JPH0426309B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention is a print laminate that has thermal adhesive properties that allow lamination with printing paper, etc., only by heat and pressure bonding without using adhesives or organic solvents. It's about film. [Prior Art] It is common practice to laminate a film on top of printing paper for the purpose of protecting printed parts of printed art paper, etc., imparting water resistance, oil resistance, and gloss. This process is generally referred to as "print lamination" in the art. Recently, print laminating films that can be laminated only by thermocompression bonding without using organic solvents or adhesives are known (for example, JP-A-56-42652, JP-A-59-1999).
24666, etc.). [Problems to be Solved by the Invention] However, this film for print lamination has poor slip properties and anti-blocking properties, so wrinkles may appear during film production, and the film surface may wrinkle when unrolled from a roll during use. There are problems such as the flatness of the film being deteriorated as they stick together, and the film being broken if the blocking is significant. For this reason, if large amounts of organic lubricants and inorganic particles are added to provide slipperiness and anti-blocking properties, the thermal adhesion to the printing paper may be poor during print lamination, or air may be generated between the printing paper and the film. This has the serious drawback that the appearance of printed laminated paper, such as its transparency and gloss, deteriorates significantly. Furthermore, the printed laminated paper also had the disadvantage of curling. The present invention is a film for print lamination that does not have the above drawbacks, that is, a film for print lamination that does not cause the print lamination paper to curl, has strong thermal adhesion to the print paper, has gloss, and has excellent slip properties and anti-blocking properties. The purpose is to provide [Means for Solving the Problems] The present invention provides that on one side of a biaxially stretched polypropylene film (layer A), two or more peaks of melting peaks measured by a differential scanning calorimeter are between 118°C and 160°C. , and a film for print lamination in which three or more polyolefin resin layers (layer B) having a temperature between 45°C and 100°C are laminated. The biaxially oriented polypropylene film in the present invention has a propylene component of 96 mol% or more, an isotactic index (II) of 90 to 99%, and an intrinsic viscosity [η] of 1.0 to 4 (dl/
g), particularly preferably in the range of 1.2 to 2.3 (dl/g). A small amount of a second component other than propylene, such as ethylene, butene, hexene, etc., may be randomly copolymerized. Further, it is a biaxially stretched film made of the above-mentioned polypropylene resin mixed with film waste generated during film production of the present invention, and may be stretched by simultaneous, sequential, or tubular method. In addition, the biaxially oriented polypropylene film contains known additives such as crystal nucleating agents, antioxidants, heat stabilizers, slip agents, antistatic agents, antiblocking agents, fillers, viscosity modifiers, and color inhibitors. It may be included. The thickness of the film is not particularly limited, but a film thickness of 10 to 25 μm is particularly preferably used. In the present invention, the polyolefin resin layer (layer B) having two or more apexes of the melting peak measured by a differential scanning calorimeter between 118°C and 160°C and three or more points between 45°C and 100°C means the melting peak The top of
It is sufficient if the polymer layer has two or more points between 118°C and 160°C and three or more points between 45°C and 100°C, and specifically, has two or more melting peak points between 118°C and 160°C. The apex of polymer (a) and melting peak is 45℃~
It is generally blended with a polymer (b) that has three or more points at 100°C. Specifically, the polymer (a) having two or more melting peaks between 118°C and 160°C is a mixture of ethylene, propylene, and other α-olefin polymers, ethylene, propylene, and other α-olefin polymers. copolymers of olefins, mixtures of said copolymers,
This layer is made of a mixture of the above copolymer and a polymer of ethylene, propylene, or other α-olefin. Among these layers, a layer consisting of , , is preferred. More preferably, the polyolefin resin layer contains 60 to 95% by weight of an ethylene-propylene block copolymer (hereinafter abbreviated as BEPC) and 40 to 5% by weight of at least one selected from ethylene and propylene. A mixed layer is desirable, most preferably a layer of BEPC polymerized such that two melting peaks occur between 118 and 160°C. The ethylene content of these BEPCs is 10 to 40 wt%, preferably 15 to 30 wt%, based on the total copolymer weight. In the case of a blend system, the amount of ethylene is 20
~50wt%. Note that the apex of the melting peak of polymer (a) is 118
If there are no more than two points between 160°C and 160°C, the film will block or have poor slip properties. Next, polymers (b) with three or more melting peaks between 45°C and 100°C include ethylene-butene-1 copolymer (rubber), ethylene and acrylic acid, and methacrylic acid. , copolymers with (meth)acrylic esters such as methyl methacrylate, copolymers of esters with maleic anhydride, or three-dimensional copolymers of the copolymer components with maleic anhydride, ethylene-propylene copolymers, polymer (rubber),
Examples include ethylene-vinyl acetate copolymer, petroleum resin, and mixtures thereof. In addition, the top of the melting peak of polymer (b) is 45℃
If there are no more than three points at ~100°C, not only will strong thermal adhesion not be obtained when printing is laminated with printing paper, but the printed laminated paper will curl. Furthermore, air is trapped between the printing paper and the film, resulting in printed laminated paper with poor gloss. In other words, the top of the melting peak is 45℃~
By having 3 or more points at 100℃, during print lamination, the low melting point side first instantly adheres to the printing paper, and the phenomenon that gradually spreads to the high melting point side creates a strong thermal bond to the printing paper, and at the same time prevents air from being trapped. It is surmised that this enabled the printing laminated paper to be produced with excellent gloss. In addition, the temperature difference between the respective apexes of melting peaks having three or more points between 45°C and 100°C is preferably 5°C or more, more preferably 10°C, and even more preferably 20°C or more. Desirable for improving gloss. The polyolefin resin of layer B has a melting peak between 45℃ and 100℃ that accounts for 40 to 70% of the total peak.
It is preferable for the film to have a large amount of carbon dioxide, from the viewpoint of blocking properties, slip properties, thermal adhesion properties, and prevention of curling. The polyolefin resin layer (layer B) contains additives known to be usually added (thermal stabilizer, antioxidant, nucleating agent, antistatic agent, lubricant, filler, weathering agent). etc.) may be added within a range that does not impair the characteristics of the present invention. The thickness of the polyolefin resin layer (layer B) is:
Although not particularly limited, 1 to 6 μm is suitable. Moreover, it is preferable that (layer B) be at least uniaxially stretched. Note that if the surface of the B layer of the film of the present invention is subjected to corona discharge treatment or plasma treatment in the presence of carbon dioxide gas, nitrogen gas, etc. in an atmosphere substantially free of oxygen, the surface layer (usually within 100 Å from the surface) will be damaged. layer) per 100 carbon atoms, imino type or /
It is particularly preferred because it can contain one or more amino-type nitrogen atoms and has excellent thermal adhesion to printing paper. The upper limit of the number of nitrogen atoms is not particularly limited, but is preferably 8 or less. The method for producing the film for print lamination of the present invention will be described in detail below. The SPP raw material, which is the raw material for the biaxially stretched PP layer of the base, is fed to one extruder, and the melting peak reaches 118℃.
Two or more raw materials between ~160℃ and three or more points between 45℃ and 100℃ are fed to another extruder, coextruded at the same time, and brought into contact on a cooling drum maintained at 40~80℃. Then, it was made into a cast sheet. this cast
After stretching 3 to 7 times while heating to 115 to 145 degrees Celsius, it is introduced into a tenter, stretched 5 to 12 times in the transverse direction in an atmosphere of 140 to 165 degrees Celsius, and then relaxed by a few percent at 145 to 160 degrees Celsius. Heat treatment is performed while Subsequently, if necessary, layer B is subjected to corona discharge treatment or plasma treatment in the presence of carbon dioxide gas, nitrogen gas, etc. in an atmosphere substantially free of oxygen. In the manner described above, the print laminating film of the present invention can be obtained. Note that the lamination of layer B is not limited to the above-mentioned coextrusion, and may be performed before uniaxial stretching or before biaxial stretching. The methods for measuring the characteristic values of the present invention as well as the methods for evaluating the effects are as follows. (1) Melting peak Perkin-Elmer differential scanning calorimeter model
A so-called second-run melting curve when a 5 mg sample was heated to 280°C at a heating rate of 20°C/min, held for 5 minutes, cooled at the same rate, and heated again using the DSC-2 model. I take the. The apex of the melting peak refers to the inflection point or shoulder-like point of this curve, and the temperature difference between the apexes is preferably 5° C. or more. (2) Intrinsic viscosity [η] Measured in tetralin according to ASTM D 1601 and expressed in dl/g. (3) For the isotactic index (II), cut the sample film into approximately 1 cm square pieces, place them in a Soxhlet extractor, and extract with boiling methyl alcohol for 6 hours. The extracted sample is vacuum dried at 60°C for 6 hours. A sample weighing W (mg) was taken and extracted again for 6 hours with boiling n-1 heptane in the Soxhlet extractor. Next, this sample is taken out, thoroughly washed with acetone, dried under vacuum at 60°C for 6 hours, and then weighed. If its weight is W' (mg), the isotactic index is calculated by the following formula. II (%) = 100 x W'/W (4) Blocking resistance Samples measuring 3 cm wide x 10 cm long were stacked over a length of 4 cm, and a 2 kg sample was placed in an atmosphere of 40°C and 85% RH.
After being left for 24 hours under a load of The smaller this value is, the better the blocking resistance is. If the peeling force is 2.0 kg or more, the film will break when peeled off, and if it is less than 1.0 kg, the film will break when peeled off. ○
mark, and the one in between is marked △. (5) Slip property (coefficient of friction) Measured according to ASTM D-1894. The measurements were made between the B layer surfaces. μs: Static friction coefficient, μd: Dynamic friction coefficient (6) Print lamination characteristics Thermal adhesiveness Layer (B) of laminated film is superimposed on the printed surface for the book cover, and heated to 100℃ using a mirror-finished roll (100mmφ diameter ) with linear pressure 60Kg/cm, 5
Thermocompression lamination is carried out at a speed of m/min. At this time, the interlayer adhesive force between the film and paper (the force required to peel the film 180 degrees at a speed of 100 mm/min using Tensilon in a measurement atmosphere of 25°C) was 150 g/cm
The above items were evaluated as ○, those of 100 g/cm or more and less than 150 g/cm were evaluated as △, and those less than 100 g/cm were evaluated as ×. Curl Sample printed laminated paper laminated at a temperature that gives an adhesive strength of 100 g/cm between the film and the paper at a length of 30 cm in the film length direction and 10 cm in the width direction, place it on a smooth flat surface, and The lifting distance was measured. When the laminated paper rose 10 cm or more from the flat surface, the curl was marked as ×, when it was 2 cm or less, it was marked as ○, and the middle was marked as △. Glossiness The appearance of printed laminated paper, which is produced by thermocompression laminating film and printed paper with a mirror roll (100 mm diameter) heated to 100°C at a linear pressure of 60 Kg/cm and at a speed of 5 m/min, is sensually described in the following three ways. Evaluated in stages. ○: The surface is very shiny and the printed matter is clear. ×: The surface is blurred and the gloss is poor, and the printed matter is not clear. Δ: Intermediate between the two [Example] The present invention will be explained based on Examples. Example 1 A polypropylene polymer (A layer) with an intrinsic viscosity [η] = 1.9 and II = 97% was fed into a 40 mmφ extruder, and on the other hand, as a raw material for a polyolefin resin layer (B layer), a differential scanning calorimeter (hereinafter referred to as DSC 50% by weight of BEPC was polymerized so that the apex of the melting peak was at 122℃ and 149℃, and the apex of the melting peak was 47℃.
A mixture of maleic anhydride grafted ethylene-methacrylic acid resin, ethylene-butene rubber, petroleum resin, formulated as follows: °C, 79 °C, 94 °C
50% by weight was supplied to a 30 mmφ extruder, melt coextruded at 250°C, and cast on a cooling drum at 50°C to obtain an unstretched sheet. The unstretched sheet was preheated in a Teflon-coated heating oven, stretched 5 times in the longitudinal direction at 125°C, further introduced into a tenter at 160°C, stretched 8 times in the transverse direction, and then stretched at 150°C in the width direction. Heat treatment was performed while allowing 5% relaxation in the direction. The obtained film has a layer A of 11 μm and a layer B
It was a 4 μm film. Next, the B layer of the above film was superimposed on the printed surface for the book cover, and a mirror roll (100 mmφ) heated to 100°C was used to apply a linear pressure of 50 kg/cm,
Thermocompression lamination was carried out at a speed of m/min. Example 2 The top of the melting peak of DSC is 125℃ for the composition of layer B.
Ethylene-vinyl acetate copolymer with a vinyl acetate content of 10 wt%, ethylene-vinyl acetate copolymer with a vinyl acetate content of 10 wt%, which is blended with 40 wt% BEPC at two points, 151°C and 52°C, 74°C and 95°C. propylene rubber,
A film was produced in exactly the same manner as in Example 1, except that the petroleum resin mixture was 60% by weight, and laminated with printing paper. Table 1 shows the results of evaluating the blocking properties, friction coefficient, and print laminating properties of the print laminating film thus obtained. As is clear from this table, the film for print lamination of the present invention had excellent blocking resistance and excellent thermocompression print lamination properties (adhesion, gloss, curl) with printing paper. Examples 3 to 4 In Example 3, the composition of layer B was an ethylene-propylene-butene random copolymer whose melting peak peaks on DSC were at three points, 125°C, 142°C, and 152°C.
40% by weight and the top of the melting peak is 57℃, 75℃, 95℃
A mixture of low density polyethylene, ethylene-ethyl acrylate copolymer with an ethylene-acrylic acid content of 18% by weight, and ethylene-vinyl acetate copolymer with a vinyl acetate content of 15% by weight, blended at 110°C. 60% by weight, and in Example 4, the composition of layer B was such that the top of the DSC melting peak was 113°C, 119°C,
A mixture of propylene-butene random copolymer and linear polyethylene at four points at 132℃ and 145℃
30% by weight, the top of the melting peak is 48℃, 81℃, 98℃
℃, 113℃, linear low density polyethylene, ethylene-methyl methacrylate copolymer with methacrylic acid content of 10% by weight, petroleum resin mixture of 70% by weight. A film was produced in exactly the same manner as in 1 and laminated with printing paper. Table 1 shows the results of evaluating the blocking properties, friction coefficient, and print laminating properties of the print laminating film thus obtained. As is clear from this table, the film for print lamination of the present invention had excellent blocking resistance and excellent thermocompression print lamination properties (adhesion, gloss, curl) with printing paper. Comparative Examples 1-2 Instead of BEPC in the composition of layer B, high-density polyethylene whose DSC melting peak is at 132°C, and ethylene-propylene random copolymer whose melting peak is at 140°C are used. A film was produced in exactly the same manner as in Example 1, except that the film was printed and laminated with printing paper. The film properties and print laminate properties are shown in Table 1. If there are no two or more DSC melting peaks between 118℃ and 160℃,
The blocking and sliding properties of the film will be poor, and the thermal adhesion properties will also be poor. Comparative Example 3 The top of the melting peak of DSC is 122℃ for the composition of layer B.
and 149°C.
A film was produced in exactly the same manner as in Example 1, except that a mixture of 50% by weight of ethylene-vinyl acetate copolymer having a melting peak of 95° C. was used, and the film was laminated with printing paper. The film properties and print laminate properties are shown in Table 1. If there are no three or more melting peaks in the DSC range between 45°C and 100°C, the printed laminated paper will have poor gloss and curl. Comparative Example 4 The composition of the B layer was determined when the top of the DSC melting peak was 122
BEPC polymerized at two points, ℃ and 149℃.
60 parts by weight, and the melting peaks were at 72°C and 95°C. A film was produced in exactly the same manner as in Example 1, except that a mixture of an ethylene/acrylic acid copolymer containing 4.5% by weight of acrylic acid and ethylene/propylene rubber was used, and the film was printed and laminated with printing paper. The film properties and purine laminate properties are shown in Table 1. If there are no three or more melting peaks in the DSC range between 45°C and 100°C, the pudding laminated paper will have poor gloss and curl.

【table】

[Table] [Effects of the invention] The present invention provides a biaxially oriented polypropylene film (A
The apex of the melting peak measured with a differential scanning calorimeter on one side of the layer) was measured at two or more points between 118℃ and 160℃, and at 45℃～
Since the film for print lamination has a specific range of 3 or more points at 100°C, it has the following excellent effects. (1) When laminated with printing paper, it hardly curls and has excellent gloss. (2) A film with excellent thermal adhesion to printing paper could be obtained. (3) The film has excellent anti-blocking and slip properties.

Claims (1)

[Claims] 1 On one side of the biaxially stretched polypropylene film (layer A), two or more apexes of the melting peak measured by differential scanning calorimeter are between 118 °C and 160 °C, and 45
A film for print lamination that is laminated with three or more polyolefin resin layers (layer B) having a temperature between ℃ and 100℃.