Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-07-07
2001-08-21
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S173000, C526S181000, C526S209000
Reexamination Certificate
active
06277936
ABSTRACT:
The present invention relates to thermoplastic perhalogenated polymers having improved mechanical properties.
Specifically the present invention relates to chlorotrifluoroethylene (CTFE) thermoplastic copolymers having improved mechanical properties, specifically stress at break, in comparison with the CTFE (PCTFE) homopolymer at low and high temperatures.
The polymers of the invention are used for obtaining pipes, sheets, films and molded articles having the above mentioned characteristics.
It is known in the prior art that PCTFE is a fluorinated resin having excellent chemical resistance with good impermeability properties to gases and vapours, more specifically to oxygen, nitrogen and water vapor. However, the PCTFE has mechanical properties typical of a brittle material, i.e. high values of elastic modulus and yield stress combined with low values of stress and strain at break at room temperature and at high temperature. As known the PCTFE polymers having a high molecular weight show better mechanical properties than those having a low molten polymer viscosity. However the use of PCTFE having a very high viscosity is difficult in the fluorinated thermoplastic processing for obtaining pipes, sheets, films and molded articles.
U.S. Pat. No. 5,145,925 describes a CTFE copolymer with a perfluoroalkylvinylether in the range 0.01 and 1% by moles; the preferred comonomer is perfluoropropylvinylether (FPVE). The exemplified FPVE/CTFE copolymers all show, both those having a low content (0.05% by moles) and a high content (1.1% by moles) of modifying agent, stresses at break lower than those of the homopolymer.
In U.S. Pat. No. 5,498,682 in the name of the Applicant tetrafluoroethylene (TFE) and fluorodioxoles in general, and in particular TFE copolymers with 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD), are described and exemplified.
In EP 720,992 in the name of the Applicant TFE copolymers with fluorodioxoles or FPVE are exemplified. In Tables 1 and 2 of such patent the mechanical properties (stresses at break), at low and high temperature, of the TFE copolymers with TTD are similar or lower than those of the TFE copolymers with FPVE.
Therefore, the need was felt to have available a thermoplastic PCTFE with the homopolymer intrinsic characteristics (chemical resistance and impermeability) combined with good mechanical properties leading to a non-brittle PCTFE at room and high temperatures. Therefore a PCTFE showing in particular improved stresses at break, combined with acceptable deformations, in comparison with those of the homopolymer and without substantially jeopardizing the yield sress.
The Applicant has unexpectedly and surprisingly found that by the use of particular comonomers as hereinunder specified it is possible to obtain a non-brittle CTFE thermoplastic copolymers at room and at high temperatures with an optimal combination of mechanical properties characterized by higher stresses at break than those of the homopolymer. Therefore an object of the present invention are chlorotrifluoroethylene (CTFE) thermoplastic copolymers, comprising:
(a) from 0.15 to 4% by moles, preferably from 0.2 to 3% by moles, still more preferably from 0.2 to 2% by moles of one or more fluorodioxoles having the general formula:
wherein:
X
1
and X
2
, equal to or different from each other, are selected among —F or —CF
3
;
Z is selected among —F. —H, —Cl;
Y is equal to OR
f
and R
f
is a perfluoroalkyl having from
1 to 5 carbon atoms, or Y=Z;
(b) CTFE, being the remaining part to 100% by moles.
Preferred fluorodioxoles of formula (I) are those wherein X
1
, X
2
and Z are —F; Y is equal to OR
f
and R
f
is selected from —CF
3
, —C
2
F
5
, or C
3
F
7
.
The fluorodioxole of formula (I) wherein X
1
, X
2
and Z are —F and Y is equal to OR
f
and R
f
is —CF
3
i.e. the fluorodioxole 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, hereinafter mentioned as TTD, is particularly preferred.
The preferred fluorodioxoles are described in USP 5,498,682 in the name of the Applicant, herein incorporated by reference.
The copolymers of the invention can optionally contain one or more perhalogenated monomers, preferably having at least three carbon atoms, provided that the thermoplastic properties are maintained and the above mentioned mechanical properties are not jeopardized. The total amount of the optional monomers is generally in the range 0.01-4% by moles, preferably the sum of the monomers different from CTFE is in the range 0.15-4% by moles.
As optional monomers, perfluoroalkylvinylethers, for example perfluoromethylvinylether, perfluoroethylvinylether, perfluoropropylvinylether, hexafluoropropene (HFP), etc., can be mentioned.
The copolymers of the invention are CTFE termoplastic copolymers having a viscosity defined by the Melt Flow Index (MFI) measurement at 265° C. and at 10 kg load according to the ASTM D 1238-88, not lower than 0.1 g/10′.
The copolymers of the invention can be prepared according to known methods, by copolymerization of the corresponding monomers, in suspension in organic medium or in water, or in aqueous emulsion, in the presence of a suitable radical initiator, at a temperature generally in the range −20° C. -150° C., preferably 0° C. -100° C., more preferably 10° C. -60° C. The reaction pressure is generally in the range 1.5-80 bar, preferably 3-37 bar, still more preferably 4-26 bar.
As initiator any compound able to generate active radicals in the polymerization system can be used. In particular the initiators, can be selected from:
(i) bis-acylperoxides of formula (R
f
—CO—O)
2
wherein R
f
is a (per)haloalkyl C
1
-C
10
(see for example EP 185,242 and USP 4,513,129), or a perfluoropolyoxyalkylene group (see for example EP 186,215 and U.S. Pat. No. 5,021,516); among them, bis-trichloroacetylperoxide and bis-dichlorofluoroacetylperoxide (see U.S. Pat. No. 5,569,728), are particularly preferred;
(ii) inorganic peroxides soluble in water, such as monovalent cation persulphates or perphosphates; sodium and potassium persulphates are particularly preferred;
(iii) organic or inorganic redox systems, such as potassium persulphate/sodium sulphite, terbutylhydroperoxide/methabisulphite (see U.S. Pat. No. 5,453,477).
In the case of the suspension copolymerization, the reaction medium is constituted by an organic phase, to which water is sometimes added in order to favour the heat dispersion which develops during the reaction. The organic phase can be constituted by the monomers themselves, without addition of solvents, or by the monomers dissolved in a suitable organic solvent. As organic solvents chlorofluoro-carbons, such as CCl
2
F
2
(CFC-12), CCl
3
F (CFC-11), CCl
2
FCClF
2
(CFC-113), CClF
2
CClF
2
(CFC-114), etc. are conventionally used. Alternative ozone-friendly solvents, containing only carbon, fluorine, hydrogen, and optionally oxygen, described in USP 5,182,342, can be used. In particular fluoropolyethers with at least one hydrogenated end group, preferably two, of the —CF
2
H, —CF
2
CF
2
H, —CF(CF
3
)H type, can be used.
The amount of radical initiator is the standard one for the copolymerization of fluorinated monomers, and is generally in the 0.003%-10% by weight range with respect to the total amount of (co)polymerized monomers.
In the case of emulsion polymerization the reaction is carried out in the presence of a suitable surfactant, see for example those described in U.S. Pat. No. 4,360,652 and U.S. Pat. No. 4,025,709. Fluorinated surfactants are generally selected among the products of general formula:
R
f
,−X
−
M
+
wherein R
f
, is a C
5
-C
14
(per)fluoroalkyl chain or a (per)fluoropolyoxyalkylene chain, X
−
is —COO
−
or —SO
3
−
, M
+
is selected from: H
+
and alkaline metal ions. Among those commonly used: sodium perfluoro-octanoate; (per)fluoropoly-oxyalkylenes ended with one or more carboxylic groups; sulphonic acid salts of formula R
f
,—C
2
H
4
SO
3
H, wherein R
f
, is a C
4
-C
10
perfluoroalkyl (see U.S. Pat. No. 4,025,709); etc.
Preferred surfactants are those wherein M
Abusleme Julio A.
Manzoni Claudia
Arent Fox Kintner & Plotkin & Kahn, PLLC
Auismont S.p.A.
Sanders Kriellion
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