JPH0243023A - Film or sheet excellent in thermal stability of form and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve formal stability under heat, by a method wherein the title film is obtained from copolymeric resin where a composition of a monomer comprises methacrylic acid methyl, maleic anhydride and aromatic vinyl compound and MFI is not exceeding a specific value, biaxially-oriented by a tensile orientation method and ORS of each axial directions has a specific value. CONSTITUTION:The title film or sheet is of copolymer resin whose composition of a monomer is comprised of 92-45wt.% methacrylic acid methyl, 3-25wt.% maleic anhydride and a 5-30wt.% aromatic vinyl compound and melt index is not exceeding 12g/10 minutes. The title film or sheet is constituted so that the same is oriented biaxially with a tensile orientation method and ORS of axial directions each becomes 3-20kg. The film or the sheet is manufactured by a method wherein an unoriented filmy or sheetlike matter made by extrusion molding or press molding or cast polymerization is heated to an orientable temperature and tensed and oriented by a simultaneous biaxial orientation method or a successive biaxial orientation method or an inflation method. With this construction, a matter superior in thermal stability of form can be obtained while holding transparency, weather resistance and rigidity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a film suitable for, for example, a nameplate or an overhead projector (hereinafter abbreviated as OHP).
The present invention relates to films or sheets with excellent transparency, heating shape stability, mechanical strength, weather (light) resistance, and rigidity, and further relates to methods for producing these.

[Conventional technology]

As a material with excellent transparency, weather resistance (light) and rigidity,
There is a general-purpose methacrylic resin whose main component is methyl methacrylate, and it is widely used in things such as signboards, lighting covers, and automobile parts. It has been proposed to use a copolymer consisting of methyl methacrylate, maleic anhydride and an aromatic vinyl compound in fields where higher heating shape stability is required (West German Patent No. 1231013, JP-A-59 -2
21314 etc.).

These copolymers retain the transparency, weathering (light) resistance, and rigidity of general-purpose methacrylic resins, while also having improved heat distortion temperatures. A film or sheet with excellent properties suitable for nameplates and OHP films that require shape stability is expected.

However, the mechanical strength, which is considered a problem with general-purpose methacrylic resins, is further reduced in the above copolymers.
Products formed by extrusion molding or the like are easily broken, not only in films but also in thin sheets, making them unusable for practical use.Currently, it is desired to improve the brittleness of thick sheets as well.

As a method for improving the brittleness of the above copolymer, there is a method of blending a rubber component (for example, JP-A-60-60150, JP-A-60-60151) and an orientation release strike (ASTM 01504, hereinafter abbreviated as OR3). ) is 20 kg/cm" or more (Japanese Unexamined Patent Publication No. 59-15285).
No. 5, Japanese Unexamined Patent Publication No. 171918/1982).

However, the former method suffers from a decrease in transparency due to blending, and the latter method has low productivity because continuous production is difficult and requires a batch method, and it is difficult to produce thin products such as films, so it is not satisfactory. Although the brittleness is improved in the latter method,
There was a problem in that the shrinkage property due to heating was strong, and the heating shape stability improved by the modification of the resin was impaired.

[Problem that the invention seeks to solve]

The object of the present invention is to solve the problems of the copolymer film or sheet, namely, to provide a film or sheet with good heating shape stability, transparency, weather (light) resistance, and rigidity, and with improved brittleness. to develop and provide.

[Means for solving problems]

For the above purpose, the composition of the monomer is methyl methacrylate 92~
45% by weight, 3 to 25% by weight of maleic anhydride, and 5 to 30% by weight of an aromatic vinyl compound, and has a melt flow index (ASTM0123B, 1 condition, hereinafter abbreviated as MFI) of 12 g/10 minutes or less. A polymer resin film or sheet that is biaxially stretched by a tensile stretching method and has an OR3 of 3 to 2 in each axial direction.
0 kg/cm'' and a method for producing the same.

[For production]

The present invention applies brittleness improvement by biaxial stretching, and it is essential that the stretching method be a tensile stretching method.

It is generally known that stretching improves brittleness, and as mentioned above, a method of press stretching has been proposed for the resin used in the present invention. however,
The stretched product produced by the press stretching method had poor shape stability under heating, and it was considered impossible to achieve the object of the present invention by the stretching method.

However, when the present inventors investigated in detail the tensile stretching method for the resin used in the present invention, it was surprisingly possible to obtain a stretched product with improved brittleness and good heating shape stability under specific stretching conditions. This discovery led to the present invention.

Figure 1 shows a copolymer consisting of 76% by weight of methyl methacrylate, 10% by weight of maleic anhydride, and 14% by weight of styrene, and a simultaneously biaxially stretched film (thickness: 110 μm) with an MPU value of 2 g/10 min. , the relationship between the ORS value, heat shrinkage rate (heated at 115° C. for 30 minutes) and folding resistance (folding fatigue strength, MrT type testing machine manufactured by Toyo Joki Co., Ltd.) was shown. Note that OR3 is used as an index representing the degree of stretching, and is defined as the stress that occurs when the oriented molecules of the film or sheet try to return to the state of the oriented plane.

The number of breaks that can be used as a guideline for improving brittleness is when the OR3 value is 3 kg.
It rose rapidly from 7cm" and reached 22 at 8kB7cm".
0kg/cm", which is not much different. If the number of folds is 3 or more, it will not break even if handled relatively roughly. On the other hand, the heat shrinkage rate also changes greatly depending on the OR3 value, and 20 kg/cm". /c+w” or less, especially 15kg/c1
It can be seen that it is small below 1z.

As shown in FIG. 1, in order to achieve the object of the present invention, the OR3 value in each axial direction of the biaxially stretched product is 3 to 20.
kg/cm2, preferably in the range of 5 to 15 kg/cmt.If the OR3 value is less than 3 kg/cm2, brittleness improvement is insufficient;
If it exceeds ", the heating shape stability will be poor.

The above results are different from the results of press stretching, in which an OR3 value of 20 kg/cm'' or more is suitable for improving brittleness.This is because in both cases, brittleness is improved by orientation, but press stretching In contrast, in tension stretching, the molecules are oriented in a situation where the spaces between molecules are widened, that is, in a situation with a higher degree of freedom, and the oriented structure is created. This may be due to the fact that the piston flow is not perfect in press stretching, and the low elongation is high in the surface layer and low in the inner layer, resulting in a higher-order structure different from that in tensile stretching, where piston flow is easy. It will be done.

That is, the film or sheet of the present invention has a novel higher-order structure different from that of a press-stretched product, which is oriented by tension stretching and has an OR3 value of 3 to 20 kg 7 cm 2 .

Further, the film or sheet of the present invention maintains the excellent transparency and weather (light) resistance of the resin used in the present invention, unlike cases where brittleness is improved by changing the composition or adding additives. Stiffness is slightly improved by stretching.

The resin used in the present invention is methyl methacrylate 92-4
A copolymer consisting of 5% by weight, 3 to 25% maleic anhydride, and 5 to 30% by weight of an aromatic vinyl compound,
More preferably 86 to 50% by weight of methyl methacrylate,
It is a copolymer consisting of 7 to 25% by weight of maleic anhydride and 7 to 25% by weight of an aromatic vinyl compound. If the content of methyl methacrylate is less than 45%, weather resistance (light) resistance is reduced and transparency is likely to be impaired, and if it exceeds 92%, the heat distortion temperature is reduced and the heating shape stability is poor. If the amount of maleic anhydride is less than 3%, the improvement in heat distortion temperature is insufficient;
Moreover, when it exceeds 25%, coloring becomes noticeable. The aromatic vinyl compound is a component mainly for improving copolymerizability of maleic anhydride, and if it is less than 5%, the effect of improving copolymerizability is small.

Moreover, when it exceeds 30%, transparency tends to be impaired.

As the aromatic vinyl compound, styrene, alkylstyrene, α-methylstyrene, α-methylalkylstyrene, etc. can be used, but styrene, vinyltoluene, and α-methylstyrene are preferred due to the physical properties of the copolymer and the productivity of the monomer. preferable.

In addition to the constituent monomers of the copolymer, for example, acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, maleimide, N-substituted maleimide, methacrylic acid esters other than methyl methacrylate, etc. A small amount of a copolymerizable monomer can also be added as a copolymerization component to the extent that the effect of the present invention is not achieved. Additionally, polymer modifiers such as plasticizers, colorants, UV absorbers, antioxidants and lubricants can be added. In particular, when weather (light) resistance is required, it is effective to add a UV absorber, and benzotriazole-based and benzophenone-based UV absorbers are
It is preferable to use os to 3% by weight.

Other resins may be used as long as they do not deteriorate transparency or weather resistance (light).
For example, polyvinylidene fluoride or the like may be blended.

If the molecular weight of the copolymer is too low, it will not be possible to improve brittleness by stretching, so the MFI value is preferably 12 g/10 minutes or less. In addition, when producing an unstretched film or sheet as a material for stretching by extrusion molding, a film having an MFI value of 0.2 g 710 min, which is suitable for extrusion molding, is used.

The film or sheet of the present invention can be produced by heating a substantially unstretched film or sheet material made by extrusion molding, press molding, cast polymerization, etc. to a temperature that allows stretching, and applying a simultaneous biaxial stretching method. It is manufactured by sequentially pulling and stretching by a biaxial stretching method, an inflation method, or the like. The temperature suitable for stretching is 5 to 40°C, preferably 10 to 30°C higher than the glass transition temperature (hereinafter abbreviated as Tg) of the resin. If the film is stretched at a temperature less than 5° C. below Tg, it will break during stretching. Furthermore, when the temperature exceeds Tg by 40°C, the molecular motion of the resin becomes intense, making it difficult to form an oriented structure by stretching, and the OR3 value becomes 3 kg/c.
Improvement in brittleness below m2 tends to be insufficient.

The stretching ratio is 1.2 to 4 times in each axial direction, preferably 1
．． 3-3 times is selected. If it is 1.2 times or less, the OR3 value will be less than 3 kg/cm2, resulting in little improvement in brittleness. Moreover, if it exceeds 4 times, stretching unevenness will become noticeable and breakage during stretching may occur, which is not preferable.

The stretching speed varies depending on the stretching temperature and stretching method, but when stretching is performed using a batch-type pantograph stretching machine, the stretching speed is usually 50 to 5000%/min in each axial direction relative to the length of the film or sheet before stretching. When selected and continuously stretched by the sequential biaxial stretching method, the longitudinal stretching speed ranges from 2000% to 10000%. If the stretching speed is too high, the stress required for stretching becomes large and the film is likely to break during stretching.

In addition, in any method, it is necessary to avoid such a slow speed that the oriented structure due to stretching is disturbed by molecular motion and the oriented structure necessary for improving brittleness is not formed. This temperature depends on the stretching temperature, but should be at least 10%/min at a stretching temperature 20° C. higher than Tg, for example.

Stretched films of crystalline resins, such as polyethylene terephthalate, are often post-heat treated at a temperature higher than the stretching temperature after stretching to increase the degree of crystallinity, but non-grade resins are heated after stretching. If the film is allowed to stand for a long time, the stretching effect will be reduced due to orientation relaxation, so generally a method is selected in which the film is rapidly cooled to a temperature lower than Tg. Since the resin used in the present invention is of inferior quality, the latter method is chosen.

The orientation relaxation behavior at the stretching temperature will be explained with reference to FIG. Here, the same resin as in Fig. 1 was used, and the stretching temperature was 145°C, the stretching ratio was 2 times in each axial direction, and the stretching speed was 1000%/min. The tension and stretching temperature was maintained, and changes in the OR3 value were tracked. The figure shows that the OR3 value, which is an index of orientation, decreases rapidly within a short period of time after stretching.

From the above, in order to obtain the film or sheet of the present invention with improved brittleness, it is desirable that the time to remain at the stretching temperature after stretching is at most 5 minutes.

The thickness of the film or sheet of the present invention is not essentially limited, but from the viewpoint of productivity, a thickness of 3 μm to 10 μm is desirable, and a thickness of 50 μm to 1 nm is particularly preferable. If it is less than 50 μm, it is likely to break during stretching, and in this case, it is preferable to use a method of laminating the reinforcing film with another resin film, stretching it together, and then peeling it off. In addition, in the production of sheets that exceed 1 degree, the thickness of the unstretched sheet becomes thicker, and even if it is placed in an oven, it takes a long time for the inside of the unstretched sheet to reach the stretching temperature. Productivity decreases. For example, when stretching an unstretched sheet of 5 Tsuru,
It is desirable to heat for 15 minutes or more. In addition, in the present invention, a film with a thickness of 200μ or less, a film with a thickness of 200μ or less
Those exceeding 100% were distinguished from sheets.

The methods for measuring the heat shrinkage rate and the number of folds used in the description of the invention are shown below.

・Heating shrinkage rate: Draw a straight line with a length of 150 mm on the object to be measured, and after heating it for 30 minutes in a forced hot air constant temperature oven kept at a specified temperature, measure the length of the drawn straight line (7! m). It was read on a scale and the heat shrinkage rate was determined using the following calculation formula.

The number of folding times 2 The object to be measured is a short 15 mm rl, and the MI
The number of times of bending until breakage was determined using a T-type bending fatigue tester (manufactured by Toyo Seiki Co., Ltd., bending speed: 30 times/min).

Further, Tg was measured using a thermal analyzer DT-40 model (manufactured by Shimadzu Corporation).

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 3 A copolymer (MFI) consisting of 76% by weight of methyl methacrylate, 10% by weight of maleic anhydride and 14% by weight of stereno
value 1g/10min, Tg 120°C) with cylinder diameter 20
An unstretched sheet having a thickness of 4801t-1000μ was produced by extrusion using a Ryu extruder.

Using a pantograph type biaxial stretching tester (manufactured by Toyo Seiki Co., Ltd.), simultaneous biaxial stretching was carried out at the stretching temperature and stretching ratio shown in Table 1, and stretching was performed with an OR3 value in the range of 5 to 15 JH/cm. I got something.

The heating shape stability of these products is good, with a shrinkage rate of less than 1% when heated at 110°C for 30 minutes, and a shrinkage rate of 3% when heated at 115°C for 30 minutes.
The shrinkage rate was less than %.

In addition, the folding durability, which is an indicator of brittleness improvement, was significantly improved compared to the unstretched film, which breaks at the first bend. The measured values are shown in Table 1.

The stretching speed was 1000%/min in each axial direction, and the stretched product was cooled to a temperature below 'Fg with cold air within 20 seconds after the stretching was completed.

Comparative Example 1 An unstretched film having a thickness of 110 μm was produced from the copolymer described in Example 1 in the same manner as in Example 1. The film was very bulky and broke easily by folding.

Comparative Examples 2 to 3 In the method of Example 1, stretched products were obtained by changing the stretching temperature and stretching ratio to the conditions listed in Table 1.

In Comparative Example 2, in which the OR3 value exceeded 20 kg/cm'', the heated shape was inferior, and in Comparative Example 3, which was stretched at a temperature of 165°C, the OR3 value was less than 3 kg/cm'', indicating improvement in folding durability. It was easily broken by bending.

Example 4 The unstretched sheet produced by the method of Example 1 was first stretched in the extrusion direction of the unstretched sheet using a pantograph stretching machine under the stretching conditions shown in Table 1, and after 1 minute, the unstretched sheet was stretched perpendicular to the extrusion direction. A sequentially stretched product was obtained by stretching in the direction of . As shown in Table 1, the stretched product had excellent folding durability and heating shape stability. Note that the stretching speed and cooling after stretching were performed in the same manner as in Example 1.

Examples 5 to 6 An unstretched sheet with a thickness of 300 μm was prepared from the resin listed in Table 2 by the same method as in Example 1, and was processed in the same manner as in Example 1 under the conditions listed in Table 2. Simultaneous biaxial stretching was performed at a magnification of 2 times in each axial direction. As shown in Table 2, the stretched product had excellent folding durability and heating shape stability.

〔Effect of the invention〕

As a result of developing a suitable stretching method for heat-resistant methyl methacrylate-based copolymer resin, the brittleness has been greatly improved and the heating shape stability has been improved while maintaining transparency, weather resistance (light) resistance, and rigidity. An excellent new film or sheet was obtained.

The film or sheet can meet the strong demand for improved mechanical strength and heating shape stability in the field of application of conventional methacrylic acid resin films or sheets,
It can also be used in fields of application that have not been adopted due to lack of these characteristics.

[Brief explanation of the drawing]

Figure 1 shows the relationship between ORS and heat shrinkage (a) of a tensile biaxially stretched film, and the relationship between OR3 and the number of folds (a).
FIG. 2 is a graph showing orientation relaxation at stretching temperature.

Claims (10)

[Claims] (1) The monomer composition is 92 to 45% by weight of methyl methacrylate, 3 to 25% by weight of maleic anhydride, and 5 to 30% by weight of an aromatic vinyl compound, and the melt flow index is 12 g/10 minutes or less. It is obtained from a certain copolymer resin, biaxially stretched by a tensile stretching method, and has an orientation release stress of 3 to 20 in each axial direction.
A film or sheet having excellent heating shape stability, characterized by having a heating shape stability of kg/cm^2. (2) Orientation release stress is 5-15
The film or sheet according to claim 1, which has a weight of kg/cm^2. (3) A copolymer resin whose monomer composition is 50 to 86% by weight of methyl methacrylate, 7 to 25% by weight of maleic anhydride, and 7 to 25% by weight of an aromatic vinyl compound. The film or sheet according to items 1 and 2. (4) The film or sheet according to any one of claims 1 to 3, wherein the aromatic vinyl compound is at least one selected from the group consisting of styrene, vinyltoluene, and α-methylstyrene. (5) The monomer composition is 92 to 45% by weight of methyl methacrylate, 3 to 25% by weight of maleic anhydride, and 5 to 30% by weight of an aromatic vinyl compound, and the melt flow index is 12 g/10 minutes or less. In a method for producing a film or sheet of a certain copolymer resin, the stretching temperature is 5 to 40°C higher than the glass transition temperature and the stretching temperature is 1.2 to 1.2°C in each axial direction.
A film or sheet with excellent heating shape stability characterized by being biaxially stretched by a tensile stretching method so that the orientation release stress in each axial direction is 3 to 20 kg/cm^2 at a stretching ratio of 4 times. Manufacturing method. (6) Orientation release stress is 5-15
6. The method for producing a film or sheet according to claim 5, wherein the film or sheet has a weight of 1 kg/cm^2. (7) A copolymer resin having a monomer composition of 86 to 50% by weight of methyl methacrylate, 7 to 25% by weight of maleic anhydride, and 7 to 25% by weight of an aromatic vinyl compound. A method for producing a film or sheet according to item 6. (8) The method for producing a film or sheet according to claims 5 to 7, wherein the aromatic vinyl compound is at least one selected from the group consisting of styrene, vinyltoluene, and α-methylstyrene. (9) The method for producing a film or sheet according to claims 5 to 8, wherein the stretching temperature is 10 to 30°C higher than the glass transition temperature. (10) The method for producing a film or sheet according to claims 5 to 9, wherein the stretching ratio is 1.3 to 3 times.