PROCESS FOR PRODUCING LONG GLASS FIBRE-REINFORCED THERMOPLASTIC COMPOSITIONS

Abstract

Disclosed herein is a process for producing a long glass fibre-reinforced thermoplastic polymer composition, comprising the sequential steps of a) unwinding continuous glass multifilament strand containing at most 2% by mass of a sizing composition; b) applying from 0.5 to 20% by mass of an impregnating agent to form an impregnated continuous multifilament strand; and c) applying a sheath of thermoplastic polymer around the impregnated continuous multifilament strand to form a sheathed continuous multifilament strand, wherein the impregnating agent is non-volatile, has a melting point of at least 20° C. below the melting point of the thermoplastic matrix, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer to be reinforced. This process allows trouble-free handling and unwinding of packages, and results in long glass fibre-reinforced thermoplastic products that can be made into articles having good mechanical properties and high quality surface appearance.

Claims

1. A process for producing a long glass fibre-reinforced thermoplastic polymer composition, which comprises the sequential steps of: a) unwinding from a package of a continuous glass multifilament strand containing at most 2% by mass of an aminosilane compound that had been applied to the continuous glass multifilament strand as an aqueous dispersion; b) applying from 0.5 to 20% by mass of a molten impregnating agent comprising a highly branched poly(alpha-olefin) to said continuous glass multifilament strand to form an impregnated continuous glass multifilament strand; and c) applying a sheath of thermoplastic polymer around the impregnated continuous glass multifilament strand at a line speed of at least 250 m/min to form a sheathed continuous glass multifilament strand, wherein the thermoplastic polymer comprises a polypropylene; wherein the impregnating agent is non-volatile, has a melting point of at least 20° C. below a melting point of the thermoplastic polymer, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer; and wherein molded plaques of the composition have a Charpy impact strength, at 0°, of greater than or equal to 10.0 kJ/m.sup.2.

2. The process according to claim 1, wherein molded plaques of the composition have a Charpy impact strength, at 90°, of greater than or equal to 12.0 kJ/m.sup.2.

3. The process according to claim 1, further comprising a step of cutting the sheathed continuous glass multifilament strand into pellets.

4. The process according to claim 1, wherein the highly branched poly(alpha-olefin) is a polyethylene wax.

5. The process according to claim 1, wherein the amount of impregnating agent is from 2 to 10% by mass.

6. The process according to claim 1, further comprising a step of moulding the long glass fibre-reinforced thermoplastic polymer composition into (semi-)finished articles.

7. The process according to claim 1, wherein step c follows step b without intervening steps.

8. The process according to claim 1, wherein the line speed is at least 300 m/min.

9. The process according to claim 1, wherein the applying of the sheath is performed directly after the applying of the impregnating agent.

10. A process for producing a long glass fibre-reinforced thermoplastic polymer composition, which comprises the sequential steps of: a) unwinding from a package of a continuous glass multifilament strand containing at most 2% by mass of a sizing composition; b) applying from 0.5 to 20% by mass of an impregnating agent to said continuous glass multifilament strand to form an impregnated continuous glass multifilament strand; and c) applying a sheath of thermoplastic polymer around the impregnated continuous glass multifilament strand at a line speed of at least 250 m/min to form a sheathed continuous glass multifilament strand; wherein the impregnating agent is non-volatile, has a melting point of at least 20° C. below a melting point of the thermoplastic polymer, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer. (Previously presented)

11. The process according to claim 10, wherein the sizing composition has been applied as an aqueous dispersion and comprises an aminosilane compound.

12. The process according to claim 10, wherein there are no intermediate steps between the applying the impregnating agent and the applying of the sheath.

13. The process according to claim 10, wherein the applying of the sheath is performed directly after the applying of the impregnating agent.

14. The process according to claim 10, wherein the line speed is at least 300 m/min

15. The process according to claim 10, wherein the thermoplastic polymer is a polypropylene and the impregnating agent is a polyethylene wax.

Description

EXAMPLES 1-5

[0054] Several long glass fibre-reinforced polypropylene compositions, comprising 30 mass % of glass fibres and different amounts of impregnating agent (LOI) were produced by using SABIC® PP579S propylene homopolymer with a MFI of 45 g/10 min (230° C./2.16 kg) as polymer matrix. The polymer matrix further comprised 1 mass % of a 40 mass % Carbon black masterbatch, 1 mass % of a functionalized polypropylene, and stabilisers.

[0055] The glass fibres used were standard Type 30 roving SE4121 3000 Tex, supplied by Owens Corning as a roving package, have filament diameter of 19 microns and contain aminosilane-containing sizing composition applied as aqueous dispersion. A blend of 30 mass % Vybar 260 (hyper-branched polymer, supplied by Baker Petrolite) and 70 mass % Paralux oil (paraffin, supplied by Chevron) was used as impregnating agent. The impregnating agent was molten and mixed at a temperature of 160° C. and applied to the continuous glass multifilament strands after unwinding from the package, by using an applicator. The viscosity of the agent at this temperature was measured to be about 15 cS. This viscosity level appeared too low to enable a standard MFI measurement for polyolefins. The amount of impregnating agent on the glass fibres was determined by a LOI (loss on ignition) method, wherein an amount of about 5 gram of impregnated glass fibres was heated during 15 minutes at 525° C. in a furnace; and LOT was calculated as [(mass after heating*100)/mass before heating].

[0056] The sheathing step was performed in-line directly after the impregnating step, using a 75 mm twin screw extruder (manufactured by Berstorff, screw L/D ratio of 34), at a temperature of about 250° C., which fed the molten polypropylene matrix material to an extruder-head wire-coating die having a die-hole of 2.8 mm The line speed for impregnating and sheathing was 250 m/min. The sheathed strand was cut into pellets of 12 mm length. Production ran smoothly and stable during at least 8 hours; no fuzz of glass or fouling of glass guiding members was observed. In the container containing the pellets, no free glass fibres were found, meaning that all glass was effectively impregnated and sheathed. In the run wherein 10 mass % impregnating agent was applied line speed could be increased to over 300 m/min without any problems.

[0057] The results are given in Table 1.

COMPARATIVE EXPERIMENT 6

[0058] This experiment was performed similar to Examples 1-5, but now a 30 mass % long glass fibre-reinforced polypropylene composition was made using Performax® 507 Glass Fibres (supplied by Owens Corning; having filament diameter of 19 micron and containing 7 mass % of sizing components); and no impregnating agent was applied. This experiment represents the process as described in EP0921919B1. Unwinding of the roving was observed to be irregular at times, the strands adhering to each other, and members for guiding the fibres to the wire-coating unit were found to become greasy and to collect dust and glass fibre fragments. Also breakage of glass filaments, resulting in groups of protruding curled filaments (fuzz) on the strand before the sheathing step, was observed. The results of testing are given in Table 1.

TABLE-US-00001 TABLE 1 White Isotropic Isotropic Charpy Charpy Charpy FDI LOI spots Strength Modulus 0° 45° 90° FDI F.sub.max (mass %) (number) (MPa) (MPa) (kJ/m.sup.2) (kJ/m.sup.2) (kJ/m.sup.2) (J/mm) (N) Ex 6 8.1 66.5 4113 10.6 12.6 11.5 4.3 2002 1 Ex 7 6.6 66.2 4088 10.4 12.1 12.9 4.4 1982 2 Ex 8 5.3 65.2 4041 10.0 12.3 12.0 4.6 1940 3 Ex 9 3.9 64.1 3967 11.0 13.3 12.2 4.0 1921 4 Ex 10 2.3 64.4 4017 11.0 12.8 12.0 4.6 1869 5 CE 7 4.5 62.3 4120 8.78 10.4 8.89 3.7 1777 6

EXAMPLES 7-9

[0059] Analogous to Examples 1-5, 30 mass % long glass fibre-reinforced polypropylene compositions were made, but now Type 30 roving SE4121 2400 Tex glass fibres containing filaments of 17 micron diameter were used. The results are given in Table 2, and indicate that a smaller filament diameter has a positive effect on mechanical properties, but that more impregnating agent is needed for optimum fibre dispersion (likely related to higher glass surface area).

EXAMPLE 10

[0060] Example 3 was repeated, but now a polypropylene composition based on SABIC® PP513MNK10 polypropylene impact copolymer, with a MFI of 70 g/10 min (230° C./2.16 kg) was used as polymer matrix. The results given in Table 2 indicate that the propylene copolymer results in better fibre dispersion, but somewhat lower mechanical strength and stiffness compared with a homopolymer matrix.

COMPARATIVE EXPERIMENT 11

[0061] Analogous to Example 10, a 30 mass % long glass fibre-reinforced thermoplastic composition was made, but now based on Performax® 507 Glass Fibres, in accordance to the process of EP0921919B1. The results are given in Table 2. Compared to Example 10, the process ran less stable (fuzz and fouling) and also mechanical properties are found to be lower.

TABLE-US-00002 TABLE 2 White Isotropic Isotropic FDI LOI spots Strength Modulus FDI F.sub.max (mass %) (number) (MPa) (MPa) (J/mm) (N) Ex 7 6 15.2 68.1 4239 4.3 1969 Ex 8 7 10.1 66.9 4195 4.2 1937 Ex 9 8 9 66.3 4162 4.1 1883 Ex 10 8 1.3 55.4 3658 4.6 2085 CE 11 7 1 51.0 3705 4.0 1850