JPS6015120A - Manufacture of crystalline polymeric sheet - Google Patents

Abstract

PURPOSE:To obtain the titled sheet that has a smooth surface, and is transparent, and high in strength and elasticity modulus, by passing a crystalline polymeric sheet stock sheet between a pair of rollers that have been heated to a specified temperature, and drawing the sheet at a draw ratio of down to a specified value. CONSTITUTION:A crystalline polymeric stock sheet is passed between a pair of rollers that have been heated to a temperature down to a transformation start temperature T1, which is measured when a load of 10MPa is applied to the stock sheet and the stock sheet is heated at a rate of 1 deg.C/min, but not exceeding the kick-off temperature T2 of the melting curve of measurements by differential scanning and is drawn at a draw ratio of down to 2.5 and preferably at a drawing speed of not more than 500mm./min to obtain the intended sheet. It is preferable to preheat the stock sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a transparent crystalline polymer sheet with a smooth surface, high strength, and high modulus of elasticity by a pultrusion method.

Generally, when molding a polymer material, a method is used in which the material is poured into a mold in a molten state or extruded from a die. Polymer materials molded using these methods have low molecular chain orientation and a small number of tie molecules connecting crystals, so they do not have high strength or elastic modulus. Therefore, in order to produce a sheet with high strength and high elastic modulus, it is necessary to deform the sheet in a specific direction by a method such as stretching or rolling to orient the molecular chains. In particular, rolling has the potential to be applied to thick polymer sheets, but because the elastic recovery of amorphous chains causes the thickness to return immediately after passing through the rollers, so-called springback, it is difficult to process with high precision. Moreover, a large deformation ratio cannot be obtained. On the other hand, in pultrusion molding, there is a restriction that the pultrusion stress must be smaller than the breaking strength of the material, and pultrusion molding of polymer sheets has not been attempted.

In view of these circumstances, the present inventors conducted various research in order to develop a method for manufacturing a crystalline polymer sheet that exhibits high strength and high elastic modulus by forming a crystalline polymer sheet by pultrusion molding. As a result of stacking, the crystalline polymer sheet is pulled out (strain hardening occurs during the process, making the sheet difficult to break, so under certain temperature conditions, the sheet can be deformed to a high deformation ratio by pultrusion. It was discovered that the sheet formed by pultrusion exhibits excellent mechanical properties, and based on this knowledge, the present invention was completed.

That is, the present invention is capable of melting a crystalline polymer raw sheet by differential scanning calorimetry at a temperature higher than the deformation start temperature when the sheet is heated at a heating rate of 1° C./min with a load of 0 MPa applied to the sheet. The present invention provides a method for producing a crystalline polymer sheet, which is characterized in that the sheet is drawn through a pair of rollers heated to a temperature not exceeding the rising temperature of the curve to a drawing ratio of at least 2.5 times or more.

The resin used in the method of the present invention is polyethylene, polypropylene, polyacetal resin, nylon, or other crystalline polymer. Furthermore, there are no particular restrictions on the molecular weight or molecular weight distribution of the resin used, as long as it is generally used for fibers, films, and molded products.

In the method of the present invention, a crystalline polymer is formed into a sheet and cut into a certain width. The sheet is then pulled through a pair of rollers maintained at a predetermined temperature, with the distance between the rollers being adjusted to a low stretching ratio (both 2.5
It needs to be adjusted to more than double. The stretching ratio here means the ratio of the length of the sheet after being drawn to the length of the sheet before being drawn.

The method of the present invention needs to be carried out under predetermined temperature conditions. In other words, the temperature of the roller needs to be set to a temperature that is higher than the deformation start temperature when the temperature is raised at a heating rate of 1 °C/min with a load of 10 MPa, but does not exceed the rising temperature of the differential scanning calorimetry melting curve. There is. The deformation start temperature herein refers to the temperature at which the strain-temperature curve deviates from the straight line portion on the low temperature side when the temperature is increased at a temperature increase rate of 1°C/min with a load of 10 MPa applied. Figure 1 shows the strain-temperature curves and deformation onset temperatures (Tl) of major crystalline polymers. Further, the rising temperature of the differential scanning calorimetry melting curve refers to the temperature at the intersection of the tangent at the inflection point on the low temperature side of the melting curve and the extension of the baseline. FIG. 2 shows differential scanning calorimetry melting curves of major crystalline polymers and how to calculate their rise temperatures (T2). Differential Scanning Calorimetry Melting curves were measured using a Perkin Elmer DSC-2 differential scanning calorimeter at a heating rate of 5°C/min. If the temperature of the roller is lower than Tl, the drawing stress becomes thick (and pultrusion becomes difficult).In addition, at a temperature of T2 or higher, the sheet melts and the molecular chains are oriented in the drawing direction. I can't.

Therefore, it is necessary to set the temperature of the roller to a temperature that is higher than T1 and does not exceed the temperature of the hair.

The T1 and T2 values of main crystalline polymers are shown in the table below, and the method of the present invention will be explained with reference to the accompanying drawings.

FIG. 3 is a sectional view showing an embodiment of the present invention, in which a pair of rollers 2 are used to heat the material sheet 1 to a predetermined temperature.
Apply tension from between 2 and pull it out to obtain the desired sheet. It is desirable that the material sheet be preheated in the preheating section 3. The spacing between the rollers 22 is adjustable, allowing drawn sheets of various thicknesses to be obtained. The temperature of each roller is set to a temperature that is higher than the deformation start temperature when a load of 10 MPa is applied and the temperature is increased at a rate of 1°C/min, and does not exceed the rising temperature of the differential scanning calorimetry melting curve. The preferred drawing speed varies depending on the type and molecular weight of the resin, but if it is too fast, the sheet is likely to break between the rollers, so the drawing speed is desirably 500 mm 7 minutes or less.

It is necessary to select the spacing between the rollers in order to obtain a predetermined stretching ratio, but it is preferable that the spacing between the rollers is approximately 7 to 40% of the thickness of the material sheet.If the spacing between the rollers is too narrow, the sheet will If the sheet is too wide, the deformation ratio is sufficient, which prevents the sheet from returning (springback) immediately after passing the rollers, as seen in rolling, and rather stretches the sheet even after passing the rollers. A high deformation ratio can be obtained. The molecular chains of the material sheet are in a non-oriented state, but due to pultrusion, the molecular chains become highly oriented in the drawing direction.
The number of tie molecules connecting microcrystals also increases. Such structural changes have a significant impact on the mechanical properties of the sheet. In the stress-strain curve in a tensile test, most of the material sheets show a yield point, but sheets that have been deformed to a high deformation ratio by pultrusion do not yield to the breaking point.

Also, as the stretching ratio increases, the elongation decreases and the tensile strength and elastic modulus increase. It has been found for many crystalline polymers that the strength and modulus of the sheet deformed by pultrusion to the maximum stretch ratio are 5 to 30 times the values of the raw sheet. Furthermore, the material sheet is opaque due to the presence of a spherulite structure, but since the spherulite structure is destroyed during the drawing process, the transparency of the drawn sheet is extremely good.

If the method of the present invention is carried out in combination with sheet melt extrusion molding, a sheet with high strength and high modulus of elasticity can be obtained continuously, so it is suitable as an industrial method for producing crystalline polymer sheets.

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

In each example, a pair of stainless steel rollers with an outer diameter of 50 mm and a width of 70 mm were used.

Elongation, tensile strength, and elastic modulus were measured using an Instron type tensile testing machine (manufactured by Toyo Baldwin Co., Ltd., Tensilon UTM).
- Using IIT-100+, J I 5K7113-1
Measured according to 980. The meaning of each measurement value is as follows.

Elongation at break: Strain value at tensile break. Yield elongation: Strain value at yield. Tensile strength: The value obtained by dividing the load at tensile break by the original cross-sectional area of the test piece. Value divided by the original cross-sectional area Elastic modulus: Ratio of tensile stress to strain at the deformation start point Example 1 High-density polyethylene with a viscosity average molecular weight of 40,000 (manufactured by Mitsui Petrochemical Industries, Ltd., registered trade name "HIZEX 2200J")
J] and a sheet of high-density polyethylene C having a viscosity average molecular weight of 63,000 manufactured by Mitsui Petrochemical Industries, Ltd. and having a registered trademark name [Hyzex 5000BJl] was subjected to pultrusion molding. The thickness of each material sheet is 1 mm, and the width is 22 mm.
20 mm for 00 J, 30 for 5000 B
It is mm. The material sheet was passed through rollers heated to 75°C, 1100°C, or 120°C and pulled out. The ratio of the distance between the rollers (tr) and the thickness of the material sheet (to) when the roller temperature is set to 100°C
Figure 4 shows the relationship between the drawing stress (pulling tension/cross-sectional area of the material sheet), the stretching ratio, and the ratio of the thickness of the drawing sheet (1) to the thickness of the material sheet (t/lo). Shown as In the figure, O is 2200 J and the drawing speed is 50 mm.
/min, opening is 5000B, drawing speed is 50mm/min, is 5
000 B and a drawing speed of 10 mm/min. As is clear from the figure, in the case of 2200J, t/
to <:: tr/ to, the thickness of the drawn sheet is thinner than the roll spacing, and a high drawing ratio of about 25 times at most can be obtained. On the other hand, in the case of 5000B, t/toζt
r/to, the thickness of the drawn sheet and the roll spacing are approximately equal, and a maximum drawing ratio of about 14 times is achieved.

In the case of 2200 J, considerable deformation occurs in the post-stretching section, but in the case of 5000 B, the deformation region is limited between the rolls.

The relationship between the mechanical properties of the drawn sheet and the stretching ratio is shown in FIG. In the figure, ○ indicates 2200 J and roller temperature 100°.
C1△ is 2200J Theo-ra-temperature 75°C1<l
2000 J material sheet, Roba 5000 B
Temperature: 100°C, [) is the measurement result for a 5000B material sheet.

In addition, in the figure, black symbols indicate yield strength and yield elongation, and white symbols indicate tensile strength, elongation at break, and elastic modulus.

Material sheet and pultruded sheet with small stretching ratio (5000
5 times or less for B, 9 times or less for 2200 J)
shows a yield point in the stress-strain curve in a tensile test, but sheets drawn to a higher stretching ratio break without yielding in the tensile test. As the stretching ratio increases, the elongation at break decreases and the tensile strength, yield strength and elastic modulus increase.

For 2200J, roller temperature 75°C and 100
Tensile strength of 0.6-0.7GPa and 40G at °C
A sheet having an elastic modulus of approximately Pa was obtained. Also, 5(
In the case of XXE, the tensile strength and elastic modulus are 0.43 GPa and 14 GPa, respectively, at a roller temperature of 100°C.
reached a.

Example 2 Polypropylene with a viscosity average molecular weight of 2.17 x 105 (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name Noblen FL-10)
A 1 mm thick sheet of 0) was cut to a width of 30 mm, and pultrusion molding was performed at roller temperatures of 110°C and 135°C. The ratio of the distance between the rollers and the thickness of the material sheet (t
The relationship between the drawing stress, the drawing ratio, and the ratio of the thickness of the drawn sheet to the thickness of the material sheet (t/lo) is shown in the sixth
Shown in the figure. In the figure, ○ indicates roller temperature 135°C, pulling speed 50 mm/min, opening indicates roller temperature 135°C, drawing speed 500 mm, 7 minutes, and △ indicates roller temperature 110°C.
1 These are measurement results at a drawing speed of 50 mm/min.

As is clear from the figure, when the roller spacing is the same, the higher the roller temperature and the faster the drawing speed, the higher the stretching ratio, that is, the more deformation occurs in the post-stretching region. In addition, the lower the roller temperature, the lower the pull-out stress.
Moreover, the larger the deformation ratio is, the larger the deformation ratio becomes.

FIG. 7 shows the relationship between the mechanical properties of a drawn polypropylene sheet and the stretching ratio. In the figure, ○ indicates roller temperature 135
°C1△ is a roller temperature of 110 °C1〈 is a measured value for a material sheet. Black symbols represent yield elongation and yield strength, and white symbols represent elongation at break, tensile strength, and elastic modulus.

A drawn sheet with a stretching ratio of 5 times or more breaks without yielding in a tensile test. However, there is a tendency for the tensile strength and elastic modulus to become higher at lower draw ratios, but the maximum draw ratio obtained at each temperature is larger when the roller temperature is higher. was gotten.

Example 3 Polyoxymethylene (copolymer with melt index 2)
．． 5. Made by Polyplastics Co., Ltd., registered trade name [DURACON M-25J] A sheet of 1 mm thick and 15 mm wide was pultruded at a roller temperature of 140°C. Ratio between roller spacing and material sheet thickness (
The relationship between the drawing stress, the drawing ratio, and the ratio of the thickness of the drawn sheet to the thickness of the material sheet (t/lo) is shown in FIG. 8 by symbols ○ and . ○ and ・ are measured values at a drawing speed of 50 mm/min and 10 mm/min, respectively. The maximum elongation is 13.5 times and the sheet thickness is approximately equal. The relationship between the stretching ratio and the mechanical properties of a drawn sheet of polyoxymethylene is shown in FIG. 9 by the symbol ◯. Further, the symbol .in the figure represents the yield elongation and yield strength of the polyoxymethylene material sheet. In a tensile test, the material sheet shows a yield point, but the drawn sheet breaks without yielding. Tensile strength IGPa 11 elasticity''・1'.

A drawn sheet with a tensile strength of 11 GPa was obtained. ``''''Example 4 Nylon-6 (manufactured by Toshiku Co., Ltd.) thickness: 1 mm, width: 30 m
A sheet of No. m was pultruded at a roller temperature of 150°C. The relationship between the ratio of the roller interval and the thickness of the material sheet (tr/lO), the drawing stress, the stretching ratio, and the ratio of the thickness of the drawing sheet to the thickness of the material sheet (t/lo) is shown in Fig. 8 by △. Indicated.

When tr/to≦0.3, t/to) t
r/to, springback is occurring,
Moreover, the obtained relationship is shown in FIG. 9 by △. The maximum draw ratio obtained was 4.5 times, which was small, but the tensile strength was relatively high, and a pultruded sheet having a maximum tensile strength of 0.5 GPa was obtained.

[Brief explanation of the drawing]

Figure 1 shows the strain-temperature curve and the deformation onset temperature when a constant load of 10 MPa is applied and the temperature is raised at a rate of 1°C/min. Figure 2 shows the differential scanning calorimetry of major crystalline polymers. Measured melting curves and how to calculate their rise temperatures; Figure 3 is a cross-sectional view showing an example of an embodiment of the method of the present invention; Figures 4, 6, and 8 are diagrams for polyethylene, polypropylene, and polyoxyethylene, respectively; 9 is a graph showing the relationship between roller spacing, drawing stress, drawing ratio, and drawing sheet thickness for methylene and nylon-6, and FIGS.
The figures show the relationship between stretch ratio and mechanical properties for polyethylene, polypropylene and nylon-6 and polyoxymethylene, respectively. Patent applicant Hirobe Yoda h-1r, Director of the Agency of Industrial Science and Technology, 15 F Chito 1-m-〉 Mori 唖-1〉 Stress 111P, L Fig. 4 °: [. . tr/l. Figure 5 Figure 6 tr/l. Stretching ratio No. 712 Fig. 8 tr/t. Figure 9 Stretching Draft of Amendment to Procedures of the Office of the Patent Office Mr. Kazuo Wakasugi, Commissioner of the Patent Office, Case Description 1982 Patent Application No. 123925 2 Name of the Invention Process for Manufacturing Crystalline Polymer Sheet 3, Person Making Amendment Case and Relationship between patent applicant Kawa 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo (114) Director of the Agency of Industrial Science and Technology 1) Yubemoto Designated Agent Spontaneous a Number of inventions to be increased by the amendment 0 7, of the specification subject to the amendment Column for Detailed Description of the Invention & Contents of Amendment (1) “Cannot be obtained” in the first line of page 7 of the specification.
After that, add the following text on a new line. ``Also, unlike in general rolling, no driving power is required for the rollers, and the rollers do not necessarily need to rotate during drawing. While it is necessary to reach a desired rolling or drawing ratio, the method of the present invention is characterized in that it can be passed through a pair of heated rollers in one step.Of course, if desired, It is also possible to perform this in multiple stages.

Claims (1)

[Claims] 1. Place a crystalline polymer raw sheet into the sheet with a 1.0M
A small amount (both A method for producing a crystalline polymer sheet, characterized in that it is drawn at a stretching ratio of 2.5 times or more.