JP3990236B2 - Method for producing resin foam and resin foam - Google Patents

Method for producing resin foam and resin foam Download PDF

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Publication number
JP3990236B2
JP3990236B2 JP2002247414A JP2002247414A JP3990236B2 JP 3990236 B2 JP3990236 B2 JP 3990236B2 JP 2002247414 A JP2002247414 A JP 2002247414A JP 2002247414 A JP2002247414 A JP 2002247414A JP 3990236 B2 JP3990236 B2 JP 3990236B2
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mass
resin foam
ethylene
resin
method
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JP2004082547A (en
Inventor
浩基 坂本
章公 片桐
潤一郎 鷲山
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サンアロマー株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polypropylene resin foam and a resin foam obtained thereby.
[0002]
[Prior art]
Polypropylene resin has excellent physical properties and molding processability. In addition, its use is rapidly expanding as an environmentally friendly material because it does not generate harmful gases during incineration and is recyclable. Yes. For example, polypropylene resin foams that are lightweight and have excellent rigidity are known as automotive parts. In addition to being lightweight (high foaming ratio), such resin foams have good surface appearance. And having uniform and fine foam cells is desired.
[0003]
An injection foaming method is used for producing a polypropylene resin foam. As a conventional injection foaming method, a gas counter pressure method, a core back method, and the like are known.
The gas counter pressure method is a method in which a foamable resin composition is injected into a cavity that has been pressurized with gas in advance, and degassing is performed to make the inside of the cavity in a reduced pressure state and foaming proceeds in the resin. According to this method, foaming of the resin surface is suppressed by the pressurized gas, and a resin foam having a surface appearance equivalent to that of a normal injection-molded product and uniform fine foam cells can be obtained. However, the gas counter pressure method has a drawback that a resin foam having a high expansion ratio cannot be obtained and transferability is poor.
[0004]
On the other hand, the core back method is a method in which foaming progresses in the resin by injecting a foamable resin composition into a cavity sandwiched between a fixed mold and a movable mold and retreating the movable mold. According to this method, although a resin foam having a high expansion ratio can be obtained, foaming of the resin surface cannot be suppressed, and the foaming gas escapes before the movable mold is retracted, resulting in poor appearance due to flash. There was a drawback that it occurred. Moreover, since the foam cell formed in the resin foam becomes a continuous cell, there is a disadvantage that it is large and non-uniform.
[0005]
As a method for obtaining a resin foam having a good surface appearance and a high magnification, as shown in FIG. 5, a final product in which a part of a foamable resin composition is sandwiched between a fixed mold 1 and a movable mold 2 is used. A primary injection step of injecting from the injection nozzle (not shown) through the sprue 4 into the narrow cavity 3 smaller than the volume of the resin, and then the remaining foamable resin composition as shown in FIG. An injection foaming method comprising a secondary injection step of injecting the resin into the enlarged cavity 3 and a foaming step of foaming the foamable resin composition by further retracting the movable mold 2 as shown in FIG. JP-A-2002-11748, JP-A-2002-120252, and the like.
[0006]
In such a method, since the resin surface in contact with the mold is cooled by the mold, foaming is suppressed and a skin layer is formed, and the inside thereof is a foam layer. However, in this method, since the volume of the initial cavity 3 is quite small, in order to fill the entire interior of the cavity 3 with the foamable resin composition, a foamable resin composition having high fluidity is required. Further, when the foamable resin composition is injected while enlarging the cavity 3, the cavity 3 is enlarged until just before the completion of the injection, so that the swirl is placed on the outer edge portion 5 of the resin foam along the moving direction of the movable mold 2. Marks (foamed patterns) and silver (streaked patterns) occurred, and there was a problem that appearance defects occurred partially. Moreover, since the foam cell formed in the resin foam becomes a continuous cell, there is a disadvantage that it is large and non-uniform.
[0007]
Another method for obtaining a resin foam with a good surface appearance is to inject the foamable resin composition into the cavity and then retract the movable mold while maintaining contact with the mold wall surface by the expansion of the resin by the foaming gas. This method is disclosed in Japanese Patent Laid-Open No. 8-267526. However, in such a method, since the resin surface that is expanding and the mold wall surface are always in contact with each other and the resin surface is constantly cooled, the skin layer on the resin surface becomes too thick and the foaming ratio is not increased. It was difficult.
[0008]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a production method capable of obtaining a resin foam having a good surface appearance, uniform foamed cells, good transferability, and a high foaming ratio. is there.
[0009]
[Means for Solving the Problems]
  That is, the method for producing a resin foam of the present invention comprises a polypropylene component (A) containing at least a crystalline propylene / ethylene copolymer (77% by mass to 95% by mass), an ethylene / 1-octene random copolymer (B). Resin component containing 5% by mass or more and 13% by mass or less and ethylene / 1-butene random copolymer (C) 0% by mass or more and 10% by mass or less, and 0.1 parts by mass or more with respect to 100 parts by mass of the resin component A foamable resin composition containing 5 parts by mass or less of a foaming agent (D)3kg / cm 2 10 kg / cm 2 less thanIt is characterized by having an injection step of injecting into a pressurized cavity, and a foaming step of expanding the volume of the cavity after the injection step to foam the foamable resin composition.
[0010]
In the method for producing a resin foam of the present invention, the propylene / ethylene block copolymer (A), the ethylene / 1-octene random copolymer (B), and the ethylene / 1-butene random copolymer (C It is desirable that the melt flow rate of the resin component containing 5) is 5 g / 10 min or more and less than 100 g / 10 min.
The foaming agent (D) is preferably composed of 10% by mass or more and 70% by mass or less of carbonate or bicarbonate and 30% by mass or more and 90% by mass or less of organic carboxylic acid.
[0011]
  In the foaming step, it is desirable to expand the cavity volume faster than the expansion rate of the foamable resin composition.
  The resin foam of the present invention is obtained by the method for producing a resin foam of the present invention.The expansion ratio is 2.0 or more and the cell structure is independent.It is characterized by that.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
[Polypropylene component (A)]
The polypropylene component (A), which is the main component of the foamable resin composition, comprises a crystalline propylene / ethylene copolymer as a main component, and if necessary, a crystalline propylene homopolymer and / or a crystalline propylene random copolymer. It further contains a coalescence.
[0013]
The crystalline propylene / ethylene copolymer contains a crystalline propylene homopolymer and a copolymer of ethylene and propylene or an α-olefin having 4 to 8 carbon atoms. The proportion of the crystalline propylene / ethylene copolymer soluble in para-xylene at room temperature is preferably 10% by mass or more and less than 70% by mass. If the proportion of the component soluble in para-xylene at room temperature is less than 10% by mass, the impact resistance of the resulting resin foam deteriorates. On the other hand, if it is 70% by mass or more, blocking is likely to occur during the production of the crystalline propylene / ethylene copolymer, causing a problem in stable productivity.
[0014]
The melt flow rate (MFR) at 230 ° C. of the crystalline propylene / ethylene copolymer is preferably 5 g / 10 min or more and 100 g / 10 min or less, more preferably 10 g / 10 min or more and 80 g / 10 min or less. is there. If MFR is less than 5 g / 10 minutes, dispersibility and moldability will deteriorate. On the other hand, if it exceeds 100 g / 10 min, there is a problem that the impact resistance of the obtained resin foam is lowered.
In the present invention, the MFR of the crystalline propylene / ethylene copolymer is measured under the load of 230 ° C. and 2.16 kg by the method described in JIS K6921-2.
[0015]
Further, a crystalline propylene homopolymer may be used in combination in order to improve the fluidity and foam moldability of the crystalline propylene / ethylene copolymer.
In particular, in order to improve fluidity, a crystalline propylene homopolymer having a melt flow rate at 230 ° C. of 500 g / 10 min or more and 3000 g / 10 min or less is suitable. The melt flow rate is more preferably from 800 g / 10 min to 2500 g / 10 min, and even more preferably from 1000 g / 10 min to 2000 g / 10 min. If the melt flow rate of the crystalline propylene homopolymer is 500 g / 10 min or more, the fluidity is greatly improved, and if it is less than 3000 g / 10 min, the impact resistance of the resin foam can be kept high. it can.
In the present invention, the melt flow rate of the crystalline propylene homopolymer is measured under the load of 230 ° C. and 2.16 kg by the method described in JIS K6921-2.
[0016]
Moreover, it is preferable that a boiling p-xylene soluble part is 6.0 mass% or less. More preferably, it is 3.0 mass% or less.
Here, the boiling p-xylene-soluble content is determined as follows.
5 g of homopolypropylene was extracted with boiling p-xylene, soxhlet extracted, and the filtrate was allowed to stand overnight at 20 ° C., then acetone was added to the filtrate to precipitate, and the precipitate was filtered and dried.1(G)) is measured and calculated from the following equation.
((W1) / 5) × 100 (%)
[0017]
As a method for adjusting the melt flow rate of this crystalline propylene homopolymer, a method of adjusting the polymerization conditions such as the amount of molecular weight regulator such as hydrogen, polymerization temperature, pressure, etc. at the time of polymerization, or JP-A-8-302105 As disclosed in JP-A No. 11-230, there is a method of adjusting with an organic peroxide such as diacyl peroxide or dialkyl peroxide after polymerization. The adjustment of the melt flow rate is preferably the former adjustment method by polymerization in view of the appearance of the resin foam.
[0018]
As the catalyst used in the preparation method by this polymerization, almost all catalysts that give crystalline isotactic polypropylene can be used, and among them, JP-A-3-706, JP-A-8-170984, and JP-A-9-20803. The most preferable method is to use a catalyst comprising an electron donor containing a plurality of ether bonds in the titanium catalyst component disclosed in Japanese Patent Publication No. H11.
[0019]
Furthermore, a high melt tension crystalline propylene homopolymer may be used in combination with the crystalline propylene / ethylene copolymer as necessary to improve the appearance of the resin foam. High melt tension crystalline propylene homopolymer is a crystal whose melt flow rate (MFR) (g / 10 min) at 230 ° C. and melt tension (MT) (g) at 230 ° C. satisfy the relationship of the following formula: Propylene homopolymer.
11.32 x MFR-0.7854≦ MT
[0020]
As a preferable high melt tension crystalline propylene homopolymer, a polypropylene resin having a melt tension (MT) at 230 ° C. of 0.01 N (0.980665 gf) or more and a melt flow rate at 230 ° C. of 1 g / 10 min or more. Is mentioned. Here, the melt flow rate is measured under the load of 230 ° C. and 2.16 kg by the method described in JIS K6921-2. Moreover, melt tension is measured according to the apparatus for MFR measurement shown by JISK6921-2. Specifically, about 5 g of resin is preheated in a cylinder at 230 ° C. for 5 minutes, and then discharged from a capillary at an extrusion speed of 20 mm / min by a piston, and the discharged strand is drawn at a constant speed of 15.7 m / min. The load is read with a stress gauge via a pulley on the way and recorded. The average value of readings for 120 to 180 seconds from the start of measurement is taken as the melt tension.
[0021]
Further, if necessary, a crystalline random copolymer that is a copolymer of propylene and ethylene or an α-olefin having 4 to 8 carbon atoms may be used in combination with the crystalline propylene / ethylene copolymer. Good. The copolymerization ratio of ethylene or α-olefin having 4 to 8 carbon atoms in the crystalline random copolymer is preferably 5% by mass or less. When the copolymerization ratio exceeds 5% by mass, the heat resistance of the resin foam deteriorates.
[0022]
The melt flow rate (MFR) at 230 ° C. of the crystalline random copolymer is preferably 5 g / 10 min or more and 100 g / 10 min or less, more preferably 10 g / 10 min or more and 80 g / 10 min or less. If MFR is less than 5 g / 10 minutes, dispersibility and moldability will deteriorate. On the other hand, if it exceeds 100 g / 10 min, there is a problem that the impact resistance of the obtained resin foam is lowered.
[0023]
[Ethylene / 1-octene random copolymer (B)]
The ethylene / 1-octene random copolymer (B) is a component for improving the impact resistance of the resin foam.
The ethylene / 1-octene random copolymer (B) has an ethylene content of preferably 70 mol% or more and 90 mol% or less, more preferably 75 mol% or more and 85 mol% or less, and the density is preferably 0. .86 g / cmThree 0.88 g / cmThree It is as follows. A copolymer having an ethylene content and a density in this range has physical properties as an elastomer and can increase the impact strength of the resin foam.
[0024]
The melt flow rate (MFR) of the ethylene / 1-octene random copolymer (B) is a value measured under a load of 2.16 kg at 230 ° C. according to JIS K69211-2, preferably 3 g / 10 min or more. 70 g / 10 min or less, more preferably 10 g / 10 min or more and 65 g / 10 min or less. When the MFR value is within this range, the impact resistance can be improved without impairing the fluidity of the block copolymer, so that a resin foam having high impact strength, gloss, and excellent appearance can be obtained. Can do.
[0025]
The ethylene / 1-octene random copolymer (B) can be produced by copolymerizing ethylene and 1-octene in the gas phase or liquid phase, usually in the presence of a transition metal catalyst. There is no restriction | limiting in particular in a polymerization catalyst, a polymerization method, etc., For example, it can manufacture by polymerization methods, such as a gas phase method, a solution method, and a bulk polymerization method, using a Ziegler type catalyst, a Philips type catalyst, a metallocene type catalyst etc.
[0026]
[Ethylene / 1-butene random copolymer (C)]
The ethylene / 1-butene random copolymer (C) is blended with a resin component as necessary in order to improve mechanical strength (impact resistance).
[0027]
The melt flow rate (MFR) of the ethylene / 1-butene random copolymer (C) is a value measured under a load of 2.16 kg at 230 ° C. according to JIS K69211-2, preferably 0.5 g / 10. Min to 10 g / 10 min, more preferably 0.6 g / 10 min to 5 g / 10 min. When the MFR value is within this range, the mechanical strength (impact resistance) is improved.
[0028]
The ethylene / 1-butene random copolymer (C) can be usually produced by copolymerizing ethylene and 1-butene in the gas phase or liquid phase in the presence of a transition metal catalyst. There is no restriction | limiting in particular in a polymerization catalyst, a polymerization method, etc., For example, it can manufacture by polymerization methods, such as a gas phase method, a solution method, and a bulk polymerization method, using a Ziegler type catalyst, a Philips type catalyst, a metallocene type catalyst etc.
[0029]
[Foaming agent (D)]
The foaming agent (D) is not particularly limited, and may be a solvent-type foaming agent or a decomposable foaming agent.
A solvent-type foaming agent is a substance that functions as a foaming agent by being injected from a cylinder portion of an injection molding machine and absorbed or dissolved in a raw material resin, and then evaporated in an injection mold. Low boiling point aliphatic hydrocarbons such as propane, butane, neopentane, heptane, isohexane, hexane, isoheptane, heptane, low boiling point fluorine-containing hydrocarbons typified by Freon gas, and the like can be used.
[0030]
A decomposable foaming agent is a compound that is pre-blended with a raw material resin and then supplied to an injection molding machine. The foaming agent decomposes under the cylinder temperature conditions of the injection molding machine and generates a gas such as carbon dioxide or nitrogen. is there. The decomposable foaming agent may be an inorganic decomposable foaming agent or an organic decomposable foaming agent, and an organic acid that promotes gas generation may be used in combination as a foaming aid. .
[0031]
Examples of the inorganic decomposable foaming agent include sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite, citric acid, sodium citrate and the like.
Examples of organic decomposable foaming agents include N-nitroso compounds such as N, N′-dinitrosoterephthalamide and N, N′-dinitrosopentamethylenetetramine; azodicarbonamide, azobisisobutyronitrile, azocyclohexyl Azo compounds such as nitrile, azodiaminobenzene, barium azodicarboxylate; benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, p, p'-oxybis (benzenesulfenylhydrazide), diphenylsulfone-3,3'-disulfonylhydrazide Sulfonyl hydrazide compounds; azide compounds such as calcium azide, 4,4′-diphenyldisulfonyl azide, p-toluenesulfonyl azide and the like.
[0032]
Among these foaming agents, carbonates or hydrogencarbonates such as sodium bicarbonate are preferable in that they have little impact on the environment, are safe, and the foamed cells are stabilized. It is preferable to use it together as a foaming aid. The blending ratio of the carbonate or bicarbonate to the organic carboxylic acid is preferably in the range of 10 to 70 mass% for the carbonate or bicarbonate and 30 to 90 mass% for the organic carboxylic acid. In using the foaming agent and foaming aid, a masterbatch containing them may be prepared in advance and blended with the resin component.
[0033]
[Foaming resin composition]
The resin component of the foamable resin composition contains a polypropylene component (A), an ethylene / 1-octene random copolymer (B), and, if necessary, an ethylene / 1-butene random copolymer (C).
[0034]
The proportion of the polypropylene component (A) in the resin component is 77% by mass or more and 95% by mass or less. When the polypropylene component (A) is less than 77% by mass, there is a problem in that the rigidity of the obtained resin foam is lowered and it becomes expensive. On the other hand, when it exceeds 95 mass%, impact resistance will fall.
The proportions of the crystalline propylene / ethylene copolymer, crystalline propylene homopolymer, and crystalline propylene random copolymer in the resin component are preferably 40% by mass to 95% by mass, and 35% by mass or less, respectively. It is 20 mass% or less. If the content of each of the crystalline propylene / ethylene copolymer, the crystalline propylene homopolymer, and the crystalline propylene random copolymer is within the above range, a composition having good mechanical properties can be obtained.
[0035]
The ratio of the ethylene / 1-octene random copolymer (B) in the resin component is 5% by mass or more and 13% by mass or less. When the ethylene / 1-octene random copolymer (B) is less than 5% by mass, the foaming ratio of the obtained resin foam does not increase, and the formed cells are coarsely continuous, and when it exceeds 13% by mass, The flexural modulus decreases and becomes expensive.
The proportion of the ethylene / 1-butene random copolymer (C) in the resin component is 0% by mass or more and 10% by mass or less, preferably 0% by mass or more and 8% by mass or less. When the ethylene / 1-butene random copolymer (C) exceeds 10% by mass, the foam cell becomes rough.
[0036]
The melt flow rate (MFR) of this resin component is preferably in the range of 5 g / 10 min or more and less than 100 g / 10 min. When the MFR is within this range, it is suitable for high-speed injection molding, it is easy to adjust the balance between the rigidity and impact resistance of the foam, the foamed cells are easy to take a closed cell shape, and the cell shape is uniform. There are easy advantages.
In the present invention, the melt flow rate of the resin component is measured under the load of 230 ° C. and 2.16 kg by the method described in JIS K6921-2.
[0037]
The addition amount of the foaming agent (D) is in the range of 0.1 to 5 parts by mass, preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the resin component. In accordance with the required physical properties of the resin foam, it is selected in consideration of the amount of gas generated from the foaming agent and the desired expansion ratio. From the foamable resin composition within this range, a resin foam having uniform cell diameters and uniformly dispersed cells can be obtained.
[0038]
Various additives can be added to the foamable resin composition according to the present invention, if necessary, within a range not impairing the object of the present invention. Additives include antioxidants, hydrochloric acid absorbers, heat stabilizers, weathering stabilizers, light stabilizers, UV absorbers, lubricants, antistatic agents, flame retardants, pigments, dyes, dispersants, copper damage inhibitors, Examples include neutralizers, plasticizers, crosslinking agents, flowability improvers such as peroxides, weld strength improvers, natural oils, synthetic oils, waxes and the like.
[0039]
[Method for producing resin foam]
Next, the manufacturing method of the resin foam of this invention is demonstrated.
FIG. 1 is a cross-sectional view showing an example of a mold used in the method for producing a resin foam of the present invention. The mold 10 includes a fixed mold 11 and a movable mold 12 (core mold), and a cavity 13 is formed between the fixed mold 11 and the movable mold 12. The fixed mold 11 is provided with a gate 14 for injecting a foamable resin composition supplied from an injection nozzle (not shown) into the cavity 13. Further, the movable mold 12 is provided with a gas pipe 15 that supplies a gas such as nitrogen from the gas supply pipe 16 into the cavity 13 and supplies the gas in the cavity to the gas discharge pipe 17. The gas supply pipe 16 and the gas discharge pipe 17 are provided with valves 18 and 19, respectively. Further, the movable die 12 is provided with an O-ring 20 for keeping the inside of the cavity 13 airtight at a contact portion with the fixed die 11.
[0040]
The production of the resin foam using the mold 10 is performed, for example, as follows.
First, in a high-pressure mold clamping state in which the fixed mold 11 and the movable mold 12 are brought into contact with each other at a high pressure, a gas such as nitrogen is sealed in the cavity 13 from the gas supply pipe 16 through the gas pipe 15 and kept at a predetermined gas pressure. . As shown in FIG. 2, the foamable resin composition 21 plasticized by heating is injected into the cavity 13 pressurized by this gas from the injection nozzle (not shown) through the gate 14 (injection process). In the injection process, since the gas pressure is constantly applied in the cavity 13, the skin layer is formed with almost no foaming on the resin surface.
[0041]
After completion of the injection, a gas such as nitrogen in the cavity 13 is discharged from the gas pipe 15 through the gas discharge pipe 17. At this time, foaming progresses in the resin, and uniform and fine independent foam cells are formed. Next, as shown in FIG. 3, the movable mold 12 is retracted to enlarge the volume of the cavity 13, and the foamable resin composition 21 is further foamed (foaming step). In this foaming step, when the movable mold 12 is retracted in a state where injection of the foamable resin composition is stopped, foaming proceeds in the resin.
[0042]
When the movable mold 12 is retracted to a predetermined position (the volume of the cavity is expanded to the volume of the final product), the movable mold 12 is stopped and the foamed resin is cooled (cooling step). After cooling, the movable mold 12 is further retracted to take out the resin foam (final product).
After the foaming step, the resin foam can be taken out by cooling as it is, or after being lightly cooled, the movable mold 12 can be advanced and clamped, compressed and adjusted to a predetermined size, and taken out. When compressed, the volume of the resin foam that does not come into contact with the mold will be re-contacted with the inner surface of the mold, so that the cooling efficiency will be improved and the shape will be regulated in the mold. Later deformation can be prevented and a good appearance can be obtained.
[0043]
The gas pressure in the cavity 13 before injecting the foamable resin composition into the cavity 13 is 3 kg / cm.2 10 kg / cm2 The following is preferable. The gas pressure in the cavity 13 is 3 kg / cm2 If it is less than 1, the suppression of foaming on the resin surface becomes insufficient, the surface appearance of the resulting resin foam may be deteriorated, and further, uniform and fine foamed cells may not be obtained. The gas pressure in the cavity 13 is 10 kg / cm2 If it exceeds, the equipment may be costly.
[0044]
The temperature of the foamable resin composition injected into the cavity 13 is preferably 190 ° C. or higher and 220 ° C. or lower. The mold temperature of the fixed mold 11 and the movable mold 12 is preferably 30 ° C. or higher and 70 ° C. or lower.
[0045]
It is preferable that the retraction speed of the movable mold 12 in the foaming step is faster than the expansion speed of the foamable resin composition, that is, the cavity volume is enlarged faster than the expansion speed of the foamable resin composition. As a result, the expanding resin surface and the mold wall surface hardly come into contact with each other, so that the resin surface is not excessively cooled, and therefore, it becomes easy to increase the expansion ratio of the resin foam. .
[0046]
In the method for producing a resin foam as described above, the foamable resin composition having a specific composition is injected into the cavity 13 pressurized with gas, so that it is equivalent to the gas counter pressure method. The resin foam intermediate having the surface appearance and uniform and fine independent foam cells can be obtained, and the volume of the cavity is expanded after the injection process to further foam the resin foam intermediate. High foaming ratio resin foam can be obtained with good transferability, and a good surface appearance and uniform and fine closed cell remain in the final resin foam. .
[0047]
The resin foam obtained by such a production method does not generate harmful gas even when incinerated, and can be recycled. Such a resin foam can be suitably used for automobile interior parts such as door trims and instrument panels, and automobile exterior parts such as side protect moldings, bumpers, soft fascias and mudguards.
[0048]
The method for producing a resin foam of the present invention includes an injection step of injecting a specific foamable resin composition into a cavity pressurized by a gas, and expanding the volume of the cavity after the injection step to expand the foamable resin composition Any method may be used as long as it has a foaming step for foaming a product, and the method is not limited to the above-described production method.
In addition, the mold used in the method for producing the resin foam of the present invention is not limited to the illustrated example, and a mechanism that expands the volume of the cavity as long as the volume of the cavity can be expanded after the injection process, There is no particular limitation on the shape of the mold.
[0049]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[Polypropylene component (A)]
The following were used as a polypropylene component (A).
(A-1): Sun Allomer Co., Ltd., crystalline propylene / ethylene copolymer, PAB70A, MFR (230 ° C.) = 60 g / 10 min.
(A-2): Sun Allomer Co., Ltd., crystalline propylene / ethylene copolymer, PMA80X, MFR (230 ° C.) = 45 g / 10 min.
(A-3): Sun Allomer Co., Ltd., crystalline propylene homopolymer, PF814, MFR (230 ° C.) = 2.5 g / 10 min, MT (230 ° C.) = 22 g.
[0050]
<Production of (A-4)>
(Solid catalyst)
As the solid catalyst for polymerization, a highly stereoregular Ziegler-Natta catalyst was used. Specifically, MgCl2 Further, 2.5% by mass of Ti and diisobutyl phthalate as an internal donor are supported by the method described in European Patent No. 674991.
(Catalyst system and prepolymerization)
The solid catalyst was contacted with a mixture of triethylaluminum (TEAL) and dicyclopentylmethoxysilane (DCPMS) at -5 ° C for 5 minutes. Here, TEAL / DCMPS = 15 (mass ratio) and TEAL / Ti = 65 (molar ratio). Before the reaction in the first reactor, the catalyst system obtained here was suspended in liquefied propylene and held at 20 ° C. for 20 minutes.
[0051]
(polymerization)
The polymerization of the monomers was carried out using a three-stage gas phase reactor with a device that can immediately send the synthesized polymer components to the next reactor. The synthesis of the polypropylene homopolymer was performed by supplying propylene gas to the first reactor together with the previously prepared prepolymerized catalyst and hydrogen (used for the purpose of molecular weight adjustment) at a continuous and constant speed. Hydrogen and propylene monomer were continuously analyzed and supplied so that the concentration in the reactor was constant.
[0052]
In order to obtain a rubber component which is a propylene / ethylene copolymer, the polypropylene homopolymer obtained in the first reactor is discharged after purging the unreacted monomer at a constant flow rate, and the second reactor together with propylene and ethylene gas at a constant flow rate. Introduced.
Subsequently, in order to obtain a polypropylene homopolymer component, the polymer component produced in the second reactor was discharged after purging unreacted monomers at a constant flow rate, and introduced into the third reactor together with gaseous propylene and hydrogen at a constant flow rate.
[0053]
The polymer particles present in the third reactor were treated with steam to remove reactive monomers and volatiles. In this way, a crystalline propylene / ethylene copolymer (A-4) was produced at MFR (230 ° C.) = 2 g / 10 min. Table 1 shows the conditions of each reactor.
[0054]
[Table 1]
[0055]
<Production of (A-5)>
(Preparation of catalyst)
(1) Synthesis of 9,9-bis (hydroxymethyl) fluorene:
1. In a 500 ml flask, sodium ethylate dissolved in 100 ml of dimethyl sulfoxide (DMSO) distilled over CaH, 8 g of paraformaldehyde (dehydrated at room temperature and pressure of 2 torr for 8 hours), and 6 ml of ethanol in order in an anhydrous atmosphere. 4 g was added. After cooling the suspension in an ice bath (the melting temperature of the DMSO / EtOH mixture is 13 ° C.), 100 ml of a DMSO solution of 16 g of fluorene was added over 30 seconds while stirring the suspension. Three minutes after the start of adding fluorene in DMSO, the reaction was quenched with 1.5 ml of 37% HCl and then diluted with 400 ml of water. The mixture was saturated with NaCl and 9,9-bis (hydroxymethyl) fluorene was extracted with ethyl acetate. The organic phase is then dried over anhydrous Na2 SOFour And the solvent was distilled off. After crystallization with toluene, 15.2 g (70% yield) of product was obtained.
[0056]
(2) Synthesis of 9,9-bis (methoxymethyl) fluorene:
In a 100 ml flask, in a nitrogen atmosphere, in order, 30 ml of tetrahydrofuran (THF), 11.9 g of 9,9-bis (hydroxymethyl) fluorene prepared above, and CHThreeI 31.1 ml was added. While stirring and operating at room temperature, 4 g of 60% by weight NaH in mineral oil was added over 2 hours and 30 minutes, and then the contents were reacted for 1 hour and 30 minutes. Unreacted CH by distillationThreeI was recovered, the remaining contents were diluted with 100 ml of water, and the resulting floating solid was filtered and dried at 40 ° C. under reduced pressure. Crystallization with ethanol gave 11.3 g (90% yield) of product.
[0057]
(polymerization)
A solid catalyst component prepared by the method described in Example 1 of JP 09-020803 A, a catalyst component composed of triethylaluminum, propylene monomer, and hydrogen for adjusting MFR were added to a loop type polymerization tank having a volume of 290 L. Continuously fed. Specifically:
In a 500 ml cylindrical glass reactor equipped with a filtration barrier at 0 ° C., TiClFour 225 ml, and micro-long spherical MgCl obtained as follows for 15 minutes with stirring:2 ・ 2.1C2HFive10.1 g (54 mmol) of OH was added. The temperature was then raised to 70 ° C. and 9 mmol of 9,9-bis (methoxymethyl) fluorene was added. The temperature is raised to 100 ° C. and after 2 hours TiClFour Was removed by filtration. TiClFour After adding 200 ml and 9,9-bis (methoxymethyl) fluorene 9 mmol and treating at 120 ° C. for 1 hour, the contents were filtered again and another 200 ml of TiCl 2 was added.Four And the treatment was continued for an additional hour at 120 ° C., and finally the contents were filtered and washed with n-heptane at 60 ° C. until the chlorine ions disappeared completely from the filtrate.
The catalyst component thus obtained contains Ti = 3.5% by mass and 9,9-bis (methoxymethyl) fluorene = 16.2% by mass.
[0058]
Micro long spherical MgCl2 ・ 2.1C2HFiveOH was produced as follows. In a 2 liter autoclave equipped with a turbine stirrer and suction pipe, anhydrous MgCl in inert gas at room temperature2 48g, anhydrous C2HFiveOH 77g and kerosene 830ml were added. By heating the contents to 120 ° C. with stirring, MgCl2 An adduct is formed between the alcohol and the alcohol, which melts and is mixed with the dispersant. The nitrogen pressure in the autoclave was maintained at 15 atmospheres. The suction pipe of the autoclave was heated to 120 ° C. from the outside with a heating jacket. The suction pipe has an inner diameter of 1 mm and a length from one end of the heating jacket to the other end of 3 meters. The mixture was flowed through this pipe at a speed of 7 m / sec. At the outlet of the pipe, the dispersion was collected with stirring in a 5 liter flask containing 2.5 liters of kerosene and cooled from the outside with a jacket maintained at an initial temperature of -40 ° C. The final temperature of the dispersion is 0 ° C. The spherical solid product constituting the dispersed phase of the emulsion was allowed to settle, separated by filtration, washed with heptane and dried. All these operations were performed in an inert gas atmosphere. MgCl in the form of solid spherical particles with a maximum diameter of 50 microns or less2 ・ 2.3C2HFive130 g of OH was obtained. From the product thus obtained, MgCl2 The alcohol was removed by gradually increasing the temperature from 50 ° C. to 100 ° C. in a nitrogen stream until the alcohol content per mole decreased to 2.1 mol.
[0059]
In a 4 liter autoclave previously purged with gaseous propylene at 70 ° C. for 1 hour, 70 ml of anhydrous n-hexane containing 7 mmol of triethylaluminum and 4 mg of the solid catalyst component produced as described above was placed in a propylene stream at room temperature. . The autoclave was closed, 1.7 N liters of hydrogen and 1.2 kg of liquid propylene were introduced, the stirrer was activated and the temperature was raised to 70 ° C. in 5 minutes. After 2 hours at 70 ° C., stirring was stopped, unpolymerized monomers were removed, and the contents were cooled to room temperature. Although 380 g of polypropylene was released from the autoclave, the polypropylene had a xylene-insoluble fraction (XI) at 25 ° C. = 97.7% and a melt index MFR / L = 4.5 g / 10 min. The polymer yield was 95,000 g of polypropylene per 1 g of the solid catalyst component.
[0060]
Triethylaluminum was supplied at a molar fraction of 60 molppm per propylene monomer, and was continuously polymerized at a production rate of 20 kg / hour while maintaining a polymerization pressure of 4.5 MPa and a polymerization temperature of 70 ° C. The obtained homopolypropylene was taken out as a sample after leaving the polymerization tank and removing unreacted monomers with a flash drum, followed by catalyst deactivation by steam and a drying process. During the polymerization, hydrogen was introduced so that the hydrogen concentration in the system was 18000 molppm with respect to the unreacted propylene monomer to obtain a crystalline propylene homopolymer (A-5) having an MFR of 2000 g / 10 min. The boiling p-xylene soluble content at this time was 2% by mass.
[0061]
(A-6): Sun Allomer Co., Ltd., crystalline propylene random copolymer, PW822N, MFR (230 ° C.) = 20 g / 10 min, ethylene content = 3.1 mass%.
[0062]
[Ethylene / 1-octene random copolymer (B)]
The following were used as the ethylene / 1-octene random copolymer (B).
(B-1): ethylene / 1-octene random copolymer manufactured by DuPont Dow Elastomer, ENGAGE 8407, MFR (230 ° C.) = 60 g / 10 min.
(B-2): ethylene / 1-octene random copolymer manufactured by DuPont Dow Elastomer, ENGAGE 8130, MFR (230 ° C.) = 30 g / 10 min.
[0063]
[Ethylene / 1-butene random copolymer (C)]
The following were used as the ethylene / 1-butene random copolymer (C).
(C-1): DuPont Dow Elastomer ethylene / 1-butene random copolymer, EG7467, MFR (230 ° C.) = 2.0 g / 10 min.
(C-2): JSR-produced ethylene / 1-butene random copolymer, EBM3021P, MFR (230 ° C.) = 2.5 g / 10 min.
For comparison, an ethylene / propylene random copolymer (EPR) was used.
(C′-3): ethylene / propylene random copolymer manufactured by Sun Allomer Co., Ltd., ST150T, MFR (230 ° C.) = 2.5 g / 10 min.
[0064]
[Foaming agent (D)]
A foaming agent EE205 manufactured by Eiwa Chemical Co., Ltd. was used.
[0065]
[Example 1]
The resin components having the formulations shown in Table 2 were melted and kneaded with an extruder to obtain resin component pellets. The physical properties of the obtained pellets were evaluated. The results are shown in Table 4.
(Evaluation of the physical properties)
[1] Preparation of physical property test specimens:
Using an injection molding machine (Fanuc α100C, manufactured by FANUC Co., Ltd.), a test specimen for measurement was produced using a test specimen mold. The molding conditions are shown below.
<Molding conditions> Cylinder temperature: 200 ° C., mold temperature: 40 ° C., injection pressure: 90 MPa, cooling time: 20 seconds.
[2] Melt flow rate:
Conforms to JIS K6921-2.
<Sample> Pellets
<Test conditions> Temperature: 230 ° C., load value: 2.16 kg.
[0066]
[3] Flexural modulus:
Conforms to JIS K7203.
<Test piece> 12.7 (width) x 4.0 (thickness) x 127 mm (length)
<Test conditions> Temperature: 23 ° C., span: 60 mm, bending speed: 2.0 mm / min.
[4] Izod impact test:
Using a test piece notched by mechanical cutting, measurement was performed in accordance with JIS K7110. The test was performed in an atmosphere at 23 ° C.
<Test piece> 12.7 (width) x 4.0 (thickness) x 64 mm (length)
[0067]
(Evaluation of resin foam)
[1] Swirl mark evaluation:
First, nitrogen gas is sealed from a gas supply pipe into a cavity of a mold having a central one-point direct gate, and the gas pressure is 4 kg / cm.Three Kept. The mold temperature was adjusted to 40 ° C. In a cavity pressurized by this gas, a predetermined amount of a foamable resin composition comprising the above pellets and 5 parts by mass of a foaming agent (D) with respect to 100 parts by mass of the pellets is injected into an injection molding machine ( It was injected for 2 seconds using Fanuc α100C (manufactured by FANUC CORPORATION, cylinder temperature 200 ° C.). After the injection is completed, the nitrogen gas in the cavity is exhausted, and the movable mold is retracted to a predetermined position at a speed that retracts in 2 seconds, thereby expanding the cavity volume faster than the expansion rate of the foamable resin composition. The foamable resin composition was further foamed. When the movable mold was retracted to a predetermined position, the movable mold was stopped, and the foamed resin was cooled for 30 seconds. After cooling, the movable mold was further retracted to take out the resin foam (final product) to obtain a flat (200 mm × 200 mm × 4 mm) test piece as shown in FIG.
[0068]
The swirl mark on the surface of the resin foam was visually observed and evaluated in the following five stages. The results are shown in Table 4.
5: No occurrence of swirl marks or extremely inconspicuous.
4: The swirl mark is not noticeable.
3: The swirl mark is slightly noticeable.
2: The swirl mark is conspicuous.
1: The swirl mark is very conspicuous.
[0069]
[2] Cell structure evaluation:
Using the test piece evaluated for the swirl mark, the cross section of the resin foam was observed with a stereomicroscope to obtain the average cell diameter. We also observed whether the cells were continuous or independent. The results are shown in Table 4.
[0070]
[3] Dimple evaluation:
Using the test piece evaluated for the swirl mark, surface irregularities were observed. The dimples on the surface of the resin foam were visually observed and evaluated according to the following five levels. The results are shown in Table 4.
5: No occurrence of dimples or extremely inconspicuous.
4: Dimples are not noticeable.
3: Dimples are slightly noticeable.
2: Dimple is conspicuous.
1: The dimple is very conspicuous.
[0071]
[4] Foaming ratio evaluation:
From the density of the test piece obtained by the swirl mark evaluation and the unfoamed product, the expansion ratio was calculated using the following formula. The results are shown in Table 4.
Foaming ratio = (density of unfoamed test piece) / (density of test piece injection-molded with a foaming agent added)
[0072]
[Examples 2 to 7]
Except having changed the prescription | regulation of the resin component as shown in Table 2, it obtained the pellet and the resin foam like Example 1, and performed these evaluations. The results are shown in Table 4.
[0073]
[Comparative Example 1]
First, nitrogen gas is sealed from a gas supply pipe into a cavity of a mold having a central one-point direct gate, and the gas pressure is 4 kg / cm.Three Kept. The mold temperature was adjusted to 40 ° C. A predetermined amount of the foamable resin composition used in Example 1 was injected into the cavity pressurized by this gas for 2 seconds using an injection molding machine (Fanuc α100C, manufactured by Fanuc Co., Ltd., cylinder temperature 200 ° C.). did. After completion of injection, nitrogen gas in the cavity was discharged, and the foamed resin was cooled for 30 seconds. After cooling, the movable mold was further retracted to take out the resin foam (final product) to obtain a flat (200 mm × 200 mm × 4 mm) test piece as shown in FIG. This resin foam was evaluated in the same manner as in Example 1. The results are shown in Table 4.
[0074]
[Comparative Example 2]
A predetermined amount of the foamable resin composition used in Example 1 was placed in a cavity of a mold (40 ° C.) having a central one-point direct gate, and an injection molding machine (manufactured by Fanuc α100C FANUC, cylinder temperature 200 ° C.). ) For 2 seconds. After the injection was completed, the movable mold was retracted to a predetermined position at a speed that retracted in 2 seconds to expand the volume of the cavity, and the foamable resin composition was further foamed. When the movable mold was retracted to a predetermined position, the movable mold was stopped, and the foamed resin was cooled for 30 seconds. After cooling, the movable mold was further retracted to take out the resin foam (final product) to obtain a flat (200 mm × 200 mm × 4 mm) test piece as shown in FIG. This resin foam was evaluated in the same manner as in Example 1. The results are shown in Table 4.
[0075]
[Comparative Examples 3 to 5]
Except having changed the prescription | regulation of the resin component as shown in Table 3, it obtained the pellet and the resin foam like Example 1, and performed these evaluations. The results are shown in Table 4.
[0076]
[Table 2]
[0077]
[Table 3]
[0078]
[Table 4]
[0079]
[Summary of results]
As can be seen from the results of Examples and Comparative Examples in Table 4, according to the present invention, it is possible to obtain a resin foam having a high swirl mark level, a small cell size, no dimples, and a high expansion ratio. Is possible.
On the other hand, when the core back was not performed, the expansion ratio was not improved (Comparative Example 1). In addition, when the gas counter was not used, the swirl mark was poor, the cell size was coarse, and there was a tendency to continue (Comparative Example 2). Further, when the ethylene / 1-octene random copolymer (B) was small, the expansion ratio did not increase, and the cells tended to be coarse and continuous (Comparative Example 3). Moreover, when there were too many ethylene 1-octene random copolymers (B), there existed a fault that rigidity fell and there existed a fault that cost increased (comparative example 4). Further, when the ethylene / 1-octene random copolymer (B) or the ethylene / 1-butene random copolymer (C) is not contained in a predetermined amount, the impact resistance is lowered and the foamed state is also deteriorated (Comparative Example). 5, 6).
[0080]
【The invention's effect】
As described above, the method for producing a resin foam of the present invention includes a polypropylene component (A) containing at least a crystalline propylene / ethylene copolymer (77% by mass to 95% by mass), ethylene / 1-octene random copolymer. The resin component containing 5% by mass or more and 13% by mass or less of the combined body (B) and 0% by mass or more and 10% by mass or less of the ethylene / 1-butene random copolymer (C); An injection process in which a foamable resin composition containing 1 part by mass or more and 5 parts by mass or less of a foaming agent (D) is injected into a cavity pressurized by a gas, and the volume of the cavity is increased after the injection process. A foaming step of foaming the foamable resin composition, so that the surface appearance is good, the foamed cells are uniform and fine, the transferability is good, and the foaming ratio is high. Foam can be obtained.
[0081]
Moreover, in the manufacturing method of the resin foam of this invention, the resin component containing the said polypropylene component (A), the ethylene / 1-octene random copolymer (B), and the ethylene / 1-butene random copolymer (C). If the melt flow rate is 5 g / 10 min or more and less than 100 g / 10 min, it is suitable for high-speed injection molding, it is easy to adjust the balance between the rigidity and impact resistance of the foam, and the foam cell has a closed cell shape. It is easy to remove and the cell shape is easy to be uniformed.
Moreover, if the said foaming agent (D) consists of carbonate or hydrogencarbonate 10 mass% or more and 70 mass% or less and organic carboxylic acid 30 mass% or more and 90 mass% or less, it will provide the outstanding foamability. In addition, the cell structure can be stabilized.
[0082]
The gas pressure in the cavity before injecting the foamable resin composition into the cavity is 3 kg / cm.2 10 kg / cm2 Within the following range, a resin foam having a good surface appearance and uniform and fine foam cells can be easily obtained.
In the foaming step, if the volume of the cavity is increased faster than the expansion rate of the foamable resin composition, it becomes easy to increase the foaming ratio of the resin foam.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a mold used in a method for producing a resin foam according to the present invention.
FIG. 2 is a view showing a cross section of a mold during an injection process in the method for producing a resin foam of the present invention.
FIG. 3 is a view showing a cross section of a mold during a foaming step in the method for producing a resin foam of the present invention.
FIG. 4 is a view showing a test piece used for evaluation of a resin foam.
FIG. 5 is a view showing a cross section of a mold during a primary injection step in a conventional method for producing a resin foam.
FIG. 6 is a view showing a cross section of a mold at the time of a secondary injection step in a conventional method for producing a resin foam.
FIG. 7 is a view showing a cross section of a mold during a foaming step in a conventional method for producing a resin foam.
[Explanation of symbols]
13 cavity

Claims (5)

  1. Polypropylene component (A) containing at least crystalline propylene / ethylene copolymer (77% by mass to 95% by mass), ethylene / 1-octene random copolymer (B) 5% by mass to 13% by mass and ethylene / 1- A resin component containing 0% by mass to 10% by mass of a butene random copolymer (C) and a foaming agent (D) of 0.1 parts by mass to 5 parts by mass with respect to 100 parts by mass of the resin component The foamable resin composition is 3 kg / cm 2 by gas. 10 kg / cm 2 or more An injection process for injecting into the pressurized cavity below ,
    And a foaming step of foaming the foamable resin composition by expanding the volume of the cavity after the injection step.
  2.   The melt flow rate of the resin component containing the polypropylene component (A), the ethylene / 1-octene random copolymer (B) and the ethylene / 1-butene random copolymer (C) is 5 g / 10 min or more and 100 g / 10. The method for producing a resin foam according to claim 1, wherein the resin foam is less than a minute.
  3.   The foaming agent (D) is composed of 10% by mass or more and 70% by mass or less of carbonate or bicarbonate and 30% by mass or more and 90% by mass or less of an organic carboxylic acid. Item 3. A method for producing a resin foam according to Item 2.
  4. The method for producing a resin foam according to any one of claims 1 to 3 , wherein in the foaming step, the volume of the cavity is enlarged faster than the expansion rate of the foamable resin composition.
  5. What claims 1 to 4 or der those obtained by the method for producing a resin foam according to an item, and the expansion ratio of 2.0 or more, and cell structure and said independent der Rukoto Resin foam.
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