Hollow plastic object, particularly preform, resp. container, with a polymer barrier and manufacturing method thereof

Abstract

The invention relates to a hollow article with rigid walls (18 98), surrounding an enclosed space (19, . . . , 99) that occupies the interior of the hollow article (10, . . . , 90), made of a primary plastic base material (1) in which there is provided a secondary plastic material (2), consisting of a polymer, characterized in that this secondary polymer (2) is formed by a first component (A), being a cyclic diisocyanate as a cyclic compound, with an aromatic or optionally an aliphatic structure, and by at least one additional component (B), wherein this secondary plastic material (2) forms a barrier (12, . . . , 92) in the hollow article (10, . . . , 90), and method for producing thereof.

Claims

1. A hollow article with rigid walls, surrounding an enclosed space that occupies the interior of the hollow article, made of a primary plastic base material in which there is provided a secondary plastic material, consisting of a polymer, wherein this secondary polymer is formed by a first component A, being a cyclic diisocyanate as a cyclic compound, with an aromatic or optionally an aliphatic structure, and by at least one additional component B, wherein this secondary plastic material forms a barrier in the hollow article, wherein said secondary plastic material is formed by polyurethane.

2. The hollow article according to claim 1, wherein said cyclic compound with an aromatic ring structure is formed by MDI (methylene diphenyl diisocyanate).

3. The hollow article according to claim 1, wherein said cyclic compound contains a C.sub.n ring, notably a C.sub.6 ring.

4. The hollow article according to claim 1, wherein said polyurethane is formed from a reaction of said aromatic or possibly aliphatic diisocyanate+a diol, wherein the latter is selectable from diethylene glycol, 1,3-propanediol, 1,12-dodecanediol, 1,3-butanediol, 1,2-propanediol, 1,6-hexanediol, 1,4-cyclohexane dimethanol, 1,9-nonanediol and/or 1,10-decanediol.

5. The hollow article according to claim 1, wherein said secondary plastic material has a ring structure that is aliphatic, wherein the aliphatic block is formed by CHDI (hydrogenated xylylene diisocyanate), incorporated as a barrier element.

6. The hollow article according to claim 1, wherein said primary plastic base material is selected from the polyester family, particularly wherein said primary plastic base material is selected from PET (polyethylene terephthalate).

7. The hollow article according to claim 1, wherein said primary plastic base material is selected from the polyolefin family, particularly wherein said primary plastic base material is selected from among the polyethylenes or polypropylenes, respectively.

8. The hollow article according to claim 1, wherein it has a multi-layer structure, especially a three-layer structure consisting of the base layer that is made of a primary plastic material and in which a barrier layer, especially a passive barrier, is included, which is made of a secondary plastic material that blocks unwanted components.

9. The hollow article according to claim 1, wherein said secondary plastic material has a structure containing an aromatic ring structure, wherein the aromatic block is also formed as a base by MXDI (1,3-dimethylxylylene diisocyanate), which is incorporated as a barrier element.

10. The hollow article according to claim 9, wherein said secondary plastic material is formed by a non-reactive polymer.

11. The hollow article according to claim 10, wherein said polyurethane is formed from a reaction of said aromatic or optionally aliphatic diisocyanate+a diol, wherein the latter is selectable from 1,4-butanediol, 1,5-pentanediol and/or diethylene glycol.

12. The hollow article according to claim 1, wherein additives are added to said secondary plastic material, and/or to the primary base material.

13. The hollow article according to claim 12, wherein adhesive promoters with an adhesive function are added to said secondary barrier material, wherein the adhesion of the materials is enhanced.

14. The hollow article according to claim 1, wherein it consists of a preform for blow moulding a container, comprising a neck part, a bottom part, with a wall part between them, extending along the axis thereof, particularly wherein it is composed of a biaxially stretchable plastic material for manufacturing a plastic container.

15. The hollow article according to claim 14, wherein said preform consists of an injection moulded piece.

16. The hollow article according to claim 14, wherein it consists of an overmoulding preform, possibly comprising two different materials, possibly with an inner and an outer preform.

17. A method for manufacturing a hollow as a preform for container according to claim 14, wherein the reaction for forming the barrier polymer with various monomers proceeds with the following step: the monomers are placed together in an anhydrous solvent, in which the formation of the secondary plastic material takes place.

18. The method according to claim 17 for producing a hollow article, notably a preform respectively container, wherein the secondary plastic is introduced into the preform either by co-injection or by overmoulding or by blending, and thereby generating a plastic barrier against undesirable components, such as liquid or vapour among others, forming in the preform, respectively container.

19. A method for manufacturing a hollow article according to claim 1, wherein the reaction for forming the barrier polymer with various monomers proceeds with the following step: the monomers are placed together in an anhydrous solvent, in which the formation of the secondary plastic material takes place.

20. The method according to claim 19, wherein the polymerisation reaction is carried on until the polymer gets a molar mass which is greater than 20 kD, particularly >50 kD, wherein after the reaction, the polymer is precipitated and is further purified.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a general schematic representation of an embodiment of a preform according to the invention in a side view.

(2) FIGS. 2 to 7 show schematic representations of a first embodiment of a preform according to the invention, specifically longitudinal and transverse sections thereof, a cross-sectional view along line A-A, and a perspective view.

(3) FIGS. 8 to 13 show schematic representations of a second embodiment of a preform according to the invention, as in the previous group of figures.

(4) FIGS. 14 to 18 show still analogous schematic representations of a third embodiment of a preform according to the invention as in both previous groups of figures.

(5) FIGS. 19 to 32 show schematic representations of three analogous embodiments of a possibly corresponding container according to the invention, possibly derived from the above-mentioned preform shown in the previous corresponding figures, specifically in side view, in longitudinal and transverse sections thereof, a cross-sectional side view along line A-A, and a perspective view.

(6) FIGS. 33 to 39 show schematic representations of various embodiments of a hollow article according to the invention in the packaging type in general, specifically in side view, in longitudinal and transverse sections thereof, a cross-sectional view along line A-A, and a perspective view.

(7) FIG. 40 shows a graphical representation of the barrier effect for oxygen at various percentages as a function of time in number of days for a series of plastic materials according to the invention compared to a reference material, MXD6, each of which is shown in a separate curve labelled as sample i, where i ranges from 7 to 16.

(8) FIG. 41 shows another graphical representation analogous to the previous FIG. 40, but in greater detail for the best ones among the series of plastic materials according to the invention.

(9) FIG. 42 shows a still further graphical representation thereof.

(10) FIG. 43 shows a graphical representation of barrier results in the case of production of plastic according to the method of the invention in solvent versus production without solvent.

(11) FIG. 44 shows a further graphical representation of barrier results analogous to the previous FIG. 43, but comparing dry plastic to plastic after water absorption.

DESCRIPTION

(12) In general, this invention relates to a hollow article 70, 80, 90 with rigid walls, as specifically represented as a packaging in FIGS. 33 to 39, largely composed of a primary plastic base material being a first type of plastic, namely the base polymer. Within this primary plastic base material, a secondary plastic material is provided, consisting of a polymer having a ring structure, which is advantageously aromatic. Here the aromatic ring structure is also made of MXDI (metaxylene diisocyanate) as a basis. The structure of the latter polymer provides for good barrier properties due to the incorporation of an improved barrier material.

(13) A variant thereof is formed by a ring structure, which is aliphatic, wherein the aliphatic ring structure consists of CHDI (hydrogenated xylylene diisocyanate or C6XDI).

(14) Said secondary plastic material is a second polymer type that, when combined with the base polymer, imparts better properties to the hollow article, especially keg container 70, 80, 90 than if the hollow article were made with the base polymer alone.

(15) Said hollow article 90 may be composed of a so-called blend obtained by blending the secondary and primary plastic materials together. FIG. 36, resp. 8 shows an example of an alternative thereto, consisting of a multi-layered article 80 or preform 10 comprising a primary base layer 81 within which a secondary plastic material 82 is provided.

(16) Some specific application examples are given below, which were subjected to a first series of tests, wherein the oxygen permeation through polymeric materials was measured. These are shown in the corresponding graphics, in the first instance for polyurethane based on MXDI. The polymer used here is also indicated, and the behaviour of each material is also shown.

(17) The data are presented in the corresponding graphics from FIGS. 40 to 44. From tests on the basis whereof these graphics were derived, it can be concluded that linear chains originating from the diols gave good results.

(18) In addition, it can be noted that there is an optimal chain length for diol with good barrier properties. It may presumably be comprised between C.sub.3 and C.sub.10, with an optimum around C.sub.6, which is visible in the corresponding graphics from the figures. However, the chain length formed by C.sub.12 is too long and C.sub.2 is too short owing to the brittleness and flexibility, respectively, of the materials.

(19) FIGS. 1 to 18 show a preform as a prominent use of a hollow article 10, 20, 30, intended for blow moulding of a container. For this purpose, it is particularly composed of a biaxially stretchable plastic material for making a plastic container, for example 40, 50 or 60 of the type shown in FIGS. 19 to 32. The preform 10, 20, 30 can thus consist of an injection-moulded article.

(20) More specifically, FIG. 2 shows the preform 10 with a neck part 15 and a bottom part 17, with a wall part 16 between them, extending along the axis l thereof.

(21) FIGS. 8 to 13 show a preform 20 made up of a multi-layered structure comprising a primary base layer 21, wherein a secondary barrier layer 22 is provided, made up of said secondary polymer mentioned, for example a three-layer structure, wherein the base layer 21 is composed of a primary plastic material and the barrier layer forms a passive barrier, through which unwanted particles are blocked. The melt of the proposed secondary polymers is to be applied herein by means of injection, particularly co-injection, as visible in FIG. 8.

(22) The above-mentioned barrier may also form a passive barrier against moisture or vapours. The secondary plastic material is a second polymer type that, when combined with the primary base polymer, imparts better properties to the preform 20 than if the hollow article preform were made with the base polymer alone.

(23) FIG. 2 shows a variant of an embodiment consisting of an overmoulding preform 10, comprising two different materials, with an inner and an outer preform 11, 12, wherein one of them forms a secondary barrier layer 22. Similarly, the secondary plastic material is a second polymer type that, when combined with the primary base polymer, imparts better properties to the preform 10 than if this preform were made with the primary base polymer alone.

(24) The preform 30 is also composed of a so-called blend, obtained by blending the secondary and primary plastic materials together. FIG. 14 shows the example of such a variant thereof, here consisting of a monolithic preform 30 that can be made virtually homogeneously, i.e. without multilayers.

(25) Thus, the barrier 22 can also be incorporated herein by overmoulding, or 32 by blending.

Tests and Examples

(26) Some specific application examples are given below; which were subjected to a first series of tests, wherein the oxygen permeation through polymeric materials, was measured. These are shown in the corresponding graphics, in the first instance for polyurethane based on MXDI. The polymer used here is also indicated, and the behaviour of each material is also shown.

(27) The T.sub.g of the barrier polymers, which ranges between 30 and 100 C., however, is comparable with that of nylon-MXD6, being about 85 C. This means that when blowing of PET bottles with a middle layer made of the secondary polymers, the PET and the secondary polymers can be blown at the same normal blowing temperature.

(28) MXDI or 1,3-dimethylxylylene diisocyanate is used as the base:

(29) primarily, the composition of the polyurethanes is further a reaction product thereof with diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol.

(30) Other compositions of the polyurethanes in decreasing order of preference are a reaction product thereof with 1,12-dodecanediol, diethylene glycol, 1,3-butanediol, 1,2-propanediol, 1,6-hexanediol, 1,4-cyclohexane dimethanol, 1,9-nonanediol and/or 1,10-decanediol.

(31) As far as the polyurea is concerned, it can be advantageously described similarly as being a reaction product thereof with ethylenediamine.

(32) Other compositions of the polyurethanes in decreasing order of preference are a reaction product thereof with 1,3-aminopropane, 1,4-diaminobutane and/or 1,6-diaminohexane.

(33) Regarding the properties of the secondary plastic, they are as follows: in contrast to MXD6, this barrier polymer remains clear when it has absorbed the moisture; in case of moisture absorption, the plastic keeps its barrier properties at least even well. The barrier properties may even be improved by water absorption; the plastic can become more flexible after absorbing water.

(34) These properties are apparent from the results of the following tests, which are shown in the corresponding Figure, which presents the barrier results for polymers being made in solvent vs. produced without solvent.

(35) In a method for making a barrier polymer structure, the reaction for forming the barrier polymer with the various monomers takes place as follows: the monomers can be put together in an anhydrous solvent, in which the formation of the polymer takes place. Solvents that may possibly be used are DMF or ethyl acetate. For the good progress of the reaction, a catalyst (Sn or Ti complex) may be necessary. The atmosphere above the mixture should be anhydrous and oxygen acid-free. Possible gases that may be used are argon (Ar) or nitrogen (N.sub.2). The polymerisation should be continued until the plastic has a molar mass that is greater than 20 kD, especially 50 kD (kiloDalton). After the reaction, the polymer will precipitate and can be purified. The advantage of this method of polymerization is that the reaction temperature can be better controlled.

(36) However, the monomers may also react with one another directly, thus without a solvent, to form the above-mentioned plastic. A catalyst may be necessary or not. The advantage of this method is that the polymer no longer needs to be purified, unless simply to remove the catalyst. It is important in this method to have good equipment available for keeping the temperature under control or to properly control the reaction.

(37) With the two above-mentioned methods the desired polymer can be prepared directly. However, it is also possible to make intermediate forms of the polymeroligomerswhich are converted in a second step via reactive extrusion to the polymer with the desired molar mass.

(38) In addition to the use of MXDI or CHDI as the base, other diisocyanates may be used. In the expansion of diisocyanate monomers, the basis is that these contain a C.sub.6 ring, which may be both aromatic and aliphatic. An example is methylene diphenyl diisocyanate.