JPS6328096B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface treatment agent for plastic films used in packaging materials and the like. Plastic film is used in large quantities as a packaging material. This is because it meets the requirements of Particularly in the field of food packaging, plastic film has created new product formats and has had remarkable effects, such as helping to maintain quality and promote sales. These films include polystyrene, polypropylene, polyvinyl chloride, polycarbonate, polystyrene, polyester, and polyamide, but they do not have sufficient properties in all respects as packaging materials. Since individual plastic films have some defects such as water vapor permeability, oxygen permeability, heat sealability, blocking resistance, oil resistance, or mechanical packaging suitability, various coatings are used as a means of improving the quality of plastic films. being done. Conventionally, chlorinated polypropylene has been used as a quality improving material for plastic film for the following purposes. The film surface is used as an easily heat-sealable resin to make it possible to heat-seal films with a narrow heat-sealable range such as biaxially oriented polypropylene film, biaxially oriented polyester film, and polyamide film, and films that do not have heat-sealable properties such as cellophane. coated with. Used as an anchor coating material on the film surface when coating polyvinylidene chloride on the film to improve oxygen permeability, water vapor permeability, and oil resistance, such as polyethylene film, polypropylene film, polyvinyl chloride, polyester film, and vinylon film. applied to. As a printing ink binder for polyethylene film and polypropylene film, it is mixed with printing ink and applied to the film surface. As described above, however, the following problems have been pointed out since the chlorinated polypropylene used for these purposes is dissolved and dispersed in a solvent such as toluene, xylene, or cyclohexane. First, when used as an easily heat-sealable resin, solvents such as toluene, xylene, and cyclohexane remain partially dissolved in the film even after coating, and after it is manufactured and heat-sealed with food, it changes over time. The dissolved solvent is desorbed,
It may reduce the flavor of the food. Furthermore, since the seal strength decreases at low temperatures, the bag may break when handled at low temperatures. Next, when used as an anchor coating material or a printing ink binder, adhesiveness decreases at low temperatures and physical properties deteriorate. However, in all cases, approximately 80 parts by weight of organic solvents such as toluene, xylol, cyclohexane, etc. are used for approximately 20 parts by weight of chlorinated polypropylene, so there is a risk of flammability and explosion, and safety concerns such as organic solvent poisoning. There are also hygiene issues. The present invention relates to a film surface treating agent that improves the above-mentioned drawbacks of chlorinated polypropylene, and because it is water-based, there are fewer safety and health problems. The gist of the present invention is the formula (However, X is H or an alkyl group, R ₁ is an alkylene group, and R ₂ and R ₃ are an alkyl group.) 0.1 to 10 mol% of a vinyl group-containing tertiary amine,
and carboxyl group-containing vinyl monomer 0.1~
This is a plastic film surface treatment agent made of a copolymer of a monomer mixture consisting of 20 mol% and the remainder consisting of other vinyl monomers that can be copolymerized with both of these monomers. In the present invention, the vinyl group-containing tertiary amine is represented by the formula described above, and such a monomer is preferably a tertiary amine having an acryloyl group or a methacryloyl group, and specifically, dimethyl Aminomethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, dipropylamino n-butyl acrylate or methacrylate, dipropylamino n-butyl acrylate or methacrylate,
Examples include isobutylamino n-butyl acrylate or methacrylate. The vinyl group-containing tertiary amine is a component that cannot be used as a coating agent in the surface treatment agent of the present invention because of its adhesion to the film.
Further, after coating a film, it reacts with carboxyl groups by heating to become three-dimensional, thereby improving durability. The content of vinyl group-containing tertiary amine is 0.1 mol% to 10 mol%.
If it is less than 0.1 mol%, the effect will not be recognized,
If it exceeds 10 mol%, it will react with other copolymerization components, such as carboxyl group-containing vinyl monomers, during polymerization.
Stable polymers cannot be obtained because of thickening and gelation. Carboxyl group-containing vinyl monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, citraconic acid,
Examples include crotonic acid. This monomer is necessary for the stability of the coating liquid, and also reacts with the tertiary amine when heated after coating, thereby improving the durability of the coating agent. If the content is less than 0.1 mol%, the effect will not be recognized, and if it exceeds 20 mol%, the hydrophilicity will become strong and water resistance will deteriorate. Next, as vinyl monomers copolymerizable with both of the above monomers, acrylic esters and methacrylic esters (methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n
-hexyl, 2-ethylhexyl, etc.), styrene,
Vinyl acetate, acrylonitrile, methacrylonitrile, vinyl ethers (methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, etc.), hydroxyalkyl esters of acrylic acid and methacrylic acid (the alkyl group in this case can have an ether chain -0-) 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polypropylene glycol monomethacrylate, polyethylene glycol monomethacrylate, etc.), acrylamide, methacrylamide and its derivatives (methylol acrylamide, methoxymethyl Typical examples are acrylamide, methylolmethacrylamide, methoxymethylacrylamide, butoxymethylacrylamide, etc.), and glycidyl methacrylate, and include all other copolymerizable vinyl monomers, and their blending amount is limited to the total amount. This is the amount that makes up the remainder of the monomer. In addition to heat-sealability and adhesion, the properties required for surface treatment agents for improving the quality of plastics include blocking resistance. Blocking resistance is achieved by coating a continuous film and ensuring that the coated and uncoated surfaces do not stick together under their own weight when rolled up, or that the coated surfaces do not stick together after making a bag out of the film and putting food in it before heat sealing. The surface treatment agent of the present invention adjusts sealing strength and adhesion by combining a vinyl group-containing tertiary amine and a carboxyl group-containing vinyl monomer, and has other properties that are necessary for copolymerization. Blocking resistance can be adjusted with available monomers. The surface treatment agent of the present invention can be produced using a solution polymerization method in which a monomer mixture and an initiator are added to an alcohol solvent such as methanol, ethanol, isopropanol, etc., or an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier, etc. It is obtained by an emulsion polymerization method in which a monomer mixture is emulsified in water and polymerized by adding an initiator. In the case of solution polymerization, the standard polymerization conditions are a temperature of 60 to 80°C and a time of 5 to 8 hours, and in the case of emulsion polymerization, a temperature of room temperature to 90°C and a time of 3 to 5 hours. The carboxyl groups in the polymer thus obtained are combined with hydroxides of alkali metals or alkaline earth metals such as caustic soda, caustic potash, calcium hydroxide, ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethylamine, etc. It is desirable to neutralize or partially neutralize with a base such as ethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, morpholine, etc. to improve the stability of the aqueous dilution or dispersion of the composition. . Although the above-mentioned neutralizing agent is not intended to limit the present invention, it is preferable to neutralize with a volatile amine such as ammonia or lower amine in order to accelerate the reaction during heating. An example of how to use the treatment agent of the present invention is as follows. Dilute with pure water to a non-volatile content (hereinafter abbreviated as NV) of 20-30%, coat the film with a roll, and dry at 120-140°C for 30 seconds. In this case, the coating is applied to the entire surface of the film or only to the heat-sealed portion. Next, temperature 90-120℃, pressure 1-2
Kg/cm ² and heat-sealed for 0.5 to 2 seconds, leaving the entrance open, to make bags of central gassho seal type, envelope type, pleated type, etc. Materials to be packaged, such as seaweed, potato chips, rice crackers, and hail, are placed in this bag and heat-sealed under the heat-sealing conditions described above. Thereby, a sealed package with excellent sealing strength can be obtained. In addition, the processing agent of the present invention is roll coated on the entire surface of one side of the film,
By drying under substantially the same conditions as above, and applying and drying a polyvinylidene chloride emulsion thereon, it is possible to obtain a film that has excellent adhesion to polyvinylidene chloride and fully utilizes the properties of polyvinylidene chloride. I can do it. Furthermore, a printed film with good adhesion can be obtained by adding and mixing color pigments to make a printing ink and printing on the film surface using this ink. It exhibits extremely excellent effects in direct or indirect surface treatment of plastic films. The advantages of the treatment agent of the present invention compared to conventional chlorinated polypropylene treatment agents are as follows. B The processing agent of the present invention is a liquid substance mainly composed of water, and even if it is a solvent-based one, it uses a solvent such as methanol, ethanol, isopropanol, etc. that does not have the ability to dissolve the film, so it is usually exposed to problems caused by the solvent. There is no deterioration in the flavor of the packaging material. (b) As mentioned above, since the solvent is mainly water-based, there are no safety and hygiene problems compared to the case of chlorinated polypropylene. C. In the case of chlorinated polypropylene, heat seal strength and adhesion can only be adjusted by the degree of polymerization and degree of chlorination, and there is a limit to adhesion, especially at low temperatures. However, with the treatment agent of the present invention, each monomer The combination and quantitative blending ratio can be freely adjusted. The present invention will be explained below with reference to Examples and Comparative Examples. Example 1 Isopropanol is added to a glass reaction vessel equipped with a stirrer, thermometer, reflux condenser and addition funnel.
Fill 35 parts by weight and heat the contents to 75℃
It rose to Then butyl acrylate
As a polymerization initiator, 2,2'-azo A solution containing 1 part of bisisobutyronitrile was added dropwise over a period of 6 hours, and after completion of the addition, polymerization was continued for 2 hours, and the polymerization was completed while maintaining the temperature at 75°C. Then, enough ammonia to neutralize the methacrylic acid in the polymer was added, and stirring was continued at the same temperature for 30 minutes to obtain a water-soluble vinyl polymer. This water-soluble vinyl polymer was diluted with pure water to N.V 25% and part-coated on a biaxially stretched polypropylene film with a film thickness of 40μ that had been treated with corona discharge.
C/30 seconds to obtain a coating with a film thickness of 2 μm.
After making bags by heat-sealing this film on three sides at 100℃, pressure 1Kg/cm ² and sealing time 1 second,
Rice crackers were put in and the inlet was heat-sealed under the same conditions. Seal strength is 350g/cm at 25℃, 300g/cm at -10℃
g/cm, and sufficient sealing strength was obtained. Fifty bags of rice crackers were stored in the same bag at room temperature for three months in summer, but no change was observed in the flavor of the rice crackers inside. The above sealing strength is determined by applying a 1.5cm wide surface treatment agent to a predetermined area of two films, overlapping them and heat-pressing them at 1Kg/ ^cm2 at 100℃, and then tensile them at a predetermined temperature using a tensile tester. Speed 20cm/mm
This is the value when peeled off. (The same applies hereinafter) Comparative Example 1 20 of chlorinated polypropylene with a degree of chlorination of 26% by weight
Similarly, biaxially oriented polypropylene was partially coated with a wt % toluene solution and dried at 120° C. for 30 seconds. The film thickness was adjusted to 2μ. 110 with this film
℃, pressure 1Kg/cm ² , sealing time 1.2 seconds 3
One side was heat-sealed and a bag was made. Rice crackers were placed in this and the inlet section was heat sealed under the same conditions. The seal strength was 250g/cm at 25℃, but -10
At ℃, it decreased to 80g/cm. Fifty bags containing rice crackers were left at room temperature for three months in the summer. 50
Abnormalities were observed in the flavor of four of the bags of rice crackers. Comparative Examples 2, 3, and 4 Surface treatment agents obtained under the same conditions as in the examples except for changing the monomer composition showed the following results.

[Table] Example 2 A glass reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel was filled with 25 parts of pure water, and the content was raised to 80°C by heating. Next, 65 mol% of ethyl acrylate, 20 mol% of methyl methacrylate, 4 mol% of dimethylaminoethyl acrylate, 5 mol% of polypropylene glycol monomethacrylate, and 6 mol of itaconic acid.
% mixture, 20 parts of pure water, and 2 parts of sodium polyoxyethylene nonyl phenyl ether sulfate were mixed and stirred to emulsify. This emulsion and a solution of 0.2 parts of ammonium persulfate dissolved in 5 parts of pure water were added dropwise over 4 hours to effect polymerization. Dimethylamine was added to the obtained emulsion polymer to adjust the pH to 7.5, and then diluted with pure water so that the NV was 25%. A polyester film with a thickness of 25 μm was roll coated and dried at 120° C. for 30 seconds to obtain a coating with a thickness of 1 μm. Apply 4μ of polyvinylidene chloride emulsion on top of this coating at 120℃/30
Dry for seconds. The obtained polyester film had excellent oxygen permeability, water vapor permeability, and oil resistance, and had no problems with adhesion at low temperatures. Example 3 After neutralizing the polymer obtained in Example 1 with ammonia,
10 parts of blue coloring pigment (resin-dispersed water-based processed pigment manufactured by Dainichiseika) per 100 parts diluted to NV25%
A blue printing ink was prepared by adding and mixing the following parts. This product was used for gravure printing on cellophane having a film thickness of 30 μm, and then dried at 120° C. for 30 seconds to obtain a blue printed matter, with no problems in adhesion.

Claims (1)

[Claims] 1 formula (However, X is H or an alkyl group, R ₁ is an alkylene group, and R ₂ and R ₃ are an alkyl group) 0.1 to 10 mol% of a vinyl group-containing tertiary amine,
Carboxyl group-containing vinyl monomer 0.1-20mol
A surface treatment agent for plastic film comprising a copolymer of a monomer mixture in which % and the remainder are composed of other vinyl monomers that can be copolymerized with both of these monomers.