JP5568350B2 - Method for producing polypropylene-based modified resin - Google Patents

Description

The present invention relates to a polypropylene-based modifying resins manufacturing how the polypropylene resin is cross-linked.

Conventionally, polypropylene resins have been used as raw materials for various molded products because of their excellent mechanical properties and chemical resistance.
In the case of producing a molded product using this polypropylene resin, extrusion molding, blow molding, foam molding, etc. are generally performed. However, since polypropylene resin generally has crystallinity. In some cases, the viscosity and melt tension at the time of melting are low, and a molded product having a desired property cannot be obtained even if highly accurate conditions are set when performing the molding as described above.
For example, when extrusion foaming is performed to produce a foamed molded article such as a foamed sheet, a foamed foamed article having a dense foamed state is obtained as a result of foam breaking due to insufficient tension of the cell membrane occurring during extrusion foaming. Can be difficult.
Moreover, when beads are foamed to form a foamed molded product such as a cushioning material, foaming may be insufficient and the appearance may be impaired, or the foamed molded product may not exhibit sufficient strength.

Attempts have been made to improve the melt tension by modifying the polypropylene resin in order to solve such problems, and various types of polypropylene-based modified resins have been studied.
For example, in Patent Document 1 below, a polypropylene resin is subjected to radiation cross-linking in a gas atmosphere adjusted to a specific oxygen concentration, so that the viscosity and tension at the time of melting are higher than those of the polypropylene resin before irradiation. A method of making a resin is described.
However, the invention described in Patent Document 1 has a problem that it is difficult to easily obtain a polypropylene-based modified resin because of the large equipment required to use radiation.

On the other hand, various studies have been made on chemical cross-linking with organic peroxides. In Patent Document 2 below, a polypropylene resin having a predetermined melt mass flow rate value and a specific organic peroxide are melt-kneaded. Thus, it is described that a polypropylene-based modified resin is produced.
Furthermore, Patent Document 3 below describes that a polypropylene-based modified resin is prepared by melt-kneading a plurality of polypropylene-based resins having different melt mass flow rates and peroxydicarbonate.
In the inventions described in these patent documents, since the polypropylene-based modified resin is produced by melt-kneading, it can be said that the production method is simpler than the method using radiation.
However, as in the inventions described in Patent Documents 2 and 3, simply by melting and kneading a polypropylene resin and an organic peroxide, an effect of improving the melt tension corresponding to the amount of the organic peroxide added can be obtained. Have no fear.

In other words, conventionally, it has been difficult to effectively crosslink polypropylene resins with organic peroxides to improve melt tension, and it has been difficult to efficiently obtain polypropylene-based modified resins having high melt tension. .
In addition, from this, there is a problem that it is difficult to obtain a polypropylene-based modified resin that can be easily produced while having a high melt tension, for example, suitable for the production of a foam molded article. ing.

Japanese Patent Laid-Open No. 62-121704 Japanese Patent No. 4267187 Japanese Patent No. 3808843

  In view of the above problems, the present invention relates to a method for efficiently producing a polypropylene-based modified resin having a high melt tension, and a polypropylene that can be easily produced while having a high melt tension. It is an object of the present invention to provide a system-modified resin, and thus to provide a foamed molded article having a good foamed state.

  The present invention has been made to solve the above-mentioned problems, and the present invention relating to a method for producing a polypropylene-based modified resin comprises a plurality of polypropylene-based resins having different melt mass flow rates and peroxydicarbonate. The ratio of peroxydicarbonate to 100 parts by mass of the total amount of the resin is supplied to the extruder so that the ratio is 0.3 parts by mass or more and 3.0 parts by mass or less. A method for producing a polypropylene-based modified resin that is produced by crosslinking with a peroxydicarbonate, wherein a melt mass flow rate of one of the plurality of polypropylene-based resins is 0. .2g / 10min to 3.0g / 10min, other polypropylenes The resin has a melt mass flow rate exceeding 3.0 g / 10 min, and resin particles are prepared before the melt kneading with a mixed resin in which these polypropylene resins are mixed. The resin particles and the peroxydicarbonate And the cross-linking is carried out by melting and kneading.

In the method for producing a polypropylene-based modified resin according to the present invention, when the polypropylene-based resin and the organic peroxide are melt-kneaded and cross-linked, peroxydicarbonate is used as the organic peroxide. Since the oxydicarbonate and the polypropylene resin are melt mixed at a predetermined ratio, a polypropylene modified resin having a high melt tension can be produced.
In order to improve the melt tension, it is effective to crosslink bulky molecules.
That is, it is possible to generate more crosslinking reactions that contribute to the effect of improving the melt tension by forming in the extruder a situation where the crosslinking agent is more likely to act on a polypropylene resin having a low melt mass flow rate value. .

  In this regard, a polypropylene resin having a low melt mass flow rate (hereinafter also referred to as “low flow PP”) is extruded together with a polypropylene resin having a higher melt mass flow rate than the polypropylene resin (hereinafter also referred to as “high flow PP”). In order to improve the melt tension of the polypropylene-based modified resin, the dispersibility of the low-flow PP in the extruder is increased by melting and kneading in a machine, and the opportunity for the low-flow PP and the crosslinking agent to react is increased. It can be an effective means.

However, if the low flow PP and the high flow PP are supplied to the extruder at a time, the high flow PP starts to flow first in the extruder, so it is difficult to apply a shearing force due to the screw to the low flow PP. There is a risk of causing a time lag from when the flow PP is melted until the low flow PP is uniformly dispersed.
On the other hand, peroxydicarbonate is actively cleaved when the resin temperature reaches a certain temperature range and generates radicals. At this point, the low flow PP may not be uniformly dispersed. Have.

Here, in the method for producing a polypropylene-based modified resin according to the present invention, after producing resin particles with a mixed resin in which low flow PP and high flow PP are mixed, the resin particles and peroxydicarbonate are mixed. Since melt kneading with an extruder, the low-flow PP is already sufficiently dispersed at the time when radicals are generated by peroxydicarbonate.
Therefore, the opportunity for the low flow PP to be cross-linked increases, and a polypropylene-based modified resin having a higher melt tension than the conventional one can be obtained even with the same amount of peroxydicarbonate added.
That is, a high melt tension polypropylene-based modified resin can be obtained efficiently.
Furthermore, a foamed molded product having a high foaming degree in a dense foamed state can be obtained by foaming such a high melt tension polypropylene-based modified resin.

Embodiments of the present invention will be described.
In producing the polypropylene-based modified resin of the present invention, a) polypropylene-based resin particles and b) peroxydicarbonate are used as starting materials.
In addition, the polypropylene-based modified resin of the present invention can appropriately contain various c) additives other than the above components.

And the manufacturing method of the polypropylene-type modified resin which concerns on this invention supplies the above starting materials to an extruder, implements melt kneading | mixing, In this melt kneading, it is made into polypropylene resin particles with the said peroxydicarbonate. Resin modification is performed by causing a crosslinking reaction so that the melt tension is higher than that of the polypropylene resin particles before crosslinking.
First, the starting material that constitutes the polypropylene-based modified resin of the present invention will be described.

a) Polypropylene resin The polypropylene resin is not particularly limited, and examples thereof include homopolypropylene, copolymers of propylene and other olefins, and the like to constitute the polypropylene-based modified resin of the present embodiment. As the component, a copolymer of propylene and another olefin is preferable.
The copolymer of propylene and another olefin may be either a random copolymer or a block copolymer, but is preferably a block copolymer because of excellent heat resistance.
In addition, as other olefin which comprises a copolymer with propylene, for example, in addition to ethylene, 1-butene, 1-pentene, 4-methyl 1-pentene, 1-hexene, 1-octene, 1-nonene And α-olefins having 4 to 10 carbon atoms such as 1-decene.

  In this embodiment, it is important to use a plurality of polypropylene resins having different melt mass flow rates (MFR) when tested at a test temperature of 230 ° C. and a load of 21.18 N in accordance with JIS K7210: 1999 method B. One of the polypropylene resins is a low flow polypropylene resin (low flow PP) having an MFR of 0.2 g / 10 min to 3 g / 10 min, and the other polypropylene resin is 3.0 g / 10 min. It is important to be a high flow polypropylene resin (high flow PP) having an MFR greater than.

The MFR of the low flow PP is defined in the range of 0.2 g / 10 min or more and 3.0 g / 10 min or less because a low flow PP having an MFR lower than 0.2 g / 10 min is used. When the dispersibility in mixing with the flow PP is deteriorated or the ratio of the low flow PP to the total of the low flow PP and the high flow PP is increased, an excessive load is applied in the melt kneading in the extruder. It is because there is a possibility of doing.
In addition, the upper limit of the low flow PP MFR is set to 3.0 g / 10 min. When the MFR polypropylene resin exceeds 3.0 g / 10 min, a polypropylene modified resin having a high melt tension can be obtained. This is because it becomes difficult.
Therefore, the MFR of the low flow PP is preferably 0.3 g / 10 min or more and 2.0 g / 10 min or less.

In addition, the lower limit value of the MFR of the high flow PP is set to 3.0 g / 10 min. When an MFR polypropylene resin having an MFR of 3.0 g / 10 min or less is adopted, the lower MFR is lower than that of the polypropylene resin. This is because when the mixed resin with the flow PP is melt-kneaded with peroxydicarbonate, the extruder may be overloaded.
Although the upper limit is not particularly defined, the maximum MFR of a commercially available polypropylene resin is about 50 g / 10 min. Therefore, the MFR is 50 g in that the high flow PP can be easily obtained. / 10 min or less is preferable.
Furthermore, the MFR of the high flow PP is preferably 5.0 g / 10 min or more and 20 g / 10 min or less from the viewpoint that the melt-kneading process can be easily performed with easily available materials.

Note that the starting material of the polypropylene-based modified resin according to the present embodiment does not need to be only one kind of the low flow PP and the high flow PP, for example, MFR is 0.2 g / 10 min or more. It is also possible to employ a plurality of low flow PPs in a range of 0 g / 10 min or less, and it is also possible to employ a plurality of high flow PPs having an MFR exceeding 3.0 g / 10 min.
Furthermore, it is possible to employ a plurality of both low flow PP and high flow PP.

  Regarding the content of the low flow PP and the high flow PP in the starting material of the polypropylene-based modified resin according to the present embodiment, the ratio of the low flow PP to the total polypropylene resin is 10% by mass or more and 90% by mass or less. It is preferable that the balance (10 mass% or more and 90 mass% or less) is high flow PP.

b) Peroxydicarbonate The peroxydicarbonate is an organic peroxide and acts as a cross-linking agent for polypropylene resins.
Specifically, diethyl peroxydicarbonate, dipropyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-n-butyl peroxydicarbonate, bismethoxybutyl peroxydicarbonate, bis-2-ethylhexyl peroxydicarbonate, Examples include dioctyl peroxydicarbonate, bis-t-butylcyclohexyl peroxydicarbonate, dimyristyl peroxydicarbonate, dicetyl peroxydicarbonate, among others bis-t-butylcyclohexyl peroxydicarbonate, dimyristyl peroxydicarbonate. Carbonate and dicetyl peroxydicarbonate are preferred because they have a high self-accelerating decomposition temperature (SADT) and are excellent in thermal stability and handling during storage.

In addition, the compounding quantity of this peroxydicarbonate and the said polypropylene resin is taken as the ratio of 0.3 to 3.0 mass parts with respect to 100 mass parts of said polypropylene resin (total amount). .
The reason why the amount of peroxydicarbonate is within the above range is that if it is less than the above lower limit value, it becomes difficult to impart sufficient melt tension to the polypropylene-based modified resin, and the above upper limit. Even if it exceeds the value, the effect of improving the melt tension corresponding to the blending amount is not obtained, but the decomposed peroxydicarbonate causes problems of odor and fuming, and gelation occurs due to excessive reaction. It is because there is a possibility of doing.

In addition, when organic peroxides other than those based on peroxydicarbonate are used, it is easy to cause decomposition of the polypropylene resin at the time of melt kneading, and it is difficult to form a crosslinked structure effective for improving the melt tension. is there.
In addition, since crosslinking by organic peroxide is caused by a reaction in which the radical generated by thermal decomposition of the organic peroxide pulls out protons from the polymer, the radical generated by the organic peroxide is recombined to form a radical. May disappear, or the generated radicals may cut the molecular chain of the polypropylene resin and cause a decrease in molecular weight.
Moreover, if it reacts with another substance not intended, the crosslinking efficiency is extremely lowered, and there is a possibility that a good crosslinked structure cannot be imparted to the polypropylene-based modified resin.
Therefore, it is important to react with a crosslinking agent or the like faster than the generated radical causes a recombination reaction or the like to stabilize the generated radical and increase the crosslinking efficiency.

In such a point, in the method for producing a polypropylene-based modified resin according to the present embodiment, the low-flow PP having a bulky molecular structure is mixed with the high-flow PP that is easy to flow in the extruder to be converted into the high-flow PP. Resin particles in which the low flow PP is dispersed are prepared in advance.
Since the resin particles and peroxydicarbonate are melt-kneaded by an extruder, radicals due to peroxydicarbonate organic peroxide are generated in a situation where the bulky polypropylene resin is not sufficiently dispersed. It can be suppressed that a large amount of peroxydicarbonate is consumed for crosslinking of high flow PP.
That is, the cross-linking efficiency is improved by improving the dispersibility of the low flow PP. For example, a polypropylene-based modified resin having a high melt tension of about 3 cN or more suitable as a material for forming a foam molded article or the like. Can be produced efficiently.

c) Additives In addition to the components a) and b), various additives can be included as starting materials for the polypropylene-based modified resin according to this embodiment.
This additive may be added when the components a) and b) are melt-kneaded, or the components a) and b) may be once melt-kneaded and then mixed again.
Furthermore, when the low-flow PP and high-flow PP of a) are mixed to produce resin particles, the additive may be mixed with them.
Specific examples of the additive include, but are not limited to, a weather resistance stabilizer, an antistatic agent, an antioxidant, a light stabilizer, a crystal nucleating agent, a pigment, a dye, a lubricant, a slipperiness, and an antiblocking property. Surfactants, inorganic fillers and higher fatty acids, higher fatty acid esters or higher fatty acid amides for the purpose of improving the dispersibility thereof.
Further, for example, other resin components such as a polyolefin resin highly compatible with a polypropylene resin such as a polyethylene resin may be contained as an additive within a range in which the effect of the invention is not significantly impaired.

  Next, a method for producing a polypropylene-based modified resin using these components to produce a polypropylene-based modified resin will be described.

  In the method for producing a polypropylene-based modified resin according to the present embodiment, after the step of mixing the polypropylene-based resin (low flow PP, high flow PP) and producing resin particles with the mixed resin, the resin is performed. The step of supplying the particles and the peroxydicarbonate to an extruder and melt-kneading with the extruder is performed.

  As a method for producing resin particles with a mixed resin of the low flow PP and the high flow PP, a polypropylene resin solution is prepared by dissolving these resins in a soluble solvent, and the polypropylene resin solution is sprayed. A method of obtaining resin particles by drying, a method of melting and kneading low flow PP and high flow PP with an extruder or the like, extruding into a strand shape, and cutting with a pelletizer, or a resin extruded from an extruder with a hot cut facility The method of granulation is mentioned

  In addition, when the obtained resin particles are then supplied to an extruder together with peroxydicarbonate to cause a crosslinking reaction, the resin particles are 0.1 mm or more in that a more efficient crosslinking reaction can be caused. It is preferable that the average particle diameter is 2.0 mm or less.

This will be explained in more detail. Polypropylene resins are generally commercially available in the form of pellets having a diameter of about 3 to 5 mm, but such size resin pellets are supplied to an extruder or the like. When the melt kneading is performed, the heat capacity of each grain is large, so that even if a part of the pellet is melted, the remaining part remains undissolved for a certain period of time in the extruder.
On the other hand, peroxydicarbonate is cleaved when the temperature of the resin rises to some extent to generate radicals. Therefore, generally commercially available polypropylene resin pellets and peroxydicarbonate are simply melt-kneaded. If only this is done, radicals are likely to be generated in the state where a part of the pellets remains undissolved, and the crosslinking efficiency may not be sufficient.

On the other hand, by making the average particle diameter of the resin particles 0.1 mm or more and 2.0 mm or less as described above, it is easy to make the entire temperature uniform in the extruder, and before the melting unevenness is eliminated in the resin particles. In addition, it is possible to prevent the problem that the radicals generated due to the increased activity of peroxydicarbonate cannot effectively act on the crosslinking reaction.
Therefore, a synergistic effect with the dispersion effect of the low flow PP can be expected, and a high melt tension polypropylene-based modified resin can be produced more efficiently.
In addition, if necessary, resin particles having a diameter of about 3 to 5 mm similar to those of ordinary pellets are once prepared with a mixed resin, and then mechanically pulverized by a pulverizer or the like to reduce the average particle size to 0. It is also possible to set it to 1 mm or more and 2.0 mm or less.

In addition, the method of spray drying after dissolving the resin in a solvent or the like is easy to obtain porous resin particles, although it takes time and effort to recover and regenerate the vaporized solvent. In the case of being supplied to the extruder in the form of powder, it becomes easy to adhere (adsorb) these to the surface.
That is, uneven distribution of peroxydicarbonate in the extruder can be suppressed in melt kneading described later.
In addition, the method using an extruder is easy to obtain resin particles of a uniform size that will give stress due to heat and shear to the polypropylene resin, and does not require labor as in the case of using a solvent. Can be said to be excellent.

  Furthermore, in the case of pulverization as described above, the shape of the resulting resin particles becomes indefinite, although it may generate labor for pulverization, and it is easy to obtain particles with a large specific surface area. ).

The average particle diameter is preferably in the range of 0.1 mm to 2.0 mm. When the average particle diameter is larger than 2 mm, melting unevenness occurs in the extruder, and the This is because it becomes difficult to maintain a balance with the decomposition rate of carbonate.
In addition, when the average particle size is less than 0.1 mm, the amount of input to the extruder is reduced because the bulk density is small although there is a low possibility of causing a problem from the viewpoint of the balance with the decomposition rate of peroxydicarbonate. This may reduce the productivity of the polypropylene-based modified resin.

In addition, the average particle diameter of the resin particles can be measured, for example, in the following manner.
Aperture 4.00 mm, Aperture 3.35 mm, Aperture 2.80 mm, Aperture 2.36 mm, Aperture 2.00 mm, Aperture 1.70 mm, Daily Aperture 1.40 mm, Aperture 1.18 mm, Aperture 1.00 mm, aperture 0.85 mm, aperture 0.71 mm, aperture 0.60 mm, aperture 0.50 mm, aperture 0.425 mm, aperture 0.355 mm, aperture 0.300 mm, aperture 0. Set JIS standard sieve with 250mm, 0.212mm aperture, and 0.180mm aperture on a low-tap type sieve shaker (made by Iida Seisakusho Co., Ltd.), classify about 50g of sample over 10 minutes, and sample on sieve mesh Measure the weight.
Next, an arithmetic average value of the mesh opening of each sieve and the mesh opening of the mesh having the next largest mesh after this mesh is obtained and used as the particle size value of the mesh.
In addition, in the case of a sieve having a mesh opening of 4.00 mm, the mesh opening of the JIS standard sieve having the next largest mesh opening is 4.75 mm. An arithmetic average value of 4.375 mm with an opening of 4.00 mm is taken as the particle size value.
The particle size value of the resin particles remaining on the sieve is determined for each sieve as described above, the mass of the resin particles remaining on the sieve is calculated for each sieve, and the mass of the resin particles remaining on each sieve is calculated. Divide by the total mass of the measurement sample to calculate the mass percentage.
And the mass percentage of the resin particle which remained on all the sieves which have an opening smaller than the opening of each sieve is totaled, and let this value be a cumulative mass percentage.
Next, a graph with the horizontal axis as the particle size value and the vertical axis as the cumulative mass percentage is prepared, and the particle size value and cumulative mass percentage determined for each sieve are plotted on this graph as a set of data. Create an approximate curve connecting the two.
On the approximate curve, the particle diameter (median diameter) at which the cumulative mass percentage is 50% by mass is defined as the average particle diameter.

The resin particles having such an average particle diameter are then supplied to an extruder together with the peroxydicarbonate, and melt kneading is performed with the extruder.
At this time, as described above, the peroxydicarbonate is adjusted to a ratio of 0.3 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the polypropylene-based resin (total amount). Oxydicarbonate is fed to the extruder.

Examples of the extruder include a single-screw extruder, a twin-screw extruder, and the like, and these can be used for producing a polypropylene-based modified resin as a single or a plurality of connected tandem types.
In particular, a twin screw extruder is suitable from the viewpoint of dispersibility and reactivity of other compounding agents with respect to the polypropylene resin as the base resin.

  First, resin particles and peroxydicarbonate are introduced into this extruder at room temperature, and then heated by heat transfer from the inner wall of the cylinder, etc. as the inside of the extruder proceeds while being stirred by a screw. Will be.

At this time, when the low flow PP and the high flow PP are introduced into the extruder without being mixed in advance, the high flow PP with high fluidity is melted first, and the high flow PP is melted into the molten resin. The low flow PP is melted and dispersed in a state that does not run out.
As described above, in order to improve the melt tension, it is effective to crosslink bulky molecules. In this case, high flow PP is cross-linked more than low flow PP having a bulky molecular structure. Since the reaction is likely to occur, the crosslinking effect by peroxydicarbonate may not be sufficiently reflected in the effect of improving the melt tension.

On the other hand, in the method for producing a polypropylene-based modified resin according to this embodiment, resin particles are formed in advance using a mixed resin of low flow PP and high flow PP, and then melt kneaded with an extruder together with peroxydicarbonate. Therefore, the dispersibility of the low flow PP in the extruder is improved, and the opportunity for causing the crosslinking reaction to occur in the low flow PP having a bulky molecular structure is increased.
That is, according to the present invention, a polypropylene-based modified resin having a high melt tension can be produced with a small addition amount of peroxydicarbonate.

In particular, a polypropylene-based modified resin having a high melt tension can be obtained more efficiently by making the average particle diameter of resin particles produced by a mixed resin of low flow PP and high flow PP 0.1 mm or more and 2.0 mm or less. be able to.
That is, if the particle size of the resin particles is large, the heat capacity of each particle is large, so that even if a part of the particles is melted, the remaining part may not be sufficiently softened.
If it does so, it will be in the state in which resin (henceforth "the unmelted part") which is not completely melt | dissolved disperses in high temperature molten resin.
Thus, peroxydicarbonate actively generates radicals as the resin temperature of the molten resin rises, resulting in the generation of radicals in a state where the molten resin and unmelted components are mixed. .

When radicals are generated in this manner, excessive radicals are supplied to the molten resin that is likely to cause a crosslinking reaction. Compared to this, radical recombination is likely to occur.
At this time, the molten resin is brought into an effective state for improving the melt tension by a crosslinking reaction, but thereafter, the crosslinked polypropylene resin is diluted by an unmelted portion that has not been crosslinked.
That is, the effect of improving the melt tension is sufficiently achieved by the fact that a polypropylene resin that is not in a state capable of undergoing a crosslinking reaction at the radical generation peak is easily present, and that the crosslinking efficiency of the organic peroxide is not sufficient. It may not be demonstrated.

  On the other hand, by supplying resin particles adjusted to an average particle diameter of 0.1 mm or more and 2.0 mm or less to the extruder as described above, the whole tends to have a uniform temperature, and crosslinking occurs at the radical generation peak. The possibility of forming an unmelted portion that is not in a reactive state can be reduced.

Although not described in detail here, the temperature setting of the extruder and the average residence time in the extruder can be appropriately adjusted for the extrusion conditions such as the type of screw used and the rotation speed, and these conditions should be adjusted. The melt tension of the polypropylene-based modified resin obtained by the above can be adjusted to be, for example, 3 cN or more (at 230 ° C.).
When this polypropylene-based modified resin is used as a raw material for foam molded articles, the melt tension is preferably 3 cN or more, and more preferably 5 cN or more.
In addition, although it does not specifically limit about an upper limit, Usually, the melt tension of the polypropylene-type modified resin which concerns on this embodiment is 30 cN or less, and it is preferable to set it as 20 cN or less.

  As described above, according to the present invention, a polypropylene-based modified resin having a high melt tension suitable for forming a foam-molded product can be obtained by a simple means of melt kneading with an extruder.

Since the polypropylene-based modified resin obtained in the present embodiment has excellent melt tension, various foams such as a foam sheet, a container such as a tray obtained by secondary molding of the foam sheet, and a bead foam product are obtained. It becomes a suitable material for forming a molded product.
By using the polypropylene-based modified resin of the present invention, for example, if it is a foam sheet, a sheet having a beautiful appearance and a high expansion ratio can be easily produced.

Examples of a method for producing such a foam sheet include a method in which a component for foaming is mixed with the above-described polypropylene-based modified resin and extruded and foamed with an extruder.
As the component for foaming, for example, a gas component that is in a gas state in a temperature range where the polypropylene-based modified resin is softened, a nucleating agent that is a core when bubbles are formed by the gas component, and both And pyrolytic foaming agents that exhibit the above functions.

Examples of the gas component include aliphatic hydrocarbons such as propane, butane, and pentane; 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), 2 -Freon such as chloro-1,1,1,2-tetrafluoroethane (HCFC-124), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a) System gas components: nitrogen, carbon dioxide, argon, water and the like.
These gas components may be used alone or in combination.

  Examples of the nucleating agent include talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, and sulfuric acid. Examples thereof include inorganic compound particles such as potassium, barium sulfate and glass beads, and organic compound particles such as polytetrafluoroethylene.

  Further, as the heat decomposable foaming agent, a general heat decomposable foaming agent that generates a substrate by causing thermal decomposition at least in a temperature range where the resin particles are softened can be used. Examples thereof include dicarbonamide, sodium hydrogen carbonate, a mixture of sodium hydrogen carbonate and citric acid, and the like.

In order to produce a foam sheet using such a forming material, a method of performing extrusion foaming using a general extruder as a foam sheet production facility can be mentioned.
For example, a polypropylene-based modified resin as a base polymer and a heat-decomposable foaming agent are introduced into an extruder on the upstream side of a tandem extruder, and in this extruder, for example, a temperature advantageous for dissolving the gas components After melt-kneading the polypropylene-based modified resin under conditions, for example, a gas component such as butane is injected and further kneaded in the middle of the extruder to obtain a resin composition containing the gas component. A method of producing a foam sheet by adjusting a temperature condition suitable for extrusion with a downstream extruder and extruding and foaming from a flat die or a circular die can be employed.

Since the polypropylene-based modified resin according to this embodiment has a high melt tension, it can have a beautiful appearance while the foamed sheet has a high expansion ratio.
The present invention does not limit the use of the polypropylene-based modified resin to the foamed sheet as described above, and the polypropylene-based modified resin can be used as a material for forming a bead foam molded product. The characteristics can be suitably exhibited.
Moreover, the use of the polypropylene-based modified resin of the present invention is not limited to foam molded products.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

Example 1
A low-flow polypropylene resin (manufactured by Prime Polymer, Homopolypropylene resin, trade name “E111G”, MFR = 0.5 / 10 min) and a high-flow polypropylene resin (manufactured by Sun Allomer, homopolypropylene resin, trade name “PL500A” ”, MFR = 3.3 / 10 min) at a mass ratio of 30/70, these resin particles were mixed by stirring in a ribbon blender, and then a twin screw extruder (L / D = 47) having a diameter of 30 mm. ), Melt-kneaded in a twin screw extruder at a resin temperature of 200 ° C. and a rotation speed of 100 rpm, and a discharge amount of 10 kg / h from a die having a diameter of 4 mm, a land of 5 mm, and a number of holes of 2 attached to the tip. Extruded into a strand.
Next, the strand-shaped mixed resin was passed through a 2 m long cooling water tank containing 30 ° C. water, cooled, and cut with a pelletizer to produce resin particles made of the mixed resin.
The average particle diameter of the resin particles was 0.7 mm.

Subsequently, with respect to 100 parts by mass of the polypropylene resin particles having an average particle diameter of 0.7 mm, the dicetyl peroxydicarbonate and the resin particles are mixed at a ratio of 1.5 parts by mass of dicetyl peroxydicarbonate. The mixture stirred and mixed in the ribbon blender is supplied to a twin screw extruder (L / D = 47) having a diameter of 30 mm, and melt kneaded in the twin screw extruder at a resin temperature of 200 ° C. and a rotation speed of 150 rpm. Polypropylene-based modified resin was extruded in a strand form from a die having a diameter of 4 mm, a land of 5 mm, and a number of holes of 2 attached to the substrate at a discharge rate of 5 kg / h.
The strand-like polypropylene-based modified resin was also cooled by passing through a 2 m long cooling water tank containing 30 ° C. water and cut with a pelletizer to obtain a pellet made of the polypropylene-based modified resin.
Table 1 shows the results of measurement of melt tension using the pellets.
The melt tension was measured as follows.

(Measurement of melt tension)
A polypropylene-based modified resin serving as a sample was accommodated in a cylinder with an inner diameter of 15 mm arranged in the vertical direction of a twin bore capillary rheometer (Rheological 5000T) manufactured by Thiast, and heated at 230 ° C. for 5 minutes to be melted. Later, a piston was inserted from the upper part of the cylinder, and a capillary (die diameter: 2.095 mm, die length: provided at the lower end of the cylinder so that the extrusion speed was a constant speed of 0.0773 / s with the piston. The molten resin was extruded in a string shape from 8 mm, inflow angle: 90 degrees (conical), and then wound up using a winding roll.
At this time, the initial speed at the beginning of winding is 4 mm / s, the subsequent acceleration is 12 mm / s ² , the winding speed is gradually increased, and the winding speed when the tension observed by the tension detection pulley is drastically reduced is set. The breaking point speed was determined, and the maximum tension until the breaking point speed was observed was measured as the melt tension.

(Example 2)
The high-flow polypropylene resin was changed to the trade name “PM600A” (homopolypropylene resin, MFR = 7.5 g / 10 min) made by Sun Allomer instead of the trade name “PL500A” made by Sun Allomer, dicetyl peroxy A polypropylene-based modified resin was produced in the same manner as in Example 1 except that the blending amount of dicarbonate was changed to 2.0 parts by mass instead of 1.5 parts by mass, and the melt tension of the obtained polypropylene-based modified resin Was measured. The results are shown in Table 1.

(Example 3)
The high-flow polypropylene resin is changed to the product name “PM600A” manufactured by Sun Allomer instead of the product name “PL500A” manufactured by Sun Allomer, and the low-flow polypropylene resin (trade name “E111G”) and high-flow polypropylene are used. A polypropylene-based modified resin was prepared in the same manner as in Example 1 except that the mass ratio with the resin based on the product (trade name “PM600A”) was 50/50, and the melt tension of the obtained polypropylene-based modified resin was measured. Went.
The results are shown in Table 1.

(Example 4)
The high-flow polypropylene resin was replaced by the product name “PM802A” (homopolypropylene, MFR = 20/10 min) of Sun Allomer, instead of the product name “PM600A” (MFR = 7.5 / 10 min) of Sun Allomer. A polypropylene modified resin was prepared in the same manner as in Example 3 except that the amount of dicetyl peroxydicarbonate was changed to 2.0 parts by mass instead of 1.5 parts by mass. The melt tension of the quality resin was measured. The results are shown in Table 1.

(Comparative Examples 1-4)
A polypropylene system similar to each of Examples 1 to 4, except that a low-flow polypropylene resin and a high-flow polypropylene resin were melt-kneaded directly with dicetyl peroxydicarbonate in a twin-screw extruder without being mixed in advance. A modified resin was prepared, and the melt tension of the obtained polypropylene-based modified resin was measured.
The low-flow polypropylene resin and the high-flow polypropylene resin are supplied to the twin screw extruder after adjusting the particle size so that the average particle diameter is 0.7 mm, which is the same as in Examples 1 to 4. did.
Table 1 shows the measurement results of the melt tension of the obtained polypropylene-based modified resin.

(Example 5)
A polypropylene modified resin was prepared in the same manner as in Example 3 except that dimyristyl peroxydicarbonate was used instead of dicetyl peroxydicarbonate, and the melt tension of the obtained polypropylene modified resin was measured. went. The results are shown in Table 1.

(Examples 6 and 7)
The resin particle size of the mixed resin of the low flow PP (trade name “E111G”) and the high flow PP (trade name “PM600A”) is changed so that the average particle diameter becomes 1.1 mm and 1.5 mm, respectively. A polypropylene modified resin was prepared in the same manner as in Example 3 except that the melt tension was measured, and the melt tension of the obtained polypropylene modified resin was measured. The results are shown in Table 1.

  As can be seen from this table, even when the amount of the organic peroxide used is the same, a high melt tension polypropylene-based modified resin can be obtained by employing the production method of the present invention.

(Example 8, Comparative Example 5)
Implemented except that the average particle size of the resin particles by the mixed resin was changed to 2.4 mm instead of 0.7 mm and the amount of dicetyl peroxydicarbonate was reduced from 2.0 parts by weight to 1.5 parts by weight. In the same manner as in Example 2, the polypropylene-based modified resin of Example 8 was produced.
Further, Comparative Example 5 was the same as Example 8 except that the low-flow polypropylene resin and the high-flow polypropylene resin were melt kneaded directly with dicetyl peroxydicarbonate with a twin-screw extruder without being mixed in advance. A polypropylene-based modified resin was prepared.
Table 2 shows the results of measuring the melt tension of these polypropylene-based modified resins in the same manner as in the previous examples.

In addition, since the amount of dicetyl peroxydicarbonate in Example 8 is less than that in Example 2 and the resin type is different from Example 7, the average particle diameter exceeds 2.0 mm although simple comparison is not possible. Since it is 2.4 mm, it is recognized that the value of the melt tension is lower than that of the other examples.
From this, it can be seen that when the average particle diameter of the resin particles is 0.1 mm or more and 2.0 mm or less, a more excellent effect on the melt tension is exhibited.

(Comparative Examples 6 and 7)
A polypropylene-based modified resin of Comparative Example 6 was produced in the same manner as in Example 2 except that the amount of dicetyl peroxydicarbonate was 0.2 parts by mass.
Further, a polypropylene-based modified resin of Comparative Example 7 was produced in the same manner as in Example 2 except that dicumyl peroxide (0.3 parts by mass) was used instead of dicetyl peroxydicarbonate.
Table 3 shows the results of measuring the melt tension of these polypropylene-based modified resins in the same manner as in the previous examples.
The polypropylene-based modified resin of Comparative Example 7 was not measurable because the melt tension was too low.

  Also from Table 3, it is important to employ peroxydicarbonate as the organic peroxide, and the blending amount is 0.3 parts by mass or more with respect to 100 parts by mass of the polypropylene resin. It can be confirmed that it is important.

(Example of foam sheet production)
Foam extrusion was carried out using a tandem extruder in which a second extruder having a diameter of 65 mm was connected to the tip of a first extruder having a diameter of 50 mm to produce a foam sheet.
For the production of the foam sheet, a baking soda-citric acid foaming agent (master batch manufactured by Dainichi Seika Co., Ltd. A polymer composition containing master PO410K ") was used.
The polymer composition is supplied to the first extruder, melted and kneaded, and is a gas component from the middle of the first extruder so that the ratio to 100 parts by mass of the polypropylene-based modified resin is 1.5 parts by mass. Butane (isobutane / normal butane = 35/65 mass%) was injected and kneaded.
The molten polymer composition and the gas component are uniformly mixed and kneaded and then continuously supplied to the second extruder and cooled to a resin temperature suitable for foaming while continuing the melt kneading. Discharge rate of 20 kg / h (discharge rate: V = 30 kg / (cm ² .multidot.cm) from a circular die (caliber φ70 mm, die slit interval 0.3 mm (cross-sectional area of the resin outlet: 0.660 cm ² )) h)), the resulting cylindrical foam is put on a cooled mandrel, and its outer surface is cooled by blowing air from an air ring. A foam sheet was produced by cutting the foam-like material.
The foaming ratio of the obtained foamed sheet was 2.3 times and the appearance was beautiful.

Further, when a foamed sheet was produced in the same manner using the polypropylene-based modified resin of Example 3, a product having a beautiful appearance with an expansion ratio of 2.5 was obtained.
On the other hand, instead of these polypropylene-based modified resins, a foamed sheet was produced in the same manner using a homo-polypropylene resin, product name “PL500A” manufactured by Sun Allomer Co. The state was as low as 1.8 times.
Furthermore, when a high melt tension polypropylene resin manufactured by Nippon Polypro Co., Ltd., “New Former FB3312” was used, a 3.0 times higher foaming ratio was observed, but a striped pattern along the extrusion direction. A foam sheet with a beautiful appearance was not obtained.
This also shows that the polypropylene-based modified resin of the present invention is suitable as a material for forming a foam molded article.

Claims (4)

A plurality of polypropylene resins and peroxydicarbonates having different melt mass flow rates so that the ratio of peroxydicarbonate to 100 parts by mass of the total amount of polypropylene resins is 0.3 parts by mass or more and 3.0 parts by mass or less. A process for producing a polypropylene-based modified resin, wherein the polypropylene-based modified resin is produced by being melt-kneaded by the extruder and cross-linked with the peroxydicarbonate.
The melt mass flow rate of one polypropylene resin among the plurality of polypropylene resins is 0.2 g / 10 min or more and 3.0 g / 10 min or less, and the other polypropylene resin exceeds 3.0 g / 10 min. The resin particles are prepared with the mixed resin in which these polypropylene resins are mixed before the melt-kneading, and the crosslinking is performed by melt-kneading the resin particles and the peroxydicarbonate. A method for producing a polypropylene-based modified resin.   The proportion of the polypropylene resin having a melt mass flow rate of 0.2 g / 10 min or more and 3.0 g / 10 min or less of the plurality of polypropylene resins is 10 mass% or more and 90 mass% or less, and the balance is 3.0 g / The method for producing a polypropylene-based modified resin according to claim 1, which is a polypropylene-based resin having a melt mass flow rate exceeding 10 min.   The method for producing a polypropylene-based modified resin according to claim 1 or 2, wherein an average particle diameter of the resin particles is 0.1 mm or more and 2.0 mm or less.   The method for producing a polypropylene-based modified resin according to any one of claims 1 to 3, wherein the peroxydicarbonate is dicetyl peroxydicarbonate.