Vermeersch, Bernard (370 Rijsenbergstraat, Gent, Gent Belgium, US)
Batlaw, Rajnish (102 Coventry Court, Spartanburg, SC, 29301, US)
Vermeersch, Bernard (370 Rijsenbergstraat, Gent, Gent Belgium, US)
|1.||A process of making a preform article, the process comprising: (a) providing a chemical composition of polypropylene, said chemical composition comprising at least one ultraviolet light absorbing compound selected from the group of compounds consisting of benzotriazoles, benzophenones, and triazines; said composition having a melt flow index between about 6 and about 50 grams/10 minutes; (b) injecting said chemical composition into a mold; (c) forming said chemical composition into a preform article,; and (d) removing said preform article from said mold.|
|2.||The process of claim 1 wherein said chemical composition comprises at least two ultraviolet light absorbing compound species, wherein one of said two species comprises a derivative of benzene.|
|3.||The process of claim 2 wherein said two ultraviolet light absorbing compound species comprise (a) a benzotriazole compound and (b) a benzophenone compound.|
|4.||The process of claim 3 wherein said ratio of benzophenone to benzotriazole is between about 95:5 and about 5:95.|
|5.||The process of claim 4 wherein said ratio of benzophenone to benzotriazole is between about 2:1 and about 1 :2.|
|6.||The process of claim 5 wherein said ratio of benzophenone to benzotriazole is about 80:20.|
|7.||The process of any one of the preceding claims, wherein said at least one ultraviolet light absorbing compound is provided in said polypropylene at a concentration of between about 1200 and about 2400 ppm.|
|8.||The process of any one of the preceding claims, wherein the chemical composition is injected into the mold at a fill rate of greater than about 5 grams of chemical composition per second.|
|9.||The process of any one of the preceding claims, wherein said preform article has a closed end connected to a side wall, said side wall having a maximum thickness of less than about 3.5 mm.|
|10.||A preform article which is obtainable by the process of one or more of the preceding claims.|
|11.||A process of making containers, comprising the steps: (e) reheating the preform article of claim 10; and (f) stretch blow molding said preform article to form a container.|
|12.||The process of claim 11 , wherein said steps (e) and (f) are repeated in a manufacturing operation at a rate of container production of at least about 1500 containers per hour per mold.|
|13.||A container which is obtainable by the process of one or more of claims 11 and 12.|
|14.||A use of the container of claim 13 for filling the container with a heated food product.|
|15.||The use of claim 14, wherein the food product is deposited into said container at a temperature of at least about 71 degrees C.|
|16.||The use of any one of claim 14 and claim 15, wherein said food product is protected from excess UV light exposure by said ultraviolet light absorbing compound.|
Field of the Invention
This invention relates to production of two-stage injection stretch blow molded polypropylene articles, including such articles which have ultraviolet light (UV) protection.
Background of the Invention
Injection stretch blow molding is a process of producing thermoplastic articles, such as liquid containers. This process involves the initial production of a preform article by injection molding. Then, the preform article that after reheating is subjected to stretching and gas pressure to expand (blow) the preform article against a mold surface to form a container.
There are several different processes that employ stretch blow molding. A first type is a single stage process in which a preform is made on a machine and allowed to cool somewhat to a predetermined blow molding temperature. While still at this elevated temperature, the preform is stretch blow molded into a container on the same machine, as part of a single manufacturing procedure. This is a one step or so-called "single stage" manufacturing procedure. In a typical single stage blow molding process for polypropylene, the temperature of the preform is cooled (reduced) following preform formation from about 230 0 C to about 120-14O 0 C. The preform is not returned to ambient temperature, but instead is blown to a container while at about 120 to 140 0 C.
Another type of process is a two stage process. In a two stage process, preforms first are formed in an injection machine. Then, preforms are cooled to ambient temperature. In some cases, preforms are shipped from one location to another (or from one company to another) prior to stretch blowing the preforms into containers. In the second stage of the two-stage process, preforms are
heated from an initial ambient temperature to an elevated temperature for stretch blowing on a molding machine to form a container. The injection machine and the molding machine typically are located apart from one another in such a two stage procedure. Two stage manufacturing processes are sometimes referred to as "reheat stretch blow molding" (RSBM) processes, because preform articles formed in the first stage are subsequently reheated during the second stage of manufacture to form finished containers.
Two stage container manufacture is comprised of: (1) injection and cooling of a preform to ambient temperature, followed by (2) stretch blow molding to form a container. Two stage manufacturing reveals certain advantages over single stage processes. For example, preform articles are smaller and more compact than containers. Therefore, it is easier and less costly to transport large numbers of preform articles, as compared to transporting large numbers of containers. This fact encourages producers to make preform articles in one location, and manufacture containers in a second location, reducing overall production costs. Thus, one advantage of two stage container manufacture is that it facilitates separate optimization of each stage of manufacturing. Furthermore, it is recognized that the two stage process is more productive and provides more opportunities for cost savings for large volume applications.
It is common, therefore, for a two-stage process to be used in applications for which large volumes of containers are to be made. Thus, a preform may be shipped to a location at which the finished containers will be employed in the marketplace. Then, in that instance, actual shipping costs for completed containers will be greatly reduced. The explanation for this is that the shipping costs for fully blown containers are significantly greater than shipping costs for preforms, which are much smaller and more compact. Thus, two-stage processes are used commonly for large volume product applications such as drink bottles, soda bottles, water bottles and the like. On the other hand, it is common in the industry for one stage processes to be used for bottles which are used commercially in much smaller volumes.
Stretch blown thermoplastic articles formed of polyethylene terephthalate (PET) are common in the industry. Such polyesters provide highly transparent and aesthetically pleasing container articles. PET bottle production has enjoyed tremendous success in the last twenty years. However, there is a continuing drive in the industry to reduce costs while still providing containers of suitable quality and clarity. Overall production cost for containers is a function of many factors, including raw material cost and also manufacturing speed or efficiency.
In the industry, it is known to make containers from polypropylene. Polypropylene in general is a lower cost raw material as compared to PET. However, polypropylene has not significantly replaced PET as the material of choice for drink bottle manufacturing. One reason that polypropylene has not replaced PET as the material of choice, given its lower overall raw material costs, is that the injection and blow molding cycle time for polypropylene has been excessively long. The long cycle time for preform and bottle production drives up the cost for using polypropylene as compared to PET for container manufacture.
Productivity for polypropylene preform production in conventional processes is low in part because of the undesirably high preform thickness and the use of thermal gates. This is a surprising and unexpected discovery of the invention, that is, a process of achieving suitable container structure and morphology by reducing preform thickness.
In the past, conventional processes have employed a rapid injection rate. It has been mainly the long cooling time that has caused the cycle time for polypropylene preforms to be cost prohibitive. Using a relatively fast injection rate (could still be a short cycle-time) for thin walled preforms unexpectedly can lead to bottles having low clarity. High injection rates in conventional prior art preform manufacture sometimes have adversely affected the orientation of the crystal structure in the preform, which induces undesirable haze in the final container. To produce containers with sufficient clarity, it has been common to
use relatively long cycle times (for preforms and containers) when employing polypropylene.
There has been a long felt need in the industry for a process of making polypropylene containers on existing PET manufacturing equipment that is already deployed in the industry. Currently known methods of injection stretch blow molding PET preforms have generally not been successfully employed for polypropylene container manufacture.
The shape and thickness of preforms will determine their suitability for container manufacture and the speed at which containers may be stretch molded from such preforms. It has been common in conventional polypropylene processes to employ polypropylene preforms having fairly thick walls. However, thick preform walls reduce the processing speeds that can be achieved. Thick- walled preforms must be cooled longer before removal from a preform mold, thus undesirably increasing processing time in preform manufacture.
U.S. Patent No. 4,357,288 to Oas et al. discloses a method of manufacture of biaxially oriented polyolefin bottles. The injection rate for production of preforms, however, is relatively slow. This patent describes an injection rate of polypropylene to fill a mold cavity which uses an injection time of about 3 to 10 seconds to fill the mold cavity. Examples of the Oas patent disclosure recite a machine cycle of about 7 seconds, which corresponds to a container production of about 500 containers per hour.
Several prior art references are directed to single stage bottle manufacturing processes, or extrusion-type processes. For example, European patent application
0 151 741 A2 to Ueki et. al. (Mitsui Toatsu Chemicals) is directed to single stage manufacturing of containers or bottles. EP 0 309 138 A2 (Exxon) teaches the use of polypropylene to form containers. This Exxon patent disclosure is directed to one stage preform/container manufacturing processes.
An additional publication, WO03/0353368 to Richards et.al (Pechiney Emballage Flexible Europe) is directed to the two stage production of multilayer containers from polypropylene. An additional barrier layer of EVOH is provided in addition to the polypropylene layer. However, this patent disclosure teaches the use of a melt flow index that is relatively low, resulting in a relatively viscous polypropylene resin. Viscous resins are not easily adapted to rapid injection rates in the manufacture of preforms. This reduces overall productivity and manufacturing efficiency.
Yet another publication, WO 95/11791 to Gittner et al, (Bekum Maschinenfabriken GMBH) is directed to a two stage process for container manufacture using polypropylene. This process employs an injection cavity fill rate during manufacture of the preform of about 3-5 grams per second. It is believed that the process cannot reliably form polypropylene containers at a container production rate of more than about 900 containers per cavity per hour.
Until the development of this invention, many attempts to injection stretch blow mold polypropylene have been commercially undesirable. This has been believed to be due in part to a relatively slow production speed for such polypropylene articles at acceptable container haze levels. In addition, it was generally believed that special stretch blow molding machines equipped with longer re-heating ovens were required to reliably produce polypropylene containers.
A disadvantage of polypropylene containers has been the inability to make containers of high clarity (i.e. low haze) at a high rate of speed. For example, it has been known to make relatively clear polypropylene containers having a percentage haze value of about 1-1.5 percent haze. However, conventional methods for making polypropylene containers having such low levels of haze have been relatively slow. Slow processes are not economically viable in the marketplace. It is a significant and difficult challenge to develop a process that
will facilitate increased stretch molding speed while not sacrificing clarity of the resulting container.
Containers used for fruit juices, milk, and the like sometimes must be hot filled to achieve the greatest manufacturing efficiency. However, many containers are not capable of withstanding the hot filling of the container with hot liquids without deformation, or undesirable leaching of the contents of the plastic into the food product, which is highly undesirable. A hot fill-able container that is capable of rapid manufacture would be highly desirable. Also, such a container that has Ultraviolet light protection to protect the food contents also would be highly desirable.
There has been a long felt need in the industry of container manufacturing to provide polypropylene materials, preforms, and container articles in a process that will afford a cost-effective manufacture of low-haze, high clarity products, which are capable of providing ultraviolet protection to the contents of such container articles. A process of employing polypropylene in a manner that will result in highly efficient preform and container production at a minumum cost with a fast cycle time is very desirable.
Brief Description of the Drawings
The invention will now be described by way of example with reference to the drawings:
Figure 1 shows a typical polypropylene container that may be manufactured according to the process of the invention;
Figure 2A is a schematic flow diagram showing the processing steps employed in the first stage of the two stage process, which relates to injection manufacture of preform articles;
Figure 2B illustrates processing steps in the second stage of manufacturing in accord with the invention, wherein a preform article is stretch blow molded to form a container;
Figure 3 is a side view of a conventional thick-walled preform article;
Figure 3A shows a side cross-sectional view of the conventional preform article of Figure 3;
Figures 3B and 3C show a first embodiment of a relatively thin walled preform with an external profile that may be employed in the invention;
Figure 4 shows a side view of a second preform that may be used in the invention, i.e. a relatively thin-walled preform article according to the practice of the invention, in which the preform article optionally may have a profile on the inside rather than the outside of the preform article structure;
Figure 4A shows a cross-sectional view of the thin-walled preform article of Figure 4;
Figure 5 is a longitudinal sectional view of an injection molding assembly for the production of a preform article;
Figure 6 is an illustration of stage two of the manufacturing process, showing a vertical cross-sectional view of stretch blow mold apparatus that is used to produce the containers from a perform, in this view showing a start up position with the preform article in place;
Figure 7 is a view of the apparatus of Figure 6 showing the mold closed on the preform article; and
Figure 8 shows a fully blown container with a stretch rod and swage in a down position with the container decompressing in the mold.
Detailed Description of the Invention
Reference now will be made to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not as a limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations
can be made in this invention without departing from the scope or spirit of the invention.
A two-stage process of injection stretch blow molding polypropylene to form a container is disclosed in the practice of the invention. A first stage of this process comprises forming a preform article. A second subsequent stage comprises reheating and blow molding the preform article to form a container. The invention is directed to both preform articles and containers, in addition to the specific method or process for forming these products. Surprisingly beneficial results have been achieved in the practice of the invention.
In the first stage of forming a preform article, a process is provided having at least the following steps. First, a chemical composition comprising at least in part polypropylene is provided. This chemical composition provides a melt flow index in the range of between about 6 and about 50 grams/10 minutes, according to ASTM D 1238 at 230 degrees C/2.16 kg.
Further, the chemical composition is injected into a mold at a fill rate of greater than about 5 grams of chemical composition per second. This injection may be made through an orifice or gate, as further described herein. A preform article is formed in a mold. The preform article is removed from the mold. The preform article includes a closed end adapted for subsequent second stage reheating and stretch blow molding. The closed end may be integral with a side wall. The side wall of the preform provides a thickness of less than about 3.5 mm, in one aspect of the invention.
Processing parameters are employed in the practice of the invention to produce preform articles that facilitate fast and efficient stretch blow molding to produce containers having a desirably low haze. The melt flow index (MFI) of the polypropylene chemical compositions (i.e. resins) will be tuned to the injection speed of resin in molding the preform article, the thickness and structure of the preform article, and the proper selection of injection gate diameter during such the preform production stage. Each of these factors are important to the
successful production of desirable low-haze container articles. Improved containers, preforms, and processing conditions are within the scope of this invention.
The invention has overcome limitations in the art, in part by the unexpected discovery that processing parameters may be established to impart necessary conditions and benefits to form superior polypropylene-based preforms. This invention facilitates efficient and cost-effective production of clear, low haze polypropylene articles from preforms using injection to make a preform, followed in some instances by stretch blow molding to form a container.
It is highly desirable to improve the speed of production and reduce the level of haze in the thickest regions of the resultant container articles as well. Nucleating agents may be employed in the practice of the invention, but are not always necessary. For injection stretch blow-molded bottles, as one example, the neck and the bottom are generally the most difficult areas to clarify due to the thickness of such regions. In particular, the aesthetic qualities of neck areas can be compromised if the appearance is too hazy or cloudy.
The advantages of the process disclosed herein comprise, among other things, appropriate selection of melt flow polypropylene resins, appropriate selection of nucleating and clarifying agents, appropriate thickness of performs, appropriate rate or speed of injecting the resin for preform production, and also perhaps the appropriate gate width during preform production. Surprisingly, it has been found that there are ranges for each of these criteria which cause stretch blow molded articles to be produced at high rates with superior clarity.
Polypropylene has long been known to exist in several forms, and essentially any known form could be used in the practice of the invention. Thus, the invention is not limited to any particular type of polypropylene, lsotactic propylene (iPP) may be described as having the methyl groups attached to the tertiary carbon atoms of successive monomeric units on the same side of a hypothetical plane through the polymer chain, whereas syndiotactic
polypropylene (sPP) generally may be described as having the methyl groups attached on alternating sides of the polymer chain.
Additionally, container articles produced in accordance with the criteria noted above exhibit specific haze to thickness ratios, and such is within the scope of the present invention. The invention provides a vast improvement in polypropylene injection stretch blow-molded article technology whereby efficient methods of producing very clear articles is accorded as proper replacements for previous PET types.
The practice of the invention makes it possible to provide injection stretch blow-molded polypropylene articles that may be produced at very high rates and exhibit substantially uniform clarity levels. The invention may provide polypropylene preforms that facilitate production of very low haze container articles with injection stretch blow molding in a very efficient manner. One application of the invention provides improved containers, wherein such containers exhibit low haze levels.
Ultraviolet Light Protection
Many colorants and nutritional additives used in consumer products , such as beverages, are susceptible to degradation and loss of potency from exposure to ultraviolet (UV) light. UV degradation is also responsible for flavor changes in many types of beverages and foods, resulting in decreased shelf life. There are several classes of compounds that can be used in polyolefin packaging which absorb UV light as it passes through the container, providing UV protection for the contents of the package. These classes include benzophenones, benzotriazoles, and triazines, and others. Benzophenone compounds are available under many trade names including Cyasorb 531 , Cyasorb UV-9, ATL UV-12, Lowilite 20, Lowilite 22, and Lowilite 24. There are also many trade names for benzotriazole UV absorbers including, Chisorb 326,
Chisorb 5103, Tinuvin 326, Tinuvin P-UV 326, Tinuvin 327, BLS® 234, BLS® 1326, and ATL UV-71.
Triazine compounds may be used in the practice of the invention, as UV absorbers. Triazines are available under several trade names including Chiguard 1084, and others, that may be employed in the practice of the invention. Depending upon the class of compound, and the specific molecule within each class, the area of the UV spectrum where absorption occurs can vary, and therefore is to some degree tunable. Triazines include those compounds in which the organic additive is a compound containing a six- membered hetero ring containing three or more N- hetero atoms therein and including hydrogenated compounds.
Unfortunately, no single compound, or class of compounds, provides protection across the entire UV spectrum to a degree that is acceptable in certain applications. Optimum protection for the contents of a polypropylene container, at the least cost, can best be provided by blending UV absorbers to match the application.
One UV inventive additive comprises a blend of (1) benzotriazole or hydrozybenzotriazole and (2) benzophenone, UV absorbers. . Compositions ranging from 5% benzotriazole / 95% benzophenone to 95% benzotriazole / 5% benzophenone would give the enhanced performance characteristics, and is believed to be useful in the practice of the invention. In other embodiments, a ratio of between about 2:1 and about 1 :2 of benzophenone to hydroxyphenone is employed. In one particular embodiment, a ratio of benzophenone to
Hot Filling Containers
Hot filling is a process in which the product is introduced into the container immediately after it undergoes a thermal processing step. The temperature range for a product in a hot fill process is approximately 71 - 96 0 C. Filling with a product in this temperature range serves to sanitize the container, thereby
enhancing safety. Sanitization is especially important in non-carbonated beverages. The filled container is then cooled to near ambient temperature. In order to hot fill a polyethylene terephthalate (PET) container, specialized, high cost types of heat set PET must be used to prevent deformation of the container. An additional processing step is also required to heat set the container. This results in longer cycle times, and increased raw material and processing costs as compared to the claimed invention.
Optional Nucleating Agents
An effective clarifying agent, that also functions as a nucleator, for polypropylene is 1 ,3-O-2,4-bis(3,4-dimethylbenzylidene) sorbitol (hereinafter DMDBS), available from Milliken & Company under the trade name Miliad® 3988. Such a compound provides highly effective haze reductions within polypropylenes with concomitant low taste and odor problems. Disubstituted DBS compounds are broadly described in U.S. Patent Numbers 5,049,605 and 5,135,975 to Rekers. As it is, in terms of providing excellent clarity, particularly within the neck and bottom regions of target injection stretch blow-molded polypropylene bottle articles within this invention, DMDBS is a useful compound for such a result.
An effective thermoplastic nucleator in terms of high crystallization temperatures is available from Milliken & Company using the tradename HPN- 68™. Other like thermoplastic nucleating compounds that may be employed in the practice of the invention are disclosed in U.S. Patent Numbers. 6,465,551 and 6,534,574. The HPN-68™ compound is disodium bicyclo[2.2.1]heptanedicarboxylate. The ability to provide highly effective crystallization, or, in this specific situation, control targeted levels of crystallization within polypropylene preforms prior to injection stretch blow molding sometimes is facilitated by utilization of such a nucleating agent. Low amounts of this additive can be provided to produce the desired and intended amorphous-
crystalline combination within the target performs. Other nucleating agents can be employed in the practice of the invention as well.
The polypropylene polymers employed in the practice of the invention may include homopolymers (known as HPs), impact or block copolymers (known as ICPs)(combinations of propylene with certain elastomeric additives, such as rubber, and the like), and random copolymers (known as RCPs) made from at least one propylene and one or more ethylenically unsaturated comonomers. Generally, co-monomers, if present, constitute a relatively minor amount, i.e., about 10 percent or less, or about 5 percent or less, of the entire polypropylene, based upon the total weight of the polymer. Such co-monomers may serve to assist in clarity improvement of the polypropylene, or they may function to improve other properties of the polymer. Co-monomer examples include acrylic acid and vinyl acetate, polyethylene, polybutylene, and other like compounds.
Polypropylene provides an average molecular weight of from about 10,000 to about 2,000,000, preferably from about 30,000 to about 300,000, and it may be mixed with additives such as polyethylene, linear low density polyethylene, crystalline ethylenepropylene copolymer, poly(i-butene), 1-hexene, 1-octene, vinyl cyclohexane, and polymethylpentene, as examples. Other polymers that may be added to the base polypropylene for physical, aesthetic, or other reasons, include polyethylene terephthalate, polybutylene terephthalate, and polyamides, among others.
Resin compositions utilized to produce the preform articles and injection stretch blow-molded containers of the invention can be obtained by adding a specific amount of a nucleating agent/clarifying agent directly to the polypropylene, either in dry form or in molten form, and mixing them by any suitable means while in molten form to provide a substantially homogenous formulation. Alternatively, a concentrate containing as much as about 20 percent by weight of a nucleator/clarifier in a polypropylene masterbatch may be
prepared and be subsequently mixed with the resin. Furthermore, the desired nucleator/clarifier (and other additives, if desired) may be present in any type of standard polypropylene additive form, including, without limitation, powder, prill, agglomerate, liquid suspension, and the like, particularly comprising dispersion aids such as polyolefin (e.g., polyethylene) waxes, stearate esters of glycerin, waxes, mineral oil, and the like. Essentially any form may be exhibited by such a combination or composition including such combination made from blending, agglomeration, compaction, and/or extrusion. The produced resins are then utilized to form preforms, as noted herein, which are then subsequently utilized to form the desired container articles in an injection stretch blow molding procedure.
It is contemplated that certain organoleptic improvement additives be added for the purpose of reducing the migration of degraded benzaldehydes from reaching the surface of the desired article. The term "organoleptic improvement additive" is intended to encompass such compounds and formulations as antioxidants (to prevent degradation of both the polyolefin and possibly the target alditol derivatives present within such polyolefin), acid neutralizers (to prevent the ability of appreciable amounts of residual acids from attacking the alditol derivatives), and benzaldehyde scavengers (such as hydrazides, hydrazines, and the like, to prevent the migration of foul tasting and smelling benzaldehydes to the target polyolefin surface).
High rate production of preforms contributes significantly to the improved efficiency in producing of injection stretch blow-molded articles, in terms of high clarity, acceptable physical properties, and high manufacturing efficiency.
Polypropylene compositions having an melt flow index (MFI) of between about 6 and about 60 are useful in the practice of the invention. Furthermore, MFI values of between about 13 and about 35 are particularly useful in the practice of the invention, as further described below.
An injection speed of the chemical composition (i.e. polypropylene and various additives) into a preform cavity mold at a fill rate of greater than about 5
grams of chemical composition per second has been found to be particularly valuable in the practice of the invention. Table A shows values for various parameters that may be employed in the practice of the invention, as further discussed herein.
In addition to the injection speed of the specific MFI resin, the thickness and design of the target preform is important for a number of reasons. The thickness of such an article should be thin, as compared with the thickness of previously produced polypropylene preforms. This facilitates low haze results as noted above, and also facilitates utilization within prior PET injection stretch blow molding machinery. The side wall thickness of preforms desirably may be less than about 3.5 mm for effective results. In some applications, side wall thickness of between about 1.5 mm and 3.5 is very useful. Some applications may use a thickness of as much as 4.0 mm, as set forth in Table A.
A gate, as further described herein, comprises the opening through which liquid chemical composition (polypropylene and additive mixture) is admitted into the preform mold cavity. The gate diameter employed during preform production is particularly important, and may be related to other processing variables. A wider gate during injection into the mold cavity, coupled with the particular speed or speed range at which the resin is injected, facilitates greater control and influence upon the degree of polymer crystal orientation resulting therefrom. In the practice of the invention, a gate diameter of 1.5 mm may be used. In other applications, a gate diameter of 3.8 mm has been used. Other gate sizes could be used as well, but each factor or factor must be adjusted to account for gate diameter. Gate diameters between about 1.5 mm and 3.8 mm can be advantageously employed in the practice of the invention.
Further Detailed Description of the Drawings
Figure 1 shows a stretch blow molded polypropylene container that may be manufactured in accordance with the practice of the invention. Container 10 (sometimes referred to herein as a "bottle") is shown. The container 10 of
Figure 1 has a relatively concave bottom 11, a cylindrical main sidewall 12, a conical upper portion 13, and a thickened externally threaded neck 14 on the convergent end of the upper portion 13. A neck ring 15 provides a physical point of reference, and may be used to carry the container 10 along processing machinery during manufacture and subsequent filling of the container 10.
The container 10 may be of any desired size or shape with sizes of from 0.5 to 4 liters being very useful, for example. The neck 14 usually is rigid to support a pressure retaining screw type cap (not shown). Thus, the neck 14 may be many times the thickness of the sidewall 12. Furthermore, the conical upper portion 13 may be gradually thickened as it approaches neck 14.
Turning now to Figure 2A, a flow schematic is provided showing the steps in the first stage of a two-stage stretch blow molding process. In the invention, a two stage (two step) procedure is provided for production of containers 10. Figure 2A shows the first stage of the manufacturing procedure, that is, the injection molding process of preforms production. A chemical composition containing polypropylene is acquired from a source, such as a polypropylene manufacturer. The polypropylene-containing chemical composition may comprise a homopolymer, copolymer or other polymeric composition. Furthermore, the chemical composition (also known as a "resin") may contain various additives, including (for example) nucleating agents, antioxidants, lubricants, acid -scavengers, UV absorbers and the like, as further described herein. The polypropylene chemical composition is provided into an injection machine and heated. The heated chemical composition then is injected at a relatively high rate of speed through a valve or "gate", and into the mold of the injection machine. A preform article is formed in a mold. The preform article is cooled and removed from the mold.
Figure 2B shows a second stage of a two-stage stretch blow molding process. In the second stage, a preform article (which may or may not have been manufactured at a location distant from the stretch blow molding apparatus)
is converted to a container 10. A preform article (usually at ambient temperature) is provided in a stretch blow molding machine. Then, the preform article is heated from ambient temperature to an elevated temperature. The elevated temperature employed is also known as the "orientation" temperature, and it is typically in the range of about 120-13O 0 C for random copolymers.
The inner surface temperature of the preform needs to be sufficiently high to ensure that containers have the best optical properties. This has been found to be one important variable in the stretch blow molding process which sometimes determines whether the container will be transparent or hazy. When the preform article is sufficiently softened, the preform is stretch blow molded into a container 10. The formed container 10 is cooled and removed from the stretch mold apparatus.
Conventional Thick -Walled Preform
Figures 3-3A show a thick-walled polypropylene preform having a relatively thick side wall 80 (in this example, the side wall thickness is about 5 mm). The preform article 60 shown in Figure 3 includes a closed end 62 and an open end 72. Furthermore, a neck 66 is shown, with threads 68 at the base of the neck 66. A main body portion 64 with side wall 80 is shown. It is common for polypropylene-based preforms 60 such as that shown in Figure 3 to have a side wall 80 having a thickness of about 5 mm, or more.
This preform article 60 happens to also be "stepped out" or tapered at each end, on its exterior profile. Thus, a "profile" is found on the exterior of many preform articles. In many cases, the size of the threads at the open end 72 are fixed, and cannot be subject to variation.
First Type of Preform Article That May be Employed in the Practice of the Invention
Figure 3B and corresponding Figure 3C show a first embodiment of a thin walled preform article that may be employed in the practice of the invention. It
should be noted that the invention may include the use of "stepped out" preforms with an exterior profile, such as shown in Figures 3B/3C so long as the preforms are less than about 3.5 mm in side wall width.
Thus, one discovery of the invention is that thin-walled preforms, in conjunction with processing conditions presented herein, provide surprisingly unexpected results as compared to conventional thick walled preforms. In the Figures 3B/3C a preform 90 having thin side wall 91 is shown.
Second Type of Preform Article Employed in the Invention
The geometry of a preform article is important in the manufacturing of containers 10. In the practice of the invention, a preform article 115 having a relatively thin side wall may be employed, as further described herein and as shown in Figures 4-4A. The geometry of the preform article 115 of Figure 3 shows a tapered neck 114, and a main body portion 102 with side walls 101 and 104 that are approximately parallel to each other along their length. Furthermore, a closed end portion 116 tapers from the main body portion 102. Threads 110 are provided adjacent the open end 103 of preform article 115. A transition area 105 represents the tapering region of the side wall 101 into the neck 114.
In Figure 4, a preform article 115 of the invention is shown in which the outer wall surfaces 109a-b of the preform article are generally parallel and straight, forming a substantially symmtrical tube on its outer dimension from a point near the closed end 116 to a point near the open end 103. The inner wall 108 of the preform 115 is profiled due to a transition zone 105. When blown in stage two of manufacture, the preform article 115 engages a mold so as to make a container 10 of the appropriate geometry.
By "profiled", it is meant that a given wall has a changing angle or slope which deviates from 180 degrees. Thus, the invention may in some embodiments take advantage of a profiled inner wall 108, as opposed to a profiled exterior wall, as is common in the conventional devices (see Figures 3- 3A). The use of a profiled inner wall 108 has been found to be a useful feature in application of the preform 115 to container 10 manufacture. One reason for this fact is that it facilitates the use of relatively uniform outer wall dimensions. Thus, preforms 115 can be used that have differing inner wall 108 profile for various container sizes, while still exhibiting a common outer dimension or shape. This is useful in manufacturing, to avoid or minimize tooling and/or machinery changes for each size preform 115 that may be used to make containers 10 of various sizes.
Thus, a relatively uniform outer dimension to the preform articles 115 may provide an advantage that may be realized in the practice of the invention. It should be recognized that the use of a profiled inner wall 108 is not required in the practice of the invention, but is one useful manner of practicing the invention. Thus, preforms having either an exterior profile or an exterior profile may be used in the practice of the invention.
Injection Molding of Preforms
Figure 5 shows a schematic vertical cross-sectional view of an injection molding machine for making preform articles in a first stage. A preform article 115 may be formed in an injection molding unit 120 having a barrel 121 fed by an hopper 122 and ejecting the melt through a round nose nozzle 123. A chemical composition (i.e. polypropylene-containing pellets or portions, with optional additives or optional nucleating agents, etc) is provided into inlet hopper 122. Barrel 121 rotatably mounts a melting and mixing screw 124 with a non-return valve nose 125. Heater bands 126 may be provided in the barrel 121. Crystalline polypropylene stretch blow mold formulations are fed through the hopper 122 into the barrel 121 where they are advanced by the melting and
mixing screw 124 to a molten condition at the valve end 125 whereupon the screw is advanced to the dotted line position where the valve nose 125 will force the molten material through the nozzle orifice 127. Gate 137a received a determined the amount of liquid flow that proceeds into the molding cavity 135. Other similar apparatus could be used to form a preform, which achieves the same or similar result as that shown in Figure 5.
The apparatus includes a two-part mold 130 with a first core part 131 and a second molding cavity defining part 132. The part 131 has a cylindrical core 133 with a hemispherical end 134. The part 132 has a molding cavity 135 with a hemispherical bottom end 136 fed by a conduit 137. The end wall of the part 132 has a recess 138 receiving the rounded nose of the nozzle 123.
With the apparatus in the position of Figure 4 the molten plastics material ahead of the valve 125 may be ejected through the orifice 127 by moving the screw rod to the dotted line position as shown in Figure 5. The molten material will flow through the conduit 137 into the mold cavity 135.
The surface of core 133 and the molding cavity surfaces 135 and 136 typically are polished, but may be treated as well to facilitate the ejection of preforms 115. Steel is a desired metal for manufacture of such mold surfaces 135. Chilled mold temperatures from about 11 - 20 degrees C. may be employed.
One feature employed when injection molding preform articles 115, as shown in Figure 5, is the Gate 137a. The gate 137a refers is the opening between the point at which the liquid polypropylene is injected and the actual core 134 of the mold cavity 135. Gate size is a parameter that may vary for different applications. The size of the gate 137a can be important in the manufacture of preformed articles 115. This is because the size of the gate 137a determines the shear forces applied to the molten polypropylene as it is injected into the mold cavity. The size of gate 137a will affect the filing rate. The size of the gate 137a will in some cases determine the rate by at which the chemical composition may be injected, which affects the ultimate clarity of the containers
10 produced by the preformed article 115 in the second stage of the container 10 manufacture (see Figure 2B).
To improve the economics of making polypropylene preforms, it may be important to inject chemical compositions quickly (shorter preform cycle time) into the mold cavity 135. However, when injecting quickly, the clarity of the container 10 produced may be compromised because of the characteristics imparted to the preform article 115 during such mold fill step. Thus, using a relatively wide or large gate 37a allows one to inject at a faster rate while still achieving the same or sufficient clarity in the final container. In some applications, this is desirable. Gate diameter may vary, depending upon the application. The invention is not limited to any particular gate diameter, but it has been found that diameters between about 1.5 mm and about 3.8 mm are useful, and may be found in equipment in the industry. It may be an advantage in the practice of the invention to be capable of employing gate diameter settings that already are in existence and used on existing commercial PET processing equipment.
The injection rate usually is relatively slow. Cavity filling time is typically about 1 to about 4.5 total seconds to fill mold cavity 135. This corresponds generally to an injection rate greater than about 5 grams/second. In other cases, the rate may be between about 5 and about 22 grams per second. Table A shows various parameters that may be advantageously employed in the practice of the invention.
Upon solidification of the preform article 115 in the mold 130, the mold 130 is opened by withdrawing part 131 (and core 133) from part 132. The preform 115 is stripped from the mold.
Melt Flow Index (MFI)
The melt flow index (MFI), also known as the melt flow rate, is an important factor in the manufacturing of preform articles 115. In general, melt flow index is measured according to American Society of Testing Materials ASTM D-1238. This testing method is a nationally (or internationally) known
standard. It is a standard test method for measuring the melt flow rates of thermoplastics. Unless otherwise indicated herein, all references to melt flow index, melt flow rate, MFI, or MFR, refer to measurements according to this industry standard. For polypropylene, measurements are at 230 degrees C, and using 2.16 kg, as per this standard.
In general, the more viscous is a material at a given temperature, the lower will be the MFI value of that material. For example, a given polymer or copolymer composition will have an MFI that is specified by a manufacturer. Thus, each particular type of polypropylene-containing composition to be employed in the practice of the invention will have a given or predetermined MFI. The MFI is also determined and affected by the length of the polymer chains in a given polypropylene composition. The longer the polymeric chains, the more viscous the material. The more viscous the material, the lower the MFI value will be for a given composition.
MFI values are important in determining the speed at which a chemical composition may be fed into an injection mold cavity to form a preform article. This is true because the MFI also will affect the clarity of the final container which is produced from the preform. By clarity, it is meant the degree of haze that will be present in a given container 10 made according to the invention. In general, the higher percentage of haze in the container 10, the less transparent is the container 10 produced in the invention. Higher levels of haze are undesirable.
One unexpected result of the invention is that it has been found that using a given polymeric composition having a predetermined melt flow index, and injecting that composition at a fill rate of greater than about 5 grams per second, a highly desired preform article may be formed. Furthermore, it has been found that the sidewall thickness of the preform is very important in container manufacture. In the practice of the invention, a preform article 115 with a side wall thickness of less than about 3.5 millimeters has proved to be very desirable. This achieves a high productivity of container manufacture while still maintaining
a low degree of haze, i.e. a clear container. Cycle time necessary to make a preform article 115 is significantly reduced by using a preform design with a minimum side wall thickness. Hot plastic (polypropylene) is capable of cooling in the preform mold more quickly using a reduced wall thickness for the preform stage. This facilitates faster preform cycle times, thereby increasing the number of preform articles 115 that can be made in a given period of time, increasing manufacturing capacity and efficiency.
Stretch Blow Molding Preform Articles to Form Containers
Stage two (step 2) of manufacture is shown generally in Figures 2B, and Figures 6-8. A preform article 115 is taken at ambient temperature, and then uniformly heated. The preform article 115 is placed in a stretch blow mold apparatus 140 in a position with its open end 103 resting on a platform 141 on a base 142 surrounding a reciprocal swage 143. The closed end 116 of the preform 115 is shown near the center of Figure 6. The apparatus freely receives the retracted end of the stretch rod 144 of the apparatus 140. The molding dies 145 of the apparatus 140 are in an opened condition. Threaded neck forming wall portions 146 are shown, as well as tapered cone forming portions 147, cylindrical main body forming portions 148, and concave bottom forming portions 149.
Alternatively, and in some embodiments, it may be that a rotary system is employed to transfer preforms using transfer wheels equipped with grippers into a blow mold cavity. Thus, rotary stretch blow molding equipment is known in the art, and may be applied in the practice of the invention. From the open position of Figure 6 the 'apparatus 140 is closed to the position of Figure 7 with the mold halves 145 coming together and with the swage 143 extended into the open end of the preform 115 so that the neck and thread forming portions 146 of the die can mold the thick neck 114 of the bottle on the preform 115. The projection of the swage 143 into the position of Figure 7 also moves the stretch rod 144 against the closed end 116 of the preform 115.
From the position of Figure 7 the apparatus 140 is further activated to eject the stretch rod 144 beyond the swage 143 into closely spaced relation from the bottom forming portion 149 of the dies 145 thereby effecting a stretching of the preform 115 to the full height of the dies. As shown in Figure 8, the stretch rod 144 and the swage 143 are retracted from the container 10. The gas pressure in the bottle is released, and the dies 45 are separated. A blowing
agent is introduced into the preform article 115 forming an axially elongated and hoop stretched balloon in the closed die. The balloon (not shown) is blown into a finished container 10, as shown in Figure 8, with the polypropylene material biaxially stretched to produce a strong container 10.
Roughness on the inner container 10 surface has a negative influence on the container clarity. If, during reheating of the preform 115 (within the window of process stability), the temperature in the skin-layer (at the side of the core) is insufficiently high, the material undesirably may be ruptured apart during the stretch blow molding (stage two) process, resulting in a rough inner container 10 surface and containers 10 having low clarity. Additionally, it has been observed that a low amount of "pre-blowing" (intermediate shape of the stretched and pre- blown preform part, i.e. before the final pressure is applied) may contribute to a relatively rough inner container 10 surface (i.e. undesirable high haze) for the same reason. More specifically the primary pressure, flow of air and pre-blow time usually need to be sufficiently high to prevent that the material gets ruptured apart what gives the part an undesirable high haze.
Correlation of Processing Parameters
In the practice of the invention, it is important that several variables and factors be correlated to each other. Variables that are important in the practice of the invention include, for example, injection speed, MFI of the polypropylene- containing resin, the preform article thickness. In some instances, the gate diameter used during injection of the preform article is a factor. These factors may be optimized and correlated to each other for a given container application. It is possible using the practice of the invention to maximize productivity of the preform and to maximize productivity polypropylene containers in a two-stage stretch blow molding process.
In one particularly useful aspect of the invention, a preform thickness may be of a value less than about 3.5 mm. Thickness is measured along side walls 101 ,104 as shown in Figure 4A, measured as the maximum or thickest portion of
the side wall. In yet another embodiment of the invention, the preform thickness may be in the range of about 2 - 3.5 mm. Furthermore, in the practice of the invention it has been found that an injection fill rate into the cavity mold of greater than about 5 grams of chemical composition (resin) per second is quite useful. Furthermore, in other aspects of the invention it is advantageous to use a cavity mold fill rate of between 5 and 22 grams per second.
Table A shows a correlation between processing variables in the practice of the invention. In Table A, the MFI values and preform wall thickness values are correlated to the optimized injection mold filling rate in the practice of the invention. It is important to note in Table A that for a given preform wall thickness an increase in the MFI value allows an operator to use a higher injection mold filling rate while still obtaining containers 10 of sufficient clarity. Thus, as a result of the practice of the invention it is possible to reduce the cycle time as compared to prior art processes, and yet still obtain containers of relatively low haze and high quality.
Looking from left to right in Table A, a greater preform wall thickness at a given level of MFI value enables an operator employing the invention to use an injection mold filling rate which is greater, resulting in faster production, reduced cycle times, and good container clarity.
Table A reports values for a (valve) gate thickness of 1.5 mm. In the practice of the invention, the use of a wider gate such as about 3.8 mm can result in a filling rate of about 13 g/sec at a MFI value of 13. This compares to the data in Table A in which a MFI of 13 at a (valve) gate diameter of 1.5 mm was successfully employed using an injection speed of about 5-6 g/sec. Furthermore, it has been found in the practice of the invention that using a (valve) gate diameter of 3.8mm at MFI value 20 may result in an injection speed of about 22 g/sec. This value of 22 g/sec may be compared to the injection speed shown in Table A (valve diameter 1.5 mm) of 5-7 g/s. T
Table A - Processing Variables Correlated to Injection Mold Filling Rate for Invention*
Measurements of percent haze/thickness ratios have been obtained on various containers 10 in the practice of the invention. It has been found that a percent haze/thickness reported as percent haze/mils with a value of less than about 0.05 is particularly highly desirable.
In the practice of the invention, it is possible in a manufacturing operation to achieve a rate of container production of greater than about 900 containers per hour per mold. In other applications, it is possible to provide a stretch blow molding step in a manufacturing operation at a rate of container production of at least about 1200 containers per hour per mold. In an even more desirable
aspect, the invention makes it possible to achieve a rate of container production of at least about 1500 containers per hour per mold.
In the reported data herein, the loadings of UV absorber are total loadings of all absorbers used (regardless of how many different UV absorbing species are used), unless clearly indicated otherwise.
Example 1 : Control Preforms Containing No UV Absorber
A commercial random copolymer resin containing Millad 3988 (Borealis RM365MO) was used. The extrusion conditions were standard on the MPM extruder for polypropylene (barrel zone temperatures of 400 0 F, 425°F, 45O 0 F, die temperature of 450 0 F). The preforms were produced on a 90-ton Husky injection-molding machine with a two-cavity mold. The total cycle time was 22.47 seconds, with 11 seconds of cooling and holding time of 3.8 seconds. Barrel temperature was set at 250°C and mold temperatures were 16°C. The preforms had a final weight of 21.3 grams. The preforms were later blow molded into bottles using the procedure described below.
Example 2: Preforms with 1200 ppm of UV Absorber
A commercial random copolymer resin containing Millad 3988 (Borealis RM365MO) was compounded at a 1200 ppm total loading of UV absorber compounds (80% Tinuvin 326 / 20% Cyasorb 531 by weight) on an MPM extruder. The extrusion conditions were standard on the MPM extruder for polypropylene (barrel zone temperatures of 400°F, 425 0 F, 450 0 F, die temperature of 450°F). The preforms were produced on a 90-ton Husky injection-molding machine with a two-cavity mold. The total cycle time was 22.47 seconds, with 11 seconds of cooling and holding time of 3.8 seconds. Barrel temperature was set at 25O 0 C and mold temperatures were 16°C. The preforms have a final weight of 21.3 grams. The preforms were later blown into bottles using the procedure described below.
Example 3 -
Preforms with 2400 ppm UV Absorber
A commercial random copolymer resin containing Millad 3988 (Borealis RM365MO) were compounded at a 2400 ppm total loading of UV absorber compounds (80% Tinuvin 326 / 20% Cyasorb 531 by weight) on an MPM extruder. The extrusion conditions were standard on the MPM extruder for polypropylene (barrel zone temperatures of 400 0 F, 425°F, 450 0 F, die temp of 45O 0 F). The preforms were produced on a 90-ton Husky injection-molding machine with a two-cavity mold. The total cycle time was 22.47 seconds, with 11.00 seconds of cooling and holding time of 3.8 seconds. Barrel temperature was set at 250°C and mold temperatures were 16°C. The preforms have a final weight of 21.3 grams. The preforms were later blown into bottles using the procedure described below.
Procedure of Injection Stretch Blow Molding Preforms into Bottles
Polypropylene bottles (500 ml) were blown at high speed (1 ,500 bottles/cavity/hour) on a Sidel SBO-8 Series-ll stretch blow molding machine designed to blow PET preforms using the polypropylene preforms described in Examplei , Example 2 and Example 3, described above. Axial stretch ratio is 2.5/1 , Hoop Stretch ratio = 2.54 & Total Stretch Ratio = 6.36/1. Machine settings were adjusted to accommodate high clarity, high speed bottle production. Preforms were subjected to a pre-blow pressure of 4 Bar for 0.3 seconds & nozzle for 3 rotations open activated at 'point zero 1 . Blowing time is 0.97 sec & Exhaust time is 0.4 sec. Stretch speed is 1 ,384 m/sec & a standard stretch rod with 14 mm diameter was used. Preform temperature is about 115-127°C. Heating profile: Z1=49.5%,Z2=90%, Z3=36.5%, Z4=38.5%, Z5=41.3%, Z6=75.5%, & Z7=4.5 with Z1 in an advanced position. % GP = 80 %. Used 95 % ventilation to cool the preform surface.
Preparation of Stock Solutions for Use in UV Stability Testing
FD&C Blue 1
A solution of FD&C Blue 1 , a commonly used colorant in food products and beverages, was prepared as follows for use in efficacy testing. Three liters of tap water, 0.0094g FeCI 3 (iron trichloride), and 0.0065g of Acid Blue 1 in powder form (Spectra Colors Corporation, lot #AF0801) were combined in a one gallon glass jar. The solution was covered and stirred for 10 minutes with a magnetic stir bar at ambient temperature. The pH was measured and found to be 6.21.
In a beaker, a solution of approximately 5g of citric acid in 100 ml of water was prepared and well mixed. The pH of the citric acid solution was measured and found to be 2.10. This solution was used to lower the pH of the previously prepared FD&C Blue solution so as to better mimic commercial beverage formulations.
While continuously stirring and monitoring the pH, the citric acid solution was added dropwise until the pH of the FD&C Blue 1 reached 3.7-3.8. This pH adjusted solution is the form in which the stock solution was tested.
Pyroxidine (Vitamin Bg)
In a beaker, 0.046g of Vitamin B6 (Aldrich, lot 02914TO) was combined with 3 liters of tap water and stirred at room temperature with a magnetic stir bar to mix.
Ascorbic Acid (Vitamin C) / Cyanocobalamine (Vitamin B12)
In a beaker, 0.045g of Vitamin C (Fluka, lot # 413620/1) , 0.045g of Vitamin B 12 , and three ( 3) liters of tap water were combined. A magnetic stir bar was added and the solution was stirred at room temperature to mix. Vitamin C and Vitamin B12 are often found in the same beverage and are photosensitive in the presence of each other.
All stock solutions were protected from light by wrapping in aluminum foil until ready to be placed in bottles for stability testing.
UV Stability Testing - Sample Preparation and Exposure Procedure
All sample bottles were blown as described above. Test sample bottles were prepared for each stock solution and labeled as follows:
-Polypropylene (PP)control - Bottle produced as described in example one.
-Foiled control- Bottle produced as described in example 1 then wrapped in aluminum foil when test solution is added to prevent light from entering.
-1200 ppm UV Absorber- Bottle produced as described in example 2
-2400 ppm UV Absorber- Bottle produced as described in example 3
The bottles were filled with the stock solution to be tested and sealed with screw caps. The bottles were then placed inside a VWR/ SheiLab model 2015 temperature controlled light exposure refrigerator. The temperature was set at 20 0 C 1 and the samples were exposed to light from eight UV-351 bulbs . The samples were placed on a rack approximately two inches from the light source and positioned in an equivalent manner relative to the light source to ensure that they received equivalent UV exposure. The solution in each bottle was sampled
immediately after filling (To), after 30 minutes (T-i), 1 hour (T 2 ), 1.5 hours (T3), 2.0 hours (T 4 ), 2.5 hours (T 5 ), 3.0 hours (T 6 ), 4.0 hours (T 7 ), 5.0 hours (T 8 ). 6.0 hours (T 9 ), 8.0 hours (T 10 ), 10.0 hours (T 11 ), 12.0 hours T 12 ), 14.0 hours (T 13 ), 16.0 hours (T 14 ), and 20 hours (T 15 ). Not all samples were exposed and measured for the full 20 hours of exposure. Exposure and sampling times are indicated in each data table. Stability samples were analyzed using test method A at the wavelength(s) indicated in each data table.
Test Method A
The amount of degradation / retention of the test component was measured on a lambda 35 spectrophotometer in a 10mm quartz cell at the maximum wavelength(s) indicated in individual examples. The instrument background absorbance was measured using an empty 10mm quartz cell.
Table B- FD&C Blue 1 UV Stability Data
TABLE C - Vitamin B12 Stability Data
Table O- Vitamin B6 Stability Data
Taste Test Procedures and Data
Sports Beverage Taste Test Procedure:
Three flavors of Gatorade brand sports beverages were tested in separate comparisons. The three flavors tested were Lemon - Lime, Fruit Punch, and Frost Glacier Breeze.
All bottles were blown as previously described. Test sample bottles were prepared and labeled as follows:
-Polypropylene (PP)control - Bottles produced as described in example one
-Foiled control (taste control)- Bottles produced as described in example 1 then wrapped in aluminum foil when test solution is added to prevent light from entering.
-4% UV Absorber- Bottle produced as described in example three.
The bottles were filled with the test beverage and sealed with screw caps. The bottles were then placed inside a VWR/ SheiLab model 2015 temperature controlled light exposure refrigerator. The temperature was set at 20 0 C, and the samples were exposed to light from eight UV-351 bulbs for a period of approximately 8 hours. The samples were placed on a rack approximately two inches from the light source and positioned in an equivalent manner relative to the light source to ensure that they received equivalent UV exposure.
When the UV exposure period was complete, the UV sources were turned off and the temperature of the test chamber was lowered to 6 0 C for approximately eight hours. The taste test was conducted with the beverage temperature at 6 0 C.
Each panelist is given a grouping of three samples for each head to head taste comparison The three samples are comprised of two blind samples plus the taste control, which is beverage from the foil wrapped bottle described earlier. Panelists are instructed to choose which one of the blind sample pair tastes most like the taste control sample. After tasting a sample set and recording their results, they are instructed to eat an unsalted cracker and thoroughly rinse their mouth with tap water to cleanse the palate before tasting the next group of samples. All three combinations of samples for each beverage flavor were tested in this manner.
A total of fifteen panelists tasted each sample set and the results of the head to head comparisons are shown in table(s) below. The statistical confidence level of each taste comparison follows the data table.
Table E- Sports Beverage (Gatorade Frost Glacier Breeze)
Taste Test Comparison Data
Glacier Breeze Sports Beverage Taste Comparison Confidence Levels:
2400 ppm UV Absorber over PP Control - Significant at 99% confidence level
Foil Wrapped over PP Control - Significant at 99% confidence level Foil Wrapped over 2400 UV Absorber - Not Significant
Table F- Sports Beverage (Gatorade Lemon- Lime)
Taste Test Comparison Data
Fruit Punch Sports Beverage Taste Comparison Confidence Levels:
2400 ppm UV Absorber over PP Control - Significant at 99% confidence level
Foil Wrapped over PP Control - Significant at 99% confidence level
Foil Wrapped over 2400 UV Absorber - Not Significant
Table G - Sports Beverage (Gatorade Fruit Punch)
Taste Test Comparison Data
Lemon - Lime Sports Beverage Taste Comparison Confidence Levels:
2400 ppm UV Absorber over PP Control - Significant at 99% confidence level
Foil Wrapped over PP Control - Significant at 99% confidence level
Foil Wrapped over 2400 UV Absorber - Not Significant
Milk taste test procedure:
Sample Preparation and Exposure
Whole milk (Mayfield brand) was used for this procedure. The brand chosen for testing is packaged at the manufacturer in an opaque, yellow high density polypropylene container that is purported to block all light from the contents. This type of packaging is typical of that currently in use in the dairy industry.
All bottles were blown as previously described. Test sample bottles were prepared and labeled as follows:
-Polypropylene (PP)control - Bottles produced as described in example one
-Foiled control- Bottles produced as described in example 1 then wrapped in aluminum foil when test solution is added to prevent light from entering.
-2400 ppm UV Absorber- Bottle produced as described in example three
The bottles were filled with milk and sealed with screw caps. The bottles were then placed inside a VWR/ SheiLah model 2015 temperature controlled light exposure refrigerator. The temperature was set at 6 0 C, and the samples were exposed to light from eight UV-351 bulbs for a period of 4 hours. The samples were placed on a rack approximately two inches from the light source and positioned in an equivalent manner relative to the light source to ensure that they received equivalent UV exposure.
When the 4 hours of UV exposure was complete, the temperature of the test chamber was raised to 15 0 C for approximately 8 hours. This temperature is one often used for taste tests in the dairy industry, as subtle taste variations are enhanced at this temperature.
Each panelist is given a grouping of three samples for each head to head taste comparison The three samples are comprised of two blind samples plus the taste control, which is milk from the foil wrapped bottle described earlier. Panelists are instructed to choose which one of the blind sample pair tastes most like the taste control sample. After tasting a sample set and recording their results, they are instructed to eat an unsalted cracker and thoroughly rinse their mouth with tap water to cleanse the palate before tasting the next group of samples. All three combinations of samples were tested in this manner.
A total of fifteen panelists tasted each sample set and the results of the head to head comparisons are shown in table below.
Table G- Milk Taste Test Comparison Data
ilk Taste Test Comparison- Confidence Levels:
2400 ppm UV Absorber over PP Control - Significant at 95% confidence level
Foil Wrapped over PP Control - Significant at 99% confidence level
Foil Wrapped over 2400 ppm UV Absorber- Significant at 99% confidence level
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