USE OF HYDROTREATED SYNTHETIC FISCHER-TROPSCH-WAXES IN POLYOLEFIN-BASED HOT MELT ADHESIVES

Abstract

The present invention is concerned with the use of hydrotreated synthetic Fischer-Tropsch waxes in polyolefin-based hot melt adhesive compositions, wherein the hydrotreated synthetic Fischer-Tropsch waxes modify the color degradation in the polyolefin-based hot melt adhesive compositions and are characterized by a polydispersity between 1.02 and 1.06.

Claims

1. Use of a hydrotreated synthetic Fischer-Tropsch wax in polyolefin-based hot melt adhesive compositions to modify the color degradation of the hot melt adhesive composition, wherein the hydrotreated synthetic Fischer-Tropsch wax is characterized by a congealing point in a range of 75 to 110° C.; a Saybolt-color according to ASTM D 156 below or equal to 29; and a polydispersity ÐM=Mw/Mn of between 1.02 and 1.06.

2. The use according to claim 1, wherein the hydrotreated synthetic Fischer-Tropsch wax has a molecular mass (number average) between 500 and 1200 g.Math.mol.sup.−1, preferably between 600 and 1000 g.Math.mol.sup.−1 and more preferably between 880 and 920 g.Math.mol.sup.−1.

3. The use according to any of the preceding claims, wherein the hydrotreated synthetic Fischer-Tropsch wax has a content of branched hydrocarbons be-tween 10 and 25 wt.-%.

4. The use according to any of the preceding claims, wherein the hydrotreated synthetic Fischer-Tropsch wax has a congealing point the range of 90 to 105° C.

5. The use according to any of the preceding claims, wherein the hydrotreated synthetic Fischer-Tropsch wax has a Saybolt-color according to ASTM D 156 of below or equal to 10.

6. The use according to any of the preceding claims, wherein the hydrotreated synthetic Fischer-Tropsch wax has polydispersity ÐM=Mw/Mn of between 1.03 and 1.05.

7. The use according to any of the preceding claims, wherein the hydrotreated synthetic Fischer-Tropsch wax is further characterized by one or more of the following properties: a heat of fusion determined with differential scanning calorimetry of 200 to 250 J/g, more preferably of 207 to 245 J/g, even more preferably of 210 to 240 J/g and most preferably of 220 to 235 J/g; a penetration at 25° C. of below or equal to 5 1/10 mm, more preferably below or equal to 1 1/10 mm; a penetration at 40° C. of below or equal to 10 1/10 mm; and a Brookfield viscosity at 135° C. of above or equal to 10 mPa.Math.s, more preferably above or equal to 12 mPa.Math.s.

8. The use according to any of the preceding claims, wherein the hydrotreated synthetic Fischer-Tropsch wax is used in an amount of 2 to 40 wt.-%, preferably 5 to 30 wt.-%, in the polyolefin-based hot melt adhesive composition.

9. The use according to any of the preceding claims, wherein at least one polyolefin polymer is present in the hot melt adhesive composition, preferably in the range of 20 to 80 wt.-%, more preferably in the range of 40 to 50 wt.-%.

10. The use according to any of the preceding claims, wherein an antioxidant is present in the hot melt adhesive composition, preferably in the range of 0.1 to 2 wt.-%.

11. The use according to any of the preceding claims, wherein a tackifier is present in the hot melt adhesive composition, preferably in an amount of 10 to 50 wt.-% and more preferably 20 to 40 wt.-%.

12. The use according to any of the preceding claims, wherein a process oil is present in the hot melt adhesive composition, preferably in an amount of 5 to 15 wt.-%.

13. The use according to claim 9, wherein the polyolefin polymer is selected from the group of amorphous poly-alpha-olefin copolymers (APAO), polypropylene homopolymers or polybutene homopolymers, preferably from the group of ethylene-propylene copolymers, ethylene-butene copolymers or ethylene-octene copolymers, more preferably with an ethylene- or propylene content of more than or equal to 50 wt.-%.

Description

EXAMPLES

[0100] Different polymers (see table 1) and Fischer-Tropsch waxes (see table 2) have been used to prepare a variety of hot melt adhesive compositions (hereinafter from time to time referred to as “formulations”) (see tables 3 to 5) by melt blending.

[0101] The melt blending was conducted in a mixing vessel at 150° C. In the first step the antioxidant and half the amount of polymer, as well as half the amount of wax were mixed for 10 minutes at 60 rpm until the polymer was completely molten. In a second step half the amount of resin was added and mixed for 15 minutes at 60 rpm. In a third step the rest of the polymer and wax were added and mixed for 10 minutes at 60 rpm until completely molten. In a last step the mixture was transferred into a release coated container, cooled down and solidified.

TABLE-US-00001 TABLE 1 Data of used polymers Affinity Koattro Vistamaxx GA 1950 PB M 600M 8880 Brookfield 17000 13500 1200 viscosity @190° C. @177° C. [mPa .Math. s] ASTM D 3236 R&B softening 70 n.d. 97 point [° C.] ASTM E 28 Density [g .Math. cm.sup.−3] 0.874 0.89 0.879 Tg [° C.] −56.1 n.d. −22 ASTM D 3418

TABLE-US-00002 TABLE 2 Data of used Fischer-Tropsch waxes SX 105-1 C105-1 C105-2 C105-3 C105-4 C80 C80M Congealing point [° C.] 101 102 102 102 102 83 78 ASTM D 938 Saybolt color ASTM D 156 30 3 21 23 26 28 16 Brookfield viscosity 10.9 13.0 13.0 13.0 13.0 4.0 3.7 @135° C. [mPa .Math. s] Penetration @25° C. 1 1 1 1 1 7 7 [1/10 mm] ASTM D 1321 Penetration @65° C. 9 9 9 9 9 66 51 [1/10 mm] ASTM D 1321 Molar mass (number 920 900 900 900 900 600 600 average) [g .Math. mol.sup.−1] Iso-alkanes [wt.-%] 10 10 10 10 10 12.4 12.4 Polydispersity 1.069 1.038 1.038 1.038 1.038 1.023 1.023

TABLE-US-00003 TABLE 3 Composition of hot melt adhesives with Affinity GA 150 1 2 3 Formulation comp. comp. comp. 4 5 6 7 Polymer 45.5 45.5 45.5 45.5 45.5 45.5 45.5 (Affinity GA 1950) Tackifier 34 34 34 34 34 34 34 (Eastotac H130W) Antioxidant 0.5 0.5 0.5 0.5 0.5 0.5 0.5 (Irganox 1010) C80M 20 C80 20 SX105 20 C105-1 20 C105-2 20 C105-3 20 C105-4 20

TABLE-US-00004 TABLE 4 Composition of hot melt adhesives with Koattro PB M 600M 8 9 10 Formulation comp. comp. comp. 11 12 13 Polymer 45.5 45.5 45.5 45.5 45.5 45.5 (Koattro PB M 600M) Tackifier 34 34 34 34 34 34 (Eastotac H130W) Antioxidant 0.5 0.5 0.5 0.5 0.5 0.5 (Irganox 1010) C80M 20 C80 20 SX105 20 C105-1 20 C105-3 20 C105-4 20

TABLE-US-00005 TABLE 5 Composition of hot melt adhesives with Vistamaxx 8880 Formulation 14 comp. 15 comp. 16 comp. 17 18 Polymer (Vistamaxx 8880) 45.5 45.5 45.5 45.5 45.5 Tackifier (Eastotac H130W) 34 34 34 34 34 Antioxidant (Irganox 1010) 0.5 0.5 0.5 0.5 0.5 C80M 20 C80 20 SX105 20 C105-3 20 C105-4 20

[0102] All formulations have been thermally aged for 96 hours in an oven at 170° C. At certain time intervals HMA buttons were cast in a silicone mould to produce test samples for colour stability analyses. The test samples, in a specific set, were then compared against the zero aged sample to produce comparative results. For that the CIElab-color values of the test samples were determined by taking a picture of the according sample with a digital camera and converting the RGB colors thereof in CIELab values with the ImageJ-software. The relative color perception change was calculated based on the formula below and plotted over time. The gradient of the linear fit of this plotted data resulted in the average linear color degradation rate of each formulation (see tables 6 to 8).

[00002]$\Delta E_{00}^{\star }=\sqrt{{\left(\frac{\Delta L^{\prime }}{k_L{S}_L}\right)}^2+{\left(\frac{\Delta C^{\prime }}{k_C{S}_C}\right)}^2+{\left(\frac{\Delta H^{\prime }}{k_H{S}_H}\right)}^2+R_T\frac{\Delta C^{\prime }}{k_C{S}_C}\frac{\Delta H^{\prime }}{k_H{S}_H}}$

TABLE-US-00006 TABLE 6 Average linear color degradation rate of formulations 1 to 7 Average linear color degradation rate Formulation Run 1 Run 2 1 comp. 0.28 2 comp. 0.25 3 comp. 0.15 0.28 4 0.32 5 0.29 6 0.13 7 0.34

TABLE-US-00007 TABLE 7 Average linear color degradation rate of formulations 8 to 13 Average linear color degradation rate Formulation Run 1 Run 2  8 comp. 0.27  9 comp. 0.20 10 comp. 0.27 0.30 11 0.22 12 0.12 13 0.19

TABLE-US-00008 TABLE 8 Average linear color degradation rate of formulations 9 to 18 Average linear color degradation rate Formulation Run 1 Run 2 14 comp. 0.29 15 comp. 0.19 16 comp. 0.19 0.24 17 0.10 18 0.26

[0103] From this data it can be clearly seen that not only the congealing point of the Fischer-Tropsch waxes is important for reducing the color degradation in hot melt adhesives (the higher the congealing point the better), but also that it is important that the waxes are hydrotreated. Nevertheless, it can also be seen that hydrotreating alone is not decisive and that hydrotreated waxes with a low Saybolt-color can surprisingly outperform similar waxes with a high Saybolt-color in reducing the color degradation. Without being bound to this theory it is assumed that one reason for that is the carbon chain distribution of the according waxes and that a narrower distribution represented by a smaller polydispersity value is more important than a low Saybolt-color of the used wax.