JPH05279494A - Flame retardant white polyester film - Google Patents

Abstract

PURPOSE:To obtain the subject flame retardant film, having a specific apparent density, comprising a flame retardant, excellent in picture drawing, cushioning properties, whiteness and flame retardancy and suitable as wallpaper, decorative displays, posters, decorative paper, building materials, etc. CONSTITUTION:The objective white polyester film is obtained by adding 20 pts.wt. polystyrene having 3.0g/10min melt flow index to 100 pts.wt. polyethylene terephthalate resin, further adding 10 pts.wt. polyphenyl bromide and 10 pts.wt. antimony trioxide as a flame retardant thereto, melt extruding the resultant mixture through a T-die at 290 deg.C using a twin-screw extruder, electrostatically bringing the extrudate into close contact with a cooling rotating roll, subsequently longitudinally stretching the film at 90 deg.C at 3.4 times stretch ratio, then transversely stretching the obtained film at 130 deg.C at 3.5 times stretch ratio with a tenter and heat-setting the prepared film at 230 deg.C. This polyester film has 0.5-1.3g/cm<3> apparent density and is excellent in picture drawing and cushioning properties, whiteness and flame retardancy.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is excellent in label, poster, recording paper, wrapping material, building material and the like, and particularly excellent in flame retardancy, and is a polyester film having a drawing property containing a large amount of fine voids inside the film. Regarding

[0002]

2. Description of the Related Art Synthetic paper, which is a paper substitute mainly made of synthetic resin, has a higher water resistance, higher dimensional stability in moisture absorption, and a higher dimensional stability than natural paper.
It has excellent surface stability, gloss and clarity of printing, and mechanical strength. In recent years, application development has been promoted by making use of these advantages. Polyethylene, polypropylene, polyester, etc. are used as the main raw material of synthetic paper. Among them, polyester typified by polyethylene terephthalate is excellent in that it has high heat resistance and is strong and has a wide range. Applications can be expanded.

As a method for obtaining a film having a function similar to that of a paper mainly made of polyester, (1) a method of containing a large amount of fine voids in the film or an ordinary flat polyester film (2-1 ) Sandplast treatment or (2-2) Chemical etching treatment or (2-
3) A method of roughening by a matting treatment (a method of laminating a matting agent together with a binder) and the like are disclosed. Among these, in the method of (1) containing a large amount of fine voids inside the film, the film itself can be reduced in weight and appropriate flexibility can be imparted, which enables clear printing and transfer. There is an advantage that. As a method for forming fine voids inside the film, conventionally, a polymer incompatible with polyester is melt-kneaded with an extruder to obtain a sheet in which the polymer is dispersed in fine particles to further stretch the sheet. Discloses a method of generating cavities around fine particles.

As a polymer which is incompatible with polyester used for cavities (hereinafter referred to as cavity developing agent), a polyolefin resin (for example, JP-A-49-13) is used.
No. 4755), polystyrene resin (for example, Japanese Patent Publication No. 49-2016, Japanese Patent Publication No. 54-29550), and polyarylate resin (for example, Japanese Patent Publication No. 58-28).
097). Of these, polypropylene and polystyrene are particularly preferable because they easily form voids, have a low density, and are inexpensive. These films have recently been widely used in the fields of labels, bar code labels, commercial printing, maps, dust-free paper, photographic paper, printer image receiving paper and the like. Among them, because of its excellent water resistance, it is also used for posters, wallpapers, building materials and the like. However, since these contain a large number of combustible polymers such as polypropylene and polystyrene and voids inside the polyester, they have the drawback that they are much more prone to combustion than ordinary polyester films. Recently, these films are required to be flame retardant from the viewpoint of fire prevention.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a void-containing polyester film which is flame-retardant and which is excellent in water resistance and writability.

[0006]

That is, the present invention relates to a flame-retardant white polyester film having an apparent density of 0.5 to 1.3 g / cm ³ . The polyester in the present invention is produced by polycondensing an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid or an ester thereof with a glycol such as ethylene glycol, diethylene glycol, 1,4-butanediol or neopentyl glycol. Polyester. These polyesters may be obtained by directly reacting an aromatic dicarboxylic acid with a glycol, and then subjecting an alkyl ester of an aromatic dicarboxylic acid and a glycol to an ester exchange reaction followed by polycondensation, or a diglycol ester of an aromatic dicarboxylic acid. Is produced by a method such as polycondensation. Typical examples of such polyesters include polyethylene terephthalate, polyethylene butylene terephthalate or polyethylene 2,
6 naphthalate and the like. This polyester may be a homopolymer or a copolymer of a third component. In any case, in the present invention, a polyester having an ethylene terephthalate unit, a butylene terephthalate unit or an ethylene-2,6-naphthalate unit in an amount of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable.

Incompatible with the polyester used in the present invention
Thermoplastic resins are incompatible with the above polyesters
Must be Specifically, polystyrene
Resin, polyolefin resin, polyacrylic resin,
Examples include polycarbonate resins and polysulfone resins.
However, it is preferable to use a polyolefin resin or a polystyrene.
Len-based resin can be used. Also particularly important in the present invention
The point is that the apparent density is 0.5 to 1.3 g / cm.³Preferred
Ku-0.7-1.3g / cm³ More preferably 0.8
~ 1.2 g / cm ³ Including flame retardant for polyester
Having and / or having a flame retardant layer
It Density is 0.5g / cm³ Below is a weak film
When 1.3g / cm3 or more, the drawability and cushion
Lack of sex. Flame retardant inside the polyester film
If it is, preferably 100 parts by weight of polyester
The flame retardant is preferably 1 to 100 parts by weight. 1 weight of flame retardant
If it is less than 1 part, it is difficult to have sufficient flame retardancy.
If it is more than 00 parts by weight, it may cause heat deterioration in the extruder.
The resulting film has become yellowed or stretched.
This is because there are things that cannot be done.

The flame retardant used in the present invention is not particularly limited as long as it does not burn the film or has an effect of suppressing the burning rate. Specifically, the inorganic phosphoric acid is used. Salts, aromatic phosphates, alkyl phosphates, halogen-containing esters, acidic phosphates, polyphosphonitriles, nitrogen-containing phosphorus compounds,
Polymerizable phosphorus compound monomer, halogenated paraffin, halogenated polyethylene, halogenated polyphenyl, halogenated diphenyl, halogenated acid anhydride, chlorhetic acid, brominated inorganic substance, brominated chain hydrocarbon, brominated cyclic hydrocarbon, phosphorus Examples thereof include bromine compounds, organic chlorine compounds, vinyl compounds, antimony oxides, metal oxides and metal hydroxides. These may be used alone, but a plurality of flame retardants may be used in combination. These flame retardants may be mixed in polyester, coated on the film surface, or laminated with a flame retardant layer by a coextrusion method.

The polymer mixture obtained by mixing the polyester of the present invention and an incompatible thermoplastic resin with the polyester is prepared by, for example, mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. Method, or a method in which both resins are kneaded in advance by a kneader to be melt-extruded and solidified by an extruder, or an incompatible thermoplastic resin is added to the polyester in the polyester polymerization step and dispersed by stirring. It can also be obtained by a method of melt-extruding and solidifying the obtained chips. The polymer obtained by solidifying (unstretched sheet) is usually in a non-oriented state or a weakly oriented state. Further, the thermoplastic resin incompatible with the polyester exists in the polyester in the form of being dispersed in various shapes such as spherical or elliptic spherical or thread-like.

If necessary, the polymer mixture may contain inorganic particles. Examples of the inorganic particles include titanium dioxide, silicon dioxide, calcium carbonate, barium sulfate and the like, but are not particularly limited.

It is possible to add a colorant, a light-proofing agent, a fluorescent agent, an antistatic agent, etc. to the polymer mixture depending on the application. The polymer mixture thus obtained is further stretched between rolls having different speeds (roll stretch), stretched by gripping and expanding with a clip (tenter stretch), and stretched by expanding by air pressure (inflation stretch). At least one axis is subjected to orientation treatment by, for example,
At this time, peeling occurs at the interface between the polyester and the incompatible thermoplastic resin dispersed in the polyester, and a large number of cavities are generated in the polymer mixture.

Therefore, the amount of the thermoplastic resin which is incompatible with the polyester to be mixed with the polyester varies depending on the amount of the target voids.
3 to 45 parts by weight is preferable, and 10 to 40 parts by weight is particularly preferable, relative to 0 parts by weight. If the amount is less than 3 parts by weight, there is a limit to increase the amount of cavities to be produced, and the desired flexibility, light weight, and drawability cannot be obtained. On the other hand, when it is 50 parts by weight or more, the heat resistance and strength of the polyester film are significantly impaired.

The film of the present invention may be provided with a layer (B) made of a thermoplastic resin on at least one surface of the layer containing voids. At that time, the aforementioned additives such as the flame retardant and the inorganic particles are added to the layer containing the cavities and / or B.
It may be added to the layer. The method for laminating two or more layers is not particularly limited in the present invention. However, from the viewpoint of productivity, it is most preferable to use the so-called coextrusion method in which the raw materials for the surface layer and the central layer are extruded from different extruders, introduced into one die to obtain an unstretched sheet, and then oriented at least uniaxially. ..

Further, by providing a coating layer on the film surface, the wettability and adhesiveness of ink, coating agent and the like are improved. As the compound constituting the coating layer,
Polyester resins are preferred, but in addition to these, compounds disclosed as means for improving the adhesiveness of ordinary polyester films such as polyurethane resins, polyester urethane resins and acrylic resins can be applied. As a method of providing the coating layer, a commonly used method such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, and a reverse roll coating method can be applied. As the step of applying, a method of previously applying to the surface of the mixed polymer before the orientation treatment, a method of applying to the surface of the uniaxially oriented cavity-containing film and further orienting it in the orthogonal direction, Any method such as coating on the surface of the finished void-containing film is possible. It is possible to include a flame retardant in these coating layers, to coat the flame retardant on a surface different from the coating layer, or to coat the flame retardant on or below the coating layer.

The conditions for orienting the polymer mixture are closely related to the formation of cavities. Therefore, the conditions for achieving the object of the present invention include, for example, the most commonly used sequential biaxial stretching step, in which a continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction and then in the width direction. In the case of the sequential biaxial stretching method in which the tenter stretching is performed, it is as follows. In the roll stretching, it is preferable that the temperature is not higher than the second-order transition temperature of polyester + 30 ° C. and the magnification is 1.2 to 5 times in order to generate a large number of cavities. In the tenter stretching, the temperature is 80 to 150 for stable film formation without breaking.
It is preferable that the temperature and the magnification are 1.2 to 5 times. However,
It is not limited to these methods. The void-containing film that has been stretched and oriented is preferably 130 ° C. or higher, preferably 180 ° C. or higher.
When heat setting is performed at a temperature of ℃ or more, dimensional stability at high temperature can be improved. The void-containing film oriented only in the uniaxial direction is useful as a shrinkable film or an easily tearable film. Since the present invention relates to a void-containing polyester film in which voids have been generated by the orientation treatment, it is necessary to orient it at least uniaxially.

[0016]

In the present invention, the polyester is used
This is because the heat resistance and mechanical strength of the void-containing polyester film are satisfied. In the present invention, a polyester is mixed with an incompatible thermoplastic resin to the polyester to obtain a polymer mixture by dispersing fine particles of an incompatible thermoplastic resin in the polyester in the polyester, This is to form a nucleus of a cavity generated by the next alignment treatment.

In the present invention, the polymer mixture is oriented at least uniaxially in order to generate a large number of fine voids in the polymer mixture. By creating cavities, the film can be made lighter, workability is improved, and price per area is reduced. In addition, the inclusion of the cavities increases flexibility, and enables clear printing when printing or transferring. Further, by containing a cavity, light hiding property and whiteness can be obtained. Further, a large number of protrusions derived from the thermoplastic resin which is incompatible with the polyester are formed on the surface of the film, which enables writing with a pencil or a ballpoint pen. The void-containing polyester film thus obtained has excellent heat resistance, mechanical strength, and flame retardancy, so that it has been improved in terms of fire protection even when used for wallpaper, decorative displays, posters, decorative paper, etc. Became.

[0018]

EXAMPLES Next, examples and comparative examples of the present invention will be shown. The measurement / evaluation methods used in the present invention are shown below. 1) Density The film was cut into a square of 5.00 cm × 5.00 cm, and its thickness was measured at 50 points, and the average thickness was t μm.
Was calculated, and the weight thereof was measured up to 0.1 mg to be wg, which was calculated by the following formula.

[0019]

[Equation 1] 2) Flame retardance Oxygen index (O based on JIS-K7201-1976 method)
It is represented by I). 3) Light transmittance According to JIS-K6714, Poic integrating sphere type H.264. T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.). The smaller this value is, the higher the hiding property is.

Example 1 To 100 parts by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 as a raw material, 20 parts by weight of polystyrene for general use having a melt flow index of 3.0 g / 10 minutes was added, and brominated polyphenyl 10 as a flame retardant. 2 parts by weight and 10 parts by weight of antimony trioxide are added, and these are added to
It is melt-extruded from a T-die at 290 ° C. by an axial screw extruder, electrostatically adhered to a cooling rotary roll and solidified, and then longitudinally stretched by a roll stretching machine at 90 ° C. for 3.4 times, and then at a tenter at 130 ° C. Horizontally stretched 3.5 times, 230
Heat setting was performed at 0 ° C. to obtain a polyester film having a thickness of 75 μm and containing many cavities inside. The flame retardancy was good.

Example 2 A void-containing polyester film was obtained in the same manner as in Example 1 except that crystalline polypropylene having a melt flow index of 2.7 / 10 min was used as the raw material instead of polystyrene.

Comparative Examples 1 and 2 Cavity-containing polyester films were obtained in the same manner as in Examples 1 and 2 except that brominated polyphenyl and antimony trioxide were removed from the raw materials. The flame retardance was poor as compared with Examples 1 and 2.

Example 3 Anatase type titanium dioxide was used as a raw material in Example 1
A void-containing polyester film was obtained in exactly the same manner except that parts by weight were added.

Example 4 100 parts by weight of polyethylene terephthalate, 20 parts by weight of polystyrene used in Example 1 100 parts by weight of polyethylene terephthalate, 15 parts by weight of titanium dioxide, and 15 parts by weight of brominated polyphenyl on both sides of layer A added. Provide a layer B containing 12 parts by weight of antimony trioxide,
A laminated void-containing polyester film was obtained in the same manner as in Example 1 except that the thickness of each layer was B / A / B = 5/70/5.

[0025]

INDUSTRIAL APPLICABILITY The void-containing polyester film of the present invention, like the void-containing polyester film obtained by using conventional polystyrene or polyolefin as a void-developing agent, is lightweight, flexible, concealing, matte and drawing. In addition to having properties such as flame retardancy compared to conventional void-containing polyester film, it is particularly excellent in terms of disaster prevention,
Suitable for wallpapers, decorative displays, posters, building materials, etc.

[0026]

[Table 1]

Claims (2)

[Claims] 1. An apparent density of 0.5 to 1.3 g / cm ^3.
1. A flame-retardant white polyester film characterized in that the polyester contains a flame retardant. 2. The apparent density is 0.5 to 1.3 g / cm ^3.
A flame-retardant white polyester film having a flame-retardant layer provided on at least one surface of the polyester film.