GB1558877A

GB1558877A - Polyamide moulding compositions

Info

Publication number: GB1558877A
Application number: GB51804/76A
Authority: GB
Original assignee: British Industrial Plastics Ltd
Current assignee: British Industrial Plastics Ltd
Priority date: 1976-12-11
Filing date: 1976-12-11
Publication date: 1980-01-09
Also published as: JPS5394539A; CH625262A5; BE861722A; FR2392077B1; NL7713663A; DE2755169A1; FR2392077A1; ZA777368B

Abstract

The moulding composition comprises a nylon modified with 0.1 to 10 % by weight of an acrylic polymer. The acrylic polymer represents between 10 and 15 % by weight of the units of an alpha , beta -unsaturated carboxylic acid and 90 to 85 of units derived from one or a number of alkyl esters of an ethylenically unsaturated carboxylic acid. This composition can be blow-moulded on account of its high melt viscosity.

Description

(54) IMPROVEMENTS IN OR RELATING TO POLYAMIDE MOULDING COMPOSITIONS (71) We, BRITISH INDUSTRIAL PLASTICS LIMITED a Company organised under the laws of Great Britain, of 20 St. Mary's Parsonage, Manchester M3 2NL (formerly of 77 Fountain Street, Manchester M2 2EA), do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to polyamide moulding compositions, and in particular to polyamide moulding compositions having a melt viscosity such as to permit their use in a blow moulding process.

It is proposed in Patent 1,047,069 to make useful blends of polyamide resins and methyl methacrylate based polymers by intimately melt blending from 1 to 99% by weight of a polyamide thermoplastic resin with from 99 to 1% by weight of a polymethyl methacrylate resin having copolymerised therein from 1 to 20 equivalents of an ethylenically unsaturated carboxylic acid per 100 moles of total monomers. Example 1 in the Patent illustrates the physical properties obtained by blending various proportions of a polyamide (Nylon 66), of which the largest forms 90% by weight of the blend. with a methyl methacrylate polymer made by polymerizing a mixture of 89 parts by weight of methyl methacrylate, 6 parts by weight of ethyl acrylate and 5 parts by weight of methacrylic acid.Among the properties recorded for the 90% polyamide/10% methacrylate blend is an improved melt viscosity, but this is accompanied by a substantially reduced impact strength.

According to the present invention, there is provided a thermoplastic polyamide moulding composition capable of being blow moulded, comprising the product obtained by heating at a temperature of at least 1800C a mixture of the following materials A and B; A. a thermoplastic aliphatic polyamide in an amount forming from 95 to 99.8% by weight of A + B, and B. a copolymer consisting essentially of (i) acrylic or methacrylic acid, and (ii) a mixture of an alkyl ester of acrylic acid and an alkyl ester of methacrylic acid, the weight proportions of (i) and (ii) in the copolymer being in the ranges 10-15% and 90-85% respectively: the amount of the copolymer B employed being within the range of 0.2 to 5% by weight of A + B and such as to increase the melt viscosity of the polyamide A without substantially descreasing its impact strength.

The aliphatic polyamide may be, for example, nylon 6 or nylon 66. or a polyamide which has been co-condensed with a polyester as described in our U.K. patent 1 538 544. The amount of polyester in the co-condensate is preferably in the range of 5 to 20 per cent by weight.

The alkyl esters of copolymer B are preferably lower alkyl esters incorporating an alkyl group such as methyl, ethyl, propyl, butyl or hexyl. Preferably a mixture of methyl methacrylate and butyl acrylate is used. Preferably the acrylic polymer i.e. copolymer B is one of the kind described in U.K. patent No. 1,442,086, in which the amount of acrylic or methacrylic acid is from 11% by weight to 15% by weight based on the weight of co-polymer. The preferred proportions of acrylic polymer in the mixture of A and B are in the range 0.5 to 3 percent by weight.

The moulding composition is preferably prepared by passing a blend of the polyamide and the acrylic polymer through a vented extruder, a vacuum preferably being applied to the vent to remove any water evolved by condensation reaction between the polymers.

The mouldings formed from the composition are translucent, and contain only a low proportion of acrylic polymer.

The invention is further illustrated by the following Examples.

Examples 1 to 4, and Example 5 (comparative) In each of Examples 1 to 5 nylon 6 was modified with an acrylic polymer which was composed of 47% by weight methyl methacrylate 40% by weight butyl acrylate, and 13% by weight acrylic acid.

Modification of the nylon 6 was carried out by blending finely ground acrylic polymer with chips of the nylon and feeding the blend through a vented Welding Engineers twin screw extruder, a vacuum of 15 inches of mercury being applied to the vent to remove water of condensation. The extrusion conditions for Examples 1 to 5 are given in Table 1 in which zone 1 is the barrel temperature closest to the hopper and zone 6 is closest to the die. The extrudate was in the form of a lace which was cooled in a water bath and then chopped to grannular form.

TABLE 1 Example No. 1 2 3 4 5 Nylon 6 MD3 (% by weight) 99 98.5 98 95 90 Acrylic copolymer (") 1 1.5 2 5 10 1 180 210 210 175 170 2 210 235 240 220 215 Zone 3 240 255 260 240 235 Temperatures 4 255 260 275 265 250 ( C) 45 270 300 300 280 280 (6 270 295 295 285 300 Test speciments were moulded from the polymer grannules on a BIPEL 70/31 machine (BIPEL is a Registered Trade Mark) under the conditions given in Table 11.

TABLE 11 Example No. 1 2 3 4 5 Barrel 1 230 290 255 240 240 Zone 2 260 300 285 270 270 Temperatures 3 260 300 280 280 280 ( C) 4 255 285 265 255 255 Mould Temp ("C) 90 90 90 80 80 Injection pressure (psig) 480 450 500 400 500 Injection time (sec) 10 10 10 10 10 Freeze time (sec) 15 30 30 10 10 The physical properties evaluated on the test specimens were (i) water absorption, (ii) tensile properties, (iii) flexural properties, (iv) impact strength, (v) solution viscosity and (vi) melt flow index (at 230 C 12.5 kg load). The results of these tests are given in table III. The properties of unmodified Nylon 6 are also given for comparison.

TABLE 111 Nylon 6 Examples Units only 1 2 3 4 5 %Acrylic % O 1 1.5 2 5 10 Tensile Strength MNmZ 77 76 69 68 67 59 Tensile Modulus GNm 3.0 3.0 3.2 3.2 3.0 3.0 %Elongation % 6.1 5.6 4.7 4.5 4.5 4.3 Flexural Strength MNm2 97 - 90 90 103 96 to Break Flexural Strength to 6 mm deflection Mum~2 - 81 72 73 - Flexural Modulus Gum~2 2.5 2.6 2.4 2.6 2.6 2.6 Charpy Notched I.S. kJm2 3.4 3.8 4.5 4.3 3.2 2.4 % Water absorption 150/R62(A) % 1.8 1.7 1.6 1.4 150/R62(B) % 1.3 1.3 1.3 1.0 Melt Flow Index dg mint * 37.7 5.3 4.6 10.7 15.5 12.5 kg, 230"C Viscosity Number 0.5% W/V in 90% Formic acid - 155 428 371 345 329 271 *The melt flow index of the nylon 6 was too high to be measured by the same test as the other Examples.

It was found that the modified nylon 6 had a very much greater viscosity than nylon 6, as indicated by the melt flow index and viscosity number. the level of acrylic polymer addition to achieve maximum viscosity being in the region of 1.5 to 2 per cent. At these levels of acrylic polymer the impact strength of the material as evidenced by the notched charpy impact strength was also improved. However. at a level of addition of 10% by weight of acrylic polymer (comparative Example 5) the impact strength was markedly reduced.

The mouldings obtained from the modified nvlon had the translucency of the nylon base polymer, which is also an advantage when coupled with the ability of the modified nylon to be blow moulded permitting containers. bottles etc. to be manufactured from it.

Example 6 This example illustrates the effect of added acrylic polymer (5 parts by weight) on a polyamide obtained by co-condensation of nylon 6 (85 parts by weight) and a polyester (15 parts by weight). In this case nylon 6. the polyester and the acrylic polymer were blended and fed through the twin-screw extruder used in Examples 1 to 5. A vacuum of 19 inches of mercury was applied to the vent and the zone temperatures on the extruder were as follows zone 1 - 138"C; 2 - 219"C: 3 - 22l C: 4 - 245 C: 5 - '30 C: 6 - 230"C.

The polyester was one made from propylene glycol. isophthalic acid and trimellitic anhydride in the molar ratio 1.12:1.00:0.16 and the acrvlic polymer was the same as that used in the previous examples.

Test mouldings were made from the extrudate as in Examples 1 to 5 under the conditions indicated in Table IV.

TABLE IV Barrel ) 1 243 Zone ) 2 255 Temperatures ) 3 256 ( C) ) 4 239 Mould Temp ("C) 83 Injection Pressure (psi) 300 Injection Time (secs) 14 Freeze Time (secs) 20 The physical properties of the moulded test specimens were measured, these results being given in Table V.

TABLE V Tensile Strength 65MNm Notch Charpy Impact 2.3 KJm Strength Tensile Modulus 3.1GNm' Water absorption A 1.45% Elongation to break 4.0% Water absorption B 1.11% Flexural Strength 95MNm2 Melt Flow Index 49.5dgmin (12.5kg: 230"C) Flexural Modulus 3.0GNm Viscosity Number (0.5% W/V in 90% formalin) 90 In connection with the melt flow index figure obtained in Table V it should be noted that the 85% nylon 15% polyester co-condensate alone has an even higher melt flow index than unmodified nylon 6 and so a comparable measurement was not possible. The impact strength of test specimens moulded from the co-condensate was 2.3KJm~2.

Examples 7 to 10 The previous examples show that the melt-flow index of nylon 6 and polyester-modified nylon 6 is drastically reduced by the presence of an acrylic polymer.

Examples 7 to 10 investigate the effect of varying the acrylic polymer.

Three samples of acrylic polymer were made, each containing the same three ingredients as in the earlier examples. The relative proportions of methyl methacrylate were unchanged but the amount of acrylic acid in one sample was 11% and in the others was 15%.

The sample containing 11% of acrylic acid had a relatively high molecular weight of the same order as the acrylic polymer used in examples 1 to 6. One of the samples containing 15% acrylic acid was again of comparable molecular weight but the other sample containing 15% acrylic acid was of lower molecular weight (made by early termination of the polymerization reaction).

Four examples of modified nylon 6 were prepared as indicated in Table VI using the same extruder as in the previous examples the extrusion condition being those used for the same amount added of acrylic polymer in Table 1. The melt flow index of the modified nylons produced was measured by the same method as in the previous examples.

TABLE VI Example No. 7 8 9 10 Acrylic polymer type (% Acrylic Acid: MW) 11%(thigh) 15%(high) 15%(high) 15%(low) Amount of acrylic polymer added to nylon 6 2% 2% 1% 2% Melt Flow Index (12.5kg; 230"C) 17.5 12.0 6.0 * Not tested.

Examples 7, 9 and 10 show that these acrylic polymers have the same effect of lowering melt flow index. Example 8 illustrates the difficulties which arise from the increasing content of acrylic acid since this composition cross-linked in the compounding extruder under the extrusion conditions.

The example 9 does show. however. that the acrylic polymer used in example 8 will lower the melt flow index in the same way as the other polymers, and example 10 shows that when compounding is difficult because of cross-linking in the extruder, lowering the molecular weight of the acrylic polymer will assist in alleviating the problem.

WHAT WE CLAIM IS: 1. A thermoplastic polyamide moulding composition capable of being blow moulded, comprising the product obtained by heating at a temperature of at least 1800C a mixture of the following materials A and B; A. a thermoplastic aliphatic polyamide in an amount forming from 95 to 99.8% by weight of A + B, and B. a copolymer consisting essentiallv of (i) acrylic or methacrylic acid, and (ii) a mixture of an alkyl ester of acrvlic acid and an alkyl ester of methacrylic acid, the weight proportions of (i) and (iij in the copolymer being in the ranges 10-15C/e and 90-85Yo respectively:

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Claims

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TABLE V Tensile Strength 65MNm Notch Charpy Impact 2.3 KJm Strength Tensile Modulus 3.1GNm' Water absorption A 1.45% Elongation to break 4.0% Water absorption B 1.11% Flexural Strength 95MNm2 Melt Flow Index 49.5dgmin (12.5kg: 230"C) Flexural Modulus 3.0GNm Viscosity Number (0.5% W/V in 90% formalin) 90 In connection with the melt flow index figure obtained in Table V it should be noted that the 85% nylon 15% polyester co-condensate alone has an even higher melt flow index than unmodified nylon 6 and so a comparable measurement was not possible. The impact strength of test specimens moulded from the co-condensate was 2.3KJm~2.

Examples 7 to 10 The previous examples show that the melt-flow index of nylon 6 and polyester-modified nylon 6 is drastically reduced by the presence of an acrylic polymer.

Examples 7 to 10 investigate the effect of varying the acrylic polymer.

Three samples of acrylic polymer were made, each containing the same three ingredients as in the earlier examples. The relative proportions of methyl methacrylate were unchanged but the amount of acrylic acid in one sample was 11% and in the others was 15%.

The sample containing 11% of acrylic acid had a relatively high molecular weight of the same order as the acrylic polymer used in examples 1 to 6. One of the samples containing 15% acrylic acid was again of comparable molecular weight but the other sample containing 15% acrylic acid was of lower molecular weight (made by early termination of the polymerization reaction).

Four examples of modified nylon 6 were prepared as indicated in Table VI using the same extruder as in the previous examples the extrusion condition being those used for the same amount added of acrylic polymer in Table 1. The melt flow index of the modified nylons produced was measured by the same method as in the previous examples.

TABLE VI Example No. 7 8 9 10 Acrylic polymer type (% Acrylic Acid: MW) 11%(thigh) 15%(high) 15%(high) 15%(low) Amount of acrylic polymer added to nylon 6 2% 2% 1% 2% Melt Flow Index (12.5kg; 230"C) 17.5 12.0 6.0 * Not tested.

Examples 7, 9 and 10 show that these acrylic polymers have the same effect of lowering melt flow index. Example 8 illustrates the difficulties which arise from the increasing content of acrylic acid since this composition cross-linked in the compounding extruder under the extrusion conditions.

The example 9 does show. however. that the acrylic polymer used in example 8 will lower the melt flow index in the same way as the other polymers, and example 10 shows that when compounding is difficult because of cross-linking in the extruder, lowering the molecular weight of the acrylic polymer will assist in alleviating the problem.

WHAT WE CLAIM IS: 1. A thermoplastic polyamide moulding composition capable of being blow moulded, comprising the product obtained by heating at a temperature of at least 1800C a mixture of the following materials A and B; A. a thermoplastic aliphatic polyamide in an amount forming from 95 to 99.8% by weight of A + B, and B. a copolymer consisting essentiallv of (i) acrylic or methacrylic acid, and (ii) a mixture of an alkyl ester of acrvlic acid and an alkyl ester of methacrylic acid, the weight proportions of (i) and (iij in the copolymer being in the ranges 10-15C/e and 90-85Yo respectively:

the amount of the copolymer B employed being within the range 0.2 to 5% by weight of A + B and such as to increase the melt viscosity of the polyamide A without substantially decreasing its impact strength.
2. A moulding composition according to Claim 1 in which the aliphatic polyamide is Nylon 6 or Nylon 66.
3. A moulding composition according to Claim 1 in which the aliphatic polyamide is a polyester/polyamide co-condensate obtained bv the process claimed in Patent 1,538.544.
4. A moulding composition according to Claim 3 in which the polyester forms 5 to 20 per cent by weight of the co-condensate.
5. A moulding composition according to any one of Claims 1 to 4 in which the esters set forth in B (ii) have up to 6 carbon atoms in the alkyl group.
6. A moulding composition according to Claim 5 in which the esters are methyl methacrylate and butyl acrylate.
7. A moulding composition according to any one of claims 1 to 6 in which the co-polymer B contains 11% or more by weight of acrylic or methacrylic acid.
8. A moulding composition according to any one of Claims 1 to 7 in which the amount of co-polymer B is in the range 0.5 to 3 per cent by weight of A + B.
9. A moulding composition according to Claim 1 substantially as described herein in any of the foregoing Examples 1 to 4.
10. A moulding composition according to Claim 1 substantially as described herein in any of the foregoing Examples 6, 7, 9 and 10.