Stretched film of thermoplastic resin

Details Stretched film of thermoplastic resin Stretched film of thermoplastic resin

2000-12-29

2003-03-18

Loney, Donald J. (Department: 1772)

Stock material or miscellaneous articles

Structurally defined web or sheet

Continuous and nonuniform or irregular surface on layer or...

C428S172000, C428S212000, C428S312200, C428S316600, C264S210100, C264S241000, C264S288800, C264S291000, C156S229000, C052S311100

Reexamination Certificate

active

06534150

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a stretched film of a thermoplastic resin having a high surface hardness, excellent processability in embossing and desirable ink adhesiveness, and to a method for producing such film. The stretched film of a thermoplastic resin of the present invention can effectively be used in a variety of applications including building decorative materials having micropores.
RELATED ART
Vinyl chloride-base resin, such as vinyl chloride resin or vinyl chloride-vinyl acetate copolymer resin, is known as a thermoplastic resin excellent in applicability to printing or processability in embossing. The vinyl chloride-base resin has a diversity of industrial uses by virtue of its simplicity in controlling the hardness with a plasticizer and its inexpensiveness. Vinyl chloride resin is also a major component of a resin film which is widely used as building decorative materials.
A problem, however, resides in the vinyl chloride resin in that it may generate hazardous gases such as chlorine gas and hydrogen chloride gas in the case of the waste treatment or fire disaster, and is thus causative of deterioration of incinerators and of environmental pollution. Another problem resides in that bleeding of the plasticizer contained therein may cause indoor pollution, so that limiting the use of vinyl chloride-base resin is becoming a worldwide trend.
Solutions for these problems can be found in developmental activities for materials using polyolefin-base resin in place of vinyl chloride-base resin.
The polyolefin-base resin is, however, disadvantageous in that having crystallinity. When the polyolefin-base resin is used in a form of a stretched film, the processability in embossing will be degraded as compared with that of vinyl chloride-base film due to the molecular orientation induced by the stretching. The poor ink adhesiveness also raises problems in printing picture or pattern by gravure printing, silk screen printing, offset printing and water-base flexographic printing, which is known to result in misalignment of picture or pattern in multi-color printing.
A known general solution for improving the ink adhesiveness relates to, for example, anchor treatment of the film surface, whereas it is not feasible since it tends to push up the production cost. On the other hand, multi-color printing on a polyolefin-base unstretched film has to be carried out under a low tension since the film has only a limited tensile strength in the printing direction, which tends to result in snaking of the film. Raising the tension to prevent such snaking is now likely to cause dimensional change due to elongation, which may result in misalignment of a printed pattern in a first color and that in a second or successive color, to thereby ruin fine printing.
It is therefore an object of the present invention to overcome the foregoing problems in the conventional technology.
That is, the present invention is to provide a stretched film of a thermoplastic resin having a high surface hardness, excellent processability in embossing and desirable ink adhesiveness. It is another object of the present invention is to provide an inexpensive stretched film of a thermoplastic resin allowing fine printing without causing misalignment of patterns in multi-color printing. It is further an object of the present invention is to provide a stretched film of a thermoplastic resin being not causative of environmental pollution nor degradation of incinerators at the time of the waste treatment.
It is still another object of the present invention is to provide a building decorative material having such properties and a method for producing the stretched film of a thermoplastic resin.
DISCLOSURE OF THE INVENTION
The present inventors found out after the extensive studies to accomplish the foregoing objects that desirable effects can be obtained by using a stretched film of a thermoplastic resin comprising a plurality of stretched films individually containing a fine powder differ in the average particle size, and having a porosity of 5 to 60%, which led us to propose the present invention.
That is, the present invention relates to a stretched film of a thermoplastic resin comprising a stretched film base layer (A) containing 40 to 85 wt % of a thermoplastic resin and 60 to 15 wt % of an inorganic or organic fine powder; and a stretched film surface layer(B), being provided at least on one surface of said stretched film base layer (A), containing 30 to 90 wt % of a thermoplastic resin and 70 to 10 wt % of inorganic or organic fine powder having an average particle size smaller than that of the inorganic or organic fine powder contained in the stretched film base layer (A), and has a porosity as expressed by the formula (1) below
ρ
0
-
ρ
1
ρ
0
×
100
(
1
)
(where &rgr;
0
is the true density of the stretched film of a thermoplastic resin, and &rgr;
1
is the density of the stretched film of a thermoplastic resin) of 5 to 60%.
In a preferred embodiment of the present invention, the inorganic or organic fine powder contained in the stretched film base layer (A) has an average particle size of 0.6 to 3 &mgr;m, and the inorganic or organic fine powder contained in the stretched film surface layer (B) has an average particle size of 0.1 to 2 &mgr;m. On the surface of the stretched film base layer (A) opposite to the stretched film surface layer (B), a back layer (C) containing 30 to 70 wt % of a thermoplastic resin and 70 to 30 wt % of an inorganic or organic fine powder may further be provided. The inorganic or organic fine powder contained in the back layer (C) preferably has an average particle size of 0.6 to 3 &mgr;m.
In another preferred embodiment of the present invention, porosities of the individual layers as expressed by the formula (1) above satisfy the relation of
porosity of the surface layer (B)<porosity of the base layer (A)<porosity of the back layer (C).
In still another preferred embodiment of the present invention, any one of the thermoplastic resins is a mixture of a thermoplastic non-elastomer and a thermoplastic elastomer. Any one of the thermoplastic resins is preferably a polyolefin-base resin, an olefin-base thermoplastic elastomer, or a mixture thereof. The mixture preferably contains 5 to 100 weight parts of the olefin-base thermoplastic elastomer per 100 weight parts of the polyolefin-base resin. The melting point of the thermoplastic resin contained in the stretched film surface layer (B) is preferably lower by 10° C. or more than the melting point of the thermoplastic resin contained in the stretched film base layer (A).
In still another preferred embodiment of the present invention, the stretched film surface layer (B) is embossed. It is also preferable that the inorganic or organic fine powder contained in the back layer (C) has a surface finished by hydrophilic treatment. The back layer (C) preferably has a contact angle to water of 10 to 80°.
The present invention is to provide also a building decorative material using any one of the above-described stretched film of a thermoplastic resin.
The present invention also provides a method for producing the above-described stretched film of a thermoplastic resin comprising at least:
a step for stacking at least on one surface of the film base layer (A) a film surface layer (B),
said film base layer (A) containing 40 to 85 wt % of a thermoplastic resin and 60 to 15 wt % of inorganic or organic fine powder, and
said film surface layer (B) containing 30 to 90 wt % of a thermoplastic resin and 70 to 10 wt % of an inorganic or organic fine powder having an average particle size smaller than that of an inorganic or organic fine powder contained in the film base layer (A); and
a step for stretching the obtained stack.
In a preferred embodiment of the present invention, the film base layer (A) is stretched in advance of the stacking. The melting point of the thermoplastic resin contained in the film surface layer (B) is preferably lower by 10° C. or more than the melting point of the thermoplastic resi

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