JP5356679B2 - Method for producing ultra high molecular weight polyolefin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an ultra-high molecular weight polyolefine sheet excelling in transparency and mechanical material property while being comparatively thick-walled. <P>SOLUTION: The method for manufacturing the ultra-high molecular weight polyolefine sheet includes preheating and then rolling a sheet to be rolled in a temperature range exceeding a fusion starting temperature of ultra-high molecular weight polyolefine but not exceeding a 25% heat absorption quantity of the total heat quantity of fusion of the ultra-high molecular weight polyolefine in a method for manufacturing an ultra-high molecular weight polyolefine rolled sheet which is obtained by rolling an ultra-high molecular weight polyolefine polymer whose limiting viscosity measured in 135&deg;C decalin solution is at least 7 dl/g, and which has a thickness of 0.3 mm or more and internal haze in a thickness direction at a thickness of 2 mm being 60% or less. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an ultrahigh molecular weight polyolefin sheet having excellent transparency and mechanical properties. In particular, the present invention relates to a method for producing an ultra-high molecular weight polyolefin sheet that can be industrially produced and is relatively thick and excellent in transparency.

Ultra-high-molecular-weight polyolefin molded products such as ultra-high-molecular-weight polyethylene have mechanical properties such as impact resistance, abrasion resistance, low friction coefficient and tensile strength, and chemical resistance compared to general-purpose high-molecular-weight polyolefins. Are better. Taking advantage of such features, molded articles of ultra-high molecular weight polyolefin are used for machine parts such as gears, pulleys or sprockets, and various linings such as guide rails or hopper tank lining materials.
On the other hand, ultra-high molecular weight polyolefin has a very high melt viscosity and poor fluidity compared to general-purpose polyethylene, so it is very difficult to mold by extrusion molding or injection molding, and the molding process is difficult. is there. For this reason, compression molding or the like is generally employed as a method for molding ultrahigh molecular weight polyethylene, and in some other cases, it is called ram extrusion molding in order to obtain a rod-shaped or pipe-shaped molded product. A technique of forming under a condition where the forming speed is extremely low is employed.

One of the uses of ultra-high molecular weight polyethylene is ski sole and the like, and this kind of sheet material application requiring high mechanical properties is considered to take advantage of the characteristics of ultra-high molecular weight polyethylene.
In recent years, in this type of use, for example, a sheet having excellent transparency has been demanded for the purpose of improving the design of characters and drawings drawn on the bottom of a ski sole. However, a molded body obtained from a crystalline resin such as polyolefin typified by polyethylene is usually white and has a cloudy state with poor transparency. That is, the present situation is that a product that sufficiently satisfies the performance with respect to transparency has not yet been obtained.

Conventionally, as a polyethylene molded article excellent in transparency, many films, sheets, pipes and the like using high-pressure method low-density polyethylene and linear low-density polyethylene have been reported so far, and high transparency has been achieved. However, those using low density polyethylene have a molecular weight lower than that of ultra high molecular weight polyethylene, and therefore it is not possible to expect a sufficient effect in terms of mechanical properties such as wear resistance and impact resistance.
On the other hand, several methods have been used to improve transparency by subjecting ultra-high molecular weight polyolefin to a stretching process such as rolling.
For example, Patent Document 1 discloses a technique of rolling an ultrahigh molecular weight polyethylene sheet so that its thickness is 50% or less of the original thickness under heating conditions. However, what is disclosed here is that the thickness of the finished product is about 100 μm, and with this thickness, the rigidity is not satisfactory for use in industrial members. Also, the total light transmittance disclosed as one of the transparency measures is not so much improved as compared with the unrolled one.

In Patent Document 2, at least an ultrahigh molecular weight polyethylene sheet having an intrinsic viscosity [η] of 5.0 dl / g or more is pulled and tensioned while being rolled at a temperature not lower than the melting point or lower than the melting point + 15 ° C. A method is disclosed.
However, in this method, since the processing exceeds the melting point, it is considered that the sheet rolled in the molten state is hindered in transparency by subsequent recrystallization, and the finished product has a thick thickness (360 μm). Despite this, transparency has not improved so much.
Furthermore, in Patent Document 3, the rolling roll is composed of a pair of rolls that are set at a temperature that is 80 ° C. lower than the melting point of the polyolefin resin and lower than the melting point of the resin and that rotate in opposite directions with different circumferential speeds. The sheet roll made of the resin is brought into close contact with the low-speed roll side of the rolling roll, deformed in the gap of the rolling roll, sequentially passed through the rolling roll, and the sheet is deformed and drawn out while being in close contact with the final high-speed roll. A method for producing a high-strength and high-transparency sheet material is disclosed in which the relationship between the sheet width and the sheet width and the relationship between the rolling roll and the sheet width satisfy a specific relationship.

However, this method exemplifies polyolefin having a low molecular weight, and the thickness of the product is thin. Therefore, it is not so difficult to increase transparency. Moreover, in order to change the peripheral speed of a rolling roll, it must be a complicated structure, an apparatus becomes expensive and operation is complicated.
Japanese Patent Publication No. 55-135630 Japanese Patent Publication No. 3-73452 JP-A-7-164461

As described above, ultra-high molecular weight polyolefin molded products have been studied for a wide variety of applications due to their excellent mechanical properties, but they are sufficient to meet the rapidly changing new industry demands and new market demands. No one with a completely new function has been obtained.
In particular, polyolefin, which is a crystalline resin, is greatly different from other amorphous resins in properties such as transparency and shrinkage. Therefore, if an ultra-high molecular weight polyolefin molded body having a relatively thick wall and excellent transparency and mechanical properties can be realized, it is expected that new applications will be expanded.
However, ultra high molecular weight polyolefin polymers are highly entangled due to their high molecular weight, so unlike low molecular weight polyolefins, high density polyethylene, etc., the range of material selection and manufacturing conditions is narrow, and it is thick and transparent. It was not possible to realize a product having both functions of mechanical properties and mechanical properties.
The present invention has been made in order to solve the above-mentioned problems, and its purpose is to make an ultrahigh molecular weight polyolefin sheet excellent in transparency and mechanical properties while being relatively thick, without requiring complicated steps. An object of the present invention is to provide a manufacturing method that can be easily manufactured and has excellent productivity.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research, and as a result of rolling under specific conditions, ultrahigh molecular weight polyolefins that are exceptionally excellent in transparency and mechanical properties while being relatively thick. The inventors have found that a sheet can be obtained and have completed the present invention.
That is, the present invention provides the following (1) to (4).
(1) Thickness of 0.3 mm or more obtained by rolling an ultrahigh molecular weight polyolefin polymer having an intrinsic viscosity of 7 dl / g or more measured in a 135 ° C. decalin solution, and in the thickness direction at a thickness of 2 mm. In the method for producing a rolled sheet of ultrahigh molecular weight polyolefin having an internal haze of 60% or less, the temperature range that does not exceed the melting start temperature of the ultrahigh molecular weight polyolefin and does not exceed the endothermic amount of 25% of the total heat of fusion of the ultrahigh molecular weight polyolefin A method for producing an ultrahigh molecular weight polyolefin sheet, wherein the sheet to be rolled is preheated and then rolled.
(2) In the rolling process, rolling is performed in a temperature range that does not exceed the melting start temperature of the ultrahigh molecular weight polyolefin and does not exceed the endothermic amount of 30% of the total heat of fusion of the ultra high molecular weight polyolefin. The manufacturing method of the ultra high molecular weight polyolefin sheet as described in 1).

(3) The ultra high molecular weight polyolefin molded body obtained by rolling the ultra high molecular weight polyolefin molded product at a rolling ratio (χ) represented by the following formula (1) to 1.3 times or more, (1) or (2) A method for producing a high molecular weight polyolefin sheet.
χ = t1 / t2 (1)
t1: Thickness before rolling (mm)
t2: Thickness after rolling (mm)
(4) The ultrahigh molecular weight polyolefin polymer is an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and any one of (1) to (3) The method for producing an ultrahigh molecular weight polyolefin sheet according to one item.

  The method for producing an ultrahigh molecular weight polyolefin sheet according to the present invention can provide a sheet that is thicker than the conventional sheet and excellent in transparency and mechanical properties. The sheet can enhance the design properties in various uses where high mechanical properties are required. In addition, the production method of the present invention is simple and low-cost and can produce an ultra-high molecular weight polyolefin sheet without requiring a complicated process as compared with the conventional method. Therefore, the production method is excellent in productivity and economical.

Embodiments of the present invention will be described below. In addition, this invention is not limited only to this embodiment, Unless it deviates from the summary, it can implement with a various form.
In this embodiment, the ultrahigh molecular weight polyolefin sheet is obtained by rolling an ultrahigh molecular weight polyolefin polymer having an intrinsic viscosity of 7 dl / g or more measured in a 135 ° C. decalin solution, and has a thickness of 0.3 mm or more. And in the manufacturing method of the ultra high molecular weight polyolefin rolled sheet whose internal haze in the thickness direction at a thickness of 2 mm is 60% or less, the melting start temperature of the ultra high molecular weight polyolefin exceeds 25% of the total heat of fusion of the ultra high molecular weight polyolefin. It is obtained by preheating and then rolling a sheet to be subjected to rolling in a temperature range not exceeding the endothermic amount.
That is, the present invention obtains an ultrahigh molecular weight polyolefin sheet having excellent transparency and mechanical properties by preheating and then rolling an ultrahigh molecular weight polyolefin molded body under specific conditions.

(Ultra high molecular weight polyolefin polymer)
Specific examples of the ultrahigh molecular weight polyolefin polymer include, for example, a homopolymer of ethylene, a homopolymer of propylene, or a copolymer of ethylene or propylene and an α-olefin having 3 to 10 carbon atoms. Can be mentioned. Here, specific examples of the α-olefin having 3 to 10 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 1-pentene, 1-hexene, 1-octene, 1-decene and the like. Is mentioned. Among these, the ultrahigh molecular weight polyolefin polymer is preferably a homopolymer of ethylene or a copolymer of the above α-olefin mainly composed of ethylene, from the viewpoint of economy and the like. A copolymer in which a comonomer such as an α-olefin is introduced into ethylene as a branch is preferably used.

The ultra-high molecular weight polyolefin polymer can be produced by a conventionally known method. For example, the raw material compound is prepared by using a known catalyst such as a Ziegler catalyst or a metallocene catalyst by a suspension polymerization method or a gas phase polymerization method. (Co) polymerization.
In the present invention, an ultrahigh molecular weight polyolefin having an intrinsic viscosity measured in a decalin solution at 135 ° C. of 7 dl / g or more is used. When the intrinsic viscosity is less than 7 dl / g, it tends to be difficult to obtain high performance in mechanical properties such as abrasion resistance and impact resistance. Such intrinsic viscosity is preferably 10 dl / g or more, and more preferably 14 dl / g or more. The upper limit of the intrinsic viscosity is not particularly limited, but is preferably less than 30 dl / g. When the intrinsic viscosity is 30 dl / g or more, the molecular chain entanglement is probably too strong in the process such as compression molding for producing an ultra-high molecular weight polyolefin molded body, which will be described later. Is not sufficiently melted, voids and the like are expected to cause inconveniences such as cloudiness. Also, in the process of rolling the ultra-high molecular weight polyolefin molded body, which will be described later, it is expected that inconveniences such as inability to sufficiently roll may occur due to the fact that such an interface is not sufficiently fused and adhered. The

In the present invention, the density of the ultrahigh molecular weight polyolefin is not particularly limited, and those having a normal density are used. In general, in the ultra-high molecular weight region where the molecular weight exceeds 1,000,000, the interaction between the molecular chains is large and the crystal cannot move and crystallize freely, so the density does not tend to increase. Usually, the density of ultra-high molecular weight polyethylene that is commercially available depends on the molecular weight, but many of them are 930 to 940 kg / m ³ , and in the present invention, these can be suitably used. Alternatively, the crystallinity may be lowered by copolymerization and the density may be lowered to 920 kg / m ³ or less. The lower limit of the density is not particularly limited, but is preferably 910 kg / m ³ or more because physical properties such as the rigidity of the molded body can be lowered as the density is lowered.

(Ultra high molecular weight polyolefin molded product)
In the present invention, in order to obtain an ultra-high molecular weight polyolefin sheet, a sheet that has been previously molded into a shape other than a sheet by a known means such as compression molding can be cut into a sheet and subjected to rolling. Alternatively, it is possible to obtain a sheet-like molded product by means such as extrusion molding of ultra-high molecular weight polyolefin and subject it to rolling. Furthermore, it is also possible to heat and press powdery ultrahigh molecular weight polyolefin to obtain a sintered compact, which can be subjected to rolling.
In addition, in order to obtain a desired ultra-high molecular weight polyolefin molded body, the bulk density of the raw material powder is preferably high. If the bulk density of the raw material powder is low, there are many bubbles between the raw material powders, so that when the material powder is put into a molding die and compressed, the oxygen contained in the bubbles causes oxidative degradation and the mechanical properties due to the decrease in molecular weight. A phenomenon such as a decrease may occur. Moreover, since air bubbles may remain in the preform and an air scatterer may be formed, it is expected to affect the transparency. Accordingly, the bulk density of the raw material powder is preferably 0.35 g / cc or more, and more preferably 0.40 g / cc or more.

In addition, it is generally known that the bulk density of the raw material powder can be increased by adding an additive such as a lubricant such as calcium stearate. On the other hand, when an additive is included in the raw material powder, it is generally possible that problems such as deterioration of heat-fusibility during molding or contamination of the surface due to bleeding of the additive on the surface of the molded product may occur. Known. From the above, it is preferable to increase the bulk density of the raw material powder in the absence of additives.
In addition, when added to polyolefin polymerized using a Ziegler-based catalyst, metal soap typified by calcium stearate also acts as a catalyst deactivator for trace amounts of catalyst. Further, it may be inactivated by adding an inorganic substance or the like.
An arbitrary shape can be adopted as the shape of the ultrahigh molecular weight polyolefin molded body produced as described above, and it is not particularly limited, but a sheet shape is preferable from the viewpoint of ease of molding.

(Ultra high molecular weight polyolefin rolled sheet)
By rolling the preheated sheet-like ultrahigh molecular weight polyolefin molded body to a specific ultrahigh molecular weight polyolefin molded body prepared in advance as described above to a thickness of 0.3 mm or more by roll rolling, the transparency of the present invention is achieved. In addition, an ultrahigh molecular weight polyolefin sheet having excellent mechanical properties can be obtained.
Rolling can be performed in one stage, or multi-stage rolling in which two or more stages are rolled. When performing in multiple stages, it may be continuously subjected to multiple stages of rolling, or rolled up once and can be used for the same rolling roll multiple times, or it may be used for different rolling rolls for multi-stage rolling treatment. You may do it.
In the present invention, the sheet to be rolled is preheated to a temperature range exceeding the melting start temperature of the ultrahigh molecular weight polyolefin and not exceeding 25% of the total heat of fusion of the ultra high molecular weight polyolefin, and then rolling. Is essential. Preheating is preferably performed in a temperature range that does not exceed the endothermic amount of 20%, and further in a temperature range that does not exceed the endothermic amount of 15%. Preheating to a temperature range exceeding the endothermic amount of 25% of the total heat of fusion may result in fusion to the rolling roll to inhibit smooth rolling, or loss of transparency due to an increase in crystal size during recrystallization. It is not preferable.

Examples of the preheating method include a method in which the sheet is placed in an oven set at a predetermined temperature, the state is adjusted for 30 minutes or more, and then the sheet is immediately rolled so as not to decrease the temperature of the sheet.
Moreover, the method of heating by supplying a sheet | seat continuously in a heating machine and making it pass may be used. As a heating method at this time, the inside of the tank can be heated using warm air, a heater, or a combination thereof. The temperature of the sheet can be measured with an infrared sensor thermometer immediately before the sheet leaves the heater and enters the roll.
The adjustment of the sheet temperature at this time needs to adjust the temperature of hot air, a heater, etc. so that it may become predetermined temperature within the residence time which passes the inside of a heating machine by rolling speed.

In rolling, the rolling is preferably performed at a temperature in a region not exceeding the melting start temperature of the ultrahigh molecular weight polyolefin and not exceeding 30% of the total heat of fusion of the ultra high molecular weight polyolefin, and more preferably 25%. It is preferable to perform rolling in a temperature range that does not exceed the endothermic amount, particularly in a temperature range that does not exceed the 20% endothermic amount.
When rolling in a temperature range exceeding the endothermic amount of 30% of the total heat of fusion, it may be fused to the rolling roll to hinder smooth rolling, or the crystal size may increase when recrystallization is performed and transparency may be impaired. is there.
On the other hand, when the rolling temperature is lower than the melting start temperature, the viscosity is too high, and it is necessary to pass the roll without being sufficiently rolled by the rolling roll, or it is necessary to make the pressure applied to the rolling roll extremely large, which is not economical.

There are also documents that define the rolling temperature based on the melting point, for example, but the melting behavior of the resin is not generally governed solely by the melting point. For example, the melting curve of DSC varies depending on the molecular weight, molecular weight distribution, comonomer amount, comonomer distribution, and the like. That is, when the average molecular weight is the same and the samples having different molecular weight distributions are compared, the melting points are almost the same, but the wider the molecular weight distribution, the lower the melting start temperature. The endothermic amount at each temperature increases for samples with a wide molecular weight distribution.
Furthermore, when it is made into a copolymer, it varies depending on the distribution of the comonomer. In general, when a copolymer is polymerized with a Ziegler-based catalyst, a large amount of comonomer may enter the relatively low molecular weight side and a small amount of comonomer may enter the high molecular weight side. On the other hand, when a metallocene-based catalyst is used, the amount of comonomer may be almost uniform in any molecular weight region, and further, it may enter a large amount on the high molecular weight side.

In this way, even if the samples with the same average molecular weight and the same comonomer amount are compared, the melting points are almost the same, but the sample with many conomomers on the low molecular weight side has a lower melting start temperature, and the comonomer distribution causes melting. The endothermic amount at each temperature from the start to the melting point also changes.
In particular, when trying to provide transparency with a relatively thick wall as in the present invention, when the rolling temperature is simply determined based only on the melting point of the resin, a high degree of transparency must be maintained. May not be possible. It is necessary to determine the temperature in accordance with the melting characteristics of each resin.
In the present invention, the total heat of fusion is measured by a differential scanning calorimeter (DSC) based on JIS K7121-1987 at a heating rate of 10 ° C. per minute. The area surrounded by the obtained melting curve and the baseline is the total heat of fusion. “Temperature range not exceeding 25% of the endothermic amount” refers to a temperature in a range not exceeding the endothermic amount of 25% of the total melting heat amount by integrating the melting curve from the melting start temperature.

In this invention, the operation | work which transfers to the rolling process from the formation process of the sheet | seat used for rolling may be performed continuously, or may be performed discontinuously.
In the present invention, the rolling is preferably performed at a speed at which the ultrahigh molecular weight polyolefin can move sufficiently, and is preferably performed at 0.2 to 20 m / min. Preferably it is 0.5-10 m / min, More preferably, it is 0.8-5 m / min. The pressing time varies depending on the diameter of the rolling roll to be used, etc., but if it exceeds 20 m / min, the sheet is pressed for too short time to be elastically recovered and a desired thickness can be obtained. Problems such as not occurring. In order to increase the rolling speed, it is possible to perform rolling in a continuous multi-stage, but the initial investment becomes large and it is not economical. Moreover, at 0.2 m / min or less, efficiency is too bad for industrial production.

In addition, when the preheated sheet is continuously rolled, the residence time in the heating tank for preheating depends on the rolling speed, so the length of the heating tank necessary to preheat the sheet to a predetermined temperature. It is necessary to design to.
The rolling ratio (χ) at the time of rolling is represented by the following formula (1). If the rolling ratio (χ) is less than 1.3 times, sufficient transparency and mechanical properties may not be obtained. In the present invention, the rolling ratio is preferably 1.3 times or more, more preferably 3 times or more, and further preferably 5 times or more. The upper limit of the rolling ratio (χ) is not particularly limited, but is preferably 20 times or less, more preferably 15 times or less, and further preferably 10 times or less from the viewpoint of formability.
χ = t1 / t2 (1)
t1: Thickness before rolling (mm)
t2: Thickness after rolling (mm)

In the present invention, heat treatment can also be performed at a temperature not exceeding the melting point in order to alleviate internal strain after rolling. This heat treatment may be exposed to a temperature atmosphere in which the ultra-high-part polyolefin can be relaxed with tension applied to the sheet. Normally, ultrahigh molecular weight polyolefin takes a long time to relax because of its large size, and may be heat-treated for a long time with a rolled sheet.
Although the ultrahigh molecular weight polyolefin sheet thus obtained is relatively thick with a thickness of 0.3 mm or more, it has very high transparency and excellent mechanical properties as compared with the conventional one.
The ultrahigh molecular weight polyolefin sheet has a thickness of 0.3 mm or more, preferably 0.4 mm or more and 10.0 mm or less, and more preferably 0.7 mm or more and 5.0 mm or less. When the thickness is less than 0.3 mm, it is useful in film applications where high transparency is required, but in molded sheet applications where excellent mechanical properties are required, the absolute value of mechanical strength is insufficient or due to its own weight. There may be inconveniences in practical use, such as inability to maintain the shape.

  The value of the internal haze in the thickness direction at a thickness of 2 mm of the ultrahigh molecular weight polyolefin sheet is 60% or less, preferably 30% or less, more preferably 20% or less, and particularly preferably 10% or less. . When the internal haze in the thickness direction is greater than 60%, it cannot be said that the film has sufficiently high transparency, and practical applications can be limited. Generally, when the internal haze in the thickness direction is in the range of 30% to less than 70%, it is slightly cloudy, but has transparency to such an extent that the characters can be easily seen when viewed through the characters. . Moreover, when the internal haze in the thickness direction is 20% or less, no white turbidity is felt by visual observation, and a substantially transparent state appears.

The internal haze in the thickness direction of the ultrahigh molecular weight polyolefin sheet can be measured according to JIS-K7136.
In addition, since haze is affected by scratches and surface roughness of the rolled sheet, in this specification, measurement of internal haze was performed without the influence of external haze under conditions immersed in water or alcohol. did.
Here, the haze value in the thickness direction at a thickness of 2 mm may be measured using a sheet having a thickness of 2 mm. However, a rolled molded sheet having a thickness of 2 mm was handled as follows.
From experience, the relationship between the haze value and the thickness of the sheet can be defined by the relational expression (haze;%) = a × t (rolled sheet thickness; mm) + b, where a and b are related to the density of the compact. In addition, it has been found that the thickness dependence of haze is different from the vicinity of the thickness of 2 mm of the rolled molded sheet.

That is, in the case of a roll-formed sheet having a thickness of 2 mm or less, the inclination a in the relational expression of the haze thickness dependency can be obtained by a = 309 × d (density: g / cm ³ ) −264. Therefore, the parameter b can be calculated by inserting the obtained parameter a and the known thickness t (mm) and haze value Ht (%) of the rolled molded sheet to be measured into the above relational expression. From the relational expression thus completed, the haze value at a thickness of 2 mm, which is the case of t = 2, is extrapolated.
On the other hand, when the thickness of the roll-formed sheet exceeds 2 mm, the slope a in the relational expression of the haze thickness dependency can be obtained by a = −640 × d (density: g / cm ³ ) +600. Therefore, similarly to the above, by inserting the obtained parameter a and the known thickness t (mm) and haze value Ht (%) of the rolled molded sheet to be measured into the above relational expression, the parameter b is From the completed relational expression, the haze value at a thickness of 2 mm, which is the case of t = 2, is extrapolated.

The above empirical formula is a result of intensive studies by the present inventors in order to calculate haze regardless of the thickness of the ultrahigh molecular weight polyolefin roll-formed sheet, and as a result, the behavior differs with a specific thickness as a boundary. In addition, the present inventors have found that the correlation formula indicating the thickness dependence of haze depends on the density of the molded body, and have completed it. Such an empirical formula is a parameter that is an important index in determining the haze of a rolled molded sheet when converted to a specific thickness.
In addition, the inclination a of the haze thickness dependence in a 2 mm or less rolled forming sheet shows the tendency larger than the inclination a of the haze thickness dependence in a 2 mm or more rolled forming sheet. Further, even if the densely formed sheet has a thickness of 2 mm or less, it often shows 80% or more in the haze measurement, and the haze of the thickness of 2 mm is excluded from the relational expression of the haze and thickness of 2 mm or less. If inserted, it may exceed 100%. In this case, even if the thickness of the roll-formed sheet is 2 mm or less, the value extrapolated by the thickness dependency relational expression of haze of 2 mm or more becomes a value closer to the actual value.

Moreover, the said relational expression is applicable also to the relationship between the value of the haze of a molded object and thickness which are not rolling.
The ultrahigh molecular weight polyolefin sheet obtained by the present invention may be used in a single layer, laminated with other films or sheets, or coated with a coating material or the like.
The ultra-high molecular weight polyolefin sheet obtained by the present invention takes advantage of the characteristics thereof, for example, a lining such as a sliding tape, a thrust washer, a sliding sheet, a guide, a ski, a snowboard and the like; a lining such as a hopper and a chute Materials; Transport pipes / sheets for food materials, etc .; Shielding shields, fenders, rolls, pipes, steel pipes, etc .; Electrical insulation materials; Agricultural materials such as agricultural materials for farmhouses and propellers for agricultural equipment It can be suitably used for aviation window materials and the like.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, unless it deviates from the summary, it is not specifically limited to these.
In the examples and comparative examples, the measurement was performed by the following methods.
<Intrinsic viscosity>
20 mg of decalin was charged with 20 mg of a powdery ultrahigh molecular weight polyethylene polymer sample (Sunfine UH900, UL901) and stirred at 150 ° C. for 2 hours to dissolve the polymer. The dropping time (t _s ) between the marked lines was measured using a Ubbelohde type viscometer with the solution at a high temperature of 135 ° C. Incidentally, not putting the polymer as a blank was measured drop time of only decahydronaphthalene a (t _b). And according to the following formula | equation, the specific viscosity ((eta) _sp / C) of the polymer was plotted and the intrinsic viscosity ((eta)) extrapolated to the density | concentration 0 was calculated | required.
_{η sp / C = (t s} / t b -1) /0.1

<Bulk density>
The measurement was performed according to JIS K6722-1995.

<Melting point>
Using Perkin Elmer DSC (PYRIS-1), about 8 mg of powdery ultra-high molecular weight polyethylene polymer sample is placed in an aluminum pan and sealed, and the temperature is raised from 50 ° C. to 180 ° C. at 10 ° C./min. After maintaining the state for 5 minutes, the temperature was decreased to 50 ° C. at a temperature decreasing rate of 10 ° C./min, and again increased to 180 ° C. at 10 ° C./min. The temperature of the endothermic peak accompanying melting at this time was measured as the melting point.

<Total heat of fusion>
Using the DSC apparatus, the temperature was measured at a rate of temperature increase of 10 ° C./min in accordance with JIS K7121-1987. The area enclosed by the melting curve and the baseline is the total heat of fusion.

<Melting start temperature>
The temperature at which the melting curve of the chart obtained by the DSC measurement departs from the baseline.

<Temperature not exceeding 25% or 30% of the total heat of fusion>
From the chart obtained by the DSC measurement, after the melting start temperature, the endothermic amount required for the melting is measured at each temperature, integrated from the melting start temperature, and 25% or 30% of the heat amount necessary for the total melting. Temperature reaching%.

<Thickness>
The thickness of the molded body and the rolled molded sheet was measured using a Mitutoyo micrometer (395-541: BMD-25DM). The thickness was measured to the third decimal place and rounded off to the third decimal place.

<Internal haze>
The internal haze was measured according to JIS-K7136 using the sheets of each example and the final processed product (molded sheet or rolled molded sheet) of each comparative example as test pieces. Here, in order to eliminate the cause of external haze, a quartz glass holder was filled with special grade ethanol manufactured by Wako Pure Chemical Industries, and a test piece was placed therein to measure internal haze. As a measuring instrument, Nippon Denshoku Industries Co., Ltd. Haze Meter NDH2000 was used. Further, the internal haze in terms of thickness 2 mm was calculated using the above-described relational expression (haze;%) = a × t (rolled sheet thickness; mm) + b.

<Total light transmittance>
The total light transmittance T was measured according to JIS-K7316-1 using the sheet of each example and the roll-formed sheet of each comparative example as a test piece. Nippon Denshoku Industries Co., Ltd. Haze meter NDH2000 was used as a measuring instrument.

<Tensile properties>
Test rolls were produced by punching the rolled molded sheets of each Example and Comparative Example using a JIS No. 2 dumbbell described in JIS K7113. Using the obtained dumbbell test piece, a tensile test was performed under the conditions of a tensile speed of 50 mm / min and a temperature of 23 ° C., and the maximum stress was measured.

<Falling weight impact test>
The roll-formed sheet of each example and comparative example is cut into a 10 cm square, and the striker having a striker tip R diameter of 10 mmφ and a striker weight of 3.2 kg is formed on the sheet when freely dropped from a height of 1.9 m. The breaking energy was measured. Since the value of fracture energy greatly depends on the thickness of the test piece, the fracture energy value obtained by actual measurement is divided by the thickness (mm) of the test piece used for measurement and compared as the fracture energy value per unit thickness. Used for.

[Example 1]
<Preparation of ultra-high molecular weight polyolefin molding>
As the ultra high molecular weight polyolefin, Sun Fine UH900 (manufactured by Asahi Kasei Chemicals Corporation), which is ultra high molecular weight polyethylene, was used. This was powdery and had an intrinsic viscosity of 15.5 dg / l and a bulk density of 0.48 g / cc.
A roll-shaped thick molded product was produced using the powder, and the thick molded product was skived to a thickness of about 4 mm to produce a skive sheet. When the thickness of this skive sheet was measured accurately, the thickness was 3.90 mm. Further, the density of this skive sheet was 944 kg / m ³ . The results of DSC measurement using 8.4 mg of the powder showed a melting point of 137 ° C., a melting start temperature of 92 ° C., and a total heat of fusion of 142 J / g. The temperature showing an endothermic amount of 25% of the total heat of fusion was 128 ° C, and the temperature showing an endothermic amount of 30% of the total heat of fusion was 129 ° C.

<Preparation of ultra high molecular weight polyolefin roll-formed sheet>
The skive sheet was set so that the sheet temperature immediately before the roll would be 110 ° C. in the range of 130 ° C. to 140 ° C., and 10 to 15 minutes for the sheet to pass through the heater. It adjusted so that it might become. This preheated sheet is rolled at a speed of 1.0 m / min using a rolling roll machine having a roll diameter of 300 mmφ and a roll length of 400 mm, with a roll gap of 0.8 mm and a roll surface temperature of 110 ° C. did. The thickness of the obtained sheet was 1.20 mm, the internal haze in the thickness direction was 36.3%, and the total light transmittance was 82.5%. Moreover, the value which converted this internal haze into thickness 2mm was 58.5%.
The maximum stress obtained from the tensile properties was 118 MPa, and the fracture energy obtained from the result of the falling water impact test was 13.0 J / mm.

[Example 2]
The same procedure as in Example 1 was performed except that the preheating temperature of the skive sheet was 125 ° C. and the rolling temperature was 125 ° C. The thickness of the obtained sheet was 0.96 mm, the internal haze in the thickness direction was 24.9%, and the total light transmittance was 89.5%. A value obtained by converting the internal haze into a thickness of 2 mm was 53.7%.
The maximum stress obtained from the tensile properties was 124 MPa, and the fracture energy obtained from the result of the falling water impact test was 16.3 J / mm.

[Example 3]
<Preparation of ultra-high molecular weight polyolefin molding>
As the ultra high molecular weight polyolefin, Sun Fine UL901 (manufactured by Asahi Kasei Chemicals Corporation), which is a copolymer of ethylene and butene-1, was used as the ultra high molecular weight polyethylene. This was powdery, had an intrinsic viscosity of 16.9 dg / l, and a bulk density of 0.44 g / cc.
A roll-shaped thick molded product was produced using the powder, and the thick molded product was skived to a thickness of about 4 mm to produce a skive sheet. When the thickness of this skive sheet was measured accurately, the thickness was 3.90 mm. Further, the density of this skive sheet was 924 kg / m ³ . The results of DSC measurement using 8.4 mg of the powder showed a melting point of 129 ° C., a melting start temperature of 77 ° C., and a total heat of fusion of 115 J / g. The temperature showing an endothermic amount of 25% of the total heat of fusion was 119 ° C., and the temperature showing an endothermic amount of 30% of the total heat of fusion was 121 ° C.

<Preparation of ultra-high molecular weight polyolefin roll-formed sheet>
The skive sheet is set in a range of 80 ° C. to 90 ° C. so that the sheet temperature immediately before the roll is 80 ° C., and 10 to 15 minutes for the sheet to pass through the heater. It adjusted so that it might become. This preheated sheet is rolled at a speed of 1.0 m / min using a rolling roll machine having a roll diameter of 300 mmφ and a roll length of 400 mm, with a roll gap of 1.0 mm and a roll surface temperature of 80 ° C. did. The thickness of the obtained sheet was 2.18 mm, the internal haze in the thickness direction was 20.7%, and the total light transmittance was 83.3%. A value obtained by converting the internal haze into a thickness of 2 mm was 16.8%.
The maximum stress obtained from the tensile properties was 65 MPa, and the fracture energy obtained from the result of the falling water impact test was 10.6 J / mm.

[Example 4]
The same operation as in Example 3 was performed except that the rolling temperature of the skive sheet was 115 ° C. The thickness of the obtained sheet was 1.28 mm, the internal haze in the thickness direction was 5.7%, and the total light transmittance was 93.5%. A value obtained by converting the internal haze into a thickness of 2 mm was 21.2%.
Further, the maximum stress obtained from the tensile properties was 82 MPa, and the fracture energy obtained from the result of the falling water impact test was 13.0 J / mm.

[Example 5]
The same operation as in Example 4 was performed except that the rolling speed was 0.3 m / min. The thickness of the obtained sheet was 1.32 mm, the internal haze in the thickness direction was 5.6%, and the total light transmittance was 94.1%. The value obtained by converting the internal haze to a thickness of 2 mm was 20.2%.
The maximum stress obtained from the tensile properties was 81 MPa, and the fracture energy obtained from the results of the falling water impact test was 13.4 J / mm.

[Example 6]
The same operation as in Example 4 was conducted except that the preheating temperature of the skive sheet was 115 ° C. The thickness of the obtained sheet was 1.21 mm, the internal haze in the thickness direction was 4.7%, and the total light transmittance was 95.3%. A value obtained by converting the internal haze into a thickness of 2 mm was 21.7%.
The maximum stress obtained from the tensile properties was 85 MPa, and the fracture energy obtained from the result of the falling water impact test was 14.6 J / mm.

[Example 7]
The same operation as in Example 6 was performed except that the rolling speed was 2.0 m / min. The thickness of the obtained sheet was 1.22 mm, the internal haze in the thickness direction was 7.6%, and the total light transmittance was 93.1%. The value obtained by converting the internal haze to a thickness of 2 mm was 24.4%.
The maximum stress obtained from the tensile properties was 88 MPa, and the fracture energy obtained from the result of the falling water impact test was 15.6 J / mm.

[Comparative Example 1]
A skive sheet having a thickness of 3.90 mm was carried out in the same manner as in Example 1 except that the preheating temperature was 80 ° C. and the rolling temperature was 80 ° C. As a result, the rigidity was too high to be rolled with a roll. Therefore, the same procedure as in Example 1 was performed except that the thickness of the skive sheet was 2 mm, the preheating temperature of the sheet was 80 ° C., and the rolling temperature was 80 ° C. The thickness of the obtained sheet was 1.28 mm. The internal haze in the thickness direction was 53.9%, and the total light transmittance was 68.7%. A value obtained by converting the internal haze into a thickness of 2 mm was 73.8%.
The maximum stress obtained from the tensile properties was 51 MPa, and the fracture energy obtained from the result of the falling water impact test was 10.9 J / mm.

[Comparative Example 2]
The same procedure as in Example 3 was performed except that the preheating temperature of the skive sheet was 125 ° C. and the rolling temperature was 125 ° C. The sheet was fused to the rolling roll and could not be rolled.

[Comparative Example 3]
The same procedure as in Example 3 was performed except that the preheating temperature of the skive sheet was 125 ° C. The sheet was fused to the rolling roll and could not be rolled.

[Comparative Example 4]
In order to compare the physical properties of the sheet when not rolled, the thickness of the skive sheet obtained from Example 1 was skived to 1 mm, and haze, tensile properties, and a falling impact test were performed. The thickness of the sheet obtained by skiving was 0.93 mm. The internal haze in the thickness direction was 93.9%, and the total light transmittance was 45%. The value obtained by converting the inner height into 2 mm was almost 100%.
The maximum stress obtained from the tensile properties was 50 MPa, and the fracture energy obtained from the result of the falling water impact test was 13.9 J / mm.

[Comparative Example 5]
In order to compare the physical properties of the sheet without rolling, the thickness of the skive sheet obtained from Example 3 was skived to 1 mm, and haze, tensile properties, and a falling impact test were performed. The thickness of the sheet obtained by skiving was 0.92 mm. The internal haze in the thickness direction was 66.1%, and the total light transmittance was 69.6%. The value obtained by converting the inner height into 2 mm was 89.3%.
The maximum stress obtained from the tensile properties was 39 MPa, and the fracture energy obtained from the result of the falling water impact test was 8.6 J / mm.

  The method for producing an ultrahigh molecular weight polyolefin sheet of the present invention can provide a product that is transparent and excellent in wear resistance. The product makes use of these characteristics and can be used in various applications as a new functional material that has not existed before. For example, the back of sliding tape, thrust washer, sliding sheet, guide, ski, snowboard, etc. Upholstery and surface coating materials; Lining materials such as hoppers and chutes; Transport pipes and sheets for food materials, etc .; Coating materials for protective shields, fenders, rolls, pipes, steel pipes, etc .; Electrical insulation materials; Agriculture for agricultural houses It can be used as a suitable material in the fields of agricultural equipment members such as construction materials and agricultural equipment propellers;

Claims (4)

  Thickness of 0.3 mm or more obtained by rolling an ultrahigh molecular weight polyolefin polymer having an intrinsic viscosity of 7 dl / g or more measured in a decalin solution at 135 ° C., and an internal haze in the thickness direction at a thickness of 2 mm. In the method for producing a rolled sheet of ultrahigh molecular weight polyolefin of 60% or less, rolling is performed in a temperature range that does not exceed the melting start temperature of the ultrahigh molecular weight polyolefin and does not exceed the endothermic amount of 25% of the total heat of fusion of the ultrahigh molecular weight polyolefin. A method for producing an ultrahigh molecular weight polyolefin sheet, comprising preheating a sheet to be subjected to heating and then rolling the sheet.   In the rolling process, rolling is performed in a temperature range that exceeds a melting start temperature of the ultrahigh molecular weight polyolefin and does not exceed an endothermic amount of 30% of the total heat of fusion of the ultra high molecular weight polyolefin. The manufacturing method of the ultra high molecular weight polyolefin sheet of description. The ultra-high-molecular-weight polyolefin sheet according to claim 1 or 2, obtained by rolling the ultra-high-molecular-weight polyolefin molded product to 1.3 times or more at a rolling ratio (χ) represented by the following formula (1). Production method.
χ = t1 / t2 (1)
t1: Thickness before rolling (mm)
t2: Thickness after rolling (mm) The ultra-high molecular weight polyolefin polymer is an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, according to any one of claims 1 to 3. Method for producing ultra-high molecular weight polyolefin sheet.