GB2096047A - Moulding articles from polylaurinlactam - Google Patents

Abstract

Polylaurinlactam which is obtained by melting laurinlactam, intermixing the melt with a catalyst and subsequent mixing of the mixture with an activator under polymerisation and which is cast into threads or strands is in accordance with the invention comminuted in known 'per se' manner into granulated material or chips and is injection moulded at temperatures from 220 to 255 DEG C at pressures from 50 to 100 kp/cm<2>. The shaped body obtained in accordance therewith is distinguished by superior physical properties.

Description

SPECIFICATION Method of producing shaped bodies from polylaurinlactam The invention relates to a method of producing shaped bodies from polylaurinlactam as well as the shape bodies obtained in accordance therewith.

A method is known from United States Patent No. 3 793 255 for producing shaped bodies by the activated anionic polymerisation of laurinlectam in which two lactam melts are mixed separately with a catalyst and an activator along with respective nitrogen impingement and are supplied to a mixing device by way of separate pipelines at the same temperature as the melts, and afterwards flows into a mould, in which the partial melts, on their way to the mixing device, are caused to flow through respectively a spiral tube system designed in a siphon-like manner. Properties of the polymer are obtained which differ completely from the customary polycaprolactam.

The disadvantage of this method however, is that serviceable polymerised cast products can indeed be obtained at the initial time, but the properties thereof deteriorate very severely after a short interval of time.

The German offenlegungsschrift No, 25 07 549 describes a method of producing shaped bodies from polylactams, more especially polylaurinlactam, in which the monomeric lactam is melted, the melt is initially intermixed with a catalyst and the mixture obtained in this way is mixed with an activator and the polymerised product is cast immediately afterwards into moulds.

A modification of this method is described in German Offenlegungsschrift No. 2559749, according to which polylaurinlactam shaped bodies are produced by the addition of a polymerisation catalyst during stirring at a temperature above 1 69"C and below 170 C, to provide a partial lactam melt held in a separate vessel and the mixture is stirred; staggered in time in contrast thereto an activator is added, during stirring, at a temperature which lies a few C lower than that of the first melt but which lies in the temperature range from below 170"C to above 1600C, to an equivalent partial lactam meltwhich is held in a separate vessel, and is stirred, the melts obtained in this way are, along with maintenance of their temperatures, in each case drawn off by a gear pump from their vessels and are conducted through gently inclined pipelines, which have a volume which is greater by at least 1/3rd than that of the pump, to the mxing zone, are mixed there at 170 to 175 C and are injection moulded or cast through a spraying head without pressure or at low pressure.

The polylaurinlactam products obtained in accordance with German Offenlegungsschrift No. 2 507 549 and 2 559 749 have the following physical distinguishing features: a yield stress 6S, measured in accordance with DIN 53 455, from approximately 470 to about 520 kp/cm2; an elongation, measured in accordance with DIN 53 455, upon yield stresses from approximately 17 to approximately 25 percent; a tearing strength 6R, measured in accordance with ISO R 527, from approximately 500 to approximately 630 kp/cm2; a tearing elongation eR, measured in accordance with ISO R 527, from approximately 200 to 350 percent; a modulus of elasticity E, measured in accordance with DIN 53457 Para 2.3 from approximately 19000 to approximately 22 000 kp/cm2.; a Limiting bending stress 6B, measured in accordance with ISO R 178, from approximately 750 to approximately 1000 kp/cm2; a notched bar impart strength ak, measured in accordance with DIN 53 453, from approximately 55 to 65 kp/cm2; a bell thrust hardness 10", measured in accordance with DIN 53456 stage C, from approximately 1000 to approximately 1050 kp/cm2; an abrasion resistance, measured by means of Taber-Abrazer from approximately 158 to approximately 129 mm3/Upm; a creep rate stress 61/1000 (23 C/95 percent), measured in accordance with DIN 53 444, from approximately 50 to approximately 60 kp/cm2; and a creep modulus EJ1000 (6 20.0), measured in accordance with DIN 53 444, from approximately 13000 to approximately 14000 kp/cm2.

Further, a thread casting installation in which the polylaurinlactam melts as quoted above can be cast into threads is known from German Offenlegungsschrift No.2602312.

The problem underlying the invention is to provide a method which is simple and which is smoothly feasible and which leads to polylaurinlactam shaped bodies having improved physical properties.

In a surprising way it has now been found that, if the polylaurinlactam material which is known from the above-mentioned Offenlegungsschrits, and which does not melt upon the heating, but disintegrates in the air in the range from approximately 217 to 271 C and is no longer regeneratable turns into a granulated material and this granulate-shaped material is shaped in the injection moulding process into shaped bodies, having new improved properties.

The object of the invention is a method of producing shaped bodies made from polylaurinlactam in which laurinlactam is melted, the melt is initially intermixed with a catalyst and then the mixture is mixed with an activator and is polymerised, is characterised in that the polymerising material is cast into threads or strands which consist of a polymer which does not melt upon heating, but disintegrates in the range from approximately 217 to 271 C in the air and is no longer regeneratable, the threads or strands are comminuted in known manner into granulated material or chips and the comminuted material is injection moulded at temperatures from 220 to 2550C at pressure from 50 to 100 kp/cm2.

Afurther object of the invention comprises the polylaurinlactam shaped bodies obtained in accordance with the above method.

The polylaurinlactam shaped bodies of the invention have the following physical properties; a yield stress 6s, measured in accordance with DIN 53 455, from approximately 480 to approximately 500 kp/cm2; an elongation, measured in accordance with DIN 53 455, upon yield stress ES from approximately 28 to 36 percent; a tearing strength 6R, measured in accordance with ISO R 527, from approximately 550 to approximately 670 kg/cm2; a tearing elongation eR, measured in accordance with ISO R 527, from approximately 220 to approximately 330 percent; A modulus of elasticity E, measured in accordance with DIN 53457 Para 2.3, from approximately 20 000 to approximately 24000 kp/cm2; a limiting bending stress 6B, measured in accordance with ISO R 178, from approximately 730 to approximately 920 kp/cm2; a notched bar impact strength ak, measured in accordance with DIN 53 453, from approximately 70 to approximately 84 kpcm/cm2; a ball thrust hardness from (of?) 10", measured in accordance with DIN 53456 stage C, from approximately 1030 to 1060 kp/cm2.

The polylaurinlactam obtained in accordance with German Offenlegungsschrift No. 2 507 549 or German Offenlegungsschrift No. 2 559749 is used as starting material for performing the method in accordance with the invention.

To produce the starting material, initially laurinlactam is melted and the catalyst is mixed into this melt.

After thorough intermixing, the activator is added to the mixture. The addition of the catalyst to the laurinlactam melt, the subsequent admixture of the activator and the polymerisation are preferably effected at a constant temperature, advantageously in the range from 150 to 200 , in which respect a temperature of 1600C proved to be optimum.

One can also in accordance with German Offenlegunsschrift No. 2559749 proceed in such a way that equivalent quantities of laurinlactam are introduced into two separate vessels and are melted during stirring.

Whilst preserving a temperature below 1700C and above 160 C, a catalyst is introduced into one vessel and stirred. Offsettimewise as compared with this operation, along with stirring an activator is added into a separate vessel, containing an equivalent quantity of lactam melt, at a temperature which lies a few C lower than that of the first melt, but also within the range from below 170 C to above 1600C. The two container contents are then drawn off, whilst maintaining their temperatures, by a gear pump from their vessels and conducted from the two gear pumps by way of pipelines with a maximum inclination to the horizontal of 100C (sic !) to a mixing zone, the pipelines have a volume which is greater by at least one-third than the delivery of the pump. The material is briefly intermixed in the mixing zone.

In accordance with the invention, the polymerising material is cast immediately into threads or strands.

For example, the thread casting installation indicated in German Patent No. 2 602312 can be used for this operation. The threads or strands are then comminuted into a granulated material or into chips.

For example, the threads or strands can initially be processed by rolling into bands which are then cut into strips and finally comminuted into granulated material. Conventional mills of granulating machines can be used for comminuting the starting polymer. The granulated materials can have any desired, uniform or non-uniform shapes. For example, the granulated material used may have a rectangular, more especially square cross-section. Preferably the granulated material used has an average particle diameter of 2 to 5 mm.

A cubic granulated material having edge lengths of 3mm proved to be particularly favourable.

The polylaurinlactam granulated material accruing as an intermediate product within the framework of the method in accordance with the invention is then injection moulded. In this respect, temperatures from 220 to 2550C as well as pressures frmom 50 to 100 kp/cm2 are used. The moulding operation can be effected in conventional injection moulding machines having heated extruder worms and nozzles. Preferably the rear region of the worm is heated to 240 C, whilst the front region of the worm is heated to 250"C.

The nozzle heating is preferably 250 C.

The production of the polylaurinlactam shaped body in accordance with the invention can be effected, for example, in the manner described hereinafter.

In accordance with the method described in German Offenlegungsschrift No. 2 507 549 or German Offenlegungsschrift No. 2 559 749, from laurinlactam there is produced a polymerisation product which is supplied in the polymerising state, advantageously at temperatures from 160 to 1 680C, to a thread casting installation. Advantageously the polymerising material is conducted by way of a pump into the installation, designed as a discharge transverse, for the continuous casting of threads or strands. The polymerisation product then emerges as a liquid, filamentary material from the thread casting installation and runs over a haif-open guide channel, for example as on approximately round-profiled liquid plastics thread, to a set of mixing rollers, the roll nip of which is continuously variable and is brought to the desired thickness and width. The band running out of the roll nip by way of a guide channel is then cut upon passage through cutter rollers into parallel-extending strips, which are then comminuted by a subsequently-arrnnged cutter head of a cutter roller into granulated material or chips. For example, the granulated materials have, by virtue of a square cross-section of the strips, a cubic shape. The granulated materials or chips are, after passage through a dust removal device passed to an injection moulding machine.

The granulated material is injection moulded, using heated extruderworms and a heated nozzle, along with application of pressure. The temperatures used lie between 220 and 255"C, whilst pressure from 50 to 100 kp/cm2 are applied. The granulated material can be injection moulded into any desired shaped bodies.

The polylaurinlactam shaped bodies obtained in accordance with the method of the invention are distinguished by excellent properties, in which they are superior to the previously-known polylaurinlactam materials.

The mechanical and thermal properties of the material in accordance with the invention are set out in the following Tables I and II.

TABLE I Mechanical Properties Measuring Dimension Method Yield stress 6s DIN 53455 kp/cm2 480-500 Elongation upon DIN 53455 percent 28-36 yield stress Es Tearing strength 6R ISO R 527 kp/cm2 550-670 Tearing elongation ER ISO R 527 percent 220-330 Modulus of DIN 53457 kp/cm2 20000-24000 elasticity E Para 2.3 Limiting bending ISO R 178 kp/cm2 730-920 stress 68 Notched bar impact DIN 53453 kpcm/cm2 70-84 strength aK Ball thrust hardness DIN 53456 kp/cm2 1030-1060 10" stage C TABLE II Thermal Properties Measuring Dimension Method Destruction tempera- Depending on C 200-260 ture in atmosphere recipe Melting temperature VICATBDIN C 194 53460 Coefficient of linear at -60 to +30"C 104/OC 0.3-0.5 expansion a Coefficient of thermal kcal/ conductivity X m.h. grd 0.24 Temperature limits of upto some hours C 210 the use upwards upto 4 months "C 160 unto years C 135 The polylaurinlactam shaped bodies in accordance with the invention stand out in an advantageous manner from the properties of previously known polyamides. In the Figures 1 to 9 listed hereinafter, the properties of the new product are compared on the one hand with those of the polylaurinlactam product, used as starting material, in accordance with German Offenlegungsschrift No. 2507 549 and on the other hand with those of other known polyamides such as polymide 12, polyamide 11, polyamide 6.6 and polyamide 6.As can be seen, the product in accordance with the invention combines excellent elongation upon yield stress, tearing strength, excellent modulus of elasticity, noted bar impact strength and ball thrust hardness with good yield stress, tearing elongation and limiting bending stress with extremely slight shrinkage of the material.

Furthermore, the polylaurinlactam shaped bodies in accordance with the invention are distinguished by excellent compressive strength. Reproduced in the accompanying Figure 10 as the result of compression tests is a force - upsetting diagram of the polylaurinlactam material in accordance with the invention. To carry out the compression tests, five cubes obtained from the polyaurinlactam shaped body produced in accordance with the invention and having an edge length of 25 mm were used as test bodies which were tested using a universal testing machine 200 kN whilst adhering to a test climate of 23"C/50 percent relative air moisture and a deformation speed of 2.0mm/min. The compression tests are reproduced in Tabe Ill.

TABLE III Compression tests TEST PIECE NO. it%1) ops2) 1a20%3) Es 4) N/mm2 N/mm2 N/mm2 1. 17.01 45.76 58.73 2.71 2. 15.95 45.23 56.74 2.91 3. 17.44 49.58 61.81 2.91 4. 17;21 50.60 64.09 2.95 5. 17.68 46.73 57.97 2.91 Average 17.06 47.58 59.87 2.88 1) Compressive stress at 1 percent upsetting 2) Compressive stress at upsetting limit, in which respective the upsetting limit was ascertained as the point of intersection of the two main equalising straight lines onto the curve (see diagram Figure 10) 3) Compressive stress at 10 percent upsetting 4) Elongation at upsetting limit.

As a result of the compressive tests, no failure or breakage occured during and after the tests.

The compressive test was terminated at a compressive force of 60kN or respectively at a compressive stress of about 96 N/mm2.

The new polylaurinlactam shaped bodies in accordance with the invention are also distinguished by a high resistance to energy-rich radiation.

In a surprising manner it has furthermore been ascertained that the mechanical properties of the polylaurinlactam material in accordance with the invention are improved by irradiation with energy-rich radiation. As can be seen from the following Table IV, four test pieces of the material in accordance with the invention were irradiated with y-radiation.

Irradiation o the polylaurinlactam material in accordance with the invention with y-rays IRRADIATED MATERIAL IN ACCORDANCE ENERGY DOSE WITH THE INVENTION 1 not irradiated (1) 2 40.104J/kg 3 100.104J/kg 4 200.10# J/kg (1) as comparison base value The irradiated test pieces 2 to 4 as well as the non-irradiated reference sample were tested with respect to their mechanical properties. The values obtained are reproduced in the following Table V.

TABLE V Mechanical properties of the polylaurinlactam material in accordance with the invention after irradiation with - radiation.

TEST STANDARD UNIT 1. 2. 3. 4.

refer Shore D DIN 53505 - 69 71 71 72 Tensile strength at the flow limit DIN 53455 N/mm2 50 52 52 54 Elongation at the flow limit DIN 53455 % 38 20 18 14 Breaking strength DIN 53455 N/mm2 50 52 55 53 Breaking elongation DIN 53455 % 38 20 18 14 Bending-E-modulus DIN 53452 N/mm2 1230 1425 1615 1735 Limiting bending strength DIN 53452 N/mm2 81 85 86 92 The rise in the mechanical properties of the polylaurinlactam material, in accordance with the invention, after irradiation with y -rays is reproduced as a diagram as a function of the ray does in Figure 11.

Claims (5)

1. A method of producing shaped bodies from polylaurinlactam, in which laurinlactam is melted, the molten mass is initially intermixed with a catatlyst and then the mixture is mixed with an activator and is polymerised, characterised in that the polymerising material is cast into threads or strands which consist of a polymer which does not melt upon the heating, but in the range from about 217 to 271"C disintegrates in the air and is no longer regeneratable, the threads or strands being comminuted in known manner into granulated material or chips and the comminuted material being injection moulded at temperatures from 220 to 255"C at pressures from 50 to 1 00kp/cm2.

2. A method as claimed in claim 1, characterised in that granulated materials having an average particle diameter of 2 to 5mm are used.

3. A method as claimed in claim 1 or 2, characterised in that work is effected at a temperature of 240"C in the rear region of the worm of the injection moulding machine and at 250"C in the front region of the worm of the injection moulding machine.

4. Polyaurinlactam shaped bodies, obtained in accordance with the method of claims 1 to 3.

5. Polylaurinlactam shaped bodies, obtained in accordance with the method of claims 1 to 3 having the following physical distinguishing features; a yield stress 6s, measured in accordance with DIN 53 455, from approximately 480 to approximately 500kp/cm2. an elongation, measured in accordance with DIN 53 455, upon yield stress Es, from approximately 28 to approximately 36 percent; a tearing strength 6R, measured in accordance with ISO R 527, from approximately 550 to approximately 670 kp/cm2; a tearing elongation ER, measured in accordance with ISO R 527, from approximately 220 to approximately 330 percent; a modulus of elasticity E, measured in accordance with DIN 53457 Para 2.3, from approximately 20000 to approximately 24000 kp/cm2; a limiting bending stress 6B, measured in accordance with ISO R 178, from approximately 730 to approximately 920 kp/cm2; a notched bar impact strength ak, measured in accordance with DIN 53 453, from approximately 70 to approximately 84 kpcm/cm2; a ball thrust hardness 10", measured in accordance with DIN 53456 stage 6, from approximately 1030 to 1060 kp/cm2.