Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Reexamination Certificate
1999-12-29
2003-11-04
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
C428S297400, C428S300100, C052S306000, C052S309100
Reexamination Certificate
active
06641903
ABSTRACT:
The present invention relates to transparent plastic panes of acrylic glass with internal plastic filaments, which largely hold together fragments formed in the event of a break, to a process for making such transparent plastic panes and to the use of the said plastic panes. In particular, the invention relates to transparent plastic panes which in the event of break of the plastic pane essentially do not produce any splinters or loose fragments, the panes of such type being suitable in particular for noise protection walls.
Noise protection walls with transparent plastic panes are known, for example, from European Patent EP 0407852. The plastic panes disclosed therein very successfully perform their function of preventing formation and falling of loose fragments. Stripes, ornaments or figures to ward off birds can additionally be embedded in the plastic panes described in the cited European Patent.
European Patent EP 0531982 also discloses transparent plastic panes with internal plastic filaments, which largely hold together fragments formed in the event of a break, the panes disclosed in the cited European Patent being provided with embedded filaments that are contrast-rich and thus can also act as particularly esthetic protection against birds.
Although the noise protection elements according to the prior art can excellently perform their function, which is to prevent release of splinters or fragments in the event of an automobile accident, crash or similar incident, it has been found during the use of such plates in practice that the inherently excellently homogeneous optical impression of the transparent plastic pane with internal filaments can be distorted off and on by a glitter or sheen. This can be due at least in part to detachment of the embedded plastic filaments from the PMMA matrix of the acrylic glass pane. Filament detachment at points or even over entire portions certainly does not substantially jeopardize the retention of fragments upon destruction of the noise protection wall, but total reflection of light in the PMMA channels along the detached portions causes just such glitter or sheen that can adversely influence the esthetic impression.
It is merely possible to speculate about the cause of the filament detachment that may occur from time to time. Conceivably it could relate to different coefficients of linear thermal expansion of the plastic material of filament and matrix of the acrylic glass pane in the relevant temperature range of about −20 to 120° C. For example, the dependence upon temperature of the coefficient of linear thermal expansion of the filament material is greater in the case of polyamide than the dependence on temperature of the coefficient of thermal expansion of PMMA. This means that one of the materials contracts at a relevant temperature, while the other material expands. Under certain circumstances, such behavior of the materials can promote detachment of the embedded filaments from the matrix.
In view of the cited and discussed prior art, the object of the present invention was to provide a transparent plastic pane of acrylic glass with internal filaments of plastic which, during continuous use under normal conditions, such as use as a noise protection wall, imparts an excellent homogeneous optical impression.
Another object of the invention was to provide such a plate in which the optical impression is not distorted by sheen or glitter even in prolonged use and after numerous temperature cycles.
Yet another object of the invention was to provide a corresponding pane or plate in which the optical impression is not distorted but which at the same time has the excellent positive properties of the known plates, especially the absence of excessive adhesion to the surrounding acrylic glass, so that in the event of breakage of the acrylic glass the filaments retain their ability to stretch, with the result that they do not break and therefore hold the fragments together.
As regards the method, the object of the present invention was to find a simply and favorably achievable method which permits the manufacture of transparent plastic panes of acrylic glass with internal plastic filaments, the adhesion of the embedded filaments to the matrix being sufficiently great that any fragments which may be formed in the event of breakage of the pane are secured without permitting undesired detachment of the filaments during continuous use under normal load, for example as a noise protection wall.
Finally, another object of the invention was to specify the use of transparent plastic panes of acrylic glass according to the invention.
The cited objects as well as other objects that are not specifically mentioned individually but are clearly evident from the introduction are achieved by a transparent plastic pane of the type mentioned in the introduction and comprising:
internal plastic filaments which hold together fragments of said acrylic glass formed in the event of a break;
wherein said plastic filaments are sized over a length of about 2 to 10 cm at intervals of from about 0.5 to 1.5 m with a solution comprising a) a sizing agent which comprises ≦ 10% of phenol; ≦ 2% of formaldehyde; ≦ 2% of methanol; and ≦ 30% of ethanol and b) p-toluenesulfonic acid in ethanol.
Preferred embodiments are the subject matter of the dependent claims referring back to the independent claims.
The method for making a transparent plastic pane of acrylic glass, provides a solution to the problems underlying the invention. Expedient modifications of the method are the subject matter of the claims dependent on the independent method claim. The method for making a transparent plastic pane of acrylic glass comprises:
sizing plastic filaments over a length of about 2 to 10 cm at intervals of about 0.5 to 1.5 m, to obtain sized plastic filaments;
embedding said sized plastic filaments in said acrylic glass to obtain internal plastic filaments;
wherein said plastic filaments are sized with a solution comprising a) a sizing agent which comprises ≦ 10% of phenol; ≦ 2% of formaldehyde; ≦ 2
5
of methanol; and ≦ 30% of ethanol and b) p-toluenesulfonic acid in ethanol;
wherein said internal plastic filaments hold together fragments of said acrylic glass formed in the event of a break.
It was a surprising discovery, which could not have been easily foreseen, that unpleasant glitter or sheen in a transparent plastic pane of acrylic glass with internal filaments of plastic, which hold together the fragments formed in the event of a break, can be prevented, without adversely influencing the splinter-retaining function of the embedded filaments, by sizing the plastic filaments at least partly. For the first time, therefore, it is possible with the invention to achieve an esthetically pleasing and optically satisfactory form of noise protection elements of acrylic glass which does not exhibit any detrimental optical properties even in continuous use and during normal temperature cycles of day and night.
The transparent plastic panes of acrylic glass according to the invention are known in themselves to the person skilled in the art. Pane thicknesses are typically 4 to 40 mm and preferably 12 to 25 mm. The panes are normally made with measurements of 1.5 m×1 m to 2 m×3 m, but larger or smaller measurements are also possible for special applications.
The panes are usually extensively transparent and preferably colorless or lightly tinted in colors such as smoke-brown. The colorless, transparent plastic panes usually have a transmittance of at least 70%, although a transmittance of 90 to 95% is advantageous. Tinted models usually have a transmittance of 45 to 75%, usually between 50 and 60%.
The embedded plastic filaments are usually made of a plastic which is incompatible with the polymer matrix of the acrylic glass pane. For example, polyamide filaments or polypropylene filaments are suitable. Single-strand filaments, or in other words monofilaments are preferred. Usually the filaments run horizontally in the plastic pane, since the panes are la
Molnar Gerald
Ruzicka Mojmir
Schoela Egbert
Gray J. M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Roehm GmbH & Co. KG
Yamnitzky Marie
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