WO1995003217A1

WO1995003217A1 - POLYOLEFIN COMPOSITONS, ARTICLES AND PRODUCTION METHODS CONTAINING FINELY DIVIDED TiO¿2?

Info

Publication number: WO1995003217A1
Application number: PCT/US1994/008144
Authority: WO
Inventors: Steven D. Blazey; Kristina N. Buehrle
Original assignee: A. Schulman, Inc.
Priority date: 1993-07-20
Filing date: 1994-07-19
Publication date: 1995-02-02

Abstract

The invention relates to thermoplastic molding compositions, especially polyolefin compositions such as HDPE and EP copolymer compositions, concentrates thereof adapted to be diluted by addition of further thermoplastic, and molded transparent products made therefrom which are characterized by effective UV light screening capacity, while still retaining transparency, due to incorporation therein of low-levels of ultrafine titanium dioxide, the TiO2 being present therein in an amount of 0.15 to 1.0, preferably 0.2 to 0.5 percent by weight, the particle size of the TiO2 being between 0.015 and 0.1 micron, preferably 0.015 and 0.08 micron, and a process for the production thereof. Preferred molded products are plastic milk containers whereby the Vitamin A content is protected against UV destruction and taste deterioration without introduction of adverse flavors or odors. Percentages of TiO2 in the concentrates are adapted to produce the desired amounts in the molding compositon upon dilution, and are between 5 and 30 percent, preferably between 7.5 and 15 percent, by weight.

Description

POLYOLEFIN COMPOSITIONS, ARTICLES AND PRODUCTION METHODS CONTAINING FINELY DIVIDEDTiO2

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to molded thermoplastic, especially polyolefin, products incorporating low levels of an ultra-fine titanium dioxide pigment which effectively screens out UV light without, at the same time, adding any observable degree of opacity to the product, compositions suitable for the production thereof, concentrates adapted to be diluted for the production of such compositions, and a process for the production thereof. In particular, the invention relates to plastic packaging applications of the thermoplastic, especially polyolefin, composition in the form of molded plastic packaging which, with its UV screening characteristics, assists in protection of the stability and/or nutritional value of the packaged contents from the harmful and destructive effects of UV radiation while at the same time not adversely diminishing visual transparency of the container or its fill-level visibility or introducing adverse or deleterious flavors or odors into the packaged contents. 2. Prior Art

The adverse effects of ultraviolet (UV) radiation upon foods and colors has been well documented in the literature and numerous commercial approaches have been undertaken in efforts to protect packaged materials from the harmful UV effects. Representative articles are listed upon the enclosed Appendix and copies thereof are provided herewith and listed upon an accompanying PTO 1449 for the conve¬ nience of the U.S.P.T.O. These items are 1, 2, 3, 4, 5 and 6 on the attached Appendix.

Ultraviolet radiation is generally defined as being the light region of about 400 nanometers down to about 190 nanometers. Different materials and foodstuffs are negatively influenced by different wavelengths. The presence of various additives in plastic-packaging materi¬ als has successfully blocked or absorbed UV radiation and protected the contents within, but only with limited success.

Numerous organic chemical additives are currently available for use by the plastics industry for such purpose. These are items 7 and 8 on the Appendix.

When used alone in plastics, these additives permit visual transparency of the plastics and function by absorb¬ ing ultraviolet light to reduce its transmission through the plastics packaging, thus protecting the package contents from UV-induced degradation.

Both inorganic and organic pigments have also been employed in attempts to block out all light frequencies, including UV frequencies, but transparency is often sacrificed and in many cases opacity and color result from their use. See item 9 on the attached Appendix. The most effective inorganic pigment for blocking UV light is the white pigment titanium dioxide, which according to the standard article of commerce has a mean particle size ranging from 0.17 to 5 microns. However, levels of 2 to 10 weight percent of such titanium dioxide particles yield opaque white plastic materials. The employment of other pigments in plastic applications may effectively block UV light, but to date they have been found also to impart color to the plastic container and thus mask the true color of the contents, which is impermissible from the standpoint of consumer acceptance and governmental regulations.

In the Soltex Polymer Corporation 9/83 copyrighted brochure, it is disclosed that 2% titanium dioxide pigment in HDPE "significantly reduces, but does not eliminate, light transmission in the harmful blue-violet region". By reference to the chart in this brochure identified as Figure 8, it is apparent that the 200 nanometer or 0.2 micron standard white titanium dioxide pigment at the 2% level in HDPE not only made the bottle opaque, but com- pletely blocked light waves below 400 nanometers in wave length and diminished transmission of light waves above 400 nanometers extending to the 800 nanometer wave length up to about 80%. However, this amount of pigment is totally unacceptable from the standpoint of processing, impact strength of the container, opacity imparted to the jug or bottle, excessive pigment content for acceptable recycling, general economics, and opacity which does not permit inspection of the product contained therein or even determination of its fill level. Moreover, the inventors know of no suggestion in that brochure or elsewhere to indicate or suggest that minimal reductions in transparency of the plastic could be effected, along with very consider¬ able reduction in transmission of light rays both in the ultraviolet range and in the blue-violet range, by the employment of a relatively insignificant amount of titanium dioxide particles having an extremely reduced particle size. It is apparent that the available art has suffered from the unavailability of plastic packaging which, while blocking or screening out deleterious ultraviolet rays, at the same time permits the necessary transparency to visualize the product content and fill level of the container and thus ensure consumer acceptance and compli¬ ance with governmental regulations. It is an object of the present invention to provide such suitable packaging materials, as well as other similar materials, and thus to overcome the stated shortcomings of the prior art as well as others.

OBJECTS OF THE INVENTION It is an object of the present invention to provide novel thermoplastic, especially polyolefin, molding compositions, concentrates to be let-down or diluted for the production thereof, transparent molded products produced therefrom, and a process for the production thereof, wherein the compositions contain a sufficient amount of finely-divided titanium dioxide which is effec- tive to block UV transmission through the final molded polymer but insufficient to interfere essentially with the transparency of the final molded product. Another object of the invention is to provide such compositions and process wherein the amount of finely-divided titanium dioxide is sufficient to provide final molded products in the form of thermoplastic polymer, e.g., polyolefin packaging, for example, milk containers, wherein the packaging is characterized by transparency but also UV- screening capacity which protects the nutritional contents of the packaged material from harmful deleterious effects of UV radiation while introducing no deleterious or adverse flavors or odors thereinto. Another object of the inven¬ tion is the provision of such compositions and molded products made therefrom wherein the amount of the finely- divided titanium dioxide is between about 0.15 and about 1.0 percent by weight, preferably about 0.2 to about 0.5 percent by weight, and wherein the size of the individual particles is between about .015 and about 0.1 micron, preferably between about 0.015 and 0.08 micron on their greatest dimension. Other objects of the invention will become apparent hereinafter and still others will be obvious to one skilled in the art to which this invention pertains.

SUMMARY OF THE INVENTION The invention therefore is directed to an improvement in the production of plastic containers as well as other molded plastic products wherein the transparency of the plastic is not essentially affected but wherein important quantities of UV light are screened out, especially from the contents of a packaging, polymeric compositions for the production of such molded products, concentrates designed to be let down and incorporated into such final polymeric molding compositions, and a process for the production of such compositions.

The invention, then, inter alia. comprises the following aspects, singly or in combination:

A process for production of a thermoplastic composi- tion suitable for molding into a transparent product, having incorporated therein a sufficient amount of ultra- fine titanium dioxide of a sufficiently small particle size so that, upon molding, the molded plastic product retains transparency but provides an effective block against penetration by UV light, the amount of titanium dioxide present in said composition being between about 0.15 and about 1.0 percent by weight and the particle size of said titanium dioxide being between about 0.015 and about 0.1 micron on its largest dimension; such a process wherein the ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight, such a process wherein the particle size of the titanium dioxide is between about 0.015 and about 0.08 micron on its largest dimension, such a process wherein the thermoplastic composition is a polyolefin composition, such a process wherein the polyolefin has a density between about 0.850 and 0.970, such a process in which the polyolefin composition consists essentially of HDPE or ethylene-propylene copolymer material, such a process in which the ultrafine titanium dioxide particles have a surface area between about 40 and about 130 square meters per gram, and such a process in which the ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight and has a particle size between about 0.015 and about 0.08 microns.

Also, a thermoplastic molding composition, or a concentrate convertible into said composition by the addition of additional thermoplastic thereto, which is suitable for molding into a transparent product, having incorporated therein a sufficient amount of ultrafine titanium dioxide of a sufficiently small particle size so that, upon molding, the molded plastic product retains transparency but provides an effective block against penetration by UV light, the amount of titanium dioxide present in said composition being between about 0.15 and about 1.0 percent by weight and the particle size of said titanium dioxide being between about 0.015 and about 0.1 micron on its largest dimension, such a composition wherein the ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight, such a composition wherein the particle size of the titanium dioxide is between about 0.015 and about 0.08 micron on its largest dimension, such a composition wherein the thermoplastic composition is a polyolefin composition, such a composition wherein the polyolefin has a density between about 0.850 and 0.970, such a composition wherein the polyolefin composition consists essentially of HDPE or ethylene-propylene copoly- mer material, such a composition wherein the ultrafine titanium dioxide particles have a surface area between about 40 and about 130 square meters per gram, and such a composition wherein the ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight and has a particle size between about 0.015 and about 0.08 microns.

In addition, a transparent molded thermoplastic resin product which is molded from a thermoplastic molding composition, the molded product obtained from said molding composition, without the addition of ultrafine titanium dioxide particles, as further defined in the following, being characterized by a tendency to permit the transfer of ultraviolet light therethrough in an essentially unimpeded manner, and the amount and size of the ultrafine titanium particles present in said product not interfering substan¬ tially with the transparency thereof, said molding composi¬ tion having incorporated therein a sufficient amount of ultrafine titanium dioxide of a sufficiently small particle size so that, upon molding, the molded product retains transparency but provides an effective block against penetration by UV light, the amount of the titanium dioxide in said composition being between about 0.15 and about 1.0 percent by weight and the particle size of said titanium dioxide being between about 0.015 and about 0.1 micron on its largest dimension, such a product wherein the ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight, such a product wherein the particle size of the titanium dioxide particles is between about 0.015 and about 0.08 micron on its largest dimension, such a product wherein the thermoplastic composition is a polyolefin composition, such a product wherein the polyolefin has a density between about 0.850 and 0.970, such a product wherein the polyolefin composition consists essentially of HDPE or ethylene-propylene copolymer material, such a product wherein the ultrafine titanium dioxide particles have a surface area between about 40 and about 130 square meters per gram, and such a product wherein said ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight and has a particle size between about 0.015 and about 0.08 microns.

Moreover, a thermoplastic polymer concentrate composi- tion which is adapted to be converted by the addition of additional thermoplastic polymer thereto into a thermoplas¬ tic molding composition adapted to be molded into a transparent molded thermoplastic product, said concentrate composition having incorporated therein a sufficient amount of ultrafine titanium dioxide of a sufficiently small particle size so that, upon molding, the molded thermoplas¬ tic product retains transparency but provides an effective block against penetration by UV light, the amount of the titanium dioxide pigment in said composition being between about 5 and about 30 percent by weight and the particle size of said pigment being between about 0.015 and about 0.1 micron on its largest dimension, such a concentrate wherein the molded product obtained from said polyolefin molding composition, without the addition of said ultrafine titanium dioxide pigment, is character¬ ized by the essentially unimpeded transmission of ultravio¬ let light therethrough, such a concentrate wherein the ultrafine titanium dioxide is present in an amount between about 7 and about 15 percent by weight, such a concentrate wherein the particle size of the titanium dioxide is between about 0.015 and about 0.08 micron on its largest dimension, such a concentrate wherein the thermoplastic composition is a polyolefin composition, such a concentrate wherein the polyolefin has a density between about 0.850 and 0.970, such a concentrate wherein the polyolefin composition consists essentially of HDPE or an ethylene-propylene copolymer material, such a concentrate wherein the ultrafine titanium dioxide particles have a surface area between about 40 and about 130 square meters per gram, and such a concentrate wherein said ultrafine titanium dioxide is present in an amount between about 7 and about 15 percent by weight and has a particle size between about 0.015 and about 0.08 microns.

Finally, such a process, polyolefin molding composi¬ tion or concentrate convertible into said composition by the addition of polyolefin, molded thermoplastic resin product, or polyolefin concentrate composition, wherein the titanium dioxide is food grade titanium dioxide and wherein the ultimate molded thermoplastic resin product is a transparent plastic milk container.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the drawings for a better understanding of the invention, wherein:

FIG. 1 is a graph showing percent light transmission plotted against wave length at various thicknesses in mils for the 100% HDPE control of Example 25 hereof having a density of 0.965. As will be noted, at 5 mils thickness, only approximately 18% of the visible light transmission is lost whereas, at 35 mils thickness, approximately 44% of the visible light transmission is lost to the plastic without any additive being present.

FIG. 2 is the same as FIG. 1, with 0.2% ultrafine titanium dioxide added according to the present invention, showing a loss of only 4% visible light transmission to the totally unpigmented plastic at 5 mils and a loss of only 15 percent visible light transmission as against the totally unpigmented plastic at a 35 mil thickness. At the approxi¬ mately 20 mil thickness, which is a normal thickness of the plastic wall of a milk jug, the percentage of visible light transmission lost to the unpigmented bottle of FIG. 1 is less than 15%.

FIG. 3 is the same, with 0.5% ultrafine titanium dioxide pigment added, showing a loss of light transmission in the visible range of only 12% compared to the totally unpigmented bottle of FIG. 1 at a thickness of 5 mils and a loss of 20% visible light transmission at a thickness of 35 mils as compared with the totally unpigmented plastic of FIG. 1. Again, at a 20 mil thickness approximately characteristic of the walls of most milk jugs, it is seen that the loss of visible light transmission with respect to the totally unpigmented bottle of FIG. 1 is slightly in excess of 15%.

FIG. 4 is a graph showing percent light transmission in the visible region plotted against the thickness in mils of an HDPE molding composition containing no ultrafine titanium dioxide additive, thus corresponding to the molding composition of Example 21, and containing 2%, 5%, and 10% titanium dioxide concentrate of Example 1 (all identified as PB H925), so as to correspond with the molding compositions of Examples 13 and 14, and a further molding composition containing 10% of the concentrate of Example 1, and

FIG. 5 is the same except that it relates to a random copolymer of ethylene and propylene (the base polymer having a density of 0.902) showing the percent transmission of light in the visible region as plotted against thickness in mils, like FIG. 4, but in this case showing the results using no additive, 2% concentrate, 5% concentrate, and 10% concentrate, the concentrates employed in this case all being identified as PB H930 and corresponding essentially to the concentrate of Example 1, but employing the ethylene propylene copolymer just identified in place of the high density polyethylene for producing the concentrate of Example 1.

In each of Figures 4 and 5, the retention of substan¬ tial transmission of light in the visible region is apparent in the plastic molding composition and molded products produced therefrom according to the present invention, whereas FIGS. 2 and 3 show the complete blocking of light rays below 345 nm and substantially diminished transmission of light rays of 400 nm or less, especially as compared with the curve of the control having no additive, as depicted in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The base compositions to which the present invention is directed are thermoplastic resins, especially poly- olefins, which are normally employed in the production of molded thermoplastics to produce a transparent product, such as, inter alia, polymers or copolymers of alpha- olefins, such as ethylene, especially high-density polyeth¬ ylene (HDPE), propylene (PP polymers and copolymers), butene, 1,4-methylpentene, 1,3-methylbutene, and the like, as well as mixtures thereof, as is well known in the art.

Other elastomeric resins which may be used as the base compositions of the invention or as a part thereof include polymers or copolymers which are elastomeric and compatible polyolefin modifiers such as EP, EPDM, EVA, EEA, SBS block copolymers, CPE, polybutadiene, polyisoprene, polybutylene, polyurethane elastomers, and so forth, to the extent that they do not interfere with the transparency of the ultimate molded product, which is of the essence of the present invention.

Thus, other compositions which may be employed as base compositions according to the invention, and which ulti¬ mately require transparency and UV screening to protect the contents of packaging or any material to be protected or enclosed by the molded plastic, whether in the form of sheet material or packaging, include polypropylenes (homopolymers and co- and terpolymers with other monomers), polyesters (PET, co-PET, PBT, PC and the like), styrenics (such as polystyrene, crystal and impact grades, and styrene copolymers), polymethylpentenes (homopolymer and copolymer), and blends of various of these resins with each other as well as with other resins capable of employment without diminishing the transparency of the final molded polyolefin product.

High-density polyethylene (HDPE), polypropylene homopolymers (PP), and ethylene-propylene copolymers (PC), are preferred base compositions, with HDPE being especially preferred.

THE ULTRAFINE TiO.

Levels of ultrafine Ti0₂ in the concentrate of the invention are between about 5 weight percent and 30 weight percent with the optimum range falling between 7 weight percent and 15 weight percent. All grades of ultrafine titanium dioxide, whether rutile or anatase types, are included in the invention with particle sizes ranging from about 15 to 100 nanometers (0.015 to 0.1 micron).

The particle size of the titanium dioxide pigment, as previously set forth, and in the recommended amount, is also a measure of the surface characteristics of the finely-divided pigment, and it is ordinarily desirable to have the material so finely comminuted that it has an extremely large surface area as compared with normal titanium dioxide pigments of commerce. Any titanium dioxide material having the defined and required particle size lending such greatly enhanced surface characteristics can be used as the UV blocking agent according to the present invention. The preferred surface area of the particles involved is usually between about 40 and 130 square meters, preferably between about 44 and about 118 square meters, per gram. The particle size of the individ¬ ual titanium dioxide particles should accordingly be between about 0.015 and about 0.1 micron for the particles to function as set forth in the following.

Different grades of titanium dioxide pigment are available, and any one of these can be employed advanta- geously in the compositions and according to the process of the invention, so long as the prescribed amounts and particle sizes as well as surface areas as set forth in the foregoing are observed.

In addition to the foregoing, it is recognized that the ultrafine titanium oxide may have a surface treatment involving silica, silica/alumina, or zirconia/alumina, and such surface-treated finely-divided or ultrafine titanium dioxide is commercially available. Such surface-treated particles are utilizable according to the present invention as well as those especially surface-treated from the standpoint of classification as a "food-grade" material, as well as also the un-surface-treated pigments, as will be well understood by one skilled in the art. They are all inert and do not migrate out of the plastic or polymer in which employed.

When used herein, the term "food-grade" titanium dioxide means titanium dioxide which is allowed for use without limit as to particle size or level of use in polyolefin films as listed under 21 CFR 177.1520 "Olefin polymers" and 21 CFR 181.30, and which may or may not be coated with lauric acid or isostearic acid, as is common for food packaging, or with another fatty acid permitted for food use in accord with 21 CFR 175.105, 176.170, 176.180, and 175.300, which include fatty acids derived from vegetable sources and refined fish, comprising as a representative example isostearic acid. CARRIER RESINS FOR THE CONCENTRATE, AND BASE RESINS

The carrier or base resins for the concentrate and for dilution of the same to form the molding composition of the invention can be any of a large number of resins, especial- ly polyolefins including polyethylenes and/or poly- propylenes and/or ethylene-propylene copolymers, or mixtures thereof, as mentioned in the foregoing, with densities ranging from 0.850 to 0.970 and melt indexes under ASTM condition E ranging from 0.01 to 125. THE FINAL POLYOLEFIN COMPOSITION AND PRODUCT

The employment of ultrafine Ti0₂ in HDPE or other polyolefin milk jugs as UV block to protect the Vitamin A content and taste of milk contained therein from the harmful effects of UV light exposure during processing and during shelf-life in the store, while at the same time maintaining the transparency of the container, is effected by employing ultrafine food-grade Ti0₂ usage levels between 0.15 weight percent up to 1.0 weight percent and having the said particle size ranging from 15 to 100 nanometers and preferably from 0.015 to 0.08 microns on their largest dimension.

In the amounts employed, the finely-comminuted titanium dioxide particles have several requisites in accord with the present invention. First, they must not substantially block or interfere with the transparency of the final molded product. Further, they must essentially reduce or block the amount of UV light transmitted through the transparent molded plastic product even though not substantially interfering with the transparency thereof or the fill-level view therethrough. The amount of ultrafine titanium dioxide pigment employed is obviously much less than that amount at which it would function as a filler, so that its function is exclusively as a light-blocking agent, especially a UV light-blocking agent.

As already stated, the final compositions of the Examples are advantageously initially formulated as concentrates with only a portion of the ultimate amount of polyolefin present therein to be extended, let down, or diluted to produce the final molding composition formula¬ tions of the Examples. In such cases, the amount of resin, especially polyolefin, in the concentrate is such that the appropriate additional amount of the resin, especially olefin, which may be the same or different, produces the final composition for molding. Suitable such concentrates are set forth in the following Examples 1-6.

Upon the addition of resin, especially polyolefin, to the concentrate, e.g., as exemplified in the above-identi¬ fied Examples 1-6, in the proper proportions, molding compositions corresponding respectively to those of Examples 1-6 are obtained. These molding compositions, whether formulated directly or from a concentrate, produce a molded product having the desired UV blocking character¬ istics and transparency.

In the Example 1 given, a portion or all of the HDPE may be replaced by a polypropylene homopolymer such as Himont βSOl¹"¹ having a density of 0.901, characteristic of polypropylene homopolymers generally, or other equivalent polyolefin having the proper density to give a transparent product upon molding.

Likewise, upon addition of the requisite parts of such a polyolefin polymer to the concentrate of Example 1, there is obtained essentially the same molding composition as in Example 7 or 13. Moreover, addition of the requisite number of parts of HDPE or Himont 6501"" or equivalent to the concentrate of Example 4 gives essentially the same molding composition as in Examples 10 or 17, as will be well understood by one skilled in the art.

As to the Examples, part or all of the polyolefin there employed can be replaced or substituted by other polyalkylenes, for example the polyethylenes Norchem 953 of 0.918 density or Fortiflex + 50-1000 of 0.952 density or like homopolymer or copolymer which gives a transparent product upon molding.

SPECIFIC DESCRIPTION OF THE INVENTION The following Examples and test results are given to illustrate the present invention but are not to be con¬ strued as limiting.

The experiments carried out involve the compounding of different grades of ultrafine titanium dioxide into carrier resins to serve as masterbatches or concentrates to be extended in the generation of final polymeric compositions to be used in films, sheets, and especially blow molding for plastic packaging. The plastic packaging was filled with milk and tested for Vitamin A retention in a time-con- trolled UV exposure study. Further experiments were carried out to evaluate the influence of the titanium dioxide UV screen upon flavor of the milk contained within the packaging. An evaluation of the effectiveness of ultrafine Ti0₂ as a UV block or screen was undertaken in HDPE and ethylene-propylene copolymer and the results of these experimentations and studies are reported in the following.

MASTER BATCH OR CONCENTRATE PREPARATION EXAMPLE 1. A preweighed amount of 10 weight % of ultrafine titanium dioxide (UF-10 supplied by Tioxide-USA) was added to 90 weight % high density (0.965) polyethylene (SOLTEX T-60-800 supplied by Solvay-USA) and melt-mixed using a number of acceptable plastic mixers (Banbury, twin screw, single screw, continuous mixer, co-kneader, etc. )

For this example, a Banbury mixer was used to disperse the UF-10 and a single screw with breaker plate and screens was used to strand the material for pelletization. The amount of Ti0₂ was 0.8 lb. and the amount of HDPE was 7.2 lbs. The Ti0₂ had a particle size of 0.018 micron and a surface area of 118 square meters per gram.

EXAMPLE 2. Same as EXAMPLE 1 except the materials were mixed and stranded in a twin screw to achieve dispersion of the additive into the high density polyethylene.

EXAMPLE 3.

Same as EXAMPLE 1 except the materials were mixed in a single screw to achieve dispersion of the additive into the high density polyethylene.

EXAMPLE 4.

Same as EXAMPLE 1 except another grade of ultrafine titanium dioxide (UF-01, supplied by Tioxide-USA) was substituted for the UF-10. Particle size was 0.018 micron and the surface area was 44 square meters per gram.

EXAMPLE 5.

Same as EXAMPLE 1 except another grade of high density polyethylene (SOLTEX T-60-3000-119, supplied by Solvay-USA) was substituted for the initial grade.

EXAMPLE 6.

Same as EXAMPLE 4 except another grade of high density polyethylene (SOLTEX T-60-3000-119, supplied by Solvay-USA) was also substituted for the original grade. Each of the concentrates produced from EXAMPLES 1, 2,

3, 4, 5 and 6 were evaluated for dispersion of the additive by first mixing together the concentrate pellets and a high density resin and then blowing film and counting the points of undispersed additive.

DILUTION OF THE CONCENTRATE AND EVALUATION OF THE POLY¬ OLEFIN PRODUCTS IN THE FORM OF FILM EXAMPLE 7.

Five (5) weight % of the concentrate pellets pro¬ duced from Example 1 and 95% high density polyethylene pellets (SOLTEX T-60-800 supplied by Solvay) were pellet blended in a shaker. Film (thickness from 0.5 to 2.0 mil) was then produced on a Killion 1.5" extruder film blower at 450°F and evaluated for the dispersion of the additive. The quality of the dispersion is evaluated by physically counting the points of undispersed additive per unit square measure of film. Less than 10 points per square meter of film is defined as "good". EXAMPLE 8.

Same as EXAMPLE 7 except the concentrate from EXAMPLE

2 was used. EXAMPLE 9. Same as EXAMPLE 7 except the concentrate from EXAMPLE

3 was used. EXAMPLE 10.

Same as EXAMPLE 7 except the concentrate from EXAMPLE

4 was used. EXAMPLE 11.

Same as EXAMPLE 7 except the concentrate from EXAMPLE

5 was used. EXAMPLE 12.

Same as EXAMPLE 7 except the concentrate from EXAMPLE 6 was used.

The results from the evaluations of the dispersions of the concentrates produced from EXAMPLES 7, 8, 9, 10, 11, and 12 are shown in TABLE 1. TABLE 1: EVALUATIONS OF MIXING DISPERSIONS OF THE CONCENTRATES PRODUCED FROM EXAMPLES 1-6

SAMPLE DISPERSION EVALUATION

(points/sq.meter)

EXAMPLE 7 7

EXAMPLE 8 10 - unacceptable, further mixing required

EXAMPLE 9 43 - unacceptable, further mixing required

EXAMPLE 10 9

EXAMPLE 11 8

EXAMPLE 12 5

PREPARATION OF BLOW MOLDING COMPOSITIONS CONTAINING THE

CONCENTRATE AND EVALUATION THEREOF EXAMPLE 13.

Two (2.0) weight % of the concentrate made from

EXAMPLE 1 was compounded into 98 weight % high density polyethylene (SOLTEX T-60-800, supplied by Solvay-USA) and processed through a single screw extruder to homogenize the additive throughout the plastic material and pelletized.

EXAMPLE 14.

Same as EXAMPLE 13 except 5 weight % EXAMPLE 1 was compounded into 95 weight % of the same high density polyethylene. EXAMPLE 15.

Same as EXAMPLE 13 except 2 weight % EXAMPLE 5 was compounded into 98 weight % of the same high density polyethylene.

EXAMPLE 16. Same as EXAMPLE 13 except 5 weight % EXAMPLE 5 was compounded into 95 weight % of the same high density polyethylene. EXAMPLE 17.

Same as EXAMPLE 13 except 2 weight % EXAMPLE 4 was compounded into 98 weight % of the same high density polyethylene. EXAMPLE 18.

Same as EXAMPLE 13 except 5 weight % EXAMPLE 4 was compounded into 95 weight % of the same high density polyethylene. EXAMPLE 19.

Same as EXAMPLE 13 except 2 weight % EXAMPLE 6 was compounded into 98 weight % of the same high density polyethylene. EXAMPLE 20.

Same as EXAMPLE 13 except 5 weight % EXAMPLE 6 was compounded into 95 weight % of the same high density polyethylene. EXAMPLE 21.

100 weight % SOLTEX T-60-800 HDPE was compounded in the same manner as EXAMPLE 13 to serve as the control container which would contain NO ultrafine Ti0₂

The above compounded materials were tested for their additive content by burning off the combustible portions and observing the residual ash values. These residual additive values are shown in TABLE 2 below: TABLE 2: RESIDUAL ADDITIVE CONTENTS IN EXAMPLES 13-21

ADDITIVE CONTENT

SAMPLE (parts per mi .llion)

EXAMPLE 13 2330

EXAMPLE 14 4650

EXAMPLE 15 2470

EXAMPLE 16 5250

EXAMPLE 17 4950

EXAMPLE 18 9690 silica surface

EXAMPLE 19 3070 treated

EXAMPLE 20 6720

EXAMPLE 21 none BLOW MOLDING OF ONE ( 1. GALLON HDPE MILK BOTTLES

Each compounded high density material containing the ultrafine titanium dioxide described in EXAMPLES 13 - 21 was blow molded using a UNILOY™¹ single cavity blow molding machine into one (1) gallon standard size milk jugs as shown in TABLE 3 below:

TABLE 3. PARAMETERS FOR BLOW MOLDING EXAMPLES 13 - 21

EXAMPLE 13 14 15 16 17 18 19 20 21

TEMPERATURE SETTING

FEED 350^βF TRANS 350°F METER 375°F HEAD 325^βF DIE 325°F

EXAMPLE 13 14 15 16 17 18 19 20 21

TEMPERATURE READING

FEED (°F) 350 350 350 348 349 352 346 349 353 TRANS (^βF) 389 389 389 389 389 389 385 390 389 METER (^βF) 388 388 388 388 383 387 383 387 386

HEAD (^βF) 326 326 325 325 326 327 326 325 328 DIE (^βF) 346 345 346 345 342 347 344 344 345

MELT (^βF) 343 342 341 342 342 341 342 341 344

EXAMPLE 13 14 15 16 17 18 19 20 21

OPERATION CONDITIONS

RPM 1200

AMP 26-28 26-7 26-7 25-6 26-7 26-7 26-7 26-7 26-7 25-6

CYCLE (sec) 9.44 9.52 9.36 9.40 9.40 9.36 9.36 9.44 9.68

DROP (sec) 1.76 1.78 1.78 1.78 1.80 1.81 1.81 1.77 1.80

SHOT WT. 108 ± 2 g 108 108- 108 108 108 108 108 108 108

BOTTLE WT. 68 g 68 68 68 68 68 68 68 68 68

CHANGE IN BOTTLE WT SAME +ig SAME -.Sq SAME +2g SAME -2g CTRL

FLARE ^■5.85 5.80 5.75 5.75 5.80 5.80 5.70 5.80 5.75

ODOR (SUBJECTIVE) LITE LITE LITE LITE LITE LITE LITE LITE LITE It can be noted that there was no significant variation of blow molding conditions required to blow mold EXAMPLES 13-21. Physical property measurements of the milk bottles were qualitatively determined to be comparable to those of the CONTROL material which did not contain any ultrafine titanium dioxide.

EVALUATION OF MILK BOTTLES FOR UV BLOCK EFFECTIVENESS IN PRESERVING VITAMIN A CONTENT OF MILK

A testing program was established with Cornell Univer- sity to evaluate the effectiveness of the blow molded milk containers made from EXAMPLES 13-21 compounded materials to protect the Vitamin A content within the milk upon various exposure times to UV light.

Test jugs and control jugs were filled from single source milk produced within Cornell University. Test jugs were placed one foot from the light source of 80 foot candles in a specially-designed vented cooler at 3.3°C (38°F) with circulating fan. The interior of the cooler was painted a dark gray and the light source consisted of a four-foot long light fixture containing two fluorescent bulbs. The intensity of the light was measured by a GE Model 214 light meter.

Samples were removed at programmed exposure intervals of 24 hours and the Vitamin A content was determined and compared with the "day-zero" initial amount.

The Vitamin A was measured using the modified fluoro- metric method of Senyk et al., J. Dairy Sci. 53, 558-560 (April 1975), developed at Cornell from the method of Thompson et al., J. Dairy Sci. 5_5_, No. 8, 1077-1080 (1973). The results are shown below in Tabular form (TABLE 4). TABLE 4

Vitamin A International Units per quart - Evaluation After four (4) days in light

Initial Value 2700 IU/qt.

Control (Example 21) 1700 IU/qt. (-1000 = -37%)

Example 13 (0.2% Ti0₂) 2250 IU/qt. (-450 = -16%)

Example 14 (0.5%) 2500 IU/qt. (-200 = -7%)

Example 15 (0.2%) 2150 IU/qt. (-550 = -20%)

Example 16 (0.5%) 2500 IU/qt. (-200 = -7%)

Initial Value 2800 IU/qt.

Control (Example 21) 1700 IU/qt. (-1000 = -37%)

Example 17 (0.2% Ti0₂) 2350 IU/qt. (-450 = -16%)

Example 18 (0.5%) 2550 IU/qt. (-250 = -9%)

Example 19 (0.2%) 2200 IU/qt. (-600 = -21%)

Example 20 (0.5%) 2550 IU/qt. (-250 = -9%)

N.B. 2100 - 2300 IU/qt. is the minimum USDA recommended requirement.

The loss of Vitamin A in IU/qt. was accordingly reduced by between 43% (21/37 - 100) and 81% (7/37 - 100) over the control.

EVALUATION OF BLOW MOLDED MILK BOTTLES FOR EFFECTIVENESS OF THE UV BLOCK IN FLAVOR RETENTION

A testing program was established with Cornell Univer¬ sity to evaluate the effectiveness of the blow molded containers made from EXAMPLES 13-21 to preserve the taste of 2% milk once exposed to UV light. The taste was found to be well preserved and not adversely affected by the Ti0₂ additive.

Samples of the exposed milk were evaluated by a controlled "taste panel" which determined any changes in the taste of the milk relative to the control and the UV exposure times.

The results of the taste evaluations concluded that all samples had a "scorched" or "burnt" in taste after 24- hour exposure. However, the control was more intense than the test samples. After 4 days, all samples were rated as equally "scorched" by the taste panel at Cornell.

EVALUATION OF UV-BLOCKING EFFECTIVENESS OF COMPOSITIONS OF THE INVENTION IN THE VISIBLE LIGHT SPECTRUM IN HDPE AND ETHYLENE-PROPYLENE COPOLYMER

Experiments were performed to determine the effective¬ ness of ultrafine Ti0₂ in both HDPE and ethylene-propylene copolymer materials at varying thicknesses. EXAMPLE 22. Two (2) weight % EXAMPLE 1 was mixed with 98 weight %

HDPE (Solvay T-60-800) in a 45 gram electrically heated Brabender mixer for 5 minutes at 190°C. Samples were then compression molded into various thicknesses, the light transmissions were measured over the range of 500 to 190 nanometers (nm), and the curves were generated at varying thicknesses ranging from 0.005 inches to 0.035 inches. These curves are shown in FIG. 2. EXAMPLE 23.

Same as EXAMPLE 22 except 5 weight % EXAMPLE 1 was mixed with 95 weight % HDPE (Solvay T-60-800). These curves are shown in FIG. 3. EXAMPLE 24.

Same as EXAMPLE 22 except 10 weight % EXAMPLE 1 was mixed with 90 weight % HDPE (Solvay T-60-800). These curves showed greater UV blocking than the curves of FIGS. 2 and 3. EXAMPLE 25.

Same as EXAMPLE 22 except 100 weight % HDPE (Solvay T-69-800) was mixed and compression molded into the varying thicknesses and measured. These curves represent the controls and are shown in FIG.l (Control). EXAMPLE 26.

Same as EXAMPLE 22 except 2 weight % EXAMPLE 1 was mixed with 98 weight % random ethylene-propylene copolymer (Fina 8473), compression molded into varying thicknesses and the light scans measured. These curves closely approxi¬ mated those of FIG. 2. EXAMPLE 27.

Same as EXAMPLE 22 except 5 weight % EXAMPLE 1 was mixed with 95 weight % random ethylene-propylene copolymer (Fina 8473). These curves closely approximated those of FIG. 3. EXAMPLE 28.

Same as EXAMPLE 22 except 10 weight % EXAMPLE 1 was mixed with 90 weight % random ethylene-propylene copolymer (Fina 8473). These curves showed greater UV blocking than the curves of FIGS. 2 and 3. EXAMPLE 29.

Same as EXAMPLE 22 except 100 weight % random ethyl¬ ene-propylene copolymer was mixed and used to generate the curves for the control. These curves approximated those of FIG. 1.

The curves from Examples 26 through 28 all evidence a much greater UV-blocking capacity in the products of these Examples as compared with the product of control Example 29.

UV light transmissions were also measured on the blow molded milk jugs to further establish the effectiveness of the Ultrafine Ti0₂ in HDPE applications. These results corresponded essentially to those reported earlier in TABLE

4, the less the transmission the higher the Vitamin A content of the milk.

* * * * * Although it is entirely possible to make direct addition of low levels, i.e., of the prescribed amount, of the prescribed-size titanium dioxide particles to the poly¬ olefin or other thermoplastic resin to be employed in the molding procedure, this approach offers an increased risk of variation and also for poor dispersion of the additive into the polyolefin or other plastic composition, the effective distribution of the ultra-fine Ti0₂ into the polymer matrix being extremely important from the stand¬ point of achieving optimum UV screening results, part performance, and maximization of transparency. According¬ ly, to achieve optimum performance in any case, but espe¬ cially in the production of transparent packaging contain¬ ers containing the prescribed amounts of the prescribed- size titanium dioxide pigment, a masterbatch or concentrate containing higher levels of the additive is definitely preferred and recommended for the most efficient distribu¬ tion of the additive in the final molding composition and the let down, dilution, or extension of such a masterbatch concentrate is well-established procedure in the industry and causes no inconvenience to the operator.

In summary, the employment of ultra-fine titanium dioxide pigment particles has been established as an effective UV screen or block when used at levels between 0.15 and 1.0, especially 0.2 and 0.5, weight percent in various transparent plastic, especially HDPE and other polyolefin applications. The adverse effects of UV light on the Vitamin A content of milk packaged in HDPE jugs con¬ taining the necessary amounts of the necessarily-sized Ti0₂ pigment have been shown to be minimized with potentially increased shelf life for the Vitamin A nutritional content of the milk. It has also been shown that the taste of milk packaged in such containers is not adversely affected by the employment of ultra-fine Ti0₂ in the plastic milk jugs employed.

The advantages accruing to the incorporation of the additive of the present invention into plastic food con¬ tainers as a protection for the contents thereof are many, including the economic advantages, particularly in the milk-packaging industry, involving 1) reducing the need for adding additional levels of Vitamin A at the diary, 2) extended shelf life of the Vitamin A, 3) competitiveness with paper milk containers, 4) recycle potential for the plastic milk jugs containing the necessary low-level Ti0₂ UV-screening feature, and 5) maintenance of the visibility of the content levels and quality, which is important from the standpoint of consumer acceptance and safety.

Packaging applications to which the present invention is particularly directed and in which the present invention is particularly useful, include the following:

1) Any application in which the molded plastic is de¬ signed to protect any material on the other side thereof from the deleterious effects of ultraviolet light but which application requires that the protecting molded plastic, whether sheet or otherwise, be essentially transparent,

2) Plastic packaging requiring a UV screen to ensure the nutritional or assayable value of the contents of the packaging, such as dairy products, pharmaceuticals, vita- mins, foodstuffs, and the like, and

3) Plastic packaging which requires a UV screen to ensure the color or other physical property retention of UV- sensitive contents, for example, UV-sensitive colored fabrics, items, foodstuffs, and the like.

It is thereby seen that all of the objects of the present invention have been accomplished and that poly- olefin and other plastic compositions and concentrates thereof, as well as transparent molded products made therefrom, containing an effective amount of ultrafine titanium dioxide pigment, which is efficient to block the transfer of UV light through the molded polymer but insuf- ficient to cause opacity of the polymer, have been provided and whereby all of the other objects of the present inven¬ tion have been accomplished, including a process for the production thereof.

It is to be understood that the present invention is not to be limited to the exact details of operation or exact compounds, compositions, formulations, methods, or procedures shown and described, as various modifications and equivalents will be apparent to one skilled in the art, wherefore the present invention is to be understood as limited only by the full scope which can be accorded to the ensuing claims.

A P P E N D I X

REFERENCES

(1) Correspondence from OTTO MILK COMPANY May 12, 1969.

(2) S. L. Bray, A. H. Duthie, and R. P. Rogers, "Consum- ers Can Detect Light-Induce Flavor in Milk", Journal of Food Protection. Vol. 40, No. 9, pages 586-587.

(3) Correspondence from the Pennsylvania State University which evaluated the light induced flavor of milk samples between 1986 and 1992. (4) S. Barnard, "Milk Should Be Packaged in Light- Blocking Plastic Jugs", PENN STATE NEWS, March 22, 1993.

(5) S. Barnard, R. Hollender, L. Moir, Correspondence from the Pennsylvania State University : "Consumer Sensory Evaluation of Milk With and Without Light induced Flavor".

(6) P. Dimick, J. Can. Inst. Food Sci. Technol.. Vol. 15, No. 4, pp. 247-256 (1982). "Photochemical Effects on Flavor and Nutrients of Fluid Milk" (7) Ciba-Geigy, supplier of chemical additives to block

UV light.

(8) American Cyanamid, supplier of chemical additives to block UV light.

(9) Soltex Polymer Corporation, copyrighted presentation, September, 1983.

(10) Thompson, et al., J. Dairy Sci. 55_., No. 8, pp 1077-1080 (1973) "Fluorometric Determination of Vitamin A in Diary Products".

(11) Senyk, et al., Journal of Dairy Sci. Vol. 5_8, 558-560 (April 1975) Technical Notes - "Modified Fluorometric

Determination of Vitamin A in Milk".

Claims

WE CLAIM:

-1- A molded thermoplastic resin jug product which is molded from a thermoplastic molding composition consisting essentially of HDPE or an ethylene-propylene copolymer material having a density between about 0.85 and 0.97 and ultrafine titanium dioxide particles, the molded product obtained from said molding composition, without the addi¬ tion of ultrafine titanium dioxide particles, as further defined in the following, being characterized by a tendency to permit the transfer of ultraviolet light therethrough in an essentially unimpeded manner, and the amount and size of the ultrafine titanium dioxide particles present in said product being non-migrating and not interfering substan¬ tially with the transparency thereof, said molding composi¬ tion having incorporated therein a sufficient amount of food-grade ultrafine titanium dioxide of a sufficiently small particle size so that, upon molding, the molded product retains transparency but provides an effective block against penetration by UV light, thus preserving a high percentage of Vitamin A content of milk when contained therein, the amount of the titanium dioxide in said compo¬ sition being between about 0.15 and about 1.0 percent by weight and the particle size of said titanium dioxide being between about 0.015 and about 0.1 micron on its largest dimension. -2- A product of Claim 1, wherein the ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight.

-3- A product of Claim 1, wherein the particle size of the titanium dioxide is between about 0.015 and about 0.08 micron on its largest dimension.

-4- A product of Claim 1, wherein the thermoplastic composition is an HDPE composition.

-5- A product of Claim 4, wherein the jug contains milk.

-6- A product of Claim 4, wherein the ultrafine titanium dioxide particles have a surface area between about 40 and about 130 square meters per gram.

_7_

A product of Claim 4, wherein said ultrafine titanium dioxide is present in an amount between about 0.2 and about 0.5 percent by weight and has a particle size between about 0.015 and about 0.08 microns.