JPH0763984B2 - Resin parts - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resin part required to have impact resistance, for example, a resin part applied to an automobile bumper, etc., and particularly adopts a masterbatch method in a molding process. The present invention relates to a resin component molded by

(Prior Art) As a bumper 1 for automobiles in recent years as shown in FIG. 1, those molded by injection molding using polypropylene (hereinafter referred to as PP) resin are often used. Originally, the bumper 1 for automobiles is required to have improved impact resistance at the time of collision, rigidity, and appearance quality in order to protect automobiles and passengers. Even with the PP resin, ethylene propylene rubber (hereinafter referred to as EPR) To improve the impact resistance. Further, talc or the like is mixed in order to increase the rigidity of the bumper, and as a method for coloring the bumper, a dry coloring method, a kneading coloring method, etc. are adopted.

Here, the dry co-coloring method is a method in which a coloring agent is dispersed and adhered to the surface of the raw material pellets and is supplied to a molding machine. However, it has a drawback that color unevenness is likely to occur. On the other hand, the kneading coloring method is a method in which a dry-colored raw material is re-granulated by an extruder or the like and a coloring agent is kneaded into pellets. Is advantageous, but it may cause thermal deterioration of the raw material.

Further, as a method for polymerizing the PP resin, a method called a slurry method has been conventionally adopted, but in recent years, a gas phase method has been frequently used in order to improve productivity in the polymerization step.

The slurry method is a method in which propylene is put in a hydrocarbon solvent and titanium trichloride or titanium tetrachloride is used as a polymerization catalyst, which requires a centrifugal separation step for taking out crystalline PP after polymerization. On the other hand, the vapor phase method is a method in which titanium trichloride is put into propylene gas under pressure to polymerize, and the centrifugal separation step in the slurry method is unnecessary, and the crystallinity is high. The feature is that PP resin can be obtained.

FIG. 2 is a polymerization process by the conventional slurry method.
10 is a process diagram showing a coloring step 11 by a tri-coloring method and a molding step 12 by an injection molding method, and in the polymerization step 10, after PP and EPR are polymerized and pelletized, respectively, a PP pellet and an EPR pellet. And talc, and a predetermined coloring agent are mixed to perform re-pelletization. Molding raw material colored in each color obtained in this way
13 is housed in containers 14a to 14c, and a valve 17 of a pipe 16 connected to a hopper 15 of an injection molding machine is switched to feed a raw material 13 of a desired color to a molding machine 18.

According to such a molding method, it is necessary to re-pelletize the PP resin and the EPR resin which have been pelletized once, and when the number of colors of the bumper 1 increases, the container 14 containing the coloring raw material 13 In addition to the increase in the number, each time the color is changed, the valve 17 of the pipe must be switched and the coloring material 13 must be sent to the molding machine 18 by the material feeder, which extends the molding cycle and makes its control complicated. there were.

Therefore, in order to solve such a conventional productivity problem, as shown in FIG. 3, a polymerization process employing a gas phase method is performed.
A molding method having 20 and a coloring step 21 by a masterbatch method has been developed.

In this method, a natural material 22 is obtained by polymerizing PP by a gas phase method, mixing EPR and talc which have been pelletized in advance, and pelletizing the mixture. Then, the natural material 22 is sent from the container 23 to the molding machine 25 through the pipe 24, and at the same time, the master batch 26 in which the high-concentration colorant manufactured in advance is kneaded is also injected into the molding machine 25. And mixed with the natural color pellets 22 to be molded.

Therefore, as compared with the conventional molding method (slurry method) described above, it is possible to realize the step of re-pelletizing and the shortening of the color change time.

(Problems to be Solved by the Invention) However, even when a PP resin component is molded by such a highly productive molding method, there are various problems. First, it is necessary to modify the mixing capacity of the molding machine in order to improve the mixing property of the masterbatch and the natural material. For example, the conventional molding machine was only the tumbling method, but a mixing head was added to this. Second, it is necessary to apply a back pressure to the cylinder of the molding machine in order to improve the mixing property, which lengthens the molding cycle. A third problem is that the process control becomes complicated because the variation of various molding conditions affects the above-mentioned mixing property.

Table 1 shows that the master batch used in the past was used to appropriately change the mixing performance of the molding machine, the addition amount of the master batch, the molding temperature, the mold temperature during molding, and the part of the work in the mold. It is a table showing the results of the impact test, when the mixing performance of the molding machine is not modified and the molding machine used conventionally is used, the addition amount of the masterbatch is usually the set value. Is 2.0 wt%, and the specified impact resistance is satisfied only when the molding temperature and the mold temperature are higher than the standard temperature and the position of the work in the mold is near the gate. The bumper was obtained.
In addition, if the molding machine was modified to improve its mixing performance, the kneading properties of the masterbatch and PP would deteriorate even if the masterbatch addition amount was 2.0 wt%, which is the normal setting value. Under the conditions, that is, when the molding temperature and the mold temperature were low, a bumper having a predetermined impact resistance could not be obtained. Furthermore, if the molding machine is modified and the masterbatch addition amount is increased to 3.0 wt%, the molding temperature and mold temperature must be high, and the material must be near the gate where a large share of the material acts. No good product was obtained.

As is clear from this test result, conventional resin parts using a masterbatch require facility modification to enhance the mixing performance of the molding machine, and the addition amount of the masterbatch and the resin temperature during molding In addition, there is a problem in quality or productivity that strict control of process such as mold temperature is required, which increases the frequency of sampling inspection in the inspection process.

Therefore, the present inventors, by a molding method with high productivity,
As a result of intensive research aimed at obtaining a resin part having excellent impact resistance, it was found that the particle size of the pigment acting in the coloring process by the masterbatch method controls the impact resistance value of the resin part.

The present invention has been made in view of the above-described conventional problems, and provides a resin component having a short molding cycle and excellent impact resistance without requiring modification of a molding machine or complicated process control. The purpose is to

(Means for Solving the Problems) The present invention for achieving the above-mentioned object is to inject a high-concentration pellet colored in a predetermined color in advance and a natural color pellet exhibiting the color of the resin itself into a mold. In the resin part, which is kneaded and colored when the above is performed, the high-concentration pellet contains a pigment particle size of 40 μm or less.

(Function) Under the understanding that there is a correlation between the impact resistance of the molded resin part and the particle size of the pigment in the masterbatch, the resin part according to the present invention thus configured has , When the high-concentration pellets colored in a predetermined color and natural color pellets are molded by a masterbatch molding method,
Since the particle size of the pigment contained in the high-concentration pellets is 40 μm or less, it is possible to obtain a resin component having excellent impact resistance without the need for modifying the molding machine or complicated process control.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. Incidentally, the present invention is not limited to the present embodiment unless it exceeds the scope of the invention.

[Example 1] PP resin A manufactured by Mitsui Petrochemical Co., Ltd. and masterbatch a manufactured by Toyo Ink Co., Ltd. having a pigment particle size of 1 μm or less (see FIGS. 4 and 7) were used and shown in FIG. The bumper 1 was molded in the polymerization step 20 and the coloring molding step 21 as shown. As shown in Table 2, this molding condition includes various factors such as whether or not the mixing performance of the molding machine is modified, the amount of masterbatch added, the resin temperature during molding, the mold temperature during molding, and the part of the work in the mold. The conditions were changed. Further, the impact test after molding, using a high-rate impact tester manufactured by Rheometric Co. as shown in FIG. 10, visually evaluate the fracture state of the cut out sample pieces at -40 ℃, if the ductile fracture state Pass (○), fail if brittle fracture state (x)
And The results are shown in Table 2.

As a result, it is understood that the process control range is wider and the impact resistance is extremely excellent, as compared with [Comparative Example 1] described later.

[Example 2] Next, the size of the pigment particle size contained in the masterbatch was changed to understand the relationship between the particle size and the impact resistance. Moreover, the same relationship was grasped by changing the types of PP and masterbatch (No. 1 to 4 in Table 3). That is, the third
Each polypropylene shown in the table is polymerized by a gas phase method, and by a masterbatch molding method as shown in FIG.
Color molding was performed using the master batch shown in the table. Table 3 is a table showing combinations of PP types and masterbatch types.

Table 3 No. PP material Masterbatch 1 Sumitomo Chemical Co., Ltd. A Sumika Color Co., Ltd. a 2 Mitsubishi Chemical Co., Ltd. B Dainichi Seika Co., Ltd. b 3 Chisso Co., Ltd. C Toyo Ink Co., Ltd. c 4 Idemitsu Petrochemical Co., Ltd. D Manufactured by Toyo Ink Co., Ltd. Here, the pigment contained in the masterbatch was molded with various particle sizes (3 to 8 μm), and the plastic strain energy value of the bumper was measured. At this time, as the molding machine, an injection molding machine manufactured by Kobe Steel, which is equipped with only a tumbling method, is used, and the molding conditions are such that the additive amount of the masterbatch is 3.0 wt% and the molding condition is the worst condition for impact resistance. The resin temperature at that time was [standard temperature-5 [deg.] C.], the mold temperature during molding was [standard temperature-5 [deg.] C.], and the measurement sample position was the most position from the mold gate. Further, as shown in FIG. 8, the plastic strain energy value, which is an evaluation value, was obtained as an integral value between the maximum value of the force and the maximum displacement in the relationship of the force to the displacement of the strain. The results are shown in FIG.

According to this, if the particle size of the pigment is 40 μm or less, the plastic strain energy value becomes large and any complicated process control is not performed regardless of any combination of PP and masterbatch in Table 3 above. Thus, it is possible to obtain a resin component having excellent impact resistance. The lower limit of the particle size of the pigment contained in the masterbatch is not particularly limited, but is preferably about 3 μm. Moreover, this result is consistent with the results shown in Tables 1 and 2 described above.

[Comparative Example 1] A master batch manufactured by Toyo Ink Co., Ltd.
(See the drawing), molding was performed under the same molding conditions as in [Practical example 1], and then an impact resistance test of the molded bumper was performed. The results are shown in Table 1.

As is clear from this result, when the mixing performance of the molding machine is not modified and the molding machine that has been used conventionally is used, the addition amount of the masterbatch is 2.0 wt% which is the normal setting value.
%, The molding temperature and the mold temperature are higher than the standard temperature, and the bumper satisfying the predetermined impact resistance can be obtained only under the condition that the position of the work in the mold is near the gate. It was

In addition, if the molding machine was modified to improve its mixing performance, the kneading properties of the masterbatch and PP would deteriorate even if the masterbatch addition amount was 2.0 wt%, which is the normal setting value. Under the conditions, that is, when the molding temperature and the mold temperature were low, a bumper having a predetermined impact resistance could not be obtained. Furthermore, when the molding machine is modified, the molding temperature and mold temperature are high and the material is not near the gate where a large share of the material acts even under the condition that the amount of masterbatch added is increased to 3.0 wt%. And good product was not obtained.

[Example 3] PP resin C manufactured by Chisso Co. and carbon pigment having a particle size of 1 µm
Using the master batch i colored by Toyo Ink Co., Ltd. (see FIGS. 4 and 7), which is shown below, in a polymerization step 20 and a coloring and molding step 21 as shown in FIG. Molded. As shown in the sixth method, the molding conditions vary depending on whether or not the mixing performance of the molding machine is modified, the amount of the master batch added, the resin temperature during molding, the mold temperature during molding, and the part of the work in the mold. Let Further, the impact test after molding, using a high-rate impact tester manufactured by Rheometric Co. as shown in FIG. 10, visually evaluate the fracture state of the cut out sample pieces at -40 ℃, if the ductile fracture state Pass (○), fail (x) if the state is brittle, and visually evaluate color unevenness if it is within the normal criteria, pass (○), and if it is out of the criteria. Was rejected (x). The results are shown in Table 6.

As a result, it is understood that the process control range is wider and the impact resistance is extremely excellent, as compared with [Comparative Example 1] described later.

[Example 4] Furthermore, as shown in Table 4, the type of pigment contained in the masterbatch, that is, the relationship with the impact resistance performance when the color of the masterbatch is changed (see FIG. 5) is understood. did. That is, each polypropylene shown in Table 4 was polymerized by the gas phase method, and colored molding was carried out by the master batch type molding method as shown in FIG. 3 using each master batch shown in the same table. Table 4 shows the combinations of PP types, masterbatch types and their colors.

Here, the particle size of the pigment contained in the masterbatch was variously changed (3 to 80 μm), the molding was performed, and the plastic strain energy value of the bumper was measured. The molding machine used at this time was an injection molding machine made by Kobe Steel Co., Ltd. equipped only with a tumbling system.The molding conditions were 3.0 wt%, the amount of masterbatch added, and the worst condition for impact resistance. The resin temperature at that time was [standard temperature-5 [deg.] C.], the mold temperature during molding was [standard temperature-5 [deg.] C.], and the measurement sample position was the position furthest from the gate of the mold. Further, as shown in FIG. 8, the plastic strain energy value, which is an evaluation value, was obtained as an integral value from the maximum value of the force to the maximum displacement in the relationship of the force with respect to the strain displacement. These results are shown in FIG.

According to this, as long as the particle size of the pigment is 40 μm or less, the plastic strain energy value can be obtained regardless of the combination of PP and masterbatch in Table 4 above, that is, regardless of the color and type of the masterbatch. Therefore, it is possible to obtain a resin component having excellent impact resistance without performing complicated process control. Even in this case, the lower limit of the pigment particle size is not particularly limited as in the case of [Example 2], but it is preferably about 3 μm. Further, this result is consistent with the results shown in Tables 1 and 2 described above.

[Comparative Example 2] Using PP resin C manufactured by Chisso Co. and masterbatch j colored by gray color manufactured by Toyo Ink Co., Ltd., which was conventionally used, a polymerization step 20, coloring as shown in FIG. The bumper 1 was molded in the molding step 21. As shown in Table 5, the molding conditions vary depending on whether or not the mixing performance of the molding machine is modified, the amount of masterbatch added, the resin temperature during molding, the mold temperature during molding, and the part of the work in the mold. Let Further, the impact test after molding is performed by using a high rate impact tester manufactured by Rheometric Co. as shown in FIG.
The fracture state of the cut-out sample piece at 40 ° C is visually evaluated, and if it is a ductile fracture state, it is judged as pass (○), and if it is a brittle fracture state, it is judged as fail (x). When it was within the standard of (2), it was passed (○), and when it was out of the standard, it was rejected (x). The results are shown in Table 5.

From this, it can be understood that when the PP resin and the masterbatch are molded with a low kneading property, the predetermined quality is not satisfied in both impact resistance and color unevenness.

(Effects of the Invention) As described above, according to the present invention, high-concentration pellets colored in advance in a predetermined color and natural-colored pellets exhibiting the color of the resin itself are kneaded when injected into a mold. Since the pigment particle size of the high-concentration pellets is 40 μm or less in the resin component that is colored by, the molding machine need not be modified or complicated process management, and the molding cycle can be shortened.
Moreover, it is possible to provide a resin component having excellent impact resistance.

[Brief description of drawings]

FIG. 1 is a perspective view showing a general automobile bumper, and FIG.
FIG. 4 is a process diagram showing a conventional PP polymerization and coloring molding process, FIG. 3 is a process diagram showing the PP polymerization and coloring molding process according to the present invention, and FIG. 4 is a resin component according to Examples 1 and 2 of the present invention. FIG. 5 is an enlarged cross-sectional view showing a resin part according to Example 3 of the present invention, FIG. 6 is a cross-sectional micrograph of a cross-section of a conventional resin part, and FIG. 8 is a graph showing a relationship between the maximum particle diameter and the plastic strain energy of the resin component according to Example 2 of the present invention, and FIG. 9 is a book showing the cross section of the resin component according to Example 1. FIG. 10 is a graph showing the relationship between the maximum particle size and the plastic strain energy of the resin part according to Example 3 of the invention, and FIG. 10 is a conceptual diagram showing a shock resistance test measuring device.

Claims (1)

[Claims] 1. A resin component in which high-density pellets colored in a predetermined color in advance and natural-colored pellets exhibiting the color of the resin itself are kneaded and colored when injected into a mold. The particle size of the pigment contained in the pellet is 40 μm
The following is a resin part characterized by the following.