Polymeric materials

Abstract

A preform for a container comprises a polymer composition which includes tungsten oxide particles, for example WO.sub.2.72 or WO.sub.2.92.

Claims

1. A preform for a container comprising a polymer composition and particles, the polymer composition consisting essentially of polyethylene terephthalate and the particles consisting of tungsten oxide particles of general formula WOx where 2.65<=x<=2.95, wherein said polymer composition includes 5 ppm to 150 ppm tungsten oxide particles, wherein at least 99 wt % of said preform is made up of said polymer composition, wherein said polymer composition includes at least 99 wt % of a polyester polymer, wherein said preform has an L* of at least 63, wherein at least 99 wt % of said tungsten oxide particles have size of less than 20 μm, wherein said tungsten oxide particles have a span (S) from 0 to 5 where S is calculated by the following equation:
S=(d.sub.90-d.sub.10)/d.sub.50 where d.sub.90 represents a particle size in which 90% of the volume is composed of particles having a smaller diameter than the stated d.sub.90; d.sub.10 represents a particle size in which 10% of the volume is composed of particles having a diameter smaller than the stated d.sub.10; and d.sub.50 represents a particle size in which 50% of the volume is composed of particles having a diameter larger than the stated d.sub.50 value and 50% of the volume is composed of particles having a diameter smaller than the stated d.sub.50 value.

2. The preform according to claim 1, wherein the tungsten oxide particles are of formula WO.sub.2.72 or WO.sub.2.9.

3. The preform according to claim 1, wherein the tungsten oxide particles are of formula WO.sub.2.72.

4. The preform according to claim 1, wherein said polymer composition includes 20 ppm to 50 ppm tungsten oxide particles.

5. The preform according to claim 1, wherein said tungsten oxide particles have a d.sub.50 of less than 50 μm.

6. The preform according to claim 1, wherein said tungsten oxide particles have a d.sub.50 of less than 0.05 μm.

7. The preform according to claim 1, wherein said preform has a b* of less than 2.0 and a* in the range −1 to 0.

8. The preform according to claim 1, wherein about 100 wt % of said preform is made up of a polyester composition, said polyester composition comprising 5 to 100 ppm of said tungsten oxide particles which consist essentially of WO.sub.2.72.

9. The preform of claim 1, wherein said preform comprises an injection moulded preform for a container which is arranged to be stretch blow moulded to define the container.

10. The preform of claim 1, comprising 5 to 100 ppm of said tungsten oxide particles.

11. The preform according to claim 1, wherein S is in the range 0.01 to 2.

12. The preform according to claim 11, wherein said preform is test-tube shaped.

13. The preform according to claim 1, wherein said preform has a weight in the range 15 to 40 g.

14. The preform according to claim 13, wherein said preform includes 0.00009 g to 0.006 g tungsten oxide particles.

15. The preform of claim 1 wherein the tungsten oxide particles provide at least 20 ppm tungsten oxide and less than 50 ppm tungsten oxide particles in said polymer composition.

16. A preform for a container comprising a polymer composition and particles, the polymer composition consisting essentially of polyethylene terephthalate and the particles consisting of tungsten oxide particles of general formula WOx where 2.65<=x<=2.95, said tungsten oxide particles providing reheat improvement to the polymer composition, wherein said polymer composition includes 5 ppm to 150 ppm tungsten oxide particles, wherein said preform is a test-tube shaped bottle preform suitable for manufacturing the container by stretch blow molding, and wherein said preform has an L* of at least 70.

17. The preform of claim 16, wherein said tungsten oxide particles have a span (S) from 0 to 5 where S is calculated by the following equation:
S=(d.sub.90-d.sub.10)/d.sub.50 where d90 represents a particle size in which 90% of the volume is composed of particles having a smaller diameter than the stated d.sub.90; d.sub.10 represents a particle size in which 10% of the volume is composed of particles having a diameter smaller than the stated d.sub.10; and d.sub.50 represents a particle size in which 50% of the volume is composed of particles having a diameter larger than the stated d.sub.50 value and 50% of the volume is composed of particles having a diameter smaller than the stated d.sub.50 value.

Description

(1) Specific embodiments of the inventions will now be described, by way of example, with reference to accompanying figures in which:

(2) FIG. 1 is a plot of light transmission v peak preform reheat for selected preforms;

(3) FIG. 2 is a plot of peak preform reheat temperature v. loading (ppm) of various tungsten oxide (WO) additives;

(4) FIGS. 3 and 4 include plots of peak preform reheat v. active loading; and plots of preform reheat v. preform L* for different reheat additives;

(5) FIG. 5 includes plots of peak preform reheat v. active loading; and plots of preform reheat v. preform L* for two different tungsten oxide samples; and

(6) FIG. 6 is a plot of b* v. loading (ppm) for reheat additives.

(7) The following materials are referred to hereinafter:

(8) C93—refers to Lighter™ C93 which is a standard (non-reheat) PET bottle grade polymer from Equipolymers. It has an IV of 0.08. This was used as a control.

(9) Un-milled WO2.72—refers to WO.sub.2.72.

(10) Milled WO2.72—refers to a milled WO.sub.2.72.

(11) Un-milled WO2.9—refers to WO.sub.2.9.

(12) Milled WO2.9—refers to milled WO.sub.2.9.

(13) The particle sizes of the aforementioned tungsten oxide (WO) samples were examined. A Beckman Coulter LS230 Laser Diffraction Particle Size Analyzer, fitted with a Micro Volume Module filled with dichloromethane was used. The samples were pre-diluted in mineral oil before addition to the module. Samples were run many times and data averaged.

(14) Results were as follows:

(15) TABLE-US-00001 Mean Median Sample μm μm Un-milled WO2.72 5.98 4.04 Milled WO2.72 1.22 0.97 Un-milled WO2.9 9.91 7.23 Milled WO2.9 2.40 1.89

(16) Titanium nitride—commercially available titanium nitride reheat additive.

(17) U1—activated carbon reheat additive sold by Polytrade, having D50=<0.5 μm and a maximum particle size of 2 μm.

(18) Optical, for example L*a*b*, data for preforms was measured in transmittance using a Minolta CM-3700d spectrophotometer (D65 illumination 10° observer, specular included, UV included) linked to an IBM compatible PC. Tests are undertaken using a standard preform holder supplied by Minolta.

EXAMPLE 1

Preparation of Preforms

(19) Liquid dispersions comprising the reheat additives in a carrier medium were formulated and added at the throat of an injection moulding machine onto dry C93 polymer. Preforms were then made from the polymer, using a 160-ton HUSKY injection moulding machine which made two preforms per shot. The injection moulding was conducted at 270° C. Each preform weighed approximately 35 grams and was cylindrical, approximately 130 mm in length with a screw top base. The preforms could be blown into one litre bottles with a petaloid base.

EXAMPLE 2

Method for Assessing Reheat

(20) Preforms for all samples/batches are stored in the same area and are allowed to condition for at least 24 hours to ensure that all the preforms being tested are of the same starting temperature.

(21) Standard settings are entered into a Sidel SB-01 stretch blow moulding machine. The machine houses two banks of ovens each bank containing 9×1500 W+1×2000 watt infra red heating lamps. 10 lamps per oven 20 lamps in total.

(22) A set throughput rate is entered which is 1000 b/p/h (bottles per hour). At this production rate the preforms take approximately 45 seconds to pass through the ovens. As the preforms pass through the ovens they are automatically rotated at a constant rate so the entire outside surface of the preforms are equally exposed to the oven lamps.

(23) The machine heating coefficient is switched off (this is a function that when active automatically controls the energy supplied to the oven lamps in an attempt to guide the preform reheat temperature to a predetermined set point) as a set amount of I.R. energy is supplied to every preform so there is no bias.

(24) Each lamp is set at 60% power and a master energy setting that controls the power to every lamp is also set to 60%. At these conditions the oven lamps are all operating at 60% of 60% of their maximum operating ability.

(25) After the preforms pass through the ovens there is approximately a 3 second conditioning period (no I.R. energy exposure) before they pass an infra red camera that measures the preform surface temperature. The camera is connected to a data capture station which records all preform surface temperatures as they pass by.

(26) A minimum of five preforms from a batch are tested and an average reheat figure gained. Preforms representing each batch are entered into the machine in a staggered formation so no one batch gains any bias. By way of example, if a comparison is to be drawn of the reheat behaviour of three different resins (A, B and C), a minimum of 5 preforms produced from each resin would be selected for reheat testing and the preforms would be entered into the machine in a random order (e.g. A-C-B-B-C-C-A-C-B-A-C-A-A-B-B, not all A's, then B's then C's). An average reheat figure would then be gained for each set of preforms.

(27) The reheat improvement (defined as a temperature attained by the test preform minus the temperature attained by a C93 control (i.e. not containing any reheat additive)) was calculated.

EXAMPLE 3

LAB and Reheat Assessment of Preforms

(28) Preforms were made as described in Example 1 using selected levels of additives and the preforms were assessed by measuring L*, a* and b* and reheat as described in Example 2. Results are provided in Table 1.

(29) TABLE-US-00002 TABLE 1 Reheat L* L* a* b* improvement Reduction C93 CONTROL 81.57 −0.17 1.70 N/A N/A 25 ppm Un-milled 78.81 −1.51 1.81 9.36 2.75 WO2.72 25 ppm Un-milled 80.25 −0.61 2.28 5.56 1.31 WO2.9 25 ppm milled WO2.72 78.02 −1.76 0.26 15.76 3.55 25 ppm milled WO2.9 80.66 −0.63 2.09 4.48 0.91 6 ppm U1 74.73 0.16 3.05 7.7 6.83 6 ppm TiN 73.51 −0.70 −0.28 10.16 8.06

(30) Table 1 shows that the milled WO.sub.2.72 material is slightly darker (lower L*) than the un-milled WO.sub.2.72 but there is a substantial reheat improvement. In contrast, there is little difference between the reheat improvement for the un-milled and milled WO.sub.2.9. The comparative commercial materials U1 and TiN at typical loadings used (6 ppm) are darker than each of the WO samples (despite the fact that significantly more WO is used in each case) and yet similar reheat levels can be obtained. This effect is explored further in the following examples.

(31) It will also be noted from Table 1 that each of the tungsten oxide samples is less yellow compared to the U1 sample. Also, unexpectedly, the milled WO.sub.2.72 sample has a b* which is closest to zero which is particularly advantageous for use in clear bottles. Whilst the TiN has a negative b*, implying a blue tint, any increase of the level of TiN in an attempt to increase the level of reheat (e.g. towards the level seen in the WO samples) will increase the level of blue tint (increase in b*) to detrimental and/or unacceptable levels.

EXAMPLE 4

Assessment of Light Transmission (%) v. Peak Preform Reheat

(32) A range of preforms were made as described as in Example 1 including different levels of reheat agents (milled WO.sub.2.72, U1 and TiN) and optical and reheat data obtained. Results are reported in FIG. 1 from which it will be noted that for all peak preform reheat values (° C.) the milled WO.sub.2.72 has a higher light transmission (%) than the commercially available U1 and TiN materials.

EXAMPLE 5

Comparison of Reheat Attainable Using Various WO Additives

(33) By processes analogous to those described in Examples 1 to 3, the peak preform reheat temperature was assessed for a range of loadings of additives. Results are presented in graphical form in FIG. 2.

(34) It is clear from FIG. 2 that for all loadings the milled WO.sub.2.72 material provides a significant improvement in reheat efficiency. Additionally, it is clear that for the WO.sub.2.72 material reducing particle size has improved the performance of the WO.sub.2.72 material. This contrasts with the WO.sub.2.9 material wherein the differences between milled and Un-milled materials is relatively small. Advantageously, a reduced level of WO.sub.2.72 material may be used to achieve the same reheat level as other WO additives.

EXAMPLE 6

(35) For a series of loadings of WO.sub.2.72, U1 and TiN, the preform reheat and preform L* were assessed and results are presented graphically in FIG. 3. If an acceptable preform colour (L*) is taken to be L*=79, the vertical lines A, B, C, D show the loading used to achieve it and the level of reheat achieved. It will be appreciated that line D which intersects the L* for the milled WO.sub.2.72 produce a reheat of about 109° C. whereas in all other cases (e.g. for U1 and TiN) the reheat achievable is inferior—for U1 the reheat achievable at L*=79 is associated with line B which leads to a reheat of about 99° C.; as does the TiN examples illustrated by line A. Line C (the un-milled WO.sub.2.72) is inferior to the milled WO.sub.2.72 but is still far superior to the U1 and TiN since it provides a reheat of about 107° C.

EXAMPLE 7

(36) This is similar to Example 6 except it compares WO.sub.2.9 materials to U1 and TiN. For a L* of 81, lines E and F, illustrate the reheat attained for milled WO.sub.2.9 and un-milled WO.sub.2.9 respectively (both have reheats of greater than 99° C.) whereas lines G and H (for a lower L* of 79) produce a lower reheat.

EXAMPLE 8

(37) This is similar to Examples 6 and 7 except it compares milled and un-milled WO.sub.2.72 and WO.sub.2.9 samples. For a selected L* value of just over 76% illustrated by line H, a peak reheat temperature of over 115° C. is achieved for the WO.sub.2.72 sample at less than 40 ppm addition (see line I); whereas over 130 ppm of WO.sub.2.9 is needed to achieve the same effect (see line J).

(38) The results illustrate the advantages resulting from use of tungsten oxide materials and, particularly the unexpectedly superior L* and b* values associated with using WO.sub.2.72 materials.

EXAMPLE 9

(39) For a series of loadings of WO.sub.2.72, WO.sub.2.9, U1 and TiN, preform b* was assessed and results are presented graphically in FIG. 6. The figure illustrates how, for TiN, b* disadvantageously becomes rapidly more negative as the level in ppm increases, meaning that higher reheats can only be achieved along with unacceptably high blueing of the preform; whereas milled WO.sub.2.72 is within 1 unit of b* for a wide range of ppm levels. Thus, reheat can be increased with a lower detrimental effect on b*.