Composite materials based on vegetable materials

Details Composite materials based on vegetable materials Composite materials based on vegetable materials

1999-05-03

2002-03-05

Gallagher, John J. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C156S283000, C427S180000, C516S009000, C516S055000

Reexamination Certificate

active

06352610

ABSTRACT:

The invention relates to composite materials characterized by a substrate based on vegetable materials, in particular vegetable fibres, vegetable fibre raw materials or vegetable fibre semifinished 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 be, for example, particulate, flocculent, fibrous, strip-shaped, plate-shaped, foil-shaped, sheet-shaped or block-shaped, or have a layered structure, or be a shaped article of any desired shape.
The nanocomposite, too, may be present in many different forms. It may, for example, cover the substrate entirely or partially, as a continuous coating or covering, or may be similar to a laminate between a number of substrates. Alternatively, the nanocomposite can form discontinuous or punctiform contacts between a plurality of substrates and, for example, act as a matrix in bonding a particulate, flocculent or fibrous substrate, as for example in insulating materials.
Suitable substrate materials for the novel composite materials are substrates based on vegetable materials, in particular vegetable fibres, vegetable fibre raw materials or vegetable fibre semifinished products, wood being excluded.
Examples of suitable substrate materials are natural fibres, e.g. seed fibres, such as cotton; fruit wall fibres, such as kapok; bast fibres, such as flax, hemp, jute or ramie; and hard fibres, such as sisal or coconut. Suitable vegetable fibre raw materials are, e.g., reed and rice or cereal and straw. Suitable vegetable fibre semifinished (processed) products are, e.g., fibre bundles, threads, cords, ropes, twines and yarns as well as semifinished products, such as wovens, fabrics, knits, braids, textiles, non-wovens, felts, webs and mats.
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, 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 or alkoxy.
The radicals R which are not hydrolytically removable are preferably selected from the group consisting of 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
-alkyl 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 novel composite materials may be prepared, for example, from pure methyltriethoxysilane (MTEOS) or from mixtures of MTEOS and tetraethoxysilane (TEOS), as component (b).
The use of silanes with one or more groups R which are substituted is advisable in particular where special properties are to be given to the composite material. For example, the introduction of fluorine atoms (e.g. in the form of substituted aliphatic (in particular alkyl) radicals) can give a composite material which has water-, dirt-, dust- and oil-repellent properties.
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 precondensate

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