Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2002-03-22
2003-07-01
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S436000, C524S306000, C524S394000, C524S400000
Reexamination Certificate
active
06586103
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an interlayer film for laminated glass characterized by high moisture resistance and small plasticizer vapor emanation, and a laminated glass in which said interlayer film is used.
BACKGROUND ART
Laminated glass comprising at least two glass sheets with a plasticized poly(vinyl acetal) resin interlayer film interposed has the fundamental characteristics required of laminated glass, namely good transparency, high weathering resistance, and high penetration resistance scarcely allowing its fragments to scatter and, as such, has been used extensively as the laminated glass for automotive and architectural use.
Although such laminated glass is satisfactory in said fundamental characteristics and safety, it is not only poor in moisture resistance but has the drawback of emanating a substantial amount of vapor due to the plasticizer contained.
With regard to moisture resistance, the problem is that, when such laminated glass is put to use in a highly humid atmosphere, its interlayer film, exposed at its peripheral edge to the surrounding atmosphere, causes whitening in its marginal area of the interlayer film.
As an attempt to reduce such marginal whitening of laminated glass in case of setting it in a highly humid environment, Japanese Kokai Publication Hei-7-41340 discloses an “interlayer film for laminated glass which comprises a resin composition comprising a poly(vinyl acetal) resin, a plasticizer, a metal carboxylate and a straight-chain fatty acid”.
The laminated glass containing the above interlayer film for laminated glass has been improved in reducing said marginal whitening after a moisture resistance test but the effect is not fully satisfactory. Moreover, reducing the addition amount of the metal salt results in improved resistance to said whitening but causes a reduction in penetration resistance.
In addition, the recent deployment of the laminated glass interlayer film in such applications as automotive side glass and the increasing trend toward the open-edge construction of front glass are imposing a greater emphasis on the moisture resistance of laminated glass.
Furthermore, while dihexyl adipate, triethylene glycol di-2-ethylbutyrate or the like is generally used as the plasticizer for the laminated glass interlayer film, these plasticizers are so low-boiling that they are liable to be evaporated and tend to present the risk for a fire hazard associated with autoclaving in the course of production of the interlayer film and the difficulties in edge trimming after autoclaving. Therefore, the switch-over to plasticizers having higher boiling points is demanded.
SUMMARY OF THE INVENTION
In view of the above state of the art, the present invention has for its object to provide an interlayer film for laminated glass which, when assembled into laminated glass, offers good transparency, weathering resistance, adhesion, penetration resistance and other characteristics, does not cause marginal whitening of laminated glass even exposed to a highly humid atmosphere, and free from the risk for a fire hazard in autoclaving or the problem associated with edge trimming and a laminate glass comprising said interlayer film.
The present invention, therefore, is concerned with an interlayer film for laminated glass comprising a plasticized poly(vinyl acetal) resin film,
wherein, when a laminated glass fabricated by interposing said interlayer film for laminated glass between a pair of glass sheets each 2.0 to 4.0 mm thick is allowed to sit in an environment of 80° C. and 95% relative humidity for 2 weeks, the distance of whitening from its edge is not greater than 7 mm,
and when said interlayer film for laminated glass is allowed to sit at 150° C. for 1 hour, its weight loss is not greater than 3 weight %.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is now described in detail.
The interlayer film for laminated glass according to the present invention is such that, when a laminated glass comprising it is allowed to sit in an environment of 80° C. and 95% RH for 2 weeks, the distance of whitening from its edge is not greater than 7 mm. If the limit of 7 mm is exceeded, the whitening tends to progress further to affect the moisture resistance of the laminated glass so that the above limit is critical. The term “edge” is used herein with reference to the side closest to whitening of the four sides of the laminated glass.
The weight loss of said interlayer film for laminated glass which occurs, when it is allowed to sit at 150° C. for 1 hour, should not be greater than 3 weight %. If this limit of 3 weight % is exceeded, the risk for a fire hazard at autoclaving tends to become high and the edge trimming after autoclaving will become difficult. Therefore, the above limit is critical.
Insofar as it comprises a plasticized poly(vinyl acetal) resin film, the interlayer film for laminated glass of the present invention is not particularly restricted. However, if a metal salt is added at a large amount for the purpose of improving the penetration resistance of laminated glass, the moisture resistance of the glass will be considerably decreased. In this connection, the use of at least two kinds of salts selected from the group consisting of magnesium salts of carboxylic acids containing 2 to 10 carbon atoms and potassium salts of carboxylic acids containing 2 to 10 carbon atoms contributes to improved moisture resistance while securing the penetration resistance at low amounts of addition.
Moreover, by using triethylene glycol di-2-ethylhexanoate, oligo-ethylene glycol di-2-ethylhexanoate or tetraethylene glycol-di-n-heptanoate as the plasticizer for the interlayer film for laminated glass, said risk for a fire hazard in autoclaving and difficulties in edge trimming can be remarkably obviated. Therefore, the interlayer film for laminated glass of the present invention is preferably a plasticized poly(vinyl acetal) resin film comprising 100 weight parts of a poly(vinyl acetal) with an average acetalization degree of 66 to 72 mole % and 30 to 50 weight parts of at least one plasticizer selected from the group consisting of triethylene glycol di-2-ethylhexanoate, oligoethylene glycol di-2-ethylhexanoate and tetraethylene glycol di-n-heptanoat, and being supplemented with at least two kinds of salts selected from the group consisting of magnesium salts of carboxylic acids containing 2 to 10 carbon atoms and potassium salts of carboxylic acids containing 2 to 10 carbon atoms in a total concentration of not less than 5 ppm. If the salt content is less than 5 ppm, the bond strength control effect may not be sufficient, while an excessively high salt content may detract from moisture resistance.
While the poly(vinyl acetal) mentioned above is obtainable by acetalization of polyvinyl alcohol, the particularly preferred resin is poly(vinyl butyral) which is obtainable by butyralization of polyvinyl alcohol.
The technology of acetalizing polyvinyl alcohol to provide poly(vinyl acetal) includes a method which comprises dissolving polyvinyl alcohol in warm water, adding the necessary acid catalyst and aldehyde while the aqueous solution is maintained at a predetermined temperature, for example 0 to 95° C., and allowing the acetalization reaction to go to completion with constant stirring and subjecting the reaction product to neutralization, aqueous washing and drying to provide powders of poly(vinyl acetal) resin.
The polyvinyl alcohol mentioned above preferably has an average polymerization degree of 500 to 5000 and more preferably 1000 to 2500. If the average degree of polymerization is less than 500, the laminated glass fabricated with the interlayer film for laminated glass tends to be low in penetration resistance. On the other hand, if the average degree of polymerization exceeds 5000, the formation of an interlayer film for laminated glass tends to become difficult and, in addition, the strength of the interlayer film for laminated glass will become too great in some instances.
The poly(vinyl acetal) mentioned above comprises a vinyl
Hattori Tsuyoshi
Miyai Jiro
Shohi Hajime
Nakarani D. S.
Sekisui Chemical Co. Ltd.
Sughrue & Mion, PLLC
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