JPH0745607B2 - Weatherproof acrylic resin film and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a weather resistant acrylic resin film and a method for producing the same, which has excellent transparency and weather resistance, and is further laminated on various substrates to obtain The present invention relates to a weather-resistant acrylic resin film capable of imparting excellent weather resistance to a substrate for long-term outdoor use and a method for producing the same.

(Prior Art) In recent years, from the standpoints of resource saving, energy saving, and cost saving, there has been a strong demand for imparting weather resistance to an object used outdoors and enabling continuous use as long as possible. Building materials, notification towers, traffic signs, etc. are typical fields,
In many cases, outdoor use for 10 years or more is required.

Currently, a method generally used for imparting weather resistance to a substrate is a film obtained by mixing an ultraviolet absorber with an acrylic resin having excellent weather resistance and transparency, which is used as a protective film. It is a method of sticking to the material. An acrylic resin film has excellent weather resistance and transparency, but no matter how excellent the weather resistance of the film itself is, it is not possible to impart weather resistance to a substrate. In order to impart weather resistance to the substrate, it is necessary to mix an ultraviolet absorber in the protective film so that ultraviolet rays do not reach the substrate. It has been conventionally practiced to mix an acrylic resin with an ultraviolet absorber, and a benzotriazole-based 2- (2'hydroxy-5'-methylphenyl) benzotriazole, 2 is used as an ultraviolet absorber having excellent ultraviolet absorbing properties. -(2 'hydroxy-
3'-t-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2- (2'hydroxy 3'5'-
Di-t-betylphenyl) -5-chlorobenzotriazole and the like are known.

The use of these UV absorbers is usually intended for acrylic resin sheets with a thickness of 1 mm or more, and in a sheet of such a thickness, a UV absorber mixture amount of 0.1% by weight or less will provide sufficient UV absorption characteristics. Can be granted.

However, the thickness is 0.2mm or less (usually 0.05 to 0.10mm)
In order to impart the same level of ultraviolet absorbing performance to the above-mentioned sheet having a thickness of 1.0 mm or more, which is usually used, the protective film must contain at least 1.0% by weight or more of an ultraviolet absorber.

That is, since the ultraviolet absorption performance of the protective film is proportional to the amount of the ultraviolet absorber per unit surface area, it is necessary to mix a large amount of the ultraviolet absorber as the film becomes thinner.
Currently, 0.05-0.1mm film is used as a protective film, and 1.0-1.5% by weight of UV absorber is mixed, but even if thinner film can be used in terms of film strength, The film thickness of 0.05 mm is the limit because a large amount of absorbent cannot be mixed.

(Problems to be Solved by the Invention) However, in order to improve the ultraviolet absorption performance, when a large amount (1% by weight or more) of the above ultraviolet absorber is mixed and a film is formed by an extrusion molding method, the extrusion molding is performed. Operational problems such as vent clogging of the machine and whitening of chill rolls occur, and problems such as roughening and migration of the film surface occur when a larger amount of mixture (2.0 wt% or more) is required.

Here, vent clogging of an extrusion molding machine means that the amount of ultraviolet absorber volatilized due to high temperatures and pressure during extrusion molding is so large that the normal decompression pump cannot exhaust the gas and the exhaust line is clogged, making the original deaeration operation impossible. The whitening of the cooling roll is a phenomenon in which the ultraviolet absorber volatilized at a high temperature at the sheet die outlet is cooled by the cooling roll and adheres to the roll, and when the whitening phenomenon of the cooling roll occurs, the surface of the film Sex decreases.

In order to solve such problems, at present, when vent clogging or bleaching of the cooling roll occurs, the operation of the device is stopped and the white matter is mechanically removed. In reality, it is inevitable that the deterioration of the film property, the increase of the cost, and the deterioration of the film surface property are inevitable.

The purpose of the present invention, in an acrylic resin film having a thickness of 0.2 mm or less, a decrease in productivity, an increase in cost, without causing a decrease in the surface property of the film, a weather resistant acrylic resin film having excellent ultraviolet absorption performance and It is to provide the manufacturing method.

(Means for Solving the Problems) As a result of intensive studies, the present inventors have found that a low-melting-point ultraviolet absorber is compatible with the ultraviolet-absorbing agent and has a higher melting point than that of a specific ratio. The inventors have found that the above objects can be achieved by mixing and using the above method, and have reached the present invention.

That is, the acrylic resin film of the present invention has a melting point of 80.
A mixture of an ultraviolet absorber (A) having a temperature of up to 120 ° C. and an ultraviolet absorber (B) having a melting point higher than that of (A) and compatible with (A), calculated by (B) / (A) Ratio is 0.7 ~
Thickness of 1% by weight or more containing a mixture of 1.5
A weather-resistant acrylic resin film having a thickness of 0.2 mm or less. Further, the method for producing an acrylic resin film of the present invention comprises: an acrylic resin, an ultraviolet absorber (A) having a melting point of 80 to 120 ° C.,
An ultraviolet absorber (B) which is compatible with (A) and has a melting point higher than that of (A) was mixed in a mixing ratio of 0.7 to 1.5 (B) / (A) of 1% by weight or more. After that, it is characterized by forming a film of 0.2 mm or less.

Hereinafter, the background to the present invention and the experimental results will be described.

The present inventor first examined prevention of the whitening phenomenon of the cooling roll. An acrylic resin film prepared by mixing 1% by weight of each of the ultraviolet absorbers (1) to (6) shown in Table 1 was extruded to form a film, and the presence or absence of the whitening phenomenon of the cooling roll was examined. The acrylic resin used was Parapet EH.
(Product name is Kyowa Gas Chemical Co., Ltd.). The results are shown in Table 1. From the results in Table 1, it was found that the whitening phenomenon of the cooling roll is related to the melting point of the ultraviolet absorber, and that the lower melting point with respect to the cooling roll temperature does not cause whitening.

Next, UV absorber No. 3 which is a typical example of the UV absorber (A) having a low melting point and which does not whiten the cooling roll, and the UV absorber which is a typical example of the UV absorber (B) usually used for acrylic sheets. A film (thickness: 75μ) in which 1.0% by weight of absorbent No. 6 was mixed in acrylic resin.
Was examined, and the ultraviolet absorption performance of these films was evaluated by the wavelength of the rising portion of the spectral transmittance curve (Fig. 1). You can see how many microns can be cut by the wavelength of this rising portion. By the way, the acrylic resin film for imparting weather resistance to the substrate is required to block at least 370μ of ultraviolet rays, that is, the wavelength of the rising portion of the spectral transmittance curve is 370μ or more. From the results of the above, the ultraviolet absorber No. 3 is the ultraviolet absorber in the ultraviolet absorbing performance.
Inferior to No.6, the UV absorber No.3 does not cause whitening of the cooling roll, but the UV absorber N does not cause whitening.
It has been found that it cannot be used alone as a substitute for o.6.

However, the present inventors have excellent ultraviolet absorption performance, but the ultraviolet absorbers No. 4 to No. 6, which have a high melting point with respect to the temperature of the cooling roll and cause the whitening phenomenon of the cooling roll, have a melting point on the cooling roll. It was found that all of them can be dissolved in the ultraviolet absorbers No. 1 to No. 3 which have been heated to a liquid state and have a low melting point with respect to the temperature of the cooling roll. For various cases using a mixture of ultraviolet absorber No. 3 and ultraviolet absorber No. 6,
Table 2 shows the results of examining the presence or absence of the whitening phenomenon of the cooling roll and the rising wavelength of the spectral transmittance curve of the obtained film when the film was formed by extrusion.

From this, by using a mixture of UV absorber No. 3 and UV absorber No. 6, it has excellent UV absorption performance without whitening the cooling roll, that is, the wavelength of the rising part of the spectral transmittance curve is 370 μm or more. It was found that a film of Furthermore, it has been conventionally impossible to mix without deteriorating the surface properties of films and sheets.
It has been revealed that it is possible to produce an acrylic resin extruded film which does not suffer from the whitening phenomenon of the cooling roll and the deterioration of the film surface property, since it is possible to mix the ultraviolet absorber in an amount of not less than wt%.

Conventionally, a large amount of UV absorbers not only brings about a decrease in surface property, but also has little improvement in UV absorption performance with respect to the amount of mixture, so it was not so important, but it is a thin layer for improving the weather resistance of the base material. When making a protective film (film of 0.2 mm or less), it is a great advantage to be able to mix a large amount.

In the present invention, 3.0% by weight, which has been considered impossible in the past
Since the above-mentioned large amount mixing is possible, it is possible to manufacture a good protective film without lowering the ultraviolet absorption performance of a thinner film and without lowering the productivity or increasing the cost.

Next, Table 3 shows the results of an examination of the relationship between the thickness of the film and the amount of the ultraviolet absorber mixed with the ultraviolet absorber.

From the results in Table 3, the UV absorption performance is greatly affected by the film thickness, and in the case of a film with a thickness of 25 μ (A), (B)
It can be seen that sufficient ultraviolet absorption performance cannot be obtained with an addition amount of the ultraviolet absorber of 1.0 to 1.5% by weight.

The acrylic resin used in the present invention is not particularly limited as long as it can be used for producing a film having a thickness of 0.2 mm or less, and is made of a special copolymer of butyl acrylate or the like and methyl methacrylate, So-called rubber component is 30
A resin containing about 35% by weight to 90% by weight or more of a methyl methacrylate resin used for a sheet (thickness of 1.0 mm or more) and the like are preferably used. 90% by weight
The above-mentioned acrylic resin for a sheet containing methyl methacrylate is inferior in mechanical strength as a film even when formed into a film as it is, so that the mechanical strength is improved by stretching, particularly biaxial stretching (Japanese Patent Publication No. Sho 49-13220). (Japanese patent publication) is preferred. The biaxially stretched acrylic resin film is well balanced in physical properties for practical use (Japanese Patent Publication No. 40787/1987). The present invention is most effective for films in these fields.

The ultraviolet absorber (A) may be any one as long as it has a melting point of 80 ° C. to 120 ° C. (preferably 100 to 120 ° C.) and can dissolve the ultraviolet absorber (B) usually used for acrylic sheets in a molten state, A benzophenone type and a benzotriazole type are preferable in terms of compatibility with an acrylic resin and ultraviolet ray absorbing performance. 2- (2'-Hydroxy-5'-t-octylphenyl) benzotriazole is particularly preferable when used in an acrylic resin containing 90% by weight or more of methyl methacrylate. If the melting point is lower than 80 ° C., it may migrate over time to deteriorate the surface properties of the film, and in extrusion molding, it may cause clogging at high temperature and reduced pressure. Especially when acrylic resins containing a large amount of rubber components are used, the melting temperature of those resins is low and it is necessary to lower the temperature of the cooling roll as well, so UV absorption with a low melting point is required to prevent whitening of the cooling roll. Must be used.

The UV absorber (B) is not particularly limited as long as it is a UV absorber for acrylic resin having a melting point higher than that of (A) and having compatibility with (A). Agent, 2- (2'-hydroxy-
5'-methylphenyl) benzotriazole, 2-
(2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-
(2'-hydroxy-3 ', 5'-di-t-butyl) -5
-Chlorobenzotriazole is preferred.

The mixing ratio (B) / (A) of the ultraviolet absorbers (A) and (B) used in the present invention is 0.7 to 1.5, preferably about 1.0 to 1.3, but the ultraviolet absorber having a melting point of 80 ° C to 120 ° C. It is preferable that the mixing ratio of (A) is small, but if the mixing ratio is out of the above range, uniform mixing, particularly uniform dissolution mixing of the ultraviolet absorber (B) may be difficult. Further, it goes without saying that in the present invention, the ultraviolet absorber (A) and the ultraviolet absorber (B) can be used as a mixture of a plurality thereof.

(Function) The whitening phenomenon of the cooling roll which has been the biggest problem in the method for producing an acrylic resin extruded film of the present invention is that the ultraviolet absorber volatilized from the high temperature resin extruded from the sheet die of the extruder is the cooling roll. It occurs when it solidifies when cooled, and it does not occur in the liquid state. According to the present invention, a low melting point ultraviolet absorber (A) that does not whiten the cooling roll when it becomes liquid on the cooling roll is mixed with a relatively high melting point ultraviolet absorber (B) having excellent ultraviolet absorbing performance,
By dissolving, the whitening phenomenon of the cooling roll, the bend clogging of the extruder, and the like can be prevented, and the productivity and the surface property of the film can be improved.

The film of the present invention is effectively used as a protective film by being attached to various base materials such as building materials and traffic signs.

(Examples) Hereinafter, embodiments of the present invention will be described based on Examples.

Examples 1-6, Comparative Examples 1-8 PMMA resin (trade name: Parapet EH (manufactured by Kyowa Gas Chemical Industry Co., Ltd.)) to 100 parts by weight of TINUVIN P as an ultraviolet absorber.
(Ciba Geigy; 2- (2'-hydroxy-5'methylphenyl) benzotriazole) and Siasorb UV5411
(Nihon Cyamide Co .; 2- (2'-hydroxy-5'-t
-Octylphenyl) benzotriazole) in the proportions of the respective examples and comparative examples shown in Table 4 and mixed in a Labo Plastomill extruder (manufactured by Toyo Seiki Seisakusho Ltd .; screw 20Φ, sheet die width 150 mm). A 0.2 mm thick film was extruded. Extrusion temperature conditions are C ₁ = 240 ° C, C ₂ = 260 ° C, C ₃ =
The temperature was 260 ° C and the die temperature was 250 ° C. The film was obtained by cooling it with a cooling roll of 100Φ and then winding it up. The whitening phenomenon of the cooling roll and the surface property of the film at the cooling roll temperature shown in Table 4 were observed, and evaluated by ○ and ×. Further, the 0.2 mm film thus obtained was subjected to an area stretching ratio of 2 times, 4 times or 8 times at a drawing temperature of 130 ° C. using a test biaxial stretching machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.). The film was stretched to obtain films having thicknesses of 100μ, 50μ and 25μ.

Spectral transmittance curves of three types of films having different thicknesses were measured, and their ultraviolet absorption performances were evaluated in three grades of ◯, Δ and ×. The spectral transmittance curve and the wavelength of the rising portion were used as the evaluation criteria. When the value was 370 μ or more, the result was ◯, when the value was 360 or less, the value was ×, and the intermediate value was Δ.

Table 4 is a list of the evaluation results for Examples 1 to 7 and Comparative Examples 1 to 8 with respect to the mixing amount and mixing ratio of the ultraviolet absorber. The thickness of the present invention is 50μ ~ 10
As a method for forming a film having a good surface property of 0 μ without whitening the cooling roll, Example 2 shown in Table 4 was used.
~ 6 can be applied. When the thickness is 50 μ to 100 μ, Examples 3 and 4 have an excessive amount of the ultraviolet absorber mixed and do not require such a large amount of the ultraviolet absorber, but when the thickness is 25 μ, the results are shown in Examples 3 and 4. The amount of UV absorber must be mixed. According to Example 4 made possible by the present invention, it was possible to obtain an acrylic film having a thickness of 25 μm and having an excellent ultraviolet absorbing performance.

Example 7 Instead of the PMMA resin used in Examples 1 to 6 and Comparative Examples 1 to 8, Hipet HBS was used as a rubber component acrylic resin.
(Mitsubishi Rayon Co., Ltd.) was used, 0.7 part of TINUVIN P and 0.7 part of Siasorb UV5411 as an ultraviolet absorber were mixed and a 0.2 mm thick film was extruded with a Labo Plastomill extruder. Extrusion conditions are C ₁ = 170 ° C, C ₂ = 210 ° C, C ₃ = 230 ° C,
The die temperature was 240 ° C. The experimental results are shown in Table 4. It can be seen that the roll whitening phenomenon at a cooling roll temperature of 90 ° C. is similar to that of the acrylic resin containing 90% by weight or more of methyl methacrylate.

(Effect of the invention) According to the present invention, troubles in the film manufacturing process such as whitening phenomenon of a cooling roll can be eliminated, productivity is improved, cost is reduced, film surface property is improved, and further 3.0
Since it is possible to mix UV absorbers in excess of weight%,
It is possible to achieve a great effect such that the protective film can be thinned without deteriorating the ultraviolet absorption performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a spectral transmittance curve of an ultraviolet absorber.

Claims (2)

[Claims] 1. An ultraviolet absorber (A) having a melting point of 80 to 120 ° C.
And a UV absorber (B) which is compatible with (A) and has a melting point higher than that of (A) at a mixing ratio of (B) / (A) of 0.7 to 1.5. A weather resistant acrylic resin film having a thickness of 0.2 mm or less, containing 1% by weight or more. 2. An acrylic resin having a melting point of 80 to 120 ° C., an ultraviolet absorber (A) and a compatibility with (A), and (A)
The ultraviolet absorber (B) having a higher melting point is (B) /
A method for producing a weather-resistant acrylic resin film, which comprises forming a film having a thickness of 0.2 mm or less after mixing 1% by weight or more at a mixing ratio of (A) of 0.7 to 1.5.