JP2003165155A - Polyethylene molding and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene molding having good physical properties which is excellent in balance of mechanical properties and applicable to various fields by a continuous method for producing the polyethylene molding inexpensively and efficiently. <P>SOLUTION: In the method for producing the polyethylene molding, after a polyethylene film is molded directly from polyethylene powder at a temperature above the melting point of the powder, the obtained film is stretched at a temperature of the melting point of the film or above to obtain the polyethylene molding at least 25 GPa in tensile modulus of elasticity (24°C). The polyethylene molding at least 0.2 GPa in loop strength (24°C), at least 25 GPa in tensile modulus of elasticity (24°C), and at least 0.4 GPa in breaking strength (24°C) is obtained by the method. <P>COPYRIGHT: (C)2003,JPO

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 polyethylene molded article, which enables inexpensive and efficient continuous production of a molded article having high physical properties, and a balance of mechanical properties obtained by the method. The present invention relates to a polyethylene molded product which is excellent and can be applied to various fields.

[0002]

2. Description of the Related Art Conventionally, polyethylene films have been manufactured by the following methods (i) and (ii) in the process of manufacturing various polyethylene molded products having high physical properties. (I) A method in which a polymer powder obtained by polymerization of ethylene is melt-kneaded to be molded into pellets, which is kneaded again and then extrusion-molded into a desired film shape. (Ii) the polymer powder is compression molded into a block,
A method of shaving this in the way of stripping a wig to obtain the desired film shape.

[0003] However, in the prior art, as the technology has become more sophisticated and more efficient, there has been a strong demand for a technology for producing a polyethylene molded article having high physical properties with higher production efficiency and at lower cost. How to improve the efficiency of intermediate processes such as the molding process and the block compression molding process has been an important issue.

Further, in Patent Document 1, a polyethylene polymer powder is continuously compression-molded at a temperature lower than the melting point of the powder, and then rolled and stretched to obtain a high-strength / high-modulus polyethylene material. How to get it is proposed. In this proposal, the roll molding is performed at 130 ° C., which is lower than the melting point of the polyethylene polymer powder, so that the excellent properties of the polymer powder such as high crystallinity are maintained in the molding film as they are. Due to this, the elastic modulus has a high value of 120 GPa and the linear strength has a high value of 2.0 GPa. However, in this proposal, the polyethylene polymer powder interface remains in the formed film, and as a result, the loop strength indicating the flexibility of the film becomes low (0.15 GPa), and therefore the film breaks during use in practical use. There was a problem. Further, there is a drawback that the film is easily broken in the molding process and is inferior in handleability.

[0005]

[Patent Document 1] JP-A-7-156173

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to meet the above-mentioned conventional demands, solve various problems, and achieve the following objects. That is, the present invention, a molded article having high physical properties, inexpensive, efficient and continuous production method of a polyethylene-made molded article, and obtained by the manufacturing method,
It is an object of the present invention to provide a polyethylene molded article which has an excellent balance of mechanical properties and can be applied to various fields.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a polyethylene film is directly molded from a polyethylene polymer powder at a temperature exceeding the melting point of the polyethylene polymer powder. After that, by stretch-molding the obtained polyethylene film at a temperature exceeding its melting point, a high melt viscosity is obtained even at a melting point or higher due to the entanglement of the molecular chains of the high-molecular-weight polyethylene, and the stretching stress is efficiently increased. Since it propagates to the entire sample, roll forming and melt drawing are possible in the molten state,
The present inventors have completed the present invention by finding that they have an excellent balance of mechanical properties and that continuous molding can be easily performed.

That is, the means for solving the above problems are as follows. <1> A polyethylene film is directly molded from the polyethylene polymer powder at a temperature exceeding the melting point of the polyethylene polymer powder, and then the obtained polyethylene film is stretch-molded at a temperature equal to or higher than the melting point to obtain a tensile elastic modulus (24
The method for producing a polyethylene molded article is characterized in that a polyethylene molded article having a temperature of 25 GPa or higher is obtained. <2> The polyethylene film is 130 in the DSC curve obtained by differential scanning calorimeter (DSC) measurement.
The method for producing a polyethylene molded article according to <1>, having one peak at ˜136 ° C. <3> Polyethylene molded body loop strength (24 ° C)
Is the method for producing a polyethylene molded article according to <1> or <2>, which has 0.2 GPa or more. <4> Breaking strength of polyethylene molding (24 ° C)
Is the method for producing a polyethylene molded article according to any one of the items <1> to <3>, which is 0.4 GPa or more. <5> The method for producing a polyethylene molded body according to any one of <1> to <4>, wherein the temperature at which the polyethylene film is molded from the polyethylene polymer powder is 135 to 155 ° C. <6> The method for producing a polyethylene molded product according to any one of <1> to <5>, wherein the molding of the polyethylene polymer powder is roll molding. <7> The method for producing a polyethylene molded article according to <6>, wherein the roll molding is performed by passing a polyethylene polymer powder through a gap between a pair of rolls. <8> A polyethylene polymer powder is passed through a gap between a pair of rolls to be roll-formed, and then conveyed in a direction in which the passed direction is substantially orthogonal to the central axis direction of one of the pair of rolls. The method for producing a polyethylene molded article according to <6> or <7> above, wherein a polyethylene film is obtained. <9> The method for producing a polyethylene molded article according to <7> or <8>, wherein the gap between the rolls is 0.005 to 10 mm. <10> The rotation speed of the roll is 0.1 to 10 m / mi
The method for producing a polyethylene molded article according to any one of <6> to <9>, wherein n is n. <11> The above-mentioned <1> in which the stretch molding is tensile stretch molding.
The method for producing a polyethylene molded article according to any one of <> to <10>. <12> The method for producing a polyethylene molded article according to any one of <1> to <11>, in which stretch molding is performed at 135 to 155 ° C. <13> The strain rate in stretch molding is 0.1 to 1
The method for producing a polyethylene molded article according to any one of <1> to <12>, which is 00 / min. <14> Obtained by the method for producing a polyethylene molded article according to any one of <1> to <13>, the loop strength (24 ° C.) is 0.2 GPa or more, and the tensile elastic modulus (2
The polyethylene molded article is characterized by having a 4 ° C.) of 25 GPa or more and a breaking strength (24 ° C.) of 0.4 GPa or more.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyethylene molded article of the present invention and the method for producing the same are described in detail below. [Method for producing polyethylene molded body] The method for producing a polyethylene molded body of the present invention was obtained after directly molding a polyethylene film from a polyethylene polymer powder at a temperature exceeding the melting point of the powder. A polyethylene film is stretch-molded at a temperature above its melting point. In addition,
The polyethylene molded body obtained by the method for producing a polyethylene molded body of the present invention has a loop strength (24 ° C.) of 0.2 GPa or more and a tensile elastic modulus (24
C) is 25 GPa or more, and the breaking strength (24 C) is 0.
It is 4 GPa or more and is excellent in balance of mechanical properties.

-Polyethylene film-The polyethylene film is a differential scanning calorimeter (DS).
C) The DSC curve obtained by the measurement has one peak at 130 to 136 ° C., which is equal to or lower than the melting point of the raw material polyethylene polymer powder. In other words, the polyethylene film is sufficiently melted to form a film. It is molded. If the melting is insufficient, voids will remain between the polyethylene particles, and a uniform polyethylene film cannot be obtained even if the polyethylene polymer powder is directly molded.

The polyethylene film has a loop strength at 24 ° C. of preferably 20 MPa or more, more preferably 50 MPa or more. If the loop strength is less than 20 MPa, it may be broken in the process of producing a polyethylene molded article, which may result in poor handleability and may be unfavorable in terms of production efficiency and cost. The loop strength was measured in accordance with JIS L1013, and a tape-shaped sample was cut out with a width of 5 mm from a polyethylene film or the like to be measured to form a loop at the center between the grips, and the strength at the time of cutting ( N) is measured at room temperature (24 ° C.) using a tensile tester (trade name: RTM1425, manufactured by Orientec Co., Ltd.), and this is the value obtained by dividing this by the cross-sectional area of one sample.

—Polyethylene Polymer Raw Material— The polyethylene polymer raw material is not particularly limited, and all known raw materials used as raw materials for various types of polyethylene molded products are preferably used. From the viewpoint of production efficiency, the shape of the polyethylene polymer raw material is preferably granular or powder, more preferably powder. The particle diameter of the polyethylene polymer raw material is the volume average particle diameter (D ₅₀ ).
It is preferably 2000 μm or less, more preferably 1 to 2000 μm, still more preferably 10 to 1000 μm. As the particle size distribution of the polyethylene polymer raw material,
From the viewpoint of excellent uniformity of the obtained polyethylene film, it is preferably narrow.

The viscosity average molecular weight (Mv) of the polyethylene polymer raw material is preferably from 500,000 to 12,000,000, more preferably from 900,000 to 9,000,000, and from 1.2,000,000.
Six million is more preferable. The viscosity average molecular weight is
It is a value measured in a decalin solvent (135 ° C.), and the intrinsic viscosity is preferably 5 to 50 dl / g,
8-40 dl / g is more preferable, 10-30 dl / g
Is more preferable.

-Molding of Polyethylene Polymer Powder- In molding the polyethylene polymer powder, a polyethylene film is directly molded from the polyethylene polymer powder. Therefore, conventionally, in the manufacturing process for obtaining a polyethylene molded body, the steps required for obtaining a polyethylene film from a polyethylene polymer powder, such as pellet molding, kneading / extrusion molding, are not necessary. Excellent manufacturing efficiency.

When molding a polyethylene film from the polyethylene polymer powder, it is preferable to mold the polyethylene polymer powder at a temperature above the melting point of the polyethylene polymer powder, and the temperature is 135 to 155 ° C.
Is preferable and 138-150 degreeC is more preferable. When the molding temperature is not higher than the melting point of the polyethylene polymer powder, the raw materials are not appropriately pressure-bonded to each other at the time of molding and do not sufficiently melt, so that a uniform polyethylene film may not be obtained. When the molding temperature of the polyethylene polymer powder exceeds 155 ° C., the polyethylene polymer powder is not efficiently supplied to the roll gap during molding,
A uniform film may not be obtained. In the present invention, the “melting point” means a differential scanning calorimeter (DSC).
It indicates the temperature (° C) at the peak of the DSC curve obtained by measuring in.

The molding of the polyethylene polymer powder is not particularly limited, but roll molding of the polyethylene polymer powder is preferable from the viewpoint of production efficiency and the like. In the roll forming, for example, a method of forming a film by passing a polyethylene polymer powder through a gap between a pair of rolls is preferable. The gap between the rolls is preferably 0.005 to 10 mm from the viewpoint of uniformity and thinness of the polyethylene film to be obtained, and is 0.0
05-0.1 mm is more preferable, 0.005-0.0
5 mm is more preferable. The rotation speed of the roll is preferably 0.1 to 10 m / min, and is excellent in the adhesiveness of the polyethylene polymer powder, the transparency and uniformity of the obtained polyethylene film, and the mechanical properties such as elastic modulus. 1 to 10 m / min is more preferable.

The shape of the roll is not particularly limited as long as it is rotatable, and examples thereof include a cylindrical body, a cylindrical body, and a rotatable infinite belt body.

The material of the roll is not particularly limited as long as the polyethylene polymer powder can be suitably roll-formed, and examples thereof include metals such as stainless steel, fluororesins such as polytetrafluoroethylene, and polyimide resins. .
Among these, stainless steel and the like are more preferable because the polyethylene polymer powder can be roll-formed.

FIG. 1 is an explanatory view showing a preferred embodiment of the roll forming. The pair of rolls 10 illustrated in FIG. 1 includes a roll 10a and a roll 10b. The roll 10a and the roll 10b have rotating shafts 10a 'and 10 respectively.
a rotatable cylindrical body having b ′ and a rotation shaft 10a ′.
And 10b 'are arranged on the same horizontal plane.
In the pair of rolls 10, the roll 10a and the roll 1
0b is heated to a temperature (for example, 140 ° C.) within a preferable numerical value range for molding the polyethylene polymer powder, and the polyethylene polymer powder 10c is placed thereon, and then the roll 10a and the roll 10b are illustrated. By rotating in the direction of the arrow, the polyethylene film 10d is continuously obtained.

In the present invention, the polyethylene polymer powder is passed through a gap between a pair of rolls to be roll-formed, and the passing direction and the central axis direction of one of the pair of rolls are It is particularly preferable to obtain a polyethylene film by transporting in a direction substantially orthogonal to the polyethylene film. This will be schematically described with reference to FIG. The pair of rolls 10 illustrated in FIG. 2 includes a roll 10a and a roll 10b. The roll 10a and the roll 10b respectively have a rotating shaft 10
It is a rotatable cylindrical body having a'and 10b ', and the rotation axes 10a' and 10b 'are arranged on the same horizontal plane. In the pair of rolls 10, the roll 10a
And the roll 10b at a temperature within a preferable numerical range for molding the polyethylene polymer powder (for example, 140
(° C), the polyethylene polymer powder 10c is placed on the polyethylene polymer powder 10c, and the rolls 10a and 10b are rotated in the directions of the arrows shown in the drawing to remove the polyethylene polymer powder 10c.
After passing through the gap between the pair of rolls 10a and 10b in the passing direction X to roll-form, the passing direction X and the roll 1
The polyethylene film 10e is obtained by transporting the polyethylene film 10e in a direction Y that is substantially orthogonal to the central axis 10b 'direction of 0b. Although not shown, the roll 10a may be conveyed by a method that is substantially orthogonal to the central axis 10a 'of the roll 10a. After roll forming, by carrying in this way to obtain a polyethylene film, there is no occurrence of warpage due to shrinkage in particular,
A polyethylene film having a uniform thickness can be efficiently obtained. In this case, for the same reason, it is particularly preferable that the later-described stretch molding is also performed in a direction substantially orthogonal to the passing direction.

-Stretch Molding- In the stretch molding, the polyethylene film is stretch molded. The stretch molding is not particularly limited, and known stretch molding such as tensile stretch molding, roll rolling molding, and the like can be suitably mentioned. However, tensile stretch molding is preferable in that high molecular orientation can be imparted. .

The temperature in the stretch-molding needs to be a temperature above the melting point of the polyethylene film. If the temperature is lower than the melting point of the polyethylene film, the polyethylene film does not melt properly at the time of stretching, and high stretching stress is applied. Therefore, the polyethylene film may break when stretched to a high ratio. is there. As the temperature in the stretch molding,
135-155 degreeC is preferable and 145-155 degreeC is more preferable. If the temperature in the stretch molding exceeds 155 ° C., the melt viscosity of the polyethylene film may be too low at the time of stretching, which may prevent efficient stretching.

The strain rate (strain rate) in the stretch molding is preferably 0.1 to 100 / min,
0.1-10 / min is more preferable, 1-5 / min
Is more preferable.

In the method for producing a polyethylene molded article of the present invention described above, a polyethylene film can be directly and continuously obtained from a polyethylene polymer powder, which is excellent in cost and efficiency. In addition, regardless of the type of polyethylene polymer powder used, publicly known ones can be widely and preferably used, and thus inexpensive raw materials and easily available raw materials can be preferably used. Further, in the stretch molding, the stretching efficiency is good and the production efficiency is excellent. Therefore, according to the present invention, a polyethylene molded body can be manufactured inexpensively and efficiently.

[Polyethylene Molded Product] The polyethylene molded product of the present invention can be obtained by the method for producing a polyethylene molded product of the present invention. The polyethylene molded body needs to have a loop strength at 24 ° C. of 0.2 GPa or more, preferably 0.3 GPa or more, and 0.4 GPa.
The above is more preferable. The loop strength is 0.2 GPa
If it is less than the above range, the polyethylene molded body is easily broken due to bending stress and the handling property is poor, which is not preferable in practice. The loop strength is a value obtained by the above measurement.

The polyethylene molded body needs to have a tensile elastic modulus at 24 ° C. of 25 GPa or more, and preferably 40 GPa or more. When the tensile elastic modulus is in the above numerical range, it has practically sufficient mechanical properties. The tensile elastic modulus was measured by a tensile tester (trade name: RTM1425, manufactured by Orientec Co., Ltd.) at room temperature (24 ° C.) (strain rate: 0.06 / min) to obtain a stress- It is a value obtained by obtaining the slope of the initial straight line portion of the distortion curve. The breaking strength (24 ° C.) of the polyethylene molded body needs to be 0.4 GPa or more, preferably 0.8 GPa or more, and more preferably 1.0 GPa or more. The breaking strength was measured by a tensile tester (trade name: RTM1425, manufactured by Orientec Co., Ltd.) at room temperature (24 ° C.) (strain rate: 0.06 / min) to obtain the stress-distortion. It is the value obtained from the maximum stress of the line.

The polyethylene molding of the present invention described above is
Good tensile elastic modulus, bending strength (loop strength), and breaking strength, practically sufficient mechanical properties, and excellent balance of mechanical properties. Therefore, adhesive tape, abrasion resistant tape, scratch resistant tape. It is preferably used in various fields such as various industrial tapes, packaging films, lithium ion battery separators, white reflective films, neutron blocking films and the like.

[0028]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Experiment 1 Production and Evaluation of Polyethylene Film Polyethylene polymer powder (viscosity average molecular weight (Mv = 4.
0 × 10 ⁶ ) and a melting point of 140 ° C.) were used to perform roll forming shown in FIG. 1 to produce a polyethylene film 10d. The gap between the rolls 10a and 10b is 0.01
mm, the rotation speed of the roll is set to each value of 0.5, 1, 2 and 3 m / min, 130, 140 and 15
Roll forming was performed at each temperature of 0 ° C. When the obtained polyethylene film was observed with an optical microscope (400 times), the polyethylene film obtained by roll molding at 140 ° C. was uniform regardless of the rotation speed of the roll, The highest transparency was obtained when the rotation speed of the roll was 3 m / min. The film roll-formed at 150 ° C. was slightly confirmed to have a plurality of holes. In the case of roll-molding at 130 ° C., polyethylene powders were not satisfactorily pressure-bonded to each other, and a uniform polyethylene film could not be obtained (differential scanning calorimeter (DSC) ) In the measurement, a DSC curve having one peak at 140 ° C. was obtained).

Experiment 2 Tensile Elastic Modulus of Polyethylene Film-The tensile elastic modulus of the polyethylene film obtained by roll molding at 140 ° C. was measured under the above-mentioned conditions, and the rotation speed of the roll (0.5, (Each value of 1, 2 and 3 m / min)
When evaluated in relation to, the rotation speed of the roll was 3 m /
In the case of min, the elastic modulus was the best (elastic modulus:
1.0 GPa).

-Experiment 3 Bending Strength (Loop Strength) of Polyethylene Film-A width of 5 mm was cut out from the polyethylene film obtained by roll forming at 140 ° C. (when the rotation speed of the roll was 3 m / min). When the loop strength of the tape-shaped sample was measured as described above, the loop strength at 24 ° C. was 80 MPa.

(Example 1) Based on the above Experiments 1 to 3,
Polyethylene polymer powder (viscosity average molecular weight (Mv = 4.
0 × 10 ⁶ ) and a melting point of 140 ° C.) were used to roll-form the embodiment shown in FIG. 1 to produce a polyethylene film 10d. Here, the gap between the rolls 10a and 10b was set to 0.01 mm, the rotation speed of the rolls was set to 3 m / min, and the roll forming temperature was set to 140 ° C. Roll forming (1
In order to confirm the meltability of the polyethylene polymer powder at 40 ° C.), the gap between the rolls 10a and 10b is opened during roll forming, and the polyethylene polymer powder does not pass through the roll gap (position shown in FIG. 3). When the polyethylene polymer powder or film existing from A) to the position where the roll gap is the narrowest (position B shown in FIG. 3) was taken out and differential scanning calorimeter (DSC) measurement was carried out, polyethylene powder and film In each case, a DSC curve having only one peak at 134 ° C., which is lower than the melting point of the raw material polyethylene polymer powder, was obtained. From this, it was confirmed that the polyethylene polymer powder was completely melted during the roll forming at 140 ° C. In addition, in FIG. 3, the polyethylene polymer powder is passed through a gap between a pair of rolls to be roll-formed, and then the polyethylene film is conveyed in a direction substantially orthogonal to the passing direction. The same applies to a mode in which the polyethylene film is conveyed in the horizontal direction as shown in FIG. Further, when a differential scanning calorimeter (DSC) measurement was performed on the obtained polyethylene film, a DSC curve having one peak at 134 ° C. was obtained. The obtained polyethylene film was used to measure 150 by the above tensile tester.
Tensile elastic modulus (24 ° C) was obtained by performing tensile stretching at ℃ (strain rate (strain rate): 1 / min) to produce a polyethylene molded product, and then determining the tensile elastic modulus and loop strength as described above. Was 50 GPa, loop strength (24 ° C.) was 0.25 GPa, and breaking strength (24 ° C.) was 0.5 GPa.

(Example 2) A polyethylene molded body was produced in the same manner as in Example 1 except that the temperature for tensile stretching was changed to 145 ° C. When the flexural strength was determined, the tensile elastic modulus (24 ° C.) was 40 GPa, the loop strength (24 ° C.) was 0.4 GPa, and the breaking strength (24 ° C.) was 0.4 GPa.

Example 3 Polyethylene polymer powder (viscosity average molecular weight (Mv = 4.0 × 10 ⁶ ), melting point 140)
2), as shown in FIG.
After being passed through the gap between b and roll-formed, it was conveyed in a direction Y substantially orthogonal to the passing direction X to produce a polyethylene film 10e. The rolls 10a and 10
The gap between b is 0.01 mm, the rotation speed of the roll is 3 m
/ Min, the roll forming temperature was set to 145 ° C.
Further, when a differential scanning calorimeter (DSC) measurement was performed on the obtained polyethylene film, a DSC curve having one peak at 134 ° C. was obtained. Using the obtained polyethylene film, by the tensile tester,
After tensile stretching at 150 ° C (strain rate (strain rate): 1 / min) to produce a polyethylene molded body, the tensile modulus and loop strength were determined as described above. ) Is 100 GPa, loop strength (24 ° C) is 0.5 GPa, breaking strength (24 ° C)
Was 1.0 GPa.

(Comparative Example 1) -Compression molding of polyethylene polymer powder- <Device specification> -Roll shape: roll diameter 150 mmφ, face length: 300
mm, ・ Number of rolls: 3 pairs, ・ Roll gap: 1st step; 2 mm, 2nd step; 1.5 m
m, 3rd stage; 1.1 mm

The same polyethylene polymer powder as used in Examples 1 and 2 was heated to 130 ° C. and continuously compression-molded using an apparatus in which three pairs of the rolls were arranged vertically.
Polyethylene film at a speed of m / min (thickness:
1.1 mm, width: 10 cm) was obtained. A tape-shaped sample obtained by cutting the obtained polyethylene film with a width of 5 mm was broken at the stage of forming a loop for measuring the loop strength, and the handleability was poor. According to the differential scanning calorimeter (DSC) measurement of the polyethylene film, it was 140
A DSC curve with one peak at ° C was obtained.

-Roll rolling-The obtained polyethylene film is horizontally fed between the rolls of the following device adjusted to a temperature of 140 ° C. and a rotation speed of the rolls of 7 m / min for rolling to obtain a rolling ratio of 7: A double rolled sheet was obtained. <Device specifications> ・ Roll shape: Roll diameter 150mmφ, Face length 300m
m ・ Number of rolls: 1 pair ・ Roll gap: 40 μm A tape-shaped sample obtained by cutting the obtained rolled sheet with a width of 5 mm had a low loop strength of 5 MPa at 24 ° C.
It was easy to break and was difficult to handle. In the differential scanning calorimeter (DSC) measurement of the rolled sheet, the peak was 1 at 145 ° C.
The resulting DSC curve was obtained.

-Stretching-The tape-shaped sample was stretch-stretched using the following stretching device. Tensile stretching is performed in three stages (first stage: preliminary roll temperature; 145 ° C, hot plate temperature; 150 ° C, second stage: preliminary roll temperature; 150 ° C, hot plate temperature; 155 ° C, third stage: preliminary roll (Temperature: 155 ° C, hot plate temperature: 155 ° C)
And

<Stretching device specifications> • Preheating metal roll: 3 rolls / set x 3 rolls • Roll shape: roll diameter 250 mmφ, face length 200 m
m-Stretching hot plate: 3 types-Hot plate length: 1st step; 50 cm, 2nd step; 100c
m, 3rd stage; 300 cm-Cooling metal roll: 3 rolls / set x 1 set-Nip roll: Inlet side: 200 mmφ silicone rubber roll for preheating Nip for 2 metal rolls, outlet side: 200 mmφ silicone rubber roll for cooling Nip for two metal rolls.

Regarding the obtained polyethylene molded article,
When the tensile elastic modulus and the loop strength were obtained as described above, the tensile elastic modulus (24 ° C.) was a high value of 120 GPa, but the loop strength (24 ° C.) was 0.15 GPa and the breaking strength (24 ° C.) was It was 2.0 GPa, and it was found that the strength against bending stress was slightly low.

[0041]

According to the present invention, a mechanical property of loop strength, tensile elastic modulus, and breaking strength can be obtained by a method for producing a polyethylene-made molded product capable of continuously and efficiently manufacturing a molded product having high physical properties at low cost. It is possible to provide a polyethylene molded article which has an excellent balance and can be applied to various fields.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a preferable aspect of roll forming in the present invention.

FIG. 2 shows an embodiment in which a polyethylene polymer powder is passed through a gap between a pair of rolls to be roll-formed, and then the polyethylene polymer powder is conveyed in a direction substantially orthogonal to the passing direction to obtain a polyethylene film. It is a figure for explaining.

FIG. 3 is a diagram for explaining a method for confirming the meltability of polyethylene polymer powder during roll molding.

[Explanation of symbols]

10 pairs of rolls 10a roll 10b roll 10a 'rotating shaft 10b 'rotating shaft 10c Polyethylene polymer powder 10d polyethylene film 10e Polyethylene film

Claims (14)

[Claims] 1. A polyethylene film is directly molded from a polyethylene polymer powder at a temperature exceeding the melting point of the polyethylene polymer powder, and the obtained polyethylene film is stretch-molded at a temperature equal to or higher than the melting point to obtain a tensile elastic modulus. A method for producing a polyethylene molded article, which comprises obtaining a polyethylene molded article having a (24 ° C.) of 25 GPa or more. 2. The method for producing a polyethylene molded article according to claim 1, wherein the polyethylene film has one peak at 130 to 136 ° C. in a DSC curve obtained by a differential scanning calorimeter (DSC) measurement. 3. A loop strength (2) of a polyethylene molded product.
4 degreeC) is 0.2 GPa or more, The manufacturing method of the polyethylene molded object of Claim 1 or 2. 4. The breaking strength of a polyethylene molding (24
C.) is 0.4 GPa or more, The manufacturing method of the polyethylene molded object in any one of Claim 1 to 3. 5. The temperature for molding a polyethylene film from polyethylene polymer powder is 135 to 155 ° C.
The method for producing a polyethylene molded body according to any one of claims 1 to 4. 6. The method for producing a polyethylene molded article according to claim 1, wherein the molding of the polyethylene polymer powder is roll molding. 7. The method for producing a polyethylene molded article according to claim 6, wherein the roll molding is performed by passing a polyethylene polymer powder through a gap between a pair of rolls. 8. A direction in which a polyethylene polymer powder is passed through a gap between a pair of rolls to be roll-formed, and the passed direction is substantially orthogonal to a central axis direction of one of the pair of rolls. The method for producing a polyethylene molded body according to claim 6 or 7, wherein the polyethylene molded film is obtained by transporting to a polyethylene. 9. The gap between the rolls is 0.005 to 10
The method for producing a polyethylene molded article according to claim 7 or 8, which has a size of mm. 10. The rotation speed of the roll is 0.1 to 10 m.
/ Min The method for producing a polyethylene molded article according to any one of claims 6 to 9. 11. The method for producing a polyethylene molded article according to claim 1, wherein the stretch molding is tensile stretch molding. 12. The method for producing a polyethylene molded article according to claim 1, wherein the stretch molding is performed at 135 to 155 ° C. 13. The strain rate in stretch forming is 0.
It is 1-100 / min, The manufacturing method of the polyethylene molded object in any one of Claim 1 to 12. 14. A polyethylene molded body according to claim 1, which has a loop strength (24 ° C.) of 0.2 GPa or more and a tensile elastic modulus (2).
A polyethylene molded article having a 4 ° C.) of 25 GPa or more and a breaking strength (24 ° C.) of 0.4 GPa or more.