JPH064273B2 - Method for stretching crystalline polymer material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for stretching a crystalline thermoplastic polymer material to obtain a polymer material having high strength and high elastic modulus.

2. Description of the Related Art Generally, for molding a polymer material, a method of solidifying a material in a molten state as it is in a mold, pouring it into a mold by applying pressure, or extruding from a die is used.

The polymer material molded by these methods has a low orientation of molecular chains and is disordered, and the mechanical properties of the material remain low.

Therefore, in order to obtain a high-strength, high-modulus polymer material, it is necessary to deform the material in a specific direction by a method such as stretching or rolling so that the molecular chains are highly oriented.

The rolling method can be applied to thick polymer materials, but a high deformation ratio cannot be obtained, and dimensional accuracy is poor due to elastic recovery (springback) after passing through the roller.

Although the spinning and drawing method can obtain a very high deformation ratio and enables the production of high-strength and high-modulus polymer materials, the total cost such as equipment cost is high and it is directly returning to the product cost. When used as a raw material, the economic merit is not sufficient.

In the draw-drawing method, the mechanism is simple and there is a high possibility that equipment costs can be kept low, but there is a constraint that the pull-out tension must be smaller than the breaking strength of the material, so the pull-out speed is low and It has not been applied yet.

Japanese Unexamined Patent Publication No. 60-15120 is intended to improve the disadvantages of such a drawing and drawing method, and in the process of drawing a material under a constant temperature condition, strain hardening occurs and it is difficult for the material to break. This is a method for obtaining a high deformation ratio by utilizing it.

However, in the above-mentioned drawing and stretching method, the drawing speed is extremely low.
It is 0.04, which is extremely low at 0.5 m / min at maximum, and the deformation ratio obtained at a drawing speed of 0.5 m / min is very low, which leaves a big problem in terms of productivity.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention focuses on a simple drawing / drawing method with a simple mechanism, improves the productivity by eliminating the problem of a remarkably low drawing speed, which is a conventional problem, and uses hot drawing together. It is intended to establish a method for stretching a crystalline thermoplastic polymer material having a high deformation ratio.

Means for Solving the Problems, Action The present invention is a method for stretching and strengthening a sheet or a bar (hereinafter, abbreviated as a material) by passing a crystalline thermoplastic polymer material through a heated drawing tool, Immediately after exiting the drawing tool, by quenching and drawing the stretched material,
In the method of performing high-speed drawing to a draw ratio of 8 or more, and performing hot-stretching by applying appropriate heat and tension to the material to perform draw-strengthening, the material immediately after the hot-drawing is subjected to a rapid cooling treatment to achieve high-speed drawing. It is a combination of things to do. Here, the reason why the stretching ratio is specified to be 8 or more is that a stretching material having a stretching ratio of 8 or more can be obtained by the stretching method of the present invention as shown in Examples described later.

Further, the former step (I) using a drawing tool and the latter step (II) having a heat drawing zone are continuously or arbitrarily combined to obtain a high-strength, high elastic modulus with high productivity. A method for stretching a crystalline thermoplastic polymer material, which comprises obtaining a polymer material.

The method for stretching the crystalline thermoplastic polymer material according to the present invention will be described in detail with reference to FIG.

First of all, the drawing tool 2 that heats the preheated material 1
The material is stretched by passing it through (for example, a die or a roll) and adjusting the distance between the drawing tools to perform drawing.

Second, the material is preheated and quenched from the temperature imparted by the drawing tool by passing through the quenching zone 3 immediately after the exit of the drawing tool.

In general, the thermoplastic polymer material used as a material has a large decrease in mechanical properties (strength, rigidity, etc.) when the temperature of itself increases.

If the drawn product is not subjected to the quenching process and does not pass through the quenching zone, the temperature of the material immediately after the outlet of the drawing tool is close to the drawing tool temperature, so the strength of the drawn product at that position is Since the strength is lower than the strength, the pulling tension cannot be increased due to the increase in the pulling speed V, which leads to fracture.

Further, even if the drawing tension is constant, the cooling rate of the material does not change, so that the temperature of the material located in the vicinity of the outlet of the drawing tool rises due to the increase of the drawing speed, and the material also breaks.

Therefore, a quenching zone 3 is provided immediately after the exit of the drawing tool to quench the material, thereby recovering the strength of the material at the position immediately after the exit of the drawing tool to the original strength, thereby increasing the drawing speed. It will be possible.

Further, the material after passing the drawing tool undergoes strain hardening and molecular orientation in a certain direction, and the strength of the material is higher than the strength of the material before passing the drawing tool.

Further, since the material 1 is a thermoplastic material whose deformation resistance becomes smaller as it approaches the melting point (Tm), the temperature of the drawing tool is set to T
Although the drawing tension is naturally lowered when it is brought closer to m, it is very difficult to raise the temperature of the drawing tool to a temperature sufficient to reduce the drawing tension when the quenching treatment is not performed.

However, it was possible to raise the temperature of the drawing tool by performing the quenching process.

For example, when high-density polyethylene is used as the material for drawing and stretching, the drawing tension can be kept low by setting the drawing tool temperature high.

When quenching is applied, pull out tool temperature (Tr) to 11
It is possible to set the temperature to 0 ° C, but if the quenching treatment is not applied, Tr cannot be set to 90 ° C or higher. In this case, the drawing speed is much lower than that when the quenching treatment is applied. Became.

In the vicinity of the melting point, it is possible to stretch the material apparently by quenching it, but it becomes difficult for the amorphous chains in the structure of the material to be oriented (the crystals are easily oriented), and the stretching of the material The effect of increasing strength and elastic modulus is reduced. Further, if the temperature is further raised, melting will occur.

The material used in the stretching method of the present invention is, for example, polyethylene, polypropylene, polyacetal, a thermoplastic polymer material generally showing crystallinity such as polyvinyl alcohol, and the molecular weight and molecular weight distribution of the material used are
There is no particular limitation as long as it is used as a fiber, a film, or a molded product.

When the material is drawn and stretched, it is necessary to preheat it to a temperature near the drawing tool temperature.
It is more preferable to adjust the temperature to a temperature not lower than the deformation start temperature when the load of a is raised at 1 ° C./min and not exceeding the rising temperature of the differential scanning calorimeter (DSC) melting curve.

If the material 1 is stretched without preheating and the drawing speed is increased, the thickness of the material to be obtained varies greatly, and the drawing tension becomes high, so that stable drawing and stretching cannot be performed.

The interval of the drawing tools 2 may be less than the thickness (or outer diameter) of the material, but it is preferable to set the cross-section rate tr / to ≦ 0.5 in order to increase the deformation ratio (tr: interval of the drawing tools,
to: material thickness or outer diameter).

The heating of the drawing tool 2 is necessary to maintain the material temperature given by preheating until the material 1 finishes passing through the drawing tool, and the drawing tool temperature is set to 1 ° C by applying a load of 10 GPa to the material. Is higher than the deformation start temperature when the temperature is raised in minutes,
It is more preferable to adjust the temperature to a temperature range not exceeding the rising temperature of the differential scanning calorimeter (DSC) melting curve.

The cooling method of the rapid cooling treatment may be a contact type or a non-contact type, and the cooling medium may be any of gas, liquid, air, water, electronic cooling, etc., and there is no particular limitation.

The temperature of the cooling medium itself is lower than or equal to the heating temperature of the drawing tool, but is lower than or equal to Tg when the glass transition temperature (Tg) of the material 1 is room temperature or higher, and lower than or equal to room temperature when Tg is room temperature or lower. It is more preferable to set the temperature of the cooling medium itself to the temperature.

Further, the quenching treatment in the present invention is a cooling treatment in which the temperature of the material becomes room temperature or lower in the region immediately after the outlet of the drawing tool (the length from the outlet is about 2 cm to 5 cm in the stretching direction), and the cooling rate is 50 ° C. / Sec or more is preferable, and the higher the drawing speed, the higher the cooling rate must be set.

The present invention can also be combined with the hot stretching method. In the hot drawing method, as shown in the step (II) of Fig. 1, the material is directly passed through the hot drawing zone 4 in a state where an arbitrary tension is applied to the material, and the material is rapidly cooled immediately after its exit. By the method of cooling the raw material after passing through the hot drawing zone to room temperature or lower, the original strength of the drawn product is restored and the hot drawing is stabilized.

For example, a material that is in a whitened state due to a sudden stretching deformation (a state in which microvoids appear to appear white: a sign of breakage) can be endured without being broken by performing a rapid cooling treatment as in step (II). Although it is possible, if it is not subjected to quenching treatment, it will break immediately after whitening.

In the thermal drawing zone 4, the orientation of the molecular chains is mainly increased. However, in the structure of the material at the exit of the thermal drawing zone 4, the reorganization (return) of the tissue due to the residual heat at the same time as the orientation of the molecular chains occurs. The rapid cooling process is also effective in suppressing the reorganization (return) of the structure as much as possible and also fixing the material structure in the highly oriented state of the molecular chain as it is. An increase in tensile strength was confirmed.

Fig. 6 shows the effect of quenching treatment after hot drawing on tensile elastic modulus (E). When the material is quenched at the same draw ratio 26, E of the material is 4500 Kgf / mm ² ( The symbol E in the figure shows the E of the material when the material is not quenched, which is 3600 Kgf / mm ² (○ in the figure). It can be seen that it contributes to immobilization as it is.

Further, if necessary to obtain a high deformation ratio, after preheating the raw material of the crystalline polymer material, passing through a heated drawing tool and stretching, immediately followed by a quenching process In the process of thermally drawing the raw material of (I) and the crystalline polymer material, the process of step (II) characterized by subjecting the material to a quenching treatment immediately after the drawing is continuously performed, or the above-mentioned process By arbitrarily combining (I) and step (II) and performing multi-stage drawing, the material can be deformed at a high magnification at a high speed.

The number of times of combining the steps (I) and (II) and repeating each step is not limited, but the drawing speed V is 0.5 m.
If you try to obtain a high deformation ratio at more than 1 minute / minute, the deformation amount of the material per one time will be large, and sudden deformation will occur and stretching will become unstable. It is preferable to suppress the above and increase the number of steps (I) and (II) for stabilization.

The heat medium in the heat drawing zone 4 includes gas, liquid, air, water,
And energy waves can be used, and there is no particular limitation.

The pressure in the heat drawing zone 4 may be either normal pressure or increased pressure, and is not particularly limited.

The temperature range of the heat medium is 1 ℃ with a load of 10GPa applied to the material.
It is preferable to control the temperature within a temperature range not lower than the deformation start temperature when the temperature is raised at a heating rate of 1 / min and not exceeding the rising temperature of the differential scanning calorimeter (DSC) melting curve.

EXAMPLES Next, the present invention will be described in more detail by way of examples.

In each example, a steel blade die (tip 25 mmR, width 100 mm) or roll (radius 25 mm, width 100 mm) was used as the drawing tool.

For the tensile test of the drawn material, an Instron type tensile tester (Autograph AG5000A manufactured by Shimadzu Corporation) was used and measured according to JIS K 7113-1980.

The meaning of each symbol in Table 1 is as follows.

Tf: preheating temperature of the material 1, ° C Tf ': ambient temperature of the heat drawing zone 4, ° C Tr: heating temperature of the drawing tool 2, ℃ tr / to: ratio of the distance tr of the drawing tool to the thickness to of the material V: its Maximum drawing speed obtained under the conditions, m / min λ: Stretch ratio, value obtained by dividing the material cross-sectional area before deformation by the material cross-sectional area after deformation λ ₁ : Stretch ratio in the first-stage stretching λ ₂ : Stretching ratio in two-stage stretching E: Tensile elastic modulus, Kgf / mm ² σ: Tensile strength, Kgf / mm ² There are three kinds of materials used here, melted and pressed into pellets and then formed into a sheet. Yes, the types and dimensions are shown below.

High Density Polyethylene (HD-PE) Thickness: 2mm, Width: 15mm Mitsui Petrochemical Industry, Hi-Zex 2200J Polypropylene (is-PP) Thickness: 1mm, Width: 15mm Mitsui Toatsu Chemicals, Noblen FL-
100 Ethylene / Vinyl Alcohol / Random Copolymer (ET-VA) Thickness: 2 mm, Width: 15 mm Kuraray Eval Example 1 Using high density polyethylene as the material, tr / to = 0.15 × 0.35
The material was sandwiched between blade dies within the range of, and the material was rapidly cooled while being drawn, and then drawn and stretched.

The conditions at this time are Tf = 105 ° C. and Tf = 120 ° C. in order to lower the deformation resistance in the die, and Tf = 110 ° C.
Room temperature air having a pressure of 2 kg / cm ² (pressure gauge) was blown onto the material, and the cooling rate was 60 ° C./second.

The maximum drawing speed V reached 10 / min.

The results are shown in Table 1, FIG. 2 and FIG. 3 (symbol Δ in the figure). FIG. 2 shows the relationship between the stretch ratio (deformation ratio (λ and the drawing speed V, and the breaking line in the figure shows tr / to of 0.15
To the 0.50 to 0.50 range, when the V is increased, the material is just about to break (Tf and Tr are examples,
According to the comparative example).

FIG. 3 shows the result of the tensile test.

Example 2 Using high-density polyethylene, as the first stage, tr / to
= 0.15, sandwich the material in a blade die, stretch the material by working out the example with Tf = 105 ° C, apply tension to a stretching area of 1200 mm in length, and immediately after that, quench the material to obtain a two-stage Stretching was performed.

5 cm from the exit for quenching the material at the hot drawing exit
The above materials were blown with room temperature air having a pressure of 2 kg / cm ² (pressure gauge).

The atmosphere temperature Tf 'in the hot stretching region was 80 to 90 ° C.

Results The results are shown in Table 1 and FIGS. 2 and 3 (indicated by a symbol ■ in the figure).

Comparative Example 1 Using high density polyethylene, tr / to = 0.15, Tf
The condition was set to 105 ° C. (the same condition as in Example 1), and the material immediately after the die exit was pulled out without being subjected to the quenching treatment, but immediately fractured.

Further, the drawing speed (V) was maintained at a remarkably low value of 0.02 m / min, but it broke and could not be stretched.

Comparative Example 2 High-density polyethylene was used and only the die temperature Tr was set to 90.
C., conditions were set to tr / to = 0.15, Tf = 105.degree. C. (except for Tr, the same conditions as in Example 1 were used), and the material immediately after the die exit was pulled out without being subjected to quenching treatment.
It was a very low speed of ≦ 0.07.

The results are shown in Table 1, FIG. 2 and FIG. 3 (indicated by a symbol ◯).

Comparative Example 3 Under the same conditions as in Comparative Example 2, the die was changed to a roll and drawn.

The results are shown in Table 1, FIG. 2 and FIG. 3 (indicated by a symbol ◯).

In the above Examples 1 and 2 and Comparative Examples 1, 2 and 3, when the high density polyethylene is used as the material, when the die temperature Tr becomes close to the melting point of the material (around 120 ° C), the amorphous chains in the material structure are oriented. Less likely (crystals are easily oriented),
The effect of increasing the strength and elastic modulus of the material by stretching is reduced.

If the temperature is further raised, it will melt.

In the range of the die temperature Tr <120 ° C., the higher the Tr is, the lower the drawing tension can be kept.

However, in the case of Comparative Example 1 in which the quenching zone for the quenching process is not provided, it cannot be extracted at Tr = 110 ° C.
Although it was significantly reduced to 0.02 m / min, fracture occurred even in this case.

In the case of Comparative Example 2, the die temperature Tr was lowered to 90 ° C., but it was not possible to draw at a drawing speed V> 0.1 m / min, and V was set to 0.
It was finally able to be pulled out by making it extremely low at 03-0.07m / min.

At this time, the one with the maximum stretching ratio λmax. = 23 was obtained, but it did not pull out stably, and it broke at the time of pulling out about 2 m.

Λ ≦ 18 was suitable for stable and continuous drawing.
(FIG. 2; ◯) In Comparative Example 3, the blade die was changed to a roll and pulled out, and the same result as in Comparative Example 2 was obtained, and V = 0.03 to 0.07 m / min because there was no quenching zone. It was the limit. (Second
In the first example, Tr = 110 ° C. could be set by providing the quenching zone for the quenching process, and V could be increased to 1 to 10.0 m / min. (Fig. 2; △
In addition, in Example 2, by combining the drawing stretching quenching treatment and the hot drawing quenching treatment, λ can be obtained in the first stage drawing.
It was possible to obtain a high stretching ratio of λ = 20 to 36 by stretching ₁ = 10 and stretching to λ2 = _{2 to} 3.6 by the second stage hot stretching. (Fig. 2; mark ■) Mechanical properties have a strong correlation with the draw ratio λ, and although there is no great difference in the above deviation method, in Example 2 in which the final reach draw ratio is large, λ≈36. And tensile elastic modulus E ≒ 6,00
It reached 0 Kgf / mm ² and tensile strength σ≈65 Kgf / mm ² . (Second
(FIG. 3, FIG. 3; mark ■) As described above, by using the drawing process capable of quenching, a high stretch ratio can be achieved at an order of magnitude higher speed than the conventional method.

Example 3 Using polypropylene as a material, the material was sandwiched between blade dies at tr / to = 0.13, and the material was rapidly cooled while being drawn and drawn and drawn.

The conditions at this time are set as Tf = 115 ° C. and Tr = 120 ° C.,
The material was rapidly cooled on the outlet side of the blade die at a cooling rate of 75 ° C./sec or more by blowing room temperature air having a pressure of 2 kg / cm ² onto the material at a quenching area up to 5 cm from the die exit.

The results are shown in Table 1, FIG. 4 and FIG. (Symbol in the figure) FIG. 4 shows the relationship between the draw ratio λ and the drawing speed V, and FIG. 5 shows the relationship between the tensile elastic modulus E and the tensile strength σ.

Comparative Example 4 Using polypropylene as a material, the material was sandwiched between blade dies at tr / to = 0.13, and drawn and stretched without subjecting the material to quenching.

The conditions at this time are Tf = 115 ° C. and Tr = 1 as in Example 3.
It was set to 20 ° C.

The results are shown in Table 1 and the materials having the maximum draw ratio (λmax.) And the maximum drawing speed (Vmax.) Are shown in FIGS. 4 and 5 (marked with a circle in the figure).

Comparative Example 5 The blade die was changed to a roll, and the blade was drawn under the same conditions as in Comparative Example 3.

The results are shown in Table 1 and the materials having the maximum draw ratio (λmax.) And the maximum drawing speed (Vmax.) Are shown in FIGS. 4 and 5 (marked with a circle in the figure).

In the case of Comparative Examples 4 and 5 not subjected to the rapid cooling treatment in Example 3 and Comparative Examples 4 and 5, V =
It becomes remarkably 0.05.

Further, if V is increased in this state, Vmax. = 1 m / min is the limit, and in this case, as V increases, the stretch ratio λ decreases. (○ in Figures 4 and 5 When a quenching zone is used in the method of the present invention (Examples 3, 4,
5), V can be increased up to 2m / min, λ
= 14 was obtained.

Example 4 Using ethylene / vinyl alcohol random copolymer as a raw material, the raw material was sandwiched between blade dies having a tr / to = 0.15, and the raw material was rapidly cooled while being drawn, and then drawn and stretched.

The conditions at this time are Tf = 140 ° C. and Tr = 145 ° C.,
For the rapid cooling of the material on the blade die exit side, the quenching area is 5 cm from the blade die outlet, and the pressure is 2 kg /
A room temperature air of cm ² was blown onto the material, and the cooling rate was 130 ° C / sec or more.

The results are shown in Table 1 and FIGS. 4 and 5.

Comparative Example 6 Using ethylene / vinyl alcohol random copolymer as a raw material, the raw material was sandwiched between blade dies having a tr / to = 0.15, and the raw material was drawn and stretched without quenching.

The conditions at this time were Tf = 140 ° C. and Tr as in Example 4.
= 120 ° C was set.

The results are shown in Table 1 and FIGS. 4 and 5.

Without quenching, V = 0.25m / min, λmax. = 5
(Marked with Δ in FIGS. 4 and 5), when the quenching process is performed in Example 4, V = 1 m / min, λmax. = 8 (4, 5)
The ∘ mark in the figure was obtained, and both the speed and the stretching ratio were remarkably improved.

Further, at λ = 8, a tensile strength σ = 28 Kgf / mm ² was obtained.

Example 5 Using high-density polyethylene, the first step is tr / to
Tf = 120 by sandwiching the material between the blade dies with = 0.35
While pulling out under conditions of ℃, Tr = 110, V = 10m / min, the material up to 5cm from the die exit is subjected to quenching treatment, and the obtained drawn material is used as the second stage, tr / to = 0.15, Tf = 125.
The material up to 5 cm from the die exit was subjected to a rapid cooling treatment while sandwiched by a blade die set to ℃, Tr = 118 ° C., V = 5 m / min, and then two-stage stretched.

Both the first-stage and second-stage materials are rapidly cooled by blowing room temperature air with a pressure of 2 kg / cm ² onto the material and cooling rate 60 ℃ /
It took more than a second.

The stretched material thus obtained had λ ₁ = 14 in the first stage and λ ₂ = 1.5 in the second stage, and finally had λ = 21.

In the above examples, the obtained polymer oriented stretched body,
It exhibits transparency and a fairly high birefringence. Also in the tensile test, it does not show a yield point and breaks at a value 15 times higher than the strength of the raw material.

These stretched polymeric materials have application fields as tension members such as ropes and nets, and as reinforcing materials for composite materials.

EFFECTS OF THE INVENTION The conventional drawing-drawing method has a big drawback that the drawing speed is extremely low in terms of productivity, but by subjecting the material to the quenching treatment in the present invention, it is high while maintaining a high deformation ratio. It has become possible to perform drawing with good productivity under drawing speed.

Further, the material subjected to the quenching treatment has a difference in tensile elastic modulus (E) and tensile strength (σ) at the same deformation ratio as compared with the material not subjected to the quenching treatment, and the E of the material subjected to the quenching treatment is different.
And σ were higher than E and σ of the material which was not applied.

[Brief description of drawings]

FIG. 1 is an explanatory view of the method of the present invention, (1) is a drawing / quenching process step, (2) is a hot drawing / quenching process step, and (3) is a step (1).
2 and 4 show the relationship between the drawing speed and the draw ratio, and FIGS. 3 and 5 show the relationship between the draw ratio and the tensile elastic modulus and the tensile strength. And FIG. 6 are views showing changes in tensile elastic modulus and tensile strength (high-density polyethylene) due to the rapid cooling treatment. 1 ... material, 2 ... drawing tool, 3 ... quenching area,
4 ... Hot drawing zone.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Isao Tanaka 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Inside Nippon Steel Co., Ltd. Technical Research Institute (72) Toshio Torai 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Address Nippon Steel & Steel Co., Ltd. Technical Research Institute No. 1 Hisashi Nao Tanaka (56) References JP 63-81023 (JP, A) JP 50-12152 (JP, A) JP 52-29874 (JP, A) JP 59-38239 (JP, A)

Claims (2)

[Claims] 1. A crystalline polymer material sheet or rod is preheated, then passed through a heated drawing tool to be stretched, and immediately after that, a quenching process is performed and a stretching ratio is 8 or more. A method for stretching a crystalline thermoplastic polymer material. 2. A step (I) of pre-heating a sheet or rod of a crystalline polymer material, passing it through a heated drawing tool and stretching it, and immediately followed by a quenching treatment, and a step of applying the crystalline polymer material. The sheet or bar is passed through a zone where it is hot-stretched, and immediately after its exit, the step (II) of subjecting the material to rapid cooling is continuously performed, or the steps (I) and (II) are optionally performed. A method for stretching a crystalline polymer material, which is characterized in that the combination is performed in multiple stages and a stretching ratio is 8 or more.