JPH10231379A - Foamable master batch and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamable master batch excellent in foaming moldability and good in usability by developing a base material having a low melting point, little in adhesive components and excellent in miscibility and affinity with a molding matrix material. SOLUTION: This foamable master batch is produced by a process for adding a carboxylic acid and an organic peroxide to a polyethylene thermoplastic polymer synthesized in the presence of a single site catalyst and subsequently kneading the mixture under heating, and a process for adding microspheres composed from shells comprising a thermoplastic resin and from a thermally expandable substance encapsulated in the shells to the carboxylic acid-grafted polymer and subsequently kneading the mixture to produce the PE-MS mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed masterbatch containing a heat-expandable microsphere as a main component and a method for producing such a foamed masterbatch.

[0002]

2. Description of the Related Art In recent years, a high-temperature type heat-expandable microsphere has been developed, and a foam molding method using the heat-expandable microsphere has been widely used. The foam molding method using the heat-expandable microspheres does not directly form foam voids in the molding base material, but expands the microspheres dispersed in the molding base material at the time of heating and forms a coarser hollow sphere. By doing
As a result, it is intended to obtain a molded article having a low density.

[0003] Therefore, according to this method, as in the conventional method using a chemical foaming agent or a high-pressure gas, the appearance of the molded product deteriorates due to the scattering of air bubbles, and the heat insulation caused by the unevenness of the air bubbles and the communication of the air bubbles. No problem such as deterioration of performance or mechanical strength occurs. Further, in this method, the density and properties of the molded article can be arbitrarily controlled by selecting microspheres having a suitable expansion start temperature and a suitable degree of expansion, and appropriately selecting the microsphere particle size and the amount of addition. Therefore, it is easy to obtain a foam molded product having desired physical properties.

However, this method also has the following problems. That is, if the microspheres are not uniformly dispersed and mixed in the base material, the distribution of the hollow spheres (foamed microspheres) is uneven, so that the mechanical strength, the heat insulation performance, and the like of the foam molded product vary. Also, if the microspheres are exposed to a temperature near the expansion start temperature for a long time,
The hollow spheres tend to stick together with the pre-expansion (expansion before heat molding), and the uniform dispersibility is significantly reduced. Further, when exposed to a temperature higher than the expansion peak temperature, the shell is broken and the volume is reduced. Therefore, the function as a hollow sphere is lost.

[0005] Therefore, in order to obtain a high quality foam molded article, it is necessary to sufficiently mix the microsphere and the base material. In addition, it is necessary to appropriately perform temperature control during mixing and to quickly complete a series of operations up to heat molding. However, since microspheres are minute spherical particles (about 10 to 80 μm), while the matrix resin is usually relatively large pellet-like particles of 2 to 3 mm, they must be uniformly mixed in an individual state. It is difficult. Further, since the melting point of the resin serving as the base material is generally high and the melt viscosity is high, it is difficult to mix the microspheres without pre-expansion into the molten base material.

For this reason, conventionally, a method has been adopted in which microspheres are preliminarily mixed with a base material having a low melting point to form a master batch, and this master batch is added to a base material immediately before molding and mixed. According to this method, the kneading efficiency with respect to the base material is improved as compared with the case where the microspheres are directly mixed with the base material, so that the deterioration of the quality of the molded article due to the pre-expansion or the mixing failure can be alleviated.

However, as a base material of this type of masterbatch, ethylene vinyl acetate (EVA) has been conventionally used. However, since EVA is very sticky, the mixing characteristics at the time of preparing a master batch are not sufficient. Also, since EVA easily sticks to a mixer or the like, a great deal of labor is required for cleaning the machine. Further, such a masterbatch using EVA has a problem that the mixing property with the base material is not sufficient, and the preservation causes blocking when stored, so that the workability and the handling property are poor.

[0008] However, no suitable base material that can be substituted for EVA has been found, and a good foamed masterbatch cannot be obtained even when, for example, a conventional type of polyethylene or polypropylene is used as the base material. This is because conventional polyethylene and the like have a high melting point, and if mixed in a molten state, the microspheres expand in advance. Further, it is difficult to lower the melting point of the conventional type polyethylene or the like. Furthermore, even if the melting point can be lowered, the molecular weight distribution is wide and the low molecular weight component (sticky component) is included, and this low molecular component causes a decrease in the mechanical strength and the like of the foam molded article. It is.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has a low melting point and a low sticky component.
It is another object of the present invention to devise a base material having good mixability and affinity with a molding base material, and to provide an easy-to-use foam masterbatch having excellent foam moldability.

[0010]

An object of the present invention is to provide a base material made of a special acid-modified polymer having a narrow molecular weight distribution and composition distribution, and mixing a thermally expandable microsphere with the base material. Can be achieved. Specifically, this can be achieved by the following configuration.

[0011] The invention according to claim 1 comprises a first step of subjecting a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst to a carboxylic acid-modifying treatment, and a step of subjecting the carboxylic acid-modified polymer to a carboxylic acid-modified polymer. A second step of adding and kneading a microsphere composed of a shell made of a thermoplastic resin and a heat-expandable substance confined inside the shell to form a PE-MS mixture, and It is a manufacturing method.

[0012] The polyethylene-based thermoplastic polymer synthesized using a single-site catalyst has a narrower molecular weight distribution and a uniform distribution of comonomer in each molecular chain as compared with a polymer synthesized using a conventional type of multi-site catalyst. The composition distribution is narrow. Therefore, a low melting point thermoplastic polymer having a narrow composition distribution can be obtained, which is advantageous as a base material precursor for a foamed masterbatch because it has a low molecular weight component which causes stickiness.

When the above-mentioned polyethylene-based thermoplastic polymer is subjected to a carboxylic acid modification treatment, the affinity and compatibility with another resin, which is a weak point of the polyethylene-based thermoplastic polymer, can be improved. Thereby, the following operation and effect can be obtained.

Since the affinity between the base material and the resin constituting the outer shell of the microspheres is improved, a foamed masterbatch in which the microspheres are uniformly mixed is obtained. Since the affinity and compatibility between the base material and the molding base material are good,
The quality of the foamed product is improved. In general, the compatibility between a polyethylene resin and a nylon resin or a styrene resin is not good. However, since the polarity of the polymer is increased by the carboxylic acid modification treatment, the compatibility with these resins is also improved. Therefore, particularly, the quality of the foam molded article using such a resin as a base material is improved. Since the main body is a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst whose molecular weight distribution and composition distribution are narrow, problems caused by sticky components such as conventional low melting point polymers such as EVA, that is, a stirring mixer machine Problems such as sticking to storage and blocking during storage can be alleviated.

Although the DSC peak melting temperature of the polymer slightly shifts to a lower temperature due to the carboxylic acid modification treatment,
This is an advantageous change in that it prevents pre-expansion of the microspheres.

According to a second aspect of the present invention, in the method for producing a foamed masterbatch according to the first aspect, the carboxylic acid modification treatment in the first step is performed on a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst. The carboxylic acid and the organic peroxide are added and kneaded under heating to graft polymerize the carboxylic acid to the polyethylene-based thermoplastic polymer.

With this configuration, the carboxylic acid can be relatively easily introduced and added to the polyethylene-based thermoplastic polymer.

According to a third aspect of the present invention, in the method for producing a foamed masterbatch according to the first aspect, the first step is performed by a single-site feed port provided on an upstream side of an extruder. A polyethylene-based thermoplastic polymer synthesized using a catalyst, a carboxylic acid, and an organic peroxide are charged, and the three components are kneaded under heating to graft-polymerize the carboxylic acid to the polyethylene-based thermoplastic polymer. In the content, the second step is to insert a heat-expandable microspheres from a second raw material supply port provided on the downstream side of the extruder, and a carboxylic acid-modified polymer in which carboxylic acid is polymerized, and It consists of kneading with microspheres to form a PE-MS mixture.

With this constitution, first, the polyethylene thermoplastic polymer, carboxylic acid and organic peroxide, which are charged through the first raw material supply port, are kneaded efficiently in an extruder. An organic peroxide and a carboxylic acid act on the thermoplastic polymer to cause graft polymerization, whereby a carboxylic acid-modified polymer is synthesized. Next, the carboxylic acid-modified polymer is kneaded with the microspheres introduced from the second raw material supply port, and the PE-MS
A mixture is prepared.

That is, in the above configuration, the extruder having at least two raw material supply ports is used, and the chemical reaction step (the carboxylic acid addition step) and the physical mixing step (PE-MS mixture preparation step) is distinguished spatially and temporally. Therefore, first, the polymer, the carboxylic acid, and the organic peroxide, which are supplied from the first raw material supply port, are kneaded and reacted. Next, microspheres supplied from the second raw material supply port are added to the reaction product, and are kneaded.

With the above configuration, a series of manufacturing steps can be performed integrally and continuously, which is extremely efficient. Also, since no unnecessary heat history or chemical action is applied to the microsphere, a high-quality foamed microsphere without damage or pre-expansion is obtained.

The invention according to claim 4 is the invention according to claims 1 to 3.
In the method for producing a foamed masterbatch according to the above, after the second step, a third step of hot-cutting and pelletizing the PE-MS mixture extruded from an extrusion port provided on the downstream side of the extruder is included. It is characterized by being added.

If the PE-MS mixture extruded from the extrusion port is immediately cut (hot cut), foamed master batch pellets can be obtained with high productivity.
Usually, since the base resin is in the form of pellets, dry blending of the two becomes possible by pelletizing the foamed master batch, which is the other mixed component.
Therefore, with this configuration, the usability of the foam master batch can be significantly improved.

The invention according to claim 5 is the invention according to claims 2 to 4
In the method for producing a foamed master batch according to the above, the carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and anhydrides thereof. Wherein the organic peroxide is selected from the group consisting of lauroyl peroxide, benzoyl peroxide, ditertiary butyl peroxide, tertiary butyl perbenzoate, dicumyl peroxide, and 1,3 bis (t-butylperoxyisopropyl) benzene. It is characterized by being selected.

When the carboxylic acid and the organic oxide are selected from the above groups, the graft polymerization reaction can be easily caused by a simple method of kneading.

The invention according to claim 6 is the invention according to claims 1 to 5
In the method for producing a foamed masterbatch according to the above, the kneading temperature in the second step is set to be equal to or higher than the DSC peak melting temperature of the carboxylic acid-modified polymer, and equal to or lower than the expansion start temperature of the microsphere.

At this kneading temperature, the carboxylic acid-modified polymer is molten, and the microspheres do not expand. Therefore, since both can be uniformly mixed without the pre-expansion of the microsphere, a high-quality foamed masterbatch can be obtained.

[0028] The invention according to claim 7 provides the invention according to claims 1 to 6.
The method for producing a foamed masterbatch according to the above, is characterized in that, at the time of kneading in the second step, microspheres which have been wetted with liquid paraffin in advance are used.

Since microspheres are minute (several tens to several hundreds of micrometers) and lightweight, they are poor in handling, such as flying into the air during mixing and the like. Microspheres moistened with liquid paraffin have no soaring,
Liquid paraffin also enhances the wettability between the microspheres and the carboxylic acid-modified polymer. Therefore, according to this configuration, the handling property and uniform mixing property of the microsphere can be improved.

[0030] The invention according to claim 8 provides the invention according to claims 1 to 7.
In the method for producing a foamed masterbatch described above, water is added for cooling during the kneading in the second step.

When the melting temperature of the carboxylic acid-modified polymer as the base material is close to the expansion start temperature of the microsphere, the kneading time of the two is reduced to a very short time (1 to 5) in order to avoid the pre-expansion of the microsphere. Minutes)
It is necessary to reduce the thermal history of the microsphere. For this purpose, it is necessary to lower the temperature of the mixture immediately after kneading. Here, when a small amount of water is added to the mixture, the water itself functions as a coolant, and evaporates with the heat of the mixture to take away heat of vaporization. Therefore, by adding an appropriate amount of water, the temperature of the mixture can be rapidly lowered, and at the same time, the added water can be removed by evaporation.

In this configuration, the amount of water to be added to the mixture is preferably set to an amount that evaporates and evaporates. Note that the “water” may be hot water. Even with hot water, a cooling effect can be obtained by the heat of vaporization. Also, if cold water is suddenly introduced, the mixture may be rapidly solidified and water may be taken in, and the water taken in hardly evaporates and may remain.

[0033] The ninth aspect of the present invention provides the first to eighth aspects.
The method for producing a foamed masterbatch according to the above, wherein the microspheres start expanding at a temperature of 90 ° C. or more at normal pressure, and have a property of breaking a shell within 5 minutes when heated to a temperature of 220 ° C. or more. It is characterized by being.

It is not preferable that the expansion start temperature of the microsphere is too low because the microsphere easily expands due to the heat of stirring during kneading. Therefore, 90 ° C. or higher is generally preferable. On the other hand, if it is a microsphere that does not break its outer shell even when heated to a high temperature, it does not require special attention to the melting point temperature of the base material and the base material, but such a microsphere does not actually exist . If the expansion completion temperature is set too high, it becomes impossible to use the method to complete the expansion simultaneously with the heat molding of the base material.

For the above reasons, the current high-temperature expansion type microspheres have an expansion start temperature of 90 ° C. or higher,
The expansion completion temperature is set at around 220 ° C. When this type of microsphere is heated to a temperature of 220 ° C. or more, the outer shell is broken within 5 minutes and the volume is reduced. The present invention specifies the conditions of a base material (carboxylic acid-modified polymer) for the purpose of improving the usability of a thermally expandable microsphere that can actually exist. In other words, the present invention uses a microsphere that starts expanding at a temperature of 90 ° C. or more and breaks a shell within 5 minutes when heated to a temperature of 220 ° C. or more.
It has a particularly remarkable effect.

According to a tenth aspect of the present invention, in the method for producing a foamed masterbatch according to the first to ninth aspects, the single-site catalyst is a composite catalyst containing a metallocene compound of a Group 4 transition metal and methylaluminoxane. It is characterized by.

When the composite catalyst is used, a polyethylene-based thermoplastic polymer having a narrow molecular weight distribution and a narrow composition distribution can be obtained. Such a polyethylene-based thermoplastic polymer modified with carboxylic acid is particularly suitable as a base material for a foamed masterbatch.

An eleventh aspect of the present invention is the method for producing a foamed masterbatch according to any one of the first to tenth aspects, wherein the polyethylene-based thermoplastic polymer is polyethylene.

Polyethylene using a single-site catalyst has a lower melting point and less low molecular weight components (sticky components) than conventional ones, and is excellent in strength, flexibility and the like. Further, a polymer obtained by modifying the polyethylene with a carboxylic acid has excellent compatibility with other polymers. Therefore, it is suitable as a base material for a foamed masterbatch,
When such a foamed master batch is used, a foamed molded product having excellent mechanical strength and excellent heat insulation properties and light weight as compared with conventional foamed molded products can be obtained.

The foamed masterbatch produced by the method for producing a foamed masterbatch according to the first to eleventh aspects can be defined as a product invention.

In other words, the invention according to claim 12 provides a polyethylene-based thermosphere synthesized using a single-site catalyst, a microsphere composed of a shell made of a thermoplastic resin and a thermally expandable substance confined inside the shell. This is a foamed master batch composed of a plastic polymer and a base material mainly composed of a carboxylic acid-modified polymer that has been subjected to a carboxylic acid-modification treatment.

According to a thirteenth aspect of the present invention, in the expanded masterbatch according to the twelfth aspect, the microspheres start expanding at a temperature of 90 ° C. or more at normal pressure and 5 minutes at a temperature of 220 ° C. or more. It has the property of breaking the shell that encapsulates the thermally expandable material within.

According to a fourteenth aspect of the present invention, in the expanded masterbatch according to the twelfth or thirteenth aspect, the carboxylic acid-modified polymer has a DSC peak melting temperature lower than the expansion start temperature of the microsphere.

According to a fifteenth aspect of the present invention, in the foamed masterbatch according to the twelfth to fourteenth aspects, the shell of the microsphere is made of a copolymer containing acrylonitrile. With this configuration, it is possible to form a film in a state in which the heat-expandable substance is confined inside the shell by the microencapsulation means, and expand at a temperature of 90 ° C. or more at normal pressure and stabilize to a temperature of about 220 ° C. A good coating can be obtained.

According to a sixteenth aspect of the present invention, in the foamed masterbatch according to the twelfth to fifteenth aspects, the thermally expandable substance of the microsphere is isopentane or isobutane. Microspheres using isopentane or isobutane as a heat-expandable substance are 90 ° C to 22 ° C.
Since the expansion pressure is large at a temperature around 0 ° C., an excellent foamed master batch is obtained.

According to a seventeenth aspect of the present invention, in the foamed master batch according to the twelfth to sixteenth aspects, the carboxylic acid-modified polymer is obtained by graft-polymerizing a carboxylic acid onto polyethylene synthesized using a single-site catalyst.

The invention according to claim 18 is the foaming masterbatch according to claims 12 to 17, wherein the foaming masterbatch has a diameter of 1 mm to 5 mm and a length of 1 mm to 5 mm.
mm pellets.

[0048]

Embodiments of the present invention will be described below.

First, the term "single-site catalyst" as used herein refers to a catalyst in which the properties of coexisting active sites are uniform.
As the single site catalyst, for example, chemical formula 1 (metallocene complex) can be mentioned. Further, a composite catalyst in which a compound (aluminoxane) represented by Chemical Formula 2 is combined with the metallocene complex of Chemical Formula 1 (hereinafter, this composite catalyst is included when referred to as a metallocene catalyst) is exemplified. Such metallocene catalysts are known and described in, for example, JP-A-5-140227, JP-A-5-140228, JP-A-5-209919, JP-A-5-209919, and the like. It is known that a polyethylene-based thermoplastic polymer synthesized using a catalyst has characteristics such as narrow molecular weight distribution and composition distribution.

[0050]

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[0051]

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In the chemical formula ¹ , M ¹ is titanium, zirconium, hafnium, vanadium, niobium or tantalum, and R ¹ and R ² may be the same or different from each other and include a hydrogen atom, a halogen atom, and a carbon atom having 1 to 1 carbon atoms. An alkyl group having 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and 7 carbon atoms ~ 40 arylalkyl groups, 7 carbon atoms
-40 alkylaryl groups or 8-40 carbon atoms
Wherein R ³ and R ⁴ are the same or different from each other, and are a mononuclear or polynuclear hydrocarbon residue capable of forming a sandwich complex with the central metal atom M ¹ .

[0053] R ⁵ is ^{= BR 6, = AlR 6,} -Ge-,
-Sn -, - O -, - S -, = SO, = SO 2, = NR
⁶ , ＣＯCO, 6PR ⁶ or P (O) R ⁶ (where R ⁶
Is a hydrogen atom, a halogen atom). R ⁹ may be the same or different from each other, and may have 1 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 18 carbon atoms, or 6 to 6 carbon atoms. 18 is a fluoroaryl group or a hydrogen atom, and n is 0-5.
It is an integer of 0.

An example of a composite catalyst comprising the compounds of Chemical Formulas 1 and 2 is shown in Chemical Formula 3. A polyethylene-based thermoplastic polymer synthesized using a composite catalyst obtained by combining a compound having cyclopentadiene as a ligand (zirconocene dichloride) shown on the left of Chemical Formula 3 and an aluminoxane compound shown on the right of Chemical Formula 3
It is suitable as a precursor polymer for producing the carboxylic acid-modified polymer according to the present invention. This is because the polyethylene-based thermoplastic polymer synthesized using this composite catalyst has a narrow molecular weight distribution and a uniform distribution of comonomers in each molecular chain (narrow composition distribution), and contains low molecular weight components and sticky components. The amount is small. Further, it is characterized by having excellent flexibility and strength.

On the other hand, multi-site catalysts such as Ziegler catalysts, which have been widely used as polymerization catalysts, have active points of various structures. Therefore, a polymer synthesized using such a catalyst has a broad molecular weight distribution and composition distribution, and is not suitable as a precursor of the carboxylic acid-modified polymer according to the present invention.

[0056]

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As the polyethylene-based thermoplastic polymer synthesized by using the above-mentioned single-site catalyst, specifically, for example, a trade name A manufactured by Dow Chemical Japan Co., Ltd.
FFINITY and ENGAGE (ethylene octene
Copolymers), but these polyethylene-based thermoplastic polymers generally do not have polar groups or have few polar groups, and thus have poor affinity and compatibility with other resins. In the present invention, such a polymer is subjected to a carboxylic acid modification treatment (introduction of a polar group) to give an affinity
Improve compatibility. Thereby, the compatibility of the polyolefin-based resin with resins other than the polyolefin-based resin can be improved.

Here, the carboxylic acid modification treatment refers to causing a graft polymerization reaction on the polyethylene-based thermoplastic polymer. As the carboxylic acid modification treatment method, various known methods can be used, and examples thereof include a method of adding a carboxylic acid to a polyethylene-based thermoplastic polymer, irradiating ultraviolet rays or gamma rays, and a method of adding a radical polymerization reactant. .

However, since the operation is simple, a method in which a radical polymerization reactant, for example, an organic peroxide is added and kneaded is preferably used. Specifically, using an extruder,
A polyethylene-based thermoplastic polymer, a carboxylic acid and an organic peroxide are kneaded and reacted. Of these, the carboxylic acid modification treatment is more preferably performed as follows.
In addition, for convenience of explanation, the entire method for producing a foamed masterbatch, including the carboxylic acid modification treatment method, will be described below.

First, a two-stage mixing twin-screw extruder having at least one raw material supply port on the upstream side and the downstream side and an extrusion port on the most downstream side is prepared. The inside of the cylinder of the extruder is heated to a temperature at which the polymer melts and the organic peroxide can act, and the polyethylene-based thermoplastic polymer, carboxylic acid and An organic peroxide is charged and kneaded (first step). Thereby, the carboxylic acid is graft-polymerized to the polyethylene-based thermoplastic polymer.

Next, heat-expandable microspheres are charged from a raw material supply port (second raw material charging port) provided on the downstream side, and microspheres are mixed with the carboxylic acid-modified polymer kneaded and reacted on the upstream side. Add. Then, both are kneaded preferably at a temperature equal to or lower than the expansion start temperature of the microsphere and equal to or higher than the melting temperature of the carboxylic acid-modified polymer (second step). Thereby, a PE-MS mixture which is a foaming masterbatch is prepared.

Further, after the second step, a third step of hot-cutting and pelletizing the PE-MS mixture is preferably provided. In this third step, the PE-MS extruded from the extrusion port provided on the most downstream side of the extruder
The mixture is immediately pelletized (before cooling) with a hot cutter. With this method, the PE-MS mixture can be pelletized with high productivity. In addition, a pelletized foamed masterbatch (foamed masterbatch pellet) is advantageous in that it is easy to use and has improved dry blending properties with the base material pellet.

In the above production method, as the polyethylene-based thermoplastic polymer, for example, Dow Chemical Japan
AFFINITY and ENGAGE manufactured by the company
(Ethylene octene copolymer) can be used. More specifically, for example, AFFINITY SM1250 or ENGAGE SM8400 can be preferably used. This is because these have a melting point sufficiently lower than the expansion start temperature of the thermally expandable microsphere.

AFFINITY SM1250
Has a density of 0.885 gm / cc and a comonomer polymerization degree of 19
%, A melt index of 30 g / 10 min, and a DSC melting point temperature of 85.3 ° C.
GAGE SM8400 has a density of 0.870 gm / c
c, comonomer polymerization degree 24%, melt index 30
g / 10 min., DSC having a melting point of 63.3 ° C.

As the above-mentioned carboxylic acid, for example, one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and anhydrides thereof can be used. Of these, maleic anhydride is preferably used because it is preferably bifunctional. On the other hand, examples of the organic peroxide include lauroyl peroxide, benzoyl peroxide, ditertiary butyl peroxide, tertiary butyl perbenzoate, dicumyl peroxide, and 1,3 bis (t-butylperoxyisopropyl) benzene. One or more selected from the group can be used. Of these, benzoyl peroxide is preferably used in terms of decomposition temperature.

Further, as the above-mentioned microspheres, various types of heat-expandable microspheres can be used, and a microcapsule type having a shell made of a copolymer containing acrylonitrile and containing isopentane or isobutane therein is used. . The shell composed of a copolymer containing acrylonitrile can be formed into a membrane by microencapsulation means, and the membrane (outer shell) is made of thermoplastic,
Excellent in strength and elongation. Further, isopentane and isobutane are excellent in terms of expansion rate and expansion pressure.

As already described, the kneading temperature in the second step is set to a temperature equal to or higher than the melting temperature (peak temperature of differential scanning calorimetry (DSC)) of the carboxylic acid-modified polymer, and to a thermal expansion microscopic temperature. The temperature is lower than the sphere expansion start temperature. If the kneading is performed in this temperature range, the mixing of the microspheres is easy because the carboxylic acid-modified polymer is molten. On the other hand, since the temperature is lower than the expansion start temperature of the thermally expandable microsphere, the microsphere does not expand in advance. Therefore, a good foaming master batch in which the microspheres are uniformly dispersed in the carboxylic acid-modified polymer (base material) can be obtained.

In order to satisfy the above-mentioned temperature conditions, the melting temperature of the carboxylic acid-modified polymer must be lower than the expansion start temperature of the microsphere. However, if a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst is used as a precursor and the precursor is a carboxylic acid-modified polymer, the low-melting polymer can be easily obtained.

When the expansion start temperature of the heat-expandable microsphere is too low, the selection range of the base material is significantly limited, and the risk of the microsphere being pre-expanded by the heat during mixing increases. On the other hand, if the expansion start temperature is set high, the expansion completion temperature also increases, so that the manufacturing workability is not always improved. For this reason, the current high-temperature type microspheres are set to start expansion at a temperature of 90 ° C. or higher, and this type of microspheres has an expansion completion temperature (expansion peak temperature).
Is set to around 220 ° C. When this type of microsphere is heated to a temperature near the expansion completion temperature, the shell breaks within 5 minutes and loses its function as a hollow sphere.

An object of the present invention is to provide a high-quality and easy-to-use foam master batch mainly using the high-temperature type microspheres. Therefore, the temperature characteristics of the base material (carboxylic acid-modified polymer) in which such microspheres are dispersed and mixed are preferably as follows. That is, the DSC peak melting temperature is 220 ° C. or lower, more preferably 90 ° C. or lower. This is because in order to uniformly mix the microspheres with the base material, it is necessary to melt the base material, and it is necessary that the microspheres do not expand or break at the temperature at the time of melting.

On the other hand, if the melting point of the base material is too low, the masterbatch softens in summer or the like, and blocking occurs. Therefore, from the viewpoint of handleability and prevention of pre-expansion, the melting point temperature of the base material (carboxylic acid-modified polymer) is from 50 ° C. to 220 ° C., preferably from 50 ° C. to 120 ° C., more preferably 50 ° C or higher and 90 ° C or lower. The reason why the temperature is set to 120 ° C. above is that microspheres having an expansion start temperature around 120 ° C. are commercially available and are easily available. However, when the melting point of the base material and the expansion start temperature of the microsphere are close to each other, kneading needs to be performed in a very short time (about 1 to 3 minutes).

The method for producing a foamed masterbatch according to the present invention will be further described.

In the above-described production method in which the graph polymerization reaction on the polymer and the kneading of the microspheres on the graph-polymerized polymer are integrally and continuously performed by using an extruder, the following two-stage mixing is preferable. A twin-screw extruder is used.

That is, when the total length of the cylinder of the extruder is L
When the cylinder diameter is D, the total L / D is 3
0 or more, and the L / D of the first stage (the kneading region used in the first step) is 20 or more, and 1/4 or more of the cylinder length of the first stage is constituted by a kneading block. Are preferred. In addition, the L / D of the second stage (region used in the second step) is 10 or more,
Further, it is preferable that at least half of the cylinder length of the second stage (the kneading area used in the second step) is constituted by a disk-type dispersion type block.

Although the above-described manufacturing method is preferable in terms of production efficiency, the manufacturing method of the present invention is not limited to this, and a manufacturing method in which each step is performed independently may be used. That is, the carboxylic acid modification treatment of the polyethylene-based thermoplastic polymer and the kneading operation of the microspheres can be performed by separate devices. However, no matter which method is used, in the carboxylic acid modification treatment operation, the inside of the apparatus is preferably replaced with an inert gas in order to stably perform the graft polymerization reaction.

It is also possible to use microspheres which have been moistened with liquid paraffin in advance. Since microspheres are microparticles, they tend to soar into the air during agitation, but if they are moistened with an appropriate amount of liquid paraffin, they can be prevented from rising, and at the same time, the liquid paraffin acts on the outer shell of the microsphere and acts against the polymer in the outer shell. This is because the affinity can be increased.

As a method of moistening the microspheres with liquid paraffin, for example, the microspheres and an appropriate amount of liquid paraffin may be put into a rotary blade type stirrer and stirred. In the method of separately and independently performing the kneading operation of the carboxylic acid-modified treatment and the microsphere, for example, the carboxylic acid-modified polymer, the microsphere, and the liquid paraffin, which have been modified in advance, are put into a stirrer such as a spar mixer, and then stirred and mixed. I do. The presence of liquid paraffin enhances the wettability, so that the microspheres are uniformly dispersed and mixed in a very short mixing time (about 1 minute), which is advantageous for producing a foamed master batch using an extruder later. It is.

Further, in the kneading step of the base material and the microsphere, an appropriate amount of water may be added. As a result, the following effects can be obtained. If the kneading temperature is close to the microsphere expansion start temperature, the microspheres will pre-expand unless kneaded and cooled in an extremely short time.However, if an appropriate amount of water is added to the kneaded material during the kneading operation, this water Thereby, the temperature of the kneaded material can be lowered. Further, the added water evaporates depending on the temperature of the mixture, and at this time, loses heat of vaporization, so that the temperature of the kneaded material can be lowered. Moreover, since the added water is removed by this evaporation, no water remains in the kneaded material. Therefore, since the heat history of the microsphere can be reduced, a high-quality foamed masterbatch can be obtained.

In the present invention, the mixing ratio of the microsphere to the carboxylic acid-modified polymer is usually 10 to 70% by weight. If it is less than 10% by weight, the concentration of the microsphere is too low, and a large amount of the foamed masterbatch must be used for the base material. Therefore, the foamed master batch is inconvenient to use. On the other hand, when the ratio of microspheres exceeds 70% by weight,
Since the amount of the base material is too small, the uniform dispersibility in the base material is reduced.

The kneading strength in an extruder or a mixer is as follows.
The kneading time should be as short as possible so that the microspheres are not broken by shearing force. As the stirring time increases, the damage to the outer shell of the microsphere increases,
Further, the risk of pre-expansion increases due to the heat of stirring and mixing.

Further, in the case where the third step of pelletizing is provided, the size of the foamed master batch pellet is 1 mm to 5 mm in diameter and 1 mm to 5 mm in length.
It is good to do. Generally, the size of the base material pellets is this size, so that the base material pellets and the dry blend can be improved with this size. Since the pellets immediately after the hot cut are easily blocked, the pellets are cooled by, for example, putting them in a rotating body and cooling while rotating.

The main components of the present invention will be further described.

FIGS. 1 and 2 show the molecular weight distributions of linear low-density polyethylene (LLDPE) synthesized using a single-site catalyst (metallocene catalyst system) and linear low-density polyethylene using a multi-site catalyst (conventional catalyst). , And the density and the DSC peak melting temperature.

As is apparent from FIG. 1, the polymer using the single-site catalyst has a narrower molecular weight distribution than that using the conventional catalyst. Also, as is apparent from FIG.
In the case of using a conventional catalyst, the melting point tends to hardly decrease even when the density decreases, while in the case of the polymer using the single-site catalyst, the DSC peak melting temperature decreases as the density decreases, and the overall temperature is lower. It has a melting point.
From these facts, it is understood that a polymer synthesized using a single-site catalyst is suitable as a precursor of a carboxylic acid-modified polymer.

FIG. 3 is an example of a temperature-expansion curve of the heat-expandable microsphere used in the present invention. As shown in FIG. 3, the temperature-expansion curve of the heat-expandable microsphere draws a parabola. That is, when the heat-expandable microsphere is heated to a predetermined temperature or more, the shell of the microsphere is broken, and the volume is rather reduced. For this reason, the melting point of the base material composing the foamed masterbatch needs to be appropriately selected in relation to the expansion start temperature and the expansion peak temperature (burst temperature) of the microsphere, and the molding base material It can be seen that it is better to determine a suitable foaming master batch composition in consideration of the temperature during heat molding.

Since the foamed masterbatch of the present invention uses a carboxylic acid-modified polymer excellent in affinity and compatibility with other resins for the base material, it can be kneaded well with various base materials, and has a light weight. Thus, a foam molded article having excellent mechanical strength as well as heat insulation properties can be obtained. Specifically, for example, conventional types of plastomers such as polyethylene, polypropylene and ethylene vinyl acetate, and polypropylene and EPR
An olefin-based thermoplastic elastomer obtained by mixing styrene-based thermoplastic elastomers, a SEBS-type or SEPS-type styrene-based thermoplastic elastomer, and nylon can also be used.

The foamed master batch of the present invention is usually used by a method of being added to a molten molding base material immediately before molding. The base material after the addition of the foaming master batch is placed in, for example, a mold as soon as possible. Extrusion or injection molding. Thereby, the microspheres expand in the base material, and a so-called foam molded article is formed. Here, when the microspheres are heated above the expansion start temperature, the expansion ends within an extremely short time of about 30 seconds to about 2 minutes. Therefore, it is necessary to sufficiently control the kneading / molding time with the base material and the temperature. There is. Note that, for example, if the stirring intensity is too high to shorten the kneading time, extra frictional heat may be generated and the microspheres may be broken instead.

[0088]

The present invention will be specifically described below with reference to examples.

[Example 1] As the thermally expandable microsphere, Expancel 092D manufactured by Expancel was used.
U-120 (particle size 3-50 μm, relative density 1.2 g / c
c, expansion start temperature 118-126 ° C, breaking temperature 188-
195 ° C). As a polyethylene-based polymer synthesized using a single-site catalyst, ENGAGE SM8400 (density: 0.870 g / cc, comonomer weight: 24%, DSC peak melting point: 63.3 ° C.) manufactured by Dow Chemical Japan Co., Ltd. was used.

As an extruder for kneading, an NRII-46 mm SG twin screw extruder manufactured by Freesia Macross was used.
This extruder is a two-stage kneading type having two raw material supply ports on the upstream side and the downstream side, and the relationship between the cylinder length and the cylinder diameter is as follows. However, in Example 1, since only the carboxylic acid modification treatment was performed by this extruder, the raw material supply port on the downstream side was not used.

Overall length of the extruder Cylinder length L / cylinder diameter D = 40 First-stage kneading area Cylinder length L ₁ / cylinder diameter D ₁ = 24 Ratio of the kneading block occupied by the kneading block = 6.5
/ 24 Second stage kneading area Cylinder length L ₂ / cylinder diameter D ₂ = 16 The proportion of the kneading block in this part = 4.0
/ 16

As a manufacturing method, first, ENGAGE
100 kg of SM8400 and 500 kg of maleic anhydride
g and benzoyl peroxide in a drum blender. Next, this mixture was charged from the raw material supply port on the upstream side of the extruder, kneaded at a cylinder temperature of 80 ° C. and a screw rotation number of 50 rpm, and extruded from the extrusion port located on the downstream side at an extrusion speed of 50 kg / hr. Thereafter, the mixture was pelletized with a pelletizer to obtain carboxylic acid-modified polymer pellets.

Next, 70 kg of the carboxylic acid-modified polymer pellets and Expancel 092DU-120 (30 kg) moistened with 0.2 kg of liquid paraffin were put into a 500 L supermixer (manufactured by Katawa Co., Ltd.). A stirring speed that does not raise the temperature to 60 ° C or more (about 360 r
pm) for about 1 minute.

Further, the mixture obtained above was put into a twin screw extruder (GT-110, manufactured by Ikegai Co., Ltd.) and kneaded under conditions of a screw rotation speed of 30 rpm and a temperature of a die part of 90 ° C. It was extruded to 3.5 mm and immediately hot-cut with a rotary hammer attached to the front of the extrusion port. The hot-cut pellet was placed in a pellet cooler provided with a hexagonal rotating body, and cooled to a temperature of 50 ° C. or less while rotating. This is because the temperature of the pellets immediately after the hot cut is close to the melting temperature and sticks to each other as they are.

As described above, the diameter is 3 to 3.5 mm,
A foamed masterbatch pellet according to the present invention having a length of 2 mm to 4 mm was prepared.

The size of the foamed masterbatch pellet is preferably adjusted to the pellet size of the resin (base material) to be foamed. This is because dry blending becomes easier when the pellet sizes are the same.

The microsphere particles in the foamed master batch pellets produced by the above-mentioned production method were observed under a microscope. As a result, expansion of the microsphere was not confirmed.
It was also confirmed that the microspheres were in a good dispersed and mixed state. Furthermore, by tactile observation, the room temperature (2
(Around 0 to 27 ° C.) without stickiness.

Further, 1 kg of the foamed master batch pellets produced above was mixed with a conventional polypropylene resin (Tokuyama M Co., Ltd.) synthesized using a multi-site catalyst.
S670) After dry blending with 10 kg, injection molding (nozzle temperature of about 165 ° C., mold temperature of 40 to 80 ° C.) was performed to produce a foam molded article, and its properties were observed. as a result,
The appearance was good, and a uniform and favorable foaming state was observed by loupe observation of the fractured surface.

Example 2 In Example 1, the carboxylic acid modification treatment step and the microsphere kneading step were performed separately and independently. In Example 2, the two-stage kneading twin-screw extrusion was performed. Using a machine, the carboxylic acid modification treatment step and the kneading step were continuously and integrally performed. Hereinafter, the manufacturing method according to the second embodiment will be described focusing on the differences from the first embodiment.

The same Expansel 092DU-120 as in Example 1 was used as the thermally expandable microsphere. On the other hand, as the polyethylene-based polymer synthesized using a single-site catalyst, the above-mentioned ENGAGE SM
8400 in place of Dow Chemical Japan Co., Ltd.
FFINITY SM1250 (density 0.885g / c
c, comonomer severity 19%, DSC peak melting point 85.3
° C). Premixing for the carboxylic acid modification treatment was performed in the same manner as in Example 1.

As the extruder, the same NRII-46 mm SG twin screw extruder manufactured by Freesia Macross Co., Ltd. was used, but the carboxylic acid modification step and the microsphere kneading step were integrally and continuously performed. Specifically, 70 kg / g of the above premix was supplied from a raw material supply port on the upstream side of the extruder.
The mixture was fed at a speed of hr and kneaded at a cylinder temperature of 90 ° C. and a screw rotation speed of 100 rpm. Thereby, the carboxylic acid is graft-polymerized to the polymer (AFFINITY SM1250).

On the other hand, after the premix reached the raw material supply port on the downstream side of the extruder, Expancel 092DU-120 was supplied from the supply port at a rate of 30 kg / hr, and at the same time, water for cooling was supplied. The mixture was supplied at about 400 g / hr and kneaded. Thereby, a PE-MS mixture in which the carboxylic acid-modified polymer and Expancel 092DU-120 are mixed is produced. Since this PE-MS mixture was extruded from an extrusion port provided at the most downstream side of the extruder, it was hot-cut into pellets. Thereby, a foamed masterbatch pellet is obtained.

The supply amount of the cooling water is an amount that evaporates before the production of the foamed masterbatch pellets is completed.

The foamed masterbatch pellets of Example 2 produced in this way were observed under a microscope in the same manner as in Example 1. As a result, there was no pre-expansion and the dispersed and mixed state was good. There was no stickiness.

[0105]

According to the present invention, a carboxylic acid-modified polymer is used as a base material of a foamed masterbatch, and a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst is used as a precursor of the carboxylic acid-modified polymer.

A polyethylene-based thermoplastic polymer synthesized using a single-site catalyst has a narrow molecular weight distribution and a narrow composition distribution. Therefore, even if the polymer has a low melting point, the sticky component is small. Therefore, the carboxylic acid-modified polymer obtained by modifying the carboxylic acid has a low melting point and a small sticky component. In addition, the carboxylic acid-modified polymer has better affinity and compatibility with other polymers than the precursor polymer because of the introduction of the polar group.

Therefore, the carboxylic acid-modified polymer has a good mixability with fine microspheres and a good mixability with the molding base material. Further, since there is no stickiness, the pellets do not block each other even when pelletized.

As described above, according to the present invention, an easy-to-use foam masterbatch having excellent foam moldability (volume expandability) and dry blending with a molding base material can be obtained.
And by using this foam masterbatch,
A remarkable effect is obtained in that the productivity and quality of the foam molded article can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining an influence of a catalyst on a molecular weight distribution.

FIG. 2 is a graph showing a relationship between a density of a polymer synthesized using a single-site catalyst and a polymer synthesized using a multi-site catalyst, and a DSC peak melting temperature (melting point).

FIG. 3 is a graph showing the relationship between the coefficient of expansion of a thermally expandable microsphere and temperature.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23/04 C08L 23/04

Claims (18)

[Claims] 1. A first step of subjecting a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst to a carboxylic acid-modifying treatment, and comprising a thermoplastic resin for the carboxylic acid-modified treated carboxylic acid-modified polymer. A second step of adding and kneading a microsphere composed of a shell and a heat-expandable substance confined inside the shell to form a PE-MS mixture, the method comprising the steps of: 2. The carboxylic acid modification treatment in the first step is performed by adding a carboxylic acid and an organic peroxide to a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst and kneading the mixture under heating. The method for producing a foamed master batch according to claim 1, wherein the method comprises graft-polymerizing a carboxylic acid onto the polyethylene-based thermoplastic polymer. 3. The first step comprises: a first raw material supply port provided upstream of an extruder, a polyethylene-based thermoplastic polymer synthesized using a single-site catalyst, a carboxylic acid, and an organic peroxide. An oxide is charged, and the three components are kneaded under heating to graft polymerize a carboxylic acid to the polyethylene-based thermoplastic polymer. The second step is performed on the downstream side of the extruder. The heat-expandable microspheres are charged from the second raw material supply port provided, and the carboxylic acid-modified polymer graft-polymerized in the first step and the microspheres are kneaded to PE-
The method for producing a foamed masterbatch according to claim 1, wherein the method comprises forming an MS mixture. 4. The method according to claim 1, further comprising a third step of hot-cutting and pelletizing the PE-MS mixture extruded from an extrusion port provided downstream of the extruder after the second step. The method for producing a foamed master batch according to any one of claims 1 to 3, wherein 5. The organic peroxide according to claim 1, wherein the carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and anhydrides thereof. Wherein the substance is selected from the group consisting of lauroyl peroxide, benzoyl peroxide, ditertiary butyl peroxide, tertiary butyl perbenzoate, dicumyl peroxide, 1,3 bis (t-butylperoxyisopropyl) benzene. 5. The method for producing a foamed masterbatch according to claim 2, wherein: 6. The method according to claim 1, wherein the kneading temperature in the second step is equal to or higher than a DSC peak melting temperature of the carboxylic acid-modified polymer and equal to or lower than an expansion start temperature of the microsphere. 6. The method for producing a foamed masterbatch according to 5. 7. The method for producing a foamed master batch according to claim 1, wherein the kneading in the second step uses microspheres wetted with liquid paraffin in advance. 8. The method according to claim 1, wherein water for cooling is added during kneading in the second step.
8. The method for producing a foamed masterbatch according to any one of items 7 to 7. 9. The microsphere has a property of starting to expand at a temperature of 90 ° C. or more at normal pressure and breaking a shell within 5 minutes when heated to a temperature of 220 ° C. or more. 9. The method for producing a foamed master batch according to any one of 1 to 8. 10. The method for producing a foamed masterbatch according to claim 1, wherein the single-site catalyst is a composite catalyst containing a metallocene compound of a Group 4 transition metal and methylaluminoxane. 11. The method for producing a foamed master batch according to claim 1, wherein the polyethylene-based thermoplastic polymer is polyethylene. 12. A carboxylic acid-modified polyethylene-based thermoplastic polymer synthesized using a single-site catalyst and a microsphere composed of a shell made of a thermoplastic resin and a heat-expandable substance confined inside the shell. A foamed master batch composed of a base material mainly composed of a carboxylic acid-modified polymer subjected to a treatment. 13. The microsphere has a property that it starts to expand at a temperature of 90 ° C. or more at normal pressure and breaks a shell for enclosing a thermally expandable substance within 5 minutes at a temperature of 220 ° C. or more. 13. The foamed masterbatch according to claim 12, wherein 14. The DSC according to claim 1, wherein the carboxylic acid-modified polymer has a temperature lower than the expansion start temperature of the microsphere.
14. The foamed masterbatch according to claim 12, which has a peak melting temperature. 15. The foamed masterbatch according to claim 12, wherein the microsphere shell is made of a copolymer containing acrylonitrile. 16. The foamed masterbatch according to claim 12, wherein the thermally expandable substance of the microsphere is isopentane or isobutane. 17. The foamed masterbatch according to claim 12, wherein the carboxylic acid-modified polymer is obtained by graft-polymerizing a carboxylic acid to polyethylene synthesized using a single-site catalyst. 18. The foamed master batch has a diameter of 1 m.
The foamed masterbatch according to any one of claims 12 to 17, which is in the form of a pellet having a length of 1 mm to 5 mm and a length of 1 mm to 5 mm.