JP6062282B2 - White polyamide film - Google Patents

Description

The present invention relates to a laminate having a concealing property suitable for packaging of non-food such as food packaging, detergents, and industrial uses.

At present, it is common to provide concealment properties in order to prevent the contents from being deteriorated by ultraviolet rays or not to show the contents in the packaging of foods and non-foods. Typical examples include an aluminum foil, a film having a concealing property, and a method of providing an ink layer having an appropriate thickness, and various methods for imparting concealing properties are known.

For packaging with excellent concealment, aluminum foil is the most suitable, but it is not compatible with metal detectors and microwave ovens, and there are problems such as damaging incinerators when discarded and incinerated. Packaging that does not use aluminum foil has been desired.

There are a white polyester film, a white polyethylene film, a white polypropylene film, and the like as the film having a concealing property, and packaging in which these films are laminated is known. However, the stretched white polyester film or white polypropylene film has insufficient pinhole resistance, and the unstretched white film has a large variation in film thickness. The white polyethylene film is not compatible with retort processing, and the white polypropylene film can be retort processed. However, when the retort process is performed, depending on the contents, the appearance of the film may be damaged or the taste of the contents may be changed easily. It was not perfect.

For these reasons, a method of providing an ink layer applied to an appropriate thickness is often employed, but the method of applying ink once does not provide sufficient concealment and is applied twice or more. Therefore, since two or more printing coaters are used for printing, it is not suitable for printing with multicolor design, and the thicker the ink layer, the higher the residual solvent amount and the higher the cost. There was a problem of becoming. Furthermore, for example, the bottom material, lid material, and packaging bags of standing packaging are provided with a white-only printing process to provide concealment in the process of printing on the film even in the process up to the bag. However, it has been desired to omit the printing process itself from the reduction of time and cost, and to shift to the laminating process without going through the printing process.

From such a background, there has been a demand for a stretched film that has concealability, can be retorted, and has excellent pinhole resistance. The white polyamide film having a hiding property contains 5 to 40% by weight of titanium oxide and 60 to 95% by weight of crystalline polyamide resin, has a hiding degree of 0.4 or more and a whiteness of 65 to 100% or more. A white film characterized by this has been proposed (Patent Document 1).

International Publication No. 2010/084846

The white film described in Patent Document 1 has excellent concealability and pinhole resistance, and the difference between the maximum value and the minimum value of the optical density (OD value) regardless of the length of the roll in the machine direction of the stretched film. Is 0.05 or less, but when the length in the width direction is 3000 mm or more, the difference between the maximum value and the minimum value of the optical density is 0.10 or more, and there is a difference in white. There was a bug. Further, the patent document discloses a laminate in which a polyamide layer (B) made of a polyamide resin is laminated on at least one side of a layer (A) containing 10 to 60% by weight of titanium oxide and 40 to 90% by weight of a crystalline polyamide resin. The body is known. With this laminate, the laminate strength when the adhesive layer and the olefin film that can be retorted are bonded together is excellent, but at the time of measuring the laminate strength after retorting at 120 ° C. for 30 minutes, 3.0 N It may be peeled off at the interface between the layers of the (A) layer having a strength of less than / cm and containing titanium oxide, and it was insufficient as a laminate that can be suitably used even after retorting.

The present invention solves the above-mentioned problems, has good concealability while maintaining the same strength as a biaxially stretched polyamide film, reduces the variation in optical density in the width direction, and is sufficient even after retorting An object of the present invention is to provide a biaxially stretched white polyamide film having an excellent laminate strength.

As a result of diligent research to solve the above-mentioned problems, the present inventors have improved the dispersion of optical density in the width direction and the strength of the laminate by adding an appropriate amount of amorphous polyamide resin to the concealing layer containing titanium oxide. I found out that I could improve.
That is, the present invention includes a biaxially stretched white polyamide containing 5 to 25% by mass of amorphous polyamide, 15 to 60% by mass of titanium oxide, and 15 to 80% by mass of crystalline polyamide. Film (hereinafter, single-layer white polyamide film) or layer containing 5 to 25% by mass of amorphous polyamide, 15 to 60% by mass of titanium oxide, and 15 to 80% by mass of crystalline polyamide (B ) (Hereinafter referred to as a titanium oxide-containing layer) is a biaxially stretched white polyamide film (hereinafter referred to as a multilayer white polyamide film) in which a layer (A) made of a polyamide resin not containing titanium oxide is laminated on at least one surface. Hereinafter, when it corresponds to both a single layer white polyamide film and a multilayer white polyamide film, it is simply referred to as a “white polyamide film”.

The white polyamide film of the present invention is a film having a small difference between the maximum value and the minimum value of optical density (OD value) in the width direction of the stretched film roll. In addition, when the multilayer white polyamide film is a laminate with a polyolefin film via an adhesive layer, it is extremely rare to peel off at a titanium oxide-containing layer at the time of laminate strength measurement even after retorting at 120 ° C. for 30 minutes, A strength of 3.0 N / cm or more is obtained, and it can be suitably used as a laminate. Moreover, the white printing process can be omitted by using the laminate of the present invention.

The white polyamide film of the present invention can be obtained by containing a certain amount of amorphous polyamide in the titanium oxide-containing layer.

Polyamide resins used in the present invention include poly-ε-capramide (nylon 6), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebamide (nylon 610), polyundecamide (nylon 11), polylauramide (Nylon 12), polytetramethylene adipamide (nylon 46), polymetaxylylene adipamide (nylon MXD6), polymetaxylylene sebacamide, polymetaxylylene veramide, polyparaxylylene adipamide and these A mixture, a copolymer, etc. can be illustrated. In particular, among the above polyamide resins, nylon 6 is particularly preferable when considering all of the cost, operability, mechanical properties, heat resistance, and shrinkage properties when formed into a film.

Various additives and modifiers that are usually blended in the polyamide resin as necessary, for example, heat resistance stabilizer, ultraviolet absorber, light stabilizer, antioxidant, antistatic agent, blocking agent, antifogging An agent, a crystal nucleating agent, a release agent, a plasticizer, a crosslinking agent, a flame retardant, and the like may be blended.

In addition, various inorganic lubricants and organic lubricants may be added to the polyamide resin in order to improve the slip property of the film in the polyamide resin. These lubricants include clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, magnesium aluminosilicate, glass balloon, carbon black, zinc oxide. , Antimony trioxide, zeolite, hydrotalcide and the like.

In the present invention, crystalline polyamide and amorphous polyamide are classified according to their heat of crystal fusion. Amorphous polyamide refers to a polyamide having a measured heat of crystal fusion of less than 1 cal / g when measured at a rate of temperature increase of 20 ° C./min using a differential thermal analyzer. Crystalline polyamide refers to those having a heat of crystal fusion of 1 cal / g or more. The glass transition point (Tg) of the amorphous polyamide is a value measured with a differential thermal analyzer as a midpoint glass transition temperature according to JIS K 7121, and is preferably 70 to 170 ° C.

The amorphous polyamide preferably has an alicyclic diamine and / or an aliphatic diamine as a main skeleton, and has adipic acid, terephthalic acid and / or isophthalic acid as an acid component. Specifically, the main skeleton is hexamethylene diamine, caprolactam, tetramethylene diamine, methylpentane diamine or nonamethylene diamine, and examples thereof include those obtained by single or multiple polymerization of adipic acid, terephthalic acid and / or isophthalic acid. More specifically, a polymer of hexamethylenediamine-isophthalic acid, a polymer of hexamethylenediamine-terephthalic acid, a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid, and the like can be exemplified.

The single-layer white polyamide film in the present invention comprises 25 to 90% by mass of crystalline polyamide, 5 to 50% by mass of titanium oxide, and 5 to 25% by mass of amorphous polyamide. When the crystalline polyamide is less than 25% by mass and / or the titanium oxide exceeds 50% by mass, the strength is lowered, which is not preferable. When the crystalline polyamide exceeds 90% by mass and / or the titanium oxide content is less than 5% by mass, the optical density (OD value) of the white film is low and sufficient concealing property cannot be obtained. When the amorphous polyamide is less than 5% by mass, titanium oxide does not spread uniformly in the width direction when the film is stretched in the width direction, and the difference between the maximum value and the minimum value of the optical density (OD value) increases. Therefore, it is not preferable. On the other hand, when the amorphous polyamide exceeds 25% by mass, not only the number of breaks of the film during stretching increases but also the strength decreases, which is not preferable.

The titanium oxide-containing layer of the multilayer white polyamide film in the present invention comprises 15 to 80% by mass of crystalline polyamide, 15 to 60% by mass of titanium oxide, and 5 to 25% by mass of amorphous polyamide. When the crystalline polyamide is less than 15% by mass and / or the titanium oxide exceeds 80% by mass, the strength is low, the laminar strength is low, and it is not preferable because it peels between the layers of the titanium oxide layer. When the crystalline polyamide exceeds 80% by mass and / or the titanium oxide content is less than 15% by mass, the optical density (OD value) of the white film is low and sufficient concealability cannot be obtained. If the amorphous polyamide is less than 5% by mass, it is easily peeled between the layers containing the titanium oxide, and not only contributes to a decrease in the laminate strength, but the titanium oxide has a width when the film is stretched in the width direction. The difference between the maximum value and the minimum value of the optical density (OD value) does not spread uniformly in the direction. On the other hand, when the amorphous polyamide exceeds 25% by mass, not only the number of breaks of the film during stretching increases but also the strength decreases, which is not preferable.

The particle type of the titanium oxide particles contained is not particularly limited and is not limited to any of anatase type, rutile type, bulcalite type and the like, but rutile type titanium oxide is preferable from the viewpoint of cost and concealment improvement.

Titanium oxide is known to have a photoactive effect. In other words, free radicals are generated on the surface of the titanium oxide particles when irradiated with ultraviolet rays. When these free radicals are incorporated into the polymer matrix, the polymer chains are decomposed and cause yellowing of the film. Therefore, the titanium oxide particles used are preferably subjected to surface treatment. Surface treatment includes inorganic treatment and organic treatment.

Examples of the inorganic treatment of titanium oxide include alumina treatment, silica treatment, titania treatment, zirconia treatment, tin oxide treatment, antimony oxide treatment, and zinc oxide treatment. Among these, alumina treatment is preferable. As the organic treatment, it can be treated with polyols such as pentaerythritol and trimethylolpropane, amines such as triethanolamine and trimethylolamine, and silicones such as silicone resin and alkylchlorosilane.

The particle size of titanium oxide to be used is not particularly limited, but the average particle size is preferably in the range of 0.1 to 0.5 μm, more preferably in the range of 0.2 to 0.4 μm. When the average particle size is less than 0.1 μm, the dispersibility in the polyamide resin is poor, and coarse aggregates are scattered in the film, generating pinholes in the film and reducing the product value. On the other hand, if the average particle size exceeds 0.5 μm, the frequency of the film breaking when the polyamide resin layer is formed tends to increase, and the productivity tends to decrease.

The method for blending titanium oxide with polyamide is not particularly limited, and can be blended at an arbitrary point in the manufacturing process. For example, a method of adding titanium oxide at the time of polymerization of polyamide, a method of manufacturing a master batch in which titanium oxide is kneaded in a high concentration in a polyamide, and adding and diluting the master batch (master batch method), Examples thereof include a method of melt-mixing titanium oxide with an extruder. In this invention, the method of adjusting to a desired titanium oxide density | concentration before forming into a film using a masterbatch method is employ | adopted preferably.

The optical density (OD value) of the white polyamide film of the present invention is required to be 0.30 or more, preferably 0.35 or more. If the optical density is less than 0.30, the light shielding and concealing properties are insufficient when the packaging bag is formed, and the contents containing fats and oils are liable to be oxidized and deteriorated mainly by light rays such as ultraviolet rays. Since it may be seen through visually, it is not preferable. In order to make the concealment degree of the white polyamide film within a range of 0.30 or more, the titanium oxide content is adjusted within the range specified in the present invention, and the thickness of the white film is adjusted. Note that the greater the optical density, the higher the concealability.

In the width direction of the stretched film roll of the white polyamide film, the difference between the maximum value and the minimum value of the optical density (OD value) needs to be 0.05 or less. When the difference between the maximum value and the minimum value exceeds 0.05, when the bag is formed, the contents are visible and transparent, which is not preferable.

The tensile strength of the white polyamide film to be used needs to be 180 MPa or more. More preferably, it is 190 to 220 MPa. When the tensile strength is less than 180 MPa, the practical strength (pinhole characteristics) after bag making is insufficient.

The thickness of the white polyamide film can be appropriately selected according to the required concealment degree, target mechanical strength, and whiteness. When the white polyamide film is used for packaging, the total thickness is preferably 10 μm to 50 μm, more preferably 15 μm to 30 μm in order to maintain the original pinhole resistance of the polyamide film.

Any surface treatment may be applied to one side or both sides of the white polyamide film as long as the effect is not hindered. Easy adhesion treatment for improving adhesion, coating treatment for improving antistatic performance, sliding performance and gas barrier performance, and corona discharge treatment for improving wettability may be performed.

The thickness structure of the polyamide layer (A) and the titanium oxide-containing layer (B) of the multilayer white polyamide film is a ratio of the total thickness (thickness 1) of the (A) layer and the total thickness (thickness 2) of the (B) layer. Is preferably in the range of (thickness 1) / (thickness 2) = 1/4 to 6/1, more preferably (thickness 1) / (thickness 2) = 1/3 to 5/1. is there. If (thickness 1) / (thickness 2) = less than 1/4, the frequency of breakage increases when the film is stretched, resulting in a decrease in productivity, and (thickness 1) / (thickness 2) = over 6/1. In this case, it becomes difficult to maintain an optical density (OD value) of 0.30 or more.

The multilayer white polyamide film has (A) / (B), (A) / (B) / (A), (A) / (B) in which a polyamide layer (A) and a titanium oxide-containing layer (B) are arranged. ) / (A) / (B) / (A). In the configuration having three or more layers, (A) and (B) may be the same or different layers.

Moreover, the layer which consists of polyamide resin which does not contain the titanium oxide of a multilayer white polyamide film may consist of a multilayer. When the polyamide layer is composed of (X) / (Y), (X) / (Y) / (Z), etc., materials for imparting surface characteristics of the polyamide layer and improving the anti-pinhole performance are appropriately met for each layer. May be blended.

For polyolefin film, for example, low density polyethylene, medium density polyethylene, high density polyethylene, linear polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid / methacrylic acid copolymer, ethylene- A film called a sealant film such as an acrylic acid / methacrylic acid ester copolymer, an acid-modified polyethylene / polypropylene resin, or a polyvinyl acetate resin can be used. These may be used alone, may be used by copolymerization or melt-mixing with other resins or components, or may be used after modification. These resin components may be used in a single layer or in multiple layers with at least one or more types of resin components. The thickness is determined according to the application, but is generally 15 to 200 μm.

An adhesive layer may be provided when the white polyamide film and the sealant film are bonded together. As the coating agent used when forming the adhesive layer, known ones are used. Examples of the coating agent include isocyanate, polyurethane, polyester, polyethyleneimine, polybutadiene, polyolefin, and alkyl titanate. Among these, in consideration of effects such as adhesion, heat resistance, and water resistance, an isocyanate-based, polyurethane-based, or polyester-based coating agent is preferable, and a mixture of one or more of isocyanate compounds, polyurethanes, and urethane prepolymers. And a reaction product, a mixture of one or more of polyester, polyol and polyether with isocyanate and a reaction product, or a solution or dispersion thereof. The adhesive used for the packaging bag used in the present invention is preferably an adhesive that can be boiled or an adhesive that can be retorted, but is not limited thereto.

As a forming method for bonding the adhesive layer and the sealant film to the white polyamide film, a known method is used. For example, lamination methods such as dry lamination method, wet lamination method, solvent-free dry lamination method, extrusion lamination method, co-extrusion method in which two or more resin layers are simultaneously extruded and laminated, coating method in which a film is formed with a coater, etc. However, the dry lamination method is preferable in view of adhesion, heat resistance, water resistance, and the like.

The thickness of the adhesive layer is preferably 0.05 to 5.0 μm in order to sufficiently enhance the adhesion between the white polyamide film and the sealant film, and is particularly 1 when the adhesive is applied by a dry lamination method. It is preferable that it is 0.0-5.0 micrometers. The concentration of the adhesive layer formation (= solid content) can be appropriately changed depending on the specifications of the coating apparatus and the drying / heating apparatus, but a laminating strength can be obtained with a too dilute solution. On the other hand, if the concentration is too high, it is difficult to obtain a uniform paint, which tends to cause problems in paintability. From such a viewpoint, the concentration (= solid content) of the adhesive layer is preferably in the range of 5 to 50%.

Although the method of apply | coating an adhesive bond layer to a white polyamide film is not specifically limited, Ordinary methods, such as gravure roll coating, reverse roll coating, wire bar coating, and air knife coating, can be used.

The laminate strength after retorting of the laminate of the present invention needs to be 3.0 N / cm or more. A laminate strength of less than 3.0 N / cm is not preferable because the possibility of delamination is increased in hot water treatment, particularly during retort treatment.

The white polyamide film of the present invention can be suitably used as a packaging material that requires concealment while utilizing the properties of the polyamide film. For example, an arbitrary sealant film can be bonded to a white polyamide film and heat-sealed to form a bag-like body, or used as a packaging body such as a lid material for tray packaging. Examples of the form of the bag include a three-side seal bag, a four-side seal bag, a pillow bag, and a standing pouch.

As the laminate using the white polyamide film of the present invention, white polyamide film / sealant film, white polyamide film / barrier layer / sealant film, white polyamide film / white polyamide film / sealant film, polyester film / white polyamide film / sealant A laminated structure of a film, polyamide film / white polyamide film / sealant film, polyester film / white polyamide film / barrier layer / sealant film or polyester film / barrier layer / white polyamide film / sealant film, etc. may be mentioned. In these laminates, an adhesive layer is provided between the films as necessary. The barrier layer is preferably a film, a coating layer, or a vapor deposition film that realizes an oxygen permeability of 100 ml / (m 2 · d · MPa) or less in an environment of a temperature of 20 ° C. and a relative humidity of 65% RH.

The white polyamide film of the present invention is produced by the following method.

For example, a chip containing crystalline polyamide, titanium oxide, and amorphous polyamide is heated and melted with an extruder and extruded into a film form from a T-die, and rotated by a known casting method such as an air knife casting method or an electrostatic application casting method. It is obtained by cooling and solidifying on a cooling drum to form an unstretched film and subjecting this unstretched film to a stretching treatment. In the present invention, the white polyamide film needs to be a stretched film in order to maintain sufficient strength. In addition, if the unstretched film is oriented, the stretchability may be lowered in a subsequent step. Therefore, it is preferable that the unstretched film is substantially amorphous and non-oriented.

The stretch ratio of the stretched film is preferably 1.5 times or more in the case of uniaxial stretching, and also in the case of longitudinal and transverse biaxial stretching, preferably 1.5 times or more in the longitudinal and lateral directions, and usually 3 times or more in area magnification, preferably area. The magnification is 6 to 20 times, more preferably 6.5 to 13 times. By setting it in this range, it becomes possible to obtain a film having excellent mechanical properties.

The film that has undergone the stretching process is heat-set at a temperature of 150 to 220 ° C. in the tenter where the stretching process has been performed, and in the range of 0 to 10%, preferably 2 to 6% as necessary, in the machine direction and A lateral relaxation treatment is performed.

In order to reduce the heat shrinkage rate, it is desirable not only to optimize the temperature and time of the heat setting time, but also to perform the heat relaxation process at a temperature lower than the maximum temperature of the heat setting process.

The stretching method of the white polyamide film is not particularly limited, and can be suitably formed by a sequential biaxial stretching method or a simultaneous biaxial stretching method.

The width of the white polyamide film after stretching is preferably 1000 mm or more, and the difference between the minimum value and the maximum value of the optical density is 0.05 or less for all rolls, regardless of how many slits are obtained. Is preferred. More preferably, the phenomenon is the same at 3000 mm or more. When the width is smaller than 1000 mm, the manufacturing cost per hour increases, which is not preferable. Moreover, in order to make the difference between the minimum value and the maximum value of the optical density 0.05 or less, a method of slitting in the width direction and adjusting to an arbitrary width can be considered. However, a roll having a large difference between the minimum value and the maximum value can be considered. Will be discarded and the yield is never high.

EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

1. Measurement Method Regarding the measurement method described below, a sample that was allowed to stand for 2 hours or more in an environment of 23 ° C. and 50% RH was measured in an environment of 23 ° C. and 50% RH.
(1) Thickness of each layer Using a universal zoom microscope MULTIZOOM AZ100 manufactured by Nikon Corporation, the cross section of the film was observed at a magnification of 1000 times, and the thickness of each layer was measured.
(2) Optical density (OD value)
A value measured using a transmission nozzle having a diameter of 3 mm by an optical densitometer TR932 manufactured by Macbeth Co. was used as an optical density (OD value). Sampling was carried out every 100 mm up to a position of 1500 mm from the center of the film width to the left and right sides. If the difference between the maximum value and the minimum value of the optical density at that time was 0.05 or less, ◯, if 0.05 to 0.10 or less, △, if it exceeded 0.10 X.
(Good) ○>△> × (Bad)
(3) Tensile strength AS-1S type autograph manufactured by Shimadzu Corporation was used and measured according to JIS-K7127, and average values in the MD direction (machine direction) and TD direction (width direction) were read. The measurement was performed on five samples, and the average value was taken as the tensile strength. When the strength of the film was 180 MPa or more for both MD and TD, it was rated as “◯”, and when it was less than 180 MPa, it was marked as “X”.
(Good) ○> × (Bad)
(4) One side of the laminate film making base film is subjected to corona discharge treatment, and the corona-treated surface is urethane-based adhesive (Takelac Main Agent A-525S / Takenate Curing Agent A-50 two-component type manufactured by Mitsui Chemicals). Was applied, and the applied film was dried at 80 ° C. for 10 seconds so that the application amount was 3 g / m 2. The corona-treated surface of the adhesive-coated surface and the sealant film (non-stretched polypropylene film, RXC-22 retortable type manufactured by Mitsui Chemicals, Inc., thickness 50 μm) were bonded together with a nip roll at 50 ° C. Next, the laminated film was subjected to an aging treatment at 40 ° C. for 5 days to obtain a laminate film.
(5) Retort processing test The laminate film obtained was cut into outer dimensions of MD 300 mm and TD 200 mm, and a three-sided bag was created with an impulse sealer manufactured by Fuji Impulse Co., Ltd. so that the outer dimensions were MD 150 mm, TD 200 mm, and seal width 10 mm. Then, 100 ml of pure water is filled and sealed, using a high-temperature and high-pressure cooking sterilizer (RCS-60SPXTG manufactured by Nisaka Manufacturing Co., Ltd.) under conditions of a temperature of 120 ° C. and a pressure of 1.8 kgf / cm ² For 30 minutes.
(6) Measurement of laminate strength after retort treatment test The retorted laminate film is cut into MD100mm x TD15mm strips, and the substrate film and sealant are peeled 30mm into the MD with tweezers to create a laminate strength test piece. did. After being left in an environment of 23 ° C. and 50% RH for 2 hours or more, each peeled end was fixed using an AS-1S type autograph manufactured by Shimadzu Corporation equipped with a 50N measurement load cell and a sample chuck. Thereafter, the test piece was kept in the “T-type” while being peeled 30 mm from the MD at a tensile speed of 300 mm / min, and the average value of the strength and the interface obtained by the measurement were specified. The measurement was performed on 20 samples, and the average value thereof was determined as the laminate strength. When the laminate strength at that time was 3.0 N / cm or more, it was evaluated as ◯, and when it was less than 3.0 N / cm, it was evaluated as x.
(Good) ○> × (Bad)
Moreover, about the obtained interface, when it was 1 point or less that it peeled between the layers of a titanium oxide content layer, it was set as (circle), and other than that was set as x. Subsequently, about the obtained interface, the case where it was an interlayer of a titanium oxide content layer was written together as interface A, and the case where it was other than that was written together as interface B. The interface B is preferable because it can be said that the interface B is satisfactorily adhered.
(Good) ○> × (Bad)

2. Raw materials The raw materials used in the following examples and comparative examples are as follows.
(1) Crystalline polyamide
Nylon 6 (Unitika A1030BRF) (Relative viscosity 3.0)
(2) Amorphous polyamide EMS Grivory G16 (glass transition point 125 ° C.)
Gribory G21 (glass transition point 125 ° C) manufactured by EMS
Gribory XE3038 (glass transition point 140 ° C) manufactured by EMS
(3) KRONOS titanium oxide (rutile type, average particle size 0.4 μm) manufactured by titanium oxide titanium industry

Example 1
Nylon 6 is dry blended with titanium oxide and Grivory G16, then melt-kneaded with a 30mm diameter twin-screw extruder with a cylinder temperature setting of 250 ° C, extruded into a strand, cooled, solidified, cut and pelleted Of titanium masterbatch 1 was obtained.
The titanium master batch 1 was supplied to a single-screw extruder set at a cylinder temperature of 260 ° C., extruded from a T die, and contacted with a cooling roll at a set temperature of 20 ° C. to obtain an unstretched sheet having a thickness of 180 μm. The obtained unstretched sheet was immersed in a hot water tank adjusted to 50 ° C. for 2 minutes, and stretched at a stretching temperature of 180 ° C. for 3 times in length and 3.3 times in width by a simultaneous biaxial stretching machine, and at 200 ° C. for 5 seconds. The film was heat-treated, further subjected to a relaxation treatment of 5% in the lateral direction, and cooled to obtain a film roll having a total film thickness of 18 μm. This is designated as white polyamide film 1.

Examples 2 and 3
In production of the titanium master batch 1, pellets of the titanium master batch 2 were obtained by performing the same operation as in Example 1 except that Grivory G21 was used instead of G16 as the amorphous polyamide. And the film white polyamide film was obtained by operation similar to Example 1 using this. This is designated as white polyamide film 2.
Further, in the same manner, a white polyamide film 3 is a film prepared by producing a pellet of titanium master batch 3 obtained using Grivory XE3038 in the same manner as in Example 1.

Example 4
An unstretched sheet having a thickness of 180 μm was obtained by the same operation as in Example 1. The obtained unstretched sheet was stretched in the longitudinal direction at a stretching temperature of 60 ° C. and a stretching ratio of 2.8 times, and then stretched in the transverse direction to 3.5 times successively, followed by heat treatment at a temperature of 200 ° C. for 5 seconds. The film was further relaxed by 5% in the lateral direction while maintaining the temperature at 210 ° C., and then cooled and wound at 80 ° C. to obtain a film roll. This is designated as white polyamide film 4.

Examples 5 and 6
Except for changing the thickness of the unstretched sheet, the same operation as in Example 1 was performed to obtain a white polyamide film having a total film thickness of 15 and 30 μm. Let this be the white polyamide films 5 and 6.

Examples 7-13, Comparative Examples 1-5
A white polyamide film was obtained by the same operation as in Example 1 except that the composition of the titanium master batch was changed according to the film composition shown in Table 1. In Examples 9 and 13, the film thickness was changed in the same manner as in Examples 5 and 6. Let this be the white polyamide films 7-13.

Example 14
Using nylon 6 (A) and titanium masterbatch 1 (B), the layer structure of the film is in the order of (A) / (B) / (A), and (A) / (B) The ratio of the thickness of / (A) is (A) / (B) / (A) = 1/1/1 and is supplied to a single screw extruder set at a cylinder temperature of 260 ° C. Extrusion and contact with a cooling roll at a set temperature of 20 ° C. gave an unstretched sheet having a thickness of 180 μm. The obtained unstretched sheet was immersed in a hot water tank adjusted to 50 ° C. for 2 minutes, and stretched at a stretching temperature of 180 ° C. for 3 times in length and 3.3 times in width by a simultaneous biaxial stretching machine, and at 200 ° C. for 5 seconds. The film was heat-treated, further subjected to a relaxation treatment of 5% in the lateral direction, and cooled to obtain a film roll having a total film thickness of 18 μm. This is a white polyamide film 19.

Examples 15 and 16
A white polyamide film was obtained by the same operation as in Example 14 using titanium masterbatches 2 and 3. These are designated as white polyamide films 20 and 21, respectively.

Example 17
An unstretched sheet having a thickness of 180 μm was obtained in the same manner as in Example 14. The obtained unstretched sheet was stretched in the longitudinal direction at a stretching temperature of 60 ° C. and a stretching ratio of 2.8 times, and then stretched in the transverse direction to 3.5 times successively, followed by heat treatment at a temperature of 200 ° C. for 5 seconds. The film was further relaxed by 5% in the lateral direction while maintaining the temperature at 210 ° C., and then cooled and wound at 80 ° C. to obtain a film roll. This is a white polyamide film 22.

Examples 18 and 19
A white polyamide film having a total film thickness of 15 and 30 μm was obtained in the same manner as in Example 14 except that the thickness of the unstretched sheet was changed. This is designated as white polyamide films 23 and 24.

Examples 20, 21 and Comparative Examples 6-12
A white polyamide film was obtained in the same manner as in Example 14 except that the composition of layer B was changed as shown in Table 2. Let this be the white polyamide films 25, 26, and 32-38.

Example 22
Titanium masterbatch was prepared by changing the composition of layer B as shown in Table 2, and the layer structure (A) / (B) / (A) of nylon 6 (A) and titanium masterbatch (B) (A) / (B) / (A) = 5 μm / 20 μm / 5 μm A white polyamide film was obtained in the same manner as in Example 14 except that. This is a white polyamide film 27.

Examples 23-25
A titanium masterbatch was prepared in which the composition of layer B was changed as shown in Table 2, and a white polyamide film was obtained in the same manner as in Example 14. At this time, Examples 23 and 24 changed the layer thickness by changing the thickness of the unstretched sheet. In Example 25, the thickness ratio of the (A) and (B) layers was changed in the same manner as in Example 22. Let this be the white polyamide films 28-30.

Example 26
Nylon 6 (A) and titanium masterbatch (B) are in the order of (A) / (B) when the film is layered to obtain a white polyamide film by the same operation as in Example 14. It was. This is a white polyamide film 31. Moreover, when making this into a laminated body, it bonded together with the sealant so that (A) layer might face an adhesive agent.

Table 1 shows the resin configurations used in the production of the films of Examples 1 to 13 and Comparative Examples 1 to 5 and the characteristics of the obtained single-layer white polyamide films. Next, Table 2 shows the resin configurations used in the production of the films of Examples 14 to 26 and Comparative Examples 6 to 12 and the characteristics of the obtained multilayer white polyamide films.

The following can be seen from Examples 1 to 26 and Comparative Examples 1 to 12.

The white polyamide films 1 to 13 had excellent optical density and tensile strength, and had a small difference between the maximum and minimum optical density values.

The white polyamide films 14 and 15 were inferior in appearance because the blending ratio of amorphous polyamide was 0 and 3% by mass, and the difference between the maximum and minimum optical density values was large.

The white polyamide film 16 had a low tensile strength because the blending ratio of amorphous polyamide was 30% by mass.

Since the white polyamide film 17 has a small titanium oxide content of 3% by mass, it cannot be said that the optical density is as low as 0.30 or less and sufficient concealing property is obtained.

Since the white polyamide film 18 has a high titanium oxide content of 60% by mass, the tensile elongation was low.

The white polyamide films 19 to 31 have excellent optical density and tensile strength, a small difference between the maximum and minimum optical density values, and good strength values and interfaces can be obtained in laminate strength measurement after retort processing. It was.

Since the white polyamide films 32 and 33 contain 0 to 3% by mass of amorphous polyamide in the titanium oxide-containing layer, the difference between the maximum and minimum optical density values is large, and the laminate after retorting In the strength measurement, the strength value was low, a peeling interface in the titanium oxide-containing layer was obtained, and the laminate performance was insufficient.

The white polyamide film 34 had a low tensile strength because the blending ratio of the amorphous polyamide in the titanium oxide-containing layer was 30% by mass.

Since the white polyamide film 35 has a small content of titanium oxide in the titanium oxide-containing layer as low as 10% by mass, the optical density is as low as 0.30 or less, and it cannot be said that the white polyamide film 35 has a sufficient concealing property.

The white polyamide film 36 has a high titanium oxide content of 70% by mass in the titanium oxide-containing layer, so the tensile elongation is low, and the strength value is low in the laminate strength measurement after retort treatment. The peeling interface was obtained, and the laminating performance was insufficient.

In the white polyamide film 37, the blending ratio of the polyamide resin in the titanium oxide-containing layer is 90% by mass, so that the blending ratio of titanium oxide is 10% by mass or less. As a result, the optical density is sufficiently low as less than 0.30. It could not be said that it had a good concealment property.

In the white polyamide film 38, the blending ratio of the polyamide resin in the titanium oxide-containing layer is 10% by mass, so that the blending ratio of titanium oxide and amorphous polyamide is 90% by mass or less, resulting in low tensile elongation. Moreover, in the laminate strength measurement after the retort treatment, the strength value was low, a peeling interface in the titanium oxide-containing layer was obtained, and the laminate performance was insufficient.

Claims (4)

A biaxially stretched white polyamide film comprising 5 to 25% by mass of amorphous polyamide, 5 to 50% by mass of titanium oxide, and 25 to 90% by mass of crystalline polyamide, A biaxially stretched white polyamide film characterized by satisfying the requirements (1) to (3).
(1) The optical density (OD value) is 0.30 or more. (2) In the width direction of the stretched film roll, the difference between the maximum value and the minimum value of the optical density (OD value) is 0.05 or less. (3) The tensile strength is 180 MPa or more in both the machine direction and the width direction. From a polyamide resin containing 5 to 25% by mass of amorphous polyamide and 15 to 60% by mass of titanium oxide and 15 to 80% by mass of crystalline polyamide and containing no titanium oxide on at least one side of the layer (B) A biaxially stretched white polyamide film obtained by laminating a layer (A) to satisfy the following requirements (1) to (4).
(1) The optical density (OD value) is 0.30 or more. (2) In the width direction of the stretched film roll, the difference between the maximum value and the minimum value of the optical density (OD value) is 0.05 or less. (3) When a polyolefin film is laminated through a biaxially stretched white polyamide film and an adhesive layer, the laminate strength is 3.0 N / cm or more after retorting at 120 ° C. for 30 minutes. (4) Tensile Strength is 180 MPa or more in both machine direction and width direction A laminate in which an adhesive layer and a polyolefin film are sequentially laminated on at least one surface of the biaxially stretched white polyamide film according to claim 1 or 2. A package comprising the laminate according to claim 3.