INTERNAL LUBRICANT COMPOSITION AND USE

Abstract

The present invention relates to an internal lubricant composition comprising two or more esters in which each individual ester has a carbon chain length of between 20 and 44. The internal lubricant composition may suitably be incorporated in to a polyester polymer matrix, preferably comprising PET, PETg or PLA. Use of the internal lubricant composition in a polyester polymer matrix to improve processes for manufacture of final products from the polyester polymer matrix is also contemplated.

Claims

1. An internal lubricant composition suitable for use in a polyester polymer matrix composition comprising a mixture of two or more esters in which each individual ester has a carbon chain length of between 20 and 44.

2. An internal lubricant composition according to claim 1 comprising a mixture of two or more esters in which each individual ester has a carbon chain length between 28 and 34.

3. An internal lubricant composition according to claim 1 comprising two or more esters selected from the group comprising myrisityl myristate, myrisityl palmitate, palmityl myristate, palmityl palmitate, palmityl stearate, stearyl myristate, stearyl palmitate, stearyl stearate, stearyl arachidate and stearyl behenate.

4. An internal lubricant composition according to claim 1 comprising two or more esters selected from the group comprising myristyl myristate, myristyl palmitate, palmityl myristate, palmityl palmitate, stearyl myristate and stearyl palmitate.

5. An internal lubricant composition according to claim 3, wherein the composition comprises between four and ten esters selected from said group.

6. An internal lubricant composition according to claim 1, wherein each individual ester component may be present in an amount of 0.5% to 95% by weight (wt) of the total internal lubricant composition

7. An internal lubricant composition according to claim 1, wherein each individual ester component may be present in an amount of 0.5% to 45% by weight (wt) of the total internal lubricant composition.

8. An internal lubricant composition according to claim 1, wherein said composition comprises <1% to 17% myristyl myristate, 0.5% to 38% myristyl palmitate, 4% to 45% palmityl myristate, 4% to 45% palmityl palmitate, 2% to 20% stearyl myristate, 4% to 45% stearyl palmitate, <1% to 4% palmityl stearate, <1% to 4% stearyl stearate, <1% to 3% stearyl arachidate, and <1% to 4% stearyl behenate, by weight.

9. An internal lubricant composition according to claim 1, wherein said composition comprises 10% to 17% myristyl myristate, 2% to 28% myristyl palmitate, 15% to 42% palmityl myristate, 8% to 42% palmityl palmitate, 4% to 18% stearyl myristate and 6% to 12% stearyl palmitate, by weight.

10. A polyester polymer matrix comprising a polyester polymer and an internal lubricant composition in accordance with claim 1.

11. A polyester polymer matrix according to claim 10, where in the polyester polymer is selected from the group comprising poly(butylene terephthalate), poly(cyclohexanedimethylene terephthalate), poly(ethylene isophthalate), poly(ethylene 2,6-naphthalenedicarboxylate), poly(ethylene phthalate), poly(ethylene terephthalate), PETg (polyethylene terephthalate glycol), polycarbonates, polylactic acid (PLA), polyhydroxyalkanoates (PHA), and co-polymers thereof.

12. A polyester polymer matrix according to claim 10, wherein the polyester polymer comprises poly(ethylene terephthalate) or polylactic acid (PLA).

13. A polyester polymer matrix according to claim 10, wherein the polymer matrix composition comprises said internal lubricant composition in an amount of between 0.05 wt % to 1.0 wt %.

14. A polyester polymer matrix according to claim 13, wherein the polymer matrix composition comprises said internal lubricant composition in an amount of between 0.1 wt % to 0.75 wt %.

15. A polyester polymer matrix according to claim 10, further comprising one or more additional polymer additives.

16. A method for processing a polyester polymer matrix to produce a final polyester product comprising contacting the polymer matrix with an internal lubricant composition according to claim 1.

17. The method in accordance with claim 16, wherein processing of the polyester polymer matrix is carried out at a lower process temperature and/or pressure and/or mechanical stress, than would be possible in the absence of said internal lubricant.

18. The method in accordance with claim 16, wherein the process is any of thermoforming, injection moulding, extrusion, cast film extrusion, extrusion blow moulding, injection stretch blow moulding, stretch blow moulding and biaxial film orientation.

19. The method in accordance with claim 16, wherein the final polyester product is in the form of a container or film.

20. The method in accordance with claim 19, wherein the final polyester product is a bottle.

21. A method of internally lubricating a polyester polymer matrix by incorporating an internal lubricant composition according to claim 1.

22. A method of internally lubricating a polyester polymer matrix in accordance with claim 21, wherein incorporation of the internal lubricant is achieved be adding directly to the polymer matrix by melt dosing at the point of polymer resin extrusion, by conventional master batch addition or by incorporation using liquid colour systems.

Description

[0097] The present invention will now be described with reference to the Examples provided below and the Figures, in which:

[0098] FIG. 1 shows stress-strain data at a drawing speed of 16 m/min along x-axis two days after PET preform preparation.

[0099] FIG. 2 shows stress-strain data at a drawing speed of 16 m/min along y-axis two days after PET preform preparation.

[0100] FIG. 3 shows stress-strain data at a drawing speed of 16 m/min along x-axis ten days after PET preform preparation.

[0101] FIG. 4 shows stress-strain data at a drawing speed of 16 m/min along y-axis ten days after PET preform preparation.

[0102] FIG. 5 shows stress-strain data at a drawing speed of 64 m/min along x-axis ten days after PET preform preparation.

[0103] FIG. 6 shows stress-strain data at a drawing speed of 64 m/min along y-axis ten days after PET preform preparation.

[0104] FIG. 7 shows the comparative stress-strain curve of PETg versus PETg including 0.5 wt % internal lubricant at 1 m/min 1 day after PETg preform preparation.

EXAMPLES

Example 1—Effectiveness in PET

[0105] To demonstrate the effectiveness of the aforementioned internal lubricant compositions in improving the internal lubricancy of a polyester matrix (PET) the following test procedure was adopted.

[0106] Control PET sample square plaque preforms of polyethylene terephthalate (PET) were formed by injection moulding using PET resin LIGHTER C93 ex. Dow. LIGHTER C93 is a PET which is commercially available for the production of containers for food, beverages, and other liquids. It is known to be suitable for use in thermoforming, injunction moulding and blow moulding techniques.

[0107] Additionally, PET plus internal lubricant sample square plaque preforms comprising PET resin LIGHTER C93 ex. Dow with the addition of 0.5 wt % of internal lubricant were also formed (identified as “blend” in the Figures). The formulation of the internal lubricant is provided in Table 1 above.

[0108] The square plaque preforms prepared were 76 mm×76 mm in length and width and 1 mm in thickness/height.

[0109] The square plaque preforms prepared were subjected to film stretching via biaxial film orientation tests in a sequential constant width mode, i.e. first stretched along the x-axis and then subsequently stretched along the y-axis. More especially, the test involves carrying out deformation of test samples at speed. The orientation can occur using different deformation modes, such as sequential or simultaneous, as well as various rates and temperatures, equivalent to an industrial process. Multiple jaws grip the square test sample along its four sides. The jaws are connected to a motor connected arm providing smooth movement in both x & y axis. The test sample and jaws are provided inside a heating chamber where uniform heating is controlled and applied. Once the test sample and air present in the chamber have reached a temperature equilibrium, then the selected deformation rate (i.e. drawing or stretch speed) is applied and the test is conducted. Information regarding suitable equipment for conducting the experiments described above can be found in:

[0110] i) McKelvey, David & Menary, G. H. & Martin, Peter & Yan, Shiyong. (2017). Thermoforming of HDPE. AIP Conference Proceedings. 1896. 060006. 10.1063/1.5008069, available on-line via https://www.researchgate.net/publication/320446584 Thermoforming of HDPE or https://aip.scitation.org/doi/abs/10.1063/1.5008069.

[0111] ii) G. H. Menary (2012), Biaxial deformation of PET in stretch blow molding. Society of Plastic Engineers, Plastic Research Online, 10.1002/spepro.003911, available on-line via, http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.474.5846&rep=rep1&type=pdf.

[0112] The purpose of these tests was to assess the effect of the internal lubricant during biaxial orientation by comparing the stress-strain behaviour between control PET and PET plus internal lubricant samples in accordance with the present invention.

[0113] The biaxial film orientation test variables are shown in Table 1, below:

TABLE-US-00003 TABLE 1 Condition Variables Temperature (° C.) 95 100 105 Strain rate (s.sup.-1) 4 16 Drawing speed (m/min) 16 64 Stretch ratio (λ) 2.5 3 3.5

[0114] The biaxial film orientation tests were conducted as two sets of tests, time spaced: the first set of tests were performed two days after the initial preparation by injection moulding of the square plaque preforms, and the second set of tests were performed ten days after the initial preparation by injection moulding of square plaque preforms.

[0115] The test condition variables detailed above were chosen because they are within the normal processing range used in industry for injection stretch blow moulding of PET bottles and thermoforming for packaging applications, as well as in biaxial orientation of PET film. As such, the tests give a good indication of the utility of the present invention across these application areas.

[0116] Test Results

[0117] The stretching behaviour of the films formed from the square plaque preforms detailed above are shown in the FIGS. 1 to 6 provided herewith and are discussed below. The reduction of stretching load observed in the “blend” samples (as they are identified in the Figures) containing internal lubricant compared to the control PET samples can be attributed to the internal lubricating effect of the internal lubricant addition; all other aspects of the polymer matrix are the same.

[0118] FIG. 1 shows the stretching behaviour of films stretched two days after preform preparation. The stress-strain graph depicts a strain rate of 4/s along the X-axis, corresponding to a drawing speed of 16 m/min, and shows that the addition of 0.5 wt % internal lubricant reduces the required load at all three drawing temperatures tested. FIG. 2 shows stretching behaviour of the same samples subsequently drawn at a speed of 16 m/min along the Y-axis, again the reduction of required loading in the presence of the internal lubricant is demonstrated.

[0119] FIG. 3 shows the stretching behaviour of films stretched ten days after preform preparation. The stress-strain graph depicts a strain rate of 4/s along the X-axis, corresponding to a drawing speed of 16 m/min, and shows that the addition of 0.5 wt % internal lubricant reduces the required load in all three drawing temperatures, but especially at 95° C. and 100° C. The same behaviour described above in FIG. 3 is also observed in Y-axis direction stretching, as shown in FIG. 4; FIG. 4 shows the stretching behaviour of the same samples subsequently drawn at a speed of 16 m/min along the Y-axis.

[0120] Advantageously, the PET with internal lubricant could be drawn at lower temperatures as compared to blank PET, as demonstrated by the assistance to polymer matrix flow provided by the presence of the internal lubricant at this relatively low test temperature of 95° C.

[0121] FIG. 5 shows the stretching behaviour of films stretched ten days after preform preparation. The stress-strain graph depicts a strain rate of 16/s along the X-axis, corresponding to a drawing speed of 64 m/min, and shows that the addition of 0.5 wt % internal lubricant reduces the required load in all three drawing temperatures. FIG. 6 shows the stretching behaviour of the samples subsequently drawn at a speed of 64 m/min along the Y-axis. Again, the reduction in required load is observed as per in FIG. 5. As such, an improvement along both the y and x-axis are observed when the preform has rested for 10 days prior to stretching. This demonstrates that there may be an additional advantage to employing the internal lubricants of the present invention in those processes where longer periods between preform preparation and final product processing occurs.

[0122] The time period between the preform preparation (moulding) and the solid-phase orientation stage (film stretching in the Examples herewith) influences the overall stretching behaviour of the material. The required stretching load is lower when the time period between the preform and the solid-phase orientation stage is longer. This effect is observed with PET control samples, but the effect is greater for samples where the internal lubricant is present. As such, there seems to be a synergy or improvement realised by virtue of “resting” the preforms.

[0123] The reduction of stretching load when the internal lubricant is used means that drawing of such materials requires less energy when compared to control PET. It also allows such a material to be be drawn further (compared to control PET), since there is provision of load tolerance for additional stretching within the polymer matrix.

Example 2—Effectiveness in PETg

[0124] To demonstrate the effectiveness of the aforementioned internal lubricant compositions in improving the internal lubricancy of an alternative polyester matrix (PETg) the following test procedure was adopted.

[0125] Control PETg sample square plaque preforms of polyethylene terephthalate glycol (PETg) were formed by injection moulding using PETg resin Eastar GN001 ex. Eastman. Eastar GN001 is a PETg which is commercially available for the production of containers for cosmetics, food, beverages, and other liquids.

[0126] Additionally, PETg plus internal lubricant sample square plaque preforms comprising PETg resin Eastar GN001 ex. Eastman with the addition of 0.5 wt % of internal lubricant were also formed. The formulation of the internal lubricant is provided in Table 1 above.

[0127] The square plaque preforms prepared were 90 mm×90 mm in length and width and 1.2 mm in thickness/height. The preforms were prepared via injection moulding. After the plaque samples were produced, they were rested at room temperature for 24 hours and were then subjected to free tensile drawing at an elevated temperature of 90° C., i.e. above the PETg's glass transition temperature (T.sub.g). The tensile machine used was a Testometric M350-10CT fitted with a heating chamber. The heating chamber was preheated to the desired temperature. Each plaque sample was clamped, to provide a 40 mm gauge length, and the sample was subject to heating for 6 minutes. The maximum elongation was set at 140 mm which corresponds to a draw ratio of 3.5 (using the gauge length of 40 mm). The maximum drawing speed of the tensile machine was used, which in this case was 1 m/min. The complete tensile drawing test conditions are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Parameter Value Temperature (° C.) 90 Haul-off speed (mm/min) 1000 Elongation (mm) 140 Draw ratio, λ 3.5 Soaking time (min) 6

[0128] A total of 6 sample plaques were tested for the control PETg and 5 sample plaques were tested for the PETg plus 0.5% internal lubricant. All the (engineering) stress-strain graphs were collected and the average curve from each material tested was calculated.

[0129] Test Results

[0130] The comparison between the average stress-strain curve of the control PETg versus the PETg plus 0.5% internal lubricant is shown in FIG. 7 and it is clear that the use of the internal lubricant in the PETg reduces the drawing stress. Here, each curve shown relates to the average of the total samples tested for each respective material. The advantage of the effect on the PETg due to the internal lubricant is the ability to stretch the material containing the internal lubricant at a lower temperature, or to stretch it more at the same temperature.

[0131] The advantages of the internal lubricant compositions of the present invention can be readily appreciated by reference to the above results.