Polypropylene molding material

Details Polypropylene molding material Polypropylene molding material

1999-08-23

2001-05-08

Lipman, Bernard (Department: 1713)

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

Synthetic resins

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

C525S387000

Reexamination Certificate

active

06228951

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a polypropylene molding material which emits a reduced amount of fumes on molding and has excellent high-speed spinnability.
BACKGROUND OF THE INVENTION
It is known that polypropylene can be used in melt spinning such as spun bonding. Polypropylene for this use is usually subjected to chemical treatment with a considerable amount of a peroxide in an additive stage following polymerization, which is called a controlled rheology treatment (hereinafter abbreviated as CR treatment). Without the CR treatment, polypropylene is unsuited to high-speed spinning because the spun filament would break even at a low take-up speed.
However, the CR treatment incurs an increase of cost of production, and the reaction between the polymer and the peroxide involves by-production of low-molecular weight fragments and color change of the polymer. In particular, the low-molecular fragments not only cause fuming on spinning, which is unfavorable to the production process, but stick to the molding machine to seriously reduce the productivity.
Polypropylene prepared by polymerization in the presence of a metallocene catalyst is known usable in high-speed spinning the CR treatment with a peroxide. However, polymerization of propylene using a metallocene catalyst tends to be accompanied with production of trace amounts of high-molecular components which also cause filament failure in high-speed spinning.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polypropylene molding material consisting mainly of a crystalline polypropylene resin which hardly gives off fumes during molding, such as spinning, and exhibits excellent high-speed spinnability.
As a result of extensive investigations, the inventors have found that the object of the invention is accomplished by a polypropylene molding material having specific physical properties which is obtained by allowing a crystalline polypropylene resin having a given composition distribution, such as one obtained by polymerization using a metallocene catalyst, to react with a peroxide. The present invention has been completed based on this finding.
The invention provides a polypropylene molding material which is obtained by the reaction of a crystalline polypropylene resin and a peroxide and has the following physical properties (A) to (D):
(A) A melt flow rate (hereinafter abbreviated as MFR) of 20 to 100 (g/10 min) and a weight average molecular weight to number average molecular weight ratio of 1.5 to 3.5 (hereinafter abbreviated as Mw/Mn) as measured by gel-permeation chromatography (hereinafter abbreviated as GPC).
(B) A content of hydrocarbons having 20 to 70 carbon atoms (hereinafter referred to as a C
20-70
hydrocarbon content) of 0.05% by weight or less.
(C) A mean elution temperature (T
50
) of 75 to 120° C. and a degree of variation of elution (&sgr;) of 9 or smaller.
(D) A Q2/Q1 ratio of 0.75 to 0.95, wherein Q1 is an Mw/Mn of the crystalline polypropylene resin as measured by GPC, and Q2 is an Mw/Mn of the propylene molding material as measured by GPC.
In a preferred embodiment of the invention, the reaction is carried out by adding 0.005 to 0.05% by weight, based on the crystalline polypropylene resin, of the peroxide to the crystalline polypropylene resin.
In a still preferred embodiment of the invention, the reaction is carried out by melt-kneading the mixture of the crystalline polypropylene resin and the peroxide at 180 to 280° C.
In another preferred embodiment of the invention, the crystalline polypropylene resin is a resin obtained by using a catalyst system comprising (A) a metallocene compound represented by formula (I):
Q
1
(C
5
H
4−a
R
1
a
)(C
5
H
4−b
R
2
b
)MeX
1
Y
1
  (I)
wherein (C
5
H
4−a
R
1
a
) and (C
5
H
4−b
R
2
b
) are each a conjugated 5-membered cyclic ligand; Q
1
represents a linking group bridging the two conjugated 5-membered cyclic ligands which is selected from a divalent hydrocarbon group having 1 to 20 carbon atoms, a silylene group having a hydrocarbon group having 1 to 20 carbon atoms, and a germylene group having a hydrocarbon group having 1 to 20 carbon atoms; Me represents zirconium or hafnium; X
1
and Y
1
each represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylamido group having 1 to 20 carbon atoms, a trifluoromethanesulfonic acid group, a phosphorus-containing hydrocarbon group having 1 to 20 carbon atoms or a silicon-containing hydrocarbon group having 1 to 20 carbon atoms; R
1
and R
2
each represent a hydrocarbon group having 1 to 30 carbon atoms, a halogen atom, an alkoxy group, a silicon-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, a nitrogen-containing hydrocarbon group or a boron-containing hydrocarbon group; a and b each represent an integer of 0 to 4; where a or b is 2 or more, two adjacent R
1
's or R
2
's may be taken together to form a ring; and the two 5-membered cyclic ligands are asymmetrical with respect to a plane containing Me when viewed as to the relative positions thereof through the linking group Q
1
,
(B) an ion exchangeable layer compound except a silicate or an inorganic silicate, and
(C) an organoaluminum compound.
The invention also provides a polypropylene molding material for spinning.
According to the invention, since trace amounts of high-molecular components, which cause filament breaking, in a polypropylene resin is decomposed by the chemical treatment with a peroxide (CR treatment), a polypropylene molding material having excellent high-speed spinnability can be obtained from a polypropylene resin having specific physical properties, such as one prepared by using a metallocene catalyst. The amount of the peroxide to be used is reduced to an minimum consistent with capability of decomposing the trace amounts of high-molecular components. It follows that by-production of low-molecular fragments, for example, components having about 20 to 70 carbon atoms, by the reaction between the polymer and the peroxide can be minimized, and fuming on molding is reduced thereby.
DETAILED DESCRIPTION OF THE INVENTION
The polypropylene molding material according to the invention is obtained by allowing a peroxide to react on a crystalline polypropylene resin.
The crystalline polypropylene resin, a base resin of the molding material of the invention, includes a propylene homopolymer and a propylene copolymer, such as a propylene random copolymer.
The propylene copolymer preferably has a propylene unit content of at least 95 mol % (i.e., less than 5 mol % of comonomers), which varies depending on the kind of the comonomer. Examples of useful comonomers include ethylene and &agr;-olefins having 4 to 20 carbon atoms, such as 1-butene, 1-pentene, 3-methylbutene-1,1-hexene, 4-methylpentene-1, 1-heptene, 1-octene, 1-nonene, 1-decene, and 1-hexadecene. The propylene and comonomer unit contents as above referred to can be determined by
13
C-NMR analysis with FT-NMR manufactured by Nihon Denshi (270 MHz).
The crystalline polypropylene resin preferably has such an Mw/Mn (=Q1) of 2 to 4, as measured by GPC.
For securing satisfactory high-speed spinnability, the crystalline polypropylene resin preferably has an MFR of 30 to 70 g/10 min, particularly 30 to 60 g/10 min.
While the process for preparing the crystalline polypropylene resin is not particularly limited, it is preferable to use the one obtained by polymerization in the presence of a metallocene catalyst system comprised of the following components A to C in order to obtain a molding material satisfying the conditions (A) to (D) hereinafter described in detail. Catalyst component A:
Component A is a metallocene compound represented by formula (I):
Q
1
(C
5
H
4−a
R
1
a
)(C
5
H
4−b
R
2
b
)MeX
1
Y
1
  (I)
wherein (C
5
H
4−a
R
1
a
) and (C
5
H
4−b
R
2
b
) are each a conjugated 5-membered cyclic ligand; Q
1
represents a linking group bridging the two conjugated 5-membered c

Affiliated with

Also associated with

Rating

Polypropylene molding material does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Polypropylene molding material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polypropylene molding material will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2567668