JP3303983B2 - Flame retardant white polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester which is used for labels, posters, recording paper, packaging materials, building materials, etc., and which has particularly excellent flame retardancy and which has a large amount of fine cavities inside a film and has drawability. About the film.

[0002]

2. Description of the Related Art Synthetic paper, which is a paper substitute made of synthetic resin as a main raw material, has a higher water resistance, a greater moisture absorption dimensional stability, and a higher stability than natural paper.
Excellent in surface stability, gloss and sharpness of printing, mechanical strength, etc. In recent years, application development utilizing these advantages has been promoted. As a main raw material of synthetic paper, polyethylene, polypropylene, polyester, etc. are used. Among them, polyester typified by polyethylene terephthalate is excellent in that it has high heat resistance and is stiff, and is widely used. Applications can be developed.

[0003] As a method for obtaining a film having a function similar to that of paper using polyester as a main raw material, there have been conventionally (1) a method in which a large amount of fine voids are contained in the film, or an ordinary flat polyester film (2-1). ) Sandplast treatment and (2-2) chemical etching treatment and (2-
3) A method of roughening the surface by a matting treatment (a method of laminating a matting agent with a binder) and the like are disclosed. Among them, the method of (1) in which a large amount of fine cavities are contained in the film can provide a point that the film itself can be reduced in weight and appropriate flexibility, thereby enabling clear printing and transfer. There is an advantage. Conventionally, as a method of forming fine cavities inside a film, a polymer incompatible with polyester is melt-kneaded with an extruder, a sheet in which the polymer is dispersed in fine particles in polyester is obtained, and the sheet is further stretched. Discloses a method for generating a cavity around fine particles.

As a polymer incompatible with the polyester used for the cavity (hereinafter, referred to as a cavity developing agent), a polyolefin resin (for example, JP-A-49-13)
No. 4755), polystyrene resins (for example, JP-B-49-2016 and JP-B-54-29550), and polyarylate resins (for example, JP-B-58-28).
No. 097). Among them, polypropylene and polystyrene are particularly preferable in that they easily form cavities, 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 receiving paper, and the like. Among them, they are used for posters, wallpapers, building materials, etc. because of their excellent water resistance. However, since these contain many flammable polymers and cavities, such as polypropylene and polystyrene, inside the polyester, there has been a problem that they are extremely flammable as compared with ordinary polyester films. Recently, these films are required to be flame-retardant from the viewpoint of fire prevention.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a void-containing polyester film which is flame-retardant and is excellent in water resistance, writing properties and the like.

[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 are prepared by directly reacting an aromatic dicarboxylic acid with a glycol, and then subjecting the alkyl ester of the aromatic dicarboxylic acid to a transesterification reaction with the glycol and then polycondensing, or a diglycol ester of an aromatic dicarboxylic acid. Is produced by a method such as polycondensation. Representative 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 the 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 of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable.

The thermoplastic resin incompatible with the polyester used in the present invention must be incompatible with the polyester described above. Specifically, polystyrene resin, polyolefin resin, polyacrylic resin,
Examples thereof include a polycarbonate resin and a polysulfone resin, and preferably include a polyolefin resin and a polystyrene resin. It is particularly important in the present invention that the apparent density is 0.5 to 1.3 g / cm ^3, preferably 0.7 to 1.3 g / cm ^{3, and} more preferably 0.8 to 1.3 g / cm ^3.
Up to 1.2 g / cm ³ for polyester with flame retardant (but
(Excluding metal oxides or metal hydroxides) and / or having a flame-retardant layer. If the density is 0.5 g / cm ³ or less, the film becomes weak,
If it is 1.3 g / cm ³ or more, the drawing property and cushioning property are insufficient. When the flame retardant is contained inside the polyester film, preferably, the flame retardant is 1 to 100 parts by weight based on 100 parts by weight of the polyester. If the flame retardant is less than 1 part by weight, it is difficult to have sufficient flame retardancy. If the flame retardant is more than 100 parts by weight, the resulting film may become yellow due to heat deterioration in the extruder, or the stretching may not be performed. This is because they may not be able to do so.

[0008] The flame retardant used in the present invention comprises a film .
May not let the combustion, as long as it has the effect of suppressing the combustion speed, it is not particularly limited (however, metal
Excluding oxides or metal hydroxides). Specifically, inorganic phosphates, aromatic phosphates, alkyl phosphates, halogen-containing esters, acidic phosphates,
Polyphosphonitrile, nitrogen-containing phosphorus compound, polymerizable phosphorus compound monomer, halogenated paraffin, halogenated polyethylene, halogenated polyphenyl, halogenated diphenyl, halogenated acid anhydride, chlorhetic acid, brominated inorganic, brominated chain Hydrocarbons, brominated cyclic hydrocarbons,
Phosphorus bromine compounds, organic chlorine compounds, it vinyl compound
Throw . These may be used alone, or a plurality of flame retardants may be used in combination. These flame retardants may be mixed in the polyester, coated on the film surface, or laminated with a flame retardant layer by a co-extrusion method.

The polymer mixture of the present invention obtained by mixing the polyester and the thermoplastic resin which is incompatible with the polyester is prepared by, for example, mixing chips of each resin, melt-kneading them in an extruder, and extruding and solidifying. A method obtained by kneading both resins with a kneading machine in advance, and a method of solidifying by extruding the mixture further from an extruder, or adding a thermoplastic resin incompatible with the polyester in the polyester polymerization step, stirring and dispersing. It can also be obtained by a method of melt-extruding the chips obtained and solidifying them. The polymer (unstretched sheet) obtained by solidification is usually in a non-oriented or weakly oriented state. In addition, the thermoplastic resin incompatible with the polyester exists in a form dispersed in the polyester in various shapes such as a spherical shape, an elliptical spherical shape, and a thread shape.

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

The polymer mixture may contain a coloring agent, a light-fast agent, a fluorescent agent, an antistatic agent, and the like, depending on the application. The polymer mixture thus obtained is further stretched between rolls having different speeds (roll stretching), stretched by gripping and expanding with clips (tenter stretching), or stretched by air pressure (inflation stretching). At least one axis orientation treatment is performed by such as.
At this time, exfoliation occurs at the interface between the thermoplastic resin incompatible with the dispersed polyester and the polyester, and many cavities are generated in the polymer mixture.

Accordingly, the amount of the thermoplastic resin which is incompatible with the polyester to be mixed with the polyester depends on the desired amount of cavities.
The amount is preferably from 3 to 45 parts by weight, more preferably from 10 to 40 parts by weight, based on 0 parts by weight. If the amount is less than 3 parts by weight, there is a limit to increasing the amount of cavities, and the desired flexibility, lightness, and drawing property cannot be obtained. Conversely, if the amount is more than 50 parts by weight, the heat resistance and strength of the polyester film will be significantly impaired.

In the film of the present invention, a layer (B) made of a thermoplastic resin may be provided on at least one side of the layer containing voids. At that time, the aforementioned additives, such as flame retardants and inorganic particles, may be added to the layer containing the cavities and / or B
It may be added to the layer. In the present invention, the method of laminating two or more layers is not particularly limited. However, in consideration of productivity, the so-called co-extrusion lamination is most preferable, in which the raw materials for the surface layer and the center layer are extruded from separate extruders, led to one die to obtain an unstretched sheet, and then oriented at least uniaxially. .

Further, by providing a coating layer on the surface of the film, the wettability and adhesion of inks and coating agents are improved. As a compound constituting the coating layer,
Polyester-based resins are preferred, but other compounds disclosed as means for improving the adhesiveness of ordinary polyester films, such as polyurethane resins, polyester urethane resins, and acrylic resins, can also be used. As a method for 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 a step of applying, a method of applying in advance to the surface of the mixed polymer material before performing the orientation treatment, a method of applying the film to the surface of the cavity-containing film oriented in the axial direction, and further orienting it in the perpendicular direction, Any method such as a method of coating the finished void-containing film surface is possible. It is possible to contain a flame retardant in these coating layers, to apply a flame retardant to a surface different from the coating layer, or to apply a flame retardant above 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 this object are, for example, the most commonly performed sequential biaxial stretching step, for example, taking a continuous sheet of the polymer mixture as a roll in the longitudinal direction and then stretching in the width direction. In the case of the sequential biaxial stretching method in which tenter stretching is performed, the following is performed. In the roll stretching, it is preferable that the temperature is not higher than the secondary transition temperature of the polyester + 30 ° C. and the magnification is 1.2 to 5 times in order to generate many cavities. In tenter stretching, the temperature is set to 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 subjected to the stretching orientation treatment is at least 130 ° C., preferably at least 180 ° C.
When heat setting is performed at a temperature of not less than ℃, dimensional stability at high temperatures can be improved. Further, the void-containing film oriented only in one axis direction is useful for a shrinkable film, an easily tearable film, and the like. The present invention relates to a void-containing polyester film in which voids have been generated by an orientation treatment, and therefore it is necessary to orient at least uniaxially.

[0016]

In the present invention, polyester is used for
This is for satisfying the heat resistance and mechanical strength of the void-containing polyester film. In the present invention, mixing a thermoplastic resin incompatible with the polyester to the polyester, to obtain a polymer mixture, by dispersing fine particles of the thermoplastic resin incompatible with the polyester in the polyester, This is because the nuclei of the cavities generated by the next alignment treatment are formed.

In the present invention, the reason why the polymer mixture is oriented at least uniaxially is to generate a large number of fine cavities in the polymer mixture. By forming cavities, the film can be reduced in weight, workability is improved, and the cost per area is reduced. Further, by containing the cavity, flexibility is increased, and clear printing and printing can be performed when performing printing and transfer. Further, by containing a cavity, light opacity and whiteness can be obtained. Further, a large number of protrusions derived from a thermoplastic resin incompatible with the polyester are formed on the film surface, and writing with a pencil or a ballpoint pen becomes possible. The thus obtained void-containing polyester film has excellent heat resistance, mechanical strength, and flame retardancy, so it has been improved in fire prevention even when used for wallpaper, decorative displays, posters, decorative paper, etc. It became.

[0018]

Next, examples of the present invention and comparative examples will be described. The measurement / evaluation method used in the present invention will be described below. 1) Density A film was cut out into a square of 5.00 cm × 5.00 cm, and its thickness was measured at 50 points to obtain an average thickness of tμm.
The weight was measured up to 0.1 mg and defined as wg, which was calculated by the following equation.

[0019]

(Equation 1) 2) Flame retardancy Oxygen index (O) according to JIS-K7201-1976 method
I). 3) Light transmittance According to JIS-K6714, Poick integrating sphere formula T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Kogaku). The smaller the value, the higher the concealment property.

EXAMPLE 1 20 parts by weight of a general-purpose polystyrene were added to 100 parts by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 as a raw material, and a melt flow index of 3.0 g / 10 minutes was added. Parts by weight of antimony trioxide and 10 parts by weight of
It is melt-extruded at 290 ° C. from a T-die with an axial screw extruder, solidified electrostatically in close contact with a cooling rotary roll, and subsequently longitudinally stretched 3.4 times at 90 ° C. with a roll stretching machine, and subsequently at 130 ° C. with a tenter. 3.5 times transverse stretching, 230
The resulting film was heat-set at a temperature of about 75 ° C. to obtain a polyester film having a thickness of 75 μm and containing a number of cavities. 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 was used instead of polystyrene as a raw material.

Comparative Examples 1 and 2 A void-containing polyester film was obtained in exactly the same manner as in Examples 1 and 2, except that the brominated polyphenyl and antimony trioxide were omitted from the raw materials. Compared with Examples 1 and 2, flame retardancy was poor.

Example 3 In Example 1, anatase type titanium dioxide was added
A void-containing polyester film was obtained in exactly the same manner except for adding the parts by weight.

Example 4 100 parts by weight of polyethylene terephthalate, 15 parts by weight of titanium dioxide, 15 parts by weight of brominated polyphenyl, and 100 parts by weight of polyethylene terephthalate, 20 parts by weight of polystyrene used in Example 1, A layer B to which 12 parts by weight of antimony trioxide is added;
A laminated cavity-containing polyester film was obtained in exactly the same manner as in Example 1 except that the thickness of each layer was changed to B / A / B = 5/70/5.

[0025]

The void-containing polyester film of the present invention has the same light weight, flexibility, concealing properties, matting properties, and drawing properties as the conventional void-containing polyester film obtained using polystyrene or polyolefin as a void-generating agent. In addition to having the properties, compared with the conventional void-containing polyester film, it is flame retardant, so it is especially excellent in disaster prevention,
It is suitable for wallpaper, decorative displays, posters, and building materials.

[0026]

[Table 1]

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-64988 (JP, A) JP-A-3-132331 (JP, A) JP-A-3-121137 (JP, A) JP-A-3-76727 (JP, A) JP-A-2-284929 (JP, A) JP-A-1-225634 (JP, A) JP-A-1-225626 (JP, A) JP-A-1-225625 (JP, A) JP-A-63-137927 (JP, A) JP-A-50-38766 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 B32B 7/02 B32B 27/36 C08J 9/00 C08L 67/02

Claims (2)

(57) [Claims] 1. An apparent density of 0.5 to 1.3 g / cm ^3.
In polyester with flame retardant (but metal oxide or metal water
(Excluding oxides) . 2. An apparent density of 0.5 to 1.3 g / cm ^3.
At least one side to the flame retardant layer (flame of in polyester film
A flame-retardant white polyester film provided with a metal oxide or a metal hydroxide as a flame retardant.