PRESERVATION OF PAPER AND TEXTILE MATERIALS

PRESERVATION DE MATIERES TEXTILES OU EN PAPIER

English Abstract

A method is disclosed for strengthening a paper or textile article. The method
involves (a) applying to the article a solution of an amorphous fluoropolymer
in a perfluoroalkane solvent; and (b) drying the article. Also disclosed are
strengthened paper and textile articles which include a fibrous paper or
textile substrate, and amorphous fluoropolymer interconnecting fibers of the
substrate.

French Abstract

L'invention concerne un procédé de renforcement d'un article en papier ou textile. Le procédé consiste a) à enduire l'article d'une solution d'un fluoropolymère amorphe dans un solvant perfluoroalkane; et b) à sécher l'article. Font aussi l'objet de cette invention des artels textiles ou en papier renforcés comprenant un substrat en papier ou textile fibreux et des fibres d'interconnexion d'un fluoropolymère amorphe du substrat.

Claims

CLAIMS
What is claimed is:
1. A method for strengthening a cellulosic paper or textile article,
comprising the steps of:
(a) applying to the article a solution of an amorphous fluoropolymer in
a perfluoroalkane solvent; and
(b) drying the article so that the solvent is essentially removed.
2. The method of Claim 1 wherein the fluoropolymer has a molecular
weight in the range of from 200,000 to 400,000.
3. The method of Claim 1 wherein the fluoropolymer is a copolymer of
4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole with either
tetrafluoroethylene or
chlorotrifluoroethylene.
4. The method of Claim 1 wherein the fluoropolymer is a copolymer of
tetrafluoroethylene with a monomer selected from fluoroolefins having from 2
to
8 carbon atoms and fluorinated alkyl vinyl ethers where the alkyl group
contains
from 1 to 5 carbons.
5. A strengthened cellulosic paper ar textile article, comprising:
(i) a fibrous cellulosic paper or textile substrate; and
(ii) amorphous fluoropolymer interconnecting fibers of said substrate.
6. The strengthened cellulosic paper or textile article of Claim 5 wherein
the fluoropolymer has a molecular weight in the range of from 200,000 to
400,000.
7. The strengthened cellulosic paper or textile article of Claim S wherein
the fluoropolymer is a copolymer of 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-
dioxole with either tetrafluoroethylene or chlorotrifluoroethylene.
8. The strengthened cellulosic paper or textile article of Claim 5 wherein
the fluoropolymer is a copolymer of tetrafluoroethylene with a monomer
selected
from fluoroolefins having from 2 to 8 carbon atoms and fluorinated alkyl vinyl
ethers where the alkyl group contains from 1 to 5 carbons.
9. A strengthened article of paper or textile, comprising:
a) a pattern or printing, and
b) an amorphous fluoropolymer coating applied from an amorphous
fluoropolymer solution such that the information conveyed by the pattern or
printing is not obscured or distorted.
10. The process of treating a patterned or printed article of paper or textile
comprising: applying to the article a solution of an amorphous fluoropolymer
in a
perfluoroalkane solvent; and drying the article so that the solvent is
essentially
removed.
7

Description

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CL1446 PCT . .
TALE
PRESERVATION OF PAPER AND TEXTILE MATERIALS
FIEL OF THE INVENTION
The p~tesent invention relates to the preservation of paper articles (e.g.,
books, manuscripts, documents) and textiles articles (e.g., paintings on
canvas,
clothing, etc.) through the application of an amorphous fluoropolymer by, for
example, spraying, dipping or brushing the article to be preserved with a
solution
of the fiuoropolymer.
BACKGROUND
Commonly owned and eopending PCT International Application
No. PCT/US98/26903 discloses coating a substrate (e.g., a metal, ceramic or
composite) including the application of a fluompolymer solution to seal pores.
The use of fluoropolymer dispersions to coat and protect paper and fabrics
is known (see e.g., U.S. Patent Nos. 4,742,140 and 5,674,96/). Generally,
these
dispersions are comprised of particles in the neighborhood of 80 to 400 nm in
'
i
diameter in as aqueous medium. The particles arc not intcndod 'to fully or
uniformly coat the fibers of paper or fabric. Also, because they are generally
aqueous dispersions, items containing water-soluble dyes would be damaged by
contact with water.
WO A 92/10532 teaches fluoimating the surface of polymers by
deposition of fluorocarbons from solution. WO A 97/19224 is a process for
preserving paper by polymerizing polycondensates in situ. GB A 007 981 .
discloses lamination of paper or textile articles. US 5,509,736 describes ,
itapregauoa of paper with paiiicies of oXides viinicil hyarate io-bases:
SUMMARY OF 'f~ INVENT1(~N
The present invention provides a method for strengthening a cellulosic
paper or textile article, comprising the steps of (a) applying to the article
a
solution of an amorphous fluoropolymer in a pcrfluoroalkane solvent; and
(b) drying the article so that the solvent is essentially removed.
The present invention also relates to a strengthened cellulosic pager or
textile article comprising (i) a f brows cellulosic paper or textile substrate
and
(ii) amorphous fluompolymer interconnecting fibers of said substrate.
BRIEF DESCRIPTION OF T~ DRA
Figure 1 represents a plot of data from Table 1.
DETAILED DESCRIPTION
The present invention employs amorphous fluoropolymers which, for
application, are dissolved in a perfluoroalkaae solvent. Articles to be
preserved
are treated with the fluoropolymer solution by any suitable method, including
but
1
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not limited to dipping, spraying and brushing. The article may be, but is not
limited to, a book, manuscript, paper, fabric, article of clothing, painting,
and the
like. Normally, the amorphous fluoropolymer is used substantially transparent,
and consequently there is no substantial difference in appearance between the
treated article and the untreated article.
~hcn fluoropolymer is deposited from solution onto a non-porous surface,
a coating of about 5 to 20 ~.rn thick typically results. This thickness is
related to
the concentration of the solution used is the deposition. Generally, a 1 %
solution
will produce a film about 5 Eun thick, and a 6% solution yields a film
thickness of
about 50 pm. However, when the object on which the fluoropolymer is deposited
is f brows or porous, the fluoropolymer penetrates into the obj oct. Commonly
owned and copending PCT International Application No. PCT/US98I26903 and
U.S. Patent Application Serial No. 215,441 describe the penetration of
fluoropolymer solutions into pores in thermal spray coatings which are used
for
corrosion protection. Fluorine x-ray fluorescence micrographs were used to
demonstrate fluoropolymer penetration into the pores.
Useful herein are solutions of fluoropolymers with molecular weights in
the range of from 200,000 to 400,000. These fluoropolymers are known to have
excellent chemical resistance; and their solutions generally have relatively
low
viscosities, on the order of about 0.050-0.300 pastel seconds (60 to
300 centipoise) at shear rates from about 50 to 300 sec-1, which enables them
to
flow into the pores. The location of the fluoropolymer in the pores is also
important because, unlike purely surface films, the material is not easily
abraded
or word$waY: i~aine=; W o ituorbpoiytner~in W a pole is protected fr'oni
abrasion - -I
by the surrounding porous coating as well as nay surface coating. Moreover,
the
fibers of the substrate are interconnected with fluoropolymer, thereby
strengthening the atticle_
Treating paper with fluoropolymer solutions can significantly increase the
tensile strength of paper, as shown in Example 2 below, as well as typically
impart other desirable properties. The films or deposits have very low surface
energies compared to untreated paper (e.g., in the range of 15 to 19
dynes/cm).
Thus, they are generally difficult to wet with liquids such as water. Solid
deposits
like dirt, dust or inks will not easily adhere to such surfaces. The
permeation of
aggressive chemical eonstxtuents of the environment which may degrade or
corrode the object is retarded, as the solutions penetrate into the bulk of
the
material as well as depositing on the surface. Finally, the fluoropolymer film
or
deposit itself is very inert to degradation from environmental chemicals.
2
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One use for this invention is the preservation of a variety of papers, !
including books, newspaper pages and documents, As paper ages, it frequently
becomes more brittle. This is a problem for historic books and documents of
great
age. Treatment of these papers with the fluoropolymer solutions, as described
in
this invention, have been shown to increase the tensile strength of the paper,
as
shown is the Irxatnples below. As outlined is Examples 1 and 2 below, a paper
or
book can be dipped into the fluoropolymerlperfluoroalkane solution and air
dried
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Minneapolis, MN). In general, the perfluoroalkaae solvents used la these
solutions are not considered aggressive to many paper and textile articles.
Most
inks will not dissolve in perfluorinated solvents. Similarly, many substrates
sre
tnnaffected by exposure to these solvents.
. The fluoropolymer solutions may be applied to the fibrous articles by
common coating methods, including but not limited to spray application,
dipping
and brushing. After application of the solutions, the articles can be dried by
conventional methods (e.g., air or vacuum drying),
EXAMPLES
Fluoroflo~ymer Solution Preoaration~
Teflon~ AF solutions were used in the examples below, and were used as
received from E. I. du Pont de Nemours and Company, Wilmington, DE, unless
otherwise noted. To dilute the Teflon~ AF2130, solvent (FC-75, 3M,
Minneapolis, MN) was weighed and was placed into a containcz, with the
calculated amount of Teflon~ AF2130 added to the solvent. The samples were
mixed before use.
EXAMPLE 1
Paper reatment
Several types of paper, including newsprint and copier paper were dipped
for about 30 seconds into several Teflon~ AF solutions, having concentrations
between 1 and 6% solids by weight, such that about half the sheet was
impregnated with the solution. The papers were removed from the solution and
I
dried for about 30 minutes. The entire sheets of paper were immersed in water
at
room temperature. The treated portion emerged in undamaged condition while r
the untreated papez fell apart. No dissolution or blurring of ink was observed
in
the treated portion of the newsprint.
I
AMPLE 2
Strength Testine of Payer
The strength of treated paper was compared to that of an untreated paper. '
Strips of paper (20 pound White Wove, Gilbert, Tnc., Menasha, WI) about 2.5 cm
(1 inch) wide, 20.3 em (8 inches) long, and 0.010 cm (0.004 inches) thick,
were
immersed for 10 minutes in solutions with varying concentrations of .
fluoropolymer_ The strips were removed and dried, leaving a fluoropolymer
deposit in the paper. The tensile strengths of the strips were measured using
a
r
model I 122 Instron test machine (Instroa Corp., Canton, MA) and ASTM Method
D 828 procedures (the test bars were held in grips with a separation of 5
inches, . .
and the cross head speed was 2 incheslminute). The fluoropolymer treatment
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increased the st~ngth of the paper. Z'he results are shown in Table 1 below,
as
well as in Figgie 1. '
TABLE 1
Fluoropolymer Concenvation S~g~~ % Iaereas~ !n
Solution Ideocificatioaof Mpa ~1 Stren va. Control
Fluoropolymer,
/o
None 0 44.0 6.38 ...
TEFLON~ AF 3 512 7.42 16.3
1600 6 ' 56.1 8.14 27.6
TFrFLON~ AF1601
'TEFLON AF2400I 48.9 7.09 11.1
TEFLON~ AFZ1306 59.3 8.60 34.8 ,
TEFLON~ AF2130'3 59.0 8.55 34_0
TEFLON~ AF21301 47.8 6.94 8.8 .
6
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Representative Drawing