PROCESS FOR PRODUCING GLASS FIBER-REINFORCED COMPOSITION

Abstract

The invention relates to a process for producing a glass fiber-reinforced thermoplastic polymer composition, comprising the sequential steps of: a) unwinding from a first package of at least one first continuous glass multifilament strand having a first filament thickness t1 and a second package of at least one second continuous glass multifilament strand having a second filament thickness t2 larger than the first filament thickness t1 and b) applying a sheath of a thermoplastic polymer composition around the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand to form a sheathed continuous multifilament strand.

Claims

1. A process for producing a glass fiber-rein forced thermoplastic polymer composition, comprising the sequential steps of: a) unwinding from a first package of at least one first continuous glass multifilament strand having a first filament thickness t1 and a second package of at least one second continuous glass multifilament strand having a second filament thickness t2 larger than the first filament thickness t1 and b) applying a sheath of a thermoplastic polymer composition around the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand to form a sheathed continuous multifilament strand comprising the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand.

2. The process according to claim 1, wherein t2 is at least 1 μm larger than t1.

3. The process according to claim 1, wherein t1 is 1 to 45 μm.

4. The process according to claim 1, wherein the thermoplastic polymer composition comprises at least 80 wt % of the thermoplastic polymer.

5. The process according to claim 1, wherein the melt flow index of the thermoplastic polymer composition is in the range from 20 to 150 dg/min as measured according to ISO1133-1:2011 2.16 kg/230° C.).

6. The process according to claim 1, wherein the amount of glass is in the range of 10 to 70 wt % based on the sheathed continuous multifilament strand.

7. The process according to claim 1, wherein the process further comprises between steps a) and b) the step a1) of applying an impregnating agent to each of the continuous glass multifilament strands to which the sheath is to be applied in step b).

8. The process according to claim 7, wherein the amount of impregnating agent in the sheathed continuous multifilament strand is 0.50 to 18 wt % based on the sheathed continuous multifilament strand.

9. The process according to claim 7, wherein the amount of the impregnated continuous multifilament strands is in the range of 10 to 70 wt % based on the sheathed continuous multifilament strand and wherein the amount of the 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 strands and the sheath is 100 wt %.

10. The process according to claim 1, wherein the process further comprises the step of cutting the sheathed continuous glass multifilament strand into pellets.

11. The process according to claim 1, wherein step a) involves unwinding from a third package of at least one third continuous glass multifilament strand having a third filament thickness t3, wherein t3 is different from t1 and t2 and step b) involves applying the sheath around the at least one third continuous glass multifilament and the sheathed continuous multifilament strand further comprises the at least one third continuous glass multifilament.

12. The glass fiber-reinforced thermoplastic polymer composition obtained by the process of claim 1.

13. A glass fiber-reinforced thermoplastic polymer composition comprising a sheathed continuous multifilament strand comprising at least one first glass multifilament strand having a first filament thickness t1 and at least one second continuous glass multifilament strand having a second filament thickness t2 larger than the first filament thickness t1 and a sheath of a thermoplastic polymer composition provided around the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament.

14. An article comprising the composition according to claim 12.

15. (canceled)

Description

EXAMPLES

[0102] Several long glass fiber-reinforced polypropylene compositions were produced. The respective amounts of the components of the compositions are shown in Table 1.

[0103] One or two types of continuous glass multifilament strands, depending on the example, were unwound from the packages and transported to the impregnating agent applicator. The impregnating agent, similar to the impregnating agent disclosed in WO2009/0808231, was molten and mixed at a temperature of 160° C. and applied to the continuous glass multifilament strand after unwinding from the package by using an applicator.

[0104] The impregnating step was carried out in a single step on the continuous glass multifilament strands.

[0105] The sheathing step was performed in-line directly after the impregnating step, using a 75 mm twin screw extruder (manufactured by Berstorff, screw UD ratio of 34), at a temperature of about 250° C., which fed the molten polypropylene matrix material and additives to an extruder-head wire-coating die. The sheathed strand was cut into pellets of 15 mm length. The pellets were moulded into appropriate shapes for the measurements of various properties as given in Table 2.

[0106] The homogeneity of the distribution of the glass fibers in the moulded article was determined by the following method:

[0107] 15 plaques with dimension 310 mm*270 mm*3 mm were made by injection moulding of the pellets according to the conditions in the table below. The pellets have a black color due to the color masterbatch. When the glass fibers are poorly dispersed, more glass fibers appear on the surface of the plaques as “white spots” on the black plaques. The number of white spots was counted and an average of the 15 plaques was determined, which represents the degree of inhomogeneity of the distribution of the glass fibers in the moulded article.

TABLE-US-00001 Feed temperature 260° C. Mould temperature at injection side  40° C. Mould temperature at closing side  50° C. Injection pressure 1300 bar

[0108] The tensile strength was measured according to ISO527/1A(II) after conditioning for 7 days at 23° C. or 7 days at 120° C.

[0109] The isotropic tensile modulus was measured according to ISO 527/1B (0°, 45°, 90°) after conditioning for 7 days at 120° C.

[0110] The free glass was measured by the following method:

[0111] 1 kg of the obtained pellets was passed through a suction pipe having a length of 2 m which has 6 bends (180 degree bend) by a suction pressure of 260 mbar at 50 Hz. At the end of the suction pipe, a container and a filter having a hole size lower than the fiber diameter are provided. The container receives the pellets and the filter catches the free glass. The weight of the free glass present in the filter was measured and divided by the initial weight of the pellets, i.e. 1 kg, which result represents the free glass.

TABLE-US-00002 TABLE 1 Composition wt % GF1 and/or GF2 30.12 Impregnating agent 2.64 PP1 or PP2 63.42 Light stabilizer 0.12 Antioxidant 0.4 Coupling agent 3 Color masterbatch 0.3 Total 100

[0112] PP1 is a propylene homopolymer having an MFI (ISO1133-1:2011, 230° C./2.16 kg) of 50 dg/min

[0113] PP2 is a propylene-ethylene copolymer with an ethylene content of 53 wt %, having an MFI (ISO1133-1:2011, 230° C./2.16 kg) of 70 dg/min.

[0114] GF1 is standard Type 30 roving SE4220, supplied by 3B as a roving package, having filament diameter of 12 μm and contain aminosilane-containing sizing composition. GF2 is standard Type 30 roving SE4220, supplied by 3B as a roving package, having filament diameter of 24 μm and contain aminosilane-containing sizing composition.

[0115] Coupling agent is polypropylene grafted with maleic anhydride; commercial name Exxelor 1020.

TABLE-US-00003 TABLE 2 CEx 1 Ex 2 CEx 3 CEx 4 Ex 5 CEx 6 Polypropylene PP1 PP1 PP1 PP2 PP2 PP2 Glass fibers 100 wt 50 wt% 100 wt 100 wt 50 wt% 100 wt % GF1 GF1- % GF2 % GF1 GF1- % GF2 50 wt% 50 wt% GF2 GF2 White spot 11.2 5.9 0.9 21.3 11.3 1.5 Tensile strength N/mm2 112 104.4 97.9 103.6 97.4 89.5 (@23° C. after 7 days) Tensile strength N/mm2 48.7 41.4 35.7 37.6 32 28.5 (@120° C. after 7 days) Isotropic Tensile N/mm2 1991.1 1933 1816.8 1953.7 1849 1628.3 Modulus @ 120° C. after 7 days Free glass cold gr/kg 0.0342 0.0615 0.6256 0.0449 0.0407 0.1537 Free glass after heat gr/kg 0.015 0.0653 0.576 0.0234 0.0258 0.0713 treatment

[0116] The use of only glass multifilament strands with a large diameter led to a large amount of free glass (CEx 3, CEx 6). Mixing of glass multifilament strands with a small diameter drastically reduced the free glass (Ex 2, Ex 5). The tensile strength and the tensile modulus also became much higher by the mixture compared to the use of only glass multifilament strands with a large diameter. The difference is especially large after the samples are subjected to a high temperature.

[0117] A further reduction of the free glass as well as a further improvement in the tensile strength and the tensile modulus were observed by using glass multifilament strands with a small diameter (CEx 1, CEx 4). However, the white spot, i.e. the inhomogeneity of the distribution of the glass fibers, became unacceptably high. Ex 2 and Ex 5 which use two types of glass multifilament strands with different diameters have a good balance of low free glass, high tensile properties and low white spot.