JP3092949B2 - Radiation-resistant polypropylene and composition using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene which is hardly reduced in molecular weight and physical properties when irradiated with radiation and a resin composition containing the same.

[0002]

2. Description of the Related Art Polypropylene is used for food and medical purposes because it is inexpensive and has a relatively good balance of physical properties. In these applications, sterilization is required, and irradiation is performed for that purpose. Sterilization by radiation is simple, but the molecular weight of the polymer is reduced and the physical properties are reduced.

[0003]

As applications requiring sterilization are increasing, there is a demand for the development of a polypropylene having an excellent balance of physical properties, in which physical properties are relatively unlikely to be reduced by irradiation with radiation.

[0004]

Means for Solving the Problems The present inventors have solved the above-mentioned problems and have intensively searched for polypropylene having excellent radiation resistance and excellent physical property balance, and completed the present invention.

That is, the present invention relates to a copolymer of propylene and ethylene, wherein the ethylene content is 0.01 to 50 mol%.
When looking at the six monomer units in the polymer chain, radiation- resistant propylene and ethylene having a continuous racemic fraction of two or three propylene of at least 0.5 or more
Is a copolymer of The present invention also relates to a composition containing the copolymer, which is a copolymer of propylene and ethylene and has an intrinsic viscosity of 0.10 as measured in a tetralin solution at 135 ° C.
As described above, when the ethylene content is 0.01 to 50 mol% and six monomer units in the polymer chain are viewed, two or three
Radiation- resistant propylene / ethylene copolymer composition comprising a propylene / ethylene copolymer and an antioxidant wherein the continuous racemic fraction of the propylene is at least 0.5 or more. is there.

The polymer or composition of the present invention will be described in detail by describing a method for producing the polymer or composition.

[0007] As a catalyst suitable for producing the copolymer of the present invention, when the homopolymerization of propylene is carried out, the obtained polymer has a highly syndiotactic structure, and further has a copolymerizability with ethylene. Are good. Specifically, J. Am. Chem. Soc., 1988, 110, 6255-625
Examples of the catalyst used for producing highly syndiotactic polypropylene as shown in Fig. 6 can be exemplified.However, even if the catalyst has a different structure, the polypropylene syndiotactic polymer obtained by homopolymerization of propylene can be used. It can be used as long as it can produce polypropylene having a tic pentad fraction of 0.7 or more,
Catalysts comprising two different bonded transition metal compounds are available.

The transition metal compounds having an asymmetric ligand include isopropyl (cyclopentadienyl-1-fluorenyl) hafnium dichloride described in the above-mentioned literature.
Alternatively, isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride and the like are exemplified. In the polymerization, the following structural formula (1) or (2)
Is a hydrocarbon residue having 1 to 3 carbon atoms, and n is an integer of 1 to 50. )
The aluminoxane represented by is used in combination.

[0009]

Embedded image

[0010]

Embedded image The aluminoxane is preferably a methylaluminoxane in which R is a methyl group and n is 5 or more, preferably 10 or more. Also, alkyl aluminum and Lewis acid,
A Lewis base or the like can be used in combination. The polymerization is carried out in the coexistence of ethylene and propylene, and the monomer composition is preferably controlled so that the ethylene content in the polymer is 0.01 to 50 mol%.

The polymerization conditions are not particularly limited, and a solvent polymerization method using an inert medium, a bulk polymerization method substantially free of an inert medium, and a gas phase polymerization method can be used.

The polymerization is generally carried out at a polymerization temperature of -100 to 200 ° C. and a polymerization pressure of normal pressure to 100 kg / cm ² . Preferably, it is -100 to 100 ° C and normal pressure to 50 kg / cm ² .

The preferred molecular weight is generally about 0.1 to 3.0 as the intrinsic viscosity measured with a tetralin solution at 135 ° C.

What is important in the present invention is that the stereoregularity of the copolymer is desired, such that when looking at the six monomer units in the polymer chain, two or three consecutive propylene units are formed. The racemic fraction is at least 0.5 or more, more preferably 0.7 or more. This three-dimensional structure distinguishes it from conventional polypropylene, and this structure can be known by ¹³ C-NMR. For example, details are given in Polymer, 1988, vol 292208, reported by Asakura et al. That is, in the ¹³ C-NMR based on tetramethylsilane measured in o-dichlorobenzene solution, the intensity of the propylene racemic diad and triad peaks observed at about 38.8 ppm is about 37.4 to 39.5 pp.
m, a propylene dyad in the peak attributed to the methylene group of the ethylene-propylene unit,
It is expressed as a fraction of the monomer unit assigned to the triad with respect to the total peak intensity of the hexad.

The polymer of the present invention is stable to irradiation with radiation, but can be made into a radiation-resistant composition by further adding a phosphorus-based or amine-based antioxidant. It is possible to more effectively avoid deterioration during molding or deterioration during sterilization.

Many specific examples of the above-mentioned antioxidants are already known. Specifically, trialkyl phosphites (isodecyl, tridecyl, etc.) and phenyldialkyl phosphites (phosphorous antioxidants, etc.) Isodecyl, isooctyl, etc.), diphenylalkyl phosphite (isodecyl, isooctyl, isodecyl, etc.),
Triphenyl phosphite, Substituted triphenyl phosphite, Phosphalas acid (1,1-biphenyl-4,4'-diylbistetrakis (2,4-bis (1,1'-dimethylethyl)
Phenyl) ester, 3,5-di-t-butyl-4-hydroxybenzylphosphate-diethyl ester, 9,10-dihydro-9-oxa-10-phosphopennanthrene-10-oxide,
Sodium bis (4-t-butylphenyl) phosphate, sodium-2,2'-methylene-bis (4,6-di-t-butylphenyl) -phosphate, 1,3-bis (diphenoxyphosphonyloxy)- Benzene and the like can be exemplified, and as an amine antioxidant, alkyl-substituted diphenylamine, diallyl-p-phenylenediamine or a substituted product thereof
-N-substituted phenylenediamine, 6-ethoxy 2,2'-4-
Examples thereof include substituted quinolines such as trimethyl-1,2-dihydroquinoline, and substituted piperidines such as 2,2 ′, 6,6′-tetraalkylpiperidine.

As for the molecular weight distribution of the copolymer of the present invention measured by gel permeation chromatography, the narrower the molecular weight distribution, the less likely it is to be decomposed by irradiation with radiation. , MW / M
(Abbreviated as N) is 1.5 to 5, more preferably about 1.5 to 4. The MW / MN is measured, for example, using a commercially available column using 1,2,4-trichlorobenzene at 135 ° C. as a solvent.

In the present invention, the above copolymer may be used as a base, and if necessary, other polyolefins such as isotactic polypropylene may be mixed to form a composition. About the same amount of isotactic polypropylene as copolymer or copolymer with small amount of other olefin, ethylene and carbon number 3
The above-mentioned copolymers with α-olefins and the like can be mixed and used.

There is no particular limitation on the method of using the composition, and the composition is molded and used by a usual method.

[0020]

The present invention will be further described with reference to examples.

Example 1 Isopropylcyclopentadiene synthesized according to a conventional method
Lithium enyl-1-fluorene is converted to zirconium tetrachloride.
Isopropyl obtained by reacting with
(Lopentadienyl-1-fluorenyl) zirconium dik
0.2 g of Lolide and methylaluminoki manufactured by Toso-Akzo
Using 30g of sun (degree of polymerization 16.1), 200 liters of internal volume
Introduce propylene in an autoclave and polymerize at 20 ° C
3kg / cm ^Two-G and introducing ethylene at 150g / hr
Polymerization pressure is 3kg / cm at 20 ℃^TwoPropylene so that -G
The polymerization was continued for 2 hours while adding methanol and methanol.
Demineralize with methyl toacetate, wash with aqueous hydrochloric acid, then
Filtration yielded 6.1 kg of the copolymer.

According to ¹³ C-NMR, this polypropylene contained 3.1 mol% of ethylene, and the racemic diad and triad fraction observed at about 38.8 ppm was 0.9. The intrinsic viscosity (hereinafter abbreviated as η) measured at 135 ° C. in tetralin solution was 1.30, and the MW / MN measured with 1,2,4-trichlorobenzene was 2.2.

Γ-rays are applied to this polypropylene at 30 ° C. at 5 Mrad /
Irradiation at 3 Mrad at hr showed that η was 1.28 and there was almost no decrease in molecular weight. 2m thick at 200 ° C using this powder
m sheet, and γ-rays were similarly irradiated at 3 Mrad, and the following physical properties before and after the measurement were measured. Flexural rigidity: kg / cm ² ASTM D-747 (23 ° C) Tensile yield strength: kg / cm ² ASTM D-638 (23 ° C) Elongation at break:% ASTM D-638 (23 ° C) Izod (notched ) Impact strength: kg ・ cm ／ cmASTM D-6
38 (23 ° C, -10 ° C) Flexural rigidity before irradiation, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C)
Were 5500, 230, 720, 20, and 3.6, respectively, and were 5600, 235, 710, 22, and 3.6, respectively, after irradiation, and were unchanged.

COMPARATIVE EXAMPLE 1 The racemic dyad and triad fraction observed at an ethylene content of 4.2 wt% and 38.8 ppm by ¹³ C-NMR was 0.05.
The procedure was the same as in Example 1 except that a commercially available isotactic propylene-ethylene copolymer having η of 1.50 and MW / MN of 5.8 was used. The η after irradiation with no stabilizer added was 1.18, and the physical properties before irradiation were the flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength.
(23 ° C, -10 ° C) are 5800, 250, 570, 3.5
, 1.5 and 5700, 240, 110,
2.8 and 1.0.

Tris is added to polypropylene as a stabilizer.
0.1 wt% of (2,4-di-t-butylphenyl) phosphite,
Dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2 ', 6,6'-tetramethylpiperidine polycondensate 0.01wt
%, 5700, 245, 180, 2.9
, 1.2.

[0026]

The copolymer and the composition of the present invention are excellent in radiation resistance and extremely excellent in the balance of physical properties.
It is extremely valuable industrially.

Claims (2)

(57) [Claims] 1. A copolymer of propylene and ethylene, having an ethylene content of 0.01 to 50% by mole, and having 6 or more monomer units in a polymer chain. A radiation-resistant copolymer of propylene and ethylene having a racemic fraction of at least 0.5. 2. A copolymer of propylene and ethylene, having an intrinsic viscosity of 0.10 as measured with a tetralin solution at 135 ° C.
As described above, when the ethylene content is 0.01 to 50 mol% and six monomer units in the polymer chain are viewed, two or three
A radiation- resistant propylene / ethylene copolymer composition comprising a propylene / ethylene copolymer having a continuous racemic fraction of propylene of at least 0.5 or more and an antioxidant .