Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-10-01
2002-04-09
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S081000, C524S401000, C524S544000, C524S546000, C524S570000, C524S558000, C524S562000
Reexamination Certificate
active
06369130
ABSTRACT:
The present invention relates to thermoplastic fluoropolymer compositions for the plenum wire insulation and cable jacketing applications, that show a high time to ignition, a low smoke and heat release when put in contact with a heat source as for example in the Cone Calorimeter (see the ASTM E1354 test).
More in particular the present invention relates to thermoplastic compositions of fluoropolymers of ethylene with tetrafluoroethylene (ETFE) and/or chlorotrifluoroethylene (ECTFE), modified with one or more hydrogenated monomers.
The copolymers of ethylene and a fluorinated monomer such as tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), or both, are known in the art. It is also known the possibility to modify them with fluorinated unsaturated monomers in an amount between 0.1 and 10% by moles. For example we mention the (per)fluoroalkylvinylethers in which the alkyl group has at least two carbon atoms, in particular the perfluoropropylvinylether (see U.S. Pat. No. 3,624,250). Other possible comonomers have the formula R′—CH═CH
2
, where R′ is a perfluoroalkyl or a perfluoroalkoxy-perfluoroalkyl (see EP 185,241, EP 185, 242)
The above mentioned ETFE and ECTFE copolymers non modified with fluoroolefins have poor affinity with hydrogenated substances, these being polymers or high molecular weight compounds (for example plasticizers).
In EP 728,776 a special fluoroolefin able to copolymerize with fluorinated olefins giving for example a modified ETFE, is disclosed. This polymer shows good affinity with hydrogenated polymers, in particular with aromatic polyesters.
In general the syntheses of special fluoroolefins are complex and therefore they are used as comonomers in ethylene fluoropolymers only when high performances are required. For example good chemical resistance combined with excellent mechanical properties at high temperatures (150°-200° C.).
The preparation of fluoropolymers blended with one or more plasticizers to make the fluoropolymers flexible and usable in the cable industry has a particular industrial interest. These polymers must be characterized by the absence of the whitening phenomenon when the cable is bended.
The whitening effect must be avoided because it visually represents the plastic deformation of the material, and due to this it cannot recover the initial state. The electrical properties required for this material are fully satisfied by the ECTFE which unfortunately has a high elastic modulus at room temperature, in general higher than 1500 MPa and therefore it is not flexible.
In addition the ECTFE has a stress-strain curve at room temperature characterized by a necking at yield that makes it sensitive to the whitening effect on the bended cable. The elastic modulus of ECTFE can be lowered by adding plasticizers, but in any case the material suffers of the whitening effect.
The Applicant, in order to overcome this problem, as disclosed in EP 866,079, has proposed the use of ETFE or ECTFE type fluoropolymers modified with hydrogenated monomers blended with plasticizers, having high flexibility and that do not show the whitening phenomenon.
However for safety reasons these flexible cables must show a high time to ignition, a low smoke and heat release when put in contact with a heat source, as for example in the Cone Calorimeter (see the ASTM E1354 test).
Unfortunately the presence of plasticizers increases the smoke and heat release.
The Applicant has found that when using fire retardants in the polymers compounded with plasticizers, it is possible to obtain flexible compositions having the following combination of properties:
good mechanical properties,
absence of the whitening effect,
decrease of smoke and heat release when tested in a Cone Calorimeter according to the ASTM E1354 test.
An object of the present invention is a composition comprising:
I) ETFE or ECTFE fluoropolymers modified with hydrogenated monomers;
II) one or more hydrogenated plasticizers;
III) one or more inorganic fire retardants;
IV) optionally other ingredients such as fillers, smoke retarders, intumescent agents, pigments, lubricants, organic fire retardants and thermal stabilizers.
More in particular the component I) of the compositions of the invention is a copolymer formed of:
(a) from 10 to 70%, preferably from 35 to 55%, by moles of ethylene,
(b) from 30 to 90%, preferably from 45 to 65%, by moles of a fluorinated monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, or mixtures thereof,
(c) from 0.1 to 30%, preferably from 1 to 15%, by moles of a hydrogenated monomer of formula:
CH
2
═CH—(CH
2
)
n
—R
1
(I)
where R
1
=—OR
2
, —(O)
t
CO(O)
p
R
2
wherein t and p are integers equal to 0 or 1 and R
2
is a hydrogenated radical from 1 to 20 carbon atoms, C
1
-C
20
, linear and/or branched alkyl radical, or cycloalkylic radical, or R
2
is H. The R
2
radical can optionally contain: heteroatoms preferably O, N; halogens preferably Cl; one or more functional groups, preferably selected from OH, COOH, epoxide, ester and ether; and double bonds. The above mentioned n is an integer in the range 0-10.
Preferably R
2
is an alkyl radical from 1 to 10 carbon atoms optionally containing one or more hydroxy functional groups, n is an integer in the range 0-5.
The preferred comonomers (c) are for example selected from the following classes:
1) Acrylic monomers of formula:
CH
2
═CH—CO—O—R
2
wherein R
2
has the aforesaid meaning.
For example ethylacrylate, n-butylacrylate, acrylic acid, hydroxyethylacrylate, hydroxypropylacrylate, (hydroxy)ethylhexylacrylate, etc., can be mentioned.
2) Vinylether monomers of formula:
CH
2
═CH—O—R
2
wherein R
2
has the aforesaid meaning.
For example propylvinylether, cyclohexylvinylether, vinyl-4-hydroxybutylether, etc., can be mentioned.
3) Vinyl monomers of the carboxylic acid of formula:
CH
2
═CH—O—CO—R
2
wherein R
2
has the aforesaid meaning.
For example vinyl-acetate, vinylpropionate, vinyl-2-ethylhexanoate, etc., can be mentioned.
4) Unsaturated carboxylic acid of formula:
CH
2
═CH—(CH
2
)
n
—COOH
wherein n has the aforesaid meaning. For instance vinylacetic acid, etc.
The most preferred monomer of formula (I) is n-butyl acrylate.
Components II) are hydrogenated plasticizers well known in the art and used in the hydrogenated (co)polymers, from 1 to 20% by weight, preferably from 5 to 10% by weight referred to the total weight of the composition.
Examples of plasticizers, not limitative for the present invention, are: 2-ethylhexyldiphenylphosphate, neopentyl glycoldibenzoate, tricresylphosphate, tetrabromophtalate ester, tri-n-hexyl-trimellitate, ethylene glycol monostearate, acetyltri-n-hexyl citrate; preferably acetyltri-n-butyl citrate (Citroflex® A4), tributyl trimellitate and tri-n-hexyltrimellitate.
Components III) are the inorganic fire retardants used in amounts from 0.2 to 35% by weight, preferably from 1 to 15% by weight, referred to the total weight of the composition.
The fire retardants are well known in the art of hydrogenated (co)polymers. We can mention for example: inorganic phosphates (for example, ammonium phosphate), metal oxides (for example, aluminum oxide, aluminum oxide trihydrate, antimony oxides, molybdenum oxide), tin oxalates, boron compounds (for example, borax, zinc borate, Firebrake® ZB), metal hydroxide (for example, magnesium hydroxide, or hydroxide mixture such as Zn(OH)
2
and Sn(OH)
4
e.g. ZnSn(OH)
6
).
Components IV) are used in amounts from 0.1 to 15% by weight, preferably from 0.5 to 5% by weight, referred to the total weight of the composition.
The optional ingredients are fillers (for example, polytetrafluoroethylene (PTFE), silicates, mica, metal oxide coated mica, mica blended with metal oxides), smoke retarders, lubricants, pigments, organic fire retardants (for example, halogenated compounds as chloroparaffins, brominated polyesters, brominated epoxy oligomers); intumescent agents and thermal stabilizers as, for example, Irganox® 1010.
Furthermore the Applicant has surprisingly found that the use of inorganic fire re
Abusleme Julio A.
Stanitis Gary
Zolotnitsky Mikhail
Arent Fox Kintner Plotkin & Kahn
Ausimont S.p.A.
Egwim Kelechi C.
Wu David W.
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