Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-04-17
2002-10-08
Mullis, Jeffrey (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...
C525S063000, C525S070000, C525S082000, C525S086000, C525S123000, C525S165000, C525S185000, C525S191000, C525S305000
Reexamination Certificate
active
06462129
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to thermoplastic resin compositions comprising a rigid dispersed phase. The thermoplastics, such as, for example, polyamides or PMMA, should, depending on their uses, exhibit improved thermal behaviour.
BACKGROUND OF THE INVENTION
The prior art has provided several solutions for enhancing the thermomechanical properties of thermoplastic matrices.
One of the solutions is to introduce, into a thermoplastic matrix, another polymer (amorphous or crystalline) with higher thermal behaviour (higher glass transition temperature than that of the thermoplastic) than the matrix itself. The main materials based on these systems were mainly developed with, in particular, alloys (i) of polyphenylene oxides (PPO), of polyphenylene sulphides (PPS), of polyetherimides (PEI) or of polyketones with (ii) thermoplastic polymers, such as polyamides, polystyrenes, or ABS or SAN copolymers. U.S. Pat. Nos. 4,681,915, 4,600,741 and EP 244 090 have disclosed polyamides comprising PPO. The disadvantage of this technique is that it requires mixing the two polymers in the molten state under specific conditions and in machines, such as extruders or mixers, while correctly choosing the screw profile and the temperatures of the different zones. Furthermore, the polymer which is added to the thermoplastic matrix in order to reinforce it often has a high melting temperature.
Patent Application JP 04-149273 A, published on May 22, 1992, discloses polyamide or polypropylene alloys with a thermosetting resin capable of crosslinking at the melting temperature of the polyamide or of the polypropylene. This thermosetting resin is an epoxy. An increase in the HDT is found, in comparison with the polyamide or the polypropylene not comprising this epoxy resin. The term “HDT” (heat deflection temperature) denotes the temperature of deformation under load (the load and deformation values being conventionally defined); it is measured according to NF Standard T 51-005. This crosslinking takes place by polycondensation reactions which cause, during extrusion, the formation of nodules having a very broad range of sizes, which damages the other mechanical properties of the polyamide-epoxy or polypropylene-epoxy alloy, such as the impact strength. Furthermore, the polycondensation reaction can last for more than 10 minutes, which is incompatible with a continuous process, for example in an extruder.
SUMMARY OF THE INVENTION
The invention consists in introducing, into a thermoplastic matrix (polystyrene, poly(meth)acrylics, polyamides, polyolefins, elastomers, fluorinated polymers, and the like), hard nodules with a morphology (beads) and with a size (of the order of or less than a micron) which are controlled to a degree sufficient to allow the thermal behaviours of these thermoplastic polymers to be enhanced while retaining, indeed even improving, the initial mechanical properties (stiffness, impact) of the base matrix. The hard nodules of controlled morphology and size are obtained by radical polymerization of (di-, tri- or multi-) unsaturated monomers (polymerizing by this route). The compositions of the invention are thermoplastic.
The compositions of the invention also have the advantage of being able to be manufactured in a very simple way. This process, which consists in forming crosslinked (or rigid) nodules in situ within a thermoplastic matrix, exhibits several advantages. The first is that the starting mixture (thermoplastic matrix+precursor of the rigid nodules) is homogeneous: which amounts to saying that the precursor is miscible with the thermoplastic matrix in a given temperature range. This also improves the processability, since, during this first stage, there is in fact a plasticization of the matrix which is reflected by milder extrusion conditions. The second is related to the fact that the crosslinking precursors are generally miscible with the thermoplastic matrix even at a high content; high levels of dispersed phase (rigid nodules) can be obtained at the end. The other advantages relate to the morphology of the rigid nodules, since the stability is guaranteed because of the crosslinked nature of the dispersed phase and the fineness and the isotropy of the dispersion, which are due to the in situ formation of the dispersed phase.
Another advantage of the present invention relates to the impact strength. Numerous thermoplastics have to be modified by incorporation of elastomers or of polymers with a lower Tg (glass transition temperature). For example, polyamide-6 or polyamide-12 can comprise from 5 to 20% by weight of EPR (ethylene-propylene rubber or EPM) or of ethylene-alkyl acrylate-maleic anhydride copolymer. However, this introduction, while improving the impact strength, leads to a fall in the Vicat point and/or in the HDT. The term “Vicat point” is understood to mean the temperature at which a cylindrical rod with a cross section of 1 mm
2
sinks 1 mm into the sample. It is measured according to NF Standard T 51-021. It has been discovered that the presence of rigid nodules in a thermoplastic matrix was compatible with the presence of other polymers, such as impact modifiers, in this thermoplastic matrix. Furthermore, this thermoplastic, comprising the rigid nodules and the impact modifier, had a Vicat point and/or an HDT at least equal to that of the thermoplastic comprising neither rigid nodules nor impact modifier and the impact strength was better than that of the thermoplastic comprising only the impact modifier.
One aspect of the present invention is, therefore, a thermoplastic composition comprising:
a matrix-forming thermoplastic polymer (M),
rigid nodules obtained by radical polymerization,
optionally an impact modifier (S).
The invention will now be described in detail.
Mention may be made, as examples of polymers (M), of polyolefins, polyamides, fluorinated polymers, saturated polyesters, polycarbonate, styrene resins, PMMA, thermoplastic polyurethanes (TPU), copolymers comprising polyamide blocks, copolymers comprising polyester blocks and polyether blocks, PVC, copolymers of ethylene and of vinyl alcohol (EVOH), and polyketones.
The term “polyamide” is understood to mean the condensation products:
of one or more amino acids, such as aminocaproic, 7-aminoheptanoic, 11-aminoundecanoic and 12-aminododecanoic acids, or of one or more lactams, such as caprolactam, oenantholactam and lauryllactam;
of one or more salts or mixtures of diamines, such as hexamethylenediamine, dodecamethylenediamine, meta-xylylenediamine, bis(p-aminocyclohexyl)methane and trimethylhexamethylenediamine, with diacids, such as isophthalic, terephthalic, adipic, azelaic, suberic, sebacic and dodecanedicarboxylic acids;
or of the mixtures of some of these monomers which results in copolyamides, for example PA-6/12 by condensation of caprolactam and lauryllactam.
The polymers comprising polyamide blocks and polyether blocks result from the copolycondensation of polyamide sequences comprising reactive ends with polyether sequences comprising reactive ends, such as, inter alia:
1) Polyamide sequences comprising diamine chain ends with polyoxyalkylene sequences comprising dicarboxyl chain ends.
2) Polyamide sequences comprising dicarboxyl chain ends with polyoxyalkylene sequences comprising diamine chain ends obtained by cyanoethylation and hydrogenation of aliphatic &agr;,&ohgr;-dihydroxylated polyoxyalkylene sequences, known as polyetherdiols.
3) Polyamide sequences comprising dicarboxyl chain ends with polyetherdiols, the products obtained being, in this specific case, polyetheresteramides.
The polyamide sequences comprising dicarboxyl chain ends originate, for example, from the condensation of &agr;,&ohgr;-aminocarboxylic acids, of lactams or of dicarboxylic acids and diamines in the presence of a chain-limiting dicarboxylic acid. The polyamide blocks are advantageously made of polyamide-12.
The number-average molar mass of the polyamide sequences is between 300 and 15,000 and preferably between 600 and 5000. The mass of the polyether sequences is between 100
Bertin Denis
Bouilloux Alain
Teze Laurent
Vivier Thierry
Atofina
Millen White Zelano & Branigan P.C.
Mullis Jeffrey
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