Patent Application
20050014892
The present invention relates to an antistatic adhesive for a water-based or solvent-based dry laminate with the excellent antistatic properties on a film surface, laminate strength, heat seal strength, compatibility with environment in the laminate processing technique; and a complex plastic film laminated with the adhesive.
Most conventional adhesives for dry laminate applications are prepared with an ethyl acetate solution. But recently, the environmental pollution problems caused by organic solutions have been kept under strict surveillance and controlled in the United States and European counties. On the other hand, in Japan, use of organic solvent-based adhesives for dry laminate is partially prohibited.
Therefore, a proposal of an adhesive for water-based laminate without using any organic solvent has been desired, but there have been no effective proposal for that purpose so far.
And, in the laminate film using an adhesive for dry laminate based on the conventional technology, generally an antistatic agent is mixed and kneaded in the laminate base film for preventing electrification of the film surface, but in the film with an antistatic agent kneaded therein, sometimes the antistatic agent disadvantageously bleeds. TO overcome this problem, the following method is generally known as a method for giving the antistatic property to a film without kneading an antistatic agent therein.
Japanese Patent Laid-Open Publication No.2002-059518 discloses a resin film for decorative sheet lamination with dust adhered little thereon and having the excellent antistatic property, and a decorative sheet laminated with the resin film therein, and the resin film according to the invention is prepared by using a copolymer polyester film as an adhesive resin layer 4 and a polybutylene terephtalate film as a base resin layer 6 to selectively form a print layer 5, and further laminating a transparent surface resin layer 7, if required, from the bottom successively. An antistatic agent is contained by 1 to 10% in an adhesive 3 for joining those resin layers together and an adhesive for adhering a decorative film to the base.
In this film, the problem of bleeding does not occur, but there is still the problem that adhesion strength of the adhesive prepared as described above becomes lower because an antistatic agent is mixed therein.
The object of the present invention is to provide an antistatic adhesive for water-based or solvent-based dry laminate with the excellent antistatic capacity, compatibility with environment, adhesion strength, and heat resistance, and a complex plastic film laminated with the adhesive.
According to one aspect of the present invention an antistatic adhesive is provided for water-based dry laminate, and the adhesive is prepared by adding an antistatic agent in a water-dispersible polyurethane resin having a carboxyl group in a side chain thereof.
According to another aspect of the present invention an antistatic adhesive is provide for water-dispersible dry laminate, and the water-dispersible polyisocyanate is used as abridging/curing agent for the water-dispersible polyurethane resin.
According to another aspect of the present invention an antistatic adhesive for water-based dry laminate as mentioned above is provided and the antistatic agent is a mixture of quarternary ammonium salt betaine and an electrolytic metallic salt.
According to another aspect of the present invention an antistatic adhesive is provided for water-based dry laminate comprising the polyurethane resin water dispersion according and the polyisocyanate water dispersion.
According to another aspect of the present invention an antistatic adhesive is provided for water-based dry laminate, and the quarternary ammonium salt betaine is alkyl dimethyl amino acetate.
According to another aspect of the present invention an antistatic adhesive is provided for water-based dry laminate, and the electrolytic metallic salt is a mixture thereof with one or more selected from the group consisting of sodium chloride, magnesium chloride, potassium chloride, sodium nitrate, magnesium nitride, potassium nitrate, and the like.
According to another aspect of the present invention a complex plastic film is provided laminated with the antistatic adhesive for water-based dry laminate discussed above.
Composition of the antistatic adhesive for water-based dry laminate and examples of the use will be explained in detail below. First, it is assumed in the following description that a component solution A is prepared by adding the antistatic agent solution that is a mixture of quarternary ammonium salt betaine and a electrolytic metallic salt to the water dispersions of the polyurethane resin having a carboxyl group in a side chain thereof. Also it is assumed that a component solution B is a polyisocyanate water dispersion which is added to the component solution A. The solutions A and B are mixed at a specific ratio to prepare a coating liquid. This coating liquid is applied on a plastic film as a base material. After the surface of the plastic film with the coating liquid applied thereon is dried, it is pressed on a sealant base material for lamination. Then, the lamination is kept in an aging bath for 24 hours at 40 degree Celsius for curing to form a laminate film.
A base material of this laminate film is any of PET, OPP, Nyl, silica evaporation PET, and the like, while a base material of sealant base material is any of CPP, PE, and the like. In any combination of any laminate base material and any sealant base material described above, excellent laminate strength and seal strength are provided. In addition, the water resistance and heat resistance thereof are comparable to those provided by antistatic adhesives based on an organic solvent.
Regarding the antistatic performance which is a feature of this adhesive, the friction-charged electrostatic potential on both surfaces of this laminate film is very small, and it is in the range from 0.1 kV. to 0.3 kV.
The solid content ratio of the carboxyl group in a side chain of the polyurethane resin in the range from 1 to 6% is effective for dispersion of this polyurethane resin in water, and more preferably the content should be in the range 1.5 to 5.0%.
The mixing ratio of the alkyl dimethyl amino acetate betaine and the electrolytic metallic salt of the antistatic agent should be in the range from 12:1 to 6:1 by the solid content weight ratio, and more preferably the ratio should be in the range from 10:1 to 7:1.
It is effective to add, preferably, poly vinyl pyrrolidone (PVP) to the component A of this adhesive described above as a stabilizer for liquid. The average molecular weight of the PVP is between 600,000 and 1,200,000. The quantity of the PVP to the component A should be in the range from 3 to 10% by the solid content weight ratio, and more preferably the content ratio should be in the range 4 to 8%
An embodiment of the present invention will be described in detail below.
Samples Used in the Embodiment 1
The water-based adhesive according to the present invention was prepared with the samples 1 to 5 above.
a. Preparation of the Antistatic Agent:
The sample 2 of alkyl dimethyl amino acetate betaine water solution was mixed in the sample 3 of potassium nitrate at the ratio of 194:6 (solid content: 36.26%, aqueous solution)
b. Preparation of the Component A of this Water-Based Adhesive Composition:
A preparation of the antistatic agent solution described in the section a above was added to the sample 1 of polyurethane resin water dispersion. The mixing ratio was 100:24 by weight
Next, the sample 5 of poly vinyl pyrrolidone water solution was added to the polyurethane resin water dispersion with the antistatic agent having been added therein. The mixing ratio was adjusted to 51:10 by weight to form the component A.
c. Preparation of the Component B
The sample 4 of water-dispersible polyisocyanate was diluted twice with water to prepare a solution with the solid content of 50%.
To prepare this adhesive agent, the solution with the solid content of 20% prepared with the component A water dispersions was used.
The mixing preparation of this adhesive agent:
This example corresponds to the complex plastic film laminated with the antistatic adhesive for water-based dry laminate in which various films are adhered to each other with the adhesive agent according to the present invention and by using a dry laminator.
As a coating base material for the adhesive agent, materials enlisted in Table 1 were selected, and this adhesive agent was applied to each surface processed by corona discharging or with silica deposited thereon. As a coating plate, a carved gravure plate (100 lines) was used for coating. After dried, the amount of the coating agent applied thereon was in the range from 3.2 to 3.5/m2.
As a sealant film, the materials in the table 2 were selected. The surface of each of those materials was pressed and adhered to the surface with the adhesive agent applied thereon. Then the lamination formed with adhesion was aged in a thermostatic chamber at 40° C. for 24 hours.
Experiment 1
The laminate strength, heat seal strength and friction-charged electrostatic potential the laminate film of the embodiment 3 were measured.
Laminate Strength Measurement:
From an edge of the sample cut into a piece with the width of 15 mm, the base material and sealant film were peeled off in the T-shaped state, and the strength at the peeling speed of 300 mm/min was measured with an autograph.
Measurement of the Heat Seal Strength:
Two samples of sealant film for the laminated film were placed face to face, and were heat-sealed at the conditions of 150° C. and 1 kgf/Cm2/sec. The heat-sealed section of the sample was cut into a piece with the width of 15 mm, and the sample piece was set at an autograph in the T-shaped state to measure the strength at the peeling speed of 300 mm/min. The result of this measurement is shown in Table 3.
The friction-charged electrostatic potential (kv) of the laminated film after curing (measuring condition: 23° C., 40% RH] is as shown in Table 4.
[Experiment 2]
The laminated film in Example 3 was adhered to a surface of LLDPE film not subjected to corona discharging treatment, and after aging for 24 hours at 40° C. in a thermostatic chamber, the LLDPE film was peeled off, and the surface resistance value of the applied adhesive agent itself was measured. The result is as shown in the table 5.
[Advantages of the Invention]
As apparent from the foregoing results, the adhesive according to the present invention and the complex plastic film are extremely effective for practical use with the excellent adhesiveness, antistatic property and compatibility with environment on account of water-based as well as with the excellent properties in heat seal strength and heat/water resistance.
According to another aspect of the invention providing an antistatic adhesive for solvent-based dry laminate prepared by adding an antistatic agent in solvent-based polyurethane, research and studies are made for expressing a function to resist generation of static on a surface of laminated film by giving antistatic properties to the solvent-based adhesive, and in result of those concentrated research and studies, the adhesive for laminate and the complex plastic film having antistatic properties of the objective of the present invention without degrading the adhesive properties of the adhesive was obtained. The composition of the present invention accomplished is as described below.
The antistatic adhesive for solvent-based dry laminate prepared was prepared by adding antistatic agent to solvent-based polyurethane resin.
An aliphatic isocyanate-based curing agent is used as a bridging/curing agent for the solvent-based polyurethane resin.
In addition, the antistatic agent is a mixture of an aliphatic dimethylethyl ammonium ethosulphate salt and a polyoxyethylene alkyl ether.
The adhesive may comprise an organic solvent solution of polyurethane resin and the organic solvent solution of aliphatic isocyanate-based curing agent.
The complex plastic film is laminated with the antistatic adhesive for solvent-based dry laminate.
Composition and the examples of use of the aforementioned antistatic adhesive for solvent-based dry laminate according to the present invention will be described in details.
The component A is prepared by previously adding ethyl acetate solution of the antistatic agent to ethyl acetate solution of the polyurethane resin. The component B is an ethyl acetate solution of isocyanate-based curing agent which is added in the component A. The coating liquid is prepared by mixing the components A and B at a predetermined ratio. The solution is applied on the plastic film base material, and after the coated surface is dried, the surface is pressed onto the sealant base material for lamination.
Then, the lamination is stored in an aging bath for 24 hours at 40 for curing to prepare a laminate film.
A base material for the laminate film base is any of PET, OPP, Nyl, silica-deposited PET or the like, while a base material for the sealant base material is any of CPP, PE or the like. Any combination of the aforementioned laminate film base material and the sealant base material provides the excellent laminate strength and sealing strength. Also the water resistance and heat resistance are excellent.
The antistatic property of the adhesive which is a feature of the present invention shows is extremely high, and for instance the friction-charged electrostatic potential is in the range from 0.0 to 0.2 kv on both sides of the laminate film.
The polyurethane resin according to the invention is polyester-based polyurethane resin, which is a mixture of high Tg polyurethane resin and low Tg polyurethane resin. The mixing ratio of high Tg polyurethane resin to low Tg polyurethane resin is in the range from 1:2 to 1:5.
In this mixing step, a temperature of the high Tg polyurethane resin is set to the range of 0 to 40, and a temperature of the low Tg polyurethane resin is set to the range from −30 to 0° C.
The mixing ratio of the aliphatic dimethylethyl ammonium ethosulphate to the polyoxyethylene alkyl is in the range from 10:1 to 12:1 by the solid content weight ratio.
An example is described in details below.
Samples used in Example 4:
The solvent-based adhesive was prepared by using any of the samples 1 to 6 above.
The component solution A prepared by mixing the antistatic agent ethyl acetate solution at the mixing ration described above and the component solution B as a curing agent were blended with each other at the mixing ratio as shown below.
(solid content of the mixed solution was about 31%).
An example in which the complex plastic film was prepared by laminating various types of films to each other with a dry laminator and by using the adhesive according to the present invention is described below. An adhesive coating base material is chosen from the materials shown in Table 6, and then the adhesive is applied on each surface processed by means of corona discharging treatment or with silica deposited thereon. An engraving gravure plate (100 lines) is used as a coating plate for application. The mount of adhesive after drying was in the range from 3.2 to 3.5/m2.
The sealant film is chosen from those shown in Table 7, and each surface processed by means of the corona discharging treatment is pressed and adhered a surface with the adhesive applied thereon, and then the laminate film was stored for aging in a thermostatic chamber for 24 hours at 40.
With the adhesive prepared in Example 5, the film as shown in Table 6 as a base material and the film shown in Table 7 as a sealant were adhered to each other at the conditions as described in Example 6, and the lamination was stored for four days in an aging chamber at 40 for curing the adhesive to obtain the following complex plastic film (laminate film).
The laminate strength, heat-seal strength and friction-charged electrostatic potential of the laminate film was measured. The result is as shown in Table 8.
For measurement of the heat-seal strength, a base material and a sealant film were peeled from the sample piece having the width of 15 mm in the T-shaped state, and then the strength was measured when peeling at the peeling speed of 300 mm/min was measured with an autograph.
Measurement of the Heat-Seal Strength
Surfaces of the sealant films in the sample laminate film were placed face to face, and heat sealing was performed (at the conditions of 150° C., 1Kgf/cm2, 1 sec.). The heat-sealed section was cut into a piece with the width of 15 mm, and the sample piece was set in an autograph in the T-shaped state, and the heat-seal strength when peeled at the peeling speed of 300 mm/min was measured. The result is as shown in Table 9.
The friction-charged electrostatic potential of the laminated after aging is shown in Table 10.
The surface-specific resistance value of each of the laminate films after aging is shown in Table 11.
A bag (8 cm×10 cm) was prepared with the laminated film of Example 7 and water (80 g) was sealed in the bag to use it as a sample. In the boiling experiment, the sample was heated in boiling water at 90 for one hour and dried after cooling with water, and then changes in the sample were observed. The result is shown in Table 12.
[Advantages of the Invention].
With a mixture solution as an antistatic agent is added in a mixture solution of the high Tg polyurethane resin and low Tg polyurethane resin each based on polyester to prepare an adhesive for lamination of plastic films, the adhesive has the antistatic property without losing the adhesion strength. The complex plastic film with the adhesive mixed therein has the high laminate strength and resistance against hot water, which is every effecting in the fields of packaging, printing, or the like. The adhesive according to the present invention is compatible with any solvent including water-based and organic material solvents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-196911 | Jul 2003 | JP | national |
| 2004-47472 | Feb 2004 | JP | national |
