JPH06278188A - Manufacture of glass fiber reinforced sheet - Google Patents

Abstract

PURPOSE:To manufacture a glass fiber reinforced sheet of which an extremely superior appearance product can be obtained with resistance to marks on the surface and low warping properties, and improved falling weight impact strength. CONSTITUTION:(A) is used as a core layer, and the following (B) is used as a skin layer covering one side or both sides of the core layer, and the thickness of the skin layer is formed at least 0.5mm on one side, and 20 to 100% the thickness of the core layer in the multi-layer extrusion molding, in the above (A) is a pellet composed of glass fiber roving impregnated with thermoplastic resin and cut into the length of 5 to 30mm, and (B) is a thermoplastic resin composition composed of thermoplastic resin of 50 to 95wt.% and a sheet-shaped filler of 5 to 50wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily producing a glass fiber reinforced sheet capable of obtaining a molded article having excellent appearance, surface scratch resistance, low warpage and drop weight impact strength.

[0002]

2. Description of the Related Art Polypropylene is used as a long glass fiber reinforcing material.
A glass fiber reinforced sheet impregnated with a thermoplastic resin such as polyester or polyamide, a so-called stampable sheet, has excellent strength, rigidity and heat resistance, and has a high impact resistance as compared with a conventional glass fiber reinforced product, In addition, because it is lighter than metal materials and requires less processing man-hours, it is being applied as a metal substitute in various structural parts for automobiles.

The glass fiber reinforced sheet is generally produced by laminating a reinforcing fiber mat such as a random mat of continuous fibers or a chopped strand mat and a molten resin extruded in a sheet shape, followed by thermocompression bonding, or glass fiber chopped strand and resin powder. And are mixed in water in the form of a slurry, and then dehydrated, dried and heated and pressure-bonded in the same manner as papermaking. The former is called the laminating method and the latter is called the papermaking method. When molding this glass fiber reinforced sheet, cut it to a predetermined size according to the weight and shape of the product to be molded and heat it to a temperature near the melting point of the resin from both sides with a heating device such as an infrared heater, or to a temperature above the melting point. After that, it is performed by a method of shaping with a mold.

However, the glass fiber reinforced sheet and its molded product have a very poor appearance due to the fibers exposed on the surface, and the falling weight impact strength is still insufficient, and the surface cracks when it is impacted. It has a drawback that it easily enters, and its use is limited in reality. Furthermore, since this glass fiber reinforced sheet is reinforced with long glass fibers having high bulk and high impact resilience, the enveloping force of the resin is weakened when it is heated to a temperature above the melting point of the resin during molding. As a result, the fibers cause springback, the sheet expands, and the fibers protrude from the surface. Then, during transfer to the mold, the protruding fibers and the sheet surface start to cool, so during shaping, the protruding fibers cannot be completely covered with the resin again in the same manner as the original. Breakage due to pressure also occurs. The ends of the fibers that cannot be covered with the resin and the broken fibers cause the appearance of the molded product to be further deteriorated. The protrusion of the fibers is particularly remarkable in the case of the glass fiber reinforced sheet manufactured by the laminating method.

[0005] In order to obtain a molded product with an improved appearance, a method of molding with a molding die provided with a grain of a specific depth (Japanese Patent Publication No. 3-17653) and a crystallization accelerator of a specific content are blended. A glass fiber reinforced sheet using the polyethylene terephthalate resin as a matrix (Japanese Patent Publication No. 3-47294) has been proposed. In addition, in order to suppress the protrusion of glass fibers when heated above the melting point, a method is proposed in which the glass fiber reinforced sheet is heated in a state of being covered with a specific coating material, after resin softening, the coating material is peeled off and molded. Has been
3-104612). Furthermore, a glass fiber reinforced sheet in which discontinuous reinforcing fibers are dispersed with a tilted structure that continuously changes from a fiber layer having a large number of bundles to a fiber layer having a small number of fibers toward the surface has also been proposed. (JP-A-3-47
740). However, not only has the appearance not been sufficiently improved, but the falling weight impact strength has not yet been improved with respect to the lamination method and the papermaking stampable.

A method has also been proposed in which a surface layer of a particulate material such as carbon black or a thermoplastic resin is bonded to a web of a glass fiber reinforced sheet produced by a papermaking method before heat-pressing (Japanese Patent Laid-Open No. 3-65312). However, the appearance has not been sufficiently improved. Further, a method has been proposed in which a skin layer sheet having a glass fiber filling ratio lower than that of a glass fiber reinforced sheet is superposed on the sheet and heated to a temperature equal to or higher than the melting point and molded (JP-A-3-115330). Further, in the mold, a non-reinforced thermoplastic resin sheet or a preform thereof, or a thermoplastic resin powder, is laminated with a molten glass long fiber reinforced sheet, while these are once melted by the heat of the sheet, A method of solidifying by molding has also been proposed (Japanese Patent Laid-Open No. 3-99812). Further, a glass fiber reinforced sheet in which a skin layer sheet of a specific composition is heat-bonded in order to improve the appearance and mechanical strength has been proposed (Japanese Patent Laid-Open No. 3-138146).

However, in any of these methods, the skin layer sheet must be manufactured, cut or preformed separately from the glass fiber reinforced sheet, or if resin powder is used, the handleability is poor. And the process is inevitably complicated. Moreover, when a glass fiber reinforced sheet produced by a lamination method is used as the core layer and heated to a temperature higher than the melting point, there is a problem that the glass fiber protrudes through the skin layer and the appearance of the molded product deteriorates. found.

Further, the inventors of the present invention have earnestly studied means for improving the drop weight impact strength of the glass fiber reinforced sheet, and as a result,
By providing the skin layer, even if minute cracks are formed in the core layer, it does not reach the surface and it can be used for practical purposes. Especially, when the skin / core / skin sandwich structure is used, the center layer is a cushion. Since it is a layer, it has been found that the effect is higher, and the following invention has been reached. That is, multi-layer extrusion molding is performed so that long glass fiber reinforced thermoplastic resin pellets (hereinafter sometimes abbreviated as LFTP) and a thermoplastic resin that does not contain fibrous filler have a specific thickness ratio. A glass fiber reinforced sheet manufacturing method has been proposed (Japanese Patent Application No. 3-337752). According to this method, a glass fiber reinforced sheet capable of obtaining a molded product having no outstanding protrusion of glass fiber even if it is heat-formed to a temperature higher than its melting point, has an extremely excellent appearance, and has improved falling weight impact strength. Can be easily manufactured. However, it is unavoidable that anisotropy occurs because it is produced by extrusion-molding LFTP, and there is a problem that a warpage occurs in a molded article due to this anisotropy, and a filler is not included. It has been found that there is a problem that the scratch resistance of the surface is poor because the thermoplastic resin is used as the skin layer.

[0009]

As described above, glass fibers do not project even if they are heat-molded to a temperature higher than the melting point, and they have an extremely excellent appearance, surface scratch resistance, and low warpage, and Although it has been desired to develop a method for easily producing a glass fiber reinforced sheet capable of obtaining a molded article with improved falling weight impact strength, a sufficiently satisfactory one has not yet been provided. Therefore, an object of the present invention is to provide a method for easily manufacturing a glass fiber reinforced sheet having excellent properties as described above.

[0010]

Originally, pellets (LFTP) produced by impregnating glass fiber roving with a thermoplastic resin and then cutting it to a desired length were developed for injection molding. Yes, the glass fiber length is
15 mm or less was common. This is because in injection molding, the molten resin is made to flow at an extremely high speed, so the glass fibers are significantly broken due to collisions at the corners of the mold, and it is meaningless to use LFTP having a fiber length of more than 15 mm. .

When the present inventors used this LFTP for extrusion molding, the number of breakage of the glass fiber was surprisingly small.
It has been found that even if the fiber length exceeds mm, it can be effectively used, and the fibers are well entangled with each other, so that a useful glass fiber reinforced sheet such as a stampable sheet can be produced. Further, they have found that a method of performing multi-layer extrusion molding using LFTP as a core layer and a resin composition composed of a thermoplastic resin and a plate-like filler as a skin layer is effective for achieving the object of the present invention, and arrived at the present invention.

That is, the present invention uses the following (A) as the core layer and the following (B) as the skin layer covering one side or both sides of the core layer, and the thickness of the skin layer is one side.
A method for producing a glass fiber reinforced sheet, comprising multi-layer extrusion molding to a thickness of 0.5 mm or more and 20% or more and 100% or less of the thickness of a core layer. (A) Glass fiber roving impregnated with thermoplastic resin
Pellets cut to a length of 5 mm or more and 30 mm or less. (B) A thermoplastic resin composition comprising 50% by weight or more and 95% by weight or less of a thermoplastic resin and 5% by weight or more and 50% by weight or less of a plate-like filler.

The pellet (A) in the present invention means a pellet-like material produced by impregnating glass fiber roving with a thermoplastic resin and then cutting it into a desired length. The impregnation method is not particularly limited, and a method in which roving is passed through a fluidized bed of resin powder to adhere the resin powder thereto, and then the resin is impregnated by heating above the melting point of the resin (Japanese Patent Publication No. 52-3985). ), A method of impregnating roving with a molten resin using a crosshead die (JP-A-62-6)
0625, JP 63-132036, JP 63-264326, JP 1-20
8118), a method in which resin fibers and glass fiber rovings are mixed and then heated above the melting point of the resin to impregnate the resin (JP-A-61-118235).

The pellet length of this (A) pellet is 5
It is preferably not less than mm and not more than 30 mm. If it is less than 5 mm, impact resistance properties such as drop weight impact strength will be deteriorated and should be avoided. On the other hand, if it exceeds 30 mm, it becomes difficult to feed to the extruder, which is not practical. The resin used for the matrix of the pellet of (A) is a thermoplastic resin, and polyolefins such as polypropylene and polyethylene, polyethylene terephthalate, polyesters such as PBT, polyamides such as 6 nylon and 66 nylon, etc. can be used without any limitation.

Further, the thermoplastic resin composition (B) in the present invention is obtained by uniformly mixing the thermoplastic resin and the plate-like filler with a melt-kneader or the like, and is usually used as a molding material. Things can be used without any restrictions. The compounding amount of the plate-like filler in the thermoplastic resin composition (B) is preferably 5% by weight or more and 50% by weight or less. If it is less than 5% by weight, the effect of improving the scratch resistance of the molded product and the effect of suppressing the warp are small, and if it exceeds 50% by weight, not only the surface appearance is deteriorated but also the falling weight strength is reduced, which should be avoided. Is.

As the thermoplastic resin in (B), the thermoplastic resin used in the pellets in (A) can be used without limitation. Further, in order to obtain sufficient adhesive strength that does not cause delamination in the core layer and the skin layer, (A)
Those which are the same as or compatible with the matrix resin of the pellets are preferable. As the plate-like filler in (B), mica, talc, etc., which are usually mixed with the thermoplastic resin, can be widely used. From the viewpoint of the effect of suppressing warpage, it is desirable to use a filler having a ratio of the average particle diameter to the average thickness of the filler, that is, an average aspect ratio of 10 or more (preferably 20 or more). When granular fillers or fibrous fillers other than plate-like fillers are used, no improvement effect can be obtained for low warpage.

Regarding the multilayer extrusion molding using the pellets of (A) and the thermoplastic resin composition of (B), a conventionally known method using two extruders and a multilayer die can be used without any limitation. However, regarding the plasticization of the pellet of (A), the conditions such as the screw compression ratio and the screw rotation speed should be determined in consideration of the balance between the breakage of the glass fiber and the openability. The multi-layer die may be of two-kind two-layer type or two-kind three-layer type and is determined by the required product performance. That is, when high appearance and high impact resistance are required on both sides, the two-kind three-layer die can be used.

The skin layer thickness of the glass fiber reinforced sheet of the present invention is 0.5 mm or more and 20% or more of the thickness of the core layer.
% Or less. The thickness range mentioned here relates to the skin layer on one side, and when the two-kind three-layer die is used, each skin layer must also be within this range. If the thickness is less than 0.5 mm or less than 20% of the thickness of the core layer, the glass fiber is exposed during molding, the appearance and the difficulty of cracking against falling weight impact are not improved, and the effect of suppressing warpage is You should avoid it because you cannot get it. On the other hand, if it exceeds 100%, brittle fracture is likely to occur against a falling weight impact, which is not preferable.

The composition (B) itself is not excellent in drop weight impact strength, but rather is prone to brittle fracture. However, when the core layer (A) is formed by multi-layer extrusion molding in the thickness range of the present invention. ), It is surprising that an excellent falling weight impact strength can be obtained by the synergistic effect of the skin layer (B). It should be further noted that the glass fiber reinforced sheet according to the production method of the present invention has a falling weight impact even though the core layer thickness is slightly thinner than that of a glass fiber reinforced sheet having the same sheet thickness and having no skin layer. It means that the difficulty of cracking is improved.

Molding of the glass fiber reinforced sheet obtained by the present invention is carried out by heating a sheet having a size substantially equal to or larger than the projected area of the final molded product and shaping by a die, that is, stamping molding. It can be molded by vacuum or pressure molding. These molding methods are preferable molding methods because they do not cause a large flow of the resin, the thickness of the skin layer of the final molded product can be maintained, and the appearance and falling weight impact strength are improved.

[0021]

[Examples] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The evaluation method is as follows. (1) Appearance The glass fiber reinforced sheet and its molded product were visually observed. When the glass fiber is not exposed and the appearance is excellent, it is ◎, when the glass fiber is extremely exposed and the appearance is inferior, X is between the ◎ and ×, the one closer to ◎ is ○, and the one closer to × is △. The judgment was made in four stages in total. (2) Drop weight impact strength Based on the ASTM-D-3029 F method. From the flat part of the molded product
A test piece of 50 mm × 50 mm was cut out and hit by a constant height method from the skin layer side for measurement. The striker has a diameter of 12.7 mm
The test piece support base used had a hole diameter of 38.1 mm, and the test piece was not clamped and was free. Regarding the judgment of breakage, the one in which a crack was generated on the surface of the test piece on the striking side was regarded as breakage.

(3) Scratch resistance According to the JIS K-5400 pencil scratch test, the appearance is ◎ to ○.
Only for the molded product judged to be, a 50 mm × 50 mm test piece was cut out from the flat part of the molded product and measured. × for HB or less, △ for F, ○ for H, 2H
In the above cases, it was judged as ◎. (4) Warp Deformation The molded product was placed on a flat surface and the height of the opposite corner that was lifted when one corner was pressed was measured. This was carried out for each of the four corners, and the maximum value of the four corners was taken as the warp deformation amount of the molded product. The amount of warp deformation was the average of 10 molded products.

Example 1 Polypropylene resin and glass fiber roving having a Tex count of 2200 g / km and an average fiber diameter of 23 μ were pultrusion-molded using a single-screw extruder having a crosshead die, and a fiber content of 40% by weight. %, A pellet having a glass fiber length of 15 mm is used as a core layer, and a polypropylene resin containing 40% by weight of mica having an average particle size of 160 μ and an average aspect ratio of 80% as a filler is used as a skin layer for a two-layer, two-layer multi-layer extrusion molding. went. The thicknesses of the core layer and the skin layer were adjusted to 3 mm and 1 mm (thus the sheet thickness was 4 mm). The obtained glass fiber reinforced sheet had a very good appearance because the core layer reinforced with glass fiber was uniformly covered with the skin layer. This glass fiber reinforced sheet was cut into 320 mm × 320 mm, heated by an infrared heater to a surface temperature of 220 ° C, softened, and kept at 60 ° C.
A molded product 3 (Fig. 2) was molded by placing it on a mold 2 (Fig. 1) of 300 mm x 300 mm x 30 mm in height. Upon heating, glass fibers did not protrude, and a molded product having a good appearance could be obtained. A test piece was cut out from the flat part of the molded product, and the falling weight impact strength and the surface scratch resistance were measured and found to be good. The above results are shown in Table 1.

(Comparative Example 1) The pellets produced in Example 1 were subjected to single layer extrusion molding to prepare a glass fiber reinforced sheet having a thickness of 4 mm and having no skin layer. The obtained sheet had a bad external appearance, and was molded and evaluated in the same manner as in Example 1. However, the external appearance of the molded product was also poor, and surface cracks were likely to occur against a falling weight impact. The results are shown in Table 1.

(Example 2, Comparative Examples 2 to 3) A two-kind two-layer glass fiber reinforced sheet was prepared in the same manner as in Example 1 except that the polypropylene resin having the mica content shown in Table 1 was used as the skin layer. It was made. The sheet was molded and evaluated in the same manner as in Example 1. The results are also shown in Table 1. The glass fiber reinforced sheet according to the present invention of Example 2 had a good appearance, and the appearance of the molded product, the falling weight impact strength, and the scratch resistance were all good. Comparative Example 2 is an example in which a polypropylene resin containing no filler was used as the skin layer, but the surface of the molded product was inferior in scratch resistance although the appearance and the falling weight impact strength were improved. . Comparative Example 3
Is an example in which the amount of mica as the resin for the skin layer was too large, but the appearance of the sheet or the molded product was poor and the falling weight impact strength was not improved.

(Comparative Example 4) The same as Example 1 except that a polypropylene resin containing 40% by weight of calcium carbonate having an average particle diameter of 5 μ (granular filler, described as “calcium charcoal” in Table 1) is used for the skin layer. Sheet production and molding,
An evaluation was carried out. Despite the good appearance, falling weight impact strength, and scratch resistance of the sheets and molded products,
The warp deformation was not improved at all. The results are shown in Table 1.

Comparative Example 5 Wollastonite having an average particle size of 10 μ (fibrous filler, described as “Wollast” in the table) was used.
A sheet was prepared, molded, and evaluated in the same manner as in Example 1 except that 40% by weight of polypropylene resin was used for the skin layer. As in Comparative Example 4, the warp deformation was not improved at all, although the appearance of the sheet and the molded product, the falling weight impact strength, and the scratch resistance were all good. The results are shown in Table 1. (Comparative Example 6) A glass fiber cake having an average fiber diameter of 23μ is formed into a mat and needle punched, a glass mat is laminated with a molten polypropylene resin, and the glass mat is impregnated with the polypropylene resin by heating and pressing to a thickness of 4 mm. A laminated stampable sheet having a fiber content of 40 wt% was prepared. The glass sheet was exposed on the surface of the obtained sheet, and the appearance was poor. Molding and evaluation were carried out in the same manner as in Example 1, but the appearance of the molded product was also poor, and surface cracks were likely to occur against a falling weight impact. The results are shown in Table 2.

(Comparative Example 7) As a skin layer, Example 1
The polypropylene resin containing 40% by weight of mica, which was the same as that used in 1., was single-layer extruded to form a sheet having a thickness of 1.5 mm. On the other hand, as a core layer, a laminated stampable sheet was produced in the same manner as in Comparative Example 4 except that the thickness was 3 mm. The former was reheated to fuse these sheets to produce a multilayer sheet having a skin layer of 1 mm and a core layer of 3 mm (thus a sheet thickness of 4 mm). In this manufacturing method, it is necessary to separately prepare the skin layer sheet and the core layer sheet and fuse them, and the process is very complicated. Further, molding and evaluation were carried out in the same manner as in Example 1, but although the sheet had a good appearance, the glass fiber protruded through the skin layer during heating, and the appearance of the molded article was The drop impact strength was inferior. The results are shown in Table 2.
It was shown to.

(Example 3) Using a two-kind three-layer die,
The thickness of the skin layer, core layer, and skin layer is 1 mm and 3 respectively.
A sheet was prepared according to Example 1 except that the thickness was adjusted to 1 mm (thus, the sheet thickness was 5 mm). The obtained glass fiber reinforced sheet had a very good appearance because both sides were covered with skin layers. Hereinafter, molding and evaluation were performed according to Example 1, and a molded product having good appearance, falling weight impact strength, and scratch resistance was obtained. The results are shown in Table 2.
It was shown to.

(Examples 4 to 7, Comparative Examples 8 to 12) The glass fiber length, that is, the LFTP pellet length, and the thicknesses of the skin layer and the core layer were adjusted to the conditions shown in Tables 2 and 3. The glass fiber reinforced sheet was manufactured, molded and evaluated in the same manner as in Example 1. In Examples 6 and 7 and Comparative Examples 10 to 12 shown in Table 3, the total thickness of the skin layer and the core layer was adjusted to 4 mm. The results are shown in Tables 2 and 3, respectively. Example 4-
7, the appearance of the glass fiber reinforced sheet according to the present invention was good, the appearance of the molded product and the falling weight impact strength were greatly improved, and the scratch resistance was also excellent.

On the other hand, in Comparative Example 8, the glass fiber length was too short, but satisfactory drop weight strength was not obtained. Comparative Example 9 is an example in which the glass fiber length was too long, that is, the pellet length was too long, but it was difficult to feed into the extruder and the sheet could not be produced. Comparative Example 10
Is an example in which the skin layer was provided but the thickness was too thin, but some glass fibers were exposed on the surface during molding, and the appearance of the molded product and the falling weight impact strength were unsatisfactory. Comparative example
11 and 12, respectively, when the thickness of the skin layer is too thick,
In the case of only the skin layer, the appearance of the sheet, the appearance of the molded product, and the scratch resistance were good, but brittle fracture occurred against the falling weight impact.

Example 8, Comparative Examples 13 to 14 A glass fiber reinforced sheet was produced in the same manner as in Example 1 except that the thicknesses of the skin layer and the core layer were adjusted to the conditions shown in Table 3. The total thickness of the skin layer and core layer was adjusted to 1.3 mm. After evaluating the appearance of the obtained sheet, it was cut into 320 mm × 320 mm and cut with an infrared heater.
It was heat-softened to ℃, placed on a mold 2 (Fig. 1) of 300 mm × 300 mm kept at 60 ℃, and molded. The molded product was evaluated in the same manner as in Example 1. The results are shown in Table 3.

Example 8 is an example of the glass fiber reinforced sheet according to the present invention, and it was excellent in sheet appearance, molded article appearance, falling weight impact strength and scratch resistance. In Comparative Example 13, the skin layer is too thin, but the sheet appearance, the appearance of the molded product, and the falling weight impact strength are not improved. In Comparative Example 14, the skin weight was too thick, but the falling weight impact strength was poor.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

The glass fiber reinforced sheet manufacturing method of the present invention comprises a glass fiber reinforced pellet as a core layer and a thermoplastic resin mixed with a plate-like filler as a skin layer for multilayer extrusion molding. The process is extremely simple and easy as compared with the case where a skin layer is attached to the.

Moreover, since the pellets in which the resin is impregnated between the glass fibers are extruded in advance, the residual stress in the glass fibers is small, and even if the sheet is heated above the melting point of the resin, the glass fibers are projected. Is rarely seen. Moreover, since the glass fiber length, the type and amount of the filler of the skin layer resin, the blending amount, the thickness of the skin layer, and the ratio of the thickness of the skin layer and the core layer were specified, not only the sheet itself but also stamping molding, vacuum, pressure molding The molded product obtained by doing so has an extremely good appearance, is resistant to cracking due to impacts such as falling weights, and is also excellent in surface scratch resistance and low warpage. Therefore, the glass fiber reinforced sheet according to the present invention,
It can be widely used as various structural parts as it is or after being molded. In particular, the good appearance, falling weight impact strength, and scratch resistance can be utilized to suitably use as a component constituting the surface.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a state in which a glass fiber reinforced sheet heating blank is placed on a mold, which is one step of stamping molding in an example of the present invention.

FIG. 2 is a schematic view showing the shape of the obtained molded product.

[Explanation of symbols]

 1 ... Glass fiber reinforced sheet heating blank, 2 ... Mold, 3 ... Molded product.

Claims (1)

[Claims] 1. The following (A) is used as a core layer, and the following (B) is used as a skin layer covering one side or both sides of the core layer, and the thickness of the skin layer is 0.5 mm or more on one side and the thickness of the core layer is Method for producing glass fiber reinforced sheet characterized by multi-layer extrusion molding from 20% to 100%: (A) glass fiber roving impregnated with thermoplastic resin
Pellets cut to a length of 5 mm or more and 30 mm or less, (B) 50
A thermoplastic resin composition comprising a thermoplastic resin in an amount of 95% by weight or more and 95% by weight or less, and a plate-like filler in an amount of 5% by weight or more and 50% by weight or less.