PREFORM AND CONTAINER WITH VARIABLE TRANSMITTANCES

Abstract

The invention relates to a preform intended for forming containers by blow molding or stretch-blow molding, the preform being made of plastic material including at least one additive giving the plastic material the property of at least partially filtering the visible light spectrum, the preform comprising a wall forming a hollow body, said one or more additive(s) giving the plastic material the property of at least partially allowing the passage of light in the infrared spectrum.

Claims

1. A preform (1) intended for forming containers (2) by blow molding or stretch-blow molding, the preform (1) being made of plastic material including at least one additive giving the plastic material the property of at least partially filtering the visible light spectrum, the preform (1) comprising a wall (120) forming a hollow body, characterized in that said one or more additive(s) give the plastic material the property of at least partially allowing the passage of light in the infrared spectrum, and in that the wall (120) has, under electromagnetic radiation emitted perpendicular to the wall (120), transmittance: in the visible spectrum, that is substantially equal to 0% in the wavelength range of 350 nm to 520 nm; and in the infrared spectrum within a transmittance range extending between a threshold transmittance and an upper transmittance, for at least one wavelength within the range of 700 nm to 2250 nm, the threshold transmittance being equal to 5% and the upper transmittance being equal to 70%.

2. The preform (1) as claimed in claim 1, wherein the transmittance in the infrared spectrum is within the transmittance range at wavelengths within the range of 750 nm to 1400 nm, and preferably within the range of 950 nm to 1400 nm.

3. The preform (1) as claimed in claim 1, wherein the transmittance in the infrared spectrum is within the transmittance range for one wavelength or within a spectrum of wavelengths within one of the following ranges: 1110-1160 nm; 1390-1450 nm; 1610-1650 nm; 1675-1700 nm; 1880-2100 nm; 2170-2230 nm.

4. The preform (1) as claimed in claim 1, wherein the transmittance in the infrared spectrum is within the transmittance range for a wavelength of 1130 nm.

5. The preform (1) as claimed in claim 2, wherein the transmittance in the infrared spectrum is within the transmittance range for a wavelength of 1130 nm.

6. The preform (1) as claimed in claim 3, wherein the transmittance in the infrared spectrum is within the transmittance range for a wavelength of 1130 nm.

7. The preform (1) as claimed in claim 1, wherein the threshold transmittance equals 8%, and preferably equals 10%.

8. The preform (1) as claimed in claim 2, wherein the threshold transmittance equals 8%, and preferably equals 10%.

9. The preform (1) as claimed in claim 3, wherein the threshold transmittance equals 8%, and preferably equals 10%.

10. The preform (1) as claimed in claim 1, wherein the upper transmittance equals 50%, and preferably equals 20%.

11. The preform (1) as claimed in claim 2, wherein the upper transmittance equals 50%, and preferably equals 20%.

12. The preform (1) as claimed in claim 3, wherein the upper transmittance equals 50%, and preferably equals 20%.

13. The preform (1) as claimed in claim 1, wherein the plastic material also includes at least one colorant.

14. The preform (1) as claimed in claim 1, wherein the thickness of the wall (120) is within the range of 1 mm to 5 mm, and preferably within the range of 2 mm to 3.5 mm.

15. The preform (1) as claimed in claim 1, wherein the transmittance measured on a wall of the container (2) for which said preform (1) is intended is less than 5% within the wavelength range of 350 nm to 520 nm, whereby the transmittance of the wall (120) of the preform (1) in the visible spectrum is considered to be substantially equal to 0%.

16. The preform (1) as claimed in claim 15, wherein the transmittance measured on a wall of said container (2) is less than 0.5%, within the wavelength range of 350 nm to 520 nm.

17. The preform (1) as claimed in claim 1, wherein the plastic material includes one or more additives forming a barrier against radiation below 350 nm.

18. A container (2) made of plastic material formed by blow molding or stretch-blow molding a preform (1) as claimed in claim 1, the container (2) comprising a wall, wherein the wall of the container (2) has, under electromagnetic radiation emitted perpendicular to said wall, transmittance, called container transmittance, of less than 5% within the wavelength range of 350 nm to 520 nm.

19. The container (2) as claimed in claim 18, wherein the transmittance of the container is less than 0.5% within the wavelength range of 350 nm to 520 nm.

20. A method for manufacturing a container (2) made of plastic material, successively comprising: manufacturing the preform (1) made of plastic material including at least one additive giving the plastic material the properties for at least partially filtering the visible light spectrum, and of allowing at least partial passage of light in the infrared spectrum, heating a preform (1), involving emitting heating radiation toward the preform (1) that is at least made up of electromagnetic radiation in an infrared spectrum for at least one wavelength within the range of 700 nm to 2250 nm; and forming a container (2) from the preform (1); wherein: the preform (1) comprises a wall (120) forming a hollow body, said wall (120) having, for the heating radiation and under electromagnetic radiation emitted perpendicular to said wall (120), transmittance within a transmittance range extending from 5% to 70%; and said wall (120) has, in the entire light spectrum within the range of 350 nm to 520 nm, transmittance of less than 5%, and preferably of less than 0.5%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Other features and advantages of the invention will become more clearly apparent on reading the following description of various embodiment, when taken in conjunction with the accompanying drawings.

[0093] FIG. 1 is a schematic representation of a method for manufacturing a container from a preform, according to the invention;

[0094] FIG. 2 is a graph illustrating the transmittance of a preform according to the invention, and the transmittance of a conventional transparent preform, connected with the irradiance of a halogen oven and of a laser oven.

DETAILED DESCRIPTION

[0095] With reference to FIG. 1, a method for manufacturing a container 2 made of plastic material according to the invention is shown.

[0096] This method, which is described in further detail hereafter, allows containers 2 to be manufactured from a preform 1 according to the invention by blow molding or stretch-blow molding.

[0097] The preform 1 comprises: [0098] a neck 11; [0099] a body 12; [0100] a base 13.

[0101] The body 12 is rotationally symmetrical about a central axis C and has a rotationally cylindrical portion 121.

[0102] This body 12 is formed by a wall 120.

[0103] The thickness of the wall 120 is within the range of 1 mm to 5 mm, and preferably within the range of 2 mm to 3.5 mm.

[0104] This wall 120 has an outer skin 122 and an inner skin 123.

[0105] The base 13 is located at one of the ends of the body 12 and closes said body.

[0106] The neck 11 extends in the extension of the body 2, at another end of the body 12. This neck 11 is open and forms a lip for a final container 2 formed from the preform 1. The neck 11 has a final form that is intended to be preserved on the container 2 formed from the preform 1.

[0107] The preform is made of plastic material, for example, from polyethylene terephtalate (PET). In other words, the preform mainly includes PET.

[0108] For its part, the container 2 comprises: [0109] a neck 21; [0110] a body 22; [0111] a base 23.

[0112] By way of analogy, the body 12 of the preform 1 becomes the body 22 of the container 2, the neck 11 of the preform 1 remains unchanged during the process of forming the container 2, and the base 13 of the preform 1 becomes the base 23 of the container 2.

[0113] In order to manufacture the container 2 from the preform 1, the method successively comprises: [0114] a step of manufacturing the preform 1 made of plastic material; [0115] a step of heating the preform 1; [0116] a step of forming the container 2 from the preform 1.

[0117] With reference to FIG. 1, the heating step is carried out within a heating unit 3, and the forming step is carried out within a forming unit 4.

[0118] The heating step involves emitting heating radiation toward the preform. The purpose of this heating step is to heat the plastic material of the preform 1 until it exceeds its glass transition temperature, yet without reaching its spherulitic crystallization temperature.

[0119] As described hereafter, the heating step can be carried out either by an oven equipped with halogen lamps, called “halogen oven”, or by an oven equipped with laser diodes, called “laser oven”.

[0120] The forming step is carried out, in a known manner, either by blow molding or by stretch-blow molding.

[0121] According to the present embodiment, the plastic material of the preform 1 also includes at least one additive, denoted using the expression “additive partially forming a light barrier”, giving the plastic material: [0122] the property of at least partially filtering the visible light spectrum; [0123] the property of at least partially allowing the passage of light in the infrared spectrum.

[0124] According to another contemplatable embodiment, the plastic material can include one or more additives forming a radiation barrier that is less than 350 nm, for example, additives that block UV radiation, in particular to the visible spectrum.

[0125] Such additives are known and described, for example, in the patent applications published under numbers WO 2019/133713 A1 and WO 2017/095931 A1.

[0126] The composition of the preform is produced so that the preform has transmittance exhibiting variations in the light spectrum.

[0127] More specifically, the transmittance is measured for the wall 120 of the body 12 of the preform 1.

[0128] More specifically, the transmittance is measured for the wall 120 at the cylindrical portion 121 of the body 12.

[0129] The transmittance, at a given point of the wall 120 under a given spectrum of electromagnetic radiation, is the ratio between the average weighted energy over the entire spectrum of radiation passing through said point of the given wall in all the emergence directions, divided by the weighted average over the entire spectrum of the incident radiation perpendicular to the wall.

[0130] The transmittance is measured as follows:

[0131] A Perkin Elmer Lambda 950 spectrophotometer is used. It comprises a 60 mm diameter integration sphere.

[0132] In order to ensure maximum stability and correct results, the following prerequisites must be followed during the installation of the measurement device: [0133] a closed base not subject to vibrations; [0134] a sufficient space around and below the appliance so that the air circulates properly; [0135] a constant temperature ranging between 15° C. and 35° C.; [0136] a constant relative humidity ranging between 20% and 80%; [0137] an atmosphere free from dust and corrosive fumes; [0138] the measurement device must be protected from sunlight; diffused lighting is recommended.

[0139] Prior preparation is required for measuring a preform 1. Indeed, the transmittance must be measured through a single wall 120 of the preform 1. To this end, the body thereof needs to be previously cut lengthwise, i.e. parallel to the axis C, using a saw or any other means that does not damage the surfaces of the sample, so as to keep only one half.

[0140] The preform 1 must be properly held against the transmittance port. For this reason, tooling needs to be added that is installed in front of the transmittance port in order to keep the preform centered on the port and so that its axis of rotation is aligned with the widest side of the beam of the source in order to minimize the form effect associated with the curvature.

[0141] FIG. 2 shows the evolution of the transmittance T as a function of the wavelength λ of the light spectrum, for: [0142] a conventional transparent preform according to the prior art, by means of the curve “O”; [0143] a preform according to the invention, by means of the curve “NA”.

[0144] FIG. 2 also adds to the aforementioned curves the curves of irradiance E.sub.e as a function of the wavelength λ for a halogen oven “HO” and for a laser oven “LO”.

[0145] As can be seen in FIG. 2, a conventional transparent preform has transmittance that is greater than 20% at 350 nm, and on average that is greater than 80% from 450 nm to 1550 nm.

[0146] This type of preform produces containers 2 that are not adapted to the preservation of all types of products.

[0147] For example, this type of preform does not allow containers to be produced that are adapted to the preservation of milk, due to the fact that the containers subsequently allow light to pass through their wall in the visible spectrum, and particularly from 350 nm to 520 nm.

[0148] According to the principle of the invention, and as can be seen in FIG. 2, the wall 120 of the preform 1 has, under electromagnetic radiation emitted perpendicular to the wall 120, transmittance: [0149] in the visible spectrum, that is substantially equal to 0% within the wavelength range of 350 nm to 520 nm; [0150] in the infrared spectrum, within a transmittance range extending between a threshold transmittance and an upper transmittance, for at least one wavelength within the range of 700 nm to 2250 nm.

[0151] Substantially equal to 0% is understood to mean that, according to the measurement protocol, the measured transmittance reaches the detection threshold of the measurement device used in this protocol. This transmittance is particularly equal to a rounded value of 0%.

[0152] As explained hereafter, this transmittance of the preform 1 in the visible spectrum allows the container 2 to have an ability to avoid the degradation of the riboflavin of the milk that will be stored in the container 2.

[0153] The threshold transmittance is equal to 5%, preferably to 8% and even more preferably to 10%.

[0154] Based on a threshold transmittance of 5%, the tests have demonstrated the possibility of heating a preform 1 at a satisfactory speed, and particularly for preforms with walls that are considered to be “very thin” (i.e. as approximately being 1 mm to 1.5 mm thick).

[0155] Indeed, with this transmittance threshold sufficient light power is able to pass through the wall 120 of the preform 1 and the absorption of this through-radiation is sufficiently distributed through the thickness of the wall 120. This thus results in a sufficiently even increase in temperature in the thickness of the wall 120, with this occurring from the first passage of the radiation from the outside to the inside of the wall 120.

[0156] From a threshold transmittance of 8%, the tests have demonstrated the possibility of heating a preform 1 quickly enough that has a wall 120 that is considered to be “thin” (i.e. as approximately 1.5 mm to 2 mm thick).

[0157] Finally, with a threshold transmittance of 10%, any preform 1 according to the invention that is more than 2 mm thick can be heated at a speed that is substantially comparable to that of the conventional transparent preforms.

[0158] The upper transmittance is, for its part, equal to 70%, preferably to 50% and even more preferably to 20%.

[0159] It has been noted by the means of tests that an upper transmittance that is equal to 70% avoids the preform 1 being “excessively” transparent to the electromagnetic radiation used for heating.

[0160] With the preforms 1 being hollow bodies, the homogeneity of the heating in the thickness of their wall is also due, in the case of highly radiation transparent preforms, to a passage from the outside to the inside of their wall, then from the inside to the outside, then optionally by virtue of reflectors, by several outside-inside-outside passages.

[0161] With the upper transmittance equal to 70%, the homogeneity of the heating in the thickness of the thick wall of the preform is obtained with a limited number of complete outside-inside-outside passages.

[0162] This reduces the energy loss of the oven in the reflectors, and accelerates the heating of the preform.

[0163] By virtue of an upper transmittance that is equal to 50%, it is possible to heat the preform 1 in a halogen oven whilst ensuring sufficient heating above the glass transition temperature of the inner skin 123 of the preform 1, without burning the outer skin 122.

[0164] Finally, the upper transmittance that is equal to 20% provides a particularly advantageous compromise in that it allows better heating rates to be achieved for the preforms 1.

[0165] By way of a reminder, in order to obtain the container 2 according to the invention from the preform 1 according to the invention, the step of heating the container involves emitting heating radiation toward the preform.

[0166] This heating radiation is made up of at least electromagnetic radiation in an infrared spectrum with at least one wavelength within the range extending from 700 nm to 2250 nm. This one or these wavelength(s) of the heating radiation correspond(s) to the one or more wavelength(s) for which the wall 120 of the preform 1 has transmittance within the transmittance range extending between the threshold transmittance and the upper transmittance.

[0167] With transmittance in the infrared spectrum in one of the aforementioned ranges, the preform 1 is eligible for laser heating. This laser heating is then carried out at one or more wavelengths within the range extending from 700 nm to 2250 nm, for which the one or more preforms 1 has suitable transmittance.

[0168] In order to optimize heating the preform 1 in a laser oven, the transmittance of the wall 120 in the infrared spectrum can be within the transmittance range for a wavelength or within a spectrum of wavelengths included in one of the following ranges: [0169] 1110-1160 nm; [0170] 1390-1450 nm; [0171] 1610-1650 nm; [0172] 1675-1700 nm; [0173] 1880-2100 nm; [0174] 2170-2230 nm.

[0175] These ranges of wavelengths or of spectra of wavelengths represent typical heating that is carried out with a laser oven.

[0176] With reference to FIG. 2, and according to a preferred embodiment of the preform 1, in order for said preform to be heated in a laser oven, then the transmittance in the infrared spectrum is within the transmittance range for a wavelength of 1130 nm. It is understood that the preform 1 then has a narrow wavelength spectrum encompassing the wavelength of 1130 nm.

[0177] In this case, the heating step of the method is carried out with a laser oven that produces heating radiation at 1130 nm. As previously stated, the preform 1 according to the invention also can be heated in a halogen oven.

[0178] In order to optimize heating the preform 1 in a halogen oven, the transmittance of the wall 120 in the infrared spectrum then can be within the transmittance range, for wavelengths within the range of 750 nm to 1400 nm, and preferably within the range of 950 nm to 1400 nm.

[0179] As illustrated in FIG. 2, these ranges of wavelengths correspond to those where a halogen oven has greater average irradiance. By virtue of the preform 1 according to the invention, a container 2 according to the invention can be obtained.

[0180] This container 2 has precise features that are derived from those of the preforms 1. More specifically, the wall of the container 2 has, under electromagnetic radiation emitted perpendicular to said wall, transmittance, called container transmittance, that is less than 5%, preferably less than 0.5%, within the wavelength range of 350 nm to 520 nm.

[0181] With transmittance of less than 5%, the container 2, which is used to contain milk, thus allows the degradation of the riboflavin of this milk to be minimized.

[0182] With transmittance of less than 0.5%, the container 2 prevents the degradation of the riboflavin by light radiation over the wavelength range of 350 to 520 nm.

[0183] According to an advantageous embodiment, the plastic material of the preform 1 also includes a colorant. Such a colorant advantageously can have transmittance that varies along the light spectrum.

[0184] However, the selected colorant does not have a cut-off wavelength (by which said plastic equipped with said colorant forms a barrier) in the infrared spectrum, but can have zero transmittance outside the infrared range.