JPH04216015A - Manufacture of thermosetting fiber reinforced resin sheet - Google Patents

Abstract

PURPOSE:To prevent the generation of blisters and lowering of strength at the time of hot press molding by manufacturing a thermosetting fiber reinforced resin sheet composed of short fiber impregnated with thermosetting paste evenly and sufficiently. CONSTITUTION:A glass roving 10 is cut short and dropped downward. Styrene monomer is sprayed to said dropping fiber by spraying devices 51 and 52. After that, said short fiber is dropped to the coated face of a substrate film 32 coated with thermo-setting unsaturated polyester resin paste and accumulated in the sheet shape. Further, the coated face of a separate substrate film 31 coated with thermosetting unsaturated polyester paste is laminated over said first film, which is clamped by a couple of endless belts 41 and 42 and transferred. A bath tub is molded by using a sheet molding component(SMC) thus manufactured and hot press molding through the conventional procedures. Blisters are not generated on said bath tub and its strength is good.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing thermosetting fiber reinforced resin sheets such as sheet molding compounds (SMC).

0002

[Prior Art] This type of thermosetting fiber-reinforced resin sheet is generally produced by cutting fiber roving such as glass roving into short lengths and letting them fall downward, and applying thermosetting unsaturated polyester resin to a large number of cut short fibers. It is manufactured by impregnating a thermosetting resin paste such as paste (for example, Japanese Patent Application Laid-Open No. 63-230742 and Japanese Patent Application Laid-open No. 2-2201).
(See Publication No. 0).

0003

[Problem to be Solved by the Invention] In this method of manufacturing a thermosetting fiber-reinforced resin sheet, since the viscosity of the thermosetting resin paste is high, the thermosetting resin paste is mixed with the cut short fibers. It is difficult to impregnate uniformly and sufficiently. Therefore, voids may remain between a large number of cut short fibers.

[0004] When a fiber-reinforced resin molded article having a desired shape is produced by curing the resin by, for example, a hot press molding method using a thermosetting fiber-reinforced resin sheet in which voids remain, it is possible to produce a fiber-reinforced resin molded article having a desired shape. There is a problem that blistering occurs and mechanical strength decreases, making it impossible to obtain a molded article of good quality. The present invention solves the above-mentioned problems, and its purpose is to uniformly and sufficiently impregnate cut short fibers with thermosetting resin paste, thereby preventing the occurrence of blistering and reduction in mechanical strength. It is an object of the present invention to provide a method for producing a thermosetting fiber-reinforced resin sheet, which allows a fiber-reinforced resin molded article of good quality to be obtained without any problems.

[0005]

[Means for Solving the Problems] The method for producing a thermosetting fiber-reinforced resin sheet of the present invention involves cutting fiber rovings into short lengths and dropping them downward, and impregnating the cut short fibers with a thermosetting resin paste. The method for producing a thermosetting fiber-reinforced resin sheet is characterized by spraying a crosslinking monomer of the resin onto short fibers that have been cut and are falling downward, thereby achieving the above object. .

[0006] The thermosetting resin paste used in the present invention is
Generally, 100 parts by weight of thermosetting resin liquid and 0 curing catalyst
．． It is prepared by blending 5 to 5 parts by weight of a chemical thickener, 0.1 to 10 parts by weight of a chemical thickener, 20 to 600 parts by weight of a filler, and, if necessary, a release agent, a stabilizer, a coloring agent, and the like. The thermosetting resin liquid is a thermosetting resin such as unsaturated polyester or vinyl ester resin (epoxy acrylate), and if necessary, 30% by weight or less of a shrinkage prevention resin such as styrene polymer. A liquid product prepared by diluting the above-mentioned resin with 5 to 70% by weight of the crosslinking monomer is preferably used. Styrene is generally used as the crosslinking monomer, and methylstyrene, vinyltoluene, diallyl phthalate, triallyl phthalate, and the like are also used.

As the curing catalyst, organic peroxides such as benzoyl peroxide and t-butyl peroxybenzoate are used. As the chemical thickener, magnesium oxide, magnesium hydroxide, etc. are used. As the filler, calcium carbonate, clay, aluminum hydroxide, etc. are used. Further, as the mold release agent, zinc stearate, calcium stearate, etc. are used. As the stabilizer, hydroquinone, parabenzoquinone, etc. are used.

[0008] The fiber roving used in the present invention includes:
Generally, glass rovings with monofilament diameters of 1 to 50 microns are used. Further, the length of short fibers obtained by cutting the fiber roving into short lengths is usually 0.5 to 500 mm, and particularly preferably 5 to 15 mm. If the length of the reinforcing fibers is less than 0.5 mm, the reinforcing effect will be small;
If it exceeds mm 2 , it becomes difficult to obtain a homogeneous fiber-reinforced resin molded article.

[0009] The proportion of short fibers when impregnating the above thermosetting resin paste with short fibers is appropriately determined depending on the physical properties required of the fiber-reinforced resin molded product, but the proportion of short fibers in the sheet is 5 to 70%. The content is preferably in the range of % by weight. If the short fiber content exceeds 70% by weight, it will be difficult to obtain a sheet uniformly impregnated with the resin paste, and conversely, if the short fiber content is less than 5% by weight, the mechanical strength of the molded product will decrease.

[0010] The crosslinking monomer to be sprayed onto the short fibers may include the same monomers as those used in preparing the thermosetting resin liquid, such as styrene, methylstyrene, vinyltoluene, diallyl phthalate, triallyl phthalate, etc. etc. are used. The amount of crosslinking monomer sprayed is
Generally, the amount of crosslinking monomer used in preparing the thermosetting resin liquid is smaller than the amount normally used, and the remaining amount is used as the crosslinking monomer for spraying. In this case, the amount of crosslinking monomer for spraying is preferably from 5 to 30% by weight of the total crosslinking monomer used.

The method of the present invention will be explained below with reference to the drawings. FIG. 1 is a side view of essential parts showing an example of the present invention. In FIG. 1, a large number of fiber rovings 10 such as glass rovings are cut into short fibers of a desired length by a rotary cutter comprising a cutter roll 21 and a rubber roll 22. The cut short fibers fall downward. The short fibers falling downward are sprayed with crosslinking monomer from both sides by crosslinking monomer spraying devices 51 and 52.

On the other hand, the upper and lower supporting films 31 and 32 are
It is supplied while being supported by a pair of upper and lower endless belts 41 and 42. The support films 31 and 32 generally have a thickness of 25 to 1
00 μm polyethylene film, polypropylene film, nylon film, polyester film, etc. are used. Thermosetting resin paste is applied to the inner surfaces of the support films 31 and 32 by thermosetting resin paste application devices 61 and 62.

The short fibers sprayed with the crosslinking monomer are attached to the lower support film 3 coated with a thermosetting resin paste.
The particles fall onto the inner coating surface (upper surface) of 2, and are transported in the direction of the arrow while being accumulated in a sheet form. 70 is a stacked layer of short fibers. On this stacked layer 70, the inner coated surface (lower surface) of the upper support film 31 coated with the thermosetting resin paste is superimposed, and the upper and lower supporting films 31, 32 coated with the thermosetting resin paste are overlapped. A laminate 80 is obtained in which the short fiber accumulated layer 70 is sandwiched between. This laminate 80 is
The sheet is passed through a gap between a pair of upper and lower endless belts 41, 42 and a conventional transfer device (not shown) such as a plurality of pairs of rolls, heated to an appropriate temperature, cooled to room temperature, and wound up.

When the laminate 80 passes through a conventional transport device such as a pair of upper and lower endless belts 41 and 42 and a plurality of pairs of rolls, the thermosetting resin paste applied to the support films 31 and 32 is removed. is impregnated into the short fiber accumulated layer 70 to form a compound. In this way, a thermosetting fiber-reinforced resin sheet in which the compound is sandwiched between supporting films is manufactured.

FIG. 2 is a side view of main parts showing another example of the present invention. In FIG. 2, instead of the thermosetting resin paste coating devices 61 and 62 shown in FIG. A scraping roll 92 is provided. Other than that, the device is the same as the device shown in FIG. In FIG. 2, a large number of fiber rovings 10 such as glass rovings are connected to a cutter roll 21 and a rubber roll 22.
The fibers are cut into short fibers of desired length by a rotary cutter consisting of. The cut short fibers fall downward. Then, the short fibers falling downward are sprayed with a crosslinking monomer from both sides by the crosslinking monomer spraying devices 51 and 52, and fall between the pair of impregnating rolls 90. On the other hand, thermosetting resin paste is supplied in a curtain shape onto the left and right impregnating rolls 90 from left and right thermosetting resin paste supplying devices 91 provided above the pair of impregnating rolls 90, respectively.

The short fibers sprayed with the crosslinking monomer and the thermosetting resin paste are impregnated and mixed while passing through the gap between a pair of impregnating rolls 90 rotating in the direction of the arrow to form a compound. Most of this compound falls onto the inner surface (upper surface) of the lower support film 32 passing under the pair of impregnating rolls 90 and is accumulated in the form of a sheet. 70 is an integrated layer of compound. Note that the remaining compound adhering to the pair of impregnating rolls 90 is scraped off downward by a scraping roll 92 provided below the pair of impregnating rolls 90. This scraping roll 32 rotates in the opposite direction to the corresponding impregnation roll 90.

The inner surface (lower surface) of the upper support film 31 is overlapped with the compound accumulated on the inner surface of the lower support film 32, and the upper and lower support films 31
, 32, with the compound layer 70 sandwiched between them to form a laminate 80. This laminate 80 is transported by a conventional transfer device such as a pair of upper and lower endless belts 41 and 42 and a plurality of pairs of rolls.
(omitted in the figure) is passed through the gap, heated to an appropriate temperature, cooled to room temperature, and wound up. In this way, a thermosetting fiber-reinforced resin sheet in which the compound is sandwiched between supporting films is manufactured.

[0018]

[Operation] Fiber roving is cut into short lengths and dropped downward, and when the cut short fibers are impregnated with thermosetting resin paste to produce a thermosetting fiber-reinforced resin sheet, they are cut and dropped downward. When the crosslinking monomer of the resin is sprayed onto the short fibers inside, the crosslinking monomer has good impregnating properties and is uniformly impregnated into the short fibers. Then, when the thermosetting resin paste comes into contact with these short fibers, the thermosetting resin paste is well mixed with the crosslinking monomer impregnated into the short fibers, and the thermosetting resin paste is uniformly applied to the short fibers. The entire area is evenly and thoroughly impregnated.

[0019] If a crosslinking monomer is sprayed on the fiber roving before it is cut into short lengths, the cut short fibers will adhere to the rotary cutter, and when these short fibers fall downward, they will not be uniformly dispersed, resulting in a paste. The impregnating property of the material also deteriorates.

[0020]

[Examples] Examples and comparative examples of the present invention will be shown below. Example 1 In this example, a sheet molding compound (SMC) was manufactured by the method shown in FIG.

40 parts by weight of unsaturated polyester, 42 parts by weight of styrene monomer, 10 parts by weight of styrene polymer, t-
A thermosetting resin paste was prepared by mixing 1 part by weight of butyl peroxybenzoate, 140 parts by weight of calcium carbonate, 1 part by weight of magnesium oxide, and 4 parts by weight of zinc stearate. In addition, a large number of reinforcing fiber rovings 10 made of glass rovings (monofilament diameter approximately 13 μm, count 4630 g/km) were used.

[0022] This large number of reinforcing fiber rovings 10 were cut into short fibers of about 25 mm in length by a rotary cutter consisting of a cutter roll 21 and a driving rubber roll 22, and the cut fibers were allowed to fall downward. Styrene monomer was then sprayed from both sides onto the short fibers falling downward. In this case, the styrene monomer sprayed onto the short fibers was adjusted to contain a total of 60 parts by weight. On the other hand, upper and lower support films 31 and 3 made of nylon film with a thickness of 50μ
2 was supplied while being supported by a pair of upper and lower endless belts 41 and 42. Then, the above thermosetting resin paste was applied to the inside of the upper and lower support films 31 and 32 using supply devices 61 and 62.

Then, the short fibers sprayed with styrene monomer are dropped onto the inner coated surface (upper surface) of the lower support film 32 coated with the thermosetting resin paste, and are transferred in the direction of the arrow while being accumulated in a sheet shape. did. Subsequently,
The inner coated surface (lower surface) of the upper support film 31 coated with thermosetting resin paste is superimposed on the short fiber layer 70 accumulated in a sheet shape, and this laminate 80 is attached to a pair of upper and lower endless belts 41, 42 and pairs of rolls, heated to about 40° C. and then wound into rolls at room temperature. In this case, the sheet production speed was 3 m/min, the sheet thickness was approximately 2 mm, and the glass fiber content was approximately 28% by weight.

[0024] The SMC scroll produced in this way (
(approximately 100 kg) was left in a thermostatic chamber at approximately 50°C for approximately one day to ripen. After cutting the aged SMC and peeling off the support film, 30 sheets were stacked and subjected to a pressure of 100.
A bathtub was manufactured by continuous hot press molding under the conditions of kgf/cm2, temperature of 150° C., and time of 200 seconds. This bathtub molded article did not have any blisters on its surface, and had excellent mechanical strength and good quality. Example 2 In this example, a sheet molding compound (SMC) was manufactured by the method shown in FIG.

The same number of reinforcing fiber rovings 10 as used in Example 1 were cut into approximately 25 m by a rotary cutter consisting of a cutter roll 21 and a driving rubber roll 22.
The fibers were cut into short fibers with a length of m and allowed to fall downward. Styrene monomer was then sprayed from both sides onto the short fibers falling downward. In this case, the styrene monomer sprayed onto the short fibers was adjusted to contain a total of 60 parts by weight. on the other hand,
The same thermosetting resin paste as used in Example 1 was supplied from supply devices 91 and 92 onto a pair of impregnated rolls 90 in a curtain shape.

The above short fibers sprayed with styrene monomer and the thermosetting resin paste are impregnated and mixed to form a compound while passing through the gap between a pair of impregnating rolls 90, and the thickness of the compound passing through the lower part of the compound is Inside the lower support film 32 made of 50μ nylon film (
The material was dropped onto the top surface) and transferred in the direction of the arrow while accumulating in a sheet shape.

Then, the inner side (lower surface) of the upper support film 31 made of a similar nylon film is superimposed on the compound layer 70 accumulated in a sheet form inside the lower support film 32, and then a pair of upper and lower endless layers are layered. It was passed through the gap of a conventional transfer device such as belts 41, 42 and pairs of rolls, heated to about 40° C., and then wound into a roll at room temperature. In this case, the sheet manufacturing speed is 3 m/
The thickness of the sheet was approximately 10 mm, and the glass fiber content was approximately 28% by weight.

[0028] The SMC scroll produced in this way (
(approximately 100 kg) was left in a thermostatic chamber at approximately 50°C for approximately one day to ripen. After cutting the aged SMC and peeling off the support film, 6 sheets were stacked and subjected to a pressure of 100k.
A bathtub was manufactured by continuous hot press molding under the conditions of gf/cm2, temperature of 150°C, and time of 200 seconds. This bathtub molded article did not have any blisters on its surface, and had excellent mechanical strength and good quality. Comparative Example 1 In Example 1, 42 parts by weight of styrene monomer was replaced with 60 parts by weight of styrene monomer.
A thermosetting resin paste was prepared by changing the parts by weight. Furthermore, the styrene monomer was not sprayed onto the short fibers that had been cut and were falling downward. Other than that, the same procedure as in Example 1 was carried out. In this case, blistering occurred on the surface of the bathtub molded body. Comparative Example 2 In Example 2, 42 parts by weight of styrene monomer was replaced with 60 parts by weight.
A thermosetting resin paste was prepared by changing the parts by weight. Furthermore, the styrene monomer was not sprayed onto the short fibers that had been cut and were falling downward. Other than that, the same procedure as in Example 2 was carried out. In this case as well, blistering occurred on the surface of the bathtub molded body.

[0029]

[Effects of the Invention] As described above, according to the method of the present invention, by spraying a crosslinking monomer of a thermosetting resin onto the cut short fibers, the thermosetting resin paste is uniformly spread over the short fibers. As a result, a thermosetting fiber-reinforced resin sheet can be obtained which is uniformly and sufficiently impregnated and leaves no voids between the short fibers.

[0030] When such a thermosetting fiber-reinforced resin sheet is used to cure the resin by, for example, a hot press molding method to produce a fiber-reinforced resin molded article of a desired shape, blisters appear on the surface of the molded article. It is possible to prevent the occurrence of cracking and decrease in mechanical strength, and to obtain a molded article of good quality.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts showing an example of the method of the present invention.

FIG. 2 is a side view of essential parts showing another example of the method of the present invention.

[Explanation of symbols]

10 Fiber roving 21 Cutter roll 31 Support film 32 Support film 41 Endless belt 42 Endless belt 51 Crosslinking monomer spraying device 52 Crosslinking monomer spraying device 61 Thermosetting resin paste coating device 62 Thermosetting resin paste coating device 90 Thermosetting resin paste impregnated roll 91 Thermosetting resin paste supply device

Claims (1)

[Claims] Claim 1. A method of manufacturing a thermosetting fiber-reinforced resin sheet by cutting a fiber roving into short lengths and letting them fall downward, and impregnating the cut short fibers with a thermosetting resin paste. A method for producing a thermosetting fiber-reinforced resin sheet, which comprises spraying a crosslinking monomer of the resin onto falling short fibers.