JP5633366B2 - Method for producing foam molded article - Google Patents

Description

  The present invention relates to a production method for molding a foam molded article using a chemical foaming agent.

  Conventionally, as one method of molding a foam molded body, there is a method in which a parison, which is a hollow molten resin having a foamed resin layer, is extruded, the parison is sandwiched between molds, and air is blown into the mold. .

  As a method for obtaining the foamed resin layer, for example, carbon dioxide gas or nitrogen gas is compressed and injected into the extruder from the outside, or gas is introduced into the raw material charged into the extruder by heat or acid-base reaction. Examples thereof include a chemical foaming method in which an additive comprising a generated chemical foaming agent is mixed. Examples of the chemical foaming agent include organic chemical foaming agents typified by azodicarbonamide and inorganic chemical foaming agents mainly composed of baking soda (see, for example, Patent Documents 1 and 2).

  Since the physical foaming method requires a gas injection device in addition to a normal blow molding device, the equipment becomes large and expensive. In order to solve such a problem, development of molding a foamed molded article using a chemical foaming agent is in progress.

  On the other hand, a colored molded body is generally formed by adding a colorant to a base resin and molding the parison in a toned state. This colorant is often used as a colored master batch in which a powder having a coloring function is kneaded with a base resin from the viewpoint of reducing uneven coloring and facilitating mixing of raw materials. That is, in order to obtain a colored foamed molded article, a method is generally employed in which a colored master batch and a chemical foaming agent are separately added to a base resin and kneaded.

JP 2009-144122 A JP 2004-285345 A

  However, according to the method of mixing the colored master batch separately from the chemical foaming agent in order to color, it takes time for mixing at the time of molding, and the chemical foaming agent and the colored master batch are uniformly applied to the base resin. There is a problem that the foaming magnification and color of the molded product are not mixed and the molded product varies.

  The present invention has been made to solve the above-described problems, and can reduce the effort of mixing different resin materials at the time of molding, and can reduce foaming magnification and color variation. It aims at providing the manufacturing method of a possible foaming molding.

In order to achieve this object, the present invention has the following features.
The method for producing a foam molded article according to the present invention is a method for producing a foam molded article for producing a foam molded article by mixing a master batch containing a chemical foaming agent and a colorant with a base resin ,
The chemical foaming agent comprises a main foaming agent and a foaming aid that reacts with the main foaming agent to foam the main foaming agent,
(A) 1st masterbatch which has the said main foaming agent, (B) 2nd masterbatch which mixed the said foaming adjuvant and the said coloring material with the base resin, (C) The said base resin, , And the main foaming agent is foamed to form the base resin into a foamed molded product.
The “master batch” refers to a pellet obtained by mixing an additive such as a foaming agent or a colorant with a resin (base resin).

  According to the present invention, it is possible to reduce the labor of mixing different resin materials at the time of molding, and it is possible to reduce the expansion ratio and color variation.

It is a figure which shows the result of having measured MT of the string-like object detected with the detector connected with the pulley for tension detection with time. It is a figure which shows the preparation apparatus of a masterbatch. It is a figure which shows the relationship between the ratio of a main foaming agent and foaming adjuvant, the specific gravity of a foam, and a bubble diameter.

In the embodiment described below, a method of foaming by reacting a main foaming agent with a foaming auxiliary agent is used as the chemical foaming agent. Here, the main foaming agent is a foaming agent that reacts with the foaming aid to foam.
In this embodiment, baking soda is used as the main foaming agent, and citric acid is used as the foaming aid.
Baking soda and citric acid are each mixed with a base resin, formed into pellets and used (master batch). Thus, by making it into a master batch, when mixed with pellets of the base resin, uneven mixing is less likely to occur, and the supply amount into the extruder is also stabilized.
The particle size of the baking soda and citric acid powder (before masterbatch) is not particularly limited, but from the viewpoint of handling and dispersibility, baking soda averages 30 µm to 200 µm and citric acid 1 µm to 50 µm Preferably there is.

In this embodiment, carbon black is used as a colorant in order to form a black foamed molded product. In addition, since the pigment is more suitable for coloring than the dye as the apparent density of the foamed molded product decreases, carbon black as a pigment is desirable.
Since the foam has cells (pores), the foam has a smaller amount of resin per unit volume than the non-foam. The dye dissolves itself and mixes with the resin to be colored. However, the pigment is dispersed and colored in a solid state. For this reason, dyeing tends to cause variation in coloring, and it is difficult to express dark colors.

  The baking soda master batch is preferably added so that the concentration of baking soda with respect to the base resin is 0.3 to 1.8 wt%, and more preferably 0.6 to 1.5 wt%. This is because if the concentration of baking soda with respect to the base resin is less than 0.3 wt%, it is difficult to improve the expansion ratio, that is, to reduce the apparent density. This is to cause resin foaming.

  In the present embodiment, carbon black powder, which is a colorant, is mixed when a citric acid master batch is produced. The reason why it is preferable to mix the colorant in the citric acid master batch instead of the baking soda master batch is as shown in (1) and (2) below.

(1) When foam molding is performed, it is better that the added weight of citric acid is smaller than the added weight of baking soda. Therefore, if a baking soda masterbatch and a citric acid masterbatch are prepared so that the concentration of sodium bicarbonate in the baking soda masterbatch and the concentration of citric acid in the citric acid masterbatch are the same, this is used for foam molding. Compared to the number of baking soda master batches, the number of citric acid master batches is significantly reduced. In this case, there is a possibility that the two do not sufficiently contact and foaming is not sufficiently performed.
Here, when producing a masterbatch, the quantity of the additive which can be mixed with a base resin is limited. Therefore, if the colorant is mixed in the baking soda master batch, the amount of sodium bicarbonate that can be mixed in the baking soda master batch is reduced by the amount of the colorant mixed. In this case, the number of baking soda master batches required for foam molding increases, and the difference from the number of citric acid master batches required for foam molding widens greatly.
On the other hand, when the colorant is mixed with the citric acid master batch, the citric acid concentration in the citric acid master batch can be reduced, so the number of baking soda master batches required for foam molding, the number of citric acid master batches, Can be brought closer. Thereby, an acid-base reaction can be generated efficiently.

(2) During the baking of a baking soda master batch, if the temperature is raised too much, gas will be released, so the kneading temperature needs to be set near the melting point of the base resin. Therefore, the melt viscosity of the base resin resin is increased, and the extrusion load during kneading is increased.
On the other hand, citric acid is less likely to release gas even when the temperature is raised, compared to baking soda. Therefore, when producing a citric acid masterbatch, it can knead with base resin at high temperature compared with the case where a sodium bicarbonate masterbatch is produced, and the extrusion load at the time of kneading is small. Therefore, even if the extrusion load is slightly increased by mixing the colorant, there is little influence.

  The method of creating the master batch is not particularly limited, but it is desirable to create it with a strand cut type twin-screw kneader. If it is a strand cut system, since the cooling time of kneaded resin can be controlled easily, the performance fall of a foaming agent can be suppressed. Moreover, the state of the resin immediately after kneading can be confirmed.

  The strand is preferably passed through water at around 20 ° C. for 0.5 to 1.5 seconds, slowly cooled in the atmosphere for 20 seconds or more, and then cut with a pelletizer. If the strand passage time in water is too long, additives, particularly citric acid, may elute in water, which may impair the function of the masterbatch. Moreover, when the slow cooling time in air | atmosphere is short, there exists a possibility that it may become difficult to cut | disconnect a strand softly.

  When the masterbatch is used in the subsequent foam molding, in order to facilitate dry blending with other base material raw materials, the particle size of the masterbatch is preferably 2 to 6 mm, 3 to 4 mm is more preferable. When the particle size of the master batch is significantly different from the pellet diameter of the base resin, the foaming agent, the foaming aid, and the colorant may not be sufficiently dispersed during the mixing process and storage with the blow molding raw material.

  When producing a masterbatch, since it is necessary to form a strand at a low temperature, the melting point of the base resin resin is preferably 120 ° C. or less, particularly preferably 110 ° C. or less.

  Furthermore, if the fluidity of the base resin resin is too low, the load applied to the kneader may be high, and if the resin with too high fluidity may cause unevenness in kneading, the MFR of the resin used as the base resin is 5 to 50 g / 10 min is preferable, 10 to 40 g / 10 min is more preferable, and 20 to 35 g / 10 min is particularly preferable.

The amount of carbon black contained in the citric acid master batch is determined by the amounts of the baking soda master batch and the citric acid master batch added to the base resin when foam molding is performed.
Since the volume per unit weight increases as the apparent density required for the foamed molded product decreases, a large amount of carbon black is required to maintain the colorability.

  The amount of carbon black contained in the citric acid masterbatch also depends on the ratio of the main foaming agent (bicarbonate) and foaming aid (citric acid) added to the foamed molded product. The concentration of carbon black needs to be set lower as the amount of citric acid masterbatch added increases.

  Moreover, a bubble diameter can be adjusted using a bubble regulator as needed. Typical examples include inorganic bubble regulators such as talc, silica, zinc oxide, and calcium carbonate. These inorganic bubble regulators serve as nuclei at the time of bubble generation and can make the bubbles finer.

  The citric acid masterbatch mixed with the above baking soda masterbatch and colorant is suitable for foam molding using polypropylene resins or polyethylene resins such as high density polyethylene, low density polyethylene, and linear low density polyethylene as the base resin. Suitable for use. The base resin may be used by blending two or more kinds of raw materials. Further, butene resin, styrene resin, EPR or the like may be included as a base resin within a range not impairing blow moldability.

In foam blow molding, when the resin used as the base material is a propylene-based resin, the MT value at 200 ° C is 3.0 gf or more, the MFR at 200 ° C is 0.2 g / 10 min or more, and MT and MFR It is desirable that the integrated value of is 13 gf · g / 10 min or more.
Resins with a small MT value tend to cause cell destruction in the molten resin, that is, foam breakage, and it is difficult to sufficiently foam the parison. It becomes difficult to transfer the shape because it is difficult to stretch. In addition, a resin having low resin fluidity may cause inhomogeneous bubble growth because of poor mixing of the foaming agent and foaming aid.

  The MT of the resin described above is measured by a melt tension tester type II manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, using a melt tension tester having an orifice with an orifice diameter of 2.095 mm and a length of 8 mm, the resin is extruded into a string from the orifice under the conditions of a resin temperature of 200 ° C. and an extrusion piston speed of 10 mm / min. The product is hung on a 45mm diameter tension detection pulley, and then wound at a speed of 4rpm with a 50mm diameter roller.

  To obtain MT, put the raw material in the piston, apply a preload after the temperature in the piston reaches 170 ± 0.2 ° C or 200 ± 0.2 ° C, and hold it for 4 minutes. Three types are possible: virgin raw material resin, pre-melted and kneaded resin, and resin cut and shredded from molded products). The preload varies according to the MFR and is shown in Table 1. Thereafter, winding is performed at a winding speed of 5 rpm, and the MT of the string-like material detected by a detector connected to the tension detection pulley is measured over time. MT (gf) is plotted on the vertical axis and MT (gf) is plotted on the horizontal axis. When time (seconds) is taken and shown in the chart, a graph having an amplitude as shown in FIG. 1 is obtained. In FIG. 1, MT in the present embodiment takes the median value (X) of the amplitude of the portion where the amplitude is stable. It should be noted that a specific amplitude that occurs rarely is ignored. The value measured at 200 ° C and a load of 2.16 kgf described in JIS K7210 shall be adopted for MFR.

The specific gravity of the foamed molded product is determined by taking the weight (g) of the test piece as the volume of the test piece with respect to each test piece, using both ends and the central part (excluding the compression part) of the foamed molded product cut out. Divide by (cm ³ ) to obtain the specific gravity, and the average value is taken as the specific gravity of the foamed molded product.

<Preparation of master batch>
A method for producing a master batch will be described with reference to FIG. 2 showing a production apparatus (biaxial kneader). The base resin of the master batch is put into the resin supply hopper 1 and transported to the shooter unit 5 by the resin supply hopper feeder 2 that receives power from an external motor. Powders of blowing agent baking soda, blowing aid citric acid, and colorant carbon black are put into a powder hopper 3 and transported to a shooter unit 5 by a powder hopper feeder 4 that receives power from an external motor. The raw material of the foaming agent or the colored foaming aid blended in the shooter unit 5 is sent to the twin screw kneader cylinder 6 where the resin is kneaded and transported by the screw in the cylinder. The resin kneaded in the cylinder is extruded out of the cylinder from the die 7 to form a strand 8. The strand 8 is guided to the pelletizer 11 through the strand guide roller 10 in the water tank 9, and the strand 8 is cut with a blade inside the pelletizer 11 to obtain a master batch pellet 12.

  The main foaming agent master batches used in Examples 1 to 4 and Comparative Examples 1 and 2 are low-density polyethylene having a melting point of 106 ° C. and MFR 20 g / 10 min as a base resin. This was prepared by kneading sodium bicarbonate. The main foaming agent master batch was kneaded so that the concentration of sodium bicarbonate was 40 wt%. The baking soda powder used has a minimum particle size of 38 μm, a maximum particle size of 150 μm, and an average particle size of 65 μm.

In addition, the coloring foaming auxiliary masterbatch used in Examples 1 to 4 uses low density polyethylene having a melting point of 106 ° C. and MFR 20 g / 10 min as a base resin, and the base resin and carbon black in a φ26 mm biaxial kneader. And citric acid.
The concentrations of carbon black and citric acid in the master batches in Examples 1 to 4 are as shown in Table 2. The citric acid powder used has a minimum particle size of 1.53 μm, a maximum particle size of 38.8 μm, and an average particle size of 7.1 μm. The average particle size of carbon black is 30 nm.

  Moreover, the foaming auxiliary agent masterbatch used in Comparative Examples 1 and 2 uses a low-density polyethylene having a melting point of 106 ° C. and MFR 20 g / 10 min as a base resin, and the base resin and citric acid with a φ26 mm twin-screw kneader. Were prepared by kneading. The foaming aid masterbatch was kneaded so that the concentration of citric acid was 40 wt%. The citric acid powder used has a minimum particle size of 1.53 μm, a maximum particle size of 38.8 μm, and an average particle size of 7.1 μm.

<Extrusion of polypropylene colored foam sheet>
The black foamed sheets shown in Examples 1 to 4 and Comparative Example 1 were obtained using a φ25 mm extruder, and the apparent density and the color difference by the Lab method were measured for each sheet. The length of the extruded sheet was set to 280 mm in order to prevent the change of the bubble shape inside the sheet due to its own weight as much as possible. Table 2 shows the results measured for N = 9.

Example 1
BOREALIS HMS-PP DaployWB140 and Nippon Polypro PP Novatec FB3312 dry blended at a ratio of 70/30 to a base resin of 100 parts by weight of foaming agent masterbatch with sodium bicarbonate concentration of 40.0wt% 2.57 parts of the carbon black concentration 14.0 wt%, citric acid concentration 6.0 wt% of the coloring auxiliary blowing agent master batch 2.86 parts added extruded result, the average apparent density of 0.393 g / cm ^3, the average color difference L value is 20.27 A sheet was obtained.

(Example 2)
BOREALIS HMS-PP DaployWB140 and Nippon Polypro PP Novatec FB3312 dry blended at a ratio of 70/30 to a base resin of 100 parts by weight of foaming agent masterbatch with sodium bicarbonate concentration of 40.0wt% 2.57 parts of the carbon black concentration 24.4Wt%, citric acid concentration 15.7Wt% of the coloring auxiliary blowing agent master batch 1.64 parts added extruded result, the average apparent density of 0.424 g / cm ^3, the average color difference L value is 20.10 A sheet was obtained.

Example 3
BOREALIS HMS-PP DaployWB140 and Nippon Polypro PP Novatec FB3312 dry blended at a ratio of 70/30 to a base resin of 100 parts by weight of foaming agent masterbatch with sodium bicarbonate concentration of 40.0wt% 1.57 parts, carbon black concentration of 28.0 wt%, citric acid concentration of 12.0 wt% 1.43 parts of a colored foaming aid masterbatch was added and extruded, resulting in an average apparent density of 0.400 g / cm ³ and an average color difference L value of 20.41. A sheet was obtained.

Example 4
BOREALIS HMS-PP DaployWB140 and Nippon Polypro PP Novatec FB3312 dry blended at a ratio of 70/30 to a base resin of 100 parts by weight of foaming agent masterbatch with sodium bicarbonate concentration of 40.0wt% 2.57 parts of the carbon black concentration 30.3Wt%, citric acid concentration 9.7 wt% of the coloring auxiliary blowing agent master batch 1.32 parts added extruded result, the average apparent density of 0.398 g / cm ^3, the average color difference L value is 20.78 A sheet was obtained.

(Comparative Example 1)
BOREALIS's HMS-PP DaployWB140 and Nippon Polypro's PP Novatec FB3312 are dry blended at a ratio of 70/30 to 100 parts by weight of resin, and a foaming agent master batch with a sodium bicarbonate concentration of 40.0 wt% is 2.57 Part, 0.43 part of a foaming aid masterbatch with a citric acid concentration of 40.0 wt% and 1 part of a coloring masterbatch with a carbon black concentration of 40.0 wt% were added and extruded, resulting in an average apparent density of 0.419 g / cm ³ and an average color difference of L A sheet with a value of 19.99 was obtained.

(Comparative Example 2)
BOREALIS's HMS-PP DaployWB140 and Nippon Polypro's PP Novatec FB3312 are dry blended at a ratio of 70/30 to 100 parts by weight of resin, and a foaming agent master batch with a sodium bicarbonate concentration of 40.0 wt% is 2.57 Part, 0.32 parts of a foaming aid masterbatch with a citric acid concentration of 40.0 wt% and 1 part of a colored masterbatch with a carbon black concentration of 40.0 wt% were added and extruded, resulting in an average apparent density of 0.411 g / cm ³ and an average color difference of L A sheet with a value of 19.87 was obtained.

  When Example 1 and Comparative Example 1 are compared, the average values of the apparent density measurement result and the color difference measurement result are almost the same, but the standard deviation in the apparent density measurement is 63 in Example 1 compared to Comparative Example 1. The L value standard deviation in Lab color difference measurement was 35% smaller in Example 1 than in Comparative Example 1.

  In Comparative Example 1, the number of auxiliary master batches was smaller than that in Example 1, and the number of contacts between the foaming agent master batch and the foaming auxiliary master batch was not sufficiently obtained. It is thought that it became.

  In comparison between Example 2 and Example 4, as the citric acid ratio decreased, the average value of the apparent density decreased, and the standard deviation of the apparent density and the color difference L value increased.

  From this result, it can be seen that the standard deviation regarding the coloring performance and the apparent density depends on the number of pellets of the colored foaming auxiliary masterbatch. In addition, compared with Example 3, Example 2 was considered that the amount of citric acid added was excessive with respect to the amount of sodium bicarbonate added, so that foaming was inhibited and the apparent density did not decrease. In addition, compared to Example 3, Example 4 is expected to have a large variation in apparent density due to an increase in bubbles due to a smaller amount of foaming aid added.

  In comparison between Comparative Example 1 and Example 3, the average apparent density of Example 3 is 5% smaller than that of Comparative Example 1, the standard deviation of apparent density is 34% smaller, and the standard deviation of color difference L value is 33% smaller. became. In comparison between Comparative Example 2 and Example 4, the average apparent density of Example 4 is 3% smaller than that of Comparative Example 2, the standard deviation of the apparent density is 47% smaller, and the standard deviation of the color difference L value is 30%. % Smaller.

  In Comparative Example 1 and Comparative Example 2, the number of auxiliary master batches was smaller than in Example 3 and Example 4, and the apparent number of contact times between the foaming agent master batch and the foaming auxiliary master batch was not sufficiently obtained. It is considered that the standard deviation has increased in both color difference measurement results.

<Creation of colored foamed polyethylene blow molded duct>
(Example 5)
Main foam with a sodium bicarbonate concentration of 40.0wt% as in Example 3 for 100 parts by weight of resin obtained by dry blending 08S55A (HMS-PE manufactured by Tosoh Corporation) and G201F (LDPE manufactured by Sumitomo Polyethylene Co., Ltd.) in a ratio of 87/13 As a result of adding 1.43 parts of a coloring foaming auxiliary masterbatch with 2.57 parts, carbon black concentration, 28.0% citric acid concentration 12.0 wt%, and performing blow molding, the average apparent density was 0.438 g / cm ³ and the average L A foam duct having a value of 31.02 and an average cell diameter of 241 μm was obtained.

(Comparative Example 3)
For 100 parts by weight of the same base resin as in Example 5, 2.57 parts of a main foaming agent masterbatch with a sodium bicarbonate concentration of 40.0 wt% and 0.43 parts of a foaming aid masterbatch with a citric acid concentration of 40.0 wt% as in Comparative Example 1 As a result of adding one part of a colored master batch having a carbon black concentration of 40.0 wt% and performing blow molding, a duct having an average apparent density of 0.438 g / cm ³ , an average L value of 31.07, and an average cell diameter of 267 μm was obtained. This duct is formed by setting the molding conditions such as the resin temperature, the parison thickness, and the blow-air blowing time to the same values as in Example 5.

  The results of Example 5 and Comparative Example 3 are shown in Table 3.

Example 5 has an average apparent density of 0.009 g / cm ³ , a color difference L value standard deviation of 0.20 and an average cell diameter of 25.9 μm smaller than those of Comparative Example 3, and is superior to using a colored foaming aid. It was observed.

  Since Example 5 has a larger number of citric acid-containing master batches than Comparative Example 3, the contact probability between baking soda and citric acid was increased, and it was considered that the bubble diameter was reduced due to uniform foaming.

  The apparent density and bubble diameter in this test were determined from the average value of three points cut out from the duct at the upper, middle, and lower three locations of the parison.

  In addition, the bubble diameter was calculated from the average value of all the bubbles measured by expanding the cross section of the parison in the TD direction with a digital microscope, measuring the short diameter and long diameter of all the bubbles intersecting the line segment for measuring the thickness of the duct. . The TD direction means a direction perpendicular to the resin flow direction.

<Examination of optimal content ratio of baking soda and citric acid>
Foam with a baking soda concentration of 40.0 wt% with respect to 100 parts by weight of a resin obtained by dry blending 70/30 ratio of DaployWB140, which is HMS-PP manufactured by BOREALIS, and Novatec FB3312, which is PP manufactured by Nippon Polypro, using a φ25mm extruder. A sheet was prepared using as a raw material a total of 3.5 parts of an agent master batch and a foaming aid master batch having a citric acid concentration of 40.0 wt%. The blending ratio of the foaming agent masterbatch and the foaming aid masterbatch was changed so that the weight of baking soda was 2 to 9 with respect to the weight of citric acid, and the apparent density and the cell diameter of the cross section in the TD direction for each sheet. Measurements were made. The results are shown in FIG. The length of the extruded sheet was 280 mm in order to prevent changes in the bubble shape inside the sheet due to its own weight as much as possible, and the test piece was cut 20 mm from a position 130 mm from the end.

  The bubble diameter was calculated from the average value of all the bubbles measured by enlarging the cross section of the parison in the TD direction with a digital microscope, measuring the short diameter and the long diameter of all the bubbles intersecting the line segment for measuring the thickness of the duct.

As shown in FIG. 1, when the weight of baking soda (main foaming agent) is 8 or more with respect to the weight of citric acid (foaming aid), the bubble diameter tends to increase. Therefore, the weight of baking soda is desirably less than 8.
Moreover, when the weight of baking soda (main foaming agent) is 2 or less with respect to the weight of citric acid (foaming aid), the foaming ratio of the molded product is difficult to increase. Therefore, the weight of baking soda is desirably more than 2. In addition, when the weight of baking soda with respect to the weight 1 of citric acid exceeds 4, foaming ratio can be made higher. Therefore, in order to obtain a foam having a fine cell shape at a high expansion ratio, the weight of baking soda is more than 2 and preferably less than 8 with respect to the weight of citric acid.

  The main foaming agent and the colored foaming aid are not limited to separate masterbatches, and the main foaming agent and the colored foaming aid can be used as a single masterbatch. That is, a main foaming agent, a foaming aid, a coloring material, and a base resin are mixed to produce a master batch for coloring and foaming, and the pellets of the master batch are mixed with the pellets of the base resin and the extruder. It is also possible to perform foam molding by mixing with the above.

  The above-described embodiments and examples are preferred embodiments and examples of the present invention, and the scope of the present invention is not limited only to the above-described embodiments and examples, and does not depart from the gist of the present invention. Implementation in a form in which various changes are made in the range is possible.

DESCRIPTION OF SYMBOLS 1 Resin supply hopper 2 Resin supply hopper feeder 3 Powder hopper 4 Powder hopper feeder 5 Shutter 6 Twin screw kneader cylinder 7 Dies 8 Strand 9 Water tank 10 Strand guide roller 11 Pelletizer 12 Master batch pellet

Claims (2)

A masterbatch containing a chemical foaming agent and a coloring material is mixed with a base resin to produce a foam molded article ,
The chemical foaming agent comprises a main foaming agent and a foaming aid that reacts with the main foaming agent to foam the main foaming agent,
(A) 1st masterbatch which has the said main foaming agent, (B) 2nd masterbatch which mixed the said foaming adjuvant and the said coloring material with the base resin, (C) The said base resin, , By mixing the main foaming agent to make the base resin into a foamed molded product. The first masterbatch and the second masterbatch so that the weight of the baking soda as the main foaming agent is more than 2 and less than 8 with respect to the weight 1 of citric acid as the foaming aid. method for producing a foamed molded article according to claim 1, characterized in that mixing.

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