FR2659599A1 - Method of manufacturing a plastic container having a removable lid and having a sealing layer, and container obtained - Google Patents

Abstract

The invention relates to a method of manufacturing a plastic container (10) having a wide opening for solvent-based liquid products, for example a paint, this method consisting in moulding a lid ring (16) and a lid (14) made of a solvent-resistant polymer material, this lid being intended to be force fitted into the ring, in allowing the moulded components to cool down after the moulding so as to allow inherent shrinkage and distortion, and in applying, to a closure region of the lid (14) or of the lid ring (16), a second, different polymer material or composition which is softer than the other polymer material, this application being made in liquid or semi-liquid form so as to form an annular laminar sealing layer (38) which adheres to the said other polymer material.

Description

The present invention relates to containers or

  plastic containers It relates more particularly to

  rement, but not exclusively, a manufacturing process for

  plastic containers with a wide opening for solvent-based liquid products such as paints

  gloss or lacquer, varnishes, inks and the like.

  It also relates to plastic containers

  themselves, as well as the plastic containers manufactured

  according to the process cited above.

  Plastic containers for water-based paints are now widespread and an important variant of metal containers or cans

  for paintings known for a very long time.

  However, difficulties have arisen in the provision of

  supply of plastic containers for glossy paints or lacquers, varnishes, inks and the like

  reason, among other things, for the unexpected disadvantages in the

  results of these containers in relation to the formation of a

  seal or airtight closure.

  These difficulties have absolutely not been foreseen because of the success of plastic containers for water-based paints, these containers being for example molded to

  from polypropylene and polyethylene These latter materials

  res have not been found suitable for use

  with the solvents contained in glossy paints or

  ques, and we have therefore found other plastics for this purpose, for example mixtures of plastics based on polyethylene terephthalate We can, for example, use a

  polyester type plastic material sold by the Company

  té Du Pont under the brand name SELAR-P-T È. Admittedly, it is reasonable to expect that a cover ring and a cooperating force-fitted cover, which are molded from these solvent-resistant plastics, will provide a properly closed seal for this purpose.

  waterproof In fact, plastic products tolerant-

  these narrow ones are now widespread in many areas.

  maines and therefore we were not expecting

  serious difficulties arise in closing reci-

  plastic customers, especially with

  the elasticity of these materials and the state of the art

nique related to their molding.

  However, experience and practice have proved the contrary. The existence of this difficulty is confirmed by

  the current absence on the market of a plastic container

  tick for glossy or lacquer paintings and by publica-

  tion of previous proposals for farm arrangements-

new and improved.

  Of course, most difficulties of this kind can

  be solved, in an expensive way, by laboratory techniques

  rake and workshop using manufacturing processes

  precision, reduced tolerances to a strict minimum

  mum, to the most rigorous quality control, etc. Any-

  times, such an approach is not acceptable in the case of a

  product which must necessarily compete with the pro-

  metallic product which is comparatively manufactured

  eyelash and which is widely spread Therefore, the line ge-

  General approach to the solution of the problem requires agents

  cements or improved sealing arrangements which are incorporated

  res in the lid ring and / or in the lid itself of the container The merit of such an approach lies in the fact that, whatever the complexity of the sealing arrangement,

  assuming it is suitable for mass production by mold-

  lage, the unit cost for mass production is

  relatively small, due to the simplicity and speed

  relative tee of molding the product from a feed

  uniform in a single plastic material.

  Research has shown that this prior approach

  re in solving the problem probably can't know-

  satisfy the double requirement of mass production following normal manufacturing tolerances and an appropriate level of tightness so as to avoid the formation of a skin on glossy paints or lacquers after a relatively long period

short storage.

  An object of the present invention is to provide a pro-

  assigned to manufacture a plastic container, as well as plastic containers themselves which have improvements is related to the disadvantages mentioned

  above, or in general.

  To this end, the process according to the invention for manufacturing

  a large opening plastic container for

  solvent-based liquid products, such as paint

  re, this container comprising a cover that is forced into place and the method comprising the steps consisting in: molding a cover ring for the container so as to define said wide opening; mold a cover intended to fit on

  said wide opening; said cover ring and said cover

  ring being molded from a solvent or solvent resistant polymeric material of said solvent based liquid products, and

  having cooperating closing zones intended to cooperate

  rer mutually in a closed relationship when forcibly fitting said cover into said ring

  lid, this process being characterized by the fact that it

  consists in applying to said closing zones a second different material or polymer composition which,

  in operation, is softer than said other poly-

  mother; said second polymeric material being applied to said

  closing zones in liquid or semi-liquid form of

  in order to produce an annular laminar layer of sealing which

  adheres to said other polymeric material and defines a cooperation

  S ection between the closing parts of the cover and

  of the ring in the closed areas thereof, while

  putting, during the use of the container,

  forceful place and repeated opening of the cover.

  In an embodiment described below, research results and experiments have been put into practice which have been carried out in connection with the above difficulties.

  this mode of implementation, we developed a simple technique

  full of manufacturing that can easily be added or adapted

  to the existing manufacturing process to produce recipes

  pients in plastic material, this technique largely eliminating the above sealing difficulties or at least reducing them significantly By avoiding the need for a significant improvement in manufacturing tolerances, and by

  consequent on the fact that the need for all structures is avoided

  unduly complex sealing res, simplicity and ease

  production tee normally inherent in molded products

  plastic are preserved In addition, this has been done

  joint with the resolution of the sealing problem for a cost

  additional minor perfectly acceptable Indeed, there

  te no additional cost if the additional cost is taken into account

  inherent in previous proposals to

  sophisticated sealing structures, manufacturing techniques

  precision cation and / or grinding operations or the like.

  In this embodiment, the container made of material

  re plastic, including the cover ring and the cover itself, is conventionally molded from a plastic which resists solvents in

  glossy paints or lacquers, etc. The first polymer, or po-

  main lymer, is a much harder material than the polypropylene or polyethylene mentioned above In addition,

  it is a material that is very difficult to mold uniformly.

  However, in this embodiment, the shrinkage and / or distortion, which occurs when the cover and the cover ring are cooled after molding, are considered acceptable due to the subsequent application to the areas.

  sealing of these two elements of the second material or

  different polymer position which is softer than polypro-

pylene or polyethylene.

  So far, it has been considered to be absolutely

  unacceptable to mass produce a molded product

  bearing two different polymer materials due to the com-

  plexity of production techniques which are inherent in a

  such a proposal However, since provision is made for the second-

  of polymeric material or composition only in a zone of

  sealing or closing, which is located in one place

  normally without direct contact with the liquid itself

  even, this problem was solved at an acceptable cost.

  An embodiment of the invention will now be described by way of example with reference to the accompanying drawings.

  which are part of the description and in which:

  Figure 1 shows, on a relatively large scale, a vertical section through the cover ring portion of a plastic container for paint, as well as of the cover itself, this cover being simply placed and not yet pressed towards the low in its sealed and locked position, this view showing only part of the total container assembly; and

  Figure 2 is a view similar to Figure 1, the cou-

  this time being pressed into its sealed position and

blocking.

  As shown in the drawings, the container 10 in

  plastic material has a cylindrical body 12 and a cover

  key 14 cooperating with a cover ring 16 secured to the body 12, for example by welding All these elements are molded

  polyethylene terephthalate or other resistant polymeric material

  both to the solvents used in glossy paints or

  ques, printing inks, varnishes and the like.

  The structure itself of the container 10 does not

  part of the present invention; it will therefore not be de-

  written; however, for more details, reference may be made to

  PCT patent application N O WO 88/05015.

  We will only indicate that the container 10 has

  means 18 for retaining, blocking or locking released

  ble of the lid which are tamper-proof, which resist handling

  children who constitute part of the cost

circle 14.

  There are, in addition to the locking means 18 released

  table, closing means 20 comprising a skirt 22 in the cylindrical assembly, which constitutes a part of the cover 14 and which has an annular rib 24 projecting radially outwards and of a cross section generally in the form of a wedge, the skirt 22 being intended to cooperate by its rib 24 with an annular closure flange 26 formed on the cover ring

  16 As indicated above, the rib 24 is turned radial-

  ment outwards, while the closing rim 26 is turned radially inwards. The rib 24 and the rim 26 are shaped and proportioned to cooperate in the manner shown in FIG. 1 before their tight closing cooperation shown in the Figure 2 This Figure 2 shows the mutual relationship of these two elements after the cover 14 has been forced down to occupy its sealed and locked position, and this by clipping effect. We understand that, when the cover 14 is removed,

  the upper edge of the container 10 open upwards is cons-

  titled by the edge 28 of the cover ring 16 The locked

  ge releasable locking means 18, for the position re-

  presented in figure 2, is obtained by mutual cooperation-

  the shoulders or locking faces 30, 32, which are pa-

  parallel and horizontal, that is to say radial, and which are mena-

  gés respectively on the locking means 18, and more precisely on the cover 14, and on the cover ring 16.

  As shown in Figure 1, the cover ring

  key 16 and the cover 14 have respective annular zones of closure or sealing 34, 36 which are intended to cooperate mutually in a sealing relationship when the cover 14 is forced into place in its position of the Figure 2 The area 34 is generally convex and formed by the surface of the rim 26, while the area 36, so

  complementary, is concave and in the general shape of a gutter.

  The cover 14 and the cover ring 16 are made

  bricks following known molding techniques After extraction

  tion of the mold, there is a cooling of the plastic material together with the inherent shrinkage and distortion

  at this cooling Then at this point we apply to the pro-

  duit, uniformly made of polyethylene terephthalate, a second second material or different polymer composition which is softer or softer than this latter material so as to produce an annular laminar sealing layer 38 which

  adheres to the cover 14 The layer 38 allows a cooperation of

  sealing between the parts or zones 34, 36 for closing the cover

  ring and ring, while allowing, in use

  tion of the container, repeated placement and removal of the lid In axial section, the thickness of the layer 38 preferably decreases from its central part to

  at least one of its annular edges.

  The sealing layer 38 is formed by applying the

  polymeric material or composition in liquid or semi-form

  liquid gradually around the annular zone 36 of the

  cover 14, for example by rotating it.

  The preferred composition for sealing layer 38 is a water-based rubber composition in which the water acts as a crosslinking inhibitor.

  place of the lid, the evaporation of the water allows the crosslink

  tion to occur Alternatively, a composition may be used

  hot melt polyethylene Of course, other com-

  positions can be developed Indeed, any polymer suitable for

  proprié, including natural and synthetic elastomers, as well as their compositions with fillers and additives, can be used, as well as compositions

  containing the polymers usually used for molding

  age of plastic containers, or any other composite

  sealing The exact nature of the composition chosen for a given application will depend on the solvent used in the

liquid to be stored.

  As can be clearly seen in FIG. 1, the sealing layer 38 is applied at the exact location where the closing zone 34 of the cover ring 16 cooperates with the cover for the position of sealing and blocking of

Figure 2.

  After application of the waterproofing composition

  in liquid or semi-liquid form, it is left to dry or cross-link

  this composition, after which the product passes to the following station

  before, for example for shipping Application of the composition

  sealing can be carried out immediately after molding, so that the relatively high temperature of the

  plastic molded components promotes cross-linking

  tion and rapid drying of the composition.

  In operation, the sealing layer 38 has a hardness significantly lower than that of the material of the rest of the container 10, so that an effective and sealed closure is achieved for the position of the lid shown in Figure 2 All normal tolerances manufacturing due to shrinkage and distortions of the molded material components

  plastic are compensated by the flexibility and natural elasticity

  of the sealing layer This is applied in a unique additional manufacturing phase which is simple and

  fast and the cost is relatively low.

  Interestingly, in the implementation mode

  vre above, the existence of a sealing layer 38 constitutes

  killed by a softer second material or polymer composition eliminates the sealing difficulties inherent in the constituents

  molded from polyethylene terephthalate, as shown above.

  The manufacturing techniques used are so simple

  ples than the additional cost inherent in adopting two poly-

  instead of the conventional single polymer is acceptable

  ble, in particular because this additional phase eliminates

  do the more stringent manufacturing tolerances and the mid rate

  its discarded which otherwise would be needed.

  The above embodiment can easily be adapted in the application to different configurations of container lid and lid ring The materials used for these may vary from those which have been indicated above On considers that practically all suitable plastics (polymers) which resist the solvents used in glossy paints or lacquers, varnishes, printing inks and the like have a hardness significantly greater than that of polypropylene or polyethylene. at least any of these polymers to obtain the advantages of the invention In fact, the sealing effect is also obtained with polypropylene

  and high density polyethylene, although it may be easier

  These materials should also be used for sealing in use.

  reading only sealing components incorporated by molding. Among other materials which are suitable for the body 12 of the plastic container, to which the invention can

  be applied, mention will be made of polyamides.

  Of course, if necessary, it is possible to modify the profile or the configuration of the cover and / or of the cover ring for the reception of the sealing layer 38 For example, a small step or shoulder can be provided on the

  cover in the region of the closing area for this purpose.

  Of course, the invention is not limited to the mode of

  not only in the mode of application, which have been determined

  crits; on the contrary, it would be possible to conceive of various variants without thereby departing from its scope. This is how the annular sealing layer 38 could be made to comprise an annular formation intended to receive the annular part 26 of

  the ring 16 Furthermore, the annular layer 38 of watertight

  could be provided on the ring 16, the cover 14

  comprising or not comprising such a layer.

Claims (11)

  1 Method for manufacturing a container (10) of ma-   wide opening plastic container for solvent-based liquid products, including paint, this container having   a cover (14) forcing into place and the method comprising   both: molding a cover ring (16) for the container so as to define said wide opening;   the molding of the cover (14) intended to fit ter on said wide opening;   said cover ring (16) and said cover   key (14) being molded from a polymer material which resists the solvent or solvents of said liquid products and having cooperating closing zones (34, 36) for mutual closing cooperation during the force-fitting of said lid (14 ) in said cover ring (16) characterized by: the application to said closure zones of a second different material or polymer composition which, in   is softer than said other poly-   mother; said second polymeric material being applied   on said closure zones in liquid or semi-form   liquid so as to form an annular laminar layer (38)   sealant which adheres to said other polymeric material and provides   nit a sealing cooperation between the closing parts   cover (14) and cover ring (16) in the zo-   closing nes (34, 36) thereof, while allowing half   its in place by force and repeated removal of said cover (14) during use.   2 Method for manufacturing a container (10) made of   plastic container comprising a cover (14) which can be force-fitted, characterized by the application in a liquid or semi-liquid form of a second material or polymer composition plus   soft on a closed area of said container and / or said neck   circle to form an annular sealing layer (38) therein.   3 Method according to one of claims 1 and 2,   characterized in that said second material or composition for   lymer is applied to a zone (36) for closing the lid (14) of said container.   4 Method according to claim 3, characterized in that said closure zone (36) is located in an annular part in the general shape of gutter arranged to receive with a clipping action a cooperating annular part (26) of said cover ring (16).   Method according to one of claims 1 to 4, ca-   characterized in that said annular sealing layer (38) has a decreasing thickness, in cross section, from   its central region to at least one of its annular edges   res. 6 Method according to claim 4, characterized in that said sealing layer (38) has an annular formation for receiving said annular part (26) of the ring cover (16).   7 Method according to one of the preceding claims.   tes, characterized in that said second polymeric material or composition crosslinks gradually after its application to said container.   8 Plastic container, or at least one of its constituents, in particular its cover (14) or its cover ring (16), characterized in that it is obtained by the   method according to one of claims 1 to 7.   9 Large plastic container (10) or   groove for solvent-based liquid products, in particular a paint, which comprises a cover (14) and a cover ring (16) and in which the cover (14) can be forced into place in the cover ring ( 16), the cover (14)   and the cover ring (16) being molded from a poly-   solvent or solvent resistant mother of said li-   which have cooperating closing zones (34, 36) intended to cooperate mutually in a closing relationship when the cover (14) is forced into place in the ring   cover (16), characterized by an annular laminar layer   re (38) sealing made of a second material or compound   polymeric composition which is applied to said closure zones (34, 36) and which adheres to said cover (14) or to said ring   cover (16) to provide sealing cooperation between   the closing parts of the cover and the cover ring   circle in their closed areas, while allowing   its in place by force and repeated removal of said cover (14) in use.   Plastic container with a   cover (14) press fit, characterized by a cover   sealing seal (38) on said cover (14) or on a cooperating cover ring (16), said sealing layer (38) being made of a more polymeric material or composition   soft as the material of the container (10) itself.   11 Plastic container as claimed   cation 9 or 10, characterized in that said second material or polymer composition is applied to a closure zone   (36) of the lid (14) of the container.   12 Plastic container as claimed   cation 11, characterized in that said closure zone (36)   is located in an annular part in the general shape of a drop   faceplate arranged to receive with a clipping action a part   cooperating annular tie (26) provided on said cover ring key (16).   13 Plastic container according to one of the   claims 9 to 12, characterized in that said annular layer   the sealing area (38) has a thickness which decreases   naked, in cross section, from its central region to at minus one of its annular edges.   14 Plastic container as claimed   cation 12, characterized in that said sealing layer (38)   has an annular formation to receive said part an-   ring (26) of the cover ring (16).