JPH05245866A - Method and apparatus for continuously reinforcing and molding fiber reinforced thermoplastic resin sheet - Google Patents

Abstract

PURPOSE:To continuously mold a high strength sheet having uniform thickness by providing a preheating device on the front stage of a double belt press and further heating a web heated to a specific range of temp. to a specific range of temp. by a top roll and pressing said web before cooling the same by a cooling roll. CONSTITUTION:A preheating device 2 is provided on the front stage of a double belt press 3 and the resin in a web 1a produced by a papermaking process is heated to the m.p. (a range of + or -20 deg.C) thereof. The web 1a is further rapidly heated to temp. (a range of + or -20-60 deg.C) by the top rolls 10 in a press 3 to be subjected to pressure molding by a pressure means 8. Subsequently, the web is fed while grasped by the cooling rolls 4 arranged in the press 3 to be cooled. Therefore, the flowability of the resin of the web 1a is enhanced and the heating load at the time of pressure molding is reduced and air at the time of pressure molding is certainly discharged to uniformize the thickness of the web 1a and the molded sheet 1c can be made excellent in physical properties and dimensional stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous reinforced molding method for a fiber reinforced thermoplastic resin sheet (stampable sheet) and an apparatus therefor, and is particularly suitable for automobiles, pipe joints, industrial materials, etc. TECHNICAL FIELD The present invention relates to a method for molding a fiber-reinforced thermoplastic resin sheet and an apparatus therefor.

[0002]

2. Description of the Related Art Recently, a heat-moldable stampable sheet has been known as a fiber reinforced resin member most suitable for automobile bumpers and the like. This stampable sheet may be produced by laminating a resin sheet and long fibers, followed by heat molding, or by dispersing the short fibers and the thermoplastic resin in a wet state as shown in JP-B-55-9119. A paper-making method (also referred to as a paper-making method) in which a blanket-like web obtained by making a paper on a wire is dried and heat-formed is known.

However, the above-mentioned laminating method has many problems in terms of formability and recycling, and at present, the paper-making method is more advantageous. A so-called double belt press system (hereinafter referred to as DBP), which is a molding apparatus applicable to both the above-mentioned laminating method and paper-making method, performs heating, pressurizing, and cooling molding with a material sandwiched between two belts. For example, it is known from Japanese Examined Patent Publication No. 63-15135.

An outline of a conventional method for producing a stampable sheet by a laminating method using DBP equipment will be described with reference to FIG.
A pair of lower belts 21 is arranged, and two zones of a heating / pressurizing section 22 and a cooling / pressurizing section 23 are arranged within a specific range of the belts 20 and 21. The pressing mechanism of the heating / pressurizing unit 22 and the cooling / pressurizing unit 23 is configured by arranging a pair of upper and lower roll groups 24 capable of rolling in an endless manner in a vertical pair.
The heating / pressurizing unit 22 includes a heating means 25 and a cooling / pressurizing unit 23.
A cooling means 26 is installed in the.

From the upstream side of the belts 20 and 21, however, a material in which a thin sheet 27 of polypropylene at room temperature and a glass fiber mat 28 are alternately stacked is placed with a molten resin 29 therebetween, and a heating / pressurizing section is provided. It is supplied to No. 22 and sufficient heat is applied to the material to fluidly impregnate the resin into the glass fiber mat, and then solidified to have a predetermined thickness in the cooling / pressurizing unit 23 to obtain a sheet.

At this time, at the time of heating and press-molding the above-mentioned material, in order to uniformly soften and melt the thin polypropylene sheet 27 at room temperature and evenly raise the temperature of the glass fiber mat 28 having poor heat transfer efficiency, It is necessary to lengthen the machine length of the pressure section 22 to correspond to the maximum material thickness.

Further, in order to discharge the air existing in the material, it is desirable to eliminate the roll interval of the plurality of roll groups 24, but since there is a roll interval in the plurality of roll groups 24 due to the equipment configuration, Exhaustion of air gas is incomplete and the presence of air in the sheet is unavoidable.

Even when the heating / pressurizing molding in which the air is present is cooled by the cooling / pressurizing section 23, a plurality of roll groups 24 are provided.
As long as there is a roll interval, the existing air is not exhausted sufficiently, causing wrinkles, unevenness, and local swelling, and a good sheet molded product cannot be obtained. The above problem similarly occurs in the paper-making method in which the blanket-like web is dried and heat-molded, although the degree of the paper-making process varies.

Usually, the stampable sheet is, for example, 20 mm.
It is an intermediate molded product that heats and presses a web etc. with a thickness of 3 mm and cools it to a thickness of 3.8 mm. Especially, in order to obtain a stampable sheet in the absence of air, other gases, etc. It is necessary to combine cooling capacity. Therefore, the equipment is oversized and has a complicated structure, and the productivity is low and it is not economical.

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The web for stampable sheet consisting of defibrated fibers and thermoplastic resin particles based on the papermaking method has a large amount of air (at least 50% or more) before being heat-molded, and therefore the existing DBP described above is used. There were the following problems when making sheets with equipment.

That is, heat conduction is poor due to the presence of a large amount of air layer, and it takes a long time to heat. In addition, the temperature distribution tends to occur in the web thickness direction, and unless the inside temperature reaches the melting temperature, the predetermined sheet thickness cannot be achieved even if high pressure is applied. Further, if there is an unmelted resin portion having poor fluidity, air remains in the sheet, which causes wrinkles and unevenness, and a good sheet molded product cannot be obtained. Therefore, the conventional D
There has been a demand for new equipment suitable for webs based on a papermaking method that can solve the problems in forming with a BP apparatus.

The present invention has been made in view of such circumstances, and an optimum forming method capable of obtaining a stampable sheet having a good surface quality and high strength with high efficiency, and effectively carrying out this method. It is an object of the present invention to provide a molding device capable of

[0013]

According to the present invention, a fiber-reinforced thermoplastic resin paper web is formed into a sheet by a double belt press comprising a pair of top rolls, a pair of end rolls, and two endless belts stretched between the rolls. In the method of forming into 1., after heating the web to a melting point of the resin in the web ± 20 ° C by a preheating device provided in the preceding stage of the double belt press, the web is treated with a top roll of the subsequent double belt press. A continuous reinforced molding method for a fiber-reinforced thermoplastic resin sheet, which comprises press-molding while rapidly heating to the preheating temperature + 20 ° C to 60 ° C, and then nipping and cooling by a cooling means arranged in a double belt press. The present invention also provides a fiber-reinforced thermoplastic resin sheet characterized in that the heating means of the preheating device is ventilation heating. Of a continuous reinforced molding method, also,
The present invention is a continuous reinforced molding method for a fiber reinforced thermoplastic resin sheet, wherein the top roll of the double belt press has a roll radius R defined by the following formula: 0.00035M <R < 0.0110M R: Roll radius (m) M: Web weight to be treated (kg / Hr · m) Further, in the continuous reinforced molding apparatus for fiber reinforced thermoplastic resin sheet according to the present invention, the preliminary stage is constituted by ventilation heating means. A heating device is provided, the heating means and pressurizing means are provided on the top roll of the subsequent double belt press, and a cooling device for pressing the belt of the double belt press is arranged between the top roll and the end roll of the double belt press. Is a continuous reinforced molding apparatus for a fiber reinforced thermoplastic resin sheet.

[0014]

The present invention relates to a method for forming a fiber-reinforced thermoplastic resin paper web into a sheet by the double belt press system, wherein the web is melted within a range of ± 20 by means of a preheating device provided before the double belt press. ℃
After being heated to the above, the web is heated by the top roll of the double belt press at the subsequent stage to the preheating temperature + 20 ° C to 60
Since the two-stage heating / cooling method is adopted, in which the web is heated and pressed while being rapidly heated to ℃, it is pressed and then sandwiched and cooled by the cooling means arranged in the double belt press. Since the resin is preheated to near the melting point of the resin before the pressure molding and the fluidity of the resin is sufficiently increased,
The amount of heat supplied for pressure molding can be achieved by continuous surface heat conduction only by the top roll set to the thickness of the stampable sheet, reducing the heating load and reliably discharging air during pressure molding. .. Further, the cooling of the formed sheet immediately after the pressure forming may be performed while sandwiching the double belt with a pressure that can counter the swelling caused by the fibers in the formed sheet.

Further, in the present invention, since ventilation heating is adopted as the preheating means, the air permeability of the web, which usually has a porosity of 50% or more, is utilized to make the web uniform and efficient in its thickness direction. Can be preheated. Also,
Since the web is compressed by the wind pressure to reduce the porosity, the web can be fed to the double belt press in a preloaded state.

The present invention also provides a predetermined amount of heat from the top roll to the fiber reinforced thermoplastic resin web,
0.00035M <R depending on the web weight M to be treated
Since the top roll having the roll radius R defined by the formula of <0.0110M is equipped, the heating and the heating pressure of the preheated web to the forming temperature can be performed under the continuous surface pressure in the strand direction.

Further, according to the present invention, in a continuous reinforced molding apparatus for a fiber reinforced thermoplastic resin sheet, a preliminary heating apparatus constituted by ventilation heating means is provided in the preceding stage, and heating means and pressure are applied to a top roll of a double belt press in the subsequent step. Equipped with means,
Since the cooling device that presses the belt of the double belt press is arranged between the top roll and the end roll of the double belt press, most of the heat quantity of the web temperature required for pressure molding is efficiently supplied by the preheating device. Since the remaining amount of heat can be added in the double belt press, the forming temperature can be secured only by the top roll equipped with the heating means. Further, the cooling device may be under a slight pressure against swelling caused by the fibers in the stampable sheet, so that a cooling device that presses the structurally simplified belt can be adopted, and as a result, the continuous reinforcement molding device The captain can be shortened.

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example of the apparatus of the present invention for carrying out the molding method according to the present invention. As shown in the figure, the molding apparatus has a required composition and thickness dimension which are formed and sent in the previous step. , For example, web 1a of 20-40 mm
Are installed along the transport line.

In the continuous reinforced molding apparatus of the present invention, first, a preheating device 2 for preheating the web 1a is arranged in the front stage, and in the rear stage of the preheating device 2, the endless upper and lower ends for holding the web 1a in the thickness direction. It has a basic structure in which a DBP device 3 having a steel belt 12 capable of heating / pressurizing and cooling / pressurizing is arranged.

The preheating device 2 has an air-permeable endless belt 4 on which the web 1a is placed and moves, the web 1a provided in the path of the belt 4 and a chamber 5 surrounding the belt 4,
A blower 6 for heating a constant temperature in the chamber 5, for example, the melting point of the resin in the web 1a ± 20 ° C., and forcing a warm air of a predetermined pressure to pass in the thickness direction of the web 1a, a warm air It can be composed of a heat supply device 7 such as an electric heater to be generated.

At the tip of the entrance side of the conveying path of the DBP device 3, the web 1a is formed into a molten sheet 1b having a desired thickness, for example, 2 to 4 mm, and air existing in the web 1a is discharged, for example. Pressurizing means 8 driven by hydraulic pressure and web 1a preheated by the preheating device 2
Is provided with a pair of top rolls 10 that rapidly heats to a preheating temperature of + 20 ° C. to 60 ° C. and has a heating means 9 including an induction heating coil, and a pair of end rolls 11 is provided at the rear end. An endless steel belt 12 is stretched between the rolls 10 and 11.

On the downstream side of the top roll 10, there is arranged a cooling device 13 for cooling the molten sheet 1b which has been heated and pressed to form a molded sheet 1c. The cooling device 13 is constituted by a plurality of pairs of cooling rolls 14 for pressing the upper and lower belts 12 with a pressing force against the swelling caused by reinforcing fibers in a sheet containing a molten resin, a cooling guide shoe 15, or a combination of both. It

When passing through the preheating device 2 of the ventilation heating means, the web 1a is heated to a predetermined temperature in a short time, that is, the melting point temperature of the resin in the web 1a ± 20 ° C. by utilizing the air permeability of the web itself. As a result, the web 1a is partially melted or softened, and the web 1a is compressed by wind pressure to reduce the porosity.

When the resin is preheated to a temperature exceeding the melting point of the resin + 20 ° C., the resin flows and drops to contaminate the inside of the preheating device 2, and the amount of the resin as the molten sheet 1b is insufficient, resulting in defective products. Cause. On the other hand, heating at a melting point temperature lower than −20 ° C. is not preferable because the additional supply of the amount of heat required for pressure molding in the subsequent top roll 10 increases.

The web 1a preheated to the vicinity of the melting point of the resin in the web as described above is provided with the heating means 9 for thermoforming provided on the inlet side of the DBP device 3, and the sheet 1b.
Forming temperature by the top roll 10 set to the thickness of (1c), specifically preheating temperature + 20 ° C to 60 ° C
It is heated up rapidly all at once.

The heating of the web 1a by the top roll 10 becomes surface heating by the roll 10, and heat conduction can be greatly promoted. Web 1 by roll 10
Since the pressure of a is a continuous surface pressure, the discharge of the air contained in the web 1a can be reliably achieved.

On the other hand, when the heating and pressurizing operations are not sufficiently performed so that the film is not uniformly heated to a predetermined temperature, roll pressurization at a high pressure in the subsequent cooling molding process may result in insufficient fluidity or surface layer. Due to the difference in fluidity between the inside and the inside, wrinkles and irregularities occur, and a good sheet cannot be obtained. Therefore, the top roll 10
It is important to properly apply pressure and heat.

Taking a polypropylene / glass fiber stampable sheet as an example, a pair of heat-forming top rolls 10 for a web 1a preheated to 150 ° C. to 200 ° C.
The temperature rising conditions necessary for rapid and uniform heating will be specifically described below.

This temperature raising condition is obtained if the surface temperature of the top roll 10 and the contact state between the top roll 10 and the web 1a via the steel belt 12, that is, the overall heat transfer coefficient and the contact arc length are determined. .. The surface temperature of the roll here has an upper limit because the resin deteriorates remarkably when the temperature becomes too high, and is 250 ° C. in this example. In the latter case, the overall heat transfer coefficient and contact arc length can be obtained by chemical engineering experiments to determine the overall heat transfer coefficient U and the roll contact arc length angle θ. Specifically, U = 2000 kcal / m ² Hr ° C, θ = 0.0873rad
Is determined. Based on the premise thus obtained, the roll radius and the temperature rising rate will be calculated below.

The roll radius R is determined by the amount of heat required in proportion to the unit roll width and the weight M of the web processed per unit time, and as a result of examination, it is necessary to satisfy the following relational expressions (1) and (2). I understood. R = (0.0956 × M) / (U × θ) (1) R; Roll radius (m) M; Web weight to be treated (kg / Hr · m) U; Overall heat transfer coefficient (kcal / m ² Hr) ℃) θ; Roll contact arc length angle (rad) 0.00035M <R <0.0110M (2)

Since U and θ in the above equation (1) are separately determined as described above, the roll radius can be represented only by the web weight M to be processed, and U = 2000 kcal / m ² Hr
Substituting θ = 0.0873 rad for ℃, R = 0.000
It becomes 55M. Therefore, for example, the roll radius for heating the web weight basis gramage 4500 g / m ² (corresponding to a thickness of 3.8 mm) to a predetermined temperature at a line speed of 2 m / min is 300 mm from the above formula (1). It is satisfied if it is more than the value.

As a result of repeating such experiments and examinations, the preferable roll radius becomes the range shown by the formula (2) in consideration of the preheating temperature of the web, the contact state, the upper limit of the roll radius in terms of equipment, and the like. That is, the lower limit is a region in which the temperature does not reach the predetermined temperature uniformly, defects such as wrinkles are generated, or the preheating temperature is too high and the biting into the roll becomes poor. Further, the upper limit is a region where the roll diameter becomes excessively large and the economical efficiency of equipment is impaired.

The pressure applied to the top roll 10 is
Since the web 1a is pre-heated to near the melting temperature and is heated and heated sufficiently on the inlet side of the top roll 10, the resin has high fluidity so that the pressure is low (1-2 kg).
The range is / m ² ). Therefore, it can be molded into a predetermined sheet thickness that is sufficiently impregnated with the resin and the glass fiber.

Next, by combining the cooling forming roll 14 and the cooling guide shoe 15, the molten sheet 1b is placed on top.
While being held by the lower belt 12, pressure cooling is performed to form a formed sheet 1c having a predetermined plate thickness. Specifically, a plurality of pairs of cooling forming rolls 14 are arranged in the line direction to maintain the rigidity in the width direction. Further, the guide shoes 15 are arranged in the line direction to form a rigid flat body. With the above-described basic configuration, the frictional force between the cooling forming roll group 14 and the belt 12 can be reduced by performing centering, and the sheet 1b melt-pressed and formed like the top roll 10 is cooled and formed by the roll 14. be able to.

The cooling conditions necessary for rapid cooling of the molten sheet 1b from the forming temperature to the take-out temperature by the cooling forming roll 14 and the cooling guide shoe 15 which have been paired are described in the heating conditions of the top roll 10. This is the same as the above, and is obtained if the contact state between the surface temperature of the cooling forming roll 14 and the guide shoe 15 and the molten sheet 1b, that is, the overall heat transfer coefficient, the contact arc length, and the contact length are determined.

For example, the weight of the sheet weight gramage 4
The roll radius for cooling 500 g / m ² at a line speed of 2 m / min to a predetermined temperature is θ = 0.0698 when the belt thickness is 0.3 mm, although detailed formula configuration and explanation are omitted.
rad, U = 3500 Kcal / m ² ) and the optimum roll radius is 150 mm.

Here, in terms of the practicality of the equipment, the belt 1
If 2 is thickened, a tension of about 5 kg / mm ^{2 is} required with respect to the plate thickness, and if the roll diameter is large, there is a space limitation on the configuration of the cooling roll 14 and the cooling guide shoe 15. As a result, the equipment becomes large, and the belt thickness is 0.3 to 0.6 even in consideration of practical durability.
mm is preferred.

Next, the cooling guide shoe 15 is provided between the cooling forming roll groups 14 so as to be brought into close contact with the belt 12 to suppress a slight expansion of the sheet and cool the sheet strongly. The pressing force is applied by a hydraulic cylinder 16 provided in the cooling guide shoe 15, but 1 kg /
Low pressures below cm ² are preferred.

As the structure of the cooling guide shoe 15, it is preferable that a body plate having high heat conductivity is detachably fixed to a water-cooled metal block. The temperature can be adjusted by changing the contact area. As a material that contacts the belt 12, other materials may be practically used as long as the material is softer than the belt and has high heat conductivity. Next, an example of operation using the molding apparatus shown in FIG. 1 will be described.

[0040]

[Examples] Production of polypropylene / glass fiber type sheet Paper web Material: Polypropylene (melting point 165 ° C) powder 70% by weight Glass fiber (length 13 mm) 30% by weight Composition: Porosity 50% or more, basis weight 4500 g / m ² Pre-forming web thickness 20-40 mm, forming sheet 3.8 mm Preheating device Hot air temperature: 220 ° C Hot air pressure: 200 mmAq Passing time: 20-30 sec Belt press machine Top roll Forming pressure: 2 kg / cm ² , Roll surface temperature: 250 ℃ Roll radius: 300mm Cooling forming roll Forming pressure: 2kg / cm ² , Roll radius: 150mm Number of installations: 3 pairs, Roll surface temperature (water cooling jacket): Room temperature guide shoe Contact surface pressure: 0.5kg / cm ² , Width: 100mm Material: Copper, Number of installations: 2 pairs Belt Material: Stainless steel, Thickness: 0.6mm, Width: 1000mm, Belt speed: m / min

Using the apparatus shown in FIG. 1 having the above specifications, the papermaking web was formed into a sheet while being fed at a feed rate of 2.0 m / min. FIG. 2 shows transition trends of the web thickness, temperature and applied pressure at this time. It was confirmed that the formed sheet was excellent in physical properties and dimensional stability.

[0042]

As described above, according to the molding method of the present invention, it is possible to continuously form a web manufactured by the paper-making method into a sheet, and conventionally, the heat transfer characteristics are poor and molding is difficult. From the existing papermaking web, a sheet-shaped molded product having a uniform desired thickness and excellent surface properties and high strength can be obtained, and its industrial value is extremely large.

According to the molding apparatus of the present invention,
The above method can be performed effectively and in a consistent line. In addition, the heating / cooling capacity has been greatly improved compared to the conventional apparatus, so that the machine length can be greatly shortened, and the equipment is simple and economical.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram showing an outline of a continuous molding apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing changes in web temperature and pressure in each step of the example of the present invention.

FIG. 3 is a schematic view showing a method of manufacturing a stampable sheet by a conventional laminating method.

[Explanation of symbols]

 1a web 1b molten sheet 1c formed sheet 2 preheating device 3 double belt press 4 breathable endless belt 5 chamber 6 blower 7 electric heater 8 pressurizing means 9 heating means 10 top roll 11 end roll 12 endless steel belt 13 cooling device 14 cooling Roll 15 Cooling guide shoe 16 Pressurizing means

Front Page Continuation (72) Inventor Masaaki Sawa 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Nagoya Steel Works (72) Inventor Masahiro Ono 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Inside the Yokkaichi Research Institute

Claims (4)

[Claims] 1. A method for forming a fiber-reinforced thermoplastic resin paper web into a sheet by a double belt press comprising a pair of top rolls, a pair of end rolls, and two endless belts stretched between the rolls. After heating the web to a melting point of the resin in the web ± 20 ° C by a preheating device provided in the previous stage of the belt press, the preheating temperature of the web is + 20 ° C to 60 ° C with a top roll of a double belt press in the subsequent stage. A continuous reinforced molding method for a fiber-reinforced thermoplastic resin sheet, which comprises press-molding while rapidly heating to ℃, and then nipping and cooling by a cooling means arranged in a double belt press. 2. The continuous reinforced molding method for a fiber-reinforced thermoplastic resin sheet according to claim 1, wherein the heating means of the preheating device is ventilation heating. 3. The continuous reinforced molding method for a fiber reinforced thermoplastic resin sheet according to claim 1, wherein the top roll of the double belt press has a roll radius R defined by the following formula. 0.00035M <R <0.0110M R: Roll radius (m) M: Web weight to be treated (kg / Hr · m) 4. A continuous reinforced molding apparatus for a fiber reinforced thermoplastic resin sheet, wherein a pre-heating device constituted by ventilation heating means is provided in the preceding stage, and a pair of top rolls, a pair of end rolls, and a stretch between both rolls are provided in the subsequent stage. A double belt press consisting of two endless belts is installed and the top roll of the double belt press is equipped with heating means and pressurizing means, and the belt of the double belt press is placed between the top roll and end roll of the double belt press. A continuous reinforced molding apparatus for a fiber-reinforced thermoplastic resin sheet, characterized in that a cooling device for press-contacting is arranged.