JP2003026837A - Method for producing biodegradable peelable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a method for producing a biodegradable peelable film, not having defects such as crease or loss of flexibility. SOLUTION: This method for producing the biodegradable peelable film comprises a step for producing the film by applying a silicone resin to a biodegradable film of a fatty acid polyester. (a) The silicone resin curable at <100 deg.C low temperature is used and (b) the silicone resin is applied while controlling the amount of the silicone resin to the minimum amount of forming peeling layer and (c) the silicone resin is cured without stretching while keeping the film at <100 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a release film used for pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, etc. More specifically, a biodegradable film is used as the release film, and at the same time, physical properties of the film are deteriorated in the production process. The present invention relates to the development of a manufacturing method which is excellent in economic efficiency while preventing the above.

[0002]

2. Description of the Related Art Conventionally, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate has generally been used as a material for the above-mentioned release film, and a silicone film rich in releasability is formed on the surface thereof. However, the production method is generally applied by coating stabilized polyester on a polyester film with a coating machine such as a gravure coater and exposing it to a high temperature of about 120 ° C. to accelerate the curing reaction of the silicone. The fixing film is fixed on the surface to obtain a release film.

However, since the above polyethylene terephthalate and polyethylene naphthalate materials lack biodegradability, they must be incinerated at the time of disposal, and even if they are left as they are today, due to problems such as lack of an incinerator and environmental pollution. A biodegradable film that is decomposed by the action of microorganisms has been studied, and as the biodegradable film, for example, a film containing an aliphatic polyester as a main component such as a polylactic acid film is known.

By the way, it has been found that the following problems occur when the aliphatic polyester such as polylactic acid is used as a release film. (A) Since the biodegradable film of the aliphatic polyester has poor resistance to heat, when a high temperature of 120 ° C. or higher is applied in the manufacturing process of the release film to accelerate the curing of the silicone, the film having a smooth surface becomes uneven. Wrinkles are generated and the rigidity of the film is increased, resulting in a film with a stiff and inflexible feeling. (B) In order to smooth the wrinkles, there is a method of removing the wrinkles by stretching the film by applying a biaxial stretching machine in a post-process, but the biaxial stretching machine is an extremely expensive device. This will increase manufacturing costs and impair economic efficiency.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and on the premise that a biodegradable film is used as a release film, the above-mentioned problems occurring at that time are examined and the problems are eliminated. This is an attempt to develop a possible manufacturing method.

[0006]

The method for producing a biodegradable release film according to claim 1 is the step of producing a release film in which a silicone resin is applied to a biodegradable film of a fatty acid polyester. 10 for silicone resin
Using a resin that cures at a low temperature of less than 0 ° C., (b)
Peeling by adjusting the amount of the silicone resin mixed with the curing agent to the minimum necessary amount to form the peeling layer without adding the catalyst inhibitor or suppressing the addition amount to a small amount. (C) The release film is applied to a film at 100 ° C.
It is characterized in that the silicone is cured without adding a stretching step while being kept at a low temperature of less than.

In the method for producing a biodegradable release film according to claim 2, the fatty acid polyester is constituted by polylactic acid.

In the method for producing a biodegradable release film according to claim 3, the silicone resin is Shin-Etsu Silicone KS830.
Configured as.

The method for producing a biodegradable release film according to a fourth aspect of the present invention is configured by supplying a silicone resin in an amount close to a necessary minimum amount using a constant amount supply device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION For the release film of the present invention, a biodegradable film is used for the intended purpose, and an aliphatic polyester film is adopted as the biodegradable film. The film of the aliphatic polyester has the general formula [-O
-CHR-CO-] (R is an alkyl group having 1 to 3 carbon atoms)
Examples of the polymer having a repeating unit of are polylactic acid, polyglycol, polyoxybutyric acid, and the like. For example, polylactic acid is characterized by being converted into oligolactic acid by hydrolysis, undergoing enzymatic decomposition, and then being reduced by microorganisms into CO ₂ and H ₂ O, which functions as an excellent biodegradable film. Is. However, in the test of the present inventor, when the polylactic acid film was heated to 100 ° C. or higher, heat shrinkage occurred in the film and the flexibility as the film was lost.
It was confirmed that the film was stiff and stiff. Although this tendency is slightly observed in the conventional PET film, the tendency is much larger in the polylactic acid film. For example, assuming that a high temperature of 120 ° C. or higher is applied for the post-process silicone curing reaction. However, large deterioration of physical properties is inevitable. The reason for this is that when the surface of a film rich in hydrophilicity containing -CO groups and the like is exposed to high temperatures, some of the water that had functioned as a softening agent is lost, and the film shrinks, and the flexibility increases. It is presumed that it loses viscoelasticity and becomes hard. By the way, when the difference in the heat shrinkage rate and the melting point between the PET film and the polylactic acid film is examined from the literature, it is as shown in the table below.

[0011]

[Table 1]

Next, a curable silicone resin is used for the release layer. Conventionally, the silicone resin has a curing temperature of 100 ° C. or higher and a curing time of 20 seconds or longer, that is, 1
It is common to use a type of silicone resin that does not cure easily at a temperature below 00 ° C. and has a slow curing time. The reason is that when the release agent is applied by a roll coating method such as a gravure coating method, a reverse coating method, etc., which will be described later, or when the release agent is quickly dried at a low temperature, a curing reaction starts in the middle of the application, and the coating composition is uniform. This is because it becomes difficult to apply the coating sufficiently. Thus, in the present invention, the silicone resin is
A silicone resin of the type in which the reaction starts rapidly at a temperature of less than 100 ° C. (preferably about 80 ° C.) is used. Examples of the silicone resin include Shin-Etsu Silicone KS830.
Can be mentioned. That is, the present inventor makes trial and error to eliminate the deterioration phenomenon of the fatty acid polyester film at high temperature, and setting the temperature of the film to 120 ° C. or higher delays the curing reaction of the silicone resin in the coating step, Since we tried to accelerate the curing reaction all at once in the subsequent process, we noticed a contradiction that the problem of high temperature deterioration could not be solved from this viewpoint. Therefore, in consideration of the relative relationship with the coating step to be described later, first, it was decided to select a silicone resin of a type in which the curing reaction of the silicone is promoted at about 80 ° C. This is because if the curing reaction is performed at a low temperature of about 80 ° C., the fatty acid polyester resin does not deteriorate and the curing speed does not delay the process. This silicone resin contains a catalyst inhibitor (reaction retarder) for suppressing the reaction of the catalyst for the purpose of delaying the above reaction.
Is added in many cases, and in this case, the catalyst inhibitor is not added or the addition amount is adjusted to a small amount to obtain a silicone resin of the type that cures at low temperatures. be able to.

Next, in the correlating coating steps,
Conventional silicone resin coating methods have used a gravure coating method, a reverse coating method, or the like to store excess silicone resin in a liquid reservoir, but in coating the silicone resin according to the present invention, the silicone resin is used. Adjust the resin to the minimum amount necessary to form the release layer,
It was applied to the release film after being mixed with the required curing agent. That is, in the conventional method, as described above, the reaction of the silicone resin is delayed to achieve stabilization, and the stabilized silicone resin is stored in the liquid reservoir part in anticipation of a large excess amount. The use of catalyst inhibitors (reaction delay agents) is unavoidable. Therefore, in the present invention, the minimum amount of silicone resin necessary for forming the release layer of the fatty acid polyester film is supplied to the coating machine, and the supplied resin is used up without being circulated. In this case, in the process of feeding the silicone resin from the silicone resin supply tank to the applicator, a constant amount supply device having an accuracy capable of adjusting the minimum required amount of silicone is interposed. That is, the conventional idea of delaying the reaction of silicone is abandoned, and the minimum necessary amount is supplied to bring the surplus to as close to zero as possible. The purpose of the present invention is to eliminate the adverse effects such as instability of the work and promote the formation of the silicone coating within a short time in which the increase in viscosity does not occur. In detail, conventionally, there is a liquid reservoir for storing silicone at the bottom of the rotating roll, and excess silicone is stored in this liquid reservoir, and a circulation pipe for returning the excess after completion is provided. However, in the present invention, an amount of silicone resin that is as close as possible to the amount required for forming the release layer is supplied to the liquid reservoir portion without being mixed with the catalyst inhibitor and mixed with the curing agent. I decided. However, there is no perfect agreement, so only a very small amount was added, and this was supplied in a used-up state without being circulated. The quantitative supply device, for example,
An existing two-liquid mixing device whose supply amount can be adjusted with an accuracy of 0.1 g can be used. When the silicone resin is supplied to the liquid reservoir of the coating machine with constant accuracy, when the film fed from the rotating roll and the silicone resin come into contact with each other, the minimum value necessary for forming the release layer is obtained in advance. The approached amount of silicone resin adheres and is sent directly to the curing process.

In the curing step, unlike the conventional case, the temperature is not higher than about 120 ° C., the temperature is lower than 100 ° C. (preferably about 80 ° C.), and the biaxial stretching step is not added. , Promotes fixing by curing the applied silicone resin.

In order to examine changes in the physical properties of the film of the present invention obtained according to the above invention when heated at high temperature, first, a tensile test was conducted under the following conditions. <Test Conditions> Film: Film of the present invention obtained in Example 1 Temperature conditions: Film left at each temperature of 80 ° C., 100 ° C., 120 ° C., 140 ° C. for 5 minutes Test method: Tensile test based on JISK7161 and 7162 Tensile speed: 100 mm / min <Results> The results are shown in Table 2, and graphs thereof are shown in FIGS. 1, 2 and 3. As shown in FIG. 1, the strength at the initial peak tends to increase as the treatment temperature increases, and as shown in FIG. 2, the strength at break does not change so much even when the treatment temperature changes. However, it was found that the elongation at break becomes lower as the treatment temperature is higher, and the elongation is particularly remarkable in the longitudinal direction, and the flexibility is lost.

[0016]

[Table 2]

Next, a loop repulsion test was conducted under the following conditions in order to see the change in strength of the tape-shaped film. <Test conditions> Film: Film of the present invention obtained in Example 1 Test piece: Cut into a tape shape having a length of 100 mm and a width of 50 mm Tester: Tensilon Test method: The above test piece was formed into a loop, and the head of the loop was formed. From here, push the piece of Tensilon downward, and measure the strength at that time with Tensilon. Push-down speed: 100 mm / min <Results> The results are shown in Table 3, and FIG. 4 is a graph thereof. As shown in FIG. 4, the higher the temperature, the higher the repulsive force and the higher the rigidity value.
It was found that at 0 ° C a low stiffness value was maintained.

[0018]

[Table 3]

Further, in order to see the change in shrinkage of the film of the present invention when heated at a high temperature, a shrinkage measurement test was conducted under the following conditions. <Test Conditions> Film: Film of the present invention obtained in Example 1 Test piece: Same as in Example 1 Test method: The test piece was left at each temperature of 80 to 160 ° C. for 5 minutes, and the shrinked dimension was measured thereafter. did. <Results> The results are shown in Table 4, and a graph of them is shown in FIG. As shown in FIG. 5, the shrinkage rate increases as the treatment temperature increases, and is 6 to 18 at 120 ° C. or higher.
It was proved that the shrinkage rate was 80% or less, but the shrinkage rate was 2% or less.

[0020]

[Table 4]

[0021]

Example 1 A unitika polylactic acid film (manufactured by Unitika) was used as a film, and a silicone resin Shin-Etsu Silicone KS830 was mixed with a curing agent and applied (catalyst inhibitor is not included). A gravure coat type applicator was used as the applicator, and a fixed-quantity supply device of an existing two-liquid mixing device was interposed in the supply process to the liquid reservoir of the applicator. After coating, the film was kept at 80 ° C. for 1 minute, and it was cured as it was. Of course, it was not hung on a stretching machine. As a result, the release agent film thickness is 0.1 μm, the release force is 100 g / 5 cm,
The residual adhesion rate was as high as 100%, which proves that the curing is almost complete.

[0022]

Comparative Example Shin-Etsu Silicone KS847 was taken as a comparative example. A Unitika polylactic acid film (manufactured by Unitika Ltd.) was used as the film as above, and a silicone resin Shin-Etsu Silicone KS847 was mixed with a curing agent and applied (catalyst inhibitor is not included). A gravure coat type applicator was used as the applicator, and a fixed-quantity supply device of an existing two-liquid mixing device was interposed in the supply process to the liquid reservoir of the applicator. After coating, the film was kept at 80 ° C. for 1 minute, and it was cured as it was. Of course, it was not hung on a stretching machine. As a result, the release agent film thickness was 0.1 μm and the release force was 10 g /
Shin-Etsu Silicone KS847, which is as low as 5 cm and has a residual adhesion ratio of 50%, and which is inferior in low-temperature curing property to Shin-Etsu Silicone KS830, transferred a considerable amount of uncured release agent.

[0023]

The present invention has the following excellent effects based on the above-mentioned constitution and operation.

The problem of deterioration due to heat, which was a defect of the biodegradable film of the aliphatic polyester, was solved, and even after the silicone layer was formed on the film surface, the shrinkage rate was kept at 2% or less, and the surface was smooth without unevenness. It is possible to obtain a film having a flat surface and to obtain an excellent film that retains flexibility without a stiff feeling.

Further, the residual adhesion rate of the film is extremely high, and a release film without transfer of release agent can be obtained.

Further, since a smooth film without wrinkles can be obtained as it is, it is not necessary to apply it to a biaxial stretching machine in a subsequent step, and an extremely expensive biaxial stretching machine can be omitted, and the manufacturing cost can be significantly reduced. .

Furthermore, since a biodegradable film having no physical property deterioration was obtained, the characteristics of the biodegradable film can be utilized in the true sense, which contributes to environmental problems.

[Brief description of drawings]

FIG. 1 is a graph showing the part of the first peak in Table 2.

FIG. 2 is a graph showing the strength at break in Table 2.

FIG. 3 is a graph showing elongation at break in Table 2.

FIG. 4 is a diagram showing Table 3 as a graph.

FIG. 5 is a diagram showing Table 4 as a graph.

Claims (5)

[Claims] 1. A process for producing a release film, which comprises coating a biodegradable film of a fatty acid polyester with a silicone resin, comprising: (a) using a resin of a type curable at a low temperature of less than 100 ° C. as the silicone resin; b) The addition of the catalyst inhibitor may be eliminated or the amount thereof may be suppressed to a small amount, and the silicone resin mixed with the curing agent may be adjusted to the minimum amount necessary for forming the release layer. And (c) curing the silicone without adding a stretching step while maintaining the release film at a low temperature of less than 100 ° C. (c) A method for producing a biodegradable release film. 2. The method for producing a biodegradable release film according to claim 1, wherein the fatty acid polyester is polylactic acid. 3. The Shin-Etsu Silicone KS8 is a silicone resin.
The method for producing a biodegradable release film according to any one of claims 1 and 2, which is 30. 4. The method for producing a biodegradable release film according to any one of claims 1 to 3, wherein the silicone resin is supplied in an amount close to the minimum required by using a constant amount supply device. 5. The method for producing a biodegradable release film according to claim 1, wherein the applied silicone resin is cured at 80 ° C.