JP3451306B2 - Method for producing high-strength, high-transparency sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength, highly transparent sheet material. More specifically, it relates to a method for producing a high-strength / high-transparency sheet-like article, which comprises passing a polyolefin resin sheet-like article through rolling rolls having different peripheral speeds.

[0002]

A stretching method is well known as a method for improving the strength and transparency of a polyolefin resin in the longitudinal direction. In the stretching method, uneven stretching is likely to occur in the case of stretching at a low magnification, and uniform stretching becomes difficult in the case of a thick sheet. Therefore, the stretching method is applied to relatively thin film products. The rolling method is used for a thick sheet. It is difficult to obtain a product having a uniform thickness unless the roll strength is made sufficiently strong in order to give a large deformation to the material by the rolling method. Therefore, the cost of rolling equipment and driving power increases, which leads to an increase in product cost. In order to give a large deformation at a relatively low rolling, there are a rolling method that forms a liquid film between the roll and the material (liquid film method) and a rolling method that uses a roll rotating at a non-constant speed (non-constant speed method). . In the liquid film method, it is necessary to remove the liquid attached to the product.

On the other hand, the non-uniform velocity method has an advantage that the conventional apparatus can be used as it is, and it is not necessary to remove the liquid unlike the liquid film method. For example, JP-B-55-17694 and JP-B-55-31725 show a method of rolling a sheet or film of a thermoplastic resin at a temperature lower than its crystal melting point or softening point by narrowing pressure between rolling rolls. Has been done. However, in the non-constant velocity method, when a polyolefin resin sheet is deformed, there are drawbacks such as a decrease in transparency due to whitening and uneven thickness in the width direction.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems. That is, it is to provide a method for producing a sheet material having high transparency in the longitudinal direction, small thickness unevenness in the width direction and excellent transparency by a rolling method.

[0005]

As a result of earnest studies, the inventors of the present invention have found that when a polyolefin resin sheet material is processed by a non-constant speed method, a rolling roll speed ratio (high speed roll peripheral speed /
When the combination of the (low roll peripheral speed) and the reduction ratio of the sheet width is a specific value, the transparency and strength in the longitudinal direction of the sheet can be significantly improved, and the sheet with an extremely uniform thickness can be obtained. It was found that a product was obtained, and the present invention was completed based on this finding.

In the method for producing a high-strength / high-transparency sheet material of the present invention, the rolling roll is set at a temperature not lower than 80 ° C. lower than the melting point of the polyolefin resin and not higher than the melting point of the resin, and the peripheral speed is sequentially set. It consists of a pair of rolls that rotate in different opposite directions, and a sheet-shaped material made of the resin is brought into close contact with the low-speed roll side of the rolling roll and deformed in the gap between the rolling rolls to sequentially pass through the rolling rolls to deform the sheet Finally, it is characterized in that the relationship between the rolling roll and the sheet width D, and the relationship between the rolling roll and the sheet thickness P satisfy the following expressions (I) and (II) while being drawn out while closely adhering to the high-speed roll.

[0007]

[Equation 2]

In the production method of the present invention, the polyolefin resin is melt-kneaded, and the obtained sheet material is rolled by a known molding method such as a T-die method or an inflation method.

The rolling roll in the manufacturing method of the present invention is
It consists of a pair of rolling rolls that rotate in opposite directions,
Also, they are installed so that they rotate at different peripheral velocities in sequence, and gradually increase from low velocity to high velocity. In the case of a pair of rolling rolls, the sheet is first fed in close contact with the low speed roll,
Then, the peripheral speed is faster than that, and it is deformed in the gap between the high-speed roll and the low-speed roll opposite in the direction of rotation and allowed to pass,
Wrap it around the high-speed roll and pull out the take-up roll.

The rolling conditions in the manufacturing method of the present invention are represented by the following equations (I) and (II).

[Equation 3]

The value of D is 0.5 or less, preferably 0.4, and more preferably 0.35. When the value of D exceeds 0.5, whitening and wrinkles occur, and the transparency and thickness uniformity of the sheet-like material deteriorate. The value of P is 0.5 to 3
0, but preferably 1 to 30, more preferably 1 to
Twenty. When the value of P is less than 0.5, whitening occurs. If it exceeds 30, the load on the rolling roll and the equipment is large and it is not practical.

If necessary, the rolling operation may be repeated, the sheet may be preheated before rolling, or the sheet may be heat-treated after rolling. The rolling magnification (M) in the present invention can be expressed by the following formula from the cross-sectional area (A1) of the material resin before rolling and the cross-sectional area (A2) of the sheet material after rolling. M = A1 / A2 (III) The surface roughness (according to JIS B0601) of the rolling roll used in the method for producing a sheet-like material of the present invention is set so as to reduce visible light scattering on the surface of the sheet-like material. , Usually 1 S or less, preferably 0.5 S or less, more preferably 0.2
It must be set to S or less.

In the production method of the present invention, the rolling temperature needs to be set to a temperature lower than the melting point of the polyolefin resin by 80 ° C. and lower than the melting point of the resin. The temperature is preferably 10 ° C. or lower below the melting point of the polyolefin resin and 80 ° C. or higher below the melting point. When the sheet is subjected to a rolling treatment at a high temperature exceeding the melting point of the polyolefin resin, the sheet adheres to the roll, which causes problems such as wrinkles and thickness unevenness, and sufficient strength in the longitudinal direction cannot be obtained. Further, when the sheet is rolled at a temperature lower than the melting point by 80 ° C., the deformation resistance of the sheet becomes large, and the cost of the device, driving power, etc. becomes large, which causes industrial problems.

The sheet-like material obtained by the production method of the present invention has a total haze of 5% or less, an internal haze of 2% or less, preferably a total haze of 3% and an internal haze of 1% or less. When the total haze exceeds 5% and the internal haze exceeds 2%, the visible light is largely scattered and the transparency as a transparent sheet is insufficient. The sheet-like material obtained by the production method of the present invention has a tensile strength in the longitudinal direction of 20 kg / mm ² or more, preferably 25 kg / mm ² or more, more preferably 30 kg / mm ² or more. A plate-like material having a tensile strength of less than 20 kg / mm ² is insufficient for the requirements of the present invention in terms of strength.

Examples of the polyolefin resin used in the sheet-like material of the production method of the present invention include the following: high-density polyethylene, homopolymerized polypropylene or copolymerized polypropylene, and propylene as a main component. Polypropylene resins of copolymers of ethylene with other α-olefins or polar monomers and 2 of these resins
Any mixture of at least one kind may be used as long as it is a polypropylene resin having crystallinity, and is not limited to the kind of raw material resin. Further, maleic acid, acrylic acid, unsaturated carboxylic acid such as fumaric acid, a modified resin obtained by copolymerizing or grafting a derivative such as other acid anhydride or ester to the above resin, or the above resin is subjected to ionizing radiation treatment, A modified resin cross-linked with a cross-linking agent can also be used depending on the application.

Various kinds of fillers (or reinforcing materials) can be added to the polyolefin resin used for the sheet material used in the production method of the present invention to the extent that the transparency thereof is not substantially reduced. As the filler used, glass fiber, carbon fiber, fibrous filler such as vinylon fiber,
Examples thereof include flake fillers such as mica and talc, spherical fillers such as glass beads, and amorphous fillers such as calcium carbonate and wood chips. The surface of these fillers (or reinforcing materials) is preferably subjected to a treatment for imparting an affinity to the resin to be blended. Examples of such treatment include addition of unsaturated carboxylic acid, its acid anhydride, unsaturated amine and the like, or treatment of rubber coating.

In addition to these fillers, a filler,
Coloring agents, flame retardants, deterioration inhibitors, antistatic agents, lubricants and the like can be added.

[0018]

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. In addition, evaluation of the physical properties of the sheet-like material in Examples and Comparative Examples is based on the following methods. 1) Melting point: DSC measured according to JIS K7121
It represents the temperature at the peak of the curve. 2) Tensile strength: Tensile yield strength obtained from a stress-strain curve measured according to JIS K7113. If there is no yield point, the tensile strength at break is used. 3) Total haze: Measured according to ASTM D1003. 4) Internal haze: Liquid paraffin was applied to both sides of the sheet-like material and measured in the same manner as the total haze.

Example 1 Polypropylene homopolymer (abbreviated as PP, melt flow rate 1.0 g / 10 minutes, density 0.90 g / cc, melting point 162 ° C.) was melt-kneaded by a granulator and thickness was measured by T-die method. A sheet having a width of 1.0 mm and a width of 100 mm was manufactured. Using a device having a pair of rolling rolls having a radius (r) of 60 mm, a width of 130 mm and a surface roughness of 0.2 S as shown in FIG. 1, the rolling roll temperature was set to 110 ° C., and the rolling roll speed ratio [R: high speed roll peripheral speed ( 3.6 rpm) / low-speed roll peripheral speed (5.6 rpm)] is 6, and the load [rolling down force (F)] applied to the rolling roll shaft is 2800 kg, and the sheet is fed from the feeding roll (1) to a low-speed roll of the rolling roll. It is supplied in close contact with (2), is deformed between the low speed roll (2) and the high speed roll (3) and is sufficiently adhered to the high speed roll (3), and is wound around the draw-up roll (4). A sheet having a rolling ratio (M) of 5.8 was obtained. Table 1 shows the total haze, internal haze, and tensile strength of the sheet.

Example 2 Rolling roll speed ratio (R), gap (s), rolling force (F)
Example 1 was repeated except that Table 1 shows the rolling conditions and results.

Comparative Example 1 Example 1 was repeated except that the rolling force (F) and the gap (s) of the rolling roll were changed. Table 1 shows the rolling conditions and results.

Comparative Example 2 Rolling roll speed ratio (R), rolling force (F), gap (s)
Example 1 was repeated except that Table 1 shows the rolling conditions and results.

Example 3 Ethylene-propylene random copolymer (abbreviated as R-PP, melt flow rate 2.2 g / 10 minutes, density 0.
90 g / cc, melting point 142 ° C., ethylene content 4 mol%, propylene content 96%) are melt-kneaded in a granulator,
A sheet having a thickness of 1.0 mm and a width of 100 mm was manufactured by the T-die method. This sheet was rolled according to Example 1 except that the rolling roll temperature was 85 ° C. and the rolling force (F) was 2200 kg to obtain a sheet having a rolling magnification (M) of 6.2. The evaluation of the sheet is shown in Table 1.

Example 4 Rolling roll speed ratio (R), rolling force (F), gap (s)
The procedure of Example 3 was repeated except that

Comparative Example 3 Example 3 was repeated except that the rolling force (F) and the gap (s) were changed. A sheet having a rolling ratio (M) of 6.0 was obtained.
The above results are shown in Table 1.

[0026]

[0027]

According to the manufacturing method of the present invention, a polyolefin resin sheet having high strength in the longitudinal direction, small thickness unevenness in the width direction and excellent transparency can be provided by a rolling method.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for producing a high-strength / highly transparent sheet material of the present invention.

[Explanation of symbols] 1 Feeding roll 2 rolling rolls (low speed rolls) 3 rolling rolls (high-speed rolls) 4 winding roll 5 Auxiliary roll 6 sheets 7 Rolled sheet

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-4-94918 (JP, A) JP-A-4-341810 (JP, A) JP-A 53-8675 (JP, A) JP-A 53- 4077 (JP, A) JP 52-5874 (JP, A) JP 51-16360 (JP, A) JP 42-26948 (JP, B1) JP 41-15309 (JP, B1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 43/00-43/58

Claims (2)

(57) [Claims] 1. A rolling roll comprises a pair of rolls which are set at a temperature 80 ° C. lower than the melting point of the polyolefin resin and lower than the melting point of the resin and rotate in mutually opposite directions having different peripheral speeds. A sheet material made of the resin is closely attached to the low-speed roll side of the rolling roll, deformed in the gap of the rolling roll, successively passed through the rolling roll to deform the sheet, and finally drawn out while closely adhering to the high-speed roll. The width relationship D and the relationship P between the rolling roll and the sheet thickness are expressed by the following equations (I) and (II). A method for producing a high-strength, highly transparent sheet-like material, characterized by satisfying: 2. A high-strength, highly transparent sheet material according to claim 1, which comprises obtaining a polyolefin resin sheet having a total haze of 5% or less, an internal haze of 2% or less, and a tensile strength in the longitudinal direction of 20 kg / mm ² or more. Manufacturing method.