JPWO2018212179A1 - Manufacturing method of sheet-like resin molding - Google Patents

Abstract

A method for producing a sheet-shaped resin molded article, in which a resin composition containing at least a thermoplastic resin mainly comprising polyolefin and an inorganic filler is formed into a sheet shape, the resin composition comprising the thermoplastic resin and an inorganic material A first step in which the mass ratio of the filler is 15:85 to 50:50, and the sheet extruded from the annular die after kneading is stretched by an inflation method at a temperature equal to or higher than the melting point of the thermoplastic resin, and at least The manufacturing method of a sheet-like resin molding which has a 2nd process extended | stretched in any one of a film forming direction and the direction perpendicular | vertical to a film forming direction.

Description

  The present invention relates to a method for producing a sheet-shaped resin molded article having excellent strength characteristics and whiteness.

  Conventionally, a sheet-like resin molded body has been manufactured by melt-molding a resin composition highly filled with inorganic particles (Patent Documents 1 and 2). When these sheet-like resin moldings are used for applications as synthetic paper, not only strength but also whiteness is required, and production by biaxial stretching is also performed by an inflation method.

JP 2011-31623 A Patent No. 5461614

  However, the above-described production method based on the inflation method cannot sufficiently satisfy both the strength and the whiteness, and the specific gravity is not sufficiently lowered, so that the application has been limited.

  An object of this invention is to provide the manufacturing method of the sheet-like resin molding which is excellent in intensity | strength and whiteness, and has low specific gravity.

  The object of the present invention has been achieved by the following.

(1) A method for producing a sheet-shaped resin molded body in which a resin composition containing at least a thermoplastic resin mainly comprising polyolefin and an inorganic filler is formed into a sheet shape, wherein the resin composition is the thermoplastic resin. The first step in which the mass ratio of the resin and the inorganic filler is 15:85 to 50:50, and the sheet extruded from the annular die after kneading is stretched by the inflation method at a temperature equal to or higher than the melting point of the thermoplastic resin. And the manufacturing method of a sheet-like resin molding which has a 2nd process extended | stretched to any one of the direction perpendicular | vertical to a film forming direction and a film forming direction at least.
(2) The method for producing a sheet-shaped resin molded article according to (1), wherein the second step is simultaneous biaxial stretching or sequential biaxial stretching.

  According to the present invention, in the first step, by stretching at a melting point or higher, so-called melt stretching is performed and sheet strength is improved. However, even if the filler is present, there is little increase in voids in the sheet, and therefore there is little improvement in the whiteness of the sheet and a decrease in density. Therefore, in the second step, a sheet-shaped resin molded article having excellent strength and whiteness and low specific gravity can be obtained by stretching at a temperature lower than the melting point of the resin used to generate voids in the sheet.

It is a figure which shows the inflation apparatus of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing a sheet-shaped resin molded body of the present invention is a method for producing a sheet-shaped resin molded body in which a resin composition containing a thermoplastic resin containing at least a polyolefin as a main component and an inorganic filler is formed into a sheet shape. The resin composition has a mass ratio of the thermoplastic resin to the inorganic filler of 15:85 to 50:50, and the sheet extruded from the annular die after kneading is heated to a temperature equal to or higher than the melting point of the thermoplastic resin. The method includes a first step of stretching by an inflation method and a second step of stretching in at least one of the film forming direction and a direction perpendicular to the film forming direction.

<Resin composition containing thermoplastic resin and inorganic filler>
The resin composition of the present invention contains at least a thermoplastic resin mainly composed of polyolefin and an inorganic filler, and the mass ratio of the thermoplastic resin to the inorganic filler is 15:85 to 50:50. Features.
≪Thermoplastic resin≫
As the thermoplastic resin of the present invention, a polyolefin resin is a main component. The main component is to contain 50% by mass or more as a thermoplastic resin.

  Specific examples include polyethylene (high density, low density, ultrahigh molecular weight), polypropylene, polycycloolefin, and the like, and one or more can be selected as appropriate in consideration of the melting point and the elastic modulus.

The melt mass flow rate (MFR) is preferably 0.02 g / 10 min or more and 2.0 g / 10 min or less, more preferably 0.1 g / 10 or more and 1.0 g / 10 min or less (JIS K). Measured according to 7210). Specifically, there is a method of measuring the melt flow rate with a melt indexer under the conditions of a load of 21.18 N, a temperature of 230 ° C. for a polypropylene resin, and a temperature of 190 ° C. for a polyethylene resin. Preferred are B5803 (MFR = 0.30) manufactured by Polyethylene Co., Ltd., F3001 (MFR = 0.04), 7000F manufactured by PTT (MFR = 0.04), H5604 manufactured by SCG (MFR = 0.04), and the like. Can be mentioned.

≪Inorganic filler≫
The inorganic filler of the present invention is not particularly limited. For example, calcium carbonate, titanium oxide, silica, clay, talc, kaolin, aluminum hydroxide, calcium sulfate, barium sulfate, mica, zinc oxide, dolomite, glass fiber, hollow glass, etc. Can be mentioned. Preferably it is calcium carbonate. It is also preferable to use calcium carbonate mixed with titanium oxide. In this case, it is preferable to use titanium oxide in the range of 0.1 to 30% by mass with respect to calcium carbonate.

  The inorganic filler is contained in the form of inorganic particles, and any of granular, acicular, and flat shapes can be used. An average particle diameter of 0.01 to 20 μm (50% particle diameter (d50) obtained from an integrated% distribution curve measured with a laser diffraction particle size distribution analyzer) can be used as appropriate.

≪Resin composition≫
The resin composition of the present invention has at least a thermoplastic resin and an inorganic filler, and the inorganic filler is 50% by mass or more, preferably 70% by mass or more and 85% by mass or less of the resin composition. The thermoplastic resin is preferably 1% by mass or more and 50% by mass or less of the resin composition.

  In the resin composition of the present invention, in addition, one or more auxiliary agents selected from a lubricant, an antioxidant, an ultraviolet absorber, a coloring pigment, a dispersant, a compatibilizer, an antistatic agent, a flame retardant, and the like. An agent can be added within a range not detrimental to the purpose. Preferably, it is 0.1-5 mass% of a resin composition.

<Process for forming a resin composition into a sheet>
The step of forming the resin composition of the present invention into a sheet has a first step and a second step.

  The first step of the present invention is mainly performed to improve the strength of the sheet-like material, and the second step is mainly performed to improve the whiteness of the sheet-like material and lower the specific gravity. Is.

≪First process≫
The first step of the present invention is a stretching step included in the inflation method. In the inflation method, a generally known device can be used, for example, a device described in JP2011-31623A can be applied.

  The stretching temperature is appropriately selected depending on the melting point of the thermoplastic resin, but is required to be a temperature equal to or higher than the melting point of the thermoplastic resin. In a system with many inorganic fillers, the strength characteristics of the sheet are improved as the stretching temperature is increased, and it is very effective in terms of strength to perform stretching at a temperature higher than the melting point of the resin. For example, in the case of high-density polyethylene, it has a melting point of about 120 to 140 ° C, the melting point of low-density polyethylene is about 95 to 130 ° C, and that of polypropylene is about 165 to 168 ° C. It is necessary to stretch at a temperature. The upper limit is preferably in the range from the thermal stability of the thermoplastic resin and additives to the melting temperature at the time of extrusion before stretching. More preferably, it can be determined as appropriate within a range up to a temperature 50 ° C. higher than the melting point.

Referring to FIG. 1, the stretching temperature of the present invention refers to the temperature at one temperature adjustment site immediately after being extruded from the annular die. The melting temperature at the time of extrusion before stretching refers to the temperature at 2.
The melting point means the maximum temperature of the endothermic peak accompanying the melting of the crystal in the thermal analysis of the differential scanning calorimeter (DSC).

  A draw ratio can be suitably selected in the range of 1.01 to 10 times. In the case of biaxial stretching, the film is preferably stretched in the range of 1.1 to 8 times in a direction perpendicular to the axis of the film forming direction (hereinafter abbreviated as TD direction). The stretching conditions can be determined based on the required characteristics of the product.

≪Second process≫
The second step of the present invention is a stretching step which is at least one of a film forming direction (hereinafter abbreviated as MD direction) and a direction perpendicular to the film forming direction (hereinafter abbreviated as TD direction). It may be a sequential biaxial stretching step. Simultaneous biaxial stretching can be the same step as the first stretching step, and in the sequential stretching step, the stretching in the MD direction and the TD direction can be shifted with time. The biaxial stretching step in the second stage is preferably a longitudinal stretching step by an inflation method or a roll stretching method, and particularly preferably a longitudinal stretching step by a roll stretching method in terms of improving whiteness.

  The stretching temperature is appropriately determined depending on the thermoplastic resin, but it is preferably 5 to 70 ° C. lower than the stretching temperature in the first stretching step. The draw ratio can also be appropriately selected within the range of the draw ratio similar to the first stretching step. In roll drawing, for example, the draw ratio can be adjusted by the difference in peripheral speed between two sets of metal nip rolls. A roll having a crown shape can also be preferably used.

The first step and the second step are preferably carried out continuously. For example, apparatuses described in JP-B 51-12669 and JP-A-6-340032 can be applied.
It is also preferable to have a step of adjusting the temperature between the first step and the second step.

<Bending process>
In the present invention, in addition to the above-mentioned two steps, the solid object in a direction perpendicular to the crystal orientation axis is in the process of moving the target sheet or film in the MD direction, although the stretching is not clearly defined. The method may include a step of bringing a contact state so as to be pressed and generating a bent state. As this method, for example, a method described in WO2015 / 060271 can be employed.

  In the present invention, a long solid object such as a rod, a plate or a beam is placed on the surface of the sheet that has undergone the second step (hereinafter sometimes simply referred to as a sheet), and the longitudinal direction is the sheet conveyance direction ( It is preferable to provide a step of bending the sheet by pressing so as to cross the machine direction and the MD direction. At that time, it is preferable to apply a stress so that the object and the sheet are relatively moved in a state where the sheet is bent and bent at a contact portion of the solid object with the sheet.

  In the present invention, the bending treatment may be performed at least once on the front surface or the back surface of the sheet. The bending process can be performed on only one or both of the front surface and the back surface of the sheet. From the viewpoint of preventing warpage, it is preferable to perform the bending process on both sides of the sheet.

  When performing the bending process on both the front and back surfaces of the sheet, the bending process can be performed continuously on the front surface and the back surface, or after the first bending process is performed on either the front surface or the back surface, It is also possible to perform a bending process on the surface. Moreover, after winding the sheet | seat after a 2nd process once to a roll and producing an original fabric roll, a bending process can also be performed with respect to this original fabric roll, and manufacture and a bending process of a sheet | seat are performed continuously. However, it is preferable to carry out continuously.

  Since the solid object in the present invention is brought into contact with a sheet having various widths and pressed against the sheet with a constant pressing force, it is effective to employ a long member. Specifically, it can be a member having a shape such as a bar, a plate, or a beam. When using a plate member, it uses as a part for pressing the end.

In order to apply pressure without variation to each position in the width direction of the sheet, the length of the solid object in the longitudinal direction is sufficiently longer than the width direction (MD direction or TD direction) of the sheet, It is preferable to arrange so as to cross the transport direction. At that time, it is preferable that the longitudinal direction of the solid object and the conveying direction of the formed sheet be perpendicular or close to each other in order to apply a pressing force without variation at each position in the width direction of the sheet.
It is desirable that the angle between the longitudinal direction of the solid object and the conveying direction of the sheet is vertical, but for example, it is set within a range of ± 20 degrees, preferably ± 10 degrees, more preferably ± 5 degrees with respect to the vertical. Can do.

  The material of the solid object in the present invention is not particularly limited, and can be selected from well-known materials according to the purpose. For example, various metal materials such as SUS, FRP, and the like can be mentioned, but are not limited thereto. In order to apply a uniform stress without variation in the width direction of the sheet, it is preferable to select a material having high rigidity as the material of the solid object.

  The cross-sectional shape when the solid object in the present invention is viewed in the longitudinal direction can be adopted without particular limitation, such as a circle, an ellipse, a triangle, a square, and other polygons. By using triangles, squares, or other polygons, a single solid object can be bent twice or more at the same time.

  Furthermore, it is desirable that the cross-sectional shape of the contact portion between the solid object and the molded sheet has an acute corner that does not break the sheet, or an R portion having a small curvature radius. By making the shape of the contact portion of the solid object to the sheet as described above, a sufficient vertical force (force applied in the thickness direction of the film) can be applied to the sheet, and as a result, the sheet can be handled. And mold followability are improved.

  When the sheet is bent at the contact portion with the solid object while being pulled, the bending process can be performed to improve the strength of the sheet highly filled with the filler. This is a process in which tensile stress is applied to the inside of the sheet, and if a strong vertical force is applied due to the contact of the solid object, the vertical stress acts in the thickness direction of the molded sheet, and as a result, in the sheet conveying direction. It is considered that shear stress is generated to relax the internal structure of the sheet.

  In the bending process of the present invention, only one solid object may be used, but two or more solid objects may be used simultaneously.

<Sheet-shaped resin molding>
The sheet-shaped resin molded product of the present invention has a film thickness of 25 to 300 μm, whiteness of 78 to 95% (measured according to JIS P8148), and opacity of 80 to 95% (measured according to JIS P8149). It is. Preferably, the whiteness is 80-92% and the opacity is 85-92%. The apparent specific gravity (JIS K 7112) is preferably 0.55 to 1.40 in terms of whiteness.
The sheet-like resin molded product of the present invention is useful as a synthetic paper or the like.

Example 1
As a resin composition, a high-density polyethylene resin (B5803 MFR = 0.30 manufactured by Keiyo Polyethylene Co., Ltd.) and calcium carbonate powder (Ryton S4 average particle size 5.7 μm, manufactured by Bihoku Powdered Industries Co., Ltd.) are used in a mass ratio of 40. : 60, and glycerol monostearate (Rikemar AS-003 manufactured by Riken Vitamin Co., Ltd.) is blended so as to be 1% by mass of the resin composition. Raw material pellets were prepared by melt mixing and kneading using a shaft extruder (CTC Co., Ltd.).

The pellet was extruded into a bag shape from a die outlet at a melting temperature of 210 ° C. and a die outlet temperature of 190 ° C. using an inflation device (die diameter: 100 mm, manufactured by Sumitomo Heavy Industries Modern Co., Ltd.). Air is pushed in so that it becomes 7 times, 2.7 times in the direction perpendicular to the take-up direction, 2.7 times at a take-up direction speed of 23.6 m / min, and simultaneous biaxial first stretching at 190 ° C. went. The sheet-shaped resin composition at this time had a thickness of 197 μm, a density of 1.382 g / cm ³ , an elastic modulus of 1047 MPa, and a whiteness of 78.1%.

  Furthermore, these sheets were subjected to a tenter type experimental biaxial stretching apparatus (manufactured by Toyo Seiki Seisakusho for high temperature) at 45 ° C., 60 ° C., 70 ° C., and draw ratios MD and TD were all 1.2 times. Simultaneously biaxial second stretched samples were obtained at a speed of 5 times, 2 times, and 10 m / min. The strength was evaluated based on the elastic modulus and indicated by a tensile elastic modulus according to JIS-C-2051. The specific gravity determined the density according to JIS-K-6760. The results are shown in Table 1. Each measurement was performed in an atmosphere of 23 ° C. and 55% RH.

(Example 2)
As a resin composition, a high-density polyethylene resin (F3001 MFR = 0.04 manufactured by Keiyo Polyethylene Co., Ltd.) and calcium carbonate powder (Ryton S4 average particle size 5.7 μm manufactured by Bihoku Powdered Industries Co., Ltd.) are used at a mass ratio of 30. : 70, and glycerol monostearate (Rikemar AS-003 manufactured by Riken Vitamin Co., Ltd.) is blended so as to be 1% by mass of the resin composition. Raw material pellets were prepared by melt mixing and kneading using a shaft extruder (CTC Co., Ltd.).

The above pellets were extruded into a bag shape from a die outlet with a melt temperature of 180 ° C., a die outlet temperature of 190 ° C. using an inflation device (die diameter: 85 m, manufactured by Placo Corporation), and a blow ratio of 2.0 was inserted into the bag-like sheet. Air is pushed in so that it is doubled, and simultaneous biaxial first stretching is performed at 190 ° C. so as to be 2.0 times perpendicular to the take-up direction and take-up speed 15.0 m / min 2.0 times. It was. The sheet-shaped resin composition at this time had a thickness of 90 μm, a density of 1.390 g / cm ³ , an elastic modulus of 761.3 MPa (take-up direction), 335.2 MPa (perpendicular to the take-up direction), and a whiteness of 87.2%. .

  Furthermore, using a roll type uniaxial stretching apparatus (manufactured by Hirano Giken), a sample obtained by stretching the sheet 2.0 times in the MD direction (the roll take-up direction during inflation) was obtained. The strength was evaluated based on the elastic modulus and indicated by a tensile elastic modulus according to JIS-C-2051. The specific gravity determined the density according to JIS-K-6760. The results are shown in Table 2. Each measurement was performed in an atmosphere of 23 ° C. and 55% RH.

上記表１、２で示す通り２段階延伸した場合に強度、白色度の改善が顕著である。

As shown in Tables 1 and 2 above, the improvement in strength and whiteness is remarkable when the film is stretched in two stages.

DESCRIPTION OF SYMBOLS 1 Temperature controller 2 at the time of drawing 2 Ring die 3 Extruder 4 Resin composition pipe 5 Nip roll 6 Guide roll

Claims (3)

  A method for producing a sheet-shaped resin molded body, comprising forming a resin composition containing at least a thermoplastic resin mainly comprising polyolefin and an inorganic filler into a sheet shape, the resin composition comprising the thermoplastic resin and an inorganic material. A first step in which the mass ratio of the filler is 15:85 to 50:50, and the sheet extruded from the annular die after kneading is stretched by an inflation method at a temperature equal to or higher than the melting point of the thermoplastic resin; The manufacturing method of the sheet-like resin molding which has a 2nd process extended | stretched in any one of a film | membrane direction and the direction perpendicular | vertical to a film forming direction.   The method for producing a sheet-shaped resin molded body according to claim 1, wherein the second step is a roll stretching step.   After the second step, in the middle of moving the sheet in the conveying direction, a solid object is pressed against the surface of the sheet, and the sheet is bent at the contact portion to act on the inside of the sheet. The manufacturing method of the sheet-like resin molding of Claim 1 or 2 which has the bending process process which generate | occur | produces the stress to perform.

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