WO2006082297A1

WO2006082297A1 - Packaging articles such as opaque bottles and method for making same

Info

Publication number: WO2006082297A1
Application number: PCT/FR2006/000190
Authority: WO
Inventors: Jean François BRIOIS; Jean-Luc Lepage
Original assignee: Tergal Fibres
Priority date: 2005-02-04
Filing date: 2006-01-27
Publication date: 2006-08-10
Also published as: FR2881714A1; AR054105A1

Abstract

The invention concerns packaging articles such as opaque bottles for storage protected against visible et UV radiation of certain products such as milk. More particularly, the invention concerns an opaque bottle obtained by extrusion blow molding of a polyolefin composition and a method for making packaging articles, in particular a bottle. The polyolefin composition comprises a mineral filler consisting of a white pigment such as titanium oxide or zinc sulphide.

Description

Packing articles such as opaque bottles and method of making such articles

The present invention relates to opaque packaging articles such as bottles for storage protected from visible and UV radiation of certain products such as milk.

It relates more particularly to an opaque bottle obtained by blow extrusion of a polyolefin composition or by extrusion blow molding or polyvinyl chloride blow molding and a method of manufacturing packaging articles, including a bottle.

Thermoplastic bottles and more particularly polyolefin or polyester bottles are increasingly used for the storage of various and varied liquids, including liquid foodstuffs such as water, beer, carbonated soft drinks or not generally called Soda. They are also used for storing milk.

However, the milk can be in various forms, depending on the treatment method applied, allowing storage for longer or shorter periods. Thus, raw or pasteurized milks must be used very quickly after bottling, on the contrary, UHT (ultra high temperature) or sterilized milks can be kept several months after bottling.

This very long shelf life imposes constraints for the storage container such as bottle or box.

Indeed, the taste of milk evolves under the effect of U.V and / or visible radiation. A milk with a taste altered by this phenomenon is qualified as "having a light taste".

This change is due in particular to the degradation of certain vitamins contained in milk such as vitamin B2 (Riboflavin) under the effect of a light exposure. Indeed, the degradation of this vitamin in milk varies according to the intensity of the light source, the exposure time and also the wavelength range of the light source.

Wavelength radiation below 550 nm seems to be responsible for the degradation of some of these vitamins and thus the alteration of the taste of milk. Consequently, the storage containers or the packaging of these containers must have a very low percentage of light transmission, or even zero, advantageously for radiation of wavelengths between 350 and 550 nm. This specification is all the more important as the storage time of the milk is long.

This constraint is very important for long-life milks such as ultra-high temperature (UHT) milks, as well as for certain radiation-sensitive vitamin milks.

Solutions for producing compatible containers for the long-term storage of milk have already been proposed and are widely used.

One of the most used is the cardboard box or brick with many layers to achieve zero light transmission for the UV and visible wavelength range.

However, the design of these boxes, after a first use, does not guarantee an effective closure.

To overcome the disadvantages of these boxes, such as stiffness, dead space, shape, size, handling, it has been proposed bottles including bottles of high density polyethylene (HDPE).

Nevertheless, to obtain a low level of light transmission throughout the wavelength range 350 nm -550 nm, these bottles are formed by multilayer walls which may comprise from three to six layers made of different materials.

The outer layers generally contain a white pigment consisting of titanium oxide to provide an aesthetic appearance compatible with the stored product.

As the intermediate layer, a low transmission layer is present. This layer generally comprises a carbon black as an absorbent charge of light. Finally, an oxygen barrier layer may also be present as well as layers of adhesives to obtain a good stability of the structure. These bottles require complex manufacturing processes. In others, their recovery and recyclability are difficult to implement given the presence of several different materials.

It has also been proposed, in particular by French Patent 1591905, bottles obtained by extrusion blow molding of a high density polyethylene comprising titanium oxide as mineral filler at a maximum concentration by weight of 5% by weight. According to this document, the presence of titanium oxide at a low concentration by weight (from 2% by weight) makes it possible to greatly reduce the transmission coefficient of wavelength radiations of between 350 and 380 nm. say corresponding to the near UV rays. However, for wavelength rays greater than 400 nm, the transmission coefficient remains high (above 5%) even at high concentrations of titanium oxide. In addition, this coefficient seems to stabilize at a minimum value of between 5 and 10% for titanium oxide concentrations greater than 3% by weight.

Such levels of transmission in the field of visible radiation are not compatible for the storage of many foodstuffs and more particularly UHT milk or sterilized milk.

The object of the invention is in particular to remedy these drawbacks by proposing a process for the manufacture of containers or packaging articles having a very low normal light transmission rate (less than 1%), particularly in the field of lengths of light. wave between 400 and 550 nm.

Such articles can be manufactured by simple methods already used for the manufacture of conventional containers and also have the advantage of being easily recycled for the same use because they are obtained from a single material and their recycling does not degrade not the intrinsic properties of the material.

For this purpose, the invention proposes a method for manufacturing articles for packaging products such as foodstuffs by shaping a composition comprising a thermoplastic polyolefin or polyvinyl chloride material and at least one opacifying filler. constituted by a white mineral filler selected from the group comprising titanium oxides, zinc sulphide, at a weight concentration greater than 5% and less than or equal to 40% by weight relative to the total weight of the composition, preferably between 6 and 20%, terminals included. As articles for packaging, it is meant flexible films obtained by extrusion, boxes or containers obtained by extrusion molding, and more particularly hollow bodies such as bottles obtained by extrusion blow molding. Depending on the properties of the thermoplastic material, these articles can also be obtained by injection blow molding processes.

According to the invention, the articles are formed by a single layer obtained from a composition as defined above.

According to a preferred feature of the invention, the articles obtained according to the process of the invention having a normal light transmission rate of less than 0.25% for wavelengths between 350 and 550 nm, in particular between 400 nm. and 550 nm and preferably less than 0.1% in this range of wavelengths.

By normal transmission rate of light is meant the ratio between the luminous intensity of the radiation exiting the wall and the luminous intensity of the incident radiation applied to the wall. The measurement of these intensities is carried out on the radiation in a direction perpendicular to the surface of the wall.

This transmission rate is a function of the nature of the charge, the concentration thereof and the thickness of the wall of the article.

Thus, the articles obtained by the method of the invention has a transmission rate of less than 0.25% for wall thicknesses of between 0.2 and 0.6 mm. Advantageously, the transmission rate is less than 0.20%, preferably less than 0.1%.

According to the invention, the inorganic filler is a white pigment such as titanium oxides in rutile and / or anatase form. These titanium oxides are in the form of particles of various sizes, advantageously between 0.1 .mu.m and 1 .mu.m.

According to the invention, another inorganic filler forming a white pigment, namely zinc sulphide, makes it possible to obtain compositions suitable for the manufacture of packaging articles having a light opacification suitable for a concentration of filler compatible with the methods of shaping the composition and its manufacture.

According to another characteristic of the invention, the processes for shaping the composition according to the invention are processes conventionally used for shaping polyolefins or polyvinyl chloride. Thus, the extrusion blow molding processes used for the manufacture of bottles used in particular for storing different liquid products are suitable for producing bottles from a composition according to the invention comprising a mineral filler. The adaptations of the extrusion and blowing conditions with the present charge ratio are customary for those skilled in the art and comparable to those necessary to adapt the extrusion blow molding process to a conventional polyolefin or polyvinyl chloride.

The articles obtained, in particular the bottles, are formed by a single layer and have a suitable aesthetic appearance especially for the storage of milk.

The properties of very weak transmission of light through the walls of the bottle allow the use of such a bottle for the storage of milk for a long time, from several days to a few months, without noticing an alteration of the taste of the milk . Consequently, this bottle is suitable for bottling fresh, pasteurized, vitaminized or long-lasting milk, and more particularly for milks that can be stored for long periods such as UHT milks, sterilized milks.

According to the invention, polyolefin means a high density polyolefin resin having a density of between 0.850 and 0.970 g / cm ³ , such as high density polyethylenes (HDPE), ethylene-propylene copolymers, polypropylenes.

The thermoplastic composition of the invention may contain other components such as dyes, brighteners, agents for protection against light and heat, antioxidants, for example. This list is given for information only and is not exhaustive.

According to the invention, the composition is manufactured according to conventional methods of manufacturing compositions based on polyolefins or PVC. In a preferred embodiment, the inorganic filler or white pigment is added to the polymeric matrix in the form of concentrated solutions or compositions also known as masterbatches.

Thus, the granules or particles of concentrated solutions are mixed with the polyolefin or PVC granules prior to the melt for feeding in shaping processes such as extrusion blow molding or injection blow molding.

These concentrated solutions or masterbatches are obtained by mixing the powder or particles of opacifying agent, for example titanium oxide, in a matrix advantageously constituted by the polyolefin or PVC used for the final composition. This mixture is made in any mixing device such as screw mixers, double or single screw. The concentration of titanium oxide is advantageously between 10 and 80% by weight, preferably between 20 and 60% by weight.

Titanium oxide may also be added directly to the molten polymer prior to feeding in the above shaping processes or mixed into powders or particles with the polymer pellets.

These compositions can find many applications such as film making, for example, for packaging

However, one of the particular and important uses of these compositions and which forms an object of the present invention is the manufacture of hollow bodies such as bottles by the technique of extrusion blow molding or injection blow molding.

In this use, the thermoplastic composition according to the invention is produced in the form of granules of more or less variable dimensions.

The granules are then introduced into extrusion blow molding processes for the manufacture of hollow containers such as bottles. These methods described in numerous publications and used industrially, on a large scale, include the manufacture of parisons in a first step. In a second step, the cooled or non-cooled parisons are heated to be blown to the shape of the desired bottles, possibly with a double-drawing.

The parisons are obtained, for example, by melting the resin in a single or double screw extrusion press, and feed it under pressure into a heated extrusion head, for example at a temperature of between 140 ^° C. and 200 ^° C.

Examples of conditions and processes for obtaining parisons and high density polyethylene bottles are already described in the literature, for example in the patent WO 95/03217.

The bottles thus obtained are made with walls formed by a single layer of material. They have a compatible white aesthetic appearance for the storage of foodstuffs such as milk. Other colors can be obtained by combining the fillers of the invention with colored pigments which can be advantageously mixed with the polyolefin granules before melting for extrusion molding.

As illustrated above, they can be obtained by conventional methods of manufacturing hollow bodies by extrusion blow molding.

The bottles thus obtained have a very low light transmission. Thus, after storing milk for a week, the taste of the milk was not altered according to a panel of taster.

The invention also makes it possible to produce bottles of different capacities and shapes, such as for translucent polyolefin bottles already used for the storage of liquid products.

Other advantages, details of the invention will become apparent from the examples given below by way of illustration, non-limiting.

A composition A according to the invention is produced using a thermoplastic matrix high density polyethylene (PEHDA) sold by BP SOLVAY under the name Eltex B4020LGN1963.

HDPE-A granules are reduced to powder by cryomilling to obtain a powder of particle size less than 200 .mu.m. This HDPE-A powder is mixed in a mixer with a TiO ₂ powder marketed by the company Sachtleben under the trade name Hombitan LO CR SM to obtain a 50/50 masterbatch by weight PEHDATiO ₂ . The homogeneity of the mixture is controlled by measuring the ash content.

This mixture of HDPE + TiO ₂ powder and natural PEHDA granules are mixed in an L / D extruder = 35.3. They are added by gravimetric feeders whose flow rates are set at 3.0 kg / h (HDPE + TiO ₂ ) and 12.0 kg / h (HDPE). The extruder is a co-rotating twin screw mounted with a dispersing screw profile. The temperature profile (set point) is as follows: Feeding area: 160 ⁰ C 5 Transport area: 165 ⁰ C Compression area: 17O ⁰ C Mixing area: 175 ⁰ C Head zone: 175 ⁰ C Filière: 17O ⁰ IOC

The rod obtained is cooled in a water tank and granulated in a dry granulator.

Similar compositions are made with the same HDPE but without the addition of HDPE / TiO2 blend (Composition B).

15

Films are produced by hot pressing (18O ⁰ C) in teflon molds of granules respectively obtained with composition A (Film A), with composition B (Film B) and with a composition C consisting solely of HDPE granules. sold by the company BP Solvay under the commercial reference Eltex C (film C). The thickness of the films obtained 0 are of the same order of magnitude as that of the wall of the bottles obtained by extrusion-blowing.

The residual normal transmissions for a wavelength of between 300 and 600 nm (UV / Visible) of the films are measured on Perkin Elmer Lambda spectrophotometer.

25 9.

The results are summarized in Table I below

Board

( ^* ) wavelength (λ) below which no residual transmission is detectable, ie less than 0.01%

These results are representative of those obtained with the walls of a bottle made with a composition according to the examples above.

In addition, bottles of 0.5 liter capacity were produced with compositions A, B and C. These bottles were filled with milk according to the UHT method and stored for 3 months in a lighting of 200 Lux. A tasting of the stored milk was organized according to the traditional taste evaluation procedure.

The milk of the bottles A has an unaltered taste ie "without taste light", unlike the milk of the bottles B and C.

Claims

claims

1. A method of manufacturing articles for packaging or storage of materials characterized in that it consists in shaping a composition comprising a polyolefin or polyvinyl chloride matrix and at least one white pigment-forming inorganic filler selected from the group comprising titanium oxides, zinc sulphide, the mineral filler being present at a weight concentration greater than 5% and less than or equal to 40% relative to the total weight of the composition.

2. Method according to claim 1, characterized in that the titanium oxide is selected from titanium oxides in rutile form and / or titanium oxides in anatase form.

3. Method according to claim 2, characterized in that the titanium oxide is in the form of particles coated with one or more protective layers.

4. Method according to one of the preceding claims characterized in that the polyolefin is selected from the group consisting of high density polyethylenes, polypropylenes, polyethylene-polypropylene copolymers.

5. Method according to one of the preceding claims, characterized in that the packaging articles are in the form of film, hollow body obtained by extrusion blow molding or injection blow molding.

6. Method according to claim 5, characterized in that the hollow bodies are bottles obtained by extrusion blow molding.

7. Packaging articles obtained by the method according to one of the preceding claims and having a normal transmission rate of light in the wavelength range of between 350 and 550 nm, preferably less than 0.25%. less than 0.1% for a wall thickness of between 0.2 mm and 0.6 mm.

8. Articles according to claim 7, characterized in that the article is a bottle obtained by extrusion blow molding, the wall of the body of the bottle having a normal light transmission rate of less than 0.25%.

9. Use of the articles according to claim 8 for the storage of milk.