Filler mixtures

Details Filler mixtures Filler mixtures

2002-01-14

2004-01-27

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C523S216000, C523S466000, C524S445000, C524S714000, C524S789000

Reexamination Certificate

active

06683122

ABSTRACT:

FILLER MIXTURES
The present invention relates to novel filler mixtures, to compositions comprising those filler mixtures and to their use, and to a process for the preparation of nanocomposites.
The preparation of organophilic layer silicates by treatment of layer silicates with onium salts, e.g. quaternary ammonium salts, in the presence of a dispersion medium is known from U.S. Pat. No. 4,810,734. In that treatment an exchange of ions takes place, the cation of the onium salt being inserted into the interlayer space of the layer silicate. Layer silicates modified in that manner become organophilic as a result of the organic radical of the inter-calated amine. When that organic radical contains functional groups, the organophilic layer silicate is capable of forming chemical bonds with suitable monomers or polymers.
WO 96/08526 describes the use of such organophilic layer silicates as filler materials for epoxy resins, there being obtained nanocomposites having improved physical and mechanical properties. It is of special interest that there is an increase in rigidity while the toughness at least remains the same. Especially good properties are exhibited by nano-composites that contain the layer silicate in exfoliated form. However, the addition of such organophilic layer silicates gives rise not only to an improvement in rigidity but also to a reduction in tensile strength.
It has been found, surprisingly, that a combination of organophilic layer silicates and mineral fillers can yield considerably better mechanical properties than the individual components. In thermosetting resins, the addition of the filler mixtures according to the invention results in a considerable increase in rigidity as compared with the use of pure mineral fillers at the same total filler content, while the substantial reduction in tensile strength which occurs when organophilic layer silicates are used alone is prevented. The filler mixtures according to the invention therefore allow the preparation of filled resins which, while having a relatively low filler content, have good mechanical properties and can be processed without problems. By varying the mixing ratio of mineral filler to organophilic layer silicate it is possible to obtain tailored system-specific property profiles.
The present invention relates to a filler mixture comprising an organophilic layer silicate obtainable by treatment of a natural or synthetic layer silicate with a swelling agent selected from sulfonium, phosphonium and ammonium compounds (salts of melamine compounds and cyclic amidine compounds being excluded as ammonium compounds) and a mineral filler different therefrom.
As layer silicates for the preparation of the organophilic layer silicates of the filler mixtures according to the invention there come into consideration especially natural and synthetic smectite clay minerals, more especially bentonite, vermiculite, halloysite, saponite, beidellite, nontronite, hectorite, sauconite, stevensite and montmorillonite. Montmorillonite and hectorite are preferred.
The layer silicate montmorillonite, for example, corresponds generally to the formula Al
2
[(OH)
2
/Si
4
O
10
].nH
2
O, it being possible for some of the aluminium to have been replaced by magnesium. The composition varies according to the silicate deposit. A preferred composition of the layer silicate corresponds to the formula
(Al
3.15
Mg
0.85
)Si
8.00
O
20
(OH)
4
X
11.8
.nH
2
O,
wherein X is an exchangeable cation, generally sodium or potassium, and some of the hydroxyl groups may have been replaced by fluoride ions. By exchanging hydroxyl groups for fluoride ions, synthetic layer silicates are obtained.
The sulfonium, phosphonium and ammonium compounds required as swelling agents for the preparation of the organophilic layer silicates are known and some of them are commercially available. They are generally compounds having an onium ion, for example trimethylammonium, trimethylphosphonium and dimethylsulfonium, and a functional group that is capable of reacting or bonding with a polymeric compound. Suitable ammonium salts can be prepared, for example, by protonation or quaternisation of corresponding aliphatic, cycloaliphatic or aromatic amines, diamines, polyamines or aminated polyethylene or polypropylene glycols (Jeffamine® M series, D series or T series).
Suitable swelling agents are, for example, salts that contain cations of formulae II-IV
R
1
R
2
R
3
N
⊕
—Z—Y  (II),
R
1
R
2
R
3
P
⊕
—Z—Y  (III),
R
1
R
2
S
⊕
—Z—Y  (IV),
wherein R
1
, R
2
and R
3
are each independently of the others hydrogen or C
1
-C
6
alkyl, Z is the divalent radical of a C
2
-C
30
alkane that is unsubstituted or substituted by one or more phenyl groups, C
1
-C
4
alkoxy groups, hydroxyl groups or halogen atoms and Y is —OH, —COOH, —NH
2
, vinyl, glycidyl or &bgr;-methylglycidyl.
It is preferable to use as swelling agents ammonium salts that are obtainable by reaction of amino acids with mineral acids.
Especially preferred are salts of 4-aminobutyric acid, 6-aminocaproic acid, &ohgr;-aminocaprylic acid, 10-aminodecanoic acid, 12-aminododecanoic acid, 14-aminotetradecanoic acid, 16-aminohexadecanoic acid and 18-aminooctadecanoic acid.
Special preference is given to layer silicates in which the layers have a layer spacing of about from 0.7 nm to 1.2 nm and which have a cation exchange capacity in the region of 50 to 200 meq./100 g (milliequivalents per 100 grams). After treatment with the swelling agent (sulfonium, phosphonium or ammonium compound), the layer spacing in the organophilic layer silicates so obtained is preferably at least 1.2 nm. Such layer silicates are described, for example, in A. D. Wilson, H. T. Posser, Developments in Ionic Polymers, London, Applied Science Publishers, Chapter 2, 1986. Synthetic layer silicates can be obtained, for example, by reaction of natural layer silicates with sodium hexafluorosilicate and are commercially available inter alia from the CO-OP Chemical Company, Ltd., Tokyo, Japan.
For the preparation of the organophilic layer silicates, the swelling agent is first advantageously dispersed or dissolved, with stirring, in a dispersion medium, preferably at elevated temperature of about from 40° C. to 90° C. The layer silicate is then added and dispersed, with stirring. The organophilic layer silicate so obtained is filtered off, washed with water and dried.
It is, of course, also possible to prepare the dispersion of the layer silicate as initial batch and then to add the solution or dispersion of the swelling agent.
Suitable dispersion media are water, methanol, ethanol, propanol, isopropanol, ethylene glycol, 1,4-butanediol, glycerol, dimethyl sulfoxide, N,N-dimethylformamide, acetic acid, formic acid, pyridine, aniline, phenol, nitrobenzene, acetonitrile, acetone, 2-butanone, chloroform, carbon disulfide, propylene carbonate, 2-methoxyethanol, diethyl ether, tetrachloromethane and n-hexane. Preferred dispersion media are methanol, ethanol and especially water.
The swelling agent brings about a widening of the interlayer spacing of the layer silicate, so that the layer silicate is able to take up monomers into the interlayer space. The subsequent polymerisation, polyaddition or polycondensation of the monomer or monomer mixture results in the formation of a composite material, a nanocomposite.
In the filler mixtures according to the invention it is preferable to use layer silicates that have been pre-treated with a polymerisable monomer prior to swelling. When the swelling is complete, the compositions are polymerised. Such monomers are, for example, acrylate monomers, methacrylate monomers, caprolactam, laurinlactam, aminoundecanoic acid, aminocaproic acid or aminododecanoic acid. The resin component or the hardener component of an epoxy resin system or the components of a polyurethane system can likewise be such monomers.
Suitable mineral fillers that can be used in the filler mixtures according to the invention are, for example, glass powder, glass beads, semi-metal and metal oxides, e

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