JP2016097564A - Molding method of glass fiber reinforced resin molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method capable of providing an injection molded article having enhanced not only tensile strength but also other mechanical strength such as impact absorption energy by mixing and injection molding a pellet containing only long fiber and a pellet containing only short fiber.SOLUTION: A first pellet containing a glass long fiber having diameter of 10 μm to 20 μm and length of 5 mm to 20 mm in a polypropylene resin and a second pellet containing a grass short fiber having diameter of 10 μm to 20 μm and length of 0.5 mm to 3 mm in the polypropylene resin are mixed at a percentage of 19:1 to 7:3 of a ratio of the long fiber and the short fiber and injection molded to make residue weight average fiber length of the glass fiber of a molded injection molded article longer than residue weight average fiber length of the glass fiber when obtaining a molded article by injection molding the first pellet only and the second pellet only respectively and set impact absorption energy at high value.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for molding a glass fiber reinforced resin molded product, and in particular, a pellet containing a long glass fiber having a long fiber length and a pellet containing a short glass fiber having a short fiber length are mixed and injection molded. The present invention relates to a glass fiber reinforced resin molded product molding method for molding a glass fiber reinforced resin molded product.

In recent years, in the automobile industry, weight reduction is urgently required from the viewpoint of global warming, CO ₂ gas countermeasures, and fuel efficiency improvement, and development of replacement of a conventional metal plate structure to a resin structure has been accelerated. Since the resin material used for the structure is required to have high rigidity, high strength, impact resistance, and the like, fiber reinforced composite materials using glass fibers, carbon fibers, and the like have been widely studied.

  Conventionally, for example, glass fiber reinforced thermoplastic synthetic resin molded products such as glass fiber reinforced polypropylene are known. There are two known types of glass fibers that should be premixed in the synthetic resin pellets: short and long. Injection molded products using long fiber-containing pellets generally have the advantages of higher tensile strength and bending strength and less sinking than those using short fiber-containing pellets, while short fiber-containing pellets are used. In injection molding, it is said that since the fibers are short, the moldability is excellent, and the molded product is excellent in appearance and fatigue strength. Here, the long fiber-containing pellet itself has a length of about 6 mm to 12 mm, and the length of the glass fiber as a raw material mixed in the pellet ranges from about 3 mm to approximately the full length of the pellet. On the other hand, the short fiber-containing pellet has a length of about 3 mm, and the length of glass fiber as a raw material mixed in the pellet is said to be about 0.2 to 1.25 mm.

  By the way, with the recent development of injection molding technology, glass fiber reinforced synthetic resin molded products are produced by injection molding. At that time, when glass-fiber pellets containing long glass fibers are used for injection molding, as explained in Patent Document 1 and Patent Document 2, the injection molding machine screws and nozzles are used at the time of injection molding. There is a problem that the glass fiber breaks when the glass fiber passes along with the molten resin through the location and the location of the inflow passage (sprue, runner, gate portion, etc.) to the cavity of the molding die. It is said that mechanical strength is not obtained.

  Therefore, as in Patent Document 3, a technique is known in which a pellet containing short fibers and a pellet containing long fibers are mixed and injection molded. For example, in Patent Document 3, a long fiber-containing pellet containing 30 to 70% by weight of glass fiber having a length of 3 mm or more and 30 to 70% by weight of glass fiber having a length of about 0.3 to 1.25 mm are contained. The obtained short fiber-containing pellets were mixed at a ratio of 2: 8 to 6: 4, and injection molded with a raw material adjusted to contain 30 to 40% by weight of glass fiber in the thermoplastic resin, Further, it contains 30 to 60% by weight of a thermoplastic resin and a glass fiber having a diameter of 3 to 20 μm and a length of 0.25 to 0.5 mm, and contains 30% or more by weight. A glass fiber having an average length of 0.6 to 0.7 mm by frequency distribution is disclosed.

  In Patent Document 3, the tensile strength is higher than that of a product obtained by injection molding using only a long fiber-containing pellet or only a short fiber-containing pellet by mixing and injection-molding a long fiber-containing pellet and a short fiber-containing pellet. Describes that an injection-molded product having a high value can be obtained. Specifically, Patent Document 3 discloses that when mixed at a ratio of short fibers: long fibers = 8: 2 to 4: 6, the tensile strength is higher than that of only short fibers or only long fibers. Yes. In addition, it is disclosed that the tensile strength decreases in the case of short fiber: long fiber = 3: 7 to 1: 9.

JP-A-2-292009 JP-A-8-104774 JP 2001-179738 A (Item 0018, FIG. 5)

  As in Patent Document 3 above, products obtained by mixing long fiber-containing pellets and short fiber-containing pellets and injection-molding are molded with a higher tensile strength than when only long fibers or only short fibers are used. Goods are obtained.

  However, when applying the above injection-molded products to automobile parts, performance such as high rigidity, high strength, impact resistance, etc. is required. However, it was not possible to obtain a product satisfying the required performance as an automobile part. In particular, when applied to automobile parts, it has been strongly demanded to further improve the impact absorption energy.

  Therefore, the present inventors have advanced research from various viewpoints in order to increase the impact absorption energy of a molded article obtained by mixing long fiber-containing pellets and short fiber-containing pellets and injection molding. Among them, even when pellets containing fibers having a long fiber length are used, the fiber length after molding (that is, the remaining fiber length) is significantly shortened after injection molding. Therefore, it was predicted that the impact absorption energy could be increased if the remaining fiber length of the injection-molded product was increased, and research was conducted focusing on increasing the remaining fiber length of the injection-molded product.

  As disclosed in Patent Document 3 above, the remaining fiber length of the injection-molded product is obtained by mixing the 9 mm pellets and the short fiber pellets, which are the same as the pellets, and performing injection molding. The average remaining fiber length is 0.6 to 0.7 mm, which is 10% or less of the original long fiber. In this way, even when mixed with pellets containing long fibers and pellets containing short fibers, generally, the fiber length of the remaining fibers is close to the length of the short fibers. It is said to become.

  For this purpose, the present inventors have accumulated further research to increase the residual fiber length of the injection-molded product, and have delved into it. Among them, when the molding conditions, the size of the long fibers and the short fibers, and the mixing ratio were specified, the fiber length of the injection-molded product could be about 50% or more of the fiber length of the original long fibers.

  The present invention has been made on the basis of the above-mentioned knowledge. When mixing and injection-molding pellets containing only long fibers and pellets containing only short fibers, not only the tensile strength but also impact absorption energy, etc. Another object of the present invention is to provide a molding method capable of obtaining an injection-molded article having improved mechanical strength.

  In order to achieve the above-mentioned object, in the present invention, long fibers remain so as to mix the long glass fibers and the short glass fibers and perform injection molding.

  Specifically, in the first invention, there is provided a method for forming a glass fiber reinforced resin molded article containing glass fiber in polypropylene resin, wherein the polypropylene resin has a glass length of 10 to 20 μm in diameter and 5 to 20 mm in length. A first pellet containing fibers and a second pellet containing short glass fibers having a diameter of 10 μm to 20 μm and a length of 0.5 mm to 3 mm are prepared in a polypropylene resin, and the first pellet and the second pellet are prepared. The pellets were mixed by injection molding with a ratio of the above-mentioned long fibers and the above short fibers of 19: 1 to 7: 3, and the remaining weight average fiber length of the glass fibers of the formed injection-molded product was determined. The residual weight average fiber length of the glass fiber when only the first pellet is injection molded to obtain a molded product, and the glass when the molded product is obtained by injection molding only the second pellet alone Characterized by longer than remaining weight average fiber length of Wei.

  In the second invention, in the first invention, the length of the glass long fiber contained in the first pellet is 7 mm to 15 mm, and the first pellet contains the first pellet and the second pellet. The long fibers and the short fibers contained in the second pellet are mixed at a ratio of 19: 1 to 17: 3 and injection molded.

  In 3rd invention, 1st or 2nd invention WHEREIN: Both said 1st pellet and said 2nd pellet contain glass fiber 30 to 70weight% of the total weight, It is characterized by the above-mentioned.

  According to a fourth invention, in any one of the first to third inventions, the remaining weight average fiber length of the long fibers when the injection molded product of only the first pellet is obtained is the first pellet. In comparison with the fiber length of the long glass fiber contained in the glass, the molding condition is 0.4 times or more, and the first pellet and the second pellet are mixed and injection molded under the molding condition. Features.

  According to a fifth invention, in any one of the first to fourth inventions, the second pellet is composed of pellets obtained by re-kneading the first pellet with a twin screw extruder. .

  According to a sixth invention, in any one of the first to fifth inventions, the injection molding is performed using a low shear screw injection molding machine or a pre-plunger type injection molding machine. .

  According to the first invention, it is possible to obtain an injection-molded article having improved mechanical properties such as impact absorption energy as well as tensile strength.

  According to 2nd invention, the freedom degree of the range which selects the fiber length of a long fiber spreads, and the ratio of the residual weight average fiber length with respect to the residual weight average fiber length after shape | molding only a long fiber with a pellet reliably Can be made 1.00 or more.

  According to the third invention, the amount of fibers to be contained is suitable, and a molded product that can maintain high mechanical strength and is excellent in moldability can be obtained.

  According to the fourth aspect of the present invention, a molding condition is found in which the remaining weight average fiber length after molding only the long fiber with the pellet is 0.4 times or more than the length of the long fiber in the pellet. Since the long fiber pellets and the short fiber pellets are mixed and molded, the ratio of the remaining weight average fiber length to the remaining weight average fiber length after molding only the long fibers with the pellet can be 1.00 or more. .

  In the present invention, the molding conditions include the diameter and length of long fibers, the diameter and length of short fibers, the ratio of these fibers to polypropylene resin, the molding temperature by the molding machine, the number of screw rotations, the back pressure, the screw Including forward speed.

  According to 5th invention, since a 2nd pellet consists of a pellet obtained by re-kneading a 1st pellet with a twin-screw extruder, the familiarity of a 2nd pellet and a 1st pellet is good, and both tangles become good. Thus, the remaining weight average fiber length is expected to be 1.00 or more.

  According to the sixth invention, the residual weight average fiber length can be increased by selecting the injection molding machine so as to achieve low shear.

  General characteristics of low shear are low shear force using screws such as low compression (deep groove), wide flight interval (single flight), wide check ring flow path, etc. It is possible to shear under certain conditions. Examples of the low shear type screw include Japanese Patent Application Laid-Open No. 2005-169646, Republished 2012-056565, and the like.

FIG. 1 is a table showing the average fiber length, the remaining weight average fiber length, the ratio of the remaining weight average fiber length, and the like for samples and comparative examples. FIG. 2 is a graph showing the ratio of the remaining weight average fiber length to the mixing ratio of long fibers and short fibers. FIG. 3 is a graph showing the flexural modulus with respect to the mixing ratio of long fibers and short fibers. FIG. 4 is a graph showing the tensile strength with respect to the mixing ratio of long fibers and short fibers. FIG. 5 is a graph showing the impact absorption energy with respect to the mixing ratio of long fibers and short fibers.

  Hereinafter, an embodiment of the present invention will be described. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

  The thermoplastic synthetic resin used as the basic material of the present invention is a polypropylene resin. The glass fiber contained in the first pellet having a predetermined length has a diameter of approximately 10 μm to 20 μm and a fiber length of approximately 5 mm to 20 mm. On the other hand, in the short fiber-containing pellet, the raw material synthetic resin is also polypropylene resin, and the glass fiber contained in the second pellet having a length of 3 mm has a diameter of about 10 μm to 20 μm, and the fiber length is about 0.5 to 3 mm. Things are lined up almost in one direction.

  The injection molding machine used the model which applies the 1st pellet containing long fiber, and used the upper and lower metal mold | die which has the cavity of the shape of a sample. The injection molding conditions (mold temperature, injection pressure, etc.) were molded under the molding conditions with low shearing force so that the glass fiber remained as long as possible.

  Since the thermoplastic synthetic resin used as the basic material of the present invention is low in cost and friendly to the environment because it does not emit harmful substances during incineration, a polypropylene resin is used.

  In the present invention, the size of the glass fiber used for the first pellet is preferably 10 μm to 20 μm in diameter and 5 mm to 20 mm in length. When the length of the glass fiber is long, the biting into the screw is deteriorated, and problems on the molding surface such as molding cycle and filling failure appear. On the contrary, if it is short, desired physical properties cannot be obtained. Further, if the diameter of the glass fiber is small, the bending rigidity of the desired molded product is lowered. Conversely, if the glass fiber is large, the fluidity is hindered and defects on the molding surface such as poor filling appear. Therefore, the above range is preferable.

  The size of the glass fiber used for the second pellet is preferably 10 μm to 20 μm in diameter and 0.5 mm to 3 mm in length. If the length of the glass fiber is short, it cannot be molded. On the other hand, if the length is long, the length becomes close to the long glass fiber, and the meaning of mixing the short fiber is lost. Similarly to the glass fiber used for the first pellet, if the diameter of the glass fiber is small, the bending rigidity of the desired molded product is lowered. On the other hand, if the glass fiber is large, the flowability is hindered and defects on the molding surface such as defective filling occur. . Therefore, the above range is preferable.

  The ratio of the long glass fiber to the short glass fiber is preferably 19: 1 to 7: 3, particularly 19: 1 to 17: 3. The ratio between the long glass fiber and the short glass fiber is different depending on the length of the long fiber and the content in the first pellet. When the fiber length of the long glass fiber is increased, the above range of ratio increases the short fiber. Tend to be wide in a good direction. However, when the number of short glass fibers increases, the mechanical strength tends to decrease, and the above range is preferable.

  The weights of the glass fibers in the polypropylene resin are preferably long fibers: 30 to 50% by weight / total weight, and short fibers: 30 to 50% by weight / total weight.

  The residual weight average fiber length (described later) of the injection molded product is the residual weight average fiber length of the long fiber when the injection molded product of only the first pellet is molded is contained in the first pellet. It is preferable to mold under molding conditions that are 0.4 times or more compared to the fiber length of the long glass fiber. The upper limit is not basically limited, but in practice, it is sufficient that 0.6 times is obtained.

(Injection molding conditions)
In injection molding, it is preferable to use a low-shear specification screw and to consider molding conditions such as screw rotation speed and back pressure in order to leave glass fibers in the molded product for a long time.

  “Shearing screw” is a general in-line injection molding machine that measures, plasticizes, and extrudes (injects) synthetic resin (injection molding material) with a single screw. It is a screw designed not to apply a shearing force to the resin as much as possible. Specifically, for example, Mitsubishi Heavy Industries Plastic Technology Co., Ltd. long fiber reinforced resin screw, high viscosity resin F screw, Guangzhou Impulse Electric Technology Co., Ltd. conical twin screw or parallel twin screw, Nippon Steel Injection molding machine (J220AD-2M, K-type screw).

  In the injection molding machine as described above, in order to leave the glass fiber in the molded product for a long time, the molding conditions are preferably as follows. The screw rotation speed is preferably 20 to 75 RPM. If the rotational speed is low, defects on the molding surface such as molding cycle and filling failure will occur. On the other hand, when the rotation speed is high, the influence of physical properties due to fiber breakage cannot be ignored. Therefore, the above range is preferable.

  The back pressure is preferably 1 to 15 MPa. If the back pressure is low, defects on the molding surface such as molding cycle and filling failure will occur. Conversely, when the back pressure is high, the influence of physical properties due to fiber breakage cannot be ignored. Therefore, the above range is preferable.

  The screw advance speed is preferably 0.2 to 10 mm / sec. If the screw advance speed is low, defects on the molding surface such as molding cycle and filling failure will occur. On the other hand, if the screw advance speed is high, the influence of physical properties due to fiber breakage cannot be ignored. Therefore, the above range is preferable.

  The injection temperature is preferably 250 to 300 ° C. If the injection temperature is low, defects on the molding surface such as molding cycle and filling failure will occur. Conversely, if the injection temperature is high, the influence of physical properties due to fiber breakage cannot be ignored. Therefore, the above range is preferable.

  Next, specific examples will be described.

(sample)
The first pellet of glass fiber reinforced polypropylene resin (GFPP) is manufactured by a manufacturing method in which glass fiber bundles of glass fibers having a diameter of 15 μm are bundled in one direction and impregnated with molten plastic. As GFPP, Plastron PP-GF40-01 (trade name) manufactured by Daicel Polymer Co., Ltd. containing 40% by weight of glass fiber with respect to the total weight was used. This first pellet is a type in which the length of the pellet (that is, the length of the glass fiber) is long, and is hereinafter referred to as LFP (Long Fiber Plastic). LFP fiber lengths of 15 mm (hereinafter referred to as L15), 11 mm (hereinafter referred to as L11), and 7 mm (hereinafter referred to as L7) are prepared.

  Moreover, the glass fiber reinforced polypropylene resin of the same composition which re-kneaded said LFP with the twin-screw extruder was used for the 2nd pellet. This is a type in which the length of the pellet (that is, the length of the glass fiber) is short, and is hereinafter referred to as SFP (Short Fiber Plastic). The SFP has a fiber length of 3 mm (hereinafter referred to as D3).

  The injection molding machine used was an injection molding machine J220AD-2M (300H K type screw) manufactured by Nippon Steel Co., Ltd. Injection molding conditions are: injection temperature: 280 ° C., screw rotation speed: 60 RPM (the maximum rotation speed of J220AD-2M is 400 RPM, but it is used at a low rotation speed of 60 RPM in order to achieve a low shear force. Back pressure: 5 MPa. And the flat sample was shape | molded. The sample dimensions were 180 mm in the resin flow direction (hereinafter referred to as MD), 175 mm in the resin non-flow direction (hereinafter referred to as TD), and a plate thickness of 3 mm. The test piece was cut out according to JIS K7139.

  Samples were prepared using polypropylene resin pellets containing only D3, L7, L11, and L15 at 40% by weight, respectively, and Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 were prepared. It was. And the molded article was produced using the pellet which mixed the pellet of LFP and the pellet of SFP with the predetermined | prescribed compounding ratio. Samples 21 to 26 are examples in which the molded product includes D3 of 5%, 10%, 15%, 20%, 25%, and 50% with respect to L7 (Comparative Example 2). Further, samples with D3 of 5%, 10%, 15%, 20%, 25% and 50% relative to L11 (Comparative Example 3) were designated as Samples 31 to 36, respectively. In addition, samples with D3 of 5%, 10%, 15%, 20%, 25%, and 50% were set to Samples 41 to 46 with respect to L15 (Comparative Example 4), respectively. These samples and comparative examples are shown in FIG.

(Measurement of residual weight average fiber length)
The remaining fiber lengths of the sample and the comparative example were determined as the remaining weight average fiber length. In the present invention, the remaining weight average fiber length was determined as follows.

  The remaining fiber length (X) is classified into three fiber groups, a short fiber group (2 mm or less), a medium fiber group (2 to 5 mm), and a long fiber group (5 mm or more), and the weight of each fiber group is calculated. To do.

Weight of short fiber group: Wa
Medium fiber group weight: Wb
Weight of long fiber group: Wc
From this weight, the total fiber weight W is calculated.

W = Wa + Wb + Wc
Then, the weight ratio of each fiber group is calculated.

Weight ratio of short fiber group: Wa / W
Medium fiber group weight ratio: Wb / W
Weight ratio of long fiber group: Wc / W
Next, the fiber length of each fiber group is measured by microscopic observation.

Fiber length of short fiber group: d1, d2, d3, ...
Medium fiber group fiber length: e1, e2, e3, ...
Fiber length of long fiber group: f1, f2, f3, ...
The average fiber length is calculated from these fiber lengths.

Average fiber length D of short fiber group: d1 + d2 + d3 + ..., number of fibers Average fiber length of medium fiber group E: e1 + e2 + e3 + ..., number of fibers Average fiber length of long fiber group F: f1 + f2 + f3 + ..., number of fibers The total remaining weight average fiber length was determined by the sum of the products of the average fiber length and the weight ratio.

Residual weight average fiber length H
= (Wa / WxD) + (Wb / WxE) + (Wc / WxF)
(Calculation of ratio of remaining weight average fiber length)
The residual weight average fiber length H was sequentially calculated for each comparative example and sample. The ratio of the remaining weight average fiber length was the ratio of the sample to each comparative example, and was determined as follows.

Residual weight average fiber length (H21) of sample 21 (L7: 95% + D3: 5%) relative to residual weight average fiber length (H2) of Comparative Example 2 (L7: 100%), ie, H21 / H2, Sample 22 Residual weight average fiber length (H22), that is, H222 / H2...
Residual weight average fiber length (H31) of sample 31 (L11: 95% + D3: 5%) relative to residual weight average fiber length (H3) of Comparative Example 3 (L11: 100%), ie, H31 / H3, Sample 32 Residual weight average fiber length (H32), that is, H32 / H3,.
Residual weight average fiber length (H41) of sample 41 (L15: 95% + D3: 5%) relative to residual weight average fiber length (H4) of Comparative Example 4 (L15: 100%), ie, H41 / H4, sample 422 Remaining weight average fiber length (H42), that is, H42 / H42,...
Were sequentially calculated. The results are shown in FIGS.

(Measuring mechanical properties)
For the mechanical property test, a three-point bending test (based on JIS K7171) and a tensile test (based on JIS K7162) were performed using a precision universal testing machine (Autograph AG-5kNX, manufactured by Shimadzu Corporation). In the three-point bending test, the test speed was 2 mm / min, the span was 48 mm, and the tensile test was performed at room temperature, with the test speed being 20 mm / min and the distance between chucks being 115 mm. From the results of the three-point bending test, the flexural modulus was obtained. Moreover, the punching surface impact test calculated | required the energy spent to the maximum impact force with the puncture impact tester (JISK7211 conformity, Daikyo Nishikawa Co., Ltd. product), and made this the impact absorption energy.

  The graph showing the flexural modulus, the graph showing the tensile strength, and the graph showing the impact absorption energy with respect to the mixing ratio of the long fibers and the short fibers are shown in FIGS. 3, 4, and 5, respectively.

  As shown in FIG. 1, the first pellet containing 40% by weight of glass long fibers having a diameter of 15 μm and lengths of 7 mm, 11 mm, and 15 mm and a first pellet formed by subdividing the first pellet into a polypropylene resin. Is prepared, and a second pellet containing short glass fibers having a length of 3 mm is prepared, and the ratio of the long fibers and the short fibers is a predetermined ratio of the first pellets and the second pellets. Were mixed and injection molded. As shown in FIG. 1, the remaining weight average fiber length of the molded product obtained from the pellet containing only the long fibers of L7 is 4.2 mm, 5.1 mm for L11, 8.4 mm for L15, L7 was 60%, L11 was 46%, and L15 was 56% of the original fiber length. That is, in any case of L7, L11, and L15, a molded product having a residual weight average fiber length of 40% or more with respect to the original fiber length was obtained.

  Under the above molding conditions, the remaining weight average fiber length and the ratio thereof were determined for each sample and comparative example in FIG. As a result, as shown in FIG. 2, the obtained injection-molded product was obtained by using the remaining weight average fiber length of the glass fiber in the case of obtaining the molded product by injection molding only the first pellet alone. It calculated | required by the ratio with respect to residual weight average fiber length. As shown in FIG. 2, in a specific range, when the ratio exceeds 1.0, that is, when the remaining weight average fiber length of the glass fiber is injection-molded only by the first pellet alone, a molded product is obtained. A glass fiber having a longer length than the remaining weight average fiber length was obtained. Specifically, in the case of mixing L7 long fibers and D3 short fibers, the ratio exceeded 1.0 in the range of 23% by weight from the case where the short fibers were slightly added. In the case of mixing the long fiber of L11 and the short fiber of D3, the ratio exceeded 1.0 in the range of 35% by weight from the case where the short fiber was slightly added. In the case of mixing the long fibers of L15 and the short fibers of D3, the ratio exceeded 1.0 in the range of 15% by weight from the case where the short fibers were slightly added.

  As shown in FIG. 3, when the long fibers of L7, L11, and L15 and the short fibers of D3 are mixed, the bending elastic modulus increases as the mixing ratio of D3 increases. That is, even in the range where the ratio of the remaining weight average fiber length exceeds 1.0, the bending elastic modulus is increased, and it is estimated that the ratio of the remaining weight average fiber length is not affected.

  As shown in FIG. 4, the tensile strength tends to decrease in any of the long fibers L7, L11, and L15 by increasing the mixing ratio of the short fibers D3, but the mixing of the short fibers D3. When the ratio is small, 68 MPa or more can be secured, so that the tensile strength satisfies the requirement. Specifically, in the case of mixing L7 and D3, up to about 10% by weight of short fibers is the same as in the case of L7 alone, and decreases when the number of short fibers increases. In the case of mixing L11 and D3, up to about 25% by weight of short fibers is almost the same as in the case of L11 alone, and then gradually decreases as the number of short fibers increases. In the case of the mixture of L15 and D3, the short fiber is decreased even by about 10% by weight, and the value is maintained up to about 25%, but then gradually decreases as the short fiber increases.

  On the other hand, as shown in FIG. 5, the impact energy is 10% of D3 short fibers as compared with L7 only, L11 only, and L15 only in any of L7, L11, and L15. Is rising. In L7 and L11, a high value can be maintained up to about 25% of short fibers as compared with the case of only a long fiber, and a high value can be maintained up to about 15% in L15. These high values overlap with a range in which the ratio of the remaining weight average fiber length exceeds 10 and can be said to be an effect of increasing the remaining weight average fiber length.

  Although the detailed reason is not clear, mixing a small amount of short fibers reduces the stress applied to the fibers, making it difficult for the fibers to break. As a result, the impact energy increases and the residual weight average fiber length increases. It is presumed that

  In the above samples and comparative examples, the first pellet and the second pellet were glass fibers having a diameter of 15 μm, but the present invention can be empirically applied to those having a diameter in the range of 10 μm to 20 μm. In the above samples and comparative examples, the glass fiber content was 40% by weight with respect to the total weight, but the present invention is empirically applied to those containing in the range of 30 to 50% by weight. I can say that.

  The glass fibers in the first pellet and the second pellet are preferably manufactured by a manufacturing method in which a glass fiber bundle that is bundled in one direction is impregnated with molten plastic.

  INDUSTRIAL APPLICABILITY The present invention is extremely useful for a method for forming a glass fiber reinforced resin molded product by mixing and injection-molding a pellet containing long glass fibers and a pellet containing short glass fibers. It can be suitably applied to parts for OA equipment, parts for OA equipment and the like.

Claims (6)

A method for molding a glass fiber reinforced resin molded article containing glass fiber in polypropylene resin,
A first pellet containing long glass fibers having a diameter of 10 to 20 μm and a length of 5 to 20 mm in polypropylene resin;
A second pellet containing short glass fibers having a diameter of 10 μm to 20 μm and a length of 0.5 mm to 3 mm is prepared in a polypropylene resin,
The first pellet and the second pellet are mixed at a ratio of the long fiber and the short fiber in a ratio of 19: 1 to 7: 3 and injection molded.
The remaining weight average fiber length of the glass fiber of the molded injection molded product is the remaining weight average fiber length of the glass fiber and the second pellet when the molded product is obtained by injection molding only the first pellet alone. A method for molding a glass fiber reinforced resin molded product, characterized in that it is longer than the remaining weight average fiber length of the glass fiber when a molded product is obtained by injection molding only a simple substance. In claim 1,
The length of the glass long fiber contained in the first pellet is 7 mm to 15 mm,
The first pellet and the second pellet are mixed at a ratio of 19: 1 to 17: 3 of the long fiber contained in the first pellet and the short fiber contained in the second pellet. A method of molding a glass fiber reinforced resin molded product, characterized by injection molding. In claim 1 or 2,
Both said 1st pellet and said 2nd pellet contain glass fiber 30 to 70weight% of the total weight, The shaping | molding method of the glass fiber reinforced resin molded product characterized by the above-mentioned. In any one of Claims 1 thru | or 3,
The residual weight average fiber length of the long fibers when only the first pellet single injection molded product is obtained is 0.4 compared to the fiber length of the glass long fibers contained in the first pellet. A molding method for a glass fiber reinforced resin molded article, characterized in that molding conditions that are doubled or more are obtained, and the first pellets and the second pellets are mixed and injection molded under the molding conditions. In any one of Claims 1 thru | or 4,
The method for molding a glass fiber reinforced resin molded product, wherein the second pellet is a pellet obtained by re-kneading the first pellet with a twin screw extruder. In any one of claims 1 to 5,
In the above-mentioned injection molding, the glass fiber reinforced resin molded product is molded by using a low shear screw injection molding machine or a pre-plunger type injection molding machine.

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