NZ272104A

NZ272104A - Preform and use in blow molding to produce a hot fill container, preferential thinning of neck portion of container

Info

Publication number: NZ272104A
Application number: NZ272104A
Authority: NZ
Inventors: Wayne N Collette; Suppayan M Krishnakumar; David P Piccioli
Original assignee: Continental Pet Technologies
Priority date: 1987-12-24
Filing date: 1988-12-22
Publication date: 1997-05-26
Also published as: NZ245610A; NZ238715A

Description

<div class="application article clearfix" id="description"> Priority Dat»(s): 5U*|.!3:.\50 Complete Specification Filed: ..3£|A •?.!?$. Claa«: (6) .633.??.BrS.^».ft;.JBfeSg3>iJ.pa;. Publication Dote: 2..6..#Uu..|yy?, P.O. Journal No: i.lfcb.lfe?. Under tho provision.*; of Regulation 23 (1) th;> ... Cbkufikh. SpacJficsJou hi;:' r.i<:;>• t c.n:. to 10 Irirttsts Patents Form Ho. 5 Our Re£: ES204614 This is a Divisional out of New Zealand Patent Application No. 227482 dated 22 December 1988 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION N-Z. PATENT OPFIP-F 11 MAY 1995 fifCgiyep A METHOD AND PREFORM FOR FORMING A CONTAINER We, CONTINENTAL PET TECHNOLOGIES, mc, a body corporate organised under the laws of the USA of Suite 490, 7310 Turfway Road, Florence, Kentucky 41042, United States Of America, hereby declare the invention, for which We pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: -1- PT0584419 (followed by page la) 2721n 4 A METHOD AND PREFORM FOR FORMING A CONTAINER This is a divisional application of New Zealand patent application no. 227482, the contents of which are herein incorporated by reference. The invention relates to a preform useful in preparation of blow molded hot fill containers and to a method of forming such containers. One of the problems of forming a container with an injection molded neck finish is that immediately adjacent to the neck finish is a neck to body transition which normally has low biaxial orientation. This region tends to distort to a high degree when exposed to temperatures above 160°F. In the past this distortion problem has been solved by increasing the temperature resistance of PET through thermal crystallization since the degree of orientation is not adequate to yield sufficient strain crystallization to increase the temperature resistance of PET in this region. One of the features of this invention is to solve that problem. It has now been found that the problems of the neck to body transition may be specifically reduced by causing preferential thinning of a portion of the neck to body transition in a preform. According to one aspect of the invention there is provided a preform for forming a blow molded hot fill container, said preform being formed of a polyester resin and including a base portion, a body portion, a neck finish portion and a neck to body transition, said neck finish portion including a flange immediately adjacent said neck to body transition, said neck to body transition having a portion of minimum cross section spaced from said flange, said minimum cross section portion being of a lesser thickness than said body portion, said neck -la- (followed by page 2) 272104 to body transition flaring in thickness toward said flange and flaring in thickness to said body portion. Preferably, the thickness of the cylindrical portion adjacent the flange is in the range of from 60 to 70% of the cross-sectional area of the body portion. Preferably the cross sectional area of said portion of minimum cross section is in the range of from 40 to 60% of the cross sectional area of the body portion. Preferably, the cross sectional area of the body portion is in the range of from 0.5 to 1 square inches. Preferably, the wall thickness of the body portion is in the range of from 0.1'to 0.3 inches. According to another aspect of the invention there is provided a method of forming a blow molded hot fill container, the method comprising the steps of: (a) providing a preform according to the one aspect of the invention; (b) heating the neck to body transition, the body portion and the base portion to blow molding temperatures; (c) placing the heated preform in a blow mold; (d) axially elongating the preform thereby causing preferential thinning and necking in all or part of the neck to body transition; and (e) blow molding the elongated preform to form a container. - 2a - 27210 An example of the present invention will be described with reference to the following detailed description in which: Figure 1 is an elevational view with parts broken away of a preform formed in accordance with this invention. Figure 2 is a schematic sectional view showing the preform of Figure 1 initially being placed in a blow mold. Figure 3 is a schematic vertical sectional view similar to Figure 2 and shows a mechanical axial elongation of the preform. Figure 4 is a schematic vertical sectional view showing the previously axially elongated preform being blow molded to match the configuration of the blow mold. Figure 5 is an enlarged fragmentary sectional view of that portion of the preform identified in Figure 1. 1825S 272104 - 3 - Figure 6 is an enlarged fragmentary vertical sectional view of that form of the preform identified in Figure 1. Figure 7 is an enlarged fragmentary sectional view of the upper portion of the preform as shown in Figure 5 after the preform has been stretched in the manner shown in Figure 3. Figure 8 is an enlarged fragmentary sectional view of the lower part of the preform shown in Figure 6 after the axial elongation of the preform as shown in Figure 3. Figure 9 is an-elevational view with parts broken away and shown in section of a container formed from the preform of this invention, in the blow mold as shown in Figure 4 and having a label applied to the body thereof. Figure 10 is a horizontal sectional view taken generally along the line 10-10 of Figure 9 and shows further the details of the container and the associated label. With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, and the several views illustrated in the accompanying drawings. The following description is of a preform according to the present invention and its application in forming a hot fill container, which is the subject of the applicant's New Zealand Patent Specification No. 245610. 2721 - 4 - This invention starts with a special preform 10 which is best illustrated in Figures 1 and 5-8. The preform 10 is injection molded of a polyester resin with particular reference being made to PET (polyethylene terephthalate). Basically speaking, the various portions of the preform 10 may be identified as including a base portion 12, a body portion 14, a neck finish portion 16 and a neck to body transition 18. Referring now to Figure 5, it will be seen that the upper part of the preform 10 is illustrated in detail. First of all, the illustrated neck finish portion 16 is in the form of a conventional neck finish which may include external threads 20 for receiving a closure, a locking bead 22 for engagement by a closure tamper indicating ring or band, and a lower flange 24. Immediately below the flange 24 is the neck to body transition 18. It starts with an internal thickening to define a seat 26 for receiving, for example, a blow nozzle in seated engagement. Immediately below the seat, the transition may include a cylindrical part 28. Below the cylindrical part 28, the transition 18 downwardly tapers in thickness externally as ac 30 terminating in a further cylindrica-1 part 32 of minimal cross section. Below the cylindrical part 32, the transition 13 flares both internally and externally as at 34 to join the greater thickness body portion 14. Referring now to Figure 6, it will be seen that the base portion begins at the lower end of the body 14 with a radius part 36 which joins a f rus toconica 1 part 38 to the body-portion 14. The frustoconica1 part, in turn, carries a part spherical bottom 40 which tapers in thickness from the frustoconical part 38. 5 It is to be understood that the preform 10 is formed by injection molding and when presented to the blow molding apparatus (not shown) is at room temperature. A preform, in a normal blow molding operation, is heated 10 by a series of quartz heaters which results in the heating of the outer surface of the preform to a higher temperature than the inner surface. On the other hand, radio frequency heating has been utilized with the result that the inner 15 surface of the preform is heated to a higher temperature. Hybrid heating utilizing a combination of quartz heaters and radio frequency heaters has been utilized in the past to obtain a uniform temperature throughout the 20 wall of the preform. Such a heating process is disclosed in U.S. Patent No. 4,407,651. More recently it has been found that if the average preform temperature is increased to 225 ° F. as compared to the permissible 25 average temperature in the 200°- 210° F. range permissible with quartz heating and the 210°-220°F. range permissible with radio frequency heating, shrinkage of a biaxially oriented PET container is reduced to 2 percent or less and 30 by increasing the average temperature of the reheated preform at the time o£ stretch blowing to as high as 260°F., the container shrinkage is reduced to on the order of less than 1 percent. 35 In accordance with this recent 27210 4 - 6 - development in reheating of preforms, which is the subject of a pending U.S. application, the preform 10 will be reheated first utilizing a quartz oven or like quartz heater with this first reheating treatment resulting in the outside surface temperature of the preform rising to on the order of 240°F. while the inside surface of the preform is only slightly heated to a temperature on the order of 120°F. The temperature of the center of the body wall of the preform is only slightly greater than the inside surface temperature and is on the order of 140°F. The initial reheating time is on the order of 14.5 seconds. After the first quartz reheating, the reheating is discontinued and the preform is permitted to equilibrate for a period of time on the order of 5 seconds. The temperature of the outside surface of the preform body continues to increase to a temperature on the order of 250°F. and then begins to cool down to a temperature on the order of 230°F. At the same time, the temperature of the center of the preform body remains generally constant while the temperature of the inside surface of the preform body increases gradually to a temperature on the order of 135° F., the temperature of the inside surface of the preform body approaching that of the center of the preform body. Thereafter, it is preferred that further reheating of the preform be also by way of a quartz heater for a reheating period. The time of this further quartz reheating is on the order of 12.5 seconds and during this second period of quartz reheating, the temperature of the exterior surface of the preform body continues to rise above the temperature of the center of the preform body and the inside surface of the preform body. The exterior surface temperature rises to on the order of 350°F. while the inside surface temperature slowly gradually rises to a temperature on the order of 180°F. and the temperature at the center of the preform wall slowly rises at a slightly greater rate to a temperature on the order of 220°F. After the second quartz reheating, once again the temperature of the exterior surface of the preform body is much greater than that of the interior surface and the temperature at the center of the preform body has also gradually increased above that of the interior surface of the preform body. The preform body is immediately thereafter further reheated by way of radio frequency heating. While the temperature of the outside surface of the preform body rises only slightly during the radio frequency heating, the heating of the inside surface of the preform body very rapidly increases from the temperature generally on the order of 160°F. to a temperature slightly greater than 300*^?. The time of radio frequency heating is on the order of 2 seconds. During this time there is only a minor increase in the temperature of the preform body at the center of the cross section thereof to a temperature on the order of 240°F. Thus the temperature of the center of the preform body cross section is 27210 4 - 8 - the lowest and the temperatures of the inside surface and outside surface are greater. At this point, the application of external heat to the preform is stopped and the 5 preform is directed into a blow mold, as will be discussed hereinafter, and blow molding steps are initiated with there being a total lapse of time on the order of 6 seconds. During these 6 seconds, there is a second 10 equilibration of the preform. During the second temperature equilibration, the temperature of the outside surfaces of the preform body will rapidly decrease to a temperature on the order of, but 15 below 280°F. At the same time, the temperature on the inside surface of the preform body will continue to increase and then taper off to a temperature on the order of 350°F. In a like manner, the temperature of the preform at the 20 center of the body cross section will rise and then taper off at a temperature on the order of 260°F. It will thus be seen that the temperature at the center of the cross section of the preform body is still the lowest, but 25 the temperature of the outside surface is only slightly greater. Inasmuch as crystallization is a factor of temperature and time and since the time during which surface crystallization may 30 occur after reheating of the preform to its maximum temperature is reduced, the desired high reheat temperature may be obtained in accordance with this reheating method without the undesired surface crystallization. 35 It is known to utilize a stretch rod 27 <1 fS v -J - 9 - to axially elongate a preform within a blow mold to assure the complete axial elongation of the preform. However, normally a similar rod is utilized solely for the purpose of 5 maintaining the preform in a centered relationship with respect to the blow mold as the preform is inflated. However, in accordance with this invention, it is proposed to utilize the normal centering rod initially 10 as a stretch rod, but prior to the introduction of a blowing gas into the preform. Thus, as is schematically shown in Figure 2, the preform 10, duly heated in the manner described above, is placed within an open split blow mold, 15 generally identified by the numeral 42 in a conventional manner. After the blow mold 42 has been closed, as shown in Figure 3, instead of immediately beginning the inflation of the preform, the customary centering rod 44 is 20 directed down into the preform 10 and engages the bottom part 40. Th. ^ rod 44 is utilized to elongate the preform on the order of 25 percent, as is shown in Figure 3. The results of this elongation of the preform 10 are best 25 shown in Figures 7 and 8. Since the reheating of the preform 10 stops on the order of 2mm below the flange 24, and_ since the preform is supported against axial movement within the blow mold by the flange 24, there is no 30 deformation or elongation of the neck finish portion 16. On the other hand, since the central part of the neck to body transition 18 is of minimum cross section, it will be seen that there will be considerable elongation of 35 the neck to body transition 18. This will 27210 - 10 - occur primarily in the cylindrical part 32 buo will also occur partially within the downwardly tapering portion 30 and the downwardly flaring portion 34. Further, and most particularly, it 5 will be seen that when the transitier 13 is. axially elongated, it will also neck down so as to assume a radially inwardly direccod bowed configuration thus in effect reducing the diameter of the central part of the transition 10 18. Because of the radially inwardly directed bowing of the transition 18, it will be seen that in the blow molding of the preform 10 within the blow mold 42 there will be a greater stretching of this portion of the preform in 15 the hoop direction. With reference to Figure 8, it will be seen that since the base portion 12 of the preform 10 is also heated to a high temperature, when it is engaged by the stretch 20 rod 44, its resistance to thinning will not be as great as that of the body 14 so that there will be an elongation of the base portion 12 as is best shown in Figure 8. This elongation will be primarily in the radially outer portion 25 of the body part 40 and in the frustoconical part 38 with the result that there will be a newly formed body part 4° which is generally hemispherical together with a cylindrical part 48 in accordance with the diameter of the 30 stretch rod 44. Finally there will be an upwardly flaring generally frustoconical pare 50 which joins the cylindrical part 48 to the body 14 by way of a curved part 52. The preform 10, having been elongated 35 on the order of 25 percent, is now ready for 2721! -lithe introduction of a blow gas so that the preform 10 may be inflated in the customary manner to match the configuration of the blow mold 42. If desired, during the inflation of 5 the stretched preform 10, the stretch rod 44 may be permitted to follow the axial elongation of the preform during inflation so as to make certain that the base portion 12 of the preform remains centered relative to the blow mold. 10 The inflation of the preform 10 within the blow mold 42 results in the formation of a container in the form of a bottle generally identified by the numeral 54. It is to be understood that the shape 15 of the container or bottle 54 is also critical in the hot fill shrinkage thereof. As will be apparent, the bottle 5 4 will have a neck finish which is identical with the original neck finish 16 of the preform 10 including the 20 flange 24 and a portion of the preform immediately below the flange which was not heated, as previously described. This portion is generally in accordance with the previously described part 28 of the preform. 25 The bottle 54 also includes a downwardly and outwardly sloping shoulder portion 5 6 which is formed from the previously stretched neck to body transition portion 18. The shoulder portion 56 in conventional 30 container constructions is generally of a low orientation and is gradually formed during the inflation of the preform. However, inasmuch as the shoulder portion 56 is defined by that part of the preform which was very rapidly 35 mechanically stretched followed by the 27210 - 12 - inflation of the preform, the shoulder portion 56 has a high strain crystallization. In accordance w-i th the design configuration of the illustrated bottle 54, the 5 shoulder portion 56 is connected by a radius 58' to an upper body portion 60 whi.cc. flares slightly outwardly and downwardly. rhe upper body portion 60 terminates in a radially inwardly directed rib 62 which, in turn, is 10 connected to a generally cylindrical main body portion 64. The main body portion 64 includes upper and lower cylindrical band": 66, 68 with the body portion 64 between the bands 66, 68 including a plurality of radially inwardly 15 recessed vacuum pressure panels 70. Each pressure panel 70, as is best shown in Figure 9, is of a vertically elongated rectangular configuration with rounded corners and is generally chordal in configuration. Each 20 pressure panel 70 is reinforced against deformation by a plurality of transverse horizontally extending radially recessed ribs 72 which are also of an elongated rectangular outline, but the elongation being in the 25 horizontal or circumferential direction. Adjacent pressure deformable vacuum panels 70 .are separated by a vertically elongated land area 74. Each land area 74 extends between the bands 6 6 , 6 8 and is 30 reinforced by a vertically extending, radially inwardly directed rib 76. The bottle 54 also includes a base 78 which includes a ribbed recessed bottom 80 which is joined to the body 64 by a rounded 35 base portion -82. The ribbed bottom, which is 27210 - 13 - best shown in Figure 10, may include five circumferentially spaced, radiating downwardly directed ribs 84 which are defined by the base configuration of the blow mold 42. 5 As is best shown in Figure 9, the • bands 66, 68 are recessed radially inwardly a slight distance with respect to the lower part of the rib 6 2 and the rounded portion 8 2 of the base portion 78. This permits a conventional, 10 low cost, full wrap label 86 to be applied to the body portion 64 in a protected position. As is clearly shown in Figure 10, the label 86 bridges the recessed pressure deformable vacuum panel 70 so as to give the bottle 54 the 15 appearance of one wherein the body portion 64 is cylindrical. It is to be understood that due to the specific high temperature of the preform 10 which is possible in accordance with the 20 heating procedure outlined above, and because of the specific stretch ratio of the blow bottle 54 with respect to the preform 10 in both the axial and hoop directions, the resultant bottle 54 has in the body portions 25 thereof a 2 3-30 percent sidewall crystallization, which is a stress induced crystal! iz.a tion as opposed to being a temperature induced crystallization. Further, because of the specific cross sectional 30 configuration of the body portion 64 as well as the specific stress induced crystallization of the shoulder portion 55, when the bottle 54 is hot filled with a liquid at a temperature on the order of 180°- 185°F., the shrinkage of the 35 bottle 54 by volume will be no greater than 1 - 14 - percent, i.e. the volumetric shrinkage should be between 0 and 1 percent. Thus the bottle 54, when hot filled with a heated liquid, will maintain this configuration. Farther, because 5 the neck finish 16 is non-oriented, it will be subjected to heat deformation. However, because the neck finish 16 is injection molded and relatively thick, it will be able to withstand the momentary heating thereof to £■ 10 relatively high temperature without deformation which will prevent'the closing and sealing of the bottle 54 utilizing conventional closures, particularly screw threaded closures. It will also be noted that the 15 recessed bottom or base portion 80 is of a relatively thick wall configuration and will resist deformation when the bottle 54 is filled with a heated liquid. Although only a preferred embodiment 2> of the preform has been specifically described and illustrated, it is to be understood that minor variations may be made in the invention without 25 departing from the ■ ■ ■ ■ ^ scope of the invention as defined by the appended claims. 30 35 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 27210 4 WHAT WE CLAIM IS:

1. A preform for forming a blow molded hot fill container, said preform being formed of a polyester resin and including a base portion, a body portion, a neck finish portion and a neck to body transition, said neck finish portion including a flange immediately adjacent said neck to body transition, said neck to body transition having a portion of minimum cross section spaced from said flange, said minimum cross section portion being of a lesser thickness than said body portion, said neck to body transition flaring in thickness toward said flange and flaring in thickness to said body portion.

2. A preform according to claim 1 wherein said flaring in thickness to said body is both internal and external.

3. A preform according to claim 1 or claim 2 wherein said minimum cross section portion is substantially cylindrical.

4. a preform according to any one of claims 1 to 3 wherein the neck to body transition comprises a cylindrical part adjacent said flange, an inwardly tapering portion between said cylindrical part and portion of minimum cross-section an an outwardly tapering portion between the portion of minimum cross-section and body portion.

5. A preform according to claim 4 wherein the flaring toward the flange is external.

6. A preform according to any one of claims 1 to 5 wherein the neck to body transition starts with an internal thickening to define a seal for receiving a blow nozzle.

7. A preform according to claim 1 wherein the flaring in thickness toward the flange is at a greater increase in thickness per unit of length of preform than the flaring of said neck to body transition adjacent the body portion.

8. A preform according to any one of claims 1 to 7, wherein the base portion includes a lowermost part hemispherical part and frustoconical part joining said part-hemispherical part.

9. A preform according to claim 8 wherein the part-hemispherical part tapers in thickness from the frustoconical part.

10. A preform according to claim 8 or claim 9 wherein the base portion further includes a radius part which joins the frustoconical part to the body part.

11. A preform according to claim 4 wherein the length of the cylindrical part adjacent the flange is equal to or less than the axial length of the flange portion.

12. A preform according to any one of claims 1 to 11 wherein the minimum cross section portion is substantially cylindrical and is of length less than the length of the part between said minimum cross section portion and said body portion.

13. A preform according to claim 4 wherein the length of the flaring portion between the said cylindrical portion adjacent the neck and said part of minimum cross section is greater than the length of said portion of minimum cross section.

14. A preform according to claim 4 wherein the thickness of the cylindrical portion adjacent the flange is in the range of from 60 to 70% of the cross sectional area of the body portion.

15. A preform according to any one of claims 1 to 14 wherein the cross sectional area of said portion of minimum cross section is in the range of from 40 to 60% of the cross sectional area of the body portion.

16. A preform according to any one of claims 1 to 15 wherein the cross sectional area of the body portion is in the -16- x r b : range of from 0.5 to 1 square inches.

17. A preform according to any one of claims 1 to 16 wherein the wall thickness of the body portion is in the range of f rom 0.1 to 0.3 inches . ^ '* f' '

18. A preform according to any one of claims 1 to 10 wherein the minimum cross section portion is adapted inwardly td ne_ck- on axial elongation of the preform and blow molding temperature.

19. A method of forming a blow molded hot fill container, the method comprising the steps of:- (a) providing a preform according to any one of claims 1 to 10 j (b) heating the neck to body transition, the body portion and the base portion to blow molding temperatures; (c) placing the heated preform in a blow mold- (d) axially elongating the preform thereby causing preferential thinning and necking in all or part of the neck to body transition ; and (e) blow molding the elongated preform to form a container,

20. A method according to claim 19 wherein the axial elongation and blow molding steps (d) and (e) are carried out whereby the container has a biaxially oriented relatively thin shoulder region formed from the neck to body transition adjacent to a relatively thick portion beneath the flange of the neck finish portion of the container.

21. A method according to claim 19 or claim 20 wherein in step (d) axial elongation of the neck to body transition results in inward necking of the preform at the portion of 27 -17- 27210 minimum cross section in the neck to body transition.

22. A method according to any one of claims 19 to 21 wherein after heating step (b) the neck to body transition is free of heat crystallization.

23. A method according to any one of claims 19 to 22 wherein in axial elongation step (d) the axial elongation is effected by a push rod internally engaging the base portion of the preform.

24. A method according to any one of claims 19 to 23 wherein the axial elongation of the preform prior to inflation is on the order of 25 percent.

25. A method according to any one of claims 19 to 24 wherein in heating step (b) a portion of the neck to body transition of the preform which extends on the order of 2mm below the flange is unheated.

26. A method according to any one of claims 19 to 25 wherein the body portion of the container has a strain induced sidewall crystallization of from 28 to 20 percent.

27. A method according to any one of claims 19 to 26 wherein there is no elongation or deformation of the neck finish portion. \ • 4080S -18- 27210^

28. A method according to any one of claims 19 to 27 wherein the body portion of the container has a strain induced side wall crystallisation of up to about 30%.

29. A method according to any one of claims 19 to 28 wherein the container has a volume shrinkage of no greater than 1% when hot filled with a liquid at a temperature of from 82-85°C (180-185°F).

30. A method according to any one of claims 19 to 29 wherein the preform is formed of a polyester.

31. A method according to claim 30 wherein the polyester is polyethylene terephthalate.

32. A preform according to claim 1 substantially as herein described with reference to the drawings.

33. A method according to claim 19 substantially as herein described with reference to the drawings. END OF c CONTINENTAL..PET TECHNOLOGIES INC -19- 4080S </div>