JP2000351155A - Polyethylene raw fabric sheet for orientation mold and manufacture of the sheet using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve orientation formability and to facilitate molding of an oriented sheet of a high orientation ratio by using an α-olefin (co)polymer becoming a specific weight-average molecular weight and a melted state or a liquid state at a specific temperature as a sub-component of an orientation molding polyethylene raw fabric sheet. SOLUTION: A resin composition obtained by mixing 1.0 pt.wt. of an ethylene- propylene copolymer (weight-average molecular weight: 2×104 and a viscosity at 60 deg.C: 210 poises (liquid state)) with 100 pts.wt. of a crystalline high-density polyethylene is melt kneaded at a resin temperature of 200 deg.C by using an isotropic biaxial kneading extruder. Then, the composition is molded to a sheet having a width of 70 mm and a thickness of 2.5 mm by a calendering machine (roll temperature: 90 deg.C), wound, and rolled 10 times by using hot rolls (125 deg.C), thereby obtaining a rolled polyethylene raw fabric sheet. An oriented polyethylene sheet having an orientation temperature of 100 deg.C, an orientation ratio of first stage of 2.0 times, an orientation ratio of second stage of 1.6 times, and a total orientation ratio of 32 times is formed by a hot air heating type orienting machine.

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 drawn polyethylene sheet which can be suitably used as a substitute for a glass fiber reinforced sheet, and a raw sheet used therefor.

[0002]

2. Description of the Related Art Conventionally, glass fiber reinforced sheets have been obtained by combining glass fibers with synthetic resin sheets, and the mechanical strength is increased by such a structure. Widely used. As this type of glass fiber reinforced sheet, for example, Japanese Patent Publication No. 63-67446 discloses a sheet-like sheet formed by bonding glass long fibers arranged so as to extend in one direction by using a powdery thermoplastic resin. A so-called prepreg sheet is disclosed.

However, when manufacturing the glass fiber reinforced sheet, it is necessary to supply the glass fiber in a tensioned state to the resin and to impregnate the glass fiber with the resin, so that the manufacturing process is complicated. there were. further,
Since the glass fiber is transported to each process while being continuously wound in one direction while being tensioned, there is a problem that the glass fiber is cut or skin irritation is caused by the fluffy glass fiber.

On the other hand, as a method for improving the heat resistance and mechanical strength of a material without using glass fiber, there is a method disclosed in Japanese Patent Application Laid-Open No. 63-135429. This method is to produce a stretched molded article that is crosslinked in a state where polyethylene molecular chains are oriented in a certain direction by performing stretching and crosslinking treatment on a gel-like mixture composed of polyethylene and polypropylene,
It is described that the obtained stretch molded article has excellent heat resistance and mechanical strength.

However, since the so-called gel spinning method, which requires a solvent such as decalin, is used in the production of the above-mentioned stretched molded product, for example, powder of ultrahigh molecular weight polyethylene and polypropylene is dissolved in a heating solvent and quenched. As a result, it was necessary to carry out heating and stretching using, as a raw material, a gel obtained by removing the solvent from the obtained gel. As a result, there has been a problem that the manufacturing process becomes complicated and the cost increases.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of conventional glass fiber reinforced sheet substitutes and to provide a mechanical strength equivalent to that reinforced without glass fibers and without glass fibers. It is an object of the present invention to provide a high-strength resin sheet having a high strength, and a high-strength resin sheet that can be manufactured by a dry process without using a solvent or the like.

[0007]

According to a first aspect of the present invention, there is provided a raw sheet comprising a high-density crystalline polyethylene, and an α-olefin (co) polymer as a sub-component. In the anti-sheet, the α-olefin (co) polymer is a (co) polymer of two or more α-olefins, and has a weight average molecular weight of 100,000 or less and 60 ° C.
A stretchable polyethylene raw sheet characterized by being an α-olefin (co) polymer in a molten state or a liquid state.

In the method for producing a stretched polyethylene sheet according to a second aspect of the present invention, the step of stretching and forming the raw sheet is a step of stretching after rolling the raw sheet. This is a sheet manufacturing method.

The crystalline high-density polyethylene (hereinafter referred to as polyethylene) used in the present invention preferably has a weight average molecular weight of 50,000 to 500,000. If the weight average molecular weight is 50,000 or less, the resin itself becomes brittle and loses stretchability. When the weight-average molecular weight exceeds 500,000, not only is extrusion molding difficult, but also drawbacks occur in that the stretching process cannot be performed unless the process is a complicated process using a large amount of a plasticizer such as a solvent. Does not fit the purpose of

When the melt flow rate (MFR) of the above polyethylene is too small, a molding machine such as an extruder is overloaded, and when it is too large, the stretchability is poor.
20 is preferred. The MFR is a value measured according to JIS K6760.

The density of polyethylene is 0.94 g / cm
^Three or more are preferred. The density of polyethylene is 0.94 g /
If it is less than cm ^{3, the} mechanical strength and the elastic modulus cannot be expected to be improved much even when the film is stretched.

Α-olefin (co) used in the present invention
As the polymer, a polymer in a molten or liquid state at 60 ° C., that is, a polymer having a melting point of 60 ° C. or less is used. By using such an α-olefin (co) polymer, stretch formability is improved and a stretched sheet having a high draw ratio can be easily formed.

The α-olefin (co) polymer having a weight average molecular weight of 100,000 or less is used. If it is 100,000 or more, not only the dispersibility in polyethylene becomes poor, but also the stretch moldability becomes difficult to improve.

The α-olefin (co) polymer of the present invention has a high crystallinity and a melting point of at least 60 ° C., so that the effects of the present invention cannot be expected.
-It must be (co) polymerized with two or more olefins.

The α-olefin (co) polymer is a (co) polymer of two or more α-olefins such as ethylene, propylene, 1-butene and 1-pentene, provided that they have the same chemical structure. Not limited to this. For example, a resin obtained by hydrogenating a part or all of the double bonds of a non-conjugated diene-based resin such as polybutadiene and polyisoprene may be used. However, a resin component other than those described above, for example, vinyl acetate, vinyl alcohol, acrylic acid, methacrylic acid, methyl acrylate, or the like may be copolymerized at 10% by weight or less.

The amount of the α-olefin (co) polymer used is
The amount is preferably from 0.1 to 100 parts by weight, more preferably from 0.5 to 20 parts by weight, based on 100 parts by weight of polyethylene. If the amount of the α-olefin (co) polymer is 0.1 parts by weight or less, improvement in stretch formability cannot be expected, and if it is 100 parts by weight or more, the mechanical strength of the stretched sheet is low.

In the present invention, the resin molded sheet may be composed of only polyethylene and α-olefin (co) polymer, or may be a mixture of other resins and additives. Is also good.

The above polyethylene and α-olefin (co)
When the resin composition composed of a polymer is melt-molded by an extruder or the like, the molding temperature is preferably 130 ° C. or higher, more preferably 150 ° C. or higher. When the melting temperature is lower than 130 ° C., the melting of the resin composition becomes incomplete, and a molding machine such as an extruder may be overloaded. However, if melt molding is performed at an excessively high temperature, the polyethylene may be decomposed to cause discoloration or the like, or the strength may be reduced due to a decrease in the molecular weight. Therefore, the melting temperature is preferably 250 ° C. or lower.

The method for forming the above-mentioned molten polyethylene into a raw sheet is not particularly limited, and a roll forming method, a calender forming method and the like generally used for forming plastics are used.

The thickness of the raw sheet is 2 mm to 15 m.
m is preferred. If the thickness is less than 2 mm, the thickness of the sheet after stretching becomes too thin, and if it exceeds 15 mm, processing in subsequent steps becomes difficult.

Next, a method for producing a stretched polyethylene sheet will be described. In the present invention, the raw sheet is formed to be relatively thick, and is subjected to a rolling treatment before stretching. Rolling treatment, for example, insert the raw sheet between a pair of rolling rolls rotating in opposite directions with a narrower clearance than the thickness of the raw sheet, reduce the thickness of the raw sheet and length This is done by stretching in the direction.

The temperature of the raw sheet at the time of the rolling treatment is preferably from 70 to 125 ° C., more preferably from 90 to 125 ° C.
120 ° C. If the temperature is lower than 70 ° C., uniform rolling becomes difficult because the rolling force is increased. If the temperature is higher than 125 ° C., the raw sheet may be cut off during rolling.

When the rolling ratio is reduced, not only the effect of the rolling cannot be expected, but also a load is applied to the subsequent stretching step, and when the rolling ratio is increased, the rolling force increases, so that not only uniform rolling becomes difficult, but also the rolling ratio after the rolling is increased. Since the thickness of the raw sheet becomes too thin and the raw sheet may be cut during the subsequent stretching step, the rolling magnification is preferably 2 to 10 times. The rolling ratio is defined by the following equation. Rolling ratio = cross-sectional area of raw sheet before rolling / cross-sectional area of raw sheet after rolling

As a method for stretching the raw sheet after rolling, a generally used uniaxial stretching method is used. 1
As the axial stretching method, for example, there is a method in which a raw sheet is strongly oriented in only one axial direction by being sandwiched between two pairs of pinch rolls (feeding roll and take-up roll) having different speeds in a state where the raw sheet is heated. No. The stretching ratio of the polyethylene sheet defined by the rotation speed ratio between the feeding roll and the take-up roll (rotation speed of the take-up roll / rotation speed of the feeding roll) is determined in consideration of the mechanical strength and productivity of the drawn polyethylene sheet. It is preferably 2 to 10 times.

Needless to say, the higher the stretching ratio, the better. However, if the stretching ratio is 2 times or less, the mechanical strength of the stretched and stretched polyethylene sheet cannot be obtained, and the purpose cannot be achieved. On the other hand, if the draw ratio is to be increased to 10 times or more, the rolling force of the feeding roll and the take-up roll of the drawing machine must be extremely large in order to prevent slipping, and the apparatus becomes oversized, and If there is a slight partial thickness difference,
The part where the sheet becomes too thin during stretch molding tends to appear,
As a result, the possibility that the stretched polyethylene sheet is torn or broken increases.

The temperature of the raw sheet in the stretching step is 7
A range from 0 to 120 ° C is preferred. Less than 70 ° C or 120
If the temperature exceeds ℃, the sheet may be broken during the stretching process.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to non-limiting examples.

(Example 1) Crystalline high density polyethylene
(Manufactured by Nippon Polychem; trade name "HY540"; weight average
Molecular weight 3.3 × 10^Five, Melt flow rate (MFR)
1.0, melting point 135 ° C)
Lopylene copolymer (Uniroyal Chemical Company)
Made; trade name "TRILENE CP40"; weight average
Child size 2 × 10 ^Four, Viscosity of 210 poise at 60 ° C (liquid form
State)) A resin composition mixed with 1.0 part by weight was mixed in the same direction 2
Shaft kneading extruder (Ikegai Iron & Steel Co., Ltd .; PCM30 type)
Melt and knead at a resin temperature of 200 ° C using
70mm width, thickness by calender molding machine controlled at 90 ° C
After molding into a 2.5 mm sheet and winding it up, 125 ° C
Heat roll (made by Kodaira Seisakusho: Roll diameter 6)
Inch), rolled 10 times, and rolled polyethylene
Got anti-sheet.

Then, the rolled polyethylene raw sheet was stretched at a stretching temperature of 100 using a hot-air heating stretching machine.
At ℃, the first-stage stretch ratio was 2.0 times, and the second-stage stretch ratio was 1.6 times, whereby a stretched polyethylene sheet having a total stretch ratio of 32 times could be stably obtained. Here, the total stretching ratio is the maximum stretching ratio that allows stable molding, and in the present invention, the product of the above-mentioned rolling ratio and the stretching ratio is defined as the total stretching ratio.

(Comparative example) A rolled polyethylene raw sheet was formed in the same manner as in Example except that the ethylene-propylene copolymer was not used, and stretched so that the total stretch ratio became 26 times. I got

Table 1 shows the results of evaluating the tensile properties of the stretched polyethylene sheet according to the tensile test method of JIS K7113.

[0032]

[Table 1]

[0033]

The crystalline high-density polyethylene contains an α-olefin (co) polymer having a weight average molecular weight of 100,000 or less and being in a molten state or a liquid state at 60 ° C., so that it can be used with a usual stretching machine. Also, the stretch moldability is improved, and stretch molding at a high stretch ratio can be easily performed.

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Claims (2)

[Claims] 1. A stretch-formed polyethylene raw sheet mainly composed of crystalline high-density polyethylene and having an α-olefin (co) polymer as a subcomponent, wherein two or more α-olefin (co) polymers are used. α-olefin (co) polymer having a weight average molecular weight of 100,000 or less and 60 ° C.
A stretchable polyethylene raw sheet, characterized by being an α-olefin (co) polymer in a molten state or a liquid state. 2. The step of stretching the raw sheet according to claim 1 is a step of stretching the raw sheet after rolling it. Method of producing stretched polyethylene sheet.