An extrusion coatable polyester film having an aminofunctional silane primer, and extrusion coated laminates thereof.

Description: TECHNICAL FIELD [Detailed description of the invention]

[Industrial application field] The present invention relates to a primer-coated stretched polyester film having a primer film formed by coating at least one side of a water-soluble primer coating material containing a hydrolyzate of aminofunctional silane. This coating makes the surface of the polyester film more receptive to extrusion coatings of other polymeric film materials such as polyolefins.

[Conventional technology] Stretched polyester films made of polyethylene terephthalate (PET), especially biaxially stretched films, have been widely used as packaging materials or as supports (bases) for microfilms, electrophotographic films, proofing films and the like. This film has good optical transparency and toughness, which makes it extremely suitable for such applications. The main use of PET film is to laminate it with other polymers as well as paper or foil. To impart heat sealability or adhesion to other materials such as aluminum foil to PET film, to increase its thickness (bulk) or rigidity, or to impart properties to this film that cannot be obtained by PET alone. In addition, it is often practiced to extrude a polyethylene or ethylene copolymer onto a PET film. Unfortunately, the surface of PET film is not highly receptive to extrusion coating with other polymers. Many primer paints for applying to the surface of a polyester film for the purpose of improving the adhesiveness of the polyester film to various materials have been conventionally known. Examples of such paints are materials such as compositions using vinylidene chloride polymer as the main component (US Pat. No. 2,698,240) and compositions using thermosetting acrylic or methacrylic polymer (US Pat. No. 3,819,773). There is. Adhesives of certain water-dispersible copolyesters to laminate polyester film sheets or to laminate nylon film sheets, as described in US Pat. Nos. 3,563,942 and 3,779,993. It is also known to be used as. More commonly, solvent-based polyurethane adhesives and polyethyleneimine primers are used, but this is accompanied by solvent volatilization and safety issues. It has also been proposed to use corona discharge treatment, with or without primer coating, to obtain adhesion between extruded films. The usual work of extrusion coating is to use PET film purchased from the film manufacturer, the processor corona discharge treatment, apply the primer to the corona treated film, dry the primer, and then add to this film. It is carried out in the process of extruding and coating the polymer of. Since a separate coating process of applying a primer to the film is required, it is necessary to install a separate expensive coating facility, and this process adversely affects the production speed. In addition, when a solvent-based primer is required, separate equipment for safety and prevention of environmental pollution is required, which imposes another burden of imposing various regulatory obligations. For the above reasons, it would be advantageous for the processor if a film that had already been subjected to corona treatment or primer coating, which could be extruded and coated as it was without separate primer coating or corona discharge treatment, could be obtained. Let's go. Further, it would be advantageous to produce a film that can be directly extruded and coated by discharging the film or applying a primer in the production line at the time of producing the film from the viewpoint of avoiding the above costs and problems. For the in-line primer coating process, the primer coating is water-based and reproducible for safety and health reasons (ie, the scraps of the primer-coated film are mixed with a new polymer to form a film. Does not cause excessive yellowing or deterioration of physical properties when re-extruded and regenerated. This regeneration is necessary due to low conversion efficiency in in-line treatment), and further causes adhesion and blocking of the film. Ideally, it should be hard enough to be rolled into a roll (which is a necessary property for films that can be directly extruded and coated). Directly extrudable polyester films are disclosed in US Pat. No. 4,410,600. Disclosed in this US patent is a biaxially stretched PET film in-line coated with a crosslinked styrene-maleic anhydride copolymer. However, this primer coating film still needs to be corona discharged before extrusion coating. It is known to use a silane coupling agent to improve the bondability between a polyethylene sheet and a polyester sheet. For example, E. Plueddemann, "Coupling Agent Bonding" Plenum As disclosed in Press (1985), a polyester sheet coated with either vinyltrimethoxysilane or chloropropyltrimethoxysilane as a primer and a polyethylene sheet are hot, such as ethylene / vinyl acetate terpolymer or elastomeric polyester. It was successfully laminated using a melt adhesive. In addition, N-2-aminoethyl-3-aminopropyltrimethoxysilane (commercially available under the brand name Z-6020 from Dow Chemical Co., Ltd.) is used as a primer paint to make an ionomer resin (a copolymer of ethylene and methacrylic acid). Increasing the adhesion of salt) to glass and polycarbonate sheets is disclosed in US Pat. No. 4,663,228. It is also known that related silanes such as N-3-aminopropyltrialkoxysilane enhance the adhesion between the polyurethane film and the glass substrate, as disclosed in European Patent Application Publication No. 171,917.

[Problems to be solved by the invention] The above disclosure of the prior art includes coating of polyethylene, ethylene copolymers and ionomer or other polymer films directly extruded onto polymer films, especially polyester films, without separate primer coating or separate corona discharge treatment. No one has dealt with the issue of aptitude. Therefore, an object of the present invention is to provide a stretched polyester film that can be directly extruded and coated with another polymer without the need for separate primer coating or corona discharge treatment. Another object of the present invention is to provide a polyester film having a primer film capable of regenerating a primer-coated film waste without excessive yellowing or deterioration of properties of the regenerated polymer. Since most of the conventional primer paints use volatile solvents, it is necessary to provide ancillary facilities such as solvent treatment equipment, worker protection equipment, and waste solvent disposal equipment. Therefore, yet another object of the present invention is to develop a water-based primer coating that can be used in most existing systems without the need for expensive ancillary equipment.

[Means to solve problems] The above and other objects of the present invention are primer coating in which a stretched polyester film is coated with a hydrolyzate of aminofunctional silane as a primer to make the film acceptable for direct extrusion coating with other polymers. This can be achieved by providing a polyester film. The aminofunctional silane compound useful as a primer for the purpose of the present invention is represented by the following general formula in the state before hydrolysis. (R¹)_aSi (R²)_b(R³)_cIn the above formula, R¹Is a functional group having at least one primary amino group; R²Is a hydrolyzable group such as a lower alkoxy group, acetoxy group or halogen; R³Means non-reactive, non-hydrolyzable groups such as lower alkyl or phenyl groups, respectively; a is greater than or equal to 1, b is greater than or equal to 1, c is greater than or equal to 0 or 1, and a + b + c = 4 Is. Generally, the aminofunctional silane compound is hydrolyzed in water and applied to one or more surfaces of a stretched polyester film by any conventional coating method such as spray coating or roll coating. When the silane primer coating dries, the primer-coated polyester film becomes receptive to direct extrusion coating with one or more polymers. Extrusion coating can be carried out by any conventional method. The primer film acts to bond the polyester film and the extruded film to form a laminate (laminate). In the broadest sense, the present invention relates to a stretched polyester film provided with an amount of primer coating effective to make the film acceptable for direct extrusion coating with one or more polymers. , This primer is in the state before hydrolysis with the following general formula: (R¹)_aSi (R²)_b(R³)_c[In the formula, R¹Is a functional group having at least one primary amino group; R²Is a hydrolyzable group; R³Means non-reactive and non-hydrolyzable groups, respectively; a is 1 or more, b is 1 or more, c is 0 or more, and a + b + c = 4] is there. In the broadest sense, the present invention also relates to a stretched polyester film, a primer coating, and a laminate with one or more directly extruded polymer layers, which the primer coating, in its pre-hydrolyzed state, has the following general formula: (R¹)_aSi (R²)_b(R³)_c[In the formula, R¹Is a functional group having at least one primary amino group; R²Is a hydrolyzable group; R³Means non-reactive and non-hydrolyzable groups, respectively; a is 1 or more, b is 1 or more, c is 0 or more, and a + b + c = 4] is there.

[Action] Silanes become water-soluble or water-dispersible after hydrolysis, but amino-functional silane compounds in particular become water-soluble. The present inventor has found that aminosilanes can impart good adhesion of the directly extruded polymer to the polyester film without the need for separate primer coating or corona treatment. We also found that scraps of polyester film primed with aminosilane paint are renewable. The aminofunctional silane compound that can be used as a primer for the purpose of the present invention is represented by the following general formula in the state before hydrolysis. (R¹)_aSi (R²)_b(R³)_cIn the above formula, R¹Is a functional group having at least one primary amino group; R²Is a hydrolyzable group selected from the group consisting of lower alkoxy groups with 1 to 8 carbon atoms, acetoxy groups and halogen groups; R³Means non-reactive, non-hydrolyzable groups selected from the group consisting of lower alkyl and phenyl groups with 1-8 carbon atoms; a is 1 or more, b is 1 or more, c Is 0 or more, and a + b + c = 4. Examples of aminosilane compounds conforming to the above general formula include N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 4-aminobutyl. There are triethoxysilane, 4-aminobutyldimethylmethoxysilane, and p-aminophenyltrimethoxysilane. A preferred silane compound is N-2- (aminoethyl) -3-aminopropyltrimethoxysilane represented by the following formula. H₂N (CH₂)₂NH (CH)₂)₃Si (OCH₃)₃The hydrolyzed aminosilane may be applied to the polyester film as an aqueous solution at any suitable step during film production (that is, before or during the stretching operation), or applied to the stretched film after production. You can also. It was found that the obtained primer-coated polyester film exhibited adhesiveness to the polymer film extruded and coated on the film. The primer coating material used in the present invention is prepared by mixing aminosilane with water so as to have a concentration in the range of about 0.2 to 6% by weight. In some cases, a weak acid such as acetic acid may be added to promote hydrolysis. At least one hydrolyzable group of silane is hydrolyzed to silanol groups (SiOH). The hydrolyzed product of the aminosilane compound has a partially hydrolyzed cyclic structure, and the amino group is presumably forming an ionic bond with the silicon moiety of this molecule. That is, in the present specification, the hydrolyzate may also mean such a partially hydrolyzed structure. A preferred stretched polyester film for the purposes of the present invention is polyethylene terephthalate, but with glycol components such as ethylene glycol or butanediol or mixtures thereof, terephthalic acid, or other terephthalic acid and isophthalic acid, diphenylic acid or sebacic acid. The present invention can be similarly applied to a mixture with a dicarboxylic acid or any film based on a crystalline polyester obtained by polycondensation with a dicarboxylic acid component such as these polyester-forming derivatives. .. Such polyester resins are produced by methods well known in the art. The production of the film can also be carried out by using a well-known apparatus by a technique well-known in the technical field. For example, polyester is melted and extruded into an amorphous sheet on a rotating drum for casting whose surface is polished to form a polymer casting sheet. Then, the obtained film is stretched in one of the extrusion direction (longitudinal direction) or the direction perpendicular to the extrusion direction (horizontal direction) in the case of a uniaxially stretched film, and in the case of a biaxially stretched film. Stretches the film in two directions, i.e., both vertically and horizontally. The initial stretching that imparts strength and toughness to the film can be in the range of about 3.0 to 5.0 times. The hydrolyzed aminosilane primer coating of the present invention in aqueous form is between three steps during film production, ie, between casting and initial stretching of an amorphous sheet, as disclosed, for example, in US Pat. No. 1,411,564. In either the pre-stretching step at the time point, eg, the inter-stretching step after uniaxial stretching and before biaxial stretching, as disclosed in US Pat. No. 4,214,035, and the post-stretching step after biaxial stretching and before film winding. Can be applied in-line. Normally, the heating applied to the film during stretching or the final conditioning step causes the water and other solvents to evaporate sufficiently and the primer coating to dry, but after such a heating step the primer coating If you want to apply, a separate drying process will be required. In a preferred embodiment, the primer coating is applied after the film is uniaxially stretched, that is, after the film is stretched in one direction and before it is stretched in a direction orthogonal to the film. In another preferred embodiment, the polyester film is first stretched in the longitudinal direction before application. In this preferred embodiment, the film is coated with a primer by any coating method well known in the art after stretching in the longitudinal direction. For example, coating can be performed by roll coating, spray coating, slot coating, or dip coating. In a preferred embodiment, the polyester film is coated with a primer by gravure roll coating. Further, as is known in the art, the uniaxially stretched film may be subjected to a corona discharge treatment by a corona discharge device before coating. Since the corona discharge treatment reduces the hydrophobicity of the polyester film surface, the aqueous primer coating can more easily wet the film surface, and the adhesion of the primer film to the surface is improved. The hydrolyzed aminosilane of the present invention can be applied to a film as an aqueous solution containing a hydrolyzate of aminosilane at a concentration of about 0.2 to 6% by weight. About 0.2% by weight of a weak acid (eg, acetic acid, phosphoric acid, etc.) is then added to promote hydrolysis. The preferred concentration of hydrolyzed aminosilane is in the range of about 0.25 to 2.5% by weight. The preferred concentration is the target adhesion amount of about 0.10 × 10.^-61b / ft²(0.4mg / m²) Is a concentration that causes the final dry primer film adhesion amount. When the primer paint is applied off-line (ie, applied to the finished polyester stretched film as a separate application operation), the amount of coating can be quite high, 10x10.^-61b / ft²(49mg / m²) Or more dry film adhesion will give good results. The primer coating material of the present invention can be applied to one side or both sides of a film. In the case of single-sided coating, another paint such as thermosetting acrylic or methacrylic resin paint as described in US Pat. No. 4,214,035 can be applied to the opposite side. In addition, a film formed from another primer paint such as the thermosetting acrylic paint described in US Pat. No. 3,819,773, which exhibits adhesiveness to the aminosilane primer film, is previously provided on the surface of the film, and the film is formed. Aminosilane primer paint can also be applied on top. The primer coating material of the present invention may further contain other components as long as it does not inhibit the adhesion promoting action of the hydrolyzed aminosilane compound. Such other components include small amounts of colloidal silica, dyes, pH regulators, wetting agents and the like. The primer film is allowed to exist as a continuous film on the film surface. The continuous coating also includes the case where the primer can form a large number of island-shaped portions or separated coating portions. The film scraps coated with the primer coating material of the present invention generated as scraps in the manufacturing process are crushed, mixed with new polyester, remelted, and reextruded to produce a stretched film. The polyester film thus obtained, which contains a considerable amount of the reclaimed product of the primer-coated waste, has very little deterioration in physical properties due to the inclusion of the paint as an impurity, and has little coloring. That is, the primer-coated film of the present invention is commercially advantageous to film manufacturers as compared to many other primer-coated films. Examples of other films include films coated with the vinylidene chloride-containing polymer disclosed in US Pat. Nos. 2,627,088 and 2,698,240 as a primer, which deteriorates or discolors physical properties when regenerated as described above. Shows the tendency of. The laminate can be produced by a well-known extrusion coating method in which a molten polymer sheet is continuously adhered to a primer-coated surface of a moving web of a polyester film. Laminations of polyester with polyethylene, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl acetate, ionomers and other polymers can be easily produced by extrusion coating. Laminates made by extruding polyethylene onto a PET film exhibit particularly useful properties such as heat sealability and good adhesion to other materials such as aluminum foil. Although it cannot be determined, it is considered that the amino group in the primer reacts with the heated and oxidized polyethylene when the polyethylene is extruded onto the PET film, and the primer is firmly bonded to the polyethylene. The thickness of the polyester film suitable for use in the present invention may generally be in the range of about 0.25 to 10 mils or more. The following examples are examples of the present invention.

[Example] Film manufacturing method N-2- (aminoethyl) -3-aminopropyltrimethoxysilane (AE-APTMS) (commercially available as Z-6020 from Dow Corning and A-1120 from Union Carbide) or N-3-amino Propyltrimethoxysilane (APTMS) was dispersed in plain tap water to a concentration of about 0.25 to 1.5% by weight of AE-APTMS (or other aminosilane). Acetic acid at a concentration of 0.2% by weight was added to promote hydrolysis. The polyethylene terephthalate polymer was melted and extruded from a slot die onto a rotating drum for casting kept at a temperature of about 20 ° C. The melt solidified to give a cast sheet. The cast sheet was stretched in the longitudinal direction at a stretching ratio of about 3.5: 1 while maintaining the temperature at about 80 ° C. The vertically stretched film was subjected to corona discharge treatment by a corona discharge device, and then an aqueous solution of the hydrolyzed aminosilane compound was applied by a reverse gravure roll. The film subjected to longitudinal stretching, corona discharge treatment and primer coating was dried at a temperature of about 100 ° C. Then, the film was stretched laterally at a stretching ratio of about 3.9: 1 to obtain a biaxially stretched film. The thickness of this stretched film was about 0.5 to 3 mils. The biaxially stretched film was then heat set at a maximum temperature of 230 ° C. The amount of dry adhesion of the primer film is approximately 0.50 x 10 per square foot of film.^-61b (2.4mg / m²)Met. Examples 1 to 8 A polyethylene terephthalate film was produced, stretched and primed by the method described in the above film structure method. The aqueous coating solution of aminosilane shown in Table 1 below was applied to this film. For each primer coating composition, a 100-foot-long primer coating film was produced and rolled into a composite roll, which was then sent to an extrusion coating device to make a low density polyethylene (LDPE) (LDPE) about 1 mil thick. (USI resin with melt index 14) was extruded and coated. The melting temperature was about 620 ° F (326 ° C) and the height of the extrusion die on the film was about 8 inches (20 cm). No further corona discharge treatment or primer coating was performed during extrusion coating.<img file="JPH0627209B2_D0001.tif" />The adhesiveness of polyethylene to the primer-uncoated control film of Example 1 was measured using ASTM tests D882 and E4 and found to be 0.091 b / in. The adhesiveness of polyethylene to the films of Examples 2 to 8 was very good, and even if peeling was attempted for a peeling test, the two layers could not be peeled. In addition, peeling at the PET / LDPE interface could not be performed with hot water, toluene, or tetrahydrofuran. Adhesion was excellent when either APTMS (N-3-aminopropyltrimethoxysilane) or AE-APTMS (N-2- (aminoethyl) -3-aminopropyltrimethoxysilane) was applied. Examples 9 to 28 As described in the above film production method, a polyethylene terephthalate film was produced, stretched, and primer-coated. The thickness of the film was 0.5 mil. The aqueous coating solution of aminosilane shown in Table 2 was applied to the film. A 100-foot long primer coating film was produced for each primer coating composition and rolled up into composite rolls. This roll is sent to an extrusion coating device and is SURLYN, an ionomer resin with a thickness of about 0.75 mil.1652 was extruded and coated. The melting temperature was about 585 ° F (307 ° C). Half of each sample was corona discharged at 2.5 KVA before extrusion coating, and the other half was not corona discharged. Norchem, a low density polyethylene (LDPE) resin, on another composite roll of the same film1014 (thickness 0.75 mil, melt extrusion temperature 625 ° F = 329 ° C) was extruded and coated. SURLYNHalf of the sample was corona discharged and the other half was not corona treated, as was the case with the coating. The peel strength was measured according to ASTM D882 and E-4 using an Instron tester. During the extrusion coating operation, an untreated polyester film piece is inserted between the end portions of the two layers to be laminated to form a non-adhesive portion capable of peeling the two layers for a peeling test. There was.<img file="JPH0627209B2_D0002.tif" />For uncoated PET film and copolyester coated film, SURLYN for polyester film1652 and NorchemCorona discharge treatment is required prior to extrusion coating to obtain some degree of adhesion of 1014. Even after the corona discharge treatment, the adhesiveness to the uncoated PET and the copolyester coated film is not as good as the adhesiveness to the film coated with aminosilane according to the present invention. Further, the corona discharge treatment of the aminosilane coated film was not necessary, and there was no difference in adhesiveness. For both AE-APTMS and APTMS, the adhesiveness was sufficiently good even at a low concentration of about 0.25% by weight. From the above, it is clear that the present invention provides a primer coating film and an extrusion coating laminate capable of extrusion coating that completely satisfy the above-mentioned purposes and advantages. Although the present invention has been described above with respect to specific embodiments thereof, many changes, modifications and modifications will be apparent to those skilled in the art based on the above description. That is, all such changes, modifications and modifications are included within the scope of the present invention.