Thermoplastic fluoropolymers

Details Thermoplastic fluoropolymers Thermoplastic fluoropolymers

2001-02-13

2003-05-27

Nutter, Nathan M. (Department: 1711)

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

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S193000, C525S194000, C525S197000, C525S198000, C525S199000, C525S213000, C525S215000, C525S221000, C525S222000, C525S233000, C525S240000

Reexamination Certificate

active

06569946

ABSTRACT:

The present invention relates to thermoplastic fluoropolymers having improved mechanical properties in combination with low permeability to gases and water vapour, optionally with improved processability.
Specifically the present invention relates to thermoplastic fluoropolymers formed by copolymers based on chlorotrifluoroethylene (PCTFE) and by copolymers based on ethylene/chlorotrifluoroethylene (ECTFE) and/or ethylene/tetrafluoroethylene (ETFE).
The polymers of the invention are to be used to obtain pipes, sheets, molded articles and above all films to be used for example in the packaging industry and more specifically in the food and pharmaceutical industry.
It is known in the prior art that PCTFE is a fluorinated resin having a good chemical resistance characterized by very good properties of impermeability to gases and vapours, more specifically to oxygen, nitrogen and water vapour. These PCTFE copolymers have however poor mechanical properties, typical of a brittle material, i.e. high values of elastic modulus and yield stress combined with poor stress and strain at break.
As known the PCTFE polymers having a high molecular weight show better mechanical properties than those having a low viscosity. However the processing of fluoropolymers (e.g. PCTFE) having a very high viscosity is extremely difficult for the obtainment of pipes, sheets, films and molded articles.
The need was therefore felt to have available fluoropolymers having a very good impermeability to gases and vapours combined with improved mechanical properties, i.e. higher values of stress and strain at break, preferably having good processability.
The Applicant has surprisingly and unexpectedly found fluoropolymers having the above mentioned properties.
An object of the preent invention is a polymer composition comprising: (A) (co)polymers based on chlorotrifluoroethylene (PCTFE) and (B) (co)polymers based on ethylene/chlorotrifluoroethylene (ECTFE) and/or ethylene/tetrafluoroethylene (ETFE), wherein the E:CTFE (or TFE) ratio by moles is between 1:3 and 3:1. Preferably the amount of the (co)polymer based on chlorotrifluoroethylene (PCTFE) in the polymer composition is at least 5% by weight, more preferably at least 20% by weight, still more preferably at least 40% by weight.
The PCTFE (co)polymers according to the present invention contain at least 99% by moles of chlorotrifluoroethylene (CTFE) being the complement to 100 one or more fluorinated or non-fluorinated monomers. Among fluorinated monomers, (per)fluoropropylvinylether and (per)fluorodioxoles, as described in European patent applications EP 1.067,145 and EP 1,067,148, can for example be mentioned. Among non-fluorinated monomers, acrylic monomers as described in EP-A-964010 can for example be mentioned. Preferably PCTFE is the CTFE homopolymer (as described in European patent application EP 1,067,146). The PCTFE homopolymer having a Melt Flow Index (MFI) lower than 10.0 g/10′ measured at 265° C. and at 10 Kg load according to the ASTM D 1238-88 method is still more preferred.
The (co)polymers (B) ECTFE or ETFE according to the present invention are preferably formed by:
(a) from 35 to 65%, preferably from 45 to 55%, more preferably from 48 to 52% by moles of ethylene (E),
(b) from 65 to 35%, preferably from 55 to 45%, more preferably from 52 to 48% by moles of chlorotrifluoroethylene (CTFE) (for the ECTFE copolymers) or tetrafluoroethylene (TFE) (for the ETFE copolymers), and optionally
(c) from 0.1 to 30%, by moles, preferably 0.1-10, more preferably 0.1-5 based on the total amount of monomers (a) and (b), of one or more fluorinated or non-fluorinated monomers. Among fluorinated monomers we can for example mention (per)fluoroalkylvinylethers (perfluoropropylvinylether), (per)fluorodioxoles as described in U.S. Pat. No. 5,597,880), vinylidenefluoride (VDF). Among non-fluorinated monomers, the hydrogenated monomers having the general formula:
CH
2
═CH—(CH
2
)
n
—R
1
  (I)
can be mentioned, wherein R
1
═OR
2
, or —(O)
t
CO(O)
p
R
2
wherein t and p are integers equal to 0, 1 and R
2
is a hydrogenated radical C
1
-C
20
from 1 to 20 carbon atoms, of alkyl type, linear or branched when possible, or cycloalkyl, optionally containing heteroatoms and/or chlorine atoms, the heteroatoms preferably being O or N, R
2
optionally contains one or more functional groups, preferably selected from OH, COOH, epoxide, ester and ether, R
2
optionally contains double bonds, or R
2
is H, n is an integer in the range 0-10.
Preferably R
2
is of alkyl type from 1 to 10 carbon atoms containing functional groups of hydroxide type, n is an integer in the range 0-5.
The preferred comonomers (c) are for example selected from the following classes:
1) Acrylic monomers having the general formula:
CH
2
═CH—CO—O—R
2
wherein R
2
has the above mentioned meaning.
Ethylacrylate, n-butylacrylate, acrylic acid, hydroxyethylacrylate, hydroxypropylacrylate, (hydroxy) ethylhexylacrylate, etc. can for example be mentioned.
2) Vinylether monomers having the general formula:
CH
2
═CH—O—R
2
wherein R
2
has the above mentioned meaning.
Propylvinylether, cyclohexylvinylether, vinyl-4-hydroxybutylether, etc. can for example be mentioned.
3) Vinyl monomers of the carboxylic acid having the general formula:
CH
2
═CH—O—CO—R
2
wherein R
2
has the above mentioned meaning.
Vinyl-acetate, vinylpropionate, vinyl-2-ethylhexanoate, etc. can for example be mentioned.
4) Unsaturated carboxylic acids having the general formula:
CH
2
═CH—(CH
2
)
n
—COOH
wherein n has the above mentioned meaning. For example vinylacetic acid, etc.
The preferred (co)polymers of component (B) of the polymer composition of the invention are based on ethylene/chlorotrifluoroethylene (ECTFE) (co)polymers.
It has been found by the Applicant that to obtain also a good processability in combination with the other above mentioned properties of the polymer composition, the component (B) is an ECTFE having a Melt Flow Index (MFI) higher than 5 g/10′, preferably higher than 10 g/10′ measured at 275° C. and at 2.16 Kg load (according to the ASTM 3275-89 method).
Another object is a process for the preparation of the polymer composition according to the present invention based on PCTFE and ECTFE or ETFE. For example a preferable process is the radical synthesis of the ECTFE or ETFE (co)polymer (B) in the presence of the PCTFE (co)polymer (A), or the radical synthesis of the PCTFE (co) polymer (A) in the presence of the ECTFE or ETFE (co) polymer (B). These syntheses, (co)polymerizations, are carried out in the presence of radical initiators, in suspension in organic medium or in aqueous emulsion, at a temperature between −60° and 150° C., preferably −20° and 100° C., more preferably −10° and 50° C., and at a reaction pressure in the range 0.5-100 bar, preferably 5-40 bar.
Among the radical initiators that can be in particular used are:
(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 U.S. Pat. No. 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) dialkylperoxides of formula (R
H
—O)
2
, wherein RH is an alkyl C
1
-C
10
; diterbutylperoxide (DTBP) is particularly preferred;
(iii) inorganic peroxides soluble in water, such as ammonium or alkaline metal persulphates or perphosphates; sodium and potassium persulphates are particularly preferred;
(iv) dialkylperoxydicarbonates, wherein the alkyl has from 1 to 8 carbon atoms, such as for example di-n-propyl-peroxydicarbonate and di-isopropyl-peroxydicarbonate (see EP 526,216);
(v) organic or inorganic redox systems, such as ammonium persulphate/sodium sulphite, hydrogen peroxide/aminoiminomethansulphinic acid, terbutylhydroperoxide/methabisulphite (see U.S. Pat. No. 5,453,477).
(vi) photoinitiators activated by UV radiation such as inorganic

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