JP2017105865A - Sheet-like molded product and method for producing the same - Google Patents

Abstract

An object of the present invention is to enhance the mechanical strength of general-purpose plastics.
A fibrous filler having a higher thermal conductivity than that of a crystalline resin is melt-mixed with the crystalline resin (step 1) to form a mesophase (step 2). Since the crystal part is formed and the fibrous filler is oriented at the surface part, the mechanical strength of the sheet-like molded product can be enhanced.
[Selection] Figure 2

Description

  The present invention relates to a sheet-like molded product used for press molding and a method for producing the same.

  So-called “general-purpose plastics” such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) are not only very inexpensive but also easy to mold, compared to metals or ceramics. The weight is a fraction of the weight. Therefore, general-purpose plastics are often used as materials for various daily necessities such as bags, various types of packaging, various types of containers, sheets, etc., as well as for industrial parts such as automobile parts and electrical parts, and as materials for daily necessities and miscellaneous goods. Has been.

  However, general-purpose plastics have drawbacks such as insufficient mechanical strength. Therefore, general-purpose plastics do not have sufficient characteristics required for materials used in various industrial products such as machinery products such as automobiles and electrical, electronic, and information products. The current situation is limited.

  On the other hand, engineering plastics such as polycarbonate, fluororesin, acrylic resin, and polyamide are excellent in mechanical properties and are used in various industrial products including machinery products such as automobiles and electrical / electronic / information products. .

JP 2010-168485 A JP2012-207110A

However, engineered plastics are expensive, have difficulty in monomer recycling, and have a large environmental burden.
Therefore, there is a demand for greatly improving the material properties (such as mechanical strength) of general-purpose plastics. If general-purpose plastics can be used as a substitute for engineering plastics or metal materials by improving material properties, the cost of manufacturing various industrial products made of polymers or metals, or household goods will be greatly reduced. Is possible.

  In view of the above-described conventional problems, an object of the present invention is to enhance the mechanical strength of a general-purpose plastic.

  In order to achieve the above object, a method for producing a sheet-shaped molded product according to an embodiment of the present invention includes a crystalline resin and a fibrous filler having a higher thermal conductivity than the crystalline resin, the melting point of the crystalline resin or higher. A heating and melting step of melting and mixing at a temperature of; a cooling step of cooling the sheet-like mixture at a temperature below the melting point of the crystalline resin; and the melting point of the cooled sheet-like mixture above the glass transition temperature of the crystalline resin And a heating and stretching step of stretching in the following temperature range.

  Further, the sheet-like molded product according to an embodiment of the present invention is a composite resin including a crystalline resin and a fibrous filler having a higher thermal conductivity than the crystalline resin, and includes a crystalline part and an amorphous part. The average crystallinity of the composite resin is 45% or more and 80% or less.

  As described above, a fibrous filler having a higher thermal conductivity than the crystalline resin is melt-mixed with the crystalline resin to form a mesophase, whereby a crystalline part and an amorphous part are formed in the sheet-like molded product, and the fiber Since the filler is oriented at the surface portion, the mechanical strength of the sheet-like molded product can be enhanced.

The schematic diagram which illustrates the manufacturing process of the sheet-like molded object of this invention The flowchart which illustrates the manufacturing process of the sheet-like molded object of this invention The figure explaining the relationship between a fiber diameter and a fiber space | interval The figure explaining the relationship between the stretching of the crystalline resin and the concentration distribution of the filler on the resin Configuration diagram explaining the process of high-speed pressing of conventional resin Figure showing a table summarizing the measurement results

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and description thereof is omitted as appropriate.
(Embodiment)
First, the manufacturing method of a sheet-like molded object is demonstrated using FIG. 1, FIG.

FIG. 1 is a schematic view illustrating a manufacturing process of a sheet-like molded body of the present invention, and FIG. 2 is a flow diagram illustrating a manufacturing process of the sheet-shaped molded body of the present invention.
First, in the heating and melting step, the crystalline resin is heated and melted, and the fibrous filler is added to the melted crystalline resin to melt and disperse the fibrous filler in the crystalline resin (Step 1 in FIG. 2). . Next, in a state where the temperature equal to or higher than the melting point is maintained, the crystalline resin to which the fibrous filler is added is hot-rolled to form a sheet (Step 2 in FIG. 2). Next, in the cooling step, the sheet is cooled to form a mesophase of crystalline resin. The sheet is cooled by allowing the heated sheet to cool at a temperature not higher than the melting point of the crystalline resin such as room temperature. For example, the heated sheet is left to cool in the room temperature environment. Normally, when a resin sheet-like material is produced, the molten crystalline resin is rapidly cooled in order to cool the sheet-like material. On the other hand, in the manufacturing method of the sheet-like molded body of the present embodiment, by using a material having a higher thermal conductivity than the crystalline resin as the dispersed fibrous filler, the inside of the sheet-like material is uniformly cooled. Can be allowed to cool. Moreover, since the fibrous filler is attached, the crystalline resin becomes a mesophase. Further, since the fibrous filler is attached, the crystalline resin inhibits crystal growth and the crystal grain size is reduced to 100 nm or less. In the conventional sheet-like material in which the fibrous filler is melt-dispersed, the crystal grain size is larger than 100 nm and smaller than several tens of μm (step 3 in FIG. 2). Thereafter, in the heating and stretching step, the cooled sheet material is heated and stretched to a temperature not lower than the glass transition temperature of the crystalline resin and not higher than the melting point. The cooled sheet-like material has a crystal part and an amorphous part mixed together, so that a highly tough sheet-like molded product can be obtained, and the crystal part is oriented by stretching so that the crystal part is highly oriented. A high-strength sheet-like molded body can be obtained (step 4 in FIG. 2).

  Since the sheet-like molded body produced by the above method becomes a mesophase in the cooling process due to the action of the fibrous filler, the formed sheet-like molded body is in a state where the crystal part and the amorphous part are mixed. become. A conventional sheet-like molded body increases mechanical strength by increasing the crystallinity to, for example, 90% or more by rapid cooling. For example, by air cooling, the overall average crystallinity of the sheet-like molded body is 45% or more and 80% or less. Thus, toughness can be improved by increasing the proportion of amorphous parts. Moreover, by cooling from the surface side, the mesophase of the surface portion increases in the thickness direction of the sheet-like molded body, and as a result, the crystallinity of the surface portion becomes higher than the crystallinity of the internal portion. Thereby, mechanical strength can be ensured at the surface portion having a high degree of crystallinity while improving toughness mainly by the amorphous portion of the inner portion. Further, by stretching, the fibrous filler is oriented in the stretching direction, particularly at the surface portion. Therefore, in the thickness direction of the sheet-like molded body, the concentration of the fiber filler increases as it goes from the inner part to the surface part by stretching, and the mechanical strength can be improved in the surface part. The mechanical strength is improved regardless of the crystal size.

  In order to improve the mechanical strength of general-purpose plastics, conventionally, a polymer melt is stretched at a temperature equal to or lower than the melting point at a speed equal to or higher than the critical elongation strain rate. In some cases, a polymer oriented crystal such as polypropylene having improved mechanical strength is produced by cooling and polymerizing the polymer melt. However, the polymer oriented crystals produced by this method have increased crystallinity and increased strength, but on the other hand, there are fewer amorphous parts and the toughness such as impact strength and elongation is weakened. In addition, it is necessary to stretch the resin at a high speed that is higher than the critical elongation strain rate.If the resin size is large, a large pressure is required, and a very large press machine is required. It is not constant and the distribution of mechanical strength becomes non-uniform. On the other hand, in the method for producing a sheet-like molded product according to the present embodiment, an amorphous part is formed in the inner part, so that toughness can be ensured, there is no need to stretch at a high speed, and it is easily uniform. Mechanical strength can be ensured.

Hereinafter, these will be described in detail with reference to FIGS.
FIG. 3 is a diagram for explaining the relationship between the fiber diameter and the fiber spacing, FIG. 4 is a diagram for explaining the relationship between the stretching of the crystalline resin and the concentration distribution of the filler on the resin, and FIG. 5 is a process for pressing the conventional resin at high speed. FIG.

  The crystalline resin here refers to all polymer materials and organic materials having crystals in which molecular chains are regularly arranged. For example, general-purpose resins include polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, and engineer plastics include polyamide, polyacetal, polybutylene terephthalate, GF reinforced polyethylene terephthalate, ultrahigh molecular weight polyethylene, polyphenylene sulfide, polyether. Examples include ether ketone, liquid crystal polymer, and fluororesin. In addition, as long as it has crystallinity, it is not limited to these materials, that is, any resin having crystallinity is applicable. For this reason, according to the present invention, it is possible to achieve both mechanical strength and toughness in various resin sheet-like molded articles including general-purpose plastics. These crystalline resins may be used alone, or may be used in combination with the same type and different molecular weights, or may be used in combination with an amorphous resin.

  Next, the fibrous filler will be described. The fibrous filler contained in the sheet-like molded product of the present invention imparts thermal conductivity that cools uniformly and quickly to the inside of the molded product during cooling after resin melting, and the growth of resin crystals generated during resin cooling. Two of the main purposes are to crystallize the crystalline resin by inhibiting it with a fibrous filler. Further, by adding a fibrous filler, effects such as improvement in mechanical properties and dimensional stability due to a decrease in linear expansion coefficient can be obtained.

  For the above two purposes, it is preferable that the fibrous filler has a higher thermal conductivity than the resin, and specifically, carbon fiber (carbon fiber), carbon nanotube, pulp, cellulose, cellulose nanofiber, lignocellulose, lignocellulose. Nanofiber, basic magnesium sulfate fiber (magnesium oxysulfate fiber), potassium titanate fiber, aluminum borate fiber, calcium silicate fiber, calcium carbonate fiber, glass fiber, silicon carbide fiber, wollastonite, zonotlite, various metal fibers Natural fibers such as cotton, silk, wool or hemp, recycled fibers such as jute fibers, rayon or cupra, semi-synthetic fibers such as acetate and promix, polyester, polyacrylonitrile, polyamide, aramid, polyolefin Synthetic fibers such as, more like modified fibers chemically modified on their surface and ends. Of these, carbons, celluloses, and glasses are particularly preferred from the viewpoints of availability, high thermal conductivity, and low linear expansion coefficient, and fibrous fillers composed of these are mixed. Also good.

  The average fiber diameter of the fibrous filler is preferably 5 μm or less in order to microcrystallize crystals in the resin. The reason for this will be described below. From the viewpoint of moldability, the upper limit volume concentration of the filler that can be melted and injected into the resin is determined. As shown in FIG. 3, since the amount of the fibrous filler 2 is smaller than the amount of the fibrous filler 1 at the same fibrous filler volume concentration, the interval N between the large-diameter fibrous fillers 2 having a large fiber diameter is the fiber diameter. Becomes larger than the interval n of the thin fibrous filler 1. Crystals are generated in the crystalline resin 3 upon cooling after melting, but the vicinity of the fibrous filler is particularly easily cooled, and the crystalline resin 3 is rapidly crystallized by the heat transfer effect through the fibrous filler. Therefore, the closer the resin to the fibrous filler, the smaller the crystal grain size, and the farther the resin from the fibrous filler, the larger the crystal. Therefore, when the distance between the fibrous fillers that promotes microcrystallization of the resin is increased, the crystal size is consequently increased. The average fiber diameter of the fibrous filler 1 that can be microcrystallized is calculated by simulation, and is preferably 5 μm or less. The average fiber diameter of the fibrous filler 1 is preferably 5 nm or more in order to microcrystallize the crystals in the resin. The reason for this will be described below. The fibrous filler 1 has a high thermal conductivity, thereby improving the cooling efficiency and realizing the microcrystallization of the resin. However, if the fibrous filler 1 is thin, a sufficient heat conduction effect cannot be obtained, resulting in a crystal grain size. Becomes larger. Similarly to the above, the average fiber diameter of the fibrous filler that can be microcrystallized is calculated by simulation, and is preferably 5 nm or more. From the above, the fiber diameter of the average fibrous filler is preferably 5 nm or more and 5 μm or less.

  The form of the fibrous filler is a variety of three-dimensional directions such as a defibrated cotton, a sheet solidified by papermaking, a compressed soul, and a granule with a certain size or more in any three-dimensional direction. Is used. A fiber-dispersed resin can be obtained by melt-kneading these together with a resin. Other forms include short fiber form, long fiber form, and cloth form, but in the manufacturing method in which these linear or planar fibrous fillers are impregnated and melted, the fibers aggregate at the center in the film thickness direction during impregnation. Therefore, a large amount of fibrous filler is present in the central part in the film thickness direction, and the mechanical properties and wear properties in the vicinity of the surface are deteriorated.

  The structure of the fibrous filler in the heat stretching process (step 4 in FIG. 2) will be described. As shown in FIG. 4, by dispersing the fibrous filler 7 in the crystalline resin 3 by melt kneading, it can be uniformly dispersed in the film thickness direction (step 1 in FIG. 2, step A in FIG. 4). ). Thereafter, when heated and stretched, the surface side of the crystalline resin 3 is further stretched. This is because the load applied during stretching is a frictional force and is transmitted from the surface of the crystalline resin 3 (step B in FIG. 4). By stretching the surface side, the fiber filler 7 on the surface side is oriented in the stretching direction and the film thickness is reduced at the same time. As a result, a large amount of fibrous filler 1 is present on the surface side. Therefore, the concentration in the thickness direction of the fibrous filler 7 in the sheet-like molded product is such that the concentration on the surface side> the concentration on the inner surface side. That is, in the thickness direction of the fibrous filler 7, the concentration of the fibrous filler 7 increases from the center to the surface side. Therefore, the mechanical characteristics and wear characteristics near the surface can be improved (step C in FIG. 4). Heretofore, there has been a case where resin molding is performed by impregnating a fibrous filler in a mold. In this case, as shown in FIG. 5, when the resin 6 is pressed with the two molds 4, the impregnated fibrous filler 5 tends to remain in the center of the resin 6, and mechanical properties such as the hardness and wear characteristics of the resin surface. In some cases, the strength was weakened. On the other hand, in the said method, the density | concentration of the fibrous filler 7 becomes high as it goes to the surface side from a center part, and it can improve the mechanical characteristic and wear characteristic of the surface vicinity.

  These fibrous fillers are used for various titanate coupling agents, silane coupling agents, unsaturated carboxylic acids for the purpose of improving the adhesiveness with the crystalline resin or the dispersibility in the resin composition. , Maleic acid, maleic anhydride, or a modified polyolefin grafted with an anhydride thereof, fatty acid, fatty acid metal salt, fatty acid ester or the like may be used. Or even if the surface is treated with a thermosetting or thermoplastic polymer component and modified, there is no problem.

  Next, a manufacturing method will be described. First, as a heating step, a crystalline resin having the above-described configuration, a fibrous filler, a dispersant, and other additives as necessary are mixed and heated to a temperature equal to or higher than the melting point of the crystalline resin to obtain a melt. . Next, as a cooling step, the melted mixture is formed into a sheet shape, and then the sheet material is air-cooled and cooled to a temperature below the melting point to form a mesophase in the crystalline resin. Next, as the heating and stretching step, the crystalline resin containing the mesophase is heated to a temperature range between the glass transition temperature and the melting point of the crystalline resin, and the sheet-shaped material formed into a sheet shape is stretched. Here, since it has been confirmed by experiments and simulations that the sheet material is stretched by 1.2 times to 5 times, it can be stretched by 1.2 times to 5 times. preferable.

  In the manufacturing method described above, in the cooling step, the crystalline resin melt is allowed to cool to air below the crystallization temperature range by air cooling, thereby suppressing crystal growth in the crystalline resin. A mesophase, which is an intermediate phase with amorphous, is formed. Usually, when crystallizing the melt of the crystalline resin, it is necessary to quench with cold water or the like. However, by adding a fibrous filler having a high thermal conductivity, cooling is promoted. A mesophase is formed by partly crystallizing and partly remaining as an amorphous part. Thus, the fibrous filler plays the following two roles in forming the mesophase during cooling. The first role is that the thermal conductivity of the fibrous filler is higher than that of the resin, so that the inside is uniformly and efficiently cooled. When the fibrous filler is not added, in order to cool and crystallize sufficiently inside the crystalline resin, it was necessary to rapidly cool at a low temperature and rapidly, but by adding a fibrous filler, it was cooled by air. However, it can be sufficiently cooled to the inside, and a mesophase can also be formed inside. As described above, it is cooled by addition of fibrous filler, but depending on the crystallization characteristics of the crystalline resin material, water, ice water, antifreeze, cooling solvent, cooling roll, so that a mesophase in an appropriate state is formed. You may cool using a cooling plate, cold wind, etc. The second role is to promote the formation of a mesophase by causing the fibrous filler to physically inhibit crystal growth, thereby inhibiting crystallization and leaving an amorphous part. In addition, since the crystal growth is physically inhibited, the grain size of the crystal portion can be reduced. Due to the two roles of the fibrous filler, a mesophase can be formed inside the crystalline resin.

  The mesophase becomes microcrystals in the heating and stretching step, but since the mesophase is cooled in order from the surface in the film thickness direction, the mesophase is internally formed with a lot of mesophase on the surface side of the amorphous part, As a result, the crystallinity on the surface side becomes higher than the crystallinity on the inner surface side. The high crystallinity on the sheet surface side improves the mechanical and wear characteristics of the sheet surface.

  In the heating and stretching step, the crystalline resin is heated, whereby the mesophase becomes α-phase microcrystals. By forming a large amount of α-phase microcrystals, the difference in density between the crystalline portion and the amorphous portion becomes large. Stretching is difficult if the crystal is large or the degree of crystallinity is high, but since a large amount of microcrystals can be formed and there are many amorphous parts, breakage does not easily occur even when stretched, and the crystal size is small. Therefore, the degree of orientation can be improved. The optimum crystallinity at this time is estimated by simulation, and is preferably 45% or more and 80% or less. Further, since the molecular chain is stretched by stretching and the molecular chain is arranged and stiffened even in the amorphous part, a high strength can be realized even if the crystallinity is not extremely high. Specific stretching methods that can achieve the above include uniaxial stretching, biaxial simultaneous stretching, biaxial sequential stretching, roll stretching, and the like. In these stretching methods, since the inner side in the stretching direction is further stretched, the fibrous filler is oriented in the stretching direction. As a result, the degree of orientation of the fibrous filler in the film thickness direction is smaller on the inner side in the direction perpendicular to the stretching direction than on the outer side. When molding a resin molded product, this sheet-like molded product is used for press molding, placed in a mold so as to cancel the orientation generated at the time of press molding, and the portion stretched by bending is a region with a small orientation, By making the portion that shrinks by bending work into a region having a large orientation, the orientation of the resin can be entirely smoothed even in a molded body having a large curvature, and the appearance after press molding is improved.

Hereinafter, each example and each comparative example in the experiment conducted by the inventors will be described.
Example 1
Pulp-dispersed polypropylene pellets were produced as sheet-like molded products by the following production method.

  Polypropylene (manufactured by Prime Polymer Co., Ltd.) (product name: J108M), cotton-made soft cotton pulp (trade name: NBKP Celgar) as a fibrous filler, and maleic anhydride (trade name: Umex (trade name: Sanyo Kasei Kogyo Co., Ltd.) as a dispersant. (Registered trademark)) was weighed to a weight ratio of 100: 15: 5 and dry blended. Pulp having an average fiber diameter of 1 μm and a thermal conductivity of 0.6 W / (m · K) was used. The thermal conductivity of polypropylene was 0.15 W / (m · K). Thereafter, the mixture was melt-kneaded and dispersed with a twin-screw kneader (KRC kneader manufactured by Kurimoto Iron Works Co., Ltd.) to produce pulp-dispersed polypropylene pellets.

  The produced pulp-dispersed polypropylene pellets are placed on a SUS plate, the pellets are surrounded by a 2 mm thick shim plate in a rectangular shape, and another SUS plate is placed thereon, and a flat plate heat press with a temperature of 200 ° C. (11FD manufactured by Imoto Seisakusho Co., Ltd.), and a 3t load was applied to obtain a sheet-like melt.

The molten sheet resin was sandwiched between SUS plates, left on an iron plate, and allowed to cool at room temperature. After cooling to room temperature, the resin sheet was taken out to obtain a 2 mm thick resin sheet.
The obtained resin sheet was sequentially biaxially stretched at 150 ° C. with a biaxial stretching machine (11A9, manufactured by Imoto Seisakusho Co., Ltd.). The draw ratio was 3 times. Thus, a pulp fiber-dispersed polypropylene sheet was obtained.

The obtained pulp-dispersed polypropylene sheet was evaluated by the following method.
The obtained sheet was punched into a dumbbell shape, and the tensile strength and elastic modulus were measured with a tensile test apparatus. As a result, it was confirmed that the tensile strength was 200 MPa and the elastic modulus was 4 GPa, which was higher than that of general unstretched polypropylene.

  The obtained sheet was subjected to wide-angle X-ray diffraction measurement, and the crystallinity was calculated. First, from the wide-angle X-ray diffraction measurement of the sheet surface, the crystallinity on the outer surface of the sheet was 74%. The sheet was then polished to half thickness. From the wide-angle X-ray diffraction measurement of the polished surface, the crystallinity on the inner surface side of the sheet was 70%.

The obtained sheet was subjected to small-angle X-ray scattering measurement to estimate the crystal size. As a result, it was estimated that it was 100 nm or less, and it was confirmed that it was microcrystallized.
About the obtained sheet | seat, the thermogravimetric analysis was performed and content of the pulp was computed. Similarly to the above, by polishing to half the thickness of the sheet, the pulp contents on the outer side of the sheet and on the inner side of the sheet were calculated and were 15.2% and 15%, respectively.

  About the obtained sheet | seat, TMA thermal analysis was performed and the thermal linear expansion coefficient was computed. The thermal expansion coefficient of the obtained sheet was 40 ppm / K, which was a low linear expansion coefficient for the resin, and the dimensional stability was better than that of the sheet of polypropylene alone.

  About the obtained sheet | seat, the abrasion test was done and the abrasion property of the sheet | seat surface was evaluated relatively. The member to be worn is SUS, a wear test is performed at a load of 30 MPa for 10 minutes, and a three-level evaluation (○: no wear, Δ: no decrease in film thickness, but surface roughening, ×: film thickness decrease) Went. The sheet of Example 1 resulted without wear.

About the obtained sheet | seat, press molding was performed and the external appearance evaluation after shaping | molding was performed. Since the sheet was produced by stretching, the stretching ratio was relatively low on the inner side in the sheet thickness direction, and therefore the degree of orientation in the film thickness direction of the pulp fibers was lower than on the outer side. As described above, since the degree of orientation in the film thickness direction varies depending on the location of a single sheet, by arranging a portion having a high degree of orientation in a portion that is stretched during press molding, color unevenness of the sheet after press molding is reduced. The appearance is uniform and the appearance is improved.
(Example 2)
In Example 2, only the cooling method of Example 1 and the sheet was changed, and a pulp-dispersed polypropylene sheet was produced. While the molten resin sheet was sandwiched between SUS plates, it was immersed in ice water and rapidly cooled. A fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except for rapid cooling, and the same evaluation was performed.
(Example 3)
In Example 3, a pulp-dispersed polypropylene sheet was prepared with a thickness before stretching of 0.5 mm. By setting the shim plate thickness to 0.5 mm, a pulp-dispersed polypropylene sheet having a thickness of 0.5 mm was obtained. A fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that the thickness was reduced, and the same evaluation was performed.
Example 4
In Example 4, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that the fibrous filler was carbon fiber, and the same evaluation was performed.
(Example 5)
In Example 5, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that the fibrous filler was glass fiber, and the same evaluation was performed.
(Comparative Example 1)
In Comparative Example 1, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that the fibrous filler was a polypropylene fiber having an average fiber diameter of 5 μm and low thermal conductivity (hereinafter referred to as PPFRP), and the same evaluation was performed. .
(Comparative Example 2)
In Comparative Example 2, a fiber-dispersed polypropylene sheet was produced in the same manner as in Example 1 except that the sheet cooling method was gradually cooled, and the same evaluation was performed. As a method of gradual cooling, a molten resin sheet was produced by a flat plate press, and the flat plate press was turned off and slowly cooled without taking out the resin sheet.
(Comparative Example 3)
In Comparative Example 3, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that the average fiber diameter of the pulp fibers was 10 μm, and the same evaluation was performed.
(Comparative Example 4)
In Comparative Example 4, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that the fibrous filler mixing method was impregnated, and the same evaluation was performed. The impregnation was performed when the resin was melted with a flat plate press. The pulp was placed together with the resin pellets, sandwiched between flat plate heat presses at a temperature of 200 ° C., and a load of 3 t was applied to obtain a sheet-like melt impregnated with the pulp. Thereafter, a fiber-dispersed polypropylene sheet was produced in the same manner as in Example 1.
(Comparative Example 5)
In Comparative Example 5, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that only the base material resin to which no fibrous filler was added was used, and the same evaluation was performed.
(Comparative Example 6)
In Comparative Example 6, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that a crystal nucleating agent (Gerol (registered trademark) manufactured by Shin Nippon Rika Co., Ltd.) was added to the polypropylene material, and the same evaluation was performed.
(Comparative Example 7)
In Comparative Example 7, a fiber-dispersed polypropylene sheet was prepared in the same manner as in Example 1 except that the film manufacturing method was an extrusion method using a T-die, and the same evaluation was performed. Extrusion was performed by attaching a T-die unit to a KRC kneader to produce a fiber-dispersed polypropylene sheet.

  The measurement results in Examples 1 to 5 and Comparative Examples 1 to 7 will be described with reference to FIG. FIG. 6 shows a table summarizing the measurement results. The standard of evaluation is mainly performed by comparing with a conventional polypropylene sheet-like molded product.

  As is clear from FIG. 6, in Example 2 in which only the sheet cooling method was changed to rapid cooling using pulp, the crystallinity became higher and the strength and elastic modulus increased. That is, the strength increases even if the pulp is allowed to cool by adding pulp, but the strength increases more by rapid cooling. Even in Example 3 in which the thickness of the resin was reduced, it was easily cooled, resulting in an increase in strength and elastic modulus. In Examples 4 and 5 using carbon fibers and glass fibers, which are fibers other than pulp, the strength was increased even if the crystallinity was not so high. In Examples 2 to 5, as in Example 1, the outer crystallinity was high and the concentration of the fibrous filler was high, resulting in good wear resistance. Moreover, since the linear expansion coefficient was lowered by the fibrous filler, the dimensional stability was also good.

  In Comparative Example 1 in which the filler was PPFRP having a low thermal conductivity, the internal cooling rate was slow, the crystal size was large, and the crystallinity was high. As a result, strength and elastic modulus decreased. Moreover, since the linear expansion coefficient of the filler was not low, dimensional stability was poor.

In Comparative Example 2 in which the sheet cooling method was gradually cooled, the cooling rate inside was slow, the crystal size was increased, and the crystallinity was increased. As a result, strength and elastic modulus were insufficient.
In Comparative Example 3 in which the filler diameter was increased to 10 μm, it was not sufficiently dispersed in the resin and a cooling effect could not be obtained, so that the crystal size was increased and the crystallinity was increased. As a result, strength and elastic modulus were insufficient.

In Comparative Example 4 in which the filler mixing method was impregnated, the strength was ensured, but the crystallinity was low and the filler concentration was also on the inner surface side> surface side, resulting in insufficient wear resistance.
In Comparative Example 5 in which the filler was not added and only the base material resin was used, the cooling was not sufficient, the crystal size increased, and the crystallinity increased. As a result, the strength and elastic modulus were unexpected. Moreover, the linear expansion coefficient did not decrease, resulting in poor dimensional stability.

In Comparative Example 6 in which the crystal nucleating agent was added, the degree of crystallinity was increased to 85% or more and the elastic modulus was increased, but because the strength was low, the toughness was low and the result was easily broken.
In Comparative Example 7 in which the film manufacturing method was T-die extrusion, the appearance during press molding was not uniform and the appearance was poor. In addition, the strength was not increased by stretching.

  From the above evaluation, a fiber-dispersed sheet is produced by stretching, including a fibrous filler having a higher thermal conductivity than the crystalline resin of the base material so that the fiber diameter of the fibrous filler is 5 nm to 5 μm. As a result, it was found that even if the degree of crystallinity is not so high, a sheet-like molded article having high strength can be obtained. Further, it was found that a sheet-like molded article having improved surface wear resistance can be obtained by easily forming microcrystals on the surface side during cooling and easily gathering fillers on the surface by stretching.

  INDUSTRIAL APPLICATION This invention can aim at reinforcement | strengthening of the mechanical strength of a sheet-like molded object, and is useful for the sheet-like molded object used for press molding, its manufacturing method, etc.

DESCRIPTION OF SYMBOLS 1 Fibrous filler 2 Fibrous filler 3 Crystalline resin 4 Mold 5 Fibrous filler 6 Resin 7 Fibrous filler

Claims (10)

A heating and melting step of melting and mixing the crystalline resin and a fibrous filler having a higher thermal conductivity than the crystalline resin at a temperature equal to or higher than the melting point of the crystalline resin;
A molding step of molding the melted mixture into a sheet-like mixture;
A cooling step of cooling the sheet-like mixture at a temperature below the melting point of the crystalline resin;
A method of producing a sheet-like molded product, comprising: a heating and stretching step of stretching the cooled sheet-like mixture in a temperature range of a glass transition temperature to a melting point of the crystalline resin.   The method for producing a sheet-like molded product according to claim 1, wherein in the heating and stretching step, the sheet-like mixture is stretched 1.2 times or more and 5 times or less.   A composite resin comprising a crystalline resin and a fibrous filler having a higher thermal conductivity than the crystalline resin, wherein a crystal part and an amorphous part are mixed, and the average crystallinity of the composite resin is 45% or more and 80% A sheet-like molded product characterized by the following.   The sheet-like molded product according to claim 3, wherein in the thickness direction in the composite resin, the concentration of the fibrous filler increases from the inside toward the surface portion.   The fibrous filler is oriented in the direction parallel to the stretching direction in the heating and stretching step, and in the thickness direction in the composite resin, the degree of orientation of the fibrous filler increases from the inside toward the surface portion. The sheet-like molded product according to claim 3 or 4, characterized by the above.   The sheet-like molded product according to any one of claims 3 to 5, wherein in the thickness direction in the composite resin, the degree of crystallization increases from the inside toward the surface portion.   The sheet-like molded product according to any one of claims 3 to 6, wherein the fibrous filler is fibrous, and an average central diameter of the fibrous filler is 5 nm or more and 5 µm or less.   The sheet-like molded product according to any one of claims 3 to 7, wherein the fibrous filler is any one of a carbon filler, a cellulose filler, and a glass filler, or a combination thereof.   The sheet-like molded product according to any one of claims 3 to 8, wherein an absolute value of a linear expansion coefficient of the composite resin is smaller than an absolute value of a linear expansion coefficient of the crystalline resin.   The sheet-like molded product according to any one of claims 3 to 9, wherein an average diameter of crystals in the crystal part is 5 nm or more and 5 µm or less.

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