JPH0153991B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing release paper using an extrusion lamination method, and more particularly to a method for efficiently and economically producing release paper using an extrusion lamination method. Conventionally, the main method for manufacturing silicone release paper has been a coating method, in which a resin layer is usually formed by polyethylene laminate on a base material such as paper, and a release layer is further coated on the surface of the resin layer.
The release agent used in this method is composed of, for example, polymethylhydrodienesiloxane and vinyl group-containing polydimethylsiloxane, which undergoes an addition reaction due to the addition of a platinum catalyst and heat, and is cured to form a release film. On the other hand, similar to the present invention, there is a method in which a release layer is formed on a base material all at once using an extrusion lamination method, but in this method, the resin itself to be laminated has releasability. As such a removable resin, an ethylene-α olefin copolymer elastomer or the like is used, and is suitable for use in acrylic pressure-sensitive adhesives. However, in the case of the former coating method, the base material is first laminated with polyethylene, and then a silicone release agent, etc. It cannot be said that it is advantageous. Furthermore, the stripping agent used in the coating method generally uses an organic solvent, which is associated with serious problems such as fire, explosion, and environmental pollution. On the other hand, in the latter extrusion lamination method using an ethylene-α-olefin copolymer elastomer or the like, the peeling force against the acrylic pressure-sensitive adhesive varies, and the peeling force becomes heavier as time passes. Ethylene-α-olefin copolymer elastomer is difficult to extrude when used alone, so it is used in combination with polyethylene; however, the lower the blending ratio of the elastomer, the less the release effect is
On the other hand, if the amount increases, the properties of the elastomer become stronger, the strength of the coating film becomes poor, and problems such as blocking occur during processing. In an attempt to overcome both of these drawbacks, the present inventors attempted a method of mixing the release agent used in the coating method with polyethylene resin and extruding it, but extrusion was extremely difficult, and even if laminated Even if it were possible, curing would have been extremely difficult. Therefore, we continued to conduct intensive research and found that extrusion was surprisingly improved by adding a specific substance, curing was achieved easily and effectively, and furthermore, by using a specific base resin, remarkable peelability was achieved. The present invention has been completed based on the new finding that the present invention is provided. That is, in the present invention, a mixture of a polyolefin resin and a silicone release agent having compatibility with the polyolefin resin is extruded onto a base material such as paper, cloth, or film to form a laminate, and then the laminate is heat-treated to release the above-mentioned material. A method for producing a release paper, characterized by bleeding a release agent contained in a mixture layer of a laminate onto the surface of the mixture layer to make it unevenly distributed, and further curing and fixing the unevenly distributed release agent. It is. The release agent used in the present invention is a silicone release agent that is compatible with polyolefin resins, such as polymethylhydrodiene siloxane and vinyl group-containing polydimethylsiloxane, and 1,
Reaction products with 2-polybutadiene or polyethylene waxes are preferred. An example of a method for producing a release agent is to mix polymethylhydrodiene siloxane, vinyl group-containing polydimethylsiloxane, and 1,2-polybutadiene, add di-tertiary butyl peroxide as a catalyst, and heat the mixture. The reaction is allowed to proceed, and the reaction is stopped at the same time as the start of gelation is observed. If the reaction is stopped before gelation is observed, subsequent curing will be incomplete, while if gelation progresses too much, it will be difficult to unevenly distribute bleed onto the surface of the release layer.
After the reaction has stopped, the reaction product is purified by removing unreacted volatile components under reduced pressure. When using polyethylene wax, polyethylene wax is reacted with vinyl group-containing polydimethylsiloxane in the presence of a dicumyl peroxide catalyst, and then polymethylhydrodienesiloxane is added, heated, and reacted to form a gel. Stop the reaction as soon as it starts. The product is purified by removing unreacted volatiles under reduced pressure. The release agent synthesized as described above is mixed with the polyolefin resin in an amount of 1 to 5% by weight, and is kneaded into pellets using a pelletizer to obtain a mixture layer resin (extrusion resin). Suitable polyolefin resins used in the present invention include polyethylene resins, polypropylene resins, ethylene-vinyl acetate copolymer resins, and mixtures thereof. Polyethylene resin is 0.910~
Linear low-density polyethylene resin having a density of 0.935 g/cm ³ has particularly excellent peelability in a low-speed range and can be heat-treated and cured at high temperatures, so it has the advantage of being able to be heat-treated and cured in a short time. Moreover, the ethylene-vinyl acetate copolymer resin has a synergistic effect with the release agent, and the releasability increases dramatically.
Of course, the ethylene-vinyl acetate copolymer resin gives good results when used alone, but a mixture in which the ratio of the copolymer resin to polyethylene is in the range of 1:2 to 9:1 is more preferable, and more preferably 2:1 to 2:1. Particularly preferred are mixtures of 1 to 3:1. The ethylene-vinyl acetate copolymer resin used in the present invention has a vinyl acetate content of
It is preferably 10 to 40% by weight, and particularly preferably about 28% of the content has an MI of 5 to 20. The release layer resin thus obtained is extruded onto the base material using an extrusion laminator to form a release layer on the base material. The base material used in the present invention includes:
Paper, cloth, films such as polyolefin films such as polyethylene and polypropylene, polyethylene terephthalate films, and laminates thereof are used. The laminate laminated onto the substrate is heat treated. The heat treatment is performed by leaving the laminate for about 10 minutes to about 60 minutes after the surface temperature of the laminate reaches 70° C. to 120° C. Due to the heat treatment, the release agent contained in the mixture layer bleeds onto the surface of the mixture layer and is unevenly distributed, resulting in a state similar to that obtained by coating the surface of the polyethylene layer with a release agent as in the conventional method. This means that FT−
Confirmed by ATR-IR measurements. The unevenly distributed release agent is completely cured by, for example, catalytic treatment with chloroplatinic acid. Curing is preferably performed at a temperature of 100 to 130°C and for a time of 10 to 80 minutes. Therefore, in the range where the temperature and time of heat treatment and curing overlap, uneven distribution and curing may be performed at the same time. The amount of chloroplatinic acid used is preferably in the range of 2×10 ⁻² to 3×10 ⁻¹ mg/m ² . In the present invention, in order to improve the adhesive strength between the release layer and the base material, an adhesion enhancing layer such as polyethylene may be interposed between the two. The first feature of the present invention is that by reacting 1,2-polybutadiene or polyethylene wax with a release agent component, compatibility with the polyolefin resin is improved and extrusion processability is surprisingly good.
The second feature of the present invention is that a high concentration of release agent is unevenly distributed and fixed on the surface of the release layer through heat treatment and curing. A great peeling effect is achieved. Furthermore, the third feature of the present invention is that by using linear low-density polyethylene, ethylene-vinyl acetate copolymer, or a mixture thereof as the base resin, the releasability is dramatically improved. The present invention will be described below with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited thereto. In the following, parts by weight and % by weight are respectively meant unless otherwise specified. Example 1 Polymethylhydrodiene siloxane (5-
7) 100 parts, 400 parts of vinyl group-containing polydimethyloxane (150, 0.7% vinyl group) and 1,2-polybutadiene (1050, 85% or more of 1,2 bonds)
55.6 parts were charged into a reactor, heated to 120°C, then 4.3 parts of di-tertiary butyl peroxide was added as a catalyst, and further heated to 140°C.
The reaction was allowed to proceed for 100 minutes, and at the same time as gelation started, the reactor was cooled to stop the reaction. The reaction product is at 110℃,
Unreacted volatile components were removed under reduced pressure of 10 mmHg for 24 hours to obtain a white viscous liquid stripping agent. The obtained release agent was added to linear low-density polyethylene ("Stamirex-0066", manufactured by Idemitsu Petrochemical Co., Ltd.).
MI: 6, density: 0.920 g/cm ³ ) was added in an amount of 3%, and pellets for the mixture layer were prepared using a pelletizer at a die temperature of about 200°C. The same linear low-density polyethylene used for the mixture layer was separately prepared as an adhesion-enhancing layer. Using Kurupakku unbleached kraft 73g/ ^m2 as the base material, the polyethylene for the adhesion reinforcing layer was extruded at a die temperature of 310°C using an ordinary coextrusion laminator, and the pellets for the mixture layer were simultaneously extruded at a die temperature of 280°C to form the base material layer. A laminate having a three-layer structure of -adhesion enhancing layer-mixture layer was produced. The thickness of the mixture layer is
The thickness of the adhesion enhancing layer was 20μ. The adhesive strength between each layer of the three-layer laminate thus obtained was sufficient. Note that Table 2 shows the extrusion performance at this time. Next, the three-layer laminate was cut into a sheet, and heat-treated at 120° C. for 40 minutes with the surface of the release layer facing up.
After the heat treatment, 2.7×10 ⁻¹ mg/m ² of chloroplatinic acid (0.001% IPA solution) was applied to the surface of the mixture layer and cured again at 120° C. for 60 minutes to prepare a release paper. The peeling force and residual adhesive force of the obtained release paper were evaluated in the following manner. Adhesive tape: Acrylic adhesive craft tape ("Elm Tape", manufactured by Soken Kako, initial adhesion strength to SUS stainless steel: 600 g/25 mm) was adjusted to a width of 25 mm x length of 210 mm and tested. Measurement conditions: The above adhesive tape is rolled with a rubber roller weighing 4.5 kg.
The film was bonded to the above-mentioned release paper by applying pressure back and forth at a speed of 5 mm per second, and the peel force and residual adhesive strength were measured under the following conditions. After pasting the tape, the load is 20g/cm ² ,
After aging for 20 hours in an atmosphere with a temperature of 70°C and a humidity of 65% RH, measurements were taken after cooling. Measurement method: Measurement method is low speed range (0.3 m/min) peeling using Autograph tensile tester ("Strograph-R", manufactured by Toyo Seiki), high speed range (3 m/min, 20 m/min) peeling Measurement was performed using a peel tester (manufactured by Tester Sangyo) at a peel angle of 180 degrees. The conditions during measurement are
The temperature was 23℃ and 65%RH. The measurement results are shown in Table 1. Example 2 In Example 1, heat treatment and curing were
It was carried out simultaneously at 120°C for 60 minutes. The results are shown in Table 1. Comparative Example 1 A conventional silicone release agent for coatings, which is composed of polymethylhydrodiene siloxane and vinyl group-containing polydimethylsiloxane and forms a release film through an addition reaction, was applied to "Stamilex-0066" in the same manner as in Example 1. A pellet for a mixture layer was prepared by adding 3%. The lamination conditions are a coextrusion laminator using a die temperature of 310°C for polyethylene for the adhesion enhancing layer.
The layer was extruded to a thickness of 20 μm. We attempted to extrude the pellets for the mixture layer with a die temperature of 280°C and a layer thickness of 20μ, but there was a considerable decrease in the extrusion rate and fluctuations.Although we tried to extrude the pellets by force, there were also variations in film thickness and laminated film width. A large laminate was obtained which was completely unbearable for practical use. The extrusion performance is shown in Table 2. Regarding curing, even though it was carried out under the same conditions as in the present invention, it could not be cured, and the silicone release agent in the release layer migrated to the adhesive tape layer, resulting in a low release force. As is clear from the above results, conventional silicone release agents for coatings are neither suitable for lamination nor curing, and cannot be used as the release agent of the present invention. Comparative Example 2 Of the release paper obtained in Example 1, one without heat treatment (A) and one without curing after heat treatment (B) were prepared, and the release strength and strength were determined in the same manner as in Example 1. The residual adhesive strength was measured. The measurement results are shown in Table 1. From Table 1, the peeling force becomes heavier for both (A) and (B).
The residual adhesive strength decreased. Comparative Example 3 "Stamilex-0066" used in Example 1 was extruded with an extrusion laminator at a die temperature of 310 DEG C. onto a base material of Lupack unbleached kraft 73 g/m ² to a thickness of 40 μ without a release agent. The obtained laminate was heated to 120℃,
After heat treatment for 40 minutes, peel strength and residual adhesive strength were measured in the same manner as in Example 1. The results are shown in Table 1. Example 3 The same release agent as in Example 1 was used in the same linear low-density polyethylene "Stamilex-0066" 30 as in Example 1.
% and ethylene-vinyl acetate copolymer resin (Evaflex-250, manufactured by Mitsui Polychemicals, vinyl acetate content: 28 MI: 15, density: 0.950 g/cm ³ ) 70%
3% was added to a mixed resin consisting of the following, and pellets for the mixture layer were produced using a pelletizer at a die temperature of 170°C. On the same base material as in Example 1, the same polyethylene for the adhesion enhancing layer as in Example 1 was extruded using a coextrusion laminator at a die temperature of 300°C, and the pellets for the mixture layer were simultaneously extruded at a die temperature of 235°C. By extrusion, a laminate having a three-layer structure consisting of a base layer, an adhesion enhancing layer and a mixture layer was obtained. The thickness of the adhesion enhancing layer and the mixture layer was each 20μ. Next, the obtained three-layer laminate was subjected to heat treatment and curing by repeating the same operations as in Example 1, and the release agent and residual adhesive strength of the obtained release paper were measured. The results are shown in Table 1, and it was confirmed that the peeling force increased dramatically. Comparative Example 4 In Example 3, linear low density polyethylene “Stamilex-0066” 30 was prepared without adding a release agent.
% and 70% ethylene-vinyl acetate copolymer "Evaflex-250" was extruded and laminated to a thickness of 40μ on a base material (Kurupakku unbleached Kraft 73g/m ² ) at a die temperature of 235℃ using a laminator. did. The obtained laminate was heat treated at 120° C. for 40 minutes, and the peel force and residual adhesive strength were measured in the same manner as in Example 3. The results are shown in Table 1.

【table】

【table】

【table】

Claims (1)

[Claims] 1 A mixture of a polyolefin resin and a silicone release agent that is compatible with the polyolefin resin is extruded onto a base material such as paper, cloth, or film to form a laminate, and then the laminate is subjected to heat treatment. A method for producing a release paper, comprising: bleeding the release agent contained in the mixture layer of the laminate onto the surface of the mixture layer to make it unevenly distributed; and further curing and fixing the unevenly distributed release agent. 2. The manufacturing method according to claim 1, wherein the silicone release agent is a reaction product of polymethylhydrodiene siloxane, vinyl group-containing polydimethylsiloxane, and 1,2-polybutadiene or polyethylene wax. 3. The manufacturing method according to claim 1, wherein the polyolefin resin is a linear low-density polyethylene resin having a density of 0.910 to 0.935 g/cm ³ . 4. The manufacturing method according to claim 1, wherein the polyolefin resin is an ethylene-vinyl acetate copolymer resin (vinyl acetate content: 10 to 40% by weight). 5 The polyolefin resin has a ratio of ethylene-vinyl acetate copolymer resin to polyethylene of 1:2 to 9:
1. The manufacturing method according to claim 1, which is a mixture of 1 and 2.