Process for the production of multilayer blow-molded hollow articles

Abstract

The present invention relates to blow molded multilayer hollow articles and a coextrusion blow molding process for the production of said multilayer hollow articles, made of thermoplastic polymers and characterized by a specific visual effect. More in particular, the present invention relates to multilayer hollow articles and a coextrusion blow molding process for the production of said multilayer hollow articles, wherein at least one layer is a continuous layer with a uniform degree of thickness and at least one layer is a discontinuous or a non-uniform continuous layer with varying degree of thickness, which results in a specific surface pattern and/or visual color effect.

Claims

1. A multilayer blow-molded hollow article comprising at least an outside layer and an inside layer comprising thermoplastic polymers, optionally one or more layers located between the outside layer and the inside layer, wherein both the outside layer and the inside layer have only one of their two principal surfaces directly adhered to another layer of the article, wherein any middle layer has both of its principal surfaces directly adhered to another layer of the article, wherein at least one of the layers is a uniform continuous layer with a uniform degree of thickness in both a longitudinal and circumference direction, wherein at least one of the layers is a non-uniform continuous layer with varying degrees of thickness that includes variations in both circumferential thickness and longitudinal thickness, resulting in a visual surface pattern effect of areas with elevations, cavities, grooves, ridges, streaks or swirls, and/or a visual color effect of streaks, waves and/or swirls caused by varying color or translucency, and wherein a ratio of dynamic viscosity of the thermoplastic polymer forming the non-uniform layer to the thermoplastic polymer forming the uniform layer is in the range of from 9.0 to 4.0.

2. The article of claim 1, wherein the uniform continuous layer has a thickness of between 0.1 to 5 mm.

3. The article of claim 1, wherein the thermoplastic polymers are selected from the group consisting of polyolefins, polyolefin copolymers, polystyrenes and combinations thereof.

4. The article of claim 1, wherein the thermoplastic polymers are selected from the group consisting of high density polyethylene, medium density polyethylene, linear low density polyethylene, polypropylene homopolymer, polypropylene random copolymer and combinations thereof.

5. The article of claim 1, wherein any layer contains one or more colorants.

6. The article of claim 1, wherein the article is a two-layer article and wherein the outside layer is the uniform continuous layer and the inside layer is the non-uniform continuous layer.

7. The article of claim 1, wherein the article is a two-layer article and wherein the outside layer is the non-uniform continuous layer and the inside layer is the uniform continuous layer.

8. The article of claim 1, further comprising a middle layer, wherein the outside layer is the uniform continuous layer and the middle layer and the inside layer are non-uniform continuous layers.

9. The article of claim 1, further comprising a middle layer, wherein the outside layer and the inside layer are non-uniform continuous layers and the middle layer is the uninform continuous layer.

10. The article of claim 1, wherein non-uniform layer thickness is either continuous and varies along the circumference and along the longitudinal direction of the non-uniform layer of the article, or the non-uniform layer thickness is discontinuous and becomes zero at one or more parts along the circumference and along the longitudinal direction of the non-uniform layer of the article and is interrupted by any of the other layers of the article.

11. A multilayer blow-molded hollow article comprising at least an outside layer and an inside layer comprising thermoplastic polymers, optionally one or more layers located between the outside layer and the inside layer, wherein both the outside layer and the inside layer have only one of their two principal surfaces directly adhered to another layer of the article, wherein any middle layer has both of its principal surfaces directly adhered to another layer of the article, wherein at least one of the layers is a uniform continuous layer with a uniform degree of thickness in both a longitudinal and circumference direction, wherein at least one of the layers is a non-uniform continuous layer with varying degrees of thickness that includes variations in both circumferential thickness and longitudinal thickness, resulting in a visual surface pattern effect of areas with streaks or swirls, and/or a visual color effect of streaks, waves and/or swirls caused by varying color or translucency, and wherein the article is prepared by coextrusion blow-molding in two consecutive steps, where in the first step an at least two-layer tubular parison is formed by coextrusion of at least two different thermoplastic polymers from a multilayer coextrusion die head whereby (i) the polymer forming a continuous layer with a uniform degree of thickness has a lower dynamic viscosity when passing through the coextrusion die head than the polymer forming a discontinuous or a nonuniform continuous layer; and (ii) the polymer forming a continuous layer with a uniform degree of thickness is extruded at a higher extrusion rate than the polymer forming a discontinuous or a non-uniform continuous layer, and in the second step, said parison is blow-molded to form the multilayer polymeric hollow article.

12. The article as claimed in claim 11, wherein the ratio of dynamic viscosity of the polymer forming the non-uniform continuous layer to the dynamic viscosity of the polymer forming the uniform continuous layer, when passing through the die head, is of from 9.0 to 4.0.

13. The article as claimed in claim 12, wherein the ratio of dynamic viscosity is of from 7.7 to 4.6.

14. The article as claimed in claim 11, wherein the rate of extrusion of the polymer forming the uniform continuous layer to the rate of extrusion of the polymer forming the non-uniform continuous layer is of from 30.0 to 2.5.

15. The article as claimed in claim 14, wherein the rate of extrusion is of from 8.9 to 4.2.

16. The article as claimed in claim 11, wherein the thermoplastic polymers are selected from the group consisting of polyolefins, polyolefin copolymers and polystyrenes.

17. The article of claim 1, wherein the non-uniform continuous layer with varying degrees of thickness results in a visual surface pattern effect of areas with streaks or swirls, and/or a visual color effect of streaks, waves and/or swirls caused by varying color or translucency.

Description

EXAMPLES

(1) % by weight are based on the total weight of the mixture, composition or article; parts are parts by weight;

(2) LDR means let-down ratio and indicates the masterbatch dilution in the finished product; it is expressed in terms of % by weight of masterbatch based on the total weight of the mixture;

(3) ex means example; MB means masterbatch;

(4) L/D describes the relative length of the extruder screw in terms of the length of the screw from the forward edge of the feed opening to the forward end of the screw flight divided by the screw diameter; the ratio is expressed with its denominator reduced to 1; for example, a 24/1 screw has a screw length 24 times its diameter.

(5) Substances Used:

(6) Component A0:

(7) Low density polyethylene (LDPE) having a density of 0.919 g/cm.sup.3 (ISO 1183) and MFR of 8.0 g/10 min (ISO 1133; measured at 190 C./2.16 kg).

(8) Component A1 or B1 or C1:

(9) Low density polyethylene (LDPE) having a density of 0.924 g/cm.sup.3 (ASTM D1505) and MFR of 2.2 g/10 min (ASTM D1238; measured at 190 C./2.16 kg).

(10) Component A2 or B2 or C2:

(11) High density polyethylene (HDPE) having a density of 0.960 g/cm.sup.3 (ISO 1183) and MFR of 0.3 g/10 min (ISO 1133; measured at 190 C./2.16 kg).

(12) Component A3 or B3 or C3:

(13) High-gloss, high density polyethylene (HDPE) having a density of 0.957 g/cm.sup.3 (ISO 1183) and MFR of 1.1 g/10 min (ISO 1133; measured at 190 C./2.16 kg).

(14) Component A4 or B4 or C4:

(15) High density polyethylene (HDPE) having a density of 0.960 g/cm.sup.3 (ISO 1183) and MFR of 8.0 g/10 min (ISO 1133; measured at 190 C./2.16 kg).

(16) Component A5 or B5 or C5:

(17) Polypropylene homopolymer (PPH) having specific gravity of 0.903 g/cm.sup.3 (ASTM D792) and MFR of 11 g/10 min (ASTM D1238; measured at 230 C./2.16 kg).

(18) Component A6 or B6 or C6:

(19) Polypropylene random copolymer (PP-R) having density of 0.900 g/cm.sup.3 (ISO 1183) and MFR of 1.8 g/10 min (ISO 1133; measured at 230 C./2.16 kg).

(20) Component A7 or B7 or C7:

(21) Highly-transparent polypropylene random copolymer (PP-R) having density of 0.905 g/cm.sup.3 (ISO 1183) and MFR of 8 g/10 min (ISO 1133; measured at 230 C./2.16 kg).

(22) Component P1:

(23) C.I. Pigment Blue 15:3 (C.I. No. 74160).

(24) Component P2:

(25) C.I. Pigment Brown 24 (C.I. No. 77310).

(26) Component P3.

(27) C.I. Pigment Red 101 (C.I. No. 77491).

(28) Masterbatches MB1 to MB3

(29) The components were homogenized together on a twin screw extruder at a temperature of 160 to 220 C. and the color concentrates MB1 to MB3 were obtained; Table 1 gives the details.

(30) TABLE-US-00001 TABLE 1 Components used [parts] MB colorant polymeric carrier MB1 P1 [38] A0 [62] MB2 P2 [60] A0 [40] MB3 P3 [60] A0 [40]

(31) ex 1 to ex 22

(32) Bi-layer and tri-layer bottles were prepared on a multilayer blow molding machine Magic MP IB500/ND equipped with three separate extruders 1, 2 and 3 each having a relative screw length L/D of 24 and a coextrusion multilayer die head with feedblock design and with a maximum annular diameter of 43 mm. Extruder 1 operates with the polymer A forming the outside layer, extruder 2 operates with the polymer B forming an optional middle layer and extruder 3 operates with the polymer C forming the inside layer of the multilayer hollow article with polymers A, B or C optionally mixed with color concentrates MB1 to MB3 in order to impart color to one or more than one layer of the multilayer hollow article. Table 2 gives the details of the temperature profile of the extruders; Table 3 gives the details of the temperature profile of the die head.

(33) TABLE-US-00002 TABLE 2 Temperature Sections of an extruder [ C.] profile of Zone 1 Zone Zone Zone Zone Zone 6 extruder (hopper) 2 3 4 5 (die) 1E 175 175 175 175 175 175 2E 185 185 185 185 185 185 3E 180 180 180 180 180 180 4E 220 220 220 220 220 220 5E 200 200 200 200 200 200 6E 240 240 240 240 240 240

(34) TABLE-US-00003 TABLE 3 Temperature Sections of the die head [ C.] profile of Zone 1 die head (extruder) Zone 2 Zone 3 Zone 4 1D 180 180 185 185 2D 185 185 220 220 3D 185 185 185 185

(35) Polymers A, B and C were homogenized and eventually mixed with the color concentrates MB1 to MB3 in the ratios reported in table 4. Table 4 also gives the measured values of the dynamic viscosity and rate of extrusion for each layer and corresponding ratios for a given example. Depending on the chosen process parameters, various visual effects and/or patterns, in at least one layer of the multilayer structure, are obtained. Such visual effects and/or patterns have been rated according to the following scale:

(36) (+++) Very pronounced

(37) (++) Pronounced

(38) (+) Light

(39) Based on the series of conducted trials, it is evident that the swirls and streaks effect is produced under a variety of conditions within the limits of the present invention.

(40) In Table 4, ex1 to ex22, the outside layer A is a uniform continuous layer and the inside layer C is a discontinuous or non-uniform continuous layer.

(41) TABLE-US-00004 TABLE 4 Outside Inside Inside T Rate of Rate of Ratio of Effect layer layer layer profile extrusion Viscosity extrusion Viscosity Ratio of Rate of layers (extruder (extruder color die A A C C Viscosity extrusion (effect ex profile) profile) (LDR) head [kg/h] [Pa .Math. s] [kg/h] [Pa .Math. s] C/A A/C rating) ex 1 A3(2E) C2(2E) MB1(2) 1D 5.87 3.241 0.611 18.249 5.631 9.61 C(+++) ex 2 A3(2E) C2(2E) MB1(2) 1D 5.87 3.241 0.935 15.669 4.835 6.28 C(++) ex 3 A3(2E) C2(2E) MB1(2) 1D 5.05 3.479 0.334 21.356 6.139 15.12 C(+++) ex 4 A3(2E) C2(2E) MB1(2) 1D 4.48 3.689 0.168 25.383 6.881 26.67 C(+) ex 5 A3(2E) C2(2E) MB1(2) 1D 4.48 3.689 0.334 21.356 5.789 13.41 C(+++) ex 6 A3(2E) C2(2E) MB1(2) 1D 3.83 3.933 0.168 25.383 6.454 22.80 C(+) ex 7 A3(2E) C2(2E) MB1(2) 1D 3.83 3.933 0.611 18.249 4.640 6.27 C(+++) ex 8 A3(2E) C2(2E) MB1(2) 1D 3.83 3.933 0.748 16.803 4.272 5.12 C(++) ex 9 A3(2E) C2(2E) MB1(2) 1D 3.17 4.221 0.168 25.383 6.014 18.87 C(+++) ex 10 A3(2E) C2(2E) MB1(2) 1D 2.58 4.574 0.168 25.383 5.549 15.36 C(+++) ex 11 A7(2E) C6(2E) MB1(2) 3D 5.72 1.783 0.63 13.812 7.746 9.08 C(+) ex 12 A7(2E) C6(2E) MB1(2) 3D 5.72 1.783 0.79 12.783 7.169 7.24 C(+++) ex 13 A7(2E) C6(2E) MB1(2) 3D 5.72 1.783 1.11 10.898 6.112 5.15 C(+++) ex 14 A7(2E) C6(2E) MB1(2) 3D 5.72 1.783 1.37 10.405 5.836 4.18 C(+++) ex 15 A7(2E) C6(2E) MB1(2) 3D 4.81 1.887 0.79 12.783 6.774 6.09 C(+++) ex 16 A7(2E) C6(2E) MB1(2) 3D 4.81 1.887 1.61 9.958 5.277 2.99 C(++) ex 17 A7(2E) C6(2E) MB1(2) 3D 3.95 1.979 0.63 13.812 6.979 6.27 C(+++) ex 18 A7(2E) C6(2E) MB1(2) 3D 3.95 1.979 0.98 11.976 6.052 4.03 C(++) ex 19 A7(2E) C6(2E) MB1(2) 3D 3.66 2.085 0.34 16.021 7.684 10.76 C(+++) ex 20 A7(2E) C6(2E) MB1(2) 3D 3.66 2.085 0.79 12.783 6.131 4.63 C(+++) ex 21 A7(2E) C6(2E) MB1(2) 3D 3.24 2.211 0.17 18.886 8.542 19.06 C(+) ex 22 A7(2E) C6(2E) MB1(2) 3D 3.24 2.211 0.34 16.021 7.246 9.53 C(+++)