JP2021042309A - Recycled resources-derived polyester film and method for producing the same - Google Patents

Abstract

To provide a recycled resources-derived polyester film that is obtained by using a raw material derived from the recycled resources recovered from a polyester film substantially by 100%, and has high strength.SOLUTION: A recycled resources-derived polyester film is formed of a material containing a raw material derived from the recycled resources recovered from a polyester film, the raw material derived from the recycled resources contains two or more polyesters with different inherent viscosities (IV), and at least one of the polyesters has an inherent viscosity (IV) of 0.80 dl/g or more.SELECTED DRAWING: None

Description

The present invention relates to a recycled polyester film obtained from recycled resources recovered from the polyester film.

The polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc. For example, a biaxially stretched polyester film is used as a base material, and a release layer containing a silicone resin or the like as a main component is provided. Release film is used in many fields.

On the other hand, in recent years, due to the reuse of resources and environmental problems, attempts have been made to recover and reuse polyester raw materials generated after use or during the manufacturing process.

For example, Patent Document 1 discloses a laminated polyester film characterized by using a recycled raw material of a polyester bottle at least in one layer.

Further, Patent Document 2 states that the film contains 25% by weight or more of a recycled PET bottle material, and the heat shrinkage rate in the main shrinkage direction when the film is immersed in warm water at 80 ° C. for 10 seconds and pulled up is 30% or more. , A tensile test was conducted in the direction orthogonal to the main shrinkage direction after the film was stored for 28 days in an atmosphere with a temperature of 30 ° C. and a relative humidity of 85%, and the heat shrinkage rate in the direction orthogonal to the main shrinkage direction was 10% or less. A heat-shrinkable polyester-based film is disclosed, wherein the ratio of the number of test pieces broken at an elongation of 5% or less to the total number of test pieces is 25% or less.

However, as disclosed in Patent Documents 1 and 2, the ratio of recycled raw materials of the polyester film is 75% or less.

In Patent Document 3, a biaxially oriented polyethylene terephthalate film using a PET bottle recycled materials, is within the melting specific resistance is 1.0 × 10 ⁸ Ω · cm at a temperature 285 ° C., are included in the film A biaxially oriented polyester film characterized by a sodium content and a potassium content of more than 0 ppm and 150 ppm or less is disclosed, and the polyester film has a recycled raw material ratio increased to nearly 95%. Polyester films obtained from 100% recycled materials are not disclosed.

Japanese Unexamined Patent Publication No. 07-323511 JP-A-2007-2008 Japanese Unexamined Patent Publication No. 2014-65282

In the recycled polyester film, the recycled resource raw material recovered from the polyester film has a low intrinsic viscosity (IV) because it has undergone a thermal history in the manufacturing process, etc., and the film is manufactured using 100% recycled resource raw material. There is a problem that a high-strength film cannot be obtained.

Further, the recycled resource raw material recovered from the PET bottle has a large variation in viscosity, and if a film is produced using the 100% recycled resource raw material, a high-strength film cannot be obtained.

Further, if the ratio of the raw material derived from recycled resources recovered from the polyester product is increased, the color tone becomes yellow and there is a problem that the product cannot be used.

As described above, in the production of film products using recycled resource raw materials, virgin raw materials must still be used, and it is desired to develop film products obtained from substantially 100% recycled raw materials.

Therefore, one of the objects of the present invention is to provide a recycled resource-derived polyester film obtained by using substantially 100% of the recycled resource-derived raw material recovered from the polyester film and having high strength. It is a thing.
Another object of the present invention is to provide a recycled resource-derived polyester film obtained by using substantially 100% of the recycled resource-derived raw material recovered from the polyester film and having an improved color tone. Is what you do.

The present authors have found that the above problems can be solved by the means shown below, and have completed the present invention.

That is, the present invention has the following configuration.

[1] The recycled resource-derived polyester film of the present invention is formed from a material containing a recycled resource-derived raw material recovered from the polyester film, and the recycled resource-derived raw material contains two or more kinds of polyesters having different intrinsic viscosities (IV). At least one of the polyesters contained has an intrinsic viscosity (IV) of 0.80 dl / g or more.

[2] The method for producing a recycled resource-derived polyester film of the present invention has the following steps (1) to (4).
(1) Step of preparing recycled resource-derived raw material recovered from polyester film (2) Solid-phase polymerization of polyester contained in the recycled resource-derived raw material is performed to increase the intrinsic viscosity (IV) of the polyester to 0.80 dl /. Step of producing the recycled resource-derived raw material (a) containing polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more by setting the intrinsic viscosity (IV) to g or more (3) The intrinsic viscosity (IV) recovered from the polyester film. Step of producing recycled resource-derived raw material (b) containing polyester having an intrinsic value of 0.60 dl / g or less (4) Step of melt-kneading the mixed raw materials of (a) and (b) and then molding them into a film.

The recycled resource-derived polyester film of the present invention is formed from substantially 100% recycled resource-derived raw material recovered from the polyester film, but is equivalent to a polyester film obtained by using a conventional virgin raw material. It has the advantage of having strength.

Further, the recycled resource-derived polyester film of the present invention is formed from substantially 100% recycled resource-derived raw material recovered from the polyester film by containing a fluorescent whitening agent, but is conventionally regenerated. It has the advantage that the color tone is improved compared to the product.

<Polyester film derived from recycled resources>
The recycled resource-derived polyester film of the present invention (hereinafter, also referred to as “the present film”) is a recycled resource-derived raw material recovered from the polyester film, more specifically, a polyester film product and / or a polyester film after use (hereinafter, also referred to as “the present film”). Hereinafter, it is formed from recycled resource-derived raw materials recovered from a process or the like for producing (hereinafter referred to as "the present recycled film") together or individually.

(Composition of this film)
This film can adopt either a single layer or a laminated structure having two or more layers (laminated film), but it is particularly preferable to have a laminated structure having three or more layers.

When this film has a laminated structure having two or more layers, A / B / C composed of base layer B and surface layers A and C and A / B / A composed of base layer B and surface layer A. The three-layer structure of is preferable.

(Recycled raw materials)
"Raw material derived from recycled resources" means a raw material that has been melted at least once after the production of raw materials such as polyester that composes this resource film.
Further, the resource film is preferably formed from a self-recoverable recycled resource-derived raw material produced in the process of producing the polyester film.
By using the self-recovery type recycled resource-derived raw material, the characteristics of the recycled resource-derived raw material can be accurately grasped, and a recycled resource-derived polyester film having stable quality can be provided.
Further, the term "film" is a concept including a sheet, and even if it is referred to as a "film", it shall include a "sheet", and even if it is referred to as a "sheet", it shall include a "film".

In addition, the present film is preferably formed from substantially 100% recycled resource-derived raw materials, and "substantially" means that polyester virgin raw materials are not intentionally used, and is manufactured. It means that it is inevitably allowed to be mixed in a process or the like.
More specifically, in the present invention, "substantially 100% recycled resource-derived raw material" means that 99% or more, preferably 99.5% or more is a recycled resource-derived raw material.

Therefore, this film does not need to be strictly formed from 100% recycled resource-derived raw materials, and is made from a material containing 99% by mass or more, preferably 99.5% by mass or more of recycled resource-derived raw materials. It is what is formed.

As described above, the recycled resource-derived raw material is recovered from the present resource film, and the recovered polyester film is reused by crushing, repelletizing, or the like.

Since the resource film has undergone a thermal history in the manufacturing process or the like, the recycled resource-derived raw material has a low intrinsic viscosity (IV) when reused, and it is difficult to secure the strength.
Therefore, it is preferable that the recycled resource-derived raw material contains two or more kinds of polyesters having different intrinsic viscosities (IV), and at least one of the polyesters has an intrinsic viscosity (IV) of 0.80 dl / g or more. ..
From this point of view, at least one of the polyesters preferably has an intrinsic viscosity (IV) of 0.82 dl / g or more, and most preferably 0.85 dl / g or more.
The intrinsic viscosity (IV) is measured at 30 ° C. using an uperode type viscometer using phenol: tetrachloroethane = 1: 1 as a solvent.

In order to obtain a polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more from the raw material recovered / reused from the present resource film, it is preferable to carry out solid phase polymerization of the polyester which is the recycled raw material.
As the solid phase polymerization method, a known method can be used, and either a continuous method or a batch method may be used.

Further, the resource-derived raw material contains two or more kinds of polyesters having different intrinsic viscosities (IV), and at least one of the polyesters preferably has an intrinsic viscosity (IV) of 0.60 dl / g or less. ..
By using a raw material derived from a recycled resource containing polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, the productivity and cost of the film can be maintained.

From the raw materials recovered and reused from this resource film, use polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more and at least two types of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less. Therefore, it is possible to suppress the breakage of the film during production due to the decrease in the strength of the polyester film, which is a concern when using the recovered / reused raw material, and it is equivalent to the polyester film obtained by using the conventional virgin raw material. Can be provided with the strength of.

From the above, the present film preferably contains 50% by mass or less of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more, more preferably 30% by mass or less, and 25% by mass. It is most preferably contained below.

Further, the present film preferably contains 50% by mass or more of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, more preferably 60% by mass or more, and 70% by mass or more. Most preferably it is contained.

(Other component 1; fluorescent whitening agent)
When a film is formed from a raw material derived from substantially 100% recycled resources, the color tone becomes yellow due to deterioration of the polymer, and it is difficult to use it as it is as a product.
Therefore, it is preferable that this film contains a fluorescent whitening agent as a component other than the raw material derived from the recycled resource.
By adding a fluorescent whitening agent, the yellowness of the film can be improved.

Further, since the fluorescent whitening agent excites when irradiated with ultraviolet rays and emits visible light of blue light, it can also serve as a marker that the film is a recycled product.

Examples of the fluorescent whitening agent include those having a structure such as stilbene-based, coumarin-based, oxazole-based, imidazole-based, and naphthalimide-based.
Specifically, 4,4'-bis (benzoxazole-2-yl) stilbene, 2,5-bis (5-t-butyl-2-benzoxazolyl) thiophene, 1,2-di (5-di). Methyl-2-benzazolyl) ethylene, 1,2-bis (5-methyl-2-benzoxazole) ethylene, 2,2'-(4,4'-diphenolvinyl) dibenzoxazole, 1,1'-biphenyl -4,4'-bis-benzoxazole, 2,5-bis (benzoxazole-2-) thiophene, 4-4'-bis (5-methyl-2-benzoxazole) ethylene, 1,4-bis (benz) Oxazolyl-2-yl) ethylene, 1,4-bis (benzoxazolyl-2-yl) naphthalene, 4-4'-bis [(4-amino-6-morpholino-1,3,5-triazine) -2-yl) amino] stilbene-disulfonate, 2,2'-(1,4-naphthalenediyl) bis-benzoxazole, etc. can be mentioned, and one of these can be used alone or 2 It is also possible to use a combination of seeds and above.

The content of the fluorescent whitening agent in this film is preferably 0.01 to 1.0% by mass, more preferably 0.02 to 0.08% by mass.
If the content of the fluorescent whitening agent exceeds 1.0% by weight, not only the color tone improving effect is saturated, but also the fluorescent whitening agent excessively bleeds out on the surface of the film, which causes a problem such as adverse effects during use. appear.

(Other component 2: Particles)
From the viewpoint of imparting slipperiness and scratch prevention, the film preferably contains particles as a component other than the recycled resource-derived raw material.

Examples of the particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, as well as crosslinked silicone resin particles and crosslinked acrylic resin particles. Examples thereof include crosslinked polymers such as crosslinked styrene-acrylic resin particles and crosslinked polyester particles, and organic particles such as calcium oxalate and ion exchange resin.

The content of the particles in the film is preferably 0.001 to 1.0% by mass, more preferably 0.01 to 0.08% by mass.

(This resource film)
This resource film is obtained by molding polyester or a composition containing polyester into a film, and is composed of polyester as a main constituent component.
The "main constituent component" means that it occupies 50% by mass or more, preferably 70% by mass or more, of the components constituting the film.

(A) Polyester The polyester refers to a polymer compound having an ester bond continuously in the main chain, and may be a homopolyester or a copolymerized polyester, and specifically, a dicarboxylic acid component and a diol component. Examples thereof include polyesters obtained by subjecting and to a polycondensation reaction.

In the present invention, when the dicarboxylic acid component is 100 mol%, it is preferable to use a polyester containing an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid in an amount of more than 50%.

Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-diphenyldicarboxylic acid. Aromatic dicarboxylic acids such as 4,4'-diphenyl ether dicarboxylic acid and 4,4'-diphenylsulfone dicarboxylic acid, for example adipic acid, suberic acid, sebacic acid, dimer acid, dodecandioic acid, cyclohexanedicarboxylic acid and esters thereof. Examples thereof include aliphatic dicarboxylic acids such as derivatives.

Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1, , 6-Hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-hexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis (4-hydroxyethoxy) Phenyl) propane, isosorbate, spiroglycol and the like can be mentioned.

When the polyester is made of homopolyester, it is preferably obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol.
Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol and 1,4-cyclohexanedimethanol.
Typical polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN) and the like.
Of these, polyethylene terephthalate (PET) is particularly preferable.

On the other hand, when the polyester is a copolymerized polyester, it is preferably a copolymer containing 30 mol% or less of a third component.
Examples of the dicarboxylic acid component of the copolymerized polyester include one or more of isophthalic acid, terephthalic phthalate, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid.
Examples of the glycol component of the copolymerized polyester include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like.

Further, as the polyester, 80 mol% or more, preferably 90 mol% or more, is preferably polyethylene terephthalate, which is an ethylene terephthalate unit, polyethylene-2,6-naphthalate, which is an ethylene-2,6-naphthalate unit, or the like.

(B) Polyester polycondensation catalyst Examples of the polycondensation catalyst for polycondensing the polyester include antimony compounds, germanium compounds, aluminum compounds, titanium compounds and the like. In particular, polyesters obtained by using antimony compounds are used. It is preferable to do so.

(C) Particles The resource film may be formed from a polyester composition containing particles.
As the particles, those described above can be appropriately used.

(D) Fluorescent whitening agent The resource film may be formed from a polyester composition containing a fluorescent whitening agent.
As the fluorescent whitening agent, the above-mentioned one can be appropriately used.

(E) Additives This resource film is formed from a polyester composition containing various additives such as antioxidants, lightfasteners, antigelling agents, organic wetting agents, antistatic agents, ultraviolet absorbers, and surfactants. It may be something that is done.

(Form of this film)
The present film may be a non-stretched film, a uniaxially stretched film, or a biaxially stretched film.
Above all, from the viewpoint of film strength, a biaxially stretched film is particularly preferable.

(Release layer)
This film can also be used in the form of having a release layer on at least one side, that is, in the form of a release film.
At this time, it is particularly preferable that the release layer is also composed of a raw material derived from recycled resources.

(Especially preferred embodiment 1)
(1) This film has a multilayer structure including at least three layers of A / B / A, and the A layer is a layer constituting the outermost surface and is derived from recycled resources recovered from the polyester film. The recycled resource-derived raw material (A-1) formed from the raw material and for forming the A layer contains a polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, and the B layer is recovered from the polyester film. The recycled resource-derived raw material (B-1) formed from the recycled resource-derived raw material for forming the B layer contains a polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more.
(2) In the above (1), the recycled resource-derived raw material (B-1) for forming the B layer contains 30% by mass or less of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more in the B layer. Form (3) In the above (1) or (2), the recycled resource-derived raw material (B-1) for forming the B layer further contains a polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less. ..
(4) In the above (3), the recycled resource-derived raw material (B-1) for forming the B layer contains 50% by mass or more of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less in the B layer. Form (5) In any of the above (1) to (4), the B layer further contains a fluorescent whitening agent.
(6) In any of the above (1) to (5), the A layer further contains particles.
(7) In any of the above (1) to (6), the present film is a biaxially stretched film.
(8) In any of the above (1) to (7), the recycled resource-derived raw material (B-1) for forming the B layer is the recycled resource-derived raw material (b-) recovered from the polyester film provided with the coating layer. Form (9) including 1) In any of the above (1) to (8), the recycled resource-derived raw material (A-1) for forming the A layer is substantially the same as the recycled resource-derived raw material (b-1). (10) A form having a release layer on at least one side of the present film according to any one of (1) to (9) above.

According to the above-mentioned particularly preferable embodiment 1, the recycled resource-derived raw material (B-1) for forming the B layer is excellent in this film because it contains a polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more. Strength can be imparted.
Further, in particular, the recycled resource-derived raw material (B-1) for forming the B layer further contains a polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, so that the mechanical strength of this film is maintained. On the other hand, there are advantages such as maintaining the productivity and cost of the film.

Further, from the viewpoint of suppressing film breakage during production, the recycled resource-derived raw material (B-1) for forming the B layer is a polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more in the B layer. Is preferably contained in an amount of 30% by mass or less, and more preferably 25% by mass or less.

From the same viewpoint as above, the recycled resource-derived raw material (B-1) for forming the B layer contains 50% by mass of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less in the B layer. It is preferably contained in an amount of 70% by mass or more, and more preferably 70% by mass or more.

Further, by containing the fluorescent whitening agent in the B layer, there is an advantage that the fluorescent whitening agent does not bleed out to the outermost surface layer.

In addition, by containing the particles in the A layer, it is possible to impart slipperiness and scratch prevention property to the film.

Further, from the viewpoint of securing the recycled resource-derived raw material, the recycled resource-derived raw material (B-1) for forming the B layer includes the recycled resource-derived raw material (b-1) recovered from the polyester film provided with the coating layer. From the same viewpoint, it is preferable that the recycled resource-derived raw material (A-1) for forming the A layer does not substantially contain the recycled resource-derived raw material (b-1).
In addition, "substantially" means that the recycled resource-derived raw material (b-1) is intentionally not contained, and specifically, in the A layer, the recycled resource-derived raw material (b-) is contained. It means that the content of 1) is less than 5% by mass, and more preferably less than 1% by mass.

The coating layer has various functions such as easy adhesion, and a coating liquid containing a solvent, a binder resin, a cross-linking agent, etc. is prepared, the coating liquid is applied to a film, and then dried to obtain a layer. Say.

Examples of the binder resin used in the coating liquid include acrylic resin, urethane resin, polyester resin, olefin resin, fluorine resin, vinyl resin, chlorine resin, styrene resin, epoxy resin, and silicone. Examples thereof include based resins and mixtures of these resins.

<Manufacturing method of this film>
Hereinafter, as an example of the method for producing this film, a method for producing a biaxially stretched film will be shown.
First, by a known method, the above-mentioned recycled resource-derived raw materials, for example, recycled polyester chips are supplied to a melt extruder, heated to a temperature equal to or higher than the melting point of each polymer, the molten polymer is extruded from a die, and the polymer is placed on a rotary cooling drum. It may be cooled and solidified so as to have a temperature equal to or lower than the glass transition point of the above, so that a substantially amorphous unaligned sheet can be obtained.

Next, the unaligned sheet is stretched in one direction by a roll or tenter type stretching machine.
At this time, the stretching temperature is usually 25 to 120 ° C., preferably 35 to 100 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 2.8 to 6 times.

Then, it is stretched in a direction orthogonal to the stretching direction of the first stage.
At this time, the stretching temperature is usually 50 to 140 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 4.5 times or more, and more preferably 4.5 to 5.0 times.

Then, the heat fixing treatment is subsequently carried out at a temperature of 180 to 220 ° C. under tension or relaxation within 30% to obtain the present polyester film as a biaxially oriented film.
In the above-mentioned stretching, a method of stretching in one direction in two or more steps can also be adopted.

(Especially preferred embodiment 2)
(1) In the method for producing this film, a form having the following steps A to D.
A. Step B. Preparation of raw materials derived from recycled resources recovered from polyester film. By solid-phase polymerization of the polyester contained in the raw material derived from the recycled resource and setting the intrinsic viscosity (IV) of the polyester to 0.80 dl / g or more, the polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more. Step of producing the recycled resource-derived raw material (a) containing the above C.I. Step D. To prepare a recycled resource-derived raw material (b) containing polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, which is recovered from the polyester film. Steps of melt-kneading the mixed raw materials of (a) and (b) and then molding them into a film (2) In the step (1) of the above step D, the mixed raw materials are melt-kneaded, then melt-extruded and cooled. A form that is a molding process of molding into a film.
(3) In the above (1) or (2), the following step E is provided after the step D.
E. Stretching step to stretch in the longitudinal direction and / or the width direction

As described above, according to a particularly preferable production method of this film, the recycled resource-derived raw material (a) having an intrinsic viscosity (IV) adjusted to 0.80 dl / g or more and the intrinsic viscosity (IV) being 0.60 dl / g. By using the recycled resource-derived raw material (b) of g or less, it is possible to obtain a film having excellent strength while being a film obtained from substantially 100% recycled resource raw material.

Further, by incorporating a fluorescent whitening agent in the film, the color tone of the present film can be improved, and it is possible to identify that the present film is obtained from a recycled product.

In the above step A, for example, the recovered polyester film is crushed by a crusher to produce polyester flakes, and the polyester flakes are extruded by an extruder and then rapidly cooled and solidified to produce recycled polyester pellets, that is, raw materials derived from recycled resources. Obtainable.

In the step B, the intrinsic viscosity (IV) is 0.80 dl / g or more by solid-phase polymerization of the recycled resource-derived raw material at 220 ° C. under vacuum to increase the intrinsic viscosity (IV) to 0.80 dl / g or more. The recycled resource-derived raw material (a) containing the polyester of the above can be obtained.

In the above step C, for example, the recovered polyester film having an intrinsic viscosity (IV) of 0.60 dl / g or less is pulverized by a pulverizer to produce polyester flakes, and the polyester flakes are extruded by an extruder and then rapidly cooled. By solidifying, recycled polyester pellets, that is, a raw material derived from recycled resources (b) can be obtained.
Further, by using the raw material derived from the recycled resource (b), there is an advantage that the productivity and cost of the film can be maintained while maintaining the mechanical strength of the film.

In the above step D, for example, in addition to a manufacturing method by a coextrusion method including a step of putting the raw materials of each layer into different extruders and melt-extruding them into a sheet from a T die, they are separately among a plurality of extruders and the like. It can be molded into a film shape by a method of laminating films that are melted into a film and extruded from a die outlet.
In particular, a method of molding into a film by a coextrusion method is preferable.

In the step E, a stretched film can be obtained by stretching the unstretched film produced in the step D in one direction and / or in a direction orthogonal to the unstretched film with a roll or tenter type stretching machine.

More specifically, in the stretching step, the unstretched sheet is stretched in the longitudinal direction (longitudinal direction (MD)) by a roll or tenter type stretching machine in one direction.
The stretching temperature at this time is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.0 to 7.0 times, preferably 2.5 to 5.0 times.

Next, it is stretched in a direction orthogonal to the stretching direction of the first stage (lateral direction (TD)), in which case the stretching temperature is usually 70 to 170 ° C. and the stretching ratio is usually 3.0 to 7.0. It is double, preferably 3.5 to 6.0 times.
Then, the heat treatment is subsequently performed at a temperature of 180 to 270 ° C. under tension or relaxation within 30% to obtain a biaxially oriented film.

In the above stretching, a method of stretching in one direction in two or more steps can also be adopted.
In that case, it is preferable that the stretching ratios in the two directions are finally within the above ranges.

(Use)
This film includes optical filters such as AR film, NIR film, and EMI film, optical films such as diffusion film and prism film, card materials, label materials, electronic materials, packaging materials, graphic materials (photographic materials), and plate-making films. It can be used for general industrial materials such as magnetic recording media, various process papers, and OHP films, and since it is composed of substantially 100% recycled resource-derived raw materials, it contributes greatly to the environment and reduces the environmental load. Can contribute to.

(Explanation of words, etc.)
In the present invention, when "X to Y" (X, Y are arbitrary numbers) is described, it means "X or more and Y or less" and "preferably larger than X" or "preferably Y". It also includes the meaning of "smaller".

Further, when described as "X or more" (X is an arbitrary number), it includes the meaning of "preferably larger than X" and is described as "Y or less" (Y is an arbitrary number). In this case, unless otherwise specified, it also includes the meaning of "preferably smaller than Y".

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Manufacturing of raw materials derived from recycled resources>
a) Preparation of regenerated polyester pellets (1) A self-recovering polyester film having no coating layer was pulverized and treated to obtain regenerated polyester pellets (a) having an intrinsic viscosity (IV) of 0.57 dl / g.
(2) A self-recovering polyester film having no coating layer was pulverized and treated to obtain recycled polyester pellets (b1) having an intrinsic viscosity (IV) of 0.54 dl / g.
(3) A self-recoverable polyester film having a coating layer was pulverized and treated to obtain a regenerated polyester pellet (c) having an intrinsic viscosity (IV) of 0.58 dl / g.
(4) Regenerated polyester pellets (b1) having an intrinsic viscosity (IV) of 0.54 dl / g are solid-phase polymerized at 220 ° C. under vacuum, and recycled polyester pellets (b2) having an intrinsic viscosity (IV) of 0.85 dl / g. ) Was obtained.

b) Production of recovered polyester In a film obtained as raw materials for the front and back layers, recycled polyester pellets (a), recycled polyester pellets (b1), and silica particles (x1) having an average particle size of 2.7 μm as a virgin raw material. The contents were mixed so as to be (a) 16.48% by mass, (b1) 4.08% by mass, and (x1) 0.04% by mass, respectively, and used as a raw material for the intermediate layer with the recycled polyester pellet (c). , Recycled polyester pellet (b2), regenerated polyester pellet (b1), and (x2) virgin raw material fluorescent whitening agent (4,5'-Biz (2-benzozolly) stilbene) in the film. (C) 52.93% by mass, (b2) 23.41% by mass, (b1) 3.01% by mass, and (x2) 0.05% by mass, respectively. Each of them was supplied to a shaft extruder, melted and kneaded at 280 ° C., merged with a multilayer T-die so as to have a composition ratio of A / B / A = 3/32/3, and extruded. An unstretched film composed of two types and three layers was obtained by quenching and solidifying on a casting drum whose surface temperature was set to 28 ° C.
Then, after stretching 3.40 times in the longitudinal direction (longitudinal direction) at 87 ° C, it is guided to a tenter, stretched 4.04 times in the width direction (horizontal direction) at 120 ° C, and then heat-treated at 233 ° C. A biaxially stretched film having a thickness of 38 μm was obtained by relaxing 4.76% in the transverse direction.
Next, slits were made from positions 255 mm from both ends of the obtained biaxially stretched film, and the surplus generated at the time of the slit was collected as slit ears, crushed and processed, and the recovered polyester (d) was obtained. did.
The intrinsic viscosity (IV) of the recovered polyester (d) is calculated to be 0.60.

[Example 1]
Recycled polyester pellets (a), regenerated polyester pellets (b1), and silica particles (x1) having an average particle size of 2.7 μm as raw materials for the front and back layers are contained in the film (a). ) 13.47% by mass, (b1) 3.33% by mass, (x1) 0.03% by mass, and as raw materials for the intermediate layer, recycled polyester pellets (c) and recycled polyester pellets (b2). ), Recycled polyester pellets (b1), (x2) virgin raw material fluorescent whitening agent (4,5'-Bis (2-benzozollyl) stilbene), and recovered polyester (d) in the film obtained. The amounts are (c) 43.24% by mass, (b2) 19.13% by mass, (b1) 2.46% by mass, (x2) 0.04% by mass, and (d) 18.30% by mass, respectively. To each of the two vented twin-screw extruders, melted and kneaded at 280 ° C., and merged with a multi-layer T-die so that the composition ratio was A / B / A = 3/32/3. Extruded. An unstretched film composed of two types and three layers was obtained by quenching and solidifying on a casting drum whose surface temperature was set to 28 ° C.
Then, after stretching 3.40 times in the longitudinal direction (longitudinal direction) at 87 ° C, it is guided to a tenter, stretched 4.04 times in the width direction (horizontal direction) at 120 ° C, and then heat-treated at 233 ° C. A polyester film 1 derived from a recycled resource having a thickness of 38 μm was obtained by relaxing 4.76% in the lateral direction.
The recycled resource-derived polyester film 1 is formed from a material containing 99.93% by mass of a recycled resource-derived raw material.
Further, the color tone of the recycled resource-derived polyester film 1 was improved.
The content of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less in the A layer is 99.80% by mass, and the intrinsic viscosity (IV) in the B layer is 0.60 dl / g. The content of polyester having g or less is 76.96% by mass, and the content of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more is 23.00% by mass.

[Example 2]
A recycled resource-derived polyester film 2 was obtained in the same manner as in Example 1 except that the film had a thickness of 50 μm and had a composition ratio of A / B / A = 4/4 / 42/4.
The recycled resource-derived polyester film 2 is formed from a material containing 99.93% by mass of a recycled resource-derived raw material.
Further, the color tone of the recycled resource-derived polyester film 2 was improved.
The content of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less in the A layer is 99.80% by mass, and the intrinsic viscosity (IV) in the B layer is 0.60 dl / g. The content of polyester having g or less is 76.96% by mass, and the content of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more is 23.00% by mass.

Table 1 shows various physical characteristics of the recycled resource-derived polyester films 1 and 2 produced in Examples 1 and 2.

The tensile strength (MPa) was measured as follows.

(Tensile strength)
Recycled resource-derived polyester films 1 and 2 were cut into a rectangle with a width of 15 mm and stretched at a tensile speed of 200 mm / min with a section length of 50 mm using a tensile tester to determine the tensile strength, that is, the stress at break.

The recycling rate means the usage rate of the recycled resource-derived raw material with respect to the entire material constituting the recycled resource-derived polyester film, and the unit is mass%.

Claims (12)

Formed from materials containing recycled resource-derived raw materials recovered from polyester film,
The recycled resource-derived raw material contains two or more kinds of polyesters having different intrinsic viscosities (IV).
At least one of the polyesters is a recycled resource-derived polyester film having an intrinsic viscosity (IV) of 0.80 dl / g or more. The recycled resource-derived polyester film according to claim 1, wherein at least one of the two or more kinds of polyesters has an intrinsic viscosity (IV) of 0.60 dl / g or less. The recycled resource-derived polyester film according to claim 1 or 2, wherein the recycled resource-derived raw material comprises a self-recovering raw material produced in the production process of the polyester film. The recycled resource-derived polyester film according to any one of claims 1 to 3, wherein the material contains a fluorescent whitening agent. The recycled resource-derived polyester film according to any one of claims 1 to 4, wherein the polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more is solid-phase polymerized. The recycled resource-derived polyester film according to any one of claims 1 to 5, which has a laminated structure of two or more layers. The recycled resource-derived polyester film according to claim 6, wherein a layer other than the outermost layer contains a fluorescent whitening agent. The recycled resource-derived polyester film according to any one of claims 1 to 7, wherein the material contains 99% by mass or more of a recycled resource-derived raw material. A release film provided with a release layer on at least one side of the recycled resource-derived polyester film according to any one of claims 1 to 8. A method for producing a recycled resource-derived polyester film, which comprises the following steps (1) to (4).
(1) Step of preparing recycled resource-derived raw material recovered from polyester film (2) Solid-phase polymerization of polyester contained in the recycled resource-derived raw material is performed to increase the intrinsic viscosity (IV) of the polyester to 0.80 dl /. Step of producing the recycled resource-derived raw material (a) containing polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more by setting the intrinsic viscosity (IV) to g or more (3) The intrinsic viscosity (IV) recovered from the polyester film. Step of producing recycled resource-derived raw material (b) containing polyester having an intrinsic value of 0.60 dl / g or less (4) Step of melt-kneading the mixed raw materials of (a) and (b) and then molding them into a film. The method for producing a recycled resource-derived polyester film according to claim 10, wherein the step (4) is a molding step in which the mixed raw materials are melt-kneaded, melt-extruded, cooled, and molded into a film. The method for producing a recycled resource-derived polyester film according to claim 10 or 11, further comprising the following step (5) after the step (4).
(5) Stretching step of stretching in the longitudinal direction and / or the width direction