Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1994-01-18
2001-01-30
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S103000, C428S201000, C428S210000, C428S212000, C428S442000, C428S520000
Reexamination Certificate
active
06180246
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to compositions and interlayers for laminated glazings and, more particularly, to plasticized polyvinyl chloride resin forming such interlayers.
2. Summary of Related Art
Safety glass is a well known term for a glass sandwich composed of an interlayer bonding together two glass plates or sheets so that breaking the glass results in minimum dispersion of broken glass fragments. The interlayer must possess a number of properties, including the following: high impact energy adsorption to minimize concussive injury; shear and tear strength sufficient to prevent rupture of the interlayer by the broken glass; sufficient adhesion to the glass to inhibit laceration on contact with, and prevent dispersion of, broken glass; acceptable thermal heat stability and weatherability; and good optical quality. The interlayer must possess these properties over the wide range of temperatures in which these laminated glazings are used.
It has been widely known to use a film of plasticized polyvinyl butyral as the interlayer material in safety glass for automobiles, air planes and building materials because of its high adhesiveness and superior light stability, transparency and low-temperature flexibility. However, the use of plasticized polyvinyl butyral films makes the production of laminated safety glass relatively expensive.
The surface of plasticized polyvinyl butyral film is very tacky, and presents a problem of blocking at the time of windup after film formation. Thus, plasticized polyvinyl butyral film must be provided with some parting means if it is to be stored or transported in the form of stacks of die-cut blanks or in the form of rolls. Furthermore, the production of plasticized polyvinyl butyral films requires specialized equipment and, due to their sensitivity to moisture, plasticized polyvinyl butyral films must generally be handled under controlled atmosphere conditions during manufacture, storage and immediately prior to their incorporation into the laminated safety glass. This all adds to the expense of utilizing plasticized polyvinyl butyral films in laminated safety glass.
Alternative interlayer materials have been proposed. For instance, U.S. Pat. No. 4,277,538 to Beckmann et al discloses a laminated safety glass employing a sheet of plasticized polyvinyl chloride (PVC) as the interlayer. The use of PVC would be advantageous in that it may be produced on conventional equipment and would be much less expensive to manufacture and process into a laminated safety glass when compared with polyvinyl butyral. However, by itself, a PVC film will not adhere to glass. To increase the adhesion of the PVC to glass, Beckmann et al suggest the use of an organofunctional silane, either as a primer or uniformly dispersed within the PVC film.
At least certain of the silicon-organofunctional silanes proposed by Beckmann et al are effective to increase the adhesion of a PVC interlayer to the glass sheets of a laminated safety glass. However, the laminated safety glass employing a PVC interlayer as taught by Beckmann et al does not possess all of the properties required of an interlayer for laminated safety glass, and therefore has not been placed into general use. For instance, the Beckmann et al interlayer has poor long term heat stability at service use temperatures. In addition, Beckmann et al were primarily concerned with increasing adhesion, not with improving impact resistance. It was found that the Beckmann et al laminated safety glass exhibits low energy adsorption characteristics. To compensate, a relatively thick PVC interlayer is required.
SUMMARY OF THE INVENTION
The present invention relates to an improved plasticized polyvinyl chloride interlayer for laminated safety glass, and an improved method of manufacturing a laminated safety glass wherein a pair of glass sheets are bonded to opposed sides of a plasticized polyvinyl chloride containing film at elevated temperature. In accordance with one aspect of the invention, the PVC film includes a plasticizer comprising a linear or branched aliphatic diester, triester or tetraester, or aromatic diester, triester or tetraester, or mixtures thereof, the concentration of said plasticizer being between about 40 to about 70 parts per hundred parts of resin (phr).
In another aspect of the invention, an interlayer is formed of a plasticized polyvinyl chloride containing film including about 1 to 5, preferably 2 to 4 phr of a primary heat stabilizer including an organometallic compound, such as salts of the alkaline metals and selected transition metals. The primary heat stabilizer preferably includes from about 1.6 to 4.0% atomic zinc as a zinc salt of an organic acid, and from about 7.0 to 14.0% atomic barium as a barium salt of an organic acid.
The plasticized polyvinyl chloride containing film preferably includes about 1 to 5, preferably 2 to 4 phr of primary heat stabilizer comprising organometallic compound and a phosphite, and secondary heat stabilizers including epoxidized oils, perchlorates, and 1,3 [beta]-diketones.
An improved safety glass also results from providing a plasticized PVC containing interlayer bonded to a pair of silicate glass sheets with an adhesion promoter comprising a mercapto-functional silane.
In a still further aspect of the present invention, wherein a pair of glass sheets are bonded to opposed sides of a plasticized polyvinyl chloride containing film at elevated temperature with an adhesion promoter comprising a functional silane, an improvement results wherein the functional silane is applied to only a portion of the plasticized PVC containing film or to only a portion of the glass sheets to achieve a controlled level of adhesion between the plasticized PVC containing film and the glass sheets.
In another aspect of the invention, an improved safety glass results where more of the functional silane is applied around the periphery of the plasticized polyvinyl chloride containing film than is applied near the center thereof, to achieve a higher level of adhesion between the plasticized polyvinyl chloride containing film and the glass sheets around the periphery thereof.
It has also been found that to obtain adequate adhesion between the plasticized PVC containing film and the glass, the PVC film must be treated so as to increase the level of unsaturation in the film.
In an additional aspect of the invention, an improved vehicle safety glass results wherein the level of adhesion between the inboard glass sheet and the plasticized PVC containing film is greater than the level of adhesion between the outboard glass sheet and the plasticized PVC containing film.
Moreover, an improved safety glass results where the plasticized PVC containing film is comprised of at least two distinct polyvinyl chloride containing layers having different levels of plasticization.
Further, an improved safety glass results where a material which absorbs ultraviolet radiation is applied to the surface of the plasticized PVC containing film or to the surface of the outer glass sheet.
An object of the present invention, therefore, is to provide an improved PVC interlayer for laminated safety glass;
A further object is to provide a controlled level of adhesion between the PVC interlayer and the two glass sheets, so that impact energy dissipation is maximized while structural integrity is maintained;
Another object of the invention is to provide such a laminated safety glass utilizing an improved functional silane adhesion promoter;
Another object of the invention is to provide such a laminated safety glass having a relatively thin interlayer of PVC;
A still further object is to provide such a laminated safety glass which possesses improved long term heat stability at service use temperatures;
Other objects and advantages will become more apparent during the course of the following description.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The numerous and varied properties required of an interlayer material for use in laminated safety glass has made it v
Holmes Paul A.
MacLachlan Julia B.
Negishi Yasuo
Parker Anthony A.
Purvis Michael B.
Libbey-Owens-Ford Co.
Marshall & Melhorn
Nakarani D. S.
LandOfFree
Plasticized polyvinyl chloride and interlayer thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plasticized polyvinyl chloride and interlayer thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plasticized polyvinyl chloride and interlayer thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2507483