Polybutylene Terephthalate With Low THF Content

Abstract

The invention relates to the use of at least one copolymer of at least one olefin, preferably an alpha-olefin, and at least one acrylic ester of an aliphatic alcohol, wherein the Melt Flow Index of the copolymer is not less than 100 g/10 min, for production of polybutylene terephthalate-based automotive interior parts having a low tetrahydrofuran content by injection molding.

Claims

1. An automotive interior part containing a composition based on polybutylene terephthalate and at least one copolymer of at least one olefin and at least one acrylic ester of an aliphatic alcohol, wherein the Melt Flow Index of the copolymer to be determined according to DIN EN ISO 1133 [2] at 190° C. and a test weight of 2.16 kg is not less than 100 g/10 min and based on 100 parts by mass of polybutylene terephthalate the composition employs 0.1 to 20 parts by mass of copolymer.

2. The automotive interior part as claimed in claim 1, wherein the Melt Flow Index is not less than 150 g/10 min.

3. The automotive interior part as claimed in claim 1, wherein the olefin employed is an alpha-olefin.

4. The automotive interior part as claimed in claim 3, wherein the olefin employed is at least one selected from the group of ethene, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 3-methyl-1-pentene.

5. The automotive interior part as claimed in claim 1, wherein an aliphatic alcohol having 1 to 30 carbon atoms is employed.

6. The automotive interior part as claimed in claim 1, wherein the copolymer consists of at least one olefin and at least one acrylic ester of an aliphatic alcohol, wherein the Melt Flow Index of the copolymer is not less than 100 g/10 min.

7. The automotive interior part as claimed in claim 6, wherein the copolymer consists of ethene and (2-ethyl)hexyl acrylate.

8. The automotive interior part as claimed in claim 1, having a TVOC to be determined according to VDA 277 of <50 μgC/g and a VOC.sub.THF to be determined according to VDA 278 of <8 μg/g.

9. The automotive interior part as claimed in claim 1, wherein the copolymer is employed in combination with at least one filler.

10. The automotive interior part as claimed in claim 9, wherein 0.001 to 70 parts by mass of filler per 100 parts by mass of polybutylene terephthalate are employed.

11. The automotive interior part as claimed in claim 9, wherein the filler is selected from the group comprising talc, mica, silicate, quartz, titanium dioxide, wollastonite, kaolin, kyanite, amorphous silicas, magnesium carbonate, chalk, feldspar, barium sulfate, glass spheres, glass fibers and carbon fibers.

12. A method for preparing polybutylene terephthalate-based compounds for processing into injection molded parts having a TVOC to be determined according to VDA 277 of <50 μgC/g and a VOC.sub.THF to be determined according to VDA 278 of <8 μg/g, comprising compounding polybutylene terephthalate with least one copolymer of at least one olefin and at least one acrylic ester of an aliphatic alcohol, wherein the Melt Flow Index (MFI) of the copolymer to be determined according to DIN EN ISO 1133 [2] at 190° C. and a test weight of 2.16 kg is not less than 100 g/10 min, wherein per 100 parts by mass of PBT 0.1 to 20 parts by mass of copolymer are employed.

13. A method for reducing the outgassing of tetrahydrofuran from injection molded polybutylene terephthalate-based automotive interior parts, comprising compounding polybutylene terephthalate with at least one copolymer of at least one olefin and at least one acrylic ester of an aliphatic alcohol, wherein the Melt Flow Index of the copolymer to be determined according to DIN EN ISO 1133 [2] at 190° C. and a test weight of 2.16 kg is not less than 100 g/10 min and per 100 parts by mass of polybutylene terephthalate the compounds employ 0.1 to 20 parts by mass of copolymer.

14. The method as claimed in claim 12, wherein the olefin is an alpha-olefin.

15. The method as claimed in claim 12, wherein the aliphatic alcohol has 1 to 30 carbon atoms.

16. The method as claimed in claim 12, wherein the Melt Flow Index is not less than 150 g/10 min.

Description

EXAMPLES

TVOC

[0099] In order to determine the TVOC value of samples in the context of the present invention about 2 g in each case of a comminuted sample were according to the specification of VDA 277 (pieces of about 20 mg) weighed into a 20 mL sample vial having a screw cap and septum. These were heated in a headspace oven for 5 hours at 120° C. A small sample of the gas space was then injected into the gas chromatograph (Agilent 7890B GC) and analyzed. An Agilent 5977B MSD detector was used. The analysis was performed in triplicate and evaluated semi-quantitatively by means of acetone calibration. The result was determined in μgC/g. The threshold value not to be exceeded in the context of the present invention was 50 μgC/g. The analysis was based on the VDA 277 test specification.

VOC

[0100] The VOC value was determined when according to the specification of VDA 278 20 mg of a sample was weighed into a thermal desorption tube for a GERSTEL-TD 3.5 instrument with a frit from Gerstel (020801-005-00). Said sample was heated to 90° C. for 30 minutes in a helium stream and the thus-desorbed substances were frozen out at −150° C. in a downstream cold trap Once the desorption time had elapsed the cold trap was quickly heated to 280° C. and the collected substances were separated by chromatography (Agilent 7890B GC). Detection was effected using an Agilent 5977B MSD. Evaluation was effected semi-quantitatively by means of toluene calibration. The result was determined in μg/g. The threshold value not to be exceeded in the context of the present invention was 100 μg/g of total VOC and 8 μg/g of THF. The analysis was based on the VDA 278 test specification.

Reactants

[0101] Polybutylene terephthalate (PBT): LANXESS Pocan® B1300

[0102] Copolymer (XF): Arkema Lotryl® 37EH550

[0103] Glass fiber (GF): LANXESS CS7967D, glass fibers made of E glass surface-coated with 0.9% by weight of silane having an average length in the range of 4.5 mm and an average filament diameter of 10 micrometers.

Preparation of the Samples

Example 1

[0104] The employed compounder was a ZSK 92 from Coperion. The machine was operated at a melt temperature of about 270° C. and a throughput of 4 tons per hour. The strands were cooled in a water bath, dried on a ramp in an air stream and then subjected to dry pelletization.

[0105] The example employed a PBT molding compound containing 47.3 parts by mass of chopped glass fibers per 100 parts by mass of PET, and 9.5 parts by mass of copolymer per 100 parts by mass of PBT. The thus-employed PBT had a TVOC value determined according to VDA 277 of 170 μgC/g.

[0106] The compounded material was then dried for 4 h at 120° C. in a dry air dryer and processed by injection molding under standard conditions (260° C. melt temperature, 80° C. mold temperature).

Comparative Example

[0107] The employed compounder was a ZSK 92 from Coperion. The machine was operated at a melt temperature of about 270° C. and a throughput of 4 tons per hour. The strands were cooled in a water bath, dried on a ramp in an air stream and then subjected to dry pelletization.

[0108] The example employed a PBT molding compound containing 43.3 parts by mass of chopped glass fibers per 100 parts by mass of PBT. The thus-employed PBT had a TVOC value determined according to VDA 277 of 170 μgC/g.

[0109] The compounded material was dried for 4 h at 120° C. in a dry air dryer and processed by injection molding under standard conditions (260° C. melt temperature, 80° C. mold temperature).

TABLE-US-00002 TABLE 2 VDA 277: VDA 278: Parts by mass based TVOC R.sub.THF THF R.sub.THF on 100 parts by mass of PBT [μgC/g] [μgC/g %] [μg/g] [μg/g %] Comparative example: 43.3 parts by mass of GF Pellets 50 0.65 4.9 0.07 Component (injection molded) 63.0 0.81 6.0 0.09 Example (inventive): 47.3 parts by mass of GF + 9.5 parts by mass of copolymer Pellets 10.1 0.06 <0.95 <0.02 Component (injection molded) 43.2 0.23 3.2 0.02

[0110] Tab. 2 shows the TVOC values measured according to the specification of VDA 277 on the dried pellets and on the injection molded molded part, and also the THF response (R.sub.THF) which is derived from the THF content on the TVOC in μgC/g divided by the percentage of PBT in the molding compound. The lower this value, the less THF is produced per PBT chain. Also shown are the THF values measured according to the specification of VDA 278 on the dried pellets and on the injection molded molded part in the state according to the specification—and the associated R.sub.THF values.

[0111] The test results reported in Tab. 2 show that the addition of 9.5 parts by mass of copolymer to 100 parts by mass of PBT in the inventive example results in a marked reduction in the amount of THF and thus in the total emission. What is particularly surprising here is the significant reduction in THF equivalents based on the amount of PBT substance. This effect on the formation of THF from PBT during processing was unexpected for those skilled in the art since a person skilled in the art would not have expected the copolymer to have any reactive effect.