymer S having been grafted with 0.1-5.0% by weight of an ethylenically un~aturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viæcosity at low shear stress compared to the polyamide of (a)-~; n preferred e~bodiments of the processes of the invention, the polyamide haæ an amine end group content of at least 30 equivalents/10~ grams of polymer.
The present inv ntion also provides a polyamide composition comprising:
(a) 55-90% by w~ight of a polya~ide selected fro~
the group consi~ting of (i) polyamides having a weight average molecular weight of gre~ter than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in for~ic acid of at least 40; and b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said 2s ~rafted polymer and ungrafted polymer being independently selected from polyolefins having a malt index of less ~han 10 dg/min, the polyolefin of said grafted polymer having been grafted with 0.1-5.0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, ,; 30 Ithe grafted polymer being 2S-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity ~t low shear stress compared to the polyamide of (~) ~ In a preferred embodiment of the composition of the ,, ~,, i., , ~,~3~6 - 6-invention, the polyamide has an amine end group content of at least 30 eguivalents/l06 grams of polymer.
Tn the drawing, Fig. 1 illustrates melt vi~cosity-shear stress~data for a number of compositions of Ex~mple I.
The invention rel~tes to polyamide compositions and their use in certain proces~e~ viz. blow moulding and extrusion proce~es. The polyamide i~ ~ conden~ation polymer, commonly known as ~nylon", having recurring units of aliphatic and/or aromatic amide groups in the molecular chain. Examples of aliphatic polyamides are nylon 6, nylon 66, nylon 610, nylon 612, and their related copolymers e.g. nylon 6/66. Aromatic polya~ides may be formed from aromatic acids e.g. terephthalic ~5 and/or isophthalic acids, especially in which the diamine is hex~methylene diamine, 2-methyl pentamethylene di~mine, dodec~methylene diamine and/or other related branched and unbra~ched diamines. The polyamide forms 55-90% by weight of the composition, especially 60-85% of the composition.
In one embodiment of the invention, the polyamides used in the composition have a weight average molecular weight of greater than 25 000. Polyamides with a weight ~ve~ge molecular weight of less than 25 000 generally will not exhibit an acceptable melt vi~cosity at low she~r rates. Preferably, the weight a~erage ~olecular weight is less than 100 000, especially less than 50 000 for acceptable melt viscosity under high shear i.e.
during extrusion.
! In another embodiment, the polyamides are soluble in formic acid, and the molecular weight of the polymers may be characterized in terms of relative viscosity (RV), which is defined as the ratio of the viscosity of an 8.4%
solution of tbe polymer (by weight) in 90% formic acid solvent to the viscosity of the formic acid solvent at W094/137~ 213 U ~ 7 6 PCT/CA93/00503 room temperature. In this embodiment, the polyamides used in the compositions have an RV of at least about 40;
such polymers are commercially avail~ble e.g. as injection moulding grade nylon polymers. Polymers with an RV of le~s than 40 will generally not exhibit an acceptable melt viscosity at low shear rates. The RV
should be less than 200, preferably less than 100, for acceptable melt viscosity under high shear e.g. during extrusion.
The polyamide preferably has an amine end group content of at leaæt 30 equivalentR/l06 grams of polymer, especially at least 35 equivalents/l06 grams of polymer, for acoeptable co~patibilization of the polyamide and polyolefin phases of the composition by the acid or anhydride-grafted polymers. At lower amine end group contents, the compatibilization of the nylon and polyolefin phases ~ay be inadeguate; this can manifest itself as, for exa~ple, insufficient enhancement of low shear viscosity or poor pinch-off strength in the blow ; 20 moulded parts. Poor pinch-off strength occurs when two p~rts e.g. the two halvès, of a finished blow moulded article are not bonded together wit~ ~deguate strength, and the two halves may be readily pulled ~part.
The polyolefins used in the present invention may be polyethylene, polypropylene, copolymers of two or more of ethylene, propylene, butene, hexene, octene, butadiene, hexadiene and related monomers, or olefinic t~ermoplastic ~; elastomers. The polyolefins preferably have a low melt index i.e. a high melt viscosity; melt index is measured - 30 !by the procedure of ASTM D-1238, at tQmperatures appropriate to the particular polymer. T~e melt index of the polyolefin should be less than about lO dg/min, preferably less than about 2 dg/min. ~t is preferred to u~e ~polyolefin with a density of less than about 0.~4 35- glcm3, especially less than about 0.935 g/cm3, to improve ' C~,~3~916 - 8 -modification of the rheology of the composition and increase toughness of the fabricated articles. In espQcially preferred embodiments, at lea6t part of the polyolefin is a low modulus el~6tomeric polymer e.g.
s ethylene/propylene/diene ~EPDM) thermoplastic elastomer, to improve modification oi the rheology of the compocition and incrQase toughness.
The compatibilization between the nylon and polyolefin phafies is achieved by the use of lo functionalized or grafted polymers that are reactive and/or comparative with both the nylon and polyolefin phases. The grafted polymers are polyolefins, as defined above, that have been grafted with acid and/or anhydride group-containing monomers. Examples of the acids and lS anhydrides, which ~ay be mono-, di or polycarboxylic acids, are acrylic acid, methacrylic acid, maleic acid, fum~ric acid, itaconic acid, crotonic acid, itaconic^
anhydride~, maleic anhydride, and substituted maleic anhydr~de e.g. dimethyl maleic anhydride or citraconic anhydride, nadic anhydride, nadic methyl anhydride and tetrahydric phthalic anhydride. Examples of the derivatives of the unsaturated acids are salts, amides, imides and esters e.g. mono- and disodium maleate, acrylamide, maleimide, glycidyl me~h~crylate and diethyl fumaraSe. The preferred gr~fting mono~er i8 maleic anhydride. Such polymers should also have high viscosity, as characterized by low melt index which has to be measured at a temperature appropriate to the particular polymer. A melt index of less than about 10 dg/min is acceptable for the grafted polyolefins, with melt indices of less than 2 dg/min being preferred~ The acid and/or anhydride graft level should be in the range of about 0.1%-5%, especi~lly 0.3-4%, by weight. A method for the grafting of ethylenically unsaturated carboxylic acids or anhydrides onto polyolefins is described in U.S.
`:
:
WO94/137~ 21~ O Pcr/c~93/oosn3 Patent 4 612 155 of R.A. Zelonka and C.S. Wong, issued 1986 September 16. It is preferred to use grafted polymer with a density of less than 0.94 g/cm3, especially les~ than ~bout 0.935 g/c~3, to improve modification of S the rheoloqy of the compo~ition and incrQase toughness of the r~bricated article. It i8 especially preferred that at l~st part of the gra~ted polymer ~ a gr~fted low moldulu~ elastomeric polymer e.g. ethylene-propylene-diene tEPDM) thermoplastic e~astomer qrafted with acid ~nd/or anhydride group-containing monomers, to improve modification of the rheology of the composition and to increase toughness.
The polyolefins and grafted polymer are used in amount such that the ratio is in the range of about 0:1 to 3:1, by weight, especially 0.2 to 2.5~ start]
Fillers aild reinforcements used for improving physical mechanical properties of thermoplastic polymer6 may ~l~o be incorporated into the compositions. ~xamples of ~uch reinforcements and fillers are glass fibres, glass flakes, qlas~ ~pheres, particulate minerals e.g.
calc~um carbonate, talc, mica, wolla~tonite, clay, silica and the like, minerals ~ynthetic fibre~ e.g. calcium sulphate fibreæ, aramid fibres etc. The fillers and reinforcements, generally tend to incr~ase the melt viscosity at low shear rates to higher Yalues than f or the equi~alent unfilled or unreinforced compositions, and - thus provide even greater resistance to ~elt sagging.ta~]
The compositions may be prepared using conventional apparatus for the mixing ~nd blending of polymer compositions, examples of which are single and multiple screw extruders, internal batch and continuous mixers, roll mills, kneaders and the like. Alternatively, the compositions may be prepared by dry mixing the components 3s together, and melt fabricating the resulting mixtures ~r~ ~ - 10 -directly into articles using blow moulding or extrusion processes.
The compositions may be used in blow moulding and extrusion processes e.g. in the manufacture of bottles, S containers, hollow under-the-hood automotive components and o~her blow moulded article~, and in the manufacture of rods, tubing, cable ~ackets and other extruded profiles.
The invention i8 illustrated by the following examples.
, ~ml21~
The shear rate - melt viscosity curves were deter~ined for the polymer compositions list~d below, at temperatures appropriate to the polymers in the compo~ition~ and using a Kayness capillary vi~cometer.
Further details and the shear rate-melt viscosity data ar~ t~bulated in Table I.
The.composition were:
Composition (a) is a comparative composition that is an in~ection ~oulding grade nylon 6 having a relative ~ viscosity (RV) of Sl;
- ~ Composition tb) i8 a comparative composition that is.an .~ injection moulding grade nylon 66 having an RV of 52;
Composition (c) i8 a comparative composition th~t is an extrusion grade nylon 6 with an RV of 140;
Composition (d) is a comparative composition that is an extrusion grade nylon 6 with an RV o 253;
;~ Composition (e) is a comparative composition that is an extrusion grade nylon 6 with an RV of 285;
IComposition (f) is a blend, on a weight b~sis, of (i) 59.75% Nylon 66 having an RV of 52 and an amine end level of 55 equivalent/106 gm, (ii) 25% polyethylene having a melt index of 0~6 dg/min and a density of 0.919 g/cm3, iii) 15~ of a grafted polyethylene having a melt index of about 2 dg/min, a density of 0.92 g/cm3 and containing 0 4 7 ~i approximately 1% grafted maleic anhydride, and ( iv) O . 25%
of thermal stabilizers;
Composition (g) is a blend, on a weight basis, of (i) 59.75% nylon 6 having ~n RV of 46 and ~mine end ~evel of 23 equiv~lents/106 gm, ~ii) 25% polyethylene having ~ melt index of 1.4 dg/min ~nd ~ density of 0.92 g/cm3, tiii) 10%
grafted polyethylene ~aving ~ melt index of about 2 dg/min, a density of 0.92 g/cm3 and containing ~pproximately 1% grafted maleic ~nhydride, (iv) 5%
grafted ethylene-propylene-diene thermoplastic elastomer containing approximately 1.7% grafted fumaric acid, and (v) 0.25% of thermal stabilizers;
Composition (h) is a blend, on a weight basis, of (i)69.75% nylon 6 having an RV of 48 and amine end level of 37 equivalents/10~ gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min ~nd a density of 0.92 g/c~, (iii) 6.5% grafted polyethylene with a melt index of about 2 dg/min, ~ density of about 0.92 g/cm3 and containing approximately 1% grafted maleic anhydride, (iv) 6.5% grafted ethylene-propylene-diene thermoplastic ela~tomer containlng approximately 1.7% grafted fumaric . acid, (v) 4.4% black pigment concentrate, and (vi) 0.25%
of therm~l ~tab~lizer~;
Composition (i) i5 a blend, on a weight ba~is, of (i) 69.75% nylon 6 ha~ing an RV of 67 and amine end level of 51 eguivalents/106 gm, (ii) 13% polyethylene with a melt index of 1.4 dg/min and a density of 0.92 g/cm3, (iii) 6.5~ grafted polyethylene with a melt index ~f about 2 dg/min, a density of ~bout 0.92 gJcm3 ~nd containing approximately 1% grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene therMoplastic elastomer with approximately 1.7% grafted fumaric acid, (v) 4,4%
black pigment concentrate, and (vi) 0.25% of thermal stabilizers;
~3~ - 12 -Composition (~) is a blend, on a weight basis, of (i) 69.75% nylon 6 having an RV of 140 and amine end level of 36 equivalents/10~ gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min ~nd a density of 0.92 g/cm3, (iii) 6~5% gr~fted polyethylene having a melt index of about 2 dg/min, a den~ity of ~bout 0.92 g/cm3 and containing approximately 1~ grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene thermoplastic el~stomer having approximately 1.7% grafted fumaric ~cid, (v) 4.4%
black pigment concentrate, and (vi) 0.25% of thermal ~tabilizer~;
Composition (k) is a blend, on a weight basis, of (i) 69.75% nylon 6 having an RV of 78 and amine end level of 14 equivalents/10~ gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min and a density of 0.92 glcm3, (iii) 6.5% grafted polyethylene having a melt index of about 2 dg/min, a density of about 0.92 g/cm3 and containing pproximately 1% grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene thermoplastic elastomer with approximately 1.7% grafted fumaric ~cid, (v) 4.4%
~ black pigment concentrate, and (vi) 0.25% of thermal ;~ stabilizers; and Composition tl) is a blend, on a weight basis, of (i) 69.75~ nylon 6 having an RV an amine end level of 23 equivalents/106 gm, (ii) 13% polyethylene having a melt index of 1.4 dg/min and a density of 0.92 gfcm3~ (iii) .5% grafted polyethylene having a melt index o~ about 2 dg/min, a density of about 0.92 g~cm3 and containing approximately 1% grafted maleic anhydride, (iv) 6.5%
grafted ethylene-propylene-diene thermoplastic elastomer having approximately 1.7% grafted fumaric acid, (v) 4.4%
black pigment concentrate, and tvi) 0.25% thermal stabilizers.
In the above compositions, the polyethylene was an :
ethylene/butene-l copolymer containing 6.7~ butene-1 The same type of polymer was used for the grafted polymer. The EPDM elastomer contained 70~ by weight of ethylene, 26S by weight of propylene and 4~ by weight of hexadiene.
The above compositions were prepared by dry mixing the components of th- co~position, ~nd then ~elt blending the resultant ~ixture in a Werner ~ Pfleiderer 53 mm twin screw extruder at 250 rp~. For compositions based on nylon 6, a temperature profi~e of 210-C in the feed section, 230-235-C in the barrel section and 235C at the die was used. For composit~ons based on nylon 66, a temperature profile of 240-C in the feed section, 270-280-C in the barrel section and 280-C at the die was used. The resulting poly~er melt was pelletized to obtain the composition in the form of pellets.
Compositions were evaluated in blow moulding and extrusion processes. Blow ~oulding evaluation was carried out using a blow ~oulding apparatus with an accumulator head of 1.4 kg capacity and a representative mould for an automotive plenum chamber. Extrusion evaluation was carried out by making nominally 6 mm diameter tubing. A melt temperature of about 228C was ; used for nylon 6 compositions, and a melt temperature of ~5 about 265C wa~ used for ~ylon 66 compositions.
Compositisns (a) and (b) are comparative examples of low RV nylon 6 ~nd nylon 66 compositions that are intended for use in injection moulding apparatus. T~e melt viscosities are extremely low, compared with i 30 Icompositions required for blow moulding and extrusion.
Thus, these compositions are unsuitable for blow moulding and extrusion process.
Compositions (c~, (d) and (e) are comparative examples of nylon 6 compositions having higher R~ values -35 ~ ~than`Compositions (a) and (b), and were evaluated in blow 0~ 14 -~oulding processes. Compositions (c) and (d) were difficult to blow mould because the melt viscosities of these compositions at low levels of stress were not sufficiently higb to;prevent excessive sagging of the S melt parison. Compositions (e) exhibited extremely high melt viscosity, which mado the composition difficult to oxtrude into a parison at a~ceptable rates; however, the parison exhibitod excellent resistance to sagging under its own weight.
Compositions tf), (g), (h) and (i) illustrate the prQsent invention. Compositions (f) and ~g) were evaluated in small diameter tubing extrusion process.
oth compositions were processed successfully into tubing with nominal di~meter of about 6 mm.
lS Compositions (h) and (i) were evaluated in thè blow ~ moulding operation, and comp~red ~gainst high RV nylon 6 - co~positions (c), (d) and (e). In a blow moulding operation involving the samo size of parison, tbe stress acting on the parison due to the weight of tbe parison ~ .-will be the same for all compositions, thereby providing a comparison at common levels of stress.
In a blow moulding process, Compositions (h) and (i) exhibited excellent re~istance to melt sagqing, and yet were easy to extrude at high tbroughput. It took less than half the time to extrude suf~icient melt to make the blow moulded parts, aæ compared with the time required for Composit~on (e). Composition (i) exhibited even greater resistance to sagging than (h), due to tho higher RV of the nylon 6 composition.
, 30 I Composition (;) is similar to Composition (b), except that it is based on nylon 6 with a substantially higher ~V. This composition exhibited extremely high melt viscosity at high shear stress, and was extremely difficult to extrude into parisons.
Composition (i) is also similar to Composition (h), , ~
- 15- 213~0q7~
except that it is based on nylon 6 with higher Rv but a lower level of amine ends. Blow moulding evaluation of this composition showed that although it has sufficiently bigh viscosity at low stress levels to exhibit good s resi~tance to melt parison sagging, it lacked so-called pinch-o~f strength, which i8 defined as the stress nQcessary to pull apart two halves of th~ ~oulded article ;~ bonded by pinch-o~ in the mould cavity, a~ter the ;~ article has been ~oulded.
Composition ~1) is similar to (h), being based on nylon 6 with a low level of amine ends. While t is po~sible to blow mould this composition, its resistance to sagging of the par~son was not as great as that of ::~
either of Compositions (h) or (i).
Figure 1 illustrates melt viscosity - sbear stre~s relationships for Compositions (c), (d), (e), (h and (i). In the case of the high RV nylon 6 composit~ons (c), (d) and (e),-the ~elt viscosity curve flattens out towards the low shear tress end, and the viscosity does not show a rapid rise as the shear stress is reduced;
consequently, any attempt to increase the melt viscosity at low stress by increasing the molecular weight i.e.
increasing RV, also increases the mel~ viscosity under high ~hear stress lev~ls thereby making the composition difficult to extrude. In contrast, Compositions (h) and (i) exhibit a completely different behaviour, characterized by a steep viscosity curve with the melt viscosity rising sharply as the shear stress is reduced.
Such high viscosity at low shear stress levels provides lexcellent resist~nce to melt sagging or drawing of the parison during a blow moulding operation. On the other hand, the melt viscosity drops to low values at high shear stress, below tbat of Compositions (c), (d) or (e), , ~ .
which allows for relatively easy extrusion of material.
~ Thus,~the present invention provides a way of modifying ,, W094/137~ PCT/CA93/00503 .~304~ - 16 -rheology of relatively low molecular weight polyamides such that the resistance to melt sagging is improved without comprising the ease of extrusion.
TABLE I
Shear Rate - Viscos~ty Relationships Comp. Temp.<~ - Shear Rate (1/~ -->
(-C) 0.087 0.174 0~26 0.347 0.52 1 2 (a) 240 (c) 240 4270 3440 3420 (d) 240 13470 10110 10720 (e)~ 240 36830 31890 30090 2g640 26570 19310 (f) 280 (g) 240 (h) 240 35030 23130 18260 15380 12870 8910 6890 (i) 240 53890 35920 33080 29420 24100 16020 (;) 240 (k) 240 (1) 240 S~ear Rate - Viscosity Relationships (cont.) Comp. Temp. <~ Shear Rate (1/8)~
(C) 10 30 50 100 25~ 300 S00 1000 (a) 240 480 460 390 340 210 (c) 240 3340 2220 2190 172~ 114~ 1080 710 490 ~d~ 240 S570 3720 2560 1570 1080 (e) 240 ~220 4370 3020 1440 990 ~.F.**
(f) 280 3000 1600 850 450 240 (g) 24~ 2540 1380 1010 6~0 410 280 (h) 240 4180 2110 1520 970 6S0 (i) 240 6430 3700 2840 1930 1130 430 (j) 240 8510 4920 2420 M.F.** M~F.**
(k) 240 3080 1900 1130 650 340 (1) 24Q 23B0 1520 970 570 290 WO 94113740 PCT/CA93/00~03 - 17 - 2130~7~
Shear Rate - Viscosity Relationships (cont.) Comp. Temp. <----------Shear Rate (1/s)---------->
(C) 25 1~0 350 830 1200 (b) 280 250 270 230 190 170 s Note: Data for Composition (e) i~ representative data, as melt v~scosity data was changing during measurement.
MF - melt fracture occurred.
Viscosity i8 reported in Pa.s The amples of the compo~itions wero dried at 80-C
for two hours in a de~umidified drier to moisture levels below 0.05S by weight prior to measurements being conducted.
The dat~ represent apparent viscosity and shear stress; 8agley and ~obinowitch corrections were not applied.
- E~ple II
Short qlaæs fibre reinforced compositions were prepared by melt blending and uniformly dispersing ~ ~ var~ OU8 levels of short glass fibres into Composition (h) ; o~ Ex~mple I. On a weight basis, these compositions were nom~nally as ~ollows:
Composition (m) 87% Composition (h) 13% short of Example 1 glass fibres Compo ition (n) 80~ Composition ~h) 20~ short of Examp~e 1 glass fibres Composition (o) 75% Composition (h) 25% short of Exampl~ 1 glass fibres Composition (p) 70~ Composition (h) 30S short 3S of Example 1 glass fibres The melt blending and glass dispersion was carried out in a 53 mm~Werner and Pfleiderer twin screw extruder running at 200 rpm using a temperature profile of 210C
; in the feed section, 230-235C in the barrel section and ,~
wos4/137~ PCT/CA~3/00~03 ~3~4~G -18 -2350C at the die. In each case, the resulting ~elt was pelletized to obtain the composition in the form of pellets.
The shear rate-viscosity relationships for these S compositions wer~ d~e~t.~rminad using a Kayne~ capillary viscometer at 24QC. The dat~ are tabulated in Tabla II.
TABLE II
Shear Rate - vis~08ity Relationsh~p~
Comp.~ ----Shear Rate (l/s)~ ------>
0.52 1 2 10 50 100 250 500 (m) 51000 29000 1900 8400 3400 2200 1200 740 (n) 70000 40000 26000 10600 3900 2500 1400 900 (o) 61000 35000 23000 9900 3700 ~400 1400 940 (p) 63000 31000 21000 1050~ 3700 2400 1400 sO0 Viscosity is reported in units of P~. 8 The ~amples ~f the compositions were dried at 80OC
for two hours in a dehumidified drier to moisture levels below 0.05% by weight prior to measurements being conducted.
The data represent ~pp~rent viscosity and shear stress; Bagley and Ro~inowitch corrections were not ~pplied.
Compositions were evaluated in the blow moulding process of Example I. The mould used was de~igned to produce hollow rectangul~ p~ques ~ea~uring roughly 42 x 10 x 5 cm. It had inserts to produce either textured sections or two qu~re draw pockets measurin~
approximately 3.8 x 3.8 x 0.6 cm and 1.9 x 1.9 x 0.6 cm on one side of the blow moulded parts. The draw pockets provide a measure of the ability of the composition to be drawn into features representing sharp changas in geometry. A melt temperature of about 235C was used for blow moulding evaluation of all of the compositions.
- 19 _ 2130~76 All of the compositions exhibited excellent resistance to melt sagging. Compared to the unreinforced compo~ition (h) of Example 1, the above composition exhlbited signlficantly lower die swell in the thickness and dia~eter of the pari~on. All the co~positions were able to produce good blow ~oulded p~rts when the textured insert was u~ed in the ~ould. When th- in~ert with ~quare draw pocket~ wa~ u~ed, compo~itionR (m) and (n) produced good parts. In case of compo~itions (o~ and (p), the draw pockete were not ~harply defined and had thin rounded corners. This indicate~ a reduced drawability o~ the melt at higher glass loadings.
Claims (14)
1 A blow moulding process in which a parison is formed from a polyamide composition, characterized in that said composition comprises:
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at least 40; and (b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently selected from the polyolefins having a melt index of less than 10 dg/min, the w polyolefin of said grafted polymer having been grafted with 0.1-5 0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity at low shear stress compared to the polyamide of (a).
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at least 40; and (b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently selected from the polyolefins having a melt index of less than 10 dg/min, the w polyolefin of said grafted polymer having been grafted with 0.1-5 0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity at low shear stress compared to the polyamide of (a).
2. An extrusion process in which a profile is extruded from a polyamide composition, characterized in that said composition comprises:
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at least 40; and (b) 10-45% by weight of polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently selected from polyolefins having a melt index of less than 10 dg/min, the polyolefin of said grafted polymer having been grafted with 0.1-5.0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity at low shear stress compared to the polyamide of (a).
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamides having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at least 40; and (b) 10-45% by weight of polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently selected from polyolefins having a melt index of less than 10 dg/min, the polyolefin of said grafted polymer having been grafted with 0.1-5.0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity at low shear stress compared to the polyamide of (a).
3. The process of Claim 1 or Claim 2 in which the polyamide has an amine end group content of at least 30 equivalents/106 grams of polymer.
4. The process of any one of Claims 1-3 in which the weight average molecular weight of any polyamide of (a)(i) is less than 100 000 and the RV of any polyamide of (a)(ii) is less than 200.
5. The process of any one of Claims 1-4 in which the polyamide is a polyamide of (a)(i).
6. The process of any one of Claims 1-4 in which the polyamide is a polyamide of (a)(ii).
7. The process of any one of Claims 1-6 in which the polyamide is an aliphatic polyamide.
8. The process of any one of Claims 1-7 in which the polyolefin is grafted with maleic anhydride.
9. A polyamide composition comprising:
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamdies having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at lest 40; and (b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently selected from polyolefins having a melt index of less than 10 dg/min, the polyolefin of said grafted polymer having been grafted with 0.1-5.0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity at low shear stress compared to the polyamide of (a).
(a) 55-90% by weight of a polyamide selected from the group consisting of (i) polyamdies having a weight average molecular weight of greater than 25 000, and (ii) polyamides that are soluble in formic acid and which have an RV measured in formic acid of at lest 40; and (b) 10-45% by weight of a polymer selected from the group consisting of grafted polymer and mixtures of grafted polymer and ungrafted polymer, each of said grafted polymer and ungrafted polymer being independently selected from polyolefins having a melt index of less than 10 dg/min, the polyolefin of said grafted polymer having been grafted with 0.1-5.0% by weight of an ethylenically unsaturated carboxylic acid or anhydride, the grafted polymer being 25-100% by weight of the polymer of (b); and said composition exhibiting a relative increase in melt viscosity at low shear stress compared to the polyamide of (a).
10. The composition of Claim 9 in which the polyamide has an amine end group content of at least 30 equivalents/106 grams of polymer.
11. The compositions of Claim 9 or Claim 10 in which the weight average molecular weight of any polyamide of (a)(i) is less than 100 000 and the RV of any polyamide of (a)(ii) is less than 200.
12. The composition of any one of Claims 9-11 in which the polyamide is a polyamide of (a)(i).
13. The composition of any one of Claims 9-11 in which the polyamide is a polyamide of (a)(ii).
14. The composition of any one of Claims 9-13 in which the polyolefin is grafted with maleic anhydride.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB929225811A GB9225811D0 (en) | 1992-12-10 | 1992-12-10 | Extrusion or blow-moulding polyamide compositions |
| GB9225811.0 | 1992-12-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2130476A1 true CA2130476A1 (en) | 1994-06-23 |
Family
ID=10726407
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2130476 Abandoned CA2130476A1 (en) | 1992-12-10 | 1993-11-24 | Extrusion or blow-moulding of polyamide compositions |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU5556794A (en) |
| CA (1) | CA2130476A1 (en) |
| GB (1) | GB9225811D0 (en) |
| WO (1) | WO1994013740A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022168020A1 (en) * | 2021-02-08 | 2022-08-11 | Inv Nylon Chemicals Americas, Llc | Blow-moldable polyamide compositions |
| US11787939B2 (en) | 2019-10-24 | 2023-10-17 | Inv Nylon Polymers Americas, Llc | Polyamide compositions and articles made therefrom |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ATE179738T1 (en) * | 1994-06-17 | 1999-05-15 | Allied Signal Inc | LOW DENSITY POLYAMIDE AND POLYETHYLENE MIXTURES AND EXTRUDED ARTICLES MADE THEREFROM |
| DE4425437A1 (en) * | 1994-07-19 | 1996-01-25 | Basf Ag | Glass-reinforced polyamide molding compounds for blow molding applications |
| DE19948850A1 (en) | 1999-10-08 | 2001-04-12 | Bayer Ag | Thermoformable polyamides |
| FR2946652B1 (en) * | 2009-06-12 | 2012-07-20 | Rhodia Operations | POLYAMIDE OF HIGH VISCOSITY. |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59232135A (en) * | 1983-06-15 | 1984-12-26 | Showa Denko Kk | Polyolefin composition |
| JPS60177073A (en) * | 1984-02-22 | 1985-09-11 | Mitsubishi Chem Ind Ltd | Polyamide resin composition |
| EP0235876B1 (en) * | 1986-01-07 | 1993-04-21 | Tonen Sekiyukagaku K.K. | Thermoplastic resin composition |
| CH671022A5 (en) * | 1986-08-26 | 1989-07-31 | Inventa Ag | |
| US4814379A (en) * | 1988-04-11 | 1989-03-21 | Ashland Oil, Inc. | Toughened, low permeability, solvent and salt resistant polyamide blends |
| GB2225582A (en) * | 1988-12-05 | 1990-06-06 | Du Pont Canada | Film of polyamide and grafted polyolefin |
| ATE138959T1 (en) * | 1990-08-02 | 1996-06-15 | Buna Sow Leuna Olefinverb Gmbh | IMPACT-RESISTANT POLYAMIDE MOLDING COMPOUNDS |
-
1992
- 1992-12-10 GB GB929225811A patent/GB9225811D0/en active Pending
-
1993
- 1993-11-24 AU AU55567/94A patent/AU5556794A/en not_active Abandoned
- 1993-11-24 CA CA 2130476 patent/CA2130476A1/en not_active Abandoned
- 1993-11-24 WO PCT/CA1993/000503 patent/WO1994013740A1/en active Application Filing
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11787939B2 (en) | 2019-10-24 | 2023-10-17 | Inv Nylon Polymers Americas, Llc | Polyamide compositions and articles made therefrom |
| WO2022168020A1 (en) * | 2021-02-08 | 2022-08-11 | Inv Nylon Chemicals Americas, Llc | Blow-moldable polyamide compositions |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9225811D0 (en) | 1993-02-03 |
| WO1994013740A1 (en) | 1994-06-23 |
| AU5556794A (en) | 1994-07-04 |
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