JP7603501B2 - Method for manufacturing plate-shaped resin molded body - Google Patents

Description

The present invention relates to a method and apparatus for producing a plate-shaped resin molding by extrusion molding of a thermoplastic resin, and to a plate-shaped resin molding produced by this method and apparatus.

A plate-shaped resin molding (resin plate) is generally produced by extruding molten thermoplastic resin downward from a die and then cooling it using a cooling roll (see, for example, Patent Document 1). A method of cooling using a combination of a cooling roll and water cooling has also been proposed (see, for example, Patent Document 2). In the method of producing a crystalline thermoplastic resin plate described in Patent Document 2, cooled nip rolls are placed directly below the die, and the plate-shaped crystalline thermoplastic resin extruded in a molten state from the die is primarily cooled while being pinched between the nip rolls to harden the surface of the plate-shaped body, and then the plate-shaped body is further guided into a water tank placed below the nip rolls for cooling.

Furthermore, in the case of a fluororesin molded product, there is a problem that the surface becomes rough when the product is extruded. To obtain a molded product with a smoother surface, a method has been proposed in which the product is sandwiched between smooth molds and compression molded under molding conditions of a molding temperature of 270 to 340°C, a molding pressure of 10 kg/cm2 ^or more, and a compression time of 2 minutes or more (see Patent Document 3).

JP 2012-121142 A JP 2000-351148 A Japanese Patent Application Publication No. 6-293069

However, the conventional manufacturing methods described in Patent Documents 1 and 2 have the problem that when molding using a resin with high hardness or bending elasticity, the diameter of the cooling roll or the roll for changing the take-off direction must be large, limiting the resins that can be used. In addition, the manufacturing method described in Patent Document 2 allows for continuous molding, so it can produce long molded products, but depending on the nip roll conditions and the resin used, there is a risk of the molded product having poor appearance such as foaming or warping.

On the other hand, the compression molding method described in Patent Document 3 can be applied to resins with high hardness and bending elasticity, and is less prone to warping, but is not suitable for producing long molded bodies and has poor productivity due to the long processing time.

Therefore, the present invention aims to provide a method and apparatus for continuously producing plate-shaped resin moldings with good appearance and high thickness accuracy using a thermoplastic resin with a fast crystallization rate, and to provide a plate-shaped resin molding that is made of a thermoplastic resin with a fast crystallization rate and has good appearance and high thickness accuracy.

The inventors conducted extensive research to solve the above-mentioned problems, and came to the following findings. One of the factors to consider when processing crystalline thermoplastic resins is the crystallization rate. If the crystallization rate is fast, the time it takes for the molten resin to solidify is short. If the resin is deformed during solidification, it may solidify into that shape, and the desired dimensions and shape may not be obtained. On the other hand, as solidification progresses, the rigidity increases, making it difficult to change direction within the production line. The inventors therefore discovered a manufacturing method and manufacturing device configuration that is useful even for resins with a fast crystallization rate, and arrived at the present invention.

The method for producing a plate-shaped resin molding according to the present invention includes the steps of heating and melting a thermoplastic resin having a difference between its melting point and crystallization temperature of 50° C. or less, and extruding the resin melt extruded from the die in a horizontal or oblique direction, and clamping the resin melt extruded from the die from above and below with multiple pairs of cooling rolls arranged in series and cooling the resin melt while taking it up in the same direction as the extrusion direction, to obtain a resin original plate having a side length perpendicular to the take-up direction of 10 to 3000 mm and a thickness of 1 to 50 mm, wherein the temperature of the downstream cooling roll is lower than that of the upstream cooling roll, and when the melting point of the thermoplastic resin is T _mp (° C.), the temperature T ₁ (° C.) of the first pair of cooling rolls counting from the die satisfies the following mathematical formula 1, and when the temperature of the nth pair of cooling rolls counting from the die is T _n (° C.) and the temperature of the (n-1)th pair of cooling rolls is T _n-1 (° C.), the following mathematical formula 2 is satisfied .

In the method for producing a plate-shaped resin molding of the present invention, a thermoplastic fluorine-based resin can be used as the thermoplastic resin.
The resin base plate has, for example, a flexural modulus of 500 MPa or more and a durometer D hardness of 56 or more .

The method for producing a plate-shaped resin molding of the present invention may involve cooling a resin melt using one or more cooling rolls having a surface formed with a concave-convex shape and/or pattern, thereby imparting a concave-convex shape to one or both surfaces of the resulting plate-shaped resin molding.
The method for producing a plate-shaped resin molding of the present invention may further include a step of cutting the resin base plate into a predetermined size.

The manufacturing device for plate-shaped resin moldings according to the present invention has an extruder that extrudes the resin melt in a horizontal or oblique direction from a die with a rectangular opening, and multiple pairs of cooling rolls that are arranged immediately after the extruder and clamp the resin melt extruded from the die from above and below, and cool it while taking it up in the same direction as the extrusion direction, and the extruder and each pair of cooling rolls are arranged in series so that the take-up direction of the resin melt is constant.

The plate-shaped resin molding according to the present invention is a plate-shaped resin molding formed by extrusion molding, made of a thermoplastic resin with a difference between the melting point and the crystallization temperature of 50°C or less, with short sides of 10 to 1500 mm, long sides of 10 to 3000 mm, a thickness of 1 to 50 mm, a flexural modulus of 500 MPa or more, and a durometer D hardness of 56 or more.

In addition, "horizontal" in this invention also includes "approximately horizontal," and the same applies in the following explanation.

According to the present invention, a plate-shaped molded product with good appearance and high thickness accuracy can be manufactured using a thermoplastic resin with a fast crystallization rate.

2 is a flowchart showing steps of a method for producing a plate-shaped resin molding according to an embodiment of the present invention. 1 is a schematic diagram showing a configuration of a manufacturing apparatus for a plate-shaped resin molding according to an embodiment of the present invention.

The following describes in detail the embodiments of the present invention with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

Figure 1 is a flow chart showing the steps of a method for producing a plate-shaped resin molding according to an embodiment of the present invention. The method for producing a plate-shaped resin molding according to this embodiment is a method for producing a plate-shaped resin molding by melt extrusion molding, and as shown in Figure 1, includes an extrusion step S1 in which a resin melt is extruded horizontally or obliquely from a die, and a cooling step S2 in which the resin melt is cooled by a cooling roll. In addition, the method for producing a plate-shaped resin molding according to this embodiment also includes a cutting step S3 in which the resin base plate obtained by the extrusion step S1 and the cooling step S2 is cut, as necessary.

[Extrusion step S1]
In the extrusion step S1, a thermoplastic resin having a difference between its melting point and crystallization temperature of 50° C. or less is heated and melted by an extrusion molding machine, and extruded from a die in a horizontal or oblique direction. The "melting point" and "crystallization temperature" of a thermoplastic resin can be measured by a method specified in ASTM D3418. One of the problems that can occur in processing a thermoplastic resin is "foaming." One of the factors that causes foaming in a resin molded product is that when the resin melt is cooled and solidified, the volume shrinks by about several percent due to crystallization at the crystallization temperature. Since the resin melt is cooled from the surface, the solidification of the resin progresses from the surface toward the inside, and it is considered that there is insufficient shrinkage allowance when the resin inside the resin melt solidifies and shrinks, causing foaming inside the molded product.

When foaming occurs in a molded product, it not only causes a loss of product value due to poor appearance, but also often leads to other problems such as dimensional variation and deformation. To prevent this, it is necessary to control the crystallization rate and cooling rate, but generally, the smaller the difference between the melting point and crystallization temperature, the higher the crystallization rate becomes, making it more difficult to control. Polypropylene, which is widely used around the world, also has a difference between its melting point and crystallization temperature of about 50°C, but due to its general-purpose convenience, processing know-how is being accumulated. On the other hand, among thermoplastic resins that are not used as much as polypropylene and have a difference between their melting point and crystallization temperature of 50°C or less, there are some materials that are more difficult to suppress foaming. If it were possible to obtain molded products with excellent appearance without foaming from these materials, it would be possible to expand the range of applications for these resins.

Examples of thermoplastic resins with a difference between the melting point and the crystallization temperature of 50°C or less include aliphatic polyamide resins, aromatic polyamide resins, polyacetal resins, polyester resins, PEEK (polyether ether ketone) resins, LCP (liquid crystal polymer) resins, PPS (polyphenylene sulfide) resins, and thermoplastic fluorine-based resins. Each of the aforementioned resins may be used alone, or multiple resins may be mixed together.

Among the resins mentioned above, it has been considered difficult to manufacture long plate-shaped molded products from thermoplastic fluororesins in the past, but by applying the manufacturing method of this embodiment, it is possible to obtain long plate-shaped molded products with excellent appearance and thickness accuracy. Examples of thermoplastic fluororesins used in the manufacturing method of this embodiment include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVdF), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinyl fluoride (PVF), chlorotrifluoroethylene-ethylene copolymer (ECTFE), and mixtures thereof.

The extrusion conditions for the thermoplastic resin are not particularly limited and can be set appropriately depending on the type of resin used. The type of die used for extrusion molding is also not particularly limited, and a T-die, a coat hanger die, or any other die with an opening can be used. Furthermore, the height of the die opening is preferably 1.1 to 2.0 times the thickness of the plate-shaped resin molding (resin base plate) to be manufactured. If the height of the opening is less than 1.1 times the thickness of the plate-shaped resin molding, there is a risk that some parts will not come into contact with the cooling roll due to slight differences in the flow rate distribution in the width direction of the resin melt, and if the height of the die opening exceeds 2.0 times, it becomes difficult to press the resin to the specified thickness with the cooling roll.

The thickness of the final plate-shaped resin molding is largely determined by the spacing between the cooling rolls, but is also affected by the subsequent elongation caused by the take-up. Therefore, it is preferable to adjust the height of the die opening, the spacing between the cooling rolls, the temperature of each cooling roll, the number of cooling rolls, and the extruder temperature while taking into account the take-up speed.

[Cooling step S2]
In the cooling step S2, the resin melt extruded from the die is clamped from above and below between multiple pairs of cooling rolls arranged in series and cooled while being drawn in the same direction as the extrusion direction, to obtain a resin base plate having a side length perpendicular to the drawing direction of 10 to 3000 mm and a thickness of 1 to 50 mm. By thus clamping and cooling between a pair of upper and lower cooling rolls, the shaping and cooling of the resin melt can be performed simultaneously and continuously, improving productivity.

In addition, in the manufacturing method of the plate-shaped resin molding of this embodiment, the cooling rate can be adjusted to the optimum for the resin used by arbitrarily setting the number of cooling rolls and the temperature, so that the plate-shaped resin molding can be prevented from having poor appearance such as foaming. Furthermore, by using a rotating body such as a roller, the resistance when the molten resin passes through can be minimized, preventing surface defects on the plate-shaped resin molding and improving dimensional stability.

The temperature of each cooling roll is not particularly limited, but the temperature of the downstream cooling roll is set to be lower than that of the upstream cooling roll, and further, when the melting point of the thermoplastic resin is _Tmp (°C), the temperature _T1 (°C) of the first pair of cooling rolls counting from the die satisfies the following mathematical formula 3. This makes it possible to obtain a resin base plate that is free from foaming, warping, and scratches and has a good appearance.

It is preferable to set the temperature of each cooling roll so as to satisfy the following formula 4, where T _n (°C) is the temperature of the nth cooling roll counting from the die, and T _n-1 (°C) is the temperature of the (n-1)th cooling roll.

This makes it possible to prevent foaming through slow cooling while ensuring production stability and warping suppression through effective cooling. As slow cooling to prevent foaming in the manufacturing process of resin molded products, methods that use warm water or a cooling medium with a small heat transfer coefficient (such as air) are generally known, but methods that use warm water cannot be applied because it is difficult to use at temperatures above 100°C. In addition, methods that use steam are not preferred because water droplets adhere to the molten resin, causing a defective appearance known as a watermark.

The method using air is not preferred because the resin melt will deform depending on the air volume and speed when a heating device is used. On the other hand, oil can be used by heating it to 100°C or higher, but there is a possibility that the resin melt will swell, and there are restrictions on the materials that can be used. Furthermore, a process of washing the plate-shaped resin molding (resin base plate) after cooling is required, which is not preferred because it increases the number of steps. In contrast, if a cooling roll with a temperature adjusted by a heat medium or the like is used, these problems can be solved and the resin melt can be slowly cooled.

The temperature of the cooling rolls can be controlled by using heat from the resin melt or by using an external heat transfer medium. By using multiple pairs of cooling rolls, the distance between them can be adjusted at any time even if the resin melt shrinks due to cooling. This allows the resin melt to maintain contact with the cooling rolls, enabling effective slow cooling and shaping.

The resin base plate obtained by the cooling step S2 has, for example, a flexural modulus of 500 MPa or more and a durometer D hardness of 56 or more. In the manufacturing method of the plate-shaped resin molding of this embodiment, the take-up direction is constant, so even when using a resin material with such a high flexural modulus or hardness, the resin melt or the resin base plate can be cooled stably without applying a load.

Furthermore, in the method for producing a plate-shaped resin molding of this embodiment, the resin melt may be cooled using one or more cooling rolls having an irregular shape and/or pattern formed on the surface. This results in a plate-shaped resin molding having an irregular shape formed on one or both surfaces. By providing the cooling roll with irregularities in this way, an arbitrary shape can be continuously and consistently imparted to the surface of the resin melt, making it possible to mass-produce plate-shaped resin moldings having irregularities on the surface at low cost. The irregularities imparted to the plate-shaped resin molding may be asymmetric in the top and bottom directions, and even in this case, in the method for producing a plate-shaped resin molding of this embodiment, the occurrence of warping can be suppressed by adjusting the temperature of the cooling roll.

The resin melt cooled by the cooling rolls is taken up by a take-up machine installed, for example, behind (downstream of) the cooling rolls. By passing the resin melt through the cooling rolls, whose temperature is appropriately controlled, the surface state of the resin melt is fixed before it comes into contact with the take-up machine, and a plate-shaped resin molded body (resin base plate) with little foaming, warping, or thickness variation can be obtained. If the resin melt is taken up without cooling by the cooling rolls, there is a risk of deformation or scratches occurring in the take-up machine. Furthermore, if the cooling by the cooling rolls is not gradual, foaming will occur in the plate-shaped resin molded body (resin base plate). Furthermore, if only one pair of cooling rolls is installed, insufficient cooling will cause warping and other problems in the plate-shaped resin molded body.

[Cutting step S3]
The cutting step S3 is a step of cutting the resin original plate obtained by cooling the resin melt in the cooling step S2 to a predetermined size, and is performed as necessary. For example, a resin original plate longer than the required length may be produced and cut to an arbitrary length to obtain a plate-shaped resin molding. The cutting step S3 may be performed continuously from the cooling step S2, or may be performed in a separate step from the extrusion step S1 and the cooling step S2. In either case, the manufacturing efficiency is improved and the manufacturing cost can be reduced compared to molding one sheet at a time to a predetermined size.

[Manufacturing equipment]
Next, an apparatus for carrying out the above-mentioned method for producing a plate-shaped resin molding, i.e., an apparatus for producing a plate-shaped resin molding, will be described. Fig. 2 is a schematic diagram showing the configuration of the apparatus for producing a plate-shaped resin molding of this embodiment. As shown in Fig. 2, the production apparatus 1 of this embodiment includes an extruder 2, a plurality of cooling roll pairs 3, and a take-up machine 4.

<Extruder 2>
The extruder 2 is equipped with a die 5 such as a T-die, a coat hanger die, or a die having any opening, and is arranged so that the opening of the die 5 faces horizontally, diagonally upward, or diagonally downward. In this embodiment, the extruder 2 kneads the thermoplastic resin while heating it, and extrudes the resin melt horizontally or diagonally from the die 5 having a rectangular opening.

<Cooling roll pair 3>
The cooling roll pair 3 is composed of an upper and lower pair of cooling rolls 3a, 3b, which clamp the resin melt extruded from the die 5 from above and below and cool it while taking it up in the same direction as the extrusion direction. The extruder 2 and each cooling roll pair 3 are arranged in series so that the take-up direction of the resin melt is constant. Specifically, multiple pairs are arranged downstream of the die 5 so that the center point of the opening of the die 5 of the extruder 2 and the center point of the interval (gap) between the cooling roll pairs 3 are located on the same straight line, that is, so that the take-up direction of the resin melt is constant.

Each of the cooling rolls 3a, 3b of the cooling roll pair 3 has a mechanism that can rotate while sandwiching the resin melt between the top and bottom, and is structured to be heated from either the inside or the outside, or both. For example, an example of heating from the inside is a structure that forcibly circulates a heat medium inside. In addition, the surfaces of the cooling rolls 3a, 3b may be plated with a metal material such as chrome, or coated with a fluororesin. By applying a fluororesin coating, it is possible to reduce surface unevenness caused by sticking when using a highly sticky resin.

<Removal machine 4>
The take-up machine 4 may be any device capable of gripping the plate-shaped resin molding (resin base plate) and taking it up at a constant speed. The take-up machine 4 is disposed behind (downstream of) the pair of cooling rolls 3 so that the take-up direction of the resin melt is constant.

<Operation>
When a plate-shaped resin molding is manufactured using the above-mentioned manufacturing apparatus, the temperature of each of the cooling rolls 3a and 3b of the cooling roll pair 3 is adjusted in advance. Then, the resin melt melted by the extruder 2 is extruded from the die 5 in a horizontal or oblique direction, and is sandwiched from above and below by the cooling rolls 3a and 3b of the cooling roll pair 3, and is cooled while being taken up in the same direction as the extrusion direction. At this time, the temperature T ₁ (°C) of the first pair of cooling rolls 3 is set to a temperature that is 0.2 times or more the melting point T _mp (°C) of the thermoplastic resin and less than the melting point T _mp (°C), and further, the temperature of the cooling roll pair 3 is made lower toward the downstream side. As a result, the resin melt is slowly cooled by the cooling roll pair 3, the surface of the resin melt is hardened, and a plate-shaped resin molding (resin original plate) with a predetermined thickness and good surface condition is manufactured.

[Plate-shaped resin molded body]
Next, a plate-shaped resin molded product manufactured by the above-mentioned method and device will be described. The plate-shaped resin molded product of this embodiment is a plate-shaped resin molded product formed by extrusion molding, made of a thermoplastic resin with a difference between the melting point and the crystallization temperature of 50° C. or less, with a short side of 10 to 1500 mm, a long side of 10 to 3000 mm, a thickness of 1 to 50 mm, a flexural modulus of 500 MPa or more, preferably 500 to 20000 MPa, and a hardness of 56 or more in Durometer D hardness, preferably 56 or more in Durometer D hardness and 130 or less in Rockwell R hardness.

As described above in detail, in the method for producing a plate-shaped resin molding of this embodiment, the resin melt extruded from the die in a horizontal or oblique direction is cooled while being pulled in the same direction as the extrusion direction while being clamped from above and below between multiple pairs of cooling rolls, so that the pulling direction is constant and the resin melt can be cooled without being deformed. As a result, even if a resin with a high bending modulus or hardness is used, a plate-shaped resin molding of the desired thickness without scratches or deformation can be produced.

In addition, the temperature of the downstream cooling roll is set lower than that of the upstream cooling roll, and the temperature _T1 (°C) of the first pair of cooling rolls counting from the die satisfies the above formula 3. Therefore, the resin melt can be slowly cooled at an appropriate temperature according to the thermal properties of the thermoplastic resin used, and foaming in the plate-shaped resin molding can be prevented.

On the other hand, when the resin melt is passed through the cooling roll in an S-shape or U-shape as in the conventional manufacturing method, deformation due to bending tendency may occur in the plate-shaped resin molding, and when it is passed while twisting, deformation due to twisting may occur in the plate-shaped resin molding. Furthermore, the rigidity of the plate-shaped resin molding (resin original plate) varies depending on the type of resin material used and the dimensions and structure of the molding to be manufactured. For example, moldings with high rigidity generally have a large minimum bending radius, and in the equipment configuration of the conventional manufacturing method, the roll diameter of the cooling roll must be increased to cope with this, resulting in increased equipment costs and installation space. Furthermore, forcible bending may damage the molding and impair the product characteristics (transparency, bending resistance, flatness, etc.).

In contrast, the method for manufacturing a resin plate according to this embodiment requires less installation space and can mold a highly rigid resin plate without causing foaming, deformation, or scratches.

The effects of the present invention will be specifically described below with reference to examples and comparative examples. In these examples, plate-shaped resin molded bodies of the examples and comparative examples were produced by the methods described below, and the thickness accuracy and appearance were evaluated.

Example 1
Using the manufacturing apparatus 1 shown in FIG. 1, five pairs of cooling rolls 3a and 3b were installed, and the take-up speed was set to 4 cm/min. A plate-shaped resin molded body was manufactured from PFA (Solvay's Hyflon P420, melting point 315°C, crystallization temperature 275°C) having a thickness of 10 mm, a length (cut length) of 2000 mm, and a width of 1000 mm. At that time, a coat hanger die having a width of 1100 mm was used as the die 5, and the die lip interval (height of the die opening) was set to 13 mm. The extrusion conditions were a die temperature of 420°C and a rotation speed of 50 rpm (equivalent to 40 kg/h). The temperature of each cooling roll 3a and 3b was set to be successively lower from upstream to downstream in the range of 65 to 25°C.

Example 2
A plate-shaped resin molding made of PFA and having a thickness of 10 mm was produced under the same method and conditions as in Example 1 described above, except that the temperature of each cooling roll 3a, 3b was successively decreased from upstream to downstream within the range of 250 to 50°C.

Example 3
A plate-shaped resin molding made of PFA and having a thickness of 10 mm was produced under the same method and conditions as in Example 1 described above, except that the temperature of each cooling roll 3a, 3b was successively decreased from upstream to downstream within the range of 250 to 170°C.

Example 4
A plate-shaped resin molding made of PFA and having a thickness of 1 mm was produced under the same method and conditions as in Example 1 described above, except that the die lip interval (height of the die opening) was set to 1.3 mm, the number of pairs of cooling rolls 3a, 3b was set to three, the temperature of each of the cooling rolls 3a, 3b was set to be successively lower from upstream to downstream in the range of 250 to 210°C, and the take-up speed was set to 40 cm/min.

<Comparative Example 1>
A plate-shaped resin molding made of PFA and having a thickness of 10 mm was produced under the same method and conditions as in Example 1 described above, except that the temperature of each cooling roll 3a, 3b was successively decreased from upstream to downstream within the range of 50 to 20°C.

<Comparative Example 2>
A plate-shaped resin molding made of PFA and having a thickness of 10 mm was produced in the same manner and under the same conditions as in Example 1, except that a pair of cooling rolls was used and the temperature of each of the cooling rolls 3a, 3b was set to 250°C.

<Comparative Example 3>
Except for the fact that shaping and cooling were performed by sizing instead of the cooling rolls 3a and 3b, a plate-shaped resin molding made of PFA and having a thickness of 10 mm was produced in the same manner and under the same conditions as in Example 1. The sizing temperature was 80°C.

[evaluation]
Next, the plate-shaped resin moldings of the Examples and Comparative Examples produced by the above-mentioned methods were evaluated by the following methods.

(1) Thickness The thickness of each plate-shaped resin molding was measured using a measuring device such as a thickness gauge. Specifically, an arbitrary location was selected for each plate-shaped resin molding, and measurements were taken at intervals of 1/10 of the total width in the width direction. The measurement positions, as viewed from the take-up direction of each plate-shaped resin molding, were R1, R2, R3, R4, and R5 on the right side from the center, and L1, L2, L3, L4, and L5 on the left side.

(2) Thickness Accuracy: This was calculated by subtracting the minimum thickness from the maximum thickness measured by the method described above.

(3) Flexural modulus: Measured according to the method specified in ASTM D790. The measurement was performed three times, and the average value was calculated.

(4) Hardness Durometer D hardness was measured according to the method specified in ASTM D 790. The measurement was performed three times, and the average value was calculated.

(5) Appearance The appearance of each plate-shaped resin molding was visually observed, and the presence or absence of bubbles, warping, and scratches was evaluated according to the following criteria.
Regarding "foaming," the presence of hollow spaces or unevenness caused by hollow spaces inside and on the surface was rated as x (fail), and the absence of such spaces was rated as ◯ (pass).
For "warpage," a plate-shaped resin molding cut to a length of 50 cm was placed on a horizontal surface such as a desk, and the distance between the horizontal surface and the bottom surface of the plate-shaped resin molding was measured using a microscope, etc., and the maximum value was taken as the amount of warpage. A warpage of less than 0.1 mm was rated as ○ (pass), and a warpage of more than 0.1 mm was rated as × (fail).

"Defects" were evaluated based on the size of harmful abrasions and scratches that were not anticipated during processing and use of the plate-shaped resin molding. Specifically, a product was rated as "○" (pass) when there were no defects or when the maximum value of the defect width was less than 0.05 mm and the maximum value of the defect length was less than 1.0 mm, and "×" (fail) when the minimum value of the defect width was 0.05 mm or more or the minimum value of the defect length was 1 mm or more.
The overall evaluation was made as follows: ◯ (pass) if all three evaluation items were passed, and × (fail) if any one of them was not passed.

The above results are summarized in Table 1 below. Note that the cooling roll temperature shown in Table 1 is the set temperature of the temperature control device, and the sizing temperature is the set temperature of the mold temperature regulator. In addition, the notes in Table 1 below list any defects discovered other than those mentioned above.

As shown in Tables 1 and 2 above, the plate-shaped resin moldings of Examples 1 to 4 produced within the scope of the present invention were good, with little variation in thickness and no appearance defects such as foaming, warping, or scratches. On the other hand, the plate-shaped resin molding of Comparative Example 1, which falls outside the scope of the present invention, had foaming and warping due to the low temperature of the cooling rolls, and the thickness precision was also reduced. Furthermore, the plate-shaped resin molding of Comparative Example 2 had warping and deformation due to the small number of cooling rolls and insufficient cooling time, and the thickness precision was also reduced. Furthermore, the plate-shaped resin molding of Comparative Example 3 had warping and surface scratches due to the resistance caused by the contact of the resin melt with the sizing and the tension caused by the take-up, and the thickness precision was also reduced.

From the above results, it was confirmed that, according to the present invention, it is possible to manufacture plate-shaped resin molded products with excellent thickness accuracy and without foaming, warping, or scratches on the outside, from thin sheets of about 1 mm to thick plates of about 10 mm, using a highly rigid material with a flexural modulus of 500 MPa and a durometer D hardness of 56 or more.

Reference Signs List 1 Apparatus for producing plate-shaped resin molded body 2 Extruder 3 Pair of cooling rolls 3a, 3b Cooling roll 4 Take-up machine 5 Die 6 Plate-shaped resin molded body (resin base plate)

Claims (5)

A step of heating and melting a thermoplastic resin having a difference between its melting point and crystallization temperature of 50° C. or less, and extruding the resin from a die in a horizontal or oblique direction;
the resin molten material extruded from the die is sandwiched between a plurality of pairs of cooling rolls arranged in series from above and below, and cooled while being drawn in the same direction as the extrusion direction, to obtain a resin base plate having a side length perpendicular to the drawing direction of 10 to 3000 mm and a thickness of 1 to 50 mm;
The temperature of the downstream chill roll is lower than that of the upstream chill roll.
When the melting point of the thermoplastic resin is T _mp (° C.), the temperature T ₁ (° C.) of the first pair of cooling rolls counted from the die satisfies the following mathematical formula I:
When the temperature of the nth chill roll counting from the die is T _n (° C.) and the temperature of the (n-1)th chill roll is T _n-1 (° C.), the following formula II is satisfied:
A method for producing a plate-shaped resin molding.

The method for producing a plate-shaped resin molding according to claim 1, wherein the thermoplastic resin is a thermoplastic fluorine-based resin. The method for producing a plate-shaped resin molded body according to claim 1 or 2, wherein the resin base plate has a flexural modulus of 500 MPa or more and a durometer D hardness of 56 or more. The method for producing a plate-shaped resin molding according to any one of claims 1 to 3, further comprising cooling a resin melt using one or more cooling rolls having a surface formed with irregularities of a desired shape and/or pattern, and imparting an irregular shape to one or both surfaces of the obtained plate-shaped resin molding. The method for producing a plate-shaped resin molding according to any one of claims 1 to 4 , further comprising a step of cutting the resin base plate to a predetermined size.

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