JPH0444813A - Preparation of thermosetting resin molding - Google Patents

Abstract

PURPOSE:To reduce anisotropy of strength caused by orientation of a reinforcing material, to improve strength as a whole, to change the position of a weld line at every feeding of a molding material and to reduce decrease in strength caused by the weld line by changing a feeding position of the molding material. CONSTITUTION:A molded item 1 prepd. by injection molding or transfer molding consists of a part 11 molded by the first feeding of the molding material and the second molded part 12. Each weld line produced on each molding on the first feeding position 21 of the molding material and the second feeding position 22 of the molding material crosses in the thickness direction at the first time 111 and the second time 121 to reduce decrease in strength of the weld line. In addition, as the flow direction of the molding material in a mold differs at the first time and the second time, orientation of a reinforcing material correspondingly differs to reduce anisotropy of the strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a thermosetting resin molded article using a thermosetting resin molding material such as BMC or SMO.

[Conventional technology]

Conventionally, BMC (Park Moding Compound),
When manufacturing molded products using a thermosetting resin molding material (hereinafter simply referred to as molding material) such as SMC (sheet molding compound) by a molding method such as compression molding, transfer molding, or injection molding. , the required amount of molding material is fed into the mold at once and cured.

By the way, in the above case, reinforcing materials such as fibers in the molding material are generally oriented in accordance with the flow of the molding material within the molding die, so the molded product is mechanically oriented in the direction in which the reinforcing materials are not oriented. There was a problem that the mechanical strength decreased, resulting in a molded product with so-called large strength anisotropy. Further, there was also a problem that the strength of the part (weld line) where the molding material separates and joins again is reduced.

In response to such a decrease in mechanical strength, (11) increasing the product wall thickness, (2) providing reinforcing ribs, (3) simultaneously molding a wire mesh inside the molded product (Japanese Patent Laid-Open No. 61-215026
Methods such as the following were taken.

[Problems to be Solved by the Invention] However, the methods (1) and (2) above not only increase the weight of the product, but are also limited by the shape of the product. In addition, dents were likely to occur on the surface of the molded product in thick parts and reinforcing rib parts, which was not desirable in terms of appearance.

Furthermore, in method (3), the wire mesh tends to appear on the surface of the molded product due to the internal pressure of the resin, and cannot be applied to products where surface quality (appearance) is important. Furthermore, when the molding material supply rate is high, the wire mesh may be pushed to one side by a lil length due to the resin pressure when the molding material flows, making it impossible to obtain a reinforcing function. Furthermore, the weight of the product increases by the weight of the wire mesh.

In view of the above points, the present invention has been developed to minimize the provision of reinforcing ribs without increasing the thickness of the product.2.
4. Another object of the present invention is to obtain a thermosetting resin molded product with little strength anisotropy and, as a result, high strength, without using special reinforcing materials such as wire mesh.

[Means to solve the problem]

The method J for producing a thermosetting resin molded article of this invention is a method in which the thermosetting resin molding material is supplied to the mold in at least two parts, and the thermosetting resin molding is carried out after the second The material is supplied after the previously supplied thermosetting resin molding material has hardened, and the feeding position of the mold of the thermosetting resin molding material is the same as that of the previous thermosetting resin molding material. The main feature is that the supply position of the resin molding material is different, thereby achieving the above object.

The thermosetting resin molding materials (hereinafter sometimes simply referred to as molding materials) used in this invention include conventionally used fiber-reinforced materials such as pulc molding compound (BMC) and sheet molding compound (SMC). Thermosetting resin molding materials are particularly preferably used.

7. As the thermosetting resin, unsaturated polyester resin, vinyl ester resin, etc. are preferably used, and as reinforcing fibers, for example, glass fiber, carbon fiber, boron fiber, copper fiber, stainless steel etc. Inorganic fibers such as fibers and synthetic fibers such as polyamide fibers and polyester fibers are used.

In addition, methods for supplying a molding material into a mold and curing it to mold a thermosetting resin molded product include compression molding,
. Molding methods include transfer molding, injection molding, and the like, and in the present invention, compression molding equipment, transfer molding equipment, and injection molding equipment used in conventional molding of thermosetting resins are used.

In these devices, the molding material is supplied to the mold in at least two parts7, and the cavities of the second and subsequent molds are sequentially enlarged at the time of closing so that the molding material is molded and hardened each time the molding material is supplied. It is said to be a mechanism like this. That is, when the molding material is supplied for the second and subsequent times, the mold is opened further by a predetermined amount, and a new mold cavity is formed at that position. In this way, a cylindrical molded product cannot be formed using a mechanism that gradually widens the gap between molds. When molding a cylindrical molded product, a common core is used, and the second and subsequent cavities are each equipped with gates, runners, etc. in different positions, and the core in which the molding material is molded and solidified is used. The mechanism may be such that it can be attached to the next cavity, and the molding material is sequentially supplied and molded and solidified.

The smell of injection molding method, transfer molding method, etc. The gate and runner of the mold can be switched by, for example, a shirt-off mechanism, so that the supply position of the molding material can be changed. Furthermore, instead of sequentially supplying the molding material from one injection molding machine, two or more injection molding machines may be used and the molding material may be sequentially supplied from each of the injection molding machines.

It is preferable that operations such as measuring and supplying the amount of molding material, opening and closing of the mold, switching of the gate and launch, etc., be automatically performed by the control device.

In this invention, the molding material supply position means the gate position for supplying the molding material into the cavity formed by closing the mold in transfer molding, injection molding, etc. In compression molding, it refers to the position where the molding material is loaded into the mold cavity.

The supply position of the molding material will be further explained with reference to the drawings.

Figure 1 is a perspective view for explaining the relationship between the supply position of molding material and the molded product in the injection molding method or transfer molding method of this invention, and Figures 2 (a) and (b) are FIG. 2 is an explanatory diagram showing the position where the molding material is loaded into the cavity of the mold according to the method of the present invention in compression molding.

In FIG. 1, reference numeral 1 denotes a molded article molded by the injection molding method or transfer molding method of the present invention, and is a rectangular plate having a through hole 13 on the right side. This molded product 1 consists of a part 11 molded by the first supply of molding material and a part 12 molded by the second molding.

21 is the first molding material supply position II (gate position), and 22 is the second molding material supply position (gate position). The weld lines generated during each molding are indicated by 111 for the first molding and 111 for the second molding.
As shown by 21, they appear at different angles in the thickness direction, and the decrease in strength of the weld line portion is reduced. Further, since the flow direction of the molding material in the mold is different between the first and second times, the orientation of the reinforcing material is different, and the anisotropy of the strength is reduced. This is demonstrated in the examples described below.

FIGS. 2A and 2B are two examples showing the relationship between the cavity and the molding material supply position in the compression molding method of this invention. First, the first example will be explained based on FIG. 2 (A). 3 is a cavity, 41 is a sheet-shaped molding material that is supplied first, and 42 is a sheet-shaped molding material that is supplied next. As shown in the figure, the supply position is changed by orthogonal to each other.

Next, in the case of FIG. 2 (b), the molding material is supplied in four parts, and the mold 5 which forms the through-hole part of the molded product
A sheet-like molding material 61.6 is placed in the cavity 5 equipped with 1
2, 63, and 64 are sequentially supplied to the positions shown after the previously supplied molding material has hardened. In addition, 641 is the fourth
This is the position where the weld line caused by the supply of the molding material 64 for the second time occurs, and although not shown, it overlaps with each weld line caused by the first to third molding materials.
The orientation of the reinforcement will also be different.

Note that when the molding material is supplied to the mold in three or more portions, this does not mean that the molding material is supplied to different positions in the present invention. For example, in Figure 2 (a), the molding material is further added to the molding material 1 for the first time.
The molding material may be supplied to the same position as in 1, that is, the position where the molding material is supplied for the third time may be the same as that for the first time.

[Effect]

In this invention, due to the different supply positions of the molding materials, the flow of each molding material in the mold is different, and therefore the orientation of the reinforcing material is different from the orientation of the reinforcing material of the molding material layer supplied before. It becomes like this. Therefore, the anisotropy in strength caused by the orientation of the reinforcing material is alleviated, and a molded article with improved strength as a whole can be obtained. Furthermore, the position of the weld line is changed each time the molding material is supplied, and strength reduction due to the weld line portion is reduced.

〔Example〕

(Example 1, Comparative Example 1) In carrying out the method of this invention, a normal injection molding machine exclusively for SMC was used. However, in order to inject the molding material in two or more separate injections, the mechanism was modified so that the amount of mold opening can be controlled in multiple stages using a hydraulic cylinder, and the necessary amount of molding material can be injected each time.

Using this equipment, in order to mold a rectangular plate (150x360x3WM) with punched holes 3 in some parts as shown in Fig. 1, the molding material SMC (polyester resin content 2
4i1t%, filler: 48-t%, reinforcing material: 1-inch glass fiber: 28-t%).
The SMC was divided into two portions of 0 g each, and as shown in FIG. 1, the first SMC supply position was at 11, and the second SMC supply position was at 21. Of course, the first SMC
During the injection, the mold cavity of the mold was set to 1/2 the thickness of the one-time injection, and after curing, the mold cavity was set to correspond to the remaining part of the molded product, and a second injection molding was performed. At this time, the mold temperature was approximately 150° C., and the curing time was 1.5 minutes each.

For comparison, a molded product similar to Example F was molded except that 300 g was injected at once from position 11 in Figure 1 (mold temperature: approximately 150°C, curing time: 3 minutes). ).

These molded products are the best. Six test pieces were taken from the position shown in FIG. 3 in the a direction and the b direction, and the bending strength was measured based on the industry standard (JIS 7055). The results (average values) are shown in Table 1.

Table 1 As is clear from the results, the molded product produced by the method of this invention has anisotropy of strength in the a direction and the b direction (h /a)
is significantly smaller, and the overall strength is excellent. Further, the position of the weld line was also as shown in FIG.

(Examples 2 and 3, Comparative Example 2) As molding materials, polyester resin content 24wt%, filler 48-t%, reinforcing material (1 inch glass fiber) 28w
t% containing SMC (wall thickness 1.2, gelling time 42 seconds at 135°C), top press type hydraulic press (mold clamping force 3
50 tons) and compression molding mold with pinch-off (cavity; 300 x 3ooxion, travel 15 m1)
), the square plate (3
00x300x4 fl) was molded. The total amount of molding material was 600 g, the mold temperature was 150° C., and the molding pressure was 100 kgf/cd.

(1) Example 2 First, a 200 x 120 m (weight 300 g) seal l-
A shaped molding material was applied to the position shown at 2 in Figure 2 (a) and cured for 1.5 minutes, and then the same molding material was applied on top of it at the position shown at 3 in Figure 2 (a). supply to 1
．． Allowed to cure for 5 minutes. The result is 1.300X300X4n
A molded product of i was obtained.

(2) Example 3 First, a sheet-shaped molding material of 200 x 80 mm (weight 200 g) was supplied to the position indicated by 2 in Fig. 2 (A) and cured for 1 minute, and then the same molding material was placed on top of it. The molding material was supplied to the position indicated by 3 in FIG. 2(a) and cured for 1 minute.The same molding material as before was then supplied to the same position as the first time and cured for 1 minute. As a result, 300x300x4m'm
A molded product was obtained.

(3) Comparative Example 2 Three sheets of 200 x 80 m+ sheet molding material (weighing 600 g) were supplied to the position indicated by 2 in Figure 2 (a) and cured for 3 minutes to form a 300 x 300 x 4 m molded product. Obtained.

Regarding these molded products, the position 11 as shown in Figure 4
Six test pieces were taken from each of 2B (for tensile test) 7, C (for bending test, b direction) and II) (for bending test, a direction), and the tensile strength and bending strength were measured according to the Japanese Industrial Standards (JIS). K 7055.JiS K 7055). The results (average values) are shown in Table 21
That's right.

Table 2 As is clear from the results, the molded product produced by the method of this invention has anisotropy in strength in the a direction and b direction (b/a ) is significantly smaller, and the overall strength is excellent.

〔Effect of the invention〕

As described above, in the method for manufacturing a thermosetting resin molded product of the present invention, the molding material is supplied to the mold twice or more, and after the previously supplied molding material has hardened, the feeding position is changed and the next supply is performed. Since the molding material is supplied with molding material of The position of the weld line can be changed.

Therefore, in the thermosetting resin molded product obtained by the method of the present invention, the anisotropy in strength due to the orientation of the reinforcing material is alleviated, and the decrease in strength due to the weld line portion is reduced.
The overall strength is excellent.

[Brief explanation of drawings]

Figure 1 is a perspective view for explaining the relationship between the supply position of molding material and the molded product in the injection molding method or transfer molding method of this invention, and Figures 2 (a) and (b) are FIG. 2 is an explanatory diagram showing the position where the molding material is loaded into the cavity of the mold according to the method of the present invention in compression molding. 1... Molded product, 21.22-... Molding material supply position 3.5-Cavity, 41, 42.61.62°63.
64 - Molding material, A, B, C, D - Sampling position of test piece.

Claims (1)

[Claims] (1) In a method of supplying a thermosetting resin molding material into a mold and curing it to mold a thermosetting resin molded article, the thermosetting resin molding material is supplied to the mold in at least two parts, The second and subsequent supply of thermosetting resin molding material is performed after the previously supplied thermosetting resin molding material has been cured, and the supply position of the thermosetting resin molding material to the mold is is different from the previous feeding position of the thermosetting resin molding material.