JP2008093919A - Method for producing mini-pellet made of polypropylene resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing mini-pellets with particle weight suitable for preliminary foaming particles arranged uniformly, by melting/kneading a polypropylene resin and a hydrogenated petroleum resin stably in high discharge by a single screw extruder. <P>SOLUTION: In the method for producing the mini-pellets made of a polypropylene resin composition containing 1-10 wt.% of the hydrogenated petroleum resin by melting/kneading the composition with the single screw extruder, the temperature of a cylinder (C<SB>1</SB>) in the feed part of the extruder is adjusted to be 200°C or above. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing mini-pellets made of a polypropylene resin composition that can be stably melt-kneaded at a high discharge rate in a single screw extruder and have a uniform grain weight.

  In the in-mold foam molding method for beads, it is known that pre-expanded particles made of a resin composition obtained by adding a hydrogenated petroleum resin to a polypropylene resin have the effect of reducing the molding vapor pressure during in-mold foam molding. (Patent Document 1). However, when producing resin particles for making pre-expanded particles, so-called mini-pellets, polypropylene resin and hydrogenated petroleum resin are melt-kneaded with a single screw extruder and extruded at a high discharge rate that can withstand industrial production. In general, a master batch or a twin-screw extruder is used because it is difficult to form the pellet into a simple pellet shape. For example, Patent Document 2 is a document relating to a film production method, but discloses that a polypropylene resin and a hydrogenated petroleum resin are used to produce pellets with a single screw extruder at an extruder temperature of 210 ° C. In this document, since a pellet for producing a sheet is manufactured, the uniformity of the pellet weight is not particularly required or mentioned. However, as inferred from the description of the examples of the document, since the hydrogenated petroleum resin 15 to 30% by weight is blended with the polypropylene-based resin, the shape of the pellet obtained when the strand becomes too soft becomes non-uniform. Moreover, since the pellets are fused when the discharge amount is increased, it is expected that the pellets can be formed only with a low discharge amount.

On the other hand, the pre-expanded particles are required to have a uniform particle weight. To that end, the resin particles are required to have a uniform particle weight. However, in such a state, it is not possible to produce mini pellets with uniform particle weights suitable for pre-expanded particles.
JP 59-68340 A Japanese Patent Laid-Open No. 10-60196

  The object of the present invention is to produce mini-pellets that can stably melt and knead polypropylene resin and hydrogenated petroleum resin with high discharge in a single-screw extruder, and have uniform particle weights suitable for pre-expanded particles. It is to provide a method.

  The inventors of the present invention have intensively studied to achieve this problem. As a result, in the polypropylene resin composition, the amount of hydrogenated petroleum resin added is 1 to 10% by weight, and the cylinder temperature of the feed part of the single screw extruder is set to 200 ° C. or higher, whereby the polypropylene resin composition The present inventors have found that mini-pellets made of can be obtained with a uniform grain weight and have completed the present invention.

  That is, the first of the present invention is a method of producing mini-pellets made of a polypropylene resin composition containing 1 to 10% by weight of hydrogenated petroleum resin by melt-kneading with a single screw extruder, The present invention relates to a method for producing mini-pellets made of a polypropylene resin composition, characterized in that the cylinder temperature of the feed section is 200 ° C. or higher.

As a preferred embodiment,
(1) The softening point of the hydrogenated petroleum resin is 110 ° C. or higher.
(2) The hydrogenated petroleum resin is an alicyclic hydrogenated petroleum resin,
The present invention relates to a method for producing the mini-pellets described above.

  According to the method for producing mini-pellets of the present invention, a polypropylene resin and a hydrogenated petroleum resin can be stably melt-kneaded at a high discharge rate with a single-screw extruder, and mini-pellets having a uniform grain weight can be obtained. Can be provided.

  The present invention relates to a method for producing mini-pellets made of a polypropylene resin composition containing 1 to 10% by weight of a hydrogenated petroleum resin by melt-kneading with a single screw extruder, the cylinder of the extruder feed section It is a manufacturing method of the mini pellet which consists of a polypropylene resin composition characterized by making temperature 200 degreeC or more.

The polypropylene resin of the present invention may contain propylene as a monomer, preferably 90% by weight or more, more preferably 95% by weight or more. For example, propylene homopolymer, ethylene-propylene random copolymer. Examples thereof include polymers, propylene-butene random copolymers, ethylene-propylene block copolymers, ethylene-propylene-butene terpolymers, and these modified products. There is no particular limitation on the synthesis method, and these polypropylene resins are generally known methods, that is, gas phase polymerization methods such as BASF method, AMDCD method, UCC method, and Hypol method using a MgCl ₂ type supported catalyst, It can be produced by a method using a highly active metallocene catalyst or a method using a conventional TiCl ₃ catalyst.

  Moreover, you may add synthetic resins other than a polypropylene resin in a polypropylene resin composition. Synthetic resins other than polypropylene resins include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, linear ultra-low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic. Examples thereof include ethylene resins such as acid copolymers and ethylene-methacrylic acid copolymers, and styrene resins such as polystyrene and styrene-maleic anhydride copolymers.

  Although there is no restriction | limiting in particular in melting | fusing point of the polypropylene resin in this invention, 130 to 170 degreeC is preferable, 135 to 160 degreeC is more preferable, 140 to 150 degreeC is further more preferable.

  There is no restriction | limiting in particular in the melt index of the polypropylene resin in this invention, Preferably it is 0.2g / 10min or more and 50g / 10min or less, More preferably, it is 1g / 10min or more and 30g / 10min or less, More preferably, it is 3g / 10min or more and 12g / 10min. It is as follows. When the melt index is less than 0.2 g / 10 min, the melt viscosity tends to be too high and it is difficult to obtain highly expanded pre-expanded particles. When the melt index is greater than 50 g / 10 min, the melt viscosity with respect to the elongation of the resin at the time of expansion is low. It is low and tends to break. The melt index can be adjusted, for example, by using an organic peroxide.

  The hydrogenated petroleum resin used in the present invention refers to a thermoplastic resin obtained by cationically polymerizing a cracked oil fraction generated by thermal decomposition of petroleum, and is a petroleum unsaturated carbonization such as cyclopentadiene. This refers to hydrogenated petroleum resin containing hydrogen, higher olefinic hydrocarbons, or aromatic hydrocarbons as the main raw material (50% by weight or more). Of the hydrogenated petroleum resins, those having a hydrogenation rate of 80% or more, particularly 90% or more are preferred. Furthermore, the softening point of the hydrogenated petroleum resin of the present invention is preferably 110 ° C. or higher. The softening point here is a measured value based on JIS-K2207 (ring and ball type). If the softening point is less than 110 ° C., the difference from the cylinder temperature of the extruder feed section is too large, so that the hydrogenated petroleum resin dissolves quickly and the dissolution in the polypropylene resin may become uneven. The addition amount of the hydrogenated petroleum resin is 1 to 10% by weight, preferably 1 to 5% by weight, in the polypropylene resin composition.

  Hydrogenated petroleum resins can be broadly classified into aliphatic hydrogenated petroleum resins, alicyclic hydrogenated petroleum resins, and aromatic hydrogenated petroleum resins.

The aliphatic hydrogenated petroleum resin is a resin using a olefin or diolefin of a C ₄ or C ₅ fraction, for example, isobutylene, butadiene, isoprene, piperine or the like as a main component as a polymerization raw material. Typical commercial products include Clearon P-125 (manufactured by Yashara Chemical Co., Ltd.), Quinton A100 (manufactured by Nippon Zeon Co., Ltd.), Quinton K100 (manufactured by Nippon Zeon Co., Ltd.), Hiretsu C110X (manufactured by Mitsui Chemicals, Inc.) Highlets R100X (manufactured by Mitsui Chemicals, Inc.), tackolol (manufactured by Sumitomo Chemical Co., Ltd.) and the like.

  The alicyclic hydrogenated petroleum resin is obtained by polymerizing an alicyclic fraction such as cyclopentadiene or dicyclopentadiene or hydrogenating an aromatic petroleum resin. Typical commercial products include Alcon P-115 (Arakawa Chemical Co., Ltd.), Alcon P-125 (Arakawa Chemical Co., Ltd.), Alcon P-140 (Arakawa Chemical Co., Ltd.), Quinton 1325 ( ZEON Co., Ltd.), Quinton 1345 (Nihon Zeon Co., Ltd.), Quinton 1500 (Nihon Zeon Co., Ltd.), Quinton 1700 (Nihon Zeon Co., Ltd.), Marukaretsu M-845A (Maruzen Petrochemical Co., Ltd.) Co., Ltd.), Marcaretz M-890A (manufactured by Maruzen Petrochemical Co., Ltd.), Escorez 5320 (manufactured by Exxon Mobile Chemical), Escorez 5340 (manufactured by Exxon Mobile Chemical Company), Escorez 5415 (manufactured by Exxon Mobile Corp.) Mobile Chemical), Opera PR102J (Exxon Mobile Chemical), Opera PR103J (Exxon Mobile Chemical 11), Opera PR104J (Exxon Mobile), PR 100J (Exxon Mobile Chemical). And Plastolyn R1140 (manufactured by Eastman).

The aromatic hydrogenated petroleum resin is a resin made from a C ₉ or C ₁₀ fraction, for example, vinyl toluene, indene, methyl indene or the like as a main component. Typical commercial products include Archon M-115 (Arakawa Chemical Co., Ltd.), Archon M-135 (Arakawa Chemical Co., Ltd.), Neopolymer 120 (Shin Nippon Oil Co., Ltd.), Neopolymer 130. (Manufactured by Nippon Oil Corporation), Neopolymer 140 (manufactured by Nippon Oil Corporation), Petrogin 120 (manufactured by Mitsui Chemicals) and the like.

In the present invention, a terpene-based hydrogenated resin can be used instead of the hydrogenated petroleum resin. The terpene-based hydrogenated resin here is a hydrocarbon compound represented by a composition of (C ₅ H ₈ ), for example, pinene, dipentene, limonene, osimene, myrcene, karen, terpinolene, terpinene, totalene, mylene, camphorene. , Santalene, Genghibelen, Bisabolene, Tricyclene, etc.

  Among these, aliphatic hydrogenated petroleum resins and alicyclic hydrogenated petroleum resins having high compatibility with polypropylene resins are preferable, and alicyclic hydrogenated petroleum resins having a high effect of low molding pressure are also preferable. preferable.

  In the present invention, if necessary, cell nucleating agents such as talc, antioxidants, metal deactivators, phosphorus processing stabilizers, UV absorbers, UV stabilizers, fluorescent brighteners, metal soaps, etc. These stabilizers or crosslinking agents, chain transfer agents, lubricants, plasticizers, fillers, reinforcing agents, pigments, dyes, flame retardants, antistatic agents and the like may be contained in the polypropylene resin composition.

  The single screw extruder in the present invention refers to an extruder having a single screw mounted on a cylinder, and is generally used. The main structure consists of a hopper, drive unit, speed reducer, screw, cylinder, heating / cooling device (heater / blower), temperature control device, etc., and a desired die is attached to the tip of the cylinder via an adapter.

In the present invention, the cylinder (C ₁ ) of the feed section of the extruder refers to a portion under the hopper into which the resin is charged in the cylinder, and the portions where the set temperature can be changed according to the direction in which the resin is extruded from C ₁ are sequentially C ₂ , C ₃ ,..., C _n . The position of the die (D) may be next to or below the adapter (A). In the present invention, the set temperature of the cylinder (C ₁ ) of the extruder feed section needs to be 200 ° C. or higher, preferably 210 ° C. or higher and 260 ° C. or lower. When the set temperature exceeds 260 ° C., decomposition of the hydrogenated petroleum resin starts and smoke from the dice tends to increase. Furthermore, the type of screw of the single screw extruder is not particularly limited, and examples thereof include a full flight type and a dalmage type, both of which can be used for the production of the mini pellet of the present invention. It is preferable because of its excellent properties. The diameter of a die for extruding a melt-kneaded product of a polypropylene resin composition in the form of a string is preferably 1.0 to 3.0 mm, and in order to obtain a mini pellet having a high discharge rate and a uniform grain weight, 1.0 -1.8 mm is more preferable. Next, set temperature conditions for the remaining cylinders (C _{2 to} C _n ), adapter (A), and die (D) will be described. The temperature of each part is
C ₁ −30 ° C. ≦ C _{2 to} C _n ≦ C ₁ + 50 ° C.,
C ₁ −30 ° C. ≦ A ≦ C ₁ + 50 ° C.,
C ₁ −30 ° C. ≦ D ≦ C ₁ + 50 ° C.
It is preferable that both the cylinder, the adapter, and the die are more preferably 260 ° C. or lower.

  The mini-pellet in the present invention is preferably a cylindrical shape having a length of 1.5 to 4.0 mm and a thickness of 0.4 to 1.0 mm, and its particle weight is 0.3 to 3.0 mg. It is preferable. When making this minipellet into pre-expanded particles to form a molded body, the particle weight is more preferably 0.5 to 1.2 mg. Pre-expanded particles as used herein means, for example, that mini-pellets are dispersed in water in a pressure-resistant container together with a foaming agent, heated above the temperature at which the mini-pellets soften, and impregnated with the foaming agent in the mini-pellets. This refers to expanded particles obtained by discharging into a low-pressure atmosphere, and can be produced by a known method. The pre-expanded particles thus obtained are packed in a mold and heated and foamed with water vapor to produce a molded body with a low heating pressure.

Mini-pellets produced by the production method of the present invention preferably have small particle weight variations of 0.15 or less, and can be suitably used for pre-expanded particles. In the present invention, the particle size variation of mini-pellets is obtained by randomly collecting 30 particles of the obtained mini-pellets and setting the average value of the 30 particles as Aav. The i-th grain weight measurement value is Ai and is a value calculated by the following formula.
Grain weight variation (σ) = [{Σ (Ai−Aav) ² } / 29] ^1/2

<Melt flow index measurement>
The melt flow index was measured under the conditions of orifice 2.0959 ± 0.005 mmφ, orifice length 8.000 ± 0.025 mm, load 2160 g, 230 ± 0.2 ° C. in accordance with JIS-K7210.

<Grain weight variation (σ)>
Thirty mini-pellets cut with a pelletizer are randomly sampled, and the average value of the weights of the 30 pellets is defined as Aav. The grain weight variation (σ) is expressed by the following formula, where the i-th grain weight measurement value is Ai.
Grain weight variation (σ) = [{Σ (Ai−Aav) ² } / 29] ^1/2
<Discharge stability>
The ejection stability was evaluated according to the following criteria, and a pass / fail judgment was made.
A: No change in discharge amount, resin pressure fluctuation range within 10 kgf / cm ² and grain weight variation (σ) within 0.15 ○: No change in discharge amount, but resin pressure fluctuation range is 10 kgf / cm ² Greater than 15 kgf / cm ² and grain weight variation (σ) is within 0.15 ×: grain weight variation (σ) exceeds 0.15 (Example 1)
Alcon P manufactured by Arakawa Chemical Co., Ltd., which is a hydrogenated petroleum resin with 97% by weight of ethylene-propylene random copolymer (resin density 0.90 g / cm ³ , melt flow index 4.8 g / 10 min, crystal melting point 146 ° C.) -Blend of a resin mixture containing 3% by weight of -140 (softening point 140 ° C.), and the temperature of the cylinder, adapter and die is adjusted using a 50 mm single screw extruder equipped with a die having a diameter of 1.2 mm. C ₁ = 210 ° C., C ₂ = 210 ° C., C ₃ = 210 ° C., C ₄ = 220 ° C., A = 230 ° C., D = 230 ° C. To obtain a mini-pellet. It can be said that the ejection stability was good because the resin pressure fluctuation range was within 10 kgf / cm ² and the grain weight variation (σ) was within 0.15 without changing the ejection amount for 2 hours. The results are shown in Table 1.

（実施例２）
実施例１においてスクリューの回転数を５０ｍｍ押出機の最大回転数である１００ｒｐｍに代えた以外は実施例１と同様の方法により押出した。２時間吐出量が変化することなく、樹脂圧力変動幅も１０ｋｇｆ／ｃｍ²以内で粒重量バラツキ（σ）が０．１５以内だったので吐出安定性が良好であったといえる。結果を表１に示す。

(Example 2)
Extrusion was carried out in the same manner as in Example 1, except that the screw rotation speed was changed to 100 rpm which is the maximum rotation speed of the 50 mm extruder in Example 1. It can be said that the discharge stability was good because the resin pressure fluctuation range was within 10 kgf / cm ² and the particle weight variation (σ) was within 0.15 without changing the discharge amount for 2 hours. The results are shown in Table 1.

(Example 3)
Extrusion was carried out in the same manner as in Example 1 except that the cylinder temperature was changed to C ₁ = 250 ° C., C ₂ = 230 ° C., and C ₃ = 220 ° C. in Example 1. The discharge amount did not change for 2 hours, the resin pressure fluctuation range was within 10 kgf / cm ² , and the grain weight variation (σ) was within 0.15, so it can be said that the discharge stability was good. The results are shown in Table 1.

Example 4
Extrusion was carried out in the same manner as in Example 1, except that 90% by weight of the ethylene-propylene random copolymer and 10% by weight of the hydrogenated petroleum resin Alcon P-140 were added. Without 2 hours discharge amount is changed, the resin pressure fluctuation width 10 kgf / cm ² or more 15 kgf / cm ² within the grain weight variation (sigma) was good ejection stability because it was 0.15. The results are shown in Table 1.

(Example 5)
In Example 1, instead of the alicyclic hydrogenated petroleum resin Alcon P-140, Example 1 was used except that Clearon P-125 (softening point 125 ° C.) manufactured by Yashara Chemical Co., which is an aliphatic hydrogenated petroleum resin, was used. Extrusion was carried out in the same manner as in 1. Without changing the discharge amount for 2 hours, the resin pressure fluctuation range was within 10 kgf / cm ² , and the grain weight variation (σ) was within 0.15, so the discharge stability was excellent. The results are shown in Table 1.

(Example 6)
Extrusion was performed in the same manner as in Example 1, except that Alcon P-115 (softening point 115 ° C.) was used instead of Alcon P-140 in Example 1. The discharge amount did not change for 2 hours, the resin pressure fluctuation range was within 10 kgf / cm ² , and the variation (σ) in grain weight was within 0.15, so the discharge stability was excellent. The results are shown in Table 1.

(Comparative Example 1)
Extrusion was carried out in the same manner as in Example 1 except that the cylinder temperature was changed to C ₁ = 170 ° C., C ₂ = 180 ° C., and C ₃ = 200 ° C. In 20 minutes, the screw began to slide, and the discharge amount decreased significantly, making it impossible to extrude the resin from the single screw extruder. The results are shown in Table 1.

(Comparative Example 2)
Extrusion was carried out in the same manner as in Example 1 except that the cylinder temperature was changed to C ₁ = 190 ° C., C ₂ = 200 ° C., and C ₃ = 200 ° C. The fluctuation range of the resin pressure was within 10 kgf / cm ² , but the discharge amount gradually decreased and the grain weight variation became severe. The results are shown in Table 1.

(Comparative Example 3)
Extrusion was performed in the same manner as in Example 1, except that 85% by weight of the ethylene-propylene random copolymer and 15% of the hydrogenated petroleum resin Alcon P-140 were added. As a result, the screw began to slide gradually and the discharge amount decreased, resulting in poor discharge stability. The results are shown in Table 1.

  As shown in Examples 1 to 6 and Comparative Examples 1 to 3, according to the present invention, a polypropylene resin and a hydrogenated petroleum resin can be stably melt-kneaded with high discharge in a single screw extruder, and pre-expanded particles It can be seen that mini-pellets with uniform grain weights suitable for can be provided.

The schematic diagram of a 50 mm single-screw extruder is shown.

Claims (3)

  A method for producing mini-pellets comprising a polypropylene resin composition containing 1 to 10% by weight of hydrogenated petroleum resin by melt-kneading with a single screw extruder, wherein the cylinder temperature of the extruder feed section is 200 ° C. The manufacturing method of the mini pellet which consists of a polypropylene resin composition characterized by the above-mentioned.   The method for producing mini-pellets according to claim 1, wherein the hydrogenated petroleum resin has a softening point of 110 ° C or higher.   The method for producing a mini-pellet according to claim 1 or 2, wherein the hydrogenated petroleum resin is an alicyclic hydrogenated petroleum resin.

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