Composite materials

Details Composite materials Composite materials

1999-05-03

2001-02-13

Cain, Edward J. (Department: 1714)

Stock material or miscellaneous articles

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C523S216000

Reexamination Certificate

active

06187426

ABSTRACT:

The invention relates to composite materials characterized by a substrate based on glass fibers, mineral fibers or derived timber products and by a nanocomposite which is in functional contact with said substrate and is obtainable by surface modification of
a) colloidal inorganic particles with
b) one or more silanes of the general formula (I)
R
x
—Si—A
4-x
  (I)
where the radicals A are identical or different and are hydroxyl groups or groups which can be removed hydrolytically, except methoxy, the radicals R are identical or different and are groups which cannot be removed hydrolytically and x is 0, 1, 2 or 3, where x≧1 in at least 50 mol % of the silanes;
under the conditions of the sol-gel process with a sub-stoichiometric amount of water, based on the hydrolysable groups which are present, with formation of a nanocomposite sol, and further hydrolysis and condensation of the nanocomposite sol, if desired, before it is brought into contact with the substrate, followed by curing.
The substrate may be of very different physical forms, and the nanocomposite may also be present in different forms of distribution. For example, the nanocomposite may cover the substrate partially or entirely in the form of a continuous covering or coating or it may be present between a plurality of substrates in lamellar form. Specific examples of composite materials of this type are fibers, twines, yarns, and semifinished products such as wovens, knits, braids and non-wovens provided with a thermally stable impregnation.
Alternatively the nanocomposite may form discontinuous or even point-shaped sites of contact between a plurality of substrates and may, for example, bind a particulate, flocculant or fibrous substrate in a matrix-like manner. Specific examples of composite materials of the latter type are insulating materials based on glass or mineral fibers and materials made of wood such as wood fiber slabs, particle boards, wood core plywood, plywood and wood-wool building slabs. For special purposes mixtures of glass fibers and timber materials may also be employed, e.g., for chip boards having flame-retardant properties.
Examples of suitable substrates are glass fibers, natural or man-made mineral fibers such as asbestos, mineral wool, slag wool, and fibers of ceramic materials including those of oxide ceramic; materials derived from timber in the form of cellulose, wood wool, wood flour, wood chips, paper, cardboard, wooden plates, wood borders and wood laminates.
The term fibrous substrates is taken to mean either individual fibers, including hollow fibers and whiskers, or corresponding fiber bundles, threads, ropes, twines and yarns, or semifinished products such as wovens, knits, braids, textiles, non-wovens, felts, webs, sheets and mats. Concrete examples of these are glass wool, glass fiber mats and mineral wool, e.g., slag wool, cinder wool, rock wool or basalt fibers.
The nanocomposite employed according to the invention is prepared by surface modification of colloidal inorganic particles (a) with one or more silanes (b), if desired in the presence of other additives (c) under the conditions of the sol-gel process.
Details of the sol-gel process are described in C. J. Brinker, G. W. Scherer: “Sol-Gel Science—The Physics and Chemistry of Sol-Gel-Processing”, Academic Press, Boston, San Diego, New York, Sydney (1990) and in DE 1941191, DE 3719339, DE 4020316 and DE 4217432.
Here, specific examples of the silanes (b) which can be employed according to the invention and of their radicals A which are hydrolytically removable and their radicals R which are not hydrolytically removable are given.
Preferred examples of groups A which are removable hydrolytically are hydrogen, halogen (F, Cl, Br and I, in particular Cl and Br), alkoxy (in particular C
2-4
-alkoxy, such as ethoxy, n-propoxy, isopropoxy and butoxy), aryloxy (in particular C
6-10
-aryloxy, such as phenoxy), alkaryloxy (e.g. benzyloxy), acyloxy (in particular C
1-4
-acyloxy, such as acetoxy and propionyloxy) and alkylcarbonyl (e.g. acetyl). Radicals A which are likewise suitable are amino groups (e.g. mono- or dialkyl-, -aryl- and -aralkylamino groups having the abovementioned alkyl, aryl and aralkyl radicals), amide groups (e.g. benzamido) and aldoxime or ketoxime groups. Two or three radicals A may also together form a moiety which complexes the Si atom, as for example in Si-polyol complexes derived from glycol, glycerol or pyrocatechol. Particularly preferred radicals A are C
2-4
-alkoxy groups, in particular ethoxy. Methoxy groups are less suitable for the purposes of the invention, since they have an excessively high reactivity (short processing time of the nanocomposite sol) and can give nanocomposites and/or composite materials with insufficient flexibility.
The abovementioned hydrolysable groups A may, if desired, carry one or more usual substituents, for example halogen atoms or alkoxy groups.
The radicals R which are not hydrolytically removable are preferably selected from alkyl (in particular C
1-4
-alkyl, such as methyl, ethyl, propyl and butyl), alkenyl (in particular C
2-4
-alkenyl, such as vinyl, 1-propenyl, 2-propenyl and butenyl), alkynyl (in particular C
2-4
-alkynyl, such as acetylenyl and propargyl), aryl (in particular C
6-10
-aryl, such as phenyl and naphthyl) and the corresponding alkaryl and arylalkyl groups. These groups may also, if desired, have one or more usual substituents, for example halogen, alkoxy, hydroxy, amino or epoxide groups.
The abovementioned alkyl, alkenyl and alkynyl groups include the corresponding cyclic radicals, such as cyclopropyl, cyclopentyl and cyclohexyl.
Particularly preferred radicals R are substituted or unsubstituted C
1-4
-alkyl groups, in particular methyl and ethyl, and substituted or unsubstituted C
6-10
-aryl groups, in particular phenyl.
It is also preferable that x in the above formula (I) is 0, 1 or 2, particularly preferably 0 or 1. It is also preferable if x=1 in at least 60 mol %, in particular at least 70 mol %, of the silanes of the formula (I). In particular cases, it may be even more favourable if x=1 in more than 80 mol %, or even more than 90 mol % (e.g. 100 mol %), of the silanes of the formula (I).
The composite materials according to the invention may be prepared, for example, from pure methyltriethoxysilane (MTEOS) or from mixtures of MTEOS and tetraethoxysilane (TEOS), as component (b).
Concrete examples of silanes of the general formula (I) are compounds of the following formulae:
Si(OC
2
H
5
)
4
, Si(O-n-or iso-C
3
H
7
)
4
, Si(OC
4
H
9
)
4
, SiCl
4
,
Si(OOCCH
3
)
4
, CH
3
—SiCl
3
, CH
3
—Si(OC
2
H
5
)
3
, C
2
H
5
—SiCl
3
,
C
2
H
5
—Si(OC
2
H
5
)
3
, C
3
H
7
—Si(OC
2
H
5
)
3
, C
6
H
5
—Si—(OC
2
H
5
)
3
,
C
6
H
5
—Si(OC
2
H
5
)
3
, (C
2
H
5
O)
3
—Si—C
3
H
6
—Cl, (CH
3
)
2
SiCl
2
,
(CH
3
)
2
Si(OC
2
H
5
)
2
, (CH
3
)
2
Si(OH)
2
, (C
6
H
5
)
2
SiCl
2
,
(C
6
H
5
)
2
Si(OC
2
H
5
)
2
, (C
6
H
5
)
2
Si(OC
2
H
5
)
2
,
(iso-C
3
H
7
)
3
SiOH, CH
2
═CH—Si(OOCCH
3
)
3
, CH
2
═CH—SiCl
3
,
CH
2
═CH—Si(OC
2
H
5
)
3
, HSiCl
3
,
CH
2
═CH—Si(OC
2
H
4
OCH
3
)
3
, CH
2
═CH—CH
2
—Si(OC
2
H
5
)
3
,
CH
2
═CH—CH
2
—Si(OOCCH
3
)
3
, CH
2
═C(CH
3
)COO—C
3
H
7
—Si—(OC
2
H
5
)
3
,
CH
2
═C(CH
3
)—COO—C
3
H
7
—Si(OC
2
H
5
)
3
, n—C
6
H
13
—CH
2
—CH
2
—Si(OC
2
H
5
)
3
,
n-C
8
H
17
—CH
2
—CH
2
—Si(OC
2
H
5
)
3
,
These silanes can be prepared by known methods; cf. W. Noll, “Chemie und Technologie der Silicone” [Chemistry and Technology of the Silicones], Verlag Chemie GmbH, Weinheim/Bergstra&bgr;e, Germany (1968).
Based on the abovementioned components (a), (b) and (c), the proportion of component (b) is usually from 20 to 95% by weight, preferably from 40 to 90% by weight, and particularly preferably from 70 to 90% by weight, expressed as polysiloxane of the formula: R
x
SiO
(2−0.5x)
which is formed in the condensation.
The silanes of the general formula (I) used according to the invention may be employed wholly or partially in the form of precondensates, i.e. compounds produced by partial hydro

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