JP2010116492A - Production method and quality control method of polypropylene resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a high-quality polypropylene resin composition for processing into a molded article having a good appearance. <P>SOLUTION: The method for producing a polypropylene resin composition includes a deaeration step of deaerating a melt-kneaded material obtained by melting and kneading a mixture containing an inorganic filler and polypropylene. The deaeration step is a step of deaerating the melt-kneaded material in such a manner that the specific gravity of the polypropylene resin composition to be obtained by the deaeration step is higher than a preliminarily determined set value. The set value is determined based on a relation between the content of the inorganic filler included in the polypropylene resin composition and the specific gravity of pellets causing no silver streak when the pellet of the polypropylene resin composition containing the inorganic filler in such the content is molded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a polypropylene resin composition and a quality control method for obtaining a molded article having an excellent appearance.

  In recent years, industrial parts used for automotive parts such as bumpers, instrument panels, door trims, pillar trims, etc. are polypropylene-based composite materials blended with inorganic fillers such as talc and elastomers, which have excellent physical property balance and moldability. Many polypropylene resin compositions are used.

  Generally, these polypropylene resin compositions are produced by melting and kneading a raw material polypropylene, an elastomer component, and an inorganic filler component (such as talc) in a kneader.

Regarding a method for producing a polypropylene resin composition by melting and kneading polypropylene, an elastomer component and an inorganic filler component, Patent Document 1 describes a deaeration method for discharging volatile components of a molding material using a specific vent device. ing. Patent Document 2 describes a method for producing a polyolefin resin composition using an inorganic filler compressed to a specific compression ratio by deaeration in order to obtain an inorganic filler-containing resin composition having an excellent appearance. Specifically, it is described that a tandem-type kneading / granulating apparatus is employed as an apparatus used for kneading / granulating, and a compressed inorganic filler having a preferable compression ratio is used. Patent Document 3 describes a polypropylene resin composition containing degassed compressed talc having specific physical properties for the purpose of providing a talc-containing polypropylene resin composition having no white spots due to poor talc dispersion.
Japanese Patent Laid-Open No. 8-28176 (published on October 29, 1996) JP 2002-302554 A (published on October 18, 2002) JP 2006-104457 A (published April 20, 2006)

  However, the inventions described in Patent Documents 1 to 3 do not sufficiently suppress appearance defects due to silver streaks or the like.

  This invention is made | formed in view of said problem, The objective is to provide the method of manufacturing the good-quality polypropylene resin composition for processing into the molded article which has a favorable external appearance.

  In order to solve the above problems, a method for producing a polypropylene resin composition according to the present invention has a degassing step of degassing a melt-kneaded product obtained by melt-kneading a mixture containing an inorganic filler and polypropylene. In the degassing step, the degassing step is performed by degassing the melt-kneaded material so that the specific gravity of the polypropylene resin composition pellets obtained by the degassing step is higher than a preset value. The set value is the content of the inorganic filler contained in the polypropylene resin composition, and when the pellet of the polypropylene resin composition containing the inorganic filler is molded with the content, silver streak occurs. It is characterized in that it is set based on the relationship between the specific gravity of the non-pellet.

In the method for producing a polypropylene resin composition according to the present invention, the set value is the following formula (1):
(Set value) = 0.008 × (inorganic filler content (% by weight)) + 0.84 (1)
More preferably, it is set by

  In the method for producing a polypropylene resin composition according to the present invention, the polypropylene is more preferably at least one selected from the group consisting of a propylene homopolymer, a propylene block copolymer, and a propylene random copolymer.

  In the method for producing a polypropylene resin composition according to the present invention, the total amount of the polypropylene resin composition is 100% by weight, and the content of the inorganic filler is more preferably 1 to 70% by weight.

  In the method for producing a polypropylene resin composition according to the present invention, the inorganic filler is more preferably talc.

  The quality control method according to the present invention is a quality control method for a polypropylene resin composition containing an inorganic filler, and determines whether or not the specific gravity of a pellet of the polypropylene resin composition is higher than a preset value. When the above set value has a content of the inorganic filler contained in the polypropylene resin composition and a pellet of the polypropylene resin composition containing the inorganic filler at the content, a silver streak occurs. It is characterized in that it is set based on the relationship between the specific gravity of the non-pellet.

  According to the production method of the present invention, by controlling the specific gravity of the polypropylene resin composition, the gas content in the polypropylene resin composition can be adjusted, and the molded product having a good appearance can be processed. A high-quality polypropylene resin composition can be produced.

  A method for producing a polypropylene resin composition according to the present invention is a method for producing a polypropylene resin composition having a degassing step of degassing a melt-kneaded product obtained by melt-kneading a mixture containing an inorganic filler and polypropylene, The degassing step is a step of degassing the melt-kneaded product so that the specific gravity of the polypropylene resin composition pellets obtained by the degassing step is higher than a preset set value. Is the relationship between the content of the inorganic filler contained in the polypropylene resin composition and the specific gravity of the pellet in which silver streaks do not occur when molding the pellet of the polypropylene resin composition containing the inorganic filler at the content. It is set based on.

  The inorganic filler is added mainly for improving the rigidity of the polypropylene resin composition. Examples of the inorganic filler used in the present invention include glass fiber, carbon fiber, metal fiber, glass bead, mica, calcium carbonate, potassium titanate whisker, talc, bentonite, smectite, sepiolite, wollastonite, allophane, imogolite, Examples thereof include fibrous magnesium oxysulfate, barium sulfate, and glass flakes, and talc is preferable.

  As an average particle diameter of an inorganic filler, it is 0.01-50 micrometers normally, Preferably it is 0.1-30 micrometers, More preferably, it is 0.1-5 micrometers. Here, the average particle diameter of the inorganic filler is a 50% equivalent particle determined from an integral distribution curve of a sieving method measured by suspending in a dispersion medium such as water or alcohol using a centrifugal sedimentation type particle size distribution measuring device. It means the diameter D50.

  The inorganic filler may be used without treatment, or in order to improve interfacial adhesion or dispersibility with the propylene-based polymer composition, various known silane coupling agents, titanium coupling agents, The surface may be treated with a fatty acid, a higher fatty acid ester, a higher fatty acid amide, a higher fatty acid salt or other surfactant.

  The content of the inorganic filler may be appropriately set according to the use of the polypropylene resin composition to be produced, etc., but the total amount of the polypropylene resin composition is 100% by weight, preferably 1 to 70% by weight, and further rigid. From the viewpoint of improvement, it is preferably 5 to 70% by weight, more preferably 10 to 50% by weight.

  The melt-kneaded product obtained by melt-kneading a mixture containing an inorganic filler and polypropylene is a melt-kneaded product obtained by melting and kneading a mixture containing an inorganic filler and polypropylene, which are raw materials for a polypropylene resin composition. The mixture is a mixture containing an inorganic filler and polypropylene, and may further contain an elastomer described later, other additives, and the like. The melt-kneaded product can be obtained, for example, by polymerizing propylene and then melt-kneading a mixture in which an inorganic filler or the like is mixed in a kneader.

  The polypropylene is preferably at least one selected from the group consisting of a propylene homopolymer, a propylene block copolymer, and a propylene random copolymer. Examples of polypropylene include homopolypropylene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, and propylene-butene-1 copolymer.

  A deaeration process is a process deaerated from the melt-kneaded material containing an inorganic filler and a polypropylene. Examples of the deaeration method include a deaeration method described in Patent Document 1 described above and a method using a vacuum vent device.

  In the production method according to the present invention, a preferred form for the degassing step is a form in which the gas in the kneader is forcibly removed by providing a vacuum vent device in the kneader for performing melt kneading, for example.

  In the degassing step, the specific gravity of the pellets obtained by solidifying the melt-kneaded material containing the inorganic filler and polypropylene is adjusted to be higher than a preset set value.

  A pellet is a pellet-shaped polypropylene resin composition obtained by granulation after solidifying a melt-kneaded material containing an inorganic filler and polypropylene.

The preset value is the relationship between the content of the inorganic filler and the specific gravity of the pellet that does not cause silver streak when the polypropylene resin composition containing the inorganic filler is molded at the content. It is a value set based on. For example, with a constant inorganic filler content, several types of polypropylene resin composition pellets having different specific gravities are molded and observed for the occurrence of silver streaks. From the specific gravity of the pellets when silver streaks do not occur, A set value of specific gravity in content can be set. In this way, for example, the set value can be set as a linear function of the inorganic filler content (% by weight). The set value is the following formula (1)
(Set value) = 0.008 × (inorganic filler content (% by weight)) + 0.84 (1)
More preferably, it is set by In addition, said Formula (1) is the density | concentration of the pellet which does not produce silver streak, when the content of an inorganic filler and the pellet of the polypropylene resin composition containing an inorganic filler in the said content are shape-processed. This is an expression set based on the relationship.

  The molding processing is processing into a molded product made of a polypropylene resin composition, and examples thereof include processing into a molded product such as industrial parts used for automobile parts and the like. Generally, a method of forming by heating is used.

  Further, the silver streak is a streak generated on the surface of the molded product due to the foaming phenomenon caused by the gas contained in the polypropylene resin composition when it is molded by heating, and causes a poor appearance.

  A preferred form of the production method according to the present invention is a form in which the deaeration step is performed after the melting / kneading step or the melting / kneading step is performed, and then the granulation step is performed. The melting / kneading step is a step of melting and kneading polypropylene and additives (such as inorganic filler) in a kneader, and a melt-kneaded material containing polypropylene and additives is obtained by this step. The granulation step is a step of obtaining pellets by granulating after the melt-kneaded product is solidified. A preferred form of the production method according to the present invention is, for example, a melt-kneaded product obtained by melting and homogenizing a polypropylene resin, an inorganic filler, an elastomer and other additives in a melting / kneading step, and a melt-kneaded product in a degassing step. Is deaerated and then solidified in the granulation step to form a pellet-shaped polypropylene resin composition.

  Examples of the apparatus used in the above-described melting / kneading step and granulation step include a uniaxial granulator, a twin-screw granulator, a continuous mixer kneader, and a tandem-type kneader / granulator combined with a single-shaft granulator. Is mentioned. In order to suppress deterioration of the polypropylene resin composition due to oxidation and yellowing, it is preferable to seal an apparatus used for the melting / kneading step and the granulating step with an inert gas such as nitrogen. In addition, in the melting and kneading process, in order to remove volatile substances, moisture, etc. contained in the melt-kneaded product containing polypropylene and additives, a vacuum vent device is installed in the kneader to remove volatile substances, moisture, etc. It is particularly preferable to force exhaust.

  The production rate of the polypropylene resin composition containing the inorganic filler in the apparatus used for the melting / kneading step and the granulation step is not particularly limited, but is preferably 300 kg / hr or more in consideration of economy, and is 1 ton / hr or more. It is more preferable. The production rate is not particularly limited, but is preferably 30 ton / hr or less, more preferably 25 ton / hr or less in consideration of dispersion of the inorganic filler and other additives.

  It is more preferable to add an elastomer and other additives to the raw material of the polypropylene resin composition.

  The elastomer is a copolymer of ethylene and α-olefin, and examples thereof include copolymers of ethylene-octene, ethylene-hexene, ethylene-pentene, ethylene-butene, ethylene-propylene, and the like. Among these, it is preferable that an appropriate material is selected and added for improving the physical properties according to the use of the polypropylene resin composition. Examples of improving physical properties include improving impact resistance, imparting softness, and improving appearance.

  Other additives are preferably added to impart various properties necessary for the polypropylene resin composition. For example, antioxidants, lubricants, UV inhibitors, antistatic agents, antiblocking agents, and nucleating agents. Etc. It is preferable to add at least one of the above-described additives to the polypropylene resin composition according to the present invention.

  Examples of the antioxidant include calcium stearate, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 1,3,5-tris (3,5- Di-t-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, dimyristyl-3,3′-thiodipropionate, tris (2 , 4-di-t-butylphenyl) phosphite, basic aluminum magnesium carbonate, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, 3,9-bis [2 {3 ( 3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} 1,1-dimethylethyl] 2,4,8,10-tetraoxa Pyro - [5.5] undecane, and the like.

  Examples of the lubricant include erucic acid amide, oleic acid amide, ethylene bisstearyl aluminide, erucyl amide, dimethylpolysiloxane and the like.

  Examples of UV inhibitors include 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate, bis (2,2,6,6-tetramethyl- 4-piperidine) sebacate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate and the like.

  Examples of the antistatic agent include glycerin fatty acid ester, polyoxyalkylamine mixed composition, alcohol fatty acid ester, nonionic surfactant, polyoxyethylene alkylamine / higher alcohol mixture, and the like.

  Examples of the anti-blocking agent include silicon dioxide, polymethylsilsesquioxane, aluminum silicate salt, and a crosslinked polymethyl methacrylate.

  Examples of the nucleating agent include bis [4- (1,1-dimethylethyl) benzoate-0] hydroxyaluminum, dibenzylidene sorbitol, 2,2′-methylenebis (4,6-di-t-butylphenyl phosphate). ) Sodium, phosphate ester compounds and the like.

  According to the production method of the present invention, by controlling the specific gravity of the polypropylene resin composition, the gas content in the polypropylene resin composition can be adjusted, and the molded product having a good appearance can be processed. A high-quality polypropylene resin composition can be produced.

<Quality control method>
The quality control method according to the present invention is a quality control method for a polypropylene resin composition containing an inorganic filler, and determines whether or not the specific gravity of a pellet of the polypropylene resin composition is higher than a preset value. When the above set value has a content of the inorganic filler contained in the polypropylene resin composition and a pellet of the polypropylene resin composition containing the inorganic filler at the content, a silver streak occurs. This is set based on the relationship between the specific gravity of the pellets and the specific gravity.

  For the preset setting value in the quality control method according to the present invention, the description relating to the description of the set value in the manufacturing method according to the present invention can be applied mutatis mutandis.

  The determination step is a step of determining whether or not the specific gravity of the pellet of the polypropylene resin composition is higher than a preset set value, and examples include a method of determining by directly measuring the specific gravity of the pellet. . Examples of the method for measuring the specific gravity of the pellet include an underwater substitution method based on JIS K7112.

  By using the quality control method according to the present invention, by controlling the specific gravity in the production of the polypropylene resin composition, the gas content in the polypropylene resin composition can be adjusted and processed into a molded product having a good appearance. A high-quality polypropylene resin composition can be produced.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  In this example, it was confirmed whether or not silver streaks occurred when pellets of polypropylene resin compositions having different specific gravities were produced and molded using the pellets.

  A biaxial granulator was used for the production of the polypropylene resin composition. As the inorganic filler, talc was used, and as shown in Table 1 below, four types of polypropylene resin compositions having different talc contents (% by weight) were produced for each of Examples and Comparative Examples. From the content of talc in each, a set value of specific gravity was set using the above-described formula (1).

  Polypropylene and talc were melted and kneaded with a twin-screw granulator, and the obtained melt-kneaded product was deaerated with a vacuum vent device provided in the twin-screw granulator. The vent suction pressure was -50 kPaG in Examples 1 to 4, -20 kPaG in Comparative Examples 1 and 2, and -30 kPaG in Comparative Examples 3 to 4. Then, it granulated and obtained the pellet of the polypropylene resin composition.

  The specific gravity of the pellets of the obtained polypropylene resin composition was measured using an underwater substitution method based on JIS K7112. As shown in Table 1 below, the measured values of the specific gravity of the pellets in Examples 1 to 4 were equal to or higher than the set value. On the other hand, the measured value of the specific gravity of the pellets in Comparative Examples 1 to 4 was not more than the set value.

  Next, each pellet was molded by an injection molding method. Specifically, using a mixture obtained by dry blending the pellets of the obtained polypropylene resin composition and a pigment master batch, the molding temperature was set to 220 ° C. and the mold cooling temperature was set to 50 ° C. using a SE180D injection molding machine manufactured by Sumitomo Heavy Industries. Then, injection molding was performed to obtain a flat plate test piece of 400 (mm) × 100 (mm) × 3 (mm).

  About the obtained flat plate test piece, the presence or absence of generation | occurrence | production of silver streak was confirmed visually. And when there was, it determined with x, and when there was none, it determined with (circle). As shown in Table 1, the occurrence of silver streaks was not confirmed on the surface of the flat plate test pieces obtained in Examples 1 to 4, and the appearance was good. On the other hand, the occurrence of silver streaks was confirmed on the surfaces of the flat plate test pieces obtained in Comparative Examples 1 to 4, and the appearance was poor.

  The results in this example are shown in FIG. FIG. 1 is a graph showing the relationship between the content (% by weight) of talc (inorganic filler) and the measured value of the specific gravity of pellets when the total amount of the polypropylene resin composition is 100% by weight in this example. It is. A graph indicated by a solid line as a “specific gravity lower limit line” in FIG. 1 is a graph showing the above-described formula (1). The points showing the results of Examples 1 to 4 are all higher than the graph showing the above-described formula (1), while the points showing the results of Comparative Examples 1 to 4 all show the above-described formula (1). It was below the graph.

  Therefore, as a conditional expression for setting the specific gravity setting value in the present invention, the above-described expression (1) can be derived based on the result of this embodiment. Further, as a conditional expression for setting the set value of specific gravity, it is possible to derive a new expression that replaces the above-described expression (1) based on the result of this embodiment.

  This example showed that by controlling the specific gravity of the polypropylene resin composition, a high-quality polypropylene resin composition for processing into a molded article having a good appearance can be produced.

  If the production method and quality control method according to the present invention are used, a high-quality polypropylene resin composition for processing into a molded product having a good appearance can be produced, and therefore, for example, it is applied to the production of industrial parts used for automobile parts and the like. it can.

The graph which showed the relationship between content (weight%) of a talc (inorganic filler) when the whole quantity of a polypropylene resin composition is 100 weight% in one Example of this invention, and the measured value of the specific gravity of a pellet. is there.

Claims (6)

A method for producing a polypropylene resin composition having a degassing step of degassing a melt-kneaded product obtained by melt-kneading a mixture containing an inorganic filler and polypropylene,
The degassing step is a step of degassing the melt-kneaded product so that the specific gravity of the pellets of the polypropylene resin composition obtained by the degassing step is higher than a preset set value.
The above set values are the content of the inorganic filler contained in the polypropylene resin composition, and the specific gravity of the pellet in which silver streak does not occur when molding the pellet of the polypropylene resin composition containing the inorganic filler at the content. A method for producing a polypropylene resin composition, which is set based on the relationship. The set value is the following formula (1)
(Set value) = 0.008 × (inorganic filler content (% by weight)) + 0.84 (1)
The manufacturing method according to claim 1, which is set by:   The said polypropylene is a manufacturing method of Claim 1 or 2 which is at least 1 sort (s) chosen from the group which consists of a propylene homopolymer, a propylene block copolymer, and a propylene random copolymer.   The manufacturing method according to any one of claims 1 to 3, wherein the total amount of the polypropylene resin composition is 100% by weight, and the content of the inorganic filler is 1 to 70% by weight.   The manufacturing method of any one of Claims 1-4 whose said inorganic filler is a talc. A quality control method for a polypropylene resin composition containing an inorganic filler,
A determination step of determining whether the specific gravity of the pellet of the polypropylene resin composition is higher than a preset set value;
The above set values are the content of the inorganic filler contained in the polypropylene resin composition, and the specific gravity of the pellet in which silver streak does not occur when molding the pellet of the polypropylene resin composition containing the inorganic filler at the content. A quality control method that is set based on the relationship.

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