JPH0788993A - Fiber-reinforced thermoplastic resin sheet, its manufacturing and molding method - Google Patents

Abstract

PURPOSE:To improve surface properties of a molded product of a stampable sheet (fiber-reinforced thermoplastic resin sheet) molded by an ordinary press molding machine without performing post-treatment. CONSTITUTION:At least one layer of a thermosetting resin layer is formed on at least one surface of a stampable sheet by coating and baking of a thermosetting resin coating. Hereby, since stamping molding can be performed similarly to a conventional method and neither exposure nor raising of a reinforcing fiber are generated during preheating, a molded product superior in surface properties can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a fiber reinforced thermoplastic resin sheet called a stampable sheet because it can be compression-molded (stamping molding) with a press die (hereinafter also referred to as stampable sheet in this specification). And the manufacturing method and the molding method thereof. More specifically, the present invention relates to a fiber-reinforced thermoplastic resin sheet having excellent surface properties and a method for producing and molding the same.

[0002]

2. Description of the Related Art Stampable sheets are excellent in weight saving, mechanical properties, and in addition to being capable of producing molded products of complicated shapes in a short cycle by stamping molding, they are used in various industrial fields such as the automobile field. Demand is increasing year by year. Stamping molding (also called sheet molding) is a technique that cuts a stampable sheet to an appropriate size (that is, blank cut), preheats the obtained sheet fragment (blank) to soften the resin, and then immediately presses the die. It is carried out by inserting a predetermined number of sheets and pressing.

However, on the surface of a stampable sheet molded product, there are generally many irregularities due to the exposure of reinforcing fibers (generally glass fibers) and the embossing of the reinforcing fibers during preheating, and the surface quality is not always good. Is hard to say. For this reason, the present situation is that stampable seats are used only for bumper beams of automobiles, seat backs, and the like, which are not required to have very good surface properties.
Under such circumstances, improvement of the surface properties of stampable sheet molded products is strongly desired to develop new applications such as outer panels of automobiles and home electric appliances.

As a means for solving this problem, Japanese Unexamined Patent Publication No.
In Japanese Patent Publication No. 47740, a sheet structure is adopted in which the number of bundles of reinforcing fibers is changed in an inclined manner in the sheet cross section, and fibers in a state close to an opened monofilament are arranged on the surface. However, the improvement of the surface properties by this method cannot be said to be sufficient.

It is also known to apply a coating to the surface of a molded article having poor surface properties to improve the surface properties. Generally, a polyolefin resin such as polypropylene does not have a good affinity for paints, but it is described in JP-A-4-185614 that it can be improved by applying a primer or the like. However, the coating work after molding not only causes an increase in cost due to the addition of a process, but this method also causes a large number of fibers due to the embossing of the fibers which occurs on the surface of the stampable sheet molded product during the molding process. It is difficult to improve the unevenness.

Further, a method of opening the mold slightly after molding and filling the mold with a thermosetting resin, a so-called in-mold coating method has been proposed. However, with this method, the molding machine and the mold are complicated and large, and an increase in cost cannot be avoided.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a molded product in which the above-mentioned drawbacks of the conventional method are eliminated, that is, a surface property is improved by a normal press molding machine without post-processing. (EN) A stampable sheet (that is, a fiber-reinforced thermoplastic resin sheet) that can be obtained at low cost and a method for producing the stampable sheet. Another object of the present invention is to provide a molding method for obtaining a molded product having excellent surface properties by using an existing stampable sheet.

[0008]

When the present invention provides a thin layer of thermosetting resin on the surface of a stampable sheet, the resin layer conceals the reinforcing fibers and prevents the embossing during preheating. In addition, since the thermosetting resin layer with a thin surface can follow stamping molding by pressing, stamping molding can be performed without problems with the same method as before, and the surface quality does not change during molding, and the molded product with excellent surface quality The present invention has been achieved by finding that the above can be obtained.

Here, the gist of the present invention is a fiber-reinforced thermoplastic resin sheet capable of stamping molding, which has at least one thermosetting resin layer on its surface.

This fiber-reinforced thermoplastic resin sheet can be manufactured by forming at least one thermosetting resin layer on the surface of the fiber-reinforced thermoplastic resin sheet by applying and baking a thermosetting resin paint.

In another aspect, the present invention provides that at least one thermosetting resin layer is formed on the surface of a fiber-reinforced thermoplastic resin sheet by molding and baking a thermosetting resin paint before molding. It also relates to a method for forming a characteristic fiber-reinforced thermoplastic resin sheet.

Here, the "thermosetting resin layer" may be a layer made of only a thermosetting resin or a layer made of a resin containing a non-fiber type additive such as a pigment.

[0013]

The structure of the present invention will be described in detail below together with its operation.

The feature of the present invention resides in that a thermosetting resin layer is formed on the surface of the fiber reinforced thermoplastic resin sheet (stampable sheet), and the fiber reinforced thermoplastic resin sheet of the main body is not particularly limited. Various conventionally known stampable sheets can be used.

The thermoplastic resin which is the matrix of the fiber reinforced thermoplastic resin sheet is preferably a polyolefin resin such as polypropylene or a thermoplastic polyester resin such as polyethylene terephthalate, but is preferably vinyl chloride, styrene or polycarbonate. Various other thermoplastic resins such as polyacetal type and polyamide type can also be used. The melt index of the thermoplastic resin used is preferably in the range of 5 to 500 g / 10 minutes, and more preferably 80 to 300 g / 10 minutes, from the viewpoint of moldability, workability, and mechanical properties of the molded product.

When polypropylene is used as the thermoplastic resin, it may be a homopolymer of propylene or a copolymer with other olefins such as ethylene. In this case, the copolymerization degree of ethylene (or other olefin) is preferably 0.05 to 50% by weight, particularly preferably 1 to 10% by weight. Generally, copolymerizing ethylene with polypropylene can improve the toughness of the resin.

In the case of a fiber-reinforced thermoplastic resin sheet having a matrix resin of a polyolefin resin such as polypropylene having a poor affinity with a coating material, it is used in order to improve the interfacial adhesion with the thermosetting resin coating material. Part of the polypropylene resin (0.05 to 20% by weight) is graft-polymerized with an unsaturated carboxylic acid such as maleic acid, itaconic acid, acrylic acid, methacrylic acid, maleic anhydride, or itaconic anhydride, or an anhydride thereof. It is desirable to modify.

As reinforcing fibers, in addition to glass fibers,
Various fibers such as organic fibers such as aramid fibers and carbon fibers, inorganic fibers such as metal fibers and ceramic fibers can be used. From the viewpoint of cost and weight reduction effect, glass fiber is generally used, but when a lighter material is required, organic fiber such as carbon fiber can be used.

The reinforcing fibers may be in the form of continuous or cut monofilaments, chopped strands obtained by cutting monofilament bundles, or the like. However, when monofilament fiber is used, the sheet itself tends to expand in the preheating process of the blank sheet during stamping, and the surface quality of the thermosetting resin layer tends to deteriorate, so chopped strands are preferably used.

The length of the fibers is not limited and may be continuous fibers, but preferably 1 to 100 mm, more preferably 10 mm.
The one having a thickness of up to 50 mm is advantageous in terms of mechanical strength and ensuring fluidity during molding. It is generally desirable to treat the reinforcing fibers with a coupling agent such as aminosilane or epoxysilane in order to increase the interfacial adhesion strength with the thermoplastic resin that is the matrix.

From the above thermoplastic resin and reinforcing fibers,
The fiber-reinforced thermoplastic resin sheet can be prepared by a known papermaking method or lamination method. In the papermaking method, resin powder and short fibers are dispersed in water or an emulsion to form a slurry, and a sheet is formed from this slurry in the same manner as papermaking, and the obtained sheet is hot-pressed to melt the resin to form fibers. This is a method of obtaining a fiber-reinforced resin sheet by integrating with a resin.

The laminating method is a method in which a thermoplastic resin sheet formed in advance and a fiber mat are laminated and heated and pressed at a temperature not lower than the melting point of the resin by a belt press or a roll press to obtain an integrated sheet.

The fiber-reinforced thermoplastic resin sheet obtained by the papermaking method has good dispersibility of reinforcing fibers and excellent moldability, but the strength characteristics such as tensile strength of the sheet tend to be lower than those of the lamination method. There is. Therefore, an appropriate sheet forming method may be selected according to the application and the shape of the molded product. It is known that the surface properties of molded articles are generally worse when a sheet obtained by a papermaking method is used. In that sense, it can be said that the effect is more remarkable when the present invention is applied to the fiber-reinforced thermoplastic resin sheet produced by the papermaking method. However, even with the sheet obtained by the lamination method, the surface property of the molded product is deteriorated by the above-mentioned embossing during the preheating, so the present invention is sufficiently effective even for the fiber-reinforced thermoplastic resin sheet obtained by the lamination method. .

According to the present invention, in order to improve the surface texture, at least one thermosetting resin layer is provided on the surface of the fiber reinforced thermoplastic resin sheet. This thermosetting resin layer is conveniently formed by applying and baking a thermosetting resin coating material. At that time, in order to improve the interfacial adhesion between the paint and the sheet, it is desirable to irradiate the surface of the fiber-reinforced thermoplastic resin sheet with ultraviolet rays before applying the paint.

Further, particularly when the matrix resin of the fiber reinforced thermoplastic resin sheet is a polyolefin resin such as polypropylene, a primer may be applied to the surface of the sheet before applying the paint. As the primer used here, a polyolefin polymer compound having at least one polar group such as polypropylene chloride or a maleic anhydride modified product of an ethylene-polypropylene copolymer is used as an aromatic hydrocarbon solvent such as toluene. It is generally dissolved.

If necessary, a thermosetting resin coating material (baking type coating material) is applied to the surface of the fiber-reinforced thermoplastic resin sheet whose surface has been pretreated by the above method. As the thermosetting resin coating used here, epoxy-based, polyester-based, acrylic-based, urethane-based coating, etc. can be used. It is desirable that these paints have heat resistance that can withstand preheating during molding. In particular, when the thermoplastic resin is a polyester resin such as polyethylene terephthalate, the preheating temperature in the molding process reaches 200 to 300 ° C., so careful consideration must be given to the selection of the paint. Examples of thermosetting resin coatings with excellent heat resistance that can withstand such temperatures include:
Examples thereof include polyethylene tersulphone-based paint.

The thermosetting resin coating used may be a clear coating containing no pigment or may contain a pigment, but a coating containing a pigment is preferable from the viewpoint of hiding power of the fiber. The application can be performed by a general method such as roll coating, bar coating, spraying, dipping and the like.

The sheet applied after coating is heated to bake the paint to form a cured film on the surface. The cured film formed on the surface of the fiber-reinforced thermoplastic resin sheet in this way prevents the fibers from protruding or being exposed during molding, so that a molded product having excellent surface properties can be obtained. The baking is preferably performed at a temperature below the melting point of the thermoplastic resin. Specifically, in the case of a polypropylene-based sheet, it is generally desirable to perform baking at 140 to 170 ° C, although it depends on the paint and the degree of ethylene copolymerization.

The thickness of the thermosetting resin film may be such that this thermosetting film can follow the deformation caused by molding and prevent the fibers from rising during preheating.
Generally, it is desirable that the thickness is in the range of 30 to 200 μm.
If it is too thin, the effect of improving the surface properties is hardly obtained, and if it is too thick, molding becomes difficult. When the required thickness of the thermosetting resin film cannot be obtained by one-time application and baking, the application and baking may be repeated several times to form two or more thermosetting resin layers. At that time, the type of coating material to be applied may be changed.

By the above method, a fiber-reinforced thermoplastic resin sheet having a thermosetting resin layer having excellent surface properties on its surface can be obtained. The thermosetting resin layer on the surface may be provided on only one side of the sheet or on both sides.
It is advantageous in terms of work efficiency to apply the above-mentioned thermosetting paint at the time of manufacturing the fiber-reinforced thermoplastic resin sheet. However, the existing fiber-reinforced thermoplastic resin sheet can be stamped and molded by the user by applying and baking a thermosetting paint before molding. In this case, the coating material may be applied to either the blank-cut sheet or the blank-cut sheet. The baking may be carried out immediately after coating, but the coating can be baked simultaneously with the preheating by utilizing the heating in the preheating step of the blank during molding.

Hereinafter, using the sheet obtained in the present invention,
A method for obtaining a molded product by stamping molding by a press will be described in detail.

The fiber-reinforced thermoplastic resin sheet having the thermosetting resin surface layer of the present invention can be stamped and molded similarly to the conventional stampable sheet. That is, after blank-cutting a sheet into a predetermined size, it is preheated to a temperature not lower than the melting point of the thermoplastic resin and immediately put into a press die for press molding.

Generally, in stamping molding, a method in which a sheet cut into an area smaller than the projected area of the molded product is put into a mold to flow and fill the material to obtain a molded product, and an area equivalent to the projected area of the molded product There is a method in which the sheet is put into a mold and the sheet is deformed by press molding to obtain a molded product. In the case of the molding method of the present invention, since the thermosetting resin layer on the surface of the sheet is not suitable for flow molding, it is desirable to apply the latter molding method. In order to obtain a molded product having a thickness equal to or greater than the thickness of the sheet, or to obtain a molded product having a complicated shape such as ribs, a sheet having a surface thermosetting resin layer according to the present invention It is advisable to stack a sheet that does not have it and put it in a mold to mold it.

The surface properties of the obtained molded product are greatly affected by the surface roughness of the mold. For this reason, it is preferable that the mold surface, which is in contact with the thermosetting resin layer on the surface, be plated with chrome or the like to be mirror-finished. The preheating temperature of the sheet depends on the melting temperature of the thermoplastic resin, but is 150 to 220 ° C. in the case of polypropylene type and 200 to 300 ° C. in the case of polyethylene terephthalate. It is desirable to select the temperature so that the thermosetting resin layer does not deteriorate.
The mold temperature is generally in the range of normal temperature to 200 ° C., and may be set according to the crystallization temperature of the thermoplastic resin used.
Specifically, the temperature is preferably 40 to 80 ° C in the case of polypropylene, and 130 to 180 ° C in the case of polyethylene terephthalate.

[0035]

【Example】

(Example 1) First, a fiber reinforced thermoplastic resin sheet was prepared by the following method. As the thermoplastic resin, 0.5% by weight of polypropylene is graft-modified with maleic anhydride,
Polypropylene-ethylene block copolymer with an ethylene content of 1.0% by weight (melt index = 100 g / 10 minutes)
Was used. This resin was heated to 190 ° C using a cold press.
A sheet having a thickness of 0.7 mm was formed at 100 ° C and a pressure of 100 kgf / cm ² . Four polypropylene resin sheets thus obtained,
Glass fiber length 50 mm, fiber diameter 13 μm, bundling number 80, and 3 chopped strand glass mats with a basis weight of 460 g / m ² are laminated alternately, using a cold heat press, temperature 190 ℃, pressure
Thermally laminated at 100 kgf / cm ^2, a thickness of 3.3 mm, a specific gravity 1.2,
A fiber-reinforced thermoplastic resin sheet having a fiber content of 40% by weight was obtained.

The fiber-reinforced thermoplastic resin sheet thus prepared was cut into 300 mm square pieces and irradiated with ultraviolet rays to modify the surface thereof. Ultraviolet irradiation was carried out by passing the sheet 5 times at a line speed of 5 m / min under 80 cm under two 120 W / cm high pressure mercury lamps arranged at 10 cm intervals.

Next, the surface-modified surface of the sheet was coated with Nippon Paint Flex Coat 1000, which is a thermosetting polyester-based paint, with a No. 26 bar coater, and at 150 ° C.
The paint was cured by heating for 10 minutes. By this coating and baking process, the thickness of one side of the fiber reinforced thermoplastic resin sheet is about
A 100 μm thermosetting resin layer was formed.

The fiber-reinforced thermoplastic resin sheet having this thermosetting resin layer is cut into a width of 250 mm and a depth of 200 mm,
Sheet without surface thermosetting resin layer (150mm square)
Together with a far infrared furnace H7GS-71234 made by Nippon Insulator,
Preheated to 180 ° C. After that, put the preheated sheet into the mold whose surface is chrome-plated to give a mirror finish so that the thermosetting resin layer contacts the lower mold.
Using Tonpress TFMP2-300, press speed 100 mm / sec,
Molded at a pressing pressure of 200 kgf / cm ² and a mold surface temperature of 60 ° C
A dish-shaped molded product with an edge of 300 mm, a depth of 250 mm, and a depth of 40 mm was obtained.

Lower mold contact surface of the thus obtained molded product
The (bottom part of the dish-shaped molded product) was covered with a thermosetting resin layer, and no deterioration of the surface quality due to embossing of the glass or other causes was observed.

As a comparative example, when the same molding was carried out using only the fiber reinforced resin sheet having no thermosetting resin layer, the surface texture was found to have a large number of irregularities due to the glass being exposed and raised, and the surface was smooth. A molded product having poor properties was obtained, and the effectiveness of the product of the present invention was confirmed.

Example 2 As a thermoplastic resin, polyethylene terephthalate having a melt index of 130 g / 10 min was used, and the same trial production test as in Example 1 was conducted. First, the resin pellets were placed in a cold press at a temperature of 280 ° C and a pressure of 10
It was formed into a sheet having a thickness of 0 mmf / cm ² and a thickness of 0.7 mm. Four resin sheets thus obtained and three chopped strand glass mats used in Example 1 were alternately laminated,
Using a cold press, heat lamination was performed at a temperature of 280 ° C. and a pressure of 100 kgf / cm ² to obtain a fiber-reinforced thermoplastic resin sheet having a thickness of 3.3 mm, a specific gravity of 1.7 and a fiber content of 40% by weight.

The produced fiber-reinforced thermoplastic resin sheet
It was cut into 300 mm square and surface-modified with ultraviolet rays in the same manner as in Example 1. Then, the surface-modified surface of the sheet was coated with a polyether sulfone-based paint using a No. 26 bar coater and heated at 150 ° C. for 20 minutes to cure the paint.
In this way, the thickness of about 10
A thermosetting resin layer of 0 μm was formed.

The fiber-reinforced thermoplastic resin sheet having the surface thermosetting resin layer was stamped and molded in the same manner as in Example 1 (preheating temperature was 230 ° C.), and the portion covered with the thermosetting resin layer was obtained. No deterioration of the surface quality due to the swelling of the glass or other causes was observed.

As a comparative example, when the same molding was carried out using only a fiber reinforced resin sheet having no thermosetting resin layer, the surface texture was smooth and smooth, with many irregularities due to the exposure and protrusion of the glass. A molded product having poor properties was obtained, and the effectiveness of the product of the present invention was confirmed again.

Example 3 A commercially available polypropylene stampable sheet (fiber length 50 mm, laminating method) was used.
When surface modification by ultraviolet rays and application and baking of a thermosetting resin coating material were carried out in the same manner as in Example 1, and then cutting and molding were carried out in the same manner as described in Example 1, a molded product having a surface property improved to the same extent as in Example 1 was obtained. Was obtained. As a comparative example, when molded in the same manner without a coating process, the surface of the glass is exposed,
Many irregularities due to embossing were observed.

[0046]

As described above, according to the present invention, even when preheated to a temperature higher than the melting temperature of the matrix resin in the molding step, the reinforcing fibers are not exposed or raised, so that a molded article having excellent surface properties is obtained. Can be obtained. As a result, it becomes possible to apply the stampable sheet to, for example, visible parts such as an automobile outer panel, which contributes to the expansion of the field of use thereof.

Claims (3)

[Claims] 1. A stamping-moldable fiber-reinforced thermoplastic resin sheet having at least one thermosetting resin layer on its surface. 2. The surface of the fiber-reinforced thermoplastic resin sheet,
The method for producing a fiber-reinforced thermoplastic resin sheet according to claim 1, which comprises forming at least one thermosetting resin layer by applying and baking a thermosetting resin coating material. 3. A fiber-reinforced thermoplastic resin sheet characterized by forming at least one thermosetting resin layer on the surface of the fiber-reinforced thermoplastic resin sheet by molding and baking a thermosetting resin coating before molding. Molding method for plastic resin sheet.