Polypropylene resin-based films and sheets

Details Polypropylene resin-based films and sheets Polypropylene resin-based films and sheets

2001-04-24

2003-04-08

Mulcahy, Peter D. (Department: 1713)

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

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S094000, C524S100000, C428S500000, C428S516000

Reexamination Certificate

active

06545069

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polypropylene-based films and sheets having good ultraviolet shieldability, especially to such films and sheets that the ultraviolet absorbent additive existing therein does not bleed out, while they are stored, to detract from the outward appearance of the films and sheets stored.
2. Description of the Related Art
Heretofore, vinyl chloride-based resins have been used for surface-protective films for construction materials, furniture, etc. Because of the environmental problems with them, however, safer materials alternative to them are being investigated.
Polypropylene-based resins could be taken into consideration as candidates for the alternative materials, but their weather resistance is poor. Therefore, in order to establish the formulation of additives to the resins, especially to those for printed films, sheets and dry lamination films as laminated with adhesive, various studies have been made relating to the weather resistance and the adhesiveness retentivity of the films and sheets of the resins (see JP-A-5-92514, JP-A-6-212033).
In the additive formulation, it has heretofore been said that additives that vaporize less on molding are better, for which the data of heating loss are regarded as important. Surprisingly, however, it has been noted that, while shaped products of films or sheets are stored for about 10 days or so after their production, the additives existing therein often bleed out to greatly detract from the outward appearance of the films and sheets stored. The problem is often serious, but the reason for it is not clear.
SUMMARY OF THE INVENTION
The object of the invention is to provide polypropylene-based films and sheets having good ultraviolet shieldability, especially to provide such films and sheets that the additive existing therein does not bleed out, while they are stored, to detract from the outward appearance of the films and sheets stored.
We, the present inventors have assiduously studied so as to attain the object, and, as a result, have found that the reason for the additive bleeding that may occur during storage of molded articles has close relation to the compatibility between the resin and the additive in the molding materials, and that, for solving the problem of such additive bleeding, specific compounds are effective.
Based on these findings, we have completed the present invention, which is as follows:
(1) A film or sheet formed from a composition comprising 100 parts by weight of a polypropylene-based resin and from 0.01 to 5 parts by weight of one or more compounds selected from the following (A) to (D)
(A) 2-(2-hydroxy-5-t-octylphenyl)benzotriazole,
(B) 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol,
(C) a compound of a formula (I):
 wherein R
1
to R
8
each represent a hydrogen atom, or an alkyl, aryl or alkoxy group having from 1 to 10 carbon atoms, and
(D) a compound of a formula (II):
 wherein R
1
to R
3
each represent a hydrogen atom, or an alkyl, aryl or alkoxy group having from 1 to 10 carbon atoms.
(2) The film or sheet of (1), wherein the compound of formula (I) is 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-n-octyloxyphenyl)-1,3,5-triazine.
(3) The film or sheet of (1), wherein the compound of formula (II) is 6-(2-benzotriazolyl)-4-t-octyl-6′-t-butyl-4′-methyl-2,2′-methylenebisphenol.
(4) A film or sheet formed from a composition comprising 100 parts by weight of a polypropylene-based resin and from 0.01 to 5 parts by weight of a combination of the following compounds (E) and (F):
(E) 2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-[(2H-benzotriazol-2-yl)phenol]], and
(F) 2-[2-hydroxy-3,5-bis(&agr;,&agr;′-dimethylbenzyl)phenyl]-2H-benzotriazole.
(5) The film or sheet of any one of (1) to (4), wherein the polypropylene-based resin has (i) a peak melting temperature (Tm) of 150° C. or above as measured through differential scanning calorimetry (DSC) and (ii) a tensile modulus of elasticity of from 200 to 700 MPa.
(6) The film or sheet of any one of (1) to (4), wherein the polypropylene-based resin comprises (a) from 20 to 100% by weight of a propylene homopolymer and/or copolymer with at most 4% by weight of other olefin units, which has (i) a peak melting temperature (Tm) of 150° C. or above as measured through differential scanning calorimetry (DSC), (ii) a tensile modulus of elasticity of from 200 to 700 MPa, (iii) 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) 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.
(7) The film or sheet of (1), wherein the compound of formula (I) is 2-[4,6-di(2,4-xylyl)-1,3,5-triazin-2-yl]-5-octyloxyphenol.
DETAILED DESCRIPTION OF THE INVENTION
The invention is described in detail hereinunder.
[1] Polypropylene-Based Resin
The polypropylene-based 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) falling between 0.1 and 200 g/10 min, especially preferably between 5 and 60 g/10 min.
As specific examples of the polypropylene-based resin, mentioned are propylene homopolymers and propylene-ethylene random or block copolymers, which may be mixed with random or block copolymers of propylene with one or more &agr;-olefins such as ethylene, butene-1, pentene-1, 4-methyl-pentene-1, hexene-1, octene-1 and the like. These may be further mixed with various types of synthetic rubber, for example, ethylene-propylene copolymer rubber, ethylene-propylene-non-conjugated diene copolymer rubber, polybutadiene, polyisoprene, polyethylene chloride, polypropylene chloride, styrene-ethylene-butadiene-styrene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SB block) and the like, to prepare resin compositions for use in the invention.
[1-1] Flexible Polypropylene-Based Resin
As the polypropylene-based resin for use in the invention, more preferred is a flexible polypropylene-based resin, which is mentioned below.
The preferred, flexible polypropylene-based resin preferably has (i) a peak melting temperature (Tm) of 150° C. or above as measured through differential scanning calorimetry (DSC) and (ii) a tensile modulus of elasticity of from 200 to 700 MPa. The flexible polypropylene-based resin of that type is not specifically defined, and it may be a propylene homopolymer, or a propylene copolymer with any other olefins, or a mixture of these. Concretely, it may be (a) a propylene homopolymer and/or a propylene copolymer containing at most 4% by weight of other olefin units; or a composition comprising a resin of the component (a), and (b) a propylene copolymer that contains from 10 to 80% by weight of non-propylene olefin units.
Especially preferably, the flexible polypropylene-based resin comprises (a) from 20 to 100% by weight of a propylene homopolymer and/or copolymer with at most 4% by weight of other olefin units, which has, in addition to the peak melting temperature (Tm) of (i) and the tensile modulus of elasticity of (ii) defined above, (iii) 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) 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.
The preferred properties (i) to (iv) of the flexible polypropylene-based resin for use in the invention are described below.
First, the resin must have (i) a peak melting temperature (Tm) of 150° C. or above as measured through differential scanning calorimetry (DSC). If Tm

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