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
2002-02-20
2003-09-16
Seidleck, James J. (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...
C525S240000, C525S242000
Reexamination Certificate
active
06620892
ABSTRACT:
This invention relates to a process for the production of a controlled-rheology resin of a homopropylene or a propylene copolymer (block copolymer or statistical copolymer) or a polymer composition that comprises a propylene homopolymer or copolymer.
At present, this technique for controlling the rheology of these homopolymers and copolymers consists of a peroxide degradation of the latter, and it is used to develop fluid products in an efficient way without having a detrimental effect in terms of production flow rates by reducing the number of basic polymerization powders.
Thus, various products with fluidity indices that are higher than that of the base are produced from the same polymer or copolymer (generally viscous) by introducing an extrusion peroxide at the outlet of the polymerization reactor. The peroxide is broken down in the extruder to create radicals that themselves will attack the polymer chains by breaking them. In addition, the longest chains preferably will be broken, which involves a reduction of the molecular weights, whereby this reduction of molecular weights is accompanied by a reduction of the distribution of molecular weights ({overscore (M)}w/{overscore (M)}n).
It is also possible to melt a propylene homopolymer or copolymer powder or a polymer composition powder that comprises such a propylene homopolymer or copolymer and to incorporate in it a peroxide (repeat synthesis) for the purpose of extrusion followed by granulation.
The drawback of this process resides in the fact that these products have mechanical properties: strength and shock resistance, that are weaker than a product that is obtained directly after polymerization, extrusion and granulation or than a powder that was again subjected to extrusion and to granulation.
Documents that illustrate the prior art are: WO-A-96/12753; EP-A-570 812; U.S. Pat. No. 5,932,660; JP-A-07/138 320; U.S. Pat. No. 5,530,073; WO-A-96/06872; U.S. Pat. No. 5,705,568; U.S. Pat. No. 3,862,265; U.S. Pat. No. 5,945,492; CA-A-2 258 305; U.S. Pat. No. 4,900,781; DE-A-1 694 563; U.S. Pat. No. 4,672,088; and EP-A-0 853 090.
Seeking to solve this problem, the applicant company discovered, surprisingly enough, that by incorporating, instead of the peroxides of the prior art or in addition to the latter, stable free radicals into the resins that are to be modified, placed in a viscous state (in a molten zone of an extruder or in solvent medium), the desired resins that therefore have a higher fluidity index and better mechanical properties are obtained with the following additional advantages:
Incorporation of stable radicals that are always present after extrusion provides a better thermal stability to the products that are obtained, improves the UV resistance of the latter and reduces their tendency to depolymerize; and
in the case where a peroxide is also incorporated into the resin, the latter has a more stable viscosity over time because of comprising a reservoir of heat-reacting counter-radicals. Actually, a polypropylene-type resin that is degraded by a peroxide may contain peroxide radicals. The presence of this peroxide runs the risk of modifying the viscosity of the resin when the latter is transformed (when hot), whereby during this transformation, the peroxide again plays its resin-degrading role to reduce its viscosity. Now, during storage, the peroxide has the tendency to migrate and therefore to leave the resin, and, during the storage period, the resin may therefore have a different behavior and show a viscosity that is different during or after transformation, depending on whether there is a little or a lot of peroxide. According to the process of this invention, however, the resin contains a reservoir with stable free radicals that have the tendency to neutralize the peroxide as soon as the latter is broken down, thus reducing its degradation effects, regardless of whether its concentration is high or low. The storage period thus no longer has as much effect on the viscosity of the transformed resin.
This invention relates to a process for the production of a controlled-rheology resin of a propylene homopolymer or copolymer or a composition that comprises a propylene homopolymer or copolymer, characterized by the fact that at least one stable free radical is incorporated into said resin in the viscous state in an amount that can increase the fluidity index of said resin, since a solid product that has an increased fluidity index is formed. This phrase means that the stable free radical does not prevent the fluidity index of the resin from increasing during the process of the invention, even if by itself, the stable free radical may sometimes tend to limit the extent of this increase. In any case, the process according to the invention leads to a resin with a fluidity index that is increased relative to the starting resin under the action of cuts of polymer chains, whereby said cuts take place under the action of heat and/or under the action of polymerization triggers. A polymerization trigger is defined as a free radical initiator that can bring about the cuts of polymer chains (no polymerization takes place during the process of the invention).
This invention therefore has as its object a process for the production of a controlled-rheology resin of a propylene homopolymer or copolymer or a composition that comprises a propylene homopolymer or copolymer in the absence of a functional monomer, whereby said process brings about an increase in the fluidity index of the resin by cuts of chains, characterized by the fact that at least one stable free radical is incorporated into said resin in the viscous state, since a solid product that has an increased fluidity index is formed.
The stable free radical or radicals is or are selected in particular from among the nitroxide radicals, i.e. that contain the ═N—O′ group, in particular from among those of formulas (Ia), (Ib) or (Ic):
in which:
R
1
to R
3
, R
5
to R
8
, and R
13
and R
14
each represent independently:
(a) a hydrogen atom;
(b) a halogen atom, such as chlorine, bromine, or iodine;
(c) a hydrocarbon-containing, saturated or unsaturated, linear, branched or monocyclic or polycyclic group that can be substituted by at least one halogen;
(d) an ester group —COOR
15
or an alkoxyl group —OR
16
, R
15
and R
16
that represent a hydrocarbon-containing group as defined in item (c) above;
(e) a group of formula
where R
17
and R
18
each independently represent a linear, branched or cyclic alkyl radical, a perfluoroalkyl radical, aryl radical, aralkyl, radical, alkaryl radical, alkoxyl radical, aryloxyl radical, aralkyloxyl radical, alkaryloxy radical, whereby these radicals can comprise 1 to 20 carbon atoms; or halogen such as chlorine, bromine, fluorine or iodine;
(f) a polymer chain that can be, for example, a poly(alkyl methacrylate) chain or a poly(alkyl acrylate) chain, such as poly(methyl methacrylate), polydiene such as polybutadiene, polyolefins such as polyethylene or polybutadiene, but that is preferably a polystyrene chain;
R
4
has the meanings that are defined in items (a), (b), (c), (d) and (f) above, and in the case where it is connected to the nitrogen atom by a carbon atom, the latter can carry at least one group as defined in item (e) above;
R
9
to R
12
, identical or different, have the meanings that are defined in items (a) to (f) above and can also represent a hydroxide group or an acid group, such as —COOH, —PO(OH)
2
or —SO
3
H;
R
3
and R
4
can be connected to one another—in the case where R
4
represents a radical —CR′
1
R′
2
R′
3
(whereby R′
1
to R′
3
equally have the meanings of R
1
to R
3
); and R
3
can be connected to R′
3
—to form a heterocycle that
comprises the nitrogen atom of
whereby said
heterocycle can be saturated or unsaturated, can comprise in the cycle at least one other heteroatom and/or at least one group
and can also comprise a cycle that is attached, saturated or unsaturated;
two from among R
1
to R
3
, R
5
and R
6
, R
7
and R
8
, R
9
and R
10
, R
11
Bertin Denis
Robert Patrice
Asinovsky Olga
Atofina
Millen White Zelano & Branigan P.C.
Seidleck James J.
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