Process for manufacturing surface-sealed hollow glass...

Details Process for manufacturing surface-sealed hollow glass... Process for manufacturing surface-sealed hollow glass...

1999-03-31

2002-04-02

Vincent, Sean (Department: 1731)

Glass manufacturing

Processes

With coating

C065S028000, C106S243000, C106S244000, C106S271000, C106S287110, C106S287130, C106S287140, C106S287150, C106S287160, C428S034100, C428S034400, C428S034700

Reexamination Certificate

active

06363749

ABSTRACT:

The invention relates to a process for producing surface-sealed hollow glass containers with the aid of a special cold end coating composition.
In the preparation process for hollow glass containers it is conventional to subject them to a surface treatment with which it is intended to cover external damage such as microcracks, and to minimize further damage. Thus immediately downstream of the production machine the so-called hot end coating is applied as a thin coat to the surface of the glass which is at from 500 to 550° C. The compounds involved in this hot end coating are, in particular, chlorides of titanium and of tin. On the glass surfaces these compounds produce a titanium or tin dioxide layer, with the chlorine released passing into the waste gas. The hot end coating composition is applied by vaporization or spray atomization.
After hot end coating, the hollow glass containers pass through an annealing lehr in which they are cooled slowly in order to avoid harmful stresses.
At the discharge end of the annealing lehr, the hollow glass containers hot end coated beforehand are cold end coated by means of either vaporization or spray atomization. This produces the lubricity required for the remainder of the process in the glass plant and in the bottling plant.
The most common substances used as cold end coating agents are surfactants, fatty acid products, partial fatty acid esters, ester wax emulsions and various polyethylene dispersions.
A coating process in which hot end coating is carried out first and then a cold end coating composition comprising an olefin polymer, a polyurethane, a polystyrene or an alkylamine acetate is applied by spraying is known from DE-C 12 91 448. The bottles coated in this way, however, do not satisfy all requirements.
A certain degree of improvement in the scratch resistance is obtained if the polyethylene dispersion sprayed on as the cold end coating composition additionally comprises a silane (U.S. Pat. Nos. 3,438,801, 3,801,361, 3,873,352, 4,130,677, 4,374,879; EP-A-0 146 142). However, the level of properties is still not sufficient for all applications.
A further development. of the prior art was to apply by spraying, as the cold end coating, first the solution or dispersion of a silane and then a further component such as, for example, a polyethylene dispersion. Reference is made here to U.S. Pat. Nos. 3,438,801, 4,130,677, 4,304,802, 5,567,235 (corresponding to WO-A-95/00259) and to EP-A-0 146 142 and EP-A-0 478 154.
It is known, furthermore, that cold end coating can also be carried out with a polysiloxane (U.S. Pat. No. 4,985,286; DE-A-31 44 457).
The coatings described do indeed ensure a good basic strength of the glass containers; however, this strength falls rapidly in the subsequent production process and in the subsequent use of the containers. Causes of this loss in strength are microscopic damage, which occurs unavoidably during shaping and during the subsequent transportation of the glass containers while being hot and which may act as a potential source of fracture depending on the level and situation of the damage and on the stress experienced by the containers.
One object of the present invention is to render such microscopic damage harmless actually in the course of the production process.
A further object is to render the hollow articles less sensitive to mechanical effects acting on the surface in the course of subsequent handling, i.e. on the conveyor belt and in the course of packaging, dispatch and filling.
Another important aspect is that the hollow articles should have an improved durability in long-term use relative to the prior art. Thus, in particular, reusable bottles for carbonated drinks should still have a sufficiently high strength and, in particular, internal pressure resistance even after many returns.
In addition, the hollow glass containers should have improved chemical resistance, especially with respect to water and washing liquors.
It is the intention, furthermore, that the dry and wet scratch resistance should be increased and so the nick scratch properties improved.
Overall, the intention is to improve the mechanical properties relative to the prior art in such a way that it is possible to reduce the weight of the container with no change in strength.
The mechanical properties are also to be improved relative to the prior art such that hot end coating can be omitted with no change in final strength.
It should be possible, relative to the customarily performed coating, to achieve improved labeling, even with conventional glues.
These improvements are intended to be obtained with an extremely simple process which can be carried out on conventional production lines without significant additional investment. The intention in this context is, in particular, to avoid the need for a curing step, since that would imply greater investment and process costs.
Overall, the effect in accordance with the invention should ensue directly after the process measure has been carried out, i.e. without a significant waiting period, so that the protective effect occurs without delay in the course of subsequent further transportation on the belt.
To achieve these objects the invention proposes a process for producing surface-sealed hollow glass containers, where as part of the production process the hollow glass containers are coated with a water-based cold end coating composition in the region of the exit from the annealing lehr, which is arranged following a machine for producing hollow glass containers, wherein the cold end coating composition comprises the following components:
I. a water-based organopolysiloxane-containing composition prepared from
a) Q moles of functional group-bearing alkoxysilanes of the general formula
A—Si(R
1
)
y
(OR*)
3−y
  I
 and
b) M moles of alkoxysilanes selected from
&agr;) trialkoxysilanes of the general formula
R
2
—Si(OR**)
3
  II
 and/or
&bgr;) dialkoxysilanes of the general formula
R
3
R
4
Si(OR***)
2
  III
 and/or
&ggr;) tetraalkoxysilanes of the general formula
Si(OR***)
4
  IV,
 where
A is a substituent possessing at least one amino, alkylamino, dialkylamino, amido, epoxy, acryloxy, methacryloxy, cyano, isocyanato, ureido, thiocyanato, mercapto, sulfane or halogen group which is attached directly or via an aliphatic or aromatic hydrocarbon radical to silicon,
R
1
=methyl, ethyl or A (as defined above),
y=0 or 1, R*, R**, R*** and R**** independently of one another are an alkyl group having 1 to 8 carbon atoms or a corresponding alkyl group that is substituted by an alkyl[(poly)ethylene glycol] radical,
R
2
, R3 and R
4
independently of one another are an alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl or aromatic group having in each case not more than 18 carbon atoms, or a group of this kind which is partially fluorinated, perfluorinated and/or substituted by alkyloxy and/or by aryloxy groups,
 in a molar ratio 0≦M/Q≦20, and
II. a silicon-free component selected from
a) a wax and/or
b) a partial fatty acid ester and/or
c) a fatty acid and/or
d) a surfactant;
and additionally wherein the water-based cold end coating composition has a dry-matter content of from 0.1 to 10% by weight and, based on dry matter, the weight ratio of the organopolysiloxane-containing composition I to the silicon-free component II is from 0.05:1 to 20:1.
The invention also provides, moreover, the hollow glass containers produced by this process.
Hollow glass containers for the purposes of this invention are, in principle, any type of glass packaging, examples being bottles, preserve jars, ampules, tablet tubes or flasks.
In the region of the entrance of the annealing lehr it is possible if desired to apply a conventional hot end coating composition by any technique of the prior art to the surfaces of the freshly produced hollow glass containers. In view, however, of the massive increase in service strength achieved in accordance with the invention it is possible to omit hot end coating, which is not on

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