Polyester for profile extrusion and/or pipe extrusion

Abstract

Thermoplastic molding compositions containing A) from 29 to 99.99% by weight of a polyester, B) from 0.01 to 3.0% by weight of an alkali metal salt of nitrous acid or of phosphoric acid or of carbonic acid, or a mixture of these, based on 100% by weight of A) and B), and C) from 0 to 70% by weight of further additives, where the sum of the % by weight values for A) to C) is 100%. The compositions are used in the production of cable sheathing or optical waveguide sheathing via blowmolding, profile extrusion, and/or tube extrusion.

Claims

1. A method of producing cable sheathing or optical waveguide sheathing comprising blowmolding, profile extruding, and pipe extruding a thermoplastic molding compositions comprising A) from 29 to 99.99% by weight of a polyester, B) from 0.01 to 3.0% by weight of an alkali metal salt of nitrous acid, phosphoric acid, carbonic acid, or a mixture of these, based on 100% by weight of A) and B), and C) from 0 to 70% by weight of further additives, where the sum of the % by weight values for A) to C) is 100, where the alkali metal of component B) is composed of sodium or potassium, or of a mixture of these.

2. The method according to claim 1, where the intrinsic viscosity (IV) of component A) is at least 140 ml/g in accordance with ISO 1628.

3. The method according to claim 1, where the terminal carboxy group content of component A) is from 10 to 50 meq/kg of polyester.

4. The method according to claim 1, where component B) comprises of NaNO.sub.2, KNO.sub.2, Na.sub.2CO.sub.3, K.sub.2CO.sub.3, NaHCO.sub.3, KHCO.sub.3, Na.sub.3PO.sub.4, K.sub.3PO.sub.4, Na.sub.2HPO.sub.4, K.sub.2HPO.sub.4, or a mixture of these.

5. A method of producing cable sheathing or optical waveguide sheathing comprising blowmolding, profile extruding, and pipe extruding a thermoplastic molding compositions comprising A) from 29 to 99.99% by weight of a polyester, B) from 0.01 to 3.0% by weight of an alkali metal salt of nitrous acid, phosphoric acid, carbonic acid, or a mixture of these, based on 100% by weight of A) and B), and C) from 0 to 70% by weight of further additives, where the sum of the % by weight values for A) to C) is 100, where the intrinsic viscosity (IV) of component A) is at least 140 ml/g in accordance with ISO 1628.

6. A method of producing cable sheathing or optical waveguide sheathing comprising blowmolding, profile extruding, and pipe extruding a thermoplastic molding compositions comprising A) from 29 to 99.99% by weight of a polyester, B) from 0.01 to 3.0% by weight of an alkali metal salt of nitrous acid, phosphoric acid, carbonic acid, or a mixture of these, based on 100% by weight of A) and B), and C) from 0 to 70% by weight of further additives, where the sum of the % by weight values for A) to C) is 100, where the terminal carboxy group content of component A) is from 10 to 50 meq/kg of polyester.

Description

EXAMPLES

(1) Component A:

(2) Polybutylene terephtalate with viscosity 155 ml/g and with terminal carboxy group content of 34 meq/kg+(Ultradur B 6500 from BASF SE) (IV measured in 0.5% by weight solution of phenol/o-dichlorobenzene, 1:1 mixture at 25 C. in accordance with ISO 1628).

(3) Component B/1

(4) Na.sub.2CO.sub.3

(5) Component B/2

(6) K.sub.2CO.sub.3

(7) Component B/3

(8) NaNO.sub.2

(9) Component C/1

(10) Talc powder

(11) Component C/2

(12) Ca stearate

(13) The molding compositions were produced in a ZSK25 with a flat temperature profile at from 250 to 260 C. with subsequent pelletization.

(14) I. Testing of the Compounded Materials

(15) TABLE-US-00002 TABLE 1 Compositions Inv. Inv. Inv. ex. ex. ex. Components comp1 (1) (2) (3) [% by wt.] [% by wt.] [% by wt.] [% by wt.] [% by wt.] A 99.9 99.6 99.6 99.6 B/1 0.4 B/2 0.4 B/3 0.4 C/1 0.04 C/2 0.06

(16) TABLE-US-00003 TABLE 2 Increase of melt stiffness/shear viscosity through use of additives: Inv. Inv. Inv. Melt volume rate ex. ex. ex. [250 C./2.16 kg] Unit comp1 (1) (2) (3) Retention time 4 min cm.sup.3/10 min 9.7 5.8 9.9 10.8 Retention time 10 min cm.sup.3/10 min 11.4 4.4 8.8 9.7 Retention time 20 min cm.sup.3/10 min 14.4 4.2 8.9 11.0 Retention time 30 min cm.sup.3/10 min 15.9 4.2 10.3 10.5

(17) The examples in Table (2) illustrate the improved melt stiffness when the salts of the invention are added in comparison with the polyester in which additives have not been used according to the invention. In the case of the polyester with no additives, when residence time is long the melt volume rate rises as a consequence of polymer degradation as retention time increases, but in the case of the specimens using additives the melt flow rate (determined in accordance with ISO 1133) remains constant.

(18) TABLE-US-00004 TABLE 3 Increase of recrystallization temperature through use of additives Inv. Inv. Inv. ex. ex. ex. Recrystallization Unit A comp1 (1) (2) (3) T.sub.pc C. 176.7 195.7 200.2 194.0 200.7

(19) Table 3 shows calorimetric DSC studies in accordance with ISO 11357, heating and cooling rate 20 K/min. The peak temperature for crystallization T.sub.pc was determined in the first cooling procedure. The examples in table (3) illustrate recrystallization at elevated temperature on addition of the salts of the invention in comparison with the polyester using no additives. A very sharp rise can already be seen with material nucleated by talc powder. A further rise of from 4.5-5.0 C. is observed for the compounded materials of the invention, in comparison with comparative example comp1.

(20) II. Production of Optical Waveguide Sheathing with Use of Additives

(21) In a preferred process of the invention, optical waveguide sheathing products are produced using metal carbonates as additives, by way of additive concentrates. The concentrates were produced in a twin-screw extruder with 25 mm screw diameter (see table (4)). The metering of the additives was achieved here together with the pellets in the cold feed system. In a further step, the concentrates were mixed in a mixer with high-viscosity polymer pellets which used no additives. This gave optical waveguide sheathing products using high-molecular-weight polybutylene terephthalate.

(22) TABLE-US-00005 TABLE 4 Production of concentrates Conc (1) Conc (2) Component [% by wt.] [% by wt.] A 95 95 B/1 5 B/2 5

(23) Production of pellet mixtures of the invention:

(24) The mixtures were produced in the form of pellets/pellet mixtures in a tumbling mixer.

(25) TABLE-US-00006 TABLE 5 Composition of cable sheathing products of the invention Component [% by wt.] comp1 Inv. ex. (4) Inv. ex. (5) A 99.9 92 92 C/1 0.04 C/2 0.06 Conc (1) 8 Conc (2) 8

(26) Production of sheathed optical waveguide cables:

(27) Said pellet mixtures were further processed by means of a single-screw extruder with annular die. Production of this type of sheathing is described by way of example in the following publication: H. J. Mair; Kunststoffe in der Kabeltechnik [Plastics in cable technology], chapter 9, Expertverlag 1983. 12 glassfiber conductors were used as core for this sheathing. The internal diameter of the sheathing, resulting from the diameter of the individual glass fibers and from the geometry of their arrangement was 1.3 mm.

(28) Characterization of the cable sheathing:

(29) The thickness distribution of the sheathing of the invention here is 0.35+/0.05 mm, whereas the wall thickness distribution in the prior art is in the region of 0.6+/0.2 mm (table 6). The compounded material of the invention can therefore give cable sheathing with very little thickness variation.

(30) TABLE-US-00007 TABLE 6 Appearance and thickness distribution of the sheathing comp1 Inv. ex. (4) Thickness of cable sheathing 0.6 +/ 0.2 mm 0.35 +/ 0.05 mm

(31) TABLE-US-00008 TABLE 7 Mechanical properties of optical waveguide sheathing Inv. ex. Inv. ex. Property Unit comp1 (4) (5) Crush resistance N/dm 600 1400 1300

(32) The crush resistance of the cable sheathing using additives in the invention is substantially higher. Crush resistance was determined in accordance with the standard EN 187000/504.

(33) As can be seen from table 8, the glassfiber sheathing produced by the process of the invention features improved hydrolysis resistance in comparison with the prior art.

(34) TABLE-US-00009 TABLE 8 Hydrolysis resistance of the materials of the invention, based on intrinsic viscosity after various storage times Residence time at 85 C. and 85% relative Inv. ex. humidity Unit (comp1) (4) 0 h cm.sup.3/g 146.5 141 100 h cm.sup.3/g 110 135.5 250 h cm.sup.3/g 102 128.5 500 h cm.sup.3/g 92.2 120 1000 h cm.sup.3/g 71.2 105 2000 h cm.sup.3/g 46 74.7