JPS6122631B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester composite film and a method for producing the same. A polyester composite film consisting of a transparent polyethylene terephthalate layer and a transparent copolyester layer is described in GB 1465973. The co-polyester layer used herein has an exposed surface that is embossed and is indicative by brushstrokes or has a decorative pattern. It is known that thermoplastic films often have poor handling properties, such that it is difficult to wind the film into a reel and that processing in a processing mechanism is not smooth. Many proposals have been made to overcome these difficulties, for example it has been proposed to add filler particles, especially filler particles made of inorganic materials, to the film. As an example, it has been proposed to incorporate particles into the film having a particle size smaller than the thickness of the film to form surface projections on the film. Further, JP-A-51-8387 discloses a polyester laminated film that has excellent blocking resistance and slipperiness while maintaining excellent transparency and thermal adhesiveness. This film has a heat of crystal fusion of 7cal/
It consists of a laminate of a polymer film layer A having a particle size of 100 g or less and a polymer film layer B containing additive particles having a large particle size. However, in this laminated film, since the additive particles are contained in the relatively crystalline polymer film layer B, the particles are transferred from the interface between both polymer film layers to the amorphous polymer during film stretching and heat setting. Protruding into the film layer
It is easy to penetrate, and as a result, the surface protrusion effect due to the additive particles is reduced, which is not sufficient to achieve the handling suitability etc. aimed at by the present invention. The polyester composite film according to the present invention includes a first layer consisting of a highly crystalline molecular orientation layer of a first linear polyester and a first layer consisting of a substantially amorphous second linear polyester. a polyester composite film comprising an adhesive heat-sealable second layer, the second layer having an adhesive bond of 0.05 to 10
% by weight (based on the weight of the second layer) of a fine particulate additive having an average particle size greater than the thickness of the second layer and substantially uniformly distributed throughout the second layer; The exposed surface of the second layer has non-adhesive surface protrusions produced by the fine particulate additive, and the density per unit area of the surface protrusions is greater than that of the polymer surface (i.e. characterized in that the number of protrusion peaks with a peak height of at least 0.4 μm, measured from the average level of the valley bottom, is at least 50 per mm ² of the surface. By heating and softening the second linear polyester without softening or melting the first linear polyester constituting the first layer, and applying pressure thereto, the second layer can be applied to itself or the first linear polyester. A heat seal bond should be formed to the second layer, preferably both to itself and to the first layer. The polyester composite film is formed by solvent casting or extrusion of a second polyester layer onto the surface of a first linear polyester self-supporting film, preferably a biaxially oriented, heat-set film of polyethylene terephthalate. I can do it. Another advantageous method of manufacturing polyester composite films is to combine composite layers in multiple layers, as described in detail in GB 1465973, for example.
It consists of multi-extrusion or simultaneous extrusion through an orifice die, stretching in one or more directions for molecular orientation, and heat setting. The advantageous process and apparatus for coextrusion, known as the single channel coextrusion technique, has been described in British Patent No.
It is described in the specifications of No. 1115004 and No. 1115007. In this technique, a first polyester and a second polyester stream are simultaneously extruded from two separate extruders, the two polyester streams are combined in a tube leading to an extrusion die manifold, and the two polyester streams are mixed together. The composite film is made by extruding the two polyesters together through a die under laminar flow conditions so that they occupy distinct regions of flow without meeting. The first layer of the composite film can be formed from any suitable synthetic linear polyester that can be obtained in highly crystalline form after stretching and heat setting. It is particularly preferred that the first layer consists of polyethylene terephthalate. Biaxial orientation of the first layer, such as a polyethylene terephthalate layer, allows the composite film to be heated in two mutually orthogonal directions, typically at 78°C.
This can be achieved by sequential stretching at a temperature of 125°C to 125°C. After the stretching operation, heat setting is preferably carried out at a normal temperature of 150 to 250° C. under conditions that suppress dimensional changes. A preferred method of stretching and heat setting is described in GB 838708. The second linear polyester constituting the second layer preferably includes one or more selected from terephthalic acid, isophthalic acid, and hexahydroterephthalic acid and one or more glycols; Preferably, it is a copolyester derived from ethylene glycol. Preferred copolyesters exhibit satisfactory heat sealing properties in the amorphous state and are comprised of ethylene terephthalate units and ethylene isophthalate units.
A particularly preferred copolyester is 60 to 90 mole percent ethylene terephthalate and correspondingly 40 to 90 mole percent ethylene terephthalate.
10 mol% of ethylene isophthalate units. More preferred copolyesters are copolyesters comprising 70 to 85 mole percent ethylene terephthalate and 30 to 15 mole percent ethylene isophthalate, such as about 80 mole percent ethylene terephthalate and about 20 mole percent ethylene isophthalate. A preferred method for producing a polyester composite film according to the present invention includes: (a) a first layer made of a first linear polyester; and a second substantially amorphous linear polyester bonded to the first layer. a heat-sealable second layer of polyester; (b) molecularly orienting the first layer by stretching the composite film in at least one direction;
and (c) heat setting said first layer, as a fine particulate additive dispersed in said second layer, having a thickness of less than 30 μm but greater than the thickness of said stretched second layer. It is characterized by using particles having an average particle size. For example, the first layer and the second layer are
Composite films can also be made by coextrusion techniques as described in No. 1 and No. 1,465,973, or by extruding the first layer and the second layer through a multi-orifice die in the molten state. It can also be manufactured by an extrusion followed by bonding technique. After completing the stretching operation, the composite film is desirably heat set under conditions that suppress dimensional changes. Generally, the conditions applied to stretch the first layer will act to partially crystallize the second linear polyester, and in such cases will be lower than the crystalline melting temperature of the second linear polyester. It is desirable to heat set the composite film under conditions that suppress dimensional changes at high temperatures and cool the composite film in order to bring the second linear polyester into a substantially amorphous state. The second layer can be placed on one or both sides of the first layer. The total thickness of the composite film is 10
The thickness of the second layer disposed on one or both sides preferably ranges from 1 to 25% of the total thickness of the composite film. The preferred thickness of the second layer is 10 μm or less, more preferably 5 μm or less. Appropriate non-adhesive properties are obtained when the peak height of the second layer is less than 5 μm. In a preferred embodiment, the height of all protrusion peaks is between 1 and 3μ.
m, and the density of surface protrusions per unit area corresponds to a peak number of protrusions of 150 or less per mm ² of surface. For spherical particle additives, the average particle size of the particles is defined as the diameter of the particles. However, the shape of many particulate additives, especially inorganic particulate additives, is non-spherical, and the average particle size of such particles is defined herein as the size of the particles at their largest dimension. That's it. Particle size can be determined by any method known in the art, such as by electron microscopy or sedimentation analysis. It has been observed in the art that certain particulate additives agglomerate into larger particles when added to polymeric materials or reaction components to form polymers. According to the above-described preferred method for producing polyester composite films, the average particle size of the particulate additive used is less than 30 μm;
This particle size should be understood to refer to the size of non-agglomerated primary particles. Preferably the average primary particle size (conveniently determined as the median particle size on a weight basis) of the added particles is in the range 2 to 10 μm. It is desirable that the particles to be added have a particle size distribution such that the particle size of 10% by weight (ie, upper decile) is greater than 5 μm. The particulate additive should be chemically inert to the second linear polyester and is preferably a material constituting such additive or other additives incorporated into the second layer. , natural or synthetic silica, glass beads, calcium borate,
Mention may be made of inorganic particles of calcium carbonate, magnesium carbonate, barium sulfate, calcium silicate, calcium phosphate, aluminum trihydrate, hydrated and calcined aluminosilicate and titanium dioxide, and mixtures thereof. Other suitable particulate additives include particles of polymers that melt at temperatures above the maximum temperatures employed in the manufacture of the composite film and/or are immiscible with the second linear polyester. Preferred additive particles are silica particles. Ideally, the particles added are substantially spherical. It is desirable that the particulate additive is incorporated in the second layer in an amount of 5% by weight or less based on the weight of the second linear polyester. In general, satisfactory surface slip and anti-stick properties are obtained when the amount of particulate additive is less than 1% by weight, especially from 0.01 to 0.5% by weight. In a composite film having a second layer of thickness typically in the range of 2 to 4 μm, the average primary particle size is in the range of 3 to 8 μm and 10% by weight of the particles
When 0.1 to 0.5% by weight of spherical silica particles having a particle size distribution exceeding μm is blended into the second layer based on the weight of the second linear polyester, a protruding peak protrudes from the surface of the second layer. The density is 25 to 150 per mm ² , and the height of the protrusion peak is in the range of 1 to 3 μm. Such a surface consists of a polyethylene terephthalate layer and 70 to 85 mol% ethylene terephthalate and 30 to 15 mol% ethylene terephthalate.
The second layer is composed of a copolyester with ethylene isophthalate, and is biaxially stretched and heat-set to impart excellent handling suitability and heat-sealing properties to the composite film. The coefficient of static friction of this superior composite film to the second layer itself is 0.40 to 0.50, and the heat seal strength, measured as the second layer seals to itself, is 40 to 0.50.
It is 70N/ ^mm2 . The composite film of the present invention is suitable for heat sealing to itself or to the surface of another film, such as a polyethylene terephthalate film. This heat sealing can be accomplished using conventional heat sealing equipment and conditions by heating the composite film to a temperature at which the substantially amorphous second layer softens and bonds to the receiving surface. A second layer of copolyester consisting of 70 to 85 mole % ethylene terephthalate units and 30 to 15 mole % ethylene isophthalate units is particularly suitable for heat sealing. The composite film of the present invention also has excellent handling properties as determined by surface friction and adhesion tests measured on the second layer. The heat-sealable composite films described above are useful for packaging a variety of articles. However, packaging films generally exhibit good optical clarity as well as, for example, good anti-stick and sliding properties or low coefficients of friction, so that the films can be processed efficiently and without hindrance in packaging machines. , handling characteristics and other desirable properties. However, particulate additives used to alter handling properties can adversely affect optical clarity and heat seal properties. In a particularly preferred embodiment of the present invention, the second layer of the composite film contains the fine particulate additive as described above in the proportion as described above, and further has an average particle size of 0.005 to 1.8 μm. A mixture containing fine particles having a small particle size in an amount of 0.1 to 1% by weight based on the weight of the second linear polyester is included. Such composite films have optical clarity,
Excellent handling suitability and heat sealing properties.
Particularly useful. Therefore, according to the above preferred embodiments of the invention,
The polyester composite film is heat sealable to adhere to a first layer consisting of a highly crystalline molecularly oriented layer of a first linear polyester and a first layer consisting of a substantially amorphous second linear polyester. The second
and the second layer comprises a fine particulate additive having an average particle size in the range of 2 to 10 μm based on the weight of the second linear polyester.
Contains 0.005 to 0.2% by weight and has an average particle size of 0.005
0.1 to 1% by weight, based on the weight of the second linear polyester, of a finely divided additive having a smaller particle size in the range of 1.8 μm to 1.8 μm and substantially uniformly dispersed throughout the second layer. The term "average particle size" used here regarding particles of smaller size.
is related to non-agglomerated primary particles and has the same meaning as explained above regarding fine particles with large particle size. Generally, smaller sized particles are used in greater amounts than larger sized particles in particle mixtures as described above, preferably in a ratio ranging from 1.2:1 to 10:1. The exposed surface of the second layer has non-tacky surface protrusions produced by the formulation of the fine particulate additive mixture described above, and the polymer surface (i.e., the average level of the base of the interparticle valleys to be dispersed) ), the number of protrusion peaks with a peak height of at least 0.4 μm, as measured from 0.4 μm, is at least 50 per mm ² of the surface, preferably the number of protrusion peaks with a peak height of greater than 1 μm, as measured from 50 per mm ² of the surface. less than Such a composite film can be manufactured by the method described above. The fine particles with a smaller particle size can also be selected from materials similar to those of the fine particles with a larger particle size as described above. It is desirable that both large and small particles in the particle mixture consist of the same chemical. Particularly preferred are particles having a refractive index similar to that of the first layer,
Silica particles are the best. In particular, spherical particles have excellent handling properties. The fine particulate mixture is preferably prepared by mixing two different sources of particulate additive. For example, it can be mixed by blending two masterbatches of the second linear polyester, each containing particles with different average particle sizes, or during the polymerization process of the second linear polyester. 0.04 to 0.15% by weight (based on the weight of the second linear polyester) of large-sized particles having an average particle size of 2.5 to 7.5 μm and 0.15 to 0.3% by weight of small-sized particles having an average particle size ranging from 0.5 to 1.5 μm.
(based on the weight of the second linear polyester) are particularly effective. Large particles have a particle size of 10% by weight (i.e. upper deciles) of 5.
It is desirable that the particles larger than μm and smaller in particle size exhibit a particle size distribution in which 10% by weight of the particles have a particle size larger than 1 μm. A composite film in which the second layer is made of a copolyester of 70 to 85 mol% ethylene terephthalate units and 30 to 15 mol% ethylene isophthalate units and exhibits the above-mentioned particle size characteristics is usually prepared as follows. It has similar characteristics. Number of protrusion peaks with a peak height of 1 to 3 μm = 20 to 50/mm ² , Number of protrusion peaks with a peak height of 0.4 to 0.6 μm = 200 to 600/mm ² Optical transparency: 5 to 15% Second layer Static friction coefficient of the second layer measured as against: 0.5 to 2.0 Heat seal strength measured by sealing the second layer to itself: 85 to 120 N/mm ² Some properties of the composite film The test methods used herein for evaluation are as follows. Heat seal strength is determined by sealing the second layer to itself or to the first layer for 0.5 seconds at 140 °C under a pressure of 103 kPa (15 psi), cooling to room temperature,
Next, the linear tension per unit seal width required to peel off the sealed film at a constant speed of 5.08 mm/sec was determined. In order to facilitate the comparison of the heat seal strength shown in the examples below, the thickness of the second layer is the same as the total thickness of the composite film.
It is expressed as the heat seal strength of the composite film, which accounts for 20%. The coefficient of static friction of the second layer is defined as the coefficient of friction with respect to the second layer itself or the first layer according to ASTM D1894-
73 Measured according to method B. However, (a) the film was not wrapped around the thread, but was loaded onto the film by placing the thread on the film and moving the thread and film using a multi-strand copper wire attached directly to the film or sheet. In addition, (b) a 1 kg weight is added to the same thread as described in ASTM D1894-73, and (c) the weighted thread and film are moved at a constant speed of 20
It ran at cm/min. The adhesion test was performed by applying a pressure of 43 g/cm ² to the test surface and a temperature of
This was done by pressing at 38°C for 3 hours.
A test piece of the adhesive material was cut into a width of 75 mm, and the maximum linear tension per unit width required to separate the two composite films was measured. The lower this force is, the greater the adhesive resistance is. Optical transparency is defined as the percentage of transmitted light that is deflected by 6 to 2 degrees from perpendicular to the film surface while passing through the film.
Measured according to. Hereinafter, the present invention will be further explained with reference to Examples. Examples 1 and 2 and Comparative Examples A to C First layer consisting of polyethylene terephthalate as the first linear polyester and 82 mol% ethylene terephthalate/18 mol% ethylene isophthalate copolyester as the second linear polyester A composite film was prepared consisting of a second layer consisting of: The first and second linear polyesters are prepared by adding ethylene glycol to an acid (i.e., terephthalic acid in the case of the first linear polyester,
In the case of the linear polyester, it was prepared by direct esterification with a mixture of 82 mol% terephthalic acid and 18 mol% isophthalic acid) followed by polycondensation. After completing the polycondensation, the polymer was cut into small particles suitable for extrusion. In Comparative Examples A and B, the particulate additive was
Example 1
and 2, by adding spherical silica particles directly to the reaction components in the esterification step.
It was mixed into linear polyester. Comparative example C
relates to a composite film in which spherical silica particles are mixed in the second layer, but the minimum protrusion surface density does not satisfy the requirements of the present invention. The first and second linear polyesters were formed into a composite film according to a single channel coextrusion technique. That is, the first
and a second linear polyester stream were combined in a tube leading to the manifold of an extrusion die and extruded simultaneously from the die under laminar flow conditions so as not to mix with each other into a composite film. The composite film extruded from the extrusion die was rapidly cooled on a water-cooled rotating metal drum with a polished surface and stretched to 3.6 times its original length in the extrusion direction at a temperature of about 90°C. This longitudinally stretched film is further heated to approximately 100°C.
The film was stretched in the transverse direction to 4.2 times its original length using a tenter. Finally, it was heat-set in a tenter furnace maintained at a temperature of about 225°C under conditions that suppressed dimensional changes. The obtained composite film consists of a first layer of polyethylene terephthalate that is biaxially oriented and heat-set, and a second layer as described below.
and a second layer of amorphous copolyester having the properties shown in Table 2. It will be seen that the handling properties (expressed as tack resistance and coefficient of static friction) of the composite films of Examples 1 and 2 are generally superior to those of the composite films of Comparative Examples A-C. Examples 3 to 5 A first polyester comprising polyethylene terephthalate as the first linear polyester was prepared according to the general procedure described in Examples 1 and 2 and Comparative Examples A to C.
A composite film was prepared consisting of a second layer consisting of a cocopolyester containing 82 mol% ethylene terephthalate/18 mol% ethylene isophthalate as a second linear polyester. In these examples, a mixture of large and small silica particles shown in Table 1 was used. The properties of the obtained composite film are as shown in Table 2. It can be seen that the composite films of Examples 3 to 5 have better heat sealing properties, better handling properties, and better optical clarity than the composite films of Comparative Examples A to C. It can also be seen that these properties of the composite films of Examples 3 to 5 are generally superior to those of the composite films of Examples 1 and 2, in which only large-sized particles were blended in the second layer. The composite films of Examples 3-5 exhibited acceptable clarity and their heat seal strength was generally comparable to the composite films of Comparative Examples A and B and superior to the composite films of Examples 1 and 2 and Comparative Example C. ing. It can be seen that the lower the surface density of protrusion peaks of at least 1 μm, the better the transparency and heat seal strength.

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Claims (1)

[Claims] 1. A first layer consisting of a highly crystalline molecular orientation layer of a first linear polyester and a first layer consisting of a substantially amorphous second linear polyester. a heat-sealable second layer, the second layer having an average particle size of 0.05 to 10% by weight (based on the weight of the second layer) of the second layer; a particulate additive greater than the thickness and substantially uniformly dispersed throughout the second layer, and the exposed surface of the second layer has a non-stick surface created by the particulate additive; The density of these surface protrusions per unit area is such that the number of protrusion peaks with a peak height of at least 0.4 μm measured from the polymer surface is at least 50 per mm ² of the surface. A polyester composite film featuring: 2 The first linear polyester constituting the first layer is biaxially oriented and heat-set crystalline polyethylene terephthalate, and the second linear polyester constituting the second layer is 60 to 90 mol%. A composite film according to claim 1, comprising an amorphous copolyester of ethylene terephthalate and a corresponding 40 to 10 mol % of ethylene isophthalate. 3. The composite film according to claim 1 or 2, wherein the protrusion peak of the second layer has a height lower than 5 μm. 4. The composite film according to claim 3, wherein all the protrusion peaks of the second layer have a height of 1 to 3 μm, and the density per unit area is 150 or less protrusion peaks per mm ² of the surface. . 5. The composite film according to any one of claims 1 to 4, wherein the average primary particle size of the fine particulate additive in the second layer is in the range of 2 to 10 μm. 6. The composite film according to any one of claims 1 to 5, wherein the fine particulate additive in the second layer has a particle size distribution such that the particle size of 10% by weight exceeds 5 μm. 7 The second layer has a static coefficient of friction measured on itself of 0.40-0.50 and a heat seal strength of 40.
70 N/min ² . The composite film according to any one of claims 1 to 6. 8 The second layer further comprises an average particle size of 0.1 to 1% by weight (based on the weight of the second linear polyester).
A composite film according to any one of claims 1 to 7, comprising finer particles having a size of 0.005 to 1.8 μm. 9. A composite film according to claim 8, wherein in the second layer the number of protrusion peaks with a peak height of at least 0.4 μm is at least 50 per mm ² of surface. 10. The composite film according to claim 8 or 9, wherein the number of protrusion peaks having a peak height exceeding 1 μm in the second layer is less than 50 per mm ² of the surface. 11 Particles with an average particle size of 2.5 to 7.5 μm from 0.04 to
0.15% by weight and particles with an average particle size of 0.5-1.5μm
11. A composite film according to claim 8, 9 or 10, wherein the second layer contains a particle mixture consisting of 0.15-0.3% by weight. 12 The composite film has an optical clarity of 5-15% and the second layer has a static friction coefficient measured on itself of 0.5-2.0 and a heat seal strength of 85-120 N/ ^mm2. A composite film according to any one of claims 8 to 11. 13 (a) a first polyester made of a first linear polyester;
and a heat-sealable second layer of a substantially amorphous second linear polyester adhered to the first layer, the second layer extending over the entire layer. (b) forming a composite film containing 0.05 to 10% by weight (based on the weight of the second layer) of a finely divided additive substantially uniformly dispersed; (b) dispersing the composite film in at least one direction; Molecularly oriented the first layer by stretching it to
and (c) heat setting said first layer, as a fine particulate additive dispersed in said second layer, having a thickness of less than 30 μm but greater than the thickness of said stretched second layer. A method for producing a polyester composite film, characterized in that a polyester composite film having an average particle size is used. 14. The manufacturing method according to claim 13, wherein the first layer is heat-set under dimensional change suppressing conditions at a temperature higher than the crystal melting temperature of the second linear polyester.