Tape of a plurality of sheathed continuous multifilament strands

Abstract

The invention relates to a tape comprising a plurality of sheathed continuous multifilament strands, wherein each of the sheathed continuous multifilament strands comprises a core that extends in the longitudinal direction and a polymer sheath which intimately surrounds said core, wherein each of the cores comprises an impregnated continuous multifilament strand comprising at least one continuous glass multifilament strand, wherein the at least one continuous glass multifilament strand is impregnated with an impregnating agent in an amount from 0.50 to 15.0 wt %, for example from 0.5 to 10.0 wt % or for example from 10.0 to 15.0 wt % based on the sheathed continuous multifilament strand, wherein the impregnating agent has a melting point of at least 20° C. below the melting point of the thermoplastic polymer composition, has a viscosity of from 2.5 to 200 cSt at 160° C., wherein the continuous glass multifilament strand comprises at most 2 wt % of a sizing composition based on the continuous glass multifilament strand and wherein the polymer sheath consists of a thermoplastic polymer composition, wherein the thermoplastic polymer composition comprises at least 60 wt %, for example at least 80 wt % of a thermoplastic polymer, wherein the amount of impregnated continuous multifilament strand is in the range of 10 to 70 wt % based on the sheathed continuous multifilament strands and wherein the amount of polymer sheath is in the range of 30 to 90 wt % based on the sheathed continuous multifilament strand and wherein the sum of the amount of impregnated continuous multifilament strand and the polymer sheath is 100 wt %.

Claims

1. Tape comprising a plurality of sheathed continuous multifilament strands, wherein each of the sheathed continuous multifilament strands comprises a core that extends in the longitudinal direction and a polymer sheath which intimately surrounds said core, wherein each of the cores comprises an impregnated continuous multifilament strand comprising at least one continuous glass multifilament strand, wherein the at least one continuous glass multifilament strand is impregnated with an impregnating agent in an amount from 0.50 to 18.0 wt %, based on the sheathed continuous multifilament strand, wherein the impregnating agent has a melting point of at least 20° C. below the melting point of the thermoplastic polymer composition, has a viscosity of from 2.5 to 200 cS at 160° C., wherein the continuous glass multifilament strand comprises at most 2 wt % of a sizing composition based on the continuous glass multifilament strand, and wherein the polymer sheath consists of a thermoplastic polymer composition, wherein the thermoplastic polymer composition comprises at least 60 wt %, of a thermoplastic polymer, wherein the amount of impregnated continuous multifilament strand is in the range of 10 to 70 wt % based on the sheathed continuous multifilament strands and wherein the amount of polymer sheath is in the range of 30 to 90 wt % based on the sheathed continuous multifilament strand and wherein the sum of the amount of impregnated continuous multifilament strand and the polymer sheath is 100 wt %.

2. Tape according to claim 1, wherein the amount of impregnated continuous multifilament strand is in the range of 25 to 70 wt % based on the sheathed continuous multifilament strands.

3. Tape according to claim 1, wherein the thermoplastic polymer is a polyolefin.

4. Tape according to claim 3, wherein the polyolefin is chosen from the group of polypropylenes or elastomers of ethylene and α-olefin comonomer having 4 to 8 carbon atoms, and any mixtures thereof.

5. Tape according to claim 1, wherein the melt flow rate of the thermoplastic polymer composition is in the range from 20 to 150 dg/min, as measured according to ISO01133 (2.16 kg/230° C.).

6. Tape according to claim 1, wherein the thermoplastic polymer composition comprises at least 80 wt % of the thermoplastic polymer, based on the thermoplastic polymer composition.

7. Tape according to claim 1, wherein the amount of impregnating agent is 1.5 to 8 wt %, based on the sheathed continuous multifilament strand.

8. Laminate of a plurality of tapes of claim 1.

9. Article comprising the tape of claim 1.

10. Process for the production of the tape of claim 1 comprising the steps of: d) providing the plurality of sheathed continuous multifilament strands, e) placing the plurality of sheathed continuous multifilament strands in parallel alignment in the longitudinal direction, f) grouping the plurality of sheathed continuous multifilament strands, wherein steps e) and f) are performed such that the sheathed continuous multifilament strand can be consolidated, and g) subsequently consolidating the plurality of sheathed continuous multifilament strands to form the tape.

11. Process according to claim 10, wherein steps e) and f) are performed by pulling the plurality of sheathed continuous multifilament strands through a slit die.

12. Process according to claim 10, wherein the consolidation of the plurality of sheathed continuous multifilament strands is performed in a consolidation unit.

13. Process according to claim 10, wherein the sheathed continuous multifilament strands are prepared by the sequential steps of: a) unwinding from a package the continuous glass multifilament strands, b) applying the impregnating agent to the continuous glass multifilament strands in an amount from 0.50 to 18.0 wt %, based on the sheathed continuous multifilament strands to form the impregnated continuous multifilament strands, and c) applying the sheath of the thermoplastic polymer composition around the impregnated continuous multifilament strands to form the sheathed continuous multifilament strands.

14. Process according to claim 10, wherein the sheathed continuous multifilament strands of step d) are the sheathed continuous multifilament strands obtained by step c) and wherein the sheathed continuous multifilament strands of step d) are subjected to step e) without cutting.

15. Tape according to claim 1, wherein the thermoplastic polymer composition comprises at least 90 wt % of the thermoplastic polymer, based on the thermoplastic polymer composition.

16. Tape according to claim 1, wherein the thermoplastic polymer composition comprises at least 95 wt % of the thermoplastic polymer, based on the thermoplastic polymer composition.

Description

EXAMPLES

(1) Materials Used.

(2) As continuous glass multifilament strand a glass roving containing a sizing agent, which roving has a diameter of 19 micron and a tex of 3000 (tex means grams glass per 1000 m) was used. Its amount based on the sheathed continuous multifilament strand is indicated herein as GF (wt %).

(3) A heterophasic propylene copolymer having a melt flow rate of 66 dg/min as measured according to ISO1133 at 230° C./2.16 kg was used (PP). The amount of ethylene-propylene copolymer in the heterophasic propylene copolymer (RC) was 18.5 wt %. The amount of ethylene in the ethylene-propylene copolymer (RCC2) was 55 wt % and the total ethylene amount in the heterophasic propylene copolymer (TC2) was 10 wt %. The matrix was a propylene homopolymer having a melt flow rate as measured according to ISO1133 at 230° C. was 156 dg/min, the melt flow rate of the ethylene-propylene copolymer as calculated as described herein was 1.5 dg/g.

(4) As a polyolefin elastomer (POE), Engage 8200 from Dow Chemicals was used. It is an ethylene-octene copolymer having a melt flow rate of 5.0 g/10 min as measured according to ASTM1238 at 190° C./2.16 kg).

(5) As impregnating agent, a highly branched polyethylene wax having a viscosity of 50 mPa.Math.s as measured according to ASTM D 3236-15 at 100° C. was used (Parafflex 4843A).

(6) Preparation of the Single Strands Composites

(7) Single sheathed continuous multifilament strands were prepared from the compositions as given in Table 1 using the wire coating process as described in the examples of WO2009/080281A1.

(8) Preparation of the Tapes

(9) The tapes were prepared from the single sheathed continuous multifilament strands by the following process. First, the single sheathed continuous multifilament strands were manually winded over the metallic cylinder. Winding was done in such a way to ensure that alignment of strands remained as straight as possible throughout the circumference of cylinder. A good alignment was found to improve the side adhesion of neighbouring strands and as a consequence improves the properties of the tapes prepared.

(10) The cylinder was then clamped or taped from the ends to prevent the strands from falling of the cylinder. The cylinder was then placed in an oven at 170-180° C. for the PP containing composition and at 100-110° C. for the POE containing composition. The cylinder was kept at this temperature for 3 minutes and was then left for 4 hours to cool to room temperature (22° C.).

(11) After cooling, the joined strands were cut from the cylinder to obtain a flat sheet of the tape.

(12) The obtained flat sheets of the tape were consolidated using a double belt press machine (KFK-XL 1900 from Mayer, RützDouble) by placing the samples on the belt, covering them in silicon and Teflon sheets and then passing the flat sheets under the double belt. The gap between the belts was set such that the thickness of the tapes was reduced to an average of 2.0 mm. The temperature of the double belt press machine was set to 120° C. for those composition containing POE and to 180° C. for those composition containing PP. As a belt speed 2.0 m/min was used.

(13) Preparation of Laminates

(14) Crossply laminates were prepared from the tapes by placing two consolidated tapes in perpendicular position to each other and by repeating the step of the double belt press. For the lamination, the belt speed was set to 1.0 m/min and the gap between the belts was set such that the thickness of the laminates was on average 4.0 mm.

(15) Methods of Characterization

(16) Samples for impact testing were cut from the crossply laminated by using a waterjet machine.

(17) Samples for tensile testing were cut from the tapes by using a shear cutter.

(18) The tensile strength of the samples was determined using ASTM D3039 using the following test conditions: Clamping pressure: 70 bar, strain rate: 0.01 min.sup.−1, test speed: 2 mm min.sup.−1, gage length: 139.7 mm and clamping length 55.1 mm, Extensiometer length: 50 mm.

(19) For testing the impact properties of the crossply laminate, the Instrumented multiaxial impact was measured using ISO 6603-2 using the following test conditions: Impact speed: 4.4 m/s, Impact type: Hydraulic controlled, Dart diameter: 20 mm, Support ring diameter: 40 mm, Specimen dimensions: 100 mm diameter circular disk. The obtained value for the impact in J was divided by the thickness of the crossply laminate to obtain the impact energy per unit of thickness.

(20) Results:

(21) The results are shown in Table 1. As can be seen from Table 1, the E-modulus (also known as Young's modulus or stiffness) as well as the impact energy per unit of thickness is higher for the examples according to the invention which contain wax (impregnating agent) as compared to the comparative examples which do not contain wax. In addition, it can be seen from the table that a higher amount of wax further increases the impact.

(22) In addition, it can be seen when comparing E1 to E2 that a higher amount of glass fibers increases the E-modulus, indicating the puncture resistance of the tape or laminate of the invention may also be improved.

(23) TABLE-US-00001 TABLE 1 Results. E1 E2 E3 CE1 CE2 CE3 GF (wt %) 20 60 60 20 60 60 Wax (wt %) 2.5 5 5 0 0 0 POE (wt %) 75.75 33.25 78.25 38.25 PP (wt %) 33.25 38.25 Stabilizer (wt %) 0.25 0.25 0.25 0.25 0.25 0.25 Coupling agent 1.5 1.5 1.5 1.5 1.5 1.5 (wt %) Thickness of the 2.8 1.9 2.2 3.1 1.9 2.0 tape (mm) E-modulus 5 15.5 17.3 3.2 7.2 14.6 (GPa) Thickness of the 5.5 3.6 3.9 6.3 4.0 3.9 laminate (mm) Impact Energy 7.4 17.1 15.3 6.1 12.2 8.8 per unit of thickness (J/mm)