Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-01-31
2002-08-13
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272200, C156S273300, C156S275700
Reexamination Certificate
active
06432251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of attaching plastic parts to a glass container and, more particularly, to a method of attaching polypropylene plastic parts, such as a handle and/or a plastic lip member for enclosing an upper edge of the glass container, with or without a spout, to a glass container by means of an adhesive or glue. It also relates to the container or vessel, which is the product of this method.
2. Prior Art
Glass vessels or containers, which are used as serving vessel and hanging containers for cold and hot drinks (for example coffee) or also for their preparation, are provided with a plastic edge piece or lip member to prevent breakage due to impacts on the container neck. For holding the container, especially when it is filled with a hot drink, a plastic handle is usually provided, which is either a separate part or is integrated into the plastic edge piece.
Acrylic nitrile-butadiene-styrene copolymer (designated ABS in the following) is an economical and easily glued plastic material. Several ABS variants are permissible according to the U.S. Food and Drug Administration and the German Health Department, so that the plastic edge member that comes into direct contact with the drink can also be made from ABS. The permissible ABS variants of course can withstand the temperatures in the standard household washing machine, but may however deform and discolor during cleaning in industrial washing machines.
Polypropylene is preferred to ABS for economic and health reasons. Furthermore polypropylene fulfills the requirements of shape and color stability at temperatures of 90° C. and higher.
Usually the bonding strength at application temperatures of 90° C. and higher has been so small that adhesion loss or rupture occurs, i.e. a crack or fissure is formed between the adhesive and the plastic part. Temperatures of 90° C. and higher occur in industrial washing machines used in professional applications.
Separate handles are only glued. Plastic edge pieces, among other things, have a circumferential groove in their lower edge, when they are made from polypropylene, by means of which they are clamped onto the glass container edge, and are also attached by adhesive, which is injected into the groove. First, the adhesive acts to fill the open space between the glass container edge and the groove in the plastic edge piece. The force transmission is primarily effected mechanically. Usually a silicone adhesive ingredient and an additionally used adhesion-promoting agent (primer) provide a sufficiently strong bond with ABS between the plastic part and the glass container. When the adhesive mass is overstressed a cohesive rupture occurs, whereby a tear is formed through the adhesive mass.
The adhesive in the plastic edge piece also performs a sealing function. It prevents liquid from flowing out of the container between the plastic edge member and the edge of the glass container. A sealing ring can also be used for this purpose. Usually in this case two separate plastic parts, which are fastened together, are used as the plastic edge piece. This is more expensive and involves more effort than using a one-piece plastic edge part.
A container is described in EP 0 413 196 B1, in which the handle is not integrated with the plastic edge piece, but both parts are separate. The handle is attached to the outside of the container, but it positively locks or form-locks with the plastic edge piece. This positive locking connection works against including a spout in the plastic edge piece. The plastic edge piece and the handle must have a complex shape, which results in an expensive and difficult manufacture and assembly. No statements are made regarding the resistance of the adhesive to high usage temperature.
The problem with gluing polypropylene is that polypropylene is nonpolar and is poorly wet by agents which are more polar than polypropylene, e.g. good adhesives for glass. Several possible methods for treating surfaces of nonpolar materials known to impart polar properties to them are described in Proceedings of the 11
th
Professional Conference, New Surfaces for Plastic Materials, Treatment and Coating, Regensburg, Sep. 23/24 1998. Plasma polymerization (loc. cit., p. 179) and gas flaming (loc. cit., p. 210) were mentioned. The plasma polymerization method comprises deposition of a polymer layer with polar functional groups on a substrate by means of a plasma in a pre-selected atmosphere. In gas flaming first the surface is oxidized and then polarized by means of ions and electrons in the flame.
The theme of the article “Adhesives of Plastic Material”, which appeared in the Journal, Plastics Advisor, Aug. 7, 1982, is that difficult-to-glue plastic materials must be pre-treated. The pre-treatments recommended for polypropylene are of a chemical nature, e.g. by steeping in chromosulfuric acid; of a thermal nature, e.g. by gas flaming, or of an electrical nature, e.g. by corona discharge. These methods are for bonding plastic materials with each other. The bonding of plastic to glass is not mentioned.
The article “Bonding of Plastics after Treatment in a Low Pressure Plasma”, appearing in the Plastics Journal 73, 3 (1983), discloses that the adhesion of polypropylene increases after pre-treatment in a low pressure plasma in the case of a steel-plastic example. This effect lasts for a few to several days. Oxygen is one of the gases suggested for the low pressure plasma activation. However this article also does not mentioned any examples of bonding plastic to glass.
In the cited prior art there is no suggestion that one could improve the bonding strength of adhesive compositions for application temperatures of 90° C. and higher.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for bonding or attaching polypropylene to glass by means of an adhesive or glue in order to provide sufficient bonding strength, even at application temperatures of 90° C. and higher.
According to the invention this object is attained by two methods for attaching polypropylene plastic parts to a glass container, for example a handle or a plastic edge piece or lip member enclosing the upper edge of the glass container, with or without spout, by means of an adhesive or glue, in which the plastic parts are each surface-activated, at least on surface portions where the adhesive or glue is applied, before the adhesive or glue is applied. The surface activation is performed, either in a low pressure plasma or by flaming.
The surface is made more polar prior to applying the glue or adhesive by the surface activation. Thus the wettability of the surface for the adhesive material is increased and thus also the bonding strength between the polypropylene and the glue. It has been shown that this increased bonding strength also persists at higher temperatures, so that sudden detachment of the plastic parts from the glass container no longer occurs during use at higher temperatures.
The first method according to the invention is based on the surface activation in a low pressure plasma. The low pressure plasma is produced by activation of an electric field of sufficient strength in a gas at low pressure. The ionization occurring under the influence of the electric field leads furthermore to cleavage of electrons and positively charged ions from electrically neutral gas atoms. Since the number of positive and negative charge carriers in the plasma is the same, it is electrically neutral from the outside, but still has an electrical conductivity. The surface activation is caused by impact of plasma particles on the atoms or molecules of the parts to be treated in the vicinity of the surface.
It has proven advantageous to work at pressures between 10 Pa and 500 Pa for surface activation of polypropylene for bonding to glass.
Chemical changes occur on the surface according to the composition of the process gas. Plasmas produced in oxygen or oxygen-containing gas mixtures produce cleaning and also activating effects. In the simp
Fischer Wolfgang
Henze Inka
Kopp Bernd
Krick Guido
Ball Michael W.
Rossi Jessica
Schott Glas
Striker Michael J.
LandOfFree
Method of attaching plastic parts to a container does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of attaching plastic parts to a container, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of attaching plastic parts to a container will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2905216