JPH0248925A - Film or sheet superior in formal stability under heat and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a film or a sheet superior in fragility and formal stability under heat, by a method wherein methyl methacrylate copolymer resin whose melt flow index is not exceeding 12g/10 minutes is biaxially stretched by a tensile stretching method so that orientation release stress of each axial direction becomes 3-20kg/cm<2>. CONSTITUTION:Copolymer resin whose composition of a monomer is comprised of 99-40wt.% methyl methacrylate, 1-50wt.% maleimide and/or N-substitution maleimide and a 0-30wt.% aromatic vinyl compound and a melt flow index is not exceeding 12g/10 minutes is extruded and an unstretched sheet is made. Then the unstretched sheet is stretched biaxially by a tensile stretching method and a stretched matter whose orientation release stress falls within a range of 3-20kg/cm<2> is obtained. A film or a sheet which has sharply improved fragility and is superior in formal stability under heat can be obtained while keeping transparency, weather resistance and rigidity like this.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a film suitable for use as a nameplate or a film for an OHP projector (hereinafter abbreviated as OHP).
Transparency 1. The present invention relates to films or sheets with excellent 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. For fields requiring higher heat shape stability, methyl methacrylate, maleimide and/or N
It has been proposed to use a copolymer consisting of -substituted maleimide and a copolymer in which an aromatic vinyl compound is further added to the above monomer (West German Patent No. 1231013, JP-A-61-171708, JP-A-61-171708, JP-A No. Showa 61-141715
number, etc.).

These copolymers maintain the transparency, weatherability (light) resistance, and rigidity of general-purpose methacrylic resins, but have improved heat deformation temperatures. When made into films or sheets, for example, A film or sheet with excellent properties is expected to be suitable for nameplates and OHP films that require shape stability when heated.

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-mentioned copolymers, a method of blending a rubber component has been proposed (for example, JP-A-60-60150 and JP-A-60-60151). However, this method is not satisfactory because of the problem that transparency decreases due to blending.

[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 the Problems] The above purpose is to achieve a monomer composition of methyl methacrylate from 99 to 99%.
40% by weight, 1% to 50% by weight of maleimide and/or N-substituted maleimide, and 0 to 30% by weight of aromatic vinyl compound.
% by weight, and melt flow index (AS
TM D1238, I condition, hereinafter abbreviated as MFJ)
A film or sheet of a copolymer resin having an orientation release stress of 12 g/10 minutes or less, biaxially stretched by a tensile stretching method, and an orientation release stress (ASTMDI504, hereinafter abbreviated as OR, S) in each axial direction of 3. This is achieved by a film or sheet and a method for producing the same, characterized in that the weight is 20 kg/d.

[For production]

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

Generally, it is known that brittleness is improved by stretching, and press stretching also improves the brittleness of resins obtained from terpolymer of methyl methacrylate, maleic anhydride, and styrene. A method has been proposed to stretch the paper so that the
-152855, JP-A-58-171918, etc.)
However, the stretched product produced by the press stretching method has 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 tensile and simultaneous biaxially stretched film (thickness 1 ( 10μ), OR5 value, heat shrinkage rate (heated at 120℃ for 30 minutes) and folding durability (
The relationship between the bending fatigue strength and the MIT type test machine (manufactured by Toyo Seiki Co., Ltd.) is shown. Note that the OR3 value is used as an index representing the degree of stretching, and is defined as the stress generated when the oriented molecules of a film or sheet try to return to the state before orientation.

The number of breaks that can be used as a guideline for improving brittleness is when the OR5 value is 3 kg.
/cm2 to rise rapidly to 8kg/cm”Qzudeni2
The value is not much different from 0 kg/cm2. If the durability is three or more times, it will not break even if handled relatively roughly. On the other hand, the heat shrinkage rate also changes greatly depending on the OR5 value, and is less than 20 kg/cm2, especially 15 kg/cm2.
It can be seen that 2 or less is small.

As shown in FIG. 1, in order to achieve the object of the present invention, the ORS angle in each axial direction of the biaxially stretched product is 3 to 20.
kg/cm2, preferably in the range of 5 to 15 kg/cm2. If the OR3 value is less than 3 kg/cm2, brittleness improvement is insufficient;
If it exceeds 2, the heating shape stability will be poor.

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 compositional changes or additives. Stiffness is slightly improved by stretching.

The resin used in the present invention is methyl methacrylate 99-4
0% by weight, maleimide and/or N-substituted maleimide 4-50% by weight and an aromatic vinyl compound 0-30% by weight, more preferably methyl methacrylate 92-51% by weight, maleimide and/or It is a copolymer consisting of 3 to 40% by weight of N-substituted maleimide and 0 to 25% by weight of an aromatic vinyl compound. If the methyl methacrylate content is less than 40%, the weather resistance (light) will decrease,
In addition, the transparency tends to deteriorate, and when it exceeds 99%, the heat distortion temperature decreases and the heating shape stability becomes poor. If the amount of maleimide and/or N-substituted maleimide is less than 1%, the improvement in heat distortion temperature will be insufficient, and if it exceeds 25%, coloring will become significant. The aromatic vinyl compound is a component mainly for increasing the copolymerizability of maleimide and N-substituted maleimide. If polymerization is performed without adding this, maleimide and N-substituted maleimide monomers tend to remain in the polymer, which causes coloring and deterioration of physical properties, so operations to remove them are performed as necessary. . Furthermore, when a large amount of aromatic vinyl compound is added, transparency is likely to be impaired, although it depends on the amount of maleimide and N-substituted maleimide added.

N-substituted maleimide is a substituent having an alkyl group having 1 to 8 carbon atoms, a 5- or 6-membered cycloalkyl group having 5 to 10 carbon atoms, an alkyl and/or halogen-substituted or unsubstituted total number of carbon atoms. Those having 6 to 14 aryl groups can be used, such as N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-
-(2-chlorophenyl)maleimide, N-(4-chlorophenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-methylphenyl)maleimide, N
-(4-t-butylphenyl)maleimide, N-naphthylmaleimide F, and the like are preferably used.

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 described above, for example, acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, maleic anhydride, methacrylic acid esters other than methyl methacrylate, etc. A small amount of the monomer can also be added as a copolymerization component within a range that does not impair the effects of the present invention. 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 an ultraviolet absorber, and it is preferable to use a benzotriazole-based or benzophenone-based ultraviolet absorber in an amount of 5 to 3% by weight. Other resins, such as polyvinylidene fluoride, may be blended within a range that does not deteriorate transparency or weather (light) resistance.

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. Furthermore, when producing an unstretched film or sheet as a material for stretching by extrusion molding, a film or sheet having an MFI value of 0.2 g/10 minutes 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. In addition, if 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 to 3 times are 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 becomes noticeable and breakage occurs frequently during stretching, which is not preferable.

The stretching speed varies depending on the stretching temperature and stretching method, but when stretching with a punch-type pantograph stretching machine, the stretching speed is usually 50 to 5 (100%/ In addition, when continuous stretching is performed by sequential biaxial stretching method, the longitudinal stretching speed ranges from 2 (100%) to 1 (10% (10%). If the stretching speed is too high, the stress required for stretching becomes It also becomes more 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, stretching temperature = 150°C, stretching ratio: 2 times in each axial direction, stretching speed: 1 (simultaneous biaxial stretching with tension at 100%/min). Thereafter, the film was maintained at the tension and stretching temperature, 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, particularly a thickness of 50 μm to 111 μm. 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, stretching it together, and then peeling it off. In addition, in the production of sheets that exceed dragons, the thickness of the unstretched sheet used as the material 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 dragons, it is desirable to heat it for 15 minutes or more. In addition, in the present invention, a film with a thickness of 2 (10 μm or less) is used as a film, and a film with a thickness of 2 (
Those with a diameter exceeding 10μ 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.

・Heat shrinkage rate: Draw a straight line 150 mm long on the object to be measured, heat it for 30 minutes in a forced hot air constant temperature oven kept at a specified temperature, and then measure the length of the drawn straight line (1 m) on a scale. The heat shrinkage rate was determined using the following calculation formula.

・Number of folding resistance: The object to be measured is a strip of 15 mm width, and ME
The number of times of bending until breakage was determined using a T-type bending fatigue tester (manufactured by Toyodan M Co., Ltd., bending speed: 30 times/min).

Moreover, Tg was measured using a thermal analyzer DT-40 model (manufactured by Konsei Seisakusho Co., Ltd.).

〔Example〕

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

Examples 1 to 3 A copolymer consisting of 70% by weight of methyl methacrylate, 20% by weight of N-phenylmaleimide and 10% by weight of styrene (MFI value 1 g/10 min, Tg 120°C) was extruded using an extruder with a cylinder diameter of 2011, Thickness 480μ~1(1
A 00μ unstretched sheet was prepared.

Using a pantograph two-biaxial stretching tester (manufactured by Toyo Seiki Co., Ltd.), tension and simultaneous biaxial stretching were performed at the stretching temperature and stretching ratio shown in Table 1 to obtain a stretched product with an OR3 value in the range of 5 to 15 kg/cm2. Obtained.

These heating shape stability properties are good, with a shrinkage rate of less than 1% when heated at 110°C for 30 minutes, and a shrinkage of 3% when heated at 120°C for 130 minutes.
The shrinkage rate was less than %.

Furthermore, the folding durability, which is an indicator of brittleness improvement, was significantly improved compared to the unstretched film, which is damaged by the first bending. The measured values are shown in Table 1.

The stretching speed was 1 (100%/min) in each axial direction, and the stretched product was cooled to a temperature below Tg with cold air within 20 seconds after the stretching was completed.

Comparative Example 1 An unstretched film having a thickness of 120 μm was produced from the copolymer described in Example 1 in the same manner as in Example 1. The film was very brittle and easily broke when folded.

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, where the OR3 value exceeded 20 kg/cm, the heated shape was inferior, and in Comparative Example 3, which was stretched at a temperature of 175°C, the OR3 value was less than 3 kg/cm2, and there was no improvement in folding durability. Easily damaged 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 7 An unstretched sheet with a thickness of 3 (10 μm) was prepared from the resin listed in Table 2 by the same method as in Example 1, and was stretched in the same manner as in Example 1 under the conditions listed in Table 2. Simultaneous biaxial stretching was carried out at a magnification of 2 times in each axial direction according to the method.As shown in Table 2, the stretched product had excellent bending durability and heating shape stability.

Example 8 A copolymer consisting of 76% by weight of methyl methacrylate and 24% by weight of N-(2-chlorophenyl)maleimide, in which the amount of residual N-(2-chlorophenyl)maleimide was reduced to 0.1% by weight or less by washing with methanol. The resin was extruded in the same manner as in Example 1 to produce an unstretched sheet with a thickness of 3 (10 μm).
Simultaneous biaxial stretching was performed at a magnification of 2 times in each axial direction under the conditions listed in the table. The stretched product had excellent bending 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 resin films or sheets,
It can also be applied to 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 the orientation relaxation property at the stretching temperature. OR5 (kg 7cm 2) Figure 2 Retention time

Claims (12)

[Claims] (1) Monomer composition: methyl methacrylate 99-40% by weight, maleimide and/or N-substituted maleimide 1
~50% by weight and 0-30% by weight of aromatic vinyl compounds
and has a melt flow index of 12g/1
0 minutes or less, is biaxially stretched by a tensile stretching method, and has an orientation release stress of 3 to 20 kg/cm^2 in each axial direction. Excellent film or sheet. (2) Orientation release stress is 5-15
The film or sheet according to claim 1, which has a weight of kg/cm^2. (3) Monomer composition: methyl methacrylate 92-51% by weight, maleimide and/or N-substituted maleimide 3
Claims 1 to 2 are copolymer resins consisting of ~40% by weight and 0 to 25% by weight of an aromatic vinyl compound.
Films or sheets as described in Section. (4) The substituent of N-substituted maleimide is an alkyl group having 1 to 8 carbon atoms, a 5- or 6-membered cycloalkyl group having 5 to 10 carbon atoms, alkyl and/or halogen-substituted or unsubstituted total carbon atoms The film or sheet according to claims 1 to 3, which is at least one type selected from the group consisting of 6 to 14 aryl groups. (5) 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. (6) Monomer composition: methyl methacrylate 99-40% by weight, maleimide and/or N-substituted maleimide 1
~50% by weight and 0-30% by weight of aromatic vinyl compounds
and has a melt flow index of 12g/1
In a method for producing a film or sheet of a copolymer resin that takes 0 minutes or less, orientation release in each axial direction is performed at a stretching temperature 5 to 40°C higher than the glass transition temperature and at a stretching ratio of 1.2 to 4 times in each axial direction. Stress is 3-20k
A method for producing a film or sheet with excellent heating shape stability, which comprises biaxially stretching the film or sheet by a tensile stretching method so that the film or sheet has a film or a sheet of 100 g/cm^2. (7) Orientation release stress is 5-15
7. The method for producing a film or sheet according to claim 6, wherein the film or sheet has a weight of 1 kg/cm^2. (8) Monomer composition: 92 to 51% by weight of methyl methacrylate, maleimide and/or N-substituted maleimide 3
~40% by weight and 0-25% by weight of aromatic vinyl compounds
A method for producing a film or sheet according to claims 6 to 7, which is a copolymer resin consisting of a copolymer resin. (9) The substituent of N-substituted maleimide is an alkyl group having 1 to 8 carbon atoms, a 5- or 6-membered cycloalkyl group having 5 to 10 carbon atoms, alkyl and/or halogen-substituted or unsubstituted total carbon 9. The method for producing a film or sheet according to claims 6 to 8, wherein the aryl group is at least one selected from the group consisting of 6 to 14 aryl groups. (10) The method for producing a film or sheet according to claims 6 to 9, wherein the aromatic vinyl compound is at least one selected from the group consisting of styrene, vinyltoluene, and α-methylstyrene. (11) The method for producing a film or sheet according to claims 6 to 10, wherein the stretching temperature is 10 to 30°C higher than the glass transition temperature. (12) The method for producing a film or sheet according to claims 6 to 11, wherein the stretching ratio is 1.3 to 3 times.