Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-07-02
2003-04-08
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S101000, C524S128000, C524S129000, C524S153000
Reexamination Certificate
active
06545072
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polypropylene resin composition with improved weather resistance, and to moldings of films and sheets comprising the composition. Precisely, it relates to a polypropylene resin composition which colors little (in pale red) even when exposed to relatively high temperatures while stored indoors, and to moldings of films and sheets comprising the composition.
2. Description of the Related Art
Polypropylene resins are known to be degraded by various factors in the environment, such as sunlight, atmospheric temperature, oxygen in air, etc. Various weatherproofing agents are added to polypropylene resins so as to retard the degradation of the resins.
However, even though ordinary weatherproofing agents are added to polypropylene resins, the moldings of films and sheets comprising the resulting resin composition often color in pale red on their surfaces in a few months if they are exposed to relatively high temperatures while they are stored indoors.
The reason for such coloration is not clear. However, it is said that the coloration is not caused by the degradation of the polymer itself but is by the additives which color by themselves, and, in experiences, it is known that the degree of coloration depends on the type of the additives. At present, therefore, phenolic antioxidants which color in a lower degree are being used for polypropylene resins, in place of amine-based antioxidants which color in a higher degree.
However, even polypropylene resin compositions comprising such a phenolic antioxidant are still not on a satisfactory level.
With no effective measures for solving the problem, polypropylene resins have heretofore been used exclusively in the field in which the coloration could be negligible. Recently, however, films of polypropylene resins as degraded with organic peroxides are being put into practical use, and their coloration is now being a serious problem in the art.
Given that situation, the object of the invention is to provide moldings of films and sheets of polypropylene resins which color little even when stored indoors at relatively high temperatures, and to provide a polypropylene resin composition useful as the starting material for the moldings.
SUMMARY OF THE INVENTION
Having studied the problem noted above, we, the present inventors have found that a specific phenolic antioxidant is effective for not only ordinary polypropylene resins but also for polypropylene resins as degraded with organic peroxides and that the phenolic antioxidant is more effective when combined with a specific phosphorus-containing antioxidant. On the basis of these findings, we have completed the present invention. The invention is summarized as follows:
(1) A polypropylene resin composition comprising the following components:
(A) 100 parts by weight of a polypropylene resin,
(B) from 0.001 to 1 part by weight of a phenolic antioxidant of a formula (I) or (II):
wherein R
1
and R
2
each represent a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms, or an alkenyl group having from 3 to 18 carbon atoms; and X
1
represents an organic residue,
wherein R
3
and R
4
each represent a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms, or an alkenyl group having from 3 to 18 carbon atoms; and X
2
represents an organic residue, and
(C) from 0.05 to 5 parts by weight of a hindered amine-based light stabilizer.
(2) A polypropylene resin composition comprising the following components:
(A) 100 parts by weight of a polypropylene resin,
(B) from 0.001 to 1 part by weight of a mixed antioxidant that comprises (B1) a phenolic antioxidant of the following formula (I) or (II) and (B2) a phosphorus-containing antioxidant selected from tris(2,4-di-t-butylphenyl) phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene diphosphite, and [bis (2,4-di-tert-butyl-5-methylphenoxy)phosphino]biphenyl in a ratio by weight, (B1) to (B2), of from 19:1 to 1:19,
wherein R
1
and R
2
each represent a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms, or an alkenyl group having from 3 to 18 carbon atoms; and X
1
represents an organic residue,
wherein R
3
and R
4
each represent a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms, or an alkenyl group having from 3 to 18 carbon atoms; and X
2
represents an organic residue, and
(C) from 0.05 to 5 parts by weight of a hindered amine-based light stabilizer.
(3) The polypropylene resin composition of (1) or (2), wherein the phenolic antioxidant of formula (II) is 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate.
(4) The polypropylene resin composition of (1) or (2), wherein the phenolic antioxidant of formula (I) is 3,9-bis[1,1-dimethyl-2-[&bgr;-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetroxaspiro[5,5]undecane.
(5) A polypropylene resin composition comprising the following components:
(A) 100 parts by weight of a polypropylene resin,
(B) from 0.001 to 1 part by weight of bis(ethyl 3,5-di-t-butyl-4-hydroxybenzylphosphonato)calcium, and
(C) from 0.05 to 5 parts by weight of a hindered amine-based light stabilizer.
(6) A polypropylene resin composition comprising the following components:
(A) 100 parts by weight of a polypropylene resin,
(B) from 0.001 to 1 part by weight of a mixed antioxidant that comprises (B1) bis(ethyl 3,5-di-t-butyl-4-hydroxybenzylphosphonato)calcium and (B2) a phosphorus-containing antioxidant selected from tris(2,4-di-t-butylphenyl) phosphate, tetrakis(2,4-di-t-butylphenyl)-4,4 ′-biphenylene diphosphite, and [bis(2,4-di-tert-butyl-5-methylphenoxy) phosphino]biphenyl in a ratio by weight, (B1) to (B2), of being of from 19:1 to 1:19, and
(C) from 0.05 to 5 parts by weight of a hindered amine-based light stabilizer.
(7) The polypropylene resin composition of any one of (1) to (6), wherein the polypropylene resin satisfies the following requirements:
(i) it has a peak melting temperature (Tm) of 150° C. or above as measured through differential scanning calorimetry (DSC), and
(ii) it has a tensile modulus of from 200 to 700 MPa.
(8) The polypropylene resin composition of (7), wherein the polypropylene resin comprises the following components (a) and (b)
(a) from 20 to 100% by weight of a propylene homopolymer and/or a propylene copolymer containing at most 4% by weight of other olefin units, the homopolymer and the copolymer satisfying the following requirements:
(iii) they have a pentad fraction, rrrr/(1-mmmm)×100, as measured through isotopic carbon nuclear magnetic resonance spectrometry (
13
C-NMR) of from 20 to 60%, and
(iv) they have a melting enthalpy (&Dgr;H) as measured through differential scanning calorimetry (DSC) of from 10 to 100 J/g, and
(b) from 0 to 80% by weight of a propylene copolymer containing from 10 to 80% by weight of non-propylene olefin units.
(9) A film or sheet made by molding the polypropylene resin composition of any one of (1) to (8).
(10) A surface-protective film or sheet as produced by forming an adhesive layer and/or an ink layer on the film or sheet of (9).
DETAILED DESCRIPTION OF THE INVENTION
The invention is described in detail hereinunder.
[1-1] Polypropylene Resin:
The polypropylene resin for use in the invention preferably has a melt flow rate (MFR, as measured at 230° C. and under a load of 2.16 kg according to JIS-K7210) of from 0.1 to 200 g/10 min, more preferably from 5 to 60 g/10 min.
The polypropylene resin includes, for example, propylene homopolymers, propylene-ethylene random or block copolymers, as well as mixtures of those polymers with one or more other random or block copolymers of propylene with &agr;-olefins such as ethylene, butene-1, pentene-1,4-methyl-pentene-1, hexene-1, octene-1, etc.
Also usable herein are resin compositions comprising those polymers and various synthetic rubbers such as ethylene-propylene copolymer rubber, ethylene-propylene-non-conjugated diene copolymer rubber, polybutadiene, poly
Azuma Yutaka
Tamura Satoshi
Idemitsu Petrochemical Co. Ltd.
Sanders Kriellion A.
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