Stock material or miscellaneous articles – Composite – Of polyamide
Reexamination Certificate
2000-04-28
2002-01-22
Hampton-Hightower, P. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamide
C428S472000, C428S474700, C428S474900, C428S475500, C428S478800, C264S165000, C264S172190, C264S173100, C264S173120, C264S173140, C264S173150, C264S173160, C264S173190, C264S174100, C264S175000, C264S176100, C281S029000
Reexamination Certificate
active
06340530
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to book covers and more particularly to a substantially transparent, coextruded, matte, bilayer nylon film, which is contact transparent. When such a film is attached to a paper stock, it is suitable for forming a soft book cover having high scratch, abrasion and mar resistance, as well as a soft feel and good curl resistance properties when contacted with moisture.
2. Description of the Related Art
It is known in the art that paper absorbs moisture from the surrounding atmosphere quickly, depending on the relative humidity and the temperature of the air with which it is in contact. As a consequence of the absorption and desorption of water by the paper there is an unwanted change in its dimensions due to changes in moisture content. Dimensional changes in paper are caused by the swelling and contraction of the individual paper fibers.
One attempted solution to this problem has been to laminate a polymeric film to an underlying paper sheet for protecting images and text on the paper surface. Paper used as cover stock for books has typically been thermally laminated to a layer of polyethylene, polypropylene or polyester. However, lamination of paper to polyethylene, polypropylene or polyester has some inherent drawbacks since the paper and polymeric film have different hydroscopic properties. For paper stock with only one side laminated, moisture is only absorbed by the paper on one side because of the protection of the film. This increases the dimension of the paper and causes the laminated paper composite to curl towards the film. The film can be applied to both sides of the paper to prevent paper moisture growth each side, however, in most book applications it is desired to protect only one side of the paper. It would therefore be desirable to provide a book cover where only one side of the paper is laminated to a protective polymeric sheet, and which eliminates the inherent tendency of book covers to curl.
U.S. Pat. No. 5,626,969 has proposed the use of nylon as the protective film because nylon has the property of absorbing moisture with a resultant increase in dimensions similar to paper. This absorption of moisture by nylon film compensates for the moisture absorption of paper. When the moisture is absorbed by nylon, it elongates to the same degree as the paper, thus allowing the overall laminated book cover to remain flat. However, in the production of book covers, it is also desired that it have a matte surface. The protective sheets of U.S. Pat. No. 5,626,969 are not taught to have a matte surface. It would therefore be desired to produce a book cover having a film which is substantially transparent when in adhesive contact with a paper sheet, has a matte surface, offers abrasion and mar resistance and still changes its dimensions in an amount approximating that of the paper sheet to which it is attached. It is known to produce matte nylon sheets by uniformly melt blending fillers such as silica into the nylon film. However, nylon sheets including uniformly blended fillers are difficult to orient and therefore reduces film strength. U.S. Pat. Nos. 5,006,394 and 5,261,899 propose multilayer films composed of a first outer layer comprised of a polymer attached to a second layer containing fillers. However, these films are not transparent, Additionally, these patents teach that the films should not be stretched, and used for diapers rather than book covers.
SUMMARY OF THE INVENTION
The invention provides a substantially transparent, coextruded film which comprises a first nylon layer attached adjacent to a second nylon layer, the first nylon layer comprising from about 20 weight percent to about 70 weight percent of a refractory filler based on the weight of the first nylon layer.
The invention also provides a method of producing an article which comprises coextruding a first nylon layer with a second nylon layer, wherein the first nylon layer comprises from about 20 weight percent to about 70 weight percent of a refractory filler based on the weight of the first nylon layer to thereby produce a substantially transparent film article.
The invention further provides a book cover which comprises a substantially transparent, coextruded film which comprises a first nylon layer attached adjacent to a second nylon layer, the first nylon layer comprising from about 20 weight percent to about 70 weight percent of a refractory filler based on the weight of the first nylon layer; and a layer of paper attached to a surface of the second nylon layer.
It is desirable to produce a film which solves the above problems and provides a substantially contact transparent, coextruded film of a first nylon layer attached to a second nylon layer wherein the first nylon layer has about 20 weight percent to about 70 weight percent of a refractory filler. The film has a matte appearance, is contact transparent when laminated to a sheet of paper, stretchable, mar and abrasion resistant, and changes its dimensions in an amount approximating that of the paper sheet to which it is attached thus being capable of producing a book cover having reduced curl.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The film for the present invention comprises a coextruded film having a first nylon layer attached adjacent to a second nylon layer. The first nylon layer comprises from about 20 weight percent to about 70 weight percent of a refractory filler based on the weight of the first nylon layer. Preferably the second nylon layer is free of fillers. Each of the first and second layers nylon layers independently comprises one or more polyamide homopolymers or polyamide copolymers.
Each of the nylon layers may comprise one or more aliphatic, aromatic or aliphatic/aromatic polyamide homopolymer or copolymer. Polyamides suitable for use in the present invention include polyamides which are film forming. Preferred polyamides are long chain polymeric amides having recurring amide groups as part of the polymer backbone and preferably a relative formic acid viscosity (for nylon 6) of from about 40 to about 250 measured in 90 percent formic acid at a concentration of 9.2 weight percent.
Non-limiting examples of polyamides homopolymers and copolymers are poly(hexamethylene adipamide) (nylon 6,6), poly(hexamethylene sebacamide) (nylon 6, 10), poly(heptamethylene pimelamide) (nylon 7,7), poly(octamethylene suberamide) (nylon 8,8), poly(nonamethylene azelamide) (nylon 9,9), poly(decamethylene azelamnide) (nylon 10,9), poly(4-aminobutyric acid) (nylon 4), nylon 4,6; nylon 6, T; nylon 6,I; poly(6-aminohexanoic acid) (nylon 6, also known as poly(caprolactam)), poly(7-aminoheptanoic acid) (nylon 7), poly(8-aminoocatanoic acid)(nylon 8), poly(9-aminononanoic acid) (nylon 9), poly(10-aminodecanoic acid) (nylon 10), poly(11-aminondecanoic acid) (nylon 11), poly(12-aminododecanoic acid) (nylon 12) and the like.
Blends of two or more aliphatic polyamides may also be employed. Copolymers formed from recurring units of the above referenced aliphatic polyamides can be used in the fabrication of the polyamide layers. By way of illustration and not limitation, such aliphatic polyamide copolymers include caprolactam/hexamethylene adipamide copolymer (nylon 6/6,6), hexamethylene adipamide/caprolactam copolymer (nylon 6,6/6), trimethylene adipamide/hexamethylene azelaiamide copolymer (nylon trimethyl 6,2/6,9), hexamethylene adipamide/hexamethylene-azelaiamide/caprolactam copolymer (nylon 6,6/6,9/6) and the like. Preferred aliphatic polyamides for use in the practice of this invention are poly(caprolactam) and poly(hexamethylene adipamide), and a copolymer of poly(caprolactam) with polyhexamethylene adipamide. Polyamides used in the practice of this invention may be obtained from commercial sources or prepared in accordance with known preparatory techniques. For example, polycaprolactam can be obtained from Honeywell International Inc., Morristown, N.J. under the trademark CAPRON®. Suitable variants of CAPRON® for use as a first polyamide in the present in
Altizer Lance R.
Moulton Jeffrey D.
Porter Simon J.
Criss Roger H.
Hampton-Hightower P.
Honeywell International , Inc.
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